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Environmental fate & pathways

Biodegradation in soil

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Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Mar 1994 - Feb 1996
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: US EPA Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 162-1: Aerobic Soil Metabolism Studies
Version / remarks:
1982
Qualifier:
according to guideline
Guideline:
other: BBA Guidelines for Official Testing of Plant Protectants, Part IV, 4-1
Version / remarks:
1986
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 Work Group on Degradation Kinetics, EC Document Reference Sanco/10058/2005 version 2
Version / remarks:
2006
Qualifier:
according to guideline
Guideline:
other: Generic guidance for Tier 1 FOCUS ground water assessments, version 2.1. FOCUS groundwater scenarios working group.
Version / remarks:
2012
GLP compliance:
yes (incl. QA statement)
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
other: DIN 19682
Year:
1998
Soil no.:
#1
Soil type:
other: Sand; Soil identification: BBA 2.1 Germany
% Clay:
0.1
% Silt:
11.4
% Sand:
88.5
% Org. C:
0.57
pH:
5.9
Bulk density (g/cm³):
2.59
Soil no.:
#2
Soil type:
other: Loamy sand; Soil identification: BBA 2.2 Germany
% Clay:
7.2
% Silt:
13.1
% Sand:
79.7
% Org. C:
2.48
Bulk density (g/cm³):
2.45
Soil no.:
#3
Soil type:
other: Loamy sand; Soil identification: Hoefchen im Tal Germany
% Clay:
15.6
% Silt:
81.9
% Sand:
2.5
% Org. C:
2.4
pH:
6
Bulk density (g/cm³):
2.5
Soil no.:
#4
Soil type:
other: Sandy loam; Soil identification: Howe USA
% Clay:
7.9
% Silt:
28.6
% Sand:
63.5
% Org. C:
1.12
pH:
6.7
Bulk density (g/cm³):
2.53
Details on soil characteristics:
SOIL COLLECTION AND STORAGE
- Geographic location:
BBA 2.1 Germany: Jockgrim/Germany
BBA 2.2 Germany: Hanhofen/Germany
Hoefchen im Tal Germany: Burscheid/Germany
Howe USA: Miles Farm, Howe, Indiana/USA
- Pesticide use history at the collection site:
BBA 2.1 Germany: no pesticides since 1991
BBA 2.2 Germany: no pesticides since 1990
Hoefchen im Tal Germany: no information
Howe USA: no pesticides since 1987
- Sampling depth (cm):
BBA 2.1 Germany: top 30 cm (surface soil)
BBA 2.2 Germany: top 30 cm (surface soil)
Hoefchen im Tal Germany: top 20 cm (surface soil)
Howe USA: top 0-6 inches (surface soil)
- Storage conditions:
BBA 2.1 Germany: Under natural vegetation for preservation of microbial activity.
BBA 2.2 Germany: Under natural vegetation for preservation of microbial activity.
Hoefchen im Tal Germany: Storage at +4 °C
Howe USA: Under natural vegetation for preservation of microbial activity.
- Soil preparation (e.g., 2 mm sieved; air dried etc.): All soils were freshly sampled, gently air-dried and sieved to <2 mm in naturally moist conditions. Subsequently the soil moisture was determined.

PROPERTIES OF THE SOILS (in addition to defined fields)
- Moisture 75% of 1/3 bar (g water in 100g dry soil):
BBA 2.1 Germany: 9.2
BBA 2.2 Germany: 16.1
Hoefchen im Tal Germany: not determined
Howe USA: 14.8
- Bulk density (g/cm3):
BBA 2.1 Germany: 2.59
BBA 2.2 Germany: 2.45
Hoefchen im Tal Germany: 2.5
Howe USA: 2.53
Soil No.:
#1
Duration:
>= 0 - <= 100 d
Soil No.:
#2
Duration:
>= 0 - <= 100 d
Soil No.:
#3
Duration:
>= 0 - <= 100 d
Soil No.:
#4
Duration:
>= 0 - <= 365 d
Soil No.:
#1
Initial conc.:
0.37 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#2
Initial conc.:
0.37 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#3
Initial conc.:
0.37 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#4
Initial conc.:
0.37 mg/kg soil d.w.
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Soil No.:
#1
Temp.:
20 °C
Soil No.:
#2
Temp.:
20 °C
Soil No.:
#3
Temp.:
20 °C
Soil No.:
#4
Temp.:
20 °C
Details on experimental conditions:
EXPERIMENTAL DESIGN
- Soil condition: The soils were adjusted to 40% of the maximum water capacity or to 75% of 1/3 bar moisture (soil Howe) by means of distilled water.
- Soil (g/replicate):
BBA 2.1 Germany: 105.5 g
BBA 2.2 Germany: 118.9 g
Hoefchen im Tal Germany: 124.0 g
Howe USA: 112.2 g

