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Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2014-01-29 - 2014-02-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
- Name of test substance: N,N Dimethyldodecane-1-amide
- Test substance No.: 13/0555-1
- Batch identification/ No: 0009565072
- CAS No.: 3007-53-2
- Purity: GC-MS: N,N-Dimethyldodecanamide: 95.9 area-%, dodecanoic acid (lauric acid): 2.26 area-%
- Homogeneity: Homogeneous
- Physical state/Appearance: Liquid/ colorless, clear
- Water solubility: Poorly soluble
Analytical monitoring:
no
Details on sampling:
No concentrations of the test substance were measured.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTIONS
- Preparation of the test substance solution: Direct addition by initial weight into the test flasks. The test substance was added in the required amounts according to the test concentrations directly to the test vessels with about 234 mL deionized water.
- Preparation of the reference substance solution: 1000.0 mg of the reference substance was added to about 800 mL of deionized water and stirred at room temperature until the reference substance was completely dissolved. The pH value of the stock solution was measured and adjusted to 7.1 with 1 M sodium hydroxide solution. Following this the stock solution was made up to 1L with deionized water. The stock solution appeared colorless-clear and no undissolved reference substance was visible. Aliquots of the reference substance stock solution were dosed to the test vessels and made up with deionized water to a volume of 234 mL.
Test organisms (species):
activated sludge, domestic
Details on inoculum:
- Source of the inoculum: Active sludge from the aeration tank of the municipal waste treatment plant of Mannheim, Germany.
- Sludge concentration in the test vessel: 1.5 g/L (dry weight)
- Preparation of inoculum for exposure: The activated sludge suspension in the test facility the suspension was sieved with a fine woven mesh (mesh size about 1 mm). This suspension was pre-aerated over night at room temperature. At the next day the sludge suspension was washed once with drinking water and the suspension was adjusted to 3 g/L dry weight.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
No data
Test temperature:
21.0 - 21.2 °C
pH:
- pH of stock solution (adjusted): 7.1
- pH values after the incubation time (not adjusted): 8.1 - 8.2
Dissolved oxygen:
- Oxygen concentration during aeration: > 2 mg/L
- Oxygen concentration immediately before measurement: > 7 mg/L
- Duration of the measurement of oxygen consumption: about 8 - 10 min
Salinity:
No data
Conductivity:
No data
Nominal and measured concentrations:
- Nominal concentrations based on the test substance: 0 (control), 9.5, 30.5, 97.7, 313, 1000 mg/L without correction of the purity.
- Nominal concentration based on the reference substance: 100, 10, 1 mg/L.
- Measured concentrations: No concentrations of the test substance/reference substance were measured.
Details on test conditions:
TEST SYSTEM
- Test vessel: Glas-beakers (nominal volume 1L)
- Test volume: 500 mL
- Aeration: yes
- No. of vessels per concentration (replicates): 3
- No. of vessels per concentration of the reference substance (replicates): 2
- No. of vessels per control (replicates): 6

TEST MEDIUM/WATER PARAMETERS
- Inoculum: Active sludge from the aeration tank of the municipal waste treatment plant of Mannheim, Germany
- Active sludge concentration in the test vessel: 1.5 g/L (dry weight)
- Synthetic medium: 16 mL/test vessel of 100-fold concentrated OECD medium. The synthetic mediums were dosed to each test vessel with test substance and reference substance afterwards.
- Intervals of water quality measurement: The oxygen uptake was measured for a period of about 8 to 10 minutes or until the oxygen concentration fell below 2 mg/L. pH and temperature were measured at the start and at end of the test.

OTHER TEST CONDITIONS
- Adjustment of pH: The pH was adjusted in the stock solution but not in the test.

EFFECT PARAMETERS MEASURED: Determination of the inhibition of oxygen consumption in the active sludge respiration over a incubation time of 3 hours. The consumption rate (mg O2/L*minutes) of each test concentration and the blank controls were determined after 3 hours of exposure. The consumption rates (mg O2/L*h) were used to calculate the inhibition effects at particular test concentrations compared to the mean consumption rate of all controls.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Range finding study: No range finding study was performed.
- Test concentrations:
- Nominal concentrations based on the test substance: 0 (control), 9.5, 30.5, 97.7, 313, 1000 mg/L without correction of the purity.
- Nominal concentration based on the reference substance: 100, 10, 1 mg/L
- Measured concentrations: No concentrations of the test substance were measured.
Reference substance (positive control):
yes
Remarks:
3,5 dichlorphenol
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (10.7 - 35.4 mg/L)
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
41 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (26.2 - 63.7 mg/L)
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
170 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (127.7 - 223.9 mg/L)
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
700 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (439.7 - 1113.6 mg/L)
Details on results:
The 3 hours effect concentrations for the test substance based on nominal concentrations in the activated sludge respiration inhibition test were obtained as following: EC10 was determined to be 20 mg/L, the EC20 was determined to be 41 mg/L, the EC50 was determined to be 170 mg/L and the EC80 was determined to be 700 mg/L.
The coefficient of variation of the six replicates of blank control was 8.2 % O2 consumption. The mean oxygen uptake of the blank controls was 32 mg/g*h. In conclusion, the results in this study are consistent with all validity criteria and the test is valid according to the guidelines used for this study.
No deviations from the test guidelines or other incidents occurred during the course of the reported test which may have influenced the results.
Results with reference substance (positive control):
The EC50 of the reference substance 3,5-dichlorphenol was determined to be 11.8 mg/L in 3 hours. These results indicate that the microorganisms are responding normally to toxicant stress.
Reported statistics and error estimates:
The consumption rates were used for the determination of the ECx by the probit method based on Finney (1971) with the software TOXRAT Professional 2.10 (2001-2010).
Validity criteria fulfilled:
yes
Conclusions:
The toxic effects of the test substance on the oxygen consumption rate of aerobic micro-organisms (activated sludge) after short-term exposure of 180 min was determined according to the OECD 209 (2010). The EC50 was determined to be 170 mg/L and the EC10 was determined to be 20 mg/L.
Executive summary:

