Most Polluted U.S. Cities

"The report finds that air pollution hovers at unhealthy levels in almost every major city, threatening people's ability to breathe and placing lives at risk. Some of the biggest sources of air pollution, including dirty power plants, dirty diesel engines and ocean-going vessels, also worsen global warming.

Many cities, like Los Angeles, New York, Atlanta, Charlotte, Philadelphia, Washington, DC and Baltimore have made considerable improvements in their air quality over the past decade. People living in some of these cities however, are breathing even dirtier air than what was reported in the Lung Association's previous report. Only one city, Fargo, North Dakota, ranked among the cleanest in all three air pollution categories covered by the research.

Sixteen cities making this year's 25 most ozone-polluted list experienced worsened ozone (smog) problems than last year."