A study on the biodegradation of methyl isocyanate (MIC) and its anticholinesterase activities in different tissues of various species of fishes from the lakes of Bhopal was carried out over a period of 6 months with bimonthly observations. The concentration of the degradation product of MIC, monomethylamine, in the water of both the lakes of Bhopal was estimated. On each occasion it was found to indicate a decreasing trend. However, a depth-wise increase of concentration of monomethlamine was observed in the Lower Lake. Bioaccumulation of monomethylamine was also estimated in different tissues of various species of fishes, collected from the Lower and Upper Lakes of Bhopal and from Aligarh. Among all the species of fishes available in the Lower Lake of Bhopal, Puntius ticto was found to be the most susceptible to MIC-poisoning. There is a change in the values of pH, ammonia-nitrogen and urea-nitrogen concentrations in the Lower Lake water. The cholinesterase activities of different tissues of various species of fishes from the lakes of Bhopal were found to be quite low compared to that of fishes from the uncontaminated lake of Aligarh indicating the anticholinesterase activity of MIC.
