Persistent organochlorine pollutants in ringed seals and polar bears collected from northern Alaska

Blubber samples from ringed seal ( Phoca hispida; n=8) and polar bear subcutaneous fat ( Ursus maritimus; n=5) were collected near Barrow, Alaska in 1996 as part of the Alaska Marine Mammal Tissue Archival Project (AMMTAP) and retained in the National Biomonitoring Specimen Bank at the National Institute of Standards and Technology in Gaithersburg, Maryland (USA). The samples were analyzed for a variety of persistent organochlorine pollutants (POPs) including polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), chlordane and metabolites, hexachlorobenzene (HCB) and DDTs and metabolites. The geometric mean, on a wet mass basis, of ΣPCBs (sum of 29 congeners and congener groups) were 732±282 ng/g (1 S.D.) in seals and 3395±1442 ng/g in polar bears. The geometric mean of ΣDDTs, ΣHCHs (α-, β- and γ- HCH) and HCB concentrations (wet mass basis) in seals and bears were 562±261 ng/g vs. 74.8±39 ng/g, 380±213 ng/g vs. 515 ng/g, and 17.4±10.1 ng/g vs. 183±153 ng/g, respectively. The geometric mean sum of chlordane (Σchlordane, sum of cis- and trans-chlordane, cis- and trans-nonachlor, oxychlordane and heptachlor epoxide) and dieldrin concentrations in ringed seals and polar bears were 753±617 ng/g vs. 720±315 ng/g and 38.6±22.8 ng/g vs. 130±65 ng/g, respectively. Apparent bioaccumulation factors (polar bear/ringed seal POP concentrations) were lower in the animals sampled near Barrow, Alaska than in those from locations in the Canadian Arctic. This suggests that polar bears are also preying on marine mammals from lower trophic levels than the ringed seals with correspondingly lower organochlorine levels, such as bowhead whale carcasses. PCB congener patterns in the samples demonstrated the metabolism of certain PCB congeners in the polar bear relative to the ringed seal in agreement with previous studies. Regional comparisons of animals collected in Alaska and Arctic Canada are presented.