### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### Date: August 4, 2010

Chemical: Imazosulfuron PC Code: 118602 Barcode: DP 362652 and 366546



## MEMORANDUM

SUBJECT: Transmittal Memo on “Ecological Risk Assessment for the First Food Use Registration of Imazosulfuron for Se lective Sedge and Broadleaf Weed Control in Tomato, Pepper, and Rice a nd Revised Use Rates in Turfgrass”

FROM: Sujatha Sankula, Ph.D. Lead Biologist Faruque Khan, Ph. D., Senior Scientist Brian Anderson, M.S., Acting Branch Chief Environmental Risk Branch I Environmental Fate and Effects Division (7507P)

TO : Bethany Benbow, Risk Manager Reviewer James Tompkins, Risk Manager Registration Division (7505P)

Valent USA Corporation (Valent) submitted a pe tition to the Environmental Protection Agency (EPA) proposing the first food use registration of the herbicide imazosulfuron (both technical grade active ingredient (TGAI) and V-10142 Ag) as a selective herbicide for the control of sedges and broadleaf weeds in tomato, pepper (bell and non-bell), and rice. Valent also submitted mitigated labels for imazosulfuron (f or the formulated product V-10142) in response to the risk assessment conducted for its registra tion as new chemical in turf, ornamentals, conifers, and bare ground non-crop areas (DP 34 8003). The revised labels for imazolsulfuron removed all other uses (ornamental plants, co nifers, deciduous trees, non -bearing fruit and nut trees, and bare ground non-crop ar eas) except turfgrass from labels; reduced the maximum single application rate in turfgrass fr om 0.75 lb ai/A to 0.67 lb ai/A; removed aerial applications in turfgrass; strengthened drift management and spra yer clean-out sections; disallowed the use of flood nozzles; and added 10-foot ve getative buffer strip between treated areas and water bodies. Therefore, this memorandum summa rizes the attached Environmen tal Fate and Effects Division (EFED)‘s ecological risk assessm ent for imazosulfuron in support of the proposed new uses in tomato, pepper, and rice and revised uses in turf grass (residential and commercial). Furthermore, the attached risk assessment se rves as EFED’s response to th e registrant’s rebuttal (MRID 477668-22) on the ecological risk an alysis conducted by EFED on th e new chemical registration of imazosulfuron in turfgrass, ornamental s, conifers, and bare ground non-crop areas (DP348003).2 

### The maximum single rate evaluated in this asse ssment is 0.3 lb ai/A for food uses and 0.67 lb ai/A for turfgrass. Maximum annual application ra tes permitted are 0.3 lb ai/A for food uses and 1.34 lb ai/A for turfgrass. The label states a sing le application in tomato and pepper whereas two applications are allowed in rice and turfgrass with a 21-day interval between applications.

Data Gaps

The available environmental fate and transpor t data set for imazosulfuron is considered complete and no additional fate da ta is required at this time.

Table A-2 identifies the status of ecological eff ects study requirements for imazosulfuron. The following are the studies bei ng requested in view of the da ta gaps identified in this environmental risk assessment:

• An aquatic vascular plant ( Lemna gibba ) study using the degradate IPSN demonstrated no toxicity to the plant. However, greater t oxicity was noted to mammals due to exposure to IPSN. Therefore, there is uncertainty regarding acute toxic ity to fish, aquatic invertebrates (water column-dwelling), and a quatic non-vascular plants exposed to the degradates. Studies (Guideline numbers: 850.1075 for fish, 850.1300 for invertebrates, and 850.5400 for non-vascular plants) are requi red to address this uncertainty.

• The recently revised (October 2007) FIFRA data requirements (CFR 40 Part 158) require an avian acute oral toxicity study (850.2100) be conducted using a passerine species (Passeriformes). Valent submitted a request to waive the study requirement for acute oral toxicity of imazosulfuron to passerine bird s because of the lack of a guideline study on passerines, unwillingness of research or ganizations to conduct the study using redwinged blackbirds (the preferred species), lack of availability of commercial source of red-winged blackbirds, and EPA’s non-approval of alternative passe rine species (MRID 47679113). However, the waiver was not gran ted as the revised Part 158 data requirements specify that acute avian oral toxicity data be submitted for either one waterfowl or one upland game species and one passerine species for pesticides with proposed terrestrial, aquatic, fore stry, and residential outdoor uses.

• Research (Fletcher et al. , 1993, 1996; Bhatti et al. , 1995) involving chlorsulfuron, the first SU registered in the US (1981) has indi cated that chlorsulfuron may have effects on plant seed/fruit production at extremely lo w concentrations. Researchers have also reported reproductive effects in cherry, canola, soybean, sunflower and Polygonum spp. at application rates as low as 1000x below the label rate. Therefore, studies that document the reproduction effects on plants due to imazosulfuron applications are required.3 

### Labeling Recommendations

According to the Label Review Manual, the fo llowing label statements are recommended for imazosulfuron:

Environmental Hazards

“Do not apply directly to water, or to areas where surface water is pres ent or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwater or rinsate."

Ground Water Advisory

Imazosulfuron and its several degradates have properties and characteristics associated with chemicals detected in ground water. Th ese chemicals may leach into ground water if used in areas where soils are permeable, partic ularly where the water table is shallow.

Surface Water Label Advisories

Imazosulfuron and its degradates may impact surface water quality through spray and runoff of rain water. This is especially tr ue for poorly draining soils and soils with shallow ground water. Imazosulfuron and degradates are classified as having high potential for reaching surface water via r unoff for several months or more after application. A level, well maintained vegeta tive buffer strip between areas to which this product is applied and surface water features such as ponds, streams, and springs will reduce the potential loading of imazosulfuron and degradat es from runoff water and sediment. Runoff of this product will be re duced by avoiding applications when rainfall is forecasted to occur within 48 hours.4 

### Table A-1: Environmental Fate Data Requirements for Imazosulfuron

Guideline # Data Requirement MRID #s Study Classification

161-1 835.2120 Hydrolysis 473051-19 47766821 Acceptable Supplemental

161-2 835.224 Photodegradation in Water 473051-20 Acceptable

161-3 835.241 Photodegradation on Soil 473051-21 Supplemental

161-4 835.237 Photodegradation in Air NA ---

162-1 835.41 Aerobic Soil Metabolism 473051-22 477668-01 Supplemental Supplemental

162-2 835.42 Anaerobic Soil Metabolism 477668-02 Supplemental

162-3 835.44 Anaerobic Aquatic Metabolism 473051-23 Supplemental

162-4 835.43 Aerobic Aquatic Metabolism 476397-02 476791-05 Supplemental Supplemental

163-1 835.1240 835.1230 Leaching-Adsorption/De sorption 473051-17 Supplemental

163-1 835.1230 Adsorption/Desorption 473051-18 Supplemental

163-2 835.141 Laboratory Volatility NA ---

163-3 835.81 Field Volatility NA ---

164-1 835.61 Terrestrial Field Dissipation 473051-26 473051-27 47679108 47679109 47679110 Acceptable Acceptable Acceptable Acceptable Acceptable 164-2 835.62 Aquatic Field Dissipation 476791-07 Supplemental

165-4 850.173 Accumulation in Fish 473052-02 Waived

201-1 840.1100 Spray droplet Size Spectrum 473051-28 Supplemental

1 Not Available5 

### Table A-2 : Available Ecological Effects Data for Imazosulfuron

Guideline # Type of Study Formulation MRID Study Classification 71-1 850.2100 Avian Oral LD 50 Technical Technical

IPSN 473052-03 473052-04 477668-10 Acceptable Acceptable Supplemental 71-2 850.2200 Avian Dietary LC 50 Technical Technical

IPSN 473052-05 473052-06 477668-11 Acceptable Acceptable Acceptable 71-4 850.2300 Avian Reproduction Technical Technical Technical 473052-07 473052-08 476791-14 Acceptable Supplemental Supplemental 72-1 850.1075 Freshwater Fish LC 50 Technical Technical Technical Technical 473051-35 473051-36 473051-37 476791-11 Supplemental Acceptable Acceptable Acceptable 72-2 850.1010 Freshwater Invertebrate LC 50 Technical Technical 473051-30 473051-31 Invalid Acceptable 72-3(a) 850.1075 Estuarine/Marine Fish LC 50 Technical 4730 51-34 Acceptable 72-3(b) 850.1025 Estuarine/Marine Mollusk EC 50 Technical 473051- 32 Acceptable

72-3(c) 850.1035 850.1045 Estuarine/Marine Shrimp LC 50 Technical 4730 51-33 Acceptable

72-4(a) 850.1400 Freshwater Fish Early Life Stage Technical 476791- 14 Acceptable

72-4(b) 850.1300 850.1350 850.1300 Aquatic Invertebrate Lifecycle Technical 473052- 01 Acceptable

OECD 219 Benthic Organisms (long-term sediment toxicity) IPSN 477821-03 Supplemental

72-5 850.1500 Freshwater Fish Life-Cycle Technical Not submitted 123-1(a) 850.4225 Seed Germination/ Seedling Emergence Tier II V-10142 75WDG 4730 52-11 Acceptable

123-1(a) 850.4225 Vegetative Vigor Tier II V-10142 75WDG 4730 52-12 Acceptable

122-2 850.4400 Aquatic Plant (Non-Vascular) Tier 1&II Technical Technical Technical Technical 470532-14 470532-15 470532-16 470532-17 Acceptable Acceptable Supplemental

Acceptable 122-2 850.4400 Aquatic Plant (Vascular) Tier 2 Technical IPSN 476397-01 473052-13 Supplemental Acceptable

141-1 850.3020 Honey Bee Acute Oral and Contact LD 50 Technical Technical 473052-09 473052-10 Supplemental Supplemental

OECD 207 OECD 207 Acute Toxicity to Earthworms Technical IPSN 477668-14 477668-12 Not available

ISO 11268- 2 Chronic Toxicity to Earthworms IPSN 477668-13 Supplemental

141-2 850.3030 Honey Bee Residue on Foliage NA NA Not available

Non-guideline Acute Toxicity to Beetles IPSN IPSN 477668-05 477821-02 Supplemental Supplemental6 

### Environmental Fate and Effects Divisions’ Resp onse to the Registrant’s Rebuttal of Risk Assessment Pertaining to the New Chemic al Registration Im azosulfuron (DP 348003)

Valent submitted a response (MRID 477668-22; DP 366546) to the ecological risk assessment conducted for the proposed first uses of imazosu lfuron (DP348003). To address the uncertainty regarding environmental persis tence of imazosulfuron, uncertain ty factors were applied by EFED to environmental parameters for modeli ng inputs including metabolites in degradation parameter estimates in the previous assessment. Va lent submitted additional data to address this uncertainty, which were incorporated into the fa te characterization and model inputs of this assessment. Model inputs from the required environmental degradation studies except anaerobic aquatic metabolism were chosen to represent the upper confidence bound of the mean, and are not expected to be exceeded in the envir onment 90% of the time. Since a single anaerobic aquatic metabolism half-life is available, input half-life was multiplied by 3 to represent upper bound value.

The Environmental Fate and Effects Division disagrees with the registrant that the PRZM/EXAMS modeling should be based on the degradation rate of imazosulfuron alone. Imazosulfuron degradates (IPSN, UDPM and ADPM) are more acutely toxic to mammals than the parent. In addition, HMS retains both IM and PM ring structures and its toxicity is likely comparable to the parent. Deductive Estimati on of Risk based on Existing Knowledge (DEREK) analysis of IPSN, ADPM, SDPM, and UDPM show ed that all of these cleavage products retained at least one of the same structural al erts as the parent. Ther efore, IPSN, ADPM, SDPM, and UDPM can not be excluded by hazard considerat ions and there is potential for exposure, these compounds cannot be excluded as residues of concern. There is no toxicity data related to aquatic species except Lemna (for both TGAI a nd IPSN) to exclude any of the degradates listed above. Therefore, a total toxic residue approach is expected to provide protective exposure estimation for aquatic organisms exposed to the major degradates of imazosulfuron.

In its comments to EFED, Valent opposed th e Recommended Ground Water Advisory Language for imazosulfuron. The recommended ground water advisory language was developed based on terrestrial field studies as well as various fate data and deemed appropriate for imazosulfuron and its degradates. The above recommendation is base d on a terrestrial field dissipation study (MRID 473051-27) in which imazosulfuron was detected in the 45-60 cm soil depth at a maximum of 0.11 ppm at 14 days and in the 60-75 cm and 75- 90 cm soil depths at a maximum of 0.03 ppm following the second application in New York. IPSN was also detected in the 30-45 cm, 45-60 cm, and 75-90 cm soil depths at 0.02 ppm following the second application.

In response to the uncertainty on the greater toxicity of the degrad ates, IPSN, UDPM and ADPM, which were found to be more acutely to xic to mammals than the parent, with IPSN, being the most toxic, the registrant submitted new studies using IPSN on midge (28-day chronic study), bobwhite quail (acute dose and dietary studi es), insects (acute studies on ground beetle and rove beetle), and earthworms (acute studies). As midge data is not available for the TGAI, toxicity comparisons could not be made between the TGAI and IPSN. The bird studies suggested that IPSN is practically non-t oxic to birds both on a single dose a nd dietary basis, similar to the parent imazosulfuron. However, the LOAEC values for IPSN were lower than the parent in both the dose and dietary-based studies suggesting that adverse eff ects could be noted at lower7 

### concentrations with IPSN compared to the pa rent. Regarding the non-target insects, although studies that evaluated the eff ects of IPSN were submitted on ground beetle and rove beetle, comparable studies were not available for TGAI. Th erefore, the uncertainty related to the effects of TGAI versus IPSN could not be resolved for terrestrial insects. New studies submitted by the registrant suggest that the t oxicity of imazosulfuron and IPSN is similar to earthworms. However, similar to that noted in bird studies , the NOAEC value for IPSN is lower compared to the TGAI, indicating effects due to IPSN at lowe r doses compared to the TGAI. Therefore, IPSN toxicity studies on fish (850.1075) , aquatic invertebrates (850 .1300), and aquatic non-vascular plants (850.5400) are needed to resolve the above uncertainty. Furthermore, a midge study using the parent imazosulfuron will be useful to understa nd the differential toxicity of TGAI and IPSN.

The registrant submitted an early life stage t oxicity study on fathead minnow, which fulfilled the data gap pointed out by EFED. Si nce the previously submitted acu te toxicity studies were on rainbow trout, an additional acute exposur e study was submitted on fathead minnow.

The registrant submitted a new mallard duck stud y to document the chronic exposure effects of imazosulfuron as the previously-submitted study did not determine a NOAEC value for egg shell thickness. Endpoints generated from this new st udy were used in the risk estimation of the current assessment. The uncertainty regarding the toxicity of degradates to birds was resolved through the submission of two avian studies whic h showed no differences between the parent and IPSN toxicity to birds.8 

## Ecological Risk Assessment for the First Food Use Registration of Imazosulfuron for Selective Sedge and Broadleaf Weed Control in Tomato, Pepper, and Rice and Revised Use rates in Turfgrass



# Imazosulfuron

CAS#: 122548-33-8 USEPA PC Code: 118602

Team Members Sujatha Sankula, Ph.D. Lead Biologist Faruque Khan, Ph.D., Senior Scientist

Peer Reviewers James Lin, Ph.D. Environmental Engineer Brian Anderson, M.S., Acting Branch Chief

Acting Branch Chief Brian Anderson, M.S.

Date of Approval August 4, 20109 

### TABLE OF CONTENTS

1 Executive Summary............................................................................................................ .. 12

1.1 Nature of Chemical Stressor ......................................................................................... 12 1.2 Potential Risks to Non-target Organisms...................................................................... 12 1.3 Conclusions: Exposure Characterization ...................................................................... 15

1.4 Conclusions: Effect s Characterization .......................................................................... 16 1.5 Uncertainties and Data Gaps......................................................................................... 17

2 Problem Formulation .......................................................................................................... .. 18 2.1 Nature of Regulatory Action......................................................................................... 18

2.2 Stressor Source and Distribution .................................................................................. 19 2.2.1 Nature of the Chemical Stressor ............................................................................... 19 2.2.2 Mode of Action......................................................................................................... 20 2.3 Overview of Pesticide Usage........................................................................................ 20 2.4 Receptors.................................................................................................................. ..... 21 2.4.1 Aquatic and Terrestrial Effects ................................................................................. 21 2.4.2 Ecosystems Potentially at Risk ................................................................................. 21 2.4.3 Ecological Effects ..................................................................................................... 22 2.5 Conceptual Model......................................................................................................... 23 2.5.1 Risk Hypotheses........................................................................................................ 23 2.5.2 Conceptual Diagram ................................................................................................. 23 2.6 Analysis Plan .............................................................................................................. .. 25 2.6.1 Measures of Effect and Exposure ............................................................................. 25 2.6.2 Data Gaps................................................................................................................ .. 27

3 ANALYSIS..................................................................................................................... ...... 28

3.1 Use Characterization..................................................................................................... 28 3.2 Exposure Assessment.................................................................................................... 29 3.2.1 Environmental Fate and Tr ansport C haracterization ................................................ 29 3.2.2 Aquatic Exposure Estimates for Imazosulfuron ....................................................... 41 3.2.3 Terrestrial Wildlife Exposures.................................................................................. 46 3.2.4 Terrestrial and Semi-Aquatic Plant Exposures......................................................... 48 3.3 Ecological Effects Characterization.............................................................................. 48 3.3.1 Aquatic Effects Characterization .............................................................................. 51 3.3.2 Terrestrial Effects Characterization .......................................................................... 54 3.3.3 Review of Incident Data ........................................................................................... 57 3.3.4 Review of ECOTOX Data ........................................................................................ 5710 

### 4 RISK CHARACTERIZATION............................................................................................ 58 4.1 Risk Estimation: Integration of Exposure and Effects Data

......................................... 59 4.1.1 Non-target Aquatic Fish, Invertebrates, and Plants

.................................................. 59 4.1.2 Non-target Terrestrial Ani mals and Plants ............................................................... 61 4.1.3 Terrestrial and Semi-aquatic Plants Risk.................................................................. 63 4.2 Risk Description........................................................................................................... . 64 4.2.1 Risks to Aquatic Organisms...................................................................................... 65 4.2.2 Risks to Terrestrial Organisms.................................................................................. 65 4.2.3 Endocrine Disruption Assessment ............................................................................ 67 4.3 Threatened and Endangered Species Concern.............................................................. 68 4.3.1 Action Area.............................................................................................................. . 68 4.3.2 Taxonomic Groups Potentially at Risk: Direct Effects............................................. 69 4.3.3 Use of Probit Slope Response Relation ship to Provide Information on the Endangered Species Levels of Concern

................................................................................ 70 4.3.4 Indirect Effects Analysis........................................................................................... 70 4.3.5 Critical Habitat for Listed Species............................................................................ 71

5 Description of Assumptions, Uncerta inties, Strengths, and Lim itations.............................. 72 5.1 Assumptions and Limitations Related to Exposure for all Taxa .............................. 72 5.2 Assumptions and Limitations Related to Exposure for Aquatic Species ................. 72 5.3 Assumptions and Limitations Related to Exposure for Terrestrial Species ............. 73 5.4 Assumptions and Limitations Related to Effects Assessment.................................. 75

6 LITERATURE CITED ......................................................................................................... 76

APPENDIX A: Status of Fate and Ecological Effects Data Requirem ents.................................. 79

APPENDIX B: Calculations of Ha lf-life for Total Toxic Residues

............................................. 81

APPENDIX C: PRZM EXAMS Output Files .............................................................................. 89

APPENDIX D: Rice Model........................................................................................................ 111

APPENDIX E: ECOTOX Output............................................................................................... 112

APPENDIX F: Example TERR-PLANT Output........................................................................ 116

APPENDIX G: EXAMPLE TREX Output ................................................................................ 11611 

### LIST OF TABLES

Table 1. Listed Species Risks Aassociated with Dir ect or Indirect Effects due to Applications of Im azosulfuron Parent..................................................................................................... 15 Table 2. Nature and Product Chemistry of the Chem ical Stressor - Imazosulfuron..................... 20 Table 3. Measures of Environmental Exposure and Ecological Effects Used to Assess the Potential Risks of Im azosulfur on to Non-Target Organisms......................................... 26 Table 4. Application Information from the Proposed Imazosulfuron Labels.............................. 29 Table 5. Summary of Environmental Fate a nd T ransport Properties of Imazosulfuron.............. 29 Table 6. Major and Minor Degradates of Imazosufuron .............................................................. 39 Table 7. Summary of Metabolites and Degradates to be Included in the Surface Water Exposure Assessm ent..................................................................................................................... 42 Table 8. PRZM/EXAMS Input Parameter Values for Total Residues of Imazosulfuron ............ 43 Table 9. Rice Model Input Parameters for Imazosulfuron ........................................................... 45 Table 10. Estimated Environmental Concentrations for Total Toxic Residues of Im azosulfuron in Surface Water................................................................................................................. 45 Table 11. Estimated Environmental Concentrati ons for Im azosulfuron Parent on Avian and Mammalian Food Items (ppm) at Maximum Application Rates................................... 46 Table 12. Avian EEC Equivalent Dose Adjusted for Body Weight for Im azo sulfuron Application to Turfgrass. ................................................................................................................... 47 Table 13. Mammalian EEC Equivalent Dose Ad justed for Body W eight for Imazosulfuron Application to Turfgrass. ............................................................................................... 47 Table 14. Imazosulfuron Estimated Environmenta l Concentrations for Terrestrial and Se miAquatic Plants for Aerial and/or Ground Application to Turfgarss............................... 48 Table 15. Imazosulfuron Toxicity Values for Aquatic Organisms.............................................. 49 Table 16. Mammalian Acute Oral and Ch ronic T oxicity to Imazosulfuron................................. 50 Table 17. Imazosulfuron Toxicity Reference Values (TRVs) for Terrestrial Organism s ........... 50 Table 18. Differential Toxicity of Sulfonyl Urea Herbicides in Aquatic Plants ........................ 50 Table 19. Aquatic Vascular Plant RQs for Imazosulfuron ........................................................... 61 Table 20. Chronic Avian RQs based on Upper Bound and Mean EECs for Imazosulfuron use on Turf grass ....................................................................................................................... 61 Table 21. Mammalian Acute Risk based on Exposure to Im osulfuron Degradates ..................... 63 Table 22. Mammalian Chronic RQs Based on U pper Bound Residues for Im azosulfuron Use on Tomato, Pepper, and Rice.............................................................................................. 62 Table 23. Mammalian Dose-Based Chronic RQs based on Upper Bound Residues for Im azosulfuron use on Turfgrass..................................................................................... 62 Table 24. Risk quotient (RQ) values for Plants in Dry and Sem i-aquatic Areas Exposed to Imazosulfuron Through Runoff and/or Spray drift........................................................ 64 Table 25. Listed Species Risks Associated with Dir ect or Indirect Effects Due to Applications of Imazosulfuron Parent..................................................................................................... 69



## LIST OF FIGURES

Figure 1. Conceptual Model Depicting Ecological Risk Based on Proposed Imazosulfuron Applications ................................................................................................................... 24 Figure 2. The Proposed Metabolic Pathways fo r the Degradation of Im azosufuron and the Formation of Major Degradates..................................................................................... 3712 

### 1 Executive Summary

1.1 Nature of Chemical Stressor

Valent USA Corporation (Valent) is seeking registration for the fi rst food uses of im azosulfuron in tomato, pepper, and rice. Additionally, Valent submitted mitigated labels for imazosulfuron in response to the risk assessment conducted for its registration as new chemical for use in turf, ornamentals, conifers, and bare ground non- crop areas (DP 348003). The revised labels for imazolsulfuron removed all uses except turfgr ass from labels; reduced the maximum single application rate in turfgrass fr om 0.75 lb ai/A to 0.67 lb ai/A; removed aerial applications in turfgrass; strengthened drift management and spra yer clean-out sections; disallowed the use of flood nozzles; and added 10-foot ve getative buffer strip between treated areas and water bodies. Therefore, this ecological risk assessment for imazosulfuron is based on its new uses in tomato, pepper, rice and revised uses in turfgrass (residential and commercial). Furthermore, this risk assessment serves as EFED’s response to the registrant’s rebuttal (MRID 477668-22) on the ecological risk analysis conducte d by EFED on the new chemical registration of imazosulfuron in turfgrass, ornamentals, conifers , and bare ground non-crop areas (DP348003).

Imazosulfuron is a sulfonylurea (S U) herbicide that provides bot h pre- or post-emergence and selective control of sedges and broadleaf weeds. It is a system ic herbicide that is absorbed both by roots and foliage and is translocated in xylem and phloem. The proposed registration is for the formulated products (V-10142 Ag) of imazosulfur on for use in tomato, pepper, rice, and V10142 for established residential and commercia l turfgrass. Both V-10142 and V-10142 Ag are formulated as water dispersible granules that contain 75% of the active ingredient.

It is proposed that imazosulfur on will be applied in row midd les, under plastic mulch, on bare soil, or as directed spray at 0.2 – 0.3 lb ai/A in pepper; as pre-transp lant spray under plastic mulch, over the top (direct-seeded or post-transplant), or directedspray (direct-seeded or posttransplant) at 0.2 – 0.3 lb ai/A in tomato; and to moist soil until 2-inch internode stage of drillseeded, dry, or water-seeded rice. The maximu m single application rate proposed for the food uses is 0.3 lb ai/A. A single application is permitted in tomato and pepper whereas two applications, 21 days apart, are allowed in rice. In view of crop injury, only ground applications are allowed in tomato and pepper. In additi on to ground application, ae rial application is permitted in rice only.

For turfgrass, the revised labels suggest the us e of 0.5 – 0.67 lb ai/A per application. Two postemergence applications are permitted with 21-day interval between applications for turfgrass. Applications in turfgras s should be made after nutsedge has reached the 3-leaf stage of growth. Similar to tomato and pepper, only ground appl ications of imazosulf uron are allowed in turfgrass.

1.2 Potential Risks to Non-target Organisms

A screening -level risk assessment, based on total toxic residue approach (parent + degradates of concern), suggests that imazosulfuron presents a high level of risk to both endangered and nonendangered species of aquatic vascul ar plants and terrestrial plants. There is also a potential for acute risk to aquatic non-vascular plants and chronic risk to birds and mammals.13 

### In response to the uncertainty pointed in the previous assessment (D P 348003) on the greater toxicity of the degradates, IPSN, UDPM and AD PM, which were found to be more acutely toxic to mammals than the parent, with IPSN, being the most toxic, the registrant submitted new studies using IPSN on midge (28-day chronic study), bobwhite quail (acute dose and dietary studies), insects (acute studies on ground beetle and rove beetle), and earthworms (acute studies). As midge data is not available for the TGAI, t oxicity comparisons could not be made between the TGAI and IPSN. The bird stud ies suggested that IPSN is pract ically non-toxic to birds both on a single dose and dietary basis, similar to the parent imazosulfuron. However, the LOAEC values for IPSN were lower than the parent in both the dose and dietary- based studies suggesting that adverse effects could be noted at lower conc entrations with IPSN compared to the parent. Regarding the non-target insects, although studies that evaluated the effects of IPSN were submitted on ground beetle and rove beetle, compar able studies were not available for TGAI. Therefore, the uncertainty related to the effects of TGAI versus IPSN could not be resolved for terrestrial insects. New studies submitted by th e registrant suggest that the toxicity of imazosulfuron and IPSN is similar to earthworms. Ho wever, similar to that noted in bird studies, the NOAEC value for IPSN is lower compared to the TGAI, indicating effects due to IPSN at lower doses compared to the TGAI.

Terrestrial Organisms

Plants

Imazosulfuron exposure results in significant redu ctions in growth and survival to non-target terrestrial plants with EC

25 

### values as low as 0.034 lbs ai/A (corresponding NOAEC value of 0.025 lbs ai/A). Many of the EC

25 

### values for terrestrial plants are ap proximately an order of magnitude lower than the proposed single application rates [0.3 (tomato, pepper, and rice) – 0.67 (turfgrass) lb ai/A). Based on a single ground application on tomato, pepper, and rice at the maximum rate, the LOC was exceeded for listed and non-listed non- target terrestrial plants in semi-aquatic environments only. For a single aerial applicati on on rice, the LOC was exceeded for listed and non-listed non-target terres trial plants in semi-aquatic enviro nments and listed plants in dry upland areas. For a single ground ap plication to turfgrass, the LOC was exceeded for listed and non-listed non-target terrestr ial plants in dry upland and semi-aquatic environments.

Effects in the seedling emergence and vegetative vi gor studies were observed for plants in a wide range of plant families. However, there were mi nimal effects observed in monocots compared to dicots because imazosulfuron is not a grass herbic ide. In addition to the growth effects observed for several plant species, unusually high mortality was observed for some plants in the seedling emergence and vegetative vigor test s. There were significant reductions in survival at 21 days for soybean at 2 lb ai/A (32%), flax at 0.67 lb ai /A (37%), and radish at 0.67 lb ai/A (60%). Imazosulfuron exposure may result in non-target plant mortality.

There is also concern for incide nce to plants at the proposed ap plication rates for imazosulfuron, given that major incidences have occurred as a re sult of application of other SU’s at much lower rates. The proposed maximum single application rates for imazosulfuron (0.3 – 0.67 lb ai/A) are much greater than other registered SU herbic ides. For example, the following are the most common use rates based on the recent RED documents for some SU herbicides:14 

### • Chlorsulfuron (Glean): 0.0625 lb ai/A

• Sulfometuron-methyl (Oust): 0.0231 - 0.375 lb ai/A

• Nicosulfuron (Accent): 0.0625 lb ai/acre

• Chlorimuron (Classic): 0.008 - 0.12 lb ai/A

Research involving chlorsulfuron, the first SU registered in th e US (1981) has indicated that chlorsulfuron may have effects on plant seed/fru it production at extremely low concentrations. Researchers (Fletcher et al. , 1993, 1996; Bhatti et al. , 1995), have reported reproductive effects in cherry, canola, soybean, sunflower and Polygonum spp. at application rates as much as 1000x below the label rate (0.0625 lb ai/A). Among the incidents recorded for chlorsulfuron, the highest profile incident is Horse Heaven Hills, where chlorsulfuron applied to nearby wheat fields was implicated in the reduced yields in cherry and peach trees over a number of years in the 1980s. At this time, it is not known whethe r reproductive effects are associated with SUs other than chlorsulfuron; however, effects to plants at very low exposures to the SU sulfometuron-methyl (the second SU registered ) have been implicated in the loss of 100,000 acres of sugar beets in Idaho in the year 2000.

Birds and Mammals

Chronic LOCs are exceeded for birds and mammal s due to imazosulfuron use in turfgrass only. Chronic avian risk LOCS were not exceeded for any of the food (tomato, pepper, and rice) uses (RQ = 0.1 – 0.7). Chronic risk LOCS exceeded for bi rds consuming short grass, tall grass, and broadleaf plants and small insects fo r turfgrass use only (RQ = 0.2 – 2.7).

Only dose-based chronic risk LOC exceeded for tu rfgrass use for all sized mammals. There are no LOC exceedances for chronic dose-based risk for any sized mammals based on imazosulfuron uses in tomato, pepper, and rice. Similarly, dietary-based chroni c risk LOCS were not exceeded for mammals for any of the proposed food or non-food uses for imazosulfuron.

There is no acute LOC exceedances for birds, mammals and terrestrial invertebrates from imazosulfuron TGAI for all of the proposed uses . However, the degradates, IPSN, UDPM and ADPM are more acutely toxic to mammals than th e parent with IPSN, being the most toxic. Therefore, there is uncertainty regarding chronic ri sk to birds and mammals and risk to terrestrial plants from these degradates.

Aquatic Organisms

There is risk to non-listed aqua tic vascular plants based on ex posure to imazosulfuron from all the proposed new uses (RQs = 7 – 607, LOC = 1). LOCs for endangered aquatic vascular plants are also exceeded for all the proposed uses (RQs = 17 - 1468). Registrant-submitted studies are not available to demonstrate the effects of imazosulfuron on aquatic non-vascular plants. RQs calculated based on an open literature study (Moh ammed et al., 2005) sugges ted that risk (RQ = 1.4) exceeded levels of concern for imazosulfuron use in rice only.15 

### Imazosulfuron is not acutely toxic to freshwater or estuarine/ma rine fish and invertebrates. Calculated chronic risk quotie nts for freshwater fish ranged from 0.001 (tomato) – 0.09 (rice). Therefore, imazosulfuron is not expected to pose any risk to freshwater fish based on chronic

exposure.

An aquatic vascular plant ( Lemna gibba ) study using the degradate, IPSN, demonstrated no toxicity to the plant. A single study submitted on th e degradate IPSN (no data is submitted on the parent) suggested that IPSN is pr actically non-toxic to the benthi c invertebrate midge larvae (RQ = 0.0004). However, there is uncerta inty regarding IPSN toxicity to fish, invertebrates, and aquatic non-vascular plants.

Listed Species

There is a potential concern for direct effects for listed aquatic vascular and non-vascular plants, terrestrial plants, bird s and mammals from the proposed imazosulfuron uses in tomato, pepper, rice, and turfgrass ( Table 1 ). There is potential for imazosulf uron to exert indirect effects upon the listed organisms by, for exampl e, perturbing forage or prey availability, altering habitat, pollination and/or dispersal, etc. With additional refinement, such as exploring more detailed use patterns and species biology ( e.g ., geographic location, specific feed ing habits, time of year the listed species are likely to utilize crop fields), it may be determined that some (or all) listed species may not be affected.

Table 1. Listed Species Risks Asso ciated with Direct or Indirect Ef fects Due to Applications of Imazosulfuron in Tomato, Pepper, Rice, and Turfgrass

Listed Taxa Direct Effects Indirect Effects Terrestrial and semi-aquatic plants – monocots Yes Yes Terrestrial and semi-aquatic plants – dicots Yes Yes Terrestrial invertebrates No Yes Birds (surrogate for terrestrial-phase amphibians and reptiles) Yes – chronic effects Yes

Mammals Yes – chronic effects Yes Aquatic vascular plants Yes Yes Aquatic non-vascular plants Yes Yes Freshwater fish (surrogate for aquatic-phase amphibians) No Yes

Freshwater Invertebrates No Yes Freshwater Benthic Invertebrates No Yes Estuarine/Marine Fish No Yes Estuarine/Marine Crustaceans No Yes Estuarine/Marine Mollusks No Yes



### 1.3 Conclusions: Exposure Characterization

Imazosulfuron is a systemic herbicide cont aining dimethoxypyrimidine and imidazopyridine rings. Major routes of imazosu lfuron dissipation are aerobic a nd anaerobic biodegradation and aqueous photolysis. Degradation half-lives in so il and water range from few weeks to several months due to aerobic soil metabolism and an aerobic aquatic metabolis m. There are several major degradates (HMS, IPSN, IOHA, AD PM, UPDM and SPDM) identified in the environmental fate studies. Photolytic half-life of 3.5 days is expected to hasten degradation of16 

### imazosulfuron in clear, shallow aqueous environmen ts but not in soil (stable). Imazosulfuron is also stable to abiotic hydrolysis except at low pH. Because imazosulfuron is mobile to moderately mobile in soil, it is expected to m ove from the application site into groundwater and surface water. Additionally, off-site movement of imazosulfuron is expected through spray drift from aerial and ground spray. A total toxic residue (p arent plus degradates of concern) approach is considered for the aquatic exposure assessment.

