At first glance, the polar bear’s natural environment seems white and pristine—far removed from the pollution in major cities and industrial areas. But in reality, polar bears in some parts of the Arctic can carry surprisingly high loads of toxic chemicals.
Why? Because wind and ocean currents transport these pollutants to parts of the Arctic, where they concentrate as they make their way up the food chain. Polar bears absorb these higher levels when they eat seals. The problem is compounded by the fact that many such chemicals are fat-soluble and the Arctic has a relatively high-fat food web.
Most polar bears sampled to date show signs of chemical contamination to some degree, but polar bears in the Barents Sea, Northeast Greenland, and the Kara Sea appear to be the most affected for certain well-known chemicals and chemical groups (e.g., DDT, PCB, and Brominated Flame Retardants). Even young cubs carry pollutant loads, absorbed from their mother’s milk.
Polar bears in the Beaufort Sea seem to have some of the lowest loads reported, at least to date. The gradient of chemical exposure from West to East is largely an artifact of pollution transport from the highly populated and industrialized Eastern U.S. and Western European areas.
Harmful effects. Well-studied contaminants have a wide range of potentially harmful effects on polar bears and their prey, while the impacts of less studied chemicals are virtually unknown. So far scientists have learned that:
- The chemical cocktail found in any polar bear is complex, consisting of up to 200+ different compounds.
- Pollutants can affect the bears’ hormonal system, including hormones essential to their growth, reproduction, and metabolism.
- Contaminants have been shown to cause shrinking genitalia in polar bears and weakened bones. Overall, this could affect their reproduction and general health.
- Vitamin levels appear to be affected too, as are some aspects of skull bone structure.
- A high load of contaminants may also suppress the polar bears’ immune system, affecting their ability to fight off disease.
- Certain toxins at high enough levels may affect the polar bears’ nervous system and thus potentially their cognitive skills.
Climate change remains the biggest threat to polar bears, but the added effects from toxins in some regions may make those polar bears even more vulnerable to this, and other, challenges.
To learn more, see Polar Bears and the Chemical Cocktail by Dr. Thea Bechshoft.