Close your eyes and stick your finger into a map of the United States. (A map. A big piece of paper with a picture of the country? Okay, look it up on Google Images, we'll wait.) Chances are you just poked a county with dangerous levels of ozone or particle pollution in the air. Nearly 50 percent of the U.S. population lives in counties that the American Lung Association gives an "F" for air quality.

California is a major offender, boasting eight of the 10 most ozone-polluted cities and half of the cities with the worst short-term and long-term particle pollution. But the whole country needs to air itself out a little. That means reducing car use, reducing or regulating coal power plants, and protecting the EPA. Believe it or not, the ALA's findings show improvement from the Clean Air Act — only 10 counties got an "F" for year-round particle pollution, which means clean air protections have been working. They just need a bit of a boost.

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