Safety of titanium dioxide nanoparticles in cosmetics

Abstract

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.

Rethinking Nano‐TiO2 Safety: Overview of Toxic Effects in Humans and Aquatic Animals

“…[29] Transdermal absorption is not considered a major exposure route for humans because nano-TiO 2 does not penetrate the deeper layers of skin. [30]…”

Highly Scattering Hierarchical Porous Polymer Microspheres with a High-Refractive Index Inorganic Surface for a Soft-Focus Effect

“…Inorganic powders with such characteristics mainly include titanium dioxide, zirconium oxide, and zinc oxide. However, the high opacity of the above particles, when accumulated in three-dimensional skin, causes troubles such as pores and wrinkles, contrasts with other skin, and interferes with natural makeup [ 36 ]. A commonly used foundation is often dispersed in water or oil, and it is important that the pigment has a stable and uniform dispersion phase.…”

Antimicrobial metal-based nanoparticles: a review on their synthesis, types and antimicrobial action

“…ZnO is a semiconductor metal oxide with significant antimicrobial properties that can be further improved when applied as a nanomaterial. ZnO NPs have potential application in food preservation as well as important antibacterial properties against drug-resistant bacteria due to their size, shape and surface-capping agents [129,130] Titanium dioxide is also an inorganic material that is widely used in several products, including cosmetics and orthodontic composites, due to its excellent whitening, photocatalytic, and antimicrobial properties [131,132]. When the size of titanium dioxide is reduced to the nanoscale (TiO 2 NPs), its photocatalytic property is greatly improved, generating more reactive oxygen species (ROS).…”