Evaluation of the contamination of edible leaves in the cotton-growing zone of Kérou and Péhunco (Benin) by metallic trace elements, pyrethroids and glyphosate

Abstract

In the regions of Kérou and Péhunco in northern Benin, vegetable crops are found within the cotton fields, exposing consumers to worrying health risks. This article therefore aims to assess the level of contamination of edible leaves by the pesticides used and associated metals. A total of ten samples of each edible leaf were collected and analysed in the laboratory. After sample preparation, heavy metals were identified by atomic absorption spectrometry, while active pesticide substances were investigated by chromatography combined with spectrometry. The results indicate that the vegetable varieties (okra, sorrel leaves, nightshade, bean leaves) have lead concentrations between 0.07 mg/kg and 0.53 mg/kg. The highest copper content was found in nightshade (6.94 mg/kg ± 1.59) and the lowest in sorrel leaves (1.13 mg/kg ± 0.08). The highest zinc content (19.7 mg/kg ± 8.04) was found in nightshade and the lowest in sorrel leaves (6.27 mg/kg ± 0.68). Bean leaves had a high concentration of cypermethrin (39.4 mg/kg ± 2.21) while okra was low (9.80 mg/kg ± 1.73). The highest content of deltamethrin was found in sorrel leaves (32.8 mg/kg ± 1.85) and the highest content of glyphosate (2.92 mg/kg ± 0.28) was found in bean leaves. These results show that almost all vegetables are contaminated with lead, copper, zinc, cypermethrin, deltamethrin and glyphosate. This could have consequences for the health of the consumers (occurrence of diseases) of these vegetables, especially those which have a high content (above the permitted threshold) of these chemicals and toxic metals. In view of these findings, farms should be zoned according to each type of crop to avoid contamination of food crops.