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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:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification
Justification for type of information:
The supporting QMRF report has been attached
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Principles of method if other than guideline:
The data is predicted using the OECD QSAR toolbox version 3.4 with logKow as the primary descriptor.
GLP compliance:
not specified
Test material information:
Composition 1
Specific details on test material used for the study:
- Name of the test material: 2-isopropyl-5-methylcyclohexanone
- Molecular formula: C10H18O
- Molecular weight: 154.2512 g/mol
- Substance type: Organic
- Physical state: Liquid
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Duration of test (contact time):
28 d
Parameter followed for biodegradation estimation:
CO2 evolution
Key result
Parameter:
% degradation (CO2 evolution)
Value:
31.6
Sampling time:
28 d
Remarks on result:
other: Other details not known
Details on results:
Test substance undergoes 31.60% degradation by CO2 evolution parameter in 28 days

The prediction was based on dataset comprised from the following descriptors: "CO2 evolution"
Estimation method: Takes average value from the 5 nearest neighbours
Domain  logical expression:Result: In Domain

((((((((("a" and ("b" and ( not "c") )  )  and ("d" and ( not "e") )  )  and "f" )  and "g" )  and "h" )  and ("i" and ( not "j") )  )  and ("k" and ( not "l") )  )  and "m" )  and ("n" and "o" )  )

Domain logical expression index: "a"

Referential boundary: The target chemical should be classified as Neutral Organics by US-EPA New Chemical Categories

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as No alert found by DNA binding by OASIS v.1.4

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as AN2 OR AN2 >> Nucleophilic addition reaction with cycloisomerization OR AN2 >> Nucleophilic addition reaction with cycloisomerization >> Hydrazine Derivatives OR AN2 >> Schiff base formation by aldehyde formed after metabolic activation OR AN2 >> Schiff base formation by aldehyde formed after metabolic activation >> Geminal Polyhaloalkane Derivatives OR Non-covalent interaction OR Non-covalent interaction >> DNA intercalation OR Non-covalent interaction >> DNA intercalation >> Acridone, Thioxanthone, Xanthone and Phenazine Derivatives OR Non-covalent interaction >> DNA intercalation >> DNA Intercalators with Carboxamide and Aminoalkylamine Side Chain OR Radical OR Radical >> Generation of ROS by glutathione depletion (indirect) OR Radical >> Generation of ROS by glutathione depletion (indirect) >> Haloalkanes Containing Heteroatom OR Radical >> Radical mechanism via ROS formation (indirect) OR Radical >> Radical mechanism via ROS formation (indirect) >> Acridone, Thioxanthone, Xanthone and Phenazine Derivatives OR Radical >> Radical mechanism via ROS formation (indirect) >> Geminal Polyhaloalkane Derivatives OR Radical >> Radical mechanism via ROS formation (indirect) >> Hydrazine Derivatives OR SN1 OR SN1 >> Carbenium ion formation OR SN1 >> Carbenium ion formation >> Alpha-Haloethers OR SN2 OR SN2 >> Acylation involving a leaving group after metabolic activation OR SN2 >> Acylation involving a leaving group after metabolic activation >> Geminal Polyhaloalkane Derivatives OR SN2 >> Alkylation, nucleophilic substitution at sp3-carbon atom OR SN2 >> Alkylation, nucleophilic substitution at sp3-carbon atom >> Haloalkanes Containing Heteroatom OR SN2 >> Alkylation, nucleophilic substitution at sp3-carbon atom >> Sulfonates and Sulfates OR SN2 >> Direct nucleophilic attack on diazonium cation OR SN2 >> Direct nucleophilic attack on diazonium cation >> Hydrazine Derivatives OR SN2 >> Nucleophilic substitution at sp3 Carbon atom OR SN2 >> Nucleophilic substitution at sp3 Carbon atom >> Haloalkanes Containing Heteroatom OR SN2 >> Nucleophilic substitution at sp3 carbon atom after thiol (glutathione) conjugation OR SN2 >> Nucleophilic substitution at sp3 carbon atom after thiol (glutathione) conjugation >> Geminal Polyhaloalkane Derivatives OR SN2 >> SN2 at sp3-carbon atom OR SN2 >> SN2 at sp3-carbon atom >> Alpha-Haloethers by DNA binding by OASIS v.1.4

Domain logical expression index: "d"

Referential boundary: The target chemical should be classified as No alert found by DNA binding by OECD

Domain logical expression index: "e"

Referential boundary: The target chemical should be classified as Michael addition OR Michael addition >> P450 Mediated Activation to Quinones and Quinone-type Chemicals OR Michael addition >> P450 Mediated Activation to Quinones and Quinone-type Chemicals >> Arenes OR SN1 OR SN1 >> Nitrenium Ion formation OR SN1 >> Nitrenium Ion formation >> Aromatic azo OR SN1 >> Nitrenium Ion formation >> Aromatic nitro OR SN1 >> Nitrenium Ion formation >> Tertiary aromatic amine by DNA binding by OECD

Domain logical expression index: "f"

Referential boundary: The target chemical should be classified as days - weeks by Biodeg primary (Biowin 4) ONLY

Domain logical expression index: "g"

Referential boundary: The target chemical should be classified as Does NOT Biodegrade Fast by Biodeg probability (Biowin 5) ONLY

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as Bioavailable by Lipinski Rule Oasis ONLY

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Non-Metals by Groups of elements

Domain logical expression index: "j"

Referential boundary: The target chemical should be classified as Halogens OR Metalloids by Groups of elements

Domain logical expression index: "k"

