POLYCHLORINATED-BIPHENYLS AND 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN EQUIVALENTS IN EGGS OF DOUBLE-CRESTED CORMORANTS FROM A COLONY NEAR GREEN-BAY, WISCONSIN, USA

Great Lakes colonial waterbirds have experienced poor reproduction and a greater incidence of birth defects than those in remote areas. An egg was collected from each of 1,000 marked cormorant nests at Spider Island (Lake Michigan): Nine pools comprised of three eggs were randomly selected for instrumental quantification of polychlorinated biphenyls (PCB) congeners, calculation of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEq) and measurement of equivalents by bioassay (TCDD-EQ). PCB analysis of the nine samples was semiautomated with high performance liquid chromatography (HPLC) columns including a porous graphitic carbon column. TEqs were calculated from concentrations of PCB congeners and bioassay-derived toxic equivalency factors (TEfs), and TCDD-EQ were measured directly with an H4IIE bioassay. Total PCB concentrations ranged from 9.7 to 38 mu g/g, wet weight (ww). Mean concentrations of PCB 77, 126, and 169 were 2, 7, and 1 ng/g, ww. The mean TEqs and TCDD-EQ were 150 and 350 pg/g, ww, respectively. Thus, PCB congeners contributed less than 50% of the total TCDD-EQs as measured by the bioassay.