ethametsulfuron-methyl (ISO); methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazin-2-yl)carbamoylsulfamoyl]benzoate

Biodegradation in soil

Administrative data

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: U.S. EPA Pesticide Assessment Guidelines Subdivision N, Series 162-1

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: Society for Environmental Toxicology and Chemistry-Europe (Procedures for Assessing the Environmental Fate and Ecotoxicology in Pesticides)

Deviations:

no

GLP compliance:

yes

Test type:

laboratory

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 002

Cas Number:

97780-06-8

Test material form:

solid

Details on test material:

Purity: Not reported

Radiolabelling:

yes

Remarks:

Phenyl and Triazinel label

Study design

Oxygen conditions:

aerobic/anaerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

2007

Soil properties

Soil properties 1

Soil no.:

#1

Soil type:

silty clay

% Clay:

43

% Silt:

57

% Sand:

0

% Org. C:

2.03

pH:

7.7

CEC:

16.2 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Soil properties 2

Soil no.:

#2

Soil type:

silty clay loam

% Clay:

41

% Silt:

59

% Sand:

0

% Org. C:

1.6

pH:

7.7

CEC:

17.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Soil properties 3

Soil no.:

#3

Soil type:

loam

% Clay:

25

% Silt:

46

% Sand:

29

% Org. C:

1.1

pH:

7.9

CEC:

1.03 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Soil properties 4

Soil no.:

#4

Soil type:

loam

% Clay:

13

% Silt:

38

% Sand:

49

% Org. C:

1.6

pH:

7.5

CEC:

7.7 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Soil properties 5

Soil no.:

#5

Soil type:

sandy loam

% Clay:

11

% Silt:

20

% Sand:

69

% Org. C:

1.7

pH:

6.8

CEC:

7.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Duration of test (contact time)

Duration of test (contact time) 1

Soil No.:

#1

Duration:

120 d

Duration of test (contact time) 2

Soil No.:

#2

Duration:

120 d

Duration of test (contact time) 3

Soil No.:

#3

Duration:

120 d

Duration of test (contact time) 4

Soil No.:

#4

Duration:

120 d

Duration of test (contact time) 5

Soil No.:

#5

Duration:

120 d

Initial test substance concentration

Initial conc.:

0.4 mg/kg soil d.w.

Based on:

act. ingr.

Remarks:

For all soil types

Parameter followed for biodegradation estimation:

radiochem. meas.

Experimental conditions

Experimental conditions 1

Soil No.:

#1

Temp.:

20 ± 2°C

Microbial biomass:

Initial: 40.6 mg C/100 g soil; at day 120: 16.9 mg C/100 g soil

Experimental conditions 2

Soil No.:

#2

Temp.:

20 ± 2°C

Microbial biomass:

Initial: 36.2 mg C/100 g soil; at day 120: 12.1 mg C/100 g soil

Experimental conditions 3

Soil No.:

#3

Temp.:

20 ± 2°C

Microbial biomass:

Initial: 18.7 mg C/100 g soil; at day 120: 9.4 mg C/100 g soil

Experimental conditions 4

Soil No.:

#4

Temp.:

20 ± 2°C

Microbial biomass:

Initial: 34.9 mg C/100 g soil; at day 120: 16.2 mg C/100 g soil

Experimental conditions 5

Soil No.:

#5

Temp.:

20 ± 2°C

Microbial biomass:

Initial: 19.3 mg C/100 g soil; at day 120: 8.0 mg C/100 g soil

Results and discussion

Material (mass) balance

Material (mass) balance 1

Soil No.:

#1

% Recovery:

14.19

Remarks on result:

other: Phenyl label

Material (mass) balance 2

Soil No.:

#2

% Recovery:

28.26

Remarks on result:

other: Phenyl lablel

Material (mass) balance 3

Soil No.:

#3

% Recovery:

7.54

Remarks on result:

other: Phenyl lablel

Material (mass) balance 4

Soil No.:

#4

% Recovery:

9.71

Remarks on result:

other: Phenyl lablel

Material (mass) balance 5

Soil No.:

#5

% Recovery:

16.2

Remarks on result:

other: Phenyl lablel

Material (mass) balance 6

Soil No.:

#1

% Recovery:

14.81

Remarks on result:

other: Triazine label

Material (mass) balance 7

Soil No.:

#2

% Recovery:

31.57

Remarks on result:

other: Triazine label

Material (mass) balance 8

Soil No.:

