There's an environmental price to pay for industrial pollution, and it is the Arctic that's footing the bill. Fred Pearce reports
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The Independent Culture
"It hurts when I have to tell my kids that they shouldn't eat so much of our food because it is poisoned; and that they shouldn't play too long outside in the snow because the sun is dangerous." For Alfred Jakobsen, an Innuit from Nuuk in Greenland, the pollution of his homeland is a daily imposition from an alien world to the south.

The once pristine Arctic has fallen victim to toxic rain. Poisons from European factories, North American rubbish dumps, Asian pesticide-soaked fields and the leftovers of nuclear weapons tests carried out a generation ago in the Pacific, are all falling on their land, poisoning their food and burning a hole in the ozone layer above them.

It is not just that nowhere is safe from pollution. Rather, many pollutants are drawn to the cold Arctic air and fragile ecosystems. A series of quirks of atmospheric chemistry is turning the Arctic into the world's pollution funnel. A report on Arctic pollution, compiled over six years by 400 scientists, was received last month by ministers from eight Arctic nations. Their response: the calling for an international treaty to phase out the toxins collecting in the region. Time is short - the toxic rain is already threatening traditional hunting cultures with obliteration.

In northern Canada, the health authorities now warn Innuit girls and young women not to eat too much of their traditional foods of whale meat and "muktuk", a delicacy comprising whale skin and blubber. Muktuk in particular is full of polychlorinated biphenyls (PCBs), which concentrate in their bodies and are passed to their children through the placenta and in breast milk. "Eat about 10 grams of muktuk - that's a piece the size of a sugar cube - and you've had the maximum recommended weekly intake of PCBs. But many people here regularly eat a hundred times that," says Norm Snow, a British biologist working for the Innuit in Inuvik, a whaling community on the shores of the Arctic ocean.

PCBs are oily man-made chemicals once widely used as insulators in electrical equipment. They've been banned in most industrialised countries for two decades because they cause cancer and birth defects and damage the neurological and hormonal development of young children. But they continue to evaporate from rubbish dumps and pour into the air when contaminated oil is burned. Most sources are far to the south. From there they travel on the winds and, like some fiendish laboratory experiment, condense out in the cold Arctic air - a process that atmospheric chemists call global distillation.

Falling into the Arctic ocean, PCBs dissolve into the fats of the animals that eat them. Seals, walruses, porpoises, whales, eagles and polar bears in the Arctic have all been discovered with levels of PCBs likely to be toxic, says Cynthia de Wit of the Institute of Applied Environmental Research in Stockholm. Norwegian researchers have recently found polar bear cubs dying in unusual numbers in the Svalbard archipelago, north of Norway, after consuming PCBs through their mothers' milk. And the discovery this year of a pair of hermaphrodite polar bear cubs in Svalbard has caused the researchers to fear that PCBs may be disrupting hormonal development.

The worry is that humans, whose diets are remarkably similar to those of polar bears, may suffer similar complaints. Eric Dewailly of Laval University in Quebec City is convinced of the potential risk. He was the first researcher to stumble on the long-distance poisoning of northern communities. In the mid-Eighties, he compared levels of PCBs in the breast milk of women in southern Quebec with what he supposed to be clean background levels among women in the north of the province. "We found the levels in breast milk in Innuit women in the north were five times higher," he says. Three-quarters of them exceeded Canadian government health limits.

At around the same time Harriet Kuhnlein of McGill University in Montreal found that two-thirds of children in northern Innuit whaling communities had dangerous levels of PCBs in their blood. She identified the source as blubber from the tusked narwhal whales hunted in Baffin Bay. Research triggered by these shock findings has uncovered similar levels throughout the Canadian north. In neighbouring Greenland, where Dewailly reports "they eat more narwhal and beluga whale than anywhere else", 95 per cent of adults exceed health guidelines. The poisons accumulate in the Innuit throughout their lives. Levels are often higher among older men than among their womenfolk - the women purge their bodies of some of the toxins by passing them on to their children during pregnancy and lactation.

Nobody yet knows what damage is being done to the Innuit people by such communal poisoning, as the long-term studies necessary to spot such subtle changes have not yet been carried out in the Arctic. But recent studies among fishing communities around the similarly polluted Great Lakes in southern Canada, where PCB levels are lower than in the Arctic, suggest that the PCBs there are damaging children's neurological development - causing slow learning, poor memory and short attention span.

PCBs are only one of many groups of chemicals that can evaporate into the atmosphere and appear to be accumulating in the Arctic. Others include the toxic pesticides lindane, chlordane and toxaphene (which in laboratory conditions have similar effects to PCBs). Toxaphene builds up in beluga whales and lake fish, says Derek Muir of the government agency Environment Canada, and Dewailly has found high levels of it and chlordane among northern Innuit.

Other unwelcome visitors include DDT, which is still used to fight malaria and control insects. "There is a systematic transfer of these chemicals from warmer to colder areas," says Frank Wania, an atmospheric chemist at the University of Toronto, who has studied the delivery mechanisms. He says the Arctic air and oceans act as a sink for a range of compounds that condense out at temperatures of between zero and -50C. The constant evaporation and distillation of some compounds could lead to them eventually concentrating almost entirely in the Arctic.

Once in the Arctic, the compounds, collectively called persistent organic pollutants (POPs), break down more slowly than in warmer climates. Many are destroyed by oxidation reactions with hydroxyl, a rare but highly reactive compound produced by photochemical reactions in the air. These reactions are driven by solar energy and the weak sun in the Arctic ensures hydroxyl is in short supply, says Wania. "So chemicals that might survive for days in the tropics will last for two years or more in the Arctic."

