OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION 

### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

June 24 , 2013

PC Code: 12101 1 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 (7509 P)

Ricardo Jones, Chemical Review Manager Neil Anderson, Branch Chief RMIB1 / PRD (7508 P)

This Environmental Fate and Effects Division (EFED) memorandum is a drinkin g water exposure assessment based on currently labeled u ses of clethodim ( list ed 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

- ethy lthiopropyl)

- 5

- hydroxycyclohexene

- 3

- one or 5

- (2

- ethylthiopropyl )cyclohexene

- 3

- one moieties

.

The maximum screening

- level acute and chronic EDWC s (1,4 30 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 contamin ation . These EDWCs are 43

- 5 3 x greater than screening

level EDWCs for ground water from SCI

- GROW and 4

- 8x greater than screening

- level EDWCs f

or surface water from FIRST ( Table 1 ). The variance with SCI

- GROW may be due, in part, to 1) PRZM

- GW being mechan istic, whereas SCI

- GROW is empirical , and 2) differences in modeling assumptions such as the duration of the modeling scenario

.

### 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) 1,4 30 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 m eter 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, 2012 a ) and up to one order of magnitude longer than observed for oxamyl (MRID 45591605). With an error of
approx imately 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, t he 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 pesticide

treated areas. Therefore, in most wells, horizontal convection and dispersion may at tenuate persistent, dissolved re sidues 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 ma gnitude 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 we re 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 li sted 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 seaso nal 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

2

### 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 r eapp lication interval of 14 days is labeled for a variety of uses. In the absence of label directions, a reapplication interva l 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) Rea pp. 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 Geo graphic Applicability
Fallow land, golf course turf, non

cropped 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, non

bearing 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 Chemi

gation 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



### 3Use Pattern Single App. Rate (lbs a.i./A) Rea pp. 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 Geo graphic 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 Rea pplication intervals of 14 days were labeled for a variety of uses . I n 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 ye ar. 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 a irports, 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, s tone 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 h ave 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 p rovided 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 ( C 12 

### H 10 

### Cl N 3 

### O) (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

- m 3 

### /mol (Calculated)



### 4

### Parameter Value Source Log octanol

- to

- water partition coefficient (log K OW 

### ) 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 4 0974522 Photolysis half

- life in soil (13

- 23 ° C) 7 days MRID 41030135 Mobility
Freundlich soil

- water partition coefficients (K F 

### ); Freundlich organic carbon

- normalized coefficients (K FOC 

### ) 0.08, 0.15, 0.46, 0.51, 1.57 L/kg; 4.9, 65, 68, 132, 271 L/kg OC 

### MRID 40974523

Field Dissipation Terrestrial field dissipation half

- life Half

- lives and leaching depths coul d 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 (steady

state, total residues); depuration rate 0.7

- 2.1 ( edible ), 3 .0

- 4 .0 (ine dible ), 2.3

- 3.6 ( whole fish ); >70% depuration in 3 days MRID 409745 24 / 409745 3 1

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 cyclohe xane 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 cis

trans 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

5

### Appendix D provides a more complete discussion of the complex i somerism 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 an d 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 lowe r 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 day s after application. Clethodim sulf one 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.

C lethodim ’s sulfoxide and sulfon e 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 mobili ty.

Table 4

. Environmental Fate Parameters of Clethodim Degradates

Parameter Degradate Value Source
Freundlich organic carbon

- normalized coefficients (K FOC 

### ) Clethodim sulfoxide 12

, 27

, 3 8, 57

, 86 L/kg OC 

### MRID 40974523 Clethodim sulfone 6
, 13

, 19

, 29

, 43 L/kg OC 

### Clethodim oxazole sulfoxide 50

, 135

, 429

, 460

, 771 L/kg OC



### 6

### Table 5

. Chemical Names and Structures of Clethodim and Its Environmental Degradates A


### Code Name/ S ynonym Chemical N ame Chemical S tructure Study Type Ref. B 

### (MRID) Maximum %AR (day) Final %AR (study length)

PARENT 

### Clethodim
RE

- 45601 (Z

- isomer is

RE

- 46116) (5 RS )

- 2

- {(1 EZ )

- 1

- [(2 E )

- 3

- chloroallyloxyimino]propyl}

- 5

- [(2 RS )

- 2

- (ethylthio)propyl]

- 3

- hydroxycyclohex

2

- en

- 1

- one

CAS No.: 99129

- 21

- 2 Formula: C 17 H 2 6 ClNO 3 S MW: 359.92 g/mol SMILES: C1C(CC(=C(C1=O) \ C(CC)= N \ OCC=CCl)O)CC(C)SCC S O H O

N O Cl

TRANSFORMATION PRODUCTS 

### Clethodim

s ulfoxide
RE

- 45924 CLSO SOX (5 RS )

- 2

- {(1 EZ )

- 1

- [(2 E )

- 3

- chloroallyloxyimino]propyl}

- 5

- [(2 RS )

- 2

- (ethy lsulfinyl )propyl]

- 3

- hydroxycyclohex

- 2

- en

- 1

- one

Formula: C 17 H 26 ClN O 4 S MW: 375.92 g/mol SMILES: C1C(CC(=C(C1=O) \ C(CC)= N \ OCC=CCl)O)CC(C)[S](CC)=O S O H 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 4 1030133 5.2% (3 d) 14% ( 3 d) 1.4% (10 d) nd (30 d) Aq. photo.

