Airborne soil and dust are potential sources of antimony to residents across Delhi: Exposure likely to occur via dermal route

Background

There is an urgent need to assess sources of toxic metals in highly urbanized environments, to identify high risk areas for testing to enable planning to minimize exposure to residents. Notable toxic metals identified in this study were Antimony (Sb) and mercury (Hg), listed as priority pollutants by USEPA that can cause a variety of diseases in humans, and cobalt (Co), compounds of which have been shown to be carcinogenic in animal studies.

Objectives

Objectives of this study were to measure the level and spatial distribution of toxic metals in roadside soil and road dust across a large area of Delhi. Toxic metals with notably high levels were identified and assessed for potential environmental exposure, non-carcinogenic and carcinogenic risks to the population in the study area.

Research methods

A sampling scheme was designed to collect soil from a wide range of roadside environments across the urban region of Delhi. The soil and dust fractions were separated and selected toxic metals extracted and analyzed on Inductively Coupled Plasma – Mass Spectroscopy (ICP–MS) adopting USEPA methodology.

Results

Mean concentrations of Sb (2.62 and 3.59 in μgg⁻¹) were 13 and 18 times higher than background level (0.2 μgg⁻¹) in fine fractions of roadside soil and road dust, respectively in all areas sampled. The Hg and Co were moderately and minimally enriched in a fine fraction of soil and dust, respectively. The fine fraction of soil and dust showed a significant decrease in the Cu/Sb ratio compared to the coarse fraction suggesting an anthropogenic addition of Sb from vehicular brake pads. This study is the first of its type to calculate the cancer risk assessment of Sb from inhalation exposure.

Conclusion

Measurements of Sb, Hg and Co in roadside soil and dust are mapped to highlight regions where testing of the population would be advisable. In addition, toxic levels of Sb may enter the human body via a dermal route and cause various diseases including diabetes mellitus and gestational diabetes mellitus. Finally, our results suggest an immediate change to antimony free brake pads for all vehicles is recommended.