Even some metals concentrate in the Arctic. Mercury, one of the most toxic metals, is widespread in the atmosphere as a gas as it evaporates at low temperatures. Concentrations in the air have roughly tripled in the past 200 years as a result of emissions from coal burning and waste incineration. In its gas-eous form, mercury has a lifetime in the air of a year or more. But not in the Arctic - as Bill Schroeder, also of Environment Canada, has discovered since he began measuring mercury at the air monitoring station on Ellesmere Island in the Canadian Arctic in 1995. He found that mercury concentrations plummeted each spring. Something was systematically removing the mercury from the atmosphere.

It turns out, says Schroeder, that the gaseous mercury was being turned into tiny particles which fell to the ground within a few days. Bizarrely, this "mer-cury rain" coincided almost exactly with the spring destruction of ozone in the air over the station. This, concluded Schroeder's colleague Leonard Barrie, was because the chemistry involved in the processes is remarkably similar. Both were set in motion by energy from the sun as it rose after the Arctic winter, and both involved reactions with chlorine and bro-mine (often naturally present in the environment).

The resulting intense fall-out of mercury occurs just as Arctic ecosystems go into spring overdrive, with plants sprouting and algal "blooms" forming across the open seas. Thanks to this process, items in the Innuit diet, such as the skins of beluga whales and the livers of ringed seals, contain high quantities of mercury. One in six Innuit Greenlanders have potentially harmful levels of mercury in their blood.

Not all the pollution arrives by air, however. Siberian rivers are also flushing toxic chemicals into the Arctic ocean, including PCBs, DDT and lindane. Concentrations of these chemicals are hundreds of times higher in Siberian rivers such as the Ob and Yenisei than in rivers draining into the Arctic from North America. According to Stanislav Belikov of the All-Russian Research Institute of Nature Conservation in Moscow, the DDT comes from old stocks sprayed in Siberia. Western scientists suspect that PCBs blow into the Arctic from Soviet towns and perhaps river boats burning oil contaminated with PCBs.

The latest candidate for a transport mechanism for pollutants in the Arctic is sea ice. Very high levels of pesticides, heavy metals and radioactive caesium are turning up in Arctic sea ice (lindane has reached higher concentrations beneath the sea ice north of Canada than anywhere else on Earth). One reason is the fall-out from global distillation. Another is that snow is very efficient at scavenging pollutants in the air and dumping them on the ice. Ice will also capture and hold pollution in sediments brought down by rivers or stirred up from the sea bed. Intriguingly the ice can float around for several years, accumulating pollutants before it eventually floats far enough south to completely melt and dump its load in the ocean.

According to Stephanie Pfirman, a biologist from Columbia University in New York, an important pollution pathway is the Transpolar Drift Stream, an ocean current which carries ice across the North Pole. It may be responsible for moving pollutants from Siberia to melting regions in the north of the Atlantic. She has used satellite pictures to source the origins of heavily contaminated ice to the Siberian coast where polluted rivers reach the sea. Pfirman believes "this process may explain the exceptionally high PCB levels found in seals and polar bears that live ... on the edge of the Arctic ocean where ice converges and melts - such as Svalbard and eastern Greenland."

Where transport processes do not single out the Arctic for attention, the region's fragile ecosystems can concentrate pollutants to an alarming degree; this is the case with radioactivity. Over 30 years after most nuclear weapons tests were banished underground, the fall-out of caesium-137 and strontium-90 from some 500 atmospheric tests conducted in the late-Fifties and early-Sixties continues. The fall-out is global and highest where rainfall is high.

Being a partly desert region, the Arctic, according to a new analysis by Per Strand of the Norwegian Radiation Protection Authority, has lower fall-out than places such as western Scotland and Norway. Despite this, says Strand, doses of radioactivity to humans living in the Arctic are on average five times higher than in Europe - and for some communities they are hundreds of times higher. The main source is the 15 million kilograms of reindeer and caribou meat eaten in the Arctic each year. Rudolf has a radioactive nose because of the high uptake of caesium by lichens, their main diet.

Total doses of radioactivity from weapons tests to the 4 million people in the Arctic today are estimated at 15,000 man-sieverts a year - 25 times the dose from all other man-made sources. These are largely from the Chernobyl nuclear accident in Ukraine in 1986 and marine discharges from the Sellafield nuclear reprocessing plant in Britain, which have worked their way across the Arctic ocean in the past 20 years. Strand says that hundreds of people in the Arctic have died from cancers caused by eating radioactive contaminated food.

All these threats come in addition to the impact of the thinning ozone layer above the Arctic. And researches warn that those living on the ice are at particular risk from skin cancer and cataract-causing UV radiation as the sun, low in the sky, reflects off the snow directly into their faces.

The UV barrage should be beginning to subside, as agreements on reducing production of ozone- eating chemicals made 10 years ago gradually make an impact on the atmosphere. But international controls on the many other dangerous compounds accumulating in the Arctic have yet to be agreed. Despite the concern of Arctic nations, POPs and heavy metals were barely mentioned at the Earth Summit in New York last month.

But an early agreement to halt their production would not stop the poisons continuing to evaporate from fields and dump sites, and blowing north. "Even if the emissions stopped immediately," says Wania, "global distillation would continue. We really don't know how long it would be before things started to improve." "It is," says Jakobsen, "not just about ecology. It is about the survival of our northern cultures. You are poisoning us."