Test material application
- Volume of test solution used/treatment:
BBA 2.1 Germany: 233 µL
BBA 2.2 Germany: 233 µL
Hoefchen im Tal Germany: 233 µL
Howe USA: 544 µL
- Application method (e.g. applied on surface, homogeneous mixing etc.): The total amount of each soil required for the test were weighed into a glass bottle. The active ingredient was mixed into the entire sample via a subsample (about 10 g). This subsample of the respective soils was air-dried and ground in a porcelain dish and treated with the respective volume of application solution.
- Is the co-solvent evaporated: After evaporation of the solvent the subsample was thoroughly mixed with a pestill and returned to the entire amount of soil. This was followed by mixing on a tumbling mixer for 2 hours

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: The water that evaporated from the soil was determined by re-weighing the flasks without the traps at selected sampling days. The lost portion was replenished accordingly.
- Continuous darkness: Yes

SAMPLING DETAILS
- Sampling intervals: Samples were taken for analysis 0, 1, 3, 8, 14, 30, 60 and 100 days and for soil "Howe" additionally 120, 179, 268 and 365 days post-treatment
- Sampling method for soil samples: The soil was extracted immediately after sampling. The total soil portion of each test vessel was transferred into a centrifuge beaker and extracted at room temperature on a mechanical shaker.
- Method of collection of CO2 and volatile organic compounds: Prior to opening the incubation vessel (for moisture control or sample processing), volatile compounds possibly still present in the vessel, were swept into the trap attachment by introducing air saturated with water.
Soil No.:
#1
% Total extractable:
64.6
% Non extractable:
21.8
% CO2:
9.6
% Other volatiles:
0
% Recovery:
96
Remarks on result:
other:
Remarks:
Recovery and distribution of radioactivity after 100 days.
Soil No.:
#2
% Total extractable:
58.3
% Non extractable:
22.7
% CO2:
14.7
% Other volatiles:
0
% Recovery:
95.7
Remarks on result:
other:
Remarks:
Recovery and distribution of radioactivity after 100 days.
Soil No.:
#3
% Total extractable:
34.3
% Non extractable:
29.9
% CO2:
33.6
% Other volatiles:
0
% Recovery:
97.7
Remarks on result:
other:
Remarks:
Recovery and distribution of radioactivity after 100 days.
Soil No.:
#4
% Total extractable:
70.3
% Non extractable:
21.7
% CO2:
6.5
% Other volatiles:
0
% Recovery:
98.6
Remarks on result:
other:
Remarks:
Recovery and distribution of radioactivity after 100 days.
Parent/product:
parent
Soil No.:
#1
% Degr.:
9.6
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other:
Remarks:
14CO2 formation
Parent/product:
parent
Soil No.:
#2
% Degr.:
14.7
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other:
Remarks:
14CO2 formation
Parent/product:
parent
Soil No.:
#3
% Degr.:
33.6
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other:
Remarks:
14CO2 formation
Parent/product:
parent
Soil No.:
#4
% Degr.:
6.5
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other:
Remarks:
14CO2 formation
Parent/product:
parent
Soil No.:
#4
% Degr.:
24.7
Parameter:
radiochem. meas.
Sampling time:
365 d
Remarks on result:
other:
Remarks:
14CO2 formation
Soil No.:
#1
DT50:
2.4 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Soil No.:
#1
DT50:
5.1 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the test compound at 12 °C, based on results at 20 °C
Soil No.:
#2
DT50:
1.5 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Soil No.:
#2
DT50:
3.2 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the test compound at 12 °C, based on results at 20 °C
Soil No.:
#3
DT50:
0.7 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Soil No.:
#3
DT50:
1.5 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the test compound at 12 °C, based on results at 20 °C
Soil No.:
#4
DT50:
4.7 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Soil No.:
#4
DT50:
10 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the test compound at 12 °C, based on results at 20 °C
Soil No.:
#1
DT50:
2.96 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Soil identification: BBA 2.1 Germany
