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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:
weight of evidence
Study period:
2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)
Version / remarks:
April 2004
Deviations:
no
GLP compliance:
yes
Radiolabelling:
yes
Remarks:
two labels: label1: [thiazole-2-14C] and label 2: [oxadiazine-4-14C]
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
- Details on collection: Sampling location: Heiminghausen Lake, 57392 Schmallenberg, Germany,
- Site description: A freshwater lake fed by a stream from a weir on the river. Woodland around the lake.
- Collection procedure: Immersion of container.
- Sampling depth: Water: 20 - 30 cm (above the sediment)
- Storage conditions: Samples kept waterlogged at 4 ºC in the dark
- Storage length: 3 weeks prior to use (over sediment)
- Temperature (°C) at time of collection: 8
- pH at time of collection: 7.08
- Oxygen concentration (mg/l) initial/final: Start of study: 8.20; End of study: 8.19
- Oxygen concentration at collection (%): 93.3
- Water filtered: yes
- Type and size of filter used, if any: passed through 100 µm sieve prior to use. The natural water was filtered through a 0.45 µm micro glass fiber filter
Details on source and properties of sediment:
- Details on collection: Sampling location: Heiminghausen Lake, 57392 Schmallenberg, Germany,
- Site description: A freshwater lake fed by a stream from a weir on the river. Woodland around the lake.
- Collection procedure: Scooped by hand,
- Sampling depth: 0 – 3 cm
- Storage conditions: Samples kept waterlogged at 4 ºC in the dark
- Storage length: 3 weeks prior to use (over sediment)
- pH at time of collection: pH (deionised water): 6.88, pH (0.01M CaCl2): 6.44
- Organic carbon (%): 5.57
- Sediment samples sieved: yes
Duration of test (contact time):
61 d
Initial conc.:
95 µg/L
Based on:
test mat.
Remarks:
High test concentration for both test materials
Initial conc.:
10 µg/L
Based on:
test mat.
Remarks:
Low test concentration for both test materials
Parameter followed for biodegradation estimation:
CO2 evolution
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Volume of test solution/treatment: [Thiazole-2-14C] label: 218.44 µL for 10 µg/L samples and 202.06 µL for 95 µg/L samples, [Oxadizine-4-14C] label:191.65 µL for 10 µg/L samples and 188.79 µL for 95 µg/L samples
- Composition of medium: water
- Test temperature: not reported
- pH: Start of study: 7.99, End of study: 8.02
- Suspended solids concentration: not reported
- Continuous darkness: yes
- Any indication of the test material adsorbing to the walls of the test apparatus: not reported

TEST SYSTEM
- Culturing apparatus: Glass flask, moist air flow through system, connections made with glass and PTFE and silicone tubing
- Number of culture flasks/concentration: 2
- Details of trap for CO2 and volatile organics: 2 M sodium hydroxide for 14CO2

SAMPLING
- Sampling frequency: See table 1 below in 'Any other information on materials and methods, incl. tables'
- Sampling method used per analysis type: Duplicate vessels were removed at each sampling time. The natural water was filtered through a 0.45 µm micro glass fiber filter. Volume was measured, an aliquot was taken for LSC quantification and sample was immediately frozen by liquid nitrogen.
- Sample storage before analysis: in liquid nitrogen

DESCRIPTION OF CONTROL AND/OR BLANK TREATMENT PREPARATION CONTROL AND BLANK SYSTEM
- Inoculum blank: Untreated, Lake water plus suspended sediment
Reference substance:
benzoic acid, sodium salt
Remarks:
10 µg/L
Compartment:
natural water / sediment: freshwater
% Recovery:
99.7
Remarks on result:
other: 10 µg/L [thiazole-2-14C]-test material - Mean Recovery at 0 days after treatment
Compartment:
natural water / sediment: freshwater
% Recovery:
101.3
Remarks on result:
other: 95 µg/L [thiazole-2-14C]-test material - Mean Recovery at 0 days after treatment
Compartment:
natural water / sediment: freshwater
% Recovery:
100.5
Remarks on result:
other: 10 µg/L [thiazole-2-14C]-test material - Overall recovery (all samples)
Compartment:
natural water / sediment: freshwater
% Recovery:
101.8
Remarks on result:
other: 95 µg/L [thiazole-2-14C]-test material - Overall recovery (all samples)
Compartment:
natural water / sediment: freshwater
% Recovery:
102.4
Remarks on result:
other: 10 µg/L [oxadiazine-4-14C]-test material - Overall recovery (all samples)
Compartment:
natural water / sediment: freshwater
% Recovery:
101.4
Remarks on result:
other: 95 µg/L [oxadiazine-4-14C]-test material - Overall recovery (all samples)
Compartment:
natural water / sediment: freshwater
% Recovery:
103.5
Remarks on result:
other: 10 µg/L [oxadiazine-4-14C]-test material - Mean Recovery at 0 days after treatment
Compartment:
natural water / sediment: freshwater
% Recovery:
100.7
Remarks on result:
other: 95 µg/L [oxadiazine-4-14C]-test material - Mean Recovery at 0 days after treatment
Key result
Compartment:
natural water / sediment: freshwater
DT50:
91.37 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: values were extrapolated beyond the period of the test
Remarks:
10 µg/L [oxadiazine-4-14C]-test material
Key result
Compartment:
natural water / sediment: freshwater
DT50:
87.33 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: values were extrapolated beyond the period of the test
Remarks:
95 µg/L [oxadiazine-4-14C]-test material
Key result
Compartment:
natural water / sediment: freshwater
DT50:
96.81 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: values were extrapolated beyond the period of the test
Remarks:
10 µg/L [thiazole-2-14C]-test material
Key result
Compartment:
natural water / sediment: freshwater
DT50:
93.39 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: values were extrapolated beyond the period of the test
Remarks:
95 µg/L [thiazole-2-14C]-test material
Transformation products:
yes
Details on transformation products:
- Formation and decline of each transformation product during test: The major degradation products observed in all incubation groups were M2 and M1. Maximum levels of 6.17 to 7.19 % AR (M2) and 33.71 to 36.56 % AR (M1) for [thiazole-2-14C] labelled and 8.80 to 7.27 % AR (M2) and 34.54 to 33.23 % AR (M1) for [oxadiazine-4-14C] labelled test material at 61 DAT. A number of discrete unknown degradation products were also observed, none individually exceeded 5 % of applied activity (AR).
- Pathways for transformation: formed by hydrolytic cleavage
Evaporation of parent compound:
not specified
Volatile metabolites:
yes
Remarks:
See Any other information on results incl. tables, tables 1 and 2
Residues:
yes
Remarks:
See Any other information on results incl. tables, tables 3 and 4
Details on results:
The mean mass balances for the low and high test concentration in lake water plus 0.01 g/L suspended sediment samples were 100.5 % and 101.8 % with ranges of 99.2 to 102.2 % (low) and 99.5 to 103.4 % (high) for [thiazole-2-14C] labelled test material and were 102.4 % and 101.4 % with ranges of 99.5 to 103.8 (low) and 100.6 to 102.2 % (high) for [oxadiazine-4-14C] labelled test material, respectively. The mass balances for the sterilised incubation groups with water plus suspended sediment were 97.6 % applied radioactivity (AR) and 99.5 % AR for the [thiazole-2-14C] labelled and [oxadiazine-4-14C] labelled test material, respectively.
Over the duration of the study, the mean levels of the test material for the low and high test concentration [thiazole-2-14C] labelled parent compound decreased from a mean of 95.1 % AR at 0 DAT, to between 61.2 and 58.7 % AR. The levels of [oxadiazine-4-14C] labelled parent compound decreased from a mean of 96.2 %AR at 0 DAT to between 59.2 % and 58.0 % AR, for low and high dose, respectively by the end of the test. The major metabolites of the test material were found to be M1 and M2 which reached maximum levels of 36.6 % and 7.2 % AR for the [thiazole-2-14C] label and 34.5 % and 8.8 % AR for [oxadiazine-4-14C] label after 61 days. In addition, three discrete unknown metabolites were also observed, none exceeded 5 % of applied activity.
Results with reference substance:
The mean degradation of 14C-sodium benzoate to 14C-carbon dioxide (79 % AR) at 18 DAT (for lake water plus suspended sediment indicated a viable microbial population was present.