1.4 Conclusions: Effects Characterization

Im azosulfuron is practically non-tox ic to freshwater and estuarin e/marine fish, water flea, and mysid shrimp at concentrations of up to 100 mg ai/L nominal concentration. It is slightly toxic to estuarine/marine mollusks. In a life cycle toxicity test using Daphnia magna , parental mortality was observed in addition to a significant decrease in the mean number offspring per parent at 3.3 mg ai/L. A freshwater fish early life-stage st udy suggested that hatching success was the most sensitive parameter affected by imazosulfuron. A 28-day study on the sediment-dwelling midge larvae suggested that IPSN did not affect emer gence or larval mortality up to 25 mg ai/L.

Toxic effects were observed in an aquatic vascular plant study using duckweed ( Lemna minor ) exposed to imazosulfuron parent. The metabo lite, IPSN, was not toxic to the duckweed ( Lemna gibba ) up to 100 mg ai/L. Imazosulfuron is not toxic to the marine diatom, Skeletonema costatum, freshwater diatom, Nitzschia palea , and the freshwater algae, Selenastrum capricornutum . The blue-green algae, Anabaena flos-aquae toxicity test resulted in a EC 50 

### of 11 mg ai/L. An ECOTOX study, Mohammad, M. et al ., 2005 (ECOTOX # 104861) supported the results of the registrant studi es. In the ECOTOX study, vascular plants were two orders of magnitude more sensitive than non-vascular plants for imazosulfuron.

Imazosulfuron is practically non-t oxic to birds, mammals, and te rrestrial invertebrates on an acute-exposure basis. Additional stud ies indicated that toxicity of IPSN to birds (both on single dose and dietary basis) and earthworms is si milar to imazosulfuron TGAI. Based on chronic avian studies, number of eggs laid was the most se nsitive affected parameter, which occurred at 202 mg ai/kg diet.

The metabolites, IHOA and M-1 ar e also not acutely toxic to mammals. The metabolites, IPSN, UDPM and ADPM are more acutely toxic to mamma ls than the parent with IPSN, being the most toxic. A 2-generation la boratory rat reproduction study with technical imazosulfuron resulted in no reproductive effects. There were parental effects based on mortality, clinical signs of toxicity, and decreased body we ight and food consumption.

Significant reductions in growth a nd survival toxicity to terrestri al plants were observed in both the seedling emergence and vegeta tive vigor tests. In the seedling emergence test, the most sensitive monocot was onion, which resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.034, 0.025, and 0.0052 lb ai/A, respectively, based on dry weight. There was 80% reduction at highest test concentration of 0.67 lb ai /A, which is the maximum single application rate proposed on the revised turfgrass label. The most sensitive dicot was lettuce and resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.041, 0.22, and 0.0028 lb ai/A, respectively, based on dry weight. There was 32% reduction of lettuce dry weight at LOAEC (0.074 lb ai/A). There were also significant reductions in survival at 21 days for soybean at 2 lb ai/A (32%) and flax at 0.67 lb ai/A (37%).17 

### In the vegetative vigor test, the most sens itive monocot was onion and resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.25, 0.025, and 0.02 lb ai/A based on dry weight. The most sensitive dicot was radish and resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.08, 0.074, and 0.0079 lb ai/A, respectively, based on percent survival. At the ma ximum dose tested for radish, 0.67 lb ai/A (the proposed maxi mum single application rate fo r turfgrass), there was a 60% reduction in survival compared to the control. There were also significant effect s on dry weight and plant height for radish. There were signif icant effects to ryegrass, buckwheat, tomato, soybean, lettuce and flax.

The nontarget terrestrial plant t oxicity studies, as specified by the Agency guidelines, are designed to evaluate sublethal effects to plant growth, which can then be extrapolated to community level effects. Mortality as an e ndpoint in these studies, as is the case with imazosulfuron, is atypical a nd of concern to Agency.

1.5 Uncertainties and Data Gaps

The following Environm ental Fate uncertainties, limitations, and data gaps ( Appendix A ) were identified in this environmental risk assessment:

• This assessment is based on limited biodegrad ation fate data. Imazosulfuron persistence is significantly affected by soil or water chem istry and may not always be easy to predict from typically available soil/wat er property data alone. A clearer picture of the range of variability in imazosulfuron persistence in the environment would require environmental fate studies on a greater variety of soils/wat ers/sediments with a greater range of pH levels and other soil properties. This is partic ularly true for the aerob ic soil and anaerobic aquatic metabolism studies.

• Even though imazosulfuron is soluble and moderately mobile to mobile based on the results of batch equilibrium st udies, unextractable residues were identified at maximums of 87.7% of applied radioactiv ity in anaerobic aquatic me tabolism and 35.7% of applied radioactivity in aerobic soil metabolism. Th e unextractable residues are uncharacterized and it is uncertain whether they consist of degradates of risk concern. Under sterile conditions these unextractable residues were not formed suggesting that the formation of them is microbially mediated. Metabolism half-lives were estimated based on total residue approach that include s parent and major degradates concentrations (excluding unextractable residues). To the extent that these unextractable residues are of risk concern, the estimated half-lives will be undere stimated compared to a total toxic residue approach for estimating half-lives. However, given the persistence of total toxic residue of imazosulfuron, inclusion of unextractable residues in total toxic approach for calculating metabolism half-life would not impact PRZM/EXAMS modeled EECs appreciably.

The following Environmental Effects uncertainties, limitations, and assumptions were identified in this environmental risk assessment:

• An aquatic vascular plant ( Lemna gibba ) study using the degradate IPSN demonstrated no toxicity to the plant. However, greater t oxicity was noted to mammals due to exposure to IPSN. Therefore, there is uncertainty regarding acute toxic ity to fish, aquatic18 

### invertebrates (water column-dwelling), and a quatic non-vascular plants exposed to the degradates. Studies are required to address this uncertainty.

• The recently revised (October 2007) FIFRA data requirements (CFR 40 Part 158) require an avian acute oral toxicity study (850.2100) be conducted using a passerine species (Passeriformes). Valent submitted a request to waive the study requirement for acute oral toxicity of imazosulfuron to passerine bird s because of the lack of a guideline study on passerines, unwillingness of research or ganizations to conduct the study using redwinged blackbirds (the preferred species), lack of availability of commercial source of red-winged blackbirds, and EPA’s non-approval of alternative passe rine species (MRID 47679113). However, the waiver was not gran ted as the revised Part 158 data requirements specify that acute avian oral toxicity data be submitted for either one waterfowl or one upland game species and one passerine species for pesticides with proposed terrestrial, aquatic, fore stry, and residential outdoor uses.

• Research (Fletcher et al. , 1993, 1996; Bhatti et al. , 1995) involving chlorsulfuron, the first SU registered in the US (1981) has indi cated that chlorsulfuron may have effects on plant seed/fruit production at extremely lo w concentrations. Researchers have also reported reproductive effects in cherry, canola, soybean, sunflower and Polygonum spp. at application rates as low as 1000x below the label rate. Therefore, studies that document the reproduction effects on plants due to imazosulfuron applications are required.

2 Problem Formulation

2.1 Nature of Regulatory Action

The purpose of this assessm ent is to evaluate the environmental fate and ecological risks resulting from the new food use registration of imazosulfuron in pepper, tomato, and rice. Additionally, this assessment will focus on analyzing risk from the revised use rates of imazosulfuron in turfgrass. In re sponse to the risk assessment conducted for its registration as new chemical for use in turf, ornamentals, conifers, and bare ground non-crop areas (DP 348003), the registrant of imazosulfuron, Valent, submitted revised labels to the Agency. The label changes include re moval of all uses excep t turfgrass; reduction of the maximum single application rate in turfgrass from 0.75 lb ai/A to 0.67 lb ai/A; re moval of aerial applications in turfgrass; strengthening of drift management a nd sprayer clean-out sec tions; disallowing the use of flood nozzles; and addition of 10-foot vegetativ e buffer strip between treated areas and water bodies. Therefore, this ecological risk assessmen t for imazosulfuron is in support of the proposed new uses in tomato, pepper, rice and revised use rates in turfgrass (residential and commercial).

Imazosulfuron is a pre/post-emergence herbicid e to selectively cont rol sedges and certain broadleaf weed. As the first food use being proposed for use in the United States, EPA is required under the Federal Insecticide Fungicide and Rodenticide Act (FIFRA) to ensure that imazosulfuron does not have the potential to cause unreasonable adverse effects to the environment. Potential effects to listed species ( i.e ., species on the Federal list of endangered and threatened wildlife and pl ants) are also considered under the Endangered Species Act in order to ensure that the registration of imazosu lfuron is not likely to jeopardize the continued existence of such listed species or adversely modify their habitat. To these ends, this assessment follows EPA guidance on conducting ecological risk assessments (USEPA 1998) and the Office19 

### of Pesticide Program’s policies for assessing risk to non-target and listed organisms (USEPA 2004).

Among the end products of the EPA pesticide regist ration process is a determination of whether a product is eligible for registra tion and, if so, a description of how the product may be used. A label represents the legal document which stipul ates how and where a given pesticide may be used. End-use labels describe the formulation ty pe, acceptable methods of application, where the product may be applied, and any restrictions on how applications may be conducted. Thus, the use, or potential use, described by the pesticid e’s labels is consider ed “the action” being assessed. This assessment is in s upport of the first food use and revised non-food use registration of imazosulfuron.

2.2 Stressor Source and Distribution

2.2.1 Nature of the Chemical Stressor

Imazosulfuron is a selectiv e sulfonylurea herbicide cont aining dimethoxypyridine and imididazopyridine rings. The major routes of degradation are aerobic and anaerobic biodegradation and abiotic aqueous photolysis. De gradation half-lives in soil and water range from few days to several months due to aerob ic soil metabolism, anaerobic aquatic metabolism and photolysis. There are several major degr adates (HMS, IPSN, IOHA, ADPM, UPDM and SPDM) identified in the environmental fate studies. HMS, retains both imidazolyl (IM) and pyrimidinyl (PM) ring structures , its toxicity is likely comp arable to the parent. Deductive Estimation of Risk based on Existing Knowledge (DEREK) analysis of IPSN, IHOA, ADPM, SDPM, and UDPM showed that all of these cl eavage products except IHOA (a low molecular weight acid) retained at least one of the same st ructural alerts as the parent. Therefore aquatic exposure of total toxic resi due (parent plus HMS, IPSN , ADPM, UPDM and SPDM) is considered in this assessment Imazosulfur on is mobile to moderately mobile (FAO classification) in the environment. Im azosulfuron is a non-volatile (<2.63 x 10 -8 

### Torr at 20°C) compound. Imazosulfuron has two ionizable functional groups (pKa 0.30 and 3.54), therefore it water solubility limit varies with pH. Water solu bility is 429 mg/L at pH 7 but less soluble (1mg/l at pH 4) in acidic environment. Based on the log Kow of -0.07 at pH 7, the potential for bioaccumulation in organisms is very low for im azosulfuron under neutral environment. A brief summary of the product chemistry da ta on imazosulfuron is provided in Table 2

.20 

### 2.2.2 Mode of Action

Im azosulfuron is a systemic sulfonylurea herbicide that is absorbed both by roots and foliage of treated plants. The mode of action of imazosulf uron is through the inhibition of the enzyme acetolactate synthase (ALS) leading to the blocki ng of the synthesis of the branch-chain amino acids such as valine, leucine, and isoleucine th at are essential in the formation of new cells. Injury symptoms, which may not be apparent unt il 1-2 weeks after treatment, include interveinal chlorosis, red venation, purpling, stun ting, root pruning, and gradual death.

2.3 Overview of Pesticide Usage

Imazosulfuron, a systemic herbicide, is being pr oposed for the control of sedges and broadleaf weeds in tomato, pepper, rice, and turfgrass. The proposed first food uses are not limited to a geographical region in the United States. Accord ing to proposed labels, imazosulfuron can be applied in row middles, under plasti c mulch, on bare soil, or as dire cted spray at 0.2 – 0.3 lb ai/A in pepper; as pre-transplant spray under plas tic mulch, over the top (d irect-seeded or posttransplant), or directed spray (dir ect-seeded or post-transplant) at 0.2 – 0.3 lb ai/A in tomato; and to moist soil until 2-inch internode stage of drill-seeded, dry, or water-seeded rice. The Table 2. Nature and Product Chemistry 1 

### of the Stressor - Imazosulfuron

Pesticide Class: Sulfonyl urea herbicide



### EPA PC Code: 118602 

### IUPAC Name: 1-(2-chloroimidazo[1,2- a ]pyridin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea



### CAS Name: 2-chloro- N -[[(4,6-dimethoxy-2-p yrimidinyl)amino]car bonyl] imidazo[1,2- a ]pyridine3-sulfonamide] 

### CAS No: 122548-33-8 

### Formula: C 14 H 13 ClN 6 O 5 S 

### Structure:

Molecular Mass (g/mol) 412.81 Vapor pressure (torr) at 25 o C < 2.63 x 10 -8 Henry’s Law Constant at 25 o C (atm m3/mol) < 3.33 x 10 -11

Solubility in water (mg/L)at 20 0 C 1.00 at pH 4 429 at pH 7 3936 at pH 9

Octanol- water Coefficient (Log K ow ) 2.43 at pH 4 - 0.07 at pH 7 -1.56 at pH 9 Dissociation Constant pKa at 20°C 3.94, 0.30

1 MRID 473051-0121 

### maximum single application rate proposed for the food uses is 0.3 lb ai/A. A single application of imazosulfuron is proposed in tomato and peppe r where as two applications are proposed in rice. A 21-day interval between applications is pr oposed for sequential application in rice. Aerial application is limited to rice only. For turfgrass, the revised labels suggest the use of 0.5 – 0.67 lb ai/A per application. Two post-emergence appl ications are permitted with 21-day interval between applications. Applications in turfgrass should be made after nut sedge has reached the 3- leaf stage of growth. Similar to tomato and pepper, only ground applic ations are allowed in turfgrass.

2.4 Receptors

2.4.1 Aquatic and Terrestrial Effects

The receptor is the biological entity that is e xposed to the stressor (EPA , 1998). Consistent with the process described in the Overview Document (EPA, 2004), this risk assessment uses a surrogate species approach in its evaluation of imazosulfuron. Toxicological data generated from surrogate test species, which are intended to be representative of broad taxonomic groups, are used to extrapolate to potential effects on a variety of species (receptors) included under these taxonomic groupings.

Acute and chronic toxicity data from studies submitted by pesticide registrants along with the available open literature are used to evaluate th e potential direct effects of imazosulfuron to the aquatic and terrestrial receptors identified in this section. This includes toxicity data on the technical grade active ingredient, degradates, and when available, formulated products (e.g. “SixPack” studies). The open literature studies are identified through EP A’s ECOTOX database ( http://cfpub.epa.gov/ecotox/ ), which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The eval uation of both sources of data can also provide insight in to the direct and indirect e ffects of imazosulfuron on biotic communities from loss of species that are sensitive to the chemical and from changes in structure and functional characteristics of the affected communities.

2.4.2 Ecosystems Potentially at Risk

An ecosystem m ay be defined as a functional unit made up of all living organisms (animals, plants, and microbes) in a desi gnated area, and all th e non-living physical and chemical factors of their environment, linked together through nutrient cycling and energy flow. Moreover, an ecosystem can be of any size, i.e. , a log, pond, field, forest, or the earth's biosphere, but it always functions as a whole unit. Ecosystems are comm only described according to the major type of vegetation, for example, forest ecosystem, old-growth ecosystem, or range ecosystem.

Ecosystems potentially at risk are expressed in term s of the selected assessment endpoints. The typical assessment endpoints for screening-level pesticide ecological risks are reduced survival, and reproductive and growth impairment for both aquatic and terrestrial animal species. Aquatic animal species of potential concern include freshw ater fish and invertebrates, estuarine/marine fish and invertebrates, and amphibians. Terrestri al animal species of potential concern include birds, mammals, and beneficial insects. For bot h aquatic and terrestrial animal species, direct22 

### acute and direct chronic exposures are considered. In order to pr otect threatened and endangered species, all assessment endpoints are measured at the individual level. Although endpoints are measured at the individual level, they provide insight about risks at hi gher levels of biological organization ( e.g. , populations and communities). For exam ple, pesticide effects on individual survivorship have important implications fo r both population rates of increase and habitat carrying capacity.

For terrestrial and semi-aquatic plants, the scr eening assessment endpoint is the perpetuation of populations of non-target plant species (cro ps and non-crop species). Existing testing requirements have the capacity to evaluate emergence of seedlings and vegetative vigor. Although it is recognized that the endpoints of seedling emergence and vegetative vigor may not address all terrestrial and semi-a quatic plant life cycle components, it is assumed that impacts at emergence and in active growth have the potentia l to impact individual competitive ability and reproductive success.

For aquatic plants, the assessment endpoint is th e maintenance and growth of standing crop or biomass. Measurement endpoints for this as sessment endpoint focus on vascular plant ( i.e.

, duckweed) growth rates and biomass measurements.

The ecological relevance of selecting the above-mentioned assessment endpoints is as follows: 1) the identification of exposure pathways for these receptors; 2) the receptors may be potentially sensitive to pesticides in affected media and in residues on plants, seeds, and insects; and 3) the receptors could potentially inhabit areas where pesticides are applied, or areas where runoff and/or spray drift may impact the sites because suitable habitat is available.

Given the relative persistence of imazosulfuron an d its degradates in soil and water environments and the widespread distribution of the plant speci es with proposed uses, ecosystems at risk can be generally defined as any adjoining fiel d or water body where imazosulfuron is applied.

2.4.3 Ecological Effects

Each assessm ent endpoint requires one or more “measures of ecological effect,” which are defined as changes in the attrib utes of an assessment endpoint itself or changes in a surrogate entity or attribute in response to exposure to a pesticide. Ecological measurement endpoints for this risk assessment are based on toxicity information for imazosulfuron in the ECOTOX database and a suite of registrant-submitted toxicity studies performed on a limited number of organisms in the following broad groupings:

1. Birds (mallard duck and bobwhite quail), also used as a surrogate for terrestrial-phase amphibians and reptiles, 2. Mammals (laboratory rat and mouse), 3. Freshwater fish (rainbow trout), also used as a surrogate for aquatic-phase amphibians, 4. Freshwater invert ebrates (daphnid), 5. Estuarine/marine fish (sheepshead minnow), 6. Estuarine/marine invertebrates (Eastern oyster), 7. Terrestrial plants (m onocots and dicots),23 

### 8. Aquatic plants (vascular and non-vascular plants), and 9. Terrestrial invert ebrates (honeybee)

Within each of these very broad taxonomic group s, an acute and chroni c endpoint is selected from the available test data, as the data sets allow. Additional ecologi cal effects data were available for other taxa and have been incorporated into the risk characteri zation as other lines of evidence, including acute contact and oral toxicity on honeybees.

2.5 Conceptual Model

For a pesticide to pose an ecological risk, it m u st reach ecological receptors in biologically significant concentrations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an ecological recepto r. For an ecological pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, an d a feasible route of exposure.

A conceptual model provides a written descriptio n and visual representation of the predicted relationships between imazosulfuron, potential routes of exposure, and the predicted effects for the assessment endpoint. A conceptual model cons ists of two major comp onents: risk hypotheses and a conceptual diagram (USEPA, 1998).

2.5.1 Risk Hypotheses

• Terrestrial and aquatic organism s are subject to adverse direct effects such as reduced survival, growth, and reproduction when exposed to imazosulfuron/degradate residues as a result of labeled use of the pesticide.

• Non-target terrestrial, semi-aquatic , and aquatic plants are subject to adverse effects such as reductions in vegetative vigor and seedling emer gence (terrestrial) or biomass and growth rate (aquatic) when exposed to imazosulfuron/degr adate residues as a re sult of labeled use of the pesticide

• Indirect effects, such as habitat, food web dyna mics, perturbing forage or prey availability, and altering the extent and nature of nesting, wi ll potentially occur if residue concentrations exceed levels of concern for acute or chronic ex posure for terrestrial and/or aquatic species.

• Listed species are subject to a dverse effects if calculated risk quotients exceed acute Listed or chronic levels of concern

2.5.2 Conceptual Diagram

In order for a chem ical to pose an ecologica l risk, it must reach ecological receptors in biologically significant concen trations. An exposure pathway is the means by which a contaminant moves in the environment from a sour ce to an ecological receptor. For an ecological exposure pathway to be complete, it must have a source, a releas e mechanism, an environmental transport medium, a point of exposure for ecological receptors, and a feasible route of exposure. In addition, the potential mechanisms of transformation ( i.e. , which degradates may form in the environment, in which media, and how much) mu st be known, especially for a chemical whose metabolites/degradates are of greater toxicological concern. The assessment of ecological24 

### exposure pathways, therefore, includes an exam ination of the source and potential migration pathways for constituents, and the dete rmination of potentia l exposure routes ( e.g. , ingestion, inhalation, and dermal absorption).

Figure 1. Conceptual Model Depicting Ecologic al Risk Based on Proposed Imazosulfuron Applications*

*The pathways include both the parent a nd the degradates; Dotted boxes indicate pathways not considered in the risk assessment

Based on the labels submitted by the registrant, the source, and mechanisms of release for imazosulfuron are aerial (for uses in rice only) and/or ground (tom ato, pepper, rice, and turfgrass) application in the fo rm of water dispersible granul ar formulation. The conceptual model and subsequent analysis of exposure a nd effects are all based both on the parent and degradates of imazosulfuron. Potential emission of volatile compounds is not considered as a viable release mechanism for imazosulfuron, becau se vapor pressure information (less than 2.63 x 10 -8 

### torr at 20°C) suggests that vo latilization is not expected to be a significant route of dissipation for this chemical (indicated by dashed lines in the diagram). Imazosulfuron concentrations in surface waters may be rela tively high when significant runoff events occur after application and / or spray drift to water bodies in close proximity to the treatment area occurs. Imazosulfuron and its degradates also ha ve the potential to leach to groundwater which Aquatic Invertebrates Aquatic Vertebrates Aquatic Plants Stressor

Source/ Transport Pathway

Source/ Exposure Media

Exposure Method

Receptors

Direct Effects:NonEndangered Species

Indirect Effects: Perturbing Forage or Prey Availability Habitat Alteration: impacting nesting ability, ability to seek cover, etc. Individual Terrestrial Animals Reduced Survival Reduced Growth Reduced Reproduction Individual Terrestrial Plants Seedling Emergence Vegetative Vigor Individual Aquatic Vertebrates and Invertebrates Reduced Survival Reduced Growth Reduced Reproduction Bioaccumulation Aquatic Plant Population Reduced Growth Rates and Biomass Terrestrial Animals Birds, Mammals,Reptiles, Terrestrialphase Amphibians, Bees Terrestrial Upland Plants Wetland/ Riparian Plants Imazosulfuron A pp lied as Aerial and Ground S p ra y

Volatilization/ Wind Suspension Ground De p osition Spray Drift Runoff/ Erosion Leaching (Infiltration/ Percolation )

Terrestrial Food Residues (foliage, fruit, insects)/ Soil Upland Foliage/ Soil Riparian/ Wetland Foliage/Soil Surface Water, Sediment

Dietary U p take Direct Contact/ Root Uptake Gill/ Integument Uptake Direct Contact/ Root Uptake Ground water

Direct In g estion25 

### can serve as inputs to surface water, although this is not explicitly modeled for ecological effects in this risk assessment due to modeling and data limitations. Persistence of total toxic residue in soil is sufficient such that vulnerable aquifers ma y be expected to be impacted but the exposure will be minimal compared to surface water exposure. The conceptual model shown in Figure 1 generically depicts the potentia l source of imazosulfuron, release mechanisms, abiotic receiving media, and biological receptor types.

2.6 Analysis Plan

This document characterizes the env ironmenta l fate and effects of imazosulfuron based on proposed uses in tomato, pepper, rice, and turfgrass. Available environmental fate, ecotoxicity, and physicochemical property data were taken from submitted studies to the Agency. The environmental fate and effect studies underwen t formal data evaluation review (DER) to determine their acceptability relative to published EPA guidelines. For the ecotoxicity data, the studies and/or DERs were reviewed to ensure that studies met cu rrent acceptability guidelines.

The maximum proposed label application rates fo r use of imazosulfuron on turf (0.67 lb ai/A) and tomato, pepper, and rice (0.3 lb ai/A) were selected for modeling environmental concentrations for this screening-level deterministic (risk-quotient based) assessment. The most sensitive toxicity endpoints from surrogate test species are used to es timate treatment-related effects on growth, and survival. Estimated e nvironmental concentrations (EECs) used in terrestrial and aquatic ecologica l risk assessments are based on imazosulfuron parent compound and several major degradates of parent.

The following sections characterize the use, en vironmental fate, and ecological effects of imazosulfuron and, the use of risk quotient (r atio of exposure concentration to effects concentration) approach to estimate the potential for adverse effects on non- target terrestrial and aquatic animals and plants. Although risk is of ten defined as the likelihood and magnitude of adverse ecological effects, the risk quotient-b ased approach does not provide a quantitative estimate of likelihood and/or magnitude of an a dverse effect. Such estimates may be possible through a more refined, probabilis tic assessment; however, they are beyond the scope of this base-level assessment.

2.6.1 Measures of Effect and Exposure

Table 3 lists the measures of environmental exposur e and ecological effects used to assess the potential risks of imazosulfuron to non-target organisms (USEPA, 2004).26 

### Table 3. Measures of Environmental Exposure and Ecologi cal Effects Used to Asse ss the Potential Risks of Imazosulfuron to Non-Target Organisms Assessment Endpoint Measures of Effect Measures of Exposure 1. Abundance ( i.e. , survival, reproduction, and growth) of individuals and populations of birds 1a. Bobwhite quail/ mallard duck acute oral LD 50 1b. Bobwhite quail/ mallard duck sub-acute dietary LC 50 1c. Bobwhite quail/ mallard duck chronic reproduction NOAEC and LOAEC Abundance ( i.e. , survival, reproduction, and growth) of individuals and populations of mammals Laboratory rat acute oral LD 50 Laboratory rat 2-generation NOAEC and LOAEC Maximum residues on food items (foliar)

Rainbow trout, carp, bluegill sunfish LC 50 Peak EEC 4 Abundance ( i.e. , survival, reproduction, and growth) of individuals and communities of freshwater fish Fathead minnow NOAEC and LOAEC

60-day average EEC 4

Daphnid EC 50 Peak EEC 4 Abundance ( i.e. , survival, reproduction, and growth) of individuals and communities of freshwater invertebrates Daphnid life cycle NOAEC and LOAEC Midge NOAEC and LOAEC 21-day average EEC 4

Sheepshead minnow acute LC 50 Eastern oyster EC 50 Mysid shrimp LC 50 Peak EEC 4 Abundance ( i.e. , survival, reproduction, and growth) of individuals and communities of estuarine/marine fish and invertebrates Chronic marine invertebrate study not submitted 21-day average EEC 4

Survival of beneficial organisms, insect populations and natural Lepidoptera predators Honeybee acute contact LD 50 Earthworm LC 50 and NOAEC Single Maximum application rate Maintenance and growth of individuals and

p opulations of terrestrial plants from standing crop or biomass Monocot EC 25 and NOAEC values fo r seedling emergence and vegetative vigor (survival and growth rate) Dicot EC 25 and NOAEC values for seedling emergence and vegetative vigor (survival and growth rate) Estimates of runoff and spray drift to non-target

areas Maintenance and growth of individuals and populations of aquatic plants from standing crop or biomass Vascular plant ( i.e. , Lemna) EC 50 and NOAEC values for growth rate and biomass measurements Non-vascular plant ( i.e. , green algae) EC 50 and NOAEC values for growth rate an d biomass measurements Peak EEC 4

1 If species listed in this table represent most commonly encountered species from registrant-submitted studies, risk assessment guidance indicates most sensitive species tested within taxonomic group are to be used for baseline risk assessments.

2 Birds represent surrogates for amphibian s (terrestrial phase) and reptiles.

3 Freshwater fish may be surrogate s for amphibians (aquatic phase).

4 One in 10-year return frequency.

5 Four species of two families of monocots - one is corn, six species of at least four dicot families, of which one is soybeans. LD 50 = Lethal dose to 50% of the test population; NOAEC = No observed adverse effect concentration; LOAEC = Lowest observed adverse effect concentration; LC 50 = Lethal concentration to 50% of the test population; EC 50 /EC 25 = Effect concentration to 50%/25% of the test population.27 

### Data Gaps

The following Environmental Fate uncertainties, limitations, and assumptions were identified in this environmental risk assessment:

• This assessment is based on limited biodegrad ation fate data. Imazosulfuron persistence is significantly affected by soil or water chem istry and may not always be easy to predict from typically available soil / water property data alone. A cl earer picture of the range of variability in imazosulfuron persistence in the environment would require environmental fate studies on a greater variety of soils / wa ters / sediments with a greater range of pH levels and other soil properties. This is partic ularly true for the aerob ic soil and anaerobic aquatic metabolism studies.

• Even though imazosulfuron is soluble and moderately mobile to mobile based on the results of batch equilibrium st udies, unextractable residues were identified at maximums of 87.7% of applied radioactiv ity in anaerobic aquatic me tabolism and 35.7% of applied radioactivity in aerobic soil metabolism. Th e unextractable residues are uncharacterized and it is uncertain whether they consist of degradates of risk concern. Under sterile conditions these unextractable residues were not formed suggesting that the formation of them is microbially mediated. Metabolism half-lives were estimated based on total residue approach that include s parent and major degradates concentrations (excluding unextractable residues). To the extent that these unextractable residues are of risk concern, the estimated half-lives will be undere stimated compared to a total toxic residue approach for estimating half-lives. However, given the persistence of total toxic residue of imazosulfuron, inclusion of unextractable residues in total toxic approach for calculating metabolism half-life would not impact PRZM/EXAMS modeled EECs appreciably.

The following Environmental Effects uncertainties, limitations, and assumptions were identified in this environmental risk assessment:

• An aquatic vascular plant ( Lemna gibba ) study using the degradate IPSN demonstrated no toxicity to the plant. However, greater t oxicity was noted to mammals due to exposure to IPSN. Therefore, there is uncertainty regarding acute toxic ity to fish, aquatic invertebrates (water column-dwelling), and a quatic non-vascular plants exposed to the degradates. Studies are required to address this uncertainty.

• The recently revised FIFRA data requirements (CFR 40 Part 158) require an avian acute oral toxicity study (850.2100) be conducted using a passerine species (Passeriformes)

• Research (Fletcher et al. , 1993, 1996; Bhatti et al. , 1995) involving chlorsulfuron, the first SU registered in the US (1981) has indi cated that chlorsulfuron may have effects on plant seed/fruit production at extremely lo w concentrations. Researchers have also reported reproductive effects in cherry, canola, soybean, sunflower and Polygonum spp. at application rates as low as 1000x below the label rate. Therefore, studies that document the reproduction effects on plants due to imazosulfuron applications are required.28 

### 3 ANALYSIS

3.1 Use Characterization

Imazosulfuron is a new systemic herbicide th at is undergoing regist ration (as the active ingredient with two end-use products) by the registrant Valent Corporation. The imazosulfuron end-use products being proposed for registration in the Unit ed States are V-10142 and V-10142 Ag, both of which water dispersi ble granules with 75.0% ai.

According to the proposed labels for the food us es of imazosulfuron, this product would be used to control of sedges and broadleaf weeds in to mato, pepper, and rice. It is proposed that imazosulfuron will be applied in row middles, under plastic mulch, on bare soil, or as directed spray at 0.2 – 0.3 lb ai/A in pepper; as pre-tr ansplant spray under pl astic mulch, over the top (direct-seeded or post-transplant), or directed spray (direct-seeded or pos t-transplant) at 0.2 – 0.3 lb ai/A in tomato; and to moist soil until 2-in ch internode stage of drill-seeded, dry, or waterseeded rice. The maximum single application rate proposed for the food uses is 0.3 lb ai/A. A single application is permitted in tomato and peppe r whereas two applications, 21 days apart, are allowed in rice. In view of crop injury, only ground applications are allowed in tomato and pepper. In addition to ground a pplication, aerial application is permitted in rice only.

For turfgrass (residential and commercial), the re vised label suggest the use of 0.5 – 0.67 lb ai/A per application. Two post-emergence applications are permitted with 21- day interval between applications. Applications in turfgrass should be made after nutsedge has r eached the 3-leaf stage of growth. Similar to tomato and pepper, only ground applications of im azosulfuron are allowed in turfgrass ( Table 4 ).

The label for imazosulfuron specifies that a rainfall event or over head irrigation supplying 0.5 to 1 inch of water no sooner than 12 hours and not late r than 5 days after app lication is necessary to move the herbicide to the root zone of the germinating weed seedlings. The label disallows` aerial applications in tomato, pe pper, and turfgrass and applicati ons to ratoon rice. Furthermore, the label instructs to apply imazosulfuron in fiel d grown tomato and pepper only; in drill-seeded, dry, or water-seeded rice; and to well-established pepper that is at least 10 inches tall, tomato that is at least in 4 – 5 leaf stage of development, rice (drill-seeded) that is at least in 2-leaf stage, and in established turfgrass when nutsedge ha s reached 3-leaf st age of growth.

