What do you need to know about titanium dioxide?

The most common industry method to produce titanium dioxide is the sulphate process. This method involves treating ilmenite ore with sulphuric acid at high temperature to produce titanium sulfate. The resulting titanium sulfate is purified and converted into titanium dioxide. The method is common due to low cost and raw material availability. It produces large volumes of titanium dioxide for applications such as paints, cosmetic products and food. However, it generates substantial by-products and is less environmentally friendly than newer methods.

There are other titanium dioxide production techniques: sol-gel, hydrothermal/solvothermal, co-precipitation, microemulsion, molten salt and aerosol synthesis. These methods control particle size, morphology and crystalline phase, and suit specific applications such as photocatalysts or industrial pigments. They see limited large-scale use due to high cost, energy demand and technical complexity. Aerosol synthesis requires temperatures of 1,000 °C to 1,500 °C.

The titanium dioxide is one of the most versatile and widely used nanomaterials in industry, with varied applications. In skincare, it functions as sunscreen filter and white pigment in sun care and colour products to provide protection and opacity. In textiles, it enhances UV resistance, thereby increasing the durability of materials exposed to sunlight. In paints and coatings, its UV-blocking ability and whiteness protect surfaces against photochemical degradation. In pharmaceuticals, it acts as an opacifier and stabiliser in formulations. It is also found in various household products, building materials, and fabrics for its protective and stabilising properties.

The titanium dioxide is well known for its sun-protecting properties. It acts as a physical sunscreen filter that absorbs UV rays across a wavelength range from about 290 nm to 390 nm, covering both UVA (320–400 nm) and UVB (290–320 nm). This helps prevent sunburn, slow skin ageing, and reduce the risk of skin cancer. At the same time, titanium dioxide acts as an antioxidant by neutralising free radicals through an electron transfer mechanism, which helps prevent signs of skin ageing.

It is also used to brighten and even out skin tone, as its opacifying and reflective properties help scatter visible light, giving skin a natural finish and temporarily camouflaging imperfections. Titanium dioxide is also used as a colourant in tinted products.

When combined with other ingredients, titanium dioxide can enhance the anti-inflammatory properties, helping to soothe skin and protect it from irritation caused by external factors such as pollution and stress. When combined with silver oxide nanoparticles encapsulated in gelatine, titanium dioxide can accelerate the regeneration of skin tissues. This combination has anti-inflammatory and antibacterial effects that promote more rapid wound healing.

In hair care, titanium dioxide is sometimes added to products for its opacifying properties and UV protection. Although it is used for its protective and cosmetic benefits, no scientific study has demonstrated a significant effect of titanium dioxide on hair growth. This issue remains unconfirmed and requires further research to assess any potential effects on hair growth.

The titanium dioxide has been used for decades in its micro-TiO₂ form in cosmetic, food, and industrial sectors. This form, with particles measuring between 250 and 400 nm, is considered safe for human health under normal use conditions. However, with the advent of nanotechnology, the nano-TiO₂ form, with particles smaller than 250 nm, has raised concerns due to its increased reactivity and potential to interact with biological tissues.

The nano-TiO₂ form, which appeared recently, raises questions due to its small size and increased reactivity. Nano-TiO₂ can access biological tissues, prompting detailed studies on their potential health effects. Here is a summary of the risks associated with each exposure route.

• Cutaneous risk of titanium dioxide.

  The nano-TiO₂ form raises concerns due to its potential to enter the bloodstream. Although a few studies have detected traces of nano-TiO₂ in urine, evidence indicates it does not pass through intact skin. Human skin has unique barrier properties that prevent nano-TiO₂ particles from reaching the dermis. Multiple studies show that particles under 100 nm do not traverse the skin. In rare cases where small amounts of nano-TiO₂ penetrate, no significant toxicity has been observed under specific conditions. Further research is needed to assess long-term effects, including on damaged skin.

• Oral risk associated with titanium dioxide.

  The titanium dioxide in nanometric form is now banned in food in all its forms due to growing concerns about its health effects. Upon ingestion, nano-TiO₂ may accumulate in organs such as the liver, spleen, kidneys, and lungs, where it can trigger toxic effects, including nephrotoxicity and liver injury. Although excreted via faeces, prolonged deposition in tissues may cause long-term effects whose mechanisms remain unclear.

  However, cosmetic products containing titanium dioxide, such as sunscreens and tinted formulations, contain much lower concentrations of titanium dioxide, and their application is topical on skin or near mucous membranes. The difference in concentration and mode of application reduces the risk of internal absorption. In cosmetic products, TiO₂ provides pigmentation and UV protection, not for food use.

• Risk of inhaling titanium dioxide.

  In industrial settings, inhalation of nano-TiO₂ may carry greater risk. Fine particles in anatase form pose higher hazards as they can cause respiratory issues. This is why the use of nano-TiO₂ in spray form is prohibited. It is crucial to implement adequate safety measures in workplaces handling titanium dioxide to minimise risk.

Nano‐TiO2 particles, due to their reactivity and persistence in aquatic environments, may pose a risk to ecosystems. In soil, they may reduce microbial diversity and disrupt ecological processes. Plant roots may absorb these particles, facilitating their spread in the environment. This may disturb photosynthesis and affect plant growth.

In aquatic environments, they accumulate in living organisms and disrupt the food chain, causing multiple toxic effects in phytoplankton and some fish. Their interaction with heavy metals and other toxic compounds increases environmental toxicity. This toxicity threatens animals, plants, and wildlife and underscores the need for research to limit contamination.

As for micro-TiO₂, although less reactive than their nano counterparts, their persistence in the environment raises concerns. They could accumulate in soils and aquatic sediments, affecting living organisms and ecological processes over the long term.

These impacts highlight the need to continue research to better understand the environmental effects of titanium dioxide, both in nano and micro forms, and to develop strategies to limit its contamination.