Propanenitrile, 2,3,3,3-tetrafluoro-2-(trifluoromethyl)-

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:

14 May - 11 Jun 2020

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:

no

GLP compliance:

yes

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material: 3M NB us278898.001-096
- Expiration date of the lot/batch: 2021-10-30
- Purity: 97.7%
- Purity test date: 2019-10-30
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature
- Stability under storage conditions: stable

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Zhu Yuan domestic wastewater treatment plant, Shanghai, China.
- Storage conditions: Aeration until use
- Storage length: one day
- Pretreatment: After receipt at lab, sludge was washed 3x with mineral medium by centrifugation (20 min, 4000 RPM, 4 °C). A sample of the concentrated sludge sludge was dried one hour at 105 °C to determine dry weight. Concentrated sludge was then resuspended to a final concentration of 3g suspended solids (dw) / L.
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

104 mg/L

Based on:

test mat.

Initial conc.:

50.96 mg/L

Based on:

ThOD

Remarks:

Value in report

Initial conc.:

23.4 mg/L

Based on:

ThOD

Remarks:

corrected on corrected value

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium per OECD301
- Test temperature: 21.4 - 22.5 °C
- pH: 7.40-7.46
- pH adjusted: no
- Suspended solids concentration: 30
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: OxyTop 110C respirometers (WTW, Weilheim, Germany) in an MI-250A incubator (STIK)
- Number of culture flasks/concentration: two
- Measuring equipment: WTW Multi 9430 water quality meters. Oxygen consumption measured directly from Oxytop respirometers every 112 minutes. Daily results were tabulated.
- Test performed in closed vessels due to significant volatility of test substance: Test in closed vessels based on apparatus, substance is not significantly volatile

CONTROL AND BLANK SYSTEM
- Inoculum blank: Duplicate
- Abiotic sterile control: None
- Toxicity control: Single
- Other: Reference substance in duplicate. Also, an additional flask was set up for all conditions for pH measurement

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

28 d

Remarks on result:

other: 2-5% in duplicate flasks

Remarks:

Value quoted from study report

Parameter:

% degradation (O2 consumption)

Value:

7

Sampling time:

28 d

Remarks on result:

other: Corrected on corrected ThOD value

Details on results:

The test substance did not cause large changes in oxygen utilization versus blanks (Table 1). Similarly, the toxicity control showed little change in oxygen utilization versus the procedural control. Differences were more pronounced when theoretical oxygen demand was considered (Table 2), but little biodegradation was observed in test samples before day 28.

Results with reference substance:

Pass levels reached by day 4 in procedural controls.

Table 1, Oxygen utilization (mg/L) during the biodegradation experiment

Day	IB1¹	IB2	TS1	TS2	PC1	PC2	TC
1	6.20	4.50	4.20	5.60	30.90	33.80	39.40
2	10.20	8.50	8.50	8.50	87.20	81.60	84.40
3	13.60	11.30	12.70	14.10	118.00	107.00	115.00
4	13.60	11.30	11.30	11.30	127.00	118.00	121.00
5	14.70	12.40	11.30	12.70	135.00	127.00	129.00
6	15.80	13.60	12.70	12.70	141.00	129.00	135.00
7	17.00	15.30	14.10	15.50	149.00	138.00	143.00
8	18.10	15.80	15.50	15.50	152.00	143.00	149.00
9	18.70	17.00	16.90	16.90	158.00	149.00	152.00
10	19.80	17.50	18.30	18.30	160.00	155.00	158.00
11	20.30	18.70	19.70	18.30	163.00	158.00	158.00
12	21.50	19.20	19.70	19.70	166.00	160.00	160.00
13	22.00	20.30	21.10	19.70	169.00	163.00	163.00
14	23.20	20.90	21.10	21.10	172.00	166.00	169.00
15	23.20	20.90	21.10	21.10	172.00	169.00	166.00
16	23.70	22.00	21.10	21.10	174.00	169.00	169.00
17	24.30	22.00	22.50	24.00	174.00	172.00	174.00
18	24.90	23.20	24.00	22.50	177.00	174.00	172.00
19	25.40	23.20	24.00	22.50	177.00	174.00	174.00
20	26.00	23.70	24.00	24.00	180.00	177.00	174.00
21	26.00	23.70	25.40	24.00	180.00	177.00	174.00
22	26.60	24.30	25.40	25.40	183.00	177.00	177.00
23	26.60	24.30	25.40	24.00	180.00	177.00	174.00
24	26.60	24.30	26.80	25.40	180.00	177.00	174.00
25	27.10	24.90	26.80	25.40	186.00	180.00	177.00
26	27.10	24.90	26.80	26.80	186.00	180.00	177.00
27	27.70	25.40	28.20	26.80	186.00	180.00	177.00
28	27.70	26.60	29.60	28.20	189.00	183.00	183.00

