Registration Dossier
Registration Dossier
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EC number: 220-449-8 | CAS number: 2768-02-7
Endpoint summary
Administrative data
Description of key information
Additional information
No terrestrial toxicity data are available with the registered substance. Terrestrial testing is currently waived for the following reasons:
In accordance with Column 2 of REACH Annex IX, there is no need to further investigate the effects of this substance in long-term terrestrial toxicity studies because, as indicated in guidance R.7.11.6 (ECHA 2016), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio is well below 1 and therefore the risk is already adequately controlled and further testing is not justifiable.
The silanol hydrolysis product, vinylsilanetriol (CAS 143-48-6), upon which the chemical safety assessment is based, is highly water soluble and has a low log Kow value and therefore, exposure of the soil compartment is expected to be low.
Vinylsilanetriol has a low potential for adsorption (based on log Koc -0.02), low potential for bioaccumulation (based on log Kow <3 (-2.0)) and there is no reason to expect any specific mechanism of toxicity beyond narcosis.
In the context of the Integrated Testing Strategy for the terrestrial compartment (ECHA guidance Chapter R.7c, terrestrial hazard classification scheme, Table R.7.11-2) (ECHA 2017) the aquatic toxicity tests do not indicate that the substance is very toxic (EC/LC50 >1 mg/l for algae, Daphnia and fish). However, despite rapid degradation of the parent substance, the silanol hydrolysis product, vinylsilanetriol, is not readily biodegradable and may persist in the environment. The substance is therefore assigned to Hazard Category 3.
In this situation, a screening approach is applied: a confirmatory long-term terrestrial test is usually appropriate, in addition to the equilibrium partitioning approach with an extra factor of ten, in order to determine whether further full tests are necessary.
The PNECscreen(EQPM) for vinylsilanetriol is derived from the long-term test result with Daphnia and has a value of 0.06 mg/kg dwt. For the purpose of the screening assessment comparison only, an extra factor of ten is applied (PECx10/PNECscreen(EQPM)). Based on the exposure assessment of the silanol hydrolysis product, the highest terrestrial (PECx10)/PNECscreen(EQPM) for vinylsilanetriol is (0.00437 x 10) / 0.06 = 0.728.
A confirmatory long-term terrestrial toxicity test is therefore required in accordance with the recommendations for Hazard Category 3 substances.
No toxicity was observed in the aquatic microorganism tests, therefore a toxicity to soil microorganisms test is not required.
However, prior to terrestrial toxicity tests being carried out, the technical feasibility of testing the silanol hydrolysis product, vinylsilanetriol, would need to be assessed. To achieve the test concentrations required by terrestrial testing guidance (up to 1000 mg/kg), aqueous stock solutions would need to be prepared at very high concentrations, well above 1000 mg/l. Silanetriols are susceptible to condensation reactions. Condensation of vinylsilanetriol is expected to become important at loadings above about 1000 mg/l, causing the formation of insoluble polymeric particles (sols) and gels over time. It therefore may not be possible to test terrestrial organisms at high enough test concentrations to meaningfully assess the terrestrial toxicity of vinylsilanetriol. Prior to any testing, the feasibility of dosing at concentrations up to 1000 mg/kg dw would have to be assessed. Further details on technical feasibility of terrestrial testing with silanetriol substances are given in Annex 4 of the CSR and attached in Section 13 of IUCLID.
In addition, if a confirmatory long-term terrestrial test were to be conducted, an assessment factor of 100 would be applied to derive PNECsoil from one long-term test. For this value to be more conservative than the PNECsoil derived by the equilibrium partitioning method, the NOEC derived in the terrestrial test would have to be <6 mg/kg dw. There is no basis to expect such toxicity for vinylsilanetriol based on the absence of significant toxicity observed in aquatic tests and the low potential for adsorption to and bioaccumulation in soil.
In the case of vinylsilanetriol, the Registrant considers that a long-term terrestrial study is unlikely to affect the outcomes of the chemical safety assessment. As such the Registrant proposes that further testing is currently not necessary.
Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0, and Chapters 7, 9 and 10 of the Chemical Safety Report.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
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