2-Propenoic acid, 2-[[1,1,2-trifluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)ethyl]thio]ethyl ester

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:

2019-11-07 to 2020-01-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

30 May 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted July 17, 1992

Deviations:

no

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: the sewage treatment plant Rossdorf, Germany
- Preparation of inoculum for exposure: The aerobic activated sludge used for this study was deposited for 15 min, washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined.
- Pretreatment: Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.
- Water filtered: no, decanted

Duration of test (contact time):

28 d

Initial conc.:

101.8 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: reconstituted water
- Test temperature: 22 °C ± 1 °C
- pH: 7.4 (measured at the start of the test), 7.4 to 9.6 (measured at the end of the test)
- pH adjusted: yes
- Surrounding Type: Climatised chamber
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of approximately 500 mL.
- Number of culture flasks/concentration: 2
- Method used to create anaerobic conditions: The test flasks were closed gas-tight by a measuring head.
- Measuring equipment: BSB/BOD-Sensor-System
- Test performed in closed vessels due to significant volatility of test substance: yes

CONTROL AND BLANK SYSTEM
- Test suspension: 2
- Inoculum blank: 2
- Abiotic sterile control: 1
- Toxicity control: 1
- Procedure control: 1

Reference substance:

benzoic acid, sodium salt

Test performance:

The amounts of test item and reference item were directly weighed into the test flasks. No emulsifiers or solvents were used, but the solutions were dispersed by stirring to achieve a homogeneous solution of the test item. The closed test flasks were incubated in a climatised chamber under continuous stirring. The consumption of oxygen was determined by measuring the change of pressure in the flasks. Evolved carbon dioxide was absorbed in an aqueous solution (45 %) of potassium hydroxide. The change of pressure in the test flasks was measured by means of a manometric method (BSB/BOD-Sensor-System).

Key result

Parameter:

% degradation (O2 consumption)

Value:

29

Sampling time:

28 d

Details on results:

The mean biodegradation percentage at the end of the 28-day exposure period was 29 % (ThODNH4).

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded to 88 % after 14 days and to 96 % after 28 days of incubation. The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Table 2: Cumulative Biochemical Oxygen Demand (mg O₂/L) in Test Flasks during the Test Period of 28 Days

Time (days)	Flask No.
	1	2	3	4	5	6	7
1	0	0	0	0	15	0	15
2	5	0	0	0	80	0	70
3	10	10	0	0	95	0	95
4	15	15	5	0	105	0	110
5	15	15	5	5	115	0	130
6	15	20	5	5	125	0	140
7	20	20	5	5	130	0	150
8	20	25	5	5	135	0	160
9	20	25	5	5	140	0	165
10	20	25	5	5	140	0	165
11	20	30	5	5	145	0	165
12	25	30	5	5	150	0	165
13	25	30	5	5	150	0	170
14	25	30	5	5	155	0	170
15	25	30	5	5	155	0	175
16	30	30	5	5	160	0	175
17	30	35	5	5	160	0	175
18	30	35	5	5	160	0	175
19	30	35	5	5	160	0	175
20	30	35	5	5	165	0	180
21	30	35	5	5	165	0	180
22	30	35	5	5	165	0	180
23	30	35	10	10	170	0	185
24	30	35	10	10	170	0	185
25	30	35	10	10	170	0	185
26	30	35	10	10	170	0	185
27	30	35	10	10	175	0	185
28	30	35	10	10	175	0	185

Flasks 1 and 2: test item

Flasks 3 and 4: inoculum control

Flask 5: reference (procedure control)

Flask 6: abiotic control

Flask 7: toxicity control

 

Table 3: Percentage Biodegradation of Test Item, of Sodium Benzoate and of the Toxicity Control based on ThOD_NH4

Time (Days)	Percentage Biodegradation
	Test Item^1		Sodium Benzoate^2	Toxicity control^1,2
	Flask 1 [%]	Flask 2 [%]	Flask 5 [%]	Flask 7 [%]
1	0	0	9	6
2	7	0	47	28
3	13	13	55	38
4	16	16	60	43
5	13	13	64	50
6	13	19	70	54
7	20	19	73	58
8	20	25	76	62
9	20	25	79	64
10	20	25	79	64
11	20	32	82	64
12	26	32	85	64
13	26	32	85	66
14	26	32	88	66
15	26	32	88	68
16	33	32	90	68
17	33	38	90	68
18	33	38	90	68
19	33	38	90	68
20	33	38	93	70
21	33	38	93	70
22	33	38	93	70
23	26	32	93	70
24	26	32	93	70
25	26	32	93	70
26	26	32	93	70
27	26	32	96	70
28	26	32	96	70

¹ ThOD_NH4 of test item: 0.763 mg O₂/mg test item

² ThOD_NH4 of sodium benzoate: 1.666 mg O₂/mg reference item

 

 

Validity Criteria of the Study

Inoculum Control: The oxygen demand of the inoculum control (medium and inoculum) was 10 mg O₂/L and thus not greater than 60 mg O₂/L within 28 days as required by the test guideline.

pH-Value: The pH-value of the test item flasks at the end of the test was 9.5 and 9.6 and therefore not within the range of pH 6.0 to 8.5 as required by the test guideline.

