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Ecotoxicological information

Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Data waiving:
other justification
Justification for data waiving:
other:

Description of key information

Key value for chemical safety assessment

Additional information

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

In accordance with Column 2 of REACH Annex IX, there is no need to further investigate the effects of this substance in a long or short-term terrestrial toxicity 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 is below 1, and therefore, the risk is already adequately controlled and further testing is not justifiable.

 

The silanol hydrolysis product is not readily biodegradable but has low potential for bioaccumulation (based on log Kow <3 (-2.9)) and there is no reason to expect any specific mechanism of toxicity beyond narcosis. The low log Kow indicates that partitioning to the terrestrial compartment is expected to be minimal.

 

The terrestrial chemical safety assessment has been conducted using the Equilibrium Partitioning method (EQPM). It is recognised that the aquatic PNEC used in the EQPM does not take into account any indicator for effects in aquatic microorganisms. However, aquatic microorganism data have been read across from a structural analogue where no inhibitory effects on respiration of activated sludge were observed. Therefore, it is unlikely that the PNECterrestrial based on aquatic ecotoxicity test results would not be protective for terrestrial microorganisms.

 

Short-term toxicity testing has been carried out with a structural analogue of the registered substance. The occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in these aquatic studies (conducted at concentrations of parent substance loaded up to 120 mg/l) would be considered unlikely.

 

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. Therefore, further toxicity testing with terrestrial microorganisms does not need to be conducted.

 

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.