Trimethoxyoctylsilane

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Additional information

Testing for long-term toxicity to fish is not considered necessary because:

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

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 fish 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 potential for bioaccumulation (based on log K_ow <3 (1.1)) 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 nominal concentrations up to 100 mg/L) would be considered unlikely.

Based on the aquatic data set, read across from structurally similar substances, no effects were seen in the short-term fish or algal studies up to nominal concentrations of 100 mg/L. Effects were seen in the long-term invertebrate test and the result from this test is used to derive aquatic PNEC.

The hydrolysis product of the registration substance and the substances used for read-across are part of a class of low functionality compounds acting via a non-polar narcosis mechanism of toxicity, and as such log K_ow drives toxicity. It is therefore expected that fish will not be any more sensitive than invertebrates or algae. As no short-term toxic effects were expressed in these organisms, and long-term invertebrates data are available from which PNEC can be derived, a long-term fish toxicity test is not necessary.

A PNEC has been derived for the purpose of chemical safety assessment. An assessment factor of 100 was applied to derive the freshwater PNEC. 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 or justified on ethical grounds.

 

Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0 and Chapters 7, 9 and 10 of the Chemical Safety Report.