Pentasodium bis{7-[4-(1-butyl-5-cyano-1,2-dihydro-2-hydroxy-4-methyl-6-oxo-3-pyridylazo)phenylsulfonylamino]-5'-nitro-3,3'-disulfonatonaphthalene-2-azobenzene-1,2'-diolato} chromate (III)

Toxicity to aquatic algae and cyanobacteria

Description of key information

ErC50 (72 h, Scenedesmus subspicatus) > 100 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

Additional information

The acute toxicity of the test item to aquatic algae and cyanobacteria was investigated in a 72 –hour static test to Scenedesmus subspicatus, according to the OECD Guideline 201 (1984) and the method C.3 of EEC-Directive 92/69 EEC. The test method was modified to differentiate between a reduced growth of algae due to real toxic effects of the test substance on the algal cells or due to an indirect effect, a reduced algal growth by light absorption in coloured test solutions. The nominal test concentrations ranged from 0.10 to 100 mg/l in parallel with a control. All test media down to the lowest test concentration were slightly to strongly coloured by the test substance.

The biological results of both experimental parts A (where the algae grew in test media) and B (where the algae grew in test water without test substance but under reduced light intensities by the filter effect of the coloured test media) are identical. This could be demonstrated by several calculated parameters, the NOEC/LOEC, the percentage inhibition of algal growth and the EC-values. All biological results were related to the nominal concentrations of the test substance, in accordance with the analytically determined test substance concentrations in the analysed test media of the test concentrations. The test substance was sufficiently stable in the test media under the test conditions at least during the test period of 72 hours.