#3

% Recovery:

17.66

Remarks on result:

other: Triazine label

Material (mass) balance 9

Soil No.:

#4

% Recovery:

8.71

Remarks on result:

other: Triazine label

Material (mass) balance 10

Soil No.:

#5

% Recovery:

15.08

Remarks on result:

other: Triazine label

Half-life / dissipation time of parent compound

Half-life / dissipation time of parent compound 1

Key result

Soil No.:

#1

DT50:

29.9 d

Type:

other: FOMC

Temp.:

20 °C

Half-life / dissipation time of parent compound 2

Key result

Soil No.:

#2

DT50:

57.4 d

Type:

other: DFOP

Temp.:

20 °C

Half-life / dissipation time of parent compound 3

Key result

Soil No.:

#3

DT50:

29.6 d

Type:

other: DFOP

Temp.:

20 °C

Half-life / dissipation time of parent compound 4

Key result

Soil No.:

#4

DT50:

22.6 d

Type:

other: DFOP

Temp.:

20 °C

Half-life / dissipation time of parent compound 5

Key result

Soil No.:

#5

DT50:

26.9 d

Type:

other: DFOP

Temp.:

20 °C

Transformation products:

yes

Remarks:

Nine transformation products that exceeded 5% of the applied radioacitivty at two sequential time points were observed in the study: IN-D5803, IN-A8768, IN-N7469, IN-N7468, IN-RXR81, IN-D5119, IN-B9161, IN-D7556, and IN-A9795.

Evaporation of parent compound:

no

Volatile metabolites:

yes

Remarks:

CO2

Any other information on results incl. tables

Mass balance was calculated as the percent of applied radioactivity (% AR) as presented in the table below. The extractability of DPX-A7881 decreased while the non-extractable residues (NER) increased as the study progressed. Non-extractable residues reached a peak at Day 120 for all systems ranging from 10.83-22.93%.

Volatile organics were produced in significant levels. For systems dosed with [phenyl-14C] DPX-A7881, the amount of 14CO2 evolved ranged from 25.47-51.59% AR whereas 14CO2 evolved from the triazine systems ranged from 0.96-11.92% AR. The amounts of CaCl2 and organic extractable and mineralized radioactivity in each system for Day 120 samples are summarized in the following table.

Soil (texture)	A7881 Label	Extractable with CaCl2 at Day 120 (%AR)	Extractable with Organic Solvents at Day 120 (%AR)	NER at Day 120 (%AR)	Evolved 14CO2 at Day 120 (%AR)	Overall Mean Mass Balance (%AR)
Lleida (Silty Clay)	Phenyl	2.7	14.67	22.7	51.59	96.89± 5.11
	Triazine	7.6	62.41	22.93	1.37	98.48±1.74
Tama (Silty Clay )	Phenyl	5.92	50.45	14.88	25.47	100.14±2.91
	Triazine	2.55	76.34	18.68	0.96	98.90±1.19
Gross-Umstadt (Loam)	Phenyl	15.82	20.03	17.99	46.33	99.61±1.69
	Triazine	24.51	55.21	13.28	8.17	100.52±2.40
Nambsheim(Loam)	Phenyl	30.17	27.84	13.37	34.23	100.99±3.42
	Triazine	25.07	47.51	12.79	11.92	100.01±1.87
Sassafras No. 16 (Sandy Loam)	Phenyl	8.05	19.47	19.46	35.42	93.48±7.74
	Triazine	21.51	62.32	10.83	3.05	99.73±0.95

A summary of the amount of test substance and major and minor transformation products at the termination time point and the maximum amount reached for each is presented in the following tables.

Nine transformation products that exceeded 5% of the applied radioacitivty at two sequential time points were observed in the study: IN-D5803, IN-A8768, IN-N7469, IN-N7468, IN-RXR81, IN-D5119, IN-B9161, IN-D7556, and IN-A9795.

