Ethylene di(acetate)

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

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

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

other: EPA OPPTS 835.3110 (Ready Biodegradability)

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

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.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

14 d

Test temperature:

25.2 - 26.0 °C

pH:

7.2 - 7.3

Nominal and measured concentrations:

nominal concentration: 100 mg/L

Details on test conditions:

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 (positive control):

yes

Remarks:

aniline

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Result from ready biodegradability test

Results with reference substance (positive control):

The reference substance attained 74% degradation after 14 d in the absence of the test item.

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.

The test substance (100 mg/L) attained a mean biodegradation of 50.3% (O2 consumption) after 14 d and 60% (O2 consumption) after 28 d. Thus, the test substance is readily biodegradable according to the OECD criteria and the test item is not considered to be inhibitory to activated sludge microorganisms.

Description of key information

NOEC (28 d) ≥ 100 mg/L for activated sludge microorganisms (OECD 301C)

Additional information

Since no studies investigating the toxicity to microorganisms are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to 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. 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 toxicity of 2,2'-[ethane-1,2-diylbis(oxy)]bisethyl diacetate (CAS 111-21-7) to microorganisms was investigated in a biodegradation study according to OECD 301C under GLP conditions (Clarke, 2012). The study was performed with a mixed population of active sewage sludge microorganisms. A toxicity control included in the biodegradation study could not be evaluated because of technical problems. Nevertheless, no inhibition of biodegradation was observed after 28 d since the substance turned to be readily biodegradable (60% biodegradation in 28 d). The test concentration from a biodegradation study which indicated that the test substance is readily biodegradable can be used to derive a NOEC for this endpoint as stated in the ECHA Guidance R.7b (ECHA, 2012). Therefore, the test item concentration of 100 mg/L can be used as NOEC value for the toxicity to activates sludge microorganisms (NOEC (28 d) of ≥ 100 mg/L). 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 structure and ecotoxicological profile, it can be concluded that ethylene diacetate will not exhibit toxicity to aquatic microorganisms up to 100 mg/L.