Food safety in Thailand 5: the effect of washing pesticide residues found in cabbages and tomatoes

Plant protection products including pesticides are extensively used in worldwide agriculture. In order to protect consumer health, maximum residue limits (MRL) have been established in many countries and by the Codex Alimentarius Commission. In Thailand, the MRL regulation exists but is not fully enforced. Thus, the purpose of this study was to determine pesticide residues in cabbages and tomatoes sold in Thailand and to evaluate if washing vegetables by running water method can remove pesticide residues. 82 cabbage and 100 tomato samples were collected from markets in Bangkok and the metropolitan Bangkok area. They were extracted and quantitatively analyzed for 42 pesticides by GC-MS/MS. Pesticide residues were detected in all of the cabbage samples, representing a rate of pesticide detection of 100%. These samples contained pesticides at levels that exceeded the recommended MRL, denoting a 100% rate of MRL exceedance. Pesticide residues were also detected in all of tomato samples but incidence of MRL exceedance in tomato samples was 82%. Washing cabbages under running water significantly reduced carbofuran residues by 93% and dimethoate residues by 65% (p < 0.05). In contrast, the running water method did not significantly reduce pesticide residues (p > 0.05) in tomato samples. Therefore, this study has documented evidence of remarkable pesticide residues detected in the cabbage and tomato sold in Thailand. These strongly suggest that Thai government authorities should implement the proper routine monitoring program of pesticide residues in vegetables and fruits. Washing vegetables before consumption is advisable as this considerably reduces the risk of exposure to pesticide residues.