OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION **UNITED STATES ENVIRONMENTAL PROTECTION AGENCY**

WA SHINGTON, D.C. 20460



### MEMORANDUM **DATE:** March 2 6 , 2013 **SUBJECT:** Halosulfuron meth yl Drinking Water Assessment for Additional Food/Feed Uses

on Art ichoke s and Caneberry Subgroup 13
- 07A ( **DP Barcode D 404096**  **; PC Code 128721**  ) **TO:** Barbara Madden , Risk Manager

Sidney Jackson , Risk Manager Reviewer Luis Sugui yam a , Acting Chief Risk I ntegration Minor Use, and Emergency Response Br anch Registration Division (7505P) **&** Sheila Heal y , 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 Water Concentrations (EDWCs) for halosulfuron methy l, a sulfony lurea 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; wil d raspberry ; cultivars, varieties, and/or hy brids of these ” ). Conclusions from our evaluation about the potential level of acute and chronic exposure to halosulfuron methy l in drinking water remain the

### 2

same as in the Environmental Fate and Effects Divison ’s ( EFED’s ) previous assessment (see DP Barcode **D394244 ,**  review dated 5/15/2012 1 

### ). The current acute and chronic drinking water exposure estimates are summarized in Table 1 . **Table 1**  **.** Tier IEstimated Drinking Water Concentrations (EDWCs) for human health drinking water risk assessment. **DRINKING WATER SOURCE**  **(M ODEL USED)**  **USE (rate m**  **od eled)**  **MAXIMUM ESTIMATED DRINKING WATER CONCENTRATION**  **(EDWC) c**  **( ppb)** Groundwater (SCI
- GROW) Fallow ground (0.125 lb a.i./A/season) a Ac ute 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 Ac ute 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 mo del. **b** Seasonal rate is 0.0625 lb a.i . /A , which is half of the rate of fallow ground
. **c** Surface w ater concentrations calculated by the Tier I Rice Model v1.0 and ground w ater concentrations calculated by SCI
- GROW do not distinguish between peak and chronic concentration
. 

## Background: The proposed use rates for the specialt y 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, t he highest drinking water exposures are 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.

1 The mo st recent review (D394244) is designated as **Attachment 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**  ).

### 3

**Table 2**  . Proposed uses of halosulfuron
- methy l. Us e 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 abilit y to conduct refined exposure assessments for drinking water from both surface water and ground water 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 For surface water based drinking water supplies impacted b y uses at sites where flooding is expected during part of th e crop production cy cle, the **P** esticide **F** looded **A** pplication **M** odel. (PFAM) has been approved by EFED to provide more refined exposure estimates for acute and especiall y chronic drinking water exposure. This model is not y et posted on the EPA website, but cur rentl y, additional details can be found here: https://sites.google.com/site/pfamodel/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 drinking 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 conservative estimate of drinking water exposure; but we do note that more refined estimates are possible with the newly

implem ented PFAM model, should such refinements become necessary in the future (the Health Effects Division is not requesting such refinements at this time.)

### 1 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION **UNITED STATES ENVIRONMENTAL PROTECTION AGENCY**

WA SHINGTON, D.C. 20460



## ATTACHMENT A: **Copy of DWA**  **dated 5/15/2012. MEMORANDUM**  **DATE:** May

15 , 2012 **SUBJECT:** Halosulfuron meth yl 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 Kenn y, 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 Wat er Concentrations (EDWCs) for halosulfuron methy l , a sulfon yl urea herbicide, were e valuated for the proposed new uses
. This drinking water 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 chronic exposure to halosulfuron methy l in ground drinking water remain the same as in EFED’s previous assessment ; furthermore, exposure due to the use on rice was calculated . Se e

### 2

the **Attachment B**  for a copy of the previous review ( includes DP Barcode D358032 dated 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, chemical structures, and several other details about halosulfuron methy l wer e previously provided. Although it has been found that some degradates of halosulfuron methy l are present in the environment and could occur in drinking water, the residues of concern for the drinking water assessment (DWA) include parent halosulfuron met hy l onl y ( 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 methy l onl y. In previous assessments, t he uses on rice were not includ ed. Therefore, besides the EDWCs for several crop uses, the EDWCs for the uses on rice were calculated. The results for the use on rice are significantl y higher than for previous crops. For modeling approach, assumptions, and uncertainties, see below. A more definitive assessment and refinements are possible if needed b y 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 Ac ute 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 Ac ute 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 calculated by the Tier I Rice Model v1.0 and ground w ater concentrations calculated by SCI
- GROW do not distinguish between peak and chronic concentration
. 

