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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: screening test, other
Type of information:
(Q)SAR
Adequacy of study:
key study
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 adequate and reliable documentation / justification
Remarks:
The value is not an experimental result. However, the QSAR model is recommended by the ECHA guidance on information requirements and chemical safety assessment, and is well documented with regard to validation parameters according to OECD principles. Moreover, the substance is fully characterised towards the applicability domain.
Justification for type of information:
1. SOFTWARE
EPI Suite version 4.1 (U.S. Environmental Protection Agency)

2. MODEL (incl. version number)
BIOWIN version 4.10

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CAS number: 1493-27-2
SMILES: O=N(=O)c(c(F)ccc1)c1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: BIOWIN estimates the probability of rapid aerobic and anaerobic biodegradation of an organic compound in the presence of mixed populations of environmental microorganisms. BIOWIN contains seven separate models. This version (v4.10) designates the models as follows:
Biowin1 = linear probability model
Biowin2 = nonlinear probability model
(Biowin 1 and 2 are intended to convey a general indication of biodegradability under aerobic conditions, and not for any particular medium)
Biowin3 = expert survey ultimate biodegradation model
Biowin4 = expert survey primary biodegradation model
(Biowin3 and 4 yield estimates for the time required to achieve complete ultimate and primary biodegradation in a typical or "evaluative" aquatic environment)
Biowin5 = MITI linear model
Biowin6 = MITI nonlinear model
(Biowin5 and 6 are predictive models for assessing a compound’s biodegradability in the Japanese MITI ready biodegradation test; i.e. OECD 301C)
Biowin7 = anaerobic biodegradation model
(Biowin7 is a model predictive of degradation in a typical anaerobic digester)

- Unambiguous algorithm: Biodegradability estimates are based upon fragment constants that were developed using multiple linear or non-linear regression analyses, depending on the model. A discussion of the methodology used to derive the linear and non-linear fragment constants in the first two models is presented in a journal article by Howard et al. (1992). The same basic methodology was used for all the other models, and abbreviated descriptions may be found in the corresponding publications (Boethling et al. 1994, Tunkel et al. 2000, Meylan et al. 2007).

- Defined domain of applicability: The intended application domain of EPI Suite is organic chemicals. Inorganic and organometallic chemicals are generally outside the domain. The following molecular weight ranges are covered by the different models of BIOWIN:
Biowin1 and 2: 31.06 to 697.7 g/mol
Biowin3 and 4: 53.06 to 697.65 g/mol
Biowin5 and 6: 30.02 to 959.2 g/mol
Biowin7: 46.07 to 885.46 g/mol
The fragments and coefficient factor descriptors covered by BIOWIN, the maximum number of the fragment that occurs in any individual compound and the number of individual compounds having the fragment in the dataset can be found in Appendix D of the BIOWIN Help.

- Appropriate measures of goodness-of-fit and robustness and predictivity: Model accuracy and validation are detailed for each model in the dedicated section of the BIOWIN help. As a matter of concision, only classification performance for the training/validation sets of the different models were provided here in the field “Any other information on materials and methods incl. tables”. For further details, it is referred to the BIOWIN help.

- Mechanistic interpretation: Biodegradability estimates are based upon fragment coefficients that were developed using multiple linear or non-linear regression analyses, depending on the model. The fragment coefficients used in version 4.10 are listed in Appendix D of the BIOWIN Help.
Biowin1 and 2: The fragment coefficients were used to determine the biodegradation probability for each compound. A biodegradation probability greater than or equal to 0.5 is considered as "biodegrades fast". A biodegradation probability less than 0.5 is considered as "does not biodegrades fast".
Biowin3 and 4: The ultimate or primary rating of a compound is calculated based on fragment coefficients. The degradation timeframe is then assigned depending on the calculated rating. For ratings of “> 4.75 to 5”, “> 4.25 to 4.75”, “> 3.75 to 4.25”, “> 3.25 to 3.75”, “> 2.75 to 3.25”, “>2.25 to 2.75”, “> 1.75 to 2.25” and “<1.75”, the conclusions are “hours”, “hours to days”, “days”, “days to weeks”, “weeks”, “weeks to months”, “months” and “recalcitrant”, respectively.
Biowin5 and 6: The fragment coefficients were used to determine the biodegradation probability for each compound. A biodegradation probability greater than or equal to 0.5 is considered as "readily degradable". A biodegradation probability less than 0.5 is considered as "not readily degradable".
Biowin7: The fragment coefficients were used to determine the biodegradation probability for each compound. A biodegradation probability greater than or equal to 0.5 is considered as "biodegrades fast". A biodegradation probability less than 0.5 is considered as "does not biodegrades fast".
Ready Biodegradability Prediction: This prediction appears at the end of the BIOWIN prediction results. The criteria for the “YES” or “NO” prediction are as follows: if the Biowin3 result is "weeks" or faster (i.e. days, days to weeks, or weeks) AND the Biowin5 probability is >= 0.5, then the prediction is “YES” (readily biodegradable). If this condition is not satisfied, the prediction is “NO” (not readily biodegradable).

