## UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES



# Environmental Fate and Ecological Risk Assessment

For the Proposed New Use of Rimsulfuran on

OPTIMUM® GAT® Soybean and Amended

T olerance for OPTIMUM® GAT® Field Corn

For Use as Pre/Early post Emergence Herbicide for Selective Control of Certain Broadleaf Weeds & Grasses



# RIMSULFURON

CAS Name: N

- [[(4,6

- dimethoxy

- 2

- pyrimidinyl)amino]carbonyl]

- 3

- (ethylsulfonyl)

- 2

-

py ridinesulfonamide ; PC Code: 129009; CAS Number: 122931

- 48

- 0

Prepared by:

Jos é L. Mel é ndez , Chemist

, Environmental Fate Reviewer, ERB V

Joseph DeCant

, Ec ologist,

Ecological Effects Reviewer, ERB V

Approved by:

Mah Shamim, PhD, Chief ERB V 8/4 /09

United States Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch V

1200 Pennsylvania Ave.

Mail Code 7507P

Washington, D.C. 20460 

# N N O

O C H

3



# C H

3 

# N

H N S O

O C H

2 

# C H

3



# N

H S O

O

O

## 2 

# TABLE OF CONTENTS

I. EXECUTIVE SUMMAR Y

................................ ................................ ................................ ...... 3

A. N ATURE OF 

## C HEMICAL 

## S TRESSOR



## ................................ ................................ ........................... 3

B. P OTENTIAL 

## R ISK TO 

## N ON



## - TARGET 

## O RGANISMS



## ................................ ................................ ...... 3

C. C ONCLUSIONS 

## : E XPOSURE 

## C HARACTERIZATION



## ................................ ................................ ..... 3

D. C ONCLUSIONS 

## : E FFECTS 

## C HARACTERIZATION



## ................................ ................................ ........ 4

E. D ATA 

## G APS AND 

## U NCERTAINTIES



## ................................ ................................ ........................... 5

II. PROBLEM FORMULAT ION

................................ ................................ ............................... 6

A. S TRESSOR 

## S OURCE AND 

## D ISTRIBUTION



## ................................ ................................ .................. 6

B. R ECEPTORS



## ................................ ................................ ................................ .............................. 7

C. A SSESSMENT 

## E NDPOINTS



## ................................ ................................ ................................ ........ 8

D. C ONCEPTUAL 

## M ODEL



## ................................ ................................ ................................ .............. 9

E. A NALYSIS 

## P LAN



## ................................ ................................ ................................ ...................... 9

III. ANALYSIS

................................ ................................ ................................ ............................ 11

A. U SE 

## C HARACTERIZATION



## ................................ ................................ ................................ ...... 11

B. E XPOSURE 

## C HARACTERIZATION



## ................................ ................................ ............................ 14

C. E COLOGICAL 

## E FFECTS 

## C HARACTERIZATION



## ................................ ................................ ......... 25

IV. RISK CHARACTERIZ ATION

................................ ................................ .......................... 26

A. R ISK 

## E STIMATION



## ................................ ................................ ................................ ................. 26

B. R ISK 

## D ESCRIPTION



## ................................ ................................ ................................ ................ 27

C. E NDANGERED 

## S PECIES 

## A SSESSMENT



## ................................ ................................ ..................... 28

REFERENCES

................................ ................................ ................................ ............................ 37

APPENDIX I. ECOLOGI CAL EFFECTS INFORMAT ION

................................ ............... 39

APPENDIX II. TERRPLA NT SPREADSHEET

................................ ................................ ..... 42

APPENDIX III. ECOLOG ICAL AQUATIC EXPOSUR E MODELING

............................ 44

APPENDIX IV. LOCATE S PRINTOUT

................. ERROR! BOOKMARK NOT DEFINED.

## 3 

# I. EXECUTIVE SUMMARY

**A. Nature of Chemical Stressor**

Rimsulfuron is a pyrimidinyl sulfonylurea selective/systematic herbicide which belongs to the

sulfonylurea family 1 

## (HRAC Group B). The chemical is proposed for new uses on OPTIMUM®

GAT® soybeans and an amended tolerance on OPTIMUM ® GAT® field corn

. The mode of

action of rimsulfuron involves i nhibiti on of acetolactate synthase, also known as

acetohydroxyacid synthase AHAS 2



## B. Potential Risk to **Non**

**- target Organisms**  , a key enzyme in the biosynthesis of certain amino acids in

plants. Rimsulfuron selectively control s certain broadleaf weeds and grasses and is proposed to

be ap plied as preemergence or post emergence. Resistance management may be required with

repeated use. The chemical is formulated as a water soluble granule (25% a.i.) and proposed to

be applied by ground broadcast or aerial spray

.

For the purpose of this risk assessment, exposure is calculated based on expected terrest rial and

aquatic residues of parent rimsulfuron. If studies determine that transformation

products/degradates pose a hazard to non

- target plants, for example, then the period of risk to

plants (already identified) would be extended.

