Triflumezopyrim

Biodegradation in soil

Link to relevant study record(s)

Reference

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)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.4100 (Aerobic Soil Metabolism)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: MAFF Japan Guideline No 12-Nousan-8147, 2-5-2 (2000) – Studies of Fate in Aerobic Soil

Deviations:

no

GLP compliance:

yes

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

USDA (US Department of Agriculture)

Soil no.:

#1

Soil type:

silty clay loam

% Clay:

33

% Silt:

55

% Sand:

12

% Org. C:

2

pH:

6.2

CEC:

15.8 meq/100 g soil d.w.

Bulk density (g/cm³):

1.05

Soil no.:

#2

Soil type:

loam

% Clay:

24

% Silt:

37

% Sand:

39

% Org. C:

0.9

pH:

5.5

CEC:

13.7 meq/100 g soil d.w.

Bulk density (g/cm³):

1.28

Soil No.:

#1

Duration:

178 d

Soil No.:

#2

Duration:

178 d

Soil No.:

#1

Initial conc.:

1 other: µg/g

Based on:

act. ingr.

Soil No.:

#2

Initial conc.:

1 other: µg/g

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Soil No.:

#1

Temp.:

25 ± 2°C

Humidity:

36.18% moisture content

Microbial biomass:

285.53, 136.73 and 131.33 μg extractable organic carbon/g dry soil at application day, day 120 and day 178 respectively

Soil No.:

#2

Temp.:

25 ± 2°C

Humidity:

28.02% moisture content

Microbial biomass:

162.53, 127.40 and 108.80 μg extractable organic carbon/g dry soil at application day, day 120 and day 178 respectively

Soil No.:

#1

% Recovery:

103.52

Remarks on result:

other: treated with pyridine-labelled test substance

Soil No.:

#1

% Recovery:

99.28

Remarks on result:

other: treated with fused pyrimidine-labelled test substance

Soil No.:

#1

% Recovery:

101.13

Remarks on result:

other: treated with methylene-labelled test substance

Soil No.:

#2

% Recovery:

106.27

Remarks on result:

other: treated with pyridine-labelled test substance

Soil No.:

#2

% Recovery:

103.89

Remarks on result:

other: treated with fused pyrimidine-labelled test substance

Soil No.:

#2

% Recovery:

99.95

Remarks on result:

other: treated with methylene-labelled test substance

Key result

Soil No.:

#1

DT50:

52.9 d

Type:

other: SFO

Temp.:

>= 23 - <= 27 °C

Key result

Soil No.:

#2

DT50:

71.9 d

Type:

other: SFO

Temp.:

>= 23 - <= 27 °C

Transformation products:

yes

Remarks:

IN-SBY68 >5% but <10% AR

Volatile metabolites:

yes

Remarks:

Radiolabelled volatile organics were below the limit of quantification throughout the study except for the Kumagaya soil system treated with fused pyrimidine-labelled test system which accounted for a maximum value of 0.10% AR from Day 14 to Day 178

Residues:

yes

Conclusions:

The test substance degrades under aerobic conditions in Tama soil with a SFO DT50 of 52.9 days and in the Kumagaya soil with a SFO DT50 of 71.9 days.
In this laboratory study, the test substance degraded in aerobic soil in the dark to multiple minor components (IN-RPD47, IN-RPA16, IN-SBV06, IN-SBY68) and ultimately mineralized to CO2 and bound residue via microbial degradation.

Executive summary:

The fate of [14C]-test substance under aerobic conditions was studied in two soils. The soils identified as Tama (a silty clay loam field soil) and Kumagaya (a loam paddy soil) were collected from, Illinois, USA and, Saitama, Japan, respectively. The Tama soil had an organic matter content of 3.4% and a pH of 6.2 and the Kumagaya soil had an organic matter content of 1.6% and a pH of 5.5. In the laboratory, the soil systems were allowed to acclimatize for 18-19 days prior to test item application. Three radiolabelled forms of the test item were used, [14C]-radiolabelled in the pyridine, fused pyrimidine or methylene position. The radiolabelled test item was applied to the soil at a nominal rate of 1.0 μg/g oven dry soil. Treated vessels were incubated for up to 178 days under aerobic conditions in the dark at 25 ± 2°C.

