Elemental composition of indoor dust and health risk assessment in preschools located in a seasonal haze-affected area: Lampang Province, Thailand

This study investigated trace element contamination, source characteristics, and associated health risks of indoor dust collected from 22 preschools across six districts of haze-affected Lampang Province, Thailand. Dust samples from urban, coal power plant, sub-urban, and rural areas were analyzed for As, Cr, Ni, Pb, Cu, Fe, Mn, Zn, and K using ICP-OES following acid digestion. Contamination levels were evaluated using the enrichment factor (EF), geo-accumulation index (Igeo), and potential ecological risk index (RI), while human health risks were assessed using non-carcinogenic (HQ, HI) and carcinogenic (CR, TCR) models. Fe, K, Zn, and Mn were the dominant elements, with Zn showing moderate contamination and strong anthropogenic influence, particularly from traffic emissions and biomass burning. Source apportionment indicated mixed contributions from soil dust, industrial activities, and combustion processes. Ecological risk remained low across all sites (RI < 150). Non-carcinogenic risks were negligible (HI < 1), although children were more susceptible than adults. Carcinogenic risks for As, Cr, and Ni through both ingestion and inhalation pathways were within acceptable limits (10-6 to 10-4), with ingestion representing the dominant exposure pathway. Overall, indoor dust posed low ecological and health risks; however, continued monitoring is recommended due to potential long-term exposure effects on children.