OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460



### MEMORANDUM

DA TE: April 15 , 2015

SUBJECT: Halosulfuron methyl Drinking Water Assessment for Additional Food/Feed Uses

on Pome Fruits Group 11

- 10 and Climbing Vines Subgroup 13

- 07F ( DP Barcode

D 4 21820 ; PC Code 128721 )

TO: Barbara Madden , Risk Manager

Sidney Jackson

, Risk Manager Reviewer

Marion Johnson , Chief Minor Use, and Emergency Response Branch Registration Division (7505P)

& Kristin Rury , Risk Assessor

Christine Olinger , Chief

Risk Assessment Branch III Health Effects Division (7509P)

FROM: Michael R. Barrett, Senior Chemist

Environmental Risk Branch V

Environmental Fate and Effec ts Division (7507P)

THROUGH: Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V Environmental Fate and Effects Division ( 7507P)

Tier I Estimated Surface and Ground Drinking Water Concentrations (EDWCs) for halosulfuron methyl, a sulfonylurea herbicide, were evalua ted for the proposed new uses on Crop Group 11

- 10 and Subgroup 13

- 07F. The highest estimated drinking water concentration (EDWC) continue to be from the existing use on rice (59.2 ug/L for acute and chronic exposure, see Table 1).

### 2

More specifically, t his drinking water exposure assessment incorporates proposed use patterns

for Pome Fruits Group 11

- 10 (apple and pear; includes Apple; azarole; crabapple; loquat; mayhaw; medlar; pear; pear, Asian; quince; quince, Chinese; quince, Japan ese; tejocote; cultivars, varieties, and/or hybrids of these) and Climbing Vines Subgroup 13

- 07F ( grape; includes Amur river grape; gooseberry; grape; kiwifruit, hardy; maypop; schisandra berry; cultivars, varieties, and/or hybrids of these ).

Conclusio ns from our evaluation about the potential level of acute and chronic exposure to halosulfuron methyl in drinking water remain essentially the same as in the Enviro nmental Fate

and Effects Divis i on’s ( EFED’s ) previous assessment (see DP Barcode D394244

, review dated

3 / 26 /201 3 1 

### ). Results of the groundwater and surface water source exposure models run are summarized in Table 1. Additional details are provided in the Appendix.

Table 1

. Tier I Estimated Drinking Water Concentrations (EDWCs) for human health drinking water risk assessment.

DRINKING WATER

SOURCE (MODEL USED) USE SITE (rate modeled) MAXIMUM ESTIMATED

DRINKING WATER CONCENTRATION (EDWC) c (ug/L or ppb)

Groundwater (SCI

- GROW) Fallow ground

(0.125 lb a.i./A/season) a Acute 0.065

Chronic <0.065

Groundwater (PRZM

- GW Multiple terrestrial crops;
( 2 Applications at 0.0469 lb ai/A per year / growing season; 45d

interval. ) Acute 0.2880

Groundwater (PRZM

- GW Multiple terrestrial crops;
( 2 Applications at 0.0469 lb ai/A per year / growing season; 45d

interval. ) Chronic 0.0264

Surface Water , rice use (Tier 1 Rice Model v.1.0) Rice use Paddy Water/Tail Water;
(0.0625 lb a.i./A/season) b Acute 

### 59.2

Chronic 

### <59.2

a Covers ground water exposure from all uses other than rice; for the corn, fallow ground, and sugarcane use

patterns of halosulfuron

- methyl, based on a seasonal application 0.125 lb a.i./A. Tier 1 estimates for exposure to parent halosulfuron methyl with the PFAM model may be higher but a re not expected to be as high as with the

Tier 1 Rice model.

b Seasonal rate is 0.0625 lb a.i . / A. Modeling involve s assumption of direct application to fields which are flooded and from which water may be released into surface waters which are used as drinking water supplies. Chronic value of 59.2 ppb does not account for possible degradation in the water.

c Surface water concentrat ions calculated by the Tier I Rice Model v1.0 and ground water concentrations calculated by SCI

- GROW do not distinguish between peak and chronic concentration.

1 The mo st recent review (D394244) is designated as Attachment A 2013, this review further cites the previous

reviews : (1.) DP Barcode D358032 dated 6/4/2009 and (2.) DP Barcode D366411 dated 8/5/2010 (both designated

here as Attachment B ) and DP Barcode D394244 dated 5/15/2012 (designated here as Attachment A ).

### 3

Table 2 . Proposed uses of halosulfuron

- methyl. Use information was obtained from the proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2] and SANDEA Herbicide [EPA Reg.

No. 81880

- 18].

Crop(s) Single

Application

rate (lb a.i./A) Max. #

applications per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a.i./A)
Pome Fruit Group 11

- 10 (apple, pear, etc.);

West of Rockies 0.0352

- 0.0938 2 NS NS 0.0938

Pome Fruit Group 11

- 10 (apple, pear, etc.);

West of Rockies 0.0234

- 0.0469 2 NS NS 0.0938

Small Fruit Climbing Subgroup 13

- 07F 0.0234

- 0.0469 2 45 NS 0.0938



## Conclusions

The highest exposure potential is still estimated with the use of halosulfuron methyl on rice, the proposed new uses, l ike the previously evaluated terrestrial crop and non

- crop uses are expected

to result in lower exposures than the rice use

. The proposed new uses are have similar application patterns and use rates to previously registered uses.

### 4



## APPENDIX

– Update on Drinking Wa ter Exposure Modeling

Background:

The proposed use rates for the specialty crop groups pome fruits such as apple and pear (Crop Group 11

- 10) and climbing vines such as grapes (Crop Subgroup 13

- 07F) are similar to other registered crops with the maximum season / annual rates equal to the highest such rates allowed on other crops (the proposed uses are summa rized in Table 2 3 ; summaries of other current uses is found in the previous Drinking Water Assessments attached at the end of this document.)

Table 3 . Proposed uses of halosulfuron

- methyl. Use information was obtained from the proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2] and SANDEA Herbicide [EPA Reg.

No. 81880

- 18].

Crop(s) Single

Application

rate (lb a.i./A) Max. #

applications per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a.i./A)
Pome Fruit Group 11

- 10 (apple, pear, etc.);

West of Rockies 0.0352

- 0.0938 2 NS NS 0.0938

Pome Fruit Group 11

- 10 (apple, pear, etc.);

West of Rockies 0.0234

- 0.0469 2 NS NS 0.0938

Small Fruit Climbing Subgroup 13

- 07F 0.0234

- 0.0469 2 45 NS 0.0938



### Since the previous assessment there have been new developments in Terms of EFED models which provide the ability to conduct refined exposure assessments for drinking water from both surface water and groundwater sources, as follows:

For groundwater, the P esticide R oot Z one M odel for G round W ater (PRZM

- GW) provides Tier 1 and higher Tier site and region

- specific exposure estimates for vulnerable groundwaters used as drinking water sources. More details can be found at: http://www.epa.gov/oppefed1/models/water/index.htm#przm_gw

PRZM

- GW model inputs are summarized in Table 4 . The ED WCs are presented in Table 1. Additional details on the modeling are available in Appendix A.

For surface water based drinking water supplies impacted by uses at sites where flooding is expected during part of the crop production cycle, the P esticide F loo ded A pplication M odel. (PFAM) has been approved by EFED to provide more refined exposure estimates for acute and especially chronic drinking water exposure. A dditional details on PFAM can be found here:

http://www.epa.gov/pesticides/science/models_pg.htm

### 5

With the additional capabilities of the new PFAM model it may be possible to refine the drinking water exposure assessments should it become necessary in the future.

For surface water ex posure from the other terrestrial crop / noncrop sites where halosulfuron methyl is used, the Surface Water Concentration Calculator (SWCC) may be used. The SWCC is designed to simulate the environmental concentration of a pesticide in the water column and sediment and is used for regulatory purposes by the USEPA Office of Pesticide Programs (OPP). The SWCC uses PRZM version 5.0+ (PRZM5) and the Variable Volume Water Body Model (VVWM), r eplacing the older PE5 shell (last updated November 2006), which used PRZM3 (Carousel et al., 2005) and EXAMS (Burns, 2003). Results from this model are expected to be similar to those with the previous FIRST (a conservative Tier 1 screening model) runs a nd are not updated for this review since they are not expected to be as high from the Tier 1 rice model. Note that highest FIRST screening concentrations were well over an order of magnitude lower for the terrestrial crop / non

- crop sites than the EDWCs ca lculated for the rice use.

The acute groundwater Tier 1 exposure value has increased to 0.29 ug/L (ppb) but this is still much smaller than the EDWCs previously determined for the rice use (59.2 ppb)

.



### Summary of Current EDWCs for Groundwater and Surfa ce Water
Sources

The highest exposure potential is still estimated with the use of halosulfuron methyl on rice, the proposed new uses, like the previously evaluated terrestrial crop and non

- crop uses are expected to result in lower exposures than the rice use.

The proposed new uses have similar application patterns and use rates to previously registered uses. There is therefore no change in the estimation of exposure from surface water sources from terrestrial uses as previously calculated with the Tier 1 screening model FIRST. Groundwater EDWCs were redetermined with a new model (PRZM

- GW) but did not change substantially from previous assessments and are still lower than estimates from surface water (both terrestrial and aquatic / rice uses).

Updated gro undwater modeling to support this new use drinking water assessment confirms that even the most vulnerable drinking water wells are not expected to have as high an exposure potential as surface drinking water sources directly impacted by effluent / dischar ge from rice fields. EFED will therefore continue to rely upon the Tier 1 rice model estimates for a conservative estimate of drinking water exposure; but we do note that more refined estimates maybe possible with the newly implemented PFAM model, should s uch refinements become necessary in the future (the Health Effects Division is not requesting such refinements at this time.)

### 6



### PRZM

- GW Modeling Input and Output

A summary of the model input parameters is provided in Table 4 . Summary results of the Tier 1 groundwater modeling with PRZM

- GW are provided in Table 5 . A sample input file ( *.pgi file)

for the PRZM

- GW model and model output report are provided further below.

Table 4

. Environmental Fate model input values used with PRZM

- GW drinking water exposure assessment model ( pome fruits such as apple and pear and climbing fruit such as grape uses).

