To Örebro University

Metals and metalloids are ubiquitously found in indoor environments due to their high crustal and soil abundance as well as their usage as different additives in materials. However, their presence in indoor environments is of high concern because they are nondegradable and some may be toxic, causing adverse health effects in occupants, especially children. In this study, 19 metals and metalloids were measured in indoor dust samples collected from 26 preschools in December 2023 (winter) to investigate their potential indoor sources and exposure risks. Among the 19 elements, 18 were detected in one or more of the participating preschools, while 13 were detected in all preschools. The detected indoor dust concentrations were in general lower compared to other studies possibly due to different exposure patterns such as the location of the preschools, indoor settings, and interior decorations as well as sampling techniques. Furthermore, the results revealed that the indoor dust concentrations of several metals could be attributed to anthropogenic sources due to high enrichment factors (EFs). The statistical tests (Student ' s t-test and Pearson ' s correlation coefficient) further identified the following potential indoor sources: Manganese (Mn) concentrations were linked to usage of foam mattresses, while dust concentrations of Mn, iron (Fe), cobalt (Co), and lead (Pb) were linked to usage of wallpaper. Antimony (Sb) posed the largest non-carcinogenic exposure risk, with hazard indexes at 0.14 and 0.34 calculated from the median value and 95th percentile, respectively. In addition, total chromium (Crtot), nickel (Ni), and arsenic (As) showed potential carcinogenic risks. The result from this study offers valuable insights into potential sources of indoor contamination sources and associated exposure risks, which can be used to identify preventive measures to reduce children ' s exposure during preschool attendance.