Nanomaterials have been emerging as a new group of contaminants in the environment. We reported the use of a bacterial reverse mutation assay (Ames assay) to evaluate the mutagenicity of five metal oxide nanoparticles Al(2)O(3), Co(3)O(4), CuO, TiO(2), and ZnO in this study. Results showed the mutagenicity was negative for four nanoparticles (Al(2)O(3), Co(3)O(4), TiO(2), and ZnO) up to 1000mug/plate to all three tested strains without S9 metabolic activation. Using a preincubation procedure and high S9 (9%) activation, TiO(2) and ZnO induced marginal mutagenesis to strain Escherichia coli WP2 trp uvrA. CuO displayed low mutagenic potential to Salmonella typhimurium TA97a and TA100 at specific concentrations. However, the colony inhibition effect of CuO was predominant to the strain E. coli WP2 trp uvrA. A dose-dependent inhibition of Escherichia coli WP2 colony was found under CuO exposure at concentration range of 100-1600mug/plate. No growth inhibition of tested bacterial strains by Al(2)O(3), Co(3)O(4), and ZnO was observed at the concentrations used.
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