Study: Air Pollution Slows Marathon Runners’ Finish Times — Why?

JAKARTA — Air pollution affects not only health but can also influence marathon runners’ performance. A new study has found that higher nitrogen dioxide levels on race days are associated with slower finish times, particularly among non-elite runners.

Researchers at the University of Leicester analysed more than 2.7 million runner performance records from six World Marathon Majors: Berlin, Boston, Chicago, London, New York City and Tokyo. The data covered races held between 2010 and 2024.

The analysis found a strong association between nitrogen dioxide levels on race day and runners’ finishing times. Nitrogen dioxide primarily comes from the burning of fossil fuels through human activities such as the use of cars and lorries and factory operations, as well as from natural processes and chemical reactions in the air. The pollutant has also been linked to impaired lung function, inflammation of the airways and adverse effects on the cardiovascular system.

“For every increase of one microgram per cubic metre in nitrogen dioxide, finish times were 1.43 minutes slower for men and 1.56 minutes slower for women,” said the study’s lead researcher, James Donaldson, according to Euro News on Thursday (1 October 2026).

This means that on more polluted days, the effect on race times can amount to several minutes. When nitrogen dioxide levels reached 10.3 micrograms per cubic metre, compared with a lower level of 5.2 micrograms per cubic metre, runners’ finishing times were around seven to eight minutes longer.

The researchers also analysed exposure to fine particulate matter, PM2.5. Unlike nitrogen dioxide, however, they found no statistically significant association between PM2.5 levels and finish times.