Nitrate levels across parts of 502 districts in 26 states and UTs are beyond the permissible levels, the Central Ground Water Board has informed.
Citing CGWB's 2025 Annual Ground Water Quality Report, Minister of State for Chemicals and Fertilisers Anupriya Patel told the Lok Sabha in a written reply that 20.71 per cent of the groundwater samples analysed showed nitrate concentrations exceeding the permissible limit of 45 mg per litre.
"Nitrate contamination above the permissible limit has been observed in parts of 502 districts across 26 states/UTs," the minister said. The government, however, admitted that the CGWB has not carried out any specific studies on pesticide residues, the environmental impact of excessive fertiliser use, health effects of agrochemical use, or soil degradation linked to agricultural chemicals.
The minister was responding to a question from Congress MP Prabha Mallikarjun, who represents Davanagere in Karnataka. In Davanagere constituency, Patel said that of 19 groundwater samples tested in the district, seven (36.8 per cent) exceeded the permissible nitrate limit and two (10.53 per cent) exceeded the permissible fluoride limit, while none breached the electrical conductivity threshold.
What are the harmful effects of nitrate contamination?
As per the CDC, acute acquired methemoglobinemia is the most important adverse health effect caused by excessive nitrate or nitrite exposure.
Experts also point out that the risk of specific cancers and birth defects may be increased when nitrate is ingested. According to a review cited in the National Library of Medicine, the strongest evidence for a relationship between drinking water nitrate ingestion and adverse health outcomes (besides methemoglobinemia) is for colorectal cancer, thyroid disease, and neural tube defects.
Methemoglobinemia (MetHb) is a rare blood disorder that affects how the red blood cells deliver oxygen throughout the body.
