Titanium dioxide is persistently causing concern in the coatings industry.
This applies to Pharmaceuticals, Food, Cosmetics, Food Supplements Industry.
We have asked Didier Leroy, Technical Director at CEPE, to comment on the current state of affairs.
In June 2017, the European Chemicals Agency (ECHA) announced the Committee for Risk Assessment’s (RAC) conclusion that the available scientific evidence meets the criteria in the CLP regulation to classify titanium dioxide as a substance suspected of causing cancer through the inhalation route. Due to extensive need for discussion, the European Commission brought the issue to the November 2017 meeting of the Competent Authorities for REACH and CLP (Caracal).
What is the current situation regarding a potential classification of TiO2?
Didier Leroy: ECHA’s Committee for Risk Assessment (RAC) proposed to classify TiO2 as a Category 2 carcinogen by inhalation. In most cases the European Commission takes RAC’s opinion as such to propose it to the REACH Committee. In this case the Commission brought it to the Competent Authorities for REACH and CLP (Caracal), as it noted that the dossier is ‘particular’ and requires discussion. The agenda point turned initially from ‘Classification of mixtures containing TiO2’ to ‘Classification of TiO2 and mixtures containing TiO2’, which we considered as a favorable sign to widen the discussion. The Commission noted that it is a non-intrinsic mode of action in the classical sense, as it is a ‘particle effect’ (named PSLTs for Poorly Soluble particles of Low Toxicity). In their paper explained during the November Caracal meeting they raise three questions and ask views of stakeholders, especially of member states.
What has been the outcome of the recent Caracal meeting?
Leroy: There have been enough member states speaking up to recognise the particularity of this dossier and the need to have enough time for proper discussion. The European Commission asked written comments and will bring the topic to the March 2018 Caracal meeting. The written comments received by the end of December 2017 (which are publicly available) overall confirm the singularity of this dossier, and the need to have more time to discuss it during the coming months. We think that several member states have not yet made up their mind, but given the reaction of others they will now also take particular care of addressing this issue.
What is CEPE’s attitude toward this outcome?
Leroy: CEPE considers that there is still a chance to discuss whether CLP is the appropriate tool to deal with such a substance, as raised in our letter from May 2017 to the Commission. Some member states think that indeed CLP may not be the appropriate tool to regulate such ‘dust effect’ by inhalation. Others do not question the point of principle that without new scientific evidence the RAC opinion cannot be challenged, but they understand the negative consequences that the TiO2 case may bring and would like to mitigate the impact. However, so far we have not seen anyone proposing a viable solution for an exemption/derogation (whether in the form of a specific Note in Annex VI entry or through the CLP Articles raised by the Commission in their paper tabled at the November Caracal meeting), and we aim at having further discussions with them. No member state requested that the case should not be discussed at all.
In how far will it affect the final decision on whether TiO2 will be classified?
Leroy: The outcome of the November Caracal meeting built a good momentum. We think that most member states are now seriously considering this dossier and the various negative consequences that the classification would have on CLP, on other legislations and on other PSLTs. At this stage it is difficult to predict whether TiO2 will not be classified at all because this case is unprecedented and the decision to consider that CLP is not the appropriate tool is not easy to make at this stage of the CLH process. It may require further data, evidence and discussion after the March 2018 Caracal meeting.
How does CEPE react, do you plan any measurements in the meantime?
Leroy: CEPE is actively engaged with the authorities in charge in advocating to explain those negative consequences and the precedent that it would make. We think that TiO2 does not deserve a classification because the proposed hazard based classification will not better protect human health. It would on the other hand create confusion, be detrimental to the legislation itself and create downstream consequences on others. The current proposal is not based on strong evidence, as can be noted in the RAC opinion. The dossier evaluation under the Community Rolling Action Plan (Corap) will start in 2018 and the REACH registrants have committed to answer all relevant open question. When new studies are available to clarify the intrinsic hazard, when clarification on the relevance of the rat dust lung overload issue is available, when the CLP guidance will be updated to clarify this still open issue and when risk assessment for all possible routes will confirm safe use, then the regulators will be in a better position to decide if TiO2should be regulated and if so, how.
After the French authorities have proposed to classify TiO2 as classify it as Carcinogenic Category 1B, there has been much discussion of alternatives. Akzo Nobel Decorative Paints has studied the formulation of white opaque coatings with alternative substances.
Hans de Jong and Jitte Flapper of Akzo Nobel Decorative Paints carried out a theoretical study to estimate the potential of other opacifying materials to replace TiO2 as a white pigment. The maximum theoretical hiding power of other non-absorbing (i.e. white) opacifying substances was assessed. In order to do this, the Scattering Coefficient was calculated as a function of particle diameter. Calculations were then performed to determine how thick a coating layer should be, compared to one containing TiO2, to achieve equal hiding.
Substances evaluated in the study
Inorganic pigments were selected from the international Colour Index. The best pigment without any associated adverse labelling is zirconium dioxide, with a refractive index of 2.13. Widely used filler materials such as calcium carbonate (CaCO3) and barium sulfate (BaSO4) were also studied, but their refractive indices (1.4-1.7 and 1.6 respectively) are very close to those of theresins used in paints and consequently they will not be effective opacifiers.
Even the best alternatives show great limitations
The best result for a material with no associated adverse labelling was obtained for zirconium dioxide. Using this material, a four-fold increase in layer thickness would be required to achieve similar hiding compared to a titanium dioxide pigmented coating. Frequently used filler materials such as calcium carbonate or barium sulfate would require a layer more than 100 times thicker.
This also means that four times more raw materials would have to be used (binders and solvents etc.). All of this would mean a considerable increase in (for example) labour, raw material depletion, VOC emissions and end-user costs.
Table 1: Calculated optimal Scattering Coefficient and relative layer thickness:
Substances show no sufficient hiding power
The theoretical calculations carried out in this project conclude that titanium dioxide is by far the most efficient opacifier for use in coatings and that is no other material or other way of opacifying available that would give sufficient hiding power to a coating. The only other way to achieve hiding would be to increase layer thickness. Even in the best-case scenario, a layer four times thicker would be required. But this would bring along unacceptable disadvantages, both from a practical point of view (e.g. costs, labour) as well as from environmental point of view (e.g. raw material use, VOC emission). Hans de Jong and Jitte Flapper therefore conclude that the coating industry cannot create opaque white coatings without the use of titanium dioxide.
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