Fatty acids, tall-oil, 1-methyl-1,2-ethanediyl esters

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

yes

Remarks:

(on four measurements the temperatures recorded for the water bath were below the recommended minimum temperature. As the validity criteria were met, this deviation was not considered to have affected the integrity of the study.)

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Deviations:

yes

Remarks:

(on four measurements the temperatures recorded for the water bath were below the recommended minimum temperature. As the validity criteria were met, this deviation was not considered to have affected the integrity of the study.)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Worlingworth sewage treatment works (Suffolk, UK)
- Method of cultivation / Preparation of inoculum for exposure: At the time of collection, the sludge was sieved (1 mm²) then transported to the laboratory and left stand for approximately 14 minutes to allow the sewage solids to settle. A portion of the supernatant was removed and the sludge aerated until required.

Duration of test (contact time):

28 d

Initial conc.:

50 mg/L

Based on:

ThOD/L

Initial conc.:

ca. 18 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral salts medium (MSM) according to guideline, prepared using tap-water that had been softened and treated by reverse osmosis and then purified; nominal resistivity ≥ 18 MegOhm.cm. The pH was adjusted to 7.41 with 5M HCl. This water complies with the relevant standards (British Standard (BS) 3978, 1987; American Society for Testing and Materials (ASTM) D 1193-06) for classification as Grade 1 or Type 1 water for laboratory use).
- Test temperature: 21.3 to 23.1°C (except on Day 1, 6, 15 and 19 where the minimum temperatures recorded for the water bath were below this range (12.2, 18.2, 18.0 and 7.8°C, respectively). These low temperature values were considered anomalous as the ambient room temperature over the course of the study was considered acceptable. The reasons for these low recorded values are unknown. As the validity criteria for the study were met, this deviation from guideline is not considered to have affected the integrity of the study.)
- pH: 7.3 at the start of the test and 7.3 to 7.5 at the end
- pH adjusted: not necessary
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes (amber glass bottles)
- Other: The inoculum was added to the culture bottles 1 day before test initiation to allow a period of ageing.

TEST SYSTEM
- Culturing apparatus: amber glass culture bottles in a thermostatically controlled water bath
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: internal oxygen generating process
- Measuring equipment: Co-ordinated Environmental Services (CES) Ltd automated respirometer with associated software to monitor the cumulative amount of oxygen consumed

SAMPLING
- Sampling frequency: continuous monitoring of the cumulative amount of oxygen consumed; the cumulative oxygen demand made by each cell was printed at, typically, hourly intervals

CONTROL AND BLANK SYSTEM
- Inoculum blank (2 flasks): inoculated mineral salts medium (MSM)
- Reference (1 flask): inoculated MSM + sodium benzoate (50 mg O₂/L)
- Toxicity control (1 flask): inoculated MSM + test material (50 mg O₂/L) + sodium benzoate (50 mg O₂/L)

PREPARATION OF TEST SUBSTANCE
At test initiation, a stock solution of the test material was prepared in acetone at a concentration of 1.84 g/L. An aliquot (5 mL) of the stock was added to empty test bottles. The acetone was evaporated off by a steady stream of nitrogen. Vessels were then left to stand for 1 hour, after which a further flush with nitrogen was performed and inoculated mineral salts medium (final volume 500 mL) was added. Control and reference mixtures were treated in an identical manner, except no test substance was added to the 5 mL of acetone added.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

79

Sampling time:

28 d

Remarks on result:

other: mean value

Details on results:

Mean oxygen consumption in biotic mixtures containing the test material was equivalent to 10% of the ThOD value after approximately 1 day, 62% after approximately 11 days and 79% at the end of the test (Day 28). Thus, the test material was ready biodegradable (Table 1).
In the presence of test material the degradation of sodium benzoate achieved 62% by Day 6 indicating that the test substance was not inhibitory to the microbial inoculum (Table 1).

Results with reference substance:

The reference substance sodium benzoate had achieved 61% of the ThOD after 3 days of incubation and 91% by Day 28 (Table 1).

Table 1: Biodegradation of the test and reference substances

 

	% Biodegradation
Day	Test material (50 mgO2/L)			Sodium Benzoate (50 mgO2/L)	Sodium Benzoate (50 mgO2/L) in the inhibition mixture
	Test 1	Test 2	Mean
1	10	16	13	38	40
2	29	34	32	53	37
3	40	45	42	61	43
4	48	52	50	68	52
5	53	57	55	73	58
6	57	61	59	76	62
7	60	63	62	78	-
8	62	66	64	80	-
9	64	68	66	81	-
10	65	70	67	82	-
11	66	71	69	83	-
12	67	73	70	84	-
13	68	74	71	85	-
14	69	75	72	86	-
15	70	76	73	87	-
16	70	77	73	88	-
17	71	77	74	88	-
18	71	78	75	89	-
19	72	78	75	89	-
20	72	79	75	89	-
21	73	79	76	89	-
22	73	80	76	90	-
23	73	80	77	90	-
24	74	81	77	90	-
25	74	81	78	90	-
26	75	81	78	91	-
27	75	82	79	91	-
28	75	82	79	91	-

The data presented were calculated using unrounded values stored in the computer database. Minor numerical differences may be observed if rounded values are used to calculate the data. This minor discrepancy is not considered to be significant.

Validity criteria fulfilled:

yes

Remarks:

the removal of the test substance in replicate values differed less than 20%, the reference compound reached the pass level by day 3, and the cumulative amount of oxygen consumed by the control mixtures was 40 and 43 mg O₂/L

Interpretation of results:

readily biodegradable

Description of key information

Biodegradation in water: screening test: aerobic biodegradation 79% (ThOD) in 28 days (OECD 301F, EU C.4-D)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater