1,1,2,2,3,3,4,4,4-nonafluoro-N,N-bis(2-hydroxyethyl)butane-1-sulphonamide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Jan - 19 Feb 2016

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
- Lot/batch No.of test material: JA9215
- Expiration date of the lot/batch: 2017.08.21
- Purity test date: 2015.09.02


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature (15-25 °C)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Shenyang Northern Sewage Treatment Plant, aeration tank. Activated sludge was collected two days before the test
- Storage conditions: aerated until use
- Preparation of inoculum for exposure: removal of coarse particles by sieve. Sludge was settled, decanted, resuspended in mineral medium and concentrated twice, final resuspension in mineral medium
- Concentration of sludge: 3806 mg/L suspended solids at time of test.

Duration of test (contact time):

28 d

Initial conc.:

86.7 mg/L

Based on:

test mat.

Initial conc.:

50.3 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: standard mineral medium per OECD 301F
- Test temperature: 21.2 - 22.9 °C
- pH: 7.48-7.50 (initial), 7.63-7.96 (final)
- pH adjusted: no
- Aeration of dilution water: no
- Suspended solids concentration: 30 mg/L
- Continuous darkness: not stated

TEST SYSTEM
- Culturing apparatus: respirometers, 1-L flasks
- Number of culture flasks/concentration: two
- Measuring equipment: pressure sensors in cap of flask with daily automated data storage
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: 4 mL of 10 M NaOH

CONTROL AND BLANK SYSTEM
- Inoculum blank: two
- Toxicity control: one, 86.7 mg/L test substance + 31.4 mg/L reference

Reference substance:

benzoic acid, sodium salt

Remarks:

32.5 mg/L

Key result

Parameter:

% degradation (O2 consumption)

Value:

26.1

Sampling time:

28 d

Details on results:

Toxicity controls reached 58.1% BOD/ThOD by day 14. Substance is not inhibitory to activated sludge.

The reference substance was 66.2% degraded by day 4, 87.2% by day 14, and 89.5% by day 28

Table 1, Oxygen demand and biodegradation of the test substance.