Table 1. Volatile Degradation Products for [thiazole-2-14C]-test material

Small amounts of radioactivity were evolved as volatile products throughout the course of the test.

14CO2 evolved at end of test

[thiazole-2-14C]-test material

Lake Water plus Suspended Sediment (10 µg/L)

0.7 % AR

Lake Water plus Suspended Sediment (95 µg/L)

0.7 % AR

Sterilised Lake Water plus Suspended Sediment (95 µg/L)

0.2 % AR

AR – applied radioactivity

 

Table 2. Volatile Degradation Products for [oxadiazine-2-14C]-test material

Small amounts of radioactivity were evolved as volatile products throughout the course of the test.

14CO2 evolved at end of test

[oxadiazine-4-14C]-test material

Lake Water plus Suspended Sediment (10 µg/L)

1.2 % AR

Lake Water plus Suspended Sediment (95 µg/L)

1.2 % AR

Sterilised Lake Water plus Suspended Sediment (95 µg/L)

0.8 % AR

Table 3. Radioactive Residues for [thiazole-2-14C]-test material

[thiazole-2-14C]-test material

Water residues

Water residues did not decline with time in both test systems.

Total water residues at 0 DAT (10 µg/L)

99.7 %

Total water residues at 0 DAT (95 µg/L)

101.3 %

Total water residues at end of study (10 µg/L)

101.1 %

Total water residues at end of study (95 µg/L)

102.7 %

Extractable residues

No extraction of the sediment performed

Bound residues

Bound residues increased throughout the incubation period in both test systems.

Bound residues at end of study (10 µg/L)

0.0 %

Bound residues at end of study (95 µg/L)

0.0 %

DAT – days after treatment

Table 4. Radioactive Residues for [oxadiazine-2-14C]-test material

[oxadiazine-4-14C]-test material

Water residues

Water residues did not decline with time in both test systems.

Total water residues at 0 DAT (10 µg/L)

101.3 %

Total water residues at 0 DAT (95 µg/L)

103.4 %

Total water residues at end of study (10 µg/L)

102.7 %

Total water residues at end of study (95 µg/L)

102.5 %

Extractable residues

No extraction of the sediment performed

Bound residues

Bound residues increased throughout the incubation period in both test systems.

Bound residues at end of study (10 µg/L)

0.0 %

Bound residues at end of study (95 µg/L)

0.0 %

The degradation rates (DegT50) of test material were estimated using CAKE software (Tessella, version 1.4) by fitting single first-order kinetics (SFO) to the data. The DegT50 values are summarised in Table 5.

Table 5: DegT50 values for The test material

System

Test concentration (µg/L)

SFO

DegT50 (days)

k

Chi2

R2

Prob > t

Natural water plus suspended sediment

[thiazole-2-14C] label

10

96.81

0.00716

1.272

0.9754

1.014E-12

95

93.39

0.00742

1.503

0.9846

4.442E-14

Natural water plus suspended sediment

[oxadiazine-4-14C]-label

10

91.37

0.00758

2.638

0.9477

2.320E-10

95

87.33

0.00793

1.285

0.9733

1.484E-11

Note: DegT50 values were extrapolated beyond the duration of the incubation period.

Validity criteria fulfilled:
not specified
Conclusions:
The mineralisation rate and the rate and route of degradation of (thiazole-2-14C) and (oxadiazine-4-14C) labelled test material was investigated in Heiminghausen natural lake water amended with 0.01 g/L suspended sediment.
The mass balances in all samples (both radiolabels) at low and high concentration ranged from 99.2 to 103.8 % AR, with an overall mean of 101.5 % AR. For the non-sterilised, viable test systems, the mean levels of the test material for each of the low and high dosed systems, decreased to between 61.2 and 58.7 % AR [thiazole-2-14C] labelled test material and 59.2 and 58.0 % AR [oxadiazine-4-14C] labelled test material at the end of the incubation period (61 DAT), with resulting DegT50 values for both labels ranging from 96 to 87 days respectively. For the sterilised samples, the test material was found not to be stable with 48.8% AR (mean for both labels) remaining at 61 DAT. The two major metabolites identified were M2 and M1. There was no significant difference in the levels for either metabolite between the two test concentrations and the two test item labels. M2 was present at levels of 6.17 % AR and 7.19 % AR in the low and high dosed systems of the [thiazole-2-14C] labelled test material and at levels of 8.80 % AR and 7.27 % AR in the low and high dosed systems of the [oxadiazine-4-14C] labelled test material. M1 was present at levels of 33.71 % AR and 36.56 % AR in the low and high dosed systems of the [thiazole-2-14C] labelled test material and at levels of 34.54 % AR and 33.23 % AR in the low and high dosed systems of the [oxadiazine-4-14C] labelled test material. Three discrete unknown metabolites were also observed, none exceeded 5 % AR. Chemical hydrolysis was determined to be the major route of degradation for the test material in sediment amended natural water. Only < 1.7 % AR was mineralised to carbon dioxide. The SFO half-life range for the test material in natural sediment amended lake water was 87 to 96 days. There were no significant observed differences between the degradation rate of the low and the high dosed systems.
Executive summary:

The extent of mineralisation, rate and route of degradation of [thiazole-2-14C] and [oxadiazine-4-14C] labelled test material, were investigated in Heiminghausen lake water systems amended with 0.01 g/L suspended sediment. The test material [thiazole-2-14C] and [oxadiazine-4-14C] labels were separately applied to the water at nominal application rates of 10 and 95 µg/L (low and high, respectively). The 95 µg/L rate was also applied to sterilised test systems (lake water plus 0.01 g/L suspended sediment). The systems were incubated under aerobic conditions and maintained in the dark at 20 °C for up to 61 days. For each system, duplicate samples were taken for analysis at up to eight intervals.


