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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
17.05-15-06.16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
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
- Laboratory culture:
- Method of cultivation:
- Storage conditions:
- Storage length: 4 days
- Preparation of inoculum for exposure: aeration
- Pretreatment: filtration, washing (2x tap water), washing & re-suspension with test medium
- Concentration of sludge:
- Initial cell/biomass concentration: 4840 mg suspended solids/L
- Water filtered: yes/no
- Type and size of filter used, if any:
Duration of test (contact time):
28 d
Initial conc.:
32.1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: standard medium
- Additional substrate:
- Solubilising agent (type and concentration if used):
- Test temperature: 19.6-21.0 °C
- pH: test medium (day 28): 7.4/7.4, positive control (day 28) 7.3/7.3
- pH adjusted: yes/no
- CEC (meq/100 g):
- Aeration of dilution water:
- Suspended solids concentration: 25.0 mg/L
- Continuous darkness: yes/no
- Other:

TEST SYSTEM
- Culturing apparatus: 2000 mL flasks
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: aeration with purified air (by activated charcoal, CO2-scrubbed, moistened)
- 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:
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: 2 scrubber (0.25 M NaOH)
- Other:

SAMPLING
- Sampling frequency: day 0, 3, 6, 8, 10, 14, 17, 23, 29
- Sampling method: sampling 1 mL
- 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 apparatus blanks, 2 positive

STATISTICAL METHODS:
Reference substance:
aniline
Key result
Parameter:
% degradation (CO2 evolution)
Value:
28
Sampling time:
28 d
Results with reference substance:
63 % after 10 days

Day

Blank Control 1

Blank Control 2

Positive Control 1

Positive Control 2

Test 1

Test 2

Abiotic control

Toxicity control

3

0.77

0.54

0.63

0.27

0.69

0.84

0.17

0.51

6

1.27

1.30

8.82

6.78

1.44

1.57

0.17

7.14

8

1.80

1.62

12.61

12.16

2.44

2.26

0.24

9.94

10

2.07

1.86

14.30

15.01

3.49

2.92

0.25

11.77

14

2.34

2.37

17.83

17.54

4.81

4.23

0.26

14.48

17

2.76

2.63

19.24

18.87

6.22

5.37

0.35

16.40

23

2.84

.266

17.80

17.58

7.19

6.45

0.33

16.20

29

2.78

2.72

19.25

19.24

8.63

7.94

0.08

18.47

emitted carbon in mg/L

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Under test conditions 28 % of the test item is degraded within 28 days reaching no plateau at the end of the testing period. Therefore, further biodegradation can be assumed.
Executive summary:

The test item 2,2'-Azobis(4 -methoxy-2,4 -dimethyl valeronitrile) was tested using a concentration of nominally 20 mg organic carbon/L (corresponding to 32.1 mg 2,2'-Azobis(4 -methoxy-2,4 -diemethyl valeronitrile)/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 fot the test item 2,2'-Azobis(4 -methoxy-2,4 -dimethyl valeronitrile):

10 -day window                                                                                    day 13 -23

degradation at the end of 10 -day window                                                 20 %

degradation at the end of the test                                                               28 %

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

respective 60 % at the end of the test for mixtures

Therefore, when applying the 10 -day window, 2,2'-Azobis (4 -methoxy-2,4 -dimethylvaleronitrile) is not readily biodegradable following OECD 301B/EU C.4 -C.

However, at the end of the test no plateau of degradation was reached yet, indicating further biodegradation possible.

Description of key information

A biodegradation of 28 % after 28 days is found in an OECD 301B guideline study. At the end of the exposure period no plateau is observed, therefore further biodegradation can be assumed. For the initial chemical safety assessment no biodegradation is considered as worst case assumption.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information