Average annual PM2.5 concentrations in the United States 2000-2022, by region
The West United States recorded the highest average concentration of particle pollution (PM2.5) in 2022, at 9.4 micrograms per cubic meter (µg/m3). This was slightly above the national average concentration of PM2.5 pollution that year, and almost double the World Health Organization guideline of five µg/m3.