This study was conducted in accordance with the guidelines OPPTS 835.4100 and OECD 307.

The test system consisted of glass incubation vessels connected to air flow-through systems with traps for the collection of CO2 and non-specific volatile organic compounds. Samples were analysed immediately following test item application (zero time) and after 7, 14, 28, 60, 90, 120, 150 and 178 days of aerobic incubation. The stability of the test substance during the extraction process had been confirmed. Soil samples were extracted in acetonitrile. Extractable soil radioactivity was quantified by LSC. Radioactive components in soil extracts were quantified by reversed phase HPLC with on-line radio detection. Non-extractable 14C-residues were quantified by combustion analysis.

The material balance for the pyridine-labelled test systems was quantitative with individual values ranging between 99.51% to 107.57% AR over the incubation period, except for the zero time and Day 150 Kumagaya soil samples which had values of 115.44% and 112.04% AR, respectively. The material balance for the fused pyrimidine-labelled test systems were quantitative, with individual values ranging between 94.78% to 107.44% AR over the incubation period. The material balance for the methylene labelled test sytems were quantitative, with individual values ranging from 93.84 to 105.67% AR over the incubation period.

In the Tama soil system treated with pyridine-labelled [14C]-test substance, the solvent extractable 14C-residues in the soil decreased from values of 96.91% at Day 0 to a minimum value of 36.90% AR after 178 days. Non-extractable residues increased to a maximum value of 42.39% AR at Day 178. Based on the high levels of 14CO2 generated in this study, it is believed that the non-extractable residues consist of natural products resulting from the mineralization of the test substance to 14CO2. Radiolabelled volatile organics were below the limit of quantification throughout the study. 14CO2 accounted for a maximum of 22.75% AR at Day 178.

In the Tama system treated with fused pyrimidine-labelled [14C]-test substance, the solvent extractable 14C-residues in the soil decreased from values of 93.77% at Day 0 to a minimum value of 29.60% AR after 178 days. Non-extractable residues increased to a maximum value of 34.30% AR at Day 120, and decreased to 30.37% AR at Day 178. Based on the high levels of 14CO2 generated in this study, it is believed that the non-extractable residues consist of natural products resulting from the mineralization of the test substance to 14CO2. Radiolabelled volatile organics were below the limit of quantification throughout the study. 14CO2 accounted for a maximum of 37.19% AR at Day 178.

In the Tama soil system treated with methylene-labelled [14C]-test substance, the solvent extractable 14C-residues in the soil decreased from values of 100.23% AR at Day 0 to a minimum value of 26.19% AR after 150 days, and were 27.68% AR at Day 178. Non-extractable residues increased to a maximum value of 45.98% AR at Day 120, and decreased to 39.68% AR at Day 178. Based on the high levels of 14CO2 generated in this study, it is believed that the non-extractable residues consist of natural products resulting from the mineralization of the test substance to 14CO2. Radiolabelled volatile organics were below the limit of quantification throughout the study. 14CO2 accounted for a maximum of 32.31% AR at Day 178.

In the Kumagaya soil system treated with pyridine-labelled [14C]-test substance, the solvent extractable 14C-residues in the soil decreased from values of 107.46% AR at Day 0 to a minimum value of 35.02% AR after 178 days. Non-extractable residues increased to a maximum value of 60.86% AR at Day 150, and decreased to 58.16% AR at Day 178. Based on the high levels of 14CO2 generated in this study, it is believed that the non-extractable residues consist of natural products resulting from the mineralization of the test substance to 14CO2. Radiolabelled volatile organics were below the limit of quantification throughout the study. 14CO2 accounted for a maximum of 9.46% AR at Day 178.

