A 2-year (104-week) study was conducted by general exposure using rats and mice for the purpose of investigating carcinogenicity of tetrachloroethylene by inhalation. The laboratory animals used in the study were F344DuCrj (Fischer) rats and Crj:BDF1 mice. Four-hundred rats and 400 mice were used in a total of 4 groups, 3 study sample treatment groups and 1 control group, of 50 males and females each. Two-week and 13-week preliminary studies were conducted and based on these results, the concentration administered in the carcinogenicity study was set at 600 ppm, 200 ppm and 50 ppm in rats and 250 ppm, 50 ppm, and 10 ppm in mice, with these concentrations being administered for 6 hours/day, 5 days a week for 104 weeks. The observation and test items were observation of general status, body weight and food consumption determinations, urinalyses, hematological tests, blood chemistry tests, autopsy, organ weight determination, and histopathological tests. When compared to the control groups, a significant reduction in the number of animals that survived (percentage) was seen in both rats and mice of the maximum tetrachloroethylene concentration groups, apparently the result of administration. There was a tendency toward an increase in monocytic leukemia of the spleen among male and female rats administered tetrachloroethylene, with the incidence among males of the 600 ppm group being significantly increased when compared to the control group. This increase in monocytic leukemia apparently lead to a reduction in the survival rate among the treatment groups. Moreover, the increase in spongiosis hepatitis and hyperplasia of the liver among males, the nuclear enlargement of proximal tubules of the kidneys among males and females, and the increase in atypical tubular dilation of the proximal uriniferous tubules and exacerbation of chronic renal disease among males appear to have been due to administration of tetrachloroethylene.
