### 2 EXECUTIVE SUMMARY

The subject chemical addressed in this drinking water assessment is identified by the chemical name nicosulfuron (DPX-V9630) with the chemi cal synthesis (IUPAC) name of 2-[[[[(4,6- dimethoxy-2- pyrimidinyl)amino]carbonyl ]amino]sulfonyl]-N,Ndimethyl- 3- pyridinecarboxamide. Figure 1 below shows the chemical co mposition of nicosulfuron. Nicosulfuron is composed of molecular struct ures attached to pyrim ide and pyridine rings bonded together by a sulfonylurea bridge (-NH-CO-NH-SO2-).

Figure 1. Chemical structure of nicosulfuron.

Nicosulfuron is proposed to be used in convent ional ground and aerial foli ar applications on the ALS inhibition tolerant sorghum crops. Table 1 in the Use Characterization section shows the complete proposed use information for nicosulf uron on ALS inhibition tolerant sorghum crops. Proposed maximum application rates range be tween 0.031 to0.061 lbs. a.i./A with seasonal application rates ranging between 0.057 – 0.084 lbs. a.i./A with a minimum of 7 seven days between applications specified on the draft pr oduct label. The most recent drinking water assessment for nicosulfuron (DP Barcode Nos. 301842, 302623, and 302624, dated August 3, 2004) was conducted for corn new uses with ma ximum single application rates of up to 0.0625 lbs. a.i./A. Although this maximum single app lication rate is higher than the proposed ALS inhibition tolerant sorghum crops (0.061 lbs. a.i. /A), the maximum seasonal application rate of 0.0625 lbs. a.i./A for the existing corn use is lowe r than the new ALS inhibition tolerant soybean crop new use (0.084 lbs. a.i./A). Therefore, exposure in surface water and ground water is expected to be higher for the proposed sorghum use.

Nicosulfuron is a sulfonylurea herbicide curre ntly used on crops othe r than corn including Bermuda grass, switch grass, fodder, rights of way, and fields (within construction sites, flood plains, swamps, and sewage disposal areas). Ni cosulfuron is applied to crop foliage and grass via ground (broadcast and banded ap plications) and aerial applic ations. In addition, spot treatments are allowed in uses for Bermuda gr ass, fields, and rights of way. Nicosulfuron products are available as an emulsifiable concen trate or dispersible gr anules. Maximum single application rates for existing uses range be tween 0.00023 – 0.0703 lbs. a.i./A. The number of applications per year and the minimum time inte rval between treatments are not specified on many labels for current uses.

Nicosulfuron belongs to the sulfonyl urea class of herbicides, which act s by inhibiting the plant enzyme acetolactate synthetase (ALS). The inhib ition of this enzyme blocks the production of amino acids, valine and isoleucine, which are impo rtant in the production of plant proteins and

### 3 other components. This leads to the disruption of cell division and elongation in the plant. It is intended to control a variety of annual and perennial broa dleaf and grass weeds in both agricultural and non-agricultu ral settings such as barnyardgra ss, crabgrass, foxtail, panicum, volunteer wheat, Johnson grass and shattercane. The application of nicosulfuron to ALS inhibition tolerant sorghum crops will enable fo r nicosulfuron to treat these crops without damage while killing other target weeds. The ne w use for ALS inhibition tolerant soybean crops is proposed for DuPontTM Accent® and DuPont TM Steadfast® which possess 75 and 55 percent of the active ingredient nicosu lfuron, respectively. Both produc ts are water soluble granule formulations. Details on the ni cosulfuron products wh ich the new use encompasses are provided in Table 1 of the Use Characterization section.

This Tier I Drinking Water A ssessment for the proposed ne w use of nicosulfuron on ALS inhibition tolerant sorghum crops provides estimates of the uppe r bound residue concentration of nicosulfuron in surface and ground water drinking water sources resulting from its proposed uses. In addition, the proposed uses and fate prop erties of nicosulfuron are evaluated to identify the exposure pathways to drinking water. Both modeling tools and monitoring data are measures of exposure used to evaluate the impact of th e new proposed nicosulfuron uses on drinking water resources. The tier 2 model PRZM/E XAMS (PRZM version 3.12.2, May 2005 and EXAMS version 2.98.4.6, April 2005) will be used to evalua te surface water exposure. The tier 1 model PRZM-GW (version 1.0, December 2012) will be used to evaluate ground water exposure. Nicosulfuron existing monitoring data found from stream water, spring water, and ground water sources from the United States Geological Su rvey National Water Quality Assessment (USGS NAWQA) program will also be presented to ve rify modeled exposures for drinking water.

Nicosulfuron foliar applications using ground an d aerial sprays both may impact both surface and ground water drinking water sources given that it possesses similar physical chemical properties and persistence to other chemicals which are known to translocate to these media. Nicosulfuron mainly degrades in soil and wa ter to the following degradates: IN-HYY21 and IN37740 which maintain the sulfonylurea bridge , and pyridine sulfona mide (IN-V9367) and pyrimidine amine (IN-J0290). Since IN-HYY21 and IN-37740 are expected to possess similar environmental fate and toxicity to parent nicosulf uron due to similarities in molecular structure, these degradates are included in the drinking wa ter assessment. Please refer to the Problem Formulation section of this drinking water asse ssment for the full discussion on how degradates were considered in this drinki ng water assessment. Acute exposur e of nicosulfuron total residues (including parent, IN-HYY21 and IN-37740) in su rface drinking water sources is represented by annual peak concentrations and chronic exposure represents annual average concentrations. In this Tier I analysis, 1-in-10 year peak concen trations are representative of acute levels of exposure, the 1-in-10 year annual average concen tration are representati ve of noncancer chronic levels of exposure, and the 30-year mean concen tration is assumed to represent cancer drinking water exposure from surface drinking water sources. In ground water, estimated peak concentrations are assumed to represent acute exposure concentrations and the post-breakthrough average estimated concentrations are assumed to represent chronic and canc er concentrations.

It appears that the modeling estimates indica tes that ground water exposure will drive the drinking water assessment. The PRZM-GW mo del estimates upper-bound concentrations of

### 4 nicosulfuron, IN-HYY21, and IN -37740 in ground drinking water sources not likely to exceed 26.3  g/L (26.3 ppb) for acute exposure and 19.2  g/L (19.2 ppb) for chronic and cancer exposure. Upper-bound Tier I modeling usi ng PRZM/EXAMS predicts generally lower concentrations of 9.67 μg/L (9.67 ppb) for the acute peak concentration, 2.80 μg/L (2.80 ppb) for the chronic concentration, and 2.15 μg/L (2.15 ppb) for the cancer concentration.

The EDWCs reported above for the ALS inhib ition tolerant sorghum uses represent the maximum exposure with nicosulfuron uses that have a maximum annual application rate specified on the label since this proposed us e possesses the highest a nnual application rate specified out of all uses. However, it is importa nt to note that there are other uses that have unspecified annual application ra tes including Bermuda grass, switch grass, fodder, and rights of

way.

