DEPARTMENT OF LABOR

29 CFR Part 1910

Docket No. H-044

Occupational Exposure to 2-Methoxyethanol, 2-Ethoxyethanol and Their Acetates (Glycol Ethers)

AGENCY:Occupational Safety and Health Administration (OSHA), Labor

ACTION: Proposed rule and notice of hearing

SUMMARY:The Occupational Safety and Health Administration (OSHA) proposes to amend its existing regulation for occupational exposure to 2-Methoxyethanol (2-ME), 2-Ethoxyethanol (2-EE) and their acetates (2-MEA, 2-EEA) ("Glycol Ethers"), contained in 29 CFR 1910.1000 Table Z-1, and to be codified as new section 29 CFR 1910.1031. The Assistant Secretary has determined, based on a review and evaluation of studies conducted on the health effects of these glycol ethers, that the current permissible exposure limits (PELs) do not adequately protect employees from significant risks of adverse health effects, specifically reproductive and developmental health effects

To eliminate these significant risks of adverse health effects, OSHA is proposing for general, maritime, agriculture and construction industries to reduce the existing 8-hour time weighted average (TWA) PELs for 2-ME and 2-MEA to 0.1 ppm and for 2-EE and 2-EEA to 0.5 ppm

OSHA proposes excursion limits (ELs) for these glycol ethers of five times the proposed PELs. OSHA also proposes to set Action Levels (ALs) for these glycol ethers of one-half the proposed PELs, measured as an 8-hour TWA, to encourage lower exposure for employees while reducing administrative burdens on employers. In addition, OSHA proposes that no employee shall be exposed to these glycol ethers through dermal contact

OSHA proposes to require certain ancillary provisions for employee protection such as preferred methods to control exposure, employee exposure monitoring, medical surveillance, recordkeeping, regulated areas, emergency procedures, hazard communication, and personal protective equipment

DATES: Written comments on the proposed standard must be postmarked on or before June 7, 1993. Notices of Intention to Appear at the informal public hearings on the proposed standard must be postmarked by June 7, 1993. Parties who request more than 10 minutes for their presentations at the informal public hearing and parties who submit documentary evidence at the hearing must submit the full text of their testimony and all documentary evidence no later than June 28, 1993. The informal rulemaking hearing is scheduled to begin on July 20, 1993

ADDRESSES:Written comments should be submitted to the Docket Officer, Docket No. H-044, Room N-2625, U.S. Department of Labor, 200 Constitution Avenue, N.W., Washington, DC 20210

Notices of Intention to Appear at the informal rulemaking hearing, testimony, and documentary evidence are to be sent to Tom Hall, OSHA Division of Consumer Affairs, Docket No. H-044, Room N-3662, U.S. Department of Labor, 200 Constitution Avenue, N.W., Washington, DC 20210

FOR FURTHER INFORMATION CONTACT:Mr. James F. Foster, OSHA, U.S. Department of Labor, Office of Public Affairs, Room N-3647, 200 Constitution Avenue, N.W., Washington , DC 20210. Telephone (202) 219-8151.

SUPPLEMENTARY INFORMATION:

I. Introduction

1. Introduction

2. Pertinent Legal Authority

3. History of the Regulation

4. Chemical Identification, Production, and Use of Ethylene Glycol Ethers

5. Health Effects

1. Introduction

2. Metabolism/Metabolic-Related Health Effects

3. Acute Toxicity

4. Background Discussion on Reproductive and Developmental Toxicology

5. Effects in Animals

1. Male Reproductive Effects

2. Maternal/Developmental Effects

3. Blood Effects

6. Adverse Effects in Humans

7. Mutagenicity

8. Conclusions

9. Health Effects of Other Glycol Ethers

6. Risk Assessment

7. Significance of Risk

8. Summary of the Regulatory Impact Analyses and Regulatory Flexibility Analysis

9. Environmental Impact

10. Summary and Explanation of the Proposed Standard

11. Clearance of Information Collection Requirements

12. Public Participation - Notice of Hearings

13. Authority and Signature

14. Proposed Standard and Appendices

A. Issues

Comment is requested on all relevant issues, including health effects, risk assessment, technological and economic feasibility and provisions that should be included in a final glycol ethers standard

OSHA is especially interested in answers, supported by evidence and reasons, to the following questions

1. Do OSHA's proposed TWA permissible exposure limits (PELs) of 0.1 ppm for 2-ME and 2-MEA and 0.5 ppm for 2-EE and 2-EEA adequately protect employees from significant risk of adverse health effects? If not, what TWA permissible exposure limits would be more appropriate or would more adequately protect employees from health risks? Please provide data and evidence to support your response

2. In addition to the proposed TWA PELs and action levels, OSHA has proposed Excursion Limits (ELs) of 0.5 ppm for 2-ME and 2-MEA and 2.5 ppm for 2-EE and 2-EEA. In the preamble to this proposal OSHA has also explained the various reasons for establishing ELs for the glycol ethers included in this proposal. OSHA requests comment on this provision. Please provide data and evidence to support your response

3. In addition to the PELs for airborne exposure to glycol ethers, OSHA is also proposing that employers ensure that no employee is exposed to glycol ethers through dermal contact. OSHA requests comment on this provision. In particular:

a. Are there methods to measure dermal exposure that could be routinely used to monitor worker exposure to glycol ethers?

b. For employers whose employees are exposed to glycol ethers, what methods do you use to protect employees from dermal contact with glycol ethers?

c. What do these methods cost?

4. OSHA has limited the scope of this proposal to the four glycol ethers referred to OSHA by EPA. OSHA requests comment about whether the proposed scope of this rulemaking is appropriate. OSHA also requests comment about whether the scope of this proposed standard should be expanded to cover other ethylene glycol ethers and/or other propylene glycol ethers. Should there be separate rulemaking undertaken to cover other glycol ethers not included in this proposal? If so, what data and evidence are available to indicate that exposure to these other glycol ethers present a risk to employees?

5. In making its risk assessment, OSHA relied upon the NOEL-Uncertainty Factor approach to describe and calculate the risks associated with occupational exposure to glycol ethers. OSHA requests comment on whether this approach is appropriate for making a risk assessment regarding reproductive/developmental health effects

a. OSHA requests comment on whether there are more appropriate models for describing or calculating the risks of adverse reproductive/developmental effects among exposed workers. Are there scientifically valid quantitative models that would be more appropriate for assessing risk of reproductive/developmental health effects?

b. OSHA has used an Uncertainty Factor of 100 to determine a level below which humans are unlikely to experience significant risk of adverse reproductive/developmental effects similar to those observed in animals. Is an Uncertainty Factor of 100 appropriate in this circumstance? Would an alternative Uncertainty Factor be more appropriate? Please provide data and evidence to support your response. (Please see Section VI of this section for more detailed questions on risk assessment.)

6. Paragraph (g) of the proposed standard would require that supplied air respirators be used in those limited situations where the TWA and/or EL permissible exposure limits are not capable of being achieved solely by means of engineering and work practice controls. The requirement that respiratory protection be limited to supplied air respiratory protection is based on the fact that glycol ethers have poor warning properties at the proposed PELs. OSHA requests comment on this provision. OSHA also requests comment on the following:

a. Would the proposed requirement of supplied air respirators provide adequate protection or are there other kinds of respiratory protection that would be more appropriate and provide more protection?

b. Are there situations in which organic vapor cartridges or canisters could be used to adequately reduce exposures to or below the PELs? Do these other methods have adequate warning of potential breakthrough? Please provide evidence to support your response

c. Are there any end-of-service-life indicators for the glycol ethers covered by this rulemaking?

d. For those employers whose employees are exposed to glycol ethers, what respiratory protection is provided to employees who are exposed above the PELs? How and why was the particular type of respiratory protection selected?

e. What is the cost of the respiratory protection program?

7. The proposed standard would require that employers provide appropriate personal protective equipment (e.g. coveralls, gloves, eye shields) to prevent exposure through dermal or eye contact in those limited situations where elimination of such contact is not capable of being achieved solely by means of engineering and work practice controls. OSHA requests comment on this provision. OSHA also requests information on the following:

a. OSHA is aware that some exposures to glycol ethers may be intermittent or of short duration. In these situations the breakthrough time of protective clothing or gloves may not be exceeded during a single use. OSHA requests comment on whether the clothing or gloves should be allowed to be reused? If so, in what situations would reuse be appropriate or to what situations should reuse be limited?

b. For employers whose employees are exposed to glycol ethers, what kind of personal protective equipment is provided and in what situations? Please explain, based on the specific situation, how and why use of such equipment was determined. Do employees reuse protective clothing and gloves?

c. For employers whose employees are exposed to glycol ethers, what is the cost of the personal protective equipment that is provided?

8. A number of provisions have been proposed to prevent exposure of employees through off-gassing from and/or contact with glycol ethers from contaminated personal protective equipment. OSHA requests information on problems associated with off-gassing and/or contact in the storage, handling, and disposal of contaminated equipment (particularly at the action levels that have been proposed). Should specific change rooms and showers be required?

9. Specific clean-up procedures have not been required in the proposal. OSHA requests information on whether specific procedures and practices should be required and, if so, what procedures are necessary. Is peroxide formation a problem with these compounds?

10. Paragraph (d)(2) of the proposed standard provides that initial exposure monitoring would be required for all employees who are or may be exposed to glycol ethers. OSHA requests comment on this provision

a. For employers whose employees are exposed to glycol ethers, please describe your monitoring program and the basis for performing initial monitoring

b. What are the cost of your monitoring program?

11. Monitoring would be permitted to be discontinued if initial monitoring results show exposure levels to be below the action level and at or below the excursion limits. Should the Agency require a second sample, taken at least seven days later, to confirm the initial monitoring results before permitting discontinuance of monitoring for that employee, as has been required for discontinuance of periodic monitoring?

12. In the medical surveillance provisions of the proposed standard OSHA has not proposed a requirement for any specific tests for the detection of the early onset of adverse reproductive or developmental effects. OSHA requests information about whether there are any medical tests which can be routinely used to detect such effects? If so, what are these tests and with what frequency should they be required? Please provide data and evidence to support your response

13. The medical surveillance provisions of the proposed standard would require that counseling or tests, which are requested by the employee and deemed appropriate by the examining physician, be made available to employees exposed to glycol ethers who are having difficulty conceiving a child or who have concerns about their ability to conceive a healthy child. Are these requirements adequate and appropriate? If not, what other provisions should be added? For those employers whose employees are exposed to glycol ethers, OSHA also requests information on the following:

a. Is medical surveillance being provided to exposed employees?

b. What exposure levels or other factors trigger medical surveillance?

c. What tests and counseling are included in the medical surveillance program?

d. What provisions are included in the medical surveillance program to address reproductive/developmental health effects resulting from exposure to glycol ethers?

e. What benefits have been achieved from the medical surveillance program?

f. What are the costs of the medical surveillance program?

14. Under the recordkeeping provisions, OSHA proposes that medical records be maintained for at least the duration of employment plus 30 years. Is this recordkeeping provision adequate? If not, what other provisions would provide more protection and be more appropriate? For those employers whose employees are exposed to glycol ethers, what is the current policy regarding maintenance of medical records?

15. Data and evidence presented to OSHA in response to the ANPR indicate that a number of industry sectors are substituting away from manufacture and use of the glycol ethers covered under this proposal

The major substitutes are 2-Butoxyethanol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate and ethylene glycol monopropyl ether. OSHA requests comment on the following:

a. Where and how are these substitutes being used and to what degree have substitutes replaced the glycol ethers covered by this proposal?

b. What other substitutes are being used in place of the glycol ethers covered by this proposal?

c. What are the current employee exposure levels for the substitutes?

d. Are there known hazards and health risks associated with these substitutes?

e. For employers who have substituted, wholly or partially, away from the glycol ethers covered by this proposal, why was substitution undertaken?

f. What results, positive and negative, have been documented as a result of substitution (e.g., changes in productivity and/or production efficiency; changes in product quality; changes in employee absenteeism, medical expenses, worker compensation payments, insurance premiums; effects on compliance with environmental regulations)?

g. What were the costs of substitution?

16. For employers that currently manufacture or use glycol ethers covered by this proposal, OSHA requests the following information regarding substitution:

a. Are there substitutes for glycol ethers available for your business?

b. If you are planning to substitute, what plans and timeline do you have for replacing glycol ethers with substitute chemicals?

c. What percentage of production has been substituted and what percentage still can be substituted away from glycol ethers? What factors prevent complete substitution away from glycol ethers?

d. What will be the projected costs of substitution?

17. OSHA requests the following information from employers involved in glycol ether operations:

a. Job categories for each operation or process in which employees are potentially exposed to glycol ethers

b. The number of employees in each of those job categories

c. A brief description of each of those operations, job categories and production techniques

d. A brief description of the engineering and work practice controls associated with each of those operations

e. Raw exposure data, annotated if possible, associated with the operations described above

f. The Standard Industrial Classification (SIC) codes of the establishment(s)

18. In each job category where employees are potentially exposed to glycol ethers, please provide the following information regarding employee exposure levels:

a. The last two years of raw air monitoring results, annotated if possible, expressed as an 8-hour time weighted average for all employees who are exposed to glycol ethers and the dates of all raw air monitoring data

b. The duration and frequency of exposure for those employees

c. The job tasks or duties being performed at the time of monitoring

d. The engineering and work practice controls in place at the time of monitoring

e. The method of monitoring used to measure these exposures

f. To the extent that representative sampling is used, clearly indicate which employees within each job category were monitored, the corresponding results and which employees were represented by the sampling results. Please discuss your representative sampling strategy and why representative sampling was used

19. Please provide information on any job category and employee whose exposure to glycol ethers is so varied, intermittent, or of such short duration, etc., that the raw air monitoring data provided in response to the previous question do not adequately portray the nature of the exposures. Please explain your response and indicate peak levels, duration and frequency of exposures for employees in those job categories

20. OSHA requests the following information regarding engineering and work practice controls:

a. For employers whose employees are exposed to glycol ethers, are the proposed PELs currently being achieved in your facilities in most operations most of the time by means of engineering and work practice controls?

b. In what operations are the proposed PELs being achieved most of the time by means of engineering and work practice controls? What engineering and work practice controls have been implemented in those operations?

c. For all operations in your facilities, what engineering and work practice controls have been implemented?

d. What additional engineering and work practice controls could be implemented in each operation where exposure levels are currently above the proposed PELs to further reduce exposure levels?

e. When these additional controls are implemented, to what levels can exposure levels be expected to be reduced?

f. What are the costs and time needed to develop, install and/or implement additional controls?

g. Are there any processes or operations in which it is not reasonably possible to implement engineering and work practice controls within six months to one year to achieve the proposed PELs? If so, would allowing additional time for employers to come into compliance with paragraph (f) make compliance reasonably possible? How much time would be necessary?

21. In operations where air exposure levels are above the proposed PELs, to what extent can these operations and processes be automated and enclosed or remotely controlled? To what extent can quality control sampling be remotely controlled? Are there any restrictions on the use of automated or remote control techniques?

22. What are the benefits, other than reducing employee exposures to glycol ethers, that can be derived from implementing engineering and work practice controls (e.g., reduced exposure to other contaminants; compliance with environmental regulations; increased productivity and/or production efficiency; product improvement; reduced absenteeism; reduction in medical expenses, insurance premiums and worker compensation payments, etc.)?

23. Are engineering control technologies that have proven effective in industries not covered by this notice applicable or transferrable to the chemicals covered by this proposal? Please explain and provide evidence to support the nature and extent of compatibility or applicability

24. OSHA requests information on whether there are any limited unique conditions or job tasks in glycol ether manufacture or use where engineering and work practice controls are not available or are not capable of reducing exposure levels to or below the proposed PELs most of the time. Please provide data and evidence to support your response

25. In the Preliminary Regulatory Impact Analysis OSHA has estimated benefits by extrapolating from the NOEL-Uncertainty Factor approach. OSHA requests comment on its methodology in using the Uncertainty Factor approach to project benefits. OSHA also requests comment on whether there are alternative methods, either quantitative or qualitative, for projecting benefits associated with a reduction in exposure to glycol ethers

26. In order to perform the economic feasibility analysis for the final rule, OSHA requests employers and interested parties submit the following information from the last five years on your company and/or industry sector:

a. Profits, sales and the percentage of each which are related to the glycol ethers covered by this proposal

b. Total annual volume and dollar value of production for your company and/or industry sector. What percentages are related to the glycol ethers covered by this proposal?

c. Annual labor turnover rate of your company and/or industry sector for jobs involving exposure to the glycol ethers covered by this proposal

27. For performing an economic feasibility analysis , OSHA also requests the following:

a. A financial and economic profile of your company and/or industry sector

b. A profile of your financial position in the market and your market share in producing glycol ethers or producing products utilizing glycol ethers

c. The number of facilities in your industry sector

28. What is the age, production capacity and estimated remaining life of your plant and equipment?

29. Will major renovation or reconstruction of your company be required to bring air monitoring results into compliance with the proposed standard? If so, please provide costs and time necessary for renovation and/or reconstruction

30. The Agency has prepared a draft Regulatory Flexibility Analysis analyzing the impacts of the proposed standard on the small businesses which OSHA believes may be affected. The following information is requested for small businesses in addition to the information OSHA has gathered

(a) What kinds of small businesses or organizations and how many of them would be affected by regulating exposures?

(b) Which, if any, federal rules may duplicate, overlap, or conflict with an OSHA regulation concerning glycol ethers?

(c) Will difficulties be encountered by small entities when attempting to comply with requirements of the proposed standard? Can some of the requirements be deleted or simplified for small entities, while still achieving comparable protection for the health of employees of small entities?

(d) What timetable would be appropriate to allow small entities sufficient time to comply? 31. The National Environmental Policy Act (NEPA) of 1969 (42 U.S.C. 4321 et seq.) requires that each Federal agency consider the environmental impact of major actions significantly affecting the quality of the human environment. Any person having information, data or comments pertaining to possible environmental impacts is invited to submit them along with accompanying documentation to OSHA. Such impacts might include:

(a) Any positive or negative environmental effects that could result should a standard be adopted;

(b) Beneficial or adverse relationships between the human environment and productivity;

(c) Any irreversible commitments of natural resources which could be involved should a standard be implemented; and

(d) Estimates of the degree of reduction of glycol ethers in the environment by the proposed standard and alternatives

In particular, consideration should be given to the potential direct or indirect impacts of any action, or alternative actions, on water and air pollution, energy usage, solid waste disposal, or land use

B. Federalism

This proposed standard has been reviewed in accordance with Executive Order 12612, 52 FR 41685 (October 30, 1987), regarding Federalism. This Order requires that agencies, to the extent possible, refrain from limiting state policy options, consult with States prior to taking any actions that would restrict State policy options, and take such actions only when there is clear constitutional authority and the presence of a problem of national scope. The Order provides for preemption of State law only if there is a clear Congressional intent for the agency to do so. Any such preemption is to be limited to the extent possible

Section 18 of the Occupational Safety and Health Act (OSH Act), expresses Congress' clear intent to preempt State laws with respect to which Federal OSHA has promulgated occupational safety or health standards. Under the OSH Act a State can avoid preemption only if it submits, and obtains Federal approval of, a plan for the development of such standards and their enforcement. Occupational safety and health standards developed by such Plan-States must, among other things, be at least as effective as the Federal standards in providing safe and healthful employment and places of employment

Since these materials are present in workplaces in every state of the Union, the occupational hazard of glycol ethers is a national problem

The Federally proposed glycol ether standard is drafted so that employees in every State would be protected by the standard. To the extent that there are any State or regional peculiarities, States with occupational safety and health plans approved under Section 18 of the OSH Act would be able to develop their own State standards to deal with any special problems

In short, there is a clear national problem related to occupational safety and health for employees exposed to glycol ethers. Those States which have elected to participate under Section 18 of the OSH Act would not be preempted by this proposed regulation

State comments are invited on this proposal and will be fully considered prior to promulgation of a final rule

C. State Plans Revisions

The 23 states and 2 territories which operate their own Federally-approved occupational safety and health plans must adopt a comparable standard within six months of the publication date of a final standard. These States include: Alaska, Arizona, California, Connecticut (for State and local government employees only), Hawaii, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Nevada, New Mexico, New York (for State and local government employees only), North Carolina, Oregon, Puerto Rico, South Carolina, Tennessee, Utah, Vermont, Virginia, Virgin Islands, Washington, Wyoming. Until such time as a state or territorial standard is promulgated, Federal OSHA will provide interim enforcement assistance, as appropriate

II. Pertinent Legal Authority

This proposed standard and the issuance of a final standard are authorized primarily by sections 4(b)(2), 6(b), 8(c) and 8(g)(2) of the Occupational Safety and Health Act of 1970 (the Act) (29 U.S.C. 653(b)(2), 655(b)., 657(c), 657(g)(2))

Section 6(b)(5) governs the issuance of occupational safety and health standards dealing with toxic materials or harmful physical agents. Section 6(b)(5) provides: The Secretary, in promulgating standards dealing with toxic materials, or harmful physical agents under this subsection, shall set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life. Development of standards under this subsection shall be based upon research, demonstrations, experiments, and such other information as may be appropriate. In addition to the attainment of the highest degree of health and safety protection for the employee, other considerations shall be the latest available scientific data in the field, the feasibility of standards, and experience gained under this and other health and safety laws

Section 3(8) of the Act defines an occupational safety and health standard as : a standard which requires conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment

Under section 6(b)(7) of the Act, standards must, where appropriate, include provisions for labels or other appropriate forms of warning to apprise employees of hazards, suitable protective equipment, exposure control procedures, monitoring and measuring of employee exposure, employee access to the results of monitoring, medical examinations or other tests, at no cost to employees, to determine whether the health of employees is adversely affected by such exposure, and training and education. In addition, Section 8(c)(3) of the Act empowers the Secretary to promulgate standards prescribing recordkeeping requirements where necessary or appropriate for enforcement of the Act or for developing information regarding the causes and prevention of occupational accidents and illnesses

The Supreme Court has held that under the Act the Secretary, before issuing a new standard, must determine that it is reasonably necessary and appropriate to remedy a significant risk of material health impairment. Industrial Union Department v. American Petroleum Institute, 448 U.S. 607, 642 (1980). The Court stated that "before he can promulgate any permanent health or safety standard, the Secretary is required to make a threshold finding that a place of employment is unsafe in the sense that significant risks are present and can be eliminated or lessened by a change in practices." Id., at 642, 644, n. 49

The Court indicated, however, that the significant risk determination is "not a mathematical straightjacket." Id., at 655. "OSHA is not required to support its finding that a significant risk exists with anything approaching scientific certainty." Id., at 656. Rather, the Court stated that "a reviewing court [is] to give OSHA some leeway where its findings must be made of the frontiers of scientific knowledge." Id., at 656. The Court also stated that while the "Agency must support its findings that a certain level of risk exists with substantial evidence, we recognize that its determination that a particular level of risk is 'significant' will be based largely on policy considerations." Id., at 655- 56, n. 62

After OSHA has determined that a significant risk exists and that such a risk can be reduced or eliminated, it must set a standard "which most adequately assures, to the extent feasible on the basis of the best available evidence, that no employee will suffer material impairment of health." (Section 6(b)(5)). The Supreme Court has interpreted this section to mean that OSHA must enact the most protective standard possible to eliminate a significant risk of material health impairment, subject to the constraints of technological and economic feasibility. American Textile Manufacturers Institute v. Donovan, 452 U.S. 490, 509 (1981). The Court held that "cost-benefit analysis by OSHA is not required by the statute because feasibility analysis is." Id

Section 4(b)(2) of the Act provides that standards issued under OSHA apply to construction and maritime employment where the Secretary determines these standards to be more effective than existing standards which would otherwise apply to that employment. (OSHA has proposed the addition of new paragraph (n) to 29 CFR 1910.19, which would apply the proposed glycol ethers standard to construction and maritime employment, in addition to its coverage of general industry)

Authority to issue this proposed standard is further supported by the general rulemaking authority found in section 8(g) of the Act

Section 8(g)(2) empowers the Secretary to "prescribe such rules and regulations as he may deem necessary to carry out [his] responsibilities under the Act." The Secretary's responsibilities under the Act are defined largely by its enumerated purposes (section 2(b)), which include:

Encouraging employers and employees in their efforts to reduce the number of occupational safety and health hazards at their places of employment, and to stimulate employers and employees to institute new and to perfect existing programs for providing safe and healthful working conditions;

Building upon advances already made through employer and employee initiative for providing safe and healthful working conditions;

Developing innovative methods, techniques, and approaches for dealing with occupational safety and health problems;

Exploring ways to discover latent diseases, establishing causal connections between diseases and work in environmental conditions;

Providing for the developing and promulgation of occupational safety and health standards;

Providing for appropriate reporting procedures with respect to occupational safety and health which procedures will help achieve the objectives of this Act and accurately describe the nature of the occupational safety and health problems;

Encouraging joint labor-management efforts to reduce injuries and disease arising out of employment

Because the proposed glycol ethers standard is reasonably related to these statutory goals and because the Agency's preliminary judgement is that the evidence satisfies the statutory requirements and that the proposed standard is feasible and substantially reduces significant risk of adverse health effects, especially reproductive and developmental health effects, the Secretary preliminarily finds that the proposed standard is necessary and appropriate to carry out the Agency's responsibilities under the Act

III. History of the Regulation

OSHA's current Permissible Exposure Limits (PELs) for 2-ME, 2-MEA, 2-EE, and 2-EEA are 25 ppm, 25 ppm, 200 ppm, and 100 ppm, respectively. All are time weighted averages (TWAs) for an 8-hour workshift (29 CFR 1910.1000, Table Z-1-A). In the Z-1-A Table, 2-ME, 2-MEA, 2-EE, and 2-EEA are listed under the names Methyl Cellosolve, Methyl Cellosolve Acetate, 2-Ethoxyethanol, and 2-Ethoxyethanol Acetate, respectively. The OSHA standards bear a skin notation, indicating the potential contribution to the overall exposure by the cutaneous route, including mucous membranes and eye, either by airborne or more particularly, by direct contact with the substance

The current standards were adopted in 1971 pursuant to section 6(a) of the Occupational Safety and Health Act of 1970 (29 U.S.C. 655). The source of these standards was the American Conference of Governmental Industrial Hygienists (ACGIH) and they are based primarily on blood, kidney, liver and central nervous system toxicity

In the late 1970's, many studies began to be published regarding adverse effects, including testicular atrophy, infertility, fetotoxicity, and fetal malformations in laboratory animals exposed to glycol ethers. In response to these findings, the ACGIH, in its notice of Intended Changes (for 1982), proposed TWAs of 5 ppm for 2-ME, 2-EE and their acetates which were subsequently adopted in 1984. Likewise, on May 2, 1983, NIOSH published a Current Intelligence Bulletin recommending that 2-ME and 2-EE be regarded in the workplace as having the potential to cause adverse reproductive effects in male and female workers and embryotoxic effects, including teratogenesis, in the offspring of the exposed pregnant females and urged employers to reduce exposures to the lowest extent possible(Ex. 5-001)

On January 24, 1984, EPA published an Advance Notice of Proposed Rulemaking (ANPR) in which they announced their intention to regulate 2-ME, 2-EE and their acetates (49 FR 2921). EPA was concerned about the toxicity of these chemicals due to evidence of human exposure to concentrations above levels currently recommended by the ACGIH, and the potential for significant numbers of individuals to become exposed. After consideration of the record developed in connection with its ANPR, EPA determined that the risks associated with exposure to 2-ME, 2-EE and their acetates could be sufficiently reduced by action taken under the OSH Act. Following these findings, EPA, in accordance with section 9(a) of TSCA, on May 20, 1986, referred 2-ME, 2-EE and their acetates to OSHA to give this Agency an opportunity to regulate the chemicals under the OSH Act(51 FR 18488). EPA requested OSHA to determine whether the risks described in the EPA report could be prevented or reduced to a sufficient extent by action taken under the OSH Act. If such a determination was made then OSHA was requested to issue a notice declaring whether the manufacture and use described in the EPA report presented the risk therein described. EPA requested OSHA to respond within 180 days

On December 11, 1986, OSHA published a notice (51 FR 42257) responding to the EPA referral report by making a preliminary determination that a revised OSHA standard limiting occupational exposure to 2-ME, 2-EE and their acetates could prevent or reduce the risks due to exposure to a sufficient extent and that such a risk had been accurately described by EPA in the report

On April 2, 1987, OSHA decided it would proceed with permanent rulemaking to reduce exposure to 2-ME, 2-EE and their acetates and published an ANPR (52 FR 10586). OSHA based its decision on the determination that the existing standards did not adequately address the adverse health effects associated with 2-ME, 2-EE and their acetates. OSHA solicited information and comments regarding the hazards of exposures to the chemicals, control methods for reducing these hazards and the costs of controlling exposures

In September of 1991, NIOSH published a Criteria for a Recommended Standard for Ethylene Glycol Monomethyl Ether, Ethylene Glycol Monoethyl Ether, and Their Acetates (i.e., 2- ME, 2-EE and their acetates) (Ex. 5-154). In this document NIOSH recommended worker exposures to 2-ME and its acetate, 2- MEA, be limited to 0.1 ppm as time weighted average for up to 10 hours/day during a 40 hour workweek (10-hr TWA) and that worker exposure to 2-EE and its acetate, 2-EEA, be limited to 0.5 ppm as a 10-hr TWA. NIOSH also recommended that dermal contact to 2-ME, 2-EE and their acetates be prohibited. In addition to these recommended exposure limits, NIOSH also recommended various industrial hygiene provisions including exposure monitoring, medical monitoring, protective clothing and equipment, engineering controls and work practices and hazard communication. The provisions of this recommended standard were based primarily on adverse reproductive, developmental and blood effects

IV. Chemical Identification, Production and Use of Ethylene Glycol Ethers

The chemicals, 2-Methoxyethanol (2-ME), 2-Methoxyethanol acetate (2-MEA), 2-Ethoxyethanol (2-EE), and 2-Ethoxyethanol acetate (2-EEA) are members of a class of chemicals known as ethylene glycol ethers which are, in turn, members of a broader class of chemicals known as glycol ethers. In this document the terms ethylene glycol ethers or glycol ethers will refer only to 2-ME, 2-MEA, 2-EE and 2-EEA. The respective Chemical Abstract Service (CAS) Registry numbers for the subject ethylene glycol ethers are 109-86-4, 110-49-6, 110-80-5, 111-15-9. All four compounds are colorless, flammable liquids which are compatible with a broad range of resins and are miscible in both organic solvents and water. They have relatively low vapor pressures, high boiling points, low evaporation rates and high flash points. At room temperature and atmospheric pressure, these compounds are highly reactive in the presence of strong oxidizers; 2-MEA and 2-EEA are also highly reactive in the presence of nitrates and strong acids. Decomposition products during combustion include toxic gases and vapors such as carbon monoxide

2-ME, chemical formula CH(3) OCH(2)CH(2)OH, has a molecular weight of 76.1, a boiling point at 760mm Hg of 124 C, a vapor pressure at 20 C of 6mm Hg, a flash point of 42 C and possesses a mild non-residual odor. 2-MEA, chemical formula CH(3)COOCH(2)OCH(3), has a molecular weight of 118, a boiling point of 145 C , a vapor pressure of 2mm Hg, a flash point of 44 C and possesses a mild ether-like odor. 2-EE, chemical formula C(2)H(5)OCH(2)CH(2)OH, has a molecular weight of 90.1., a boiling point of 135 C, a vapor pressure of 4mm Hg, a flash point of 49 C and possesses a sweetish odor with odor. 2-EEA has chemical formula C(2)H(5)OCH(2)OCOCH(3), a molecular weight of 132, a boiling point of 156 C, a vapor pressure of 2mm Hg, a flash point of 47 C and possesses a mild non-residual odor. The odor thresholds of these compounds are discussed in the Respiratory Protection portion of this document

Ethylene glycol ethers are produced by the ethoxylation of ethylene oxide with preheated anhydrous alcohol. Methyl alcohol produces ethylene glycol monomethyl ether (2-ME) and ethyl alcohol produces ethylene glycol monoethyl ether (2-EE). The corresponding acetates, 2-MEA and 2-EEA, are produced by the esterification of 2-ME and 2-EE with acetic acid

Due to their physical characteristics, ethylene glycol ethers are useful in a wide variety of applications, particularly as solvents. In general, these ethers are used extensively in the formulation of paints and coatings, commercial printing inks, industrial solvents, and cleaners. They are also used as chemical intermediates in the production of plastisizers, as de-icing additives in jet fuels, and in electronics manufacturing

After manufacture of glycol ethers for export (45% of total sales), the utilization of these compounds as chemical intermediates accounts for the largest percentage (24%) of their sales (PEI report, Ex. 5-164). For example, the manufacture of 2-EEA is the largest single use of 2-EE while 2-ME is used in the production of 2-MEA. Both 2-ME and 2-EE are also used to produce a variety of plastisizers for use in such products as 35 mm film, insulation for high voltage wires, and high flash coatings

Another principal area of use (15% of total sales) of the four glycol ethers is in the formulation of paints and coatings (e.g., primers, varnishes, stains, etc.). These paints and coatings are utilized in original equipment manufacture (OEM) of items such as automobiles and trucks, machinery and equipment, metal cans, metal furniture and appliances, and in coil coatings. They are also found in auto refinishing and maintenance painting formulations. In addition, all four glycol ethers are used in a variety of special coating applications ranging from fingernail polish to wood stains

The electronics industry employs glycol ethers in the manufacture of semiconductors and circuit boards. Glycol ethers are a component of the photoresist used in the photolithography of semiconductor circuit designs in addition to being utilized in coating/lamination resins of circuit boards. Products used in the marking, bonding, and labeling of circuit boards may also contain ethylene glycol ethers

Substantial quantities of 2-ME are used as de-icing additive in jet fuel. Since commercial jets have in-line de- icers, this market is principally military. However, some general aviation jet fuel also requires de-icing additive

Comparable to glycol ether's use in paint and coatings is their role as solvents in the formulation of commercial printing inks, particularly those used in silk screen, flexographic, and gravure printing. Ethylene glycol ethers are also found in formulations used in textile dyeing and printing. In addition to being a component of the ink itself, glycol ethers are used in solvents and machinery cleaners for the commercial printing industry

While the above uses account for the vast bulk of glycol ether consumption, they have also been reported to be utilized in a number of diverse cleaning solvents, as solvent in adhesive, in leather dying/tanning, and in the manufacturing of pharmaceuticals

V. Health Effects

A. Introduction

The experimental studies in animals clearly demonstrate that 2-ME and 2-EE induce adverse reproductive, developmental and hematological effects. Several species (e.g., rats, rabbits and mice) exposed through several routes of exposure (e.g., oral, dermal, and inhalation) have consistently shown similar effects after exposure to these ethylene glycol ethers. Exposed males have exhibited testicular degeneration, disrupted spermatogenesis and reduced fertility. Females exposed during gestation have shown signs of maternal toxicity as well as increased incidence of resorptions. Offspring from these exposed females have exhibited a variety of teratogenic effects including cardiac, skeletal and visceral malformations. In addition new born pups have exhibited behavioral and neurochemical alterations. Adverse blood effects have also been observed after exposure. These effects include decreases in red blood cells, white blood cells, hemoglobin concentrations and hematocrit

Although less extensive, the animal data has also shown that the acetates, 2-MEA and 2-EEA, induce adverse reproductive and developmental and hematological effects similar to those observed among their parent glycol ethers. These studies confirm the findings of metabolic studies which indicate that 2-ME, 2-EE and their acetates follow similar metabolic pathways, producing similar metabolites, which are the active agents most likely responsible for the observed effects

Consistent with these experimental results is human evidence of reproductive and hematological effects. Workers exposed to 2-ME and 2-EE have exhibited decreased sperm counts, testicular atrophy and decreased red and white blood cell counts. Little data has been reported on the reproductive, maternal or developmental effects for women exposed to glycol ethers. However, the lack of data in this area may be due, in most part, to the difficulty in conducting analyses for these types of adverse effects. Although workers in some instances were exposed to multiple substances, making it difficult to ascribe exposure to a particular glycol ether to an observed effect, the human evidence is, nevertheless, consistent with and supportive of the animal evidence which indicates that these substances will induce adverse reproductive and developmental effects

