Potential Use of Esterases As Markers of Aquatic Pollution By Organophosphate and Carbamate Pesticides

Presented at the Southern African Society of Aquatic Scientists Conference 2004,Potential Use of Esterases As Markers of Aquatic Pollution By Organophosphate and Carbamate Pesticides Pesticides are used to widely in agriculture in Southern Africa. Many of these pesticides fall into the category of either organochlorines, pyrethroids, organophosphates or carbamates. We have been interested in the possible use of esterase is as biomarkers of environmental water pollution. Amongst the compounds we have studied are dimethoate, pirirniphos, malathione and monocrotophos. We have studied the effects of these pesticides on the esterase of aquatic molluscan species such as Lymnaea natalensis and Helisoma duryi and Physa acuta. The esterases studied include choline and non-choline esterases and activity was measured using different substrates namely, a-naphthyl acetate, phenyl acetate, 4-nitrophenyl acetate, acetyl thiocholine and S-butyryl thiocholine. Our data indicates that there is a marked species difference in the response to these pesticides. In addition we have found that carbamate pesticides inhibit esterase activity to a lesser extent than do organophosphates and that this inhibition is time and dose dependent. In general esterase activity has been shown to be inhibited by as little as one ppm within eight hours of exposure. Our date supports the results of studies conducted elsewhere in freshwater, estuarine, as well as marine organisms that suggest inhibition of esterase activity in aquatic organisms is a potential biomarker of water pollution. A review of the literature will be provided in addition to data generated in our laboratory.,SETAC Afric