OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

June 24, 2013

PC Code: 121011

MEMORANDUM DP Barcode: 412704

SUBJECT: Clethodim: Drinking Water Exposure Assessment for Registration Review

FROM: Greg Orrick, Environmental Scientist

ERB2/EFED (7507P)

THROUGH: R. David Jones, Ph.D., Senior Agronomist

Brian Anderson, Branch Chief

ERB2/EFED (7507P)

TO: Meheret Negussie, Risk Assessor

Christine Olinger, Branch Chief

RAB3/HED (7509P)

Ricardo Jones, Chemical Review Manager

Neil Anderson, Branch Chief

RMIB1/PRD (7508P)

This Environmental Fate and Effects Division (EFED) memorandum is a drinking water 

exposure assessment based on currently labeled uses of clethodim (listed in Table 2) to support 

the registration review of the active ingredient. This assessment provides screening-level 

estimated drinking water concentrations (EDWC) of the residues of concern (ROC), which

include clethodim and degradates with 5-(2-ethylthiopropyl)-5-hydroxycyclohexene-3-one or 5-

(2-ethylthiopropyl)cyclohexene-3-one moieties.

The maximum screening-level acute and chronic EDWCs (1,430 and 1,150 μg/L, 

respectively) are based on the maximum use pattern for clethodim (which includes non-cropped 

areas, fallow ground, and alfalfa), which includes a maximum annual application rate of 4.5 lbs 

a.i./A. The EDWCs are estimated with PRZM-GW to occur in an area of Wisconsin that is 

vulnerable to ground water contamination. These EDWCs are 43-53x greater than screeninglevel EDWCs for ground water from SCI-GROW and 4-8x greater than screening-level EDWCs 

for surface water from FIRST (Table 1). The variance with SCI-GROW may be due, in part, to

1) PRZM-GW being mechanistic, whereas SCI-GROW is empirical, and 2) differences in 

modeling assumptions such as the duration of the modeling scenario.
2

Table 1. Screening-Level ROC EDWCs for Clethodim Uses A

Source (Tier: Model) Use Site

(Max. Annual App. Rate)

Acute 

EDWC 

(μg/L)

Chronic 

EDWC 

(μg/L)

Surface water (Tier I: FIRST) Non-cropped (4.5 lbs a.i./A) 330 137

Ground water (Tier I: PRZM-GW) Non-cropped (4.5 lbs a.i./A) 1,430 1,150

Ground water (Tier I: SCI-GROW) Non-cropped (4.5 lbs a.i./A) ≤27 A Maximum values in bold.

Uncertainty regarding PRZM-GW outputs results from the extended time period of 

ground water flow and the model’s underlying assumptions, including that soils are sterile below 

a 1-meter depth. Bacteria in soils greater than one meter below the surface may degrade the 

ROC (potentially at a slower rate than on the surface) and may potentiate over years or decades 

in order to degrade the ROC at a faster rate. Clethodim ROC have an average breakthrough time 

of only 4.3 years with the Wisconsin scenario. Breakthrough times for PRZM-GW have been up 

to one order of magnitude shorter than observed for bromide (USEPA, 2012a) and up to one 

order of magnitude longer than observed for oxamyl (MRID 45591605). With an error of 

approximately one order of magnitude, average breakthrough of clethodim ROC may occur after 

0.4-40 years of use, which is a considerable uncertainty, compounded by variable usage that is

not expected to occur at the maximum labeled rate annually.

Also, the one-dimensional model represents a drinking water well that is surrounded by a 

large pesticide-treated area. Most drinking water wells are not surrounded by large pesticidetreated areas. Therefore, in most wells, horizontal convection and dispersion may attenuate 

persistent, dissolved residues such as these over time.

The main uncertainties with clethodim ROC exposure estimates are the toxicities of the 

degradates of concern and the actual usage rates. If actual annual application rates are an order 

of magnitude lower than those assumed in this assessment (e.g., 0.5 versus 4.5 lbs a.i./A), then 

exposure estimates for the actual rates are an order of magnitude lower as well (e.g., 158 versus 

1,430 μg/L). If the degradates of concern were shown to be much less toxic than clethodim, then 

exposure estimates for clethodim alone would be ≤3.2 μg/L at pH 7 and <0.1 μg/L in acidic (pH 

5) aquifers.

1. Use Characterization

Clethodim is applied with aerial, ground, hand-held, and irrigation equipment to a variety 

of agricultural and non-agricultural use sites. Approximately 67 uses and use groups (i.e., use 

sites) are listed on dozens of end-use labels registered by 21 registrants. These uses and use 

groups are organized into the following 26 maximum use patterns listed in Table 2 that are 

ranked by annual application rate. The use sites are not grouped by similarity and are not meant 

to be used as surrogates for other use sites that share the same use pattern.

Many use sites have application rate limits on a seasonal or crop basis, not on an annual 

basis. Annual application rates were assumed for use sites with multiple seasons per year, when 

not specified on labels, based on estimates in USEPA, 2007 for California agriculture. These 
3

estimates are more applicable to the lower latitudes of the United States and their applicability is 

complicated by the common practice of crop rotation. A reapplication interval of 14 days is 

labeled for a variety of uses. In the absence of label directions, a reapplication interval of 7 days 

is assumed. This is the minimum interval assumed to be practical for control of re-emerged 

weeds following an earlier treatment.

Table 2. Maximum Use Patterns for Current Uses of Clethodim A

Use Pattern

Single 

App. Rate

(lbs a.i./A)

Reapp. 

Interval B

(days)

Max. No. 

of App. 

per Crop

App. Rate 

per Crop 

(lbs a.i./A)

Annual 

App. Rate C

(lbs a.i./A)

App. 

