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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

3 h EC50 > 100 mg/L in activated sludge, OECD 209, L'Haridon 1999

Key value for chemical safety assessment

Additional information

The potential of the test material to cause toxicity to microorganisms was determined in the key activated sludge respiration inhibition test perofrmed by L'Haridon (1999) using activated sludge from a predominantly domestic sewage. The study was conducted under GLP conditions and in accordance with the standardised guideline OECD 209. Based on the principles for assessing data quality defined by Klimisch et al. (1997), the study was assigned a reliability score of 1.

The activated sludge was exposed to the test material at concentrations of 0, 1, 3.16, 10, 31.6 and 100 mg/L for 3 hours under static conditions during which time the culture was aerated. After 3 hours of aeration/contact time, the contents of the test flasks were poured into the measuring apparatus and the oxygen concentration was determined for a period of up to 10 minutes. The activated sludge was also exposed to a positive control, the reference material 3,5-dichlorophenol at concentrations of 4, 12 and 36 mg/L. 

There was no inhibition of the inoculum respiration rate measured for each test concentration in comparison to the blank control. The reference substance displayed sufficient inhibition to confirm the viability of the inoculum.

Under the conditions of the test, the 3 h EC50 was determined to be > 100 mg/L for activated sludge. Therefore the test material should be considered as non-toxic for the micro-organisms in a water treatment plant.