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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:
2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
all validity criteria of the test have been fulfilled . Minor deviation was considered not to affect the results of the test as no impact was observed on the inoculum blank respiration throughout the duration of the test
Deviations:
yes
Remarks:
Temperatures recorded continuously were situated between 20.7 and 22.4°C which was slightly higher than the requirements as laid down in the study plan (22 °C ± 2 °C and constant within 1 °C)
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
GLP compliance:
yes (incl. certificate)
Remarks:
5 March 2015
Specific details on test material used for the study:
Physico-chemical Properties:
Specific Gravity: 0.916 at 20°C
Vapour Pressure: 0.0424 Pa (25 °C)
Solubility in water: 25.83 mg.L-1 (Slow-stirring method)
log Kow: 4.4 at 35°C (HPLC Method)
Oxygen conditions:
aerobic
Inoculum or test system:
other: river water
Details on inoculum:
Origin: River water was sampled from “La Mourachonne”, situated downstream of a plant treating domestic wastewater (Pegomas, France).
Pre-conditioning: The river water was aerated for about 7 days before use as inoculum at the test temperature to reduce endogenous respiration.
Duration of test (contact time):
ca. 56 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test water: Mineral medium, Reconstituted water, as prescribed by the OECD Guideline No. 301
Composition of the mineral medium : KH2PO4 (8.50 g/L), K2HPO4 ( 21.75 g/L), NA2HPO4. 2H2O (33.40 g/L), NH4CL (0.50 g/L) CaCl2. 2H2O (36.40 g/L), MgSO4. 7H2O (22.50 g/L), FeCl3. 6H2O (0.25 g/L).
Test environment: Controlled environment cabinet (22°C ± 2°C); the test was performed in the dark.

TEST SYSTEM
Culture apparatus: All-glass sealed with ground glass stoppers BOD (Biological Oxygen Demand) bottles of approximately 300 mL capacity.
Inoculum: A concentration of inoculum of approximately 10^5 cells.L-1 was used.
Number of culture flasks/concentration: 18 bottles containing test item, inoculum, mineral medium and silica gel (test suspension)

SAMPLING
Determinations of the concentration of dissolved oxygen using an oxygen electrode in duplicate vessels were made at day 0, 7, 14, 21, 29, 35, 42, 49 and 56 for the “test suspension” and “inoculum blank with silica gel” series, at day 0, 7, 14, 21 and 29 for the “procedure control” and “inoculum blank without silica gel” series, and only at the start of the test and after 7 and 14 days of incubation for the “toxicity control” series.
Temperature: Measured continuously in the growth chamber

CONTROL AND BLANK SYSTEM
Inoculum blank with silica gel:18 bottles containing inoculum, mineral medium and silica gel
inoculum blank without silica gel: 10 bottles containing inoculum and mineral medium
procedure control: 10 bottles containing reference substance, inoculum and mineral medium
toxicity control: 6 bottles containing test item, reference substance, inoculum and mineral medium
Reference substance:
benzoic acid, sodium salt
Remarks:
2 mg/L
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 5
Sampling time:
28 d
Details on results:
Test item was biodegraded by 5% at day 29 in the Closed Bottle test . The test period was therefore extended to 56 days in order to demonstrate a potential inherent biodegradability or a non persistence of the test item. However, the biodegradation percentage at day 56 was only 7%. It should be noted that the test item had no inhibitory effect on the activity of the microbial inoculum, as demonstrated by the test results of the toxicity control, in agreement with OECD 301 (oxygen consumption in the toxicity control must be greater than 25% of the ThOD value within 14 days).
Therefore, 2-ETHYL-4-(2,2,3-TRIMETHYL-3-CYCLOPENTENE-1-YL)-(2E)-BUTEN-1-OL cannot be considered as readily biodegradable under the experimental conditions.
Results with reference substance:
The calculated ThOD of the test item were calculated from their empirical formulae to be ThOD = 3.00 mgO2.mg-1

Percentage biodegradation of the test item, the reference substance and the toxicity control throughout the test:

 

 

Time (days)

0

7

14

21

29

35

42

49

56

Test Suspension

(2 mg test item.L-1)

