A new study from the American Lung Association suggests the Clean Air Act has helped our nation breathe a little easier -- but we still have a long way to go.
Los Angeles, for example, has on average 120 days of unhealthy air. And 147 million Americans live in places with polluted air. Experts say that air pollution is tied to wheezing, asthma attacks and heart disease.
But some cities tell a different story.
The ALA's 2014 report also includes the cities with the cleanest air in the U.S., meaning none of them experienced unhealthy levels of particles or ozone from 2010-2012.
Here are the nation's four "cleanest cities," listed in alphabetical order.
1. Bangor, Maine
2. Bismarck, North Dakota
3. Cape Coral-Fort Myers, Florida
4. Salinas, California
To see detailed information about the air in your state, please visit the "State of the Air" report on the American Lung Association website.