Recent UK studies advise of strong health risks when using Titanium Dioxide (TiO2) in nanoparticle form in powdered mineral makeup. These inhaled TiO2 nanoparticles coming in contact with living tissue have a similar effect as asbestos and could cause lung cancer.
However, TiO2 is safe when contained in cream form as it cannot then become airborne. This is typically the case in sun screens. In cream form, TiO2 stays on the upper layers of the skin and does not come in contact with living tissue.
Titanium Dioxide is often used in cream form in products to provide all-natural mineral-based sun protection. It is not used in powered form. TiO2 particles in products are a larger size (not a nanoparticle) and is additionally coated with stearic acid to further prevent interaction with living tissue.
An excellent study was published in the Journal of Nanobiotechnology: Nanoparticles - known and unknown health risks