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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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The ultimate biodegradation of Coco 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 Coco AAPB in seawater is available.

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Additional information

Simulation tests

Reliable data on the ultimate biodegradation of Coco 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 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). 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, Coco 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 Coco 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 Coco 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: 4 x 10E3 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.