Acetaldehyde [factsheet]

ACETALDEHYDE

Please Note: The main sources of information for this fact sheet are EPA's Health Assessment Document for Acetaldehyde and the Integrated Risk Information System (IRIS), which contains information on inhalation chronic toxicity of acetaldehyde and the RfC. Other secondary sources include the International Agency for Research on Cancer (IARC) Monographs on Chemicals Carcinogenic to Man and the Handbook of Toxic and Hazardous Chemicals and Carcinogens.

Environmental/Occupational Exposure

* Acetaldehyde is ubiquitous in the ambient environment. It is an intermediate product of higher plant respiration and formed as a product of incomplete wood combustion in fireplaces and woodstoves, coffee roasting, burning of tobacco, vehicle exhaust fumes, and coal refining and waste processing. Hence, many individuals are exposed to acetaldehyde by breathing ambient air. It should be noted that residential fireplaces and woodstoves are the two highest sources of emissions, followed by various industrial emissions. (1)

* In Los Angeles, California, levels of acetaldehyde up to 32 ppb have been measured in the ambient environment. (1)

* Exposure may also occur in individuals occupationally exposed to acetaldehyde during its manufacture and use. (1,2)

* In addition, acetaldehyde is formed in the body from the breakdown of ethanol; this would be a source of acetaldehyde among those who consume alcoholic beverages. (1)

Assessing Personal Exposure

* No information was located regarding the measurement of personal exposure to acetaldehyde.

Health Hazard Information

Acute Effects:

* The primary acute (short-term) effect of inhalation exposure to acetaldehyde is irritation of the eyes, skin, and respiratory tract in humans. Erythema, coughing, pulmonary edema, and necrosis may also occur and, at extremely high concentrations, respiratory paralysis and death. (1)

* Acute inhalation of acetaldehyde resulted in a depressed respiratory rate and elevated blood pressure in experimental animals. (1)

* Tests involving acute exposure of animals, such as the LC₅₀ and LD₅₀ tests in rats, rabbits, and hamsters, have demonstrated acetaldehyde to have low acute toxicity from inhalation and moderate acute toxicity from oral or dermal exposure. (3)

Chronic Effects (Noncancer):

* In hamsters, chronic (long-term) inhalation exposure to acetaldehyde has produced changes in the nasal mucosa and trachea, growth retardation, slight anemia, and increased kidney weight. (1,4)

* Symptoms of chronic intoxication of acetaldehyde in humans resemble those of alcoholism. (5)

* The RfC for acetaldehyde is 0.009 mg/m³ based on degeneration of olfactory epithelium in rats. (4)

* EPA has medium confidence in the principal studies because appropriate histopathology was performed on an adequate number of animals and a no-observed-adverse-effect level (NOAEL) and a lowest-observed-adverse-effect level (LOAEL) were identified, but the duration was short and only one species was tested; low confidence in the database due to the lack of chronic data establishing NOAELs and due to the lack of reproductive and developmental toxicity data; and, consequently, low confidence in the RfC.

* EPA has not established an RfD for acetaldehyde. (4)

Reproductive/Developmental Effects:

* No information is available on the reproductive or developmental effects of acetaldehyde in humans.

* Acetaldehyde has been shown, in animals, to cross the placenta to the fetus. (1,4)

* Data from animal studies suggest that acetaldehyde may be a potential developmental toxin. In one study, a high incidence of embryonic resorptions was observed in mice injected with acetaldehyde. In rats exposed to acetaldehyde by injection, skeletal malformations, reduced birth weight, and increased postnatal mortality have been reported. (1,6)

Cancer Risk:

* Human data regarding the carcinogenic effects of acetaldehyde are inadequate. Only one epidemiology study is available that several limitations including short duration, small number of subjects, and concurrent exposure to other chemicals and cigarettes. (1,4,6)

* An increased incidence of nasal tumors in rats and laryngeal tumors in hamsters has been observed following inhalation exposure to acetaldehyde. (1,4,6)

* EPA has classified acetaldehyde as a Group B2, probable human carcinogen. (1,4)

