TOXICITY AND EROD-INDUCING POTENCY OF POLYCHLORINATED-BIPHENYLS (PCBS) AND POLYCYCLIC AROMATIC-HYDROCARBONS (PAHS) IN AVIAN EMBRYOS

1. The toxicities of various polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were studied in chick embryos (Gallus domesticus). The substances were injected into the yolks of eggs preincubated for 4 days and mortality was measured 2 weeks later. A technical PCB preparation caused 33% embryo mortality at a dose of 5 mg/kg egg and 2 mg/kg of a mixture of 18 PAHs caused 40% mortality. 2. 3,3',4,4',5-Pentachlorobiphenyl, a coplanar PCB, was the most toxic (90% mortality at 2-mu-g/kg) of 11 PCBs and 18 PAHs tested in chick embryos using the 2-week test. Benzo[k]fluoranthene, which was the most potent of the PAHs, was about 1000 times less toxic than 3,3',4,4',5-pentachlorobiphenyl in this test. 3. Several avian species were studied in a similar test and they all proved to be considerably less sensitive than the chicken to the embryotoxicity of coplanar PCBs. Embryos from the turkey (Meleagris gallopavo), domestic duck (Anas platyrhynchos) and eider (Somateria mollissima) were, however, at least as sensitive as chick embryos to the PAH mixture and to benzo[k]fluoranthene. 4. The most toxic compounds tested were also the strongest inducers of hepatic 7-ethoxyresorufin O-deethylase (EROD) activity in 10-day-old chick embryos. 3,3',4,4',5-Pentachlorobiphenyl, which was the most potent of the tested PCBs, had an ED50 of 0.1-mu-g/kg whereas the ED50 for the nonplanar 2,2',4,4',5,5'-hexachlorobiphenyl was > 40,000-mu-g/kg.