Leading Edge / Summer 2004
Banned Chemical Travels Far

Suspected carcinogen followed atmospheric and water flows across three oceans


A chemical once used in pesticides in Asia has accumulated thousands of miles away in Canada, according to a U of T study published in Environmental Science and Technology.

Relatively high concentrations of alpha-hexachlorocy-clohexane (alpha-HCH) were detected in the atmosphere of Sable Island off the coast of Nova Scotia and Newfoundland, says Professor Frank Wania of chemistry. The chemical, a suspected carcinogen, was last used about 15 years ago in countries such as China and India but followed atmospheric and water flows across the Pacific, Arctic and Atlantic oceans to eastern Canada. Frigid northern temperatures slowed its evaporation and trapped the chemical until it hit warmer waters, where it will evaporate.

In the study, Wania and his team established a network of air-sampling stations on a north-south route from the Arctic to Central America and east-west from Newfound-land to Vancouver Island. The sampling stations consist of polymer resins – pellets of a lightweight plastic material – that absorb pollutants like a sponge, allowing researchers to monitor alpha-HCH and other chemicals across the continent.


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