Trichlorobenzenes: results of a thirteen week feeding study in the rat.

Trichlorobenzenes (TRCBs) are industrial chemicals and environmental pollutants found in Great Lakes fish. The present study was carried out to provide information on the toxic effects of these chemicals in mammals. Groups of male and female weanling rats were fed diets containing TRCB isomers at 1, 10, 100 or 1000 ppm for 13 weeks. The group of males fed 1000 ppm 1,2,3-TRCB diet had reduced weight gain. No other clinical signs of toxicity were observed. Increased relative liver and kidney weights occurred in the highest dose groups of males for all 3 TRCBs. Of the 3 isomers, only 1,2,4-TRCB at 1000 ppm caused increases in hepatic aminopyrine demethylase and aniline hydroxylase activities in male rats, and aminopyrine demethylase in females. Serum biochemical and hematological parameters measured were not affected. All three TRCBs produced histological changes of a moderate degree in the liver and thyroid of male rats at 1,000 ppm. Only 1,3,5-TRCB elicited moderate renal changes in male rats fed 1,000 ppm. Microscopic changes in the females were generally milder than those of the corresponding males. Based on these data it was concluded that the nonobservable adverse effect levels for the three TRCBs were 100 ppm in the diet, or 7.6 approximately 7.8 mg/kg b.w./day depending on the dietary consumption.