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A 14-day LC50 value of >1000 mg/kg dry weight and NOEC of =1000 mg/kg dry weight have been determined for the effects of the test substance on mortality of Eisenia fetida. It is likely that the test organisms were exposed primarily to the hydrolysis products of the test substance. The 14-day LC50 is equivalent to >830 mg/kg dwt when expressed in terms of the silanol hydrolysis product.

A 28-day EC50 620 mg/kg dwt and EC25 359 mg/kg dwt (nominal) have been determined for the effects of the test substance on nitrogen transformation by terrestrial microorganisms (OECD 216). A NOEC of 100 mg/kg dwt (nominal) was derived for the study. It is likely that the test organisms were exposed primarily to the hydrolysis products of the test substance. The 28-day results are equivalent to EC50 of 515 mg/kg dwt and EC25 of 298 mg/kg dwt, and the study NOEC is equivalent to 83 mg/kg dwt, when expressed in terms of the silanol hydrolysis product.

Further testing for toxicity to terrestrial invertebrates and higher plants is not considered necessary because:

A short-term terrestrial toxicity test with soil macroorganisms and a terrestrial test with soil microorganisms have been carried out with the registered substance. However, PNECs have been calculated by Equilibrium Partitioning using the aquatic toxicity data for the purpose of chemical safety assessment. The results of these existing studies with earthworms and terrestrial microorganisms suggest that the results from Equilibrium Partitioning are relatively conservative. 

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

The silanol hydrolysis product has a low log Kow value and, therefore, exposure of the soil compartment is expected to be low.

The substance is not adsorbing (based on log Koc 0.55), has low bioavailability (based on log Kow <3 (-0.9)) and low toxicity was observed in short-term aquatic tests as well as in the available terrestrial tests. Therefore, the occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies would be considered unlikely.

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.