Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

No data are available with terrestrial organisms.

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

- the registered substance hydrolyses extremely rapidly to produce tris(1-methylethyl)silanol and acrylic acid.

- a PNECsoil for has been calculated for tris(1-methylethyl)silanol from the corresponding PNECaqua(freshwater) on the basis of the equilibrium partitioning method.

- a PNECsoil for acrylic acid has previously been calculated in an EU Risk assessment Report based on the results of a respiration inhibition test conducted with soil microflora.

The risk characterisation ratios (RCRs) derived on the basis of these PNECsoil values are all <1 (see Section 10 of the CSR).

PNECsoil has been calculated from the aquatic data using the Equilibrium Partitioning Method. The risk characterisation ratios (RCR) based on the PNECsoil are <1.

In accordance with Column 2 of REACH Annex IX, there is no need to further investigate the effects of this substance in a terrestrial toxicity to invertebrates/higher plants study because, as indicated in guidance R.7.11.6 (ECHA 2016), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio (RCR) is below 1 and therefore the risk is already adequately controlled and further testing is not justifiable.

The substance rapidly hydrolyses and the silanol hydrolysis product is not readily biodegradable but has low potential for bioaccumulation and low potential for adsorption. Toxicity was observed in aquatic tests. Distribution modelling for STP indicates that water is the main compartment to which the silanol is expected to partition in a sewage treatment plant, as well as the main compartment to which it will partition in the wider environment. Therefore, the occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies (conducted at concentrations up to 100 mg/l) would be considered unlikely. 

Overall it is concluded that the risk characterisation conclusion is sufficiently conservative and therefore further in vivo testing is not considered necessary.

Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0 and Chapters 9 and 10 of the Chemical Safety Report, respectively.