Pollution is down in the U.S., with air quality showing improvement in all cities listed in the American Lung Association's annual report on air quality. Time to celebrate? Not quite. The report indicates that 60 million Americans - roughly one in five - live in areas with unhealthy spikes in pollution levels, and 18 million live with unhealthy levels year-round. And high levels of air pollution are linked to asthma, stroke, heart attack, cancer, and other often-deadly health problems.
Just where are these air pollution hotspots? Keep clicking to see the association's list of the 10 most polluted metropolitan areas in the nation. Each is ranked according to the average concentration of microscopic particles in the air (measured in micrograms per cubic meter) from diesel exhaust, coal-fired power plants, etc.
10. Modesto, California (tie)
Does Modesto need a new slogan? It tied for 10th on the list of cities with bad air, with a score of 14.7.