USE CHARACTERIZATION

Nicosulfuron water soluble granular products are proposed to be used in conventional ground and aerial foliar applications on ALS inhibition tolerant sorghum crops. This new use is proposed for DuPontTM Accent® (75 percent ni cosulfuron) and DuPontTM Steadfast® (55 percent nicosulfuron) products. Proposed maximum applicati on rates range between 0.031 lbs. a.i./A – 0.061 lbs. a.i./A with seasonal applicatio n rates ranging between 0.057 – 0.084 lbs. a.i./A with a minimum of 7 seven days between applic ations specified on the draft product label. Table 1 in the Use Characterization section shows the complete proposed use information for nicosulfuron on ALS inhibition tolerant so rghum crops. Data from the USDA National Agricultural Statistics Serv ice (NASS) indicate that so rghum crop production is highly concentrated over an area of the country confin ed to mainly the Southern Great Plains region including Central and West Texas, the Panhandle of and Central Oklahoma, Central and Western Kansas, South Central Nebraska, and South Central South Dakota 1



### .

Table 1. Summary of application informatio n based on labels provided by DuPontTM for nicosulufuron related to the proposed Sect ion 3 new use for ALS inhibition tolerant sorghum crops.

PRODUCT % A.I. FORMULATION APPLICATION METHOD SINGLE APP. RATE (lbs. a.i./A) MAX. SEASONAL APP. RATE (lbs. a.i./A) MIN. RETREATMENT INTERVAL (days)



### DuPontTM Accent® 75 SG G, A 0.031 - 0.061 0.084 7



### DuPontTM Steadfast® 55 SG G, A 0.043 - 0.057 0.057 7

1. Formulation identifier: SG = Water soluble granule

2. Application method identifiers: G = foliar groun d application; A = foliar aerial application

1 Citation: http://www.nass.usda.gov/Charts_and_Maps/Crops_County/pdf/AS-PL12-RGBChor.pdf

### 5 ENVIRONMENTAL FATE AND TR ANSPORT CHARACTERIZATION

Physical and chemical propertie s of nicosulfuron are shown in Table 2 below. Environmental fate and transport properties of nicosulfuron based upon registrant submitted studies or other references are shown in Table 3 below.

Table 2. Physical and chemical properties of nicosulfuron. Property Value and units MRID or Source

Chemical Name 2-[(4,6-Dimethoxypyrimidin-2-ylcarbamoyl)sulfamoyl]-N,Ndimethylnicotinamide. Product chemistry (MRID 47006001)

Structure EpiSuite

Chemical Formula C 15 H 18 N 6 O 6 S Product chemistry (MRID 47006001)

Molecular

Weight 410.4 g/mol Product chemistry (MRID 47006001) Vapor Pressure (25°C) 2.17 x 10 -10 torr Product chemistry (MRID 48399916)

Water Solubility

(pH 7, 20°C) 8,070 mg/L Product chemistry (MRID 47006001)

Henry’s Law

Constant 3.51 x 10 -12 atm·m 3 /mol Calculated value from vapor pressure and water solubility Octanol – water partition coefficient (log K O W ) 0.14 Product chemistry (MRID 47006001)



### Table 3. Summary of nicosulfuron environmental fate properties.

Study/ OCSPP Guideline No. Value and unit MRID #

or Citation Study Classification, Comment

Abiotic Hydrolysis

(835.2120) pH 5, 25°C: 14.7 days pH 7; 25°C: 606 days pH 9, 25°C: 635 days 40924220, 47083601 Supplemental (All Studies)

 Sulfonylurea

### 6 Table 3. Summary of nicosulfuron environmental fate properties.

Study/ OCSPP Guideline No. Value and unit MRID #

or Citation Study Classification, Comment

bridge contraction in the degradation pathway not well understood Aqueous Photolysis

(835.2240) t 1⁄2 = Stable 4108 2620 Acceptable

Soil Photolysis

(835.2410) t 1⁄2 = 67 days 41082621 Acceptable

Degradation in air

(835.2370) Reaction with Hydroxyl Radicals

t 1⁄2 = 0.587 hours EpiSuite AopWin v. 1.92 NA

Aerobic Soil Metabolism

(835.4100) SiL Soil (Neutral, pH 7.06, OC = 1.39 %):

t 1/2 = 35.9 days SiCL Soil (Acidic, pH 6.10, OC = 2.96 %):

t 1/2 = 26 days Denmark SaL Soil (Acidic, pH 6.14, OC = 1.04 %):

t 1/2 = 88.4 days France SaL Soil (Acidic, pH 5.35, OC = 1.62 %):

t 1/2 = 27.7 days Germany L Soil (Neutral, pH 7.48, OC = 1.04 %):

t 1/2 = 25 days 41082622, 46240901, 49169703 Supplemental (All Studies)

All studies were conducted for durations between 120 – 240 days. The overall pattern of degradation for residues could not be determined over the study durations. Calculated half-lives extrapolated of the data provided within the study durations. Anaerobic Soil Metabolism

(835.4200) SiCL Soil (Acidic, pH 6.10, OC = 2.95%):

t 1/2 = 63 days 41082623 Supplemental

Only one soil was evaluated in the study.

Aerobic Aquatic Metabolism

(835.4300) Spain Water - Silt Loam Sediment , (pH 7.33 – 7.80)

t 1/2 = 83 days

North Dakota Water – Sand Sediment, (pH 6.96 – 8.20)

t 1/2 = 101 days 48354304 Supplemental (All Studies)

All studies were conducted for a duration of 102 days. The overall pattern of degradation for residues could not be determined over the study durations. Calculated half-lives

### 7 Table 3. Summary of nicosulfuron environmental fate properties.

Study/ OCSPP Guideline No. Value and unit MRID #

or Citation Study Classification, Comment

extrapolated of the data provided within the study durations.

Anaerobic

Aquatic Metabolism

(835.4400) Missouri Silt Loam Sediment , (pH 7.13 – 7.80)

t

1⁄2 = 92.3 days

Georgia Sand Sediment , (pH 7.09 – 7.6)

t 1⁄2 = 98.8 days 48790905 Supplemental (All Studies)

All studies were conducted for a duration of 102 days. The overall pattern of degradation for residues could not be determined over the study durations. Calculated half-lives extrapolated of the data provided within the study durations.

Mobility,

unaged leaching, adsorption/ desorption (K oc )

(835.1220) Dover, DE SaL : 25.07 mL/g; OC = 0.64 % Raleigh, NC SaL : 22.99 mL/g; OC = 1.22 % Rochelle, IL SiL : 69.36 mL/g; OC = 2.49 % Newark, DE SiL : 22.38 mL/g; OC = 2.73 % 40924222 Acceptable

Terrestrial Field Dissipation

(835.6100) Illinois SiCL Soil (Acidic, pH 6.00, OC = 2.30 %):

t 1/2 = 108 – 120 days

California SaL Soil , (Alkaline, pH 8.24, OC = 0.43 %)

t 1/2 = 114 – 120 days 43483901 Acceptable

Fish Bioconcen

-tration Factor (BCF)

(850.1730) No Data N/A No Data

1 NA means not applicable.

### 8 2 Soil textural classifications: SaL: Sandy Loam SiL: Silt Loam SiCL: Silty Clay Loam L: Loam



### Mobility and Transport to Drinking Water Sources

Nicosulfuron appears to be very mobile in mineral soils with an average K oc 

### value of 34.95 mL/g with a range of between 22.38 mL/g – 69.36 mL/g in sandy loam and silt loam soils. In addition, Nicosulfuron high water solubility at 8,070 mg/L suggests that residues wi ll dissolve readily and be subject to transport in runoff and drainage water. Nicosulfur on is not expected to volatilize under dry or moist environmental conditions as its vapor pressure is 5.25 x 10 -8 