	Oxygen uptake (mg O2/L)	Oxygen uptake	Oxygen uptake	Oxygen uptake	Oxygen uptake	BOD (mg O2/mg test item	BOD	BOD	% Biodegradation
Day	Inoculum control 1	Inoculum control 2	Average	Test sample 1	Test sample 2	Test sample 1	Test sample 2	Average	Test sample 1	Test sample 2	Average
1	2.29	2.79	2.5	2.58	2.50	0.001	0.000	0.001	0.2%	0.0%	0.1%
2	4.44	5.04	4.7	4.69	4.25	0.000	0.000	0.000	0.0%	0.0%	0.0%
3	6.29	6.85	6.6	6.60	6.16	0.000	0.000	0.000	0.0%	0.0%	0.0%
4	8.06	8.60	8.3	8.35	8.00	0.001	0.000	0.001	0.2%	0.0%	0.1%
5	9.91	10.35	10.1	10.62	9.95	0.006	0.000	0.003	1.0%	0.0%	0.5%
6	11.12	11.54	11.3	12.89	11.77	0.018	0.005	0.012	3.1%	0.9%	2.0%
7	11.45	11.93	11.7	16.56	13.83	0.056	0.025	0.041	9.7%	4.3%	7.0%
8	12.00	12.83	12.4	22.89	17.37	0.121	0.057	0.089	20.9%	9.8%	15.4%
9	12.43	13.24	12.8	23.89	23.03	0.128	0.118	0.123	22.1%	20.3%	21.2%
10	13.04	13.85	13.4	24.51	24.34	0.128	0.126	0.127	22.1%	21.7%	21.9%
11	13.62	14.37	14.0	25.09	24.97	0.128	0.127	0.128	22.1%	21.9%	22.0%
12	14.20	14.89	14.5	25.86	25.70	0.131	0.129	0.130	22.6%	22.2%	22.4%
13	15.20	15.66	15.4	26.89	26.41	0.133	0.127	0.130	22.9%	21.9%	22.4%
14	15.76	16.29	16.0	28.01	27.13	0.139	0.128	0.134	24.0%	22.1%	23.1%
15	16.06	16.45	16.3	28.20	27.53	0.137	0.130	0.134	23.6%	22.4%	23.0%
16	16.33	16.74	16.5	28.84	28.18	0.142	0.135	0.139	24.5%	23.3%	23.9%
17	16.95	17.45	17.2	29.65	29.16	0.144	0.138	0.141	24.8%	23.8%	24.3%
18	17.37	17.93	17.7	30.30	29.90	0.145	0.141	0.143	25.0%	24.3%	24.7%
19	17.64	18.37	18.0	30.78	30.51	0.147	0.144	0.146	25.3%	24.8%	25.1%
20	18.12	18.97	18.5	31.36	31.32	0.148	0.148	0.148	25.5%	25.5%	25.5%
21	18.72	19.60	19.2	31.95	32.03	0.147	0.148	0.148	25.3%	25.5%	25.4%
22	19.16	20.10	19.6	32.38	32.67	0.147	0.151	0.149	25.3%	26.0%	25.7%
23	19.53	20.41	20.0	32.63	33.11	0.146	0.151	0.149	25.2%	26.0%	25.6%
24	19.62	20.66	20.1	32.92	33.82	0.148	0.158	0.153	25.5%	27.2%	26.4%
25	20.62	21.20	20.9	33.72	34.42	0.148	0.156	0.152	25.5%	26.9%	26.2%
26	20.80	21.32	21.1	33.78	34.63	0.146	0.156	0.151	25.2%	26.9%	26.1%
27	21.53	21.78	21.7	34.03	35.30	0.142	0.157	0.150	24.5%	27.1%	25.8%
28	21.87	22.10	22.0	34.26	35.92	0.141	0.161	0.151	24.3%	27.8%	26.1%

Table 2, Oxygen demand and biodegradation in toxicity and positive controls.

	Oxygen uptake (mg O2/L)	Oxygen uptake	Oxygen uptake	Oxygen uptake	Oxygen uptake	BOD (mg O2/mg test item)	% Biodegradation
Day	Inoculum control 1	Inoculum control 2	Average	Tox control	Ref sample	Ref sample	Tox control	Ref sample
1	2.29	2.79	2.5	22.22	22.76	0.624	19.2%	37.4%
2	4.44	5.04	4.7	32.61	33.59	0.889	27.2%	53.2%
3	6.29	6.85	6.6	36.92	38.98	0.997	29.5%	59.7%
4	8.06	8.60	8.3	41.13	44.25	1.106	32.0%	66.2%
5	9.91	10.35	10.1	46.88	48.86	1.193	35.8%	71.4%
6	11.12	11.54	11.3	51.85	51.73	1.244	39.5%	74.5%
7	11.45	11.93	11.7	57.89	53.56	1.288	45.0%	77.1%
8	12.00	12.83	12.4	65.16	55.67	1.332	51.4%	79.8%
9	12.43	13.24	12.8	67.66	56.73	1.352	53.4%	81.0%
10	13.04	13.85	13.4	70.08	58.14	1.377	55.2%	82.5%
11	13.62	14.37	14.0	71.89	59.39	1.397	56.4%	83.7%
12	14.20	14.89	14.5	73.43	60.58	1.418	57.4%	84.9%
13	15.20	15.66	15.4	74.93	62.16	1.439	58.0%	86.2%
14	15.76	16.29	16.0	75.68	63.29	1.456	58.1%	87.2%
15	16.06	16.45	16.3	77.30	64.00	1.468	59.4%	87.9%
16	16.33	16.74	16.5	77.89	64.72	1.484	59.8%	88.9%
17	16.95	17.45	17.2	78.89	65.81	1.496	60.1%	89.6%
18	17.37	17.93	17.7	79.53	66.52	1.503	60.2%	90.0%
19	17.64	18.37	18.0	80.16	67.01	1.508	60.5%	90.3%
20	18.12	18.97	18.5	80.84	67.58	1.511	60.7%	90.5%
21	18.72	19.60	19.2	81.63	68.24	1.509	60.8%	90.4%
22	19.16	20.10	19.6	82.15	68.66	1.510	60.9%	90.4%
23	19.53	20.41	20.0	82.63	68.97	1.507	61.0%	90.2%
24	19.62	20.66	20.1	83.45	69.14	1.509	61.7%	90.4%
25	20.62	21.20	20.9	83.78	69.91	1.508	61.2%	90.3%
26	20.80	21.32	21.1	83.99	69.97	1.504	61.2%	90.1%
27	21.53	21.78	21.7	84.55	70.37	1.498	61.2%	89.7%
28	21.87	22.10	22.0	84.95	70.56	1.495	61.3%	89.5%

