In its 12th annual State of the Air report, the American Lung Association found that despite a drop in the total number of days that Californians breathe smog and diesel fumes, the state continues to be plagued by air pollution.
The association analyzed federal data collected between 2007 and 2009 on short-term and annual average concentrations of ozone, or smog - usually generated by car exhaust mixed with heat - and fine particle emissions from diesel trucks, coal-fired power plants and wood-burning fireplaces.
Roughly 50% the people in the US live in counties that have unhealthful levels of either ozone or particle pollution. Both Alameda and Orange County ranked near the bottom of the list for air quality; both received F's for high ozone days and Orange County received an F for particle pollution, while Alameda county earned a D.
Read the article on the report in the San Francisco Chronicle, or visit the State of the Air website to review the key findings and see how your county scored. The scoring and ranking methodology is explained here.