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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:
31 days
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Principles of method if other than guideline:
Disperse Blue 359 was a dark blue powder with a purity of 99%. The test item was tested in duplicate at a target concentration of 17 mg/L, corresponding to 12 mg TOC/L. The organic carbon content was based on the molecular formula.

Since Disperse Blue 359 was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L, weighed amounts were added to the 2-litres test bottles containing medium with microbial organisms and mineral components (test item bottle A: 34.2 mg; test item bottle B: 34.1 mg and toxicity control bottle: 34.0 mg). To this end, 10 mL of Milli-RO water was added to each weighing bottle containing the test item. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test, to ensure optimal contact between the test item and the test organisms.
GLP compliance:
yes
Specific details on test material used for the study:
Batch 135214 of Disperse Blue 359 was a dark blue powder with a purity of 99%.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
Treatment: The freshly obtained sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was determined to be 5 g/L in the concentrated sludge. Before use, the sludge was allowed to settle (32 minutes) and the supernatant liquid was used as inoculum at the amount of 10mL/L of mineral medium.
Reason for selection: The test has been accepted internationally for determining the 'ready' biodegradability of test items under aerobic conditions.
Duration of test (contact time):
ca. 28 d
Initial conc.:
ca. 17 mg/L
Based on:
ThCO2
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
> 0 - <= 3
Sampling time:
28 d
Remarks on result:
other: Disperse blue 359 not readily biodegradable based under conditions of the modified Sturm test presently performed.
Details on results:
Disperse blue 359 not readily biodegradable based under conditions of the modified Sturm test presently performed.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Disperse blue 359 not readily biodegradable based under conditions of the modified Sturm test presently performed.
Executive summary:

Since Disperse Blue 359 was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L, weighed amounts were added to the 2 -litres test bottles containing medium with microbial organisms and mineral components. To this end, 10 mL of Milli-RO water was added to each weighing bottle containing the test item. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test to ensure optimal contact between the test item and test organisms. Test duration was 28 days (last CO2 -measurement on day 29). The relative biodegradation values calculated from the measurements performed during the test period revealed no significant biodegradation of Disperse Blue 359. In the toxicity control, Disperse Blue 359 was found not to inhibit microbial activity. Since all criteria for acceptability of the test were met, this study was considered to be valid. Disperse Blue 359 was designated as not readily biodegradable.

Description of key information

Since Disperse Blue 359 was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L, weighed amounts were added to the 2 -litres test bottles containing medium with microbial organisms and mineral components. To this end, 10 mL of Milli-RO water was added to each weighing bottle containing the test item. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test to ensure optimal contact between the test item and test organisms. Test duration was 28 days (last CO2 -measurement on day 29). The relative biodegradation values calculated from the measurements performed during the test period revealed no significant biodegradation of Disperse Blue 359. In the toxicity control, Disperse Blue 359 was found not to inhibit microbial activity. Since all criteria for acceptability of the test were met, this study was considered to be valid. Disperse blue 359 not readily biodegradable based under conditions of the modified Sturm test presently performed.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information