Though such events happen infrequently, when large pockets of Asian pollution do make it across, the effects on air quality this side of the Pacific can be dramatic, said Daniel Jaffe, an environmental science professor at the University of Washington, Bothell.
The most pronounced effects can push the levels of atmospheric ozone and small particulates beyond limits set by the U.S. Environmental Protection Agency, which raises health issues for those with respiratory problems, Jaffe said Friday during a presentation at the American Association for the Advancement of Science meeting in Seattle.
When particulates get as small as 10 microns, about one-tenth the width of a human hair, they are small enough to pass through the nose and into the respiratory system. At 2.5 microns or smaller they can begin to have noticeable health effects, particularly for people with conditions such as asthma.
"This clearly has health implications, but it's a rare event," Jaffe said. "How rare we don't know for sure, but from the record it looks like it's something on the order of three occurrences every five years."
One such event happened last summer, when pollution from Siberian forest fires crossed the Pacific and boosted levels of atmospheric ozone, an important summertime pollutant, at stations in Washington state and British Columbia. From May 27 through June 9, surface ozone levels exceeded the long-term average for May and June. On June 6, Enumclaw, Wash., about 35 miles southeast of Seattle, recorded an eight-hour average of 96 parts per billion, well beyond the EPA limit of 80 parts per billion. The data, which has not yet been published, indicates that the plume from the Siberian fires contributed about 15 parts per billion to that read
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Contact: Vince Stricherz
vinces@u.washington.edu
206-543-2580
University of Washington
13-Feb-2004