Test Material: Chlorimuron ethyl

MRID: 49526701

Title: Aerobic Soil Metabolism of Chlorimuron Ethyl (DPX-F6025)

EPA PC Code: 128901

OCSPP Guideline: 835.4100

For CDM Smith

Primary Reviewer: Kathleen Ferguson Signature:

Date: 3/11/15

Secondary Reviewer: Mary Samuel Signature: 

Date: 3/11/15

QC/QA Manager: Joan Gaidos Signature: 

Date: 3/11/15
Chlorimuron ethyl (PC 128901) MRID 49526701

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Aerobic degradation of Chlorimuron ethyl in soil

Report: MRID 49526701. Ponte, V. 2014. Aerobic soil Metabolism of Chlorimuron Ethyl 

(DPX-F6025). Unpublished study performed by PTRL West, Hercules, California; 

sponsored and submitted by E.I. du Pont de Nemours and Company, Wilmington, 

Delaware. Sponsor Study No.: DuPont-38490. PTRL West Project No.: 2550W. 

Experiment started December 4, 2013, and completed November 12, 2014 (p. 12). 

Final report issued December 8, 2014.

Document No.: MRID 49526701

Guideline: OCSPP 835.4100 

Statements: The study was conducted according to USEPA GLP standards (p. 3). Signed and 

dated Data Confidentiality, GLP, Quality Assurance, and Certification of 

Authenticity statements were provided (pp. 2-5). 

Classification: This study is Supplemental. Both soils used in the experiment were classified as 

clay loam. Transformation product MET-1 reached 10.2% of the applied but was 

not identified. In three of the four experiments, overall recoveries were <90% of 

the applied at one or more sampling intervals. Significant levels (15.2% of the 

applied) of unextracted residues were detected in the Illinois clay loam soil, and the 

study author failed to use solvents with a range of dielectric constants (including a 

nonpolar solvent) to maximize extraction of the residues. The pesticide use history 

at the test sites was not reported, and it was not confirmed that the soils were 

pesticide-free prior to use.

PC Code: 128901

Reviewer: Richard Shamblen, Biologist Signature:

USEPA Date: October 30, 2015

EXECUTIVE SUMMARY

The aerobic transformation of [phenyl-U14

C]- and [pyrimidine-2-

14C]-labeled chlorimuron ethyl 

(DPX-F6025) was studied in a clay loam soil (pH 5.5 in CaCl2) from Illinois and a clay loam soil 

(pH 5.9 in CaCl2) from North Dakota. The experiment was conducted for up to 124 days in 

darkness at 20°C and a soil moisture content of 50% of the maximum water holding capacity. The 

soils were treated at ca. 0.2 mg a.i./kg, equivalent to a field application rate of ca. 150 g a.i./ha. 

Single samples (single flasks) of each treatment were collected at each sampling interval. It was not 

confirmed that aerobic conditions were maintained in the soils throughout the study. The soils were 

viable at study initiation and at termination. 

For the Illinois clay loam soil, overall mass balances averaged 94.9 ± 6.7% of the applied (range 

89.4-108.0%) in the samples treated with the phenyl label and 94.0 ± 3.6% (range 87.8-98.7%) in 

the samples treated with the pyrimidine label. For the North Dakota clay loam soil, overall mass 

balances averaged 96.2 ± 5.0% of the applied (range 88.5-104.1%) in the samples treated with the 

phenyl label and 95.3 ± 3.6% (range 92.5-103.0%) in the samples treated with the pyrimidine label.

Observed DT50 values, calculated half-lives, and information on transformation products are listed 

in Table 1. Chlorimuron ethyl dissipated with an tR IORE values (IORE) of 22.8 days in the Illinois 

clay loam soil and 105 days in the North Dakota clay loam soil. Seven transformation products were 

isolated, of which six were identified. 
Chlorimuron ethyl (PC 128901) MRID 49526701

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In the Illinois clay loam soil treated with the phenyl label, total extractable radioactivity declined 

from 107.3% of the applied at time 0 to 51.1% at 124 days posttreatment. Unextracted radioactivity 

increased to a maximum of 15.2% at 90 days and was 15.0% at 124 days. At study termination, CO2

totaled a maximum of 23.3%. Organic volatiles were never detected.

In the Illinois clay loam soil treated with the pyrimidine label, total extractable radioactivity 

declined from 98.1% of the applied at time 0 to 65.1% at 90 days posttreatment and was 66.6% at 

124 days. Unextracted radioactivity increased to a maximum of 12.4% at 124 days. At study 

termination, CO2 totaled a maximum of 14.9% and organic volatiles totaled 0.2%.

In the North Dakota clay loam soil treated with the phenyl label, total extractable radioactivity 

declined from 101.6% of the applied at time 0 to 82.5% at 90 days posttreatment and was 91.5% at 

124 days. Unextracted radioactivity increased to a maximum of 5.4% at 61 days and was 5.3% at 

124 days. At study termination, CO2 totaled a maximum of 1.1%. Organic volatiles were never 

detected.

In the North Dakota clay loam soil treated with the pyrimidine label, total extractable radioactivity 

declined from 99.9% of the applied at time to 82.8% at 124 days posttreatment. Unextracted 

radioactivity increased to a maximum of 9.1% at 124 days. At study termination, CO2 totaled a 

maximum of 2.5%. Organic volatiles were never detected.
Chlorimuron ethyl (PC 128901) MRID 49526701

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Table 1. Results Synopsis: Aerobic Soil Metabolism of Chlorimuron ethyl.

