Titanium dioxide (TiO2), also known as E171, is a widely used white colorant. It's found in various products, including food, pharmaceuticals, cosmetics, and toothpaste. Its primary function is to enhance the whiteness and opacity of these products. However, its safety as a food additive has been a subject of debate, particularly after a 2021 assessment by the European Food Safety Authority (EFSA).
What is Titanium Dioxide?
Titanium is the ninth most abundant element in the Earth's crust. When titanium is exposed to oxygen, it forms titanium oxides. Manufacturers obtain titanium dioxide from minerals called brookite, rutile, and anatase. Food-grade titanium dioxide, or E171, is commonly used as a white colorant. Other pigmentary TiO2 products are utilized in paints and coatings. It gains its whiteness from its light scattering properties, due to its high refractive index and absence of intrinsic color. E171 is generally an anatase-based mix of pigment-grade based TiO2 particles. However, rutile TiO2 is also allowed in the European Union as a food colorant, and there are rutile grades available on the market.
Uses of Titanium Dioxide
Titanium dioxide has many purposes in both food and product development.
Food Quality
Small amounts of titanium dioxide are added to certain foods to enhance their white color or opacity. Most food-grade titanium dioxide is around 200-300 nanometers (nm) in diameter. This size allows for ideal light scattering, resulting in the best color. To be added to food, this additive must achieve 99% purity. However, this leaves room for small amounts of potential contaminants like lead, arsenic, or mercury. The most common foods containing titanium dioxide are chewing gum, candies, pastries, chocolates, coffee creamers, and cake decorations. Studies suggest that people are more likely to buy and eat foods that are brighter or more vibrant in color.
Food Preservation and Packaging
Titanium dioxide is added to some food packaging to preserve the shelf life of a product. Packaging containing this additive has been shown to decrease ethylene production in fruit, thus delaying the ripening process and prolonging shelf life. Furthermore, this packaging has been shown to have both antibacterial and photocatalytic activity, the latter of which reduces ultraviolet (UV) exposure.
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Cosmetics
Titanium dioxide is widely used as a color-enhancer in cosmetic and over-the-counter products like lipsticks, sunscreens, toothpaste, creams, and powders. It’s usually found as nano-titanium dioxide, which is much smaller than the food-grade version. It’s particularly useful in sunscreen as it has impressive UV resistance and helps block the sun’s UVA and UVB rays from reaching your skin. However, since it’s photosensitive - meaning it can stimulate free radical production - it’s usually coated in silica or alumina to prevent potential cell damage without reducing its UV-protective properties.
Safety Assessments and Concerns
The safety of titanium dioxide has been evaluated by regulatory agencies worldwide.
EFSA's 2021 Opinion
In May 2021, the European Food Safety Authority (EFSA) expert panel concluded that a concern for genotoxicity of TiO2 particles could not be ruled out. EFSA based this new interpretation on the results of genotoxicity tests of TiO2 nanomaterials. EFSA noted that available data are insufficient to define threshold doses/concentrations of TiO2 particles below which genotoxicity will not occur in tissues containing these particles. Based on all the evidence available, a concern for genotoxicity could not be ruled out, and given the many uncertainties, the Panel concluded that E171 can no longer be considered as safe when used as a food additive.
Arguments Against EFSA's Opinion
Some scientists and agencies disagree with EFSA's opinion. They argue that the test materials used in key studies considered by EFSA are not representative of E171 TiO2 particles. A common theme voiced by the United Kingdom, Canada, Australia, and New Zealand agencies is that it is inappropriate to compare nanoparticle toxicity studies of dispersed/sonicated nanoparticles with the content of E171 TiO2 in foods because the test materials used in key studies considered by EFSA are not representative of E171 TiO2 particles. A group of experts recently considered the genotoxicity of TiO2 and could not find support for a direct DNA damaging mechanism of TiO2 (nano and other forms).
Particle Size Distribution
Based upon a particle-size distribution, E171 (like all pigmentary samples has a particle size distribution) is a mixture of TiO2 particles which can be defined as non-nano particles (>100 nm) as well as nanoparticles (<100 nm). However, it is noteworthy that greater than 98% of titanium dioxide (TiO2) particles in the commercial market by production volume are of this pigmentary size. Notably, TiO2 as an ultrafine or nanoparticulate material, comprises about 2% of global consumption of TiO2 and is applied in properties that are distinct from the prescribed pigmentary applications. This is important because TiO2 particles of sizes less than 100 nm do not scatter visible light efficiently and are not desired in pigmentary-type applications. The desired light scattering properties by titanium dioxide (TiO2) particulates occur preferentially in the 200 nm-300 nm particle size range. Therefore, nanoscale TiO2 particles (mean particle sizes <100 nm) are not utilized for these applications. It is important to note that all pigment-grade preparations of TiO2 particle-types contain a nano-sized fraction of 20%-30% (as measured by particle number).
