INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 28
ACRYLONITRILE
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experts and does not necessarily represent the decisions or the stated
policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization.
Published under the joint sponsorship of
the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization
World Health Orgnization
Geneva, 1983
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coordination of laboratory testing and epidemiological studies, and
promotion of research on the mechanisms of the biological action of
chemicals.
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR ACRYLONITRILE
1. SUMMARY AND RECOMMENDATIONS FOR FURTHER RESEARCH
1.1. Summary
1.1.1. Properties and analytical methods
1.1.2. Sources of exposure
1.1.3. Industrial and environmental levels of exposure
1.1.4. Monitoring of acrylonitrile uptake
1.1.5. Absorption, distribution, biotransformation,
and elimination
1.1.6. Effects on experimental animals
1.1.7. Effects on man
1.2. Recommendations for further research
2. PROPERTIES AND ANALYTICAL METHODS
2.1. Physical and chemical properties of acrylonitrile
2.1.1. Physical properties
2.1.2. Chemical properties
2.2. Analytical methods
2.2.1. Sampling methods
2.2.2. Analytical methods for determining acrylonitrile
2.2.2.1 Determination of acrylonitrile and its
metabolites in biological materials
3. SOURCES OF INDUSTRIAL AND ENVIRONMENTAL EXPOSURE TO ACRYLONITRILE
3.1. Natural occurrence
3.2. Industrial technology, production data, and projection
3.3. Use patterns
3.4. Disposal of wastes
3.5. Accidental release
3.6. Environmental persistence
4. INDUSTRIAL AND ENVIRONMENTAL SOURCES AND LEVELS OF EXPOSURE
4.1. Exposure of the general population
4.1.1. Air
4.1.2. Water
4.1.3. Food
4.1.4. Other sources of exposure
4.2. Occupational exposure
4.3. Estimate of human exposure from all environmental media
5. CHEMOBIOKINETICS AND METABOLISM
5.1. Absorption
5.1.1. Human studies
5.1.1.1 Uptake through inhalation
5.1.1.2 Dermal absorption
5.1.1.3 Uptake by other routes
5.1.2. Experimental animal studies
5.1.2.1 Uptake through inhalation
5.1.2.2 Dermal absorption
5.1.2.3 Uptake by other routes
5.2. Distribution and toxicokinetics
5.2.1. Human studies
5.2.2. Experimental animal studies
5.3. Biotransformation and elimination
5.3.1. Human studies
5.3.2. Experimental animal studies
5.3.2.1 The oxidative pathways of acrylonitrile
metabolism
5.3.2.2 Mercapturic acids formed in
acrylonitrile biotransformation
5.3.2.3 The glucuronic acid conjugate
of acrylonitrile metabolism
5.3.2.4 Quantitative aspects of acrylonitrile
biotransformation and elimination of
its metabolites
6. BIOLOGICAL MONITORING OF ACRYLONITRILE UPTAKE
7. EFFECTS ON EXPERIMENTAL ANIMALS AND CELL SYSTEMS
7.1. Acute toxicity
7.1.1. Lethal doses and concentrations
7.1.1.1 Lethal doses
7.1.1.2 Lethal concentrations in air
7.1.1.3 Lethal concentrations in water
7.1.2. Clinical observations
7.1.3. Biochemical changes and mechanisms of
acrylonitrile toxicity
7.1.3.1 Effect on cytochrome oxidase
7.1.3.2 Effect on sulfhydryls
7.1.3.3 Interaction with the microsomal oxidation system
as a possible mechanism of toxicity
7.1.3.4 Observations on the possible participation of
membrane lipid peroxidation in the mechanism
of toxicity
7.1.3.5 Studies on antidotes
7.2. Subacute toxicity
7.2.1. Inhalation exposure
7.2.2. Oral administration
7.2.3. Subcutaneous administration and
intraperitoneal administration
7.2.4. Clinical observations in animal studies
7.2.4.1 Body weight, food and water consumption
7.2.4.2 Organ weights and pathology
7.2.4.3 Blood
7.2.4.4 Immune system
7.2.4.5 Nervous system
7.2.4.6 Urine
7.2.4.7 Adrenals
7.2.4.8 Metabolism
7.3. Chronic toxicity
7.3.1. Body weight, food and water intake
7.3.2. Organ weights
7.3.3. Pathology and histology
7.3.4. Haematology and clinical chemistry
7.3.5. Nervous system
7.3.6. Kidney function
7.4. Teratogenicity and embryotoxicity
7.5. Mutagenicity
7.5.1. Bacterial systems
7.5.2. Yeast assays
7.5.3. Drosophila melanogaster
7.5.4. Mammalian cell in vitro assays
7.5.5. Mammalian in vivo assays
7.6. Carcinogenicity
8. EFFECTS ON MAN
8.1. Acrylonitrile
8.1.1. Acute toxicity
8.1.1.1 Inhalation exposure
8.1.1.2 Dermal exposure
8.1.2. Chronic toxicity - occupational exposure
8.1.2.1 Clinical observations
8.1.2.2 Haematology
8.1.2.3 Other organs
8.1.2.4 Nervous system
8.1.2.5 Dermal effects
8.2. Mutagenicity
8.3. Carcinogenicity
8.4. Simultaneous occupational exposure to acrylonitrile and
other chemicals
8.4.1. Acute toxicity
8.4.2. Chronic toxicity
9. EVALUATION OF HEALTH RISKS TO MAN FROM EXPOSURE TO
ACRYLONITRILE
9.1. Sources and levels of exposure
9.2. Acrylonitrile toxicity
REFERENCES
NOTE TO READERS OF THE CRITERIA DOCUMENTS
While every effort has been made to present information in
the criteria documents as accurately as possible without unduly
delaying their publication, mistakes might have occurred and are
likely to occur in the future. In the interest of all users of
the environmental health criteria documents, readers are kindly
requested to communicate any errors found to the Manager of the
International Programme on Chemical Safety, World Health
Organization, Geneva, Switzerland, in order that they may be
included in corrigenda, which will appear in subsequent volumes.
In addition, experts in any particular field dealt with in
the criteria documents are kindly requested to make available to
the WHO Secretariat any important published information that may
have inadvertently been omitted and which may change the
evaluation of health risks from exposure to the environmental
agent under examination, so that the information may be
considered in the event of updating and re-evaluation of the
conclusions contained in the criteria documents.
* * *
A detailed data profile and a legal file can be obtained from
the International Register of Potentially Toxic Chemicals, Palais
des Nations, 1211 Geneva 10, Switzerland (Telephone no. 988400 -
985850).
TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR ACRYLONITRILE
Members
Dr I. Gut, Institute of Hygiene & Epidemiology, Prague,
Czechoslovakia
Dr V.V. Ivanov, State Medical Institute, Krasnoyarsk, USSR
Dr J. Kopecky, Institute of Hygiene & Epidemiology, Prague,
Czechoslovakia
Dr W.N. Rom, Rocky Mountain Center for Occupational &
Environmental Health, School of Medicine, University of
Utah, Salt Lake City, Utah, USA
Dr M. Sharratt, BP Group Occupational Health Centre,
Sunbury-on-Thames, England (Chairman)
Dr J. Sokal, Institute of Occupational Medicine, Lodz, Poland
(Rapporteur)
Dr. L. Zisser, Department of Occupational Medicine, Kupat
Holin - District Yehuda, Rehovoth, Israel (Vice-Chairman)
Representatives of other organizations
Dr A. Berlin, Health & Safety Directorate, Commission of the
European Communities, Luxembourg
Dr R.A. Baxter, Monsanto Europe, Brussels (representing the
Association of Plastic Manufacturers in Europe - APME)
Secretariat
Dr M.H. Draper, Medical Officer-Toxicologist, International
Programme on Chemical Safety (Secretary)
Dr K.W. Jager, Consultant, International Programme on Chemical
Safety
ENVIRONMENTAL HEALTH CRITERIA FOR ACRYLONITRILE
Further to the recommendations of the Stockholm United
Nations Conference on the Human Environment in 1972, and in
response to a number of World Health Assembly resolutions
(WHA23.60, WHA24.47, WHA25.58, WHA26.68) and the recommendations
of the Governing Council of the United Nations Environment
Programme, (UNEP/GC/10, July 3 1973), a programme on the
integrated assessment of the health effects of environmental
pollution was initiated in 1973. The programme, known as the WHO
Environmental Health Criteria Programme, has been implemented
with the support of the Environment Fund of the United Nations
Environment Programme. In 1980, the Environmental Health
Criteria Programme was incorporated into the International
Programme on Chemical Safety (IPCS). The result of the
Environmental Health Criteria Programme is a series of criteria
documents.
The Institute of Hygiene and Epidemiology (Director,
Professor Bohumir Rosicky), Prague, was responsible, as a Lead
Institution of the IPCS, for the preparation of the first and
second drafts, which were written and coordinated by Dr I. Gut
and Dr J. Kopecky of that Institute.
The Task Group for the Environmental Health Criteria for
Acrylonitrile met in Prague in the Institute of Hygiene and
Epidemiology from 4-8 July 1983. The meeting was opened by
Professor B. Rosicky, and Dr M.H. Draper welcomed the
participants and representatives of the organizations on behalf
of the three organizations co-sponsoring the IPCS (UNEP/ILO/WHO).
The Task Group reviewed and revised the second draft criteria
document and made an evaluation of the health risks of exposure
to acrylonitrile.
The efforts of all who helped in the preparation and the
finalization of the document are gratefully acknowledged.
* * *
Partial financial support for the publication of this
criteria document was kindly provided by the United States
Department of Health and Human Services through a contract from
the National Institute of Environmental Health Sciences, Research
Triangle Park, North Carolina, USA - a WHO Collaborating Centre
for Environmental Health Effects.
1. SUMMARY AND RECOMMENDATIONS FOR FURTHER RESEARCH
1.1. Summary
1.1.1. Properties and analytical methods
Acrylonitrile (CH2=CH-C-N) is a volatile, colourless,
flammable liquid with a sweet characteristic odour. It is used
in the production of acrylic and modacrylic fibres, resins and
rubbers, and as a chemical intermediate. It has been employed as
a fumigant. Exposure to both the vapour and the liquid can occur
at the workplace, the highest atmospheric concentrations
occurring in acrylic fibre production.
For the control of exposure to acrylonitrile at the
workplace, sampling should preferably be from the breathing zone
of the worker; active and passive sampling techniques are
available.
The most widely used analytical techniques are the gas
chromatographic techniques; these are particularly sensitive if
nitrogen-sensitive and specific sensors are used. High-pressure
liquid chromatographic, infra-red, and colorimetric methods may
be useful, where gas chromatography is not available. Methods
have been developed for the determination of acrylonitrile in
blood, food, water, etc. Determination of acrylonitrile-derived
mercapturic acids in urine may prove to be of value for the
biological monitoring of exposure.
1.1.2. Sources of exposure
Acrylonitrile is emitted from industrial plants in the form
of vapours and in aqueous effluents; exposure of the population
living near plants cannot therefore be excluded. The total
emissions from acrylonitrile plants have been estimated to be
about 2.2% of total production, but these figures have decreased
recently. Polymers contain various concentrations of free
acrylonitrile; when used for packaging in the food industry,
minute amounts of the monomer may pass into the food.
Acrylonitrile may also enter the environment accidentally, during
its storage and transport.
1.1.3. Industrial and environmental levels of exposure
Contamination of water and food is possible but, with the
exception of the contamination of water supplies through
accidental spillage, levels of exposure would be low. The
highest potential for exposure is at the workplace, both through
inhalation of vapour and contamination of the skin by liquid
acrylonitrile.
1.1.4. Monitoring of acrylonitrile uptake
The most significant uptake of acrylonitrile vapour is
through the respiratory tract. Exposure is commonly monitored by
determining the time-weighted average atmospheric concentrations.
Estimation of acrylonitrile-derived mercapturic acids in
urine is a promising method for the biological monitoring of
exposure, but further validating studies are needed.
1.1.5. Absorption, distribution, biotransformation, and
elimination
In animals, acrylonitrile is readily absorbed both through
the skin and by inhalation. Systemic and even fatal effects are
possible via these routes.
The distribution of acrylonitrile within the animal body is
fairly uniform. There are no indications of accumulation in
animal tissues following prolonged exposure.
At least 10 different metabolites of acrylonitrile have been
identified. Mercapturic acids are the major metabolites of
acrylonitrile in vivo. Urinary excretion of acrylonitrile-
derived mercapturic acids is proportional to the internal
concentration of acrylonitrile.
Elimination of acrylonitrile, as such, in expired air is
negligible, but a small percentage is eliminated in the urine.