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

FBSEE diol is not readily biodegradable (26.1% BOD/ThOD in a 28-day OECD 301F test)

Executive summary:

Biodegradability of FBSEE diol was assessed in a OECD 301F assay. Sodium benzoate was used as reference substance and in a toxicity control. The reference bottle achieved a passing level (>60% BOD/ThOD) by day 4. FBSEE diol achieved an average of 26.1% biodegradation in duplicate test substance bottles. The toxicity control containing both the reference and test substances achieved 61.3% BOD/ThOD by the end of the test. FBSEE diol is not readily biodegradable, but does not inhibit biodegradation.

The test was conducted according to internationally accepted guidelines in accord with GLP criteria. It is considered reliable without restrictions and is acceptable for Risk Assessment, Classification & Labeling, and PBT Analysis.

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

09 Nov 2010 – 11 Jan 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3200 (Zahn-Wellens / EMPA Test)

Deviations:

yes

Remarks:

Analyte specific detection only, without BOD or DOC analysis. Sludge was used without washing.

GLP compliance:

yes

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: L-21256, lead registrant internal source. EPA consent order agreement number P-09-0485
- Expiration date of the lot/batch: 26 Nov 2015
- Purity: 98%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature
- Solubility and stability of the test substance in the solvent/vehicle: Test substance delivered as 3.37 mg/mL solution in acetone. Test substance was stable.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Remarks:

(mix of domestic, commercial, and industrial wastewater from a large urban center)

Details on inoculum:

- Source of inoculum/activated sludge: Metro Wastewater Treatment Plant, St. Paul, MN USA. Mixed liquor suspended solids were collected from the aeration basin located between primary and secondary treatment. Alternately, material was taken from secondary treatment when the aeration basin could not be accessed. Dry weight of sludge was determined.
- Storage conditions: sludge was allowed to settle overnight before use.
- Preparation of inoculum for exposure: Settled sludge was diluted 1/10x in mineral salts medium per OPPTS 835.3200.

Duration of test (contact time):

63 d

Initial conc.:

5.06 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Parameter followed for biodegradation estimation:

other: Degradation product analysis using authentic standards

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral salts medium per test guideline
- Solubilising agent: acetone, 1.5 µL/mL
- Test temperature: 25 ± 5 °C
- pH: initial pH ca. 7.0. All active cultures had acidified to pH 5.0-5.5 by Day 7. This occured in active cultures regardless of addition of test or reference substance.
- pH adjusted: yes, neutrality of medium restored by addition of either phosphate buffer (flask cultures) or 1N NaOH (vial cultures).

