Air pollution may limit exercise health benefits, according to a study from University College London (UCL). The research, which analyzed data from over 1.5 million adults across multiple countries, found that long-term exposure to polluted air can significantly reduce the positive effects of regular exercise on overall health. While physical activity still offers some protective benefits against mortality, cancer, and heart disease, these advantages are diminished for individuals living in highly polluted areas.
The study focused on fine particulate matter, or PM2.5, which are tiny particles that can penetrate deep into the lungs and bloodstream. It revealed that exercise benefits are significantly weakened when annual average PM2.5 levels exceed 25 micrograms per cubic meter (µg/m³). Alarmingly, this threshold is surpassed by nearly 46% of the global population.
Professor Po-Wen Ku from National Chung Hsing University in Taiwan emphasized the importance of improving air quality to enhance the health benefits of exercise. "Exercise remains beneficial even in polluted environments," he said, "but improving air quality can substantially enhance these health gains."
Co-author Professor Andrew Steptoe from UCL added, "Toxic air can partially block exercise benefits, though it does not eliminate them entirely. This underscores the importance of addressing fine particle pollution to support healthy ageing alongside physical activity."
The analysis combined findings from seven studies, including three unpublished ones, and re-analyzed raw participant-level data. It found that individuals who engaged in at least 2.5 hours of moderate to vigorous exercise weekly had a 30% lower risk of mortality compared to those who did not meet this threshold. However, for participants in high PM2.5 areas, the risk reduction fell to 12-15%. At levels above 35 µg/m³, exercise benefits weakened further, particularly regarding cancer mortality.
In the UK, average yearly PM2.5 levels are around 10 µg/m³, which is below the critical thresholds. However, winter pollution spikes in some cities can still surpass 25 µg/m³.
Professor Paola Zaninotto from UCL advised, "We don’t want to discourage outdoor exercise. Checking air quality, choosing cleaner routes, or reducing intensity on polluted days can help maintain exercise benefits."
The authors noted that the study was primarily conducted in high-income countries, so the results may not apply to low-income regions with higher pollution levels, often exceeding 50 µg/m³. Limitations also included limited data on indoor air quality and participants’ diets.
Other factors such as income, education, smoking habits, and pre-existing chronic diseases were accounted for in the analysis.
