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Description of key information

3 hour EC10, EC20, EC50 and EC80 were clearly higher than 1000 mg/L.

Key value for chemical safety assessment

Additional information

In a valid, reliable and conclusive study, the inhibitory effect of the test item Reaction mass of CXN1-55 on the respiration rate of aerobic wastewater micro-organisms of activated sludge was investigated during 3 hours according to the OECD Guideline for Testing of Chemicals, No. 209, adopted 2010.

A range-finding test using the following three test item concentrations 10 mg/L, 100 mg/L and 1000 mg/L was performed. Single test vessel replicates were tested for the two lower concentrations, whereas for the highest test item concentration three replicates were prepared. As a positive control, the reference item 3,5 dichlorophenol was tested under identical test conditions, at concentrations of 3.2, 10 and 32 mg/L (all single replicates). Four blank controls, containing an equal volume of activated sludge and synthetic medium but no test or reference item were included in the range-finding test.

The results of the blank and positive control treatments confirmed suitability of the activated sludge and the method used. The validity criteria were fulfilled.

The test item Reaction mass of CXN1-55 had no inhibitory effect on the respiration rate of activated sludge at all tested concentrations up to and including 1000 mg/L after the incubation period of three hours. Thus, the 3 hour NOEC of Reaction mass of CXN1-55 to activated sludge micro-organisms was at least 1000 mg/L. This value might even be higher, but concentrations exceeding 1000 mg/L were not tested. The 3 hour EC10, EC20, EC50 and EC80 could not be calculated, but were clearly higher than 1000 mg/L. The results can be summarized as follows:

EC10 > 1000 mg/L

EC20: > 1000 mg/L

EC50: > 1000 mg/L

EC80: > 1000 mg/L

NOEC: ≥ 1000 mg/L

In conformity with the guideline, a definitive test was not necessary since in the range-finding test the test item showed no inhibition of the respiration rate at the highest tested concentration (performed as triplicate).