Ethylene di(acetate)

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:

09 Aug - 06 Sep 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Qualifier:

according to guideline

Guideline:

EU Method C.4-F (Determination of the "Ready" Biodegradability - MITI Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom

Oxygen conditions:

aerobic

Inoculum or test system:

other: A mixed population of active sewage sludge microorganisms

Details on inoculum:

- Source of inoculum/activated sludge: The inoculum was obtained from ten different sampling sites around the UK between 28 May 2012 and 31 May 2012. Samples were taken from domestic sewage plants (Liverpool, Loughborough (Leicestershire), Gloucester), industrial sewage plant (Derby), freshwater samples (Leeds and Liverpool Canal, River Derwent (Belper, Derbyshire) and River Severn (Gloucester), lake water (Allestree Lake (Derby)) and sea water samples (Huttoft (Eastern coast) and Hightown (North Eastern Coast).
- Laboratory culture: no
- Preparation of inoculum for exposure: The samples obtained from the sampling sites were mixed thoroughly and the mixture allowed to settle. The floating foreign matter was removed and the supernatant filtered through a coarse filter paper. The filtrate (3 L) was then mixed with 3 L of supernatant removed from a previously established culture and transferred to a culture vessel. The pH of the culture mixture was adjusted to pH 7.0 ± 1.0 with sodium hydroxide or phosphoric acid and constantly aerated via a narrow bore glass pipette at a temperature of approximately 25 °C. The culture was allowed to settle daily for approximately 30 min and approximately 1/3 of the volume of the supernatant removed. An equal volume of 0.1% synthetic sewage was added and the aeration re-started again. Synthetic sewage was prepared by dissolving glucose, peptone and monopotassium phosphate in deionized water at a concentration of 0.1% w/v. The pH of the synthetic sewage and culture was adjusted daily to within the range pH 7.0 ± 1.0 with sodium hydroxide or phosphoric acid. The sludge was found to form a clear supernatant on settling and to have an active microflora including a variety of protozoa, including ciliates and bacteria. The sludge formed cloudy flocs when on aeration.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Parameter followed for biodegradation estimation:

DOC removal

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline with deionized water purified by reverse osmosis
- Test temperature: 25.2 - 26.0 °C
- pH: 7.2 - 7.3
- pH adjusted: no
- Aeration of dilution water: yes
- Suspended solids concentration: 30 mg ss/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 mL glass bottles. The inoculum control, procedure control, test item and toxicity control vessels were placed in the CES Multi-Channel Aerobic Respirometer. The system consists of a sample flask sealed by a sensor head/CO2 trap immersed in a temperature controlled water bath. The samples were stirred for the duration of the study with a magnetically coupled stirrer.
- Number of culture flasks/concentration: 8 replicates
- Measuring equipment: The DOC analyses were carried out using a Shimadzu TOC V-CPH TOC Analyser.
- Details of trap for CO2 and volatile organics if used: As biodegradation progresses, the micro-organisms convert oxygen to carbon dioxide which is absorbed in the ethanolamine (50% v/v) CO2 trap causing a net reduction in gas pressure within the sample flask.

SAMPLING
- Sampling frequency: Compound specific analyses were carried out on days 0 and 28 from the test vessels with inoculum and deionized water. DOC was measured on day 0 and 28. The O2 consumption was measured continuously.
- Sample storage before analysis: Samples were analyzed for compound specific analysis on day of sampling.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 4 replicates
- Abiotic sterile control: yes, 4 replicates
- Toxicity control: yes, 2 bottles
- Other: Positive control: 3 replicates

Reference substance:

aniline

Remarks:

100 mg/L

Parameter:

% degradation (O2 consumption)

Value:

60

Sampling time:

28 d

Remarks on result:

other: mean from three replicates

Parameter:

% degradation (DOC removal)

Value:

96

Sampling time:

28 d

Details on results:

The 60% pass level was reached. Since no 10 d window is required the test substance is readily biodegradable.

Results with reference substance:

72% degradation after 28 d. No 10 d window required.

Analysis of the 100 mg/L test item preparations inoculated at 30 mg ss/L at 0 h showed measured test concentrations to range from 89% to 91% of nominal, with the 100 mg/L test preparation in water giving a result of 93% of nominal. A decline in measured test concentration was observed after 28 days giving measured concentrations of less than the limit of quantitation (LOQ) of the analytical method employed which was determined to be 0.040 mg/L. Given that this decline was observed in the test item vessels with and without inoculum it was considered that the decline in measured test concentrations was due to instability, hydrolysis and/or adsorption to glassware and not complete degradation.

The degradation rates calculated from the results of the DOC analyses for the inoculated test item vessels were 94%, 97% and 96% with a mean of 96% degradation after 28 d. The degradation results obtained from DOC analysis on day 28 were higher than the results obtained from oxygen consumption. This was considered to be due to adsorption of the test item to the MITI sludge which was removed from the samples taken for DOC analysis. The DOC analyses from the test item vessel prepared in deionized water were 100% of nominal on Day 0 and 88% of nominal on day 28.

