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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
Study period:
2014-08-18 to 2014-09-17
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was performed in accordance with standard test protocols (OECD 301B resp. EU C.4-C) in a quality controlled laboratory. The study is valid according to criteria mentioned in the test protocols.
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant.
- Pretreatment: The sludge was filtered, washed with tap water twice, then washed with and resuspended in the test medium. It was then aerated until use. The dry matter was determined with 4220 mg suspended solids/litre.
Duration of test (contact time):
28 d
Initial conc.:
27 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Stock solutions:
Solution a
Potassium dihydrogen phosphate (KH2PO4) 8.5 g
Di-potassium hydrogen phosphate (K2HPO4) 21.75 g
Di-sodium hydrogen phosphate dihydrate (Na2HPO4*2H2O) 33.4 g
Ammonium chloride (NH4Cl) 0.5 g
H2O demin. ad 1000 mL
The pH was adjusted to 7.4 +/- 0.1.

Solution b
Calcium chloride dihydrate (CaCl2*2H2O) 36.4 g
H2O demin. ad 1000 mL

Solution c
Magnesium sulfate heptahydrate (MgSO4*7H2O) 22.5 g
H2O demin. ad 1000 mL

Solution d
Iron(III) chloride hexahydrate (FeCl3*6H2O) 0.25 g
Di-sodium ethylenediamine tetraacetate dihydrate (Na2EDTA*2H2O) 0.4 g
H2O demin. ad 1000 mL

- Test medium:
Solution a 10 mL
Solution b 1 mL
Solution c 1 mL
Solution d 1 mL
H2O demin. ad 1000 mL
The medium was freshly prepared.

- Test temperature: 21.6 – 23.5 °C
- pH: 7.3 at the end of the test
- Aeration of dilution water: yes
- Continuous darkness: yes

SAMPLING
- Sampling frequency: ten samples were taken within the 28 days
- Sampling method: From each front scrubber flask, ten samples were taken in order to determine the emitted CO2. 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 2 M HCl were added to each test flask in order to drive off dissolved CO2. On day 29, samples from both scrubber flasks were taken.


CONTROL AND BLANK SYSTEM
- Inoculum blank: 2, containing mineral medium and inoculum
- Abiotic sterile control: 1, containing test item, mineral medium and HgCl2
- Toxicity control: 1, containing test item, positive control, mineral medium and in-oculum

Reference substance:
aniline
Parameter:
% degradation (CO2 evolution)
Value:
71
Sampling time:
28 d
Details on results:
• The test item nicotine is considered as “readily biodegradable“.
• The degree of biodegradation reached 71% after 28 days.
• The 10-day-window began on day 3, at its end, 72% were reached, surpassing the pass level of 60% given in the OECD guideline.
• Abiotic degradation was not observed.
Results with reference substance:
See table at "Any other information on results incl. tables". Degradation of positive control was >60% within 7 days.

In the following table, the percentage biodegradation is presented

Day

Positive Control 1

Positive Control 2

Positive Control Mean

Test 1

Test 2

Test Mean

Abiotic Control

Toxicity Control

2

0.1

2.7

1.4

0.2

0.8

0.5

-0.1

0.1

4

25.6

24.4

25.0

31.0

40.8

35.9

0.1

30.7

7

69.3

73.5

71.4

64.3

66.4

65.3

-0.5

67.5

9

75.1

78.6

76.8

74.3

75.4

74.8

-1.1

74.1

11

73.9

71.5

72.7

70.7

70.2

70.4

-0.9

68.6

14

72.4

77.8

75.1

73.0

73.6

73.3

-1.3

69.5

18

76.7

80.1

78.4

74.9

78.6

76.7

-1.8

80.7

23

82.9

88.2

85.6

78.4

80.3

79.3

-2.3

79.6

29

72.0

80.9

76.4

70.7

70.8

70.8

-3.9

73.1

Validity criteria fulfilled:
yes
Remarks:
All validity criteria were met. Degradation of the positive control was 71 % after seven days.
Interpretation of results:
readily biodegradable
Conclusions:
Degradation behaviour of positive control and toxicity control was normal. Abiotic degradation was not observed. Both replicates of the test item showed very good correspondence.
The validity criteria were met and the criterion for ready biodegradability was fulfilled.
If degradation in the toxicity flask is below 25% after 14 days, the test item can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 70% after 14 days, the test item can be stated as “not toxic towards the inoculum in a concentration of 27 mg/L”.
Ready degradability is defined in the guidelines as degradation surpassing 60% within 10 days after reaching a level of 10%. Therefore, the test item nicotine can be considered as “readily biodegradable”.
No observations were made which might cause doubts concerning the validity of the study outcome.
The result of the test can be considered valid.





Executive summary:

The test item nicotine was tested using a concentration of at least 20 mg organic carbon/L (corresponding to 27.0 mg nicotine/L) in test medium following OECD 301B and EU-Method C.4-C.

 

Aniline was chosen as positive control.

Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L). The test was left running for 28 days.

All validity criteria were met. Degradation of the positive control was 71% after seven days.

 

The following data were determined for the test item nicotine:

10-day-window: day 3 – 13
degradation at the end of 10-day-window: 72%

degradation at the end of the test: 71%

pass level following guideline: 60% at the end of 10-day-window

 

Therefore, when applying the 10-day-window, nicotine is readily biodegradable following OECD 301B/EU C.4-C.

 

Description of key information

Biodegradation was tested in a valid, GLP compliant OECD 301B guideline study of high quality (Klimisch 1).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information