B. Metabolism/Metabolic-Related Health Effects

The ethylene glycol ethers, 2-ME and 2-EE, are metabolized to their corresponding acetic acids, methoxyacetic acid (MAA) and ethoxyacetic acid (EAA), by an alcohol dehydrogenase (ADH) mediated pathway. Animal studies conducted with MAA have shown that it is the metabolite, rather than the parent glycol ether, which is responsible for inducing adverse reproductive and developmental effects. 2-MEA and 2-EEA are also metabolized by the ADH pathway to MAA and EAA. Because these two acetates are metabolized to the same primary metabolites as their corresponding parent glycol ethers, it is assumed that they will induce similar adverse reproductive and developmental effects. Studies in male and female volunteers confirm that the ADH pathway is also the primary route of metabolism in humans. However these studies also indicate that the retention and biological half life of the active metabolite is longer in humans than in animals

Miller et al. (Ex. 4-131) identified MAA as the primary metabolite of 2-ME by radiogas-chromatography/mass spectrometry analysis. The investigators recovered 50-60% of the administered 14C from urine of rats within 48 hours after a single oral dose of [14C] 2-ME. Expired 14CO2 was the only other significant route of elimination (12%). Thus, urine was established as the major vehicle of elimination of 14C after a single oral dose of [14C] 2-ME. Urine collected was then analyzed by radiogas-chromatography/mass spectrometry. Analysis revealed the primary component as methoxyacetic acid. Based on these findings Miller et al. concluded that 2-ME is first oxidized to methoxyacetaldehyde by ADH and then further oxidized to MAA by aldehyde dehydrogenase

Evidence also indicates that MAA is the ultimate toxin responsible for the observed adverse reproductive and developmental effects. Brown et al. (Ex. 4-102) gave single injections of 244 mg MAA/kg to pregnant rats on days 8, 10, 12 or 14 of gestation. Exposure to MAA induced significant increases in the incidence of embryo-fetal mortality, decreases in fetal weight, and increases in structural malformations (e.g., skeletal malformations, hydrocephalus and urogenital abnormalities). Similarly Miller et al. (Ex. 4-133) found that the administration of MAA daily for two weeks by gavage to rats resulted in severe degeneration of testicular germinal epithelium and hematological abnormalities. For example significant decreases in testicular weight and in red blood cell counts were observed at 300 and 100 mg MAA/kg. These toxicological effects were remarkably similar to those observed following administration of 2-ME. The authors concluded that the adverse health effects of 2-ME are probably the result of in vivo activation of 2-ME to MAA, and that MAA is the proximate toxin following administration of 2-ME. The findings of Ritter et al. (Ex. 4-143), Yonemoto (Ex. 4-192) and Foster et al. (Ex. 5-052) are consistent with this view

In addition to their studies on the teratogenicity of MAA, Ritter al. (Ex. 4-143) also investigated the effects of the co-administration of 2-ME and 4-Methylpyrazole. 4- Methylprazole(4-MP) is an inhibitor of alcohol dehydrogenase(ADH) and thus may block metabolism occurring by an ADH pathway. In this study it was observed that embryotoxicity (i.e., the number of dead, resorbed and malformed fetuses) following co-administration of the two substance was 16.8%, as compared to 100% for the same dose and the same route of 2-ME alone. The observation that the co-administration of 4-MP provided significant protection against the embryotoxic of 2-ME is consistent with the hypothesis that metabolism of 2-ME occurs via the alcohol dehydrogenase(ADH) pathway and that it is the primary metabolite that is most likely the active agent in the induction of adverse effects

Similar findings have been reported by Sleet et al (Ex. 5-118). In this study pregnant mice were exposed to either 2-ME (1.3 to 1.6 mmole/kg) or MAA (1.1 to 1.7 mmole/kg) by gavage on day 11 of gestation. 2-ME and MAA were found to be equally potent in producing significant increases in the incidence of paw malformations (e.g., webbed, missing or additional digits). The co-administration of 4-Methyl Pyrazole was found to reduce the teratogenic potency of 2- ME. For example, the incidence of malformations induced by 4.6 mmole/kg 2-ME was reduced from 94% to 59% when 4-MP was administered at a dose of 0.12 mmole/kg. The incidence of malformations was reduced to 0% when 4-MP was administered at a dose of 1.2 mmole/kg. These data further indicate the role of metabolism in inducing teratogenic effects and strongly points to MAA as the active agent

Similar to the metabolic studies on 2-ME, the evidence also indicates that the primary metabolite of 2-EE is also an alkoxyacetic acid; in this case ethoxyacetic acid (EAA). Cheever et al. (Ex. 5-089) gave single oral doses of 230 mg 2-EE/kg body weight. The major metabolites detected in the urine were EAA and N-ethoxyacetyl glycine. EAA was also detected in the rat testes. The authors concluded that the most probable route of metabolism was the oxidation of 2-EE through ADH to EAA with some subsequent conjugation of EAA to glycine to form N-ethoxyacetyl glycine

Similar to the findings in animal studies, experimental studies using male and female volunteers, have shown alkoxyacetic acids to be the primary metabolites in humans. In a series of experiments Groeseneken et al. (Exs. 5-112, 5-113, and 5-114) exposed 10 male volunteers by inhalation to 2.7, 5.4 or 10.8 ppm 2-EE for 4 hours, both at rest and during physical exercise. Consistent with findings in animal studies, EAA was found to be the major urinary metabolite. However the biological half life in humans was found to be approximately 21-24 hours compared to the biological half life of 8-12 hours reported in animals. It was also observed that EAA excretion increased with increasing dose and/or physical activity. Due to the long half life, the authors stated that EAA will not be cleared from the urine by the next morning following exposure and accumulation of the metabolite may be expected through repetitive exposures. Thus EAA may build up in the body over the course of the workweek

In a similar study Groeseneken et al. (Ex. 5-115) exposed 10 male volunteers by inhalation to 2-EEA. Five volunteers were exposed at rest to 2.6, 5.2 and 9.3 ppm 2- EEA and 5 were exposed to 5.2 ppm 2-EEA during physical exercise. Again, EAA was detected as the major metabolite with a biological half life of approximately 23 hours. It was observed that the metabolism of 2-EEA followed the same time course as 2-EE (Ex. 5-112) and that for equivalent doses of 2-EE and 2-EEA, equivalent amounts of EAA were excreted. The authors concluded that 2-EEA is first converted to 2-EE by esterases and then to EAA by an ADH mediated pathway. Similarly it was found that EAA is not cleared from urine by the next morning and thus may build up over the work week following repetitive exposures

In field study of workers, Veulemans et al. (Ex. 5-114) studied the urinary excretion of EAA for a group of 5 female silk screen operators who were exposed, by inhalation, to mixtures of 2-EE and 2-EEA at approximately 5.6 and 5 ppm, respectively. In this study the women were monitored for 5 days during a normal production period. They were also monitored during another 7 day period after a 12 day production stop. Similar to the experimental studies among human volunteers, EAA was detected in the urine as the major metabolite during the 5 days of production and was also found to accumulate during the workweek. The authors also reported that even after 12 days of non-exposure, traces of EAA were still detectable in the urine. The authors stated that these findings confirmed the earlier short term studies by Groeseneken (Exs. 5-112 and 5-115) and suggested that the biological half life of EAA may even be greater than 24 hours. Moreover they added that from a toxicological point of view, "it would certainly warrant extra caution in the extrapolation of experimental data from laboratory animals to man, since comparable accumulation effects apparently are not found in all species."

To further investigate the metabolic differences between rats and humans, Groeseneken et al. (Ex. 5-137) compared the urinary excretion of EEA in man and rat. In this study rats were orally exposed to 2-EE at low doses comparable to the inhalation doses used on male volunteers in previous experimental studies(Ex. 5-112). The authors stated that oral doses were used in rats due to the lack of animal data necessary to calculate respiratory uptake of 2- EE (e.g., 2-EE pulmonary retention and respiratory minute volume). Data for calculating respiratory uptake were available in human studies. It was assumed that metabolism was independent of the route of administration. Groups of five rats were exposed to single oral doses of 0.5 mg/kg, 1 mg/kg, 5 mg/kg, 10 mg/kg, 50 mg/kg or 100 mg/kg 2-EE. Exposure levels of 0.5 mg/kg and 1 mg/kg were noted by the authors to be equivalent to human exposures of 5.4 ppm or 10.8 ppm 2-EE used in the human experimental studies. After a correction for body weight on urinary excretion, results from these studies showed that, for humans, the maximal excretion rate of the primary metabolite, EEA, declined at a slower rate (48 hours after exposure) than in rats (12 hours after exposure) at equivalent doses. In addition the half life for EEA in humans was calculated at 42 hours compared to 7.2 hours for rats: almost 6 times higher for man. The authors suggested that these findings could have important consequences for the toxicity of 2-EE in man as the toxic properties of 2-EE have been associated with the alkoxyacetic acid metabolite, EEA. Romer et al. (Ex. 5-033) have also shown that the co-administration of ethanol with 2-ME and 2-EE prolonged the retention of 2-ME and 2-EE in the blood. In this study rats were pretreated with ethanol and then exposed by inhalation to 1600 ppm 2-ME or 420 ppm 2-EE or ip- administration to 5 ml/kg body weight 2-ME or 2-EE). In both cases it was observed that degradation of 2-ME and 2-EE was almost completely inhibited when rats were pretreated with ethanol. Only after the elimination of ethanol was complete, did the blood levels of 2-ME and 2-EE begin to decrease. The authors concluded that ethanol, which is also metabolized by the alcohol dehydrogenase (ADH) pathway, must have a higher affinity for ADH enzymes than 2-ME or 2-EE. Because of its higher affinity, ethanol is preferentially metabolized. The authors suggested that blood levels of 2- ME and 2-EE may persist in workers who use 2-ME or 2-EE in combination with alcoholic consumption. This persistence of 2-ME and 2-EE in the blood could result in an enhanced health risk

C. Acute Toxicity

The acute toxicity of ethylene glycol ethers have been shown in several animal species (e.g., mice, rats, rabbits, guinea pigs and cats) by various routes of administration (e.g., oral, injection, dermal and inhalation). Smyth et al. (Ex. 5-138) examined the single dose toxicity of a variety of compounds, including 2-ME, 2-EE, 2-MEA and 2-EEA. In this study rats and guinea pigs were exposed through oral administration to varying concentrations in order to determine the lethal dose (LD50) of the various compounds. In rats, the LD50 identified for 2-ME, 2-MEA, 2-EE and 2-EEA were respectively 2460 mg/kg, 3920 mg/kg, 3000 mg/kg and 5100 mg/kg body weight. In guinea pigs the LD50's for these same 4 compounds were 0.95, 1.25, 1.4 and 1.91 mg/ kg body weight, respectively. The authors noted that these compounds induced narcosis but only at exposures at or above the LD50. Pathological examination revealed the primary effect was kidney damage

Reviews of the data also report relatively high lethal doses (LD50) and lethal concentrations (LC50) (Exs. 5-134, 5- 046 and 5-140). For example, the LC50's observed in mice exposed for 7 hours to 2-EE and 2-ME were 1820 ppm and 1480 ppm, respectively. A LC50 of 7000 ppm was observed among rats exposed to 2-MEA for 4 hours. For 2-EEA, a LC50 of 4000 ppm was reported for cats exposed from 4 to 6 hours. In most cases deaths were attributed to lung and kidney damage. Pathological examination revealed lung edema, slight liver damage and marked kidney injury. Prior to death animals exhibited difficulty in breathing, sleepiness, weakness and loss of muscular coordination

Little evidence is available on acute toxicity in humans. Most of the available evidence is limited to case studies of accidental poisonings where glycol ethers have been ingested (Ex. 5-134, pp.21-24). For example, two men hospitalized after drinking 100 ml of 2-ME, exhibited signs of confusion, disorientation, and progressive muscular weakness. They also suffered from hyperventilation, tachycardia and moderate renal failure. Similarly a woman who drank 40 ml of 2-EE exhibited renal failure and adverse central nervous system effects (e.g., vertigo and unconsciousness). Other effects observed among humans after acute exposures include irritation of the eyes and mucous membranes including the respiratory system

D. Background Discussion On Reproductive And Developmental Toxicity

Reproductive and developmental effects are the primary health concerns associated with exposure to ethylene glycol ethers. The term reproductive effects refers to effects on the male and female reproductive systems and the term developmental effects refers to effects on the developing organism. Various terms have been used in the field of reproductive and developmental toxicology, many of which are ambiguous and open to different interpretations. In order to provide guidance and assistance in assessing reproductive and developmental risks, the EPA has published proposed guidelines on assessing female and male reproductive toxicity (Exs. 5-122 and 5-123) and developmental toxicity (Exs. 5-106, 5-153). These guidelines discuss many of the critical issues in reproductive and developmental toxicology. Much of the terminology in the following discussion is adopted and modified from the EPA guidelines

Male reproductive toxicity is generally defined as the occurrence of adverse effects on the male reproductive system that may result from exposure to chemical, biological, or physical agents

The toxicity may be expressed as alterations to the male reproductive organs and/or related endocrine system. For example toxic exposures may interfere with spermatogenesis (the production of sperm), resulting in adverse effects in number, morphology (e.g., size and shape), or function (e.g., motility) of sperm. These effects in turn may adversely affect fertility. The process of spermatogenesis is a cyclical process marked by distinct stages that may be sensitive to toxic agents. In this process germ cells (spermatogonia) differentiate into primary spermatocytes then to secondary spermatocytes, to spermatids and finally into spermatozoa

Men produce sperm continually from puberty throughout life and thus the risk of disrupted spermatogenesis is of concern for the entire adult life of a man. Reproductive toxicity may also include dysfunction in sexual behavior or processes which are integral to reproductive success

Female reproductive toxicity is generally defined as the occurrence of adverse effects on the female reproductive system that may result from exposure to chemical, biological, or physical agents

This toxicity includes adverse effects in sexual behavior, onset of puberty, ovulation, menstrual cycling, fertility, gestation, parturition, lactation, or premature reproductive senescence(the loss of reproductive capability associated with aging)

Developmental toxicity is defined as adverse effects on the developing organism that may result from exposure prior to conception (either parent), during prenatal development, or postnatally to the time of sexual maturation. Developmental effects induced by exposures prior to conception may occur, for example, when mutations are chemically induced in sperm. If the mutated sperm fertilizes an egg, adverse developmental effects may be manifested in developing fetuses. Mutations may also be induced in the eggs. Such effects are often referred to as dominant lethal effects

The major manifestations of developmental toxicity include: (1) death of the developing organism, (2) structural abnormality, (3) altered growth, and (4) functional deficiency. Structural abnormalities include malformations and variations. As stated in the EPA Guidelines, a malformation is usually defined as a permanent structural change that may adversely affect survival, development, or function. These types of effects are often referred to as teratogenic effects. The term variation is used to indicate a divergence or a change in structure which is beyond the range of what is generally considered to be normal development. This divergence may not adversely affect survival, or health. However as noted by EPA in its guidelines, distinguishing between variations and malformations is difficult since there exists a continuum of responses from the normal to the extreme deviant. There is no generally accepted classification of malformations and variations. Other terminology that is often used, but no better defined, includes anomalies, deformations, and aberrations

Altered growth is an alteration in offspring organ or body weight or size. Altered growth can be induced at any stage of development, may be reversible, or may result in a permanent change

Functional deficiency includes alterations in the functional competence of an organ or a variety of organ systems. This functional deficiency may be expressed as behavioral abnormalities. Such effects may often not be apparent at birth but may instead be noted during postnatal development. Similarly, exposure during development may lead to adverse reproductive functioning. For example, a female's entire complement of oocytes (eggs) are formed during gestation, as opposed to males who produce spermatocytes continually throughout their adult life. Thus toxic insults during gestation may adversely effect oogenesis (the formation of eggs) . However because structural and functional maturity of eggs does not occur until puberty, adverse effects may not be manifested until females reach reproductive maturity

One of the critical phases in development, is the period of gestation referred to as organogenesis. During this phase of gestation, embryonic cells migrate and associate into tissues and organ rudiments and establish the basic organizational patterns of organ systems. Because this is a period marked by rapid cell proliferation and organ development it is vulnerable to the induction of structural defects. It is generally assumed that a single exposure, of sufficient dose, during such critical periods of development, may be sufficient to produce an adverse developmental effect. Thus repeated exposures may not be necessary to induce developmental toxicity. However developing organisms are also known to have the capacity to compensate for or to repair certain amounts of damage at the cellular, tissue or organ level. Thus it is also generally assumed that there may be thresholds for developmental toxins

The level of concern for a developmental toxic effect is related to several issues, including the relative toxicity of an agent to the offspring versus the adult animal and the long-term consequences of findings in the fetus or neonate. The developing organism is dependent on the maternal animal to provide nutrients and to maintain a protective environment in which the conceptus can grow and develop

Thus any agent which adversely affects the maternal animal may have the potential to adversely affect the offspring. However it is often difficult to differentiate between effects which are a result of stress to the maternal animal and effects which are solely a result of the sensitivity of the developing organism. Those agents which produce developmental toxicity at a dose that is not toxic to the maternal animal are of the greatest concern because the developing organism appears to be more sensitive than the adult. The adult/developmental toxicity ratio (A/D Ratio) was introduced to account or describe the differential susceptibility between the maternal animal and the developing organism (Exs. 4-147 and 5-106). This ratio is calculated by dividing the Lowest Observed Effect Level (LOEL) in the maternal animal by the LOEL observed for the developing organism. A/D ratios greater than 1 suggest that the developing organism is more sensitive to a chemical insult than the mother and is therefore of greater concern. However, there is no consensus on the predictive value of the A/D ratio (Exs. 5-098 and 5-099). One reason is that the A/D ratio can be influenced by the design of the underlying bioassay (e.g., the spacing of doses chosen for study). Secondly, the maternal-developmental relationship may be misrepresented if insensitive developmental endpoints are compared to sensitive maternal endpoints or vice-versa. In these cases the power of the experimental study may influence the level at which an effect is observed and thus influence the calculation of the A/D ratio. Thus, developmental effects which are produced only at maternally toxic doses cannot be discounted as being secondary to maternal toxicity. Current information is inadequate to assume that developmental effects at maternally toxic doses result only from the maternal toxicity. Rather, when the lowest observed effect level is the same for the adult and the developing organism, it may simply indicate that both are sensitive to that dose level. Moreover, the maternal effects may be reversible while effects on the offspring may be permanent. These are important considerations for agents to which humans may be exposed at minimally toxic levels in the workplace

Most of the evidence on the reproductive and developmental toxicity of the four subject glycol ethers, as will be discussed later, is limited to data from experimental studies in mice, rats and rabbits. This, in major part, is due to the difficulty in conducting epidemiological analyses to detect adverse reproductive and/or developmental outcomes. For example, many outcomes such as early embryonic loss, spontaneous abortions, or reproductive capacity of offspring are not easily observed in humans. Epidemiological analysis is also complicated by the fact that, because there is a wide spectrum of inter- related effects, different types of effects may occur at different exposure levels. Thus multiple endpoints may result from a single toxicant. Some reproductive outcomes are rare and thus a large number of births are required to give the study enough power to detect a possible effect. For example, it has been estimated that to detect a two fold increase in spontaneous abortions a sample size of 322 pregnancies (161 exposed and 161 controls) would be required (Ex. 5-135, p. 167). More rare outcomes such as severe mental retardation, neural tube defects and chromosomal abnormalities would require samples sizes of 1819, 8986 and 17,907 live births respectively, to detect a two fold increase. Large populations of workers would be required to observe this many pregnancies or live births. Adequate sample sizes may be difficult to obtain due to factors such as marital status, education, age, use of birth control or prior reproductive history. These factors may affect couples' ability or attempts to have children and thus affect the number of outcomes available for study

Because adequate human data are rarely available for reproductive or developmental outcomes, animal studies have been used and are generally considered to be useful in the prediction of reproductive/developmental toxicity for humans. A basic tenet of toxicology is that if an agent produces adverse effects in experimental animals, this agent may pose potential hazards to humans. This tenet is supported by reviews of studies in both humans and experimental animals on the reproductive effects of selected agents which have shown parallels among the adverse effect observed in animal experiments and effects reported in humans (Exs. 4-103, p. 96 and 5-135, pp. 169-170). For example, disturbances in estrous cycles in rats were observed after exposure to benzene and menstrual disorders were reported among humans exposed to benzene. DBCP induced testicular atrophy and decreased fertility in rats and has also been associated with similar effects in men. EDB has caused sterility in rats and reduced fertility in men. Similar concordance of effects have been observed with other agents such as carbon disulfide, arsenic, lead, alcohol and vinyl chloride

While there are parallels in observed effects between experimental animals and humans, it is not necessarily assumed that there is site concordance of effects seen in animals and effects potentially occurring in humans. That is, effects observed in experimental animals may not exactly be the same as those which may occur in humans. For example within the period of organogenesis, different organ systems may form at different times. In addition an individual organ system may have a narrow time span when it is vulnerable. Furthermore, the time during organogenesis when a particular organ system develops may vary across species. Therefore, exposures occurring in different developing systems or even in similar systems, but at different times, may result in different types of adverse developmental effects. Thus although a particular adverse effect may not be observed in humans, the presence of the effect in experimental animals indicates the potential of an agent to perturb development and therefore is an outcome of concern for human development

E. Effects In Animals

Experimental studies in rats, rabbits, mice and monkeys through inhalation, dermal and oral exposure, have shown clearly and consistently that 2-ME, 2-EE and their acetates cause adverse hematologic, reproductive and developmental effects. These effects include decreased white and red blood cell counts, decreased hemoglobin concentrations, decreased fertility, decreased sperm count, decreased testes size and weight, early embryonic death, fetal malformations, delayed development and behavioral and neurochemical alterations

1. Male Reproductive Toxicity

a. 2-ME. 2-ME was shown to induce testicular degeneration in rats by Rao et al.(Ex. 4-142). In this study male rats were exposed, by inhalation, to 0, 30, 100 or 300 ppm 2-ME, 6 hours/day for 13 weeks. These rats were then bred with unexposed females to evaluate male reproductive function and dominant lethality. Dominant lethal tests are conducted to detect mutagenic effects in the spermatogenic process which may lead to fetal effects on the embryo/fetus. Male rats exposed to 300 ppm exhibited significant decreases in testes size and atrophy of the seminiferous tubules. Only 4 of 20 unexposed females mated to this group of exposed males were successfully inseminated and all 4 pregnancies ended in resorptions. The authors stated that at 300 ppm there was a complete suppression of fertility which they attributed to an interference in spermatogenesis. No significant decreases in fertility were reported for males exposed to 100 or 30 ppm 2-ME. Because no litters were produced in the 300 ppm exposure group, the authors stated that dominant lethality could not be assessed. However the authors did not address the issue as to whether the resorptions observed in the 300 ppm group may have been a possible dominant lethal effect. Among the litters from rats exposed to 30 and 100 ppm there were no significant increases in pre- implantation loss or resorption rate compared to controls. The authors thus concluded that there was no dominant lethal effect from exposure at these doses. The authors did note that there was a significant increase in the resorption rate at 30 ppm . However because this effect was not observed at 100 ppm, it was not considered to be treatment related. Thus the NOEL for this study was identified as 100 ppm

In this same study by Rao et al., male rats exposed at 300 ppm were additionally bred with unexposed females 13 and 19 weeks after exposure was terminated. Fifty percent of the males sired litters with viable implantations. Rats bred 13 weeks post exposure had regained 55% fertility. Rats bred 19 weeks post exposure had regained 50% fertility. These results suggest that adverse effects on fertility may be partially reversible after exposure is stopped. However these results also indicate that recovery may not be complete as 50% of the exposed males still showed signs of reduced fertility

Testicular degeneration was also observed in a study by Miller et al. (Ex. 5-023, see also Ex. 4-045) where both rats and rabbits were exposed to 0, 30, 100, or 300 ppm 2-ME for 6 hours/day, 5 days/week for 13 weeks. Rats exposed to 300 ppm exhibited significant decreases in testes weight as a result of degeneration of the germinal epithelium of the seminiferous tubules. The authors reported that rats exposed to 300 ppm showed reduced numbers of spermatozoa and degenerating spermatozoa in the epididymis. However the authors did not state whether these were significant reductions. No treatment related effects were observed among rats exposed to 30 or 100 ppm 2-ME. A more sensitive response was observed among the exposed rabbits which exhibited testicular effects at 300, 100 and 30 ppm. All male rabbits exposed to 300 ppm had small and flaccid testes. Significant but less severe decreases in testes size were observed in rabbits exposed at 100 and 30 ppm. Histological examination of the rabbits revealed that the testicular effects were related to atrophy of the seminiferous tubules. The effects observed in rabbits at 30 ppm were questioned by the authors as they noted that only a small percentage of the animals (1 of 5 rabbits) were effected and rabbits exposed to 30 ppm in a subsequent study (Ex. 5-057) showed no adverse testicular response

2-ME has also been shown to induce adverse testicular effects in shorter term tests. In an inhalation study by Doe et al.(Ex. 4-111) male rats were exposed to 100 or 300 ppm 2-ME, 6 hours/day for 10 consecutive days. Adverse testicular effects were only observed among rats exposed at 300 ppm. In these animals the testes were significantly decreased in both size and weight. Histological examination of the testes revealed atrophy of the seminiferous tubules and degeneration of the primary spermatocytes. No significant adverse effects were observed among rats exposed at 100 ppm, and thus this level was identified as the NOEL

Similarly adverse effects were produced in a short term (9-day) inhalation test conducted by Miller et al. (Ex. 4- 132). Male rats and mice were exposed 6 hours/day to 0, 100, 300 or 1000 ppm 2-ME. Severe testicular degeneration was observed in both rats and mice exposed at 1000 ppm. Histopathological examination revealed a degeneration and necrosis of all spermatogenic elements as well as a cessation of spermatogenesis. Similar but less severe testicular effects were observed in the 300 ppm exposure groups. However theese effects were not statistically significantly different from control groups. No treatment related changes were observed in the 100 ppm exposed animals

2-ME also induces adverse testicular effects when administered orally. For example, Nagano et al. (Ex. 4-135) exposed male mice to 62.5, 125, 250, 500, 1000, or 2000 mg 2-ME/kg body weight, 5 days a week for 5 weeks. In the high dose group 4 out of 5 mice died before examination. Significant decreases in testes weight were observed for the 1000, 500, and 250 mg/kg dose groups as a result of seminiferous tubule atrophy. The authors noted that the degree of changes in atrophy were related to increases in dosage thus implying the presence of a dose-response relationship. For example histopathological examination showed that at 1000 mg/kg no germ cells were present. At 500 mg/kg only small numbers of spermatozoa, spermatocytes and spermatids were present

Similar effects were observed by Foster et al.(Ex. 4- 119) where male rats were exposed orally to 50, 100, 250 or 500 mg 2-ME/kg body weight for 11 days. A significant degeneration of the testes was observed in the 100, 250 and 500 mg/kg dose groups. A single dose exposure to 100 mg/kg 2-ME resulted in testicular damage within 24 hours of exposure. In this study meiotic cells of the testes were identified as the primary site of testicular damage. Primary spermatocytes were damaged initially. Prolonged exposure damaged late spermatocytes and led to a depletion of the spermatid population. Results of this study indicated that testicular damage may be partially reversible. After exposure was stopped, testes weight returned to control values and spermatogenesis resumed. However some animals exposed at high doses still exhibited a small proportion of atrophied seminiferous tubules. Thus the authors concluded that prolonged high exposure may prevent total recovery of testicular function

Adverse effects in spermatogenesis and mating performance were observed in short term tests conducted by Chapin (Ex. 5-007). In the first phase of this study male rats were exposed to 0, 50, 100 or 200 mg 2-ME/kg body weight for 5 days and then mated with untreated females for 8 weeks. Significant decreases in the percentage of pregnancies and the number of live fetuses were observed among females mated with males from the 200 and 100 mg/kg dose groups. No significant effects were observed among females mated with 50 mg/kg dosed males. Females mated to rats exposed at 200 mg/kg exhibited an increase in the incidence of resorptions but only at weeks 5 and 6. No increases in resorption rates were observed among any other group

Significant increases in preimplantation losses were observed among females mated with males exposed to 200 and 100 mg/kg. The authors noted that the decrease in litter size is a possible indication of a dominant lethal effect. However because there was no significant increase in the number of dead fetuses and only a slightly significant increase in resorptions at weeks 5 and 6 of the high dose group, the authors stated that the decrease in litter size was probably due to decreased number of viable sperm number rather than a dominant lethal effect. The authors added that this conclusion is supported by the evidence of pre- implantation loss as well as by the findings of others researchers (e.g., Rao et al., Ex. 4-142)

In the second phase of this study by Chapin, additional groups of male rats were exposed similar to rats in the first phase of the study but this time were not allowed to mate. Rats exposed at 100 and 200 mg/kg showed significant sperm count reductions throughout the study. In addition, these groups showed significant decreases in the percentage of motile sperm and increases in the frequency of abnormal sperm morphology. A reduction in sperm counts was observed in the 50 mg/kg group at week 5 only. In this group sperm motility was unaffected. The findings of this study also indicated that as dose increased, different types of testicular cells were affected. For example, at 100 mg/kg only spermatocytes were affected, while at 200 mg/kg the later stage spermatids and spermatogonia were effected

In a subsequent study using a similar protocol, Chapin et al.(Ex. 5-006) examined testicular recovery from 2-ME treatment. Again male rats were exposed orally to 0, 50, 100, or 200 mg 2-ME/kg body weight for 5 days and followed for 8 weeks. Rats exposed to 200 and 100 mg 2-ME/kg exhibited significant signs of testicular damage including abnormal sperm morphology, delayed spermatogenesis, and cell death. All animals exposed to 200 mg 2-ME/kg showed significant signs of testicular toxicity during the first week of observation. These animals exhibited widespread death of all stages of spermatocytes and abnormal sperm morphology. By weeks 5-8, 50% of the tubules appeared normal for the 200 mg/kg exposed groups. Cell death and abnormal sperm morphology were also observed at 100 mg/kg. Similarly by week 8 a 50% recovery was noted. In the 50 mg/kg exposure group, changes in morphology were not noted until week 4. By week 8 no treatment related changes were observed

Similar findings have been reported in more recent studies by Anderson et al.(Ex. 5-100). Male mice and rats were exposed to single doses of 0, 500, 750, 1000 or 1500 mg 2-ME/kg body weight. Selected groups were additionally mated to untreated females to examine dominant lethality. As in earlier studies increasing doses resulted in increased levels of testicular damage. In the rat, testes weight and sperm counts were significantly reduced at all dose levels. Abnormal sperm morphology was also observed among treated rats. In mice, significant decreases in testes weight and sperm count were observed in the 750 mg/kg group at week 3 and in the 500 and 1000 mg/kg groups at week 4. In the dominant lethal studies female rats mated to exposed males, exhibited a significant reduction in the number of implants. No statically significant increase in the incidence of abnormalities in offspring or any other signs of dominant lethality were observed among the rat offspring. In the mice, no significant decreases in fertility or signs of dominant lethality were observed

b. 2-MEA

Evidence strongly indicates that 2-MEA will induce adverse reproductive effects similar to its parent glycol ether 2-ME. As was discussed in the section on metabolism, MAA is thought to be the primary metabolite of 2-MEA. Metabolic studies indicate that the adverse reproductive effects of 2-ME are mediated by its primary metabolite methoxyacetic acid (MAA). Therefore it is likely that equal doses of 2-MEA would induce adverse reproductive effects similar to 2-ME, as these two compounds appear to follow similar metabolic pathways

The metabolic data are supported by the findings of testicular degeneration in mice by Nagano et al. (Ex. 4- 135). In this study, male mice were orally exposed to 62.5, 125, 250, 500, 1000, or 2000 mg 2-MEA/kg body weight, 5 days/week for 5 weeks. Significant decreases in testicular weight were observed only in the 500 mg/kg dose group. Converting this dosage to mmole/kg the authors noted that on an equimolar basis 2-ME and 2-MEA resulted in similar effects

c. 2-EE

Like 2-ME, 2-EE has also been shown to cause male reproductive toxicity in laboratory animals although 2-EE has not been tested as extensively. For example, Barbee and Terrill et al. (Exs. 5-084 and 4-108) exposed male rats and rabbits by inhalation to 25, 100 or 400 ppm of 2-EE, 6 hours/day, 5 days a week, for 13 weeks. In rats the only significant effects observed were decreased pituitary weights at 400 ppm. Pathological examination of these organs did not reveal any lesion indicative of a treatment related effect. Thus the authors concluded that the increased pituitary weight was not likely to be a treatment related effect. Rabbits exhibited a significant decrease in testes weight when exposed to 400 ppm. Based on the pathological analyses this decreased weight was attributed, by the authors, to the degeneration of the seminiferous tubules. No adverse effects were observed at 100 or 25 ppm. From these findings the NOEL for reproductive effects in male rats was identified as 400 ppm while the NOEL for reproductive effects in male rabbits was 100 ppm

2-EE also induces testicular degeneration after oral exposure. For example, Nagano et al. (Ex. 4-135) exposed male mice to 500, 1000, 2000, or 4000 mg 2-EE/kg body weight, 5 days/week over a 5 week period. At 4000 mg 2- EE/kg, all animals died before examination. Significant decreases in testes weights were observed in the 1000 and 2000 mg/kg exposure groups. Histopathological examinations revealed dosage related degrees of seminiferous atrophy among groups exhibiting a significant reduction in testes weight. For example, at 500 mg/kg no significant effects on the testes were observed. At 1000 mg/kg there were significant reductions in the testes weight and a corresponding decrease in the number of spermatozoa, spermatids and spermatocytes. At 2000 mg/kg there were also a significant decrease in testes weight with a corresponding decreae in spermatozoa and spermatids had completely vanished

Similar effects were observed in short term oral studies by Foster et al. (Ex. 4-119). In this study male rats were exposed to 250, 500 or 1000 mg 2-EE /kg body weight for 11 days. Significant decreases in testes weight were observed at 500 and 1000 mg/kg after the 11th day of exposure. The authors noted that rats appeared to be slightly more sensitive than mice. Histological examination of the testes revealed spermatocyte degeneration of the primary and secondary spermatocytes. No significant testicular abnormalities were observed at 250 mg/kg. The NOEL was identified as 250 mg/kg body weight

d. 2-EEA

As in the case of 2-MEA, evidence strongly indicates that 2-EEA will induce adverse reproductive effects similar to 2-EE. As discussed earlier, metabolic studies indicate that ethoxyacetic acid (EAA) is the primary metabolite of both 2-EE and 2-EEA and thus 2-EEA is likely to produce similar effects to those of 2-EE. This evidence is supported by the studies of Nagano et al. (Ex. 4-135) who exposed male mice to 500, 1000, 2000, or 4000 mg 2-EEA/kg body weight, 5 days/week, for 5 weeks. Significant decreases in testicular weight were observed in mice exposed to 1000, 2000 and 4000 mg/kg 2-EEA. Histopathological examinations revealed dose related changes in seminiferous tubule atrophy. For example at 200 and 100 mg/kg the exposed groups exhibited a significant reduction in testes weight and a corresponding reduction in the number of spermatozoa, spermatids and spermatocytes. At 400 mg/kg there was also a significant reduction in testes weight but at this dose the spermatozoa and spermatids had completely vanished. Conversion of dosage to mmole/kg revealed that equimolar doses of 2-EE and 2-EEA induced similar effects. Thus the authors concluded that these results suggest that a glycol ether and its corresponding acetate have similar toxic potential

In summary, the evidence clearly shows that 2-ME, 2-EE and their acetates induce adverse male reproductive effects. Both through inhalation and oral exposure of these compounds, several animal species have exhibited infertility and testicular degeneration. 2. Maternal/Developmental Effects

2-ME and 2-EE and their acetates also induce adverse developmental and maternal effects. Rats, mice, rabbits and monkeys after oral and dermal exposures to these compounds have exhibited adverse effects including decreased maternal weight gain, increased lengths of gestation, increased resorptions, fetal malformations and delayed development

a. 2-ME

Hanley et al. (Exs. 4-120, 4-106, and 4-042a) studied the effects of inhaled 2-ME on fetal development in rats, mice and rabbits. Pregnant rats were exposed to 0, 3, 10, or 50 ppm 2-ME for 6 hours/day on days 6 through 15 of gestation. Pregnant mice were exposed to 0, 10 or 50 ppm for 6 hours/day on days 6 through 15 of gestation. Pregnant rabbits were exposed to 0, 3, 10, or 50 ppm for 6 hours/day on days 6 through 18 of gestation. Female rats exposed to 50 ppm exhibited a significant decrease in maternal body weight gain. No other signs of maternal toxicity for any other test doses were noted. A significant decreased in maternal body weight gain was also observed in mice but again only at 50 ppm. The only statistically significant dose-related developmental effects in rats were an increased incidence of lumbar spurs and delayed ossification after exposure to 50 ppm 2-ME. In mice the only significant dose related developmental effects observed were increased incidence of lumbar spurs and unilateral testicular hypoplasia at 50 ppm. No statistically significant effects were observed at 10 or 3 ppm in mice. Rabbits however exhibited a more sensitive response to 2-ME exposure. At 50 ppm significant decreases in maternal body weight gain and increases in maternal liver weight were observed. At 50 ppm rabbits had a significant increase in the incidence of resorptions. Fetuses from this group exhibited a significant decrease in mean fetal body weight and a significant increase in the incidence of malformations of all organ systems (e.g., joint contracture, shortness and absence of digits, ventricular septal defects of the heart, missing paw bones and rib malformations). Despite the strong effect observed at 50 ppm, there was no statistically significant increased incidence of malformations at 10 or 3 ppm for rabbits. However a statistically significant increase in resorption rate was observed at 10 ppm. The authors of the study however dismissed this effect stating that the observed increase was a result of an unusually low concurrent control value for resorptions. The authors stated that the observed increase at 10 ppm was within the range observed among historical controls

