Testing Status of Agents at NTP
Executive Summary Ethyl Bromoacetate
SUMMARY OF DATA FOR CHEMICAL SELECTION
ETHYL BROMOACETATE
105-36-2
105-36-2
Prepared for NCI by Technical Resources International, Inc. under Contract No. N01-CP-05619
2/95; rev. 8/96
- Basis of Nomination to the CSWG
- Selection Status
- Input from Government Agencies/Industry
- Chemical Identification
- Exposure Information
- Evidence for Possible Carcinogenic Activity
- References
BASIS OF NOMINATION TO THE CSWG
The nomination of EBA is based on the potential
for human exposure through its uses as a chemical intermediate
and alkylating agent, a lack of adequate chronic toxicity data
and a suspicion of carcinogenicity associated with halogenated
aliphatic compounds.
EBA is used as a synthetic organic chemical intermediate
as well as a pharmaceutical and agricultural intermediate. In
addition, it has a history of prior use as a lacrimator and tear
gas agent for chemical warfare, an odorant, and an illicit biocide
in European food and beverage products. Potential low-level human
exposures could occur in occupational or consumer settings by
any of the three major routes-inhalation, ingestion or dermal.
Suspicion of carcinogenicity is based on EBA's bromo-substituted
carboxylate structure. Because of the potential alkylating activity
of EBA as an a-halo
acetate. Because of a lack of supporting mutagenicity data, this
chemical has been submitted to the National Cancer Institute's
Division of Cancer Etiology (NCI/DCE) Short-Term Testing Program
for Ames and mouse lymphoma assays. Nomination of EBA for testing
would provide the opportunity for elucidating mechanisms of bromoacetate
toxicity. It would also reinforce the nomination of the closely
related compound monobromoacetic acid (MBAA), which was nominated
to the National Toxicology Program (NTP) in 1991 as a water disinfection
by-product and is currently under review for possible testing.
SELECTION STATUS
ACTION BY CSWG: 6/13/95
Studies Requested:
Rationale/Remarks:
Priority: Moderate
| CAS Registry No.: | 105-36-2 |
| Chemical Abstract Names: | Acetic acid, bromo-, ethyl ester (8CI, 9CI) |
| Synonyms and Trade Names: | Bromoacetic acid, ethyl ester; (ethoxycarbonyl)methyl bromide; ethyl a-bromoacetate; ethyl bromoethanoate; ethyl monobromoacetate; Antol; EBA |
C4H7BrO2
Mol. wt.: 167.02
Chemical and Physical Properties:
| Description: | Clear, colorless to straw colored, flammable liquid with a fruity odor (Lewis, 1993a,b; Criswell et al., 1980) |
| Boiling Point: | 162-163oC (Lide, 1993) |
| Melting Point: | -13.8oC (Lide, 1993) |
| Flash Point: | 47.8oC (Lewis, 1993b) |
| Density: | 1.514 at 20oC/4oC (Lide, 1993) |
| Solubility: | Soluble in water, benzene, chloroform, diethyl ether, and ethanol (Anon, 1991; Lewis, 1993a) |
| Volatility: | Relative vapor density, 5.8 (Lewis, 1993a) |
| Reactivity: | Flammable when exposed to heat,
flame and oxidizers; will react with water or steam to produce
toxic and corrosive fumes; when heated to decomposition or on
contact with acid or acid fumes, emits highly toxic fumes of bromine
(Lewis, 1993b) |
Technical Products and Impurities: EBA is commercially available with purities ranging from 97 to 98% (Anon, 1991; Kuney, 1993; Dialog Information Services, 1995). In addition, several suppliers provide technical or practical grade products. It is available in research and bulk (drum) quantities. No information identifying any impurities was found in the available literature.
EXPOSURE INFORMATION
Production and Producers: EBA is commonly
synthesized by sulfuric acid catalyzed esterification of monobromoacetic
acid (MBAA). After reaction completion, excess acid is washed
out and the product purified via distillation under reduced pressure
if necessary (Stenger, 1978; Korhonen, 1984). The following general
scheme described this synthesis.
EBA is listed on the US EPA's TSCA Inventory (STN
International, 1995a). The annual US production of EBA was reported
to be in the range of 16,376 to 42,937 pounds based on nonconfidential
data received by the EPA for 1898. No other annual US production
data for EBA were found in the available literature, including
recent issues of Synthetic Organic Chemicals, Production and
Sales, for 1988-1992 (US International Trade Commission, 1989-1994).
EBA is current available from the following suppliers
in the United States (Kuney, 1993; Van, 1994).
