In its statement to USA TODAY, the FDA maintained that, in all post-approvals for food additives, our scientists continue to review relevant new information to determine whether there are safety questions and whether the use of such substance is no longer safe under the Federal Food, Drug, and Cosmetic Act.

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Due to its light-scattering properties, small amounts of titanium dioxide are added to certain foods to enhance their white color or opacity (1Trusted Source, 3Trusted Source).

However, it’s also important to note that such adverse effects depend heavily on the form of the titanium dioxide. It can come down to characteristics like “particle shape, purity, surface charge, solubility, agglomeration rate, photo-activation, etc.”

Lithopone is produced by coprecipitation of barium sulfate and zinc sulfide. Most commonly coprecipitation is effected by combining equimolar amounts of zinc sulfate and barium sulfide:

Having thus described the origin and uses of the pigment, we now come to the question, what is lithopone? It is, in short, a chemical compound usually consisting of 30.5 per cent zinc sulphide, 1.5 per cent zinc oxide and 68 per cent barium sulphate, but these proportions vary slightly in the different makes. Lithopone of this composition is sold as the highest grade, either as red seal or green seal, as it best suits the idea of the manufacturer. Many manufacturers, especially in Europe, sell and also export other brands under other seals, containing 24, 20, 18 and as little as 12 per cent of zinc sulphide with very small percentages of zinc oxide, the balance being usually barium sulphate, but sometimes certain portions of China clay or gypsum (calcium sulphate) or whiting (calcium carbonate). Such brands are not a chemical compound, but mechanical mixtures of the chemically compounded lithopone and the admixtures referred to.

There is some concern regarding skin and intestinal absorption of titanium dioxide nanoparticles, which are less than 100 nm in diameter.

The vitaminC@P25TiO₂NPs, on the other hand, were obtained through an optimized method based on Mallakpour et al. [27]. Initially, 0.02 g of P25TiO₂NPs were dispersed in 1 mL of ultrapure water and stirred in a Vortex. Next, 100 μL of HCl (0.01 M) were added (pH 2) to 100 uL of P25TiO₂NPs to avoid gel formation. Then, 100 μL of vitamin C dissolved in ultra-pure water (5.0 × 10⁻³ M) solution were added to the mixture and was ultrasonicated for 30 min. Finally, vitamin C was added in excess to gain a beige-orange color suspension, and the ultrasonication continued for another 30 min. The pellet obtained after centrifuging the suspension for 10 min at 4500 rpm was resuspended in ultrapure water, centrifuged again, and then lyophilized.