nonapotassium 2,4,6-trihydroxy-4-methyl-3,5-dioxa-2,4,6-trisilaheptane-2,6-bis(olate) 2,6,8-trihydroxy-4,6-dimethyl-3,5,7-trioxa-2,4,6,8-tetrasilanonane-2,4,8-tris(olate) 6-hydroxy-2,4,6-trimethyl-1,3,5,2,4,6-trioxatrisilinane-2,4-bis(olate) dihydroxy(methyl)silanolate {[dihydroxy(methyl)silyl]oxy}(hydroxy)methylsilanolate

Endpoint summary

Additional information

No genetic toxicity data are available for reaction mass of potassium methylsiliconate. However, data are available for the read-across substance potassium methylsilanetriolate which is a multi-constituent substance containing methylsilanetriolate, dimers and oligomers of methylsilanetriolate, and potassium hydroxide at high pH in aqueous solution (EC number 250-807-9).

In contact with water reaction mass of potassium methylsiliconate is dissolving. The resulting aqueous solution is very similar to the read-across substance potassium methylsilanetriolate. Both aqueous solutions are only stable at high pH. As the pH is lowered, polymerisation occurs. Therefore it is considered appropriate to read across the available date on potassium methylsilanetriolate. The read-across substance, Reaction mass of monomer, dimer, trimer and oligomer potassium methylsilanetriolate (EC 259-807-9) has been tested for bacterial mutagenicity. The result was negative.

 

An in vitro cytogenicity study is available for the surrogate substance trimethoxy(methyl) silane (CAS 1185-55-3) which gave apositive result. However the positive result was not confirmed in an in vivo micronucleus study with trimethoxy(methyl) silane (CAS 1185-55-3). Reaction mass of potassium methylsiliconate is a multi-constituent substance containing methylsilanetriolate, dimers and oligomers of methylsilanetriolate, and potassium hydroxide. In contact with water the substance is dissolving. The resulting aqueous solution is only stable at high pH. As the pH is lowered, polymerisation occurs. Under comparable conditions of concentration and pH methylsilanetriolate is equivalent to the parent acid, methylsilanetriol.

The surrogate substance, trimethoxy(methyl)silane (CAS 1185-55-3), hydrolyses in contact with water at pH 7 (half-life approx. 2 hours), producing methanol and methylsilanetriol. The properties of methanol are well characterised: as it is not genotoxic it is considered unlikely that its presence would significantly affect the results of tests performed with trimethoxy(methyl) silane. Therefore, since both substances share the same silanol product it is considered appropriate to read across the available data on trimethoxy(methyl)silane.

Short description of key information:
In vitro:
Gene mutation (Bacterial reverse mutation assay / Ames test) read across from reaction mass of monomer, dimer, trimer and oligomer potassium methylsilanetriolate (EC 259-807-9): negative with and without activation in all strains tested (OECD TG 471)
Cytogenicity in mammalian cells: read-across from analogous substance trimethoxy(methyl)silane (1185-55-3): positive in CHO cells (with activation) (OECD TG 473)
In vivo:
Micronucleus assay oral study in mouse: the related substance trimethoxy(methyl)silane was negative (OECD TG 474)

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

The available information for the read across substances indicates that when tested in vitro, the read-across substance potassium methylsilanetriolate (EC number 250-807-9) did not induce mutations in bacteria.The analogous substance trimethoxy(methyl) silane (CAS number 1185-55-0), although producing an increase in the percentage of cells with aberrations in the presence of activation in anin vitrocytogenicity study, did not cause induction of micronuclei in thein vivomouse micronucleus assay. Therefore it is considered that classification for mutagenicity is not required.