Triethoxy(phenyl)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 phenylsilanetriol in short- or long-term terrestrial toxicity studies because exposure of terrestrial organisms to phenylsilanetriol is absent or not significant (RCR < 1). The hazard assessment based on acute aquatic toxicity data shows no or only moderate toxicity toward aquatic organisms of the three trophic levels (acute effect values in fish and algae EC/LC50 > 100 mg/L; 48-h EC50 in daphnia = 37 mg/L). The substance is well soluble and thus, greater toxicity in 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 1.5 h at pH 7 and 20-25 °C. Therefore, the hazard assessment for the terrestrial compartment is based on the silanol hydrolysis product phenylsilanetriol. 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 phenylsilanetriol in short- or long-term terrestrial toxicity studies because exposure of terrestrial organisms to phenylsilanetriol is absent or not significant (RCR < 1). The hazard assessment based on acute aquatic toxicity data shows no or only moderate toxicity toward aquatic organisms of the three trophic levels (acute effect values in fish and algae EC/LC50 > 100 mg/L; 48-h EC50 in daphnia = 37 mg/L). The silanol hydrolysis product is well soluble and thus, greater 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, phenylsilanetriol, upon which the chemical safety assessment for the terrestrial compartment is based, is highly water soluble and has a low log Pow value and therefore, exposure of the soil compartment is expected to be low.  

-Phenylsilanetriol has a low potential for adsorption and low potential for bioaccumulation and there is no reason to expect any specific mechanism of toxicity beyond narcosis.

-Terrestrial testing is technically difficult for trialkoxysilanes in general due to condensation reactions at high test-concentrations. A feasibility study is currently ongoing. For further information, please see attached justification IUCLID chapter 13.

-No toxicity was observed in the aquatic microorganism tests, therefore a toxicity to soil microorganisms test is not required.

 

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.