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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The EC50 value was determined to be > 0.10 mg/L and the No Observed Effect Concentration was ≥ 0.10 mg/L. The EC50 values based on the time-weighted mean measured test concentration were > 0.080 mg/L, and correspondingly the No Observed Effect Concentration was ≥ 0.080 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.1 mg/L
EC10 or NOEC for freshwater algae:
0.1 mg/L

Additional information

Methods

A study was performed to assess the effect of the test material on the growth of the green alga Scenedesmus subspicatus. The method followed that described in the OECD Guidelines for Testing of Chemicals No. 201, "Alga, Growth Inhibition Test" referenced as Method C.3 of Commission Directive 92/69/EEC.

Procedure

Following a preliminary range-finding study, Scenedesmus subspicatus was exposed to an aqueous dispersion of the test material at a concentration of 0.10 mg/l (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group.

Results

Exposure of Scenedesmus subspicatus to the test material gave EC50 values of greater than 0.1 mg/l and correspondingly the No Observed Effect Concentration was greater than or equal to 0.10 mg/l.

The test concentration of 0.10 mg/L was the highest attainable test concentration that could be prepared due to the limited solubility of the test material in water and auxiliary solvent and having due regard to the amount of auxiliary solvent permitted in the test under the OECD Guidelines.

Analysis of the test solutions at 0 and 72 h showed a marked decline in test concentrations and so it was considered justifiable to base the results on the time-weighted mean measured test concentration also. The EC50, values, based on the time-weighted mean measured test concentration were > 0.080 mg/l and correspondingly the No Observed Effect Concentration was ≥ 0.080 mg/l.