Rinsulfuron poses a risk to non

- target terrestrial endangered and non

- endangered plants (RQs =

6.25

– 264.42) and aquatic endangered plants (RQ = 5.10

– 15.3 across all crops, using

PRZM/EXAMS )

. Because of potential direct effects to plants, indirect effects are also possible

to all other endangered species taxonomic groups.

**C. Conclusions: Exposure Characterization**

Upon application of rimsulfuron to bare soils, the major quantities of the applied material is

expected to be deposited on soil surfaces and be distributed within the surface layer of the soil

depending on the amount of rainfall/irrigation for the required wetting

- in. Other relatively

smaller quantities of the parent are expected to reach nearby terrestrial/aqua tic systems by drift.

Later un degraded parent and aerobic soil transformation products/degradates are expected to

reach surface waters by run

- off/erosion.

Rimsulfuron has a low vapor pressure (1.447 x10

- 11 

## atms. at 25 o 

## C) and is highly soluble in water

(solubilit y 7.3 ppm at 20 o 

## C 3

1 

## ULR: ). Based on submitted environmental fate studies, the chemical is

short lived in aqueous systems (mainly affected by hydrolysis with hydrolysis half

- lives ranging

http://www.alanwood.net /pesticides/

2 

## URL: http://www.plantprotection.org/hrac/Bindex.cfm?doc=moa2002.htm

## 4 from 5

- 7 days in acidic/neutral conditions and <day in alkaline condition s) . Also the chemical is

short

- lived in aerobic/anaerobic soil systems (t 1/2 

## = 19

- 21 days determined for only one soil,

shorter half

- lives were determined under field conditions: t 1/2 

## = 5 to 18 days). Rimsulfuron

appears not to be affected by aqueous or soi l photolysis. In the natural environment, the major

route of dissipation of rimsulfuron is expected to be hydrolysis followed by bio

- transformation.

Adsorption/desorption studie s suggest that rimsulfuron may be highly mobile and vulnerable to

run

- off and leaching ( K

oc 

## ranged from 19

- 74 L Kg

- 1 

## ). Therefore, the chemical may enter aquatic

systems via run

- off and erosion.

Rimsulfuron is expected to transform/degrade into a number of transformation/ degradation

products under different environmental conditio ns. The three major degradates for rimsulfuron

result from contraction or cleavage of the sulfonurea

- bridge (IN

- 70941 and IN

- 7 0942 from

contraction while IN

- E 9260 from cleavage). In contrast, the minor degradates are cleavage

degradates (IN

- J9260 in syst ems other than aerobic soil, IN

- J290 and IN

- T5831). Mobility of

the transformation products/degradates were checked by TLC (thin layer chromatography) and

results indicate high mobility to IN

- E9260 and high to medium mobility for IN

- 70941, IN

- 70942

and IN

- J290. Solubility was reported for only IN

- 70941 and IN

- 70942 and was 0.7 ppm for the

first and 0.2 ppm for the second. Considering quantities formed and relative persistent of

transformation products/degradates , all are expected to reach aquatic systems i n varied

concentrations. In addition, most of the parent that reaches aquatic systems by drift is expected

to transform by hydrolysis into transient IN

- 70941 then into the persistent IN

- 70942. The time

line for this event is expected to be as follows: IN

- 79041 at the short to medium

- term (because it

transforms into IN

- 70942), IN

- 70942/IN

- E9290/In

- J290 at the medium to long

- term. Finally, IN

70942 is expected to be the terminal and persistent degradate.

The risk assessment for rimsulfuron is based on its EEC ’ s in important environmental

compartments. These EEC ’ s were estimated using available physicochemical and fate properties

. The EEC ’ s along with related ecological effects data (i.e., available aquatic and terrestrial

toxicity data) were used to evalua te and characterize ecological risk of rimsulfuron application to

the environment.

**D. Conclusions: Effects Characterization**

Ri msulfuron is considered practically non

- toxic to most terrestrial animals. This includes birds

(mallard LD50 > 2000 mg/kg; bobwhi te quail LD50 > 2250 mg/kg; mallard and bobwhite quail

LC50s > 5620 ppm) and mammals (rat LD50 > 5000 mg/kg).

Rimsulfuron is considered practically non

- toxic to most aquatic animals. This includes

freshwater fish (rainbow trout LC50 > 390 ppm; bluegill s unfish LC50 > 390 ppm), freshwater

invertebrates ( Daphnia magna LC50 > 360 ppm), and estuarine/marine organisms (sheepshead

minnow LC50 > 110 ppm; mysid shrimp LC50 > 110 ppm; oyster shell deposition EC50 > 120

ppm).