The imazosulfuron label for tomato and pepper indi cates that it controls wild buckwheat, burning nettle, hairy galinsoga, common lambsquarters, Mayweed, yello w nutsedge, pigweeds, common purslane, common ragweed, shephe rd’s purse, sowthistle, Russian thistle, wild turnip, and morning glory and suppresses bar nyardgrass, crabgrass, giant f oxtail, black nightshade, purple nutsedge, and Pennsylvania smartweed. Imazosulfuron is labeled for the control of ducksalad, eclipta, flat sedge, hemp sesbania, yellow nutse dge, pigweed, Texasweed, dayflower, northern joint vetch, pitted morning glory, red stem, and ri cefield bulrush in rice. The turfgrass label for imazosulfuron suggest that it selectively contro ls sedges (purple and yellow nutsedge and annual and cylindric sedge) and certain broadleaf weeds (California burcl over, lawn burweed, chickweed, Carolina geranium, henbit, Piert pars ley, and common purslane) in residential and commercial areas.29 

### 3.2 Exposure Assessment

3.2.1 Environmental Fate and Transport Characterization

Imazosulfuron is a sulfonyl urea herbicide c ontaining dimethoxypyrimidine and imidazopyridine rings. Environmental fate properties ( Table 5 ) described below are based on the combined labels [imidazolyl (IM) and pyrimidinyl (PM)]. Major routes of imazosulfuron dissipation are aerobic and anaerobic biodegradation and aqueous photolysis. Imazosulfuron is expected to degrade with half-lives of several weeks in aerobic soil en vironment and anaerobic aquatic environment. Aquatic photolysis (half-life of 3.5 days) is expected to hasten degradation of imazosulfuron but not in soil (stable). Imazosulfuron is also stable to abiotic hydrolysis except at low pH. Because imazosulfuron is mobile to moderately mobile in soil, it is expected to move from the application site into groundwater and surface water. Additio nally, off-site movement of imazosulfuron is expected through spray drift from aerial and ground spray.

Table 5. Summary of Environmental Fate and Transport Properties of Imazosulfuron

Parameter [Guideline #] Value MRID(s)

Hydrolysis [161-1] Combined labels [imidazolyl (IM) and pyrimidinyl (PM)] results:

t 1⁄2 = 7 days @ 25 o C at pH 4;

t 1⁄2 =stable @ 25 o C at pH 7;

t 1⁄2 = stable @ 25 o C at pH 9.

Major degradates: 1. 2-chloroimidazo[1,2- α ]pyridin-3-sulfonamide (IPSN)- maximum 90.7% of the applied in IM label 2. 2-amino-4,6-dimethoxypyrimidine (ADPM)- maximum 90.2% of the applied in PM label

IPSN: t 1⁄2 = Stable @ 25 o C at pH 5; ADPM: t 1⁄2 = Stable @ 25 o C at pH 5; 473051-19

477668-21 

### Table 4. Application Information from the Proposed/Revised Imazosulfuron Labels

Product (% AI) Uses Application Methods Single application Rate (lb ai/A) Maximum # of Applications Maximum Application Rate/Year (lb ai/A)

Tomato and Pepper Ground 0.2 – 0.3 1 0.3

Rice Ground Aerial 0.2 – 0.3 1
0.15 – 0.2 2 0.15 fb 0.15 3 2 21-day interval 0.3 V-10142 (75% ai)

Turf Ground 0.5 - 0.67 2 21-day interval 1.34

1 Preemergence in drill-seeded rice; 2 Postemergence in drill-seeded rice; 3 Preemergence application followed by postemergence application30 

### Table 5. Summary of Environmental Fate and Transport Properties of Imazosulfuron

Parameter [Guideline #] Value MRID(s)

Direct photolysis in water [161-2] Combined labels (IM and PM) results:

t 1⁄2 = 3.5 days @ 25 o C at pH 7

Major degradates (irradiated water): 1. 2-(2-imino-1,2-dihydropyridin-1-yl)oxalic acid (IHOA)- maximum 20.4% of the applied in IM label 2. ADPM – maximum 35.3% of the applied (PM ring) 3. (4,6-dimethoxypyridine-2-yl) aminocarbonylsufamic acid (SDPM) – maximum 13.9% of the applied in PM label 4. 4,6-dimethoxy-2-ureidopyrimidine (UDPM)- maximum 11.1% of the applied in PM label 473051-20

Photolysis on soil [161-3] Combined labels (IM and PM) results:

t 1⁄2 = Stable The estimated half-life is of uncertain value since it is extrapolated well beyond the duration of the study. Th erefore, photolysis in soil is considered as stable. Major degradates: Maximum concentrations of the transformation products are not certain since only the 30-day samples we re exhaustively extracted. All maximum concentrations were measur ed at 30 days posttreatment. 473051-21

Aerobic soil metabolism [162-1] Combined labels (IM and PM) results:

1. Loam soil ((pH 6.9, organic carbon content 1.2%) from New Jersey

Linear half-life: 76.2 days (r 2 = 0.93). Non-linear half-life: 36.5 days (r 2 = 0.98). Observed DT50: ca . 27 days.

Major transformation products: 1. 1-(2-chloroimidazo [1,2a]pyridin-3-ylsulfonyl)-3-(4-hydroxy-6- methoxypyrimidin-2-yl)urea (HMS) detected in both IM and IP labels -Maximum 11.9 % of the applied in IM label -Maximum 11.0 % of the applied in PM Label 2. IPSN - maximum 14.2% of the applied in IM label.

2. Loamy sand soil ((pH 6.1, organic carbon content 2.27%) from Germany

Linear half-life: 58.2 days (r 2 = 0.88). Non-linear half-life: 42.3 days (r 2 = 0.90). Observed DT50: ca . 23 days.

Major transformation products: IPSN - maximum 26.0% of the applied in IM label at the time of study termination (120 days). 473051-22

477668-01

Anaerobic soil metabolism Combined labels (IM and PM) results: 477668-0231 

### Table 5. Summary of Environmental Fate and Transport Properties of Imazosulfuron

Parameter [Guideline #] Value MRID(s)

[162-2] 1. Loam soil ((pH 6.7, organic carbon content 2.0%) from New Jersey Half–life/DT50 values re ported as post-flood

Linear half-life in water: 48.8 days (r 2 = 0.89). Linear half-life in soil: 72.2 days (r 2 = 0.87). Linear half-life in the total system: 73.7 days (r 2 = 0.88).

Non-linear half-life in water: 61.9 days (r 2 = 0.91). Non-linear half-life in soil: 77.0days (r 2 = 0.83). Non-linear half-life in the total system: 90.0 days (r 2 = 0.90).

Observed DT50 in water: ca . 77 days. Observed DT50 in soil: ca . 88 days. Observed DT50 in the total system: ca . 88 days.

Major transformation products: 1. 1-(2-chloroimidazo [1,2a]pyridin-3-ylsulfonyl)-3-(4-hydroxy-6- methoxypyrimidin-2-yl)urea (HMS) detected in both IM and IP labels -Maximum 15.5 % of the applied in IM label -Maximum 17.4 % of the applied in PM Label 2. IPSN - maximum 20.1% of the applied in IM label. 3. ADPM - Maximum 12.7 % of the applied in PM Label

Anaerobic aquatic metabolism [162-3] Combined labels (IM and PM) results:

Matrix: Creek water-clay sediment (w ater pH 7.8; sediment pH 6.5, organic matter 3.6%) sy stems from Mississippi.

Linear half-life in the total system: 47.2 days (r 2 = 0.78). Non-linear half-life in total system: 16.5 days (r 2 = 0.99) Observed DT50 in total system: ca. 21 days.

Major transformation products in the total system: 1. HMS -Maximum 20.0 % of the applied in IM label -Maximum 21.8 % of the applied in PM Label 2. IPSN - maximum 19.8 % of the applied in IM label. 473051-23

Aerobic aquatic metabolism [162-4] Combined labels (IM and PM) results:

Matrix: Millstream pond water-loam sediment (water pH 8.02; sediment pH 7.4-7.6, organic matter 7.0%) systems from U.K.

Linear half-life in water: 20.6 days (r 2 = 0.93). Linear half-life in sediment: 31.9 days (r 2 = 0.87). Linear half-life in the total system: 22.1 days (r 2 = 0.89).

Non-linear half-life in water: 17.6 days (r 2 = 0.97). Non-linear half-life in sediment: 43.3 days (r 2 = 0.70). Non-linear half-life in the total system: 27.9 days (r 2 = 0.97). 476397-0232 

### Table 5. Summary of Environmental Fate and Transport Properties of Imazosulfuron

Parameter [Guideline #] Value MRID(s)

Observed DT50 in water: ca . 14 days. Observed DT50 in sediment: ca . 23 days. Observed DT50 in the total system: ca . 40 days.

Major transformation products in the total system: 1. HMS -Maximum 9.89 % of the applied in PM Label

Matrix: Arkansas water-silt loam sediment (water pH 7.2; sediment pH 6.0, organic matter 1.3%) systems from U.K.

Linear half-life in water: 24.2 days (r 2 = 0.60). Linear half-life in sediment: 117.5 days (r 2 = 0.46). Linear half-life in the total system: 52.5 days (r 2 = 0.71).

Non-linear half-life in water: 10.7 days (r 2 = 0.75). Non-linear half-life in sediment: 111.8 days (r 2 = 0.49). Non-linear half-life in the total system: 44.1 days (r 2 = 0.76).

Observed DT50 in water: ca . 0-6 days. Observed DT50 in sediment: > 36 days. Observed DT50 in the total system: ca . 42 days.

Major transformation products in the total system: 2. HMS -Maximum 17.5 % of the applied in IM Label -Maximum 15.8 % of the applied in PM Label 476791-05

Adsorption/ Desorption (K d and K oc in L Kg -1 ) [163-1] Parent: imazosulfuron :

Soil type: Penn Loam. Adsorption K d : 1.64. Adsorption K oc : 135. Freundlich adsorption K f : 1.20. Freundlich adsorption K foc : 98. 1/N: 0.84

Desorption K d : 3.10. Desorption K oc : 254. Freundlich desorption K f : 1.14. Freundlich desorption K foc : 93. 1/N: 0.87

Soil type: Atwater Loamy sand. Adsorption K d : 0.57. Adsorption K oc : 198. Freundlich adsorption K f : 1.15. Freundlich adsorption K foc : 397 1/N: 0.87 473051-1733 

### Table 5. Summary of Environmental Fate and Transport Properties of Imazosulfuron

Parameter [Guideline #] Value MRID(s) Desorption K d : 3.38. Desorption K oc : 1165. Freundlich desorption K d : 1.01. Freundlich desorption K oc : 348. 1/N: 1.00

Soil type: Bosket Silt loam. Adsorption K d : 0.60. Adsorption K oc : 208. Freundlich adsorption K f : 1.13. Freundlich adsorption K foc : 390. 1/N: 0.87

Desorption K d : 0.99. Desorption K oc : 341. Freundlich desorption K f : 1.16. Freundlich desorption K foc : 400. 1/N: 0.87

Soil type: Rilla Silt loam

. Adsorption K d : 5.71. Adsorption K oc : 428. Freundlich adsorption K f : 1.28. Freundlich adsorption K foc : 96. 1/N: 0.78

Desorption K d : 7.06. Desorption K oc : 529. Freundlich desorption K f : 1.22. Freundlich desorption K foc : 92. 1/N: 0.82

Adsorption/ Desorption of Degradates The adsorption coefficients (K oc ) of five transformation products of imazosulfuron were estimated using established HPLC estimation methods. This study was conducted in accordance with OECD Guideline for the Testing of Chemicals No. 121 and in compliance with USEPA GLP 40 CFR Part 160. Imazosulfuron is ionized at neutral pH and has a pKa of 3.94 at 20 ° C (pp. 15, 20). Based on the study results, the HPLCestimated K oc values for imazosulfuron changed greatly when the pH was reduced from pH 7 to pH 3. This was reportedly due to the transition below the pKa (to the non-ionized form).

At pH 7, the calculated K oc values were <1 for imazosulfuron, HMS, SDPM, and IHOA, 33 for IPSN, and 38 for ADPM. At pH 3, the calculated K oc values were 2210 for imazosulfuron, <1 for HMS, SDPM, and IHOA, 36 for IPSN, and 69 for ADPM.

At pH 3, the calculated K oc values were 2210 for imazosulfuron, <1 for HMS, SDPM, and IHOA, 36 for IPSN, and 69 for ADPM. 473051-18

Terrestrial Field Dissipation [164-1] Location/soil type: Near Athens, Georgia/Sandy clay (0-30 cm) over clay (30-90 cm).

a) Soil 473051-2634 

### Table 5. Summary of Environmental Fate and Transport Properties of Imazosulfuron

Parameter [Guideline #] Value MRID(s) Half-life: 6.2 days (r 2 = 0.76) after first application; 15.2 days following the second application (r 2 = 0.41; based on residue data from 3 to 42 days).

Major transformation products detected : None greater than 10% of the total applied imazosulfuron.

b) Turfgrass

Half-life: Half-life: 5.6 days (r 2 = 0.93) after first application and 25.2 days following the second application (r 2 = 0.66); 4.3 days (r 2 = 0.82) based on residue data from 0 to 10 days;).

Major transformation products detected : Not analyzed for transformation products.

Location/soil type: Near North Rose, New York/Loamy sand (0-60 cm) over sand (60-90 cm).



### a) Soil Half-life: 75.3 days following the second application (r 2 = 0.71; based on residue data from 1 to 180 days;).

Major transformation products detected : None greater than 10% of the total applied imazosulfuron.

b) Turfgrass Half-life: Half-life values of 6.4 days (r 2 = 0.72) and 30.4 days (r 2 = 0.64) following the first and second applications, respectively, calculated using linear regression. 2.4 days following the second application (r 2 = 0.92; based on residue data from 0 to 10 days;).

Major transformation products detected : Turfgrass was not analyzed for

t ransformation products. 473051-27

Location/soil type: Madera, California/Loamy sand (0-60 cm) over sandy loam (60-90 cm).

c) Soil (Bare Field) Half-life: 18.0 days (r 2 = 0.81, linear, first-order). 4.9 days (r 2 = 0.89, nonlinear). DT50: Between 1 and 5 days (2.8 days). DT90: Between 14 and 28 days (25.1 days).

Transformation products detected: ADPM, IPSN, and HMS 4 76791-0835 

### Table 5. Summary of Environmental Fate and Transport Properties of Imazosulfuron

Parameter [Guideline #] Value MRID(s) Location/soil type: Greenville, Mississippi/Silt loam (0-30 cm).



### a) Soil (Bare Field) Half-life: 12.0 days (r 2 = 0.8870, linear). 6.1 days (r 2 = 0.8561, nonlinear). DT50: Between 3 and 7 days (5.9 days). DT90: Between 14 and 28 days (26.9 days).

Transformation products detected: ADPM, IPSN, and HMS. 476791-09

Location/soil type: Bumpass, Virg inia/Sandy clay loam (0-30 cm) over clay/clay loam (30-90 cm).



### a) Soil (Bare Field) Application 1 Half-life: 8.4 days (r 2 = 0.9101, linear, first-order). 6.4 days (r 2 = 0.7943, nonlinear). DT50: Between 3 and 10 days (4.4 days). DT90: Not determined. Transformation products detected: IPSN. Application 2

Half-life: 9.0 days (r 2 = 0.8080, linear, first-order). 7.5 days (r 2 = 0.7425, nonlinear.. DT50: Between 5 and 10 days (7.0 days. DT90: Between 28 and 44 days (value could not be calculated). Transformation products detected: IPSN and ADPM. 476791-10

Aquatic Field Dissipation [164-2] Location/soil type: Yuba City, California/Clay loam (0-15 cm).

(a) Water Half-life: 5.3 days (r 2 = 0.84, linear). 5.8 days (r 2 = 0.93, nonlinear).. DT50: Between 5 and 7 days (6.6 days.). DT90: Between 14 and 28 days (21.5 days). Transformation products detected: UDPM, ADPM, and IPSN Dissipation routes: Transformation

(b) Sediment Half-life: 83.5 days (r 2 = 0.36, linear, 5-120 day data). 65.4 days (r 2 = 0.89, nonlinear; reviewer-calculated, 5-120 day data). DT50: Not determined. DT90: Not determined. Transformation products detected: IPSN, ADPM, and HMS Dissipation routes: Transformation 476791-0136 

### Degradation

The major route of dissipation for imazosulfuron is believed to be aerobic and anaerobic degradation/metabolism in soil and water (non-linear degrada tion half-lives generally around 10.7 to 90 days) with a short ha lf-life of 3.5 days for photolys is potentially dominant under aquatic conditions. The biodegr adation of imazosulfuron was bi phasic in aerobic and anaerobic systems with an initial rapid phase followed by much slower degrada tion rate for residual imazosulfuron. The biotransformation of imidazoly l and pyrimidinyl ring s of imazosulfuron was studied in loam and loamy sand soils to eval uate aerobic soil metabolism. Based on non-linear regression analysis, imazosulfuron (combined labe ls) dissipated with ha lf-lives of 36.5 and 42.3 days and the observed DT 50 

### s were ca . 23 to 27 days. Two majo r transformation products (>10%), HMS and IPSN were detected in the aerobic soil metabolism study.

In the anaerobic soil study, im azosulfuron (combined labels) di ssipated from the total system with a nonlinear half-life of 90 days and a first or der half-life of 74 days. In the soil, nonlinear and linear half lives were 77 and 72 days, respectively. The observed DT50 was ca. 88 days in the both the total system and so il. Three major transformation pr oducts (>10%), HMS, IPSN and ADPM were detected in the anaerobic soil metabolism study.

The biotransformation of imidazolyl and pyrimidi nyl rings of imazosulfuron was studied in two water-sediment system to evaluate aerobic a quatic metabolism. In the Millstream pond waterloam sediment system (combined labels), base d on nonlinear regression analysis, imazosulfuron dissipated with a calculated the half-lives of 28 days in the total system, 25 days in the water, and 43 days in the sediment. HMS was a major tran sformation product in th e Millstream pond waterloam sediment systems (both labels). In a water-silt loam soil system from Arkansas, based on combined labels and nonlinear regression analysis, imazosulfuron dissipated with half-lives of 44 days in the total system, 11 days in the water, an d 112 days in the soil. Linear half-lives were 53 days in the total system, 24 days in the water layer and 118 days in the soil. HMS was a major transformation product in both labels.

In the anaerobic aquatic metabo lism study, imazosulfuron (combined labels) decreased from an average of 90.0-93.7% of the applied at time 0 to 66.7-74.1% at 8 days posttreatment, 45.2- 54.0% at 17 days, 26.9-28.4% at 28 days and ≤ 2.0% at and after 112 da ys. Based on nonlinear regression analysis, imazosulfuron (combined labels ) dissipated with calculated half-life of 16.5 days and the observed DT50 was ca . 21 days in the total syst em. Two major transformation products (>10%), HMS and IPSN were also det ected in the anaerobic aquatic metabolism study.

In general, the pseudo first-order degradation ha lf-lives are longer than the non-linear and DT50 in the aerobic and anaerobic biodegradation studies. The biodegradation of imazosulfuron was biphasic with an initial rapid phase followed by much slower degrada tion rate for residual imazosulfuron in these studies. The biphasic degradation pattern in aerobic soil and anaerobic aquatic metabolism studies and the methods of cal culating half-live have resulted discrepancies between calculated linear and non-linear ha lf-lives as well as observed DT50.

Considering abiotic degradation, imazosulfuron is photolyzed at pH 7 in water (half-life of 3.5 days) but a longer half-life of 154 days in soil environments. Similar photolytic degradation half-37 

### life of 3.5 days was also observed in synthe tic humic water sample. The four major transformation products were IHOA, ADPM, SD PM, and UDMP in aquatic photolysis study. Imazosulfuron can be hydrolyzed under acidic environment (pH 4.0) but stable at neutral and alkaline conditions (pH 7-9). The proposed me tabolic pathways for the degradation of imazosulfuron and the formation of major degradates are shown in Figure 2

. Figure 2. The Proposed Metabolic Pathways for the Degradation of Imazosulfuron and the Formation of Major Degradates38 

### Field Studies

The soil dissipation/accumula tion of imazosulfuron under bare ground and cropped (turf) conditions was studied in Georgia, New York, California, Missi ssippi and Virginia in the United States (MRIDs 473051-26, 473051-27, 476791-08, 476791-09, and 476791-10. Under bare ground conditions, imazosulfuron dissipated fr om the entire so il profile with DT 50 

### s and DT 90 

### s ranging from 2.8 -5.9 days and 25.1 – 26.9 days, respectively. However, the observed DT 90 

### value for sandy clay loam of Virginia could not be determined (beyond the range of the data).

The soil dissipation/accumulati on of imazosulfuron under cropped (turfgrass) conditions was studied in Georgia and New Jersey . Under field conditions in th e soil, the calcu lated half-life values were 6.2 to 9.5 days following the first and 15.2 to 75.3 days following second applications, respectively, calculated using lin ear regression. Carryover of residues following the second application was 0% of the total applied imazosulfuron, based on two applications at the target application rates in Georgia and New York Sites.

Under field conditions in the turf grass, imazosulfuron had reviewer-calculated half-life values of 5.6 to 6.4 days following the first and 25.9 to 30.4 days following second applications, respectively, calculated using lin ear regression. However, the dissi pation patterns in both sites following the second application we re bi-phasic and the observed DT 50 

### values were approximately 0.75 to 5 days. Carryover of residues could not be determined because the calculation is based upon bulk density and correspondi ng soil layer. However, at the end of the study following the second application in Georgi a and New York, imazosulfuron residues totaled 0.08 0.15 ppm, at 120 days which is 4.5 to 7.1 % of the total residues originally recovered.

In terrestrial field dissipation study (MRID 473051-27), imazosulfuron was detected in the 45-60 cm soil depth at a maximum of 0.11 ppm at 14 days and in the 60-75 cm and 75-90 cm soil depths at a maximum of 0.03 ppm following the second application in New York. IPSN was also detected in the 30-45 cm, 45-60 cm, and 75-90 cm soil depths at 0.02 ppm following the second application. However, imazosulfuron and its degr adates were not detect ed in soil below the 30- 45 cm depth in other terrestria l field dissipation studies.

The aquatic field dissipation of imazosulfuron under U.S. field conditions was studied using a flooded plot of clay loam soil planted with rice at one site in California. Under aquatic field conditions, the calculated half-life value is 5.3 days in water for imazosulfuron

. The calculated half-life value is 65.4 days based on nonlinear regre ssion. The observed DT 50 

### value could not be reliably determined due to data variability, and the observed DT 90 

### value occurred beyond the range of the data set. The tran sformation products UDPM and IPSN we re detected in the water at concentrations above the LOD. The transforma tion products ADPM, HMS, and IPSN were also detected in sediment at concentrations above the LOD.

Degradates of Exposure Concern

The environmental degradates of imazosulfuron that are of possible exposure concern for surface water include the parent com pound’s major degradates, HMS, IPSN, IOHA, ADPM, UPDM and SPDM ( Table 6 ). HMS is the only degradate that reta ins both imidazolyl (IM) and pyrimidinyl39 

### (PM) ring structures. HMS has been detected usi ng both IM and PM radio-label rings in aquatic photolysis, aerobic soil metabolism and anaerobic aquatic metabolism studies. IPSN and ADPM are included for maximum formation at lowe r pH. IPSN (14.2%) and ADPM (35.3 %) in were also major degradates formed in aerobic soil metabolism and aquatic photolysis studies respectively. Carbon dioxide is a major degrad ate in the aerobic soil metabolism study of imazosulfuron, in which it was up to 53.3% of the applied. Major and minor degradates of imazosulfuron and their structures are listed in Table 6

.

Table 6. Major and Minor Degradates of Imazosulfuron Name of Degradate And Structure IUPAC Name Maximum Detected (%) Comments

Major degradates HMS

N N Cl

S

O O N

H N

O

H N N

O O H

CH 3 1-(2-chloroimidazo[1,2- α ]pyridin-3- ylsulfonyl)-3-(4-hydroxy-6- methoxypyrimidin-2-yl)urea 20.9 Detected under both imidazolyl (IM) and pyrimidinyl (PM) labels

IPSN

N N Cl

S

O O N

H H 2-Chloroimidazo[1,2-a]pyridin-3- sulfonamide. 90.7 IM label at pH 4.0

IOHA

N NH O

OH

O 2-(2-imino-1,2-dihydropyridin-1-yl)oxalic acid 20.4 IM label

ADPM

H

N

N N

O O CH 3

CH 3 H 2-amino-4,6-dimethoxypyrimidine 91.2 PM label at pH 4.0

UPDM

N

H N

O

H N N

O O CH 3

CH 3 H 4,6-dimethoxy-2-ureidopyrimidine 11.2 PM label

SDPM

S

O O N

H N

O

H N N

O O CH 3

CH 3 OH (4,6-dimethoxypyridine-2- yl)aminocarbonylsufamic acid 13.9 PM label

CO 2 

## C O O Carbon dioxide 53.3 PM label

Minor degradates IP 2-Chloroimidazo[1,2- α ]pyridine 3.2 IM label at pH 4.040 

### Table 6. Major and Minor Degradates of Imazosulfuron Name of Degradate And Structure IUPAC Name Maximum Detected (%) Comments

N N Cl

IPSA

N N Cl

S

O O OH 2-chloroimidazo[1,2- α ]pyridin-3-yl sulfonic acid 5.8 IM label

CDPM

N

N N

O O CH 3

CH 3 H N 2-cyano-4,6-dimethoxypyrimidine 5.3 PM label

AHMP

N

N N

O O H

CH 3 H

H 2-Amino-4-hydroxy-6-methoxypyrimidine 4.7 PM label

ACIS

N N Cl

S

O O N

H N

O

H NH 2 NH N- ({[Amino(imino)methyl]amino}carbonyl)- 2-chloroimidazo[1,2-a]pyridine-3- sulfonamide 9.4 IM Label



### Mobility

Based on the batch equilibrium data, adsorption of imazosulfuron (K oc 

### = 135 to 428 L/Kg) is characterized as being mobile to moderately mob ile in the test soils. Desorption constants ranges from 254 to 1165 L/Kg for the same soil suggest th at the compound desorbs at slower rates from soil metrics. In addition, a study was conducted to estimate the K oc 

### of five transformation products (HMS, IPSN, IOHA, ADPM and SPDM of imazosulfuron using established HPLC estimation methods. The calculated K oc 

### values were <1 L/Kg for HMS, SDPM, and IHOA, 33- 36 for IPSN, and 38-69 for ADPM. The HPLC estimated K oc 

### values, SDPM, IHOA and HMS would be categorized as highly mobile in most soils. ADPM and IPSN would be categorized as mobile. The mobility classification of parent a nd degradates is based on mobility class of FAO (FAO 2000). However, for imazosulfuron, the calculat ed Koc values were <1 L/Kg at pH 7 and 2210 L/Kg at pH 3, which are significantly diffe rent from the batch equilibrium values (K oc 

### = 135 to 428 L/Kg) suggest that the HPLC may no t be a comparable method to characterize mobility class for this chemical.41 

### Imazosulfuron is a non-volatile ( ≤ 2.63 x 10 -8 

### Torr at 20 ° C) compound and soluble (429 mg/L at 20°C) in water. Therefore, dissipation of imazosu lfuron in the environment is expected to occur predominantly via runoff and leaching. Imazosulfuron was detected in the 30- to 45-cm depth of soil at 14 days after second application, and was not detected at lower soil depths, which indicates that leaching of residues may occur und er certain conditions. No major transformation products were detected in any so il depth at a concentr ation equivalent to >10% of the total applied imazosulfuron. Imazosulfuron in leachate is not expected to persist under an anaerobic soil conditions.

Low vapor pressure and Henry’s Law Constant of imazosulfuron s uggest that volatilization to atmosphere is an unlikely route of dissipation. Pe rsistence of total toxi c residue [imazosulfuron and degradates (HMS, IPSN, ADPM, IHOA and SPDM)] in soil is sufficient such that vulnerable aquifers may be expected to be imp acted but exposure will be minimal compared to surface water concentrations. Imazosulfuron concen trations in surface waters may be relatively high when significant runoff events occur after applicati on and / or spray drift to water bodies in close proximity to the treatment area occurs.

3.2.2 Aquatic Exposure Estimates for Imazosulfuron

A Tier II screening-level surface water exposure for aquatic risk assessment was conducted for the Section 3 proposed new use registration. Modeled application rates re present the maximum uses pattern of the proposed label for use on to mato, pepper, rice, and turfgrass. The aquatic exposure estimates presented in this assessment were based on the use of models as no surface and groundwater monitoring data is available for imazosulfuron with in the continental U.S. To simulate surface water exposure for the ecologi cal risk assessment, the Tier II PRZM/EXAMS model and Tier I Rice models were used.

PRZM-EXAMS Model Inputs and Scenarios for Imazosulfuron

The Pesticide Root Zone Model, (PRZM, Carsel et al ., 1997) and the Exposure Analysis Modeling System (EXAMS, Burns, 1997) were used in tandem to generate aquatic estimated environmental concentrations (EECs). PRZM (3.12.2 dated May 12, 2005) simulates fate and transport on the agricultural field whereas EXAMS (2.98.04.06, dated April 25, 2005) simulates the fate and resulting daily con centrations in the water body. Si mulations are carried out with the linkage program shell, PE5V01.pl (dated November 15, 2006), which incorporates the standard agricultural and non-agri cultural scenarios developed by EFED. Simulations are run for multiple (usually 30) years, and the EECs represent peak values that are expected once every ten years based on the thirty years of daily valu es generated during the simulation. Additional information on these models can be found at: http://www.epa.gov/oppefed1/models/water /index.htm

. The aquatic exposure is estimated for the maximu m application pattern to a 10-ha field bordering a 1-ha pond, 2-m deep (20,000 m 3 

### ) with no outlet. Exposure estimates generated using this standard pond are intended to represent a wide variety of vulnerable wate r bodies that occur at the top of watersheds including prairie pot holes , playa lakes, wetlands, vernal pools, man-made and natural ponds, and intermittent and first-order streams. As a group, there are factors that42 

### make these water bodies more or less vulnerable than the standard surrogate pond. Static water bodies that have larger ratios of pesticide-treated drainage area to water body volume would be expected to have higher peak EECs than the st andard pond. These water bodi es will be either smaller in size or have large drainage areas. Sm aller water bodies have limited storage capacity and thus may overflow and carry pesticide in th e discharge, whereas th e standard pond has no discharge. As watershed size increases beyond 10-ha, it becomes increasingly unlikely that the entire watershed is planted with a non-major sing le crop that is all treated simultaneously with the pesticide. Headwater streams can also have peak concentrations high er than the standard pond, but they likely persist for only short periods of time and are then ca rried and dissipated downstream.

There are several major degradat es identified in the environmental fate studies (DP 358472). The Residues of Concern Knowledgebase Subcommitt ee (ROCKS) of the Hea lth Effects Division (HED) and EFED reviewed the stru ctures of these degradates to determine residues of concern (DP Barcode: 359190). As the degradate HMS reta ins both imidazolyl (IM) and pyrimidinyl (PM) ring structures, its toxicity is likely comparable to the parent. Structure-activity relationship (SAR) analysis using the DEREK system (D eductive Estimate of Risk from Existing Knowledge) revealed the same structural alerts as the parent compound; therefore, HMS is considered a residue of concern. DEREK anal ysis of IPSN, IHOA, ADPM, SDPM, and UDPM showed that all of these cleavage products exce pt IHOA (a low molecular weight acid) retained at least one of the same structural alerts as th e parent. Therefore aquati c exposure of total toxic residue is considered in this assessment (parent plus five degradates listed in Table 7 ).

Table 7. Metabolites and Degradates to be In cluded in the Surface Water Exposure Assessment

Residues of concern- Imazosulfuron, HMS, IPSN, ADPM, UDPM, and SDPM

CAS Name: Imazosulfuron = 2-chloro- N -[[(4,6-dimethoxy-2-pyrimidinyl )amino]carbonyl]imidazo[1,2- α ]pyridine-3- sulfonamide HMS = 2-chloro- N -[[(4-hydroxy-6-methoxy-2-pyrimidinyl)amino]carbonyl]imidazo[1,2- α ]pyridine-3-sulfonamide IPSN = 2

- chloroimidazo[1,2-alpha] pyridin-3-sulfonamide] ADPM = 2-amino-4,6-dimethoxypyrimidine UDPM = 4,6-dimethoxy-2-ureidopyrimidine SDPM = (4,6-dimethoxypyrimidine- 2-yl)aminocarbonylsulfamic acid

Table 8 summarizes the model input paramete r values used in PRZM/EXAMS. These parameters were selected in accordance with EFED’s input parameter guidance (Environmental Fate and Effects Division, 2002). Aerobic so il metabolism half-life of 207.2 days, aerobic aquatic half-life of 207.2 and anaer obic aquatic metabolism half-lif e of 64.2 days for total toxic residue (imazosulfuron and listed degradates in Table 6 ) were used for surface water modeling with PRZM/EXAMS. Abiotic degradation half-lif e of 61.69 days for aquatic photolysis for total toxic residue was also used for surface water modeling. Since the experimental phototransformation half-lives of IM and PM labe ls are based on the continuous irradiation used in the laboratory study, estimated half-lives we re adjusted by multiplying with 0.5 based on a 12- hour light/12-hour dark cycle. Also, the intensity of the xenon lamp over the wavelengths 290- 800 nm was 558 W/m 2 

### , compared to 380 W/m 2 

### for natural sunlight over a 12-hour (solar) day at 40 ° N latitude during June through August. Therefore, 1 hour of artificial li ght was equivalent to43 

### 1.47 hours of natural sunlight. Calculation of first- order degradation rates for total toxic residue can be found in Appendix B

. OPP standard PRZM crop scenarios, which cons ist of location-specifi c soils, weather, and cropping practices, were used in the simulations to represent proposed labeled uses of imazosulfuron. These scenarios were developed to represent high-e nd exposure sites in terms of vulnerability to runoff and erosi on and subsequent off-site tran sport of pesticide. A 10-foot vegetative buffer strip between treated area s and water bodies was recommended in the submitted labels to reduce off-site movement of applied pesticide. However, current PRZM/EXAMS model does not have a specific rou tine to evaluate the effect of vegetative buffer. For the purposes of this assessment, it was assumed that applications were made week after the weed emergence (as specified in the standard scenarios). A summary of the input parameters and crop scenarios us ed to estimate imazosulfuron c oncentrations in the aquatic systems for ecological risk assessment are listed in Table 8 . PRZM/EXAMS output files are provided in Appendix C of this document.

