INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 49
ACRYLAMIDE
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, 1985
The International Programme on Chemical Safety (IPCS) is a
joint venture of the United Nations Environment Programme, the
International Labour Organisation, and the World Health
Organization. The main objective of the IPCS is to carry out and
disseminate evaluations of the effects of chemicals on human health
and the quality of the environment. Supporting activities include
the development of epidemiological, experimental laboratory, and
risk-assessment methods that could produce internationally
comparable results, and the development of manpower in the field of
toxicology. Other activities carried out by the IPCS include the
development of know-how for coping with chemical accidents,
coordination of laboratory testing and epidemiological studies, and
promotion of research on the mechanisms of the biological action of
chemicals.
ISBN 92 4 154189 X
The World Health Organization welcomes requests for permission
to reproduce or translate its publications, in part or in full.
Applications and enquiries should be addressed to the Office of
Publications, World Health Organization, Geneva, Switzerland, which
will be glad to provide the latest information on any changes made
to the text, plans for new editions, and reprints and translations
already available.
(c) World Health Organization 1985
Publications of the World Health Organization enjoy copyright
protection in accordance with the provisions of Protocol 2 of the
Universal Copyright Convention. All rights reserved.
The designations employed and the presentation of the material
in this publication do not imply the expression of any opinion
whatsoever on the part of the Secretariat of the World Health
Organization concerning the legal status of any country, territory,
city or area or of its authorities, or concerning the delimitation
of its frontiers or boundaries.
The mention of specific companies or of certain manufacturers'
products does not imply that they are endorsed or recommended by the
World Health Organization in preference to others of a similar
nature that are not mentioned. Errors and omissions excepted, the
names of proprietary products are distinguished by initial capital
letters.
CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR ACRYLAMIDE
1. SUMMARY AND RECOMMENDATIONS FOR FURTHER RESEARCH
1.1. Summary
1.1.1. Properties, uses, and analytical methods
1.1.2. Environmental sources and environmental
transport and distribution
1.1.3. Environmental levels and exposures
1.1.4. Metabolism of acrylamide
1.1.5. Effects on man and animals
1.1.6. Mutagenicity and carcinogenicity
1.1.7. Teratogenicity and reproduction
1.1.8. Dose-effect and dose-response relationships
1.1.9. Evaluation of health risks for man
1.2. Recommendations for further research
1.2.1. Analysis
1.2.2. Exposure
1.2.3. Metabolism and indicators of exposure
1.2.4. Effects
2. PROPERTIES AND ANALYTICAL METHODS
2.1. Identity
2.2. Chemical and physical properties
2.3. Sampling and analytical methods
3. SOURCES IN THE ENVIRONMENT
3.1. Production levels, processes, and uses
3.1.1. World production
3.1.2. Production processes
3.1.3. Uses
3.2. Release into the environment
3.3. Disposal of wastes
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
4.1. Transport in the environment
4.2. Biomagnification and bioconcentration
4.3. Transformation
5. ENVIRONMENTAL LEVELS AND EXPOSURES
5.1. Environmental levels
5.1.1. Ambient air and soil
5.1.2. Water
5.1.3. Food
5.2. General population exposure
5.3. Occupational exposure
6. KINETICS AND METABOLISM
6.1. Experimental animal studies
6.1.1. Absorption and distribution
6.1.2. Metabolism
6.1.3. Elimination and excretion
6.1.3.1 Elimination
6.1.3.2 Excretion
6.2. Human studies
7. EFFECTS ON ANIMALS
7.1. Neurological effects
7.1.1. Neurobehavioural effects
7.1.2. Electrophysiological effects
7.1.2.1 Peripheral effects
7.1.2.2 Central nervous system effects
7.1.3. Morphological effects
7.1.4. Biochemical effects
7.1.4.1 Effects on axonal transport
7.1.4.2 Effects on energy production
and neuronal metabolism
7.1.4.3 Effects on CNS neurochemistry
7.2. In vitro toxicity studies
7.3. Effects on other organs
7.4. Genotoxic effects and carcinogenicity studies
7.4.1. Mutagenicity and other related short-term tests
7.4.2. Carcinogenicity studies
7.5. Teratogenicity and reproductive studies
7.6. Factors modifying effects
7.6.1. Chemical modification of acrylamide toxicity
7.6.2. Age
7.6.3. Sex differences
7.6.4. Species
7.7. Dose-response and dose-effect relationships
7.7.1. Dose-response relationships
7.7.2. Dose-effect relationships
7.7.2.1 Manifestations of neuropathy
7.7.2.2 Electrophysiological effects
7.7.2.3 Morphological effects
7.7.2.4 Effects on axonal transport
7.7.2.5 Neurobehavioural effects
8. EFFECTS ON MAN
8.1. Clinical studies and case reports
8.2. Epidemiological studies
8.3. Dose-effect and dose-response relationships
9. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
9.1. Aquatic organisms
9.1.1. Invertebrates
9.1.2. Fish and amphibia
9.2. Terrestrial plants
9.3. Microorganisms
10. STRUCTURE-NEUROTOXICITY RELATIONSHIPS
11. EVALUATION OF HEALTH RISKS FOR MAN AND EFFECTS
ON THE ENVIRONMENT FROM EXPOSURE TO ACRYLAMIDE
11.1. General considerations
11.2. Assessment of exposure
11.3. Assessment of adverse effects
11.4. Exposure of the environment
11.5. Occupational exposure
REFERENCES
WHO TASK GROUP ON ACRYLAMIDE
Members
Dr N. Aldridge, Medical Research Council, Carshalton, Surrey,
United Kingdom (Chairman)
Dr M. Berlin, Monitoring and Assessment Research Centre,
University of London, London, United Kingdom
Prof J. Cavanagh, Institute of Neurology, London, United
Kingdom
Dr K. Hashimoto, Department of Hygiene, School of Medicine,
Kanazawa University, Ishikawa, Japan (Vice-Chairman)
Dr D.G. Hatton, US Food and Drug Administration, Department of
Health and Human Services (Rapporteur)
Prof M. Ikeda, Department of Environmental Health, Tohoku
University School of Medicine, Sendai, Japan
Dr P. Le Quesne, National Hospital for Nervous Diseases,
London, United Kingdom
Prof A. Massoud, Ain Shams University, Cairo, Egypt
Dr P.K. Ray, Industrial Toxicology Research Centre, Lucknow,
India
Prof I.V. Sanotsky, Research Institute of Industrial Hygiene
and Occupational Diseases, USSR Academy of Medical
Sciences, Moscow, USSR
Dr H.A. Tilson, Laboratory of Behavioral and Neurological
Toxicology, NIEHS, Research Triangle Park, North Carolina,
USA
Representatives from Other Organizations
Mr S. Batt, Monitoring and Assessment Research Centre,
University of London, London, United Kingdom
Dr L. Shukar, Monitoring and Assessment Research Centre,
University of London, London, United Kingdom
Mr J.D. Wilbourn, International Agency for Research on Cancer,
Unit of Carcinogen Identification and Evaluation, Lyons,
France
WHO Secretariat
Dr M. Draper, International Programme on Chemical Safety,
World Health Organization, Geneva, Switzerland
Dr E.M.B. Smith, International Programme on Chemical Safety,
World Health Organization, Geneva, Switzerland (Secretary)
Ms A. Sunden, International Register of Potentiallly Toxic
Chemicals, Geneva, Switzerland
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)
ENVIRONMENTAL HEALTH CRITERIA FOR ACRYLAMIDE
Following the recommendations of the United Nations
Conference on the Human Environment held in Stockholm in 1972,
and in response to a number of World Health Assembly resolutions
(WHA23.60, WHA24.47, WHA25.58, WHA26.68), and the recommendation
of the Governing Council of the United Nations Environment
Programme, (UNEP/GC/10, 3 July 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.
A WHO Task Group on Environmental Health Criteria for
Acrylamide was held at the British Industries Biological Research
Association (BIBRA), Carshalton, Surrey, United Kingdom, from
3-5 December, 1984. Dr E.M.B. Smith opened the meeting on behalf
of the Director-General. The Task Group reviewed and revised the
draft criteria document and made an evaluation of the health risks
of exposure to acrylamide.
The initial draft was prepared by DR M. BERLIN with the
assistance of DR L. SHUKAR and MR S. BATT of the MONITORING AND
ASSESSMENT RESEARCH CENTRE (MARC) London, United Kingdom.
The efforts of all who helped in the preparation and
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. The UK Department of Health
and Social Security generously supported the cost of printing.
1. SUMMARY AND RECOMMENDATIONS FOR FURTHER RESEARCH
1.1. Summary
1.1.1. Properties, uses, and analytical methods
Acrylamide is a white crystalline solid produced from
acrylonitrile, which is present as a residue in technical grades
of acrylamide at concentrations ranging from 1 to 100 mg/kg.
Acrylamide readily undergoes polymerization, resulting in a
highly cross-linked insoluble gel of polyacrylamide. Commercial
polyacrylamide contains 0.05 - 5.0% acrylamide. Hydroquinone
monomethylether, t-butylpyrocatechol, N-phenyl-2-naphthylamine,
and copper (ion) may be used as stabilizers.
Acrylamide is mainly used in the production of polymers and
copolymers for various purposes. Polyacrylamides are useful as
flocculents in the treatment of waste water and the purification
of drinking-water. Acrylamide is also used as a grouting agent
and in the construction of dam foundations and tunnels.
Methods for the determination of acrylamide in polymers, air,
water, and biological materials have been devised using gas
chromatography, high-performance liquid chromatography, and
differential pulse polarography. No method has so far been
described for the determination of either acrylamide bound to
blood and tissue proteins or its metabolites in the urine.
The reported sensitivity for the determination of acrylamide
in air, using gas chromatography, is 5 µg/m3 and, using electron
capture and flame ionization detection, 30 µg/m3. Sampling of
acrylamide (vapour and dust) in air is performed using midget
impingers. Determination of acrylamide in polyacrylamide can be
accomplished, with a sensitivity of less than 1 mg/kg, using
differential pulse polarography. The detection limit for
acrylamide in water is 0.1 µg/litre, using electron capture gas
chromatography after derivatization, though the recovery of
acrylamide is rather poor. Derivatization followed by high-
performance liquid chromatography is less sensitive (0.2 µg/litre),
but is more suitable for the routine analysis of both natural and
polluted water. Free acrylamide in biological samples such as
plasma and tissue homogenates can be determined, by electron
capture-gas chromatography, with a detection limit of 10
µg/litre.
1.1.2. Environmental sources and environmental transport and
distribution
All acrylamide in the environment is man-made, the main
source being the release of the monomer residues from
polyacrylamide used in water treatment or in industry. The most
important environmental contamination results from the use of
acrylamide in soil grouting, because of contamination of ground
water. Chemical decontamination of acrylamide-containing liquid
wastes and solids is possible, but the costs, in most instances,
are high.
Because it is highly soluble in water, acrylamide is
extremely mobile in the aqueous environment and is readily
leachable in soil. It is unlikely to enter and be transported in
the atmosphere to any significant extent, because of its low
vapour pressure. Biodegradation is likely to occur.
A wide variety of microbes possess the ability to degrade
acrylamide. However, there is a latent period of several days
before there is any significant degradation. The residence
period for acrylamide may be of the order of days, weeks, or
months, in rivers and coastal areas of low microbial activity.
The half-life in aerobic soil, which is of the order of several
days at 20 °C, increases with decreasing temperature.
Acrylamide is unlikely to be removed during sewage treatment
and has been shown to pass through waterworks mainly unchanged.
1.1.3. Environmental levels and exposures
Because polyacrylamide is used in water treatment, residues
of acrylamide may be found in potable water. In most countries,
such residues are limited to 0.25 µg/litre by maintaining the
concentration of acrylamide monomer in the polyacrylamide used
for water treatment at 0.05%. Concentrations of acrylamide in
effluents from polyacrylamide-using factories generally range
from less than 1 to 50 µg/litre. However, 1.5 mg
acrylamide/litre has been measured downstream from industrial
effluent discharges. Levels reported in receiving streams and
rivers are variable and dependent on the extent of dilution. A
level of 0.3 µg/litre was detected at a waterworks intake
downstream from an effluent discharge from a clay pit. In the
vicinity of local grouting operations, high levels of acrylamide
may be found in wells and ground water; a concentration of 400
mg/litre was reported in one such well.
Monitoring of acrylamide concentrations in air and soil close
to 6 acrylamide-producing plants in the USA failed to demonstrate
any acrylamide in the air (detection limit 0.1 µg/m3) or in the
soil (detection limit 0.02 mg/kg).
Polyacrylamides are also used in the washing and packaging of
prepacked foods and vegetables. The US Food and Drug
Administration has limited the amount of monomer in
polyacrylamide for use in paper or cardboard in contact with food
to 0.2% (2 g/kg). In the Federal Republic of Germany, the level
of polyacrylamide used in foodstuff packaging is limited to 0.3%
(3 g/kg) and the level of residual acrylamide monomer to 0.2%
(2 g/kg)a.
-------------------------------------------------------------------
a Bundesministerium für Jugend, Familie und Gesundheit,
personal communication, 1984.
Occupational exposure to acrylamide occurs mainly through
skin absorption and inhalation in acrylamide-producing plants.
Personal sampling in such plants has shown average levels in
workplace air of about 0.6 mg/m3, with a range of 0.1 - 3.6 mg/m3
in heavily-exposed areas. Measurements resulting from stationary
sampling were generally 2 - 3 times lower. This indicates the
importance of taking work procedures into account in the
assessment of exposure. Published figures from the USA indicate
that about 20 000 workers may be exposed to acrylamide. Although
exposure levels have not been reported for grouters, the
potential for hazard from this use is probably greater than from
other uses, because of the uncontrolled nature of the exposure.
1.1.4. Metabolism of acrylamide
Acrylamide is readily absorbed by ingestion, inhalation, and
through the skin. Absorbed acrylamide is distributed in body
water compartments and passes through the placental barrier. In
rats, biotransformation of acrylamide occurs through glutathione
conjugation and through decarboxylation. At least 4 urinary
metabolites have been found in rat urine, of which mercapturic
acid and cysteine- S-propionamide have been identified.
Acrylamide and its metabolites are accumulated (protein-bound) in
both nervous system tissue and blood (bound to haemoglobin).
Accumulation in the liver and kidney as well as the male
reproductive system has also been demonstrated. The results of
animal studies indicate that acrylamide is largely excreted as
metabolites in urine and bile. Because of the enterohepatic
circulation of biliary metabolites, faecal excretion is minimal.
Two-thirds of the absorbed dose is excreted with a half-life of a
few hours. However, protein-bound acrylamide or acrylamide
metabolites in the blood, and possibly in the central nervous
system, have a half-life of about 10 days. The net elimination
in urine of acrylamide metabolites is constant in the rat and is
independent of dose within the range 1 - 200 mg/kg body weight.
Acrylamide has been identified in rat milk during lactation.
There are no data indicating any major differences in acrylamide
metabolism between man and other mammals.
1.1.5. Effects on man and animals
Acrylamide is toxic and an irritant. Cases of acrylamide
poisoning show signs and symptoms of local effects due to
irritation of the skin and mucous membranes and systemic effects
due to the involvement of the central, peripheral, and autonomic
nervous systems. Local irritation of the skin or mucous
membranes is characterized by blistering and desquamation of the
skin of the hands (palms) and feet (soles) combined with blueness
of the hands and feet. Effects on the central nervous system are
characterized by abnormal fatigue, sleepiness, memory
difficulties, and dizziness. With severe poisoning, confusion,
disorientation, and hallucinations occur. Truncal ataxia is a
characteristic feature, sometimes combined with nystagmus and
slurred speech. Excessive sweating in the limb extremities is a
common observation.
Signs of central nervous system and local skin involvement
may precede peripheral neuropathy by as much as several weeks.
Peripheral neuropathy can involve loss of tendon reflexes,
impairment of vibration sense, loss of other sensation, and
muscular wasting in peripheral parts of the extremities. Nerve
biopsy shows loss of large diameter nerve fibres as well as
regenerating fibres. Autonomic nervous system involvement is
indicated by excessive sweating, peripheral vasodilation, and
difficulties in micturition and defaecation. After cessation of
exposure to acrylamide, most cases recover, although the course
of improvement is prolonged and can extend over months to years.
In animal studies, early changes in visual-evoked potentials
(VEP), preceding clinical signs, as well as changes in
somatosensory-evoked potentials (SEP), have been seen.
Morphological studies have revealed degenerative changes
principally in peripheral nerve axons, with less severe changes
in the longer fibres of the central nervous system. Degeneration
of Purkinje cells has been observed in chronically-intoxicated
animals. The changes are most pronounced in the nerve endings of
myelinated sensory fibres. The nerve endings show enlarged
"boutons terminaux" and a widespread enlargement of nerve terminals
from the accumulation of neurofilaments. This occurs in both the
peripheral and central nervous systems. Impairment of retrograde
and, to a lesser degree, anterograde axonal transport has been
found in sensory fibres, and interference with glycolysis and
protein synthesis, the latter preceding the onset of clinical
signs, has been observed in biochemical studies. Studies of
neurotransmitter distribution and receptor binding in the brains of
rats have revealed changes induced by acrylamide. In rats, changes
in the concentration of neurotransmitters and in striatal dopamine
receptor binding have been related to behavioural changes.
Degenerative changes in renal convoluted tubular epithelium
and glomeruli and fatty degeneration and necrosis of the liver
have been seen in monkeys given large doses of acrylamide. In
rats, impairment of hepatic porphyrin metabolism has been
observed.
1.1.6. Mutagenicity and carcinogenicity
Acrylamide (> 99% pure) was not mutagenic in Salmonella
typhimurium in the presence or absence of a metabolic activation
system.
Acrylamide of unknown purity induced chromosomal aberrations
in the spermatocytes of male mice and was reported to increase
cell transformation frequency in Balb 3T3 cells, in the presence
of a metabolic activation system.
Acrylamide was shown to be an initiator for skin tumours in
mice when administered by various routes. It increased the
incidence of lung tumours in mice-screening assays.
A 2-year study on rats administered acrylamide in the
drinking-water has been conducted but has not been fully reported
or evaluated.
No epidemiological data on cancer due to exposure to
acrylamide are available and, from the available data, it is not
possible to form a conclusion concerning the carcinogenicity of
acrylamide.
1.1.7. Teratogenicity and reproduction
There is no evidence in either man or animals of any gross
teratogenic effects resulting from acrylamide exposure.
Absorption of acrylamide by the fetus has been demonstrated in
animal (pig, dog, rabbit, rat) studies. Oral administration of
acrylamide, between the 7 - 16th days of gestation in rats,
decreased the binding of dopamine receptors in the striatal
membranes in 2-week-old pups, a fact that may be explained by
postnatal exposure through lactation as well as prenatal effects.
Degeneration of seminiferous tubules, and chromosome aberrations
in spermatocytes have been seen in acrylamide-treated male mice.
Depressed plasma levels of testosterone and prolactin have also
been observed. However, fertility studies have not been
reported.
1.1.8. Dose-effect and dose-response relationships
A total of over 60 cases of acrylamide poisoning in man have
been reported in the literature. No human epidemiological
studies relating exposures to effects are available; the current
lack of methods for biological monitoring or assessing the extent
of exposure makes such studies impossible. From clinical
experience, it appears that acute exposure to high doses of
acrylamide induces signs and symptoms of effects on the central
nervous system, whereas peripheral neuropathy is a feature of
long-term cumulative exposure to smaller doses. Peripheral signs
of neuropathy appear after a latent period. This latent period
is dose-dependent and decreases with increasing dose. In animal
studies, the onset of peripheral neuropathy parallels the
accumulation of acrylamide bound to protein in the nervous system
and, similarly, acrylamide bound to haemoglobin in erythrocytes.
The LD50 was of the same order of magnitude for all mammals
studied.
A statistically-significant increase in the incidence of
mesothelioma of the scrotal cavity was observed in rats after
long-term (2-year) administration in the drinking-water of
acrylamide at 0.5 mg/kg body weight per day. There are no
reports of increases in any other types of tumour at this dose
level. However, administration over 2 years of 2 mg
acrylamide/kg body weight per day not only increased the
incidence of a variety of tumour types (both benign and
malignant) but also decreased the life expectancy in both male
and female rats. The smallest long-term dose of acrylamide
reported in one study to be associated with adverse neurological
effects in rats was 1 mg/kg body weight per day. This dose caused
morphological changes in the sciatic nerves.
1.1.9. Evaluation of health risks for man
There are insufficient epidemiological data regarding
occupational or environmental exposure to acrylamide to serve as
a basis for a quantitative risk evaluation. Experimental animal
data indicate that there are no major species differences among
mammals with respect to acrylamide metabolism or sensitivity to
its neurotoxic effects. Extrapolation from animal dose-effect
data suggests that an absorbed dose of 0.12 mg/kg body weight per
day (derived from total dose to surface area data) could cause
adverse neurological effects in man. As acrylamide is readily
absorbed through the skin and by inhalation and ingestion, these
effects are probably independent of the route of exposure.
Applying a safety factor of 10 to the extrapolated minimum dose
for neurological effects would indicate that an absorbed dose of
0.012 mg/kg body weight per day should not be exceeded. Animal
data are not sufficient to draw any conclusions concerning the
carcinogenicity of acrylamide. Acrylamide is associated with
adverse effects on testicular function in experimental animals.
No data regarding these effects in human beings are available.
Biological monitoring would be the method of choice in the
assessment of human exposure to acrylamide, particularly as skin
absorption is the major route of exposure. So far, no such
method has been devised, though results of experimental animal
studies indicate that the level of acrylamide bound to
erythrocytes in blood is a measure of the absorbed dose.
The most suitable method for the early assessment of adverse
effects in human beings exposed to acrylamide is the
electrophysiological examination of peripheral nerves, such as
measurements of both sensory and motor nerve action potential
amplitudes and electromyography (EMG). The sensitivity of this
method is strongly enhanced if pre-exposure baseline measurements
have been performed. Quantitative assessment of vibration
sensation offers considerable promise as a sensitive and easily
applicable method. The results of experimental animal studies
indicate that other electrophysiological procedures or parameters
such as sensory and visual evoked potentials may also be useful.
Exposure of the environment to acrylamide is mainly limited
to the contamination of water. Grouting operations may
contaminate drinking-water supplies. Special precautions must
therefore be taken to limit ground water contamination and, where
necessary, to prevent its use as drinking-water. Effluents from
industries producing or using polyacrylamide, communal sewage
plants, and from waterworks may also contaminate drinking-water
supplies, if they are taken from polluted water sources. The
current limit for the acrylamide content of drinking-water in
many countries is 0.25 µg/litre. The acrylamide content of
drinking-water can be maintained at an acceptable level by
limiting the amount of acrylamide monomer in the polyacrylamide
used for water treatment to 0.05%. Under exceptional conditions,
swimming in water close to industrial effluents containing
acrylamide may present a hazard.
Preventive measures, such as the enclosure of production
procedures and the wearing of protective clothing, should be used
to prevent occupationally-exposed workers absorbing more than
0.012 mg/kg body weight per day. The concentration in the
workroom air should not exceed 0.1 mg/m3. Ventilated face masks
may be used to prevent inhalation of acrylamide. It is possible
that underlying neurological disease and/or the administration of
neuroactive drugs might alter human sensitivity to acrylamide
but, in the absence of definite evidence that this has occurred,
no specific recommendations can be made.
1.2. Recommendations for Further Research
1.2.1. Analysis
A method for the determination of acrylamide, bound to
haemoglobin in red blood cells, should be devised to provide a
means for the biological monitoring of human exposure to
acrylamide. No methods for assessing the concentration of
acrylamide metabolites in urine are available; such analyses
would be useful for the assessment of recent exposure, and
methods should be devised.
1.2.2. Exposure
The development of biological monitoring methods would be
useful in the routine screening of occupationally-exposed
workers.
1.2.3. Metabolism and indicators of exposure
To evaluate fully the health effects and risks associated
with acrylamide exposure, it is important to elucidate the
mechanism of neurotoxicity. Both the proximal toxic agent and
the primary biochemical lesion need to be identified. Studies
should be carried out to investigate further the relationship
between the concentration of the toxic moiety in the central
nervous system and possible indicators of exposure, such as the
concentration of erythrocyte-bound acrylamide or metabolites in
the urine.
1.2.4. Effects
Further studies on animals are required to establish the no-
observed-adverse-effect levels for morphological changes in the
central nervous system and to assess the carcinogenic potential
of acrylamide.
Provided that methods for the biological monitoring of
acrylamide exposure can be devised, epidemiological studies
should be performed to relate exposure to both neurological
effects and to the incidence of cancer in acrylamide-exposed
workers. Electrophysiological methods, such as the measurement
of visual and sensory-evoked potentials, that have proved to be
useful in experimental animal studies, should be evaluated in
human studies. More experience is needed in assessing the
sensitivity and value of quantitative sensory testing. Further
studies should be performed to design suitable procedures for the
health monitoring of an occupationally-exposed population.
Further animal studies are needed on the effects of acrylamide on
the developing nervous system and the process of ageing.
2. PROPERTIES AND ANALYTICAL METHODS
2.1. Identity
Chemical structure: H H O H
| | || |
C = C - C - N
| |
H H
Chemical formula: C3H5NO
Synonyms: acrylic amide, akrylamide, propen-
amide, propenoic acid amide
CAS registry number: 79-06-1
RTECS registry number: AS 3325000
Relative molecular mass: 71.08
2.2. Chemical and Physical Properties
Acrylamide is a white, odourless, crystalline solid that is
highly soluble in water and reacts through its amide group or
double bond. Reactions of the amide group include hydrolysis,
dehydration, and alcoholysis. The Diels-Alder reaction,
polymerization, and the addition of nucleophilic reactants across
the conjugated ethylenic bond are characteristic reactions. The
chemical is stable in solution at room temperature and does not
polymerize spontaneously. Commercial solutions of the monomer may
be stabilized with hydroquinone, t-butylpyrocatechol, N-phenyl-2-
naphthylamine, or other antioxidants (Windholz et al., 1976). In
addition to carbamoylethylation and hydrolysis to acrylic acid,
acrylamide readily undergoes polymerization and copolymerization
resulting in a highly cross-linked insoluble gel. The physical
properties of acrylamide are summarized in Table 1.
Polyacrylamide is a white, odourless solid, soluble in water,
insoluble in solvents such as methanol, ethanol, and hexane, and
at least 1% soluble in glycerol, ethyl acetate, glacial acetic
acid, and lactic acid. The polymer is safe in relation to both
fire and explosion (Bikales, 1973). Levels of residual
acrylamide monomer in polyacrylamide range from 0.05 to 5%,
depending on the intended use of the product (Croll et al.,
1974).
The level of residual acrylonitrile monomer in polyacrylamide
has been estimated to be approximately 1 mg/kg (1 ppm). In
addition to polyacrylamide, N-hydroxymethylacrylamide and
N,N'-methylenebisacrylamide are produced commercially from
acrylamide. The levels of residual acrylamide in these products
are not known.
Table 1. Physical properties of acrylamide
-------------------------------------------------------------
Appearance white crystals
Relative molecular mass 71.08
Melting point 84.5 ± 0.3 °C
Vapour pressure 0.009 kPa at 25 °C
0.004 kPa at 40 °C
0.09 kPa at 50 °C
Boiling point 87 °C at 0.267 kPa
103 °C at 0.667 kPa
125 °C at 3.33 kPa
Heat of polymerization 19.8 Kcal/mole
Density 1.122 g/cm at 30 °C
Solubility in g/litre acetone 631
solvent at 30 °C benzene 3.46
chloroform 26.6
ethanol 862
ethylacetate 126
n-heptane 0.068
methanol 155
water 2155
Conversion factor
1 ppm acrylamide in air = 5 mg/m3
-------------------------------------------------------------
Adapted from: Bikales (1973).
2.3. Sampling and Analytical Methods
A number of sampling methods have been devised for
acrylamide, though no one technique has proved suitable for
collecting both aerosol and vapour. A portable pump with a
membrane filter has been used to collect samples of acrylamide
aerosol, and midget fritted glass bubblers have been used for the
determination of acrylamide vapour in air. Silica-gel sampling
tubes with membrane filters and midget impingers have been used
to collect both dust and vapour, the use of midget impingers
being more efficient than sampling tubes for vapour collection.
However, a method for sampling gaseous acrylamide using a
specially-designed sampling tube packed with Flucin-F as the
solid absorbent has been reported (Suzuki & Suzumura, 1977).
A variety of methods has been reported in the literature for
determining levels of acrylamide in environmental media and
biological tissues. Those shown in Table 2 represent the most
sensitive and/or most widely-used methods. Acrylamide reacts
with diazomethane in methanol-ether solution to form a pyrazoline
derivative that can react with 4-dimethylaminocinnamaldehyde to
form a brightly coloured (purple) Schiff base complex (Mattocks,
1968). This reaction is not specific for acrylamide and is
insufficiently sensitive for determination in environmental
media.