Several major US pharmaceutical manufacturers have
recently been assigned patents in which EBA is reportedly used
in the synthesis of a variety of pharmaceutical products including
drugs and therapeutic aids, such as diagnostic imaging agents.
Some companies whose patents are cited in the open literature
include: Bristol-Myers Squibb; Ciba-Geigy Corp.; Eastman Kodak
Co.; ICI Americas, Inc.; Merck and Co., Inc.; Merrill Dow Pharmaceuticals,
Inc.; Rorer, Inc.; Sterling Winthrop, Inc.; and the Upjohn Co.
(STN, 1995b).
Imports: Major producers of EBA for the
world market have been reported to include two companies in France,
one in Great Britain, one in Germany, one in Japan and two in
Israel (Chemical Information Services, Inc., 1994). According
to the Journal of Commerce Piers Imports database, Ameribrom,
Inc., reported imports of 1,300 lbs of EBA in 1994 and approximately
1,000 lbs of EBA in 1993 from a manufacturer in Israel (Dialog
Information Services, 1995b). No other information on specific
import volumes was found in the available literature.
Use Pattern: EBA, a lacrimator, has been
used as a chemical warfare agent, tear gas agent, and warning
agent for poisonous, odorless gases (NLM, 1995). It was reportedly
first used as a tear gas by the French in 1914 (Holmberg, 1975).
Arena (1979) listed EBA as one of several extensively used tear
gases. EBA is also widely used as an alkylating agent and as
a versatile intermediate in organic, pharmaceutical and agrochemical
syntheses (O-, N- and S-alkylations).
As a synthetic organic reagent and chemical intermediate,
EBA and similar a-halo
esters are commonly used as alkylating agents in the Reformatsky
reaction for the alkylation of aldehydes and ketones, using zinc
as catalyst. The aldehyde or ketone can be aliphatic, aromatic,
heterocyclic or contain various functional groups (March, 1992).
According to Van Ness (1981) abromo
esters generally give the best results in the Reformatsky reaction,
which is analogous to the Grignard reaction; a-chloro
esters react slowly or not at all, and the a-iodo
esters are generally not available. For example, Williams (1978)
described the Reformatsky reaction of benzaldehyde with EBA, a
condensation reaction yielding cinnamic acid. Variations on the
Reformatsky reaction include the reaction of nitriles with EBA
(called the Blaise reaction) and substitution reactions of EBA
with other carboxylic esters (March, 1992). Criswell and coworkers
(1980) reported EBA to be widely used for modification of enzymes
and other proteins based on its much higher reactivity with sulfhydryl
groups than with amino groups.
EBA is used as a starting material or chemical
intermediate in the preparation of a wide variety of drugs and
cosmetics (e.g., UV protectants, perfumes). For example,
Bock and coworkers (1989) of the Merck Sharp & Dohme Research
Laboratories in West Point, PA, in a report on their drug development
work with benzodiazepines, described the use of EBA as an alkylating
agent for the preparation of aminobenzodiazepine derivatives.
A research group at Alcon Laboratories, Inc., in Fort Worth,
TX, reported using EBA as an alkylating reagent in the synthesis
of a group of aldose reductase inhibitors for the treatment of
diabetes (DuPriest et al., 1991). EBA has also been patented
for use in the synthesis of complexing agents as contrast media
for diagnostic/therapeutic imaging by several pharmaceutical manufacturers,
including Bristol-Myers Squibb and Schering (Desreux et al.,
1994; Gries et al, 1987).
American Cyanamid Co. has patented the use of EBA
in the manufacture of agricultural chemicals. This company was
assigned a patent for the synthesis of bioregulators in which
EBA is used as a chemical intermediate in the preparation of benzopyran
and tetrahydronaphthalene derivatives as herbicide safeners.
These safeners are applied to barley seeds to act as carbamate
pesticide antidotes (Cary & Quinn, 1994). A safener is a
chemical used in conjunction with the application of a pesticide
to protect against damage from a pesticidal ingredient (Plimmer,
1980).
A Japanese manufacturer and processor of plastics
has described (in a patent) the use of EBA as a component of a
hydrochlorofluorocarbon (HCFC) decomposition inhibitor and stabilizing
agent for polyurethane foam (Ide et al., 1993). Furthermore,
EBA has reportedly been used as a tear gas in joke-type toys,
(a use now prohibited), and illicitly as a preservative in alcoholic
beverages in Europe (Christoph et al., 1985; Hild, 1990).
