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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:
(Q)SAR
Adequacy of study:
weight of evidence
Study period:
Not applicable
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 well documented with regard to validation parameters according to OECD principles. Moreover, the substance is fully characterised and falls within the applicability domain.
Justification for type of information:
1. SOFTWARE
OASIS CATALOGIC v.5.11.15

2. MODEL (incl. version number)
CATALOGIC Kinetic 301B v.02.08 (July, 2014)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CCCc1ccc(O)c(OC)c1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached QMRF

5. APPLICABILITY DOMAIN
See attached QPRF

6. ADEQUACY OF THE RESULT
See attached QPRF
Qualifier:
according to guideline
Guideline:
other: Reach Guidance on QSAR - R.6
Deviations:
no
Principles of method if other than guideline:
QSAR, CATALOGIC Kinetic 301B v.02.08. More details are given in QMRF/QPRF attached to the dossier.
GLP compliance:
no
Specific details on test material used for the study:
No additional information
Oxygen conditions:
aerobic
Inoculum or test system:
other: Aerobic microorganisms. The inoculum may be derived from a variety of sources: activated sludge; sewage effluents; surface waters; soils; or from a mixture of these.
Details on inoculum:
No additional information
Duration of test (contact time):
28 d
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
not applicable
Preliminary study:
not applicable
Test performance:
not applicable
Key result
Parameter:
% degradation (CO2 evolution)
Value:
94
Sampling time:
28 d
Remarks on result:
other: Concomitant predictions : Ready degradable; Primary Half Life = 2.00 days; Ultimate Half Life = 8.63 days.
Details on results:
The chemical fulfils the general properties requirements (log Kow, molecular weight and water solubility). The chemical is in the interpolation structural space and in the metabolic domain.
For additional informations, see the attached QPRF.
Results with reference substance:
not applicable

No additional information

Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
Conclusions:
It is expected that the substance is readily biodegradable (CO2 production of 94% after 28d).
Executive summary:

The substance ready biodegradation property was investigated using QSAR approach with CATALOGIC Kinetic 301B v.02.08, plug-in from OASIS CATALOGIC v.5.11.15.

According to the results of this prediction (CO2 production of 94% after 28d), the substance is expected to be readily biodegradable. This compound fulfills the general properties requirements (in terms of log Kow, molecular weight and water solubility) and is in the interpolation structural space and in the metabolic domain.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
[further information is included as attachment in section 13]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the structural similarity between the source and the target substances. Their environmental properties are expected to be similar because of this structural similarity and because they are anticipated to follow the same environmental fate.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target and the source substances are structurally related, in that each has a 2-methoxyphenol ring, and a chain with three carbons (propyl or propenyl) in 4-position. The source substance is substituted with a propenyl group, while the target substance has a propyl (i.e. no double bond). It is not expected that any of the impurities will affect the environmental fate parameters of concern. No other impurities that may contribute to the classification of the substances were identified. Therefore, it is concluded that the impurities will not affect the read-across.

3. ANALOGUE APPROACH JUSTIFICATION
In the absence of a biodegradation study on the target substance, a reliable QSAR model was used to predict the biodegradation of this substance. To confirm this prediction, a weight of evidence approach was used with an experimental study performed on the source substance. Based on structural similarity, no significant difference on the biodegradability potential is anticipated between both substances. This statement was proved as the results of the biodegradation data are the same for the target and the source substances (readily biodegradable). Hence, it is considered suitable and scientifically justified to read-across the data between the two substances to fill the biodegradation endpoint in the present dossier.

4. DATA MATRIX
See attached document in section 13
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Key result
Parameter:
% degradation (O2 consumption)
Value:
79
Sampling time:
28 d
Remarks on result:
other: >60% within the 10d window
Details on results:
Test substance undergoes 79 % biodegradation after 28 days in the test conditions. Biodegradation starts on day 2 and reaches 79 % at the end of the 10-day window (days 2 to 12).
Test substance at 100 mg/L is not inhibitory to the micro-organisms.
Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
Conclusions:
Based on data available on the source substance (79 % biodegradation after 28 days within the 10-day window), the target and the source substances are readily biodegradable and non-toxic to microorganisms up to 100 mg/L.
Executive summary:

The ready biodegradability of the target substance has been determined by the Manometric Respirometry Test, performed on the source substance according to the OECD Guideline No. 301F with GLP compliance.

A nominal concentration of test substance (100 mg/L) was introduce in the system. Test substance at 100 mg/L is not inhibitory to the micro-organisms. The test item undergoes 79 % biodegradation after 28 days in the test conditions. Biodegradation starts on day 2 and reaches 79 % at the end of the 10-day window (days 2 to 12). Degradation of aniline exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified.

According to this test, the conclusion is that the source and target substances should be regarded as readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
1996-10-15 to 1996-11-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 301F with GLP compliance. All validity criteria were fulfilled and no deviations were observed.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes
Remarks:
Statement of compliance with GLP in date of 1996-11-29
Specific details on test material used for the study:
No additional information
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aire) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day,
Concentration of sludge: 2.982 g/L (dry weight of suspended solids); to obtain a concentration of 30 mg/L (dry weight) in a 250 mL flask, 2.52 mL of sludge is needed (inoculum).
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: compliant with recommendations of TG on mineral medium
The pH is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.
- Solubilising agent (type and concentration if used): None
- Test temperature: 22 °C
- CEC (meq/100 g): No data
- Aeration of dilution water: No data
- Suspended solids concentration: 30 mg/L
- Continuous darkness: No data
- Water: The water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.

