Regarding flavoring substances, JECFA concluded that there is no safety concern and established specifications for 21 agents across three classes: aliphatic primary alcohols, aldehydes, carboxylic acids, acetals, and esters containing additional oxygenated functional groups; linear and branched-chain aliphatic, unsaturated and unconjugated alcohols, aldehydes, acids, and related esters; and saturated aliphatic acyclic linear primary alcohols, aldehydes, and acids.

Titanium dioxide nanoparticles have also been found in human placentae and in infant meconium, indicating its ability to be transferred from mother to fetus. 

Because of its ability to absorb UV light, it's particularly useful as an ingredient in sunscreens — while its light-scattering properties are great for applications that require white opacity and brightness, such as in paint and paper.

In food products, E171 is not a singular ingredient; it’s always combined with other ingredients (e.g., proteins and fats) in the food product. Digesting food is a slow process for the body compared to drinking a beverage, which passes much faster through the body. 

What is an exposure route? 

The principal natural source of titanium dioxide is mined ilmenite ore, which contains 45-60 percent TiO₂. From this, or an enriched derivative (known as titanium slag), pure TiO₂ can be produced using the sulphate or chloride process.

The FDA's Code of Federal Regulations allows for the legal, regulated use of titanium dioxide in food products, under some restrictions.