Registration Dossier

Diss Factsheets

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Test data are only available for short-term toxicity to terrestrial plants. A NOEC of =100 mg/kg dwt has been determined for the effects of the test substance on emergence of Triticum aestivum, Lepidium sativum and Brassica alba seedlings. 17-day EC50 values for effects on growth of the three species were 29, 94 and >100 mg/kg dwt. respectively (determined graphically). The NOEC is equivalent to =38 mg/kg dwt and the EC50 values are equivalent to 11, 36 and >38 mg/kg dwt, respectively, when expressed in terms of the silanol hydrolysis product. 17-day LOECs for growth are reported as 10 mg/kg, 100 mg/kg and >100 mg/kg dwt respectively (or 3.8, 38 and >38 mg/kg dwt, respectively, expressed in terms of the silanol hydrolysis product) in Triticum aestivum, Lepidium sativum and Brassica alba (determined by t-test based on mean plant weight). Whilst indicative NOECs can therefore be determined as 1 mg/kg, 10 mg/kg and >10 mg/kg dwt (or 0.38, 3.8, >3.8 mg/kg dwt when expressed in terms of the silanol hydrolysis product), this would be a highly conservative interpretation in view of the unusually large spacing of the dose levels for a test of this type.

OECD 208 is technically a short-term study, designed to assess the potential effects of substances on seedling emergence and growth. Therefore, it is specific to a part of the plants life-cycle and does not cover chronic effects or effects on reproduction, however as ECHA guidance on information requirements and chemical safety assessment makes clear, this test is assumed to cover a sensitive stage in the life-cycle of a plant and therefore data obtained from this study can be used to estimate chronic toxicity. A full life cycle higher plant test is not usually a REACH requirement and is not recommended in this case.

Further testing for toxicity to terrestrial organisms 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 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 products, vinylsilanetriol and 2-methoxyethanol, upon which the chemical safety assessment is based, are highly water soluble and have low log Kowvalues, therefore exposure of and accumulation in the sediment compartment is expected to be low.

The hydrolysis products have low potential for adsorption and low bioavailability (based on log Kow<3 (-2.0 and -0.77 for vinylsilanetriol and 2-methoxyethanol, respectively)), low toxicity was observed in short- and long-term aquatic tests, and there is no reason to expect any specific mechanism of toxicity beyond narcosis. Therefore, the occurrence of more severe toxic effects in the sediment compartment that were not expressed in the aquatic studies would be considered unlikely.

The PNEC was derived from both the Equilibrium Partitioning Method and from experimental data with an appropriate assessment factor, then the most conservative value was used. It can be assumed that this value is protective for the rest of the terrestrial compartment. The PNEC that has been determined for the purpose of deriving a chemical safety assessment and 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 6.0 and Chapters 9 and 10 of the Chemical Safety Report, respectively.