Method D

Geographic

Applicability

Fallow land, golf course turf, noncropped areas E 0.25 NS F NS NS 4.5 G Aerial United States

Alfalfa I 0.25 NS NS 0.50 4.5 J Aerial United States

Ornamentals, landscaped areas, nonbearing food crops H, around 

buildings, bare soil, mulched areas

0.25 14 NS NS 4.5 G Ground United States

Grass forage/fodder/hay 0.19 NS NS NS 3.4 G Sprayer MO only

Clover 0.25 NS NS 0.25 2.25 J Aerial United States

Herbs, turnip greens 0.125 14 NS 0.50 2.0 N Aerial United States

Mustard, vegetables 0.12 14 NS 0.485 1.9 N Aerial

ID only (and 

OR & WA for 

mustard)

Radishes 0.125 14 NS 0.25 1.25 M Aerial United States

Mint 0.25 14 NS 0.50 1.0 K Aerial United States

Sod farms 0.25 NS NS 0.50 1.0 L Aerial AL, FL, GA, 

NC, SC only

Beets, brassica vegetables, carrots, 

cranberries, cucurbit vegetables, 

fruiting vegetables, leafy vegetables, 

strawberries

0.125 14 NS 0.50 1.0 L Aerial United States

Dried beans, Christmas trees, cotton, 

forest trees, peanuts, potatoes, root & 

tuber vegetables, sainfoin, soybeans, 

sugar beets, sunflowers, sweet 

potatoes, tomatoes, trefoil, yams

0.25 NS NS 0.50 0.50 Aerial United States

Lentils 0.25 14 NS 0.50 0.50 Aerial United States

Garlic, onions 0.25 NS 2 0.50 0.50 Chemigation

Except ID, 

MT, OR, WA

Tree fruits, tree nuts, asparagus, hops, 

safflower, sesame 0.125 NS NS 0.50 0.50 Aerial United States

Sage 0.24 NS NS 0.485 0.485 Ground NC only

Shallots 0.24 14 NS 0.485 0.485 Aerial United States

Artichokes, bushberries including 

cranberries, caneberries, peaches 0.12 14 NS 0.485 0.485 Aerial United States

Flax 0.125 NS NS 0.25 0.25 Aerial Except CA

Meadowfoam 0.125 NS NS 0.25 0.25 Aerial OR only

Seeds 0.125 NS NS 0.25 0.25 Aerial MN, ND only

Kenaf 0.125 NS NS 0.25 0.25 Ground NC only

Canola 0.10 NS NS 0.25 0.25 Aerial United States

Wildlife food plots 0.24 14 NS NA F 0.24 Not stated United States
4

Use Pattern

Single 

App. Rate

(lbs a.i./A)

Reapp. 

Interval B

(days)

Max. No. 

of App. 

per Crop

App. Rate 

per Crop 

(lbs a.i./A)

Annual 

App. Rate C

(lbs a.i./A)

App. 

Method D

Geographic

Applicability

Succulent beans, legume vegetables, 

dried & succulent peas 0.125 NA 1 0.125 O 0.125 Aerial United States

Corn (field) 0.045 NA 1 0.045 0.045 Aerial United States

A Listed use patterns represent those of the maximum use pattern and do not represent all labeled use patterns for 

that use.

B Reapplication intervals of 14 days were labeled for a variety of uses. In the absence of label directions, a 

reapplication interval of 7 days is assumed for control of emerged weeds.

C The annual application rate accounts for how many crops may occur per year. For perennial crops (e.g., alfalfa), 

the number of cuttings per year was used. Source: USEPA, 2007.

D Aerial application is assessed unless it is not allowed for the use.

E Non-cropped areas include fallow agricultural land, rights-of-way, around airports, electric utilities, commercial 

buildings, manufacturing plants, storage yards, rail yards, fence lines, parkways, golf courses, uncultivated 

areas, and beneath greenhouse benches.

F NS means “not stated.” NA means “not applicable.”

G For non-cropped areas, fallow land, golf course turf, and hay, eighteen applications were assumed in the absence 

of a labeled annual application limit.

H Non-bearing crops include apples, berries including strawberries, citrus fruits, grapes, olives, pears, stone fruits, 

and tree nuts.

I Alfalfa use pattern includes an alfalfa plus clover mixture.

J For alfalfa, nine cuttings may occur per year in California. Nine cuttings were assumed for clover as well

(USEPA, 2007).

K Annual application rate is 1.04 lbs a.i./A for spearmint and 0.52 lbs a.i./A for peppermint.

L Two crops of sod, beets, and most brassica and leafy vegetables may be grown per year (USEPA, 2007).

M Radishes may have 5 crops per year (USEPA, 2007).

N Turnip greens and mustard greens may have 4 crops per year (USEPA, 2007).

O The seasonal application rate limit is stated as 0.50 lbs a.i./A; however, no more than one application of 0.125 lbs 

a.i./A may be applied per season. Therefore, the practical seasonal rate limit is 0.125 lbs a.i./A.

2. Environmental Fate Characterization

Clethodim is microbially oxidized to moderately persistent degradates within days of 

application. Clethodim is soluble in water up to 29 mg/L and will not appreciably volatilize or 

bioconcentrate in fish. The compound and its degradates are mobile in soil and may be 

transported to surface and ground waters. The available environmental fate data for clethodim 

are listed in Table 3. The information in this section is provided to expand the brief 

characterization provided in the 2008 problem formulation for registration review (USEPA, 

2008).

Table 3. Chemical Properties and Environmental Fate Parameters of Clethodim

Parameter Value Source

Selected Physical/Chemical Parameters

Molecular mass (molecular formula) 359.92 g/mol (C12H10ClN3O) (Calculated)

Vapor pressure (25 °C) <1 x 10-7 torr MRID 48881401

Aqueous solubility (20°C) 29 mg/L MRID 48881405

Henry’s Law Constant (25 °C) <2 x10-9 atm-m3/mol (Calculated)
5

Parameter Value Source

Log octanol-to-water partition 

coefficient (log KOW)

4.81 MRID 48881405

Dissociation constant (pKa) 4.62 MRID 48881405

Persistence in Water

Hydrolysis half-life (25°C) A pH 5: 28 days

pH 7: 289 days

pH 9: 305 days

MRID 40974520

Aqueous photolysis half-life (25°C) pH 5: 1.5-1.7 days

pH 7: 2.5-6.8 days

pH 9: 6.0-9.6 days

MRID 41030133,

41030134

Anaerobic aquatic metabolism half-life 

(25°C)

233 days MRID 41652301

Persistence in Soil

Aerobic soil metabolism half-life 

(25°C)

1.2 days MRID 41376801

2.5 days MRID 40974522

Photolysis half-life in soil (13-23°C) 7 days MRID 41030135

Mobility

Freundlich soil-water partition 

coefficients (KF); Freundlich organic 

carbon-normalized coefficients (KFOC)

