50 U.S. Cities With the Dirtiest Air

Tiffany Onyejiaka

Almost half of all Americans—45.8 percent, or 150 million people—live in counties with unhealthy air quality, according to the American Lung Association's 2020 State of the Air report. Poor air quality, including unhealthy ozone or particle pollution, can lead to respiratory issues that are known to shorten lifespans, contribute to the risk of lower birth weight in newborns, and cause myriad tangential health problems.

Despite this knowledge, the number of people living amid unsafe air quality continues to grow; 2020 numbers are up from 134 million people reported in 2018. To learn more about where in the country the air is the dirtiest, Stacker analyzed the 2019 Air Quality Statistics Report from the Environmental Protection Agency (EPA), released in May 2020. From there, we compiled a list of the 50 cities with the dirtiest air.

To help track air quality around the country, the Environmental Protection Agency (EPA) created National Ambient Air Quality standards. The two most relevant thresholds are 150 micrograms of pollutants per cubic meter of air over a 24-hour period for coarse particulate matter (PM10) and 12 micrograms of pollutants for fine particulate matter (PM2.5).