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
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
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