Sister-chromatid exchanges in human lymphocytes induced by dimethoate, omethoate, deltamethrin, benomyl and their mixture

Abstract

Dimethoate and omethoate, two common organophosphorus insecticides, induced a dose-related increase inthe frequency of siter-chromatid exchanges (SCEs) in human lymphocytes in vitro ( P of the regression lines < 0.01). Two other common pesticides, the pyrethroid insecticide deltamethrin and the systemic fungicide benomyl, induced a modest increase in SCEs which bordered on statistical significance ( P = 0.053 and 0.055, respectively). Mixtures of the four pesticides at total concentrations of 41.5 and 83 μg/ml (composed of 43% dimethoate, 43% omethoate, 12% deltamethrin and 1.2% benomyl) induced a dose-dependent increase in SCEs ( P < 0.01). The effects of these mixtures of pesticides were variable using lymphocytes from different individuals, although these difference did not attain statistical significance. Moreover, low concentrations of the four pesticides that did not increase SCEs significantly when tested alone, were positive for SCE induction when tested as a mixture. The experiments show that sub-threshold doses of pesticides may increase SCEs when present in a mixture.