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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This is an older study was conducted at an reputable laboratory with known expertise in this type of testing. Sufficient details were available to assess the biodegradation of the test substance
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, industrial (adaptation not specified)
Duration of test (contact time):
ca. 18 d
Initial conc.:
ca. 400 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Reference substance:
other: not reported
Parameter:
% degradation (DOC removal)
Value:
ca. 35
Sampling time:
5 d
Parameter:
% degradation (DOC removal)
Value:
ca. 51
Sampling time:
8 d
Parameter:
% degradation (DOC removal)
Value:
ca. 70
Sampling time:
18 d
Validity criteria fulfilled:
not specified
Interpretation of results:
inherently biodegradable
Conclusions:
Methyl ethyl ketoxmime was inherently biodegradable in this 18-day test.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The test parameters evaluated in this study are expected to be well documented and scientifically acceptable. However, the study is considered valid with restriction due to use of a 21-day test rather than a 28 day test, and because it was not conducted according to GLP.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Concentration of sludge: 100 mg/L (as suspended solid)
Duration of test (contact time):
<= 21 d
Initial conc.:
ca. 30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: BOD, TOC and gas chromatography after 21 days
Details on study design:
TEST CONDITIONS
- Test temperature: 25 degrees C
Reference substance:
aniline
Parameter:
other: BOD
Value:
ca. 14.5
Sampling time:
21 d
Parameter:
% degradation (TOC removal)
Value:
ca. 27
Sampling time:
21 d
Details on results:
- Degree of biodegradation was 14.5% by BOD after 21 days.
- Degradation by total organic carbon (TOC) was 27% (average of 19 and 34%) after 21 days.
- Degradation by GC analysis was 27% (average of 21 and 31%) after 21 days.
- No degradation products were detected by GC chromatogram at the end of the test
Validity criteria fulfilled:
not specified
Interpretation of results:
not readily biodegradable
Conclusions:
Methyl ethyl ketoxime is exhibited some biodegradation but did not meet the criteria to be considered readily biodegradable based on the results of this 21-day test.

Description of key information

MEKO is not readily biodegradable based on a modified MITI test, but is inherently biodegradable based on an OECD Guideline 302B test. In the assessment MEKO is characterised as “Inherently biodegradable, not fulfilling specific criteria”.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria
Type of water:
freshwater

Additional information

In a modified MITI test for ready biodegradation (METI, 1976), 14.5% degradation was observed after 21 days, based on BOD. Degradation by total organic carbon (TOC) was 27% (average of 19 and 34%) after 21 days. Degradation by GC analysis was 27% (average of 21 and 31%) after 21 days. Based on these results, MEKO is not readily biodegradable. In an OECD Guideline 302B (inherent biodegradability) test (BASF, 1978), 35% biodegradation was observed after 5 days, 51% after 8 days and 70% degradation was observed after 14 days, based on DOC removal. Thus the substance is inherently biodegradable but does not fulfil specific criteria (≥70 % mineralisation (DOC removal) within 7 d).