Testing samples were made mixing 100 uL of TiO₂NPs suspensions (0.2 mg/mL and 0.02 mg/mL) and vitamins@P25TiO₂NPs (0.2 mg/mL and 0.02 mg/mL) with 100 μL ATCC 29,213 methicillin-sensitive Staphylococcus aureus (MSSA) (10⁷ in PBS, pH 7). Controls were made replacing nanoparticles with the same volume of PBS. The concentrations of nanoparticle suspensions were chosen based on the FDA approved maximal and the minimal amount usually found in sunscreens, which are 20% and 2% (this is equivalent to 0.2 mg/mL and 0.02 mg/mL for nanoparticles suspensions). The cream concentration, on the other hand, was an intermediate value of 10%.

But in the U.S., titanium dioxide is found all over the grocery shelves. Candy like Skittles, Starbursts, and Jell-O, gum like Trident White peppermint gum and Mentos Freshmint Gum, cake products like Duncan Hines Creamy Vanilla Frosting, and Nabisco Chips Ahoy! cookies are just a few of the myriad food items that contain the additive.

For years scientists have raised concerns about the potential toxicity of titanium dioxide. 

Relative Density Among commonly used white pigments, lithopone has the smallest relative density. Among white pigments of the same mass, titanium dioxide has the largest surface area and the highest pigment volume.

The ROS seemed to be endlessly produced by P25TiO₂NPs upon irradiation, since the values detected after 6 h are similar to the ones after 3 h. However, the amount of vitamin B2 in the surface of the NPs proved to be enough to decrease the ROS detected even after 6 h. Statistical analysis showed a significant difference between C and A. p < 0.05

Lithopone: an alternative to titanium dioxide

Prof Matthew Wright, both a member of the FAF Panel and chair of EFSA’s working group on E 171, said: “Although the evidence for general toxic effects was not conclusive, on the basis of the new data and strengthened methods we could not rule out a concern for genotoxicity and consequently we could not establish a safe level for daily intake of the food additive.”

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].

From dyes to flavorings, many people are becoming increasingly aware of the ingredients in their food.

The mineral appears to have low skin penetration, but it is a greater concern when inhaled frequently over time.