Title : Assessment of water quality and its suitability for drinking purposes in streams of the Olifants River Basin, South Africa
Abstract:
Heavy metal pollution in freshwater ecosystems is a major environmental concern, and it constitutes a significant limitation to access to drinking water by humans. Mobilization of heavy metals from natural and human activities into freshwater sources may represent an important threat to human health. The Olifants River Basin in South Africa is facing severe pressure due to increasing mining and agricultural activities in the catchment. Many of the people in the area depend on the freshwater resources in the basin for drinking water and food (fish), and degradation of these water resources may pose a health risk to them. In this study, the health risk to humans from exposure to chemicals especially heavy metals in water from two rivers; the Blyde and Steelpoort rivers in the basin was assessed. Water samples were collected from the upstream, midstream and downstream of the rivers and concentrations of nine trace metal(loid)s (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) from the sites were determined using inductively coupled plasma–optical emission spectrophotometer. Furthermore, two pathways of exposure (direct ingestion and dermal absorption) from the rivers were calculated to assess the potential effects on human health. Generally, the Hazard Quotient (HQ) dermal values were lower than the HQ ingestion, showing that the pathways of direct ingestion pose more danger to human health. The metal(loid)s in the two rivers pose little risks for adults with HQ ingestion, HQ dermal, and Hazard Index (HI) were less than 1. However, in children, the HQ ingestion and HI for As and Cr in the two rivers were greater than threshold value of 1. Hence, the non-carcinogenic adverse effect is significant. Thus, HI values were higher for children than adults, suggesting that children are more sensitive to the risk of exposure to chemical pollution. Cancer risk (CR) for adults and children was also computed in relation to As, Cr, Ni and Pb levels. The CR values were all below the threshold limit except for Cr in children, indicating a possible carcinogenic risk. This study therefore recommends an effective monitoring of chemical pollution in the rivers at regular intervals and implementation of an effective plan of action to mitigate the effects of chemical pollution on the rivers and human health.
Audience take-away:
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