Unusually High Levels of Fluoride and Nitrate in Groundwater in Southern India: Water Quality Indices and Associated Health Hazard Implications

Groundwater is crucial for supporting the global population, with water quality having a significant impact on human health. In this study, we examined the groundwater geochemistry, health risks, and water quality index associated with consuming water contaminated by high levels of fluoride and nitrate in and around Gokak, Belgaum district, Karnataka. Fifty (50) groundwater samples were collected, and thirteen (13) physicochemical parameters were analysed following APHA methods. Results indicates that levels of pH, EC, TDS, fluoride, nitrate, and chloride exceed the WHO recommended standards. Fluoride concentrations range from 0.05 mg/L to 6.5 mg/L, while nitrate concentrations range from 2.66 mg/L to 118.8 mg/L. Excessive fluoride levels were observed in 14% of samples, and nitrate levels exceeded limits in 26%. Through Principal Component Analysis (PCA), four components explained 82.70% of the dataset variance. The water quality index (WQI) results categorize 26% of samples as excellent, 44% as good, 14% as poor, and 16% as unsuitable for any purpose, with 30% of samples overall being unfit for drinking. Health risk assessments for fluoride and nitrate indicate that 68% of samples had a hazard index (HI) value >1, highlighting a considerable health risk associated with groundwater consumption, particularly for women. Our findings suggest that both natural and human activities contribute to groundwater contamination. To further delineate pollution sources, stable isotopic studies are recommended. Keywords: Fluoride, Nitrate, Health, Karnataka, South India