UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON D.C.

, 20460



### MEMORANDUM

DATE: 

### February 28, 2013 OFF I CE OF CHEMICAL SAFETY AND
POLLUTION PREVENTION



### SUBJECT: 

### Registration Review

- Preliminary Problem Formula tion for the Ecological Exposure and Risk Assessment for Iodosulfuron-methyl-sodium (PC Code 122021; DP Barcode 404946)

FROM:

THRU:

## ~ Rochelle F.



### - H. Bohaty, Ph.D., Chemi 

# 9**Katherine** 

### R. Stebbins, Biologist

Rosanna Louie-Juzwiak, RAPL

Environmental Risk Branch 3
Environmental Fate and Effects Division (7507P)

Dana Spatz,

# Chie**~.....__............__** 

# c:::_"" z__\ "2 

# Q)**-~** 

# \ 3
Environmental

## RiAs**~~ ~**  

# 'I

Environmental Fate and Effects Division (7507P)

·- 

### TO: 

### Katherine St. Clair, Chemical Review Manager
Kevin Costello, Branch Chief

RMIB4
Pesticide Reevaluation Division

The Envi ronmental Fate and Effects Division (EFED) has completed the preliminary problem
formulation (attached) for the ecological risk, environmental fate, and endangered species

assessments to be conducted as part ofthe Registration Review ofiodosulfuron-methyl-sodium (also referred to as iodosulfuron). This document is intended to provide an overview of what is currently known regarding the environme ntal fate and ecological effects associated with

iodosulfuron and its degradation products, and outlines uncertainties regarding attributes of the
parent compound and its transformation products. It 

### describes the preliminary ecological risk hypothesis and the processes that will be used during the completion of the ecological risk

assessment in support of Registration Review

.



# ' 1

### 2 1. INTRODUCTION

Iodosulfuron-methyl-sodium (iodosulfuron) is a sulfonylurea herbicide used to control annual and perennial grasses and broadlea f weeds. Iodosulfuron slows or stunts plant growth (or causes ultimate plant death) by limiting amino acid synthesi s in plants through inhibition of acetolactate synthase (ALS). Iodosulfuron is absorbed thro ugh the leaves and root s of susceptible weed species. The structure of iodosulfuron, as well as the chemical name and other identifiers are provided in Table 1

.

Table 1. Iodosulfuron Chemical Identifiers

Parameter Identifier

Chemical Structure 

### C O 2 

### C H 3



### I S O 2 

### N H N

O N N N

CH 3 

### OCH 3



### Na

Chemical Name 4-Iodo-2-[[[[(4-methoxy-6-methyl,-3i, 5-triazin-2-yl)amino]carbonyl]amino]sulfonyl benzoic acid methyl ester, monosodium salt
SMILES [Na+].COC(=O)C1=CC=C(I)C=C1S(=O)(=O)[N-]C(=O)NC1=NC(OC)=NC(C)=N1
CAS Number 144550-36-7 Company Code AE F115008



### In addition to the technical product (Reg. No.264 -687), there are eight end-use products that
contain iodosulfuron. Two different safener ingredients, isoxadif en-ethyl and mefenpyr-diethyl,
are included in some of the formulations to protect the sprayed field corn (Reg. No. 264-686), triticale and wheat (Reg. Nos. 264-1103; 264-820) from damage. Se veral of the products contain additional active ingredients including: meso sulfuron-methyl (PC 122009), thiencarbazonemethyl (PC 015804), foramsulfuron (PC 122020), and dicamba (PC 029801). A summary of all the iodosulfuron formulated products is provided in Table 2

.

Table 2. Iodosulfuron Formulated Products

Product EPA Registration
Number Active Ingredient (Product Code) Safener 1

Atlantis Herbicide 264-1103 0.6 % Iodosulfuron-methyl-sodium (122021) 9.0% mefenpyr-diethyl 3.0 % Mesosulfuron-methyl (122009)

Autumn Super 51
WDG Herbicide 264-1134 6.0% Iodosulfuron-methyl-sodium (122021) 45% Thiencarbazone-methyl (15804)
Tribute Solo WG32 (also known as Equip Corn Herbicide) 264-686 2.0% Iodosulfuron-methyl-sodium (122021) 30% isoxadifen-ethyl 30 % Foramsulfuron (122020)

Hussar Herbicide 264-820 5.0% Iodosulfuron-methyl-sodium (122021) 15% mefenpyr-diethyl

### 3 Product EPA Registration
Number Active Ingredient (Product Code) Safener 1

Iodosulfuron 10
WDG Herbicide 264-843 10 % Iodosulfuron-methyl-sodium (122021)
Iodosulfuron 10
WDG
Herbicide 264-856 10 % Iodosulfuron-methyl-sodium (122021)

Iodosulfuron Turf
Herbicide 432-1404 10 % Iodosulfuron-methyl-sodium (122021)

Celsius WG 432-1507 1.9% Iodosulfuron-methyl-sodium (122021) 8.7% Thiencarbazone-methyl (15804) 57.4% Dicamba (029801)

1. Reported percentages are based on data provided on the material safety data sheet (MSDS)



### Iodosulfuron is registered for use on the following agricultural crops : cereal grains, corn (field, pop and sweet), cotton, sorghum, soybeans, triticale, and wheat. In addition, iodosulfuron is registered for use on lawns (residential and commercial), turf/sod farms, roadsides, and recreational areas including golf courses, sports fields, pa rks, campsites, and school grounds. All currently registered uses of iodosulfuron are listed in Table 3

.

Based on the BEAD Chemical Pr ofile prepared by OPP’s Biol ogical and Economic Analysis Division, from 2006-2010, an annual average of < 500 pounds of iodosulfuron was used on corn and soybeans. 1 

### Pesticide use was surveyed but not re ported during this time period for cotton, sorghum, and wheat. Usage data are not available for triticale and the non-agricultural use sites such as: lawns, turf/sod farms, ri ghts of way, and recreational areas.

1 Ratnayake, S.; Prieto, R.; Smearman, S. BEAD Chemical Profile for Registration Review: Iodosulfuron-methylsodium (122021) August 28, 2012

.4Table 3. Currently Registered Iodosulfuron UsesCrop/Site(Reg. Nos.) Residential Agricultural ForestryTiming;ApplicationTypeMethod/EquipmentMaximumSingleApplicationRate byFormulation1(lb a.i./A)MaximumApplication RateMaximumApplicationNumber PHI (days) 3 REI (hours) 3 MRI (days) 3GeographicRestrictions/Comments4Per Yearlb a.i./APerCC2lb a.i./APerYearPerCC2CEREAL GRAINS,SWEET, AND POPCORNCOTTON,SORGHUM264-856Postharvest, burndown treatmentground boom0.002WDG0.002 NA 1 NS NA NS NSProduct is usedas a burn downapplication atleast 60 d (forsweet corn,popcorn orcorn grown forseed or cotton)or 30 d forfield corn,sorghum priorto planting.FIELD, CORN264-686Foliar,broadcast,ground boom0.002WDG0.002 NA NS 1 45 NS NSPHI: 45 d forcorn forage; 70d for corngrain264-1134; 264-856Postharvest, burndown treatmentground boom0.002WDG0.002 NA 1 NS 30 NS NSProduct is usedas a burn downapplication atleast 30 d priorto planting.GOLF COURSETURF/ORNAMENTALLAWNS ANDTURF/ORNAMENTALSOD FARM (TURF)/RECREATIONAREA LAWNS/RESIDENTIALLAWNS432-1404; 432-1507foliar,establishedplantingsbroadcastground boom0.009WDG0.009 NA NS NA NS NS NS432-1507foliar, spottreatmenthandheld0.0001 lb/galWDG0.009 NA NS NS NS NS NS5432-1507foliar, zoneapplication0.006WDG0.009 NA NS NA NS NS NSRECREATIONALAREAS432-1404Weedpostemergence,establishedplantingsbroadcastground boom0.009WDG0.009 NA NS NA NS NS NSSOYBEAN264-1134; 264-856Postharvest, burndown treatmentground boom0.002WDG0.002 NA 1 NS NA NS NSProduct usedas a burn downapplication atleast 60 d priorto planting.TRITICALE264-1103Postemergence,broadcastground boom0.002/0.003 (ID, OR,WA) WDG0.0090.0023/0.0026(ID,OR,WA)NS 1 NS NS NSHigher ratespermitted inIdaho, Oregon,WashingtonWHEAT264-1103Postemergence,broadcast, sprayground boom0.002/ 0.003(ID, OR, WA)WDG0.0090.0023/0.0026(ID,OR,WA)NS NS 30 NS NSHigher ratespermitted inIdaho, Oregon,WashingtonPHI: 30 d forforage; 60 dfor hay, grain,and straw264-820Foliar, broadcast ground boom0.009WDG0.009 NS 2 NS 21 NS 14PHI: 21 d forforage; 55 dfor grain, andstraw, and 50 dfor hay1.WDG – water dispersible granular in water soluble packet2.Reported as per crop cycle or per season3.PHI – Preharvest interval; REI – reentry interval; MRI – Minimum retreatment interval4.Rotational crop rotation intervals are provided on product labels.NA not applicable; NS not specified

### 6 2. PREVIOUS RISK ASSESSMENTS

Three ecological risk assessments have been completed for iodosulfuron: the new chemical assessment (field corn; DP267567; March 2002), and two new use assessments (turf, soybeans; DP315491; March 2006) and (wheat; DP350049; Marc h 2008). All three of the previous assessments assessed both iodosulfuron (parent) and an environmental transformation product, metsulfuron methyl. Metsulfuron methyl also re ferred to as metsulfuron and is a registered sulfonylurea herbicide (PC 122010). EFED evaluated these assessments in association with the current toxicity, exposure, and usage information to determine if sufficient data are available and if further updates are needed to support registration review.

Potential direct risk to terrestri al and aquatic vascular and non-v ascular plants from the use of iodosulfuron is expected. There is also the potential for various indirect effects on non-target animal species due to the effects on the plant co mmunity (for example, depletion of food sources and habitat). The major conclusions presented in the most recent assessments for iodosulfuron
are summarized in Table 4

.

Table 4. Summary of Risk Concerns Identified for Iodosulfuron in Previous Assessments

Birds Mammals Terrestrial
Plants Terrestrial
Inverts Fish Aquatic
Inverts Aquatic
Plants Groundwater
Contamination Persistence Degradates
of Concern

-- -- √

-- -- -- √

-- -- √

√

Risk/concern identified in previous assessment



### Previous Drinking Water Assessments

A drinking water assessment for iodosulfuron wa s conducted at the time of the new chemical assessment, and updated with each subse quent new use, as highlighted in Table 5 and Table 6

. The uses assessed include applications made to field, sweet and pop corn, soybean, turf, and
wheat. These assessments included estimated drinking water concentrations for both iodosulfuron and metsulfuron, modeled usi ng FIRST, PRZM-EXAMS, and SCI-GROW. The two residues were modeled independently.