Soil Location and 

Texture

(Temperature, pH)

Observed 

DT50 (days)

Calculated 

Half-lifeA

(days)

Model Parameters 

and Statistics

Transformation Products (maximum % AR, associated interval)B,C

Major Minor

Illinois USA

Clay loam soil

(20°C, pH 5.5)

14-29 tR IORE = 22.8

IORE

C0 = 99.4

N =1.49

k = 0.00589

IN-L8330 (39.4%, 124 days)

IN-N6186 (20.1%, 29 days)

CO2 (23.3%, 124 days)

Unextracted residues (15.2%, 90 days)

IN-B4450 (2.6%, 7 days)

IN-00581 (5.3%, 7 days)

IN-B7497 (2.0%, 61-90 days)

IN-V9662 (2.7%, 29 days) 

Met-1 (8.4%, 29 days)

North Dakota USA

Clay loam soil

(20°C, pH 5.9)

14-61 tR IORE = 105

IORE

C0 = 98.4

N =2.43

k = 7.34e-05

IN-B4450 (41.3%, 124 days)

IN-00581 (46.3%, 29 days)

IN-N6186 (56.9%, 124 days)

MET-1 (10.2%, 29 days)

IN-L8330 (6.8%, 90 days) 

IN-B7497 (2.4%, 7 days)

CO2 (2.5%, 124 days)

A Calculated half-lives, model parameters, and kinetics models in accordance with the NAFTA kinetics guidance (USEPA, 2012); Indeterminate Order Rate 

Equation (IORE).

B AR means “applied radioactivity”.

C IN B4450, IN 00581, IN B7497, and MET-1 are products of the phenyl moiety only. IN N6186 and IN V9662 are products of the pyrimidine moiety only.
Chlorimuron ethyl (PC 128901) MRID 49526701

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I. Materials And Methods

A. Materials:

1. Test Material [Phenyl-U14C]- and [pyrimidine-2-

14C]-labeled chlorimuron ethyl 

(pp. 19-20)

Phenyl label

Specific activity: 43.5 μCi/mg; 1.61 MBq/mg (p. 20)

Radiochemical purity: 97.6%

Chemical purity: Not reported

Lot No.: CFQ41767

Pyrimidine label

Specific activity: 47.9 μCi/mg; 1.77 MBq/mg (p. 20)

Radiochemical purity: 99.9%

Chemical purity: Not reported

Lot No.: CFQ41768

Solubility in water: 8.55 g/L in HPLC water (p. 20)

2. Reference Compounds: The following standards were used in the analysis (Table 2).

Table 2. Reference Compounds.

Applicant’s Code Name Chemical Name Purity (%) Lot No.

Chlorimuron ethyl (DPX-F6025) -- 98.8 E62740-69

IN-L8330 -- 99.1 E108786-91B

IN-00581 -- 99.9 03111DD

IN-N6186 -- 99.7 E43079-021A

IN-H1427 -- 95.7 AG0135-104

IN-B4450 -- 99.6 004

IN-B7497 -- 99.7 E118288-56

IN-V9662 -- 99.4 E118288-74

IN-D5119-001 -- 99.5 E100035-086

IN-F8174-001 -- 99.5 E49662-15

IN-H9235 -- 97.2 9377-103

Data obtained from pp. 20-21 and Figure 2, pp. 60-61, of the study report.

-- = No information.

3. Soil: Soil collection and characterization are summarized in Table 3 and Table 4, respectively. 

Table 3. Description of Soil Collection and Storage.

Description Illinois Clay loam North Dakota Clay loam

Geographic location Toulon/Doug Murray Farm, Stark County, 

Illinois

Agvise Research, Grand Forks, North 

Dakota

Site Description Permanent grass pasture Flat field

Soil series Tama/Toulon Not reported.

Pesticide use history at 

the collection site Not reported.
Chlorimuron ethyl (PC 128901) MRID 49526701

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Description Illinois Clay loam North Dakota Clay loam

Collection date September 19, 2013 September 16, 2013

Collection procedures Shovel

Sampling depth ≤20 cm

Storage conditions Refrigerated at the test facility, conditions during ca. 3 weeks between collection and 

receipt were not reported.

Storage length 49 days (from receipt at test facility)

Soil preparation Sieved (2 mm screen)

Data obtained from p. 22, Table 1, p. 46, and Appendix 1, pp. 126-127, of the study report.

Table 4. Properties of the Soils.

Property Illinois Clay loam North Dakota Clay loam

Soil Texture (USDA) Clay loam Clay loam

% Sand 20 34

% Silt 46 38

% Clay 34 28

pH 1:1 in water 6.1 6.0

1:2 in 0.01M CaCl2 5.5 5.9

Organic carbon (%) 1.62 2.73

Organic matter (%) (Walkley Black) 2.8 4.7

Cation Exchange Capacity (meq/100 g)

(method not reported) 17.1 24.3

Ca Base Saturation (%) 52.4 63.4

Soil Moisture Content (%)

1/3 Bar 30.7 31.6

Maximum Water Holding Capacity 47.2 51.4

Bulk density (disturbed, g/cm3) 0.95 1.03

Microbial Biomass (μg C/g dry soil)

Initial 263 372

Final 169 195

Soil taxonomic classification 

Fine-silty, mixed, superactive, mesic typic 

Argiudoll/ sandy-skeletal, mixed, mesic 

typic Haplocambid

Not reported

Data obtained from Table 1, p. 46, of the study report. The soil texture was confirmed and the soil taxonomic 

classification determined using USDA-NRCS technical support tools.

