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Long-term toxicity to aquatic invertebrates

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Description of key information

Key value for chemical safety assessment

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Due to the rapid hydrolysis of the substance, the chemical safely assessment is based on the silanol hydrolysis product methylphenylsilanediol.

The hydrolysis half-life of the registration substance is approximately very rapid therefore the hazard assessment for the terrestrial compartments is based on the silanol hydrolysis product.

 

In accordance with Column 2 of REACH Annex IX, there is no need to further investigate the effects of this substance in a long-term aquatic toxicity to invertebrates study because, as indicated in guidance R.7.8.4.3 (ECHA 2016), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio is well below 1, even with due consideration of contributing uncertainties, and therefore the risk is already adequately controlled and further testing is not justifiable.

 

The substance is highly water-soluble, has low bioavailability (based on log Kow <3 (0.8)) and there is no reason to expect any specific mechanism of toxicity beyond narcosis. Therefore, the occurrence of toxic effects that were not expressed in the existing short-term aquatic studies (conducted at concentrations up to 1000 mg/l) would be considered unlikely.

 

A PNEC has been derived for the purpose of chemical safety assessment. An assessment factor of 1000 was applied to derive the freshwater PNEC, this high assessment factor to derive the predicted no-effect level already reflects the typically higher value of a short-term EC50compared to a long-term EC10. For a narcotic chemical without a specific mode of toxic action, it is unlikely that the aquatic PNEC would be significantly over-estimated using this method.

 

Overall it is concluded that the risk characterisation conclusion is sufficiently conservative in respect of any uncertainties 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.