A drinking water assessment will be conducted to support future human health dietary risk assessments of iodosulfuron. Using EFED aqua tic models, the drinki ng water assessment will incorporate model estimates of iodosulfuron in surface water ( e.g. , PRZM-EXAMS) and groundwater ( e.g. , (PRZM-GW). The major degradate, metsulfuron is currently considered a residue of concern in drinking water; however , all environmental tran sformation products of iodosulfuron will be reevaluated as potential residue s of concern in drinking water as part of the registration review risk assessm ent process. Any additional resi dues identified as a potential toxicological concern with similar toxicity will also be considered using a total toxic residue (TTR) approach.7Table 5. Summary of Prior Drinking Water Assessmentsfor Iodosulfuron and Metsulfuron in Surface WaterAssessmentCropTier I Surface Water (FIRST)IodosulfuronMetsulfuron1-in-10 Year PeakConcentrationμg/L (ppb)1-in-10 Year AnnualAverageConcentrationμg/L(ppb)1-in-10 Year PeakConcentrationμg/L (ppb)1-in-10 Year AnnualAverage Concentrationμg/L (ppb)D279400/DWANew ChemicalField Corn0.056 0.0058 0.068 0.014D315491/DWATurf0.6 0.06 0.53 0.11D318084/DWASoybean(preplant)Tier II Surface Water (PRZM-EXAMS)1-in-10 YearPeakConcentrationμg/L (ppb)1-in-10 YearAnnualAverageConcentrationμg/L (ppb)30 YearAverageYearlyConcentrationμg/L (ppb)1-in-10 YearPeakConcentrationμg/L (ppb)1-in-10 YearAnnual AverageConcentrationμg/L (ppb)30 YearAverageYearlyConcentrationμg/L (ppb)D350049/DWAWheat 0.36 0.067 0.025 0.26 0.077 0.027Table 6. Summary of Prior Drinking Water Assessmentsfor Iodosulfuron and Metsulfuron in GroundwaterAssessmentCropTier I Groundwater (SCI-GROW)IodosulfuronMetsulfuronPeak Concentrationμg/L (ppb)Yearly MeanConcentrationμg/L (ppb)PeakConcentrationμg/L (ppb)Yearly MeanConcentrationμg/L (ppb)D279400/DWANew ChemicalField Corn0.0006 0.0006 0.005 0.005D315491/ DWA Turf0.00004 0.00004 0.02 0.02D318084/ DWASoybeanpreplantD350049/DWA Wheat 0.00002 0.00002 0.02 0.02

### 8 Clean Water Act Programs

Iodosulfuron is not identified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act. No Total Maximum Daily Load (TMDL) criteria have been developed for iodosulfuron. Aquatic Li fe Ambient Water Quality Criteria documents or Aquatic life benchmarks have not been published for iodosulfuron.

3. ENVIRONMENTAL FATE AND TRANSPORT

Physical and Chemical Properties

The physicochemical properties of iodosulfuron are shown in Table 7 . Based on these properties alone, iodosulfuron is not expected to be volatile or to bioaccumulate. It is highly soluble in water. Solubility is pH dependent and has been shown to increase at higher pHs.

Table 7. Selected Physical/Chemical Parameters of Iodosulfuron

Parameter Value Source/Classification

Molecular mass (molecular formula) 529.24 g/mol (C 14 H 13 IN 5 O 6 SNa) EPISuite v4.0



### Vapor pressure (20°C) 2.6 x 10 -9 Pa; 1.95 x 10 -11 mmHg (20 °C)
6.7 x 10 -9 Pa; 5.03 x 10 -11 mmHg (25 °C)
1.6 x 10 -8 Pa; 1.2 x 10 -10 mmHg (30 °C) MRID 45108609



### Aqueous solubility (20  C) 170 mg/L (20 °C; pH 5) 25,000 mg/L (20 °C; pH 7) 65,000 mg/L (20 °C; pH 9) MRID 45108619
MRID 45108620 (corrected values)



### pK
a 3.22±0.06 (20 °C) MRID 45108626



### Log octanol-to-water partition
coefficient (log K O W 

### ) 3.96 (pH 4) -0.70 (pH 7) -1.22 (pH 9) MRID 45108622

MRID 45108621 provides iodosulfuron solubility data for a number of common solvents.



### Environmental Fate Properties

Environmental fate properties of iodosulfuron are summarized in Table 8 . These half-life values presented in the table have been updated from previous assessments to reflect the NAFTA degradation kinetics guidance 2 

### for characterization purposes and will be used to calculate model input values. Updated model input values will be cal culated based on current model input guidance for each respective exposure model at the time the assessment is completed. The updated kinetic analyses are presented in APPENDIX A . The results of the revised kinetic analyses are similar to those previously reporte d in the data evaluation documents. In general terms, iodosulfuron is susceptible to microbial mediated degradati on in soil as well as in aquatic

2 Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media , Health Canada, U.S.
Environmental Protection Agency, December 2012.

### 9 environments. Iodosulfuron does not persist long in soil and is only slightly more persistent in aquatic environments under both aerobic and anae robic conditions. It forms several different environmental transformation products (discusse d in the section below). Hydrolysis of iodosulfuron is pH dependent with increased hydrolysis occurring under acidic conditions. Photodegradation in aquatic environments is not expected for iodosulfuron; however, it is susceptible to indirect photolys is (primarily observed in soil ). Like all of the sulfonylurea herbicides, iodosulfuron does not bi nd strongly to soils and sedime nts, and is expected to be
mobile.

Table 8. Environmental Fate Parameters of Iodosulfuron

Parameter 

### Conditions Value Source/Classification

Persistence 1

Hydrolysis halflife 25  C pH 4: 2.5 d 2 pH 5: 18.4 d 2 pH 7: >365 d 2 pH 9: 167 d 2 MRID 45108623/ acceptable

Aqueousphotolysis halflife 25  C 212 d 30 °N
334 d 40 °N
644 d 50 °N MRIDs 45108624, 45108625/ Supplemental

Soil photolysis
half-life

25  C SFO 4.2 d 30 °N
SFO 5.0 d 40 °N
SFO 7.0 d 50 °N
DFOP Slow t 1/2 = 11.3 d 30 °N
DFOP Slow t 1/2 = 13.4 d 40 °N
DFOP Slow t 1/2 = 17.5 d 50 °N 45109003
Reclassified to supplemental 3 Phenyl label

A clear pattern of
formation and decline of the transformation product
was not established.

Aerobic soil
metabolism halflife

20°C, 40%
MWRC IORE DT50= 2.9 d; DT90= 12 d;

tR IORE = 3.6 d (Germany, silt loam) MRIDs 45108934, 45109005/ Supplemental 3

Triazine label IORE DT50= 3.3 d; DT90= 13.7 d;

tR IORE = 4.1 d (France, clay loam)

IORE DT50= 2.9 d; DT90= 13 d;

tR IORE = 3.9d (United Kingdom, loamy sand) MRIDs 45108935,
45109006/ Supplemental 4

Phenyl label

IORE DT50= 4.3 d; DT90= 26.5 d;

tR IORE = 8.0 d (United Kingdom, silt loam) MRIDs 45108936,
45109007/ Supplemental 4

Triazine label 20°C, 30%

MWRC IORE DT50= 6.0 d; DT90= 41.2 d;

tR IORE = 12.4 d (United Kingdom, silt loam)

10°C, 40%

MWRC IORE DT50= 13.8 d; DT90= 104 d;

tR IORE = 31.3 d (United Kingdom, silt loam)

20°C, 25%

MWRC DFOP DT50= 16.2 d; DT90=132 d;
Slow t 1/2 = 50.5 d (Germany, clay) MRIDs 45109001,
45109008/ Supplemental 4

Triazine label IORE DT50= 9.2 d; DT90= 51.4 d;

tR IORE = 15.5 d (France, clay loam)

### 10 Parameter 

### Conditions Value Source/Classification

20°C, 50%

MWRC IORE DT50= 2.3 d; DT90= 24 d;

tR IORE = 7.3 d (Germany, clay)

IORE DT50= 3 d; DT90= 11.9 d;

tR IORE = 3.6 d (France, clay loam)

20°C IORE DT50= 1.5 d; DT90= 7.43 d;

tR IORE = 2.2 d (Germany, sandy loam)

MRID 45108933/
45109004 Supplemental 5

triazine label 20°C SFO DT50= 1.6 d; DT90= 5.2 d; (Germany, loamy sandy)

20°C DFOP DT50= 3.1 d; DT90= 10.2 d;
DFOP Slow t 1/2 = 3.1 d (USA, sand)
Same as SFO

20°C SFO DT50= <1 d; DT90= 2.5 d; (Germany, silt loam)

Aerobic aquatic
metabolism halflife 20°C, Nidda SFO t 1/2 = 19.1 d; DT90= 63.3 d (water)
SFO t 1/2 = 20.1 d; DT90= 66.9 d (total system) MRID 45109021 Supplemental

Storage stability data was not provided.

Up to 30% of the applied radioactivity was not
extracted. 20°C, Rhine SFO t 1/2 = 10.5 d; DT90= 34.9 d (water)
SFO t 1/2 = 11 d; DT90= 36.5 d (total system)

Anaerobic aquatic
metabolism halflife

20°C DFOP DT50= 21.3 d; DT90= 90.1 d;
Slow t 1/2 = 29.6 d (water; silt loam) IORE DT50= 25.6 d; DT90= 108 d;

tR IORE = 32.6 d (total system; silt loam)

MRID 45109002,
45109009/ Supplemental (model input
value calculations will be

based on total system) SFO DT50= 15.1 d; DT90= 50.1 d;
SFO t 1/2 = 15.1 d (water; loamy sand)

IORE DT50= 17 d; DT90= 45.8 d;

tR IORE = 13.8 d (total system; loamy sand) SFO DT50= 15.6 d; DT90= 51.9 d;
SFO t 1/2 = 15.6 d (total system; loamy sand) IORE N value <1; SFO is an appropriately conservative model

### 11 Parameter 

### Conditions Value Source/Classification

20°C SFO t 1/2 = 11.8 d; DT90= 39.1 d IORE N value <1; SFO is an appropriately conservative model MRID 45109023/ Supplemental

A highly polar unknown
was not identified. Up to 10% of the applied radioactivity was
unextracted.

The concentration of CO 2 varied substantially between days 275 and 366.

Storage stability data are not adequate.

