It is in paint, paper, sunscreen, cosmetics, toothpaste and food. The International Agency for Research on Cancer (IARC) lists it in its Group 2B, “possibly carcinogenic in humans.” In Europe it is not allowed as a food additive, but in Canada you’ll find it in candies, chewing gum, pastries, cake decorations and coffee creamers. Should you worry about consuming titanium dioxide, TiO2?
We are talking about a bright, white powder that is produced from a titanium-iron oxide mineral called ilmenite and is added to foods to increase visual appeal. It has no nutritional value. A recent episode of Marketplace, the excellent CBC television program that investigates consumer products, focused on the conundrum of why some food additives such as titanium dioxide are banned in Europe and allowed here. Interviewees who ranged from ordinary consumers to a spokesperson for “Center for Science in the Public Interest,” an American activist organization, expressed concern that Canadians are not getting the same protection as Europeans when it comes to ensuring the safety of our food supply.
Before going further, let me say that I am not a friend of food colourants, including titanium dioxide. That’s because these chemicals have no purpose other than to make foods of low nutritional quality more attractive. However, after delving into the relevant scientific literature, I do not think that the European ban of titanium dioxide in food is justified. On the other hand, I believe Health Canada’s position that titanium dioxide as a food additive poses no health risk is supported by evidence.
How can European and Canadian scientists look at the same data and come to different conclusions? European regulatory agencies favour the precautionary principle, which is the philosophical view that any hint of risk should preclude the use of a substance. Health Canada, on the other hand, evaluates risk by taking into account the manner in which a substance is actually encountered. The European ban referenced laboratory studies that showed some damage to DNA in certain cell lines upon exposure to titanium dioxide. Although the meaning of these studies is unclear in terms of human exposure, the regulators concluded that the genotoxicity of the chemical could not be ruled out and invoked the precautionary principle to justify a ban.
Health Canada scientists were totally aware of the genotoxicity concern when they undertook a government mandated review of titanium dioxide as a food additive in 2022. Their report, which ran to an astounding 180 pages with hundreds of references, concluded that the use of food grade titanium dioxide as an additive is not a concern for human health. The reason for re-evaluating titanium dioxide was the emergence of new information about the chemical, namely the finding that a portion of the particles in a sample may be in the “nano” range. Nanoparticles are smaller than 100 nanometers in size, thousands of times smaller than the width of a human hair. The issue is that on this scale, particles can behave differently than larger ones even though they have the same chemical composition.
The European ban was based on how cells cultured in the laboratory were affected when treated with titanium dioxide. But in these experiments, either the titanium dioxide was not food grade or had been ground to produce nanoparticles. There were also some animal trials that raised concern due to adverse effects seen in the gastrointestinal tract. But in this case, rats were fed titanium dioxide directly. Quite a different scenario from the chemical being present in food as an additive.
Health Canada’s decision, in turn, was based on studies in which food grade titanium dioxide was administered to animals in their food, often at much higher doses than any possible human exposure. This is a more realistic way to get a handle on consumer risk. Rats exposed from conception to adulthood showed no genotoxic or carcinogenic effects, nor were there any adverse consequences noted on the reproductive, immune, gastric or nervous systems. Furthermore, the particles in food grade titanium dioxide are mostly in the 200-300 nanometer range. Particles of this size make for optimal light scattering and produce the best colour. Therefore, when it comes to food, attributing risk based on the behaviour of titanium dioxide nanoparticles is not appropriate.
What then do we make of IARC listing titanium dioxide as a possible human carcinogen? IARC’s evaluation is based on a hazard analysis, not a risk analysis. Hazard is an innate property of a substance and cannot be changed, while risk takes into account the extent and mode of exposure. It was experiments that linked the inhalation of titanium dioxide with lung tumours in animals that led to IARC listing the chemical as a possible human carcinogen. This may be relevant to occupational exposure in the paint and paper industries, but not to food additives, as is indeed pointed out by IARC. Furthermore, titanium dioxide is poorly absorbed from the gut, with most of it being excreted in the feces.
In summary, if we go by the studies that are relevant to humans, there is no reason to worry about titanium dioxide in food. However, there is reason to worry about the foods in which this colouring agent is found. Consumption of candies, chewing gum, gummies and coffee creamers should be limited, not because they may contain titanium dioxide, but because they are nutritional paupers. In any case, if you snack on apples, oranges, peppers, carrots or nuts instead of Snickers or Nerds, you can sweep the issue of titanium dioxide under the carpet.