### torr and Henry’s Law Constant is 3.51 x 10 -12 

### atm•m 3 

### /mol. Therefore, it appears that nicosulfuron can reach nearby water bodies, ground water, and terrestrial ha bitats adjacent to appl ication sites primarily via dissolved residues within leaching and runoff wa ter. Nicosulfuron is expected to remain in the water column once reaching surface water bodi es and ground water given its low soil-water partition coefficient value (average K oc 

### of 34.95 mL/g). It is also noted that the chemical is expected to reach surfac e water bodies by drift.

### 9 Degradation of Nicosulfuron and Identification of Transformation Products in Soil and Water

Environmental laboratory and fiel d data suggest that in general, nicosulfuron is moderately persistent to persistent in the environment. The predominant degradation mechanism appears to be hydrolysis in acidic environments and soil biodegradation in aerobic soil environments. Nicosulfuron appears to hydrolyze to some extent under acidic conditions with a half-life of 15 days. Otherwise, nicosulfuron is practically stable to hydrolysis in neutral and alkaline environments. In addition, for aerobic soil metabo lism, the variation of half-lives is limited, ranging between 25 – 36 days over a variety of soils with different properties with one exception. The aerobic soil half-life in De nmark sandy loam soil is longer at 88.4 days, and one reason for this is possibly due to the low organic matter co ntent of the soil relative to the other soils. Otherwise, nicosulfuron tends to be relatively persistent to soil a nd aquatic photodegradation with half lives of 67 and 250 days , respectively. In addition, nico sulfuron appears to biodegrade slowly in aerobic aquatic environments with ha lf-lives rangin g between 83 – 100 days. Field dissipation half-lives of be tween 108 – 120 days confirm ni cosulfuron’s relatively high persistence in the field as these half-lives were generally higher than labo ratory fate studies. In the field, nicosulfuron tended to exhibit bi-phasi c degradation behavior possibly contributing to the higher half-lives.

Several sulfonylurea degradates form at major quant ities (>10 percent of the applied) including AUSN (IN-HYY21) in the soil system as well as IN-37740 in the water/sediment system, both of which possess the sulfonylurea bridge (-NH-CO- NH-SO2-) entact forming as a result of molecular contraction on either side of the sulfonylurea bridge. In addition, pyridine sulfonamide (IN-V9367) and pyrimidine amine (IN-J0290), degradates which form resulting from cleavage of the sulfonyl urea bridge, are obse rved in significant qua ntities in both soil and water. The percent formation of these degradat es which form in each fate laboratory study are described in Table C-1 in Appendix C.

### 10 Figure 1. Biodegradation pathway of nicosulfuron in soil system.

### 11 Figure 2. Biodegradation pathway of nicosulfuron in water

It should be noted that Figures 1 and 2 above depict that nicosulf uron and degradates are all expected to all terminally mineralize to carbon dioxide or be embedded w ithin soil and sediment particles. However, the pattern of formation and decline of th e degradates from nicosulfuron applications is not fully established in many cas es since the environmental degradation studies were conducted for an insufficient amount of time to determine the terminal fate of nicosulfuron. This is the case for all of the hydrolysis, aer obic soil metabolism, anaerobic soil metabolism, and the aerobic aquatic metabolism studies fo r nicosulfuron. This is evident in Table C-1 in Appendix C as it shows that in numerous cases, the maximum formation amount of the degradates occur at the last sample period of these studies.

Bioconcentration of Nicosulfuron and Degradate Residues in Fish

Bioaccumulation occurring from nicosulfuron applica tions is not expected in tissues of fish, aquatic, or terrestrial organisms due to its lo w octanol-water partiti on coefficient of Log K ow 

### = 0.14 (K ow 

### = 1.38).

Fate and Transport Characterist ics of Transformation Products + Major

### 12 Metabolites which form in the environmental fate laboratory a nd field studies described above along with the maximum levels that they form at is summarized in Table C-1 of Appendix C.

There are no physical-chemical or environmental fate data which have been submitted by registrants or available from the open literature for the degradates discussed above including AUSN (IN-HYY21), pyridine sulfonamide (IN-V 9367), pyrimidine amine (IN-J0290), and IN37740. However, physical chemical property values for these metabolites were estimated from EPISuite 2



### . . 

### Table 4 shows the comparison of physical chemi cal properties of selected degradates estimated by EPISuite to the physical chemical properties of nicosulfuron that have been measured and resulting values submitted to the Ag ency. In general, physical chemical properties between nicosulfuron and the degradates are simi lar. All constituents are highly soluble in water, are highly mobile in soil as indicated by K oc 

### values less than 100 mL/g, and would not likely bind to tissue from biota as indicated by very low Log K ow 

### values. The only notable exception is for pyrimidine amine with estimates of vapor pressure and Henry’s Law Constant values that are much greater than parent nicosulfuron. Howe ver, the existing aerobic soil, anaerobic soil, and aerobic aquatic metabolism st udies do not indicate the presence of volatile elements of pyrimidine amine. This suggests th at the estimated values of vapor pressure and Henry’s Law Constant for pyrimidine amine may not be accurate.

Table 4. Comparison of physical chemical properties of nicosu lfuron degradation products to parent nicosulfuron.

Property/ EPISuite Estimator Program Value from Existing Database EPISuite Value

Nicosulfuron IN-HYY21 1 IN-37740 1 Pyridine Sulfonamide (IN-V9367) Pyrimidine Amine (IN-J0290) Solubility in Water (25 °C) (WSKOW v. 1.41) 8,070 mg/L 37,280 mg/L 5,064 mg/L 90,380 mg/L 11,080 mg/L

Vapor Pressure (25 °C) (MPBPVP v. 1.43) 5.25 x 10 -8

torr 7.87 x 10 -12

torr 2.05 x 10 -15

torr 4.01 x 10 -7

torr 1.74 x 10 -3 torr

Henry’s Law Constant (25 °C) (HENRYWIN v. 3.20) 3.51 x 10 -12

atm·m 3 /mol 3.05 x 10 -23

atm·m 3 /mol 2.68 x 10 -22

atm·m 3 /mol 4.24 x 10- 14

atm·m 3 /mol 1.07 x 10 -6

atm·m 3 /mol

Octanol-Water Partition Coefficient 0.14 -2.20 -1.76 -2.08 0.95

2 EPISuite (Estimati on Programs Interface Suite) version 4.0 was used. EPISuite is a software developed by the EPA Office of Chemical Safety and Pollution Prevention in collaboration with the Syra cuse Research Corporation (SRC). EPISuite is a collection of programs which estimate physical chemical and enviro nmental fate properties for mainly organic compounds.

