monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol

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:

02 Aug - 02 Sep 2011

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)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Cambridge Sewage Treatment Works, Cowley Road, UK
- Date of collection: 02 Aug 2011
- Storage length: Test start same date as sludge collection date
- Pretreatment: Sieved to 850 µm, settled, decanted and re-suspended using mineral media. Centrifuged at ~ 4000 rpm for ~ 10 min, supernatant discarded, re-suspended and re-centrifuged at ~ 4000 rpm for ~ 10 min and supernatant discarded. Dry sludge solids content was determined on the pellet produced.
- Concentration of sludge (dry sludge solids): 7.4%
- Dry sludge solids in test: 0.03 g/L

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Initial conc.:

>= 26.2 - <= 26.26 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
- Suspended solids concentration: 0.03 g/L dry sludge solids (in test)

TEST SYSTEM
- Culturing apparatus: Conical flasks with a nominal volume of 2000 mL, filled with 1500 mL inoculated mineral medium.
- Number of culture flasks/concentration: 2
- Number of replicates for blank & reference: 2
- Number of replicates for toxicity control: 1
- Method used to create aerobic conditions: Atmospheric air was pumped into the test system and scrubbed clean of carbon dioxide by passing over soda lime. The air continued into the test vessel where it collects any evolved carbon dioxide before moving into the carbon dioxide traps.
- Measuring equipment: Tekmar-Dohrmann Phoenix 8000 Analyser (UV-Persulfate)
- Details of trap for CO2 and volatile organics if used: The carbon dioxide traps contained 200 mL sodium hydroxide solution (0.05 M).
- Other: The test solutions were stirred for the duration of the study.
- Other: On Day 28, 2 mL of 50% hydrochloric acid was added to each bioreactor, which were then aerated overnight, to drive off the remaining carbon dioxide. One last analysis of evolved carbon dioxdie is performed on Day 29.
- Test material: 39.3 mg / 39.4 mg test item in 1500 mL test medium (inoculated mineral medium). Total organic carbon = 30.21 mg / 30.29 mg. Percentage carbon in test item = 76.87%
- Other: Since the test item is insoluble, it was weighed onto a microscope cover slip and added directly to the test bioreactors.

SAMPLING
- Sampling frequency: Day 2, 5, 7, 9, 14, 19, 23, 28, and 29

CONTROL AND BLANK SYSTEM
- Reference substance: 102.48 mg sodium acetate (reference substance) in 1500 mL test medium (inoculated mineral medium). Percentage carbon in sodium acetate = 29.3%. Total organic carbon = 30.03 mg.
- Toxicity control: 39.5 mg test item + 102.48 mg sodium acetate (reference substance) in 1500 mL test medium (inoculated mineral medium). Total organic carbon = 60.39 mg.
- Other:

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

86

Sampling time:

29 d

Details on results:

10% degradation was achieved after approximately 3 days, and 60% was reached after 11.5 days, Monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol therefore achieved the 10-day window.
A maximum of 86% recorded on day 29. It is therefore concluded that there is a potential for biodegradation under environmental conditions.

Results with reference substance:

The guideline requires that the reference material degrades by at least 60% of its ThCO2 value. The mean degradation of the reference substance sodium acetate was 71% on Day 14 and a maximum of 88% on Day 29.

VALIDITY CRITERIA

The test met the validity criteria prescribed by the guideline and is thus considered valid.

 

Table 1: Validity criteria for OECD 301 B.

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%.	After 29 d, degradation was 79% and 92% in the two replicates.	Yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	The reference item was degraded by 71% after 14 d.	Yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	The toxicity control degraded by 50% within 14 d.	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 the test item in suspension was < 5% of the TC at the beginning of the test.	Yes
The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	A value of 21.8 mg/L CO2 (6.0 mg/L C) was recorded.	Yes

 

RESULTS

10% degradation (lag phase) was achieved after approximately 3 d and 60% degradation was reached after 11.5 d (exponential phase). Thus, the 10-d window was met. After 29 d, 86% degradation was recorded (≥ 60% degradation relative to the ThCO2). Results are summarized in Tables 2 – 4.

Table 2. Inorganic carbon [mg] in 200 mL NaOH.