0.08, 0.15, 0.46, 0.51, 1.57 L/kg;

4.9, 65, 68, 132, 271 L/kgOC

MRID 40974523

Field Dissipation

Terrestrial field dissipation half-life Half-lives and leaching depths could not 

be calculated due to high LOQs (20 ppb) 

relative to dose rates (MS cotton; CA 

cotton; NC soybean; and IA soybean sites)

MRID 41030207

MRID 41030208

(MRID 41030209) B

(MRID 41030210) B

Fish Bioconcentration

Fish bioconcentration factors (steadystate, total residues); depuration rate0.7-2.1 (edible), 3.0-4.0 (inedible), 2.3-3.6 

(whole fish); >70% depuration in 3 days

MRID 40974524/ 

40974531 A Technically, clethodim underwent nonhydrolytic, abiotic, thermal degradation in the presence of aqueous buffers. 

Half-life values only represent the propyl-labeled studies because allyl-labeled clethodim was not studied at pH 9 

and was studied at an elevated concentration at pH 5 and 7.

B Studies with MRIDs in parentheses are provisional until reviewed.

Clethodim and many of its degradates have multiple types of isomerization. The 

compound is an equilibrium mixture of four tautomers, which are predominantly two keto-enol 

tautomers at the cyclohexene ring (MRID 41376801). The other two tautomers, which are 

cyclohexane diones with tautomerization at the oxime, may be intermediates. Clethodim also 

has two chiral centers along the thiopropyl side chain and two double bonds that can form cistrans isomers. Clethodim and its degradates include only the E-isomer of the chloropropenyl 

group. Clethodim is a racemic mixture, however, of the sixteen combinations of the other two 

cis-trans isomers, four enantiomers, and two predominant tautomers. MRID 41376801 
6

Appendix D provides a more complete discussion of the complex isomerism in clethodim and its 

degradates. Isomerism complexity often complicates study results because multiple observed 

chromatograph peaks may represent isomers or tautomers of the same compound.

In the fish bioconcentration (BCF) studies, clethodim and its sulfoxide were identified 

and quantified in the tank water and identified in the fish. Residue concentrations were too low 

to quantify clethodim or its sulfoxide in fish or to identify any other metabolites in fish that may 

have been present at lower concentrations than the sulfoxide. Total-residue fish BCF values for 

whole fish were 2.3-3.6x. Allyl-labeled residues depurated from fish by 72% in 14 days. 

Cyclohexenone-labeled residues depurated from fish faster, by >70% in 3 days. Due to the low 

bioconcentration of clethodim residues and their relatively rapid depuration, bioaccumulation of 

clethodim residues of concern in aquatic organisms is not expected.

Degradates of clethodim and their amounts formed in submitted studies are listed in 

Table 5. Clethodim sulfoxide is the main degradate of clethodim, formed in soil at up to 75% of 

the applied compound three days after application. Clethodim sulfone forms up to 16% of the 

applied 30 days after application. These degradates are more persistent than the parent 

compound, but not expected to generally persist, with 0.4-0.9% of the applied remaining 380 

days after application. Clethodim oxazole sulfone does persist, with up to 10% of the applied at 

study termination, 380 days after application. Nine additional major photolysis degradates are 

formed in shallow, clear, well-lit water bodies; however, most of the applied clethodim is likely 

to biodegrade prior to reaching a water body, prior to photolyzing, or both.

Clethodim’s sulfoxide and sulfone are more mobile than clethodim in soil. However, 

clethodim’s oxazole sulfoxide is less mobile in soil than the parent compound. Table 4 lists the 

available environmental fate information for degradates of clethodim, which is only focused on 

soil mobility.

Table 4. Environmental Fate Parameters of Clethodim Degradates

Parameter Degradate Value Source

Freundlich organic 

carbon-normalized 

coefficients (KFOC)

Clethodim sulfoxide 12, 27, 38, 57, 86 L/kgOC

Clethodim sulfone 6, 13, 19, 29, 43 L/kgOC MRID 40974523

Clethodim oxazole sulfoxide 50, 135, 429, 460, 771 L/kgOC
Table 5. Chemical Names and Structures of Clethodim and Its Environmental Degradates A

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

PARENT

Clethodim

RE-45601

(Z-isomer is 

RE-46116)

(5RS)-2-{(1EZ)-1-[(2E)-3-

chloroallyloxyimino]propyl}-5-[(2RS)-

2-(ethylthio)propyl]-3-hydroxycyclohex2-en-1-one

CAS No.: 99129-21-2

Formula: C17H26ClNO3S

MW: 359.92 g/mol

SMILES:C1C(CC(=C(C1=O)\C(CC)=

N\OCC=CCl)O)CC(C)SCC

S OH

O

N

O Cl

TRANSFORMATION PRODUCTS

Clethodim 

sulfoxide

RE-45924

CLSO

SOX

(5RS)-2-{(1EZ)-1-[(2E)-3-

chloroallyloxyimino]propyl}-5-[(2RS)-

2-(ethylsulfinyl)propyl]-3-

hydroxycyclohex-2-en-1-one

Formula: C17H26ClNO4S

MW: 375.92 g/mol

SMILES:C1C(CC(=C(C1=O)\C(CC)=

N\OCC=CCl)O)CC(C)[S](CC)=O S OH

O

N

O Cl

O

Hydrolysis –pH 5

Hydrolysis –pH 7

Hydrolysis –pH 9

40974520

2.6% (0 d)

3.0% (14 d)

5.3% (14 d)

1.7% (32 d)

2.0% (32 d)

4.5% (32 d)

Aq. photo.– dark

Aq. photo.– light 41030133 5.2% (3 d)14% (3 d)

1.4% (10 d)

nd (30 d)

Aq. photo.– dark

Aq. photo.– light 41030134 3.6% (3 d)14% (30 d)

2.7% (10 d)

14% (30 d)

Aq. photo.– dark

Aq. photo.– light 44066701 4.6% (25 d)7.6% (1 d)

4.4% (30 d)

nd (30 d)

Soil photo.– dark

Soil photo.– light 41030135 64% (7 d)74% (4 d)

64% (7 d)

71% (7 d)

