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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Under the conditions of the test, there were no statistically significant effects on respiration observed during the definitive test. The 3 hour EC50 for the test material was greater than 320 mg/L. The NOAEC value was determined to be 320 mg/L, the highest concentration tested.

Key value for chemical safety assessment

EC50 for microorganisms:
320 mg/L
EC10 or NOEC for microorganisms:
320 mg/L

Additional information

The potential of the test material to cause toxic effects to microorganisms was investigated in accordance with the standardised guideline OECD 209 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria of Klimisch (1997).

The activated sludge inoculum was collected from a sludge return line which has a predominantly domestic sewage catchment. The point of collection was to ensure that the activated sludge sample was relatively free of exogenous material. A range-finder test, employing nominal test material concentrations of 1, 10, 100 and 1000 mg/L, was undertaken to determine the appropriate concentration levels for a definitive test. The range-finding test showed limited inhibition ( less than 30%) of total, heterotrophic and nitrification respiration at 10 and 100 mg/L, but negative inhibition was observed at both 1 and 1000 mg/L.

Based on the results of the range-finding test, a 3 hour definitive toxicity test was conducted at concentrations of 3.05, 9.77, 31.25, 100 and 320 mg/L. Reference substance inhibition, blank control respiration rate and the coefficient of variation between replicates were observed to be within the validity criteria. The results of the definitive test can therefore be considered to be valid. As enhancement effects were noted (observed as negative inhibition), the endpoints are reported as EC50 and No Observed Adverse Effect Concentration (NOAEC).

Under the conditions of the test, there were no statistically significant effects in heterotrophic, nitrification or total respiration inhibition observed during the definitive test. The 3 hour EC50 for the test material was greater than 320 mg/L. The NOAEC value was determined to be 320 mg/L, the highest concentration tested.