At each sampling time, the quantity of radioactivity in the water was determined by liquid scintillation counting (LSC). Prior to chromatographic analysis, samples were filtered, lyophilised and the residue successively re-dissolved using organic solvent and water. Both extracts and sediment remaining on the filter were analysed separately. The sediment residues were only analysed by combustion and LSC. Any volatile radioactivity was continuously flushed from the vessels, collected in traps and analysed. A mass balance was determined for each sample. Separate reference samples (treated with 14C sodium benzoate at 10 µg/L) of natural water plus 0.01 g/L suspended sediment were prepared to determine whether a viable microbial population was present in the test system. Separate blank control samples were similarly incubated to allow water quality measurements at each sampling interval. The mean mass balances for the low and high test concentration in lake water plus 0.01 g/L suspended sediment samples were 100.5 % and 101.8 % with ranges of 99.2 to 102.2 % (low) and 99.5 to 103.4 % (high) for [thiazole-2-14C] labelled test material and were 102.4 % and 101.4 % with ranges of 99.5 to 103.8 (low) and 100.6 to 102.2 % (high) for [oxadiazine-4-14C] labelled test material, respectively. The mass balances for the sterilised incubation groups with water plus suspended sediment were 97.6 % applied radioactivity (AR) and 99.5 % AR for the [thiazole-2-14C] labelled and [oxadiazine-4-14C] labelled test material, respectively. Over the duration of the study, the mean levels of the test material for the low and high test concentration [thiazole-2-14C] labelled parent compound decreased from a mean of 95.1 % AR at 0 DAT, to between 61.2 and 58.7 % AR. The levels of [oxadiazine-4-14C] labelled parent compound decreased from a mean of 96.2 %AR at 0 DAT to between 59.2 % and 58.0 % AR, for low and high dose, respectively by the end of the test. The major metabolites of the test material were found to be M1 and M2 which reached maximum levels of 36.6 % and 7.2 % AR for the [thiazole-2-14C] label and 34.5 % and 8.8 % AR for [oxadiazine-4-14C] label after 61 days. In addition, three discrete unknown metabolites were also observed, none exceeded 5 % of applied activity. The degradation rates (DegT50) of test material were estimated using CAKE software (Tessella, version 1.4) by fitting single first-order kinetics (SFO) to the data. The DegT50 values are summarised in Table 1.


Table 1: DegT50 values for The test material




















































System



Test concentration (µg/L)



SFO



DegT50 (days)



k



Chi2



R2



Prob > t



Natural water plus suspended sediment


[thiazole-2-14C] label



10



96.81



0.00716



1.272



0.9754



1.014E-12



95



93.39



0.00742



1.503



0.9846



4.442E-14



Natural water plus suspended sediment


[oxadiazine-4-14C]-label



10



91.37



0.00758



2.638



0.9477



2.320E-10



95



87.33



0.00793



1.285



0.9733



1.484E-11



Note: DegT50 values were extrapolated beyond the duration of the incubation period.


 


The mean degradation of 14C- sodium benzoate to 14C-carbon dioxide (79 % AR) at 18 DAT (for lake water plus suspended sediment) indicated a viable microbial population was present.

Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
Version / remarks:
April 2002
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4300 (Aerobic Aquatic Metabolism)
Version / remarks:
October 2008
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
yes
Remarks:
14C-labelled at position 2 of thiazole ring or position 4 of the oxadiazine ring
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
SOURCE AND SAMPLING OF RIVER WATER
- Source: Taunton River at Bridgewater (Massachusetts, USA)
- Site description: River - sandy loam sediment
- Geographical region / Global co-ordinates: North Eastern U.S.A / 41º56.863N - 70º56.201W.
- Date of collection: 24 October 2013
- Sampling: Water was sampled down to a depth of 30 cm above the sediment with a container. Water samples were clear.
- Storage conditions after sampling: Stored refrigerated in open container with access to air.

RIVER WATER PROPERTIES
- Oxygen concentration: 7.5 % at sampling
- pH: 6.0 at sampling
- Redox potential: 152.1 mV at the start of acclimation
Details on source and properties of sediment:
SOURCE AND SAMPLING OF SEDIMENT
- Source: Same as water
- Site description: Same as water
- Geographical region / Global co-ordinates: Same as water
- Date of collection: Same as water
- Sampling: 0 - 7.6 cm of sediment was sampled using a shovel and sieved to 2 mm.
- Storage conditions after sampling: Stored refrigerated in separate open container with access to air

PROPERTIES OF RIVER SEDIMENT
- % Clay (<2 µm): 5
- % Silt (50-2 µm): 49
- % Sand (2000-50 µm: 46
- Soil type (USDA): Sandy loam
- pH (water) in 1:1 sediment:water: 5.5
- Redox potential: 155.7 mV at the start of acclimation
- Organic matter (%): 6.6
- Organic carbon (%): 3.8
- Cation Exchange Capacity (meq/100g soil): 7.1
- Nitrogen (total, %): 0.23
- Phosphorus (total, mg/kg): 78
- Moisture (w/w %): 60.34
Duration of test (contact time):
100 d
Initial conc.:
0.1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
radiochem. meas.
Details on study design:
TEST SYSTEM
- Apparatus: Glass flask, moist air bubbled through system, connections made with glass and Teflon® tubing
- Number of replicates: 2 replicates per radiolabel for each sampling interval
- Sediment condition: Fresh, passed through 2 mm sieve prior to use
- Water condition: Fresh, collected before sediment, allowed any particulates to settle before use.
- Control conditions: Not applicable
- Incubation conditions: Aerobic - aerated continuously with ambient hydrated air.