Referential boundary: The target chemical should be classified as Group 14 - Carbon C AND Group 16 - Oxygen O by Chemical elements

Domain logical expression index: "l"

Referential boundary: The target chemical should be classified as Group 15 - Nitrogen N by Chemical elements

Domain logical expression index: "m"

Referential boundary: The target chemical should be classified as Basesurface narcotics by Acute aquatic toxicity MOA by OASIS ONLY

Domain logical expression index: "n"

Parametric boundary:The target chemical should have a value of Molecular weight which is >= 148 Da

Domain logical expression index: "o"

Parametric boundary:The target chemical should have a value of Molecular weight which is <= 196 Da

Validity criteria fulfilled:
not specified
Interpretation of results:
not readily biodegradable
Conclusions:
The test chemical 2-isopropyl-5-methylcyclohexanone was estimated to be not readily biodegradable in water.
Executive summary:

Biodegradability of 2 -isopropyl-5 -methylcyclohexanone is predicted using QSAR toolbox version 3.4. Test substance undergoes 31.60% degradation by CO2 evolution parameter in 28 days. Thus, based on percentage degradation, the test chemical 2-isopropyl-5-methylcyclohexanone was estimated to be not readily biodegradable in water.

Description of key information

Biodegradability of 2 -isopropyl-5 -methylcyclohexanone (CAS no. 1074-95-9) is predicted using OECD QSAR toolbox version 3.4 (2017). Test substance undergoes 31.60% degradation by CO2 evolution parameter in 28 days. Thus, based on percentage degradation, the test chemical 2 -isopropyl-5 -methylcyclohexanone was estimated to be not readily biodegradable in water.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Various predicted data for the target compound 2-isopropyl-5-methylcyclohexanone (CAS No. 1074-95-9) and 3 supporting studies (1 study from authoritative database and 2 studies from secondary source) for its closest read across substance with logKow as the primary descriptor were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done by SSS (2017) by using QSAR toolbox version 3.4 with log Kow as the primary descriptor, percentagebiodegradability of test chemical 2 -isopropyl-5 -methylcyclohexanone (CAS no. 1074-95-9) was estimated. Test substance undergoes 31.60% degradation by CO2 evolution parameter in 28 days. Thus, based on percentage degradation, the test chemical 2-isopropyl-5-methylcyclohexanone was estimated to be not readily biodegradable in water.

 

In another prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compound 2 -isopropyl-5 -methylcyclohexano ne (CAS no. 1074 -95 -9) in the presence of mixed populations of environmental microorganisms was estimated. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI LInear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that 2 -isopropyl-5 -methylcyclohexanone is expected to be not readily biodegradable.

 

Biodegradation study was conducted for 20 days for evaluating the percentage biodegradability of read across substance Dipropylene glycol monomethyl ether (CAS no. 34590-94-8) (HSDB, 2016). The percentage degradation of read across substance was determined to 0, 0 and 31% degradation by ThOD parameter in 5, 10 and 20 days, respectively. Thus, based on percentage degradation, Dipropylene glycol monomethyl ether was considered to be not readily biodegradable in nature.

 

Another weight of evidence study of biodegradation was conducted for 28 days for evaluating the percentage biodegradability of read across substance Dipropylene glycol monomethyl ether (CAS no. 34590-94-8) (OECD SIDS, 2001). Initial test substance conc. used in the study was10 mg/l, respectively. The percentage degradation of read across substance was determined to be 34% degradation in 28 days. At a concentration of 20 mg/l degradation was <10% after 28 days. Thus, based on percentage degradation, Dipropylene glycol monomethyl ether was considered to be not readily biodegradable in nature.

 

In addition to the above weight of evidence studies, another biodegradation study of read across substance Dipropylene glycol monobutyl ether (CAS no. 29911-28-2) from secondary source (OECD SIDS, 2003), was carried out for 28 days for evaluating the percentage biodegradability of read across substance Dipropylene glycol monobutyl ether. The study was performed according to OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test). Initial test substance conc. used in the study was 0, 1.86, or 9.29 mg/l, respectively. Domestic sewage was used as a test inoculum collected from a local municipal sewage treatment facility. To test for its ready biodegradability potential, read across chemical was incubated for 28 days in continuously agitated closed bottles in the dark at two concentrations with inoculum (secondary effluent) collected from a local municipal sewage treatment facility. The incubation temperature of the water was 19.7-20.0°C, pH ranged from 7.2 to 7.4, hardness was not reported, and the concentration of inoculum was one droplet per liter of test solution. Oxygen concentration was the measured variable. Degradation of read across chemical was monitored by assessing the dissipation of oxygen in the test solution over time (i.e., measuring dissolved oxygen content with an oxygen electrode at various time points). Oxygen content was measured (in duplicate bottles) on days 0, 5, 15, and 28. Degradation was calculated by dividing the biochemical oxygen demand (BOD) expressed as mg O2 per mg DPnB, by the theoretical oxygen demand (ThOD).The percentage degradation of read across substance was determined to be 0% by %ThOD parameter in 28 days. Thus, based on percentage degradation, Dipropylene glycol monobutyl ether was considered to be not readily biodegradable in water.

 

On the basis of above results for target chemical 2-isopropyl-5-methylcyclohexanone (study 1, 2 from OECD QSAR toolbox 3.4 and EPI suite) and for its read across substance (study 3 from authoritative database HSDB and study 4 and 5 from secondary source), it can be concluded that the test substance 2 -isopropyl-5 -methylcyclohexanone can be expected to be not readily biodegradable in nature.