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Toxicity to microorganisms

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Description of key information

The test item C.I. Leuco Sulphur Brown 37 has no inhibitory effect on the respiration rate of activated sludge after the incubation period of three hours up to and including the test item concentration of 1000 mg/L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

The inhibitory effect of the test item C.I. Leuco Sulphur Brown 37 on the respiration rate of aerobic wastewater micro-organisms of activated sludge was investigated in a 3‑hour respiration inhibition test 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 vessels were prepared in the following order: two blank controls, the reference item group (with ascending concentrations), the test item group (with ascending concentrations) and at last again two blank control vessels.

 

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 C.I. Leuco Sulphur Brown 37 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 C.I. Leuco Sulphur Brown 37 to activated sludge micro-organisms was 1000 mg/L. This value might even be higher, but concentrations exceeding 1000 mg/L were not tested. The 3‑hour EC10, EC20, EC50and EC80could not be calculated, but were clearly higher than 1000 mg/L.

 

In conformity with the guideline, since in the range-finding test the test item showed at the highest tested concentration (performed as triplicate) no inhibition of the respiration rate a definitive test is unnecessary.