In early April, the EPA finalized a January proposal to re-designate the Truckee meadows area of Washoe County, Nev., as an attainment area for CO. The agency also approved the county's plan to maintain healthy levels going forward.

"The hard work invested by Washoe County and the State of Nevada has paid off. Washoe County has met the federal CO standard, so you can all breathe easier," said Deborah Jordan, Air Division director for EPA's Pacific Southwest region. "We commend your efforts, which can serve as a model for other areas."

In the past 30 years, the region has seen significant improvements in CO conditions thanks to the federal motor vehicle control program, state vehicle inspection and maintenance program, local oxygenated gasoline program, and local residential wood-burning regulations.