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    INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY



    ENVIRONMENTAL HEALTH CRITERIA 28 






    ACRYLONITRILE







    This report contains the collective views of an international group of
    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


         The International Programme on Chemical Safety (IPCS) is a
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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.

FIGURE 1

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. 

FIGURE 2

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 than 
rabbits; the application of a 2% solution of acrylonitrile in 
acetone for 24 h, under occlusion, did not induce any effects, but 
8% or higher concentrations induced dose-dependent erythema 
followed by desquamation and mild necrosis (Gut et al., unpublished 
data).  Erythema of the nose, face, ears, legs, and genital organs 
may follow inhalation and oral administration of acrylonitrile. 

(b)  Effects on the eye

    McOmie (1949) instilled one drop of acrylonitrile into the eye 
of a rabbit.  After 1 h, there was mild conjunctivitis without 
corneal clouding or pupillary damage and no effects were observed 
after 24 h.  Oedema and slight necrosis of the conjunctiva after 8 
days were observed in rabbits by Zeller et al. (1969). 

(c)  Effects on respiration

    It was stressed by Paulet et al. (1966) that, after a lethal 
intravenous dose of acrylonitrile (120 mg/kg body weight), the 
respiratory rate in rabbits did not increase as is characteristic 
in cyanide poisoning.  However, respiratory disturbance was 
observed in: guinea-pigs given a sc lethal dose of acrylonitrile 
(130 mg/kg body weight) (Ghiringhelli, 1954), anaesthetized dogs 
given 100 mg/kg body weight intravenously (Graham, 1965), mice 
given an oral lethal dose (Benesh & Cherna, 1959), and in guinea-
pigs given 100 mg/kg body weight orally (Jedlicka et al., 1958).  
Pulmonary oedema was also seen. 

    An increased respiratory rate followed the application of 
liquid acrylonitrile (3 ml/kg body weight) to the skin of rabbits 
(McOmie, 1949), and "respiratory distress" was reported in rhesus 
monkeys exposed to 163 mg/m3 for 7 h (Brieger et al., 1952).  When 
rats, rabbits, cats, dogs, and monkeys were exposed to lethal 
concentrations of acrylonitrile, Dudley & Neal (1942) observed an 
initial stimulation of respiration followed by shallow rapid 
breathing, slow gasping breathing, convulsions, coma, and death.  
These respiratory effects were absent in guinea-pigs, but 
irritation of the pulmonary membranes and some delayed deaths from 
lung oedema occurred. 

(d)  Effects on circulation

    Acrylonitrile administered iv at 13, 27, 55, or 110 mg/kg body 
weight had little effect on the respiratory and blood pressure 
responses of anaesthetized rabbits to adrenalin, noradrenalin, or 
acetylcholine, and Gravczyk & Zwierzchovski (1973) believed that 
the circulation was not the primary target organ in acrylonitrile 
poisoning.  However, lethal doses (50 or 100 mg/kg body weight) in 
guinea-pigs caused dilation of the right ventricle, congestion of 
the coronary blood vessels, hepatic and splenic hyperaemia, and 
inflammation of the intestinal mucosa (Jedlicka et al., 1958).  In 
Sprague-Dawley rats administered a lethal dose of acrylonitrile, 
there were haemorrhagic areas in the lung and liver and acute 
gastrointestinal inflammation (Monsanto, 1975).  Whether the 

reddening of nose, ears, legs, face, and genital organs in rats and 
other species, after inhalation and oral administration of 
acrylonitrile, is due to a direct effect on small vessels or is an 
inflammatory response is not known. 

(e)  Effects on adrenals

    The effect of lethal doses of acrylonitrile on the adrenals 
became evident in the reports of Szabo & Selye (1971, 1972) and 
Szabo et al. (1976).  After iv administration of high doses (150 or 
200 mg/kg body weight), haemorrhage was observed in both adrenals 
of most animals, and there was adrenal haemorrhage in some rats 
following oral administration of 10, 15, or 20 mg/kg body weight.  
Various types of histological damage were observed in the adrenal 
cortex and medulla, some of them within 30 min of acrylonitrile 
administration. 

    A possible mechanism involving the peroxidative action of 
acrylonitrile in acrylonitrile-induced adrenal injury has been 
suggested recently by Silver & Szabo (1982).  Szabo et al. (1980) 
investigated the pathogenesis of experimental adrenal haemorrhagic 
necrosis using various morphological, biochemical, and 
pharmacological methods.  Their results suggest that the presence 
of a functional adrenocortex is necessary for the development of 
cortical damage. 

(f)  Blood chemistry

    Intraperitoneal administration of acrylonitrile to male rats at 
33 mg/kg body weight per day for 3 days decreased serum 
corticosterone to 30%, prolactin to 40%, but increased follicle-
stimulating hormone (FSH) to 200% of control levels and did not 
affect luteinizing hormone (LH) (Nilsen et al., 1980).  In adult 
male Wistar rats, a single ip administration of acrylonitrile of 10 
mg/kg body weight did not have any effect on serum glutamic 
oxaloacetic transferase (SGOT) and serum glutamic pyruvate 
transaminase (SGPT) activity, but increased lactate dehydrogenase 
(EC 1.1.1.27) (LDH) to 200% and sorbitol dehydrogenase (SDH) (EC 
1.1.1.14) to 300% compared with the controls (Noel et al., 1978).  
The same dose in male rats inhibited butyrylcholineesterase (EC 
3.1.1.8), did not have any effect on alkaline phosphatase (EC 
3.1.3.1), and increased fructose monophosphate aldolase activity, 
suggesting that there had been an adverse effect on the liver 
(Ivanov et al., 1979).  Administraton of L-cysteine, alpha 
tocopherol, or ionol prevented these effects.  A single oral dose 
of acrylonitrile (l/2 LD50, 41 mg/kg body weight) in rats resulted 
in changes in the elution patterns of serum gel chromatography and 
paper-electrophoresis of globulins (Franzen & Wagner, 1978).  Serum 
SDH was significantly elevated (approximately 4-fold) in rats, 24 h 
after administration of acrylonitrile at 150 mg/kg body weight. A 
60% increase in serum SDH was found in rats administered 
acrylonitrile at 500 mg/litre in drinking-water for 21 days (Silver 
et al., 1982). 

(g)  Effects on other organs

    Focal superficial necrosis of the liver associated with 
haemorrhagic gastritis was found in rats necropsied 24 h after 
administration of acrylonitrile at 150 mg/kg body weight in the 
drinking-water (Silver et al., 1982). 

    Acrylonitrile shows an inhibitory effect on K-stimulated 
respiration of guinea-pig brain cortex slices at 1 mM, but little 
effect on the liver at the same concentration.  A stronger 
anaesthetic action of acrylonitrile was detected  in vitro on the 
sciatic nerve of  Rana nigra maculata, compared with some other 
anaesthetic agents (Hashimoto & Kanai, 1965). The recovery phase of 
nerve excitation was also affected by acrylonitrile (Ando & 
Hashimoto, 1967). 

7.1.3.  Biochemical changes and mechanisms of acrylonitrile 
toxicity

7.1.3.1.  Effect on cytochrome oxidase

    Evidence has been presented that cytochrome oxidase (EC 
1.9.3.1) activity may be significantly inhibited in acrylonitrile 
poisoning.  This was suspected after Dudley & Neal (1942) and 
Brieger et al. (1952) had reported significant concentrations of 
cyanide in dogs and monkeys exposed to acrylonitrile vapours.  
Tarkowski (1968) observed inhibited cytochrome oxidase activity in 
the brain, kidneys, and liver of rats after ip injection of 
acrylonitrile at 100 mg/kg body weight.   In vitro, a 50% 
inhibition of the enzyme was observed in homogenates of brain, 
kidneys, and liver with an acrylonitrile concentration of 10-3M.  
Such concentrations have been observed  in vivo, shortly after 
lethal doses of acrylonitrile (Tarkowski, 1968; Nerudova et al., 
1980; Gut et al., 1981b), but acrylonitrile has a short half-life 
in blood and liver after ip or iv administration (15-20 min).  
There are correspondingly increased blood and liver concentrations 
of cyanide in rats after acrylonitrile administration (up to 180 µM, 
Gut et al., 1981b), together with an even greater inhibition of 
cytochrome oxidase, and a much higher sensitivity of cytochrome 
oxidase activity to cyanide (50% inhibition  in vitro at 10-8M 
(Tarkowski, 1966). 

    A significantly decreased ratio of oxidized to reduced 
nicotinamide-adenine dinucleotides was observed by Sokal et al. 
(1972, 1977) in the brain of rats after sc administration of 
acrylonitrile at 100-120 mg/kg body weight, indicating inhibition 
of NADH oxidation in the mitochondria, possibly also at the level 
of cytochrome oxidase.  These changes seem to be of biological 
importance, because their magnitude was similar to that observed at 
the death of animals subjected to experimental hypoxia.  Thus, the 
cyanide-mediated inhibition of cytochrome oxidase would seem to be 
of importance in the later stages of intoxication and death.  This 
"cyanide effect" is apparently more pronounced at higher 
acrylonitrile doses (Willhite & Smith, 1981) and appears to be more 
significant in mice and dogs (Brieger et al., 1952; Benesh & 

Cherna, 1959; Gut et al., 1981b) than in rats.  This is in 
agreement with the greater efficacy in mice than in rats of 
thiosulfate (an antidote to cyanide) in acrylonitrile poisoning, 
and with the higher cyanide concentration in the blood of dogs than 
in that of rats (101 µM versus 10 µM), after breathing the same 
concentration of acrylonitrile (217 mg/m3 for 7 h) (Brieger et al., 
1952).  The protective effect of another cyanide antidote, nitrite 
(Dudley & Neal, 1942; Ghiringhelli, 1954; Benesh & Cherna, 1959), 
in acrylonitrile poisoning also points to the participation of 
cyanide in lethal acrylonitrile poisoning. 

