Health risk assessment of the exposure of heavy metal contamination in surface water of lower Sindh, Pakistan

In developing countries like Pakistan, there is a lack of implementation of the environmental laws to manage discharges of untreated effluents, loaded with heavy metals, into freshwater. To evaluate the potential human health impacts from exposure to such polluted water, this study assessed the concentration of six heavy metals (i.e., Zn, Fe, Pb, Cu, Cd, and Mn) in the surface water in lower Sindh, Pakistan. Water samples were collected from eight locations around Kotri barrage at Indus River both during pre-monsoon and monsoon seasons to determine the temporal variations of the concentration of heavy metals. The concentrations of heavy metals were then compared with the drinking water quality guidelines of the World Health Organization (WHO). It was observed that in most cases, the concentrations of metals were significantly higher compared to WHO guidelines during the pre-monsoon period. To determine the potential human health risk associated with the exposure of heavy metals, both oral hazard index (HIoral) and dermal hazard index (HIdermal) were estimated. The results indicated that during pre-monsoon, HIoral was higher than the threshold limits at every location, while HIdermal was higher only at three locations. Nonetheless, during monsoon, these indices were within limits. It suggested that the health of the people dependent on these freshwater streams in the study area is at considerable risk. Finally, the findings of this study recommended the enforcement of the laws in its true spirit to regulate effluent discharges into these streams in order to avoid health vulnerability of millions of people.