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July 1, 1977
ACRYLONITRILE
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CURRENT INTELLIGENCE BULLETIN:
ACRYLON1TRILE
July 1, 1977
The National Institute for Occupational Safety and Health (NIOSH) has
recently been informed that occupational exposure to acrylonitrile may be
associated with an excess of lung and colon cancer.
In May 1977, E. I. du Pont de Nemours & Company,Inc., informed NIOSH of
results of a preliminary epidemiologic study demonstrating an excess of
cancer among workers exposed to acrylonitrile at a Du Pont textile fibers
plant in Camden, South Carolina. Additionally, in April, NIOSH received
from the Manufacturing Chemists Association (MCA) a one-year interim
report of on-going ingestion and inhalation studies of acrylonitrile in
laboratory rats; the rats developed a variety of tumors, including
carcinomas.
Background
Acrylonitrile is an explosive, flammable liquid having a normal boiling point
of 77°C and a vapor pressure of 80 mm (20°C). The toxic effects of
acrylonitrile are similar to cyanide poisoning. The chemical structure of
acrylonitrile, CH2=CICN, resembles that of vinyl chloride, a material
known to cause human cancer. Synonyms for acrylonitrile include acrylon,
carbacryl, cyanoethylene, fumigrain, 2-propenenitrile, VCN, ventox and
vinyl cyanide.
Approximately one and one-half billion pounds per year of acrylonitrile are
manufactured in the United States by the reaction of propylene with
ammonia and oxygen in the presence of a catalyst. A number of other
processes have been used in the past. Current domestic producers of
acrylonitrile are American Cyanamid Company (New Orleans, Louisiana),
E. I. du Pont de Nemours & Company, Inc. (Beaumont, Texas and Memphis,
Tennessee), Monsanto Company (Chocolate Bayou, Texas), and The Standard
Oil Company (Ohio) (Lima, Ohio).
The major use of acrylonitrile is in the production of acrylic and modacrylic
fibers by copolymerization with methyl acrylate, methyl methacrylate, vinyl
acetate, vinyl chloride, or vinylidene chloride. Acrylic fibers, marketed
under tradenames including Acrilan, Creslan, OrIon, and Zefran, are used in
the manufacture of apparel, carpeting, blankets, draperies, and upholstery.
Some applications of modacrylic fibers are synthetic furs and hair wigs;
tradenames for modacrylic fibers include Acrylan, Elura, SEF, and Verel.
Acrylic and/or modacrylic fibers are manufactured from acrylonitrile by
American Cyanamid Company (Milton, Florida), Dow Badishe Company
(Williamsburg, Virginia), E. I. du Pont de Nemours & Company,Inc. (Camden,
South Carolina and Waynesboro, Virginia), Eastman Kodak Company
(Kingsport, Tennessee), and Monsanto Company (Decatur, Alabama).
Other major uses of acrylonitrile include the manufacture of acrylonitrile—
butadiene—styrene (ABS) andstyrene-acrylonitrile (SAN) resins (used to
produce a variety of plastic products), nitrile elastomers and latexes, and
other chemicals (e.g., adiponitrile, acrylamide). Acrylonitrile is also used as
a fumigant. The U.S. Food and Drug Administration has recently banned the
use of an acrylonitrile resin for soft drink bottles.
NIOSH estimates that 125,000 persons are potentially exposed to
acrylonitrile in the workplace.
Human Epidemiologic Studies
A preliminary epidemiologic study conducted by the E. I. du Pont de
Nemours & Company,Inc., indicated an excess risk of lung and colon cancer
among workers with potential acrylonitrile exposure. This study examined
the cancer experience of a cohort of 470 male workers who began working in
the polymerization operation at Du Pont's Camden, South Carolina textile
fibers plant between 1950 and 1955; only persons who are actively employed
or who have retired from Du Pont were included in the study. A more
complete analysis will include an approximately 400 additional workers also
employed during this time, but who quit or were laid off.
