Sister chromatid exchange and proliferative rate index in the longitudinal risk assessment of occupational exposure to pesticides.

At present, there are more than 1,000 chemicals classified as pesticides and many reports have shown that some of them have genotoxic properties. In the present longitudinal study, possible genetic damage on a population of workers occupationally exposed to a mixture of pesticides by using sister chromatid exchange (SCE) analysis has been evaluated. As an additional cytogenetic parameter, the proportion of lymphocytes that undergo one, two or three cell divisions as well as proliferative rate index have been determined. This study was performed on the exposed group of workers employed in pesticide production, simultaneously exposed to a complex mixture of pesticides (atrazine, alachlor, cyanazine, 2,4-dichlorophenoxyacetic acid, and malathion). The blood samples of the exposed subjects were collected in three different periods: before the beginning of the new pesticide production period, after 8 months of everyday work in the pesticide production, and 8 months after the removal of subjects out of the production. In all three samplings, the mean value of SCE and number of cells with high sister chromatid exchange frequency (HFC) in the exposed group was significantly higher in the comparison with the control group. There were no differences in the proliferative rate index (PRI) between the control and exposed group, regardless of the sampling period. In both groups examined, the majority of lymphocytes were found in the second cell division, following cultivation. These results suggest that the increase in the number of SCE found in the exposed subjects is not the result of either cytotoxic or epigenetic action of pesticide mixture, but chronic occupational exposure to mixture of pesticides.