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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Link to relevant study record(s)

Description of key information

EC50 (96h) - growth rate = 821.42 mg/l (nominal)

NOEC (96h) - growth rate < 62.5 mg/l (nominal)

Key value for chemical safety assessment

EC50 for freshwater algae:
821.42 mg/L
EC10 or NOEC for freshwater algae:
62.5 mg/L

Additional information

The toxicity of the substance to aquatic algae was evaluated concerning data from two studies on the substance.

In the key study performed according to EPA OPPTS 850.5400 and in GLP compliance. Selenastrum capricorbutum were exposed to for 96 hours under static conditions to 62.5, 125, 250, 500 and 1000 mg/l. For each test concentration, three test flasks containing the freshwater algae (50000 cells/ml) were treated with the appropriate concentration of the test substance. A control group consisted of six test flasks containing sterile medium and the test culture only and a positive control consisted of three flasks treated with 10 mg/l zinc chloride. The cell density in each test and control container was measured daily using a hemacytometer. The pH of each test and control container was determined at test termination.

EC50 (96h) - growth rate = 821.42 mg/l (nominal)

NOEC (96h) - growth rate < 62.5 mg/l (nominal)

In the supporting study performed according to OECD Guideline 201 and EPA OPPTS 850.5400 in compliance with GLP. Exponentially growing algal cells were exposed for a period of 96 h to the nominal test concentrations of 31.25, 62.5, 125, 250, and 500 mg/l of test substance dissolved in water. The cell densities were measured at 24, 48, 72 and 96 hrs following each dosing, each flask was checked for inhibition by measuring the mean cell density with a haemocytometer. Inhibition of the algal population was measured as inhibition/reduction in growth and cell density, relative to control.

IC50 (96 h) = 441.83 mg/l (nominal)

NOEC (96 h) = 125 mg/l (nominal)

The value chosen as key for the chemical safety assessment is the effect level based on growth rate inhibition as it is the preferred observational endpoint in the algae study is algal growth rate inhibition since it is not dependent on the test design, whereas biomass depends both on growth rate of the test species as well as test duration and other elements of test design.