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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The 72-h ErC50 and NOErC values in the freswater alga Scenedesmus subspicatus are >100 mg/L and 100 mg/L, repectively.	

Key value for chemical safety assessment

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

Additional information

The influence of the test substance on the growth of the green algal species Scenedesmus subspicatus was investigated in a 72-hour static test according to GLP and according to OECD Guideline 201 (RCC 2001). However, the test method was modified to quantify the algicidal effect of the test item, but also the growth inhibition effect caused by reduced light intensities in the colored test solutions.

The nominal test concentrations were 1.0, 3.2, 10, 32 and 100 mg/L and a control. All test media down to the lowest test concentration were slightly to strongly colored by the test item. The analytically determined test item concentrations in the analyzed test media varied in the range from 96 to 101% of the nominal values. The test substance was stable in the test media under the test conditions during the test period of 72 hours. Therefore, all biological results are related to the nominal concentrations of the test item. The same growth inhibition of Scenedesmus subspicatus was observed when the algae grew in test water without test item, but under reduced light intensities by the filter effect of the colored test media as in the second parallel experimental part, where the algae grew in the test media with dissolved test item. Thus, in conclusion, this modified algal test has clearly demonstrated that the observed growth inhibition effect of the test substance on Scenedesmus subspicatus 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.