1.1.6. Effects on experimental animals
Acrylonitrile induces a variety of toxic effects. Effects
due to over-exposure are non-specific and mainly related to the
gastro-intestinal and respiratory tracts, the central nervous
system, and the kidneys. Respiratory distress, lethargy,
convulsions, and coma occur with lethal or near-lethal exposures
(7500 mg/m3, inhalation). Dogs are most sensitive, and rats
least sensitive to acrylonitrile, with mice, guinea-pigs, cats,
and monkeys in an intermediate position. However, the
information available from these studies is too fragmentary to
indicate clear no-observed-adverse-effect levels.
Extensive dermal exposure to the liquid may be lethal. At
lower exposures, irritation of the skin and mucous membranes can
occur.
The most typical biochemical changes caused by acrylonitrile
are inhibition of sulfhydryl-dependent enzymes (lactate
dehydrogenase, LDH (EC 1.1.1.27), sorbitol dehydrogenase, SDH (EC
1.1.1.14), pyruvate oxidase (EC 1.2.3.3)) and a reduction in the
concentrations of glutathione and protein sulfhydryls in the
blood and various organs, resulting in a disturbance of glucose
utilization. The cyanide generated causes inhibition of
cytochrome oxidase (EC 1.9.3.1) but this seems to be of less
significance than the above-mentioned metabolic disturbances, at
low exposure levels.
Exposure to some organic solvents in addition to
acrylonitrile may significantly enhance its toxic effects.
Acrylonitrile can cause embryotoxic and teratogenic effects,
but only at levels near the toxic dose level for the specific
experimental animal.
It is probable that acrylonitrile is not mutagenic itself,
but that its metabolites are responsible for the positive effects
in various test systems. It is mutagenic in in vitro systems
(bacterial tests and cell cultures), but not in in vivo systems,
such as the dominant lethal assay.
On the basis of the results of several animal studies, using
a wide dose-range, there is sufficient evidence to suggest that
acrylonitrile is a carcinogen in the rat.
1.1.7. Effects on man
Symptoms of over-exposure in man are non-specific. They are
related to the gastrointestinal and respiratory tracts, and to
the central nervous system and include headache, insomnia,
nausea, vomiting, diarrhoea, fatigue, mild jaundice, and
irritation and inflammation of the respiratory tract and mucous
membranes. In more severe cases, unconsciousness and convulsions
may occur. Fatalities have been reported following exposure to
acrylonitrile, especially following its use as a fumigant.
Dermal exposure, especially to liquid acrylonitrile, may cause
irritation, erythema, and blisters. Toxic and allergic dermatitis
can occur.
While a correlation between exposure to acrylonitrile and the
incidence of cancer in man has not been demonstrated conclusively
in human epidemiological studies, the findings are not
incompatible with this supposition. Thus, there is no reason to
disregard the evidence that has been provided by animal studies.
It follows that exposure to acrylonitrile should be kept as
low as possible at the workplace and in the general environment,
and that skin contact with liquid acrylonitrile should be
avoided.
1.2. Recommendations for Further Research
The Task Group noted that valuable information from industry,
while available to national and international bodies, had not
been published. This greatly reduces the value of these studies,
as they are unavailab1e for peer review and critical examination
by the scientific community.
The Group recommended the following studies:
(a) Improvement and validation of passive sampling techniques
with special attention to interfering substances;
(b) Validation of the measurement of acrylonitrile and
acrylonitrile-derived mercapturic acids in urine as
methods for biological monitoring for workplace exposure,
with regard to analytical aspects and sampling conditions;
(c) Investigation of the environmental fate of acrylonitrile
including photochemical degradation;
(d) Further investigation of the mechanisms of action and the
nature of acute and chronic toxic effects in conditions
relevant to human exposure;
(e) Studies on the carcinogenicity of acrylonitrile in
relation to animal species other than the rat;
(f) Further investigation of the metabolism and toxicokinetics
of acrylonitrile in different animal species, in order to
obtain information that will assist in the interpretation
of biological monitoring data in man;
(g) Further examination of the immunological aspects of the
action of acrylonitrile in man and animals;
(h) Further studies on the effects of acrylonitrile on
reproduction;
(i) Investigations on reproductive outcome and mutagenicity in
human beings occupationally exposed to acrylonitrile.
Epidemiological data with good indications of past and
present exposure levels should be available, to ensure an
adequate health risk evaluation.
2. PROPERTIES AND ANALYTICAL METHODS
2.1. Physical and Chemical Properties of Acrylonitrile
2.1.1. Physical properties
Acrylonitrile (CH2=CH-C-N) is a volatile, colourless,
flammable liquid with a sweet, characteristic odour. It is
slightly soluble in water and miscible with most organic solvents
(American Cyanamid, 1959). The vapours are explosive, cyanide
gas being produced. The explosive range in air at 25 °C has a
lower limit of 3.05%, and an upper limit of 17.0%, by volume
(Patty, 1963). The olfactory threshold level for acrylonitrile
averages 40.4 mg/m3 (18.6 ppm) and ranges from 0.007 to 109.4
mg/m3 (0.0031 to 50.4 ppm) (Baker, 1963). Important physical
constants and properties of acrylonitrile are summarized in
Table 1.
2.1.2. Chemical properties
Structural formula: H H
\ /
\3 2/
C = C
/ \
/ \
H C - N
1
Synonyms: cyanoethylene, 2-propenenitrile, vinyl
cyanide.
CAS Registry Number: 107-13-1.
The reactions of acrylonitrile involve the double bond (C=C)
and/or the cyano group (CN) (American Cyanamid, 1959). It
polymerizes to polyacrylonitrile, and copolymerizes with, e.g.,
styrene, butadiene, esters of acrylic or methacrylic acid, to
form various resins, nitrile rubber, and acrylic and modacrylic
fibres. Hydration produces acrylamide or acrylic acid and
esterification the corresponding acrylic esters. Reductive
coupling produces adiponitrile. With compounds containing active
hydrogen(s) (AH molecules such as the biologically-important
compounds containing the nucleophilic -CH, -NH, and -SH groups),
cyanoethylation takes place:
A-H + CH2 = CH-CN + A-CH2CH2CN
(American Cyanamid, 1959). This reaction is of particular
importance in relation to its fate in biological systems;
covalent binding of acrylonitrile to the tissue components has
been demonstrated (section 7.1.3.3). Direct oxidation of
acrylonitrile with hydroperoxide compounds affects the cyano
group of acrylonitrile, although in biological systems, it is
probable that oxidation of the double bond to the oxirane,
glycidonitrile (CH2 - CH-CN) occurs (Kopecky et al., 1980a,b).
\ /
O
Table 1. Physical properties of acrylonitrilea
-----------------------------------------------------------------
appearance colourless liquid
boiling point 77.3 °C at 760 mm pressure
density 0.8060 (20 °C), 0.8004 (25 °C)
flash point (tag open cup) 0 °C
(closed cup) -4.4 °C
freezing point -83.55, ± 0.05 °C
ignition temperature 481 °C
relative molecular mass 53.06
octanol/H2O partition coefficient 0.12b
odour faintly pungent
refractive index nD 25 = 1.3888
% solubility in waterc 7.2% (0 °C)
7.35% (20 °C)
7.9% (40 °C)
vapour pressure (mm Hg) 50 (8.7 °C)
100 (23.6 °C)
250 (45.5 °C)
500 (64.7 °C)
760 (77.3 °C)
partial vapour pressure log P = 7.518 - 1644.7
water azeotrope TK
(i.e., 80 mm at 20 °C)
Conversion factor for vapour 1 mg/m3 = 0.4605 ppm
(25 °C; 760 mm Hg) 1 ppm = 2.17 mg/m3
1 mg/litre water = 1 ppm
-----------------------------------------------------------------
a From: American Cyanamid (1959, 1974).
b From: Dorigan et al. (1976); antilog of -0.92.
c Acrylonitrile is miscible with most organic solvents.
There have not been any experimental studies but, as a
reactive olefine, it would be expected that acrylonitrile would
be oxidized in the atmosphere under the influence of ultraviolet
radiation (UVR) or by reactive oxygen species (atomic oxygen, OH
radicals, ozone). The atmospheric half-life of acrylonitrile is
estimated to be 9-10 h (Suta, 1979).
Technical-grade acrylonitrile is more than 99% pure. Except
for water, impurities and stabilizers are present at mg/kg levels
only. Possible contaminants are shown in Table 2. Spontaneous
explosive polymerization of pure acrylonitrile may occur, in the
absence of oxygen, on exposure to visible light or alkali
(DuPont, 1977). A yellow colour may slowly develop on standing,
particularly after excessive exposure to light. Water improves
the stability of acrylonitrile, and the technical-grade product
is stabilized against self-polymerization and colour formation by
the addition of hydroquinone monomethyl ether and water.
2.2. Analytical Methods
In this section, sampling methods, sample storage, and
analytical methods for determining acrylonitrile and its
metabolites are discussed. The only breakdown products
considered are those detected in vivo, as these are the only
ones of importance for assessing levels of exposure to
acrylonitrile.
2.2.1. Sampling methods
Sorption tubes are widely used for sampling acrylonitrile in
air, because samples can be taken over a prolonged period from
the breathing zone of the worker. The solid sorbent gas samplers
have been critically reviewed by Crisp (1980). Of the solid
sorbents, activated charcoal, porous polymers, or silica gel are
most commonly used. Adsorbed acrylonitrile is later desorbed,
generally by a solvent (methanol or carbon disulfide) or
thermally, and determined by gas chromatography. Several devices
have been developed for sampling workplace air. A sorbent
sampling tube fastened to the worker's shoulder and a pump
fastened to the belt may be worn for a whole working shift
without discomfort. Muhtarova (1977) described significant
differences between the results of static sampling and personal
monitoring in determining acrylonitrile exposure in workers.
Personal monitoring gives a better indication. Area
concentrations can be determined by detector tubes, to give an
immediate indication of the level (CIA, 1978; Grote et al.,
1978).
In the widely-used NIOSH method S156 (NIOSH, 1976), a known
volume of air is drawn through a charcoal tube (divided into 2
sections in order to check that the adsorption capacity has not
been swamped), and the charcoal is desorbed by methanol for 30
min. This method was validated by NIOSH over a concentration
range of 17.5-70.0 mg/m3 (8.1-32.3 ppm) at 22 °C and 760 mm Hg
using a 20-litre sample; the coefficient of variation was 0.073.
However, the suspicion that acrylonitrile may be a human
carcinogen (NIOSH, 1978) led to the need to determine lower
concentrations of acrylonitrile in air. With a simple
modification in method S156, using a desorbing solvent of 2% v/v
acetone solution in carbon disulfide, Gagnon & Posner (1979) were
able to achieve a sensitivity of 1.1 mg/m3 (0.5 ppm) based on an
air sample volume of 15 litres. The samples are stable for at
least a week, even in the absence of a stabilizer. A similar
method, developed by the Midwest Research Institute for sampling
air near acrylonitrile plants (Going et al., 1979), involves the
use of charcoal tubes, sampling air at 1 litre/min, desorbing the
sample with carbon disulfide, and analysing by gas
chromatography. However, high humidity and interference from
other substances can reduce collection efficiency on charcoal;
these problems can be overcome by the use of porous polymer
absorbents and thermal desorption techniques (Campbell & Moore,
1979; United Kingdom Health and Safety Executive, 1981).
Table 2. Specifications for acrylonitrile from two producersa
------------------------------------------------------------------
Specifications DuPont Monsanto
------------------------------------------------------------------
acetone, mg/kg max. n.r.b 300
acetonitrile, mg/kg max. 500 500
aldehydes, as acetaldehyde
mg/kg max. 50 50
iron, mg/kg max. 0.1 0.2
hydrocyanic acid, mg/kg max. 10 5
peroxides, as hydrogen
peroxide, mg/kg max. 0.3 1.0
water, % 2.5-4.5 2.5-4.5
inhibitor, MEHQc, mg/kg 35 - 50 35 - 50
acidity, as acetic acid,
mg/kg max. 35 20
pH, 5% aqueous solution 5.5-7.5 n.r.b
non-volatile matter,
mg/kg max. 100 100
refractive index at 25 °C 1.3880 - 1.3892 1.3880 - 1.3892
appearance clear & free clear & free
flowing flowing
------------------------------------------------------------------
a From: DuPont (1977) and Monsanto (1977a).
b n.r. = not reported.
c MEHQ - hydroquinone monomethyl ether (methylhydroquinone).