Similar results were observed by Doe et al. (Ex. 4-111). In this study pregnant rats were exposed by inhalation to 0, 100 or 300 ppm 2-ME for 6 hours/day on days 6 through 17 gestation. Rats exposed to 300 ppm exhibited a significant decrease in maternal body weight gains and failed to produce any litters. Nine of the 20 rats exposed to 100 ppm 2-ME produced litters, but the gestation period was significantly increased over controls. Exposure to 100 ppm also induced a significant reduction in the total numbers of pups, the proportion of pups live at birth and the proportion of pups surviving to day 3 postpartum. The authors stated that all pups from the 100 ppm group were normal externally, but no further examination of the pups was performed to determine whether or not there was any other evidence of a developmental effect. Because statistically significant effects were observed at both of the tested doses a NOEL was not established in this study

Inhalation studies by Nelson et al.(Ex. 4-136) examined the behavioral and neurochemical effects in offspring after parental exposure to 2-ME. In these studies both male and female rats were exposed to 25 ppm 2-ME. Twenty-five ppm was chosen as a test level as this dose represented the current allowable limit of exposure under the OSHA standards. Male rats were exposed for 7 hours/day, 7 days/week, for 5 weeks. These rats were then mated with untreated females which were allowed to deliver their young. Separate groups of pregnant rats were exposed 7 hours/day on days 7 through 13 or days 14 through 20 gestation and were also allowed to deliver their young. Behavioral testing to evaluate central nervous system effects (i.e motor, sensory and cognitive functions) were conducted on offspring from both groups of rats and the brains from selected offspring were analyzed for neurochemical levels (e.g., dopamine, acetylcholine, and norepinephrine). The only statistically significant effect in behavior observed was the difference in avoidance conditioning in offspring from female rats exposed on days 7-13 gestation. In the neurochemical analyses offspring from both the paternally and maternally exposed rats exhibited significant neurochemical deviations particularly in the brainstem and cerebrum. These results indicate that both paternal and maternal exposure may result in teratogenic effects on the offspring. However only one dose was used in this study and thus no conclusions about dose-response effects or NOEL's can be drawn

Studies have shown that oral exposure to 2-ME also induces adverse developmental effects. Nagano et al. (Ex. 5-026) orally exposed pregnant mice to 31.25, 62.5, 125, 250, 500 or 1000 mg 2-ME/kg body weight on days 7 through 14 gestation. A significant increase in the incidence of dead fetuses was observed among mice exposed to 250, 500 and 1000 mg/kg 2-ME. There were also significant reductions in fetal weight among fetuses from the 125 and 250 mg/kg dosed groups. At 250 mg/kg there was a significant increase in the incidence of gross malformations, including exencephaly, umbilical hernia and abnormal fingers. Increased skeletal malformations including fused ribs, fused vertebrae, spina bifida, syndactly (fused fingers), oligodactly (absence of fingers), and polydactly (extra fingers) were observed after exposure to 62.5, 125, and 250 mg/kg. Delayed ossification was observed in fetuses from all dose levels. Thus in this study a NOEL was not established

Similarly, Toraason et al.(Ex. 5-042) exposed pregnant rats by gavage to 0, 25, 50, or 100 mg 2-ME/kg body weight on days 7 through 13 gestation. At day 20 of gestation fetuses were removed for electrocardiographic (EKG) analysis and later examined for physical defects. The EKG evaluation involved measuring rhythm variations of the heart, the presence or absence of peaks produced by EKG output (i.e., R, QRS, QT and R-R peaks). All fetuses were resorbed at 100 mg/kg 2-ME and thus no EKG analysis was possible at this dose. There was a significant increase in the number of fetuses with abnormal QRS's from both the 25 and 50 mg/kg exposure groups. At these doses no other EKG characteristics were significantly affected by 2-ME exposure. The most prevelant cardiovascular defect, ventricular septal defect and ductus arteriosis, was observed in fetuses from the 50 mg/kg exposure group. However the authors concluded that the abnormal QRS's did not appear to be related to the cardiovascular malformation. For example the authors noted that four fetuses with abnormal QRS's had heart defects but 4 fetuses without heart malformations also had abnormal QRS's. The authors attributed the abnormal QRS's to a delay in conduction. Nevertheless the results of this study indicate that 2-ME exposure may adversely effect fetal heart function

Adverse developmental effects of 2-ME have also recently been reported in non-human primates. Scott et al.(Ex. 5-125) exposed pregnant monkeys by gavage to 0, 12, 24 or 36 mg/kg body weight, on days 20 to 45 of gestation. Signs of maternal toxicity including a reduction in maternal body weight and loss of appetite were observed at all dose levels. At the highest dose (36 mg/kg) all pregnancies ended in abortion. Three of 10 pregnancies were also aborted in the 24 mg/kg dose group and 3 of 13 pregnancies were aborted in the 12 mg/kg dose group. Fetuses were removed on day 100 of gestation and examined for abnormalities. No malformations were observed among any of the fetuses surviving to day 100 of gestation

b. 2-MEA

The studies discussed above clearly show that 2-ME induces adverse maternal and developmental effects. As discussed earlier, metabolic data indicate that the toxicity of 2-ME is mediated by its primary metabolite, methoxyacetic acid (MAA). MAA is also the primary metabolite of 2-MEA and thus it is likely that 2-MEA will induce similar adverse effects to 2-ME

c. 2-EE

Similar to 2-ME, 2-EE has also induced adverse developmental effects. Doe and Tinston et al. (Exs. 5-071, 4-038, 4-039 and 4-105) exposed pregnant rats, by inhalation, to 0, 10, 50 or 250 ppm 2-EE for 7 hours/day on days 6 through 15 gestation. Pregnant rabbits were exposed to 0, 10, 50 or 175 ppm 2-EE for 7 hours/day on days 6 through 18 gestation. No adverse maternal effects were observed among either exposed rats or rabbits. Among rats, exposure to 250 ppm induced a significant increase in late interuterine death and a decrease in fetal growth. Fetuses from the 250 ppm group exhibited significant increases in skeletal defects, (e.g., partial and/or nonossification of the skull and the thoracic and lumbar vertebrae) and increases in sternebrae abnormalities. No significant adverse effects were observed in the 50 or 10 ppm exposed groups. In the high dose rabbits (175 ppm) there were no significant increases in late interuterine death or decreases in fetal growth. The only statistically significant effect observed at this dose was an increased number of fetuses with extra ribs. As neither species showed any significant adverse effects at 50 ppm, the authors stated that a clear no effect level of 50 ppm for 2- EE was identified in this study

Similar findings were reported by Andrew et al. (Exs. 4-065 and 5-069) who exposed pregnant rabbits by inhalation to 0, 160, or 615 ppm 2-EE for 7 hours/day on days 1-18 gestation. Rabbits exposed to 615 ppm exhibited maternal toxicity including severe anorexia, reduced weight gain and an increased incidence of maternal mortality (5 of 19 died). Rabbits exposed to 160 ppm exhibited significant reductions in food consumption and maternal body weight gain. All litters, from the surviving does, in the 615 ppm exposure group, were resorbed. Resorptions were also significantly increased in the 160 ppm exposure group. In addition there was a significant reduction in the number of live fetuses. Fetuses from the 160 ppm group exhibited a significant increase in malformations including cardiovascular effects (e.g., fused aorta and pulmonary artery), renal effects (e.g., fused kidneys) and skeletal effects (e.g., extra and malformed ribs)

In the Andrew study, female rats were also exposed to 2-EE by inhalation to 0, 150, or 650 ppm for 7 hours/day, 5 days/week for a 3 week pregestational period followed by exposure to 0, 200 or 760 ppm 2-EE during days 1-19 gestation. Pregestational exposure had no effect on maternal toxicity or the establishment of pregnancy. Significant decreases in liver weights and kidney weights were observed in the rats exposed to 760 ppm during gestation. All litters in the 760 ppm exposure group were resorbed. The number of resorptions was not increased in the 200 ppm exposure group. However exposure to 200 ppm during gestation significantly increased the incidence of cardiovascular malformations, and skeletal defects (e.g., extra ribs and vertebrae, and reduced skeletal ossification) in the pups

Nelson et al.(Ex. 4-138) examined developmental effects in the behavior of offspring from rats exposed to 2-EE. Pregnant rats were exposed by inhalation to 100 ppm 2-EE, 7 hours/day on days 7-13 or days 14-20 of gestation. Behavioral tests were subsequently conducted on offspring from the control and exposed groups to evaluate CNS function (e.g., motor, sensory and cognitive functions). Selected offspring were also used for neurochemical analyses (e.g., acetylcholine, norepinephrine and dopamine levels). The only evidence of any maternal toxicity was a significant increase in the duration of pregnancy compared to controls. Offspring from rats exposed on days 7-13 of gestation exhibited impaired performance in the rotorod and open field test and marginal superiority in the avoidance conditioning test. Offspring from the 14- 20 gestation day exposure group had impaired performance in the running wheel and avoidance conditioning tests. Neurochemical analyses revealed that in both the 7-13 and 14-20 day exposure groups, whole brain samples from offspring showed significantly decreased levels of norepinephrine. In the 7- 13 day groups the cerebrum and cerebellum had significant elevations in acetylcholine and dopamine. Thus the results of this study indicate that at 100 ppm 2-EE can induce behavioral and neurochemical alterations. Because only one dose was tested the study was not able to evaluate any potential dose-response trend or identify a NOEL

2-EE has also induced adverse developmental effects after dermal exposure. Hardin et al. (Ex. 4-121) applied 0.25 ml or 0.50 ml 2-EE dermally four times daily to pregnant rats on days 7-16 gestation. Rats exposed to 0.50 ml 2-EE exhibited ataxia (loss of muscular coordination) and reduced body weight gain during the later days of exposure. No other significant signs of maternal toxicity were noted. All fetuses from the 0.50 ml exposure group were resorbed. There was also a significant increase in the numbers of resorptions in the 0.25 ml exposure group. The 0.25 ml group also exhibited significantly increased incidence of cardiovascular malformations and skeletal defects (e.g., incomplete ossification, extra and malformed ribs and vertebrae). The results of this study indicate that skin exposure is a significant route of exposure for inducing teratogenic effects

d. 2-EEA

Inhalation, dermal and oral studies have clearly shown a teratogenic response from exposure to 2-EE. As discussed earlier, metabolic studies also indicate that it is the primary metabolite, EAA, which is likely to be the active agent. EAA is also the primary metabolite of 2-EEA and thus it is likely that 2-EEA will induce teratogenic effects similar to 2-EE. Several inhalation studies support these conclusions. For example, Nelson et al. (Ex. 5-091) exposed pregnant rats by inhalation to 0, 130, 390, or 600 ppm 2- EEA, 7 hours/day, on days 7-15 gestation. At 600 ppm rats exhibited a significant decrease in maternal body weight. However the authors attributed this reduction in maternal weight at high dose to be due to resorptions. They thus concluded that no significant signs of maternal toxicity were observed. All fetuses from the 600 ppm group were resorbed. Resorptions were also significantly increased in the 390 ppm exposure group. Fetuses from both the 390 and 130 ppm exposure groups exhibited significant decreases in weight, as well as significant increases in visceral malformations (e.g., septal defects of the heart and umbilical hernia) and skeletal defects (e.g., wavy and fused ribs). A NOEL was not established for this study

Adverse effects were also reported by Doe et al. (Ex. 5-071) who exposed pregnant rabbits to 0, 25, 100 or 400 ppm 2-EEA for 6 hours/day on days 6 through 18 of gestation. Maternal toxicity was only observed among the 400 ppm exposed rabbits. In this group rabbits exhibited significant decreases in maternal body weight gain and food consumption. Mean live fetal weights were significantly reduced for fetuses from both the 400 and 100 ppm exposure groups. Fetuses from the 400 ppm exposure group exhibited significant increases in visceral defects (e.g., opaque/empty gall bladders, reduced/pale spleens) and skeletal defects (e.g., retarded ossification). Fetuses from the 100 ppm group also showed a significantly increased incidence of partial ossification. The only significant effect observed among fetuses from the low dose exposure group (25 ppm) was an extra center of ossification above the 1st sternebra. However because significant skeletal defects were observed only at 400 and 25 ppm the authors concluded that the effects at 25 ppm were probably not dose related and thus the NOEL for this study was 25 ppm

More recent investigations by Tyl et al. (Ex. 5-124) have further confirmed the teratogenic potential of 2-EEA. In this inhalation study pregnant rabbits and rats were exposed to 0, 50, 100, 200 or 300 ppm 2-EEA, 6 hours/day for days 6-15 (rats) or days 6-18 (rabbits) of gestation. Rabbits exhibited significant decreases in maternal weight gain at 300, 200 and 100 ppm 2-EEA. After exposure to 300 and 200 ppm rabbits also exhibited significant decreases in gravid uterine weight and increases in absolute liver weight. Rats exposed to 2-EEA exhibited a significant decrease in maternal weight gain and food consumption at 300 and 200 ppm. A significant decrease in absolute liver weight was observed in rats at 100, 200 and 300 ppm. A significantly increased incidence of nonviable implantations was observed at 300 and 200 ppm in rabbits and at 300 ppm in rats. Rabbits also exhibited a significant increase in the incidence of resorptions after exposure to 300 ppm. Significant reductions in fetal body weight per litter were observed only among rats exposed to 300 and 200 ppm 2-EEA. Examinations of rabbit fetuses revealed a significant increase in the incidence of skeletal, cardiovascular and renal effects at 300 and 200 ppm. Similarly rats exhibited significant increases in malformations (e.g., cardiovascular, renal and skeletal effects) at both 200 and 300 ppm. No signs of maternal or fetal toxicity were observed at 50 ppm for either species and thus this exposure dose was identified as the NOEL for this study

Similar to findings in dermal studies on 2-EE, studies on 2-EEA have also shown that dermal exposure induces teratogenic effects similar to those observed in inhalation studies. Hardin et al. (Ex. 5-073) dermally exposed pregnant rats to 0.35 ml 2-EEA, twice daily for days 7 through 16 of gestation. Dermal exposure induced significant decreases in maternal body weight gain, significant increases in the incidence of dead implants per litter and significant increases in the frequency of resorbed litters. Fetal examination revealed a significant increase in the incidence of cardiovascular and skeletal defects (e.g., reduced ossification and mishaped vertebrae). Thus the findings of this study further demonstrate the teratogenic potential of 2-EEA. In addition these findings indicate that dermal exposure may be a significant route of exposure

3. Blood Effects

In addition to adverse reproductive and developmental effects, the animal studies provide evidence that 2-ME, 2-EE and their acetates also induce adverse hematological effects. Various studies in rats, rabbits and mice by both inhalation and oral exposure have demonstrated exposure related decreases in various blood parameters including white blood cell counts (WBC), hemoglobin concentration (HGB), platelet count and red blood cell count (RBC)

a. 2-ME and 2-MEA

Miller et al. (Ex. 4-132) exposed rats and mice to 0, 100, 300 or 1000 ppm 2-ME, 6 hours/day for 9 days. At 1000 ppm both male and female rats exhibited significant decreases in WBCs, RBCs, HGB and packed cell volume. Male mice showed similar significant effects at 1000 ppm while female mice showed a significant decrease in WBC only at 1000 ppm. WBC was also decreased at 300 ppm for male rats and at 100 ppm for female rats

In a similar study, Doe et al. (Ex. 4-111) exposed male rats to 0, 100 or 300 ppm 2-ME, 6 hours/day for 10 consecutive days. Exposures at 300 ppm resulted in significant reductions in whole blood count, red blood cell count, hemoglobin concentration, hematocrit and mean cell hemoglobin. No significant blood effects were observed among rats exposed to 100 ppm

Thirteen week inhalation studies by Miller et al. (Ex. 5-023) support the authors' earlier findings (Ex. 4-132) of adverse blood effects. In this study rats and rabbits were exposed to 0, 30, 100 or 300 ppm 2-ME for 6 hours/day, 5 days/week for 13 weeks. Both rats and rabbits, male and female, exposed to 300 ppm 2-ME exhibited significant decreases in WBC, platelet counts, packed cell volume, and HGB. Rabbits exposed to 300 ppm also showed a significant decrease in RBC. No adverse effects in blood were observed at 100 or 30 ppm 2-ME for rats or rabbits

Similarly, Hanley et al. (Ex. 4-120) exposed pregnant rats, rabbits and mice to 0, 3, 10 or 50 ppm 2-ME for 6 hours/day on days 6-15, 6-18 and 6-15 respectively. Rats exhibited a significant decrease in HGB and packed cell volume at all dose levels and a significant decrease in RBC at 50 ppm only. Neither mice nor rabbits showed any significant dose related blood effects

Oral studies in mice by Nagano et al. (Exs. 5-026 and 4-135) have observed significant decreases in WBC after high dose exposure. Pregnant mice exposed during days 7-14 gestation to 31.25, 62.5, 125, 250, 500 or 1000 mg 2-ME/kg body weight showed significantly decreased WBCs at 1000 mg/kg (5-026). Male mice exposed at 12.5, 125, 250 500, 1000 or 2000 mg/kg over a five week period also exhibited significant decreases in WBC at 500 mg/kg and above (Ex. 4- 135). Nagano et al. also exposed male mice to 2-MEA, resulting in a significant decrease in WBC at 1000 mg/kg. The authors noted that when expressed in equimolar doses, the dose-effect levels are similar for 2-ME and 2-MEA. No other studies have investigated the hematological effects of 2-MEA

b. 2-EE

Barbee et al.(Ex. 5-084) exposed male and female, rats and rabbits, to 0, 25, 100 or 400 ppm 2-EE, 6 hours/day for 5 days/week for 13 weeks. Adverse blood effects were only observed among male and female rabbits exposed at 400 ppm. These rabbits exhibited a significant decrease in HGB, hematocrit and RBC

In their teratology studies Doe et al. (Ex. 5-071) exposed pregnant rats to 0, 10, 50 or 250 ppm 2-EE, 6 hours/day on days 6-15 gestation and rabbits to 0, 10, 50 or 175 ppm 2-EE, 6 hours/day on days 6-18 gestation. Rats exposed to 250 ppm exhibited a decrease in HGB, hematocrit and RBC. It is not stated clearly as to whether or not these effects were statistically significant. No treatment related effects were observed at 50 or 10 ppm. No adverse blood effects were observed at any of the test doses for rabbits

Nagano et al. (Ex. 4-135) exposed male mice to 500, 1000, 2000 or 4000 mg 2-EE/kg body weight 5 days/week for 5 weeks. Significant decreases in WBC were observed in the 2000 and 4000 mg/kg exposure groups

c. 2-EEA

Tyl et al. (Ex. 5-124) exposed pregnant rats and rabbits to 0, 50, 100, 200 or 300 ppm 2-EEA 6 hours/day on days 6-15 and days 6-18 gestation, respectively. Rabbits showed significant decreases in platelet counts at 200 and 300 ppm. Rats also had decreased platelet counts at 200 and 300 ppm. In addition rats exhibited a significant increase in WBC at 200 and 300 ppm and a decrease in RBC at 100, 200, and 300 ppm exposure. Barbee et al. (Ex. 5-071) also exposed pregnant rabbits to 2-EEA at doses of 0, 25, 100 or 400 ppm. The only statistically significant effect observed was a decrease in HGB at 400 ppm. Oral studies by Nagano (Ex. 4-135) exposed mice to 500, 1000, 2000, or 4000 mg 2- EEA/kg body weight. The only significant effect in this study was a decrease in packed cell volume in mice exposed at 4000 mg/kg

F. Adverse Health Effects In Humans

Workers exposed to 2-ME and 2-EE have exhibited adverse effects on the hematologic and male reproductive systems. Blood effects among exposed workers include bone marrow injury, reduced red and white blood cell counts and anemia. The major reproductive effect observed among exposed workers is reduced sperm count. OSHA is unaware of any female reproductive or developmental toxicity data among workers exposed to glycol ethers. OSHA believes however that the lack of data in this area is due in major part, to the difficulty in structuring and conducting analyses to detect these types of adverse effects. Thus, although the human data are limited, there is positive evidence among exposed workers and this evidence supports the strong body of evidence observed in experimental animals

1. 2-ME

Ohi and Wegman (Ex. 4-139) reported on two workers in a textile printing plant who developed clinical manifestations of encephalopathy (brain disease) after the acetone that was usually used in a hand cleaning operation had been substituted with 2-ME. Protective gloves were not worn. In addition to the neurological symptoms of encephalopathy, both workers had evidence of bone marrow injury. One had pancytopenia (reduction in the numbers of all of the formed elements of the blood). Air samples collected during the washing operation averaged 8 ppm. Although no estimate was made of the magnitude of skin absorption, exposure was characterized as being "predominantly dermal." Thus dermal exposure may have played a significant part in the observed effects. The authors noted that blood counts returned to normal after removal from exposure indicating that blood effects may be reversible

Cohen (Ex. 5-049) presented a case report of subjective central nervous system complaints and asymptomatic hematopoietic effects following inhalation and skin exposure to 2-ME in a microfilm coating and mixing operator. The worker's job in this case report entailed mixing chemicals, often while standing directly over open 1500 gallon kettles which contained 33% 2-ME. 2-ME was also used in the manual cleaning of the kettles, usually done without gloves. Breathing zone exposures revealed time-weighted average 2-ME levels of 18.2 ppm to 57.8 ppm (average being approximately 35 ppm). Small quantities of methylethyl ketone (MEK) (1-5 ppm) were present. During a periodic examination less than a year after starting his job, it was found that the blood indices of this 32-year old worker, which had previously been normal, dropped. His white blood cell (WBC) count, red blood cell (RBC) count, hemoglobin, hematocrit, and platlets were all found to have fallen to abnormally low levels. The worker also noted an increase in sleep time, increase in weight, decrease in appetite, increased fatigue, and feelings of apathy. When the worker was removed from skin and inhalation exposure to 2-ME, all hematologic parameters returned to normal

Cook et al. (Ex. 5-002) conducted a cross-sectional study among male manufacturing and processing employees, 40 with potential exposure to 2-ME, to determine if anemia, leukopenia (reduction in number of white blood cells), or sterility were present and, if so, if they were more prevalent among the exposed workers. Manufacturing of 2-ME was by a continuous enclosed process. In a separate packaging and distribution facility, 2-ME was loaded into drums, tank cars, or rail cars. Drums were filled automatically, but there was manual capping. TWA air samples of 2-ME collected in the packaging and distribution facility in 1980 indicated personal exposures of 5 to 9 ppm 2-ME and area concentrations of 4 to 20 ppm. However, because of the potential for skin contact and absorption, continued use of protective gloves was recommended to avoid skin contact during sampling and maintenance. Workers exposed to 2-ME were also potentially exposed to 2-EE, polyols and polyoxypropylene glycols, brake fluids, butylene oxide, and polyglycols. Complete blood counts (CBC), hormone levels [i.e., Luteinizing hormone (LH), Follicle Stimulating hormone (FSH), testosterone], length and width of testis, and sperm counts were evaluated for frequencies of abnormal outcomes and percentage differences of grouped means in workers exposed to 2-ME and in the unexposed workers. Hematologic variables in 40 exposed and 25 controls were compared to determine prevalence of anemia and/or leukopenia. Clinical fertility indices for a subgroup of 15 (6 exposed, 9 control) were supplemented by medical history and responses to the question: "Looking back, do you feel you have had any trouble having children?"

Study results indicated little difference between exposed and controls. The only difference between means that approached statistical significance was testicular width (p=.08); however, testicular length was also diminished among the total exposed (p=.19). The authors acknowledged a variety of chemical exposures for both study groups. They also suggested the likelihood of interobserver bias, given that one physician consistently measured lower values and examined appreciably more exposed individuals than controls

2. 2-EE

In 1984 NIOSH conducted a Health Hazard Evaluation of possible reproductive effects among male workers exposed to 2-EE at Precision Castparts Corporation (Ex. 5-003). 2-EE was used as a binder in the preparation of ceramic shells used to cast precision metal parts from wax molds. Approximately 80 male workers engaged in this process were potentially exposed to 2-EE. Full shift breathing zone airborne exposures ranged from non-detectable to 23.8 ppm. Because of the potential for skin exposure to 2-EE, urine measurements of ethoxyacetic acid (EAA), a metabolite of 2- EE, were also determined

Urine excretion of EAA ranged from non-detectable to 163 ug/g creatinine. Blood samples analyzed for 2-EE concentrations did not reveal any detectable levels of 2-EE

In this study NIOSH also conducted a cross-sectional evaluation of semen quality (sperm concentration, pH, volume, viability, motility, velocity and morphology) among 37 men exposed to 2-EE in this plant. The evaluation included a comparison group of 38 unexposed men from elsewhere in the plant. A questionnaire to determine personal habits, medical and work histories and a brief examination of the genital tract, including measurements of testicular size, were also administered

The average sperm count per ejaculate among the 2-EE exposed workers was significantly lower than that of the unexposed group (113 v. 154 million sperm per ejaculate; (p < 0.05). For exposed workers, this difference was statistically highly significant (p < 0.001). The two groups did not differ significantly with respect to other semen characteristics or testicular size. Consideration of the other factors (e.g., abstinence, sample age, subject's age, tobacco, alcohol, and caffeine use, history of urogenital disorders, fever, and other illness) which affect semen quality did not alter these results. However the authors noted that the average sperm concentrations of both groups were lower than the average for other occupational populations studied by NIOSH. Historical control sperm concentration is 70 million/ml. In the present study the mean sperm concentration of the unexposed group was 60 million/ml and that of the exposed group was 48 million/ml

NIOSH concluded that there was a possible effect of 2- EE on sperm count among these workers, and recommended limiting exposure to 2-EE to the fullest extent feasible, given the known testicular toxicity in animals

In the first of three related papers Sparer, Welch, McManus and Cullen (Ex. 5-103) characterized exposure to ethylene glycol ethers in a group of shipyard painters. Painters employed at the shipyard worked in four crews: shop crew, interior crew, tank crew, and exterior crew. The shop crew worked in the paint shop where they formulated and mixed paints and issued respirators. The majority of men in the shop crew had worked on other crews in the past. Interior, exterior, and tank crews worked on the boats. Assignment of a painter to a crew depended on the stage of completion of the boat. Painters may have been assigned to one crew and worked overtime on another. In any given month a painter may have worked on the interior, exterior, and tank crews

Much of the painting performed by the interior crews was by brush application. Tanks were primarily spray painted, and air-supplied respirators were always worn during this operation. Half-face filter respirators with organic vapor cartridges and paint filters were worn by painters whenever they sprayed on interior jobs and were available, but seemed to be optional, for those doing brush painting

One hundred and two air samples from thirty-six painters were analyzed for 2-EE, and 2-ME. 2-EE was detected in 90 samples, 2-ME in 81. For 2-ME the mean was 0.8 +/- 1.0 ppm; median 0.44 ppm and the range 0-5.6 ppm. The mean value for 2-EE was 2.6 +/- 4.2 ppm; the median 1.2; the range 0 - 21.5 ppm. The mean air exposure of the interior crew was 2.6 +/- 4.2 ppm for 2-EE and 0.8 +/- 1.0 ppm for 2-ME. Visible paint on the painters indicated that 60% of the men sampled had skin contact. Painters who were using paints without ethylene glycol ethers, or not painting at all, still had exposure to these solvents as demonstrated by air sampling

Sparer and Welch et al. stated that although these sampling observations do serve to help characterize the exposure of these painters to ethylene glycol ethers, several factors suggest that these measurements may underestimate exposure. A NIOSH investigation of 2-EE exposures reported variable results in recovering analyte from field samples that are shipped to an analytical laboratory and stored for extended periods. Recovery was found to be between 60% and 100% (Ex. 5-003). The painters also reported that, perhaps because of the sampling in progress, work on the study days was much slower than usual. This may have resulted in measured values lower than usual levels

Welch et al. (Ex. 5-104) conducted semen, hematologic, and fertility studies for the entire study population, 94 painters and 55 nonexposed controls. The workers supplied information on demographic characteristics, medical conditions, personal habits, and reproductive history and underwent a physical examination. The questionnaire elicited basic demographic information and information about medical conditions and personal habits that have been reported to effect semen parameters, including smoking, alcohol consumption, caffeine consumption, medications, radiotherapy or chemotherapy, recent febrile illness, past history of mumps, and genitourinary conditions. Each participant was asked about his work history and hobbies. He was asked if he and his wife ever had difficulty conceiving a child, whether he ever saw a physician for this problem, and the physician's diagnosis

A sample of blood was obtained for a complete blood count (CBC), and for determination for serum follicular stimulating hormone (FSH), luteinizing hormone (LH) and testosterone. Urine samples were obtained from each painter at the beginning and end of each sampling period. These samples were frozen and transported to the NIOSH laboratories for analysis for the alkoxyacetic acid metabolites of 2-ME and 2-EE

Semen samples were collected from 73 of the painters and 40 controls to determine whether 2-EE and 2-ME affects the reproductive potential of exposed men. Semen samples were analyzed for pH, volume, turbidity, liquidity , viability, sperm density and count per ejaculate, motility, morphology and morphometry

The proportion of men with a sperm density< 20 million/cc was higher in the exposed group than in the unexposed group, 13.5% (10 painters) vs. 5% (2 controls) (p=0.12). The authors noted that the proportion found in the controls, 5%, was in agreement with population surveys of sperm density. When oligospermia (deficiency in number of sperm) is defined as a sperm count per ejaculate< 100 million, 33% (24 painters) and 20% (18 controls) were oligospermic (p=0.20). The rate of oligospermia was analyzed separately for smokers and non-smokers. Among the non-smokers, the exposed group had a higher rate of oligospermia (p=0.05). When smoking was controlled, the odds ratio calculated for a decreased count per ejaculate among the painters was 1.85, with a 95% confidence interval of 0.6 - 5.6

Because of the regular rotation of painters from one job to another at the shipyard, the painters could not be classified into dose groups. Because of the cyclical nature of spermatogenesis the authors stated that exposure from two to six months prior to semen analysis was likely to have produced an effect at the time of the study, and it was not possible to determine each man's job and exposure at that time. Therefore, the researchers assumed that all the painters had the same exposure

Painters were also exposed to two other substances that have been reported in the past to affect semen quality, lead and epichlorohydrin. Lead is known to cause a depression of sperm count

The mean lead levels of the 45 men who had been monitored for lead were mostly below 20 ug/deciliter(dl), and the highest single level in any individual was 40 ug/dl. The authors stated that this level of lead exposure has not been documented to cause a depressed count. Epichlorohydrin was not detected in air sampling during the study

The authors thus concluded that exposure to the ethylene glycol ethers 2-EE and 2-ME lowered sperm count in this group of painters. The authors pointed out that this finding is consistent with the effect seen in animal studies. Studies in several species show that these glycol ethers cause loss of germinal epithelium and testicular atrophy. Cellular studies show that this effect occurs by inhibition of cell division in the early pachytene stage of spermatogenesis, an effect that would be expected to result in a decreased count rather than an effect on motility or morphology

Welch and Cullen (Ex. 5-102) undertook a cross- sectional clinical appraisal of a sample of painters and unexposed workers to evaluate the relationship between measurements of peripheral blood of the workers and ethylene glycol ether exposure. The study of hematologic function included : a complete blood count, a manual differential count of 200 cells, and a manual platelet count. In addition, each subject's past medical record from the employer's medical department was requested, including routine blood counts and whole blood levels. Complete records were obtained for two-thirds of the subjects

The authors reported that the only other compounds known to be toxic to bone marrow or circulating blood cells that painters at the shipyard were exposed to, in addition to ethylene glycol ethers, were lead and benzene. Lead exposure was limited to abrasive blasting operations; the highest lead level detected during brushing or cleaning operations was 10 ug/m3. Sampled levels during blasting were as high as 11 mg/m3. Painters engaged in blasting use air-supplied respirators and their blood lead was routinely monitored. Forty-five of 94 painters were categorized by the employer as "lead exposed" and were participating in the routine blood testing; only nine of the forty-five men had a mean lead level greater than 15 ug/dl, and only two had a mean greater than 20 ug/dl, with the highest at 30 ug/dl. The highest single value was 40 ug/dl

Paints or cleaning solutions containing more than 1% benzene have not been used in the shipyard sine 1977. Ten air samples for benzene were obtained by NIOSH during the 1978 survey; levels of 0.08 to 0.53 mg/m3 were detectable in eight samples. None of the bulk samples of paints or cleaning solutions in the current industrial hygiene survey revealed any benzene. Mean hemoglobin levels did not differ between the painters (15.43 g/dl + 1.09 S.D.) and controls (15.67 g/dl + 0.84); p=0.14 in a two-tailed test. Additionally, there were no statistically significant correlations between hemoglobin and cumulative exposure measured as years painting at the shipyard

The hemoglobin data were rank ordered and analyzed by the Wilcoxon rank order test. There was no significant difference in rank for the entire group. However, when only those study subjects in the lowest quartile for hemoglobin were included in the analysis, the majority of low values were in painters (p=0.028)

Using an a priori standard for anemia in working age adult males of less than 14 grams hemoglobin/dl blood, nine of the 147 subjects with adequately coded data were below this cutoff; all nine were painters. The past medical records of the shipyard for the anemic painters were reviewed; complete medical records were available on 7 of the 9. Normal hemoglobins were noted on hire in four of the seven anemic men with available records. In a fifth, the initial hemoglobin of 13.8 g/dl had dropped steadily to 12 at the time of the study. For the two men for whom there were no preemployment blood counts, their hemoglobins were compared to those of the respondents of the National Health and Nutrition Examination Survey of the same age, sex, and race, and found to be less than the 10th percentile. In the remaining two, hemoglobins were 13.1 and 13.7 g/dl on hire, comparable to those found during the study. After eliminating these two, whose values did not change since first employed, the rate of anemia is significantly different between painters and controls (p= 0.04). Two of the anemic painters also had an abnormal semen analysis; one was oligospermic, and one was azoospermic(lack of sperm)

Total polymorphonuclear leukocyte (PMN) count was calculated by multiplying the total white count by the percentage PMNs in the differential count. The mean values did not differ significantly between the two groups (painters, 4,602 cell/ul + 2,041 S.D.; controls,4,650 + 1,771). A lower limit of 1,800 cells/ul was used to define "normal" and "abnormal" groups of painters and controls. The lowest total counts were found among painters; five, or 3.4% of the painters had values below 1,800 cell/ul, whereas none of the controls had such low levels (p=0.07)

The authors concluded that the differences in hematologic values seen between the groups of painters and the unexposed controls is significant and that preexisting host factors or rates of participation are not able to explain their results. Welch and Cullen concluded that an analysis of other exposures demonstrates that the difference is attributable to ethylene glycol ethers. They added that the absence of a significant effect on the group as a whole and the inability to detect a dose-response pattern, make strong conclusions unwarranted. The authors called for further research on hematologic effects of these compounds in human populations

In summary, although limited in part by confounding exposures to other solvents, data among workers exposed to 2-ME and 2-EE have exhibited anemia, reduced white and red blood cell counts, bone marrow injury and reduced sperm counts. In some cases these effects were observed at levels which were reportedly below those of the current permissible exposure limits for 2-ME and 2-EE. These findings support the strong body of experimental animal evidence, which show, in several species, that 2-ME and 2-EE induce adverse hematologic, reproductive and developmental effects

G. Mutagenicity

Studies in general indicate a lack of mutagenic potential for 2-ME and 2-EE. Mutagenicity is the ability to induce genetic mutation, i.e., a change in the genetic material. Mutations may give rise to developmental effects in cases where the genetic material of the egg or the sperm has been changed such as to induce abnormal development in the fetus. (Mutations may also give rise to cancer. However, there are substances which may be carcinogenic which are not mutagenic. The carcinogenicity of these glycol ethers has not been tested.)

