A few non-dietary studies have reported adverse effects in the gastrointestinal tract of laboratory animals given food-grade TiO2. However, these same effects were not seen when the same or higher doses of food-grade TiO2 were administered in the animals' diet. Dietary studies best reflect how humans are exposed to TiO2 from food. Thus, the Food Directorate placed the most emphasis on the results of these studies in the state of the science report.
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While IARC listed titanium dioxide as “possibly carcinogenic to humans,” they also add that “there is inadequate evidence in humans for the carcinogenicity of titanium dioxide.” Of the four human studies that they reviewed, only one showed a potential risk for occupational workers inhaling titanium dioxide particles and lung cancer, while the other three showed no risk for cancer at all. And it’s key to note that IARC did not assess the effects of titanium dioxide found in foods.