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Toxicity to aquatic algae and cyanobacteria

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Description of key information

A 72h-EC50 of 0.044 mg/L and a 72h-NOEC of 0.00757 mg/L was obtained on the alga Desmodesmus subspicatus.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.044 mg/L
EC10 or NOEC for freshwater algae:
0.008 mg/L

Additional information

In order to test acute toxicity to algae of the substance, Desmodesmus subspicatus was exposed to the test solution of 5 nominal concentration of the test substance (0.1, 0.32, 1.0, 3.2 and 10 mg/L) and blank control solution for a period of 72 h under static conditions. The cell densities were measured at 24 hour intervals. Inhibition of the algal population was measured as reduction in growth rate (index r), relative to control cultures grown under identical conditions. A 72h-EC50 of 0.044 mg/L and a 72h-NOEC of 0.00757 mg/L were obtained. The test was performed using the OECD Guideline 201 (Alga, Growth Inhibition Test).

The results are expressed in terms of geometric mean measured concentrations. Effective concentrations ranged from 1.5 % to 1.7 % of nominal values at 0 hours. After 24 hours the highest test item concentration 10 mg/L corresponds to 0.2 % of nominal values while the next test item concentration 3.2 mg/L dropped below the quantification limit (0.0098 mg/L). After 48 hours also the test item concentration 10 mg/L dropped below the quantification limit. Analysis of all test item concentrations after 72 hours of exposure confirms that all concentrations were below the quantification limit.

This toxicity study is classified as acceptable and satisfies the guideline requirements for the actue algae study.