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Titanium dioxide nanoparticles, also called ultrafine titanium dioxide or nanocrystalline titanium dioxide or microcrystalline titanium dioxide, are particles of titanium dioxide (TiO2) with diameters less than 100 nm. Ultrafine TiO2 is used in sunscreens due to its ability to block ultraviolet radiation while remaining transparent on the skin. It is in rutile crystal structure and coated with silica or/and alumina to prevent photocatalytic phenomena. The health risks of ultrafine TiO2 from dermal exposure on intact skin are considered extremely low,[1] and it is considered safer than other substances used for ultraviolet protection.
Nanosized particles of titanium dioxide tend to form in the metastable anatase phase, due to the lower surface energy of this phase, relative to the equilibrium rutile phase.[2] Surfaces of ultrafine titanium dioxide in the anatase structure have photocatalytic sterilizing properties, which make it useful as an additive in construction materials, for example in antifogging coatings and self-cleaning windows.
In the context of TiO2 production workers, inhalation exposure potentially presents a lung cancer risk, and standard hazard controls for nanomaterials are relevant for TiO2 nanoparticles.