Occurrence, Distribution and Ecological Health Risk Assessment of Heavy Metals Through Consumption of Drinking Water in Urban, Industrial, and Mining Areas of Semi - Arid to Humid Subtropical Areas

The current study assessed ecological and human health risks associated with heavy metals (HMs) consumption via drinking water from urban, industrial, and mining areas across semi-arid to humid subtropical areas of Pakistan. A total of 180 water samples were collected and analyzed. The physical parameters including pH, electrical conductivity, nitrates, carbonates, and total soluble salts remained within thepermissible limits. However, the average concentrations of cadmium (Cd), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) surpassed World Health Organization (WHO) guidelines, with ranges from 1.45-14.5, 3.75-15.8, 11.5-44.3, 4.12-33.2, 0.95-15.8, 0.85-14.9, and 0.35-10.9 mg.L-1, respectively. Contamination factor (CF) analysis indicated highest pollution levels from Cd, while pollution load index (PLI) values were > 1 across all sites, confirming significant HM pollution. Further, ecological risk assessment (ERA) showed varying levels of ecological risk, from low to high, associated with HM exposure. Average daily intake (ADI) of HMs was remarkably higher in children than adults. Health hazard quotient (HQ) values for Cd (2.9E+03-1.8E+04) and Pb (1.6E+00-3.8E+01), along with hazard indices (HI), indicated non-carcinogenic health risks. Moreover, carcinogenic risk (CR) exceeded threshold (CR > 1.0E-06) for Pb at all sites, with Cr and Ni posing risks at numerous sites. Statistical analyses, including principal component analysis (PCA) and pearson's correlation, revealed significant correlations (p<0.05) among several HMs. Effective treatment of drinking water is essential to mitigate the health and ecological risks associated with HMs contamination in the study area.