BIOTRANSFORMATION OF ORGANOCHLORINE PESTICIDES IN RINGED SEALS (PHOCA HISPIDA) FROM THE BALTIC SEA AND FROM SVALBARD

One of the major classes of persistent organic pollutants (POPs) detected in seals from the Baltic and from the Norwegian Arctic are organachlorine pesticides (OCPs). In the present study, the concentrations and patterns of a suite of OCPs and metabolic byproducts including DDE-compounds (3- methylsulfonyl (MeSO2-) -p,p’- and p,p’-DDE), chlordanes, hexachlorobenzene (HCB) and pentachlorophenol (PCP) were investigated in the liver of two ringed seals populations (Phoca hispida). These populations are contrasted by the degree of contamination exposure, i.e. highly contaminated Baltic Sea (n = 30-31) and less contaminated Svalbard (n = 18). Among the OCPs determined, p,p’-DDE and chlordanes were at the highest concentrations in both populations. OCP concentrations were positively related to phase I, cytochrome P450 (CYP) (i.e., ethoxyresorufin-Odeethylation (EROD), benzyloxyresorufin-O-dealkylation (BROD), methoxyresorufin-O-demethylation (MROD) and pentoxyresorufin-Odealkylation (PROD)) and conjugating phase II (glutathione-S-transferase (GST)) enzyme-mediated catalytic activities leading to changes in OCP patterns. In the highly contaminated Baltic seals, the DDE pattern shifted more towards 3-MeSO2-p,p’-DDE and less towards p,p’-DDE compared to the seals from Svalbard. Concentrations of PCP, which is a possible metabolite of HCB, were also higher in the seals from the Baltic compared to those from Svalbard. Concentrations of chlordane metabolites were relatively higher in the seals from Svalbard compared to the seals from the Baltic, while the trend was opposite for nonachlors. Observed changes in OCP patterns are likely to be related to phase I and II enzymes, and also to dietary exposure differences.