Dimethyl 2,2'-azobis(2-methylpropionate)

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:

supporting study

Study period:

17.05-15.06.16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): ESN (Stadtentsorgung Neustadt), Im Altenschemel, NW-Lachen-Speyerdorf (date of collection: 13.05.16)
- Laboratory culture:
- Method of cultivation:
- Storage conditions: in test medium under aeration
- Storage length: 4 days
- Preparation of inoculum for exposure:
- Pretreatment: filtration, 2x washing (tap water), wash and re-suspension in test medium
- Concentration of sludge: 4840 mg/L dw
- Initial cell/biomass concentration:
- Water filtered: yes/no
- Type and size of filter used, if any:

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

ThCO2

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: standard test medium
- Additional substrate: -
- Solubilising agent (type and concentration if used): -
- Test temperature: 19.6 - 21.0 °C
- pH:
- pH adjusted: no
- CEC (meq/100 g):
- Aeration of dilution water:
- Suspended solids concentration: 25 mg/L
- Continuous darkness: yes/no
- Other:

TEST SYSTEM
- Culturing apparatus: 2 L Flask
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: aeration with purified (by activated charcoal), CO2-scrubbed, moistened air
- Method used to create anaerobic conditions: -
- Measuring equipment: Carbon analyser TOC multi N/C 2100S, Analytik Jena
- Test performed in closed vessels due to significant volatility of test substance: no
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: NaOH (0.25 M)
- Other:

SAMPLING
- Sampling frequency: day 0, 3, 6, 8, 10, 14, 17, 23 and 29
- Sampling method: 1 mL from scrubber flask
- Sterility check if applicable:
- Sample storage before analysis:
- Other:

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2
- Abiotic sterile control: 1
- Toxicity control: 1
- Other: 2 system blanks

STATISTICAL METHODS:

Reference substance:

aniline

Key result

Parameter:

% degradation (CO2 evolution)

Value:

53

Sampling time:

28 d

Results with reference substance:

63 % after 10 d

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

The substance does ot fulfil the criteria for readily biodegradability. However, the substance is degraded by 53 % after 28 days showing no plateau at the end of the test. Therefore, further biodegradation can be assumed. Based on these findings the substance is considered to be inherently biodegradable.

Executive summary:

The test item dimethyl-2,2'-azobisisobutyrate was tested using a concentration of nominally 20 mg organic carbon/L (corresponding to 38.3 mg dimethyl-2,2'-azobisisobutyrate/L) in test medium following OECD 301B and EU Method C.4 -C.

Aniline was chosen as positive control.

Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L). The test was left running for 28 days. All validity criteria were met. Degradation of the positive control was 63 % after 10 days.

The following data were determined for the test item dimethyl-2,2'-azobisisobutyrate:

10 -day window:                                                                      day 11 -21

degradation at the end of the 10 -day window                                   38 %

degradation at the end of the test:                                                      53 %

pass level following guideline:              60 % at the end of the 10 -day-window for pure substances

respective 60 % at the end of the test for mixtures

Therefore, when applying the 10 -day-window, dimethyl-2,2'-azobisisobutyrate is not readily biodegradable following OECD 301B/EU C.4 -C. However, at the end of the test no plateau was reached yet, indicating further biodegradation is possible.

Description of key information

Based on the two available biodegradation screening studies (OECD 301B and OECD 301B) the substance is considered to be readily biodegradable in the further assessment. The key study shows a degradation more than 90 % after 28 days. The supporting study shows a degradation of 53 % after 28 days, but no plateau is reached indicating further possibility of biodegradation.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable but failing 10-day window

Type of water:

freshwater