Genotoxicity induced by pesticide mixtures: in-vitro studies on human peripheral blood lymphocytes

To assess the damage caused by pesticides and their mixtures on humans, we designed in-vitro experiments to evaluate their cytotoxicity and genotoxicity. Three equimolar pesticide mixtures were investigated for their capability to affect cultured human peripheral blood lymphocytes. The LC50 values for cytotoxicity, using standard trypan blue dye exclusion and calculated by probit analysis, were 4.18, 5.76, and 7.5 mu M for endosulfan, carbofuran, and monocrotophos, respectively. When combined in equimolar concentrations, the LC50 values for cytotoxicity were 0.7, 0.9, and 1.0 mu M for monocrotophos + carbofuran, endosulfan + monocrotophos, and endosulfan + carbofuran, respectively, using the method. DNA damage was estimated using chromosomal aberrations (chromatid breaks, fragments, gaps, aneuploidy, and satellite association) and comet assays using 1/10 of the LC50 concentrations. Using a standard alkaline comet assay procedure, high concentrations of individual pesticides (0.5-4.0 mu M) caused significant DNA damage as indicated by visible tail lengths. Lower concentrations (0.05-0.5 mu M) of their binary mixtures could cause the same effect. The results suggest that analysis of genotoxicity may serve as an important biomarker for occupational and household exposure to pesticides, especially mixtures of pesticides, with different modes of action.