The in vitro genotoxicity of imazalil and thiabendazole fungicides and the insecticide chlorpyrifos, compounds used in Costa Rican banana plantations, was evaluated with the single-cell gel electrophoresis technique (comet assay). The comet assay is a simple, rapid and low cost technique for quantification of DNA damage. This assay detects DNA single- strand breaks and alkali-labile sites in individual cells. The effects were analyzed by using human lymphocytes exposed to doses of 0, 25, 50, 75 and 100 µg/ml of each pesticide for 30 min at 37°C. The cells were embedded in agarose, lysed, subjected to alkaline electrophoresis (pH> 13) for 20 min at 25V, neutralized and dehydrated to be stained with a fluorescent dye and later comets visualization with the epifluorescence microscope. Chlorpyrifos and imazalil induced significant DNA damage in a dose-dependent manner. Chlorpyrifos was the major inductor of DNA breaks. These results indicate that both are genotoxic compounds in vitro. Thiabendazole fungicide did not induced DNA damage using the comet assay for all concentrations tested
Keywords: single-cell gel electrophoresis, comet assay, imazalil, chlorpyrifos, thiabendazole, lymphocytes], genotoxic