In a recent study done, that was released on July 6, 2009, states that not only is global warming threading the existence of polar bears, but also harmful chemicals that man is releasing into the environment.

Mercury has been found in polar bear bodies.  Mercury is ingested by the polar bear through other animals.  It can simply start our as a small fish, then as it goes through the food chain, it becomes more and more concentrated.  By the time the polar bear eats the seal, the mercury levels could have a lethal effect on the polar bear.