Below are selected applications of photocatalytic pollutant decomposition processes on titanium oxide:
1. Self-cleaning surfaces: for the production of glass for spotlights, traffic lights, car mirrors, window panes, for road paints, for covering sound-absorbing screens and tunnel walls.
2. Air cleaning and odor removal: filters that are used in enclosed spaces (e.g. public toilets) or filters for air-conditioning equipment.
3. Water treatment: groundwater treatment installations, water purification installations in the intakes of drinking water from rivers.
4. Self-disinfecting materials: towels, linings, clothing, equipment in hospitals, wall surfaces of operating rooms.
5. Removal of lesions: anti-cancer therapy.

Mexican researchers sought to evaluate the effects of E171 across a span of conditions in mice, including its influence on behavior, along with the effects on the colon and liver. The research, published in 2020 in the journal Food and Chemical Toxicology, showed that E171 promoted anxiety and induced adenomas, or noncancerous tumors, in the colon. They also found that E171 heightened goblet cells hypertrophy and hyperplasia, which is typically seen in asthma patients and triggered by smoking or external pollutants and toxins. They also noted mucins overexpression in the mice, which can be linked to cancer cell formation. 

What's the deal with titanium dioxide?

Infrared analysis showed that the characteristics bands for the bare nanoparticles are still exhibited in the vitamins@P25TiO₂NPs spectra, such as a wide peak in 450–1028 cm⁻¹ related to the stretching vibration of Ti-O-Ti and other peaks in 1630 cm⁻¹ and 3400 cm⁻¹, which represent the surface OH groups stretching. The IR spectrum of vitaminB2@P25TiO₂NPs showed signs of binding between compounds. The OH bending peak (1634 cm⁻¹) corresponding to bare nanoparticles disappeared, and the NH₂ bending band characteristic of vitamin B2 appeared (1650 cm⁻¹). The IR spectrum of vitaminC@P25TiO₂NPs also showed signs of successful functionalization. Bands at 1075 cm⁻¹; 1120 cm⁻¹; 1141 cm⁻¹ were observed, which are originated by CO-C vibrations present in the vitamin C. The intense band at 1672 cm⁻¹ is attributed to the C = O stretching in the lactone ring while the peak at 1026 cm⁻¹ is ascribed to the stretching vibration Ti-O-C. Wide bands at 3880–3600 cm⁻¹ are related to stretching vibration OH groups, but those disappear in the modified nanoparticles spectrum. These observations confirm the interactions between the P25TiO₂NPs and the vitamins [35].