Disclaimer: The information contained in these guidelines is intended for reference purposes only. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The information contained in these guidelines is current as of date of publication (September, 1996); recommendations may be superseded by new developments in the field of industrial hygiene. Readers are therefore advised to regard these recomendations as general guidelines and to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR XYLIDINE

INTRODUCTION

This guideline summarizes pertinent information about xylidine for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine periodically whether new information is available.

SUBSTANCE IDENTIFICATION

* Formula

(CH(3))(2)C(6)H(3)NH(2)

* Structure

(For Structure, see paper copy)

* Synonyms

Dimethylaminobenzene, dimethylaniline, dimethyl-phenylamine, aminodimethyl benzene, xylidine mixed ortho-meta-para isomers, xylidine isomers, acid leatherbrown 2G, resorcine brown J, resorcine brown R, acid orange 24.

* Identifiers

1. CAS 1300-73-8.

2. RTECS ZE8575000.

3. DOT UN: 1711 55.

4. DOT label: Poison.

* Appearance and odor

Xylidine is a combustible, pale yellow to brown liquid with a weak, ammonia-like odor. The commercial product is a mixture of xylidine isomers in which the 2,4-, 2,5-, and 2,6-isomers predominate.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 121.2.

2. Boiling point (760 torr): 213-226 degrees C (416-439 degrees F) (for the commercial product).

3. Specific gravity (water = 1): 0.97 to 0.99 at 20 degrees C (68 degrees F) (for the commercial product).

4. Vapor density (air = 1 at boiling point of xylidine): 4.17.

5. Melting point: 1.5 to 2.5 degrees C (34.7 to 36.5 degrees F).

6. Vapor pressure at 20 degrees C (68 degrees F): Less than 1 torr (for the commercial product).

7. Solubility: Sparingly soluble in water; miscible with alcohol and ether.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Heat, flames, or sparks.

2. Incompatibilities: Contact of xylidine with strong oxidizers may cause fires and explosions. Contact of this substance with hypochlorite bleaches may evolve chloroamines, which are explosive.

3. Hazardous decomposition products: Toxic gases (such as oxides of nitrogen and carbon monoxide) may be released in a fire involving xylidine.

4. Special precautions: Liquid xylidine attacks some coatings and some forms of plastic and rubber.

* Flammability

The National Fire Protection Association has assigned a flammability rating of 1 (slight fire hazard) to xylidine.

1. Flash point: 97 degrees C (206 degrees F) (closed cup).

2. Autoignition temperature: Data not available.

3. Flammable limits in air (percent by volume): Lower, 1.5; upper, data not available.

4. Extinguishant: Use carbon dioxide, dry chemical, alcohol foam, or water fog to fight fires involving xylidine. Do not use a solid stream of water because the stream will scatter and spread the fire; water or foam may cause frothing.

Fires involving xylidine should be fought upwind and from the maximum distance possible. Keep unnecessary people away; isolate hazard area and deny entry. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Vapor explosion and poison hazards may occur indoors, outdoors, or in sewers. Vapors may travel to a source of ignition and flash back. Con-tainers of xylidine may explode in the heat of the fire and should be moved from the fire area if it is possible to do so safely. If this is not possible, cool containers from the sides with water until well after the fire is out. Stay away from the ends of containers. Personnel should withdraw immediately if a rising sound from a venting safety device is heard or if there is discolor-ation of a container due to fire. Dikes should be used to contain fire-control water for later disposal. If a tank car or truck is involved in a fire, personnel should isolate an area of a half a mile in all directions. Firefighters should wear a full set of protective clothing, including a self-contained breathing apparatus, when fighting fires involving xylidine. Chemical protective clothing that is specifically recommended for xylidine may not provide thermal protection unless so stated by the clothing manufacturer. Firefighters' protective clothing is not effective against fires involving xylidine.

* Warning properties

The odor threshold for xylidine is 0.0048 part per million (ppm) parts of air. Because this value is below the Occupational Safety and Health Administration (OSHA) current permissible exposure limit (PEL) of 2 ppm [29 CFR 1910.1000, Table Z-1-A], xylidine is considered to have adequate warning properties.

* Eye irritation properties

No quantitative data are available on the eye irritation threshold for xylidine.

