Story at-a-glance

• Titanium dioxide nanoparticles may lead to neurological dysfunction, genetic disorders, and possibly cancer
• Candies, sweets and chewing gum, along with toothpaste and sunscreen, have been found to contain the highest levels of titanium dioxide nanoparticles
• Children may receive the highest exposure levels (two to four times more than adults) of titanium dioxide nanoparticles

Millions of tons of titanium dioxide are produced globally each year. It adds whiteness and brightness to products and also helps them resist discoloration. Titanium dioxide also reflects ultraviolet (UV) light, which is why it's often used as an ingredient in sunscreens.

Most titanium dioxide (close to 70 percent) is used as a pigment in paints, but it's also added to cosmetics, toothpastes, pharmaceuticals, paper and food.

Titanium dioxide is generally considered to be a relatively inert, safe material, but an increasing number of products are now using titanium dioxide nanoparticles, and that may change everything.

Nanoparticles are ultramicroscopic in size, making them able to readily penetrate your skin and travel to underlying blood vessels and your bloodstream.

Evidence suggests that some nanoparticles may induce toxic effects in your brain and cause nerve damage, and some may also be carcinogenic.

The International Agency for Research on Cancer (IARC) classifies titanium dioxide as a Group 2B carcinogen, which means it's "possibly carcinogenic to humans." This was based on an animal study showing inhaling high concentrations of titanium dioxide dust may lead to lung cancer.

Is Titanium Dioxide in Foods Dangerous?

Candies, sweets and chewing gum have been found to contain the highest levels of titanium dioxide. White powdered doughnuts, candies and gums with hard shells, products with white icing and even bread, mayonnaise, yogurt and other dairy products may contain titanium dioxide.

As such, one analysis of exposure to titanium dioxide through foods found children receive the highest exposure levels (two to four times more than adults) because it's so commonly added to sweets.1 Only a "limited number" of the products tested in one study listed titanium dioxide on the label.2

The U.S. Food and Drug Administration actually allows manufacturers to use up to 1 percent food-grade titanium dioxide without declaring it on labels.3

It should be noted that many titanium particles used in food products are not nanoparticles (defined as smaller than 100 nanometers in diameter). However, some are.

According to research published in Environmental Science and Technology, up to 36 percent of the titanium dioxide found in nearly 90 food products was of the nanoparticle variety.4  

It's unclear what health risks may be linked to ingestion of titanium dioxide nanoparticles, but research suggests there's cause for concern.

One animal study published in Cancer Research, for instance, found titanium dioxide nanoparticles may induce clastogenicity (causing breaks in chromosomes), genotoxicity, oxidative DNA damage and inflammation.

The researchers suggested they may be a cause of caner or genetic disorders and concluded:5

"These results have been observed after only 5 days of treatment via drinking water, and in multiple organs suggesting a systemic effect …

We also showed that in utero exposure to TiO2 NPs [titanium dioxide nanoparticles] results in an increased frequency in DNA deletions in the fetus.

… These data suggest that we should be concerned about a potential risk of cancer or genetic disorders especially for people occupationally exposed to high concentrations of TiO2 NPs

…[A]nd that it might be prudent to limit ingestion of TiO2 NPs through nonessential drug additives, food colors etc."

Titanium Dioxide Nanoparticles May Harm Your Brain

The use of nanoparticles is increasing rapidly, and titanium dioxide nanoparticles are the second most produced engineered nanomaterial in the world.6

Its usage in consumer products has outpaced the research into its safety, such that humans are being repeatedly exposed before we know the consequences. What is known, however, is that titanium dioxide nanoparticles are capable of moving from your lungs or gastrointestinal tract to other organs.7

Further, animal studies indicate significant accumulation of nanoparticles in the brain, while toxicity studies have shown the particles have negative effects on brain cell viability and function.8

One recent study even showed titanium dioxide nanoparticles induced "an increase in reactive oxygen species generation, and a decrease in mitochondrial membrane potential, suggesting mitochondrial damage."