– dark Aq. photo.

– light 4 1030134 3.6% (3 d) 14% ( 30 d) 2.7% (10 d) 14% ( 30 d) Aq. photo.

– dark Aq. photo.

– light 4 4066701 4.6% (25 d) 7.6% (1 d) 4.4% (3 0 d) nd (30 d) Soil photo.

– dark Soil photo.

– light 4 1030135 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 (5 RS )

- 2

- {(1 EZ )

- 1

- [(2 E )

- 3

- chloroallyloxyimino]propyl}

- 5

- [(2 RS )

- 2

- (ethy lsulfonyl )propyl]

- 3

- hydroxycyclohex

- 2

- en

- 1

- one

Formula: C 17 H 26 ClN O 5 S MW: 391.92 g/mol SMILES: C1C(CC(=C(C1=O) \ C(CC)= N \ OCC=CCl)O)CC(C)[S](CC) (=O) =O S O H 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)

### Code Name/ S ynonym Chemical N ame Chemical S tructure 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: C 14 H 21 N O 2 S 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 4 1030134 14% (2.5 d) 5.5 % ( 3 d) 14% (2.5 d) 0.5% (14 d) Aq. photo.

– dark Aq. photo.

– light 4 4066701 34% (30 d) 12% (1 .5 d) 34% (3 0 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: C 14 H 21 N O 3 S 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 4 1030134 1.2% (2.5 d) 5.9% (10 d) 1.0% (14 d) nd (30 d) Aq. photo.

– dark Aq. photo.

– light 4 4066701 1.9% (30 d) 8.9 % ( 6 d) 1.9% (3 0 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: C 14 H 21 N O 4 S 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: C 14 H 23 N O 2 S MW: 269.41 g/mol SMILES: C1C(CC(=C(C1=O)C(CC)=N )O)CC(C)SCC S O H O

N H Aq. photo.

– light 4 1030134 18% ( 2.5 d) 18% ( 2.5 d)
Aq. photo.

– dark Aq. photo.

– light 4 4066701 1.4% (25

- 30 d) 28% ( 2 d) 1.4% (3 0 d) nd (30 d)

Anaerobic aquatic 41652301 1.3

- 17 % B (181 d) 1.3

- 17 % B (181 d)



### 8

### Code Name/ S ynonym Chemical N ame Chemical S tructure 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: C 14 H 23 N O 3 S MW: 285.41 g/mol SMILES: C1C(CC(=C(C1=O)C(CC)=N )O)CC(C)[S](CC)=O S O H O

N H

O Aq. photo.

– light 4 1030134 23 % ( 21 d) 20 % ( 30 d) Aq. photo.

– dark Aq. photo.

– light 4 4066701 0.5% (25 d) 30% (1 0 d) 0.4% (3 0 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: C 12 H 17 N O 3 MW: 223.27 g/mol SMILES: C1C(CC(=C(C1=O)C(CC)=N )O)CC(=O)C O

O H O

N H Aq. photo.

– light 4 1030134 12% ( 15, 25 d) 9.5 % ( 30 d)

Aq. photo.

– light 4 4066701 15 % ( 2

- 4 d) 5.8% (30 d)



### Clethodim

trione TRIONE (±)

- 5

- [2

- (ethylthio)propyl]

- 3

- hydroxy

- 2

- (1

- oxopropyl)cyclohex

- 2

- enone

Formula: C 14 H 22 O 3 S MW: 270.39 g/mol SMILES: C1C(CC(=C(C1=O)C(CC)=O )O)CC(C)SCC S O H O

O Aq. photo.

– light 4 4066701 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: C 14 H 22 O 4 S MW: 286.39 g/mol SMILES: C1C(CC(=C(C1=O)C(CC)=O )O)CC(C)[S](CC)=O S O H O

O

O Aq. photo.

– light 4 1030134 4.4% ( 0.5 d) 2.7% (2.5 d)

Aq. photo.

