Hazard Summary

• Acute (short-term) exposure of humans to methanol by inhalation or ingestion may result in visual disturbances, such as blurred or dimness of vision, leading to blindness. Neurological damage, specifically permanent motor dysfunction, may also result.
• Chronic (long-term) inhalation or oral exposure to methanol may result in conjunctivitis, headache, giddiness, insomnia, gastric disturbances, visual disturbances, and blindness in humans.
• The Reference Concentration (RfC) for methanol is under review by the U.S. Environmental Protection Agency (EPA).
• The Reference Dose (RfD) for methanol is 0.5 mg/kg/d.^a EPA estimates that consumption of this dose or less, over a lifetime, would not likely result in the occurrence of chronic, noncancer effects.^b
• No information is available on the reproductive or developmental effects of methanol in humans. Birth defects have been observed in the offspring of rats exposed to methanol by inhalation.
• No information is available on the carcinogenic effects of methanol in humans or animals. EPA has not classified methanol with respect to carcinogenicity.

^a Milligrams per kilogram per day is one way to measure the amount of the contaminant that is consumed in food.
^b The RfD is not a direct estimator of risk but rather a reference point to gauge the potential effects. Exceedance of the RfD does not imply that an adverse health effect would necessarily occur. As the amount and frequency of exposures exceeding the RfD increase, the probability of adverse health effects also increases.

Please Note: The main sources of information for this fact sheet are the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and EPA's Integrated Risk Information System (IRIS), which contains information on oral chronic toxicity and the RfD. Other secondary sources include the Handbook of Toxic and Hazardous Chemicals and Carcinogens and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational Exposure

• Occupational exposure to methanol through inhalation and dermal contact is widespread. (1,2)
• Individuals may be exposed to methanol in the ambient air from its evaporation during solvent uses or from automobile exhaust, through the consumption of various foods, and through dermal contact with various consumer products such as paint thinners and strippers, adhesives, cleaners, and inks. (1)
• Natural emission sources of methanol include volcanic gases, vegetation, microbes, and insects; methanol is also formed during biological decomposition of biological wastes, sewage, and sludge. (1)

Assessing Personal Exposure

• Personal exposure to methanol may be monitored through the measurement of methanol in the blood and measurement of methanol and formic acid in urine. (2)

Health Hazard Information

• Acute (short-term) exposure of humans to methanol by inhalation or ingestion may result in visual disturbances, such as blurred or dimness of vision, leading to blindness. Neurological damage, specifically permanent motor dysfunction, may also result. Coma or death due to respiratory failure may occur in individuals exposed to high doses of methanol. (1,2,3)
• Contact of skin with methanol can produce mild dermatitis. (2)
• Tests involving acute exposure of animals, such as the LC₅₀ and LD₅₀ tests in rats, mice, and rabbits, have demonstrated methanol to have low acute toxicity from oral or inhalation exposure, and moderate acute toxicity from dermal exposure. (4)

Chronic Effects (Noncancer):

• Chronic (long-term) inhalation or oral exposure to methanol may result in conjunctivitis, headache, giddiness, insomnia, gastric disturbances, visual disturbances, and blindness in humans. (1)
• Elevated levels of liver enzymes and decreased brain weight were observed in rats chronically exposed to methanol via gavage (experimentally placing the chemical in the stomach). (5)
• The RfC for methanol is under review by EPA. (5)
• The RfD for methanol is 0.5 mg/kg/d based on increased SAP and SGPT, and decreased brain weight in rats. (5)
• EPA has medium confidence in the principal study on which the RfD was based because it was well-designed and provided adequate toxicological endpoints, but the method of administration was not ideal; low confidence in the database because it is weak, lacking data on reproductive, developmental, or other toxicological endpoints; and, consequently, medium confidence in the RfD.
• EPA's Office of Air Quality Planning and Standards, for a hazard ranking under Section 112(g) of the Clean Air Act Amendments, has evaluated methanol for chronic toxicity and has given it a composite score of 7 (scores range from 1 to 100, with 100 being the most toxic). These scores are nonlinear and are the product of two ratings: a rating based on the minimal-effect-dose and a rating based on the type of effect. (6)

Reproductive/Developmental Effects:

• No information is available on the reproductive or developmental effects of methanol in humans.
• Birth defects, involving skeletal, cardiac, and urinary system deformities, have been observed in the offspring of rats exposed to methanol by inhalation. (1)

Cancer Risk:

• No information is available on the carcinogenic effects of methanol in humans or animals.
• EPA has not classified methanol with respect to carcinogenicity. (5)

Physical Properties

• The chemical formula for methanol is CH₄O, and its molecular weight is 32.04 g/mol. (3)
• Methanol occurs as a flammable, mobile, colorless liquid that is miscible with water. (3)
• Methanol has a slightly alcoholic odor when pure and a repulsive, pungent odor when in its crude form; it is difficult to smell methanol in the air at less than 2,000 ppm (2,622 mg/m³). (1,2)
• The log octanol/water partition coefficient (log K_ow) is -0.77. (1)

Uses

• Methanol is primarily used as an industrial solvent for inks, resins, adhesives, and dyes. It is also used as a solvent in the manufacture of cholesterol, streptomycin, vitamins, hormones, and other pharmaceuticals. (1-3)
• Methanol is also used as an antifreeze for automotive radiators, an ingredient of gasoline (as an antifreezing agent and octane booster), and as fuel for picnic stoves. Methanol is also an ingredient in paint and varnish removers. (1-3)

ACGIH TLV--American 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)--A 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.
MSHA--Mine Safety and Health Administration.
NIOSH REL--National Institute of Occupational Safety and Health's recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.
OSHA PEL--Occupational 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.

^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.

References

1. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
2. M. Sittig. Handbook of Toxic and Hazardous Chemicals and Carcinogens. 2nd ed. Noyes Publications. Park Ridge, NJ. 1985.
3. The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. 11th ed. Ed. S. Budavari. Merck and Co. Inc., Rahway, NJ. 1989.
4. 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.
5. U.S. Environmenal Protection Agency. Integrated Risk Information System (IRIS) on Methanol. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.
6. U.S. Environmental Protection Agency. Technical Background Document to Support Rulemaking Pursuant to the Clean Air Act--Section 112(g). Ranking of Pollutants with Respect to Hazard to Human Health. EPA­450/3-92-010. Emissions Standards Division, Office of Air Quality Planning and Standards, Research Triangle Park, NC. 1994.