TOXICOKINETICS OF CHLOROBIPHENYLS AND ASSOCIATED PHYSIOLOGICAL-RESPONSES IN MARINE MAMMALS, WITH PARTICULAR REFERENCE TO THEIR POTENTIAL FOR ECOTOXICOLOGICAL RISK ASSESSMENT

For the conservation of marine mammals and their ecosystem, it is important to know whether or not they are exposed to intolerable levels of environmental pollutants. In some case studies on marine mammals, xenobiotics can be linked to reproductive and immunological disorders. Disturbed endocrine systems seem to be a common denominator, whereby metabolization systems dealing with xenobiotic as well as endocrine compounds are involved. Two sets of indicators are distinguished to evaluate the toxicity of organochlorine residues found in marine mammal tissues. These are (1) interactions of chlorobiphenyls with the cytochrome P450 enzyme system and (2) comparative physical and chemical blood parameters directly and indirectly obtained via functional immunoassays. Apart from the constitutive enzymes, the induction of each of the other 150 isoenzymes of the P450 system exhibits substrate (= compound) specificity and moreover organisms develop species and even organ specific induction profiles. Therefore, a specific enzyme profile for each compound in a given species/organ may exist. The biotransformation capacity, constitutive and/or induced, will be reflected in the extent to which biotransformation of the chlorinated biphenyls in question has occurred. This can be expressed in the ratio of the concentration of a given individual biphenyl to the concentration of a persistent reference individual biphenyl. Both these indicators will provide information on which compounds are most likely involved and to what extent. The directly obtained blood parameters include levels of vitamin A, steroid hormones and thyroxine. The blood parameters acquired via functional immunoassays include mitogen- and antigen-induced proliferative responses of peripheral blood mononuclear cells (PBMC) and natural killer (NK) activity. These parameters provide comparative information on the state of impact, inter alia immunocompetence, of environmentally exposed individual animals. It is concluded that both sets of indicators are a basis for a multiple response assessment in a nondestructive approach. They are, as such, important elements in a conceptual framework which allow prediction of the impact of pollution on marine mammals.