Mobility

Freundlich soilwater partition coefficients (K F );organic carbonnormalized
Freundlich
coefficients (K FOC ) Loam, Loivre, France; pH 7.3,
3.1% OC 0.694 L/kg; 22.6 L/kg OC MRID 45109015/ Acceptable Clay loam, Bourgogne, France; 7.2, 2.4%
OC 0.368 L/kg; 15.5 L/kg OC

Sand, Germany; pH 5.62, 1.3% OC 0.12 L/kg; 10 L/kg OC

MRID 45109014/ Supplemental

The soils used in this study were autoclaved. Generally this would invalidate the study; however, the results indicate low sorption and
are consistent with MRID
45109015 as well as known mobility of other sulfonylurea herbicides. For this reason, the study
was classified as supplemental; however, the results should only be
used for characterization and not for quantitative
risk assessment. Loamy sand, Germany; pH 5.7,
2.5 % OC 0.54 L/kg; 22 L/kg OC

Sandy loam, Germany; pH 6.0,
1.1 % OC 0.13 L/kg; 12 L/kg OC

Silt loam, Mississippi, pH 5.4, 0.69 % OC 1.1 L/kg; 152 L/kg OC

Loamy sand, Arizona; pH 8.0,
0.16 % OC 0.01 L/kg;

ND

Sandy Loam, Illinois; pH 7.5,
2.5 % OC 2.0 L/kg; 82 L/kg OC

Clay loam, Minnesota; pH 7.2, 2.8% OC 2.5 L/kg; 90 L/kg OC

Loamy sand, United Kingdom; pH 7.9, 1.3% OC 0.02 L/kg; 0.8 L/kg OC

### 12 Parameter 

### Conditions Value Source/Classification

Field Dissipation

Terrestrial fielddissipation halflife; Silt loam, France; pH 7.4 8.8 d 0.2 lb a.i./A bareground 7.1 d 0.9 lb a.i./A bareground

6.4 d 0.9 lb a.i./A grassed

MRID 45109010/ supplemental

Only one transformation product was analyzed and the study was conducted in Europe. Silt, France; pH
5.8 7.1 d 0.2 lb a.i./A bareground 9.4 d 10.9 lb a.i./A bareground 9.1 d 0.9 lb a.i./A grassed

Silt loam, Duerrn, Germany; pH 6.9 8.9 d 0.2 lb a.i./A bareground 14.8 d 0.9 lb a.i./A bareground

11.6 d 0.9 lb a.i./A grassed

Silt loam, Warpe, Germany; pH 6.4 6.5 d 0.2 lb a.i./A bareground 2.0 d 0.9 lb a.i./A bareground

7.6 d 0.9 lb a.i./A grassed

Silt loam, United Kingdom; pH 6.2 <3 d 0.2 lb a.i./A bareground 11.2 d 0.9 lb a.i./A bareground <1d 0.9 lb a.i./A grassed

Silt loam, Spain, pH 7.8 11.3 d 0.2 lb a.i./A bareground 9.3 d 0.9 lb a.i./A bareground

12.5 d 0.9 lb a.i./A grassed

Fish Bioconcentration

Fish
bioconcentrationfactor (steadystate); depuration

rate -- No data available

MWRC= maximum water retention capacity
1. Reported half-life values were calculated using the draft NAFTA degradation kinetics ( Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media , Health Canada, U.S. Environmental Protection Agency, December 2012 .) document: Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media (draft document June 29, 2011); Single First Order (SFO), Nth-Order Rate Model or Indeterminate Order Rate Equation Model (IORE), and Double First-Order in Parallel (DFOP); Representativ e half-life to be used to calculate model input value for IORE (tR IORE )
2. First-order rate constant and hydrolysis half-lives at 25 °C were estimated using the Arrhenius equation. Half-lives were extrapolated beyond the experimental data.
3. This study was originally classified as acceptable (n oting the deficiency of not having data on the triazine moiety); however, it is being reclassified as supplemental because the study only provides information on the dissipation of the phenyl moiety of iodosulfuron and formation and decline of the observed transformation products is not clear.
4. Several study deficiencies were noted. The studies were conducted outsid e the United States.
5. This study has multiple deficiencies including inadequate sampling times pH: One divided by the log of the hydrogen ion concentration; Organic Carbon (OC); days (d)



### Transformation Products

Several major degradates of iodosulfuron were reported in the submitted environmental fate studies. These major transformation products as well as a few minor degradates are listed in
Table 9 with the maximum amounts of each chemi cal formed in the various studies.

### 13 One of the major environmental transformation pr oducts of iodosulfuron is metsulfuron-methyl, a registered sulfonylurea herbicid e. Metsulfuron forms in high levels (up to 70% applied) under aerobic conditions. Two mobility studies have been submitted for metsulfuron-methyl to support the registration of iodosulfuron. Metsulfuron does not bind to soils/sediments and is expected to be mobile in soils. In addition, since metsulfuron-methyl is registered as an active ingredient
fate data for metsulfuron has been submitted to EPA to support the metsulfuron registration. 3 

### As part of the registration review process for me tsulfuron methyl severa l studies have been requested including: batch equi librium (adsorption/desorption) , soil photolysis, aerobic soil metabolism, anaerobic soil, aerobic aquatic, a nd anaerobic aquatic. Fate characteristics of
metsulfuron are summarized in Table 10

. 4 

### In general, metsulfuron is mobile and is expected to be more persistent than iodosulfuron.

No environmental fate data for the other i odosulfuron transformation products have been submitted to EPA. Many of these transformation pr oducts retain the sulfonyl urea bridge and; therefore, may pose toxicological concerns.

3 Registered uses of metsulfuron methyl include: agricultural crops (wheat, barley, sorghum, and pastureland), noncrop and industrial areas, pasture and rangeland, and turf (r esidential lawns, golf courses, and ornamental grasses).

4 With the exception of the highlighted mobility data th e data are taken directly from the metsulfuron-methyl registration review problem formulation: Kiernan, B. D.; Baris, R. Registration Review: Preliminary Problem Formulation for Environmental Fate and Ecological Risk, Endangered Species, and Drinking Water Assessments for Metsulfuron-methyl (Case 7205) PC 122010 DP389258 September 22, 2011.14Table 9. Iodosulfuron Environmental Transformation ProductsCode Name/SynonymChemical NameChemical StructureStudy TypeRef.(MRID)Maximum%AR (day)Final %AR(studylength)MAJORAE F075736Metsulfuron methyl;methyl 2-[3-(4-methoxy-6-methyl1,3,5-triazin-2-y1)ureidosulfonyl]benzoateC14H15N5O6SMol. Wt.: 381.3638CO2CH3SO2HNHNON NNCH3OCH3Aerobic Soil4510893455.31 DAT2.9120 d4510893570.114 DAT25.5120 d4510893647.714 DAT10120 d4510900158.611 DAT4.4120 dAerobic Aquatic 4510902167.843 DAT1.4365 dAnaerobicAquatic451090231.55 DAT<LOD366 dAE F161778methyl 2-[3-(4-hydroxy6-methyl-1,3,5-triazin-2-yl)ureidosulfonyl]benzoateC13H13N5O6SMol. Wt.: 367.3372CO2CH3SO2HNHNON NNCH3OHAerobic Soil4510893412.228 DAT3.5120 d451089355.863 DAT3.5120 d4510893613.742 DAT9.3120 d451090018.528 DAT3.3120 dAE 00149662-[3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)ureidosulfonyl]benzoic acidC13H13N5O6SMol. Wt.: 367.3372CO2HSO2HNHNON NNCH3OCH3Aerobic Aquatic 4510902115.591 DATn.d.365 dAnaerobicAquatic4510902333.2113 DAT<LOD366 dAE 0014965Dimethoxy-metsulfuronfree acid2-[3-(4-hydroxy-6-methyl-1,3,5-triazin-2-yl)ureidosulfonyl]benzoic acidC12H11N5O6SMol. Wt.: 353.3106CO2HSO2HNHNON NNCH3OHAnaerobicAquatic4510902316.0113 DAT2.5366 d15AE F1457404-iodo-2-[3-(4-methoxy6-methyl-1,3,5-~idosulfonylbenzoic acidC14H14IN5O6SMol. Wt.: 507.2603CO2CH3ISO2HNHNON NNCH3OCH3Aerobic Soil451089343.211 DAT1.3120 d451089351.04 DATn.d.120 d451089361.442 DAT0.7120 d451090014.464 DAT3.6120 dAnaerobicAquatic4510902350.628 DAT<LOD366 d4510893618.8120 DAT18.8120 d4510900133.4120 DAT33.4120 dAerobic Aquatic 4510902127.5365 DAT13.7365 dAE0002166Methyl 4-hydroxy-2-[3-(4-methoxy-6-methyl1,3,5-triazin-2-yl)ureido]benzoateC14H15N5O6SMol. Wt.: 381.3638CO2CH3HOSO2HNHNON NNCH3OCH3Soil Photolysis 4510900321.4144 HAT21.4144 hAE0 0348554-hydroxy-6-methyl1,3,5-triazine-2-yl)ureaC5H7N5O2Mol. Wt.: 169.1414H2NHNON NNCH3OHAerobic Aquatic 4510902124.2182 DAT16.5365 dAE 0000119(4-methoxy-6-methyl1,3,5-triazin-2-yl)ureaC6H9N5O2Mol. Wt.: 183.1680H2NHNON NNCH3OCH3Aerobic Soil 451089344.228 DAT4.1120 dAerobic Aquatic451089365.4120 DAT5.4120 d451090014.064 DAT3.9120 d4510902124.9120 DAT12.4365 d16AEF159737saccharin1,2-benzisothiazol3(2H)-one 1,1-dioxideC7H5NO3SMol. Wt.: 183.1845SO2NHOAnaerobicAquatic451090239.7182 DAT<LOD366 dUnknownsSoil Photolysis 451090039.5 (combined)327 HAT6.9393 hAerobic Soil451089346.263 DAT3.3120 d451089357.2 (combined)120 DAT1.2120 d451090019.8 (single)120 DAT9.8120 dNon-extractedResiduesAerobic Soil4510893439.3120 DAT39.3(120 d)451089359.391 DAT9.0120 d4510893633.8120 DAT33.8120 d4510900135.7120 DAT135.7120 dAerobic Aquatic 4510902130.3365 DAT30.3365 dMINORAE F143133Iodo saccharin6-iodo-1,2-benzisothiazol-3(2H)-one 1, 1-dioxideC7H4INO3SMol. Wt.: 309.0810SO2NHOIAnaerobicAquatic451090232.23 DAT<LOD366 dAE FI45741methyl 2-[3-(4-hydroxy6-methyl-1,3,5-triazin-2-yl)16reidosulfonyl4-iodobenzoateC13H12IN5O6SMol. Wt.: 493.2337CO2CH3ISO2HNHNON NNCH3OHAerobic Soil451089343.24, 7 DAT1.6120 d451089353.40 DATn.d.120 d451089364.914 DAT2.2120 d451090014.364 DAT3.8120 dBoldfont indicates the highest percentage observed for a given transformation product.MW: molecular weightAR: Applied radioactivityn.d. not detected <LOD

### 17 Table 10. General Chemical Properties and Envi ronmental Fate Properties of Metsulfuron Methyl

Parameter Value Reference (MRID #)
/Comment
Physical/Chemical Parameters

Molecular mass 381.4 g/mol ACC 072767
Vapor pressure (20°C) 2.5 x 10 -12 torr ACC 072767
Henry’s Law Constant 2.35 x 10 -16 EPISuite v4.0

Water solubility (25°C) 109 mg/L (in water) Solubility significantly increases with increasing pH.
ACC 072767
Octanol-water partition coefficient (K O W ) 0.018 ACC 072767
Dissociation Constant (pKa) 3.5 ACC 072767
Mobility

Soil Partitioning Coefficient (Koc, 1/n) † 214, 134, 226, and 46 mL/goc 0.84, 0.78, 0.84, and 0.87 (1/n values) 44143301 supplemental
Data should not be used quantitatively.
EPISuite calculated value is 22 mL/g oc.
0.106 L/kg; 5.3 L/kg OC (silt loam,

Hattersheium, Germany, pH 7)

45109016 supplemental 0.145 L/kg; 7.7 L/kg OC (loam sand, Speyer, Germany, pH 6.0)
0.065 L/kg; 15.1 L/kg OC (Tor Sud, Speyer, Germany, pH 6.0)
0.5304 L/kg; 24 L/kg OC (loamy sand, Hanhofen, Germany, pH 5.8) 45133410 Supplemental; study was
conducted at 10 °C 0.2413 L/kg; 27 L/kg OC (silt loam, Honville, France pH 6.7)

Persistence in Water
Hydrolysis half-life (25°C, pH 5, 7, & 9) † Stable ACC 072767
Aqueous photolysis half-life (25°C) † Stable ACC 072767
Aerobic aquatic metabolism half-life No available data
--

Anaerobic aquatic metabolism half-life 35 – 365 days ACC 260973
41395501

Persistence in Soil

Soil photolysis † No available data
--

Aerobic soil metabolism half-life (25°C) 54.2 days 25.9, and 28 days 44491201
ACC 071434

Triazine amine ‡ : 240 days 40340317

Anaerobic soil metabolism † No available data
--

### 18 Parameter Value Reference (MRID #)
/Comment
Field Dissipation

Terrestrial field dissipation half-life (DT 50 ) † 1 – 10.5 months 42016507 Note: sampling/depth of analysis was insufficient to define the extent of leaching (35 cm).

