Comparative evaluation of the genotoxicity of carbendazim technical grade active ingredients in the Ames test and micronucleus in vivo test

Abstract

Introduction. Carbendazim is a systemic benzimidazole fungicide used against a wide range of crop diseases. The ability of carbendazim to induce the incidence of chromosomal aberrations and micronuclei in mammalian cells by influencing the processes of mitotic spindle formation in the cell cycle have been shown in various in vitro and in vivo tests. Contradictory data were obtained in the bacterial test system Salmonella/microsomes, indicating both the absence and the presence of mutagenic activity of carbendazim. The discrepancy in the results may stem from the presence of impurities. The aim of the study was a comparative evaluation of the genotoxicity of various technical products of carbendazim. Materials and methods. The genotoxicity of carbendazim was studied using the plate incorporation version of the Ames test on 5 strains of Salmonella typhimurium in the presence and the absence of metabolic activation system (+S9/-S9) and in a micronucleus test in CD-1 mice. Two technical grade active ingredients (TGAI) and an analytical standard for carbendazim were tested. Results. In the Ames test, the analytical standard of carbendazim possessed no mutagenic activity (±S9) on any of the strains. The most pronounced mutagenic effect was observed for the TGAI I in TA98 strain, the number of revertants at the maximum concentration was 5-7 times higher than that in the negative control. The positive effects of carbendazim TGAIs in the Ames test are likely mediated by the presence of impurities. Under in vivo conditions, all tested TGAIs of carbendazim induced a statistically significant and dose-dependent formation of micronuclei in polychromatic erythrocytes (PCE) of mouse bone marrow. The mean frequency of PCE with micronuclei at the maximum dose exceeded this rate in the negative control by 21-24 times. Research limitations. The study is limited to testing the mutagenic activity of two samples of carbendazim technical products and one sample of its analytical standard in both in vivo and in vitro tests. Conclusion. Taking into account the high content of the active substance in the tested TGAIs, the bacterial reverse mutation test is a highly sensitive method for assessment of the equivalence of carbendazim generic products. The use of a micronucleus test for evaluating of the equivalence of carbendazim TGAIs to the original substance is inappropriate due to the pronounced aneugenic effect.