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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study meets the criteria for Klimisch score 1 because it followed an internationally recognised method (OECD Guideline 301D) and was carried out to Good Laboratory Practice.
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Activated sludge bacteria from domestic sewage treatment plant used at about 1 drop sludge filterate inoculum basal medium.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
COD
Parameter followed for biodegradation estimation:
other: COD
Details on study design:
Duplicate test vessels were used for the test substance, positive control and control blank. Test vessels were incubated at 20 ± 1°C.
Reference substance:
benzoic acid, sodium salt
Reference substance:
aniline
Preliminary study:
Not applicable
Test performance:
The positive controls were degraded by >60% within 28 days.
Key result
Parameter:
other: COD
Value:
8
Sampling time:
28 d
Remarks on result:
other: Additional sampling conducted on days 1, 3, 6, 10, 14 and 21 days.
Key result
Parameter:
COD
Value:
8 g O2/g test mat.
Results with reference substance:
Sodium benzoate 97% after 28 days; aniline 61% after 28 days.
Validity criteria fulfilled:
yes
Remarks:
Both the reference substances achieved greater or equal to 60% degradation, and therefore, the test was valid.
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The substance is not readily biodegradable, achieving 8% degradation over 28 days. The substance is therefore considered to be persistent, but the small amount of biodegradation suggests the substance is not unduly toxic to sewage sludge.
Executive summary:

A 28 day aerobic ready biodegradability study (to OECD Guideline No. 301D – Closed Bottle Test) was carried out using an analogue of the submission substance (CAS Number 70024-71-4). The effects of the test substance on ready biodegradability were assessed based on the measurement of chemical oxygen demand (COD) using an activated sludge inoculum (from a domestic wastewater plant) that was not pre-adapted to the test substance. Test performance was evaluated using the reference substances sodium benzoate and aniline.

 

This toxicity study is classified as reliable without restriction (Klimisch Code 1) and satisfies the guideline requirement for biodegradation in water-screening tests.

 

Results Synopsis

 

There was only 8.6% degradation of the test substance after 28 days.

There was 97% and 61% degradation of the reference substances sodium benzoate and aniline after 28 days meaning the test was considered valid.

Description of key information

The ready biodegradability of the substance is considered as a screening study to consider the persistence of the substance in the aquatic environment.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

As an organo-metal salt the substance could never be considered to undergo complete biodegradation to CO2and water. The molecule does, however, include long aliphatic chains that could, in principle, partially degrade abiotically. In fact, several of the studies available demonstrate a small amount of biodegradation that is likely to be attributable to these aliphatic chains. The substance is considered not readily biodegradable.