### Modeling was previousl y 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 o btained 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 co nservative concentration s as described below)
. 2 

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

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:

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

### 3 = 0 . 00105 + 0 . 00013 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 greatl y simplifies the model. The absence of degradation adds conservatism to the model ( i.e. , estimated concentrations should be higher than those usuall y found in rice paddies). The absence of mass transfer processes can either add or reduce conservatism depending on numerous conditions such as wh ether the pesticide is soil or water applied and whether actual degradation occurs preferentiall y in the sediment or the water compartment; however, consideration of this parameter is a refinement bey ond a Tier I conceptualization. **Table 1 -**  **2** provides a su mmary 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 = 0 . 00105 + 0 . 00013

= 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. 5. Water is available for human or wildlife exposure instantaneousl y. 6. Water column depth is 10 c m. 7. Sediment depth is 1 cm. 8. All po re space is saturated with water.

### 4

9. Organic carbon fraction is 0.01. 10. Bulk density

is 1300 kg/m 3



### . 11. Grain densit y 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 uncontaminated 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 generall y do not represent t ypical concentrations found in human drinking water, as they represent paddy

discharge water. The chronic conc entrations as well as offsite concentrations are expected to be conservative. If Tier I estimates calculated b y this screening method do not exceed the HED’s concern level in a risk assessment, there is high confidence that there will be little or no ris k 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 conservative, exceeding peak measured concentrations of pesticides in water bodies well downstream of rice pad dies in five evaluated studies by less than one order of magnitude to multiple orders of magnitude . The five studies assessed were conducted in Louisiana and California using four different pesticides (USEPA 2007)
. Itappears that t he range of modeled es timate exceedances over measured concentrations is most likely in response to chemical, environmental, and stud y - specific factors. Estimates from the Tier I model generall y do not represent ty

pical concentrations found in human drinking water, as they rep resent direct padd y discharge water. 

## Updated Use **Information** T he current and proposed use sites for halosulfuron methy l 3 

### are summarized in **Table 1 -**  **3** (the proposed uses are shaded blue ). Halosulfuron methy l is a selective preemergence or post
emergence sulfon yl urea herbicide. It is currentl y registered for a number of food crops and fallow ground by Can yo n Group, LL C for the products GWN - 3061 [ contains 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 States in 1994 by Nissan Chemical Industries, Inc. (NC I) and Monsanto Company
. Gowan Company and Nissan Chemical Industries, Inc. have formed a joint venture named Can yon Group LLC in 1994
. The current petition for registration for proso millet , and pasture and rangeland ( Crop Group 17 ) was submitted on behalf of Cany on Group LLC .

3 M ethyl 5
- {[(dim ethoxy
- 2 - py rim idinyl) amino] carbonylaminosulfonyl
- 3 - chloro
- 1 - methyl
- 1 - H - py razole
- 4 - carboxylate

### 5

**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 allow ed. 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 )

### 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)**  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 Bushberry subgroup 13 - 07B 0.023 - 0.0 47 NS 45 14 0.094 Apples (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 em ergence, 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 ma ke 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** Som e labels are unclear and imply that the second application to sw eet 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 DA** **TED 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 meth yl Drinking Water Assessment for Additional food uses on

Dried Shelled Peas & Beans (Except Soy bean), 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 methy l 4 

### (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. 5 

### Conclusions about the potential level of acute and chronic exposure to halosulfuron methy l in drinking water remain the same as in our previous assessment (see Appendix 2 for a cop y of the previous review):

4 met hyl 5
- {[(dimethoxy
- 2 - pyrimidinyl) amino] carbonylaminosulfonyl
- 3 - chloro
- 1 - methyl
- 1 - H - pyrazole
- 4 - carboxylate 5 In cluding dried shelled peas & beans (except soybean), succulent shelled peas & beans, apples, rhubarb, bushberry, fruiting vegetables and tuberous & corm vegetables; proposed and current uses are summarized in Table 1.

### 3

For par ent alone:  **8.3** μg/l or ppb for acute exposure (1 in 10 y ear annual peak dail y concentration)  **1.7** μg/l for (non
- cancer) chronic exposure (1 in 10 y ear annual mean concentration) These EDWCs were calculated using the FIRST mode run for the corn, fallow gr ound, and sugarcane use patterns (further details are provided in our previous review cited above.) EDWCs were also previousl y 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 assessment consist of parent halosulfuron
- methy l only and these estimates are , as in previous assessments, for exposure to parent halosulfuron methy l onl y. Modeling was with the Tier 1 PRZM
- EXAMS metamodel “FIRST” (FQPA I ndex 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 currentl y 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 methy l are summarized in **Table** (the proposed uses are marked by an asterisk). Halosulfuron
- methy l is a selective preemergence or post - emergence sulfon yl urea herbicide. Halosulfuron is currentl y registered for a number of food crops and fallow ground under Section 3 b y 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 1994 by Nissan Chemical I ndustries, Inc. (NCI) and Monsanto Company . Gowan Co mpan y and NCIhave formed a joint venture named Cany on Group LL C. The current petition for registration for several minor use crops being reviewed here has been submitted by Interregional 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 allow ed. 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, w e m odeled this use in that way. a Som e labels are unclear and imply that the second application to sw eet 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 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 current EFED rice model for ecological aquatic exposure from a rice use overestimates levels that would occur in drinking water because it does not consider the degradation of the pesticide or the dilu tion 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 . Environme ntal 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 directions allowing a split application in the period from spike to layby for corn; a 45 - day interval between applications was also mode led. 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 w ere 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 in the field studies were equal to 1.2 times the dissipation half
- lives for the top soil layer. Additional indication of t he 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 active ingredient that persists in the environment for years (in this case, at phytotoxic levels). 2 Values given in this tabl e 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 significantl y lower (0.065 ppb for both acu te and chronic exposure). **Table 3**  **.** Summary