Aquatic Bioconcentration

Bioconcentration Factor (BCF) in fish Low Kow indicates low potential to
bioaccumulate. ACC 072767

‡ Major degradate of metsulfuron

† At least one study was under review as of September 11, 2011.



### In summary, iodosulfuron and its environm ental transformation products may leach to groundwater and runoff or drift during application to surfac e water. Once in aquatic environments, iodosulfuron and its environmenta l transformation products including metsulfuron are expected to remain predominantly in the water phase.

Safeners

Isoxadifen-ethyl, the safener included in co rn use formulations (Reg. No. 264-686) of iodosulfuron, is reported to be at concen trations approximately 15-times higher than iodosulfuron; therefore, the field application rate is expected to be 0.03 lb/A. Chemical identifiers for isoxadifen-ethyl are included in Table 11 . Limited environmental fate data for isoxadifen-ethyl are provided in Table 12 . Another safener, mefenpyr-diethyl, is included in wheat and triticale formulations (Reg. Nos. 264- 1103; 264-820). The reported concentration of the safener is up to 15-times higher than the conc entrations of iodosulfuron in the formulated products. The corresponding maximum field app lication rate is assumed to be 0.045 lb/A.
Chemical identifiers for mefe npyr-diethyl are included in Table 13 . Limited environmental fate data for mefenpyr-diethyl are provided in Table 14

.

Table 11. Isoxadifen-ethyl Chemical Identifiers

Parameter Identifier

Chemical Structure

N O

O O

Chemical Name ethyl 4,5-dihydro-5,5-diphenyl-1,2-oxazole-3-carboxylate ethyl 4,5-dihydro-5,5-diphenyl-3-isoxazolecarboxylate SMILES C1(C(OCC)=O)=NOC(C1)(c1ccccc1)c1ccccc1
CAS Number 163520-33-0

### 19 Table 12. Physical/Chemical Parameters 

### of Isoxadifen-ethyl

Parameter Value Source/Classification

Molecular mass (molecular formula) 295.34 g/mol (C 18 H 17 O 3 N) Calculated using EPI Suite

Vapor pressure (25°C) 6.79 x 10 -5 Pa Calculated using EPI Suite
Modified Grain Method

Aqueous solubility (20  C) 1.26 mg/L MRID 44739133 (algal toxicity study)

Log octanol-to-water partition coefficient (log K O W ) 3.8 MRID 44739121

Koc 9777 L/kg Calculated using EPI Suite
Kow method

Hydrolysis Stable Calculated using EPI Suite



### Table 13. Mefenpyr-diethyl Chemical Identifiers

Parameter Identifier

Chemical Structure 

### N N O

O Cl Cl

O O

Chemical Name 1H-Pyrazole-3,5-di carboxylicacid, 1-(2,4-d ichlorophenyl)-4,5-dihy dro-5-methyl-, 3,5- diethyl ester 1-(2,4-Dichlorophenyl)-4,5-dihydro-5-m ethyl-1H-pyrazole-3,5-dicarboxylic acid diethyl SMILES CCOC(=O)C2=NN(c1ccc( Cl)cc1Cl)C(C)(C(=O)OCC)C2
CAS Number 135590-91-9



### Table 14. Physical/Chemical Parameters 

### of Mefenpyr-diethyl

Parameter Value Source/Classification

Molecular mass (molecular formula) 373.24 g/mol (C 16 H 18 C l2 N 2 O 4 ) Calculated using EPI Suite

Vapor pressure (25°C) 4.42 x 10 -4 Pa Calculated using EPI Suite
Modified Grain Method

Aqueous solubility (25  C) 2.4 mg/L Calculated using EPI Suite
WSKOW v1.41

Log octanol-to-water partition coefficient (log K OW ) 3.83 Calculated using EPI Suite [Exper. database match

(Tomlin, C 1997)]

4.82 Calculated using EPI Suite (KOWWIN v 1.67)

Koc 740 L/kg Calculated using EPI Suite
Kow method

Hydrolysis stable Calculated using EPI Suite

### 20 4. RECEPTORS

Table 15 and Table 16 provide a summary of the aquati c and terrestrial taxonomic groups, respectively, and the most sensitive surrogate sp ecies tested to characterize the potential acute and chronic ecological effects of iodosulfuron. The tables provide an overview of the available acute toxicity information on iodosulfuron, and pr ovide the acute toxicity classifications. Based on the available ecotoxicity inform ation, the most sensitive organisms are aquatic and terrestrial plants, however, it is noted that there is some uncertainty with the available terrestrial plant studies because they have been conducted on formulations containing a safener. There are several products that are not formulated with a safener including two for use on turf, which, along with a product for use on wheat (formulated w ith a safener) have the highest use rates. Because the safener may influence the final toxici ty estimation, terrestrial plant toxicity studies for a product formulated for use on turf would re duce the uncertainty in the upcoming analysis.

Table 15. Summary of the Most Sensitive Endp oints from Aquatic Toxicity Studies for
Iodosulfuron

Taxonomic

Group Study Type Surrogate Species
and
Test Material Toxicity Value (all units in terms
of measured active ingredient) MRID and
Classification Acute Toxicity
Classification

Freshwater fish 1 Acute Rainbow Trout ( Oncorhynchus mykiss )

TGAI LC 50 > 88.1 mg
a.i./L

Most sensitive endpoint: none
No sublethal effects reported. 45109035 Supplemental
classification
based on water quality deviations
from 850 guideline
recommendations. No more than slightly toxic

Chronic (Early
Life Stage) Fathead Minnow ( Pimephales promelas )

TGAI NOAEC 10.2 mg
a.i./L LOAEC >10.2 mg
a.i./L

Most sensitive endpoint: none
No sublethal effects reported. 46431804 Acceptable
--

Estuarine/Marine
fish Acute Sheepshead Minnow ( Cyprinodon variegatus )

TGAI LC 50 > 100 mg
a.i./L

Most sensitive endpoint: none
No sublethal effects reported. 45109127 Acceptable Practically
non-toxic

Chronic No Data

### 21 Taxonomic

Group Study Type Surrogate Species
and
Test Material Toxicity Value (all units in terms
of measured active ingredient) MRID and
Classification Acute Toxicity
Classification

Freshwater
invertebrates Acute Water Flea ( Daphnia magna )

TGAI EC 50 > 86.9 mg
a.i./L NOAEC= 28.1 mg
a.i./L
Most sensitive endpoint:
immobilization
No sublethal effects reported. 45109103 Supplemental
classification
based on water quality deviations
from 850 guideline
recommendations. No more than slightly toxic

Chronic Water Flea ( Daphnia magna )

TGAI NOAEC = 9.1 mg
a.i./L
LOAEC = 15.9 mg a.i./L

Most sensitive endpoint:
reduced number of young per female and dry weight 45109104 Acceptable --

Estuarine/Marine
invertebrates Acute Mysid shrimp ( Mysidopsis bahia ) LC50 = >100 mg
a.i./L NOAEC = 100 mg
a.i./L No mortality or
sublethal effects reported 45109128 Acceptable Practically
non-toxic

Chronic No Data

Aquatic plants and algae Nonvascular Green algae ( Pseudokirchneriella subcapitata )
TGAI EC 50 = 0.041 mg
a.i./L
NOAEC = 0.014 mg a.i./L

Most sensitive endpoint: cell density 45109105 Acceptable --

Vascular Duckweed ( Lemna gibba )

TGAI EC 50 = 0.00070 mg a.i./L
NOAEC = 0.00039 mg a.i./L

Most sensitive endpoint: cell density 45109111 Acceptable --

1. Freshwater fish repr esent surrogates for aquatic-phase amphibians.

### 22 Table 16. Summary of the Most Sensitive Endp oints from Terrestrial Toxicity Studies for
Iodosulfuron

Taxonomic

Group Study Type Surrogate Species

and
Test Material Toxicity Value (all units in terms of

measured active ingredient) MRID and
Classification Acute Toxicity
Classification

Birds 1 Acute Bobwhite quail ( Colinus virginianus )
and Mallard (

Anas platyrhynchos )

TGAI LD 50 > 1744 mg/kg-bw
Most sensitive endpoint: none.
No sublethal effects reported. 45109029/
45109028 Acceptable No more than slightly toxic

Sub-acute dietary Bobwhite quail ( Colinus virginianus )

TGAI LC 50 = > 4360 mg/kg diet
Most sensitive endpoint: none.
No sublethal effects reported. 45109030 Acceptable Practically
non-toxic

Chronic Bobwhite quail ( Colinus virginianus )

TGAI NOAEC = 372 ppm LOAEC = 1077 ppm

Most sensitive endpoint: Adult male weight gain 46431803 Acceptable --

Mammals Acute Oral Laboratory rat ( Rattus norvegicus ) LD 50 = 2448 mg a.i./kg 45133404 Acceptable Practically
nontoxic 3

Acute
Inhalation Laboratory rat ( Rattus norvegicus ) LC 50 = > 2.81 mg/L 45108805 Acceptable --

Chronic Laboratory rat ( Rattus norvegicus ) NOAEL = 500 ppm LOAEL = 5000 ppm Endpoint: Based on pup mortality 45108818 Acceptable --

Insects Acute

contact Honey bee ( Apis mellifera L. )

TGAI LD 50 > 150 μg a.i./bee
No sublethal effects reported. 45109115 Acceptable Practically
nontoxic 2

Acute Oral Honey bee ( Apis mellifera L. )

TGAI LD 50 > 81 μg a.i./bee
No sublethal effects reported. 4510914 Acceptable Practically
nontoxic 2

Terrestrial plants Vegetative Vigor Dicot – Lettuce

Formulated Corn
Product EC 25 = 0.00000037 lbs
a.i./acre
EC 05 = 0.00000000018
NOAEC = 0.00000066
lbs a.i./acre

