Geogenic Fluoride Enrichment in Dharmapuri District, Tamil Nadu, India: Hydro-chemical Patterns and Public Health Implications

Abstract

This study investigates geogenic fluoride contamination in groundwater throughout Dharmapuri District, Tamil Nadu, using seven years of hydrogeochemical data and a community health assessment. Water samples from 55 villages were analysed for fluoride and other water quality parameters, such as pH, EC, TDS, calcium, sodium, and bicarbonate, during pre- and post-monsoon seasons from 2011 to 2017. Statistical methods, including Pearson correlation and R² regression, were applied to identify predictors of elevated fluoride levels. A community survey using a 5-point Likert scale captured self-reported symptoms of fluorosis from 1,375 residents. Findings revealed widespread fluoride enrichment, with 30.9% of villages classified as moderate-risk and 12.7% as very high-risk in the pre-monsoon period; post-monsoon, 36.4% were moderate-risk and 10.9% very high-risk. Seasonal comparisons showed that fluoride levels decreased in 24 villages but increased in 31 others, with changes up to 0.36 mg/L. Potassium and bicarbonate were found to be the strongest predictors of fluoride, while sodium had a positive relationship and calcium an inverse one. The health survey indicated high prevalence of yellowish teeth (49%) and joint pain (45%), but only 19% recognised personal fluorosis. The research underscores the geogenic origin of fluoride, its seasonal variability, and the need for bi-seasonal monitoring and targeted mitigation strategies to address public health risks.