Parameter Input Source

Aerobic soil t 1/2 (days) 1 48 90% Upper

- bound confidence limit on mean 2
(MRID 42139410; additional data considered from MRIDs 42661413, 42661413, 42976302, 42976303, and 42976304.)

Aerobic aquatic t 1/2 (days) 96 EFED Input Guidance for compound with no aerobic aquatic study (2x the aerobic soil half

life.

Hydro lysis t 1/2 in water (days) 42 3 x the measured hydrolysis half

- life at pH 7 in

sterile buffer solution. The 3x factor was used because the hydrolysis rate does not appear to

uni

- modally vary with an increase / decrease in solution pH. ( MRID 42139409 with amendment in MRID

42846801

. )

Organic carbon partition coefficient

– K OC (mL/g) 103 Average or median value from batch

- equilibrium adsorption studies (MRID 42139411)

Application rate (lb a.i./Acre) 2 0.0 469 Label

- maximum single rate for applications to pome fruits West of the Rockies (proposed) and existing uses such as field corn or sugarcane. Lower rates for other crops (refer to the usage summary table in the attached previous assessments for details.)

Application timing (days relative to

crop emerg ence) - 1 and 44 or

1 and 46 - 1 and 44 for all scenarios except the FL central

ridge / citrus scenario (which would not accept split applications before and after the standard January 1 emergence date for this scenario)

# applications/year 2 Apparent l abel maximum for pome fruits or climbing fruits such as grapes

. Total application rate modeled per year was equal to the highest permitted annual rate for all registered uses.

Application interval, days 45 Estimated from label directions allowing a split application (explicitly listed minimum interval for climbing fruits such as grapes)

### 7

Application Method Ground Only ground applications allowed for proposed uses; groundwater exposure estimates are not significantly different with aerial applications.

1 For halosulfuron, field dissipation half

- lives and monolith lysimeter dissipation half

- lives were on average much longer than for the aerobic metabolism studies. An overall mean of these studies was calculated after first assuming the degradation half

- liv es in the field studies were equal to 1.2 times the dissipation half

- lives for the top soil layer. Additional indication of the potentially high persistence of halosulfuron is provided by the halosulfuron registration label which strongly implicates that halosulfuron may persist in soil at phytotoxic levels for up to three years after application. After application of halosulfuron, rotational restrictions of one year to three years exist on various crops.

These label restrictions are consistent with an a ctive ingredient that persists in the environment for years (in this case, at phytotoxic levels).

2 Values given in this table are for halosulfuron methyl corn/ sugarcane uses, which were the crops which yielded the highest EECs with both models. Model i nput and output files are provided in Appendix B.

### 8



### Table 5. Summary of Modeling Results for Six Tier 1 Scenarios

Scenario ID Total

app. Rate Peak(ppb) PBT

Avg(ppb) Sim ula

tion
Avg BT(d) Throughputs 90

- day
Avg. 

### Delmarva_Std.Scn 0.0938 0.0417 0.0109 0.0081 2288 4.79 0.0375



### Flcitrus .Std.Scn 0.0938 0.2880 0.0264 0.0251 1752 6.26 0.2160 

### Flpotato_Std.Scn 0.0938 0.0074 0.0008 0.0007 2800 3.91 0.0059 

### Gacoastal_Std.Scn 0.0938 0.0006 0.0000 0.0001 2920 3.75 0.0005 

### Nccoastal_Std.Scn 0.0938 0.0024 0.0003 0.0002 2906 3.77 0.0019 

### Wisands_Std.Scn 0.0938 0.0032 0.0010 0.0007 3751 2.92 0.0029



### FL Central Ridge PRZM

- GW Scenario Input (“.PGI”) File

Halosulfuron (42d

- hydroly)

42

48

True

103

2

1

,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,,,,,,,,,,,,,,,,,,,, 0.0526,0.0526,,,,,,,,,,,,,,,,,,,,,,,,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,46,,,,,,,,,,,,,,,,,,,,,,,,

False

1

last
0,0,0

,,,,,,,,,,,,,,,,,,,,,,,,, future expansion future expansion future expansion future expansion future expansion

future expansion future expansion

Florida Citrus

- FL Central Ridge, Polk County

- (Tampa) Met File (12842.dvf)

- Astatula sand, hrgb A

C: \ Models \ Inputs \ Metfiles \ w12842.dvf

0.78

0

33
200,450

60

### 9

0.25

01

01

01

02

31

12

3

3

0.1

0.90

7.0

3
1.35,1.58,1.58,1.45,1.5,1.5,1.59,1.58
0.30,0.25,0.25,0.33,0.27,0.34,0.25
0.014,0.016,0.016,0.015,0.015,0.015,0.014
0.144,0.144,1.44,0.144,0.144,0.144,0.144,0.144

True 96,95,95,95,95,95,96,87
2.4,2.8,2.8,2.8,2.8,2.8,2.8,11

21

0.2

50

1



### Input / Output Summa ry for PRZM

- GW Simulation of Halosulfuron Methyl Application in the FL Central Ridge Scenario

Groundwater Analysis for Halosulfuron (42d

- hydroly) and the Florida Citrus

- FL Central Ridge, Polk County

- (Tampa) Met File (12842.Dvf)

- Astatula Sand, Hrgb A Scenario

Estimated groundwater concentrations and breakthrough times for Halosulfuron (42d

- hydroly) are presented in Table 1 for the Florida Citrus

- FL Central Ridge, Polk County

- (Tampa) Met File (12842.dvf)

- Astatula sand, hrgb A groundwater scenario. A graphical presentation of the daily concentrations in the aquifer is presented in Figure 1. These values were generated with the PRZM

- GW (Version 1.07). Critical input values for the model are summarized in Tables 2 and 3.

Table 1. Groundwater Results for Halosulfuron (42d

- hydroly) and the Florida Citrus

- FL Central Ridge, Polk County

- (Tampa) Met File (12842.dvf)

- Astatula sand, hrgb A Scenario.

Peak Concentration (ppb) 0.288

Post

- Breakthrough Mean Concentration (ppb) 0.0264

Entire Simulation Mean Concentration (ppb) 0.0251

Average Breakthrough Time (days) 1752.059

Throughputs 6.255496

### 10

Table 2. Chemical Properties for Groundwater Modeling of Halosulfuron (42d

- hydroly).

Koc (ml/g) 103

Surface Soil Half Life (days) 48

Hydrolysis Half Life (days) 42

Diffusion Coefficent Air (cm2/day) 0

Henry's Constant 0

Enthalpy (kcal/mol) 0

Table 3. Pesticide application scheme used for Halosulfuron (42d

- hydroly). This application scheme was applied every year of the simulation.

Application Days

Relative to Emergence Date (01/01) 2 Application Method Application Rate

(kg/ha)

1 Ground application with mass

distribution increasing proportionally with depth to 4 cm 0.0526

46 Ground application with mass

distribution increasing proportionally with depth to 4 cm 0.0526

Figure 1. Aquifer Breakthrough Curve for Halosulfuron (42d

- hydroly) and the Florida Citrus

- FL Central Ridge, Polk County

- (Tampa) Met File (12842.Dvf)

- Astatula Sand, Hrgb A Scenario



### 4

2 The FL Central Ridge / Citrus scenario application timing was slightly different from the other 5 scenarios modeled: 1 and 46 days after emergence compared to

- 1 and 44 days for the other 5 scenarios.

### 11 OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460



## ATTACHMENT A2013 : Copy of DWA dated 3/26/2013.

MEMORANDUM

DATE: March 26 , 2013

SUBJECT: Halosulfuron methyl Drinking Water Assessment for Additional Food/Feed Uses

on Artichokes and Caneberry Subgroup 13

- 07A ( DP Barcode D404096; PC

Code 128721 )

TO: Barbara Madden , Risk Manager

Sidney Jackson, Risk Manager Reviewer Luis Suguiyama

, Acting Chief Risk Integration Minor Use, and Emergency Response Branch Registration Division (7505P)

& Sheila Healy, Risk Assessor

Christine Olinger, Chief

Risk Assessment Branch III Health Effects Division (7509P)

FROM: Michael R. Barrett, Senior Chemist

Environmental Risk Branch V Environmental Fate and Effects Division (7507P)

THROUGH: Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V Environmental Fate and Effects Division (7507P)

Tier I Estimated Surface and Ground Drinking Wat er Concentrations (EDWCs) for halosulfuron methyl, a sulfonylurea herbicide, were evaluated for the proposed new uses

. This drinking water exposure assessment incorporates proposed use patterns for artichokes and Caneberry crop Subgroup 13

- 07A (includes “ Blackberry; loganberry; raspberry, black and red; wild raspberry; cultivars, varieties, and/or hybrids of these ”). Conclusions from our evaluation about the

### 12

potential level of acute and chronic exposure to halosulfuron methyl in drinking water remain the same as in the Environmental Fate and Effects Divison’s (EFED’s) previous assessment (see DP

Barcode D394244

, review dated 5/15/2012 3 

### ). The current acute and chronic drinking water exposure estimates are summarized in Table 1

.

Table 4

. Tier I Estimated Drinking Water Concentrations (EDWCs) for human health drinking water risk assessment.

DRINKING WATER

SOURCE (MODEL USED) USE (rate modeled) MAXIMUM ESTIMATED

DRINKING WATER CONCENTRATION (EDWC) c ( ppb)

Groundwater (SCI

- GROW) Fallow ground
(0.125 lb a.i./A/season) a Acute 0.065

Chronic <0.065

Surface Water (Tier 1 Rice Model v.1.0) Paddy Water/Tail Water; Rice
(0.0625 lb a.i./A/season) b Acute 59.2

Chronic <59.2

a Covers ground water exposure all uses other than rice ; for the corn, fallow ground, and sugarcane use patterns

of halosulfuron

- methyl, based on a seasonal application 0.125 lb a.i./A. Tier 1 estimates for exposure to parent halosulfuron methyl with the PFAM model may be higher but are not expected to be as high as with the Tier 1

Rice model.

b Seasonal rate is 0.0625 lb a.i. /A , which is half of the rate of fallow ground

.

c Surface water concentrations calculated by the Tier I Rice Model v1.0 and ground water concentrations calculated by SCI

- GROW do not distinguish between peak and chronic concentration

.



