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Data are available for triacetoxyethylsilane (CAS 17689-77-9) from two in vitro bacterial mutagenicity studies. No further data are available for the registered substance, however, data are available for three other related substances, methylsilanetriyl triacetate (CAS 4253-34-3), triethoxy(methyl)silane (CAS 2031-67-6) and trichloro(methyl)silane (CAS 75-79-6).

It is considered appropriate to read across the genetic toxicity results for methylsilanetriyl triacetate, triethoxy(methyl)silane and trichloro(methyl)silane because triacetoxyethylsilane and triethoxy(methyl)silane hydrolyse to ethylsilanetriol and methylsilanetriol respectively, which are structural analogues, and acetic acid and ethanol, which are not genotoxic. Trichloro(methyl)silane and methylsilanetriyl triacetate also hydrolyse to methylsilanetriol. The other hydrolysis products are hydrogen chloride and acetic acid. Hydrogen chloride and ethanol are not expected to contribute to genetic toxicity. Information on acetic acid in the public domain shows no evidence for genetic toxicity for this hydrolysis substance, which supports the conclusion from the data for methylsilantriyl triacetate, which also produces acetic acid as the second product of hydrolysis.

The two bacterial studies on triacetoxyethylsilane gave conflicting results. In the earlier study, a mixture of triacetoxyethylsilane and triacetoxymethylsilane was tested in an assay according to a protocol that is similar to OECD 471. The range of strains was not compliant with the current guideline, and the plates were not replicated. An increase in the number of revertants was observed in Salmonella typhimurium strains TA 100 and TA 1535 with and without metabolic activation. However, as the study differs from the guideline in a number of respects, and the increase in mutant colonies although considerable in magnitude was not dose-dependent, it is not considered that this increase indicates a biologically relevant effect (Dow Corning 1979).

Triacetoxyethylsilane has been tested in a further study according to a protocol that is equivalent to OECD 471. No increase in the number of revertants was observed at any concentration in any of the strains tested, with and without metabolic activation, in either the initial spot plate test or the repeat assay using the plate incorporation method. The positive and solvent controls gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test. (Dow Corning 1984).

In view of the deficiencies in the first study, and the lack of dose-dependence of the positive result, the second study (Dow Corning 1984) was selected as key.

Triethoxy(methyl)silane has been tested according to a protocol that is similar to OECD 473. Appropriate concurrent negative and positive controls were included and the expected responses were observed. The test substance did not cause a statistically significant, dose related increase in chromosome aberrations. The test substance was considered non-clastogenic in mouse lymphoma L5178Y cells under the conditions of the test (Jagannath 1979).

Methylsilanetriyl triacetate has been tested according to OECD 473 and under GLP. No increase in the number of chromosome aberrations per cell or the number of cells with aberrations was detected at any concentration with and without metabolic activation in Chinese hamster ovary cells. Solvent and positive controls gave expected results. It is considered that the test substance is negative for the induction of chromosome aberrations under the conditions of the test (Gudi and Brown 2002).

Trichloro(methyl)silane was tested for mutagenicity in mammalian cells in a reliable and reproducible assay according to a protocol that is similar to OECD 476. Appropriate concurrent negative and positive controls were included and the expected responses were observed. There was no evidence of gene mutation. It is concluded that trichloro(methyl)silane is negative for the induction of mutation in mammalian cells under the conditions of the test (Litton Bionetics 1978).

Triethoxy(methyl)silane has been tested according to a protocol that is similar to OECD 476, without replication. No increase in mutant frequency was observed at any concentration with or without metabolic activation. The solvent and positive controls gave expected results. It is concluded that the test substance is negative for mutagenicity in mouse lymphoma L5178Y cells under the conditions of the test (Jagannath 1978).

In vivo testing is not required as the overall conclusion of the in vitro genetic toxicity studies is negative.


Short description of key information:
In vitro
Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without metabolic activation in Salmonella typhimurium TA 97, 98, 100, 1535 and E.coli WP2 (OECD draft protocols 471 and 472 (1983)) (Dow Corning 1984).
Cytogenicity in mammalian cells: read-across from analogous substance Methylsilanetriyl triacetate (CAS 4253-34-3): negative in CHO cells (OECD TG 473) (Gudi and Brown 2002).
Cytogenicity in mammalian cells: read-across from analogous substance triethoxy(methyl)silane (CAS 2031-67-6): negative in CHO cells (similar to OECD TG 473) (Jagannath 1979).
Mutagenicity in mammalian cells: read-across from analogous substance trichloro(methyl)silane (CAS 75-79-6): negative in mouse lymphoma L5178Y cells (similar to OECD 476) (Litton Bionetics 1978).
Mutagenicity in mammalian cells: read-across from analogous substance triethoxy(methyl)silane (CAS 2031-67-6): negative in mouse lymphoma L5178Y cells (similar to OECD 476) (Jagannath 1978)

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the available in vitro genotoxicity data, triacetoxyethylsilane is not classified for mutagenicity according to Regulation 1272/2008/EC.