Acrylamide can be converted to its 2,3-dibromopropionamide
derivative for use with the electron capture detector (ECD). For
waste water, as little as 0.1 µg acrylamide/litre (as its 2,3-
dibromopropionamide derivative) has been detected by this method
(Croll & Simkins, 1972). The detection limit for biological
samples was 20 µg/litre in a biological extract of 0.5 ml (Poole et
al., 1981). Levels of 0.1 mg acrylamide/kg (0.1 ppm) in polymer or
impinger samples (Skelly & Husser, 1978) and 0.2 µg/litre (as the
2,3-dibromopropionamide derivative) in natural and polluted water
samples (Brown & Rhead, 1979) can be determined by means of the UV
detection of acrylamide after separation by high-performance liquid
chromatography (HPLC). Differential pulse polarography can be used
to determine acrylamide residues in polyacrylamide with a detection
limit of less than 1 mg/kg (1 ppm) (Betso & McLean, 1976). Dust
and airborne samples (collected by particle and vapour filtration
in a water impinger) have also been analysed by this technique with
a reported sensitivity of 0.5 µg/litre in the final extract (NIOSH,
1976).
The gas chromatography (GC) method using the 2,3-
dibromopropionamide derivative and the selective and sensitive
ECD are the most suitable for trace level determination of
acrylamide in environmental and biological samples though, for
the analysis of water samples (natural and polluted), the assay
of the derivative by HPLC has several advantages over ECGLC.
These include the suitability for routine analysis, speed of
determination, and stability of the calibration curve using
different UV lamps and columns (Brown & Rhead, 1979).
Methods for determining impurities found in commercial
acrylamide (acrylate, ammonium salts, acrylonitrile,
nitrilotrispropionamide, and butanol insolubles) have been
described by Norris (1967).
Table 2. Analytical techniques for determining acrylamide concentrations in environmental media and
biological tissues
---------------------------------------------------------------------------------------------------------
Technique Sensitivity Application Comments Reference
---------------------------------------------------------------------------------------------------------
Titration precision assay of commercial interference by acrylic Norris (1967)
(bromate- ± 0.3% product (sales acid, ethyl acrylate,
bromide method) specification) N,N'-methylene-bis-
acrylamide
Bromination/elec- 5 µg/m3 determination of no interference reported; NIOSH (1976)
tron capture gas acrylamide vapour in air conversion efficiencies
chromatography from monomer to brominated
derivative unknown
Flame ionization 0.05 - 5 mg/m3 determination of using sampling tube Suzuki &
detector; gas (0.01 - 1 ppm) acrylamide vapour in air packed with Flusin-F Suzumura (1977)
chromatography treated with phosphoric
(FID/GC) acid), the recovery of
acrylamide = 82 - 86%
High-performance 0.1 mg/kg (a) determination of acryl- no prior separation of Skelly & Husser
liquid chroma- (0.1 ppm) amide monomer in polyacryl- impurities is required; (1978)
tography amide; (b) acrylamide in recovery of acrylamide
(reverse phase) wipe and impinger samples = 96%
Direct current optimum range determination of monomeric interference by acrylo- MacWilliams
(DC) polaro- = 0.01 - 0.5% acrylamide in poly- nitrile; cationic and et al. (1965)
graphy (100 - 5000 acrylamide anionic species
mg/kg)
Differential < 1 mg/kg determination of monomeric interference by acrylo- Betso & McLean
pulse polaro- acrylamide in poly- nitrile, ethyl acrylates, (1976)
graphy (DPP) acrylamides cationic and anionic
species; some substituted
acrylamides; recovery of
acrylamide > 90%
---------------------------------------------------------------------------------------------------------
Table 2. (contd.)
---------------------------------------------------------------------------------------------------------
Technique Sensitivity Application Comments Reference
---------------------------------------------------------------------------------------------------------
Bromination/electron optimum range determination at low concentrations Croll & Simkins
capture-gas chromat- = 0.1 µg/litre of acrylamide (> 0.25 µg/litre) (1972)
ography - 1 mg/litre in water analytical interferences
must be removed; conversion
to derivative varies with
water quality; recovery of
acrylamide = 34 - 66%
Bromination/high- 0.2 µg/litre determination of interference by natural Brown & Rhead
performance liquid acrylamide in organic compounds; (1979)
chromatography natural and recovery of acrylamide (as
(reverse phase) polluted water derivative) = 70 ± 9%
Colorimetry 0.1 µg/ml urine analysis interference by aldehydes Mattocks (1968)
(0.1 ppm) ketones, pyrroles, indoles,
hydrazines, chromatic
amines
Bromination/electron 20 µg/litre determination of only suitable for Poole et al.
capture-gas chromat- (corresponding acrylamide in measuring unbound (free) (1981)
ography to a final biological samples: acrylamide; recovery of
derivatized (a) plasma acrylamide 80-90% (in the
extract of (b) tissue concentration range 10 -
0.5 ml from a homogenates 1000 ppb)
0.5 ml tissue
homogenate)
---------------------------------------------------------------------------------------------------------
3. SOURCES IN THE ENVIRONMENT
There is no evidence that acrylamide or its commercially
significant derivatives are directly produced in the environment.
3.1. Production Levels, Processes, and Uses
3.1.1. World production
Acrylamide was first produced in 1893 in Germany, and
commercial production began in 1954. The annual production of
acrylamide in the USA for 1979, 1980, and 1981 was approximately
30 000, 35 000, and 37 000 tonnes, respectively. The estimated
production of acrylamide in Japan for 1984 was approximately 36 000
tonnes (Kagaken Kogyo Nippo, 1980). The Stanford Research
Institute estimated the total annual production capacity of firms
manufacturing acrylamide in 1982 to be 63 500 tonnes. Conway et
al. (1979) forecast an increase in the level of production over the
next few years.
3.1.2. Production processes
Acrylamide monomer is produced commercially by either the
sulfuric acid hydration or the catalytic hydration of
acrylonitrile. Since its introduction in the early 1970s, the
catalytic process has become the preferred process, and has been
the only process used in the USA since 1981 (US EPA, 1981). It
possesses many advantages over the sulfate process in that high-
purity acrylamide is produced (99.5 - 99.9% compared with 98%),
there are no undesirable by-products, the conversion efficiency
is greater (97% compared with 80%), and an expensive acrylamide
purification step is avoided (Conway et al., 1979; US EPA, 1981).
In the catalytic process, acrylonitrile is hydrated to
acrylamide in the following reaction:
Catalyst
(copper)
CH2 = CHCN + H2O ------------> CH2 = CHCONH2
70 - 120 °C
This is essentially a continuous process in which unreacted
acrylonitrile is recycled back to the reactor. Acrylonitrile and
the catalyst are removed from the product by evaporation and
filtration, respectively. The aqueous acrylamide solution
produced requires no further treatment or purification.
Polymerization inhibitors are not required at any stage in the
process (Davis et al., 1976). A typical 50% aqueous acrylamide
solution produced by this process contains 48 - 52% acrylamide
and a maximum of 0.05% of polymer (ECT, 1978). Residual
acrylonitrile has been reported at levels between 1 and 100 mg/kg
(i.e., up to 0.01%) (US EPA, 1980a).
Although monomer manufacture does not generate large volumes
of by-products, acrylamide-containing waste streams are generated
during polyacrylamide production (Conway et al., 1979).
3.1.3. Uses
The major use of acrylamide and its derivatives is in the
production of polymers and copolymers for various purposes. In
the USA, the only large-scale use of acrylamide, other than in
the manufacture of polymers, is as a chemical grout; this
consumed 1100 tonnes (3%) of domestically-produced monomer in
1980 (US EPA, 1980a). The relative amounts of acrylamide used in
water treatment may vary from country to country. The various
uses of acrylamide monomer, domestically produced and imported,
are summarized in Fig. 1.
Polyacrylamides are used as flocculents to separate solids
from aqueous solutions in mining operations, in the disposal of
industrial wastes, and in the purification of water supplies
(Tilson, 1981). The largest market for acrylamide polymers is in
the treatment of sewage and wastewater (40% of total acrylamide
production in 1973 in the USA) (Blackford, 1974).
Numerous derivatives of acrylamide appear in the literature.
The two most commercially important are N-hydroxymethyl-
acrylamide and N,N-methylenebisacrylamide. N-hydroxymethyl-
acrylamide is used in the textile industry as a cross-linking
agent and N,N-methylenebisacrylamide is used mainly as a
copolymer in acrylamide grout and in the manufacture of
photo-polymer printing plates. Some of the minor uses of
polyacrylamides are summarized in Table 3.
Table 3. Minor uses of polyacrylamides
-----------------------------------------------------------------------
Coal dust loss preventative Pigment-binding resins
Coal floatation Polyester laminating resins
Dental fillers Printing pastes
Drilling fluid additives Propellant binders
Elastomer curing agent Rodent repellents
Electro-refining Shaving creams
Emulsion stabilizers Soil stabilizers
Flooding agents for petroleum Suspending agents
recovery Textile resins for warp sizing,
Hair sprays printing, shrinkproofing, anti-
Ion-exchange polymers static treatments, binding non-
Leather-treating agents woven fabrics, improving dye
Moulding resins to increase receptivity, increasing dimen-
strength, raise softening temp- sional stability of viscose
erature, or to serve as plasti- rayon
cizing components Thickening agents
Paper additives and resins for Gel electrophoretic separation
faster draining, improved filler of biochemicals
retention, coating, sizing, wet
and dry strength improvements
-----------------------------------------------------------------------
From: US EPA (1981).
3.2. Release into the Environment
Acrylamide monomer may enter the environment from a number of
sources. Because closed systems are now used in acrylamide
manufacture (section 3.1.2), production processes are unlikely to
be a source of environmental contamination, except in the event
of a leak from the reactor.
Contamination of water by acrylamide, discharged in effluent
from industries using or manufacturing polyacrylamide, has been
reported (Croll et al., 1974; Conway et al., 1979; Brown et al.,
1980b).
Another potential source is the release of acrylamide monomer
residues from polyacrylamide flocculents used in processes such
as sludge or conditioning of oil tailings and clarification of
waste and drinking-waters. Croll et al. (1974) demonstrated
that, in many water-treatment processes, acrylamide is not
removed (section 4.3).
Localized contamination may also arise from the use of
acrylamide in grouting operations. The technology exists for the
in situ cross-linking of the polymer as opposed to the monomer
in such operations, thereby decreasing environmental exposure.
However, it is not known to what extent this technique is
employed (US EPA, 1980a).
Direct contamination from spills and leaks may also occur
during transportation, storage, use, and disposal of either
acrylamide or polyacrylamide (Conway et al., 1979).
The Dow Chemical Company has estimated that releases of
acrylamide monomer into the environment during manufacture and
use could amount to 95 tonnes annually. A draft report prepared
for the US EPA estimated a higher figure of 250 tonnes (US EPA,
1978).
3.3. Disposal of Wastes
Decontamination of solid and liquid wastes containing
acrylamide may be achieved by chemical means, e.g., using
potassium permanganate or ozone (Croll et al., 1974) or by
biological degradation (Davis et al., 1976; Arai et al., 1981).
Acrylamide waste may be disposed of by incineration, provided
nitrogen oxides are scrubbed from flue gases (HBTHC, 1981).
However, the cost of removing a large percentage of acrylamide in
waste streams is high.
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
4.1. Transport in the Environment
Acrylamide and its monomeric analogues have a high mobility
in an aqueous environment and are readily leachable in soil.
Acrylamide may travel great distances in the ground water of deep
rock aquifers, where biodegradability is reportedly absent
(Conway et al., 1979). Lande et al. (1979) found acrylamide to
have a higher mobility (leaching) and lower rate of degradation
in sandy soils than in clay soils. Since grouting with acrylamide
is recommended for sandy soils, a potential hazard for ground water
contamination may exist. However, no studies have been made of its
behaviour in subsurface soil where most grouting applications take
place. Acrylamide is unlikely to enter and be distributed in the
atmosphere to any significant extent, because of its low vapour
pressure. Biodegradation is liable to occur to some extent;
acrylamide should not be regarded as a persistent substance,
although its rate of degradation may vary with environmental
conditions (Davis et al., 1976).
4.2. Biomagnification and Bioconcentration
Solubility, partition coefficients, and polarity will affect
the fate of acrylamide analogues. Since many acrylamides are
highly water soluble and are degraded by microorganisms (Brown et
al., 1980c), it is unlikely that they will bioconcentrate in food
chain organisms in significant quantities (Metcalf et al., 1973;
Neely et al., 1974). Log Po/w (n-octanol/water partition
coefficient), based on methods of Hansch & Leo (1979), yields an
approximate value of -1.65 (US EPA, 1980a). This value indicates
that the solubility of acrylamide in water is very high compared
with its solubility in lipids. Thus, it is considered that
bioconcentration of organisms in the fatty tissues will be
minimal. Similarly, on the basis of its water solubility,
biomagnification of acrylamide in the food chain is not expected
(Metcalf et al., 1973).
4.3. Transformation
A wide variety of microbes possess the ability to degrade
acrylamide (Croll et al., 1974; Lande et al., 1979; Brown et al.,
1980a) under light or dark, anaerobic or aerobic conditions.
However, periods of several days may elapse prior to any
significant degradative losses (Conway et al., 1979; Brown et
al., 1982). An amidase-producing microorganism belonging to the
genus Rhodococcus (strain 10 021R), isolated from the sewage of
an acrylamide plant, was found to convert acrylamide monomer
(even in an acrylamide gel stabilizer) into the less toxic
acrylic acid. This microorganism was found to be non-virulent in
experimental animals (even at high doses) and hence, its possible
use in the control of environmental pollution has been suggested
(Arai et al., 1981).
The residence period of acrylamide may be of the order of
days, weeks, or months in a river of low microbial activity.
Brown et al. (1980a) also showed that degradation rates in
samples of river water, continuously exposed to low levels of
acrylamide (6 - 50 µg/litre), were faster than those in river
samples not previously exposed. Acrylamide entering a water
course may be present for several days (Brown et al., 1980a).
Under aerobic conditions, acrylamide has been shown to be readily
degraded in fresh water by bacteria, with a half-life of 55 - 70
h, after acclimatization of the bacteria to the compound for 33 -
50 h (Conway et al., 1979). Half-lives in estuarine or salt
water are slightly longer (Croll et al., 1974). Cherry et al.
(1956) studied the effects of acrylamide (10 mg/litre) on the
chemical oxygen demand (COD) in filtered river water. The
initial half-life was approximately 5 days. When the samples were
re-exposed to acrylamide, the COD decreased more rapidly. Croll et
al. (1974) monitored the concentration of acrylamide in river water
containing acrylamide at 8 µg/litre. After a time-lag of
approximately 100 h, the acrylamide degraded rapidly. The addition
of acrylamide at 10 µg/litre to natural waters, which had already
been exposed to acrylamide, resulted in a shorter time-lag and
faster degradation rates.
In laboratory experiments, acrylamide was not adsorbed by
sewage sludge, natural sediments, clays, peat, or synthetic
resins over the pH range 4 - 10. Therefore, removal by this
means seems unlikely unless converted to a less polar and/or
charged compound. Temporary entrainment in a polymeracrylamide-
particle matrix may occur during flocculation processes, and rapid
leaching will occur should such a matrix remain in contact with
water for a period of time (Brown et al., 1980c). Polyacrylamide
is used for the conditioning of waterworks sludge. Since 92 - 100%
of the residual acrylamide in the polymer is leached out in the
sludge-conditioning process, care must be taken to ensure that any
conditioned sludge supernatant which is returned to the main flow,
does not raise the acrylamide concentration in finished water above
acceptable levels. A removal rate of 75% was calculated by Croll
et al. (1974) for an overloaded sewage works receiving an
acrylamide effluent of 1.1 mg/litre.
Lande et al. (1979) found a faster rate of degradation and
lower mobility of acrylamide in silt clay soils than in clay
loam, loamy fine sand, or loam. Acrylamide is recommended for
grouting on sandy soils, in which it has a relatively low rate of
degradation and a high mobility. Unfortunately, no studies have
been carried out on the behaviour of acrylamide in subsurface
soil where most grouting applications take place.
The half-life of acrylamide in aerobic silt loam was of the
order of 20 - 45 h at a concentration of 25 mg/kg and a
temperature of 22 °C, and 94.5 h at 500 mg/kg and 20 °C.
Increasing the acrylamide concentration or decreasing the
temperature increased the half-life (Lande et al., 1979;
Abdelmagid & Tabatabai, 1982). The behaviour of acrylamide
(100 mg/kg) in soil-plant systems was investigated by Nishikawa
et al. (1979). Acrylamide decomposed mainly by hydrolysis to
form acrylic acid. In upland farming conditions (aerobic
conditions), there was a rapid decrease in total organic carbon
(TOC), up to 15 days after application, whereas in wet-land
(rice) conditions, the decrease was slow. These fluctuations in
TOC under both types of farming conditions corresponded closely
to the changes in TOC originating from acrylamide and acrylic
acid (Nishikawa et al., 1979).
Polyacrylamide may be hydrolysed, but acrylamide monomer is
not formed in solutions. Some photosensitized polymerization is
possible for certain acrylamide derivatives. However, major
modification of the molecule as a consequence of
chemical/photochemical reaction seems unlikely (Davis et al.,
1976).
5. ENVIRONMENTAL LEVELS AND EXPOSURES
5.1. Environmental Levels
5.1.1. Ambient air and soil
The results of monitoring studies in the USA, performed near
6 plants producing acrylamide and/or polyacrylamides, showed
average acrylamide levels in the air of less than 0.2 µg/m3, in
either vapour or particulate form, and less than 0.02 mg/kg (0.02
ppm) in soil or sediment samples (Going, 1978).
5.1.2. Water
The Committee on New Chemicals for Water Treatment in the
United Kingdom recommended that: commercial polyacrylamide used in
the treatment of drinking-water should not contain more than 0.05%
acrylamide monomer, the average amount of polymer added to water
should not exceed 0.5 mg/litre, and the maximum dose should not
exceed 1.0 mg/litre (UK Ministry of Housing and Local Government,
1969).
Although limits have been recommended for the amount of
polyacrylamide used in the clarification of drinking-water, much
higher levels may be encountered in other uses, where polymers
with a higher monomer content are used at much higher levels.
For example, polyacrylamides used for effluent treatment may
contain monomer levels of between 1 and 50 g/kg (Croll et al.,
1974). If effluent from such processes were to enter water
subsequently treated for public supply, then the acrylamide
concentration derived from the raw water source might be higher
than that resulting from the clarification process. The
acrylamide contents of effluents from several industries using
polyacrylamide are shown in Table 4.
Brown et al. (1980b) did not detect any acrylamide in
effluents from the china-clay industry, after several months of
polymer use (analytical detection limit, 0.2 µg/litre). Croll et
al. (1974) detected 16 µg acrylamide/litre in the effluent from a
clay pit, which resulted in an acrylamide level of 1.2 µg/litre in
the receiving stream. Further downstream at a waterworks intake,
this level had dropped to 0.3 µg/litre.
Environmental monitoring at sites of acrylamide and
polyacrylamide production in the United Kingdom and the USA
indicates that levels of acrylamide reaching surface waters from
industrial effluent would generally be difficult to detect below
1 µg/litre (Croll & Simkins, 1972; Going & Thomas, 1979). A
value of 1.5 mg/litre was recorded by Going (1978) in a small
stream receiving effluent directly downstream from a
polyacrylamide producing plant in the USA. High levels have also
been found in the vicinity of local grouting operations (Croll et
al., 1974). Igisu et al. (1975) reported a level of 400 mg
acrylamide/litre in well-water in Japan that had been
contaminated from a grouting operation 2.5 metres away.
Table 4. Concentrations of acrylamide in some industrial effluents
-----------------------------------------------------------------------
Effluent Acrylamide Reference
concentration
(µg/litre)
-----------------------------------------------------------------------
Colliery A; tailings lagoon 42 Croll et al. (1974)
Colliery B; tailings lagoon 39 Croll et al. (1974)
Colliery C; coal washing; 1.8 Croll et al. (1974)
effluent lagoon
Colliery/coking plant effluent 0.74 Croll et al. (1974)
Paper mill A; treated effluent 0.47 Croll et al. (1974)
Paper mill B; treated effluent 1.2 Croll et al. (1974)
Clay pit 16.0 Croll et al. (1974)
Paper mill A & B; treated effluent < 1.0 Brown et al. (1980b)
Paper mill A & B; process water < 1.0 Brown et al. (1980b)
Paper mill C; treated effluent 14.4 Brown et al. (1980b)
Paper mill C; process water 45.4 Brown et al. (1980b)
-----------------------------------------------------------------------
No acrylamide (detection limit 4 µg/litre) was detected in
process waters from a sewage works, either before or after
polymer addition (Brown et al., 1980a). In another works,
samples of vacuum- and pressure-filtered sewage sludge,
conditioned with polyacrylamide, were found to contain up to 0.1
µg acrylamide/litre. On the basis of the acrylamide content and
polymer dosage, these filtrates would have contained up to 25 µg
acrylamide/litre, had no degradation and/or adsorption occurred
(Croll et al., 1974).
The fate of acrylamide monomer in waterworks sludge
conditioning (using the polymer) was investigated by Croll et al.
(1974). In 2 waterworks, between 74 and 87% of acrylamide
(residual monomer from the polymer) passed into the recovered
water. This water was either returned directly to the waterworks
intake or disposed of as an effluent. No acrylamide was detected
by Brown et al. (1980b) in process waters from a waterworks using
polyacrylamide for effluent treatment (detection limit 0.2
µg/litre). The authors also investigated the effects of
accidental polymer overdosing. A maximum concentration of 8.6 µg
acrylamide/litre was detected in backwash water, 30 min after
spiking with 100 times the normal polymer dosage. The effluent
was diluted approximately 12 times, in river water 500 metres
downstream from the discharge (0.7 µg/litre). Such effluents
from over-loaded water- or sewage sludge-conditioning works could
present a hazard to water supplies taken downstream of the
effluent discharge (Croll et al., 1974).
5.1.3. Food
The US Food and Drug Administration has established a maximum
acrylamide residue level of 0.2% (2 g/kg) for acrylamide polymers
used in paper or paperboard in contact with foodstuffs (Bikales,
1973). Similarly, in the Federal Republic of Germany, the
Federal Health Authority have recommended that the level of
polyacrylamide used as an agent for retention (Table 3) in
foodstuff packaging should not exceed 0.3%. This should not
include more than 0.2% monomer. The use of polyacrylamides in the
washing of pre-packed foods and vegetables and the clarification
and stabilization of wines has been described (MacWilliams, 1973;
Croll et al., 1974). In the USA, polyacrylamide used in the
washing of fruits and vegetables must not contain more than 0.2% (2
g/kg) acrylamide monomer (IRPTC, 1983). No data regarding the
levels of acrylamide in foods or the potential effects that such
contamination might have on the environment are available. Brown
et al. (1980b) mentioned the possibility of acrylamide consumption
by farm animals, via feed containing industrial or sewage sludges.
5.2. General Population Exposure
The general population is potentially exposed to acrylamide
by inhalation, skin absorption, water, and by ingestion of food.
In the Federal Republic of Germany, the level of residual
monomer in polyacrylamide used in hair sprays is limited to 0.01%
(0.1 g/kg)a.
5.3. Occupational Exposure
Information on occupational exposure to acrylamide is sparse.
In 1976, NIOSH estimated that approximately 20 000 workers might
be exposed to acrylamide in the USA; however, there is no
indication that this figure included grouting workers and Conway
et al. (1979) estimated that this group of workers could number
at least 2000 by 1980. A large number of laboratory workers are
also potentially exposed to acrylamide during the preparation of
polyacrylamide gels for electrophoresis. Although exposure
levels have not been reported for grouters, the potential for
hazard from this use is probably greater than that from other
uses because of the uncontrolled nature of the grouters'
exposure.
No epidemiological studies are available, and only limited
air monitoring data (Vistron Company, USA), on acrylamide
concentrations in the workplace. Stationary air sampling
showed acrylamide concentrations ranging from 0.1 to 0.4 mg/m3
for a control room, from 0.1 to 0.9 mg/m3 for a bagging room,
and from 0.1 to 0.4 mg/m3 for a processing area. The sampling
was performed during an 8-h working day, and the values cited
represented weekly averages. In another factory in the USA,
personal sampling (4 h) revealed acrylamide exposure levels of
0.76 mg/m3 and 0.52 mg/m3 for 2 packers, 0.48 mg/m3 for a
reactor operator, and 0.52 mg/m3 for a dryer operator (NIOSH,
1976). In another factory, both personal sampling and stationary
sampling were performed during 1974-75. Personal sampling
concentrations ranged from 0.1 to 3.6 mg/m3, with the highest
concentrations seen in the bagging area. The median value for
all personal monitoring data was 0.6 mg/m3, while the stationary
-------------------------------------------------------------------
a Bundesministerium für Jugend, Familie und Gesundheit, 1984.
sampling showed concentrations ranging from 0.1 to 0.3 mg/m3.
Thus, in 2 factories, the personal sampling measurements were
between 2 and 3 times higher than stationary sampling measurements
(NIOSH, 1976).
A recommended threshold limit value/time-weighted average
(TLV/TWA) for acrylamide in workroom air is 0.3 mg/m3 and the
short-term exposure limit (TLV-STEL) is 0.6 mg/m3 (ACGIH,
1984). Other recommended occupational exposure levels (for
acrylamide in workroom air) for various countries are shown in
Table 5.
Table 5. Occupational exposure levels for acrylamide in workroom
air of various countriesa
--------------------------------------------------------------------
Country Exposure limit Category of Notation
(mg/m3) limitb
--------------------------------------------------------------------
Australia 0.3 TWAc Sd
Belgium 0.3 S
Finland 0.3 TWA S
Germany, Federal 0.3 MAKe Sf
Republic of
Hungaryg 0.3 TWA
1.5 STEL
Italy 0.3 TWA S
Japan 0.3 MACh S
Netherlands 0.3 TWA S
Sweden 0.3 TWA S
0.9 STELi
Switzerland 0.3 MAC S
United Kingdom 0.3 TWA S
0.6 STEL
USA
(a) NIOSH/OSHA 0.3 PELj S
(b) ACGIH 0.3 TWA S
0.6 STEL
USSRk 0.2 MAC
Yugoslavia 0.3 TWA S
--------------------------------------------------------------------
a From: ILO (1980) and IRPTC (1983).
b Category of limit: broad definition of type of limit stated.
For exact meaning of terms, refer to individual country
requirements.
c TWA (time-weighted average): a mean exposure limit averaged
generally over a working day whereby, within prescribed limits,
excursions above the level specified are permitted, provided
they are compensated for by excursions below the level specified.
d SI: specified as a skin irritant.
e MAK: maximum worksite concentration.
Table 5. (contd.)
--------------------------------------------------------------------
f S (skin absorption): this designation refers to the potential
contribution of cutaneous absorption either by airborne or, more
particularly, by direct contact.
g From: Hungary, State Ministry of Health (1978).
h MAC: maximum allowable concentration.
i STEL (short-term exposure limit): a maximum concentration
allowed for a short specified duration.
j PEL: permissible exposure limit.
k From: USSR, Ministry of Health (1979).
Note: Occupational exposure levels and limits are derived in
different ways, possibly using different data and expressed
and applied in accordance with national practices. These
aspects should be taken into account when making comparisons.
6. KINETICS AND METABOLISM
6.1. Experimental Animal Studies
6.1.1. Absorption and distribution
Acrylamide has been reported to induce neurotoxic effects in
many animal species following absorption via the respiratory,
dermal, and oral routes (Hamblin, 1956). The absorption and
distribution of acrylamide applied dermally to rabbits was
studied by Hashimoto & Ando (1975). A single 30-min application
of a 10 - 30% aqueous solution of [1-14C]-acrylamide rapidly
penetrated the skin (auto-radiography showed a concentration of
14C in the hair follicles) and appeared in the blood in 2 forms,
mainly protein-bound, and in a free water-soluble form. About
50% of the radioactivity in the blood was associated with the
protein-bound fraction, 24 h after cessation of contact. This
value increased to about 90%, when there was daily contact with
acrylamide (30-min duration) for 7 days. Similar patterns of
distribution were observed after intravenous (iv) administration.
In rats, Hashimoto & Aldridge (1970) found that the highest
levels of radioactivity after a single iv dose (100 mg/kg body
weight) were in whole blood. After 24 h, the plasma contained
little radiolabel and in vitro binding to haemoglobin was
demonstrated; this suggested that the protein-bound radioactivity
in the blood was associated with the red blood cells. By 14
days, the majority of free/soluble radiolabel had disappeared in
both blood and tissues. However, the protein-bound radiolabel
remained at 100% and 25% of the 24-h levels in blood and tissues,
respectively. During the 48 h following an iv dose of [1,3-14C]-
acrylamide at 50 mg/kg (Young et al., 1979), the concentration of
radiolabel decreased in selected rat tissues but increased in red
blood cells to a plateau that was between 10 and 90 times higher
than the levels in the other tissues examined.
