Chlorinated/brominated organic pollutants in aquatic birds and mammals: species- and food web-specific fate, biotransformation, trends and thyroid system effects

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There is increasing evidence that exposure to man-made environmental chemicals, particularly organic compounds that persistent and bioaccumulate in the environment, cause adverse effects in exposed wildlife and humans. Many of these environmental chemicals can be described as organohalogens as they contain the atoms chlorine, bromine or fluorine. "Legacy" organohalogen contaminants include polychlorinated biphenyls (PCBs) and numerous organochlorines pesticides. There are numerous new or "emerging" chemicals being found in the tissues of aquatic wildlife including brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs). However, there are numerous current-use BFRs unknown in the environment. All organisms possess enzymes that can mediate the metabolism, or biotransformation of foreign chemicals, which is meant facilitate their elimination from the body. Although the understanding has increased for bothh "legacy" and "emerging" organohalogens, mucb remains unknown on how biotransformation (oxidative processes and debromination) determines the fate, environmental chemistry and formation of hydroxyl- (OH-) containing metabolites at the tissue-, species, food web- and population-specific levels in aquatic wildlife. In the case of chlorinated and brominated organohalogens, formation of OH-containing metabolites can occur (e.g., OH-PCBs and OH-PBDEs) and be retained in the animal although there remains little understanding of how accumulative these metabolites are in food webs. OH-PCBs, OH-PBDEs and related compounds also possess the ability to act as hormones (e.g., thyroid), and thus affect hormone-dependent functions in an exposed animals. However, research is limited on endocrine activity of OH-containing organohalogens in wildlife species. The overall objective of the proposed research program to expand and undertake new research on the role of biotransformation on spatial/temporal dynamics and distribution, physiological fate and dynamics, and interaction of effects on the thyroid system, of organohalogens and OH-containing metabolites in model aquatic species and food webs in the Great Lakes and Arctic aquatic environments.