2-ME and 2-EE have been tested in various tests including Ames tests, unscheduled DNA synthesis(UDS) assays in human embryo fibroblasts, sister chromatid exchange (SCE) tests in hamster ovary cells, cytogenic analyses in rat bone marrow cells, dominant lethal tests in rats, sperm abnormality tests in mice and sex linked recessive (SLR) tests in fruit flies. (Exs. 5-022, 5-056 and 5-076)

Neither 2-ME nor 2-EE induced effects in either the Ames test or UDS assays. 2-EE did induce chromosomal abnormalities in SCE tests. The authors stated that the positive findings in 2-EE are in contrast to the general negative findings in most mutagenic assays. Thus the authors concluded that it may be premature to classify these substances as mutagenic. In the SLR assays 2-EE was found to be negative while inconsistent results were observed for 2-ME. Positive results were observed for 2-ME in the sperm abnormality and dominant lethal tests. For example, 2-ME induced abnormal sperm head morphology and a reduction in male rat fertility. While the dominant lethal test showed a decrease in male fertility, the authors raised the possibility that the reduction in fertility could also be attributed to reduced sperm number rather than a dominant mutation

Thus, the majority of the available data indicates that 2-ME and 2-EE lack mutagenic potential. However the presence of positive findings raise the possibility that these substances may have some weak mutagenic potential. No mutagenicity testing has been conducted with 2-MEA or 2-EEA, but the metabolic data discussed earlier suggest that all four compounds are metabolized by similar pathways and are thus likely to induce similar effects. Thus the results observed for 2-ME and 2-EE are predictive of mutagenic potential in their respective acetates

H. Conclusions

Health effects data from experimental animal studies clearly and consistently show that 2-ME, 2-EE and their acetates produce dose related adverse hematologic, reproductive and developmental effects. These effects include testicular damage, reduced fertility, maternal toxicity, early embryonic death, external, skeletal and visceral malformations, delayed development, and adverse effects on the blood

Evidence also indicates that both inhalation and dermal exposures are significant routes of exposure for glycol ethers and the induction of adverse effects. In addition persons occupationally exposed to 2-ME and 2-EE through inhalation and dermal exposures have exhibited adverse reproductive and hematologic effects. Although not as extensive, in major part due to methodological limitations, the human data are nevertheless highly consistent with and supportive of the strong body of data in experimental animals showing adverse hematologic, reproductive and developmental effects

I. Other Glycol Ethers

Past research on the health effects of glycol ether compounds has primarily been concentrated on 2-ME and 2-EE as these two compounds and their acetates have represented a major percentage of the industrial use of glycol ethers

Although less extensive there is also research on other glycol ether compounds. Much of the concentration in this area has been on substitutes for 2-ME and 2-EE such as 2- Butoxyethanol and the propylene glycol ethers (e.g., propylene glycol monomethyl ether and its acetate)

1. 2-Butoxyethanol (2-BE)

In a series of experiments Carpenter et al (Ex. 5-146) exposed various animal species (e.g., rats, guinea pigs and mice) to 2-BE by inhalation. Groups of rats and guinea pigs were exposed for 7 hours/day, 5 days/week for 30 days at doses of 54, 107, 203, 314 or 432 ppm (rats) and doses of 54, 107, 203 376, or 494 ppm (guinea pigs). Significant increases in osmotic fragility in red blood cells was observed in rats at doses of 107 ppm 2-BE and higher. Osmotic fragility was also observed at 54 ppm when doses were administered daily for 30 days. No statistically significant evidence of osmotic fragility was observed among the guinea pigs at any of the doses tested. Mice were exposed to exposed 7 hours/day for 30, 60 or 90 days to 100, 200 or 400 ppm. No controls were included. Osmotic fragility was observed at all doses tested

Hematologic analyses were also conducted by Tyl et al.(Ex. 4-152) on pregnant rats and rabbits exposed to 2-BE by inhalation. Rabbits and rats were exposed to 0, 25, 50, 100 or 200 ppm 2-BE on days 6-18 (rabbits) and days 6-15 (rats) of gestation. Red blood cell counts, hemoglobin and hematocrit were analyzed in blood samples from both pregnant rats and rabbits. In rats osmotic fragility of red blood cells were not detected at any of the tested doses. However, significant reductions in red blood cell count and mean corpuscular hemoglobin concentration were observed at both 200 and 100 ppm. Mean cell volume and hemoglobin were significantly increased at 200 and 100 ppm. The only significantly treatment related effects observed among rabbits were increases in hemoglobin content and hematocrit at 100 ppm. However these same blood effects were not observed at 200 ppm

Dodd et al. (Ex. 5-050) performed acute, 9-day and 13 week inhalation studies in rats to investigate the toxicity of 2-BE. In the acute study rats were exposed for 4 hours to target concentrations of 200, 500 and 850 ppm 2-BE. The acute 4 hour LC50 was 486 ppm for males and 450 ppm for females. Rats exposed to 500 and 850 ppm exhibited loss of coordination. Post mortem examinations of these animals revealed red stained urine and kidney damage. Rats exposed to 200 ppm appeared normal. In the 9-day study rats were exposed 6 hours/day to 0, 25, 100 and 250 ppm 2-BE. At 250 ppm rats exhibited significant decreases in red blood cell count and hemoglobin concentration. SSignificant effects in the blood were also observed among rats in the 100 ppm exposure group. However the authors stated that the effects were less profound. No statistically significant adverse hematological effects were observed among the rats exposed to 25 ppm. In the 13 week study, rats were exposed to 0, 5, 25 or 75 ppm 2-BE, 6 hours/day, 5 days a week for 13 weeks. At 75 ppm female rats exhibited significant decreases in red blood cell count and hemoglobin concentration and increases in mean corpuscular hemaglobin after 6 weeks of exposure. However by the end of the study these decreases had either lessened or returned to controls levels. Male rats exposed at 75 ppm showed a significant decrease only in red blood cell count. No other dose related effects were observed among male or female rats. In particular there were no alterations in testes weight among males exposed to 2-BE, nor were any lesions observed which would have been indicative of a testicular effect

A similar lack of testicular effect after exposure to 2-BE was noted by Nagano et al. (Ex. 4-135). In this study mice were orally exposed to 500, 1000, or 2000 mg/kg body weight of 2-BE, 5 days/week for 5 weeks. Animals exposed at 2000 mg/kg died. Decreases in red blood cell count were observed among both the 1000 and 500 mg/kg exposure groups. However males at 100 and 500 mg/kg 2-BE did not exhibit any statistically changes in testicular weight. This observation was in contrast to results from this same study which showed marked testicular degeneration after exposure to 2-ME, 2-EE and their acetates

Doe (Ex. 4-112) studied the testicular effects of single high dose exposures to 2-BE, in addition to examining the effects of 2-ME and 2-EE. Rats were exposed for 3 hours to single high doses of 2-BE (800 ppm), 2-ME (7500 ppm), or 2-EE (3500 ppm) and then were followed for 14 days. 2-ME and 2-EE significantly induced testicular atrophy however no significant reduction in testes weight were seen among the 2-BE exposed rats

Similar comparative analyses were performed by Foster et al (Ex. 5-052). However in this study the metabolites of 2-BE, 2-ME and 2-EE were administered rather than the parent glycol ethers. Male rats were exposed by gavage to single oral doses of butoxyacetic acid (0, 174, 434 or 868 mg/kg), methoxyacetic acid (0, 118, 296, or 595 mg/kg) or ethoxyacetic acid (0, 137, 342, or 684 mg/kg). No statistically significant evidence of testicular toxicity was observed at any of the test doses for butoxyacetic acid whereas both methoxy- and ethoxyacetic acid were found to significantly decrease testicular weight (at all doses for 2-ME and at high doses only for 2-EE). As a part of this same study in vitro testicular cell cultures were exposed to the above metabolites to investigate the effects on testicular germ cells. Adverse effects in spermatocytes were observed after administration of methoxy- and ethoxyacetic acids. For example, MAA and EAA produced an enhancement of germ cell loss from Sertoli cell cultures. In contrast no specific effects such as those that were observed after administration of butoxyacetic acid

The developmental effects of 2-BE were studied by Tyl et al (Ex. 4-152). Pregnant rats and rabbits were exposed to either 0, 25, 50 100 or 200 ppm 2-BE for 6 hours/day on days 6-15 (rats) or days 6-18 (rabbits) of gestation. Signs of maternal toxicity were observed in rats at 100 and 200 ppm (e.g., significant reductions in body weight, food consumption and absolute and relative organ weights). A significant increase in the number of resorbed litters, a significant decrease in the number of viable implantation per litter and a significant reduction in skeletal ossification were also observed after exposure to 200 ppm 2- BE. No significant increases in the incidence of malformations were observed at any doses among the rats

In rabbits, increases in resorptions and reduced body weight gain were observed at 200 ppm however these effects were not statistically significant. Significant reductions in the number of viable implants were observed at 200 ppm. No evidence of statistically significantly increased incidences of malformations were found among any of the exposed rabbits. The authors concluded that 2-BE induced maternal and fetotoxic effects but not teratogenic effects

No significant increases in maternal or developmental effects of 2-BE were observed by Nelson et al (Ex. 5-091). In this study pregnant rats were exposed to 0, 150, or 200 ppm 2-BE for 7 hours/day on days 7-15 gestation. These levels were chosen as earlier findings reported death at doses from 250 to 500 ppm 2-BE. The only significant adverse effect observed was "slight" hematuria among the maternal animals after the first day of exposure. Otherwise, no other significant maternal or developmental adverse effects were observed. Effects examined included resorptions, fetal weights and incidence of malformations. These findings are in contrast to results of this same study in which 2-ME and 2-EE were shown to induce adverse maternal and developmental effects

Dermal application of 2-BE has also shown a similar lack of maternal or developmental effect. Hardin et al (Ex. 5-073) exposed pregnant rats by dermal application to 0.35 mL 2-BE, four times daily on days 9-13 of gestation. Deaths occurred through the third and seventh days of exposure. Only one of the 11 rats treated survived. Therefore, tests were repeated at 0.12 mL, four times daily. No significant adverse maternal or developmental effects were observed at this exposure dose

In the recent final Air Contaminants standard (54 FR 2332) OSHA revised the Permissible Exposure Limit (PEL) for 2-BE from 50 ppm to 25 ppm. OSHA concluded that, [T]he former PEL of 50 ppm was insufficiently protective against the risk of 2-butoxyethanol's irritant, hematological, and other potential systemic effects, which constitute material health impairments. The limit of 25 ppm included in the final rule will reduce this significant risk to a level below that at which these toxic effects have been observed in animals and humans. This lower limit will also prevent the discomfort experienced by workers at exposure levels of 40 ppm. (Air Contaminants Final Rule, 54 FR 2554)

In 1990 NIOSH published a Criteria Document for 2-BE and its acetate, 2-BEA (Ex. 5-145). NIOSH reported that data from animals indicate that 2-BE and 2-BEA do not cause adverse reproductive or development effects. However they report that the animal evidence shows that these substances do induce marked adverse effects on the blood. Based on the adverse blood effects observed in animals, NIOSH recommended occupational exposure limits of 5 ppm for both 2-BE and 2-BEA

2. Propylene Glycol Ethers

The production of propylene glycol ethers is analogous to that of ethylene glycol ethers. Ethylene glycol ethers are made by reacting ethylene oxide and the appropriate alcohol. Propylene glycol ethers are produced by reacting propylene oxide with the appropriate alcohol. As such the propylene and ethylene glycol ethers are structurally analogous. For example, ethylene glycol monomethyl ether (2-ME) is structurally very similar to propylene glycol monomethyl ether. However despite some structural similarities, differences in toxicities have been observed between the two general types of compounds

For example, in a series of experimental studies Hanley et al. (Exs. 5-068 and 4-120) compared the developmental effects of 2-ME and propylene glycol monomethyl ether (2- PGME). In studies on 2-ME (Ex. 4-120) rats and rabbits were exposed to 0, 3, 10, or 50 ppm 2-ME, 6 hours/day on days 6- 15 and days 6-18 of gestation respectively. In rabbits, exposure at 50 ppm 2-ME resulted in a significant decrease in maternal body weight gain, a significant increase in resorption rates and significant increases in major malformations. Increased resorption rates were also observed at 10 ppm compared to concurrent controls, but because the resorption rates were not statistically different from historical control values, the authors did not consider the effects to be dose related. Rats did not show any signs of maternal toxicity after exposure to 50 ppm. However fetuses from this exposure group exhibited a significant increase in the incidence in lumbar spurs and delayed ossification. Neither rats nor rabbits had any other significant adverse effects at 10 or 3 ppm. In comparison, Hanley et al.( Ex. 5-068) exposed rats and rabbits to 0, 500, 1500 or 300 ppm 2-PGME to similar periods of gestation for 6 hours/day. At 3000 ppm both rats and rabbits exhibited maternal effects including central nervous system depression and a significant decrease in body weight gain. No significant maternal effects were observed at 1500 or 500 ppm for either species. Neither rats nor rabbits exhibited any significant increase in resorption rates or major malformations at any of the dose levels tested. It was noted by the authors that a significant increase in malformations among rat fetuses at 3000 ppm was observed compared to concurrent controls. However this increase was similar to historical control values and thus was not considered to be dose related. The only significant effect observed, delayed sternebral ossification, was observed at 3000 ppm in rats. This result was interpreted by the authors to be an indication of slight fetotoxicity

Miller et al. (Ex. 5-088) also compared the toxicities of 2-ME and 2-PGME in rats and rabbits. Rats and rabbits were exposed to 0, 30, 100 or 300 ppm 2-ME or 0, 300, 1000 or 5000 ppm 2-PGME, 6 hours/day for 13 weeks. Exposure to 300 ppm 2-ME induced testicular degeneration, decreased sperm count, decreased white blood cell counts and decreased hemoglobin concentrations. No significant effects were observed among the 100 or 30 ppm exposure groups. In contrast, no significant effects on testes weight or blood were observed among rats or rabbits exposed to 2-PGME at any dose tested. The authors attributed the difference in toxicity to differences in metabolism. The authors noted that 2-ME is a primary alcohol and has been shown to be metabolized by an alcohol dehydrogenase mediated pathway to methoxyacetic acid. In addition methoxyacetic acid is considered to be the active metabolite in the induction of reproductive and developmental toxicity. In contrast, 2- PGME is a secondary alcohol and is metabolized by microsomal enzymes to propylene glycol. The authors concluded that this difference in metabolism is most likely to be responsible for the differing toxicities of 2-ME and 2-PGME

However Miller et al. (Ex. 5-093) have also noted that there are two isomeric forms of 2-PGME; the alpha isomer (which is a secondary alcohol) and the beta isomer (which is a primary alcohol). Because of their differences in structure the two isomers are metabolized differently. The alpha isomer is metabolized by microsomal enzymes to propylene glycol and the beta isomer is metabolized by the alcohol/aldehyde dehydrogenase pathway to 2-methoxypropionic acid. The beta isomer follows a metabolic pathway similar to that of the ethylene glycol ethers, 2-ME and 2-EE, which are also primary alcohol glycol ethers. Thus it was postulated that the beta isomer may have toxic properties different from its alpha isomer and may possibly be more similar to ethylene glycol ethers. These conclusions are supported by studies by Merkle et al. (Ex. 5-092) on the pure beta isomer of 2-PGME Acetate. In this study pregnant rats were exposed to 0, 110, 550 or 2700 ppm 2-PGME Acetate and pregnant rabbits were exposed to 0, 36, 145 or 550 ppm 2-PGME Acetate. In rats, exposure to 2700 ppm resulted in a significant increase in the number of litters with skeletal anomalies (e.g., dumbbell shaped notches of the thoracic vertebrae). A slight, but significant, decrease in fetal body weight was also noted at 2700 ppm. No significant effects were observed at the lower test doses. Rabbits however showed a more sensitive response. At 550 ppm, all fetuses exhibited severe malformations (e.g., heart defects and anomalies of the paw and sternum). No significant increases in malformations were observed at other tested doses. It was concluded from these results that the beta isomer of the 2-PGME Acetate has teratogenic potential. By analogy, the beta isomer of its parent glycol ether, 2-PGME was also considered to have teratogenic potential

While the beta isomers of the propylene glycol ethers appear to have teratogenic potential Miller et al. (Ex. 5- 093) also note in their metabolic study that the commercial product of 2-PGME is usually a mixture of the two isomers, with the alpha isomer accounting for up to 95% of the mixture. In its comment on the ANPR, the ARCO Chemical Company, a primary producer of propylene glycol ethers, has also stated that 2-PGME and its acetate routinely contain less than 2% of the beta isomer (Ex. 7-19). These types of commercial products were used by Miller et al. (Ex. 5-088) and Hanley et al. (Ex. 5-068) in their reproductive and developmental studies and were shown to have a low degree of biological activity in comparison to ethylene glycol ethers

3. Ethylene Glycol Monopropyl Ether (EGPE)

Katz et al. (Ex. 5-085) conducted a series of acute and subchronic toxicity tests on EGPE and its acetate EGPEA in rats. In single dose oral studies rats were exposed to 1090, 2180, 4360, 8720 mg/kg (EGPE&EGPEA) or 17,470 mg/kg (EGPEA only). The LD50 of EGPE and EGPEA were observed to be 3089 and 9456 mg/kg, respectively. Prior to death animals exhibited weakness, anorexia and hemoglobinuria. In single inhalation dose studies rats were exposed to target concentrations of 0, 250, 100 or 200 ppm EGPE and 0, 250, 500 or 100 pp, EGPEA. No lethality was observed at any dose, therefore the LC50 was concluded to be greater than 2132 ppm for EGPE and greater than 934 ppm for EGPEA. In six week oral studies male rats were exposed to 0, 195, 390, 780 or 1560 mg/kg body weight EGPE or 0, 1097, 2193, or 4386 mg/kg EGPEA. Adverse blood effects (e.g., significant decreases in hemoglobin concentration and significant increases in platelet counts and nucleated red blood cells) were observed for both compounds at all dose levels. However, only rats exposed to EGPEA at 4386 mg/kg exhibited significant decreases in testicular weight. Pathological examinations revealed atrophy of the seminiferous tubules and degenerated sperm. In the two week inhalation studies both male and female rats were exposed for 6 hours/day to either 0, 100, 200, 400, 800 ppm EGPE or 0, 100, 200, 400 or 800 ppm EGPEA. Slight, but significant changes in red blood cells (e.g., decreased count, and increased corpuscular volume) were observed at 800 and 400 ppm for both compounds. Hemoglobinuria was observed in males and females at 800 ppm EGPE and males only at 400 ppm. Both males(4 out of 5) and females(5 out of 5) exhibited hemoglobinuria after exposure to 400 and 200 ppm EGPEA. A significant increase in spleen weights were observed at 800 and 400 ppm for both compounds. No significant changes in testicular weight were observed for either compound. Based on these results the authors concluded that the NOELs in this study were 200 ppm for EGPE and 100 EGPEA

Krasavage and Katz (Ex. 5-070) studied the developmental toxicity of EGPEA. In this study pregnant rats were exposed to 100, 200, 400 or 800 ppm EGPEA, 6 hours/day on days 6-15 gestation. Exposure to 800 and 400 ppm resulted in decreases in mean maternal body weight, feed intake, and red blood cell counts. Exposure at 800 ppm also resulted in a significant increase in the incidence in resorptions and a significant reduction in mean fetal body weight. No significant increases in theincidence of major malformations were observed among fetuses exposed up to 800 ppm. The authors stated that a significant increases in the incidence of minor skeletal effects (e.g., wavy, knobby, fused and partially ossified ribs and decreased ossification of the skull) were observed at 800 and 400 ppm. A significant increase in rudimentary ribs was observed in the 200, 400 and 800 ppm exposure groups. The authors concluded that adverse fetal effects occur after exposure to EGPEA. However they stated that these effects occurred only after doses which were overtly toxic to the maternal animal (i.e., 800 and 400 ppm)

4. Di-Ethylene Glycol Monomethyl Ether (DEGME)

In inhalation studies by Miller et al. (Ex.5-058) male and female rats were exposed to 0, 30, 100 or 216 ppm DEGME, 6 hours/day, five days/week for 13 weeks. No dose related significant effects were observed among the male or female animals for any of the doses tested. Based on the lack of effects the authors concluded that DEGME is unlikely to present the same degree of hazard as its structural homolog 2-ME

The teratogenic potential of DEGME was examined by Scortichini et al. (Ex. 5-060). In this study pregnant rabbits were exposed by dermal application to 0, 50, 250 or 750 mg/kg day of DEGME on days 6-18 gestation. Rabbits exposed at 750 mg/kg exhibited a significant decrease in maternal weight gain and red blood cell counts. No statistically significant maternal effects were observed at 250 or 50 mg/kg/day. The authors noted an increase in resorptions at 750 mg/kg/day, although this effect was not statistically significantly different from controls. In addition no statistically significant increases in major malformations were observed at any of the doses tested. A significant increase in minor skeletal defects such as forelimb flexure, fused ribs, delayed ossification, forked ribs and cervical spurs were observed among litters from rabbits exposed to 250 and 750 mg/kg DEGME. The authors considered these to be significant signs of fetotoxicity rather than teratogenicity and suggested that these types of fetal defects might be associated with maternal toxicity

5. Ethylene Glycol Monophenyl Ether (2-Phenoxyethanol)

Scortichini et al (Ex. 5-059) have also examined the teratogenic potential of 2-Phenoxyethanol. Pregnant rabbits were dermally exposed to 0, 300, 600 or 1000 mg/kg/day of 2- Phenoxyethanol on days 6-18 gestation. Nine of 25 rabbits died after exposure to 1000 mg/kg/day and 5 of 25 rabbits died after exposure to 600 mg/kg/day. Death was attributed to intravascular hemolysis. The animals surviving in these groups showed no statistically significant treatment related effects. In addition no statistically significant signs of maternal toxicity were observed after exposure to 300 mg/kg/day. Among fetuses examined, there were no statically significant increases in the incidence of external, visceral or skeletal malformations at 300 or 600 mg/kg/day. (Fetal observations were not available at 1000 mg/kg/day due to the high lethality at 1000 mg/kg. Animals were sacrificed with no further observations. In addition, no other reproductive parameters such as resorptions or fetal body measurements were adversely affected at 600 or 300 mg/kg/day. Based on these results the authors concluded that doses up to 600 mg/kg/day produced no significant signs of developmental toxicity

6. Conclusions

The available data for other glycol ether compounds suggests that there are differential toxicities between the longer chain glycol ethers and shorter chain glycol ethers such as 2-ME, 2-EE and their acetates. For example, in the case of 2-butoxyethanol, there were observations of adverse hematological effects but no observations of adverse reproductive or developmental effects. Similarly for propylene glycol ethers there was little evidence of any reproductive or developmental toxicity except in the case of the beta isomeric forms of these compounds. There are scattered reports on other ethylene glycol ether compounds showing adverse hematological effects and, in some cases, slight evidence of testicular effects and minor skeletal defects. In some studies the authors have suggested that defects observed in some of the fetuses may be due to maternal toxicity rather than a direct effect on the conceptus. However, as discussed earlier, developmental effects observed at maternally toxic doses do not necessarily imply that the developmental effects are secondary to maternal effects

In general, the toxicities of these compounds appear less potent than those of shorter chain glycol ethers. The results from toxicity tests on other glycol ethers strongly contrast with the evidence observed after exposures to 2-ME and 2-EE. The evidence on 2-ME and 2-EE clearly and consistently show reduced sperm count, decreased fertility, testicular degeneration, early fetal death, major external, visceral and skeletal malformations, delayed development and functional deficiency. These effects have been observed in several species and through various routes of exposure. The totality and consistency of the evidence on 2-ME, 2-EE and their acetates in experimental animals, clearly indicate that these agents are potential reproductive and developmental toxins in humans. However, OSHA reiterates that past research primarily concentrated on 2-ME, 2-EE and their acetates. The lack of evidence on other glycol ethers may be due, in part, because less research has been conducted on these compounds. Thus, OSHA requests data and analyses on other glycol ethers and their potential reproductive and developmental toxicity

VI. Preliminary Risk Assessment

A. Introduction

The United States Supreme Court, in the "benzene" decision, Industrial Union Department, AFL-CIO v. American Petroleum Institute, 448 U.S. 607 (1980), has ruled that the OSH Act requires that, prior to the issuance of a new standard, a determination must be made, based on substantial evidence in the record considered as a whole, that there is a significant risk of health impairment at existing permissible exposure limits and that issuance of a new standard will significantly reduce or eliminate that risk. The Court stated that "before he can promulgate any permanent health or safety standard, the Secretary is required to make a threshold finding that a place of employment is unsafe in the sense that significant risks are present and can be eliminated or lessened by a change in practices." 448 U.S. 642. The Court also stated "that the Act does limit the Secretary's power to require the elimination of significant risks." 448 U.S. 644

Although the Court in the "cotton dust" case, American Textile Manufacturers Institute v. Donovan, 452 U.S. 490 (1981), rejected the use of cost-benefit analysis in setting OSHA standards, it reaffirmed its previous position in "benzene" that a risk assessment is not only appropriate, but also required to identify significant health risk to workers and to determine if a proposed standard will achieve a reduction in that risk. Although the Court did not require OSHA to perform a quantitative risk assessment in every case, the Court implied, and OSHA as a matter of policy agrees, that assessments should be put into quantitative terms to the extent possible

The extent to which a risk assessment may be put in quantitative terms is limited in the case of glycol ethers. This is not because there are no data suitable for assessing the risk. On the contrary, there are a number of well conducted rodent bioassays which clearly demonstrate the adverse health effects associated with exposure to glycol ethers (see the discussion of health effects above). The problem lies in the fact that there is not a quantitative model for extrapolating the risk of developmental and reproductive effects either from high doses to low doses or across species, that is generally accepted in the scientific community. Therefore, unlike other risk assessments which OSHA has prepared in the past, this risk assessment will be far more qualitative than quantitative and will closely follow the guidelines of the Environmental Protection Agency for assessing the risks of suspect developmental and reproductive toxicants (Ex. 5-153) to determine those levels of occupational exposure to the glycol ethers below which significant risk of adverse health outcomes is unlikely. This approach, which is described in detail in the following sections, is one that has been generally accepted in both the scientific and regulatory communities and is generally accepted as the best methodology for assessing the risks associated with reproductive and developmental toxins

Risk assessment is a process in which scientific judgments are made concerning the potential for toxicity to occur in humans. Because human data are often not available, the risk assessment process often requires the use of models to extrapolate experimental data to humans. These models may be quantitative or qualitative. Quantitative models generally involve mathematical descriptions of dose-response relationships which allow one to calculate numerical estimates of potential risk for a given exposure. Qualitative models, on the other hand, rely more on narrative descriptions of dose-response relationships to describe the likelihood of an adverse effect for a given exposure. However both approaches are based on scientific judgments and scientifically based assumptions about dose response relationships and the predictive value of experimental data

The scientific and regulatory communities have chosen a preference for quantitative models especially in the case of carcinogens. However the scientific and regulatory communities also consider qualitative models as an acceptable means of extrapolating animal data to humans. The No Observed Effect Level-Uncertainty Factor (NOEL-UF) approach, described herein, is such a qualitative model

As a matter of policy, OSHA has chosen to use the NOEL- UF approach in describing the risks associated with exposure to glycol ethers. OSHA has chosen to use this qualitative approach because it is the most generally well accepted approach for assessing the risks from reproductive and developmental toxins. OSHA's decision to use the NOEL-UF approach is based on agreement in the scientific community that this approach is the best methodology currently available for assessing reproductive health risks. This approach, in addition to its general acceptance in the scientific community, is also the methodology that has been consistently used by both EPA and FDA to assess reproductive health risks in their rulemaking procedures. As such it represents the best evidence available to OSHA for making its risk determinations. However while this is a policy choice it should be kept in mind that OSHA's decision to use the NOEL-UF approach is a scientifically informed choice that is supported by scientific expertise and judgment. The selection of the NOEL-UF approach, as well as the steps involved in the process (e.g., the selection of the size of uncertainty factors to extrapolate from animals to humans) are choices based on underlying scientific data and assumptions to account for certain basic scientific uncertainties and are not choices borne solely from a public health perspective to provide a safe workplace in the face of scientific uncertainty

B. Assessing the Risk of Developmental and Reproductive Effects

Most OSHA risk assessments have focused on the risk of cancer from occupational exposure to toxic substances. In the case of carcinogen risk assessment, mathematical models are fit to dose-response data, and the fitted models are used to make predictions of risk at a variety of doses. Although there are a number of mathematical models available to fit to carcinogen dose-response data, within the risk assessment community in general, and the regulatory community in particular, a consensus exists as to which are the "best" models

In the case of non-carcinogen risk assessment, no such generally accepted mathematical models exist for predicting risks. The traditional approach to assessing the risk of non-cancer effects has been first to make a qualitative determination that a toxic substance poses a risk of inducing an adverse effect and then to determine the level of exposure below which that adverse effect is unlikely to be induced in humans using an uncertainty or safety factor approach

This approach is relatively simple. It is most often applied to experimental (animal) data, but it can be applied to epidemiological data when such data are available. The first step in this approach is to determine whether an effect occurs in each exposure group at a rate which is statistically significantly elevated over the rate at which the effect occurs in the unexposed or control group. The highest exposure level which does not induce the effect at a statistically significantly elevated rate is called the no observed effect level or NOEL. In its most recent guidelines (Ex. 5-153), the EPA uses the term NOAEL or no observed adverse effect level instead of NOEL, to make clear that effects being considered are of toxicological significance. For purposes of this document, NOEL is synonomous with NOAEL. The lowest exposure level which does induce the effect at a statistically significantly elevated rate is called the lowest observed effect level or LOEL. (EPA also refers to this level as the LOAEL or Lowest Observed Adverse Effect Level. Again, for purposes of this document, LOEL and LOAEL are synonomous.) In this approach the NOEL is usually the value of interest, but a substance may induce an effect at a statistically significantly elevated rate at each exposure level under study. In that case, the LOEL becomes the value of interest. Determination of the NOEL and/or the LOEL is the purpose of this first step

The next step in this approach is to divide the NOEL or, in the absence of a NOEL, the LOEL by an uncertainty factor. Choice of the uncertainty factor will depend, in part, upon whether one uses the NOEL or the LOEL, and this is discussed at greater length below. The value NOEL

Uncertainty Factor is termed the "acceptable daily intake" or ADI and is considered to represent the level of exposure at which humans are unlikely to experience an adverse effect. (OSHA notes that for purposes of this document, the ADI is not to be interpreted as a regulatory limit, but rather as a health-based level upon which regulatory considerations can be referenced.)

Although this approach requires only two steps, each step introduces uncertainty as to whether the final ADI estimate does indeed represent an exposure level below which an adverse effect is unlikely to be induced. Implicit in the uncertainty factor approach is the assumption that there is a threshold level of exposure below which a toxic response will not be induced, and the NOEL is an estimate of that threshold. There is debate, however, as to whether non-cancer effects, in particular developmental effects, are indeed threshold phenomena. Brent, for example, has argued that teratogenesis "is by and large a threshold phenomena, which means that the vast majority of teratogenic agents have a 'no effect' dose." (Ex.5-126). He cites thalidomide as an example of a developmental toxin which if administered at 50 mg during the critical gestation period can effect a majority of embryos but which will have no effect on the development of embryos administered at 0.5 mg during the same period

Others, however, maintain that not all developmental toxins have a threshold. Gaylor et al argue that "if a chemical produces a malformation by different mechanism than spontaneous malformations, then there is a possibility for a threshold dose. However, if a chemical produces a malformation by augmenting or accelerating an already existing mechanism that produces spontaneous malformations, then no population threshold can exist" (Ex. 5-128). Rodricks et al maintain that "in cases in which the mechanisms of toxic or carcinogenic action are not understood, it is not possible to establish or reject the threshold hypothesis or no-threshold hypothesis, at least with the degree of certainty usually sought in scientific proof. There are numerous reasons to believe that thresholds must exist . . ., but generalization to all agents and all effects is not possible" (Ex. 5-130)

In its comments in response to OSHA's Advance Notice of Proposed Rulemaking (ANPR), the Chemical Manufacturer's Association (CMA) argues that acceptance of the existence of thresholds is central to evaluating reproductive and developmental risk (Ex. 7-17). CMA bases its position in part on the "demonstrated regenerative, repair and regulation abilities of an embryo and fetus." In addition, CMA notes that fetuses are protected by maternal placenta and the metabolic processes of the pregnant female that break down, excrete, store, or otherwise inactivate chemicals before they can damage the embryo. CMA concludes that "to make appropriate decisions about potential human reproductive risks, OSHA must focus its attention on studies that determine the threshold below which adverse effects on the adult or the conceptus will not occur" (Ex. 7-17)

While OSHA believes it is likely that most chemically- induced developmental effects have a threshold, it would seem that CMA is confusing the finding of a NOEL in an animal bioassay with the certainty a threshold exists. As noted by Rodricks et al, the existence of a NOEL from experimental data is consistent with the hypothesis of a threshold but is not sufficient to prove it (Ex. 5-130). Furthermore, if a threshold does exist, there is little reason to believe that the NOEL is indeed the threshold as CMA implies. The exposure level at which no effect is observed is not only a function of the potency of the substance under test but also a function of the experimental design of a study. For example, an exposure level which is not tested cannot be a NOEL. If a researcher tests a substance at 10, 25, and 50 ppm, then the NOEL can only be 10, 25, or 50 ppm. As noted by Rodricks et al, "[f]or practical reasons, only a few doses can be used in experimental studies. While these doses may fall above and below the true threshold doses, it is only by chance that any will precisely match the true threshold doses (and this chance is very small)."