Miller et al. (1982) determined the extractable fraction of
parent acrylamide in tissues obtained from rats, at various time
intervals after an iv dose of [14C]-acrylamide at 10 mg/kg body
weight. Values, which ranged from 85 to 100% at 15 min,
decreased as time progressed (10 - 50% at 12 h and less than 1%
after 24 h). The extractable fraction from the blood was only
50% at 15 min and less than 1% at 12 h. Covalent binding of
acrylamide to cysteine residues in rat haemoglobin was
demonstrated by Hashimoto & Aldridge (1970) and binding occurred
at the 4 active sulphydryl groups in the haemoglobin molecule. It
seems likely that the non-extractable fraction in vivo is due to
this reaction or its metabolites.
The only biological component that has substantial irreversible
binding and has been found to concentrate acrylamide (as 14C) is
the red blood cell. Pastoor & Richardson (1981) found that 3 h
after iv administration to rats, uptake of acrylamide by red blood
cells was essentially complete and had plateaued. The plateau
level was closely correlated with dose (r2 = 0.995) and was
determined to be 2.0 ± 0.2% of the dose per ml of red blood
cells. After iv administration of 10 mg [14C]-acrylamide/kg body
weight, the binding to erythrocytes in rats plateaued at 12% of
the dose and accounted for essentially all of the 14C in the
blood (Miller et al., 1982). When acrylamide was given to rats
(30 mg/kg body weight per day), the blood concentration rose to a
plateau of about 400 mg/kg, on day 9 (Young et al., 1979).
Measurements of unbound acrylamide in the blood of rats given
a single iv dose indicated that acrylamide is distributed
throughout total body water within 30 min (Edwards, 1975a).
Fetal absorption of acrylamide has been reported in various
mammalian species demonstrating the permeability of the placenta
(section 7.5) (Edwards, 1976a; Ikeda et al., 1983). Miller et
al. (1982) studied the distribution and fate of orally-
administered [14C]-acrylamide (10 mg/kg body weight) in rats.
An absorption phase, which had peaked by the end of the first
hour, was observed in liver, fat, kidney, and testis. Acrylamide
is highly soluble in water and poorly soluble in lipids.
Concentration in particular tissues is due, either to covalent
binding to particular proteins, or to an accumulation of
metabolites, e.g., in the liver and kidney. The concentration of
radiolabel in neural tissue (brain, spinal cord, and sciatic
nerve) did not differ significantly from that in non-neural
tissue, except for that in red blood cells (Poole et al., 1981;
Miller et al., 1982). Ando & Hashimoto (1972) reported that the
distribution of radiolabel in the sciatic nerve was 2.5 times
greater in the distal half of this tissue. Acrylamide has also
been reported to concentrate in the sciatic nerve terminals, with
accumulation taking place directly from the blood stream
(Hashimoto, 1980). Hashimoto & Aldridge (1970) detected a
considerable amount of protein-bound radioactivity in the brain
and spinal cord of rats, 14 days after a single iv dose (100
mg/kg body weight) of [14C]-acrylamide. They suggested that this
finding could be significant if protein binding were involved in
the primary lesion.
6.1.2. Metabolism
The biotransformation of acrylamide has been shown to be
mainly mediated through glutathione conjugation (Pastoor et al.,
1980; Dixit et al., 1981a; Miller et al., 1982). Studies by
Dixit et al. (1981a) established that the reaction of acrylamide
with glutathione occurs by both non-enzymic and enzymic
(catalysed by glutathione- S-transferase (GST) (EC 2.5.1.18))
reactions and occurs in both the liver and the brain. Edwards
(1975a) demonstrated biliary excretion of a glutathione conjugate
of acrylamide ( S-beta-propionamido-glutathione) after iv
administration to rats. In studies by Miller et al. (1982), 15%
of the dose (as total 14C) was excreted in the bile within 6 h of
oral administration to rats; only 1% was parent acrylamide.
Miller et al. (1982) detected at least 4 urinary metabolites
after the oral administration of [14C]-acrylamide to rats. The
major metabolite was mercapturic acid ( N-acetyl-cysteine- S-
propionamide), which accounted for 48% of the dose. Unmetabolized
acrylamide (2%) and 3 non-sulfur-containing metabolites (total
14%) were also present in the urine; cysteine- S-propionamide was
identified as a urinary metabolite by Dixit et al. (1982).
Glutathione conjugation is presumed to be a detoxifying
process, since Dixit et al. (1980a) demonstrated an earlier onset
of toxicity after depletion of hepatic glutathione stores and
Edwards (1975b) found that the glutathione conjugate did not
induce any neurotoxic effects. Concurrent administration of
methionine (involved in the synthesis of glutathione) with
acrylamide has also been shown to reduce the neurotoxic potency
of acrylamide (Hashimoto & Ando, 1971). Inhibition of GST by
acrylamide has been reported by Dixit et al. (1981b), Mukhtar et
al. (1981), and Das et al. (1982). Thus, acrylamide may inhibit
not only its own detoxification, but also that of other toxic
xenobiotics along this pathway. Pre-exposure of rats to
acrylamide has been shown to inhibit the biliary excretion of
methylmercury, which requires glutathione for its
biotransformation (Refsvik, 1978).
Hashimoto & Aldridge (1970) reported that 6% of an iv dose
of [1-14C]-acrylamide, was exhaled by rats as [14C]-carbon
dioxide (14CO2), for 8 h after administration. No exhaled
14CO2 was detected by Miller et al. (1982) using
[2,3-14C]-acrylamide. It would appear, therefore, that
acrylamide is metabolized, to a small extent, by cleavage of
the carbonyl group. Apparently, the remaining 2-carbon
fragment is not metabolized to carbon dioxide.
Efforts to demonstrate the role of the microsomal mixed-
function oxidase (MFO) (EC 1.14.14.1) system in the
biotransformation of acrylamide have not been successful. There is
evidence suggesting that, under in vitro conditions, a reactive
metabolite of acrylamide is formed by the MFO system, which
inhibits aniline hydroxylase activity and cytochrome P-450 in rats
(Ortiz et al., 1981). In vivo studies by Das et al. (1982) also
demonstrated a decrease in hepatic MFO enzyme levels. Similar
studies on mice by Nilsen et al. (1978) demonstrated a reduction in
only one form of hepatic cytochrome P-450 (P-45047), without any
change in the total amount of cytochrome P-450. A reduction in
both cutaneous and hepatic aryl hydrocarbon hydroxylase (AHH)
activity was observed in mice following topical application of
acrylamide (Mukhtar et al., 1981). Edwards et al. (1978) reported
a 15% depletion of microsomal cytochrome P-450 in rats after a
single subcutaneous (sc) dose of acrylamide. This observation was
accompanied by a 100% increase in liver porphyrins; there is
evidence that reactive metabolites of allyl groups formed via
cytochrome P-450 are responsible for the abnormal degradation of
haem (Ortiz de Montellano & Mico, 1980).
SKF 525A is an inhibitor of hepatic mixed-function oxidases
(decreased detoxification or bioactivation) while phenobarbital
increases them (increases bioactivation and/or detoxification)
and also induces glutathione S-transferases (detoxification).
Kaplan et al. (1973) reported that pretreatment of rats with SKF
525A, to inhibit hepatic mixed-function oxidase activity,
enhanced the neurological effects and lethality of acrylamide.
On the other hand, acrylamide-induced changes in striatal
dopaminergic receptors were completely prevented by SKF 525A
(Agrawal et al., 1981a). With regard to the effects of hepatic
microsomal inducers on the development of acrylamide neuropathy,
Kaplan et al. (1973) reported a significantly delayed onset of
ataxia after ip administration of acrylamide following
pretreatment of rats with phenobarbital (or DDT), while Edwards
(1975b) failed to obtain similar results after oral
administration. Hashimoto & Tanii (1981) reported that
phenobarbital treatment reduced neuro- and testicular toxic
effects due to acrylamide, or selected analogues in mice.
However, Kaplan et al. (1973) found that the delayed onset of
neurotoxicity was accompanied by a greater degree of peripheral
nerve injury in pretreated animals. In studies by Tanii &
Hashimoto (1981), phenobarbital pretreatment did not increase the
rate of in vitro metabolism of acrylamide, but increased the
rate of reaction of acrylamide with glutathione by some 40%.
Because it has not yet been established whether the biological
effects of acrylamide are due to the parent compound or to a
bioactivated derivative, it is difficult to interpret the results
of these studies.
6.1.3. Elimination and excretion
6.1.3.1. Elimination
Acrylamide (as total 14C) was eliminated from rat tissues
in a biphasic manner (Miller et al., 1982). In the first
component, the elimination half-life in most tissues was less
than 5 h and, in the second, 8 days or less. Testes and skin had
slower elimination rates with initial half-lives of 8 and 11 h,
respectively. An interesting observation was that the
elimination of radiolabel in neural tissue did not differ
significantly from that in non-neural tissue.
The amount of 14C in blood remained constant at 12% of the
dose for up to 7 days. However, 14C in plasma was eliminated
very rapidly. The terminal elimination half-life for acrylamide
in blood (as 14C) was reported by Pastoor & Richardson (1981) to
be about 10 days, which is close to the figure of 13 days
suggested by Hashimoto & Aldridge (1970).
In contrast to the kinetics for total 14C, the elimination of
parent acrylamide fitted a monoexponential curve. The half-life
of parent acrylamide in blood was 1.7 h (Miller et al., 1982),
which is comparable with the figure of 1.9 h reported by Edwards
(1975a). Pastoor & Richardson (1981) estimated that the half-
life of plasma acrylamide was approximately 2.5 h. They also
observed that the semi-log plasma elimination curves became more
linear as the dose increased from 2 to 20 mg/kg body weight (iv
administration), which implied a saturation of elimination
pathways at higher doses. The elimination of parent acrylamide
from tissues corresponded with that seen in the blood. Within 24
h, no detectable levels were found in any tissue (Miller et al.,
1982). The conclusion is that the half-life for parent
acrylamide in blood and tissues makes it unlikely that this form
accumulates in the body.
6.1.3.2. Excretion
The excretion half-life of parent acrylamide in rat urine
was 7.8 h (Miller et al., 1982) (section 6.1.1). Using
[1-14C]-acrylamide, Hashimoto & Aldridge (1970) reported that
approximately 6% of the dose was exhaled as 14CO2. In an
extensive study of the kinetics of both orally- and iv-administered
[2,3-14C]-acrylamide, it was shown that the rate of elimination
of the radiolabel in urine was independent of the route of
administration. Within 24 h, about two-thirds of the dose was
excreted in the urine and three-quarters in 7 days. Faecal
excretion was small (4.8% in 24 h and 6% by 7 days). Since 15%
of the dose appeared in the bile within 6 h, acrylamide or its
derivatives must undergo enterohepatic circulation. Thus,
approximately 80% of the radiolabel was excreted within 7 days
and, of this, a very large proportion (90%) was in the form of
metabolites.
When [14C]-acrylamide was given to rats daily by gavage or
in the drinking-water at 30 mg/kg body weight per day, the daily
excretion of radioactivity in the urine was nearly constant
during the 14-day period (Young et al., 1979), most of the dose
being excreted as 2 major metabolites together with a small
amount of the parent compound. Miller et al. (1982) reported
that the excretion rates of radiolabel in urine, following
administration of 1 - 100 mg acrylamide/kg body weight were
independent of dose, implying zero order elimination kinetics.
Excretion of both free and protein-bound [14C] acrylamide has
been demonstrated in the milk of rats, during lactation (section
7.5) (Walden & Schiller, 1981).
6.2. Human Studies
Limited data are available on absorption, distribution,
elimination, and metabolism in human beings, and these have
mainly been derived from clinical observations in cases of
poisoning. The findings in animal studies that acrylamide is
readily absorbed, whatever the route of exposure, is supported by
clinical observations. The majority of human cases of acrylamide
poisoning reported in the literature have occurred through skin
absorption (Fujita et al., 1961; Auld & Bedwell, 1967; Garland &
Patterson, 1967; Morviller, 1969; Graveleau et al., 1970;
Takahashi et al., 1971; Cavigneaux & Cabasson, 1972; Davenport et
al., 1976; Mapp et al., 1977). Poisoning by ingestion of
contaminated water has also been reported (Igisu et al., 1975),
indicating efficient gastrointestinal absorption of acrylamide.
However, quantitative data on absorption or excretion in human
beings are not available at present. There are no methods for
determining acrylamide or its metabolites in blood or excreta,
and such methods are urgently needed. Animal data suggest that
the concentration of acrylamide in red blood cells might serve as
an index of body burden of acrylamide (Edwards, 1976b; Pastoor &
Richardson, 1981). However, no studies are available on the
relationship between the blood concentration of acrylamide and
its toxic effects or on human urinary excretion of acrylamide and
its metabolites.
7. EFFECTS ON ANIMALS
7.1. Neurological Effects
Regardless of species, nearly all studies on acrylamide
intoxication involve manifestations of various degrees of
neurotoxicity; however, it must be emphasized that polyacrylamide
itself is not neurotoxic. Some effects of acute acrylamide
intoxication are shown in Table 6. Results of experimental
animal studies suggest that central nervous system (CNS) effects
predominate in acute acrylamide poisoning, whereas, on repeated
administration of divided doses, signs of peripheral neuropathy
become more evident (Le Quesne, 1980). The general toxicological
profile of poisoning, following prolonged exposure to repeated
doses, includes tremors, incoordination, ataxia, muscular
weakness, distended bladder, and loss of weight. In acute
single-dose studies on cats, Kuperman (1958) described ataxic
tremors together with severe tonic-clonic convulsions and other
signs of diffuse central excitation. With prolonged intoxication
in cats, incoordination was the first malfunction observed,
followed by limb weakness (McCollister et al., 1964; Le Quesne,
1980). The development of neuropathy usually begins with the
involvement of the distal parts of limbs and slowly progresses to
the proximal regions of the body.
7.1.1. Neurobehavioural effects
Numerous investigators have used neurobehavioural techniques
to detect and quantify the neurotoxic effects of acrylamide,
including effects on motor and sensory function, on-going
performance, and cognitive processes.
The procedures and the effects of acrylamide on neuromotor
function in rats are listed in Table 7 according to sensitivity,
i.e., the lowest cumulative dose required to produce a
significant alteration. Motor dysfunction, as measured by
impaired rotarod performance, hind-limb splay, and hind-limb
weakness, can be observed in the dose range 100 - 320 mg/kg. In
other procedures involving a conditioned motor response, such as
food-reinforced, schedule-controlled behaviour (VI or FR), changes
in performance have been observed in the dose range 25 - 75 mg/kg.
Tilson et al. (1979) associated neuromuscular weakness with
histopathological alterations, i.e., loss of fibres and axonal
swelling in peripheral nerves, both during dosing and following
cessation of exposure. Other studies with mice have also shown
that motor dysfunction can be quantified using neurobehavioural
procedures that assess motor coordination and neuromuscular
strength (Gilbert & Maurissen, 1982; Teal & Evans, 1982).
Table 6. Clinical signs of acute acrylamide intoxication in mammals
--------------------------------------------------------------------------------------------------------
Species Route Dose Mortality Clinical signs Reference
(mg/kg
body weight)
--------------------------------------------------------------------------------------------------------
Mouse oral 100 - 1000 - postural and motor incoordination; Kuperman (1957)
convulsions; death
Mouse dermal (40% sol.) 100% 50% mortality within 45 min Novikova (1979)
Rat oral 100 - 200 - tremor; general weakness; death Fullerton & Barnes
(1966)
Rat ip 100 - 1000 - ataxia; general weakness; death Kuperman (1958)
Rat oral 126 0/5 slight weight loss; coma McCollister et al.
(1964)
Rat oral 256 5/5 death within 24 h McCollister et al.
(1964)
Guinea-pig oral 126 1/4 tremors; pupil dilation McCollister et al.
(1964)
Guinea-pig oral 252 4/4 death within 24 h McCollister et al.
(1964)
--------------------------------------------------------------------------------------------------------
Table 6. (contd.)
--------------------------------------------------------------------------------------------------------
Species Route Dose Mortality Clinical signs Reference
(mg/kg
body weight)
--------------------------------------------------------------------------------------------------------
Rabbit sc 500 - postural and motor incoordination; Kuperman (1957)
convulsions; death
Rabbit oral 63 0/4 slight weight loss McCollister et al.
(1964)
Rabbit oral 126 1/4 tremors; pupil dilation McCollister et al.
(1964)
Rabbit oral 252 4/4 death within 24 h McCollister et al.
(1964)
Rabbit dermal 500 - 1000 1/5 oedema; death McCollister et al.
(1964)
Cat iv or ip 65 - 70 - postural and motor incoordination Kuperman (1957)
Cat iv 5000 - general weakness; circulatory Kuperman (1957)
collapse; death
Cat ip 100 - unconsciousness after 24 h; severe McCollister et al.
effects or death (1964)
Dog oral 100 - convulsions; postural and motor Kuperman (1957)
incoordination
--------------------------------------------------------------------------------------------------------
Table 7. Summary of effects of acrylamide on motor function of rats
----------------------------------------------------------------------
Test Route Least effective Reference
cumulative dose
(mg/kg)
----------------------------------------------------------------------
Taste aversion oral 10 Anderson et al.
(1982)
Food-reinforced gavage 25 Tilson & Squibb
variable-interval (1982)
(VI) responding
Open-field ip 50 Gipon et al.
rearing (1977)
Altered gait ip 50 Jolicoeur et al.
(1979)
Food-reinforced gavage 75 Tilson et al.
fixed-ratio (FR) (1980)
Horizontal motor ip 100 Gipon et al.
activity (1977)
Hind-limb gavage 100 Tilson & Cabe
weakness (1979)
Hind-limb splay ip 150 Edwards &
Parker (1977)
ip 200 Jolicoeur et al.
(1979)
(oral) 280 Edwards &
diet Parker (1977)
Rotarod ip 300 Gipon et al.
(1977)
ip 320 Kaplan & Murphy
(1972); Kaplan
et al. (1973)
Inclined board gavage 500 Fullerton &
Barnes (1966)
Running wheel (oral) 550 Lewkowski et al.
activity diet (1978)
Motor activity gavage 600 Tilson et al.
(automex) (1979)
---------------------------------------------------------------------------
Responses associated with appetitive and/or consummatory
behaviour have also been used to quantify acrylamide-induced
toxicity. Teal & Evans (1982) found that administration of
acrylamide for 30 days produced a considerable increase in
periodic milk-licking, even in severely intoxicated animals.
These effects are presumed to be associated with disturbances in
water balance (Gipon et al., 1977) and may be associated with
alterations in thirst and hunger regulation in the hypothalamus.
Blunting of tactile sensitivity is recognized as an early
effect following exposure to acrylamide; such sensory signs
usually precede motor involvement. Recently, Maurissen et al.
(1983) used operant psychophysical techniques to assess vibratory
or electrical stimuli applied to the fingertips. Monkeys dosed
orally with 10 mg/kg acrylamide, 5 days per week, for up to 9
weeks, were found to exhibit impaired vibration sensitivity
before the onset of neuromuscular effects. Sensory effects were
evident for several months after dosing ceased. Sural nerve
biopsies did not reveal a clear association between loss of nerve
fibres and degree of sensory loss. These and other data suggest
that vibration sensory loss is probably due to dysfunction of the
end-organ receptors. Spencer & Schaumburg (1977) reported that
the generator potential of the Pacinian corpuscle was decreased
by acrylamide exposure at a time when pathology was not evident.
Maurissen et al. (1983) also found that sensitivity to the
electrical stimulus did not change, suggesting that acrylamide
differentially affected the mechanoreceptors. Studies on rats
have shown that acrylamide does not markedly affect
responsiveness to thermal stimuli, even when motor dysfunction is
present (Pryor et al., 1983).
Anderson et al. (1982) studied the effects of acrylamide on
conditioned taste aversion, considered to be due to interoceptive
effects discernible by the animal. Taste aversion was observed
following a single dose of acrylamide given by gavage, suggesting
that acrylamide can induce effects at doses much lower than those
required to induce neurohistopathological changes, and the
neurological substrates or processes involved may be different
from those mediating the expression of central peripheral distal
axonopathy.
Where animals survived the effects of acute poisoning,
recovery was usually rapid and complete (Spencer & Schaumburg,
1974b). Similarly, after long-term poisoning, neuropathy was
reversible, though recovery was often slow (McCollister et al.,
1964; Hopkins & Gilliatt, 1971).
7.1.2. Electrophysiological effects
7.1.2.1. Peripheral effects
Various electrophysiological parameters have been used to
help characterize the development of the lesion in acrylamide-
induced peripheral neuropathy. Fullerton & Barnes (1966)
administered repeated doses (20 - 30 and 10 - 14 mg acrylamide/kg
body weight per day) to rats. Concomitant with the appearance of
major clinical symptoms (after 3 weeks on the high dose and 12
weeks on the low dose), the maximal motor conduction velocity
(MCV) was reduced significantly by about 20%. Similar reductions
in MCV have been reported for cats (29%) and monkeys (24%) by
Leswing & Ribelin (1969) and dogs (11%) by Satchell et al. (1982)
with various dosage regimens and durations of exposure. The
reduction in MCV has been correlated with selective degeneration
of the fast-conducting, large-diameter fibres (Fullerton &
Barnes, 1966; Hopkins & Gilliatt, 1971; Spencer & Schaumburg,
1974b).
Hopkins & Gilliatt (1971) carried out serial conduction
studies on motor and sensory nerves in baboons, given relatively
large total amounts of acrylamide (10 or 15 mg per day for
several months). Conduction velocity became reduced in all
nerves, the greatest reduction being 38% in the anterior tibial
nerve. This occurred when there had already been considerable
reduction in the amplitude of the evoked muscle action potential.
The authors also studied recovery of conduction velocity and
action potential amplitude on cessation of intoxication. In a
severely affected baboon treated with 15 mg acrylamide/kg body
weight per day for 94 days, the amplitude of the nerve action
potentials was still reduced after 1 year, but, after 2 years, it
had returned to 80% of normal. The amplitude of the muscle
action potentials of less severely affected baboons (receiving
acrylamide at 10 mg/kg body weight per day for 89 or 115 days)
returned to normal within 2 - 3 months.
Sumner & Asbury (1974) measured conduction velocities in
single sensory nerve fibres in acrylamide-intoxicated cats. They
reported that the earliest change was failure of muscle spindle
(type 1a) and Golgi tendon organ (type 1b) afferent terminals to
initiate impulses. An important conclusion of the single fibre
study was that no reduction in conduction velocity could be
demonstrated in surviving nerve fibres or in the proximal parts
of fibres that had degenerated peripherally. These findings
confirm the suggestion that reduction in MCV is due to
degeneration of the largest, most rapidly conducting nerve
fibres. Lowndes et al. (1978) studied the changes in the
responses of primary and secondary endings of muscle spindles
during the early stages of acrylamide intoxication in the cat.
They reported that the earliest detectable change was an elevated
threshold and diminished response of muscle spindle endings,
which occurred prior to abnormalities in neuromuscular function.
These findings confirmed previous data that large diameter
sensory fibres are involved early in the toxicity. Surviving
axons did not display any slowing of conduction velocity.
Von Burg et al. (1981) determined the conduction velocities
of sensory and motor nerves, both in vivo and in vitro, in
mice administered acrylamide (300 mg/kg body weight per week,
ip). Despite an early decrease in isolated sensory (sural) nerve
conduction velocity, a significant reduction (13%) was not
observed until the third week of treatment, when tibial nerve MCV
was also reduced (20%). Similarly, significant in vivo
differences in conduction velocity were not observed until the
third week, when the conduction velocities of the sciatic-sural
and sciatic-tibial nerves were reduced by 24% and 43%,
respectively, although a reduced velocity of the sciatic-sural
nerve was first observed after 2 weeks of treatment.
Anderson (1981) studied nerve action potentials using
isolated sural and sciatic nerves from rats given a cumulative
dose of 100 mg/kg body weight. A change in the waveform of the
sural nerve action potential and an increase in the relative
refractory period were observed as little as 24 h after a single
dose of 100 mg/kg body weight. In a further study (Anderson,
1982), no effects were observed on sciatic nerve action
potential, amplitude, or velocity 24 h after administration of
25 - 100 mg/kg body weight, despite a significant increase in the
duration of the evoked muscle action potential. The significance
of these findings in the context of early nerve changes is not
clear.
7.1.2.2. Central nervous system effects
There have been relatively few electrophysiological studies
on the central nervous system. Kuperman (1958) found
electroencephalographic (EEG) abnormalities in acrylamide-treated
cats prior to the development of ataxia (Table 8). These studies
clearly indicated that the primary neural locus was subcortical
and it was proposed that this locus was the mesencephalic
tegmentum. The effects of acrylamide on spinal cord function
were investigated in the cat by Goldstein & Lowndes (1979).
Animals receiving 7.5 mg acrylamide/kg body weight per day were
observed to have a reduced unconditioned spinal monosynaptic
reflex (MSR), when the cumulative dose reached 75 mg/kg body
weight, with no observable signs of peripheral neuropathy.
Boyes & Cooper (1981) measured the far-field somato-sensory-
evoked potentials (SSEPs) in acrylamide-intoxicated rats in order
to determine the location of dysfunction in the specific
somatosensory pathway. The results indicated that damage may
have occurred throughout the ascending somato-sensory system
without damage to cortical areas.
Table 8. Dose-effect relationship between EEG change and signs of acrylamide intoxication in catsa
------------------------------------------------------------------------------------------------------
Daily dose Number of Number Days to 25% Cumulative dose resulting in:
(mg/kg cats showing 25% increasec 25% increaseb Maximum Ataxiac First neurolog-
body frequency (range) increasec (mg/kg) ical deficit
weight) increaseb (mg/kg) (mg/kg) (range in mg/kg)
------------------------------------------------------------------------------------------------------
15 5 4 4.5 ± 2 60 - 75 86 ± 11 95 ± 4 75 - 105
25 9 6 3.3 ± 25 25 - 75 71 ± 11 104 ± 15 50 - 100
40 6 6 2.8 ± 29 40 - 80 80 ± 0 80 ± 0 40 - 80
65 5 4 1.3 ± 7 65 65 ± 0 65 ± 0 65
Total 25 20
------------------------------------------------------------------------------------------------------
a Adapted from: Kuperman (1958).
b Asynchronous high-frequency pattern.
c Mean ± percent SD.
Short-latency somatosensory evoked potentials (SLSEP) in
monkeys during acrylamide intoxication were studied by Arezzo et
al. (1982). The potential produced by activity at the rostral
end of the fasiculus gracilis (SLSEP2) was reduced, before
abnormalities were detected in other central tracts or peripheral
nerves.
Electrophysiological evidence of damage to optic nerve
components was reported by Vidyasagar (1981). Alterations in
visual-evoked potentials (VEPs) in female monkeys (macaque) were
reported by Merigan et al. (1982) following short-term acrylamide
exposure. VEP latencies were prolonged after 20 daily doses (10
mg/kg body weight per day), well before overt signs of toxicity
appeared.
7.1.3. Morphological effects
The histopathological effects of acrylamide in peripheral
nerves were investigated by Fullerton & Barnes (1966). At doses
inducing clinical effects in animals (section 7.1.2.1), primary
axonal degeneration was observed with secondary demyelination of
the sciatic, tibial, median, and ulnar nerves (as seen in
Wallerian degeneration). Distal nerve segments were more
severely affected than proximal segments. Medium- to large-
diameter fibres (8 - 9 µm) were more susceptible to degeneration.
Hopkins & Gilliatt (1971) also reported that the longest and
largest fibres (10 - 16 µm) of both motor and sensory nerves were
most severely affected in acrylamide-intoxicated baboons (19
mg/kg body weight per day for 118 days). No abnormalities were
reported in the proximal sciatic nerve or spinal cord in animals
exhibiting severe peripheral axonal (distal) degeneration
(Fullerton & Barnes, 1966).
Ultrastructural changes in the nerves of cats, administered
3 mg acrylamide/kg body weight per day in the drinking-water (252 -
294 days), were studied by Schaumburg et al. (1974). Tissue
biopsies from hind feet, after completion of the study, showed a
loss of all types of myelinated fibres in distal nerves. Only a
few small and large myelinated nerve fibres were seen in plantar
nerve twigs and most fibres had completely degenerated (bands of
Bungner). Many unmyelinated nerve fibres were present. Most of
the muscle fibres were vacuolated and shrunken.
In studies by Gipon et al. (1977), significant swelling in
terminal axons and arborizations in rat muscle were reported at a
cumulative dose of acrylamide of 550 mg/kg body weight (50 mg/kg,
every other day). At this dose, 50 - 60% of large peripheral
nerve fibres showed signs of degeneration. No histological
abnormalities were reported in the spinal cord, but the
techniques employed may not have been adequate.
Axonal degeneration in cats given 10 mg acrylamide/kg body
weight per day was evident by 49 days and was preceded by massive
accumulation of neurofilaments and enlarged mitochondria in the
peripheral nerve fibres, which were evident by 22 days (Prineas,
1969). Similar findings were reported in the sciatic nerves of
adult and suckling rats (4 - 12 injections of acrylamide at 50
mg/kg body weight, 3 doses per week), when no evidence of
abnormalities could be seen by light microscopy (Suzuki & Pfaff,
1973). Accumulation of neurofilaments and invaginations of the
axolemna have also been observed under similar conditions in dogs
(Thomann et al., 1974; Satchell et al., 1982).