There was a leak in the toxicity control. Thus, no biodegradation values are presented for the toxicity control. However, thre results from degradation indicate that the test substance was not inhibitory to the inoculum.

Table 1: % degradation in procedure control, test item vessel and abiotic control

Day	% Degradation
	Procedure Control	Test item plus inoculum			Test item in deionized water
		R1	R2	R3
0	0	0	0	0	0
1	0	0	0	0	0
2	0	7	6	13	-2
3	1	19	20	20	-3
4	1	19	20	20	-3
5	11	20	20	21	-3
6	31	21	23	23	-3
7	49	22	25	24	-3
8	60	24	29	26	-3
9	65	27	33	28	-2
10	67	30	38	31	-2
11	69	35	42	36	-1
12	71	41	47	40	0
13	73	46	51	43	1
14	74	51	54	46	2
15	75	55	57	49	3
16	76	59	60	52	3
17	76	62	62	54	4
18	77	65	64	56	5
19	77	68	66	59	6
20	77	70	67	60	6
21	76	69	66	60	4
22	75	67	64	59	2
23	74	66	63	58	1
24	74	65	63	57	-1
25	73	63	62	56	-2
26	73	63	63	55	-3
27	72	62	63	55	-4
28	72	62	63	54	-4

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Reference 2

Endpoint:

biodegradation in water: screening tests

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Validated QSAR model

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Principles of method if other than guideline:

Calculation based on BIOWIN v4.10, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Table 1. Ready biodegradability prediction using BIOWIN v4.1

Biowin1 (Linear Model Prediction)	1.0263	Biodegrades Fast
Biowin2 (Non-Linear Model Prediction):	0.9999	Biodegrades Fast
Biowin3 (Ultimate Biodegradation Timeframe)	3.1566	Weeks
Biowin4 (Primary Biodegradation Timeframe)	4.0948	Days
Biowin5 (MITI Linear Model Prediction)	1.0645	Biodegrades Fast
Biowin6 (MITI Non-Linear Model Prediction)	0.9836	Biodegrades Fast
Biowin7 (Anaerobic Model Prediction)	1.0726	Biodegrades Fast
Ready Biodegradability Prediction: YES

Interpretation of results:

readily biodegradable

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Only a final conclusion without documentation of methods and % degradation of test substance.

Principles of method if other than guideline:

Measured in the Hach respirometric and OECD Screening (die-away) tests

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: sewage (adaption and origin not specified)

No information about the rate of degradation and the performance of the test are given. Only a final conclusion is mentioned in the publication.

Interpretation of results:

readily biodegradable

Description of key information

Readily biodegradable: 60% (O2 consumption) after 28 d (OECD 301C)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Since no studies investigating the biodegradation of ethylene diacetate (CAS 111-55-7) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to another structurally related substance 2,2'-[ethane-1,2-diylbis(oxy)]bisethyl diacetate (CAS 111-21-7) was conducted. This read-across is justified in detail in the overall summary (IUCLID chapter 6.1) and within the analogue justification in IUCLID Section 13. In this case, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment. The read-across substance is characterized by a similar alcohol component (triethylene glycol compared to ethylene glycol) diesterified with acetic acid. Since the potential for biodegradation is expected to decrease at longer C-chain lengths, the source substance containing triethylene glycol can be regarded as a worst-case read-across substance for the target substance. As it can be seen in the data matrix of the analogue justification in section 13 and the overall summary, all reliable aquatic data support the read-across by showing a consistent pattern of results.

The GLP-Guideline study according to OECD 301C investigated the ready biodegradability of the read-across substance 2,2'-[ethane-1,2-diylbis(oxy)]bisethyl diacetate (CAS 111-21-7). The study was performed using a mixed culture of sewage sludge microorganisms from ten different sites containing domestic and industrial sewage plants, lakes, rivers and sea as inoculum. After incubation of 28 d the test substance was degraded to 60% (mean) based on O2 consumption and 96% based on DOC removal. The much higher extent in biodegradation was considered to be due to adsorption of the test item to the MITI sludge which was removed from the samples taken for DOC analysis. An analytical determination of test substance by GC/FID resulted in degradation below the Limit of Quantification (LOQ) of 0.04 mg/L. A complete degradation was not assumed because the same result was also measured in the test item vessels without inoculum. Thus, degradation by hydrolysis and/or adsorption to glassware is assumed. Nevertheless, DOC measurement is an unspecific method and the result might not reflect completely the biodegradation of the substance. Since the substance reached a biodegradation ≥ 60% based on the O2 consumption after 28 d it is considered to be readily biodegradable according to the OECD criteria.

Additional published data support the result from the read-across substance (Cain, 1981). A Hach respirometric and OECD Screening (die-away) test indicated that ethylene diacetate is readily biodegradable. However, the documentation is very limited without data on performance of the test and detailed degradation kinetics. Only a final conclusion was drawn.

Based on the results from a structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological and environmental fate profile and additional published data, it can be concluded that ethylene diacetate (CAS 111-55-7) is readily biodegradable according to the OECD criteria.