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

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

toxicity control of standard ready biodegradability test according to OECD 301 B

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 Aug - 02 Sep 2011

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: OECD 301 B (CO2 evolution test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Conical flasks of a nominal volume of 2000 mL were filled with 1500 mL inoculated mineral medium. The blanks, reference and test bottles were set up in duplicate, with a single replicate for the toxicity control. Test and reference materials were added to appropriate bottles to a final concentration of 20 mg C/L. Atmospheric air was pumped into the test system and scrubbed clean of carbon dioxide by passing over soda lime.
- Differential loading: Yes, as an insoluble material, the test item was weighed onto a microscope cover slip and added directly to the test bioreactors.
- Controls: The toxicity control contained 39.5 test item, 102.48 mg reference item (sodium acetate) totaling to 60.39 mg TOC in 1500 mL inoculated mineral medium.
- Evidence of undissolved material:

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture:
- Name and location of sewage treatment plant where inoculum was collected: Cambridge Sewage Treatment Works, Cowley Road
- Pretreatment: Sieved to 850 µm, settled, decanted and resuspended using mineral media. Centrifuged at 4000 rpm for 10 min, discarded the supernatant, re-suspended and centriuged again at 4000 rpm for 10 min and discarded the supernatant. Dry sludge soldids determinatin was conducted aon the pellet produced.
- Dry sludge solids: 7.4%
- Dry sludge solids in the test: 0.03 g/L

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

28 d

Nominal and measured concentrations:

20 mg Carbon/L corresponding to 60.39 mg Total Organic Carbon (39.5 mg test item + 102.48 mg reference item in 1500 mL mineral medium) in the toxicity control

Details on test conditions:

TEST SYSTEM
- Test vessel: Conical flasks of a nominal volume of 2000 mL filled with 1500 mL
- Aeration: 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.
- No. of vessels per concentration (replicates): 2
- No. of vessels per reference control (replicates): 1
- No. of vessels per toxicity control (replicates): 1
- Sludge concentration: 0.03 g/L
- Nutrients provided for bacteria: Mineral medium + test item as the nominal source of organic carbon

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Mineral medium

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Details on termination of incubation: On Day 28, 2 mL of 50% hydrochloric acid is added to each bioreactor, which are then aerated overnight, to drive off the remaining carbon dioxide. One last analysis of evolved carbon dioxide is made on Day 29.

EFFECT PARAMETERS MEASURED:
CO2 evolution expressed as percentage of the theoretical carbon dioxide

Reference substance (positive control):

yes

Remarks:

sodium acetate

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 26.33 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: CO2 evolution

Remarks on result:

other: The test item was not inhibitory to activated sludge microorganisms at the tested concentration.

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

BIOLOGICAL RESULTS

Percentage degradation is summarized in Table 2.

 

Table 2. Percentage degradation as a function of time.

Time [d]	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”.

Description of key information

NOEC (14 d) ≥ 26.33 mg/L (nominal, OECD 301 B)

Additional information

There is no respiration inhibition study available, in which the toxicity of Monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol to microorganisms was assessed. However, a standard ready biodegradability test conducted according to OECD guideline 301 B and GLP is available, whose toxicity control can be used to derive a NOEC. According tothe Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA, 2017), a concentration can be used as NOEC value, if a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration.

The available ready biodegradability test included a toxicity control containing 39.5 mg test item and 102.48 mg reference item (sodium acetate) in 1500 mL mineral medium, amounting to a test item concentration of 20 mg/L in terms of Carbon content (based on a calculated carbon content of 76.87% in the test item) to determine the toxicity to microorganisms of activated sludge. After 14 d, a mean biodegradation of 50% was observed and after 28 d, a mean biodegradation of 89% was attained in the toxicity control. The procedural control confirmed the suitability of the test. Therefore, Monoesters of C16 and C18 (branched and linear) fatty acids with decan-1-ol had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration and a NOEC (14 d) of ≥ 26.33 mg/L (nominal) was derived.

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