ACETALDEHYDE

CAS No. 75-07-0

First Listed in the Sixth Annual Report on Carcinogens
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CARCINOGENICITY

Acetaldehyde is reasonably anticipated to be a human carcinogen based on sufficient

evidence of carcinogenicity in experimental animals (IARC 1985, 1987, 1999). When
administered by inhalation, acetaldehyde increased the incidence of squamous cell carcinomas
and adenocarcinomas in the nasal mucosa in rats of both sexes and laryngeal carcinomas in
hamsters of both sexes. In another inhalation study using a lower exposure level and in an
intratracheal instillation study, no increased incidence of tumors in hamsters was observed.
When administered by inhalation, acetaldehyde enhanced the incidence of respiratory tract
tumors as induced by intratracheal instillation of benzo[a]pyrene in hamsters of both sexes.

There is inadequate evidence for the carcinogenicity of acetaldehyde in humans (IARC

1985, 1987, 1999). A single study of workers in an aldehyde plant reported nine cases of cancer,
including five cases of bronchial tumors and two cases of carcinomas of the oral cavity. This
study was considered to be inadequate for evaluation because of mixed exposure, the small
number of cases, and the poorly defined population. Three case control studies investigated the
risk of oral, throat, and esophageal cancers following heavy alcohol intake. These studies
consistently showed an increased risk of these cancers in people with genetic polymorphisms;
these polymorphisms resulted in higher blood acetaldehyde concentrations after drinking alcohol
(IARC 1999).

PROPERTIES

Acetaldehyde occurs as a volatile, flammable, colorless liquid. It has a pungent,

suffocating odor, but at dilute concentrations it emits a pleasant, fruity odor. The vapor pressure
of acetaldehyde is 755 mm Hg at 200°C and the vapor density is 1.5. It has a melting point of -
123.5°C, and it boils at 20.2 to 20.8°C with a flash point of -38°C (closed cup). It decomposes
above 400°C to form principally methane and carbon monoxide. Acetaldehyde is miscible in
water, alcohol, ether, benzene, gasoline, solvent naphtha, toluene, xylene, turpentine, acetone,
and other common organic solvents. It is a highly reactive compound that undergoes numerous
condensation, addition, and polymerization reactions. Acetaldehyde is dangerous when exposed
to heat or flame; it can react vigorously with oxidizing material. Acetaldehyde is also
incompatible with acids, bases, alcohol, ammonia, amines, phenols, ketones, and hydrogen
cyanide. It oxidizes readily to form corrosive acetic acid. It will polymerize readily in the
presence of trace metals (iron). Acetaldehyde can form unstable/explosive peroxides with
exposure to air. It may polymerize under influence of air and heat, acids, or bases with potential
of fire or explosion. Acetaldehyde is polymerized violently by concentrated sulfuric acid.
Rubber products decompose on contact with acetaldehyde, but it is not corrosive to most metals
(IARC 1999).

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 Acetaldehyde (Continued)

USE

Acetaldehyde is used primarily as a chemical intermediate, principally for the production

of acetic acid, pyridine and pyridine bases, peracetic acid, pentaerythritol, butylene glycol, and
chloral. It is used in the production of esters, particularly ethyl acetate and isobutyl acetate
(IARC 1985, 1999, Chem. Prod. 1985). It is also used in the synthesis of crotonaldehyde, as well
as flavor and fragrance acetals, acetaldehyde 1,1-dimethylhydrazone, acetaldehyde cyanohydrin,
acetaldehyde oxime, and various acetic esters, paraldehyde, metaldehyde (a molluscicide widely
used to kill slugs and snails), polymers, and various halogenated derivatives (IARC 1985).
Acetaldehyde has been used in the manufacture of aniline dyes and synthetic rubber, to silver
mirrors, and to harden gelatin fibers (Merck 1989). It has been used in the production of
polyvinyl acetal resins, in fuel compositions, and to inhibit mold growth on leather (IARC 1985).
Acetaldehyde is also used in the manufacture of disinfectants, drugs, perfumes, explosives,
lacquers and varnishes, photographic chemicals, phenolic and urea resins, rubber accelerators and
antioxidants, and room air deodorizers; acetaldehyde is a pesticide intermediate (Sittig 1985,
Gosselin et al. 1984).

Acetaldehyde, an alcohol denaturant, is a GRAS (generally recognized as safe) compound

for the intended use as a flavoring agent and adjuvant (Furia and Bellanca 1975, HSDB 2000). It
is an important component of food flavorings and is added to milk products, baked goods, fruit
juices, candy, desserts, and soft drinks; the concentration of acetaldehyde in food is generally up
to 0.047%. In 1976, approximately 19,000 lb of acetaldehyde were used as food additives. It is
an especially useful synthetic flavoring ingredient to impart orange, apple, and butter flavors. It
is used in the manufacture of vinegar and yeast and as a fruit and fish preservative. Acetaldehyde
is approved for use in phenolic resins in molded containers for contact with nonacidic foods.
Acetaldehyde is exempted from a residue tolerance when it is used as a fumigant for storage of
apples and strawberries (IARC 1985).