1. Replicate identification: IB, inoculum blank; TS, test substance; PC, procedural control (reference substance); TC, toxicity control (reference substance + test substance)

Table 2, Percent biodegradation¹ in test replicates

Day	TS1²	TS2	TS Average	PC1	PC2	PC Average	TC
1	-2	0	-1	15	17	16	16
2	-2	-2	-2	47	43	45	34
3	0	3	2	63	57	60	47
4	-2	-2	-2	69	63	66	50
5	-4	-2	-3	73	68	71	53
6	-4	-4	-4	76	68	72	55
7	-4	-1	-3	80	73	77	58
8	-3	-3	-3	81	75	78	60
9	-2	-2	-2	84	79	82	61
10	-1	-1	-1	85	82	84	64
11	0	-2	-1	86	83	85	63
12	-1	-1	-1	87	84	86	64
13	0	-3	-2	89	85	87	65
14	-2	-2	-2	90	86	88	67
15	-2	-2	-2	90	88	89	66
16	-3	-3	-3	91	88	90	67
17	-1	2	1	90	89	90	69
18	0	-3	-2	92	90	91	68
19	-1	-4	-3	91	90	91	69
20	-2	-2	-2	93	91	92	68
21	1	-2	-1	93	91	92	68
22	0	0	0	94	91	93	69
23	0	-3	-2	93	91	92	68
24	3	0	2	93	91	92	68
25	2	-1	1	96	92	94	69
26	2	2	2	96	92	94	69
27	3	0	2	95	92	94	69
28	5	2	4	97	93	95	71

1. Percent biodegradation = 100% * (BODx - average blank BOD)/(concentrationx * ThODx)

2. Replicate identification: IB, inoculum blank; TS, test substance; PC, procedural control (reference substance); TC, toxicity control (reference substance + test substance)

Validity criteria fulfilled:

yes

Remarks:

oxygen uptake in blanks 20-30 mg/L (27 mg/L), difference in removal of test substance <20% (6%), pass level reference substance by day 14 (day 4), pass level reached in toxicity control by day 14 (day 6)

Interpretation of results:

not inherently biodegradable

Conclusions:

The test substance had an average %BOD of 4% after 28 days (OECD301F)

Executive summary:

Biodegradation of the degradation product heptafluoroisopropylamide was examined in a test done under OECD 301F guidelines. Test substance concentration was ca. 100 mg/L. The reported BOD as calculated without taking fluorination into account was 0.49 mg O2/mg.  Given the high degree of fluorination, the BOD was recalculated for this study summary as 0.225 mg O2/mg.  The recalculated ThOD loading in test vessels was ca. 23 mg O2/L.  No impact on the validity of the study is expected.  The effect of decreased BOD is an increase to the absolute values of the observed BODs by a factor of approximately two. Sodium benzoate was used as reference substance in procedural and toxicity controls. Oxygen utilization by test substance differed little from inoculum blanks until day 28. Oxygen utilization by reference substance reached pass level by day 4 in procedural controls and by day 6 in the toxicity control, and little difference was seen in absolute oxygen utilization between the controls.

The study was done under accepted international test guidelines and was GLP compliant. The modest reduction in ThOD loading for the test substance v. guideline recommendations is not expected to affect the outcome of the study. The results are considered reliable without restriction and are acceptable for use in Risk Assessment, Classification & Labelling, and PBT Analysis

Description of key information

C4 F-isonitrile is hydrolytically active. The hydrolysis product shows little or no biodegradation in ready biodegradability studies.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

Biodegradation of C4 F-isonitrile was examined directly in a screening level biodegradation study based on OECD 301D test methods and by QSAR. The hydrolysis product was examined in a GLP-compliant biodegradation study done according to OECD 301F test methods. In the screening level test there was complete loss of test substance after 28 days by chemical analysis, with 103% of the expected amount of heptafluoroisopropylamine formed on exposure to the inoculum. Conversely, there was no difference in BOD between a test flask with natural water inoculum and an abiotic control flask after 28 days. As a screening test, no reference substance and no blank control were included. Lack of biodegradation is supported by a QSAR result using the BIOWIN5 module in Episuite software. When the hydrolysis product was tested directly, no biodegradation was observed until day 28. An average of 4% BOD was measured on day 28. However, a considerable amount of variability in %BOD was observed for the test substance throughout the experiment. It is believed the observed oxygen depletion was an aberration.