Daijiworld Media Network – London

London, Nov 30: A major international study led by University College London (UCL) has found that long-term exposure to polluted air can significantly reduce the health benefits typically gained through regular exercise.

The research analysed data from more than 1.5 million adults tracked over a decade across the UK, Taiwan, China, Denmark, and the US. While the study confirmed that physical activity continues to protect against overall mortality, cancer, and heart disease, the extent of these benefits is notably reduced for those living in areas with high air pollution.

Researchers focused on PM2.5, tiny particles small enough to enter the lungs and bloodstream. They observed that the protective effect of exercise declines sharply when annual PM2.5 levels rise above 25 micrograms per cubic metre (µg/m³)—a limit exceeded by almost 46% of the world’s population.

“Exercise remains beneficial even in polluted environments. But improving air quality can substantially enhance these health gains,” said Professor Po-Wen Ku of National Chung Hsing University, Taiwan.

Echoing this, Professor Andrew Steptoe of UCL noted, “Toxic air can partially block exercise benefits, though it does not eliminate them entirely. This highlights the need to tackle fine particle pollution to ensure healthier ageing.”

The study combined results from seven major datasets—including three unpublished ones—and re-analysed raw participant-level data from three studies. Overall, individuals who performed at least 2.5 hours of moderate to vigorous activity weekly had a 30% lower risk of death compared to those who did not meet this benchmark.

However, in regions where PM2.5 exceeded 25 µg/m³, the risk reduction dropped to 12–15%. When pollution levels rose above 35 µg/m³, exercise benefits weakened further—especially in reducing cancer-related deaths. About 36% of the global population lives in areas exceeding this higher pollution threshold.

In the UK, annual PM2.5 averages remain around 10 µg/m³, though winter spikes in some cities occasionally push levels beyond 25 µg/m³.

UCL’s Professor Paola Zaninotto advised that people should continue exercising outdoors but take precautions: “Checking air quality, choosing cleaner routes, or reducing intensity on polluted days can help maintain exercise benefits.”

The authors noted that most data came from high-income countries. Outcomes may differ in low-income regions where pollution often exceeds 50 µg/m³. They also highlighted gaps in data related to indoor air quality and participants’ diets.