Test Material: Chlorimuron ethyl

MRID: 49526702

Title: Aerobic Aquatic Metabolism of Chlorimuron Ethyl [14C] DPX-F6025 in 

Two Water-Sediment Systems

EPA PC Code: 128901

OCSPP Guideline: 835.4300

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 49526702

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Aerobic degradation of Chlorimuron ethyl in aquatic systems

Report: MRID 49526702. Ponte, V. 2014. Aerobic Aquatic Metabolism of Chlorimuron 

Ethyl [14C] DPX-F6025 in Two Water-Sediment Systems. Unpublished study 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-38491. PTRL West Project No.: 2551W. Experiment started June 16, 

2014, and completed November 4, 2014 (p. 6). Final report issued December 8, 

2014.

Document No.: MRID 49526702

Guideline: OPPTS 835.4300

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 classified Supplemental. 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

U.S. EPA Date: October 30, 2015

Executive Summary

The aerobic transformation of [phenyl-U14C]- and [pyrimidine-2-

14C]-labeled chlorimuron ethyl 

(DPX-F6025) was studied in a water:clay loam sediment system (Goose River; water pH 8.3, 

sediment pH 8.0 and organic carbon 2.4%) from North Dakota and a water:sand sediment system 

(Choptank River; water pH 6.9, sediment pH 6.7 and organic carbon 0.72%) from Maryland in 

closed systems treated at 0.16-0.18 μg/mL and incubated in the dark at 20°C for 100 days. Single 

samples (one entire flask) of each label treatment/system were collected at each sampling interval. 

In the water column of the water:clay loam sediment systems following treatment, standard redox 

potentials, oxygen saturation and pH were +202.3 to +465.3 mV, 4.16-8.70 ppm and 5.98-7.93, 

respectively, with redox potentials and pH in the sediment of +78.3 to +448.3 mV and 6.13-7.53, 

respectively. In the water column of the water:sand sediment systems following treatment, standard 

redox potentials, oxygen saturation and pH were +243.3 to +467.3 mV, 2.45-8.20 ppm and 5.73-

8.29, respectively, with redox potentials and pH in the sediment of +39.3 to +474.3 mV and 5.65-

7.57, respectively. In both test systems, the water layer was generally oxic and the sediment varied 

from oxic to suboxic with no clear pattern during the experiment. Both test systems were viable 

throughout the experiment.

In the water:clay loam sediment system, recoveries averaged 97.3 ± 1.8% (sample range 95.8-

100.7%) of the applied for samples treated with the phenyl label and 97.1 ± 1.7% (95.1-99.8%) for 

samples treated with the pyrimidine label. Recoveries were within guideline criteria (>90% -

<110%). In the water column, chlorimuron ethyl decreased from a maximum of 98.5% of the 

applied at time 0 to 11.6% at 100 days posttreatment. In the sediment, chlorimuron ethyl was a 

maximum of 29.4% of the applied at 62 days posttreatment and decreased to 4.8% at 100 days.
Chlorimuron ethyl (PC 128901) MRID 49526702

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In the water:sand sediment system, recoveries averaged 96.5 ± 3.7% (sample range 91.0-103.9%) of 

the applied for samples treated with the phenyl label and 95.3 ± 2.0% (91.7-97.9%) for samples 

treated with the pyrimidine label. Recoveries were within guideline criteria (>90% - <110%). In the 

water column, chlorimuron ethyl decreased from a maximum of 97.0% of the applied at time 0 to 

5.0% in the phenyl treatment and 26.2% in the pyrimidine treatment at 100 days posttreatment. In 

the sediment, chlorimuron ethyl was a maximum of 10.1% of the applied at 79 days posttreatment 

and decreased to 8.3% at 100 days.

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

in Table 1. Chlorimuron ethyl dissipated with a DFOP Slow t1/2 of 50.8 days in the water:clay loam 

sediment system. The SFO half-life in the water:sand system was 59.8 days. Product profiles were 

comparable between the two systems. Six transformation products were identified. 

