Registration Dossier
Registration Dossier
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EC number: 217-982-3 | CAS number: 2031-62-1
Endpoint summary
Administrative data
Description of key information
Additional information
Diethoxy(methyl)silane (CAS 2031-62-1) hydrolyses rapidly to methylsilanetriol and ethanol (< 2 min at pH 7 and 25 °C). REACH guidance R.16 states that “for substances where hydrolytic DT50 is less than 12 h, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself” (ECHA, 2016). TGD (EC, 2003) and REACh guidance R.16 (ECHA, 2016) also suggest that when the hydrolysis half-life is less than 12 h, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity testing. Additional information is given in a supporting report attached in IUCLID Section 13 (PFA, 2016).
Suitable experimental data on the toxicity of diethoxy(methyl)silane (CAS 2031-62-1) to aquatic species were not available. Therefore good quality data from the analogous substance, triethoxy(methyl)silane (CAS 2031-67-6), have been read across. Both substances share the same silanol hydrolysis product (i.e. methylsilanetriol), the other hydrolysis product is ethanol. Both substances are expected to hydrolyse within the timescale of an aquatic toxicity test. Further information on the read across approach can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.
Studies conducted with the read across substance and representative organisms of each trophic level (fish, aquatic invertebrates and algae), showed no toxic effects up to the highest tested concentration of 500 mg/L (nominal). Moreover, no inhibition of respiration was recorded on activated sludge microorganisms. All studies were performed according to standard guidelines (EU Method C.1, C.2 and C.3) and GLP. Since the substance hydrolyses rapidly, the organisms were very likely exposed predominantly to the hydrolysis products, which showed no toxic effects.
The other hydrolysis product ethanol is well characterised in the public domain literature and is not hazardous at the concentrations relevant to the studies; the short-term EC50 and LC50 values for this substance is in excess of 1000 mg/L (OECD, 2004b - SIDS for ethanol, CAS 64-17-5).
On this basis, no toxic effects are anticipated by the target substance to aquatic organisms.
References
EC (2003). European Union Technical Guidance Document on Risk Assessment for New and Existing Substances, Part II, European Chemicals Bureau, 2003.
ECHA (2016). REACH Guidance on Information Requirements and Chemical Safety Assessment Chapter R16: Environmental Exposure Estimation Version: 3.0 February 2016.
OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.
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