Comprehensive chemical profiling of roadside soil and road dust of Delhi, India: Estimation of health risk and city fuel consumption

Roadside soil and dust are relatively underexplored as sources of toxic metal exposure in the massively urbanized city of Delhi. Here we report a large-scale study of 44 elements analyzed at 33 sites. Environmental exposure to carcinogenic and non-carcinogenic risks from toxic elements has been estimated for male, female and children of the city Delhi for the first time. The concentrations of 44 elements, including 16 Rare Earth Elements, were analyzed. The maps of the non-carcinogenic risk from 17 elements and the carcinogenic risks from 5 elements were prepared. Hotspots of city fossil fuel consumption were also mapped using the total carbon/nitrogen ratio of the soils. Lead isotope ratios support the anthropogenic accumulation of lead in soil and dust. The total Hazard Index (HI) values for the fine fraction of soil and dust were beyond the unity level (>1) for males, females and were especially high in children. Excess cancer cases due to exposure of fine fractions of soil and dust were estimated for males (>180,000), females (>210,000) and children (>21,000). These findings suggest that all inhabitants of Delhi are facing potential non-cancer and cancer risks. Data from this study also contributes to our understanding of the threat from toxic metals in urban soil and dust from other immensely urbanized global cities like Delhi.