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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Toxicity to algae: 72 hr ErC50 >89 mg/l (measured TWA) (OECD TG 201), read-across from an analogous substance, trimethoxy(vinyl)silane (CAS 2768-02-7). The observations in this study are attributed to the exposure of test organisms to the hydrolysis products in the test system. The EC50 is equivalent to >64 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

Additional information

There are no reliable algal growth rate toxicity data available for tri(isopropoxy)(vinyl)silane (CAS 18023-33-1), therefore good quality data for an appropriate structural analogue, trimethoxy(vinyl)silane (CAS 2768-02-7), have been read across. Both substances share the same silanol hydrolysis products, vinylsilanetriol. The other hydrolysis products are isopropanol and methanol, respectively. In the tests with trimethoxy(vinyl)silane, the observations are attributed to the exposure of test organisms to vinylsilanetriol in the test system. There is no basis to expect that methanol significantly influenced the results of the test. The toxicity of isopropanol is discussed further in the ecotoxicological information overview endpoint summary (additional information).

A 72-h ErC50 value of >89 mg/l (measured TWA) have been determined for the effects of trimethoxy(vinyl)silane (CAS 2768-02-7) on growth rate of Pseudokirchneriella subcapitata. In view of the test media preparation method and exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results may be expressed in terms of concentration of the hydrolysis product, vinylsilanetriol, by applying a molecular weight correction: (MW of silanol=106.15 / MW of parent=148.24) * 89 = 64 mg/l. This value is read across to vinylsilanetriol generated by hydrolysis of the registered substance without further correction.

Above a concentration of approximately 1000 mg/l, oligomeric, cyclic or cross-linked condensation products could potentially form over time in the aqueous test media. No evidence of undissolved material (parent substance or precipitated products) is indicated in the study report for this test.  

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.