Mapping human health risk from exposure to potential toxic metal contamination in groundwater of Lower Dir, Pakistan: Application of multivariate and geographical information system.

The study aimed to assess the physicochemical parameters (pH, electrical conductivity (EC), total dissolve solid (TDS), oxidation reduction potential (ORP), Temperature) and potential toxic metals (PTMs), including Ni, Mn, Cr, Cu, Cd, Pb, Co, Fe and Zn in the groundwater of Lower Dir, Pakistan. Furthermore, the pollution sources and spatial distribution pattern of PTMs were also investigated via principal component analysis (PCA) and geographic information system (GIS) application to understand the changing behaviors of PTMs in groundwater. The average concentrations of physicochemical parameters such as pH, EC, TDS, ORP and Temperature were 7.1, 418 μS/cm, 251 mg/L, 193 mV and 25.7 ○C, while the concentrations of PTMs; Ni, Mn, Cr, Cu, Cd, Pb, Co, Fe and Zn were 0.25, 0.34, 0.09, 0.29, 0.10, 0.08, 0.10, 0.83 and 0.25  mg/L, respectively. Among the selected metals, Mn, Cr, Cd, Pb, Co and Fe were exceeded the WHO guidelines and their percentage contribution were 43%, 57%, 45%, 70%, 70% and 62%, respectively. The increasing order of PTMs were; Pb > Co > Fe > Cr > Cd > Mn > Cu > Ni > Zn in the study area. PCA represented three significant factors, which explained 76% variability in the groundwater. Whereas, clustering analysis (CA) grouped groundwater into three distinct clusters less polluted (C1), moderate polluted (C2) and highly polluted (C3). Human health risk assessment was carried out to check the suitability of groundwater for drinking and domestic uses. The HQ and HRIs values of Cd were >1, suggested that the groundwater sources are unfit for drinking and domestic purposes and may be caused potential health risk after long term ingestion.