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Toxicity to aquatic algae and cyanobacteria

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Description of key information

In conclusion, this modified algal test has clearly demonstrated that the observed growth inhibition effect of the test item on Pseudokirchneriella subcapitata was caused only by an indirect effect, the light filter effect in the colored test solutions. Thus, a toxic effect of the test item on the algal cells can be excluded up to the highest test concentration of 100 mg/l. For this substance, the following values considering the growth rate were determined: EC50 (72 h) > 100 mg/L and NOEC (72 h) = 3.2 mg/L. The second test with Scenedesmus subspicatus the EC50 (72 h) is 12.5 mg/L based on biomass and 66.5 mg/L based on growth rate.

Key value for chemical safety assessment

EC50 for freshwater algae:
66.5 mg/L
EC10 or NOEC for freshwater algae:
3.2 mg/L

Additional information

The influence of the substance on the growth of the green alga Scenedesmus subspicatus was investigated. The test method was based on the OECD Guideline No. 201 and the EEC Directive 92/69 Part C.3, and was modified to differentiate between a reduced growth of algae due to direct inhibitory effects of the test article on the algal cells and a reduced growth of algae due to an indirect effect caused by the light absorption of the colored test solutions.

In a second test the influence of the substance on the growth of the green alga Pseudokirchneriella subcapitata  was investigated. The test method also based on the OECD Guidelien No. 201 with same modifications.

In the test with Scenedesmus subspicatus an 72h EC50 of 12.5 mg/L based on biomass and 66.5 mg/L based on growth rate was reported. The NOEC for both endpoints is 3.2 mg/L and the LOEC is 10 mg/L. In conclusion, the modified algal test has clearly demonstrated that the observed growth inhibition effect of the test item on Pseudokirchneriella subcapitata was caused only by an indirect effect, the light filter effect in the colored test solutions. Thus, a toxic effect of the test item on the algal cells can be excluded up to the highest test concentration of 100 mg/l. For this substance, the following values considering the growth rate were determined: EC50 (72 h) > 100 mg/L and NOEC (72 h) = 3.2 mg/L.