Registration Dossier
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EC number: 250-807-9 | CAS number: 31795-24-1
Toxicity to aquatic algae and cyanobacteria
Administrative data
Link to relevant study record(s)
Description of key information
Toxicity to Algae: 72 EC50 >120 mg/l and NOEC of >=120 mg/l (nominal) (>3.6 and >= 3.6 mg/l, respectively, measured) (highest concentration tested) (OECD 201 (Alga, Growth Inhibition test)), read-across from an analogous/structurally related substance, trimethoxy(methyl)silane (CAS 1185-55-3). For risk assessment purposes a 72 EC50 value of >120 mg/l and NOEC of ≥120 mg/l is used. The EC50 is equivalent to >83 mg/l when expressed in terms of the silanol hydrolysis product.
Key value for chemical safety assessment
Additional information
The properties of this substance can be read-across from tests carried out for trimethoxy(methyl)silane (CAS 1185-55-3), which hydrolyses rapidly to give methylsilanetriol and methanol. The properties of methanol are well characterised; it is non-toxic to the environment and it is considered unlikely that its presence would significantly affect the results of tests performed with trimethoxy(methyl)silane.
There are no reliable algal toxicity data available for potassium methylsilanetriolate (CAS 31795-24-1), therefore good quality data for an appropriate structural analogue trimethoxy(methyl)silane, (CAS 1185-55-3), have been read across. The silanol hydrolysis product of the surrogate substance is the same substance as that upon which this chemical safety assessment is based, i.e. methylsilanetriol (CAS 2445-53-6). The other hydrolysis product of the surrogate substance is methanol.
A 72-h EC50 value of >120 mg/l and NOEC of >=120 mg/l (nominal) (>3.6 and >=3.6 mg/l, respectively, measured) (highest concentration tested) have been determined for the effects of trimethoxy(methyl)silane (CAS 1185-55-3) on growth rate of Pseudokirchneriella subcapitata. In view of the test media preparation method/exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results may be expressed in terms of concentration of the hydrolysis product, methylsilanetriol, by applying a molecular weight correction: (MW of silanol = 94.14 / MW of parent = 136.22) * (CONCENTRATION OF PARENT = >120 (3.6 mg/l measured)) = >83 mg/l as methylsilanetriol, nominal concentration (>2.5 mg/l measured concentration).
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