As their native habitat melts, polar bears have been forced into close contact with grizzly bears and humans—both of which have limited the iconic carnivore's ability to obtain food. This, however, is not the only problem the bears face.
New research has shown that, even in their relatively remote arctic homes, exposure to toxins and chemicals have compounded to make polar bears the most contaminated creatures on the planet.
The problem begins in Europe, Asia, and North America, where industrial and agricultural pollutants are released into the air and water. Ocean and atmospheric currents carry these pollutants north and they eventually settle in the Arctic.
Once there, the process of biomagnification begins. Small lifeforms at the bottom of the food chain consume the toxins and chemicals. These small organisms are consumed, and eventually so too are their predators. The process continues across the food web until it ends when a polar bear—a pinnacle predator—eats a seal.
At each link of the chain, each joint of the web, slowly-metabolized toxins are not only transferred, they are concentrated. This means that by the time they are consumed by polar bears, they have reached levels potent enough to stress the animal.
Researchers have found elevated levels of PCBs, brominated flame retardants, and mercury in polar bears.
Read more about polar bears:
Global Warming Not the Only Thing Threatening Polar Bears
Grizzlies Move into Polar Bear Territory
Melting Ice Increasing the Chance of Polar Bear-Human Meet-Ups
Polar Bear Mothers Spotted Swimming With Their Cubs on Their Backs