2

surface water and ground water for use in all other crops. It is important to note that the modeled 

total residues of concern of saflufenacil included saflufenacil parent, M01, M02, M07, M08, 

M15, M22, and Product 8, all of which are assumed to have similar toxicity to saflufenacil

parent.

The above stated values represent upper-bound estimates of total concentrations that might be 

found in surface water and ground water due to the use of saflufenacil as a herbicide on the 

current/proposed use patterns. If more information or refinement is needed, please call 

Mohammed A. Ruhman at (703) 605-0644 or email: ruhman.mohammed@epa.gov

I. BACKGROUND

Four drinking water exposure assessments were conducted:

The 1st Assessment 1

: A surface/ground drinking water exposure assessment for section 3 new 

chemical uses on agricultural and non-agricultural areas (DP Barcode: 349860 dated April 15, 

2009): This assessment reported the modeled EDWCs for the stressor (i.e., residues of concern) 

in drinking water resulting labeled uses at that time. This assessment was based on labeled uses 

on Christmas trees; citrus; conifer and hardwood plantations; corn (field, sweet, and pop); cotton, 

fallow and post-harvest applications; grape vines; legume vegetables; non-agricultural areas; 

pome fruits; small grains; sorghum; soybeans and sunflower. The maximum label rate consisting 

from a single application rate of 0.356 lb a.i/A for use on Christmas trees; citrus; conifer and 

hardwood plantations; and non-agricultural areas. Tier 1 FIRST modeling for surface water and

older version of PRZM-GW for ground water were used. In this respect it is noted that input 

parameters for the current PRZM-GW were changed following this assessment.

The 2nd Assessment 2

: A surface drinking water exposure assessment for section 3 new 

chemical use on rice “Pre-plant burn-down” (DP Barcode: 384975 dated March, 03, 2011) This 

assessment was based on pre-plant/pre-flood use on rice at a rate of 0.0445 lb a.i/A with specific 

use restrictions. Tier 1 Rice Model (ver. 2) was used in modeling which allows aerobic soil 

degradation of the pre-flood applied chemical in addition to partitioning and degradation in the 

rice paddy for the left over chemical residues.

The 3rd Assessment 3

: A Tier II Drinking Water Exposure Assessment for Saflufenacil (Section 

3 New Chemical Uses as a harvest aid on dry edible beans, dry peas, soybean, oilseeds 

“sunflower subgroup 20B”, oilseeds “cotton subgroup 20C”, and oilseeds canola “subgroup 

20A”.

 1 The 1st Assessment: Tiered Drinking Water Exposure Assessment for Saflufenacil (Section 3 New Chemical Uses 

on Agricultural and Non-agricultural Areas; DP Barcode: 349860 dated April 15, 2009. 2 The 2nd Assessment: Tier II Drinking Water Exposure Assessment for Saflufenacil (Section 3 New

Chemical Uses on Rice (Pre-plant Bum-down); DP Barcode: 3849750 dated March 3, 2011. 3 The 3rd Assessment: Tier II Drinking Water Exposure Assessment for Saflufenacil (Section 3 New Chemical Uses 

as a harvest aid on dry edible beans, dry peas, soybean, oilseeds “sunflower subgroup 20B”, oilseeds “cotton 

subgroup 20C”, and oilseeds canola “subgroup 20A”; DP Barcodes: 380641 and 381294 dated April 1, 2011.
3

The 4th Assessment(Attached): A surface drinking water exposure assessment for the proposed

new use pattern on rice (EPA Reg. No. 7969-278)4 and the new master label for saflufenacil 

formulations (EPA Reg. No. 7969-323)

5

. This assessment was based on these two labels which 

included the following changes:

(a) A maximum application rate for all crops, including rice, is 0.134 lb a.i/A instead of the 

previous maximum rate of 0.356 lb a.i/A ;

(b) The aerobic soil half life and partitioning coefficient (Koc) were entered as per guidance 

to the current version of PRZM-GW (refer to referenced document for these changes)

(c) New crop-specific use restrictions/limitations for rice (refer to referenced document for 

these changes)

II. CURRENT ASSESSMENT

This current assessment is for the new use patterns on Barley, Wheat and Triticale; Perennial 

forage grasses (grown in pastures and range land or in field grown for forage, silage and hay; 

and on Olive Trees. Important application parameters for the new use labels are summarized 

in Table 1.

