Yet another study, this one published in 2006 by the International Agency for Research on Cancer said there was insufficient evidence to conclude that titanium dioxide causes cancer. However, the study also categorized the ingredient as a potential human carcinogen.

The Process of Gravimetric Determination of TiO2

The US and Canada, however, approve the use of titanium dioxide as a food additive. Canada's recent review of titanium dioxide reconfirmed its safety and pointed out that many of the toxicity studies the EU reviewed were not relevant to the safety of titanium dioxide as a food ingredient, and that the ban is based on an abundance of caution and uncertainty.

In a study published in the journal Environmental Toxicology and Pharmacology in 2020, researchers examined the effects of food additives titanium dioxide and silica on the intestinal tract by grouping and feeding mice three different food-grade particles — micro-TiO2, nano-TiO2, and nano-SiO2.  With all three groups, researchers observed changes in the gut microbiota, particularly mucus-associated bacteria. Furthermore, all three groups experienced inflammatory damage to the intestine, but the nano-TiO2 displayed the most pronounced changes. The researchers wrote: “Our results suggest that the toxic effects on the intestine were due to reduced intestinal mucus barrier function and an increase in metabolite lipopolysaccharides which activated the expression of inflammatory factors downstream. In mice exposed to nano-TiO2, the intestinal PKC/TLR4/NF-κB signaling pathway was activated. These findings will raise awareness of toxicities associated with the use of food-grade TiO2 and SiO2.”