HEALTH / The poisoned North: Banned pollutants are still accumulating in the Arctic. Fred Pearce explains why

SOME OF the world's most toxic chemicals - including dioxins and polychlorinated biphenyls (PCBs) - are turning up in ever higher concentrations in the Arctic, thousands of miles from where they have been produced and used. This discovery, made by researchers in Canada and Scandinavia, is all the more surprising because the manufacture of many of them has been banned for more than a decade.

Scientists fear the chemicals, used as pesticides and in industry, are evaporating from the soils, waste dumps and polluted lakes of Europe and North America, and condensing on to the snow and ice of the Arctic. Frank Wania, of the University of Toronto, says the atmosphere is carrying out 'a systematic transfer of these chemicals from warmer to colder areas'. They are then eaten in dangerous quantities by whales, seals, polar bears - and Eskimos.

Most of the chemicals involved are organochlorines, which contain various combinations of chlorine and carbon atoms. Some - such as DDT, dieldrin and lindane - have been widely used as pesticides. Those used in industry include PCBs, which were first manufactured in 1929 and became a widespread substitute for mineral oil in electrical transformers. Others were unwanted by-products of the manufacture of other organochlorines, including dioxins - among the most potent of all poisons.

Most organochlorines are toxic. They accumulate in the environment, but build up to their highest concentrations in the fatty tissue of birds, fish and mammals. Animal fats act as a reservoir for these chemicals, which can enter the bloodstream in a toxic rush when the animal uses up its fat for some reason - if its food runs short, for example, or during pregnancy. Once in the bloodstream, PCBs reach the kidneys, liver and brain - and can kill.

Organochlorine pollution of the Great Lakes in the US has been blamed for the disappearance of Beluga whales from the St Lawrence Sound, which links the lakes to the Atlantic. These chemicals were probably behind the death of 15,000 guillemots in the Irish Sea in 1969. They also appear to make many animals infertile and more prone to disease; they may have left the North Sea's harbour seals vulnerable to the virus that killed thousands in 1988, though the link was never proved.

Some research suggests that human males with fertility problems may have above-average amounts of organochlorines, including PCBs, in their bodies. The widespread decline in the number of sperm in the semen of late 20th- century men has also been linked to PCBs.

In the industrialised world, the amount of banned organochlorines such as DDT, PCBs and dieldrin in plants, soils, rivers and animal and human flesh has fallen as these chemicals have disappeared from use. The populations of many animals have revived as a result. Among the most notable British beneficiaries are the golden eagles of Scotland, which successfully bred again after dieldrin ceased to be used in sheep dip, and the otters of eastern England.

But those chemicals have not broken down or disappeared. Far from it, says Kevin Jones of the Institute of Environmental and Biological Sciences at the University of Lancaster. 'They have simply evaporated into the air again,' he said recently. 'Soils are now the principal source of PCBs in the air.'

Evaporation is quickest in warm climates, such as the tropics, where many pesticides leave the soil for the air soon after being sprayed. But it occurs in colder countries too, and what goes up must come down. 'These long-lasting poisons are evaporating from soils in the industrial regions, travelling in the air for several weeks and then condensing out in the cold Arctic air,' Jones says.

Toronto University's Frank Wania calls the process 'global distillation', and says the atmosphere works like a vast oil refinery. Just as different fractions of crude oil are separated out as they condense at different temperatures, so different organochlorines condense out in different parts of the Arctic.

The result is that hundreds of tons of poisons seeping into the environment thousands of miles south are turning up in the flesh of polar bears, seals, whales and Eskimos. The threat is compounded because Arctic animals carry a lot of fat to keep out the cold. Old male mammals, such as polar bears, usually have the most poison; females pass on organochlorines to young through the placenta and in milk.

Research has only been completed on a few organochlorines, but the evidence is alarming. PCBs, which ceased to be manufactured in

the 1970s, are concentrating in ever-increasing amounts in the far north. Recently, Norwegian researchers found male polar bears with 90 parts per million of PCBs in their fat on the remote island of Spitsbergen. Bears in the Canadian Arctic contain more PCBs than in the 1960s. Most worrying of all, the amount in the milk of Eskimo mothers in northern Canada is now five times greater than in milk from mothers hundreds of miles further south.

Much more poison may be on its way. The north-east Atlantic, stretching into the Arctic Circle, is the largest reservoir for the 370,000 tons of PCBs estimated to have entered the environment over the past 60 years. With some of the best-known organochlorines banned, scientists are becoming more concerned about the hundreds of others still in wide use. Wania says levels of hexachlorobenzene, an industrial chemical, 'are higher on Arctic plants than on temperate and tropical ones. There is more lindane, an insecticide, in Arctic seals than in Baltic and North Sea seals.'

According to Derek Muir of the Canadian government's Freshwater Institute in Winnipeg, concentrations of the most dangerous dioxin (known as 2,3,7,8-TCDD) among Canadian ring seals 'are greatest in the most remote high Arctic, and lowest further south.' But Muir's greatest concern is toxaphene, which has turned up in the Canadian Arctic at concentrations greater than any other organochlorine. He recently found high levels in the breast milk of Eskimo women. Wania says these new findings mean the use of dozens of chemicals now known to accumulate in the Arctic 'should probably be discontinued'.

Not all organochlorines condense out on to the ice and snow, but that does not make them harmless to the Arctic. CFCs, which are also organochlorines, do their worst damage over the Arctic and Antarctic. Here, they gather on tiny ice particles in polar clouds, and destroy ozone, which shields the planet from ultra-violet radiation, creating annual ozone holes.

Organochlorines are among the world's most intractable environmental problems. No wonder Greenpeace recently called them 'arguably the most dangerous group of chemicals to which natural systems can be exposed'.

(Photograph omitted)