In the clay loam sediments, extractable radioactivity increased from 4.1% of the applied at time 0 to 

a maximum of 40.9% at 62 days posttreatment and was 36.5% at 100 days. Unextracted 

radioactivity increased from 0.3% at time 0 to a maximum of 8.1% at 100 days. 14CO2 was 0.0% 

during the experiment, and organic volatiles totaled a maximum of 1.1% at 100 days. 

In the sand sediments, extractable radioactivity increased from 2.3% of the applied at time 0 to a 

maximum of 28.1% at 79 days posttreatment and was 26.8% at 100 days. Unextracted radioactivity 

increased from 0.0% at time 0 to a maximum of 1.1% at 62 and 100 days. 14CO2 was 0.5-0.7% at 

79-100 days, and organic volatiles were 0.0% during the experiment.

Table 1. Results Synopsis: Aerobic Aquatic Metabolism of Chlorimuron ethyl in the Total 

System1

Total System

Observed 

DT50

(days)

Calculated 

Half-life 

(days)1

Model 

Parameters and 

Statistics1

Transformation Products Common Name

(maximum % AR, associated interval)B,C

Major Minor

Goose River, North 

Dakota USA

Water:clay loam 

sediment

(20°C, water pH 8.3, 

sediment pH 8.0)

28-62

Slow t1/2 = 

50.8

DFPO

C0 = 98.2

f = 0.192

k0 = 0.136

k1 = 0.0136

IN-L8330 (66.6%, 100

days)

IN-B4450 (1.0%, 28 days)

IN-00581 (6.5%, 100 days)

IN-B7497 (2.9%, 62 days)

IN-N6186 (2.9%, 7 days)

IN-H1427 (2.0%, 100 

days)

Choptank River, 

Maryland, USA

Water: sand sediment

(20°C, water pH 6.9, 

sediment pH 6.7)

28-79 59.8

SFO

C0 = 102

k = 0.0116

SC = 1.53e+03

SSFO = 1.67e+03

IN-B4450 (39.8%, 100

days)

IN-L8330 (29.2%, 79

days)

IN-00581 (32.1%, 100

days)

IN-N6186 (33.0%, 100

days)

IN-B7497 (3.2%, 79-100 

days)

IN-H1427 (4.0%, 79 days)

CO2 (0.7%, 79 days)

1 Calculated half-lives and model parameters in accordance with NAFTA kinetics guidance (USEPA, 2012); Double 

First Order in Parallel (DFOP), Single First Order (SFO). B AR means “applied radioactivity”.

C IN-B4450, IN-00581, and IN-B7497 are products of the phenyl moiety only. IN-N6186 and IN-H1427 are products 

of the pyrimidine moiety only.
Chlorimuron ethyl (PC 128901) MRID 49526702

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I. Materials And Methods

A. Materials:

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

14C]-labeled chlorimuron ethyl (p. 19; 

Figure 1, p. 61)

Phenyl label

Specific activity: 43.5 μCi/mg; 1.61 MBq/mg

Radiochemical purity: 97.6%

Chemical purity: Not reported

Lot No.: CFQ41767

Pyrimidine label

Specific activity: 47.9 μCi/mg; 1.77 MBq/mg

Radiochemical purity: 99.9%

Chemical purity: Not reported

Lot No.: CFQ41768

Solubility in water: 8.55 g/L in HPLC water (p. 19)

2. Reference Compounds: The following compounds were used in the analysis.

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

Data obtained from p. 20 and Figure 1, pp. 62-63, of the study report.

-- = No information.

3. Water:Sediment: Water and sediment collection and characterization are summarized in Table 

3 and Tables 4a-4b, respectively. 

Table 3. Water:Sediment Collection and Storage.

Description Goose River Choptank River

Geographic location Grand Forks County, North 

Dakota Denton, Maryland

Site description Goose River Choptank River, tidal impact

Pesticide use history at the collection site Not reported

Collection date May 12, 2014 May 13, 2014
Chlorimuron ethyl (PC 128901) MRID 49526702

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Description Goose River Choptank River

Collection 

procedures

Water:

Sediment auger Clear plastic container Sediment:

Storage conditions

Water:

Stored refrigerated (ca. 4°C) in the dark

Sediment:

Storage length 17 days 19 days

Preparation 

Water: Sieved (ca. 2-mm mesh)

Sediment: Sieved (ca. 2-mm mesh)

Data obtained from pp. 21-22 and Appendix 1, pp. 142-143, in the study report.

