Another study by Canadian researchers at Quebec's Laval University showed that Inuit mothers carried about five times as much PCB contamination as other Canadians.
Experts say the reason is diet. The Inuit rely heavily on subsistence hunting of walruses, whales, seals, and other animals near the top of the food chain. Muktuk, or whale skin, and other fatty animal foods are important dietary staples in Arctic communities.
While such fats are sources of high energy, they are also laden with industrial chemicals. PCB levels in beluga whale blubber, for example, is about 80 parts per million. By contrast, most people have average PCB levels of less than 1 part per million, according to Ross, the Canadian government toxicologist.
Studies have shown that persistent organic pollutants accumulate in the fat of mammals and are taken in by eating animals lower on the food chain and, in the case of young animals, by nursing their mothers.
Many of these toxins are endocrine disruptors, which can impair reproduction by mimicking or changing hormonal activity. The disruptors can also cause developmental or skeletal abnormalities, weaken immunity, and cause neurological problems.
Ross notes that persistent organic pollutant toxicity is mediated through a cell structure known as an aryl hydrocarbon receptor, which is found in any mammal. As a result, a given chemical can have the same effect in mice, killer whales, and humans. "These chemicals are toxic to all these species, though sensitivity may change," he said.
Just as scientists have grasped the prevalence of certain well-known industrial pollutants in the Artic environment, new contaminants have been detected in the region's animals and human populations.
Last fall the Arctic Council, an intergovernmental forum of indigenous communities and eight Arctic countries, published a five-year assessment of Arctic pollution. The report cited growing concentrations of two persistent new chemicals, PBDEs and PFOS.
Polybrominated diphenyl ethers (PBDEs) are bromine-based flame-retardants used in an array of products, from fabrics to computers. Perfluorooctane sulfonate (PFOS) is a type of stain repellent.
The data, which updates an initial Arctic pollution overview in 1997, was produced by a monitoring group of the Arctic Council, whose members include the governments of Canada, Denmark, Iceland, Norway, Sweden, Russia, and the United States.
The report noted that the use of bromine-based flame-retardants has increased significantly over the past ten years. Annual worldwide production exceeds 200,000 tons (180,000 metric tons) and is concentrated in northern industrial areas, the report said.
"Some [flame retardants] are known to behave in a way that is similar to PCBs," the report said. "PBDEs seem to travel over long distances in the atmosphere, and some studies have shown that they can be toxic to the immune system and can affect neurobehavioral development."
The report also found that perfluorooctane sulfonates "do not seem to break down under any circumstances."
But "legacy contaminants" like PCBs and DDT are the dominant contaminants in Arctic wildlife, according to Sang, the WWF Canada Arctic specialist. Her environmental advocacy group's studies focus on contaminants in two Arctic marine mammals: bearded seals and walruses.
Scientists say other toxic threats to Arctic peoples and wildlife may lurk in oil production. A new, three-year study initiated this spring by researchers from Mote Marine Laboratory in Sarasota, Florida, will test bearded seals, walruses, and bowhead whales for petroleum hydrocarbon contamination from crude oil.
"Because of drillingand increases in drilling slated for the Arcticthere's been concern that Inuit food sources may be at risk for oil contamination," said Dana Wetzel, an aquatic toxicologist at the Florida research facility.
In March, Wetzel and marine biologist John Reynolds journeyed to Barrow, Alaska, to take tissue, muscle, and fat samples from bowhead whales during the Inuit's annual spring hunt. The thousand-year-old ritual is timed to the whales' yearly migration.
The team will also test walruses, sea otters, and clams in Alaska's Aleutian Islands for traces of PCBs, pesticides, and petroleum. Some scientists are concerned that a string of abandoned military sites there may be contaminating the environment.
For related coverage, watch Secret Killers of Monterey Bay on National Geographic Channel Presents II airing Sunday, August 29, at 9 p.m. ET/PT on the National Geographic Channel (U.S. only).
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