The exposure level found to be the NOEL in a study, (and the exposure level found to be the LOEL in a study), will depend not only upon the exposure levels chosen by a researcher but also upon the numbers of animals in each exposure group. This is because exposure group size is an important factor in determining whether an observed excess of an effect is statistically significant. For example, suppose an experiment is run, and an effect is found to occur in 20% of the animals in the unexposed group. If there are 15 animals in each exposure group, then 60% of the animals exposed at some level X, (9 out of 15), must experience the effect in order to find that level X is the LOEL (i.e. 60% is the lowest rate at which the effect can occur in order to be statistically significantly elevated at the p=0.05 level over the 20% rate in the unexposed animals using a Fisher's Exact Test). If level X induces the effect in only 8 of the 15 exposed animals, then the rate for the effect in this exposure group will not be statistically significant

If, in the example above, the number of animals in each exposure group were larger, then the proportion of exposed animals which must experience the effect to achieve statistical significance over the 20% rate in the unexposed group decreases. Thus, if there were 30 animals in each exposure group, then only 43.3% of the animals exposed to some level Y, (13 out of 30), must experience the effect in order to find that level Y is the LOEL. If there were 1000 animals in each exposure group, then only 23.2% of the animals exposed to some level Z, (232 out of 1000), must experience the effect in order to find that level Z is the LOEL

It is clear from this example that the exposure levels determined to be the NOEL and LOEL will depend on study group size. The "true" NOEL may be lower than the NOEL determined for a particular study, but the study may not be sensitive enough to detect it. Few studies employ 1000 animals per group in their study design, and thus the direction of uncertainty due to sample size is towards overestimating the NOEL and LOEL; a response rate which is statistically significant for a small number of study animals will always be statistically significant for any larger number of animals

Because small exposure group size and therefore lack of statistical power can lead to the erroneous conclusion that exposure induces no effect, the NOEL is not taken by itself to represent the "acceptable daily intake" (ADI). Instead, the NOEL is adjusted by an uncertainty factor not only to account for uncertainties associated with the experimental design but also to account for uncertainties associated with extrapolation across species (i.e. from experimental animals to humans) and to account for the variability of responses within a human population (i.e. intra-species variability)

In their chapter on risk assessment for effects other than cancer, Rodricks et al provide a brief history of the origins of the uncertainty factor (Ex. 5-130). Referring to uncertainty factors as safety factors, these authors write:

The safety factor approach was originated by Lehman and Fitzhugh of the FDA who indicated that variability in sensitivity to chemicals (expressed as differences in dose causing similar responses) across several species was usually in the range of two or threefold and did not appear to exceed tenfold. They also indicated that the variability among extensively outbred individuals and individuals of all ages and degrees of susceptibility (e.g., persons in the general population) appeared also to be less than one order of magnitude. They consequently founded the 100-fold safety factor as a general method of dealing with the uncertainties of extrapolation. This incorporated a factor of 10 when extrapolating from animals to humans and an additional factor of 10 to account for differential sensitivities within the human population. When this 100-fold safety factor is applied to the highest experimental animal NOEL, it is considered to approximate a NOEL for humans in the general population, and becomes the ADI

Since the concept of uncertainty factors was first introduced, it has been modified to derive an ADI from data of varying quality. For example, the FDA has expanded the original 100-fold uncertainty factor approach. When a NOEL is derived from subchronic animal data but that NOEL has been identified in two species, then the FDA recommends an uncertainty factor of 1000. Here, the additional factor of 10 is needed to account for the added uncertainty in estimating a chronic ADI from subchronic data. When a NOEL is derived from subchronic animal data but that NOEL has been identified in only one species, FDA recommends an uncertainty factor of 2000. The additional two-fold factor is intended to account for possible interspecies differences (Ex. 5-130)

If a NOEL can not be identified from study data, that is, if the lowest exposure level used in a study induces an effect at a rate statistically significantly greater than observed among the unexposed group, then the uncertainty factor is applied to the LOEL instead of the NOEL to derive the ADI. As with the NOEL, the uncertainty factor applied to the LOEL is used to account for the uncertainties and variability described above, but EPA recommends that an additional uncertainty factor, usually between one and 10, be used to account for the fact that no NOEL was identified from the data (Ex. 5-131)

Although the selection of uncertainty factors in the multiples of ten may appear to be arbitrary, there is some experimental support for their selection, and this is discussed at some length in an article by Dourson and Stara (Ex. 4-113). (The scientific basis underlying the selection and use of uncertainty factors is further discussed in OSHA Exhibit 5-155.) In addition, these choices of uncertainty factors as well as the entire uncertainty factor approach for non-cancer health effects have been adopted by a number of governmental agencies and international organizations including the U.S. Environmental Protection Agency (EPA), the U.S., Food and Drug Administration (FDA), the Joint Food and Agricultural Organization of the World Health Organization (FAO/WHO), and the National Academy of Sciences (NAS). The uncertainty factor approach for regulating occupational exposure to glycol ethers is supported by many of the commentors responding to OSHA's ANPR including CMA (Ex. 7-17), DOW Chemical (Ex. 7-21), and Du Pont (Ex. 7-28), among others, although not all agree on the value of the uncertainty factor which should be used

As CMA points out in its comments, the uncertainty factor approach "has been well established for regulating reproductive risks" (Ex. 7-17). As noted above, the ADI represents an exposure level below which an adverse effect is unlikely, and confidence that the ADI is an exposure level below which an adverse effect is unlikely will depend, to a large extent, upon the quality of the data from which it is derived. If we know something of the mechanism which induces an effect and if we know that that mechanism is activated when exposure exceeds some threshold level, then our confidence that an adverse effect is unlikely at exposures levels at or below the ADI increases further

C. Assessment of the Developmental Risk from Exposures to Glycol Ethers

1. Introduction

According to the EPA Guidelines for Developmental Toxicity Risk Assessment (Ex. 5-153), the major manifestations of developmental toxicity include 1) death of the developing organism; 2) malformations; 3) altered growth, and 4) functional deficiency. The studies used by OSHA for its assessment of developmental risk from glycol ethers employed a protocol exposing fetuses in utero during organogenesis, the phase of gestation during which the major organ systems develop. The pregnant dams were sacrificed at the end of this gestational phase and prior to giving birth. Each of the unborn fetuses was then examined. Under this protocol the endpoints of interest in these studies are the first three of the outcomes listed above

The endpoint "death of the developing organism" includes resorptions and intra-uterine deaths. Pre- implantation loss is not a measure of developmental toxicity in these studies because the pregnant females were not exposed to any glycol ether until after implantation had occurred

A malformation is usually defined as a permanent structural change that may adversely affect survival, development, or function. A malformation is different than a variation which is usually defined as a divergence beyond the usual range of structural constitution that may not adversely affect survival or health. It is not always possible, however, to distinguish between variations and malformations because, as noted by EPA in its Guidelines, "there exists a continuum of responses from the normal to extreme deviant." Furthermore, there is no generally accepted classification of malformations. Other terminology which is also used includes anomalies, deformations, and aberrations, but, as EPA points out, these terms are no better defined. Nonetheless, these effects indicate toxicity to the developing organism when associated with exposure to a chemical

Altered growth is defined by EPA as an alteration in offspring organ or body weight or size. This endpoint may be reversible or may result in a permanent change

As noted by the Interagency Regulatory Liaison Group (IRLG) in its Workshop on Reproductive Toxicity Risk Assessment, "the developmental toxicity endpoints encountered in experimental animals do not and should not be expected necessarily to mimic those observed in humans exposed to the same toxicant" and "the specific agent-related endpoints in humans are not always reproduced in experimental animals" (Ex. 5-018). All substances known to cause developmental effects in humans, however, have also been found to induce developmental effects in animals with the exception of the coumarin anticoagulants which have not been studied extensively in animals (Ex. 4-147). Schardein has compared the effects of all "known or possible" teratogens in humans with the teratogenic responses observed in laboratory animals exposed to these substances (Ex. 4-147). Each of the developmental toxicants he looked at induced some developmental effect in at least one animal species, but only one class of substances, androgenic hormones, induced the same effect as observed in humans in each species which experienced an effect. Androgenic hormones have been tested in fourteen species, and only one species tested, sheep, experienced no effect

The more common result in cross-species testing of developmental toxicants can be found in the case of thalidomide which was found to induce limb defects (i.e. missing limbs) in humans. In laboratory animals, the drug was found to induce developmental effects in seventeen species, but an effect concordant to the effect observed in humans was observed in only nine species. Furthermore, eight of these nine species, the rhesus monkey, the marmoset, the baboon, the bonnet monkey, the crab-eating monkey, the green monkey, the Japanese monkey, and the stump-tailed monkey, are not the usual animals used in animal bioassays. The rabbit was the sole rodent species to exhibit an effect concordant to the effect observed in humans (Ex. 4-147)

The IRLG has noted that there is "no evidence that any particular species or strain more consistently predicts human susceptibility to animal teratogens than any other species or strain "(Ex. 5-018). This is borne out by Schardein (Ex. 4-147). He found that the rabbit, which experienced an effect from thalidomide concordant to the effect induced humans, experienced no adverse developmental effects from alcohol or diethylstilbestrol (DES), both known to cause birth defects in humans. The mouse experienced effects concordant to those in humans for a number of substances including alcohol, diethylstilbestrol, and antithyroid compounds, but neither aminopterin nor streptomycin, substances found to induce developmental effects in humans, induced any developmental effects in this species. Rats experienced adverse developmental effects from exposure to most of the toxicants considered by Schardein, (rats, and mice were the most commonly used animals in tests of the toxicants considered by Schardein), but the effects were concordant with those in humans in only little more than half the substances and at least one substance considered by Schardein, trimethadione, induced no effect in this species

The response to a developmental toxicant in animal bioassay can be measured in a number of ways. One of these is the number of fetuses affected per number of fetuses exposed. This shall be referred to as the "fetus measure of response". While this measure gives some indication of the potency of a developmental toxicant, it treats each fetus independently of all other fetuses thereby ignoring the "litter effect". The litter effect is the tendency for littermates to respond more like each other than like animals from different litters. Furthermore, the fetus measure cannot distinguish between the case where all litters have one or two affected fetuses and the case where all affected fetuses are from only one or two litters, although these two scenarios have different implications for the potency of a developmental toxicant

An alternative measure of response is number of litters with at least one affected fetus per total number of litters exposed, referred to as the "litter measure of response". This measure treats the litters as the experimental unit because, as noted by EPA in its Guidelines, it is the maternal animal and not the conceptus which is treated during gestation (Ex. 5-153). This is the measure of response favored by EPA for evaluating the potency of a developmental toxicant. The drawback to this measure, however, is that it gives equal weight to a litter with one affected fetus as it gives to a litter with all affected fetuses

In addition to both of these measures, a third measure which OSHA has considered for evaluating response in animals exposed to developmental toxicants is average number of fetuses affected per affected litter. This shall be referred to as the "fetus/litter measure of response". This measure provides a compliment to the fetus measure of response and the litter measure of response, for, whereas the former indicates only the number of fetuses affected and the latter indicates only the number of litters affected, the fetus/litter measure provides an indication of how severe an effect may be within an affected litter. For example, a fetus/litter value of 1.0 would indicate that only one fetus was affected in each of the affected litters. A fetus/litter value of 2.0 would indicate that on average, two fetuses were affected in each of the litters with affected fetuses. Comparison of fetus/litter values across exposure groups would allow one to determine whether more fetuses were affected in each affected litter as dose increases. The limitation of this measure, however, is that unlike the other two measures discussed above, the fetus/litter measure of response has utility only as a descriptive measure and can not be used for statistical inference because the statistical distribution of this measure is unknown

2. Choice of Data

a. 2-ME

OSHA has identified three well conducted animal bioassays for 2-ME which are suitable for assessing the risk of developmental effects from occupational exposure to this glycol ether and for determining the acceptable daily intake or ADI. (As noted earlier for purposed of this document,the ADI is not a regulatory limit but rather a health-based level which describes the level at which humans are unlikely to exhibit effects similar to those obseved in experimental data.) These studies were chosen because in each of these studies, exposure levels were documented, the routes of exposure were the same as is found in most occupational settings (i.e. inhalation), concurrent controls were used, two or more exposure levels of the test substance were employed, statistically significant excesses of developmental effects were observed in exposed groups, and individual litter data were available

Hanley and associates of the Dow Chemical Company conducted three animal inhalation bioassays for 2-ME using female rats, rabbits, and mice (Exs. 4-042a and 4-106). Groups of 30 to 31 bred Fisher 344 rats and 20 to 30 bred New Zealand white rabbits were exposed to 2-ME at levels of 3, 10, or 50 ppm. Groups of 30 to 32 bred CF-1 mice were exposed to 2-ME at levels of 10 or 50 ppm. The test article was supplied by Dow and was 99.96% pure. Thirty bred rats, 30 bred rabbits, and 31 bred mice served as controls

The female rats were bred one to one with male rats of the same strain. The female mice were bred two to one with male mice of the same strain (two females to one male), and the rabbits were bred through artificial insemination. Animals were randomly assigned to exposure groups. Exposure occurred six hours per day through the organogenesis phase of gestation: from day 6 through day 15 of gestation for rats and mice and from day 6 through day 18 gestation for rabbits. All animals were given food and water ad libitum except during periods of exposure and were observed daily throughout the experimental period for indications of toxicity and adverse effects of treatment

Animals found dead or moribund during the course of the study were submitted for gross pathological examination. Surviving mice were sacrificed on day 18 of gestation, surviving rats were sacrificed on day 21 of gestation, and surviving rabbits were sacrificed on day 29 of gestation. Caesarean sections and examinations were preformed on all animals to determine: (1) the number and position of fetuses in utero; (2) the number of live and dead fetuses; (3) the number and position of resorption sites; (4) the sex, and body weight, and crown-rump length of each fetus; and (5) any gross external alternations. In addition, the rats and the rabbits were examined for number of corpora lutea. The uteri of apparently non-pregnant animals were stained and examined for evidence of implantation sites to determine whether pregnancy had occurred. One half of each litter was dissected and examined for soft tissue alternations. All fetuses were examined for skeletal alternations

b. 2-EE

OSHA has identified two well conducted animal inhalation bioassays for 2-EE which are suitable for assessing the risk of developmental effects from occupational exposure to this glycol ether and for determining the acceptable daily intake or ADI. As with 2- ME, both of these studies were chosen because in each, exposure levels were documented, the routes of exposure were the same as is found in most occupational settings (i.e. inhalation), concurrent controls were used, two or more exposure levels of the test substance were employed, statistically significant excesses of developmental effects were observed in exposed groups, and individual litter data were available

Tinston, Doe and associates of Imperial Chemical Industries PLC conducted two animal inhalation studies for 2-EE using rats and rabbits (Exs. 4-038 and 4-039; see also Ex. 5-071). These studies were sponsored by the Chemical Manufacturer's Association (CMA) and followed a protocol similar to the one used by Hanley et al. Groups of 24 bred rats of the Alpk/AP (Wistar-derived) strain were exposed to 2-EE at levels of 10, 50, or 250 ppm. Groups of 24 bred Dutch rabbits were exposed to 2-EE at levels of 10, 50, and 175 ppm. The test article was supplied by Imperial Chemical Industries and was more than 99% pure. Twenty-four bred rats and 24 bred rabbits served as controls

The female rats were bred one to one with male rats of the same strain, and female rabbits were bred with 2 male rabbits of the same strain. Animals were randomly assigned to exposure groups. Exposure occurred six hours per day throughout the organogenesis phase of gestation: from day 6 through day 15 of gestation for the rats and from day 6 through day 18 of gestation for the rabbits. All animals were given food and water ad libitum except during periods of exposure and were observed daily for their clinical condition

Terminal sacrifice of the animals occurred on day 21 of gestation for the rats and day 29 of gestation for the rabbits. After sacrifice, the number of corpora lutea in each animal's ovaries was counted. The uterus of each animal was cut open and the number of implantations as well as the number of early and late intra-uterine deaths was determined. An intra-uterine death was judged to be late if fetal tissues were distinguishable. Each fetus which had not died in utero was removed from the uterus. These fetuses were weighed and examined for gross defects. Half of the rat fetuses and all of the rabbit fetuses were examined for skeletal defects. All fetuses of both species were examined for external and visceral defects

3. Bioassay Results

a. 2-ME

In measuring the incidence of effects of 2-ME in fetal rats, rabbits, and mice, Hanley et al grouped the effects into three categories: external alterations, soft tissue alterations, and skeletal alterations. Each of these categories of defects was subdivided further into major defects and minor defects. The study authors provided no explanation as to the criteria used to subdivide these categories, and one must assume it was professional judgement (Exs. 4-047 and 4-106)

Table VI-A presents the incidence of developmental effects in fetal rats exposed to 2-ME. Incidence is reported using each of the measures of response discussed above (i.e. fetus, litter and fetus/litter). The only effects presented in this discussion are those which occurred in any exposed group at a rate statistically significantly greater than the rate in the unexposed group at the p=0.05 level using either the fetus measure of response or the litter measure of response. Statistical significance was determined using Fisher's Exact Test

1 - Data from Hanley et al, Ex. 4-042a.

2 - Incidence is number of fetuses affected divided by the total number of fetuses

3 - Significantly different than controls at the p< .01 level

4 - Incidence is number of litters with at least one fetus affected

5 - Significantly different than controls at the p< .05 level

6 - Average number of affected fetuses per affected litter

Delayed ossification of the centra and rib spurs are the two developmental effects which occurred at a rate statistically significantly greater in an exposed group than in the controls. Both of these effects were classified as minor skeletal alterations. Both effects were elevated for the 50 ppm group only, but incidence was significant at the p=0.012 level or lower regardless of measure of response, and the fetus/litter measure of response increases with dose. Delayed ossification of the sternebra was significantly reduced for the 50 ppm group when measured using the fetus measure of response, but it was not significant using the litter measure of response and the fetus/litter measure does not show a dose related trend. The authors attribute the observed deficit of delayed ossification of the sternebra to normal variation and not to exposure to 2-ME

Table VI-B presents the incidence of developmental effects in fetal rabbits exposed to 2-ME. The same measures of incidence presented for the rats are presented for the rabbits,and the same statistical criteria were used for inclusion of an effect in the table

1 -Data from Hanley et al, Ex. 4-042a
2 -Incidence is number of fetuses affected divided by the total number of fetuses
3 -Significantly different than controls at the p< .01 level.
4 -Incidence is number of litters with at least one fetus affected
5 -Significantly different than controls at the p< .05 level.
6 -Average number of affected fetuses per affected litter.
7 -Denominator (i.e. the number of animals at risk) is adjusted for resorptions
8 -Only a portion of fetuses in each exposure group were examined for soft tissue alterations.
9 -Denominator not specified by study authors. Number of fetuses at risk estimated by applying male/female ratio for each exposure group to number of fetuses examined for soft tissue alterations
10 - Denominator is number of litters with at least one female fetus.
11 - Denominator is number of litters with at least on male fetus.

Incidence of resorptions was statistically significantly increased using both the fetus and the litter measures of response for the 10 ppm and the 50 ppm group. The fetus/litter measure of incidence shows a dose related increase. The study authors note that although resorptions are significantly elevated for the 10 ppm group, the observed rate for fetuses (11%) and for litters (58%) are comparable to the historical incidence of resorptions observed in other studies in the same laboratory (7% to 15% for fetuses and 38% to 74% for litters). They attribute the finding of statistical significance of resorptions in this exposure group to the unusually low control group incidence of resorptions (4% for fetuses and 22% for litters) and not to exposure

Major external alterations in rabbits occurred at a significant excess in the 50 ppm group only. Incidence of arthrogryposis (abnormal flexure of the forelimbs), anonychia (absence of nails), brachydactyly (short digits), ectrodactyly (absence of part or all of a digit), and kinky tail occurred at a statistically significantly elevated rate for both the fetus measure of response and the litter measure of response. Incidence of omphalocele (protrusion of the intestines through the abdominal wall), and thinning of the abdominal wall was significant for fetuses but not for litters

As with the major external alterations, the minor external alterations, misalignment of the palatine rugae and narrowed tip of tail, occurred at a significant excess only in the 50 ppm group. Both were statistically significant using both the fetus and the litter measure of response

What is most striking about these data is that every external alteration observed, major or minor, was observed only in the 50 ppm group except for one fetus in the 3 ppm group observed with arthrogryposis. The almost total absence of background incidence of these effects reduces the uncertainty as to whether the response in the 50 ppm group could be attributed to chance variation rather than exposure to 2-ME

While all the fetal rabbits were examined for external alterations, only half were examined for soft tissue alterations. Thus, the study had less power to detect this type of developmental effect. Nonetheless, a large number of soft tissue alterations were observed at a significant excess in 50 ppm group. Incidence of these effects was not significantly elevated over controls in any other exposure group. The major soft tissue alterations were coarctation of the aortic arch, ventricular septal defect, hypoplastic spleen, and dilated renal pelvis, and incidence of these effects in the 50 ppm group were statistically significant using both the fetus and the litter measure of response at the p=0.009 level or lower. All but one minor soft tissue alteration occurred at a statistically significant rate in the 50 ppm group using both measures of response

These alterations were patent ductus arteriosis, hypoplastic gall bladder, pale spleen, dilated ureter, convoluted ureter, and parovarian cysts. Testicular cysts were statistically significant in male fetal rabbits in the 50 ppm group using the fetus measure but not using the litter measure. Here again, the almost total absence of any of these effects in the control group, the 3 ppm group, or the 10 ppm group lends further support to 2-ME as the cause for these effects in the 50 ppm group

All fetuses were examined for skeletal alterations, yet incidence of all but two of these alterations was significantly elevated in the 50 ppm group only. The major skeletal alterations which occurred at a significantly elevated rate in this group using both measures of response were missing phalanges and missing metatarsal; the minor skeletal alterations were delayed ossification of the hyoid, delayed ossification of the tarsals, and extra lumbar ribs. Incidence of shortened nasals, maxillae and mandibles and shortened ribs, both major external alterations, were significantly elevated in the 50 ppm group also but only when measured in fetuses. Likewise, incidence of enlarged interparietals, shortened lumbar ribs, delayed ossification of the centra, fused sternebra, and extra site of sternebra ossification, all minor external alterations, were significantly elevated in the 50 ppm group but again, only for the fetus measure of response. There was a statistically significant deficit of delayed ossification of the centra in litters in the 10 ppm group, this most likely is attributable to chance variation and not to exposure. Delayed ossification of the sternebra was significantly elevated over controls in fetuses in the 10 ppm and the 50 ppm exposure groups, but the incidence of this effect measured in litters at both exposure levels was the same (100%) as in the control and 3 ppm exposure group

Exposure to 2-ME did not have as strong an effect in fetal mice as it did in fetal rabbits. Table VI-C presents the results of the mouse bioassay. Criteria for inclusion of an effect in the table in the same as was used for both rats and rabbits. Only one effect, extra lumbar ribs, a minor skeletal alteration, was significantly elevated using both the fetus and the litter measure of response, and this was in the 50 ppm group. Incidences of resorption, hypoplastic testicle, and extra site of sternebra ossification in the 50 ppm group were significantly elevated over controls but only in fetuses and not in litters. Incidence of testicular hemorrhage and delayed ossification of the sternebra was significantly elevated over controls in the 10 ppm group and the 50 ppm using the fetus measure of response, but incidence of these effects was not significant when response was measured in litters

___________________________________________________________________________

1 - Data from Hanley et al, Ex. 4-106. 2 - Incidence is number of fetuses affected divided by the total number of fetuses

3 - Significantly different than controls at the p< .05 level. 4 - Incidence is number of litters with at least one fetus affected

5 - Average number of affected fetuses per affected litter. 6 - Only a portion of fetuses in each exposure group were examined for soft tissue alterations

7 - Denominator not specified by study authors. Number of fetuses at risk estimated by applying male/female ratio for each exposure group to number of fetuses examined for soft tissue alterations

8 - Denominator is number of litters with at least on male fetus. 9 - Denominator (i.e. the number of animals at risk) is adjusted for resorptions

10 - Significantly different than controls at the p< .01 level

b. 2-EE

In their studies of the developmental effects of 2-EE on fetal rats and fetal rabbits, Tinston, Doe et al, (Exs. 4-038 and 4-039; see also Ex. 5-071), classified effects differently than Hanley et al. Abnormalities which were deemed either rare or lethal or both were classified as major external and visceral defects or major skeletal defects while those defects which were judged to be small changes that would not normally impair survival and that occur at a moderate to low frequency in the strain were classified as minor external and visceral defects or minor skeletal defects. A third classification, variant, was used to describe those defects which are common in the species and are not normally deleterious

Another difference between the 2-EE bioassays and the 2-ME bioassays is that the investigators in the 2-EE bioassays considered much more specific effects than did the investigators in the 2-ME bioassays. For example, Tinston et al looked at the degree of ossification (i.e. partially ossified or not ossified) of each centrum and sternebra in each fetus examined. Thus, the study authors report the incidence of partial ossification of the first sternebra, partial ossification of the second sternebra, and so forth. In the 2-ME bioassays, on the other hand, Hanley et al grouped any ossification defect of any sternebra into the category "delayed ossification of the sternebra" and any ossification defect of any centrum into the category "delayed ossification of the centra." The different approaches for measuring the incidence of effects have implications for the inferences which can be drawn from analysis of the study results, and these implications will be discussed in the next section

Table VI-D presents the incidence of developmental effects in fetal rats exposed to 2-EE. As with the results from the 2-ME bioassays, incidence is reported using the fetus, litter, and fetus/litter measures of response, and only those effects which occurred in any exposed group at a statistically significantly greater rate than in control using either the fetus or the litter measure of response are included. Again, statistical significance was determined using Fisher's Exact Test with a critical value of p=0.05.

Table VI-D
Incidence of Developmental Effects
Observed in Wistar Rats
Exposed to 2-EE days 6 through 15 of Gestation (a)
		Control	10 ppm	50 ppm	250 ppm
All Intra-uterine Deaths:
	Fetus (b)	16/297	22/277	12/261	32/266 **
	Litters (c)	12/23	15/24	10/22	12/21
	Fetus/Litter (d)	1.33	1.47	1.20	2.67
Late Intra-uterine Deaths:
	Fetus (e)	3/284	3/258	2/251	17/251 **
	Litters	2/23	2/24	2/22	7/21 *
	Fetus/Litter	1.50	1.50	1.00	2.43
MINOR SKELETAL ANOMALIES (f)
Skull - Partially Ossified Frontals:
	Fetus	1/147	0/131	4/129	14/122 **
	Litters	1/23	0/24	4/22	7/21 *
	Fetus/Litter	1.00	0.00	1.00	2.00
Skull - Partially Ossified Parietal:
	Fetus	10/147	1/131 **	15/129	35/122 **
	Litters	6/23	1/24 *	8/22	17/21 **
	Fetus/Litter	1.67	1.00	1.88	2.06
Skull - Partially Ossified Interparietal:
	Fetus	26/147	3/131 **	24/129	40/122 **
	Litters	10/23	3/24 *	12/22	17/21 *
	Fetus/Litter	2.60	1.00	2.00	2.35
Skull - Odontoid Not Ossified:
	Fetus	26/147	19/131	32/129	93/122 **
	Litters	13/23	10/24	16/22	20/21 **
	Fetus/Litter	2.00	1.90	2.00	4.65
Cervical centrum # 3 Not Ossified:
	Fetus	14/147	21/131	25/129 *	115/122 **
	Litters	6/23	9/24	12/22 *	21/21 **
	Fetus/Litter	2.33	2.33	2.08	5.48
Cervical Centrum # 4 Not Ossified:
	Fetus	10/147	7/131	16/129	109/122 **
	Litters	5/23	4/24	11/22 *	21/21 **
	Fetus/Litter	2.00	1.75	1.45	5.19
Cervical Centrum #5 Not Ossified:
	Fetus	2/147	5/131	9/129 *	98/122 **
	Litters	1/23	3/24	6/22 *	21/21 **
	Fetus/Litter	2.00	1.67	1.50	4.67
Cervical Centrum #6 Not Ossified:
	Fetus	1/147	2/131	6/129 *	84/122 **
	Litters	1/23	2/24	4/22	20/21 **
	Fetus/Litter	1.00	1.00	1.50	4.20
Cervical Centrum #7 Not Ossified:
	Fetus	0/147	0/131	2/129	26/122 **
	Litters	0/23	0/24	2/22	10/21 **
	Fetus/Litter	0.00	0.00	1.00	2.60
Thoracic Centrum #8 Partially Ossified:
	Fetus	0/147	0/131	0/129	6/122 **
	Litters	0/23	0/24	0/22	6/21 **
	Fetus/Litter	0.00	0.00	0.00	1.00
Thoracic Centrum #9 Partially Ossified:
	Fetus	0/147	1/131	0/129	7/122 **
	Litters	0/23	1/24	0/22	5/21 *
	Fetus/Litter	0.00	1.00	0.00	1.40
Thoracic Centrum #10 Partially Ossified:
	Fetus	0/147	0/131	0/129	18/122 **
	Litters	0/23	0/24	0/22	12/21 **
	Fetus/Litter	0.00	0.00	0.00	1.50
Thoracic Centrum #11 Partiall Ossified:
	Fetus	5/147	0/131	1/129	19/122 **
	Litters	5/23	0/24	1/22	10/21
	Fetus/Litter	1.00	0.00	1.00	1.90
Thoracic Centrum #12 Partially Ossified:
	Fetus	2/147	1/131	4/129	17/122 **
	Litters	2/23	1/24	4/22	10/21 **
	Fetus/Litter	1.00	1.00	1.00	1.70
Thoracic Centrum #13 Partially Ossified:
	Fetus	1/147	2/131	3/129	12/122 **
	Litters	1/23	2/24	3/22	8/21 **
	Fetus/Litter	1.00	1.00	1.00	1.50
Lumbar Centrum #1 Partially Ossified:
	Fetus	0/147	0/131	1/129	9/122 **
	Litters	0/23	0/24	1/22	6/21 **
	Fetus/Litter	0.00	0.00	1.00	1.50
Lumbar Traverse Process Partially Ossified - 4th Right:
	Fetus	0/147	5/131	1/129	6/122 **
	Litters	0/23	5/24	1/22	5/21 *
	Fetus/Litter	0.00	1.00	1.00	1.20
Lumbar Traverse Process Partially Ossified - 4th Both:
	Fetus	0/147	3/131	0/129	4/122 *
	Litters	0/23	2/24	0/22	3/21
	Fetus/Litter	0.00	1.50	0.00	1.33
Sternebra #1 Partially Ossified:
	Fetus	4/147	2/131	4/129	35/122 **
	Litters	3/23	2/24	4/22	14/21 **
	Fetus/Litter	1.33	1.00	1.00	2.50
Sternebra #2 Partially Ossified:
	Fetus	1/147	2/131	6/129 *	10/122 **
	Litters	1/23	2/24	5/22	7/21 *
	Fetus/Litter	1.00	1.00	1.20	1.43
SKELETAL VARIANTS
Sternebra #6 Partially Ossified:
	Fetus	0/147	0/131	1/129	8/122 **
	Litters	0/23	0/24	1/22	3/21
	Fetus/Litter	0.00	0.00	1.00	2.67
Sternebra #4 Misaligned:
	Fetus	1/147	0/131	4/129	6/122 *
	Litters	1/23	0/24	4/22	5/21
	Fetus/Litter	1.00	0.00	1.00	1.20
Sternebra #5 Misaligned:
	Fetus	1/147	0/131	2/129	6/122 *
	Litters	1/23	0/24	2/22	4/21
	Fetus/Litter	1.00	0.00	1.00	1.50
Sternebra #1 Bipartite:
	Fetus	0/147	0/131	0/129	9/122 **
	Litters	0/23	0/24	0/22	8/21 **
	Fetus/Litter	0.00	0.00	0.00	1.13
Skull - Partially Ossified Occipitals:
	Fetus	141/147	113/131	124/129	122/122 *
	Litters	23/23	23/24	22/22	21/21
	Fetus/Litter	6.13	4.91	5.64	5.81
cervical Centrum #1 Not Ossified:
	Fetus	28/147	40/131 *	48/129 **	94/122 **
	Litters	13/23	15/24	17/22	21/21 **
	Fetus/Litter	2.15	2.67	2.82	4.48
Cervical Centrum #2 Not Ossified:
	Fetus	52/147	63/131 *	80/129 **	118/122 **
	Litters	17/23	22/24	21/22	21/21 *
	Fetus/Litter	3.06	2.86	3.81	5.62
Extra (14th) Rib - Unilateral Left Short:
	Fetus	5/147	7/131	4/129	15/122 **
	Litters	5/23	7/24	3/22	8/21
	Fetus/Litter	1.00	1.00	1.33	1.88
Extra (14th) Bilateral Short:
	Fetus	14/147	12/131	33/129 **	75/122**
	Litters	10/23	6/24	15/22	18/21 **
	Fetus/Litter	1.40	2.00	2.22	4.17
Pelvic Girdle Moved Posteriorly - 27 Pre-Sacral Vertebrae (g):
	Fetus	1/147	3/131	2/129	15/122 **
	Litters	1/23	2/24	2/22	7/21 *
	Fetus/Litter	1.00	1.50	1.00	2.14
Both Calcaneum Not Ossified:
	Fetus	136/147	115/131	119/129	122/122 **
	Litters	23/23	24/24	22/22	21/21
	Fetus/Litter	5.91	4.79	5.41	5.81
MINOR EXTERNAL AND VISCERAL DEFECTS h
Renal Pelvic Dilation:
	Fetus	19/281	25/255	22/249	30/234 *
	Litters	12/23	14/24	12/22	18/21 *
	Fetus/Litter	1.58	1.79	1.83	1.67
Hydroureter:
	Fetus	13/281	6/255	4/249 *	10/234
	Litters	5/23	6/24	3/22	5/21
	Fetus/Litter	2.60	1.00	1.33	2.00
Limb Malrotation:
	Fetus	0/281	9/255 **	2/249	3/234
	Litters	0/23	4/24	1/22	2/21
	Fetus/Litter	0.00	2.25	2.00	1.50

a -Data from Tinston, Doe et al, Exs. 4-038.See also Ex. 5-071
b -Incidence is number of fetuses affected divided by the total number of fetuses
c -Incidence is number of litters with at least one fetus affected
d -Average number of affected fetuses per affected litter
e -Denominator (i.e. the number of animals at risk) is adjusted for early intra-uterine deaths
f -Only a portion of fetuses in each exposure group were examined for soft tissue alterations
g -This skeletal defect was not classified as either a minor skeltal anomalie or a skeletal variant
h -Denominator (i.e. the number of animals at risk) is adjusted for all intra-uterine deaths
* -Significantly different than controls at the p <.05 level
** - Significantly different than controls at the p <.01 level

A significant excess of late intra-uterine deaths occurred in the 250 ppm group using both the fetus and the litter measures of response, but when combined with early intra-uterine deaths (i.e. all intra-uterine deaths) the effect is significant for the 250 ppm group in fetuses only. Early intra-uterine deaths considered separately were not found to be related to exposure

Most of the minor skeletal defects which occurred at a significantly elevated rate were also in the 250 ppm group. The effects which are significant using both measures of response were partially ossified frontals, partially ossified parietals, partially ossified interparietals, odontoid not ossified, third, fourth, fifth, sixth, and seventh cervical centra not ossified, eighth ninth, tenth, eleventh, twelfth, and thirteenth thoracic centra partially ossified, first lumbar centrum partially ossified, fourth right lumbar traverse process partially ossified, and first and second sternebrae partially ossified. One minor skeletal defect, fourth right lumbar traverse process partially ossified, was significant for fetuses in the 250 ppm group but not for litters

Two minor skeletal defects were significant for the 50 ppm group using both measures of response: third cervical centrum not ossified and fifth cervical centrum not ossified. The minor skeletal defects of unossified sixth cervical centrum and partially ossified second sternebra shows a significant excess in this exposure group but only for fetuses. The incidence of unossified fourth cervical centrum was significantly elevated over controls in the 50 ppm group for litters but not for fetuses

Two minor skeletal defects showed a significant deficit of occurrence in the 10 ppm group. Using both the fetus and the litter measure of response, study results show that fetal rats exposed to 10 ppm of 2-EE were significantly less likely to experience partially ossified parietals or partially ossified interparietals than were controls. The study authors offer no explanation for this, but given the large number of effects for which each fetus was examined, the statistical significance of this deficit can easily be attributed to chance variation

A number of skeletal variants were observed to be associated with exposure in fetal rats. Those which were found to be statistically significantly elevated over controls using both the fetus and the litter measures of response, bipartite first sternebra, unossified first cervical centrum, and extra (14th) rib - bilateral short, were found only in the 250 ppm group. Interestingly, incidence of unossified first and second cervical centra were also significantly elevated in the 10 ppm group and the 50 ppm group when measured in fetuses but not when measured in litters. The fetus/litter measure shows a dose-related trend for ossified first cervical centrum but not for unossified second cervical centrum. The effect extra (14th) rib - bilateral short showed a showed a significant excess in 50 ppm fetuses but not in 50 ppm litters

There were an additional number of skeletal variants which were statistically significant in the 250 ppm group but only when response was measured in fetuses. These effects were partially ossified sixth sternebra, misaligned fifth sternebra, partially ossified occipital and extra (14th) rib - unilateral (left) short, and although these effects were not significant when measured in litters, when measured in fetuses these effects were significant at the P=0.035 level or lower

Three minor external and visceral defects were found to be statistically significant. Renal pelvic dilation occurred at a significantly elevated rate in fetuses and in litters in the 250 ppm group. Incidence of hydroureter was significantly reduced in the 50 ppm fetuses but in no other group of fetuses and in no group of litters. Incidence of limb malrotation was significantly elevated in the 10 ppm group of fetuses but in no other group of fetuses and in no groups of litters

There were two skeletal defects which occurred at a statistically significant rate in the 250 ppm group which were not classified. "Pelvic girdle moved posteriorly (27 pre-sacral vertebrae)" was not categorized as either a major or minor skeletal defect or as a variant. This effect was significant in both fetuses and litters. Likewise, "both calcaneum not ossified" was not classified as either a major or minor skeletal defect or as a variant. This effect was significant only in fetuses in the 250 ppm group

The incidence of developmental effects in fetal rabbits exposed to 2-EE are presented in Table VI-E. As for fetal rats, three measures of response are presented, and the same statistical criteria were used for inclusion of an effect in the table

a - Data from Tinston, Doe et al, Exs. 4-039. See also Ex. 5-071
b - Only a portion of fetuses in each exposure group were examined for soft tissue alterations
c - Incidence is number of fetuses affected divided by the total number of fetuses
d - Incidence is number of litters with at least one fetus affected
e - Average number of affected fetuses per affected litter
* - Significantly different than controls at the p< .05 level
** - Significantly different than controls at the p< .01 level

Only one skeletal defect, 27 pre-sacral vertebrae, which Tinston et al classified as minor in rabbits, was statistically significant in fetuses and litters and this was in the 175 ppm group. Three minor skeletal defects, partially ossified hyoid, partially ossified sixth sternebra, and unossified pubes, were significant in fetuses in the 175 ppm group but not in litters. The defect partially ossified hyoid occurred at a significantly elevated rate in 10 ppm fetuses but was not significant in this group when measured in litters. The same result was seen for the defect unossified fifth sternebra which was significant in fetuses in the 10 ppm group but not in litters and not in any other exposure group