Table 4a. Parameters for Characterization of Water:Sediment Samples – Goose River.

Parameter

(unit)

Field Sampling/Post 

Handling

Stage of Test Procedure

Prior to Test1 During Test2 End of Test3

Water

Temperature (oC) --

pH 8.3 6.03, 7.02 5.98, 6.55 6.0, 6.1

Hardness (mg/L as CaCO3) 584

TOC (μg/g) -- 272 10.89

O2 Content (ppm) -- 6.70, 7.04 7.26, 7.54 7.90, 8.70

Standard redox potential (mV) +369.3, +398.3 +356.3, +371.3 +202.3, +223.3

Sediment

Sampling Depth 0-5 cm

pH 1:1 in water 8.0 6.24, 6.66 6.43, 7.05 6.13, 6.33

Soil Texture (USDA) Clay loam

Particle Size 

Distribution 

(%)

Sand 30

Silt 42

Clay 28

Organic matter (%) 4.1

Organic carbon (%) 2.4

CEC (meq/100 g) 18.8

Microbial biomass (μg C/g sediment) -- 383 125

Standard redox potential (mV) +373.3, +392.3 +258.3, +281.3 +204.3, +222.3

Data obtained from p. 32; Table 1, pp. 42-43; Table 4, p. 49; and Appendix 1, p. 142, in the study report. USDA 

sediment texture confirmed determined by the reviewer using USDA-NRCS technical support tools.

-- = not reported

1 Post acclimation (Day 0)

2 Day 62

3 Day 100

Table 4b. Parameters for Characterization of Water:Sediment Samples – Choptank River.

Parameter

(unit)

Field Sampling/Post 

Handling

Stage of Test Procedure

Prior to Test1 During Test2 End of Test3

Water

Temperature (oC) --

pH 6.9 6.89, 7.13 6.85, 7.35 6.31, 6.58

Hardness (mg/L as CaCO3) 39

TOC (μg/g) -- 287 15.67

O2 Content (ppm) -- 4.73, 5.25 7.63, 7.64 7.82, 8.20

Standard redox potential (mV) +309.3, +379.3 +338.3, +350.3 +243.3, +265.3

Sediment

Sampling Depth 5-10 cm

pH 1:1 in water 6.7 6.67, 6.84 6.20, 7.04 5.65, 6.22
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Parameter

(unit)

Field Sampling/Post 

Handling

Stage of Test Procedure

Prior to Test1 During Test2 End of Test3

Soil Texture (USDA) Sand

Particle Size 

Distribution 

(%)

Sand 96

Silt 3

Clay 1

Organic matter (%) 1.2

Organic carbon (%) 0.72

CEC (meq/100 g) 3.2

Microbial biomass (μg C/g sediment) -- 278 58

Standard redox potential (mV) +114.3, +141.3 +333.3, +379.3 +256.3, 267.3

Data obtained from p. 32; Table 1, pp. 42-43; Table 5, p. 50; and Appendix 1, p. 143, in the study report. USDA 

sediment texture confirmed determined by the reviewer using USDA-NRCS technical support tools.

-- = not reported

1 Post acclimation (Day 0)

2 Day 62.

3 Day 100.

B. Study Design

1. Experimental Conditions: Table 5 summarizes the experimental conditions.

Table 5. Experimental Design.

Experimental Design Goose River Choptank River

Duration of the test 100 days

Water:

Type and size of filter used 2-mm mesh

Amount of sediment and water per treatment:

Water (mL) 209 ca. 189

Sediment (g dry wt) ca. 43 ca. 65.0

Water:sediment ratio 1:3, v:v (2.2-2.5 cm layer of sediment covered with 6.6-7.5 cm of 

water)

Application rates:

Nominal Not reported

Actual 0.16-0.18 μg a.i./mL

Number of replicates:

Control, if used Sterile controls were not used.

