Wednesday :: May 7, 2008

Toxic


by Turkana

Elizabeth Grossman, in Salon:

When coal is burned in power plants in the U.S., China and elsewhere, mercury is released into the atmosphere. Airborne, mercury can travel great distances before settling to the ground, or into lakes, rivers and oceans. Air and ocean currents, propelled by weather patterns and storm systems, sweep the mercury north. But the recent increases in Arctic mercury outpace and cannot be explained by smokestack emissions alone, says Gary A. Stern, a senior scientist with Canada's Department of Fisheries and Oceans, professor at the University of Manitoba and co-leader of the Amundsen expedition. Rather, signs point to global warming and other disruptive impacts of climate change.

As temperatures rise, causing sea ice, permafrost and snow to melt, the mercury that had been frozen in place is now being released, causing exposure up and down the food web. "Climate change alters exposure in the north and increases the system's vulnerability," says Robie Macdonald, a research scientist with Canada's Department of Fisheries and Oceans.

Yet the Arctic researchers are routinely recording a lot more than mercury. They are seeing synthetic chemicals such as the brominated flame retardants known as PBDE's (used in upholstery, textiles and plastics), as well as perfluorinated and chlorine compounds. And while long banned in many countries, lingering amounts of DDT and PCBs continue to turn up in people and animals in the Far North. Of concern due to their persistence and ability to accumulate in plant and animal tissue -- particularly the fat prevalent in Arctic animals -- these chemicals are also known to disrupt the endocrine hormones that regulate reproduction and metabolism. Some are considered carcinogens.

Alaskan polar bears, for instance, have some of the highest levels yet found in Arctic mammals of hexachlorohexane (HCH), a pesticide used to kill fungi on food crops. Carrie's ice samples, collected hundreds of miles from any agricultural sites, contain HCH. Polar bears also have some of the highest recorded levels of perfluorinated compounds, chemicals used in waterproofing and in fire and stain retardants. Indigenous people in both the Canadian and Greenland Arctic have some of the world's highest exposures to these persistent pollutants.

In the summer of 2007, Arctic sea ice reached a record low. Scientists monitoring the 2008 winter ice pack suspect this year's summer ice may also be remarkably low. As David Barber, Canada Research Chair in Arctic system science at the University of Manitoba, puts it, "Well over a million years of all ecosystems evolved to take advantage of this ice cover." With markedly less substantial sea ice cover, the hemispheric system is being thrown off balance, prompting changes that are increasing the load of contaminants in the Arctic.

Turkana :: 7:34 PM :: Comments (17) :: Digg It!