While many industrial hygiene personal monitoring
measurements have been carried out using these methods, over the
last 3-4 years an increasing number of "passive" samplers (gas
badges) (Silverstein, 1977) have been developed. The advantages
of these devices are that there are no moving parts to break
down, regular flow calibration is unnecessary, and no bulky,
expensive pumps are required.
Benson & Boyce (1981) and Benson et al. (1981) described a
passive dosimeter in which acrylonitrile was adsorbed on a porous
polymer (PorapakRN) contained in a removable element, and
determined by thermal desorption gas chromatography. It can be
used satisfactorily for determining acrylonitrile concentrations
in air under a range of atmospheric conditions, when working to
a control limit of 8.7 mg/m3 (4 ppm) but, at a concentration of
4.4 mg/m3 (2 ppm), a 40% error has been reported. These devices
are now considered to be as reliable as the more conventional
pump and tube methods (Rose & Perkins, 1982).
The head-space sampling method is useful for the
determination of residual acrylonitrile monomer in copolymers and
by-products, since it is more sensitive (detection limit 1.1
mg/m3 (0.5 ppm)) than direct injection (detection limit 21.7
mg/m3 (10 ppm)) (Steichen, 1976). It involves the equilibration
of a solid polymer with air in a closed vessel. Free monomer is
partitioned between the polymer phase and the "head-space" air,
and the monomer concentration in the head-space is then
determined (Steichen, 1976). Oomens (1980) gives a detection
limit for acrylonitrile of 0.02 mg/m3 (0.01 ppm) with the aid of
a similar method, applying the more sensitive and specific PND
detector. The procedure has been used for determining the
acrylonitrile monomer in copolymer solutions (McNeal & Breder,
1981), plastic packaging, and beverages (Gawell, 1979). Gawell's
method is suitable for determining acrylonitrile at
concentrations as low as 0.1 mg/kg, in plastics, and 0.005 mg/kg,
in beverages. The method has also been used for determining
acrylonitrile in food-simulating solvents (US FDA, 1977a) and,
with a detection limit of 0.5 mg/kg, in acrylonitrile-derived
copolymers (Steichen, 1976).
Continuously recording gas chromatographic methods have been
developed for monitoring atmospheric concentrations of
acrylonitrile.
Samples of water containing acrylonitrile can be acidified by
sulfuric acid to a pH < 4 and then kept at 0 °C until analysed
(Going et al., 1979).
2.2.2. Analytical methods for determinating acrylonitrile
Acrylonitrile can be determined using instrumental methods:
gas chromatography, possibly high-pressure liquid chromatography,
infrared spectroscopy, polarography, and chemical titrimetric and
colorimetric methods.
(a) Gas chromatography
This is the most frequently used method for acrylonitrile
determination, particularly in conjunction with the charcoal
sampling method. A number of gas chromatographic procedures have
been developed for different types of samples. Until recently,
almost all involved flame ionization detection, but attention is
now being paid to thermoionic nitrogen-selective detectors
(Shevchik, 1976) in the determination of acrylonitrile (e.g., US
FDA, 1977a; Gawell, 1979; McNeal & Breder, 1981).
Various column packings have been evaluated for the
determination of acrylonitrile by gas chromatography, e.g., in
the air (Parsons & Mitzner, 1975; Russell, 1975) (Table 3).
Porous polymer column packings have the advantage of resolving
acrylonitrile from methanol (frequently used to desorb
acrylonitrile from charcoal) and of being useful for direct
injection of aqueous acrylonitrile samples.
Examples of gas chromatographic methods for determining
acrylonitrile in a variety of products and samples containing
acrylonitrile are given in Table 4, together with the detection
limits.
Borg-Warner Chemicals (1977) developed a continuous-recording
gas chromatograph that reportedly detects acrylonitrile below 1.1
mg/m3 (0.5 ppm). A portable gas chromatograph for the
determination of acrylonitrile in air was developed by Vistron
(personal communication, 1978) and a direct injection gas
chromatograph for acrylonitrile determinations was tested by
Union Carbide Corporation (1977); preliminary results indicate a
detection limit below 2.2 mg/m3 (1 ppm).
(b) High-pressure liquid chromatography
A high-pressure liquid chromatograph method has been
developed for the determination of residual acrylonitrile monomer
in acrylic polymer and fibre (US Consumer Product Safety
Commission, 1978). The acrylic polymer or fibre is heated above
its glass transition temperature and refluxed continuously under
water. The extract is distilled and analysed. No interference
from contaminants has been noted.
(c) Infrared spectroscopy
Direct determination of acrylonitrile in air by IR
spectroscopy, using wavelength 10.49 µm, 20 °C and 760 mm Hg, and
a 250 cm gas cell, has been reported to have a detection limit of
about 0.5 ppm (v/v). The equipment is expensive, requires skill
to use, and is sensitive to physical damage. A portable IR
analyser for "on-the-spot" detection of acrylonitrile in air,
with a detection limit of 0.4 mg/m3 (0.2 ppm), has been
recommended by Jacobs & Syrjala (1978).
Table 3. Gas chromatographic conditions for acrylonitrile determination
--------------------------------------------------------------------------------------------------------
Packing Conditions Comments Reference
--------------------------------------------------------------------------------------------------------
Tenax 80 °C, 15 cc/min N2, -, Used by American Cyanamid
60 x 0.3 cm, Teflon for water analysis
0.4% Carbowax 1500 on 100 °C, 30 cc/min He, -, Head space analysis of Steichen (1976)
Carbopax A 80 x 0.3 cm, stainless steel residual monomer
Porapak Q, 50/80 mesh 155 °C, 50 cc/min N2, -, NIOSH method for acrylo- NIOSH (1976)
120 x 0.6 cm stainless steel nitrile in air
Porapak Q, 50/80 mesh 160 °C, 30 cc/min N2, Poor resolution from Barrett (1974)
3.2 min, 150 x 0.3 cm methanol
stainless steel
Porapak N, 50/80 mesh 170 °C, 40 cc/min N2, Resolved from methanol Barrett (1974)
10.5 min, 270 x 0.3 cm
stainless steel
Chromosorb 101, 50/60 or 110 °C to 200 °C at ASTM approved method for ASTM (1981)
porous styrene divinyl 10 °C/min, 25 ml/min He, nitriles in water
benzene polymer 240 x 0.3 cm stainless
steel
Porapak Q, 50/80 mesh 156 °C, 50 cc/min He, Used with a trapping Bellar & Sigsby
11.8 min, 360 x 0.3 cm column for combustion (1980)
stainless steel effluents
10% SP - 1000, 60/80 150 °C, 45 cm/min Acrylonitrile plus various Marano et al. (1978)
mesh supelcopore organic vapours
--------------------------------------------------------------------------------------------------------
a Column temperature, carrier gas and flow rate, retention time, column parameters.
Table 4. Determination of acrylonitrile in different acrylonitrile-containing
samples and products
-------------------------------------------------------------------------------
Sample source Detection limit Reference
-------------------------------------------------------------------------------
water solution 10 mg/kg Ramstad & Nicholson (1982)
polyacrylonitrile 10 - 100 mg/kg Reichle & Tengler (1968)
vinylidene chloride- 10 mg/kg UK Ministry of Agriculture,
acrylonitrile coated film Fisheries & Food (1982)
food samples 0.01 - 0.02 mg/kg UK Ministry of Agriculture,
Fisheries & Food (1982)
acrylic co-polymers 0.5 mg/kg Steichen (1976)
70 mg/kg McNeal & Breder (1981)
carbonated beverage (simulated) 1 mg/kg McNeal & Breder (1982)
fumigant residue in cereals & 0.1 mg/kg Heuser & Scudmore (1969)
other foods
air of acrylonitrile plants n.s. Cincolella et al. (1981)
acetone extract of styrene- 1 mg/kg US Consumer Product Safety
acrylonitrile resins Commission (1978)
-------------------------------------------------------------------------------
n.s. = not stated
(d) Polarography
A polarographic method for the determination of acrylonitrile
was first reported by Bird & Hale (1952). Berck (1960) used the
method of Daues & Hamner (1957) to determine acrylonitrile
residues in walnuts. Aqueous extracts of styrene-acrylonitrile
copolymer (Petrova et al., 1972), the volatile fractions of
styrene copolymer (Uhde & Koehler, 1967), and industrial waste
water (Ponomarev et al., 1974) have also been analysed using
polarography. A method developed by Rogaczewska (1964) had a
sensitivity of 10 mg/litre and 40 mg/m3 for the determination of
acrylonitrile in solution and in air, respectively.
(e) Colorimetric methods
In one method, the acrylonitrile-containing sample is
hydrolysed by a strong base to ammonia, which is determined by
the Nessler reagent (Rogaczewska, 1965; Aarato & Bittera, 1972).
The detection limit of this method is about 6 mg/m3 (3 ppm) in
air. A modification using hypochlorite and sodium salicylate has
a detection limit of 0.5 mg/m3 (Rogaczewska, 1976).
A modified hydrolytic method using hydrogen peroxide under
acidic conditions has been developed for the determination of
acrylonitrile in air (American Industrial Hygiene Association,
1970; Maddock et al., 1977). The sensitivity is in the range of
20-300 µg/ml of absorbing solution.
Another colorimetric method is based on the formation of
cyanogen bromide under the influence of UVR and the production of
a pink colour by coupling the cyanogen bromide with benzidine in
pyridine solution. Using this method, Kanai & Hashimoto (1965)
determined acrylonitrile in the expired air, blood, and urine of
exposed animals. This method has been further used for the
determination of acrylonitrile in air (Krynska, 1970; Tada, 1971;
Russkih, 1972, 1973) with a detection limit of 0.4 - 0.5 mg/m3,
and in food (Kroeller, 1970) and waste water (Ghersin et al.,
1969) with a detection limit of 2 mg/1itre. When the sample
contains both acrylonitrile and cyanide, the cyanide should be
removed before analysis (Aldridge, 1944; Bruce et al., 1955;
Kanai & Hashimoto, 1965).
(f) Titrimetric methods
A titrimetric method based on the cyanoethylation of a
sulfhydryl compound (lauryl mercaptan), by acrylonitrile, has
been described (Haslam & Newlands, 1955). An excess of the thiol
is added to the acrylonitrile sample and, after the reaction, it
is determined by iodometric or amperometric titration or by
Ellman's reagent. Although this method is specific, it is
neither rapid nor sensitive enough.
A titrimetric method for determining acrylonitrile, developed
by Terent'ev & Obtemperanskaya (1956), consists of the release of
sodium hydroxide by the reaction of acrylonitrile with sodium
sulfite. A paper-strip modification of this method has recently
been reported by Rajendran & Muthu (1981). It is used for the
detection of acrylonitrile in air and fumigated foodstuffs.
(g) Other analytical methods
Other methods are not frequently used. The
spectrophotometric method of Hall & Stevens (1977), in which
formation of a pyridine-acrylonitrile complex is determined at
435.4 nm, suffers from interference from cyanide, which must be
separated out of the solution.
2.2.2.1. Determination of acrylonitrile and its metabolites in
biological materials
(a) Acrylonitrile in urine
Sato et al. (1975) have modified the method of Aldridge
(1944); acrylonitrile in urine is separated by azeotropic
distillation and then determined by gas chromatography. The
detection limit is 5 µg/litre.
More recently, Houthuijs et al. (1982) developed a method
using head-space chromatography, which has a detection limit of 2
µg/litre. Two millilitre aliquots of urine are equilibrated at
90 °C in 25 ml vials for 3-5 h; the vapour phase is injected
automatically in a gas chromatograph, with a 15% carbowax column
and a phosphor-nitrogen detector.
(b) Acrylonitrile metabolites in urine
(i) Acrylonitrile-derived mercapturic acids
A gas-chromatographic method has been developed by Draminski
& Trojanowska (in press) for the determination of 2-cyanoethyl-
mercapturic acid in the urine of workers exposed to acrylonitrile.
The mercapturic acid is extracted from urine and derivatized by
diazomethane to the methyl ester. The precision of this method is
10% for 2-cyanoethyl-mercapturic acid in the concentration range
of 50-350 mg/litre of urine.
A general procedure for determining the total amount of
mercapturic acids (more generally the total amount of thioethers)
in urine has been described by Seutter-Berlage et al. (1977,
1978) and modified by Van Doorn et al. (1979) and Buffoni et al.
(1982). Deproteinized urine is hydrolysed with sodium hydroxide
for 50 min at 100 °C; this converts the mercapturic acids (and
generally all thioethers) to the corresponding thiols. After
cooling and acidification, SH-groups are assayed by the method of
Ellman (1959).
(ii) Thiocyanate levels
The colorimetric method (the formation of a coloured complex
of thiocyanate with ferric ion) was developed in 1943 (Lawton et
al., 1943).
