Environment Pollution 7 U.S. Cities With the Worst Air Pollution By Staff Author Updated November 10, 2019 Mbbirdy / iStockphoto Share Twitter Pinterest Email Environment Planet Earth Climate Crisis Pollution Recycling & Waste Natural Disasters Transportation The American Lung Association's State of the Air 2010 report found that more than half the population of the U.S. lives with dangerous pollution levels. Despite progress in many places, the report found the air in some California cities was more polluted than before. Cities were ranked in three areas: year-round particle pollution, short-term particle pollution, and ozone. 1 of 9 Phoenix Photo: By Sean Pavone/Shutterstock A new area moved to the top of the most-polluted list when judged by year-round particle levels: Phoenix-Mesa-Scottsdale, Ariz. Particle pollution is a combination of soot, dust and aerosols that are suspended in the air. Cities with year-round particle pollution face unhealthy levels day-in and day-out, while those with problems with short-term levels have "spikes" in particle pollution that last anywhere from hours to days. 2 of 9 Bakersfield, Calif. djbones/Flickr. Bakersfield, Calif., had higher levels of year-round particle pollution compared to the 2009 report. It ranked #2. Nearby cities that also made the top 10 in year-round particle pollution were Visalia (#3), Fresno (#6) and Hanford (#8). Like Bakersfield, Visalia and Fresno worsened; Hanford improved. 3 of 9 Los Angeles Photo: By logoboom/Shutterstock Alas, no report on dirty air would be complete without L.A. Los Angeles-Long Beach-Riverside, Calif., ranked #3 in long-term particle pollution, #1 in ozone pollution and #4 in short-term particle pollution. Although Los Angeles had slightly worse ozone average levels than in the 2009 report, the metro area still reported its second lowest ozone levels since the lung association’s first report was released in 2000. 4 of 9 Pittsburgh Keith Srakocic/AP. Pittsburgh-New Castle, Pa. — which ranked#5 for year-round particle pollution — was among 16 metropolitan areas that reported the lowest air pollution levels ever. 5 of 9 Birmingham, Ala. sailorbill/Flickr. Birmingham-Hoover-Cullman, Ala., which earned the seventh spot for year-round particle pollution, also ranked #19 in ozone pollution and #5 in short-term particle pollution. 6 of 9 Cincinnati rainbowbeth/Flickr. Cincinnati-Middletown, Ky.-Wilmington, Ind., ranked #9 for year-round particle pollution. This was one of the 16 metropolitan areas that reported the lowest levels ever. 7 of 9 St. Louis Photo: By Sean Pavone/Shutterstock St. Louis-St. Charles, Mo.-Farmington, Ill., tied with Cincinnati at #9 for year-round particle pollution, and this area also reported the lowest levels ever. 8 of 9 Get the facts Jupiterimages. According to the report, busy highways are high risk zones. Pollution from highway traffic contributes to higher risk for heart attack, allergies, premature births and the death of infants near the time they are born. New studies looking at the impact of traffic pollution — even in cities with generally “cleaner” air — show increased negative health effects from chronic exposure to exhaust from heavy traffic. 9 of 9 Clean air cities Maitri/Flickr. The report also listed the top 25 cleanest U.S. cities for year-round particle pollution. The top five were Cheyenne, Wyo.; Santa Fe-Espanola, N.M. (pictured); Honolulu; Anchorage, Alaska; and Great Falls, Mont.