The skin of an adult person is, in most places, covered with a relatively thick (∼10 μm) barrier of keratinised dead cells. One of the main questions is still whether TiO₂ NPs are able to penetrate into the deeper layers of the skin. The majority of studies suggest that TiO₂ NPs, neither uncoated nor coated (SiO₂, Al₂O₃ and SiO₂/Al₂O₃) of different crystalline structures, penetrate normal animal or human skin. However, in most of these studies the exposures were short term (up to 48 h); only few long-term or repeated exposure studies have been published. Wu et al.83 have shown that dermal application of nano-TiO₂ of different crystal structures and sizes (4–90 nm) to pig ears for 30 days did not result in penetration of NPs beyond deep epidermis. On the other hand, in the same study the authors reported dermal penetration of TiO₂ NPs with subsequent appearance of lesions in multiple organs in hairless mice, that were dermal exposed to nano-TiO₂ for 60 days. However, the relevance of this study for human exposure is not conclusive because hairless mice skin has abnormal hair follicles, and mice stratum corneum has higher lipid content than human stratum corneum, which may contribute to different penetration. Recently Sadrieh et al. performed a 4 week dermal exposure to three different TiO₂ particles (uncoated submicron-sized, uncoated nano-sized and coated nano-sized) in 5 % sunscreen formulation with minipigs. They found elevated titanium levels in epidermis, dermis and in inguinal lymph nodes, but not in precapsular and submandibular lymph nodes and in liver. With the energy dispersive X-ray spectrometry and transmission electron microscopy (TEM) analysis the authors confirmed presence of few TiO₂ particles in dermis and calculated that uncoated nano-sized TiO₂ particles observed in dermis represented only 0.00008 % of the total applied amount of TiO₂ particles. Based on the same assumptions used by the authors in their calculations it can be calculated that the total number of particles applied was 1.8 × 10¹³ /cm² and of these 1.4 x10⁷/cm² penetrated. The surface area of skin in humans is around 1.8 m²  and for sun protection the cream is applied over whole body, which would mean that 4 week usage of such cream with 5 % TiO₂ would result in penetration of totally 2.6 × 10¹⁰ particles. Although Sadrieh et al.concluded that there was no significant penetration of TiO₂ NPs through intact normal epidermis, the results are not completely confirmative.

One of the key players in the titanium dioxide manufacturing industry is CAS 13463-67-7. This factory is known for its high-quality products and state-of-the-art facilities. With a focus on innovation and sustainability, CAS 13463-67-7 has become a go-to choice for companies looking to source titanium dioxide for their dyes and pigments.

Lithopone B311 Datasheet

In summary, the Food Directorate's position is that there is no conclusive scientific evidence that the food additive TiO₂ is a concern for human health. This is based on a review of the available scientific data relevant to food uses of TiO₂. However, we will continue to monitor the emerging science on the safety of TiO₂ as a food additive and may revisit our position if new scientific information becomes available.

The trouble with titanium dioxide, by Siloam Springs Regional Hospital, Herald Leader, October 4, 2023

The biological activity, biocompatibility, and corrosion resistance of implants depend primarily on titanium dioxide (TiO₂) film on biomedical titanium alloy (Ti6Al4V). This research is aimed at getting an ideal temperature range for forming a dense titanium dioxide (TiO₂) film during titanium alloy cutting. This article is based on Gibbs free energy, entropy changes, and oxygen partial pressure equations to perform thermodynamic calculations on the oxidation reaction of titanium alloys, studies the oxidation reaction history of titanium alloys, and analyzes the formation conditions of titanium dioxide. The heat oxidation experiment was carried out. The chemical composition was analyzed with an energy dispersive spectrometer (EDS). The results revealed that titanium dioxide (TiO₂) is the main reaction product on the surface below 900°C. Excellent porous oxidation films can be obtained between 670°C and 750°C, which is helpful to improve the bioactivity and osseointegration of implants.

Titanium dioxide (E 171) is authorised as a food additive in the EU according to Annex II of Regulation (EC) No 1333/2008.  

① Coatings: The downstream demand structure of domestic and overseas titanium dioxide is similar. Coatings are the largest application fields, accounting for 61% of the consumption. Among the four components of paint products, namely resin, pigments and fillers, solvents and additives, titanium dioxide accounts for 10% to 25% of the total cost, accounting for more than 90% of the total amount of pigments and fillers, and more than 95% of the total amount of white pigments.

Hiding power

Conclusion

Titanium dioxide has a number of unique characteristics that make it ideally suited to many different applications.

There’s also concern that exposure to the mineral over time, even in small amounts, can build up in the body, particularly in the kidneys, spleen and liver. Although most of the mineral is excreted in feces, there is evidence that a small percentage may remain in bodily organs.

4. Should I stop eating products that contain TiO₂?

Overall, the Food Directorate's comprehensive review of the available science of TiO₂ as a food additive showed:

4. Refractive index: 1.70~2.25

Blanc de Comines, 27 per cent zinc sulphide, 70.5 per cent barium sulphate, 2.5 per cent zinc carbonate.