7.1.3.2.  Effect on sulfhydryls

    There is considerable evidence to demonstrate that 
acrylonitrile significantly depresses the concentrations of soluble 
glutathione and protein sulfhydryls in the blood, liver, brain, and 
kidney.  Acrylonitrile also inhibits some SH-dependent enzymes that 
participate in carbohydrate metabolism.  Wisniewska-Knypl (1970, 
1978), Hashimoto & Kanai (1972), and Vainio & Mäkinen (1977) 
observed that the inhibition of sulfhydryls was dose-dependent in 
the range of 10-100 mg/kg body weight  in vivo, and in the 
concentraton range 0.01-10 nM  in vitro (Wisniewska-Knypl, 1978).  
A significant decrease in brain sulfhydryls was reported after a 
single dermal application of acrylonitrile of as little as 2.82 
mg/kg body weight (Zotova, 1976).  These effects were observed 
after sc, ip, or iv administration to rats, rabbits, hamsters, 
guinea-pigs, and mice.  There were some decreases in the activity 
of serum or tissue - SH-dependent enzymes including oxoglutarate 
dehydrogenase (EC 1.2.4.2).  However, the activity of succinate 
dehydrogenase (EC 1.3.99.1) was not reduced (Wisniewska-Knypl, 
1978), and there were corresponding increases in the liver, blood, 
and brain concentrations of glucose, pyruvate, and lactate 
(Hashimoto & Ando, 1966; Dinu & Klein, 1976). 

    It was shown by Zitting et al. (1981) that short-term exposure 
to acrylonitrile decreased the liver glutathione content within 4 h 
of poisoning, but that the glutathione contents returned to normal 
in brain, liver, and kidney, within 24 h.  At the same time, the 
activity of cerebral succinate dehydrogenase and of ethoxycoumarin 
demethylase in liver and kidney decreased.  Increased glucose, 
pyruvate, and lactate concentrations in blood, liver, and brain 
were also found, immediately after the fifth exposure, in rats 
exposed through inhalation to an acrylonitrile concentration of 300 
mg/m3, 8 h daily, for 5 days.  In protein, sulfhydryl-dependent 
enzyme inhibition was absent and the glutathione level was 
significantly reduced in the liver but not in the brain (Gut et 
al., 1982).  The effects of acrylonitrile on sulfhydryls were 
significantly reduced by co-administering L-cysteine and other 
sulfhydryls and there were corresponding decreases in lethal 
effects (Hashimoto & Kanai, 1965; Bondarev et al., 1976; McLaughlin 
et al., 1976; Appel et al., 1981). The results of these studies 
demonstrate the protective role of SH-groups in acrylonitrile 
poisoning. 

    The role of hypoxia in the acute thiol-depressive effect of 
acrylonitrile in male rats was investigated by Jaeger (1978) and 
Jaeger & Cote (1982).  Hypoxia was found to enhance non-protein SH 
loss in the liver, when there was exposure to acrylonitrile (Jaeger 
& Cote, 1982). 

    Evidence has been presented (Holechek & Kopecky, 1981) that 
inhibition of tissue sulfhydryls may be due not only to the 
acrylonitrile itself, but also to its reactive metabolite, 
glycidonitrile. 

7.1.3.3.  Interaction with the microsomal oxidation system as a
possible mechanism of toxicity

    Acrylonitrile added to mouse, rat, and human liver microsomes 
caused characteristic spectral complexes with cytochrome P-450 
(Ivanov et al., 1979; Appel et al., 1981). 

    It was shown  in vitro that glycidonitrile, which is
generated in rat-liver microsomes by mixed-function oxidases (EC 
1.14.14.1), covalently binds to microsomal membrane and albumin 
(Ivanov et al., 1982).  The biological significance of this 
phenomenon may be inferred from experiments with inhibitors and 
inducers of the mixed-function oxidases (Ivanov, 1981).  In rats 
pre-treated with phenobarbital, an increased amount of 
glycidonitrile was covalently bound to macromolecules and 
substantially higher activity of fructose-bisphosphate aldolase (EC 
4.1.2.13) was observed in the blood, indicating liver damage.  On 
the other hand, SKF-525A, the inhibitor of cytochrome P-450, 
reduced both effects  in vivo and  in vitro .  Activation of 
acrylonitrile by cytochrome P-450 may therefore result in a 
cytotoxic effect. 

    A previous injection of SKF-525A or of cobalt(II) chloride 
(CoCl2), another inhibitor of cytochrome P-450, resulted in 
significant protection against the gastrointestinal bleeding in 
rats caused by acrylonitrile (Ghanayem & Ahmed, 1982). 

    Some data show that acrylonitrile and its epoxide,
glycidonitrile, bind covalently,  in vitro, to DNA and RNA
(Guengenrich et al., 1981; Peter et al., 1983a).  However, the 
quantitative extent of truly irreversible binding is much less than 
that observed in experiments with other vinyl monomers (Peter et 
al., 1983). 

    A lower content of cytochrome P-450 in the liver and reduced 
oxidative microsomal metabolism of xenobiotics were observed in 
rats after an ip injection of acrylonitrile at 10 or 33 mg/kg body 
weight, for 3 days (Noel et al., 1978; Nilsen et al., 1980), after 
inhalation exposure to 300 mg/m3 of acrylonitrile, 8 h day, for 5 
days (Gut et al., in press), and in Chinese hamsters after an ip 
injection of 30 mg/kg (Zitting et al., 1981).  Inhibition of 
microsomal oxidation of xenobiotics by acrylonitrile was observed 
 in vitro (Ivanov et al., 1979). 

    Pre-treatment of rats with inducers of microsomal oxidases such 
as phenobarbital, 3-methylcholantrene, or Arochlor 1254, nullified 
the effect of acrylonitrile on the total cytochrome P-450 content.  
The activity of other microsomal enzymes, glucose-6-phosphatase (EC 
3.1.3.9), and NADPH cytochrome-c-reductase (EC 1.6.2.4), was 
unaffected by acrylonitrile (Duverger-van Bogaert et al., 1978; 
Noel et al., 1978). 

    Ghanayem & Ahmed (1982) showed that Arochlor 1254 drastically 
increased acrylonitrile-induced gastric bleeding in rats.  
Phenobarbital significantly increased acrylonitrile-induced 
hepatocyte damage in rats (Ivanov, 1981). 

    Acrylonitrile binds with liver microsomal and S-9 fractions,  in 
 vitro, by direct alkylation.  The microsomal activation of 
acrylonitrile into reactive intermediates was also detected 
(Duverger-van Bogaert et al., 1982a).  The irreversible binding of 
acrylonitrile to liver microsomal proteins was inhibited by thiols 
and even more by dithiocarb (Peter & Bolt, 1981). 

7.1.3.4.  Observations on the possible participation of membrane
lipid peroxidation in the mechanism of toxicity

    The ip administration of acrylonitrile at 10 mg/kg body weight 
induced lipid peroxidation in rat liver (Dinu, 1975a; Ivanov et 
al., 1979) and erythrocyte membranes (Ivanov et al., 1982), 
indicating possible damage of cellular membranes. NADPH-dependent 
lipid peroxidation in rat liver microsomes was only slightly 
stimulated (Ivanov et al., 1978; Duverger-van Bogaert et al., 1981) 
whereas substantial stimulation was found in the post-mitochondrial 
fraction of rat liver, lung, and brain, as well as in brain-marrow 
homogenate (Ivanov et al., 1978; Ivanov, 1979; Al'shansky et al., 
1980).  There was a correlation between an increased amount of 
malondialdehyde and a decreased content of -SH groups in the post-
mitochondrial supernatant of rat liver (Ivanov, 1981) and brain 
(Al'shansky et al., 1980).  Conjugated diene concentrations in rat 
liver microsomes were significantly elevated after iv 
administration of acrylonitrile to rats (150 mg/kg body weight), 
but no change was seen in the adrenal glands (Silver & Szabo, 
1982). 

    Pre-treatment of rats with antioxidants, in doses equivalent to 
those of the acrylonitrile administered, afforded protection 
against the pro-oxidant effect of acrylonitrile and elevation of 
blood fructose-1-phosphate aldolase, decreased the activity of 
butyrylcholine esterase (EC 3.1.1.8) (Ivanov et al., 1979), and 
reduced the GABA content and activity of glutamate decarboxylase 
(EC 4.1.1.15) in the brain (Al'shansky et al., 1980). 

7.1.3.5.  Studies on antidotes

    Appel et al. (1981a) found that the cyanide antidotes, 4-
dimethylaminophenol plus thiosulfate, protected rats against the 
lethal effects of orally-administered acrylonitrile.  A comparative 
evaluation was made by McLaughlin et al. (1975) of the efficacy of 

thiols (cysteine hydrochloride) and cyanide antidotes. The authors 
showed that thiols were more effective in protecting rats against 
acrylonitrile poisoning.  Bondarev et al. (1976) demonstrated the 
protective role of some sulfur-containing compounds in the 
acrylonitrile poisoning of rats.  The protective effects of some 
antioxidants, such as vitamin E and ionol, have also been 
demonstrated (Ivanov et al., 1979). 

    The possible toxic mechanisms and theoretical protective 
mechanisms are summarized in Fig. 3, which indicates the complex 
nature of the interference of acrylonitrile with cellular 
mechanisms, as far as can be derived from current knowledge. 

FIGURE 3

7.2.  Subacute Toxicity

7.2.1.  Inhalation exposure

    Rats, guinea-pigs, rabbits, monkeys, and cats were exposed to 
acrylonitrile at 330 mg/m3 air for 4 h per day, 5 days a week, for 
8 weeks.  All adult rats survived 8 weeks, but 5 out of 8 young 
rats died by the 6th week, 3 out of 16 guinea-pigs and 1 out of 4 
rabbits died during the 5th week, and 1 out of 2 monkeys died after 
6 weeks of exposure.  At 220 mg/m3 for 4 h/day, 5 days a week, for 
8 weeks, all rats, rabbits, and guinea-pigs survived for 8 weeks, 
but 1 out of 4 cats died during the third week.  After the first 4-
h exposure to 120 mg/m3, 1 out of 2 dogs died, but the other 

survived 4 weeks' exposure.  Four rhesus monkeys survived 4 weeks' 
exposure to 120 mg/m3 for 4 h/day (Dudley et al., 1942). 

