Americans are breathing easier and better thanks to less polluted air.
The American Lung Association released its annual State of the Air report found that southern California remains the region with the highest air pollution in the country.
Los Angeles, Long Beach and Riverside have the worst ozone levels in the nation.
Bakersfield and Fresno also showed high pollution levels.
Other cities with high-levels of pollution were Houston, Dallas, Oklahoma City, Cincinnati, New York City and Washington, DC.
The report said that the areas with the cleanest air are Bismarck, N.D.; Rapid City, S.D.; Fort Meyers, Fla. and Palm Beach Fla.
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The good news is that LA has significantly reduced particulate and ozone pollution more than any of the years the group has been measuring.
The report measured 1000 cities and counties in the United States between 2009 and 2011.
Half of the most polluted cities from previous reports showed improvements.
"The long-term trend is positive and headed to much cleaner air," said study author Janice Nolen of the American Lung Association.
"There is an uptick in some areas that are a concern and some areas where the problem remains very, very serious."