Fluoride enrichment in groundwater and associated human health risk in a tropical hard rock terrain in South India

Abstract

This study is conducted in Dharapuram, a water-stressed semi-arid region in south India with an aim to understand the hydrochemistry of F-rich groundwater and perform a systematic human health risk assessment. Results indicate that groundwater is alkaline, dominated with Na, Mg, HCO₃, and Cl. Gibb’s plot shows that groundwater is influenced by rock–water interaction and evaporation processes. The concentration of fluoride exceeded the acceptable limits of 1 mg/L of Indian drinking water standard in 73% of the samples. However, no samples exceeded maximum permissible limit of 1.5 mg/L. Higher concentrations were observed in the eastern, southeastern, northeastern regions in this category. Geochemical investigation showed that the Na-rich–Ca-poor groundwater favoring fluoride release from the geological formations and increase in F-levels in groundwater. Saturation indices show that groundwater is undersaturated with fluoride, which is agreed with the hydrochemical analysis. Hazard quotient (HQ) shows that the groundwater is posing noncarcinogenic threats to 62% of children and 34% of females. In contrast, men were found to be safer than compared to the other two groups. The individuals with higher body weight are proved to be less affected by the same concentration of fluoride in drinking water.

Keywords:

• Hydrogeochemistry
• fluoride
• chronic daily intake (CDI)
• human health risk assessment (HHRA)
• south India