BALD EAGLE MORTALITY AND CHLORINATED-HYDROCARBON CONTAMINANTS IN LIVERS FROM BRITISH-COLUMBIA, CANADA, 1989-1994

Between 1989 and 1994, we obtained 278 carcasses of bald eagles (Halia eetus leucocephalus) found dead or dying in British Columbia, Canada. All specimens were necropsied and the cause of death determined wherev er possible. Livers from a subset of 75 birds were analyzed for polych lorinated biphenyl (PCB) and organochlorine (OC) pesticide residues. A further subset of 19 eagles found dead around the Strait of Georgia, an area of known pulp mill pollution, in summer, and therefore presuma bly resident birds, were analyzed for polychlorinated dibenzo-p-dioxin s, (PCDDs) and polychlorinated dibenzofurans (PCDFs) and non-ortho PCB s. Liver concentrations ranged from less than 1 to 190 mg/kg for DDE, and up to 72 mg/kg for total PCBs. Concentrations of other OCs were ge nerally less than 1 mg/kg, with the exception of chlordane-related com pounds which were occasionally over 2 mg/kg. All birds analyzed for PC DDs and PCDFs contained detectable concentrations of the major 2,3,7,8 -substituted isomers. Some birds were very contaminated; one eagle fou nd near a kraft pulp mill site in 1990 contained: 400 ng/kg 2,3,7,8-TC DD, 1400 ng/kg 1,2,3,7,8-PnCDD and 4400 ng/kg 1,2,3,6,7,8-HxCDD. Birds with higher PCB and dichlorodiphenyldichloroethane (DDE) concentratio ns appeared to weight less, and there was a significant negative relat ionship between both PCBs and DDE and numeric scoring of body conditio n, reflecting the well known process of starvation-induced mobilizatio n of body lipids and contaminants. Birds with higher 2,3,6,8-TCDD conc entrations tended to have unusually low concentrations of 2,3,7,8-TCDF , interpreted to indicate hepatic cytochrome P4501A-type induction by TCDD and subsequent metabolism of TCDF. Copyright (C) 1996 Elsevier Sc ience Ltd.