Very recently, Imanari et al. (1982) applied the high-
performance liquid chromatographic technique, using a strong base
ion-exchanger column for such determinations. The method has
been shown to differentiate well between the urinary thiocyanate
levels found in smokers and non-smokers.
3. SOURCES OF INDUSTRIAL AND ENVIRONMENTAL EXPOSURE TO ACRYLONITRILE
3.1. Natural Occurrence
Acrylonitrile does not occur as a natural product.
3.2. Industrial Technology, Production Data and Projection
Current production is based on catalytic ammoxidation of
propylene in the vapour phase (Idol, 1974):
catalyst
2CH2 = CH-CH3 + 2 NH3 + 3 O2 -------> 2 CH2 = CH-CN + 6 H2O
Bismuth phosphomolybdate is the most frequently used catalyst.
The chief by-products are acetonitrile and hydrogen cyanide.
Processes previously used in the production of acrylonitrile
were: (i) the catalytic addition of hydrogen cyanide to
acetylene; (ii) the catalytic dehydration of ethylene to
cyanohydrin; and (iii) the catalytic reaction of propylene with
nitric oxide. These processes are no longer used by the major
manufacturers in the world.
In 1976, the known production of acrylonitrile was about 2.4
million tonnes (IARC, 1979). US manufacturers produced 0.69
million tonnes, Western European manufacturers, 0.92 million
tonnes, and Japanese manufacturers, 0.63 million tonnes.
Production figures for East European countries and the USSR are
not available.
The average annual growth of acrylonitrile production was
about 11% during 1965-1975 (Anonymous, 1977). While further
growth was expected during the early 1980s, because of increased
demands for polyacrylamide in tertiary oil recovery (Pujado et
al., 1977), this did not occur owing to a general recession in
world trade. The West European figure for 1981 is of the order
of 800 000 tonnes (Personal communication), approximately 15%
less than in 1976.
3.3. Use Patterns
The use pattern for acrylonitrile and its products in the USA
in 1976 and Western Europe in 1977 are presented in Table 5
(IARC, 1979).
In a mixture with carbon tetrachloride, acrylonitrile has
also been used as a fumigant for tobacco (Berg, ed., 1977) and
for flour milling and bakery equipment.
Table 5. The use patterns of acrylonitrile and its products in the
USA (1976) and Western Europe (1977)a
-------------------------------------------------------------------------
Product % of % of product production
acrylonitrile
production
-------------------------------------------------------------------------
USA W. Europe
acrylic and 48 68 82 - clothing and home
modacrylic fibres furnishings
18 - export
acrylonitrile- 21 15 88 - pipe fittings, automotive
butadiene-styrene and vehicle components, etc.
acrylonitrile-styrene 12 - automobile instrument
resins panels, household items
etc.
adiponitrile 12 -- mainly hexamethylenediamine
other products 19 17 21 - nitrile elastomers
21 - acrylamide
16 - barrier resins
42 - polyether polymer
polyols, fatty diamines,
etc.
-------------------------------------------------------------------------
a From: IARC (1979).
Pesticides containing acrylonitrile have been withdrawn by
the manufacturers. Acrylonitrile polymers and copolymers are
components of products intended for use in contact with food,
e.g., (i) vinyl resin coatings; (ii) adhesives; (iii)
cellophane; (iv) paper and paperboard components (limited); (v)
polyolefin films; (vi) elastomers - for repeated use; and (vii)
rigid, semi-rigid, and modified acrylic and vinyl plastics. In
the USA, the amount of acrylic component may not exceed that
which is reasonably required to produce the intended effect (US
FDA, 1977b).
The acrylonitrile content of containers fabricated from
acrylonitrile copolymers and the possible migration of
acrylonitrile into foods and beverages have been reviewed (US
FDA, 1977a). The use of copolymers of acrylonitrile for making
beverage bottles was banned in the USA in September, 1977.
The Canada Food and Drugs Act and Regulations (1982) prohibit
the sale of any food in packaging containing acrylonitrile, such
that the compound may pass into the food.
Table 6 shows the levels of residual acrylonitrile in several
polymers, some acrylonitrile derivatives, and products fumigated
with acrylonitrile (US Consumer Product Safety Commission, 1978).
Table 6. Levels of residual acrylonitrile found in various
products
---------------------------------------------------------------
Product Acrylonitrile
content
---------------------------------------------------------------
acrylic and modacrylic fibres 1 mg/kga
acrylonitrile-butadiene-styrene resins 30-50 mg/kga
styrene-acrylonitrile resins 15 mg/kga
nitrile rubber and latex material 0-750 mg/kga
acrylamide 25-50 mg/kga
polyether polymer polyols 100-300 mg/kga
shelled walnuts 0-8.5 mg/kgb
US cigarettes (non-filtered) 1-2 mg/100 cigarettesc
---------------------------------------------------------------
a From: US Consumer Product Safety Commission (1978).
b 38 days after fumigation with a mixture of acrylonitrile
and carbon tetrachloride (Berck, 1960).
c From: Buérin et al. (1974); Wynder & Hoffmann (1967).
The total emissions from acrylonitrile plants in the USA, in
1974, have been estimated to be about 2.2% of the total
production (Table 7) (Patterson et al., 1976). More recent
estimates (Suta, personal communication, 1982), following the
introduction of stricter emission controls, indicate an overall
reduction in emissions and a change in pattern (for 1981, 800
tonnes for acrylonitrile production and 3000 tonnes for end-
product manufacture).
3.4. Disposal of Wastes
Acrylonitrile may also enter the environment during storage,
transport, transfer, and end-use. A detailed study on the entry
of acrylonitrile into the environment was carried out by the
Midwest Research Institute for the EPA (Going et al., 1979).
Air, water, and soil were sampled at, and near to, acrylonitrile
and acrylamide production plants and acrylonitrile-derived resin,
fibre, and elastomer production plants.
During acrylonitrile production, the fo1lowing wastes are
produced: gaseous wastes; liquid wastes (waste water column
bottoms, acetonitrile column bottoms, heavy ends, crude
acetonitrile, hydrogen cyanide); and solid wastes (catalyst fines
and organic polymers). Three types of on-site disposal methods
have been described by Hughes & Horn (1977): (a) flare; (b)
thermal incineration; and (c) deep-well pond and deep-well
injection.
Table 7. Acrylonitrile emissions from plants
in the USA in 1974a
-----------------------------------------------
Source Emission (tonnes)
-----------------------------------------------
acrylonitrile production 6400
end-product manufacture 5900
bulk storage 1800
total emission 14 100
-----------------------------------------------
a From: Patterson et al. (1976).
Much liquid waste from acrylonitrile-manufacturing plants is
discharged directly into deep wells, after pre-treatment using
alkaline hydrolysis, the biodegradable effluent being disposed of
in publicly-owned treatment works. In some cases, organic wastes
are incinerated (Lowenbach et al., 1978).
Deep-well injection is no longer considered a viable method
in the USA; to control the drilling of new wells, an industrial
discharger must re-apply for a permit (US EPA, 1977).
Lowenbach et al. (1978) extensively reviewed the alternative
biological, chemical, and physical methods of treating waste
waters from acrylonitrile manufacture, but a detailed discussion
of these is not within the scope of this report.
3.5. Accidental Release
Acrylonitrile may be released accidentally into the
environment. Its half-life in air is estimated to be 9-10 h
(section 2.1.2). In water, the half-life, as estimated by the
BOD test, is 5-7 days. Although these data would indicate that
small spillages would not present a problem, initial high levels
of acrylonitrile may have severe local effects. No
bioaccumulation or food chain concentration potential has been
noted (US Dept of Transportation, 1974), but it was observed that
the concentration of acylonitrile in the ground water increased
when it rained several months after an accidental spillage
occurred. The persistence of acrylonitrile in the water of wells
located within 30 m of a spill of 91 000 litres of acrylonitrile
from a tank car was followed for about 1 year (Miller & Villaume,
1978). No attempt was made to contain or clean up the spill for
108 days and water from 5 wells showed acrylonitrile
concentrations ranging from 46 up to 3520 mg/litre during this
time. On day 108, contaminated soil was removed, but levels of
acrylonitrile actually increased in some wells. Levels decreased
after about 170 days, when contaminated ground water was pumped
away; a sample of this ground water contained an acrylonitrile
concentration of 144 mg/litre. It is possible that the high
concentration of acrylonitrile produced by the spill was lethal
to bacteria, precluding biological degradation. However, no
quantitative measurements of soil or water organisms were made.
3.6. Environmental Persistence
Acrylonitrile is readily degraded by acclimated anaerobic
microorganisms (Mills & Stack, 1955). Aerobic degradation with
activated sludge is complete in 20 days (Miller & Villaume, 1978;
Freeman et al., 1981). The residual level after aerated
activated sludge treatment was below 0.1 mg/kg. Acrylonitrile has
been shown to inhibit anaerobic organisms (For fish toxicity, see
Table 11).
4. INDUSTRIAL AND ENVIRONMENTAL SOURCES AND LEVELS OF EXPOSURE
4.1. Exposure of the General Population
4.1.1. Air
The possibility of exposure to acrylonitrile-contaminated air
is limited to residents near industrial production and processing
sites. In the vicinity of 2 plants producing acrylonitrile, high
concentrations of the monomer, ranging from 390 to 608 mg/m3
(180-280 ppm) were found near the exhausts of both ships and
storage tanks (Sato et al., 1979). Going et al. (1979) determined
acrylonitrile concentrations in samples of air, soil, water, and
sediments around 11 industrial sites. The concentrations of
acrylonitrile in air varied from < 0.1 - 325 µg/m3 ; the highest
levels were found at an acrylonitrile-, butadiene-styrene resin
plant and an acrylonitrile/acrylamide plant. The occurrence of
acrylonitrile was highly correlated with the wind patterns; the
highest levels were found downwind of the plant or at points
crosswind but close to the plant. The air also contained
xylenes, ethylbenzene, dichlorobenzenes, toluene,
trimethylbenzenes, and styrene.
4.1.2. Water
Acrylonitrile was present in effluent discharged from
chemical and latex manufacturing plants (Shackelford & Keith,
1976), and was detected at 0.1 g/litre in effluent discharged
from an acrylic fibre-manufacturing plant in the USA (Europ-Cost,
1976). Near 11 industrial sites (Going et al., 1979), the
highest acrylonitrile levels in water were 3.5 and 4.3 mg/litre
from an acrylic/modacrylic fibre plant and a nitrile elastomer
plant, respectively. There was no apparent correlation between
air levels and water concentrations. No acrylonitrile was found
in the soil and sediments. Water samples from some plants also
contained propionitrile.
4.1.3. Food
Contamination of food from polymer packaging material
containing free acrylonitrile has been reported. Following a
study on the migration of acrylonitrile from ABS and AS resins,
Tatsuno et al. (1979) concluded that after long-term preservation
of food in ABS and AS resins the concentration of acrylonitrile
in food may rise to 0.05 mg/kg. Further studies on food-
simulating solvents showed that migration of acrylonitrile
occurred from ABS and AS resins into 4% acetic acid, 20% ethanol,
heptane, and olive oil; it was concluded that resins containing
acrylonitrile levels of more than 10 mg/kg should not be used for
packaging foods containing alcohol (Tatsuno et al., 1980).
Nitrile resins made from copolymers of acrylonitrile and other
monomers (e.g., methyl acrylate) are no longer used in the USA to
make beverage bottles (US FDA, 1977a). In a study performed in
Sweden, the amount of acrylonitrile monomer found in nitrile
resin bottles was 2-5 mg/kg. The amount in the beverage was
generally 0.002 - 0.003 mg/kg, but two samples contained as much
as 0.009 mg/kg (Vaz, 1981, personal communication). A government
survey of the acrylonitrile content of food suggested that the
average intake of acrylonitrile in the United Kingdom was likely
to be less than 0.3 µg/person per day (United Kingdom Ministry of
Agriculture, Fisheries & Food, 1982).
An acrylonitrile concentration of 0-19 mg/kg was detected in
dry food fumigated with acrylonitrile at a concentration of 10
g/m3 . The study was carried out using radioactive acrylonitrile
and provided information that acrylonitrile levels in the stored
food decreased by 30-70% over a period of 2 months (Pfeilsticker
et al., 1977).
4.1.4. Other sources of exposure
Free acrylonitrile monomer has been found in commercial
acrylonitrile polymers at levels of less than 1 mg/kg (acrylic
and modacrylic fibres), 15 mg/kg (styrene-acrylonitrile resins),
30-50 mg/kg (ABS resins) and 0-750 mg/kg (nitrile rubbers and
latex materials) (US Consumer Product Safety Commission, 1978).