Aerobic soil 40974522 65% (7 d) nd (380 d)

Aerobic soil 41376801 75% (3 d) 0.9% (121 d)

Anaerobic aquatic 41652301 23-38%B (181 d) 23-38%B (181 d)

Clethodim 

sulfone

RE-47253

ONE

(5RS)-2-{(1EZ)-1-[(2E)-3-

chloroallyloxyimino]propyl}-5-[(2RS)-

2-(ethylsulfonyl)propyl]-3-

hydroxycyclohex-2-en-1-one

Formula: C17H26ClNO5S

MW: 391.92 g/mol

SMILES:C1C(CC(=C(C1=O)\C(CC)=

N\OCC=CCl)O)CC(C)[S](CC)(=O)=O

S OH

O

N

O Cl

O

O

Aerobic soil 40974522 12% (62 d) 0.4% (380 d)

Aerobic soil 41376801 16% (30 d) 5.6% (121 d)

Anaerobic aquatic 41652301 0.6% (42 d) nd (181 d)
8

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Clethodim 

oxazole

RE-47365

CLOX

OX

(±)-6,7-dihydro-2-ethyl-6-[2-

(ethylthio)propyl]-4(5H)-benzoxazolone

Formula: C14H21NO2S

MW: 267.39 g/mol

SMILES:C12=C(OC(=N1)CC)CC(CC2

=O)CC(C)SCC O

N

S

O

Hydrolysis –pH 5

Hydrolysis –pH 7

Hydrolysis –pH 9

40974520

54% (32 d)

7.3% (32 d)

5.1% (32 d)

54% (32 d)

7.3% (32 d)

5.1% (32 d)

Aq. photo.– dark

Aq. photo.– light 41030134 14% (2.5 d)5.5% (3 d)

14% (2.5 d)

0.5% (14 d)

Aq. photo.– dark

Aq. photo.– light 44066701 34% (30 d)12% (1.5 d)

34% (30 d)

nd (30 d)

Aerobic soil 40974522 2.1% (3 d) nd (380 d)

Anaerobic aquatic 41652301 1.2% (181 d) 1.2% (181 d)

Clethodim 

oxazole 

sulfoxide

RE-47796

OXSO

OXSOX

(±)-6,7-dihydro-2-ethyl-6-[2-

(ethylsulfinyl)propyl]-4(5H)-

benzoxazolone

Formula: C14H21NO3S

MW: 283.39 g/mol

SMILES:C12=C(OC(=N1)CC)CC(CC2

=O)CC(C)[S](CC)=O

O

N

S

O

O

Aq. photo.– dark

Aq. photo.– light 41030134 1.2% (2.5 d)5.9% (10 d)

1.0% (14 d)

nd (30 d)

Aq. photo.– dark

Aq. photo.– light 44066701 1.9% (30 d)8.9% (6 d)

1.9% (30 d)

2.2% (30 d)

Aerobic soil 40974522 6.1% (90 d) 3.0% (380 d)

Aerobic soil 41376801 5.3% (30 d) 4.9% (121 d)

Anaerobic aquatic 41652301 10% (70 d) 7.7% (181 d)

Clethodim 

oxazole 

sulfone

RE-47797

OXONE

(±)-6,7-dihydro-2-ethyl-6-[2-

(ethylsulfonyl)propyl]-4(5H)-

benzoxazolone

Formula: C14H21NO4S

MW: 299.39 g/mol

SMILES:C12=C(OC(=N1)CC)CC(CC2

=O)CC(C)[S](CC)(=O)=O

O

N

S

O

O

O

Aerobic soil 40974522 10% (380 d) 10% (380 d)

Aerobic soil 41376801 8.6% (121 d) 8.6% (121 d)

Anaerobic aquatic 41652301 5.1% (181 d) 5.1% (181 d)

Clethodim 

imine

RE-47686

CLIM

IMINE

(±)-5-[2-(ethylthio)propyl]-3-hydroxy-2-

(1-iminopropyl)cyclohex-2-enone

Formula: C14H23NO2S

MW: 269.41 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N

)O)CC(C)SCC S OH

O

NH

Aq. photo.– light 41030134 18% (2.5 d) 18% (2.5 d)

Aq. photo.– dark

Aq. photo.– light 44066701 1.4% (25-30 d)28% (2 d)

1.4% (30 d)

nd (30 d)

Anaerobic aquatic 41652301 1.3-17%B (181 d) 1.3-17%B (181 d)
9

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Clethodim 

imine 

sulfoxide

RE-47718

IMSO

IMSOX

(±)-5-[2-(ethylsulfinyl)propyl]-3-

hydroxy-2-(1-iminopropyl)cyclohex-2-

enone

Formula: C14H23NO3S

MW: 285.41 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N

)O)CC(C)[S](CC)=O

S OH

O

NH

O

Aq. photo.– light 41030134 23% (21 d) 20% (30 d)

Aq. photo.– dark

Aq. photo.– light 44066701 0.5% (25 d)30% (10 d)

0.4% (30 d)

11% (30 d)

Aerobic soil 40974522 1.1% (14-30 d) nd (380 d)

Aerobic soil 41376801 2.1% (3 d) 2.0% (121 d)

Anaerobic aquatic 41652301 1.6% (181 d) 1.6% (181 d)

Clethodim 

imine ketone

IMK

(±)-5-[propyl-2-one]-3-hydroxy-2-(1-

iminopropyl)cyclohex-2-enone

Formula: C12H17NO3

MW: 223.27 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N

)O)CC(=O)C

O

OH

O

NH

Aq. photo.– light 41030134 12% (15, 25 d) 9.5% (30 d)

Aq. photo.– light 44066701 15% (2-4 d) 5.8% (30 d)

Clethodim 

trione

TRIONE

(±)-5-[2-(ethylthio)propyl]-3-hydroxy-2-

(1-oxopropyl)cyclohex-2-enone

Formula: C14H22O3S

MW: 270.39 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=O

)O)CC(C)SCC S OH

O

O Aq. photo.– light 44066701 2.9% (7 d) nd (30 d)

