Document ID: EPA-HQ-OPP-2010-0755-0009
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-05-11T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON, D.C.  20460
                                       
                                   OFFICE OF
                          PREVENTION, PESTICIDES, AND
                               TOXIC SUBSTANCES

	PC Code: 118203
	DP Barcode: 380641 and 381294

MEMORANDUM	Friday, April 01, 2011	

SUBJECT:	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".

TO:	Kathryn Montague, M.S., Product Manager 23
	Herbicide Branch
	Registration Division (RD) (7505P) 
	
	Dana Vogel, Branch Chief,
	Risk Assessment Branch 1,
	Health Effects Division (7509P)

FROM:	Mohammed Ruhman, Ph.D., Agronomist
	Environmental Risk Branch VI
	Environmental Fate and Effects Division (7507P)

THROUGH:	Mah Shamim, Ph.D., Branch Chief
	Environmental Risk Branch VI
	Environmental Fate and Effects Division (7507P)

Analysis of the proposed use for this submittal suggests that there is no need for additional modeling as it is expected that resultant EDWCs for the use patterns in this submittal would not exceed those reported in the earlier submittal referenced below. Therefore, the EDWCs of 173-180 ug/L for ground water and 24-37 ug/L for surface water may be considered conservatively acceptable for the use patterns included in this submittal.

This conclusion is based on analysis of the use pattern for this submittal compared to the use patterns considered in the previously estimated drinking water concentrations (EDWCs) for the screening drinking water exposure.  Previous use patterns and EDWCs were reported in EFED Memo entitled: Tiered Drinking Water Exposure Assessment for Saflufenacil: Section 3 New Chemical Uses on Agricultural and Non-agricultural Areas, April 15, 2009 (DP Barcode: 349860). The referenced EDWCs Memo covered the proposed saflufenacil uses on selected row crops, orchard trees, vineyards, tree plantations, and non-agricultural areas. Estimates were based on modeling of the use pattern on Christmas tree, conifer, and hardwood plantations and non-agricultural areas as it represent the maximum use rate (one aerial application per year at 0.356 lbs a.i./A).  In modeling, the 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.  EDWCs of the exposure estimates were reported 

Analysis of the application rates for the proposed use patterns for this submittal (a maximum seasonal rate of 0.089 lbs a.i/A) suggest that there is no need for additional modeling as it is much lower than the rate used previously (0.356 lbs a.i/A) and it is expected to give lower EDWCs compared to EDWCs reported for the earlier submittal referenced above (Table 1). Therefore, the EDWCs of 173-180 ug/L for ground water and 24-37 ug/L for surface water are considered conservatively acceptable for the use patterns included in this submittal.

Table 1 Previously calculated 1-in-10-year EDWCs for the proposed saflufenacil uses contained in EDWC Memo dated April, 15, 2009 (DP Barcode: 349860)
Source (Tier: Model)
                             Peak Exposure (μg/L)
                         Annual Mean Exposure (μg/L)
Surface water (Tier I: FIRST)
                                     37.3
                                     23.8
Ground water (Tier II: PRZM GW)
                                      180
                                      173

1. INTRODUCTION

Saflufenacil, is a new contact and residual herbicide in the uracil class of compounds that is absorbed by roots and foliage, with limited systemic activity, according to the proposed end-use product label, BAS 800 04H.  The compound belongs to the mode-of-action Group 14/Group E, meaning that it inhibits protoporphyrinogen-oxidase (PPO), resulting in an accumulation of protoporphyrins that, in the presence of UV light, can be photoactivated into reactive oxygen radicals that have the potential to cause oxidative damage to cell membranes.  Saflufenacil is proposed for use on broadleaf weeds via pre-plant and pre-emergence applications as well as desiccant and/or defoliant.