### 13 Table 4. Comparison of physical chemical properties of nicosu lfuron degradation products to parent nicosulfuron.

Property/ EPISuite Estimator Program Value from Existing Database EPISuite Value

Nicosulfuron IN-HYY21 1 IN-37740 1 Pyridine Sulfonamide (IN-V9367) Pyrimidine Amine (IN-J0290) (Log K ow ) (WSKOW v. 1.41) Soil-Water Partition Coefficient (K oc ) (KOCWIN v. 2.00) 22.4 – 69.4 mL/g 0.5241 mL/g 4.036 mL/g 0.6911 mL/g 86.94 mL/g

1 Degradates maintained sulfonylurea bridge.

2 Other identified degradates including DPX-V9360 Ipso Precursor, IN-77799, IN-GDC42, IN-R5Q09,

and IN-37740 are not likel y to form at major levels in the environmen t, as they formed at less than 10 percent of applied in laboratory fate studies.

3 Nicosulfuron physical chemical property values ge nerally agreed well with estimates from EPISuite.



### PROBLEM FORMULATION

The environmental fate properties of nicosulf uron indicate that drinking water exposure potentially may occur in surface reservoir water or in drinking water wells. Application of nicosulfuron granules from aer ial and ground applications and subsequent washoff from crop foliage, runoff, leaching, and the drift of gra nules to water bodies are potential transport mechanisms to surface and ground water. The po tential for nicosulfuron exposure in surface and ground drinking waters also exists based on the ni cosulfuron’s moderate persistence, high water solubility, and high mobility in the environment. Therefore, this drinking water assessment will address scenarios which depict the potential for nicosulfuron to be transported off-site to drinking water sources.

As per meeting with the Health Effects Divisi on’s Risk Assessment Branch 3 (meeting dated December 17, 2013) the residues of concern for dr inking water include parent nicosulfuron and all major degradates which maintain the su lfonylurea bridge. These include degradates identified as IN-HYY21 and IN-37740. Table C-1 in Appendix C indicates that these degradates were detected at significant levels (greater than 10 percent of applied) in soil, sediment, and water.

These degradates possess similar physical chemi cal properties. Furthermore, each of these degradates possess similar structures to parent nicosulfuron. Therefore, the total residue method will be used to estimate exposure in drinking water sources. In es timated drinking water concentrations (EDWCs) using th e total residue method, degradate residues from environmental fate laboratory studies were adde d to the parent nicosulfuron to calculate the total residue halflife. This approach assumes that degradates posse ss equivalent toxicity and fate properties to the parent active ingredient. An ove rview of the total residue method is provided in the white paper on the FIFRA SAP Meeting on, “Selected Issues A ssociated with the Risk Assessment Process

### 14 for Pesticides with Persistent, Bioaccumulative, and Toxic Charac teristics” held in October 2008 (EPA, 2008).

EXPOSURE ANALYSIS

Estimated drinking water concentrations (EDWCs) in surface waters are estimated using the Tier 2 model PRZM/EXAMS (PRZM version 3.12.2, May 2005 and EXAMS version 2.98.4.6, April 2005). PRZM/EXAMS is publical ly available on-line at http://www.epa.gov/oppefed1/models/water/#przmexamsshell . The index reservoir scenario simulating inflow and pesticide tran sport from streams into a reservoir intake is simulated for the drinking water assessment. Crop and regional sp ecific percent crop area s (PCAs) are accounted for in EDWCs specific to each crop to factor in the portion of watersheds that are typically subject to pesticide lo adings and subsequent transport to water bodies. The guidance, “Development and Use of Percent Cropped Area a nd Percent Turf Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update”, are used to determine PCA values for each crop (EPA, 2012).

Ground water estimates of concentrations ar e estimated using the PRZM-GW (version 1.0, December 2012) will be used to evaluate gr ound water exposure. PRZM-GW is publically available on-line at http://www.epa.gov/oppefed1/models/water/#przm_gw . Results from the long-standing tier I SCI-GROW model (Screening Concentra tion in GRound Water model, Version 2.3, May 16, 2006) will also be shown in comparison with the PRZM-GW modeling results according to EFED guidance related to the evaluation period for the recent release of PRZM-GW. SCI-GROW is publically available on-line at http://www.epa.gov/oppefed1/models/water/#scigrow . The SCI-GROW model inputs and results are shown in Appendix B.

Nicosulfuron existing monitoring data found from stream water, spring water, and ground water sources from the United States Geological Su rvey National Water Quality Assessment (USGS NAWQA) program will also be presented to ve rify modeled exposures for drinking water. Monitoring data from NAWQA ar e available on-line at: http://infotrek.er.usgs.gov /traverse/f?p=NAWQA:HOME:1405517206944567

 Surface Water

The fate parameters and use-specific input parameters for the PRZM/EXAMS surface water modeling are shown in Table 5 . The EDWCs of nicosulfuron in surface water are shown for aerial applications in Table 6 . Aerial applications are only ev aluated in this Tier 1 drinking water assessment since this is considered to be the application method resulting in the most conservative exposure scenario. The PRZM /EXAMS output files are provided in Appendix A.

### 15 Table 5. PRZM/EXAMS input parameter va lues for physical chemical and fate properties used for nicosulfuron and tota l toxic residues (including IN-HYY21 and IN-37740) surface water aquatic exposure estimation. PRZM/EXAMS Input Parameter Input Value and Unit Source

Physical Chemical Properties Molecular Weight (g/mol) 410.4 MRID 47006001 

### Vapor Pressure (torr) 2.17 x 10 -10 MRID 48399916 

### Solubility in Water (mg/L) 8,070 MRID 48399916 

### Henry’s Law Constant (atm

∙ m 3 

### /mol) 3.51 x 10 -12 Calculated value from vapor pressure and water solubility



### Soil-Water Partition Coefficient (K oc 

### ) (mL/g) 34.95 MRID 40924222

EFED Input Parameter Guidance Mean value between:

DE Sandy Loam – 25.07 mL/g NC Sandy Loam – 22.99 mL/g IL Silt Loam – 69.36 mL/g DE Silt Loam – 22.38 mL/g 

### Environmental Fate Properties Hydrolysis at pH7 (t 1/2 

### ) 606 days MRID 40924220 1 

### Aerobic soil metabolism (t 1/2 

### ) 253.37 days MRID 41082622, 46240901, and 49169703

EFED Input Parameter Guidance

Upper 90 TH percentile confidence interval between 2,4 :

Silt Loam Soil: 175 days Silty Clay Loam Soil: 31.1 days Denmark Sandy Loam: 142 days France Sandy Loam: 33.6 days Germany Loam: 387 days 

### Aerobic aquatic metabolism (t 1/2 

### ) 260.62 days MRID 48354304

EFED Input Parameter Guidance Upper 90 th percentile confidence interval between 2,4 :

Water - Silt Loam Sed.: 244 days Water – Sand Sed.: 228 days 

### Anaerobic aquatic metabolism (t 1/2 

### ) 177.78 days MRID 48790905

EFED Input Parameter Guidance Upper 90 th percentile confidence interval between 2,4 :

### 16 Table 5. PRZM/EXAMS input parameter va lues for physical chemical and fate properties used for nicosulfuron and tota l toxic residues (including IN-HYY21 and IN-37740) surface water aquatic exposure estimation. PRZM/EXAMS Input Parameter Input Value and Unit Source