In contrast, vascular plants are extre mely sensitive to rimsulfuron. For seedling emergence, plant

height was the most sensitive parameter (EC25 = 0.0006 lb ai/A for the most sensitive monocot

and 0.00013 for the most sensitive dicot). For vegetative vigor, root weight was the most

sensitive parameter (EC25 = 0.00004 lb ai/A for the most sensitive monocot and 0.00003 lb ai/A

## 5 for the most sensitive dicot). The most sensitive aquatic plant tested is duckweed (EC50 = 11.6

ppb).

**E. Data Gaps and Uncertainties**

The screening level assessment for rimsulfuron has been conducted despite unfulfilled guideline

requirements and existing environmental fate and ecological data gaps.

The evaluation of the environmental fate and transport data identified three impo rtant data gaps

. An a erobic soil half

- li fe was determined for only one soil (MRID 41356334, Acceptable)

, an

ae robic aquatic metabolism study was conducted in the presence of light (MRID 43288502,

supplemental) , and no anaerobic aquatic metabolism study has been submitted . The se data gaps

may re sult in non

- representati ve estimated aquatic exposure concentrations ( EECs )

. These data

gaps also cause uncertainty in conclusions associated with the behavior of the chemical in these

relevant systems. In order to address these data gaps, the following f ate studies have been

required :

**•** One aerobic soil metabolism study ( § 835.4100) ( using two US soils from relevant use

areas )

**•** One anaerobic aquatic metabolism study (§835.4400) ( in a relevant natural water

sediment system)

**•** One aerobic aquatic metabolism stud y (§835.4300) ( in a relevant natural water sediment

system)

Since the EFED LOC ’ s for plants are based on acute risk, the plant risk assessment is also based

on acute risk (to parent rimsulfuron). While studies of the toxicity of the degradates IN

- 70941,

IN

- 70942, and IN

- E9260 to both terrestrial and aquatic plants have been submitted, they have

not yet been reviewied. However, if the degradates are similarly phytotoxic, the period of

phytotoxicity in the field (in both terrestrial and aquatic environmen ts) would be longer.

The following studies on the transformation product/degradate IN

- 70942 have not been

submitted but are needed for ecological risk assessment:

**•** Freshwater fish ear ly life

- stage ( § 850.1400)

**•** aquati c invertebrate life

- cycle ( § 850.1300 )

## 6 

# II. PROBLEM FORMULATION

**A. Stressor Source and Distribution**

1. Sources and Intensity

The source of stressor is the proposed application of rimsulfuron as a water soluble granule (25%

a.i.) . This systematic herb icide is proposed to be applied by aerial spray or by ground broadcast

application to OPTIMUM® GAT® soybeans and OPTIMUM® GAT® field corn . The proposed

maximum rate of application to these crops is 0.0625 lb a.i./A/crop season.

Rimsulfuron and its major t ransformation/degradation products (IN

- 70941, IN

- 70942, and IN

E9260) are considered, at this problem formulation stage, to be the important stressors that

would result from the proposed application. Application of the rimsulfuron formulation is the

sourc e of parent while parent transformation/degradation and transport are the source of

transformation products/degradates. Processes dominant in various compartments of the natural

environment are expected to control exposure timing/intensity of assigned str essors where th e

chemical is expected to reach

.

2. Physicochemical, Fate, and Transport Properties

Rimsulfuron is characterized by relative high solubility (7 300 ppm) and low vapor

pressure/Henrys’ Law constant (1.45x10

- 11 

## atms. and 1.40x10

- 12 

## atms. m 3 

## m ole

- 1 

## , respectively).

Therefore, rimsulfuron is not expected to partition into the air from water and/or dry/wet soil

surfaces. Available data suggest that rimsulfuron is not expected to be bio

- concentrated by

aquatic organisms such as fish (K

ow 

## <1 at pH 7).

Rimsulfuron is expected to be of relative low persistence in important compartments of the

environment. The chemical is highly vulnerable to hydrolysis as it hydrolyzes with half

- lives in

the range of 5

- 7 days at pHs 5 and 7. In alkaline conditions , the chemical hydrolyzes with half

lives in hours (half

- lives of 4

- 11 hours at pH 9). Relatively longer half

- lives were observed in

aerobic/anaerobic soil systems (18

- 21 days) and in the field (5

- 18 days). Data suggest that

higher persistence is expecte d in colder climates and in dry soil systems. The same studies had

also shown the chemical to transform into many transformation products/ degradates including

three major ones , namely : IN

- 70941, IN

- 70942, and IN

- E9260. Combined data on rimsulfuron

and it s major transformation products/ degradates indicate that sh ort

- term environmental

exposure will involve the parent and its major transient transformation product s IN

- 70941

(transforms into IN

- 70942), IN

- 70942 and IN

- E9260 at the medium

- term and the termina l

transformation product IN

- 70942 at the long

- term. Parent rimsulfuron appears to be highly

mobile in tested soils. In comparison, the two contraction transf ormation products (IN

- 70941

and IN

- 7094 2) and one of the cleavage degradates (IN

- E9260) appear to be similar or slightly

less mobile than their parent. In most natural environmental compartments, the transformation

product IN

- 70942 is expected to persist with relatively high potential for mobility.

