Integrated Assessment of Heavy Metal Pollution and Human Health Risks in Waters from a Former Iron Mining Site: A Case Study of the Canton of Bangeli, Togo

Abstract

Drinking water requires excellent physico-chemical quality. It must therefore not contain any substance which is harmful, or which may harm the health of the consumer. The drinking water supply of Bangeli canton (Togo) is provided by ground water and surface water which have been polluted by several industrial discharges as a result of Togo’s intensive industrialization in the last few decades. In order to contribute to the control of drinking water in this locality, our study focused on the state of metal pollution in the waters of this canton. To assess the spatiotemporal evolution of the metallic contamination in Bangeli waters, surface and groundwater samples were taken during dry and rainy seasons in the last three years. This comparative study will allow for a more in-depth assessment of the study area. These samples were analysed by ICP-MS for heavy metals such as Fe, Pb, Cr, Zn, Cu, Co, As, Mn, Sb, Ni, and Cd. The mean values obtained for these metals from groundwater are, respectively, 1144.87; 2.53; 3.42; 3.63; 6.49; 0.69; 143.76; 160.03; 5.67; and 0.036 µg/L. Except for Fe, Sb, and Mn, all the other metals have values below WHO guidelines. The heavy metal pollution index (HPI) applied to these waters gave values between 31.49 and 307.51, with 88.66% of samples below the limit value (100). Health risk assessment factors, including average daily doses, hazard quotient, carcinogenic risks, and hazard index indices, were computed for children and adults. Finally, the HPI index of Fe and Sb in both child and adult cases showed a value greater than the safe limits, which causes harmful health hazards and potential non-carcinogenic health risks to humans. However, carcinogenic risk for Cr, Cd, Pb, and As is less than the limit value (10−4), indicating that there is no risk of cancer. The interpretation of PCA results made it possible to understand that mining has contributed to the pollution of some water resources in Bangeli, and cluster analysis (CA) applied to the data showed that the sampling points can be grouped into four groups, which were primarily formed by extravagant concentrations of Fe, Mn, Cu, and Sr.