Water - Silt Loam Sed.: 137 days Water – Sand Sed.: 157 days 

### Aqueous Photolysis (t 1/2 

### ) Stable MRID 41082620 1



### Application Methods and Crop Management Input Parameters Crop Scenario and Weather KS Sorghum w13996 (Topeka, KS) Representative scenario for ALS inhibition tolerant sorghum

crops 

### Application Rate 1 rst 

### App.: 0.0683 kg/ha 2 nd 

### App.: 0.0265 kg/ha Maximum single application rate (0.061 lbs. a.i./A) and maximum seasonal application rate (0.084 lbs. a.i./A) spec ified on Product Labels 3 

### Application Date June 25 Conservatively selected based on maximum rainfall climatological date at meteorological station after crop emergence date specified in PRZM crop scenario 

### Number of Applications and Retreatment Interval 2 applications every 7 days Product Labels



### Regional PCA 0.87 Region 10 (Missouri) All Agriculture PCA from Table 7 of EPA, 2012, “Development and Use of Percent Cropped Area and Percent Turf Are Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update” 

### Application Methods CAM = 2, linearly applied to crop canopy Most conservative application method from product label 

### Application Efficiency 0.95 EFED input parameter guidance for aerial applications 

### Spray Drift Fraction 0.20 Spray drift fraction for aerial applications, fine to medium drop size distribution for windspeed of 15 mph from Table C1 of EPA, 2013, “Guidance on Modeling Offsite Deposition of Pesticides via Spray Drift”. 

### Foliar Extraction FEXTRC = 0.5 Default assumption for foliar applications 

### Pesticide Removal After Harvest ISPCND = 1.0, pesticide remaining on Conservative default assumption

### 17 Table 5. PRZM/EXAMS input parameter va lues for physical chemical and fate properties used for nicosulfuron and tota l toxic residues (including IN-HYY21 and IN-37740) surface water aquatic exposure estimation. PRZM/EXAMS Input Parameter Input Value and Unit Source

foliage is converted to surface application to the top soil layer

1 Half-lives for parent nicosulfuron only as IN-HYY21 and IN-37740 did not form in hydrolysis or aqueous

photolysis studies.

2 Half-lives based on total residues including parent nicosulfuron, IN-HYY21, and IN-37740.

3 Identified from proposed la bel DuPontTM Accent® label.

4 The upper 90 th percentile half life calculated as follows: t 1/2 input = ݐ ଵ/ଶ ത ത ത ത ത + (t 90, n-1 x σ )

n 1/2

where ݐ ଵ/ଶ ത ത ത ത ത

is the mean of the set of half lives from each study, t 90, n-1 is the one-sided t value for the 90 th percentile level, σ is the standard deviation of the set of half lives dete rmined from each study, and n is the sample size of the set of half lives determined from each study.



### Table 6. PRZM/EXAMS estimated upper bound concentrations in surface water (ppb) of nicosulfuron and degradates of concern including IN-HYY21 and IN-37740.

PRZM Crop Scenario PCA 1-in-10 yr. Annual Peak (Acute) 1-in-10 yr. Annual Mean (Chronic) 30-year Mean (Cancer) KS Sorghum 0.87 9.67 2.80 2.15

 Ground Water

Tables 7 and 8 show the input parameter values used in PRZM-GW and its predicted concentrations of nicosulfuron and degrad ates IN-HYY21 and IN -37740 in ground water, respectively. Tier I scenario s are run in this assessment to capture upper-bound screening exposure based on vulnerable environmental co nditions. The PRZM-GW output files for both scenarios are provided in Appendix B.

Table 7. PRZM-GW input parameter valu es for physical chemical and fate properties used for nicosulfuron and tota l toxic residues (including IN-HYY21 and IN-37740) surface water aquatic exposure estimation. PRZM/EXAMS Input Parameter Input Value and Unit Source

Pesticide Properties Hydrolysis at pH7 (t 1/2 

### ) 606 days MRID 40924220 1 

### Surface soil metabolism (t 1/2 

### ) 253.37 days MRID 41082622, 46240901, and 49169703

EFED Input Parameter Guidance

Upper 90 TH percentile confidence interval between 2,4 :

### 18 Table 7. PRZM-GW input parameter valu es for physical chemical and fate properties used for nicosulfuron and tota l toxic residues (including IN-HYY21 and IN-37740) surface water aquatic exposure estimation. PRZM/EXAMS Input Parameter Input Value and Unit Source

Silt Loam Soil: 175 days Silty Clay Loam Soil: 31.1 days Denmark Sandy Loam: 142 days France Sandy Loam: 33.6 days Germany Loam: 387 days 

### Soil-Water Partition Coefficient (K oc 

### ) (mL/g) 34.95 MRID 40924222

EFED Input Parameter Guidance Mean value between:

DE Sandy Loam – 25.07 mL/g NC Sandy Loam – 22.99 mL/g IL Silt Loam – 69.36 mL/g DE Silt Loam – 22.38 mL/g 

### Application Methods and Crop Management Input Parameters Crop Scenarios, Application Date 5 

### , and Weather WI Sands: Sept. 15, w14920 (La Crosse, WI) NC Coastal: May 25, w13722 (Raleigh, NC) GA Coastal: June 10, w93805 (Tallahasse, FL) Delmarva Peninsula: May 7, w13781 (Wilmington, DE) FL Citrus: August 5, w12842 (Tampa, FL) FL Potato: Sept. 5, w13889 (Jacksonville, FL)

Application Rate 1 rst 

### App.: 0.0683 kg/ha 2 nd 

### App.: 0.0265 kg/ha Maximum single application rate (0.061 lbs. a.i./A) and maximum seasonal application rate (0.084 lbs. a.i./A) spec ified on Product Labels 3 

### Application Date September 15 Conservatively selected based on maximum rainfall climatological date at meteorological station after crop emergence date specified in PRZM crop scenario 

### Number of Applications and Retreatment Interval 2 applications with a 7- day interval Product Labels



### Application Methods Ground application Most conservative application method from product label

1 Half-lives for parent nicosulfuron only as IN-HYY21 and IN-37740 did not form in hydrolysis or aqueous

photolysis studies.

2 Half-lives based on total residues including parent nicosulfuron, IN-HYY21, and IN-37740.

3 Identified from proposed la bel DuPontTM Accent® label.

4 The upper 90 th percentile half life calculated as follows: t 1/2 input = ݐ ଵ/ଶ ത ത ത ത ത + (t 90, n-1 x σ )

n 1/2

### 19 where ݐ ଵ/ଶ ത ത ത ത ത

is the mean of the set of half lives from each study, t 90, n-1 is the one-sided t value for the 90 th percentile level, σ is the standard deviation of the set of half lives dete rmined from each study, and n is the sample size of the set of half lives determined from each study.

5 Conservatively selected based on maximum rainfall climatological date at meteorological station after crop

emergence date specified in PRZM crop scenario.



### Table 8. PRZM-GW estimated upper bound concentrations in ground water (ppb) for nicosulfuron and degradates of concern including IN-HYY21 and IN-37740.

Tier I Scenario Highest Daily Value (Acute) Post-Breakthrough Average (Chronic and Cancer) WI Sands 26.3 19.2 NC Coastal 9.53 7.10 GA Coastal 4.70 3.39 FL Citrus 14.5 10.2 FL Potato 6.95 5.46 Delmarva Peninsula 17.1 11.6 *Bolded values show the highest ground water EDWC.



