Comprehensive insight into heavy metal(loid)s in road dust from industrial and urban areas in northern Vietnam: concentrations, fractionation characteristics, and risk assessment

Road dust samples were collected from 6 cities and provinces in northern Vietnam to evaluate contamination levels and distribution characteristics of 5 toxic elements, including Cu, Zn, Pb, Cd, and As. Total concentrations of 5 elements in road dust samples ranged from 18.4 to 470 (median 96.4) mg/kg, in declining order of Zn > Cu > Pb > As > Cd. Pollution levels in urban road dust from Hanoi (median 266; range 205-366 mg/kg) were generally higher than those measured in samples taken from other industrial areas (median 91.1; range 18.4-470 mg/kg). Our results showed that the emission of some heavy metals from urban areas with high population density and heavy traffic was comparable to or even higher than in manufacturing areas of electronic components, construction materials, and mining. The chemical fractions of heavy metals in road dust were also evaluated. More than 60% of heavy metals are present in the potential mobile phases, indicating that the anthropogenic metals are still in a relatively weakly bound form. These metals can be mobile and bioaccumulative, affecting ecosystems and humans. The geological accumulation indexes indicate moderate contamination of heavy metals in many locations of this study. Cd poses an ecological threat in several urban and industrial sites. There were no serious human health risks associated with heavy metals in road dust. However, relatively high levels of Cu and Pb in road dust imply a health risk for children living in some urban and industrial areas. Further monitoring and risk assessment studies on toxic elements in road dust should be conducted, especially in developing countries' highly urbanised and industrialised areas.