of halosulfuron methy l 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 flow ering vegetables. This model run is also representative of dried shell beans east of the Rockies (only low er rates permitted for dry beans west of the Rockies) and apples east of the Rockies. 

### Table **4 .**  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 (day s) 48 Average value.
**Table 5**  **.** Summary

of halosulfuron methy l 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 PESTICIDE EXPOSURE SciGrow version 2.3 chemical:Halosulfuron - methyl time is 5/22/2009 17:29:40

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

------------------------------------------------------------------------ 0.063 2.0 0.125 1.0 3E+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 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 1.1.0 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 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

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

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 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) CONCEN TRATION 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 meth yl Drinking Water Assessment for Additional food uses

(including proposed use on soy bean) (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
- methy l (meth yl 5 - {[(dimethox y - 2 - py

rimidiny l) amino] carbon yl aminosulfony l
- 3 - chloro
- 1 - methy l
- 1 - H - py razole
4 - carbox yl ate) that incorporates a proposed use pattern for so yb eans 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 L abel” (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 ethy l 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 allow ed. 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 Bushberry subgroup 13 - 07B 0.023 - 0.0 47 NS 45 14 0.094 Apples (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 em ergence, 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 ma ke 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** Som e labels are unclear and imply that the second application to sw eet 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 I ndex 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 pattern. Tier 1 EDWC for ground
- water (using the SCI
- GROW model) were s ignificantly lower. A suitable model for estimation of drinking water concentrations from the rice use is not currentl y available (EFED’s tier 1 rice model does not provide concentration estimates that can be associated with levels expected in drinking wat er.)

### 15

**I I**  **. Discussion**  A. USE PROFILE Halosulfuron
- methy l is a selective preemergence or post
- emergence sulfonylurea herbicide. Halosulfuron is currently registered under Section 3 by Nissan Chemical Industries, I nc. 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 I ndustries, Inc. (NCI) and Monsanto Company . Gowan Company and NCIhave formed a joint venture named Cany on Group LL C. Can yon Group LLC has submitted a request for a new use on soy beans. Halosulfuron
- methy l is currentl y registered for use on some fruiting vegetables, field corn, sweet corn, grain sorghum, rice, sugarcane, tree nuts, and turfgrass. This drinking water assessm ent also considers the impact of a proposed use on soy beans. 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 allow ed. 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 Bushberry subgroup 13 - 07B 0.023 - 0.0 47 NS 45 14 0.094 Apples (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 em ergence, 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 ma ke 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** Som e labels are unclear and imply that the second application to sw eet 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.



### . **Table 6**  **.** General usage information for halosulfuron
- methy l. **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

### 18

**Crop(s) Max.** 

**Application rate (range)**  **Max. #**

**applications / Season**  **Interval PHI**  **(days) Maximum** 

**Annual Rate (1b ai/A)**  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 allow ed. 

### 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) 

### Soy beans 0.0625

(Range 0.031
- 0.62) 2 (?)

Preemg or Preplt

– 21 days bef. Planting to em g. Fall burndown

– anytime after harvest until ground freezes 

### NS (probably about 150 days) 

### NS 0.125 (?)

NA = not applicable. NS = not specified. 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.** ENVI RONMENTAL FATE AND TRANSPORT CHARACTERIZATION

