Groundwater quality assessment flags elevated nitrate and iron contamination in Kerala

The groundwater quality assessment carried out by the Central Ground Water Authority across the country for the pre-monsoon period of 2025 has revealed elevated levels of nitrate and iron contamination in Kerala.

Of the 699 groundwater samples collected from the State, 32 showed nitrate concentrations above the permissible limit of 45 mg/litre. Forty-nine samples showed iron concentrations above the permissible limit.

Nitrate contamination in groundwater arises from the leaching of nitrogen-based fertilisers, animal waste and effluents from septic systems into the subsurface. Fluoride concentrations in three samples were above the maximum permissible limit of 1.5 mg/litre. None of the groundwater samples showed the presence of arsenic or uranium.

The pre-monsoon groundwater quality assessment was carried out to evaluate changes in the groundwater quality in the pre-monsoon period, focussing on key water quality parameters including electrical conductivity, fluoride, nitrate, iron, arsenic, and uranium. The samples were collected from background monitoring stations in each State.

A bulletin published by the Central Ground Water Authority based on the pre-monsoon 2025 data pointed out that elevated concentrations of nitrate may have implications for drinking water quality, including potential health concerns such as methemoglobinemia (blue baby syndrome) in infants.

While not harmful to health at low levels, high concentrations of iron can cause aesthetic and operational issues, including a metallic taste, staining of laundry and plumbing fixtures, and clogging of pipes and water systems. Iron levels above 1 mg/litre are generally considered undesirable under drinking water standards, it said.

Dr. Rajeev Jayadevan, Convener of the Research Cell of the Indian Medical Association, Kerala, pointed out that the long-term health risk of higher concentration of nitrate in groundwater involved two mechanisms, the foremost being thyroid disorders due to nitrates competitively blocking iodine uptake, and the second being a potential cancer risk. “The latter is a theoretical possibility stemming from the human gut converting the excess nitrate in drinking water to nitrosamines, which are classified by the International Agency for Research on Cancer (IARC) as Group 2A carcinogen”, he said.

Prof. V. Sivanandan Achari, Dean of the Faculty of Science and Professor at the School of Environmental Studies, Cochin University of Science and Technology, recommended regular inspection and maintenance of septic systems to avoid leaks and overflow resulting in nitrate contamination. He also suggested regular monitoring to check the increased concentration of heavy metals contamination in groundwater.