TEST SYSTEM
- Culturing apparatus: Test flasks of the SAPROMAT
- Number of culture flasks/concentration: 2
- Measuring equipment: The respirometer used during this study is a SAPROMAT D 12, made by J. M. VOITH GmbH, D-7920 Heidenheim.
- Test performed in closed vessels: Yes
- Test performed in open system: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Procedure control: Yes with the reference substance
- Toxicity control: Yes
Reference substance:
aniline
Preliminary study:
None
Test performance:
Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked. At the end of the test period (normally 28 days), the pH of each flask is measured again.
Key result
Parameter:
% degradation (O2 consumption)
Value:
79
Sampling time:
28 d
Details on results:
Test substance undergoes 79 % biodegradation after 28 days in the test conditions. Biodegradation starts on day 2 and reaches 79 % at the end of the 10-day window (days 2 to 12).
Test substance at 100 mg/L is not inhibitory to the micro-organisms.
Results with reference substance:
Degradation of aniline exceeded 40 % after 7 days and 65 % after 14 days: the activity of the inoculum was thus verified (validity criterion).

Table 5.2.1/2: Test substance - Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations)

 

Days:

2

7

12

14

21

28

BOD sludge

1st flask

B1

6.0

15.0

19.0

21.0

26.0

32.0

2nd flask

B2

7.0

17.0

20.0

23.0

29.0

35.0

mean

B

6.5

16.0

19.5

22.0

27.5

33.5

BOD test substance

1st flask

C1

48.7

181.3

204.0

208.0

215.9

219.8

2nd flask

C2

52.5

185.2

206.0

209.8

214.5

217.4

1st flask corr.

C1-B

42.2

165.3

184.5

186.0

188.4

186.3

2nd flask corr.

C2-B

46.0

169.2

186.5

187.8

187.0

183.9

% biodegradation

 

1st flask

D1

18

71

79

79

80

80

2nd flask

D2

20

72

80

80

80

79

mean

D

19

71

79

80

80

79

 

Calculations:

B = (B1 + B2) / 2

DI = 100 * (C1 - B) / ThOD * [S]

D2 = 100 * (C2 - B) / ThOD * [S]

D = (DI + D2)/2

[S] : Initial test substance concentration (mg/L)

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item undergoes 79 % biodegradation after 28 days in the test conditions. The 10-day window criterion is also fulfilled. Thus, the test item should be regarded as readily biodegradable according to this test. In addition, no toxic effects of the test substance were observed to microorganisms at the test concentration.
Executive summary:

The ready biodegradability of the test item has been determined by the Manometric Respirometry Test according to the OECD Guideline No. 301F with GLP compliance.

A nominal concentration of test substance (100 mg/L) introduce in the system.

Test substance at 100 mg/L is not inhibitory to the micro-organisms. The test item undergoes 79 % biodegradation after 28 days in the test conditions. Biodegradation starts on day 2 and reaches 79 % at the end of the 10-day window (days 2 to 12). Degradation of aniline exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified.

 

According to this test, the conclusion is that the test item should be regarded as readily biodegradable.

Description of key information

Weight of evidence approach, one experimental GLP study (1996) performed on a source substance and one QSAR data point on the registered substance (CATALOGIC Kintetic 301B v.02.08):

Readily biodegradable.

Non-toxic to microorganisms up to 100 mg/L.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

To assess the biodegradation potential of the registered substance, 2 -Methoxy-4 -propylphenol, a weight of evidence approach was used based on an experimental GLP study (performed in 1996) and QSAR.

The GLP experimental study (Givaudan, 1996) was performed on a read-across substance, 2 -Methoxy-4 -prop-1 -en-1 -ylphenol, according to OECD Guideline 301F with GLP compliance, and is considered valid. Read-across is justified because both substances (the registered substance and the test substance) are structural analogues with similar basic physico-chemical properties and similar environmental profile. They are both a phenol to which a methoxy- group is attached at the ortho position and an alkyl chain (4 carbons length) at the para position. The only difference is the presence of a double bond in the alkyl chain of the read-across substance which is not present in the registered substance. In this study, the test substance at 100 mg/L was inoculated with activated sludge from a biological wastewater treatment plant treating predomantly domestic sewage.The degradation of the test substance was assessed by the determination of the oxygen consumption. The test substance undergoes 79% biodegradation after 28 -day exposure period. Biodegradation starts on day 2 and reaches 79% at the end of the 10 day window (days 2 to 12). Therefore, the test substance is also considered readily biodegradable. In addition, according to the toxicity control, the test substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L.

The QSAR data was performed to support the experimental result. The registered substance ready biodegradation property was investigated using CATALOGIC Kinetic 301B v.02.08, plug-in from OASIS CATALOGIC v.5.11.15. The registered substance fulfills the general property requirements (in terms of log Kow, molecular weight and water solubility) and is in the interpolation structural space and in the metabolic domain. According to the results of this prediction, 94% biodegradability (CO2 production) would be expected after 28 days.

Since the outcome of the biodegradability prediction of the registered substance is supported by the experimental result from structural analogue, it can be concluded that the registered substance is readily biodegradable. In addition, by read-across with the analogue substance, the registered substance is considered non-toxic to microorganisms up to 100 mg/L.