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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 > 230 mg/L
NOEC: 230 mg/L

Key value for chemical safety assessment

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

Additional information

The influence of the test substance Reaktiv-Rot F-52 167 FW on the growth of the green alga scenedesmus was investigated in a 72 -hour static test according to the OECD Gudeline No. 201. However, 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 grwoth by light absorption in coloured test solutions. The test included two experimental parts: A: the algae grew in test media with dissolved dyestuff in Erlenmeyer flasks, each placed in a black cylinder. The cylinders were covered with glass dishes, containing untreated test water in thsi pexerimental part. In part B the glass dishes above the cylinders contained the coloured dyestuff solutions with the same five test concentrations as in Part A, however without algae. In the erlenmeyer flasks below the algae grew in test water without dyestuff, however under changed light conditions due to the filter effect of the coloured test solutions in the glass dishes. the biolgoical results of both experimental parts A and B are identical. The LOEC for both, the algal biomass and the growth rate amounted to 10 mg test substance/L, the NOEC amounted to 3.2 mg/L. The percentage inhibition after 72 hours exposure period differed only in the range of - 5.2% to 8%.

In conclusion, this modified algal test has clearly demonstrated that the observed growth inhibtion effect of the test substance was caused only due to the indirect effect, the light absorption in the coloured test solutions. Thus, a real toxic effect of the test substance on the algal cells can be excluded up to at least the highest tested concentration of 320 mg test substance/L.