ε-Caprolactone, oligomers, esters with acrylic acid and 2,2,2',2'-tetrakis (hydroxymethyl)-3,3'-oxydipropan-1-ol

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 Oct - 22 Nov 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

1992

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

No. 440/2008

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom

Test material

Test material information

Constituent 1

Reference substance name:

ε-Caprolactone, oligomers, esters with acrylic acid and 2,2,2',2'-tetrakis (hydroxymethyl)-3,3'-oxydipropan-1-ol

EC Number:

500-276-7

EC Name:

ε-Caprolactone, oligomers, esters with acrylic acid and 2,2,2',2'-tetrakis (hydroxymethyl)-3,3'-oxydipropan-1-ol

Cas Number:

89800-10-2

Molecular formula:

{(C10H16O7).(C3H3O)b.[(C6H10O2)m.(C3H3O)a]} (i.e., UVCB substance)

IUPAC Name:

ε-Caprolactone, oligomers, esters with acrylic acid and 2,2,2',2'-tetrakis (hydroxymethyl)-3,3'-oxydipropan-1-ol

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: activated sewage sludge from the aeration stage of the treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage (sampled on 23 Oct 2017)
- Preparation of inoculum for exposure: Activated sewage sludge sample was washed twice by settlement and re-suspension in mineral medium to remove any excessive amounts of dissolved organic carbon (DOC) washed sample was then maintained on continuous aeration in the laboratory at a temperature of approximately 21 °C and used on the day of collection.
- Pretreatment: Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the washed activated sewage sludge by suction through pre- weighed GF/A filter paper using a Buchner funnel. Filtration was then continued for a further 3 min after rinsing the filter three successive times with 10 mL of deionized reverse osmosis water. The filter paper was then dried in an oven at approximately 105 °C for at least 1 h and allowed to cool before weighing. This process was repeated until a constant weight was attained.
- Concentration of sludge: The suspended solids concentration was equal to 2.4 g/L prior to use
- Initial cell/biomass concentration: 30 mg suspended solids (ss)/L per vessel

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

10 mg/L

Based on:

TOC

Initial test substance concentration 2

Initial conc.:

16.9 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium was used according to the OECD guideline 301
- Test temperature: between 22 and 24 °C in a temperature controlled room
- pH: 7.4 - 7.7
- pH adjusted: yes
- Aeration of dilution water: The test vessels were sealed and CO2-free air bubbled through the solution at a rate of 30 to 100 mL/min per vessel and stirred continuously by magnetic stirrer; CO2-free air was produced by passing compressed air through a glass column containing self-indicating soda lime (Carbosorb®) granules
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 liter test culture vessels each containing 3 liters of solution
- Number of culture flasks/concentration: 2
- Measuring equipment: Samples were analyzed for IC and TC using a Shimadzu TOC-VCPH TOC Analyzer
- Test performed in closed vessels: No
- Test performed in open system: Yes
- Details of trap for CO2: The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified water.

SAMPLING
- Sampling frequency and method: Samples (2 mL) were taken from the first CO2 absorber vessels on Days 0, 2, 6, 8, 10, 14, 21, 28 and 29. The second absorber vessels were sampled on Days 0 and 29. On Day 28, 1 mL of concentrated hydrochloric acid was added to each vessel to drive off any inorganic carbonates formed. The vessels were resealed, aerated overnight and the final samples taken from both absorber vessels on Day 29.
- Sample storage before analysis: All samples were analyzed for IC immediately. The remainder of all samples with the exception of the Day 0 and Day 29 samples were frozen for further analysis if required.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 (inoculated mineral medium)
- Toxicity control: 1 (test item plus the reference item in inoculated mineral medium)
- Other: Reference control: 2 (sodium benzoate and inoculated mineral medium)

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

82

Sampling time:

28 d

Details on results:

The toxicity control attained 67% biodegradation after 14 days and 82% biodegradation after 28 days thereby confirming that the test item did not exhibit an inhibitory effect on the sewage treatment micro-organisms used in the test.

BOD5 / COD results

Results with reference substance:

Sodium benzoate attained 74% biodegradation after 14 days and 102% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.

Any other information on results incl. tables

Table 1: Biological Results: Percentage Biodegradation Values

Day	% Biodegradation
	Procedure Control	Test Item	Toxicity Control
0	0	0	0
2	54	5	23
6	76	21	49
8	72	26	52
10	79	38	65
14	74	42	67
21	92	61	92
28	97	87	85
29*	102	82	82

 

Table 2: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	<20%	Yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	74%	Yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	67%	Yes
The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.	<5%	Yes
The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	39.06 mg/L	Yes

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

For further details please see table 2 in section “Any other information on results incl. tables”.

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The test item attained 82% biodegradation after 28 days. Under the strict terms and conditions of OECD Guideline No. 301B the test item cannot be considered to be readily biodegradable as the test item failed to satisfy the 10-Day window validation criterion, whereby 60% biodegradation must be attained within 10 days of the biodegradation exceeding 10%. However, the test item has exhibited the potential for rapid biodegradation. According to ECHA Guidance Chapter R. 7b (2017), the 10-day window does not need to be applied if the test is carried out on a mixture of structurally similar constituents and if it is anticipated that a sequential biodegradation of the individual components is taking place, based on the OECD “Guidelines for the Testing of Chemicals, Revised Introduction To The OECD Guidelines For Testing of Chemicals (Section 3, Part I, OECD, 2006b). Thus, the % degradation at the end of exposure is used instead to assess the ready biodegradability of the substance as a whole. Since degradation was > 60 % after 28 d, the substance is regarded as readily biodegradable.