Abstract
Background: Research into indoor environment has shown that schools are buildings with high-levels of particulate matter (PM) concentrations. Methods: Size resolved mass concentrations of aerosol were measured in three elementary Schools in Prague.
Results: The PM indoor concentrations in the gym exceeded limits recommended by World Health Organization. The average 24hour PM2.5 µm indoor concentration did not differ significantly from the data outdoor values with the correlation coefficient reaching 0.91.
When comparing indoor and outdoor aerosol level, the correlation coefficient increased with decresing aerodynamic diameter of the aerosol monitored (r = 0.32 to 0.87). This indicates a higher infiltration of fine and quasi-ultrafine particles in the indoor environment.
Coarse fraction (PM2.5 µm - PM10 µm) was related to the number of exercising pupils (r = 0.77). The results show that human activity is its main source.
In comparison to outside values, the indoor concentration of coarse aerosol increased several times during physical education days. Scanning electron microscopy showed that apart from numerous inorganic particles, the aerosol is composed mainly from organic residues such as various types of fibres and fungi, mite debris and most of all skin scales, which are the major part of organic aerosol in gyms.
Based on the laboratory tests results the estimated ratio between the pulmonary ventilation during exercis and rest was 3.8 (max. = 5.4; min. = 2.7; standard deviation 0.72) showing that physical exercise may cause a 4-fold increase in exposure to inhaled aerosol. Conclusion: The results have shown that the conditions in these, especially during the heating period of the year, are above the limits for health protection.
The same is probably true for most school gyms in Prague and the Czech Republic. More monitored outdoor air has often better quality than the one in the gym when measured simultaneously.