SAMPLE SIZES
- River water: 212 mL (resulting in 4:1 water: sediment ratio)
- Pond water: 109 g wet weight (52 g dry weight)

TEST MATERIAL APPLICATION
- Solvent: Acetonitrile
- Volume of test solution used per treatment: 230 µL for [oxadiazine-4-14C]-test substance and 235 µL for [thiazole-2-14C]-test substance
- % of co-solvent per sample (mL/g x 100 %): < 0.1 %
- Application method: Hamilton syringe followed by gentle mixing

EXPERIMENTAL WATER CONDITIONS
- Temperature: 20 ± 2 °C
- Light: Continuous darkness
- pH river water: 6.5 at acclimation and study initiation and 4.4 at study termination.
- Redox potential river water (mV): 152.1 at acclimation, 92.5 at study initiation and 238.4 at study termination.
- Oxygen concentration river water (%): 5.3 at acclimation and study initiation and 4.0 at study termination

EXPERIMENTAL SEDIMENT CONDITIONS
- Redox potential river sediment (mV): 155.7 at acclimation, -78.0 at study initiation and 19.3 at study termination.
- Biomass river sediment (mg carbon/100 g soil): 13.7 at study initiation and 11.2 at study termination

CALCULATIONS
The rate of dissipation of the test substance from the water phase and the rate of degradation in the total aquatic sediment system were calculated using the Simple First-Order (SFO) kinetic model.

STATISTICS
The dissipation rate (DT50) from water and the degradation rate (DegT50) of the parent in the total system were determined from the best-fit model (SFO, CAKE, Version 1.4) based on acceptable visual fits (high correlation coefficient, r2) as well as statistical evaluation (lowest X2 % error).
Reference substance:
not required
Test performance:
The overall mass balance for the [oxadiazine-4-14C]-test substance and [thiazole-2-14C]-test substance in the Taunton River test system was 95.8 % and 97.9 % AR, during the 100-day study, which satisfied the guideline requirement of maintaining material balance between 90 % and 110 % AR.
Compartment:
other:
% Recovery:
97.93
St. dev.:
4.18
Remarks on result:
other: Recovery rates ranged from 92.02 to 105.25% AR for river aquatic system
Remarks:
mean overall recovery (all samples) of applied radioactivity (RA) of [oxadiazine-4-14C]-test substance. Total recovery is the sum of activity in the surface water, sediment extracts, sediment residue following combustion and that trapped as 14CO2 in the 1M KOH traps.
Compartment:
natural water / sediment: freshwater
% Recovery:
95.81
St. dev.:
2.64
Remarks on result:
other: Recovery rates ranged from 91.26 to 103.06% AR for river aquatic system.
Remarks:
mean overall recovery (all samples) of applied radioactivity (RA) of [thiazole-2-14C]-test substance. Total recovery is the sum of activity in the surface water, sediment extracts, sediment residue following combustion and that trapped as 14CO2 in the 1M KOH traps.
% Degr.:
82.8
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other: [oxadiazine-4-14C]-test substance parent compound degradation in the total water/sediment test system
% Degr.:
86.6
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other: [thiazole-2-14C]-test substance parent compound degradation in the total water/sediment test system
Compartment:
natural water / sediment: freshwater
DT50:
29.2 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: [Oxadiazine-4-14C]-test substance rate of degradation in whole system
Compartment:
natural water / sediment: freshwater
DT50:
25.2 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: [Thiazole-2-14C]-test substance rate of degradation in whole system
Compartment:
natural water: freshwater
DT50:
19.2 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: [Oxadiazine-4-14C]-test substance rate of dissipation from the water phase.
Compartment:
natural water: freshwater
DT50:
14.8 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: [Thiazole-2-14C]-test substance rate of dissipation from the water phase.
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
Details on transformation products:
- Formation and decline of each transformation product during test: In both water-sediment systems, during the aerobic phase, the major degradation products were M1, M2 and M3. Mineralization was a major route of aerobic degradation. With the oxadiazine ring or the thiazole ring labels, M3 reached maximum mean levels of 17.8 % and 17.0 % AR, at 70 days after treatment, and decreased to 16.2 % and 13.8 % AR, respectively, by the end of the study. Levels of M2 in the oxadiazine ring or the thiazole ring reached maximum mean levels of 3.54 % and 6.84 % AR at 48 days after treatment and decreased to 1.28 % and 0.67 % AR, respectively, by the end of the study. With the oxadiazine ring or the thiazole ring labels, M1 reached maximum mean levels of 5.98 % and 6.01 % AR, at 48 days after treatment, and decreased to 1.3 % and 2.27 % AR, respectively, by the end of the study. A fourth transformation product eluted at a retention time of approximately 2 to 3 min as a polar product, which did not correspond to any reference standard. This polar product was present at average maximum levels of 3.96 % at 48 days after treatment and 7.43 % AR at 14 days after treatment in the system treated with the oxadiazine ring or the thiazole ring (>5 % at one interval and in one label only), but decreased to 1.44 % and 0.18 % AR, respectively by the end of the study. The individual peaks of the polar product represented <5 % AR and were not considered further.
Evaporation of parent compound:
no
Volatile metabolites:
no
Remarks:
Negligible reaching a maximum of 0.58 % AR at 30 days after treatment
Residues:
not specified
Details on results:
The results are tabulated in 'Any other information on results incl. tables'.

TEST CONDITIONS
- Indication of test material adsorbing to walls of test apparatus: No

DEGRADATION OF THE TEST SUBSTANCE
Levels of the parent compound in the total water/sediment test system decreased from 96.6 and 94.5% AR at 0 days after treatment to 17.2 and 13.4 % AR at 100 days after treatment in the aerobic test system dosed with [oxadiazine-4-14C]-test substance and [thiazole-2-14C]-test substance, respectively.

WATER RESIDUES
Water residues declined with time in all test systems.
- Total water residues at 0 days after treatment: Oxadiazine label: Mean 94.90%; Thiazole label: Mean 93.7%
- Total water residues at end of study: Oxadiazine label: Mean 16.82%; Thiazole label: Mean 9.45%

EXTRACTABLES RESIDUES
Extractable residues decreased with time in all test systems.
- Total extractable residues at 0 days after treatment (including radioactivity in water phase): Oxadiazine label: Mean 96.56%; Thiazole label: Mean 94.51%
- Total extractable residues at end of study (including radioactivity in water phase): Oxadiazine label: Mean 41.84 %; Thiazole label: Mean 31.50 %

BOUND RESIDUES
The average amount of bound residue increased from 0.51% and 0.24% AR at 0 days after treatment to 48.8% and 51.32% AR by 100 days after treatment in the test systems dosed with [oxadiazine-4 14C]-test substance and [thiazole-2-14C]-test substance, respectively. The un-extracted residue remaining after the harsh extraction (of the 100 days after treatment sample) was characterized by organic matter fractionation, i.e. fulvic acid, humic acid, and humin. The most of the radioactivity remaining after the harsh extraction was characterized as being bound to the humin fraction, i.e., from 18.2 to 19.5% AR.

