clothianidin (ISO); (E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2-nitroguanidine

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 June 1997 - 27 Jan 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: BBA Guidelines for Testing of Plant Protectants in the Registration Procedure, Part IV, 5-1

Version / remarks:

1990

Qualifier:

according to guideline

Guideline:

other: EC Commision Directive 95/36/EC amending Council Directive 14th 91/414/EEC Annexes I + II, Fate and Behavior in the Environment

Version / remarks:

1995

Qualifier:

according to guideline

Guideline:

other: SETAC Procedures for Assessing the Environmental Fate and Ecotoxicity of Pesticides

Version / remarks:

1995

Qualifier:

according to guideline

Guideline:

other: “Guidance Document on Estimating Persistence and Degradation Kinetics from Environmental Fate Studies on Pesticides in EU Registration”. Report of the FOCUS Working Group on Degradation Kinetics. EC Document Reference Sanco/10058/2005 version 2.0

Version / remarks:

2006

Qualifier:

according to guideline

Guideline:

other: Generic Guidance for Estimating Persistence and Degradation Kinetics from Environmental Fate Studies on Pesticides in EU Registration, version 1.0

Version / remarks:

2011

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment: freshwater

Details on source and properties of surface water:

- The study was carried out using two natural water / sediment systems from different locations:
1) Hoenniger Weiher (near Wipperfurth, Germany): This is an artificially dammed pond in the course of the "Hoenniger Creek" forming "Hoenniger Weiher". On account of its in- and outlet the pond of about 1000 m2 in surface area had a strong water current.
2) Anglerweiher (Koeln, Germany): This small lake is a reclaimed gravel pit which is used for fishing only. The lake is entirely enclosed by a fence.
- Storage conditions: The samples collected from both origins had been kept under aerated conditions in the laboratories
- Temperature (°C) at time of collection: 8.0 (Hoenninger Weiher), 11.9 (Anglerweiher)
- Water and sediment from both locations were sampled on 24th April 1997
- pH at time of collection: 7.7 (Hoenninger Weiher), 8.2 (Anglerweiher)
- Redox potential (mv) initial/final: 449 (Hoenninger Weiher), 452 (Anglerweiher)
- Oxygen concentration (mg/l) initial/final: 92 % (Hoenninger Weiher), 109 (Anglerweiher)
- Hardness (CaCO3): 4.1 dH° (Hoenninger Weiher), 12.1 dH° (Anglerweiher)
- Dissolved organic carbon (mg/L): 1.6 (Hoenninger Weiher), 1.7 (Anglerweiher)
- Water filtered: Yes

Details on source and properties of sediment:

- Details on collection (e.g. location, sampling depth, contamination history, procedure): see “Details of source and properties of surface water”
- Storage conditions: The samples collected from both origins had been kept under aerated conditions in the laboratories
- Textural classification (i.e. %sand/silt/clay): 38.5 % sand, 47.1 % silt, 14.4 % clay (Hoenninger Weiher, loam) and 69 % sand, 21.8 % silt, 9.2 % clay (Anglerweiher, sandy loam)
- pH at time of collection: 5.8 (Hoenninger Weiher), 7.3 (Anglerweiher)
- Organic carbon (mg/100 g dry mass): 4070 (Hoenninger Weiher), 2310 (Anglerweiher)
- CEC (meq/100 g): 10 (Hoenninger Weiher), <1 (Anglerweiher)
- Biomass (e.g. in mg microbial CO2/1 kg x 1 hour): 17 (Hoenninger Weiher), 8.0 (Anglerweiher)
- Sediment samples sieved: No, but stones and plant debris were removed from the sediment
- Pesticides use history: Not directly affected by pesticide use: no documented history available (Hoenninger Weiher, Anglerweiher)

Duration of test (contact time):

>= 0 - <= 100 d

Initial conc.:

50 µg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: An amount of sediment corresponding to 50 g dry matter was weighed into the incubation vessels and filtered water was added to reach a total weight of 500 g. Prior to application of the test substance, the system was maintained under test conditions for the purpose of equilibration. The application was performed in a dark room by dosing 1 mL of Application Solution (72.07 kBq, 22.5 ng test substance) to each test vessel (total volume: 450 mL water) using a calibrated microlitre syringe.
- Temperature: 20 ± 2 °C, recorded by a data logging system
- Continuous darkness: yes
- Stagnant/in motion: Supernatant water in smooth motion
- Oxygen conditions: aerobic
- Incubation period: 100 days

TEST SYSTEM
- Culturing apparatus: 1 L laboratory microcosm fitted with trap attachment for absorption of volatile compounds (CO2 and organic volatiles).

