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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report date:
2018

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
2,3-epoxypropyl o-tolyl ether
EC Number:
218-645-3
EC Name:
2,3-epoxypropyl o-tolyl ether
Cas Number:
2210-79-9
Molecular formula:
C10H12O2
IUPAC Name:
2-[(2-methylphenoxy)methyl]oxirane
Specific details on test material used for the study:
Position of radiolabel: Aromatic ring of cresol structure to be radio labeled
Specific activity: 2.50 GBq/mmol (15.2 MBq/mg)
Source: Envigo
Lot number: FK12YK/OOE02/01
Radiochemical purity: The radiochemical purity will be measured prior to application and should be greater than 97%
Storage: -20 C +/- 10 C under nitrogen
Radiolabelling:
yes

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
natural water: freshwater
Details on source and properties of surface water:
Surface water was provided by Envigo as part of this study. Water was transported in containers and, upon receipt at the testing facility and prior to use, the surface water was passed through a 0.2 mm sieve and a coarse filter paper (GF/A). The surface water was used on the day of collection. Characterization of the surface water was carried out, not to GLP, by NRM Ltd, Bracknell, UK. Microbiological assays of the surface water were conducted at Envigo as part of this study.
Initial test substance concentration
Initial conc.:
50 µg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
Study Conduct
Preparation and Incubation of the Test Systems
Portions of filtered surface water (100 mL) were added to cylindrical 500 mL glass bottles.

For each concentration of 2,3-epoxypropyl o-tolylether, the following vessels were established:
Symbol Details Total vessels
FT Triplicate flasks at 7 sampling times plus six spare flasks 27
(duplicate flasks for determination of proportions of
2,3-epoxypropyl o-tolylether and degradates, a single flask for
measurement of 14CO2)

FS Duplicate sterile controls at 61 days, sterilized by autoclaving, 2
prior to addition of 2,3-epoxypropyl o-tolylether (a single flask for
determination of proportions of 2,3-epoxypropyl o-tolylether and
degradates, a single flask for measurement of 14CO2)

The following additional vessels were prepared:

Symbol Details Total vessels
FC Reference control containing [14C]-benzoic acid at 10 μg/L (to 2
confirm minimum microbial activity)
FSolvent Reference control containing [14C]-benzoic acid at 10 μg/L and 2
solvent used for the test item (to determine possible adverse
effects of solvent)

In addition, five vessels of surface water were set up for microbiological analysis. Two vessels were treated with the same proportion of solvent that was used to treat the 100 μg/L vessels in the main experiment and the three remaining vessels were not treated. These vessels were not treated with 2,3-epoxypropyl o-tolylether.
Two vessels were used for system parameter measurements (pH and oxygen content). These vessels were not treated with 2,3-epoxypropyl o-tolylether.
With the exception of the reference control vessels, all test vessels were sealed.

Samples established for treatment with the reference control [14C]-benzoic acid were incorporated into individual flow-through systems arranged as follows (Appendix 3).

(i) Humidifying vessel (with sintered stem for uniform gas dispersion) containing water to humidify the air-flow;
(ii) Test vessel containing the surface water;
(iii) Vessel containing 1 M aqueous potassium hydroxide solution with phenolphthalein indicator (to trap 14CO2);
(iv) Vessel containing 1 M aqueous potassium hydroxide solution with phenolphthalein indicator (to trap 14CO2);
(v) A non-return valve to prevent accidental backflow through the test apparatus.

Air was drawn through each system at a flow rate of approximately 50 mL/minute. Flow rates were checked and adjusted throughout the incubation period.
All test systems were stirred continuously to facilitate oxygen transfer and maintained in darkness at approximately 12C ± 2C in a temperature-controlled room. The temperature in the room was recorded electronically by REES (REES Scientific).

Preparation and Application of the Test Item
[14C]-2,3-Epoxypropyl o-tolylether was used without radiodilution. Aliquots of the test item stock solution, 2.65 mL (0.50 mg) and 1.33 mL (0.25 mg) were dispensed into individual vessels and diluted with water to 10 mL and 5 mL, respectively. The concentrations of the application solutions were 0.05 mg/mL.