The 175 ppm group had statistically significant excess of two skeletal variants when measured in fetuses and in litters: extra (13th) rib - unilateral short and extra (13th) rib - bilateral normal. The skeletal variant extra (13th) rib - one normal and one short was significantly elevated in fetuses in the 175 ppm group but was not significant in litters

One skeletal variant was significantly elevated in the 10 ppm group. This variant was partially ossified fifth sternebra. Incidence was significant only when measured in litters but not when measured in fetuses and was not significant for any other exposure group using any measure of response. Incidence of partially ossified fifth sternebra does not show a dose-related trend using the fetus/litter measure of response, and the study authors attribute the observed excess to coincidence because similar increases in this variant were not observed in the 50 and 175 ppm groups

4. Derivation of the No Observed Effect Level

a. 2-ME

In reviewing Table VI-A, VI-B, and VI-C, it is clear that almost all effects which occurred in an exposed group at rates statistically significantly elevated over controls occurred in the highest dose group, the 50 ppm 2-ME dose group, in each species. Only one effect, resorptions, was statistically significant in litters at a dose below 50 ppm, but, as noted by the study authors, the rate of resorptions in exposed rabbits fell well within the range of historical controls

It is apparent from these data that 10 ppm is the no observed effect level (NOEL) in each of the species studied by Hanley et al despite the varying sensitivity of each of the species to 2-ME

Still, the question arises as to how the incidence of effects can or should be combined to arrive at a measure of overall response

Intuitively, one would have greater confidence in a NOEL derived from an overall measure of response rather than one derived from specific effects which may be statistically significant due to chance alone

OSHA proposes that an overall measure of the incidence of developmental effects be arrived at by pooling the incidence of effects which occurred at a statistically significant excess in any exposed group when measured in litters. The Agency has chosen litters as the most appropriate unit of measure for a number of reasons. First, as noted above, it is the pregnant female that is exposed to the test substance, therefore it is her litter which is the affected unit. Because dose is administered to the fetus through the pregnant dam, the dose each fetus receives is unknown and may depend upon the individual sensitivity of the mother animal to the test substance. Furthermore, the dose the fetus does receive may be affected by the number of littermates in utereo

Another reason for prefering the litter as the unit of measure is that fetuses in a litter are more likely to respond like each other than like fetuses from other litter (i.e. the litter effect). Therefore, if an effect is observed in some number of fetuses, but all affected fetuses come from only one or two litters, then it is possible to attribute the effect to exposure when in fact it is due to variation among the mother animals

The use of litters as the unit of measure in studies of developmental effects in animals is recommended by the EPA in its Guidelines (Ex. 5-153), and this unit of measure enjoys wide support in the literature (see, for example, Ex. 5-018)

OSHA's decision to include in an overall measure of response only those effects which are statistically significant when considered individually is based on its belief that by so restricting inclusion of an effect in an overall measure one obtains a more accurate measure of overall response. Inclusion of effects which are not dose related and are attributable solely to chance dilutes the overall measure of the potency of a developmental toxicant

This position is easily illustrated. Hanley et al counted all the rabbit litters in the control and exposed groups which had at least one fetus with any major malformation. The incidence of major malformations was found to be 6/23 in controls (26%), 4/23 in the 3 ppm group (17%), 3/24 in the 10 ppm group (13%) and 20/22 in the 50 ppm group (91%). If only those major malformations which were statistically significant in exposed litters had been included, the overall incidence of major malformations would have been 0/23 in the control group (0%), 2/23 in the 3 ppm group (13%) 1/24 in the 10 ppm group (4%) and 20/22 in the 50 ppm group (91%). While the NOEL is 10 ppm regardless of how the overall incidence of major malformations is measured, the effect attributable to exposure at 50 ppm is clearer and starker when those major malformations attributable to chance are excluded

Tables VI-F, VI-G, and VI-H present the overall incidence of developmental effects in rats, rabbits, and mice, respectively. For rabbits, resorptions were not included in the overall measure of response because the rate for all three exposure groups (42% to 67%) was well within the historical range reported by Hanley et al (mean 55%, range 38% to 74%) and only the rate of resorption among controls (22%) was outside of that range. The tables clearly indicate that 2-ME induces developmental effects in all three species at 50 ppm and that the NOEL for all three species in these studies is 10 ppm

a - Data from Hanley et al, Ex. 4-042a
b - The numerator is the number of litters with at least one fetus presenting either delayed ossification of centra or rib spurs; the denominator is the number of litters at risk
** - Significantly different than controls at the p < .01 level

a - Data from Hanley et al, Ex. 4-042a
b - The numerator is the number of litters with at least one fetus presenting any of the following major external alterations: arthrogryposis, anonychia, brachydactyly, ectrodactyly, or kinky tail; the denominator is the number of litters at risk
c - The numerator is the number of litters with at least one fetus presenting any of the following minor external alterations: misalignment of the palatine rugae or narrowed tip of tail; the denominator is the number of litters at risk
d - The numerator is the number of litters with at least one fetus presenting any of the following major soft tissue alterations: coarctation of the aortic arch, ventricular septal defect, hypoplastic spleen, or dilated renal pelvis; the denominator is the number of litters at risk
e - The numerator is the number of litters with at least one fetus presenting any of the following minor soft tissue alterations: patent ductus arteriosis, hypoplastic gall bladder, pale spleen, dilated ureter, convoluted ureter, or parovarian cyst; the denominator is the number of litters at risk
f - The numerator is the number of litters with at least one fetus presenting any of the following major skeletal alterations: missing phalange or missing metatarsal; the denominator is the number of litters at risk
g - The numerator is the number of litters with at least one fetus presenting any of the following minor skeletal alterations: delayed ossification of the hyoid, delayed ossification of the tarsal, or extra lumbar ribs; the denominator is the number of litters at risk
h - The numerator is the number of litters with at least one fetus presenting any major external alterations, any major soft tissue alteration or any major skeletal alterations listed above; the denominator is the number of litters at risk
i - The numerator is the number of litters with at least one fetus presenting any minor external alterations, any minor soft tissue alteration or any minor skeletal alterations listed above; the denominator is the number of litters at risk
j - The numerator is the number of litters with at least one fetus presenting any major or minor external alterations, soft tissue alteration or skeletal alterations listed above; the denominator is the number of litters at risk
* - Significantly different than controls at the p < .05 level
** - Significantly different than controls at the p < .01 level

a - Data from Hanley et al, Ex. 4-106
b - The numerator is the number of litters with at least one fetus presenting extra lumbar ribs; the denominator is the number of litters at risk
* - Significantly different than controls at the p< .05 level

In its comments to OSHA's ANPR, Du Pont states that it is "appropriate to look at all adverse effects, but not to accumulate these effects into one endpoint" (Ex. 7-28). OSHA seeks additional information on how the approach suggested by Du Pont could be used for quantitative risk assessment. Specifically, it is unclear how different NOELs for different endpoints from the same study would be treated. In addition, OSHA seeks comment on whether adverse developmental effects should be combined, and if so, how this should be done

Given that the NOEL for 2-ME has been derived from animal studies, OSHA believes that an uncertainty factor of 100 is appropriate for derivation of the acceptable daily intake (ADI) i.e. the dose at which humans are unlikely to exhibit effects similar to those observed in animals. An uncertainty factor of 100 provides a factor of 10 for inter- species variability and a factor of 10 for intra-species variability (i.e. individual human sensitivity to 2-ME). Therefore, based on the studies of Hanley et al, OSHA estimates the ADI to be 10 ppm/100 or 0.1 ppm. That is, at 0.1 ppm of 2-ME, humans are unlikey to exhibit effects similar to those observed in animals

b. 2-EE

Table VI-D and VI-E show clearly that exposure to 2-EE had an effect on developing animals although the results of the 2-EE bioassay are not as strong as those from the 2-ME bioassay. While most of the developmental effects observed in the 2-EE bioassay were observed in the high dose groups for both rats and rabbits (250 ppm and 175 ppm respectively), there were statistically significant effects in the 50 ppm group of rats and the 10 ppm group of rabbits. Thus, determination of the NOEL for 2-EE is more difficult than for 2-ME

Table VI-I presents the overall incidence of developmental effects in fetal rats exposed to 2-EE. Only those effects which were statistically significant when measured in litters are included in the overall measure of incidence

a - Data from Tinston, Doe et al, Ex. 4-038a
b - The numerator is the number of litters with at least one late intra-uterine death; the denominator is the number of litters at risk
c - The numerator is the number of litters with at least one fetus presenting any of the following minor skeletal defects: frontal partially ossified, parietal partially ossified, interparietal partially ossified, odontoid not ossified, third, fourth, fifth, sixth or seventh cervical centrum not ossified, eighth, ninth, tenth, twelfth, or thirteenth thoracic centrum partially ossified, first lumbar centrum partially ossified, fourth right lumbar traverse process partially ossified, or first or second sternebra partially ossified; the denominator is the number of litters at risk
d - The numerator is the number of litters with at least one fetus presenting any of the following skeletal variants: first sternebra bipartite, first or second cervical centrum not ossified, or extra (14th) rib bilaterally short; the denominator is the number of litters at risk
e - The numerator is the number of litters with at least one fetus presenting renal pelvic dilation; the denominator is the number of litters at risk
f - The numerator is the number of litters with at least one fetus presenting a posteriorly moved pelvic girdle (27 pre-sacral vertebrae); the denominator is the number of litters at risk. The defect "pelvic girdle moved posteriorly" was not classified as a major or minor external and visceral defect, a major or minor skeletal defect, or a skeletal defect. Thus it is "unclassified."
g - The numerator is the number of litters with at least one fetus dying late in utero or presenting any minor skeletal defect, skeletal variant, minor external or visceral defect, or unclassified defect listed above; the denominator is the number of litters at risk
* - Significantly different than controls at the p< .05 level

The surprising result in table VI-I is that when all the effects are combined, it would appear that 2-EE has no effect on developing rats despite the fact that there is a significant excess of late intra-uterine deaths in the 250 ppm group, a significant excess of minor skeletal defects in the 250 ppm group, and a significant excess of external and visceral defects in the 250 ppm group. Furthermore, Table VI-D shows that there were twenty-four effects that were significantly elevated in the 250 ppm group in both litters and fetuses

The reason the overall incidence of effects in fetal rats exposed to 2-EE is not significant is that the study authors looked at the developmental effects in such minute detail. While this results in there being a large number of effects which are statistically significant in the 250 ppm group when each effect is considered individually, when combined the incidence of these effects in the other exposure groups dilutes the association between dose and response

Examination of the data reveals that the incidence of non-ossification of the cervical centra is one effect which is diluting the overall dose-response relationship. When ossification of each of the seven cervical centra is considered individually, it is clear that exposure to 250 ppm of 2-EE in fetal rats results in non-ossification of each of the centrum. Incidence of non-ossification of each of the centrum in the 250 ppm group is statistically significant at the p=.014 level or lower. If all the centra were combined into a category "delayed ossification of the cervical centra", however, this effect would not be statistically significant when measured in litters. The litter incidence of delayed ossification of any cervical centrum is 19/23 in control (83%), 23/24 in the 10 ppm group (96%), 21/22 in the 50 ppm group (95%), and 21/21 in the 250 ppm group (100%). Thus, when each centrum is considered individually, there is clearly a dose-related effect at the 250 ppm level, but when the centra are considered together, this effect disappears. Because of the high background incidence of the effect and the small number of litters in each group, the overall incidence of developmental effects in the 250 ppm group appears to be unrelated to dose

OSHA does not believe that there is no developmental effect on fetal rats exposed to 2-EE. When the incidence of late intra-uterine deaths is considered, when the overall incidence of minor skeletal defects is considered and when the overall incidence of minor external and visceral defects are considered, it is clear that exposure to 250 ppm of 2-EE results in detrimental effects on the developing fetus. No such effect is seen at 50 ppm or lower, and therefore OSHA concludes that the NOEL for 2-EE is 50 ppm in rats

The results presented in Table VI-J demonstrate that 50 ppm is also the NOEL for fetal rabbits exposed to 2-EE. The overall incidence of developmental effects is statistically significant for the 175 ppm group at the p=0.004 level. This indicates that exposure below the 250 ppm level, the level observed to have an adverse effect on developing rats, can have an adverse effect on developing rabbits

Although fewer effects were observed in the rabbit at 175 ppm than in the rat at 250 ppm, dose-related adverse effects were nonetheless induced at the 175 ppm level.

Table VI-J
Overall Incidence of Developmental Effects
Observed in Litters of Dutch Rabbits
Exposed to 2-EE Days 6 through 18 of Gestation (a)
		Control	10 ppm	50 ppm	175 ppm
Minor Skeletal Defects (b)
	Litters	3/21	4/20	2/16	10/22 *
Skeletal Variants (c)
	Litters	7/21	10/20	9/16	18/22 **
Any Defect or Variant (d)
	Litters	8/21	11/20	9/16	18/22 **

a - Data from Tinston, Doe et al, Ex. 4-039a
b - The numerator is the number of litters with at least one fetus presenting 27 pre-sacral vertebrae; the denominator is the number of litters at risk
c - The numerator is the number of litters with at least one fetus presenting an extra (13th) rib unilaterally short or bilaterally normal; the denominator is the number of litters at risk
d - The numerator is the number of litters with at least one fetus presenting any minor skeletal defect or skeletal variant listed above; the denominator is the number of litters at risk
* - Significantly different than controls at the p< .05 level
** - Significantly different than controls at the p< .01 level

Given, as with 2-ME, that the NOEL for 2-EE has been derived from animal studies, OSHA believes that an uncertainty factor of 100 is again appropriate for derivation of the ADI. As with 2-ME, an uncertainty factor of 100 provides a factor of 10 for inter-species variability and a factor of 10 for intra-species variability. Therefore, based on the studies by Tinston et al, OSHA estimates the ADI to be 50 ppm/100 or 0.5 ppm. That is, at 0.5 ppm of 2-EE, humans are unlikely to exhibit adverse effects similar to those observed in animals

5. Alternative Uncertainty Factors

As discussed in a previous section, an ADI (i.e the levels at ewhich humans are unlikely to exhibit effects similar to those observed in humans) is derived by dividing a NOEL by an uncertainty factor. To derive ADIs for glycol ethers, OSHA has used an uncertainty factor of 100; a factor of ten to account for inter-species variability and a factor of 10 to account for intra-species variability. Several of the commentors who responded to OSHA's ANPR for glycol ethers advocated use of a lower uncertainty factor (see, for example, Kodak, Ex. 7-16, and Du Pont, Ex. 7-28). In its comments, CMA argues that an uncertainty factor well below 100 should be used to arrive at new PELs (Ex. 7-17). While CMA presents a number of reasons for its position, OSHA does not find any of its reasons sufficiently compelling to depart from the traditional uncertainty factor for derivation of ADIs across species. What follows here is a brief description of each of the arguments presented by CMA and OSHA's response to these arguments

To begin, CMA states that lower safety factors are appropriate with high quality animal studies. OSHA agrees that the Hanley et al studies and the Tinston et al studies are high quality studies, but the Agency does not see how the quality of these studies reduces either inter-species variability or intra-species variability. Both types of variability are issues in determining a "safe" occupational exposure level from animal data even when such studies are of high quality

CMA argues that lower safety factors are appropriate when NOELs have been established in more than one species. CMA notes that not only have NOELs been established for a number of species but the NOELs and the observed effects have also been quite similar across species

While OSHA agrees that one has greater confidence in a NOEL determined in more than one species, the Agency is concerned the CMA has confused the finding of the same NOEL in more than one species with the finding of the same threshold in more than one species. The exposure levels employed by Hanley et al and by Tinston et al were almost identical in each of the species tested. In the case of 2- ME, for example, rats and rabbits were exposed at identical exposure levels and mice were exposed to two of the three same levels. Given this similarity of exposure, it is not surprising that the same NOEL was identified in all three species. One cannot conclude from this, however, that the exposure threshold for developmental effects is the same in all three species. Based on the data from the Hanley et al bioassays, for example, one cannot reject a hypothesis that the "true" NOELs might be 40 ppm for mice, 25 ppm for rats, and 10 ppm for rabbits. The exposure levels employed do not allow one to reject this hypothesis, thus one cannot conclude there is no inter-species variability for 2-ME. The same is true for 2-EE. In addition, the small number of animals used in each of these bioassays, (no study used more than 30 animals in each exposure group and most used less), limited the power of these bioassays to detect lower NOELs. For these reasons, OSHA cannot support the use of a lower safety factor on these grounds as advocated by CMA

In addition, OSHA does not agree that the effects observed across species exposed to the same glycol ethers were quite as similar as CMA maintains. In the case of 2- ME, the only effects observed to occur at a statistically significantly greater rate in the high dose groups of rats and mice were minor skeletal defects. In high dose rabbits, however, the effects were far and away more severe including major external alterations, major soft tissue alterations, and major skeletal alterations. In the case of 2-EE, it is difficult to compare effects across species because of differences in exposure levels used for the high dose group

CMA`s third reason for advocating an uncertainty factor well below 100 is that data on inter-species metabolism and pharmacokinetics can be employed to justify this. As discussed in the Health Effects section of this preamble, the evidence indicates that the four glycol ethers of interest here are most likely metabolized via the alcohol dehydrogenase (ADH) pathway in both animals and humans. Although all species seem to share the same metabolic pathway, however, there is also evidence that the species do not metabolize glycol ethers at the same rate. Groeseneken et al found that the biological half-life of 2-EE in humans was 21 to 24 hours compared to the biological half-life of 8 to 12 hours reported in animals (Exs. 5-112, 5-113, and 5- 114). This finding led the study authors to conclude that the metabolites of 2-EE will not be cleared from the urine by the next morning following exposure and accumulation of the metabolites may be expected through repetitive exposures. In a study of 2-EEA in humans, Groesenken et al found similar results (Ex. 5-115), and these results were confirmed in study of female silk screen operators exposed to 2-EE and 2-EEA by Veulemans et al (Ex. 5-114). The finding of a longer biological half-life for 2-EE and 2-EEA in humans prompted Veulemans et al to note that "it would certainly warrant extra caution in the extrapolation of experimental data from laboratory animals to man, since comparable accumulation effects apparently are not found in all species." Although 2-EE and 2-EEA are the only glycol ethers which have been studied in humans, these findings raise enough questions about the similarities of the metabolism and pharmacokinetics of glycol ethers across species to deter the Agency from reducing the uncertainty factor used based on the similarity of the pharmacokinetics and metabolism of glycol ethers across species

CMA's fourth argument is that when dose is expressed in the correct units using the correct cross-species scaling factor, then a lower uncertainty factor can be used. OSHA intends to discuss this issue later in this section in its review of the risk assessment performed by Environ et al (Ex. 4-016f). The Agency does agree with CMA that uncertainty is reduced when dose is expressed in the correct units, but the Agency is not as confident as CMA regarding what are the correct units

CMA's final argument for supporting a lower uncertainty factor is that lower uncertainty factors should be used because exposure is occupational. In an appendix to CMA's comments, E.M. Johnson argues that the 10-fold factor for intra-species variability can be reduced when the exposed population is less diverse than the total population as in the case of workers who tend to be healthier and more homogeneous than the general population (Ex. 7-17, Appendix A)

OSHA cannot agree with this position for a number of reasons. First of all, while it is plausible that a woman who is a worker may be healthier than a woman who is not a worker, CMA presents no evidence that the "healthy worker effect" is conferred upon the developing fetus. Furthermore, a fetus has two parents who contribute to its genetic identity, and there is no reason to assume that the father of a fetus of a working mother is also a "healthy worker". Finally, although "healthy workers" may constitute a homogeneous population, it does not follow that their offspring will constitute a homogenous population, healthy or otherwise

Although OSHA's approach of using an uncertainty factor of 100 may appear conservative, OSHA believes that the uncertainties associated with deriving an ADI for occupational exposure to glycol ethers require the use of this factor. Some of the uncertainties stem from the qualitative nature of the uncertainty factor approach as outlined earlier in this risk assessment (e.g. the unlikelihood that an exposure level used in a bioassay will be the "true" threshold, varying susceptibilities across species, etc.). Other uncertainties stem specifically from the data available for assessing the risk from glycol ethers as noted above (e.g. similar exposure levels used across species, possible differences in metabolism and pharmacokinetics across species, etc.). For these reasons, OSHA has used an uncertainty factor of 100. The Agency seeks comment on its choice of uncertainty factor and its justification for this choice. The Agency seeks detailed reasons for either accepting or rejecting the choice of a 100-fold uncertainty factor and any data available to support the position

D . Assessment of the Reproductive Risk from Exposure to Glycol Ethers

1. Introduction

The Interagency Regulatory Liaison Group, (IRLG), describes reproductive toxicity as dealing with "the effects of toxicants on adult reproductive function and development of the offspring which may be produced by alteration of a wide range of processes in either the female or the male." As noted by the IRLG, these processes include "those associated with the primary and accessory sexual organs and with fertilization, as well as those which impact more indirectly on normal reproductive function; e.g., neuroendocrine control, general physiological and psychological health, and nutrition." The IRLG continues, "[f]ollowing fertilization, processes associated specifically with pregnancy are also vulnerable; e.g., implantation, placental formation and function, conceptal development, and parturation and lactation" (Ex. 5-018)

In its Proposed Guidelines for Assessing Male Reproductive Risk (Ex. 5-123), the EPA identifies a number of measures which may be evaluated to assess the reproductive effects of exposure of males to a potential reproductive toxicant. In animals, these include body weight; weight and histopathology of the testes, epididymides, seminal vesicles, prostate, and pituitary gland; mating ratio and pregnancy ratio; and pregnancy outcomes such as litter size, pre- and post-implantation loss, the ratio of live to dead pups, sex ratios, malformations, birth and postnatal weights, and survival. Supplemental end points of male reproductive toxicity may be identified through sperm and endocrine evaluations. EPA points out that while these measures are useful for evaluating reproductive risk in humans as well as animals, many of these measures such as early fetal loss, reproductive capacity of the offspring, and the invasive measures of reproductive function are not easily observed in humans

The most feasible measures used in studies of reproductive effects in human males are semen evaluations, indirect measures of fertility/infertility, and certain pregnancy outcomes such as fetal loss, birth weight, sex ratio, congenital malformations, postnatal function, and neonatal growth and survival

The measures recommended by EPA for evaluation to determine reproductive effects in female laboratory animals include capacity to conceive; length of time required for conception; alterations in the onset of puberty; alterations in the reproductive cycle; oocyte toxicity; premature reproductive senescence; weight and histopathology of the ovary, the uterus, and the pituitary gland; and the pregnancy outcomes described for males above. In human females, the feasible measures of reproductive toxicity are the measures of fertility and pregnancy outcomes (Ex. 5- 122)

While studies of human populations provide the strongest evidence of the reproductive toxicity of a substance, such studies are usually limited in their ability to detect risk. Like epidemiological studies of cancer mortality and other discrete outcomes, studies of reproductive toxicity in human populations often suffer from lack of statistical power (usually due to small sample size), inexact exposure measurements, and an inability to control for all potential confounding factors. Studies of reproductive toxicity in human populations, however, have additional limitations. Assessment of reproductive endpoints is often dependent upon voluntary participation and self-reporting of outcomes which, in turn, may be influenced by privacy considerations and religious considerations. In addition, there are fewer endpoints which may be feasibly measured in humans than may be measured in laboratory animals. Thus, because of these limitations, reproductive risks are usually assessed from animal studies

2. 2-ME

A number of studies showing reproductive effects in male animals exposed to 2-ME are described in the Health Effects section of this preamble. Results from studies of animals exposed to 2-ME through inhalation are supported by the results from studies of animals exposed to 2-ME through ingestion

The lowest NOEL observed in laboratory animals was observed in a study of New Zealand white rabbits by Miller et al of the Dow Chemical Company (Exs. 4-045 and 5-023). Groups of five male rabbits were exposed to 2-ME at concentrations of 30, 100, or 300 ppm through inhalation for 6 hours per day, 5 days per week, for 13 weeks. A group of 5 male rabbits served as controls. Food and water was provided to the animals ad libitum except during periods of exposure when neither was available

Following 13 weeks of exposure, all surviving animals were sacrificed. Two rabbits in the 300 ppm group died during the exposure phase of the study. The cause of death for one was bronchopneumonia. The cause of death for the second was unknown. All animals were given a complete gross pathological exam, and a histological exam was performed on selected tissues from each animal

Reduced testes weight was observed in rabbits in the 300 ppm and 100 ppm exposure groups, and although this effect was statistically significant for the 300 ppm group only, the study authors attributed the observation in both groups to exposure. Gross pathological exam showed that all of the rabbits in the 300 ppm group had very small and flaccid testes. A slight to moderate decrease in testes size relative to the control animals was observed in 4 out of 5 of the rabbits in the 100 ppm group (p=0.024, Fisher's Exact Test), and 2 out of 5 of the rabbits in the 30 ppm, group (p > 0.05). Histopathologic exam confirmed the gross pathological observations. A dose-related increase in both the incidence and severity of testicular degenerative changes was seen in the test animals. In all three of the rabbits on the 300 ppm group, which survived through the end of the study, the degeneration was diffuse and severe with virtually every tubule affected. In the three rabbits with testicular degeneration in the 100 ppm group, more of a spectrum of effects was noted in that within the same testes, some tubules were relatively normal in appearance while others contained no germinal elements at all. In the 30 ppm group, the microscopic degenerative changes were apparent in the testes of only one of the two rabbits observed to have decreased testes size in the gross pathological exam. The microscopic degenerative changes observed in this animal were an excess of tubules in which the germinal epithelium was thinner than normal, with a complete complement of germinal stages but very few spermatozoa

Histopathologic exam of the epididymis found that the epididymal sperm content generally reflected the degree of testicular damage with noticeable decreases in those cases which were moderately to severely affected. Degenerating spermatic elements were commonly observed, but secondary changes in accessory sex glands were not seen

Despite the small number of animals in each exposure group, a significant dose-related effect was observed. Based upon the outcome of decreased testes size, one of the outcomes identified by EPA as an adverse reproductive outcome, the NOEL for reproductive effects of 2-ME in rabbits is 30 ppm

Given that the NOEL for reproductive effects from 2-ME has been derived from animal studies, OSHA believes that an uncertainty factor of 100 is appropriate for derivation of the ADI as was the case for the assessment of developmental risks from exposure to 2-ME. Here again, an uncertainty factor of 100 provides a factor of 10 for inter-species variability and a factor of 10 for intra-species variability. Therefore, based upon this study Miller et al, the ADI for 2-ME would be 30/100 or 0.3 ppm on the basis of reproductive risks. The ADI for 2-ME based on developmental risks is 0.1 ppm, somewhat lower than the ADI based on reproductive risks but the two ADIs are very close. Thus an ADI, of 0.1 ppm would cover both reproductive and developmental effects, i.e. at this level humans are unlikey to exhibit adverse effects (both reproductive and developmental) similar to those observed in animals

3. 2-EE

There are fewer studies of the reproductive effects of 2-EE in the literature than there are of 2-ME, but like 2- ME, 2-EE has been found to induce adverse reproductive effects in laboratory animals

This was the finding of Terrill et al who conducted a study for the Chemical Manufacturers Association exposing rabbits to 2-EE (Exs. 4-108 and 5-084). Groups of ten male New Zealand white rabbits were exposed to 2-EE at concentrations of 25, 100, and 400 ppm through inhalation for 6 hours per day, 5 days per week, for 13 weeks. A group of ten male rabbits served as controls. Food and water was provided to the animals ad libitum except during periods of exposure when neither was available

All animals survived the exposure phase of the study. At terminal sacrifice, all animals were given a complete gross post mortem exam. Animals in the control and high dose groups were given a complete histopathological exam, but for the low and middle dose groups, only the bone marrow, the testes with epididymis, the kidneys, the liver, the lymph nodes, the spleen, the thymus, and any observed gross lesion or tissue mass were examined

In the 400 ppm group, there was a statistically significant decrease in absolute testes weight and in testes weight relative to body weight. Gross postmortem examination revealed that in three of the ten rabbits from this group, there was slight focal tubule degeneration. Based upon decreased testes weight, the NOEL for reproductive effects for 2-EE in rabbits is 100 ppm

Although there are fewer animal studies of the reproductive effects of exposure to 2-EE than 2-ME, the results of the animal studies are supported by observation in human populations. In a study of male workers at Precision Castparts Corporation, NIOSH reported significantly reduced sperm count among workers exposed to 2-EE compared to workers with no such exposure (Ex. 5-003). Welch et al also found reduced sperm in a group of shipyard painters exposed to 2-EE, but theses workers were also exposed to 2-ME, so it is impossible to determine whether the effect was due to 2-EE, 2-ME, or both glycol ethers (Ex. 5-104). These studies are discussed in greater detail in the Health Effects Section of this preamble

Applying an uncertainty factor of 100 to the NOEL of 100 ppm reported by Terrill et al in their study of New Zealand white rabbits, one would arrive at an ADI of 100/100 or 1 ppm for 2-EE basee on reproductive risk. Here again, however, the ADI must be based on developmental risks as well as reproductive risks. The ADI for 2-EE based on developmental risks is 0.5 ppm, lower than the ADI based reproductive risks. As is the case for 2-ME, for 2-EE the ADI based on reproductive risks is very close to the ADI based on developmental risks. At an ADI of 0.5ppm 2-EE humans are unlikely to exhibit effects (both reproductive and developmental) similar to those observed in animals

E. Assessment of Risk from Exposure to Glycol Ether Acetates

The acetates of 2-ME and 2-EE, 2-MEA and 2-EEA, have not been studied as extensively as have the parent compounds. As noted in the Health Effects section of this preamble, however, the acetates have been shown to induce adverse reproductive, developmental, and hematological effects in animals similar to those induced by 2-ME and 2- EE. Furthermore, as discussed in the Health Effects section, it has been shown that 2-MEA and 2-EEA are metabolized to the same acetic acids, methoxyacetic acid (MAA) and ethoxyacetic acid (EEA) respectively, by the same mediated pathway, an alcohol dehydrogenase (ADH) mediated pathway, as their parent compounds

Because of the similarity in induced effects between the acetates and their parent compounds and because of the similarity in metabolism between the acetates and their parent compounds, OSHA proposes that the ADIs derived for the acetates be the same as for their parent compounds. That is, the ADI for for 2-MEA is 0.1 ppm and the ADI for 2- EEA. is 0.5 ppm

There is some experimental evidence to support OSHA's proposal. As reproductive toxicants, the acetates have been shown not only to induce similar effects as their parent compounds, but also to induce these effects at equivalent doses. Nagano et al found that male mice exposed orally to 2-MEA at 500 mg/kg of body weight experienced significant decreases in testicular weight. When this dose was converted to mmole/kg, the authors found that on an equimolar basis, exposure to 2-ME and 2-MEA resulted in similar effects (Ex. 4-135). Likewise, these authors found that on an equimolar basis, male mice exposed to 2-EE and male mice exposed to 2-EEA experienced similar adverse reproductive outcomes (Ex. 4-135)

The acetate 2-MEA has not been tested for its potential to adversely affect reproductive outcomes. Only limited data exist on 2-MEA, according to CMA, because of the small production volume of this acetate (Ex. 7-17). Nonetheless, CMA argues that although detailed evaluation of the developmental toxicity of 2-MEA has not been conducted as it has for 2-ME, "the NOELs determined for 2-ME can be reasonably employed for assessing this compound. The likelihood that any effect it may cause would occur through human metabolism of 2-MEA to 2-ME and then to the active metabolite makes it reasonable to employ the NOELs for 2-ME to protect humans against effects of 2-MEA" (Ex. 7-17). OSHA concurs with CMA's position

Unlike 2-MEA, 2-EEA has been tested to determine its potential as a developmental toxicant. Nelson et al reported a statistically significant excess of developmental effects in rats exposed to 2-EEA at levels as low as 130 ppm (Ex. 5-091). This level was the lowest exposure level used in this bioassay therefore no NOEL was established for this study. Doe et al exposed pregnant Dutch rabbits to 0, 25, 100, or 400 ppm of 2-EEA, and the fetuses of rabbits exposed to levels as low as 100 ppm showed a dose-related increase in skeletal defects (Ex. 5-071). Tyl et al exposed pregnant Fischer 344 rats and pregnant New Zealand white rabbits to 0, 50, 100, 200, or 300 ppm of 2-EEA (Ex. 5-124). Here again, 100 ppm was the LOEL for developmental effects in both species. This level, 100 ppm, is OSHA's current PEL for 2-EEA. Fifty ppm was established to be the NOEL for both the rats and the rabbits. Because Doe et al and Tyl et al established the same LOEL in two separate studies and in two different species, it is reasonable to use the NOEL from the Tyl et al study, 50 ppm of 2-EEA, as the NOEL for calculating the ADI. As with the parent compounds, an uncertainty factor of 100 is appropriate, and this would lead to an ADI of 50 ppm/100 or 0.5 ppm. That is, at an ADI of 0.5 ppm 2-EEA, humans are likely to exhibit effects similar to those observed in humans

OSHA's proposal for deriving ADIs for the acetates at the same level as those for the parent compound also has support from a number of commentors who responded to OSHA's ANPR. For example, NIOSH wrote that a separate PEL for each of the acetates and their parent compounds "should not be necessary because of the similarities in the adverse effects, the similarity in route of exposure, and the fact that in many situations, several of the ethers and their acetates are used simultaneously" (Ex. 7-22). Similarly, Du Pont noted that "2-methoxyethanol (2-ME) and its acetate (2- MEA) and the [sic] 2-ethoxyethanol (2-EE) and its acetate (2-EEA) could be regulated together because the toxic effects of these glycol ethers and their respective acetates are the same" (Ex. 7-28), and Kodak proposed the same PELs for 2-ME and 2-MEA and for 2-EE and for 2-EEA, (Ex. 7-23), although the levels proposed are different than those proposed by OSHA. OSHA seeks comment on this approach to deriving ADIs for the glycol ether acetates

F. Other Approaches to the Assessment of Risk for Glycol Ethers

1. The Crump Risk Assessment

Under contract to OSHA, K.S. Crump and Company performed a risk assessment for developmental and reproductive effects from exposure to 2-ME, 2-EE, and their acetates (Ex. 5-136). The data used for this analysis were from the studies of developmental effects of exposure to 2- ME by Hanley et al (Exs. 4-042a and 4-106) and to 2-EE by Tinston, Doe et al (Exs. 4-038 and 4-039; see also Ex. 5- 071) and the studies of reproductive effects of exposure to 2-ME by Miller et al (Ex. 5-057) and to 2-EE by Terrill et al (Exs. 4-108 and 5-084). At the time Crump performed its analysis, no data were available on the developmental effects of 2-EE as measured in litters. Therefore, Crump limited its analysis of the developmental effects of 2-EE exposure to responses observed in fetuses. No analyses were done on data from studies of the acetates. Crump noted that "2-MEA and 2-EEA are believed to be quickly hydrolized to their corresponding glycol ether. Furthermore, evidence suggests that from that point on, their metabolism and distribution proceed in the same manner as the ether. If that is the case, a mole of an ether will yield the same amounts of products as a mole of the corresponding acetate. Moreover, a given air concentration in ppm contains the same number of moles (1 ppm is about 41 micromoles per cubic meter at standard temperature and pressure), for all chemicals. Consequently, in the absence of data on the acetates needed for risk assessment, it is reasonable to assume that the acetates and their corresponding ethers will produce the same risks at equal air concentrations, in ppm" (Ex. 5-136)

The goal of the Crump risk assessment was to develop dose-response models for developmental and reproductive effects. Only brief descriptions of the models and methods used by Crump are presented here, and the reader is referred to the Crump report (Ex. 5-136) for additional details. Two approaches were taken to develop these models for the outcomes of interest. The first of these applied methods similar to those applied to cancer data, but the dose- response models considered were non-linear or incorporated a threshold. Four models employed this approach: the quantal linear regression (QLR) model, the Weibull model, the continuous linear regression (QCR) model, and the continuous power (CP) model. The QLR and Weibull models were used for incidence data measured in fetuses, and therefore do not take litter size or intra-litter correlation (i.e. the litter effect) into account. The QCR and CP models were used for incidence data measured in litters, and they account for the litter effect but not for litter size. The QLR and QCR models assume a threshold with a linear response above the threshold. The Weibull and CP models are non- threshold models but can be non-linear if indicated by the data

The second approach taken by Crump was to consider two models recently developed specifically for assessing developmental effects, (these models use only litter data), and to modify these for the analysis of the glycol ethers data. The first of these was developed by Kodell et al. This model uses the beta-binomial distribution to account for the litter effect and takes into account the effect of litter size on the probability of a developmental effect. The second model considered by Crump was originally put forth by Rai and Van Ryzin. This model takes litter size into account but does not account for the litter effect. In its analysis, Crump used two special cases of the Kodell model, the Kodell-QLR model which assumes a threshold but is linear above the threshold, and the Kodell-Weibull model which assumes no threshold but can be non-linear. Only one case of the Rai and Van Ryzin model was considered. This model assumes no threshold and is linear. Crump felt the shortcomings of the Rai and Van Ryzin model made it less appropriate for assessing risk than the other models considered

Crump applied the models described here only to data on developmental outcomes. The models developed for use with litter data could not be used with the data Crump had on reproductive outcomes because the data Crump had measured these outcomes in individual animals and not litters. Likewise, the models developed for use with litter data could not be used with the data Crump had on developmental outcomes from 2-EE exposure because, as noted above, litter data for these effects were not available to Crump when it did its analysis. The models developed for use with fetal data could have been used with the data on reproductive outcomes, but Crump did not use these models to analyze the data on reproductive effects because of the small number of animals used in these bioassays

Although the goal of the Crump risk assessment was to develop dose-response models for the outcomes of interest, two additional approaches for determining a "safe" level of exposure were considered. The first of these was to calculate a NOEL using a no-statistical-significance-of- trend or NOSTASOT approach. In this approach, tests of statistical hypothesis were conducted to determine whether the bioassay data provided sufficient statistical evidence to conclude that a dose-related trend existed, (i.e. whether response increased with dose), and if so, to determine the highest dose used in the bioassay such that there was no statistical evidence of a dose-related trend in response at that dose or at lower doses. The highest dose which showed no statistical evidence of a dose-related trend is called the NOSTASOT dose and is considered to be a statistically determined NOEL. This approach was used for both developmental and reproductive outcomes for both 2-ME and 2- EE

The final approach considered by Crump was calculation of a benchmark dose as an alternative to the NOEL. A benchmark dose is defined as the statistical 95% lower confidence limit on the dose corresponding to a 1% increase in the extra risk. The dose corresponding to a 1% increase in extra risk was estimated using both the QLR model and Weibull model, but only the lower of the two benchmark doses was reported. Crump chose to use only these two models to estimate the benchmark doses because these two models were the only two used to analyze all of the data on adverse reproductive outcomes for both 2-ME and 2-EE

The NOSTASOT dose and the benchmark dose calculated by Crump are much like the NOELs calculated by OSHA in that neither of these doses alone represents a "safe" level of exposure. Rather, Crump intended an uncertainty factor to be applied to either of these doses, although Crump did not recommend a particular uncertainty factor in his report. Crump argues that either is preferable to a NOEL established using traditional methods because they make use of all of the dose-response data. Crump notes that NOELs "determined by comparing treatment groups individually to the control group . have low power because they involve only the animals in two of the treatment groups, when in fact the data from any intermediate doses are also relevant. Thus a common result is that the trend test is significant, but none of the treated groups differ significantly from the control group."