	% AR Observed on Day 120, Phenyl Label
Component	Lleida	Tama	Gross-Umstadt	Nambsheim	Sassafras No. 16
Test substance	14.19	28.26	7.54	9.71	16.2
IN‑A8768	ND	15.42	21.6	36.63	11.3
IN‑N7469	ND	NA	2.51	2.30	ND
IN‑N7468	1.75	1.31	ND	ND	ND
IN‑RXR81	ND	ND	< 5.0	3.01	< 5.0
IN‑D5803	NA	ND	NA	2.89	ND
IN‑D5119	1.44	ND	2.22	1.48	ND
ND = Not detected, NA = Not applicable, metabolite was not found in this test system. IN-RXR81 is shown as < 5.0 since it was not reported independently, but reported in the sum of “Other” metabolites that accounted for < 5 % A.R

	% AR Observed on Day 120, Triazine Label
Component	Lleida	Tama	Gross-Umstadt	Nambsheim	Sassafras No. 16
Test substance	14.81	31.57	17.66	8.71	15.08
IN‑A8768	ND	7.90	3.51	3.50	9.52
IN‑N7469	3.63	NA	8.25	20.06	5.77
IN‑N7468	1.02	2.11	2.09	ND	1.79
IN‑RXR81	ND	ND	< 5.0	6.14	< 5.0
IN‑B9161	43.81	11.87	27.59	18.72	23.35
IN‑D7556	6.74	21.75	11.68	9.06	25.90
IN‑A9795	ND	ND	1.36	4.70	0.00
ND = Not detected, NA = Not applicable, metabolite was not found in this test system. IN-RXR81 is shown as < 5.0 since it was not reported independently, but reported in the sum of “Other” metabolites that accounted for < 5 % A.R

	Maximum % AR, Phenyl Label
Component	Lleida	Tama	Gross-Umstadt	Nambsheim	Sassafras No. 16
Test substance	93.70 (Day 0)	89.85 (Day 0)	95.06 (Day 0)	97.47 (Day 0)	95.12 (Day 0)
IN‑A8768	4.99 (Day 13)	15.42 (Day 120)	28.48 (Day 90)	33.63 (Day 120)	13.84 (Day 64)
IN‑N7469	1.05 (Day 64)	ND	2.96 (Day 41)	6.51 (Day 64)	1.49 (Day 41)
IN‑N7468	3.57 (Day 41)	3.67 (Day 13)	3.8 (Day 41)	7.04 (Day 13)	5.14 (Day 20)
IN‑RXR81	*	*	*	4.83 (Day 64)	*
IN‑D5803	NA	8.02 (Day 90)	1.94	2.88 (Day 90)	0.93 (Day 14)
IN‑D5119	3.34 (Day 41)	2.56 (20)	2.74 (Day 13)	5.24 (Day 90)	5.95 (Day 41)
ND = Not detected, NA = Not applicable, metabolite was not found in this test system, * = exact quantification of IN-RXR81 is not available for every sampling point, but in all instances the metabolite accounted for < 5 % A.R.

	Maximum % AR, Triazine Label
Component	Lleida	Tama	Gross-Umstadt	Nambsheim	Sassafras No. 16
Test substance	92.54 (Day 0)	94.73 (Day 0)	94.82 (Day 0)	98.00 (Day 0)	94.51 (Day 0)
IN‑A8768	4.95 (Day 7)	9.86 (Day 90)	22.77 (Day 90)	22.46 (Day 64)	23.17 (Day 64)
IN‑N7469	4.64 (Day 90)	ND	8.25 (Day 120)	20.06 (Day 120)	5.77 (Day120)
IN‑N7468	7.55 (Day 41)	11.43 (Day 41)	6.38 (Day 20)	7.66 (Day 64)	12.28 (Day 41)
IN‑RXR81	*	*	*	9.15 (Day 90)	*
IN‑B9161	59.01 (Day 90)	14.37 (Day 64)	27.59 (Day 120)	18.72 (Day 120)	25.61 (Day 90)
IN‑D7556	7.66 (Day 90)	21.75 (Day 120)	11.68 (Day 120)	9.06 (Day 120)	25.90 (Day 120)
IN‑A9795	2.28 (Day 20)	7.04 (Day 41)	9.04 (Day 41)	4.7 (Day 120	12.13 (Day 41)
ND = Not detected, NA = Not applicable, metabolite was not found in this test system, * = exact quantification of IN-RXR81 is not available for every sampling point, but in all instances the metabolite accounted for < 5 % A.R.

Soil	Model	DT50	DT90	chi² error	r²
Lleida	FOMC	29.9	153.7	3	0.987
Tama	DFOP	57.4	320.4	4	0.975
Gross-Umstadt	DFOP	29.6	118.7	3	0.985
Nambsheim	DFOP	22.6	111.2	3	0.986
Sassafras No. 16	DFOP	26.9	145.8	5	0.979
The r² value reported in this table was calculated using the formula for model efficiency in the FOCUS (2006) guidance.

