Titanium Dioxide in Food — Should You Be Concerned?

This article reviews the uses, benefits, and safety of titanium dioxide.

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Still, you may wonder whether it&#;s safe for consumption.

Variations of titanium dioxide are added to enhance the whiteness of paint, plastics, and paper products, though these variations differ from the food-grade ones for things we eat ( 1 , 2 ).

One of the most widely used food pigments is titanium dioxide, an odorless powder that enhances the white color or opacity of foods and over-the-counter products, including coffee creamers, candies, sunscreen, and toothpaste ( 1 , 2 ).

From dyes to flavorings, many people are becoming increasingly aware of the ingredients in their food.

Titanium dioxide is a whitening ingredient in foods, cosmetics, and other products. The FDA considers it safe, but high intake could be harmful.

Due to its excellent light-reflecting abilities, titanium dioxide is used in many food and cosmetic products to improve their white color and block ultraviolet rays.

Although cosmetics are not meant for consumption, there are concerns that titanium dioxide in lipstick and toothpaste may be swallowed or absorbed through the 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 ( 7 ).

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 ( 6 ).

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 ( 7 ).

Furthermore, this packaging has been shown to have both antibacterial and photocatalytic activity, the latter of which reduces ultraviolet (UV) exposure ( 5 , 6 ).

Packaging containing this additive has been shown to decrease ethylene production in fruit, thus delaying the ripening process and prolonging shelf life ( 4 ).

Titanium dioxide is added to some food packaging to preserve the shelf life of a product.

The most common foods containing titanium dioxide are chewing gum , candies, pastries, chocolates, coffee creamers, and cake decorations ( 1 , 3 ).

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 ( 1 ).

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 ( 1 ).

Due to its light-scattering properties, small amounts of titanium dioxide are added to certain foods to enhance their white color or opacity ( 1 , 3 ).

Titanium dioxide has many purposes in both food and product development.

In recent decades, concerns for the risks of titanium dioxide consumption have grown.

Group 2B carcinogen

Though the Food and Drug Administration (FDA) categorizes titanium dioxide as Generally Recognized as Safe (8), other organizations have issued warnings.

The European Food Safety Authority (EFSA) has concluded that titanium oxide should not be considered safe as a food additive, due to uncertainties about possible inflammation and neurotoxicity (9).

The Scientific Committee on Consumer Safety (SCCS) warns against sprayable products and powders that may expose users&#; lungs to titanium dioxide through inhalation (10).

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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 has caused concern for its safety in food products (11, 12).

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 (11).

Therefore, today, they only recommend limiting titanium dioxide inhalation in industries with high dust exposure, such as paper production (11).

Absorption

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 (13, 14, 15).

Moreover, a 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 (3).

Finally, research has shown that titanium dioxide nanoparticles do not pass the first layer of the skin &#; the stratum corneum &#; and are not carcinogenic (7, 15).

Organ accumulation

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 (16).

A review by the European Food Safety Authority concluded that titanium dioxide absorption is extremely low and any absorbed particles are mostly excreted through feces (17).

However, they did find that minor levels of 0.01% were absorbed by immune cells &#; known as gut-associated lymphoid tissue &#; and may be delivered to other organs. Currently, it&#;s unknown how this may affect human health (17).

Although most studies to date show no harmful effects of titanium dioxide consumption, few long-term human studies are available. Therefore, more research is needed to better understand its role in human health (16, 18).

Summary

Titanium dioxide is classified as a Group 2B carcinogen as animal studies have linked its inhalation to lung tumor development. However, no research has shown that titanium dioxide in food harms your health.

(a) Production

Titanium dioxide is the principal white pigment used commercially, due to its high refractive index, its ease of dispersion into a variety of matrices, and its inertness towards those matrices during processing and throughout product life (Considine, ).

Two main processes exist for making titanium dioxide pigments: the sulfate process and the chloride process. The sulfate process, the older of the two, was first used in Europe and the USA around and was the primary process until the early s, when the chloride process was developed. By , the chloride process accounted for approximately 78% of US production and by for 68% of world titanium dioxide pigment production (Considine, ; Lynd & Lefond, ).

