Organochlorine residues in marine mammals from the northern hemisphere--a consideration of the composition of organochlorine residues in the blubber of marine mammals.

Levels of organochlorines (PCBs, sigma DDT, lindane and its isomers, HCB, chlordane, and toxaphene) were determined in blubber of marine mammals from the northern hemisphere. Differences in both levels and ratios of organochlorine compounds were detected in different species of marine mammals living in the same region, e.g. blubber of harbour seals (Phoca vitulina) accumulated significantly lower levels of lindane, HCB, toxaphene, and DDT and its metabolites than harbour porpoises (Phocoena phocoena). Compared to such elementary differences in the organochlorine pattern in different marine mammals, the influence of age and sex on the results was only minimal. Varying ratios of contaminants in individual harbour porpoises were explained by migration. Constant PCB/DDT ratios were measured in harbour seals. Due to the sedentariness of harbour seals, even local sources of contaminants could be recognized. Careful evaluation of the organochlorine levels and ratios in marine mammals made it possible to monitor the transport of PCBs from the European continent to European Arctic regions.