    CD-1 mice, Charles River rats, and beagle dogs were exposed to 
acrylonitrile 57 times for 6 h a day, 5 days a week, over a 90-day 
period.  Some dogs were killed by exposure to 117 mg/m3 (54 ppm) 
but not 58 mg/m3 (24 ppm).  Mice and rats were unaffected by these 
concentrations, but a concentration of 234 mg/m3 (108 ppm) was 
lethal for half the rats and mice.  As with acute exposures, dogs 
were more sensitive than rats and mice, but mice did not appear to 
be more sensitive than rats.  Atmospheric concentrations of 
acrylonitrile of 58, 117, and 117 mg/m3 did not induce any lethal 
effects in dogs, rats, and mice, respectively (Brewer, 1976). 

7.2.2.  Oral administration

    Over a period of 7 weeks, 6 rats were administered orally 15 
doses of acrylonitrile at 30 mg/kg body weight, then 7 doses at 50 
mg/kg, followed by 13 doses at 75 mg/kg, without lethal effects 
being induced (Barnes, 1970).  No deaths occurred when Sprague-
Dawley rats were offered 85 mg or less of acrylonitrile per litre 
of drinking-water for 90 days (Humiston & Frauson, 1975).  Given 
the slow absorption of acrylonitrile from the gastrointestinal 
tract, blood levels could have been low, and it can be calculated 
that the daily dose could have been about 8.5 mg/kg body weight.  
The studies are compatible with the view that acrylonitrile is 
unlikely to have a significant cumulative effect. 

7.2.3.  Subcutaneous administration and intraperitoneal 
administration

    Daily sc doses of 40 mg/kg body weight over 4 weeks, or daily 
ip injections of 20 mg acrylonitrile/kg body weight over 6 weeks, 
were not fatal for rats (Krysiak & Knobloch, 1971). 

7.2.4.  Clinical observations in animal studies

    Rats exposed to acrylonitrile concentrations of 220 mg/m3 for 4 
h daily, 5 days a week (Dudley et al., 1942) over a period of 8 
weeks, showed slight lethargy but gained weight, as did guinea-
pigs.  Rabbits failed to gain weight and were listless, while cats 
became listless, vomited, and lost weight.  One cat developed a 
transitory weakness of the hind legs after the third exposure and 
died after the eleventh exposure; the 3 remaining cats survived 8 
weeks with few untoward effects.  Exposure to an atmospheric 
concentration of 330 mg/m3 resulted in weight loss in rats, their 
coats became rough, and their general physical condition poor 
(Dudley et al., 1942).  Young rats and guinea-pigs showed impaired 
growth and marked irritation of the eyes and nose during the first 
week of exposure.  Marked eye and nose irritation was also seen in 
rabbits and cats and the latter developed transitory weakness of 
the hind legs.  Monkeys appeared sleepy and weak and frequently 
salivated and vomited.  Thus, the 220 mg/m3 exposure level markedly 
affected cats, while rabbits and guinea-pigs were little affected; 
a concentration of 330 mg/m3 induced various effects including 
death.  Brewer (1976) exposed CD-1 mice, Charles River rats, and 
beagle dogs to acrylonitrile concentrations of 0, 58, 117, 234 
mg/m3 (0, 24, 54, or 108 ppm) for 6 h daily, 5 days a week, for 13 

weeks.  Signs observed included ataxia, ptosis, emaciation, 
rhinitis, and diuresis.  As is common with acrylonitrile over-
exposure, convulsions usually preceded death (e.g., Benesh & 
Cherna, 1959; Paulet et al., 1966). 

7.2.4.1.  Body weight, food and water consumption

    Loss of body weight or failure to gain body weight was seen in 
rats exposed to acrylonitrile at 330 mg/m3 and in cats and rabbits 
exposed to 220 mg/m3 for 4 h a day, 5 days a week, for 13 weeks.  
Loss of appetite was seen in rhesus monkeys exposed to 330 mg/m3, 
while 120 mg/m3 did not elicit any toxic effects (Dudley et al., 
1942).  No adverse effects were seen in 6 rats administered 
successively 15 doses of 30 mg/kg body weight, 7 doses of 50 mg/kg, 
and 13 doses of 75 mg/kg over a period of 7 weeks (Barnes, 1970).  
Adult Sprague-Dawley rats received between 0 and 42 mg 
acrylonitrile/kg body weight in drinking-water for 90 days.  The 
body weight was depressed in males receiving 42 mg/kg, while 
females were affected by 22 mg/kg, but only after the 57th day.  
The mean weekly food consumption of males was lower for 7 weeks on 
38 mg/kg and for 2 weeks on l7 mg/kg.  Food consumption decreased 
in females receiving 42 or 22 mg/kg for 6 weeks and 1 week, 
respectively (Humiston & Frauson, 1975). 

7.2.4.2.  Organ weights and pathology

    The weights of the liver, kidney, spleen, pituitary gland, 
lungs, gonads, thyroid gland, adrenals, heart, and brain of rats, 
mice, and dogs exposed to an acrylonitrile concentration of 234 
mg/m3 for 6 h a day, 5 days a week, for 13 weeks, were within 
normal limits (Brewer, 1976).  In rats receiving acrylonitrile in 
drinking-water for 90 days, no changes in absolute or relative 
organ weights were seen in males receiving 4 mg/kg body weight or 
females receiving 5 mg/kg, daily (Humiston & Frauson, 1975).  The 
relative liver weight was significantly increased in males and 
females receiving 17 mg/kg (males) or 22 mg/kg (females) or more.  
The weights of the heart and liver were increased significantly in 
adult Wistar rats administered 50 mg acrylonitrile/kg body weight, 
intraperitoneally, daily, for 3 weeks (Knobloch et al., 1971); 
their weight loss caused an increase in the relative weights not 
only of the heart and liver, but also of the kidney and spleen. 

    Dudley et al. (1942) examined the livers of rats, guinea-pigs, 
rabbits, cats, dogs, and rhesus monkeys exposed to acrylonitrile at 
220 or 230 mg/m3, and observed histological changes only in cats.  
Liver parenchymal degeneration was reported in adult Wistar rats 
after daily ip administration of 50 mg/kg body weight for 3 weeks 
(Knobloch et al., 1971).  In the above-mentioned study, Dudley et 
al. (1942) also reported signs of renal damage, such as hyaline 
casts in the straight collecting tubules of all species, and 
limited subacute interstitial nephritis; this was especially seen 
in guinea-pigs and rabbits.  Parenchymal degeneration of the 
kidneys was reported by Knobloch et al. (1971).  In the study by 
Dudley et al. (1942), lungs were affected by subacute 
bronchopneumonia, congestion, and oedema of the alveolar walls, 
extravasation of erythrocytes and serum into the alveoli, focal 

collection of lymphyocytes and polymorphonuclear leukocytes, in 
most guinea-pigs, rabbits, the monkey, and 1 out of 3 of the rats.  
The authors also reported slight haemosiderosis in the spleen of 
rats, but negligible siderosis in cats, guinea-pigs, and rabbits.  
Exposure of rats to acrylonitrile (22 mg/m3, 10 ppm) for 7 weeks 
and (100 mg/m3, 50 ppm) for another 6 weeks caused enlargement of 
the liver, kidney, heart, and spleen, but co-administration of 
vitamins B1, B2, and cystine had a protective effect against 
enlargement of the heart.  Alcohol dehydrogenase activity in the 
liver decreased after exposure, but the above-mentioned drugs 
alleviated this decrease, to some extent (Takagi et al., 1968). 

7.2.4.3.  Blood

    A normal haematological picture was reported in rats and dogs 
repeatedly exposed to acrylonitrile vapours at up to 240 mg/m3 
(Brewer, 1976), and in rats and rabbits (except for a raised 
eosinophil count) repeatedly exposed to up to 330 mg/m3 (Dudley et 
al., 1942). 

    Minami et al. (1973) exposed male rabbits to 54 mg/m3 for 1 day 
per week (8 h) for 8 weeks; haematocrit and haemoglobin were 
unaffected, but pO2 and pH were raised and pCO2 lowered by the 
treatment. 

    In rats receiving acrylonitrile in the drinking-water for 90 
days, the only significant haematological change was a decrease in 
the red-cell count, on the 83rd day, in females receiving 42 mg/kg 
body weight per day (Humiston & Frauson, 1975).  The blood urea and 
alkaline phosphatase (EC 3.1.3.1) levels in the males receiving 38 
mg/kg body weight per day were raised, but SGPT activity was 
normal.  While rats administered ip 50 mg acrylonitrile/kg body 
weight, daily, for 3 weeks (Knobloch et al., 1971) developed 
leukocytosis and increased serum asparagine-oxo-aminotransferase 
(EC 2.6.1.14) activity, mice exposed for 70 days to 225 mg/m3 (100 
ppm) or 340 mg/m3 (150 ppm) 6 h daily, did not develop any 
haematological abnormalities (Hashimoto, 1962).  Rats exposed to 
9.7 mg/m3, 4 h daily, 5 days a week for 2 months, did not show any 
effects on the erythrocyte count or on the haemoglobin 
concentration (Vissarionova et al., 1979). 

    As a whole, the studies failed to demonstrate any consistent 
effect of acrylonitrile on red or white blood cell production or 
viability.  Leukocytosis following repeated intraperitoneal 
administration of an irritant material is to be expected. 

7.2.4.4.  Immune system

    Wistar rats were exposed to an acrylonitrile concentration of 
10 mg/m3 for 6 h daily, 5 days a week, for 16 weeks.  Acrylonitrile 
depressed both T helper and T suppressor functions, and a 
diminished degree of B lymphocyte transformation was observed.  
Alpha tocopherol (im 0.21 mmol/kg body weight on alternate days for 
16 weeks) protected against this effect (Krivova et al., 1982). 

7.2.4.5.  Nervous system

    Some findings in the experimental animal studies on 
acrylonitrile were indicative of an effect on the nervous system.  
Rats, mice, and dogs exposed to up to 240 mg/m3, for 6 h daily, 5 
days per week, for 13 weeks, showed ataxia and convulsions, prior 
to death (Brewer, 1976).  Transitory hind-leg weakness was seen in 
cats exposed for 8 weeks (4 h per day, 5 days per week) to 330 
mg/m3 (Dudley et al., 1942). Krysiak & Knobloch (1971) found that 
rats receiving acrylonitrile intraperitoneally at 20 mg/kg body 
weight daily for 6 weeks, or sc at 40 mg/kg daily for 4 weeks, 
showed a significant lengthening of the time to perform correctly 
in a conditioned food reflex test, and a significant decrease in 
the number of correct reactions, compared with pre-treatment 
observations or controls.  Performance improved when the treatment 
was discontinued.  Daily ip administration to rats of acrylonitrile 
at 50 mg/kg body weight for 3 weeks caused a vacuolization of 
neuronal cells of the cortex and brain stem (Knobloch et al., 
1971). 

