Hydrogeochemical characterization and non-carcinogenic health risk assessment of fluoride and nitrate-affected groundwater in northern parts of Tumkur district, Karnataka, India

Abstract

Groundwater contamination from geogenic and anthropogenic sources is a significant concern for the public health across the globe. In India, fluoride and nitrate contamination are the most prevalent contaminants in the groundwater. This study evaluated groundwater quality in four over-exploited sub-districts of Tumkur district in Karnataka by collecting 143 samples from post and pre-monsoon seasons and using different hydrogeochemical, statistical and bivariate graphical approaches. Comparison with Drinking Water Standard guidelines revealed elevated levels of fluoride, nitrate, and total dissolved solids (TDS), rendering the groundwater unsuitable for drinking. According to Chadha’s diagram, the predominant groundwater type is Na-Cl, and Gibbs diagram suggested the influence of rock dissolution and weathering. Bivariate plots indicated that hydrogeochemical characteristics were primarily influenced by silicate weathering of minerals, cation ion exchange processes, and anthropogenic factors. A non-carcinogenic health risk assessment was conducted using two different hazard index (HI) approaches from United States Environmental Protection Agency (USEPA) and Agency for Toxic Substances and Disease Registry (ATSDR). It was found that health risk associated with fluoride is more significant than the health risk from nitrate, with children being the most affected, followed by adolescents and adults. A holistic approach to assess cumulative health risks from fluoride and nitrate contamination in groundwater, as demonstrated in this study, promotes the synergistic advancement of SDG 3: Good health and well-being and SDG 6: Clean water and sanitation.