Screening Health Risks of Trace Metals in Indoor Dust and Settleable Particles in an Industrial Coastal Basin in Chile

Industrial coastal basins that host heavy industry can concentrate metal-bearing dust in school environments. We performed a screening multi-matrix assessment across six schools in Quintero–Puchuncaví (central Chile). We measured As, Cd, Cr, Cu, Ni, Pb, and Mn in surface soils (winter 2023; E1–E4 only), indoor settled dust, and settleable particulate matter (SPM) collected in winter (July 2023) and summer (November 2023). Concentrations were determined by ICP-OES/ICP-MS and interpreted with enrichment factors and the geoaccumulation index. A U.S. EPA screening framework was used to estimate non-carcinogenic hazard (HQ) and incremental lifetime cancer risk (ILCR) for ingestion, inhalation, and dermal contact, as well as cumulative indices for non-carcinogenic (HI) and carcinogenic risk (Risk). SPM carried the strongest anthropogenic signal (EF up to 9900 for Cd, 408 for Cu, and 143 for Pb) and the highest summer loads (Cu > 5000 mg kg−1; Ni > 1000 mg kg−1). Cu dominated non-carcinogenic hazard (HQ up to 137), whereas ILCR was driven by Ni, As, and Cr, exceeding 10−4 and reaching 10−3 at inland/valley schools in summer. Indoor dust showed intermediate burdens, indicating indoor accumulation of outdoor-derived metals, while the winter soil survey provides a baseline indication of outdoor metal reservoirs at the sampled schools. Despite the limited sample size, the results provide screening-level evidence to inform emission control and dust mitigation in school microenvironments.