Comparative effects of embryonic exposure to polybrominated diphenyl ethers in domestic and wild birds

Abstract

Concentrations of polybrominated diphenyl ethers (PBDEs) in eggs of wild birds have increased dramatically over the past 25 years, yet only limited data are available to interpret toxicological consequences of exposure. Embryonic survival, pipping and hatching success, and sublethal biochemical, endocrine, and histological endpoints were examined in chicken (Gallus gallus), mallard (Anas platyrhynchos), and American kestrel (Falco sparverius) hatchlings following in ovo (air cell) administration of the commercial penta-BDE mixture DE-71 (0.01-20 µg DE-71/g egg). Environmentally realistic concentrations of DE-71 induced ethoxyresorufin-O-dealkylase activity, and reduced bursa of Fabricius follicle size and number in chicken hatchlings, but not in other species. Pipping and hatching success decreased in American kestrels receiving 10 and 20 µg DE-71/g egg, but these endpoints were unaffected in other species. Absorption of air cell administered DE-71 (dose = 11.1 µg/g egg) into the contents of eggs varied among species and uptake rate tended to increase during the later half of development (dose absorbed by pipping: chicken 29.6%, kestrel 18.8%). At least six PBDE congeners and two metabolites were detected in DE-71 dosed eggs that were not present in the dosing solution, suggesting evidence of debromination and methoxylation. Uptake of the commercial octa-BDE mixture DE-79 (dose = 15.4 µg /g egg) following air cell administration to avian eggs was found to be low (dose absorbed <6.5%). Based on the DE-71 uptake rate in kestrels, the lowest observable effect level on pipping and hatching success may be 1.8 µg total PBDE/g egg, which approaches concentrations detected in eggs of free-ranging birds. As some PBDE congeners are still increasing in the environment, the embryotoxic effects observed following DE-71 administration are cause for concern.