Sodium 4-[(9,10-dihydro-4-hydroxy-9,10-dioxo-1-anthryl)amino]toluene-3-sulphonate

Toxicity to microorganisms

Description of key information

For the three replicates of the highest test concentration of 1000 mg/L the mean inhibition of the respiration rate was calculated to be 10.0 %, compared to the control. Although this low reduction in the respiration rate was mathematically found to be statistically significantly different from the control, the inhibition is considered as biologically not relevant.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The inhibitory effect of the test item 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 Guidelines 209 and to the Commission Regulation (EU) No. 2016/266, C.11. (2015) and following GLP.

A range-finding test using the following three test item concentrations 10, 100 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.

For the three replicates of the highest test concentration of 1000 mg/L the mean inhibition of the respiration rate was calculated to be 10.0 %, compared to the control. Although this low reduction in the respiration rate was mathematically found to be statistically significantly different from the control, the inhibition is considered as biologically not relevant. Thus, the 3-hour NOEC of the test item to activated sludge micro-organisms was 1000 mg/L. Concentrations exceeding 1000 mg/L were not tested. The 3-hour EC10, EC20, EC50 and EC80 could not be calculated.

The results can be summarized as follows:

NOEC: 1000 mg/L; EC50: > 1000 mg/L

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

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