"Six in 10 Americans -- about 175 million people -- are living in places where air pollution often reaches dangerous levels, despite progress in reducing particle pollution, the American Lung Association said in a report released Wednesday.

The Los Angeles area had the nation's worst ozone pollution.

The report examined fine particulate matter over 24-hour periods and as a year-round average. Bakersfield, Calif., had the worst short-term particle pollution, and the Phoenix-Mesa-Scottsdale area of Arizona had the worst year-round particle pollution.

The U.S. cities with the cleanest air were Fargo, N.D., Wahpeton, N.D., and Lincoln, Neb."

Sue Manning reports for the Associated Press April 28, 2010. [2]