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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Activated sewage sludge, OECD 209: EC50(3h) > 1000 mg/L, NOEC(3h): 1000 mg/L 

Key value for chemical safety assessment

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

Additional information

Activated sewage sludge, obtained from a predominantly domestic sewage, was exposed to the test substance to investigate the toxic effects towards aquatic microorganisms (Wadsley, 2012). The suspended solid concentration was determined as 3 g/L prior to the start of the experiment. After stock solution preparation, the 25, 250 and 2500 mg/L stock solution were used to prepare the test concentrations of 10, 100 and 1000 mg/L. The 1000 mg/L test concentration was prepared in triplicate. Synthetic sewage acted as a respiratory substrate. 3,5-dichlorophenol was used as reference item and resulted in an EC50(3h) of 14 mg/L and confirmed thereby the suitability of the inoculum. The control group (three replicates) were maintained under identical conditions but not exposed to the test item. The test was performed in a temperature controlled room at 20 +/- 2 °C under normal laboratory lighting with continuous illumination. The oxygen concentrations in all vessels were measured after 30 minutes contact time. The test item vessels thereby oxygen concentrations between 45 to 70 % of saturation. This deviation was considered to have had no adverse effect on the study given that all oxygen consumption values were measured/calculated over the linear portion of the traces. No statistically significant toxic effects were shown at all of the test concentration employed in the range-finding study. It was therefore considered justifiable not to perform a definitive test. The EC50(3h) is greater than 1000 mg/L with the corresponding NOEC of 1000 mg/L. It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/L.