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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
Summary of available data used for the endpoint assessment of the target substance
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to the attached analogue justification provided in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Parameter:
% degradation (CO2 evolution)
Value:
82
Sampling time:
28 d
Remarks on result:
other: Source: CAS 68583-51-7
Parameter:
% degradation (O2 consumption)
Value:
61
Sampling time:
28 d
Remarks on result:
other: Source: CAS 91031-31-1
Parameter:
% degradation (O2 consumption)
Value:
75
Sampling time:
56 d
Remarks on result:
other: Source: CAS 91031-31-1
Interpretation of results:
readily biodegradable
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 is not 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.
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:
readily biodegradable based on QSAR/QSPR prediction

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

Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
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:
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.
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:
readily biodegradable based on QSAR/QSPR prediction

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

Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
11 Jul - 10 Aug 1995
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
yes
Remarks:
Temperature exceeded 24 °C on one day of the test
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: obtained from sewage treatment plant 'Marl Ost', Germany (11 Jul 1995)
- Initial cell/biomass concentration: 102*10^4 colony-forming units/mL
- Other: dry weight of inoculum: 4.2 g/L
Duration of test (contact time):
29 d
Initial conc.:
21.2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium according to guideline 92/69/EWG C.4-C
- Test temperature: 22.2 - 24.2 °C
- pH: 7.6 - 7.7 after 28 d
- Suspended solids concentration: 28.0 mg/L

TEST SYSTEM
- Culturing apparatus: 5 L glass vessels
- Number of culture flasks/concentration: 2
- Measuring equipment: TAC analyser (Shimadzu)
- Details of trap for CO2 and volatile organics if used: sodium hydroxide solution
- Other: 2.4 L of constantly aerated mineral medium was added to each vessel, incoulated and filled-up to a final volume of 3 L. The test vessels were acidified to eliminate the remaining dissolved CO2 on day 28. The bacteria were crucified and the degradation was stopped. The biodegradation rate obtained on day 29 was allocated to the result on day 28.

SAMPLING
- Sampling frequency: days 0, 2, 5, 8, 14, 19, 23, 28, 29

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates
- Other: positive control: sodium benzoate, 1 bottle
Reference substance:
benzoic acid, sodium salt
Remarks:
concentration: 25 mg/L
Parameter:
% degradation (CO2 evolution)
Value:
82
Sampling time:
28 d
Details on results:
Within the 10-day window the 60% level was passed. Therefore, the test substance is regarded as readily biodegradable.
Results with reference substance:
The reference substance is degraded by 89% after 28 days and it meets the 10-day window requirement.

The temperature exceeded 24 °C on one day of the test. This has not affected the outcome of the study since the biodegradation of the reference substance was normal.

Table 1: Biodegradation (%) of test substance (TS) and reference substance (RS)

Day

TS I

TS II

TS Mean

RS

0

0

0

0

0

2

22

16

19

45

5

57

53

55

70

8

59

68

69

80

14

78

78

78

85

19

80

81

81

85

23

81

79

80

88

28

82

81

82

88

29

83

82

83

89

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
14 Nov 1997 - 09 Jan 1998
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions (temperature variations of > 0.5 °C).
Qualifier:
equivalent or similar to guideline
Guideline:
other: ISO 10708: Determination of biochemical oxygen demand in a two-phase closed bottle test
Deviations:
yes
Remarks:
temperature variations of > 0.5 °C
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Sewage from the wastewater treatment plant 'Hochdahl', Germany
- Laboratory culture: No
- Concentration of sludge: 1 mL sewage / inoculum
Duration of test (contact time):
56 d
Initial conc.:
100 mg/L
Based on:
COD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 18-22 °C

TEST SYSTEM
- Culturing apparatus: bottles with conical shoulder (approx. 296 mL volume)
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: Stabilisation phase of one week (18-22 °C). Saturated with oxygen after stabilisation phase.
- Measuring equipment: WTW oxygen meter 'OXI 3000'
- Test performed in open system: no

