EVALUATION OF HEAVY METALS AND PESTICIDES CONTENTS IN MARKET-GARDENING PRODUCTS SOLD IN SOME PRINCIPAL MARKETS OF OUAGADOUGOU (BURKINA FASO)

Pesticides and heavy metals are persistent organic pollutants responsible for immune deficiency, certain types of cancer, and decreased length of pregnancy.In this study, 20 chemical pesticides and 4 heavy metals were detected from 120 samples of 4 types of vegetables and 40 samples of babenda collected from Ouagadougou principal markets. The "babenda" is a Burkinabe dish made mainly of leafy vegetables (Hibiscus sabdariffa, Amaranthus hybridus, and Cleome gynandra) coarsely chopped and millet or rice that was boiled together.A multi-residue method was developed to detect the pesticides in the samples collected by gas chromatography, with micro electron capture detector. The concentration of cadmium, lead, mercury and arsenic were obtained from the 120 vegetables samples by using an atomic absorption spectrometer. Residues of pesticides were detected in 87% of the samples, and among the positive samples, 58.40% contained concentrations higher than the limit of maximum residue (LMR). Thirteen active pesticide residues were detected in the vegetables. The contents of the majority of pesticides residues were higher than the LMR. Seven active ingredients were detected in the babenda. 50% of the samples had more than one pesticide residue. The heavy metal concentrations ranged from 0.0098 to 2.66 mg.kg -1 for Hg; 0.01 to 1.146 mg.kg -1 for Pb; 0.016 to 1.72 mg.kg -1 for Cd and 0.012 to 1.885 mg.kg -1 for As. The relative abundance of heavy metals in the vegetables followed the sequence Cd (0.018 mg.kg -1) > Pb (0.016 mg.kg -1) > As (0.012 mg.kg -1) > Hg (0.0098 mg.kg -1). In addition, the concentration of heavy metals in the samples collected from the different markets exceeded the threshold according to the lawful maximum concentration (CMR) established in France. The continuous follow-up and a strict regulation of these pollutants in the vegetables particularly, are necessary.