An ecological risk assessment was conducted for saflufenacil (BAS 800 H) as a new chemical
for use as a herbicide in the following crops cereal small grains, corn, chickpeas, cotton, edible beans, edible peas, lentils, lupine, sorghum, soybeans, sunflowers, fruit tree orchards, nut tree orchards, vineyards, fallow croplands, and non-agricultural areas including pine plantations, rights-of-way, bare ground, and Christmas tree plantations in addition to use as a desiccant and/or defoliant on sunflower (Memo and Section 3 New Chemical Environmental Fate and Ecological Risk Assessment dated June 16, 2009 (DP Barcode 349855). In addition a Tiered Drinking Water Exposure Assessment for Saflufenacil (Section 3 New Chemical Uses on Agricultural and Non-agricultural Areas was issued April 15, 2009 (DP Barcode: 349860) for these same uses.

In 2010, the registrant requested a label amendment for use on citrus and nut trees in addition to   proposing a new use on rice as a pre-plant weeds burn-down. The Environmental Fate and Effects Division (EFED) have issued a preliminarily review for that use and responded to both proposals in a Memo entitled Preliminary Review of Proposed Label Amendments for Saflufenacil dated August 4, 2010 (DP Barcodes 378968 and 379645).  For citrus and nut trees, EFED recommended the acceptance of the referenced amendment in addition to requesting an update to the crop-specific restrictions and limitations on the label with respect to drift for uses on citrus and nut trees to reflect those for uses with the proposed application rate of 0.088 lbs a.i./A.  For this particular amendment, EFED recommended that there is no need for conducting ecological risk assessments. In contrast, for the use on rice, EFED recommended conducting an ecological risk assessment, a drinking water exposure assessment and requesting aquatic field dissipation. Furthermore, clarification was encouraged of the proposed label language for use on rice to specify all application restrictions. 

In 2011, the registrant submitted a modified label for rice in addition to a waiver request for conducting aquatic field dissipation (AFD) study to support this use. Following the review of the new label and waiver request, EFED executed the following:

 (1) A drinking water exposure assessment (Saflufenacil Rice revised Drinking Water Assessment (DP Barcode 384975, March 03, 2011); and
    
 (2) An ecological risk assessment for the proposed Section 3 New Use for Saflufenacil (Rice, Pre-plant Burn-down) (DP Barcode: 387336, March 09, 2011).

In addition, EFED rejected the registrant waiver request for conducting the aquatic field dissipation study (AFD, guideline OPPTS 835.6200). An AFD study is requested for two main rice producing areas of the country with different water holding periods (Refer to Memo on Waiver Request for Aquatic Field Dissipation Study for Saflufenacil (Section 3 New Chemical Uses in Rice; Pre-plant Burn-down) dated March 03, 2011 (DP Barcode 385078).

This memo contains the findings of a drinking water assessment for the proposed 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". 

Use Summary

Table 1 contains a summary of use patterns for saflufenacil including the 2009 Section 3 crop use patterns, the 2010 Labels for new use and amendments, and the Labels for new use and/or amendments for this submission. 

Table 1. A summary of all crop use patterns for saflufenacil
Use
MS Rate 
(lbs a.i/A) [1]
MA Rate
 (lbs a.i/A) [2]
Additional Application Information
   (1) 2009 section 3 crop use patterns
Fallow, post-harvest
                                     0.13
                                     0.13
Equipment: ground or aerial.
Field corn [a], sweet corn [b], and popcorn
                                     0.13
                                     0.13
Application timing: 14-30 days prior to planting (incorporated or surface) or pre-emergence.
Application rates 15-30 days prior to planting vary by soil texture and organic matter (higher rates on finer soils and soils with higher organic matter); not so 14 days prior to planting. Equipment: ground or aerial.
Sorghum
                                       
                                       

Cotton
                                     0.045
                                     0.045
Application timing: prior to accumulation of 1-inch of rainfall or irrigation to occur 21 days prior to planting. Equipment: ground or aerial.
Legume vegetables [c]
                                     0.089
                                     0.089
Application timing: pre-plant or pre-emergence (pre-plant only for lentils). Equipment: ground or aerial.
Soybeans (tolerant)
                                       
                                       

