El Paso, Los Angeles among the most polluted cities in the US by 2025, says a new report.
El Paso and Los Angeles were among the most polluted areas in the United States last year, according to a new air quality report which assessed global pollution levels by 2025.
The report is the latest iteration of the global analysis published by Swiss technology company IQAir every year. This focused on some of the causes of global warming, including wildfires, which the report’s authors say is the leading cause of global warming.
Fire played a major role in US pollution levels, according to the report. It found that air quality is getting worse across the country, with pollution levels rising by 3% between 2024 and 2025. Air pollution in a certain area is measured as the concentration of pollutants per cubic meter of air in that area, where pollutants are measured in micrograms, on an annual basis.
That’s based on air quality standards set by the World Health Organization that recommend limiting exposure to air that exceeds 5 micrograms of pollutants per cubic meter. By the end of 2025, the average US air pollution concentration had reached 7.3 on that scale.
US cities are highly polluted
Air pollution levels varied by region and even state, sometimes significantly, the report showed. In Texas, pollution concentrations dropped by 9% on average in some major cities, such as Austin, Fort Worth and Houston, while skyrocketing in others, such as El Paso. Historic storms that blanketed the area last spring caused a spike in pollution, according to the report, which said those storms caused a 46 percent increase.
East Los Angeles experienced one of the worst air quality conditions in 2025, the report said, due to the wildfires that devastated the city and surrounding areas. The accumulated pollution seen in East LA and nearby Huntington Park, Cudahy and Florence-Graham as a result of the fires made that part of Southern California the most polluted area in the country last year.
Some major US cities ended 2025 with worse air quality than ever, including Chicago, Los Angeles, New York City and Washington, DC, according to the report. Denver’s average pollution levels have fallen slightly over that time, while other West Coast cities, such as San Francisco and Seattle, have consistently met annual guidelines established by the WHO.
However, the report showed that the western regions held the positions of most of the most polluted North American cities in 2025, mostly in California.
Wildfires, industrial emissions
The authors of the report cited wildfires, incl those that arose in Canada last year during what was the second-worst fire season on record, one of the leading causes of air pollution in North America last year.
Wildfire smoke can be a major source of pollution which greatly affect human health through atmospheric emissions. The effects of last year’s wildfires on air levels were also exacerbated by dust storms, such as those that hit El Paso, as well as emissions from transportation, power generation and other industrial sources, the report said.
It screamed in particular artificial intelligence data centers as an “emerging source” of air pollution. By 2025, the facilities contributed “indirectly through increased power plant emissions needed to meet their peak power needs, and through their reliance on diesel generators for backup power,” the report said.