## 7 3. Pesticide Type, Class, and Mode of Action

Rimsulf uron is a selective/systemic pyrimidinyl sulfonylurea herbicide and a member of the

sulfonylurea class of compounds 4



## . It has a mode of action that i nhibit s acetolactate synthase

ALS (ALS is also known as acetohydroxyacid synthase AHAS) (HRAC Group B) 5



## 4. Overview of Pesticide Usage

Currently, this herbicide is registered as pre/post emergen ce weed control in field corn, potatoes,

potatoes grow n for seed, field grown tomatoes

, grapes, stone fruit, tree nuts, pistachios, pome

fruit, and citrus fruit (first registered in 1994). It is also registered for the control of grasses and

broadleaf wee ds in grassland restoration as well as roadside control. This assessment addresses

the proposed new use on OPTIMUM® GAT® soybeans and the amended application rate to

OPTIMUM® GAT® field corn. The application methods associated with the new uses are as a

water soluble granule applied through ground broadcast application or aerial spray. I t is expected

that rimsulfuron will be widely used in many areas of the United States. . AL S or

AHAS is a key enzyme in the biosynthesis of certain amino acids in plants. The mode of action

appears to require relatively low concentrations of the chemical. It is noted that repeated

application might cause weeds to develop resistance to the sulfo nurea family of herbicides that

would require the application of an herbicide resistance program.

**B. Receptors**

1 . Ecological Effects

Ecological measures of effect for rimsulfuro n are based on registrant

- submitted toxicity studies.

Acute and chronic endpoints are selected from available test data, as the data set allows. A

discussion of available toxicity data is located in Section III. C. (Analysis/Ecological Effects

Characteriza tion )

.

2. Ecosystems at Risk

Aquatic ecosystems potentially at risk include wetlands and water bodies that could be exposed

via runoff. Such ecosystems could be coastal (saltwater) or inland (freshwater). Since plants are

highly sensitive to rimsulfuro n, they could be directly affected. Other organisms dependent on

plants could then be indirectly affected.

Terrestrial ecosystems potentially at risk include areas which might receive direct use, drift, and

runoff or erosion. These areas might include other cultivated fields, fence rows and hedgerows,

meadows, fallow fields or grasslands, woodlands, riparian habitats and other uncultivated areas

that may be exposed. Since plants are highly sensitive to rimsulfuron, they could be directly

affected. Oth er organisms dependent on plants could then be indirectly affected.

4 

## URL: http://www.alanwood.net/pestic ides/

5 

## URL: http://www.plantprotection.org/hrac/Bindex.cfm?doc=moa2002.htm

## 8 **C. Assessment Endpoints**

Assessment endpoints are explicit expressions of the actual environmental value that is to be

protected. Assessment endpoint selection is based on valued entiti es or ecological receptors, the

ecosystems potentially at risk, pesticide migration pathways, and routes by which ecological

receptors may be exposed to the stressor. A generic listing of potential assessment endpoints and

measures of ecological effect (d epending on data availability and other factors) that may be used

to characterize potential ecological risks is shown in Table 1

.

Table 1. Potential Assessment Endpoints for Ecological Risk Assessment.

Taxonomic Group Assessment

Endpoint Measures of Effe ct

(Toxicity Endpoints) Measures of Exposure

(Exposure Endpoints)

Birds Survival Oral LD 50 and dietary LC 50 (most sensitive

species), adjusted for size for 20 g bird Maximum residue on food

items (foliar) or LD 50 /ft 2

Reproduction,

Growth NOAEC/LOAEC fr om avian chronic study

(most sensitive species) Maximum residue on food

items (foliar) or LD 50 /ft 2

Mammals Survival Acute oral LD 50 , dietary LC 50 (most

sensitive species) Maximum concentration on

food items (foliar) or LD 50 /ft 2

Reproduction,

Growth NOAE C/LOAEC from chronic reproduction

study (most sensitive species) Maximum concentration on

food items

Non

- target Terrestrial

Invertebrates Survival Honey

- bee acute contact LD 50 Maximum application rate

Terrestrial Plants Survival and

Growth Tier I, Tier II plant toxicity data; EC 25 Estimates of runoff to non

target areas

Freshwater Fish Survival 96

- hr LC 50 (most sensitive species) Peak EEC

Reproduction,

Growth Fish Early Life Stage NOAEC/LOAEC for

Growth 60

- day average EEC

Freshwater

Invertebrate Survival 48

- hr LC 50 (most sensitive species) Peak EEC

Reproduction,

Growth Invertebrate Life Cycle NOAEC 21

- day average EEC

Marine/estuarine Fish Survival 96

- hr LC50 (most sensitive species) Peak EEC

Reproduction,

Growth Estuarine/Marine Fish NOAEC f or growth 60

- day average EEC

Marine/estuarine

Invertebrate Survival 48

- hr EC 50 (most sensitive species) Peak EEC

Reproduction,

Growth NOAEC for reproduction for most sensitive

species 21

- day average EEC

Aquatic Plants Survival, Growth Tier I, Tier II plant toxicity estimates; EC 25 1