Endpoint: Shoot length 45109131 4AcceptableSupplemental
for lettuce and
onion --

### 23 Taxonomic

Group Study Type Surrogate Species

and
Test Material Toxicity Value (all units in terms of

measured active ingredient) MRID and
Classification Acute Toxicity
Classification

Monocot – Onion

Formulated Corn
Product EC 25 = 0.0000067 lbs
a.i./acre
EC 05 = 0.00000043
NOAEC = 0.0000026
lbs a.i./acre Endpoint: Shoot dry weight --

Terrestrial plants Seedling Emergence Dicot – Tomato

Formulated Corn
Product EC 25 = 0.0000035 lbs
a.i./acre
EC 05 = 0.000000035
lbs a.i./acre
NOAEC = <0.000084
lbs a.i./acre Endpoint: Shoot length 45109132AcceptableSupplemental

for tomato --

Monocot – Onion

Formulated Corn
Product EC 25 =0.00028 lbs
a.i./acre
EC 05 = 0.00000057 lbs
a.i./acre
NOAEC = 0.000011
lbs a.i./acre Endpoint: Shoot length 1. Birds represent surrogates for terr estrial-phase amphibians and reptiles. 2. Based on acute contact LD50 ( μ g a.i./bee) <2 highly toxic; 2-10.99 moderately toxic; ≥ 11 practically non-toxic 3. Acute Oral (avian/mammal): Based on LD50 (mg/kg) <10 very highly toxic; 10-50 highly toxic; 51-500 moderately toxic; 501-2000 slightly toxic; >2000 practically nontoxic 4. A vegetative vigor study is available (MRID 47731901 with amendment 47746701) but has not been fully reviewed. A preliminary review suggests that the toxic ity values are less sensitive than the current endpoints.



### Effects on Plant Reproduction

EFED's Plant Technical Team (PTT) conducted an analysis of available SU plant reproduction data from the open literature and the registrant -submitted data for chlors ulfuron, a representative SU, and concluded that data from the 850.4150 ve getative vigor guideline study are sufficiently protective of potential impacts to plant reproduction. Acetolacta te synthase (ALS) inhibitors primarily affect metabolically active meristem tissues. When plants are exposed at a young, vigorously growing life-stage, effects are expressed primarily as inhibition of vegetative growth ( i.e., biomass, shoot length). As plants mature these effects are less pronounced. However, as plants enter their reproductive life-stage, the metabolically active tissue will include flower and seed production. Plants exposed to SU herbicides during the reproductive life stage are likely to exhibit adverse effects on repr oduction, generally expressed as re duced seed number or reduced seed weight. Based on the latest data analysis, th ese effects are expected to occur at similar rates to those effects determined in the guideline ve getative vigor studies ( 850.4150), so further data are not requested at this time.

### 24 Degradate Toxicity

Metsulfuron, another registered herbicide (P C 122010), is a biotrans formation product of
iodosulfuron in aerobic soils as well as aerob ic aquatic environments. The most sensitive terrestrial and aquatic toxicity data are summarized in Tables 17 and 18 and are discussed in more detail in previous assessments (D P315491, 03/06; D350049, 03/08) and also the recent problem formulation for metsulfuron 5



### .

Table 17. Aquatic Wildlife Toxicity Profile for Metsulfuron

Taxonomic Group Study Type Species (Common Name) Endpoint (mg ai/L) Acute
Classification Reference (MRID)

Freshwater Fish Acute Lepomis
macrochirus (Bluegill sunfish) LC 50 >150 Practically
nontoxic 00125817

Chronic Oncorhynchus mykiss (rainbow trout) NOAEC=4.5 -- 44122801

Freshwater
Invertebrates Acute Daphnia magna (Water flea) LC 50 >150 Practically
nontoxic 00125818

Chronic Daphnia magna ( Water flea) NOAEC = 100 b

-- 44704901

Estuarine/marine
Fish No data

Estuarine/marine
Invertebrates No data

Vascular plants Vascular Lemna minor (duckweed) EC 50 =0.00036
NOAEC=0.00016 -- 41773902 a

Nonvascular plants NonVascular Pseudokirchneriella subcapitata EC 50 =0.031
NOAEC=0.005 -- 40639302 a

a appears to be the most sensitive endpoint for Mets ulfuron (pending full review of other studies)

b provisional value pending full review.

5 Kiernan, B. D.; Baris, R. Regist ration Review: Preliminary Problem Fo rmulation for Environmental Fate and Ecological Risk, Endangered Species, and Drinking Wate r Assessments for Metsulfuron-methyl (Case 7205) PC
122010 DP389258 September 22, 2011.

### 25 Table 18. Terrestrial Organism Toxicity Profile for Metsulfuron

In general, the toxicity profiles for iodosulfur on and metsulfuron are similar for terrestrial and aquatic animals. Based on the available data, the toxicity to plants is also similar for
iodosulfuron and metsulfuron. A total toxic re sidue approach will be used unless the pending
data review shows that metsulfur on is more toxic to plants. Taxonomic

Group Study Type Surrogate Species (Common

Name) Endpoint Acute
Classification/
Chronic effect Reference (MRID)

Birds

Acute Anas platyrhynchos (Mallard duck) LD 50 >2150 mg a.i./kg-bw a,b Practically
nontoxic a,b 00125819

Colinus virginianus (Bobwhite quail) LC 50 >5620 mg ai/kg diet Practically
nontoxic 00125821

Chronic Anas platyrhynchos (Mallard duck) NOAEC=209 mg ai/kg-diet -- 44115702

Mammals Acute Rattus norvegicus (Laboratory rat) LD 50 >5000 mg a.i./kg-bw Practically
nontoxic 47018706

Chronic Laboratory rat LOAEL=5000 mg a.i./kg-diet NOAEC=500 mg ai/kg-diet Adult body weight gain 00151028

Terrestrial
Invertebrates Acute Apis mellifera (Honey bee) LD 50 >25 μ g/bee Practically
nontoxic 00141829

Terrestrial Plants Seedling

emergence Dicot (tomato) EC 25 = 0.0000032
lb a.i./A c

EC 05 or NOAEC =
0.0000000012 lb
a.i./A c -- 44050301 c

Monocot (onion) EC 25 = 0.0001 lb
a.i./A c

EC 05 or NOAEC
0.000013 lb a.i./A c -- 44050301 c

Vegetative Vigor -- -- -- 44050301 d

a Data under review (provisional data reported here)

b Data are incomplete pend ing passerine submission.

c Data under review(provisional data reported here). The previous iodosulfuron a ssessment used the Seedling Emergence values reported in MRID 44050301, however, the recent probl em formulation for metsulfuron identified that MRID 44050301 is under review and may have deficiencies. Therefore, the values for this endpoint are pending study review

d Data under review. A cursory review of the Vegetative Vigor study submitted in 4405301 shows the toxicity is similar to the seedling emergence toxicity however, at this time, the provisional data cannot be repor ted without further review of the data and the supporting stat istical analysis.

### 26 In addition to metsulfuron, there are also five major degradates for iodosulfuron that contain an intact sulfonyl urea (SU) br idge (-NH-CO-NH-SO2-), incl uding: AE F161778, AE 0014966, AE 0014965 (only formed in anaerobic aquatic e nvironments), AE F145740, and AE 0002166 (see
structures in Table 9 ). The intact sulfonyl urea (SU) bridge has been identifie d as an important
functional structure of SU toxicity. For degradates AE F161778 and AE 0014966, aquatic toxicity data are available and wh ile the data have not been fully reviewed, the data suggest that both degradates are less toxic than the parent to aquatic vascular plants ( Lemna gibba ) with EC 50 

### values of 0.418 mg/L (MRID 46319201) and >10 mg/L (45791502), for AE F161778 and AE 0014966, respectively. Data are not available for AE0014965, however, this transformation product only forms in anaerobic aquatic envir onments; thus this degradate will only be considered in groundwater simulatio ns (for irrigation). Data are also not available for the other two major degradates that retain an intact sulfonyl urea (SU) br idge (AE F145740 and AE 0002166). In the absence of additional toxicity data, these transformation products will be considered to be as toxic as the parent. In summary, four major degradates (AE F161778, AE 0014966, AE F145740, and AE 0002166) that retain the SU bridge will be included in the TTR along with metsulfuron and the parent.

Safener Toxicity

For isoxadifen-ethyl (AEF122006), the safener added to formulations intended for corn use, a preliminary review of the availa ble acute toxicity data suggests that isoxadifen-ethyl is highly toxic to the bluegill (MRID 44739131; LC 50 

### = 0.22 mg /L, NOAEC = 0.09 mg /L) and the rainbow trout (MRID 44739130; LC 50 

### = 0.34 mg /L, NOAEC = 0.12 mg /L). For aquatic invertebrates and non-vascular plan ts the available data reports EC 50 

### values of >0.51 mg/L (MRID 44739132) and >100 mg/L (MRID 45360901), resp ectively. For chronic exposure, data are not available, however, a st ructure activity screen using EC OSAR (V 1.1-based on “aliphatic amines” as the chemical class/training set) shows a predicted high toxicity to fish, invertebrates, and algae with predicted toxi city values of 0.004, 0.005, and 0.007 mg /L for fish, invertebrates, and algae, respectively. For terrestrial organisms, the available data suggest that isoxadifen has low toxicity to birds and mammals on an acute exposure basis (MRIDs 44739135, 44739126, 44739127). On a chronic exposure basis, data ar e only available for mammals with a reported NOAEL of 12.6 mg/kg-bw-day (MRID 44995801). See the Stressors of Concern discussion below, which discusses a cursory analysis conducted to assess pot ential exposure of the safener to aquatic animals and plants.

### 27 Toxicity data are not available to the EP A for the safener mefenpyr-diethyl (added to formulations for wheat and triticale uses). According to a screen in ECOSAR (using “esters” as the training set), mefenpyr-diethyl is about 1-2 orders of magn itude more toxic to fish and
invertebrates than iodosulfuron. On an acute exposure basis, mefe npyr-diethyl is estimated to be moderately toxic to fish (LD 50 

### =1.28 mg/L) and highly toxic to aquatic invertebrates (LC 50 

### =0.354 mg/L). Chronic toxicity estimates are (0.047mg/L) for fish and (0.084 mg/L) for invertebrates. Toxicity estimates for terrestrial taxa are not available in ECOSAR, however, an evaluation of mefenpyr-diethyl was conducted by the Food and Agriculture Organiza tion of the United
Nations 6 

### and the reported toxicity to birds, mamma ls and invertebrates can be classified as practically non-toxic. See the Stressors of Concern discussion below, which discusses a cursory analysis conducted to assess potential exposure of the safener to aquatic animals.

See APPENDIX D for ECOSAR output.