Soil No.:
#1
DT50:
6.3 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Recalculated to 12 °C; Soil identification: BBA 2.1 Germany
Soil No.:
#2
DT50:
2.16 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Soil identification: BBA 2.2 Germany
Soil No.:
#2
DT50:
4.6 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Recalculated to 12 °C; Soil identification: BBA 2.2 Germany
Soil No.:
#3
DT50:
0.66 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Soil identification: Hoefchen im Tal Germany
Soil No.:
#3
DT50:
1.4 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Recalculated to 12 °C; Soil identification: Hoefchen im Tal Germany
Soil No.:
#4
DT50:
5.39 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Soil identification: Howe USA
Soil No.:
#4
DT50:
11.4 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Recalculated to 12 °C; Soil identification: Howe USA
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
No.:
#4
No.:
#5
No.:
#6
No.:
#7
Details on transformation products:
- Formation and decline of each transformation product during test: Owing to the low concentration levels in the course of the main study, the degradation products were isolated from batches of soil "Howe" which had been treated and incubated with the test substance at the 20-fold dose rate (0.8 mg/100 g soil dry wt). During the course of the experiment at least 8 radioactive zones were detected along with unchanged test substance. Five of them could be identified by means of spectroscopic methods and quantified in the soil extracts. Two additional degradation products which were identified by spectroscopic methods were only found in soil treated with the 20x dose rate (metabolite production batch).
- Pathways for transformation: From the metabolites identified it was concluded that the degradation of YRC 2894 was essentially based on hydrolysis and oxidation steps. The breakdown of the molecule started by addition of water to the nitril group and formed the amide. Cleavage of the thiazole ring was also a major degradation step probably by addition of water to the imino group, ring opening and rapid oxidation of the sulfur. As a consequence the sulfonic acid was identified as a main metabolite. Desalkylation at the tertiary amino group resulted in Ja752-l which was hydrolysed to the urea DIJ 10739. Oxidation at the pyridinyl-methylene group also occurred (Ja752-B) and was certainly a general reaction for the formation of the 6-chloronicotinic acid (possibly from DIJ 10739 and KTU 3072). The metabolite 6-chloronicotinic acid can also be obtained directly from Ja752-B by hydrolysis. 14CO2 was the final degradation product.
- Maximum occurrence of each transformation product: Major metabolites >10% of the applied radioactivity were the amide (KKO 2254) and the sulfonic acid (WAK 6999). All other individual compounds accounted for less than 5.7% during the course of the study. Depending on soil type the amide (KKO 2254) accounted for a maximum portion of 73.8% of the applied radioactivity. In soil "BBA 2.1" the sulfonic acid (WAK 6999) accounted for 19.7%. However, in the other soils the sulfonic acid did not exceed a maximum value of 8.5% (soil Howe, 100d).
Evaporation of parent compound:
no
Remarks:
Volatile organic compounds were not detected at any sampling interval.
Volatile metabolites:
no
Remarks:
Volatile organic compounds were not detected at any sampling interval.
Details on results:
TEST CONDITIONS
- Anomalies or problems encountered (if yes): Determinations of microbial biomass [3] were carried out at the beginning of the test in order to check the biological activity of the freshly sampled soils. Further determinations of the biomass were made after 100 (BBA 2.1, BBA 2.2, Hoefchen) and 365 days (Howe). The microbial activity clearly decreased in all soils during the 100 and 365 day incubation period.

MAJOR TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount at end of study period: Seven transformation products were found and further characterized. The mayor transformation product was KKO 2254 accounting for up to 47.0% (in Howe soil) of the applied radioactivity after 100 days.