5. APPLICABILITY DOMAIN
- Descriptor domain: The molecular weight of the target chemical (2FNB) is 141.1 g/mol, hence covered by the seven models of BIOWIN (see above).

- Structural and mechanistic domains: The fragments found in the target chemical (2FNB) are included in the list of fragments of the BIOWIN models and the occurrence of each fragment does not exceed the maximum number of that fragment that occurs in any individual compound of the training sets (see detailed data in “Any other information on results incl. tables”).

6. ADEQUACY OF THE RESULT
As above described, the QSAR model is valid with respect to the five OECD principles on scientific validity (a defined endpoint, an unambiguous algorithm, a defined domain of applicability, appropriate measures of goodness-of-fit / robustness / predictivity, a mechanistic interpretation). The target substance (2FNB) was demonstrated to fall within the applicability domain of the models for both molecular weight and fragments. The present prediction is thus adequate to be used as a key study to conclude on the ready biodegradability potential.

Data source

Reference
Reference Type:
other: QSAR
Title:
Unnamed
Year:
2019

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
QSAR estimation using BIOWIN version 4.10 (EPI Suite version 4.1, U.S. Environmental Protection Agency). The methodology of the BIOWIN models is described in:
- Howard, P.H., Boethling, R.S., Stiteler, W.M., Meylan, W.M., Hueber, A.E., Beauman, J.A., Larosche, M.E. 1992. Predictive model for aerobic biodegradability developed from a file of evaluated biodegradation data. Environ. Toxicol. Chem. 11:593-603.
- Boethling, R.S., Howard, P.H., Meylan, W., Stiteler, W., Beaumann, J., Tirado, N. 1994. Group contribution method for predicting probability and rate of aerobic biodegradation. Environ. Sci. Technol. 28:459-65.
- Tunkel, J., Howard, P.H., Boethling, R.S., Stiteler,W., Loonen, H. 2000. Predicting Ready Biodegradability in the Japanese Ministry of International Trade and Industry Test. Environ. Toxicol. Chem. 19:2478-2485.
- Meylan, W., Boethling, R.S., Aronson, D., Howard, P., Tunkel, J. 2007. Chemical structure-based predictive model for methanogenic anaerobic biodegradation potential. Environ. Toxicol. Chem. 26:1785-1792.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Identity: 2-fluoronitrobenzene
CAS No.: 1493-27-2
Specific details on test material used for the study:
SMILES notation: O=N(=O)c(c(F)ccc1)c1

Results and discussion

% Degradation
Remarks on result:
not readily biodegradable based on QSAR/QSPR prediction

Any other information on results incl. tables

BIOWIN predictions for 2FNB:

 

Type

Num

Fragment description

Coeff.

Value

Biowin1

Frag

1

Aromatic fluoride [-F]

-0.8100

-0.8100

Frag

1

Aromatic nitro [-NO2]

-0.3050

-0.3050

MolWt

*

Molecular Weight Parameter

 

-0.0672

Const

*

Equation Constant

 

0.7475

RESULT

Biowin1 (Linear Biodeg Probability)

 

-0.4347

CONCLUSION Biowin1: Does NOT Biodegrade Fast

Biowin2

Frag

1

Aromatic fluoride [-F]

-10.5318

-10.5318

Frag

1

Aromatic nitro [-NO2]

-2.5086

-2.5086

MolWt

*

Molecular Weight Parameter

 

-2.0037

RESULT

Biowin2 (Non-Linear Biodeg Probability)

 

0.0000

CONCLUSION Biowin2: Does NOT Biodegrade Fast

Biowin3

Frag

1

Aromatic fluoride [-F]

