tert-butyl 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:

From June 18, 2010 to August 27, 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal activated sludge from the wastewater treatment plant of Mannheim, Germany was collected on 25 June 2010 from the aeration tank of the plant.
- Preparation: A suitable aliquot of the suspension was sieved by a finely woven mesh with a mesh size of about 1 mm. To reduce the content of inorganic carbon in the blank control the activated sludge suspension was aerated with carbon dioxide free air for about 72 hours at 22 ± 2° C. At the day of exposure the aeration was stopped and the sludge was allowed to settle. The supernatant was discarded and the residue of the sludge suspension was filled up with tap water. The sludge of the suspension was adjusted to a concentration 800 mg/L of dry weight. Aliquots of 0.5 mL were added to the test vessels to obtain a sludge concentration of 4 mg/L dry substance in the test assays.

Duration of test (contact time):

60 d

Initial conc.:

30 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

other: TOC

Parameter followed for biodegradation estimation:

inorg. C analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: 90 mL mineral medium (according to guideline), 0.5 ml inoculum, filled up to a total volume of 100 mL with distilled water.
- Test temperature: 22 +/- 2 °C
- pH: 7.4

TEST SYSTEM
- Test performed in closed vessels due to significant volatility of test substance: yes
-The following test assays were prepared: 29 blank control assays
31 test substance assays
29 inhibition control test assays
8 reference substance assays
5 assays for abiotic control
-Duration of the adaptation phase: 2 days

SAMPLING
- Sampling frequency: at day 7, 14, 21, 28, 35, 42, 49 and 56 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity (inhibition) control: yes

Reference substance:

aniline

Parameter:

other: TIC/TOC

Value:

68

Sampling time:

60 d

Results with reference substance:

valid, 72% degradation within 14 days

Table 1: Degree of biodegradadtion and elimination for the different treatments within the test period. (TIC = Total Inorganic Carbon; TOC = Total Organic Carbon)

 

Treatment	Incubation time in d	Biodegradation / Elimination in % TIC/TOC (mean value)
Test material	60	68 ± 11*
Physical chemical control	60	<10
Reference substance	14	72
Inhibition control	60	87

 

* mean value of five test assays, limit of confidence 95%

 

Validity criteria fulfilled:

yes

Interpretation of results:

other: in this test biodegradable

Remarks:

10 day window criteria was not met

Conclusions:

The test material was degraded to 68 ± 11 % within the test period of 60 d. Therefor the test material can be considered as biodegradable but not as ready biodegradable since the 10 day window criteria was not met.

Executive summary:

In conclusion the test material in the Carbon Dioxide Headspace Test was biodegradable based on the quantitative determination of the formed total inorganic carbon (TIC) in comparison to the applied amount of total organic carbon (TOC). The required pass level of degree of biodegradation of 60 % TIC/TOC at the end of exposure was fulfilled but not within the required 10 day window.

The degree of biodegradation after an exposure period of 60 days was 68 ± 11 % TIC/TOC in this test.

The mean value of degree of biodegradation was calculated by the single values of five test assays at the end of exposure with a limit of confidence of 95 %.

Based on the rate of biodegradation of 68 ± 11 % TIC/TOC at the end of exposure the test substance can be evaluated as biodegradable in this test.

The results in this study are consistent with all validity criteria and the test is valid according to the OECD guideline 310. No deviations from the test guidelines or other incidents occurred during the course of the reported test which may have influenced the results.

Description of key information

The test item was degraded to 68 % ± 11 % TIC/TOC after 60 d. Therefore, it is not ready biodegradable but biodegradable under enhanced conditions according to OECD critreria.

QSAR calculations (Catalogic) of the parent compound predicted a primary half life of 1month 27 days and an ultimiate half life of 2 months 3 days.

Via QSAR calculations two main degradation products with quantities above 0.1 % could be identified, according to OECD criteria and model calculations they can be considered as ready biodegradable.

Based on this weight of evidence the tert-butyl methacrylate is determined to be inherently biodegradable, fulfilling the criteria.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater

Additional information

The test material in the Carbon Dioxide Headspace Test was biodegradable based on the quantitative determination of the formed total inorganic carbon (TIC) in comparison to the applied amount of total organic carbon (TOC). The required pass level of degree of biodegradation of 60 % TIC/TOC at the end of exposure was fulfilled but not within the required 10-day window. The degree of biodegradation after an exposure period of 60 days was 68 ± 11 % TIC/TOC in this test it was calculated as mean out of five test assays at the end of exposure with a limit of confidence of 95 %. Based on the rate of biodegradation of 68 ± 11 % TIC/TOC at the end of exposure the test substance can be evaluated as biodegradable in this test. The results in this study were consistent with all validity criteria and the test was valid according to the OECD guideline 310. No deviations from the test guidelines or other incidents occurred during the reported test which may have influenced the results.

Two main biodegradtion products of the test item were identified via QSAR calculations with the software OASIS Catalogic 5.14.1.5 and the model Kinetic 301F v.14.17. The two main biodegradation products can be considered as readily biodegradable according to the model and are within the applicability domaine.