Marathon race performance increases the amount of particulate matter deposited in the respiratory system of runners: An incentive for "clean air marathon runs"

Background. In the last decades, marathon running has become a popular form of physical activity among people around the world. It should be noticed that the main marathon races are performed in large cities, where air quality varies considerably. It is well established that breathing polluted air results in a number of harmful effects to the human body. However, there have been no studies to show the impact of marathon run performance on the amount of the deposition of varied fractions of airborne particulate matter (PM) in the respiratory tract of runners. This is why the present study sought to determine the impact of marathon run performance in the air of varying quality on the deposition of the PM1, PM2.5, PM10 in the respiratory tract in humans. Methods. The PM1, PM2.5 and PM10 deposition was determined in an "average runner"(with marathon performance time 4 h: 30 min) and in an "elite marathon runner"(with marathon performance time 2 h: 00 min) at rest, and during a marathon race, based on own measurements of the PM content in the air and the size-resolved DF(d) profile concept. Results. We have shown that breathing air containing 50 mg m-3 PM10 (a borderline value according to the 2006 WHO standard - still valid) at minute ventilation (VE) equal to 8 L min-1 when at rest, resulted in PM10 deposition rate of approximately 9 mg h-1, but a marathon run of an average marathon runner with the VE = 62 L min-1 increased the deposition rate up to 45 mg h-1. In the elite runner, marathon run with the VE = 115 L min-1 increased PM10 deposition rate to 83 mg h-1. Interestingly, breathing the air containing 50 mg m-3 of PM10 at the VE = 115 L min-1 by the elite marathon runner during the race resulted in the samePM10 deposition rate as the breathing highly polluted air containing as much as 466 mg m-3 of PM10 when at rest. Furthermore, the total PM10 deposition in the respiratory tract during a marathon race in average runners is about 22% greater (203 / 166 D 1.22) than in elite runners. According to our calculations, the concentration of PM10 in the air during a marathon race that would allow one not to exceed the PM10 deposition rate of 9 mg h-1 should be lower than 10 mg m-3 in the case of an average runner, and it should be lower than 5.5 mg m-3 in the case of an elite runner. Conclusions. We conclude that a marathon run drastically increases the rate of deposition of the airborne PM in the respiratory tract of the runners, as a consequence of the huge VE generated during the race. A decrease of the PM content in the air attenuates this rate. Based on our calculations, we postulate that the PM10 content in the air during a "clean air marathon run", involving elite marathon runners, should be below 5.5 mg m-3.