Air pollution is slowing down marathon runners, study finds

A recent study reveals that air pollution is causing marathon runners to finish their races slower, with findings applying to six major marathons worldwide. Researchers from the University of Leicester analyzed over 2.7 million marathon performances between 2010 and 2024. James Donaldson, the study's lead author, discovered that nitrogen dioxide levels had a strong association with finishing times.

For every µg/m³ increase in nitrogen dioxide, men's finishing times increased by 1.43 minutes, and women's by 1.56 minutes. On a day with high pollution, nitrogen dioxide levels reaching 10.3 µg/m³ resulted in finishing times seven to eight minutes longer than on a low-pollution day with 5.2 µg/m³. The study also examined fine particulate matter, PM2.5, but found no significant link to race times.

London experienced the highest median nitrogen dioxide concentration of 10.9 µg/m³, while Berlin had the lowest at 6.1 µg/m³. Despite air pollution concerns, London's nitrogen dioxide and PM2.5 levels have decreased significantly since the 2010 race, according to Bryan Williams, the chief scientific and medical officer of the British Heart Foundation, which funded the study.

The effect was more pronounced among recreational runners, with finishing times rising 2.12 minutes per 1 µg/m³ of nitrogen dioxide, compared to elite runners, who saw a 0.34-minute increase. Nitrogen dioxide primarily originates from fossil fuel combustion and natural processes. The study suggests that slower runners are more exposed to urban pollution, while elite runners train in cleaner environments.

Donaldson posits that the physiological adaptations from high-intensity training may protect elite athletes from pollution's adverse effects. Williams emphasizes that exercise remains highly beneficial for cardiovascular health, reducing the risk of heart and circulatory diseases by up to 35%.