Report names U.S. cities with foulest, cleanest air

The nation's 25 most smoggy cities improved air quality over the last year, but half the nation's residents still live with unhealthy levels of air pollution, according to an American Lung Association report released on Wednesday.

Weighing the pluses and minuses in U.S. air quality over the past year, the "State of the Air 2011" report concluded that the U.S. Clean Air Act, the federal law aimed at limiting pollution in the nation's skies, is working.

Cities with the foulest air were broken down into three categories and the worst three in each were Los Angeles, Bakersfield and Visalia, all in California, as most ozone polluted; Bakersfield and Fresno, both in California, and Pittsburgh, Pennsylvania, as most polluted by short-term particle pollution; and Bakersfield, Los Angeles and Phoenix as most polluted by year-round particle pollution.

Cities with nation's best overall air quality were Honolulu and Santa Fe, New Mexico, the report said.