EXTRACTABLE RESIDUES
- % of applied amount at end of study period: The total amount of extracted radioactivity declined over time and on average accounted for 96.7 to 98.4% of the applied radiocarbon right after treatment (day 0) and ranged from 34.2 to 70.3% 100 days post treatment. In soil "Howe" the extracted portion declined from 70.3% at day 100 to 45.2% at day 365.

NON-EXTRACTABLE RESIDUES
- % of applied amount at end of study period: In all soils the decreasing portion of extracted radioactivity was matched by an increase in non-extracted residues (bound residues). Maximum amounts were reached after a period of 60-100 days of incubation yielding 21.8% (BBA 2.1), 22.7% (BBA 2.2) and 30.0% (Hoefchen) of the radioactivity applied. The percentage of unextracted radioactivity in soil "Howe" reached a maximum of 30.9% 365 days post-treatment.

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: Depending on the type of soil the mineralization of the methylene-label of the test substance reached 6.5% to 33.6% of the applied radiocarbon after 100 days of incubation. The total amount of 14CO2 was 24.7% after 365 days of incubation in soil "Howe".

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: Volatile organic compounds were not detected at any sampling interval.
Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
other: Commission Directive, 95/36/EC, amending Council Directive 91/414/EEC concerning the placing of plant protection products on the market: Annex II, Fate and Behavior in the Environment, 7171/VI/94-EN, 7.1.1 Route and Rate of Degradation
Version / remarks:
1995
Qualifier:
according to guideline
Guideline:
other: SETAC-Europe: Procedures for Assessing the Environmental Fate and Ecotoxicity of Pesticides, March 1995, Part 1, Section 1.1
Version / remarks:
1995
Qualifier:
according to guideline
Guideline:
other: German BBA Guideline, Part IV, 4-1
Version / remarks:
1986
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 Work Group on Degradation Kinetics, EC Document Reference Sanco/10058/2005 version 2
Version / remarks:
2006
Qualifier:
according to guideline
Guideline:
other: Generic guidance for Tier 1 FOCUS ground water assessments, version 2.1. FOCUS groundwater scenarios working group.
Version / remarks:
2012
GLP compliance:
yes (incl. QA statement)
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
sandy loam
% Clay:
5
% Silt:
22.6
% Sand:
72.4
% Org. C:
1.02
pH:
7.2
CEC:
8 meq/100 g soil d.w.
Bulk density (g/cm³):
2.5
Soil No.:
#1
Duration:
>= 0 - <= 120 d
Soil No.:
#1
Initial conc.:
53 other: µg/100g dry soil
Based on:
test mat.
Soil No.:
#1
% Total extractable:
63.3
% Non extractable:
24.9
% CO2:
10.2
% Other volatiles:
< 0.1
% Recovery:
98.4
Remarks on result:
other:
Remarks:
% Recovery of the applied radioactivity after 120 days.
Parent/product:
parent
Soil No.:
#1
% Degr.:
10.2
Parameter:
radiochem. meas.
Remarks:
14CO2 formation
Sampling time:
120 d
Soil No.:
#1
DT50:
1.3 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other:
Remarks:
DT50 of the test substance
Soil No.:
#1
DT50:
2.8 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 based on results at 20 °C.
Soil No.:
#1
DT50:
1.83 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
20 °C
Remarks on result:
other:
Remarks:
DT50 of the test substance
Soil No.:
#1
DT50:
3.9 d
Type:
other: Kinetic evaluation using FOCUS 2006
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 based on results at 20 °C.
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
Conclusions:
The biotransformation of Thiacloprid (3-(2-chloro-5-pyridylmethyl)-2-cyaniminothiazolidine) was studied in the soil Laacherhof AXXa (sandy loam, pH in CaCl2 = 6.32, org. C = 1.02%) for a maximum of 120 days under aerobic conditions in the dark at 20 °C. The soil moisture corresponded to 49% of maximum water holding capacity. [Methylene -14C]Thiacloprid was applied at a rate of 53 µg a.s./100 g soil dry weight soil (based on a soil layer of 5 cm and a density of 1.5 kg/L) equivalent to the proposed maximum annual use rate of 400 g a.s./ha.
The test system consisted of an Erlenmeyer flask attached with a trap for collection of CO2 and volatile organic compounds. Entire flasks were processed and investigated at DAT-0 (ca. 2 hrs), 1, 2, 5, 12, 28, 49, 69, 90 and 120 days. The 100-g soil samples were extracted three times with methanol at room temperature and once with water/methanol (1/1, v/v) under hot conditions in a ®Soxtec equipment. Thiacloprid residues were analysed by radio-thin-layer chromatography on normal phase. Cochromatographic methods were used for identification of Thiacloprid and/or the transformation products.
