Determination of Organ chlorine Pesticide Residue Levels in Chewable and Leftover Parts of the Khat (Catha Edulis) Plant from Jimma Zone, Southwest Ethiopia

Abstract

Khat is one of the most consumed plants in the horn of African countries. However, it is a stimulant plant that has several side effects on the health of consumers. In addition, the fresh Khat (tender leaves) used for human consumption and the leftover part used as feed for goats and sheep often contain contaminants such as pesticide residues. The main objective of this study was to determine the concentrations of selected organochlorine pesticides in chewable and leftover parts of Khat from the Jimma zone, southwest Ethiopia. A total of 120 Khat leaves were sampled, 60 of which were chewable and purchased from local markets in Jimma city. The other 60 mature leaves were leftover Khat samples collected from three predominantly Khat-producing districts in the Jimma zone. A newly modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method was used for the extraction of the pesticides from both the chewable and leftover Khat samples. The method was validated before it was applied. Accordingly, the limit of detection (LOD), limit of quantification (LOQ), repeatability and reproducibility, and percentage recovery were determined. Target analytes were determined using GC‒MS. The spiked recovery results for eight analytes were within the acceptable range of the European Union SANCO. The study revealed that both the chewable and leftover Khat samples were contaminated by two types of OCPs out of eight target analytes. Accordingly, p,p’-DDE and p,p’-DDT were detected in 88.3% and 76.6%, respectively, of the chewable samples and in 86% and 69%, respectively, of the leftover Khat samples. The concentrations of p,p’-DDE and p,p’-DDT in chewable Khat were in the range of 34.07–45.39 and 11.17–34.15 µg/kg, respectively, and the concentrations of p,p’-DDE and p,p’ DDT in leftover Khat were in the range of 30.12–45.04 and 22.21–32.16 µg/kg, respectively. A high concentration of the metabolite (p,p’-DDE) compared to the precursor compound (p,p’-DDT) revealed the historical use of DDT in the study area. The concentrations of pesticides did not vary significantly between the sample sources (P = 0.823). Among the detected analytes, none were above the MRL values set by the FAO/WHO or the European Commission (EC). However, the chewable and leftover Khat available for consumption were contaminated with p,p-DDT and its principal metabolite p,p-DDE. Thus, the cumulative effect and synergistic toxic effect of these pesticides on Khat Consumers should be considered. Therefore, all the bodies of concern in the country need to play the crucial role of ensuring that the Khat consumed by humans and animals is not a health concern.