## Background:

The proposed use rates for the specialty crop groups artichokes and caneberries are similar to other registered crops with the maximum season / annual rates equal to the highest such rates allowed on other crops (the proposed uses are summarized in Table 2 ; a summary of current uses is found in the previous Drinking Water Assessment attached at the end of this document.) However, the highest drinking water exposures ar e still expected from the use on rice which can involve direct application to fields which are flooded and from which water may be released into surface waters which are used as drinking water supplies.

3 The most recent review (D394244) is designated as At tachment A

, this review further cites the previous reviews (includes DP Barcode D358032 dated 6/4/2009, and subsequently DP Barcode D366411 dated 8/5/2010 ) , designated

here as Attachment B ).

### 13

Table 5 . Proposed uses of halosulfuron

- methyl. Use information was obtained from the current and proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2] and SANDEA Herbicide [EPA Reg. No. 81880

- 18]

.

Crop(s ) Single

Application

rate ( lb a.i./A ) Max. #

applications

per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a

. i

. /A)

Artichoke (ground application) 0.0 469

- 0.0 938 2 NS NS 0.0 938

Caneberry subgroup

13

- 07A ; East of

Rockies (ground application) 0.0234

- 0.0 469 2 45 14 0.0 938

Caneberry subgroup

13

- 07A ; West of

Rockies (ground application) 0.03 52

- 0.0 938 2 45 14 0.0 938



### Since the previous assessment there have been new developments in Terms of EFED models which provide the ability to conduct refined exposure assessments for drinking water from both

surface water and groundwater sources, as follows:

For groundwater, the P esticide R oot Z one M odel for G round W ater (PRZM

- GW) provides Tier 1 and higher Tier site and region

- specific exposure estimates for vulnerable groundwaters used as drinking water sources. Mor e details can be found at: http://www.epa.gov/oppefed1/models/water/index.htm#przm_gw

For surface water based drinking water supplies impacted by uses at sites where flooding is expected during part of the crop production cycle, the P esticide F looded A pplication M odel. (PFAM) has been approved by EFED to provide more refined exposure estima tes for acute and especially chronic drinking water exposure. This model is not yet posted on the EPA website, but currently, additional details can be found here: https://sites.google.com/site/pf amodel/home



## Conclusions

Although it is expected that the exposure levels estimated with PRZM

- GW might be higher at the Tier 1 level than previously estimated we did not update the groundwater modeling for this

review because even the most vulnerable drin king water wells are not expected to have as high an exposure potential as surface drinking water sources directly impacted by effluent / discharge from rice fields. EFED will therefore continue to rely upon the Tier 1 rice model estimates for a

conservati ve estimate of drinking water exposure; but we do note that more refined estimates are possible with the newly implemented PFAM model, should such refinements become necessary in the future (the Health Effects Division is not requesting such refinements at this time.)

### 2 OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460



## ATTACHMENT A : Copy of DWA dated 5/15/2012.

MEMORANDUM

DATE: May 15 , 2012

SUBJECT: Halosulfuron methyl Drinking Water Assessment for Additional Food/Feed U ses

on Proso Millet, Pasture and Rangeland Grass Forage, Fodder and Hay (Crop Group 17) ( DP Barcode D 394244 ; PC Code 128721 )

TO: Maggie Rudick, Risk Manager

Kable Davis, Product Manager #25 Dan Kenny, Chief

Herbicide Branch Registration Division (7505P)

& Whang Phang, Risk Assessor

Nancy Dodd, Chemist Paula Deschamp, Chief

R isk Assessment Branch III Health Effects Division (7509P)

FROM: José L. Meléndez, Chemist

Environmental Risk Branch V Environmental Fate and Effects Division (7507P)

THROUGH: Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V Environmental Fate and Effects Division (7507P)

Tier I Estimated Surface and Ground Drinking Water Concentrations (EDWCs) for halosulfuron methyl , a sulfonylurea herbicide, were e valuated for the proposed new uses

. This drinking water

### 2

exposure assessment incorporates proposed use patterns for proso millet, pasture and rangeland grass forage, fodder and hay (Crop Group 17)

. Conclusions about the potential level of acute

and chroni c exposure to halosulfuron methyl in ground drinking water remain the same as in

EFED’s previous assessment ; furthermore, exposure due to the use on rice was calculated . See

the Attachment B for a copy of the previous review ( includes DP Barcode D358032 d ated 6/4/2009, and subsequently DP Barcode D366411 dated 8/5/2010 )

.

This drinking waters assessment (DWA) relies heavily on the previous assessment in that the groundwater values, a summary of the environmental fate characteristics, uncertainties, chemica l structures, and several other details about halosulfuron methyl were previously provided. Although it has been found that some degradates of halosulfuron methyl are present in the environment and could occur in drinking water, the residues of concern fo r the drinking water

assessment (DWA) include parent halosulfuron methyl only ( e.g. , refer to HEDs Scoping Document, DP Barcode D394808)

. A summary of the modeling results is provided in Table 1

- 1

. These estimates are, as in previous assessments, for exposure to parent halosulfuron methyl only. In previous assessments, the uses on rice were not includ ed. Therefore, besides the EDWCs for

several crop uses, the EDWCs for the uses on rice were calcu lated. The results for the use on rice are significantly higher than for previous crops. For modeling approach, assumptions, and uncertainties, see below. A more definitive assessment and refinements are possible if needed by

HED

. Should any questions arise, contact EFED.

Table 1

- 1 . Tier I Estimated Drinking Water Concentrations (EDWCs) for human health drinking water risk assessment

DRINKING WATER SOURCE (MODEL USED) USE (rate modeled) MAXIMUM ESTIMATED DRINKING

WATER CONCENTRATION (EDWC) c ( ppb)

Groundwater (SCI

- GROW) Fallow ground
(0.125 lb a.i./A/season) a Acute 0.065

Chronic <0.065

Surface Water (Tier 1 Rice Model v.1.0) Paddy Water/Tail Water; Rice
(0.0625 lb a.i./A/season) b Acute 59.2

Chronic <59.2

a Covers all uses other than rice ; for the corn, fallow ground, and sugarcane use patterns of halosulfuron

- methyl, based on a seasonal application 0.125 lb a.i./A.

b Seasonal rate is 0.0625 lb a.i./A , which is half of the rate of fallow ground

.

c Surface water concentrations calculate d by the Tier I Rice Model v1.0 and ground water concentrations calculated by SCI

- GROW do not distinguish between peak and chronic concentration

.



### Modeling was previously performed with the Tier 1 S creening C oncentration I n GRO und W ater (SCI

- GROW ) model for ground water ( these results were previously obtained and are described

in the A ttachment B )

. Besides

, in this assessment the Tier 1 Rice Model v.1.0 was used to

estimate drinking water concentrations from the rice use ( it is noted, however, that EFED’ s Tier

1 R ice M odel v.1.0 is likely to provide conservative concentration s as described below)

. 4



## The Tier 1 Rice Model v.1.0 , Modeling Approach and Uncertainties

The Tier I Rice Model v1.0 relies on an equilibrium partitioning concept to provide conservative

estimates of environmental concentrations resulting from application of pesticides to rice

4 http://www.epa.gov/oppefed1/models/water/index.htm (accessed 5/7/12)

.

### 3

paddies. W hen a pesticide is applied to a rice paddy, the model assumes that it will

instantan eously partition between a water phase and a sediment phase. The simplified equation for the Tier 1 Rice Model v.1.0 (USEPA 2007) is as follows:

C
w 

### = m ai ′



### 0

. 00105 + 0

. 00013 K d



### W here: C

w 

### = water concentration or the EDWC [μg/L or ppb ]

m ai 

### ' = mass applied per unit area [kg/ha] ( i.e. , the seasonal application rate)

K d 

### = water

- sediment partitioning coefficient [L/kg]

Note that neither the degradation of the pesticide nor the mass transfer from the aqueous phase to

the sediment is considered in this conceptualization, which greatly simplifies the model. The

absence of degradation adds conservatism to the model ( i.e. , estimated concentrations should be higher than those usually found in rice paddies). The absence of mass transfer processes can either add or reduce conservatism depending on numerous conditions such as whether the pesticide is soil or water applied and whether actual degradation occurs preferentially in the sediment or the water compartment; however, consideration of this paramete r is a refinement beyond a Tier I conceptualization. Table 1

- 2 provides a summary of the input parameters and

results of the rice model.

Table 1

- 2 . Tier I Rice Model v1.0 input parameters for halosulfuron

- methyl use on rice

P arameter Value Justification 1 Source

Application Rate ( m ai ' ) (kg a.i./ha) 0. 07005 0.0 625 lb a.i./A /application x 1 application = 0. 0625

lb a.i./A x 1.1208 k g·A/ha·lb = 0. 07005 k g a.i./ha Product label

Soil

- to

- Water Partition Coefficient (K d ) (L/kg) 1.03 K d = Mean K OC ( 103 L/k g OC ) x 1% organic carbon = 1.03 L/kg MRID 42139411

EDWC s (acute and chronic) (ppb) 59.2 C
w = m ai ′

0

. 00105 + 0

. 00013 K d

C
w = 0

. 07005

0

. 00105 + ( 0

. 00013 ) ( 1

. 03 )

C W = 59.2 ppb USEPA 2007

1 Refer to the Appendix III of the Tier 1 Rice Model v.1.0 Documentation (USEPA 2007)

.



### Most of the assumptions used in this model help ensure that the output s are protective of most environments associated with rice agriculture . The model assumptions include the following:

1. Movement of pesticide on suspended sediment is not considered. 2. Degradation does not occur. 3. Volatilization and other dissipation processes are not considered.

