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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984), No. 209 "Activated Sludge, Respiration Inhibition Test".
Activated sewage sludge was exposed to directly added test material at concentrations of 1, 10, 100, 1000 and 10000 ppm, a duplicate control group, and an assessment of the sensitivity of the inoculum used in the test to a reference toxicant 3,5-dichlorophenol. The test duration was a 3 hour exposure period at 20 degrees C to the test material followed by measurement of oxygen consumption.
 
The effect of the test material on the respiration of activated sewage sludge gave an EC50 of 1,650 mg/L. The reference material gave an EC50 value of 12.5 mg/L. The activated sludge respiration test passed the quality control criteria for an acceptable test. The two control replicates produced oxygen consumption rates within the required 15% of each other.

Key value for chemical safety assessment

EC50 for microorganisms:
1 650 mg/L

Additional information

- In the key study (Goodrich, 1994; WCC report number: Inv.#109308) for the acute toxicity to activated sewage sludge, the study was conducted according to the the OECD Guidelines for Testing of Chemicals (1984), No. 209 "Activated Sludge, Respiration Inhibition Test".

This study is presented as the key information as the reliability rating for this study is 2, according to the criteria of Klimisch, 1997 as analytical measurements on the test material were not conducted. This is the most recent study available.

- The Ward & Boeri, 1994 study was conducted to recognised OECD guidelines and GLP, however the test material was added directly to the dilution water resulting in surface slick, undissolved test material and globules of test material being seen at all concentrations tested. The non dissolved material present in test media has the potential to exert physical effects on test organisms which are unrelated to toxicity and so a reliability rating of 3 was assigned according to the criteria of Klimisch, 1997.

Results: Inhibition of activated sludge respiration was less than 50% of the control rate at all tested concentrations, indicating that the test material was not acutely toxic. Exposure of activated sludge to the test material resulted in a median effective concentration (EC50) greater than 1,000 mg/L, the highest tested concentration.