Environment/Climate Change
Running on Fumes: An Analysis of Fine Particulate Matter’s Impact on Finish Times in Ten Major US Marathons, 2003-2019 Elvira Fleury* Elvira Fleury Gray Bittker Allan Just Joseph Braun
Objective: Assess the effect of race-day fine particulate matter air pollution (PM2.5) on marathon finish times.
Methods: Using a spatiotemporal machine-learning model, we estimated the average daily PM2.5 concentration along ten major US marathon courses (2003-2019). For the 157 included event-years, we web-scraped 1,630,170 male and 1,182,732 female finish times. We used multivariable quantile regression to estimate the temperature, humidity, and windspeed-adjusted association of one µg/m3 higher race-day PM2.5 with net finish times in each decile and the 1st, 25th and 75th percentiles (%ile) of finishers in sex- and marathon-stratified samples. We pooled estimates for the 1st percentile of finishers across the ten events using random-effects meta-analysis.
Results: In the 1st percentile of finishers, pooling estimates from the ten races, one µg/m3 higher race-day PM2.5 was associated with 7.25 seconds (s) (95% CI: -2.2 – 16.7 (s)) and 13.3 seconds (95% CI: -0.3 – 26.9 (s)) slower finish times in men and women, respectively. In eight of the ten marathons, PM2.5 was consistently associated with increased finish time in faster-than-median female runners (Range Estimates: β10th %ile: 10.8–44.4 (s); β20th %ile: 11.5–57.5 (s); β25th %ile: 8.2–56.7 (s); β30th %ile: 7.3–58.2 (s); β40th %ile: 2.7–65.3 (s)). In six of the ten marathons, PM2.5 was consistently associated with increased finish time for the first quartile of male finishers (Range Estimates: β10th %ile: 13.2–58.2 (s); β20th %ile: 10.5–60.4 (s); β25th %ile: 5.1–66.9 (s)). The association of PM2.5 with finish time was inconsistent at other percentiles.
Conclusion: Greater race-day PM2.5 estimates were associated with slower finish times in faster-than-average marathoners. While more research is needed to characterize the potential benefits of interventions that reduce race-day PM2.5, events seeking to facilitate record-breaking performances should consider strategies to limit PM2.5 emissions on race days.