### EXPOSURE CHARACTERIZATION



### The comparison between the PRZM/EXAMS surface water modeling and PRZM-GW ground water modeling, shown in Tables 4 and 6 , respectively, suggest that nicosulfuron applications will predominately impact ground water resources. Estimated peak ground water concentrations of nicosulfuron and degradates IN-HYY21 and IN-37740 are approximately three times higher the estimated surface water concentration. L onger term ground water concentrations are approximately a magnitude of six higher than su rface water. This is expected for nicosulfuron due to its high mobility and resul ting ability to leach through the top soil to the water table. Considering this, the predicted ground wa ter concentration in PRZM-GW should be conservative, consistent with the high porosity of the sandy soil of the Wisconsin scenario modeled and relatively shallow water table representative of the scenario (30 feet). However, it is important to note that these results based on Tier 1 vulnerable scenarios are intended to be a screening upper-bound estimate of the impact of nicosulfuron applications to ground water. Further consideration of addition al refinements or scenario development representative of nicosulfuron applications to sorghum crops is possible, if needed.

One significant contributing factor to the relatively large concen trations of nicosulfuron, INHYY21, and IN-37740 in estimated ground water is due to the assumption that the ground water possesses a neutral pH. Nicosulfur on is practically hydrolytically stable in neutral and alkaline environments. However, in more acidic envi ronments, nicosulfuron can degrade much more rapidly with a hydrolysis half-lif e of 14.7 days. Therefore, in acid ic ground water, concentrations of nicosulfuron would be drastically reduced. Estimated peak concentrations in PRZM-GW at 0.128 ppb are calculated, and only tr ace long-term average ground concentrations amounting to

### 20 <0.01 ppb are expected in acidic environments . These concentrations could be more representative of conditions mos tly in the eastern part of th e area where sorghum is grown. However, in the western part of the sorghum gr owing area, calcareous soil and more alkaline environments are generally more likely to dominate in the drier climate (citation: http://www.fao.org/soils-portal/soil-man agement/management-of-some-problemsoils/calcareous-soils/en/ ). Therefore, the screening gr ound water concentrations shown in Table 9 may more represent nicosulfuron applicati ons occurring in this region. The growing region of sorghum crops is shown in the map in Figure 1

. At this time, nicosulfuron monitoring da ta is only available through the USGS NAWQA program. Despite the results of the modeling analysis in this drinking water assessment suggesting that nicosulfuron would be predom inate in ground water, nicosulfuron was only detected in surface water (in streams) but not in ground water. 88 wells were sampled, and 2 springs were sampled as well. Nicosulfuron may have not been found at these sites for a number of reasons including the possibili ty that monitoring was random and non-targeted to pesticide applications or that conditions were dry during the observing period. For surface water, 5 out of 23 stream water sites (23 percent) contained dete ctions of nicosulfuron, mainly in Alabama. PRZM/EXAMS peak nicosulfuron estimated surface water concentrations were over an order of magnitude higher than the monitoring data (9.67 ppb 3 

### /0.2161 ppb = 44.7X). The main reason for the large departure of monitoring detections versus the modeling re sults is due to that screening modeled concentrations are based on a static pond, and lower concentra tions in stream water would be expected in a flowing water body such as the stream as monitored at the site of nicosulfuron detections. Furthermore, the monitoring retrievals do not measure composite residues including IN-HYY21 and IN-37740 such as the modeling calculations reflect.

UNCERTAINTIES AND LIMITATIONS



### The main uncertainty in this drinking water as sessment is the degradation of the fate of degradates IN-HYY21 and IN-37740 in soil and wate r are uncertain in most cases. Aerobic soil metabolism, aerobic aquatic, and anaerobic aqua tic metabolism studies were all terminated before substantial decline was observed with these degradates. However, in all cases, levels of these degradates were observed to level off several sampling period before study termination coincident with continued nico sulfuron degradation. This sugge sts that the degradates were biodegrading at the same rate that they were forming due to nicosulfuron biodegradation. Therefore, the total toxic residue half- life between nicosulfur on, IN-HYY21, and IN-37740 would not likely change given that the degradates would not be stable, and eventually degrade at a rate similar to the total toxic residue half-lif e as parameterized in the models used in this drinking water assessment.

REFERENCES

FIFRA SAP Final Meeting Minutes 2008. Tran smittal of Meeting Minutes of the FIFRA

3 Since parent nicosulfuron alone is moderately persiste nt in soil and water, it is not anticipated that peak concentrations in surface water including IN-HYY21 and IN-37740 would be much diff erent from just parent nicosulfuron alone.

### 21 Scientific Advisory Panel Meeting Held Oct ober 28 - 31, 2008 on Selected Issues Associated with the Risk Assessment Process for Pesticides with Persistent, Bioaccumulative, and Toxic Characteristics. http://www.epa.gov/scipoly/sap/ meetings/2008/october/minutes.pdf

USEPA. 2002. Guidance for Selecting Input Pa rameters in Modeling th e Environmental Fate and Transport of Pesticides. U.S. Environm ental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pest icide Programs, Environmental Fate and Effects Division. Feb. 28, 2002. Online at: http://www.epa.gov/oppefed1/mode ls/water/input_guidance2_28_02.htm

.

U.S. Environmental Protection Agency 2012.. De velopment and Use of Percent Cropped Area and Percent Turf Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update. EPA Office of Pestic ide Programs. Washington, DC.

USEPA. 2013. Guidance on Modeling Offsite Depos ition of Pesticides via Spray Drift. U.S. Environmental Protection Agency, Office of Prev ention, Pesticides and Toxic Substances, Office of Pesticide Programs, Environmental Fa te and Effects Division. Dec. 20, 2013.

### 22 Appendix A – Surface Water Modeling Supporting Documentation

PRZM/EXAMS Modeling File stored as Nico_Sorgm.out Chemical: Nicosulfuron PRZM environment: KSsorghumSTD.txt modified Tueday, 26 August 2008 at 05:16:38 EXAMS environment: ir298.exv modified Tueday, 26 August 2008 at 05:14:08 Metfile: w13996.dvf modified Tueday, 26 August 2008 at 05:14:52 Water segment concentrations (ppb)

Year Peak 96 hr 21 Da y 60 Day 90 Day Yearly 1961 7.555 7.417 6.962 5.929 5.334 1.962 1962 6.367 6.249 5.991 5.325 4.763 2.19 1963 15.1 14.78 13.51 11.2 9.825 3.962 1964 5.925 5.798 5.449 4.629 4.157 2.341 1965 8.108 7.941 7.326 6.222 5.485 2.349 1966 6.885 6.734 6.144 5.158 4.587 2.123 1967 5.562 5.45 5.005 4.715 4.261 1.952 1968 11.8 11.55 10.78 9.021 7.95 3.332 1969 6.734 6.594 6.322 5.375 4.737 2.439 1970 5.565 5.448 4.99 4.675 4.247 1.963 1971 7.207 7.079 6.555 5.516 4.849 2.112 1972 8.112 7.949 7.399 6.274 5.583 2.402 1973 10.09 9.906 9.322 8.077 7.137 3.029 1974 7.645 7.48 6.832 6.452 5.824 2.713 1975 5.664 5.547 5.083 4.322 3.895 1.939 1976 7.187 7.093 6.54 5.635 5.059 2.19 1977 6.472 6.35 5.876 5.556 5.144 2.364 1978 5.637 5.52 5.066 4.515 4.046 1.947 1979 11.17 11.02 10.23 8.619 7.584 3.1 1980 6.658 6.517 5.967 5.211 4.938 2.491 1981 7.524 7.383 7.005 6.514 5.836 2.63 1982 10.62 10.39 9.518 8.074 7.213 3.122 1983 7.393 7.235 6.611 5.434 4.755 2.332 1984 6.995 6.85 6.443 5.364 4.713 2.086 1985 5.882 5.758 5.548 5.144 4.714 2.134 1986 7.675 7.512 7.037 6.025 5.328 2.344 1987 6.654 6.515 6.144 5.235 4.624 2.095 1988 8.301 8.131 7.75 6.611 5.848 2.498 1989 8.733 8.562 7.879 6.843 6.165 2.756 1990 10.45 10.24 9.503 8.003 7.14 3.23