In a study based on Du Pont's Mortality File, the cohort experienced a total
of 8 deaths due to cancer between 1969 and 1975 (allowing for a 20-year
latency period). Only 4 deaths would have been expected among this cohort
based on Du Pont company mortality rates, 1969-75 (excluding the mortality
experience of the cohort), and about 5 deaths would have been expected
based on rates for U.S. white males, 1970. Of the eight cancer deaths, four
were due to cancer of the lung while the expected number of lung cancer
deaths was 1.5.
In another analysis, data from the Du Pont Cancer Registry (including only
cancer diagnoses for active employees enrolled in Du Pont's insurance
program) revealed 16 cancer cases occurring between 1969 and 1975 among
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the cohort of workers (again allowing for a 20-year latency period). Only 5.8
cases would have been expected based on Du Pont company rates (excluding
the cohort). Six of these cases were lung cancers (1.5 expected), three were
cancers of the large intestine (0.5 expected), and the remaining seven
cancers were from seven other primary sites. Because of incomplete
reporting, skin cancer cases were excluded from this analysis.
A total of 18 cancers (appearing on Du Pont's Mortality File and/or Cancer
Registry) occurred between 1969 and 1975 among the cohort of 470 workers
first exposed between 1950 and 1955. All cancer cases occurred among the
approximately 350 workers who were first exposed to acrylonitrile during
the start—up of the plant between 1950 and 1952. Du Pont stresses the
preliminary nature of these findings and does "not consider this study to
provide definitive evidence of the carcinogenicity of acrylonitrile in man;"
however, Du Pont did state that these findings, when considered in light of
the recent animal tests, '1raise a serious suspicion that it [acrylonitrilell may
be a human carcinogen."
Laboratory Animal Studies
In April 1977, the Manufacturing Chemists Association reported interim
results of two-year feeding and inhalation studies of acrylonitrile in
laboratory rats. The following results were reported at the end of the first
year of investigation by The Dow Chemical Company.
In the ingestion study, acrylonitrile is being incorporated into the thinking
water of laboratory rats at concentrations of 0, 35, 100, or 300 ppm
(corresponding to doses of approximately 0, 4, 10, or 30 mg/kg body
weight/day). Rats ingesting 35 ppm acrylonitrile exhibited mild signs of
toxicity (decreased water and food consumption, and decreased body weight
gain), while those ingesting 100 or 300 ppm showed marked signs of toxicity.
Male and female rats that ingested 100 or 300 ppm acrylonitrile for 12
months were reported to have developed stomach papillomas (1 of 20 rats at
100 ppm, and 12 of 20 at 300 ppm), central nervous system tumors (2 of 20
at 35 ppm, 6 of 20 at 100 ppm, and 3 of 20 at 300 ppm), and Zymbal gland
carcinoma (2 of 20 at 100 ppm, and 2 of 20 at 300 ppm); no such tumors were
seen in controlanimals.
In the inhalation study, male and female rats are being exposed to 0, 20, or
80 ppm acrylonitrile for six hours per day, five days per week. Following
one year of exposure to 80 ppm acrylonitrile, 26 rats were killed; three of
these were found to have developed central nervous system tumors
comparable to those reported in the ingestion study. The investigators also
reported that gross examination of other rats in this study exposed to 80
ppm acrylonitrile has revealed an increased incidence of ear canal tumors
and mammary region masses. In animals exposed to 20 ppm, there was an
apparent increase in subcutaneous masses of the mammary region although
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no ear canal or central nervous system tumors were observed at this dose
level.
Acute toxic effects of acrylonitrile have been extensively studied in a wide
variety of laboratory animals. There is considerable variation in resistance
to acrylonitrile exposure in different species. Guinea pigs seem to be the
most resistant to the toxic effects of acrylonitrile inhalation while dogs are
least resistant. Toxic effects of acrylonitrile inhalation which have been
noted in animals include damage to the central nervous system, lung, liver,
and kidneys (Krysiak, Medycyna Pracy, 22:601-10, 1971; Knobloch, Medycyna
Pracy, 22:257—69, 1971). When administered to pregnant mice, acrylonitrile
has also been found to be embryotoxic (Scheufler, Biol. Rundsch., 14:227-9,
1976).