In the Kumagaya soil system treated with fused pyrimidine-labelled [14C]-test substance, the solvent extractable 14C-residues in the soil decreased from values of 96.84% AR at Day 0 to a minimum value of 29.37% AR after 178 days. Non-extractable residues increased to a maximum value of 41.43% AR at Day 150, and decreased to 39.15% AR at Day 178. Based on the high levels of 14CO2 generated in this study, it is believed that the non-extractable residues consist of natural products resulting from the mineralization of the test substance to 14CO2. Radiolabelled volatile organics accounted for a maximum value of 0.10% AR from Day 14 to Day 178. 14CO2 accounted for a maximum of 32.24% AR at Day 178.

In the Kumagaya soil system treated with methylene-labelled [14C]-test substance, the solvent extractable 14C-residues in the soil decreased from values of 92.77% AR at Day 0 to a minimum value of 17.52% AR at Day 178. Non-extractable residues increased to a maximum value of 58.84% AR at Day 90, and decreased to 56.49% AR at Day 178. Based on the high levels of 14CO2 generated in this study, it is believed that the non-extractable residues consist of natural products resulting from the mineralization of the test substance to 14CO2. Radiolabelled volatile organics were below the limit of quantification throughout the study. 14CO2 accounted for a maximum of 22.09% AR at Day 178.

HPLC analysis of Tama soil extracts demonstrated that the test substance was significantly degraded during the incubation period, decreasing to a value of 24.80% AR in the pyridine labelled samples, 18.10% AR in the fused pyrimidine labelled samples and 16.33% AR in the methylene labelled samples by Day 178.

The test substance was also significantly degraded during the incubation period in the Kumagaya soil decreasing to a value of 27.74% AR in the pyridine labelled samples, 24.04% AR in the fused pyrimidine labelled samples and 13.09% AR in the methylene labelled samples by Day 178.

Four minor degradation products were detected during the study. A chromatographic peak eluting at ca 39 minutes, identified as IN-SBY68, was detected in the Tama samples at maximum values of 6.80% AR at Day 178 in the pyridine labelled samples, 7.72% AR at Day 150 in the fused pyrimidine labelled samples and 7.45% AR at Day 60 in the methylene labelled samples. The IN-SBY68 was detected in the Kumagaya samples at a maximum value of 1.61% AR. A chromatographic peak eluting at ca 44 minutes, identified as IN-SBV06, was detected in the Tama samples at a maximum value of 3.37% AR, and in Kumagaya samples at a maximum value of 1.05% AR. Two minor metabolites co-eluted with supplied reference standards IN-RPD47 and IN-RPA16. IN-RPD47 was a minor degradation product and was detected in both the pyridine and fused pyrimidine labelled samples and in both soil types at <1%AR in the Tama soil and at <3% AR in the Kumagaya soil samples. IN-RPA16 was a minor degradation product and was detected in the methylene labelled samples of both soil types reaching a maximum of <2% AR in the Tama and Kumagaya samples. No unidentified metabolites exceeded 5% applied radioactivity (% AR) at any sampling interval.

The test substance degrades under aerobic conditions in Tama soil with a SFO DT50 of 52.9 days. The test substance also degraded under aerobic conditions in the Kumagaya soil with a SFO DT50 of 71.9 days.

In this laboratory study, the test substance degraded in aerobic soil in the dark to multiple minor components (IN-RPD47, IN-RPA16, IN-SBV06, IN-SBY68) and ultimately mineralized to CO2 and bound residue via microbial degradation.

Description of key information

OECD Guideline 307

Key value for chemical safety assessment

Half-life in soil:

302.7 d

at the temperature of:

25 °C

Additional information

In one study, the test substance degraded under aerobic conditions in Tama soil with a DT50 of 52.9 days and in the Kumagaya soil with a DT50 of 71.9 days. The test substance degraded in aerobic soil in the dark to multiple minor components (IN-RPD47, IN-RPA16, IN-SBV06, IN-SBY68) and ultimately mineralized to CO2 and bound residue via microbial degradation. In a second study, the test substance dissipated slowly from the soil under anaerobic conditions. The DT50 was reported as 302.7 days and no major metabolites were observed. In a third study,the calculated DT50 values for the test substance were 60.5, 131.9 and 133.4 days, respectively for Lleida, Speyer and Sassafras soils. No major metabolites were observed above 10% of applied radioactivity.