Non-carcinogenic health risk assessment of nitrate and fluoride contamination in the groundwater of Noyyal basin, India

The study aims to assess the nitrate and fluoride concentration in groundwater and its adverse effects on human health. In 2019, 42 groundwater samples were collected from various bore wells within the western Noyyal basin, India. Sodium and chloride are the dominant cation and anion, respectively. The nitrate concentration in groundwater samples varies from 2 to 89 mg/L, of which 33.33% are above the permissible limit of 45 mg/L for drinking water. The fluoride concentration ranges from 0.2 to 2.4 mg/L, with 28.57% of the samples exceeding the safe value of 1.5 mg/L for drinking water. Correlation plots demonstrate that the potential of hydrogen (pH), electrical conductivity (EC), total dissolved solids (TDS), ${\text{Na}}^{+}$ and ${\text{HCO}}_3^{-}$ are positively correlated with ${\text{F}}^{-}$, whereas ${\text{Ca}}^{2+}$ is negatively correlated. Mixed Ca–Mg–Cl is the most common water type in the investigated region. The Gibbs diagram demonstrates that the interaction between rock and water impacts the groundwater chemistry. Using the method of the United States Environmental Production Agency (USEPA), this study assesses the non-carcinogenic health risk posed by nitrate and fluoride in different age groups (infants, children, and adults). The values of total hazard index (THI) vary from 0.59 to 10.07 (mean = 4.76) for infants, 0.36 to 6.23 (mean = 2.95) for children, and 0.19 to 3.32 (mean = 1.57) for adults. Furthermore, 97.62%, 92.86%, and 73.81% of the samples surpass the recommended limit (THI = 1) for infants, children, and adults, respectively. Thus, the health risk assessment (HRA) indicates that infants and children are more susceptible to non-carcinogenic health hazards than adults. The THI spatial variation map shows that central and southern regions of the study area have been identified as high health risk areas (THI >3.0) for all age groups.