- in

- 10 year peak concentration

## 9 **D. Conceptual Model**

1. Risk Hypotheses

Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in

assessment endpoints) and may be based on theory and logic , empirical data, mathematical

models, or probability models (EPA 1998a). For this assessment, the risk is stressor

- initiated,

where the stressor is the release of rimsulfuron into the environment. The following risk

hypothesis is presumed for this scree ning

- level assessment:

The proposed new use of rimsulfuron on OPTIMUM® GAT® soybeans and the amended

application rate on OPTIMUM® GAT® field corn will likely involve situations where terrestrial

and aquatic animals and plants will be exposed to the chemic al and/or its

transformation/degradation products. Based on information on environmental fate, mode of

action, direct toxicity and potential indirect effects, EFED assumes that rimsulfuron may have

the potential to cause reduced survival, growth, and repro duction to terrestrial and/or aquatic

plants as a result of the proposed uses of the pesticide.

Various ecological receptors may potentially be exposed to rimsulfuron and its transformation

products/degradates in the short

, medium , and long term. The rece ptors are as follows : terrestrial

and semi

- aquatic wildlife (i.e., mammals, birds, amphibians, and reptiles), terrestrial and semi

aquatic plants, and soil invertebrates. In addition, aquatic receptors (e.g., freshwater and

estuarine/marine fish and inver tebrates, amphibians

, and aquatic plants) may also be exposed as

a result of potential migration of rimsulfuron and its transformation products/degradates via

spray drift and/or runoff/erosion.

2. Diagram

Based on the prelimina ry iterative process of examining fate and effects data, the conceptual

model or the risk hypothesis model for spray application of rimsulfuron to OPTIMUM® GAT®

soybeans and OPTIMUM® GAT® field corn has been establis hed, refined and included in

Figure 1

. I n establishing the diagram for the conceptual model it was necessary to go through an

iterative process to identify: (1) likely stressors/exposure pathways and (2) organisms that are

most relevant and applicable to this assessment.

**E. Analysis Plan**

1. Methods for Conducting Ecological Risk Assessment and Identification of Data Gaps

This document characterizes the environmental fate and effects of rimsulfuron to assess whether

proposed label new uses of this compound results in potential risk to non

- target organisms at

levels above the Agency’s level of concern (LOC)

. The primary method used to assess risk in

this screening

- level assessment is the risk quotient (RQ). The RQ is the result of comparing

measures of exposure to m easures of effect. A commonly used measure of exposure is the

estimated exposure concentration (EEC)

, and commonly used measures of effect include toxicity

values such as the LD50 or NOAEC. The resulting RQ is then compared to a specified LOC

. If the RQ exceeds an LOC, then risks are identified

.

## 10 Figure 1

. The conceptual model for rimsulfuron

. Rimsulfuron applied on corn and soybeans via ground broadcast and aerial spray Stressor

Source a nd

Transport

Pathways

Water/

Sediment Volatilization/

Wind Suspension Direct

Deposition

(Parent) Spray

Drift



## (Parent) Runoff/

Erosion

(Parent + Deg 1+2+3 

### )

Source and

Transport

Pathways Terrestrial Food

Residues (Foliage,

fruits, insets) Upland

Foliage/Soil Riparian/

Wetland

Foliage/Soil Groundwater

Terrestrial

Organisms:



## Birds, Mammals,

Reptiles & Insects Terrestrial

Upland

Plants Wet land /

Riparian

Plants Aquatic

Plants Aquatic

Invertebrate s,

Vertebrates &

Amphibians Exposure



## Point

Individual Animals



## Reduced survival,

growth and/or

reproduction Individual Plants



## Seedling

emer gence and

/or Vegetative

vigor Plant Population



## Reduced

population

growth Individual Animals



## Reduced survival,

growth and/or

reproduction Leaching/Infiltration

/Percolation

(Parent+ Deg 1+2+3



### Direct Contact & Root Uptake Gill/Integument

Uptake & Ingestion



## Receptors

Attribute

Change Ingestion & Dermal

Deg 1 

### = IN

- 70941; Deg 2



### = IN

- 70942 ; Deg 3



### = IN

- E9260

Dotted lines represe nt unlikely routes of exposure while bold arrows/boxes represent important routes of

## 11 Available environmental fate, ecotoxicity , and physicochemical property data were taken from

previous assessments conducted by EFED. Previously submitted data were not re

- evaluated for

this assessment. Generation of robust RQs is dependent on the quality of data from both fate and

toxicological studies. The adequacy of the submitted data was evaluated relative to Agency

guidelines.

2. Measures to Evaluate Risk Hypotheses and Conceptual Model

a. Measures of Exposure

Exposure to aquatic plants is assumed to occur through direct contact with contaminated water.

