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Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Triethoxy(methyl)silane (CAS 2031 -67 -6) is part of a group of organosilicones, the toxicity of which is determined by a non-polar mechanism of toxicity, and as such log Kow drives toxicity. Substances in this group include alkoxy- and chloro-silanes having secondary features that do not affect the toxicity of the substances. Additional information is given in a supporting report (PFA, 2013) attached in Section 13 of the IUCLID dossier.

Measured data were available for the acute toxicity of triethoxy(methyl)silane (CAS 2031-67-6) for fish, invertebrates and algae. In the studies selected as key, for each of the trophic level, no effects were observed at the test concentration of 500 mg/l (nominal) for Danio rerio (OECD Guideline 203), Daphnia magna (OECD Guideline 202) and algae (OECD Guideline 201). Several supporting studies were also available for fish, algae and invertebrates. The supporting studies reported an LC50 of >1000 mg/l for fish (Fundulus heteroclitus and Lepomis macrochrius), an EC50 of >1000 mg/l for invertebrates (Daphnia magna) and an EC50 of >1000 mg/l for algae (Selenastrum capricornutum).

However, the substance rapidly hydrolyses (half-life approximately 5.5 hours) to methylsilanetriol and ethanol. REACH guidance (ECHA 2010A, 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”. TGD and ECHA guidance (EC 2003, ECHA 2010A) also suggest that when the hydrolysis half-life is less than 12 hours, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Therefore, the environmental hazard assessment, including sediment and soil compartments due to pore water, is based on the properties of the silanol hydrolysis product, in accordance to REACH guidance. As described in Section 1, condensation reactions of the silanetriol are possible.

 

- Considerations on the non-silanol hydrolysis products:

Methanol and ethanol are well characterised in the public domain literature and are not hazardous at concentrations relevant for the studies; the short-term EC50 and LC50 values for these substances are in excess of 1000 mg/l (OECD 2004a - SIDS for methanol, CAS 67-56-1, OECD 2004b - SIDS for ethanol, CAS 64-17-5).

 

- QSAR:

QSAR data were derived via calculations for the silanol hydrolysis product and all trophic levels. These data were used to derive PNECs. A 96-h LC50 of 10000 mg/l was determined for fish, a 48-h LC50 of 29600 mg/l for aquatic invertebrates and a 96-h EC50 of 2115 mg/l for algae.