Over 120 million Americans live in areas with pollution levels that make breathing dangerous, according to a report by the American Lung Association. The organization released its State of the Air 2012 report on Wednesday detailing the levels of air pollution in cities across the United States.

The report found that while many cities made improvements over their pollution levels from 2011, pollution is still a very real problem.

State of the Air shows that we're making real and steady progress in cutting dangerous pollution from the air we breathe, Charles Connor, American Lung Association president, said in a statement. But despite these improvements, America's air quality standards are woefully outdated, and unhealthy levels of air pollution still exist across the nation, putting the health of millions of Americans at stake.

Air pollution can seriously impact your health, causing and aggravating asthma, chronic bronchitis and emphysema, according to the National Institute of Environmental Health Sciences.

Research conducted by NIEHS scientists has shown that long-term exposure to air pollutants increases the risk of respiratory illnesses such as allergies, asthma, chronic obstructive pulmonary disease, and lung cancer, the organization says on its website. Data collected by NIEHS-funded scientists at the University of Southern California suggest that exposure to pollutants in vehicle and fossil fuel emissions may hinder lung development and limit breathing capacity for a lifetime. Their research shows that children who live in highly polluted communities are five times more likely to have clinically low lung function-less than 80% of the lung function normal for their age.

If you live in an area with heavy air pollution, the American Lung Association recommends you limit your exposure by avoiding exercise near high-traffic areas, avoiding smoke and reducing the use of fireplaces.

The American Lung Association analyzed data from air quality monitors to determine the most heavily polluted areas in the country. Do you live in one of the most polluted cities in America? Click through the slideshow to see.

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10. Merced, Calif.
Merced, Calif. is home to Yosemite National ParkPopulation: 255,793People with asthma: 18,655People with chronic bronchitis: 7,191People with emphysema: 2,853 City of Merced
9. Fairbanks, Alaska
Aerial view of the University of FairbanksPopulation: 97,581People with asthma: 8,915People with chronic bronchitis: 2,919People with emphysema: 1,026 City of Fairbanks
8. Logan, Utah
The downtown Logan courthousePopulation: 125,442People with asthma:10,375People with chronic bronchitis: 3,345People with emphysema: 1,228 Creative Commons
7. Salt Lake City, Utah
Goldman Sachs' office building in Salt Lake City, UtahPopulation: 1,744,866People with asthma: 113,851People with chronic bronchitis: 15,544People with emphysema: 6,401 Reuters
6. Pittsburgh, Penn.
A view of Station Square in PittsburghPopulation: 2,447,393People with asthma: 239,833People with chronic bronchitis: 88,118People with emphysema: 42,691 City of Pittsburgh
5. Modesto, Calif.
A view of the archway at the entrance to ModestoPopulation: 514,543People with asthma: 37,896People with chronic bronchitis: 15,444People with emphysema: 6,401 Creative Commons
4. Los Angeles, Calif.
A view of downtown Los AngelesPopulation: 17,877,006People with asthma: 1,320,826People with chronic bronchitis: 557,067People with emphysema: 228,858 Reuters
3. Hanford, Calif.
A truck enters a plant in Hanford, Calif.Population: 152,982People with asthma: 11,170People with chronic bronchitis: 4,423People with emphysema: 1,619 Reuters
2. Fresno, Calif.
A view of downtown Fresno.Population: 1,081,315People with asthma: 79,242People with chronic bronchitis: 31,596People with emphysema: 12,865 Creative Commons
1. Bakersfield, Calif.
A view of downtown Bakersfield, the most polluted city in AmericaPopulation: 839,631People with asthma: 79,242People with chronic bronchitis: 24,047People with emphysema: 9,398 Creative Commons
How Bad Is the Air Pollution Where You Live The 10 Most Polluted Cities In The Country SLIDESHOW
Air pollution may be declining, but over 40 percent of the U.S. population lives in areas where pollution makes breathing dangerous, according to a report by the American Lung Association Reuters
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