The total mineralisation of [methylene-14C]Thiacloprid to carbon dioxide reached 10.2% of AR during the testing period of 120 days The bound residues exceeded a maximum portion of 28.0% at DAT-49 and declined to 24.9% of AR till DAT-120, then.
Thiacloprid degraded in soil Laacherhof AXXa with a simple first order DT50 of 1.3 days (DT90 of 4.5 days) when incubated under aerobic conditions at 20°C. The major metabolite KKO2254 was then degraded with a DT50 of approx. 83 days.
Two major degradation products occurred, i.e. accounted for >10% of AR at any time during the study. The first metabolite was identified as KKO2254 (max. was reached fast, i.e. exceeded 70.2% of AR at DAT-5), and the other was identified as WAK6999 (max. was not reached till the end of the study, i.e. exceeded 11.3% of AR at DAT-120). One minor degradation product, the [trade name]-thiazolidinimine, reached a maximum of 5.5% of AR at DAT-120. All the other detected individual unknown 14C-zones (including origin zone) corresponded to <3.6% of AR during the entire study.
Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Version / remarks:
2002
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4100 (Aerobic Soil Metabolism)
Version / remarks:
2008
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4200 (Anaerobic Soil Metabolism)
Version / remarks:
2008
Qualifier:
according to guideline
Guideline:
other: Commission Directive 95/36/EC amending Council Directive 91/414/EEC (Annexes II and III, Fate and Behaviour in the Environment)
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 Work Group on Degradation Kinetics, EC Document Reference Sanco/10058/2005 version 2
Version / remarks:
2006
Qualifier:
according to guideline
Guideline:
other: Generic guidance for Tier 1 FOCUS ground water assessments, version 2.1. FOCUS groundwater scenarios working group.
Version / remarks:
2012
GLP compliance:
yes (incl. QA statement)
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
silt loam
% Clay:
7
% Silt:
51
% Sand:
42
% Org. C:
2.4
pH:
6.5
CEC:
12.8 meq/100 g soil d.w.
Bulk density (g/cm³):
0.99
Soil No.:
#1
Duration:
>= 0 - <= 120 d
Soil No.:
#1
Initial conc.:
16 other: µg/100 g dry soil
Based on:
test mat.
Soil No.:
#1
% Total extractable:
29.4
% Non extractable:
29.4
% CO2:
41.5
% Other volatiles:
0.1
% Recovery:
100
Remarks on result:
other:
Remarks:
% Recovery of the applied radioactivity after 120 days.
Parent/product:
parent
Soil No.:
#1
% Degr.:
41.5
Parameter:
radiochem. meas.
Sampling time:
120 d
Remarks on result:
other:
Remarks:
14CO2 formation
Soil No.:
#1
DT50:
0.35 d
Type:
other: double first order in parallel
Temp.:
20 °C
Soil No.:
#1
DT50:
0.7 d
Type:
other: double first order in parallel
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 based on results at 20 °C.
Soil No.:
#1
DT50:
0.35 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Updated kinetic evaluation, according to FOCUS 2006
Soil No.:
#1
DT50:
0.7 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Updated kinetic evaluation, according to FOCUS 2006
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
Conclusions:
The biotransformation of [thiazolidine-2-14C]Thiacloprid was studied in a silt loam (Hoefchen Am Hohenseh 4a, ID: HaH, organic carbon 2.4 %, pH (in CaCl2) 6.3, Burscheid, Germany) for 120 days under aerobic conditions in the dark at 20 ± 1°C and 55 ± 5 % WHCmax (maximum water holding capacity). 16 µg Thiacloprid/100 g soil dry weight were applied in this study, corresponding to the intended maximum single use rate of 120 g Thiacloprid/ha.
The test system consisted of Erlenmeyer flasks equipped with traps for the collection of CO2 and volatile organic compounds. Samples were analyzed at 0, 0.25, 1, 2, 4, 7, 14, 21, 30, 45, 72 and 120 days of incubation. At each sampling date the soil samples were extracted four times by shaking at ambient temperature and with respect to the formation of non-extractable residues by hot (microwave) extraction with acetonitrile/water solution mixtures. The extracts were analyzed and quantified by HPLC.
The test conditions outlined in the study protocol were maintained throughout the study. Material balances for individual samples account for 97.6% up to 101.8% of the applied radioactivity (AR).
The maximum amount of 14CO2 was 41.5 % of AR recovered at study termination (DAT-120). Volatile organic compounds were not formed in the course of the study (= 0.1 % of AR at all sampling intervals).
