America's Most Polluted Cities

First the good news. "The American Lung Association's annual 'State of the Air' report -- based on EPA findings for 2009 through 2011 -- found that the three types of air pollution they track have all declined," reports Les Christie. The report's authors credit the Clean Air Act with helping to "prevent 160,000 deaths in 2010 (the last year data was available); avoid 1.7 million asthma attacks; and reduce hospital admissions and emergency room visits by 86,000 each."

"Still," say the authors, "over 131.8 million people—42 percent of the nation—live where pollution levels are too often dangerous to breathe." And though "California has led the nation in implementing clean-air programs," polluted air remains a challenge throughout the state. "Four cities in the Golden State -- Bakersfield, Fresno, Hanford, and Los Angeles -- are in the top 10 in all three categories of pollution and have been for years," notes Christie. "Bakersfield had the worst air quality for any metro area for the third year in a row."