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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:
22 Nov 2017 - 18 Jan 2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Two concentrations were tested but not in duplicates. Respective validity criterion on difference of extremes of replicate cannot be evaluated.
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
Only one vessel per test concentration was set up. The guideline advises that determinations should be carried out at least in duplicates.
GLP compliance:
yes (incl. certificate)
Remarks:
Department of Health of the Government of the United Kingdom, London, United Kingdom
Oxygen conditions:
aerobic
Inoculum or test system:
natural water: freshwater
Details on inoculum:
- Source of inoculum: Surface water was collected from Malmesbury Pond, Sandymoor, Runcorn on 13 November 2017.
- Preparation of inoculum for exposure: The sample was filtered to remove coarse particles and aerated at 22 ± 2°C prior to use. The surface water was then added to test media so as to achieve a final concentration of 100 mL/L of test media.
- Storage length: After preparing the inoculum for exposure, it was areated until 17 November 2018 (start of pre-conditioning period).
- Concentration of surface water: 100 mL surface water per L of test media
- Initial cell/biomass concentration: not reported
Duration of test (contact time):
56 d
Initial conc.:
11.6 mg/L
Based on:
test mat.
Initial conc.:
23.2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 22 ± 2°C. The temperature slightly exceeded the 24°C upper tolerance limit on Day 21. This deviation was corrected at the time and did not recure during the remainder of the study.
- Photoperiod: continuous darkness

TEST SYSTEM
- Culturing apparatus: 3 L flat bottomed flasks
- Number of culture flasks/concentration: 1
- Method used to create aerobic conditions: CO2-free air was passed through two dreschel bottles, per test vessel, containing barium hydroxide of known concentration and volume.

SAMPLING
- Sampling frequency: Days 1, 3, 5, 8, 10, 14, 19, 23, 28, 35, 42, 49, 56 and 57

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, two bottles
- Toxicity control: yes, one bottle
- Reference control: yes, one bottle
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
28.5
Sampling time:
28 d
Remarks on result:
other: Test concentration: 11.6 mg/L
Parameter:
% degradation (CO2 evolution)
Value:
45.1
Sampling time:
28 d
Remarks on result:
other: Test concentration: 23.2 mg/L
Details on results:
The test item did not fulfill the criteria for ready biodegradability according to OECD criteria (60% of ThCO2 within a 10-d window).
The degradation extent in the toxicity control was 85.5% degradation after 14 days. The test material is therefore considered to have no inhibitory effect on the inoculum according to the criterion of the guideline.
For details on biodegradation rates, please refer to Table 1 in section "Any other information on results incl. tables".
Results with reference substance:
The reference control achieved 63.8% degradation after 14 d (pass level: 60%). The degradation after 28 d was 71.1%.

Table 1: Cumulative degradation

Cumulative degradation [%]

Day of titration

Reference substance

Test item at 11.6 mg/L

Test item 23.2 mg/L

Toxicity control

1

22.4

*

*

3.5

3

44.0

5.5

*

39.1

5

50.1

6.8

1.6

61.0

8

54.9

11.4

19.1

71.2

10

58.0

9.6

22.2

76.5

14

63.8

14.6

27.9

85.5

19

66.7

19.4

35.8

94.1

23

68.9

20.9

39.7

99.4

28

71.1

28.5

45.1

101.8

35

70.2

32.7

51.2

111.6

42

76.4

29.8

51.9

114.9

49

79.8

32.3

57.3

120.6

56

83.4

31.1

58.8

122.3

57

87.2

32.1

60.6

124.5

Table 2: Validity criteria

Criterion from the guideline

Outcome

Validity criterion fulfilled

Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.

cannot be verified since only single vessels were tested per concentration

n/a

Percentage degradation of the reference compound has reached the pass levels by day 14.

 63.8%

 yes

The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.

 85.5%

 yes

The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.

< 5%

 yes

The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.

Critical threshold level: 70 mg/L

 50.3 mg/L

yes; the value is within the critical threshold level of 70 mg/L

Validity criteria fulfilled:
yes
Remarks:
However the validity criterion on the % difference of extremes of replicates could not be evaluated since two concentrations were tested but not in duplicates. For further details please refer to “Any other information on results incl. tables”.
Interpretation of results:
not readily biodegradable

Description of key information

Fatty acids lanolin, di, tri- and tetraesters with pentaerythritol and rape fatty acid is not readily biodegradable according to OECD criteria.

Key value for chemical safety assessment

Additional information

Experimental data is available for the biodegradation of Fatty acids lanolin, di, tri- and tetraesters with pentaerythritol and rape fatty acid. The study was conducted under GLP conditions according to OECD 301B (CO2 evolution). The substance was tested in two different initial concentrations of 11.6 and 23.2 mg/L based on test material. The study deviated from the guideline in that only a single vessel was tested per concentration level. The study was performed under aerobic conditions using surface pond water as inoculum. After 28 days, degradation rates of 28.5% and 45.1% were achieved for the concentration levels of 11.6 mg/L and 23.2 mg/L, respectively. Fatty acids lanolin, di, tri- and tetraesters with pentaerythritol and rape fatty acid is therefore not readily biodegradable according to OECD criteria.

Within this study, microorganism toxicity also was assessed. The toxicity control achieved a degradation rate of 85.5% after 14 d. The substance is therefore considered not inhibitory to microorganisms.