The present paper summarizes the genotoxicity of titanium dioxide（TiO2），widely used in the production of paints paper and plastics, as food additives and colorants, and increasingly, as nanpoparticles in pharmaceutical and cosmetics products, based on data published in openly available scientific literature. Many studies have examined the genotoxicity of TiO2 nanoparticles, using in vitro comet assays, bacterial and mammalian cell mutation tests, chromosomal aberration assays and micronucleus assays, and in vivo and ex vivo assays. Positive results were observed in tests on DNA damage, mammalian cell mutation, mammalian cell chromosome aberration, sister chromatid exchange, conventional and cytokinesis-blocked micronuclei frequency, and hprt mutation frequency. Some studies suggest that the genotoxicity of TiO2 nanoparticles results from oxidative DNA damage. Results of studies in vivo correlated with results obtained in vitro are helpful for interpretation of the data. Genotoxicity studies with negative outcomes are also reported. A battery of standard genotoxicity testing methods covering a wide range of mechanisms is adequate to clarify the genotoxicity of TiO2 particles.
