Potency of polycyclic aromatic hydrocarbons in chicken and Japanese quail embryos

Birds are receptors of concern for polycyclic aromatic hydrocarbons (PAHs), yet limited data describing the relative potency of PAH congeners are available for avian species. In the present study, we determined embryonic median lethal dose (LD50) values for 5 PAH congeners in chicken (Gallus gallus) and one PAH congener in Japanese quail (Coturnix japonica). Graded concentrations of each test compound were injected into the air cell of chicken or quail eggs before incubation. Embryos were monitored through development (quail) or hatching (chicken). All PAHs tested caused dose-dependent increases in embryo mortality, but few other effects (e.g., weight changes, deformities) were observed. In chicken, windows of developmental sensitivity were identified between embryonic days 4 and 9 and between embryonic days 20 and 22. The rank order potency of benzo[k]fluoranthene (BkF; 76 μg/kg) ≈ dibenz[ah]anthracene (83 μg/kg) > indeno[1,2,3-cd]pyrene (325 μg/kg) > benzo[a]pyrene (461 μg/kg) > benz[a]anthracene (529 μg/kg) corresponded well with previous in vitro estimates in birds. Previously published ethoxyresorufin-O-deethylase median effect concentrations from cultured chicken embryo hepatocytes were highly predictive of our LD50s (p < 0.001, r²  = 0.99). To explore differences in sensitivity between species, Japanese quail eggs were injected with BkF, the most potent PAH. We found that chicken and quail were nearly equally sensitive to BkF. The present results contribute to our developing understanding of variability in responses to PAHs among congeners and species. Environ Toxicol Chem 2018;37:1556-1564. © 2018 SETAC.