Ecological Incidents

A query of the Ecological Incident Information System (EIIS) database identified six incidents that were linked to exposure to iodosulfuron ( Table 18 ). All of the incidents involved alleged damage to corn following a direct application of the herbicide to the crop. One incident, which was assigned a certainty of “probable,” was attributed to misuse of the pesticide. The other four incidents were assigned a certainty of “possible” and were attributed to legal use of the pesticide. Incidents of this nature, in which an herbicide allegedly damaged a crop on which it was directly applied, are no longer entered into EI IS since they have little releva nce to risk to nontarget plants growing off the treatment site. No incident in the EIIS database attributes damage to crops or other nontarget plants resulting fr om spray drift or runoff of iodos ulfuron from a treated field. Also, no incident in the EIIS da tabase link exposure to iodosulfuron to a ny adverse effects to fish, wildlife, or invertebrates.

The Incident Data System (IDS) database was qu eried for minor ecological incidents that were reported by the pesticide registra nts in aggregated incident re ports. Nineteen minor ecological
incidents were linked to iodosulfu ron exposure. All of these inci dents were of damage to crops or other nontarget plants.

A search of the Avian Incident Monitoring Sy stem (AIMS) database did not provide any
additional incident data.

6 FAO Specifications and Evaluations for Agricultural Pesticides-Mefenpyr diethyl. Food and Agriculture Organization of the United Nations. 2011. http://www.fao.org/fileadmin/templates/agphome/documen ts/Pests_Pesticides/Specs/Mefenpyr_diethyl_2011.pdf

### 28 Table 18. Ecological Incidents in EIIS Linked to Exposure to Iodosulfuron

Use Site Species
Affected Date Exposure Certainty Misuse? ID Number

Corn Corn 6/16/2003 Direct Application Probable Yes I014216-035
Corn 6/2/2004 Direct Application Possible No I015291-020
Corn 6/24/2004 Direct Application Possible No I015291-037
Corn 7/1/2004 Direct Application Possible No I015406-004
Corn 7/1/2004 Direct Application Possible No I015406-003



### Incidents attributed to exposure to metsulfuron are given in Table 19 to provide information on the potential risk of this degr adation product. It should be recognized, however, that these incidents likely resulted from use of herbicide products contai ning metsulfuron-methyl as an active ingredient rather than from degradation of iodosulfuron. Nevertheless, the numerous plant damage incidents linked to exposure this ingred ient demonstrate that nontarget plants may be harmed if they are exposed to this compound through sp ray drift, runoff , or carryover of soil
residues.

Table 19. Ecological Incidents in EIIS Li nked to Exposure to Metsulfuron-Methyl (Degradation Product of Iodosulfuron)

Use Site Species
Affected Date Exposure Certainty Misuse? ID Number

Agricultural

area (unspecified) Woody plants 9/1/1991 Spray drift and
runoff Probable No I000903-001

Potatoes and

tomatoes 8/25/1993 Spray drift and
runoff Probable No I000903-004

Fish 7/1/1996 Runoff Unlikely No I005925-008
Hay 4/25/2000 Carryover Probable NR I012366-047

Wheat 2001 NR Possible Yes I020627-006

Barley Vegetables 5/16/2008 Carryover Highly
Probable No I020340-001

Conservation
Reserve Area Cotton 8/12/2003 Spray drift Possible NR I014415-001

Fence row Birds, fish, and algae 5/26/1992 Spray drift and
runoff Possible NR I000022-001

Residential
property NR NR Spray drift Possible Yes I005192-001

Turf 6/7/2004 Runoff Possible NR I015266-001

Right-of way Peach 7/15/2004 Spray drif t Probable No I015218-001
Vegetables 9/9/1997 Spray drift Probable No I007371-024
Cantaloupe, watermelon,
and tomato 6/4/2004 Spry drift Possible No I015280-001

Ornamental plants 7/3/2003 Spray drift Highly probable Yes I014290-001

Wheat Sweet cherry 4/11/1994 Spray drift Possible Yes I003386-001

Ornamental plants 4/18/2001 Spray drift Possible NR I020627-007

### 29 Use Site Species
Affected Date Exposure Certainty Misuse? ID Number

Wheat 5/17/2005 Treated direct ly Possible No I06328-036



### 5. CONCEPTUAL MODEL

The environmental fate properties of iodosulfuron i ndicate that direct spra y, spray drift, leaching to groundwater, and runoff represen t potential transport mechanisms. These pathways may result in a wide range of potential aquatic and terrestr ial exposure scenarios to both iodosulfuron as
well as its environmental tr ansformation products.

6. ANALYSIS PLAN

Ecological Risk Assessment



## Stressors of Concern

The exposure assessments will consider the pare nt, iodosulfuron, the degradate metsulfuron as well as four major degradates that retain an intact SU bridge (AE F161778, AE 0014966, AE F145740, and AE 0002166) using a TTR approach. For more information on the selection of the transformation products included in the TTR an alysis see the section above on degradate toxicity. Based on available toxicity data for the two safeners include d in some iodosulfuronmethyl formulations, a cursory analysis was conducted to determine if additional information or data are needed to address potential risk concer ns associated with form ulated products containing
the safeners.

While the toxicity of the safener, isoxadifen-eth yl, to some species including aquatic organisms may be greater than the parent, a quatic exposure to the safener at levels of toxicological concern are not expected based on the cu rrent products registered for us e on corn. This was determined by calculating a high-end exposur e concentration [0.21μg/L (peak)] using the GENEEC (v. 2.0 August 2, 2001) 7 

### . Since the high-end estimated exposure c oncentration is orders of magnitude
less than the most sensitive e ndpoints (freshwater fish acute LC 50 

### value of 220 μg/L; freshwater invertebrate acute toxicity estimate = 41 μg/L; fish chronic toxicity estimate = 4 μg/L), risk is not expected. Risk to terrestrial animals is not expected based on a prelim inary screen using the TREX model (V 1.5.1).

The same analysis was completed for other sa fener, mefenpyr-diethyl. The high-end estimated exposure concentration is 3.93μg/L (peak) 8 

### . Since this high-end exposure concentration is orders of magnitude less than the most sensi tive acute endpoints (fish toxicity estimate = 1128 μg/L; invertebrate toxicity estimate = 354 μg/L), risk is not expected on an acute exposure basis. On a chronic exposure basis, risk is also not expe cted based on the estimated toxicity values (fish

7 Modeling assumptions: 1 applications at 0.03 lb/a; ground application; high boom; no spray drift buffer; fine spray; no incorporation; solubility 1.3 mg/L; Koc = 9777 L/kg; and stable to degradation.

8 Modeling assumptions: 2 applications at 0.008 lb/A; 3 d minimum retreatment interval; ground application; high boom; no spray drift buffer; fine spray no incorporation; solubility 2.4 mg/L; Koc = 740 L/kg; and stable to degradation.

### 30 toxicity estimate = 47 μg/L; invertebrate toxici ty estimate = 84 μg/L). Additionally, there are several aquatic toxicity studies cited in the recent FAO evaluation 9 

### that suggest the ECOSAR estimates are overestimating the toxicity. A final c onsideration for this safener is that with a log

K OW 

### of 4.82 (highest value reported in EPI Suite ), this chemical ha s the potential to bioaccumulate; however, a fish bioaccumulation study also referenced in the FAO review of mefenpyr diethyl has a reported BCF of 232 which tentatively suggests (until EPA reviews the data) that mefenpyr diethyl is unlik ely to bioaccumulate in organism s. If these toxicity/BCF data
are made available to the EPA it will be useful to improve our understanding of the toxicity profile for this safener.

Although this cursory analysis i ndicates a low potential for risk to aquatic organisms from exposures to the safeners at the levels estim ated, alternative assumptions on mobility were explored to better understand the potential impact of the estimated Koc value on estimated EECs for the safeners. For isoxadifen-ethyl [Koc =977 L/kg (10X less than the EPI estimate) the estimated peak high-end exposure concentration was estimated to be 0.74 μg/L]. This is considerably lower than the endpoint for the most sensitive species assessed. For mefenpyrdiethyl ([Koc =74 L/kg (10X less than the EP I estimate), the estimated peak high-end concentration was estimated to be 7.1 μg/L]. Agai n, these results suggest that concentrations at levels of toxicological concern are not like to occur. The results of the GENEEC analysis are provided in APPENDIX E

.



## Measures of Exposure

In order to estimate exposure a nd potential risks of iodosulfuron exposure to aquatic and terrestrial organisms, all exposur e modeling and resulting risk conclusions will be made based on maximum application rates, application methods , and any mitigation measures specifically
indicated on the label. The models that will be used to predict the estimated environmental concentrations (EECs) of iodosulfuron are discussed on OPP’s model website. 10 

### These models include: PRZM (Pesticide Root Zone Mode l) and EXAMS (EXposur e Analysis Modeling System), PRZM-groundwater (GW), AgDrift, AgDisp, T-REX, TerrPlant, SIP (Screening Imbibition Program), and STIR (Scr eening Tool for Inhalation Risk).

The results of running the SIP and STIR models are presented in APPENDIX B and
APPENDIX C . While the SIP model suggests that th ere are expected concerns for both mammals and birds, the model does not perform well with chemicals that have a high aqueous solubility and have low toxicity to these organisms. This route of exposure is not likely to be significant enough to cause concern. The analysis with STIR indicates no risk to birds or mammals through inhalation of iodosulfuron.

9 FAO Specifications and Evaluations for Agricultural Pesticides-Mefenpyr diethyl. Food and Agriculture Organization of the United Nations. 2011. http://www.fao.org/fileadmin/templates/agphome/documen ts/Pests_Pesticides/Specs/Mefenpyr_diethyl_2011.pdf

10 http://www.epa.gov/opp00001/science/models_pg.htm

### 31 

## Measure of Effects

Ecological effects data are used as measures of di rect and indirect effect s to biological receptors. Data are typically obtained from registrant-submitte d studies or from literature studies identified by ECOTOX. The ECOTOX database provides more ecological effects data in an attempt to bridge existing data gaps. ECOTOX is a source fo r locating single chemical toxicity data and potential chemical mixture toxicity data for aq uatic life, terrestrial plants, and wildlife. ECOTOX was created and is maintained by the US EPA, Office of Research and Development,
and the National Health and Environmental Ef fects Research Laboratory's Mid-Continent Ecology Division.



## Integration of Exposure and Effects

Risk characterization is the integration of e xposure and ecological effects to determine the potential ecological risk from the use of pestic ides and the likelihood of direct and indirect effects to non-target organisms in aquatic and terrestrial habitats. For the assessment of risks, the risk quotient (RQ) method is used to compare e xposure and measured toxicity values. EECs are divided by acute and chronic toxicity values. The resulting RQs are then compared to the Agency’s Levels of Concern (LOCs) (USEPA 2004) . These criteria will be used to indicate when iodosulfuron use, as directed on the label, has the potential to cause adverse direct or indirect effects to non-target organisms. In addition, incident data from the EIIS, IDS, and AIMS will be considered as part of the risk characterization.

Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to federally listed th reatened and/or endangere d (listed) species from registered uses of pesticides in registration review.

Endocrine Disruptor Screening Program

Iodosulfuron is not included in the first group of 67 chemicals issued an order to conduct Tier 1 EDSP testing. For additional information on the EDSP program, visit http://www.epa.gov/endo/.

