Fifteen dogs were made to inhale tetrachloroethylene at concentrations of 700, 1, 500, 2, 000 ppm for one hour, and the changes in its concentrations in the expired air, the arterial blood, the venous blood and its metabolites (trichloroacetic acid (TCA), free-trichloroethanol (F-TCE)) in the serum and the urine were measured from the beginning of exposure until two hours after it had been terminated. The results obtained were as follows. 1. Levels of cumulative intake of tetrachloroethylene after one hour (i.e., at the termination of the inhalation) were 47 mg/kg for 700 ppm, 79 mg/kg for 1, 500 ppm and 103 mg/kg for 2, 000 ppm. 2. Mean cumulative excretion ratio against the total intake two hours after the termination of the inhalation was 69% as the average for the three exposure levels. 3. Mean ratio of the total absorption to the total intake for one hour was 23% as the average for the three levels. 4. Using the above results, the authors did the multiple regression analysis of cumulative absorption (Y1) as well as cumulative excretion (Y2) taking two independent variables (X) and (Insp. or Z), which are as follows. a) During the exposure period Y1:cumulative absorption (mg/kg) X1:exposure duration (min) Insp.:levels of solvent value in the inspired air (μg/ml) log Y1=-2.2819+0.5681 log X1+0.8232 log Insp. b) During the post exposure period Y2:cumulative amounts of solvent excreted (mg/kg) X2:time in minutes after exposure end (min) Z2:cumulative absorption when exposure ended (mg/kg) log Y2=-2.016+0.6976 log X2+0.7397 log Z2 It was found that both equations were fit and significant. 5. As the changes of TCA and F-TCE in urine and serum during and after exposure to tetrachloroethylene at the three levels, the concentrations of TCA and F-TCE in high concentrations of exposure were higher than those of low concentrations of exposure, but these metabolites did not increase in proportion to the levels of exposure concentrations.