Table 8. PRZM/EXAMS Input Parameter Values for Total Residue a 

### of Imazosulfuron

Parameter Value Source Comments

Maximum application Rate lb ai/A (kg ai/ha) Turfgrass: 0.67 (0.75) Food uses 0.30 (0.34) V-10142 Herbicide (75.0%) V-10142 Ag Herbicide (75.0%) FL and PA turf STD scenarios;

FL and PA tomato STD scenarios FL Pepper STD scenario

Number of Applications 2 (turfgrass) 1 (food uses) V-10142 Herbicide (75.0%) --

Minimum Application Intervals (days) 21 V-10142 Herbicide (75.0%) V-10142 Ag Herbicide (75.0%) For turf use only

Application Date FL Turf February 8 PA Turf April 8 FL Tomato February 8 PA Tomato April 23 FL pepper September 8 Based on PRZM/EXAMS Scenarios One week after crop emergence described in these scenarios

Wetted in? No V-10142 Herbicide (75.0%) ---

Depth of Incorporation (inches) 0 V-10142 Herbicide (75.0%) V-10142 Ag Herbicide (75.0%) For foliar application according to Input parameter guidance (USEPA, 2009)

Method of Application Ground spray V-10142 Herbicide (75.0%) V-10142 Ag Herbicide (75.0%) ---

Application Efficiency Ground: 0.99 Input parameter guidance (USEPA, 2009) Default values for ground spray44 

### Table 8. PRZM/EXAMS Input Parameter Values for Total Residue a 

### of Imazosulfuron

Parameter Value Source Comments Spray Drift Fraction Ground: 0.01 Input parameter guidance (USEPA, 2009) Default values for ground spray Default values for aerial spray

Molecular Mass (g/mol) 412.81 MRID 473051-01 Product chemistry data

Vapor Pressure (Torr) 

### ≤ 2.63 x 10 -8 MRID 473051-16 Product chemistry data

Henry’s Law Constant (atm m3/mol) 

### ≤ 3.33 x 10 -11 Estimated Input parameter guidance (USEPA, 2009)

Solubility in Water (mg/L) 429 MRID 473051-15 Input parameter guidance (USEPA, 2009)

Hydrolysis t 1/2 at pH 7.0 (days) 0 MRID 473051-19 Stable to hydrolysis @ pH 7.0

Aquatic Photolysis t 1/2 (d) 61.7 MRID 473051-20 90 th percentile upper confidence bound on the mean of imidazolyl (IM) and pyrimidinyl (PM) rings of imazosulfuron

Aerobic Soil Metabolism t 1/2 (d) 207.2 MRID 473051-17

MRID 477668-01 90 th percentile upper confidence bound on the mean half-life of total toxic residue of imazosulfuron

Aerobic Aquatic Metabolism t 1/2 (d) 192.0 MRID 476397-02

MRID 476791-05 90 th percentile upper confidence bound on the mean half-life of total toxic residue of imazosulfuron

Anaerobic Aquatic Metabolism t 1/2 (d) 21.4 x 3 b MRID 473051-23 Input parameter guidance (USEPA, 2009)

Soil Partitioning Coefficient (K foc ; ml/g oc ) 154 MRID 473051-22 Represent average K foc from 4 soils

a = Residues of concern: total toxic residue (Parent pl us degradates, i.e., HMS, IPSN, UDPM, ADPN and SDPM)

b = Due to reported half-life for a single anaerobic aquatic meta bolism study, input half-life was multiplied by 3 according to Guidance for selecting input parameters in modeling for environm ental fate and transport of pes ticides. Version 2.1 October 22, 2009.



### The EFED Rice Model (USEPA, 20 07) was also used to estimate the concentration of imazosulfuron expected in surface water following application to rice. The model calculates exposure as a function of the amount of pestic ide applied and the pes ticide’s soil-to-water partition coefficient. Concentr ations are assumed to immedi ately and evenly distribute throughout the rice paddy water. Dissipation pr ocesses, such as degr adation, volatilization, and potential dilution with uncontaminated water outside the paddy are not accounted for by the model. The RICE model does not differentiate the concentrations of surface water and pore water. In addition, multiple applicat ion and application intervals as well as spray drift from aerial application were not consider ed in Tier I RICE model.45 

### Input parameters for the Rice Model are listed in Table 9 and Appendix D ; data source and justification descriptors accomp any values for each parameter. The mean Freundlich soil-towater partition coefficient (K f 

### ) from four soils (1.19) was used to model partitioning to rice paddy sediment. The organic carbon partition coefficient (K OC 

### ) was not used, as it is a less precise descriptor of imazosulfuron’s mobility. The single exposure estimate produced with the Rice Model’s acute/chronic screening EECs represen t high-end exposure in released flood water.

Table 9. Rice Model Input Parameters for Imazosulfuron

Input Parameter Value Justification Source 

### Application Rate (kg ai/ha) 0.3 0.3 lb ai/A x 1.121 kg·A/ha·lb = 0.336 kg ai/ha Proposed label

Soil-to-Water Partition Coefficient (K f 

### ) (L/kg) 1.19 Mean K f 

### is used when mean K OC 

### use is not appropriate. MRID 46219074 MRID 46578971



### The aquatic EECs for the various scenarios and application practices are listed in Table 10

. EECs were highest for rice with peak and chroni c values of 278 μg/L. The next highest peak exposure concentration is based on pepper with peak EEC of 12.21 μg/L, followed by turfgrass and tomato. Similar trend was also observ ed for the pore water concentrations.

Table 10. Estimated Aquatic Concentrations for Imazosulfuron Total Toxic Residues Use/Application rate/ frequency Scenarios Peak EEC ( μ g ai/L) 21-day Average EEC ( μ g ai/L) 60-day Average EEC ( μ g ai/L)

Surface Water

FL Turf 4.67 4.49 4.28 Turfgrass - 0.67 lb x 2 per season PA Turf 10.11 9.57 8.93

FL Tomato 9.22 8.66 7.78 Tomato 0.3 lb x 1 per season PA Tomato 3.04 2.93 2.82

Pepper 0.3 lb x 1 per season FL Pepper 12.21 11.56 10.37

Rice 0.3 lb x 1 per season Tier I Rice 278.90 278.90 278.90

Pore Water

FL Turf 4.80 4.76 4.71 Turfgrass - 0.67 lb x 2 per season PA Turf 4.74 4.73 4.70

FL Tomato 4.03 4.01 3.99 Tomato 0.3 lb x 1 per season PA Tomato 1.55 1.54 1.50

Pepper 0.3 lb x 1 per season FL Pepper 4.80 4.76 4.71

Rice 0.3 lb x 1 per season Tier I Rice 278.90 278.90 278.9046 

### Aquatic Exposure Monitoring and Field Data

Since imazosulfuron is a new active ingredient, th ere were no national-scale monitoring data for this chemical available for this assessment.

3.2.3 Terrestrial Wildlife Exposures

Terres trial wildlife exposure estimates are typically calculated for birds and mammals emphasizing a dietary exposure route for uptake of pesticide residues on vegetative matter and insects. These exposures are considered as surrog ates for terrestrial-phase amphibians as well as reptiles. For exposure to terres trial organisms, pesticide resi dues on food items are estimated based on the assumption that organisms are exposed to a single pesticide residue in a given exposure scenario. The residue estimates from spray applications are based on a nomogram by Hoerger and Kenaga (1972) as modified by Fletcher et al. (1994) that co rrelated residue levels, based on application rate, on various terrestrial items immediately following application in the field. The “maximum” residue concentration, an upper bound defined by Fl etcher et al. (1994), for each food group was derived from literature and tolerance data.

Determination of residue dissipa tion of the parent compound ove r time on food items following single and multiple applications are predicted us ing a first-order residue degradation half-life with EFED's “T-REX_V.1.3.1” model. The risk a ssessment uses a default foliar dissipation halflife estimate of 35 days. This half-l ife is used in lieu of representa tive foliar dissipation data for imazosulfuron parent, because no such data we re provided to EFED. The predicted maximum residues on avian and mammalian food items based on applications to tomato, pepper, rice, and turfgrass as calculated by T-REX are provided in Table 11.

Table 11. Estimated Environmental Co ncentrations for Imazosulfuron Parent on Avian and Mammalian Food Items at Maximum Application Rates Food Items

Crop Broa dl

e af /f

o

ra g

e pl

a nt

s

a

n d

s

m al l in

s

e ct

s Fruits, pods

, seed

s, and larg

e inse

cts ppm Tom

at

o, pe pp er,

an d ric

e 1 (a

si

ng le

ap pl ic ati

on of 0. 3 lb ai/ A ) 41 5

Turf

gr

as

s (0.67 lb ai/ A/

ap pl ic ati

on

, 2

ap pl ic ati

on s, 21

da

y in

ter

va l) 150 17

1 The sequential applications of imazosulfuron in rice at 0.15 lb ai/A each yielded lower EECs than a single application of 0.3 l b ai/A; therefore, EECs resulting from single application in rice were only presented in this assessment



### The residues or EECs on food items may be compar ed directly with sub- acute dietary toxicity data or converted to an ingest ed whole-body dose (single oral dose, as the later is the case for small mammals and birds. Single-oral dose estimate s represent, for many pesticides, an exposure scenario where absorption of the pesticide is ma ximized over a single inge stion event. Sub-acute dietary estimates provide for possible effects of th e dietary matrix and more extended time of gut exposure to pesticide absorption across the gut. However, dietary exposur e endpoints are limited in their utility because the curr ent food ingestion estimates are uncertain and may not be directly47 

### comparable from laboratory conditions to field c onditions. The EEC is converted to an oral dose by multiplying the EEC by the percentage of body weight consumed as estimated through allometric relationships. Thes e consumption-weighted EECs ( i.e. EEC equivalent dose) are determined for each food source and body size for mammals (15, 35, and 1000 g) and birds (20, 100, and 1000 g). The EEC equivalent doses for birds and mammals based on application to tomato, pepper, rice, and turfgrass are given in Tables 12 and 13 , respectively. An example output from T-REX for turfgrass is included in Appendix G

Table 12. Avian EEC Equivalent Dose Adjust ed for Body Weight for Imazosulfuron Application to Tomato, Pepper, Rice and Turfgrass Avian Classes and Body Weights Small Mid Large EEC Equivalent Dose 1 (mg/kg-body weight) 20 g 100 g 1000 g Percent Body Weight Consumed 114% 65% 29% Tomato, Pepper and Rice (a single application of 0.3 lb ai/A) Short Grass 82 47 21 Tall Grass 38 21 10 Broadleaf plants/small insects 46 26 12 Fruits/pods/large insects 5 3 1 Turf grass (0.67 lb ai/A/application, 2 applications, 21 day interval) Short Grass 304 173 78 Tall Grass 139 79 36 Broadleaf plants/small insects 171 98 44 Fruits/pods/large insects 19 11 5

1 EEC equivalent dose = EEC (from Table 10) * (percent body weight consumed/100)



### Table 13. Mammalian EEC Equivalent Dose Adju sted for Body Weight for Imazosulfuron Application to Tomato, Pepper, Rice and Turfgrass Mammalian Classes and Body weight Herbivores/ Insectivores Granivores EEC Equivalent Dose 1 (mg/kg-body weight) 15 g 35 g 1000 g 15 g 35 g 1000 g Percent Body Weight Consumed 95% 66% 15% 21% 15% 3% Tomato, Pepper and Rice (a single application of 0.3 lb ai/A)
Short Grass 69 47 11

Tall Grass 31 22 5 Broadleaf plants/sm Insects 39 27 6 Fruits/pods/seeds/lg insects 4 3 1 1.0 0.7 0.2 Turf grass (0.67 lb ai/A/application, 2 applications, 21 day interval)
Short Grass 254 176 41

Tall Grass 117 81 19 Broadleaf plants/small insects 143 99 23 Fruits/pods/large insects 16 11 3 4 2 0.6

1 EEC equivalent dose = EEC (from Table 10) * (percent body weight consumed / 100)48 

### 3.2.4 Terrestrial and Semi-Aquatic Plant Exposures

Terrestrial and semi-aquatic plants may be exposed to pesticides from runoff, spray drift, or volatilization. Semi-aquatic plants are those that inhabit low-laying wet areas that may be dry at certain times of the year. The runoff scenario in TERRPLANT 1.2.2 is: (1) based on a pesticide's water solubility and the amount of pesticide present on the soil surface and its top one centimeter, (2) characterized as "sheet runoff" (one treated acre to an adjacent acre) for dry areas, (3) characterized as "channel runoff" (10 acres to a distant low-lying acre) for semi-aquatic or wetland areas, and (4) based on percent runoff values of 0.01, 0.02, and 0.05% for water solubility values of <10, 10-100, and >100 ppm, re spectively. Spray drift is assumed as (1) 1% for ground application, (2) 5% for aerial, airblast, forced air, and spray chemigation applications, and (3) 0% for granular applic ations. Currently, EFED derives plant exposure concentrations from a single maximum application rate only. Ex posure through volatiliza tion is not accounted for in this screening-level assessment, and based on the low vapor pressure it is not expected to be a significant route of exposure. EECs for the proposed new uses are presented in Table 14

. The TERRPLANT output for exposure due to use on turfgrass is provided in Appendix F

Table 14. Estimated Environmental Concen trations of Imazosulfuron Parent for Terrestrial and Semi-Aquatic Plants Tomato, Pepper, and Rice (0.3 lb ai/A) Rice (0.3 lb ai/A) Turfgrass (0.67 lb ai/A) Description Ground Aerial Ground 

### EEC (lb ai/A) Runoff to dry areas 0.015 0.015 0.033 Runoff to semi-aquatic areas 0.15 0.15 0.335 Spray drift 0.003 0.015 0.007 Total for dry areas 0.018 0.03 0.04 Total for semi-aquatic areas 0.153 0.165 0.342



### 3.3 Ecological Effects Characterization

In screening-level ecological risk assessments, effects characterization describes the types of effects a pesticide can produce in an animal or plan t. This characterization is based on registrantsubmitted studies and the ECOTOX database that describe acute and chronic effects toxicity information for various aquatic and terrestrial animals and plants.

Appendix E summarizes the results of all of the registra nt-submitted toxicity studies for this risk assessment. Toxicity testing reported in this se ction does not represent all species of birds, mammals, or aquatic organisms. Only a few surrogate species for both freshwater fish and birds are used to represent all freshwat er fish (2000+) and bird (680+) species in the United States. For mammals, toxicity studies are typica lly limited to the laboratory rat. Estuarine/marine testing is limited to a crustacean, a mollusk, and a fish. Als o, neither reptiles nor amphibians are tested. The risk assessment assumes that avian and rept ilian and terrestrial-pha se amphibian toxicities are similar. The same assumption is used for fish and aquatic-phase amphibians. The most sensitive ecological toxicity endpoints for aquatic organisms, terrestrial organisms, and aquatic and terrestrial plants were us ed for risk characterization.49 

### The most sensitive ecological toxicity endpoints for aquatic organisms ( Table 15 ), mammals ( Table 16 ), birds, terrestrial i nvertebrates and plants ( Table 17 ) which were used for risk characterization of imazosulfuron and th e formulations are summarized below. Table 16 summarizes the acute mammalian toxicity endpoints tested with the degradates of imazosulfuron. Discussions of the effects of imazosulfuron on a quatic and terrestrial ta xonomic groups are also presented below. In addition, a review of the Ec ological Incident Information System (EIIS) was conducted to further refine the characte rization of potential ecological effects.

In response to the data gaps identified in th e previous risk assessment dated (DP 348003), Valent submitted 13 additional studies in support of the re gistration of imazosulfuron. Of these, 3 were classified as acceptable, 8 as supplemental, and 2 as invalid. Findings from both the acceptable and supplemental studies are incor porated into this assessment.

Table 15. Imazosulfuron Toxicity Values for Aquatic Organisms

Acute/ Chronic Species Exposure Duration Toxicity Value MRID (Classification) Freshwater Fish Acute Rainbow Trout 96 hours 96-Hour LC 50 > 69 mg ai/L NOAEC = 69 mg/L MRID 47305137 (Acceptable) Acute Fathead minnow 96 hours 96-Hour LC 50 > 89 mg ai/L NOAEC = 89 mg/L MRID 47679111 (Acceptable) Chronic* Fathead minnow 32 days NOAEC = 2.9 mg ai/L LOAEC = 8.8 mg ai/L (reduced hatching success) MRID 679112 (Acceptable)

Freshwater Invertebrates Acute Waterflea 48 hours 48-hour LC 50 > 91 mg ai/L NOAEC = 12 mg ai/L MRID 47305131 (Acceptable) Chronic Waterflea 21 days NOAEC = 0.84 mg ai/L LOAEC = 3.3 mg ai/L

(parental mortality) MRID 47305137 (Acceptable)

Chronic* Degradate, IPSN Midge larvae 28 days 28-Day EC 50 = 45.7 mg ai/L NOAEC = 11mg/L (pore water) NOAEC = 50 mg/L MRID 47782103 (Supplemental)

Estuarine/Marine Fish Acute Sheepshead minnow 96 hours 96-Hour LC 50 >94 mg ai/L NOAEC: 94 mg ai/L MRID 47305134 (Acceptable) Chronic No data submitted

Estuarine/Marine Invertebrates Acute Mysid shrimp 96 hours 96-Hour LC 50 > 79 mg ai/L NOAEC: 79 mg ai/L MRID 47305133 (Acceptable) Acute Eastern oyster 96 hours 96-hour EC 50 = 63 mg ai/L NOAEC = 13 mg ai/L MRID 473051-32 (Acceptable) Chronic No data submitted Aquatic Plants Vascular Duckweed 7 days EC 50 = 0.00146 mg ai/L ECOTOX 104861 Vascular Degradate, IPSN Duckweed 7 days EC 50 > 113 mg ai/L NOAEC = 113 mg ai/L MRID 47035213 (Acceptable) Non-Vascular Pseudokirchneriella subcapitata 3 days EC 50 = 0.206 mg ai/L ECOTOX 104861



### *New studies submitted by the registrant50 

### Table 17. Imazosulfuron Toxicity Reference Values (TRVs) for Terrestrial Organisms

Exposure Scenario Species Exposure Duration Toxicity Reference Value Reference (Classification) Birds Acute (Dose-based) Mallard duck Single dose LD 50 > 2250 mg ai/kg bw NOAEC = 1350 mg ai/kg bw MRID 473052-03 (Acceptable) Acute* (Dose-based) Degradate, IPSN Bobwhite quail Single dose LD 50 > 2000 mg ai/kg bw NOAEC = 100 mg ai/kg bw MRID 477668-10 (Supplemental) Acute (Diet-based) Mallard duck; Bobwhite quail Acute dietary LC 50 > 5042 mg ai/kg diet NOAEC = 5042 mg ai/kg diet MRID 473052-05 MRID 473052-06 (Acceptable) Acute* (Diet-based) Degradate, IPSN Bobwhite quail Acute dietary LC 50 > 5720 mg ai/kg diet NOAEC = 1020 mg ai/kg diet MRID 477668-11 (Acceptable) Chronic (Diet-based) Bobwhite quail 22 weeks LOAEC = 484 mg ai/kg diet NOAEC = 194 mg ai/kg diet Cracked eggs, number of hatchlings/eggs laid MRID 473052-07 (Acceptable)

Chronic (Diet-based) Mallard duck 22 weeks LOAEC = 242mg ai/kg diet NOAEC = <242 mg ai/kg diet Egg shell thickness and ratio of hatchling survivors to number hatched MRID 476791-14 (Supplemental)

Chronic* (Diet-based) Mallard duck 21 weeks LOAEC = 202 mg ai/kg diet NOAEC = 100 mg ai/kg diet Reduced number of eggs laid MRID 476791-14 (Supplemental)

Non-target Insects Oral Acute LD 50 = 45.9 μg ai/bee

Contact Acute Honey bee 96 hour LD 50 = 59.9 μg ai/bee MRID 473052-09 (Acceptable)

Acute* Degradate, IPSN Ground beetle 14 days LD 50 = >1000 mg ai/kg dw soil MRID 477668-05 (Supplemental) Acute* Degradate, IPSN Rove beetle 28 days LD 50 = >1000 mg ai/kg dw soil MRID 477821-02 (Supplemental) 

### Table 16. Mammalian Acute Oral and Chronic Toxicity to Imazosulfuron

Species Test Substance 

### Toxicity Reference Value MRID #, Author, Year Classification

LD 50 >5000 mg/kg (combined sexes) 473052-21 Laboratory rat (Rattus norvegicus) Technical NOAEC = 1,000 mg/kg diet 473053-04 Acceptable

Laboratory Mouse IHOA (Metabolite) LD 50 >5212 mg/kg M; LD 50 >5060 mg/kg (F) 473052-22 Acceptable

Laboratory rat UDPM (Metabolite) LD 50 = 677 mg/kg M; LD 50 = 698 mg/kg (F) 473052-23 Acceptable Laboratory rat IPSN (Metabolite) LD 50 = 513 mg/kg M; LD 50 = 445 mg/kg (F) 473052-24 Acceptable Laboratory rat M-1 (Metabolite) LD 50 >5000 (combined sexes) 473052-25 Acceptable Laboratory rat ADPM (Metabolite) LD 50 = 879 mg/kg M; LD 50 = 836 mg/kg (F) 473052-26 Acceptable51 

### Table 17. Imazosulfuron Toxicity Reference Values (TRVs) for Terrestrial Organisms

Exposure Scenario Species Exposure Duration Toxicity Reference Value Reference (Classification) Other Non-target organisms Acute* Degradate, IPSN Earthworm 14 days LC 50 = >1000 mg ai/kg dw soil NOAEC = <100 mg ai/kg dw soil MRID 477668-12 (Supplemental) Acute* Earthworm 14 days LC 50 = >996 mg ai/kg dw soil NOAEC = 308 mg ai/kg dw soil MRID 477668-14 (Supplemental) Chronic* Degradate, IPSN Earthworm 56 days LC 50 = >165 mg ai/kg dw soil NOAEC = 1.7 mg ai/kg dw soil MRID 477668-13 (Supplemental) Plants – Seedling Emergence Monocot Onion Single application EC 25 = 0.034 lbs ai/A NOAEC = 0.025 lbs ai/A Slope= 1.19 Dry weight Dicot Lettuce Single application EC 25 = 0.041 lbs ai/A NOAEC = 0.022 lbs ai/A Slope= 0.836 Dry weight MRID 473052-11 (Acceptable)

Plants – Vegetative Vigor Monocot Onion Single application EC 25 = 0.25 lbs ai/A NOAEC = 0.025 lbs ai/A Slope= 0.893 Dry weight Dicot Radish Single application EC 25 = 0.08 lbs ai/A NOAEC = 0.074 lbs ai/A Slope= 0.965

Survival MRID 473052-11 (Acceptable)



### *New studies submitted by the registrant

3.3.1 Aquatic Effects Characterization

Toxicity to Freshwater Fish Four acute toxicity fish studies indicate im azosulfuron was not toxic up to 100 mg ai/L nominal concentration. The LC 50 

### values using mean measured concen trations ranged from >69 mg ai/L for the rainbow trout (MRID 473051-37), >112 mg ai/L for the carp (MRID 473051-35), >74 mg ai/L for the bluegill sunfish (MRID 473051-36) , and >89 mg ai/L for the fathead minnow (MRID 476791-11). No sublethal effects were obse rved. Although the percent recovery of test material in the rainbow trout study (69%) is le ss than the established acceptable range in the guidelines (70- 120%) the measured concentrati on was stable over the course of the study (0- hour to 96 hours). The rainbow trout, bluegill, and fathead minnow studies were classified as acceptable. However, the carp study was classified as supplemental because the sample size of seven fish per treatment (less than 1 gram of fish per liter) was smaller than recommended by guidelines.

An early life-stage study was submitted on fa thead minnow to document chronic exposure effects of imazosulfuron to freshwater fish (MRID 476791-12). Reported 32-day NOAEC and LOAEC values were 2.9 and 8.8 mg ai/L, respec tively, based upon a trea tment-related reduction in hatching success, the only endpoint affected in the study at the 8.8 mg ai/L level.52 

### Toxicity to Freshwater Invertebrates

Acute freshwater toxicity tests using Daphnia magna indicate that imazosulfuron is not toxic up to 100 mg ai/L nominal concentration, yielding an EC 50 

### value of >91 mg ai/L based on mean measured concentration (MRID 473051-31). Th e NOAEC value is 12 mg ai/L based on immobilization (5%) and lethargy. A solvent wa s not used in this study. This study was classified as Acceptable.

In the freshwater life cycle toxicity test using Daphnia magna (MRID 473052-01), the NOAEC and LOAEC are 0.84 and 3.3 mg ai/L, respectivel y, based on parental mortality using timeweighted averages of the measured test concen trations. There was 20% and 40% mortality in the 3.3 and 8.9 mg ai/L treatment groups, respectively. The EC 50 

### is > 8.9 mg ai/L, the highest test concentration. There was a signifi cant decrease in the mean numb er offspring per parent (19%) in the 8.9 mg ai/L treatment group. The NOAEC and LOAEC are 3.3 and 8.9 mg ai/L, respectively, based on reduction in offspring per pa rent. This study was classified as Acceptable.

Long-term effects of IPSN on the larvae of the midge, Chironomus riparius, was evaluated using the OECD Draft Guideline 219 (MRID 477851-03). The 28-day EC 50 

### reported in this study was 45.7 mg ai/L and NOAEC values were 18.3 (ove rlying water) and 11 (pore water) mg ai/L, based on mortality and decreased emergence rate. This study was classified as Supplemental as it did not fulfill any current U.S. EPA data requirement.

Toxicity to Estuarine/Marine Fish

An estuarine/m arine fish acute toxi city test with sheepshead minnow ( Cyprinodon variegates) indicates that imazosulfuron wa s not toxic up to 100 mg ai/L nominal concentration (MRID 473051-34). The LC 50 

### is >94 mg ai/L using mean measured concentrations. No sublethal effects were observed. This study was classified as Acceptable.

Toxicity to Estuarine/Marine Invertebrates

Results from an acute toxicity study with m ysid shrimp ( Americamysis bahia ) indicates that imazosulfuron was not toxic and was tested up to 100 mg ai/L nominal concentration (MRID 473051-33). The LC 50 

### is >79 mg ai/L using mean measur ed concentrations. This study was classified as Acceptable.

Toxicity to Estuarine/Marine Mollusks

The results from an estuarine/marine acute shell deposition toxicity test using the eastern oyster, Crassostrea virginica indicate that imazosulfuron is slightly toxic (EC 50 

### = 63 mg ai/L, MRID 473051-33). The NOAEC is 13 mg ai/L based on reduced shell deposit ion. This study was classified as Acceptable.53 

### Aquatic Plant Toxicity

The results from the aquatic plan t toxicity test using duckweed ( Lemna minor ) indicate that imazosulfuron technical is very highly toxic to aquatic vascular plants (MRID 476397-01). The measured concentrations were not reliable ; therefore the results are based on nominal concentrations. The NOAEC and EC 50 

### values, based on reduction in number of fronds at Day 14 are 0.18 and 0.46 μg ai/L, respectively. Phytotoxic effects were reported. It was noted that fronds were smaller and roots were shorter than the c ontrol group in nominal test concentrations 0.58 – 10 μg ai/A after both 7 and 14 days. In ad dition, roots were observed to be shorter after 7 days in the 0.32 μg ai/A treatment group and in the 0.1 – 0.32 μg ai/A treatment groups after 14 days.

The results from the vascular aquatic plant toxicity test using duckweed ( Lemna gibba ) indicate that the imazosulfuron metabolite, IPSN, was not toxic and was tested up to 100 mg ai/L nominal concentration (MRID 473052-13). The EC 50 

### is >113 mg ai/L using mean measured concentrations. This study was classified as Acceptable.

Four non-vascular aquatic plant st udies were submitted. Imazosulfuron is not toxic to the marine diatom, Skeletonema costatum and was tested up to 100 mg ai/L nominal concentration (MRID 473052-14). The EC 50 

### is >100 mg ai/L using mean measur ed concentrations. This study was classified as Acceptable. Imazosulfuron is also not toxic to the freshwater diatom, Nitzschia palea and was tested up to 100 mg ai/L nominal concentration (MRID 473052-16). The EC 50 

### is >97 mg ai/L using mean measured concentrations. This toxicity study is classified as Supplemental based on guideline requirements for a tier II acute alga l toxicity study. The recommended test species was not used and there is uncertainty regarding the sensitivity of the tested species. There were no effects observed an d a positive control was not included. However, this study is upgradeable to Acceptable if the study author can demonstrate that the test species is as sensitive as the recommended test species.

Imazosulfuron is not toxic to the freshwater algae, Selenastrum capricornutum . The NOAEC and EC 50 

### values based on a lack of significant inhib itions in biomass, area under the growth curve and growth rate, were 5.10 and >5.10 mg ai/L, re spectively, based on absorb ance. The % growth inhibition in the treated algal cu lture as compared to the control was -3.8% for absorbance, - 0.50% for area under the growth cu rve and 3.5% for growth rate. The results are based on the absorbance values because initial and final cel l density was not determined in the treatment group. Counts were performed only in the negative and solvent cont rol cultures. There was no correlation given between absorbance and cell density. The study is classified as Acceptable.

The green algae, Anabaena flos-aquae toxicity test resulted in a EC 50 

### of 11 mg ai/L. The NOAEC and EC 05 

### are 8.6 and 4.4 mg ai/L, respectively, based on cell density (MRID 470352- 15). This study is classified as Acceptable.

An ECOTOX study, Mohammad, M. et al (2005, ECOTOX 104861) indicates vascular plants [ Lemna gibba (EC 50 

### = 1.46 μg ai/L)] are two orders of magnitude more sensitive than nonvascular plants Pseudokirchneriella subcapitata (EC 50 

### = 206 μg ai/L) for imazosulfuron. The results for Lemna gibba is similar to the results f ound in the registrant study ( Lemna minor (EC 5054 

### = 0.46 μg ai/L)) and the results for the P seudokirchneriella subcapitata is more sensitive than the 4 algae and diatom studies submitted by the regi strant. The ECOTOX study results will be used quantitatively in this assessment. More information is provided in Section 3.3.4.

3.3.2 Terrestrial Effects Characterization

Acute (oral-gavage) Toxicity to Birds

Acute avian oral-g avage studies were submitted for the northern bobwhite quail and the mallard duck using the technical grad e active ingredient. The LD 50 

### values (LD 50 

### >2250 mg ai/kg-body weight) for both studies show that imazosulfuron is practically non-toxic to avian receptors on an acute oral-gavage basis as no mortalities were reported in this study. In the quail study, no treatment-related effects were observed ( NOAEC = 2250 mg ai/kg bw, MRID 473052-04). In the mallard study, there was a significant reduction in female body weight gain at highest treatment level (NOAEC = 1350 mg ai/kg bw, MRID 473052- 03). These studies we re classified as acceptable.

An additional study was submitted to document the effects of the degradate IPSN on bobwhite quail (MRID 477668-10). Based on the 14-day LD 50 

### value of >2000 mg ai/kg bw, IPSN is classified as practically non-toxic to birds. Reduction in body weight gain was the sublethal effect reported from this study, t hough it is uncertain whet her the reduction in weight gain is due to treatment effect or food avoidance. This study was classified as Supplemental due to guideline deviations.

Sub-acute (dietary) Toxicity to Birds

Sub-acute a vian dietary toxicity studies were submitted for the northern bobwhite quail (MRID 473052-06) and the mallard duck (MRI D 473052-05) using the TGAI. The LC 50 

### values (LC 50 

### >5042 mg ai/kg-diet) for both studies show th at imazosulfuron is pr actically non-toxic to avian receptors on an acute dietary basis as no mort alities were reported in this study. There were no treatment effects observed in both studies (NOAEC = 5042 mg a i/kg diet). These studies were classified as acceptable.

A bobwhite quail study that tested th e effects of the degradate IPSN demonstrated that IPSN is practically non-toxic based on dietar y exposure (MRID 477668-11). Reported LC 50 

### and NOAEC values were >5720 and 1020 mg ai/kg diet, respectiv ely. This study was classi fied as Acceptable.

Chronic Toxicity to Birds

Three chron ic toxicity studies were submitted to the Agency, 1 for northern bobwhite quail and 2 for mallard duck using TGAI of imazosulfur on. In the first mallard duck study (MRID 473052- 08), there was a statistically significant reduction in eggshell thickness at all treatment levels, resulting in NOAEC and LOAEC values of <242 and 242 mg ai/kg diet. There was 5% reduction in the lowest treatment level. The ratio of hatc hling survivors to number hatched was slightly adversely affected at the lowe st (4.7%) and highest (2.9%) treat ment levels. A definitive NOAEC could not be determined in this study, therefore this study is classi fied as Supplemental.55 

### The second mallard duck study (MRID 476791-14), however, reported definitive NOAEC/LOAEC values of 100/202 mg ai/kg diet based on reduced number of eggs laid. In view of guideline deviations such as the use of younge r birds, smaller cages, and non-inclusion of male birds in the study, this study wa s classified as Supplemental. In the bobwhite quail study (MRID 473052-07), there was a statistically si gnificant number of cracked eggs (5%) and a significan t reduction in the number of hatc hlings/eggs laid (14%) in the 1230 mg ai/kg diet treatment group resulting in a NOAEC of 484 mg ai/kg diet. There was also a statistically significant reduction in female wei ght gain (28%) and reduction in shell thickness resulting in a NOAEC value of 194 mg ai/kg diet, however these effects were not doseresponsive and there is some uncer tainty whether these effects were treatment related. This study is classified as Acceptable.

Acute Oral Toxicity to Mammals

W ild mammal testing is required on a case-by-case basis, depending on the results of lower tier laboratory mammalian studies, intended use pa ttern, and pertinent environmental fate characteristics. In most cases, rat or mouse toxicity values obtained from the Agency's Registration Division (RD) and the Health Effect s Division (HED) substitute for wild mammal testing.

An acute oral mammalian (laborat ory rat) study indicated techni cal imazosulfuron is not toxic (HED Toxicity Category IV) and resulted in the LD 50 

### > 5000 mg ai/kg-bw (combined sexes, MRID 473052-21). This study is cla ssified as Acceptable by HED.

Five additional acute mammalian studies were submitted for the metabolites of imazosulfuron. Two of the metabolites, IHOA and M-1 are not toxic (no mortality was observed) and resulted in LD 50 

### > 5060 mg ai/kg-bw (female, MRID 473052-22) and LD 50 

### > 5000 mg ai/kg-bw (combined sexes, MRID 473052-25), respectively. Three me tabolites, UDPM, ADPM and IPSN are more toxic than the parent. UDPM and ADPM resulted in LD 50 

### = 677 mg ai/kg-bw (male, MRID 473052-23) and LD 50 

### = 836 mg ai/kg-bw (female, MRID 473052-26), respectively. The metabolite, UDPM, is the most toxic and resulted in LD 50 

### = 445 mg ai/kg-bw (male, MRID 473052-24). These studies are classi fied as Acceptable by HED.

Chronic Toxicity to Mammals

A 2-generation laboratory rat reproducti on study (MRID 473053-04), with technical im azosulfuron resulted in no reproductive effect s. The NOAEC and LOAEC for parental effects are 1,000 and 10,000 mg ai/kg diet, respectively, base d on mortality, clinical signs of toxicity, and decreased body weight and food consump tion. The NOAEC and LOAEC for offspring effects are also 1,000 and 10,000 mg ai/kg diet, respectively, based on decreased pup viability and body weights. This study is clas sified as Acceptable by HED.

