Fresh evidence has emerged about prevalence of endosulfan residues in the groundwater of Kasaragod district and recent use of the pesticide in the area.
A study by P.S. Akhil and C.H. Sujatha of the Department of Chemical Oceanography of Cochin University of Science and Technology (Cusat) reported that organochlorine insecticides, particularly high concentrations of endosulfan and BHC (hexachlorobenzene), were persisting in the environment. This was despite restrictions on use of BHC, and ban imposed by the High Court and the government on use of endosulfan. The pesticide residues which remained in the soil from earlier application become the source of pollution of water bodies through land runoff, leaching and ultimately contaminate drinking water sources.
The study, published in the journal Toxicological and Environmental Chemistry this month, found that contamination by alpha isomer of endosulfan was the highest at Panathur (58 microgram per litre) followed by Periya (37 mcg/L) in the post-monsoon season of 2010. Before monsoon in 2011, the residue levels in water were highest at Panathady (56mcg/L), followed by Rajapuram (40mcg/L). Endosulfan residues have been detected at Parappa and Perla also.
Water samples for the study were collected from different cropping fields, public and private wells across the district. High levels of alpha isomer found in water at places such as Panathady and Rajapuram suggest continued illegal use of the pesticide in the area. For, alpha isomer disappears from the environment faster than the beta isomer. (Both isomers are present in commercial endosulfan. However, it was notable that beta isomer was not detected in water except at one place, Malakkallu; that too in very low concentration. The exact reason for this is not known, though it may have something to do with solubility and binding of the isomer with soil sediments.)
The study found high levels of pesticide Aldrin (used for underground control of termites) also in water at places such as Cheemeni and Rajapuram in 2010. Highest concentrations of total residues of all organochlorine pesticides were observed at Mulleria and Cheemeni (pre-monsoon 2010), followed by Panathur and Periya (post-monsoon 2010). High levels of BHC were detected in water in these areas in 2010.
Need for protected water supply
It is notable that the study did not test soil samples which are likely to contain higher concentrations of endosulfan residues. Though the presence of endosulfan in soil sediments had long been known, the government has not taken any steps so far to decontaminate the areas. Arrangements for protected water supply are also lacking in many areas. Though quite a large number of rural drinking water projects were taken up in Kasaragod district in recent years, priority was not accorded to endosulfan-affected villages. Even the second phase of Jalanidhi scheme skipped many of those areas. Now, the study indicates that enforcement of ban on endosulfan is also lacking in effectiveness.