While the FDA maintains that the regulated use of titanium dioxide is safe, the European Food Safety Authority and some other experts warn of potential, serious health risks.

In a study published in the journal Toxicology, researchers examined the effects of exposing human colon cancer cell line (HTC116) titanium dioxide food additives in vitro. “In the absence of cytotoxicity, E171 was accumulated in the cells after 24 hours of exposure, increasing granularity and reactive oxygen species, inducing alterations in the molecular pattern of nucleic acids and lipids, and causing nuclei enlargement, DNA damage and tubulin depolymerization,” the scientists wrote. Researchers removed the additive from the culture, then examined the results 48 hours later. They found, “The removal of E171 was unable to revert the alterations found after 24 h of exposure in colon cells. In conclusion, exposure to E171 causes alterations that cannot be reverted after 48 h if E171 is removed from colon cells.”

French researchers studied how and where E171 nanoparticles enter the bloodstream, first studying the route through pigs and then in vitro with human buccal cells, for a 2023 study published in the journal Nanotoxicology. The research showed that the nanoparticles absorbed quickly through the mouth and then into the bloodstream, before damaging DNA and hindering cell regeneration.

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