In a study by Schaumburg et al. (1974), morphological changes
in the terminals of sensory and motor nerve fibres were examined
in the paws of cats administered acrylamide intraperitoneally at
10 mg/kg body weight per day, for 7 - 32 days. Pacinian
corpuscle axons in the hind feet were the first terminals to
display degeneration. The first change was a loss of filopod
axonal processes, sometimes accompanied by neurofilamentous
hyperplasia. The axolemna disappeared and the axoplasm was
phagocytosed by inner core cells. Shortly afterwards, changes
were seen in juxtaposed Pacinian corpuscles, followed by
degeneration of primary annulospiral endings of muscle spindles,
secondary muscle spindle endings, and motor nerve terminals, in
that order. All these endings accumulated neurofilaments prior
to degeneration. These results not only demonstrated
ultrastructural changes prior to clinical signs, but also that
sensory nerve terminals were more sensitive than motor nerve
terminals. Unmyelinated fibres in somatic nerves were observed
to be relatively resistant to the effects of acrylamide.
Concurrent with axonal degeneration and secondary myelin
breakdown, Suzuki & Pfaff (1973) reported the appearance of
endoneural macrophages and a proliferation of Schwann cells in
the sciatic nerves of adult rats after 26 injections of
acrylamide (50 mg/kg body weight, 3 doses per week). After 4
injections, microscopic examination revealed myelin figures in
Schwann cells and enlarged fibres within the sciatic nerve. These
changes became more prominent after 8 injections. Examination of
nerves from rats receiving 26 injections revealed numerous axonal
sprouts growing within the Schwann cells. Honeycomb-like
interdigitation of Schwann cell-axon networks was observed prior to
hind limb weakness in acrylamide-intoxicated rats (Spencer &
Schaumburg, 1977). Ultrastructural observations in mice led to the
suggestion that Schwann cell damage occurred after the onset of
axonal demyelination (Von Burg et al., 1981).
Accumulation of smooth endoplasmic reticulum (SER) and other
organelles within peripheral and central nervous system neuronal
axons has been reported following acrylamide exposure (Cavanagh &
Gysbers, 1981; Chrétien et al., 1981). Such accumulation in
tibial nerves was observed several days before the onset of
axonal degeneration (Cavanagh & Gysbers, 1981). The same changes
have, however, been observed in other toxic neuropathies and are
probably of a non-specific nature.
Regenerating fibres have been found in nerves of rats
administered repeated low doses of acrylamide, as shown by the
presence of fibres with inappropriately short internodal lengths
for their diameter (Fullerton & Barnes, 1966). In long-term
acrylamide intoxication, regeneration may occur simultaneously
with continuing degeneration, but the regeneration is severely
retarded. Kemplay & Cavanagh (1984) reported a prolonged
inhibition of spontaneous sprouting from motor end-plates at the
neuromuscular junction in female rats. This inhibition was
apparent 24 h after a single dose (90 mg/kg body weight) and
lasted for 4 weeks. Acrylamide also reduced the number and
length of reactionary terminal sprouts following partial
denervation.
Degeneration in large sympathetic and parasympathetic and,
therefore, probably sensory-myelinated fibres, demonstrating the
involvement of the autonomic nervous system in acrylamide
neuropathy, has been observed (Post & McLeod, 1977a). Studies in
cats showed impaired neural control of the mesenteric vascular
bed of a type indicating damage to post-ganglionic unmyelinated
fibres (Post & McLeod, 1977b). Acrylamide has been shown to
cause megaoesophagus in greyhounds (Satchell & McLeod, 1981) due
to impairment of mechanoreceptors, the afferent fibres of which
pass through the vagus nerve (Satchell et al., 1982).
Ultrastructural changes in the cell bodies (perikarya) of
dorsal root ganglia (DRG) in cats that had received a cumulative
dose of 320 mg acrylamide/kg body weight subcutaneously, at 10
mg/kg body weight per day, were studied by Prineas (1969). A
disturbance in granular endoplasmic reticulum (GER), a breakdown
in polyribosomes, ribosomal dislocation, and an increase in the
amount of electron-dense material in the cytoplasm were reported.
Using light microscopy, Sterman (1982) detected a spectrum of
perikaryal changes in both large and small neurons of lumbar DRG
in rats administered a cumulative dose of acrylamide at 350 mg/kg
body weight (50 mg/kg body weight per day). These changes
occurred prior to significant peripheral nerve damage and
included nuclear eccentricity, peripherally-located Nissl bodies,
and increased numbers of perineuronal cells. In a further study,
Sterman (1983) observed ultrastructural changes between days 5
and 9 of acrylamide treatment (50 mg/kg body weight per day).
Quantitative morphometric study revealed significant perikaryal
modifications after 5 - 6 days of treatment, which had progressed
by 8 - 9 days. Qualitatively, altered profiles had nuclear
eccentricity and capping, marked changes in mitochondrial
morphology, and modifications of ribosomes and Nissl granules.
Neurons that appeared normal by light microscopy often displayed
ultrastructural changes.
The results of microscopic examination of the brain and/or
spinal cord have been reported in acrylamide-intoxicated rats
(Fullerton & Barnes, 1966), mice (Bradley & Asbury, 1970), cats
(Kuperman, 1958; McCollister et al., 1964), dogs (Thomann et al.,
1974), and monkeys (McCollister et al., 1964). No abnormalities
attributable to acrylamide were reported in these studies.
Prineas (1969) demonstrated ultrastructural changes in nerve
fibres and boutons terminaux in the anterior spinal grey matter
after subcutaneous injection of a cumulative dose of 320 mg
acrylamide/kg body weight (10 mg/kg per day). Small myelinated
fibres frequently contained excessive numbers of neurofilaments
associated with local fibre swelling. Similarly, 5 - 15% of the
boutons terminaux were enlarged and contained large numbers of
neurofilaments. At the cervical level, in the latter stages of
intoxication (between 32 and 49 days), there were pronounced
changes in the gracile nucleus. Small myelinated fibres
displayed neurofilamentous hyperplasia, many mitochondria, dense
body and fine granular material, and unusual tubulo-vesicular
profiles. Myelin degeneration and axonal abnormalities were
rarely observed.
A selective and progressive loss of Purkinje cells, in the
cerebella of rats administered 30 mg acrylamide/kg body weight
per day, was visible from 5 days onwards (Cavanagh, 1982). The
ultrastructural features of Purkinje cell damage in the rat have
been studied in detail by Cavanagh & Gysbers (1983). No other
species has so far been studied for these effects.
Information on other CNS pathology in acrylamide neuropathy
is sparse. Suzuki & Pfaff (1973) demonstrated degeneration of
spinal cord white matter and the presence of axonal spheroids in
the cuneate nuclei in the medulla oblongata of rats (cumulative
dose of 1300 mg acrylamide/kg body weight), and Prineas (1969)
reported extensive fibre destruction in the dorsal spino-cerebellar
tracts in the medulla of cats. Widespread swelling of terminals
was noted by Cavanagh (1982) in the gracile and cuneate nucleii
(10th day onwards), and in lumbar and cervical grey matter and
superior colliculi (14th day onwards), following ip administration
of acrylamide (30 mg/kg body weight per day) to rats. Apart from
Purkinje cell axons, degeneration was uncommon in the CNS regions
affected.
In summary, long-term absorption of 10 mg acrylamide/kg body
weight per day, or more, leads consistently to degeneration of
the distal regions of long sensory, and, later, motor peripheral
nerve fibres and, also, to a lesser degree, to degeneration of
the distal regions of long axons in spinal cord tracts. These
changes are preceded by accumulation of neurofilaments in the
distal regions of many axons of the peripheral nervous system
(PNS) and in the boutons terminaux in the CNS. Degeneration of
Purkinje cells of the cerebellum may occur early in intoxication
with large doses. Subsequently, degenerative changes also occur
in autonomic nerve fibres.
7.1.4. Biochemical effects
The primary biochemical interaction responsible for the
pathogenesis of acrylamide-induced neuropathy is not known.
However, the effects of acrylamide on various neuronal metabolic
processes have been the subject of considerable investigation in
attempts to elucidate the mechanism of toxicity. These effects
are discussed in detail in the following sections.
7.1.4.1. Effects on axonal transport
Pleasure et al. (1969) injected cats with 3H-leucine and
compared the flow rates of radiolabelled proteins along axons of
motor and sensory neurons. An absence of slow axonal transport
was reported in most acrylamide-treated animals. This was
considered to be due to inhibition of protein synthesis or to a
slight defect in the transport mechanism. It is suggested that
acrylamide interferes with "slow" axonal transport and, that such
an abnormality might result in the observed distal axonal
degeneration.
In a subsequent study, Bradley & Williams (1973) injected
3H-L-leucine into the seventh lumbar dorsal root ganglion.
Contrary to the findings of Pleasure et al. (1969), no change was
found in slow axonal transport (1 - 5 mm/day) in acrylamide-
treated cats; however, there was a decrease in the velocity of
"fast" axonal transport (100 - 500 mm/day). Griffin et al. (1977)
observed a smaller proportion of transported radioactivity (from
3H-leucine) beyond a nerve crush (sensory and motor) in acrylamide-
treated rats. Electromicroscopic autoradiography studies indicated
that this difference might reflect changes in membrane permeability
followed by impaired sprouting of acrylamide-regenerating nerves
rather than an abnormality in fast axonal transport. This
particular abnormality of regenerative capacity has not been seen
with other neurotoxic agents, so far examined.
Inhibition of "anterograde" transport of acetylcholinesterase
(AChE) (EC 3.1.1.7) was demonstrated by Rasool & Bradley (1978)
and Couraud et al. (1982) in ligated sciatic nerves of
acrylamide-intoxicated rats. A marked decrease in the 3H-
colchicine binding (75%) capacity in sciatic nerves (distal
segments) was also reported in these animals (colchicine
interferes with protein transport in peripheral nerves by binding
with tubulin, the major protein component of neurotubules) (James
et al., 1970). As only 5% of nerve fibres underwent
degeneration, a decrease in colchicine binding could not be
attributed to a loss of neurotubular protein during axonal
degeneration. It was concluded that the decrease in the axonal
transport rate of AChE in acrylamide-treated rat sciatic nerves
was probably the result of changes in the biophysical
characteristics of the microtubules.
Souyri et al. (1981) studied the transport of proteins in the
ciliary ganglia of acrylamide-treated chickens after an
intracerebral injection of 3H-lysine. Multifocal retention of
labelled proteins occurred in certain preganglionic axons,
reflecting a local stasis of fast proteins transported in the
axonal periphery. In a follow-up study, Chrétien et al. (1981)
demonstrated that the sites of abnormal retention of fast
proteins in the ciliary ganglia of chickens were associated with
multifocal lesions of smooth endoplasmic reticulum (SER),
characterized by a complex network of tubules intermingled with
vesicles and mitochondria. It was reported by Couraud et al.
(1982) that a 5-fold increase in the A12 form of AChE in the
sciatic nerves of acrylamide-treated chickens was associated with
focal disorganizations of SER. These changes in axonal
concentrations were found to coincide with a 60% reduction in A12
AChE anterograde transport. This observation was in agreement
with previous reports of impaired fast anterograde axonal
transport of AChE in the rat (Rasool & Bradley, 1978). Further
evidence in support of impaired fast anterograde axonal transport
in chickens was obtained from the normal mobilities of the G1 and
G2 molecular forms of AChE that are transported via the slow
axonal transport system (Couraud et al., 1982). In contrast, the
retrograde transport of all AChE forms in chickens was normal.
In a study on rats administered acute doses of acrylamide, no
anterograde transport abnormalities were observed in sciatic
sensory fibres (Sidenius & Jakobsen, 1983). However, in a
similar study by Jakobsen & Sidenius (1983), retrograde build-up
of protein label was significantly reduced after an acute dose of
100 mg/kg body weight. Not only was this abnormality observed
before neurological signs of neuropathy (motor incoordination)
had appeared, but it had improved by the time these signs
disappeared. Furthermore, the severity of retrograde transport
abnormalities was related to the degree of neurological
disturbance. The retrograde transport of horseradish peroxidase
(HRP) in rat trigeminal motor neurons was inhibited after a
cumulative dose of 150 mg acrylamide (30 mg/kg body weight per
day) (Kemplay & Cavanagh, 1983). The relationship between
altered retrograde transport and acrylamide neurotoxicity was
recently studied in rats (Miller et al., 1983) using labelled
iodinated nerve growth factor 125I-NGF). They reported that a
significant inhibition in retrograde transport that appeared at
75 mg/kg body weight was correlated with the cumulative dose and
preceded detectable peripheral nerve dysfunction (seen at 225
mg/kg). It was suggested that a reduction in retrograde
axoplasmic transport might reflect the primary biochemical event
in acrylamide-induced neuropathy.
7.1.4.2. Effects on energy production and neuronal metabolism
The effects of acrylamide on various pathways in intermediary
metabolism have been extensively investigated. Hashimoto &
Aldridge (1970) investigated the effects of acrylamide on in
vitro and in vivo mitochondrial respiration. It was concluded that
oxidative phosphorylation was unaffected, as no effects were
observed on oxygen uptake and on the ratios of pyruvic and lactic
acid concentrations in brain cortex slices.
Acrylamide might affect pyridine nucleotide (NADP) metabolism
or function (Kaplan et al., 1973), which could account for the
greater sensitivity of cats to acrylamide compared with other
mammals (cats are unable to convert tryptophan to nicotinamide).
Johnson & Murphy (1977) found that rats administered a cumulative
dose of acrylamide of 668 mg/kg body weight had elevated levels
of NAD+ in the cerebral cortex, but there was little evidence of
interference with pyridine nucleotide function. In a study by
Sharma & Obersteiner (1977a), the acrylamide-induced inhibition
of nerve growth and neuroglia cell growth in chicken embryo
cultures was attenuated by the addition of nicotinamide, NAD,
NADP, and glutathione. More recently, Loeb & Anderson (1981)
found that supplementing the diet with vitamin B6 (which consists
of substituted pyridines) delayed the onset and severity of
acrylamide toxicity in rats.
Acrylamide may affect axonal function by interfering with
glycolysis (Spencer et al., 1979). Howland et al. (1980) and
Sabri & Spencer (1980) reported that acrylamide inhibited
glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (EC 1.2.1.9),
phosphofructokinase (PFK), and neuron-specific enolase (NSE) (EC
4.2.1.11) activities in vitro. Lactate dehydrogenase (LDH) (EC
1.1.1.27) (an enzyme not directly involved in energy production)
was not affected. The association of acrylamide neuropathy with
inhibition of glycolysis is supported by the results of a study
by the same group (Dairman et al., 1981), in which the diet of
acrylamide-exposed rats was supplemented with pyruvate (a key
molecule in glycolysis). The authors reported that treated rats
were protected from the neurotoxic effects of acrylamide.
However, results of a similar study by Sterman et al. (1983a)
failed to show a protective effect on acrylamide-intoxicated rats
despite a 2-fold increase in the dose of pyruvate. Howland
(1981) studied the effects of acrylamide on the activities of
neuron-specific enolase, glyceraldehyde-3-phosphate, and
phosphofructokinase in the peripheral nerve (sciatic), spinal
cord, brain, and skeletal muscle of acrylamide-treated cats
(acrylamide administered at 15 mg/kg body weight per day or 30
mg/kg per day, sc, for 10 days). Phosphofructokinase activity
was not affected in any of the tissues studied. A decrease in
the activity of both neuron-specific enolase and glyceraldehyde-
3-phosphate was found in both the CNS and the PNS. In proximal
peripheral nerve, only glyceraldehyde-3-phosphate activity was
reduced. However, in the distal segment, where both neuron-
specific enolase and glyceraldehyde-3-phosphate activities were
diminished, the former showing a greater decrease (60%) than the
latter (25%), at both doses of acrylamide. A decrease in the
activity of enolase isoenzymes was found to be specific to
neurons, whereas glyceraldehyde-3-phosphate was also
significantly reduced in skeletal muscle. From these results,
Howland (1981) suggested that the inhibition of neuron-specific
enolase might account for the tissue specificity of acrylamide
toxicity.
The effect of acrylamide on perikaryal protein metabolism has
been extensively investigated. Hashimoto & Ando (1973) observed
a decrease in the in vitro incorporation of [14C] lysine into
the sciatic nerve of acrylamide-treated (500 mg/kg diet) rats
before the onset of neurological symptoms. After 4 weeks, when
neurological signs developed, an increase in radiolabel was seen
in the spinal cord, which was interpreted as an increase in
protein metabolism because of repair processes. In studies by
Kemplay & Cavanagh (1983), a more rapid removal of horseradish
peroxidase (HRP) from motor neurons was observed in acrylamide-
treated rats compared with controls, suggesting that the
perikaryon is more catabolically active as a consequence of
acrylamide intoxication. A 60% reduction in radiolabel was found
in the anterior horn cells (AHCs) of the lumbar spinal cord of
mice given acrylamide at 250 mg/litre in the drinking-water, 7
days after ip administration of [3H] leucine (Asbury et al.,
1973). Clinical signs of neuropathy appeared between 14 and 21
days after treatment. Ultrastructurally, no alterations were
seen in the AHCs. In a later study, Schotman et al. (1977)
measured the in vivo incorporation of [3H] leucine into proteins
of the spinal cord, brain stem, and heart of acrylamide-treated
rats. The incorporation of radioactivity into the spinal cord
and brain stem decreased at a time when animals displayed
clinical signs of neuropathy. Increased incorporation of
radiolabel was observed following cessation of exposure. A
similar depression was also observed in heart muscle. In the
recovery period, however, labelling of heart proteins was normal.
No changes were observed in the incorporation of [3H] leucine
into proteins in vitro.
The above observations indicate a relationship between
changes in protein metabolism and acrylamide-induced neuropathy.
7.1.4.3. Effects on CNS neurochemistry
Dixit et al. (1981c) investigated the effects of acrylamide
exposure (25 mg/kg body weight, per day, orally, for 21 days) on
the metabolic disposition of neurotransmitters in the rat brain.
A significant reduction was reported in the levels of dopamine
(DA), noradrenaline (NA), and 5-hydroxytryptamine (5-HT) in whole
brain, at days 14 and 21 of treatment (chronic convulsions and
mild ataxia were apparent after 14 days of treatment). The
distribution of these neurotransmitters in selected regions of
the brain was also found to be significantly different from that
in the controls. Increased monoamine oxidase (EC 1.4.3.4)
activity (involved in the breakdown of catecholamines) was also
detected at all stages of treatment. However, this increase was
not considered to be directly attributable to the observed
decrease in neurotransmitters. Farr et al. (1981) reported a
dose-dependent increase in the whole brain concentration of
5-hydroxyindoleacetic acid (5-HIAA) in rats administered acrylamide
at 5, 15, or 50 mg/kg body weight, per day, for 5 days. Since
neither the level nor turnover rate of 5-HT were affected, it was
suggested that acrylamide interfered with the normal efflux of
5-HIAA from the brain. Using the same dosing regime, Aldous et al.
(1981) found that acrylamide caused a significant increase in the
levels of dihydroxyphenylacetic acid (DOPAC) in the brains of rats
in the 5 and 50 mg/kg body weight per day groups. As there was no
effect on the rate of DA turnover, the authors concluded that
acrylamide had an inhibitory effect on the normal efflux of DOPAC
from the brain. In a recent report, Fatehyab Ali et al. (1983)
determined the levels of DA and 5-HT and their acid
metabolites in several brain regions of the rat. Both single (50
or 100 mg/kg body weight) and repeated (10 mg/kg body weight per
day for 10 days) doses of acrylamide resulted in elevated levels
of 5-HIAA in all regions studied. The level of 5-HT was also
significantly elevated in the frontal cortex and brain stem.
These responses were dose-dependent. Turnover studies, following
inhibition of monoamine oxidase (EC 1.4.3.4) (with pargyline),
indicated that elevated 5-HIAA levels occurred because of an
increased rate of 5-HT catabolism. The only changes in DA and
DOPAC levels were found in the frontal cortex after repeated
administration (10 days) of acrylamide.
Changes in neuropeptide levels were also observed (Fatehyab
Ali et al., 1983) 24 h after a single injection of acrylamide (50
or 100 mg/kg body weight). At the higher dose, elevated levels
of beta-endorphin and sustance P were detected in the hypothalamus,
whereas neurotensin was decreased in the striatum, only at the
lower dose.
Recent studies have focused attention on the effects of
acrylamide on receptor binding in the CNS. Agrawal et al.
(1981b) first reported that rats receiving acrylamide at 25 - 100
mg/kg body weight, orally, had elevated [3H] spiroperidol binding
in the striatum, 24 h after dosing. No significant changes were
observed in striatal DA levels. Results showed that acrylamide
increased both the affinity for spiroperidol and the number of DA
receptor sites. In a similar study by Uphouse & Russell (1981),
rapid changes were detected in [3H] spiroperidol binding and 5-HT
binding 30 min and 2 h, respectively, after acrylamide treatment
(100 mg/kg body weight). For spiroperidol binding, 2 peaks were
observed during the 24-h period following dosing.
When acrylamide was administered prenatally to rats, a
reduction in striatal dopamine binding sites occurred in the
offspring, the opposite effect to that seen in adults (Agrawal &
Squibb, 1981a). A return to normal values in spiroperidol
binding was observed within the first 3 weeks after birth.
Similarly, effects in adults were also reversible; normal values
were restored within 8 days of cessation of dosing (Agrawal et
al., 1981a; Uphouse & Russell, 1981). In a subsequent study
(Agrawal et al., 1981b), attempts were made to determine the
specificity of receptor binding changes following a single oral
dose of 25 - 100 mg acrylamide/kg body weight. A significant
increase in the level of striatal [3H] spiroperidol binding was
observed in rats exposed to 25 or 50 mg/kg body weight.
Significant increases in glycine in the medulla and 5-HT in the
frontal cortex were observed after 100 mg/kg body weight. No
changes were seen in muscarinic binding in the striatum,
benzodiazepine binding in the frontal cortex, or qamma-
aminobutyric acid binding in the cerebellum. Hong et al. (1982)
showed that acrylamide could affect the postsynaptic DA receptor.
Postsynaptic receptors in rats were destroyed by the injection
into the striatum (unilaterally) of kainic acid. When animals
were injected with acrylamide (cumulative 200 mg/kg body weight
over 14 days), significant increases in [3H] spiroperidol binding
were observed in uninjected striata only. A parallel acrylamide
treatment of uninjected animals did not have any significant
effects on striatal levels of dihydroxyphenylacetic acid and
homovanillic acid, suggesting that presynaptic events were
unaffected. The results of studies on the effects of acrylamide
on apomorphine-induced stereotypes (Agrawal et al., 1981a; Bondy
et al., 1981; Tilson & Squibb, 1982) also suggest a postsynaptic
location of altered DA receptors.
In an attempt to determine the functional significance of
changes in DA receptor binding, the effects of psychoactive
compounds on motor activity were investigated in acrylamide-
treated rats. Apomorphine-induced motility was significantly
attenuated, 24 h after a single dose of 100 mg/kg body weight
(Agrawal et al., 1981a) and after doses of 10 mg/kg per day for
10 days (Bondy et al., 1981), indicating a change in the
sensitivity of the DA receptor. Similarly, Rafales et al. (1982)
observed an increased locomotor activity due to a single alpha-
amphetamine challenge in acrylamide-pretreated rats. This
increased sensitivity persisted at least 5 - 6 weeks beyond
cessation of acrylamide treatment. Pretreatment of rats with
acrylamide at 12.5 mg/kg body weight did not have any significant
effect on the behavioural suppressant effects of clonidine
(alpha-adrenergic agonist) and chlordiazepoxide (administered
24 h after acrylamide treatment), but enhanced the effects of
apomorphine and alpha-amphetamine (dopaminergic agonists) (Tilson &
Squibb, 1982). These data support previous work indicating that
acrylamide increases the affinity and density of striatal DA
receptors.
The effects of prior handling on acrylamide-induced
alterations in the striatal DA receptor were investigated by
Uphouse (1981). Rats were either handled or were left
undisturbed for one week prior to oral administration of 100 mg
acrylamide/kg body weight. A reduction in [3H] spiroperiodol
binding was seen, 24 h after exposure to acrylamide, in rats that
had been gentled. However, in "non-handled" animals, significant
effects of acrylamide were not seen. In a further study, Uphouse
et al. (1982) found that serum prolactin levels were
significantly reduced and corticosterone levels, significantly
increased, in acrylamide-exposed (100 mg/kg body weight) "non-
handled" animals.
7.2. In Vitro Toxicity Studies
The use of in vitro tests in the screening of acrylamide
for mutagenic effects is described in section 7.4.1. There
have been a small number of studies on the toxicity of
acrylamide in isolated cell systems. Hooisma et al. (1980)
investigated the neurotoxic and cytotoxic effects of various
concentrations of acrylamide on several cell culture systems
(chick spinal ganglia, chick muscle cells plus spinal cord
explant, C1300 neuroblastoma cells, Chinese hamster ovary
(CHO) cells, and new-born rat cerebral cells). Results
indicated that the new-born rat cerebral cell culture was the
most sensitive assay, exhibiting a dose-related and
statistically-significant reduction in the number of neurons
with neurites, after a 16-h exposure to acrylamide solutions
of 7.1 µg/litre and 710 µg/litre. Of the other cell types
investigated, only the neurons of chick spinal ganglia were
affected, and then only at a high concentration (7.1 mg/litre).
Sharma & Obersteiner (1977a) also used chick spinal ganglia
(dorsal root) to investigate the short-term neurotoxicity of
acrylamide. Morphological alteration of nerve fibres and
neuroglia provided the criteria for the quantification of
effects. The concentrations of acrylamide producing half-maximal
effects for nerve fibres and neuroglia were 15 mg/litre and 27
mg/litre, respectively; these concentrations are in agreement
with those reported by Hooisma et al. (1980). The addition of
NAD, NADP, nicotinamide, and glutathione (10-4 M) protected
against the cytotoxic effects of acrylamide (7.1 mg/litre) to
different extents (Sharma & Oberstemer, 1977a). Ericsson & Walum
(1984) reported that acrylamide at concentrations of 35 - 350
mg/litre elicited dose-dependent cytotoxic effects in cultures of
rat glioma or mouse neuroblastoma cells. The addition of
phenobarbital-induced chick hepatocytes increased the toxicity of
the highest concentration of acrylamide (350 mg/litre) for both
cell types, but only significantly for neuroblastoma cells.
The use of in vitro studies in the investigation of the
effects of acrylamide on neuronal biochemistry has already been
described (section 7.1.3).
7.3. Effects on Other Organs
A few reports on non-neurological effects have been reported
following both acute and long-term acrylamide administration.
Congestion of the lungs and kidneys was reported by
McCollister et al. (1964), after adminstration of a lethal dose
(200 mg/kg body weight) of acrylamide to a monkey. Microscopic
examination of the kidneys revealed degeneration of the
convoluted tubular epithelium and glomerular degeneration with
albuminous material in the capsular space. Examination of the
liver revealed congestion of the sinusoids with fatty
degeneration and necrosis.
An accumulation of porphyrins in the liver was reported by
Edwards et al. (1978), 5 h after subcutaneous administration of
acrylamide at 1.5 mmol/kg body weight (107 mg/kg) to rats (Porton
strain). An increase in serum aspartate aminotransferase (EC
2.6.6.1) and leucine aminopeptidase (EC 3.4.11.1) was found in
rats after long-term administration of 5 mg acrylamide/kg body
weight, per day, indicating an impairment of liver function. An
increase in blood thiol levels in rats followed a single dermal
application of acrylamide at 320 mg/kg body weight (Novikova,
1979).
Another report (Hashimoto & Aldridge, 1970) showed a rapid
fall and a gradual return of non-protein sulfhydryl content in
liver as well as in brain and spinal cord, after a single oral
dose of acrylamide in rats.
Sterman et al. (1983b) found that administration of 50 mg
acrylamide/kg body weight, per day, to rats caused a significant
increase in heart rate and systolic arterial blood pressure,
apparent after the first dose, and progressing throughout the
exposure period. Although the exact morphological correlates of
this dysfunction are not known, these findings expand the work of
Post & McLeod (1977a,b) (section 7.1.3), which demonstrated an
involvement of the autonomic nervous system in acrylamide-induced
neuropathy.
Degeneration of seminiferous tubules has been reported after
short-term administration of acrylamide to mice (Hashimoto &
Tanii, 1981) and rats (McCollister et al., 1964). Huang et al.
(1982) reported atrophy of the epididymal fat pad, accompanied by
a severe triglyceride depletion and an increase in tissue
phospholipids and cholesterol, following ip injection of
acrylamide in rats at 50 mg/kg body weight, per day, for 10 days.
Animal studies have shown that acrylamide is an eye and skin
irritant. When acrylamide (concentration not reported) was
applied to the crown of rabbits' heads, dermatitis, scab
formation, burns, and ulceration occurred (Hashimoto, 1980).
