‘Whiter than white’ – titanium dioxide nanoparticles

‘Whiter than white’ is a claim often used by washing powder manufacturers to describe the superior effects of their products. Equally, ‘whiter than white’ is a product attribute strived for by some food manufacturers although rarely boasted about as such as it might have been achieved through a now questionable food colourant, titanium dioxide.

Titanium dioxide in any form can be identified through the number E171 on the product label. It is commonly used in high quantities in food, chewing gum, toothpaste and some medicines as a whitening agent.

A proportion of this colourant most likely comprise of titanium dioxide nanoparticles.

What are nanoparticles?

Nanoparticles are particles between 1 and 100 nanometres (nm) in size, a thousand times smaller than the width of a strand of hair. Although substances that make up the nanoparticles are not necessarily regarded as toxic, nanoparticles are so small that their behaviour can be quite different from what we see for larger particles of the same substance. This is a new challenge for toxicologists.

While nanoparticles have been commonly used in medicines, food, clothing, and other applications, the possible impacts of nanoparticles, especially their long term effects, are still poorly understood. Nanoparticles in sunscreens and cosmetics can penetrate the skin, and this raises questions about what they can do in the body. Ingested nanoparticles can, and do, get into the body in places where larger particles cannot.

Nanoparticles of titanium dioxide in food

Titanium dioxide has been used in a range of foods, from sweets to processed cheese as consumers are more likely to buy and eat foods that are brighter or more vibrant in colour, as they look fresher. It gives a natural whiteness and opacity to foods, such as ice cream and the icing on cakes, helping to create great-looking food.

Food-grade titanium dioxide has a long history in helping make our meals and snacks aesthetically appealing. Food manufacturers have been using it presumably safely in approved uses for more than 50 years. It is assumed that titanium dioxide doesn’t enter the bloodstream as it passes through the digestive system unchanged and unabsorbed. But what about when the colourant contains nanoparticles?

In the past there has been little understanding of the size of any food-grade titanium dioxide particles, but this is changing with a recent focus on the health impact of nanoparticles in general. To provide the characteristic white colour of titanium dioxide, a large part of the particles must be between 200 and 300 nanometres in size. Particles of this size are not considered nanoparticles. However, the titanium dioxide production process results in a small fraction of the particles being nanoparticles.

The food industry claim that there has been no significant change in the particle size of titanium dioxide supplied to the food industry over the years, but acknowledge that there is a variation allowing for between 11% to 39% of the particles to be of nano size. As they are smaller this would equate to about 3.2% of the mass of any supplied titanium dioxide.

Is titanium dioxide still safe to eat?

The Joint FAO/WHO Expert Committee on Food Additives in 1970 considered it unnecessary to establish an acceptable daily intake (ADI) for titanium dioxide in food. This decision was taken on the basis of the low solubility, poor absorption into internal organs like liver and the absence of acute toxic effects.

In the USA, the FDA considers titanium dioxide as safe for use as a colouring agent in food and in 1966 allowed its addition to food up to a level of one percent. 

In Europe, titanium dioxide has been allowed for use as a food colourant for decades at a level required by food manufacturers to achieve desired effects. In 2016, the European Food Safety Authority (EFSA) published a re-evaluation of titanium dioxide including the potential risks of titanium dioxide nanoparticles to human health. EFSA concluded that, based on the information available, it was no reason for concern.

In Australia, titanium dioxide is an approved food additive and has been used in consumer products for many years. In 2016, Food Standards Australia New Zealand (FSANZ) published a review into the oral ingestion of titanium dioxide, including in nanoscale form, finding that there was not strong evidence to support claims of significant health risks.

In Japan, titanium dioxide is used without limitations other than for certain food categories in which it is not permitted.

In India, titanium dioxide is only authorised for use in chewing gum and bubble gum at not more than one percent, and in powdered concentrate mixes for fruit drinks at not more than 100 mg/kg.

But that is not the end of the matter as more scientific information is published.

What are the new findings?

