Potential toxic elements in groundwater: a health risk in parts of northern Delhi

Groundwater quality and its implication on human health is a matter of concern in the semi-arid region of northern India. The present work deals with the elevated concentration of potential toxic elements (PTEs) in the groundwater in parts of Northern Delhi and their impact on human health. Groundwater samples were collected from thirty-three locations during the 2019-2021 sampling campaigns. The collected groundwater samples were analyzed for Electrical Conductivity (EC), and 'As', Mn, Cd, Cu, Cr, Pb, and Zn elements. The mean concentration of PTEs followed the order of Pb < Cr < Cd < As < Cu < Zn < Mn. Almost all the groundwater samples had EC beyond the desired drinking water limits. Pb, Cr, Cu, and Zn concentrations were within permissible limits. However, the Cd concentration in the study area's sampled groundwater was found in the range of 6.54 to 7.03 mu g/l, with a mean of 6.69 mu g/l, which is beyond the World Health Organization (WHO) permissible limit of 3.0 mu g/l. The 'As' values were in the range of 0.49 to 73.75 mu g/l, where in around 24% of the groundwater samples, it was above the WHO permissible limit of 10 mu g/l. Further, the Mn concentration in groundwater beyond the permissible limit was observed in a single sample. The research in the article proposes a possible reason for the observed concentration of the PTEs in the study area. The cancer and non-cancer health risks were analyzed for both adults and children. The health risk assessment investigated using the Total Hazard Index (THI) indicates that in thirteen groundwater samples, both age groups are vulnerable to non-carcinogenic risks. However, children are more vulnerable than adults. About 39% and 42% of water samples showed high carcinogenic risk, respectively, for both adults and children. The spatial distribution map for the carcinogenic risk reveals that except for a few small patches, the whole study area is highly vulnerable to the carcinogenic risk for adults and children. Thus, it is imperative that the water quality is monitored with an evenly distributed denser network of sampling stations by the concerned Government institutions and adequate mitigation measures are adopted. Awareness regarding the health impacts of PTEs exposure and its further magnification will prevent the health hazards.