Replicate 1

0.00

3.25

3.00

5.75

6.58

3.33

2.58

1.42

4.92

Replicate 2

0.00

3.25

4.67

1.75

4.25

5.17

0.75

4.75

9.25

Mean

0

3

4

4

5

4

2

3

7

Procedure Control

(2 mg reference substance.L-1)

Replicate 1

0.00

79.49

84.88

69.46

88.17

-

-

-

-

Replicate 2

0.00

75.90

83.38

73.05

85.18

-

-

-

-

Mean

0

78

84

71

87

-

-

-

-

Toxicity Control *

(2 mg reference substance.L-1

+ 2 mg test item.L-1)

Mean

0

71

78

-

-

-

-

-

-

* % biodegradationtox.Control=    BOD tox. cont. x 100

                                           ThODref. subst.

 

with BOD tox. cont =    (mTox(o) - mTox(n)) - (ma(o) - ma(n))

                                       mg test ref susbst.L-1in vessel

 

              and where:

                                           n = number of days after the start of the test

                                           mTox(0) = mean toxicity control value at day 0

                                           mTox (n) = mean toxicity control value at day n

                                           ma(0) = mean test suspension value at day 0

                                           ma(n) = mean test suspension value at day n.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
2-ETHYL-4-(2,2,3-TRIMETHYL-3-CYCLOPENTENE-1-YL)-(2E)-BUTEN-1-OL cannot be considered as readily biodegradable.
Executive summary:

An enhanced biodegradability study was performed to assess the biotic degradation of test item 2-ETHYL-4-(2,2,3-TRIMETHYL-3-CYCLOPENTENE-1-YL)-(2E)-BUTEN-1-OL according to OECD Guideline 301 D and in compliance with GLP.

18 BOD bottles were filled with mineral medium inoculated with river water (5 mL/L) and test item added at a nominal concentration of 2 mg/L with the help of silica gel. In the meantime, two series of ten blanks (with and without silica gel) were filled with inoculated mineral medium. Furthermore, six bottles containing the reference substance sodium benzoate (2 mg/L) were tested in order to check the procedure. The concentrations of dissolved oxygen in duplicate bottles from each group incubated between 20.7 and 22.4°C in darkness were measured at the start of the test and thereafter once a week until the end of the test (56 days for each group except the procedure control until 14 days).

The validity of the test was demonstrated by an endogenous respiration < 1.5 mg O2/L and by a biodegradation of the reference substance of 84 % of its ThOD after 14 days of incubation. Moreover, the differences of the replicate values at day 56 were less than 20 % and oxygen concentrations were > 0.5 mg/L in all bottles during the test period. The test item was biodegraded by 5 % at day 29. Substances are considered to be readily biodegradable in the Closed Bottle test if oxygen consumption is equal to or greater than 60 % of the ThOD value within ten days from the day by which the level exceeding 10 % and this pass level is attained within 28 days. In this study, the pass level of 60 % was not reached.

Therefore, 2-ETHYL-4-(2,2,3-TRIMETHYL-3-CYCLOPENTENE-1-YL)-(2E)-BUTEN-1-OL cannot be considered as readily biodegradable.

Description of key information

An enhanced biodegradability study was performed to assess the biotic degradation of the test itemaccording to OECD Guideline 301 D and in compliance with GLP.

18 BOD bottles were filled with mineral medium inoculated with river water (5 mL/L) and test item added at a nominal concentration of 2 mg/L with the help of silica gel.

The test item was biodegraded by 5 % at day 29.

It is therefore considered that the test substance is not readily biodegradable according to the criteria of OECD 301 D guideline.

The result of this key study is proposed as end point value for the chemical safety assessment.

2-ethyl-4-(2,2,3-trimethyl-3-cyclopenten-1-yl)-(2E)-buten-1-ol is not readily biodegradable according to the criteria of OECD 301D guideline.

The test item is not considered as readily biodegradable according to OECD 301 D guideline.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

An enhanced biodegradability study was performed to assess the biotic degradation of the test itemaccording to OECD Guideline 301 D and in compliance with GLP.

18 BOD bottles were filled with mineral medium inoculated with river water (5 mL/L) and test item added at a nominal concentration of 2 mg/L with the help of silica gel.

The test item was biodegraded by 5 % at day 29.

It is therefore considered that the test substance is not readily biodegradable according to the criteria of OECD 301 D guideline.

The result of this key study is proposed as end point value for the chemical safety assessment.