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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
25 Jan - 22 Feb 1991
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: Test Guideline is not appropriate for lipophilic substances, disappearance may be caused by sorption
Qualifier:
according to
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
Qualifier:
according to
Guideline:
other: USTC Procedure PRO/BIO-E SFT/AC 232-7
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
mixture of sewage, soil and natural water
Duration of test (contact time):
28 d
Initial conc.:
20 - 25 mg/L
Based on:
DOC
Parameter:
% degradation (DOC removal)
Value:
44.9
Sampling time:
28 d
Parameter:
% degradation (DOC removal)
Value:
41.5
Sampling time:
21 d
Parameter:
% degradation (DOC removal)
Value:
30.8
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
37.2
Sampling time:
7 d
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test substance [6339-20 Aqueous Potassium Salt of Diacid 1595, 38.09% Active] is not readily biodegradable under these conditions.
Executive summary:

The test substance [6339-20 Aqueous Potassium Salt of Diacid 1595, 38.09% Active] was tested under TG OECD 301E using the disappearance of DOC as the test parameter. The biodegradability (~45% DOC removal in 28 days) was below the threshold level of 70% DOC reduction. Therefore, the substance is not readily biodegradable under these conditions.

This test method is not suitable for substances with a high log Kow.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
19 April - 24 May 1991
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: Test Guideline is not appropriate for lipophilic substances, disappearance may be caused by sorption
Qualifier:
according to
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
Qualifier:
according to
Guideline:
other: USTC Procedure PRO/BIO-E SFT/AC 232-7
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
mixture of sewage, soil and natural water
Duration of test (contact time):
35 d
Initial conc.:
19 mg/L
Based on:
DOC
Parameter:
% degradation (DOC removal)
Value:
41.1
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
49.7
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
62.2
Sampling time:
21 d
Parameter:
% degradation (DOC removal)
Value:
64.9
Sampling time:
28 d
Parameter:
% degradation (DOC removal)
Value:
63.2
Sampling time:
35 d
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test substance [Diacid 1550 Potassium salt (6339-33) 39.18%] is not readily biodegradable under these conditions.
Executive summary:

The test substance fatty acids tall-oil, reaction products with acrylic acid, potassium salt was tested under TG OECD 301E using the disappearance of DOC as the test parameter. The biodegradability (~65% after 28 days) was below the threshold level of 70% DOC reduction. Therefore, the substance is not readily biodegradable under these conditions.

This test method is not suitable for substances with a high log Kow.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
20-6-2012 to 19-07-2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
12 september 2012
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material: not relevant
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on inoculum:
River water was sampled from the river Rhine near Heveadorp, The Netherlands (14-06-2012). The nearest plant (Arnhem-Zuid) treating domestic waste water biologically was 3 km upstream. The river water was aerated for 7 days before use to reduce the endogenous respiration. River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating. The dry weight of suspended solids after removal of sediment particles is <2.0 mg/L.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
In the preliminary study (van Ginkel en Meussen, 2012) the appropriate conditions for the performance of the closed bottle test were investigated. The focus was on the method of introduction of the poorly water soluble test substance into the test solution and optimising the bioavailability. The results were used for optimalisation of the setup of the definitive study.

For the definitive test (van Ginkel, 2012) use was made of 10 bottles containing only inoculum, 10 bottles containing inoculum and test substance, and 6 bottles containing inoculum and sodium acetate. The zero time bottles were immediately analysed for dissolved oxygen. The remaining bottles were incubated in the dark. Dissolved oxygen concentration was analysed in two replicate bottles at days 7, 14, 21, and 28.


TEST CONDITIONS
- Composition of medium: The river water used in the Closed Bottle test was spiked per liter of water with 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.3 mg Na2HPO4•2H2O, 22.5 mg MgSO4•7H2O, 27.5 mg Ca¬Cl2, 0.25 mg FeCl3•6H2O. Ammoniumchloride was omitted from the medium to prevent nitrification.
- Test temperature: 22-24 °C
- pH: 8.2 at start of test, pH 8.1 and 8.0 at day 28.
- Suspended solids concentration: < 2.0 mg/L (dryweight)
- Continuous darkness: yes

SAMPLING
- Sampling frequency: day 0, 7, 14, 21 and 28


CONTROL AND BLANK SYSTEM
- Inoculum blank: 10 bottles

Reference substance:
acetic acid, sodium salt
Remarks:
initial test concentration 6.7 mg/L, ThOD is 0.78 mg/mg
Preliminary study:
The optimum conditions were the use of alkaline test solution and riverwater as inoculum. These have been selected for the definitive test.
Test performance:
The validity of the test is demonstrated by an endogenous respiration of 1.2 mg/L at day 28 (Table I). According to the criteria, it should be below 1.5
mg/L. Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 92. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.
Parameter:
% degradation (O2 consumption)
Value:
63
Sampling time:
28 d
Details on results:
Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected. Therefore, no inhibition of the biodegradation due to the initial test substance concentration is expected.
Results with reference substance:
The biodegradation of the reference compound, sodium actetate, at day 14 was 92%.

