The incidence of adverse health effects at low ambient air levels (approx. 100 ppt.) is unknown. Because methyl chloroform accumulates in the body, long-term exposure to even low ambient air levels might represent a health hazard. A no-observed-effect-level for long-term occupational exposure of humans to methyl chloroform is presently assumed to be around 53 ppm. At exposure levels around 1,000 ppm, inhalation produces cardiovascular effects in humans that include sensitization of the heart to spontaneous or catecholamine-provoked arrhythmias and hypotension. Methyl chloroform has been demonstrated to have mutagenic activity in the Ames assay, with and without metabolic activation, and in cultured mammalian cell transformation systems. However, definitive evidence that it has carcinogenic potential has not been demonstrated in animal bioassays. While it may have teratogenic potential, limitations of the available data do not allow for a full assessment of its effects. Because of its lipophilic nature, methyl chloroform is expected to cross membrane barriers and diffuse into the brain and milk of nursing mothers, as well as into the fetus during pregnancy.

EPA project coordinators: Mark M. Greenberg and Jean C. Parker. "November 1982." "Revised Draft." "Draft, Do not cite or quote." "Notice: This document is a preliminary draft. It has not been formally released by EPA and should not at this stage be construed to represent Agency policy. It is being circulated for comment on its technical accuracy and policy implications." "The Office of Health and Environmental Assessment has prepared this health assessment to serve as a "source document" for EPA use."--Page iii. Includes bibliographical references. "EPA-600/8-82-003." PB83-129585.