Recent analysis show that Endosulfan residues remain in sediments at drinking water sources in some villages of Kasaragod district though their presence in water is below detectable levels.
Studies done by the State Council for Science, Technology and Environment, on orders from the government, reported that Endosulfan was still present in soil and sediment in and around the estates of Plantation Corporation of Kerala; ten years after the company discontinued aerial spraying of the pesticide in its plantations.
Endsoulfan was present in ponds and surangams (a horizontal well usually dug into hard laterite rock formations). Surangam is a traditional water harvesting system commonly used by people of the district.
The Centre for Water Resources Development and Management (CWRDM), Kozhikode, and Salim Ali Centre for Ornithology and Natural History (SACON), Anakatty, analysed water, soil and sediment samples from 11 villages of the district exposed to the spraying of the pesticide. Endosulfan was detected in at least one of the soil or sediment samples collected from all those villages. (The villages surveyed are Badiyaduka, Bellur, Muliyar, Enmakaje, Karaduka, Kumbadaje, Ajanur, Kallar, Panathady, Kayyur-Cheemani and Pullur- Periya).
The concentration of Endosulfan detected in water samples was lower than in sediment or soil samples and was within the safe limits prescribed by the World Health Organisation. (The latest view among scientists is that there are no safe limits for endocrine disruptors such as Endosulfan). They were reported as below detection level of one part per billion.
The research team from CWRDM had collected 20 sediment samples from the panchayats including some depth samples. Endosulfan was detected in 11 samples. The maximum concentration of Endosulfan detected was in the sample from Kallar panchayat (6.22 microgram/Kg). The source of sediment was a valley slope where the runoff water from the nearby plantation area got clogged and sorted down. Of ten soil samples collected, Endosulfan was detected in six samples.
SACON detected Endosulfan in five of ten soil samples collected and four of the 20 sediment samples collected. The maximum concentrations were detected from Bellur (25.96 microgram/Kg) and Kallar (20.85 microgram/Kg). The CWRDM reported a high value of 16.91 mcirogram per kilogram in sample collected from near the helipad in Periya plantation. The site was primary used for cleaning as well as filling pesticides into the sprayers of helicopters. Spraying was continued from the late nineteen seventies to December 2000.
Endosulfan sulphate, metabolite of endosulfan, was detected in two of the 30 soil and sediment samples collected. Endosulfan suphate is of comparable toxicity with Endosulfan and the estimated half-lives for the combined toxic residues range from nine months to six years, the study report said. Endosulfan is more persistent in acidic environment and all water, soil and sediment samples showed acidity.