Delhi groundwater among India’s most toxic: Report

Delhi’s groundwater continues to rank among the most contaminated in the country, with the latest annual report of the Central Ground Water Board (CGWB) revealing dangerously high levels of uranium, lead, nitrate, fluoride and salinity-related indicators. Released this month, the report warns that several contaminants exceed national drinking water standards, posing long-term health risks to lakhs of residents who rely on borewells and hand pumps.

According to the CGWB, “significant concerns have emerged” following a detailed analysis of samples collected across the Capital. The findings show that Delhi now reports one of the highest proportions of lead-contaminated groundwater in India. Lead, a potent neurotoxin, exceeded permissible limits in 9.3 per cent of pre-monsoon samples, far higher than states such as Assam (3.23 per cent) and Rajasthan (2.04 per cent). Even at low levels, lead exposure can impair cognitive development in children, damage kidneys, raise blood pressure and is classified as a probable human carcinogen.

Uranium contamination also remains a major concern. Delhi recorded the third highest proportion of uranium-affected samples after Punjab and Haryana, with 13–15 per cent of samples exceeding safe limits. Uranium ingestion is known to cause kidney damage and heightens long-term cancer risk.

Beyond heavy metals, nitrate levels in the city’s groundwater remain troubling. The CGWB attributed the exceedances primarily to human-driven factors such as agricultural runoff and improper waste disposal. Elevated fluoride concentrations were found to stem largely from natural geological processes, especially in hard rock aquifers where groundwater interacts with minerals in granite and gneiss formations.

Indicators linked to salinity also reflected persistent stress. Electrical conductivity, a measure of dissolved solids, exceeded safe standards in 23.3 per cent of samples.

The report further noted that monsoon-related groundwater recharge does not necessarily improve water quality. A Central Pollution Control Board review of post-monsoon variations found several locations where conditions worsened, owing largely to site-specific factors such as aquifer characteristics and local contamination loads.