Heavy metals in road dust across contrasting urban settings and screening assessment of noncarcinogenic risk for adults and children

Abstract Road dust can retain metals from traffic and other urban sources and create repeated contact opportunities in pedestrian environments, yet evidence from smaller settlements remains limited. We compared Cr, Cu, Ni, Pb and Zn in 35 road-dust samples from four towns in north-eastern Poland selected as contrasting urban and transport settings. Pseudo-total concentrations were determined after aqua regia digestion, contamination was assessed using the geoaccumulation index (Igeo), contamination factor (CF) and pollution load index (PLI), and non-carcinogenic hazard was screened for adults and children using the United States Environmental Protection Agency (USEPA) framework. Zambrów had the highest median Cu, Zn, Cr and Ni concentrations, while statistically significant among-town differences were confined to Cr, Zn and Cu. Town-mean PLI values were below 1, but three Zambrów sites exceeded 1, indicating localised rather than town-wide multi-metal enrichment. The unrefined total hazard index across the five metals remained below 1 at all locations, reaching maximum values of 0.0238 for adults and 0.214 for children at Z11; among the metal-specific indices, median values were highest for Pb and maximum values for Cr, and ingestion was the dominant pathway. Because each town represented a unique combination of population size, transport function, road-network structure and local environmental conditions, the study could not estimate the independent effects of town size or transport pressure. The results therefore support an exploratory comparison of four case-study towns rather than causal source attribution, broad generalisation or site-specific risk prediction. Within this screening framework, transit-exposed towns and pedestrian-sensitive locations may warrant targeted repeated sampling, with Cu and Zn used as initial screening parameters followed by broader analysis where elevated concentrations persist.