Neue Daten von 2,5 Millionen Marathon-Finishern zeigen, dass geringfügige Änderungen der Luftqualität Ihre Rennzeit beeinflussen können | Eine Analyse der Auswirkungen von Feinstaub auf die Zielzeiten bei neun großen US-Marathons, 2003–2019

Highlights from the magazine column:

>Fine particulate matter—also known as PM2.5 or, more familiarly, soot—refers to particles that are less than 2.5 microns in diameter, and is produced by internal combustion engines, forest fires, and other sources. It’s easy to inhale, and can cross from your lungs into your bloodstream, triggering inflammation and oxidative damage that raises the risk of heart disease, diabetes, and other conditions. When you’re running, you breathe more air than usual, and suck it in through your mouth, which bypasses the nasal filtration (i.e. hairs) that would otherwise catch some of the particles. This triggers a variety of problems, including constricting the blood vessels that supply your muscles with oxygen—bad news for a marathoner.
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>The machine learning model showed that PM2.5 levels varied widely from place to place and year to year. Levels in Boston and Chicago were as high as 20 micrograms per cubic meter in some years, and as low as 2 or 3 micrograms per cubic meter in others. Other courses like New York, Houston, and Los Angeles were in a similar range. The study, which appears in the journal Sports Medicine, combined this pollution data with 2.5 million finishing times, adjusting for other factors like heat and humidity.
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>The idea that air pollution hurts athletic performance certainly isn’t new—recall the furor when U.S. athletes wore breathing masks to protect their lungs with they arrived in Beijing for the 2008 Olympics. What’s different here is that the effects are showing up even at very modest levels of air pollution. The current EPA safety standard for 24-hour exposure to PM2.5 is 35 micrograms per cubic meter, well above the levels seen in any of the races. The full-year standard was lowered last year from 12 to 9 micrograms per cubic meter. Of all the race-years analyzed, 61 percent of them were below this more rigid 9 micrograms per cubic meter standard—and yet these pollution levels still impacted race times.
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>One takeaway, then, is that if you’re going for a big marathon PR and you have a private pace car guiding you, it might be worth going electric. More generally, add air quality to the long list of factors to consider in choosing a race or evaluating a performance after the fact. If you set your PR at Boston in 2004, or Chicago in 2011, or Philadelphia pretty much any year before 2015, your coulda-shoulda-woulda time just got a few minutes faster.

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Link to research: [Running on Fumes: An Analysis of Fine Particulate Matter’s Impact on Finish Times in Nine Major US Marathons, 2003-2019](https://pubmed.ncbi.nlm.nih.gov/39690352/)

Abstract:

>Background: Under controlled conditions and in some observational studies of runners, airborne fine particulate matter smaller than 2.5 microns in diameter (PM2.5) is associated with exercise performance decrements.
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>Objective: To assess the association between event-day fine particulate matter air pollution (PM2.5) and marathon finish times.
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>Methods: Using a spatiotemporal machine-learning model, we estimated event-day racecourse-averaged PM2.5 concentrations for nine major US marathons (2003-2019). We obtained 1,506,137 male and 1,058,674 female finish times from 140 event-years of public marathon data. We used linear and quantile mixed models to estimate the mean and percentile-specific year and heat index-adjusted effect of 1 µg/m3 higher event-day racecourse-averaged PM2.5 on marathon finish times in sex-stratified samples.
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>Results: Analyzing all finish times, 1 µg/m3 higher race-day PM2.5 was associated with 32-s slower average finish times among men (95% confidence limits (CL) 30, 33 s) and 25-s slower average finish times among women (95% CL 23, 27 s). Quantile-specific associations of event-day PM2.5 with finish times were larger for faster-than-median finishers. While PM2.5 was generally associated with slower finish times in single-event models, there was effect heterogeneity, and most 95% confidence intervals included the null.
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>Conclusion: Greater race-day PM2.5 was associated with slower average marathon finish times, with more pronounced effects in faster-than-median runners. While more research is needed to characterize effect heterogeneity across the performance spectrum, these findings show the impact of PM2.5 on marathon performance and the importance of considering data from multiple competitions when estimating PM2.5 effects from event-level data.

edit: wordsmithing