One in 50 female polar bears on an Arctic island have male and female sex organs, researchers have found, in a study linking pollution and flame retardant chemicals used in the Western world with dangers to wildlife.
Scientists from Canada, Alaska, Denmark and Norway say significant deposits of flame retardant PBDEs have been found in polar bears, especially in eastern Greenland and Norway's Svalbard islands.
Studies are still being carried out on what impact the chemicals might be having on bears. Tests on lab animals such as mice indicate they attack the sex and thyroid glands, motor skills and brain function.
There is also evidence that compounds similar to PBDEs have contributed to a surprisingly high rate of hermaphroditism in polar bears. About one in 50 female bears on Svalbard has both male and female sex organs, a phenomenon scientists link directly to the effects of pollution.
"The Arctic is now a chemical sink," said Colin Butfield, a campaign leader for the Worldwide Fund for Nature, which last month indicated that killer whales in the Arctic were also suffering from elevated levels of contamination with fire retardants as well as other man-made compounds.
"Chemicals from products that we use in our homes every day are contaminating Arctic wildlife."
The pollutants are carried northwards from industrialised regions of the United States and western Europe on currents and particularly on northbound winds.
Contaminated moisture often condenses on arriving in the cold Arctic climes and is then deposited, ready to enter the food chain.
For several years, scientists have observed how the concentrations of the pollutants are magnified as they ascend the food chain, from plankton to fish and then to marine mammals such as seals, whales and polar bears.
The new study, published in the journal Environmental Science and Technology, shows, for instance, that one compound was 71 times more concentrated in polar bears than in the seals they normally feed upon.
Conservationists are especially alarmed by these new findings because of the already fragile condition of the Arctic polar bear populations, some of which could be devastated before the end of the century.
As warming temperatures erode their hunting grounds, polar bears in Canada's western Hudson Bay region, for instance, saw their numbers slide from 1100 in 1995 to only 950 in 2004.
The dangers now posed by the PBDEs are reminiscent of the crisis 30 years ago over PCBs - polychlorinated biphenyls - a highly toxic byproduct of many industries that was also found to be migrating in large quantities to the Arctic.
The dumping of PCBs was swiftly banned. Since 2004, manufacturing has stopped in the US of two of the most toxic retardants, called penta and octa. Stockpiles of both still exist, however.
According to Derek Muir, of Canada's Environmental Department and a leader of the new research, there are signs of a slightly different retardant, typically used in construction materials and furnishings, also showing up in the Arctic and in the bears, called HBCD.
"It's a chemical that needs to be watched, because it does biomagnify in the aquatic food webs and appears to be a widespread pollutant."
The research team tested 139 bears captured in 10 locations across the Arctic region. They found that the bears in Norway's Svalbard, a wildlife refuge where all hunting is banned, had 10 times the levels of the chemicals than bears in Alaska and four times those in Canada.
Scientists believe PBDEs - polybrominated diphenyls - are contributing to hermaphroditism in polar bears.
One in 50 female bears have male and female sex organs on Svalbard island.
Researchers say the chemicals used as flame retardants move from the Western world and condense in the cold Arctic air.
The chemicals appear to become more concentrated as they pass up the food chain, from plankton to polar bears.
One compound was 71 times more concentrated in polar bears as in seals, the bears' main food source.