Acute Toxicity to Non-target Insects

In a 48-hr acute contact a nd oral test, honey bees ( Apis mellife ra ) were exposed to technicalgrade imazosulfuron at one test concen tration 20 μg ai/bee. The resulting LD 50 

### values for oral56 

### and contact endpoints were <20 μg ai/bee. Mortality was observed at the test concentration of 20 μg ai/bee but the mortality was less than 50% (MRID 473052-10). In a su bsequent 48-hr acute contact and oral test with honey bees, the resulting LD 50 

### values for the oral and contact endpoints were 45.9 and 59.9 μg ai/bee, respectively, with a NOAEC of 35.2 μg ai/bee based on mortality for both tests. The slope was 5.3 the oral test and 4.3 for the c ontact test. Imazosulfuron is categorized as practically non-t oxic to honey-bees. These studies are classified as acceptable.

The effects of IPSN on non-target insects we re documented through 2 non-guideline studies, using ground beetles (MRID 477668-05) and rove beetles (MRID 477821-02). Both the 14-day study on ground beetle and 28-day st udy on rove beetle reported LD 50 

### values of >1000 mg ai/kg dw soil and no effects due to IPSN on the beetles. This study was classified as Supplemental as it is a non-guideline study.

Toxicity to Earthworms

Non-guideline studies were subm itted to the Ag ency to demonstrate the acute (MRID 477668-12 using IPSN and MRID 477668-14 using TGAI) and sub-chronic (MRID 477668-14 using IPSN) effects of imazosulfuron on earthworms. Th e 14-day acute exposure studies reported LC 50 

### /NOAEC values of >1000/<100 and >996/308 mg ai/kg dw soil for IPSN and TGAI, respectively. Reduced body weight was the repor ted endpoint in both studies. The sub-chronic reproduction study reported LC 50 

### /NOAEC values of 165/1.65 mg ai/kg dw soil, based on decreased juvenile producti on. All three studies were cl assified as Supplemental.

Toxicity to Terrestrial Plants

Four Tier II studies were subm itted to assess the effects of the imazosulfuron formulation, V10142 75WDG, on the seedling emergence and vegeta tive vigor of monocot and dicot terrestrial plant species. In the seedling emergence test (MRID 473052-11), the maximum dose tested for following crops: onion, flax, and lettuce was 0.67 lb ai/A. The maximum dose tested for the remaining crops was 2.0 lb ai/A. The most sens itive monocot was onion and resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.034, 0.025, and 0.0052 lb ai/A based on dry weight. There was 44% reduction at the LOAEC (0.074 lb ai/A) and 80% at highest test co ncentration (0.67 lb ai/A). The growth inhibition at the proposed labe l maximum single applicati on rate (1.0 lb ai/A) is unknown. The most sensitive dicot was lettuce and resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.041, 0.22, and 0.0028 lb ai/A based on dry weight. There was 32% reduction of lettuce dry weight at LOAEC (0.07 4 lb ai/A). There were also si gnificant reductions in survival at 21 days for soybean at 2 lb ai/A (32%) and fl ax at 0.67 lb ai/A (37%). There were no adverse effects to wheat, corn, buckwheat and tomato. This study is classified as Acceptable.

In the vegetative vigor test (MRID 473052-12), the maximum dose tested for all crops, except radish, was 2.0 lb ai/A. The most sensitive monocot was onion and resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.25, 0.025, and 0.02 lb ai/A based on dry weight. The most dicot was radish and resulted in the EC 25 

### , NOAEC and EC 05 

### values of 0.08, 0.074, and 0.0079 lb ai/A based on percent survival. At the maximum dose tested fo r radish, 0.67 lb ai/A there was a 60% reduction in survival compared to the control. The reduc tion in survival at the proposed label maximum single application rate (1.0 lb ai/A) is unknown. There were also si gnificant effect s on dry weight57 

### and plant height for radish. There were signif icant effects to ryegrass, buckwheat, tomato, soybean, lettuce and flax. There were no advers e effects to wheat and corn. This study is classified as Acceptable.

3.3.3 Review of Incident Data

Three databases, the E cological Incident Info rmation System or EIIS maintained by the Environmental Fate and Effects Division, the Aggregate Summary Module (ASM) of Office of Pesticide Program’s Incident database maintained by the Information Technology and Resource Management Division, and the Avian Incident Monitoring System (AIMS) maintained by the American Bird Conservancy, were searched on Ju ly 13, 2010 to locate inci dents resulting from the use of imazosulfuron. There were no reported incidents in all three 3 databases. These results are expected with new pesticides because such ch emicals have typically not been used widely in the environment. Although there were no reported inci dences for this chemical, this does not rule out any existing risks that may potentially im pact terrestrial and aquatic organisms.

There is concern for incidence to plants to result at the proposed application rates for imazosulfuron, given that major incidences have occu rred as a result of a pplication of other SU’s at much lower rates (although comprehensive ev aluation of toxicity/efficacy data was not performed). The proposed maxi mum single application rates for imazosulfuron (0.3 – 0.67 lb ai/A) are much greater than othe r registered SU herbicides. Fo r example, the following are the most common use rates based on the recent RED documents some SU herbicides:

• Chlorsulfuron (Glean): 0.0625 lb ai/A

• Sulfometuron-methyl (Oust): 0.0231 - 0.375 lb ai/A

• Nicosulfuron (Accent): 0.0625 lb ai/acre

• Chlorimuron (Classic): 0.008 - 0.12 lb ai/A

Research involving chlorsulfuron, the first SU registered in th e US (1981) has indicated that chlorsulfuron may have effects on plant seed/fru it production at extremel y low concentrations. Researchers (Fletcher et al. , 1993, 1996; Bhatti et al. , 1995), have reported reproductive effects in cherry, canola, soybean, sunflower and Polygonum spp. at application rates as much as 1000x below the label rate (0.0625 lb ai/A). Among the incidents recorded for chlorsulfuron, the highest profile incident is Horse Heaven Hills, where chlorsulfuron applied to nearby wheat fields was implicated in the reduced yields in cherry and peach trees over a number of years in the 1980s. At this time, it is not known whethe r reproductive effects are associated with SUs other than chlorsulfuron; however, effects to plants at very low exposures to the SU sulfometuron-methyl (the second SU registered ) have been implicated in the loss of 100,000 acres of sugar beets in Idaho in 2000.

3.3.4 Review of ECOTOX Data

A search of the ECOTOX database was com plete d on July 13, 2010 in which four papers were identified for aquatic organisms. These studies , classified as “Acceptable” for ECOTOX and OPP standards ( Appendix E ), evaluated the toxicity of im azosulfuron to aquatic plants. The papers: Kuk Y.I. et al (2002), Ta naka, Y. (2003), Wang G. X. et al (2000) will not be used in this58 

### risk assessment because they te sted the resistance pattern of plant species to imazosulfuron and did not provide additional information a bout toxicity to non-target species.

Mohammad, M et al (2005, ECOTOX 104861) investig ated the relative sensitivity of the floating vascular plant, Lemna gibba and the unicellular algae, Pseudokirchneriella subcapitata to eight sulfonylurea (SU) herbicides in Japan to ge neralize previous work which showed that Lemna gibba had higher sensitivity (Fairchild et al. 1997). The results indicate that for five of the eight SU herbicides, Lemna gibba was more sensitive than P seudokirchneriella subcapitata ( Table 18 ). For imazosulfuron, Lemna gibba (EC 50 

### = 1.46 μg ai/L, 7-day st udy) was two orders of magnitude more sensitive than Pseudokirchneriella subcapitata (EC 50 

### = 206 μg ai/L, 3-day study). The results for Lemna gibba is similar to the re sults found in the regi strant study and the results for the P seudokirchneriella subcapitata suggest that endpoints from open-literature study is more sensitive than the studies submitted by the registrant. The ECOTOX study results will be used quantitatively in this assessment.

In this study, it was also noted that there was a highly significa nt correlation between Log Kow and toxicity to P. subcapitata (R 2 

### = 0.987). Less water soluble SU s have greater toxicity ( Table 18 ). The same tendency was observed for Lemna species however the correlation is weaker (R 2 

### = 0.630), in which pyrasulfuron-ethyl and imazosu lfuron were somewhat outliers due to poor correlation of toxicity between the two species us ed in the study. In a previous study, the uptake of non-ionized chemicals by plant roots was repo rted to be greater when their lipophilicity increased within a Log Kow range from -0.57 – 4.6 (Briggs et al. 1982). This could be attributed to the lipophilic nature of the plasma membrane, with makes chemicals with low Kow easier to diffuse across the membrane into the cytoplasm. Stronger toxicity of SU with lower Kow may be explained by the hydrophobic property. Water solubil ity of SUs pesticides is pH dependent, in which they are less soluble in lower pH. Therefor e, environmental acidity influences the toxicity of the SUs. Fahl et al (1995) reported that toxicity and bioconcentration of SUs were enhanced by lowering pH in the green algae, Chlorella fusca.

* Tomlin (2000); ** Uesugi et al. (1997) Values are at pH 7; pH not stated for pyrazo sulfuron-ethyl & flazasulfuron



### 4 RISK CHARACTERIZATION

Risk characterization is the inte gration of exposure and effects ch aracterization to determine the ecological risk from the use of imazosulfuron and the likeliho od of effects on aquatic life, wildlife, and plants based on different pesticide- use scenarios. The risk characterization provides an estimation and description of the risk; articulates risk assessment assumptions, limitations, Table 18. Differential Toxicity of Sulfonyl Urea Herbicides on Aquatic Plants Sulfonylurea herbicide Kow P. subcapitata [E C 50 (μg ai/L)] Lemna species [ EC 50 (μg ai/L)] Bensulfuron-methyl 0.62* 11.8 2.23 Pyrasulfuron-ethyl 1.3* 0.96 3.49

Imazosulfuron 0.049* 206 1.46 Cyclosulfamuron 1.41* 0.27 0.91

Flazasulfuron 1. 08** 1.29 1.66 Ethoxysulfuron -1.01** 2.84 1.72 Thifensulfuron-methyl 0.02* 359 7.16 Nicosulfuron -1.8* >1000 14.559 

### and uncertainties; synthesizes an overall conclu sion; and provides the risk managers with information to make regulatory decisions.

4.1 Risk Estimation: Integration of Exposure and Effects Data

Results of the exposure and toxic ity effects data are used to ev aluate the likelihood of adverse ecological effects on non-target sp ecies. For the assessm ent of imazosulfuron risks, the risk quotient (RQ) method is used to compare exposure and measured toxicity values:

RQ = EEC / (Acute or Chronic Toxicity Values)

where: EEC is the estimated environmental concentr ation generated by the exposure scenarios. The RQs are compared to the Agency’s levels of concern (LOCs). These LOCs are the Agency’s interpretive policy and are used to analyze potentia l risk to non-target or ganisms and the need to consider regulatory action. These cr iteria are used to indicate when a pesticide’s use as directed on the label has the potentia l to cause adverse effects on non-target organisms.

4.1.1 Non-target Aquatic Fish, Invertebrates, and Plants

The highest surface water concen tr ations resulting from imazosulf uron application was predicted for rice (imazosulfuron total residues as peak EEC = 279 μ g ai/L) followed by the Florida pepper scenario (imazosulfuron tota l residues as peak EEC = 12.2 μ g ai/L). Application scenarios were selected to represent the enti re range of soil and environmen tal conditions of the proposed actions. The estimated environmental concentrat ions are based on total residues; however the aquatic toxicity values are based on imazosulfuron parent or in some cases, specific degradates. This conservative approach will approximate maximum exposure.

Peak EECs were compared to acute toxicity end points to derive acute ri sk quotients. The 21-day EECs were compared to chronic toxicity endpo ints (NOAEC values) to derive chronic risk quotients for invertebrates. The 60-day EECs were compared to chronic toxicity endpoints (NOAEC values) to derive chr onic risk quotients for fish.

Fish (Freshwater and Estuarine/Marine)

For acute risk to freshwater and m arine fis h, there was no toxicity observed at the highest concentration of the technical gr ade imazosulfuron tested, at 100 mg ai/L nominal concentration. Therefore, acute risk quotients were not calcula ted and there is not a potential acute risk to freshwater fish.

Estimated chronic freshwater fish RQ, based on the highest EEC of 279 μ g ai/L for rice and NOAEC value of 2900 μ g ai/L, was 0.09. As the calculated RQ was less than the chronic risk LOC of 1.0 for all the proposed new uses including turfgrass, imazosulfuron is not expected to pose risk to freshwater fish at concern levels based on chronic expos ure. Chronic toxicity data is not available for estuarine/marine fish. As the NOAEC value based on acute exposure studies on fathead minnow (for which chronic data is ava ilable) and sheepshead minnow were similar, it is reasonable to use the fathead minnow NOAE C value from chronic exposure study for60 

### sheepshead minnow. RQs calculated using the fathead minnow NOAEC value suggests that imazosulfuron may not pose risk to estuarine/marine fish.

Freshwater Invertebrates

For acute risk to freshwater invertebrates, there was no toxicity observed at the highest concentration of the technical gr ade imazosulfuron tested, at 100 mg ai/L nominal concentration. Therefore, acute risk quotients were not calcula ted and potential for acute risk does not exceed concern levels for freshw ater invertebrates.

In the freshwater life cycle toxicity test using Daphnia magna (MRID 473052-01), the NOAEC and LOAEC are 0.84 and 3.3 mg ai/L, respectively, based on parental mortality. There was 20% and 40% mortality in the 3.3 and 8.9 mg a i/L treatment groups, respectively. The EC 50 

### is > 8.9 mg ai/L, the highest test concen tration. The RQ (0.093) was calcul ated using the highest EEC at 21 days (279 μ g ai/L for rice) and the NOAEC (0.84 mg ai/L). Chronic LOCs (1.0) are not exceeded for any of the proposed uses.

Chronic RQs were also calculated for the sedi ment-dwelling midge larvae by comparing the highest pore water concentration of imazosulf uron that resulted from Rice scenario (279 μ g /L) to the pore water-based NOAEC (11,000 μ g ai/L ). The resulting RQ of 0.02 suggest that imazosulfuron is not expected to po se risk to freshwater benthic organisms at levels of concern due to chronic exposure. Comparison of EC 50 

### value (45,7000 μ g ai/L) generated from the above chronic study with peak EEC reported in rice (279 μ g ai/L) also indicates that imazosulfuron does not pose risk to benthic invertebrates on acute exposure basis at concern levels.

Estuarine/Marine Invertebrates

For acute risk to marine crustaceans (mysid), there was no toxicity observed at the highest concentration of the technical gr ade imazosulfuron tested, at 100 mg ai/L nominal concentration. Therefore, acute risk quotients were not calcula ted and risk was presumably lower than concern levels for acute risk to estuarine/marine inverteb rates. In the toxicity test for marine mollusks using the Eastern Oyster, the EC 50 

### and NOAEC values were 63 and 13 mg ai/L, respectively, based on reduced shell deposition. The RQ (<0.01) was calculated using the highest peak EEC (279 μ g ai/L for rice) and the EC 50 

### (63,000 μ g ai/L). There are no LOC exceedances for estuarine/marine mollusks.

Aquatic Plants

Based on a Lemna minor study (MRID 476397-01), the NOAEC and EC 50 

### values, based on reduction in number of fronds at Day 14 are 0.18 and 0.46 μg ai/L , respectively. LOCs for nonlisted aquatic vascular plants are exceeded for all the proposed uses (RQs = 7 - 607, Table 19 ). LOCs for endangered aquatic vascular plants are exceeded for all the proposed uses (RQs = 17 - 1468, Table 19 ).

There was no toxicity observed at the highest concentration of the imazosulfuron degradate, IPSN, at 100 mg ai/L nominal c oncentration in the duckweed ( Lemna gibba ) aquatic plant test.61 

### Therefore, acute risk quotients were not calcula ted and there is no a pot ential acute risk to vascular aquatic plants ba sed on exposure to IPSN.

Table 19. Aquatic Vascular Plant RQs for Imazosulfuron

Use Scenario Peak EEC (μg ai/L) Acute (non-listed) RQ * Acute (Listed) RQ * FL Tomato

Ground 9.22 20* 51* Tomato

PA Tomato Ground 3.04 7* 17* Pepper FL pepper 12.2 27* 68*

Rice Rice – Tier 1 279 607* 1468* PA Turf Ground 10.1 22* 56* Turf

FL Turf Ground 4.7 10* 26*

*LOC exceeded based on Lemna study (MRID 476397-01), EC 50 = 0.46 μg ai/L and NOAEC = 0.18 μg ai/L



### Based on the study by Mohamm ad et al (2005) using Pseudokirchneriella subcapitata , the calculated RQ (1.4) exceeded risk LOC for ri ce only. No LOCs (1.0) exceeded for tomato, pepper, and turfgrass.

4.1.2 Non-target Terrestrial Animals and Plants

Avian Risk

Since the L D 50 

### and LC 50 

### for birds (for TGAI) were both non -definitive values of >2250 mg/kg bw and >5042 mg/kg diet, respectively, and no tr eatment related mortality was observed, risk quotients were not calculated. Sim ilar to TGAI, degradate IPSN LD 50 

### for bobwhite quail was non-definitive (>2000 mg/kg bw) and no treatment- related mortality or effects were noted. Therefore, risk quotients were not calculated. Based on applicati on rates and the results of the acute toxicity studies, acute risk concern levels would not be exceeded for birds.

Based on the mallard duck NOAEC/LOAEC value of 100/202 mg ai/kg diet, chronic dose-based LOCs are exceeded for birds consuming shortgrass, tallgrass, and broadl eaf plants/small insects for turfgrass use only ( Table 20 ). Chronic dose-based LOCs were not exceeded for any of the food use. Chronic dietary-based RQs, on the other hand, were not exceeded for any of the proposed food or nonfood uses.

Table 20. Dietary-Based Avian RQs Based on Imazosulfuron New Uses in Turfgrass

Short Grass Tall Grass Broadleaf Plants and Small Insects Tomato, pepper, and rice 0.7 0.3 0.4 Turfgrass 2.7* 1.2* 1.5* *Exceeds chronic avian LOC of 1.062 

### Mammalian Risk

For imazosulfuron TGAI, the LD 50 

### for mammals was a non-definitive value of >5000 mg/kg bw and no treatment related mortalit y was observed. Therefore, acu te risk quotients were not calculated and there is not a poten tial acute risk to mammals.

The dietary-based chronic risk quotients for mammals did not exceed concern levels for any of the proposed uses for imazosulfuron. Similarl y, chronic dose-based risk LOCS were not exceeded for any sized mammals based on imazosulfuron uses in tomato, pepper, and rice. However, dose-based chronic risk LOC exceeded for turfgrass use for all sized mammals ( Tables 21 and 22 ). Based on this, potential risk exists for mammals due to imazosulfuron uses in turfgrass only.

There was increased acute sensitivity in mamma ls to the metabolites IPSN, ADPM and UDPM observed in the acute oral toxi city studies. In order to assess acute risk to mammals, the application rate for turfgrass (t he highest proposed rate for imaz osulfuron) was adjusted to the percent of the metabolite that may result from degradation processes on the leaf surface. The hydrolysis and aqueous photolysis study results were chosen fo r this reason. For all three metabolites, hydrolysis was stable at pH 7. Theref ore, the results from the aqueous photolysis study (at pH 7) were used to adjust the application rate ( Table 23 ). The percent detected for IPSN, ADPM and UPDM are 1.6, 35.3, and 11.2% , respectively. Based on the adjusted application rate, acute mammalian LOCs are not exceeded for these degradates. There is some uncertainty in this analysis as not all degradation processes in field may be incorporated.

Table 21. Mammalian Dose-Based Chronic RQs Based on Upper Bound Residues for Imazosulfuron Use on Tomato, Pepper, and Rice 15 g 35 g 1000 g Short Grass 0.6 0.5 0.3 Tall Grass 0.3 0.2 0.1 Broadleaf plants/sm insects 0.4 0.3 0.2 Fruits/pods/lg insects 0.04 0.03 0.02

Seeds (granivore) 0.01 0.01 <0.01



### Table 22. Mammalian Dose-based Chronic RQs for Imazosulfuron use on Turfgrass 15 g 35 g 1000 g Short Grass 2.3* 2.0* 1.1* Tall Grass 1.1* 0.9 0.5 Broadleaf plants/sm insects 1.3* 1.1* 0.6 Fruits/pods/lg insects 0.1 0.1 0.07

Seeds (granivore) 0.03 0.03 0.01 *Exceeds chronic mammalian LOC of 1.063 

### Table 23. Mammalian Acute Risk Based on Exposure to Imazosulfuron Degradates Degradate Maximum 1 Percent Detected Adjusted Turf grass Application Rate Acute Oral LD 50 LOC Exceedances IPSN 1.6% (aqueous photolysis at pH 7) 0.67 * 1.6 % = 0.01 lb ai/A, 2 applications 513 mg/kg M 445 mg/kg F No

ADPM 35.3% (aqueous photolysis at pH 7) 0.67 * 35.3 % = 0.24 lb ai/A, 2 applications 879 mg/kg M 836 mg/kg F No

UPDM 11.2% (aqueous photolysis at pH 7) 0.67 * 11.2 % = 0.08 lb ai/A, 2 applications 677 mg/kg M 698 mg/kg F No

1 Percent of degradates formed under natural envi ronment are considered fo r the risk assessment



### Terrestrial Invertebrates

EFED currently does not routinely quantify risks to terrestrial non-target insects. Risk quotients are therefore not calculated for th ese organism s. Imazosulfuron is classified as practically nontoxic based on the acute contact honey bee study (LD 50 

### = 59.9 μg ai/bee); therefore, label statements are not warranted to protect pollinators.

Earthworms

The registrant submitted two 14-day acute earthw orm toxicity studies that resulted in LC 50 

### values of >1000 mg/kg-dw soil fo r imazosulfuron TGAI and >996 mg/kg dw soil for IPSN. Risk to earthworms was evaluated using the formula outlined below.

RQ application rate mg cm

soil incorporation depth cm bulk density kg cm

LC mg ai kg soil = ×



### ⎡ ⎣ ⎢ ⎢ ⎤ ⎦ ⎥ ⎥ (/ )

() (/ )

(/ ) 2

3

50



### Soil bulk density of 1.3 g/cm 3 

### and incorporation depth of 3 cm (as imazosulfuron is most effective in the zone where germinations weed seedlings emerge from) were assumed for this analysis. Using the sing le maximum application rate of 0.67 lb ai/acr e for turfgrass which resulted in imazosulfuron soil concentrati on of 1.9 mg/kg soil and a conservative LC 50 

### of >966 mg/kg soil, calculated RQ was <0.01. Based on th is, minimal risk to earthworms is assumed from all the proposed new imazosulfuron uses. This screening assessment doe s not consider risks to earthworms from multiple applications of imazosulfuron in a single year or risks to earthworms if imazosulfuron accumulates in th e soil over multiple years of applications. Accumulation of imazosulfuron in the soil is li kely as this is a persistent chemical.

4.1.3 Terrestrial and Semi-aquatic Plants Risk

Terrestrial and sem i-aquatic plants may be exposed to pesticides from runoff and spray drift. Semi-aquatic plants are those that inhabit low-lyi ng wet areas that may be dry at certain times of the year. EECs for terrestrial and semi-aquatic pl ants are derived for areas adjacent to the treatment site. Acute RQs for terrestrial pl ants are derived by di viding the EEC by the EC 25 

### from64 

### Tier II seedling emergence and ve getative vigor toxicity tests. Ac ute RQs for listed plant species are calculated by dividing the EEC by the NOAEC (if not available, an EC 05 

### is used) value from Tier II toxicity tests.

To calculate RQs, the results of the seedling emergence test (MRID 473052-11) were used. The most sensitive monocot was onion which resulted in the EC 25 

### and NOAEC values of 0.034 and 0.025 lb ai/A based on dry weight. The most sens itive dicot was lettuce which resulted in the EC 25 

### and NOAEC values of 0.041 and 0.22 lb ai/A based on dry weight.

In the vegetative vigor test (MRID 473052-12) , the most sensitive monocot was onion and resulted in the EC 25 

### and NOAEC values of 0.25 and 0.025 lb ai/A based on dry weight. The most dicot was radish and resulted in the EC 25 

### and NOAEC values of 0.08 and 0.074 lb ai/A based on percent survival.

Terrestrial plant EECs and toxi city endpoints are provided in Table 13 . EECs and RQs for turf are calculated using TERRPLANT 1.2.2 ( Appendix F and summarized in Table 24 . For a single ground application on tomato, pepper, and rice at the maximum rate, the LOC was exceeded for listed and non-listed non-target te rrestrial plants in semi-aquatic environments only. For a single aerial application on rice, the LOC was exceeded for listed and non-listed non-target terrestrial plants in semi-aquatic environments and liste d plants in dry upland areas. For a single ground application to turfgrass, the LOC was exceeded for listed and non-listed non-target terrestrial plants in dry upland and se mi-aquatic environments.

Table 24. Risk Quotients (RQ) for Plants in Dry and Semi-Aquatic Areas Exposed to Imazosulfuron Through Runoff and/or Spray Drift*

Listed Status Dry Semi-Aquatic Spray Drift Monocot non-listed 0.5 4.5* <0.1 Monocot listed 0.7 6.1* 0.1

Dicot non-listed 0.4 3.7* <0.1 Tomato, pepper, and rice 0.3 lb ai/A, Ground application Dicot listed 0.8 7.0* 0.1 Monocot non-listed 0.9 4.9* 0.4 Monocot listed 1.2* 6.6* 0.6

Dicot non-listed 0.7 4.0* 0.4 Rice 0.3 lb ai/A Aerial application Dicot listed 1.4* 7.5* 0.7 Monocot non-listed 1.2* 10.0* 0.2 Monocot listed 1.6* 13.7* 0.3

Dicot non-listed 1.0* 8.3* 0.2 Turfgrass 0.67 lb ai/A Ground application Dicot listed 1.8* 15.5* 0.3 *If RQ > 1.0, the LOC is exceeded, resulting in potential for risk



### 4.2 Risk Description

A screening-level (Level I) risk assessment, based on the proposed uses of imazosulfuron on tomato, pepper, rice, and turfgr ass, suggests that imazosulfuron exposure may result in direct chronic effects to birds and mammal s and direct effects to aquatic va scular and terrestrial plants. These direct effects may also result in indirect risk to non-target species. Potential for risk does exist for neither fish, aquatic invertebrates a nd non-vascular plants nor birds, mammals, and terrestrial invertebra tes based on acute exposure to imazosulfuron.65 

### 4.2.1 Risks to Aquatic Organisms

Potential for acute and chronic ri sk to freshwater and marine fi sh and aquatic invertebrates is lower than concern levels. However, there is a potential risk to va scular (all uses) and nonvascular (rice use only) aquatic plants. Imazosulf uron technical was very highly toxic to vascular plants ( Lemna minor , MRID 476397-01). The NOAEC and EC 50 

### values, based on reduction in number of fronds at Day 14 ar e 0.18 and 0.46 μg ai/L, respectively. LOCs for listed and nonlisted aquatic vascular plants ar e exceeded for all the proposed uses. Non-vascular plant RQs, on the other hand, exceeded concern levels for imazosu lfuron use in rice only. This may have been due to the use of the RICE model which provided the most conservative EECs.

An aquatic vascular plant ( Lemna gibba ) study using the degradate, IPSN demonstrated no toxicity to the plant. However, there is un certainty regarding toxi city to fish, aquatic invertebrates, and aquatic non-vascular plants exposed to the degradates.

4.2.2 Risks to Terrestrial Organisms

Birds and Mammals

The screen ing assessment for imazosulfuron sugges ts that potential acut e risk to birds and mammals is lower than concern level for all prop osed uses. Because the avian (oral and dietary) and mammalian (oral) acute studies did not establish definitive endpoints as no mortality was noted with the highest tested concentrations, st andard RQ values for acute exposure were not calculated in the Risk Estimati on section of this assessment. In order to gain a better understanding of how the EECs for the maximum proposed imazosulfuron application rate (for both food and non-food uses) relate to the toxic ity data currently available for birds and mammals, TREX was used to calculate RQs usin g the conservative assumption that the highest concentration tested in the avian and mammalian studies represent endpoints ( i.e ., acute: LD 50 

### s = 2250 mg/kg bw and 5042 mg/kg diet fo r birds; 5000 mg/kg bw for mamm als). In this exercise all of the acute RQs calculated using upper bound Kenaga values were less than the listed species LOC of 0.1 for all size and dietary classes for bot h food and non-food uses. Therefore, direct risk to non-listed and listed birds and mammals from acute exposure to imazosulfuron is lower than concern levels.

Reproductive effects were observed at similar co ncentrations in both the mallard duck (MRID 47305-08) and bobwhite quail (MRI D 47305-07) studies. In the bobw hite quail study, there was a statistically significant number of cracked eg gs (5%) and a significant reduction in the number of hatchlings/eggs laid (14%) in the 1230 mg ai /kg diet treatment group resulting in a NOAEC of 484 mg ai/kg diet. There was also a statistically significant reduction in female weight gain (28%) and reduction in shell thickness resul ting in a NOAEC value of 194 mg ai/kg diet, however these effects were not dose-responsive and there is some uncertainty whether these effects were treatment related. However, simila r results were reported in the mallard duck study, in which there was a statistically significant reduction in eggshell thickness (5%) at similar test concentration (242 mg ai/kg diet). The ratio of hatchling survivors to number hatched was slightly adversely affected at the lowest (4.7% ) and highest (2.9%) treatment levels. A definitive NOAEC could not be determined in this study. To address the above uncerta inty, the registrant66 

### submitted an additional study (MRID 476791- 14) on mallard duck based on which a NOAEC/LOAEC value of 100/202 mg ai/kg diet was established. These endpoints were used in imazosulfuron effects determination to birds. Based on the mallard duck study NOAEC (100 mg ai/kg diet), chronic LOCs are exceeded based on upper bound residues for birds consuming shortgrass, tallgrass, and broadleaf plants/small insects for turfgrass us e only. Chronic LOCs were not exceeded for any of the food uses.

The potential for adverse effects to mammals a ppear to be likely based on chronic dose-based RQs. Chronic dose-based risk LOC exceeded for turfgrass use for all sized mammals. However, potential for dietary-based chroni c risk for mammals was lower than concern levels for all the proposed food uses of imazosulfuron.

Imazosulfuron degradates, IPSN, UDPM and ADPM are more acutely toxic to mammals than the parent with IPSN, being the most toxic. To ad dress this uncertainty that was identified in the earlier assessment regarding the risk from degradates, the registrant submitted new acute exposure studies on birds and chronic exposure st udies on terrestrial invertebrates. The bird studies suggested that the LOAEC values for IPSN were lower than the parent in both the dose and dietary-based studies and adverse effects were noted at lo wer concentrations with IPSN compared to the parent. Similar conclusions we re also drawn based on ea rthworm toxicity data. Regarding the non-target insects, although studies that evaluated the effects of IPSN were submitted on ground beetle and rove beetle, compar able studies were not available for TGAI. Therefore, the uncertainty related to the effects of TGAI versus IPSN could not be resolved for terrestrial insects.

Terrestrial plants

Im azosulfuron exposure results in significant redu ctions in growth and survival of non-target terrestrial plants with EC

25 

### values as low as 0.034 lbs ai/A (corresponding NOAEC value of 0.025 lbs ai/A). Many of the EC

25 

### values for terrestrial plants are approximately two orders of magnitude less than the proposed single applicat ion rates (0.3 – 0.67 lb ai/A). For a single ground application on tomato, pepper, and rice at the maximum rate, the LOC was exceeded for listed and non-listed non-target te rrestrial plants in semi-aquatic environments only. For a single aerial application on rice, the LOC was exceeded for listed and non-listed non-target terrestrial plants in semi-aquatic environments and liste d plants in dry upland areas. For a single ground application to turfgrass, the LOC was exceeded for listed and non-listed non-target terrestrial plants in dry upland and se mi-aquatic environments.

In addition to the growth effects observed for se veral plant species, unusually high mortality was observed for some plants in the seedling emer gence and vegetative vigor tests. There were significant reductions in survival at 21 days for s oybean at 2 lb ai/A (32%), flax at 0.67 lb ai/A (37%), and radish at 0.67 lb ai/A (60%). Imazosulfuron exposur e may result in non-target plant mortality, especially for aerial ap plications. The nontarge t terrestrial plant toxicity studies, as specified by the Agency guidelines, are designed to evaluate subl ethal effects to plant growth, which can then be extrapolated to community le vel effects. Mortality as an endpoint in these studies, as is the case with imazosulfuron, is atypical and of concern to Agency.67 

### Effects in the seedling emergence and vegetative vi gor studies were observed in a wide range of plants families, however, there were minimal effects observed in the Poaceae family (wheat, corn, and ryegrass). This is supported by the fact that imazosulfuron is not a grass herbicide.

There is also concern for incidence to plants to result at the proposed application rates for imazosulfuron, given that major incidences have occu rred as a result of a pplication of other SU’s at much lower rates. The proposed maximum sing le application rates for imazosulfuron (0.3 – 0.67 lb ai/A) are much greater than other register ed SU herbicides. For example, the following are the most common use rates based on the re cent RED documents some SU herbicides:

• Chlorsulfuron (Glean): 0.0625 lb ai/A

• Sulfometuron-methyl (Oust): 0.0231 - 0.375 lb ai/A

• Nicosulfuron (Accent): 0.0625 lb ai/acre

• Chlorimuron (Classic): 0.008 - 0.12 lb ai/A

Research involving chlorsulfuron, the first SU registered in th e US (1981) has indicated that chlorsulfuron may have effects on plant seed/fru it production at extremel y low concentrations. Researchers (Fletcher et al. , 1993, 1996; Bhatti et al. , 1995), have reported reproductive effects in cherry, canola, soybean, sunflower and Polygonum spp. at application rates as much as 1000x below the label rate (0.0625 lb ai/A). Among the incidents recorded for chlorsulfuron, the highest profile incident is Horse Heaven Hills, where chlorsulfuron applied to nearby wheat fields was implicated in the reduced yields in cherry and peach trees over a number of years in the 1980s. At this time, it is not known whethe r reproductive effects are associated with SUs other than chlorsulfuron; however, effects to plants at very low exposures to the SU sulfometuron-methyl (the second SU registered ) have been implicated in the loss of 100,000 acres of sugar beets in Idaho in the year 2000.

4.2.3 Endocrine Disruption Potential

The potential for endocrine disruptor-related e ffects was observed in avian toxicity studies submitted to the Agency. Significant reproductive effects were observed in the bobwhite quail and mallard duck studies. In the bobwhite quail st udy, there was a statistica lly significant number of cracked eggs and a significant reduction in the number of hatchlings/eggs laid. There was also a statistically significant reduction in female we ight gain and reduction in shell thickness, however these effects were not dose-responsive and there is some uncertainty whether these effects were treatment related. In mallard duck studies, there was a statistically significant reduction in number of eggs laid and eggshell thickness. The ra tio of hatchling survivors to number hatched was slightly adversely affected.