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly 0.032258064516129 15.1 14.78 13.51 11.2 9.825 3.962 0.0645161290322581 11.8 11.55 10.78 9.021 7.95 3.332 0.0967741935483871 11.17 11.02 10.23 8.619 7.584 3.23 0.129032258064516 10.62 10.39 9.518 8.077 7.213 3.122 0.161290322580645 10.45 10.24 9.503 8.074 7.14 3.1 0.193548387096774 10.09 9.906 9.322 8.003 7.137 3.029 0.225806451612903 8.733 8.562 7.879 6.843 6.165 2.756 0.258064516129032 8.301 8.131 7.75 6.611 5.848 2.713 0.290322580645161 8.112 7.949 7.399 6.514 5.836 2.63

### 23 0.32258064516129 8.108 7.941 7.326 6.452 5.824 2.498 0.354838709677419 7.675 7.512 7.037 6.274 5.583 2.491 0.387096774193548 7.645 7.48 7.005 6.222 5.485 2.439 0.419354838709677 7.555 7.417 6.962 6.025 5.334 2.402 0.451612903225806 7.524 7.383 6.832 5.929 5.328 2.364 0.483870967741936 7.393 7.235 6.611 5.635 5.144 2.349 0.516129032258065 7.207 7.093 6.555 5.556 5.059 2.344 0.548387096774194 7.187 7.079 6.54 5.516 4.938 2.341 0.580645161290323 6.995 6.85 6.443 5.434 4.849 2.332 0.612903225806452 6.885 6.734 6.322 5.375 4.763 2.19 0.645161290322581 6.734 6.594 6.144 5.364 4.755 2.19 0.67741935483871 6.658 6.517 6.144 5.325 4.737 2.134 0.709677419354839 6.654 6.515 5.991 5.235 4.714 2.123 0.741935483870968 6.472 6.35 5.967 5.211 4.713 2.112 0.774193548387097 6.367 6.249 5.876 5.158 4.624 2.095 0.806451612903226 5.925 5.798 5.548 5.144 4.587 2.086 0.838709677419355 5.882 5.758 5.449 4.715 4.261 1.963 0.870967741935484 5.664 5.547 5.083 4.675 4.247 1.962 0.903225806451613 5.637 5.52 5.066 4.629 4.157 1.952 0.935483870967742 5.565 5.45 5.005 4.515 4.046 1.947 0.967741935483871 5.562 5.448 4.99 4.322 3.895 1.939

0.1 11.115 10.957 10.1588 8.5648 7.5469 3.2192 Average of yearly averages: 2.4709

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Nico_Sorgm Metfile: w13996.dvf PRZM scenario: KSsorghumSTD.txt EXAMS environment file: ir298.exv Chemical Name: Nicosulfuron Description Variable Name Value Units Comments Molecular weight mwt 410.4 g/mol Henry's Law Const. henry 3.51e-12 atm-m^3/mol Vapor Pressure vapr 5.25e-8 torr Solubility sol 8070 mg/L Kd Kd mg/L Koc Koc 34.95 mg/L Photolysis half-life kdp 0 days Half-life Aerobic Aquatic Metabolism kbacw 260.62 days Halfife Anaerobic Aquatic Metabolism kbacs 177.78 days Halfife Aerobic Soil Metabolism as m 253.37 days Halfife Hydrolysis: pH 7 606 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.0683 kg/ha Application Efficiency: APPEFF 0.95 fraction Spray Drift DRFT 0.2 fraction of application rate applied to pond Application Date Date 25-06 dd/mm or dd/mmm or dd-mm or dd-mmm Interval 1 interval 7 days Set to 0 or delete line for single app. app. rate 1 apprate 0.02625 kg/ha Record 17: FILTRA

### 24 IPSCND 1 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR Reservoir Flag for runoff calc. RUNOFF total none, monthly or total(average of entire run)

### 25 Appendix B – Ground Water Modeling Supporting Documentation

PRZM-GW Modeling Output File

Figure B-1. PRZM-GW daily aquifer nicosulfuron, IN-HYY21, and IN-37740 concentration time series chemograph (30-years) for WI Sands scenario.

SCI-GROW Modeling Input Parameter Values and Output File

Table B-1. SCI-GROW input parameter values for physical chemical and fate properties used for nicosulfuron and to tal toxic residues (IN-HYY21 and IN-37740 ) ground water exposure estimation. SCI-GROW Input Parameter Input Value and Unit Source Application Methods and Crop Management Input Parameters Maximum Application Rate 0.061 lbs. a.i./A Product Label 1



### Number of Applications 2 Conservative input value based on maximum seasonal application rate (0.084 lbs. a.i./A) 1

### 26 Table B-1. SCI-GROW input parameter values for physical chemical and fate properties used for nicosulfuron and to tal toxic residues (IN-HYY21 and IN-37740 ) ground water exposure estimation. SCI-GROW Input Parameter Input Value and Unit Source Physical Chemical Properties Soil-Water Partition Coefficient (K oc 

### ) 24.0 mL/g MRID 40924222

EFED Input Parameter Guidance Median value between: DE Sandy Loam – 25.07 mL/g NC Sandy Loam – 22.99 mL/g IL Silt Loam – 69.36 mL/g DE Silt Loam – 22.38 mL/g 

### Environmental Fate Properties Aerobic soil metabolism (t 1/2 

### ) 142 days MRID 48399928 EFED Input Parameter Guidance Median value between 2 :

Silt Loam Soil: 175 days Silty Clay Loam Soil: 31.1 days Denmark Sandy Loam: 142 days France Sandy Loam: 33.6 days Germany Loam: 387 days

1 Identified from proposed la bel DuPontTM Accent® label.

2 Half-lives based on total residues including parent nicosulfuron, IN-HYY21, and IN-37740.



### Figure B-2. SCI-GROW output file for nico sulfuron applications to ALS inhibition tolerant sorghum.

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

SCIGROW 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:nicosulfuron time is 1/13/2014 14:28:45

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

------------------------------------------------------------------------ 0.061 2.0 0.122 2.40E+01 142.0

------------------------------------------------------------------------ groundwater screening cond (ppb) = 1.42E+00 ************************************************************************

### 27 Comparison of PRZM-GW Modeling Re sults to SCI-GROW Modeling Results

Table B-2. Comparison of PRZM-GW and SCI-GROW estimated upper bound concentrations in ground water (ppb) for nicosulfuron and degradates of concern including IN-HYY21 and IN-37740.