Treated Single samples (one entire flask) of each label treatment/system was 

collected at each sampling interval.

Test apparatus:

Type/material/volume

Amber glass bottles (250 mL) containing water and sediment were 

attached to individual flow-through volatile trapping systems and 

incubated in darkness in a temperature-controlled room. The test 

systems were treated after at least 10 days of pre-incubation. The test 

system is illustrated in Figure 2, p. 64.

Details of traps for CO2 and organic volatile, if 

any

Humidified air was drawn through a sample, then through one bottle of 

ethylene glycol and two bottles of 1N KOH. The volatile trapping 

system is illustrated in Figure 2, p. 64.

If no traps were used, is the system closed? Volatile traps were used.

Identity and final concentration (based on 

water volume) of co-solvent Acetonitrile, 0.05% by volume

Test material application method:
Chlorimuron ethyl (PC 128901) MRID 49526702

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Experimental Design Goose River Choptank River

Volume of the test solution used/treatment 100 μL/sample

Application method (i.e., mixed/not mixed) To the water surface using a glass volumetric syringe.

Any indication of the test material adsorbing 

to the walls of the test apparatus? None. 

Microbial biomass in untreated samples (μg 

C/g sediment) Initial Final Initial Final

Water Not reported

Sediment 383 125 278 58

Experimental conditions:

Temperature 20 ± 2°C, range not reported

Continuous darkness (yes/no) Yes

Other details (if any) Microbial activity was determined in samples that were treated with 

pesticide-free acetonitrile.

Data obtained from pp. 22-25, 32; Table 2, p. 45; and Figure 2, p. 64, of the study report.

2. Sampling during Study Period: Table 6 summarizes sampling during the study period.

Table 6. Sampling during Study Period.

Parameter Details

Sampling intervals (duration) 0, 1, 7, 14, 28, 62, 79, and 100 days posttreatment.

Sampling method Per label/system type, single samples (one entire flask) was collected at each 

sampling interval.

Method of collection of CO2 and 

organic volatile compounds Volatile traps were collected at each sampling interval.

Sampling Intervals/Times

Redox potential in water layer

Measured at each sampling interval

Dissolved oxygen in water layer

pH in water layer

Redox potential in sediment

pH in sediment

Other details, if any

Water and sediment extracts were analyzed by LSC on the day of sampling. Samples 

were analyzed using HPLC within 24 hours for water and 1 week for the sediment 

extracts. Water and soil extracts were stored frozen when not in use.

Data obtained from pp. 25-26, 38; Table 2, p. 47; and Tables 4-5, pp. 49-50, of the study report.

3. Analytical Procedures: 

Separation of the Water and Sediment: The water layer was decanted into graduated cylinders (p. 

26).

Extraction/Clean Up/Concentration Methods: Aliquots of the water were analyzed without 

modification using LSC (p. 26; Table 2, p. 47; Figure 3, p. 65). Additional aliquots were 

microfuged and/or filtered and analyzed using HPLC (p. 21). 

The sediment was soaked overnight with 0.1M ammonium acetate at ca. 5°C (p. 26; Figure 3, p. 

65). The next day, the soils were extracted three times with methylene chloride:methanol:formic

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. The extracts were combined 
Chlorimuron ethyl (PC 128901) MRID 49526702

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aliquots were analyzed using LSC. The remaining extracts were concentrated by rotary 

evaporation, adjusted to ca. pH 9, and refrigerated overnight. 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. The precipitate from the day 62 Goose River clay loam 

sediment/pyrimidine label (7.1% of the applied) was analyzed using HPLC.

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

were analyzed for total remaining radioactivity using LSC following combustion (p. 27; Figure 3, p. 

65). 

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

(p. 27; Figure 3, p. 65). It was not confirmed that residues in the KOH traps were CO2 . 

Total Radioactivity Measurement: Total [14C]residues were determined by summing the 

concentrations of residues measured in the water layer, sediment extracts, extracted sediment and 

trapping solutions (Tables 6-7, pp. 51-54).

Derivatization Method: A derivatization method was not described.