A two-generation laboratory rat reproducti on study (MRID 473053-04), with imazosulfuron TGAI resulted in no reproductive effects. Th e NOAEC and LOAEC for parental effects are 1,000 and 10,000, respectively, based on mortality, clin ical signs of toxicity, and decreased body weight and food consumption. The NOAEC and L OAEC for offspring effects are also 1,000 and 10,000, respectively, based on decreased pup viability and body weights.68 

### EPA is required under the Federal Food, Drug, a nd Cosmetic Act (FFDCA), as amended by FQPA, to develop a screening program to determ ine whether certain substances (including all pesticide active and other ingredients) “may have an effect in humans t hat is similar to an effect produced by a naturally occurring estrogen, or othe r such endocrine effects as the Administrator may designate.” Following the recommendations of its Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC), EPA determined that there were scientific bases for including, as part of the program, androgen and thyroid hormone systems, in addition to the estrogen hormone system. EPA also adopted EDSTAC’s recommendation that the Program include evaluations of potential effects in wildlife. When th e appropriate screening and/or testing protocols being considered under the Ag ency’s Endocrine Disrupter Screening Program (EDSP) have been developed and vetted, imazosu lfuron may be subjected to additional screening and/or testing to better characterize effects related to endocrine disruption.

4.3 Threatened and Endangered Species Concern

4.3.1 Action Area

For listed species assessm ent pur poses, the action area is consider ed to be the area affected directly or indirectly by the Federal action and not merely th e immediate area involved in the action. At the initial screening- level, the risk assessment cons iders broadly described taxonomic groups and so conservatively assumes that lis ted species within those broad groups are colocated with the pesticide treatment area. This means that terrestrial plants and wildlife are assumed to be located on or adjacent to the treat ed site and aquatic organisms are assumed to be located in a surface water body adj acent to the treated site. The assessment also assumes that listed species are located within an assumed area, which has the relatively highest potential exposure to the pesticide, and that exposures are likely to decrease with distance from the treatment area. This risk assessment presents th e use of imazosulfuron and establishes initial colocation of species with treatment areas.

If the assumptions associated with the screeni ng-level action area result in RQs that are below the listed species LOCs, a "no effect" determina tion conclusion is made with respect to listed species in that taxa, and no furt her refinement of the action area is necessary. Furthermore, RQs below the listed species LOCs for a given taxonomic group indicate no concern for indirect effects upon listed species that depend upon th e taxonomic group covered by the RQ as a resource. However, in situations where the scre ening assumptions lead to RQs in excess of the listed species LOCs for a given ta xonomic group, a potential for a "may affect" conclusion exists and may be associated with direct effects on listed species belonging to that taxonomic group or may extend to indirect effects upon listed spec ies that depend upon that taxonomic group as a resource. In such cases, additional information on the biology of listed species, the locations of these species, and the locations of use sites could be considered to determine the extent to which screening assumptions regarding an action area a pply to a particular listed organism. These subsequent refinement steps c ould consider how this information would impact the action area for a particular listed organism and may potentially include areas of exposure that are downwind and downstream of the pesticide use site.69 

### 4.3.2 Taxonomic Groups Potentia lly at Risk: Direct Effects

Based on available screening level information, fo r the proposed uses of imazosulfuron, there is a potential for direct effects to listed birds, mammals, aqua tic non-vascular plants, aquatic vascular plants, and terrestrial plants. Conseque ntly, there is a potential concern for indirect effects upon the listed organisms by, for example, pe rturbing habitat, forage or prey availability. In conducting a screen for indirect effects, dire ct effect LOCs for each taxonomic group are used to make inferences concerning the potential for indirect effects upon listed species that rely upon non-endangered organisms in these taxonomic groups as resources critical to their life cycle. A summary of the risk conclusions and direct and indirect effects determinations is presented in Table 24

.

Table 25. Listed Species Risks Associated with Direct or Indirect Effects Due to Applications of Imazosulfuron Parent Listed Taxonomy Direct Effects Indirect Effects Terrestrial and semi-aquatic plants – monocots Yes Yes Terrestrial and semi-aquatic plants – dicots Yes Yes Terrestrial invertebrates No Yes Birds (surrogate for terrestrial-phase amphibians and reptiles) Yes – chronic effects Yes

Mammals Yes – chronic effects Yes Aquatic vascular plants Yes Yes Aquatic non-vascular plants Yes Yes Freshwater fish (surrogate for aquatic-phase amphibians) No Yes

Freshwater Invertebrates No Yes Freshwater Benthic Invertebrates No Yes Estuarine/Marine Fish No Yes Estuarine/Marine Crustaceans No Yes Estuarine/Marine Mollusks No Yes



### The LOCATES database (version 2.9.7) identifie s those U.S. counties that include tomato, pepper, rice, and turfgrass areas and that have federally-listed endangered or threatened species that may be directly or indirectly affected. Th e list of affected spec ies derived from LOCATES was not included in this assessment because the uses cover most of the United States and the direct and indirect effects includes most species. With additional refinement by exploring more detailed use patterns and species biology (e.g., ge ographic location, specific feeding habits, time of year likely to utilize crop fields ), some species listed may be dete rmined to be not likely to be affected.70 

### 4.3.3 Use of Probit Slope Dose-Response Rela tionship to Provide Information on the Endangered Species Levels of Concern

The Agency uses the probit dose-response rela tionship as a tool fo r providing additional information on the listed animal species acute levels of concern. The acute listed species LOCs of 0.1 and 0.05 are used for terrestr ial and aquatic animals, respec tively. As part of the risk characterization, an interpreta tion of acute LOCs for listed species is discussed. This interpretation is presented in terms of the chance of an individual event ( i.e ., mortality or immobilization) should exposure at the estimated environmental concentration actually occur for a species with sensitivity to imazosulfuron on par with the acute toxicity endpoint selected for RQ calculation. To accomplish this interpretation, the Agency uses the slope of the dose response relationship available from the toxicity study used to establish the acute toxicity measurement endpoints for each taxonomic group. The individual effects probability associated with the LOCs is based on the mean estimate of the slope and an assumption of a probit dose response relationship. In addition to a single e ffects probability estimate based on the mean, upper and lower estimates of the effects probabilit y are also provided to account for variance in the slope. The upper and lower bounds of the effects probability are based on available information on the 95% confidence interval of the slope. A statement regarding the confidence in the applicability of the assumed probit dos e response relationship fo r predicting individual event probabilities is also included. Studies with good probit fit characteristics (i.e., statistically appropriate for the data set) ar e associated with a high degree of confidence. Conversely, a low degree of confidence is associated with data from studies that do not sta tistically support a probit dose response relationship. In addition, confid ence in the data set may be reduced by high variance in the slope (i.e., larg e 95% confidence intervals), despite good probit fit characteristics.

Individual effect probabilitie s are calculated based on an Ex cel spreadsheet tool IECV1.1 (Individual Effect Chance Model Version 1.1) deve loped by Ed Odenkirchen of the U.S. EPA, OPP, Environmental Fate and Effects Divisi on (June 22, 2004). The model allows for such calculations by entering the mean slope esti mate (and the 95% confidence bounds of that estimate) as the slope parameter for the spread sheet. In addition, the LOC (0.1 for terrestrial animals and 0.05 for aquatic animals) is entered as the desired threshold.

Probit dose analysis was not completed for acute ri sk to aquatic and terrestrial fauna because no mortalities were observed in the toxicity testing. Probit dose analysis was not completed for risk to aquatic vascular plants, chroni c risk to birds and mammals, nor terrestrial plants because it is not appropriate for these endpoints.

4.3.4 Indirect Effects Analysis

The Agency acknowledges that pesticides have the potential to exert indirect effects upon the listed organism s by, for example, perturbing forage or prey availability, altering the extent of nesting habitat, etc. In conducting a screen for indirect effects, direct effect LOCs for each taxonomic group are used to make inferences co ncerning the potential fo r indirect effects upon listed species that rely upon non-endangered orga nisms in these taxonomic groups as resources critical to their life cycle.71 

### Based on direct chronic risk to birds and mammals, there may be potential indirect effects to terrestrial species that depend on these organisms (including their surrogates) as a source of food or pollination.

Vascular aquatic plants serve se veral important functions in aqua tic ecosystems. They provide structure as attachment sites a nd refugia for many aquatic inve rtebrates, fish, and juvenile organisms, such as fish and frogs. In addition, vascular plants also pr ovide primary productivity and oxygen to the aquatic ecosystem. Rooted plan ts help reduce sediment loading and provide stability to nearshore areas and lower streamba nks. In addition, vascular aquatic plants are important as attachment sites for egg masses.

Based on direct risk to terrestri al plants, there may be potential indirect effects to aquatic and terrestrial species that depend on these organisms (including their surrogates) as a source of food or habitat, including riparian ha bitats. Terrestrial plants serve several important habitat-related functions for listed species. In addition to providing habitat and c over for, terrestrial vegetation also provides shelter for and c over from predators while foraging. Terrestrial plants also provide energy to the terrestrial ecosystem through primary production. Upland vegetation including grassland and woodlands provides cover during disp ersal. Riparian vegetation helps to maintain the integrity of aquatic system s by providing bank and thermal stab ility, serving as a buffer to filter out sediment, nutrients, and contaminants before they reach the watershed, and serving as

an energy source.

4.3.5 Critical Habitat for Listed Species

In the evaluation of pesticide eff ects on designated critical habitat, consideration is given to the physical and biological f eatures (primary constitue nt elements) of a critic al habitat identified by the U.S Fish and Wildlife and National Marine Fisheries Services as essential to the conservation of a listed species and which may require special management cons iderations or protection. The evaluation of impacts for a screening level pest icide risk assessment focuses on the biological features that are primary cons tituent elements and is accomplis hed using the screening-level taxonomic analysis (RQs) and listed species’ levels of concern (LOCs) that are used to evaluate direct and indirect effects to listed organisms.

The screening-level risk assessment for imazosulfur on has identified potentia l concerns for direct effects on listed birds, mammals, aquatic non-vas cular plants, aquatic vascular plants and terrestrial plants and indirect effect to those organisms de pendant upon them for food and/or habitat. In light of the potential for indirect effects, the next step for EPA and the Service(s) is to identify which listed species and critical habitat are potentially implicated.

Analytically, the identification of such species and critical hab itat can occur in either of two ways. First, the agencies could determine whethe r the action area overlaps critical habitat or the occupied range of any listed sp ecies. If so, EPA w ould examine whether the pesticide’s potential impacts on non-endangered species would affect the lis ted species indirectly or directly affect a primary constituent element of the critical habita t. Alternatively, the agencies could determine which listed species depend on biological resources, or have constituent elements that fall into the taxa that may be directly or indirectly im pacted by a pesticide. Then EPA would determine72 

### whether or not use of the pesticide overlaps the critical habitat or the occupied range of those listed species. At present, the information re viewed by EPA is not sufficient to permit use of either analytical approach to make a definitiv e identification of species that are potentially impacted indirectly or critical habitats that are potentially impacted directly by the use of pesticides. EPA and the Service(s) are worki ng together to conduct the necessary analysis.

This screening-level risk assessment for critical habitat provides a listi ng of potential biological features that, if they are primary constituent elem ents of one or more critical habitats, would be of potential concern. These corres pond to the taxa identified above as being of potential concern for indirect effects and include birds, reptiles, terrestrial phase amphibians, mammals, terrestrial plants and aquatic organisms. This list should se rve as an initial step in problem formulation for further assessment of critical habitat impact s outlined above, should additional work be

necessary.

5 Description of Assumptions, Uncertainties, Strengths, and Limitations

5.1 Assumptions and Limitations Related to Exposure for all Taxa

There are a number of areas of uncertainty in the aquatic and terrestrial risk assessments. The toxicity assessment for terrestrial and aquatic an imals is limited by the number of species tested in the available toxicity studies. Use of toxicity data on repres entative species does not provide information on the potential variability in susc eptibility to acute a nd chronic exposures.

This screening-level risk assessment relies on labeled statements of the maximum rate of imazosulfuron application, the maximum number of applications, and the shortest interval between applications. Together , these assumptions constitute a maximum use scenario. The frequency at which actual uses approach these maximums is dependant on resistance to the fungicide, timing of applicat ions, and market forces.

5.2 Assumptions and Limitations Related to Exposure for Aquatic Species

The fate and transport database for imazosulfuron was sufficient to conduct aquatic modeling for exposure assessment of aquatic species. Howeve r, this assessment is based on limited and supplemental biodegradation fate data. Imazosulfur on persistence is significantly affected by soil types or water chemistry and may not always be easy to predict from typically available soil/water property data alone. A clearer picture of the range of variability in imazosulfuron persistence in the environment w ould require environmental fate studies on a greater variety of soils/waters/ sediments with a gr eater range of pH levels and other soil properties. This is particularly true for the aerobic soil a nd anaerobic aquatic metabolism studies.

Even though imazosulfuron is soluble and moderately mobile to mobile based on the results of batch equilibrium studies, unextractable residues were identified at maximums of 87.7 of applied radioactivity in anaer obic aquatic metabolism and 35.7% of a pplied radioactivity in aerobic soil metabolism. The unextractable residues are uncharacterized and it is uncertain whether they consist of degradates of risk c oncern. Under sterile conditions th ese unextractable residues were not formed suggesting that the formation of them is microbially mediated. Metabolism half-lives73 

### were estimated based on parent and major degrad ates concentrations (e xcluding unextractable residues). To the extent that these unextractable residues are of risk conc ern, the estimated halflives will be underestimated compar ed to a total toxic residue appr oach for estimating half-lives. However, given the persistence of total to xic residue of imazosulfuron, inclusion of unextractable residues in tota l toxic approach for calculating metabolism half-life would not impact PRZM/EXAMS modeled EECs appreciably.

5.3 Assumptions and Limitations Related to Exposure for Terrestrial Species

Variation in habitat and dietary requirements

For screening terrestrial risk assessments, a generic bird or mammal is assumed to occupy either the treated field or adjacent areas receiving pes ticide at a rate commensurate with the treatment rate on the field. The habitat a nd feeding requirements of the m odeled species and the wildlife species may be different. It is assumed that species occupy, exclusivel y and permanently, the treated area being modeled. This assumption leads to a maximum level of exposure in the risk

assessment.

The acute studies have a fixed exposure period, not allowing for the differences in response of individuals to different durations of exposure. Further, fo r the acute oral study, imazosulfuron is administered in a single dose which does not mimic wild birds' exposure through multiple feedings. Also, it does not account for the effect of different environmental matrices on the absorption rate of the chemical into the animal . Because exposure occurs over several days, both the accumulated dose and elimination of the ch emical from the body for the duration of the exposure determine the exact exposur e to wildlife, however they are not taken into account in the screening assessment. There was also no assumption of an effect of repeated doses that change the tolerance of an indivi dual to successive doses.

Variation in diet composition

The risk assessment and calculated RQs assume 100% of the diet is rele gated to single food types foraged only from treated fields. The a ssumption of 100% diet from a single food type may be realistic for acute exposures, but diets are likely to be more variable over longer periods of time. This assumption is likel y to be conservative and will te nd to overestimate potential risks for chronic exposure, especially for larger orga nisms that have larger home ranges. These large animals ( e.g ., deer and geese) will tend to forage from a variety of areas and move on and off of treated fields. Small animals ( e.g ., mice, voles, and small birds) may have home ranges smaller than the size of a treated field a nd will have little or no opportunity to obtain foodstuffs that have not been treated with imazosulfur on. Even if their home range doe s cover area outside the treated field, imazosulfuron may have runoff to areas adjacent to the treated field.

Exposure routes other than dietary

Only dietary and incident al ingestion of contaminated soils exposure is included in the exposure assessment. Other exposure routes are possible for animals in treated areas. These routes include ingestion of contaminated drinking water, de rmal contact, inhalation, and preening. Because74 

### imazosulfuron does not volatili ze appreciably (vapor pres sure less than 2.63 x 10 -8 

### torr), inhalation does not appear to be a significant contributor to the overa ll exposure. Given that imazosulfuron is soluble in water there exists th e potential to dissolve in runoff and puddles on the treated field may contain the chemical. If t oxicity is expected through any of these other routes of exposure, then the risk s of a toxic response to imazosulf uron is underestimated in this risk assessment.

Dietary Intake - The Differences Be tween Laboratory and Field Conditions

There are several aspects of the dietary test that introduce uncert ainty into calculation of the LC 50 

### value (Mineau, et al ., 1994; ECOFRAM, 1999). The endpoint of this test is reported as the concentration mixed with food that produces a response rather than as the dose ingested. Although food consumption sometimes allows for the estimate of a dose, calculations of the mg/kg/day are confounded by undocumented spillage of feed and how consumption is measured over the duration of the test. Usually, if measur ed at all, food consumption is estimated once at the end of the five-day exposure period. Further, group housing of bird s undergoing testing only allows for a measure of the av erage consumption per day for a group; consumption estimates can be further confounded if birds die within a treatment group. The exponential growth of young birds also complicates the estimate of the dose; controls often nearly double in size over the duration of the test. Since weights are only taken at the initiation of the exposure period and at the end, the dose per body weight (mg/kg) is di fficult to estimate w ith any precision. The interpretation of this test is also confounded because the response of birds is not only a function of the intrinsic toxicity of the pesticide, but also th e willingness of the birds to consume treated food.

Further, the acute and chronic characterization of risk rely on comparisons of wildlife dietary residues with LC 50 

### or NOAEC values expressed in concentr ations of pesticides in laboratory feed. These comparisons assume that ingestion of food items in the field occurs at rates commensurate with those in the laboratory. Alth ough the screening assess ment process adjusts dry-weight estimates of food inta ke to reflect the increased mass in fresh-weight wildlife food intake estimates, it does not allow for gross energy and assimilative efficiency differences between wildlife food items and laboratory f eed. On gross energy content alone, direct comparison of a laboratory dietary concentration- based effects threshol d to a fresh-weight pesticide residue estimate would result in an underestimation of field exposure by food consumption by a factor of 1.25 - 2.5 for most f ood items. Only for seeds would the direct comparison of dietary threshold to residue estimate lead to an overestimate of exposure.

Differences in assimilative efficiency between laboratory and wild diet s suggest that current screening assessment methods do not account fo r a potentially important aspect of food requirements. Depending upon species and dietary matrix, bird assimilation of wild diet energy ranges from 23 - 80%, and mammal's assimilati on ranges from 41 - 85% (U.S. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is formulated to maximize assimilative efficiency (e.g., a value of 85%), a potential for underestimation of exposure may exist by assuming that consumption of food in th e wild is comparable with consumption during laboratory testing. In the screening process, e xposure may be underestimated because metabolic rates are not related to food consumption.75 

### Finally, the screening procedure does not account for situations wh ere the feeding rate may be above or below requirements to m eet free living metabolic requireme nts. Gorging behavior is a possibility under some specific wildlife scenar ios (e.g., bird migration) where the food intake rate may be greatly increased. Kirkwood (1983) has suggested that an upper-bound limit to this behavior might be the typical intake rate multiplie d by a factor of 5. In contrast is the potential for avoidance, operationally defined as animal s responding to the presence of noxious chemicals in their food by reducing consumption of treated dietary elements. This response is seen in nature where herbivores a void plant secondary compounds.

In the absence of additional information, the acute oral LD 50 

### test provides th e best estimate of acute effects for chemicals where exposure can be considered to occur over relatively short feeding periods, such as the diurnal feeding peaks common to avian species (ECOFRAM, 1999).

Incidental Pesticide Releases Associated with Use

This risk assessment is based on the assumption that the entire treatm ent area is subject to imazosulfuron application at the rate s specified on the label. In reality, there is the potential for uneven application of imazosulfuron through such plausible incidents as changes in calibration of application equipment, spillage, and localized releases at specifi c areas of the treated field that are associated with specifics of the type of application equipment used (e.g., increased application at turnabouts when us ing older application equipment).

5.4 Assumptions and Limitations Related to Effects Assessment

There is uncertainty as to the significance of the reproductive endpoint used for assessment purposes with respect to wild mammal popul ations because frank developmental and reproductive effects were not observed in the study. Observed chronic effects in the twogeneration rat reproduction study (MRID 473053-04), with technical imazosulfuron resulted in no reproductive effects. The NOAEC and LO AEC for parental effects are 1,000 and 10,000, respectively, based on mortality, clinical signs of toxicity, an d decreased body weight and food consumption. The NOAEC and LOAEC for offspring effects are also 1,000 and 10,000, respectively, based on decreas ed pup viability and body weight s. The resulting NOAEC is 200 mg/kg-diet. There were no reproduc tive effects or signs of repr oductive impairment in males or females. This study is classified as Acceptable by HED.

There is no potential acute oral risk to mammals exposed to imazosulfuron parent; however, there was increased acute sensitivity in ma mmals to the metabolites IPSN, ADPM and UDPM observed in the acute oral toxic ity studies. Therefore, there is uncertainty regarding risk terrestrial plants exposed to these degradates.

Age class and sensitivity of effects thresholds

It is generally recognized that test organism age may have a significant impact on the observed sensitivity to a toxicant. The sc reening risk assessment acute toxic ity data for fish are collected on juvenile fish between 0.1 and 5 grams. Aqua tic invertebrate acute testing is performed on76 

### recommended immature age classe s (e.g., first instar for daphnids , second instar for amphipods, stoneflies and mayflies, a nd third instar for midges). Similarly, acute dietary testing with birds is also performed on juveniles, with mallard being 5-10 days old and quail 10-14 days old.

Testing of juveniles may overest imate toxicity of older age classes for pesticidal active ingredients, such as imazosulfuron, that act dir ectly (without metabolic transformation) because younger age classes may not have the enzymatic systems associated with detoxifying xenobiotics. The screening risk assessment ha s no current provisions for a generally applied method that accounts for this uncertainty. In so far as the available toxicity data may provide ranges of sensitivity information with respect to age class, the risk assessment uses the most sensitive life-stage information as the conservative screening endpoint.

Use of the Most Sensitive Species Tested

Although the screening risk asse ssment relies on a sele cted toxicity endpoint from the most sensitive species tested, it does not necessarily mean that the se lected toxicity endpoint reflect sensitivity of the most sensitive species existing in a given environment. The relative position of the most sensitive species tested in the distribu tion of all possible species is a function of the overall variability among species to a particular chemical. In the case of listed species, there is uncertainty regarding the relationship of the listed species' sensitivity and the most sensitive species tested. Furthermore, the Agency is not limited to a base set of surrogate toxicity information in establishing risk assessment conclu sions. The Agency also c onsiders toxicity data on non-standard test species when available.

6 LITERATURE CITED

Beyer, W. N., E. E. Connor and S. Geroul d. 1994. Estimates of Soil Ingestion by Wildlife. Journal of Wildlife Mana gement. 58(2):375-382.

Bhatti, M.A., K. Al- Khatib, A.S. Felsot, R. Pa rker and S. Kadir. 1995. Effects of Simulated Chlorsulfuron Drift on Fruit Yield and Quality of Sweet Cherries ( Prunus Avium L. ). Environ. Tox. Chem. Vol 14 No. 3, pp. 537-544.

Briggs GG, Bromilow RH, Evans AA (1982) Relati onships between lipophilicity and root uptake and translocation of non-ionised chem icals by barley. Pestic Sci 13: 495-504.

ECOFRAM. 1999. ECOFRAM Terrestrial Draft Re port. Ecological Committee on FIFRA Risk Assessment Methods. USEPA, Washington D.C.

Fahl GM, Kreft L, Altenburger R, Faust M, Boedeker W, Grimme LH (1995) pH-dependent sorption, bioconcentration and algal toxicity of sulfonurea herbicides. Aquat Toxicol 31: 175-187.77 

### Fletcher, J.S. 1991. Horse Heaven Hills/Badger Canyon, A case Study of Alleged Pesticide Drift Damage. Presentation at the 84 th 

### Annual Meeting & Exhibition, Vancouver, British Columbia 91-150.7

Fletcher J.S., T. G. Pfleeger and H.C. Ratsch 1993. Potential Environm ental Risks Associated with the New Sulfonylurea Herbicides. Environ. Sci. Technol. Vol 27, No 10, pp. 2250- 2252.

Fletcher, J.S., J.E. Nellesson, and T. G. Pfleeg er. 1994. Literature review and evaluation of the EPA food-chain (Kenaga) nomogram, an instru ment for estimating pesticide residues on plants. Environ Toxicol Chem 13(9):1383–1391.

Fletcher J.S., T. G. Pfleeger and H.C. Rats ch 1995. Chlorsulfuron Influence on Garden Pea Reproduction. Physiologia Plantarum 94: pp 261-267.

Fletcher J.S., T. G. Pfleeger, H.C. Ratsch and R. Hayes 1996. Potential Impacts of Low Levels of Chlorsulfuron and Other Herbicides on Gr owth and Yields of Non-target Plants. Environ, Tox. and Chem. Vol. 15, No. 7. pp 1189-1196.

Food and Agriculture Organization of the United Nations. FAO PESTICIDE DISPOSAL SERIES 8. Assessing Soil Contaminatio n: A Reference Manual. Appendix 2. Parameters of pesticides th at influence processes in th e soil. Editorial Group, FAO Information Division: Rome, 2000. http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm

Gusey W.F., Z.D. Maturgo. 1973. Wildlife Utilization of Croplands. Environmental Conservation Department. Sh ell Oil Company, Houston, TX.

Hoerger, F. and E.E. Kenaga. 1972. Pesticide re sidues on plants: correlati on of representative data as a basis for estimation of their magnitude in the environment. In F. Coulston and F. Korte, eds., Environmental Quality and Sa fety: Chemistry, Toxicology, and Technology, Georg Thieme Publ, Stuttgart, West Germany, pp. 9–28.

HSDB, 2002 [Hazardous Substances Data Bank]. Na tional Library of Medicine. Last update: 6- 8-2002. Access date: 6-5-2003. http://toxnet .nlm.nih.gov/cgibin/sis/htmlgen?HSDB.

Kirkwood, J. 1983. A limit to metabolizable ener gy intake in mammals and birds. Comp. Biochem. Physiol. 75A:1-3.

Martin, C. M., H. S. Zim & A. C. Nelson, 1951. American Wildlife and Plants - A Guide to Wildlife Food Habits, Dover Publ. Inc., New York.

Merritt, R. W. and K. W. Cummins, eds. 1984. An Introduction to the Aquatic Insects of North America 2nd ed. Kendall/Hunt Publishing Company, Dubuque, Idaho. 722 pp.

Mineau, P., B. Jobin and A. Baril. 1994. A criti que of the avian 5-day dietary test (LC50) as the78 

### basis of avian risk assessment. Techni cal Report No. 215, Hea dquarters, Canadian Wildlife Service, Hull, Quebec. p. 23.

NatureServe. 2005. NatureServe Explorer: An onlin e encyclopedia of lif e [web application]. Version 4.5. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer

. Syracuse Research Corporation. 2006. Surface Water Scenario Development for the Pesticide Root Zone Model (PRZM) for Modeling Pe sticide Exposure in Outdoor Nurseries: Supplement to Metadata. GSA Contract No. GS-00F-0019L, Report No. SRC TR-06- 081, North Syracuse, NY.

Tomlin CDS (ed) (2000) The Pesticide Manual, 12 th 

### Edition. British Crop Protection Council, UK.

Uesugi Y, Ueji M, Koshioka M (e d) (1997) Pesticide Data Book, 3 rd 

### Edition. Soft Science Publications, Tokyo, Japan.

Urban D.J. and N.J. Cook. 1986. Hazard Eval uation Division Standard Evaluation Procedure Ecological Risk Assessment . EPA 540/9-85-001. U.S. Environmental Protection Agency, Office of Pesticide Programs, Washington, DC.

USDA Crop Profiles. http://www.ipmcenters.org/cropprofiles/CP_form.cfm

USEPA 1993. Wildlife Exposure Factors Ha ndbook. Volume I of II. EPA/600/R-93/187a. Office of Research and De velopment, Washington, D. C. 20460. EPA/600/R-93/187a.

USEPA 1998. Guidance for Ecological Risk Assessment. Risk Assessment Forum. EPA/630/R-95/002F, April 1998.

USEPA 2002. Guidance for Selecting Input Paramete rs in Modeling the Environmental Fate and Transport of Pesticides Input Parameter Guidance. Version II February 28, 2002. U.S. Environmental Protection Agency, Office of Pe sticide Programs, Environmental Fate and Effects Division.

USEPA 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs. Office of Prevention, Pesticides, and Toxic Substances. Office of Pesticide Programs. Washington, D.C. January 23, 2004.79 

### APPENDIX A: Status of Fate and Ec ological Effects Data Requirements

Table A-1: Environmental Fate Data Requirements for Imazosulfuron

Guideline # Data Requirement MRID #s Study Classification

161-1 835.212 Hydrolysis 473051-19 Acceptable

161-2 835.224 Photodegradation in Water 473051-20 Acceptable

161-3 835.241 Photodegradation on Soil 473051-21 Supplemental

161-4 835.237 Photodegradation in Air NA ---

162-1 835.41 Aerobic Soil Metabolism 473051-22 Supplemental

162-2 835.42 Anaerobic Soil Metabolism NA ---

162-3 835.44 Anaerobic Aquatic Metabolism 473051-23 Supplemental

162-4 835.43 Aerobic Aquatic Metabolism 476397-02 In review

163-1 835.1240 835.1230 LeachingAdsorption/Desorption 473051-17 Supplemental

163-1 835.1230 Adsorption/Desorption 473051-18 Supplemental

163-2 835.141 Laboratory Volatility NA ---

163-3 835.81 Field Volatility NA --- 164-1 835.61 Terrestrial Field Dissipation 473051-26 473051-27 Acceptable Acceptable

165-4 850.173 Accumulation in Fish 473052-02 Request for waiver

201-1 840.1100 Spray droplet Size Spectrum 473051-28 In review

1 Not Available.80 

### Table A-2 : Available Ecological Effects Data for Imazosulfuron

Guideline # Type of Study Formulation MRID Study Classification 71-1 850.2100 Avian Oral LD 50 Technical Technical

IPSN 473052-03 473052-04 477668-10 Acceptable Acceptable Supplemental 71-2 850.2200 Avian Dietary LC 50 Technical Technical

IPSN 473052-05 473052-06 477668-11 Acceptable Acceptable Acceptable 71-4 850.2300 Avian Reproduction Technical Technical Technical 473052-07 473052-08 476791-14 Acceptable Supplemental Supplemental 72-1 850.1075 Freshwater Fish LC 50 Technical Technical Technical Technical 473051-35 473051-36 473051-37 476791-11 Supplemental Acceptable Acceptable Acceptable 72-2 850.1010 Freshwater Invertebrate LC 50 Technical Technical 473051-30 473051-31 Invalid Acceptable 72-3(a) 850.1075 Estuarine/Marine Fish LC 50 Technical 473051-34 Acceptable 72-3(b) 850.1025 Estuarine/Marine Mollusk EC 50 Technical 473051-32 Acceptable

72-3(c) 850.1035 850.1045 Estuarine/Marine Shrimp LC 50 Technical 473051-33 Acceptable

72-4(a) 850.1400 Freshwater Fish Early Life Stage Technical 476791-14 Acceptable

72-4(b) 850.1300 850.1350 850.1300 Aquatic Invertebrate Lifecycle Technical 473052-01 Acceptable

OECD 219 Benthic Organisms (longterm sediment toxicity) IPSN 477821-03 Supplemental

72-5 850.1500 Freshwater Fish LifeCycle Technical Not submitted

123-1(a) 850.4225 Seed Germination/ Seedling Emergence Tier II V-10142 75WDG 473052-11 Acceptable

123-1(a) 850.4225 Vegetative Vigor Tier II V-10142 75WDG 473052-12 Acceptable

122-2 850.4400 Aquatic Plant (NonVascular) Tier 1&II Technical Technical Technical Technical 470532-14 470532-15 470532-16 470532-17 Acceptable Acceptable Supplemental

Acceptable 122-2 850.4400 Aquatic Plant (Vascular) Tier 2 Technical IPSN 476397-01 473052-13 Supplemental Acceptable

141-1 850.3020 Honey Bee Acute Oral and Contact LD 50 Technical Technical 473052-09 473052-10 Supplemental Supplemental

OECD 207 OECD 207 Acute Toxicity to Earthworms TGAI IPSN 477668-14 477668-12 Not available

ISO 11268-2 Chronic Toxicity to Earthworms IPSN 477668-13 Supplemental

141-2 850.3030 Honey Bee Residue on Foliage NA NA Not available

Non-guideline Acute Toxicity to Beetles IPSN IPSN 477668-05 477821-02 Supplemental Supplemental81 

### APPENDIX B: Calculations of Ha lf-life for total toxic residue

Aerobic Soil Metabolism (MRID 473051-1782 

### Aerobic Soil Metabolism (MRID 477668-01

-83 

### Aerobic Aquatic Metabolism (MRID 476397-02)84 

### Aerobic aquatic Metabolism (MRID 476791-0585 

### Anaerobic aquatic Metabolism (MRID 473051-23

### 86 Total Toxic Residue (Anane robic Aquatic Metabolism)

Days 0 100 200 300 400Total Toxic Residue (%)

0 20 40 60 80 100

y= -0.0324X +93.35, r 2 = 0.95

Calculated Half-life = 21.4 Days

Nonlinear Regression

Data Source: Data 1 in Notebook1 Equation: Exponential Decay, Single, 2 Parameter f = a*exp(-b*x)

R Rsqr Adj Rsqr Standard Error of Estimate

0.9739 0.9485 0.9472 8.5793

Coefficient Std. Error t P VIF

a 93.3543 2.3368 39.9501 <0.0001 1.4005 b 0.0324 0.0028 11.7346 <0.0001 1.4005

Analysis of Variance:

Uncorrected for the mean of the observations: DF SS MS Regression 2 164525.7142 82262.8571 Residual 42 3091.3858 73.6044 Total 44 167617.1000 3809.4795

Corrected for the mean of the observations: DF SS MS F P Regression 1 56892.8406 56892.8406 772.9541 <0.0001 Residual 42 3091.3858 73.6044 Total 43 59984.2264 1394.9820

### 87 Aquatic Photolysis (IM Ring)

### 88 Aquatic Photolysis (PM Ring)

Half life calculation for total system:

PM ring 32.66 Days IM Ring 4.72 Days 90th %ile 61.69 Days

### 89 APPENDIX C: PRZM E XAMS Output Files

This appendix documents the output of water column and pore water from PRZM / EXAMS simulations for each of five location/cr op scenarios: Florida/Turf, Tomato and Papper (ground application), Pennsylvani a Turf and Tomato. The settings for each model run are presented first, followed by the raw data sorted by year and sorted in descending order by EEC. Values represent the estimated environmental concentrations (EECs) in units of micrograms per liter ( μ g/L) or parts per billion (ppb). The 1-in -10 year summary statistics for each run are presented at the very end of the sorted results in the row assigned a probability level of 0.10.