NIOSH Action
In light of the flu Pont data, the National Institute for Occupational Safety
and Health (NIOSH) has apprised major manufacturers and users of the
possible health effects associated with acrylonitrile exposure. NIOSH has
also suggested that these firms examine medical records of their employees
in order to determine the existence of any such health effects. In addition,
NIOSH is taking action to identify a suitable worker population for possible
epidemiologic studies.
NIOSH is conducting an assessment of control technology in the plastics and
resins industry (including acrylonitrile processes), which will identify and
define technology for reducing occupational exposures. NIOSH is also
developing a criteria document containing a recommended standard for
occupational exposure to nitriles, including acrylonitrile.
Recommendation
The current Occupational Safety and Health Administration (OSHA) standard
for occupational exposure to acrylonitrile is an 8-hour Time Weighted
Average of 20 ppm. However, in light of the new human information
generated by flu Pont, as well as the animal data provided by MCA, NIOSH
believes it would be prudent to handle acrylonitrile in the workplace as if it
were a human carcinogen. The attached interim recommended industrial
hygiene practices were developed by NIOSH to help reduce occupational
exposure to acrylonitrile.
Attachment
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INDUSTRIAL HYGIENE PRACTICES TO REDUCE
EXPOSURE TO ACRYLON1TRILE
The recent finding of cancer associated with workers occupationally exposed
to acrylonitrile has indicated a need to reduce worker exposure. The follow-
ing are suggested good industrial hygiene practices that can help to reduce
exposure to acrylonitrile.
A. Regulated Area. Regulated areas should be established
during manufacture, polymerization, use, handling or
storage.
Access. Access should be restricted to employees
who have been properly informed of the potential
hazard of acrylonitrile and proper control
measures.
1. Engineering Controls. The most effective
controlof any contaminant is controlat the
source of generation wherever possible. Effec-
tive engineering measures may include enclosure
and/or specific local exhaust ventilation with
suitable collectors to prevent community air
pollution.
a. Wherever possible the operations
utilizing acrylonitrile should be
enclosed (with appropriate venti-
lation) to reduce exposures to the
operators and others in the area.
b. Due to the explosivepotential
of acrylonitrile,spark proof venti-
lation systems should be selected.
c. Regularly scheduled examinations
for leakageof acrylonitrile from
the system should be performed
using appropriate instrumentation,
or sampling and analytical tech-
niques.
d. With specific respect to the poly-
merization operation, double me-
chanical pump seals have reduced
leakage. Effective stripping of
the acrylonitrile monomerbefore
the polymer is dried and blended
has decreased occupational expo-
sure to the monomer.
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3. Respirators. Personal respiratory protective
devices should only be used as an interim meas-
ure while engineering controls are being in-
stalled, for non-routine use and during emer-
gencies. Considering the carcinogenic po-
tential of acrylonitrile,the appropriate per-
sonal respiratoryprotective measure is the
use of a positive pressure supplied air respi-
rator, or a positive pressure self-contained
breathing apparatus.
4. Protective Clothing. Protective full body
clothing should be provided and its use required
for employees entering the regulated area.
Upon exiting from the regulated area, the
protective clothing should be left at the point
of exit. With the last exit of the day, the
protective clothing should be placed in a suit-
ably marked and closed container for disposal
or laundering. (Laundry personnel should be
made aware of the potential hazard from han-
dling contaminated clothing.)
5. Cleanliness. Employees should be required
to wash all exposed areas of the body upon
exiting from the regulated areas.
6. Isolation. Any operations involving acrylo-
nitrile should be placed in an isolated area,
in combination with other engineering con-
trols, to reduce exposure to employeesnot
directly concerned with the operations.
B. Medical Monitoring. All employees with a potential ex-
posure to acrylonitrile should be placed under a medical
monitoring program including history and periodic medical
examinations.
6 ° WRNtNIITEfU;I79657-O61/I9O6
