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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms, other
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:
Large degradation values beyond 100% indicate that unidentified material may have been present in the test solution which was also degraded by the microorganisms of the inoculum.
Qualifier:
according to
Guideline:
other: Toxicity control from Ready Biodegradability study OECD 301 B
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Department of Health of the Government of the United Kingdom, London, United
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION:
- Method: The test substance was directly added to the test vessel to achieve a final concentration of 102.9 mg/L of the reference material sodium benzoate and 23.2 mg/L of the test substance in 3 L of test media.

Test organisms (species):
other: Surface pond water
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 sludge: 100 mL surface water per L of test media
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
56 d
Remarks on exposure duration:
The test was continued beyond day 28 due to poor biodegradability of the test substance.
Test temperature:
22 ± 2°C
Nominal and measured concentrations:
The toxicity control contained 102.9 mg/L of the reference substance sodium benzoate and 23.2 mg/L of the test substance.
Details on test conditions:
TEST SYSTEM
- Test vessel: 3 L flat bottomed flasks
- 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.
- Number of culture flasks/concentration: 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline OECD 301 B

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continuous darkness

EFFECT PARAMETERS MEASURED : The biodegradation of the test substance was recorded after 14 days.
Reference substance (positive control):
not required
Duration:
14 d
Dose descriptor:
other: % degradation based on CO2 evolution
Effect conc.:
85.5 other: % degradation based on CO2 evolution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: CO2 evolution

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 of study OECD 301 B

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”.
Conclusions:
The substance shows no inhibitory effect on microorganisms.

Description of key information

Key value for chemical safety assessment

Additional information

A toxicity control from a ready biodegradability study is available. If a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2017).

A substance can be assumed to be not inhibitory to aquatic microorganisms, if in the toxicity control of a ready biodegradation test more than 25% degradation based on oxygen demand (BOD/ThOD) occurred within 14 days (OECD guideline 301).

The study for Fatty acids lanolin, di, tri- and tetraesters with pentaerythritol and rape fatty acid was conducted according to OECD 301 B. An inoculum from surface pond water was exposed to 23.2 mg/L of the test material and 34.3 mg/L of the reference substance sodium benzoate. The toxicity control attained 85.5% degradation after 14 days of incubation. Hence, the substance is not toxic to aquatic microorganisms in the toxicity control and the test item concentration of 23.2 mg/L can be used as NOEC.