5-[(2,3-dihydro-6-methyl-2-oxo-1H-benzimidazol-5-yl)azo]barbituric acid

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

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:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: Deutsche Einhheitsverfahren DEV H-5

Deviations:

yes

Remarks:

see "Principles of method if other than guideline"

Principles of method if other than guideline:

Instead of testing various dilutions of a waste-water the test substance was tested in 5 concentrations chosen on the basis of the TOD (Theoretical Oxygen Demand).

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial, non-adapted

Details on inoculum:

Polyvalent waste-water bacteria collected on February 18, 1981, in the aeration unit of the sewage treatment plant of Rheinfelden (Switzerland).

Duration of test (contact time):

5 d

Initial conc.:

> 1 - < 5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

- Vessels: 100 mL BOD-flasks
- Test concentrations: Blank, 1, 2, 3, 4, 5 mg/L
- Test medium:
- 8.5 mg KH2PO4
- 21.75 mg K2HPO4
- 33.4 mg NaHPO4
- 1.7 mg NH4CI
- 22.5 mg MgSO4.7H2O
- 27.5 mg CaCl2.2H2O
- 0.25 mg FeCl3.6H2O
- Temperature: 20±1 °C
- Measurement : Oxygen concentration in mg/L with ORION-Electrode Type 97-08

Reference substance:

benzoic acid, sodium salt

Test performance:

No abnormalities were seen during the performance of the test.

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

5 d

Details on results:

A BOD5 value of 0 mg O2/ mg test substance was observed at all tested concenterations. The TOD was calculated to be 0.384 mg O2/mg test substance.

Parameter:

BOD5

Value:

0 mg O2/g test mat.

Results with reference substance:

The BOD value for the reference substance (sodium benzoate) was measured with 1.275 mg Oxygen/mg (equal to 95.8 % Biodegradation).

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The test substance is not readily biodegradable.

Reference 2

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, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

Please refer to the QMRF and QPRF files provided under the section attached justification.

Principles of method if other than guideline:

Estimation of results of OECD screening tests on ready biodegradation in water: CATALOGIC (v5.13.1.156) BOD 28 days MITI (OECD 301C) v11.15)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Duration of test (contact time):

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

ca. 10

Sampling time:

28 d

Details on results:

Model domain similarity:
- Parametric domain: 100%
- Structural domain: 65% (35% unknown)
- Mechanistic domain: 100%

Interpretation of results:

other: not readily biodegradable (according to OECD criteria)

Reference 3

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 adequate and reliable documentation / justification

Justification for type of information:

Please refer to the QMRF and QPRF files provided under the section attached justification.

Principles of method if other than guideline:

Prediction of ready biodegradability based on six QSAR models

GLP compliance:

no

Oxygen conditions:

aerobic

Duration of test (contact time):

28 d

Key result

Parameter:

other: biodegradation

Sampling time:

28 d

Remarks on result:

other: Biowin1: Does Not Biodegrade Fast; Biowin2: Does Not Biodegrade Fast; Biowin3: Months; Biowin4: Days-Weeks; Biowin5: Does Not Biodegrade Fast; Biowin6: Does Not Biodegrade Fast; Biowin7: Does Not Biodegrade Fast; Ready Biodegradability Prediction: NO

BIOWIN v4.10 Results

Biowin1 (Linear Model Prediction): Does Not Biodegrade Fast

Biowin2 (Non-Linear Model Prediction): Does Not Biodegrade Fast

Biowin3 (Ultimate Biodegradation Timeframe): Months

Biowin4 (Primary Biodegradation Timeframe): Days-Weeks

Biowin5 (MITI Linear Model Prediction): Does Not Biodegrade Fast

Biowin6 (MITI Non-Linear Model Prediction): Does Not Biodegrade Fast

Biowin7 (Anaerobic Model Prediction): Does Not Biodegrade Fast

Ready Biodegradability Prediction: NO

 

TYPE	NUM	Biowin1 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	1	Alkyl substituent on aromatic ring	0.0547	0.0547
Frag	1	Azo group  [-N=N-]	-0.2418	-0.2418
MolWt	*	Molecular Weight Parameter		-0.1439
Const	*	Equation Constant		0.7475
RESULT	Biowin1 (Linear Biodeg Probability)			0.4165

 

TYPE	NUM	Biowin2 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	1	Alkyl substituent on aromatic ring	0.5771	0.5771
Frag	1	Azo group  [-N=N-]	-8.2194	-8.2194
MolWt	*	Molecular Weight Parameter		-4.2920
RESULT	Biowin2 (Non-Linear Biodeg Probability)			0.0001

A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast

A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

 

TYPE	NUM	Biowin3 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	1	Alkyl substituent on aromatic ring	-0.0749	-0.0749
Frag	1	Azo group  [-N=N-]	-0.3004	-0.3004
MolWt	*	Molecular Weight Parameter		-0.6679
Const	*	Equation Constant		3.1992
RESULT	Biowin3 (Survey Model - Ultimate Biodeg)			2.1560

 

 

TYPE	NUM	Biowin4 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	1	Alkyl substituent on aromatic ring	-0.0685	-0.0685
Frag	1	Azo group  [-N=N-]	-0.0528	-0.0528
MolWt	*	Molecular Weight Parameter		-0.4361
Const	*	Equation Constant		3.8477
RESULT	Biowin4 (Survey Model - Primary Biodeg)			3.2903

 

Result Classification:  5.00 -> hours    4.00 -> days   3.00 -> weeks

(Primary & Ultimate)   2.00 -> months   1.00 -> longer

 

 