Reddening of the skin was observed in rabbits treated with dermal
applications of 500 mg acrylamide/kg body weight (12.5% solution)
(McCollister et al., 1964). The effects of eye contact with
aqueous solutions containing acrylamide levels of 100 - 400
g/litre were also studied by McCollister et al. (1964). The
application of a 10 g/litre solution produced discomfort and mild
conjunctival irritation (recovery was complete within 24 h). The
application of a 40 g/litre solution caused signs of moderate
pain, slight conjunctival irritation, and corneal injury (corneal
healing complete within 24 h).
7.4. Genotoxic Effects and Carcinogenicity Studies
7.4.1. Mutagenicity and other related short-term tests
Incorporation of low levels of acrylamide into RNA and DNA,
isolated from the liver and brain of rats 24 h after iv
administration of 100 mg [1-14C]-acrylamide/kg body weight, was
demonstrated by Hashimoto & Aldridge (1970): some of the
radiolabel was available to the carbon pool.
Acrylamide (purity unspecified) inhibited transfection of
colitis bacteriophage DNA in Escherichia coli CR 63 cells
(Vasavada & Padayatty, 1981) and resulted in a weak induction of
the amplification of SV40 DNA inserts in Chinese hamster CO60
cells, suggesting that acrylamide may produce DNA damage.
Acrylamide (purity > 99%) was not mutagenic in Salmonella
typhimurium TA 1535, TA 1537, TA 98, and TA 100, with and
without metabolic activation systems, in both plate and liquid
suspension assays (Bull et al., 1984). Similar results were
reported by Lijinski & Andrews (1980). Mukhtar et al. (1981)
found acrylamide to be non-mutagenic in S. typhimurium TA 100.
Negative results in Ames standard tester strains were also
reported (US EPA, 1982a).
American Cyanamid (US EPA, 1982a) reported that acrylamide
did not induce sister-chromatid exchanges (SCEs) in Chinese
hamster ovary cells and was inactive in an in vivo micronucleus
test on mice. No details of dosing were given.
An increase was found in the frequency of chromosome
aberrations in the primary spermatocytes of mice treated with
100, 150, or 250 mg acrylamide/kg body weight (purity
unspecified) administered intraperitoneally and in mice
administered a diet containing 500 mg acrylamide/kg for 3 weeks
(Shiraishi, 1978). The frequency of chromosomal aberrations was
not increased in bone marrow cells.
Acrylamide was reported to induce cell transformation in
mouse Balb 3T3 cells in the presence of a metabolic activation
system and in BHK 21 cells (US EPA, 1982a).
It should be noted that acrylonitrile, which is genotoxic in
a number of test systems, can occur as an impurity in acrylamide
at concentrations ranging from 1 - 100 mg/kg.
7.4.2. Carcinogenicity studies
Acrylamide (purity > 99%) was tested as an initiator for
skin tumours in groups of 40 female Senar mice. Doses of
12.5, 25, and 50 mg/kg body weight were given 6 times, over a
period of 2 weeks, by gavage, ip injection, or dermal
application. Two weeks later, 1 µg TPA/animal was applied to
the skin in acetone, 3 times weekly, for 20 weeks. All
surviving animals were killed at 52 weeks. Controls received
acrylamide followed by no treatment, or water followed by
TPA. A dose-related increase in skin tumours occurred with
each route of administration. In the same study, groups of 16
male and 16 female A/J mice were administered 1, 3, 10, and
30 mg acrylamide/kg body weight by ip injection, 3 times per
week, for 8 weeks. All animals were killed at 9 months of
age. Dose-related increases in the number of mice with lung
tumours and the number of lung tumours per mouse were
observed. The number of lung tumours per mouse were 0.31 and
0.5 in male and female controls and 1.87 and 2.53 in males and
females receiving the high dose. Similar results were
obtained with oral doses of 6.25, 12.5, and 25 mg/kg body
weight given to groups of 40 male and 40 female A/J mice 3
times per week, for 8 weeks, and killed at 9 months of age
(Bull et al., 1984).
Groups of 90 male and 90 female Fischer 344 rats, 5 - 6 weeks
of age, were administered acrylamide (containing less than 1 - 10
mg acrylonitrile/kg) at 0, 0.01, 0.1, 0.5, or 2 mg/kg body weight
per day in the drinking-water for 2 years. Groups of 10 males
and 10 females were killed at 6, 12, and 18 months. According to
a draft final report (Johnson et al., 1984), increased incidences
of pheochromocytomas, mesotheliomas of the testes, and adenomas
of the thyroid were observed in males. At the 0, 0.01, 0.1, 0.5,
and 2 mg/kg body weight doses, the number of animals with
pheochromocytomas were 3, 7, 7, 5, and 10, respectively; with
mesotheliomas of the testes, 3, 0, 7, 11, and 10, respectively;
and with adenomas of the thyroid, 1, 0, 2, 1, and 7,
respectively. The increased incidences of phenochromocytomas at
the highest dose, mesotheliomas at the 2 highest doses, and
follicular adenomas at the highest dose were statistically
significant.
In female rats, increased incidences of pituitary adenomas,
thyroid follicular tumours, mammary adenomas, adenocarcinomas,
and oral cavity papillomas were observed. At the 0, 0.01, 0.1,
0.5, and 2 mg/kg body weight dose levels, the number of rats with
pituitary adenomas were 25, 32, 27, and 32, respectively; with
thyroid follicular tumours, 1, 0, 1, 1, and 5, respectively; with
mammary adenomas, 10, 11, 9, 19, and 23, respectively; with
adenocarcinomas, 2, 1, 1, 2, and 6, respectively; and with oral
cavity papillomas, 0, 3, 2, 1, and 5, respectively. The
increased incidences of these tumours at the highest dose level
were statistically significant compared with controls, and the
incidence of mammary adenocarcinomas in female rats was
significantly higher than the incidence in controls, when tested
by a trend test.
7.5. Teratogenicity and Reproductive Studies
In a 90-day fetal toxicity study of acrylamide in Sprague-
Dawley rats, female rats received 25 or 50 mg acrylamide/kg diet,
for 2 weeks prior to mating and for 19 days during gestation (US
EPA, 1980b). Evaluation of mortality rate, body weight, food
consumption, mating and pregnancy indices, litter and offspring
data, and gross post-mortem observations did not reveal any
significant differences from controls. There were some fine
structural differences in the nerves of a number of treated
animals, such as scattered fibre degeneration in sciatic nerves
and in one optic nerve; these were considered to be of doubtful
relationship to any acrylamide effect. The brain was
microscopically normal, with no abnormalities in the arrangement
of cellular components or in the degree of cytological
development. There was no evidence of any major teratogenic
effects.
In another study by Edwards (1976a), acrylamide was
administered to pregnant Porton rats either as a single iv dose
(100 mg/kg body weight) on day 9 of gestation or in the diet as a
cumulative dose of either 200 mg/kg or 400 mg/kg between days 0
and 20 of gestation. Apart from a slight decrease in the weight
of individual fetuses from rats dosed with 400 mg acrylamide/kg,
no fetal abnormalities were seen, even at doses that induced
neuropathy in the dams. No neurological abnormalities were
observed in weanling rats. The fetal tissue concentration of free
acrylamide (1.41 ± 0.03 mmol/kg), measured 1 h after iv
administration to the dams, was very close to that obtained in
maternal blood (1.28 ± 0.04 mmol/litre), indicating that
acrylamide crosses the placenta. Ikeda et al. (1983) examined the
intra-litter distribution of [14C] acrylamide in 4 species of
animals (rat, rabbit, dog, and miniature pig) with different
types of placentation. Acrylamide (as 14C) was present in the
fetuses of all 4 species at concentrations inversely proportional
to the number of membrane layers comprising the placenta, i.e.,
fetal concentration in rat > rabbit > dog > pig. The
distribution was uniform throughout all litters in each species
and was independent of fetal sex or uterine position.
The effects of acrylamide on the striatal dopamine receptor
in Fischer 344 rat pups were studied by Agrawal & Squibb (1981).
An oral dose of 20 mg/kg body weight, administered from day 7 to
16 of gestation, did not affect the weight or size of litters
obtained, but did decrease the [3H] spiroperidol (CNS
catecholamine involved in motor control) binding in the striatal
membranes of 2-week-old pups (male and female). The results of
cross-fostering studies indicated that postnatal (lactational) as
well as prenatal effects might account for this abnormality.
Using the same dosing regime, Walden et al. (1981) demonstrated
that both prenatal and lactational exposure to acrylamide had
significant effect on the development of certain intestinal
enzymes (acid phosphatase (EC 3.1.3.2), alkaline phosphatase
(EC 3.1.3.1), beta-glucuronidase, and lactate dehydrogenase (EC
1.1.1.27)) in rat pups. Analysis of milk samples after the
administration of a single oral dose of 14C-labelled acrylamide
(100 mg/kg body weight) on day 14 of lactation demonstrated the
presence of both free and protein-bound compound (Walden &
Schiller, 1981).
No malformations were observed in acrylamide-treated chick
embryos at dose levels that were clearly associated with
embryolethality (Kankaanpää et al., 1979). However, similar
observations were also reported for acrylonitrile, and as this
compound has been demonstrated to be teratogenic in rats (IARC,
1979), the significance of these results is not clear.
An in vitro study by Sharma & Obersteiner (1977a) using
chicken embryo cultures showed a dose-dependent inhibition of
growth of both nerve and neuroglial cells at concentrations of
between 0.7 and 700 mg acrylamide/litre. The addition of
glutathione, NAD, NADP, and nicotinamide reduced or prevented
inhibition.
A marked degeneration of seminiferous tubules was observed by
McCollister et al. (1964) in male rats, during histological
assessment, following a short-term feeding study. Both
testicular damage with degeneration of the epithelial cells of
the seminiferous tubules (Hashimoto & Tanii, 1981) and
spermatocyte chromosome aberrations (Shiraishi, 1978) have been
reported in mice following acrylamide treatment. Fatehyab Ali et
al. (1983) reported that repeated injection of acrylamide (20 mg/kg
body weight, per day, for 20 days) caused a major depression in the
plasma levels of testosterone and prolactin in male Fischer-344
rats.
7.6. Factors Modifying Effects
7.6.1. Chemical modification of acrylamide toxicity
Acrylamide-induced neuropathy can be modified by pre- or
co-administration of various organic compounds.
Agrawal et al. (1981a) found that acrylamide-induced changes
in striatal dopaminergic receptors were completely prevented by
SKF 525A. Pretreatment of rats with SKF 525A enhanced
neurological effects and lethality caused by acrylamide (Kaplan
et al., 1973) (section 6.1.2).
Hashimoto & Tanaii (1981) reported that phenobarbital
treatment reduced both neuro- and testicular toxicities in
acrylamide-treated mice. Pretreatment of rats with either
phenobarbital or DDT caused a significant delay in the onset of
ataxia (Kaplan et al., 1973) (section 6.1.2).
Concurrent administration of methionine with acrylamide has
also been shown to reduce the neurotoxic potency of acrylamide
(Hashimoto & Ando, 1971).
Loeb & Anderson (1981) found that supplementing the diet with
vitamin B6 delayed the onset and severity of acrylamide toxicity
in rats.
It was reported by Dairman et al. (1981) that pretreatment
with sodium pyruvate partially protected rats from the neurotoxic
effects of acrylamide based on morphological, biochemical, and
quantitative behavioural measures. A similar study by Sterman et
al. (1983a) failed to show a protective effect despite a 2-fold
increase in the dose of pyruvate.
When N-hydroxymethylacrylamide was co-administered with
acrylamide, the time to the onset of acrylamide-related
neurotoxic effects was reduced (Hashimoto & Aldridge, 1970).
The toxicity of acrylamide may also be potentiated by the co-
administration of xenobiotics (diethylmaleate cyclohexene oxide)
which, like acrylamide, is metabolized via glutathione conjugation
(Refsvik, 1978).
7.6.2. Age
The few studies on the influence of age on acrylamide
neurotoxicity have produced conflicting results. Fullerton &
Barnes (1966) found that rats aged 52 weeks developed
neurological abnormalities after fewer doses of acrylamide than
young animals aged 5 weeks. Similarly, Kaplan & Murphy (1972)
found that abnormalities of rotarod performance occurred earlier
in rats aged 11 weeks than in those aged 5 weeks. Assessment of
the effects of age on recovery time was not possible because the
duration of dosing differed at different ages.
Dixit et al. (1981b) reported that younger rats exposed to
acrylamide showed an earlier development of paralysis than older
rats. There was also an increased inhibition of hepatic
glutathione- S-transferase (GST) in young rats. Maximum
inhibition of GST was seen on day 15, concurrent with the
development of hind limb paralysis. This suggests that the
enhanced sensitivity of younger animals may be due to reduced
glutathione (GSH) conjugation with acrylamide, which is a
detoxification process (section 6.1.2).
In studies by Suzuki & Pfaff (1973), suckling rats showed
signs of neurotoxicity (weight loss and hind limb weakness) after
5 or 6 injections of 50 mg acrylamide/kg body weight, whereas
adult rats showed signs after 7 or 8 injections. The authors
reported that degenerative changes in the peripheral nerves were
more severe in suckling rats than in adult rats.
Spiroperidol binding was decreased in the striatum of the
offspring of dams that had been administered acrylamide on days
7 - 16 of gestation (Agrawal & Squibb, 1981). The opposite effect
was seen in adult animals (Agrawal et al., 1981a,b). As acrylamide
induces effects on CNS neuro-transmitter functioning, and, as much
development of the central nervous system occurs post-natally in
the rat, it might be expected that early post-natal exposure to
acrylamide would result in permanent CNS damage. However, there
have been few studies on this period of development.
7.6.3. Sex differences
There is little information in the literature regarding the
differences in the responses of male and female animals to
acrylamide exposure. An 18-month interim report on the rat, in a
2-year toxicity-oncogenicity study (US EPA, 1982b), indicated
that both the incidence of neoplasia and the degree of tibial
nerve degeneration were significantly increased in male rats
compared with female rats at a dose level of 2 mg acrylamide/kg
body weight per day.
7.6.4. Species
No major species differences in response to acrylamide
exposure have been reported so far, although the cat has an
increased sensitivity to such exposure. It has been suggested
that acrylamide might produce some of its neurotoxic effects by
affecting pyridine nucleotide metabolism and/or function. The
dimer of acrylamide resembles nicotinamide, and it has been
postulated that the synthesis or metabolism of pyridine
nucleotides in nervous tissue might be inhibited. This could
explain the increased sensitivity of the cat, because it cannot
convert tryptophan to nicotinamide (Kaplan et al., 1973).
Greyhounds exposed to acrylamide developed peripheral neuropathy
that was clinically similar to that observed in other species,
except for the development of megaoesophagus in some exposed
animals (Satchell & McLeod, 1981; Satchell et al., 1982). The
association of megaoesophagus with acrylamide-induced toxicity is
apparently unique to canines.
7.7. Dose-Response and Dose-Effect Relationships
7.7.1. Dose-response relationships
Acute LD50 studies have been performed on various mammalian
species. McCollister et al. (1964) estimated the LD50 for a
single oral dose in rats, guinea-pigs, and rabbits to be about
150 - 180 mg/kg body weight. The susceptibility of cats and
monkeys was similar, with iv or ip injections of 100 - 200 mg/kg
body weight producing severe symptoms or death. Acute values for
other mammalian species are shown in Table 9.
Acute dose-response data for non-mammalian species are
scarce. The LD50 for Japanese quail is 214 (194 - 236) mg/kg
body weight (Cabe & Colwell, 1981). Edwards (1975b) found
considerable variation in the susceptibility of hens to subacute
doses of acrylamide. Out of 9 hens treated with acrylamide (50
mg/kg body weight, orally, 3 times per week), 2 showed ataxia
after 4 doses, 5 after 6 doses, and 2 after 9 doses. Similar
findings were reported in chickens by Souyri et al. (1981).
Terminal histopathology in a 2-year toxicity-oncogenicity
study on acrylamide in Fischer 344 rats revealed a statistically-
significant increase in neoplasms in both male and female animals
at a dose level of 2.0 mg/kg body weight per day (PTCN, 1983;
Johnson et al., 1984). In addition, the incidence of
mesotheliomas of the scrotal cavity was significantly increased
in male rats at a dose level of 0.5 mg/kg body weight per day.
Empirical data from which to construct dose-response
relationships for effects other than lethality are lacking for
aquatic organisms (section 9.1.2).
7.7.2. Dose-effect relationships
Although data from which to construct formal dose-effect
relationships are lacking, a variety of effects have been
investigated during the development of acrylamide-induced
neuropathy and, where possible, these will be discussed in
relation to the minimum doses required to elicit such effects
and/or to the no-observed-adverse-effect levels.
7.7.2.1. Manifestations of neuropathy
The most extensively studied criteria for the assessment of
acrylamide-induced neuropathy have been the signs of neuropathy
observed. A variety of clinical signs resulting from a single
administration of acrylamide (via different routes) to various
mammalian species are given Table 6. Kuperman (1958) reported
that during repeated administration of acrylamide to cats, signs
of ataxia (postural and motor incoordination) appeared at
approximately the same total dose, irrespective of the individual
dosing schedule (Table 10). Similarly, a total dose of 500 - 600
mg/kg body weight, administered in daily (oral) doses of 25, 40,
or 50 mg/kg, was required to produce ataxia in rats (McCollister
et al., 1964; Fullerton & Barnes, 1966). Similar observations
have been made in dogs (Hamblin, 1956; Thomann et al., 1974) and
baboons (Hopkins, 1970).
This relationship between cumulative dose and the onset of
clinical signs is less quantitative after long-term
administration of smaller divided doses. This is exemplified by
the data in Table 11. For example, the cumulative dose of
acrylamide required to induce initial neuropathic effects (hind-
limb weakness) in rats was 1200 - 1800 mg/kg body weight, after
daily administration of 6 - 9 mg/kg body weight, in contrast to
300 - 450 mg/kg, after administration of 20 - 30 mg/kg per day
(Fullerton & Barnes, 1966).
In an attempt to construct a dose-effect relationship in
rats, Hashimoto (1980) found a better correlation with the
severity of symptoms using the estimated "steady state"
concentration of acrylamide in nervous tissue rather than the
cumulative dose (Table 12). From this and other data, Hashimoto
(1980) constructed a graphic relationship between dose,
administration frequency, the estimated mean concentration of
acrylamide in nervous tissue, and the severity of ataxia
following oral administration of acrylamide to rats. In general,
a dosing schedule producing a "steady state" nerve concentration
of between 100 - 300 µmol/kg was predicted to produce slight to
severe ataxia, 300 - 500 µmol/kg, severe ataxia, and above 500
µmol/kg, death.
In a similar study, Young et al. (1979) demonstrated a
relationship between the "plateau" concentration of radiolabelled
acrylamide in the blood and the onset of neuropathy in rats (as
indicated by a foot-splay test). The red blood cell
concentration of radiolabel plateaued at 400 mg acrylamide/kg
after a total dose of 270 mg acrylamide/kg body weight (30 mg/kg,
daily, for 9 days), which directly preceded neuropathic
manifestations. When acrylamide was administered at 0.05 mg/kg
body weight per day, the red blood cell concentration rose to a
level equivalent to 1 mg acrylamide/kg, and no adverse effects
were observed.
Novikova (1979) reported that long-term dermal application of
acrylamide at 5 mg/kg body weight per day to rats' tails
(equivalent to 5% body surface area) induced pronounced
functional neurotoxic effects, characterized by a decrease in
motor activity, impaired conditioned reflex response, and a
reduction in body weight (average 31 g). No consistent adverse
effects were seen at a dose of 0.5 mg/kg body weight per day.
Table 9. Acute LD50 values for acrylamide in mammals
------------------------------------------------------------------------------------------------------
Species Strain Sex Route LD50 (mg/kg Survival time Reference
body weight) (less than)
------------------------------------------------------------------------------------------------------
Mouse albino M oral 170 (130 - 220)a - Hamblin (1956)
Mouse ddy M oral 107 (76 - 151)a 1 week Hashimoto & Sakamoto (1979)
Rat - - ip 120 2 days Druckrey et al. (1953)
Rat Porton F oral 203 (166 - 249)a 3 days Fullerton & Barnes (1966)
Rat Wistar - oral 124 - Paulet & Vidal (1975)
Rat Fisher 344 M oral 251 (203 - 300)a 1 day Tilson & Cabe (1979)
Rat Fisher 344 M oral 175 (159 - 191)a 1 week Tilson & Cabe (1979)
Rat - - dermalb 400 - Novikova (1979)
Guinea- - - oral 170 - Ghiringhelli (1956)
pig
Cat - - iv 85 - American Cyanamid (1961)
------------------------------------------------------------------------------------------------------
a 95% confidence intervals.
b A 4-h application time.
Table 10. Cumulative dose and time to ataxia in cats given repeated
doses of acrylamide (iv and ip)a
-----------------------------------------------------------------------
Dose per day Number of cats Cumulative dose Days to
(mg/kg (mg/kg body ataxia
body weight) weight SD)
-----------------------------------------------------------------------
1 5 101 ± 30 125 ± 26
2 7 132 ± 24 91 ± 18
5 3 78 ± 5 22 ± 3
10 8 126 ± 29 19 ± 6
15 5 102 ± 10 9 ± 11
25 11 102 ± 20 6 ± 2
40 6 73 ± 21 3 ± 1
50 3 100 ± 0 2 ± 0
Total: 48 Mean: 102 ± 6 (SE)
-----------------------------------------------------------------------
a Adapted from: Kuperman (1958).
In a 12-week study on new-born rabbits, haematological,
serum, biochemical, gross, and microscopic examinations did not
reveal any abnormalities in animals administered 0.5 or 5 mg
acrylamide/kg per day. However, clinical signs of neuropathy
were observed in animals administered 50 mg/kg per day (first
seen on day 24) (Drees et al., 1976).
McCollister et al. (1964) reported that doses of 0.3, 0.9,
and 3 mg acrylamide/kg, administered in the diet to rats (10
rats/sex per dose, Dow Wistar strain), for 90 days, did not cause
any adverse effects.
An 18-month interim report (US EPA, 1982b) indicated that
there were no signs of neurological changes in rats (10 rats/sex
per dose) administered acrylamide at doses of 0.01, 0.1, 0.5, and
2 mg/kg body weight per day, though a slight, but significant,
reduction in body weight was seen after 3 months in rats
administered 2 mg/kg per day. A statistically-significant
increase in mortality rate was seen in acrylamide-treated rats
(male and female) at completion of the study (2 years) (Johnson
et al., 1985).
Table 11. Acrylamide doses producing early clinical signs of peripheral neuropathy in various mammals
-------------------------------------------------------------------------------------------------------
Animal Route of Dose Schedule Days to initial Total administered Reference
adminis- (mg/kg effect dose (mg/kg body
tration body (No. of doses) weight)
weight)
-------------------------------------------------------------------------------------------------------
Rat oral 100 2 doses per weeka 21(6)b 600 Fullerton &
(adult) oral 100 1 dose per week 42(6) 600 Barnes (1966)
oral 100 1 dose per 2 weeks 210(15) 1500
ip 75 1 dose per day 4.6c 345 Kaplan & Murphy
(1972)
ip 50 1 dose per day 2(2)d 100 Gipon et al.
(1977)
ip 50 3 doses per week 18(7-8) 350 - 400 Suzuki & Pfaff
(1973)
oral 40 daya 14 560 McCollister et
al. (1964)
ip 40 1 dose per day 6.7c 268 Kaplan et al.
(1973)
oral 30 daya 21 630 McCollister et
al. (1964)
ip 30 1 dose per day 10.7c 321 Kaplan et al.
(1973)
oral 30 1 dose per day 12 360 Loeb & Anderson
(1981)
oral 25 5 doses per week 28(20) 500 Fullerton &
Barnes (1966)
ip 25 1 dose per day 16.8c 420 Kaplan & Murphy
(1972)
oral in 20-30f 5 doses per week 21(15) 300 - 450 Fullerton &
diet Barnes (1966)
-------------------------------------------------------------------------------------------------------
Table 11. (contd.)
-------------------------------------------------------------------------------------------------------
Animal Route of Dose Schedule Days to initial Total administered Reference
adminis- (mg/kg effect dose (mg/kg body
tration body (No. of doses) weight)
weight)
-------------------------------------------------------------------------------------------------------
Rat oral in 15-18f 5 doses per week 28(20) 360 - 630 Fullerton &
(contd.) diet Barnes (1966)
oral in 10-14f 5 doses per week 84(60) 600 - 840 Fullerton &
diet Barnes (1966)
oral 9 daya 56e 504 McCollister et
al. (1964)
oral in 6-9f 5 doses per week 280(200) 1200 - 1800 Fullerton &
diet Barnes (1966)
Cats ip 50 1 dose per day 2(2) 100 Kuperman (1958)
oral 20 1 dose per day 14 - 21 280 - 420 Leswing &
Ribelin (1969)
ip 20 1 dose per day 5 100 Schaumburg et
al. (1974)
ip 10 1 dose per day 13 - 16 130 - 160 Schaumburg et
al. (1974)
oral 10 5 doses per day 26(20) 200 McCollister et
al. (1964)
sc 10 1 dose per day 17 - 22 170 - 220 Prineas (1969)
oral in 3 5 doses per week 68 144 McCollister et
food al. (1964)
oral in 3 1 dose per day 70, 163 210, 489 Schaumburg et
water al. (1974)
ip 1 5-6 doses per week 125 101 Kuperman (1958)
iv 1 5 doses per week 180 130 Hamblin (1956)
-------------------------------------------------------------------------------------------------------
Table 11. (contd.)
-------------------------------------------------------------------------------------------------------
Animal Route of Dose Schedule Days to initial Total administered Reference
adminis- (mg/kg effect dose (mg/kg body
tration body (No. of doses) weight)
weight)
-------------------------------------------------------------------------------------------------------
Dogs oral 15 1 dose per day 21b 315 Thomann et al.
(1974)
Dogs oral 10 1 dose per day 28 - 35b 280 - 350 Hamblin (1956)
(contd)
oral 7 1 dose per day 44 - 67 340 - 460 Satchell &
McLeod (1981)
oral 5 1 dose per day 21b 105 Thomann et al.
(1974)
Mice oral 54 2 doses per week 14(4)c 216 Hashimoto &
Sakamoto (1979)
Rabbits dermal 200 2 doses per week 1 - 3 400 - 1200 Hashimoto (1980)
dermal 50 1 dose per day 24 900 Drees et al.
(1976)
sc 40 2-3 doses per week 14 - 21 240 Inomata (1967)
Primates oral in 25 1 dose per day 42 630 Hopkins (1970)
fruit
oral in 20 1 dose per day 16 320 Hopkins (1970)
fruit
oral in 10 1 dose per day 42 - 97 420 - 970 Hopkins (1970)
fruit
oral in 10 5 doses per week 48(34) 340 McCollister et
water al. (1964)
------------------------------------------------------------------------------------------------------
Adapted from: Conway et al. (1979).
a Signs of intoxication based on electrorod measurements.
b Acrylamide mixed with food; dose estimated by McCollister et al. (1964).
c Signs of intoxication probably appeared earlier than noted.
d Signs of neuropathy based on decreased rearing ability.
e Effect noted in only 1/20 exposed animals.
f Estimated by authors.
Table 12. Dose-effect relationships of repeated acrylamide administration to ratsa
-------------------------------------------------------------------------------------------------------
Route Dose Schedule Days to Cumulative Estimated mean Signs Reference
(mg/kg signs dose (mg/kg concentration
body (number body weight) of acrylamide
weight) of doses) in nervous
tissue (µmol/kg)
-------------------------------------------------------------------------------------------------------
Oral 100 2 doses 21 (6) 600 310 - 450 severe para- Fullerton
per week lysis of & Barnes
hindlimbs (1966)
Oral 100 1 dose 56 (8) 800 150 - 300 severe para- Fullerton
per week lysis of & Barnes
hindlimbs (1966)
Oral 100 1 dose every 240 (24) 2400 90 - 240 severe para- Fullerton
10 days lysis of & Barnes
hindlimbs (1966)
Oral 100 1 dose 28 (4) 400 140 - 280 moderate Fullerton
per week paralysis of & Barnes
hindlimbs (1966)
Oral 100 1 dose every 392 (28) 2800 50 - 200 slight weak- Fullerton
2 days ness of & Barnes
hindlimbs (1966)
Oral 50 5 doses 15 (12) 600 410 - 470 severe weak- Fullerton
per week ness and & Barnes
death (1966)
Oral 25 5 doses 28 (20) 500 230 - 270 slight weak- Fullerton
per week ness of & Barnes
hindlimbs (1966)
Oral 10 5 doses 77 (55) 550 100 - 110 no effects Fullerton
per week & Barnes
(1966)
-------------------------------------------------------------------------------------------------------
a Adapted from: Hashimoto (1980).
