Most food-grade titanium dioxide is around 200–300 nanometers (nm) in diameter. This size allows for ideal light scattering, resulting in the best color (1Trusted Source).
Another important application of titanium dioxide is in the production of sunscreen and other skincare products. Titanium dioxide is a key ingredient in many sunscreens due to its ability to reflect and scatter ultraviolet (UV) radiation, providing protection against harmful UV rays. Manufacturers of titanium dioxide for sunscreen products often use special coatings and surface treatments to enhance its UV-blocking properties.



A 2023 study published in the journal Environmental Research, scientists examined the effect of titanium dioxide nanoparticles on important gut bacteria in mice. Their results showed “the growth inhibitory effects could be associated with cell membrane damage caused by titanium dioxide nanoparticles to the bacterial strains. Metabolomics analysis showed that TiO2 NPs caused alterations in multiple metabolic pathways of gut bacteria, such as tryptophan and arginine metabolism, which were demonstrated to play crucial roles in regulating gut and host health.” The researchers also found that four different neuroprotective metabolites “were significantly reduced” in urine and in vitro bacteria and vivo urine samples. The researchers concluded: “Increasing evidence implies that the gut microbiome plays a profound role in regulating host metabolism. Our results illustrated that TiO2 NPs hindered the growth of four beneficial gut bacterial strains.”
Numerous studies have linked titanium dioxide to genotoxicity and cytotoxicity. Genotoxicity refers to a chemical’s potential to cause DNA damage, which can, in turn, lead to cancer. Cytotoxicity is a general term that refers to a characteristic of being harmful to cells.
On the other hand, the U.S. Food and Drug Administration (FDA) in their Final Administrative Order on Sunscreen Drug Products posted in September 2021 still accepts titanium dioxide up to 25% in the list of Generally Recognized As Safe and Effective (GRASE) in the main document, without further clarification on what kind or size of particles [9]. However, on page 24 (Sunscreen containing nanomaterials) FDA clearly “distinguish nanomaterials from other forms of these ingredients'' (zinc oxide and titanium dioxide) and ask for comments on “any particular nanomaterials that you believe should not be permitted for use in OTC sunscreen products”. To the best of our knowledge, this Agency did not ban the use of nanoparticulate titanium dioxide in any form, even though it is mentioned on page 34 that the anatase form is the more photoactive one, due to the lack of evidence with real sunscreens OTC (over the counter) in vivo. Moreover, other regulations in Latin America (MERCOSUR agreement, 2006) do not state clearly their position on the use of nanoparticulate TiO2NPs [10].

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Declaration of Competing Interest
The refractive index, represented by the letter n, of a material describes how light propagates through and is bent by, that material. The magnitude of the refractive index, depending upon the electronic structure of the molecules, governs to what extent the path of light changes, when entering or leaving a material.
Particles in a matrix, like pigment particles surrounded by the binder system in a coating, ink or plastic, can change the propagation direction of light when the particles and the matrix have a different refractive index. This phenomenon, called scattering, results in both white color (provided that the particles do not absorb visible light) and the hiding power of the coating.


Worldwide Lithopone Industry to 2027 - Use of Lithopone in the Paints & Coatings Industry is Driving Growth - ResearchAndMarkets.com


The Sydney Morning Herald reported on the finding of nano particles in our food supply here in Australia, despite no testing every carried out on the safety of these products by our food safety body.