Average exposure to PM2.5 in the United States 2020-2022, by state
The state of California had the worst air quality in the United States from 2020 to 2022, with average fine particulate matter (PM2.5) concentrations of 13.4 micrograms per cubic meter (µg/m³). This was more than three times higher than the average PM2.5 concentration in Hawaii, the U.S. state with the cleanest air. Some of the factors affecting air pollution in California include vehicle emissions, industrial processes, and wildfires.