Polar bear circumpolar health assessment in relation to toxicants and climate changing.

Anthropogenic pollution and climate change are the two most significant threats for arctic biodiversity and ecosystem functioning. Because of food chain biomagnification of lipophilic persistent organic pollutants (POPs), the polar bear is one of the spec ies which have the highest levels of these harmful chemicals. Since POPs may have effects on hormone regulation and physiological homeostasis, reproduction and survival, POPs may adversely affect the plasticity of responses that polar bears have to enviro nmental changes. Thus, in combination these two major anthropogenic factors may have a significant effect on Arctic ecosystem functions. In BearHealth (IPY activity #134) partners from the USA, Canada, Russia, Denmark and Norway will study adverse health effects of POPs in polar bears, and the interacting effects of POPs and climate change on polar bears. Analyses of chemicals and biomarkers will be conducted on archived material from biobanks, and on samples which will be sampled during the project perio d. In the Norwegian part of the project we will focus on health effects of POPs related to thyroid and reproductive hormone homeostasis and on vitamin A, E and D status, and on interactions between biomarkers, environmental pollutants and climate change v ariables, and on including new samples from polar bears from Svalbard and the Barents Sea region into the study. In cooperation with Danish researchers (which are the coordinators of the international BearHealth project), a study on POP related effects on bone density and structure will be performed on a large collection of polar bears skulls from the Norwegian arctic and Greenland, and Russia if possible. The results from the Norwegian study will be integrated with the studies conducted by the other part icipating countries, and the project will end up in an integrated health risk assessment of the interactive effects of POPs and climate change in polar bears.