4. P artitioning to sediment is instantaneous.

### 4

5. Water is available for human or wildlife exposure instantaneously.

6. Water column d epth is 10 c m. 7. Sediment depth is 1 cm. 8. All pore space is saturated with water. 9. Organic carbon fraction is 0.01. 10. Bulk density is 1300 kg/m 3



### . 11. Grain density is 2650 kg/m 3



### .

T he T ier 1 Rice M odel v.1.0 provides screening

- level estimates and as such, are expected to exceed peak values found in the environment in most cases. This expectation is due to the protective assumptions of the model listed above, such as exclusion of degradation as well as dilution with unconta minated water outside the paddy. They represent paddy discharge water that has not degraded , and has not diluted with uncontaminated water outside the paddy

.

Estimates from the Tier I model generally do not represent typical conc entrations found in

human drinking water, as they represent paddy discharge water. The chronic concentrations as well as offsite concentrations are expected to be conservative. If Tier I estimates calculated by this screening method do not exceed the HE D’s concern level in a risk assessment, there is high confidence that there will be little or no risk above the level of concern from exposure through water resources. However, because of the uncertainties associated with a screening method

, when a level of concern is exceeded it cannot be determined whether the exceedance will in fact occur or whether this method has overestimated the exposure

.

For DWA, e valuation of the Tier I Rice Model v

. 1.0 indicate d that modeled within

- paddy

estimates are conservati ve, exceeding peak measured concentrations of pesticides in water bodies well downstream of rice paddies in five evaluated studies by less than one order of magnitude to multiple orders of magnitude . The five studies assessed were conducted in Louisiana a nd California using four different pesticides (USEPA 2007)

. It appears that t he range of modeled estimate exceedances over measured concentrations is most likely in response to chemical, environmental, and study

- specific factors. Estimates from the Tier I model generally do not represent typical concentrations found in human drinking water, as they represent direct paddy discharge water.



## Updated Use Information

T he current and proposed use sites for halosulfuron methyl 5 

### are summarized in Table 1

- 3 (the proposed uses are shaded blue ). Halosulfuron methyl is a selective preemergence or post

emergence sulfonylurea herbicide. It is currently registered for a number of food crops and fallow ground by Canyon Group, LLC for the products GWN

- 3061 [ contai ns 75% A.I., EPA Reg. No. 81880

- 2] , YUKON Herbicide [ contains 12.5% A.I. plus 55% of the sodium salt of dicamba, EPA Reg. No. 81880

- 6] and SANDEA Herbicide [ contains 75% A.I., EPA Reg. No.

81880

- 18 ]

. Halosulfuron was originally registered in the United St ates in 1994 by Nissan Chemical Industries, Inc. (NCI) and Monsanto Company. Gowan Company and Nissan

5 M ethyl 5

- {[(dimethoxy

- 2

- pyrimidinyl) amino] carbonylaminosulfonyl

- 3

- chloro

- 1

- methyl

- 1

- H

- pyrazole

- 4

- carboxylate

### 5

Chemical Industries, Inc. have formed a joint venture named Canyon Group LLC in 1994

. The current petition for registration for proso millet , and pastur e and rangeland ( Crop Group 17 ) was submitted on behalf of Canyon Group LLC

.

### 6

Table 1

- 3

. Registered and proposed uses of halosulfuron

- methyl. New uses shaded blue

. Use information was obtained from the current and proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2], YUKON Herbicide [EPA Reg. No. 81880

- 6] and SANDEA Herbicide [EPA Reg. No. 81880

- 18]

Crop(s ) Application

rate ( lb a.i./A ) Max. #

applications

per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a

. i

. /A)

Proso Millet (ground application) 0.0234

- 0.0313 1 NS 37 0.0313

Pasture & Rangeland (ground application) 0.0313

- 0.0625 2 NS N/A 0.0625

Field corn (including grown for seed) 0.031

- 0.0625 2 NS 30 0.125

Sweet corn and

popcorn 0.0313 2 NS 30 day pre

grazing or forage harvesting

interval 0.0625 3

Grain sorghum (milo) 0.031

- 0.047 1 N / A 30 day pre

grazing or forage harvesting

interval 0.047

Rice 1 0.0313

- 0.0625 2 (?) Preplant, postplant, and post flood ; preplant and at plant

burndown applications

allowed. NS 48 0.0625

Sugarcane 0.031

- 0.0625 3 NS 30 day pre

grazing or forage / silage harvesting

interval 0.125

Cotton 0.031

- 0.0625 NS
Poe up to row

closure permitted NS 28 0.0625

Fallow ground 0.031

- 0.0625 2 NS N / A 0.125

Dry shelled beans 0.023

- 0.031 NS NS 30 0.094 4

(0.047 /cc

, 0.094 / 12 months)
Pea and bean, succulent shelled, subgroup 6B 0.023 NS NS NS (0.0 23 per

year )

### 7

Table 1

- 3

. Registered and proposed uses of halosulfuron

- methyl. New uses shaded blue

. Use information was obtained from the current and proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2], YUKON Herbicide [EPA Reg. No. 81880

- 6] and SANDEA Herbicide [EPA Reg. No. 81880

- 18]

Crop(s ) Application

rate ( lb a.i./A ) Max. #

applications

per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a

. i

. /A)
Pea and bean, succulent shelled, subgroup 6B (west of the Rockies) 0.023

- 0.0 47 NS NS 30 (0.0 47 per

year )

Vegetabl e, tuberous

and corm, subgroup

1 C 0.023

- 0.0 47 1 N / A 45 0.047

Rhubarb 0.023

- 0.0 47 2 N / A 60 0.047

Bushberr y subgroup

13

- 07B 0.023

- 0.0 47 NS 45 14 0.094

A pples (east of the Rockies) 0.023

- 0.0 47 NS NS 14 0.094

Apples (west of the Rockies) 0.035

- 0.094 NS NS 14 0.094

Soybeans 0.031

- 0.0625 2 (?)

Preem ergence or Prepl an t Spring

– 21 days bef ore planting to

emergence, Fall burndown NS

(probably

~ 150 days) NS 0.125 (?)

Okra 0.023

- 0.0 47 NS 0.094 30 0.094

1 Do not reintroduce water into rice fields or checks for at least five days following dry broadcast applications of product. D o not make more than one pre

- plant or at planting application of product to rice per growing season.

2 N / A = not applicable. NS = not specified.

3 Some labels are unclear and imply that the second application to sweet corn/popcorn may not exceed 0.047 lb

a

. i

. / A

. 4 Although these are the limits stated on the label, it also states “Make only one Sandea application per crop cycle”. Since it does not appear to be possible to have more than 2 crops per year, EFED modeled this use in that way.



## References
U.S. Environmental Protection Agency 2007. Guidance for Tier I Estimation of Aqueous Pesticide Concentrations in Rice Paddies (dated 05/08/2007)

. Available at http://www.epa.gov/oppefed1/models/water/rice_tier_i.htm (accessed 0 5/02 /2012)

.

### 1

### 2 Attachment B . COPY OF DWA DATED 8/5/10

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES



### PC Code: 128721

DP Barcode: D366411

MEMORANDUM August 5 , 20 10

SUBJECT: Halosulfuron methyl Drinking Water Assessment for Additional food uses on

Dried Shelled Peas & Beans (Except Soybean), Succulent Shelled Peas & Bean s, Apples, Rhubarb, Bushberry, Fruiting Vegetables and Tuberous & Corm Vegetables

(DP Barcode: D366411; PC Code 128721)

TO: Whang Phang, Risk Assessor

Nancy Dodd, Chemist Health Effects Division (7509P)

FROM: Michael R. Barrett, Ph.D. Senior Chemist

Environmental Fate and Effects Division (7507P)

THROUGH: Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V Environmental Fate and Effects Division (7507P)

Previously calculated (DP Barcode D358032

– 6/4/2009 a ssessment) Tier I Estimated Surface Drinking Water Concentrations (EDWCs) for halosulfuron methyl 6 

### (the residues of concern include parent compound only) were reevaluated for the proposed new uses

. This drinking water exposure assessment incorporates propo sed use patterns for several new crops. 7 

### Conclusions about the potential level of acute and chronic exposure to halosulfuron methyl in drinking water

6 methyl 5

- {[(dimethoxy

- 2

- pyrimidinyl) amino] carbonylaminosulfonyl

- 3

- chloro

- 1

- methyl

- 1

- H

- pyrazole

- 4

- carboxylate

7 Including dried shelled peas & beans (except soybean), succulent shelled peas & beans, apples, rhubarb, bushberry, fruiting vegetables and tuberous & corm vegetables; proposed and curr ent uses are summarized in Table 1.

### 3

remain the same as in our previous assessment (see Appendix 2 for a copy of the previous review):

For par ent alone:

 8.3 μg/l or ppb for acute exposure (1 in 10 year annual peak daily concentration)

 1.7 μg/l for (non

- cancer) chronic exposure (1 in 10 year annual mean concentration)

These EDWCs were calculated using the FIRST mode run for the corn, fallow ground, and sugarcane use patterns (further details are provided in our previous review cited above.) EDWCs were also previously estimated for ground

- water source drinking water and remain unchanged (0.065 μg/l for acute and chronic exposure.)

Discussion

Although some degradates of halosulfuron

- methyl have been found to be present in the environment and could occur in drinking water, the residues of concern for the drinking water

a ssessment consist of parent halosulfuron

- methyl only and these estimates are, as in previous assessments, for exposure to parent halosulfuron methyl only.

Modeling was with the Tier 1 PRZM

- EXAMS metamodel “FIRST” (FQPA Index Reservoir Screening Tool) for surface water and the SCI

- GROW ( S creening C oncentration I n GRO und

W ater) model for ground water (see Appendix 1 for details) . A suitable model for estimation of drinking water concentrations from the rice use is not currently available (EFED’s tier 1 rice model does not provide concentration estimates that can be associated with levels expected in drinking water.)

Updated Use Profile

T he current and proposed use sites for halosulfuron methyl are summarized in Table (the proposed uses are marked by an asterisk). Halosulfuron

- methyl is a selective preemergence or

post

- emergence sulfonylurea herbicide. Halosulfuron is currently registered for a number of food crops and fallow ground under Section 3 by Nissan Chemical Industries, Inc. product

GWN

- 3061 [EPA Reg. No. 81880

- 2] and other products and the Gowan Company product Permit Herbicide [81880

- 2

- 10163]. Halosulfuron was originally registered in the United States in

199 4 by Nissan Chemical Industries, Inc. (NCI) and Monsanto Company. Gowan Company and NCI have formed a joint venture named Canyon Group LLC. The current petition for registration for several minor use crops being reviewed here has been submitted by Interreg ional Research Project No.4

.

