State Of The Air 2013: American Lung Association Report Reveals America's Most Polluted Cities

Air quality continues to improve across the United States, but over 40 percent of Americans live in counties with unhealthy levels of particle or ozone pollution. 

The American Lung Association released their annual State of the Air report Wednesday, and cities across California are at the top of the list for those with the worst year-round particle pollution.

Particle, or particulate matter, pollution includes microscopic liquids and solids which can be found in vehicle exhaust, industrial emissions and other sources. Ozone pollution -- the main component of smog -- forms in the atmosphere when vehicle, power plant and other emissions react with sunlight.

California cities also dominated the list of areas most polluted by short-term particle and ozone pollution. The state's weather, combined with agricultural processes and the emissions from vehicles and machines needed to move goods, create an air pollution challenge for California.

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