B. STUDY DESIGN

1. Experimental Conditions: (Summarized in Table 5).

Table 5. Experimental Design

Property Details

Duration of the test (days) 124 days

Soil condition (Air dried/fresh) Fresh. Soil was acclimated to study conditions for 9 days prior to treatment.

Soil (g/replicate) 50 g (dry wt)

Application rates

Nominal 0.2 mg a.i./kg; equivalent to a field rate of ca. 150 g a.i./ha1

Actual 0.19-0.20 mg a.i./kg

Control conditions (if used) Sterile controls were not used.
Chlorimuron ethyl (PC 128901) MRID 49526701

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Property Details

Number of Replicates

Controls (if used) Sterile controls were not used.

Treatment One flask of each soil was collected at each sampling interval.

Test apparatus

Type/material/volume

The test system consisted of glass bottles (250-mL volume) containing moist 

treated soil (ca. 50 g dry wt) that were attached to individual continuous flowthrough volatile trapping systems and incubated in a dark temperature 

controlled room. The test system is illustrated in Figure 3, p. 62. 

Details of traps for CO2 and 

other volatiles (if any)

Humidified air was continually passed (flow rate ca. 4 mL/minute) through a 

sample flask, then through one bottle of ethylene glycol and two bottles of 1M 

aqueous KOH. The volatile trapping system is illustrated in Figure 3, p. 62.

If no traps were used, is the 

system closed/open? Volatile traps were used.

Identity and concentration of cosolvent Acetonitrile, 0.1% by volume

Test Material:

Volume of the test solution 

used/treatment 50 μL/50 g 

Application method The test solution was applied uniformly to the soil surface using a glass 

syringe.

Is the co-solvent evaporated? Yes

Any indication of the test material 

adsorbing to the walls of the test 

apparatus?

None

Experimental conditions:

Temperature (°C) 20 ± 2°C (range not reported)

Continuous darkness Yes 

Moisture content 50% of the maximum water holding capacity 

Moisture maintenance method Samples were weighed at regular intervals and remoistened if necessary. 

Other details (if any) Separate samples treated with an equal volume of pesticide-free acetonitrile 

were used for microbial biomass analysis.

Data obtained from pp. 23-26; Table 2, p. 47; and Figure 3, p. 62, of the study report.

1 Application rate assumes an even distribution of the test material in the top 5 cm of soil and a soil bulk density of 1.5 

g/cm3 (p. 47).

2. Sampling During Study Period: (Details summarized in Table 6).

Table 6. Sampling During Study Period

Criteria Details

Sampling intervals (days) 0, 7, 14, 29, 61, 90, and 124 days

Sampling method Single flasks of each soil were collected at each sampling interval.

Method of collection of CO2

and organic volatile compounds

Volatile traps were collected at each sampling interval. KOH traps were also 

changed after 3 months or when analysis at any sampling interval exceeded 

3,000 dpm/mL.

Sampling intervals/times for: 

Sterility check (if used) Sterile controls were not used.

Moisture content Regular intervals

Redox potential, other The redox potential was not measured
Chlorimuron ethyl (PC 128901) MRID 49526701

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Criteria Details

Sample storage before analysis

Soils were processed immediately after sampling. Soil extracts were initially 

analyzed by HPLC within ca. 1 week of extraction. Sample extracts and 

extracted soils were stored in a freezer (ca. -20°C) when not in use. Trapping 

solutions were stored at ambient temperatures.

Other observation (if any) None.

Data obtained from p. 26 and Table 3, p. 48, of the study report.

3. Analytical Procedures: (Analytical procedures are illustrated in Figure 4, p. 63).

Extraction Methods: The soil (entire flask) was transferred into a flurinated plastic centrifuge 

bottle and soaked overnight with 0.1M ammonium acetate at ca. 5°C (p. 26; Table 3, p. 48; Figure 

4, p. 63). The next day, the soils were extracted three times with methylene 

chloride:methanol:acetic acid (75:25:1, v:v:v) by shaking for 1 hour/extraction at ambient 

temperatures. After each extraction, the samples were centrifuged and the supernatant decanted; 

aliquots of the individual extracts were analyzed using LSC. The extracts were then combined and 

concentrated by rotary evaporation, adjusted to ca. pH 9, and refrigerated overnight (p. 27). The 

concentrate was centrifuged and the supernatant decanted. The supernatant was further 

concentrated, and aliquots were analyzed using LSC, HPLC, and TLC. The precipitate was 

dissolved in methylene chloride:methanol (75:25, v:v), and aliquots analyzed using LSC. 

Determination of Unextracted Residues: The extracted soils were homogenized and portions 

were analyzed for total remaining radioactivity using LSC following combustion (p. 26; Figure 4, p. 

63). 

Determination of Volatile Compounds: Aliquots of the trapping solutions were analyzed by LSC 

(Table 3, p. 48). The identification of residues as CO2 in the trapping solutions was confirmed by 

precipitation with barium chloride (p. 31). 

Total radioactivity measurement: Total [14C]residues were determined by summing the 

concentrations of residues in the soil extracts, extracted soil, and volatile traps (Tables 4-7, pp. 49-

52). 

Derivatization method A derivatization method was not employed.