Aquatic exposures can be estimated from monitoring data or by simulation modeling. In this

assessment, measures of exposu re are made with simulation modeling. Generally, aquatic

exposure estimates are generated from EFED models and incorporate maximum proposed use

rates and empirically

- derived fate properties. Rimsulfuron aquatic exposure concentrations were

calculated to ca pture the proposed new use patterns using Tier II linked PRZM/EXAMS

modeling. Further details of the exposure models are discussed on the web at:

http://epa.gov/oppefed1/models/water/index.htm

.

Measures of exposure for terrestrial and semi

- aquatic plants are incorporated as part of the model

TerrPlant. This model uses application rate and a runoff value dependent on solubility.

b. Measures of Effect



# III. ANALYSIS The measure of effect for aquatic plants is the EC50 for the most sensitive species available. The

measures of effect for terrestrial and semi

- aquatic plants are the seedling emergence EC25 and

vegetative vigor EC25 for the most sensitive monocot and dicot plant species available. More

details concerning measures of effects used in this assessment can be found in the Ecological

Effects Characterization section of this document.

**A. Use Characterization**

1. Acreage

Currently, rimsulfuron is registered for use on field corn, potatoes, and tomatoes, grapes, citrus,

tree nuts, and pome/stone fruits. According to the 2007 Census of Agriculture by the USDA, the

total acreages harvested in 2007 for the various crops were nearly 1.6 million acr es of potatoes

and tomatoes together, 86 million acres of field corn , 1.1 million acres of grapes, 1 million acres

of citrus, 1.8 million acres of tree nuts, and nearly 1 million acres of pome and stone fruits

. These figures may underestimate the total ap plication area due to the additional registered uses

of roadsides and natural area restoration. The n ew use on OPTIMUM® GAT® soybeans could

potentially apply rimsulfuron to an additional 64 million acres of cropland, which was harvested

for soybeans in 200 7. Figure s 2 and 3 show the USA acreage for the proposed new uses

(USDA,

## 12 NASS ../../../../../../../../../Users/Tom/AppData/L ocal/Temp/notesF17874/(http:/ca.water.usgs.gov/

pnsp/use92/metiram.html) Agriculture Census county

- level crop data for 2007 ).

## 13 Figure 2. Area planted for all purposes of field corn in 2008 by county.

2 . Label

The herbicide formulation ( RESOLVE TM 

## SG ) c ontains 25.0% of the active ingredient

rimsulfuron and is proposed to be applied as a water soluble granule through ground broadcast or

aerial spray . For ground application, the herbicide may be applied as a broadcast spray to

OPTIMUM® GAT® corn and OPTIMU M® GAT® soybeans for weed control, and may be

used in combination with other suitable registered pesticides

. Applications of the formulation

may be made pre

- plant, pre

- emergence, post

- emergence, and/or post

- harvest

. Rainfall or

irrigation is required to m ove the herbicide into the soil for root uptake. Residual weed control

depends on rainfall or sprinkler irrigation for herbicide activation . One single application of 0.5

to 4 ounces of product in 15 gallons of clean water/acre/year is recommended for tr eatments.

Both uses on soybeans and field corn have a maximum use rate of 4 ounces active ingredient per

acre per crop season.

## 14 Figure 3

. Area planted for all purposes of soybeans in 2008 by county.

**B. Exposure Characterization**

1. Environmental Fate and Transport Characterization

The fate of rimsulfuron was evaluated by considering previously submitted data on its stability to

both hydrolysis and direct photolysis and its degrada tion processes in aqueous phases as well as

soil and field environments. Rimsulfur o n is short

- lived in systems examined as it appears to be

highly affected by hydrolysis, direct photolysis followed by aerobic soil degradation. Ta ble 2

contains a su mmar y o f important physiochemical properties of rimsulfuron.

Table 2

. Nomenclature and physicochemical properties of rimsulfuron.

Parameter Value Reference



### Chemical Classification Pyrimidinyl Sulfonylurea

Registrant

Data and

the Web 1 

### Molecular Formula C 1 4 

### H 17 

### N 5 

### O 7 

### S 2



### P C Code 129009

Chemical Name (IUPAC) 1

- (4,6

- dimethoxypyrimidin

- 2

- yl)

- 3

- (3

- ethylsulfonyl

- 2

- pyridylsulfonyl)urea

Chemical Name (CAS) N

- [[(4,6

- dimethoxy

- 2

- pyrimidinyl)amino]carbonyl]

- 3

- (ethylsulfonyl)

- 2

- pyridine sulfonamide

CAS Number 12293 1

- 48

- 0

## 15 Parameter Value Reference



### Pesticide Classification Herbicide

MRIDs

413563

- 01 Molecular Weight 431.44

Physical State Solid

pKa 4

Water

Solubility

(ppm) Parent 7

, 3 00 @ pH 7/25 o 

### C

IN

- 70941 0.7 @ pH 7/25 o 

### C

IN

- 70942 0.2 @ pH 7/25 o 

### C

Vapor pressure (25 o 

### C) 1.1x10

- 8 

### torr Equal to 1.447x10

- 11 

### atm s

.

