MONDAY, DECEMBER 8, 2025 (HealthDay News) — Air pollution may erode some of the health benefits active people hope to get from regular exercise, according to a new study.
The protective effect that exercise was supposed to have on people’s risk of death was halved in people living in areas with high levels of air pollution, researchers recently reported in the journal BMC Medicine.
“Our study shows that toxic air can block the benefits of exercise to some extent, but cannot eliminate them,” said researcher Andrew Steptoe, professor of psychology and epidemiology at University College London, in a press release.
“The results are further evidence of how harmful particulate matter pollution can be to our health,” Steptoe continued. “We believe that clean air and physical activity are important for healthy aging, so we encourage greater efforts to reduce harmful pollution.”
For the study, researchers pooled data from seven previous studies of more than 1.5 million people, 115,000 of whom had died. People lived in countries such as the United States, the United Kingdom, Taiwan, China and Denmark.
The results showed that people who did at least two and a half hours of moderate to vigorous exercise each week had a 30% lower risk of death than those who exercised less.
However, this reduction in death risk was halved, to between 12 and 15 percent, if people lived in an area with high particle pollution, according to the researchers.
And when researchers looked at higher levels of particle pollution, the benefits of exercise diminished even further, the results show.
Almost half of the world’s population (46%) lives in places that exceed the safe limit for particle pollution, the researchers found.
According to the U.S. Environmental Protection Agency, particulate matter pollution is airborne particles 2.5 micrometers in diameter. For comparison: a human hair is between 50 and 70 micrometers wide.
“Our results highlight that exercise is beneficial even in polluted environments. However, improving air quality can significantly increase these health benefits,” said lead researcher Po-Wen Ku, a professor at National Chung Hsing University in Taiwan, in a press release.
The researchers emphasized that active people should not let this news discourage their efforts.
“We don’t want to stop people from exercising outdoors,” said researcher Paola Zaninotto, professor of medical and social statistics at University College London, in a press release. “Checking air quality, choosing cleaner routes, or reducing intensity on polluted days can help you get the most health benefits from your exercise.”
More information
The U.S. Environmental Protection Agency has more information on particulate pollution.
SOURCES: University College London, press release, November 27, 2025; BMC Medicine, November 28, 2025
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