Chemical Profile: Titanium Dioxide

Titanium dioxide is a naturally-occurring mineral found in the earth’s crust. Because of its white color, opacity, and ability to refract light, the ingredient is often used as a pigment, brightener, and opacifier in consumer products, meaning that it helps make a formulation more opaque. Most notably, it is used as an inorganic, mineral UV filter in sunscreens for its ability to absorb UV radiation, in lieu of toxic chemical UV filters (e.g., oxybenzone, avobenzone, octinoxate, etc.). Titanium dioxide exists in three crystalline forms – anatase, rutile, and brookite – though anatase and rutile are the primary forms used industrially and in consumer products. 

Titanium dioxide is used as a UV filter in sunscreens. It is also used as a pigment in makeup, as well as in personal care like toothpaste, soap, skincare, and more. You’ll also find it in food and candy in some countries, where it’s used as a pigment. 

Titanium dioxide can be both safe and unsafe, depending on its use and form. The safety of titanium dioxide can change depending on a) how we are exposed to it (i.e., by inhalation, skin contact, or ingestion) and b) the size and other physicochemical properties of the titanium dioxide particles. For instance, the crystalline structure of titanium dioxide particles (anatase vs. rutile) can have impacts on its toxicity. Anatase and rutile mixtures are suspected of inducing cytotoxicity (toxicity to cells) or oxidative stress.¹ These complexities are what make titanium dioxide a tricky ingredient to understand, especially for the conscientious consumer deciphering contradictory news headlines.

Titanium dioxide particles vary by size and can be classified as nanoparticles (<100 nanometers in diameter) or non-nanoparticles (>100 nanometers in diameter). Generally, nanoparticles can be 1000 times smaller than the width of a human hair. Despite nanoparticles becoming increasingly common across industries, they have not been properly assessed for human or environmental health effects, nor are they adequately regulated. However, because of their infinitesimally small size, nanoparticles may be more chemically reactive and therefore more bioavailable.² The dramatic difference in size can also cause nanoparticles of a substance to behave differently than larger particles of the same substance; these characteristics may lead to potential damage in the human body or ecosystem.³ For this reason, nanoparticles and non-nanoparticles of titanium dioxide are considered distinct ingredients by MADEWORKs and therefore assessed separately.

Next, the way in which you’re exposed to titanium dioxide can impact its effects:

Inhalation of Titanium Dioxide 

The International Agency for Research on Cancer (IARC) classifies inhalable titanium dioxide as a group 2B carcinogen, or “possibly carcinogenic to humans”.⁴ Titanium dioxide can be inhaled from products containing powdered titanium dioxide, like loose powders, pressed powders, eyeshadows, and blushes, or from aerosolized sunscreens or dry shampoos. Titanium dioxide is also an occupational chemical of concern, as workers might inhale titanium dioxide when manufacturing products.⁵

Ingestion of Titanium Dioxide

Oral exposure to titanium dioxide particles is potentially linked to DNA strand breaks, chromosomal damage, and oxidatively generated DNA lesions. Both nanoparticles and microparticles of titanium dioxide (anatase and rutile) exhibit the ability to induce oxidation of DNA. The crystalline form (anatase or rutile), size, and extent to which titanium dioxide nanoparticles may group together are hypothesized to impact genotoxic potential. However, the extent of genotoxicity with reference to these and other physicochemical properties of titanium dioxide particles is not clear. Regardless, both nanoparticles and microparticles of titanium dioxide (anatase and rutile) exhibit the ability to induce oxidation of DNA, suggesting varying sizes of titanium dioxide to pose a potential human health risk when ingested.⁶

Because of the issues associated with ingesting titanium dioxide, it has been banned as a food additive by the European Union. In the United States, California introduced a bill in 2024 that would prohibit titanium dioxide (as well as some other food dyes) from foods that are served in California public schools. Our collaborator, Consumer Reports, signed on to support the bill. Ultimately, titanium dioxide was removed from the legislation by lawmakers prior to being signed.

