The National Cancer Institute tested TiO₂ for possible carcinogenicity by the oral route of exposure by feeding rats and mice with TiO₂ (size not specified) at doses 25,000 or 50,000 ppm TiO₂ for 103 weeks. They concluded that TiO₂ was not carcinogenic.Also, the study with rats fed diets containing up to 5 % TiO₂ coated mica for 130 weeks showed no treatment-related carcinogenicity. Since the size and other TiO₂ properties were not specified or determined, we cannot generalize this conclusion and we have to take into account other possible outcomes of this scenario in different exposure conditions (other size/crystalline structure of TiO₂ etc.).

So what does this have to do with you?

In sunscreen, titanium dioxide is used as a barrier to keep the sun's ultraviolet (UV) rays from damaging your skin. It's processed into much smaller particles than what goes into food, called nanoparticles. In this form, it becomes transparent, and also absorbs UV light so it doesn't reach your skin.

Lithopone B301, Lithopone B311 powder is also called C.I. 77115; Pigment White 5; Barium zinc sulfate sulfide and belongs to Product Categories of Inorganic & organic chemicals; uvcbs-inorganic. Lithopone B301, Lithopone B311 powder is used in water-based paints because of its excellent alkali resistance. It is widely utilized as a whitener and reinforcing agent for rubber and as a filler and whitener for paper. Lithopone B301, Lithopone B311 powder is considered to be poisonous because it is able to liberate hydrogen sulfide upon decomposition by heat, moisture, and acids. When heated to decomposition Lithopone B301, Lithopone B311 powder emits highly toxic fumes of SOx, ZnO, and H2S.

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].

Increased severity of ulcerative colitis

The price of Titanium Dioxide in Taiwan rose considerably throughout December 2018, reaching 3,750 USD per metric ton.  The price in Taiwan is 10% higher than the average price in the previous month and 1% higher than the average price one year before. In contrast, Titanium Dioxide prices in India were flat during December 2018, and were decline when compared to the average price in the preceding yeara decline of 3% from the previous year’s price. 

There are many uses of titanium dioxide that we don't know about because they were made exempt from being on the package in 1977, said Faber, who added that nothing much has changed since – other than the FDA approving some other uses of the color additive, such as expanding the use of mica-based pearlescent pigments (prepared from titanium dioxide) as color additives in distilled spirits over recent years.

This constant high rate of ROS production leads rapidly to extreme macromolecular oxidation, here it is observed in the AOPP and MDA detected after 3 h in samples treated with bare P25TiO₂NPs (Fig. 6, Fig. 7). Macromolecular oxidation includes, among others, both protein and lipid oxidation. The ROS causes protein oxidation by direct reaction or indirect reactions with secondary by-products of oxidative stress. Protein fragmentation or cross-linkages could be produced after the oxidation of amino acid side chains and protein backbones. These and later dityrosine-containing protein products formed during excessive production of oxidants are known as advanced oxidation protein products (AOPP). They absorb at 340 nm and are used to estimate the damage to structural cell amino acids. Lipid oxidation is detected by the conjugation of oxidized polyunsaturated lipids with thiobarbituric acid, forming a molecule that absorbs light at 532 nm. Polyunsaturated lipids are oxidized as a result of a free-radical-mediated chain of reactions. The most exposed targets are usually membrane lipids. The macromolecular damage could represent a deadly danger if it is too extensive, and this might be the case. Moreover, it could be observed that cellular damage continues further and becomes irrevocable after 6 h and MDA could not be detected. This may be due to the fact that the lipids were completely degraded and cells were no longer viable. Lipids from the cell membrane are the most prone to oxidation. In fact, lipid peroxidation biomarkers are used to screen the oxidative body balance [51]. At the same time, AOPP values are up to 30 times higher for bare nanoparticles in comparison to the functionalized ones.

The so-called “barrier effect” makes it possible to achieve good anti-corrosion protection in primers.