Absorption, Distribution and Excretion of Four Forms of Titanium Dioxide Pigment in the Rat

Titanium dioxide (TiO₂ ) is a white color additive that has a long history of global approval and use in food. There is, however, considerable confusion regarding the applicability of the biological effects of novel, engineered, nano-sized forms of TiO₂ developed for nonpigmentary applications to the safety of oral exposure to food grade TiO₂ pigment. The objective of this study was to assess the absorption, distribution, and routes of excretion in rats after oral exposure to food grade TiO₂ . Four different grades of TiO₂ (200 ppm) or control (0 ppm) diets were fed to rats for 7 consecutive days, followed by control diet only for 1, 24, or 72 h. Concentrations of titanium in liver, kidney and muscle were mainly below the limit of detection (<0.1 to < 0.2 mg/kg wet weight); tissue concentrations of titanium above the LOD were in the range of 0.1 to 0.3 mg/kg wet weight for all groups. Whole blood concentrations of titanium were <0.04 mg/L for all groups. Urinary excretion of titanium was equivalent to <2% daily dose/L of urine for all groups and was generally below the limit of quantification (<0.04 mg/L). Feces represented the predominant route of excretion. These results demonstrate that there is no accumulation of titanium in tissues following consumption of diets containing 200 ppm food grade TiO₂ . No differences in systemic absorption of the 4 forms of TiO₂ were observed indicating that the bioavailability of TiO₂ is consistently low for the range of particle sizes and morphologies examined in this study.