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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

LC50 (96 h): 260 - 310 mg/L (Onchorhynchus mykiss), RA sodium silicate
LC50 (96 h): 1108 mg/L (Brachydanio rerio), RA sodium silicate
NOEC (96 h, Mortality): 348 mg/L (Brachydanio rerio), RA sodium silicate
LC50 (96 h): >100 mg/L (Poecilia reticulata, limit test), lithium silicate solution; equivalent to 27.5 mg active matter/L
However, for the purpose of risk assessment and as explained in the section on the calculation of Predicted No Effect Concentrations, the PNEC is derived from the ubiquitous SiO2 background concentration in freshwater in Europe, which is 7.5 mg/L.

Key value for chemical safety assessment

LC50 for freshwater fish:
260 mg/L

Additional information

Two studies conducted with a related substance (sodium silicate) were selected as key studies. A semi-static study with Brachydanio rerio by Adema (1988), following OECD guideline 203, was performed under GLP for a sodium silicate solution (MR 3.46, 34.8 wt %). The 96 h LC50 was determined to be 1108 mg active matter/L. The NOEC values for mortality and swimming behaviour were 348 and 1114 mg active matter/L, respectively. The pH varied depending on the test substance concentration from 7.9 to 10.3.

In another non-GLP study, Maruyama et al. (1989) examined the toxicity of a neutralised sodium silicate solution (MR 3.1, concentration not indicated) to rainbow trout (Oncorhynchus mykiss). In four replicates the 96 h LC50 varied from 260 mg/L (pH 6.8 - 7.5) to 310 mg/L (pH 7.2 - 8.0). Necrosis of gill filaments as a result of the formation of colloidal silica was observed. However, this is considered a physical rather than toxic effect.

One non-GLP study is available reporting on the short-term toxicity to fish of silicic acid, lithium salt (aqueous solution, MR 4.05, solid content 27.5%), conducted according to OECD Guideline 203 as a limit test (Häner 1998). This study resulted in a 96 h LC50 value for Poecilia reticulata of > 100 mg/L nominal (test material), equivalent to 27.5 mg active matter/L. As one fish died during the test, this would have implied the conduct of a full study. However, the results are reported here as supporting study as they fit into the toxicity profile established by data from related analogue substances.