Abstract
The study investigated qualitatively and quantitatively the presence of organophosphate pesticide (OPP) residues in cabbages, tomatoes and soil from vegetable gardens of Manzini region and assessed the health risk to consumers. Samples were analysed using QuEChERS extraction technique and GC-ECD. Mean recoveries of the pesticides range from 70.61% to 103.76%. Among 26 samples of cabbages analysed, 8 samples (30.77%) contained residues of dichlorvos with a mean concentration of 2.889 ± 0.617 mg/kg, 8 samples (30.77%) contained residues of dimethoate with mean concentration of 2.898 ± 0.894 mg/kg while 5 samples (19.23%) contained both dichlorvos and dimethoate. The highest concentration of dichlorvos of 5.460 ± 0.911 mg/kg was found in Ngwempisi cabbages while the lowest concentration of 0.415 mg/kg was in Mgazini cabbages. The highest amount of dimethoate of 13.150 ± 3.246 mg/kg was in Matfunjwa cabbages while the lowest amount of dimethoate of 0.106 ± 0.187 mg/kg was in Boyane cabbages. All the contaminated cabbages had residue levels above the Codex (FAO/WHO) and EU MRLs. None of the 15 samples of tomatoes was found to be contaminated with organophosphate pesticides. Out of 41 samples of soil, chlorpyrifos was detected in only 3 samples (7.32%) with mean concentration of 1.145 ± 0.136 mg/kg. The highest amount of 2.778 ± 0.134 mg/kg was found in soil from Buoyane. The health risk estimate also demonstrated that the levels of pesticides residues in cabbages pose health threat to consumers. The results of this study provide a database on the levels of organophosphate pesticide residues in vegetables in the Manzini region to the Ministries of Agriculture and Health. This will help introduce safer pesticide management practices. It will also bring awareness to the general public on the dangers of OPPs to human health and environment.
Highlights
Vegetables are rich in minerals and notable diets of Emaswati people
The concentration and peak area were used to prepare calibration curves for each analyte as shown in figures 3, 4, 5, 6 and 7 for dichlorvos, dimethoate, chlorpyrifos, malathion and profenofos respectively by using linear regression to obtain the equation of the standard curves for the tested pesticides
The results suggest that the consumers of cabbages were exposed to high concentrations of some organophosphate pesticides that may cause chronic diseases
Summary
Vegetables are rich in minerals and notable diets of Emaswati people. Because of pest and insect infestation, they are preserved with pesticides by farmers. Pesticides include chemical substances used to kill animals, plants and insects in agricultural and domestic settings such as herbicides, insecticides, fumigants, rodenticides and fungicides with different mechanisms [1]. Major classes of pesticides include; organochlorine, organophosphates, carbamates and pyrethroids. After the cessation of use of organochlorine insecticides, organophosphate pesticides (OPPs) which are derivatives of phosphoric acid became the most commonly used pesticides. Organophosphate pesticides were originally developed in the 1940s as highly toxic biological warfare agents referred to as Nerve Agents [2]
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