Dissolved oxygen concentrations (mg/L) in the closed bottles.

Time (days)

Oxygen concentration (mg/L)

 

Oc

Ot

Oa

0

8.9

8.9

8.9

 

8.9

8.9

8.9

Mean (M)

8.9

8.9

8.9

7

8.3

6.5

3.7

 

8.2

6.2

3.5

Mean (M)

8.3

6.4

3.6

14

8.1

6.1

3.3

 

7.9

5.7

3.1

Mean (M)

8.0

5.9

3.2

21

7.9

5.1

 

 

7.9

4.9

 

Mean (M)

7.9

5.0

 

28

7.8

4.4

 

 

7.6

4.5

 

Mean (M)

7.7

4.5

 

Oc       Mineral nutrient solution with only inoculum.

Ot       Mineral nutrient solution with test material (2.0 mg/L), and inoculum.

Oa       Mineral nutrient solution with sodium acetate (6.7 mg/L) and with inoculum.

 

 

 

Oxygen consumption (mg/L) and the percentages biodegradation of the test substance, 2-cyclohexene-1-octanoic acid, 5(or 6)-carboxy-4-hexyl- (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test.

Time (days)

Oxygen consumption (mg/L)

Biodegradation (%)

 

Test substance

Acetate

Test substance

Acetate

0

0.0

0.0

0

0

7

1.9

4.7

37

90

14

2.1

4.8

41

92

21

2.9

 

57

 

28

3.2

 

63

 

 

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Diacid 1550 was degraded by 63% after 28 days in the Closed Bottle Test. Diacid 1550 consists of alkyl chains and an cyclic moiety. The two phase degradation curve shows that the two moieties of Diacid 1550 are probably degradaded sequentially. The biodegradation of the seperate moieties is probably in line with the time window criterion. Therefore, it is concluded that the substance is readily biodegradable.
Executive summary:

In order to assess the biotic degradation, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to OECD (TG 301 D), EU (Method C.4.) and ISO (TG 10107), and in compliance with GLP. Diacid 1550 did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. Diacid 1550 was biodegraded by 63% at day 28. Hence, this substance is classified as readily biodegradable. The test is valid as shown by an endogenous respiration of 1.2 mg/L. The oxygen concentration was always >0.5 mg/L in all bottles during the test period. The reference substance sodium acetate was degraded by 92% of its theoretical oxygen demand after 14 days, showing the test system being valid.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Rationale for reliability incl. deficiencies:
other: Read across to GLP guideline study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance fatty acids, tall-oil, reaction products with acrylic acid potassium salt is the corresponding potassium salt of the source substance fatty acids, tall-oil, reaction products with acrylic acid and manufactured accordingly by neutralisation with potassium hydroxide. As the potassium salt does not contribute to biodegradability, a read-across to the free acids is justified.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The traget substance actually is manufactured form the source substance by neutralisation of fatty acids, tall-oil, reaction products with acrylic acid (source substance) with potassium hydroxide, forming the target substance fatty acids, tall-oil, reaction products with acrylic acids potassium salt. The source substance has been registered already and was found being readily biodegradable. The potassium cation does not influence biodegradability as inorganic cations are by defintion not biodegradable.

3. ANALOGUE APPROACH JUSTIFICATION
The structure of the organic moiety of source and target substance is identical and thus read-across form the free acid to its salt is common practice and justified.

4. DATA MATRIX
Not relevant here as organic moieties of source and target substance are identical and both only do differ by the cation potassium present in the target substance (compared to a proton in the source substance), not relevant to oxygen consumption measured in the OECD 301D study.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Parameter:
% degradation (O2 consumption)
Value:
63
Sampling time:
28 d
Interpretation of results:
readily biodegradable
Conclusions:
Diacid 1550 was degraded by 63% after 28 days in the Closed Bottle Test. Diacid 1550 consists of alkyl chains and a cyclic moiety. The two phase degradation curve shows that the two moieties of Diacid 1550 are probably degradaded sequentially. The biodegradation of the seperate moieties is probably in line with the time window criterion. Therefore, it is concluded that the substance is readily biodegradable. The organic moieties of Diacid 1550 (source substance) and Diacid 1550 potassium salt (target substance) are identical, justifying a read-across approach.

Description of key information

Based on available study data, the substance fatty acids, tall-oil, reaction products with acrylic acid, potassium salt is considered readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information