Effectiveness of Common Household Washing of Tomatoes on the Removal of Pesticide Residues

The effectiveness of common household washing processes of tomatoes on the removal of pesticide residues was investigated in Iringa, Tanzania. Analyses of cleaned-up extracts were carried out using gas chromatography-mass spectrometry (GC-MS). Nine pesticide residues were detected in unwashed and washed samples. The compounds detected were chlorothalonil, pirimiphos-methyl, chlorpyrifos, profenofos, endosulfan sulphate, endosulfan ether, lambda cyhalothrin, cypermethrin and metalaxyl. The concentrations of chlorothalonil, pirimiphos-methyl, chlorpyrifos, profenofos, cypermethrin and lambda cyhalothrin in some unwashed and washed samples exceeded the maximum residue limits (MRLs). Washing reduced the concentrations of chlorothalonil and endosulfan sulphate in tomatoes by 22.2–98.0% (mean = 70%) and 33.3–55.6% (mean = 44.4%), respectively. The effectiveness of washing processes on the removal of pirimiphos methyl, chlorpyrifos and profenofos residues in tomatoes had mean values of 78.1%, 73.2% and 47.4%, respectively. The mean reduction of cypermethrin residues due to washing process was 70.2%, whereas that for lambda cyhalothrin was 56.7%. The effectiveness of washing process on the removal of metalaxyl residues had a mean of 44.9%. The results have shown that household washing removes large amounts of pesticide residues from contaminated crop produce, although large proportions of some compounds remain and can pose health risks to the consumers. Keywords: pesticide; organophosphorus; pyrethroid; organochlorine; tomato; household washing