Toxicity and distribution in chick embryos of 3,3',4,4'-tetrachlorobiphenyl injected into the eggs.

3,3',4,4'-Tetrachlorobiphenyl (3TCB) was injected into the yolk of embryonated hens' eggs in doses of 4, 20 or 100 micrograms/kg egg. Twenty and 100 micrograms/kg resulted in the death of all the embryos. The hatching rate of the eggs treated with 4 micrograms/kg was 60% while that of the control eggs was 88%. This means that 3TCB is at least 10 000 times more toxic in chick embryos than a previously studied isomer, 2,2',4,5'-tetrachlorobiphenyl (2TCB). 3,3',4,4'-Tetrachlorobiphenyl might be teratogenic in chick embryos since eye and beak deformities were seen in 3 unhatched tetrachlorobiphenyl-treated embryos. In addition rump edema and excess fluid in the body cavity was observed in some embryos. The distribution of the 2 tetrachlorobiphenyls in chick embryos was studied by means of whole-body autoradiography. No differences in distribution, which could explain the extreme difference in toxicity, were detected. High amounts of radioactivity were found in the bile of the embryos, indicating a capacity of the embryos to metabolize and excrete the tetrachlorobiphenyls.