Nitrogen dioxide levels linked to slower marathon times

Researchers from the University of Leicester have identified a significant link between nitrogen dioxide (NO2) levels and decreased performance in marathon runners. An analysis of over 2.7 million race results from 2010 to 2024, covering World Marathon Majors in cities such as Berlin, Boston, Chicago, London, New York, and Tokyo, was published in the journal ‘Sports Medicine - Open’.

The study found that every increase of 1 microgram per cubic meter of NO2 resulted in an average increase in finishing times of approximately 1.43 minutes for men and 1.56 minutes for women. This correlation was notably stronger—about six times higher—among amateur runners compared to professional athletes. Additionally, the impact was more pronounced in participants aged 18 to 29 than in older runners.

While both NO2 and PM2.5 particulate matter are known to negatively affect the lungs and circulatory system, the researchers found no similar correlation between PM2.5 levels and marathon completion times. The study suggests that the increased impact on amateurs may be due to longer exposure times on the course or physiological differences in how professional athletes handle physical stress.