Titanium dioxide (TiO2)
Titanium dioxide (TiO2) (CAS# 13463-67-7, EC# 236-675-5) is an ubiquitous white material found in a diverse range of products including foods, food contact materials, pharmaceuticals and cosmetics as a pigment. It is widely used in the formulation of printing inks as a white pigment and has the highest degree of opacity of any white pigment. In order to act as a suitable pigment for inks, TiO2 powder will be dispersed in a binder down to micrometer size, which is the optimum size for light scattering. In general, the nano form is not used as a pigment in printing inks as it is transparent.
Classification of Titanium dioxide by the European Commission
In February 2020, the European Commission (EC) classified TiO2 in powder form containing 1% or more of particles with aerodynamic diameter ≤10 μm as “Carcinogenic category 2 (H351) by inhalation”. Liquid mixtures containing 1% or more of titanium dioxide particles with aerodynamic diameter ≤ 10 μm have to be labelled with the warning that hazardous respirable droplets may be formed when sprayed, which should not be inhaled. Solid mixtures containing 1% or more of titanium dioxide have to be labelled with the warning that hazardous respirable dust may be formed when used, which should not be inhaled (EU 2020/217). This hazard classification to TiO2 in powder form by the EC is based on the induction of lung cancer in various animal studies via impaired clearance and chronic inflammation.
The current hazard classification of TiO2 in Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation) is more complex than other typical entries as it is limited to inhalation only and further accompanied by several restrictions intended to limit its scope. The EC attempted to limit the TiO2 hazard classification to powders and included the following text “in a powder form containing 1% or more of particles with aerodynamic diameter ≤10 μm”. This means that currently the classification does not apply for TiO2 or mixtures containing TiO2 which are not in the respective specified forms. In a testing program conducted by the Titanium Dioxide Manufacturers Association (TDMA) to measure the content of particles with aerodynamic diameter ≤10 μm, a vast majority of grades of TiO2 did not meet this criteria for classification. In addition, TiO2 was subjected to a significant amount of robust safety assessments by a large number of global regulatory authorities and has consistently been found to be safe for a broad variety of applications. Hence, the current CLP hazard classification of “Carcinogenic category 2 (H351) by inhalation” for TiO2 was challenged by the industry and a recent judgement delivered on 23 November 2022 by the Court of Justice of the European Union annulled this classification. The principal reason for the annulment was that an error had been made in the assessment of the reliability and acceptability of the study on which the classification was based and can only apply to a substance that has the intrinsic property to cause cancer. Nevertheless, the existing hazard classification “Carcinogenic category 2 (H351) by inhalation” for TiO2 is still applicable as the respective EU court judgement is currently being appealed to the European Court of Justice (ECJ).
Scientific Opinion of EFSA to TiO2
On March 25, 2021, the European Food Safety Authority (EFSA) has published a scientific opinion based on an updated safety assessment of the food additive titanium dioxide (E 171). EFSA announced that “it is not possible to rule out genotoxicity from TiO2 and therefore E 171 can no longer be considered as safe when used as a food additive”. In January 2022, the European Commission adopted a Regulation removing the authorization of E 171 as a food additive. However, several uncertainties were noticed in the scientific data reviewed by EFSA. In contrast, regulatory authorities like Health Canada, Food Standards Australia New Zealand (FSANZ), the United Kingdom Food Standards Agency (UK FSA) and the United States Food and Drug Administration (FDA) have all concluded that they do not foresee safety concerns for the use of TiO2 as a food additive and have allowed its continued use. In a recent independent study by the Japanese National Institute of Health Sciences (NIHS) no effects whatsoever were observed either due to the use of TiO2 as a food additive.
E171 is a specific grade of TiO2 used as a food additive and is normally not used for food contact applications including printing inks. It is important to note that there is no direct link between this updated regulation and the use of TiO2 in food contact applications. TiO2 is authorized for the use as an additive in food contact materials made of plastic in line with Regulation (EU) No 10/2011. It is also listed in the Swiss Ordinance of the FDHA on articles and materials (RS 817.023.21) in Annex 10 Part A (toxicologically evaluated) with no specific migration limit or other restrictions, hence a generic specific migration limit of 60 mg/kg shall apply for printing inks.
Siegwerk’s position on the use of TiO2 as white pigment in printing inks
For Siegwerk manufactured printing inks containing TiO2, the warning statement EUH211: “Warning! Hazardous respirable droplets may be formed when sprayed. Do not breathe spray or mist.” is shown on the labels as per Regulation (EC) No 1272/2008 (CLP Regulation). This warning statement is mandatory regardless of whether a liquid mixture is suitable for spray applications or not. It is therefore shown on relevant Siegwerk product labels, but is of limited relevance in practice. Inhalation exposure due to potential ink misting on high-speed printing machines does not raise concerns under typical printing conditions. Additionally, TiO2 particles in the printing inks are firmly embedded in the binder matrix and, as such cannot be inhaled. It should also be noted that Siegwerk manufactured printing inks containing TiO2, carrying exclusively warning statement EUH211 are still considered to be non-hazardous.
With regard to occupational safety, Siegwerk implements all necessary measures to comply with standard occupational health and safety requirements for the safe handling of TiO2 materials during the manufacturing of the printing inks.
Siegwerk is committed to ink safety and its efforts to supply the safest inks go far beyond legal requirements. It proactively invest utmost efforts on the product safety and abide to the latest global regulatory guidelines and scientific techniques to address emerging safety concerns, if any due to the use of TiO2 as a white coloring pigment in its printing inks. For now, Siegwerk continues to share the conviction of the German Paint and Printing Ink Industry Association (VdL), the European Council of the Paint, Printing Inks and Artists’ Colours Industry (CEPE) and the Titanium Dioxide Manufacturers Association (TDMA) that the use of titanium dioxide is safe in paints, coatings and printing inks.