7.2.4.6.  Urine

    No significant changes in urine composition were observed in 
the experimental studies of Humiston & Frauson (1975) (sections 
7.2.4.1 - 7.2.4.3). 

7.2.4.7.  Adrenals

    The adrenals of rats exposed for 21-60 days to acrylonitrile 
in drinking-water (0.05% and 0.2%) showed an atrophic zona 
fasciculata and an enlarged zona glomerulosa.  The animals on the 
higher dose had a reduced plasma corticosteroid level and an 
increased plasma Na+Concentration.  The K+ level was unchanged 
(Szabo et al., 1976).  Serum corticosterone in rats was decreased 
by 3 ip doses of acrylonitrile (33 mg/kg body weight) on successive 
days (Nilsen et al., 1980). 

7.2.4.8.  Metabolism

    After repeated exposure of rabbits to acrylonitrile, the  in 
 vitro metabolism in the liver of acrylonitrile into cyanide and 
thiocyanate decreased with time, while the excretion of unchanged 
acrylonitrile in the urine increased (Sato, 1978). 

7.3.  Chronic Toxicity

    Observations have been made on animals administered 
acrylonitrile in drinking-water, food, through inhalation, and by 
dermal application. 

    Tuller (1947) administered acrylonitrile at 500 mg/litre in the 
drinking-water or acrylonitrile-fumigated food (dose not precisely 
specified) to rats.  After 2 years, the mortality was higher in 
rats drinking acrylonitrile solution (50% deaths) than in paired 
controls (25%), another control group (15%), and in rats on 
acrylonitrile-fumigated food (5%).  However, when acrylonitrile was 

administered at 0.5, 5, and 90 mg/litre in the drinking-water to 
male and female CFW rats for 2 years, the mortality rate was 
unaffected (Svirbely & Floyd, 1961).  Groups of 4 male and 4 female 
beagle dogs were administered acrylonitrile at concentrations of 
100, 200, or 300 mg/litre in the drinking-water, for 6 months.  
Average intakes of acrylonitrile were the following for males 
(females): 10(8) mg/kg body weight at 100 mg/litre; 16(17) mg/kg at 
200 mg/litre; and 17(18) mg/kg at 300 mg/litre.  Five dogs died, or 
were killed because debilitated, in each of the 2 higher dosage 
groups (Quast et al., 1975). 

    In the dogs receiving acrylonitrile at 100-300 mg/litre in the 
drinking-water, early signs of toxicity included roughening of the 
coat and, later, retching and vomiting. Terminal signs of lethargy, 
weakness, emaciation, and respiratory distress were noted (Quast et 
al., 1975). 

7.3.1.  Body weight, food and water intake

    Body-weight gain was reduced during 4 of the 11 weeks at the 
higher dose level (240 mg/m3) in a test in which male and female 
Wistar rats and albino rabbits were exposed to acrylonitrile vapour 
at concentrations of 0, 50, and 240 mg/m3, for 3 h/day, 6 days a 
week, for 6 months (Knobloch et al., 1972). 

    Growth retardation was observed in male rats drinking 500 mg 
acrylonitrile per litre water, for 2 years (Tuller, 1947). Svirbely 
& Floyd (1961) administered acrylonitrile at 0.5, 5, or 50 mg/litre 
in the drinking-water of rats and found a slight decrease in water 
consumption at the highest concentration in both sexes.  
Statistically significant reductions in the body weight of rats 
receiving drinking-water containing acrylonitrile concentrations of 
35, 100, or 300 mg/litre were associated with decreased water 
consumption and decreased food consumption at 300 mg/litre in males 
and 100 mg/litre in females (Ouast et al., 1977).  Decreased food 
and water consumption and body weight was reported with beagle dogs 
drinking acrylonitrile at 200 or 300 mg/litre water for 6 months 
(Quast et al., 1975).  Marked weight decreases were seen in dogs 
that eventually died or had to be killed. 

7.3.2.  Organ weights

    In rabbits exposed to atmospheric acrylonitrile concentrations 
of 250 mg/m3, for 3 h/day, 6 days a week for 6 months, a 
significant increase in the heart weight was noted, and some 
fluctuations in blood pressure were described (Knobloch et al., 
1972). 

    Ferin et al. (1961) exposed rats to drinking-water containing 
an acrylonitrile concentration of 20 or 1000 mg/litre for 6 months.  
At the higher dose, increased relative weights of the liver, 
spleen, and kidneys were noted.  The relative weights of the heart, 
liver, and brain in males, and of the liver and kidneys in females, 
were increased in rats receiving 300 mg/litre in drinking-water.  
The males drinking 100 mg/litre showed a significantly increased 
brain weight, and the females receiving 100 mg/litre had 

significantly lower relative heart weights (Quast et al., 1977).  
The weights of brain, heart, liver, and kidneys of beagle dogs 
drinking an acrylonitrile concentration of 100 mg/litre in 
drinking-water (Quast et al., 1977) were normal but, at 200 
mg/litre, the 2 remaining males had a lower absolute brain weight 
and higher relative kidney weight than controls.  The 2 remaining 
females receiving 300 mg/litre also had significantly lower relative 
brain weights compared with controls. 

7.3.3.  Pathology and histology

    Inflammation of the pulmonary system accompanied by an
inflammatory exudate into the bronchial lumen occurred in rats
exposed to acrylonitrile at 240 mg/m3 for 3 h a day, 6 days a
week, for 6 months (Knobloch et al., 1972).  Various pathological 
changes occurred in male and female rats maintained on water 
containing acrylonitrile at 35, 100, or 300 mg/litre for 12 months 
(Quast et al., 1977).  Males and females on the 2 higher doses 
developed paleness and thickening of the mucosa, erosions, ulcers, 
and sometimes papilloma formations in the non-glandular portion of 
the stomach.  Three females receiving 300 and 100 mg/litre and one 
male at 300 mg/litre had ear canal tumours.  Microscopic findings 
of tissue with tumorous growth revealed an increased frequency of 
gastric cell papillomas, Zymbal (sebaceous) gland tumours of the 
ear canal, and microtumours of the nervous system, in rats 
receiving a concentration of acrylonitrile of 100 or 300 mg/litre.  
These tumours do not occur spontaneously at such a high frequency 
in the strain of rat used.  The nervous system lesions were 
consistent with the diagnosis of astrocytoma. 

    Minimal lesions were seen in the liver of rats drinking 
acrylonitrile at 100 or 300 mg/litre and chronic renal disease 
occurred in females drinking 300 mg/litre.  The squamous epithelium 
of the stomach was hyperplastic in rats drinking 100 or 300 
mg/litre. 

    Histopathological changes in dogs receiving acrylonitrile 
concentrations of 200 and 300 mg/litre in water (Quast et al., 
1975) were similar to those in untreated controls.  The pneumonia 
present may have resulted from irritation of the mucosa of the 
tongue and oesophagus, which produced abnormal swallowing, 
resulting in aspiration of some food. 

7.3.4.  Haematology and clinical chemistry

    In rats exposed for 3 h/day, 6 days a week, for 6 months to 
acrylonitrile in air concentrations of either 50 or 240 mg/m3, the 
eosinophil count had significantly increased after 4 months.  Total 
serum protein was unchanged, while albumin and alpha-globulin had 
increased and gamma-globulin decreased in both test groups 
(Knobloch et al., 1971).  Leukocytosis was observed in rats 
drinking acrylonitrile in water at 1000 mg/litre (Ferin et al., 
1961).  Periodic examinations of rats drinking 0.5, 5, or 50 
mg/litre in water (Svirbely & Floyd, 1961), or 0 - 300 mg/litre in 
water (Quast et al., 1977), showed normal haematological findings.  
A significant elevation in alkaline phosphatase activity was found 

in female rats exposed to 300 mg/litre.  Half-way through the 
study, beagle dogs drinking acrylonitrile concentrations of 0, 100, 
200, or 300 mg/litre in water showed a significant decrease in 
haematocrit, erythrocyte count, and haemoglobin concentration at 
300 mg/litre and decreased erythrocyte count at 200 mg/litre, in 
males.  Females on 300 mg/litre also showed a significant decrease  
in the erythrocyte count.  However, all haematological findings 
were within normal ranges towards the end of the study, except in 
males at 300 mg/litre, which had a lower erythrocyte count. Blood 
urea nitrogen, serum alkaline phosphatase activity, SGPT, and SGOT 
were measured periodically; the findings in males were always 
within normal limits, but females receiving 300 and 200 mg/litre 
showed some increase in SGOT and SPGT activity.  Total and 
individual serum proteins were unaffected at the end of the study.  
Zotova (1976) exposed rats by applying acrylonitrile solution to 
the skin of the tail at doses of 2.82, 0.56, or 0.11 mg/kg body 
weight per day and observed a decreased haemoglobin concentration 
at the highest dosage level after 2 months.  Blood catalase (EC 
1.11.1.6) activity increased, and blood peroxidase (EC 1.11.1.7) 
activity decreased, initially, but later became normal; there was 
no change in sulfhydryl levels. 

    A decrease in blood -SH groups was reported in rats exposed to 
acrylonitrile at 10 mg/m3 for 5 days/week, 4 h a day, for 4 months 
(Efremov, 1976d). 

7.3.5.  Nervous system

    Changes in central nervous function, as elicited by a 
conditioned avoidance test, were found in rats drinking water 
containing acrylonitrile at 20 mg/litre, for 6 months (Ferin et 
al., 1961).  Rats exposed through inhalation to acrylonitrile 
concentrations of 50 and 240 mg/m3 for 3 h a day, 6 days a week, 
for 6 months, showed significant defects in performance in a "Y" 
maze (Krysiak, 1971).  Rats exposed to 10 mg/m3, 5 days/week, 4 h a 
day, for 4 months, showed a 59% decrease in the activity of brain 
catalase, a 59% decrease in brain peroxidase, and a 37% decrease in 
-SH groups (Efremov, 1976d).  Histopathological changes in the 
nervous system, consistent with a diagnosis of astrocytoma, were 
observed in rats exposed to acrylonitrile at 35, 100, or 300 
mg/litre in drinking-water (Quast et al., 1977). 