Clethodim 

trione 

sulfoxide

RE-47386

TRISO

(±)-5-[2-(ethylsulfinyl)propyl]-3-

hydroxy-2-(1-oxopropyl)cyclohex-2-

enone

Formula: C14H22O4S

MW: 286.39 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=O

)O)CC(C)[S](CC)=O

S OH

O

O

O

Aq. photo.– light 41030134 4.4% (0.5 d) 2.7% (2.5 d)

Aq. photo.– light 44066701 18% (20-30 d) 18% (30 d)

Clethodim 

trione 

ketone

(±)-5-[propyl-2-one]-3-hydroxy-2-(1-

oxopropyl)cyclohex-2-enone

Formula: C12H16O4

MW: 224.26 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=O

)O)CC(=O)C

O

OH

O

O Aq. photo.– light 41030134 5.3% (20 d) 4.8% (30 d)
10

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Clethodim 

imine ketone

IMK

(±)-5-[propyl-2-one]-3-hydroxy-2-(1-

iminopropyl)cyclohex-2-enone

Formula: C12H17NO3

MW: 223.27 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N

)O)CC(=O)C

O

OH

O

NH

Aq. photo.– light 41030134 12% (15, 25 d) 9.5% (30 d)

Aq. photo.– light 44066701 15% (2-4 d) 5.8% (30 d)

DME 

sulfoxide

RE-52453

DMESO

(±)-3-[2-

(ethylsulfinyl)propyl]pentanedioic acid

Formula: C10H18O5S

MW: 250.32 g/mol

SMILES:C(C(CC(=O)O)CC(C)[S](CC)

=O)C(=O)O

S

O

O

O

OH

OH

Aq. photo.– light 41030134 49% (30 d) 49% (30 d)

Aq. photo.– light 44066701 11% (20-30 d) 11% (30 d)

DME sulfone

DMESO2

(±)-3-[2-

(ethylsulfonyl)propyl]pentanedioic acid

Formula: C10H18O6S

MW: 266.32 g/mol

SMILES:C(C(CC(=O)O)CC(C)[S](CC)

(=O)=O)C(=O)O

S

O

O

O

OH

O OH Aq. photo.– light 41030134 7.4% (30 d) 7.4% (30 d)

Unknown-2 (±)-3-[propyl-2-one]pentanedioic acid

(proposed chemical name)

O

O

O

OH

OH

(proposed chemical structure)

Aq. photo.– light 41030134 7.4% (30 d) 7.4% (30 d)

3-chloroprop

enal

(E)-3-chloropropenal

Formula: C3H3ClO

MW: 90.51 g/mol

SMILES:O=CC=CCl

O Cl Aq. photo.– light 41030133 31% (2.5 d) 31% (2.5 d)

Chloroallyl 

alcohol

RE-46261

(E)-3-chloroallyl alcohol

Formula: C3H5ClO

MW: 92.53 g/mol

SMILES:OCC=CCl

HO Cl

Hydrolysis –pH 5

Hydrolysis –pH 7 40974520 35% (30 d)

5.3% (30 d)

35% (30 d)

5.3% (30 d)

Aq. photo.– dark

Aq. photo.– light 41030133 11% (2.5 d)

31% (15 d)

11% (2.5 d)

29% (30 d)
11

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Unextracted 

residues

(not applicable)

(not applicable)

Soil photo.– dark

Soil photo.– light 41030135 5.5% (7 d)6.2% (7 d)

5.5% (7 d)

6.2% (7 d)

Aerobic soil 40974522 23% (183 d) 18% (380 d)

Aerobic soil 41376801 29% (125 d) 29% (125 d)

Anaerobic aquatic 41652301 11% (181 d) 11% (181 d)

Carbon 

dioxide

Carbon dioxide

Formula: CO2

MW: 44.01 g/mol

SMILES:O=C=O

O O

Aq. photo.– light 41030133 12% (30 d) 12% (30 d)

Soil photo.– dark

Soil photo.– light 41030135 3.7% (7 d)4.2% (7 d)

3.7% (7 d)

4.2% (7 d)

Aerobic soil 40974522 54% (380 d) 54% (380 d)

Aerobic soil 41376801 57% (121 d) 57% (121 d)

Anaerobic aquatic 41652301 0.1% (181 d) 0.1% (181 d) A nd means “not detected”. AR means “applied radioactivity”. MW means “molecular weight”. Bolded values are laboratory study values >10%AR. B These values have a range because portions of the sulfoxide and imine degradates co-eluted and the proportions of the mixture are unclear, i.e., whether the residue was one 

degradate, the other, or both.
12

3. Exposure Modeling

The available physical/chemical and environmental fate properties of clethodim and its 

degradates of concern were used to calculate exposure model input parameters to estimate 

potential drinking water concentrations (EDWC). The compounds of concern include those with 

5-(2-ethylthiopropyl)-5-hydroxycyclohexene-3-one or 5-(2-ethylthiopropyl)cyclohexene-3-one 

moieties. Half-lives calculated for the residues of concern (ROC) are listed in Table 6. Also 

listed is the soil mobility of the most prominent residue of concern, clethodim sulfoxide, which is 

used to represent the residues of concern.

Table 6. Environmental Fate Parameters of Clethodim Residues of Concern (ROC)

Parameter Value Source

Persistence in Water

Hydrolysis half-life (25°C) pH 5: 414 days

pH 7: 3,660 days

pH 9: 45,000 days

MRID 40974520

Aqueous photolysis half-life (25°C) pH 5: 2.1-8.0 days

pH 7: 4.1-24 days

pH 9: 7.5-27 days

MRID 41030133,

41030134

Anaerobic aquatic metabolism half-life 

(25°C)

1217 days MRID 41652301

Persistence in Soil

Aerobic soil metabolism half-life (25°C) 44 days MRID 41376801

87 days MRID 40974522

Photolysis half-life in soil (13-23°C) No observable degradation MRID 41030135

Mobility

Freundlich organic carbon-normalized 

coefficients (KFOC)

12, 27, 38, 57, 86 L/kgOC MRID 40974523

The Total Residue (TR) modeling approach was used to estimate aquatic exposure with 

the ROC half-lives (from Table 6), the soil mobility of clethodim sulfoxide (from Table 6), and 

the physical/chemical properties of clethodim (from Table 3). The TR approach is appropriate 

because there are multiple degradates of concern, for none of which a full environmental fate 

data profile is available. Because up to 75% of clethodim oxidizes to its sulfoxide, the sulfoxide 

is the most prominent degradate of concern. With a mean KOC value of 44 L/kg, clethodim 

sulfoxide is more mobile in soil than clethodim and its oxazole sulfoxide, but less mobile in soil 

than clethodim sulfone; therefore, use of its KOC value in modeling may be representative and 

may be conservative, but is not a worst case assumption.