Identification and quantification of Parent and Transformation Compounds: Aliquots of the 

concentrated extracts were analyzed by HPLC using a LiChrospher 100 RP-8 column eluted with a 

mobile gradient phase of (A) phosphoric acid in HPLC grade water (ca. pH 2.2) and (B) HPLC 

grade acetonitrile, and by HPLC using a LUNA C18 column eluted with a gradient mobile phase of 

(a) 20mM ammonium acetate in HPLC grade water and (B) HPLC grade acetonitrile (pp 28-29). 

Samples were cochromatographed with a mixture of reference standards (p. 29).

Samples were also analyzed using one-dimensional TLC on silica gel plates develop in 

chloroform:methanol:2M ammonium carbonate aqueous (150:25:3 or 150:30:3, v:v:v; p. 29). 

Samples were cochromatographed with a mixture of reference standards.

Identification of radiolabeled compounds was confirmed using LS/MS (pp. 27, 29-31).
Chlorimuron ethyl (PC 128901) MRID 49526701

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Detection Limits (LOD, LOQ) for the Parent and Transformation Products: For LSC, Limits 

of Detection (LOD) were 9.8 cpm for combusted soil, 9.3 cpm for the ethylene glycol solution, 4.2 

cpm for the KOH solution, 11.6 cpm for the soil extract, 12.6 cpm for the aqueous supernatant

(Appendix 5, p. 165). Limits of Quantification (LOQ) were 46, 39, 50, 128, and 139 cpm, 

respectively. For HPLC, LOD were 19.6 cpm and LOQ were 230 cpm. For LSC, LOQ were 0.89% 

for the soil extracts, 0.53% for the combusted soil, and 0.18% for the trapping solutions (Appendix 

5, p. 164). For HPLC, LOQ were 3.97% (Appendix 5, p. 165).

II. Results and Discussion

A. Data

Study results including total mass balances and distribution of radioactivity are presented in Tables 

7a-7b. No determinations were made to verify that aerobic conditions were maintained in the soils. 

Soils were viable at study initiation and termination (Table 1, p. 46).

B. Mass Balance

For the Illinois clay loam soil, overall mass balances averaged 94.9 ± 6.7% of the applied (range 

89.4-108.0%) in the samples treated with the phenyl label and 94.0 ± 3.6% (range 87.8-98.7%) in 

the samples treated with the pyrimidine label (Tables 4-5, pp. 49-50). For the North Dakota clay 

loam soil, overall mass balances averaged 96.2 ± 5.0% of the applied (range 88.5-104.1%) in the 

samples treated with the phenyl label and 95.3 ± 3.6% (range 92.5-103.0%) in the samples treated 

with the pyrimidine label (Tables 6-7, pp. 51-52). Recoveries tended to be lower at later sampling 

intervals but there was no clear downward trend since recoveries at the final sampling interval were 

similar to those at 14-29 days posttreatment. 

C. Unextracted and Extractable Residues

In the Illinois clay loam soil treated with the phenyl label, total extractable radioactivity declined 

from 107.3% of the applied at time 0 to 51.1% at 124 days posttreatment (Table 4, p. 49). 

Unextracted radioactivity increased to a maximum of 15.2% at 90 days and was 15.0% at 124 days. 

In the same soil treated with the pyrimidine label, total extractable radioactivity declined from 

98.1% of the applied at time 0 to 65.1% at 90 days and was 66.6% at 124 days (Table 5, p. 50). 

Unextracted radioactivity increased to a maximum of 12.4% at 124 days.

In the North Dakota clay loam soil treated with the phenyl label, total extractable radioactivity 

declined from 101.6% of the applied at time 0 to 82.5% at 90 days posttreatment and was 91.5% at 

124 days (Table 6, p. 51). Unextracted radioactivity increased to a maximum of 5.4% at 61 days and 

was 5.3% at 124 days. In the same soil treated with the pyrimidine label, total extractable 

radioactivity declined from 99.9% of the applied at time to 82.8% at 124 days (Table 7, p. 52). 

Unextracted radioactivity increased to a maximum of 9.1% at 124 days.

D. Volatilization

At study termination, CO2 totaled maximums of 23.3% and 14.9% in the Illinois clay loam soils 

treated with the phenyl and pyrimidine labels, respectively (Tables 4-5, pp. 49-50). CO2 totaled 

maximums of 1.1% and 2.5% in the North Dakota clay loam soils treated with the phenyl and 
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 10 of 21

pyrimidine labels, respectively (Tables 6-7, pp. 51-52). Organic volatiles were detected only once in 

the experiments, at 0.2% of the applied in the Illinois clay loam soil treated with the pyrimidine 

label at 124 days (Table 5, p. 50).

Table 7a. Transformation of [phenyl-U14C]chlorimuron ethyl, expressed as a percentage of the 

applied radioactivity, in an aerobic Illinois clay loam soil.

Sampling Interval (days) 0 7 14 29 61 90 124

Replicate A A A A A A A

Chlorimuron ethyl (DPX-F6025) 103.9 65.6 54.6 25.4 14.3 7.0 5.7

IN-B4450 0.0 2.6 0.0 0.0 0.0 1.9 1.0

IN-L8330 0.0 11.6 24.1 32.6 34.8 26.1 37.8

IN-00581 0.0 5.3 0.0 0.0 0.0 1.8 4.7

IN-B7497 0.0 1.5 0.0 0.0 2.0 2.0 0.0

Met-1 3.4 4.1 3.4 8.4 4.7 5.1 0.0

Others 0.0 2.8 0.0 1.8 3.6 8.3 3.0

Extracted residues 107.3 93.3 82.1 68.2 59.4 52.4 51.1

Unextracted residues 0.7 3.6 5.9 9.3 12.7 15.2 15.0

CO2 n.a. 2.1 5.5 12.4 22.4 22.7 23.3

Organic Volatiles n.a. 0.0 0.0 0.0 0.0 0.0 0.0

Mass balance 108.0 99.0 93.5 89.9 94.5 90.3 89.4

Data obtained from Table 4, p. 49, and Table 8, p. 53, of the study report.

n.a. = not analyzed.

