Registration Dossier
Registration Dossier
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EC number: 213-050-5 | CAS number: 919-31-3
Ecotoxicological Summary
Administrative data
Hazard for aquatic organisms
Hazard for air
Hazard for terrestrial organisms
Hazard for predators
Additional information
The hydrolysis half-life of 3-(triethoxysilyl)propiononitrile (CAS 919-31-3) is 6.5 hours at pH 7 and 20°C; the substance will therefore undergo rapid hydrolysis in contact with water to form 3-(trihydroxysilyl)propiononitrile (CAS 182156-21-4) and ethanol. The predicted water solubility of the parent substance is high (4000 mg/l) and the predicted log Kow is low (1.7).
REACH guidance (ECHA 2016, R.16) states that “for substances where hydrolytic DT50 is less than 12 hours, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself”. ECHA Guidance Chapter R.7b (ECHA, 2017) states that where degradation rates fall between >1 hour and <72 hours, testing of parent and/or degradation product(s) should be considered on a case-by-case basis.
As described in Section 4.8 of this IUCLID data set, the silanol hydrolysis product may be susceptible to condensation reactions.
3-(Triethoxysilyl)propiononitrile is part of a class of low functionality compounds acting via a non-polar narcosis mechanism of toxicity. The group of organosilicon substances in this group contain alkyl, aryl, alkoxy or hydroxy groups attached to the Si atom when present in aqueous solution. Secondary features may be present in the alkyl chain (e.g. halogen, nitrile, unsaturated bonds) that do not affect the toxicity of the substances. The side chain of the registered substance is propiononitrile.
The silanol hydrolysis product, 3-(trihydroxysilyl)propiononitrile, is not subject to further hydrolysis. It has a low predicted log Kow of -2.9 and a predicted water solubility of 1.0E+06 mg/l, although concentration in water is limited to approximately 1000 mg/l by condensation reactions.
Consideration of the non-Si hydrolysis product
The non-silicon-containing hydrolysis product of 3-(triethoxysilyl)propiononitrile is ethanol. Ethanol is well-characterised in public domain literature and is not hazardous at the concentrations relevant to the aquatic toxicity studies; the short-term EC50 and LC50 values are in excess of 1000 mg/l (OECD 2004b). Therefore, at the loading rates experienced in the tests with 3-(triethoxysilyl)propiononitrile it is unlikely that the presence of ethanol significantly affected the results of the tests.
References
ECHA 2016. REACH Guidance on Information Requirements and Chemical Safety Assessment Chapter R16: Environmental Exposure Assessment Version: 3.0. February 2016.
ECHA 2017. European Chemicals Agency. Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7b: Endpoint specific guidance. Version 4.0 June 2017.
OECD 2004b. SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.
Conclusion on classification
The substance has reliable short-term E(L)C50 values of >100 mg/l in fish, Daphnia and algae.
The substance hydrolyses rapidly in water. The silanol hydrolysis product, 3-(trihydroxysilyl)propiononitrile (CAS 182156-21-4), is not readily biodegradable but has a log Kow <3.
These data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):
Acute toxicity: Not classified
Chronic toxicity: Not classified
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