(NBC) - A new report reveals half of all Americans are living in counties with unhealthy air quality.
The 15th annual "State of the Air" report card from the American Lung Association shows although particle pollution is down, smog levels are much higher than last year.
Researchers also found almost one in ten Americans live in one of the 17 counties with unhealthy levels of all types of pollutants.
Despite vast improvements, the Los Angeles, California area was listed as the most ozone polluted city, while Anchorage, Alaska was the city with the fewest polluted days.
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