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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The substance is moderately biodegradable (not readily biodegradable).

Key value for chemical safety assessment

Additional information

Parent compound:

No reliable data are available for tris-2-ethylhexylamine (CAS 1860-26-0). Therefore, in order to assess the biodegradation potential of tris-2-ethylhexylamine (CAS 1860-26-0), a read across to the analogue substance di-(2-ethylhexyl)amine (CAS 106-20 -7) with structural similarity was performed. Experimental data are available from an enhanced ready biodegradability test according to OECD 301B, conducted with non-adapted, domestic activated sludge as inoculum (BASF SE, 2016). Elimination of the test item was determined to be 91% after 60 days of exposure, based on CO2 evolution. However, after 28 days, biodegradation was determined to be 69%, but the pass level of the 10-day window was slightly failed as biodegradation was approximately 58% at the end of the 10-day window.

In addition, the results from an enhanced ready biodegradability test according to OECD 301B, conducted with non-adapted, domestic activated sludge as inoculum are available (BASF SE, 2012). Elimination of the test item was determined to be 0.9% after 28 days based on CO2 evolution. Based on DOC removal, 83% of the substance was eliminated after 28 days, which is, however, interpreted to be likely due to adsorption to the sludge and/or test vessels. Additional experimental data are available from a CO2 evolution test conducted similar to OECD 301B (BASF AG, 1997; report no. 97/0028/22/1) with non-adapted, domestic activated sludge as inoculum. The substance was degraded to approximately 50% after 39 days of incubation. However, the plateau phase of the biodegradation curve was not reached after 39 days. The biodegradation curve still showed an upward trend indicating that the biodegradation of the molecule was not completed.

In addition to the read-across approach, the ready biodegradability was assessed using two QSAR models. The substance was within the applicability domains of the used models. The substance was predicted to be not readily biodegradable by both models. Based on the estimated degree of degradation, moderate biodegradability is a realistic assumption.

- BIOWIN v4.10 (EPI Suite v4.11): not readily biodegradable

- CATALOGIC Kinetic OECD 301C v.11.15: 7% in 28 d, not readily biodegradable

Metabolites:

CATALOGIC 301C v11.15 (OASIS Catalogic v5.13.1) predicted for the parent compound 33 metabolites, identifying 16 metabolites as relevant degradation products in terms of PBT/vPvB assessment, with an estimated quantity of ≥ 0.1% (for details see ‘Attached background material’ of the respective Endpoint Study Record).

Five of the relevant metabolites were calculated to be readily biodegradable (≥ 60% after 28 days, based on BOD). The other relevant metabolites were estimated to be not readily biodegradable (4 to 44% after 28 days, based on BOD). In conclusion, the majority of the predicted metabolites present in a concentration of ≥ 0.1% (equivalent to >=0.001 mol/mol parent) are estimated to be not readily biodegradable.

Table 1. The predicted metabolites from the CATALOGIC 301C v11.15 estimation model.

#

Metabolite
(no)

Smiles

Quantity
(mol/mol parent)

LogKow

BOD prediction
(% after 28 d)

parent

1

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CCCC

7.01E-01

10.1

7

1

3

CCCCC(CC)C=O

1.01E-02

2.7

78

2

2

CCCCC(CC)CNCC(CC)CCCC

1.50E-02

6.6

44

3

18

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CCCCO

9.61E-07

8.7

24

4

29

CCCCC(CC)CN(CC(CC)CCCC)CC(CCCC)CCO

9.61E-07

8.7

17

5

37

CCCCC(CC)CN(CC(CC)CCCC)C(O)C(CC)CCCC

1.17E-08

8.6

47

6

4

CCCCC(CC)C(O)=O

3.12E-02

3.0

77

7

16

CCCCC(CC)CN

4.06E-02

2.7

40

8

19

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CCCC=O

9.61E-07

8.6

24

9

30

CCCCC(CC)CN(CC(CC)CCCC)CC(CCCC)CC=O

9.61E-07

8.6

17

10

5

CCCC=C(CC)C(O)=O

2.71E-02

2.9

67

11

20

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CCCC(O)=O

9.61E-07

5.7

23

12

31

CCCCC(CC)CN(CC(CC)CCCC)CC(CCCC)CC(O)=O

9.61E-07

5.7

16

13

6

CCCC(O)C(CC)C(O)=O

2.36E-02

1.4

66

14

21

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CC=CC(O)=O

9.61E-07

7.0

23

15

32

CCCCC(CC)CN(CC(CC)CCCC)CC(O)(CCCC)CC(O)=O

3.08E-02

4.2

15

16

13

CC(O)=O

7.71E-06

0.1

100

17

7

CCCC(O)=C(CC)C(O)=O

1.57E-06

2.0

91

18

22

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CC(O)CC(O)=O

9.61E-07

4.2

22

19

33

CCCCC(CC)CN(CC(CC)CCCC)CC(=O)CCCC

5.41E-02

7.9

4

20

8

CCCC(=O)C(CC)C(O)=O

2.05E-02

0.9

91

21

23

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CC(=O)CC(O)=O

9.61E-07

3.6

22

22

34

CCCCC(CC)CN(CC(CC)CCCC)CC(=O)CCCCO

2.24E-03

6.5

22

23

35

CCCCC(CC)CN(CC(CC)CCCCO)CC(=O)CCCC

4.48E-03

6.5

22

24

36

CCCCC(CC)CN(CC(CCCC)CCO)CC(=O)CCCC

4.48E-03

6.5

13

25

9

CCCC(O)=O

2.72E-06

1.1

100

26

24

CCCCC(CC)CN(CC(CC)CCCC)CC(CC)CC(O)=O

9.61E-07

4.7

16

27

10

CC=CC(O)=O

2.72E-06

0.9

100

28

25

CCCCC(CC)CN(CC(CC)CCCC)CC(O)(CC)CC(O)=O

3.08E-02

3.2

14

29

11

CC(O)CC(O)=O

2.72E-06

-0.5

100

30

26

CCCCC(CC)CN(CC(CC)CCCC)CC(=O)CC

5.62E-02

7.0

4

31

12

CC(=O)CC(O)=O

2.72E-06

-1.0

100

32

27

CCCCC(CC)CN(CC(CC)CCCCO)CC(=O)CC

4.56E-03

5.5

23

33

28

CCCCC(CC)CN(CC(CCCC)CCO)CC(=O)CC

4.56E-03

5.5

13

(metabolites which are predicted at quantity >0.001 after 28 d are highlighted in grey and written in bold letters)

(metabolite no: according to (Q)SAR model CATALOGIC 301C v11.15 – July 2018 (OASIS CATALOGIC v5.13.1.156))

Conclusion: Based on the available experimental data from a read-across to a structurally similar substance bis(2-ethylhexyl) (CAS 106-20-7) along with the estimated data for tris-2-ethylhexylamine (1860-26-0) itself, it can be considered that the substance is moderately biodegradable (not readily biodegradable) and is not persistent.