In a 1-year feeding study by McCollister et al. (1964),
acrylamide was administered to cats at concentrations of 0.03,
0.1, 0.3, 1, 3, or 10 mg/kg diet per day, for 5 days per week (2
animals per dose level and 2 controls). Cats administered 10
mg/kg per day developed definite weakness of the hind limbs after
26 days. Both cats exposed to 3 mg/kg per day showed twitching
motion in the hindquarters after 26 days and signs of hind-limb
weakness after 68 days. In a study by Schaumburg et al. (1974),
2 cats receiving 3 mg acrylamide/kg per day developed a gait
disorder (after 70 and 163 days, respectively) and hind-foot drop
and muscle weakness within 7 months. One cat receiving 1 mg/kg
per day, for 1 year, showed slight signs of neuropathy as
diagnosed by twitching (after 26 days) and stretching of the
hindquarters (after 240 days). No adverse effects were seen in
the cat receiving 0.3 mg/kg per day (cumulative dose 78 mg/kg
body weight), which survived to the end of the study (McCollister
et al., 1964).
The same authors (McCollister et al., 1964) carried out a
long-term study on female monkeys (daily doses of 0.03, 0.1, 0.3,
1, 3, or 10 mg acrylamide/kg) (1 animal at each dose level). The
monkey receiving 10 mg/kg per day developed weakness of the
hindquarters after 48 days (cumulative dose 340 mg/kg body
weight) and severe weakness after 69 days. No significant
clinical signs of neuropathy were observed in the monkey
administered 3 mg/kg per day. Spencer (1979) reported that
Rhesus monkeys (number of animals not stated) exposed to
acrylamide at 0.5, 1, and 2 mg/kg body weight per day, for 546,
338, 325 days, respectively, did not show any adverse clinical
effects.
7.7.2.2. Electrophysiological effects
No-observed-adverse-effect levels and/or minimum-effect
levels are not available for any acrylamide-induced
electrophysiological effects (section 7.1.1). However, there are
some quantitative data relating electrophysiological measurements
with the development of other neurological effects.
Goldstein & Lowndes (1979) found that cats administered
acrylamide at 7.5 mg/kg body weight per day exhibited a reduced
unconditional spinal monosynaptic reflex (MSR) at a cumulative
dose of 75 mg/kg body weight, when no clinical signs of
neuropathy were evident.
Electroencephalographic (EEG) abnormalities were found in
acrylamide-treated cats prior to the development of ataxia
(Kuperman, 1958). The dose-effect relationship between EEG
change and signs of intoxication are shown in Table 8.
7.7.2.3. Morphological effects
Fullerton & Barnes (1966) did not find any abnormalities
(using light microscopy) in the brain and spinal cord tissue of
neuropathic rats that had been administered acrylamide in
approximate daily doses of between 6 and 30 mg/kg body weight,
the total dose ranging from 300 - 1800 mg/kg.
Changes in peripheral nerves that were considered significant
were reported in both the 93-day study of Burek et al. (1980) and
the 2-year study reported to the US EPA (1980c). In the former
study, these changes occurred with a daily intake of 1 mg/kg,
while in the latter, they occurred more frequently, with an
intake of 2 mg/kg per day. However, similar changes were found
in nerves from the low-dose groups (0.01, 0.05, 0.1, and 0.5
mg/kg per day), and also in the nerves of the control animals.
Moreover, the interpretation of these changes, which are not
necessarily degenerative in nature (e.g., Schwann cell
invaginations into axons and dense body accummulations), is
questionable. This is particularly so in the context of tissue
changes in the ageing rat. Because of these uncertainties, and
because of the importance of determining the lowest doses at
which, with long-term intake, significant morphological changes
may be found, there is a strong need to confirm these findings.
Cavanagh (1982) observed a selective loss of Purkinje cells
in rats given 30 mg acrylamide/kg body weight per day. The first
changes were seen on day 3. The same dose caused inhibition of
nerve regeneration and spontaneous terminal sprouting induced by
partial denervation of motor nerves (Kemplay & Cavanagh, 1984).
Accumulation of neurofilaments and enlarged mitochondria in
the peripheral nerve fibres, seen after 22 days in cats (5
animals per sex) administered 10 mg acrylamide/kg per day,
preceded axonal degeneration, which was observed after 49 days
(Prineas, 1969). Similar findings were reported in rats by
Suzuki & Pfaff (1973) (section 7.1.2).
Schaumburg et al. (1974) observed degeneration of myelinated
distal nerve fibres in cats (2 animals) administered 3 mg
acrylamide/kg body weight per day (in the drinking-water) for 252
and 294 days, respectively. At terminal necropsy (1 year),
microscopic examination of cats (1 animal per dose) did not
reveal any evidence of adverse effects on CNS tissues (brain and
spinal cord) after administration of 0.3, 1, or 3 mg
acrylamide/kg per day. Similar findings were reported in monkeys
administered between 0.03 and 10 mg/kg body weight per day for
one year (McCollister et al., 1964). Spencer (1979) reported
that Rhesus monkeys exposed to 3 mg/kg per day for 49 weeks
developed minor pathological changes in the CNS. No adverse
effects were seen in monkeys exposed to 0.5, 1, and 2 mg
acrylamide/kg per day for 546, 338, and 325 days, respectively.
7.7.2.4. Effects on axonal transport
Miller et al. (1983) reported that administration of single
doses of acrylamide (25 - 100 mg/kg body weight) to rats
inhibited the fast axonal retrograde transport of the iodinated
nerve growth factor [125I-NGF], in a dose-dependent manner. On
repeated administration (15 mg/kg body weight per day),
acrylamide caused significant inhibition in retrograde transport
at a cumulative dose of 75 mg/kg body weight, which preceded
clinical detection (using a foot-splay method) of peripheral
nerve dysfunction, seen at a cumulative dose of 225 mg/kg body
weight.
7.7.2.5. Neurobehavioural effects
Pryor et al. (1983) used a battery of neurobehavioural tests
to examine the dose- and time-dependent effects of acrylamide.
Rats were dosed by gavage, 5 days per week, with 0, 6.6, 9.6,
13.8, or 19.9 mg/kg body weight per day for 15 weeks.
Neurobehavioural assessment of sensory function (responsiveness
to a novel auditory and tactile stimulus, reactivity to a noxious
thermal stimulus, quasi-psychophysical assessment of auditory,
visual, and pain modalities), motor function (grip strength,
motor coordination), and conditioned avoidance responding was
made prior to exposure, and every 3 weeks during dosing. The
high dose of acrylamide resulted in some deaths by the 7th week
of dosing (cumulative dose of about 700 mg/kg). Lower doses of
acrylamide (9.6 or 13.8 mg/kg per day) resulted in significant
dose- and time-dependent decreases in motor function (fore and
hind limb grip strength, impaired motor coordination). The onset
of these effects was independent of alterations in body weight.
Full or partial recovery of function was observed up to 6 weeks
after dosing ceased. Acrylamide had little or no effect on the
sensory modalities assessed. Any alterations in sensory function
or the ability to perform a discriminated avoidance response were
always associated with impaired motor function. However, tactile
or vibration sense modalities were not assessed in these studies.
The lowest dose of acrylamide (6.6 mg/kg per day) did not induce
any statistically-reliable effects in any of these screening
tests. The determination of no-observed-adverse-effect levels
for neurobehavioural func-tions, using more sensitive or
selective (for vibration or tactile sensations) methods, or
species other than the rat, has still to be carried out.
8. EFFECTS ON MAN
8.1. Clinical Studies and Case Reports
In man, as in animals, acrylamide causes local irritation on
contact with the skin, neurological symptoms, and weight loss due
to systemic effects produced following skin absorption,
inhalation, and ingestion.
A variety of symptoms have been described in cases of
acrylamide poisoning, suggesting involvement of both the central
and peripheral nervous systems, as well as the autonomic nervous
system. Symptoms include local irritation of the skin or mucous
membranes, with blistering and desquamation of the skin of the
hands (palms) and/or feet (soles) (Kesson et al., 1977; Mapp et
al., 1977), muscular weakness, paraesthesia, numbness in hands,
feet, lower legs, and lower arms (Garland & Patterson, 1967; Mapp
et al., 1977), and unsteadiness, with difficulties in walking and
standing (Takahashi et al., 1971). Some patients also experience
unusual fatigue and sleepiness, memory difficulties, and
dizziness (Takahashi et al., 1971). Vegetative symptoms such as
micturition and defaecation difficulties (Garland & Patterson,
1967), and excessive sweating and reddening of the hands and feet
(Takahashi et al., 1971; Kesson et al., 1977) can occur.
The clinical signs exhibited in cases of poisoning are
consistent with the reported symptoms. Thus, contact dermatitis,
blueness and sometimes redness of feet and hands (Auld & Bedwell,
1967), loss of peripheral tendon reflexes (ankle and lower arm),
impairment of vibration sense and loss of other sensation, as
well as muscular wasting in peripheral parts of the extremities,
have been observed (Takahashi et al., 1971; Kesson et al., 1977).
Truncal ataxia, nystagmus, and slurred speech have also been
observed (Igisu et al., 1975).
In severe subacute poisoning, occurring after exposure for
about one month, Igisu et al. (1975) described confusion,
disorientation, memory disturbances, and hallucinations. In
other cases of poisoning, after high, but less extreme levels of
exposure, drowsiness and lack of concentration have been
described. Truncal ataxia may be prominent. This may be due
either to involvement of the cerebellum (Cavanagh & Gysberg,
1983) or to sensory degeneration. Peripheral neuropathy develops
insidiously after the appearance of local dermatitis or central
nervous system involvement. Following long-term low-level
exposure, dermatitis and peripheral neuropathy may be the only
detectable manifestations (Garland & Patterson, 1967).
In most reported cases of poisoning, signs and symptoms
slowly disappeared after exposure to acrylamide ceased and,
although improvement sometimes took from months to years, most
cases finally recovered (Kesson et al., 1977; Mapp et al., 1977).
However, in more severely affected cases, various combinations of
residual ataxia, distal weakness, reflex loss, and sensory
disturbances have been observed for up to at least 15 months
after cessation of exposure (Garland & Patterson, 1967;
Fullerton, 1969).
Although cerebrospinal fluid cell counts and glucose contents
remain normal, fluid proteins may be slightly increased; levels
ranging from 300 to 700 mg/litre have been reported in 3 cases
(Garland & Patterson, 1967; Igisu et al., 1975).
Electrophysiologically, the most consistent finding is a
reduction in nerve action potential amplitude in distal parts of
sensory nerves (Fullerton, 1969; Takahashi et al., 1971). In
contrast to findings in animal studies, changes in maximal motor
nerve conduction velocity in human beings have been found to be
minimal (Le Quesne, 1980). Neuropathy, reported in human cases,
has been less severe than that in animals, which show a greater
reduction in conduction velocity.
8.2. Epidemiological Studies
Epidemiological studies relating acrylamide exposure to the
prevalence of signs of adverse effects or to body burden have not
been reported in the literature so far. Because most cases of
poisoning have occurred through skin absorption, and a suitable
biological index of body burden is lacking, the dose factor is
difficult to determine at present.
8.3. Dose-Effect and Dose-Response Relationships
A total of over 60 cases of acrylamide poisoning has been
reported in the literature (Table 13). In no case has it been
possible to reconstruct dose level reliably, and no information
concerning acrylamide concentrations in body organs or body
fluids has been reported. Thus, quantitative human data
concerning dose-effect and dose-response relationships are not
available. However, the clinical reports are consistent with
observations from animal studies (section 7.1) in that after
acute exposure to relatively high levels of acrylamide, signs and
symptoms of toxicity indicate early central nervous system
involvement, while long-term exposure to low levels is
characterized by an insidious onset of signs of peripheral
neuropathy. In cases of acute exposure, signs of peripheral
neuropathy generally appear with a latency of several weeks
following the development of signs of central nervous system
toxicity. Thus, Igisu et al. (1975) reported 5 cases of
acrylamide poisoning due to the ingestion of contaminated well
water. It is likely that the exposure was high, as all 5 cases
had a variety of signs and symptoms of central nervous system
toxicity. However, after a few weeks, signs of peripheral
neuropathy also appeared. In a report by Hashimoto (1980), the
estimated cumulative ingestion of acrylamide was calculated to be
about 200 mg/kg body weight based on an estimated average
concentration of 800 mg/litre in the drinking-water. This is the
only dose-effect relationship reported in human beings. Similar
cases with central nervous system symptoms have been reported
from occupational exposure to acrylamide, where absorption
occurred mainly through the skin (Mapp et al., 1977). However,
in general, acrylamide exposure levels in the occupational
environment are low and, therefore, most cases of poisoning show
only signs and symptoms of peripheral nerve dysfunction. Thus,
it appears that the central nervous system is the critical organ
following acute acrylamide poisoning, but that the peripheral
nervous system is more sensitive to prolonged exposure.
Table 13. Cases of acrylamide intoxication in mana
------------------------------------------------------------------------------------------
Report Year Number of Occupation Length of Reference
patients exposure
------------------------------------------------------------------------------------------
1 1953- 5 - 6 production of 5 months Kuperman (1957)
54 acrylamide from
acrylonitrile
2 1961 10 production of 3 months - Fujita et al. (1960)
acrylamide from 1 year
acrylonitrile
3 1967 1 production of 5 months Anon (1967)
flocculators
4 1967 1 production of 1 month Garland & Patterson (1967)
flocculators
4 production of 2 months -
flocculators 1 year
1 production of 4 weeks
flocculators
5 1967 1 dissolution of 2 weeks Auld & Bedwell (1967)
acrylamide
6 1969 6 production of 6 months Morviller (1969)
acrylamide
7 1970 1 construction work 6 months Graveleau et al. (1970);
for waterproofing Cavigneaux & Cabasson (1971)
8 1971 10 production of paper 2 months - Takahashi et al. (1971)
strengtheners 1 year
9 1971 3 weighing of 10 days Satoyoshi et al. (1971)
acrylamide
10 1975 5 non-occupational 10 days Morimoto et al. (1975);
exposure Mori (1975); Igisu et al.
(1975)
11 1976 1 mixing of 3 months Davenport et al. (1976)
acrylamide
12 1977 6 polymerization of 2 weeks Kesson et al. (1977)
acrylamide in
tunnel
13 1977 5 polymerization of 4 - 12 Mapp et al. (1977)
acrylamide in weeks
road tunnelling
------------------------------------------------------------------------------------------
a Adapted from: Hashimoto (1980).
9. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
9.1. Aquatic Organisms
9.1.1. Invertebrates
A qualitative survey of aquatic insects in a brook before and
after exposure to approximately 50 µg acrylamide/litre, for 6 h,
showed a decrease in the population size and diversity of
species. Within 3 weeks, only Hydropsyche instabilis was
observed in the river. When the brook was examined 4 and 8 weeks
after the final acrylamide addition, recolonization of
Chironomidae, Baetis rhodani, and Amphinemura sulcicollis was
found at low population densities (Brown et al., 1982).
9.1.2. Fish and amphibia
In static exposures of fathead minnows to acrylamide, the
LC10, LC50, and LC90 values (96-h) were 89, 124, and 173
mg/litre, respectively (Davis et al., 1976). Goldfish tolerated
a continuous 30-day exposure to 50 mg acrylamide/litre water.
Exposure to 100 mg/litre, however, was lethal in 5 - 7 days
(Edwards, 1975b). Bridie et al. (1979b) reported that the LC50
(96-h) for goldfish was 160 mg/litre, and the LC50 (96-h) for
fathead minnows was reported to be 124 mg/litre by Davis et al.
(1976). Blackhead minnows survived for over 2 weeks in an
acrylamide concentration of 60 mg/litre, but showed marked
mortality at a concentration exceeding 1000 mg/litre (Cherry et
al., 1956). The LC50 (96-h) for Harlequin fish (Rasbora
heteromorpha) at 20 °C and pH 7 was 130 mg/litre (McKim &
Anderson, 1976) with a 3-month extrapolated figure of 10
mg/litre.
Both frogs and goldfish were sensitive to the general toxic
effects of acrylamide. Three doses of 50 mg/kg in 1 week killed
3 out of 5 frogs. Continuous exposure of goldfish to 100
mg/litre acrylamide killed all 7 in a group in 5 - 7 days, but no
effects were seen at 50 mg/litre for up to 30 days. No adverse
effects were seen in either species at sublethal doses.
9.2. Terrestrial Plants
No significant effects on either germination, pollen tube
formation, or growth of Impatiens sultanii were found, when
acrylamide (10 - 2000 mg/kg) was added to the basal medium
(Bilderback, 1981). However, Japanese workers have shown
interference with germination and growth in Chinese cabbage seeds
when the soil was treated with acrylamide concentrations at 50
mg/kg and above. Disturbances in growth were also observed at a
concentration of 10 mg/kg (Sonoda et al., 1977).
9.3. Microorganisms
No detailed studies on the effects of acrylamide on
microorganisms have been reported, but there have been a number
of studies on the degradation of acrylamide by microbes (Croll et
al., 1974; Lande et al., 1979; Brown et al., 1980a; Arai et al.,
1981).
Cherry et al. (1956) noted that the biota that developed in
river water treated with 10 mg/litre acrylamide was mixed and
healthy.
Because of the limited amount of data available on the
effects of acrylamide on the environment and the levels of
exposure, the Task Group was unable to make a full evaluation.
Acrylamide, because of its the high water solubility, has a
potential for entering ground water and thus drinking-water
supplies. However, accumulation in the environment and
biomagnification in the food chain are not likely (section 4)
under most circumstances, because of its biodegradation by
microorganisms.
10. STRUCTURE-NEUROTOXICITY RELATIONSHIPS
Numerous applications have been described for the polymers
and copolymers of acrylamide and its derivatives (MacWilliams,
1973). Many analogues and derivatives of acrylamide have been
studied for neurotoxic potential in an attempt to elucidate
structure-activity relationships (Table 14). Barnes (1970)
investigated the short-term neurological effects of 9 substances,
related to acrylamide, administered in the diet to adult rats.
Dose schedules were such that, with acrylamide, acute poisoning
and neuropathy would have resulted. Seven of the compounds were
without effect. Of these, the most important were acrylonitrile,
which is present as a residual impurity in commercial acrylamide,
and methacrylamide and N,N' -diethylacrylamide, which are used
commercially. N -methylacrylamide and N -hydroxymethylacrylamide
produced some neurotoxic effects. Animals poisoned with high
doses of N -methylacrylamide showed signs of weakness, while
those receiving N -hydroxymethylacrylamide developed fine tremors
and chronic urinary retention. The gross clinical picture of
muscular weakness was not observed with N -hydroxymethylacrylamide.
Interpretation of data from this study was, however, clouded by
the possibility of acrylamide contamination of the test compounds
(Barnes, 1970).
In another study, Hashimoto & Aldridge (1970) measured the
reactivity of several acrylamide analogues with glutathione (GSH)
in an attempt to correlate reactivity with toxicity. Acrylonitrile,
which reportedly has no neurotoxic effects, had a greater
reactivity with GSH than acrylamide. N -hydroxymethylacrylamide,
which has been reported to have minimal neurotoxic effects
(Barnes, 1970; Edwards, 1975b; Hashimoto et al., 1981), had a
reactivity with GSH that was similar to that of acrylamide. The
authors reported that acutely-administered acrylamide was
approximately 2.5 times more toxic than N -hydroxymethyl-
acrylamide. These results indicate that reactivity with GSH is
not an important criterion in the assessment of neuropathy. Rats
fed acrylamide in the diet showed decreased growth rate and
ataxia, while rats fed N -hydroxymethylacrylamide were
asymptomatic. However, when co-administered with acrylamide,
N -hydroxymethylacrylamide accelerated the onset of neurotoxic
symptoms (section 7.6.1). Edwards (1975b) described
N -hydroxymethylacrylamide, N,N -diethylacrylamide, and
N -methylacrylamide as being neurotoxic for rats.
Table 14. Summary of comparative studies on the effects1 of acrylamide and related analogues
---------------------------------------------------------------------------------------------------------
Compound Neuro- Testicular Lethality Reactivity Decrease in concentration of
and formula toxicity2 atrophy2 (mg/kg) with of non-protein sulfhydrylsb
(oral LD50) glutathioned Brain Liver Testes
(mol/min)
---------------------------------------------------------------------------------------------------------
acrylamide (+)a,b,d,i (+)b,i see Table 7 0.91 (-) (+) (+)
CH2 = CHCONH2
methyl acrylate 825e, 200f
CH2 = CHCO2CH3 (rabbit)
sodium acrylate (-)a
CH2 = CHCO2Na
N-methylacrylamide (+)a,b,d,i (+)b,i 480b, 477i 0.058 (+) (-) (+)
CH2 = CHCONHCH3
N-ethylacrylamide (+)c
CH2 = CHCONHC2H5
N-hydroxymethyl- (+)b,d,i, (+)b,i 560b, 576i 0.91 (-) (+) (+)
acrylamide (±)a, (-)g
CH2 = CHCONHCH2OH
N-isopropylacrylamide (+)b,i (+)i, (-)b 350b, 419i (-) (-) (-)
CH2 = CHCONHCH(CH3)2
N,N '-dimethylacrylamide (-)b (-)b,i 675b, 677i (-) (-) (-)
CH2 = CHCON(CH3)2
---------------------------------------------------------------------------------------------------------
Table 14. (contd.)
---------------------------------------------------------------------------------------------------------
Compound Neuro- Testicular Lethality Reactivity Decrease in concentration of
and formula toxicity2 atrophy2 (mg/kg) with non-protein sulfhydrylsb
(oral LD50) glutathioned Brain Liver Testes
(mol/min)
---------------------------------------------------------------------------------------------------------
N,N'-diethylacrylamide (+)c,d, (-)b,i 1412b, 1399i 0.058 (-) (-) (-)
CH2 = CHCON(C2H5)2 (-)a,b
Methacrylamide (+)b,i, (-)b,i 600b, 451i
CH2 = C(CH3)CONH2 (-)a
N-methylmethacrylamide (-)c
CH2 = C(CH3)CONHCH3
Crotonamide (-)a,b (-)b,i 512b, 2724i (-) (-) (-)
CH(CH3) = CHCONH2
Senecioic acid amide (-)a
(CH3)2C = CHCONH2
Allyl acetamide (-)a
CH2 = CHCH2CONH2
N,N'-methylene- (-)b,h (+)b,i 399b, 401i 0.54 (-) (-) (-)
bis-acrylamide
(CH2 = CHCONH)2CH2
Acrylonitrile (-)a
CH2 = CHCN
---------------------------------------------------------------------------------------------------------
1 Effects in rats and/or mice unless stated.
2 For dosing schedules/relative toxicities, refer to primary references.
a From: Barnes (1970).
b From: Hashimoto & Sakamoto (1979).
c From: Benesova (1979).
d From: Edwards (1975b).
e From: Tanii & Hasimoto (1982).
f From: Autian (1975).
g From: Hashimoto & Aldridge (1978).
h From: Schotman et al. (1978).
i From: Hashimoto et al. (1981).
(+) denotes positive or significant effect.
(-) denotes absence of or insignificant effect.
Hashimoto et al. (1981) studied the effects of orally-
administered acrylamide and analogues on the nervous system in
mice. Of 14 analogues tested, 5 produced neuropathy. In
decreasing order of potency (as assessed by the rotarod
performance test), these were: acrylamide > N -isopropyl-
acrylamide > N -methylacrylamide > methacrylamide >
N -hydroxymethylacrylamide. Mice treated with these compounds
gradually showed signs of weakness and ataxia of hind limbs,
with symptoms of slight behavioural changes such as aggres-
siveness and alertness (Hashimoto et al., 1981). Four
neurotoxic compounds (acrylamide, N -hydroxymethylacrylamide,
N -isopropylacrylamide, and N -methylacrylamide) and 1 non-
neurotoxic compound ( N,N -methylenebisacrylamide (MBA))
produced both atrophy and a significant reduction in the
weight of the testis. Only 1 compound, N -isopropylacrylamide,
seemed to be toxic by virtue of its biotransformation to
acrylamide (Tanii & Hashimoto, 1981). This compound also
produced marked effects on red and white blood cell counts,
haemoglobin concentration, and haematocrit values in both rats
and mice (Hashimoto et al., 1981; Hashimoto & Sakamoto, 1982).
Urinary porphyrins were elevated and ALA-D activity decreased in
rats after MBA-dosing, the origins of which seemed to be mainly
erythropoietic rather than hepatic. Similarly, a marked increase
in hepatic porphyrins was reported after subcutaneous
administration of 2-allyl-2-isopropyl-acetamide (Edwards et al.,
1978). MBA has been commonly used in chemical grouting and
chromatography, and has been identified as a component in photo-
polymerizing printing plates. Contact skin allergies have also
been reported with MBA (Malten et al., 1978) and other secondary
acrylamide derivatives (Pye & Peachey, 1976; Pedersen et al.,
1982).
Schotman et al. (1978) compared the effects of MBA and
acrylamide on several neurochemical and behavioural measures.
Both compounds affected protein synthesis, but only acrylamide
impaired rotarod performance, suggesting that this mechanism may
not be related to the neurological effects of acrylamide.
The effects of secondary acrylamides on both cell cultures
and rats were investigated by Benesova et al. (1979). Results
from cell-culture studies indicated that N -substituted
acrylamides are more toxic than the respective N -substituted
methacrylamides. Of the compounds tested in rats, N -ethyl-
acrylamide was reported to be the most toxic, producing
tonic-clonic convulsions and death after dermal applications.
Similar, but less pronounced, effects were found with
N,N' -diethylacrylamide (DEAA), indicating that the toxicity of
some N -substituted methacrylamides is quite considerable,
inducing similar effects to acrylamide.
Esters of acrylic acid (in particular methyl methacrylate)
have wide applications in a number of industrial and consumer
products. Most of the acrylic acid esters are volatile and can
produce various levels of toxicity if inhaled. The toxicity and
structure-activity relationships of a large number of acrylic
esters have been investigated (Autian, 1975; Tanii & Hashimoto,
1982). Generally, the systemic effects of the lower relative
molecular mass acrylic monomers are manifested by irregular
respiration and reduced blood pressure. With lethal doses,
reflex activity ceases and the animals die in coma. Acrylic
monomers also irritate the skin and mucous membranes. Data from
an embryonic-fetal toxicity study indicated that all 4
methacrylate esters in the study also induced deleterious effects
on the developing embryo (Autian, 1975) at a daily exposure
likely to be encountered in an occupational environment.
In summary, many analogues and derivatives of acrylamide
have been studied, but only 5 have been reported to exhibit
neurotoxic potential ( N -methylacrylamide, N -isopropyl-
acrylamide, N -hydroxymethylacrylamide, methacrylamide, and
N,N '-diethylacrylamide). The toxic potential cannot be
attributed solely to the general chemical reactivities with
thiol-containing compounds (e.g., glutathione). Comparison of
molecular structures has shown that the development of
neurotoxic effects cannot be wholly attributed to any specific
group or molecular conformation. Substitution or addition of
other groups at either the alpha or ß carbon atoms or at the NH2
group of acrylamide decreased the neurotoxicity of the molecule.
However, other effects may be retained, i.e., effects on protein
synthesis or testicular damage. Biotrans-formation of
N -isopropylacrylamide to acrylamide has been demonstrated in
mice. Such a transformation could account for the elicited
neurotoxicity of other secondary acrylamides. Completely
different systemic effects are observed with many other
acrylamide analogues, e.g., acrylates.
11. EVALUATION OF HEALTH RISKS FOR MAN AND EFFECTS ON THE
ENVIRONMENT FROM EXPOSURE TO ACRYLAMIDE
11.1. General Considerations
Epidemiological data related to occupational or environmental
exposure to acrylamide are insufficient to serve as a basis for
quantitative risk evaluation (section 8.2). Consequently, this
evaluation is based on animal studies.
Although the complete metabolic profile for acrylamide has
not been elucidated, there do not appear to be any major species
differences among mammals. Manifestations of acrylamide
poisoning were similar and dose-effect relation-ships (dose as a
function of body surface area) were also similar for all mammals
studied (rats, mice, cats, dogs, monkeys, and baboons).
In view of the limited human data, it must be assumed that
the metabolism of acrylamide in man is similar to that in other
mammalian species, with a comparable dose-effect relationship.
However, should a metabolite be the primary neurotoxic agent,
which is likely, then it would be reasonable to assume that
differences in toxic response might exist, because of differences
in metabolic profiles between species. Thus, it seems prudent to
start with the most sensitive species when extrapolating
quantitative animal data to man.
Most long-term exposure studies have been conducted on rats.
In this species, the lowest daily dose reported to cause definite
signs of adverse neurological effects was 1 mg acrylamide/kg body
weight, administered orally for 93 days (Burek et al., 1980).
For the reasons given in section 7.7.2.3., these findings need
confirmation. However, on the basis of the available long-term
studies, and taking these caveats into account, it appears that
the long-term minimal adverse neurological effect level for
acrylamide lies in the region of 1 mg/kg body weight per day and
a probable estimated no-effect level is 0.5 mg/kg body weight per
day in rats. This level is supported by findings from studies
using functional indices of acrylamide toxicity.