VOLATILISATION
Significant amount of 14CO2 was evolved as volatile products throughout the course of the study.
- 14-CO2 evolved at end of study: Oxadiazine label: Mean 6.42 %; Thiazole label: Mean 11.96 %
- Other volatiles: Negligible reaching a maximum of 0.58% AR at 30 days after treatment

NON-EXTRACTABLE RESIDUES
The un-extracted residue remaining after the harsh extraction was characterized by organic matter fractionation, i.e. fulvic acid, humic acid, and humin. Most of the radioactivity remaining after the harsh extraction was characterized as being associated with the fulvic acid fraction, i.e. a maximum of 4.38 and 8.64 % AR for the river and pond aquatic systems, respectively.

Table: Mass Balance and Distribution of Radioactivity in the Taunton River Sediment System Tested with [oxadiazine-4 14C]-test substance (values as percentage of Applied Radioactivity)

Fraction

Replicate

Incubation Time (DAT)

0

7

14

30

48

70

100

Surface Water (%)

A

96.00

69.14

65.46

33.32

26.62

11.83

16.69

B

93.80

65.12

60.32

34.47

29.39

18.45

16.96

Mean

94.90

67.13

62.89

33.89

28.00

15.14

16.82

Sediment Extraction (%)

A

1.28

20.38

25.74

23.78

26.40

26.38

25.06

B

2.04

21.77

27.03

25.36

28.00

30.11

24.96

Mean

1.66

21.1

26.4

24.6

27.2

28.3

25.0

Total Extractable

Mean

96.56

88.21

89.28

58.46

55.20

43.38

41.84

Non-Extractable (%)

A

0.40

5.56

9.69

33.52

42.37

59.09

46.48

B

0.62

5.03

12.35

29.89

37.07

49.47

51.06

Mean

0.51

5.29

11.02

31.70

39.72

54.28

48.77

14CO2(%)

A

NA

0.09

0.22

2.04

4.71

7.19

6.42

B

NA

0.09

0.22

2.04

4.71

7.19

6.42

Mean

NA

0.09

0.22

2.04

4.71

7.19

6.42

Other Volatiles (%)

A

NA

ND

ND

0.58

ND

0.03

ND

B

NA

ND

ND

0.58

ND

0.03

ND

Mean

NA

ND

ND

0.58

ND

0.03

ND

Mass Balance (%)

A

97.68

95.18

101.12

93.24

100.10

104.52

94.65

B

96.47

92.02

99.92

92.34

99.16

105.25

99.40

Mean

97.07

93.60

100.52

92.79

99.63

104.89

97.02

Mean ± SD

97.93 ± 4.18

NA - not applicable; ND - not detected or < 0.01 % AR; VOC - volatile organic compounds; SD – standard deviation

All reported values are rounded. All calculations are based on unrounded values.

Mass balance is determined by LSC analysis of the individual fractions; Mass balance = % water fraction + % extractable +% bound +% 14CO2 + % VOC

Total radioactivity applied to the water/sediment test systems at day 0 = 6,864,671 dpm; Specific Activity [oxadiazine-4-14C]-test substance used in the water/sediment study = 311,022 dpm/µg.

Total µg applied to the water/sediment test systems = 21.2 µg; Total volume of water in the test systems = 212 mL. Nominal test system ppm = 21.2 µg/212 mL = 0.10 µg/mL = 0.10 ppm

Table: Mass Balance and Distribution of Radioactivity in the Taunton River Sediment System Tested with [thiazole-2-14C]-test substance (values as percentage of Applied Radioactivity)

Fraction

Replicate

Incubation Time (DAT)

0

7

14

30

48

70

100

Surface Water (%)

A

92.84

64.22

56.11

27.91

25.54

18.56

10.35

B

94.58

64.89

56.01

27.39

21.00

19.67

8.56

Mean

93.71

64.56

56.06

27.65

23.27

19.11

9.45

Sediment Extraction (%)

A

0.93

23.22

27.93

22.38

27.52

30.59

21.90

B

0.68

20.65

27.03

23.33

24.77

31.10

22.19

Mean

0.80

21.94

27.48

22.85

26.15

30.85

22.04

Total Extractable

Mean

94.51

86.50

83.54

50.50

49.42

49.96

31.50

Non-Extractable (%)

A

0.25

7.82

14.52

33.89

33.90

43.61

47.88

B

0.22

5.55

14.46

33.14

37.27

33.20

54.75

Mean

0.24

6.68

14.49

33.51

35.59

38.41

51.32

14CO2 (%)

A

NA

0.17

1.23

9.04

10.90

10.30

11.96

B

NA

0.17

1.23

9.04

10.90

10.30

11.96

Mean

NA

0.17

1.23

9.04

10.90

10.30

11.96

Other Volatiles (%)

A

NA

ND

0.02

0.05

0.03

ND

ND

B

NA

ND

0.02

0.05

0.03

ND

ND

Mean

NA

ND

0.02

0.05

0.03

ND

ND

Mass Balance (%)

A

94.02

95.43

99.82

93.27

97.90

103.06

92.09

B

95.48

91.26

100.33

92.95

93.98

94.27

97.46

Mean

94.75

93.35

100.07

93.11

95.94

98.67

94.78

Mean ± SD

95.81 ± 2.64

NA - not applicable, ND - not detected or < 0.01 % AR, VOC - volatile organic compounds; SD – standard deviation

All reported values are rounded. All calculations are based on unrounded values.

Mass balance is determined by LSC analysis of the individual fractions. Mass balance = % water fraction + % extractable +% bound +% 14CO2 + % VOC.

