El Paso and Los Angeles were among the most polluted areas in the United States last year. The new air quality report by Swiss technology company IQAir evaluated pollution levels worldwide in 2025. Wildfires, a leading driver of declining air quality globally, significantly impacted U.S. pollution levels, with average pollutant levels increasing by 3% between 2024 and 2025.
The World Health Organization recommends limiting exposure to air exceeding 5 micrograms of pollutant per cubic meter. By year-end, the average concentration of U.S. air pollutants reached 7.3 on that scale. Air pollution varied significantly by region and state, with El Paso’s levels skyrocketing due to dust storms last spring.
East Los Angeles experienced one of the most severe air quality situations in 2025, largely attributed to massive wildfires that devastated the city and surrounding areas. These fires made East L.A. and nearby Huntington Park, Cudahy, and Florence-Graham the most polluted area in the country.
Other major U.S. cities saw worse air quality by year-end, including Chicago, Los Angeles, New York City, and Washington, D.C. Western locations dominated the rankings for most polluted North American cities in 2025, with a majority in California. Wildfires, transportation emissions, power generation, and industrial sources contributed to the pollution, while artificial intelligence data centers emerged as an emergent source of air pollution.