### 4

Table 1

. Registered and proposed uses of halosulfuron

- methyl.
Crop(s) 1 

### a Max.

Application rate ( min. ) Max. # applications /

Season 3 

### Minimum

Interval 2, 3 

### PHI

(days) Maximum

Annual

Rate (1b ai/A)

Field corn 0.0625

(0.031) 2 NS 30 0.125

Sweet corn and

popcorn 0.0313 2 NS 30 day pre

grazing or forage harvesting

interval 0.0625 a

Grain sorghum 0.047 1 NA 30 day pre

grazing or forage harvesting

interval 0.047

Rice 0.0625 2 (?) Preplant, postplant, and post flood applications

allowed. NS 48 0.0625

Sugarcane 0.0625

(Range

0.031

- 0.62) 3 NS 30 day pre

grazing or forage / silage harvesting

interval 0.125

Cotton 0.0625

(Range

0.031

- 0.62) NS

Poe up to row

closure permitted NS 28 0.0625

Fallow ground 0.0625

(Range

0.031

- 0.62) 2 NS NA 0.125

* Dry shelled beans and pea (east of the Rockies) (Ground app.) 0.031

(Range

0.023

- 0.031) NS NS 30 0.094 4 (0.047 per crop cycle, 0.094 per 12 months) * Dry shelled beans and pea (west of the Rockies) (Ground app.) 0.047

(Range

0.023

- 0.047) NS NS 30 0.094 (0.047 per crop cycle, 0.094 per 12 months)
* Pea and bean, succulent shelled, subgroup 6B 0.023

(0.023) NS NS NS 0.023

### 5

Crop(s) 1 

### a Max.

Application rate ( min. ) Max. # applications /

Season 3 

### Minimum

Interval 2, 3 

### PHI

(days) Maximum

Annual

Rate (1b ai/A) * Succulent snap beans (incl. lima beans) 0.0625

(0.031) NS NS 30 (0.0625 per crop cycle, 0.125 per 12 months) Vegetable, tuberous and corm, subgroup l

C 0 7 .047

(0.023) 1 NA 45 0.047

Rhubarb 0.047

(0.023) 2 NA 60 0.047

* Bushberry 0.047

(0.023) NS 45 60 0.094

* Apples (east of the Rockies) 0.047

(0.023) NS NS 14 0.094

* Apples (west of the Rockies) 0.094

(0.035) NS NS 14 0.094

Soybeans 0.0625

(Range

0.031

- 0.62) 2 (?)

Preemg or Preplt

– 21 days bef. Planting to emg.

Fall burndown

– anytime after

harvest until ground freezes NS

(probably

about 150 days) NS 0.125 (?)

1 Crop uses currently being proposed are marked with an “*”

2 NA = not applicable.

3 NS = not specified.

4 Although these are the limits stated on the proposed label, the label also states “Make only one Sandea application per crop cycle”. Since it does not appear to be possible to have more than 2 crops per year, we modeled this use in that way.

a Some labels are unclear and imply that the second application to sweet corn / popcorn may not exceed 0.047 lb

ai / acre.



### Note that there are rotational crop intervals of up to 36 months for many crops (including 36 months for sugar beets in ND, MN, and the Red River Valley and 24 months for spinach, red beet, and sugar beets (in other use areas).

### 6



## APPENDIX 1: Aquatic Expos ure: SCI

- GROW and FIRST Water Quality Modeling Inputs and Results

Model inputs and results (updates the previous review are summarized in Table 2

, Table 3 , and

Table 4 . No acceptable scenario for estimation of drinking water concentrations from the rice

us e exists at this time so no estimates are provided (results of the tier 1 rice model have been presented previously, see DP Barcode D278 449.) Note that the current EFED rice model for ecological aquatic exposure from a rice use overestimates levels that w ould occur in drinking water because it does not consider the degradation of the pesticide or the dilution of the pesticide as it is transported away from the rice field into the drinking water source. In the absence of an acceptable EFED and OPP approved model the rice use was therefore not directly evaluated.

Table 2

. Environmental Fate model input values used with FIRST drinking water exposure assessment
model (field corn and sugarcane uses).

Parameter Input Source

Solubility (ppm) 1630 Product chemistry submissions. Solubility decreases to 15 ppm at pH 5 and increases to 7470 ppm at pH 9.

Aerobic soil t 1/2 (days) 1 48 90% Upper

- bound confidence limit on mean 2
(MRID 42139410; additional data considered from MRIDs 42661413, 42661413, 42976302, 42976303, and 42976304.)

Aerobic aquatic t 1/2 (days) 96 EFED Input Guidance for compound with no aerobic aquatic study (2x the aerobic soil half

life.

Photolysis t 1/2 in water (days) 30 MRID 42661409.

Organic carbon partition coefficient

– K OC (mL/g) 103 Average or median value from batch

- equilibrium adsorption studies (MRID 42139411)

Application rate (lb a.i./Acre) 2 0.0625 Label

- maximum single rate for applications to field corn or sugarcane. Lower rates for other crops (refer to the usage summary table for details.)

# applications/year 2 , or... Label maximum for field corn or sugarcane. One application at the maximum rate for other crops.

Application interval, days 21 Estimated from label dir ections allowing a split application in the period from spike to layby for corn; a 45

- day interval between applications was

also modeled.

Application Method Aerial or... Allowed on label for corn, sorghum, and rice. Ground application assumed for other crops.

### 7 1 For halosulfuron, field dissipation half

- lives and monolith lysimeter dissipation half

- lives were on average much longer than for the aerobic metabolism studies. An overall mean of these studies was calculated after first assuming the degradatio n half

- lives in the field studies were equal to 1.2 times the dissipation half

- lives for the top soil layer. Additional indication of the potentially high persistence of halosulfuron is provided by the halosulfuron registration label which strongly implic ates that halosulfuron may persist in soil at phytotoxic levels for up to three years after application. After application of halosulfuron, rotational restrictions of one year to three years exist on various crops.

These label restrictions are consistent with an active ingredient that persists in the environment for years (in this case, at phytotoxic levels).

2 Values given in this table are for halosulfuron methyl corn/ sugarcane uses, which were the crops which yielded the highest EECs with both models . Model input and output files are provided in Appendix B.



### Results of surface water source modeling are summarized in Table 3 and ground

- water modeling

in Table 5

. The acute exposure c oncentrations for an index reservoir with F IRST range from 3.8

to 8.3 ppb or ug/L for the various use patterns modeled

. The c hronic exposure estimates (annual average EDWC) with FIRST ranged from 0.8 to 1.7 ppb . The highest acute and chronic exposure

EDWC were both associated with a corn and sugar cane use pattern. The Tier 1 EDWC for ground

- water (using the SCI

- GROW model) was significantly lower (0.065 ppb for both acute and chronic exposure).

Table 3

. Summary of halosulfuron methyl scenarios modeled with FIRST.

Represent

ative Crop Single

Rate, lb

ai/A # of

applica

tions Interval

between appl., days Total

seasonal rate, ai/a Acute

EDWC, ug/L Annual

EDWC, ug/L

Tomato 0.047 2 21 0.094 6.2 1.3

Asparagus 1 0.047 2 45 0.094 5.5 1.2

Sugarcane 0.042 3 21 0.125 7.3 1.5

Corn,

S ugarcane (ground) 0.063 2 21 0.125 8.3 1.7

Corn,

S ugarcane
, Fallow ground 0.063 2 45 0.125 7.3 1.5

Pioneer IR

corn
, Apples

- west of

Rockies 0.094 1 NA 0.094 3.8 0.80

Soybean 0.063 2 150 0.125 5.4 1.1

### 8

Represent

ative Crop Single

Rate, lb

ai/A # of

applica

tions Interval

between appl., days Total

seasonal rate, ai/a Acute

EDWC, ug/L Annual

EDWC, ug/L

Cotton 0.063 1 NA 0.063 4.7 1.0

Note: The EFED default 87% crop area assumption was used except for corn (46% crop area).

1 And flowering vegetables. This model run is also representative of dried shell beans east of the Rockies (only lower rates permitted for dry beans west of the Rockies) and apples east of the Rockies.



### Table 4

. Environmental Fate Input Parameters for halosu lfuron methyl in SCI

- GROW.

Parameter Halosulfuron Source

Organic Carbon Partition Coefficient (K OC 

### ) 103 (Avg.) Median value.

Aerobic Soil Metabolism Half

- Life (days) 48 Average value.

Table 5

. Summary of halosulfuron methyl ground

- water scenario modeled with SCI

- GROW.

Representative Crop Single

Rate, lb

ai/A # of

applications Total

seasonal rate, ai/a Acute EEC,

ug/L Chronic

EEC, ug/L

Field corn,

sugarcane 0.0625 2 0.125 0.065 0.065



## New and updated model runs

A. SCI

- GROW

VERSION 2.3

ENVIRONMENTAL FATE AND EFFECTS DIVISION

OFFICE OF PESTICIDE PROGRAMS

U.S. ENVIRONMENTAL PROTECTION AGENCY

SCREENING MODEL

FOR AQUATIC P ESTICIDE EXPOSURE

SciGrow version 2.3

chemical:Halosulfuron

- methyl time is 5/22/2009 17:29:40

------------------------------------------------------------------------ Application Number of Total Use Koc Soil Aerobic rate (lb/ acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------ 0.063 2.0 0.125 1.03E+02 48.0

--------------------------------------------------- --------------------- groundwater screening cond (ppb) = 6.54E

- 02

************************************************************************

### 9



## B. FIRST

RUN No. 1 FOR Halosulfuron met ON Corn, Suga * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------- ------------------------------ .063( .110) 2 21 103.0 1630.0 AERIAL(16.0) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------
METABOLIC DAYS UNTIL HYDROLYSI S PHOTOLYSIS METABOLIC COMBINED (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------

8.385 1.773

RUN No. 2 FOR Halosulfuron Met ON corn

– special** * INPUT VALUES *

-------------------------------------------- ------------------------ RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .063( .110) 2 21 103.0 1630.0 AERIAL(16.0) 46.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------
METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COM BINED (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGR AMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

----------------- ---------------------------------------------------

4.434 .937

** this run utilizes a corn

- specific PCA.