SAMPLING
- Sampling frequency: Duplicate vessels were processed at 0, 3, 7, 14, 30, 60 and 100 days after treatment.
- Other: Microbial biomass determinations were carried out for the sediments at the beginning and at the end of the study. For this purpose samples with and without active ingredient were incubated under identical conditions as in the main experiment.
After completion of the test, oxygen content, pH, redox potential, total N, total P and TOC/DOC were determined in separate test batches.
The following parameters were ascertained throughout the study at each sampling date:
1) dissolved oxygen content in the water
2) pH in the water
3) redox potential in the water
4) redox potential in the sediment

Compartment:

natural water / sediment: freshwater

% Total extractable:

37.8

% Non extractable:

43.3

% CO2:

3.2

% Other volatiles:

< 0.1

% Recovery:

96.3

Remarks on result:

other:

Remarks:

Test system: Hoenninger Weiher

Compartment:

natural water / sediment: freshwater

% Total extractable:

37.8

% Non extractable:

27.6

% CO2:

4.4

% Other volatiles:

< 0.1

% Recovery:

95.9

Remarks on result:

other:

Remarks:

Test system: Anglerweiher

Parent/product:

parent

Compartment:

total system

% Degr.:

3.2

Parameter:

radiochem. meas.

Sampling time:

100 d

Remarks on result:

other:

Remarks:

14CO2 formation in test system Hoenninger Weiher.

Parent/product:

parent

Compartment:

total system

% Degr.:

4.4

Parameter:

radiochem. meas.

Sampling time:

100 d

Remarks on result:

other:

Remarks:

14CO2 formation in test system Anglerweiher.

Compartment:

natural water / sediment: freshwater

DT50:

47.99 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other:

Remarks:

Test system: Hoenninger Weiher

Compartment:

natural water / sediment: freshwater

DT50:

101.9 d

Type:

(pseudo-)first order (= half-life)

Temp.:

12 °C

Remarks on result:

other:

Remarks:

Test system: Hoenninger Weiher; Calculated DT50 based on experimental data at 20 °C

Compartment:

natural water / sediment: freshwater

DT50:

64.83 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other:

Remarks:

Test system: Anglerweiher

Compartment:

natural water / sediment: freshwater

DT50:

137.6 d

Type:

(pseudo-)first order (= half-life)

Temp.:

12 °C

Remarks on result:

other:

Remarks:

Test system: Anglerweiher; Calculated DT50 based on experimental data at 20 °C

Compartment:

natural water / sediment: freshwater

DT50:

106.6 d

Type:

other: Hockey stick model with fixed tb

Temp.:

20 °C

Remarks on result:

other:

Remarks:

Updated kinetic evaluation using FOCUS (2006, 2011); Test system Hoenninger Weiher

Compartment:

natural water / sediment: freshwater

DT50:

226.3 d

Type:

other: Hockey stick model with fixed tb

Temp.:

12 °C

Remarks on result:

other:

Remarks:

Recalculated DT50 to 12 °C, based on updated kinetic evaluation using FOCUS (2006, 2011); Test system Hoenninger Weiher

Compartment:

natural water / sediment: freshwater

DT50:

57.9 d

Type:

other: Simple first order (SFO)

Temp.:

20 °C

Remarks on result:

other:

Remarks:

Updated kinetic evaluation using FOCUS (2006, 2011); Test system Anglerweiher

Compartment:

natural water / sediment: freshwater

DT50:

122.9 d

Type:

other:

Temp.:

12 °C

Remarks on result:

other:

Remarks:

Recalculated DT50 to 12 °C, based on updated kinetic evaluation using FOCUS (2006, 2011); Test system Anglerweiher

Transformation products:

yes

No.:

#1

Details on transformation products:

TMG (N-2-chloro-5-thiazolylmethyl)-N'-methylguanidine) was detected as the only major metabolite and was found in amounts of 21% in both sediment extracts at the end of the study. No further metabolite was detected in sediment extracts. The supernatant water did not contain any metabolite above 1.3%.

