Pesticide residues in ginned cotton and gin motes. Case study of Zimbabwe

Abstract

Pesticides that are applied by farmers on cotton can find their way to further processes such as ginning. The contamination of cotton lint and cotton waste (such as gin motes) from the ginning process with pesticides leads to a compromise in the cotton lint quality for lint intended to be sold to the export market and may also be a source of health risk due to exposure to pesticide residues. This study therefore set forth to determine the levels of endosulfan, carbaryl, dimethoate, lambda cyhalothrin and fenvalerate in ginned cotton and gin motes. Samples were obtained from two local ginneries and soxhlet extraction was used for isolation of the pesticide residues followed by sample clean-up using solid phase extraction (SPE). The analytical procedure was done using gas chromatography with electron capture detector (GC/ECD) for endosulfan and liquid chromatography tandem mass spectrometry (LC/MS/MS) for carbaryl, dimethoate, fenvalerate and lambda cyhalothrin. Results indicated that concentrations of carbaryl and dimethoate in all samples were below detection limits. In ginned cotton maximum concentrations of endosulfan, fenvalerate and lambda cyhalothrin were 0.93ppm, 0.37ppm and 0.06ppm respectively and for gin motes 0.33ppm, 0.33ppm and 0.09ppm respectively. The presence of pesticide residues in ginned cotton and gin motes was attributed to intensive application of pesticides during cotton farming and use of persistent pesticides such as endosulfan at later stages of the plant growth.