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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

Nitrogen transformation by terrestrial microorganisms: 28-day EC50 620 mg/kg dwt and EC25 359 mg/kg dwt (nominal) (OECD 216). A NOEC of 100 mg/kg dwt (nominal) was derived for the study. The 28-day results are equivalent to EC50 of 515 mg/l and EC25 of 298 mg/kg dwt, and the study NOEC is equivalent to 83 mg/kg dwt, when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:
515 mg/kg soil dw
Long-term EC10 or NOEC for soil microorganisms:
83 mg/kg soil dw

Additional information

A 7-day EC50 353 mg/kg dwt and EC25 267 mg/kg dwt; 28-day EC50 620 mg/kg dwt and EC25 359 mg/kg dwt (nominal) (OECD 216) on nitrogen transformation by a native population of soil microbes. A NOEC of 100 mg/kg dwt (nominal) was derived for the study.

In view of the test media preparation method and pH conditions during the test, it is likely that the test organisms were exposed to both the parent substance and hydrolysis products in the test system. Analytical quantification was not attempted.

In this study the ECx values progessively increase between the 7-day, 14-day and 28-day points. This may reflect increasing tolerance in the test system, progressive degradation of the test substance by hydrolysis in the moist soil substrate, or a combination of the two. The 28-day ECx values are of highest relevance to the silanol hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate, which is the subject of the chemical safety assessment for the environment.

The results may be expressed in terms of concentration of the hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate, by applying a molecular weight correction: (MW of silanol=206.27 / MW of parent=248.35) * [Conc. of parent] = [conc. of silanol]. Using this method, the 28-day results are equivalent to EC50 of 515 mg/l and EC25 of 298 mg/kg dwt, and the study NOEC is equivalent to 83 mg/kg dwt, when expressed in terms of the silanol hydrolysis product.