Henry's Law Constant 1.4 0 x10

- 1 2 

### atm s

. m 3 

### . mole

- 1 

### (Calculated)

Octanol/Water Partition, K

ow 

### 1 @ pH7 and 87 @ pH 5 (log K OW 

### 0.034 @ pH7 &1.94 @ pH 5)

1 

### U RL: http://www.scorecard.org/chemical

- profiles/text

- search.tcl?query_string=Rimsulfuron



## Rimsulfuron is a soluble compound in water and its low vapor pressure/Henry’s Law constant

suggests that partitioning i nto the air, from dry/wet soil may not be an important route of its

dissipation in the environme nt. The pKa of rimsulfuron is 4.0 suggesting that it would be anionic

in soil pHs over 4 and bind weakly to most soil particles (usually negatively charged). F inally,

the c hemical has a K

ow 

## <100 suggesting that it will not potentially be bio

- concentrated by aquatic

organisms such as fish.

Fate and transport properties, for rimsulfuron and its major degradates, are based entirely on

previously submitted studies used in previous section 3 risk assessments. A summary of this

data is included Table 3

.

Table 3

. A summary of the environmental fate data for rimsulfuron.

Parameter Value MRID



### Hydrolysis t 1⁄2 

### = 4.5

- 4.7days @ 25 o 

### C , pH 5;

t 1⁄2 

### = 7.1

- 7.3days @ 25 o 

### C , pH 7;

t 1⁄2 

### = 4.2

- 10.9Hours @ 25 o 

### C , pH 9.

Major degradates (from contraction of the sulfonurea bridge) : IN

- 70941

(degrading into IN

- 70942)

Minor degradates (from cleavage of the sulfonurea bridge) : IN

- E9260 and

IN

- J290 and IN

- T5831 (only @ pH 5 )

. 413563

- 33

, Acceptable

## 16 Parameter Value MRID



### Direct

photolysis in

water

at pH 7 Half

- lives in irradiated samples (11.0

- 12.4 days) were longer than the dark

controls (6.4

- 6.5 days) indicating that Direct photolysis is NOT an

important degradation pathway

.

Major and Minor degradates : Sim ilar to hydrolysis although irradiation

appeared to reduce conversion of the transformation product IN

- 70941 into IN

70942 and/or en hance the degradation of IN

- 70942. Formation of IN

- E9260,

IN

- J290, and the un

- identified polar compounds appeared to be enha nced

. 419316

- 08

, Acceptable

Photolysis on

soil Half

- lives in irradiated /dark control samples were in the range of 11

- 12

days indicating that photolysis on soil is NOT an important degradation

pathway

.

Major and Minor degradates : Similar to hydrolysis al though irradiation

appeared to increase the formation of soluble un

- identified polar compounds. 41 9316

- 09

, Acceptable

Aerobic soil

metabolism t 1⁄2 

### = 21.3 days for two labels (R 2 

### = 0.87

- 0.94) in Sassafras sandy loam soil from

Penns Grove, NJ (Sand= 77%, Sil t= 14%, Clay 9%, pH 6.7, Organic matter=

1.1%, CEC= 3.2 meq/100 g).

Major degradates (from contraction of the sulfonurea bridge): IN

- 70941

(degrading into IN

- 70942) plus IN

- E9260 (from cleavage of the sulfonurea

bridge)

Minor degradates (from cleavage of the sulfonurea bridge): IN

- J290 and

IN

- T5831. 413563

- 34

, Acceptable

(Partial)

A na erobic soil

metabolism t 1⁄2 

### = 17.9

- 18.1 days for two labels (R 2 

### = 0. 91

- 0.99 ) in Sassafras sandy loam soil

from Penns Grove, NJ ( same soil used in the aerobic soil study ).

Majo r /Minor degradates : Same as the aerobic soil. 413563

- 3 5

, Acceptable

Aerobic aquatic

metabolism t 1⁄2 

### =0.5

- 2 Days at 25 o 

### C in the water column;

t 1⁄2 

### = 59

- 77 Days at 5 o 

### C in the water column.

Important Note:

4 32885

- 02

, Supple

mental C alculated half

- lives may NOT represent an aerobic aq uatic

system because of exposure to light and the use of extremely diluted sediment.

Major/Minor degradates: Similar to hydrolysis.