– light 4 4066701 18% ( 20

- 30 d) 18% (30 d)



### Clethodim

trione ketone (±)

- 5

- [propyl

- 2

- one]

- 3

- hydroxy

- 2

- (1

- oxopropyl)cyclohex

- 2

- enone

Formula: C 12 H 16 O 4 MW: 224.26 g/mol SMILES: C1C(CC(=C(C1=O)C(CC)=O )O)CC(=O)C O

O H O

O Aq. photo.

– light 4 1030134 5.3% (2 0 d) 4.8 % (30 d)



### 9

### Code Name/ S ynonym Chemical N ame Chemical S tructure 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: C 12 H 17 N O 3 MW: 223.27 g/mol SMILES: C1C(CC(=C(C1=O)C(CC)=N )O)CC(=O)C O

O H O

N H Aq. photo.

– light 4 1030134 12% ( 15, 25 d) 9.5 % ( 30 d)

Aq. photo.

– light 4 4066701 15 % ( 2

- 4 d) 5.8% (30 d)



### DME

sulfoxide
RE

- 52453 DMESO (±)

- 3

- [2

- (ethylsulfinyl)propyl]pentanedioic acid

Formula: C 10 H 18 O 5 S MW: 250.32 g/mol SMILES: C(C(CC(=O)O)CC(C)[S](CC) =O)C(=O)O 

### S
O O

O O H

O H Aq. photo.

– light 4 1030134 49% ( 30 d) 49% ( 30 d)

Aq. photo.

– light 4 4066701 11 % ( 20

- 30 d) 11 % (30 d)



### DME sulfone DMESO2 (±)

- 3

- [2

- (ethylsulfonyl)propyl]pentanedioic acid

Formula: C 10 H 18 O 6 S MW: 266.32 g/mol SMILES: C(C(CC(=O)O)CC(C)[S](CC) (=O)=O)C(=O)O 

### S
O O

O O H

O H O Aq. photo.

– light 4 1030134 7.4% (30 d) 7.4% (30 d)



### Unknown

- 2 (±)

- 3

- [propyl

- 2

- one]pentanedioic acid (proposed chemical name) 

### O O

O O H

O H

(proposed chemical structure) Aq. photo.

– light 4 1030134 7.4% (30 d) 7.4% (30 d)



### 3

- chloroprop

enal ( E )

- 3

- chloro propenal

Formula: C 3 H 3 ClO MW: 90.51 g/mol SMILES: O=CC=CCl 

### O Cl Aq. photo.

– light 4 1030133 31 % ( 2.5 d) 31 % ( 2.5 d)



### Chloroallyl

alcohol
RE

- 46261 ( E )

- 3

- chloroallyl alcohol

Formula: C 3 H 5 ClO MW: 92.53 g/mol SMILES: OCC=CCl 

### O H 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 4 1030133 11% (2.5 d) 31 % ( 15 d) 11% (2.5 d) 29 % ( 30 d)



### 10

### Code Name/ S ynonym Chemical N ame Chemical S tructure Study Type Ref. B 

### (MRID) Maximum %AR (day) Final %AR (study length)
Unextracted

residues (not applicable)

(n ot 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: CO 2 MW: 44. 0 1 g/mol SMILES: O=C=O 

## O O Aq. photo.

– light 4 1030133 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. , whe ther the residue was one

degradate, the other, or both.



### 11

### 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 re sidues 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 Residue s 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 4 0974522 Photolysis half

- life in soil (13

- 23 ° C) No observable degradation MRID 41030135 Mobility Freundlich organic carbon

- normalized coefficients (K FOC 

### ) 12

, 27

, 3 8, 57

, 86 L/kg OC 

### 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 K OC 

### value of 44 L/kg, clethodim sulfoxide is more mobile in soil than clethodim and its oxazole sulfoxi de, but less mobile in soil than clethodim sulfone; therefore, use of its K OC 

### 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 u sing 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

12

### 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 P arameters for C lethodim ROC A



### Input Parameter Value Comments Source Application rate (lbs a.i./A) 0. 25 Maximum labeled single application rate Current label s Number of applications per
year 18 Maximum number of applications per
year assumed in the absence of label directions Current label s

Application interval (d) 7 Reapplication interval assumed in the absence of label directions Current label s

Percent cropped area 100% Default for agricultural plus non

agricultural uses USEPA, 2012 c

Organic Carbon Partition Coefficient (K OC 

### ) (L/kg) 44 Represents the mean K FOC 

### value (n=5 ) for clethodim sulfox ide, the most prominent degradate of concern MRID 4 0974523

Aerobic soil metabolism half

- life (days) 132 Represents the upper 90% confi dence bound on the mean of two half

- lives for the residues of concern MRID s 4 0974523 and 41376801

Wetted in? No Not required Current label s Method of application Aerial Allowed a pplication method Current label s Solubility in water (ppm) 29 Solubility in water at 20°C MRID 4 8881405 Aerobic aquatic metabolism half

- life (days) 264 Represents t he 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 se lected to be two times the soil metabolism input value

. The aqueous photolysis half

- life input represents the maximum study value at pH 7. The K OC 

### input (44 L/kg) represents the mean value for clethodim sulfoxide, which is the most prominent residue of c oncern.
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, 2012 c ). Because clethodim is labeled for use on both agricultural and non

- agricultural sites, PCA values can not be used to modify clethodim exposur e estimates.

