Circumpolar trends of PCBs and organochlorine pesticides in the arctic marine environment inferred from levels in ringed seals

Geographical trends in levels of Sigma PCB10 (sum of 10 major congeners), hexachlorocyclohexanes (HCH), Sigma DDT (sum of DDT-related compounds), and other persistent organochlorines (OCs) in ringed seal blubber were examined at 13 sampling locations in the Arctic over 175 deg longitude from northern Canada to the South Kara Sea (Yenisey Gulf) in Russia. Concentrations of OCs were adjusted, using analysis of covariance, for effects of the covariates, sex, age, and blubber thickness. Adjusted mean concentrations of Sigma PCB10 and Sigma DDT were significantly higher in the samples from the Yenisey Gulf in the Russian Arctic, Svalbard, and East Greenland than in west Greenland or the Canadian Arctic. Sigma PCB10 and Sigma DDT in Yenisey Gulf samples were 8x and 6x higher, respectively, than the average in levels from four Canadian locations. Sigma PCB10 and Sigma DDT means declined significantly with increasing westerly longitude (r(2) = 0.75 and 0.73, respectively). Sigma HCH levels for sites in the Canadian Arctic were significantly higher than those from west Greenland (Qeqertarsuaq), east Greenland (Ittoqqortoormiit), and Svalbard and increased significantly from east to west. The geographical trend Sigma HCH is in general agreement with observed trends of HCH in seawater where higher levels have been found in the Canadian Arctic. Higher proportions of more recalcitrant hexa- and pentachloro-PCB congeners were observed in seal blubber samples in the European/Russian Arctic. The continued use of PCBs in electrical equipment and other applications in Russia is a likely source of the more highly chlorinated congeners.