Total radioactivity applied to the water/sediment test systems at day 0 = 6,864,671 dpm

Specific Activity [oxadiazine-4-14C]-test substance used in the water/sediment study = 311,022 dpm/µg

Total µg applied to the water/sediment test systems = 21.2 µg; Total volume of water in the test systems = 212 mL; Nominal test system ppm = 21.2 µg/212 mL = 0.10 µg/mL = 0.10 ppm

 

Table: Distribution of [oxadiazine-4-14C]-test substance and Metabolites in the Water Fraction of the Taunton River Aerobic Test Systems (values as percentage of Applied Radioactivity)

[oxadiazine-4-14C]-test substance

Replicate

Sampling time (DAT)

0

7

14

30

48

70

100

Parent compound

A

96.00

64.56

57.70

26.32

18.56

6.78

11.18

B

93.80

62.29

53.47

30.86

16.72

11.87

9.95

Mean

94.90

63.42

55.59

28.59

17.64

9.32

10.57

Polar(a)

A

ND

1.98

2.68

0.72

1.58

0.99

0.81

B

ND

1.05

2.45

ND

3.68

0.72

1.56

Mean

ND

1.52

2.57

0.36

2.63

0.86

1.18

Unspecified metabolite

A

ND

ND

ND

ND

ND

ND

ND

B

ND

ND

ND

ND

ND

ND

ND

Mean

ND

ND

ND

ND

ND

ND

ND

M3

A

ND

ND

ND

0.55

1.34

1.70

1.10

B

ND

ND

ND

ND

1.39

0.96

1.86

Mean

ND

ND

ND

0.27

1.37

1.33

1.44

M2

A

ND

ND

2.16

1.95

2.13

0.99

0.98

B

ND

ND

1.15

1.88

3.43

1.63

1.14

Mean

ND

ND

1.65

1.91

2.78

1.31

1.06

M1

A

ND

2.61

2.91

2.22

3.00

1.36

1.57

B

ND

1.78

2.34

1.74

4.17

1.34

1.38

Mean

ND

2.20

2.62

1.98

3.59

1.35

1.47

Others(b)

A

ND

ND

ND

1.57

ND

ND

1.04

B

ND

ND

0.90

ND

ND

1.92

1.08

Mean

ND

ND

0.46

0.78

ND

0.96

1.06

a) HPLC and/or TLC chromatograms demonstrate that freely extractable “polars” were multi component and each were <5 % applied radioactivity (AR).

b) “Others” consists of multiple components and includes all peaks not quantified in the table above; HPLC and/or TLC chromatograms demonstrate that multi component “others” were < 5 % AR.

ND - Not Detected or < 0.1 %AR; % metabolite water = (% by HPLC in water) × (% of applied radioactivity in the water fraction)

Note: All reported values are rounded. All calculations are based on unrounded values.

 

Table: Distribution of [oxadiazine-4-14C]-test substance and Metabolites in the Sediment Extractable Fraction of the Taunton River Aerobic Test System (values as percentage of Applied Radioactivity)

[oxadiazine-4-14C]-test substance

Replicate

Sampling time (DAT)

0

7

14

30

48

70

100

Parent compound

A

1.28

17.81

15.30

13.78

11.20

9.43

6.66

B

2.04

19.45

20.35

12.75

12.10

7.45

6.44

Mean

1.66

18.63

17.83

13.26

11.65

8.44

6.55

Polar(a)

A

ND

ND

1.55

ND

1.60

ND

0.51

B

ND

ND

0.72

0.69

1.07

ND

ND

Mean

ND

ND

1.1

0.3

1.3

ND

0.3

Unspecified metabolite

A

ND

ND

ND

ND

ND

ND

ND

B

ND

ND

ND

ND

ND

ND

ND

Mean

ND

ND

ND

ND

ND

ND

ND

M3

A

ND

2.23

3.07

7.77

10.78

12.05

14.23

B

ND

2.32

5.10

10.42

11.34

20.82

15.13

Mean

ND

2.27

4.08

9.09

11.06

16.44

14.68

M2

A

ND

ND

0.45

0.64

0.79

0.55

0.44

B

ND

ND

ND

ND

0.74

ND

ND

Mean

ND

ND

0.23

0.32

0.76

0.27

0.22

M1

A

ND

ND

1.63

1.60

2.04

2.44

1.47

B

ND

ND

0.87

1.49

2.75

1.84

1.35

Mean

ND

ND

1.33

1.55

2.39

2.14

1.41

Others(b)

A

ND

0.34

3.74

ND

ND

1.42

1.74

B

ND

ND

ND

ND

ND

ND

2.04

Mean

ND

0.17

1.87

ND

ND

0.71

1.89

a) HPLC and/or TLC chromatograms demonstrate that freely extractable “polars” were multi component and each were < 5 % applied radioactivity (AR).

b) “Others” consists of multiple components and includes all peaks not quantified in the table above; HPLC and/or TLC chromatograms demonstrate that multi component “others” were < 5% AR.

ND - Not Detected or < 0.1%AR; % metabolite water = (% by HPLC in water) × (% of applied radioactivity in the water fraction)

Note: All reported values are rounded. All calculations are based on unrounded values.

  

Table: Distribution of [thiazole-2-14C]-test substance and Metabolites in the Water Fraction of the Taunton River Aerobic Test System (values as percentage of Applied Radioactivity)

[thiazole-2-14C]-test substance

Replicate

Sampling time (DAT)

0

7

14

30

48

70

100

Parent compound

A

92.84

62.22

47.25

15.96

14.32

13.13

6.74

B

94.58

60.49

47.32

21.52

12.00

13.61

6.87

Mean

93.71

61.35

47.29

18.74

13.16

13.37

6.80

Polar(a)

A

ND

1.13

4.11

4.39

ND

0.42

ND

B

ND

1.27

4.96

0.84

1.47

ND

ND

Mean

ND

1.20

4.54

2.61

0.74

0.21

ND

Unspecified metabolite

A

ND

ND

ND

ND

ND

ND

ND

B

ND

ND

ND

ND

ND

ND

ND

Mean

ND

ND

ND

ND

ND

ND

ND

M3

A

ND

ND

ND

1.01

ND

0.84

1.23

B

ND

ND

ND

0.68

ND

1.18

0.74

Mean

ND

ND

ND

0.85

ND

1.01

0.98

M2

A

ND

ND

1.14

2.08

6.77

1.94

0.72

B

ND

1.73

1.05

1.62

4.70

1.94

0.25

Mean

ND

0.87

1.10

1.85

5.74

1.94

0.49

M1

A

ND

0.89

1.46

2.50

4.45

2.23

1.15

B

ND

1.40

0.72

2.73

2.83

2.40

0.71

Mean

ND

1.14

1.09

2.61

3.64

2.31

0.93

Others(b)

A

ND

ND

2.15

1.97

ND

ND

0.50

B

ND

ND

1.95

ND

ND

0.54

ND

Mean

ND

ND

2.05

0.98

ND

0.27

0.25

a) HPLC and/or TLC chromatograms demonstrate that freely extractable “polars” were multi component and each were < 5 % applied radioactivity (AR).

b) “Others” consists of multiple components and includes all peaks not quantified in the table above; HPLC and/or TLC chromatograms demonstrate that multi component “others” were < 5 % AR.