Reference Item: The percentage degradation of the reference item should reach the level for ready biodegradability (>60 %) within 14 days as required by the test guideline. The reference item sodium benzoate was degraded to more than 60 % after 4 days of incubation.

Test Item: The difference of duplicate values for the degradation of the test item at the plateau, at the end of the test and at the end of the 10-day window was less than 20 %. The difference of duplicate values at day 28 differed by 6 %. The validity criterion was fulfilled.

Toxicity Control: If in a toxicity test, containing both the test item and a reference item less than 25 % biodegradation (based on ThOD_NH4) occurred within 14 days, the test item can be assumed to be inhibitory. The biodegradation was 66 % at day 14; the test item was not inhibitory.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The degradation rate of the test item did not reach 60 % within the 10-day window or after 28 days. Therefore, the test item is considered to be not readily biodegradable based on ThODNH4.

Executive summary:

The Ready biodegradability of the test item was assessed in a Manometric Respirometry Test according to OECD Guideline for Testing of Chemicals No. 301 F over a period of 28 days at 22 °C ± 1 °C in darkness. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item, sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. The test item loading rate was 101.8 mg/L corresponding to an oxygen demand of about 77.7 mg/L (ThOD_NH4) and reference item loading rate was 102.9 mg/L corresponding to an oxygen demand of about 171.4 mg/L (ThOD_NH4). The degradation rate of the test item was calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation. The reference item sodium benzoate was sufficiently degraded to 88 % after 14 days and to 96% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used. In the toxicity control containing both, the test item and the reference item sodium benzoate, 66 % (ThOD_NH4) biodegradation was noted within 14 days and 70 % (ThOD_NH4) biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was > 25 % within 14 days. The mean biodegradation of 10 % of the test item was reached at day 3 (ThOD_NH4). At the end of the 10-day window at day 13, the mean degradation of the test item was 29 % (ThOD_NH4). Therefore the 10 day window criterion was not passed. The mean biodegradation at test end after 28 days was 29% (ThOD_NH4). Therefore, the test item is considered to be not readily biodegradable based on ThOD_NH4.

Description of key information

The degradation rate of the test item did not reach 60 % within the 10-day window or after 28 days. Therefore, the test item is considered to be not readily biodegradable based on ThOD_NH4 (reference 5.2.1-1).

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The readily biodegradability of the test item was assessed in a Manometric Respirometry Test according to OECD Guideline for Testing of Chemicals No. 301 F over a period of 28 days at 22 °C ± 1 °C in darkness. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item, sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. The test item loading rate was 101.8 mg/L corresponding to an oxygen demand of about 77.7 mg/L (ThOD_NH4) and reference item loading rate was 102.9 mg/L corresponding to an oxygen demand of about 171.4 mg/L (ThOD_NH4). The degradation rate of the test item was calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation. The reference item sodium benzoate was sufficiently degraded to 88 % after 14 days and to 96% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used. In the toxicity control containing both, the test item and the reference item sodium benzoate, 66 % (ThOD_NH4) biodegradation was noted within 14 days and 70 % (ThOD_NH4) biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was > 25 % within 14 days. The mean biodegradation of 10 % of the test item was reached at day 3 (ThOD_NH4). At the end of the 10-day window at day 13, the mean degradation of the test item was 29 % (ThOD_NH4). Therefore the 10 day window criterion was not passed. The mean biodegradation at test end after 28 days was 29% (ThOD_NH4). Therefore, the test item is considered to be not readily biodegradable based on ThOD_NH4.

There are two previously unpublished studies in which the biodegradation of structurally similar substances was investigated. In one study, the atmospheric fate of a substance structurally similar to the test item was investigated. It was shown that this substance was degraded in the air within 2.8 ± 1.3 days with respect to reaction with OH. Since this target substance is structurally very similar to the test item, it can be assumed that this is also the case with the test item (Joudan et al. 2021, study report). For the other study, the aerobic biodegradation of a novel highly functionalized anionic polyfluorinated surfactant using activated sludge from a wastewater treatment plant for up to 84 days was investigated. It was shown that the polyfluorinated surfactant and its first degradation products degrade slowly and consistently in a constantly oxygenated system to terminal products which likely have lower bioaccumulation potential than the parent fluorosurfactant. Since one of the first degradation products is structurally very similar to the test item, it can be assumed that the test item could also be degraded to end products with a lower bioaccumulation potential (Joudan et al. 2021, study report).