Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

No data are available on the short-term toxicity of the registered substance to fish, aquatic invertebrates and algae. However a 96-h LC50 value of >500 mg/l and NOEC of ≥500 mg/l have been determined for the effects of a read-across substance, triethoxy(methyl)silane (CAS 2031-67-6), on mortality of Brachydanio rerio. Similarly, a 72 -h EC50 value of >120 mg/l and NOEC of ≥120 mg/l have been determined for the effects of a read-across substance, trimethoxy(methyl)silane (CAS 1185-55-3), on growth rate of Pseudokirchneriella subcapitata. It is likely that in both cases the test organisms were primarily exposed to the hydrolysis products of the substances. A 48-h EC50 value of >100 mg/l and NOEC of 10 mg/l have been determined for the effects of the read-across substance, Reaction mass of monomer, dimer, trimer and oligomer potassium methylsilanetriolate (EC 250-807-9) on mobility of Daphnia magna.

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. Since both substances share the same silanol product it is considered appropriate to read across the available data on trimethoxy(methyl)silane.

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 measured data is supported by predictions for the hydrolysis product methylsilanetriol (for details see sect.7.1.7 below).