The half-life of Thiacloprid was calculated by the best fit kinetics according to FOCUS (double first order in parallel, DFOP, for trigger evaluation) as 0.35 days under aerobic conditions.
Extractable 14C-residues decreased from 101.1 % of AR at DAT-0 to 29.4 % at the study end (DAT-120).
Besides carbon dioxide three major metabolites were detected in the course of the study. [Trade name]-amide as main metabolite was formed very rapidly reaching a maximum value of 86.6 % of the AR at DAT-2. The second transformation product in soil was [trade name]-sulfonic acid reaching a maximum concentration of 15.1 % of the AR at DAT-21. The highest value of [trade name]-des-cyano, the third major transformation product, was found with 33.0 % of the AR at DAT-72. The amount of all three metabolites further declined to the end of the study.
Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Version / remarks:
2002
GLP compliance:
yes (incl. QA statement)
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic/anaerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
silt loam
% Clay:
14
% Silt:
66
% Sand:
20
% Org. C:
1.9
pH:
6.6
CEC:
11.3 meq/100 g soil d.w.
Bulk density (g/cm³):
1.12
Soil No.:
#1
Duration:
>= 0 - <= 125 d
Soil No.:
#1
Initial conc.:
356 other: µg/kg dry soil
Based on:
test mat.
Soil No.:
#1
% Total extractable:
70.2
% Non extractable:
27
% CO2:
0.1
% Other volatiles:
< 0.1
% Recovery:
97.3
Remarks on result:
other:
Remarks:
% Recovery of the applied radioactivity after 126 days.
Parent/product:
parent
Soil No.:
#1
% Degr.:
0.1
Parameter:
radiochem. meas.
Sampling time:
126 d
Remarks on result:
other:
Remarks:
14CO2 formation
Soil No.:
#1
DT50:
0.9 d
Type:
other: First order multiple compartment (FOMC)
Temp.:
20 °C
Soil No.:
#1
DT50:
1.9 d
Type:
other: First order multiple compartment (FOMC)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50, based on results at 20 °C.
Transformation products:
yes
No.:
#1
No.:
#2
Conclusions:
The route and rate of degradation of the insecticide thiacloprid was investigated in one European soil under flooded anaerobic conditions following an aerobic incubation phase at 19.8 °C.
A test concentration of 356 µg per kg soil dry weight was applied based on the intended maximum single field use rate of thiacloprid of 120 g/ha. The test systems consisted of 300 mL glass Erlenmeyer flasks, each containing 100 g of soil (dry weight equivalent). During the aerobic study phase, air-permeable traps were attached for the collection of carbon dioxide and volatile organic compounds (static test systems). At start of the anaerobic study phase, the traps for volatile components were replaced by sealable two-valve glass stoppers connected with plastic gas sampling bags. Following application of [thiazolidine-2-14C] labeled test item to soil the samples were incubated under aerobic conditions in the dark at about 20 °C and 55% of maximum water holding capacity. After 1 day of incubation the soil samples were flooded with oxygen-depleted, de-ionized water (ca. 3 cm layer above soil level) and set under an atmosphere of argon. The water-logged samples were maintained under anaerobic conditions at approximately 20 °C in the dark for 125 days.
Duplicate test systems were analyzed immediately after application and after 1 day of aerobic incubation. Further samples were taken directly after water logging (day 1) and 5, 8, 13, 35, 63, 91 and 126 days after treatment (DAT), corresponding to 0, 4, 7, 12, 34, 62, 90 and 125 days after soil flooding (DASF).
During the aerobic phase, the maximum amount of carbon dioxide was 0.1% AR. Formation of volatile organic compounds (VOC) was insignificant as demonstrated by values of < 0.1% AR at all samplings intervals in the aerobic and anaerobic incubation phase.
The anaerobic half-life of thiacloprid after flooding and shift to anaerobic conditions was 0.9 days.
In the aerobic incubation phase, non-extractable radioactivity (NER) in soil slightly increased from 1.7 to 3.1% AR (mean values). In the course of the anaerobic incubation period NER increased to 27% AR at study end.
The amounts of the degradation product [trade name]-amide (AE 1303043) in the entire system increased to 63.7% AR during the aerobic incubation period of one day and further to 85.1% AR at DAT-8 (corresponding to DASF-7). From DAT-8 towards study termination the amount of [trade name]-amide (AE 1303043) decreased to 64.4% AR (mean values). The degradation product [trade name]-sulfonic acid (BCS-AB54351) could be detected in single samples in low amounts only.