The researchers believe exposure to the particles may lead to neurological dysfunction.9 Specifically, the nanoparticles were found to harm astrocyte cells, which help regulate serotonin, dopamine and other neurotransmitters.

High levels of exposure (100 parts per million) killed two-thirds of such brain cells within one day. It also harmed the cells' mitochondria, which may ultimately lead to cell death.

Oxidative Stress and Mitochondrial Damage

The study also revealed that astrocyte cells that weren't killed were left damaged; they became unable to absorb glutamate, a neurotransmitter, such that it accumulated outside the cell, which may be implicated in Alzheimer's and Parkinson's diseases.10

Other research also suggests titanium dioxide nanoparticles may have hidden brain risks. For instance:

• Prenatal exposure to titanium dioxide nanoparticles may result in alteration to the cerebral cortex, olfactory bulb and brain regions intimately related to dopamine systems of offspring mice.11
• Exposure to titanium dioxide nanoparticles may alter oxidative and inflammatory responses as well as the renin-angiotensin system in the brain (which plays a role in cardiovascular health, including hypertension, and aging), thereby modulating brain function.12
• Titanium dioxide nanoparticles (TiO2 NPs) induce strong oxidative stress and mitochondrial damage in glial cells in your brain. According to research published in Free Radical Biology & Medicine:13

"TiO2 NPs can enter directly into the brain through the olfactory bulb and can be deposited in the hippocampus region …

TiO2 NPs … produced morphological changes, damage of mitochondria, and an increase in mitochondrial membrane potential, indicating toxicity."

What About Titanium Dioxide Nanoparticles in Personal Care Products?

Titanium dioxide nanoparticles are found most often in personal care products such as toothpaste, sunscreen and, to a lesser extent, shampoos, deodorants, and shaving creams. As with food, use of these nanoparticles in personal care products is on the rise.

In 2005, about 1,300 metric tons were used in personal care products, but this had increased to 5,000 metric tons by 2010 and is expected to continue increasing until at least 2025.14

Although most studies suggest titanium dioxide does not penetrate human skin, even in nanoparticle form, one study found that the nanoparticles could possibly penetrate the outer layer of skin depending on the particle coating and skin (with or without hair).15

As further reported in Environmental Science and Toxicology:16

"The only FDA-stipulated limitation for sunscreens is that the TiO2 concentration be less than 25%. Most have a lower concentration, between 2% and 15%.

With the wide prevalence of sunscreen use and the lack of a distinction between TiO2 nanomaterials and larger-sized particles, the general public is being exposed to nanomaterials of which they are largely ignorant."

Environmental Risks Are Unknown

Also concerning is what happens when all of the nanoparticles in personal care products (and excreted after they're consumed in your food) are washed down the drain and flushed down the toilet. Study author Paul Westerhoff, a professor in the School of Sustainable Engineering and The Built Environment at Arizona State University and Senior Sustainability Scientist to the Global Institute of Sustainability, told Nanowerk:17

"… [W]e can expect the percentage of TiO2 [titanium dioxide] that is produced in or near the nano range to increase. TiO2 nanomaterials in foods, consumer products, and household products are discharged as feces/urine, washed off of surfaces, or disposed of to sewage that enters wastewater treatment plants.

While these plants capture most of the TiO2, nanoparticles measuring between 4 and 30 nm were still found in the treated effluent. These nanomaterials are then released to surface waters, where they can interact with living organisms."

Tips for Avoiding Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles are ubiquitous in processed foods, so the best way to avoid them is to eat real food. To avoid these particles in your toothpaste, consider making your own out of coconut oil. As for sunscreen, the other major source, first realize that titanium dioxide (and zinc oxide) is a top choice for sun protection (and doesn't carry the same risks as hormone-disrupting sunscreen chemical oxybenzone).

To be on the safe side, however, look for non-nanoparticle titanium dioxide that is tested and guaranteed to be non-nano. Further, minimize your sunscreen use as much as possible, using it only when you'll be in the sun for extended periods and the use of clothing to cover-up or going into the shade aren't options.