The addendum updates the Health Assessment Document (HAD) for Trichloroethylene (TCI) published in July 1986. The addendum focuses on the inhalation and oral carcinogenicity bioassays that have become available since the 1985 HAD was completed. The 1985 HAD concluded that the available carcinogenicity evidence for TCI was, according to EPA's Guidelines for Carcinogen Risk Assessment, inadequate in humans, and sufficient in animals, thus equivalent to a weight-of-evidence classification of Group B2. The conclusion was based primarily on mouse liver tumor responses, with support from metabolism data and other positive but compromised bioassay studies. The addendum identifies positive findings in rats, a second species, and positive findings by inhalation exposure in rats and mice with both similar and different tumor sites compared to the oral studies. A quantitative analysis of the recently reported inhalation studies shows that the upper-bound estimate of risk is very close to the earlier inhalation estimate in the 1985 HAD derived from the oral studies. The recommended upper-bound incremental unit risk for humans exposed for a 70-year lifetime to a 1 micrograms/cu. m. airborne concentration of TCI is 1.7 times 10 to the minus 6 power.

"June 1987." "EPA/600/8-82/006FA." "Review draft." Includes bibliographical references.