Exposure Duration PRZM-GW (ppb) SCI-GROW (ppb) 1 

### PRZM-GW MagnitudeDeparture from SCIGROW Results 2,3 

### Highest Daily Conc. (Acute) 26.3

1.42 18.5X

Post-Breakthrough Average Conc. (Chronic and Cancer) 19.2 13.5X

1 SCI-GROW modeling conservatively assumes that ground water concentrations are uniform over time and

therefore, acute, chr onic, and cancer concentration are the same.

2 SCI-GROW magnitude departure from PRZM-GW Results = PRZM-GW Conc./SCI-GROW Conc.

3 PRZM-GW results greater than SCI-GROW results if va lue >0. PRZM-GW results less than SCI-GROW results

if value<0.

### 28 Appendix C – Formation and Decline of Envi ronmental Degradates of Nicosulfuron

Table C-1. Nicosulfuron degradation products identified in environmental fate studies.

Degradate

Identity Structure Max% of Applied and Days Post Application Comments

Hydrolysis (pH 5 only; Nicosulfuron stable at pH 7 and pH 9) – MRID No. 40924220

IN-V9367 or Pyridine Sulfonamide

2-(aminosulfonyl)-N,Ndimethyl-3- pyridinecarboxamide 31.4% at 30 days Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 30 days.

IN-J0290 or Pyrimidine Amine

4,6-dimethoxy-2- pyrimidinamine 32.1% at 30 days Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 30 days.

DPX-V9360 Ipso Precursor

2-[(Aminocarbcnyl)(4,6- dimethoxy-pyrimidin-2-yl)- amino]-N,N-dimethyl-3- pyridinecarboxamide 6.05% at 30 days Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 30 days.

### 29 Table C-1. Nicosulfuron degradation products identified in environmental fate studies.

Degradate

Identity Structure Max% of Applied and Days Post Application Comments

Aerobic Aquatic Metabo lism (MRID No. 4854304)

IN-37740

2-[[(3,4-dihydro-6-methoxy-4- oxopyrimidin-2- yl]aminocarbonyl]aminosulfon yl]-N, Ndimethyl-3- pyridinecarboxamide 29.1% at 102 days Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 102 days.

IN-HYY21 or AUSN

2-[[[[(Aminoiminomethyl) amino]carbonyl]amino]sulfony l]-N,N-dimethyl-3- pyridinecarboxamide 6.6% at 102 days Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 102 days.

IN-77799

2-[(Aminocarbonyl) [4- methoxy-6-(methyldioxy)-2- pyrimidinyl] amino]-N, N - dimethyl-3- pyridinecarboxamide 3.0% at 102 days Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 102 days.

IN-V9367 or Pyridine Sulfonamide

2-(aminosulfonyl)-N,Ndimethyl-3- pyridinecarboxamide 4.8% at 102 days Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 102 days.

### 30 Table C-1. Nicosulfuron degradation products identified in environmental fate studies.

Degradate

Identity Structure Max% of Applied and Days Post Application Comments

Anaerobic Aquatic Metabolism (MRID No. 48790905)

IN-37740

2-[[(3,4-dihydro-6-methoxy-4- oxopyrimidin-2- yl]aminocarbonyl]aminosulfon yl]-N, Ndimethyl-3- pyridinecarboxamide 13.9% at 102 days Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 102 days.

IN-V9367 or Pyridine Sulfonamide

2-(aminosulfonyl)-N,Ndimethyl-3- pyridinecarboxamide 4.8% at 102 days Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 102 days.

IN-R5Q09

2-[[[[(l,6-Dihydro-4-hydroxy-6-

oxo2-pyrimidinyl)amino]carbonyl] amino]sulfonyl]-N-N-dimethyl-3 - pyridinecarboxamide) 6.6% at 102 days Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 102 days.

### 31 Table C-1. Nicosulfuron degradation products identified in environmental fate studies.

Degradate

Identity Structure Max% of Applied and Days Post Application Comments

Aerobic Soil Metabolism (MRID Nos. 41082622, 46240901, and 49169703)

IN-HYY21 or AUSN

2-[[[[(Aminoiminomethyl) amino]carbonyl]amino]sulfony l]-N,N-dimethyl-3- pyridinecarboxamide 34.6 % at 120 days in neutral soil Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 120 days.

IN-V9367 or Pyridine Sulfonamide

2-(aminosulfonyl)-N,Ndimethyl-3- pyridinecarboxamide 72.4% at 120 days in acidic soil Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 120 days.

IN-J0290 or Pyrimidine Amine

4,6-dimethoxy-2- pyrimidinamine 48.8% at 62 days in acidic soil Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study in acidic soil was terminated at 120 days.

IN-GDC42

2-[[[(Aminocarbonyl) amino]carbonylamino] sulfonyl]-N,N-dimethyl-3- pyridinecarboxamide 7.0% at 90 and 120 days in neutral soil Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study in alkaline soil was terminated at 120 days.

### 32 Table C-1. Nicosulfuron degradation products identified in environmental fate studies.

Degradate

Identity Structure Max% of Applied and Days Post Application Comments

IN-37740

2-[[(3,4-dihydro-6-methoxy-4- oxopyrimidin-2- yl]aminocarbonyl]aminosulfon yl]-N, Ndimethyl-3- pyridinecarboxamide 5.5% at 14 days in acidic soil Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study in alkaline soils was terminated at 120 days.

IN-77799

2-[(Aminocarbonyl) [4- methoxy-6-(methyldioxy)-2- pyrimidinyl] amino]-N, N - dimethyl-3- pyridinecarboxamide 3.1% at 30 days in acidic soil Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 120 days.

Anaerobic Soil Metabolism (MRID No. 41082623)

IN-V9367 or Pyridine Sulfonamide

2-(aminosulfonyl)-N,Ndimethyl-3- pyridinecarboxamide 29.5% at 90 days in acidic soil Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 90 days

IN-J0290 or Pyrimidine Amine

4,6-dimethoxy-2- pyrimidinamine 25% at 61 days in acidic soil Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 90 days

### 33 Table C-1. Nicosulfuron degradation products identified in environmental fate studies.

Degradate

Identity Structure Max% of Applied and Days Post Application Comments

Terrestrial Field Dissipati on (MRID No. 43483901)

IN-V9367 or Pyridine Sulfonamide

2-(aminosulfonyl)-N,Ndimethyl-3- pyridinecarboxamide 15.85% in 0 - 6 inch soil depth at 61

days in Illinois Silty Clay Loam Soil (acidic)

5.15% in 0 -6

inch soil depth at 121 days in California Sandy Loam Soil (alkaline) Detected with [Pyridine-2-

14 C]Nicosulfuron Radiolabel.

Studies were terminated at 545 days

IN-J0290 or Pyrimidine Amine

4,6-dimethoxy-2- pyrimidinamine 13.4% in 0 - 6 inch soil depth at 61

days in Illinois Silty Clay Loam Soil (acidic) Detected with [Pyrimidine-2-

14 C]Nicosulfuron Radiolabel.

Study was terminated at 545 days

*NA means half life unavailable.