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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
The sludge was taken from the activation basin of the sewage treatment plant in D-67480 Edenkoben.
Date of collection: 06. Apr. 2018, batch no: 20180406.
Duration of test (contact time):
28 d
Initial conc.:
48.3 mg/L
Based on:
test mat.
Remarks:
Test 1
Initial conc.:
48 mg/L
Based on:
test mat.
Remarks:
Test 2
Details on study design:
From each front scrubber flask, 10 samples were taken in order to determine the emitted CO2 (on day 0, 2, 4, 7, 9, 11, 14, 18, 23 and 29). The sample volume was 1 mL. The resulting change in the volume of the front flask was considered in the calculation of emitted CO2.
On day 28, 5 mL HCl 2 M was added to each test flask in order to drive off dissolved CO2. On day 29, samples from both scrubber flasks were taken.
Reference substance:
aniline
Key result
Parameter:
% degradation (CO2 evolution)
Remarks:
10-day-window from day 9 till day 19
Value:
21
Sampling time:
19 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
24
Sampling time:
28 d
Results with reference substance:
All validity criteria were met. Degradation of the positive control was 61 % after 11 days.

In the following table, the percentage biodegradation is presented:

Table 1     Degradation values in %

Day

Positive Control 1

Positive Control 2

Positive Control Mean

Test 1

Test 2

Test Mean

Abiotic Control

Toxicity Control

2

1.8

0.9

1.4

4.7

3.9

4.3

0.3

1.3

4

6.0

10.6

8.3

5.5

6.8

6.1

0.6

3.8

7

37.1

30.8

34.0

8.8

8.7

8.7

0.3

6.9

9

50.5

55.1

52.8

9.1

9.5

9.3

0.2

32.3

11

58.1

63.4

60.8

13.1

13.8

13.5

0.2

42.9

14

66.3

68.0

67.1

17.5

18.9

18.2

-0.4

50.0

18

73.8

75.5

74.7

20.8

20.0

20.4

-0.8

56.0

23

76.4

75.0

75.7

22.3

22.2

22.2

-1.1

56.0

29

86.0

85.1

85.5

23.1

24.2

23.6

-2.1

60.2

 

As the measured IC values in the abiotic control are very low, measurement uncertainties lead to negative degradation values while in fact no degradation has taken place.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Results for the Test Item L-Tyrosine, N-acetyl-3,5-dinitro-
• The test item L-Tyrosine, N-acetyl-3,5-dinitro- is considered as “not readily biodegradable“.
• The degree of biodegradation reached 24 % after 28 days.
• The 10-day-window began on day 9 at its end, 21 % (graphic evaluation), degrada-tion was reached, missing the pass level of 60 % given in the OECD guideline.
• Degradation missed 60 % within 28 days, too. Therefore, the test item L-Tyrosine, N-acetyl-3,5-dinitro- is considered as “not ultimately biodegradable within 28 days”, either.
• Abiotic degradation was not observed.

Description of key information

In the study conducted according to OECD 301B 24 % of the test substance degradaded after 28 d. Thus the substance has to be classified as not readily biodegradable but inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable
Type of water:
freshwater

Additional information