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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:
2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Type: mixed population of aquatic microorganisms (activated sludge)
Origin: aeration tank of a waste water plant treating predominantly domestic sewage (Kläranlage Odenthal)
Date of collection: 2000-01-17
Pretreatment: none
Concentration of inoculum: 30 mg/L SS
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Details on study design:
Pretreatment of the test substance:
- 25 mg test substance were weighed out and added to the test vessels to give a test concentration of 100 mg/L test substance

Exposure conditions:
- Test volume : 250 ml, Mixing: 1 magnetic stirrer per test vessel, Incubation temperature : 22 +- 1 °C

- Tests with reference compound, sodium bezoate, were run in parallel (100 mg/L)
- toxicity control (reference compound, test item, inoculum) and blank control without test item was carried out
- Test substance, blank control and reference compund were run in triplicates, toxicity control in duplett

- pH value of the test vessels at the end of the test: 7.6
Reference substance:
benzoic acid, sodium salt
Remarks:
purity 99 %
Parameter:
% degradation (O2 consumption)
Value:
5
Sampling time:
28 d
Details on results:
The used concentrations of Imidoxim did not show toxic effects to bacteria.
Results with reference substance:
The reference compound sodium benzoate showed 84 % degradation after 28 days.
Validity criteria fulfilled:
yes
Remarks:
biodegradation of reference compound >= 60 % within 14 days; in the toxicity control degradation rates > 25 % within 14 days; replicates difference < 20 %; oxygen uptake of blank inoculum <= 60mg/L; no pH influence
Interpretation of results:
not readily biodegradable
Conclusions:
Within 28 days, a degradation of 5 % was determined for Imidoxim and thus it has to be classified as "Not Readily Biodegradable".
Executive summary:

A study was performed to assess the ready biodegradability of Imidoxim and was conducted in accordance with the Council Directive 92/69/EEC Method C.4-D "Manometric Respirometry Test" which is in most parts equivalent to the OECD Guideline for Testing of Chemicals No. 301 F "Manometric Respirometry Test". A measured volume of inoculated mineral medium, containing a known concentration of test chemical 100 mg/L of the test substance, to give at least 50-100 mg ThOD/litre as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (+- 1°C) for up to 28 days. The consumption of oxygen is determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant gas volume in the respirometer flask. The amount of oxygen taken up by the test chemical (corrected for uptake by blank inoculum, run in parallel) is expressed as a percentage of theoretical oxygen demand (ThOD) or chemical oxygen demand (COD). Imidoxim showed 5 % degradation and the reference compound showed 84 % degradation after 28 days. As the toxicity control showed a degradation of 44 % after 28 days it can be concluded that the used concentration of Imidoxim is not toxic to bacteria. Therefore Imidoxim has to be classified as "Not Readily Biodegradable".

Description of key information

A study was performed to assess the ready biodegradability of Imidoxim and was conducted in accordance with the Council Directive 92/69/EEC Method C.4-D "Manometric Respirometry Test".

Within 28 days, a degradation of 5 % was determined for Imidoxim and thus it has to be classified as "Not Readily Biodegradable".

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The toxicity control showed a degradation of 44 % leading to the conclusion that the used concentration of Imidoxim is not toxic to bacteria.