Los Angeles has topped the American Lung Association's list of the most polluted American cities.
"The association found that the Los Angeles-Long Beach-Riverside metropolitan area had the worst air based on 2003 through 2005 figures."
"The Pittsburgh area was ranked as the nation's second most polluted metropolitan area followed by Bakersfield, Calif., Birmingham, Ala., Detroit and Cleveland. Visalia, Calif., Cincinnati, Indianapolis and St. Louis rounded out the top 10."
"Despite the dubious distinction, the number of days Los Angeles-area residents breathed the nation's worst ozone levels was fewer than in previous years."
"Nearly half of the U.S. population lives in counties that still have unhealthy levels of ozone or particle pollution, even though there appeared to be less ozone in many counties than previous years, the study found."