Trimethoxyphenylsilane

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).Furthermore, the hazard assessment based on acute aquatic toxicity studies showed no hazard (all acute aquatic effect values, i.e. E(L)C50, for fish, daphnia and algae were > 100 mg/L). 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.

Additional information

The hydrolysis half-life of the registration substance is approximately 0.4 h at pH 7. Therefore, the hazard assessment for the terrestrial compartments is based on the silanol hydrolysis product phenylsilanetriol.

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).Furthermore, the hazard assessment based on acute aquatic toxicity studies showed no hazard (all acute aquatic effect values, i.e. E(L)C50, for fish, daphnia and algae were > 100 mg/L). 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.

Testing for toxicity to terrestrial organisms is not considered necessary because:

- The substance is used under highly controlled conditions and therefore, exposure of the terrestrial compartment is low.

- The silanol hydrolysis product is not readily biodegradable and has a low potential for bioaccumulation (log Kow < 2.0) and there is no reason to expect any specific meachanism of toxicity beyond narcosis.

- A data set for short-term toxicity to aquatic species is available for a structural analogue, which forms the same silanol hydrolysis product phenylsilanetriol within a similar time frame as the registered substance. The test design of the studies was such that the test organisms were likely predominantly exposed to the hydrolysis products of the test substance. No effects were observed up to a nominal concentration of 100 mg/L. The occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies are considered unlikely.  

- A PNEC was calculated by Equilibrium Partitioning 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.