Most polluted cities based on PM2.5 concentration in the U.S. 2023
The city in the United States with the highest average PM2.5 concentration in 2023 was Coraopolis in Pennsylvania, at 19.3 micrograms per cubic meter of air (μg/m³). That year, Pennsylvania also featured another city in the top 10 ranking of most polluted cities in the North American country – Robesonia. Meanwhile, California's town of Happy Camp had the fourth-highest PM2.5 concentration, at about 16.8 μg/m³. The state of California typically suffers from high concentrations of PM2.5 due to the large number of wildfires that spread across the west coast of the United States, leaving many cities exposed to smoke.