A summary of the desorption coefficient results at zero time and Day 64 are summarized for each soil type in the following table:

Soil Name	at Zero Time			At (Day 64)			Change in Kd, des From Day 0
	Kd des	Kom des	Koc des	Kd des	Kom des	Koc des
PH-Lleida	0.52	14.83	25.57	7.35	210	362	14.2
PH-Tama	2.72	82.29	142	48.53	1471	2535	17.9
PH-Gross-Umstadt	0.33	17.22	29.53	3.32	175	302	10.2
PH-Nambsheim	0.34	12.31	21.22	3.70	132	228	10.7
PH-Sassafras No. 16	1.12	38.69	66.70	6.14	212	365	5.5
TR-Lleida	0.51	14.65	25.26	9.14	261	450	17.6
TR-Tama	2.62	79.26	137	100	3044	5248	38.4
TR-Gross-Umstadt	0.37	19.44	33.52	3.77	198	342	10.2
TR-Nambsheim	0.36	12.87	22.18	2.33	83.36	144	6.5
TR-Sassafras No. 16	1.07	37.00	63.80	7.19	248	427	6.7
* (Day 64) was chosen as Kd des values generally decreased for Day 90 and 120 due to an artifact that was caused by very low concentrations of DPX A7881 in the soil.

Applicant's summary and conclusion

Conclusions:

The test substance would extensively degrade to a number of metabolite products and become less prone to movement with soil water in aerobic soils.

Executive summary:

The rate of degradation and sorption of carbon-14 labeled test substance was studied in five soils according to U.S. EPA, Pesticide Assessment Guidelines, Subdivision N, 162-1 and, OECD Guideline 307, and in compliance with the GLP standards of the United States Environmental Protection Agency. The five soils were either sandy loam, loam, or silty clay, differing significantly in their sand and clay content.

The study was conducted at 20 ± 2°C in the dark for 120 days. The moisture content of the soils was maintained between 40 and 60% MWHC (close to 75% water holding capacity at 0.33 bar). The test substance used was labeled separately in two portions, the triazine and the phenyl group. The test substance was radiolabelled at stable positions and allowed detection of all significant degradation products. The test substance was applied to each soil at a nominal rate of 0.4 µg/g soil.

Nine transformation products that exceeded 5% of the applied radioacitivty at two sequential time points were observed in the study: IN-D5803, IN-A8768, IN-N7469, IN-N7468, IN-RXR81, IN-D5119, IN-B9161, IN-D7556, and IN-A9795.

The %AR for the test substance observed on Day 120 for the phenyl label ranged from 7.54 to 28.26 and from 8.71 to 31.57 for the triazine label. There were higher %AR of IN-A8768 for the phenyl label and higher amounts of %AR of IN-N7469 for the triazine label. Low levels of %AR of IN-D5803 and IN-D5119 were found for the phenyl systems and IN-A9795 for the triazine system. For the triazine system, IN-B9161 ranged from 11.87-43.81 %AR and D7556 ranged from 6.74 to 25.90 %AR. The levels of IN-RXR81 exceeded 5%AR in more than two sampling points for the triazine label in the Nambsheim soil. The chromatograms in the study records were reviewed for occurrences of this metabolite in the other four soils as well. The review revealed that IN-RXR81 never exceeded 5%AR in the Lleida, Tama, Gross-Umstadt or Sassafras soils.

The DT50 and DT90 of the test substance were calculated using the simple first-order (SFO), first-order multi-compartment (FOMC), Hockey Stick (HS), and Double First Order Parallel (DFOP) models using Model Maker for Focus Kinetics (Focus 2006). The multi-compartment models provided best fit to the observed data across all soils. The residual values were more randomly distributed and the chi² error value was lower compared to the other models.

The desorption coefficient, Kd, des, of [14C]-test substance was calculated for each soil and label at each sampling interval using the amount of test substance extracted in CaCl2 and the soil concentration. Kom, des and Koc, des are calculated from the Walkley-Black method. The Kd des in the fourth column represents the highest Kd established throughout the study. Beyond the day in parentheses no further increase was observed. The concentration of parent test substance was so low in the soil phase that the decreasing Kd des represents an artifact. No Kd des was calculated when test substance had completely degraded.

The sorption of [14C]-test substance increased over time and subsequently its potential for mobility decreased.

Based on the results of this study, The test substance would extensively degrade to a number of metabolite products, including CO2, and become less prone to movement with soil water in aerobic soils.