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Toxicity to aquatic algae and cyanobacteria

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In a reliable (reliability category 1) toxicity test performed compliant to GLP with analytical monitoring of submission substance concentration no signs of toxicity to the freshwater green alga Scenedesmus subspicatus were observed at the nominal limit concentration of 77 mg submission substance/L (saturated solution). Thus, no EC10 or EC50 could be determined and the NOEC (72 h, growth rate and yield) is larger or equal to 77 mg/L nominal concentration of the submission substance.

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Toxicity of the submission substance towards aquatic algae was assessed by means of a limit test performed compliant to GLP in accordance with Commission Directive 92/69/EEC and OECD 201 (1984) (reliability category 1) using the freshwater alga Scenedesmus subspicatus. Due to the very poor solubility of the submission substance in water, the mean measured concentrations in test medium at the nominal limit concentration of 77 mg/L (saturated solution) after filtration through a Whatman GF/C-Filter with a pore size of approximately 1.2 µm were 120 µg/L at test start and 170 µg/L after 72 hours. The slight increase of the measured submission substance concentration might have been caused by fine dispersion of particles during the test period and therefore a higher amount of submission substance that passed the filter. The test material was unevenly distributed in the test media but was continuously stirred during the test period. The mean algal cell densities in the test medium were at all counting dates identical or even slightly higher than in the parallel control cultures. Therefore, the 72-hour NOEC (highest concentration tested without toxic effects after the exposure period of 72 hours), and the 72-hour EC0 of the submission substance to Scenedesmus subspicatus were determined to be at least 77 mg submission substance/L in regard to both, growth rate and biomass.

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