Health Concerns

Methylene Chloride

Methyl chloride enters the body by inhalation of contaminated air into the lungs and by swallowing contaminated water into the digestive tract. Methyl chloride is rapidly absorbed from the air and from drinking water. It is taken up by the blood and breakdown products are distributed to the liver, brain and kidneys. A small part of the methyl chloride leaves through the lungs with the remainder changed to other breakdown products and removed through the urine. This removal may take from a few hours to several days.

Exposure to methyl chloride in the environment may produce effects on the nervous system and reproductive systems. Exposure to methyl chloride can also harm the liver and kidney, or have an effect on the heart rate and blood pressure (ATSDR, 1990a). Exposures to very high levels of methyl chloride in homes occurred in the past when the chemical was used as a refrigerant. These exposures which were frequently fatal show how the chemical is taken up into the body and metabolized but are not predictive of the effects of the lower level exposures found in the ambient air. Animal studies at lower levels (one hundred thousand to one million times higher than background levels) over a long period of time (weeks to months) have demonstrated effects on growth, reproduction and fetal development. Male mice that breathed air containing methyl chloride (one million ppb, two million ug/m 3 ) for 2 years developed tumors in the kidneys, but female mice and male and female rats did not develop tumors (ATSDR, 1990a).

Because the compound is metabolized prior to removal from the body and because the metabolites may be toxic to the brain or kidney it is necessary to consider sensitive populations. Such concern would include the elderly, the young, especially with respect to development, and the chronically ill with liver or kidney disease.

Because there are other sources of exposure such as water it is necessary to consider potential for cumulative exposures. Methyl chloride has been classified as Class C: Possible Human Carcinogen based on limited evidence of carcinogenicity in animals by the United States Environmental Protection Agency and as a Group 3: Not classifiable due to limited human or animal data by the International Agency for Research on Cancer.

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Last Updated: 1/31/03