Triethoxy(vinyl)silane

Endpoint summary

Description of key information

In accordance with REACH Annex XI, Section 3, there is no need to further investigate the effects of the silanol hydrolysis product vinylsilanetriol in short- or long-term terrestrial toxicity studies because exposure of terrestrial organisms to vinylsilanetriol is absent or not significant (RCR << 1). The hazard assessment based on acute and chronic aquatic toxicity studies showed no or only a moderate hazard (all acute aquatic effect values, i.e. E(L)C50, for fish, daphnia and algae were > 100 mg/L; 21-day NOEC in daphnia = 28.1 mg/L; 72 -h NOErC ≥ 89 mg/L in algae). The substance is well soluble and thus increased toxicity in other long-term tests is unlikely.

Therefore, the risk is already adequately controlled and further testing is not justifiable.

Additional information

The hydrolysis half-life of the registration substance is approximately 0.9 hours at pH 7 and 20-25 °C. Therefore, the hazard assessment for the terrestrial compartments is based on the silanol hydrolysis product vinylsilanetriol. The other hydrolysis product, ethanol, is known for its absence of environmental toxicity (OECD SIDS, 2004).

 

In accordance with REACH Annex XI, Section 3, there is no need to further investigate the effects of the silanol hydrolysis product vinylsilanetriol in short- or long-term terrestrial toxicity studies because exposure of terrestrial organisms to d vinylsilanetriol is absent or not significant (RCR << 1). Furthermore, the hazard assessment based on acute and chronic aquatic toxicity studies showed no to only a moderate hazard (all acute aquatic effect values, i.e. E(L)C50, for fish, daphnia and algae were > 100 mg/L; 21-day NOEC in daphnia = 28.1 mg/L; 72 -h NOErC ≥ 89 mg/L in algae). The substance is well soluble and thus increased toxicity in long-term tests is unlikely.

Therefore, the risk is already adequately controlled and further testing is not justifiable.

 

In addition, testing for toxicity to terrestrial organisms is not considered necessary because:

- The silanol hydrolysis product is not readily biodegradable but has a low potential for bioaccumulation (log Kow < 3.0) and there is no reason to expect any specific meachanism of toxicity beyond narcosis, plus partitioning to the terrestrial compartment is expected to be minimal.

- A data set for short-term and chronic toxicity to aquatic species is not available for the silanol hydrolysis product. Therefore, good quality data was read-across from a structural analogue substance trimethoxy(vinyl)silane (CAS No. 2768-02-7). The source substance hydrolyses rapidly under environmental conditions (DT50 = 0.1 h at pH 7 and 20-25 °C) to form the common silanol hydrolysis product vinylsilanetriol and the non-common alcohol hydrolysis product methanol. The alcohol hydrolysis product of the source substance is negligible for the hazard assessment as no effects occur for this substance up to the concentrations tested in the studies (OECD SIDS, 2004).  The hazard assessment showed no short-term aquatic hazard to all three trophic levels (all acute effect values > 100 mg/L). Additionally, a chronic toxicity study on aquatic invertebrate is available, which showed moderate long-term toxicity with an obtained 21-day NOEC of 28.1 mg/L (equivalent to 20 mg/L vinylsilanetriol) and the result from this test was used to derive aquatic PNECs. The occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies are considered unlikely.  

- A PNEC soil was calculated by the equilibrium partitioning method and has been derived for the purpose of the chemical safety assessment. The risk characterisation ratios are below 1.

 

Overall, it is concluded that the risk characterisation conclusion is sufficiently conservative in respect of any uncertainties and therefore further testing is not considered necessary. Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6 and Chapters 7, 9 and 10 of the Chemical Safety Report.

 

References:

OECD SIDS, 2004. Ethanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.

OECD SIDS, 2004. Methanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.