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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: screening test, other
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:
1. SOFTWARE
EPI Suite v4.11 Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
BIOWIN (v4.10)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".
Qualifier:
according to guideline
Guideline:
other: REACH Guidance on QSARs R.6
Principles of method if other than guideline:
Calculation based on BIOWIN v4.10, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.
Details on inoculum:
BIOWIN v4.10 calculation
Remarks on result:
other: please see "any other information on results incl. tables

Table: Ready biodegradability prediction using BIOWIN v4.1 for the mains substance components

Biowin1 (Linear Model Prediction)

1.1024

Biodegrades fast

Biowin2 (Non-Linear Model Prediction):

0.9749

Biodegrades fast

Biowin3 (Ultimate Biodegradation Timeframe):

2.3769

Weeks-Months

Biowin4 (Primary Biodegradation Timeframe):

3.9411

Days

Biowin5 (MITI Linear Model Prediction) :

0.8821

Biodegrades fast

Biowin6 (MITI Non-Linear Model Prediction):

0.8604

Biodegrades fast

Biowin7 (Anaerobic Model Prediction):

-0.2106

Does not biodegrade fast

Ready Biodegradability Prediction:

 

no

 

Interpretation of results:
not readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
12 Feb - 22 Apr 1991
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of activated sludge: Municipal sewage treatment plant, Schijndel, The Netherlands
- Preparation of inoculum: the activated sludge was aerated for 4 h and then left to settle at least for 1/2 h. The supernatant was decanted to provide a sufficiently large volume for a 1% inoculum for each test flask
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
test mat.
Initial conc.:
20 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 20 +/- 2 °C
- pH: pH blank, 6.2; pH positive control, 5.8; pH test substance 10 mg/L, 5.9; pH test substance 20 mg/L, 6.0

TEST SYSTEM
- Culturing apparatus: 3L bottles all-glass brown filled with 3L test medium
- Number of culture flasks/concentration: 1
- Method used to create aerobic conditions: aeration with CO2 free air at a constant rate of 50-100 mL air/min
- Details of trap for CO2: after the aeration period, three CO2-absorber bottles were filled with 80 ml 0.025 N Ba(OH)2 and connected in series to the exit air line of each test bottle.

SAMPLING
- Sampling frequency: 2, 5, 7, 9, 12, 16, 21, and 28 d
- Sampling method: CO2 was determined by titration of remaining Ba(OH)2 with 0.05 N standardized HCL, after barium carbonate precipitation (from
the reaction between CO2 and barium hydroxide). Periodically the C02—absorber nearest to the test bottle was removed for titration. The remaining
two absorbers were each moved one position in the direction of the test bottle, and a new absorber filled with 80 ml of 0025 N Ba(OH)2 (normalized
the same day) was placed at the far end of the series. All samples were stored at —20°C for three months after delivery of this report.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 1
- Reference compound: 1

Reference substance:
acetic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
2.1
Sampling time:
12 d
Remarks on result:
other: 10 mg/L test substance
Parameter:
% degradation (CO2 evolution)
Value:
15
Sampling time:
28 d
Remarks on result:
other: 10 mg/L test substance
Parameter:
% degradation (CO2 evolution)
Value:
0.7
Sampling time:
12 d
Remarks on result:
other: 20 mg/L test substance
Parameter:
% degradation (CO2 evolution)
Value:
5.5
Sampling time:
28 d
Remarks on result:
other: 20 mg/L test substance
Results with reference substance:
103.5% sodium acetate was biodegraded by day 28. Degradation of >60% of reference substance was reached within 14 days.

Table 1. Percentage biodegradation of the test substance.

