Heavy metals in road dust across China: occurrence, sources and health risk assessment

We investigated the occurrence of Cd, Cr, Cu, Ni, Pb and Zn in 28 road dust samples collected across China from June to August, 2020. The mean concentrations of Cd, Cr, Cu, Ni, Pb and Zn were 3.16, 24.2, 27.4, 10.4, 49.8 and 608 mg·kg^- 1, respectively. The mean levels of Cd and Zn exceeded the Chinese background values by 32.6- and 8.2- fold. Cd, Ni mainly distributed in southern China, whereas Cu, Pb and Zn mainly distributed in central China. Higher concentrations of Cd, Cr, Cu and Pb were found in road dusts from urban areas than those from rural areas. Cu and Ni mainly came from natural sources; Pb and Cd mainly originated from industrial emissions and vehicle exhaust. Hand-mouth ingestion was the most common exposure pathway for both adults and children, followed by dermal contact and inhalation. Pb was found to be the highest risk element via ingestion. No significant non-carcinogenic risks and carcinogenic risks were found for local residents.