An environmental group said Wednesday that it plans to sue the federal government to stop approving pesticides that end up in food eaten by polar bears.
The Center for Biological Diversity gave a 60-day notice that it will sue the Environmental Protection Agency for failing to consider the effects of pesticides on polar bears, a threatened species, and their Arctic habitat.
Spokeswoman Rebecca Noblin said the poisoning of the Arctic is a silent crisis that also threatens Arctic people. Steps taken to protect bears would also protect people who rely on subsistence hunting and fishing, she said.
"People share the top spot in the food chain with polar bears," she said. "Unfortunately, there's not an endangered people's act."
Polar bears were listed as threatened in May 2008 because of the dramatic loss in their primary habitat, sea ice. Federal law protecting endangered species requires other agencies to consult with the management agency to make sure their actions do not jeopardize the listed species.
Noblin said the EPA's registration of pesticides that wind up in polar bears violates the law.
A spokesman for EPA's regional office in Seattle, Mark MacIntyre, said the agency could not comment on pending litigation.
Chemicals in pesticides can take decades to break down. The process takes even longer in the Arctic cold. Fat samples taken from polar bears continue to find PCBs and other pollutants already banned by the EPA, Noblin said.
Pesticides still in use are starting to show up and her group fears they will be found in dangerous concentrations if allowed to be used.
Pesticides are used minimally in Alaska but reach the Arctic through the atmosphere and the ocean. They also accumulate in plants, fish, birds and the animals, Noblin said.
Natalie Dawson, a biologist with the group's Anchorage office, said the pollutants accumulate in plankton at the bottom of the food web. Fish eat plankton, seals eat thousands of fish and polar bears eat hundreds of seals.
It's called "biomagnification," the same phenomenon that harmed bald eagles ingesting DDT and other persistent pesticides. "They were eating so much of this contaminant because everything below them was eating so much of this contaminant," she said.
According to the group, polar bears are vulnerable because they eat a diet rich in fat, where the chemicals accumulate.
The chemicals lower bears' immune system and put them at a higher risk of infection, said center attorney Brendan Cummings, citing a 2004 study of bears in Svalard, Norway.
The pesticides are endocrine disrupters -- synthetic chemicals that mimic natural hormones and send false messages. They prevent synthesis of the body's own hormones and accelerate breakdown and secretion of hormones.
An east Greenland study concluded that pollutants shrink polar bear genitals, both ovaries and testes. Another Norway study observed a high rate of female pseudo-hermaphroditism, which suggested endocrine disruption.
The chemicals may also affect cub mortality. Cubs weigh only about 1.5 pounds at birth in December. Females don't eat as they nurse, and as they lose weight, their pollution loads on a per-pound basis increase. The mothers inject cubs with a heavy dose of contaminants dissolved in the fats of her milk, exposing underdeveloped cubs to a high pollution loads, Cummings said.
The lawsuit will take aim at the more than 1 billion pounds of pesticides used in the United States to control weeds, insects and other organisms.
Cummings said chemicals from 14 have been detected in the Arctic. They include Chlorpyifos, the most widely used insecticide. It's been found in sea water, sea ice, marine fog and snow samples in the Bering and Chukchi seas and in snow samples in Alaska national parks, according to the group.
So has Diazinon, now banned from residential use but still used to control soil and foliage insects on selected crops, and Endosulfan, an insecticide registered for use on vegetables, fruits, grains and cotton plus ornamental shrubs and trees.