Exposure of children to airborne particulate matter of different size fractions during indoor physical education at school

Although moderate regular aerobic exercise is recommended for good health, adverse health consequences may be incurred by people who exercise in areas with high ambient pollution, such as in the centres of large cities with dense traffic. The exposure of children during exercise is of special concern because of their higher sensitivity to air pollutants. The size-segregated mass concentration of particulate matter was measured in a naturally ventilated elementary school gym during eight campaigns, seven to ten days long, from November 2005 through August 2006 in a central part of Prague (Czech Republic). The air was sampled using a five-stage cascade impactor. The indoor concentrations of PM2.5 recorded in the gym exceeded the WHO recommended 24-hour limit of 25 μg m−3 in 50% of the days measured. The average 24-h concentrations of PM2.5 (24.03 μg m−3) in the studied school room did not differ much from those obtained from the nearest fixed site monitor (25.47 μg m−3) and the indoor and ambient concentrations were closely correlated (correlation coefficient 0.91), suggesting a high outdoor-to-indoor penetration rate. The coarse indoor fraction concentration (PM2.5–10) was associated with the number of exercising pupils (correlation coefficient 0.77), indicating that human activity is its main source. Considering the high pulmonary ventilation rate of exercising children and high outdoor particulate matter concentrations, the levels of both coarse and fine aerosols may represent a potential health risk for sensitive individuals during their physical education performed in naturally ventilated gyms in urban areas with high traffic intensity.