INDUCTION OF SISTER-CHROMATID EXCHANGES IN CULTURED HUMAN-CELLS BY AN ORGANOPHOSPHOROUS INSECTICIDE - MALATHION

Because malathion is a widely used organophosphorous insecticide, the effects of non-toxic concentrations (2.5-40 .mu.g/ml) on sister-chromatid exchange (SCE) frequencies were determined. Human fetal fibroblasts were exposed once or twice to malathion, with 20 h between exposures. A single exposure to a concentration of 40 .mu.g/ml resulted in a highly significant increase in the number of SCE. After a double exposure, a concentration of 20 .mu.g/ml induced an even greater increase in SCE frequencies. Comparison of SCE frequencies after single and double exposures indicated a cumulative effect; the number of exchanges at concentrations of 5 .mu.g/ml or higher was significantly greater after the double exposure. An analysis of SCE by chromosome group showed that exchanges were distributed approximately according to chromosome length.