Description of key information

DT50 = 0.7 to 4.7 days (1.5 to 10 days, recalculated to 12 °C), 6.5 – 41.5% degradation after 100 to 120 days, aerobic conditions

 

DT50 = 0.9 days (1.9 days, recalculated to 12 °C), 0.1% degradation after 126 days, anaerobic conditions

Key value for chemical safety assessment

Half-life in soil:
10 d
at the temperature of:
12 °C

Additional information

A simulation study on the biodegradation of 14C-labelled (Z)-3-(6-chloro-3-pyridylmethyl)-1,3-thiazolidin-2-ylidenecyanamide in four different soils was conducted at 20°C, according to GLP and “US EPA Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate § 162-1: Aerobic Soil Metabolism Studies”. After an incubation period of 100 days 6.5 to 33.6% of the test substance (initially applied radioactivity) was mineralized to 14CO2. A degradation half-life of the test substance ranging from 0.7 to 4.7 days (1.5 to 10 days, recalculated to 12 °C) was reported. A kinetic evaluation of the experimental data, according to FOCUS 2006, determined DT50 values ranging from 0.66 to 5.39 days (1.4 to 11.4 days, recalculated to 12 °C).

Another simulation study, according to GLP and “Commission Directive, 95/36/EC, amending Council Directive 91/414/EEC concerning the placing of plant protection products on the market: Annex II, Fate and Behavior in the Environment, 7171/VI/94-EN, 7.1.1 Route and Rate of Degradation”, investigated the degradation of the test substance in one test soil under aerobic conditions at 20 °C. After 120 days 10.2% of the applied radioactivity was found as 14CO2. The DT50 of the test substance was 1.3 days (2.8 days, recalculated to 12 °C). A kinetic evaluation of the experimental data, according to FOCUS 2006, determined a DT50 of 1.83 days (3.9 days, recalculated to 12 °C).

A further simulation study, according to GLP and OECD Guideline 307, investigated the degradation of the test substance in one test soil under aerobic conditions at 20 °C. After 120 days 41.5% of the applied radioactivity was found as 14CO2. The DT50 of the test substance was 0.35 days (0.7 days, recalculated to 12 °C). An updated kinetic evaluation of the experimental data, according to FOCUS 2006, came to the same result of a DT50 of 0.35 days (0.7 days, recalculated to 12 °C).

The results of a fourth simulation study, following GLP and OECD Guideline 307, reported a degradation half-life of 0.9 days (1.9 days, recalculated to 12 °C) of the test substance at 20 °C and anaerobic conditions in an agricultural soil of European origin. The final degradation product carbon dioxide was detected at levels up to 0.1% after an incubation time of 126 days.

For the sake of completeness five more studies are available.

The first study followed GLP and investigated the leaching behavior of (Z)-3-(6-chloro-3-pyridylmethyl)-1,3-thiazolidin-2-ylidenecyanamide in laboratory column experiments. After 60 days 8 % of the applied radioactivity were determined as 14CO2.

Four more studies investigated the behavior of the test compound in field lysimeters. After three years up to 40% of the applied radioactivity was mineralized.