Results of the Crump analysis are presented in Tables VI- K through VI-N. Although the sources of the data used by Crump were the same as those used by OSHA, the adverse outcomes considered and the specific estimates of incidence were different. These data are presented in the Crump report

Table VI-K shows that for 2-ME, NOELs established using the NOSTASOT approach are identical to those established by OSHA using more traditional methods. For 2-EE, Table VI-L shows that for all but one outcome in rats, total abnormal ribs, Crump's NOSTAOTs are the same as OSHA's NOELs, but for rabbits, Crump's NOELs are lower. This difference is due to the fact that Crump used fetus data for its analysis of 2-EE whereas OSHA used litter data in its analysis to establish the NOEL

a - From the Crump Report, Ex. 5-136
b - NOSTASOT = No statistical significance of trend (i.e. the NOSTASOT exposure is the highest dose for which dta did not show a statistically significant dose-related trend). See text for details
c - Benchmark exposure is the 95% lower limit on doses corresponding to an extra risk of 1%. See text for details
d - Data from Hanley et al, Ex. 4-042a
e - Data from Hanley et al, Ex. 4-106
f - Data from Miller et al, Ex. 4-045
g - N/C = not calculated

a - From the Crump Report, Ex. 5-136
b - NOSTASOT = No statistical significance of trend (i.e. the NOSTASOT exposure is the highest dose for which dta did not show a statistically significant dose-related trend). See text for details
c - Benchmark exposure is the 95% lower limit on doses corresponding to an extra risk of 1%. See text for details
d - Data from Tinston et al, Ex. 4-038
e - Data from Tinston et al, Ex. 4-039
f - Not defined. A significant effect was seen at the lowest dose
g - Data from Terrill et al, Ex. 4-108
h - N/C = not calculated

For almost every adverse outcome considered, Tables VI- K and VI-L show that the benchmark dose is lower than the NOEL estimated using the NOSTASOT approach. Here again, this could be due to the fact that benchmark doses were estimates from models which use fetal data rather than litter data. Were benchmark doses to be used to calculate the ADIs, the result would be a more conservative estimate of the exposure below which an adverse outcome is unlikely than the estimates derived by OSHA

Tables VI-M and VI-N show that despite the differences among the models used by Crump, for the majority of data sets the models predict surprisingly consistent risks. The largest difference in predicted risks are found at low doses between the threshold and non-threshold models. Much less difference can be attributed to whether the models use fetal or litter data. Crump suggests one reason that the shape of the dose-response curve is more important in determining a risk estimate than the type of data used may be the low intra-litter correlation estimated for the 2-ME data sets. Crump explains that "[f]or the rat data, intra-litter correlations, as estimated by the Kodell-QLR or Kodell- Weibull models, did not exceed 0.05 . Somewhat larger correlations were observed in some of the rabbit and mouse data sets (ranging up to about 0.27). Apparently, intra- litter correlations of this magnitude are not sufficient to cause maximum-likelihood estimates derived ignoring the litter effect to be seriously in error."

a - From the Crump Report, Ex. 5-136. The models considered are the quantal linear regression (QLR) model, the Weibull model, the continuous linear regression (QCR) model, the continuous power (CP) model, two cases of the Kodell model - the Kodel-QLR model and the Kodel-Weibull model, and the Rai and Van Ryzin model. The number in parentheses are the 95% upper confidence limit on risk. No 95% upper confidence limit was calculated for the Rai and Van Ryzin model. See text for details
b - Dose is adjusted by a factor of 8/6. See the Crump report for details
c - Data from Hanley et al, Ex. 4-042a
d - Data from Hanley et al, Ex. 4-106

a - From the Crump Report, Ex. 5-136. The models considered are the quantal linear regression (QLR) model, the Weibull model, the continuous linear regression (QCR) model, the continuous power (CP) model, two cases of the Kodell model - the Kodel-QLR model and the Kodel-Weibull model, and the Rai and Van Ryzin model. The number in parentheses are the 95% upper confidence limit on risk. No 95% upper confidence limit was calculated for the Rai and Van Ryzin model. See text for details
b - Dose is adjusted by a factor of 8/6. See the Crump report for details
c - Data from Tinston et al, Ex. 4-038
d - Data from Tinston et al, Ex. 4-039

Crump notes that although the maximum likelihood estimates (MLEs) of risk are similar regardless of whether one accounts for the litter effect, the 95% upper confidence level (UCL) can be noticeably affected. Crump states that for "several data sets for which the maximum likelihood estimates are similar when estimated by the QLR (or Weibull) model and the Kodell-QLR (or Kodell-Weibull) model (e.g. extra lumbar ribs in mice, for which the intra-litter correlation estimates are highest), the upper limits are smaller when the litter effect is ignored."

For 2-ME, the models and data sets predict a range of risks of developmental effects from 2.2 to 430 per 1000 fetuses at the current OSHA PEL of 25 ppm. The lowest risk comes from the Weibull model applied to data on total major malformations in rabbits. The highest risk comes from the QLR model applied to these same data. Crump attributes this large spread within the same data set to the non-linearity of the dose-response relationship and "the lack of experimental evidence regarding the dose-response curve between 10 and 50 ppm." Crump concludes that if "there had been an additional experimental exposure between 10 ppm and 50 ppm, the difference among the models would likely have been sharply reduced."

For 2-EE, Crump did not estimate risks at the current OSHA PEL of 200 ppm. The highest dose level which Crump considered for its analysis of 2-EE was 5 ppm. At this exposure level, the models and data sets predict a range of risk of developmental effects from 0 to 37 per 1000 fetuses. The lowest risk comes from the QLR model applied to data on minor skeletal defects in rats. The highest risk comes from the same model applied to data on total abnormal ribs in rats

At 0.1 ppm, Table VI-M shows that the predicted risks of developmental effects range from 0 to .67 per 1000 fetuses when derived from models which incorporate thresholds and from approximately zero to 1.1 per 1000 fetuses when derived from models which do not incorporate thresholds. At 0.5 ppm, Table VI-N shows that the predicted risks of developmental effects range from 0 to 3 per 1000 fetuses when derived from the model which incorporates a threshold and from approximately zero to 3 per 1000 fetuses when derived from the model which does not incorporate a threshold

Although Crump's approach provides methods for quantifying reproductive and developmental risks, none of the methods proposed in the report has been generally accepted within the risk assessment community. The NOEL/uncertainty factor approach, on the other hand, has broad acceptance for the assessment of reproductive and developmental risks. Furthermore, Crump's risk assessment provides no criteria for selecting one model or method over another. Since none of the models has a biological basis, it is impossible to determine which is the most appropriate model to use. Given the broad range of risks predicted from each of the models, some criteria must be developed for choosing one or another before Crump's approach can be used for quantitative risk assessment. For these reasons, OSHA has not relied upon the Crump report as the basis of its quantitative risk assessment for glycol ethers

Crump`s risk assessment raises a number of issues including whether developmental and reproductive risks can be quantified and these issues deserve serious discussion. In addition to proposing dose-response models for quantifying the risk of developmental effects, Crump has proposed two alternatives, the NOSTASOT dose and the benchmark dose, to the traditional NOEL used by OSHA in its risk assessment. OSHA seeks comment on the issues raised in this report as well as on the specific methodology employed by Crump to quantify the risk of adverse reproductive and developmental effects

2. The Hattis Risk Assessment

In an attempt to quantify the reproductive and developmental risks associated with glycol ethers exposure, Dale Hattis et al developed three quantitative approaches: one for estimating the risks of adverse effects on male fertility (Ex. 5-109); one for estimating the risks of adverse developmental outcomes (Ex. 5-121); and one for estimating the risks of infant mortality (Ex. 5-121). To estimate risks on male fertility, sperm counts and pharmacokinetically-derived exposures from workers exposed to 2-ME and 2-EE were used as a basis for estimating percentage reductions in fertility. Animal studies in which 2-ME and 2-EE induced fetal death and fetal malformations were used as a basis for estimating the risk of adverse developmental outcomes in human fetuses. Animal studies in which 2-ME and 2-EE induced fetal weight reduction were used as a basis for estimating the risk of infant mortality in humans. The following discussion briefly summarizes these approaches. For a more complete description of these analyses and the underlying assumptions, the original studies should be consulted

a. Risk Analysis on Male Fertility Effects (Ex. 5-109)

The goal of this analysis was to quantify the effects on male fertility that could be expected from reductions of sperm counts induced by 2-EE and 2-ME. Thus sperm count was the basic measure used to calculate a risk of infertility. The authors acknowledged that sperm counts are not ideal for this purpose because sperm counts are only one of several parameters (e.g. % normal sperm, % motile sperm, and age of patient) that are known to have an effect on male reproductive potential. In addition the authors stated that a direct relationship between sperm count and male fertility performance may be an over simplification. However the authors chose sperm counts because no other type of sperm quality parameters were available in the underlying data used for this quantitative analysis

The sources of experimental data used in this analysis included (1) a pharmacokinetic model developed by Hattis et al for 2-EE (Ex. 5-095), (2) worker exposure studies on shipyard painters (Exs.5-101, 5-102 and 5-103) and foundry workers (Ex. 5-003) and (3) a quantitative model developed by Meistrich (Ex. 4-161) for estimating sperm reduction factors and increases in excess infertility

In their pharmacokinetic analysis (Ex. 5-095), Hattis et al developed four different pharmacokinetic models using clinical data from studies in which human volunteers were exposed to 2-EE. These models described the uptake and metabolism of 2-EE to its primary metabolite ethoxyacetic acid (EAA). The models also described the urinary excretion of EAA. Mathematical formulas derived from these models were presented as a means for calculating 2-EE equivalent air exposure levels from urinary EAA excretion data

As a first step in the risk analysis, urinary EAA excretion data from the foundry workers and the shipyard painters were converted to 2-EE equivalent air exposures (ppm) using the formulas derived from the Hattis et al pharmacokinetic model. The authors noted that the shipyard painters also had "appreciable" exposures to 2-ME. Thus 2- EE equivalents for these workers were adjusted to account for 2-ME. This was accomplished by assuming that 2-ME was 4.3 times more potent than 2-EE (based on animal studies ) and that workers were exposed to 0.8 ppm 2-ME for every 2.6 ppm 2-EE

In the second step of this analysis, sperm counts were analyzed and found to decline among both sets of workers although neither of the observations from these groups was statistically significant. The percent reduction in sperm count for these groups of workers was then compared to the calculated 2-EE equivalents air levels:

The authors noted that results from both of these studies reinforced one another showing suggestive declines in sperm counts with 2-EE exposure. However these results indicate that there is a stronger sperm reduction effect with lower dose among the shipyard painters. Possible explanations offered by the authors included (1) chance statistical fluctuations in the data and (2) potential peak exposures prior to sampling the population. Nevertheless, the shipyard painter data was selected for the authors "best estimate" risk projections as this study had more complete exposure data and a larger number of workers, making this study "more likely representative of reality"

In the final step in this analysis, work by Meistrich (Ex. 4-161) was applied to sperm count reductions calculated in the previous steps to estimate an "excess infertility risk". Meistrich developed a method, using testicular toxicity data in rats and analyses of sperm count distributions in "fertile" and "infertile" couples, to calculate the "risk of infertility" as a function of sperm count. In his model Meistrich defined infertility as the degree of subfertility required to bring about a need to consult a physician. Meistrich assumed that a 1% increase in infertility (i.e. 1 in 100 couples) was an "acceptable risk". He also assumed that the background risk of infertility in the general population was 15%. Using these assumptions and definitions, Meistrich estimated that a 1% increase in excess infertility corresponds to a sperm reduction factor of 1.24. Using this basic relationship, Hattis et al. calculated sperm reduction factors and corresponding increases in excess infertility for the sperm count reductions observed among the shipyard painters at various 2-EE equivalent air exposures:

Based on the results of this analysis Hattis concluded that in order to achieve a goal of having no more than 1 in 100 couples (i.e. 1%) suffering "infertility", exposures to 2-EE must be kept below a geometric mean of 3.3 ppm. Achieving a goal of no more than 1 in 400 couples suffering infertility would require exposures 1/4 of that level (i.e. 0.82 ppm). Furthermore assuming that 2-ME is 4.3 times more potent than 2-EE, Hattis estimates that a corresponding dose for 2-ME of 0.46 ppm would be required to assure that no more than 1 in 100 couples will suffer from infertility

These quantitative estimates must be viewed in light of the uncertainties and assumptions used to calculate them. First, both the shipyard painter and foundry worker studies had a small number of exposed workers with sperm count reductions bordering on statistical significance. Furthermore, as noted by Hattis et al, as well as the original authors of the shipyard painter studies, the EAA excretion levels calculated from these may be a poor proxy for exposures associated with sperm count reduction. The EAA excretion levels represented exposure to 2-EE in the last few days whereas the sperm counts which were measured at approximately the same time. would have been effected by exposures weeks earlier. Because the shipyard painters changed tasks at the shipyard frequently, EAA excretion levels representing these workers' exposure within the last few days may not adequately represent exposure levels weeks earlier which would have been responsible for the sperm counts collected

Second, the Meistrich approach for calculating sperm reduction factors assumes a "one-hit" killing function for sperm which may or may not be biologically correct. Furthermore Meistrich uses a very subjective definition of infertility (i.e. degree of subfertility required to bring about the need to consult a physician)

These sources of uncertainty are compounded by the uncertainty of the 2-EE air equivalents which were calculated using the Hattis pharmacokinetic model. This pharmacokinetic model carries with it its own set of assumptions and uncertainties. Thus considerable uncertainty is associated with the quantitative estimates derived from this risk analysis on male fertility

b. Risk Analysis on Developmental Effects (Ex. 5-121)

The goal of this analysis was to quantify the risk of adverse developmental effects associated with in utero exposure to glycol ethers. Two separate approaches were employed. In the first approach, quantal effects data from animal studies (e.g. fetal death and malformations) were used to estimate the risk of similar adverse effects in humans. In the second approach, continuous effects data from animal studies (e.g. changes in fetal weight) were used to project changes in birth weight and potential changes in infant mortality in humans. Quantal Effects Analysis

Hattis et al selected six different animal studies examining the developmental toxicity of various glycol ethers. [Andrew and Hardin (Ex. 5-069), Doe (Ex. 5-0710, Hardin and Eisenmann (Ex. 5-097), Weir (Ex. 5-120), Greene (Ex. 5-096), and Hanley et al (Ex. 4-120)]. These studies reported statistically significant increases in the incidence of adverse developmental effects including fetal death, skeletal defects, external malformations and digit or limb malformations. Dose response data from the animal studies were used to calculate an ED50 for those effects which were statistically significantly different from the controls. An ED50 is the dose at which 50% of an otherwise unaffected proportion of the population suffers an effect. The ED50 was derived using a log-probit analysis. This probit analysis assumes that effects occur in individual animals when specific thresholds of dose are exceeded and that there is a lognormal distribution of thresholds in the exposed group of animals or humans. ED50s from the animal studies were then converted to 8 hour human ED50s (ppm). This ED50 represents a dose at which 50% of an population will be affected by the chemical after an 8 hour exposure. Overall ED50 estimates were derived by taking geometric means of ED50s calculated for 2-ME and 2-EE for individual effects. Six "best estimates" were derived in this manner. These "best estimates" were then used to calculate the doses of 2-ME or 2-EE corresponding to risks of one in a hundred (10-2), one in ten thousand (10-4) and one in a million (10-6) for a particular developmental effect (Table VI-O)

Assuming that a ppm exposure in humans would present the same risk as those observed in animals, Hattis et al concluded that these projections suggest that doses as low as 0.36 ppm 2-EE would produce a risk of one in a hundred for skeletal defects and doses as low as 0.68 ppm 2-ME would produce a risk of one in a hundred for total malformations. It is interesting to note that from these two estimates 2-ME appears to be less potent than 2-EE which is contrary to most of the experimental data

Continuous Effects Analysis

In this analysis animal data showing fetal weight reduction after exposure to 2-ME and 2-EE were used to calculate percentage reductions in fetal weight as a function of dose of 2-ME or 2-EE. For purposes of this analysis it was assumed that animals and humans would exhibit equal growth retardation for a given rate of glycol ether exposures expressed in ppm-hours per day. It was further assumed that percentage changes in fetal weight prior to birth would reflect similar percentage changes in birth weight. Percentage reductions in birth weight could then be used to project likely effects on infant mortality

As a first step, Hattis et al analyzed birth weight distributions and infant mortality rates from both black and white infants in the United States . These distributions were used to derive a relationship between infant mortality and birth weight changes

As a second step, the relationship between fetal weight reduction (i.e. birth weight reduction) and the dose of 2-ME or 2-EE from the animal studies were combined with the relationship between birth weight changes and infant mortality from human infants. These two sets of relationships were used together to estimate expected changes in infant mortality for a given 8 hour exposure to 2-EE or 2-ME. Table VI-P presents the projected changes in infant mortality due to possible changes in infant birth weight associated with 2-EE and 2-ME exposures

Extracted from Table 4-6, Hattis et al (Ex. 5-121)

As was the case for the male fertility analysis, the quantitative estimates derived from both the quantal and continuous effects data incorporate a number of large assumptions. The largest of these may be the assumption that a particular defect observed in an animal will translate into a similar defect in humans. As discussed earlier in the Health Effects section of this preamble, although adverse developmental effects in animals provide clear evidence of a chemical's potential ability to perturb development in humans, the effects observed in animals may not necessarily be identical to those which could potentially occur in humans. Even the authors themselves acknowledge that the risk calculations are based on a series of assumptions which carry considerable uncertainty. OSHA acknowledges that assumptions are often necessary for quantitative risk analyses. However given the lack of knowledge about the biological processes involved in reproductive and developmental toxicity, OSHA believes that the assumptions of these quantitative analyses may carry much more uncertainty than for other types of health outcomes such as cancer where the biological mechanisms are better understood

In summary, the quantitative approaches of Hattis et al are very innovative. These approaches however, require that a number of large assumptions be made. These assumptions create considerable uncertainty in the quantitative risk estimates which are derived. In addition, the underlying data upon which these approaches are constructed have weaknesses of their own which further compound the uncertainties in the risk estimates. Nevertheless, these approaches do provide a starting point for a discussion of the quantitative risk assessment for reproductive and developmental toxins. Therefore OSHA welcomes all comments and analyses on these approaches for deriving quantitative risk estimates for adverse reproductive and developmental effects

3. The Environ Risk Assessment

Under contract to the Chemical Manufacturer's Association (CMA), Environ Corporation prepared a report entitled "Scientific Basis for Safety Factors Needed to Protect Workers from Reproductive Toxicities of Glycol Ethers" (Ex. 4-016f). This report contains a brief review of the data available for a qualitative analysis of the health effects associated with glycol ethers and their acetates, but the primary focus of the report is the choice of uncertainty factor for determining an acceptable daily intake (ADI) for each of the substances

Environ's approach for choosing an uncertainty factor, (which Environ refers to as a safety factor), was to compare the lowest effective dose (i.e. the LOEL) in humans measured in milligrams per kilogram per day for ten substances known to cause developmental effects with the lowest effective dose measured in milligrams per kilogram per day in the most sensitive species of animal in which the substance has been tested and in which the observed effects were similar to those in humans. These data come from two sources: a 1981 report from the Council on Environmental Quality (CEQ) entitled "Chemical Hazards to Human Reproduction" and a 1984 report from the National Center for Toxicological Research (NCTR) entitled "Reliability of Experimental Studies for Prediction of Hazards to Human Development." By examining these data on other developmental toxicants, Environ sought to obtain information which could be "useful for judging the magnitude of the uncertainty factor needed to protect humans from the developmental effects of [glycol ethers]."

Environ drew two conclusions from its analysis:

1. Application of a safety factor of 10 to NOELs from the most sensitive animal species would have been adequate to protect humans from the effects of most developmental toxicants for which quantitative dose-response data are available; and



2. A safety factor of 50, similarly applied, would have been adequate to protect humans from the effects of all developmental toxicants for which quantitative human dose-response data are available, although this factor may not have been adequate for one substance, thalidomide, assuming the rabbit (rather than the most sensitive species) had been chosen as the basis for establishing acceptable human exposures. If the most sensitive species had been chosen for thalidomide, a safety factor of 10-20 would have been adequate

Environ supplemented this approach with an examination of historical precedents for the selection of uncertainty factors used to protect worker populations from the types of toxicity associated with glycol ethers or from other serious forms of toxicity. Environ stated that such information, "while not strictly scientific in nature, can further assist decision-making because it reveals the range of safety margins which other responsible decision-makers have accepted, and presumably reveals the safety margins that have proved adequate to protect worker populations. Information on the expected relative susceptibilities of the worker and the general populations and on how this has influenced the selection of safety factors will also be useful."

Environ looked at the guidelines or standards for protecting workers from reproductive hazards developed by OSHA, NIOSH, ACGIH, and the American Industrial Hygiene Association (AIHA) "in order to provide an estimation of the margin of safety associated with [their] standards and guidelines." Environ noted that "[u]nlike the case of standards developed for general population exposure to chemicals, [for worker populations] there has been no generic approach we can identify for the application of safety factors to the NOEL identified in experimental animals. This is true for both reproductive and other non- carcinogenic effects."

Environ found that as of 1985, the date of the Environ report, OSHA had regulated five substance principally on the basis of reproductive toxicity. These substances and their respective margins of safety were carbaryl, 5 times lower than the NOEL identified in animals; carbon disulfide, 1.3 times higher than the LOEL identified in animals; DBCP, 38 times lower than the NOEL identified in animals; chloroprene, 5 to 25 times higher than the LOEL identified in humans; and PCBs, 6 times lower than the LOEL identified in humans. (OSHA notes that the Environ report was written prior to promulgation of OSHA's Final Rule for Air Contaminants, 29 CFR Part 1910, published January 19, 1989. In that rulemaking, OSHA reduced the permissible exposure limits for both carbon disulfide and chloroprene.) In comparison, Environ found that NIOSH used uncertainty factors in its recommended standards for the same five substances ranging from 1 for a 15 minute exposure ceiling for chloroprene to 6000 for PCBs. The ACGIH had issued TLVs for all these substances except DBCP, and these TLVs ranged from 2 to 10 times higher than the LOEL identified in humans for chloroprene to 6 times lower than the LOEL identified in animals for PCBs. According to Environ, the AIHA had established a workplace environmental exposure level only for the reproductive toxicant piperidine, and in making its recommendation, the AIHA provided no margin of safety below the NOEL for embryotoxicity in the rat

On the basis of its analysis of the CEQ data, the NCTR data, and historical precedent, Environ concludes that "the 100-fold [safety] factor has not been used for worker protection" and "there is support for a safety factor of 10 as adequate to protect workers against the developmental toxicities of the [glycol ethers and their acetates]." Environ goes on to note that a safety factor of 10 "appears to be adequate to cover most cases and it also accords with most past occupational risk management practices. If one seeks a margin that has limited historical precedent but which appears more certain to cover all likely cases, then a factor of 50 is recommended."

Noting that the factors 10 and 50 are not alternatives and that "it may be reasonable to settle on a factor between these two values", Environ applied these two uncertainty factors to the NOELs identified for the glycol ethers and their acetates. In its review of the literature, Environ, like OSHA, found the NOELs to be 10 ppm for 2-ME, 10 ppm for 2-MEA, 50 ppm for 2-EE, and 50 ppm for 2-EEA. (Environ found no data on the reproductive effects of 2-MEA, and like OSHA, used the NOEL identified for 2-ME to estimate the ADI for 2-MEA.) In its estimation of the ADI's, however, Environ took a different approach. First, that species most sensitive to the effects of the glycol ethers or their acetates was identified. In each case, this was found to be the rabbit. Next, the NOEL was converted from units of ppm to units of milligrams per kilogram per day. Then, the safety factors of 10 or 50 were applied to the converted NOEL to arrive at two estimates of the ADI. These estimates, in turn, were converted back to units of ppm assuming human parameters. Results of these calculations are presented in Table VI-Q

a - From the Environ Report (Ex. 4-016f)
b - The NOEL identified in the most sensitive species converted from units of ppm to units of milligram per kilogram per day
c - ADI based on a safety factor of 10 and measured in units of milligrams per kilograms per day
d - ADI based on a safety factor of 50 and measured in units of milligrams per kilograms per day
e - ADI based on a safety factor of 10 and measured in units of ppm as an 8 hour time weighted average
f - ADI based on a safety factor of 50 and measured in units of ppm as an 8 hour time weighted average
g - No data available. Assumes 2-MEA is equipotent with 2-ME on a mole basis

The interesting result in Table VI-Q is that the ADIs estimated by Environ using a uncertainty factor of 50 are not very different than the ADIs estimated by OSHA using an uncertainty factor of 100 without conversion of the NOEL to milligrams per kilogram per day. For 2-ME and 2-MEA, Environ found the ADI to be 0.18 ppm whereas OSHA found the ADI to be 0.1 ppm. For 2-EE and 2-EEA, Environ found the ADI to be 0.92 ppm whereas OSHA found the ADI to be 0.5 ppm. Obviously, the results are not so similar when an uncertainty factor of 10 is used

Despite the similarity in results, OSHA has a number of concerns about the approach used by Environ to estimate the ADI for the glycol ethers and their acetates. First of all, OSHA questions the appropriateness of using the CEQ data and the NCTR data to establish the magnitude of safety factors needed to protect humans from the developmental effects of glycol ethers. Environ acknowledges a number of the data's limitations including the varying quality and extensiveness of the data bases from which these data were drawn, the subjective determination regarding the meaning of the term "lowest effective dose", the relatively small number of compounds examined, and the difficulty of obtaining accurate estimates of the human doses responsible for producing developmental toxicity

OSHA believes that these limitations alone make these data unsuitable for the use to which Environ has put them. OSHA, however, sees additional limitations. Environ is comparing experimental LOELs in the most sensitive species to LOELs observed in humans to determine adequate safety factors. Implicit in this approach is the assumption that experimental LOELs are the "true" LOELs and that any exposure below that LOEL for either humans or animals will not result in adverse effects. As noted in a previous section of this risk assessment, there is in fact little reason to believe that the LOEL (or NOEL) identified in any study is indeed the "true" LOEL. Environ's approach makes no allowance for such a possibility

Another limitation which Environ acknowledges is that it is not known whether the empirical relationships observed in the data reflect only interspecies differences or whether they reflect both interspecies differences and intraspecies differences. Environ concludes that it "seems likely although it is not certain, that the empirical relations discussed above would be protective of the most sensitive members of the human population", but OSHA notes that the opposite conclusion could just as easily be drawn. If the human data represent responses for the mid-range of the distribution of human responses, then, as Environ states, "the empirical relations reflect only interspecies differences, and an additional safety factor would seem necessary to compensate for intraspecies variability."

OSHA is also concerned about Environ's use of historical precedent to determine the margin of safety acceptable for protecting worker populations. Of the five substances reported by Environ to have been regulated by OSHA on the basis of reproductive toxicity, all but one, DBCP, were adopted as consensus standards by the Agency in 1971 under Section 6(a) of the Occupational Safety and Health Act of 1970. Under that Section of the Act, Congress directed the Agency to "promulgate as an occupational safety and health standard any national consensus standard, and any established Federal standard, unless [the Secretary of Labor] determines that the promulgation of such a standard would not result in improved safety or health for specifically designated employees" (29 U.S.C. 651 et seq). In the case of DBCP, the only one of the five substances to be considered individually in a 6(b) rulemaking, the standard set by OSHA, as Environ acknowledges, was constrained by technological feasibility and not by acceptable margin of safety. In as much as standards for four of these substances were adopted without consideration of the individual substance and the standard for the fifth was constrained by technological feasibility, it is disingenuous of Environ to conclude that OSHA finds any particular margin of safety as acceptable for working populations

Finally, OSHA questions the appropriateness of Environ's conversion of NOELs from units of ppm to units of milligrams per kilograms per day to estimate an ADI. On the one hand, Environ states that with regard to interspecies differences, "the available data on the ethers show a remarkably consistent pattern among the species tested. This suggests that the 10-fold factor conventionally used for interspecies extrapolation is not indicated." On the other hand, when the NOEL is converted into units of milligrams per kilogram per day, this "remarkable" consistency vanishes. For example, for 2-ME, Environ found that a NOEL of 10 ppm in rabbits corresponds to 4.3 mg/kg/day. For mice, however, the NOEL of 10 ppm found by Hanley et al (Ex. 4-106) corresponds to approximately 9.2 mg/kg/day, (using the mean weight for the 10 ppm exposure group on day 12, half-way through exposure, and assuming, like Environ, 100% absorption), more than two times greater than the NOEL for rabbits measured in the same units. For rats, the NOEL of 10 ppm found by Hanley et al (Ex. 4-042a) corresponds to approximately 5.93 mg/kg/day (also using the mean weight for the 10 ppm group on day 12, half-way through exposure, and assuming 100% absorption.) Thus, if Environ is going to convert the NOEL into units of milligrams per kilogram per day, an adjustment for interspecies variation must be considered

OSHA seeks comment on whether the NOEL should be expressed in units of ppm or units of milligrams per kilogram per day. A number of commentors support the latter measure including CMA (Ex. 7-17) and NIOSH (Ex. 7-22), but the Agency notes that those commentors who calculated their own ADIs did no such conversion of units (see, for example, Ex. 7-23). Furthermore, the Agency is uncertain as to how one would convert a NOEL from units of ppm to units of milligram per kilogram per day from a study of developmental effects. Animals exposed during gestation are gaining weight rapidly. Thus, as a study progresses, the dose an animal receives decreases in terms of milligrams per kilogram per day. Clearly weight gain will be a function not only of the genetics of an individual animal but also of the number of fetuses a pregnant female is carrying. OSHA seeks comment on whether these factors should be accounted for in measuring dose, and if so, how this should be done

VII. Significance Of Risk

OSHA believes that the type of significant risk analysis the Agency has undertaken in this rulemaking is consistent with the studies generally available and, for the reasons set forth below and in the section on risk assessment, is a valid, accepted and customary scientific approach

Section 6(b)(5) of the OSH Act vests authority in the Secretary of Labor to issue health standards. This section provides, in part, that :

The Secretary, in promulgating standards dealing with toxic materials or harmful physical agents under this subsection, shall set the standard which most adequately assures, to the extent feasible,on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life.

OSHA is required to make two threshold findings before it can issue a health standard under section 6 (b)(5) of the Act. In accordance with the Supreme Court's decision in the benzene case, Industrial Union Department, AFL\CIO v. American Petroleum Institute, 448 U.S. 601, 642 (1980), OSHA may promulgate a standard only if it finds that it is at least more likely than not that the risk OSHA seeks to regulate is "significant" and that the change in practices contemplated in the issuance of a standard would reduce or eliminate that risk

OSHA's analytical approach to making a determination that a significant risk of material impairment exists from exposure to hazardous materials or harmful physical agents in the workplace takes into consideration a number of factors that are consistent with recent court interpretations of the Act and with rational, objective policy formulation. As prescribed by section 6(b)(5) of the Act, OSHA examines the body of the "best available evidence" on the adverse effects of the toxic materials or harmful physical agents to determine the nature and extent of possible health consequences resulting from exposure to the hazard in question. Where possible, quantitative assessments are conducted and the results are considered along with other relevant information, such as the nature and severity of the health consequences, as well as other qualitative evidence and expert opinion, to determine whether a hazard poses a significant risk to workers

The Court gave some general guidance to the Agency for determining significant risk:

Some risks are plainly acceptable and others are plainly unacceptable. If, for example, the odds are one in a billion that a person will die from cancer by taking a drink of chlorinated water, the risk clearly could not be considered significant. On the other hand, if the odds are one in a thousand that regular inhalation of gasoline vapors that are 2 percent benzene will be fatal, a reasonable person might well consider the risk significant and take the appropriate steps to decrease or eliminate it. (I.U.D. v. A.P.I., 448 U.S., 607, 655)

The Court indicated, that where possible, the determination of significant risk should be based upon quantitative risk assessment. However, recognizing the uncertainties involved, the Court qualified its predilection for quantitative assessment, saying:

[T]he requirement that a "significant" risk be identified is "not a mathematical straitjacket. It is OSHA's responsibility to determine, in the first instance, what it considers to be a "significant" risk. Id. The Court also pointed out that: OSHA is not required to support its findings that a significant risk exists with anything approaching scientific certainty. . . .[Section] 6 (b)(5) [of the Act] specifically allows the Secretary to regulate on the basis of the "best available evidence." . . . Thus, so long as they are supported by a body of reputable scientific thought, the Agency is free to use conservative assumptions . . .risking error on the side of overprotection rather than under protection. Id., at 656.

The Court noted that the ultimate determination that a particular level of risk is significant "will be based largely on policy considerations." Id., at 655-56, n. 62

Quantification of risk, the Court understood, cannot be achieved for every hazard. The four-judge plurality, speaking for the Court in the benzene decision, did not intend to require OSHA to do what cannot be done. The concurring opinion of Mr. Justice Powell and the dissenting opinion of Mr. Justice Marshall, speaking for four other members of the Court, confirm this. Mr. Justice Powell stated:

The statutory preferences for the "best available evidence" . . .implies that OSHA must use the best known techniques for the accurate estimation of risks and benefits when such techniques are available. But neither the statute nor the legislative history suggests that OSHA's hands are tied when reasonable quantification cannot be accomplished by any known methods. . . .In this litigation, OSHA found that "it is impossible to precisely quantify the anticipated benefits. . . " If this finding is supported by substantial evidence, the statute does not prevent the Secretary from finding a significant health hazard on the basis of the weight of expert testimony and opinion. I do not understand the plurality to hold otherwise. Id., at 666-7.