PRODUCTION

Acetaldehyde was first produced commercially in the United States in 1916. Production
in 1940 was 127 million lb and 816 million lb in 1960. U.S. production of acetaldehyde reached
its peak in 1969 at approximately 1.65 billion lb (IARC 1985). U.S. production reportedly
decreased to 740 million lb in 1989 (EPA 1994). The overall decline in the demand for
acetaldehyde has been attributed to more economical starting materials for principal derivatives
and a lower demand for some acetal derivatives (Chem. Prod. 1985). USITC has reported two to
three manufacturers for each year from 1985 to 1994; production figures, however, were not
made available (USITC 1986-1991, 1993-1995). The 1997 Directory of Chemical Producers
listed one producer for acetaldehyde and two producers for natural acetaldehyde; no production
volumes were disclosed (SRI 1997). The 1998 Chemical Buyers Directory named six U.S.
suppliers of acetaldehyde and two suppliers for natural acetaldehyde (Tilton 1997).
Chemcyclopedia 98 named five such companies (Rodnan 1997). In 2001, Chem Sources (2001)
listed 23 suppliers for acetaldehyde.

U.S. imports of acetaldehyde totaled 1,350 lb in 1985 (HSDB 2000). Imports for 1987
were reported to be 10,000 lb (USDOC Imports 1988). In 2000, imports increased to 120 million
lb (ITA 2001). In 1985, estimated U.S. exports of acetaldehyde were 1.2 billion lb (Chemical
Prod. 1985). Exports for 2000 decreased to 20 million lb (ITA 2001).

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 Acetaldehyde (Continued)

EXPOSURE

The potential for exposure of the general population and workers to acetaldehyde is great.
Acetaldehyde is the product of most hydrocarbon oxidation reactions and is a normal
intermediate in the respiration of most higher plants; it is found in trace amounts in all ripe fruits
and may form in wine and other alcoholic beverages after exposure to air. It is a major
metabolite of ethyl alcohol (Kirk-Othmer 1978). It is found in leaf tobacco and in tobacco smoke
and in automobile and diesel exhaust. Therefore, many individuals are exposed to acetaldehyde
by breathing ambient air.

Acetaldehyde has a widespread natural occurrence. It is a product of alcohol

fermentation and is a metabolic intermediate in higher plants. It is a volatile component of
cotton leaves and blossoms. Acetaldehyde occurs in oak and tobacco leaves and is a natural
component of apples, broccoli, coffee, grapefruit, grapes, lemons, mushrooms, onions, oranges,
peaches, pears, pineapples, raspberries, and strawberries. It has been detected in the essential oils
of alfalfa, rosemary, balm, clary sage, daffodil, bitter orange, camphor, angelica, fennel, mustard,
and peppermint (IARC 1985). Consumers may be exposed to acetaldehyde in cheese, heated
milk, cooked beef, cooked chicken, and rum. It is a synthetic flavoring ingredient in processed
foods, especially margarine. Acetaldehyde is also tolerated as a fumigant residue on apples and
strawberries after storage. It has been detected in mother's milk. Consumers may have been
exposed to acetaldehyde in room air deodorizers (Gosselin et al. 1984, DPIM 1989).
Acetaldehyde is a component of smoke of marijuana cigarettes (1,220 µg/cigarette) and tobacco
cigarettes (980 µg/cigarette to 1.37 mg/cigarette). In addition to potential exposure from food
and cigarette sources, consumers risk exposure in the home environment from pyrolysis products.
Burning wood produces approximately 0.7 g acetaldehyde/kg wood; fireplace emissions range
from 0.083 to 0.20 g/kg wood burned. An estimated total annual emission from residential
burning in the United States is approximately 99 million lb. It is a combustion product of some
plastics (e.g., polycarbonate) and some hard and soft polyurethane foams. Acetaldehyde also
occurs in gasoline exhaust (1.4 to 8.8 mg/m3) and diesel exhaust (0.05 to 6.4 mg/m3) (IARC
1985).