Evaporation of parent compound:

no

Remarks:

No significant radioactivity was detected in the polyurethane foams for adsoption of volatile organic compounds (<0.1 %).

Volatile metabolites:

no

Remarks:

No significant radioactivity was detected in the polyurethane foams for adsoption of volatile organic compounds (<0.1 %).

Details on results:

TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: Yes.
The water layers of the micro-ecosystems were aerobic throughout the entire incubation period with oxygen saturation between 26 and 93% for Hoenniger Weiher and 47 and 90% for Anglerweiher.
The sediment of Hoenniger Weiher remained reductive through the whole incubation time whereas that of Anglerweiher changed from oxidative to reductive.
The pH values decreased from slightly basic to slightly acidic in both systems.

MAJOR TRANSFORMATION PRODUCTS
- TMG (N-2-chloro-5-thiazolylmethyl)-N'-methylguanidine) was detected as the only major metabolite and was found in amounts of 21% in both sediment extracts at the end of the study. No further metabolite was detected in sediment extracts. The supernatant water did not contain any metabolite above 1.3%.
- DT50 values for the test substance were calculated to be 31 days for the supernatant water of Hoenniger Weiher (48 days for the entire system) and 50 days for the supernatant water of Anglerweiher (65 days for the entire system).

EXTRACTABLE RESIDUES
- % of applied amount at end of study period: Radioactivity was rapidly translocated from water to sediment in both systems, whereby this process proceeded slightly faster for Hoenniger Weiher. The amount of radioactivity released from the sediments by extraction generally decreased within the course of the study due to increasing amounts of bound residues and mineralization.

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: The test substance was partly mineralised to CO2 with 3.2% of applied radioactivity in the Hoenniger Weiher system and 4.4% in Anglerweiher. Radioactivity attributable to CO2 in the supernatant water was at 0.4% maximum.

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: No significant radioactivity was detected in the polyurethane foams for adsoption of volatile organic compounds (<0.1 %).

Validity criteria fulfilled:

not applicable

Reference 2

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

Qualifier:

according to guideline

Guideline:

OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)

Version / remarks:

2004

Qualifier:

according to guideline

Guideline:

other: DG SANCO 11802/2010/rev 7 amending the Regulation (EC) No. 1107/2009 concerning the placing of plant protection products on the market and repealing Council Directives 79/117/EEC and 91/414/EEC

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water: freshwater

Details on source and properties of surface water:

- Details on collection (e.g. location, sampling depth, contamination history, procedure): Water was freshly sampled from a pond of about 700 m2 in Rheinfelden, Switzerland in November, 2013 and in April, 2014 (for benzoic acid and solvent control test). The water was sampled from the surface at a depth of about 0 to 5 cm. The sampling location was in an area not subject to effluent discharges and located far from human activity.
- Storage conditions: The sample was transported to the laboratory in sealed containers and filtered through a 0.1 mm sieve. The water was then stored at about 4 °C in the dark, until use.
- Temperature (°C) at time of collection: 6.5
- pH at time of collection: 7.42
- Redox potential (mv) initial: 161
- Oxygen concentration (mg/l) initial: 7.14
- Dissolved organic carbon (%): 6.09

Duration of test (contact time):

>= 0 - <= 60 d

Initial conc.:

0.1 mg/L

Based on:

test mat.

Initial conc.:

0.01 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

radiochem. meas.

test mat. analysis

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment:
- Test temperature: Samples were incubated at a controlled temperature of 20.5 ± 0.3 °C in the dark, under aerobic conditions.
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Each test system consisted of an open gas-flow-system with 350 mL Erlenmeyer flasks, containing 100 mL of natural water. An illustration of the test apparatus is given as “Figure 1” in the Attached background material.
- Method used to create aerobic conditions: Each flask was aerated with moistened air.
- Method used to control oxygen conditions: The samples were continuously and gently stirred to maintain particles and micro-organisms in suspension. Agitation also facilitated oxygen transfer from headspace to liquid, in a way that aerobic conditions were maintained.
- Details of trap for CO2 and volatile organics if used: After treatment, samples were connected to a trapping system equipped with a total of two absorption traps, one containing ethylene glycol and the other 2N NaOH (in this sequence) to trap organic volatiles and 14CO2, respectively.