Similarly, Mr. Justice Marshall, in dissent, stated "[i]t is fortunate indeed that at least a majority of the Justices reject the view that the Secretary is prevented from taking regulatory action when the magnitude of a health risk cannot be quantified on the basis of current techniques" and concluded that "the Court appears willing not to require quantification when it is not fairly possible." Id., 690, 716-17

As a part of the overall significant risk determination, OSHA considers a number of factors. These include the type of risk presented, the quality of the underlying data, the reasonableness of the risk assessments, the statistical significance of the findings and the significance of risk (48 FR 1864; January 14, 1983)

The types of risk posed by exposure to glycol ethers are of the most serious kind. Developing fetuses exposed to glycol ethers may suffer the effects of such exposure for a lifetime, leading to a life of dependency instead of a life as a productive member of society. As noted by the Office of Technology Assessment in its report on Reproductive Hazards in the Workplace, "risk to a fetus may also be a risk to the woman herself. It may be direct, as in the risk of her own reproductive health; less direct, as in the risk to her health posed by spontaneous abortion; or indirect, in that she may suffer psychological damage and diminished life prospects with the occurrence of a miscarriage or on the birth of a dead or damaged baby." (Ex. 5-135, p. 330). It is also important to note that the father may also share the harm caused by the birth of a dead or damaged child

The reproductive effects from exposure to glycol ethers are not solely loss of fertility, a serious effect in and of itself, but also include major dysfunction of the reproductive organs. Obviously material impairment of health includes not only death, but also impairments in basic biological processes, such as normal reproductive function, which can be of extraordinary personal importance. In its report on Reproductive Hazards in the Workplace, OTA states, and OSHA agrees, that "[c]oncern about reproductive processes is not limited to the brief periods in an individual's life during which reproduction may actually occur. Reproductive function is an integral part of everyday human health and well being. Before, during, and after the child bearing years, reproductive hormones may act, for example, on such variables as resistance to heart disease and cancer, immune function, complexion, bone mineral content, and feeling and mood. Threats to reproductive function can take place at nearly any point during an individual's life span." (Ex. 5-135, p.43)

The hematological effects associated with exposure to glycol ethers may be reversible but are nonetheless debilitating and may reduce a worker's normal functional capacity. In addition, reduction in the white blood cell count may compromise an individual's capacity to fend off diseases, and for these reasons the hematological effects from exposure to glycol ethers must be considered to represent additional material impairment of health

The data which support the finding of adverse health effects from exposure to glycol ethers are of the highest quality. As described in the Health Effects Section of this preamble, studies in several animal species, by various routes of exposure, have consistently shown that exposure to 2-ME, 2-EE and their acetates cause adverse reproductive, developmental and hematological effects. For example, male test animals exposed to 2-ME, 2-EE and their acetates have exhibited interferences in spermatogenesis resulting in reduced sperm count and decreased fertility. Exposed males have also exhibited degeneration of the seminiferous tubules resulting in testicular atrophy. Pregnant females exposed to these glycol ethers exhibited signs of maternal toxicity such as decreases in maternal weight, decreased organ weights and increases in the lengths of gestation. Developmental effects among litters from exposed females include increased rates of resorptions (early embryonic death), decreased litter sizes, decreased fetal weights, visceral malformations, skeletal malformations, heart defects, neurochemical alterations and behavioral abnormalities. Experimental studies have also demonstrated exposure related decreases in several blood parameters including white blood cell counts, red blood cell counts and hemoglobin concentrations. Studies of humans exposed to these agents have reported findings of testicular atrophy, reduced sperm count and blood abnormalities

In this preamble, OSHA has assessed the risk of adverse health effects from exposure to 2-ME, 2-EE, and their acetates and has determined that exposure to these glycol ethers poses developmental, reproductive, and hematological risks. While the Agency has assessed these risks, the present risk assessment differs from most previous OSHA risk assessments in that the Agency has not quantified the risks in the manner as it usually does. Instead, OSHA has performed a risk assessment using an uncertainty factor approach to determine its proposed permissible exposure limits (PELs)

The uncertainty factor approach entails identifying the most appropriate studies for each glycol ether (i.e., high quality studies using the most sensitive species) and determining the no observed effect level (NOEL) for each study. The NOELs are then divided by an uncertainty factor to arrive at estimates of the acceptable daily intakes (ADIs). These ADIs have been put forth as OSHA's proposed PELs

For 2-ME, the same NOEL was identified for reproductive effects in three species: rats, rabbits, and mice. The replication of the NOEL in each of these bioassays lends confidence that the finding of any individual bioassay is not a statistical artifact. Likewise the replication of the NOELs for reproductive effects in two species exposed to 2- EE, rats and rabbits, also lends confidence in these studies' results. A NOEL for reproductive effects was identified in only one species for 2-EEA and in no species for 2-MEA, (this last substance has not been tested), but knowledge of the metabolism and pharmacokinetics of 2-ME and 2-EE supports using the results of studies of these substances to assess the risk from exposure to their acetates

OSHA's approach to the assessment of reproductive and developmental risks is consistent with the approach to non- carcinogenic risk assessment adopted by a number of governmental agencies and international organizations including the U.S. Environmental Protection Agency (EPA), the U.S. Food and Drug Administration (FDA), the Joint Food and Agricultural Organization of the World Health Organization (FAO/WHO), and the National Academy of Sciences (NAS). This approach is favored because it requires no assumptions akin to those underlying carcinogenic risk assessment (i.e., that cancer is a multi-stage process). Little is known about the processes that lead to developmental and reproductive effects from exposure to toxic substances, and there are no generally accepted, biologically-based models for assessing these risks

In addition, uncertainty factors and qualitative risk assessment have been utilized in other health standards when there have not been quantitative models available like those used to assess carcinogenic risk. (e.g., Hazard Communication, 48 FR 53280; Ethylene Oxide, 49 FR 25734; Field Sanitation, 52 FR 16050; Formaldehyde, 52 FR 46196)1. In an analogous context, the Court of Appeals for the District of Columbia Circuit has upheld EPA's use of "margins of safety" in setting ambient air standards to address uncertainties associated with inconclusive scientific and technical information. American Petroleum Institute v. Costle, 665 F.2d 1176, 1186-87 (1981), cert. denied, 449 U.S. 1042 (1980)

1 In the update of the air contaminants standard, 54 FR 2332, uncertainty factors were also used in the significant risk analysis for non-carcinogens. On July 7, 1992, the Court of Appeals for the Eleventh Circuit determined that OSHA's use of uncertainty factors was unsupported. OSHA has addressed the concerns raised by the Eleventh Circuit in this preamble. In this and the preceding section, OSHA has provided a detailed analysis of the data and evidence that supports use of the NOEL-Uncertainty Factor approach as well as the appropriateness of an uncertainty factor of 100. In addition, OSHA has requested public comment on the appropriateness of the NOEL-Uncertainty Factor approach for making risk assessment regarding reproductive/developmental health effects and the use of an uncertainty factor of 100. Moreover, OSHA has requested interested parties to discuss alternative safety factors and methodologies for assessing risk of reproductive/developmental health effects

OSHA's choice of an uncertainty factor for estimating a human ADI from animal studies is also consistent with the recommendations of many of these organizations. For example, the FDA recommends using an uncertainty factor of 100 when NOELs are identified in chronic studies (such as those used by OSHA) in animals. Likewise, the NAS recommends an uncertainty factor of 100 when calculating an ADI from a NOEL found in animals. Although the choice of uncertainty factor may appear to be arbitrary, Dourson and Stara have provided a review of experimental evidence supporting this choice (Ex. 4-113)

The 100-fold uncertainty factor used by OSHA in this risk assessment is comprised of two factors: a ten-fold factor to account for inter-species variability (i.e., varying sensitivity across species) and a ten-fold factor to account for intra-species variability (i.e., varying sensitivity among members of a population). By making these adjustments, we increase the certainty that the ADI represents an exposure level below which adverse effects are unlikely

By choosing a 100-fold uncertainty factor, however, OSHA is not regulating below the level of significant risk. A ten-fold factor for inter-species variability and a ten- fold factor for intra-species variability are necessary to assure that exposure at or below the OSHA proposed PELs will be unlikely to cause adverse health effects

The ten-fold factor for inter-species variability is necessary to account for the potential differences between species' sensitivity to toxic agents. Differences in sensitivity may result from differences in metabolism or differences in reproductive function. For example, as noted by EPA in their guidelines for assessing male reproductive toxicity (Ex. 5-123), males of most test species produce sperm in numbers that greatly exceed the minimum requirements for fertility. However, human males, in general, produce fewer sperm relative to the number required for fertility. Thus, human males may be more sensitive to a reduction in sperm, as they may function nearer to the threshold for the number of sperm needed to ensure reproductive competence. Also differences in sensitivity may result from differences in metabolism. In the case of glycol ethers, both animals and humans appear to utilize the same metabolic pathway to produce the same primary metabolite. This primary metabolite is generally considered to be the active agent in the induction of adverse reproductive and developmental effects. However, the evidence also indicates that the biological half life of the metabolites in humans is greater than in animals. Thus the accumulation rates between animals and humans are not directly comparable. The above reasons reinforce the general support for the use of a ten fold uncertainty factor for inter species variability

Furthermore, while it may appear that there is no inter-species variation in the NOELs for 2-ME and 2-EE, as discussed in the Risk Assessment Section of this preamble, this is a function of the study designs used by Hanley et al and Tinston et al and does not prove there is no inter- species variation in developmental risk from these glycol ethers. Lastly, although the bounds of normal reproductive function can be very broad, the complexity in the reproductive processes and the difficulty in conducting studies on the broad range of possible outcomes have resulted in experimental studies concentrating for the most part on only a few distinct periods in normal reproductive functioning. OSHA has relied upon these studies to determine the reproductive and developmental risks associated with glycol ethers, but the limitations of these studies provide additional support for a ten-fold factor for inter-species variability

The ten-fold factor for intra-species variability is also necessary, and use of this factor does not result in reducing insignificant risk. Worker populations exposed to glycol ethers are not as homogeneous as the animal populations used in experimental studies. Furthermore, even if workers are healthier than the general population, it does not necessarily follow that this "healthy worker effect" will be conferred upon a developing fetus. In addition, both parents of the fetus need not necessarily be "healthy workers", and the fetus may inherit the genetic traits of either parent

In utilizing the uncertainty factors in setting the proper PELs for the glycol ethers under consideration in this rulemaking, it has not been the Agency's objective to apply an uncertainty factor to eliminate all risk. If that had been the Agency's objective or mandate under the Act, a much higher uncertainty factor would have to have been applied to ensure elimination of all risks. Rather, the Agency has used uncertainty factors to take into account only the highest uncertainties, such as inter-species and intra-species variability. The Agency believes that it has used the uncertainty factors in a reasonable manner and in utilizing the uncertainty factors the Agency has had as its goal reducing risks that are significant

After considering the severity of the types of risk as shown by the qualitative analysis of the data, OSHA preliminarily concludes that exposure to 2-ME, 2-EE and their acetates presents a significant risk to employees exposed to these substances at the current PELs. The current PELs for 2-ME and 2-MEA are 25 ppm, two and one-half times larger than the NOEL for 2-ME in three species (i.e., 10 ppm). The current PELs for 2-EE and 2-EEA are 200 ppm and 100 ppm respectively. For 2-EE, this PEL is four times greater than the NOEL identified in two species (i.e., 50 ppm), and for 2-EEA, this PEL is two times greater than the NOEL identified in one species (i.e., 50 ppm). If the NOEL is an estimate of the threshold of exposure resulting in adverse effects in animals, and if humans have the same degree of sensitivity as animals, exposure at the current PELs poses risk of material impairment of health. If humans are more sensitive than animals and respond to exposure in a less homogeneous manner, then the risk is greater still that workers exposed at the current PELs will suffer adverse effects from such exposure

OSHA also preliminarily concludes that the new glycol ethers standard will result in a reduction of significant risk. However as discussed earlier in the section on Risk Assessment there are uncertainties to the NOEL/Uncertainty Factor approach. It is assumed that at exposure levels derived by dividing an experimental NOEL by an uncertainty factor of 100, humans are unlikely to exhibit effects observed in experimental animals. However the ADI does not represent a level of exposure above which there is significant risk and below which there is no significant risk. For some individuals there may be some remaining risk below the ADI. For these reasons OSHA believes that the ancillary provisions of the standard such as exposure monitoring and medical surveillance will provide greater assurance that workers will not be at significant risk. Thus OSHA believes that these provisions are reasonably necessary

VIII. Summary Of The Regulatory Impact And Regulatory Flexibility Analysis

Introduction

Executive Order 12291 (46 FR 13197, Feb. 19, 1981) requires that a regulatory analysis be conducted for any rule having major economic consequences on the national economy, individual industries, geographical regions, or levels of government. The Regulatory Flexibility Act (5 U.S.C. 601 et. seq.) similarly requires the Occupational Safety and Health Administration (OSHA) to consider the impact of the proposed regulation on small entities

Consistent with these requirements, OSHA has prepared a Preliminary Regulatory Impact and Regulatory Flexibility Analysis (PRIA) for the proposed glycol ethers standard with 8-hour time-weighted average (TWA) permissible exposure limits (PELs) of 0.1 parts per million (ppm) for 2- methoxyethanol (2-ME) and 2- methoxyethanol acetate (2-MEA), and 0.5 ppm for 2-ethoxyethanol (2-EE) and 2-ethoxyethanol acetate (2-EEA) (Ex. 5-165). This analysis describes the industries affected by the standard, the regulatory alternatives considered, some of the potential benefits that will accrue to employees exposed to glycol ethers at their places of work, the costs of the proposed standard, and the technological and economic feasibility of the proposed provisions. The following is a summary of this analysis

Background

The chemicals 2-ME, 2-EE, 2-MEA, and 2-EEA are members of the family of ethylene glycol ethers. Referred to collectively in this analysis as "glycol ethers", these four chemicals have versatile solvent properties that make them useful in a wide variety of industries. The principal uses of glycol ethers are in chemical intermediates, paints and coatings, inks, and electronics

The current OSHA PELs for 8-hour TWAs are 25 ppm for 2- ME and 2-MEA, 200 ppm for 2-EE, and 100 ppm for 2-EEA. They were established in 1971 based on the 1968 Threshold Limit Values (TLVs) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). These TLVs were based on hematotoxic and neurotoxic effects and on exposure concentrations reported in the early case reports on human health effects. More recent information from animal studies, however, indicates that adverse reproductive effects may occur at much lower concentrations. The ACGIH now recommends for all four glycol ethers an 8-hour TLV of 5 ppm, plus a "skin" notation to draw attention to the need to prevent cutaneous absorption

In 1984, the U.S. Environmental Protection Agency (EPA) published an Advance Notice of Proposed Rulemaking (ANPR) regarding 2-ME, 2-EE, 2-MEA, and 2-EEA. In 1986, the EPA referred the issue of rulemaking for these chemicals to OSHA. Subsequently, OSHA made a preliminary determination that the occupational risks identified by EPA could be eliminated or reduced by a revised OSHA standard. In 1987, OSHA published an ANPR announcing its intention to initiate rulemaking action for four glycol ethers (OSHA Docket, Ex. 6.)

The objective of this analysis is to measure the regulatory impact of the proposed TWAs and associated requirements, including Excursion Limits (ELs) equivalent to five times each TWA and action levels (ALs) equivalent to one-half of each TWA

The principal source of information for this analysis is a study conducted for OSHA by PEI Associates, Inc., Technological Feasibility and Economic Impact Assessment of a Proposed Revision to the Glycol Ethers Standards, 1990, OSHA Docket, Ex. 5-164. A major source for PEI's report was an earlier study conducted for OSHA by Meridian Research, Inc., Industry Profile and Analysis of Processes, Occupational Exposures, and Substitutes for Glycol Ethers, 1987, OSHA Docket, Ex. 5-108

PEI conducted three major data collection activities:

1) All available monitoring data from work establishments were collected, categorized, and tabulated. These historical data were obtained primarily from OSHA, the National Institute for Occupational Safety and Health (NIOSH), and a study that PEI had conducted previously for EPA. Only post-1984 data were used because of a change in the limit of detection in the glycol ether sampling and analytical method in 1984

2) A joint PEI/NIOSH team visited nine facilities selected to be representative of the industries currently manufacturing, processing, and/or using at least one of the glycol ethers under consideration. Information was obtained at each site regarding processes, use of engineering and work practice controls and personal protective equipment (PPE), characteristics of the exposed work force, medical and industrial hygiene programs, and experience with substitute chemicals. To characterize full-shift and peak exposures in each job category with potential for exposure to glycol ethers, NIOSH also sampled at least one shift at each site

3 )PEI mailed a survey questionnaire to approximately 2500 randomly selected potential users of glycol ethers in order to characterize the following:

-Extent of usage of glycol ethers in different industry segments

-Process operations

-Demographics of potentially exposed workers

-Engineering and work practice controls currently in place and those necessary to achieve specified exposure levels

-PPE currently in place and PPE necessary to achieve specified exposure levels

-Financial characteristics of the industries

-Experience with potential substitutes for glycol ethers

Usable responses were obtained from 1,424 facilities through the mail questionnaire and subsequent telephone followup. Of the establishments submitting usable responses, 70 percent had never handled any of the four glycol ethers which are the subjects of this rulemaking, 13 percent had discontinued handling them, and 17 percent currently handled at least one of them

Based primarily on data from the survey questionnaire and site visits, PEI developed model plants to represent average establishments in each industry category. The model plants were used to develop an exposure profile and estimate compliance costs. The number of model plants developed for each industry category depended on market structure and work force characteristics, including exposures. PEI also developed model plants for small businesses

Industry Profile

The estimated 1987 domestic net sales (i.e., production less inventory changes) of the four glycol ethers amounted to 286 million pounds. The most widely distributed chemical was 2-EE (149 million pounds in 1987), followed by 2-EEA (85 million pounds), 2-ME (51 million pounds), and 2-MEA (1 million pounds). The largest consumption category for these chemicals was export (45 percent of sales), followed by use as chemical intermediates (24 percent of sales). The remaining 31 percent of sales of the glycol ethers was primarily for solvent use

Table VIII-1 presents estimates of the number of glycol ether-using establishments covered by the proposed regulation, percent of small establishments, total employment, and number of exposed workers. Although jet fuel additives consume much 2-ME, they are excluded from this analysis because they are used almost exclusively in military applications. All other miscellaneous uses not addressed in this analysis are estimated to account for less than 1 percent of total usage of the glycol ethers

Sales of the four glycol ethers have declined steadily over the past decade, probably as a result of increased concern over environmental and health issues

Manufacture of Glycol Ethers

Four establishments operated by three companies (Union Carbide, Eastman Chemical, and Oxy Petrochemical) currently produce at least one of the four glycol ethers. (In 1990, Union Carbide, the sole producer of 2-MEA, discontinued its manufacture and sale. A submission by the Chemical Manufacturers Association (CMA) to OSHA reported that "only a very few users" were working off inventories of 2-MEA, OSHA Docket, Ex. 3-002.) Because of similarities in the production processes, plant capacity can be shifted from one of the four

(*) Establishments with fewer than 20 employees
NA = Not Available
Source: PEI chemicals to another, as well as to other ethylene oxide derivatives

Manufacture of Chemical Intermediates

In addition to the plants that produce 2-EEA and 2-MEA, four major producers of chemicals use 2-EE or 2-MEA as an intermediate in five other plants: Eastman Chemical, Reichold Chemical, CPS Chemical, and Sartomer Company. The major use of 2-EE (86 percent of domestic consumption) is as a chemical intermediate. Its principal product is 2- EEA; 2-EE is also used as a chemical intermediate in the manufacture of ethoxyethyl methacrylate, ethoxyethyl ricinoleate, ethoxyethyl acrylate, and di(ethoxyethyl) phthalate

The use of 2-ME as an intermediate to produce other chemicals, including 2-MEA, accounts for 24 percent of its domestic consumption. These chemicals also include di(2- methoxyethyl) phthalate (DEMP), which is used as a plasticizer in the manufacture of 35-mm film, vinyl-tris-B- methoxyethoxysilane, methoxyethylacrylate, 2-methoxyethyl silicate, methoxyethyl oleate, methoxyethyl acetyl ricinoleate, methoxyethyl ricinoleate, and methoxyethyl stearate

Formulation of Paints and Coatings

Glycol ethers are used in polymerization, as a medium for pigment dispersion, and as a "let down" solvent to achieve desired coating application properties. They are used primarily in the formulation of Original Equipment Manufacture (OEM) paints for automobiles, metal furniture, and appliances and also as special-purpose coatings. The formulation of paints and coatings involves mixing glycol ethers and other solvents with resins, pigments, or base materials

Aircraft Manufacturing/Repainting

Glycol ethers are contained in aircraft top coat paint and sometimes in paint additives. Aircraft are generally repainted every 4 to 5 years. Painting takes place in open bays in aircraft hangars, where the paints are applied by brush, roller, airless spray, or electrostatic spray. Smaller parts and support equipment are usually spray painted in a separate paint shop

Motor Vehicle Body Manufacturing

Glycol ethers can be contained in electrocoat primers that are initially applied for corrosion protection, as well as in other primer and exterior color coatings. Electrocoats are applied to vehicle bodies by using conveyors to dip them into tanks containing the primer. Other primers and paints are generally applied by electrostatic guns in spray booths equipped with downdraft flow-through ventilation. Automatic spray guns are used to apply the primer coats on passenger car bodies

Other Metal Applications

This industry category includes miscellaneous other establishments at which paints and coatings are spray painted onto metal:

SIC 2514 (Metal Household Furniture)
SIC 2522 (Metal Office Furniture)
SIC 3411 (Metal Cans)
SIC 3412 (Metal Shipping Barrels, Drums, Kegs, and Pails)
SIC 34421 (Metal Doors, Sash and Frames Except Storm Doors)
SIC 34699 (Other Stamped and Pressed Metal Products)
SIC 3523 (Farm Machinery and Equipment)
SIC 3563 (Air and Gas Compressors)
SIC 3631 (Household Cooking Equipment)
SIC 3632 (Household Refrigerators and Home and Farm Freezers)
SIC 3714 (Motor Vehicle Parts and Accessories)

Automobile Refinishing

Some paints and coatings used in automobile refinishing contain small quantities of glycol ethers. Some spray painting operations take place in a spray booth, while other painting operations occur in the general shop environment. Wood Furniture Manufacturing

Glycol ethers are used in some wood stains or lacquers because of their solvent properties. In general, the stains or lacquers are applied by spraying in booths, followed by additional hand-padding operations. The stains or lacquers may also be blended prior to the finishing operations. Formulation of Inks

Glycol ethers are used as a solvent in inks, primarily in gravure, flexographic, and screen inks. They serve as co- solvents for ink resins and dyes in water-based inks. They are also used as solvents for textile printing and as active solvents to dissolve organic dyes. Glycol ethers are used in inks that are typically manufactured in small batches, to achieve the desired viscosity

Application of Inks

Glycol ethers are used as ink solvents and thinners in silk screen, flexographic, and gravure printing. In silk screening, solvent-based inks are spread over and squeezed through the pores of a screen to print an image. After printing, the screen is washed by hand with a lacquer thinner. In flexographic printing, the plate with the image area is fastened to a cylinder, which is then immersed into the ink-filled reservoir of a letterpress. The image is transferred from the raised surface of the plate to a flexible substrate. In gravure printing, an image is etched into the surface of a cylinder, which is then immersed in the reservoir of a web rotogravure or sheet-fed press. In a high-speed process, ink is transferred from the cylinder to the substrate by a capil-lary action. Printing operators may be exposed to glycol ethers during blending of inks and cleaning of printing press rollers

Semiconductor Manufacturing

Glycol ethers are used primarily as photoresists in the photolithographic portion of the wafer manufacturing process. The photoresist may be applied to the silicon wafer either manually by syringe or in an automated system that pumps the solution directly from storage to a spin coater. Glycol ethers may also be used as components of the inks used for marking the completed devices with a part number. The cleaning compounds used to dissolve the epoxy resin that mounts wafers to polishing fixtures also may contain glycol ethers

Printed Circuit Board Manufacturing

Glycol ethers are used as a solvent in epoxy resin that is laminated onto fiberglass reinforcement. It is normally applied in enclosed spray chambers. Glycol ethers also may be present in formulations used for marking, bonding, and labeling the printed circuit boards

Worker Exposures

Workers may be exposed to glycol ethers in many of the activities in the 12 industry categories evaluated in this study. Table VIII-2 lists the principal job categories in each industry category and the current weighted plant geometric mean (GM) exposures and weighted plant arithmetic mean (AM) exposures for each glycol ether

Geometric means are usually the preferred measure of expressing central tendency for observations which are log- normally distributed. By design, the formula for geometric means suppresses the value of outlying data observations. When used in combination with prescriptions for engineering controls to reduce employee exposure levels, for example, it makes the case for technological feasibility clearer by using geometric means (compared with a single arithmetic mean calculation, in which the values of outlyers are not suppressed)

But there is a problem for health analysis when the traditional geometric mean representation is used to categorize employee exposures to hazardous substances. Epidemiological and animal studies often document or suggest the greater vulnerability of the human organism to short term high dose exposures to hazardous substances, as opposed to continual, routine exposure at lower doses. In statistical terms, the intermittent, infrequent, high dose exposures represent outlyers in the data. The values which are potentially most threatening or harmful to humans are deliberately suppressed when a geometric mean is used to categorize the data

In policy terms, because the underlying distribution is normally distributed (lognormal) and susceptible to a geometric mean representation, does not require that this measure of central tendency be used for health benefits calculations. In fact, to the extent that it camouflages or distracts attention from potentially dangerous short term exposure conditions, it probably should not be used for such calculations or used only in combination with information on the distribution of the outlying data. In this analysis, geometric mean analysis is supplemented with arithmetic mean data which better reflect the influence of the outlying observations. In most industry/job categories, average exposures are already below the proposed TWAs (although it is possible that individual exposures may exceed the proposed levels). The lowest average exposures occur during the manufacture of glycol ethers and in the manufacture of semiconductors and printed circuit boards

* If no monitoring data were available for a substance, PEI assumed that exposures were equal to those for similar glycol ether in the same industry and job category:

(a) indicates 2-MEA exposures were assumed to equal 2-ME exposures
(b) indicates 2-ME exposures were assumed to equal 2-EE exposures
(c) indicates 2-MEA exposures were assumed to equal 2-EEA exposures
(d) indicates 2-EE exposures were assumed to equal 2-EEA exposures
(e) indicates 2-ME exposures were assumed to equal 2-EEA exposures

** Baseline exposures were assumed to equal those for Manufacture of Glycol Ethers

*** Baseline exposures were assumed to equal those for Other Metal Applications

**** Baseline exposures were assumed to equal those for Formulation of Paints and Coatings

N/A = Not Applicable

Source: PEI

There are a total of 45,786 exposed workers in 10,133 establishments in the 12 industry categories. The largest number of exposed workers occurs in the automobile refinishing category, which also has the lowest number of exposed workers per establishment

Benefits Analysis

The benefits of reducing employee exposure to glycol ethers are estimated using incidence data from animal studies and worker exposure data. The levels above which adverse health effects are likely to occur in humans are developed from the animal studies using an uncertainty factor of 100; that is, each "no observed effect level" (NOEL) observed in the animal studies is reduced by a factor of 100 to yield the corresponding human exposure level

OSHA's analysis of the benefits that are likely to occur as a result of limiting exposures to glycol ethers does not consider decreases in adverse hematological effects and in behavioral abnormalities in the offspring of exposed adults. Also, OSHA's analysis relies on animal studies that use inhalation as the route of exposure; the dosages of glycol ethers administered in inhalation studies are more readily quantifiable than those in absorption or ingestion studies and the majority of job categories considered at risk involve the inhalation of glycol ether vapors. However, dermal workplace exposures do occur, but these were not quantified. Thus, the benefits in this analysis are underestimated. The health effects estimated in this analysis and shown in Table VIII-3 are the estimated incidence of developmental effects of glycol ether exposure on the pregnancies of females under age 45 and the estimated incidence of adverse reproductive effects in male employees. The benefits were calculated assuming a 45 year working lifetime for both sexes. No effort is directed at delineating the types of fetal defects avoided. Since both 2-ME and 2-MEA are metabolized in humans to methoxyacetic acid, the benefits of limiting exposure to these compounds are displayed together. Similarly, the benefits associated with reductions in 2-EE and 2-EEA exposures are displayed together

An estimated total of 2.0 to 12.4 adverse effects on fetal development per year would be avoided under the proposed standard (TWAs of 0.1 ppm for 2-ME and 2-MEA; 0.5 ppm for 2-EE and 2-EEA). These adverse developmental effects would be avoided principally in ink application, electronics, formulation of paints and coatings, and wood furniture manufacturing

For male workers, an estimated 262 to 1,101 adverse reproductive conditions (reduced testes size, reduced sperm count and/or other impairment of reproductive functioning) would be avoided per year under the proposed standard. The impairments will persist in exposed workers for as long as they are exposed. New cases will develop among new workers as, over time, work forces turn over and new individuals become exposed. These benefits would occur principally in automobile refinishing, aircraft manufacturing and repainting, and formulation of paints and coatings

Technological Feasibility

OSHA has preliminarily determined that the proposed standard is technologically feasible. OSHA determines that the proposed TWAs are capable of being achieved in most of the operations most of the time by means of engineering and work practice controls. In certain situations for a very limited number of employees (i.e., under 2% of all full-time equivalent (FTE) workers exposed to glycol ethers in the industries involved) supplementary respiratory protection may be necessary. In most instances, when the 8-hour TWA has been met through engineering controls, no use of respirators would be necessary to meet the 15-minute EL

For example, in auto refinishing, which employs an estimated 26,331 exposed workers, who constitute 58% of all workers exposed to glycol ethers, OSHA estimates that the exposure levels for 98% of these workers can be reduced to or below the proposed TWAs and ELs by means of substitution, engineering, and work practice controls. OSHA estimates that, on an FTE basis, fewer than 1% of all currently exposed auto refinishing workers would require respiratory protection. In addition, OSHA preliminarily determines that exposure levels, as measured by geometric means, can be controlled to or below the proposed 8-hour TWAs solely by means of engineering and work practice controls in a vast majority of operations across the affected industries. Specifically, geometric mean exposure levels can be controlled to or below the TWAs in 16 of 22 2-ME operations, in 8 of 12 2-MEA operations, in 25 of 26 2-EE operations, and in 17 of 18 2-EEA operations

The best evidence of technological feasibility is that the proposed levels are already being achieved in the affected industries with current controls. Across industries using glycol ethers, geometric mean exposures are already at or below the proposed TWAs in a majority of operations. These exposure data suggest that relatively few additional controls would be necessary to consistently reduce 8-hour exposures and peak exposures to or below the proposed standard

In order to assess technological feasibility, PEI considered substitution of other solvents for glycol ethers, other engineering controls, personal protective equipment (PPE), and administrative measures, such as inspections to detect leaks in areas where glycol ethers are handled. PEI applied specific engineering or other controls until the predicted exposure level for each industry/job category was reduced to no more than one-half of each of the proposed alternative TWAs for each glycol ether. The exposure level for determining when additional controls would be necessary was based on weighted plant geometric mean exposures or weighted plant arithmetic mean exposures. The purpose of conducting the technological feasibility analysis using each of the two types of means was to determine if the costs and exposure levels differ significantly with the varying degrees of engineering controls and respirators necessitated by the two different approaches. In most cases, there is little difference

The technological feasibility of meeting ELs that were equivalent to five times each TWA was assessed separately. During its site visits, PEI was able to collect both short- term and full-shift monitoring data on some individuals whose jobs involved the potential for peak exposures. PEI assumed that job categories with TWA levels that are currently below one-half the proposed TWA would not experience excursions above the EL during normal operations. In establishments that required only engineering controls to meet a proposed TWA, the use of ASRs would be required for about one quarter of the workers in job categories that had a potential for peak exposures. With both respirators and engineering controls, no additional requirements were assumed to be necessary to meet the EL

Engineering Controls

The systems which PEI specified were based on American Conference of Governmental Industrial Hygienists (ACGIH) recommendations for good engineering practice. They are conventional, readily available, and in use today. The primary engineering control recommended for most categories was local exhaust ventilation (LEV). Process enclosures, which provide greater exposure control than hoods, were recommended for some operations

The following incremental engineering controls are considered technically feasible for the industry categories in this study:

Manufacture of Glycol Ethers:
- Closed-loop transfer for loading operations
- Enclosed sampling systems with sample coolers
- Laboratory hood in quality control (QC) laboratory

Manufacture of Chemical Intermediates:
- Automated drum filling station with LEV
- Enclosed sampling systems with sample coolers
- Laboratory hood in QC laboratory

Formulation of Paints and Coatings:
- Closed-loop transfer system
- LEV on packaging line
- LEV on mixing tank
- Drum hoist/scale (small formulator plants)
- Laboratory hood in QC and R&D laboratories

Aircraft Manufacturing/Repainting:
- Paint spray booth for small parts
- Airless spray guns with "cup collars"

Motor Vehicle Body Manufacturing:
- LEV on paint mixing tank
- Paint spray booth

Other Metal Applications:
- Paint spray booth

Automobile Refinishing:
- Paint spray booth

Wood Furniture Manufacturing:
- Paint spray booth

Formulation of Inks:
- Closed-loop transfer system
- LEV on packaging line
- LEV on mixing tank
- Drum hoist/scale (small formulator plants)
- Laboratory hood in QC and R&D laboratories

Application of Inks:
- LEV at press rollers and inkwell
- Process enclosure of press

Semiconductor Manufacturing:
- LEV at the application of photoresist
- Process enclosure at the application of photoresist

Printed Circuit Board Manufacturing:
- LEV on blending/mixing operations
- LEV on masking operation
- LEV on coating operation
- Process enclosure of coating operation

Personal Protective Equipment

When the implementation of engineering controls did not reduce the predicted exposures for a job category to below the target level, ASRs were prescribed. Cartridge respirators are considered inadequate because the odor thresholds of the four glycol ethers do not allow workers to adequately detect breakthrough at concentrations as low as the proposed regulatory alternatives

Dermal exposure can be reduced through gloves, protective clothing, and eye protection. Evidence indicates that butyl rubber gloves may be appropriate for operations that involve heavy handling and high potential for direct contact. Neoprene gloves may be appropriate for some production-related activities, such as loading rail cars and taking quality control samples. Latex gloves may be appropriate for operations that involve light handling and only occasional contact

Substitution

Substitution of other chemicals is an option for eliminating exposure to 2-ME, 2-MEA, 2-EE, and 2-EEA, although no single "drop in" substitute exists for all applications. The most common substitutes, according to PEI's survey, are propylene glycol monomethyl ether (PGME), ethylene glycol monobutyl ether (2-BE), ethylene glycol monopropyl ether (2-PE), and their acetates. Together, these six chemicals account for almost 90 percent of reported substitutions. Evidence suggests that they would pose a lower hazard in the workplace than the four glycol ethers being considered in this standard

A substitution rate was assumed for each industry category based on the availability, suitability, and cost of substitutes; the capital and operating and maintenance (O&M) costs of compliance techniques; and the industry category's position in the chain of distribution (i.e., its flexibility in forcing or responding to substitution). The rate of substitution is assumed to be the same for the geometric mean and arithmetic mean exposure approaches. The following substitution rates were developed:

Manufacture of Glycol Ethers and Intermediates: No substitution; export and chemical intermediate uses represent large proportions of total production of all four glycol ethers

Formulation of Paints and Coatings: 90%; most formulators already have or are developing substitutes

Aircraft Manufacturing/Repainting: 70%

Motor Vehicle Body Manufacturing: 70%

Other Metal Applications: 70%

Automobile Refinishing: 90%

Wood Furniture Manufacturing: 90%; use of glycol ethers is already dropping rapidly

Formulation and Application of Inks: 90%; much substitution has already taken place

Semiconductors: 10%; acceptable substitutes are not generally available

Printed Circuit Boards: 50%; acceptable substitutes are generally available

Exposure Reduction

Tables VIII-4 through VIII-7 show exposure reductions for each glycol ether after applying engineering controls. In many industry/job categories, no engineering controls would be needed to meet the proposed TWAs, although respirators might be needed to meet the proposed ELs

Of the workers who are currently exposed to glycol ethers, only five percent (under either the geometric mean approach or the arithmetic mean approach) would require air- supplied respirators. The highest percentages of workers who would require ASRs are found in aircraft manufacturing/repainting and "other" metal applications. On a full-time equivalent basis, only two percent (under either approach) would require ASRs. (See Tables VIII-8 and VIII- 9.)