7.3.6.  Kidney function

    Knobloch et al. (1972) exposed rats to 50 or 240 mg/m3, for 
3 h per day, 6 days per week, for 6 months; kidney dysfunction was 
indicated by increased urinary output at both concentrations and an 
increase in urinary protein and areas of degenerated proximal 
convoluted tubules at the higher concentration. 

    There were no abnormalities in the urine chemistry of rats 
drinking water containing acrylonitrile at 0, 35, 100, or 300 
mg/litre (Quast et al., 1977), or of dogs (Quast et al., 1975), 
drinking water containing 100, 200, or 300 mg/litre. When 
acrylonitrile was applied to the skin of the tail of rats, daily, 
at doses of 2.82, 0.56, or 0.11 mg/kg body weight for 4.5 months, 

the excretion of urinary chlorides increased on day 10 of exposure 
at the 2 higher doses and decreased at the lowest dose (Zotova, 
1976). 

7.4.  Teratogenicity and Embryotoxicity

    The teratogenic potential of ingested or inhaled
acrylonitrile was investigated by Murray et al. (1978).
Groups of pregnant SD rats were given acrylonitrile at 0, 10,
25, or 65 mg/kg body weight per day, by gavage, from day 6 to
day 15 of gestation.  Groups of 30 pregnant SD rats were
exposed 6 h per day to 0, 87, or 174 mg/m3 (0, 40, or 80 ppm)
acrylonitrile by inhalation, during the same period of
pregnancy.  A dose of 65 mg/kg body weight per day caused
marked maternal toxicity, significant embryotoxicity, and an
increased incidence of fetal malformations.  Findings of the
two studies suggesting a teratogenic effect were noted at 25
mg/kg per day and at 174 mg/m3 (80 ppm).  At 10 mg/kg body
weight per day and 87 mg/m3 (40 ppm), no embryotoxicity or
teratogenicity was found.  There was no apparent correlation
between the degree of toxicity seen in the individual dams and
the occurrance of malformations in their offspring.

    Embryotoxic effects in pregnant mice of 3 strains were 
described after intraperitoneal administration of unspecified doses 
of acrylonitrile (Scheufler, 1976).  A single ip injection of 
acrylonitrile of 32 mg/kg body weight, given on the 5th or 7th day 
of pregnancy, induced an embryotoxic effect in mice from an inbred 
strain of AB Jena-Hall, but not in DBA and C57 C1 mice (Scheufler, 
1980). 

    Kankaanpää et al. (1979) studied the embryotoxic effects of 
acrylonitrile using chick eggs, but did not find any clear evidence 
of its teratogenicity. 

    The exposure of Sprague-Dawley rats to an acrylonitrile 
concentration in drinking-water of 500 mg/litre led to decreased 
fertility and decreased viability of the young, and the females 
developed a progressive muscular weakness in the hind legs about 
16-19 weeks after the weaning of the second litter (Svirbely & 
Floyd, 1961). 

    Willhite (1981a,b) observed skeletal malformations in hamster 
fetuses after the administration of acrylonitrile at 80 mg/kg body 
weight to pregnant hamsters.  The histological study of both early 
embryos and term fetuses revealed mesodermal changes, including a 
reduction in the number of cells, shrinkage of the cell cytoplasm, 
and enlarged extracellular spaces.  In addition, a reduction in 
mitotic figures and focal necrosis were noted.  The affected 
embryos were smaller and their development was delayed compared 
with untreated controls.  Teratogenic effects were only observed 
when there was simultaneous maternal toxicity. 

7.5.  Mutagenicity

7.5.1.  Bacterial systems

(a) Ames test with  Salmonella typhimurium strains

    Tests have been carried out on several strains, with and 
without metabolic activation, using several methods of treatment 
with acrylonitrile.  Negative results were obtained, with and 
without activation, in 5 tested strains in 2 studies (Litton 
Bionetics, 1975; Stanford Research Institute, 1976). A weak, but 
reproducible, positive effect was observed with metabolic 
activation using between 0.5 and 1.5 mg acrylonitrile per plate in 
strain TA 1535 (Haskell Laboratory, 1975; De Meester et al., 1978, 
1979).  Three methods of exposure were examined by Milwy & Wolff 
(1977) in 3 strains of  S. typhimurium. A low level of mutagenic 
activity was noted in strain TA 1535, when plates were sprayed with 
acrylonitrile or when it was mixed with the medium, with 
activation. 

    Exposure to acrylonitrile vapour of the strains TA 1535 and TA 
100 also demonstrated acrylonitrile mutagenicity (Duverger-Van 
Bogaert et al., 1981; Ivanov, 1981).  Zhurkov et al. (1983) tested 
the mutagenicity of acrylonitrile in strains TA 1535 and TA 1538, 
with and without microsomal activation, and found a dose-dependent 
effect in strain TA 1535. 

    Urine collected from rats and mice treated with acrylonitrile 
was mutagenic in  S. typhimurium strain TA 1530, in the absence of 
metabolic activation.  Pre-treatment of the animals with 
phenobarbital abolished the direct mutagenicity of urine from rats 
and reduced that from mice.  The addition of beta-glucuronidase (EC 
3.2.1.31) to the incubation mixtures enhanced the mutagenic 
activity of urine from acrylonitrile-treated animals (Lambotte-
Vandepaer et al., 1980, 1981a). Duverger-van Bogaert et al. (1982b) 
suggested that glutathione might play a role in the formation of a 
mutagenic metabolite of acrylonitrile.  The mutagenic activity of 
acrylonitrile vapours towards  S. typhimurium strains was strictly 
dependent on the presence of an activation system, confirming the 
report of Milwy & Wolff (1977).  Lambotte-Vandepaer et al. (1980) 
indicated that animal urine might retain its mutagenic activity for 
as long as a week after collection.  The acrylonitrile-derived 
epoxide, glycidonitrile, synthesized by Kopecky & Smejkal 
(unpublished data, 1979), was shown to be the principal substance 
that exerted mutagenic activity in the absence of metabolic 
activation, whereas acrylonitrile itself required metabolic 
activation in the  S. typhimurium Ames test (Cherna et al., 1981). 

(b) Mutagenicity in  Escherichia coli

    One of 3 strains of  E. coli (WP2) revealed mutagenic activity 
of acrylonitrile; activation did not have any effect (Venitt et 
al., 1977).  The mutagenic activity of acrylonitrile was confirmed 
in other experiments using the simplified fluctuation test of Green 
et al. (1976).  The results suggested that acrylonitrile caused 
non-excisable mis-repair of DNA associated with the generation of 

DNA strand breaks (Venitt et al., 1977).  The method of Slater et 
al. (1971) did not reveal any effect with or without an activation 
system at 10 µg acrylonitrile per plate (Litton Bionetics, 1976). 

    The variability of the results, even when the same kinds of 
assays are used, could be because of differences in purity of the 
acrylonitrile, in method, or in bacterial sensitivity. However, the 
mutagenicity of acrylonitrile in bacterial systems seems to have 
been established. 

7.5.2.  Yeast assays

    Possible mutagenic activity of acrylonitrile was found with 
 Saccharomyces cerevisiae, but metabolic activation was without 
effect (Litton Bionetics, 1975). 

7.5.3.  Drosophila melanogaster

    A negative result was obtained when 0.1% acrylonitrile was 
administered by intra-abdominal injection into  D. melanogaster in 
order to examine its ability to induce a recessive lethal effect in 
the X chromosomes (Benesh & Shram, 1969). 

7.5.4.  Mammalian cell  in vitro assays

    The L5178Y kinase mouse lymphoma cell assay (Litton Bionetics, 
1976) failed to show mutagenic activity of acrylonitrile using the 
procedure of Clive & Spector (1975). Chinese hamster ovary cells 
showed an increase in sister chromatid exchange (SCE) after 
exposure to acrylonitrile, when co-cultured with rat hepatocytes 
(Ved Brat & Williams, 1982). No effect was found without the 
latter. 

    Acrylonitrile induced a slight increase in the SCE of cultured 
human lymphocytes in the presence of S-9 mix and increased 
unscheduled DNA synthesis with a very high concentration (0.5 M) 
(Perocco et al., 1982).  Application of acrylonitrile to primary 
Syrian golden hamster embryo cells in culture produced foci of 
morphologically-transformed cells. Pre-treatment with simian 
adenovirus (SA7) caused an 8 to 9-fold increase in the frequency of 
virus-transformed foci. When 3H-thymidine-labelled cells were 
treated with acrylonitrile and their DNA subjected to alkaline 
sucrose gradients, a shift in the sedimentation pattern occurred, 
which was reminiscent of that observed with carcinogen treatment.  
These observations added support to recent studies indicating that 
acrylonitrile may be carcinogenic (Parent & Castro, 1979). 

7.5.5.  Mammalian  in vivo assays

    The inhalation exposure of 16 Sprague-Dawley male rats to 
acrylonitrile levels up to 1085 mg/m3 (500 ppm) for 90 days did not 
reveal chromatid or chromosomal aberrations or bone-marrow 
abnormalities (Johnson et al., 1978).  The results of Rabello-Gray 
& Ahmed (1980) and the recent results of Leonard et al. (1981) also 
showed that acrylonitrile fails to induce chromosomal aberrations 
in somatic and germ cells. 

    Similar negative results were reported by Zhurkov et al. (1983) 
following inhalation exposure of mice to acrylonitrile concentrations 
of both 100 mg/m3 and 20 mg/m3 .  They also reported negative 
results in a dominant lethal assay in mice. 

    From preliminary results concerning DNA-alkylation by 
acrylonitrile and vinyl chloride monomer (Peter et al., 1983), it 
appears that DNA-alkylation occurs to a much lesser extent with 
acrylonitrile than with vinyl chloride monomer.  This is consistent 
with the absence of mutagenic effects  in vivo. 