Acetaldehyde has been detected in emissions from power plants that burn fossil fuels,
wood, or trash. It is a natural product of combustion and photooxidation of hydrocarbons
commonly found in the atmosphere. It naturally occurs as emissions from forest fires, volcanoes,
and animal wastes (HSDB 2000).
The 1974 National Occupational Hazard Survey estimated that 1,700 workers were
exposed to acetaldehyde in the United States in four nonagricultural industries (NIOSH 1980,
1981, IARC 1985). The greatest potential for exposure was found in the organic chemicals
industry, with some exposure in fabricated rubber products and biological products industries
(IARC 1985). The National Occupational Exposure Survey (1981-1983) estimated that 14,054
total workers, including 2,772 female workers, were exposed to acetaldehyde (NIOSH 1984).
The estimate was based on observation of actual use of acetaldehyde (97%) and its use as an
ingredient in trade name products (3%). Potential exposure exists for personnel involved in the
manufacturing or use of industrial organic chemicals, dyes, fabricated rubber, plastics, urea-
formaldehyde foam insulation, fuels, drugs, explosives, lacquers and varnishes, photographic
chemicals, pesticides, food additives, leather goods, and mirrors. Acetaldehyde is a potential
exposure problem for automobile and diesel mechanics, gas station attendants, and agricultural
and food industry personnel, as well as personnel in coffee-roasting operations, lithographic
coatings, automobile spray operations, and fat-rendering plants (IARC 1985).

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 Acetaldehyde (Continued)

The use of acetaldehyde is widespread in industry, and it may be released into waste
water or the air during production, use, transport, and storage (Kirk-Othmer 1978, HSDB 2000).
EPA’s Toxic Chemical Release Inventory (TRI) estimated that 12,938,427 lb of acetaldehyde
were released to the environment from 283 facilities that processed, produced, or used the
chemical in the United States in 1998. Of that total, 92.3% was emitted to air. Thirty-three
facilities, each emitting >100,000 lb, represented 39.9% of this release. Total releases to water,
land, and underground injection were 1.8%, 0.1%, and 5.8%, respectively (TRI99 2001).
Acetaldehyde will rapidly volatilize from water or land, and it will leach into the ground where it
will biodegrade (HSDB 2000). Acetaldehyde has been detected in 5/10 surveyed water supplies
(Sittig 1985). Acetaldehyde is degraded by aerobic and anaerobic microorganisms; it degrades
readily in soil, sewage, and natural waters (EPA 1987). In water, concentrations are generally
less than 0.1 µg/L; therefore, contribution from drinking water was considered negligible (IPCS
1995).

The main source of human exposure to acetaldehyde is through the metabolism of

alcohol. Other sources include food and other beverages, and to a lesser extent, the air (IPCS
1995). Principal human exposure occurs with inhalation of ambient air from urban areas or near
sources of combustion (HSDB 2000). Total U.S. acetaldehyde airborne emissions from all
sources in 1978 were estimated to be approximately 114 million lb, 86% of which was thought to
be from residential wood burning (IARC 1985). The current annual emission from all sources
was estimated to be 27 million lb. In ambient air, concentrations of acetaldehyde generally
average 5 µg/m3 (IPCS 1995).

REGULATIONS

EPA regulates acetaldehyde under the Clean Air Act (CAA), Clean Water Act (CWA),
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA),
Resource Conservation and Recovery Act (RCRA), Superfund Amendments and Reauthorization
Act (SARA), and Toxic Substances Control Act (TSCA). EPA has established water quality
criteria, effluent guidelines, rules for regulating hazardous spills, general threshold amounts, and
requirements for the handling and disposal of acetaldehyde wastes. A reportable quantity (RQ)
of 1,000 lb has been established for acetaldehyde under CWA and CERCLA. The compound is
regulated as a hazardous constituent of waste under RCRA.

FDA regulates acetaldehyde as a synthetic flavoring substance for food.

ACGIH recommends a ceiling concentration of 25 ppm (45 mg/m3). NIOSH recommends
that occupational exposure to acetaldehyde be limited to the lowest feasible concentration.
OSHA set the permissible exposure limit (PEL) to 200 ppm (360 mg/m3) as the 8-hr time-
weighted average (TWA). Acetaldehyde is regulated by OSHA under the Hazard Communication
Standard and as a chemical hazard in laboratories. Regulations are summarized in Volume II,
Table 1.

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 Acetaldehyde (Continued)

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EPA. Health Assessment Document for Acetaldehyde. Prepared by the Office of Health and
Environmental Assessment, Research Triangle Park, NC for the Office of Air Quality Planning
and Standards. EPA/600/8-86/015A. (External Review Draft). 1987.

EPA. U.S. Environmental Protection Agency. Chemical Summary for Acetaldehyde prepared
by the Office of Pollution Prevention and Toxics. EPA # 749-F-94-003a, 1994.

Furia, T.E. and N. Bellanca. Fenaroli’s Handbook of Flavour Ingredients. Vol. 2, 2nd ed.
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ITA. International Trade Administration. U.S. Department of Commerce.

http://www.ita.doc.gov/td/industry/otea/Trade-Detail/Latest-December/Imports/29/291212.html,

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 Acetaldehyde (Continued)

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 Acetaldehyde (Continued)

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