Analysis of pesticide residues in Citrullus lanatus Thunb. and Capsicum annuum L. in Bwaise market

Abstract

A study was conducted to analyse pesticide residues in C. lanatus Thunb. (watermelon) and C. annuum L. (green pepper) in Bwaise market, Kampala. This was driven by the increased concern that heavily sprayed fruits and vegetables have pesticide residues at the time of consumption which have long term cumulative effects. In this regard a total of 18 fruits and vegetables were purchased from stalls at Bwaise market, packaged in sterile polythene and taken to the laboratory for extraction and analysis. Sample preparation and extraction was done using the multi-residue method extraction protocols for pyrethoids and organophosphorous pesticide residues. Quantification of pesticides done using gas chromatography. Identification of respective pesticides was done by comparison of retention times of the samples with that of the library spectrums of the pesticide standards. The data was analysed using R package, Excel spread sheets and graph and from this, T-tests, Dunnet’s multiple comparison test was drawn. Pyrethroid pesticides predominated the samples analysed and organophosphorous pesticides were absent in the green pepper samples analysed. In WMa Cypermethrin - 0.04760 mg/kg, Deltamethrin - 0.02694 mg/kg, Lambda Cyhalothrin - 0.02828 mg/kg and Diazinon - 0.02715. in WMb Cypermethrin - 0.01574mg/kg, Deltamethrin - 0.02462 mg/kg, Lambda Cyhalothrin 0.01896mg/kg, Diazinon - 0.02620 mg/kg, Malathion 0.01 mg/kg and Chlorpyrifos - 0.02699 mg/kg. WMc had Cypermethrin - 0.03341 mg/kg, Lambda Cyhalothrin - 0.028 mg/kg while the rest of the active chemicals were undetected. GPa had Cpermethrin - 0.01896 mg/kg, Deltamethrin - 0.02760 mg/kg and Lamda Cyhalothrin - 0.03883 mg/kg. Only Cypermethrin - 0.03502 mg/kg was detected in GPb. The pesticide residue levels detected were below the stipulated MRLs of; Chlorpyrifos 2.0 mg/kg, Cypermethrin 2.0 mg/kg, Deltamethrin 0.1 mg/kg for Capsicum annuum, Diazinon 0.02 mg/kg, Chlorpyrifos 0.05 mg/kg, Cypermethrin 0.2 mg/kg and Deltamethrin 0.05 mg/kg for Citrullus lanatus. with the exception of Diazinon 0.02715 mg/kg and 0.02620 mg/kg in the C. lanatus samples which was significantly higher than 0.02 mg/kg. The findings point to the need for continuous monitoring of pesticide contamination in foods throughout the country so as to determine their hazard levels and safety for human consumption