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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
see "General Justification for Read-Across" attached to IUCLID section 13

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Mutual read across from the AAPBs to one another is justified:

a) Based on the information given in section 1, it can be concluded that all AAPBs mentioned above are similar in structure, since they are manufactured from similar resp. identical precursors under similar conditions and all contain the same functional groups. Thus a common mode of action can be assumed.
b) The content of minor constituents in all products are comparable and differ to an irrelevant amount.
c) The only deviation within this group of substances is a minor variety in their fatty acid moiety, which is not expected to have a relevant impact on intrinsic toxic or ecotoxic activity and environmental fate. Potential minor impact on specific endpoints will be discussed in the specific endpoint sections.

The read-across hypothesis is based on structural similarity of target and source substances. Based on the available experimental data, including key physico-chemical properties and data from toxicokinetic, acute toxicity, irritation, sensitisation, genotoxicity and repeated dose toxicity studies, the read-across strategy is supported by a quite similar toxicological profile of all five substances.
The respective data are summarised in the data matrix; robust study summaries are included in the Technical Dossier in the respective sections.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
see "General Justification for Read-Across" attached to IUCLID section 13

3. ANALOGUE APPROACH JUSTIFICATION
see "General Justification for Read-Across" attached to IUCLID section 13

4. DATA MATRIX
see "General Justification for Read-Across" attached to IUCLID section 13
Reason / purpose:
read-across: supporting information
Reason / purpose:
read-across source
Reason / purpose:
read-across source
% Degr.:
76
Parameter:
O2 consumption
Sampling time:
28 d
Transformation products:
not measured

The biodegradability of the test material was investigated in a study conducted equivalent or similar to OECD 306 (Biodegradability in seawater - Closed Bottle Test). Coco AAPB was biodegraded by 76% after 28 d. The test substance therefore can be classified as readily biodegradable in the marine environment. The reference substance sodium benzoate was biodegraded by 72% within 7 d. In the toxicity control no inhibitory effects were observed (94% biogradation after 14 d). The other validity criteria were fulfilled (blank respiration <30% of the oxygen in the test bottle; temperature in the range: 20.0 +/- 1.4°C; BOD of the mixture of test and reference substance was equal to the sum of the BOD of the separate solutions of the two substances; microbial colony count: 4 x 10E3 cfu/mL).

Validity criteria fulfilled:
yes
Conclusions:
The substance can be classified as readily biodegradable in the marine environment.
Endpoint:
biodegradation in water: sewage treatment simulation testing
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
see "General Justification for Read-Across" attached to IUCLID section 13

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Mutual read across from the AAPBs to one another is justified:

a) Based on the information given in section 1, it can be concluded that all AAPBs mentioned above are similar in structure, since they are manufactured from similar resp. identical precursors under similar conditions and all contain the same functional groups. Thus a common mode of action can be assumed.
b) The content of minor constituents in all products are comparable and differ to an irrelevant amount.
c) The only deviation within this group of substances is a minor variety in their fatty acid moiety, which is not expected to have a relevant impact on intrinsic toxic or ecotoxic activity and environmental fate. Potential minor impact on specific endpoints will be discussed in the specific endpoint sections.

The read-across hypothesis is based on structural similarity of target and source substances. Based on the available experimental data, including key physico-chemical properties and data from toxicokinetic, acute toxicity, irritation, sensitisation, genotoxicity and repeated dose toxicity studies, the read-across strategy is supported by a quite similar toxicological profile of all five substances.
The respective data are summarised in the data matrix; robust study summaries are included in the Technical Dossier in the respective sections.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
see "General Justification for Read-Across" attached to IUCLID section 13

3. ANALOGUE APPROACH JUSTIFICATION
see "General Justification for Read-Across" attached to IUCLID section 13

4. DATA MATRIX
see "General Justification for Read-Across" attached to IUCLID section 13
Reason / purpose:
read-across: supporting information
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Test performance:
The ultimate biodegradation of Coco AAPB was investigated in a study conducted according to a modification of OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units).
% Degr.:
>= 96.8 - <= 105.2
Parameter:
DOC removal
Sampling time:
161 d
% Degr.:
97
St. dev.:
8.6
Parameter:
DOC removal
Sampling time:
35 d
Transformation products:
not measured
Validity criteria fulfilled:
yes
Conclusions:
The substance is considered to be easily biodegradable and/or accessible to elimination.

