When E171 isn’t combined with other ingredients and administered in water, some studies suggest that under these artificial conditions, E171 may be processed differently in the body resulting in some biological changes in experimental animals that are poorly understood.

Prof. Maged Younes, Chair of EFSA’s expert Panel on Food Additives and Flavourings (FAF), wrote of the decision: “Taking into account all available scientific studies and data, the Panel concluded that titanium dioxide can no longer be considered safe as a food additive. A critical element in reaching this conclusion is that we could not exclude genotoxicity concerns after consumption of titanium dioxide particles. After oral ingestion, the absorption of titanium dioxide particles is low, however they can accumulate in the body.”

ZnSO4 – BaS ➔ BaSO4*ZnS

Titanium dioxide is one of the many oxides formed naturally in our environment. Manufacturers source this mined mineral from rutile, brookite, and anatase. It is then processed and refined to meet stringent safety guidelines based on the end-use for the mineral. 

Traditionally, UV-filters are categorized as either chemical or physical. The big difference is supposed to be that chemical agents absorb UV-light while physical agents reflect it like a bunch of mini umbrellas on top of the skin. While this categorization is easy and logical it turns out it's not true. A recent, 2016 study shows that inorganic sunscreens work mostly by absorption, just like chemical filters, and only a little bit by reflection (they do reflect the light in the visible spectrum, but mostly absorb in the UV spectrum).

Nanotoxicology 

The safety of the food additive E 171 was re-evaluated by the EFSA ANS Panel in 2016 in the frame of Regulation (EU) No 257/2010, as part of the re-evaluation programme for food additives authorised in the EU before 20 January 2009.  

Uses

Titanium IV oxide is also used in the pharmaceutical industry. It is often used as a coating for medications to improve their stability and appearance. Titanium dioxide helps to protect medications from degradation caused by light, moisture, and other environmental factors. It is commonly used in tablets, capsules, and other oral dosage forms to improve their shelf life and effectiveness.

North America

Production

It's also added directly to food; mainly for coloring, but also as a thickener and to keep some powdered food, like confectioner's sugar, from clumping.