7. PRELIMINARY IDENTIFICATIO N OF DATA GAPS

Fate

Table 20 identifies the environmental fate studies submitted by the registrant, as well as study
classifications and whether or not additional data are needed in order to support the registration review exposure assessments. Rationale for the additional data requested is also presented.

### 32 Table 20. Submitted Environmental Fate Data for Chemical Iodosulfuron

OCSPP
Guideline Data Requirement Submitted
Studies (MRID) Study
Classifications Are data
needed to
conduct risk
assessment? Comments

835.2120 Hydrolysis 45108623 acceptable no

835.2240 Aqueous photolysis 45108624,
45108625 supplemental no

835.2410 Soil photolysis 45109003 supplemental no 1 The study only investigated the fate of the phenyl ring. The retention of the SU bridge is an indication of the potential toxicity and the cleavage of this bridge can be followed independent of the ring structure labeled; therefore additional data on the phototransformation of
triazine labeled iodosulfuron is not being requested at this time.

The formation and decline of the transformation products was not clearly established during the course of the study. The formation of one transformation product is increasing at study termination and is approaching 10% of the applied material. Identification of this material is needed; however, if this information is not submitted to EPA it may be considered as part of the total toxic residues.

Iodosulfuron is toxic to plants. Knowledge of the persistence of
iodosulfuron in soil as well as the
identification of transformation products will help the Agency determine and estimate exposure of
iodosulfuron and other residues ofpotential toxicological concern to nontarget organisms. The results of this study will be used in the environmental fate assessment, and later on, in the ecological risk characterization.

### 33 OCSPP
Guideline Data Requirement Submitted
Studies (MRID) Study
Classifications Are data
needed to
conduct risk
assessment? Comments

835.4100 Aerobic soil
metabolism 45108934,
45109005 supplemental

no 1 Several of the studies report high levels
of unextracted residues. The extraction
methods used in these studies are not
considered exhaustive. Identification of
the unextracted materials is needed to rule out the potential that these residues are of toxicological concern. In absence of the data, these residues may be considered as part of a TTR approach in modeling to account for this uncertainty.

Several of the studies were conducted
outside the United States additional information on soil taxonomy would be helpful. 45108935,
45109006 supplemental

45108936,
45109007 supplemental

45109001,
45109008 supplemental

45108933,
45109004 supplemental

835.4200 Anaerobic soil
metabolism No data no 1 No acceptable study has been
submitted.

Iodosulfuron is toxic to plants. Knowledge of the persistence of
iodosulfuron in soil as well as the
identification of transformation products would help the Agency determine and estimate exposure of
iodosulfuron and other residues ofpotential toxicological concern to nontarget organisms. The results of this study would be used in the environmental fate assessment, drinking water assessment and later on, in the ecological risk characterization. In absence of this data, the aerobic aquatic metabolism study will be used as a surrogate for identifying residues
formed under anaerobic conditions that may be of toxicological concern.

### 34 OCSPP
Guideline Data Requirement Submitted
Studies (MRID) Study
Classifications Are data
needed to
conduct risk
assessment? Comments

835.4300 Aerobic aquatic
metabolism 45109021 supplemental no 1 Storage stability data was not provided
and is needed to confirm the residues were not degrading during storage.

Storage stability studies included as part of this study as well as those
conducted for the TFD study (MRID 45109010; differences in storage conditions is not known) indicate that samples are metabolically stable over an eight month time period (recoveries are within guidelin e criteria). Although samples were stored for up to a year, based on these data samples are expected to be stable during the reported storage period.

Identification of the unextracted
materials is needed to rule out the potential that these residues are of toxicological concern. In absence of the data, these residues may be considered as part of a TTR approach in modeling to account for this uncertainty.

Iodosulfuron is toxic to plants. Knowledge of the persistence of
iodosulfuron in soil as well as the
identification of transformation products will help the Agency determine and estimate exposure of
iodosulfuron and other residues ofpotential toxicological concern to nontarget organisms. The results of this study will be used in the environmental fate assessment, drinking water assessment and later on, in the ecological risk characterization.

835.4400 Anaerobic aquatic
metabolism 45109002,
45109009 supplemental

no
45109023 supplemental

835.1230
835.1240 Adsorption/ desorption and leaching 45109015 acceptable

no 45109014 supplemental

835.1410 Volatility – laboratory No data no Iodosulfuron is not expected to be volatile based on the reported vapor

pressure.

### 35 835.6100 Terrestrial field dissipation 45109010 supplemental no 1 The study only looked for one environmental transformation product. In addition, these studies were conducted in Europe and no data was provided on how the sites were representative of locations within the US. Storage stability studies conducted over an eight month time period
indicate that iodosulfuron and metsulfuron are relatively stable over the 8 month time period (recoveries are within guideline criteria). Study samples were stored for almost one year; however, based on the submitted storage stability data iodosulfuron and metsulfuron are expected to be stable. Despite these deficiencies, the submitted laboratory studies are expected to have identified residues of toxicological concern and using a total toxic residue approach that includes
unextracted and unidentified residues reported in the submitted laboratory studies is expected to be protective.

No independent lab validations have
been submitted for the environmental chemistry methods for iodosulfuron or
metsulfuron in soil.

The reported LOQ is 0.02 μg/kg (ppb) for iodosulfuron. Due to the high sensitivity of plants to iodosulfuron it is important that the detection limit for iodosulfuron in soil capture the level of concern for the most sensitive species including listed plants. 850.6100 Analytical
method in soil 45108502 incomplete yes

### 36 835.6200 Aquatic field dissipation No data no No independent lab validations have
been submitted for the environmental chemistry methods for iodosulfuron in

water.

The reported LOQ is 0.1 μg/L (ppb) for iodosulfuron. Due to the high sensitivity of plants to iodosulfuron it is important that the detection limit for iodosulfuron in water capture the level
of concern for the most sensitive species including listed plants. 850.6100 Analytical
method in water 45108522 incomplete yes

850.1730 Fish
bioconcentration No data no - see

comments Iodosulfuron is not expected to
bioaccumulate based on the calculated

K
ow .

The safener mefenpyr diethyl may have the potential to bioaccumulate based on
the calculated K

ow . However, a fish bioconcentration study is cited in the FAO report referenced earlier in this
document.

1. Additional data would reduce uncertainty. See comments.



### Effects

Table 21 and 22 identify the ecological effects studie s, as well as study classifications and
whether or not further data are needed in orde r to support risk assessment. Rationale for the additional data requested is presented below the tables.

### 37 Table 21. Submitted Aquatic Ecological Effects Data for Iodosulfuron

OCSPP
Guideline Data Requirement Submitted
Studies (MRID) Study
Classifications Are data
needed to
conduct

risk
assessment? Comments

850.1010 Freshwater
invertebrate acute toxicity 45109103 Supplemental No --

850.1025
850.1035
850.1045
850.1055 Saltwater
invertebrate acute toxicity 45109128 Acceptable No --

850.1075 Freshwater
fish acute toxicity 45109035 Supplemental No --

850.1075 Saltwater fish acute toxicity 45109127 Acceptable No --

850.1300 Freshwater
invertebrate life cycle 45109104 Acceptable No --

850.1350 Saltwater
invertebrates life cycle No Study -- No Due to the general low toxicity to fish and invertebrates, the value of these additional data to the ecological risk assessment is likely low.

850.1400 Freshwater
fish early-life stage 46431804 Supplemental No --

850.1400 Saltwater fish early-life stage No Study -- No Due to the general low toxicity to fish and invertebrates, the value of these additional data to the ecological risk assessment is likely low.

850.1500 Fish life cycle No Study -- No --

850.4400 Aquatic plant growth:
Tier II vascular plants 45109111 Acceptable No

850.5400 Aquatic Plant
Growth: Tier II algae 45109105 Acceptable No --

### 38 Table 22. Submitted Terrestrial Ecologi cal Effects Data for Iodosulfuron

OCSPP
Guideline Data Requirement Submitted
Studies (MRID) Study
Classifications Are data
needed for
risk
assessment? Comments

850.2100 Avian oral toxicity 45109029 Acceptable No Low toxicity to other avian species and low use rates suggest that risk to passerine species is unlikely to exceed
levels of concern. 45109028 Acceptable

850.2200 Avian dietary toxicity 45109030 Acceptable No --

850.2300 Avian reproduction 46431803 Acceptable No --

Nonguideline Avian
inhalation 45108805 Acceptable No --

850.3020 Honey bee

acute contact toxicity 45109115 Acceptable No --

Honey bee
acute oral toxicity 45109114 Acceptable No --

850.3030 Honey bee
residue on foliage No Study -- No --

850.3040 Field testing for pollinators No Study -- No --

850.4100 Terrestrial plant toxicity: seedling

emergence 45109132
45467604
45467602
46431802
45467601
47731901/
47731701 Acceptable Acceptable Supplemental Supplemental Acceptable
In review
In review- (Amendment) Yes A Seedling Emergence study is needed for a typical end use product for turf uses. Available toxicity data suggest that terrestrial plants are highly sensitive iodosulfuron, however only
formulations that contain a chemical
safener have been tested. The safener may influence the final toxicity estimation. In addition, performing a repeat for the tomato for 45109132 would reduce the uncertainty in future

assessments.

850.4150 Terrestrial plant toxicity: vegetative vigor 45109131
45467606
45467605
45467603 Acceptable Acceptable Acceptable Supplemental Yes A Vegetative Vigor study is needed for a typical end use product for turf uses. Available toxicity data suggest that terrestrial plants are highly sensitive to iodosulfuron, however only formulations that contain a
chemical safener have been tested. The safener may influence the final toxicity estimation. In addition, performing a repeat for lettuce and
onions for 45109131 would reduce the uncertainty in future assessments.

### 39 OCSPP
Guideline Data Requirement Submitted
Studies (MRID) Study
Classifications Are data
needed for
risk
assessment? Comments

124-1 Terrestrial
Plant Field Testing No Study No The November 26, 2002 Notice of Registration for EPA Reg. No. 264- 686 identified this study as a requirement. However, a waiver was submitted and accepted, therefore, data are no longer required.

124-2 Aquatic Plant Field Testing No study No The November 26, 2002 Notice of Registration for EPA Reg. No. 264- 686 identified this study as a requirement. However, a waiver was submitted and accepted, therefore, data are no longer required.



### Additional information that may be useful to the EPA includes:
1. ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and mammalian mortalities) not alr eady reported to the Agency
2. major degradate and safener fate and toxicity data

### 40 APPENDIX A
Environmental Fate Kinetic Analysis Images

### 41

### 42

### 43

### 44

### 45

### 46

### 47

### 48

### 49

### 50

### 51

### 52

### 53 APPENDIX B

SIP Analysis

Table 1. Inputs
Parameter Value
Chemical name Iodosulfuron Solubility (in water at 25 o C; mg/L) 25000

Mammalian LD 50 (mg/kg-bw) 2448 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 500 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Avian LD 50 (mg/kg-bw) 1744 Avian test species mallard duck Body weight (g) of "other" avian species Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) Bobwhite quail NOAEC (mg/kg-diet) 372 NOAEC (mg/kg-diet) for other bird species Body weight (g) of other avian species NOAEC (mg/kg-diet) for 2nd other bird species Body weight (g) of 2nd other avian species

Table 2. Mammalian Results
Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 4300.0000 4300.0000 Adjusted toxicity value (mg/kg-bw) 1882.9051 384.5803 Ratio of exposure to toxicity 2.2837 11.1810

Conclusion* Exposure through drinking water alone is a potential

concern for mammals Exposure through drinking water alone is a potential

concern for mammals

Table 3. Avian Results
Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 20250.0000 20250.0000 Adjusted toxicity value (mg/kg-bw) 905.5291 39.5430 Ratio of exposure to acute toxicity 22.3626 512.1011

Conclusion* Exposure through drinking water alone is a potential
concern for birds Exposure through drinking water alone is a potential
concern for birds
*Conclusion is for drinking water exposure al one. This does not combine all routes of exposure. Therefore, when aggregated with other routes ( i.e ., diet, inhalation, dermal), pestici de exposure through drinking water may contribute to a total exposure that has potential for effects to non-target animals.