Aliquots (202 µL or 39 µL) of the application solutions were applied to samples of surface water (vessels FT and FS). To accurately determine the amount of radioactivity (and 2,3-epoxypropyl o-tolylether) added to each sample, triplicate aliquots (as per application volume) were taken throughout the application process and diluted with a portion (20 mL) of acetonitrile. Duplicate aliquots (200 µL) were taken for LSC.

No 2,3-epoxypropyl o-tolylether was added to the samples established for microbiological activity determination or for measurement of system parameters.

Preliminary Experiments
Prior to the main experiment, preliminary experiments were performed with surface water to establish the analytical methodology and confirm the sampling schedule.
For the first preliminary experiment, three vessels were prepared and treated at the highest test concentration (100 g/L). One vessel was used for zero-time analysis; the other two vessels were incorporated into individual flow-through systems (as detailed in Section 3.5.1) and sampled after 2 and 7 days of incubation.

Due to a loss of recovered radioactivity observed after 7 days in the first preliminary experiment, a second preliminary experiment was conducted to investigate this further and establish the most appropriate experimental set-up for the main study in order to improve recovered radioactivity.

For the second preliminary experiment, four vessels were prepared and treated at the highest test concentration (100 g/L) as summarized below:
Sample identity Sampling interval (days) Incubation system Trapping media
SC55 0 - -
SC56 7 Constant flow-through Polyurethane bung, ethyl digol,
(as per Section 3.5.1) 2 x 1 M potassium hydroxide

SC57 7 Static (test vessel sealed N/A (analyzed immediately)
after test item application)

SC58 7 Static (test vessel sealed Polyurethane bung, ethyl digol,
after test item application) 1 M potassium hydroxideA

A All trapping media connected on sampling occasion and test vessel headspace purged at 30 mL/min for approx. 30 minutes

The weight of the surface water was recorded, and duplicate weighed aliquots (1.0 mL) were taken for LSC. Samples were analyzed directly for parent and metabolites by HPLC with radiodetection.

The volumes of trapping solutions were measured and duplicate aliquots (1.0 mL) taken for LSC.

The polyurethane bungs were extracted with acetonitrile, the weight of extract was recorded, and duplicate weighed aliquots (1.0 mL) taken for LSC.

Sampling Intervals (Main Experiment)
For each concentration of 2,3-epoxypropyl o-tolylether, triplicate samples of surface water were taken for analysis immediately after application and after 2, 7, 14, 30, 44 and 61 days of incubation. Duplicate sterile controls were taken for analysis after 61 days of incubation.

Sample Analysis (Main Experiment)
For the determination of total radioactivity in samples, total weights, aliquot weights and liquid scintillation counting data were recorded and processed using the DEBRA automated laboratory data capture and processing system (V5.5.4.49), LabLogic Systems Ltd, Sheffield, UK.

Samples for Chromatographic Analysis (FT): The weight of the surface water was recorded, and duplicate weighed aliquots (1.0 mL) were taken for LSC. Samples were analyzed directly for parent and metabolites by HPLC with radiodetection.

Samples for Direct 14CO2 Determination (FT and FS): Upon sampling vessels were immediately (with minimal delay) connected to a flow-through system of traps (as detailed in Section 3.5.1) for approximately 15 minutes. The surface water was then acidified (using concentrated hydrochloric acid to pH 2 - 3) and re-connected to the flow-through system, this time the glass tube bringing air flow into the test vessel was just below the surface of the water. After at least 1 hour the vessel was removed, the weight of the water was recorded, and duplicate weighed aliquots (1.0 mL) were taken for LSC. The volumes of trapping solutions were measured and duplicate aliquots (1.0 mL) taken for LSC.

