Titanium dioxide (also known as titanium(IV) oxide, chemical symbol TiO2) is a white, fine-grained powder found in nature as rutile or anastase minerals.
Its most important applications are in the manufacture of paints and varnishes, paper and plastics, which account for around 80% of world consumption of titanium dioxide. Other pigment applications such as printing inks, rubber, cosmetics and foodstuffs account for a further 8%. The remainder is used in other applications, such as the production of technical pure titanium, glass and glass ceramics, electrical ceramics, metal patinas, catalysts, electrical conductors and chemical intermediates.
Titanium dioxide is a popular paint ingredient, estimated to be present in 2/3 of all commercial paints. According to a 2018 survey, the total value of commercially available titanium dioxide-containing paints was US $13.2 billion.
In terms of cosmetic use, it is used in small amounts as a thickening, opacifying excipient and in larger amounts as a physical sunscreen in the form of sunscreen cream, as titanium dioxide also filters out harmful UV rays.
On the basis of Annex II of Regulation (EC) No 1333/2008, titanium dioxide has been authorised as a food additive (colourant) under code E171 from 20 January 2019. The role of E171 is to intensify the colour of food, giving food a more attractive visual appearance.
A 2016 food safety review raised the possibility that titanium dioxide may have adverse health effects if ingested. Size distribution analyses showed that food-grade TiO₂ batches consist of an average of 50% of particles less than 100 micrometres in diameter, and always contain a nanoscale fraction, an unavoidable by-product of manufacturing processes.
Studies have clearly not excluded the possibility of gene-damaging or mutagenic effects. The EFSA (European Food Safety Authority), after reviewing thousands of studies on the subject in recent years, has concluded that titanium dioxide is unsafe for use as a food additive. The European Commission and the Member States are considering stricter regulation of the use of titanium dioxide in the food industry on the basis of the EFSA study.
Under the current CLP Regulation, there is no mandatory hazard classification for titanium dioxide. But recent published studies suggest that inhalation of its dust may cause cancer. Therefore, the Commission has adopted an accelerated procedure to adopt an amending CLP Regulation (COMMISSION REGULATION (EU) 2020/217), which will become mandatory on 1 October 2021, with a strong emphasis on a more stringent classification of titanium dioxide containing nanoparticles.
The decision on titanium dioxide could set a precedent for chemicals with similar harmful properties, and the stakes are high. Just a few years ago, there was a danger that concerns about public health and workers’ rights – backed up by science and the law – would be sacrificed to diversionary tactics by industry, including cost, ‘over-regulation, and free trade.
Firstly, the Regulation sets out the justification for a more stringent classification: since lung cancer caused by titanium dioxide can be linked to inhalable titanium dioxide particles, it is appropriate to examine these particles more closely. The toxicity observed in the lungs and the subsequent tumour development are thought to be caused by deposited, insoluble titanium dioxide particles.
Liquid mixtures containing at least 1 % of titanium dioxide particles of 10 μm or less in diameter must be labelled with the following statement:
EUH211: – Warning! Hazardous respirable droplets may be formed when sprayed. Do not breathe spray or mist.
The label on the packaging of solid mixtures containing 1 % or more of titanium dioxide shall bear the following statement:
EUH 212 – „Warning! Hazardous respirable dust may be formed when used. Do not breathe dust.”
In addition, the label on the packaging of liquid and solid mixtures intended for non-domestic use and not classified as dangerous but labelled with the phrases EUH211 or EUH212 shall also bear the phrase EUH210.
Titanium dioxide (CAS No 13463-67-7) is classified in hazard class Carcinogenicity, chategory 2, together with the hazard statement H351 – Suspected of causing cancer (inhalation), if present in the form of dust containing at least 1 % of particles with an aerodynamic diameter of 10 μm or less.
In the case of mixtures containing titanium dioxide, classification as Suspected of causing cancer by inhalation shall apply only to mixtures in powder form containing titanium dioxide in the form of particles of at least 1 % and of an aerodynamic diameter not exceeding 10 μm or incorporated into such particles.
However, workers using TiO2 powder should not panic. Indeed, exposure to titanium dioxide dust may occur during the manufacturing process. However, there are regulations at both EU and national level for the exposure and protection of workers. In addition, the experiments on rats cited by ECHA used unrealistically high levels of titanium dioxide, which would not be allowed in a manufacturing environment. By following the appropriate occupational health and safety standards for the manufacturing technology, the exposure to workers’ health can be minimised.