Residues and fate of endosulfan on field-grown pepper and tomato

Endosulfan (Thiodan 3 EC), a mixture of alpha- and beta-isomers, was sprayed on 92-day-old field-grown pepper and tomato at the recommended rate of 0.61 kg AI ha(-1). Plant tissue samples were collected at 1 h to 14 days after application and analysed to determine the content and dissipation rate of endosulfan isomers (alpha- and beta-endosulfan) and the major metabolite, endosulfan sulfate. Analysis of samples was accomplished using gas chromatography-mass selective detection (GC-MSD). The results indicated the formation of endosulfan sulfate as a residue component on the plant tissues and also the relatively higher persistence of the beta-isomer as compared to the alpha-isomer on pepper fruits.; The initial total residues (alpha- and beta-endosulfan isomers plus endosulfan sulfate) were higher on leaves than on fruits. On pepper fruits, the alpha-isomer, which is the more toxic to mammals, dissipated faster than the less toxic beta-isomer. Total residues (alpha- and beta-endosulfan isomers plus the sulfate metabolite) on tomato leaves revealed longer persistence (t(1/2) 4.6 days) compared to the total residues detected on pepper leaves (t(1/2) 2.0 days) 3-14 days following spraying. Persistence of the beta-isomer on pepper fruits was high 3-14 days following spraying compared to on tomato fruits. This long persistence increases risk of exposure of the consumer. In addition, the longer persistence of the total residues on tomato foliage should be considered of importance for timing the safe entry of tomato harvesters due to the high mammalian toxicity of endosulfan. (C) 1998 Society of Chemical Industry.