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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:
3 August 1993 to 1 September 1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
Remarks:
Single CO2 absorber used per test vessel. Not considered a significant deviation.
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
Activated sludge from sewage plant prepared according to methods described in the test guideline.
Duration of test (contact time):
29 d
Initial conc.:
23.9 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
38
Sampling time:
29 d
Validity criteria fulfilled:
yes
Interpretation of results:
other:
Conclusions:
The mineralisation of cloquintocet-mexyl under the test conditions was 38 % in 29 days. Based on this result, cloquintocet-mexyl has to be classified as ‘not ready biodegradable’.
Executive summary:

A solution of the inoculated (activated sludge collected from a sewage treatment plant) mineral medium was spiked with 23.9 mg technical grade cloquintocet-mexyl as sole source of organic carbon and incubated at 22°C in the dark. Degradation was followed by determining the carbon dioxide produced which was trapped in sodium hydroxide solution. The amount of carbon dioxide produced from the test substance was expressed as percentage of the theoretical carbon dioxide. The mineralisation of cloquintocet-mexyl under the test conditions was 38 % in 29 days. Based on this result, cloquintocet-mexyl has to be classified as ‘not ready biodegradable’.

Description of key information

The biodegradation of cloquintocet-mexyl in water was determined in a ready biodegradation test according to the principles of the EU C4-C (CO2 Evolution Test) method.  Significant degradation of the test material was observed, but the degree of degradation was not sufficient to characterise cloquintocet-mexyl as 'readily biodegradable'.

Key value for chemical safety assessment

Biodegradation in water:
not biodegradable

Additional information

The key study (Baumann, 1993) investigated the biodegradation of cloquintocet-mexyl in water according to the EU C4 -C (CO2 Evolution Test) method. This study was GLP compliant and is considered to be reliable without restrictions.

A solution of the inoculated (activated sludge collected from a sewage treatment plant) mineral medium was spiked with 23.9 mg technical grade cloquintocet-mexyl as sole source of organic carbon and incubated at 22 °C in the dark. Degradation was followed by determining the carbon dioxide produced which was trapped in sodium hydroxide solution. The amount of carbon dioxide produced from the test substance was expressed as percentage of the theoretical carbon dioxide. The mineralisation of cloquintocet-mexyl under the test conditions was 38% in 29 days. Based on this result, cloquintocet-mexyl is classified as ‘not readily biodegradable’.