Validity of Test Determination
Application of the Reference Control
Aliquots (94 µL) of a 0.01 mg/mL stock solution of [14C]-benzoic acid in acetonitrile were applied to samples of surface water (vessels FC and FSOLVENT). To accurately determine the amount of radioactivity (and benzoic acid) added to each sample, triplicate aliquots (94 μL) were taken throughout the application process and diluted with an aliquot (20 mL) of acetonitrile. Duplicate aliquots (200 µL) were taken for LSC.

Sampling Intervals
Duplicate samples were taken for analysis after 14 days. Trapping solutions were taken for analysis after 2, 7, 9 and 14 days of incubation.

Sample Analysis
The weight of the surface water was recorded, and duplicate weighed aliquots (1.0 mL) were taken for LSC.
The volumes of trapping solutions were measured and duplicate aliquots (1.0 mL) taken for LSC.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Test performance:
Preliminary Experiments
For preliminary experiment 1 the total recoveries decreased from 100.8% applied radioactivity at Day 0 to 82.7% applied radioactivity at Day 7. Volatile radioactivity accounted for a maximum of 1.0% applied radioactivity.

For preliminary experiment 2 the total recoveries decreased from 100.5% applied radioactivity at Day 0 to 86.0% applied radioactivity at Day 7 in the test vessel connected to the constant flow-through incubation system (same set-up as for preliminary experiment 1). For the static (sealed) test vessels the recovery of radioactivity remained between 100.1% and 100.2% applied radioactivity at Day 7, demonstrating that the static (sealed) test vessel set-up was the best set-up to use for the main experiment.

HPLC analysis of the samples from the static (sealed) test vessels showed 2,3-epoxypropyl o-tolylether degraded, accounting for between 84.3% and 85.2% applied radioactivity at Day 7.

Characterization of the Test System
Additionally, this table contains the results of various measurements (pH, oxygen saturation) made at the sampling site.

The surface water was microbiologically active throughout the incubation period and solvent treatment had no adverse effects on the microbial activity.

Incubation Conditions
During the incubation period, oxygen levels in the water (in the range 88.7 to 95.4% saturation) were indicative of an aerobic surface water.

Validity of Test Determination
The total recoveries of radioactivity in the surface water treated with the reference control [14C]-benzoic acid at a concentration of 10.5 g/L were 79.0 – 93.2% applied radioactivity after 14 days. Low recoveries are assumed to be due to incomplete trapping of CO2. Direct volatile radioactivity, all associated with 14CO2, accounted for 58.1 – 68.0% applied radioactivity after 14 days.

The test was shown to be valid as the reference control degraded within the expected time interval.
% Degradationopen allclose all
Key result
% Degr.:
96.4
Parameter:
test mat. analysis
Remarks:
20 ug/ml
Sampling time:
44 d
Key result
% Degr.:
100
Parameter:
test mat. analysis
Remarks:
20 ug/ml
Sampling time:
61 d
Key result
% Degr.:
98.9
Parameter:
test mat. analysis
Remarks:
100 ug/ml
Sampling time:
61 d
Half-life of parent compound / 50% disappearance time (DT50)open allclose all
Key result
Compartment:
natural water: freshwater
DT50:
11.4 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Key result
Compartment:
natural water: freshwater
DT50:
11.8 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Transformation products:
yes
Identity of transformation products
No.:
#1
Reference
Reference substance name:
Unnamed
IUPAC name:
(2-methylphenoxy)acetic acid
Inventory number:
InventoryMultipleMappingImpl [inventoryEntryValue=EC 217-517-4]
CAS number:
1878-49-5
Identity:
o-Methylphenoxyacetic acid
Molecular formula:
C9H10O3
Molecular weight:
166.174
SMILES notation:
Cc1ccccc1OCC(=O)O
InChl:
InChI=1/C9H10O3/c1-7-4-2-3-5-8(7)12-6-9(10)11/h2-5H,6H2,1H3,(H,10,11)
Details on transformation products:
(2-methylphenoxy)acetic acid A
(Metabolite C)
Evaporation of parent compound:
no
Volatile metabolites:
no

