A new report says more than half of Americans still live in areas with unhealthy air, despite progress in reducing smog.
The report released Wednesday by the American Lung Association is based on 2006-2008 figures. It says progress has been made in reducing particle pollution such as soot and dust, thanks to cleaner diesel engines and controls on coal-fired power plants.
The Los Angeles area continued to have the nation's worst ozone pollution while Bakersfield had the worst short-term particle pollution.
The Phoenix-Mesa-Scottsdale area of Arizona had the worst year-round particle pollution.
The cleanest cities in the nation were Fargo, N.D.; Wahpeton, Minn., and Lincoln, Neb.