EXPOSURE LIMITS

The current OSHA PEL for xylidine is 2 ppm (10 milligrams per cubic meter (mg/m(3)) of air) as an 8-hour time-weighted average (TWA) concentration. The OSHA PEL also bears a "Skin" notation, which indicates that the cutaneous route of exposure (including mucous membranes and eyes) con-tributes to overall exposure [29 CFR 1910.1000, Table Z-1-A]. The National Institute for Occupational Safety and Health (NIOSH) has not issued a recommended exposure limit (REL) for xylidine; however, NIOSH concurs with the PEL established for this substance by OSHA [NIOSH 1988]. The American Conference of Governmental Industrial Hygienists (ACGIH) has designated xylidine as an A2 substance (suspected human carcinogen) and assigned xylidine a threshold limit value (TLV) of 0.5 ppm (2.5 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek. The ACGIH has also assigned xylidine a "Skin" notation [ACGIH 1988a, p. 38]. The OSHA limit is based on the risk of liver, kidney, and cardiac effects associated with exposure to xylidine; the ACGIH TLV is based on the carcinogenicity of xylidine.

HEALTH HAZARD INFORMATION

* Routes of exposure

Exposure to xylidine can occur via inhalation, ingestion, eye or skin contact, and by absorption through the skin.

* Summary of toxicology

1. Effects on Animals: Xylidine causes methemoglobinemia and damage to the lungs, liver, and kidneys of experimental animals. Xylidine also has been shown to cause lung, vascular, and nasal cavity tumors in mice and rats [ACGIH 1988b, p. 639(88)]. The oral LD(50) in rats ranges from 470 to 1300 mg/kg, depending on the study and the xylidine isomer involved [ACGIH 1988b, p. 639(88)]. Only the 2,4-isomer of xylidine has been tested for acute inhalation toxicity; the inhalation LC(50) in mice for this isomer is 149 ppm for 7 hours [ACGIH 1988b, p. 639(88)]. Xylidine can be absorbed through the skin in rabbits in sufficient quantities to cause cyanosis and death [Proctor, Hughes, and Fischman 1988, p. 512]. A single intravenous injection of xylidine (0.25 mM/kg) caused methemoglobin levels in cats that ranged from 6.3 to 38.3 percent [ACGIH 1988b, p. 639(88)]. Cats exposed repeatedly to a xylidine concentration of 138 ppm became uncoordinated, prostrate, and cyanotic before death; autopsy revealed edema of the lungs, pneumonia, and damage to the liver and kidneys [Proctor, Hughes, and Fischman 1988, p. 512]. In rabbits, exposure of the eyes to xylidine causes injury to the cornea (graded 5 on an ascending severity scale of 1 to 10) [Grant 1986, p. 1031]. Seven daily oral doses of 2,4-xylidine (25 to 250 mg/kg) produced dose-dependent increases in liver weight and decreases in glucose-6-phosphatase in the liver of rats [ACGIH 1988b, p. 639(88)]. Dietary studies in rats have shown that daily doses as low as 275 ppm affect the liver and kidneys [ACGIH 1988b, p. 640.1(88)]. Rodents, cats, and dogs exposed to a 45-ppm concentration of the vapors of 2,4-xylidine for 7 hours per day, 5 days per week for as long as 44 weeks had an increase in mortality and, at autopsy, exhibited liver damage; methemoglobin levels were elevated in cats, dogs, and mice but not in rats or rabbits [ACGIH 1988b, p. 640(88)]. A transplacental carcinogenicity study showed that feeding a diet containing 3000 ppm xylidine to the parent generation before breeding, during pregnancy, and throughout lactation and then feeding a diet containing 3000 ppm xylidine to the offspring for their lifetimes caused highly significant increases in both adenomas and carcinomas of the nasal cavity in the offspring [ACGIH 1988b, p. 640.1(88)]. Excess incidences of subcutaneous fibromas and fibrosarcomas were also reported in the offspring [ACGIH 1988b, p. 640.1(88)]. Compared with control mice, female mice fed 250 ppm 2,4-xylidine hydrochloride for 18 months had a statistically significant increase in the incidence of lung tumors [ACGIH 1988b, p. 640.1(88)]. 2,6-Xylidine is mutagenic in bacterial test systems with microsomal activation and produces chromosomal aberrations and sister chromatid exchanges in hamster ovary cells [ACGIH 1988b, p. 640.1(88)].

2. Effects on Humans: Based on effects seen in animals, xylidine is a potential human carcinogen. No information is available on industrial experience with this substance, and no epidemiological studies have been conducted in xylidine-exposed workers. However, it is believed that a 1-hour exposure to a 400-ppm concentration of xylidine or that long-term exposure to a 10-ppm concentration of this substance would be lethal to humans [ACGIH 1988b, p. 640.1(88)]. Based on effects seen in animals, it is likely that xylidine can be absorbed through the skin in sufficient amounts to cause dangerous methemoglobinemia [Gosselin, Smith, and Hodge 1984, p. II-208].

