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Short-term toxicity to aquatic invertebrates

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Short-term toxicity to aquatic invertebrates: 48 hour EC50 >9.0 mg/l and a NOEC of ≥9.0 mg/l (greater than the limit of solubility in water) (measured) (highest concentration tested) (EU Method C.2 (Acute Toxicity for Daphnia)), read-across from an analogous/structurally related substance, [2-(perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7). The EC50 is equivalent to >7.5 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 invertebrate toxicity data available for [2-(perfluorohexyl)ethyl]trichlorosilane (CAS 78560-45-9), 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 hydrochloric acid and ethanol, respectively.

A 48 hour EC50 value of >9.0 mg/l and a NOEC of ≥9.0 mg/l (greater than the limit of solubility in water) (measured) (highest concentration tested) have been determined for the effects of [2-(perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7) on mobility of Daphnia magna 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 possible that the long preparation time and high pH of the test solutions could influence the exposure of the organisms to [2-(perfluorohexyl)ethyl]triethoxysilane and its silanol hydrolysis product, [2-(perfluorohexyl)ethyl]silanetriol. However, due to the extremely low solubility of the test substance potentially limiting hydrolysis rate, it is unclear how much of the parent substance or silanol hydrolysis product was present in the test solution, but best use has been made of the available data.

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) * >9 = >7.5 mg/l.

Refer to the discussion in IUCLID Section 6.0 for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.