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The Central Groundwater Board (CGWB) reported that over 20 percent of groundwater samples in Delhi tested in 2023 contained nitrate levels above the permissible limit of 45 mg per litre. Some samples recorded extremely high concentrations, up to 994 mg per litre.
Background
Nitrate (NO₃⁻) is a compound of nitrogen and oxygen essential for plant growth. In water it typically originates from fertiliser runoff, animal waste and sewage. The World Health Organisation recommends a limit of 50 mg/L in drinking water.
Causes and impacts
- Agricultural runoff: Excessive use of chemical fertilisers and uncontrolled application of manure in peri‑urban farms leads to nitrate leaching into groundwater.
- Sewage and waste: Leaky septic systems and untreated sewage introduce nitrates into shallow aquifers.
- Health risks: High nitrate levels cause methemoglobinemia (blue‑baby syndrome), in which infants’ blood cannot carry enough oxygen. Chronic exposure may also contribute to cancers and thyroid disorders.
- Eutrophication: When nitrates reach lakes and ponds, they promote algal blooms that deplete oxygen and harm aquatic life.
Mitigation measures
- Improved farming practices: Balanced fertiliser use, organic farming and vegetative buffer strips can reduce nutrient runoff.
- Sanitation: Upgrading sewage treatment and repairing septic tanks will lower contamination from human waste.
- Public awareness: Educating farmers and residents about the dangers of nitrate contamination encourages responsible usage.
Source: Times of India