3.1. Surface Water

Surface water sourced drinking water exposure was estimated using the Tier I screening 

model FIRST (v1.1.1; Mar. 26, 2008). Input parameters for FIRST follow in Table 7. The 

modeled use pattern represents the maximum labeled use pattern for alfalfa, fallow land, and 

non-cropped areas (aerial application at 0.25 lbs a.i./A), with eighteen applications per year 
13

assumed in the absence of an annual application rate limit. A reapplication interval of 7 days 

was modeled in the absence of label directions because it is the minimum interval assumed to be 

practical for control of re-emerged weeds.

Table 7. FIRST Input Parameters for Clethodim ROC A

Input Parameter Value Comments Source

Application rate (lbs a.i./A) 0.25 Maximum labeled single application rate Current labels

Number of applications per 

year

18

Maximum number of applications per 

year assumed in the absence of label 

directions

Current labels

Application interval (d) 7 Reapplication interval assumed in the 

absence of label directions Current labels

Percent cropped area 100% Default for agricultural plus nonagricultural uses USEPA, 2012c

Organic Carbon Partition 

Coefficient (KOC) (L/kg) 44

Represents the mean KFOC value (n=5)

for clethodim sulfoxide, the most 

prominent degradate of concern 

MRID 40974523

Aerobic soil metabolism 

half-life (days) 132

Represents the upper 90% confidence 

bound on the mean of two half-lives for 

the residues of concern

MRIDs 40974523 

and 41376801

Wetted in? No Not required Current labels

Method of application Aerial Allowed application method Current labels

Solubility in water (ppm) 29 Solubility in water at 20°C MRID 48881405

Aerobic aquatic metabolism

half-life (days) 264

Represents the aerobic soil metabolism 

half-life input times two in the absence 

of data

(calculated)

Aqueous photolysis half-life 

(days) 24

Represents the maximum aqueous 

photolysis half-life at pH 7 for the 

residues of concern

MRID 41030134

A Source data are in Tables 2, 3 and 6.

Chemical property input values were chosen in accordance with current input parameter 

guidance (USEPA, 2009). Based on analysis of total residues of concern, the 90% confidence 

bound on the mean half-life for aerobic soil metabolism (132 d) was selected. In the absence of 

data, the aerobic aquatic metabolism half-life input (264 d) was selected to be two times the soil 

metabolism input value. The aqueous photolysis half-life input represents the maximum study

value at pH 7. The KOC input (44 L/kg) represents the mean value for clethodim sulfoxide, 

which is the most prominent residue of concern.

Standard percent cropped areas (PCA) are used as conservative default estimates of the 

extent of watershed on which agricultural crops of unknown specific PCA are grown (USEPA, 

2012c). Because clethodim is labeled for use on both agricultural and non-agricultural sites, 

PCA values cannot be used to modify clethodim exposure estimates.

Table 8 presents the ROC EDWCs in surface water from FIRST.
14

Table 8. Screening Surface Water EDWCs for Clethodim

Source (Tier: Model) 1-in-10-year Peak

(μg/L)

1-in-10-year Annual 

Mean (μg/L)

Surface water (Tier I: FIRST) 330 137

3.2. Ground Water

3.2.1. SCI-GROW

Current modeling methodology is to estimate exposure in ground water using both SCIGROW (v2.3, Jul. 29, 2003) and PRZM-GW (v1.01, Dec. 26, 2012) (USEPA, 2012d). Input 

parameters for SCI-GROW appear in Table 9. The lowest Freundlich organic carbon partition 

coefficient for clethodim sulfoxide (KFOC = 12 L/kgOC) was selected because the sulfoxide is 

more mobile in soil than the parent compound and is the most prominent degradate of concern. 

The mean total residue half-life (66 d) from two aerobic soils was selected to approximate the 

biodegradation kinetics of the residues of concern in aerobic soil environments.

Table 9. SCI-GROW Input Parameters for Clethodim ROC A

Input Parameter Value Comments Source

Application Rate

(lbs a.i./A) 0.25 Maximum labeled single application rate Current labels

Applications per Year 18

Maximum number of applications per 

year assumed in the absence of label 

directions

Current labels

Organic Carbon Partition 

Coefficient (KOC) (L/kgOC) 12

Represents the lowest KFOC value for 

clethodim sulfoxide, the most prominent 

degradate of concern, chosen because of 

the greater than three-fold variation in 

values

MRID 40974523

Aerobic Soil Metabolism 

Half-life (days) 66 Represents the mean of two half-lives for the residues of concern

MRIDs 40974523 

and 41376801 A Source data are in Tables 2 and 6.

The SCI-GROW output represents the highest 90-day running mean concentration 

following one year of application. The output value is 27 μg/L.

3.2.2. PRZM-GW

PRZM-GW model inputs are listed in Table 10. Application inputs represent the 

maximum use pattern of 4.5 lbs a.i./acre applied per year. PRZM-GW currently is limited to 11 

application events per year. Therefore, starting May 1st, 11 applications of 0.41 lbs a.i./A (4.5 

lbs a.i./A ÷ 11) were applied with a fourteen-day reapplication interval that spreads the 

applications across the growing season to September 19th. These dates of application are within 

the weed-growing season and selected to result in high-end concentrations in ground water due 

to vulnerability to precipitation.
15

Chemical inputs for the residues of concern follow the PRZM-GW Input Parameter 

Guidance (USEPA, 2012b). The aerobic soil metabolism half-life model input (132 days) is the 

upper 90th percentile confidence bound on the mean of two residue-of-concern half-lives from 

studies conducted at 25°C. The organic carbon partition coefficient (44 L/kgOC) is the mean of 

five values for clethodim sulfoxide, which is the most prominent degradate of concern and more 

mobile in soil than clethodim.

