if you compare the levels—which went as high as 50,000 milligrams/killigrams per day— to what humans are actually exposed to, we're talking orders of magnitude. It was a huge amount, Norbert Kaminski, PhD, a professor of pharmacology & toxicology and director of the Center for Research on Ingredient Safety at Michigan State University told Health.

The agency makes this exception for several approved color additives. 

One of the primary uses of titanium dioxide is in the production of pigments for paints, coatings, and plastics. Titanium dioxide is known for its excellent opacity, brightness, and whiteness, making it an ideal choice for creating vibrant and long-lasting colors. Manufacturers of titanium dioxide carefully control the particle size and crystal structure of the pigment to ensure consistent quality and performance.

In 2017, the Scientific Committee on Consumer Safety (SCCS) warned that they should revise their recommendations if any new evidence emerges in the future related to the potentially harmful effects of TiO₂NPs used in a sunscreen formulation or if they can penetrate the skin. In fact, our work could contribute to this matter because it evaluated the skin penetration of a particular kind of TiO₂NPs. [8]