HYDERABAD: The water beneath Greater Hyderabad may be carrying a hidden health risk. Elevated nitrate and fluoride levels in groundwater have been detected in several parts of the city, with children facing potentially higher non-carcinogenic health risks, according to a recent study.
The study analysed 44 groundwater samples collected during the pre-monsoon and post-monsoon seasons of 2023. Nitrate exceeded the permissible drinking-water limit of 45 mg/L in 36% of samples before the monsoon and 40% afterwards. Fluoride crossed the acceptable limit of 1 mg/L in 64% and 59% of samples, respectively.
Nitrate levels ranged from 3 to 230 mg/L before the monsoon and 5 to 797 mg/L afterwards, with higher concentrations mainly in southwestern and central areas.
Researchers linked the contamination largely to fertiliser use, sewage infiltration, septic-tank leakage and urban wastewater. Monsoon rains can further carry nitrogen compounds from soil into groundwater.
Fluoride levels ranged from 0.21 to 3.03 mg/L before the monsoon and 0.28 to 5.94 mg/L afterwards, with higher concentrations in northern, southern and southwestern areas. Unlike nitrate, fluoride enrichment was attributed mainly to the weathering of granitic rocks and prolonged interaction between groundwater and aquifer materials.
Children face greater risk: Study
The health-risk assessment found the hazard quotient (HQ) for nitrate and fluoride exceeded 1 at several locations. For children, the mean HQ for fluoride rose from 1.04 before the monsoon to 1.11 afterwards, while nitrate increased from 1.81 to 3.78.
The combined total hazard index (THI) for children rose from 3.07 to 3.78, compared with 2.27 to 2.79 for adults. Under US Environmental Protection Agency guidelines, an HQ above 1 indicates a potential non-carcinogenic health risk. Children were considered more vulnerable because of their lower body weight and greater exposure relative to body mass.
The study also found elevated total dissolved solids in 95% of pre-monsoon and 86% of post-monsoon samples, against the Bureau of Indian Standards’ permissible limit of 500 mg/L.
Total hardness exceeded the limit in 75% and 84% of samples, respectively.
The researchers called for closer groundwater monitoring and stronger measures to control sewage and agricultural sources of nitrate contamination.
The research was conducted by Achiraju Pallavi and Allam Edukondal of Osmania University, Laxman Kumar Duvva of JNTU-Hyderabad and Ratnakar Dhakate of CSIR-National Geophysical Research Institute.
