ASSESSMENT OF INSECTICIDE RESIDUES IN TWO TOMATO (Solanum lycopersicum L.) CULTIVARS MARKETED IN AKURE ONDO STATE, NIGERIA

Abstract

Due to the increasing food demand as well as pest infestation, the use of insecticides in agriculture is increasing. In low income countries, poor training among farmers combined with the use of multiple insecticides may result in high health risk for the consumers. In this study, nineteen organochlorines, four organophosphates and three pyrethroids were analyzed in two tomato Solanum lycopersicum L. cultivars (UTC and Roma) obtained from Shasha market in Akure, Ondo State, with the aim of assessing the level of insecticide residues in them. The analyses were carried out on unprocessed and processed (peeled, boiled and blanched) tomatoes. The insecticide in the tomato samples was extracted and cleaned using the Quick, Easy, Cheap, Efficient, Rugged and Safe (QuEChERS) European standard 15662 method for the analysis of pesticide residue in low-fat products. Aliquot from the cleaned sample was subjected to further analysis using Gas Chromatograph coupled with Mass Spectrometer detector (GC-MS). The residue levels detected in the unprocessed tomatoes were all above the European set Maximum Residue Limits (MRLs). In UTC tomato cultivar, the most effective processes for reducing insecticides includes; peeling which reduced β-cypermethrin residue by 48.60%, blanching reduced α-cypermethrin by 100%, while boiling also reduced cyfluthrin residue by 100%. It was also revealed in Roma tomato cultivar that all the processes were effective to completely remove α-cypermethrin, boiling and blanching reduced β-cypermethrin residue by 100%, while peeling was the most effective process to reduce cyfluthrin residue by 100%. Malathion and parathion insecticide residue in unprocessed tomatoes were below detectable levels until after boiling for 10 minutes before parathion residues of 1.55 and 1.28 ppm was detected in Roma and UTC tomato cultivars respectively, while malathion residue of 1.89 ppm was the only organophosphate insecticide detected in Roma tomato cultivar. In addition, dieldrin residue of 1.47 ppm was the only organochlorine insecticide that was detected in Roma tomatoes, while none was detected in UTC tomato cultivar. It can therefore be concluded that as much as persisting residues are inevitable, household processes could be effective tools for reducing and removing insecticide residues in these tomato varieties. From this study, blanching (85-87°C for 4 minutes) and boiling (100°C for 10 minutes) are the recommended household processes to reduce pyrethroid residues. In addition, Roma tomato cultivar is the best cultivar retaining lesser pyrethroid residue than UTC tomato cultivar. Furthermore, there should be regular monitoring of the tomatoes for residual pesticides by appointed regulatory government agencies. Also backyard gardens should be encouraged for the production of these vegetables for domestic consumption.