Finally, research has shown that titanium dioxide nanoparticles do not pass the first layer of the skin — the stratum corneum — and are not carcinogenic (7Trusted Source, 15Trusted Source).
In short, no, research demonstrates that E171 is safe when consumed in normal situations.
Moreover, how we're exposed to an ingredient matters significantly in terms of our health and potential toxicity.
Research shows that inhaling titanium dioxide particles in significant quantities over time can cause adverse health outcomes. Unless you work in an industrial setting, inhaling substantial amounts of titanium dioxide is highly unlikely.
Research supports that applying titanium dioxide to the skin in the form of sunscreens, makeup, and other topical products does not pose a health risk.
Overwhelmingly, research that's relevant to human exposure shows us that E171 is safe when ingested normally through foods and drugs (1,2).
Again, other research suggests that E171 could cause harm; however, those research processes did not design their studies to model how people are exposed to E171. Research that adds E171 to drinking water, utilizes direct injections, or gives research animals E171 through a feeding apparatus is not replicating typical human exposure, which occurs through food and medicine consumption.
Read more in-depth about the titanium dioxide risk at go.msu.edu/8Dp5.