Dodecyl nonan-1-oate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 Mar - 10 May 2016

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)

Version / remarks:

17 Jul 1992

Deviations:

yes

Remarks:

19.5 - 21.1 °C instead of 20 - 24 °C. No effect on study outcome (positive control normal).

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

30 May 2008

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Mainz, Germany (08 Apr 2015)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf, Germany (01 Apr 2016)
- Storage conditions: Aeration until use.
- Storage length: 01 Apr - 29 Mar 2016
- Pretreatment: The sludge was filtered, washed twice with tap water and then washed and re-suspended in test medium.
- Concentration of sludge: 3340 mg suspended solids/L
- Initial inoculum concentration in test vessel: 25.0 mg dry matter/L

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Initial conc.:

25.9 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium according to guideline
- Test temperature: 19.5 - 21.1 °C
- pH: 7.4 (test item), 7.3 (blank control), 7.2 (positive control), 6.8 (abiotic control), and 7.3 (toxicity control) at the end of the test (before addition of HCl)
- Aeration of dilution water: Yes, aeration with purified, CO2-free, moistened air during 72 h
- Suspended solids concentration: 25.0 mg dry matter/L
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 2000 mL Schott flasks were used as test vessels filled with 1500 mL test medium and magnetic stirrers. 100 mL scrubber flasks were used as absorbent vessels.
- Number of culture flasks/concentration: 2 (25.7/25.9 mg/L test item + mineral medium + 25 mg/L inoculum)
- Method used to create aerobic conditions: Aeration with purified (activated charcoal) CO2-free, moistened air
- Measuring equipment: Carbon analyser TOC multi N/C 2100S, Analytik Jena. Calibration with potassium hydrogen phthalate (TC), sodium hydrogen carbonate and sodium carbonate (IC).
- Details of trap for CO2: 100 mL 0.25 M NaOH in two scrubber flasks connected in series
- Procedure: Test vessels were filled with medium and inoculum. Then, all flasks were aerated for 72 h with purified, CO2-free, moistened air to purge the system of CO2.

SAMPLING
- Sampling frequency: After 0, 2, 4, 7, 9, 11, 14, 18, 23 and 29 d
- Sampling method: 1 mL was sampled from each front scrubber flask. On Day 28, 5 mL 2 M HCl was added to each test flask in order to drive off dissolved CO2. On Day 29, samples from both scrubber flasks were taken.
- Other: The change in the volume of the front scrubber flask was considered in the calculation of emitted CO2.

CONTROL AND BLANK SYSTEM
- Apparatus blank: 2 (mineral medium)
- Inoculum blank: 2 (mineral medium + 25 mg/L inoculum)
- Abiotic sterile control: 1 (26.4 mg/L test item + mineral medium + HgCl2)
- Toxicity control: 1 (26.1 mg/L test item + 24.8 mg/L positive control + mineral medium + 25 mg/L inoculum)
- Positive control: 2 (24.8 mg/L positive control + mineral medium + 25 mg/L inoculum)

Reference substance:

aniline

Parameter:

% degradation (CO2 evolution)

Value:

86

Sampling time:

28 d

Details on results:

The pass level for ready biodegradability, as defined by the guideline, is a pass level of 60% within 10 d after reaching the 10% pass level. The pass level of 10% marking the begin of the degradation phase was reached after 3 d. Thus, the 10-d window ended on Day 13. The mean degradation of both replicates at the end of the 10-d window was 59%. However, the first test flask reached the pass level of 60% on Day 8 and the second flask reached the 60% pass level on Day 14. Therefore, the test item was considered readily biodegradable.

Results with reference substance:

The reference substance reached a mean biodegradation of 77.8% after 14 d and 85.9% after 29 d.

VALIDITY CRITERIA

The result of the test can be considered valid (Table 1).

 

Table 1: Validity criteria for OECD 301.

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	The difference within replicates was 3.2% after 28 d.	Yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	Degradation of the positive control reached > 60% after 9 d.	Yes
The toxicity control should degrade to at least 25% (based on ThOD or ThCO2) within 14 d.	Degradation in the toxicity control was 76% on Day 14.	Yes
The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.	The IC content of test item solution in medium was ≥ 5%.	The IC content was higher than 5% of Total Carbon due to the poor solubility of the test item in water. Therefore, this validity criterion is not applicable for this test item.
The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	The CO2 emitted by the controls was 15.6 mg/L.	Yes

 

BIOLOGICAL RESULTS

Degradation of the positive control and toxicity control was normal. Abiotic degradation was not observed. Results are summarized in Table 2.

 

Table 2. Degradation values in %

Day	positive control	positive control 2	positive control mean	test item 1	test item 2	test item mean	abiotic control	toxicity control
2	-0.4	-0.7	-0.6	10.1	2.3	6.2	0.7	2.0
4	20.2	15.5	17.8	38.1	6.9	22.5	0.4	21.6
7	59.4	55.7	57.5	58.1	11.6	34.9	0.0	56.6
9	67.7	67.0	67.3	66.7	11.9	39.3	0.2	70.3
11	76.8	77.6	77.2	71.1	38.5	54.8	0.1	75.9
14	77.9	77.8	77.8	65.9	51.8	58.9	-0.1	76.0
18	80.2	83.0	81.6	76.4	65.0	70.7	-0.1	78.2
23	77.4	80.5	78.9	76.0	71.2	73.6	-0.2	75.5
29	85.1	86.6	85.9	87.2	83.9	85.5	-1.5	84.0

As the measured IC values in the abiotic control are very low, measurement uncertainties lead to negative degradation values while in fact no degradation has taken place.

 

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Remarks:

For further details on validity criteria please refer to “Any other information on results incl. tables”.

Description of key information

Readily biodegradable (85.5% in 28 d, OECD 301 B)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There is one study available, in which the ready biodegradability of the target substance lauryl nonanoate (CAS 17671-26-0) was assessed according to OECD 301 B and GLP.

25.9 mg/L test item, corresponding to 20 mg organic carbon/L, was inoculated with domestic activated sludge (25.0 mg dry matter/L) for 28 d in the dark. A positive control and a toxicity control were run in parallel. Degradation was followed by determining the produced carbon dioxide.

The degradation phase of the test item was attained after 3 d. The 10-d window ended on Day 13, after which the mean biodegradation of both test flasks was 59%. The first test flask reached the 60% pass level for biodegradation on Day 8 while the second test flask showed a delayed start of the degradation phase, which reached the 60% pass level on Day 14. After 29 d, the mean degradation of the test item was 86%. Therefore, it was concluded that the target substance can be considered as “readily biodegradable”. The degradation of the positive control and toxicity control was normal, confirming the suitability of the inoculum and indicating that the test item is not toxic towards the inoculum. In consideration of the poor water solubility of the target substance, the validity criteria of the guideline were fulfilled and the results can be considered valid.