TYPE	NUM	Biowin5 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	1	Azo group  [-N=N-]	-0.0459	-0.0459
Frag	1	Aromatic-CH3	0.0415	0.0415
Frag	2	Aromatic-H	0.0082	0.0164
Frag	1	-CH - [cyclic]	0.0124	0.0124
MolWt	*	Molecular Weight Parameter		-0.8992
Const	*	Equation Constant		0.7121
RESULT	Biowin5 (MITI Linear Biodeg Probability)			-0.1626

 

 

TYPE	NUM	Biowin6 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	1	Azo group  [-N=N-]	-10.6129	-10.6129
Frag	1	Aromatic-CH3	0.3072	0.3072
Frag	2	Aromatic-H	0.1201	0.2403
Frag	1	-CH - [cyclic]	-0.1295	-0.1295
MolWt	*	Molecular Weight Parameter		-8.7256
RESULT	Biowin6 (MITI Non-Linear Biodeg Probability)			0.0000

 

A Probability Greater Than or Equal to 0.5 indicates --> Readily Degradable

A Probability Less Than 0.5 indicates --> NOT Readily Degradable

 

 

TYPE	NUM	Biowin7 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	1	Alkyl substituent on aromatic ring	-0.1145	-0.1145
Frag	1	Azo group  [-N=N-]	0.0000	0.0000
Frag	1	Aromatic-CH3	-0.2573	-0.2573
Frag	2	Aromatic-H	-0.0954	-0.1909
Frag	1	-CH - [cyclic]	0.0395	0.0395
Const	*	Equation Constant		0.8361
RESULT	Biowin7 (Anaerobic Linear Biodeg Prob)			0.3129

 

A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast

A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

 

Ready Biodegradability Prediction: (YES or NO)

----------------------------------------------

Criteria for the YES or NO prediction: If the Biowin3 (ultimate survey

model) result is "weeks" or faster (i.e. "days", "days to weeks", or

"weeks" AND the Biowin5 (MITI linear model) probability is >= 0.5, then

the prediction is YES (readily biodegradable). If this condition is not

satisfied, the prediction is NO (not readily biodegradable). This method

is based on application of Bayesian analysis to ready biodegradation data

(see Help). Biowin5 and 6 also predict ready biodegradability, but for

degradation in the OECD301C test only; using data from the Chemicals

Evaluation and Research Institute Japan (CERIJ) database.

Interpretation of results:

other: not readily biodegradable

Description of key information

The test substance is not readily biodegradable according OECD criteria.

Additional information

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For the assessment of the test substance (Q)SAR results were used for aerobic biodegradability in water.The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

Therefore, further experimental studies on aerobic biodegradability in water are not provided.

Both QSAR models show that the test substance is not readily biodegradable according OECD criteria. The EPI Suite v4.10 (BIOWIN Program v4.10) calculation resulted in "not readily biodegradable". The test substance was within the applicability domain of the model. Additionally, the biodegradation was calculated by using CATALOGIC v5.13.1.156 (BOD 28 days MITI (OECD 301C) v11.15. It resulted in 10 % biodegradation after 28 d. Even though the structural domain was correct with only 65 % (35 % unknown) the results support the overall conclusion in the weight of evidence. Furthermore, none of the predicted metabolites are relevant for the subsequent PBT/vPvB assessment as they are either readily biodegradable or have logKow values << 4 which is indicative of a negligible potential to bioaccumulate.

ID	Quantity [%]	LogKow	Smiles	BOD [%]
parent	0.3783	0.4982	Cc1cc2c(cc1N=NC1C(=O)NC(=O)NC1=O)NC(=O)N2	10
metabolite	7.877	0.8346	Cc1cc2c(cc1N)NC(=O)N2	0
metabolite	0.2785	-1.9933	NC1C(=O)NC(=O)NC1=O	65
metabolite	60.79	0.5016	Cc1cc2c(cc1N=NC(C(O)=O)C(O)=O)NC(=O)N2	1
metabolite	6.333	-1.5553	NC(N)=O	81
metabolite	25.12	-0.1608	Cc1cc2c(cc1N=NC(C(N)=O)C(O)=O)NC(=O)N2	3
metabolite	5.728	-0.4342	Cc1cc2c(cc1N=NC(C(N)=O)C(N)=O)NC(=O)N2	6
metabolite	2.501	-4.8137	NC(C(O)=O)C(O)=O	58
metabolite	0.3809	-5.0761	NC(C(N)=O)C(O)=O	40
metabolite	0.4656	-1.0365	OC(=O)C(=O)C(O)=O	90
metabolite	0.2729	-1.6989	NC(=O)C(=O)C(O)=O	53
metabolite	1.008	-1.4027	OC(=O)C=O	100

Moreover, the pigment is practically insoluble and therefore considered to be essentially not bioavailable. Due to the large molecular size, cellular uptake of the pigment is unlikely. Hence intracellular biodegradation, which is the main degradation route of bacteria, is probably low. It can be concluded that the substance is likely to persist in the environment. For this reason no ready or inherent degradation studies are proposed.

Additionally, the weight-of-evidence is supported by the estimation of the BOD₅ (CIBA-GEIGY Limited 1981). It was tested according to the German Guideline H-5. In this study concentrations of 1, 2, 3, 4 and 5 mg/L of test substance, a negative and a positive control (sodium benzoate) were tested. No biodegradation was observed during the exposure period of 5 days. The BOD₅ for the test substance was 0 mg O₂/mg test substance, and the TOD was 0.384 mg O₂/mg test substance. The BOD₅ for the reference substance was measured at 1.275 mg O₂/mg which is equal to 95.8% biodegradation.

In overall conclusion, further tests on biodegradation are scientifically not justified.