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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Short-term toxicity to aquatic algae: 72 hr EC50 >7.1 mg/l and a NOEC of ≥7.10 mg/l (greater than the limit of solubility in water) (measured) (highest concentration tested) (EU Method C.3 (Algal Inhibition test)), read-across from an analogous/structurally related substance, [2-(perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7). The EC50 is equivalent to >5.9 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

Additional information

There are no reliable short-term fish toxicity data available for [2-(perfluorohexyl)ethyl]trimethoxysilane (CAS 85857-16-5), therefore good quality data for an appropriate structural analogue, [2-(perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7), have been read across. Both substances have the same silanol hydrolysis product, [2-(perfluorohexyl)ethyl]silanetriol. The other hydrolysis products are methanol and ethanol, respectively.

 

A 72-h EC50 value of >7.1 mg/l and NOEC of ≥7.1 mg/l (greater than the limit of solubility) (measured) (highest concentration tested) have been determined for the effects of [2 -(perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7) on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus) based on mean measured initial Dissolved Organic Carbon (DOC) concentration. The test medium was prepared at an initial loading rate of 1000 mg/l of the substance and was subsequently filtered before introducing the test organisms.

 

In view of the test media preparation method/exposure regime it is likely that the test organisms were exposed to a mixture of the test substance and its hydrolysis products at the beginning of the test, and then predominantly the hydrolysis products of the tested substance for the remainder of the test.

 

The results may be expressed in terms of concentration of the hydrolysis product, [2-(perfluorohexyl)ethyl]silanetriol, by applying a molecular weight correction: (MW of silanol = 426.21 / MW of parent = 510.37) * >7.1 = >5.9 mg/l.

 

Refer to the discussion in the Section 6 endpoint summary for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.