Reaction mass of N,N-dimethyldodecanamide and N,N-dimethyltetradecanamide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015-01-23 - 2015-02-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Agnique AMD 12, Lot no. 0009565072

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Non-adapted activated sludge from the aeration tank of the ARA Werdhölzli (CH-8048 Zürich), a municipal biological waste water treatment plant.
30 mg/l dry matter in the final mixture.

The activated sludge was used after sampling from the treatment plant without adaptation. However, the sludge was pre-conditioned for 1 day (aerated but not fed) to reduce the amount of CO2 produced by the blank controls.

Prior to the test, the sludge was washed twice with tap water and once with mineral medium. After centrifugation, the sludge was suspended in test medium, at a tenfold concentration of the final concentration to be achieved for the test.

Duration of test (contact time):

28 d

Initial conc.:

25.8 mg/L

Based on:

test mat.

Initial conc.:

19.8 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The test and reference items were both applied by direct addition to give a final test concentration of about 20 mg/l with respect to the total organic carbon (TOC).
In the toxicity control, about 20 mg/l test item and about 20 mg/l reference item with respect to the total organic carbon (TOC) was tested as a mixture.
For each test series, the following test flasks were set up:
T: Test suspension: containing inoculum, test medium and test item (three replicates)
B: Blank control: containing inoculum and test medium (three replicates)
R: Procedure control: containing inoculum, test medium and sodium benzoate as readily biodegradable reference item (three replicates)
C: Abiotic sterile control: containing test item, deionised water and 0.2 mM HgCl2 as sterilizing agent to prevent microbial decomposition (one replicate)
X: Toxicity control: containing inoculum, test medium, Test item and sodium benzoate as readily biodegradable reference item (one replicate)
The test vessels were stirred thoroughly and aerated with synthetic CO2-free air for a test period of 28 days. The air leaving the individual vessels was passed through gas-absorption bottles filled with KOH.
The pH-value was checked at the beginning and at the end of the test. At the beginning, it was adjusted to pH 7.4 (± 0.2) with NaOH or HCl, where necessary.
The biodegradation of the test item was followed by CO2 measurements at frequent intervals to allow the assessment of the 10-d window. The trapped CO2 was determined as inorganic carbon (IC).

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

24

Sampling time:

3 d

Parameter:

% degradation (CO2 evolution)

Value:

56

Sampling time:

7 d

Parameter:

% degradation (CO2 evolution)

Value:

69

Sampling time:

10 d

Parameter:

% degradation (CO2 evolution)

Value:

75

Sampling time:

14 d

Parameter:

% degradation (CO2 evolution)

Value:

86

Sampling time:

28 d

Results with reference substance:

92 % within 10 days

Toxicity control

At the applied initial test concentration, N,N Dimethyldodecane-1-amide showed no significant toxic effect on the microbial population, since the biodegradation of the

mixture (test item + reference item sodium benzoate) was within the expected theoretical value. The test was considered valid, since more than 25% degradation occurred within 14 days.

Abiotic sterile control

N,N Dimethyldodecane-1-amide was not abiotically degraded (by processes producing CO2) during the whole test period of 28 days in the absence of microorganisms as confirmed by lack of significant CO2 production in the test vessels.

At the end of exposure, the pH values of the blank control and of the procedure control were 7.3 and 7.5, respectively. The pH values of the test units and the toxicity control were 7.3 and 7.4, respectively.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

N,N Dimethyldodecane-1-amide has been tested in the OECD 301B test. Under these conditions the test substance achieved 73% ultimate degradation within the 10d window. Thus, N,N Dimethyldodecane-1-amide is readily biodegradable according to OECD criteria.

Executive summary:

The biodegradability of N,N Dimethyldodecane-1-amide exposed to microorganisms derived from the activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions. Biodegradability - based on CO2 evolution - of N,N Dimethyldodecane-1-amide and expressed as % of the theoretical value (ThCO2) was calculated to be 86% after an incubation time of 28 days.

The biodegradation of N,N Dimethyldodecane-1-amide reached 73% at the end of the 10-d window. Significant biodegradation of the test item started after a lag phase of about 1 day. The procedure control, sodium benzoate, reached a calculated biodegradation of 102% after 14 days, thus confirming suitability of inoculum and test conditions.

N,N Dimethyldodecane-1-amide reached the pass level of 60% for ready biodegradability in the CO2 Evolution Test within the 10-d window and, therefore, can be termed as readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

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 ready biodegradability.
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 be similarly available for biodegradation in aquatic media. In addition, the presence of the longer chain length constituent is not anticipated to reduce the overall rate of biodegradation.
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).
Target: Water solubility = 43.61 mg/L (EU Method A.6); Log Kow >4.6 (estimate from solubility in n-octanol and water)

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Duration of test (contact time):

d

Parameter:

% degradation (CO2 evolution)

Value:

24

Sampling time:

3 d

Parameter:

% degradation (CO2 evolution)

Value:

56

Sampling time:

7 d

Parameter:

% degradation (CO2 evolution)

Value:

69

Sampling time:

10 d

Parameter:

% degradation (CO2 evolution)

Value:

75

Sampling time:

14 d

Parameter:

% degradation (CO2 evolution)

Value:

86

Sampling time:

28 d

Description of key information

86% biodegradation after 28 days; 73% within the 10 day window (OECD 301B; N,N-dimethyldodecanamide)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The biodegradability of N,N Dimethyldodecane-1-amide exposed to microorganisms derived from the activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions. Biodegradability - based on CO2 evolution - of N,N Dimethyldodecane-1-amide and expressed as % of the theoretical value (ThCO2) was calculated to be 86% after an incubation time of 28 days.

The biodegradation of N,N Dimethyldodecane-1-amide reached 73% at the end of the 10-d window. Significant biodegradation of the test item started after a lag phase of about 1 day. The procedure control, sodium benzoate, reached a calculated biodegradation of 102% after 14 days, thus confirming suitability of inoculum and test conditions.

N,N Dimethyldodecane-1-amide reached the pass level of 60% for ready biodegradability in the CO2 Evolution Test within the 10-d window and, therefore, can be termed as readily biodegradable.

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