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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:
10.01.2014 - 13.01.2014
Reliability:
1 (reliable without restriction)
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
Temperature range was 19.3 – 21.0 °C instead of 20 – 24 °C. As degradation of the positive control was in the normal range this is considered as uncritical concerning the outcome of the study.
Qualifier:
according to guideline
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
yes
Remarks:
see above
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Duration of test (contact time):
28 d
Initial conc.:
25 mg/L
Based on:
other: see study report for more information
Key result
Parameter:
% degradation (CO2 evolution)
Value:
47
Sampling time:
28 d
Details on results:
Results for the Test Item Tar wood:The test item Tar wood is considered as “not biodegradable“. The degree of biodegradation reached 47 % after 28 days. The 10-day-window began on day 4, at its end, 37 % were reached, missing the pass level of 60 % given in the OECD guideline. Abiotic degradation was not observed.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Tar wood is not redily biodegradable following OECD 301B/EU C.4-C.
Executive summary:

Findings and Results:

The test item Tar wood was tested using a concentration of nominally 20 mg organic carbon/L (corresponding to 33.4 mg Tarwood/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 65 % after eleven days.

 

The following data were determined for the test item Tar wood:

10-day-window:

day 4 – 14

degradation at the end of 10-day-window

37 %

degradation at the end of the test

47 %

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

                                          

Therefore, regardless of the 10-day-window, Tar wood is not biodegradable following OECD 301B/EU C.4-C.

Description of key information

The test item Tar wood is considered as “not redily biodegradable“. 
The degree of biodegradation reached 47 % after 28 days.
The 10-day-window began on day 4, at its end, 37 % were reached, missing the pass level of 60 % given in the OECD guideline.
Abiotic degradation was not observed.

Key value for chemical safety assessment

Biodegradation in water:
not biodegradable

Additional information

DISCUSSION

All validity criteria were met.

Degradation behaviour of positive control and toxicity control was normal. Abiotic degradation was not observed. Both replicates of the test item showed very good correspondence.

If degradation in the toxicity flask is below 25% after 14 days, the test item can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 58% after 14 days, the test item can be stated as “not toxic towards the inoculum in a concentration of 33.4 mg/L”.

Ready degradability is defined in the guidelines as degradation surpassing 60% within 10 days after reaching a level of 10%. Therefore, the test item Tar wood cannot be considered as “readily biodegradable”. Degradation missed 60% within 28 days, too. Therefore, the test item is not considered as “biodegradable within 28 days”, either.

No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.