Chlorinated Biphenyls and Organochlorine Pesticides in Marine Mammals Stranded on the Coasts of Scotland and Ireland

Levels of organochlorine compounds (chlorobiphenyls and organochlorine pesticides) were measured in the blubber of 12 marine mammal species collected from strandings around the Scottish and Irish coast. Included are the first contaminant data to be reported in the blubber of the Sowerbys beaked whale (Mesoploden bidens). Twenty CBs were measured, including the toxic non-ortho substituted congeners (CBs 77, 126, 169). The sum of all CBs measured ranged from 0.27 to 67.9 μg/g wet weight with the highest concentration being found in a male Atlantic white sided dolphin (Lagenorhynchus acutus) stranded on the west coast of Ireland. Toxic equivalents (TEQs) to 2,3,4,8-tetrachlorodibenzo-p-dioxin have been calculated for toxic di-, monoand non-ortho substituted CBs and these show that in many species CBs 118, 126 and 156 and 170 account for a large proportion of CB toxicity. The contribution of certain congeners to the total TEQ changes with increasing contaminant burden and reproductive history. The sum of DDT components (six compounds) ranged from 0.10 to 53.4 μg/g wet weight. The organochlorine pesticides dieldrin, six chlordane components, hexachlorobenzene and αand γ-HCH were also determined in blubber. Pinnipeds were found to be more able to metabolise chlordanes and HCHs than cetaceans while differences in HCH contamination were found between coastal and oceanic cetaceans. Although concentrations of HCH s were low in all species (<0.5-128 and <0.5-139 μg/kg wet weight for α and γ-HCH respectively), coastal species such as harbour porpoises, bottlenose dolphins and white beaked dolphins have proportionally higher levels of γ-HCH (lindane) than more oceanic species indicating more localised sources of this compound around the Scottish coast. The concentrations of organochlorine pesticides determined in the majority of individuals were at the lower end of the concentration range reported for similar species elsewhere in the marine environment.