Toxicity and erod-inducing potency of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in avian embryos

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1. 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. 2. 3,3′,4,4′,5-Pentachlorobiphenyl, a coplanar PCB, was the most toxic (90% mortality at 2 μg 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. 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. 4. The most toxic compounds tested were also the strongest inducers of hepatic 7-ethoxyresonifin 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 ed 50 of 0.1 μg kg whereas the ed 50 for the nonplanar 2,2′,4,4′,5,5′-hexachlorobiphenyl was > 40,000 μg kg .