A teratological evaluation and analysis of fetal tissue levels following administration of tetrachlorobenzene isomers to the rat.

Three tetrachlorobenzene (TCB) congeners (1,2,3,4- 1,2,3,5-, and 1,2,4,5-) were administered daily by gavage to pregnant Sprague-Dawley rats at levels of 50, 100, or 200 mg/kg from day 6 through day 15 of gestation. Mothers were sacrificed on day 21 of gestation and the pups removed by cesarian section for teratological evaluation. Administration of 1,2,3,4- and 1,2,3,5-TCB failed to alter maternal body weight, organ weights, hematological, or the biochemical parameters studied. The highest dose level of 1,2,4,5-tetrachlorobenzene caused maternal death in nine of ten animals. In addition it induced mixed function oxidases and increased serum cholesterol values at 50 and 100 mg/kg. There was a decrease in the number of fetuses at the highest dose levels of 1,2,3,4- and 1,2,3,5-TCB and at the lowest dose level of the 1,2,4,5- congener. None of the congeners produced any anomalies. There were no treatment-related histopathological changes in either the mothers or fetuses. Residues of all three congeners were found in maternal and fetal tissues but generally the amounts of the 1,2,4,5- isomer were about 100 times higher than the other two.