SAMPLING
- Sampling frequency: Sampling was performed on day 0, 3, 7, 14, 21, 28, 56

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 3 replicates
- Abiotic sterile control: no
- Toxicity control: no
- Other: Positive control: sodium acetate, 3 replicates
Reference substance:
acetic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
61
St. dev.:
5
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
75
St. dev.:
5
Sampling time:
56 d
Details on results:
Day 3: 7%
Day 7: 22%
Day 14: 41%
Day 21: 53%
Day 28: 61%
Day 56: 75%
Results with reference substance:
The reference substance meets the 10-day window and was degraded by 89% after 28 days and by 92% after 56 days, respectively.

The chemical oxygen demand (COD) was defined using the Kelkenberg-method but there are indicators that is was not defined well (compared to the calculation of the theoretical oxygen demand (ThOD)). Anyway the COD was used for calculation.

According to “OECD Guidelines for the testing of chemicals – Revised introduction to the OECD guidelines for testing of chemicals, Section 3 – Part 1: Principles and strategies related to the testing of degradation of organic chemicals degradation” published by OECD (2006) the ready biodegradability data for mixtures of structurally similar chemicals should be evaluated carefully. For substances with different chain lengths the 10-day window should not be used for the interpretation of results. It is possible that a sequential biodegradation took place which might have led to a prolonged lag-Phase and therefore a slower biodegradation period although the test substance was biodegraded in a large amount after the test duration. In this case the pass level can be applied at 28 days and is therefore readily biodegradable (61% after 28 days).

Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable

Description of key information

Readily biodegradable based on read across from CAS 68583-51-7, CAS 91031-31-3 and QSAR results

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradability of dodecanoic acid, ester with 1,2-propanediol (CAS 37321 -62 -3) was assessed in the frame of a weight of evidence using read-across data from the structurally similar source substances decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7) and Fatty acids, C16-18, esters with ethylene glycol (CAS 91031-31-1) as well as appropriate QSAR calculations for the two main constituents of the substance.

Read across was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The source substances are characterized by similar fatty acid chain lengths as well as alcohol components and are therefore considered suitable representatives for the assessment of the biodegradability of the target substance. Both studies were performed according to international accepted guidelines and GLP. A detailed read-across justification is provided in IUCLID section 13.

The study with the read across substance decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7) was conducted according to the EU Method C.4-C (GLP) under aerobic conditions using domestic activated sludge as inoculum (1995). A mean biodegradation of 82% was recorded after 28 d. The substance reached the biodegradation pass level of > 60% within the 10-day window and therefore considered as readily biodegradable. Similar results were obtained from the study with the second read across substance Fatty acids, C16-18, esters with ethylene glycol (CAS 91031-31 -1). The biodegradability was evaluated according to an international guideline (ISO 10708) and GLP (1998). Non-adapted activated sludge from a domestic sewage treatment plant was used as inoculum. The test substance, which was applied at a concentration of 100 mg/L was degraded to an extent of 61% (O2 consumption) after 28 d and 75% after 56 d. Since the substance reached the pass level of biodegradation of > 60%, it is considered readily biodegradable according to international guideline criteria.

The biodegradability of the two main constituents (monoester and diester of dodecanoic acid, ester with 1,2-propanediol) of the substance was furthermore assessed using the QSAR model on ready biodegradability (v1.0.9) incorporated within the VEGA software (v1.1.4). The model is considered appropriate for the evaluation of the biodegradability of the constituents with strongly similar substances in the training set and the results are adequate and reliable for assessment. Both constituents were predicted to be readily biodegradable, which is in line with the results given by the analogue substances.

Based on the results of the read across substances and the QSAR predictions, the target substance dodecanoic acid, ester with 1,2-propanediol (CAS 37321 -62 -3) is considered readily biodegradable.