Another possible source of acrylonitrile environmental
exposure is accidental spillage during transport. The following
estimates have been made of the incidence of the accidental
release of acrylonitrile per year: during transport in barges -
0.0117; in trucks - 0.063; and by rail - 0.17 (Miller & Villaume,
1978). This means, for example, that during transport by rail,
one accident would occur approximately every 6 years.
4.2. Occupational Exposure
Up to 12 000 workers in the USA were thought to have come
into major contact with acrylonitrile during 1976 and possibly
some 125 000 workers were exposed, to some extent (Miller &
Villaume, 1978). It has also been estimated that as many as
400 000 may have had some contact with acrylonitrile in 1976.
The exposures reported in several countries are shown in Table 8.
The introduction of a lower exposure limit in several
countries is likely to have decreased the actual exposure to
acrylonitrile at the workplace.
As acrylonitrile vapour is twice as dense as air, spills
and leaks in enclosed buildings may lead to harmful
accumulations of vapour, especially in low-lying areas
(Baxter, 1979). The same author describes various
possibilities for preventing this, such as the use of double
mechanical seals, enclosed drainage systems, well-ventilated
sampling points, etc. Plant design should aim at complete
containment of acrylonitrile, both as a liquid and a vapour.
Table 8. Concentration of acrylonitrile in the air at work-places
-------------------------------------------------------------------------------------------
Operation Acrylonitrile in Reference
work-place air (mg/m3)
Average level Range
-------------------------------------------------------------------------------------------
Acrylonitrile production 5 - 0.5b - Zotova (1975a)
during loading (open air) 5 0.2 - 60 Cincolella et al. (1981)
near ACN tanks or pumps 45 4 - 125 Cincolella et al. (1981)
- 4.2 - 7.2 Gincheva et al. (1977)
Acrylic fibre production 3 - 20 Orusev et al. (1973)
- <11 Enikeeva et al. (1976)
- <11 Sakurai & Kusumota (1972)
- <45
4.6 - 31a,s <2.2 - >43 Sakurai et al. (1978)
0.2 - 9.1a,t -
polymerization 8 <4 - >20 Czajkowska et al. (1969)
<4 <1 - >10 Lodz Sanit. Inspec. Survey (1981)
25 2 - 103 Cincolella et al. (1981)
spinning 6 1.5 - 20 Czajkowska et al. (1969)
<4 <1 - >10 Lodz Sanit. Inspec. Survey (1981)
9.5 Sakurai et al. (1978)
Thermosetting plastic plant 1.4 Scupakas (1968)
Rubber footwear plant 1 - 11 Volkova & Bagdinov (1969)
Unspecified chemical 0.6 - 6 Babanov et al. (1959)
conversions
Production of acryl- 4a,s,t 0 - 22 Iwasaki et al. (1980)
butadiene-styrene resin
(A.B.S)
polymerization 30 0 - 200 Cincolella et al. (1981)
Production of nitrile rubber
rubber - polymerization 4 1 - 27 Cincolella et al. (1981)
reactor cleaning 36t 5 - 54 Cincolella et al. (1981)
Acrylic dispersions 78 9 - 600 Cincolella et al. (1981)
(Latex production
polymerization)
-------------------------------------------------------------------------------------------
a 2 or more factories evaluated.
b average levels over 5 years.
t time-weighted average concentration.
s spot.
A code of practice has recently been published for the safe
design, construction, and use of plants (CIA, 1978). Safe
handling, engineering, and work practices, controls, compliance
programmes, personal protective equipment, housekeeping, employee
information and training, signs and labels, etc. for work with
acrylonitrile have been described by the OSHA (1981).
Exposure to acrylonitrile may also occur through skin
contact. Acrylonitrile was shown to contaminate the skin of
workers, their clothing and tools, also the equipment, walls,
windows, handrails, handles, etc. in the workplace and was not
easy to remove. A protective paste of household soap, mineral
oil, glycerine, and china clay was said to reduce contamination
of the palms of the hands by 67% (Zotova, 1975a).
Acrylonitrile can penetrate clothing and leather shoes
(American Cyanamid, 1976). Dermal contact with liquid
acrylonitrile may cause local skin damage, severe dermatitis, and
systemic toxicity, and must therefore be prevented by high
standards of industrial hygiene.
4.3. Estimate of Human Exposure from All Environmental Media
The production and use of acrylonitrile at the workplace
provide the greatest potential for exposure. Airborne exposure
to acrylonitrile near industrial sites appears to pose the
highest potential risk for the general population; the potential
for exposure through water and food appears to be low by
comparison.
5. CHEMOBIOKINETICS AND METABOLISM
5.1. Absorption
5.1.1. Human studies
5.1.1.1. Uptake through inhalation
The retention of acrylonitrile in the respiratory tract in 3
volunteers exposed to a concentration of 20 mg/m3 for up to 4 h
was 46 ± 1.6% and did not change throughout the inhalation period
(Rogaczewska & Piotrowski, 1968).
5.1.1.2. Dermal absorption
Rogaczewska & Piotrowski (1968) applied liquid acrylonitrile
to the forearm skin of 4 human volunteers and estimated that the
average absorption rate was 0.6 mg/cm2 per h.
5.1.1.3. Uptake by other routes
No data avai1able.
5.1.2. Experimental animal studies
5.1.2.1. Uptake through inhalation
Young et al. (1977) determined the recovery of 14C
acrylonitrile in rats exposed to 11 or 220 mg/m3 (5 or 100 ppm)
for 6 h in a "nose only" inhalation chamber. In the first 9 days
following the start of inhalation, 82.2% of the radioactivity was
recovered from the urine, after the higher dose, and 68.5%, after
the lower dose, 3-4% occurred in the faeces; and 6% and 2.6%,
respectively, were expired as 14CO2.
5.1.2.2. Dermal absorption
Three rabbits breathing pure air while their skin (315-350
cm2 ) was exposed to an atmosphere containing an acrylonitrile
concentration of 1-4.2 g/m3, survived, whereas 3 other rabbits
breathing pure air with the skin exposed to 44-62 g/m3 died
within 2.5-4 h. Inhalation exposure to 0.58-0.67 g/m3 was fatal
for 3 rabbits within 2-3 h (Rogaczcwska, 1975). The author
interprets these data as suggesting that dermal absorption of
vapour is about 100 times less efficient than its pulmonary
absorption. The immersion of rabbit ear in liquid acrylonitrile
was fatal for the animal within a few hours (Rogaczewska, 1971).
Subcutaneous (sc) or intravenous (iv) administration of
14C-acrylonitrile at 0.5 mmole/kg body weight to rats resulted
in faster and greater elimination of radioactivity in the first 4
h than after oral administration (Gut et al., 1980).
5.1.2.3. Uptake by other routes
Young et al. (1977) calculated that after oral administration
of 0.1 mg or 10 mg of 14C-acrylonitrile per kg body weight, 85-
100% of acrylonitrile was absorbed in rats. The absorption rate
was lower in rats after oral administration than after sc or ip
administration (Nerudova et al., 1980a; Gut et al., 1981). After
ip administration, the blood concentration of acrylonitrile
reached a maximum in several minutes and then decreased rapidly
(Nerudova et al., 1980a; Gut et al., 1981). After ip and oral
administration of 1,2-14C acrylonitrile and acrylo14C-nitrile to
rats, 82-93% of the radioactivity was recovered from the urine
and some 3-7% exhaled unchanged in the breath in 24 h (Sapota,
1982).
5.2. Distribution and Toxicokinetics
5.2.1. Human studies
No data available.
5.2.2. Experimental animal studies
Acrylonitrile concentrations in blood and liver reach higher
levels after iv or ip administration than after oral
administration; concentrations rapidly decrease in blood (t0.5 =
19 min) and liver (t0.5 = 15 min after iv and 21 min after ip
administration) (Nerudova et al., 1980a; Gut et al., 1981). The
apparent t0.5 after oral administration is 61 min in blood and 70
min in liver, but this appears to be due to slow absorption
rather than to slow elimination. The area under the acrylonitrile
concentration/time curve for blood was higher than for liver
after oral, iv, or ip administration (Gut et al., 1981),
indicating rapid transformation of acrylonitrile by the liver.
Extrapolation of acrylonitrile blood levels after ip or iv
administration in rats to zero time indicated that the apparent
volume of distribution was unity, and that concentrations of free
acrylonitrile in the rest of the body were unlikely to be greater
than that in the blood (Nerudova et al., 1980a).
Young et al. (1977) followed the distribution of
radioactivity in rats after a single oral or iv dose of 14 C-
acrylonitrile. Radioactivity was found in the lung, liver,
kidney, stomach, intestines, skeletal muscle, blood, and other
organs and tissues, but high levels of radioactivity occurred in
erythrocytes, skin, and stomach regardless of the dose and route.
The high levels in the stomach wall after iv administration
support the observation of Nerudova et al. (1980a) that, after iv
administration, acrylonitrile is excreted into the stomach lumen.
After single intraperitoneal and oral administration to
rats of 1,2-14C acrylonitrile and acrylo14C-nitrile, most of
the 14C found in the tissues was associated with erythrocytes,
liver, and kidneys, lower levels being found in the lung and
brain. The 14C in the erythrocytes was still largely retained
48 h after administration. Significant differences in the
rates of 14C loss from tissues occurred with 1,2-14C
acrylonitrile and acrylo14C-nitrile given orally (Sapota &
Draminski, 1981; Sapota, 1982).
After oral administration to rats, up to a maximum of 94%
of 14C from 1-14C acrylonitrile in erythrocytes was found to
be covalently bound to cytoplasmic and membrane proteins, whereas
90% of the radioactivity from potassium cyanide in erythrocytes
was found in the haem fraction of haemoglobin (Farooqui & Ahmed,
1982).
After a single ip injection of 2,3-14C acrylonitrile in
male rats, radioactivity was generally highest in the blood,
intermediate in the spleen, liver, and kidney, and lower in other
tissues. The percentage of the dose remaining in the body after
9 days was estimated to be about 5% of the administered dose
(Hashimoto & Kimura, 1977).
A semi-quantitative study using whole-body autoradiography
(Sandberg & Slanina, 1980) confirmed that, after iv
administration to rats, acrylonitrile and/or its metabolites
accumulate in the blood, liver, kidney, stomach mucosa, adrenal
cortex, intestinal contents, and hair follicles of rats. After
oral administration to the monkey (Sandberg & Slanina, 1980),
high radioactivity levels were detected in the liver, kidney,
intestinal mucosa, adrenal cortex, and blood. As total
radioactivity was measured in the studies of Young et al. (1977),
Sandberg & Slanina (1980), and Sapota & Draminski (1981), it was
impossible to differentiate acrylonitrile from its metabolites or
from acrylonitrile bound covalently to proteins (Bolt et al.,
1978; Gut et al., 1981); thus, these studies are difficult to
interpret from the point of view of the chemobiokinetics of free
acrylonitrile.
Peter & Bolt (1981) found that 12 h after ip or iv
administration of 2,3-14C acrylonitrile, about half of the
radioactivity remaining in the tissues was irreversibly bound to
proteins. The rapid elimination of acrylonitrile mercapturic
acid after iv, ip, or sc administration (Gut et al., 1981a)
indicates that most of the acrylonitrile-derived radioactivity in
the distribution studies was associated with cyanoethylglutathione,
or subsequent intermediate metabolites including acrylonitrile
mercapturic acid.
Thus, it is impossible to determine conclusively from the
present data whether the relatively high levels of acrylonitrile-
14C radioactivity in the erythrocytes, kidney, spleen, liver,
adrenals, stomach walls, and skin are due to free acrylonitrile,
its metabolites, or cyanoethylated proteins. However, the
chemobiokinetics of free acrylonitrile in blood and liver (Nerudova
et al., 1981) suggest that its distribution is fairly uniform and
that higher levels of radioactivity in some organs and erythrocytes
are due to reaction products of acrylonitrile with soluble and
protein sulfhydryls.
Information on the subcellular distribution of 1,14C
acrylonitrile in rat can be found in Ahmed et al. (1982). Sato et
al. (1982) studied the distribution and accumulation of 2,3-14C
acrylonitrile in the rat. They observed a longer retention of
acrylonitrile in brain and muscle. The cytosol fractions of brain,
liver, and kidney showed a relatively high specific radioactivity.
The evidence, available at present, on the distribution of
acrylonitrile in the body, and on tissue damage following exposure,
does not indicate increased accumulation in any particular tissue
or organ, except erythrocytes, and there is no indication from
animal studies of tissue accumulation following long-term exposure.