ND - Not Detected or < 0.1 %AR; % metabolite water = (% by HPLC in water) × (% of applied radioactivity in the water fraction)

Note: All reported values are rounded. All calculations are based on unrounded values.

  

Table: Distribution of [thiazole-2-14C]-test substance in the Sediment Extractables Fraction of the Taunton River Aerobic Test System (values as percentage of Applied Radioactivity)

[thiazole-2-14C]-test substance

Replicate

Sampling time (DAT)

0

7

14

30

48

70

100

Parent compound

A

0.93

19.67

18.50

7.04

12.17

10.12

6.89

B

0.68

17.21

18.37

11.58

7.04

13.65

6.32

Mean

0.80

18.44

18.43

9.31

9.61

11.89

6.60

Polar(a)

A

ND

ND

3.55

1.08

1.49

ND

ND

B

ND

ND

2.17

0.74

1.04

ND

0.36

Mean

ND

ND

2.89

0.91

1.26

ND

0.18

Unspecified metabolite

A

ND

ND

ND

ND

ND

ND

ND

B

ND

ND

ND

ND

ND

ND

ND

Mean

ND

ND

ND

ND

ND

ND

ND

M3

A

ND

3.55

2.99

10.96

10.68

16.41

12.49

B

ND

2.67

2.48

9.26

12.92

15.64

13.13

Mean

ND

3.11

2.74

10.11

11.80

16.03

12.81

M2

A

ND

ND

ND

0.85

1.22

ND

0.38

B

ND

ND

ND

ND

0.97

ND

ND

Mean

ND

ND

ND

0.43

1.10

ND

0.19

M1

A

ND

ND

1.34

1.63

1.95

2.64

1.32

B

ND

ND

1.07

1.74

2.80

1.81

1.37

Mean

ND

ND

1.20

1.69

2.37

2.23

1.34

Others(b)

A

ND

ND

1.49

0.81

ND

1.42

0.83

B

ND

ND

4.53

ND

ND

ND

1.01

Mean

ND

ND

3.01

0.40

ND

0.71

0.92

a) HPLC and/or TLC chromatograms demonstrate that freely extractable “polars” were multi component and each were < 5 % applied radioactivity (AR)..

b) “Others” consists of multiple components and includes all peaks not quantified in the table above; HPLC and/or TLC chromatograms demonstrate that multi component “others” were < 5 % AR.

ND - Not Detected or < 0.1 %AR; % metabolite water = (% by HPLC in water) × (% of applied radioactivity in the water fraction)

Note: All reported values are rounded. All calculations are based on unrounded values.

  

Table:Distribution of [thiazole-2-14C]-test substance in the Total Water/Sediment Test System of the Taunton River Aerobic Test System (values as percentage of Applied Radioactivity)

[thiazole-2-14C]-test substance

Replicate

Sampling time (DAT)

0

7

14

30

48

70

100

Parent compound

A

93.76

81.88

65.75

23.01

26.50

23.25

13.63

B

95.26

77.69

65.69

33.11

19.04

27.26

13.19

Mean

94.51

79.79

65.72

28.06

22.77

25.26

13.41

Polar(a)

A

ND

1.13

7.72

5.47

1.58

0.42

ND

B

ND

1.27

7.13

1.58

2.51

ND

0.36

Mean

ND

1.20

7.43

3.52

2.00

0.21

0.18

Unspecified metabolite

A

ND

ND

ND

ND

ND

ND

ND

B

ND

ND

ND

ND

ND

ND

ND

Mean

ND

ND

ND

ND

ND

ND

ND

M3

A

ND

3.55

2.99

11.97

10.68

17.25

13.72

B

ND

2.67

2.48

9.95

12.92

16.82

13.86

Mean

ND

3.11

2.74

10.96

11.80

17.04

13.79

M2

A

ND

ND

1.14

2.93

8.00

1.94

1.10

B

ND

1.73

1.05

1.62

5.68

1.94

0.25

Mean

ND

0.87

1.10

2.28

6.84

1.94

0.67

M1

A

ND

0.89

2.79

4.13

6.40

4.87

2.47

B

ND

1.40

1.79

4.47

5.63

4.20

2.08

Mean

ND

1.14

2.29

4.30

6.01

4.54

2.27

Others(b)

A

ND

ND

3.65

2.77

ND

1.41

1.33

B

ND

ND

6.48

ND

ND

0.54

1.01

Mean

ND

ND

5.07

1.37

ND

0.98

1.17

a) HPLC and/or TLC chromatograms demonstrate that freely extractable “polars” were multi component and each were < 5 % applied radioactivity (AR)..

b) “Others” consists of multiple components and includes all peaks not quantified in the table above; HPLC and/or TLC chromatograms demonstrate that multi component “others” were < 5 % AR.

ND - Not Detected or < 0.1 %AR; % metabolite water = (% by HPLC in water) × (% of applied radioactivity in the water fraction)

Note: All reported values are rounded. All calculations are based on unrounded values. 

 

Table: Summary of Extractability and metabolite distribution by soft extraction and harsh extraction (values as percentage of Applied Radioactivity)

Day

Radiolabelled position

PES

Soft extraction

Harsh extraction

Test substance

Polars*

M3

Unknown

100

Oxadiazine

46.48

4.04

10.09

0.48

4.67

8.11

0.86

100

Thiazole

47.88

5.09

8.95

0.32

8.75

3.57

1.41

*“polars” were multi component and each were < 5 % applied radioactivity (AR).