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

13

### 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 SCI

GROW (v2.3, Jul. 29, 2003) and PRZM

- GW (v1.01, Dec. 26, 2012) (USEPA, 2012 d )

. Input parameters for SCI

- GROW appear in Table 9 . The lowest Freundlich organ ic carbon partition coefficient for clethodim sulfoxide (K FOC 

### = 12 L/kg OC 

### ) was selected because the sulfoxide is more mobile in soil than the parent compound and is the most p rominent 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 P arameters for C lethod im ROC A



### Input Parameter Value Comments Source Application Rate (lbs a.i./A) 0. 25 Maximum labeled single application rate Current label s

Applications per Year 18 Maximum number of applications per
year assumed in the absence of label directions Current label s

Organic Carbon Partition Coefficient (K OC 

### ) (L/kg OC 

### ) 12 Represents the lowest K FOC 

### value for clethodim sulfoxide, the most prominent degradate of concern , chosen because of the greater than three

- fold variation in values MRID 4 0974523

Aerobic Soil Metabolism Half

- life (days) 66 Represents the mean of two half

- lives for the residues of concern MRID s 4 0974523 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 1 st 

### , 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 19 th 

### . 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.

14

### Chemical inputs for the residues of concern follow the PRZM

- GW Input Parameter Guidance (USEPA, 2012 b ). The aerobi c soil metabolism half

- life model input (132 days) is the
upper 90 th 

### percentile con fidence bound on the mean of two residue

- of

- concern half

- lives from studies conducted at 25°C. The organic c arbon partition coefficient (44 L/kg OC 

### ) is the mean of five valu es for clethodim sulfoxide , which is the most prominent degradate of concern and more

m obile 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 a pplication 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% confi dence bound on the mean of two half

- lives for the residues of concern MRID s 4 0974523 and 41376801

Organic Carbon Partition Coefficient (K OC 

### ) 44 L/kg Represents the mean K FOC 

### value (n=5 ) for clethodim sulfoxide, the most prominent degradate of concern MRID 4 0974523

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 lb s a.i./A

. T he 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

15

### maximum daily concentration for the Wisconsin scenario was 1, 39 0 μg/L (3% less) for applications beginning on April 1 st 

### rat her than May 1 st



### .

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

4. Modeling Results Summary

T able 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) 1,4 30 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 consis tent 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 potato es, results in an acute EDWC of 148 μg/L (158 μg/L if the initial application date is moved to April 1 st 

### ). N ote that the explored reduction s in annual application rate reflect reduction s in the number of applications per year and not reduction s in the single application rate

.

16

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

concern a re 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 ROC s is reduced to 3.2 μg/L if clethodim alone were the residue of concern. In shallow

, acid ic 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.c a.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/Report s& 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, Pesticide s, and Toxic Substances

, Biological and Economic Analysis Division. Memorandum to the Environmental Fate and Effects Division . Feb. 28 , 200 7

. USEPA. 2008. Dean, R. and J. Angier. Registration Review

– Preliminary Problem Formulation for the Ecological Risk Assessment of Clethodim. DP barcode 34 9758. 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 Model ing 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. 2012 a . 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. 2012 b . Guidance for Selecting Input Parameters for Modeling Pesticide Concentrations in Groundwater Using the Pesticide Root Zone Model

. Version 1.0. U.S. Environmental Protection Agenc y , Office of Pesticide Programs, Environmental Fate and Effects Division; Health Canada, Pesticide Management Regulatory Agency, Environmental Assessment Directorate

. Oct. 15 , 2012.

17

### USEPA. 2012 c . 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. 2012 d . 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 Clethodi m 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|

- Clethod im or (Cyclohexene

- 1

- One

- 4,6

- ?carbon 14|)

- Clethodim: Pro

- ject 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|carb on| 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 MEF

0025. 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 MEF

0024. 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 Chev ron 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. Unpu blished 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: MEF

0015/0016/8914823. Unpublished study prepared by Chevron Chemical Co. 161 p.



### 18MRID Citation Reference

41652301 Tucker, B. (1990) The Anaerobic Aquatic Metabolism of Ring

- 4,6

- ?carbon 14||Clethodim: Lab 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 prep ared 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 Coeffic ient 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

19