Table 10. PRZM-GW Input Parameters for Clethodim ROC A

Input Parameter Value Justification Source

Application Rate 0.46 kg a.i./ha Maximum annual application rate 

divided by 11 applications per year 

due to PRZM-GW limitations

Current labels

Applications per Year 11; every year

Reapplication interval 14 days Spreads applications from May 1 to 

Sep. 19 Current label

Initial application date May 1

Selected within growing season and 

for high-end vulnerability due to 

precipitation

(calculated)

Hydrolysis Half-life 3660 d Represents the value at pH 7 for

clethodim residues of concern MRID 40974520

Aerobic Soil Metabolism

Half-life 132 d

Represents the upper 90% confidence 

bound on the mean of two half-lives 

for the residues of concern

MRIDs 40974523 

and 41376801

Organic Carbon Partition 

Coefficient (KOC) 44 L/kg

Represents the mean KFOC value 

(n=5) for clethodim sulfoxide, the 

most prominent degradate of concern

MRID 40974523

A

 Source data are in Tables 2 and 6.

All six available scenarios were modeled as surrogates for non-cropped, fallow, or alfalfa 

use sites with the maximum annual application rate of 4.5 lbs a.i./A. The Wisconsin corn 

scenario produced the highest EDWCs, which is typical, with the other scenarios resulting in 

EDWCs 41-84% less. PRZM-GW outputs are listed in Table 11.

Table 11. PRZM-GW Output for Clethodim Uses A

Use Site Modeled 

Scenario

Max. Daily 

Conc. (μg/L)

Mean Breakthrough 

Time (yrs)

Post-breakthrough 

Mean (μg/L)

Non-cropped/alfalfa DMV corn 828 1.6 602

Non-cropped/alfalfa FL citrus 845 1.6 608

Non-cropped/alfalfa FL potato 225 3.2 194

Non-cropped/alfalfa GA peanut 314 4.7 271

Non-cropped/alfalfa NC cotton 686 3.9 555

Non-cropped/alfalfa WI corn 1430 4.3 1150 A Maximum values are in bold.

Figure 1 displays concentrations in ground water over time for the Wisconsin corn 

scenario. EDWCs were not highly sensitive to application dates, which is expected for residues 

in ground water since the medium typically moves slower than surface water. For example, the 
16

maximum daily concentration for the Wisconsin scenario was 1,390 μg/L (3% less) for 

applications beginning on April 1st rather than May 1st

.

Figure 1. Ground Water EDWCs (ppb) per Time (years) for the Wisconsin Scenario

4. Modeling Results Summary

Table 12 summarizes the screening-level exposure model results for clethodim ROCs. 

Table 12. Screening-Level ROC EDWCs for Clethodim Uses A

Source (Tier: Model) Use Site

(Max. Annual App. Rate)

Acute 

EDWC 

(μg/L)

Chronic 

EDWC 

(μg/L)

Surface water (Tier I: FIRST) Non-cropped (4.5 lbs a.i./A) 330 137

Ground water (Tier I: PRZM-GW) Non-cropped (4.5 lbs a.i./A) 1,430 1,150

Ground water (Tier I: SCI-GROW) Non-cropped (4.5 lbs a.i./A) ≤27 A Maximum values in bold.

Because eighteen applications of clethodim per year are not expected to be applied on 

any use site, including non-cropped areas and alfalfa, reduced use patterns were modeled to 

explore the resulting exposure estimates that may better characterize typical use patterns and 

could be the result of the exposure assessment if use directions on current labels are updated to 

reflect the reduced use patterns. If the Wisconsin scenario in PRZM-GW is re-run with a 

maximum annual application rate of 2.0 lbs a.i./A (8 applications per year at 0.28 kg a.i./A each) 

rather than 4.5 lbs a.i./A, then the acute EDWC is reduced 57% from 1,430 μg/L to 613 μg/L. A 

maximum annual application rate of 1.0 lb a.i./A (4 applications per year at 0.28 kg a.i./A each), 

which is consistent with the current use on mint, results in an acute EDWC of 295 μg/L. A 

maximum annual application rate of 0.5 lbs a.i./A (2 applications per year at 0.28 kg a.i./A each), 

which is consistent with many current uses including cotton, peanuts, and potatoes, results in an 

acute EDWC of 148 μg/L (158 μg/L if the initial application date is moved to April 1st). Note 

that the explored reductions in annual application rate reflect reductions in the number of 

applications per year and not reductions in the single application rate.
17

Note, also, that clethodim biodegrades within days of application. If the degradates of 

concern are shown to be much less toxic than clethodim, then exposure estimates would be 

greatly reduced. The acute EDWC of 1,430 μg/L for the ROCs is reduced to 3.2 μg/L if 

clethodim alone were the residue of concern. In shallow, acidic aquifers that are common on the 

east coast, clethodim-only EDWCs would be <0.1 μg/L, if clethodim’s degradates were not of 

concern.

5. Monitoring Data

Clethodim does not appear to be an analyte in the following water monitoring programs:

the California Department of Pesticide Regulation (CDPR) surface water database 

(http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm, the USGS NAWQA surface and 

ground water database (http://infotrek.er.usgs.gov/apex/f?p=136:1:0::NO:::), the USEPA 

STORET Data Warehouse (http://www.epa.gov/storet/), and the USDA Pesticide Data Program 

drinking water monitoring analyses 

(http://www.ams.usda.gov/AMSv1.0/ams.fetchTemplateData.do?template=TemplateG&navID=

&rightNav1=&topNav=&leftNav=ScienceandLaboratories&page=PDPDownloadData/Reports&

resultType=&acct=pestcddataprg).

6. References

USEPA. 2007. Kaul, M. Maximum Number of Crop Cycles per Year in California for Methomyl 

Use Sites. U.S. Environmental Protection Agency, Office of Prevention, Pesticides, and 

Toxic Substances, Biological and Economic Analysis Division. Memorandum to the 

Environmental Fate and Effects Division. Feb. 28, 2007.

USEPA. 2008. Dean, R. and J. Angier. Registration Review – Preliminary Problem Formulation 

for the Ecological Risk Assessment of Clethodim. DP barcode 349758. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. Memorandum to the Special Review and Reregistration Division. Aug. 

13, 2008.

