Titanium Dioxide
Titanium Dioxide is an inorganic (physical) sunscreen agent conforming to the formula of titanium dioxide (CAS #13463-67-7). It functions as a UV absorber/filter, cosmetic colorant, and opacifying agent. It provides broad-spectrum UV coverage, with strongest protection in the UVB and UVA II range (290–350 nm) and weaker coverage in the UVA I range (350–400 nm). A 2016 study indicates it works primarily by absorption rather than reflection in the UV spectrum.
Titanium Dioxide offers broad-spectrum UV protection (UVB and UVA II) and is highly photostable, meaning it does not degrade significantly upon sun exposure. Regular (non-nano) sized particles have a strong safety profile — they are non-irritating and are not associated with estrogenic or other systemic health concerns linked to some chemical filters. It is considered one of the most reliable UV-filter agents currently approved, particularly in the US market.
Regular-sized Titanium Dioxide is cosmetically inelegant — it is difficult to spread and leaves a noticeable white cast on skin. Nano-sized particles, used to improve spreadability and reduce whitening, raise concerns about potential skin penetration, protein complex formation, and free radical generation, though studies as of the source's citations have not demonstrated significant percutaneous penetration in sunscreen formulations. Cosmetic restrictions apply (IV 143, VI 27, VI 27a for nano form).
