Geochemical processes, sources, and health implications of fluoride-rich groundwater in the central part of the Volta River Basin, Ghana

Fluoride (F−) in groundwater affects its suitability for domestic use, particularly drinking, posing health concerns for consumers. This study investigates the hydrogeochemical characteristics and potential health risks of abnormal groundwater F− concentrations in the central Volta River Basin, northern Ghana. Thirty-six borehole samples were analysed to identify the mechanisms driving variations in groundwater chemistry. Data-driven approaches, including indexical, hydrochemical, multivariate statistical, and health risk assessment models, were employed to evaluate F− contamination, toxicity, and associated risks. Groundwater F− levels ranged from 0.2 to 19.5 mg/L, with a mean of 4.3 mg/L. About 84% (n = 30) exceeded the WHO limit of 1.5 mg/L, while ~8% (n = 3) fell below the recommended 0.5 mg/L for healthy teeth and bone development. Another ~8% were within the permissible range of 0.5–1.5 mg/L. Dominant hydrochemical facies included K-HCO₃ (33.3%), Mg-K-HCO₃ (25%), and K-Mg–HCO₃ (11.1%), alongside mixed water types. Spatial mapping revealed elevated F− concentrations in the northeastern fringe and lower levels in the western fringe. F− enrichment is primarily controlled by water-rock interaction, mineral dissolution, and ion exchange. Human health risk assessment using USEPA guidelines showed hazard quotient (HQ) values between 1.06 and 27.63 across all demographic groups: infants, children, teenagers, and adults, exceeding the safe limit of 1.00. Children were most vulnerable, with HQ values ranging from 1.56 to 27.63, indicating significant susceptibility to fluoride-related health issues, notably dental fluorosis. These findings underscore the urgent need for defluoridation measures to reduce elevated F− levels and ensure safe water consumption.