America's most polluted cities

Published On: Nov 04 2011 01:51:22 PM CDT   Updated On: May 01 2014 01:00:00 AM CDT

Just how dirty is the air you breathe? The American Lung Association has released its latest list of the most polluted U.S. cities.

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20. (tie) Chicago-Naperville, Ill.-Ind.-Wis.

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