Table 7b. Transformation of [pyrimidine-2-

14C]chlorimuron ethyl, expressed as a percentage of the 

applied radioactivity, in an aerobic Illinois clay loam soil.

Sampling Interval (days) 0 7 14 29 61 90 124

Replicate A A A A A A A

Chlorimuron ethyl (DPX-F6025) 94.8 69.9 55.0 26.7 13.2 9.1 6.4

IN-N6186 3.4 6.4 9.8 20.1 19.1 17.1 18.9

IN-L8330 0.0 12.0 22.8 32.3 33.5 35.9 39.4

IN-V9662 0.0 0.5 2.2 2.7 2.2 0.0 0.0

Others 0.0 1.3 3.7 4.4 5.2 2.9 2.0

Extracted residues 98.1 90.1 93.5 86.1 73.1 65.1 66.6

Unextracted residues 0.6 3.0 3.2 4.8 9.9 10.5 12.4

CO2 n.a. 0.3 1.1 3.1 9.4 12.2 14.9

Organic Volatiles n.a. 0.0 0.0 0.0 0.0 0.0 0.2

Mass balance 98.7 93.4 97.8 94.0 92.4 87.8 94.1

Data obtained from Table 5, p. 50, and Table 9, p. 54, of the study report.

n.a. = not analyzed.
Chlorimuron ethyl (PC 128901) MRID 49526701

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Table 7c. Transformation of [phenyl-U14C]chlorimuron ethyl, expressed as a percentage of the 

applied radioactivity, in an aerobic North Dakota clay loam soil.

Sampling Interval (days) 0 7 14 29 61 90 124

Replicate A A A A A A A

Chlorimuron ethyl (DPX-F6025) 96.9 64.8 59.4 27.0 28.2 19.3 16.1

IN-B4450 0.0 2.0 2.6 0.0 9.7 13.5 41.3

IN-L8330 0.0 2.4 5.2 4.1 5.9 6.8 3.7

IN-00581 0.0 15.3 22.9 46.3 37.7 42.8 30.6

IN-B7497 0.0 2.4 0.0 0.0 0.0 0.0 0.0

Met-1 4.7 4.9 0.0 10.2 2.7 0.0 0.0

Others 0.0 4.4 4.6 0.0 4.8 0.0 0.0

Extracted residues 101.6 96.3 94.7 87.6 88.9 82.5 91.5

Unextracted residues 2.5 1.3 3.8 4.1 5.4 4.9 5.3

CO2 n.a. 0.0 0.0 0.3 0.6 1.1 1.1

Organic Volatiles n.a. 0.0 0.0 0.0 0.0 0.0 0.0

Mass balance 104.1 97.6 98.5 92.0 94.9 88.5 97.9

Data obtained from Table 6, p. 51, and Table 10, p. 55, of the study report.

n.a. = not analyzed.

Table 7d. Transformation of [pyrimidine-2-

14C]chlorimuron ethyl, expressed as a percentage of the 

applied radioactivity, in an aerobic North Dakota clay loam soil.

Sampling Interval (days) 0 7 14 29 61 90 124

Replicate A A A A A A A

Chlorimuron ethyl (DPX-F6025) 99.9 79.1 68.4 52.1 33.3 30.7 21.4

IN-N6186 0.0 13.5 19.5 34.0 45.3 49.5 56.9

IN-L8330 0.0 0.0 3.0 4.1 4.9 2.7 4.6

IN-V9662 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Others 0.0 0.0 0.0 0.0 0.0 0.1 0.0

Extracted residues 99.9 92.6 90.9 90.2 83.5 83.1 82.8

Unextracted residues 3.1 3.1 3.9 2.8 8.7 7.8 9.1

CO2 n.a. 0.0 0.0 0.4 0.8 1.6 2.5

Organic Volatiles n.a. 0.0 0.0 0.0 0.0 0.0 0.0

Mass balance 103.0 95.7 94.8 93.4 93.0 92.5 94.4

Data obtained from Table 7, p. 52, and Table 11, p. 56, of the study report.

n.a. = not analyzed.

E. Transformation of the Test Compound 

Transformation kinetics of the parent compound in the total system are summarized in the following 

Figures, with transformation product information summarized in Table 8.

Single First Order, First Order Multi-Compartment, Hockey Stick, and Double First-Order in 

Parallel models were used by the study author to predict DT50 values (p. 34). SFO DT50 values 

were 15.6-18.3 days in the Illinois clay loam soil and 29.3-47.2 days in the North Dakota clay loam 

soil (p. 44). 
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Kinetics models: Single First Order (SFO); Double First Order in Parallel (DFOP), and Indeterminate Order Rate 

Equation (IORE). Calculated half-lives and model parameters in accordance with the NAFTA kinetics guidance 

(USEPA, 2012).

Observed nonvolatile transformation products are described in Table 8. Seven transformation 

products were isolated, of which six were identified.