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

concentrated extracts were analyzed by reverse phase 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 27-28). Samples were cochromatographed with a mixture of reference 

standards.

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

chloroform:methanol:1M ammonium carbonate aqueous (150:30:3, v:v:v) or 

dichloromethane:acetone:methanol:88% formic acid (130:45:25:1, v:v:v:v; pp. 28-29). Samples 

were cochromatographed with a mixture of reference standards.

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

of Detection (LOD) were 0.03-0.04% of the applied for combusted soil, 0.004-0.005% for the KOH 

solution, 0.06% for the aqueous solutions, and 0.21-0.22% for the organic extracts (Table 3, p. 48). 

Limits of Quantification (LOQ)were 0.13-0.14%, 0.05-0.06%, 0.61-0.67%, and 2.31-2.51%, 

respectively. For HPLC, the LOD was 0.004% of the applied and LOQs were 0.006-0.007%. 

II. Results and Discussion

A. Data:

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

Tables 7a-7d. In the water column of the Goose River water:clay loam sediment systems following 

treatment, standard redox potentials, oxygen saturation and pH were +202.3 to +465.3 mV, 4.16-

8.70 ppm and 5.98-7.93, respectively, with redox potentials and pH in the sediment of +78.3 to 

+448.3 mV and 6.13-7.53, respectively (Table 4, p. 49). In the water column of the Choptank River 

water:sand sediment systems following treatment, standard redox potentials, oxygen saturation and 

pH were +243.3 to +467.3 mV, 2.45-8.20 ppm and 5.73-8.29, respectively, with redox potentials 
Chlorimuron ethyl (PC 128901) MRID 49526702

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and pH in the sediment of +39.3 to +474.3 mV and 5.65-7.57, respectively (Table 5, p. 50). In both 

test systems, the water layer was generally oxic and the sediment varied from oxic to suboxic with 

no clear pattern during the experiment. 

Sediment microbial biomass in the Goose River clay loam sediment was 383 μg C/g sediment at 

time 0 and 125 μg C/g sediment at study termination (p. 32). Untreated sediment microbial biomass 

in the Choptank River sand sediment was 278 μg C/g sediment at time 0 and 58 μg C/g sediment at 

study termination.

B. Mass Balance:

In the Goose River water:clay loam sediment system, recoveries averaged 97.3 ± 1.8% (sample 

range 95.8-100.7%) of the applied for samples treated with the phenyl label and 97.1 ± 1.7% (95.1-

99.8%) for samples treated with the pyrimidine label (Table 6, p. 51). Recoveries were within 

guideline criteria (>90% - <110%). In the water column, chlorimuron ethyl decreased from a 

maximum of 98.5% of the applied at time 0 to 11.6% at 100 days posttreatment (Table 8, pp. 55-

56). In the sediment, chlorimuron ethyl was a maximum of 29.4% of the applied at 62 days

posttreatment and decreased to 4.8% at 100 days.

In the Choptank River water:sand sediment system, recoveries averaged 96.5 ± 3.7% (sample range

91.0-103.9%) of the applied for samples treated with the phenyl label and 95.3 ± 2.0% (91.7-97.9%) 

for samples treated with the pyrimidine label (Table 7, p. 53). Recoveries were within guideline 

criteria (>90% - <110%). In the water column, chlorimuron ethyl decreased from a maximum of 

97.0% of the applied at time 0 to 5.0% in the phenyl treatment and 26.2% in the pyrimidine 

treatment at 100 days posttreatment (Table 9, pp. 57-58). In the sediment, chlorimuron ethyl was a 

maximum of 10.1% of the applied at 79 days posttreatment and decreased to 8.3% at 100 days.

C. Bound and Extractable Residues:

In the Goose River clay loam sediments, extractable radioactivity increased from 4.1% of the 

applied at time 0 to a maximum of 40.9% at 62 days posttreatment and was 36.5% at 100 days 

(Table 6, p. 51). Unextracted radioactivity increased from 0.3% of the applied at time 0 to a 

maximum of 8.1% at 100 days posttreatment. 