Assuming that the toxic dose is related to the metabolic
rate, which for mammals is related to the body weight by the
power of 0.76 (Stahl, 1967), the equivalent minimum daily toxic
dose in a 2 - 4 kg cat can be calculated to be 0.3 -0.2 mg/kg
body weight. This figure is consistent with data obtained from
long-term toxicity studies on cats, where neurological signs,
unconfirmed morphologically, were observed, in some animals,
after exposure for 240 days to 1 mg acrylamide/kg body weight per
day (McCollister et al., 1964). Similarly, extrapolation of these
data to man (applying the above relationship) provides a figure
of 0.12 mg/kg body weight per day, which might be expected to
induce minimal adverse effects in human beings. The application
of a safety factor would therefore be required in order to obtain
an acceptable exposure level.
When determining this safety factor, the limitations of the
derived human exposure level (0.12 mg/kg body weight per day)
should be realized. First, this figure has been extrapolated
from a test group of animals with a rather homogeneous genetic
background. Second, a high incidence of possible effects was
seen in these animal studies. However, in a human population, an
incidence of adverse effects below 5% is unlikely to be detected
in an epidemiological study, and this should be taken into
account in the extrapolation of animal exposure data to man.
Third, it is not clear whether the observed morphological changes
in the peripheral nerves reflect the primary adverse effects.
For example, acrylamide has been shown to interfere with both
neurotransmitter concentrations and neuroreceptor densities in
the brain (section 7.1.4.3.), although it is not possible, on the
basis of available experimental data, to assess the lowest
exposure level that induces these effects. Such effects may,
however, be secondary to those involved directly in the genesis
of neuropathy. Finally, environmental factors may influence the
toxicity of acrylamide. For example, both inducers and
inhibitors of metabolic enzymes have been shown to modify the
toxicity and metabolism of acrylamide in experimental animals
(section 6.1.2.).
Thus, applying a safety factor of 10 to the estimated minimal
adverse neurological effect level for human beings would indicate
a daily intake not exceeding 0.012 mg/kg body weight.
It should be emphasized that this value is based solely on
the neurotoxicity of acrylamide and does not take into account
the risk of cancer or interference with reproductive capability.
No epidemiological data on cancer due to exposure to
acrylamide are available. Acrylamide (> 99% pure) was not
mutagenic in S. typhimurium, in the absence or presence of a
metabolic activation system.
Acrylamide of unknown purity induced chromosomal aberrations
in the spermatocytes of mice and was reported to increase cell
transformation frequency in Balb 3T3 cells in the presence of a
metabolic activation system.
Acrylamide was shown to be an initiator for skin tumours in
mice, when administered by various routes, and increased the
incidence of lung tumours in mice-screening assays.
A 2-year study on rats, administered acrylamide in the
drinking-water, has not been fully evaluated. It is not possible
to form any conclusions concerning the carcinogenicity of
acrylamide on the basis of available data.
Acrylamide (10 - 20 mg/kg body weight per day) caused
testicular degeneration in mice (Shiraishi, 1978; Hashimoto &
Tanii, 1981) and spermatocyte chromosome aberrations. A similar
acrylamide exposure (20 mg/kg body weight per day, for 20 days)
caused a major depression in the plasma levels of testosterone in
Fischer 344 rats. No information is available concerning the
minimum long-term acrylamide exposure required to elicit such
effects; thus, it is impossible, at present, to assess the risk
of acrylamide-induced effects on reproduction in man.
11.2. Assessment of Exposure
Exposure measurements using personal sampling or stationary
sampling have obvious shortcomings in the assessment of
occupational exposure, as they do not take absorption through the
skin into account. A reasonably accurate measurement of exposure
will require biological monitoring. So far, no method for
biological monitoring has been established, though the results of
experimental animal studies (Young et al., 1979; Pastoor &
Richardson, 1981) indicate that the amount of acrylamide bound to
red blood cells would reflect both the exposure level and the
accumulated concentration in nervous tissue (section 7.7.2.1. and
6.1.1.).
11.3. Assessment of Adverse Effects
In any group of "healthy" individuals, a small proportion
will have some abnormal neurological symptoms or signs. This
makes it difficult to assess the significance of minor clinical
neurological abnormalities in any one individual. In an
epidemiological study, incidence of abnormalities in a group of
subjects exposed to acrylamide can be compared with the incidence
in a group of unexposed subjects. The same arguments may be
applied to the results of electrophysio-logical tests, where the
range of values in control subjects is wide. To obtain maximum
sensitivity, pre-exposure, base-line observations are most
valuable.
Clinical experience has shown that the most sensitive
electrophysiological parameter is the measurement of sensory
nerve action potential amplitude in the distal part of a limb
(section 8.1.).
Arezzo et al. (1983) have described the use of a quantitative
measure of the threshold of vibration sensation in the fingers to
screen acrylamide-exposed workers. Earlier neurological
abnormalities would be detected by testing the toes. This method
has great potential as it is sensitive, quick, and can be used in
the field. Equipment for measuring vibration threshold is
available commercially. A recent extensive survey of vibration
threshold measurements in a large number of healthy individuals
of different ages using a biothesiometer has been published.
This type of assessment has proved useful in assessing other
peripheral nerve diseases, e.g., diabetes. In applying such
techniques, a sensitive method of psychophysical assessment must
be used, e.g., using a type of forced choice procedure to avoid
undue bias in the results. Encouragement to pursue this type of
assessment is provided by the positive results obtained by
Maurissen et al. (1983) using a similar procedure in monkeys
(section 7.1.1.).
Animal experience indicates that sensory and visual evoked
potentials are useful indications of acrylamide interference in
central nervous system function (section 7.1.2.2.).
11.4. Exposure of the Environment
The use of acrylamide as a grouting agent has proved to be
the greatest potential hazard for man, due to contamination of
ground water. Such contamination led to an incident of
acrylamide poisoning in Japan when well water became polluted
with acrylamide (400 mg/litre) from a grouting operation (2.5
metres away) that had taken place 1 month before (section
5.1.2.). Special precautions must therefore be taken to limit
ground water contamination and, if it becomes contaminated, to
prevent its consumption.
Some effluents from the dewatering processes of industrial
and communal sewage plants and water works have been found to
contain between < 1 - 45 µg acrylamide/litre (section 5.1.2.).
Levels of acrylamide in effluent-receiving waters are highly
variable because of dilution factors. The highest reported level
is 1.5 mg/litre (section 5.1.2.). Novikova (1979) estimated the
maximum safe daily level of acrylamide that could be absorbed by
the hands, from hand-washing water, to be 3.5 mg, assuming that
the hands constitute 5% of the total surface area of the human
body. This figure was derived from the results of a long-term
dermal toxicity study on rats where 5% of the body surface area
(tail) was exposed to different concentrations of acrylamide with
a safety factor of 10 applied to the dose at which no adverse
effects were observed (section 7.7.2.1.). For swimming, with an
acrylamide concentration of 5 µg/litre in the water, a total
clearance of more than 700 litres would be required (via skin
absorption) to exceed the safety threshold of 3.5 mg. However,
at levels of 1 mg/litre in the water, a clearance of less than 5
litres would be needed. Repeated or daily swimming in waters
contaminated with acrylamide at such a concentration may present
a health hazard.
11.5. Occupational Exposure
Experience has clearly shown that occupational exposure to
acrylamide can present a hazard for workers, through dermal
absorption or inhalation, or both. As acrylamide is readily
absorbed through the skin, workers should be protected by
suitable protective clothing or by enclosing production
procedures to ensure minimum exposure. To prevent inhalation,
ventilated face masks may be necessary. Recommended occupational
exposure levels for acrylamide in workroom air for a number of
countries are listed in Table 5.
It is possible that underlying neurological disease and/or
the administration of neuroactive drugs might alter the
sensitivity of man to acrylamide and, this should be borne in
mind for workers. However, in the absence of definite evidence
that this has occurred, no specific recommendation to exclude
such workers from contact with acrylamide processes can be made.
REFERENCES
ABDELMAGID, H.M. & TABATABAI, M.A. (1982) Decomposition of
acrylamide in soils. J. environ. Qual., 11(4): 701-704.
ACGIH (1974) "Acrylamide" documentation of the threshold
limit values for substances in workroom air, 3rd ed.,
Cincinnati, Ohio, American Conference of Governmental
Industrial Hygienists.
ACGIH (1984) Threshold limit values for chemical substances
and physical agents in the work environment and biological
indices with intended changes for 1984-85, Cincinnati, Ohio,
American Conference of Governmental and Industrial Hygienists.
AGRAWAL, A.K. & SQUIBB, R.E. (1981) Effects of acrylamide
given during gestation on dopamine receptor binding in rat
pups. Toxicol. Lett., 7: 233-238.
AGRAWAL, A.K., SETH, P.K., SQUIBB, R.E., TILSON, H.A.,
UPHOUSE, L.L., & BONDY, S.C. (1981a) Neurotransmitter
receptors in brain regions of acrylamide-treated rats. I.
Effects of a single exposure to acrylamide. Pharmacol.
Biochem. Behav., 14: 527-531.
AGRAWAL, A.K., SQUIBB, R.E., & BONDY, S.C. (1981b) The
effects of acrylamide treatment upon the dopamine receptor.
Toxicol. appl. Pharmacol., 58: 89-99.
ALDOUS, C.N., SHARMA, R.P., & FARR, C.H. (1981) Acrylamide
effects on catecholamine metabolism. Toxicologist, 1: 52.
AMERICAN CYANAMID (1961) Chemistry of acrylamide, New York,
Cyanamide International, 43 pp.
ANDERSON, C.E., TILSON, H.A., & MITCHELL, C.L. (1982)
Conditioned taste aversion following acutely administered
acrylamide. Neurobehav. Toxicol. Teratol., 4: 497-499.
ANDERSON, R.J. (1981) Selective effect on peripheral nerves
after subchronic administration of acrylamide. Bull. environ.
Contam. Toxicol., 27: 888-893.
ANDERSON, R.J. (1982) Alterations in nerve and muscle
compound action potentials after acute acrylamide
administration. Environ. Health Perspect., 44: 153-157.
ANDO, K. & HASHIMOTO, K. (1972) Accumulation of [14C]-
acrylamide in mouse nerve tissue. In: Proceedings of the Osaka
Prefectural Institute of Public Health, Vol. 10, pp. 7-12.
ANON (1967) Acrylamide poisoning reports on work hygiene
branch of Kangawa labour standards office. Roco osei, 8: 68-69.
ARAI, T., KURODA, S., & WATANABE, I. (1981) Biodegradation
of acrylamide monomer by a rhodococcus strain. In: Schaal,
K.P. & Pulverer, G., ed. Actinomycetes, Stuttgart, Gustav
Fischer Verlag, pp. 297-307.
AREZZO, J.C., SCHAUMBURG, H.H., VAUGHAN, H.G., Jr, SPENCER,
P.S., & BARNA, J. (1982) Hind limb somatosensory evoked
potentials in the monkey: The effects of distal axonopathy.
Ann. Neurol., 12: 24-32.
AREZZO, J.C., SCHAUMBURG, H.H., & PETERSEN, C.A. (1983)
Rapid screening for peripheral neuropathy: A field study with
the Optacon. Neurology, 33: 626-629.
ASBURY, A.K., COX, S.C., & KANADA, D. (1973) 3H-leucine
incorporation in acrylamide neuropathy in the mouse.
Neurology, 23: 406.
AULD, R.B. & BEDWELL, S.F. (1967) Peripheral neuropathy with
sympathetic overactivity from industrial contact with
acrylamide. Can. Med. Assoc. J., 96(11): 652-654.
AUTIAN, J. (1975) Structure-toxicity relationships of
acrylic monomer. Environ. Health Perspect., 11: 141-152.
AZZAM, R.A.I. (1980) Agricultural polymers: Polyacrylamide
preparation, application, and prospects in soil conditioning.
Soil Sci. plant Anal., 11(8): 767-834.
BARNES, J.M. (1970) Observations on the effects on rats of
compounds related to acrylamide. Br. J. ind. Med., 27:
147-149.
BENESOVA, O., PLAISNER, V., ULBRICH, K., & SPRINCL, L.
(1979) Biological effects of some N-substituted
(meth)acrylamides. Polym. Med., 9: 63-68.
BETSO, S.R. & MCLEAN, J.D. (1976) Determination of
acrylamide monomer by differential pulse polarography. Anal.
Chem., 48(4): 766-770.
BIKALES, N.M. (1973) Preparation of acrylamide polymers. In:
Bikales, N.M., ed. Polymer science and technology, New York,
Plenum Press, Vol. 2, pp. 213-222.
BILDERBACK, D.E. (1981) Impatiens pollen germination and
tube growth as a bioassay for toxic substances. Environ.
Health Perspect., 37: 95-103.
BLACKFORD, J.L. (1974) In: Chemical economics handbook,
Menlo Park, California, Standford Research Institute, p. 607
(5031 A-607.5033G).
BONDY, S.C., TILSON, H.A., & AGRAWAL, A.K. (1981)
Neurotransmitter receptors in brain regions of acrylamide-
treated rats. II. Effects of extended exposure to acrylamide.
Pharmacol. Biochem. Behav., 14: 533-537.
BOYES, W.K. & COOPER, G.P. (1981) Acrylamide neurotoxicity:
Effects on far-field somatosensory evoked potentials in rats.
Neurobehav. Toxicol. Teratol., 3: 487-490.
BRADLEY, W.G. & ASBURY, A.K. (1970) Radioautographic studies
of Schwann cell behaviour. I. Acrylamide neuropathy in the
mouse. J. Neuropathol. exp. Neurol., 29: 500-506.
BRADLEY, W.G. & WILLIAMS, M.H. (1973) Axoplasmic flow in
axonal neuropathies. I. Axoplasmic flow in cats with toxic
neuropathies. Brain, 96: 235-246.
BRIDIE, A.L., WOLFF, C.J.M., & WINTER, M. (1979a) BOD and
COD of some petrochemicals. Water Res., 13: 627-630.
BRIDIE, A.L., WOLFF, C.J.M., & WINTER, M. (1979b) Acute
toxicity of some petrochemicals to goldfish. Water Res., 13:
623-626.
BROWN, L. & RHEAD, M. (1979) Liquid chromatographic
determination of acrylamide monomer in natural and polluted
aqueous environments. Analyst, 104: 391-399.
BROWN, L., RHEAD, M.M., BANCROFT, K.C.C., & ALLEN, N.
(1980a) Model studies of the degradation of acrylamide
monomer. Water Res., 14: 775-778.
BROWN, L., RHEAD, M.M., & BANCROFT, K.C.C. (1980b) Case
studies of acrylamide pollution resulting from the industrial
use of polyacrylamides. Water Pollut. Control, 79: 507-510.
BROWN, L., BANCROFT, K.C.C., & RHEAD, M.M. (1980c)
Laboratory studies on the adsorption of acrylamide monomer by
sludge, sediments, clays, peat, and synthetic resins. Water
Res., 14: 779-781.
BROWN, L., RHEAD, M.M., HILL, D., & BANCROFT, K.C.C. (1982)
Qualitative and quantitative studies on the in situ
adsorption, degradation, and toxicity of acrylamide by the
spiking of the waters of two sewage works and a river. Water
Res., 16: 579-591.
BULL, R.J., ROBINSON, M., LAURIE, R.D., STONER, G.D.,
GREISIGER, E., MEIER, J.R., & STOBER, J. (1984) Carcinogenic
effects of acrylamide in Sencar and A/J mice. Cancer Res.,
44: 107-111
BUREK, J.D., ALBEE, R.R., BEYER, J.E., BELL, T.J., CARREON,
R.M., MORDEN, D.C., WADE, C.E., HERMANN, E.A., & GORZINSKI,
S.J. (1980) Subchronic toxicity of acrylamide administered
to rats in the drinking-water followed by up to 144 days of
recovery. J. environ. Pathol. Toxicol., 4: 157-182.
CABE, P.A. & COLWELL, P.B. (1981) Toxic effects of
acrylamide in Japanese quail. J. Toxicol. environ. Health, 7:
935-940.
CAVANAGH, J.B. (1982) The pathokinetics of acrylamide
intoxication: A reassessment of the problem. Neuropathol.
appl. Neurobiol., 8: 315-336.
CAVANAGH, J.B. & GYSBERS, M.F. (1981) Ultrastructural
changes in axons caused by acrylamide above a nerve ligature.
Neuropathol. appl. Neurobiol., 7: 315-326.
CAVANAGH, J.B. & GYSBERS, M.F. (1983) Ultrastructural
features of the Purkinje cell damage caused by acrylamide in
the rat: A new phenomenon in cellular neuropathology. J.
Neurocytol., 12: 413-437.
CAVIGNEAUX, A. & CABASSON, G.B. (1971) Intoxication par
l'acrylamide. Arch. Mal. prof. Méd. Trav. Sécur. soc., 33:
115-116.
CHERRY, A.B., GABACCIA, A.J., & SENN, H.W. (1956) The
assimilation behavior of certain toxic organic compounds in
natural water. Sewage ind. Wastes, 28: 1137-1146.
CHRETIEN, M., PATEY, G., SOUYRI, F., & DROZ, B. (1981)
"Acrylamide-induced" neuropathy and impairment of axonal
transport of proteins. II. Abnormal accumulation of smooth
endoplasmic reticulum as sites of focal retention of fast
transported proteins. Electron microscope radioautographic
study. Brain Res., 205: 15-28.
CONWAY, E.J., PETERSEN, R.J., COLLINGSWORTH, R.F., GRACA,
J.G., & CARTER, J.W. (1979) Assessment of the need for and
character of limitations on acrylamide and its compounds,
Washington DC, US Environmental Protection Agency (Report
prepared for the Office of Pesticides and Toxic Substances,
Contract No. 68-10-4308).
COURAUD, J.Y., DI GIAMBERARDINO, L., CHRETIEN, M., SOUYRI, F.,
& FARDEAU, M. (1982) Acrylamide neuropathy and changes in
the axonal transport and muscular content of the molecular
forms of acetylcholinesterase. Muscle Nerve, 5: 302-312.
CROLL, B.T. & SIMKINS, G.M. (1972) The determination of
acrylamide in water by using electron-capture gas
chromatography. Analyst, 97: 281-288.
CROLL, B.T., ARKELL, G.M., & HODGE, R.P.J. (1974) Residues
of acrylamide in water. Water Res., 8: 989-993.
DAIRMAN, W., SABRI, M.I., JUHASZ, L., BISCHOFF, M., & SPENCER,
P.S. (1981) Protective effect of sodium pyruvate on
acrylamide-induced neuropathy in rats. Toxicologist, 1: 52.
DAS, M., MUKHTAR, H., & SETH, P.K. (1982) Effect of
acrylamide on brain and hepatic mixed-function oxidases and
glutathione-S-transferase in rats. Toxicol. appl. Pharmacol.,
66: 420-426.
DAVENPORT, J.G., FARRELL, D.F., & SUMI, S.M. (1976) "Giant
axonal neuropathy" caused by industrial chemicals:
Neurofilamentous axonal masses in man. Neurology, 26: 919-923.
DAVIS, L.N., DURKIN, P.R., & HOWARD, P.H. (1976)
Investigation of selected potential environmental
contaminants: Acrylamides, Washington DC, US Environmental
Protection Agency, 159 pp (EPA Report No. 560/2-76-008, PB
257-704).
DIXIT, R., HUSAIN, R., SETH, P.K., & MUKHTAR, H. (1980a)
Effect of diethyl maleate on acrylamide induced neuropathy in
rats. Toxicol. Lett., 6(6): 417-421.
DIXIT, R., MUKHTAR, H., SETH, P.K., & KRISHNA MURTI, C.R.
(1980b) Binding of acrylamide with glutathione-S-
transferases. Chem.-biol. Interact., 32: 353-359.
DIXIT, R., MUKHTAR, H., SETH, P.K., & KRISHNA MURTI, C.R.
(1981a) Conjugation of acrylamide with glutathione catalysed
by glutathione-S-transferases of rat liver and brain. Biochem.
Pharmacol., 30(13): 1739-1744.
DIXIT, R., HUSAIN, R., MUKHTAR, H., & SETH, P.K. (1981b)
Acrylamide induced inhibition of hepatic glutathione- S-
transferase activity in rats. Toxicol. Lett., 7: 207-210.
DIXIT, R., HUSAIN, R., MUKHTAR, H., SETH, P.K. (1981c)
Effect of acrylamide on biogenic amine levels, monoamine
oxidase, and cathepsin D activity of rat brain. Environ. Res.,
26: 168-173.
DIXIT, R., SETH, P.K., & MUKHTAR, H. (1982) Metabolism of
acrylamide into urinary mercapturic acid and cysteine
conjugates in rats. Drug Metab. Dispos., 10: 196-197.
DREES, D.T., CRAGO, F.L., HOPPER, C.R., & SMITH, J.M. (1976)
Subchronic percutaneous toxicity of acrylamide and
methacrylamide in the new-born rabbit. Toxicol. appl.
Pharmacol., 37: 190.
DRUCKERY, H., CONSBRUCH, U., & SCHMAHL, D. (1953) [Effects
of monomeric acrylamide on proteins.] Naturforsch., 8(b):
145-150 (in German).
ECT (1978) Encyclopedia of chemical technology, 3rd ed.,
Vol. 1, pp. 302-306.
EDWARDS, P.M. (1975a) The distribution and metabolism of
acrylamide and its neurotoxic analogues in rats. Biochem.
Pharmacol., 24: 1277-1282.
EDWARDS, P.M. (1975b) Neurotoxicity of acrylamide and its
analogues and the effects of these analogues and other agents
on acrylamide neuropathy. Br. J. ind. Med., 32: 31-38.
EDWARDS, P.M. (1976a) The insensitivity of the developing
rat fetus to the toxic effects of acrylamide. Chem.-biol.
Interact., 12: 13-18.
EDWARDS, P.M. (1976b) UK Council for National Academy Awards
(Thesis for PhD degree).
EDWARDS, P.M. & PARKER, V.H. (1977) A simple and objective
method for early assessment of acrylamide neuropathy in rats.
Toxicol. appl. Pharmacol., 40: 589-591.
EDWARDS, P.M., FRANCIS, J.E., & DE MATTEIS, F. (1978) The
glutathione-linked metabolism of 2-allyl-2-isopropylacetamide
in rats. Further evidence for the formation of a reactive
metabolite. Chem.-biol. Interact., 23: 233-241.
ERICSSON, A.-C. & WALUM, E. (1984) Cytotoxicity of
cyclophosphamide and acrylamide in glioma and neuroblastoma
cell lines cocultured with liver cells. Toxicol. Lett., 20:
251-256.
FARR, C.H., SHARMA, R.P., & ALDOUS, C.N. (1981) Acrylamide
neurotixicity: Levels of tryptophan, serotonin, and 5-hydroxy-
indole-acetic acid and serotonin turnover in rat brain.
Toxicology, 1: 52-53.
FATEHYAB ALI, S., HONG, J.S., WILSON, W.E., UPHOUSE, L.L., &
BONDY, S.C. (1983) Effect of acrylamide on neurotransmitter
metabolism and neuropeptide levels in several brain regions
and upon circulating hormones. Arch. Toxicol., 52: 35-43.
FUJITA, A., SHIBATA, J., KATO, H., AMANI, Y., ITOMI, D.,
SUZUKI, E., NAKAZAWA, T., & TAKAHASHI, T. (1960) [Clinical
observations of three cases of acrylamide poisoning.] Nippon
Ijo Shimpo, 1869: 37-40 (in Japanese).
FULLERTON, P.M. (1969) Electrophysiological and histological
observations on peripheral nerves in acrylamide poisoning in
man. J. Neurol. Neurosurg. Psychiatr., 32: 186-192.
FULLERTON, P.M. & BARNES, J.M. (1966) Peripheral neuropathy
in rats produced by acrylamide. Br. J. ind. Med., 23: 210-221.
GARLAND, T.O. & PATTERSON, M.W.H. (1967) Six cases of
acrylamide poisoning. Br. med. J., 4: 134-138.
GHIRINGHELLI, L. (1956) [Comparative study on the toxicity
of some nitriles and of some amides.] Med. Lav., 47: 1-8 (in
Italian).
GILBERT, S.G. & MAURISSEN, J.P.J. (1982) Assessment of the
effects of acrylamide, methylmercury, and 2,5-hexanedione on
motor functions in mice. J. Toxicol. environ. Health, 10:
31-41.
GIPON, L., SCHOTMAN, P., JENNEKENS, F.G.I., & GISPEN, W.H.
(1977) Polyneuropathies and CNS protein metabolism. I.
Description of the acrylamide syndrome in rats. Neuropathol.
appl. Neurobiol., 3: 115-123.
GOING, J.E. (1978) Environmental monitoring near industrial
sites, Washington DC, US Environmental Protection Agency (EPA
Contract No. 560/6-78-001, PB 281 879).
GOING, J.E. & THOMAS, K. (1979) Sampling and analysis of
selected toxic substances. Task I. Acrylamide, Washington DC,
US Environmental Protection Agency (EPA Contract No.
560/13-79-013, PB 80-128150).
GOLDSTEIN, B.D. & LOWNDES, H.E. (1979) Spinal cord defect in
the peripheral neuropathy resulting from acrylamide.
Neurotoxicology, 1: 75-87.
GRAVELEAU, J., LOIRAT, P., & NUSINOVICI, V. (1970)
Polyneurite causée par l'acrylamide. Rev. neurol. (Paris),
123: 62-65.
GRIFFIN, J.W., PRICE, D.L., & DRACHMAN, D.B. (1977) Impaired
axonal regeneration in acrylamide intoxication. J. Neurobiol.,
8(4): 355-370.
HACKADAY, T.D.R., HILLSON, R.M., & SMITH, B. (1982)
Correlates of deterioration in pedal vibration sensory
threshold over 5 years from diagnosis of maturity onset in
diabetic patients. Diabetologia, 23: 174.
HAMBLIN, D.O. (1956) The toxicity of acrylamide: A
preliminary report. In: Hommage au Doyen René Fabre (Paris),
pp. 195-199.
HANSCH, C. & LEO, A. (1979) Substituent constants for
correlation analysis in chemistry and biology, New York, John
Wiley and Sons, 336 pp.
HASHIMOTO, K. (1980) [The toxicity of acrylamide.] Jap. J.
ind. Health, 22: 233-248 (in Japanese).
HASHIMOTO, K. & ALDRIDGE, W.N. (1970) Biochemical studies on
acrylamide, a neurotoxic agent. Biochem. Pharmacol., 19:
2591-2604.
HASHIMOTO, K. & ANDO, K. (1971) [Studies on acrylamide
neuropathy. Effects of the permeability of amino acids into
nervous tissue; distribution and metabolism.] In: Proceedings
of the Osaka Prefectoral Institution, Public Health Education
and Industrial Health, Vol. 9, pp. 1-4 (in Japanese).
HASHIMOTO, K. & ANDO, K. (1973) Alteration of amino acid
incorporation into proteins of the nervous system in vitro
after administration of acrylamide to rats. Biochem.
Pharmacol., 22: 1057-1066.
HASHIMOTO, K. & ANDO, K. (1975) Studies on the percutaneous
absorption of acrylamide. In: Abstracts of the 18th
International Congress on Occupational Health, Brighton,
England, pp. 453.
HASHIMOTO, K. & SAKAMOTO, J. (1979) In: Collected Lectures
from the 52nd Conference of the Japanese Industrial Hygiene
Society, pp. 306-307.
HASHIMOTO, K. & SAKAMOTO, J. (1982) Anemia and porphyria
caused by N,N' -methylenebisacrylamide (MBA) in mice and rats.
Arch. Toxicol., 50: 47-55.
HASHIMOTO, K. & TANII, H. (1981) [Percutaneous absorption of
14C-methacrylamide.] In: Abstracts of the 54th Annual Meeting
of the Japan Association of Industrial Health, pp. 314-315 (in
Japanese).
HASHIMOTO, K., SAKAMOTO, J., & TANII, H. (1981)
Neurotoxicity of acrylamide and related compounds and their
effects on male gonads in mice. Arch. Toxicol., 47: 179-189.
HONG, J.S., TILSON, H.A., AGRAWAL, A.K., KAROUM, F., & BONDY,
S.C. (1982) Postsynaptic location of acrylamide-induced
modulation of striatal 3H-spiroperiodol binding.
Neurotoxicology, 3: 108-112.
HOOISMA, J., DE GROOT, D.M.G., MAGCHIELSE, T., & MUIJSER, H.
(1980) Sensitivity of several cell systems to acrylamide.
Toxicology, 17(2): 161-167.
HOPKINS, A.P. (1970) The effect of acrylamide on the
peripheral nervous system of the baboon. J. Neurol. Neurosurg.
Psychiatr., 33: 805-816.
HOPKINS, A.P. & GILLIATT, R.W. (1971) Motor and sensory
nerve conduction velocity in the baboon: Normal values and
changes during acrylamide neuropathy. J. Neurol. Neurosurg.
Psychiatr., 34: 415-426.
