PCBS, DDE, DDT, and TCDD-EQ in two species of albatross on Sand Island, Midway Atoll, North Pacific Ocean

Concentrations of total polychlorinated biphenyls (PCBs) and organochlorine insecticides, including the 1 1,1-trichloro-2, 2′-bis-p-chlorophenyl-ethane (DDT) complex, were measured in the plasma of chicks and adults and in eggs of Laysan albatrosses (Diomedea immutabilis) and black-footed albatrosses (Diomedea nigripes) in a remote area of the central North Pacific Ocean. Significant differences in total concentrations of PCBs, DDT, and 1,1-dichloro-2,2′-bis-p-chlorophenyl-ethylene (DDE) in the plasma were detected between species and among sampling periods. Current concentrations of DDE in eggs of Laysan albatrosses are well below the threshold for eggshell thinning, based on the sensitivities of other fish-eating birds, whereas concentrations of DDE in eggs of black-footed albatrosses were approximately one-half of the threshold concentrations necessary for eggshell thinning. The shells of Laysan and black-footed albatross eggs are not currently exhibiting significant thinning that is resulting in population-level effects. Current concentrations of PCBs are near those that could be having subtle population-level effects in the black-footed albatross, but not in the Laysan albatross. The hazard posed to the albatrosses by current concentrations of PCBs was assessed by calculating a hazard quotient (HQ), based on composite dose–response relationships for other species. Dioxin equivalents (TEq) based on mammalian toxic equivalency factors resulted in the greatest HQ, which was near the concentration when embryo lethality and deformities are observed in fish-eating colonial waterbirds of the North American Great Lakes. Current concentrations of both PCBs and the DDT complex were similar to those in some species of piscivorous birds of the North American Great Lakes region.