Genotoxicity of benomyl and its residues in somatic and germ cells of mice fed on treated stored wheat grains

Swiss mice were fed for 2, 4 and 8 weeks wheat grains treated with 1, 2, and 4 g benomyl/kg and stored for 6 and 12 weeks. The maximum effect of benomyl on the induction of chromosomal aberrations was observed after feeding mice for 8 weeks with wheat grains treated with 4 g benomyl/kg and stored for 12 weeks. Its proportion differed significantly in bone marrow and spermatocyte cells, 15+/-0.51% vs. 13.4+/-0.66%, respectively, from that in nontreated mice (background level), 4.4+/-0.24% and 3.8+/-0.20%, respectively. Lengthening the storage period of treated wheat grains caused a dose-dependent increase in the frequency of sister chromatid exchanges: 8.61+/-0.34 vs. 4.16+/-0.06/cell. The proportion of sperm-head abnormalities increased by lengthening the period of storage and feeding: 7.7+/-0.41% vs. 3.25+/-0.12%. In another experiment mice were orally treated by gavage with benomyl at 50, 100, 150, 200 mg/kg; a significant and dose-dependent increase in sperm-head abnormalities was observed. These findings demonstrate that benomyl (a 50% wettable powder formulation) and its residues in wheat grains are genotoxic in mice.