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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC(50) = 14 mg/l 72 h

Key value for chemical safety assessment

Additional information

One study was performed on similar substance 2 (1994, Synthesia) following ISO 8692 with a EC 50 at 72h based on Grow rate of 14 mg/l. This study is disregarded since several studies on algae conducted on dark dyes, including those with a modified test system for dye-stuffs, showed that the growth inhibition is not due to a toxic effect of the dye, but due to the light absorption of the stained water. It has been deduced that the observed toxicity was related to the shading effect of the dye. This method has some limitation because it focuses on the shadow effect but gives no information on the real potential toxicity for algae of the tested substance.

Another study of acute toxicity on algae (1997, Huntsman) was performed on the similar substance 3 following a modified version of OECD Guideline No. 201, as to quantify the algicidal effect of the test substance, but also the growth inhibition effect caused by reduced light intensities in the coloured test solutions. The same growth inhibition of Scenedesmus subspicatus was observed when the algae grew in test water without test substance, but under reduced light intensities by the filter effect of the coloured test media as in the second parallel experimental part, where the algae grew in the test media with dissolved test substance. In conclusion, this modified algal test has demonstrated that the observed growth inhibition effect of the test substance on Scenedesmus subspicatus was caused with high possibility only due to an indirect effect, the light filter effect in the coloured test solutions. Thus, a toxic effect of the test substance on the algal cells can be excluded up to the highest test concentration of nominal 100 mg test substance/I (mean measured 80 mg/l).

Therefore Direct Black 80 cannot be consider toxic to algae for Read Across with similar substance 2 and 3.