According to Christoph and coworkers, EBA has been in use in
Europe for the last 50 years, frequently under the trade names
of STERIL or STABILO. EBA has been considered to be a highly
efficient biocide which could be used safely at low concentrations.
It has been used in small quantities in beverages, including
wine, beer and champagne, and is also in some food products to
prevent molding or fermentation.
Human Exposure: There is potential for occupational
exposure to EBA in commercial, industrial and research laboratory
settings mainly by the inhalation or dermal route. In addition,
exposures to the general public could occur through the reported
use of EBA as a lacrimator or tear gas agent in chemical warfare
or odorant/warning agent in odorless toxic gases. Consumer exposure
to EBA could possibly have resulted from its now banned use in
joke-type toys as well as by ingestion of low levels through the
illicit use of EBA as a preservative in alcoholic beverages (Christoph,
1985; Hild, 1990).
The National Occupational Exposure Survey (NOES)
which was conducted by the National Institute for Occupational
Safety and Health (NIOSH) between 1981 and 1989, estimated that
851 workers, including 187 female employees, were potentially
exposed to EBA in the workplace. The NOES database does not contain
information on the frequency, level, or duration of exposure to
workers of any chemical listed therein (NIOSH, 1990).
Environmental Occurrence: EBA is not known
to occur naturally. EBA may be present in air as a result of
its tear gas and chemical warfare agent uses as well as its other
odorant and reagent/chemical intermediate uses. A method for
analysis has been described which is based on derivatization and
evaluation by gas chromatography coupled with atomic emission
and mass spectral analysis (Schoene et al., 1993).
Regulatory Status: No standards or guidelines
have been set by NIOSH or OSHA for occupational exposure to or
workplace maximum allowable levels of EBA. The American Conference
of Governmental Industrial Hygienists (ACGIH) has not recommended
a Threshold Limit Value (TLV) or Biological Exposure Index (BEI)
for this compound.
The US Department of Transportation (DOT) regulates
EBA as a flammable liquid and poison and has issued standards
for the labeling, packaging and transportation of EBA in FR 55(246),
52 402729, 21 Dec. 1990. EBA has been given a hazardous
materials rating by the National Fire Protection Association (Business
& Legal Reports, Inc., 1990). In Germany, the use of EBA
as a tear gas agent in toys and joke items has been prohibited
as a health hazard (Hild, 1990).
EVIDENCE FOR POSSIBLE CARCINOGENIC ACTIVITY
Human Data: No epidemiological studies or
case reports investigating the association of exposure to EBA
and cancer risk in humans were identified in the published literature.
EBA is toxic by ingestion, inhalation and skin absorption and
is a strong irritant and a lacrimator (Anon., 1991; Lewis, 1993a,
1993b). According to Grant (1974) EBA vapors are especially irritating
to the eyes. Exposure to a concentration of 8 ppm in air for
more than a minute is reported to be unbearable. Ocular exposures
to high concentrations of EBA vapor from tear gas shells can cause
temporary lesions, while eye contact with liquid EBA has been
known to cause permanent damage.
Animal Data: Van Duuren and coworkers (1974)
studied EBA for carcinogenic effects in female ICR/Ha Swiss mice
by various routes of administrating. Following skin applications
of 0.5 mg/0.1 ml acetone 3 times per week for 580 days
to a group of 50 mice (animal median survival time, 526 days)
no papillomas or carcinomas were observed. In a mouse skin initiation-promotion
study in which a single dose of 0.5 mg EBA as initiator in 0.1
ml acetone was applied dermally to a group of 30 mice followed
2 weeks later by application of 2.5 mg
of phorbol myristate acetate (PMA) in 0.1 ml acetone 3 times per
week for 385 days, the incidence of papillomas and carcinomas
in EBA-treated animals was found to be non-significant (P >
0.05) when compared with animals receiving only PMA. Another
group of 30 mice received ip injections of 0.1 mg EBA in 0.05
ml of Nujol once a week for 450 days. No local sarcomas were
observed in the test animals; furthermore, there was no increased
incidence of papillary tumors of the lungs when compared with
control animals. Finally, when EBA was administered in doses
of 0.1 mg in 0.05 ml Nujol by sc injection to a group of 50 mice
once a week for the 580 day duration of the experiment (animal
median survival time, 441 days), there was a significant increased
incidence (P < 0.01) of malignant sarcomas at the injection
sites.