7.6.  Carcinogenicity

    Although full data were not available to the Group, there was 
strong evidence from the data considered that acrylonitrile is a 
carcinogen in rats. 

    Maltoni et al. (1977, 1982) investigated the carcinogenicity of 
acrylonitrile administered to Sprague-Dawley rats by inhalation at 
87, 44, 22, and 11 mg/m3 (40, 20, 10, and 5 ppm), 4 h daily, 5 
times a week, or by stomach tube as a solution in olive oil, at a 
dose of 5 mg/kg body weight, once a day, 3 times a week.  In each 
case, the rats were treated for 52 weeks and then kept without 
further treatment until death.  An increased incidence of some 
tumours was noted in the acrylonitrile-treated animals, e.g., 
mammary tumours, forestomach papillomas and acanthomas, and 
encephalic tumours (gliomas). 

    Two-year studies on Sprague-Dawley rats, following inhalation 
exposure to acrylonitrile or ingestion in drinking-water, have been 
performed at the Dow Chemical Company laboratories (Quast et al., 
1980a,b).  In the inhalation studies, rats were exposed to 0, 44, 
or 174 mg/m3 (0, 20, or 80 ppm) for 6 h/day, 5 days a week, for 24 
months. Treatment-related tumours were found in the central nervous 
system, Zymbal gland, tongue, stomach, small intestine, mammary 
gland, and nasal turbinates.  An apparent decrease in tumours of 
the pituitary gland, the adrenals, the thyroid, the pancreas, and 
testes was observed in the exposed rats. 

    In the ingestion study, rats were maintained on water 
containing acrylonitrile levels of 0, 35, 100, and 300 mg/litre, 
equivalent to mean dosage levels of 0, 4, 9, or 22 mg/kg body 
weight per day.  Evidence of oncogenicity was found in rats at all 
dose levels of acrylonitrile.  An increased tumour incidence was 
observed in the treated rats affecting, particularly, the centra1 
nervous system and also the Zymbal gland, tongue, stomach, small 
intestine, and mammary gland.  A decreased incidence of tumours was 
observed at some sites: pituitary, thyroid, adrenals, pancreas, and 
uterus. 

    In studies performed by Hogen & Rinehart (1980), acrylonitrile 
was administered to Sprague-Dawley rats in the drinking-water at 1 
or 100 mg/litre for 19-22 months, or by gavage at 0.1 or 10 mg/kg 
body weight per day in water for about 20 months.  A second group 
of Fisher 344 rats received acrylonitrile in the drinking-water at 
1, 3, 10, 30, or 100 mg/litre for 23-26 months.  A statistically 

significant increase in tumours was reported in the group receiving 
acrylonitrile at 10 mg/kg body weight by gavage and in the groups 
receiving 10, 30, or 100 mg acrylonitrile/litre drinking-water. 

    So far, no information is available on the carcinogenicity of 
acrylonitrile for animal species other than rats. 

    After reviewing these data, IARC (IARC, 1982) and COC (UK 
Ministry of Agriculture, Fisheries and Food, 1982) concluded that 
acrylonitrile was a carcinogen in experimental animals. 

8.  EFFECTS ON MAN

    Acrylonitrile has long been known to be a toxic substance that 
induces systemic as well as local injury in both animals and man.  
It has frequently been used in combination with other chemicals; 
they may modify its toxicity, as was the case when it was used as a 
fumigant. 

8.1.  Acrylonitrile

8.1.1.  Acute Toxicity

8.1.1.1.  Inhalation exposure

    A 22-year-old chemist, who was exposed to acrylonitrile vapours 
when a distillation apparatus leaked, developed headache, vertigo, 
vomiting, tremors, uncoordinated movements, and convulsions 
(Sartorelli, 1966).  Vomiting and nausea persisted for 24 h.  One 
day after exposure, slight liver enlargement and congestion of the 
oral pharynx, but no disorders of the CNS, were noted.  After 4 
days, no kidney, liver, cardiac, or respiratory abnormalities were 
detected. Workers exposed to "mild" concentrations of acrylonitrile 
in synthetic rubber manufacture developed nausea, vomiting, 
weakness, nasal irritation, and an "oppressive feeling" in the 
upper respiratory tract (Wilson, 1944).  Headache, fatigue, and 
diarrhoea were observed in some cases, and mild jaundice lasting 
for several days and accompanied by liver tenderness and low-grade 
anaemia in a few others.  Jaundice lasted for 4 weeks in 1 case; 
this individual complained of lassitude and fatigue after one year.  
Zeller et al. (1969) observed that in 16 cases of acute inhalation 
of acrylonitrile fumes by workers, nausea, vomiting, headache, and 
vertigo appeared within 5-15 min; none of the workers needed 
hospitalization. The authors described 50 cases of skin contact 
with irritation, erythema, and blistering appearing within 5 min to 
24 h, but with no systemic consequences.  Workmen exposed to 
concentrations varying from 35 to 220 mg/m3 (16-100 ppm) for 20-45 
min during cleaning operations in polymerizers frequently 
complained of a dull headache, fullness in the chest, irritation of 
the eyes, nose, and throat, and feelings of apprehension and 
nervous irritability.  Some workmen had "intolerable itching" of 
the skin, but no accompanying dermatitis. 

8.1.1.2.  Dermal exposure

    A male laboratory worker who spilled "small quantities" of 
liquid acrylonitrile on his hands, developed diffuse erythema on 
both hands and wrists after 24 h, and blisters on the fingertips by 
the third day.  The hands were slightly swollen, erythematous, 
itchy, and painful.  The fingers remained dry and scaly on the 10th 
day (Dudley & Neal, 1942).  Wilson et al. (1948) observed that 
direct skin contact led to irritation and erythema followed by scab 
formation; healing was slow. Development of allergic dermatitis is 
possible; a 27-year-old individual developed a rash on his finger 
following the use for 6 weeks of a finger splint made from an 
acrylonitrile/methyl methacrylate copolymer.  Patch testing gave 

positive reactions to the copolymer and 0.1% acrylonitrile (Balda, 
1975).  In another case report, skin lesions were first observed at 
the site of contact with liquid acrylonitrile, which then spread 
rapidly to other neighbouring regions.  Several days after contact, 
the lesions spread rapidly to other parts of the body that had not 
been exposed, and these extensions were assumed to be an allergic 
reaction (Hashimoto & Kobayashi, 1961). 

    In addition to local dermal toxicity, dermal absorption of 
acrylonitrile may lead to systemic poisoning.  Grunske (1949) 
described a fatal case in which a 3-year-old girl had entered a 
room that had recently been sprayed with an acrylonitrile-
containing insecticide (Ventox).  Exposure was mainly through 
inhalation, but skin exposure was possible, too.  Another fatal 
case was reported by Lorz (1950) in which a 10-year-old girl had 
been treated on the scalp for lice with an insecticide that was 
identified as containing acrylonitrile (Ventox).  She had impetigo 
and widespread scratches on the skin of the scalp.  This could have 
increased the absorption of acrylonitrile. 

    Two workers who spilled liquid acrylonitrile on their legs, 
immediately washed their legs and dried their shoes, but put them 
on again.  Blisters developed at the sites of contact, 6-8 h after 
the spill.  Therapy lasted 21 and 38 days, respectively.  The skin 
of 2 workers who were cleaning apparatus (temperature 50 °C), came 
into contact with 5% acrylonitrile solution; other possible 
substances in the mixture were not specified.  Serious skin burns 
developed. Therapy lasted 35 and 72 days, respectively (Babanov, 
1957). Zeller et al. (1969) reported 50 cases of skin damage 
resulting from occupational contact with acrylonitrile.  A burning 
sensation developed within 5 min to 24 h followed by a reddening of 
the area, which often blistered after 1 day. 

8.1.2.  Chronic toxicity - occupational exposure

    Chronic effects can potentially occur after prolonged exposure 
to acrylonitrile, both in the vapour and liquid forms. 

8.1.2.1.  Clinical observations

    Complaints of poor health, headache, decreased work capacity, 
poor sleep, irritability, chest pains, poor appetite, and skin 
irritation (during the first months of employment only) came from 
workers employed in the manufacture of acrylonitrile (Zotova, 
1975a). 

    In a study by Sakurai & Kusumoto (1972), workers employed in 
acrylonitrile manufacture also complained of headache, weakness, 
fatigue, nausea, vomiting, nosebleeds, and insomnia; the symptoms 
correlated well with the length, but not with the level of exposure 
or with the age of the workers.  A total of 4439 examinations were 
made over about 10 years prior to 1970, in 576 workers  who formed 
2 cohorts, one exposed to concentrations of acrylonitrile below 11 
mg/m3 (5 ppm), the other below 45 mg/m3 (20 ppm).  However, the 
authors later stated that these exposure levels were not reliably 
reported (Sakurai et al., 1978). 

    Babanov et al. (1959) reported that workers exposed to 
acrylonitrile concentrations at 0.6-6 mg/m3 for approximately 3 
years suffered from headache, insomnia, pains in the heart region, 
general weakness, decreased working capacity, and increased 
irritability.  The vocal cords were inflamed, and non-specific 
changes in the vestibular apparatus and pale mucous membranes and 
skin were seen.  Blood pressure was said to be reduced. 

    Changes in the health status and laboratory tests were not 
observed in a group of 23 men who had been working for 3-5 years in 
an acrylonitrile plant, where, during the warm season, exposure 
levels reached 4.2-7.2 mg/m3 (Gincheva et al., 1977).  Stamova et 
al. (1976) studied workers' health in the related polyacrylic fibre 
plant in which acrylonitrile exposure levels ranged around 10 
mg/m3, but could fluctuate upwards to 25 mg/m3 .  Workers were also 
exposed to other chemical substances.  An increase was found in 
both skin diseases and various "neurasthenic" complaints and 
diseases. Dorodnova (1976) did not find any differences in the 
gynaecological health status of 410 women working in a polyacrylic 
fibre plant in Saratov compared with that of 436 unexposed women. 

