A few non-dietary studies have reported adverse effects in the gastrointestinal tract of laboratory animals given food-grade TiO2. However, these same effects were not seen when the same or higher doses of food-grade TiO2 were administered in the animals' diet. Dietary studies best reflect how humans are exposed to TiO2 from food. Thus, the Food Directorate placed the most emphasis on the results of these studies in the state of the science report.
The integrity of surface skin cells was evaluated with and without solar simulated irradiation. The integrity of the stratum corneum was significantly lower in individuals treated with P25TiO2NPs under the light in comparison to the ones that received the functionalized nanoparticles. Cell membrane suffering is evident (Fig. 9), and it is in accordance with the ROS levels and macromolecule oxidation found in vitro for the irradiated P25TiO2NPs. Disruption of the superficial skin layer was observed in all animals treated with no functionalized nanoparticles, under irradiation. This data expands the findings by the group of Professors Fubini and Fenoglio, who showed that P25TiO2NPs could impact the lipid structure at the top few microns of the stratum corneum [55]. Control skin under irradiation and without any topic formulation did not show changes in cell structure.