BIOLOGICAL EFFECTS OF POLYCHLORINATED DIBENZO-P-DIOXINS, DIBENZOFURANS, AND BIPHENYLS IN BALD EAGLE (HALIAEETUS-LEUCOCEPHALUS) CHICKS

During the 1992 breeding season, eggs of bald eagles (Haliaeetus leuco cephalus) were collected within a gradient of exposure to chlorinated hydrocarbon pollutants, particularly from pulp mill point sources, on the southern coast of British Columbia, Canada. Twenty-five eggs were placed in a laboratory incubator, of which 18 hatched; chicks were sac rificed within 24 h. Hatching success was not significantly different between eggs taken from pulp mill sites and reference sites. A hepatic cytochrome P4501A (CYP1A) cross-reactive protein was induced nearly s ixfold in chicks from near a pulp mill at Powell River compared to tho se from a reference site (p < 0.05). Hepatic ethoxyresorufin-O-deethyl ase (EROD) and benzyloxyresorufin O-dealkylase (BROD) activities were also significantly elevated in chicks from nests located near pulp mil ls compared to reference sites (p < 0.0005 and p < 0.02, respectively) . A hepatic CYP2B cross-reactive protein was threefold higher in chick s from pulp mill versus reference sites, but the difference was not si gnificant. Residual yolk sacs of eggs collected near pulp mill sites c ontained greater concentrations of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) c ompared to reference areas. No significant differences in concentratio ns of polychlorinated biphenyls (PCBs), non-ortho congeners, and organ ochlorine pesticides occurred among sites. Regressions showed that the hepatic CYP1A cross-reactive protein and EROD and BROD activities wer e positively correlated with 2,3,7,8-TCDD, 2,3,7,8-TCDE and toxic equi valents (TEQs(WHO)-World Health Organization toxic equivalence factors ) in yolk sacs. No significant concentration-related effects were foun d for morphological, physiological, or histological parameters, such a s chick growth, edema, or density of thymic lymphocytes. Using hepatic CYP1A induction as a biomarker, a no-observed-effect-level (NOEL) of 100 ng/kg and a lowest-observed-effect-level (LOEL) of 210 ng/kg TEQs( WHO) on a whole egg (wet weight basis) are suggested for bald eagle ch icks.