What should you know about titanium dioxide?

Titanium dioxide is a natural metal found in minerals such as ilmenite and rutile. Pigment production from titanium dioxide began in the 1920s using ilmenite and sulfuric acid. Anatase pigments were produced first, followed by rutile pigments in the 1940s. Chloride-process rutile pigments emerged in the late 1950s.

Titanium dioxide is now available in three forms: anatase (between 65 and 91% TiO2), rutile (between 92 and 96% TiO2) and brookite (>96% TiO2). Anatase is the most common form in industrial products, rutile is more stable, and brookite is rare. It can also occur in an amorphous form. Titanium dioxide is produced mainly in two size ranges: micrometric (micro-TiO₂) between 250 and 400 nm, and nanometric (nano-TiO₂) below 250 nm.

Micro-TiO₂ provides whiteness and opacity in paints, personal care products, and plastics. It accounts for 98% of global production. Nano-TiO₂ is valued for transparency and reactivity in UV filters and other products. Although nano-TiO₂ has many applications, its small size raises safety concerns as it can interact with biological tissues and the environment.

The most common method in the industry to produce titanium dioxide is the sulfate process. This method involves treating ilmenite ore with sulfuric acid at high temperature to produce titanium sulfate, which is then purified and converted into titanium dioxide. This process is common due to its low cost and the availability of raw materials. It allows the production of large quantities of titanium dioxide for applications such as paints, personal care products, and food. However, although this method is the most common, it generates significant amounts of by-products and is less environmentally friendly compared to more modern methods.

Other methods to produce titanium dioxide include sol-gel, hydrothermal/solvothermal, co-precipitation, microemulsion, molten salt, and aerosol synthesis. These methods control particle size, morphology, and crystal phase of titanium dioxide. They suit specific uses such as photocatalysts or industrial pigments. Large-scale use is limited by high cost, energy demand, and technical complexity. Aerosol synthesis in particular requires temperatures of 1,000 to 1,500°C.

The titanium dioxide is a versatile nanomaterial used across industry with varied applications. In skincare, it acts as a sunscreen filter and white pigment in sunscreens and tinted formulas, it provides protection and opacity. In textiles, it increases UV resistance and extends material durability under sunlight. In paints and coatings, its UV-blocking properties and whiteness shield surfaces from photochemical degradation. In pharmaceuticals, it serves as an opacifier and formulation stabilizer. It is present in various household products, building materials, and fabrics for its protective and stabilizing functions.

The titanium dioxide is known for its ability to protect skin from the sun. It acts as a physical sunscreen filter that absorbs UV rays in 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 aging, and reduce skin cancer risk. At the same time, titanium dioxide acts as an antioxidant neutralizing free radicals through electron transfer, which helps prevent signs of skin aging.

It is used to brighten and even skin tone, because its opacifying and light-reflecting properties help scatter visible light, giving skin a natural radiance and masking imperfections. Titanium dioxide is widely used as a colorant in tinted products.

When combined with other ingredients, titanium dioxide can enhance the anti-inflammatory properties, helping soothe the skin and protect it from irritation caused by external factors such as pollution and stress. When combined with gelatin-encapsulated silver oxide nanoparticles, titanium dioxide can accelerate skin tissue regeneration.This combination has anti-inflammatory and antibacterial effects that aid faster wound healing.

In hair care, titanium dioxide is used in hair products for its opacifying properties and UV protection. Although it is used for its benefits to hair protection and appearance, no scientific study has shown a significant effect of titanium dioxide on hair growth. This remains unconfirmed and requires more research to assess potential effects on hair growth.

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

Nano-TiO₂, a more recent form, raises questions because of its small size and greater reactivity. Nano-TiO₂ can interact easily with biological tissues, leading to extensive studies on potential health effects. Here is an overview 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 some studies have detected traces of nano-TiO₂ in urine, intact skin prevents its passage. Human skin has unique barrier properties that block nano-TiO₂ from reaching the dermis. Multiple studies show that even particles under 100 nm fail to cross the skin. In the rare cases where small amounts penetrate, no significant toxicity appears under specific conditions. However, more research is needed to assess long-term effects, especially on compromised skin.

• Oral risk of titanium dioxide.

  The nanometric titanium dioxide is banned in food, regardless of its form, 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 may cause toxic effects, including nephrotoxicity and liver damage. Although excreted in feces, prolonged tissue accumulation could lead to long-term effects. The mechanisms remain poorly understood.

  However, topical products using titanium dioxide, such as sunscreens and tinted products, contain much lower concentrations of titanium dioxide, and they are applied topically to skin or mucosal surfaces. The difference in concentration and application reduces the risk of internal absorption. These formulations use TiO₂ for pigmentation and UV protection and not for food applications.

• Inhalation risk of titanium dioxide.

  Inhalation of nano-TiO2 may pose greater risk in industrial settings. Fine anatase particles can cause respiratory issues. That is why the use of nano-TiO2 in spray form is prohibited. It is crucial to implement adequate safety measures in workplaces where titanium dioxide is handled to minimize risks.

Due to their reactivity and persistence in aquatic environments, nano-TiO2 pose a risk to ecosystems. In soil, they reduce microbial diversity and disrupt ecological processes. Plant roots may absorb these nanoparticles and spread them through the environment. This process could disrupt photosynthesis and affect plant growth.

In aquatic environments, they accumulate in living organisms and disrupt the food chain by causing toxic effects on phytoplankton and certain fish. If they interact with heavy metals and toxic compounds, they would increase environmental toxicity, which threatens animals, plants, and wildlife and highlights the need for research to limit their contamination.

Regarding micro-TiO₂, although they are 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 for further research to understand the environmental effects of titanium dioxide, in both nano and micro forms, and to develop strategies to limit its contamination.

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