Tetra-n-butyl titanate, polymer with water

Endpoint summary

Additional information

There is available bacterial mutagenicity test for tetra-n-butyl titanate. However, two other tests, in vitro mammalian gene mutation test and chromosome aberration test, have not been conducted for the target substance. Instead, these tests have been done for titanium tetrabutanolate, the analogue category substance. Also, in accordance with column 2 of REACH Annex XI, testing is scientifically unjustified if the relevant tests have been conducted for the analogue category substance.

Mutagenicity in bacterial test systems

In vitro mutagenic activity of tetra-n-butyl titanate, polymer with water has been evaluated in bacterial reverse mutation assay (Ames test). The study by Verspeek-Rip C. M (2012) is considered reliable without restrictions as the study was performed in compliance with GLP according to OECD guideline 471. This study was conducted by using five strains of Salmonella typhimurium bacteria (TA98, TA100, TA1535, and TA1537) and Escherichia coli (WP2uvrA) with and without metabolic activation. Tetra-n-butyl titanate, polymer with water was tested for its ability to induce mutations in the concentration of 3, 10, 33, 100, 333, 1 000, 3 330 and 5 000 µg/plate. The test substance did not induce mutations under conditions of this study.

Cytogenicity in mammalian cells

The weight of evidence approach is used to fulfill the data requirements for this endpoint. The mammalian cytogenicity study is conducted for titanium tetrabutanolate, the analogue category member of the target substance (Verbaan, I.A.J, 2013).

The analogue substance hydrolyses rapidly (half-life < 5 min) in aqueous test media releasing n-butanol with the hydrated titanium oxide precipitating out of the test solution. Due to the rapid hydrolysis, it was considered that any toxicity would be due to the presence of n-butanol and not the parent test item. The category justification is presented in the Annex I of this CSR.

The potential of titanium tetrabutanolate to induce chromosome aberrations was assessed in cultured peripheral human lymphocytes by Verbaan I. A. J (2013). This study is considered reliable without restrictions as the study was performed in compliance with GLP according to OECD guideline 473. Tetra-n-butyl titanate, polymer with water was tested with and without metabolic activation in doses up to 1 000 µg/ml. The compound was not clastogenic in human lymphocyte assay either in the presence or absence of metabolic activation, i. e., it did not increase the number of polyploid cells and cells with endoreduplicated chromosomes in the cells.

Further evidence on possible cytogenicity comes from the mammalian micronucleus test conducted for n-butanol, the degradation product of the target substance (Lasne, C., 1984). This study evaluated genotoxicity potential of n-butanol using in vitro micronucleus assay. n-Butanol at concentration up to 50 µl/dish failed to induce micronuclei in the test conditions. Based on this result n-butanol can be concluded as non genotoxic.

Mutagenicity in mammalian cells

The weight of evidence approach is used to fulfill the data requirements for this endpoint. The mammalian mutagenicity study was conducted for titanium tetrabutanolate, the analogue category member of the target substance (Verspeek-Rip, C.M., 2013).

The mammalian gene mutation study was conducted for titanium tetrabutanolate, the analogue category member of the target substance. The analogue substance hydrolyses rapidly (half-life < 5 min) in aqueous test media releasing n-butanol with the hydrated titanium oxide precipitating out of the test solution. Due to the rapid hydrolysis, it was considered that any toxicity would be due to the presence of n-butanol and not the parent test item. The category justification is presented in the Annex I of this CSR.

The potential gene mutagenic activity of titanium tetrabutanolate has been evaluated in L5178Y mouse lymphoma cells by Verspeek-Rip (2013). The test was performed according to OECD guideline 476 and the test was conducted in compliance with GLP. The substance was tested in two independent experiments with modifications in the duration of treatment time and in the concentration of the metabolic activation system (S9-mix). Titanium tetrabutanolate was not mutagenic, both in the presence and absence of S9-mix.

As conclusion, the results from genotoxicity assays of tetra-n-butyl titanate, polymer with water and the analogue substance are universally negative. In addition, neither of the decomposition products (n-butanol and TiO₂) of the target substance has classification entries for genotoxicity.

Justification for selection of genetic toxicity endpoint
Conclusion based on the following assays: Bacterial reverse mutation assay (Ames test); Mammalian cell gene mutation assay, In vitro mammalian chromosome aberration test.

Short description of key information:
Gene mutation (reverse mutation assay/Ames test): negative in all tested bacterial strains with and without metabolic activation (OECD 471).

Following data is obtained from the analogue substance, titanium tetrabutanolate:
Chromosome aberration study in mammalian cells: negative, with and without metabolic activation (OECD 473).
Gene mutation study in mammalian cells: negative, with and without metabolic activation (OECD 476).

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the results of in vitro bacterial gene mutation study conducted for the target substance, in vitro mammalian chromosomal aberration and gene mutation studies conducted for the analogue substance, tetra-n-butyl titanate, polymer with water has no potential to cause mutagenicity and genotoxicity. No classification is required according to the criteria of CLP regulation 1272/2008 and the EU directive 67/548/EEC.