## Concentrations in Water Column

FL Turf (0.67 lbs a.i x 2 ground applications)

stored as Turf_FL.out Chemical: Imazosulfuron PRZM environment: FLturfSTD.txt modified Tueday, 21 February 2006 at 15:38:26

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12834.dvf modified Tueday, 26 August 2008 at 06:14:18 Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 3.45 3.40 3.22 2.90 2.72 0.91 1962 2.03 2.01 1.93 1.83 1.76 1.49 1963 1.40 1.39 1.33 1.22 1.19 1.02 1964 4.68 4.64 4.43 4.08 3.88 1.84 1965 2.94 2.93 2.87 2.73 2.63 1.91 1966 2.80 2.76 2.62 2.37 2.22 1.36 1967 3.04 3.01 2.87 2.62 2.47 1.55 1968 3.47 3.42 3.26 2.95 2.76 1.84 1969 7.47 7.37 6.98 6.56 6.20 3.06 1970 4.61 4.58 4.50 4.30 4.15 2.80 1971 1.78 1.76 1.68 1.53 1.45 1.20 1972 7.10 7.00 6.63 5.95 5.55 2.32 1973 4.00 3.98 3.89 3.71 3.57 2.59 1974 3.07 3.04 2.90 2.68 2.58 1.64 1975 3.37 3.33 3.18 2.88 2.71 1.82 1976 3.14 3.11 2.96 2.70 2.56 1.83 1977 3.51 3.47 3.30 3.09 2.97 2.03 1978 2.17 2.15 2.11 2.02 1.96 1.67 1979 2.69 2.66 2.53 2.29 2.15 1.40 1980 1.64 1.62 1.59 1.52 1.46 1.21 1981 3.39 3.35 3.27 3.02 2.83 1.40 1982 2.12 2.11 2.06 1.97 1.89 1.42 1983 3.17 3.13 2.98 2.70 2.54 1.36 1984 1.93 1.92 1.89 1.81 1.74 1.44 1985 1.94 1.91 1.84 1.70 1.59 1.09 1986 1.22 1.20 1.16 1.13 1.10 0.94 1987 1.06 1.04 0.99 0.90 0.84 0.69 1988 1.07 1.06 1.02 0.94 0.88 0.60

### 90 1989 1.25 1.24 1.19 1.10 1.03 0.66 1990 2.30 2.27 2.15 1.92 1.79 1.02

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 7.47 7.37 6.98 6.56 6.20 3.06 0.06 7.10 7.00 6.63 5.95 5.55 2.80 0.10 4.68 4.64 4.50 4.30 4.15 2.59 0.13 4.61 4.58 4.43 4.08 3.88 2.32 0.16 4.00 3.98 3.89 3.71 3.57 2.03 0.19 3.51 3.47 3.30 3.09 2.97 1.91 0.23 3.47 3.42 3.27 3.02 2.83 1.84 0.26 3.45 3.40 3.26 2.95 2.76 1.84 0.29 3.39 3.35 3.22 2.90 2.72 1.83 0.32 3.37 3.33 3.18 2.88 2.71 1.82 0.35 3.17 3.13 2.98 2.73 2.63 1.67 0.39 3.14 3.11 2.96 2.70 2.58 1.64 0.42 3.07 3.04 2.90 2.70 2.56 1.55 0.45 3.04 3.01 2.87 2.68 2.54 1.49 0.48 2.94 2.93 2.87 2.62 2.47 1.44 0.52 2.80 2.76 2.62 2.37 2.22 1.42 0.55 2.69 2.66 2.53 2.29 2.15 1.40 0.58 2.30 2.27 2.15 2.02 1.96 1.40 0.61 2.17 2.15 2.11 1.97 1.89 1.36 0.65 2.12 2.11 2.06 1.92 1.79 1.36 0.68 2.03 2.01 1.93 1.83 1.76 1.21 0.71 1.94 1.92 1.89 1.81 1.74 1.20 0.74 1.93 1.91 1.84 1.70 1.59 1.09 0.77 1.78 1.76 1.68 1.53 1.46 1.02 0.81 1.64 1.62 1.59 1.52 1.45 1.02 0.84 1.40 1.39 1.33 1.22 1.19 0.94 0.87 1.25 1.24 1.19 1.13 1.10 0.91 0.90 1.22 1.20 1.16 1.10 1.03 0.69 0.94 1.07 1.06 1.02 0.94 0.88 0.66 0.97 1.06 1.04 0.99 0.90 0.84 0.60

0.10 4.67 4.64 4.49 4.28 4.12 2.56 Average of yearly averages: 1.54

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Turf_FL Metfile: w12834.dvf PRZM scenario: FLturfSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife

### 91 Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.75 kg/ha Application Efficiency: A PPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 8-Feb dd/mm or dd/mmm or dd-mm or dd-mmm Interval 1 interval 21 days Set to 0 or delete line for single app. app. rate 1 apprate kg/ha Record 17: FILTRA IPSCND 3 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)



### PA Turf (0.67 lbs a.i x 2 ground applications)

stored as Turf_PA.out Chemical: Imazosulfuron PRZM environment: PAturfSTD.txt modified Thuday, 23 February 2006 at 18:55:08

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12834.dvf modified Tueday, 26 August 2008 at 06:14:18 Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 8.29 8.18 7.74 6.96 6.52 2.16 1962 5.21 5.15 4.91 4.75 4.52 3.71 1963 4.21 4.15 3.97 3.64 3.46 2.72 1964 10.26 10.17 9.7 9.06 8.6 4.37 1965 6.46 6.43 6.29 6 5.77 4.05 1966 2.48 2.47 2.42 2.31 2.22 1.83 1967 4.38 4.33 4.12 3.75 3.54 1.8 1968 6.9 6.83 6.5 5.87 5.5 3.12 1969 8.07 7.97 7.65 6.96 6.57 4.04 1970 5.39 5.36 5.26 5.03 4.85 3.25 1971 3.97 3.92 3.72 3.38 3.18 1.86 1972 19.27 19.02 18.01 16.15 15.09 6.02 1973 10.9 10.84 10.6 10.1 9.71 6.85 1974 8.21 8.11 7.76 7.29 6.98 4.34 1975 6.58 6.5 6.19 5.64 5.31 4.2 1976 6.64 6.56 6.24 5.69 5.39 3.64 1977 6.5 6.42 6.09 5.54 5.24 3.78 1978 5.12 5.06 4.94 4.68 4.6 3.47 1979 6.57 6.48 6.24 5.68 5.34 3.36 1980 4.05 4.03 3.95 3.77 3.63 2.77 1981 8.81 8.7 8.38 7.79 7.32 3.33 1982 5.49 5.46 5.35 5.09 4.88 3.5 1983 7.18 7.1 6.79 6.21 5.85 3.16

### 92 1984 4.63 4.58 4.39 4.18 4.03 3.4 1985 4.39 4.34 4.19 3.9 3.66 2.58 1986 2.74 2.73 2.67 2.54 2.45 2.05 1987 1.81 1.8 1.77 1.69 1.62 1.36 1988 2.27 2.24 2.13 1.94 1.83 1.17 1989 1.7 1.69 1.63 1.51 1.42 1.13 1990 2.05 2.02 1.92 1.77 1.7 1.16

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 19.27 19.02 18.01 16.15 15.09 6.85 0.06 10.9 10.84 10.6 10.1 9.71 6.02 0.1 10.26 10.17 9.7 9.06 8.6 4.37 0.13 8.81 8.7 8.38 7.79 7.32 4.34 0.16 8.29 8.18 7.76 7.29 6.98 4.2 0.19 8.21 8.11 7.74 6.96 6.57 4.05 0.23 8.07 7.97 7.65 6.96 6.52 4.04 0.26 7.18 7.1 6.79 6.21 5.85 3.78 0.29 6.9 6.83 6.5 6 5.77 3.71 0.32 6.64 6.56 6.29 5.87 5.5 3.64 0.35 6.58 6.5 6.24 5.69 5.39 3.5 0.39 6.57 6.48 6.24 5.68 5.34 3.47 0.42 6.5 6.43 6.19 5.64 5.31 3.4 0.45 6.46 6.42 6.09 5.54 5.24 3.36 0.48 5.49 5.46 5.35 5.09 4.88 3.33 0.52 5.39 5.36 5.26 5.03 4.85 3.25 0.55 5.21 5.15 4.94 4.75 4.6 3.16 0.58 5.12 5.06 4.91 4.68 4.52 3.12 0.61 4.63 4.58 4.39 4.18 4.03 2.77 0.65 4.39 4.34 4.19 3.9 3.66 2.72 0.68 4.38 4.33 4.12 3.77 3.63 2.58 0.71 4.21 4.15 3.97 3.75 3.54 2.16 0.74 4.05 4.03 3.95 3.64 3.46 2.05 0.77 3.97 3.92 3.72 3.38 3.18 1.86 0.81 2.74 2.73 2.67 2.54 2.45 1.83 0.84 2.48 2.47 2.42 2.31 2.22 1.8 0.87 2.27 2.24 2.13 1.94 1.83 1.36 0.9 2.05 2.02 1.92 1.77 1.7 1.17 0.94 1.81 1.8 1.77 1.69 1.62 1.16 0.97 1.7 1.69 1.63 1.51 1.42 1.13

0.1 10.11 10.02 9.57 8.93 8.48 4.37 Average of yearly averages: 3.14

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Turf_PA Metfile: w12834.dvf PRZM scenario: PAturfSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr

### 93 Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.75 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 8-Apr dd/mm or dd/mmm or dd-mm or dd-mmm Interval 1 interval 21 days Set to 0 or delete line for single app. app. rate 1 apprate kg/ha Record 17: FILTRA IPSCND 3 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)



### FL Tomato (0.30 lbs a.i ground applications)

stored as Tomato_FL.out Chemical: Imazosulfuron PRZM environment: FLtomatoSTD_V2.txt modified Tueday, 20 May 2008 at 12:00:14 EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12844.dvf modified Tueday, 26 August 2008 at 06:14:22 Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 2.90 2.86 2.73 2.43 2.25 0.78 1962 4.33 4.27 4.15 3.76 3.49 1.85 1963 2.39 2.36 2.27 2.12 1.99 1.65 1964 2.57 2.53 2.42 2.18 2.03 1.27 1965 1.40 1.39 1.36 1.27 1.21 0.97 1966 9.29 9.16 8.72 7.82 7.24 2.97 1967 8.18 8.07 7.65 6.88 6.40 4.21 1968 13.61 13.42 12.72 11.53 10.73 5.65 1969 8.57 8.48 8.11 7.40 6.92 5.49 1970 4.47 4.45 4.34 4.12 3.95 3.11 1971 2.23 2.21 2.16 2.03 1.94 1.45 1972 0.96 0.95 0.92 0.86 0.81 0.65 1973 2.60 2.56 2.46 2.23 2.08 0.96 1974 3.50 3.45 3.33 3.02 2.81 1.54 1975 1.80 1.78 1.72 1.60 1.52 1.14 1976 7.37 7.27 6.90 6.23 5.87 2.45 1977 4.06 4.01 3.88 3.63 3.47 2.86 1978 2.33 2.30 2.19 2.00 1.92 1.57

### 94 1979 1.81 1.79 1.74 1.60 1.54 1.12 1980 4.80 4.74 4.61 4.21 3.92 1.77 1981 5.80 5.72 5.51 4.94 4.58 2.74 1982 3.95 3.89 3.69 3.31 3.07 2.34 1983 4.95 4.88 4.64 4.17 3.89 2.20 1984 5.36 5.31 5.16 4.78 4.49 2.64 1985 4.98 4.91 4.70 4.23 3.94 2.64 1986 2.43 2.42 2.36 2.22 2.11 1.61 1987 3.13 3.09 2.96 2.74 2.66 1.45 1988 6.57 6.48 6.11 5.42 5.04 2.53 1989 5.74 5.69 5.45 4.91 4.55 2.92 1990 11.36 11.21 10.72 9.54 8.80 4.33

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 13.61 13.42 12.72 11.53 10.73 5.65 0.06 11.36 11.21 10.72 9.54 8.80 5.49 0.10 9.29 9.16 8.72 7.82 7.24 4.33 0.13 8.57 8.48 8.11 7.40 6.92 4.21 0.16 8.18 8.07 7.65 6.88 6.40 3.11 0.19 7.37 7.27 6.90 6.23 5.87 2.97 0.23 6.57 6.48 6.11 5.42 5.04 2.92 0.26 5.80 5.72 5.51 4.94 4.58 2.86 0.29 5.74 5.69 5.45 4.91 4.55 2.74 0.32 5.36 5.31 5.16 4.78 4.49 2.64 0.35 4.98 4.91 4.70 4.23 3.95 2.64 0.39 4.95 4.88 4.64 4.21 3.94 2.53 0.42 4.80 4.74 4.61 4.17 3.92 2.45 0.45 4.47 4.45 4.34 4.12 3.89 2.34 0.48 4.33 4.27 4.15 3.76 3.49 2.20 0.52 4.06 4.01 3.88 3.63 3.47 1.85 0.55 3.95 3.89 3.69 3.31 3.07 1.77 0.58 3.50 3.45 3.33 3.02 2.81 1.65 0.61 3.13 3.09 2.96 2.74 2.66 1.61 0.65 2.90 2.86 2.73 2.43 2.25 1.57 0.68 2.60 2.56 2.46 2.23 2.11 1.54 0.71 2.57 2.53 2.42 2.22 2.08 1.45 0.74 2.43 2.42 2.36 2.18 2.03 1.45 0.77 2.39 2.36 2.27 2.12 1.99 1.27 0.81 2.33 2.30 2.19 2.03 1.94 1.14 0.84 2.23 2.21 2.16 2.00 1.92 1.12 0.87 1.81 1.79 1.74 1.60 1.54 0.97 0.90 1.80 1.78 1.72 1.60 1.52 0.96 0.94 1.40 1.39 1.36 1.27 1.21 0.78 0.97 0.96 0.95 0.92 0.86 0.81 0.65

0.10 9.22 9.10 8.66 7.78 7.21 4.32 Average of yearly averages: 2.30

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Tomato_FL Metfile: w12844.dvf PRZM scenario: FLtomatoSTD_V2.txt EXAMS environment file: pond298.exv

### 95 Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.34 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 8-Feb dd/mm or dd/mmm or dd-mm or dd-mmm Record 17: FILTRA IPSCND 3 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)



### PA Tomato (0.30 lbs a.i ground applications)

stored as Tomato_PA.out Chemical: Imazosulfuron PRZM environment: PAtomatoSTD.txt modified Tueday, 29 May 2007 at 14:01:58

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w14751.dvf modified Tueday, 26 August 2008 at 06:15:00 Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.24 0.24 0.23 0.21 0.20 0.12 1962 0.50 0.50 0.48 0.47 0.46 0.30 1963 0.42 0.41 0.41 0.40 0.39 0.30 1964 1.12 1.11 1.07 0.98 0.97 0.61 1965 0.82 0.82 0.79 0.78 0.75 0.59 1966 1.02 1.01 0.98 0.91 0.86 0.61 1967 1.12 1.11 1.08 1.01 0.96 0.68 1968 2.22 2.21 2.13 2.05 1.99 1.23 1969 1.23 1.22 1.19 1.15 1.10 0.97 1970 0.90 0.89 0.87 0.84 0.81 0.65 1971 0.94 0.93 0.90 0.84 0.80 0.56 1972 1.22 1.21 1.17 1.11 1.05 0.70 1973 1.40 1.39 1.36 1.31 1.25 0.84 1974 2.00 1.98 1.94 1.81 1.71 1.09 1975 2.67 2.64 2.57 2.42 2.30 1.51

### 96 1976 1.82 1.81 1.78 1.67 1.57 1.24 1977 1.70 1.69 1.64 1.53 1.46 1.06 1978 1.78 1.77 1.72 1.59 1.50 1.04 1979 1.40 1.39 1.35 1.26 1.20 0.92 1980 1.73 1.72 1.69 1.58 1.51 1.03 1981 0.90 0.90 0.88 0.85 0.82 0.70 1982 1.47 1.46 1.41 1.32 1.24 0.82 1983 3.09 3.06 2.97 2.86 2.72 1.67 1984 1.78 1.77 1.72 1.62 1.58 1.31 1985 3.17 3.15 3.05 2.90 2.78 1.78 1986 2.04 2.03 1.97 1.83 1.75 1.48 1987 1.57 1.56 1.52 1.46 1.42 1.11 1988 1.28 1.27 1.25 1.19 1.12 0.85 1989 3.58 3.55 3.49 3.26 3.07 1.80 1990 2.59 2.57 2.48 2.39 2.28 1.75

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 3.58 3.55 3.49 3.26 3.07 1.80 0.06 3.17 3.15 3.05 2.90 2.78 1.78 0.10 3.09 3.06 2.97 2.86 2.72 1.75 0.13 2.67 2.64 2.57 2.42 2.30 1.67 0.16 2.59 2.57 2.48 2.39 2.28 1.51 0.19 2.22 2.21 2.13 2.05 1.99 1.48 0.23 2.04 2.03 1.97 1.83 1.75 1.31 0.26 2.00 1.98 1.94 1.81 1.71 1.24 0.29 1.82 1.81 1.78 1.67 1.58 1.23 0.32 1.78 1.77 1.72 1.62 1.57 1.11 0.35 1.78 1.77 1.72 1.59 1.51 1.09 0.39 1.73 1.72 1.69 1.58 1.50 1.06 0.42 1.70 1.69 1.64 1.53 1.46 1.04 0.45 1.57 1.56 1.52 1.46 1.42 1.03 0.48 1.47 1.46 1.41 1.32 1.25 0.97 0.52 1.40 1.39 1.36 1.31 1.24 0.92 0.55 1.40 1.39 1.35 1.26 1.20 0.85 0.58 1.28 1.27 1.25 1.19 1.12 0.84 0.61 1.23 1.22 1.19 1.15 1.10 0.82 0.65 1.22 1.21 1.17 1.11 1.05 0.70 0.68 1.12 1.11 1.08 1.01 0.97 0.70 0.71 1.12 1.11 1.07 0.98 0.96 0.68 0.74 1.02 1.01 0.98 0.91 0.86 0.65 0.77 0.94 0.93 0.90 0.85 0.82 0.61 0.81 0.90 0.90 0.88 0.84 0.81 0.61 0.84 0.90 0.89 0.87 0.84 0.80 0.59 0.87 0.82 0.82 0.79 0.78 0.75 0.56 0.90 0.50 0.50 0.48 0.47 0.46 0.30 0.94 0.42 0.41 0.41 0.40 0.39 0.30 0.97 0.24 0.24 0.23 0.21 0.20 0.12

0.10 3.04 3.02 2.93 2.82 2.68 1.74 Average of yearly averages: 0.98

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Tomato_PA

### 97 Metfile: w14751.dvf PRZM scenario: PAtomatoSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.34 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 23-04 dd/mm or dd/mmm or dd-mm or dd-mmm Record 17: FILTRA IPSCND 3 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)



### FL Pepper (0.30 lbs a.i ground applications)

stored as Pepper_FL.out Chemical: Imazosulfuron PRZM environment: FLpeppersSTD.txt modified Thuday, 24 May 2007 at 10:44:22

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12844.dvf modified Tueday, 26 August 2008 at 06:14:22 Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 4.23 4.17 3.98 3.55 3.29 1.13 1962 3.95 3.90 3.75 3.49 3.25 2.04 1963 2.22 2.20 2.14 2.02 1.93 1.53 1964 5.40 5.32 5.08 4.57 4.25 1.90 1965 2.92 2.90 2.82 2.65 2.52 1.83 1966 2.14 2.11 2.05 1.86 1.74 1.11 1967 9.45 9.32 8.81 7.88 7.31 3.05 1968 18.63 18.37 17.46 16.05 14.96 7.31 1969 12.32 12.17 11.77 10.65 9.89 7.70 1970 6.55 6.51 6.36 6.04 5.78 4.52 1971 3.27 3.25 3.17 2.98 2.85 2.05

### 98 1972 1.28 1.27 1.23 1.14 1.09 0.85 1973 2.78 2.75 2.63 2.51 2.35 1.09 1974 3.72 3.67 3.54 3.28 3.07 1.69 1975 2.01 2.00 1.94 1.80 1.70 1.27 1976 10.57 10.43 9.90 8.91 8.37 3.38 1977 5.62 5.59 5.46 5.19 4.95 3.81 1978 2.74 2.72 2.65 2.51 2.41 1.81 1979 2.68 2.65 2.57 2.32 2.22 1.37 1980 6.02 5.93 5.80 5.25 4.88 2.30 1981 12.29 12.12 11.64 10.44 9.68 4.75 1982 9.63 9.50 9.02 8.07 7.47 5.25 1983 8.07 7.96 7.61 6.82 6.33 4.19 1984 7.45 7.38 7.16 6.64 6.23 3.94 1985 4.09 4.06 3.97 3.75 3.57 2.62 1986 2.77 2.74 2.62 2.37 2.20 1.48 1987 1.93 1.90 1.83 1.66 1.55 1.11 1988 9.79 9.65 9.10 8.05 7.46 3.05 1989 4.86 4.82 4.67 4.35 4.13 3.03 1990 11.53 11.36 10.85 9.70 8.95 3.90

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 18.63 18.37 17.46 16.05 14.96 7.70 0.06 12.32 12.17 11.77 10.65 9.89 7.31 0.10 12.29 12.12 11.64 10.44 9.68 5.25 0.13 11.53 11.36 10.85 9.70 8.95 4.75 0.16 10.57 10.43 9.90 8.91 8.37 4.52 0.19 9.79 9.65 9.10 8.07 7.47 4.19 0.23 9.63 9.50 9.02 8.05 7.46 3.94 0.26 9.45 9.32 8.81 7.88 7.31 3.90 0.29 8.07 7.96 7.61 6.82 6.33 3.81 0.32 7.45 7.38 7.16 6.64 6.23 3.38 0.35 6.55 6.51 6.36 6.04 5.78 3.05 0.39 6.02 5.93 5.80 5.25 4.95 3.05 0.42 5.62 5.59 5.46 5.19 4.88 3.03 0.45 5.40 5.32 5.08 4.57 4.25 2.62 0.48 4.86 4.82 4.67 4.35 4.13 2.30 0.52 4.23 4.17 3.98 3.75 3.57 2.05 0.55 4.09 4.06 3.97 3.55 3.29 2.04 0.58 3.95 3.90 3.75 3.49 3.25 1.90 0.61 3.72 3.67 3.54 3.28 3.07 1.83 0.65 3.27 3.25 3.17 2.98 2.85 1.81 0.68 2.92 2.90 2.82 2.65 2.52 1.69 0.71 2.78 2.75 2.65 2.51 2.41 1.53 0.74 2.77 2.74 2.63 2.51 2.35 1.48 0.77 2.74 2.72 2.62 2.37 2.22 1.37 0.81 2.68 2.65 2.57 2.32 2.20 1.27 0.84 2.22 2.20 2.14 2.02 1.93 1.13 0.87 2.14 2.11 2.05 1.86 1.74 1.11 0.90 2.01 2.00 1.94 1.80 1.70 1.11 0.94 1.93 1.90 1.83 1.66 1.55 1.09 0.97 1.28 1.27 1.23 1.14 1.09 0.85

0.10 12.21 12.04 11.56 10.37 9.61 5.20 Average of yearly averages: 2.83

### 99 Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Pepper_FL Metfile: w12844.dvf PRZM scenario: FLpeppersSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.34 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 8-Sep dd/mm or dd/mmm or dd-mm or dd-mmm Record 17: FILTRA IPSCND 3 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)

### 100 

## Concentrations in Pore Water

FL Turf (0.67 lbs a.i x 2 ground applications)

stored as Turf_FLben.out Chemical: Imazosulfuron PRZM environment: FLturfSTD.txt modified Tueday, 21 February 2006 at 15:38:26

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12834.dvf modified Tueday, 26 August 2008 at 06:14:18 Benthic segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 1.43 1.43 1.43 1.40 1.35 0.41 1962 1.43 1.43 1.43 1.40 1.36 1.01 1963 0.98 0.98 0.97 0.95 0.92 0.68 1964 2.15 2.15 2.15 2.13 2.07 1.00 1965 2.14 2.14 2.13 2.09 2.04 1.38 1966 1.23 1.23 1.23 1.21 1.19 0.83 1967 1.41 1.41 1.41 1.39 1.32 0.97 1968 1.57 1.57 1.57 1.54 1.49 1.17 1969 3.40 3.40 3.38 3.28 3.15 1.74 1970 3.41 3.41 3.40 3.36 3.27 2.03 1971 1.13 1.13 1.12 1.09 1.06 0.80 1972 2.88 2.88 2.88 2.83 2.73 1.21 1973 2.87 2.87 2.86 2.82 2.75 1.82 1974 1.52 1.52 1.52 1.48 1.41 0.99 1975 1.54 1.54 1.53 1.49 1.42 1.14 1976 1.55 1.55 1.55 1.53 1.48 1.18 1977 1.62 1.62 1.62 1.62 1.60 1.27 1978 1.62 1.62 1.62 1.60 1.56 1.12 1979 1.20 1.20 1.20 1.18 1.15 0.86 1980 1.20 1.20 1.19 1.18 1.15 0.82 1981 1.57 1.57 1.57 1.52 1.46 0.80 1982 1.57 1.57 1.57 1.52 1.47 1.00 1983 1.44 1.44 1.44 1.42 1.37 0.79 1984 1.44 1.44 1.44 1.41 1.38 1.00 1985 0.87 0.87 0.87 0.85 0.83 0.68 1986 0.87 0.87 0.87 0.85 0.83 0.62 1987 0.61 0.61 0.61 0.60 0.59 0.46 1988 0.48 0.48 0.48 0.48 0.47 0.38 1989 0.66 0.66 0.65 0.61 0.55 0.39 1990 0.92 0.92 0.92 0.91 0.90 0.59

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 3.41 3.41 3.40 3.36 3.27 2.03 0.06 3.40 3.40 3.38 3.28 3.15 1.82 0.10 2.88 2.88 2.88 2.83 2.75 1.74 0.13 2.87 2.87 2.86 2.82 2.73 1.38 0.16 2.15 2.15 2.15 2.13 2.07 1.27 0.19 2.14 2.14 2.13 2.09 2.04 1.21 0.23 1.62 1.62 1.62 1.62 1.60 1.18 0.26 1.62 1.62 1.62 1.60 1.56 1.17

### 101 0.29 1.57 1.57 1.57 1.54 1.49 1.14 0.32 1.57 1.57 1.57 1.53 1.48 1.12 0.35 1.57 1.57 1.57 1.52 1.47 1.01 0.39 1.55 1.55 1.55 1.52 1.46 1.00 0.42 1.54 1.54 1.53 1.49 1.42 1.00 0.45 1.52 1.52 1.52 1.48 1.41 1.00 0.48 1.44 1.44 1.44 1.42 1.38 0.99 0.52 1.44 1.44 1.44 1.41 1.37 0.97 0.55 1.43 1.43 1.43 1.40 1.36 0.86 0.58 1.43 1.43 1.43 1.40 1.35 0.83 0.61 1.41 1.41 1.41 1.39 1.32 0.82 0.65 1.23 1.23 1.23 1.21 1.19 0.80 0.68 1.20 1.20 1.20 1.18 1.15 0.80 0.71 1.20 1.20 1.19 1.18 1.15 0.79 0.74 1.13 1.13 1.12 1.09 1.06 0.68 0.77 0.98 0.98 0.97 0.95 0.92 0.68 0.81 0.92 0.92 0.92 0.91 0.90 0.62 0.84 0.87 0.87 0.87 0.85 0.83 0.59 0.87 0.87 0.87 0.87 0.85 0.83 0.46 0.90 0.66 0.66 0.65 0.61 0.59 0.41 0.94 0.61 0.61 0.61 0.60 0.55 0.39 0.97 0.48 0.48 0.48 0.48 0.47 0.38

0.10 2.88 2.88 2.87 2.83 2.74 1.70 Average of yearly averages: 0.97

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Turf_FL Metfile: w12834.dvf PRZM scenario: FLturfSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.75 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 8-Feb dd/mm or dd/mmm or dd-mm or dd-mmm Interval 1 interval 21 days Set to 0 or delete line for single app. app. rate 1 apprate kg/ha Record 17: FILTRA IPSCND 3

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



### PA Turf (0.67 lbs a.i x 2 ground applications)

stored as Turf_PAben.out Chemical: Imazosulfuron PRZM environment: PAturfSTD.txt modified Thuday, 23 February 2006 at 18:55:08

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12834.dvf modified Tueday, 26 August 2008 at 06:14:18 Benthic segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 3.44 3.44 3.43 3.36 3.21 0.96 1962 3.44 3.44 3.44 3.36 3.27 2.48 1963 2.66 2.65 2.63 2.58 2.50 1.81 1964 4.74 4.74 4.74 4.71 4.58 2.47 1965 4.70 4.70 4.69 4.60 4.48 2.95 1966 1.88 1.88 1.87 1.82 1.77 1.27 1967 1.99 1.99 1.98 1.93 1.81 1.05 1968 3.10 3.10 3.09 3.01 2.89 1.89 1969 3.88 3.87 3.83 3.65 3.39 2.50 1970 3.91 3.91 3.91 3.87 3.78 2.35 1971 1.74 1.74 1.73 1.71 1.64 1.13 1972 7.83 7.83 7.83 7.70 7.43 3.08 1973 7.80 7.80 7.79 7.69 7.47 4.87 1974 4.10 4.10 4.10 4.01 3.85 2.62 1975 4.10 4.09 4.04 3.89 3.75 2.76 1976 3.17 3.17 3.17 3.07 2.91 2.34 1977 3.21 3.21 3.21 3.18 3.09 2.43 1978 2.96 2.96 2.96 2.93 2.87 2.23 1979 2.97 2.97 2.97 2.92 2.82 2.07 1980 2.97 2.97 2.96 2.92 2.84 1.94 1981 4.06 4.05 4.04 3.92 3.75 1.85 1982 4.06 4.05 4.04 3.94 3.80 2.50 1983 3.33 3.33 3.33 3.27 3.17 1.85 1984 3.33 3.33 3.33 3.27 3.18 2.33 1985 2.18 2.18 2.18 2.15 2.08 1.64 1986 2.01 2.01 2.00 1.96 1.90 1.38 1987 1.29 1.29 1.29 1.28 1.25 0.92 1988 1.04 1.04 1.04 1.02 0.99 0.72 1989 1.04 1.04 1.02 0.99 0.95 0.72 1990 0.93 0.93 0.93 0.92 0.89 0.71

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 7.83 7.83 7.83 7.70 7.47 4.87 0.06 7.80 7.80 7.79 7.69 7.43 3.08 0.10 4.74 4.74 4.74 4.71 4.58 2.95

### 103 0.13 4.70 4.70 4.69 4.60 4.48 2.76 0.16 4.10 4.10 4.10 4.01 3.85 2.62 0.19 4.10 4.09 4.04 3.94 3.80 2.50 0.23 4.06 4.05 4.04 3.92 3.78 2.50 0.26 4.06 4.05 4.04 3.89 3.75 2.48 0.29 3.91 3.91 3.91 3.87 3.75 2.47 0.32 3.88 3.87 3.83 3.65 3.39 2.43 0.35 3.44 3.44 3.44 3.36 3.27 2.35 0.39 3.44 3.44 3.43 3.36 3.21 2.34 0.42 3.33 3.33 3.33 3.27 3.18 2.33 0.45 3.33 3.33 3.33 3.27 3.17 2.23 0.48 3.21 3.21 3.21 3.18 3.09 2.07 0.52 3.17 3.17 3.17 3.07 2.91 1.94 0.55 3.10 3.10 3.09 3.01 2.89 1.89 0.58 2.97 2.97 2.97 2.93 2.87 1.85 0.61 2.97 2.97 2.96 2.92 2.84 1.85 0.65 2.96 2.96 2.96 2.92 2.82 1.81 0.68 2.66 2.65 2.63 2.58 2.50 1.64 0.71 2.18 2.18 2.18 2.15 2.08 1.38 0.74 2.01 2.01 2.00 1.96 1.90 1.27 0.77 1.99 1.99 1.98 1.93 1.81 1.13 0.81 1.88 1.88 1.87 1.82 1.77 1.05 0.84 1.74 1.74 1.73 1.71 1.64 0.96 0.87 1.29 1.29 1.29 1.28 1.25 0.92 0.90 1.04 1.04 1.04 1.02 0.99 0.72 0.94 1.04 1.04 1.02 0.99 0.95 0.72 0.97 0.93 0.93 0.93 0.92 0.89 0.71

0.10 4.74 4.74 4.73 4.70 4.57 2.93 Average of yearly averages: 1.99

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Turf_PA Metfile: w12834.dvf PRZM scenario: PAturfSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.75 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond

### 104 Application Date Date 8-Apr dd/mm or dd/mmm or dd-mm or dd-mmm Interval 1 interval 21 days Set to 0 or delete line for single app. app. rate 1 apprate kg/ha Record 17: FILTRA IPSCND 3 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)



### FL Tomato (0.30 lbs a.i ground applications)

stored as Tomato_FLben.out Chemical: Imazosulfuron PRZM environment: FLtomatoSTD_V2.txt modified Tueday, 20 May 2008 at 12:00:14

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12844.dvf modified Tueday, 26 August 2008 at 06:14:22

Benthic segment concentrations (ppb)

