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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

72-hour EC50 value of >89 mg/L and NOEC of =89 mg/L, effects of the test substance on growth rate of Pseudokirchneriella subcapitata. Under the conditions of the test is likely that the test organisms were primarily exposed to the hydrolysis products of the substance. The EC50 and NOEC are equivalent to >64 mg/L and =64 mg/L respectively, when expressed in terms of the silanol hydrolysis product vinylsilanetriol.

Key value for chemical safety assessment

Additional information

A 72-hour EC50 value of >89 mg/L and NOEC of =89 mg/L (nominal concentration) (highest concentration tested) has been reported for the effects of the test substance on growth rate of Pseudokirchneriella subcapitata (MOE, 2006). Under the conditions of the test is likely that the test organisms were primarily exposed to the hydrolysis products of the substance. The results may be expressed in terms of the silanol hydrolysis product, by adjusting for the respective molecular weights: MW hydrolysis product/MW parent * E(L)C50 or NOEC value, thus 106.15/148.24 * EC50 of >89 mg/L and NOEC of =89 mg/L = EC50 >64 mg/L and NOEC =64 mg/L as vinylsilantriol.

A second algal study has been carried out with the test substance which was previously considered in Weight of Evidence with the MOE, 2006 test. A 7-day EC50 value of 210 mg/L and NOEC of approximately 25 mg/L have been reported for the effects of the test substance on final yield of Pseudokirchneriella subcapitata. However, the test is no longer considered to be reliable because the 7-day duration means that it is unlikely that the algae maintained exponential growth throughout the test. In addition, the result is expressed in terms of yield as opposed to growth rate, which is the relevant endpoint.

The following result is from a reliable study included as supporting data:

72-hour EC50 >957 mg/L and NOEC =957 mg/L determined for effects of the test substance on growth rate of Desmodesmus subspicatus (Huls, 1993).

Other toxicity to algal tests are available with the registration substance. No effects were observed in any of the tests. The key study has been selected because it gives the lowest reliable limit value. The results of the three further studies, for which their reliability could not be ascertained or were deemed unreliable, are as follows:

72-hour EC50 >100 mg/L and NOEC =10 mg/L determined for effects of the test substance on growth rate of Desmodesmus subspicatus (Bement, 2001).

72-hour EC50 >100 mg/L and NOEC =10 mg/L determined for effects of the test substance on biomass of Desmodesmus subspicatus (Chandra/Dow Corning, 1997).

72-hour EC50 210 mg/L and EC10 32 mg/L determined for effects of the test substance on final yield of Pseudokirchneriella subcapitata (Dow Corning, 1979).