Prevalence and Persistence of Organophosphate and Carbamate Pesticides in Cambodian Market Vegetables

The prevalence of pesticide residue contamination in market vegetables, and the rate of pesticide disappearance from field vegetables, were assessed as indicators of the health risk to vegetable consumers in Cambodia. A total of 245 leafy vegetable and long bean samples from multiple markets in Phnom Penh were screened using cholinesterase-inhibition assays, and indicated that between 15% (long bean) and 95% (white-stemmed kale) of market vegetables contain detectable levels of organophosphate/carbamate (OP/C) pesticides. OP/C levels varied significantly between vegetable types, and between individual vegetable sellers in the markets. Methylparathion, which is banned and highly toxic, but widely used in Cambodia, was not detected in 30 subsamples analyzed with HPLC. In test plots, methylparathion rapidly disappeared after spraying, reaching levels below maximum residue limits within 10 days. Field trials with water spinach indicated dithiocarbamates also have a short half-life (approximately three days), but that overall OP/C levels on crops depend on the specific pesticides used, and on the specific field conditions. These results point towards the need for a regular monitoring programme in Cambodia to assess the extent of pesticide contamination on vegetables, and to give guidance on strategies for limiting pesticide exposure to vegetable consumers.