The Veeranam lake in Cuddalore district of Tamil Nadu, which supplies water to Chennai, contains toxins above the recommended levels prescribed by the World Health Organisation (WHO), according to a study conducted by the University of Madras and Presidency College. Cyanotoxins, produced by Cyanobacteria, that can affect the liver, the nervous system and cause skin diseases in humans were identified in the samples that were collected from the 11.2 km stretch of the lake.
The samples for the study were collected between August 2018 and March 2019, across three seasons. The study, published in the Springer Nature Environmental Sciences Europe journal on January 2, said that while the WHO only recommends one microgram of toxins per litre of potable water, the Veeranam lake has around 17.72 and 19.38 micrograms of Leptolyngbya and Desertifilum toxins per litre.
While Leptolyngbya, a well-known genus of cyanobacteria, is found in various ecological habitats including marine, fresh water, swamps, and rice fields, Desertifilum is usually found in hot and dry conditions.
The existence of Cyanobacteria has been linked to the usage of fertilisers in the farms located nearby and to industries that are potentially releasing unprocessed waste into the water body. It is believed that the water containing phosphorus and nitrogen that washes away into the lake from nearby farms could also be a major reason.
M Jaikar Jesudos, Engineering Director (ED) of the Chennai Metro Water Supply and Sewerage Board (CMWSSB) told TNM that the department has taken cognisance and will be sending samples from the lake to a National Testing Laboratory to reconfirm. “At present, only 10% of Chennai is getting water from Veeranam. We will ensure that the testing is swiftly done and a decision is arrived at to tackle the problem if it exists.”