* Signs and symptoms of exposure

1. Acute exposure: The signs and symptoms of acute exposure to xylidine include cyanotic changes, such as blue discoloration of the lips, earlobes, skin, and nailbeds. Drowsiness, lightheadedness, weakness, severe headache, loss of coordination, nausea, vomiting, unconsciousness, and death may occur if the overexposure is severe. The onset of cyanotic signs and symptoms may be gradual or delayed.

2. Chronic exposure: Based on effects seen in animals, the signs and symptoms of chronic overexposure to xylidine include enlargement of the liver, jaundice, blood or pus in the urine, and cancer.

* Emergency procedures:

In the event of an emergency, remove the victim from further exposure, send for medical assistance, and initiate the following emergency procedures:

1. Eye exposure: If xylidine or a solution containing xylidine gets into the eyes, immediately flush the eyes with large amounts of water for a minimum of 15 minutes, lifting the lower and upper lids occasionally. If irritation persists, get medical attention as soon as possible.

2. Skin exposure: If xylidine contacts the skin, the contaminated skin should be washed with soap and water. If irritation persists or the exposed area is large, get medical attention.

3. Inhalation: If xylidine vapors are inhaled, move the victim at once to fresh air and get medical care as soon as possible. If the victim is not breathing, perform cardiopulmonary resuscitation; if breathing is difficult, give oxygen. Keep the victim warm and quiet until medical help arrives.

4. Ingestion: If xylidine or a solution containing xylidine is ingested, give the victim several glasses of water or milk to drink and then induce vomiting by having the victim touch the back of the throat with the finger or by giving syrup of ipecac as directed on the package. Do not force an unconscious or convulsing person to drink liquids or to vomit. Get medical help immediately. Keep the victim warm and quiet until medical help arrives.

5. Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard, 29 CFR 1910.1200). All workers should be familiar with emergency procedures and the location and proper use of emergency equipment.

EXPOSURE SOURCES AND CONTROL METHODS

The following operations may involve xylidine and lead to worker exposures to this substance:

• Manufacture of dyes (C.I. Acid Red 26, C.I. Direct Violet 14, C.I. Solvent Orange 7)
• Manufacture of pharmaceuticals
• Use as an intermediate in organic synthesis of wood preservatives, wetting agents for textiles, frothing agents for ore dressing, special lacquers, and metal complexes

Methods that are effective in controlling worker exposures to xylidine, depending on the feasibility of implementation, are

• Process enclosure,
• Local exhaust ventilation,
• General dilution ventilation, and
• Personal protective equipment.

The following publications are good sources of information on control methods:

1. ACGIH [1986]. Industrial ventilation--a manual of recommended practice. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

MEDICAL MONITORING

Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, placement of workers in jobs that do not jeopardize their safety or health, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work-related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical monitoring program is intended to supplement, not replace, such measures. To place workers effectively and to detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the period of employment, and (3) at the time of job transfer or termination.

* Preplacement medical evaluation

Before a worker is placed in a job with a potential for exposure to xylidine, the examining physician should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the blood, lungs, liver, kidneys, and cardiovascular system. Medical monitoring for respiratory disease should be conducted using the principles and methods recommended by NIOSH and the American Thoracic Society.

A preplacement medical evaluation is recommended to assess an individual's suitability for employment at a specific job and to detect and assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to xylidine at or below the prescribed exposure limit. The examining physician should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the blood, lungs, liver, kidneys, or cardiovascular system.

* Periodic medical examinations and biological monitoring

Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to xylidine exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of xylidine on the blood, lungs, liver, kidneys, or cardiovascular system. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. Methemoglobin levels cannot be correlated accurately with airborne concen-trations of methemoglobinemia-producing agents such as xylidine; however, an elevated methemoglobin level is an indicator of possible overexposure to xylidine or other methemoglobinemia-producing agents. Some sources recommend a methemoglobin level of 1.5 percent of total hemoglobin as a biological exposure index for xylidine. Blood specimens for biological monitoring should be collected on the day of the exposure (and preferably during exposure) and should be analyzed at the place of collection, if possible.

* Medical examinations recommended at the time of job transfer or termination

The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population. Because occupational exposure to xylidine may cause diseases with prolonged latent periods, the need for medical monitoring may extend well beyond the termination of employment.

