Steamy days mean smog exceeded legal limit in Puget Sound over weekend

Heavy traffic and hot weather pushed the Seattle area over the legal limit for smog this weekend, violating the federal Clean Air Act for the first time in more than a decade.

The infraction saddles local officials with the responsibility of drafting a new plan to improve air quality, which could include tougher rules for car and industrial emissions. But the Puget Sound region won't face any consequences until at least 2010.

An unusually steamy string of 90-degree days sparked chemical reactions with auto emissions and other pollutants. Low wind speeds let the smog linger over the region, creating high levels of ozone.

Ozone shields the Earth from harmful solar rays in the upper atmosphere, but closer to the ground it can harm human lungs. Smog readings usually peak outside the urban core, said Mahbubul Islam, an air-quality program manager at the U.S. Environmental Protection Agency's (EPA) Seattle office.

That was the case over the weekend when a monitor in Enumclaw, in Southeast King County, measured 77 parts ozone per 1 billion parts air. The reading was 2 parts per billion over the federal limit of 75, which was lowered from 84 in May because of new medical research, Islam said.

Now that the region failed to meet the stricter standard, Washington's governor will have to report to the EPA in 2009 which areas of the state are too polluted. Islam said he expects Gov. Christine Gregoire to designate the Puget Sound region as "non-attaining."

The EPA will then evaluate the governor's recommendation and finalize the designation in 2010, at which time local officials will have three years to develop and present a plan to clean up the air, said Dave Kircher, air-resources manager for the Puget Sound Clean Air Agency.

The details of such a plan could range from tightening auto inspections to canceling Mariners' games on hot days.

If Seattle still fails to meet the standard by about 2015, the area could risk losing federal highway funding. But no region has ever received that penalty in the Clean Air Act's 45-year history.

The only short-term consequence of the violation, Kircher said, is a different permitting process for factories in the region.

The last time Seattle fell out of compliance was in the 1990s, said Sarah Rees of the state Department of Ecology's Air Quality Program.

Isaac Arnsdorf: 206-464-2397 or iarnsdorf@seattletimes.com