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Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: screening tests
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
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Principles of method if other than guideline:
The data is predicted using the OECD QSAR toolbox version 3.3 with logKow as the primary descriptor.
GLP compliance:
not specified
Specific details on test material used for the study:
- IUPAC name: 3-methylbutyl benzoate
- Molecular formula: C12H16O2
- Molecular weight: 192.256 g/mol
- Smiles notation: c1(C(OCCC(C)C)=O)ccccc1
- InChl: 1S/C12H16O2/c1-10(2)8-9-14-12(13)11-6-4-3-5-7-11/h3-7,10H,8-9H2,1-2H3
- Substance type: Organic
- Physical state: Liquid
Oxygen conditions:
aerobic
Inoculum or test system:
other: Microorganisms
Duration of test (contact time):
28 d
Parameter followed for biodegradation estimation:
other: BOD
Key result
Parameter:
other: BOD
Value:
81.08
Sampling time:
28 d
Remarks on result:
other: Other details not known
Details on results:
Test substance undergoes 81.08% degradation by BOD in 28 days.

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

((((((((((((((("a" or "b" or "c" or "d" or "e" )  and "f" )  and "g" )  and "h" )  and "i" )  and "j" )  and "k" )  and "l" )  and ("m" and ( not "n") )  )  and "o" )  and ("p" and ( not "q") )  )  and "r" )  and ("s" and ( not "t") )  )  and "u" )  and ("v" and "w" )  )

Domain logical expression index: "a"

Referential boundary: The target chemical should be classified as Esters (Acute toxicity) by US-EPA New Chemical Categories

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as Aryl AND Carboxylic acid ester AND Isopropyl by Organic Functional groups

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as Aryl AND Carboxylic acid ester AND Isopropyl AND Overlapping groups by Organic Functional groups (nested)

Domain logical expression index: "d"

Referential boundary: The target chemical should be classified as Aliphatic Carbon [CH] AND Aliphatic Carbon [-CH2-] AND Aliphatic Carbon [-CH3] AND Aromatic Carbon [C] AND Carbonyl, olefinic attach [-C(=O)-] AND Carbonyl, one aromatic attach [-C(=O)-] AND Ester, aliphatic attach [-C(=O)O] AND Miscellaneous sulfide (=S) or oxide (=O) AND Olefinic carbon [=CH- or =C<] AND Tertiary Carbon by Organic functional groups (US EPA)

Domain logical expression index: "e"

Referential boundary: The target chemical should be classified as Aromatic compound AND Carbonic acid derivative AND Carboxylic acid derivative AND Carboxylic acid ester by Organic functional groups, Norbert Haider (checkmol)

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 Biodegrades Fast by Biodeg probability (Biowin 1) ONLY

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as Biodegrades Fast by Biodeg probability (Biowin 2) ONLY

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Biodegrades Fast by Biodeg probability (Biowin 5) ONLY

Domain logical expression index: "j"

Referential boundary: The target chemical should be classified as Biodegrades Fast by Biodeg probability (Biowin 6) ONLY

Domain logical expression index: "k"

Referential boundary: The target chemical should be classified as Does NOT Biodegrade Fast by Biodeg probability (Biowin 7) ONLY

Domain logical expression index: "l"

Referential boundary: The target chemical should be classified as weeks - months by Biodeg ultimate (Biowin 3) ONLY

Domain logical expression index: "m"

Referential boundary: The target chemical should be classified as No alert found by DNA binding by OASIS v.1.3

Domain logical expression index: "n"

Referential boundary: The target chemical should be classified as AN2 OR AN2 >> Shiff base formation after aldehyde release OR AN2 >> Shiff base formation after aldehyde release >> Specific Acetate Esters OR SN1 OR SN1 >> Nucleophilic attack after carbenium ion formation OR SN1 >> Nucleophilic attack after carbenium ion formation >> Specific Acetate Esters OR SN2 OR SN2 >> Acylation OR SN2 >> Acylation >> Specific Acetate Esters OR SN2 >> Nucleophilic substitution at sp3 Carbon atom OR SN2 >> Nucleophilic substitution at sp3 Carbon atom >> Specific Acetate Esters by DNA binding by OASIS v.1.3

Domain logical expression index: "o"

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

Domain logical expression index: "p"

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: "q"

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

Domain logical expression index: "r"

Similarity boundary:Target: CC(C)CCOC(=O)c1ccccc1
Threshold=10%,
Dice(Atom centered fragments)
Atom type; Count H attached; Hybridization