Theiss and coworkers (1979) tested EBA as one of
28 organohalides for induction of lung tumors in Strain A mice
in a 24 week study. EBA did not produce an elevated pulmonary
adenoma response under the conditions of the study. EBA was administered
to groups of 20 mice (10 males and 10 females) by ip injections
in doses of 0.01, 0.02 and 0.03 mM/kg of EBA in tricaprylin 3
times per week for a total of 24, 24 and 9 injections, respectively,
and a total dose of 0.2, 0.4 and 0.3 mM/kg, respectively. No
statistically significant elevation (P > 0.05) in lung tumor
incidence was observed. The authors suggested that the greater
toxicity or organobromides, such as EBA, relative to similar organochlorides,
may have masked potential tumorigenic activity since these compounds
could not be administered in sufficient quantities to elicit a
tumorigenic response.
Short-Term Test: No in vitro or in
vivo studies evaluating EBA for mutagenic effects were found
in the published literature. EBA was submitted to the DCB Short-Term
Test Program for mutagenicity testing and the following results
have been reported. EBA was negative in an Ames Salmonella
assay with S. typhimurium strains TA98, TA100, TA1535,
TA1537 and TA1538 both with and without S9 activation. When tested
in a mouse lymphoma assay using an L5178Y TK+/- cell
line, EBA gave a weakly positive results without S9 activation
and a positive result with S9 activation.
Metabolism: No studies on the metabolism
of EBA were found in the available literature.
Other Biological Effects: An academic research
group in Texas has studied EBA as one of a small group of "chemically
active odorants" for inhibitory effects on the frog olfactory
mucosa. EBA was chosen for study as a fast-acting tear gas with
a high vapor pressure and an identifiable fruity odor. It was
reported to block all olfactory responses of the frog nose, except
responses to certain aliphatic amines. This specific pattern
of inhibition was thought to be effected through its alkylating
ability and reactivity with protein sulfhydryl or amino groups
in the olfactory mucosa. Isoamyl acetate and several closely-related
ester odorants were found to act as protectants against the inhibitory
action of EBA (Criswell et al., 1980; Schafer et al.,
1984a,b).
Structure/Activity Relationships: EBA is
an ester of an a-halo
aliphatic carboxylic acid. A group of 15 related bromo- or chloro-substituted
carboxylates as well as the corresponding acid, MBAA, were screened
for relevant information associating these structurally similar
compounds with a mutagenic or carcinogenic effect. The limited
amount of short-term test data available indicate mixed genetic
toxicity results for this group of compounds. A summary of the
carcinogenicity and mutagenicity information identified for EBA
and several of the structurally related compounds is presented
in Table 1. No information from genetic toxicity or carcinogenicity
studies of the following structurally related compounds was found
in the available literature: ethyl 2bromobutyrate [533-68-6];
ethyl 2-chloropropionate [535-13-7]; ethyl 2-bromoisobutyrate
[60000-0]; ethyl 3-chloropropionate [623-71-2]; butyl 2-bromoacetate
[18991-98-5]; propyl 2-bromoacetate [35223-80-4].
Carcinogenic Effects
Monobromoacetic acid.
According to Linder and coworkers (1994) halogenated acetic acids,
including EBA precursor and parent acid, MBAA, have been identified
as a major class of water disinfection by-products. MBAA is one
of a group of water disinfection by-products nominated to the
NTP for carcinogenicity bioassay in March, 1991, by the American
Water Works Association. According to a spokesperson for NTP's
chemical data management, this chemical is not on test, and at
this time is under review and no testing is planned (NTP, 1995a,b).
In an early study for the identification of agents which might
inhibit tumor growth, MBAA was classified as a radiation protector,
modifying lethal effects caused by ionization radiation in mice
and an E. coli bacterial system (Price et al., 1965).
Stratton and coworkers (1981) tested a solution of MBAA in two
murine tumor cell cultures, C-1300 neuroblastoma (NB) cells and
mouse leukemia L-1210 cells and suggested that the cytotoxic effects
may be due to the alkylation of bromoacetate (BrAc), followed
by DNA strand breakage. BrAc was reported to inhibit NB cell
growth in vitro with dependence on both concentration and
exposure duration. In addition, they demonstrated cytotoxicity
in L-1210 cells in vitro and attributed it to DNA strand
breakage based on an alkaline elution assay following treatment
of the cells with 100mM
BrAc. Survival as determined by colony formation of L-1210 cells
was inhibited by treatment with BrAc for 1 hour. A log linear
dose-response effect was observed up to a dose of approximately
250mM, and
there was a plateau effect reflecting no further effect on cell
survival at concentrations greater than 500mM.
The absence of a shoulder effect in the survival curve was interpreted
as an indication that the treated cells had little ability to
accumulate or repair sublethal damage.
Ethyl 2-chloroacetate.