In the Choptank River sand sediments, extractable radioactivity increased from 2.3% of the applied 

at time 0 to a maximum of 28.1% at 79 days posttreatment, and were 26.8% at 100 days (Table 7, p. 

53). Unextracted radioactivity increased from 0.0% of the applied at time 0 to a maximum of 1.1% 

at 62 and 100 days posttreatment. 

D. Volatilization:

In the Goose River water:clay loam sediment systems, 14CO2 was 0.0% of the applied during the 

experiment (Table 6, p. 51). Organic volatiles totaled a maximum of 1.1% at 100 days posttreatment 

(Table 6, p. 51). 

In the Choptank River water:sand sediment systems, 14CO2 was 0-5-0.7% of the applied at 79-100 

days posttreatment (Table 7, p. 53). Organic volatiles were 0.0% during the experiment.
Chlorimuron ethyl (PC 128901) MRID 49526702

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

the applied radioactivity, in Goose River water:clay loam sediment.

Sampling Interval (days) 0 1 7 14 28 62 79 100

Replicate Number A A A A A A A A

Chlorimuron ethyl (DPX-F6025) 98.5 97.6 77.0 63.9 49.0 51.8 20.2 13.7

IN-B4450 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0

IN-L8330 0.0 0.7 14.0 27.7 41.0 33.3 63.5 66.6

IN-00581 0.0 0.0 2.5 0.0 0.8 6.1 5.9 6.5

IN-B7497 0.0 0.0 0.0 0.0 0.0 2.9 0.0 2.1

Unknown 1 0.0 0.3 0.9 1.8 0.0 0.0 0.0 1.4

Others 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0

Water 98.5 89.6 77.7 72.4 64.4 63.1 56.4 56.0

Extracted residues 0.0 9.3 17.3 21.9 28.3 32.0 34.9 36.5

Unextracted residues 0.0 0.2 1.5 2.4 4.0 5.9 5.2 5.4

CO2 n.a. 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Volatile organics n.a. 0.0 0.0 0.0 0.1 0.7 0.6 0.9

Mass balance 98.5 98.8 96.0 95.8 95.9 100.7 96.3 96.7

Data obtained from Table 6, p. 51, and Table 8, p. 55, of the study report.

n.a. = not analyzed.

Table 7b. Aerobic transformation of [pyrimidine-2-

14C]chlorimuron ethyl, expressed as a percentage 

of the applied radioactivity, in Goose River water:clay loam sediment.

Sampling Interval (days) 0 1 7 14 28 62 79 100

Replicate Number A A A A A A A A

Chlorimuron ethyl (DPX-F6025) 94.5 95.6 83.3 71.0 53.9 35.7 29.2 16.4

IN-N6186 0.0 0.3 2.9 0.0 0.0 1.4 1.5 0.0

IN-V9662 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

IN-L8330 0.0 0.6 10.5 21.8 36.9 53.6 55.4 64.3

IN-H1427 0.0 0.0 0.0 0.0 0.0 0.0 1.1 2.0

Others 0.0 0.0 0.0 0.0 0.0 3.2 1.0 6.2

Water 94.4 88.6 81.6 73.5 65.1 60.2 53.6 54.2

Extracted residues 4.1 8.1 15.5 19.6 26.5 40.9 35.5 35.4

Unextracted residues 0.3 0.3 1.1 2.7 4.1 5.3 6.7 8.1

CO2 n.a. 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Volatile organics n.a. 0.0 0.0 0.1 0.2 0.4 0.7 1.1

Mass balance 98.5 96.6 97.8 95.6 95.1 99.8 95.7 98.0

Data obtained from Table 6, p. 51, and Table 8, p. 56, of the study report.

n.a. = not analyzed.
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Table 7c. Aerobic transformation of [phenyl-U14C]chlorimuron ethyl, expressed as a percentage of 

the applied radioactivity, in Choptank River water:sand sediment.

