10 most polluted cities in the U.S. Pictures - CBS News

10 most polluted cities in the U.S. Pictures - CBS News: "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."