8.1.2.2.  Haematology

    Compared with the findings in blood donors, some male and
female employees exposed to acrylonitrile at 2.5-5 mg/m3 showed 
a reduced haemoglobin level, erythrocyte count, leukocyte count, 
and percentage of neutrophiles, with an increased percentage of 
lymphocytes and plasma iron. Inhibition of maturation of 
normoblasts in bone marrow was also reported (Shustov, 1968).  
Similar results were reported by Zotova (1975b).  Lower 
erythrocyte, haemoglobin, and total white counts were found in 
laboratory workers exposed to acrylonitrile, and in apparatus 
operators and machinists. Higher than normal total glutathione 
levels were found in male operators and maintenance men and reduced 
glutathione levels in male apparatus operators.  Oxidized 
glutathione was elevated and total sulfhydryl groups decreased in 
workers employed in all these occupations. 

    Lower erythrocyte counts and a relative lymphocytosis were also 
observed by Babanov et al. (1959) in the study mentioned above. 

8.1.2.3.  Other organs

(a)  Liver

    Sakurai & Kusumoto (1972) (section 8.1.2.1) reported some 
abnormal results in liver function tests; however, in a further 
study of 102 workers from some of the factories, Sakurai et al. 
(1978) did not find any significant liver function test 
abnormalities related to acrylonitrile exposure, when exposure 
levels had decreased from 11-44 mg/m3 (5-20 ppm) to 9 mg/m3 (4.2 
ppm).  Increased serum cholinesterase activity, hyperbilirubinaemia, 
decreased coloidal stability, and hypergammaglobulinaemia were 
described in workers exposed to acrylonitrile concentrations of up 
to 5 mg/m3 and to acrylonitrile-polymer dust of up to 1.5 mg/m3 
(Enikeeva et al., 1976).  These effects have not been reported 
elsewhere. 

(b)  Eye

    Blepharoconjunctivitis was reported by Delivanova et al. (1978) 
in all of 302 workers examined over a 2-year period; 42 had severe 
alterations caused by conjunctivitis, and all disorders were 
connected with exposure to acrylonitrile. 

(c)  Gastro-intestinal effects

    Symptoms of gastritis and colitis were observed in workers 
exposed to acrylonitrile concentrations of up to 5 mg/m3 (Enikeeva 
et al., 1976). 

(d)  Immune system

    Acrylonitrile has been found to have an immunodepressive 
effect.  The functional activity of T-lymphocytes was found to have 
decreased in workers exposed to acrylonitrile (Ivanov, private 
communication, 1983). 

8.1.2.4.  Nervous system

    Nausea, vomiting, headache, and vertigo (Wilson, 1944; Wilson 
et al., 1948; Zeller et al., 1969; Sakurai & Kusumoto, 1972; 
Zotova, 1975) indicate a possible effect of acrylonitrile on the 
nervous system.  Ageeva (1970) reported a significant decrease in 
an "epinephrine-like substance", and an increase in acetylcholine.  
Depression, lability of autonomic functions (lowered arterial 
pressure, labile pulse, diffuse dermographia, increased sweating, 
change in orthostatic reflex) were also observed in workers 
involved in acrylonitrile production. 

8.1.2.5.  Dermal effects

    Spassovski (1976) reported irritant and allergic dermatitis in 
acrylonitrile workers; dermatitis was also observed by Antonev & 
Rogailin (1970) and Stamova et al. (1976). 

8.2.  Mutagenicity

    Thiess & Fleig (1978) examined workers who had been exposed to 
acrylonitrile for 15.3 years and workers who had not been exposed.  
No differences were found in the incidence of chromosomal 
aberrations, including or excluding gaps, in the 100 metaphases 
examined for each person. 

8.3.  Carcinogenicity

    In a retrospective cohort epidemiological study of 1345 male 
workers with potential exposure to acrylonitrile from 1950-66, 
followed until 31 December, 1976, 25 cases  of cancer were found 
with 20.5 expected, based on company rates (O'Berg, 1980).  Of 
these, 8 were respiratory cancer cases, with 4.4 expected.  Twenty-
three cases occurred among workers first exposed during the start-
up period (1950-52) when exposures were higher; only 12.9 were 
expected (P = 0.01). 

    The standardized incidence ratio (SIR) was 179 for cancer among 
the operators and mechanics who had at least 6 months' exposure and 
began their assignments during start-up.  A "dose response" was 
shown with those with longer duration of employment, workers with 
estimated higher exposures having higher risk.  Latency was also 
demonstrated, with 17 of the 24 cases occurring 20 years after the 
onset of exposure among those with at least 6 months' employment, 
including 6 of the 8 lung cancer cases.  It should be pointed out 
that, using the National Cancer Institute's expected incidence 
rates for 1969-71, the expected rate would be 25.5 rather than 20.5 
from the company rates.  In a concomitant cancer mortality study, 
20 cancer deaths were found with 17.4 expected, using company rates 
(not significant); the expected rates exceeded the company rates 
using national, state, or regional cancer rates.  The author felt 
that it might be premature to evaluate mortality statistics, 
because of insufficient latency (many cancer cases had been 
recently diagnosed and were still living).  Smoking habits were not 
considered, though the author stated that 7 out of the 8 lung 
cancer cases were known to have smoked. 

    A follow-up study on the mortality rate among 327 employees of 
a chemical rubber plant in the USA revealed that the number of 
deaths from lung cancer was significantly higher than expected (9 
versus 5.9 for US white males and 4.7 for other rubber workers from 
the same city).  The greatest excess was seen among men who had 
worked for 5-14 years and who had started working there at least 15 
years before death (Delzell & Monson, 1982).  This study was 
confounded by the multiple exposure of workers in the nitrile 
rubber manufacturing plant. 

    Kiesselbach et al. (1979) examined the mortality rate, the 
cancer rate, and the type of cancer against the period of exposure 
to acrylonitrile in 884 workers.  The results revealed that the 
general mortality of the exposed group was markedly lower than that 
of the normal population (58 versus an expected 104), possibly 
because of the "healthy worker" effect.  The mortality rate for 
malignant tumours, cardiovascular, brain, respiratory, and gastro-
intestinal diseases, suicide, and other causes was the same as in 
the normal population.  No relationship was found between length of 
exposure and mortality from tumours. 

    An excess of deaths from lung cancer was reported in 
acrylonitrile workers by Thiess et al. (1980).  In addition, 2 
cases of Hodgkin's disease contributed to a slight excess of cancer 
of the lymphatic tissue.  However, exposure to other substances, 
some of them known carcinogens, made interpretation of the results 
difficult. 

    A cohort study on men potentially exposed to acrylonitrile 
during the start-up of a plant indicated that there was no excess 
mortality from lung cancer.  There were no deaths from lung cancer 
in maintenance workers, who possibly had the highest exposures.  
There was an excess of kidney cancers (based on 2 cases only) and 
of circulatory disease other than rheumatic and atherosclerotic 
(based on 5 cases), accompanied by a deficit of atherosclerotic 
heart disease. 

    Because the cohort was small with only 4 cancer deaths 
observed, it could not give an indication of excess cancer risk or 
association with duration of exposure to acrylonitrile.  An 
additional retrospective cohort mortality study, in two 
acrylonitrile plants in the USA, on 352 males exposed for 6 months 
or more prior to 1968 and followed up until December 1977, did not 
show any excess mortality including cancer mortality.  There were 
15 deaths from all causes, 18.11 being expected, and 3 deaths from 
cancer (2.8 expected) (Zack, unpublished data, 1980).a 

    In a study by Nakamura (1981), 9525 workers employed in the 
production of acrylonitrile, acrylonitrile rubbers, and ABS were 
studied.  Deaths due to cancers in general and to lung and colon 
cancers in particular, were not increased, while 7 deaths due to 
liver, gall bladder, or cystic duct cancer were found against the 5 
that might have been expected. 

    The mortality of 1111 men who worked on the polymerization of 
acrylonitrile and the spinning of acrylic fibre in the United 
Kingdom from 1950 to 1968 was surveyed up to the end of 1978.  
Seventy-nine deaths were identified in 6 factories. The total 
number of deaths among men exposed to acrylonitrile for at least 
one year was slightly lower than expected (68 versus 72.4) and a 
relative excess of deaths from all cancers was found, arising 
mainly from cancers of the lung, stomach, colon and brain, 
pancreas, testis, and bladder (21 versus 13 expected).  The authors 
considered particularly relevant, the excess of lung cancer in 
those aged 15-44 years. Nevertheless, the authors considered that 
their results were inconclusive and urged continued surveillance 
and analysis of the exposed population in the United Kingdom 
(Werner & Carter, 1981). 

    The epidemiological studies provide some indications that 
acrylonitrile exposure is associated with cancer, particularly of 
the lung.  However, the studies reported, while neither conclusive 
nor contradictory, are limited by insufficient latency.  Other  
difficulties, such as cohort identification and selection, and 
combined exposures have made interpretation difficult.  Further 
epidemiological data are therefore of great importance, and 
consideration of smoking and single exposures to acrylonitrile is 
desirable. 

8.4.  Simultaneous Exposure to Acrylonitrile and 
Other Chemicals

8.4.1.  Acute toxicity

    Numerous non-fatal and fatal cases of poisoning by 
acrylonitrile-containing mixtures have been described (Davis et 
al., 1973).  In home fumigation, an acrylonitrile mixture with 
carbon tetrachloride or methylene chloride is placed in shallow 
open pans and the vapours dispersed by fans for 24-72 h, the 
operator deciding when the house is safe for occupancy (Davis et 
al., 1973).  A man working in the polymerization of acrylonitrile, 
polybutadiene, and styrene for 2 years complained of numbness of 
the fingers and toes, severe fatigue in the lower extremities, and 

----------------------------------------------------------------------
a   Zack, J.A.  (1980)  The mortality experience of Monsanto
     workers exposed to acrylonitrile (Monsanto Internal
    Report).

general malaise. Decreased patellar and achilles tendon reflexes, 
and hypoaesthesia in the peripheral parts of the fingers and toes 
were observed.  Free acrylonitrile was detected in the urine. The 
exposure level of acrylonitrile was estimated to exceed 108.5 mg/m3 
(50 ppm) (Seki, 1967). 

