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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Test type:
static
Water media type:
freshwater
Total exposure duration:
3 h
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol (CAS-No. 591-35-5)
Key result
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
32 mg/L
Basis for effect:
inhibition of total respiration
Key result
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
23 mg/L
Basis for effect:
inhibition of total respiration
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
130 mg/L
Basis for effect:
inhibition of total respiration
Validity criteria fulfilled:
yes
Conclusions:
The following results for the test item β-Alanine, N-coco alkyl derivs.; water based version were determined:
3h NOEC = 32 mg/L
3h EC10 = 23 mg/L (confidence interval 17- 30 mg/L)
3h EC50 = 130 mg/L (confidence interval 100 – 160 mg/L)
Executive summary:

Two experiments were performed.

In the first experiment (pre-test) the test item was tested using 4 concentrations ranging from 1000 to 1 mg/L nominal concentration.

To avoid volatilization and for safety reasons, the experiments were performed in a closed system without aeration. In order to ensure sufficient oxygen supply, a large headspace is provided and the mixtures are stirred vigorously. This procedure is described in the OECD guideline

All validity criteria were met. For the estimation of the EC50 of the positive control, the fits showed good statistical correspondence of the data with the dose-response-equation. The positive control gave an EC50 of 8.8 mg/L (confidence interval: not determinable) first experiment (pre-test) and 12 mg/L (confidence interval 9.9 – 15 mg/L) in the second experiment (main test), which lie within the recommended range of 2 – 25 mg/L. The coefficient

of variation of oxygen uptake rate in control replicates was below 30% at the end of the test. The oxygen uptake rate of the blank controls was above 20 mg O2 per gram activated sludge in 1 hour.

Because significant inhibition was observed, an additional experiment was performed. In the second experiment (main test) the test item was tested using 5 concentrations ranging from 1000 to 10 mg/L nominal concentration. At the highest concentration 1000 mg/L total inhibition was observed. The NOEC can be stated as 32 mg/L, the EC10 as 23 mg/L and the EC50 was determined with 130 mg/L.

All replicates showed a very good agreement.

No inconsistencies in the dose-response estimation could be observed. Therefore, no further experiment was performed in order to discern between inhibition of nitrificators and inhibition of total population.

No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.

Description of key information

The following results for the test item β-Alanine, N-coco alkyl derivs.; water based version were determined:

3h NOEC = 32 mg/L

3h EC10 = 23 mg/L (confidence interval 17- 30 mg/L)

3h EC50 = 130 mg/L (confidence interval 100 – 160 mg/L)

Key value for chemical safety assessment

EC50 for microorganisms:
130 mg/L
EC10 or NOEC for microorganisms:
32 mg/L

Additional information