CHENNAI: The Tamil Nadu Pollution Control Board (TNPCB) has submitted an analysis of water and soil samples taken near Neyveli Lignite Corporation (NLC) India Limited before the southern bench of National Green Tribunal (NGT), which revealed alarming concentrations of mercury in groundwater and surface water.
The groundwater, a primary drinking source for residents, is heavily contaminated. Of nine groundwater samples tested, six showed mercury concentrations ranging from 0.0025 mg/L to 0.0626 mg/L. A sample from Vanadhirayapuram recorded an alarming 0.0626 mg/L - 62 times the permissible limit of 0.001 mg/L set for drinking water. The samples were collected on December 17, 2024.
These water sources, located 2.35-8.45km downstream of NLC’s mines, are critical for household use, possibly exposing residents to mercury’s neurotoxic effects, which include neurological disorders, kidney damage, and developmental issues in children.
Surface waterbodies, used for irrigation and domestic purposes, fared no better. The TNPCB analysed 17 samples from locations including Buckingham Canal, Paravanar, and Veeranam Lake, with 15 showing mercury levels between 0.0012 mg/L and 0.115 mg/L.
The Buckingham Canal recorded a staggering 0.115 mg/L-115 times the drinking water standard. Although classified under IS 2296 Class E (not suitable for irrigation & drinking), these waterbodies are frequently tapped by locals for domestic and agricultural use.
The contamination likely stems from fly ash from NLC’s thermal plants and mine water discharges. A 2023 Friends of the Earth (an international network of environmental organisations) study threw light on heavy metal pollution in Neyveli, though IIT Cube’s tests reported mercury below detection limits, highlighting possible discrepancies.
Mercury’s ability to bioaccumulate in fish and livestock threatens the food chain, compounding risks for communities reliant on local agriculture.
Prabhakaran Veeraarasu, environmental engineer from Poovulagin Nanbargal, who filed an intervening petition in the NGT suo motu case, said the TNPCB report clearly shows the presence of heavy metals such as mercury, lead, nickel and cadmium in both groundwater and surface water samples.
“The surface waterbodies such as Paravanar, Walajah lake, Iyyan lake and Muppaneri are used by the people for domestic and agricultural purposes and you cannot use IS 2296 class E standards for analysing it. If they are considering these lakes and rivers as class E (not fit for drinking and agriculture) then the government should declare it as not fit for drinking and agriculture. They should also say it becomes unfit because of the violations by NLC for the past 4 decades.”
The same sample tested in TNPCB lab and Cube lab shows a drastic difference in results. While most of the sample tested in TNPCB lab shows mercury presence, Cube results says mercury is below detectable levels. Similarly while Cube lab shows excess levels of nickel and lead, TNPCB lab says lead and nickel are not present.
“The contradictory results show the poor quality of the monitoring mechanisms,” Veeraarasu alleged. The NGT bench has posted the matter to June 12.
Contradiction
The same sample tested in TNPCB lab and CUBE lab shows a drastic difference. While most of the sample tested in TNPCB lab shows mercury presence, CUBE lab results says mercury is below detectable levels