Small grains [d]
                                     0.13
                                     0.13
Application timing: pre-plant or pre-emergence (dormant or during and/or after spring green up for winter wheat at 0.045 lbs a.i./A). Equipment: ground or aerial.
Sunflower
                                     0.045
                                     0.089
Maximum number of applications per year: 2 (interval not stated). Application timing: at least 7 days prior to harvest (for desiccation). Equipment: ground or aerial.
Clearfield(R) corn
                                     0.023
                                     0.023
Maximum annual app. rate from all sources: 0.134 lbs saflufenacil/A for Clearfield(R) corn; 0.089 lbs saflufenacil/A for legume vegetables and soybeans. Application timing: pre-plant or pre-emergence (pre-emergence only for Clearfield(R) corn). Equipment: ground or aerial.
Legume vegetables (per region) [e]
                                     0.017
                          (Southern peas only: 0.023)
                                     0.017
                          (Southern peas only: 0.023)

Soybeans
                                     0.023
                                     0.023

Field corn [a], sweet corn [b], and popcorn
                                     0.11
                                     0.11
Maximum annual app. rate from all sources: 0.134 lbs saflufenacil/A. Application timing: 14-30 days prior to planting (incorporated or surface) or pre-emergence.
Application rates 15-30 days prior to planting vary by soil texture and organic matter (higher rates on finer soils and soils with higher organic matter); not so 14 days prior to planting. Equipment: ground, aerial, or chemigation.
Grain sorghum
                                       
                                       

Citrus fruit, pome fruit, stone fruit, tree nuts
                                     0.045
                                     0.135
Maximum number of applications per year: 3 (at least 21 days apart). Application timing: post-emergence. Equipment: ground.
Grape vines
                                     0.022
                                     0.066

Christmas tree plantations
                                     0.356
                                     0.356
Application timing: post-emergence for Christmas tree plantations; pre-plant for conifer and hardwood plantations; no directions for non-agricultural areas. Equipment: ground or aerial.
Conifer and hardwood plantations
                                       
                                       

Non-agricultural areas
                                       
                                       

   (2) 2010 Labels for new use and amendments
Rice
                                     0.045
                                     0.045
Only one Pre-plant weed burn-down application in dry or drained rice field at least 15 days before planting and 45 days before permanent flood is established with many crop specific restrictions and limitations (refer to supplemental  label)
Citrus fruit, pome fruit, stone fruit, tree nuts
                                     0.090
                                     0.270
Same as above, only the maximum single application rate was raised to 0.090 lb a.i/A instead of 0.045 lb a.i./A
   (3) Labels for new use and/or amendments for this submission
Oilseed canola subgroup 20 A [f] 
                                     0.045
                                     0.045
One or sequential ground or aerial application (total maximum of 0.045 lb a.i./A). Timing for: Flax: when 70-80% of bolls turn brown, Canola and others: when seeds in the middle pods started to turn in color. Not to be applied for oilseed crops grown for seed.
Selected edible beans, broad beans, garbanzo beans, guar, lablab beans and lentils
                                     0.045
                                     0.045
One or sequential ground or aerial application (total maximum of 0.045 lb a.i./A). Timing for: Dry edible beans: when 80% of pods turn yellow/brown, Vine type beans and lentils: when no more than 30% of the leaves are still green, Bush type beans:  when no more than 40% of the leaves are still green. Not to be applied on dry edible beans grown for seed.
Important Note: Previous section 3 new use, allow for one application of 0.089 lb a.i/A pre-plant or pre-emergence for selected edible beans, and lentils (pre-plant only for lentils) and according to this supplemental label the Maximum rate should be as per the main label. Therefore, if this application is to be executed pre-plant applications should be reduces to a total maximum of 0.044 lb a.i./A (0.089-0.045).
Dry peas including field peas an pigeon peas 
                                     0.045
                                     0.045
One or sequential ground or aerial application (total maximum of 0.045 lb a.i./A). Timing for: Dry edible peas: when 80% of pods turn yellow/brown, Vine type peas: when no more than 30% of the leaves are still green, Bush type peas:  when no more than 40% of the leaves are still green. Not to be applied on dry peas grown for seed.
Important Note: Previous section 3 new use, allow for one application of 0.089 lb a.i/A pre-plant or pre-emergence for selected edible beans, and lentils (pre-plant only for lentils) and according to this supplemental label the Maximum rate should be as per the main label. Therefore, if this application is to be executed pre-plant applications should be reduces to a total maximum of 0.044 lb a.i./A (0.089-0.045).
Soybeans 
                                     0.045
                                     0.045
One or sequential ground or aerial application (total maximum of 0.045 lb a.i./A). Timing for: at reaching physiological maturity depending on the variety. Not to be applied on crop grown for seed.
Important Note: Previous section 3 new use, allow for one application of 0.089 lb a.i/A pre-plant or pre-emergence for soybeans and according to this supplemental label the Maximum rate should be as per the main label. Therefore, if this application is to be executed pre-plant applications should be reduces to a total maximum of 0.044 lb a.i./A (0.089-0.045).
Oilseed sunflower subgroup 20B [g] 
                                     0.045
                                     0.089
One or two sequential ground or aerial application (total maximum of 0.045 lb a.i./A). Timing for: at reaching physiological maturity depending on the crop. Not to be applied on crop grown for seed.
Important Note: Previous section 3 includes this use for as "sunflower crop". It appears that the intension for this supplemental label is to include other crops in the oilseed sunflower subgroup 20B.
Oilseed cottonseed f 
                                     0.045
                                       
