Removal of malathion residues on lettuce by washing.

Abstract

Malathion (S-1,2-bis(ethoxycarbonyl)ethyl O,O-dimethyl phosphorodithioate), a broad-spectrum insecticide, was used in California to eradicate infestations of the Mediterranean fruitfly (Medfly-Ceratitis capitata) (Segawa 1991). Under the eradication program, malathion in a protein-sugar bait was applied by helicopters over extensive agricultural and residential areas where many of the over 260 host plants susceptible to Medfly infestation could be found (Foote 1993). Homeowners were concerned about consuming fruits and vegetables grown in home gardens that were exposed to the bait sprays. Water rinsing or washing has been reported to remove malathion residues from vegetables (Smith et al. 1955, Wallis et al. 1957). The extent to which pesticide residues could be removed from treated produce by washing may be influenced by a variety of factors such as the chemical properties and formulation type of the pesticide, the nature of the commodity, the length of time that the residue has been on the commodity’s surface, and the rinsing time and rinsing agents used (Smith et al. 1955).