3-trimethoxysilylpropane-1-thiol

Toxicity to aquatic algae and cyanobacteria

Description of key information

Toxicity to algae: 72-hr ErC₅₀ 931 mg/l and ErC₁₀ 92 mg/l (nominal) (EC Guideline 92/69/EWG C3). The ErC₅₀ is equivalent to 732 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

EC50 for freshwater algae:

732 mg/L

EC10 or NOEC for freshwater algae:

72 mg/L

Additional information

A 72-h ErC₅₀ value of 931 mg/l, ErC₁₀ of 92 mg/l (nominal) have been determined for the effects of the registration substance on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus). A NOEC of 40 mg/l (nominal) was determined in the same test, for biomass effects. 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. At the loading concentration used in preparation of stock, it is expected that oligomers and/or cross-linked aggregates may have been present to some extent, though no specific evidence of precipitation or physical effects on test animals is described. While this is an uncertainty, it is considered that the study results are suitable to be used (with caution), with effects attributed in principle to intrinsic ecotoxicity of silanol (and oligomers). The results may be expressed in terms of concentration of the hydrolysis product, 3-(trihydroxysilyl)propanethiol, by applying a molecular weight correction: (MW of silanol=154.26 / MW of parent=196.34) * 931 = 732 mg/l.

The reliability of another ErC₅₀ value of 43 mg/L, that was obtained from the open literature, could not be determined.

Refer to the discussion in the Section 6 endpoint summary (Section 7.0 of CSR) for further discussion of the approach to chemical safety assessment for this registration substance.