Over the last several years, nanoparticles have come under scrutiny for adverse health effects. Nanoparticles are ultrafine particles between 1 to 100 nanometers in diameter. (To put this in perspective, the average human hair is around 80,000 nanometers thick.) Because of their size, which can be engineered and manipulated at the atomic or molecular level, nanoparticles exhibit unique physical, chemical, and biological properties. Titanium dioxide is one of the most commonly produced nanoparticles in the world.

To be added to food, this additive must achieve 99% purity. However, this leaves room for small amounts of potential contaminants like lead, arsenic, or mercury (1Trusted Source).

Amount: if too little titanium dioxide is added, the distance between particles is too large and there is not enough opacity, while if the titanium content is too high, the particles interfere with each other and poor efficiency is obtained.

However, since it’s photosensitive — meaning it can stimulate free radical production — it’s usually coated in silica or alumina to prevent potential cell damage without reducing its UV-protective properties (7Trusted Source).