Poisoning the purity of the Arctic

Scientists have long been puzzled by the fact that some of the world's most remote peoples are among the most contaminated by polychlorine biphenyls (PCBs) and pesticides. The 450 people of Broughton Island, off Baffin Island, for example, have the highest levels of PCBs in their bodies found anywhere in the world, except in victims of industrial accidents. Greenlanders contain more than 70 times as much of the pesticide hexachlorobenzene (HCB) than people from temperate areas of Canada.

� Roland Seitre/Still Pictures

Up to now they have thought that the peoples of the Arctic must receive the high levels of the toxins from eating a lot of contaminated fish and wildlife, which will have accumulated the chemicals because they are at the top of the food chain. Our Stolen Future, the book which caused a sensation by exposing the extent of pollution by oestrogen mimicking chemicals and other 'endocrine disrupters', devotes a long passage to a fictionalized, and implausible, account of how this might happen.

But clearly this cannot wholly explain the phenomenon. Quite apart from anything else the chemicals are widespread in the environment itself, as well as in the fish and wildlife. The pesticide HCH, for example, is over 100 times more concentrated in the Beaufort Sea in the Arctic than in the Java sea near where it is mainly used.

Increasingly scientists now think that 'global distillation' is responsible. Volatile chemicals - like PCBs, HCB and HCH - boil off into the air where they are used in the tropics and are carried thousands of miles by the winds: this happens, for example, to an estimated 99.9 per cent of the HCH used on rice paddies in South India. When the chemicals meet colder air they condense and fall to earth.

As in the fractional distillation equipment used in industry - and in the classroom - different groups of chemicals condense out at different temperatures. Toxaphene, for example, is less volatile than some of the others and seems to accumulate mainly in temperate areas: high levels of the pesticide are found in north sea fish even though it has rarely been used in Europe. HCB, HCH and the more volatile PCBs seem to carry on up to the Arctic; concentrations in seals increase as you go North.

Dr Frank Wania, who first stumbled across the process at the beginning of the 1990s when studying for his doctorate, says that the process can take anything from a few weeks to decades: a single favourable wind can carry the chemicals to the Arctic in a fortnight, or they may move in a long series of countless small jumps as the seasons change.

They concentrate in the Arctic because it is a relatively small area, and the cold and winter dark slow down their natural degradation. And thus the people of the Arctic, who have contributed almost nothing to the pollution and do not benefit from the use of the chemicals thousands of miles away, become its principal victims.

Geoffrey Lean is Environment Correspondent of the Independent on Sunday.

For more details of how you can help, click here.