-0.4069

-0.4069

Frag

1

Aromatic nitro [-NO2]

-0.1696

-0.1696

MolWt

*

Molecular Weight Parameter

 

-0.3118

Const

*

Equation Constant

 

3.1992

RESULT

Biowin3 (Survey Model - Ultimate Biodeg)

 

2.3108

CONCLUSION Biowin3: Weeks-Months

Biowin4

Frag

1

Aromatic fluoride [-F]

0.0135

0.0135

Frag

1

Aromatic nitro [-NO2]

-0.1084

-0.1084

MolWt

*

Molecular Weight Parameter

 

-0.2036

Const

*

Equation Constant

 

3.8477

RESULT

Biowin4 (Survey Model - Primary Biodeg)

 

3.5492

CONCLUSION Biowin4: Days-Weeks

Biowin5

Frag

1

Aromatic nitro [-NO2]

-0.1876

-0.1876

Frag

1

Fluorine [-F]

0.0174

0.0174

Frag

4

Aromatic-H

0.0082

0.0329

MolWt

*

Molecular Weight Parameter

 

-0.4198

Const

*

Equation Constant

 

0.7121

RESULT

Biowin5 (MITI Linear Biodeg Probability)

 

0.1550

CONCLUSION Biowin5: NOT Readily Degradable

Biowin6

Frag

1

Aromatic nitro [-NO2]

-2.4035

-2.4035

Frag

1

Fluorine [-F]

-3.9878

-3.9878

Frag

4

Aromatic-H

0.1201

0.4806

MolWt

*

Molecular Weight Parameter

 

-4.0735

RESULT

Biowin6 (MITI Non-Linear Biodeg Probability)

 

0.0006

CONCLUSION Biowin6: NOT Readily Degradable

Biowin7

Frag

1

Aromatic fluoride [-F]

0.0000

0.0000

Frag

1

Aromatic nitro [-NO2]

-0.2141

-0.2141

Frag

1

Fluorine [-F]

0.0000

0.0000

Frag

4

Aromatic-H

-0.0954

-0.3817

Const

*

Equation Constant

 

0.8361

RESULT

Biowin7 (Anaerobic Linear Biodeg Prob)

 

0.2403

CONCLUSION Biowin7: Does NOT Biodegrade Fast

Ready Biodegradability Prediction

CONCLUSION: NO

 

Applicability domain:

The molecular weight of the target chemical (2FNB) is 141.1 g/mol, hence covered by the seven models of BIOWIN (see above). The fragments found in the target chemical (2FNB) are included in the list of fragments of the BIOWIN models and the occurrence of each fragment does not exceed the maximum number of that fragment that occurs in any individual compound of the training sets as it can be seen below in the extract from Appendix D of the BIOWIN Help:

Models

Aromatic fluoride [-F]

Aromatic nitro [-NO2]

Fluorine [-F]

Aromatic-H

Coef.

Max

Number

Coef.

Max

Number

Coef.

Max

Number

Coef.

Max

Number

Biowin1

-0.8100

1

1

-0.3050

2

14

-

-

-

-

-

-

Biowin2

-10.5318

-2.5086

-

-

Biowin3

-0.4069

1

1

-0.1696

2

13

-

-

-

-

-

-

Biowin4

0.0135

-0.1084

-

-

Biowin5

-

-

-

-0.1876

2

33

0.0174

27

10

0.0082

15

302

Biowin6

-

-2.4035

-3.9878

0.1201

Biowin7

0.0000

Not listed

-0.2141

2

4

0.0000

Not listed

-0.0954

13

94

Applicant's summary and conclusion

Interpretation of results:
not readily biodegradable
Conclusions:
2-Fluoronitrobenzene is considered as not readily biodegradable based on predictions from the BIOWIN QSAR.
Executive summary:

The ready biodegradability potential of 2-fluoronitrobenzene was predicted using the seven models of the recommended QSAR BIOWIN v4.10 (EPI Suite version 4.1, U.S. Environmental Protection Agency), based upon fragment constants that were developed using multiple linear or non-linear regression analyses, depending on the model. The substance is within the applicability domain of the models for both molecular weight and fragments. The predictions reported by the seven BIOWIN models support the conclusion that 2-fluoronitrobenzene has to be considered as not readily biodegradable.