Registration Dossier

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
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)
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Duration of test (contact time):
<= 28 d
Initial test substance concentration
Initial conc.:
ca. 15 mg/L
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
Test conditions: 22°C, darkness
pH of 7.40 to 7.47 (test start) and 7.36 to 7.57 (test end)
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Key result
Parameter:
% degradation (CO2 evolution)
Value:
9
Sampling time:
28 d
Details on results:
To be considered readily biodegradable, a test substance must achieve 60% biodegradation by the end of the test. Additionally, the test substance must biodegrade by at least 60% within 10 days of having degraded by 10%.
Cetoxenone showed limited biodegradation during the study with a mean biodegradation of 9% not exceeding 10%. Cetoxenone cannot, therefore, be considered readily biodegradable.
Percent biodegradation values at each sampling interval, for the two replicates containing Cetoxenone did not vary by more than 3%, therefore satisfying the validity criterion of less than 20% difference.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Validity criteria were satisfied (degradation of reference material, CO2 production from blank controls). With the exception of the inorganic carbon content (<1%) over the mineral media IC of the total carbon content at the beginning of the test, which has been deemed scientifically justified as having no impact upon the outcome of the study, the results are therefore considered to be valid.
Mean carbon dioxide evolution from Cetoxenone was <10% of the theoretical carbon dioxide yield throughout the test. The level of biodegradation did not meet the requirements for ready biodegradability and Cetoxenone cannot, therefore, be classified as readily biodegradable.