The objective of this key study according to OECD 209 (2010) was to determine the toxic effects of the test substance on the oxygen consumption rate of aerobic micro-organisms (activated sludge) after short-term exposure of 180 min, compared with the blank control. The test was performed in nominal concentrations of 0 (control), 9.5, 30.5, 97.7, 313, 1000 mg/L without correction of the purity. No concentrations were measured. The inoculum was activated sludge from a municipal waste treatment plant of Mannheim, Germany. The sludge concentration was 1.5 g/L and a synthetic medium according to the guideline was used. A reference substance (3,5 dichlorphenol) was used as positive control. The EC50 value of the reference substance 3,5-dichlorphenol was determined to be 11.8 mg/L, which was within the acceptable limits, (5.0 to 30 mg/L) as specified in OECD 209 Guideline. All validation criteria were fulfilled. The EC50 for the test substance was determined to be 170 mg/L and the EC10 for the test substance was determined to be 20 mg/L. 

Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The chemical characterisation and physico-chemical properties of the source and target substances support read-across between the substance for acute ecotoxicity endpoints.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source: N,N-dimethyldodecanamide [EC 221-117-5; CAS 3007-53-2].
Target: Reaction mass of N,N-dimethyldodecanamide and N,N-dimethyltetradecanamide [EC not assigned; CAS not assigned]. Details of composition provided in section 1.2.
3. ANALOGUE APPROACH JUSTIFICATION
The source substance constitutes 65-80 %w/w of the target substance. The other main constituent (20-35 %w/w) has identical functional groups and an additional two carbons in the alkyl chain. The similarity of the measured water solubility and log Kow for the source substance and the measured water solubility and estimated log Kow for the target substance suggests that both substances will behave similarly in aquatic systems and that data available for the source may be used to read across to the target.
4. DATA MATRIX
Source: Water solubility = 28.08 mg/L (OECD TG 105); Log Kow = 5.2 (OECD TG 117); Readily biodegradable (86% after 28 days; OECD TG 301B);
96-h LC50 > 0.88 mg/L (Danio rerio; OECD TG 203); 48-h EC50 = 0.313 mg/L (Daphnia magna; OECD TG 202); 72-h ErC50 = 0.805 mg/L; 72-h NOErC = 0.351 mg/L (Pseudokirchneriella subcapitata; OECD TG 201), 3-h EC50 = 170 mg/L; EC10 = 20 mg/L (activated sewage sludge; OECD TG 209)
Target: Water solubility = 43.61 mg/L (EU Method A.6); Log Kow >4.6 (estimate from solubility in n-octanol and water)
Ecotoxicological endpoints – no data
Reason / purpose for cross-reference:
read-across source
Test organisms (species):
activated sludge
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (10.7 - 35.4 mg/L)
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
41 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (26.2 - 63.7 mg/L)
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
170 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (127.7 - 223.9 mg/L)
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
700 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % C.L. (439.7 - 1113.6 mg/L)
Validity criteria fulfilled:
yes

Description of key information

3-h EC50 = 170 mg/L; EC10 = 20 mg/L (activated sewage sludge; N,N-dimethyldodecanamide).

Key value for chemical safety assessment

EC50 for microorganisms:
170 mg/L
EC10 or NOEC for microorganisms:
20 mg/L

Additional information

The objective of this key study according to OECD 209 (2010) was to determine the toxic effects of the test substance, N,N-dimethyldodecanamide, on the oxygen consumption rate of aerobic micro-organisms (activated sludge) after short-term exposure of 180 min, compared with the blank control. The test was performed in nominal concentrations of 0 (control), 9.5, 30.5, 97.7, 313, 1000 mg/L without correction of the purity. No concentrations were measured. The inoculum was activated sludge from a municipal waste treatment plant of Mannheim, Germany. The sludge concentration was 1.5 g/L and a synthetic medium according to the guideline was used. A reference substance (3,5 dichlorphenol) was used as positive control. The EC50 value of the reference substance 3,5-dichlorphenol was determined to be 11.8 mg/L, which was within the acceptable limits, (5.0 to 30 mg/L) as specified in OECD 209 Guideline. All validation criteria were fulfilled. The EC50 for the test substance was determined to be 170 mg/L and the EC10 for the test substance was determined to be 20 mg/L. 

The results of this study are read-across to Reaction mass of N,N-dimethyldodecanamide and N,N-dimethyltetradecanamide.