Aerobic metabolism of Chlorimuron ethyl in Illinois clay loam soil

Days % AR

0

 7

 14

 29

 61

 90

 124

0

 7

 14

 29

 61

 90

 124

 104.

65.6

54.6

25.4

14.3

7.00

5.70

94.8

69.9

55.0

26.7

13.2

9.10

6.40

0 20 40 60 80 100 120

0

20

40

60

80

100

Time

Concentration

SFO

DFOP

IORE

-5

0

5

-5

0

5

-5

0

5

0 20 40 60 80 100120

DT50 DT90 

2 C0 Parameters

SFO 16.9 56.2 8.9 96.1 k 0.041

DFOP14.8 76.9 4.7 98.8f 0.827k0 0.0587k1 0.0084

IORE 14.6 75.6 4.8 99.4 N 1.49k 0.00589

SC

SSFO

Slowt1 2

tRIORE

 150

 328

82.5

22.8

Aerobic metabolism of Chlorimuron ethyl in North Dakota clay loam soil

Days % AR

0

 7

 14

 29

 61

 90

 124

0

 7

 14

 29

 61

 90

 124

96.9

64.8

59.4

27.0

28.2

19.3

16.1

99.9

79.1

68.4

52.1

33.3

30.7

21.4 0 20 40 60 80 100 120

0

20

40

60

80

Time

Concentration

SFO

DFOP

IORE

-20

-10

0

10

20

-20

-10

0

10

20

-20

-10

0

10

20

0 20 40 60 80 100 120

DT50 DT90 

2 C0 Parameters

SFO 39.2 130 13 86.8 k  0.0177

DFOP 21.9 237 4.4 97.9f  0.572k0 0.0694k1 0.00615

IORE 22.8 348 4.3 98.4 N 2.43k 7.34e-05

SC

SSFO

Slowt1 2

tRIORE

 787

1.48e+03

 113

 105
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 13 of 21

Table 8. Transformation Products of Chlorimuron ethyl in Soil.

Transformation 

Products

Maximum %AR 

Observed

Associated Interval

(days)

Final %AR 

Observed

Final Interval

(days)

Illinois USA

Clay loam soil

(20°C, pH 5.5)

IN-B4450 2.6 7 1.0 124

IN-L8330 39.4 124 39.4 124

IN-00581 5.3 7 4.7 124

IN-B7497 2.0 61, 90 0.0 124

IN-N6186 20.1 29 18.9 124

IN-V9662 2.7 29 0.0 124

Met-1 8.4 29 0.0 124

North Dakota 

USA

Clay loam soil

(20°C, pH 5.9)

IN-B4450 41.3 124 41.3 124

IN-L8330 6.8 90 4.6 124

IN-00581 46.3 29 30.6 124

IN-B7497 2.4 7 0.0 124

IN-N6186 56.9 124 56.9 124

Met-1 10.2 29 0.0 124

Data obtained from Tables 8-11, pp. 53-56, in the study report. 

An aerobic transformation pathway in soil was provided by the study author (Figure 40, p. 125).
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 14 of 21

III. STUDY DEFICIENCIES AND REVIEWER’S COMMENTS

1. Both soils used in the experiment were classified as clay loam and has similar pHs (Table 1, p. 

46). The North Dakota clay loam soil had more sand (34% vs 20%), a higher organic matter 

content (4.7% vs 2.8%), and a higher CEC (24.3 vs 17.1 meq/100 g). 

2. Transformation product Met-1 reached 10.2% of the applied at 29 days in North Dakota clay 

loam soil but was not identified (Table 10, p. 55). The study author stated that it did not coelute 

in HPLC or TLC with any standards and that purification with LC/MS analysis was 

unsuccessful (p. 42).

3. In three of the four experiments, overall recoveries were <90% of the applied at one or more 

sampling intervals (Tables 4-7, pp. 49-52).

4. Significant levels (12.4-15.2% of the applied; Tables 4-5, pp. 49-50) of unextracted residues 

were detected in the Illinois clay loam soils, and the study author failed to use solvents with a 

range of dielectric constants (including a nonpolar solvent) to maximize extraction of the 

residues. Although it was reported that extracted soil containing >10% of the applied 

radioactivity was analyzed by organic matter fractionation (p. 26; Figure 4, p. 63), the method 

was not described and no results from such an analysis were reported.

5. The pesticide use history was not reported, and the soils were not shown to be pesticide-free 

prior to use. Storage of the soils for the ca. 3 weeks between the time of collection and receipt at 

the testing laboratory were not reported.

IV. REFERENCES

1. U.S. Environmental Protection Agency. 2008. Fate, Transport and Transformation Test 

Guidelines, OCSPP 835.4100, Aerobic Soil Metabolism. Office of Chemical Safety and 

Pollution Prevention, Washington, DC. EPA 712-C-08-016.

