Nearly half of Americans in the U.S. live in areas with failing air quality, according to the American Lung Association’s annual State of the Air report. Experts warn the nation’s air pollution crisis is worsening,

Since 2000, the American Lung Association has released an annual State of the Air report analyzing air quality data across the United States. This year’s report, released on Wednesday, found the highest number of people exposed to unhealthy levels of air pollution in a decade.

The American Lung Association report finds that climate events are causing more people in the U.S. to breathe toxic air even as other pollution falls.