                                     0.045
One or sequential ground or aerial application (total maximum of 0.045 lb a.i./A). Timing for: at reaching physiological maturity depending on environmental conditions. Not to be applied on crop grown for seed.
Important Note: Previous section 3 new use, allow for one application of 0.045 lb a.i/A pre-plant or pre-emergence for cotton and according to this supplemental label the Maximum rate should be as per the main label. Therefore, if this application is to be executed pre-plant applications may not be executed (a total maximum of 0.00 lb a.i./A (0.045-0.045).
1 MS Rate= Maximum Single Application Rate
2 MA Rate= Maximum Annual Application Rate
a  Field corn includes conventional or herbicide-tolerant field corn grown for grain, seed, or silage.
b  Sweet corn does not include sweet corn grown for seed.
c  Legume vegetables include chickpeas, selected edible beans, selected edible peas, and lentils.
d  Small grains include wheat, barley, canaryseed, oats, millet, rye, and triticale.
e  Legume vegetables (per region) includes lentils, white lupins, chickpeas, dry edible peas, English peas, and Southern peas in the states east of and including North Dakota, South Dakota, Wyoming, Colorado, and New Mexico, except the states east of and including Vermont, Massachusetts, and Connecticut; succulent peas, dry edible peas, lentils, and chickpeas in Idaho, Montana, Nevada, Oregon, Utah, and Washington; and chickpeas in Arizona and California.
f  Oilseed canola (rapeseed) include canola (rapeseed) subgroup 20A including borage, crambe, cuphea, echium, flax, camelina, juncea, and mustard
g  Oil seeds sunflower subgroup 20B including calendula, castor oil plant, Chinese tallow tree, euphorbia, evening primrose, jojoba, niger seed, rose hip, safflower, Stokes' aster, sunflower, tallowwood, tea oil plant, and Veronica.

As shown in Table 1, the single and seasonal rate, for all the crops, in this submittal is 0.045 lbs a.i/A (one application/season) except for sunflower which has a seasonal rate of 0.089 (two applications/season). The range of these rates (0.045 to 0.089 lbs a.i/A) are much below the rate used for modeling in earlier submittal of 0.356 lbs a.i./A (Maximum seasonal rate for Christmas tree, conifer, and hardwood plantations and non-agricultural areas). Therefore, EDWCs exposure values calculated for the 2009 assessment (DP Barcode: 349860) may be used in the assessment for this submittal.