### 10

RUN No. 3 FOR Halosulfuron met ON Soybeans * INPUT VALUES *

---------------------------------- ---------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .063( .070) 2 150 103.0 1630.0 AERIAL(16.0) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------
METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COM BINED (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGR AMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

----------------- ---------------------------------------------------

5.381 1.138

### 11



## APPENDIX 2: Previous Drinking Water Exposur e Assessment

[Begins on following page]

### 12 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES



### PC Code: 128721

DP Barcode: D358032

MEMORANDUM June 4 , 2009

SUBJECT: Halosulfuron methyl Drinking Water Assessment for Additional food uses

(including proposed use on soybean) (DP Barcode: D358032; PC Code 128721)

TO: Whang Phang, Risk Assessor

Nancy Dodd , Chemi st Health Effects Division ( 7509P)

FROM: Michael R. Barrett, Ph.D. Senior Chemist

Environmental Fate and Effects Division (7507P)

THROUGH: Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V

Env ironmental Fate and Effects Division (7507P)

I. Summary and Conclusions

A drinking water exposure assessment was performed for halosulfuron

- methyl (methyl 5

- {[(dimethoxy

- 2

- pyrimidinyl) amino] carbonylaminosulfonyl

- 3

- chloro

- 1

- methyl

- 1

- H

- pyrazole

4

- ca rboxylate) that incorporates a proposed use pattern for soybeans and updates a previous Drinking Water Assessment (see 1/22/02 “Ex panded Section 3 and IR

- 4 Uses to a dd Asparagus and Flowering Vegetables to Halosulfuron

- methyl Label” (Pages 19

- 24 and 58

- 62, see also DP

Barcode D2784 49, reviews dated 8/13/2002 ). The current and proposed use sites for

halosulfuron m ethyl are summarized in

### 13

Table 1

- 3

. Registered and proposed uses of halosulfuron

- methyl. New uses shaded blue

. Use information was obtained from the current and proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2], YUKON Herbicide [EPA Reg. No. 81880

- 6] and SANDEA Herbicide [EPA Reg. No. 81880

- 18]

Crop(s ) Application

rate ( lb a.i./A ) Max. #

applications

per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a

. i

. /A)

Proso Millet (ground application) 0.0234

- 0.0313 1 NS 37 0.0313

Pasture & Rangeland (ground application) 0.0313

- 0.0625 2 NS N/A 0.0625

Field corn (including grown for seed) 0.031

- 0.0625 2 NS 30 0.125

Sweet corn and

popcorn 0.0313 2 NS 30 day pre

grazing or forage harvesting

interval 0.0625 3

Grain sorghum (milo) 0.031

- 0.047 1 N / A 30 day pre

grazing or forage harvesting

interval 0.047

Rice 1 0.0313

- 0.0625 2 (?) Preplant, postplant, and post flood ; preplant and at plant

burndown applications

allowed. NS 48 0.0625

Sugarcane 0.031

- 0.0625 3 NS 30 day pre

grazing or forage / silage harvesting

interval 0.125

Cotton 0.031

- 0.0625 NS
Poe up to row

closure permitted NS 28 0.0625

Fallow ground 0.031

- 0.0625 2 NS N / A 0.125

Dry shelled beans 0.023

- 0.031 NS NS 30 0.094 4

(0.047 /cc

, 0.094 / 12 months)
Pea and bean, succulent shelled, subgroup 6B 0.023 NS NS NS (0.0 23 per

year )

### 14

Table 1

- 3

. Registered and proposed uses of halosulfuron

- methyl. New uses shaded blue

. Use information was obtained from the current and proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2], YUKON Herbicide [EPA Reg. No. 81880

- 6] and SANDEA Herbicide [EPA Reg. No. 81880

- 18]

Crop(s ) Application

rate ( lb a.i./A ) Max. #

applications

per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a

. i

. /A)
Pea and bean, succulent shelled, subgroup 6B (west of the Rockies) 0.023

- 0.0 47 NS NS 30 (0.0 47 per

year )

Vegetabl e, tuberous

and corm, subgroup

1 C 0.023

- 0.0 47 1 N / A 45 0.047

Rhubarb 0.023

- 0.0 47 2 N / A 60 0.047

Bushberr y subgroup

13

- 07B 0.023

- 0.0 47 NS 45 14 0.094

A pples (east of the Rockies) 0.023

- 0.0 47 NS NS 14 0.094

Apples (west of the Rockies) 0.035

- 0.094 NS NS 14 0.094

Soybeans 0.031

- 0.0625 2 (?)

Preem ergence or Prepl an t Spring

– 21 days bef ore planting to

emergence, Fall burndown NS

(probably

~ 150 days) NS 0.125 (?)

Okra 0.023

- 0.0 47 NS 0.094 30 0.094

1 Do not reintroduce water into rice fields or checks for at least five days following dry broadcast applications of product. D o not make more than one pre

- plant or at planting application of product to rice per growing season.

2 N / A = not applicable. NS = not specified.

3 Some labels are unclear and imply that the second application to sweet corn/popcorn may not exceed 0.047 lb

a

. i

. / A

. 4 Although these are the limits stated on the label, it also states “Make only one Sandea application per crop cycle”. Since it does not appear to be possible to have more than 2 crops per year, EFED modeled this use in that way.



### .

Modelin g was with the Tier 1 PRZM

- EXAMS metamodel “FIRST” (FQPA Index Reservoir Screening Tool) for surface water and the SCI

- GROW ( S creening C oncentration I n GRO und

W ater) model for ground water . The acute exposure concentrations with FIRST ranged up to 8.3 ppb or ug/L as estimated for the use pattern for corn and sugarcane. Chronic exposure (annual average EDWC) estimates ranged up to 1.7 ppb, also calculated for the corn and sugarcane use

patt ern. Tier 1 EDWC for ground

- water (using the SCI

- GROW model) were significantly lower. A suitable model for estimation of drinking water concentrations from the rice use is not currently available (EFED’s tier 1 rice model does not provide concentration e stimates that can be associated with levels expected in drinking water.)

### 15

I I

. Discussion

A. USE PROFILE

Halosulfuron

- methyl is a selective preemergence or post

- emergence sulfonylurea herbicide. Halosulfuron is currently registered under Section 3 by N issan Chemical Industries, Inc. product

GWN

- 3061 [EPA Reg. No. 81880

- 2] and other products and the Gowan Company product Permit Herbicide [81880

- 2

- 10163]. Halosulfuron was originally registered in the United States in 1994 by Nissan Chemical Industries, In c. (NCI) and Monsanto Company. Gowan Company and NCI have formed a joint venture named Canyon Group LLC. Canyon Group LLC has submitted a request for a new use on soybeans. Halosulfuron

- methyl is currently registered for use on some fruiting vegetables, f ield corn, sweet corn, grain sorghum, rice, sugarcane, tree nuts, and turfgrass. This drinking water assessment also considers the impact of a proposed use on soybeans. Registered uses are summarized in

### 16

Table 1

- 3

. Registered and proposed uses of halosulfuron

- methyl. New uses shaded blue

. Use information was obtained from the current and proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2], YUKON Herbicide [EPA Reg. No. 81880

- 6] and SANDEA Herbicide [EPA Reg. No. 81880

- 18]

Crop(s ) Application

rate ( lb a.i./A ) Max. #

applications

per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a

. i

. /A)

Proso Millet (ground application) 0.0234

- 0.0313 1 NS 37 0.0313

Pasture & Rangeland (ground application) 0.0313

- 0.0625 2 NS N/A 0.0625

Field corn (including grown for seed) 0.031

- 0.0625 2 NS 30 0.125

Sweet corn and

popcorn 0.0313 2 NS 30 day pre

grazing or forage harvesting

interval 0.0625 3

Grain sorghum (milo) 0.031

- 0.047 1 N / A 30 day pre

grazing or forage harvesting

interval 0.047

Rice 1 0.0313

- 0.0625 2 (?) Preplant, postplant, and post flood ; preplant and at plant

burndown applications

allowed. NS 48 0.0625

Sugarcane 0.031

- 0.0625 3 NS 30 day pre

grazing or forage / silage harvesting

interval 0.125

Cotton 0.031

- 0.0625 NS
Poe up to row

closure permitted NS 28 0.0625

Fallow ground 0.031

- 0.0625 2 NS N / A 0.125

Dry shelled beans 0.023

- 0.031 NS NS 30 0.094 4

(0.047 /cc

, 0.094 / 12 months)
Pea and bean, succulent shelled, subgroup 6B 0.023 NS NS NS (0.0 23 per

year )

### 17

Table 1

- 3

. Registered and proposed uses of halosulfuron

- methyl. New uses shaded blue

. Use information was obtained from the current and proposed labels for GWN

- 3061 [EPA Reg. No. 81880

- 2], YUKON Herbicide [EPA Reg. No. 81880

- 6] and SANDEA Herbicide [EPA Reg. No. 81880

- 18]

Crop(s ) Application

rate ( lb a.i./A ) Max. #

applications

per Season 2 

### Minimum

Interval 2 

### PHI

(days) Maximum

Annual Rate (1b a

. i

. /A)
Pea and bean, succulent shelled, subgroup 6B (west of the Rockies) 0.023

- 0.0 47 NS NS 30 (0.0 47 per

year )

Vegetabl e, tuberous

and corm, subgroup

1 C 0.023

- 0.0 47 1 N / A 45 0.047

Rhubarb 0.023

- 0.0 47 2 N / A 60 0.047

Bushberr y subgroup

13

- 07B 0.023

- 0.0 47 NS 45 14 0.094

A pples (east of the Rockies) 0.023

- 0.0 47 NS NS 14 0.094

Apples (west of the Rockies) 0.035

- 0.094 NS NS 14 0.094

Soybeans 0.031

- 0.0625 2 (?)

Preem ergence or Prepl an t Spring

– 21 days bef ore planting to

emergence, Fall burndown NS

(probably

~ 150 days) NS 0.125 (?)