    Lachrymation, burning in the throat, coughing, sneezing, 
nausea, vomiting, dizziness, visual disturbance, headache, coma, 
seizures, and dermatitis have been described in non-fatal cases 
(Davis et al., 1973).  Fatalities have occurred following exposure 
to vapours (Grunske, 1949; Davis et al., 1973) and liquid (Lorz, 
1950).  Cyanide was detected in the blood in some cases.  Symptoms 
and signs prior to death varied from case to case; sore throat, 
weakness, dizziness, vomiting, eye irritation, respiratory 
disorders, pallor, tachycardia, tremors, unconsciousness, and 
epidermal necrolysis have been described.  Other pathological 
conditions occurred, but many could have been the result of pre-
existing disease or of exposure to the other component(s) of the 
mixture.  Findings in children suggest that they may be more 
sensitive to acrylonitrile exposure than adults (Grunske, 1949). 

8.4.2.  Chronic toxicity

    Abnormalities in subjects exposed simultaneously to 
acrylonitrile and several other chemicals have been described in 
several studies.  As the concentrations of the other chemicals were 
frequently higher than those of acrylonitrile, it is difficult to 
decide whether the abnormalities were caused by acrylonitrile, the 
other chemical(s), or a combination of the two. 

    An abnormally high proportion of workers exposed to 
acrylonitrile levels of 3-20 mg/m3, 33 ppm NH3, up to 1 mg 
H2SO4/m3, 0.41-0.67 mg NaOH/m3, and 2-10 mg acetic acid/m3 were 
described as suffering from a variety of symptoms ascribed to 
disorders of the autonomic nervous system ("neurasthenic syndrome") 
(e.g., irritability, headache, poor appetite, fatigue).  Intolerance 
to alcohol has also been observed (Orusev & Popovski, 1973; Orusev 
et al., 1973). 

    Apprentices exposed to acrylonitrile (0.8-1.8 mg/m3), methyl 
methacrylate (16-17 mg/m3), and sodium thiosulfate were examined 
before exposure, after 1-2 weeks, and after a further unspecified 
time.  "Neurasthenic" symptoms were rare before, but frequent after 
exposure, and the incidence of immunological reactivity against the 
chemicals increased, as did the concentration of ceruloplasmin 
(Mavrina & Il'ina, 1974).  Dermal tests for allergy were also made 
by Hromov (1974) in workers who had been in contact with 
acrylonitrile, methyl acrylate, and sodium thiocyanate.  Intradermal 
samples showed positive haemoagglutination reactions in 86.5% of 
workers exposed to acrylonitrile, 76.1% exposed to methyl acrylate, 
and 53.6% exposed to sodium thiocyanate. Dermatitis, eczema, and 
urticaria occurred. 

    Mavrina & Hromov (1974) and Shustov & Mavrina (1975) reported 
abnormalities of the liver, nervous, cardiovascular, and 
gastrointestinal systems in workers occupationally exposed to 
acrylonitrile, methyl acrylate, and sodium thiocyanate during fibre 
production.  In particular, symptoms associated with the activity 
of the autonomic nervous system were noted among the 340 workers 
examined.  Dryness, desquamation, fissures, and diffuse erythema of 
the skin were also apparent.  Women exposed to acrylonitrile and 
methyl acrylate (Chobot, 1979) were said to suffer from 
disturbances in menstrual function twice as frequently as a control 
group.  A low incidence of irritant and allergic dermatitis and 
vitiligo was noted in workers exposed to acrylonitrile, methyl 
acrylate, and dimethylformamide in fibre production (Bainova, 
1975).  In 11 out of 28 workers, delayed skin sensitization and 
allergic dermatitis were observed with dimethylformamide. 

    Ostrovskaja et al. (1976) observed workers exposed to 
acrylonitrile, acetonitrile, and hydrocyanic acid during training 
and after 1.5 years and 3 years.  In 190 men and women, aged 20 - 
30 years, many signs and symptoms were noted including modified 
reflexes, changes in blood pressure, ECG, and EEG.  However, it is 
difficult to attribute the findings of these authors solely to 
acrylonitrile exposure. 

9.  EVALUATION OF HEALTH RISKS TO MAN FROM EXPOSURE TO ACRYLONITRILE

9.1.  Sources and Levels of Exposure

    Acrylonitrile is a colourless, volatile, chemically reactive 
liquid; it does not occur as a natural product.  The monomer is 
used world-wide, on a large scale, in the manufacture of polymers, 
fibres, and rubbers and as a chemical intermediate.  Acrylonitrile-
containing polymers have been used in the manufacture of products 
that come into contact with food; the amounts of acrylonitrile that 
migrate into foods can be reduced to negligible quantities by the 
use of good manufacturing practices in the production of the 
polymers. 

    The major sources of contamination of the general environment 
are acrylonitrile-producing and -polymerizing plants.  The 
occurrence of acrylonitrile in air, water, and soil near industrial 
plants has been described.  There is evidence that acrylonitrile 
has persisted in soil for long periods following accidental 
spillage; subsequent contamination of ground water has been 
demonstrated. 

    The highest exposures occur in the workplace.  Experience shows 
that containment of such exposures can more readily be achieved in 
production plants than in those in which acrylonitrile is used to 
make other products.  In a number of countries, exposure limits or 
recommended limit values for the workplace have been arrived at; 
values recently set have tended to be lower than in the past (Table 
12). 

    Accidental exposure to acrylonitrile liquid and vapour may 
occur during the various stages of production, transport, and use. 

9.2.  Acrylonitrile Toxicity

    Inhaled acrylonitrile vapour is readily absorbed.  Acute 
systemic effects following absorption of vapour have been 
described.  Symptoms were non-specific and referable to the 
gastrointestinal and respiratory tracts, the liver, and the central 
nervous system.  No acute adverse effects have been reported 
following daily exposure (8-h) to up to 45 mg/m3.a  At higher 
concentrations rising to 220 mg/m3, 20-40 min exposure resulted  
in complaints of headache, irritation of the upper respiratory 
tract and the eyes, nervous irritability, and itching of the skin.  
Fatalities have been reported following the use of fumigant 
mixtures containing acrylonitrile together with carbon 
tetrachloride and methylene chloride.  Exact exposure conditions 
are not known, but animal data suggest that inhalation exposure to 
acrylonitrile at 500-2000 mg/m3 for 1/2-3 h could be fatal. 
Simultaneous exposure to some organic solvents may enhance the 
toxicity of acrylonitrile. 

---------------------------------------------------------------------------
a This value was for many years the occupational exposure limit 
  in many countries where acrylonitrile was manufactured.

Table 12.  Occupational exposure limits for selected countries
---------------------------------------------------------------
Country                TWA mg/m3  STEL mg/m3  Reference
---------------------------------------------------------------
France                 9          34***       INRS (1983)

Germany, Federal       -* (S)                DFG (1982)
Republic of

Hungary                0.5        0.5         Hungary (1979)

Japan                  45         -           Japan Association
                                              of Industrial
                                              Health (1972)

Poland                                        Poland (1982)

Sweden                 4** (S)   13          Sweden (1981)

United Kingdom

USA                    4.5** (S)             ACGIH (1982)

USSR                              0.5 (S)    USSR (1982)
---------------------------------------------------------------
*  Proved animal carcinogen, strongly suspected of also being
   carcinogenic for human beings.  No safe concentration can be 
   listed. 

TWA =  Time-weighted average.
STEL =  Short-term exposure limit.
**  Listed as Industrial Substance Suspect of Carcinogenic 
    Potential for Man.
***  Alarm level.
S =  Skin uptake can contribute to overall exposure.

    Liquid acrylonitrile is also absorbed through the skin, 
reportedly giving rise to non-specific symptoms similar to those 
that follow acrylonitrile vapour inhalation.  Local injury can 
occur a few hours after exposure to liquid acrylonitrile.  One 
fatality has been reported.  It is also an irritant to the eye. 

    Skin absorption of vapour does not appear to contribute 
significantly to overall acrylonitrile uptake in the workplace. 

    There are no indications that acrylonitrile accumulates in the 
body following prolonged exposure to levels found in the workplace. 

    Skin sensitization has been reported in a few cases; however, 
no evidence is available to suggest the occurrence of pulmonary 
allergic reactions. 

    Acrylonitrile has been shown to induce embryotoxic and 
teratogenic effects at high dosage levels in experimental animals. 

    Although acrylonitrile is metabolized partly to cyanide, it has 
been demonstrated that the acute toxic actions of acrylonitrile are 
not solely due to cyanide, as was once believed. 

    Acrylonitrile has been shown to be mutagenic in some  in vitro 
systems in the presence of metabolic activation systems.  So far, 
mutagenic activity has not been demonstrated in  in vivo assay 
systems. 

    Complaints of ill health in workers exposed for a number of 
years to acrylonitrile concentrations of less than 45 mg/m3 have 
been reported in several studies.  The complaints were variable in 
nature and no consistent correlation with the extent of exposure 
appears to have been established.  The studies do not provide 
evidence of a specific disease arising from long-term, low-level 
exposure. 

    Several long-term studies in which acrylonitrile was 
administered to rats orally and by inhalation demonstrated the 
induction of malignant tumours.  Data available in summary form 
suggest that the incidence was dose-related.  Eight epidemiological 
studies have been carried out on workers exposed to acrylonitrile.  
These studies have not demonstrated conclusively that there is a 
correlation between exposure to acrylonitrile and the incidence of 
cancer in man. Nevertheless, the findings are not incompatible with 
the supposition that acrylonitrile is a potential human carcinogen 
and thus give no cause for disregarding the evidence that has been 
provided by animal studies. 

    It is not possible to establish a level below which no adverse 
effects occur on the basis of the experimental and epidemiological 
data presented in this document.  However, it is evident that 
exposure to acrylonitrile should be kept as low as possible in both 
the workplace and the general environment, and that skin contact 
with the liquid should be avoided. 

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ZITTING, A., TENHUNEN, R., & SAVOLAINEN, H.  (1981) Effects
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    See Also:
       Toxicological Abbreviations
       Acrylonitrile (HSG 1, 1986)
       Acrylonitrile (ICSC)
       Acrylonitrile (WHO Food Additives Series 19)
       ACRYLONITRILE (JECFA Evaluation)
       Acrylonitrile (FAO Meeting Report PL/1965/10/2)
       Acrylonitrile (CICADS 39, 2002)
       Acrylonitrile (IARC Summary & Evaluation, Volume 71, 1999)