The most significant uncertainty identified by the EU experts was the concern that TiO₂ particles may have genotoxic effects. Genotoxicity refers to the ability of a chemical to directly damage genetic material within a cell (DNA), which may lead to cancer in certain situations. Although the experts did not conclude that TiO₂ particles in E171 are genotoxic, they could not rule out the concern that they might be.

The RGB LED panel was made ad hoc, and configured for solar simulation white light (including the absorption spectra of the nanoparticles: 390–410). No heat was detected at the working distance. The retina of the albino male Wistar rats were not affected under these conditions, because the intensity and time of the applied irradiation was lower than the regular fluorescent lamp bulb in the room (216.65 W/m2) [34].

Dongfang Titanium Industry R-5568 titanium dioxide with zinc salt stabilizer, zirconium, aluminum, silicon coating. It has the characteristics of high blue phase, easy dispersion, high weather resistance, high hiding power, low oil absorption, good system compatibility, and excellent processing rheology. It is a high-quality titanium dioxide for plastics. Dongfang Titanium R-5568 titanium dioxide is recommended to be widely used in polyolefin, PVC, ABS, PS and other color masterbatches, profiles, plates and pipes, and can also be used in leather color paste, oily paint and other industries.

Titanium dioxide is considered safe for use in cosmetics products by expert bodies around the world, including Europe's Scientific Committee on Consumer Safety (SCCS) and the U.S. Food and Drug Administration (FDA). Nano grade titanium dioxide has been assessed by the SCCS and is approved by the European Commission for use as a UV filter.

Animal studies have shown that, when consumed as a food additive, titanium dioxide can induce intestinal inflammation.

In an early study Jani et al. administred rutile TiO₂ (500 nm) as a 0.1 ml of 2.5 % w/v suspension (12.5 mg/kg BW) to female Sprague Dawley rats, by oral gavage daily for 10 days and detected presence of particles in all the major gut associated lymphoid tissue as well as in distant organs such as the liver, spleen, lung and peritoneal tissue, but not in heart and kidney. The distribution and toxicity of nano- (25 nm, 80 nm) and submicron-sized (155 nm) TiO₂ particles were evaluated in mice administered a large, single, oral dosing (5 g/kg BW) by gavage. In the animals that were sacrificed two weeks later, ICP-MS analysis showed that the particles were retained mainly in liver, spleen, kidney, and lung tissues, indicating that they can be transported to other tissues and organs after uptake by the gastrointestinal tract. Interestingly, although an extremely high dose was administrated, no acute toxicity was observed. In groups exposed to 80 nm and 155 nm particles, histopathological changes were observed in the liver, kidney and in the brain. The biochemical serum parameters also indicated liver, kidney and cardiovascular damage and were higher in mice treated with nano-sized (25 or 80 nm) TiO₂ compared to submicron-sized (155 nm) TiO₂. However, the main weaknesses of this study are the use of extremely high single dose and insufficient characterisation of the particles.

It's also used in sunscreens as a UV filtering ingredient, helping to protect a person's skin by blocking absorption the ultraviolet light that can cause sunburn and cancer.

This constant high rate of ROS production leads rapidly to extreme macromolecular oxidation, here it is observed in the AOPP and MDA detected after 3 h in samples treated with bare P25TiO₂NPs (Fig. 6, Fig. 7). Macromolecular oxidation includes, among others, both protein and lipid oxidation. The ROS causes protein oxidation by direct reaction or indirect reactions with secondary by-products of oxidative stress. Protein fragmentation or cross-linkages could be produced after the oxidation of amino acid side chains and protein backbones. These and later dityrosine-containing protein products formed during excessive production of oxidants are known as advanced oxidation protein products (AOPP). They absorb at 340 nm and are used to estimate the damage to structural cell amino acids. Lipid oxidation is detected by the conjugation of oxidized polyunsaturated lipids with thiobarbituric acid, forming a molecule that absorbs light at 532 nm. Polyunsaturated lipids are oxidized as a result of a free-radical-mediated chain of reactions. The most exposed targets are usually membrane lipids. The macromolecular damage could represent a deadly danger if it is too extensive, and this might be the case. Moreover, it could be observed that cellular damage continues further and becomes irrevocable after 6 h and MDA could not be detected. This may be due to the fact that the lipids were completely degraded and cells were no longer viable. Lipids from the cell membrane are the most prone to oxidation. In fact, lipid peroxidation biomarkers are used to screen the oxidative body balance [51]. At the same time, AOPP values are up to 30 times higher for bare nanoparticles in comparison to the functionalized ones.

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