SAMPLING
- Sampling frequency: Duplicate samples treated with the test item were taken from each test dose system (high dose HD and low dose LD) immediately after treatment (time 0) and after 3, 7, 14, 28, 41 and 60 days of incubation.
- Sampling method used per analysis type: At each sampling interval, entire samples were taken, the volume of the water phase and the trapping solutions i.e. ethylene glycol and sodium hydroxide was recorded and the radioactivity present was determined by LSC.
- Other: The pH value and oxygen content of the water were measured at each sampling interval in the respective treated samples and in two untreated control samples. Additionally, degradation of [14C (U)] benzoic acid was monitored using the same experimental set-up in order to test the microbial activity of the test water as well as possible adverse effects of the solvent used (solvent controls). Mineralisation of benzoic acid was monitored by LSC measurement and HPLC analysis of sub-samples at 3 different intervals (0, 7 and 14 days) and the amount of radioactivity in NaOH traps determined (LSC). In order to examine possible adverse effects of the solvent, within the benzoic acid system additional solvent control samples were conducted in duplicate with freshly sampled test water.

Test performance:

The mean total recovery 60 days after the application of clothianidin (0.1 mg/L, 0.1 mg/L + sterile, 0.01 mg/L) are provided in "Table 6 - 8" in the Attached background matrial.
The reference substance benzoic acid degraded completely from initially 102.8% to 0% AR within 7 days of incubation indicating high microbial activity in the test water, whereas analysis of solvent control samples demonstrated that the amount of solvent had no negative effect on the degradation rate.

Compartment:

natural water: freshwater

DT50:

> 1 yr

Type:

not specified

Temp.:

20.5 °C

Remarks on result:

other:

Remarks:

DT50 of clothianidin at an initial concentration of 0.1 mg/L

Compartment:

natural water: freshwater

DT50:

> 1 yr

Type:

not specified

Temp.:

12 °C

Remarks on result:

other:

Remarks:

DT50 of clothianidin at an initial concentration of 0.1 mg/L; calculated based on results at 20.5 °C

Compartment:

natural water: freshwater

DT50:

> 1 yr

Type:

not specified

Temp.:

20.5 °C

Remarks on result:

other:

Remarks:

DT50 of clothianidin at an initial concentration of 0.01 mg/L

Compartment:

natural water: freshwater

DT50:

> 1 yr

Type:

not specified

Temp.:

12 °C

Remarks on result:

other:

Remarks:

DT50 of clothianidin at an initial concentration of 0.10 mg/L; calculated based on results at 20.5 °C

Compartment:

natural water: freshwater

DT50:

> 1 yr

Type:

not specified

Temp.:

20.5 °C

Remarks on result:

other:

Remarks:

DT50 of clothianidin at an initial concentration of 0.1 mg/L and under sterile conditions

Compartment:

natural water: freshwater

DT50:

> 1 yr

Type:

not specified

Temp.:

12 °C

Remarks on result:

other:

Remarks:

DT50 of clothianidin at an initial concentration of 0.1 mg/L and under sterile conditions; calculated based on results at 20.5 °C

Transformation products:

no

Details on transformation products:

In all systems, Clothianidin was shown to be stable until the end of incubation (60 days), accounting for 103.0%, 101.6% and 97.2% AR (mean values) in the respective systems.

Evaporation of parent compound:

no

Remarks:

Volatile products other than 14CO2 did not exceed 0.1% AR throughout the study.

Volatile metabolites:

no

Remarks:

Volatile products other than 14CO2 did not exceed 0.1% AR throughout the study.