Time [days]	Blank		Reference		Test chemical		Toxicity control
	1	2	1	2	1	2
2	0.88	0.81	10.59	11.83	1.01	3.05	9.04
5	1.41	1.23	7.42	5.99	6.05	9.27	10.36
7	0.85	1.02	2.79	2.60	7.38	4.71	6.97
9	0.69	0.55	2.25	2.05	3.77	4.04	4.37
14	0.96	0.84	3.39	3.14	4.44	5.11	8.77
19	0.74	0.74	2.19	2.42	2.13	2.64	6.73
23	0.76	0.67	1.75	1.84	1.51	2.22	5.83
28	0.80	0.68	1.89	1.74	1.26	1.67	4.73
29	0.31	0.23	1.67	1.66	0.29	0.52	2.44
29	1.60	2.08	1.21	2.18	5.04	3.61	2.95

 

Table 3. Cumulative inorganic carbon ([mg] from test

Time [days]	Reference		Test chemical		Toxicity control
	1	2	1	2
0	0.00	0.00	0.00	0.00	0.00
2	9.74	10.98	0.16	2.20	7.01
5	15.84	15.65	4.89	10.15	9.71
7	17.69	17.31	11.33	13.92	10.63
9	19.32	18.74	14.48	17.34	11.09
14	21.81	20.98	18.02	21.55	15.08
19	23.26	22.66	19.41	23.45	19.42
23	24.29	23.78	20.20	24.95	23.38
28	25.44	24.78	20.72	25.88	26.64
29	26.84	26.17	20.74	26.13	28.67
29	26.21	26.51	23.94	27.90	27.29

 

 Table 4. Percentage degradation.

Time [days]	Reference			Test chemical			Toxicity control
	1	2	Mean	1	2	mean
0	0	0	0	0	0	0	0
2	32	37	35	1	7	4	23
5	53	52	52	16	34	25	32
7	59	58	58	38	46	42	35
9	64	62	63	48	57	53	37
14	73	70	71	60	71	65	50
19	77	75	76	64	77	71	65
23	81	79	80	67	82	75	78
28	85	83	84	69	85	77	89
29	89	87	88	69	86	77	95
29	87	88	88	79	92	86	91

 

Validity criteria fulfilled:

yes

Remarks:

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

Interpretation of results:

readily biodegradable

Conclusions:

Monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol gave a positive result (≥60% degradation relative to the ThCO2 value) with a maximum of 86% recorded on day 29. The 10 -day window was met.
Thus, the substance is readily biodegradable.

Executive summary:

A study was undertaken to evaluate the ready biodegradability of Monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol. The object of the study was to measure the ready biodegradability of the sample in a freshwater environment. The biodegradation is defined as the ratio of the carbon dioxide (determined as dissolved inorganic carbon) evolved within 28 days to the theoretical carbon dioxide (ThCO2).

 

The method followed that described in OECD guidlines for testing of chemical (1992) No 301B CO2 evolution test.

Monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol gave a positive result (≥60% degradation relative to the ThCO2 value) with a maximum of 86% recorded on day 29. The 10 -day window was met. Thus, the substance is readily biodegradable.

Description of key information

Readily biodegradable (86% in 28 d, OECD 301 B)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

One experimental study is available, in which the ready biodegradability of decyl isooctadecanoate (CAS 84605-08-3) was assessed according to OECD guideline 301 B and GLP.

In the CO2 evolution test, the test item at a final concentration of 20 mg C/L was inoculated with 0.03 g/L activated sludge (dry sludge solid) for 28 d under continuous aeration with CO2-free air. Degradation was followed by determining the produced CO2 and expressed as the percentage of the theoretical carbon dioxide (ThCO2). On Day 28, 2 mL of 50% hydrochloric acid was added to each bioreactor and then aerated overnight, to drive off the remaining carbon dioxide.

After 28 d, a maximum degradation of 86% was recorded. 10% degradation was achieved after approximately 3 d and 60% was reached after 11.5 d, therefore meeting the 10-d window. The inoculum blank confirmed the suitability of the test system. Therefore, Monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol is readily biodegradable according to OECD guideline criteria.

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