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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Based on the results of this study, the 3-hour EC20 and EC50 of Read Across substance 2 (RA2) to activated sludge respiration are greater than 1000 mg/L.
The test is regarded as valid since the variance between the two control samples was less than 15 % (8.2 %) and the 3 hour EC50 of the positive control 3,5-dichlorophenol was 28.5 mg/L. Both values are within the guideline-recommended range.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L
EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

The inhibitory effect of the Read Across test substance RA2 on the respiration rate of aerobic wastewater micro-organisms of activated sludge was investigated in a 3 hour respiration inhibition test according to the Commission Directive 87/302/EEC, No. L 133/118-122, dated May 05, 1988, and the OECD Guideline for Testing of Chemicals, Section 2, No. 209, adopted April 04, 1984.


The following nominal concentrations RA2 were tested: 10, 32, 100, 320 and 1000 mg test substance/l. Concentrations in excess of nominal 1000mg/l. were not tested. Defined aliquots of a clear colourless stock solution of RA2 were transferred into the test flasks and mixed with deionised water.


In addition, three controls and four different concentrations of the reference substance 3, 5-dichlorophenol in the range from 3.2 to 100 mg/l were tested in parallel.


Up to and including the highest concentration of nominal 1000 mg/l the test substance, RA2 had no inhibitory effect on the respiration rate of activated sludge after an incubation period of three hours. Therefore, the 4 hour EC20 and EC50 could not be quantified but are clearly higher than 1000 mg/L nominal under present conditions.


The 3 hour EC50 of the reference substance 3,5-dichlorophenol was calculated to be 28.5 mg/l (the 95 % confidence limits were not calculable) and is within the accepted range of 5 – 30 mg/L; thus, confirming suitability of the activated sludge.