OFFICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION 

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

March 31, 2015

PC Code: 12101 1
MEMORANDUM DP Barcode: 425767

SUBJECT : Clethodim : Drinking Water Exposure Assessment for Proposed New Uses and Crop Group Conversions regarding Stevia, Pome Fruit Group 11

- 10, Stone Fruit Group 12

- 12, Bulb Onion Subgroup 3

- 07A, Low

- growing Berry Subgroup 13

- 07G, Rapeseed Subgroup 20A, Sunflower Subgroup 20B, Cotton Seed Subgroup 20C, and Fruit ing Vegetable Group 8

- 10

FROM : Greg Orrick, Environmental Scientist

ERB2 /EFED (7507P)

THROUGH : Brian Anderson

, Branch Chief

ERB2 /EFED (7507P)

TO : Meheret Negussie

, Risk Assessor
Christine Olinger , Branch Chief

RAB3 /HED (7509 P)

Sydney Jackson, Risk Manager Barbara Madden, Team Leader

MUERB/RD (7505P)

Aswarthy Balan , Risk Manager Shaja Joyner

, Team Leader FHB/RD (7505 P)

This Environmental Fate and Effects Division (EFED) memorandum is a drinkin g water exposure assessment (DWA) of prop osed labeled u ses of clethodim (list ed in Table 2 )

. In light of the following three bullets, this DWA recommends use of the estimated drinking water concentrations (EDWC) of the previous DWA (USEPA, 2013) , which a re 1,430 μg/L (acute) and 1,150 μg/L (chro nic) (also listed in Table 1 ).

• The previous DWA assessed a maximum annual application rate of 4.5 pounds of active ingredient per acre (lbs a.i./A) using Tier I screening models.

• Representative uses have been assessed previously for most of the proposed crop groups

.

• Al l of the proposed uses are limited to a seasonal application rate of 0.5 or less lbs a.i./A

, which is less than the maximum assessed annual application rate of 4.5 lbs a.i./A.

1

### Table 1. Screening

- Level ROC EDWCs for Clethodim Uses A

Source (T ier: 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.



### T he clethodim residues of concern (ROC) include clethodim and degradates with 5

- (2

- ethylthiopropyl)

- 5

- hydroxycyclohexene

- 3

- one or 5

- (2

- ethylthiopropyl )cyclohexene

- 3

- one moieties

. The maximum use pattern for clethodim is for non

- cropped ar eas, fallow ground, and
alfalfa

. Table 2 lists the proposed uses and crop group conversions and their maximum use
patterns

.

Table 2

. Proposed Use Patterns of Clethodim A

Proposed Use Pattern Similar
Current Use

Pattern Single App. Rate (lbs a.i./A) Rea pp. Interval

(days) Max. No. of App. per Crop Seasonal App. Rate (lbs a.i./A) App.

Method Additional
Restrictions

Stevia Herbs 0.125 14 NS 0.50 NS

– Pome fruit group 11

- 10 (None) 0.125 14 NS 0.50 NS

– Stone fruit group 12

- 12 Peach 0.125 14 NS 0.50 NS

–

Low

- growing berry

subgroup 13

- 07G Strawberry 0. 125 14 NS 0.50 NS

–

Rapeseed subgroup 20A Rapeseed /
canola 0.094 None NS 0.094 NS Do not apply after crop has begun bolting. Not
for use in CA.

Sunflower subgroup 20B Sunflower 0.25 NS B NS 0.50 NS

–

Cotton subgroup 20C Cotton 0.25 NS B NS 0.50 NS

– Bulb onion subgroup 3

- 07A C Onion, garlic,
shallot 0.125 14 NS 0.50 NS

–
Fruiting vegetable group

8

- 10 Fruiting vegetables 0.125 14 NS 0.50 NS

–

NS = “not stated”

A Listed use patterns represent those of the maximum use pattern and do not represent all labeled use patterns for
that use. B Reapplication interval on 12.6% a.i. label is 14 days, on 26.4% a.i. label is not stated. C Bulb onion subgroup 3

- 07A appears on 12.6% a.i. label, not on 26.4% a.i. label.



### USEPA. 2013

. Orrick, G. Clethodim: Drinking Water Exposure Assessment for Registration
Review . DP barcode 412704 . U.S. Environmental Protection Agency, Office of Chemical Safety and Pollution Preventi on , Environmental Fate and Effects Division. Memorandum
to the Health Effects Division and Pesticide Re

- evaluation Division. Jun

. 24 , 20 13

.

2