* EPA uses mathematical models, based on human and animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA calculated an inhalation unit risk estimate of 2.2 H 10^-6 (m g/m³)^-1. EPA estimates that, if an individual were to breathe air containing acetaldehyde at 0.5 m g/m³* over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that breathing air containing 5.0 m g/m³ would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 50.0 m g/m³ would result in not greater than a one-in-ten thousand increased chance of developing cancer. (4)

* EPA's Office of Air Quality Planning and Standards, for a hazard ranking under Section 112(g) of the Clean Air Act Amendments, has ranked acetaldehyde in the nonthreshold category. The 1/ED₁₀ value is 0.033 per (mg/kg)/d and this would place it in the low category under Superfund's ranking for carcinogenic hazard. (7)

Physical Properties

* The chemical formula for acetaldehyde is CH₃CHO, and it has a molecular weight of 44.06 g/mol. (1)

* Acetaldehyde is a colorless mobile liquid that is flammable and miscible with water. (1,6)

* Acetaldehyde has a pungent suffocating odor, but at dilute concentrations it has a fruity and pleasant odor. The odor threshold of acetaldehyde is 0.05 ppm (0.09 mg/m³). (1,8)

* The vapor pressure for acetaldehyde is 740 mm Hg at 20 EC, and it has a log octanol/water partition coefficient (log K_ow) of 0.43. (1)

Uses

* The predominant use of acetaldehyde is as an intermediate in the synthesis of other chemicals. (1)

* Acetaldehyde is used in the production of perfumes, polyester resins, and basic dyes. Acetaldehyde is also used as a fruit and fish preservative, as a flavoring agent, and as a denaturant for alcohol, in fuel compositions, for hardening gelatin, and as a solvent in the rubber, tanning, and paper industries. (1,2)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
100,000.0
_ _ _ _ 10,000.0	* LC₅₀ (rats) (37,000 mg/m³) * LC₅₀ for (hamsters) (17,000 mg/m³)		3 3
_ _ _ _ 1,000.0
_ _ _ _ 100.0	* LOAEL^c (rats) (728 mg/m³) * NOAEL^c (rats) (273 mg/m³)	* ACGIH TLV, OSHA PEL, MSHA standard (180 mg/m³)	4 4 3
_ _ _ _ 10.0
_ _ _ _ 1.0
_ _ _ _ 0.1
_ _ _ _ 0.01
_ _ _ _ 0.001	* RfC (0.009 mg/m³)		4
_ _ _ _ 0.0001	* EPA Cancer Risk Level (1-in-a-million excess lifetime risk) = 5.0 H 10^-4mg/m³		4

See notes on following page.

ACGIH TLVCAmerican Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.

LC₅₀ (Lethal Concentration₅₀)CA calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population.

LOAELCLowest-observed-adverse-effect level.

MSHACMine Safety and Health Administration.

NOAELCNo-observed-adverse-effect level.

OSHA PELCOccupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

RfCCReference concentration.

^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.

^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.

^c The LOAEL and NOAEL are from the critical study used as the basis for the EPA RfD.

References

1. U.S. Environmental Protection Agency. Health Assessment Document for Acetaldehyde. EPA/600/8-86-015A. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Research Triangle Park, NC. 1987.

2. M. Sittig. Handbook of Toxic and Hazardous Chemicals and Carcinogens. 2nd ed. Noyes Publications, Park Ridge, NJ. 1985.

3. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

4. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Acetaldehyde. Office of Health and Environmental Assessment, Environmental Criteria and Assessment Office, Office of Research and Development, Cincinnati, OH. 1993.

5. The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. 11th ed. Ed. S. Budavari. Merck and Co. Inc., Rahway, NJ. 1989.

6. International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Allyl Compounds, Aldehydes, Epoxides and Peroxides. Volume 36. World Health Organization, Lyon. 1985.

7. U.S. Environmental Protection Agency. Technical Background Document to Support Rulemaking Pursuant to the Clean Air ActCSection 112(g). Ranking of Pollutants with Respect to Hazard to Human Health. EPAB450/3-92-010. Emissions Standards Division, Office of Air Quality Planning and Standards, Research Triangle Park, NC. 1994.

8. J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. 1983.