5.3. Biotransformation and Elimination
Levels of acrylonitrile metabolites in blood and their
relationship to atmospheric acrylonitrile concentrations or to the
dose administered are usually considered together, in studies on
the relationship between the dose or concentration of acrylonitrile
and the elimination of metabolites in urine. They will therefore be
considered together in the following section.
5.3.1. Human studies
Acrylonitrile is metabolized partly to thiocyanate. Blood
thiocyanate levels of volunteers exposed to acrylonitrile
concentrations below 45 mg/m3 (22 ppm) for 30 min returned to normal
after 24 h, while elevated levels were still present 12 h after
exposure to 110 mg/m3 (50 ppm) for 30 min (Wilson & McCormick,
1949).
Draminski & Trojanowska (in press) reported that at airborne
acrylonitrile concentrations of between 3 and 10 mg/m3,
concentrations of S-(2-cyanoethyl) mercapturic acid in the urine of
13 workers exposed to acrylonitrile, fell in the range of 50-200
mg/litre.
5.3.2. Experimental animal studies
Acrylonitrile is partly metabolized to cyanide, which is then
transformed by rhodanese (EC 2.8.1.1) to thiocyanate and eliminated
in urine (Dudley & Neal, 1942; Brieger et al., 1952; Ghiringhelli,
1954). However, the fate of the major portion of administered
acrylonitrile was not clear until recently. Recent studies have
shown that the major urinary metabolites in rats, hamsters, guinea-
pigs, rabbits, and dogs are mercapturic acids resulting from the
glutathione-S-transferase(s) (EC 2.5.1.18) -catalysed conjugation
of acrylonitrile or glycidonitrile with glutathione (section
5.3.2.2). At present, at least 10 acrylonitrile metabolites have
been isolated and/or identified in animal urine.
The oxidative pathway leads to the liberation of cyanide via an
epoxide (glycidonitrile) and cyanohydrin (Kopecky et al., 1980a,b).
Cyanohydrin spontaneously decomposes to cyanide and glycolaldehyde
which, together with 2-cyanoethanol, cyanoacetic acid, and acetic
acid, have been found as in vitro metabolites of acrylonitrile
(Duverger-van Bogaert et al., 1981). Only 2-cyanoethanol and
cyanoacetic acid were detected in the urine of rats administered
acrylonitri1e intraperitoneally (Lambotte-Vandepaer et al., 1981a).
The proposed routes of the oxidative pathway are shown
diagrammatically in Fig. 1; some of the biotransformation steps are
speculative.
The existence of a glucuronoconjugate of acrylonitrile was
reported in the urine of rats after oral administration of
acrylonitrile (Hoffman et al., 1976). Two metabolites of
acrylonitrile ( S-[2-cyanoethyl] cysteine and S-[2-cyanoethyl]
mercapturic acid) were identified by Dahm (1977) in rats given
radiolabelled acrylonitrile, but he was unable to identify a
third metabolite, as it was unstable. Young et al. (1977)
found that acrylamide was not a metabolite as had been
suggested by Hashimoto & Kanai (1965). The same authors also
identified carbon dioxide as a metabolite in rats, but they
were unable to detect significant quantities of free
acrylonitrile or cyanide in the urine of exposed rats, though
Hashimoto & Kanai (1965) estimated that 15% of an iv dose of
acrylonitrile was eliminated unchanged in the urine and
expired air of the rabbit.
5.3.2.1. The oxidative pathway of acrylonitrile metabolism
The oxidative pathway of acrylonitrile biotransformation
includes a number of consecutive enzyme-catalyzed or spontaneous
reactions. The first step, oxidation of acrylonitrile to
glycidonitrile, is catalyzed by hepatic microsomal mono-oxygenases
(Abreu & Ahmed 1980; Kopecky et al., 1980a,b; Guengerich et al.,
1981; Ahmed & Abreu, 1982). Glycidonitrile is a reactive
intermediate, and a number of its metabolites have been recorded;
in in vitro experiments it is transformed by epoxide hydrolase (EC
3.3.2.3) to glycolaldehyde cyanohydrin, which decomposes
spontaneously to hydrocyanic acid (cyanide) and glycoealdehyde
(Kopecky et al., 1979, 1980a,b; Abreu & Ahmed, 1980; Duverger-van
Bogaert, 1981a). The yield of cyanide in the in vitro experiments
depends on the techniques used (Nerudova et al., 1980b). Besides
forming conjugation products with glutathione (section 5.3.2.2),
glycidonitrile rearranges to cyanoacetaldehyde, which is further
reduced to 2-cyanoethanol or oxidized to cyanoacetic acid. Acetic
acid is also present (Duverger-van Bogaert, 1981).
The results of animal studies have shown that cyanide formed in
vivo is subsequently converted by rhodanese (EC 2.8.1.1) to
thiocyanate and eliminated in urine (e.g., Dudley & Neal, 1942;
Brieger et al., 1952; Ahmed & Patel, 1981). Thiocyanate has been
directly measured in the urine of various animals after
acrylonitrile administration (Lawton et al., 1943; Mallette, 1943;
Czajkowska, 1971; Efremov, 1976b). Rats administered acrylonitrile
at 60 mg/kg body weight, excreted thiocyanate in the urine at a
constant rate of 0.53 mg/h with an excretion half period of 13 h
(Czajkowska, 1971). Sulfhydryl compounds (cysteine, BAL, and
Unithiol) increase the activity of rhodanese in the conversion of
cyanide to thiocyanate in vitro, as well as in vivo (e.g.,
Frankenberg, 1980). A similar increase with acrylonitrile has not
been convincingly demonstrated (Gut et al., 1975), perhaps because
of the inhibiting properties of acrylonitrile on rhodanese.
5.3.2.2. Mercapturic acids formed in acrylonitrile biotransformation
Cyanoethylation of naturally-occurring sulfhydryl compounds
plays an important role in acrylonitrile metabolism. Acrylonitrile
forms stable conjugates with L-cysteine and L-glutathione in vitro
(Hashimoto & Kanai, 1965; Gut et al., 1975) and a portion of
absorbed acrylonitrile is thus prevented from being metabolized to
cyanide. Depressed levels of sulfhydryl compounds have been
reported following acrylonitrile administration (e.g., Wisniewska-
Knypl et al., 1970; Hashimoto & Kanai, 1972; Vainio & Mäkinen,
1977; Dinu & Klein, 1976; Szabo et al., 1977). The spontaneous
conjugation of glutathione with acrylonitrile or glycidonitrile
proceeds very slowly; glycidonitrile forms S-(2-cyano-2-
hydroxyethyl)-L-glutathione and S-(1-cyano-2-hydroxyethyl)-L-
glutathione in the ratio of about 1:1. In the enzyme-catalysed
conjugation this ratio shifts to about 3:1 (Holechek & Kopecky,
1981). These authors demonstrated that no cyanide was released
from the conjugation product of acrylonitrile with GSH, while
cyanide was released from the conjugation product of glycidonitrile
with GSH. This study confirmed the findings of Boyland & Chasseaud
(1967, 1968) concerning the participation of glutathione- S-
alkylene transferase(s) (EC 2.5.2.18) in the cyanoethylation
reaction of glutathione. Since glutathione conjugates are
precursors of mercapturic acids, the occurrence of mercapturic
acids derived from acrylonitrile and glycidonitrile may be expected
in the urine of animals exposed to acrylonitrile.
The major metabolite of acrylonitrile in the rat, rabbit, and
other animals was found to be 2-cyanoethylmercapturic acid (Dahm,
1977; Wright, 1977; Ahmed & Patel, 1979; Kopecky et al., 1979,
1980a,b,c, 1981; Langvardt et al., 1980; Sapota & Draminski, 1981;
Sapota & Chmielnicka, 1981; Van Bladeren et al., 1981; Ghanayem &
Ahmed, 1982). While 2-cyanoethylmer-capturic acid was the sole
mercapturic acid identified in the urine of rats after iv
administration of acrylonitrile, a second mercapturic acid of
unestablished structure was also excreted after oral
administration. Langvardt et al. (1980), using 1-14C- or 2,3-14C-
acrylonitrile, found seven radioactive metabolites in rat urine.
The 3 major metabolites included thiocyanate and 2-
cyanoethylmercapturic acid. The third was tentatively identified
as 4-acetyl-5-cyanotetra-hydro-1,4-2 H-thiazine-3-carboxylic acid.
The 4 remaining metabolites represented at least one third of the
total activity excreted; their chemical structures are not known,
but none contained the -CN group of acrylonitrile. Different
results were reported by van Bladeren et al. (1981). In common
with Kopecky & Langvardt and colleagues, they isolated
2-cyanoethylmercapturic acid from the urine of orally-dosed rats;
however, 2-hydroxyethylmercapturic acid was also excreted. It is
suggested that this second mercapturic acid may be formed via one
of the conjugates of glutathione with glycidonitrile, S-(2-cyano-
2-hydroxyethyl)-L-glutathione. The amount of mercapturic acids
excreted relative to the dose was approximately constant up to a
dose of acrylonitrile of 26.5 mg/kg body weight. At higher doses,
the amount of mercapturic acids excreted remained constant. These
authors and Wright (1977) suggested that this might be a
consequence of the depletion of available glutathion at the higher
dose levels. It seems likely that, at high exposure levels, the
preferred metabolic pathway (conjugation of glutathione with
acrylonitrile or its metabolite) is overloaded, and another unknown
metabolic pathway takes over. After an oral dose to rats of 1-14C
acrylonitrile, 4 metabolites were found in the bile, 2 major
metabolites being GSH conjugates of acrylonitrile (Ghanayem &
Ahmed, 1982).
The report by Dahm (1977) that rats administered acrylonitrile
excreted S-(2-cyanoethyl)-L-cysteine has not been confirmed by any
of the authors who have examined the glutathione conjugation
pathway of acrylonitrile biotransformation. Fig. 2 illustrates
the proposed routes of mercaptide formation from acrylonitrile.
5.3.2.3. The glucuronic acid conjugates of acrylonitrile metabolism
Rats treated with doses of acrylonitrile ranging from 20 to 40
mg/kg body weight (Hoffman et al., 1976) excreted significantly
more glucuronic acid than untreated controls or rats administered
10 mg acrylonitrile/kg body weight. This suggests that
acrylonitrile-derived glucuronide might be the alternative
substance to conjugate metabolites (van Bladereu et al., 1981).
The results of Lambotte-Vandepaer et al. (1980) support this
theory. The mutagenicity of rat urine after administration of
acrylonitrile at 30 mg/kg body weight was enhanced by treatment
with beta-D-glucuronidase (EC 3.2.1.31) prior to the Ames'
mutagenicity assay. This indicates that a glucuronide was cleaved
to give a free mutagenic agent derived from acrylonitrile. The
dose fits the dose range that evokes a significant increase in
glucuronic acid excretion (Hoffmann et al., 1976) and is of the
same magnitude as that at which van Bladeren et al. (1981)
demonstrated a depletion of glutathione in rat liver.
5.3.2.4. Quantitative aspects of acrylonitrile bio-transformation
and elimination of its metabolites
(a) Effect of acrylonitrile concentration and dose
The relationship between acrylonitrile concentrations in the
air, cyanide and thiocyanate in the blood, and thiocyanate in the
urine was described by Brieger et al. (1952). At acrylonitrile
concentrations between 55 and 220 mg/m3 (25 and 100 ppm), the blood
and urine thiocyanate concentrations were proportional to inhaled
acrylonitrile concentrations in rats. However, the cyanide content
of blood was measurable only at the highest acrylonitrile
concentration. In dogs, cyanide could be detected in blood at an
acrylonitrile concentration of 110 mg/m3 and cyanide concentrations
in blood were proportional to the inhaled acrylonitrile
concentrations in the range of 110-220 mg/m3 (50 - 100 ppm). Data
indicate that a certain acrylonitrile concentration must be exceeded
to provide conditions for the formation of enough cyanide to surpass
the metabolic capacity of rhodanese or the supply of co-factors;
this concentration is lower in the dog than in the rat.
In mice and rats, the dose of acrylonitrile was directly
related to the cyanide levels in blood, liver, kidney, and brain
(Ahmed & Patel, 1981), and, in rats, the ip administration of
acrylonitrile at 20-60 mg/kg body weight or oral administration at
15-60 mg/kg body weight also produced a proportional increase in
thiocyanate excretion in the urine.
However, thiocyanate is always present in urine (9 mg/litre in
rats) (Brieger et al., 1952), and the acrylonitrile exposures
required to exceed this level significantly are high. Thus, urine
thiocyanate levels would not give an accurate estimate of exposure
at the atmospheric acrylonitrile concentrations found in industry,
at present.
