This cytotoxic effect was also reported before; i.e. Natarajan et al. conducted an experiment that found a strong oxidative stress, morphological changes in mitochondria and substantial loss in the fusion of primary hepatocytes exposed to P25TiO₂NPs [52].

The US and Canada, however, approve the use of titanium dioxide as a food additive. Canada's recent review of titanium dioxide reconfirmed its safety and pointed out that many of the toxicity studies the EU reviewed were not relevant to the safety of titanium dioxide as a food ingredient, and that the ban is based on an abundance of caution and uncertainty.