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Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
Cited as Directive 92/69/EEC, C.4-D
GLP compliance:
Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Type: mixed population of aquatic microorganisms
- Origin: aeration tank of a waste water plant treating predominantly domestic sewage (Wupper area water authority, Germany)
- Pretreatment: none
- activated sludge concentration in test flasks: 30 mg ss/l

Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
- Direct weighing
- Test substance: 100 mg/l
- Reference substance: 100 mg/l

- 28 days incubation at 20 +/- 1 °C
Reference substance:
benzoic acid, sodium salt
purity 99 %
% degradation (O2 consumption)
Sampling time:
28 d
Details on results:
Kinetic of Desmodur W: 8 day(s) 0 %
14 day(s) 0 %
20 day(s) 0 %
Results with reference substance:
Kinetic of reference substance (in %): 79 after 8 days
87 after 14 days
91 after 28 days

The used concentration of the test substance did not show toxic effects  to bacteria (toxicity control)

Validity criteria fulfilled:
Interpretation of results:
not readily biodegradable
Executive summary:

4,4-methylenedicyclohexyl diisocyanate is not readily biodegradable. After 28 days 0 % of the test substance had been degraded in a manometric respiratory test (Directive 92/69/EEC, C.4-D) (Bayer AG, 2000).

Description of key information

In a GLP-study which was conducted according to Directive 92/69/EEC C.4-D (Manometric Respirometry Test), the biodegradation of 4,4’-methylenedicyclohexyl diisocyanate was investigated with a test substance concentration of 100 mg/l. Within the test period of 28 days, a degradation of 0 % was determined (Bayer AG, 2000a).

In a GLP-study which was conducted according to OECD TG 301F, the biodegradation of 4,4’ methylenedicyclohexyl diisocyanate was tested at an initial concentration of 12 mg/l. Within the test period of 28 days, a degradation of 0 % was observed (Bayer AG, 1992).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information