### 19

Halosulfuron
- methy l has properties with regards to persistence and sorptivity that allow for a potential for residues to oc cur in ground and surface waters from its use as a herbicide. A summary of halosulfuron
- methy l properties as included in the modeling of exposure from drinking water is provided in the “Estimation of Drinking Water Exposure” section of this document. Alth ough 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 assessment consist of parent halosulfuron
- methy l only (see Appendix A for chemica l structures)
. The environmental fate profile for halosulfuron methy l is complex indicating highl y variable 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. Some of the data would indicate relatively rapid degradation of halosulfuron under some conditions: aerobic soil metabolism half
- lives and hy drol ys is rat es of onl y a few weeks in pure water ( Table 7 ). However, there are also clear indications of very long (i.e., up to two or three ye ars) persistence of halosulfuron residues: Firstly, in some of the field studies a significant portion of the applied halosulfuron methy l 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 severel y under predicted the residue levels remaining several months to a year or more after application. Secondl y, recognition of the danger of residues persisting at phy totoxic 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 p yrimidine or pyrazole moieties, but not both due to cleavage of the sulfonylurea bridge) with the exception of the "halosulfuron
- methy l 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 py rimidine and py

razole rings are then joined together onl y b y an NH group. Since these degradates are n ot 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 in an August 13, 2002 Risk Assess ment (including drinking water) b y EFED ( DP Barcode D278449 ). **Table 7**  **.** Summary

of information on halosulfuron
- methy l persistence in soil and water. **Study or Data Source pH**  **Half -**  **life, days DT**  **50** 

### , days **DT 90**  

### , days Hy droly sis, pH 5 5.0 27 ~27 NC

### 20

**Table 7**  **.** Summary

of information on halosulfuron
- methy l persistence in soil and water. **Study or Data Source pH**  **Half -**  **life, days DT**  **50** 

### , days **DT 90**  

### , days Hy droly sis, pH 7 7.0 15 ~15 NC Hy droly sis, 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 M exico 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
- methy l 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 application and the soils sufficiently permeable. NC = Value not calcul ated due to data limitations. 1 Rainfall was extremely high early in this study (about 14 inches in the first 35 days after application), prom oting 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 residues and soil residue levels were often too low to accurately ana lyze for even right after application.


### C **.** ESTI MATION OF DRI NKI NG 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 Exposure Anal ys is Model ing Sy stem (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 measure of drinkin g 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., shallow aquifers, san dy , 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 ric e use 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 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 exposu re 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 hal f
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. # applications/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 w ere on average much longer than for the aerobic metabolism studies. An overall mean of these st udies was calculated after first assuming the degradation 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 t he 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 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 t he 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 significantl y lower (0.065 ppb for both acute and chronic exposure). **Table 9**  **.** Summary

of halosulfuron methy l 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 flow ering vegetables. 

### Table **10 .**  Environmental Fate Input Parameters for halosulfuron meth yl in SCI
- GROW.

**Parameter Halosulfuron**  **Source** Organic Carbon Partition Coefficient (K OC 

### ) 103 (Avg.) Median value. Aerobic Soil Metabolism Half
- Life (day s) 48 Average value.

**Table 11**  **.** Summary

of halosulfuron methy l 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 .**  COMPARI SON OF MODELED AND MEASURED DRI NKI NG WATER CONCENTRATIONS

### 24

Since the last major drinking water assessment for halosulfuron
- methy l no new major drinking water source monitoring studies for halosulfuron
- methy l 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) 6 

### who screened reservoir, river, and ground water samples for a variet y 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) 7 

### . Previously , a prospective Ground
- Water Monitoring Study (see EFED Review of DP Barcode D226451 dated 2/14/97) was requested, but that requireme nt has been deferred b y the Agency . Although the monitoring data demonstrate lower concentrations than those modeled, they are insufficiently

targeted towards vulnerable waters associated with halosulfuron
- methyl use to be used to calculate drinking wate r exposure.

6 Battaglin, W.A., Furlong, E.T., Burkhardt, M.R., and Peter, J.C. 1999. Occurrence of Sulfonylurea, Sulfonamide, Im idazolinone, and other herbicides in Midwestern rivers , reservoirs, and ground water, 1998 in U.S. Geological 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, Vo lume 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. Scie nce Total Environ. Vol. 248, Issues 2 - 3, 5 April 2000, Pages 123
- 133 .

7 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
- methy l methy l 5
- {[(dimethoxy
- 2 - py rimidiny l) amino] carbony laminosulfony l
- 3 - chloro
- 1 - methyl
- 1 - H py razole
- 4 - carbox yl ate

Halosulfuron rearrangement ester 1 H - Py razole
- 4 - carbox yl ic acid, 3
- chloro
- 5 - . [(4,6
- dimethoxy
- 2 - py rimidinyl)amino]
- 1 - methy l, methy l ester **OR** Methy l 3
- Chloro
- 5 - (4,6
- dimethoxy py rimidin
- 2 - yl amino)
- 1 - methy lpy

razole
- 4 - carboxy late

Halosulfuron aminop yridine

### 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 PESTICIDE 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 scre ening 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

RUN No. 2 FOR Halosulfuron Met ON corn

– special** * INPUT VALUES *

### 28

-------------------------------------------- ------------------------ 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 Halosulfuron 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 HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED (FIELD) RAI N/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
RUN No. 2 FOR Halosulfuron met ON Asparagus * INPUT VALUES *

### 30

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

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

7.276 1.531

### 31

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

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

### 32 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