Health risks due to geogenic and anthropogenic influences on groundwater quality in Southern India's hard rock terrain

Groundwater contamination poses a critical public health risk in Raichur district, Karnataka, India where groundwater is a vital resource for drinking and agriculture. A total of 54 groundwater samples were analyzed, revealing that 68.5 % exceeded the WHO's nitrate limit of 45 mg/L, with concentrations ranging from 2.2 mg/L to 830 mg/L, and 44.4 % surpassed the fluoride threshold of 1.5 mg/L, with levels ranging from 0.06 mg/L to 7.18 mg/L. A comprehensive Health Risk Assessment (HRA) identified infants, children, pregnant women, and lactating mothers as vulnerable populations, with Hazard Quotient (HQ) values reaching 67.25 for nitrate and 23.33 for fluoride. These elevated levels indicate significant risks, including methemoglobinemia and skeletal fluorosis. Geospatial analysis mapped contamination hotspots in the northern and central regions, highlighting the interplay of anthropogenic activities like excessive fertilizer use, inadequate waste management, and natural geological factors. Recommendations include precision farming, improved waste management, and community-level remediation systems, such as defluoridation and denitrification technologies. Artificial groundwater recharge and regulatory interventions are critical to maintaining water quality. By integrating geospatial tools and HRA, this study provides a replicable framework for addressing groundwater contamination and ensuring sustainable water resource management, particularly in regions with similar hydrogeological challenges.