### 54 APPENDIX C

STIR Analysis Results

Application and Chemical Information

Enter Chemical Name Iodosulfuron

Enter Chemical Use Crop

Is the Application a Spray? (enter y or n) y If Spray What Type (enter ground or air) ground
Enter Chemical Molecular Weight (g/mole) 529.24
Enter Chemical Vapor Pressure (mmHg) 5.03E-11
Enter Application Rate (lb a.i./acre) 0.0089

Toxicity Properties

Bird

Enter Lowest Bird Oral LD 50 (mg/kg bw) 1744
Enter Mineau Scaling Factor 1.15
Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD 50 (mg/kg bw) 2448

Enter Lowest Rat Inhalation LC 50 (mg/L) 2.81
Duration of Rat Inhalation Study (hrs) 4
Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 1.43E-06
Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.80E-07

Adjusted Inhalation LD 50 1.12E+01

Ratio of Vapor Dose to Adjusted Inhalation LD 50 1.61E-08 Exposure not Likely Significant
Maximum Post-treatment Spray Inhalation Dose (mg/kg) 9.40E-04

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 8.43E-05 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 1.43E-06
Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.26E-07

Adjusted Inhalation LD 50 1.67E+02

Ratio of Vapor Dose to Adjusted Inhalation LD 50 1.35E-09 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.18E-03

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 7.07E-06 Exposure not Likely Significant 

### APPENDIX D

### 55 ECOSAR Results for the Safeners Is oxadifen-ethyl and Mefenpyr-diethyl Isoxadifen-ethyl ECOSAR Version 1.10 Results Page SMILES : C2(C(=O)(OCC))=NOC(C2)(c3ccccc3)c1ccccc1
CHEM :
CAS Num:
ChemID1:
MOL FOR: C18 H17 N1 O3
MOL WT : 295.34 Log Kow: 5.660 (EPISuite Kowwin v1.68 Estimate) Log Kow: (User Entered) Log Kow: (PhysProp DB exp value - for comparison only) Melt Pt: (User Entered for Wat Sol estimate) Melt Pt: (deg C, PhysProp DB exp value for Wat Sol estimate) Wat Sol: 0.1917 (mg/L, EPISuite WSKowwin v1.43 Estimate) Wat Sol: (User Entered) Wat Sol: (PhysProp DB exp value)

-------------------------------------- Values used to Generate ECOSAR Profile

-------------------------------------- Log Kow: 5.660 (EPISuite Kowwin v1.68 Estimate) Wat Sol: 0.1917 (mg/L, EPISuite WSKowwin v1.43 Estimate)

------------------------------------------------ Available Measured Data from ECOSAR Training Set

------------------------------------------------ Measured CAS No Organism Duration End Pt mg/L (ppm) Ecosar Class Reference

=========== ========== ========== ====== ========== ===========================

========================= 163520-33-0 Daphnid 48-hr LC50 NES Aliphatic Amines OPP Pesticide Ecotoxicity DB

ECOSAR v1.1 Class- specific Estimations Aliphatic Amines
Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

=========================== ================== ======== ====== ========== Aliphatic Amines : Fish 96-hr LC50 0.223 * Aliphatic Amines : Daphnid 48-hr LC50 0.041 Aliphatic Amines : Green Algae 96-hr EC50 0.014 Aliphatic Amines : Fish ChV 0.004 Aliphatic Amines : Daphnid ChV 0.005 Aliphatic Amines : Green Algae ChV 0.007

=========================== ================== ======== ====== ========== Neutral Organic SAR : Fish 96-hr LC50 0.125 (Baseline Toxicity) : Daphnid 48-hr LC50 0.133 : Green Algae 96-hr EC50 0.126
: Fish ChV 0.018 : Daphnid ChV 0.025 : Green Algae ChV 0.167

Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect. If the effect level exceeds the water solubility by 10X, typically no effects at saturation (NES) are reported.

### 56 Mefenpyr-diethyl ECOSAR Version 1.10 Results Page SMILES : CCOC(=O)C2=NN(c1ccc(CL)cc1CL)C(C)(C(=O)OCC)C2
CHEM :
CAS Num:
ChemID1:
MOL FOR: C16 H18 CL2 N2 O4
MOL WT : 373.24 Log Kow: 4.818 (EPISuite Kowwin v1.68 Estimate) Log Kow: (User Entered) Log Kow: 3.83 (PhysProp DB exp value - for comparison only) Melt Pt: (User Entered for Wat Sol estimate) Melt Pt: 51.00 (deg C, PhysProp DB exp value for Wat Sol est) Wat Sol: 15.03 (mg/L, EP ISuite WSKowwin v1.43 Estimate) Wat Sol: (User Entered) Wat Sol: 20 (mg/L, PhysProp DB exp value)

Values used to Generate ECOSAR Profile

-------------------------------------- Log Kow: 4.818 (EPISuite Kowwin v1.68 Estimate) Wat Sol: 20 (mg/L, PhysProp DB exp value)

Available Measured Data from ECOSAR Training Set

No Data Available

ECOSAR v1.1 Class- specific Estimations

-------------------------------------- Esters
Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

=========================== ================== ======== ====== ========== Esters : Fish 96-hr LC50 1.128 Esters : Daphnid 48-hr LC50 1.734 Esters : Green Algae 96-hr EC50 0.472
Esters : Fish ChV 0.047 Esters : Daphnid ChV 0.527 Esters : Green Algae ChV 0.302 Esters : Fish (SW) 96-hr LC50 1.444 Esters : Mysid 96-hr LC50 0.354 Esters : Fish (SW) ChV 0.344 Esters : Mysid (SW) ChV 0.084 Esters : Earthworm 14-day LC50 600.663 *

Neutral Organic SAR : Fish 96-hr LC50 0.903 (Baseline Toxicity) : Daphnid 48-hr LC50 0.815 : Green Algae 96-hr EC50 0.769
: Fish ChV 0.120 : Daphnid ChV 0.134 : Green Algae ChV 0.679 Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect. If the effect level exceeds the water solubility by 10X, typically no effects at saturation (NES) are reported.

### 57 APPENDIX E
GENEEC Results for the Safeners Is oxadifen-ethyl and Mefenpyr-diethyl

Isoxadifen-ethyl

RUN No. 2 FOR isoxadifen-ethyl ON corn * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE NO-SPRAY INCORP ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) (FT) (IN)

-------------------------------------------------------------------- .030( .030) 1 1 9777.0 1.3 GRHIFI( 6.6) .0 .0

FIELD AND STANDARD POND HALFLIFE VALUES (DAYS)

-------------------------------------------------------------------- METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS ME TABOLIC COMBINED (FIELD) RAIN/RUNOFF (POND) (POND-EFF) (POND) (POND)

-------------------------------------------------------------------- .00 2 N/A .00- .00 .00 .00

GENERIC EECs (IN NANOGRAMS/LITER (PPTr)) Version 2.0 Aug 1, 2001

-------------------------------------------------------------------- PEAK MAX 4 DAY MAX 21 DAY MAX 60 DAY MAX 90 DAY
GEEC AVG GEEC AVG GEEC AVG GEEC AVG GEEC

-------------------------------------------------------------------- 207.50 201.57 168.83 118.11 93.90

RUN No. 4 FOR isoxadifen-ethyl ON any * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE NO-SPRAY INCORP ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) (FT) (IN)

-------------------------------------------------------------------- .030( .030) 1 1 977.0 1.3 GRHIFI( 6.6) .0 .0

FIELD AND STANDARD POND HALFLIFE VALUES (DAYS)

-------------------------------------------------------------------- METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS ME TABOLIC COMBINED (FIELD) RAIN/RUNOFF (POND) (POND-EFF) (POND) (POND)

-------------------------------------------------------------------- .00 2 N/A .00- .00 .00 .00

GENERIC EECs (IN NANOGRAMS/LITER (PPTr)) Version 2.0 Aug 1, 2001

-------------------------------------------------------------------- PEAK MAX 4 DAY MAX 21 DAY MAX 60 DAY MAX 90 DAY
GEEC AVG GEEC AVG GEEC AVG GEEC AVG GEEC

-------------------------------------------------------------------- 742.59 739.67 722.64 686.17 660.49

### 58 Mefenpyr-diethyl

RUN No. 1 FOR mefenpyr-diethyl ON any * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE NO-SPRAY INCORP ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) (FT) (IN)

-------------------------------------------------------------------- .045( .135) 3 3 740.0 2.4 GRHIFI( 6.6) .0 .0

FIELD AND STANDARD POND HALFLIFE VALUES (DAYS)

-------------------------------------------------------------------- METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS ME TABOLIC COMBINED (FIELD) RAIN/RUNOFF (POND) (POND-EFF) (POND) (POND)

-------------------------------------------------------------------- .00 2 N/A .00- .00 .00 .00

GENERIC EECs (IN MICROGRAMS/LITER (PPB)) Version 2.0 Aug 1, 2001

-------------------------------------------------------------------- PEAK MAX 4 DAY MAX 21 DAY MAX 60 DAY MAX 90 DAY
GEEC AVG GEEC AVG GEEC AVG GEEC AVG GEEC

-------------------------------------------------------------------- 3.93 3.92 3.84 3.69 3.57

RUN No. 2 FOR mefenpyr-diethyl ON any * INPUT VALUES *

-------------------------------------------------------------------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE NO-SPRAY INCORP ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) (FT) (IN)

-------------------------------------------------------------------- .045( .135) 3 3 74.0 2.4 GRHIFI( 6.6) .0 .0

FIELD AND STANDARD POND HALFLIFE VALUES (DAYS)

-------------------------------------------------------------------- METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS ME TABOLIC COMBINED (FIELD) RAIN/RUNOFF (POND) (POND-EFF) (POND) (POND)

-------------------------------------------------------------------- .00 2 N/A .00- .00 .00 .00

GENERIC EECs (IN MICROGRAMS/LITER (PPB)) Version 2.0 Aug 1, 2001

-------------------------------------------------------------------- PEAK MAX 4 DAY MAX 21 DAY MAX 60 DAY MAX 90 DAY
GEEC AVG GEEC AVG GEEC AVG GEEC AVG GEEC

-------------------------------------------------------------------- 7.14 7.14 7.12 7.08 7.04