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Toxicity to aquatic algae and cyanobacteria

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Description of key information

In freshwater algae (Pseudokirchnerella subcapitata) the 72-h ErC50 value is 4.61 mg/L and the 72-h ErC10 value is 1.61 mg/L (nominal).

Key value for chemical safety assessment

EC50 for freshwater algae:
4.61 mg/L
EC10 or NOEC for freshwater algae:
1.61 mg/L

Additional information

The toxicity towards freshwater algae was determined in a study according to OECD guideline No 201 and in compliance with GLP criteria (BASF SE, 2015). In this study, exponentially growing freshwater alga (Pseudokirchnerella subcapitata) at an initial concentration of 6.153E+03 cells/mL were exposed to nominal test substance concentrations of 0 (control), 0.500, 0.889, 1.58, 2.81, and 5.00 mg/L for 72 hours under static conditions. The highest tested concentration of 5.00 mg/L is the experimentally confirmed critical micelle concentration (CMC). All nominal test concentrations and the control were analytically verified via analysis of total organic carbon (TOC) measured as NPOC (Non Purgeable Organic Carbon) at the start and the end of the exposure. The initial measured concentrations of test substance were <LoQ, <LoQ, 2.04, 2.31, 2.78 and 3.41 mg C/L, respectively. The final measured concentrations of test substance were <LoQ, <LoQ, <LoQ, 2.00, 2.33 and 2.33 mg C/L, respectively. All effect values are based on the nominal concentrations of the test item. 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. Mean growth rate inhibitions were -4, -2, 11, 27, and 54 % after exposure to 0.500, 0.889, 1.58, 2.81, and 5.00 mg/L test substance, respectively. Based on these findings, the 72-h ErC50 value (growth rate) was determined to be 4.61 mg/L and the ErC10 was determined to be 1.61 mg/L.