2-butoxyethyl methacrylate

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:

February 02, 2018 to March 02, 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

yes

Remarks:

Incubation temperature ranged from 16.8 to 20.5 °C

Principles of method if other than guideline:

All bottles should be incubated at 22 ± 2ºC, however, the incubation temperature ranged from 16.8 to 20.5 °C on day 6. The temperature on all other days was within an acceptable limit. It is the opinion of the study director that the inoculum viability, and ultimate outcome of the study, was not significantly affected by this temperature deviation given that the reference material achieved the guideline validation criteria and the test item continued to steadily degrade.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: Secondary effluent from a sewage treatment work

Details on inoculum:

- Source of inoculum/activated sludge: Cambridge STW, Cowley Road, Cambridge
- Collection date: 01 February 2018
- Pretreatment: Filtered
- Concentration of sludge: 1ml/l
- Water filtered: Yes
- Type and size of filter used, if any: Whatman No. 54

Duration of test (contact time):

28 d

Initial conc.:

2.88 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: The dilution water was prepared by adding secondary effluent inoculumn and mineral nutrient stock solutions to deionised water. The buffer stock consisted of phosphate, magnesium, calcium, and iron (III) chloride. All buffer solutions were added at 1 ml/L to a total volume of 20 L of deionised water and secondary effluent was added at 1 ml/L to a total volume of 20 L of deionised water.
- Test temperature: 16.8 - 20.5 °C
- Aeration of dilution water: Aerated strongly for 25 minutes and left to stand for 23 hours and 26 minutes before adding the inoculum.
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: BOD bottles (250 ml)
- Number of culture flasks/concentration: 11 flasks with test concentration of 2.88 mg/l
- Measuring equipment: Dissolved oxygen meter
- Test performed in closed vessels due to significant volatility of test substance: Test vessel sealed with glass stoper


SAMPLING
- Sampling frequency: 0, 7, 14, 21, 28 days
- Sample storage before analysis: in the dark at 16.8-20.5C

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: No
- Toxicity control: No

Reference substance:

acetic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

21

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

61

Sampling time:

14 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

66

Sampling time:

21 d

Details on results:

A ThOD of 2232 mgO2/g 2-butoxyethyl methacrylate was calculated using structural information.

Results with reference substance:

ThOD of sodium acetate 780 mgO2/g. Average degradation on day 7, 14, 21, and 28 of 66, 68, 73, and 57 % respectively.

Validity criteria fulfilled:

yes

Remarks:

At the point where test degradation had achieved >60% degradation (day 21), all validity criteria were met.

Interpretation of results:

readily biodegradable

Conclusions:

2-Butoxyethyl methacrylate gave a positive result (60% degradation relative to the ThOD/COD value), achieving a maximum of 66% degradation at day 21, in a 28-day experiment to determine the capacity of the registered substance to biodegrade in water.

Executive summary:

A 28-day experiment was undertaken to determine the ready biodegradability potential of  2-butoxyethyl methacrylate in freshwater conditions according to Good Laboratory Practice (GLP) and OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test). Degradation is defined as the ratio of the biochemical oxygen demand (BOD) within 28 days to either the theoretical oxygen demand (ThOD) or the chemical oxygen demand (COD). A small deviation occurred in temperature on day 6 (16.8 to 20.5 °C), however, it was concluded that this did not impact the overall biodegradation outcome given that the inoculum viability was not significantly affected. A secondary effluent inoculum from a sewage treatment plant was prepared along with a mineral medium, the latter of which consisted of the effluent inoculum, mineral nutrient stock solutions, and deionised water. A final test concentration of 2.88 mg/L for the test substance was obtained via a dilution series. An inoculated mineral medium only control and a reference substance treatment (5.01 mg/L) were also prepared. Initial dissolved oxygen (DO) concentrations were measured using a dissolved oxygen meter.

All validity criteria in the study were satisfied between day 0 and 21. At day 21 the reference substance had achieved a degradation of 73 %, however, blank DO losses reached 2.06mg/l by day 28. The guideline requires that the reference material degrades by at least 60% of its ThOD, and that the blank dissolved oxygen loss does not exceed 1.5mg/l after 28 days. Experimental data collected past day 21 should subsequently be disregarded.

As the degradation of 2-butoxyethyl methacrylate achieved on day 21 was 66 %, which is >60 % (CLP Regulation (EC) No. 1272/2008), and this time point was within the acceptability limits of all validity criteria, 2-butoxyethyl methacrylate can ultimately be regarded as being readily biodegradable under the conditions of the study.

Description of key information

In a 28-day experiment to assess the capacity of 2-butoxyethyl methacrylate to biodegrade in water (OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)), the registered substance was determined to be readily biodegradable. This conclusion was based on a biodegradation result of >60 % (66 %) on day 21, which indicate that the substance is ready biodegrdable under the test conditions. The result obtained for day 28 should be disregarded given that the blank dissolved oxygen reading exceeded the threshold outlined in the guideline, invalidating the data for this sampling point.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater