In vitro aneugenic effects of the fungicide thiabendazole evaluated in human lymphocytes by the micronucleus assay

Thiabendazole is a benzimidazole-derived compound widely employed in agriculture as anthelmintic and fungicide. It is also used as a post-harvest fungicide for imported citrus fruits during transport and storage, and thus, it was found at high concentration in fruits and vegetables. Several studies have analyzed the potential genotoxic effect of thiabendazole on different prokaryotic and eukaryotic systems, but in many cases, results were contradictory. In the present study, the genotoxic potential of thiabendazole have been evaluated, by micronucleus assay in freshly isolated human peripheral lymphocytes. The cells were incubated with 0.5, 5 and 50 ?g/ml concentrations of the tested substance for 48 h at 37°C. Mitomycin C at final concentration of 0.01 ?g/ml culture was used as a positive control. The results indicated that the thiabendazole significantly (P < 0.05) increased the micronucleus frequency compared with the negative control in all treatment concentrations, indicating a potential aneugenic hazard of thiabendazole in cultured human peripheral lymphocytes. The cytokinesis-block proliferation index value, however, was not decreased significantly compared with the negative control. Significant (P < 0.05) differences in the micronuclei frequency were also found between the lower dose (0.5 ?g/ml) and the other two analyzed doses of thiabendazole. In contrast, no differences were found between 5 and 50 ?g/ml of thiabendazole and between DMSO and negative control. Finally, control cultures treated with the known mutagen MMC showed a very consistent increase in MN with respect to the negative controls.