The titanium dioxide (TiO2) referred as E171 is a commonly used food additive. Approximately 1/3 of E171 particles are of nanometric size. Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRA, ENVT, INP-Purpan, UPS, Toulouse, France conducted in vivo studies in rats, to evaluate gastrointestinal absorption and impact of E171 food grade titanium dioxide compared to TiO2 nanoparticles . Used at a relevant dose with regard to the estimated human dietary exposure to E171 (10 mg/kg/day) the researchers carried out two sets of experiment, after 7 days of intra gastric delivery or after 100 days of chronic exposure through drinking water. After one week of exposure titanium could be detected in several compartments of intestinal tract such as Peyers’ Patches’, as well as in the liver showing the translocation of TiO2 from the gut to blood stream (see Figure). However, no DNA damage was observed in these animals. Abnormalities associated to E171 exposure were found in animals exposed for 100 days (4 on 11) and consisted in colorectal preneoplastic lesions that were more frequent in rats previously treated with an experimental carcinogen. The levels of cytokine expression in colonic mucosa indicated that 100 days of E171 treatment could impair also immune functions.
The main interest of this study is to bring in vivo data that were until now missing about the consequences of chronic exposure to the E171 food additive. However, these effects cannot be specifically attributed to the fraction of nanosized particles of TiO2 contained in E171. This work highlights the necessity to perform additional studies such as carcinogenesis studies following the OECD guidelines (two years, groups of 100 animals) that should help to clarify the safety of this frequently used food additive.