Toxins Accumulate in Arctic Peoples, Animals, Study Says
National Geographic Channel
|August 27, 2004|
For many, the Arctic is synonymous with a pristine, albeit harsh,
environment. So it is an unwelcome irony, perhaps, that the region's
indigenous peoples and animal predators are reportedly among the most
chemically contaminated on Earth.
Various studies in recent decades have found that animals from polar bears to killer whales, not to mention native peoples like the Eskimos, or Inuit, carry unusually high levels of human-made chemicals in their bodies.
These toxins include industrial pollutants like dioxin and PCBs, which gained notoriety during the 1970s, and newer compounds like those now used as flame retardants and stain guards.
The chemicals reach the Arctic borne north by wind and ocean currents. "The chemicals that accumulate in Arctic wildlife and people are coming from us," said Susan Sang, a senior manager and Arctic specialist for the Toronto-based environmental group WWF Canada.
For several decades researchers have studied toxin levels in Arctic peoples and wildlife and tracked pollution sources.
Peter Ross is a marine mammal toxicologist with the Canadian Department of Fisheries and Oceans in Sidney, British Columbia. He says scientists are now trying to take a difficult next stepestablishling a link between accumulated chemicals and health effects.
The potential health threat to humans and wildlife is considered serious enough to have prompted international action. In May 151 countries signed the Stockholm Convention on Persistent Organic Pollutants. The international treaty seeks to phase out use of 12 of the most dangerous persistent organic pollutants as soon as possible.
Infiltrating the Food Chain
Persistent organic pollutants are industrial chemicals that break down slowly and collect in the fatty tissues of animals. The toxins have been found to accumulate in ever larger concentrations in species higher up the food chaina process known as bioaccumulation.
In 1970 the insecticide DDT was found in the blubber of ringed seals in the Arctic. By the mid-1970s it was also found in beluga whales, polar bears, and fish.
Further tests discovered traces of some of the world's most toxic industrial chemicals, including polychlorinated biphenyls (PCBs) and dioxin, in Arctic wildlife.
In 1987 high levels of PCBs were discovered in nursing Inuit mothers in Nunavut, a semiautonomous territory in the Canadian Arctic. The finding raised concern about human health impacts.
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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