To evaluate lung function responses to short-term indoor PM1 and PM2.5 concentrations, we conducted a panel study of healthy schoolchildren aged 13–14 years. The following lung function parameters FVC, FEV1, PEF, and mid expiratory flows MEF25, MEF50, and MEF75 were measured in 141 schoolchildren of the secondary school in Wroclaw, Poland in years 2009–2010. On days when spirometry tests were conducted, simultaneously, PM1 and PM2.5 samples were collected inside the school premises. Information about differentiating factors for children including smoking parents, sex, living close to busy streets, dust, mold, and pollen allergies were collected by means of questionnaires. To account for repeated measurements, the method of generalized estimating equations (GEE) was used. The GEE models for the entire group of children revealed the adverse effects (p < 0.05) of PM1 and PM2.5. Small differences in effects estimates per interquartile range (IQR) of PM1 and PM2.5 on MEF25 (5.1 and 4.8 %), MEF50 (3.7 and 3.9 %), MEF75 (3.5 and 3.6 %) and FEV1 (1.3 and 1.0 %) imply that PM1 was likely the component of PM2.5 that might have a principal health effect on these lung function parameters. However, the reduction of FVC and PEF per IQR for PM2.5 (2.1 and 5.2 %, respectively) was higher than for PM1 (1.0 and 4.4 %, respectively). Adjustment for potential confounders did not change the unadjusted analysis.

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The contributions of outdoor and indoor sources to the indoor concentrations of particulate matter (PM1, PM2.5, and PM10) were investigated in a secondary school in Wroclaw, Poland. PM measurements were performed one week per month from December 2009 to October 2010. The sizes of the aerosols generated form indoor sources were in the range of 1–2.5 µm in winter and 2.5–10 µm in summer. It was found that the indoor PM1 concentrations in the school were mostly due to infiltration, with an infiltration factor of 0.65 in winter and 0.68 in summer. These findings, complemented with single particle analyses (using electron probe X-ray microanalysis) revealed that the finest particles, mostly infiltrated from outdoor air, were dominated by organic carbon, sulphates and that organic carbon particles were associated with fly ash or soil dust. Organic carbon was also associated with larger particles of fly ash or soil dust. As part of mineral dust calcium carbonate, salt particles and aluminosilicates were identified. Thus, it is necessary to evaluate the health risks posed to school children associated with the high exposure to indoor PM containing potentially toxic materials in this and probably other schools.

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