According to the American Lung Association, Los Angeles again tops the list of most polluted cities in America. The association noted the Los Angeles-Long Beach-Riverside metropolitan area reported the worst air quality based on reports from 2003 through 2005. Included in the top 10 list from second to 10th worst were Pittsburgh, Bakersfield, Calif., Birmingham, Ala., Detroit, Cleveland, Visalia, Calif., Cincinnati, Indianapolis and St. Louis.

The reports also demonstrated that the number of days listed as the worst ozone levels were fewer than previous years, showing some air quality improvement.

“Nobody is surprised that L.A. has an air pollution problem,” said Janice Nolen, the association’s assistant vice president for national policy and advocacy. “The problems there are one of the reasons we have the Clean Air Act. But it is important for folks to know that there has been some improvement.”

The study also concluded that almost one-half of people in the United States live in counties that still are considered to have unhealthy levels of ozone or particle pollution.