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.

Both calcium carbonate and titanium dioxide play crucial roles in various industries, but they are used for different purposes. Calcium carbonate is primarily used as a filler and pigment, while titanium dioxide is used as a whitening agent and pigment. Additionally, titanium dioxide is more expensive to produce than calcium carbonate due to its synthetic nature and complex manufacturing process.