Safety of titanium dioxide nanoparticles in cosmetics

Titanium dioxide (TiO₂ ) is widely used in a variety of products including cosmetics. TiO₂ in its nanoparticle form (nano-TiO₂ ) is now the only form used as an ultraviolet (UV) filter in sunscreens, but also in some day creams, foundations and lip balms. While its efficacy as a UV filter is proven in the prevention of skin cancers and sunburns, some concerns have been raised about its safety. Indeed, considering its small size, nano-TiO₂ is suspected to penetrate dermal, respiratory or gastrointestinal barriers, disseminate in the body and therefore constitute a potential risk to the consumer. At the skin level, most studies performed in humans or animals showed that nano-TiO₂ did not penetrate beyond the outer layers of stratum corneum to viable cells and did not reach the general circulation, either in healthy or in compromised skin. The Scientific Committee on Consumer Safety (SCCS) considers nano-TiO₂ as a non-sensitizer and as mild- or non-irritant to skin and concludes in no evidence of carcinogenicity (supported by the European Chemicals Agency), mutagenicity or reproductive toxicity after dermal exposure to nano-TiO₂ . According to the SCCS, nano-TiO₂ from sunscreens does not present any health risk when applied on the skin at a concentration up to 25%. However, the SCCS does not recommend the use of nano-TiO₂ in formulations that may lead to exposure of the consumer's lungs by inhalation (sprayable products and powders). Indeed, even if human data are sparse and inconsistent, lung inflammation was reported in animals. In 2016, the EU Cosmetic Regulation made nano-TiO₂ as an authorized UV filter, except in products that could lead to exposure of the lungs. After oral exposure, nano-TiO₂ absorption and toxicity are limited. The incidental oral exposure to nano-TiO₂ contained in lip balms is thus not expected to induce adverse health effects.