Titanium Dioxide Skin Contact 

The existing body of literature on the dermal absorption of titanium dioxide is conflicting and is a research area requiring expansion. Many studies carried out in vitro (outside the body) indicate titanium dioxide nanoparticles do not penetrate beyond the surface of the stratum corneum, the outermost layer of the skin, and/or do not reach the viable epidermis or dermis cells.^7,8,9 In vivo studies (in live animal or human subjects) suggest otherwise.^10,11,12

Some animal studies have reported titanium dioxide nanoparticles found in the skin, subcutaneous muscle, liver, heart, lung, and spleen of hairless mice following sub-chronic exposure (exposure falling between short and long-term) in vivo.¹² Evidence of in vivo penetration of titanium dioxide nanoparticles beyond the outermost layer of skin in live pigs, however, was heavily dependent on particle size and did not reach the viable dermis, supporting previous in vitro studies using pig models.¹² The outermost layer of skin of hairless mice is less thick (<1/2) and has a lower barrier than that of human skin; thus, extrapolation of dermal absorption in hairless mice to humans is questionable. In a human study, titanium dioxide nanoparticles were detected in biological fluids (e.g., plasma, urine), indicating skin absorption in sunscreen users.^1,13

Research on the dermal absorption and potential adverse effects of non-nanoparticles of titanium dioxide is scarce; however, nanoparticles are more likely to pass through the skin’s surface due to their infinitesimally small size, indicating non-nanoparticles of titanium dioxide likely do not penetrate beyond the skin’s barrier when applied topically (and therefore do not pose systemic risk to the human body). There is some evidence that non-nanoparticles of titanium dioxide (>100 nm) do not penetrate beyond the outermost layer of skin under normal conditions, in intact healthy skin.¹⁴

There is also evidence linking titanium dioxide nanoparticles to cytotoxicity (toxicity to cells) and phototoxicity (a toxic response triggered by light) in human and animal cell lines,^15,16,17,18 as well as in aquatic life.^19,20 There are data gaps on whether non-nanoparticles of titanium dioxide are linked to phototoxicity; however, there is evidence linking larger specific particle surface area (and smaller particle size) to higher cytotoxicity and phototoxicity effects.²¹ Thus, titanium dioxide nanoparticles are more likely to induce cytotoxic and phototoxic effects than non-nanoparticles.

MADE Standards on Titanium Dioxide Health Concerns 

Non-nanomaterial: Titanium dioxide may be linked to human and environmental health issues when present in nanoparticle form. Because of the uncertainty surrounding the health and environmental impacts of nanoparticles, MADE Intelligence (the scientific process that informs the MADEWORKS certifications like MADE SAFE and MADE WISE) exercises the precautionary principle and does not permit nanoparticles smaller than 100 nanometers in certified products until more extensive scientific testing demonstrates their safety.

Specific Uses Only: Titanium dioxide presents a much safer option than conventional sunscreen chemicals like oxybenzone and octinoxate in sunscreens and other pigments and whiteners in makeup. Therefore, MADE SAFE and MADE WISE permit non-nanosized titanium dioxide particles (>100 nm) only for specific use cases such as sunscreen formulations and as a pigment in makeup, due to its varying impacts by route and existing data gaps in its safety.

Regardless of particle size, titanium dioxide is not permitted in products that increase the risk of inhalation due to scientific evidence that titanium dioxide is a probable carcinogen when inhaled. This includes products like aerosol sunscreen, dry shampoo, loose powder cosmetics, and more.

Finally, titanium dioxide is not permitted in products with a risk of ingestion – for example, lipstick and lip balm – due to the ingredient’s genotoxic potential when consumed.

• If shopping for sunscreen or color cosmetics, opt for sunscreens containing non-nanoparticle titanium dioxide.
• Avoid any products containing nano-scale titanium dioxide.
• Avoid aerosolized or loose powder products containing titanium dioxide of any particle size that might be ingested or inhaled.
• Apply these simple tips when considering products containing titanium dioxide:
  • Avoid titanium dioxide in powdered makeup – including loose and pressed powders, eyeshadows, and blush – as well as makeup you may ingest like lipstick or lip balm.
  • Opt for sunscreen lotions and creams instead of aerosol sunscreens.
  • Choose sunscreens labeled as “non-nano” or “non-nanomaterial.” If the label doesn’t specify whether the titanium dioxide is nanoparticle size, skip it altogether and choose another option, or contact the company for clarification.
  • Avoid foods and candy containing titanium dioxide of any particle size.
  • Shop MADE SAFE and MADE WISE Certified products.