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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From August 02, 2012 to October 15,2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes
Specific details on test material used for the study:
Lot #: SC00003617
Purity: isomer n-alpha 51%, isomer n-beta 10%, isomer iso-alpha 20% and isomer iso-beta 6%
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sludge from a biological WWTP of the city of Geneva treating predominatly domestic sewage
- Dry weight of suspended solids: 3.56 g/l, diluted to 1.53 g/l
Duration of test (contact time):
54 d
Initial conc.:
20 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 21.4 °C - 22.6°C


Key result
Parameter:
% degradation (O2 consumption)
Value:
81
Sampling time:
28 d
Details on results:
The 10-day window criterion is fulfilled (21% biodegradation on day 4 and 74% on day 14). The biodegradation achieved after 28 days was 81%.
The test was extended beyond the standard 28 days to 54 days. The degradation level remained at approximately 80%.
Methylionanthem 100% did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.
Validity criteria fulfilled:
yes
Remarks:
Degradation of reference substance exceeded 60% after 14d verifying activity of inoculum and the difference between replicates was less than 20%.
Interpretation of results:
readily biodegradable
Conclusions:
Methylionantheme 100% undergoes 81% biodegradation after 28 days in the test conditions. The 10-day window criterion is also fulfilled. Thus, methylionantheme 100% should be regarded as readily biodegradable according to this test.

Methylionantheme 100% did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

Methylionantheme 100% is a mixture of isomers. ECHA guidance (version 3.0, June 2017, section R.11.4.2.2.3) states that “If the selected test item consists of sufficiently similar structures and is shown to meet the stringent ultimate ready biodegradation test criterion (>60% in 28 days), it can be concluded that the underlying constituents comprising the complex substance are not expected to be persistent”. Thus Methylionantheme 100% and its underlying isomeric constituents are considered to be readily biodegradable and not persistent in the environment.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
From Jan 17, 2012 to April 27,2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes
Specific details on test material used for the study:
Cheminal Nature: 3-methyl-4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-buten-2-one (main component)
CAS: 127-51-5
Givaudan Code: 3510003
Lot: VE00185643
Purity 93.4%
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sludge from a biological WWTP of the city of Geneva treating predominatly domestic sewage
Duration of test (contact time):
43 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 22-23.5°C
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
71
Sampling time:
28 d
Details on results:
The 10-day window criterion is fulfilled (34% biodegradation on day 7 and 66% on day 17).
The test was extended beyond the standard 28 days to 43 days. The biodegradation levels remained at 67-71%
Validity criteria fulfilled:
yes
Remarks:
Degradation of reference substance exceeded the pass level of 60% after 14d verifying activity of inoculum and the difference between replicates was less than 20%.
Interpretation of results:
readily biodegradable
Conclusions:
ISORALDEINE Cetone Alpha undergoes 71% biodegradation after 28 days (67% after 43 days) in the test conditions. The 10 -day window criterion is also fulfilled (34% biodegradation on day 7 and 66% on day 17). Isoraldeine Cetone Alpha did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration. Thus, ISORALDEINE CETONE ALPHA should be regarded as READILY BIODEGRADABLE according to this test.

The ready biodegradability result of ISORALDEINE CETONE ALPHA is being used to support the biodegradation assessment of the registration substance, Reaction mass of (E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-2-one and (E)-1-(2,6,6-trimethylcyclohex-2-en-1-yl)pent-1-en-3-one and (E)-1-(2,6,6-trimethylcyclohex-1-en-1-yl)pent-1-en-3-one. ISORALDEINE CETONE ALPHA is a monoconstituent substance, containing 3-methyl-4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-buten-2-one as its main component. This is one of the isomers present in the registered substance. The registered substance contains a mixture of n-isomers and iso-isomers. The iso-isomers might be expected to be less easily degraded because of the branching in the side chain. The readily biodegradability of ISORALDEINE CETONE APLHA confirms that the iso-isomers present in the registered substance are readily biodegradable.

Description of key information

Based on two valid ready biodegradability screening studies the registered substance and its underlying isomeric constituents are considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The registered substance is a multi-constituent substance, Reaction mass of (E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-2-one and (E)-1-(2,6,6-trimethylcyclohex-2-en-1-yl)pent-1-en-3-one and (E)-1-(2,6,6-trimethylcyclohex-1-en-1-yl)pent-1-en-3-one. Other components present are isomers which are described as impurities in the REACH registration because they are typically present at < 10%. The total content of the isomers is > 97% (based on identified components present at ≥ 1%, see GCMS data in section 1.4 of this IUCLID REACH dossier).

The individual isomers present in the registered substance are expected to exhibit similar biodegradation profiles as a result of similar chemical functionality (unsaturated aliphatic ketones) and similar carbon skeletons (i.e. arrangement of atoms). The only structural difference between them is the position of the double bond associated with the cyclohexyl ring and/or the position of the methyl group in the side chain (see generic structure in attachment). Changes in the position of the double bond are not expected to significantly affect biodegradation properties. However, the position of the methyl group may have an impact on biodegradation potential with the iso-methyl ionone isomers being potentially less easily biodegraded than the n-methyl ionone isomers due to the increased branching of the side chain.

One commercial quality of the registered substance has been tested in the OECD 301F Manometric Respiratory Test : Methylionantheme 100% (Key Study, Givaudan Study Number 12 -E166). The level of degradation achieved after 28 days was 81%. The 10-day window criterion was also fulfilled. Thus, methylionantheme 100% should be regarded as readily biodegradable according to this test. The test item is described in the biodegradation study report as having a purity of isomer n-alpha (51%), isomer n-beta (10%), isomer iso-alpha (20%) and isomer iso-beta (6%). ECHA guidance (version 3.0, June 2017, section R.11.4.2.2.3) states that “If the selected test item consists of sufficiently similar structures and is shown to meet the stringent ultimate ready biodegradation test criterion (>60% in 28 days), it can be concluded that the underlying constituents comprising the complex substances are not expected to be persistent”.

An OECD 301F study is available for Isoraldeine Cetone Alpha (Supporting Study, Givaudan Study Number 12 -E010). This is a mono constituent substance, containing (E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-2-one as its major constituent and having a total iso-methyl ionone content of >98%. The level of degradation achieved after 28 days was 71%. The 10-day window criterion was also fulfilled. Thus, Isoraldeine Cetone Alpha should be regarded as readily biodegradable according to this test.

The fact that both test substances passed the stringent criteria of a ready biodegradability screening test indicates that both groups of isomers are readily biodegradable. Thus the registered substance and its underlying isomeric constituents are considered to be readily biodegradable and not persistent in the environment.