Sampling Interval (days) 0 1 7 14 28 62 79 100

Replicate Number A A A A A A A A

Chlorimuron ethyl (DPX-F6025) 97.0 95.7 94.4 96.1 81.1 32.3 30.7 10.8

IN-B4450 0.0 0.0 0.0 0.0 0.0 33.0 32.3 39.8

IN-L8330 0.0 0.0 0.7 1.6 9.7 7.7 21.6 8.5

IN-00581 0.0 0.0 0.0 0.0 2.4 13.6 13.6 32.1

IN-B7497 0.0 0.0 0.0 0.0 0.0 2.0 3.2 3.2

Unknown 1 0.0 0.0 0.6 0.4 0.0 0.0 0.0 0.0

Others 0.0 0.0 0.0 0.0 0.0 1.0 1.1 0.0

Water 97.0 95.7 85.0 87.6 80.3 68.0 75.0 68.1

Extracted residues 0.0 0.0 10.0 10.9 13.3 21.9 28.1 26.8

Unextracted residues 0.0 0.3 0.1 0.2 0.5 1.1 1.0 1.1

CO2 n.a. 0.0 0.0 0.0 0.2 0.3 0.6 0.6

Volatile organics n.a. 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Mass balance 97.0 96.0 95.8 98.3 94.0 91.0 103.9 96.0

Data obtained from Table 7, p. 53, and Table 9, p. 57, of the study report.

n.a. = not analyzed.

Table 7d. Aerobic transformation of [pyrimidine-2-

14C]chlorimuron ethyl, expressed as a percentage 

of the applied radioactivity, in Choptank River water:sand sediment.

Sampling Interval (days) 0 1 7 14 28 62 79 100

Replicate Number A A A A A A A A

Chlorimuron ethyl (DPX-F6025) 94.3 95.0 96.7 91.4 81.8 65.1 54.6 34.5

IN-N6186 0.0 0.0 0.5 0.0 0.0 5.7 1.3 33.0

IN-V9662 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

IN-L8330 0.0 0.0 0.0 2.0 13.2 19.7 29.2 21.6

IN-H1427 0.0 0.0 0.0 0.0 0.0 0.0 4.0 1.4

Others 0.0 0.0 0.0 0.0 0.0 0.0 6.7 2.6

Water 94.2 95.0 90.4 81.6 80.4 74.5 79.6 70.5

Extracted residues 2.3 0.0 7.0 12.1 15.1 16.5 17.9 23.1

Unextracted residues 0.0 0.5 0.0 0.1 0.5 0.7 0.7 1.0

CO2 n.a. 0.0 0.0 0.1 0.2 0.4 0.7 0.5

Volatile organics n.a. 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Mass balance 96.5 95.5 97.2 93.6 95.7 91.7 97.9 94.5

Data obtained from Table 7, p. 53, and Table 9, p. 58, of the study report.

n.a. = not analyzed.

E. Transformation of Parent Compound: Transformation kinetics of the parent compound in the 

total system are summarized in the following two 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 (pp. 29-30, 36-37; Table 10, 

pp. 59-60). Total system SFO half-lives were 40.8 and 41.5 days for the Goose River water:clay 
Chlorimuron ethyl (PC 128901) MRID 49526702

Page 12 of 21

loam sediment systems treated with the phenyl and pyrimidine labels, respectively (p. 37). Total 

system SFO half-lives were 44.1 and 85.2 days for the Choptank River water:sand sediment 

systems treated with the phenyl and pyrimidine labels, respectively (pp. 37-38). 

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

Equation (IORE) in accordance with NAFTA kinetics guidance (USEPA, 2012).

