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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The 72-h ErC50 is 100 mg/L in freshwater algae.

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 testsubstance on the growth of the green algal species Scenedesmus subspicatus CHODAT was investigated in a 72-hour static test according to the EU Commission Directive 92/69/EEC, Annex Part C.3, 1992, and the OECD Guideline No. 201, 1984. 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 4.6, 10, 22, 46 and 100 mg/L in parallel with a control. All test media down to the lowest test concentration were colored by the test item. The analytically determined test item concentrations in the analyzed test media varied in the range from 83 to 100% of the nominal values. Consequently, the test item was stable during the test period of 72 hours under the conditions of the test, and the reported biological results are based on the nominal concentration 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.