Dithiocarbamate residue levels in selected vegetables from Bukavu Region, Democratic Republic of Congo

Abstract

This study involved a survey on the use of dithiocarbamates in agriculture practices in Bukavu Region and the determination of their residues in vegetables (tomatoes and cabbages) from five main sites supplying Bukavu town with vegetables. The survey revealed that mancozeb, traded under the name of Dithan-45 was the main dithiocarbamate widely used, especially in the tomato crops against pests. It was also realised that farmers were not well trained in how to handle the pesticide and as a result, they were not informed of any consequence that could result from the misuse or the mishandling of mancozeb. Analytical method based on HPLC-UV, developed by Codex Committee on pesticide residues was employed for the analysis of mancozeb residues from vegetables samples (tomatoes and cabbages) collected from Bukavu region in DRC. A total of 75 vegetable samples were collected from different fields of five main sites known to supply Bukavu town with vegetables. The laboratory analysis showed a Limit of Detection of 0.01 mg/kg, the recoveries ranged from 73.5 to 82.1 % for cabbages and 64.0 to 66.9 % for tomatoes. The concentration of the residues expressed as mancozeb (the factor conversion for mancozeb derivative = 1.13) in tomatoes varied (in mg/ kg) from no detectable values (ND) to 1.33 for Kamanyola, ND to 1.87 for Nyangezi, 1.44 to 3.99 for Katana, 1.54 to 4.06 for Miti and ND to 4.65 for Mudaka samples. The average values ± SD (Standard Deviation) in mg/ kg for the five study sites were 0.89 ± 0.35, 1.31 ± 0.44, 2.48 ± 1.02, 2.71 ± 0.82 and 3.25 ± 1.25 respectively. The results further show that 24 % of the tomato samples had mancozeb residue values above the MRLs of European Food Safety Authority and 33 % above the MRLs set by EPA, while 73 % were not good for consumption with regards to the maximum permitted level for dithiocarbamates in tomatoes (1 mg/ kg) in Germany. On the other hand, 83% of cabbage samples from all sites had no detectable mancozeb residue levels and the rest had less than 0.1 mg/ kg.