2. U.S. Environmental Protection Agency. 2012. NAFTA Guidance for Evaluating and Calculating 

Degradation Kinetics in Environmental Media.
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 15 of 21

DER ATTACHMENT 1. Chlorimuron ethyl and Its Environmental Transformation Products. A

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maximum %AR (day)

Final %AR 

(study 

length)

PARENT

Chlorimuron ethyl (DPXF6025) 

IUPAC: Ethyl 2-(4-chloro-6-

methoxypyrimidin-2-

ylcarbamoylsulfamoyl)benzoate

CAS: Ethyl 2-[[[[(4-chloro-6-

methoxy-2-

pyrimidinyl)amino]carbonyl]amin

o]sulfonyl]benzoate

CAS No.: 90982-32-4

Formula: C15H15ClN4O6S

MW: 414.8 g/mol

SMILES: 

n1c(Cl)cc(OC)nc1NC(=O)NS(=O)

(=O)c2ccccc2C(=O)OCC

Cl

O

C H 3

N

N

N

H

O

N

H

S

O

O

C

H 2

C H 3

O

O

835.4100

Aerobic soil 

metabolism 49526701

Illinois 

Clay loam 103.9% (0 d) 6.4% (124 d)

North Dakota 

Clay loam 99.9% (0 d) 21.4% (124 d)

835.4300

Aerobic 

aquatic 

metabolism

49526702

River water: 

Clay loam 98.5% (0 d) 16.4% (100 d)

River water: 

Sand 97.0% (0 d) 34.5% (100 d)

MAJOR (>10%) TRANSFORMATION PRODUCTS

IN-L8330 IUPAC: Ethyl 2-[(4-chloro-6-

hydroxy-pyrimidin-2-

yl)carbamoylsulfamoyl]benzoate

Formula: C14H13ClN4O6S

MW: 400.8 g/mol

SMILES: 

[H]N(c1nc(cc(n1)Cl)O)C(=O)N([

H])S(=O)(=O)c2ccccc2C(=O)OC

C

C

H 2

C H 3

O

S

O

O

H

N

O

H

N

N

O H

N Cl

O

835.4100

Aerobic soil 

metabolism 49526701

Illinois 

Clay loam 39.4% (124 d) 39.4% (124 d)

North Dakota 

Clay loam 6.8% (90 d) 4.6% (124 d)

835.4300

Aerobic 

aquatic 

metabolism

49526702

River water: 

Clay loam 66.6% (100 d) 66.6% (100 d)

River water: 

Sand 29.2% (79 d) 21.6% (100 d)
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 16 of 21

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maximum %AR (day)

Final %AR 

(study 

length)

IN-N6186 IUPAC: 4-Chloro-6-methoxypyrimidin-2-amine

Formula: C5H6ClN3O

MW: 159.6 g/mol

SMILES: 

[H]N([H])c1nc(cc(n1)Cl)OC

N

H

H

Cl

O

C H 3

N

N

835.4100

Aerobic soil 

metabolism

49526701

Illinois 

Clay loam 20.1% (29 d) 18.9% (124 d)

North Dakota 

Clay loam 56.9% (124 d) 56.9% (124 d)

835.4300

Aerobic 

aquatic 

metabolism

49526702

River water: 

Clay loam 2.9% (7 d) 0.0% (100 d)

River water: 

Sand 33.0% (100 d) 33.0% (100 d)

IN-B4450 IUPAC: Ethyl 2-

sulfamoylbenzoate

Formula: C9H11NO4S

MW: 229.2 g/mol

SMILES: 

[H]N([H])S(=O)(=O)c1ccccc1C(=

O)OCC

C

H 2

C H 3

O

S

O

O

H

N

H

O

835.4100

Aerobic soil 

metabolism 49526701

Illinois 

Clay loam 2.6% (7 d) 1.0% (124 d)

North Dakota 

Clay loam 41.3% (124 d) 41.3% (124 d)

835.4300

Aerobic 

aquatic

metabolism

49526702

River water: 

Clay loam 1.0% (28 d) 0.0% (100 d)

River water: 

Sand 39.8% (100 d) 39.8% (100 d)

IN-00581 (Saccharin) IUPAC: 1,1-Dioxo-1,2-

benzothiazol-3-one

Formula: C7H5NO3S

MW: 183.2 g/mol

SMILES: 

[H]N1C(=O)c2ccccc2S1(=O)=O

O

N H

S O

O

835.4100

Aerobic soil 

metabolism 49526701

Illinois 

Clay loam 5.3% (7 d) 4.7% (124 d)

North Dakota 

Clay loam 46.3% (29 d) 30.6% (124 d)

835.4300

Aerobic 

aquatic 

metabolism

49526702

River water: 

Clay loam 6.5% (100 d) 6.5% (100 d)

River water: 

Sand 32.1% (100 d) 32.1% (100 d)

Met-1

NA Structure not provided

835.4100

Aerobic soil 

metabolism 49526701

Illinois 

Clay loam 8.4% (29 d) 0.0% (124 d)

North Dakota 

Clay loam 10.2% (29 d) 0.0% (124 d)
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 17 of 21

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maximum %AR (day)

Final %AR 

(study 

length)

Carbon dioxide IUPAC: Carbon dioxide

Formula: CO2

MW: 44 g/mol

SMILES: C(=O)=O

O C O

835.4100

Aerobic soil 

metabolism 49526701

Illinois 

Clay loam 23.3% (124 d) 23.3% (124 d)

North Dakota 

Clay loam 2.5% (124 d) 2.5% (124 d)

835.4300

Aerobic 

aquatic 

metabolism

49526702 River water: 

Sand 0.7% (79 d) 0.6% (100 d)

Unextractable residues

NA NA

835.4100

Aerobic soil 

metabolism 49526701 Illinois Clay loam 15.2% (90 d) 15.0% (124 d)

MINOR (<10%) TRANSFORMATION PRODUCTS

IN-B7497 IUPAC: Ethyl 2-

(carbamoylsulfamoyl)benzoate

Formula: C10H12N2O5S

MW: 272.3 g/mol

SMILES: 

