Spatial distribution, pollution levels, and risk assessment of potentially toxic metals in road dust from major tourist city, Dehradun, Uttarakhand India

Due to rapid urbanization and industrialization, road dust enriched with heavy metals (HMs) emerges as a global problem as it poses a series of threats to the human health of all age groups. The present study investigates the concentration, contamination, spatial distribution, ecological and health risks associated with road dust HMs. Seventy road dust samples were collected for three different seasons (winter, summer, and monsoon) from Dehradun city, Uttarakhand, India. The road dust samples were subjected to acid digestion and rigorously analyzed through inductively coupled plasma-mass spectrometry (ICP-MS) to determine the concentrations of seven potentially toxic HMs, i.e. Zinc (Zn), Copper (Cu), Lead (Pb), Cadmium (Cd), Chromium (Cr), Nickel (Ni), and Arsenic (As). The average concentration of Zn, Cu, Pb, Cd, Cr, Ni, and As were 172.14, 59.64, 109.83, 1.80, 32.69, 23.29, and 2.72 mg-kg(-1) respectively. The concentration of Zn, Cu, Pb, Cd, and As was found higher than the Indian natural soil background value and continental upper crust value. The principal component analysis shows that the HMs come from mixed sources such as Zn, Cu, Pb, and Ni mainly come from different traffic activities whereas Cd, Cr, and As mainly come from paint abrasion, fuel burning, and pesticides and fertilizers containing Cd and As compounds. The pollution index (PI) shows that Cd, Pb, Cu, and As come under the high contamination category. The spatial distribution of PI shows that the extent of pollution is highest in central, eastern, and northeastern zones as compared to other zones of the Dehradun city. Potential ecological risk results show that Cd accounts for 87.12% of the risk followed by Pb (5.32%) and Cu (3.43%). The health risk assessment showed that there is no non-carcinogenic risk of the studied HMs for children and adults. The ingestion pathway is turned out to be the major route of exposure for all the studied HMs calculated for carcinogenic and non-carcinogenic risk in children and adults followed by dermal contact and inhalation. The results also showed that children are more susceptible to HMs contamination in comparison to adults. The descending order of lifetime cancer risk (LCR) for four studied HMs is found as follows: Cd > NI > Cr > As for both children and adults. The LCR results reveal that the value of Cd, Cr, Ni, and As were greater than 1 x 10(-6) for both age groups, indicating the possibility of cancer development in near future.

Automated summary

This study investigates the concentration, contamination, spatial distribution, ecological and health risks associated with heavy metals (HMs) in road dust samples from Dehradun city, India. The results show that some HMs have concentrations higher than background values, and Cd, Pb, Cu, and As are classified as highly contaminated. Children are more susceptible to HM contamination, and ingestion is the primary exposure pathway. The lifetime cancer risk (LCR) for Cd, Cr, Ni, and As is greater than 1 x 10(-6), indicating the possibility of cancer development.