Description of key information

The ultimate biodegradation of C8-18 and C18 unsatd. AAPB was investigated in two guideline studies. Based on a weight of evidence approach a mean elimination of 
99 % was calculated. A further key study investigating the biodegradability of C8-18 and C18 unsatd. AAPB in seawater is available.

Key value for chemical safety assessment

Additional information

No data are available for the target substance C12 -14 AAPB. However, adequate and reliable data on the ultimate biodegradation and the biodegradability in seawater are available for the closely related source substance C8-18 and C18 unsatd. AAPB (Coco AAPB). A justification for read-across is given in IUCLID section 5.2.

Ultimate biodegradability: Aerobic Sewage Treatment

Data on the ultimate biodegradation of C8-18 and C18 unsatd. AAPB were obtained from two guideline studies (OECD 303 A and EU Method C.10). The results were within the normal scientific variation of different tests. Therefore, based on the reliable results a mean elimination of 99 % was calculated for the AAPBs using a weight of evidence approach.

The ultimate biodegradation of C8-18 and C18 unsatd. AAPB was investigated in a study conducted according to a modification of OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units). The test material was treated in a Porous Pot Activated Sludge Plant treating predominantly domestic sewage operating at a SRT of 6 d and a HRT of 6 h. The test and control plants were acclimatised at 20°C to the operating conditions and to sodium acetate for a period of 27 weeks. In the course of the definitive test, the 2 plants were coupled once a week after day 78 by interchanging half of the mixed liquor in each plant. The ultimate biodegradation (ratio DOC removal of control/DOC removal of test item) was determined to be 96.8-105.2 % (95 % confidence limit) during the test duration of 161 d. On the basis of the results, there was no evidence for the formation of water soluble residues from the principal component, C8-18 and C18 unsatd. AAPB or of the minor present ingredients present in the sample. A significant difference in the amount of biomass produced by the two plants was determined. In the test plant receiving the test material, more biomass was produced in comparison with the control plant which received sodium acetate. The test item can therefore be considered as having no adverse effect on growth of sewage organisms. The student's t-value indicated no significant difference in the amount of nitrification attained by the two plants.

In a further study, the ultimate biodegradability of C8-18 and C18 unsatd. AAPB was investigated according to OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units) and EU Method C.10 (Biodegradation: Activated Sludge Simulation Test). The test item proved to be easily biodegradable and/or accessible to elimination (97 +/- 4 % DOC removal over a period of 35 d).

Biodegradation in seawater

The biodegradability of C8-18 and C18 unsatd. AAPB in seawater was investigated in a study conducted equivalent or similar to OECD 306 (Biodegradability in seawater - Closed Bottle Test) over a 28 d period and using aged seawater as inoculum. Biodegradation was determined based on oxygen consumption. Oxygen consumption due to nitrification was determined to be 0 mg O2/L. Inoculum blank, procedural/functional control and toxicity control were performed. The substance was biodegraded by 76 % after 28 d; thus the test substance can be classified as readily biodegradable in the marine environment. The reference substance sodium benzoate was biodegraded by 72 % within 7 d. In the toxicity control no inhibitory effects were observed (94% biodegradation after 14 d). The other validity criteria were fulfilled (blank respiration < 30 % of the oxygen in the test bottle; temperature in the range: 20.0 +/- 1.4°C; BOD of the mixture of test and reference substance was equal to the sum of the BOD of the separate solutions of the two substances; microbial colony count: 4E03 cfu/mL).

In conclusion the ultimate biodegradation of the AAPBs was proven; a mean elimination of 99 % was calculated for the AAPBs. Based on the results of the biodegradation study in seawater, the AAPBs are considered as readily biodegradable in the marine environment.