The U.S. Department of Health and Human Service's Agency for Toxic Substances and Disease Registry (ATSDR) recently concluded that "[w]e do not have any clear evidence that exposure to TCE alone can cause leukemia or any other type of cancer in humans." In reaching this conclusion, ATSDR examined studies of workers exposed to TCE over extended periods of time, at levels 100's to 1,000's of times greater than the TCE levels likely to have been experienced in Woburn. These studies showed no signs of increased risk of leukemia. (ATSDR,1997)
At very high doses, TCE has been shown to cause cancer of the liver (but not leukemia) in animals in certain laboratory tests. (National Cancer Institute, 1976; National Toxicology Program, 1988) The significance of these animal findings to humans is uncertain, however, in light of the negative epidemiological (human) evidence. The doses of TCE required to produce tumors in animals are 1000's of times higher than the levels of TCE that anyone would ever experience from drinking water.
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Furthermore, TCE does not appear on the list of chemicals that are known to be human carcinogens or are reasonably anticipated to be human carcinogens, as prepared by the Department of Health and Human Services, National Toxicology Program.
View the 1998 Report on Human Carcinogens.