Exposure to indoor-outdoor particulate matter and associated trace elements within childcare facilities

Children's exposure to trace elements through indoor and outdoor pollutants could be a risk to their health. Here, we investigated the concentrations of particulate matter (PM), and PM trace elements existed in indoor and outdoor environments of childcare facilities. The coefficient of determination (R-2) was calculated to evaluate the relation between PM10 and PM2.5 concentrations in indoor and outdoor environments, and I/O ratios for PM were investigated in hallway and indoors during summer and winter seasons. We performed the factor analysis to identify the sources of trace elements in indoor PM2.5. For all childcare facilities, PM2.5 concentrations correlated well with PM10 concentrations in both indoor and outdoor environments, and their slopes are similar. In indoor-outdoor PM concentrations, the higher I/O ratios were presented in winter season, and there were significant differences between hallway and indoors in PM concentrations: childcare C (residential) for PM10 and childcare A (residential) and B (near roadway) for PM10. The factor analysis (FA) results indicated that indoor PM2.5 concentrations were contributed by outdoor pollutant sources, and the variance (%) of trace elements existed in PM2.5 determined by factors 1, 2, and 3 showed over 85%. Thus, these sources are the most significant outdoor pollutants and are sourced from re-suspended soil dust and motor vehicle emissions. More importantly, trace elements (Zn and Ni) included in PM2.5 could not be removed by an air purifier and could lead to potential pollutants in indoors of a childcare facility.