'Running through a haze'-Why air quality could be the hidden enemy in every marathon

A study done over 16 years reveals how air pollution subtly but significantly impacts marathon runners’ performance and health.

Kenya’s Kelvin Kiptum, 24, gained world fame when he broke compatriot Eliud Kipchoge’s World Record in marathon running on October 8, 2023. 

Kiptum clocked an astonishing 2:00:35 at the Chicago Marathon, shattering Kipchoge’s 2022 record of 2:01:09 set at the Berlin Marathon.

 However, Kiptum’s remarkable achievement was tragically overshadowed months later when he and his coach, Gervais Hazikimana, lost their lives in a car accident on February 11, 2024.

Kiptum’s incredible feat was a testament to the meticulous preparation elite marathoners undertake, including optimizing gear, nutrition, and training while factoring in race-day conditions like weather. 

But according to a recent study, there is another variable that runners and race organizers may need to prioritize: air quality.

A groundbreaking analysis published in Sports Medicine found that even minor increases in air pollution could significantly impact marathon performance.

 The research, which spanned 16 years and included over 2.5 million marathon finishers across nine major U.S. races, revealed that higher levels of fine particulate matter in the air—referred to as PM2.5—correlate with slower average finish times.

“Think of all the effort, time, and money that a professional runner like Eliud Kipchoge put into trying to break the world record and run a marathon in less than two hours,” says study author Elvira Fleury, a Brown University graduate and current doctoral student at Harvard.

 “Our results show that those interested in optimizing athletic performance should consider the effect of air pollution, as well.”

Using a sophisticated spatial-temporal model developed by epidemiologist Allan Just, the team plotted pollution levels along marathon routes from Boston to Los Angeles. 

Their findings were sobering: for every 1 µg/m³ increase in PM2.5 concentration, men’s marathon finish times slowed by an average of 32 seconds, while women’s times slowed by 25 seconds. 

The effects were even more pronounced among runners in faster-than-median groups, where every second is a critical marker of success.

Fine particulate matter, smaller than 2.5 microns in diameter, originates from sources like vehicle emissions, industrial activity, and agricultural burning. 

While these particles are nearly invisible, their health impacts are well-documented, ranging from reduced lung function and increased blood pressure to heart disease and cognitive impairment.

 For athletes, these physiological stressors can be particularly detrimental during peak physical exertion.

“This study revealed a negative impact from air pollution, even at levels below current health-based standards, on these very healthy people,” says Joseph Braun, professor of epidemiology at Brown’s School of Public Health. 

“This means that air pollution can be a health risk not just for those who are elderly or susceptible—it can negatively affect even the most healthy and well-trained among us.”

The researchers emphasized that the implications of their findings extend far beyond marathon runners. While professional athletes may have the resources to mitigate some effects of pollution through training and planning, millions of individuals, particularly those in urban and industrial areas, face similar exposures daily.

The study also highlights how even seemingly small changes in pollution levels can influence large-scale events. As marathons attract thousands of runners and spectators, organizers may need to collaborate with city planners and environmental regulators to ensure cleaner air on race days.

 Such efforts could not only improve performance but also safeguard the health of participants and local communities.

“Efforts to reduce pollution emissions by regulating power generation, industry, and transportation should continue,” Braun concludes, “as they benefit overall health and may benefit athletic performance.”

For athletes like Kiptum, who strived for greatness through rigorous training and discipline, these findings underscore the importance of clean air as an overlooked but essential component of sporting excellence.

 In a sport where every second counts, tackling air pollution could be the next frontier in optimizing human performance.