Okra 0.023

- 0.0 47 NS 0.094 30 0.094

1 Do not reintroduce water into rice fields or checks for at least five days following dry broadcast applications of product. D o not make more than one pre

- plant or at planting application of product to rice per growing season.

2 N / A = not applicable. NS = not specified.

3 Some labels are unclear and imply that the second application to sweet corn/popcorn may not exceed 0.047 lb

a

. i

. / A

. 4 Although these are the limits stated on the label, it also states “Make only one Sandea application per crop cycle”. Since it does not appear to be possible to have more than 2 crops per year, EFED modeled this use in that way.



### .

### 18

Table 6

. General usage information for halosulfuron

- methyl. Crop(s) Max.

Application rate (range) Max. #

applications /

Season Interval PHI (days) Maximum

Annual

Rate (1b ai/A)

Field corn 0.062

(Range 0.031

- 0.62) 2 NS 30 0.125

Sweet corn and popcorn 0.0313 2 NS 30 day pre

grazing or forage harvesting

interval 

### 0.0625

Grain sorghum 0.047 1 NA 30 day pre

grazing or forage harvesting

interval 

### 0.047

Rice 0.0625 2 (?) Preplant, postplant, and post flood applications allowed. 

### NS 48 0.0625

Sugarcane 0.0625

(Range 0.031

- 0.62) 3 NS 30 day pre

grazing or forage / silage harvesting

interval 

### 0.125

Cotton 0.0625

(Range 0.031

- 0.62) NS

Poe up to row closure permitted 

### NS 28 0.0625

Fallow ground 0.0625

(Range 0.031

- 0.62) 2 NS NA 0.125

Dry beans 0.047

(Range 0.0 23

- 0. 47 ) NS NS NS 0.094 (0.047 per crop cycle, 0.094 per 12 months) 

### Soybeans 0.0625

(Range 0.031

- 0.62) 2 (?)

Preemg or Preplt

– 21 days bef. Planting to

emg. Fall burndown

– anytime after harvest until ground freezes 

### NS
(probably

about 150 days) 

### NS 0.125 (?)

NA = not applicable. NS = not specified.

### 19

Note that there are rotational crop intervals of up to 36 months for many crops (including 36 months for sugar beets in ND, MN, and the Red River Valley and 24 months for spinach, red beet, and sugar beets (in other use areas).

B. ENVIRONMENTAL FATE AND TRANSPORT CHARACTERIZATION

Halosulfuron

- methyl has properties with regards to persistence and sorptivity that allow for a potential for residues to occur in ground and surface waters from its use as a herbicide. A summary of halosulfuron

- methyl propertie s as included in the modeling of exposure from drinking water is provided in the “Estimation of Drinking Water Exposure” section of this

document.

Although some degradates of halosulfuron

- methyl have been found to be present in the

environment and could o ccur in drinking water, the residues of concern for the drinking water assessment consist of parent halosulfuron

- methyl only (see Appendix A for chemical structures)

.

The environmental fate profile for halosulfuron methyl is complex indicating highly va riable persistence, significant mobility in many soils, and / or the presence of a number of degradation products in the environment. Laboratory studies have demonstrated that halosulfuron degradation products can also be quite persistent and mobile.

S ome of the data would indicate relatively rapid degradation of halosulfuron under some

conditions: aerobic soil metabolism half

- lives and hydrolysis rates of only a few weeks in pure water ( Table 7 ). However, there are also clear indications of very long (i.e., up to two or three years) persistence of halosulfuron residues: Firstly, in some of the field studies a significant portion of the applied halosulfuron methyl persisted for several months or longer (see the 90% disappearance times in Table 7 ) and a first

- order kinetic model poorly described the data and severely under predicted the residue levels remaining several months to a year or more after application. Secondly, recognition of the danger of residues persisting at phytotoxic levels for an extended period is captured in label restrictions that prohibit rotation into many crops for 1, 2, or even three years after the last application of halosulfuron methyl.

Of several environmental degradates all are fragments of the parent molecule (i.e., containing either the pyrimidine or pyrazole moieties, but not both due to cleavage of the sulfonyl urea bridge) with the exception of the "halosulfuron

- methyl rearrangement ester", sometimes referred

to as "RRE" or "MON 5781." This product results from the abstraction of the S0 2 

### NHCO moiety between the rings, such that the pyrimidine and pyrazole rings a re then joined together only by an NH group. Since these degradates are not included in the drinking water residues of concern, they are not discussed further in this assessment.

Additional details on the environmental fate of halosulfuron are provided i n an August 13, 2002

Risk Assess ment (including drinking water) by EFED (DP Barcode D278449 ).

### 20

Table 7

. Summary of information on halosulfuron

- methyl persistence in soil and water.

Study or Data Source pH Half

- life, days DT 50 

### , days DT 90 

### , days

Hydrolysis, pH 5 5.0 27 ~27 NC

Hydrolysis, pH 7 7.0 15 ~15 NC

Hydrolysis, pH 9 9.0 <1 <1 NC

Anaerobic aquatic degradation

- clay loam with pond water 7.0 19 to 27 28 to 30 ~60 to 90

Aerobic soil degradation, Sarpy sandy loam 8.0 11 NC 63

Aerobic soil degradation, Sable silty clay loam 5.8 16 NC 110

Lysimeter and field dissipation studies *

Lysimeter field soil, NC Norfolk sandy loam* 1 6.0 15 to 22 4 to 12 45 to 95

Lysimeter field soil, IA Black
Hawk loam* 5.9 44 to 81 38 (7 to 86) > 370

CA San Ysidoro sandy clay loam* 6.0 61 35 455

GA Dothan loamy sand* 2 6.0 4 NC NC

IA Harp loam* 6.5 18 30 365

CA Hanford sandy loam* 2 6.8 64 NC NC

MO Mexico silt loam* 7.2 25 12 <60

IL Harpster loam* 7.7 34 36 181

TX Uvalde clay loam* 8.3 6 17 65

### 21

Table 7

. Summary of information on halosulfuron

- methyl persistence in soil and water.

Study or Data Source pH Half

- life, days DT 50 

### , days DT 90 

### , days

*For these field dissipation and lysimeter studies, half

- lives and disappearance times were calculated from the dissipation data from the top six

- inch layer of soil. Note that the analytical methods were insufficiently sensitive to accurately measure halosulfuron

- methyl concentration in most of the soil samples below six inches. This could

have resulted in a substantial fraction of the halosulfuron

- methyl remaining being unaccounted for, especially in studies where rainfall was high early after applic ation and the soils sufficiently permeable.

NC = Value not calculated due to data limitations.

1 Rainfall was extremely high early in this study (about 14 inches in the first 35 days after application),

promoting substantial leaching of the pesticide. Therefore, the actual disposition of halosulfuron

- methyl could have been affected (degradation rate could have been lower in dry soil).

2 The CA Hanford sandy loam and GA loamy sand sites were turf plots leading to difficulty in accounting of the applied r esidues and soil residue levels were often too low to accurately analyze for even right after application.



### C

. ESTIMATION OF DRINKING WATER EXPOSURE

Previous modeling (DP Barcode D2784 49 ) was done with the metamodel “FIRST” (FQPA Index

Reservoir Screening Tool). The modeling results provided in this drinking water assessment update and supplement the p revious modeling

.

FIRST utilizes a fixed high

- end reservoir exposure scenario simulated with the USEPA Pesticide Root Zone Model (PRZM) and Exposur e Analysis Modeling System (EXAMS)

. FIRST provides a measure of drinking water exposure that is designed to be protective for all crops by using a standard reservoir scenario designed to be conservative for the entire US . SCI

- GROW similarly provides a me asure of drinking water exposure from ground

- water sources that is designed to be protective in that it is based on residues measured following appl ication of pesticides at

maximum allowed rates at vulnerable sites under vulnerable conditions (i.e., shall ow aquifers, sandy, permeable soils, and substantial rainfall and/or irrigation to maximize leaching). Model inputs and results are summarized in Table 2

, Table 3 , and Table 4 . No acceptable scenario for estimation of drinking water concentrations from the rice use exists at this time so no estimates are provided (results of the tier 1 rice model have been present ed previously, see DP Barcode

D278 449.) Note that the rice model overestimates levels that would occur in drinking water because it does not consider the degradation of the pesticide or the dilution of the pesticide as it is transported away from the rice field into the drinking water source.

Table 8

. Environmental Fate model input values used with FIRST drinking water exposure assessment
model (field corn and sugarcane uses).

Parameter Input Source

### 22

Solubility (ppm) 1630 Product chemistry submissions. Solubility decreases to 15 ppm at pH 5 and increases to 7470 ppm at pH 9.

Aerobic soil t 1/2 (days) 1 48 90% Upper

- bound confidence limit on mean 2
(MRID 42139410; additional data considered from MRIDs 42661413, 42661413, 42976302, 42976303, and 42976304.)

Aerobic aquatic t 1/2 (days) 96 EFED Input Guidance for compound with no aerobic aquatic study (2x the aerobic soil half

life.

Photolysis t 1/2 in water (days) 30 MRID 42661409.

Organic carbon partition coefficient

- K
oc (mL/g) 103 Average or median value from batch

- equilibrium adsorption studies (MRID 42139411)

Application rate (lb a.i./Acre) 2 0.0625 Label

- maximum single rate for applications to field corn or sugarcane.

# applicati ons/year 2 Label maximum for field corn or sugarcane.

Application interval, days 21 Estimated from label directions allowing a split application in the period from spike to layby for corn; a 45

- day interval between applications was

also modeled.

1 For halosulfuron, field dissipation half

- lives and monolith lysimeter dissipation half

- lives were on average much longer than for the aerobic metabolism studies. An overall mean of these studies was calculated after first assuming the degradation half

- lives i n the field studies were equal to 1.2 times the dissipation half

- lives for the top soil layer. Additional indication of the potentially high persistence of halosulfuron is provided by the halosulfuron registration label which strongly implicates that halo sulfuron may persist in soil at phytotoxic levels for up to three years after application. After application of halosulfuron, rotational restrictions of one year to three years exist on various crops.