TEST SYSTEM
- Culturing apparatus: Two types of vessels were used. The main experiment used loosely capped 125-mL polymethylpentene flasks. A secondary experiment used 42-mL septum-sealed amber glass vials.
- Number of culture flasks/concentration: three for each of eight time points. In addition duplicate samples were made for each time point and spiked with analyte at time of collection (laboratory matrix spikes)
- Method used to create aerobic conditions: Flask cultures were shaken at 150 RPM to maintain aerobic conditions. Headspace in the vial cultures was flushed with pure oxygen to create and maintain aerobic conditions, with additional oxygen injected on day 28 (after detection of hydrogen sulfide in the headspace). Vial cultures were also shaken to keep material suspended.
- Measuring equipment: pH was monitored using pH paper.
- Test performed in closed vessels due to significant volatility of test substance: The secondary test was conducted to evaluate potential volatile transformation products. This phase of the experiment will be referred to as the headspace test henceforth.
- Concentration of sludge: 1.58 g/L, or 31.6 mg/20-mL incubation volume. Additional settled sludge was added on days 14, 28, and 42, adding 700 mg, 748 mg, and 397 mg, respectively, during the main test.

SAMPLING
- Sampling frequency: Days 0, 1, 3, 7, 14, 28, 42, and 63
- Sampling method: Entire test vessels were sacrificed at each sampling interval. Test vessels were placed in a refrigerator to 2-4 °C to temporarily reduce the metabolic activity of the cultures, and designated LMS cultures were fortified with target analytes. Cultures were then frozen until analysis.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Duplicate for each time point.
- Abiotic sterile control: Sterile controls were either entirely abiotic (mineral salts medium only), or were set up using autoclave-sterilized sludge in an amount equal to that in the active cultures. Controls containing test substace were set up in triplicate for each time point. Controls without test substance were set up in duplicate for each time point. In addition, duplicate samples with sterilized sludge were set up and spiked with analyte at the beginning of the test (laboratory control samples). Duplicate samples with sterilized sludge were also set up and spiked at the sampling time (additional laboratory matrix samples). Duplicate mineral medium vessels were set up and spiked at the sampling time (additional laboratory matrix samples).
- Toxicity control: Triplicate samples for each time point containing FBSEE diol and sodium dodecyl sulfate (SDS). Toxicity controls were given a fresh spike of SDS as well as additional settled sludge on days 14, 28, and 42 as per the main test.

- Other:
Duplicate positive controls were set up with SDS for each time point, with addition on days 14, 28, and 42 of a secondary injection of fresh sludge.
Duplicate sterilized sludge and mineral medium controls were set up with SDS for each time point.
A negative control, potassium perfluorohexanesulfonate, was also used. Duplicate controls were set up for each time point with active sludge, sterilized sludge, and mineral medium for each time point.

HEADSPACE TEST
The headspace test, using septum-sealed glass vials, followed the same sampling schedule as the main test. Test vessel set-ups were:
- One bioactive blank per time point
- One sterilized sludge blank per time point
- Duplicate laboratory control samples (all analytes spiked at beginning of test into sterilized sludge) per time point
- Duplicate test substance in bioactive sludge per time point
- Duplicate test substance in sterilized sludge per time point

Reference substance:

other: sodium dodecyl sulfate

Key result

Parameter:

% degradation (test mat. analysis)

Value:

99.6

Sampling time:

7 d

Details on results:

SDS concentration was
Concentrations of FBSEE diol did not measurably change within the test interval in abiotic (sterilized sludge or mineral medium) controls.

FBSEE diol was almost entirely depleted within one day in active cultures (Attachments 1-3, Table 1), both by itself and in toxicity controls. The corresponding diacid (Analyte A, 2,2'-{[(Nonafluorobutyl)-sulfonyl]imino}diacetic acid) appeared within the same time period and constitues the predominant degradation product.

A series of minor degradation production were also observed. A mass balance was calculated by determining the molar concentration and volume of cultures at each time point, and comparing the amount of each analyte thus determined with the molar amount of starting material. Mass balances were essentially complete by day 3 (Table 1). It should be noted that the expected intermediates in the biochemical pathway from diol to diacid were not among the analytes and may explain the incomplete mass balance on Days 0 and 1.

