California contains the 5 most polluted cities across 3 different categories of emissions.

According to the American Lung Association's latest report, California contains the 5 most polluted cities across 3 different categories of emissions.

An excerpt of the ALA's State of the Air 2015 report is below. For the full report and lots of other data and info, follow the buttons to the left.


Millions of Americans Breathing Unhealthy, Polluted Air

More than 4 in 10 Americans — nearly 138.5 million people — live in counties where ozone or particle pollution levels make the air unhealthy to breathe. Our 16th annual “State of the Air” report, released this week, shows the nation’s air quality has improved in some places — but not everywhere.

What's Changed?

Overall, thanks to cleaner power plants and cleaner diesel fuel and engines, most air quality progress was made in the eastern half of the nation with the continued reduction of year-round particle pollution. Particle pollution was recently found to cause lung cancer, adding another reason that cleaning these sources of pollution will save lives.

This year’s report also provides evidence that a changing climate will make it harder to protect human health from the dangers of air pollution. The impact of climate change is particularly apparent in the western United States, where heat and drought create situations ripe for episodes of high particle pollution. Some cities had worse ozone pollution, as warmer temperatures make cleaning up ozone even harder.

What's the Air Quality Where You Live?

Visit to learn more about your air quality. While you're there, learn to protect yourself and your family from air pollution and share your air quality grades with others.

2015 Highlights

More than 4 in 10 people live where pollution levels are too often dangerous to breathe.


Which cities have the highest levels of air pollution? Which are the cleanest?


Ozone and particle pollution are the most widespread pollutants and among the most dangerous.


We battle air pollution because dirty air harms our health and can threaten life itself.