Any other information on results incl. tables

Table 1            Surface Water Sampling Information

Envigo batch numbers

E170418A & E170418B

Origin

River Waveney, Palgrave, Diss, Norfolk, UK

Geographic co-ordinates

52°22’2’’ N, 1°7’21’’ E

Date of sampling

17 April 2018

Water body type

River

Water:

 

Appearance

Green hue, clear

Sampling depth (cm)

30

Temperature (°C), just below water surface

11.5

pH

7.52

Oxygen saturation (%), just below water surface

65.4

Surface water was obtained, and measurements made, by Envigo

The values in this table are field measurements made at the time of collection

 

 

 

Table 2            Physical and Chemical Characteristics of the Surface Water

Total organic carbon (mg/L)

11.7

Dissolved organic carbon (mg/L)

11.3

Biological oxygen demand (mg/L)

<2

Total nitrogen (mg/L)

5.9

Total phosphorus (mg/L)

0.3

Ammonium nitrogen (mg/L)

0.3

Nitrate nitrogen (mg/L)

5.1

Nitrite nitrogen (mg/L)

<0.1

Soluble reactive phosphorus (µg/L)

41.6

Total suspended solids (mg/L)

10

Hardness as CaCO3(mg/L)

514

These parameters were measured in separate studies, not to GLP, by NRM Ltd. Some additional measurements were made at the time of collection; the results of these are shown inTable 1.

 

 

Table 3            Microbiological Characterization of the Surface Water

 

Start of incubation
(untreated)

End of incubation
(untreated)

End of incubation
(solvent treated)

Aerobic bacteria

7.30 x 105

4.40 x 105

3.45 x 105

Aerobic bacterial spores

<10

70

10

Actinomycetes

<10

<10

<10

Fungi

<10

<10

55

Results are expressed as colony forming units/g

 

 

Table 4            Recoveries of Radioactivity from Incubated Surface Water Treated with [14C]-Benzoic Acid at 10 µg/L

FCsamples:

Time after application
(days)

Sample
identity

Surface
water

Volatiles

Total
recovery

14

SC50

28.2

58.1

86.3

SC51

15.9

63.1

79.0

Results expressed as % applied radioactivity

 

FSolventsamples:

Time after application
(days)

Sample
identity

Surface
water

Volatiles

Total
recovery

14

SC52

17.4

64.6

82.0

SC53

25.2

68.0

93.2

Results expressed as % applied radioactivity

 

 

Table 5            Recoveries of Radioactivity from Incubated Surface Water Treated with [14C]-2,3-Epoxypropyl o-tolyletherat 20 µg/L

FTsamples:

Time after application
(days)

Sample
identity

Surface water

Volatiles

Total
recovery

Non-acidified

Post-acidification

0

SC25

100.5

na

na

100.5

SC26

100.4

na

na

100.4

SC27

100.1

na

na

100.1

2

SC28

96.8

na

na

96.8

SC29

100.3

na

na

100.3

SC30

na

92.2

<0.1

92.2

7

SC31

99.3

na

na

99.3

SC32

98.4

na

na

98.4

SC33

na

97.3

nd

97.3

14

SC34

97.3

na

na

97.3

SC35

96.9

na

na

96.9

SC36

na

98.5

0.1

98.6

30

SC37

98.9

na

na

98.9

SC38

81.2

na

na

81.2

SC39

na

77.0

16.8

93.8

44

SC40

83.6

na

na

83.6

SC41

80.7

na

na

80.7

SC42

na

61.1

30.2

91.3

61

SC43

64.8

na

na

64.8

SC44

71.0

na

na

71.0

SC45

na

56.9

20.5

77.4

Results expressed as % applied radioactivity

na          not applicable

nd          not detected

 

Table 6            Recoveries of Radioactivity from Incubated Surface Water Treated with [14C]-2,3-Epoxypropyl o-tolylether at 100 µg/L

FTsamples:

Time after application
(days)