Van Duuren and coworkers (1974) administered ethyl chloroacetate
(ECA) sc at a dose of 1.0 mg/0.05 ml of tricaprylin to ICR/Ha
Swiss mice. They reported that 1/50 mice developed a local sarcoma
and considered ECA non-tumorigenic in this assay whereas the subject
chemical, EBA, as reported above, was considered to have shown
notable tumorigenicity at the site of injection. Theiss and coworkers
(1979) studied 28 organohalides for induction of pulmonary adenomas
in Strain A mice. ECA was administered by ip injections 3 times
weekly for a total of no more than 24 injections to groups of
20 mice (10 males and 10 females) at the maximum tolerated dose,
one-half the maximum tolerated dose, and one-fourth or one-fifth
the maximum tolerated dose. The authors reported that the results
of the ECA study were inconclusive because the pulmonary tumor
response was significant by only one of two statistical tests.
EBA, as reported above, was non-tumorigenic in this study.
Methyl 2-bromoacetate; methyl 2-chloroacetate.
Theiss and coworkers (1979) also tested methyl 2-bromoacetate
and methyl 2-chloroacetate for induction of pulmonary adenomas
in Strain A mice in a 24 week study in which the compounds were
administered by ip injections in tricaprylin. They reported that
both of these compounds were negative, i.e. did not produce a
pulmonary tumor response in this assay.
Mutagenic Effects
Monobromoacetic acid.
Szybalski (1958) reported screening a number of compounds, including
MBAA, in a search for prospective antineoplastic agents. MBAA
was classified as a non-mutagen based on a paper-disk assay method
in which an increase in the frequency of reversion from streptomycin
dependence to independence in strain Sd-4-73 of E. coli
was utilized as a measure of mutagenicity.
Ethyl 2-bromopropionate.
Ethyl 2-bromopropionate, a closely related compound, was tested
for mutagenic activity in an Ames/Salmonella assay. Dolzani
and coworkers (1992) reported that this chemical, when tested
over a dose range of 100-4,000 mg/plate,
caused a non-significant increase in the number of his-
revertants in S. typhimurium strain TA100 without metabolic
activation of up to 343±110 per mg per plate at a dose of
1,000
Ethyl 2-chloroacetate.
Kringstad and coworkers (1981) reported that ethyl 2-chloroacetate
(ECA) tested negative for mutagenicity in an Ames/Salmonella
assay in strain TA1535 without metabolic activation. Nestmann
and Lee (1985) tested ECA for genetic activity in a yeast assay
using Saccharomyces cerevisiae strains D7 and XV185-14C
with and without S9. They reported a negative result in both
strains.
Rosenkranz et al. (1990) examined a database
of NTP-tested chemicals to develop a predictive SAR methodology
based on structural characteristics associated with induction
of sister chromatid exchanges (SCEs) and chromosomal aberrations
(CAs) in Chinese hamster ovary (CHO) cells, using the CASE (Computer
Automated Structure Evaluation) system. They reported that the
structural determinant, Br-CH2-, was an active biophore
in each of 4 occurrences with a probability (P value) of 0.063
reported only for SCEs, not for CAs. The same biophore was reported
associated with mutagenicity in Salmonella with a probability
of 0.125.
Related Biological Effects
Monobromoacetic acid.
Jones and Wells (1981) studied the metabolism of the parent acid,
MBAA, and related compounds, 2-bromoethanol and bromoacetaldehyde,
in rats. They reported that after administration of MBAA the
unchanged compound together with a metabolite, N-acetyl-S-(carboxymethyl)cysteine,
appeared in the urine within the first 24 hours. They identified
the same minor metabolite after administration of 2-bromoethanol
and proposed an oxidative metabolic pathway in which this compound
is partially metabolized via bromoacetaldehyde and MBAA to the
cysteine-conjugated metabolite. MBAA has also been described
as a metabolic inhibitor with efficacy as a protective agent in
plants. Castro and Loureiro-Dias (1994) reported that MBAA competitively
inhibited the transport of lactic acid in the yeast, Fusarium
oxysporium var. lini.
Linder and coworkers (1994) investigated MBAA for
short-term spermatotoxicity, specifically for changes that may
impact spermatogenesis, sperm transit or sperm and semen quality.
They reported observing no effects on these endpoints 2 or 14
days after rats were given a single [oral] dose of 100 mg MBAA/kg
or after 14 daily doses of 25 mg MBAA/kg/day. They concluded
that MBAA was non-spermatotoxic in this short duration test but
did not rule out the possibility that cumulative effects could
occur with exposures of longer duration
