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Toxicity to microorganisms

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Description of key information

The effect of the test item on the respiration of activated sewage sludge gave a 3‑Hour EC50 value of greater than 1000 mg ai/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000mg ai/l.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

Introduction.

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge, Respiration Inhibition Test", Method C.11 of Commission Regulation (EC) No. 440/2008 and US EPA Draft Ecological Effects Test Guidelines OPPTS 850.6800.

Methods. 

Activated sewage sludge was exposed to an aqueous solution of the test item at concentrations of 10, 32, 100, 320 and 1000 mg active ingredient (ai)/l for a period of 3 hours at a temperature of 21±1°C with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

Results.

The effect of the test item on the respiration of activated sewage sludge gave a 3 Hour EC50value of greater than 1000 mg ai/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg ai/l.

It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg ai/l.

The reference item gave a 3-Hour EC50 value of 5.4 mg/l, 95% confidence limits 4.1 – 7.1 mg/l.