The in-vitro capacity for biotransformation of the major constituents of technical chlordane was investigated with hepatic microsomal preparations of a sperm whale (Physeter macrocephalus), a white beaked dolphin (Lagenorhynchus albirostris), harbour seal (Phoca vitulina), and an eider duck (Somateria mollissima). The ability to metabolise chlordanes increased in the order sperm whale < whitebeaked dolphin < eider duck < harbour seal. Harbour seal microsomal preparations were able to metabolise all chlordane congeners except trans-chlordene. In contrast, the microsomes of sperm whale microsomes (Physeter macrocephalus) could metabolise trans-chlordene only to a significant extent. The whitebeaked dolphin was able to metabolise trans-chlordene, heptachlor and trans-chlordane. Finally, the common eider duck was able to metabolise trans-chlordene, heptachlor, trans-chlordene and cis-chlordane significantly. Three metabolites were formed in the in-vitro assays. Two could be identified as heptachlor epoxide B and oxychlordane. However, the relative amounts of oxychlordane formed in the in-vitro assays were very low in comparison to residues levels. A further metabolism to diols by epoxide hydrolase enzymes would account for the low yield of oxychlordane. The hepatochlorepoxide A isomer was not formed in the in-vitro assays, which is relative retention time of 0,53 * the retention time of CB-153, remained unknown. Chlordane residues could be detected in all wildlife samples. From the in-vitro assay as well as biota residue level it can be concluded that cis- and trans-nonachlor are the most persistent of all chlordane components. However, a slow metabolism of these compounds occured in the harbour seal microsomes. Of the chlordanes, trans-chlordane is more readily metabolised than cis-chlordane, which is therefore more bioaccumulative. Relatively high concentrations were also found in blubber of three sperm whales. Because these animals do normally not occur in shelf seas, this shows that chlordanes have also reached the deep sea. The metabolic capacity of sperm whales seems to be low even among other cetacean species. Both a mixture containing the main parent compounds of technical chlordanes and a mixture containing three oxygenated metabolites were genotoxic in the direct Mutatox® assay. This genotoxic response disappeared after the addition of rat S9 fraction, allowing for biotransformation. This means that the primary metabolites formed were still genotoxic and ongoing metabolism must have taken place to detoxify both mixtures. |
