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Groundwater in several parts of Hyderabad has elevated levels of nitrate and fluoride, with children facing higher potential 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.
According to a TNIE report, nitrate exceeded the permissible drinking-water limit of 45 mg/L in 36% of the samples collected before monsoon and 40% of the samples collected after monsoon. Nitrate concentrations ranged from 3 to 230 mg/L during the pre-monsoon period and from 5 to 797 mg/L post-monsoon, with higher levels mainly recorded in southwestern and central parts of the city.
Researchers attributed nitrate contamination largely to fertiliser use, sewage infiltration, septic-tank leakage and urban wastewater. Monsoon rainfall can also carry nitrogen compounds from the soil into groundwater, the study noted.
Fluoride exceeded the acceptable limit of 1 mg/L in 64% of pre-monsoon samples and 59% of post-monsoon samples. Concentrations ranged from 0.21 to 3.03 mg/L before the monsoon and 0.28 to 5.94 mg/L afterwards, with higher levels found 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.
The study's health-risk assessment found that the hazard quotient (HQ) for nitrate and fluoride exceeded 1 at several locations. The mean HQ for fluoride among children increased from 1.04 before the monsoon to 1.11 afterwards. For nitrate, it increased from 1.81 to 3.78.
The combined total hazard index (THI) for children increased from 3.07 to 3.78, compared with an increase from 2.27 to 2.79 among adults.
Under US Environmental Protection Agency guidelines, an HQ above 1 indicates a potential non-carcinogenic health risk. The study considered children more vulnerable because of their lower body weight and greater exposure relative to body mass.
The groundwater samples also showed elevated total dissolved solids (TDS) in 95% of pre-monsoon samples and 86% of post-monsoon samples, against the Bureau of Indian Standards' permissible limit of 500 mg/L.
Total hardness exceeded the permissible limit in 75% of samples collected before the monsoon and 84% of those collected afterwards.
The study 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.