USEPA. 2009. Guidance for Selecting Input Parameters in Modeling the Environmental Fate 

and Transport of Pesticides. Version 2.1. U.S. Environmental Protection Agency, Office 

of Pesticide Programs, Environmental Fate and Effects Division, Oct. 22, 2009. 

http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

USEPA. 2012a. Identification and Evaluation of Existing Models for Estimating Environmental 

Pesticide Transport to Groundwater. Final Report (Draft). U.S. Environmental Protection 

Agency; Health Canada. Jan. 27, 2012.

USEPA. 2012b. Guidance for Selecting Input Parameters for Modeling Pesticide Concentrations 

in Groundwater Using the Pesticide Root Zone Model. Version 1.0. U.S. Environmental 

Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects 

Division; Health Canada, Pesticide Management Regulatory Agency, Environmental 

Assessment Directorate. Oct. 15, 2012.
18

USEPA. 2012c. Guidance on Development and Use of Percent Cropped Area and Percent Turf 

Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update. 

Internal Environmental Fate and Effects Division memorandum. U.S. Environmental 

Protection Agency, Office of Chemical Safety and Pollution Prevention. Mar. 16, 2012.

USEPA. 2012d. Approval of PRZM-GW for Use in Drinking Water Exposure Assessments. 

Internal Environmental Fate and Effects Division memorandum. U.S. Environmental 

Protection Agency, Office of Chemical Safety and Pollution Prevention. Dec. 11, 2012. 

http://www.epa.gov/oppefed1/models/water/przm_gw/wqtt_przm_gw_guidance.htm

6.1. Submitted Environmental Fate and Product Chemistry Studies

MRID Citation Reference

40974520 Pack, D. (1988) Hydrolysis Study on RE-45601: Project ID: MEF-0013/ 8703899. Unpublished 

study prepared by Chevron Chemical Co. 52 p. 

40974522 Pack, D. (1988) The Aerobic Soil Metabolism of ?Propyl-1-?carbon 14|Clethodium: Project ID: 

MEF/0014/8721028. Unpublished study prepared by Chevron Chemical Co. 54 p. 

40974523 Pack, D. (1988) Freundlich Soil Adsorption/Desorption Coefficients of Clethodim and Three 

Metabolites: Project ID: MEF-0102/ 8829844. Unpublished study prepared by Chevron 

Chemical Co. 122 p. 

40974524 Rose, A.; Suzuki, J. (1988) Characterization of |carbon 14| Residues in Bluegill Sunfish Treated 

with (Allyl-2-|Carbon 14|- Clethodim or (Cyclohexene-1-One-4,6-?carbon 14|)-Clethodim: Project ID: MEF-0020. Unpublished study prepared by Chevron Chemi- cal Co. 109 p. 

40974531 Forbis, A. (1987) Uptake, Depuration and Bioconcentration of Allyl-2 |carbon| and 

Cyclohexene-1-One-4,6|carbon| RE-45601 to Bluegill Sunfish (Lepomis macrochirus): Project 

ID: S-2827. Un- published study prepared by ABC Laboratories, Inc. 87 p. 

41030133 Chen, Y. (1988) Allyl-2-Carbon 14|-Clethodim Photodegradation in Water: Project ID MEF0025. Unpublished study prepared by Chev- ron Chemical Co. 93 p. 

41030134 Chen, Y. (1988) 4,6-Ring-Carbon 14|-Clethodim Photodegradation in Water: Project ID MEF0024. Unpublished study prepared by Chev- ron Chemical Co. 97 p. 

41030135 Chen, Y. (1988) Clethodim Photodegradation on Soil: Project ID MEF- 0022. Unpublished 

study prepared by Chevron Chemical Co. 44 p. 

41030207 Ho, B. (1989) Field Dissipation Study with Clethodim on Cotton in Mississippi--T7227: Project 

ID 1641-88-7227. Unpublished study prepared by Chevron Chemical Co. 512 p. 

41030208 Ho, B. (1989) Field Dissipation Study with Clethodim on Cotton in California--T7226: Project 

ID 1641-88-7226. Unpublished study prepared by Chevron Chemical Co. 427 p. 

41030209 Ho, B. (1989) Field Dissipation Study with Clethodim on Soybean in North Carolina--T7229: 

Project ID 1641-88-7229. Unpublished study prepared by Chevron Chemical Co. 501 p. 

41030210 Ho, B. (1989) Field Dissipation Study with Clethodim on Soybean in Iowa--T7228: Project ID 

1641-88-7228. Unpublished study prepar- ed by Chevron Chemical Co. 536 p. 

41376801 Pack, D. (1990) The Aerobic Soil Metabolism of Clethodim Using ?Ring-4,6-(Carbon 14)|- and 

?Allyl-2-(Carbon 14)|-Clethodim Revised January 5, 1990: Lab Project ID: MEF0015/0016/8914823. Unpublished study prepared by Chevron Chemical Co. 161 p. 

41652301 Tucker, B. (1990) The Anaerobic Aquatic Metabolism of Ring-4,6- ?carbon 14||Clethodim: Lab 
19

MRID Citation Reference

Project Number: MEF-0141/9004983. Unpublished study prepared by Chevron Chemical Co. 85 

p. 

45591605 Hiscock, A., R. Warren, and B. Patterson. A Small-Scale Prospective Groundwater Monitoring 

Study for Oxamyl. DuPont Report No. AMR 4318-97. Unpublished study conducted by Stone 

Environmental, Inc., Ecologic, Inc., Agricultural Systems Associates, AGVISE Laboratories, 

Centre Analytical Laboratories, Inc., and E.I. du Pont de Nemours and Company; submitted by 

E.I. du Pont de Nemours and Company, Wilmington, DE. Jan. 14, 2002.

48881401 Gregory, A. (2012) Clethodim TGAI: Summary of Product Properties Test Guidelines. Project 

Number: ALB12/14. Unpublished study prepared by Albaugh, Inc. 8p.

48881405 Li, H. (2012) Chemical and Physical Characterization of Clethodim TGAI: Color, Physical 

State, Odor, Stability, pH, Oxidation/Reduction, UV-Vis, Boiling Point, Density, Viscosity, 

Dissociation Constant, Partition Coefficient and Solubility: Final Report. Project Number: 

NC/2011/083. Unpublished study prepared by Nutrichem Laboratory Co., Ltd. 87p.

Appendix A. Exposure Model Input/Output Files