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http://www.ens-newswire.com/ens/sep2...4-09-14-10.asp

Polar Bears Carry a Heavy Toxic Burden



By J.R. Pegg



WASHINGTON, DC, September 14, 2004 (ENS) - Polar bears are contaminated with poisonous chemicals that were released into the environment far from their Arctic habitat, new research confirms. The contamination may be harming the health of the polar bears and adversely affecting their development, behavior and reproduction, conservationists said Monday.


This latest research confirms the findings of other scientific studies released over the last four years, according to the global conservation organization WWF, and is further evidence of the need for an immediate phaseout of the most hazardous chemicals.


WWF says the three latest studies on the health of polar bears reveal that biological changes in the hormone and immune systems of the bears are linked to the levels of polychlorinated biphenyls (PCBs) and pesticides in their bodies.


For example, the higher the level of PCBs and several pesticides in polar bears in Canada and on the Norwegian island of Svalbard, the lower the level of antibodies in their blood.


Toxic chemicals were also correlated with steroid hormone cortisol and thyroid hormone levels in Svalbard polar bears.


Isolation has not kept polar bears free of toxic chemicals. (Photo courtesy U.S. Fish and Wildlife Service)
Reduced levels of antibodies leave bears more susceptible to infection and altered hormone levels could result in a wide range of negative health impacts, such as development, behavior, and reproductive problems.

"Most polar bears probably have several hundred man-made chemicals in their bodies and they have never evolved mechanisms to deal with them," said Dr. Andrew Derocher, a researcher at the University of Calgary who has contributed to all of the recent studies on polar bear contamination in the Arctic.


"The unintentional tinkering with the hormone and immune system of a polar bear is unlikely to be good for them," said Derocher.


The latest research on polar bears appeared in the "Journal of Toxicology and Environmental Health" in April and June, and in "Environmental Health Perspectives" in June.


The studies relied on blood and tissue samples taken between 1995 and 1999.


Some 22,000 polar bears are believed to remain in the wild, spread across the Arctic.


The bear is a top Arctic predator and conservationists caution that adverse affects on the species could impact the entire Arctic ecosystem.


In addition to chemical contamination, the bears are at risk from habitat loss and climate change.




Researchers are finding more evidence of chemical contamination of the world's largest terrestrial predator. Here Norwegian Polar Institute scientists conduct blood and fat tests on a female polar bear. (Photo by Tanya Petersen courtesy WWF-Canon )
Pollution generated by humans has a long history of turning up in the Arctic due to prevailing winds and ocean currents, but the recent studies of polar bears indicate the persistent and bioaccumulative character of modern synthetic chemicals.

The toxic contaminants that showed up in the recent polar bear studies are no longer widely used in manufacturing processes or in farming, but they are slow to break down in the environment and can remain in water, ice, and soil for many years.


Trace amounts make their way to the Arctic, and become concentrated as they make their way up the food chain into seals and other prey animals consumed by polar bears.


WWF hopes the findings about the contamination of polar bears will help energize the move for a ban on toxic chemicals still on the market today, many of which have not been fully tested to determine their impacts on human and wildlife health.
"Other contaminants, with similar properties, continue to be used on a day-to-day basis in manufacturing processes and products throughout the world," said Brettania Walker, toxics officer in WWF's Arctic Program. "It is crucial to prevent these newer generation chemicals from accumulating in, and polluting, the environment."