Air pollution cancels exercise health benefits, new study reveals - Video

Your daily workout slashes death risk by 30%, but breathing toxic air can wipe out nearly half those lifesaving gains-especially against cancer and heart disease. A groundbreaking international study published in BMC Medicine, featuring UCL researchers, tracked over 1.5 million adults for more than 10 years across the UK, Taiwan, China, Denmark, and the US, proving pollution seriously weakens exercise's power.

PM2.5-microscopic particles from cars, factories, fires, and construction smaller than 2.5 micrometers-slip deep into lungs and bloodstream, causing inflammation, oxidative stress, and organ damage.

Nearly half the world's population (46%) lives where yearly PM2.5 averages hit 25 micrograms per cubic meter (μg/m³) or higher, dramatically reducing physical activity's protective benefits. At 35 μg/m³ or above-affecting 36% globally-exercise perks fade even more, particularly for cancer prevention.

The team pooled data from seven large cohorts (three previously unpublished), combining summary statistics with fresh individual-level re-analysis from three studies. They adjusted for confounders like smoking, income, education, diet, and pre-existing conditions.

Active participants cut all-cause mortality by 30% compared to inactive ones. But in high-PM2.5 areas, protection dropped to just 12-15%. Cancer and cardiovascular death reductions weakened most sharply. UK participants averaged cleaner 10 μg/m³, but urban/winter spikes often crossed danger thresholds.

Lead researcher Professor Po-Wen Ku emphasizes exercise still delivers value in smoggy spots, but pristine air unlocks full rewards. UCL's Professor Andrew Steptoe warns pollution doesn't fully cancel benefits, calling for urgent emission cuts to support healthy aging.

Some Practical tips include checking air apps, picking low-traffic routes, or going lighter on bad days. While high-income data limits broader applicability, findings stress dual needs—exercise plus clean air—for top health.

REFERENCE: Po-Wen Ku, Andrew Steptoe, Mark Hamer, Paola Zaninotto, Emmanuel Stamatakis, Ching-Heng Lin, Bin Yu, Ulla Arthur Hvidtfeldt, Xiang Qian Lao, Hsien-Ho Lin, Wei-Cheng Lo, Ole Raaschou-Nielsen, Shengzhi Sun, Linwei Tian, Su-Fen Wang, Yiqian Zeng, Yunquan Zhang, Shang-Ti Chen, Chien-Fong Huang, Yang Xia, Li-Jung Chen. Does ambient PM2.5 reduce the protective association of leisure-time physical activity with mortality? A systematic review, meta-analysis, and individual-level pooled analysis of cohort studies involving 1.5 million adults. BMC Medicine, 2025; 23 (1) DOI: 10.1186/s12916-025-04496-y