[H]N([H])C(=O)N([H])S(=O)(=O)

c1ccccc1C(=O)OCC

C

H 2

H C3

O

O

S

O

N

H

H

O

N

H

O

835.4100

Aerobic soil 

metabolism 49526701

Illinois 

Clay loam 2.0% (61-90 d) 0.0% (124 d)

North Dakota 

Clay loam 2.4% (7 d) 0.0% (124 d)

835.4300

Aerobic 

aquatic 

metabolism

49526702

River water: 

Clay loam 2.9% (62 d) 2.1% (100 d)

River water: 

Sand

3.2% (79-100

d) 3.2% (100 d)
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 18 of 21

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maximum %AR (day)

Final %AR 

(study 

length)

IN-V9662 IUPAC: (4-Chloro-6-methoxypyrimidin-2-yl)urea

Formula: C6H7ClN4O2

MW: 202.6 g/mol

SMILES: 

[H]N([H])C(=O)N([H])c1nc(cc(n1

)Cl)OC

N

O N

H

H

N

H

N Cl

O

C H 3

835.4100

Aerobic soil 

metabolism 49526701 Illinois 

Clay loam 2.7% (29 d) 0.0% (124 d)

IN-H1427 IUPAC: 2-Amino-6-methoxypyrimidin-4-ol

Formula: C5H7N3O2

MW: 141.1 g/mol

SMILES: 

[H]N([H])c1nc(cc(n1)OC)O

N

N

H

H

N O H

O

C H 3

835.4300

Aerobic 

aquatic 

metabolism

49526702

River water: 

Clay loam 2.0% (100 d) 2.0% (100 d)

River water: 

Sand 4.0% (79 d) 1.4% (100 d)

REFERENCE COMPOUNDS NOT IDENTIFIED

IN-H9235 IUPAC: 2-Amino-6-methoxypyrimidin-4-ol

Formula: C5H7N3O2

MW: 141.1 g/mol

SMILES: 

[H]N([H])c1nc(cc(n1)OC)O

N

H

H

O H

O

C H 3

N

N

835.4100

Aerobic soil 

metabolism 49526701 NA NA

IN-D5119-001 IUPAC: 2-Sulfamoylbenzoic acid

Formula: C7H7NO4S

MW: 201.2 g/mol

SMILES: 

[H]NS(=O)(=O)c1ccccc1C(=O)O

O

H O

S

O

O

N

H

835.4100

Aerobic soil 

metabolism 49526701 NA NA

IN-F8174-001

NA Structure not provided

835.4100

Aerobic soil 

metabolism

49526701 NA NA

A AR means “applied radioactivity”. MW means “molecular weight”. NA means “not applicable”. 
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 19 of 21

Attachment 2: Statistics Spreadsheets and Graphs
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 20 of 21

DER Attachment 3: Calculations

Calculations were performed by the reviewer using PestDF, and the following equations. 

Single First-Order (SFO) Model

(eq. 1)

where, 

Ct = concentration at time t (%)

C0 = initial concentration (%)

e = Euler’s number (-)

k = SFO rate constant of decline (d-1)

t = time (d)

The SFO equation is solved with PestDF by adjusting C0 and k to minimize the objective function 

(SSFO) shown in equation 9.

DT50 = natural log (2)/k (eq. 2)

DT90 = ln (10)/k (eq. 3)

Indeterminate Order Rate Equation (IORE) Model

(eq. 4)

where, 

N = order of decline rate (-)

kIORE = IORE rate constant of decline (d-1)

This equation is solved with PestDF by adjusting C0, kIORE, and N to minimize the objective 

function for IORE (SIORE) (See equation 9). Half-lives for the IORE model are calculated using 

equation 5, which represents a first-order half-life that passes through the DT90 of the IORE model. 

(Traditional DT50 and DT90 values for the IORE model can be calculated using equations 6 and 7.)

(eq. 5)

DT50 = 

k(N -1)

(C /2) - C (1-N) 0 (1-N) 0

(eq. 6)

DT90 = 

k(N -1)

(C /10) - C (1-N) 0 (1-N) 0

(eq. 7)
Chlorimuron ethyl (PC 128901) MRID 49526701

Page 21 of 21

Double First-Order in Parallel (DFOP) Model

(eq. 8)

where,

g = the fraction of C0 applied to compartment 1 (-)

k1 = rate constant for compartment 1 (d-1)

k2 = rate constant for compartment 2 (d-1)

If C0 x g is set equal to a and C0(1-g) is set equal to c, then the equation can be solved with R 

kinetics software for a, c, k1, and k2 by minimizing the objective function (SDFOP) as described in 

equation 9.

DT50 and DT90 values can be calculated using equations 2 and 3, with k1 or k2 in place of k.

Objective Function: SFO, IORE, and DFOP are solved by minimizing the objective function (SSFO, 

SIORE, or SDFOP).

(eq. 9)

where, 

SSFO , SIORE, or SDFOP = objective function of kinetics model fit (%2

)

n = number of data points (-)

Cmodel,t = modeled value at time corresponding to Cd,t (%)

Cd,t = experimental concentration at time t (%)

Critical Value to Determine Whether SFO is an Adequate Kinetics Model

If SSFO is less than SC, the SFO model is adequate to describe kinetics. If not, the faster of tIORE or 

the DFOP DT50 for compartment 2 should be used.

(eq. 10)

where,

Sc = the critical value that defines the confidence contours (%2

)

p = number of parameters (3 in this case)

α = the confidence level (0.50 in this case)

F(α, p, n-p) = F distribution with α level of confidence and degrees of freedom p and n-p