In 2010, the International Agency for Research on Cancer (IARC) found that there were sufficient evidence in experimental animals for the carcinogenicity of titanium dioxide but not in humans. It thus placed titanium dioxide in a lower category as “possibly carcinogenic to humans” (Group 2B).

In 2016, the Dutch National Institute for Public Health and the Environment (RIVM) estimated likely human exposure to titanium dioxide nanoparticles from food, food supplements and toothpaste and concluded that toxic effects on the liver cannot be excluded. Previous studies with laboratory animals had indicated that the ingestion of very large quantities of titanium dioxide can cause damage to various organs, including the liver.

In 2017, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) published an expert appraisal of a study on the oral toxicity of titanium dioxide showing potential carcinogenesis-promoting effects in rats. At that time, the Agency stressed the need to conduct new toxicological studies in order to confirm or refute the effects reported in that study.

In 2018, RIVM and the RIKILT research institutes detected titanium dioxide particles in the liver and spleen of humans. At least 24% of the titanium dioxide particles were found to be nanoparticles. The concentration of titanium dioxide particles found in the human liver did not yet result in adverse health effects in laboratory animals, but it exceeded the level that RIVM considers safe for humans.

In 2018, US and Serbian researchers published findings from a study that exposed the fruit fly, Drosophila melanogaster, a common model species in human health research, to an estimated daily human titanium dioxide consumption level for 20 generations. They noticed a change in normal developmental and reproductive dynamics, and an increased genotoxicity. The larval stages were at a higher risk of sustaining damage and this was particularly worrisome, since children tend to consume higher daily concentrations of titanium dioxide than adults.

In 2019, University of Sydney research provided further evidence that nanoparticles may have a substantial and harmful influence on human health. Their mice study found that consumption of food containing titanium dioxide has an impact on the gut microbiota which could trigger diseases such as inflammatory bowel diseases and colorectal cancer.

Titanium dioxide did not change the composition of the gut microbiota, but instead it affected bacterial activity and promoted the formation of biofilms. Biofilms are bacteria that stick together and the formation of biofilm has been reported in diseases such as colorectal cancer.

So what now?

The above results confirm the possibility that the use of titanium dioxide may lead to adverse human health effects. Therefore, it might be that the safety of the present use cannot be fully guaranteed. In response, the European Commission has repeatedly requested EFSA to further re-examine the use of titanium dioxide in food.

EFSA in a reply of June 2018 evaluated four new studies and concluded that their findings highlighted some concerns but with uncertainties, therefore their relevance for the risk assessment was considered limited. Further research would be needed to decrease the level of uncertainties.

In a further statement of May 2019 EFSA claimed it could not identify any major new findings that would overrule its previous conclusions on the safety of titanium dioxide. However, it reiterated the importance of addressing previously identified uncertainties and data gaps, as well as further investigation of in vivo genotoxicity but only after the physico-chemical characterisation of food grade titanium dioxide had been completed.

What can you do?

Well, the answer is not much. Titanium dioxide can be found in more than 3,500 food products and is consumed in a high proportion everyday by the general population.

The highest concentrations are expected in chewing gum (up to 16,000 mg/kg), food supplements delivered in a solid form (up to 12,000 mg/kg), processed nuts (up to 7,000 mg/kg) and ready-to-use salads and sandwich spreads (up to 3,000 mg/kg).

Chewing a single piece of bubblegum can result in an intake of over 5 mg of titanium dioxide. The estimated daily maximum consumption of titanium dioxide by children is up to 32.4 mg/kg body weight.

To put those dietary intake levels into perspective hypothetical upper safe levels for dietary intake of between 0.4 and 5 mg/kg body weight per day have been calculated from rodent studies.

You could stop chewing gum but it would not help much. The best hope is that studies currently under way will produce conclusive results so that authorities can either fully clear titanium dioxide for use in food, limit its use or fully ban it from food.

Most of us have to wait and see. However, if you live in France you might benefit from the French government decision to ban the addition of titanium dioxide in food from 1 January 2020.