Domain logical expression index: "s"

Referential boundary: The target chemical should be classified as Not categorized by Repeated dose (HESS)

Domain logical expression index: "t"

Referential boundary: The target chemical should be classified as Allyl esters (Hepatotoxicity) Rank A OR Phthalate esters (Testicular toxicity) Rank C by Repeated dose (HESS)

Domain logical expression index: "u"

Referential boundary: The target chemical should be classified as Low (Class I) by Toxic hazard classification by Cramer (with extensions) ONLY

Domain logical expression index: "v"

Parametric boundary:The target chemical should have a value of Molecular weight which is >= 158 Da

Domain logical expression index: "w"

Parametric boundary:The target chemical should have a value of Molecular weight which is <= 222 Da

Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable
Conclusions:
The test chemical 3-methylbutyl benzoate was estimated to be readily biodegradable in water.
Executive summary:

Biodegradability of 3-methylbutyl benzoate (CAS no. 94 -46 -2) is predicted using QSAR toolbox version 3.3 with logKow as the primary descriptor. Test substance undergoes 81.08% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical 3 -methylbutyl benzoate was estimated to be readily biodegradable in water.

Description of key information

Biodegradability of 3-methylbutyl benzoate (CAS no. 94 -46 -2) is predicted using QSAR toolbox version 3.3 with logKow as the primary descriptor (2017). Test substance undergoes 81.08% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical 3 -methylbutyl benzoate was estimated to be readily biodegradable in water.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Various predicted data for the target compound 3-methylbutyl benzoate (CAS No. 94-46-2) and various supporting weight of evidence studies for its read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done by SSS (2017) using OECD QSAR toolbox version 3.3 with logKow as the primary descriptor, percentage biodegradability of test chemical 3-methylbutyl benzoate(CAS No. 94-46-2) was estimated. Test substance undergoes 81.08% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical 3 -methylbutyl benzoate was estimated to be readily biodegradable in water.

 

In another prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compound3-methylbutyl benzoate(CAS No. 94-46-2) 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 3-methylbutyl benzoate is expected to be readily biodegradable.

 

In a supporting weight of evidence study from peer reviewed journal (John J. Porter and Eric H. Snider, 1976), biodegradation study was conducted for 30 days for evaluating the percentage biodegradability of read across substance Butyl benzoate (CAS no. 136 -60 -7). Glucose-glutamic acid mixture was used as a reference substance for the biodegradation study. The results are compared with the chemical oxygen demand (COD) of the test chemical, which measures its maximum oxygen combining power; the results are also compared with the BOD test performed on a standard glucose-glutamic acid reference solution used for BOD caliberation. Reference substance i.e; glucose-glutamic acid mixture consumes 75 percent of its maximum oxygen requirement (COD) within 5 days and almost 100 percent in 30 days. Thus, based on this result, the reference substance is considered to be readily biodegradable. The percentage degradation of read across substance was determined to be 50 and 73% degradation by using BOD parameter after 5 and 30 days, respectively. The COD value of read across chemical was determined to be 2200000 mg/l, respectively. Thus, based on percentage degradation, Butyl benzoate is considered to be readily biodegradable in nature.

 

For the same read across chemical Butyl benzoate (CAS no. 136 -60 -7),biodegradation study was conducted for evaluating the percentage biodegradability of read across substance Butyl benzoate using an aerobic dilution method (HSDB, 2016). Test inoculum i.e an adapted culture was obtained from a treatment plant. Initial test substance conc. used in the study was 50 mg/l. The percentage degradation of read across substance was determined to be 100% in 24 hrs. Thus, based on percentage degradation, Butyl benzoate is considered to be readily biodegradable in nature.

 

Another weight of evidence study of biodegradation was conducted for 29 days for evaluating the percentage biodegradability of read across substance Methyl benzoate (CAS no. 93 -58 -3) (HSDB, 2016). The study was performed according to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test). Activated sludge was used as a test inoculum. Initial test substance conc. used in the study was 28 mg/l. The percentage degradation of read across substance was determined to be 62% degradation by CO2 evolution in 29 days. Thus, based on percentage degradation, Methyl benzoate is considered to be readily biodegradable in nature.

 

On the basis of above results for target chemical 3 -methylbutyl benzoate (from OECD QSAR toolbox version 3.3 and EPI Suite, 2017) and for its read across substance (from peer reviewed journal and authoritative database HSDB, 2016), it can be concluded that the test substance 3 -methylbutyl benzoate can be expected to be readily biodegradable in nature.