Wilkening and his coauthors summarize the current state of knowledge about trans-Pacific transport of pollutants from Asia and Europe to North America. While they comment that the available data paint only a sketchy overall picture, they report that several different types of pollutants are now known to be carried by wind currents across the Pacific. These include persistent organic pollutants (POPS), heavy metals such as mercury, ozone and coal combustion products.

Pollutant movement eastward from Asia is highest in winter and spring. Depending upon altitude and weather, transit times across the ocean can be 5 to 10 days.

The few data available indicate that pollutants arrive on the west coast of North America in bursts, as polluted air masses work eastward across the ocean. Computer simulations suggest that three to five of these "important pollution events" reach the US and Canadian west coasts each year between February and May.

A plume of air moves across the Pacific Ocean from central Asia in Spring 1998. Graphic from Wilkening et al. 2000.

Data on contaminant accumulation in natural habitats, sediments, wildlife and people indicate that at least some of the transported pollutants are "working their way into ecosystems and humans." Wilkening et al. cite one report concluding that anticipated growth in Asian ozone from fossil fuel combustions may even make ozone standard attainment in US population centers more difficult.

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