Just how dirty is the air you breathe? The American Lung Association rates the most polluted cities in the U.S.
Just how dirty is the air you breathe? The American Lung Association's annual report of the most polluted cities in the U.S. rates communities on levels of ozone, sulfur dioxide, air-borne particulates and tainted tap water. Here are the 20 cities most polluted by year-round particle pollution in 2013:
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