The observation of Hoffmann et al. (1976) suggested a possible
alternative conjugating route for metabolites at higher
acrylonitrile exposure levels involving glucuronic acid. Before
this is confirmed, the effects on carbohydrate metabolism and
glucose utilization in rats must be considered, as well as the
possibility that this alternative pathway of glucose metabolism
leading to the formation of glucuronic acid, and thus elevated
glucuronic acid levels in urine, may be stimulated by acrylonitrile.
From the standpoint of a possible exposure test, however, it is
emphasized that high doses of acrylonitrile are required to
increase excretion of glucuronic acid in urine, but such doses
would only occur in cases of accidental overexposure.
(b) Differences between species
The work of Brieger et al. (1952) revealed that, at the same
acrylonitrile exposure concentrations, cyanide blood levels in dogs
were far higher than in rats. This was apparently due to a less
efficient detoxification of cyanide to thiocyanate in dogs since,
when exposed to an acrylonitrile concentration of 217 mg/m3 (100
ppm), the total sum of cyanide and thiocyanate concentrations in
blood was about 260 µmol/litre in dogs and 840 µmol/litre in rats.
Although the normal thiocyanate blood level was about 150
µmol/litre in the rat and only about 55 µmol/litre in the dog, the
elevation caused by acrylonitrile was far higher in rats,
suggesting that rats metabolize acrylonitrile to cyanide at a
substantially higher rate and are able to detoxify it more
efficiently than dogs.
Mice excrete more thiocyanate than rats, at a given dose of
acrylonitrile, even though detoxification of cyanide to thiocyanate
in mice is apparently less efficient than in rats. Co-administration
of acrylonitrile and thiosulfate resulted in a 3-fold increase in
thiocyanate excretion in mice, while in rats the effect was much
smaller (Gut et al. 1975; Silver et al., 1982). Moreover, the
thiosulfate significantly reduced mortality in mice, but the
reduction in rat mortality was only slight, confirming that
enhanced detoxification of cyanide in mice is important.
Ahmed & Patel (1981) also observed that the rate of metabolism
of acrylonitrile was higher in mice than in rats.
(c) Time course of elimination of acrylonitrile metabolites
The excretion in urine of 14C-acrylonitrile-derived mercapturic
acids follows shortly after ip, sc, iv, or oral administration of
14C-acrylonitrile in rats (Gut et al., 1981a) and rapidly
decreases, whereas the excretion of thiocyanate from acrylonitrile
given orally or intra-peritoneally increases after a time lag
culminating between hours 8 and 12 in rats, but sooner in mice and
Chinese hamsters (Gut et al., 1975). The time course of
acrylonitrile-derived mercapturic acid excretion in rats was
closely correlated with free acrylonitrile concentrations in blood
and liver (Nerudova et al., 1980a; Gut et al., 1981a), while that
of thiocyanate was not, whatever the route of administration.
(d) Effect of the route of administration
The excretion of thiocyanate by rats, mice, and Chinese
hamsters after oral, ip, sc, and iv administration of 14C-
acrylonitrile represented 20-40%, 5%, 5%, and 1%, respectively, of
the dose administered. However, urinary excretion of radioactivity
was almost quantitative (Gut et al., 1981a); subtracting the
thiocyanate excretion from total urinary metabolites (radioactivity)
revealed that excretion of acrylonitrile-mercapturic acids (and
other possible acrylonitrile metabolites) is independent of the
route of administration (Kopecky et al., 1980a). When 1-14C-
acrylonitrile was administered orally to rats, 27% of the dose had
been excreted in the bile in 6 h, mainly in the form of 2
glutathione conjugates of acrylonitrile (Ghanayem & Ahmed, 1982).
(e) Metabolic interactions of acrylonitrile with other xenobiotics
Oral administration of an equimolar dose of acrylonitrile (0.5
mmol/kg body weight) to rats did not influence the elimination of
phenol from benzene. However, benzene, toluene, ethylbenzene, or
styrene (0.5 mmol/kg body weight) markedly decreased the rate and
total excretion of thiocyanate from an equal dose of acrylonitrile
given orally; higher doses of the solvents caused greater
inhibition (Gut et al., 1981). On the other hand, subcutaneous
administration of benzene and styrene increased the excretion of an
equal dose of 14C-acrylonitrile (0.5 mmol/kg body weight) during
the first 4 h and decreased it between the 8th and l2th hours
(owing to inhibited thiocyanate formation and excretion). The
total of metabolites excreted was unaffected. The co-administration
of industrial solvents markedly increased the lethality of
acrylonitrile (Gut et al., 1981a). Inhibition of the oxidative
metabolism of acrylonitrile in rats by a cytochrome P-450 inhibitor
(1-phenylimidazole) inhibited completely the excretion of N-
acetyl- S-(2-hydroxyethyl) L-cysteine in favour of the excretion of
N-acetyl- S-(2-cyanoethyl)-L-cysteine (van Bladeren et al., 1981).
The latter compound, the authors considered, resulted from direct
cyanoethylation of glutathione, whereas the former was formed via
the epoxide, glycidonitrile. Overnight fasting and cobaltous
chloride pre-treatment increased the biliary excretion of
metabolites, while phenobarbital did not induce any change, and
dimethyl maleate significantly decreased the excretion (Ghanayem &
Ahmed, 1982).
6. BIOLOGICAL MONITORING OF ACRYLONITRILE UPTAKE
Studies, particularly animal studies, on the absorption,
distribution, biotransformation, and elimination of acrylonitrile
have shown that a small fraction of the acrylonitrile absorbed is
rapidly eliminated in the urine without biotransformation, while
the remainder is biotransformed via several pathways, a number of
metabolites being excreted in urine; some of these metabolites are
unique to acrylonitrile.
The absorption studies have also clearly shown that, in
addition to uptake of acrylonitrile by inhalation, skin penetration
can be an important route of entry, particularly in the presence of
liquid acrylonitrile. Thus, in human studies, unless performed
under controlled conditions, a good correlation cannot necessarily
be expected between a bioindicator of uptake and ambient air
measurements of acrylonitrile, even when carried out with personal
samplers.
Possible indicators of acrylonitrile uptake at present include:
acrylonitrile in urine, acrylonitrile-derived mercapturic acids in
urine, total thioethers in urine, and thiocyanates in urine.
Houthuijs et al. (1982) studied the excretion pattern of
acrylonitrile in the urine of 15 exposed workers over a 7-day
period, with a control group of 41 unexposed workers. They noted
that the concentrations of acrylonitrile in urine peaked at the
end, or shortly after the end, of the working day, decreasing
rapidly until the beginning of the next working day without,
however, falling to the levels in the control group. Correlations
have been found between acrylonitrile concentrations in air and
those in urine. In the control group, a significant increase in
the acrylonitrile excretion in urine was found with the number of
cigarettes smoked. For a mean acrylonitrile concentration in air
of 0.28 mg/m3 (0.13 ppm), the mean acrylonitrile level in urine at
the end of the working day was 38 µg/litre, using the headspace
chromatographic technique. In the control group for non-smokers,
the mean level of acrylonitrile in urine was 2 µg/litre and for
smokers (20-30 cigarettes per day) 9.0 µg/litre.
Sakurai et al. (1978) have also established a relationship
between acrylonitrile concentrations in air and levels in urine for
a group of 102 exposed workers and compared them with 62 controls.
For an air concentration of 0.2 mg/m3 (0.1 ppm) (as measured by
personal samplers), an acrylonitrile level in urine of 3.0 µg/litre
was found, using the Sato et al. (1975) method of analysis
(separation by azeotropic distillation and determination by gas
chromatography). The urine samples were collected at the end of
the working day. At an air concentration of 1.1 mg/m3 (0.5 ppm),
the level of acrylonitrile in urine was 19.7 µg/litre, and at a
concentration in air of 9 mg/m3 (4.2 ppm) the corresponding level
in urine was 359.6 µg/litre. Acrylonitrile could not be detected
in the urine of controls. At the same time, an increase in the
thiocyanate level in urine was noted, particularly at the higher
exposure levels.
According to Houthuijs et al. (1982), the differences found
between the urine levels of acrylonitrile in the two studies are
most likely due to differences in analytical techniques.
The validity of the determination of urine levels of
acrylonitrile using gas chromatography-head space analysis for
monitoring acrylonitrile-exposed workers was established by Benchev
et al. (1982).
A promising method for estimating total acrylonitrile uptake
seems to be the determination of acrylonitrile-derived mercapturic
acids; such acids are specific for acrylonitrile and are absent
from normal urine. They have been shown in experimental animal
studies to be well correlated with the free acrylonitrile
concentration in blood (Nerudova et al., 1980; Gut et al.,
1981a,b); animal data also indicate that the capacity of the enzyme
systems to produce the acrylonitrile-derived mercapturic acids is
unlikely to be exceeded at the exposure levels of interest (van
Bladeren et al., 1981). Draminski & Trojanowska (1983) established
the presence of S-(2-cyanoethyl) mercapturic acid in the urine of
13 workers exposed to acrylonitrile, using a gas chromatographic
technique. The concentrations ranged between 50 and 200 mg/litre
for ambient acrylonitrile levels between 3.3 and 9.8 mg/m3 (1.5 and
4.5 ppm). The "total thioethers" were also determined in the urine
samples by a spectrophotometric method (Kopecky, 1982) and shown to
be strongly correlated with the S-(2-cyanoethyl) mercapturic acid
excretion, indicating that, in the case of exposure to pure
acrylonitrile, the major part of the sum of "thioethers" is
represented by this specific mercapturic acid.
Increased glucuronic acid excretion was reported by Ostrovskaja
et al. (1976) in 45.5% of workers exposed to acrylonitrile
concentrations of 0.7-1.5 mg/m3 (0.3-0.7 ppm).
The recent studies reported above show that biological
monitoring may become a suitable approach for assessing
acrylonitrile uptake, in particular in relation to the working
environment. Both acrylonitrile in urine and acrylonitrile-derived
mercapturic acids in urine seem to be the most suitable
bioindicators of uptake, at present, as they have the advantage of
specificity. More work is needed to resolve the apparent
discrepancies due to analytical techniques and to determine the
half-lives. This should make it possible to establish the most
appropriate sampling time with respect to exposure and help in the
determination of the concentrations of concern.
Interest in the determination of total "thioethers" in urine as
a bioindicator of uptake lies in the greater simplicity of the
analytical techniques used. However, more work is needed,
particularly with regard to interferences and half-lives.
The possibility of estimating acrylonitrile exposure in smokers
was suggested by Della Fiorentina & De Wiest (1979), who observed
that determination of carboxyhaemoglobin in blood makes it possible
to calculate the amount of thiocyanate present in urine that is due
to smoking, and thus to calculate the uptake of acrylonitrile.
However, experience shows that there can be marked variations in
thiocyanate levels in smokers, which greatly exceed those in non-
smokers occupationally-exposed to acrylonitrile (Czajkowska et al.,
1969).
7. EFFECTS ON EXPERIMENTAL ANIMALS AND CELL SYSTEMS
7.1. Acute Toxicity
7.1.1. Lethal doses and concentrations
7.1.1.1. Lethal doses
The range of acute LD50 values for acrylonitrile in different
laboratory mammals is generally between 25 and 186 mg/kg body
weight (Table 9), though a value of 282 mg/kg body weight was
observed when liquid acrylonitrile was applied to the skin of the
tail of male rats (Zotova, 1976). Mice are more sensitive than
rats, guinea-pigs, and rabbits. There seems to be little
consistency in the effects of route or vehicle of administration,
or of sex, on the LD50 level. The LD50 for dogs was not reported,
but they tolerated iv administration of acrylonitrile at 50 mg/kg
body weight and died after 300 mg/kg (Graham, 1965). The LD50
values reported are an order of magnitude higher than the LD50 for
cyanide (one of the metabolites of acrylonitrile), but markedly
lower than those for industrial solvents and monomers of plastics
(the LD50 for benzene and its derivatives being about 2000-3000
mg/kg body weight).
7.1.1.2. Lethal concentrations in the air
The range of acute LC50 s for 4-h inhalation of acrylonitrile is
between 150 and 1250 mg/m3 (Table 10). Dogs appeared to be the
most sensitive of the species tested and the sensitivity decreased
in the following order: mice, rabbits, cats, rats, guinea-pigs, the
latter being apparently the most resistant to inhalation exposure.