Chlorimuron ethyl in aerobic water:clay loam sediment

Days%AR

0

 1

 7

 14

 28

 62

 79

 100

0

 1

 7

 14

 28

 62

 79

 100

98.5

97.6

77.0

63.9

49.0

51.8

20.2

13.7

94.5

95.6

83.3

71.0

53.9

35.7

29.2

16.4

0 20 40 60 80 100

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

DT50 DT90 

2 C0 Parameters

SFO 41.1 137 7.5 93.3 k  0.0168

DFOP35.4 153 6.6 98.2f 0.192k0 0.136k1 0.0136

IORE 33.7 215 7 96.8 N  1.69k  0.00111

SC

SSFO

Slowt1 2

tRIORE

 740

 742

50.8

64.7

Chlorimuron ethyl in aerobic water:sand sediment

Days%AR

0

 1

 7

 14

 28

 62

 79

 100

0

 1

 7

 14

 28

 62

 79

 100

97.0

95.7

94.4

96.1

81.1

32.3

30.7

10.8

94.3

95.0

96.7

91.4

81.8

65.1

54.6

34.5

0 20 40 60 80 100

0

20

40

60

80

100

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

DT50 DT90 

2 C0 Parameters

SFO 59.8 199 6.5 102 k  0.0116

DFOP63.9 178 3.7 95.3f -0.236k0 0.137k1 0.0142

IORE 68 113 3.7 98.7 N  -0.2k  1.71

SC

SSFO

Slowt1 2

tRIORE

1.53e+03

1.67e+03

 49

33.9
Chlorimuron ethyl (PC 128901) MRID 49526702

Page 13 of 21

Table 8. Transformation Products of Chlorimuron ethyl in the Water:Sediment Systems.

Transformatio

n Products

Maximum 

%AR 

Observed

Associated 

Interval

(days)

Final %AR 

Observed

Final Interval

(days)

Goose River, North Dakota 

USA

Water:clay loam sediment

(20°C, water pH 8.3, 

sediment pH 8.0)

IN-B4450 1.0 28 0.0 100

IN-L8330 66.6 100 66.6 100

IN-00581 6.5 100 6.5 100

IN-B7497 2.9 62 2.1 100

IN-N6186 2.9 7 0.0 100

IN-H1427 2.0 100 2.0 100

Choptank River, Maryland, 

USA

Water: sand sediment

(20°C, water pH 6.9, 

sediment pH 6.7)

IN-B4450 39.8 100 39.8 100

IN-L8330 29.2 79 21.6 100

IN-00581 32.1 100 32.1 100

IN-B7497 3.2 79, 100 3.2 100

IN-N6186 33.0 100 33.0 100

IN-H1427 4.0 79 1.4 100

Data obtained from Tables 8-9, pp. 55-58, in the study report. 

IN-B4450, IN-00581, and IN-B7497 are products of the phenyl moiety only. IN-N6186 and IN-H1427 are products of 

the pyrimidine moiety only.

A transformation pathway was provided by the study authors (Figure 14, p. 141).
Chlorimuron ethyl (PC 128901) MRID 49526702

Page 14 of 21

III. Study Deficiencies and Reviewer's Comments

1. The pesticide use history at the source site was not reported, and it was not demonstrated that 

the water and sediments were pesticide-free prior to use.

2. In the Choptank River water:sand system treated with the phenyl label, the concentration of 

chlorimuron ethyl decreases ca. 50% between two sampling intervals, from 81.1% of the 

applied at 28 days posttreatment to 32.3% at 62 days (Table 9, p. 57). A similar large decrease 

was not seen with the pyrimidine label, or in the Goose River water:clay loam sediment system 

(Table 8, pp. 55-56; Table 9, p. 58). 

IV. References

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

Guidelines, OPPTS 835.4300, Aerobic Aquatic Metabolism. Office of Prevention, Pesticides 

and Toxic Substances, Washington, DC. EPA 712-C-08-018.

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

Degradation Kinetics in Environmental Media.
Chlorimuron ethyl (PC 128901) MRID 49526702

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% (100d)

River water: 

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

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 49526702

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% (124d)

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% (100d)

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 49526701 Illinois 
Chlorimuron ethyl (PC 128901) MRID 49526702

Page 17 of 21

Code Name/ Synonym Chemical Name Chemical Structure Study 

Type MRID Maximum %AR (day)

Final %AR 

(study 

length)

Aerobic soil 

metabolism

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

North Dakota 

Clay loam 10.2% (29 d) 0.0% (124 d)

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 49526702

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(n

1)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 49526702

Page 19 of 21

Attachment 2: Statistics Spreadsheets and Graphs
Chlorimuron ethyl (PC 128901) MRID 49526702

Page 20 of 21

Attachment 3: Calculations

Calculations were performed by the reviewer using R software, 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 R kinetics software 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 R kinetics software 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 49526702

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