WORKPLACE MONITORING AND MEASUREMENT PROCEDURES

Determination of a worker's exposure to airborne xylidine is made using a silica gel tube (150/75 mg sections, 20/40 mesh). Samples are collected at a maximum flow rate of 0.2 liter per minute until a maximum air volume of 20 liters is collected. The sample is then treated with ethanol to extract the xylidine. Analysis is conducted by gas chromatography using a flame ionization detector. This method has a sampling and analytical error of 0.09 and is included in the OSHA Computerized Information System [OSHA 1987], in the OSHA Chemical Information Manual [OSHA 1987], and in Method S162 of the NIOSH Manual of Analytical Methods, 2nd edition, Volume 3 [NIOSH 1984].

PERSONAL HYGIENE PROCEDURES

Because xylidine can be absorbed through the skin in toxic amounts, workers should immediately wash any areas of the skin contaminated by this substance with soap and water.

Clothing contaminated with xylidine should be removed immediately, and provisions should be made for the safe removal of the chemical from the clothing. Persons laundering the clothes should be informed of the hazardous properties of xylidine.

A worker who handles xylidine should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, or using toilet facilities.

Workers should not eat, drink, or use tobacco products in areas where xylidine or a solution containing xylidine is handled, processed, or stored.

STORAGE

Xylidine should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. The storage area must meet OSHA requirements for Class IIB combustible liquids. Containers of xylidine should be protected from physical damage and should be stored separately from oxidizing agents, hypochlorite bleaches, heat, sparks, and open flame. To prevent static sparks, metal equipment and containers used in transferring this material should be grounded and bonded. Because empty containers may still hold xylidine residues, they should be handled appropriately.

SPILLS AND LEAKS

In the event of a spill or leak involving xylidine, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Do not touch the spilled material; stop the leak if it is possible to do so without risk.

2. Notify safety personnel.

3. Remove all sources of heat and ignition.

4. Ventilate potentially explosive atmospheres.

5. For small dry spills, use a clean shovel and place the material into a clean, dry container; cover and remove the container from the spill area.

6. For small liquid spills, take up with sand or other noncombustible absorbent material and place into closed containers for later disposal.

7. For large liquid spills, build dikes far ahead of the spill to contain the xylidine for later reclamation or disposal.

EMERGENCY PLANNING, COMMUNITY RIGHT-TO-KNOW, AND HAZARDOUS WASTE MANAGEMENT REQUIREMENTS

The Environmental Protection Agency's (EPA's) regulatory requirements for emergency planning, community right-to-management may vary over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Xylidine is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (Title III).

* Reportable quantity requirements (releases of hazardous substances)

Employers are not required by the emergency release notification provisions of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) [40 CFR Part 355.40] to notify the National Response Center of an accidental release of xylidine; there is no reportable quantity for this substance.

* Community right-to-know requirements

Employers are not required by Section 313 of the Superfund Amendments and Reauthorization Act (SARA) to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of xylidine emitted or released from their facility annually.

* Hazardous waste management requirements

EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity, as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA), EPA has specifically listed many chemical wastes as hazardous. Although xylidine is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat any waste as hazardous if it exhibits any of the characteristics discussed above.

Providing more information about the removal and disposal of specific chemicals is beyond the scope of this guideline. EPA, U.S. Department of Transportation, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (202) 382-3000 (in Washington, D.C.) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of xylidine exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergency situations. If the use of respirators is necessary, the only respirators permitted are those that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).

* Respiratory protection program

Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection (see Table 1), an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].

Table 1 lists the respiratory protection that NIOSH recommends for workers exposed to xylidine. The recommended protection may vary over time because of changes in the exposure limit for xylidine or in respirator certification requirements. Users are therefore advised to determine periodically whether new information is available.

PERSONAL PROTECTIVE EQUIPMENT

Protective clothing should be worn to prevent any possibility of skin contact with xylidine. Impervious gloves, aprons, boots, coveralls, and other protective clothing are recommended as necessary when handling this material. Chemical protective clothing should be selected on the basis of available performance data, manufacturers' recommendations, and evaluation of the clothing under actual conditions of use. There is qualitative evidence that Viton/neoprene or butyl rubber/neoprene mixtures do not provide good resistance to permeation by xylidine.

If xylidine is dissolved in water or an organic solvent, the permeation properties of both the solvent and the mixture must be considered when selecting personal protective equipment and clothing.

