Most polluted cities in the world — and the U.S. — revealed in annual report

Los Angeles had the lowest air quality in the United States in 2024, according to the annual World Air Quality Report from IQAir. 

The annual report looks at data from more than more than 40,000 air quality monitoring stations across 8,954 locations in 138 countries, territories and regions, according to IQAir, an air technology company based in Switzerland.

The rankings are based on the annual average of concentrated micrograms of an air pollutant per cubic meter of air. The World Health Organization recommends 5 micrograms of pollutant per cubic meter.