Rutile (TiO2)

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Read across concept

Synthetic rutile consists primarily of a titanate phase (solid solution) most of which is titanium in an oxidised form. Upon ingestion, a low rate of dissolution in the GI tract is assumed, based on the experimental verified inertness of the material. Any material being released from Synthetic rutile under physiological conditions will be in the form of ionic titanium, which is similarly the case for titanium dioxide, thus read-across from skin sensitisation data on titanium dioxide is considered feasible without any restrictions.

Furthermore, transformation/dissolution testing according to “OECD 29 Environmental Health and Safety Publications, Series on testing and assessment, Guidance document on transformation/ dissolution of metals and metal compounds in Aqueous media” has shown that synthetic rutile compared to titanium dioxide has a similar release rate of titanium ions (please refer to the respective entry under the endpoint water solubility).

Migrated from Short description of key information:
No reliable results are available for skin sensitisation of synthetic rutile. Therefore, read-across is proposed to available data on TiO2. Titanium dioxide has been tested in two different systems for sensitising properties. Both study types show a negative response, thus titanium dioxide does not require classification as sensitiser.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

There are two reliable animal studies, performed according to OECD guidelines 406 and 429 and according to GLP, both showing that titanium dioxide has no sensitising properties.

Migrated from Short description of key information:
No reliable results are available for respiratory sensitisation of synthetic rutile. Therefore, read-across is proposed to available data on TiO2. Titanium dioxide does not show respiratory sensitising properties in animal studies or in exposure related observations in humans.

Justification for classification or non-classification

Sensitisation

The references Hoban, D.(2006) and Moore, G.E.(1994), are considered as the key studies on skin sensitisation and will be used for classification. It is considered that these conclusions can be read across to Synthetic Rutile. The overall sensitisation results are as follows:

Hoban, D.(2006) – Local lymph node assay (LLNA) in mice

SIs of less than 3.0 were observed at all test concentrations of titanium dioxide (5, 25, 50, 100%). Therefore, an EC3 value (the estimated concentration required to induce a threshold positive response, i.e., SI = 3) for the test substance under the conditions of the study was not calculable.

Moore, G.E.(1994) – Buehler method in guinea pigs

The incidence of sensitisation after the challenge application was 0/20. Thus, the classification criteria acc. to regulation (EC) 1272/2008 as skin sensitizer are not met since 0% of the test animals responded.

 

Respiratory sensitisation

There is no evidence on specific respiratory hypersensitivity in humans following repeated inhalation exposure with titanium dioxide. Furthermore, none of the repeated dose toxicity studies via inhalation reports respiratory hypersensitivity in the test animals. Thus, the classification criteria acc. to regulation (EC) 1272/2008 as respiratory sensitiser are not met. It is considered that these conclusions can be read across to Synthetic Rutile.