The exposure of 315-350 cm2 of the skin of rabbits to an
acrylonitrile concentration of 44-62 g/m3, in an exposure chamber,
such that the animals were breathing pure air, proved fatal after
2.5-4 h. Inhalation exposure to 0.58-0.67 g/m3 was fatal for 3
rabbits within 2-3 h (Rogaczewska, 1975).
In the 3 species of insects tested in a fumigation chamber
for 8 h, the LC50 value was found to be 700-1900 mg/m3 (Bond &
Buckland, 1976). Lindgren et al. (1954) exposed 8 insect
species for 2 or 6 h and found LC50 values of 1000-4500 mg/m3 .
Table 9. Acute LD50 values for acrylonitrile: effect of animal species
strain and route of administration
---------------------------------------------------------------------------------------------
Species/strain/sex Number Route LD50 (mg/kg Vehicle Reference
body weight)
---------------------------------------------------------------------------------------------
mouse/-/male M + F 333 oral 36 water Tullar (1947)
mouse/-/female M + F 333 oral 48 water Tullar (1947)
mouse/-/M + F 169 oral 40 olive oil Tullar (1947)
mouse/H strain/- - oral 25 physiol. Benesh & Cherna
saline (1959)
mouse/-/- - oral 40-46 - American Cyanamid
(1951)
mouse/-/female M + F 325 ip 48 water Tullar (1947)
mouse/-/male M + F 325 ip 40 water Tullar (1947)
mouse/NMRI or "SPF"/- - ip 50 - Zeller et al.
(1969)
mouse/ICR/female - ip 47 - Yoshikawa (1968)
mouse/H strain/- - sc 35("technical physiol. Benesh & Cherna
AN") saline (1959)
mouse/"inbred"/male 60 sc 50 (2 h) physiol. Graham (1965)
saline
25 (24 h)
mouse/BN/male 60 sc 34 - Knobloch et al.
(1971)
rat/Sherman/- groups of oral 93 - Smyth & Carpenter
6-10 (1948)
rat/Wistar/- - oral 101 - Paulet & Vidal
(1975)
rat/Wistar or Stock/- - oral 128 - Zellar et al.
(1969)
rat/Wistar-Stamm/male - oral 82 - von Borchardt
et al. (1970)
rat/Wistar-Stamm/female - oral 86 - von Borchardt
et al. (1970)
rat/-/M + F 80 oral 84 water Tullar (1947)
rat/-/M + F 51 oral 72 olive oil Tullar (1947)
rat/Wistar/- - oral 78 physiol. Benesh & Cherna
saline (1959)
rat/Sprague-Dawley/male 20 oral 186 water Monsanto (1975)
rat/Sprague-Dawley/female 20 oral 186 water Monsanto (1975)
Table 9. (contd.)
---------------------------------------------------------------------------------------------
Species/strain/sex Number Route LD50 (mg/kg Vehicle Reference
body weight)
---------------------------------------------------------------------------------------------
rat/Wistar/male 110 ip 100 - Knobloch et al.
(1971)
rat/Wistar/- - ip 65 poly- Paulet & Vidal
ethylene (1975)
glycol
rat/Wistar/male 110 sc 80 - Knobloch et al.
(1971)
rat/"albino"/male - sc 96 water Magos (1962)
rat/"white"/male - skin of 282 liquid Zotova (1976)
tail acrylonitrile
rat/"white"/male - skin of 148 liquid Zotova (1976)
abdomen acrylonitrile
guinea-pig/-/- - oral 50 - Carpenter et al.
(1949)
guinea-pig/-/- - oral 85 olive oil Tullar (1947)
guinea-pig/-/M & F 30 oral 56 - Jedlicka et al.
(1958)
guinea-pig/-/- - sc 130 - Ghiringhelli (1954)
guinea-pig/-/- 11 iv 72 water Tullar (1947)
guinea-pig/Hartley-/male 12 or more intact 0.46 ml/kg - Roudabush et al.
skin (1965)
abraded 0.86 ml/kg - Roudabush et al.
skin (1965)
guinea-pig/-/- - skin 0.25 ml/kg - Smyth & Carpenter
(1948)
rabbit/-/- - oral 93 - Lefaux (1966)
rabbit/-/- - iv 69 - Paulet & Desnos
(1961)
rabbit/"white"/M & F 12 or more abraded 0.28 ml/kg - Roudabush et al.
skin (1965)
---------------------------------------------------------------------------------------------
Table 10. Acute lethal effect of single inhalation of acrylonitrile: effect of
duration and concentration of acrylonitrile
---------------------------------------------------------------------------------------------------
Species/strain/sex Number Concentration Duration Mortality Reference
(mg/m3) (h) (died/
tested)
---------------------------------------------------------------------------------------------------
white mouse/stock/- 6 600 0.5 0/6 McOmie (1949)
6 1500 0.5 5/6 McOmie (1949)
6 5800 0.5 5/6 McOmie (1949)
6 900 1 1/6 McOmie (1949)
6 900 2 3/6 McOmie (1949)
6 1700 1 6/6 McOmie (1949)
mouse/BN/male 12 300 4 LC50 Knobloch et al. (1971)
rat/Sherman/- 6 1085 4 0/6 Smyth & Carpenter et al. (1971)
6 2170 4 6/6 Smyth & Carpenter et al. (1971)
rat/Sherman/female 6 1085 4 2/6 to Carpenter et al. (1949)
4/6
rat/Wistar/- 20 54 7 0/20 Brieger et al. (1952)
20 109 7 0/20 Brieger et al. (1952)
20 163 7 0/20 Brieger et al. (1952)
20 217 7 4/20 Brieger et al. (1952)
rat/Wistar/male 12 470 4 LC50 Knobloch et al. (1971)
rat/Osborne-Mendel/- 16 2750 1 0/16 Dudley & Neal (1942)
16 3230 1 4/16 Dudley & Neal (1942)
16 5300 1 13/16 Dudley & Neal (1942)
16 660 2 0/16 Dudley & Neal (1942)
16 1290 2 6/16 Dudley & Neal (1942)
16 2730 2 16/16 Dudley & Neal (1942)
16 280 4 0/16 Dudley & Neal (1942)
16 680 4 5/16 Dudley & Neal (1942)
16 1380 4 16/16 Dudley & Neal (1942)
16 290 8 0/16 Dudley & Neal (1942)
16 460 8 1/16 Dudley & Neal (1942)
16 590 8 7/16 Dudley & Neal (1942)
16 690 8 15/16 Dudley & Neal (1942)
---------------------------------------------------------------------------------------------------
Table 10. (contd.)
---------------------------------------------------------------------------------------------------
Species/strain/sex Number Concentration Duration Mortality Reference
(mg/m3) (h) (died/
tested)
---------------------------------------------------------------------------------------------------
rat/Wistar/male 3 650 3 1/3 Appel et al. (1981)
3 1100 2 3/3 Appel et al. (1981)
3 2600 0.5 1/3 Appel et al. (1981)
6 3000 0.5 6/6 Appel et al. (1981)
guinea-pig/-/- 8 580 4 0/8 Dudley & Neal (1942)
8 1250 4 5/8 Dudley & Neal (1942)
8 2520 4 8/8 Dudley & Neal (1942)
guinea-pig/-/- 12 990 4 LC50 Knobloch et al. (1971)
rabbit/"albino"/- 2 290 4 0/2 Dudley & Neal (1942)
2 560 4 2/2 Dudley & Neal (1942)
2 1260 4 2/2 Dudley & Neal (1942)
rabbit/-/- 5 670 - 1100 2-3 5/5 Rogaczewska (1975)
cat/-/- 4 210 4 0/4 Dudley & Neal (1942)
2 600 4 0/2 Dudley & Neal (1942)
2 1300 4 2/2 Dudley & Neal (1942)
dog/-/- 3 63 4 0/3 Dudley & Neal (1942)
2 140 4 1/2 Dudley & Neal (1942)
3 213 4 0/3 Dudley & Neal (1942)
2 240 4 2/2 Dudley & Neal (1942)
dog/-/- 4 108 7 0/4 Brieger et al. (1952)
4 163 7 0/4 Brieger et al. (1952)
6 213 7 6/6 Brieger et al. (1952)
Rhesus monkey/-/- 3 163 7 1/3 Brieger et al. (1952)
---------------------------------------------------------------------------------------------------
7.1.1.3. Lethal concentrations in water
(a) Fish
Acute toxicity, determined by a static bioassay at 25 °C,
revealed TLm (median tolerance limit, i.e., a concentration of
acrylonitrile killing 50% of the test organisms within a specified
time) values ranging from 25.5 to 44.6 mg/litre at 24 h, and from
11.8 to 33.5 mg/litre at 96 h. There were no apparent significant
differences in the sensitivity of various kinds of fish (Table 11).
(b) Invertebrates
For the brown shrimp (Crangon crangon), the LC50 for a 24-h
exposure was 10-33 mg/litre (Portman & Wilson, 1971). Bandt (1953)
exposed several species of arthropods (a shrimp-like crustaceae and
3 types of larvae) to 20-100 mg acrylonitrile/litre water and found
marked species and individual differences: a lethal effect was
observed in some species with 25 mg/litre after 48 h, while other
species were not affected after 3 days. The most resistant species
were unaffected by 100 mg/litre after 24-48 h. The results of
studies by Rajendran & Muthu (1981) showed that acrylonitrile
affects the activity of the phosphorylase and acetylcholinesterase
enzymes in Tribolium castaneum Herbst, and Trogoderma granarium
Everts.
7.1.2. Clinical observations
The inhalation studies of Dudley & Neal (1942), Brieger et al.
(1952), and Rogaczewska (1975), and the results of oral and
parenteral administration (Ghiringhelli, 1954; Benesh & Cherna,
1959; Paulet & Despos, 1961; Graham, 1965; Paulet et al., 1966)
indicate that animals inhaling lethal concentrations of
acrylonitrile, or administered lethal dosages of acrylonitrile
orally or parenterally, showed rather similar effects: excitability
and stimulated breathing, shallow rapid breathing, slow gasping
breathing, apnoea, convulsions, and death. Vomiting occurred in
cats, dogs, and monkeys after inhaling acrylonitrile, and in rats
following parenteral administration. Reddening of the skin of the
ears, nose, and feet (in rhesus monkeys, also of the face and
genital organs) and mucosa was accompanied by lachrymation, nasal
discharge, and salivation, not only after inhalation exposure, but
also following oral and sc administration, while hind-leg
incoordination, paresis or paralysis, were observed in rats after
oral administration, and in rabbits after iv administration.
Table 11. Median tolerance limit values (TLm)a for various fish exposed to
acrylonitrile
-------------------------------------------------------------------------------------
Species Water type TLm (mg/litre) Reference
24 h 48 h 96 h
-------------------------------------------------------------------------------------
Fathead minnow hard 32.7 16.7 14.3 Henderson et al. (1961)
(Pimphales promelas) soft 34.3 21.5 18.1 Henderson et al. (1961)
Minnow (Phoxinus - 38.2 17.6 - Marcoci & Ionescu (1974)
phoxinus)
Bluegill (Lepomis soft 25.5 14.3 11.8 Henderson et al. (1961)
macrochirus)
Guppy (Lebistes soft 44.6 33.5 33.5 Henderson et al. (1961)
reticulatus)
Goldfish (Carassius - - - 40 Paulet & Vidal (1975)
sp.)
Carp (Cyprinus - 37.4 24.0 - Marcoci & Ionescu (1974)
carpio)
Rainbow trout hard - 70 - Jackson & Brown (1970)
(Salmo gairdneri)
Pin perch sea 24.5 - - Daugherty & Garett (1951)
(marine fish) (30/l tank)
(Lagodon rhomboides)
Rainbow trout tap, - 5b - Sloof (1979)
(Salmo gairdneri) dechlorinated,
3.6 mg/litre
hard 15 - - Sloof (1979)
Zebra fish same (LC50)
-------------------------------------------------------------------------------------
a TLm median tolerance limit, a concentration of acrylonitrile killing
50% of the test organisms within a specified time.
b Minimal concentration changing respiratory frequency.
(a) Effects on the skin
Direct application of liquid acrylonitrile to the shaved skin
of rabbits induced slight local vasodilation immediately, without
any systemic effect (1-2 ml covering 100-200 cm2) or with an
increased respiratory rate (3 ml over 300 cm2) (McOmie, 1949).
Tuller (1947) observed erythema in only one of 3 areas of abraded
skin, following application of 1 ml of acrylonitrile on a gauze pad
covered by rubber sheeting. However, Zeller et al. (1969) found
that a 15-min application of acrylonitrile on a cotton pad to
shaved skin resulted in skin oedema, and a 20-h application, in
slight necrosis. Guinea-pigs appear to be more sensitive