HOWLAND, R.D. (1981) The etiology of acrylamide neuropathy:
enolase, phosphofructokinase, and glyceraldehyde-3-phosphate
dehydogenase activities in peripheral nerve, spinal cord,
brain, and skeletal muscle of acrylamide-intoxicated cats.
Toxicol. appl. Pharmacol., 60: 324-333.
HOWLAND, R.D., VYAS, I.L., LOWNDES, H.E., & ARGENTIERI, T.M.
(1980) The etiology of toxic peripheral neuropathies: In vivo
effects of acrylamide and 2,5-hexanedione on brain enolase and
other glycolytic enzymes. Brain Res., 202: 131-142.
HUANG, Y.S., WONG, P., BLACHE, D., BARBEAU, A., & DAVIGNON,
J. (1982) Tissue lipids in acute acrylamide intoxicated
rats. J. Can. neurol. Sci., 9(2): 181-184.
HUNGARY, STATE MINISTRY OF HEALTH (1978) Hungarian standard
MSZ No. 21461-78, The Office of Standards of the Hungarian
Republic, State Ministry of Health, Hungary.
IARC (1979) Acrylamide, Lyons, International Agency for
Research on Cancer, pp. 73-113 (IARC Monographs on the
Evaluation of the Carcinogenic Risk of Chemicals to Humans,
Supplement 19).
IGISU, H., GOTO, I., KAWAMURA, Y., KATO, M., IZUMI, D., &
KUROIWA, Y. (1975) Acrylamide encephaloneuropathy due to
well water pollution. J. Neurol. Neurosurg. Psychiatr., 38:
581-584.
IKEDA, G.J., MILLER, E., SAPIENZA, P.P., MICHEL, T.C., KING,
M.T., TURNER, V.A., BLUMENTHAL, H., JACKSON, W.E., III, &
LEVIN, S. (1983) Distribution of 14C-labelled acrylamide and
betaine in foetuses of rats, rabbits, beagle dogs, and
miniature pigs. Food Chem. Toxicol., 21(1): 49-58.
ILO (1980) Occupational exposure limits for airborne toxic
substances, Geneva, International Labour Organisation, 290 pp.
INOMATA, J. (1967) Nervous symptoms and kinetics of
porphyrin and acetyl co-enzyme A, especially on the basis of
changes in toxic nerve disturbances. J. Jpn. Organneurosis
Soc., 69: 490-516.
IRPTC (1983) Legal file, Geneva, International Register of
Potentially Toxic Chemicals, United Nations Environment
Programme.
ISMAILOVA, S.K. (1966) [Suppression of the development of
plant tumours (tomato cancer) by inhibitors of free radicals.]
Mater. Sess. Zakavkaz. Sov. Koord. Nauch-Issied. Rab. Zasch.
Rast., pp. 412-415 (in Russian).
JAKOBSEN, J. & SIDENIUS, P. (1983) Early and dose-dependent
decrease of retrograde axonal transport in acrylamide-
intoxicated rats. J. Neurochem., 40(2): 447-454.
JAMES, K.A.C., BRAY, J.J., MORGAN, I.G., & AUSTIN, L. (1970)
The effect of colchicine on the transport of axonal protein in
the chicken. Biochem. J., 117: 767-771.
JOHNSON, E.C. & MURPHY, S.D. (1977) Effect of acrylamide
intoxication on pyridine nucleotide concentrations and
functions in rat cerebral cortex. Biochem. Pharmacol., 26:
2151-2155.
JOHNSON, K.A., GORZINSKI, S.J., BODNER, K.M., & CAMPBELL,
R.A. (1984) Acrylamide: A two-year drinking water chronic
toxicity-oncogenicity study in Fischer 344 rats. Final report,
Michigan, USA, Dow Chemical Company, 257 pp.
JOLICOEUR, F.B., RONDEAU, D.B., BARBEAU, A., & WAYNER, M.J.
(1979) Comparison of neurobehavioural effects induced by
various experimental models of ataxia in the rat. Neurobehav.
Toxicol., 1(Suppl. 1): 175-178.
KANKAANPAA, J., ELOVAARA, E., HEMMINKI, K., & VAINIO, H.
(1979) Embryotoxicity of acrolein, acrylonitrile, and
acrylamide in developing chick embryos. Toxicol. Lett., 4:
93-96.
KAPLAN, M.L. & MURPHY, S.D. (1972) Effects of acrylamide on
rotarod performance and sciatic nerve beta-glucoronidase
activity of rats. Toxicol. appl. Pharmacol., 22: 259-268.
KAPLAN, M.L., MURPHY, S.D., & GILLIES, F.H. (1973)
Modification of acrylamide neuropathy in rats by selected
factors. Toxicol. appl. Pharmacol., 24: 564-579.
KEMPLAY, S. & CAVANAGH, J.B. (1983) Effects of acrylamide
and botulinum toxin on horseradish perioxidase labelling of
trigeminal motor neurons in the rat. J. Anat., 137(3): 477-482.
KEMPLAY, S. & CAVANAGH, J.B. (1984) Effects of acrylamide
and some other sulfhydryl reagents on spontaneous and
pathologically-induced terminal sprouting from motor
end-plates. Muscle Nerve, 7: 101-109.
KESSON, C.M., LAWSON, D.H., & BAIRD, A.W. (1977) Acrylamide
poisoning. Postgrad. med. J., 53: 16-17.
KOZLOV, Y.P. & DOBRINA, S.K. (1966) [Effect of acrylamide
and its hydrated derivative on the E.P.R. spectrum and growth
of normal and tumour tissues in animals.] Biofizika, 11(1):
168-170 (in Russian).
KUPERMAN, A.S. (1957) The pharmacology of acrylamides,
Ithaca, New York, Cornell University Graduate School, 86 pp.
KUPERMAN, A.S. (1958) Effects of acrylamide on the central
nervous system of the cat. J. Pharmacol. exp. Ther., 123:
180-192.
LANDE, S.S., BOSCH, S.J., & HOWARD, P.H. (1979) Degradation
and leaching of acrylamide in soil. J. environ. Qual., 8(1):
133-137.
LE QUESNE, P.M. (1978) Clinical expression of neurotoxic
injury and diagnostic use of electromyography. Environ. Health
Perspect., 26: 89-95.
LE QUESNE, P.M. (1980) Acrylamide. In: Spencer, P.S. &
Schaumburg, H.H., ed. Experimental and clinical
neurotoxicology, Baltimore, Maryland, Williams & Wilkins
Company, p. 309.
LESWING, R.J. & RIBELIN, W.E. (1969) Physiologic and
pathologic changes in acrylamide neuropathy. Arch. environ.
Health, 18: 22-29.
LEWKOWSKI, J.P., YANG, Y.Y., ORTHOEFER, J.G., FOX, D.A., &
TARDIFF, R.G. (1978) Effects of low-level exposure to
acrylamide in water on spontaneous locomotor activity.
Toxicol. appl. Pharmacol., 45(1): 251.
LIJINSKY, W. & ANDREWS, A.W. (1980) Mutagenicity of vinyl
compounds in Salmonella typhimurium. Teratog. Carcinog.
Mutagen., 1: 259-267.
LOEB, A.L. & ANDERSON, R.J. (1981) Antagonism of acrylamide
neurotoxicity by supplementation with vitamin B6.
Neurotoxicology, 2: 625-633.
LOWNDES, H.E., BAKER, T., CHO, E.S., & JORTNER, B.S. (1978)
Position sensitivity of de-afferented muscle spindles in
experimental acrylamide neuropathy. J. Pharmacol. exp. Ther.,
205(1): 40-48.
MCCOLLISTER, D.D., OYEN, F., & ROWE, V.K. (1964) Toxicology
of acrylamide. Toxicol. appl. Pharmacol., 6: 172-181.
MCKIM, J.M. & ANDERSON, R.L. (1976) Water pollution: Effects
of pollution on freshwater fish. J. Water Pollut. Control
Fed., 48(6): 1544-1620.
MACWILLIAMS, D.C. (1973) Acrylamide and other a, ß-
unsaturated amides. In: Yocum & Nygvist, ed. Functional
monomers.
MACWILLIAMS, D.C., KAUFMAN, D.C., & WALDING, B.F. (1965)
Polarographic and spectrophotometric determination of
acrylamide in acrylamide polymers and copolymers. Anal. Chem.,
37: 1546-1552.
MALTEN, K.E., VAN DER MEER-ROSEN, C.H., & SEUTTER, E. (1978)
Nyloprint-sensitive patients react to N,N '-methylenebis-
acrylamide. Contact Dermatitis, 4: 214-222.
MAPP, C., MAZZOTTA, M., BARTOLUCCI, G.B., & FABBRI, L.
(1977) [Neuropathy due to acrylamide: First observations in
Italy.] Med. Lav., 68(1): 1-12 (in Italian).
MATTOCKS, A.R. (1968) Spectrophotometric determination of
pyrazolines and some acrylic amides and esters. Anal. Chem.,
40(8): 1347-1399.
MAURISSEN, J.P.J., WEISS, B., & DAVIS, H.T. (1983)
Somatosensory thresholds in monkeys exposed to acrylamide.
Toxicol. appl. Pharmacol., 71: 266-279.
MERIGAN, W.H., BARKDOLL, E., & MAURISSEN, J.P.J. (1982)
Acrylamide-induced visual impairment in primates. Toxicol.
appl. Pharmacol., 62: 342-345.
METCALF, R.L., LU, P.-Y., & KAPOOR, I.P. (1973)
Environmental distribution and metabolic fate of key
industrial pollutants and pesticides in a "model ecosystem",
Springfield, Virginia, National Technical Information Center,
US Department of Commerce, 80 pp.
MILLER, M.J., CARTER, D.E., & SIPES, I.G. (1982)
Pharmacokinetics of acrylamide in Fischer-344 rats. Toxicol.
appl. Pharmacol., 63: 36-44.
MILLER, M.S., MILLER, M.J., BURKS, T.F., & SIPES, I.G.
(1983) Altered retrograde axonal transport of nerve growth
factor after single and repeated doses of acrylamide in the
rat. Toxicol. appl. Pharmacol., 69: 96-101.
MORI, H. (1975) Environmental pollution due to acrylamide
and its toxicity. Zankoku Kogai Kenkyukai Zasshi, 1: 59-65.
MORIMOTO, M., et al. (1975) Poison victims due to acrylamide
mixed with well water at Shingu, Fukuoka Prefecture I. Inquiry
into causes. Yusui tohaisui, 17: 1307-1318.
MORVILLER, P. (1969) Propos sur un toxique industriel peu
connu en France : L'acrylamide. Arch. Mal. prof. Méd. Trav.
Sécur. soc., 30: 527-530.
MUKHTAR, H., DIXIT, R., & SETH, P.K. (1981) Reduction in
cutaneous and hepatic glutathione contents, glutathione-S-
transferase, and aryl hydrocarbon hydroxylase activities
following topical application of acrylamide to mouse. Toxicol.
Lett., 9: 153-156.
NEELY, W.B., BRANSON, D.R., & BLAU, G.E. (1974) Partition
coefficient to measure bioconcentration potential of organic
chemicals in fish. Environ. Sci. Technol., 8(13): 1113-1115.
NILSEN, O.G., TOFTGARD, R., INGELMAN-SUNDBERG, M., &
GUSTAFSSON, J.-A. (1978) Qualitative alterations of
cytochrome P-450 in mouse liver microsomes after
administration of acrylamide and methylmethacrylate. Acta
Pharmacol. Toxicol. (Copenhagen), 43: 299-305.
NIOSH (1976) Criteria for a recommended standard -
Occupational exposure to acrylamide, Washington DC, National
Institute for Occupational Safety and Health, 127 pp.
NISHIKAWA, H., HOSOMURA, H., & SONODA, Y. (1979) [Behaviour
of acrylamide in soil-plant systems.] Gifu-Ken Kogyo Gijutsu
Kenkyu Hokoku, 11: 31-34 (in Japanese).
NORRIS, M.V. (1967) Acrylamide. In: Snell, F.D. & Hilton,
C.L., ed. Encyclopedia of industrial chemical analysis,
Interscience, Vol. 4, pp. 160-168.
NOVIKOVA, E.E. (1979) [Toxic effect of acrylamide after
entering through the skin.] Gig. i Sanit., 10: 73-74 (in
Russian).
ORTIZ, E., PATEL, J.M., & LEIBMAN, K.C. (1981) Specific
inactivation of aniline hydroxylase by a reactive intermediate
formed during acrylamide biotransformation by rat liver
microsomes. Adv. exp. Med. Biol., 136(B): 1221-1227.
ORTIZ DE MONTELLANO, P.R. & MICO, B.A. (1980) Destruction of
cytochrome P-450 by ethylene and other olefins. Mol.
Pharmacol., 18: 128.
PASTOOR, T. & RICHARDSON, R.J. (1981) Blood dynamics of
acrylamide in rats. Toxicologist, 1(1): 53.
PASTOOR, T., HEYDENS, W., & RICHARDSON, R.J. (1980) Time and
dose-related excretion of acrylamide metabolites in the urine
of Fischer-344 rats. In: Second International Congress on
Toxicology, Brussels, Belgium, 6-11 July.
PAULET, G. & VIDAL, Mme (1975) De la toxicité de quelques
esters acryliques et mèthacryliques de l'acrylamide et des
polyacrylamides. Arch. Mal. prof. Méd. Trav. Sécur. soc., 36:
58-60.
PEDERSEN, N.B., CHEVALLIER, M.-A., & SENNING, A. (1982)
Secondary acrylamides in nyloprint printing plate as a source
of contact dermatitis. Contact Dermatitis, 8: 256-262.
PLEASURE, D.E., MISHLER, K.E., & ENGEL, W.K. (1969) Axonal
transport of proteins in experimental neuropathies. Science,
166(3904): 524-525.
POOLE, C.F., SYE, W.F., ZLATKIS, A., & SPENCER, P.S. (1981)
Determination of acrylamide in nerve tissue homogenates by
electron-capture gas chromatography. J. Chromatogr., 217:
239-245.
POST, E.J. & MCLEOD, J.G. (1977a) Acrylamide autonomic
neuropathy in the cat. I. Neurophysiological and histological
studies. J. neurol. Sci., 33: 353-374.
POST, E.J. & MCLEOD, J.G. (1977b) Acrylamide autonomic
neuropathy in the cat. Part 2. Effects on mesenteric vascular
control. J. neurol. Sci., 33: 375-385.
PRINEAS, J. (1969) The pathogenesis of dying-back
polyceuropathies. II. An ultrastructural study of experimental
acrylamide intoxication in the cat. J. Neuropathol. exp.
Neurol., 28: 598-621.
PRYOR, G.T., UYENO, E.T., TILSON, H.A., & MITCHELL, C.L.
(1983) Assessment of chemicals using a battery of
neurobehavioural tests: a comparative study. Neurobehav.
Toxicol. Teratol., 5: 91-117.
PTCN (1983) Neoplasm rise in high-dose female rats.
Pesticide and toxic chemical News, 17 August, p. 4.
PYE, R.J. & PEACHEY, R.D.G. (1976) Contact dermatitis due to
nyloprint. Contact Dermatitis, 2: 144-146.
RAFALES, L.S., BORNSCHEIN, R.L., & CARUSO, V. (1982)
Behavioral and pharmacological responses following acrylamide
exposure in rats. Neurobehav. Toxicol. Teratol., 4: 355-364.
RASOOL, C.G. & BRADLEY, W.G. (1978) Studies on axoplasmic
transport of individual proteins. I. Acetylcholinestrase
(AChE) in acrylamide neuropathy. J. Neurochem., 31: 419-425.
REFSVIK, T. (1978) Excretion of methylmercury in rat bile:
The effect of diethylmaleate, cyclohexene oxide, and
acrylamide. Acta pharmacol. toxicol. (Copenhagen), 42: 135-141.
SABRI, M.I. & SPENCER, P.S. (1980) Toxic distal axonopathy:
Biochemical studies and hypothetical mechanisms. In: Spencer,
P.S. & Schaumburg, H.H., ed. Experimental and clinical
neurotoxicity, Baltimore, Maryland, Williams and Wilkins, pp.
309-325.
SATCHELL, P.M. & MCLEOD, J.G. (1981) Megaoesophagus due to
acrylamide neuropathy. J. Neurol. Neurosurg. Psychiatr., 44:
906-913.
SATCHELL, P.M., MCLEOD, J.G., HARPER, B., & GOODMAN, A.H.
(1982) Abnormalities in the vagus nerve in canine acrylamide
neuropathy. J. Neurol. Neurosurg. Psychiatr., 45: 609-619.
SATOYOSHI, E., KINOSHITA, M., YANO, H., & SUZUKI, Y. (1971)
[Three cases of peripheral polyneuropathy due to acrylamide.]
Clin. Neurol. (Tokyo), 11: 667-672 (in Japanese).
SCHAUMBURG, H.H., WISNIEWSKI, H.M., & SPENCER, P.S. (1974)
Ultrastructural studies of the dying-back process. I.
Peripheral nerve terminal and axon degeneration in systemic
acrylamide intoxication. J. Neuropathol. exp. Neurol., 33:
260-284.
SCHOTMAN, P., GIPON, L., JENNEKENS, F.G.I., & GISPEN, W.H.
(1977) Polyneuropathies and CNS protein metabolism. II.
Changes in the incorporation rate of leucine during acrylamide
intoxication. Neuropathol. appl. Neurobiol., 3: 125-136.
SCHOTMAN, P., GIPON, L., JENNEKENS, F.G.I., & GISPEN, W.H.
(1978) Polyneuropathies and CNS protein metabolism. III.
Changes in protein synthesis rate induced by acrylamide
intoxication. J. Neuropathol. exp. Neurol., 37: 820-837.
SEPPALAINEN, A.M. (1976) Applications of neurophysiological
methods in occupational medicine. A review. Scand. J. Work
Environ. Health, 1: 1-14.
SHARMA, R.P. & OBERSTEINER, E.J. (1977a) Acrylamide
cytotoxicity in chick ganglia cultures. Toxicol. appl.
Pharmacol., 42: 149-156.
SHARMA, R.P. & OBERSTEINER, E.J. (1977b) Acrylamide effects
of catecholamine metabolism. Toxicologist, 1(1): 52.
SHIRAISHI, Y. (1978) Chromosome aberrations induced by
monomeric acrylamide in bone marrow and germ cells of mice.
Mutat. Res., 57: 313-324.
SIDENIUS, P. & JAKOBSEN, J. (1983) Anterograde axonal
transport in rats during intoxication with acrylamide. J.
Neurochem., 40(3): 697-704.
SJOHOLM, I. & EDMAN, P. (1979) Acrylic microspheres in vivo.
I. Distribution and elimination of polyacrylamide
microparticles after intravenous and intraperitoneal injection
in mouse and rat. J. Pharmacol. exp. Ther., 211(3): 656-662.
SKELLY, N.E. & HUSSER, E.R. (1978) Determination of
acrylamide monomer in polyacrylamide and in environmental
samples by high performance liquid chromatography. Anal.
Chem., 50: 1959-1962.
SONGSON, P., BLOOM, S., TILL, S., & SMITH, R.S. (1984) Use
of a biothesiometer to measure individual vibration thresholds
and their variation in 519 non-diabetic subjects. Br. med. J.,
288: 1793-1795.
SONODA, Y., KANO, K., & HARA, T. (1977) [The behaviour of
polyacrylamides as cohesive agent in soil-plant system.] Gifu
Daigaku Kenkyu Hokoku, 40: 61-69 (in Japanese).
SOUYRI, F., CHRETIEN, M., & DROZ, B. (1981) "Acrylamide-
induced" neuropathy and impairment of axonal transport of
proteins. I. Multifocal retention of fast transported proteins
at the periphery of axons as revealed by light microscope
radioautography. Brain Res., 205: 1-13.
SPENCER, P.S. (1979) Unfinished final report, Washington DC,
National Institute for Occupational Safety and Health (NIOSH
Contract No. OH 00535).
SPENCER, P.S. & SCHAUMBURG, H.H. (1974a) A review of
acrylamide neurotoxicity. I. Properties, uses, and human
exposure. J. Can. neurol. Sci., 1: 143-150.
SPENCER, P.S. & SCHAUMBURG, H.H. (1974b) A review of
acrylamide neurotoxicity. II. Experimental animal
neurotoxicity and patholgic mechanism. J. Can. neurol. Sci.,
1: 152-169.
SPENCER, P.S. & SCHAUMBURG, H.H. (1977) Ultrastructural
studies of the dying-back process. IV. Differential
vulnerability of PNS and CNS fibres in experimental central-
peripheral distal-peripheral distal axonopathies. J.
Neuropathol. exp. Neurol., 36: 300-320.
SPENCER, P.S., SABRI, M.I., SCHAUMBURG, H.H., & MOORE, C.
(1979) Does a defect in energy metabolism in the nerve fibre
cause axonal degeneration in polyneuropathies? Ann. Neurol.,
5: 501.
STAHL, W.R. (1967) Scaling of respiratory variables in
mammals. J. appl. Physiol., 22: 453-460.
STERMAN, A.B. (1982) Acrylamide induces early morphologic
reorganization of the neuronal cell body. Neurology, 32(9):
1023-1026.
STERMAN, A.B. (1983) Altered sensory ganglia in acrylamide
neuropathy. Quantitative evidence of neuronal reorganization.
J. Neuropathol. exp. Neurol., 42(2): 166-176.
STERMAN, A.B., PANASCI, D.J., & PERSONS, W. (1983a) Does
pyruvate prevent acrylamide neurotoxicity? Implications for
disease pathogenesis. Exp. Neurol., 82: 148-158.
STERMAN, A.B., PANASCI, D.J., & SHEPPARD, R.C. (1983b)
Autonomic-cardiovascular dysfunction accompanies sensory-
motor impairment during acrylamide intoxication.
Neurotoxicology, 4: 45-52.
SUMNER, A.J. & ASBURY, A.K. (1974) Acrylamide neuropathy:
Selective vulnerability of sensory fibres. Arch. Neurol., 32:
170.
SUZUKI, K. & PFAFF, L.D. (1973) Acrylamide neuropathy in
rats. An electron microscopic study of degeneration and
regeneration. Acta neuropathol., 24: 197-213.
SUZUKI, H. & SUZUMURA, M. (1977) [Determination of a small
amount of acrylamide in air.] Sangyo Igaku, 19: 189-193 (in
Japanese).
TAKAHASHI, M., OHARA, T., HASHIMOTO, K. (1971) Electro-
physiological study of nerve injuries in workers handling
acrylamide. Int. Arch. Arbeitsmed., 28: 1-11.
TANII, H. & HASHIMOTO, K. (1981) Studies on in vitro
metabolism of acrylamide and related compounds. Arch.
Toxicol., 48: 157-166.
TANII, H. & HASHIMOTO, K. (1982) Structure-toxicity
relationship of acrylates and methacrylates. Toxicol. Lett.,
11: 125-129.
TEAL, J.J. & EVANS, H.L. (1982) Behavioral effects of
acrylamide in the mouse. Toxicol. appl. Pharmacol., 63:
470-480.
THOMANN, P., KOELLA, W.P., KRINKE, G., PETERMANN, H., ZAK, G.,
& HESS, R. (1974) The assessment of peripheral neurotoxicity
in dogs: Comparative studies with acrylamide and clioquinol.
Agent Actions, 4(1): 47-53.
TILSON, H.A. (1981) The neurotoxicity of acrylamide: an
overview. Neurobehav. Toxicol. Teratol., 3: 113-120.
TILSON, H.A. & CABE, P.A. (1979) The effects of acrylamide
given acutely or in repeated doses on fore- and hindlimb
function of rats. Toxicol. appl. Pharmacol., 47: 253-260.
TILSON, H.A. & SQUIBB, R.E. (1982) The effects of acrylamide
on the behavioural suppression produced by psychoactive
agents. Neurotoxicology, 3: 113-120.
TILSON, H.A., CABE, P.A., & SPENCER, P.S. (1979) Acrylamide
neurotoxicity in rats: A correlated neurobehavioural and
pathological study. Neurotoxicology, 1: 89-104.
TILSON, H.A., CABE, P.A., & BURNE, T.A. (1980) Behavioural
procedures for the assessment of neurotoxicity. In: Spencer,
P.S. & Schaumburg, H.H., ed. Experimental and clinical
neurotoxicology, Baltimore, Maryland, Williams and Wilkins,
pp. 758-766.
TOMCUFCIK, A.S., WILLSON, S.D., VOGEL, A.W., & SLOBODA, A.
(1961) N-N' -alkylene-bis (acrylamides), N -(acrylamidomethyl-
3-halopropionamides and related compounds: A new series of
anti-tumour agents. Nature (Lond.), 191: 611-612.
TSOU, K.C., DAMLE, S.B., CRICHLOW, R.W., RAVDIN, R.G., &
BLUNT, H.W. (1967) Synthesis of possible cancer
chemotherapeutic agents based on enzyme rationale. VI.
Allylamine derivatives. J. pharm. Sci., 56(4): 484-488.
TURNER, C.J. (1981) Toxin-induced inhibition of nerve
terminal growth. Neurotoxicology, 2: 313-327.
UK MINISTRY OF HOUSING AND LOCAL GOVERNMENT (1969) First
statement of the committee on new chemicals for water
treatment. Water Treat. Exam., 18: 90.
UPHOUSE, L.L. (1981) Interactions between handling and
acrylamide on the striatal dopamine receptor. Brain Res., 221:
421-424.
UPHOUSE, L.L. & RUSSELL, M. (1981) Rapid effects of
acrylamide on spiroperidol and serotonin binding in neural
tissue. Neurobehav. Toxicol. Teratol., 3: 281-284.
UPHOUSE, L.L., NEMEROFF, C.B., MASON, G., PRANGE, A.J., &
BONDY, S.C. (1982) Interactions between "handling" and
acrylamide on endocrine responses in rats. Neurotoxicology, 3:
121-125.
US EPA (1978) Environmental monitoring near industrial
sites: Acrylamide, Washington DC, US Environmental Protection
Agency (EPA Report No. 560/6-78-001, PB-281 879).
US EPA (1980a) Assessment of testing needs - acrylamide,
Washington DC, US Environmental Protection Agency (EPA Report
No. 560/11-80-016, PB 80-220312).
US EPA (1980b) A foetal toxicity study of acrylamide in
rats, Washington DC, US Environmental Protection Agency,
Information Control Branch (FYI-OTS-0680-0076).
US EPA (1980c) Acrylamide test rule, Washington DC, US
Environmental Protection Agency, Health Review Division
(TS-792), In-house memorandum, 10 March 1980.
US EPA (1981) Level 1 economic evaluation: Acrylamide,
Washington DC, US Environmental Protection Agency, Office of
Pesticides and Toxic Substances, 27 pp (Contract No.
68-01-5864).
US EPA (1982a) Communication with Dr R.W. Mast, Test Rules
Development Branch, Washington DC, US Environmental Protection
Agency, Information Control Branch, Freedom of Information Act
(TS-778).
US EPA (1982b) Acrylamide monomer: A two-year chronic
toxicity-oncogenicity study administered via the drinking
water fo CDF Fischer-344 rats, Washington DC, US Environmental
Protection Agency, Information Control Branch
(FYI-OTS-0882-0200).
US EPA (1982c) Chronic toxicity-oncogenicity study on
acrylamide in Fischer 344 rats, Washington DC, US
Environmental Protection Agency, Information Control Branch
(FYI-OTS-1282-0223).
US EPA (1983) Acrylamide response to the Interagency Testing
Committee. Fed. Reg., 48: 4.
USSR, MINISTRY OF HEALTH (1979) Maximum allowable
concentrations of harmful substances in the air of the working
zone 1972-79, Moscow, Ministry of Health of the USSR (List
No. 13).
VASAVADA, H.A. & PADAYATTI, J.D. (1981) Rapid transfection
assay for screening mutagens and carcinogens. Mutat. Res., 91:
9-14.
VIDYASAGAR, T.R. (1981) Optic nerve components may not be
equally susceptible to damage by acrylamide. Brain Res., 224:
452-455.
VON BURG, R., PENNEY, D.P., & CONROY, P.J. (1981) Acrylamide
neurotoxicity in the mouse: a behavioural, electrophysio-
logical, and morphological study. J. appl. Toxicol., 1(4):
227-233.
WALDEN, R. & SCHILLER, C.M. (1981) Quantitative analysis of
acrylamide in the milk of lactating rats following oral in
vivo exposure. Environ. Toxicol., II: 678.
WALDEN, R., SQUIBB, R.E., & SCHILLER, C.M. (1981) Effects of
prenatal and lactational exposure to acrylamide on the
development of intestinal enzymes in the rat. Toxicol. appl.
Pharmacol., 58: 363-369.
WINDHOLZ, M., BUDAVARI, S., STROUMTSOS, L.Y., & FERTIG, M.N.
(1976) The merck index, 9th ed., Rahway, New Jersey, Merck &
Co., p. 127.
YOUNG, J.D., SLAUTER, R.W., GORZINSKI, S.J., & WADE, C.W.
(1979) Toxicodynamics of acrylamide in rats. Toxicol. appl.
Pharmacol., 48(1): 91.