Safety glasses, goggles, or faceshields should be worn during operations in which xylidine might contact the eyes (e.g., through splashes of solution). Eyewash fountains and emergency showers should be available within the immediate work area whenever the potential exists for eye or skin contact with xylidine. Contact lenses should not be worn if the potential exists for xylidine exposure.

REFERENCES

ACGIH [1988a]. TLVs. Threshold limit values and biological exposure indices for 1988-1989. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1988b Update]. Documentation of the threshold limit values and biological exposure indices. 5th edition. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

Gosselin RE, Smith RP, Hodge HC [1984]. Clinical toxicology of commercial products. 5th edition. Baltimore, MD: Williams & Wilkins.

Grant WM [1986]. Toxicology of the eye. 3rd edition. Springfield, IL: Charles C Thomas.

NIOSH [1984]. NIOSH manual of analytical methods. 3rd edition. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health.

NIOSH [1987a]. NIOSH guide to industrial respiratory protection. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health. DHHS (NIOSH) Publication No. 87-116.

NIOSH [1987b]. Respirator decision logic. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health. DHHS (NIOSH) Publication No. 87-108.

NIOSH [1988]. Testimony of the National Institute for Occupational Safety and Health on the Occupational Safety and Health Administration's proposed rule: 29 CFR 1910, Docket No. H-020, August 2, 1988. NIOSH policy statements. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health.

OSHA [1987]. Chemical information manual. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.

OSHA [1987]. Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.

Proctor NH, Hughes JP, Fischman ML [1988]. Chemical hazards of the workplace. Philadelphia, PA: J.B. Lippincott Company.

BIBLIOGRAPHY

DOT [1987]. 1987 Emergency response guidebook, guide 55. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.

Hawley's condensed chemical dictionary [1987]. Sax NI, Lewis RJ. 11th edition. New York, NY: Van Nostrand Reinhold Company.

Hazardous Substance Fact Sheet [1986]. Xylidine. Trenton, NJ: New Jersey Department of Health.

HSDB [1989]. Xylidine. Bethesda, MD: The Hazardous Substances Data Bank, National Library of Medicine.

IARC [1986]. IARC monographs on the evaluation of carcinogenic risk of chemicals to man. Volume 16. Lyon, France: World Health Organization, International Agency for Research on Cancer.

Material Safety Data Sheet No. 594 [1986]. Schenectady, NY: Genium Publishing Corporation.

NFPA [1986]. Fire protection guide on hazardous materials. 9th edition. Quincy, MA: National Fire Protection Association.

NIOSH [January 1981]. NIOSH/OSHA occupational health guidelines. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health. DHHS (NIOSH) Publication No. 81-123.

Proctor NH, Hughes JP [1978]. Chemical hazards of the workplace. Philadelphia, PA: J.B. Lippincott Company.

RTECS [1989]. Xylidine. Bethesda, MD: Registry of Toxic Effects of Chemical Substances, National Library of Medicine.

Schwope AD, Costas PP, Jackson JO, Stull JO, Weitzman DJ [1987]. Guidelines for the selection of chemical protective clothing. 3rd edition. Cambridge, MA: Arthur D. Little Company. [Available from the American Conference of Governmental Industrial Hygienists, 6500 Glenway Avenue, Building 7, Cincinnati, OH 45211.]

Sittig M [1985]. Handbook of toxic and hazardous chemicals. 2nd edition. Park Ridge, NJ: Noyes Publications.

Condition	Minimum respiratory protection**
Any detectable concentration of xylidine:	Any self-contained respirator of equipped full facepiece and operated in a pressure-demand or other positive-pressure mode, or Any supplied-air respirator equipped with a full facepiece and operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained breathing apparatus operated in a pressure-demand or other positive-pressure mode
Entry into unknown concentrations(+)	Any self-contained respirator equipped with a full facepiece and operated in a pressure-demand or other positive-pressure mode, or Any supplied-air respirator equipped with a full facepiece and operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained breathing apparatus operated in a pressure-demand or other positive-pressure mode
Firefighting	Any self-contained respirator equipped with a full facepiece and operated in a pressure-demand or other positive-pressure mode
Escape	Any air-purifying, full-facepiece respirator equipped with an organic vapor canister, or Any escape-type, self-contained breathing apparatus with a suitable service life (number of minutes required to escape the environment)

* This table is based on the potential carcinogenic effects of xylidine.

** Only NIOSH/MSHA-approved equipment should be used.

(+) Use of chemical protective clothing may be necessary to prevent skin contact.