Sources and geochemistry of high fluoride groundwater in hard rock aquifer of the semi-arid region. A special focus on human health risk assessment

Abstract

Groundwater is essential for domestic and irrigation purposes in arid and semi-arid regions. However, improper management leads to a detrimental effect on human health. The study aimed to determine the quality of the groundwater and the human health hazards posed by fluoride. The fluoride concentration in groundwater samples varies from 0.04 to 1.8 mg per litre (0.72 mg/L on average). The hydrogeochemical analysis reveals that 11 % of groundwater samples exceeded the WHO drinking water permissible limit (1.5 mg/L). A higher concentration of fluoride ions is observed in the hornblende biotite gneiss, charnockites and granitic rocks. The samples were dominantly alkaline in nature, the samples with higher fluoride ${(F}^{-})$ were observed to be mixed Ca-Mg-Cl type. The interaction between water and rock formations significantly impacts high $F^{-}$ in groundwater. The Pollution Index of Groundwater (PIG) indicates that 3 % of samples were highly polluted, and 2 % were under the very high pollution category. The US Environmental Protection Agency (USEPA) technique was used to assess the potential health hazard posed by high fluoride groundwater. The results revealed that oral fluoride exposure is much higher than dermal contact. The Total Hazard Index (THI) values indicate that children (48 %) and females (13 %) were more susceptible as the values surpassed the standard limit (THI = 1). The findings also indicated a higher possibility of children being affected by fluoride's non-carcinogenic health hazards due to physiological factors and intake rates.