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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

With high probability acutely not harmful to aquatic algae. No toxic effects occur at the range of solubility.

Key value for chemical safety assessment

Additional information

Two GLP-guideline studies according to OECD 201 have been conducted. In the key study (RCC Ltd. 2008b) a dispersion (96 h saturation) with the loading rate of 100 mg/L has been tested due to the low solubility of the test substance. The undiluted filtrate without solvents or emulsifier was used. The EC50 (growth rate) after 72 h was determined to be above the solubility and the loading rate of 100 mg/L. No acute toxic effects occurred within the range of solubility. The shape and the size of the algal cells was not affected up to the highest concentration (undiluted filtrate).

The results are supported by a second study (RCC NOTOX 1993d): Exponentially growing cultures of Scenedesmus subspicatus were exposed to different dilutions of a supersaturated solution of the test item for 72 hours. Inhibition of cell growth was statistically significant only in 100% filtrate of the supersaturated solution of 100 mg/L, whereas significant stimulation of cell growth was recorded in dilutions of the filtrate.

In conclusion, exposure to test concentrations above the maximum solubility did not induce a biologically significant effect on algal

growth. The NOEC and the 72-hour EC50 for both growth inhibition and growth rate reduction were greater than the maximum solubility of the substance in water.