Most Polluted Cities in the US

Visalia and Porterville

#15: The Visalia-Porterville metropolitan area has a population of just under half a million and is located in the central valley of California. Some research suggests there may be a link between air pollution and mental health, specifically that air pollution can damage cognitive abilities.

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Review Date: 
January 6, 2014

Last Updated:
July 1, 2014