 

Table: Summary of Recovery of Radioactivity by Further Extraction and Humus Fractionation Expressed (values as percentage of Applied Radioactivity)

Day

Radiolabelled position

PES

Soft extraction

Harsh extraction

Fulvic Acid

Humic Acid

Humin

100

Oxadiazine

46.48

4.04

10.1

10.35

3.85

18.15

100

Thiazole

47.88

5.09

8.95

10.19

4.18

19.47

 

Table: Summary of DT50, DT90 and Rate Constants for the Water Phase of the Test Systems during Aerobic Transformation of [14C]-test substance

Radiolabel

SFO

Rate of Dissipation from water phase

Rate of Degradation in whole system

DT50 (days)

DT90 (days)

Χ2

DegT50 (days)

DegT90 (days)

Χ2

[Oxadiazine-4-14C]

19.2

63.8

9.034

29.2

97.9

6.35

[Thiazole-2-14C]

14.8

49.1

11.31

25.2

83.6

12.35

Validity criteria fulfilled:
yes
Conclusions:
The transformation of [oxadiazine-4-14C]-test substance and [thiazole-2-14C]-test substance in aerobic aquatic sediments was assessed in one test system (water pH characteristics < pH 7) that was continuously aerated in the dark at a temperature of 20 ± 2°C for 100 days. The overall mass balance for the [oxadiazine-4-14C]-test substance and [thiazole-2-14C]-test substance in the Taunton River test system was 95.8 % and 97.9 % AR, during the 100-day study, which satisfied the guideline requirement of maintaining material balance between 90 % and 110 % AR. The test substance was shown to partition from the water phase to the sediment with dissipation half-lives ranging from 15 to 19 days. Transformation of the test substance in the water phase and sediment resulted in degradation half-lives ranging from 25 to 29 days and the formation of four products, including CO2. Three components were identified as M3, M2 and M1 by co-chromatography using an HPLC and TLC system. In addition, two metabolites (M3 and M1) were confirmed by LC/MS/MS. The remaining unidentified components comprised seven minor peaks, with no single unknown peak greater than 5 % AR. Further degradation resulted in formation of polar products (in bound residues), mineralization and strong binding to the humin fraction of the sediment organic matter. The bound residues were composed of non-discrete polar residues with no single metabolite > 5 %. Additional levels of the test substance were detected but were present < 0.63 % AR.
Executive summary:

The biodegradation of the test substance in water/sediments system was investigated in a study according to OECD TG 308 in compliance with GLP criteria. In this study, the rate and route of degradation of [14C]-test substance, labelled in the oxadiazine or thiazole ring, was investigated in one aquatic sediment and associated overlaying water collected from Taunton River (Sandy Loam). Water was treated with [oxadizine-4-14C]-test substance or [thiazole-2-14C]-test substance to achieve target concentrations of 0.1 mg/L in the water phase (based on the maximum single label application rate of 300 g a.s./ha). The soils were incubated under aerobic conditions in the laboratory and maintained in dark conditions at 20°C for up to 100 days. Duplicate samples were taken for analysis at seven time intervals. Average mass balance for [oxadiazine-4-14C]-test substance ranged from 92.8 to 105 % of the applied radioactivity (AR). Similarly, average material balance for [thiazole-2-14C]-test substance ranged from 93.1 to 100 % over the course of the 100-day study. Half-lives (DT50) for the dissipation of [oxadiazine-4-14C]-test substance and [thiazole‑2-14C]-test substance in the water phase averaged 19.2 and 14.8 days, respectively. The half-lives of the degradation of [oxadiazine-4-14C]-test substance and [thiazole‑2-14C]‑test substance in the total aquatic sediment system averaged from 29.2 and 25.2 days, respectively. The DegT50 and DegT90 values were calculated using non-linear regression and first-order kinetics (SFO). The 14CO2 evolution due to mineralization of [oxadiazine-4-14C]-test substance ranged from 0.09 to 7.19% AR. A slightly greater degree of mineralization was observed in the test system dosed with [thiazole-2-14C]-test substance as 0.17 and 11.96 % AR were trapped. Negligible quantities of radioactivity, i.e., ≤ 0.6 % AR, were detected in the volatile organic compound (VOC) traps in the systems treated with either [oxadiazine-4-14C]-test substance or [thiazole‑2-14C]‑test substance. Transformation products of[oxadiazine-4-14C]-test substance and [thiazole‑2-14C] test substance were observed in the aquatic aerobic sediment systems as evidenced by three major and several minor peaks in the HPLC profiling with three transformation products being observed consistently. Three products had HPLC retention times of 17, 30, and 33 min (labelled as according to the original HPLC profiling) and were identified as M3, M2 and M1, respectively, by HPLC and TLC co‑chromatography with authentic reference standards. Products M3 and M1 were confirmed by LC/MS/MS. Average non-extractable residues increased to levels of 48.8 % and 51.3 % AR at 100 days after treatment in the test systems treated with [oxadiazine-4-14C]-test substance and [thiazole-2-14C]-test substance, respectively. Extensive efforts were made to further characterize the non-extractable residues (PES). No significant levels of test substance (< 0.63 % AR) were detected in either the “soft” or the “harsh” (reflux) extracts, only polar non-discrete residues at levels < 8.75 % AR and M3 were present at 8.11 % AR. Radioactivity remaining in the PES samples after soft and harsh extractions, was characterized by fractionation into humin, humic acid and fulvic acid fractions in which the majority of the bound radioactivity was associated with the humin fraction (i.e., approximately 18.2 % to 19.5 % AR).

Description of key information

All available data were assessed and the studies representing the worst-case effects were included as key or weight-of-evidence studies. Other studies are included as supporting information. The key studies are considered to be worst-case and were selected for the CSA.

DT50 (freshwater) = 19.2 days; DT50 (system) = 29.2 days, under realistic environmental conditions, OECD 308, Kang 2015.

Key value for chemical safety assessment

Half-life in freshwater:
19.2 d
at the temperature of:
20 °C
Half-life in freshwater sediment:
29.2 d
at the temperature of:
20 °C

Additional information

The biodegradation of the substance in freshwater was studied under GLP in natural surface water (OECD TG 309) and water/sediment systems from rivers and ponds (OECD TG 308). A relatively rapid biodegradation was observed in a study performed with a representative water/sediment system from a river. Depending on the position of the radiolabel (thiazole or oxadiazine), the half-life was between 14.8 and 19.2 days in the water phase and between 25.2 and 29.2 days in the sediment phase. The carbon dioxide evolution due to mineralisation of the test substance was up to 7.19% of applied radioactivity (oxadiazine label) and 11.96% (thiazole label). Three major metabolites were observed and identified as 3-[(2-chloro-1,3-thiazol-5-yl)methyl]-5-methyl-1,3,5-oxadiazinan-4-imine, 3-[(2-chloro-1,3-thiazol-5-yl)methyl]-5-methyl-1,3,5-oxadiazinan-4-one and N-[(2-chloro-1,3-thiazol-5-yl)methyl]-N'-nitrourea. The half-lives in a study conducted with natural lake water (amended with 0.01 g/L suspended sediment) were slightly higher, ranging from about 87 to 97 days. The main metabolites observed in this study were 3-[(2-chloro-1,3-thiazol-5-yl)methyl]-5-methyl-1,3,5-oxadiazinan-4-one and N-[(2-chloro-1,3-thiazol-5-yl)methyl]-N'-nitrourea.