Concerns over Delhi’s environment have deepened after new data revealed serious contamination in the city’s groundwater. According to figures submitted by the Central Groundwater Board (CGWB) to the National
Green Tribunal (NGT), more than 20 per cent of water samples tested in Delhi contained nitrate levels above the safe limit.
The permissible limit for nitrates in drinking water is 45 milligrams per litre. However, some samples from Delhi showed levels as high as 994 mg/l, more than 22 times the acceptable standard.
Delhi among worst-affected city
With a peak nitrate reading of 994 mg/l, Delhi ranked as the fifth worst-affected state or Union territory for nitrate contamination. Andhra Pradesh recorded the highest level in the country, with nitrate concentrations reaching 2,296 mg/l.
While 20.39 per cent of Delhi’s samples exceeded safe limits, placing it eighth nationally, Rajasthan reported the highest share of contaminated samples at 49.52 per cent.
The CGWB data showed that seven of Delhi’s 11 districts were affected. These include New Delhi, north, northwest, south, southeast, southwest and west Delhi. The findings are part of the CGWB’s annual groundwater quality report for 2024, based on samples collected in 2023.
Nationally, the number of districts with excessive nitrate levels increased from 359 in 2017 to 440 in 2023. The CGWB said its consolidated national groundwater quality assessment report will be released in September 2026.
Health risks
The report warned that high nitrate levels pose serious public health risks. In infants, excessive nitrate exposure can cause methemoglobinemia, commonly known as “blue baby syndrome”, which reduces the blood’s ability to carry oxygen. While adults can tolerate slightly higher levels, water exceeding the limit is considered unsafe for human consumption.
Long-term exposure has also been linked to thyroid disorders, certain cancers and oxygen deficiency in adults.
Nitrate contamination sources
Nitrate pollution is often linked to agricultural runoff, fertilisers and animal waste. The CGWB noted that nitrate levels can rise after the monsoon due to surface runoff entering aquifers. Data showed contamination increased slightly post-monsoon, with 32.66 per cent of samples exceeding limits compared to 30.77 per cent before the rains.
Groundwater near Delhi’s landfill sites at Bhalswa, Ghazipur and Okhla was found to be heavily polluted, with several parameters crossing safe limits.
According to experts, leaking sewage systems and poorly managed septic tanks also contribute to contamination. Environmentalists warned that nitrate pollution is a “silent but serious” threat that needs urgent attention to protect public health.
