LONG TERM: Determine the effects, at the individual and population level, of persistent organic pollutants (POPs) and their metabolites in the polar bear; determine trend of POPs in the Arctic marine environment using polar bear tissues as a biomonitor. SHORT TERM: a. Determine 10-year temporal trends of POPs in the Hudson Bay Sub-Arctic Ecosystem from 1990-1989 by analysis of archived polar bear biopsy samples, including changes in enantiomeric composition of -HCH and chlordane compounds and ratio of -HCH/-HCH (cross-referenced to separate proposal on HCHs). b. Determine if there is selective tissue distribution of the enantiomers of chiral contaminants in polar bears, which may influence target organ toxicity, by analysis of archived polar bear samples. c. Determine the endocrine disrupting effect of POPs on testosterone and PCB metabolite profiles by in vitro metabolism studies using polar bear liver microsomes. d. In collaboration with CWS P&N Region, the Norwegian Polar Institute and the Norwegian Veterinary Institute, determine the immunotoxic effects of PCBs and other organochlorines in polar bears throughout a gradient of exposure (Hudson Bay, low; Svalbard, high). e. Determine the effects of hydroxy-PCBs on circulating thyroid hormone and vitamin A concentrations.