The most polluted cities in the United States belong to California.

The following cities rank in the Top 10 most polluted urban areas where air pollution can cause major health problems. The findings of American Lung Association research revealed that seven of the 10 most polluted cities by ozone pollution are in California.

Six of the dirtiest air cities in America belong in California, including all of the the Top 4. 

A list of the most polluted US cities by ozone pollution:

1. Los Angeles, California

2. Bakersfield, California
3. Visalia, California
4. Fresno, California

5. Houston, Texas
6. Sacramento, California.
7. Dallas-Fort Worth, Texas
8. Charlotte, North Carolina
9. Phoenix, Arizona
10. El Centro, California

The research shows that despite growing green movements, the air in many cities has become dirtier in the past 12 months.

According to the American Lung Association, Ozone is the most widespread form of air pollution. “When inhaled, ozone irritates the lungs, resulting in something like a bad sunburn. The health effects of breathing ozone pollution can be immediate. Ozone can cause wheezing, coughing and asthma attacks. Breathing ozone pollution can even shorten lives.”