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Toxicity to aquatic algae and cyanobacteria

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Description of key information

ErC50 > 6 mg a.i./L (Pseudokirchneriella subcapitata)

ErC10 = 3.29 mg a.i./L (Pseudokirchneriella subcapitata)

Key value for chemical safety assessment

Additional information

The toxicity towards freshwater algae was determined in a study according to OECD TG 201 and in compliance with GLP criteria (Ibacon, 2017). In this study, exponentially growing freshwater algae (Pseudokirchneriella subcapitata) were exposed to nominal test substance concentrations of 0 (control), 1.3, 4.2, 13.3, 42.1 and 133 mg test item/L for 72 hours under static conditions. The test material as such exists as aqueous solution. The test material concentration corresponds to a nominal concentration of 1, 3.2, 10, 31.6 and 100 mg/L based on active ingredient (a.i.). Test concentrations were analytically verified and the geometric mean measured concentrations were determined to be <LOD, (control), 0.483, 0.632, 1.7, 3.3 and 6 mg a.i./L (corresponding to 0.719, 0.94, 2.53, 4.91 and 8.93 mg test item/L). Since the test item concentrations were not within ± 20% of the nominal concentrations during the test, all reported results refer to geometric mean concentrations. At the start of the test and after 24, 48 and 72 hours exposure duration, the algae were scored for number of cells and for microscopic abnormalities. At concentrations of nominal 10, 31.6 and 100 mg a.i./L, significant inhibition in yield and growth rate was observed at the end of the study. After 72 hours exposure, yield was inhibited for 14.6%, 40.8% and 83% and growth rate was inhibited for 3.1%, 9.0% and 30.4% test concentrations of 10, 31.6 and 100 mg a.i./L, respectively. Based on these findings, the 72-h EC50 values for growth rate and yield are determined at > 6 mg a.i./L and 3.29 mg a.i./L, respectively. The 72-h EC10 values for growth rate and yield are determined at 3.5 mg a.i./L and 1.47 mg a.i./L.