Year Peak 96 hr 21 Da y 60 Day 90 Day Yearly

1961 1.05 1.05 1.05 1.04 1.03 0.34 1962 1.66 1.66 1.66 1.66 1.65 1.03 1963 1.65 1.64 1.61 1.55 1.48 1.07 1964 1.03 1.03 1.03 1.02 1.01 0.76 1965 0.97 0.97 0.96 0.93 0.89 0.63 1966 3.43 3.43 3.42 3.40 3.39 1.45 1967 3.34 3.33 3.26 3.18 3.15 2.55 1968 5.31 5.31 5.31 5.28 5.24 3.19 1969 5.19 5.17 5.09 4.90 4.75 3.55 1970 3.30 3.29 3.26 3.16 3.04 2.07 1971 1.61 1.61 1.59 1.52 1.46 0.98 1972 0.66 0.66 0.64 0.61 0.59 0.41 1973 0.98 0.98 0.98 0.97 0.96 0.49 1974 1.34 1.34 1.34 1.33 1.32 0.86 1975 1.28 1.27 1.24 1.16 1.10 0.75 1976 2.89 2.89 2.88 2.86 2.83 1.22 1977 2.81 2.81 2.80 2.74 2.63 1.86 1978 1.57 1.57 1.55 1.51 1.46 1.02 1979 0.92 0.92 0.91 0.89 0.86 0.69 1980 1.92 1.92 1.92 1.91 1.87 0.93 1981 2.28 2.28 2.28 2.27 2.24 1.61 1982 2.24 2.23 2.19 2.08 1.97 1.46 1983 1.88 1.88 1.88 1.87 1.85 1.26 1984 2.21 2.21 2.21 2.20 2.17 1.54 1985 2.06 2.06 2.05 2.00 1.92 1.59 1986 1.73 1.73 1.71 1.64 1.57 1.06 1987 1.37 1.37 1.37 1.36 1.34 0.78 1988 2.39 2.39 2.38 2.36 2.34 1.37 1989 2.28 2.27 2.22 2.14 2.13 1.73 1990 4.09 4.09 4.08 4.05 4.01 2.27

### 105 Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 5.31 5.31 5.31 5.28 5.24 3.55 0.06 5.19 5.17 5.09 4.90 4.75 3.19 0.10 4.09 4.09 4.08 4.05 4.01 2.55 0.13 3.43 3.43 3.42 3.40 3.39 2.27 0.16 3.34 3.33 3.26 3.18 3.15 2.07 0.19 3.30 3.29 3.26 3.16 3.04 1.86 0.23 2.89 2.89 2.88 2.86 2.83 1.73 0.26 2.81 2.81 2.80 2.74 2.63 1.61 0.29 2.39 2.39 2.38 2.36 2.34 1.59 0.32 2.28 2.28 2.28 2.27 2.24 1.54 0.35 2.28 2.27 2.22 2.20 2.17 1.46 0.39 2.24 2.23 2.21 2.14 2.13 1.45 0.42 2.21 2.21 2.19 2.08 1.97 1.37 0.45 2.06 2.06 2.05 2.00 1.92 1.26 0.48 1.92 1.92 1.92 1.91 1.87 1.22 0.52 1.88 1.88 1.88 1.87 1.85 1.07 0.55 1.73 1.73 1.71 1.66 1.65 1.06 0.58 1.66 1.66 1.66 1.64 1.57 1.03 0.61 1.65 1.64 1.61 1.55 1.48 1.02 0.65 1.61 1.61 1.59 1.52 1.46 0.98 0.68 1.57 1.57 1.55 1.51 1.46 0.93 0.71 1.37 1.37 1.37 1.36 1.34 0.86 0.74 1.34 1.34 1.34 1.33 1.32 0.78 0.77 1.28 1.27 1.24 1.16 1.10 0.76 0.81 1.05 1.05 1.05 1.04 1.03 0.75 0.84 1.03 1.03 1.03 1.02 1.01 0.69 0.87 0.98 0.98 0.98 0.97 0.96 0.63 0.90 0.97 0.97 0.96 0.93 0.89 0.49 0.94 0.92 0.92 0.91 0.89 0.86 0.41 0.97 0.66 0.66 0.64 0.61 0.59 0.34

0.10 4.03 4.02 4.01 3.99 3.95 2.52 Average of yearly averages: 1.35

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Tomato_FL Metfile: w12844.dvf PRZM scenario: FLtomatoSTD_V2.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife

### 106 Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.34 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 8-Feb dd/mm or dd/mmm or dd-mm or dd-mmm Record 17: FILTRA IPSCND 3 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)



### PA Tomato (0.30 lbs a.i ground applications)

stored as Tomato_PAben.out Chemical: Imazosulfuron PRZM environment: PAtomatoSTD.txt modified Tueday, 29 May 2007 at 14:01:58 EXAMS environment: pond298.exv modified Tueday , 26 August 2008 at 06:14:08 Metfile: w14751.dvf modified Tueday, 26 August 2008 at 06:15:00 Benthic segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.12 0.12 0.12 0.12 0.12 0.07 1962 0.26 0.26 0.26 0.25 0.25 0.20 1963 0.25 0.25 0.25 0.24 0.24 0.22 1964 0.53 0.53 0.53 0.53 0.52 0.39 1965 0.51 0.51 0.51 0.50 0.50 0.45 1966 0.51 0.51 0.51 0.50 0.48 0.42 1967 0.60 0.60 0.59 0.58 0.57 0.50 1968 1.13 1.13 1.12 1.09 1.07 0.80 1969 0.94 0.94 0.94 0.93 0.92 0.76 1970 0.62 0.62 0.62 0.61 0.61 0.50 1971 0.48 0.48 0.48 0.47 0.46 0.40 1972 0.63 0.63 0.62 0.61 0.59 0.48 1973 0.74 0.74 0.74 0.73 0.71 0.58 1974 0.95 0.95 0.95 0.92 0.90 0.74 1975 1.34 1.34 1.34 1.31 1.28 1.04 1976 1.07 1.06 1.06 1.05 1.04 0.94 1977 0.93 0.93 0.93 0.91 0.89 0.78 1978 0.88 0.88 0.88 0.87 0.85 0.74 1979 0.76 0.76 0.75 0.74 0.73 0.68 1980 0.91 0.91 0.90 0.88 0.85 0.71 1981 0.73 0.73 0.73 0.72 0.71 0.56 1982 0.71 0.71 0.71 0.70 0.69 0.56 1983 1.55 1.55 1.54 1.51 1.47 1.11 1984 1.28 1.28 1.27 1.26 1.25 1.03 1985 1.64 1.64 1.64 1.61 1.58 1.22 1986 1.41 1.41 1.41 1.39 1.38 1.15 1987 0.96 0.96 0.95 0.94 0.93 0.83 1988 0.74 0.74 0.74 0.72 0.71 0.64 1989 1.66 1.66 1.65 1.63 1.60 1.16 1990 1.49 1.49 1.48 1.46 1.44 1.32

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 1.66 1.66 1.65 1.63 1.60 1.32

### 107 0.06 1.64 1.64 1.64 1.61 1.58 1.22 0.10 1.55 1.55 1.54 1.51 1.47 1.16 0.13 1.49 1.49 1.48 1.46 1.44 1.15 0.16 1.41 1.41 1.41 1.39 1.38 1.11 0.19 1.34 1.34 1.34 1.31 1.28 1.04 0.23 1.28 1.28 1.27 1.26 1.25 1.03 0.26 1.13 1.13 1.12 1.09 1.07 0.94 0.29 1.07 1.06 1.06 1.05 1.04 0.83 0.32 0.96 0.96 0.95 0.94 0.93 0.80 0.35 0.95 0.95 0.95 0.93 0.92 0.78 0.39 0.94 0.94 0.94 0.92 0.90 0.76 0.42 0.93 0.93 0.93 0.91 0.89 0.74 0.45 0.91 0.91 0.90 0.88 0.85 0.74 0.48 0.88 0.88 0.88 0.87 0.85 0.71 0.52 0.76 0.76 0.75 0.74 0.73 0.68 0.55 0.74 0.74 0.74 0.73 0.71 0.64 0.58 0.74 0.74 0.74 0.72 0.71 0.58 0.61 0.73 0.73 0.73 0.72 0.71 0.56 0.65 0.71 0.71 0.71 0.70 0.69 0.56 0.68 0.63 0.63 0.62 0.61 0.61 0.50 0.71 0.62 0.62 0.62 0.61 0.59 0.50 0.74 0.60 0.60 0.59 0.58 0.57 0.48 0.77 0.53 0.53 0.53 0.53 0.52 0.45 0.81 0.51 0.51 0.51 0.50 0.50 0.42 0.84 0.51 0.51 0.51 0.50 0.48 0.40 0.87 0.48 0.48 0.48 0.47 0.46 0.39 0.90 0.26 0.26 0.26 0.25 0.25 0.22 0.94 0.25 0.25 0.25 0.24 0.24 0.20 0.97 0.12 0.12 0.12 0.12 0.12 0.07

0.10 1.55 1.54 1.54 1.50 1.47 1.15 Average of yearly averages: 0.70

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Tomato_PA Metfile: w14751.dvf PRZM scenario: PAtomatoSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Na me Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henr y 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.34 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 23-04 dd/mm or dd/mmm or dd-mm or dd-mmm Record 17: FILTRA IPSCND 3 UPTKF

### 108 Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, mont hly or total(average of entire run)



### FL Pepper (0.30 lbs a.i ground applications)

stored as Pepper_FLben.out Chemical: Imazosulfuron PRZM environment: FLpeppersSTD.txt modified Thuday, 24 May 2007 at 10:44:22

EXAMS environment: pond298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w12844.dvf modified Tueday, 26 August 2008 at 06:14:22 Benthic segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 1.53 1.53 1.53 1.52 1.50 0.49 1962 1.63 1.63 1.63 1.62 1.60 1.20 1963 1.62 1.61 1.58 1.52 1.45 1.00 1964 2.08 2.08 2.08 2.06 2.01 0.99 1965 2.00 2.00 1.98 1.91 1.83 1.22 1966 0.89 0.89 0.89 0.88 0.87 0.67 1967 3.51 3.51 3.50 3.47 3.44 1.53 1968 7.37 7.37 7.36 7.33 7.25 4.01 1969 7.24 7.21 7.10 6.84 6.63 4.96 1970 4.80 4.80 4.76 4.62 4.45 3.01 1971 2.36 2.36 2.33 2.23 2.15 1.39 1972 0.89 0.88 0.86 0.82 0.78 0.54 1973 1.12 1.12 1.11 1.10 1.10 0.57 1974 1.48 1.48 1.48 1.47 1.46 0.95 1975 1.43 1.42 1.38 1.30 1.24 0.84 1976 4.11 4.11 4.11 4.08 4.04 1.64 1977 4.01 4.01 4.00 3.91 3.75 2.53 1978 1.96 1.96 1.95 1.90 1.83 1.21 1979 1.13 1.13 1.13 1.12 1.11 0.80 1980 2.39 2.39 2.39 2.37 2.33 1.23 1981 4.77 4.76 4.76 4.73 4.64 2.59 1982 4.69 4.67 4.60 4.36 4.13 3.20 1983 3.27 3.27 3.25 3.14 3.06 2.54 1984 3.09 3.09 3.08 3.07 3.04 2.36 1985 2.86 2.86 2.86 2.78 2.66 1.75 1986 1.21 1.21 1.20 1.15 1.10 0.89 1987 0.95 0.95 0.94 0.91 0.88 0.67 1988 3.49 3.49 3.48 3.46 3.42 1.48 1989 3.37 3.35 3.28 3.12 2.99 1.99 1990 4.06 4.06 4.05 4.03 3.99 1.96

Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.03 7.37 7.37 7.36 7.33 7.25 4.96 0.06 7.24 7.21 7.10 6.84 6.63 4.01 0.10 4.80 4.80 4.76 4.73 4.64 3.20 0.13 4.77 4.76 4.76 4.62 4.45 3.01 0.16 4.69 4.67 4.60 4.36 4.13 2.59

### 109 0.19 4.11 4.11 4.11 4.08 4.04 2.54 0.23 4.06 4.06 4.05 4.03 3.99 2.53 0.26 4.01 4.01 4.00 3.91 3.75 2.36 0.29 3.51 3.51 3.50 3.47 3.44 1.99 0.32 3.49 3.49 3.48 3.46 3.42 1.96 0.35 3.37 3.35 3.28 3.14 3.06 1.75 0.39 3.27 3.27 3.25 3.12 3.04 1.64 0.42 3.09 3.09 3.08 3.07 2.99 1.53 0.45 2.86 2.86 2.86 2.78 2.66 1.48 0.48 2.39 2.39 2.39 2.37 2.33 1.39 0.52 2.36 2.36 2.33 2.23 2.15 1.23 0.55 2.08 2.08 2.08 2.06 2.01 1.22 0.58 2.00 2.00 1.98 1.91 1.83 1.21 0.61 1.96 1.96 1.95 1.90 1.83 1.20 0.65 1.63 1.63 1.63 1.62 1.60 1.00 0.68 1.62 1.61 1.58 1.52 1.50 0.99 0.71 1.53 1.53 1.53 1.52 1.46 0.95 0.74 1.48 1.48 1.48 1.47 1.45 0.89 0.77 1.43 1.42 1.38 1.30 1.24 0.84 0.81 1.21 1.21 1.20 1.15 1.11 0.80 0.84 1.13 1.13 1.13 1.12 1.10 0.67 0.87 1.12 1.12 1.11 1.10 1.10 0.67 0.90 0.95 0.95 0.94 0.91 0.88 0.57 0.94 0.89 0.89 0.89 0.88 0.87 0.54 0.97 0.89 0.88 0.86 0.82 0.78 0.49

0.10 4.80 4.79 4.76 4.71 4.62 3.18 Average of yearly averages: 1.67

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run: Output File: Pepper_FL Metfile: w12844.dvf PRZM scenario: FLpeppersSTD.txt EXAMS environment file: pond298.exv Chemical Name: Imazosulfuron Description Variable Name Value Units Comments Molecular weight mwt 412.81 g/mol Henry's Law Const. henry 3.33E-11 atm-m^3/mol Vapor Pressure vapr 2.63E-08 torr Solubility sol 429 mg/L Kd Kd mg/L Koc Koc 154 mg/L Photolysis half-life kdp 61.7 days Half-life Aerobic Aquatic Metabolism kbacw 192 days Halfife Anaerobic Aquatic Metabolism kbacs 64.2 days Halfife Aerobic Soil Metabolism asm 207.2 days Halfife Hydrolysis: pH 7 0 days Half-life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.34 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.01 fraction of application rate applied to pond Application Date Date 8-Sep dd/mm or dd/mmm or dd-mm or dd-mmm Record 17: FILTRA

### 110 IPSCND 3 UPTKF Record 18: PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR EPA Pond Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)

### 111 APPENDIX D: RICE MODEL

Rice Model (USEPA, 2007).

The formula of the Tier I Rice Model v1.0 is as follows:

d ai

w 

### K m C 00013.0 00105.0 '

+ =



### and, if appropriate:

oc d 

### KK 01.0 =

where: C w 

### = water concentration [μg/L]

m ai 

### ' = mass applied per unit area [kg/ha] K d 

### = water-sediment partitioning coefficient [L/kg] K oc 

### = organic carbon partiti oning coefficient [L/kg]

Example calculation:

EEC = (0.336 kg a.i./ha) / [0.00105 + (0.00013 x 1.19 L/kg)] = 278.9 μg/L (ppb)

### 112 APPENDIX E: ECOTOX OUTPUT

IMAZOSULFURON Papers that Were Accepted for ECOTOX

Kuk, Y. I., Kwon, O. D., Jung, H. I., Burgos, N. R., & Guh, J. O. Cross-Resistance Pattern and Alternative Herbicides for Rotala indica Resistant to Imazosulfuron in Korea. Pestic.Biochem.Physiol. 74[3], 129-138. 2002. WATER,AQUA,MIXTURE. Notes: EcoReference No.: 71288 Chemical of Concern: BSFM,IZP ,IMQ,BTC,CFZ,TBC,MLT,MCPB,IMS

Mohammad, M., Kishimoto, T., Itoh, K., Suyama, K., & Yamamoto, H. Comparative Sensitivity of Pseudokirchnetiella subcapitata vs.Lemna sp. to Eight Sulfonylurea Herbicides. Bull.Environ.Contam.Toxicol. 75[5], 866-872. 2005. WATER,AQUA. Notes: EcoReference No.: 104861 Chemical of Concern: BSFM,IMS,FZS,NSF

Tanaka, Y. Properties of Acetolactate Synthase from Sulfonylurea-Resistant Scirpus juncoides Roxb. var. ohwianus T. Koyama. Pestic.Biochem.Physiol. 77[3 ], 147-153. 2003. SOIL,WATER,ENV. Notes: EcoReference No.: 104887 Chemical of Concern: IMS

Wang, G. X., Watanabe, H., Uchino, A., & Itoh, K. Response of a Sulfonylurea (SU)-Resistant Biotype of Limnophila sessiliflora to Selected SU and Alterna tive Herbicides. Pestic.Biochem.Physiol. 68[2], 59-66. 2000. ENV,MIXTURE. Notes: EcoReference No.: 75769 Chemical of Concern: TBC,BSFM,MCPA,MCPB,IMS

IMAZOSULFURON Bibliography of excluded ECOTOX Papers

Akiyama, Y., Yoshioka, N., and Tsuji, M. Determination of Ten Sulfonyl Urea Herbicides in Unpolished Rice by Solid-Phase Extraction Cleanup and Lc-Diode Array Detection. Shokuhin eiseigaku zasshi. 2002, apr; 43(2):99-103. [Shokuhin eiseigaku zasshi. Journal of th e food hygienic society of japan]: Shokuhin Eiseigaku Zasshi

. Ayano, Eri, Kanazawa, Hideko, Ando, Masanori, and Nish imura, Tetsuji (2004). Dete rmination and quantitation of sulfonylurea and urea herbicides in water samples using liquid chromatography with electrospray ionization mass spectrometric detection. Anal. Chim. Acta 507:211-218.

Ayano, Eri, Okada, Yuji, Sakamoto, Chikako, Kanazawa, Hideko, Okano, Teruo, Ando, Masanori, and Nishimura, Tetsuji (2005). Analysis of herbicides in water using temperature-responsive chromatography and an aqueous mobile phase. J. Chromatogr., A 1069:281-285.

Brown, H. M. and Cotterman, J. C (1994). Recent advances in sulfonylurea herbicides. Chem. Plant Prot. 10:47-81.

Degelmann, Petra, Egger, Sebastian, Juerling, Heinrich, Mueller, Josef, Niessner, Reinhard, and Knopp, Dietmar (2006). Determination of Sulfonylurea Herbicides in Water and Food Samples Using Sol-Gel Glass-Based Immunoaffinity Extraction and Liquid Chromatography-Ultraviolet/Diode Array Detection or Liquid Chromatography-Tandem Mass Spectrometry. J. Agric. Food Chem. 54:2003-2011.

Degelmann, Petra, Wenger, Jean, Niessner, Reinhard, and Knopp, Dietmar (2004). Development of a class-specific ELISA for sulfonylurea herbicides (Sulfuron Screen). Environ. Sci. Technol. 38:6795-6802.

Fidente, P., Manca, M. C., Morrica, P. , and Seccia, S (2003). Imazosulfuron: pr eliminary test of photolysis.293-297.

### 113 Inui, H., Shiota, N., Ido, Y., Inoue, T., Hirose, S., Kawahi gashi, H., Ohkawa, Y., and Ohkawa, H. (2001). Herbicide Metabolism and Tolerance in the Transgenic Rice Plants Expressing Human Cyp2c9 and Cyp2c19. Pesticide Biochemistry and Physiology [Pestic. Biochem. Physiol.]. Vol. 71, no. 3, pp. 156-169. Nov 2001.

Inui, Hideyuki, Shiota, Noriaki, Motoi, Yukiko, Ido, Yoshiko, Inoue, Tomomi, Kodama, Takuya, Ohkawa, Yasunobu, and Ohkawa, Hideo (2001). Metabolism of herbicides and other chemicals in human cytochrome P450 species and in transgenic potato plants co-expressing human CYP1A1, CYP2B6 and CYP2C19. Nippon Noyaku Gakkaishi 26:28-40.

Ishida, Y., Yoshikawa, H., Ohta, K. , and Kumazaki, Y. (1996). Developm ent of a New Sulfonylurea Herbicide Imazosulfuron. Journal of pesticide science 21:247-258.

Ishida, Yasuo, Yoshikawa, Harutoshi, Ohta, Kazunari, and Kumazaki, Yasunari (1996). Development of a new herbicide, imazosulfuron. Nippon Noyaku Gakkaishi 21:247-258.

Kawai, Kiyoshi, Kaku, Koichiro, Izawa, Norihiko, Shimizu, Tsutomu, Fukuda, Atsunori, and Tanaka, Yoshiyuki (2007). A novel mutant acetolactate synthase gene from rice cells, which confers resistance to ALSinhibiting herbicides. J. Pestic. Sci. (Tokyo, Jpn.) 32:89-98.

Lee, Jae Koo, Ahn, Ki Chang, Park, Oee Sook, Ko, Yong Kwan, and Kim, Dae-Whang (2002). Development of an immunoassay for the residues of the herbicide bensulfuron-methyl. J. Agric. Food Chem. 50:1791-1803.

Mikata, K., SchnÖ, Der, F., Brau nwarth, C., Ohta, K., and Tashiro, S. Mobility and Degradation of the Herbicide Imazosulfuron in Lysimeters Under Field Conditions. J agric food chem. 2003, jan 1; 51(1):177- 82. [Journal of agricultural and food chemistry]: J Agric Food Chem

. Mikata, K., Yamamoto, A., and Tashiro, S. (1996). Degradation of Imazosulfuron in Flooded Soils. Journal of Pesticide Science, 21 (2) pp. 171-177, 1996

. Mikata, Kazuki, Ohta, Kazunari, and Tashiro, Shigeki (2001 ). Degradation and leaching of herbicide imazosulfuron in upland soils. Nippon Noyaku Gakkaishi 26:376-382.

Mikata, Kazuki, Ohta, Kazunari, and Tashiro, Shigeki (2000). Adsorption and desorption of herbicide imazosulfuron in soils. Nippon Noyaku Gakkaishi 25:212-216.

Morrica, P., Barbato, F., Della Iacovo, R., Seccia, S., an d Ungaro, F. Kinetics and Mechanism of Imazosulfuron Hydrolysis. J agric food chem. 2001, aug; 49(8):3816-20. [Journal of agricultural and food chemistry]: J Agric Food Chem

.

Morrica, P., Barbato, F., Giordano, A., Seccia, S., and Un garo, F. Adsorption and Deso rption of Imazosulfuron by Soil. J agric food chem. 2000, dec; 48(12):6132-7. [Journal of agricultural and food chemistry]: J Agric Food Chem

.

Morrica, P., Fidente, P. , Seccia, S., and Ventriglia, M. Degradatio n of Imazosulfuron in Different Soils-Hplc Determination. Biomed chromatogr. 2002, dec; 16(8):489-94. [Biomedical chromatography : bmc]: Biomed Chromatogr

. Morrica, P., Giordano, A., Seccia, S., Ungaro, F., and Ventriglia, M. Degradation of Imazosulfuron in Soil. Pest manag sci. 2001, apr; 57(4):360-5. [Pest management science]: Pest Manag Sci

. Morrica, Patrizia, Fidente, Paola, and Seccia, Serenella ( 2004). Identification of photoproducts fr om imazosulfuron by HPLC. Biomed. Chromatogr. 18:450-456.

Saari, L. L., Cotterman, J. C., and Th ill, D. C. (1994). Resistance to Acetolactate Synthase Inhibiting Herbicides. Powles, s. B. And j. A. M. Holtum (ed.). Herbicide resistance in plants: biology and biochemistry. Xi+353p.

### 114 Crc press, inc.: Boca raton, florida, usa London, england, uk. Isbn 0-87371-713-9.; 0:83-139.

Schmuckler, Margaret E., Barefoot, Aldos C., Kleier, Daniel A., and Cobranchi, Daryl P (2000). Vapor pressures of sulfonylurea herbicides. Pest Manage. Sci. 56:521-532.

Shim, Y. S., Gil, H. W., Yang, J. O., Lee, E. Y., Kim, S. H., and Hong, S. Y. A Case of Green Urine After Ingestion of Herbicides. Korean j intern med. 2008, mar; 23(1):42-4. [The korean journal of internal medicine]: Korean J Intern Med

.

Takatsuki, S., Nemoto, S., Matsuda, R., Sasaki, K., and T oyoda, M. (1999). Determination of 21 Pesticides in Agricultural Products by Hplc-Photodiode Array Detection. Shokuhin eiseigaku zasshi 40:314-319.

Ventriglia, M., Restani, P., Morrica, P., David, P., De Angelis, L., and Galli, C. L. Liquid Chromatographic Determination of Imazosulfuron in Drinking Water and in Soil Using Ultraviolet Detection. J chromatogr a. 1999, oct 1; 857(1-2):327-30. [Journal of chromatography. A]: J Chromatogr A

. Vu, S. o. n. Hong, Ishihara Satoru, and Watanabe Hirozumi (2006). Exposure Risk Assessment and Evaluation of the Best Management Practice for Controlling Pesticide Runoff From Paddy Fields. Part 1: Paddy Watershed Monitoring. Pest Management Science [Pest Manage. Sci.]. Vol. 62, no. 12, pp. 1193-1206. Dec 2006.

Yoshii, K., Tonogai, Y., Tsumura, Y., Nakamura, Y., and Shibata, T. (1998). Studies on Simultaneous Determination of 15 Pesticides in Cereals by Sf and Hplc. Journal of the food hygienic society of japan 39:184-191.

Yun, Min-Soo, Chen, Weijun, Deng, Fan, Kiyokawa, Takahiro, Mametsuka, Koki, and Yogo, Yasuhiro (2006). An in vitro screening assay to discover novel inhibitors of 4-coumarate:CoA ligase. Pest Manage. Sci. 62:1065- 1071.

Imazosulfuron Papers that Were Not Acceptable for ECOTOX

Goto, T., Ukawa, S., & Miyauchi, H. Fentrazamide - A Ne w Herbicide Effective on Gras ses and Annual Sedges in Rice in Japan. Pflanzenschutz-Nachr.Bayer 54[1], 13-34. 2001. SOIL,WATER,ENV. Notes: EcoReference No.: 105849 Chemical of Concern: IMS,BSFM

Hirose, S., Kawahigashi, H., Inoue, T., Inui, H., Ohkawa, H., & Ohkawa, Y. Enhanced Expression of CYP2C9 and Tolerance to Sulfonylurea Herbicides in Transgenic Rice Plants. Plant Biotechnol. 22[2], 89-96. 2005. SOIL,WATER,ENV. Notes: EcoReference No.: 105846 Chemical of Concern: IMS,CSF,TSF

Ishida, Y., Ohta, K., Itoh, S., Nakahama, T., Miki, H., & Yo shikawa, H. Synthesis of Novel Herbicidal Sulfonylurea Compounds with Imidazo(1,2-a)Pyridine Moiety. J.Pestic.Sci. 18[2], 175-182. 1993. SOIL,ENV. Notes: EcoReference No.: 105002 Chemical of Concern: IMS

Kuk, Y. I., Jung, H. I., Kwon, O. D., Lee, D. J., Burgos , N. R., & Guh, J. O. Sulfonylurea Herbicide-Resistant Monochoria vaginalis in Korean Rice Culture. Pest Manag.Sci. 59[9], 949-961. 2003. SOIL,ENV,MIXTURE. Notes: EcoReference No.: 74168 Chemical of Concern: MLT,IZP,IM Q,BSFM,BTC,DTP,TBC,24DXY,BT,IMS

Sondhia, S. Determination of Imazosulfuron Persistence in Rice Crop and Soil. Environ.Monit.Assess. 137[1-3], 205-211. 2008. SOIL,ENV.

### 115 Notes: EcoReference No.: 105008 Chemical of Concern: IMS

Imazosulfuron Target Papers

Itoh, K., Wang, G. X., & Ohba, S. Sulfonylurea Resistance in Lindernia micrantha, an Annual Paddy Weed in Japan. Weed Res. 39[5], 413-423. 1999 . G.X. Wang, Laboratory of Weed Science, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan. Email: gxwang@kais.kyoto-u.ac.jp. Notes: EcoReference No.: 64651 Chemical of Concern: MCPB,IMS

Kuk, Y. I., Jung, H. I., Kwon, O. D., Lee, D. J., Burgos , N. R., & Guh, J. O. Rapid Diagnosis of Resistance to Sulfonylurea Herbicides in Monochoria (Monochoria vaginalis). Weed Sci. 51[3], 305-311. 2003. Notes: Chemical of Concern: IMS

### 116 APPENDIX F: Example TERR-PLANT Output – Turfgrass Scenario

TerrPlant v. 1.2.2 Green values signify user inputs (Tables 1, 2 and 4). Input and output guidance is in popups indicated by red arrows.

Table 1. Chemical Identity.

Chemical Name Imazosulfuron PC code 118602 Use Turfgrass Application Method Ground

Application Form Liquid Solubility in Water (ppm) 429

Table 2. Input parameters used to derive EECs. Input Parameter Symbol Value Units Application Rate A 0.67

Incorporation I 1 none Runoff Fraction R 0.05 none

Drift Fraction D 0.01 none

Table 3. EECs for Imazosulfuron . Units in . Description Equation EEC Runoff to dry areas (A/I)*R 0.0335 Runoff to semi-aquatic areas (A/I)*R*10 0.335 Spray drift A*D 0.0067 Total for dry areas ((A/I)*R)+(A*D) 0.0402 Total for semi-aquatic areas ((A/I)*R*10)+(A*D) 0.3417

Table 4. Plant survival and growth data used for RQ derivation. Units are in . Seedling Emergence Vegetative Vigor Plant type EC 25 NOAEC EC 25 NOAEC

Monocot 0.034 0.025 0.25 0.025

Dicot 0.041 0.022 0.08 0.074

Table 5. RQ values for plants in dry and semi-aquatic areas exposed to Imazosulfuron through runoff and/or spray drift.* Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Monocot non-listed 1.18 10.05 0.20 Monocot listed 1.61 13.67 0.27

Dicot non-listed 0.98 8.33 0.16 Dicot listed 1.83 15.53 0.30 *If RQ > 1.0, the LOC is exceeded, resulti ng in potential for risk to that plant group.

### 117 APPENDIX G: EXAMPLE TREX OUTPUT –Turfgrass Scenario

Acute and Chronic RQs are based on the Upper Bound Upper Bound Kenaga Residues For RQ Calculation Kenaga Residues.

Chemical Name: Imazosulfuron The maximum single day residue estimation is used for

Use Turfgrass both the acute and reproduction RQs.

Formulation 0

Application Rate 0.67 lbs a.i./acre RQs reported as "0.00" in the RQ tables below should be noted as

Half-life 35 days <0.01 in your assessment. This is due to rounding and significant

Application Interval 21 days figure issues in Excel.

Maximum # Apps./Year 2

Length of Simulation 1 year

Endpoints

Bobwhite quail LD50 (mg/kg-bw) 2250.00

Bobwhite quail LC50 (mg/kg-diet) 5042.00

Mallard duck NOAEL(mg/kg-bw) 0.00 Avian

Bobwhite quail NOAEC (mg/kg-diet) 100.00

LD50 (mg/kg-bw) 5000.00

LC50 (mg/kg-diet) 0.00

NOAEL (mg/kg-bw) 50.00 Mammals

NOAEC (mg/kg-diet) 1000.00

Kenaga Dietary-based EECs (ppm) Values

Short Grass 266.89

Tall Grass 122.32 Broadleaf plants/sm Insects 150.12 Fruits/pods/seeds/lg insects 16.68

Avian Results

Avian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g) (g bw/day) (g/day) consumed (kg-diet/day)

Small 20 5 23 114 2.28E-02

Mid 100 13 65 65 6.49E-02

Large 1000 58 291 29 2.91E-01

20 5 5 25 5.06E-03

### 118 Granivores 100 13 14 14 1.44E-02

1000 58 65 6 6.46E-02

Avian Body Adjusted LD50

Weight (g) (mg/kg-bw)

20 1620.97

100 2063.57

1000 2914.87

Avian Classes and Body Weights (grams)

small mid large Granivores(grams) Dose-based EECs (mg/kg-bw)

20 100 1000 20 100 1000

Short Grass 303.96 173.33 77.60

Tall Grass 139.31 79.44 35.57 Broadleaf plants/sm Insects 170.98 97.50 43.65 Fruits/pods/seeds/lg insects 19.00 10.83 4.85 4.22 2.41 1.08

Avian Acute RQs Size Class (grams) Dose-based RQs (Dose-based EEC/adjusted LD50) 20 100

1000

Short Grass 0.19 0.08 0.03

Tall Grass 0.09 0.04 0.01 Broadleaf plants/sm insects 0.11 0.05 0.01 Fruits/pods/seeds/lg insects 0.01 0.01 0.00

Seeds (granivore) 0.00 0.00 0.00

RQs Dietary-based RQs (Dietary-based EEC/LC50 or NOAEC)

Acute Chronic

Short Grass 0.05 2.67

Tall Grass 0.02 1.22 Broadleaf plants/sm Insects 0.03 1.50 Fruits/pods/seeds/lg insects 0.00 0.17

Imazosulfuron Turfgrass Upper bound Kenaga Residues

Mammalian Results

Mammalian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g bwt/day) (g/day) consumed (kg-diet/day)

15 3 14 95 1.43E-02

Herbivores/ 35 5 23 66 2.31E-02

insectivores 1000 31 153 15 1.53E-01

15 3 3 21 3.18E-03

Grainvores 35 5 5 15 5.13E-03

### 119 1000 31 34 3 3.40E-02

Mammalian Body Adjusted Adjusted

Class Weight LD50 NOAEL

15 10989.15 109.89

Herbivores/ 35 8891.40 88.91

insectivores 1000 3845.80 38.46

15 10989.15 109.89

Grainvores 35 8891.40 88.91

1000 3845.80 38.46

Mammalian Classes and Body weight

Herbivores/ insectivores (grams) Granivores(grams)

Dose-Based EECs (mg/kg-bw) 15 35 1000 15 35 1000

Short Grass 254.46 175.86 40.77

Tall Grass 116.63 80.60 18.69 Broadleaf plants/sm Insects 143.13 98.92 22.94 Fruits/pods/seeds/lg insects 15.90 10.99 2.55 3.53 2.44 0.57

Small mammal Medium mammal Large mammal

15 grams 35 grams 1000 grams Dose-based RQs (Dose-based EEC/LD50 or NOAEL) Acute Chronic Acute Chronic Acute Chronic

Short Grass 0.02 2.32 0.02 1.98 0.01 1.06

Tall Grass 0.01 1.06 0.01 0.91 0.00 0.49 Broadleaf plants/sm insects 0.01 1.30 0.01 1.11 0.01 0.60 Fruits/pods/lg insects 0.00 0.14 0.00 0.12 0.00 0.07

Seeds (granivore) 0.00 0.03 0.00 0.03 0.00 0.01

Mammal RQs Dietary-based RQs (Dietary-based EEC/LC50 or NOAEC)

Acute Chronic

Short Grass #DIV/0! 0.27

Tall Grass #DIV/0! 0.12 Broadleaf plants/sm insects #DIV/0! 0.15 Fruits/pods/seeds/lg insects #DIV/0! 0.02