Methylene chloride is used in a wide variety of applications: Extraction solvent for decaffeination of coffee, extraction solvent for spices and beer hops, dip-type metal cleaner, vapor degreasing of metals, carrier solvent in the textile industry, aerosol, refrigerant, low temperature heat-transfer agent, and in chemical processing (e.g., manufacture of polycarbonate plastics, insecticides and herbicides, pharmaceuticals). It is also used to fumigate grain and for oil dewaxing. See http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~OG1F60:1:use. However, it is also used in residential settings because it is a fast, efficient paint stripper; it is available in at least 42 products sold at home improvement stores and on the Internet. Unfortunately, if proper precautions are not taken, its use can be fatal.
Methylene chloride is rapidly absorbed through the lungs into the circulatory system. It is also absorbed from the stomach and gut; dermal exposure results in absorption, but at a slower rate than via other routes of exposure. Methylene chloride is quite rapidly excreted, mostly via the lungs. It can cross the blood-brain barrier and be transferred across the placenta. At high concentrations, most of the absorbed methylene chloride is exhaled unchanged. The acute effects are primarily associated with the central nervous system, lungs, kidneys, and the liver. The main toxic effects of methylene chloride are reversible CNS "depression" and carboxyhemoglobin formation (replaces oxygen in red blood cells with carbon dioxide).
Researchers at the Univ. of Michigan recently identified two deaths from workers refinishing bathtubs; methylene chloride paint strippers were apparently being used to remove epoxy paint. In both cases the workers were using paint stripping materials labeled for use in paint removal from aircraft. However, in the confined space of a bathroom, they were overcome by the fumes and died. The researchers identified 13 deaths nationwide related to methylene chloride in paint stripping materials. A confounding factor is assessing the extent of such deaths is that the mortality can be mistaken for a heart related fatality.
Most regulation in the U.S. focuses on methylene chloride as a carcinogen; it has been listed as such under California's Prop. 65 since 1988. Last year the EU banned methylene chloride from furniture stripping agents. The Michigan report suggests that more aggressive warnings should be given on labels, or the U.S. should follow the EU and ban methylene chloride from stripping agents.
The report on the fatalities can be found at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6107a2.htm.