Houston just made a list that no one wants it to be on.

Data compiled by the National Public Utilities Council ranks Houston as the 15th most polluted city in the U.S. No other Texas city appears in the ranking. Three California cities — Bakersfield, Visalia, and Fresno — took the top three spots.

The ranking considers a city’s average volume of fine particulate matter in the air per year. Fine particulate matter (formally known as PM2.5) includes soot, soil dust, and sulphates.

The council based its ranking on the average annual concentration of PM2.5 as measured in micrograms per cubic meter of air, known as µg/m3. The ranking lists Houston’s average annual µg/m3 as 11.4. The World Health Organization (WHO) recommends a top µg/m3 of 5, while the American Lung Association sets 9 µg/m as an average annual guideline.

A report released in 2024 by Smart Survey found that the Houston area had just 38 days of good air quality the previous year.

“Most of Houston’s air pollution comes from industrial sources and diesel engines, although sources as diverse as school buses and meat cooking also contribute to … the problem,” the nonprofit Air Alliance Houston says.

The U.S. Environmental Protection Agency says PM2.5 poses “the greatest risk to health” of any particulate matter. Among other health issues, fine particulate matter contributes to cardiovascular disease, lung cancer, and chronic pulmonary disease.

Among the sources of PM2.5 are wildfires, wood-burning stoves, and coal-fired plants, according to the American Lung Association.

The WHO says air pollution causes 7 million deaths annually and may cost the global economy $18 trillion to 25 trillion by 2060. With 70 percent of the population expected to live in urban centers by mid-century, cities are at the forefront of efforts to reduce pollution, according to National Public Utilities Council.