New Delhi is facing a severe public health threat as recent official data reveals widespread nitrate contamination in its groundwater. A submission by the Central Groundwater Board (CGWB) before the National Green Tribunal (NGT) shows that more than one-fifth of the samples collected in the capital in 2023 contained nitrate levels above the safe limit for human consumption.
Alarming Nitrate Levels Across Delhi Districts
The permissible limit for nitrate in drinking water, as per Indian standards, is 45 milligrams per liter (mg/l). The CGWB report, however, found that 20.39% of groundwater samples from Delhi exceeded this limit. This translates to roughly one in every five samples being chemically unfit for drinking. The contamination is not uniform but concentrated, with high levels detected in seven out of the city's eleven districts.
The affected districts are New Delhi, North, Northwest, South, Southeast, Southwest, and West Delhi. The scale of pollution in specific hotspots is staggering, with nitrate concentrations peaking at 994 mg/l in some locations. This is more than 22 times higher than the safe threshold of 45 mg/l, indicating extreme localised pollution.
National Crisis: From Delhi to Andhra Pradesh
While Delhi's situation is critical, it is part of a much larger national groundwater quality emergency. The data was presented in an ongoing case where the NGT took suo motu cognisance of a news report on the issue. The CGWB's affidavit, dated December 22, submitted its annual groundwater quality report for 2024, based on 2023 samples.
The board reported that excessive nitrate levels were found in groundwater in 440 districts across India, a significant jump from 359 districts in 2017. In the grim national ranking of peak nitrate concentration, Delhi stands as the fifth worst-affected state or Union Territory.
Andhra Pradesh recorded the highest peak level in the country at a shocking 2,296.36 mg/l. In terms of the pervasiveness of contamination—measured by the percentage of samples exceeding limits—Rajasthan is the worst performer. There, 49.52% of its 630 tested samples were found to be beyond the safe nitrate limit. Delhi ranks eighth on this scale of pervasiveness.
Public Health and Environmental Impact
Nitrate contamination is a grave environmental and public health concern, particularly in areas with intensive agriculture where nitrogen-based fertilisers and animal waste are common. When consumed, high nitrate levels in water can lead to methemoglobinemia, commonly known as blue baby syndrome, in infants, which restricts oxygen in the bloodstream.
While adults may tolerate slightly higher concentrations, the prescribed limits are critical. The CGWB submission explicitly stated, "If the limit is exceeded, water is considered unfit for human consumption." Beyond the immediate threat to infants, scientific studies link prolonged exposure to high nitrate levels with increased risks of cancer, thyroid disorders, and acute oxygen deficiency.
Contrary to the assumption that monsoon rains dilute pollutants, the CGWB report highlighted a paradoxical effect. Post-monsoon, nitrate concentrations often increase due to surface runoff from agricultural fields. During heavy rains, fertilisers and contaminants are washed from the soil into aquifers, further polluting the groundwater. Data confirms this trend, showing 30.77% of samples exceeded limits pre-monsoon, rising to 32.66% post-monsoon.
The CGWB has indicated that a detailed national groundwater quality assessment will be released in September 2026. For now, the current findings paint a dire picture of a vital resource under threat, demanding urgent policy intervention and public awareness to mitigate the escalating health crisis.
