Population: 4,192,887
Cardiovascular cases: 981,249
Rank in most ozone-polluted cities: 19
Phoenix's intense sunlight can cook emissions into a smog soup. But efforts to cut tailpipe emissions have helped cut back ozone levels in the city considerably.
"We've had a long-term vehicle emissions inspection policy for about 25 years," said Mark Shaffer, a spokesman for the Arizona Department of Environmental Quality.
But nothing can help the area deal with its never-ending supply of dust -- a factor that helps put Phoenix in sixth place for year-round particle pollution.
Huge dust storms called haboobs plagued Phoenix last summer, closing airports, downing power lines and clogging pulmonary systems throughout the area. The National Weather Service estimated Phoenix averages three haboobs a year.
"There's not much to be done to mitigate dust," said Shaffer. "It's nature."
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