Details on results:

TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: Yes
The oxygen concentration measured in the water phase ranged from 5.97 to 8.14 mg/L in the high dose, from 5.89 to 8.24 mg/L in the high dose sterile and from 6.16 to 8.17 mg/L in the low dose experiment. Corresponding values for pH were 8.20 to 8.67, 8.30 to 8.46 and 8.29 to 8.65, respectively.
Similar values were observed in the untreated control samples, ranging from 5.95 to 8.52 mg/L for the oxygen concentration and from 8.34 to 8.73 for the pH values. The results demonstrated that the test item had no significant effect on the physico-chemical parameters of the test system.
The mean temperature during incubation was 20.5 ± 0.3 °C for all systems
- Other: Microbial activity of test water: The amount of benzoic acid decreased within 7 days from initial mean amounts of 102.8% and 93.0% AR to levels below the detection limit in the reference solutions as well as in the solvent controls. Formation of radioactive carbon dioxide amounted to 52.8% and 37.4% AR, respectively. Therefore, no effect of the added solvent on the dissipation rate of benzoic acid could be observed and both systems were considered as microbiologically active.

EXTRACTABLE RESIDUES
- % of applied amount at day 0: Immediately after treatment (time 0), mean values of 101.0%, 103.5% and 100.2% AR were measured in the water phases of the high dose, high dose sterile and low dose system, respectively.
- % of applied amount at end of study period: After 60 days of incubation, the mean amount of radioactivity in the water phase of the respective systems remained stable and represented 103.0%, 101.6% and 97.2% AR.

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: Mean values for formation of radioactive carbon dioxide represented 0.5% AR in the high dose, 0.2% AR in the sterile and 1.0% AR in the low dose system after 60 days, whereas the amount of radioactive carbon dioxide, dissolved in the water layer, was negligible.

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: Volatile products other than 14CO2 did not exceed 0.1% AR throughout the study.

Validity criteria fulfilled:

yes

Conclusions:

At the first sampling interval (time 0), the test item represented mean values 101.0%, 103.5% and 100.2% AR in the high dose, high dose sterile and low dose system, respectively. The reference substance benzoic acid degraded from initially 109.8% to 0% of AR within 7 days of incubation indicating high microbial activity in the test water. In all systems, Clothianidin was shown to be stable until the end of incubation (60 days), accounting for 103.0%, 101.6% and 97.2% AR (mean values) in the respective systems. In conclusion and regardless of the test concentration, Clothianidin was degraded insignificantly under the conditions of the test.

Description of key information

DT50 in water at 20 °C: > 1 year (> 1 year, recalculated to 12 °C)

DT50 in sediment at 20 °C: 48 – 65 days (102 – 138 days, recalculated to 12 °C)

Key value for chemical safety assessment

Half-life in freshwater:

1 yr

at the temperature of:

12 °C

Half-life in freshwater sediment:

138 d

at the temperature of:

12 °C

Additional information

One simulation test was carried out to assess the biodegradation of 14C-labelled (E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2-nitroguanidine, at 20 °C, in water according to GLP and OECD Guideline 309. The study was conducted over a period of 60 days at two concentration levels (0.1 and 0.01 mg/L), whereas the higher dosage level was additionally tested under sterile conditions. In conclusion and regardless of the test concentration, the test substance was degraded insignificantly in water under the conditions of the test (DT50 > 1 year).

An additional simulation study was carried out to assess the degradation of the active ingredient (E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2-nitroguanidine in two water / sediment systems (Hoenniger Weiher and Anglerweiher) using 14C-labelled radioactive test substance, following GLP and EU Council Directive 91/414 EEC as amended by Commission Directive 95/36/EC. Test systems were incubated in the dark at 20 °C. Duplicate vessels were sacrificed at 0, 3, 7, 14, 30, 60 and 100 days after treatment. DT50 values for the test substance were calculated to be 48 days (102 days, recalculated to 12 °C) for Hoenniger Weiher and 65 days (138 days, recalculated to 12 °C) for Anglerweiher. In the aquatic micro-ecosystem the test substance was degraded to a single major metabolite, only found in the sediment, and partly mineralised to carbon dioxide (< 5%). A kinetic evaluation of the experimental data, according to FOCUS (2006, 2011), determined DT50 values ranging from 57.9 to 106.6 days (1.4 to 11.4 days, recalculated to 12 °C).