Large-scale analyzes link slower marathon finish times to lower air quality

When preparing for a marathon, runners usually don’t think much about air quality. But maybe they should, according to a new study from researchers at Brown University School of Public Health.

When the research team assessed the link between particulate matter in the air and marathon finish times, they found that greater pollution on race day was associated with slower average marathon finish times. Their findings were published in the magazine Sports medicine.

The difference seems small, says study author Elvira Fleury, who led the research while enrolled as a graduate student at Brown, but for marathon runners trying to achieve a personal best, every second matters.

“Think of all the effort, time and money that a professional runner like Eliud Kipchoge put into his attempt to break the world record and run a marathon in under two hours,” said Fleury, who has a Master of Public Health degree from Brown in 2024 and is now a doctoral student at Harvard University.

“Runners at that level think about their equipment, their nutrition, their training, the course and even the weather. Our results show that those interested in optimizing athletic performance should also consider the effect of air pollution.”

The study included 1,506,137 male marathon runners and 1,058,674 female finishers, and measured results at nine major marathons in the United States, including races in Boston, Houston and Los Angeles, from 2003 to 2019. The researchers obtained finishing times for all participants to these races from public marathon data.

They combined that information with data from a statistical model created by Allan Just, associate professor of epidemiology and environment and society at Brown, that showed the amount of particulate matter in the air at various points along the marathon routes.

“This truly sophisticated spatial-temporal model of particulate matter allowed us to map pollution on every kilometer of every course,” Fleury said. “Without a model like this, it wouldn’t have been possible to look at so many different marathons in different states in different years.”

The concentration of an air pollutant is measured in micrograms per cubic meter of air, or µg/m³. When analyzing all the finishing times, the researchers found that every 1 µg/m³ Higher particulate matter on race day was associated with 32 seconds slower average finish times in men and 25 seconds slower average finish times in women. The effects were more pronounced in faster-than-average runners.

Particulate matter refers to air pollution particles with a diameter of less than 2.5 microns, which are generated from sources such as forest fires, agricultural waste burning and inefficient fuel combustion, as well as from vehicle emissions, power generation, industrial activities and the application of fertilizers.

Previous studies have shown that daily fluctuations in air pollution are linked to mortality, heart and lung disease, and that chronic exposure to air pollution is linked to lung cancer, heart disease and premature death. The researchers stated in the study that the effect of pollution on marathon performance could be attributed to increased blood pressure, constricted blood vessels, reduced lung function, breathing problems or possibly even short-term cognitive problems.

The findings apply not only to marathon runners, but also to anyone affected by air pollution, says study author Joseph Braun, professor of epidemiology at Brown’s School of Public Health.

“People who can complete a marathon are generally quite healthy, and we can assume that they have improved their cardiorespiratory fitness,” Braun said. “This study revealed a negative impact of air pollution, even at levels below current health standards, on these very healthy people. This means that air pollution can be a health risk not just for the elderly or sensitive people – it can have a negative effect. affect even the healthiest and most educated among us.”

Based on their findings, the researchers concluded that efforts to reduce pollutant emissions by regulating energy generation, industry and transportation should continue because they benefit overall health and can benefit athletic performance come.