Table 1, Mole fraction analytes in the inherent biodegration study (main test, toxicity controls, and headspace test). Analysis by LC/MS except as indicated

Study day	FBSEE diol³	2,2'-{[(Nona- fluorobutyl)-sulfonyl]imino}diacetic acid	N-(2-Hydroxyethyl)-perfluorobutane sulfonamide	Perfluorobutane sulfonamide	Perfluorobutane sulfinic acid	Perfluorobutane sulfonic acid	n-1H- nonafluorobutane	iso-1H- nonafluorobutane	total moles of analyte	Total mass balance³
Main study
0	91.4%	<LOQ	2.1%	<LOQ	1.6%	<LOQ	─	─	0.249	95.2%
1	7.6%	58.4%	<LOQ	1.9%	5.5%	<LOQ	─	─	0.192	73.5%
3	5.2%	110%	<LOQ	2.8%	3.5%	<LOQ	─	─	0.317	121%
7	1.5%	91.7%	<LOQ	2.4%	2.3%	<LOQ	─	─	0.256	98.0%
14¹	<LOQ	85.9%	<LOQ	2.3%	2.1%	1.5%	─	─	0.240	91.8%
28¹	1.5%	98.5%	<LOQ	2.4%	2.4%	2.2%	─	─	0.280	107%
42¹	<LOQ	86.3%	<LOQ	2.3%	1.4%	2.8%	─	─	0.243	92.8%
63	<LOQ	79.0%	<LOQ	1.7%	1.4%	2.3%	─	─	0.221	84.4%
Toxicity control
0	76.9%	<LOQ	1.93%	<LOQ	1.39%	<LOQ	─	─	0.210	80.2%
1	8.81%	55.0%	<LOQ	1.90%	4.39%	<LOQ	─	─	0.183	70.1%
3	2.11%	93.9%	<LOQ	2.86%	2.91%	<LOQ	─	─	0.266	102%
7	3.14%	92.5%	<LOQ	2.99%	2.41%	<LOQ	─	─	0.264	101%
14¹	<LOQ	99.0%	<LOQ	2.69%	1.93%	1.57%	─	─	0.275	105%
28¹	<LOQ	99.1%	<LOQ	3.15%	2.05%	2.97%	─	─	0.281	107%
42¹	<LOQ	90.1%	<LOQ	2.74%	1.38%	3.22%	─	─	0.255	97.4%
63	<LOQ	104%	<LOQ	2.83%	0.00%	2.92%	─	─	0.286	109%
Headspace test							analysis by GC/MS	analysis by GC/MS
0	77.8%	<LOQ	1.52%	<LOQ	2.33%	<LOQ	<LOQ	<LOQ	0.214	81.7%
1	28.4%	40.8%	<LOQ	1.55%	4.84%	<LOQ	<LOQ	<LOQ	0.198	75.6%
3	3.00%	95.6%	<LOQ	2.74%	5.07%	<LOQ	0.019%	0.0083%	0.278	106%
7	<LOQ	112%	<LOQ	3.54%	4.48%	<LOQ	0.024%	0.0086%	0.314	120%
14	<LOQ	121%	<LOQ	3.98%	4.01%	<LOQ	0.029%	0.0085%	0.338	129%
28²	<LOQ	113%	<LOQ	3.24%	4.25%	<LOQ	0.062%	0.0075%	0.316	121%
42	<LOQ	117%	<LOQ	3.89%	3.07%	<LOQ	0.059%	0.0047%	0.324	124%
63	<LOQ	112%	<LOQ	3.54%	3.29%	<LOQ	0.098%	0.0043%	0.312	119%

1, mole fractions were calculated by determining the molar quantity of each analyte and dividing by the intial amount of FBSEE diol (0.2615 mole in test vessel). Total mass balance is calculated by summing all analytes and dividing by the initial amount of FBSEE diol.

2, additional settled sludge injection.

3, additional oxygen injection.

Validity criteria fulfilled:

yes

Remarks:

reference substance degraded within 14 days, no removal in sterilized sludge controls

Interpretation of results:

inherently biodegradable

Remarks:

rapid primary degradation to form persistent metabolites

Conclusions:

FBSEE diol was rapidly converted to a dicarboxylic acid in an inherent biodegradation test (OPPTS835.3200 as modified to identify degradation products). Other minor metabolites were observed.