These label restrictions are consistent with an activ e ingredient that persists in the environment for years (in this case, at phytotoxic levels).

2 Values given in this table are for halosulfuron methyl corn/ sugarcane uses, which were the crops which yielded the highest EECs with both models. Model input and output files are provided in Appendix B.



### Results of surface water source modeling are summarized in Table 3 and ground

- water modeling

in Table 5

. The acute exposure c oncentrations for an index reservoir with FIRST range from 3.8

to 8.3 ppb or ug/L for the various use patterns modeled

. The c hronic exposure estimates (annual average E DWC) with FIRST ranged from 0.8 to 1.7 ppb . The highest acute and chronic exposure

EDWC were both associated with a corn and sugarcane use pattern. The Tier 1 EDWC for ground

- water (using the SCI

- GROW model) was significantly lower (0.065 ppb for both acu te and chronic exposure).

Table 9

. Summary of halosulfuron methyl scenarios modeled with FIRST.

### 23

Represent

ative Crop Single

Rate, lb

ai/A # of

applica

tions Interval

between appl., days Total

seasonal rate, ai/a Acute

EDWC, ug/L Annual

EDWC, ug/L

Tomato 0.047 2 21 0.094 6.2 1.3

Asparagus 1 0.047 2 45 0.094 5.5 1.2

Sugarcane 0.042 3 21 0.125 7.3 1.5

Corn,

sugarcane 0.063 2 21 0.125 8.3 1.7

Corn,

sugarcane 0.063 2 45 0.125 7.3 1.5

Pioneer IR

corn 0.094 1 NA 0.094 3.8 0.80

Soybean 0.063 2 150 0.125 5.4 1.1

Note: The EFED default 87% crop area assumption was used except for corn (46% crop area).

1 And flowering vegetables.



### Table 10

. Environmental Fate Input Parameters for halosulfuron methyl in SCI

- GROW.

Parameter Halosulfuron Source

Organic Carbon Partition Coefficient (K OC 

### ) 103 (Avg.) Median value.

Aerobic Soil Metabolism Half

- Life (days) 48 Average value.

Table 11

. Summary of halosulfuron methyl ground

- water scenario modeled with SCI

- GROW.

Representative Crop Single

Rate, lb

ai/A # of

applications Total

seasonal rate, ai/a Acute EEC,

ug/L Chronic

EEC, ug/L

Field corn,

sugarcane 0.0625 2 0.125 

## 0.065 0.065

D

. COMPARISON OF MODELED AND MEASURED DRINKING WATER

CONCENTRATIONS

### 24

Since the last major drinking water assessment for halosulfuron

- methyl no new major drinking water source monitoring studies for halosulfuron

- methyl were identified from the literature. However, the monitoring data that do exist would suggest that concent rations in ground and surface waters are generally low (well below 1 ug/L even in waters in or very near treated areas).

L imited monitoring data exist for halosulfuron from Battaglin et al. (1999, 2000) 8 

### who screened reservoir, river, and ground water samples for a variety of low

- rate herbicides, including halosulfuron. Out of 129 water samples from Midwestern streams and rivers, halosulfuron was detected in 7 samples at concentrations above 0.01 ug/L (ppb), with a maximum concentration of 0.067 ppb. No sampling for halosulfuron was reported in the 1992 Pesticides in Ground Water

D atabase (Jacoby et al., 199 2) 9 

### . Previously, a prospective Ground

- Water Monitoring Study (see

EFED Review of DP Barcode D226451 da ted 2/14/97) was requested, but that requirement has been deferred by the Agency.

Although the monitoring data demonstrate lower concentrations than those modeled, they are insufficiently targeted towards vulnerable waters associated with halosulfuron

- me thyl use to be used to calculate drinking water exposure.

8 Battaglin, W.A., Furlong, E.T., Burkhardt, M.R., and Peter, J.C. 1999. Occurrence of Sulfonylurea, Sulfonamide, Imidazolinone, and other herbicides in Midwestern rivers, reservoirs, and ground water, 1998 in U.S. Geolo gical Survey Toxic Substances Hydrology Program

-- Proceedings of the Technical Meeting, Charleston, South Carolina,

March 8

- 12, 1999: U.S. Geological Survey Water

- Resources Investigations Report 99

- 4018B, Volume 2, pp. 215

- 225.

Battaglin, W.A., Furlong, E.T., Burkhardt, M.R., and Peter, J.C. 2000. Occurrence of Sulfonylurea, Sulfonamide, Imidazolinone, and other herbicides in rivers, reservoirs, and ground water in the Midwestern United States, 1998. Science Total Environ. Vol. 248, Issues 2

- 3, 5 April 2 000, Pages 123

- 133

.

9 Jacoby, H.J. et al. U.S. EPA. 1992. Pesticides in Ground Water Database

- A Compilation of Monitoring

Studies: 1971

- 199, EPA 734

- 12

- 92

- 001.

### 25



## APPENDIX A: Chemical structures of halosulfuron

- methyl and selected environmental degradates.

Halosulfuron

- methyl methyl 5

- {[(dimethoxy

- 2

- pyrimidinyl) amino] carbonylaminosulfonyl

- 3

- chloro

- 1

- methyl

- 1

- H

- pyrazole

- 4

- carboxylate

Halosulfuron rearrangement ester

1 H

- Pyrazole

- 4

- carboxylic acid, 3

- chloro

- 5

- . [(4,6

- dimethoxy

- 2

- pyrimidinyl)amino]

- 1

- methyl, methyl ester

OR Methyl 3

- Chloro

- 5

- (4,6

- dimethoxypyrimidin

- 2

- ylamino)

- 1

- methylpyrazole

- 4

- carboxylate

Halosulfuron aminopyridine

### 26

Halosulfuron guanidine

### 27



## APPENDIX B: Aquatic Exposure: SCI

- GROW and FIRST Water Quality Modeling Inputs and Results

New and updated model runs

A. SCI

- GROW

VERSION 2.3

ENVIRONMENTAL FATE AND EFFECTS DIVISION

OFFICE OF PESTICIDE PROGRAMS

U.S. ENVIRONMENTAL PROTECTION AGENCY

SCREENING MODEL

FOR AQUATIC PE STICIDE EXPOSURE

SciGrow version 2.3

chemical:Halosulfuron

- methyl time is 5/22/2009 17:29:40

------------------------------------------------------------------------ Application Number of Total Use Koc Soil Aerobic rate (lb/a cre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------ 0.063 2.0 0.125 1.03E+02 48.0

---------------------------------------------------- -------------------- groundwater screening cond (ppb) = 6.54E

- 02

************************************************************************



## B. FIRST

RUN No. 1 FOR Halosulfuron met ON Corn, Suga * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------- ------------------------------ .063( .110) 2 21 103.0 1630.0 AERIAL(16.0) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------
METABOLIC DAYS UNTIL HYDROLYSI S PHOTOLYSIS METABOLIC COMBINED (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------

8.385 1.773

### 28

RUN No. 2 FOR Halosulfuron Met ON corn

– special** * INPUT VALUES *

-------------------------------------------- ------------------------ RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .063( .110) 2 21 103.0 1630.0 AERIAL(16.0) 46.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------
METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COM BINED (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGR AMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

----------------- ---------------------------------------------------

4.434 .937

** this run utilizes a corn

- specific PCA.

RUN No. 3 FOR Halosulfuron met ON Soybeans * INPUT VALUES *

------------------------------------ -------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .063( .070) 2 150 103.0 1630.0 AERIAL(16.0) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------
METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COM BINED (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGR AMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

----------------- ---------------------------------------------------

5.381 1.138



## Previous model runs (see DP Barcode D278449)

A. Ground Water

- SCI

- GROW

### 29

RUN No. 1 FOR Halosulfur on methyl ** INPUT VALUES **

-------------------------------------------------------- APP RATE APPS/ TOTAL/ SOIL AEROBIC SOIL METAB

(LBS/AC) YEAR SEASON KOC HALFLIFE (DAYS)

--------------------------------------------------------

.063 2 .125 103.0 48.00

GROUND

- WATER SCREENING CONCENTRATION (IN PPB)

--------------------------------------------------------

.0 652

--------------------------------------------------------



## B. Surface Water

- FIRST

RUN No. 1 FOR Halosulfuron met ON Tomatoes e * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------- ------------------------------
.047( .082) 2 21 103.0 1630.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------

METABOLIC DAYS UNTIL HYDROLYSI S PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.0 AUG 1, 2001

--------------------------------------------------------------------
PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------

6.231 1.311

### 30

RUN No. 2 FOR Halosulfuron met ON Asparagus * INPUT VALUES *

---------------------------------------------- ---------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

--------------------------------------------------------------------
.047( .072) 2 45 103.0 1630.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.0 AUG 1, 2001

--------------------------------------------------------------------
PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------

5.465 1.150

RUN No. 3 FOR Halosulfuron met ON Sugarcane * INPUT VALUES *

---------------------------------------------- ---------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

--------------------------------------------------------------------
.042( .095) 3 21 103.0 1630.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.0 AUG 1, 2001

--------------------------------------------------------------------
PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------

### 31 7.276 1.531

RUN No. 4 FOR Halosulfuron met ON Corn, suga * INPUT VALUES *

---------------------------------------------------------- ---------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

--------------------------------------------------------------------
.063( .109) 2 21 1 03.0 1630.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.0 AU G 1, 2001

--------------------------------------------------------------------
PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

----------------------------------------------- ---------------------

8.286 1.744

RUN No. 5 FOR Halosulfuron met ON SCane, FCo * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

--------------------------------------------------------------------
.063( .095) 2 45 103.0 1630.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------------

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.0 AUG 1, 2001

------------------------- -------------------------------------------

### 32 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------

7. 267 1.530

RUN No. 6 FOR Halosulfuron met ON Pioneer IR * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

--------------------------------------------------------------------
.094( .094) 1 1 103.0 1630.0 GROUND( 6.4) 46.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DA YS)

--------------------------------------------------------------------

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

------------------------------- ------------------------------------- 48.00 2 N/A 30.00

- 3720.00 96.00 93.58

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.0 AUG 1, 2001

--------------------------------------------------------------------
PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------

3.783 .796