Day

% Degradation Sodium Acetate

% Degradation Test Material (10 mg/L)

% Degradation Test Material (20 mg/L)

2

9

0

0

5

28.6

0

0

7

40.0

1.1

0.3

9

46.6

1.1

0.3

12

62.5

2.1

0.7

16

85.8

3.6

2.5

21

92.6

6.7

3.6

28

97.4

10.4

4.1

28

99.6

12.7

4.7

28

103.5*

15

5.5

* Due to acidification

Validity criteria fulfilled:
yes
Remarks:
The control substance was biodegraded by more than 60% within 12 days and 104% degradation was reached at the end of the test period (Table 1). The total CO2 released in the blank reached a total value of 7 mg CO2.
Interpretation of results:
under test conditions no biodegradation observed
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
24 Oct - 23 Dec 1975
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Deviations:
yes
Remarks:
test duration was 2 weeks
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
mixture of sewage, soil and natural water
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): not given
- Concentration of sludge: 30 ppm
Duration of test (contact time):
14 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST SYSTEM
- Measuring equipment: Coulometer

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes

STATISTICAL METHODS: not stated
Parameter:
% degradation (O2 consumption)
Value:
1.1
Sampling time:
14 d
Details on results:
not biodegradable

Table 1. Result of biodegradability

 

Degradability

Result by O2 consumption

1.1%

Result by HPLC

(-) %

Validity criteria fulfilled:
not specified
Interpretation of results:
under test conditions no biodegradation observed
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
Remarks:
The substance may not be fully compliant with the applicability domain of the model. However, this calculation is used in a weight of evidence approach, in accordance to the REACh Regulation (EC) No 1907/2006, Annex XI General rules for adaptation of the standard testing regime set out in Annexes VII to X, 1.2. It is adequately documented and justified. For more detail see field `overall remarks, attachments´.
Justification for type of information:
1. SOFTWARE
Vega version 1.1.4

2. MODEL (incl. version number)
Ready Biodegradability Model (IRFMN) v. 1.0.9

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.
Qualifier:
according to guideline
Guideline:
other: REACH Guidance on QSARs R.6
Principles of method if other than guideline:
- Software tool(s) used including version: Vega v1.1.4

- Model(s) used: Ready biodegradability model (version 1.0.9)
Full reference and details of the used formulas can be found in:
Meylan W.M., Howard P.H., Boethling R.S. et al. Improved Method for Estimating Bioconcentration / Bioaccumulation Factor from Octanol/Water Partition Coefficient. 1999, Environ. Toxicol. Chem. 18(4): 664-672

- Model description: see field 'Justification for non-standard information', 'Attached justification' and 'any other information on Material and methods'

- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Remarks on result:
other: The prediction for the main substance components is Possible Readily Biodegradable

For detailed information on the results please refer to the attached report.

Interpretation of results:
other: Possible Readily Biodegradable

Description of key information

The substance is not readily biodegradable

Key value for chemical safety assessment

Additional information

Two studies investigating the ready biodegradability of the substance are available. The key study was performed according to OECD Guideline 301B (GLP). The CO2 evolution of the activated sludge (non-adapted) was recorded for 28 days at test material concentrations of 10 and 20 mg/L respectively. On day 28 biodegradation rates of 15% and 5.5% were determined at 10 and 20 mg/L respectively. A supporting study carried out according to the OECD guideline 301C obtained a similar result. A mixture of sewage, soil and natural water was used as inoculum. The test substance concentration was 100 mg/L. After a contact period of 14 days a biodegradation rate of 1.1% was determined. Further information was generated by QSAR predictions for the main substance components.

Based on the available experimental results the substance is not readily biodegradable according to OECD criteria. The calculation performed with the Ready biodegradability model (version 1.0.9, Vega v1.1.4 sofware) predicted a possible ready biodegradability for the substance. However the similarity to substances in the model training set was only moderate and the accuracy of prediction for similar molecules was not optimal. The data generated were considered sufficiently acceptable for a weight of evidence approach. An additional calculation was performed using BIOWIN v4.10 (EPI suite v 4.11). The independent models Biowin2 (Non-Linear Model Prediction), Biowin5 (MITI Linear Model Prediction) Biowin6 (MITI Non-Linear Model Prediction) predict a fast biodegradation of the main substance components. Whereas Biowin4 (Primary Biodegradation Timeframe) predicts a degradation within days and Biowin3 (Ultimate Biodegradation Timeframe) a degradation within weeks to months. The models predict a possible degradation of the substance and indicate non-persistency of the main substance components.

The substance is not readily biodegradable based on the data gathered in a weight of evidence approach.