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Oral Toxicity Studies
In a series of in vivo oral toxicity studies with a variety of different TiO2 particulates, Warheit et al. reported on the results of three OECD test guideline (TG) oral toxicity studies of different durations in rats. Each study was designed to assess different TiO2 particles of varying sizes and surface coatings. The results demonstrated an absence of TiO2-related toxic effects. The NOAEL was determined based upon an absence of adverse effects for any measured in-life, clinical pathology, or anatomic effects.
The National Cancer Institute (NCI) conducted a 2-year oral bioassay of TiO2 particles for possible carcinogenic effects conducted by administering the test chemical in dietary feed to Fischer 344 rats and B6C3F1 mice. The results demonstrated that administration of the TiO2 had no appreciable effects on the mean body weights of rats or mice of either sex. With the exception of white feces, there were no other clinical signs that were judged to be related to the oral exposures of titanium dioxide.
Other Regulatory Bodies
Other international regulatory bodies including the United Kingdom’s Food Standards Agency (FSA), Health Canada, and Food Standards Australia New Zealand (FSANZ) have not agreed with EFSA’s assessment. FDA notes that some of the genotoxicity tests considered in the EFSA assessment included test materials not representative of the color additive, and some tests included administration routes not relevant to human dietary exposure.
FDA's Stance
The FDA considers titanium dioxide safe when used according to regulations, which limit the quantity of titanium dioxide to no more than 1% by weight of the food. The FDA’s regulations require evidence that a color additive is safe at its intended level of use before it may be added to foods. All colors added to food require FDA evaluation and authorization through a color additive regulation. In 2023, the Joint Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) re-evaluated the safety of titanium dioxide. In its summary report, JECFA concluded that TiO2 added to food is safe.
Potential Risks and Side Effects
While titanium dioxide is generally considered safe, there are potential risks and side effects to consider.
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Group 2B Carcinogen Classification
The International Agency for Research on Cancer (IARC) has listed titanium dioxide as a Group 2B carcinogen - an agent that may be carcinogenic but lacks sufficient animal and human research. This classification was given, as some animal studies found that inhaling titanium dioxide dust might cause the development of lung tumors. However, IARC concluded that food products containing this additive do not pose this risk. Therefore, today, they only recommend limiting titanium dioxide inhalation in industries with high dust exposure, such as paper production.
Absorption and Organ Accumulation
There is some concern regarding skin and intestinal absorption of titanium dioxide nanoparticles, which are less than 100 nm in diameter. Some small test-tube research has shown that these nanoparticles are absorbed by intestinal cells and may lead to oxidative stress and cancer growth. However, other research has found limited to no effects. Moreover, a 2019 study noted that food-grade titanium dioxide was larger and not nanoparticles. Hence, the authors concluded that any titanium dioxide in food is absorbed poorly, posing no risk to human health. Research has shown that titanium dioxide nanoparticles do not pass the first layer of the skin - the stratum corneum - and are not carcinogenic. Some research in rats has observed titanium dioxide accumulation in the liver, spleen, and kidneys. That said, most studies use doses higher than what you would typically consume, making it difficult to know if these effects would happen in humans. A 2016 review by the European Food Safety Authority concluded that titanium dioxide absorption is extremely low and any absorbed particles are mostly excreted through feces.
Other Potential Risks
Titanium exposure may be harmful to your brain. Titanium nano particles can enter directly into the hippocampus region of the brain through the nose and olfactory bulb. Research conducted by Escuela Superior de Medicina at Instituto Politécnico Nacional found that titanium dioxide had a toxic effect on glial cells in the brain, suggesting that exposure to titanium dioxide may cause brain injury and be a health hazard. Studies show that titanium dioxide causes adverse effects by producing oxidative stress, resulting in cell damage, redness, and immune response.
Side Effects
There is limited research on the side effects of titanium dioxide, and it largely depends on the route of access:
- Oral consumption: There are no known side effects.
- Eyes: The compound may cause minor irritation.
- Inhalation: Breathing in titanium dioxide dust has been linked to lung cancer in animal studies.
- Skin: It may cause minor irritation.
Most side effects are related to inhalation of titanium dioxide dust. Therefore, there are industry standards in place to limit exposure.
Consumption Levels and Regulation
In the United States, products can contain no more than 1% titanium dioxide in weight, and due to its excellent light-scattering abilities, food manufacturers only need to use small amounts to achieve desirable results. Children under 10 years old consume the most of this additive, with an average of 0.08 mg per pound (0.18 mg per kg) of body weight per day. Comparatively, the average adult consumes around 0.05 mg per pound (0.1 mg per kg) per day, although these numbers vary. This is due to the higher intake of pastries and candies by children, as well as their small body size.
How to Avoid Titanium Dioxide
If you want to avoid titanium dioxide, read labels carefully and stick to minimally processed whole foods. Chewing gum, pastries, candies, coffee creamers, and cake decorations are the most common foods with titanium dioxide. Keep in mind that there may be different trade or generic names for the compound that manufacturers may list instead of “titanium dioxide,” so be sure to get informed. Considering titanium dioxide is present in mostly processed foods, it’s easy to avoid by opting for a diet of whole, unprocessed food.