In the sulfate process, rutile or anatase titanium dioxide is produced by digesting ilmenite (iron titanate) or titanium slag with sulfuric acid. The major concern in selecting the starting material for use in the process is that it contain as little as possible of impurities such as chromium, vanadium, manganese, niobium and phosphorus, which impair pigment properties. Ilmenite containing as little as 40% titanium dioxide can be used to produce pigment-grade titanium dioxide. Titanium slag may also be used as the starting material. Slag is produced by smelting ilmenite in an electric furnace and typically contains about 70% titanium dioxide, although concentrations may reach 85% (Considine, ; Lowenheim & Moran, ; Lynd & Lefond, ). Some typical materials used for pigment production throughout the world are shown in .

Table 1

Composition of typical commercial ilmenite concentrates and titaniferous slag (weight percent).

The sulfate process is a batch process in which concentrated sulfuric acid is added to ground ilmenite or titanium slag in proportions of 1.5:1 (acid to ore). An organic flocculent or antimony oxide may be added to induce aggregation of suspended titanyl and iron sulfates into a solid porous cake. The cake is dissolved in a dilute acid solution to release the sulfate agglomeration into solution. If necessary, scrap iron is added to reduce iron [III] to iron [II]. Also during this step, small amounts of titanium [IV] are reduced to titanium [III] to prevent later oxidation of iron [II]. The solution is clarified by settling and filtration. The resulting mother liquor is concentrated and subjected to steam for 6 h. Seed crystals may be added to aid nucleation. About 95% of the titanium in the mother liquor is hydrolysed to titanium hydrate or metatitanic acid (H2TiO3), which is collected on a filter and washed. The final filter cake is calcined at 900&#;°C to form titanium dioxide. The product is ground, quenched and dispersed in water; the coarse particles are separated in the thickener, re-ground and filtered; and the cake is dried in a rotary steam dryer and pulverized. The resulting product is anatase titanium dioxide. The rutile form is made by seeding the mother liquor with rutile seed crystals and conditioning the precipitated pigment with phosphates, potassium, antimony, aluminium or zinc compounds prior to calcination. The recovery of pigment-grade titanium dioxide in sulfate process plants is approximately 80% (Lowenheim & Moran, ; Lynd & Lefond, ; Lynd, ).

The chloride process is a continuous process that requires ores with a high content of titanium dioxide or concentrates such as natural or synthetic rutile. Natural rutile contains approximately 95% titanium dioxide; synthetic rutile or ilmenite (iron titanate) concentrates must have a minimum titanium dioxide content of 60% to produce economical yields of pigment in this process. The titanium dioxide content in ilmenite may be increased by reducing iron to its elemental form, followed by chemical or physical separation. Another method of enrichment is reducing iron [III] to iron [II] and chemically leaching it out of the mineral. A third method involves prior selective chlorination to remove iron and other impurities (Considine, ; Lowenheim & Moran, ; Lynd & Lefond, ).

In the chloride process, ore is ground and mixed with coke in a fluidized or static bed reactor and chlorinated at temperatures of 850&#;°C. Titanium tetrachloride is produced, along with chlorides of impurities present in the starting material, which include chlorides of iron, vanadium and silicon; these are removed chemically and through fractional distillation. Hydrogen chloride and carbon dioxide are present after chlorination and are vented prior to fractional distillation. Conversion to titanium dioxide is accomplished by burning titanium tetrachloride with air or oxygen at temperatures of &#;°C. The resulting fine-grained oxide is sometimes calcined at about 500&#;600°C to remove any residual chlorine or hydrogen chloride. These gases are separated, and the chlorine is collected and recirculated to the chlorinator. Approximately 90% of the chlorine may be recycled. Aluminium chloride is added to titanium tetrachloride to assure near-total conversion to rutile titanium dioxide. A typical yield from this process is 90% (Lowenheim & Moran, ; Lynd & Lefond, ; Lynd, ).

Current worldwide demand for titanium dioxide is about 2.8 million tonnes (Anon., a,b,c). Production volumes in &#;86 in several countries are given in .

Table 2

Titanium dioxide pigment production by country in &#;86 (thousand tonnes).

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