Sample
identity

Surface water

Volatiles

Total
recovery

Non-acidified

Post-acidification

0

SC66

99.0

na

na

99.0

SC67

99.8

na

na

99.8

SC68

99.5

na

na

99.5

2

SC07

98.7

na

na

98.7

SC08

98.5

na

na

98.5

SC09

na

96.4

<0.1

96.4

7

SC10

97.5

na

na

97.5

SC11

97.9

na

na

97.9

SC12

na

96.3

<0.1

96.3

14

SC13

97.3

na

na

97.3

SC14

97.1

na

na

97.1

SC15

na

97.1

0.1

97.2

30

SC16

98.1

na

na

98.1

SC17

97.6

na

na

97.6

SC18

na

95.4

1.0

96.4

44

SC19

94.7

na

na

94.7

SC20

96.4

na

na

96.4

SC21

na

92.1

2.2

94.3

61

SC22

95.6

na

na

95.6

SC23

76.9

na

na

76.9

SC24

na

78.6

9.6

88.2

Results expressed as % applied radioactivity

na          not applicable

 

Table 7            Recoveries of Radioactivity from Incubated Sterile Surface Water Treated with [14C]-2,3-Epoxypropyl o-tolylether at 20 µg/L

FSsamples:

Time after application
(days)

Sample
identity

Surface water

Volatiles

Total
recovery

Non-acidified

Post-acidification

61

SC48

100.3

na

na

100.3

SC49

na

97.2

0.1

97.3

Results expressed as % applied radioactivity

na          not applicable

 

 

 

Table 8            Recoveries of Radioactivity from Incubated Sterile Surface Water Treated with [14C]- 2,3-Epoxypropyl o-tolylether at 100 µg/L

FSsamples:

Time after application
(days)

Sample
identity

Surface water

Volatiles

Total
recovery

Non-acidified

Post-acidification

61

SC46

96.3

na

na

96.3

SC47

na

94.4

<0.1

94.4

Results expressed as % applied radioactivity

na          not applicable

 

 

Table 9            Proportions of Radioactive Components in Surface Water Treated with[14C]-2,3-Epoxypropyl o-tolylether at 20 µg/L

 

Time after application (days)

0

2

7

14

Sample identity

SC25

SC26

SC28

SC29

SC31

SC32

SC34

SC35

Met E (Rt ~3.9 mins)

-

-

-

-

-

-

-

-

Met B (Rt ~10.5 mins)

-

-

-

-

-

-

-

-

Met F (Rt ~11.8 mins)

-

-

-

-

-

-

-

-

Met A (Rt ~12.8 mins)

-

-

5.1

4.8

22.6

20.3

50.7

43.4

2-MP (Rt ~14.7 mins)

-

-

-

-

-

-

-

-

Met C (Rt ~15.7 mins)

-

-

-

-

-

-

-

-

Met D (Rt ~16.5 mins)

-

-

-

-

-

-

-

-

2,3-EPTE

99.3

100.2

91.4

95.0

76.6

74.8

46.1

53.2

Others (a)

1.2

0.2

0.3

0.4

0.2

3.3

0.6

0.3

 

 

Time after application (days)

30

44

61

Sample identity

SC37

SC38

SC40

SC41

SC43

SC44

Met E (Rt ~3.9 mins)

-

23.9

25.2

18.7

9.4

17.5

Met B (Rt ~10.5 mins)

-

-

2.8

-

1.2

-

Met F (Rt ~11.8 mins)

-

-

-

-

-

-

Met A (Rt ~12.8 mins)

75.8

18.9

8.1

16.5

14.2

13.8

2-MP (Rt ~14.7 mins)

2.6

-

-

-

-

-

Met C (Rt ~15.7 mins)

4.8

29.0

44.4

40.5

39.7

38.3

Met D (Rt ~16.5 mins)

3.3

-

-

-

-

-

2,3-EPTE

3.7

8.4

2.3

4.4

-

-

Others (a)

8.8

1.0

0.7

0.5

0.2

1.3

Results are expressed as % applied radioactivity

(a) Radioactivity distributed throughout regions of the chromatogram other than those specified and which did not contain any discrete radioactive components

-              Not apparent or below the limit of detection

 

 

 

 

