Titanium dioxide (TiO2) is used in hundreds of products internationally as a whitening agent and ultraviolet block. In a landmark decision, the EU Court of Justice has now recognized that the ECHA Committee for Risk Assessment, who carried out a TiO2 assessment in 2017, “committed a manifest error.” We have previously discussed TiO2 here because it is a well-established food additive in the US, Canada, and the UK, found in candies, chewing gum, white sauces, and cake icing/frosting. But, after a 6-month phasing-out period, it was banned from food use in the EU in August 2022, a result of the inconclusive evidence on genotoxicity.

The EU Court decision focused on the committee classification for chemicals uses, and ruled that two errors were made. Both of which are notable. The committee considered the consequences of inhaling TiO2 particles, and the study they relied on used rats. But past a certain point, rats in these studies can no longer clear particles from their lungs. When the overload level was correctly calculated, including the propensity of the particles to aggregate, more than 60% of their lungs were filled with particles. These results should not have been accepted as relevant to humans, as there is no reasonable scenario where that exposure level is possible. The second error concerns the word “intrinsic”: does TiO2 have an intrinsic property to cause cancer? The rat’s lung cancer was a consequence of inflammation caused by TiO2 particles that they had inhaled and could not clear. If they had encountered TiO2 in another form or particles of a different size, the outcome would have been different. The toxicity depended on the form and size of the titanium dioxide particles – which is not an intrinsic property.

The court decision also has implications for the EU ban of TiO2 in food, because both decisions did not rely on valid evidence, and unnecessarily forced manufacturers to reformulate their products. The ban was widely reported and spread unnecessary concern to consumers worldwide. The story provides a salutary case-study on the importance of evidence based decision making for substances, and the need for carefully designed toxicology studies as a basis for red-listing substances.