The most significant uncertainty identified by the EU experts was the concern that TiO₂ particles may have genotoxic effects. Genotoxicity refers to the ability of a chemical to directly damage genetic material within a cell (DNA), which may lead to cancer in certain situations. Although the experts did not conclude that TiO₂ particles in E171 are genotoxic, they could not rule out the concern that they might be.

The FDA and certain others say titanium dioxide is safe to use in foods and personal care products. The FDA provides strict guidelines on how much can be used in food. The limit is very small: no more than 1% titanium dioxide.