Table 10          Proportions of Radioactive Components in Surface Water Treated with [14C]-2,3-Epoxypropyl o-tolylether at 100 µg/L

 

Time after application (days)

0

2

7

14

Sample identity

SC66

SC67

SC07

SC08

SC10

SC11

SC13

SC14

Met E (Rt ~3.9 mins)

-

-

-

-

-

-

-

-

Met B (Rt ~10.5 mins)

-

-

-

-

-

-

0.7

1.0

Met F (Rt ~11.8 mins)

-

-

-

-

-

-

-

-

Met A (Rt ~12.8 mins)

-

-

6.7

6.3

21.2

22.9

45.8

46.3

2-MP (Rt ~14.7 mins)

-

-

-

-

-

-

-

-

Met C (Rt ~15.7 mins)

-

-

-

-

-

-

-

-

Met D (Rt ~16.5 mins)

-

-

-

-

-

-

-

-

2,3-EPTE

98.7

95.8

91.1

89.4

74.7

72.0

49.3

48.0

Others (a)

0.3

4.0

1.0

2.8

1.7

2.9

1.6

1.9

 

 

Time after application (days)

30

44

61

Sample identity

SC16

SC17

SC19

SC20

SC22

SC23

Met E (Rt ~3.9 mins)

-

-

4.2

0.9

1.1

21.9

Met B (Rt ~10.5 mins)

0.6

1.1

-

-

1.0

2.0

Met F (Rt ~11.8 mins)

-

-

1.3

-

1.5

2.8

Met A (Rt ~12.8 mins)

76.2

77.2

76.7

83.2

84.5

21.1

2-MP (Rt ~14.7 mins)

0.4

0.9

0.6

0.6

-

-

Met C (Rt ~15.7 mins)

2.2

1.1

6.3

2.0

4.6

22.7

Met D (Rt ~16.5 mins)

1.5

1.0

2.4

1.5

1.1

-

2,3-EPTE

10.9

9.7

2.2

4.7

1.4

0.8

Others (a)

6.4

6.6

1.0

3.4

0.2

5.6

Results are expressed as % applied radioactivity

(a) Radioactivity distributed throughout regions of the chromatogram other than those specified and which did not contain any discrete radioactive components

-              Not apparent or below the limit of detection

 

 

 

 

Table 11          Proportions of Radioactive Components in Sterile Surface Water Treated with [14C]-2,3-Epoxypropyl o-tolylether at 20 µg/L

 

Time after application (days)

61

Sample identity

SC48

Met E (Rt ~3.9 mins)

-

Met B (Rt ~10.5 mins)

-

Met F (Rt ~11.8 mins)

-

Met A (Rt ~12.8 mins)

72.8

2-MP (Rt ~14.7 mins)

-

Met C (Rt ~15.7 mins)

-

Met D (Rt ~16.5 mins)

-

2,3-EPTE

26.9

Others (a)

0.6

Results are expressed as % applied radioactivity

(a) Radioactivity distributed throughout regions of the chromatogram other than those specified and which did not contain any discrete radioactive components

-              Not apparent or below the limit of detection

 

 

 

Table 12          Proportions of Radioactive Components in Sterile Surface Water Treated with [14C]-2,3-Epoxypropyl o-tolylether at 100 µg/L

 

Time after application (days)

61

Sample identity

SC46

Met E (Rt ~3.9 mins)

-

Met B (Rt ~10.5 mins)

-

Met F (Rt ~11.8 mins)

-

Met A (Rt ~12.8 mins)

68.5

2-MP (Rt ~14.7 mins)

-

Met C (Rt ~15.7 mins)

-

Met D (Rt ~16.5 mins)

-

2,3-EPTE

26.4

Others (a)

1.4

Results are expressed as % applied radioactivity

(a) Radioactivity distributed throughout regions of the chromatogram other than those specified and which did not contain any discrete radioactive components

-              Not apparent or below the limit of detection

 

 

 

Table 13          Kinetic Data for the Decline of 2,3-Epoxypropyl o-tolylether and Metabolites A, C and E in Surface Water

