Spatial modeling of health risks from heavy metals in urban Road dust using land-use regression: a case study of Arak, Iran

Heavy metal (HM) contamination in urban road dust (RD) represents a significant environmental and public health concern, particularly in densely populated and industrialized regions. This study investigated the spatial distribution and associated health risks of cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), and zinc (Zn) in RD across various land-use types in Arak, Iran. During a nine-month sampling campaign, 160 RD samples were collected from twenty strategic locations representing industrial, residential, commercial, and high-traffic zones. Land-use regression (LUR) modeling was employed to map HM concentrations and identify pollution hotspots. The mean concentrations of Cd, Cr, Ni, Pb, and Zn were 0.48, 64.6, 44.4, 133.9, and 277.6 mg/kg, respectively, substantially exceeding global soil background values. Spatial analysis identified the southern, central, and southeastern sectors as critical pollution hotspots, primarily influenced by vehicular emissions and industrial activities. Health risk assessment revealed ingestion as the dominant exposure pathway, with lead posing the most significant non-carcinogenic risk to children (HI = 0.522). The cumulative hazard index for all metals reached 0.9036 in children, approaching the safety threshold of 1. Furthermore, the total carcinogenic risk for children (2.27 × 10^-4) slightly exceeded acceptable levels, with nickel being the predominant contributor. This study provides critical evidence supporting the urgent need for targeted public health interventions, stringent emission controls, and science-based urban planning strategies to mitigate heavy metal exposure risks in vulnerable urban populations.