Hydrogeochemical controls and human health risk assessment of groundwater fluoride and boron in the semi-arid North East region of Ghana

In this study, eighty-eight (88) samples were collected from active boreholes in the North East region of Ghana and analyzed for concentrations of the hydrogeochemical parameters. This helped in understanding the hydrogeochemistry, spatial distribution, origin of groundwater F- and B and the level to which the underlying geology influences the F- and B. Human health risks of F- and B were also assessed based on the model of the US Environmental Protection Agency. Groundwater is alkaline in this area and the dominant hydrochemical facies is Na-HCO3 facies, which is a reflection of the predominant carbonate lithology of the Oti/Pendjari Group in the region. The study reveals that the F- concentrations range from 0.05 to 13.29 mg/L with an average value of 3.26 mg/L, suggesting that majority of the boreholes have F- concentrations higher than the acceptable limit (1.5 mg/L) of WHO. The B concentrations also vary from 0.03 to 5.13 mg/L with an average of 1.52 mg/L in excess of the guideline value of 0.5 mg/L. The groundwater F- and B threats, respectively affect about 70% and 82% of boreholes in the region particularly around the northeastern, southeastern, central, and western parts. F- and B are mainly coming from geogenic sources and are controlled by hydrogeochemical factors such as semi-arid climatic conditions of the region, alkaline nature of the water, water-rock interaction, intense weathering, ion exchange, mineral dissolution and precipitation. The human health risk assessment reveals that non-carcinogenic risk for F- and B is higher in children than the adult population. About 89% of children in the study area are exposed to initial symptoms of dental and skeletal fluorosis and have higher chances of cardio-protection since no health threat is currently reported for high B in drinking water. We recommend immediate action towards mitigating the high groundwater F- to safeguard the health and livelihood of the people.