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Environmental fate & pathways

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:
01.06.-07.07.17
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: granular

Study design

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): ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf (Date of collection: 02. Jun. 2017)
- Laboratory culture:
- Method of cultivation:
- Storage conditions: aerated in test medium until use
- Storage length:
- Preparation of inoculum for exposure:
- Pretreatment: filtrated, washed with tap water (2x), then washed with and re-suspended in test medium
- Concentration of sludge: 4840 mg suspended solids/L
- Initial cell/biomass concentration:
- Water filtered: yes/no
- Type and size of filter used, if any:
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
29.1 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: standard test medium
- Additional substrate: -
- Solubilising agent (type and concentration if used): -
- Test temperature: 20.0 - 21.3 °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, 2, 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
Reference substance:
aniline

Results and discussion

% Degradation
Key result
Parameter:
% degradation (CO2 evolution)
Value:
1.5
St. dev.:
0.5
Sampling time:
28 d

BOD5 / COD results

Results with reference substance:
89 % after 28 days

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Under test conditions less than 60 % biodegradation was observed, therefore the substance is considered as not ultimately biodegradable.
Executive summary:

The test item 1,1'-Azobis(cyclohexane-1-carbonitrile) was tested using a concentration of nominally 20 mg organic carbon/L (corresponding to 29.1 mg 1,1'-Azobis(cyclohexane-1- carbonitrile)/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 68 % after 8 days. As degradation in the toxicity flask was 47.6 % after 14 days, the test item can be stated as “not toxic towards the inoculum in a concentration of 29.1 mg/L”.

The following data were determined for the test item 1,1'-Azobis(cyclohexane-1- carbonitrile):

10 -day-window:                                                                                    not detected

degradation at the end of 10-day-window                                                 none

degradation at the end of the test                                                               2 %

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

For the test item 1,1'-Azobis(cyclohexane-1-carbonitrile) only 2 % biodegradation was observed after 28 days. The 10-day window could not be determined. The criterion of reaching 60 % of degradation after 28 days is not met. 1,1'-Azobis(cyclohexane-1-carbonitrile is therefore considered as “not readily biodegradable”.

As degradation missed 60 % in the course of the test, 1,1'-Azobis(cyclohexane-1- carbonitrile is considered as not ultimately biodegradable.