researchers at University of Copenhagen studied polar bear brain tissue . They found toxic pollutants accumulated in the bears ' brains . Higher levels were associated with lower levels of key hormones . These levels depend on the behaviour and hormone levels in polar bears .
Researchers at University of Copenhagen studied polar bear brain tissue . They found perfluoroalkyl pollutants accumulated in the animals ' brains . Higher levels were associated with lower levels of key neurotransmitters . These may impact on the behaviour and hormone levels in polar bears .