Executive summary:

FBSEE diol biodegradation and transformation products were examined in an inherent biodegradation test done under test guideline OPPTS835.3200, as modified to optimize for analysis of parent and potential degradation products, with goal of developing a mass balance for transformation products. Sewage sludge was derived from a municipal sewage system receiving mixed domestic and industrial waste. Individual test chambers were assembled in triplicate, with multiple controls. Controls included abiotic controls (both sterilized sludge and mineral medium), toxicity controls with sodium dodecyl sulfate (SDS), positive controls with SDS, and negative controls with potassium perfluorohexanesulfonate. Flasks received additional sludge at specific time points. In addition, a parallel series of cultures were set up in sealed vials to allow examination of volatile materials in the vial headspace. These headspace test cultures had pure oxygen injected into the vial headspace to help maintain aerobic conditions. All cultures were analyzed by HPLC/MS against a series of authentic standards. Headspace test vials were initially assessed using GC/MS before HPLC. FBSEE diol was not removed from abiotic cultures, but was sharply reduced by Day 1 in all active cultures with quantitative removal by Day 14. SDS was quantitatively removed from positive and toxicity controls within one day of incubation. The predominant metabolite of FBSEE diol was 2,2'-{[(Nonafluorobutyl)-sulfonyl]imino}diacetic acid. Other materials detected in the cultures were N-(2-Hydroxyethyl)-perfluorobutane sulfonamide, Perfluorobutane sulfonamide, Perfluorobutane sulfinic acid, and Perfluorobutane sulfonic acid. Perfluorobutanoic acid was examined but not detected. Two volatile products, n-1H-nonafluorobutane and iso-1H-nonafluorobutane, were detected in the headspace test, although Perfluorobutane sulfonic acid was not. Mass balances were essentially complete by Day 3 of the experiment.

The experiment was conducted in accord with national guidelines with acceptable modifications to include analysis of test substance and potential degradation products, and was conducted under GLP criteria. It is considered reliable without restriction and is suitable for Risk Assessment, Classification & Labelling, and PBT Analysis.

Description of key information

FBSEE diol is not readily biodegradable (26.1% BOD/ThOD in a 28-day OECD 301F test), but was rapidly converted to a dicarboxylic acid in an inherent biodegradation test (OPPTS835.3200 as modified to identify degradation products).

Additional information

Biodegradation of FBSEE diol was examined in two studies. The key study was ready biodegradation test done under OECD Guideline 301F (Manometric respirometry) and in compliance with GLP criteria. FBSEE diol was not inhibitory to degradation of the sodium bonzoate reference, but was not readily biodegradable. To better characterize biodegradability, the inherent biodegradability test guideline OPPTS832.3200 was modified to identify biodegradation products and provide a mass balance for the degradation pathway. FBSEE diol was not removed from abiotic controls, but was sharply reduced by Day 1 in all active cultures with quantitative removal by Day 14. The predominant metabolite of FBSEE diol was 2,2'-{[(Nonafluorobutyl)-sulfonyl]imino}diacetic acid. Other materials detected in the cultures were N-(2-Hydroxyethyl)-perfluorobutane sulfonamide, Perfluorobutane sulfonamide, Perfluorobutane sulfinic acid, and Perfluorobutane sulfonic acid. Perfluorobutanoic acid was examined but not detected. Two volatile products, n-1H-nonafluorobutane and iso-1H-nonafluorobutane, were detected in the headspace test, although Perfluorobutane sulfonic acid was not. Mass balances were essentially complete by Day 3 of the experiment. This test was also done in compliance with GLP criteria and is considered reliable without restrictions. However, because of the optimization for determining degradation products and mass balance, this test does not provide information on fulfilling specific criteria for inherent biodegradability as defined in OECD guidelines.