Food-grade titanium dioxide (E171) contains variable percentages of TiO2 nanoparticles (NPs) posing awareness about its potential effects on human and animal health. Despite many studies, the actual relationship between the physicochemical properties of E171 NPs and their interaction with biological targets is still far from clear. We evaluated the acute toxicity of E171 in invertebrate and vertebrate animals. In the nematode C. elegans, E171 up to 1.0 mg/mL did not affect worm’s viability and lifespan but significantly impaired pharyngeal function, reproduction, and development. We also focused our attention on the fate of E171 after its penetration inside the circulatory tree, investigating whether its intravenous administration to mice could result in an acute over-absorption to filter organs. A significant increase of hepatic Ti concentration and the formation of microgranulomas were observed. Interstitial inflammation and parenchymal modification were found in lung coupled with Ti accumulation, probably due to the propensity of TiO2 NPs to agglomerate, as demonstrated by transmission electron microscopy experiments showing that the incubation of E171 with serum promoted the formation of compact clusters. Overall, these data emphasize, once again, the actual risk for human and animal exposure to E171.

Food additives are used for a variety of technological or processing reasons, including to add or restore colour in a food. In European Union (EU) the safety of food additives was in history assessed by the Scientific Committee on Food, while the role of risk accessor is not in hands of the European Food Safety Authority (EFSA). Only additives for which the proposed uses is considered safe are on the EU list of authorized additives. Very recently – in May 2020, a scientific opinion was published by the EFSA, concluding that TiO2 can no longer be considered as a safe food additive, and the European Commission is expected to remove it from list of authorized food additives in near future. Our aim was to investigate the trends in the use of TiO2 in the food supply. A case study was conducted in Slovenia, using two nationally representative cross-sectional datasets of branded foods. Original sample contained 49,919 pre-packed food items, while analyses was done on N=12.644 foods (6.012 and 6.632 in 2017 and 2020, respectively) from 15 food subcategories, where TiO2 was found as food additive. Overall, we observed significantly decrease in use of TiO2 (3.6% vs. 1.8%; p<0.01) in the course of these three years. The most TiO2-containing foods were in the Chewing gum category (36.3%) in 2017, and Chocolate and sweets (45.9%) in 2020. Meanwhile in 2017 the largest within-category share of TiO2-containing foods was Chewing gum category, namely 70.3%, and those products presented over 85% of the market-share. In 2020 only 24.6% chewing gums contained TiO2, and those were accounting only 3% of the market share. In con-clusion, we showed overall decrease of TiO2 use and considerable improvements in certain food categories (particularly in chewing gums) despite the fact, that this additive has not yet been of-ficially removed from the list of authorized additives. Specific food categories (i.e. Chocolate and sweets) were identified, where product-reformulation is needed, and where official controls by authorities will be most relevant.