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Rising PBDE levels threaten polar bears
Levels of fire-retardant PBDEs are rising dangerously in polar bears in the Canadian and European Arctic, according to a Canadian-led research study published in January in Environment Research and Technology.
The study, entitled “Brominated fire retardants in polar bears (Ursus maritimus) from Alaska the Canadian Arctic, East Greenland and Svalbard,” found that polybrominated diphenyl ethers (PBDEs) were bioaccumulating in the tissue of polar bears in the four areas studied, including Svalbard in the Norwegian Arctic. The study was led by Dr. Derek Muir of Environment Canada’s Water Research Institute and included scientists from four countries.
Their findings show that the fire retardant chemicals are biomagnifying at an alarming rate in the bears, which are at the top of the food chain in the Arctic ecosystem. In one sample, PBDEs levels were 71 times higher than those in ringed seals, which are polar bears’ principal prey.
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The world’s population of polar bears is estimated at only some 20,000-25,000 animals, whose survival is already threatened by global warming. Because of their effect on the thyroid and sex hormones, PBDEs may be a factor in the declining birth rate and even the elevated rate of hermaphroditism that has recently been documented among polar bears.
The levels were higher in Greenland and the Norwegian Arctic than in Alaska and the Canadian Arctic, suggesting that the east coast of North America and northwestern Europe have been the main sources of the chemicals. PBDEs have been used extensively in Europe and Northern Americas as flame retardants in foam furniture, clothing and electronic components.
Dr. Muir said the persistent, bioaccumulative nature of the compounds wasn’t considered when they were introduced widely in the 1970s.
“In general, we haven’t considered their long-range transport potential,” he said. “Now we’re dealing with a legacy of these chemicals in the environment.”
Europe and several U.S. states have moved recently to ban two of the three main groups of PBDE compounds, known as penta- and octaBDEs, but the chemicals are expected to persist in the environment for years. In addition, the third group, decaBDEs, are still being manufactured and used, especially in electronic components, although there is wide demand for the bans to be expanded to include all PBDEs.
Initially, decaBDEs were considered less of an environmental threat, but recent research has shown that decaBDEs can lose bromine atoms in the environment, becoming more toxic and bioaccumulating more readily.
PBDEs are actually 209 different formulations, or congeners, depending on the number and location of the bromine atoms in the chemical chain.
The PBDE congeners found in the Arctic polar bears are mainly those in the penta-and octaBDE groups. But earlier research carried out in Svalbard found decaBDEs in several polar bear samples. They were also found at even higher levels in glaucous gulls, a common northern bird that is also high on the food chain.