Table 1 New use patterns for saflufenacil herbicide for broadleaf weed control (MSR= Maximum

single application rate in lbs a.i/A; MNOA= Maximum number of applications; MA or SR= Maximum annual or seasonal 

application rate in lbs a.i/A; and MAI= Minimum application intervals in days; AP= Application procedure= G= ground and A= 

aerial)

Crop Application Types Purpose MSR MNOA MA or SR MAI AP Notes

Barely, 

Wheat and 

Triticale Desiccation

Harvest 

aid/weed 

control

0.022 

or 

0.045

One or 

Two 0.045

N/A or 

N/S1 G or A

EPA Reg. No. 7969-

278

Cool and 

Warm 

Season 

Perennial 

Forage 

Grasses in 

pastures, 

rangeland, 

and forage, 

silage and 

hay fields 

Burn-down to established 

stands of both types 

grasses during the dormant 

period

Burndown and 

residual 

weed 

control 0.090

One or 

Two 0.090 14 G or A

EPA Reg. No. 7969-

278 & EPA Reg. No. 

7969-297

Application timing as 

follows:

* For cool & warm 

dormant grasses: early 

spring, fall (postharvest) or during 

winter 

* For cool grasses: 

during the active 

growing period 

* For warm growing 

grasses: during the 

active growing period 

(after green-up in 

early spring)

Post-emergence burndown to established cool 

season grasses

In season 

weed 

control 0.045

One or 

Two 0.045 14 G or A

Post-emergence burndown to established warm 

season grasses

In season 

weed 

control 0.045

One or 

Two 0.045 14 G or A

Split application program

to established stands of 

both types grasses

Dormant 

stage 

weed 

control 0.090

One or 

Two 0.090 14 G or A

In season 

weed 

control 0.045

One or 

Two 0.045 14 G or A

Total for Cool and Warm Season Grasses 0.134 Two 0.134 14

 4 EPA Reg. No. 7969-278 (Sharpen® Powered by KIXOR® Herbicide): A supplemental Label For broadleaf weed 

control in rice production.

5 EPA Reg. No. 7969-323 (KIXOR® Herbicide): A broad leaf herbicide for use in field and row agricultural crops, 

bearing and nonbearing tree and vine crops, and in non-crop.
4

Crop Application Types Purpose MSR MNOA MA or SR MAI AP Notes

or four

Cool and 

Warm Grass 

Grown for 

Seeds

Burn-down

To newly planted seeds for 

both types of grasses 

Burndown 

weed 

control

0.022 

or 

0.045

One or 

Two 0.045

N/A or 

N/S1 G or A

Apply after 1st tiller in 

cool season grasses 

and after the 1st

rhizome in warm 

season grasses

Pre-plant/Pre-plant 

incorporated Or 

preemergence

Weed 

control 0.090

One or 

Two 0.090

14 

(Assume

d) G or A

Should target emerged 

weeds not the tree and 

prevent drift from 

reaching the trees. No 

applications are 

permitted during the 

bloom stage 

(flowering to start of 

fruiting) 

Split application program

Weed 

control 0.134

Two 

or four 0.134

14 

(Assume

d) G or A

Olive Trees

Postemergence-directed

weed control

Weed 

control 0.022

One to 

Four 0.090 21 G 1 N/A or N/S= Not applicable (only one application) or Not specified and is assumed to be 7 days because the chemical is used for desiccation at the crop 

maturation stage which is a short period of time.

Data for the new use patterns (Table 1) indicates that the maximum application rate needed for 

Tier 1 FIRST modeling is 0.134 lbs a.i/A. Therefore, surface water EDWCs for the new uses 

will be the same EDWCs obtained in the attached EFED last assessment. The same conclusion 

applies for EDWCs for ground water modeled by PRZM-GW. It is thus concluded that the 

attached assessment can cover all of the new uses.