Results of a recent study have shown that titanium dioxide nanoparticles used in sunscreens and further common household items may cause cancer in mice (Trouiller, B, Reliene, R, Westbrook, A et al. (2009). Titanium Dioxide Nanoparticles Induce DNA Damage and Genetic Instability In Vivo in Mice. Cancer Research. 69:8784-8789). TiO2 has been classified by IARC as possibly carcinogenic to humans - should it also be classified as carcinogenic to human, do we have enough study results for confirmation?  Is it necessary at all to use TiO2 in industrial processing or are there any alternatives available?

There are a couple of things that should be noted here (Troullier study)
Very high dose levels were given via drinking water(that also caused only very mild effects) in health mice. No effects are described for the GI tract. Extrapollation to humans suggest that such an exposure will never occur
No information is available on the distribution of insoluble TiO2, so it is unknown what percentage actually reaches the circulation
Bone marrow may be a sensitive tissue
Significant effects in the GI tract (inflammation, DNA damage) would have been expected given the effects on other organs that are less exposed

Seems that the study provides interesting information but does not justify an change in the classification of TiO2