2,3-Epoxypropyl o-tolylether

Concentration

Error %

r2

DT50(days)

DT90(days)

20mg/L

9.11

0.9745

11.4

37.8

100mg/L

7.75

0.9875

11.8

39.2

 

Metabolite A

Concentration

Error %

r2

DT50(days)

DT90(days)

20mg/L

21.0

0.4301

10.4

34.5

100mg/L

nd

0.2663

28.4

94.4

 

Metabolite C

Concentration

Error %

r2

DT50(days)

DT90(days)

20mg/L

nd

0.5810

139

462

 

Metabolite E

Concentration

Error %

r2

DT50(days)

DT90(days)

20mg/L

nd

0.5726

24.1

79.9

 

nd          Only two time intervals therefore no error % calculated

Kinetic model: SFO = single first order

The kinetic analysis is described in more detail inAppendix 8

Applicant's summary and conclusion

Validity criteria
Validity criteria fulfilled:
yes
Conclusions:
2,3-Epoxypropyl o-tolylether degraded rapidly in the surface water with DT50 values of 11.4 days (at 20 ug/L) and 11.8 days (at 100 ug/L).

2,3-Epoxypropyl o-tolylether degraded to Metabolites A, C and E, accounting for maximums of 84.5, 44.4 and 25.2% applied radioactivity, respectively.

Identification of the major degradation products designated as Metabolites A, C and E was attempted by liquid chromatography with mass spectrometry. Metabolite C was tentatively identified as (2-methylphenoxy)acetic acid, Metabolites A and E are unidentified. Metabolite E is considered as polar material.
Executive summary:

The biodegradation and fate of 2,3-epoxypropyl o-tolylether has been studied at low concentrations in surface water under laboratory conditions. Surface water was treated with [14C]-2,3-epoxypropyl o-tolylether at nominal application rates of 20 µg/L and 100 µg/L. Treated surface water samples were incubated with continuous stirring to maintain aerobic conditions at 12 ± 2°Cin darkness for periods of up to 61 days. 

Total recoveries of radioactivity (mass balances,post-acidification samples) for samples treated at 20 µg/L and 100 µg/L were between 77.4 and 100.1% applied radioactivity. 

Separate samples were treated for the determination of14CO2at 20 µg/L. After acidification to strip off any14CO2, the total radioactivity in the surface water decreased from 92.2% applied radioactivity at Day 2 to 56.9% applied radioactivity after 61 days. Direct volatile radioactivity (14CO2) accounted for a maximum of 30.2% applied radioactivity after 44 days.

Separate samples were treated for the determination of14CO2at 100 µg/L. After acidification to strip off any14CO2, the total radioactivity in the surface water decreased from 96.4% applied radioactivity at Day 2 to 78.6% applied radioactivity after 61 days. Direct volatile radioactivity (14CO2) accounted for a maximum of 9.6% applied radioactivity after 61 days.

Separate sterile samples were treated to provide controls (FS). Total recoveries of radioactivity (mass balances, post-acidification samples) for samples treated at 20 µg/L and 100 µg/L were 97.3% and 94.4% applied radioactivity, respectively. Carbon dioxide accounted for a maximum of 0.1% applied radioactivity.

DT50and DT90values for the decline of 2,3-epoxypropyl o-tolylether from the surface water are shown below.

Concentration

DT50(days)

DT90(days)

20mg/L

11.4

37.8

100mg/L

11.8

39.2

 

Analysis of the surface water samples showed that 2,3-epoxypropyl o-tolylether degraded to Metabolites A, C and E, accounting for maximums of 84.5, 44.4 and 25.2% applied radioactivity, respectively. 

Identification of the major degradation products designated as Metabolites A, C and E was attempted by liquid chromatography with mass spectrometry. Metabolite C was tentatively identified as (2-methylphenoxy)acetic acid, Metabolites A and E are unidentified. Metabolite E is considered as polar material.

All other (unidentified) degradation products were present at levels of ≤3.3% applied radioactivity.