When pollutants take the Arctic route

From Hamburg, Germany, at a meeting of the Society of Environmental Toxicology and Chemistry–Europe

Throughout much of world, prevailing winds come from the West. One would expect, then, that for airborne pesticides originating in China and other parts of Asia, the western edge of North America would take the biggest pollution hit. Initial findings of a new continentwide pollutant-sampling network now suggest that’s not always true. The data indicate that at least one unexpected location–Newfoundland, the easternmost point in North America–sustained the greatest annual fallout of a pesticide constituent emanating from Asia.

Frank Wania of the University of Toronto at Scarborough and his colleagues placed 45 outdoor air-sampling canisters across five countries from Canada to Costa Rica. After a year, the researchers analyzed filters collected from the canisters, looking for common pollutants, including DDT, hexachlorocyclohexanes (HCHs), and polychlorinated biphenyls. The data generally reflected patterns of the pollutants’ past use in North America.

The exception, Wania reported, was for alpha-HCH, a primary constituent of a pesticide no longer used in the United States or Canada. Its greatest fallout was in Newfoundland.

The current distribution indicates that heavy Asian use of the chemical in the 1970s and 1980s sent polluted clouds across the Pacific and into Canada’s high latitudes, Wania says. In the cold temperatures, the pollutant condenses and accumulates in the Arctic Ocean. There, it persists even 2 decades after most Asian nations phased it out.

For much of the year, Wania notes, an ice cap keeps the compound trapped in the Arctic’s frigid water. But when the spring melt comes, some dissolved alpha-HCH flows into the Atlantic. By the time that water reaches Newfoundland, it has warmed enough for substantial amounts of the chemical to vaporize.

Wania says the compound’s unexpected eastern abundance is a clear example of how environmental stores of even long-banned chemicals can show up just about anywhere.


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Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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