Adsorption/

Desorption

(K d 

### and

K

oc 

### in L Kg

- 1 

### ) 413563

- 36

, Acceptable [Pyrimidine

- 2

- 14 

### C]:

Cecil sandy loam (NC): K d 

### = 0.23 and K

oc 

### = 19

Fargo clay loam (ND): K d 

### = 1.36 and K

oc 

### = 55

Sassafras sandy loam (NJ): K d 

### = 0.32 and K

oc 

### = 55

Flanagan silt loam (IL): K d 

### = 1.52 and K

oc 

### = 61

Terrestrial

Field/Lysimeter

Dissipation 1 

### Greenville, MS : t 1⁄2 

### = 09 Days (average in the top 0

- 3”)

Madera, CA: t 1⁄2 

### = 08 Days (average in the top 0

- 3”)

Rochelle, IL: t 1⁄2 

### = 18 Days (average in the top 0

- 3”)

Newark, DE: t 1⁄2 

### = 05 Days (average in the top 0

- 3”)

Major degradates: IN

- 70941 (degrading i nto IN

- 70942)

Minor degradates: None identified as the bridge

- cleavage degradates may

have fallen below the LOD (LOD=<10% of the applied) 419316

- 0 6

, 419316

- 1 0,

Acceptable

Accumulation in Fish: Waived following request (MRID 413563

- 39) due to low K

ow =1 at pH7.

1 

### The terrestrial field dissipation study for a soil in Newark, Delaware submitted under MRID 419316

- 10 was

originally classified as unacceptable study.

## 17 Based on data summarized in Table 4 , the main process involved in rimsulfuron fate in aqueous

s ystems is hydrolysis. Its fate in the soil system appears to be also controlled by hydrolysis

followed by biotic degradation. The chemical has very low affinity to the solid phase in either

soil or sediment. Therefore, rimsulfuron is expected to be highly mobile in the natural

environment although its availability for leaching is expected to be limited by its vulnerability to

degradation. However, leaching is expected to occur in certain environmental conditions such as

low availability of moisture, cold c limatic conditions, sandy soils, and shallow ground water

.

1 

### K d 

### calculated from a 4

- hour/4 concentrations adsorption/desorption experiments;

2 

### K d 

### calculated from R f 

### values using Hamaker equation; 3 

### ND= No Data;

4 

### Mobility class as per: McCall, et al. 1980. Estimation of chemi cal mobility in soil from liquid chromatographic

retention times. Bull. Environmtal Contamination. Toxicology. 24, 190

- 195.



## appears to only form in acidic media. Therefore, the expected terminal transformation

products/degradates are the major transform ation product IN

- 70942 and the minor degradation

product IN

- J920. In neutral/acidic media the minor degradate IN

- E9260 is expected to be present

with the minor degradate IN

- T5831 being present in only acidic media. a. Abiotic Degradation

Rimsulfuran hydrolyzed in pH 5, 7, and 9 buffered solutions with half

- lives ranging from hours

(4

- 11 hours) to days (5

- 7 days) at 25 ± 1 oC. The rates in hours were observed in alkaline media

( pH 9) while rates in days were observed in neutral>acidic media. Rate s of degradation were

simila r for p yridine and p yrimidine

14 

## C labels. Results from b oth labels suggested that

contraction of the sulfon urea b ridge (transformation into IN

- 70941) is the major process of

hydrolytic transformation. In contrast, cleavage of the s ulfonurea b ridge ( degradation into IN

J920

, IN

- E9260 and IN

- T5831 ) appeared to be a minor process of hydrolytic transformation.

The degradation profile suggests that the transformation product IN

- 70941 further transforms

into IN

- 7094 2 . Additionally, the degradate IN

- J920 forms in minor amounts in all tested pHs

while the degradate IN

- E9260 forms in minor amounts at pH 7 and 5. The deg radate IN

- T5831

Table 4. Mobility of parent rimsulfuron and its transformation products/degradates (K

oc 

## values).

Aqueous direct photolysis appears to be an un

- important mechanism of transformation of

rimsulfuron (half

- lives in irradiated samples at pH 7 = 11.0

- 12.4 days) were longer than those for

the dark controls (6.4

- 6.5 days). The degradation profile is similar to hydrolysis although

irradiation appeare d to reduce conversion of the transformation product IN

- 70941 into IN

- 70942

and /or increase the degradation of IN

- 70942. Additionally, photolysis appears to enhance the

formation of IN

- E9260, IN

- J290, and the un

- identified polar compounds. Similarly, pho tolysis Ad/Des Method 1 

### TLC Method 2



### Parent Parent IN

- 70941 IN

- 70942 IN

- E9260 IN

- J290

Cecil sandy loam 19 51 58 41 44 284

Fargo clay loam 55 63 357 317 6 ND 3



### Sassafras sandy loam 55 41 79 207 110 ND

Flanagan silt loam 61 74 142 1,398* 6 834

Woodstown sandy loam ND ND ND ND ND 393

Keyport silt loam ND ND ND ND ND 362

Mobility Class 4 

### Very high

- High Hig h

- Medium (except *=Low) Medium

## 18 on soil appeared to be un

- important (half

- lives in irradiated samples and dark control were

practically the same) although radiation energy appears to increase the formation of many un

identified polar compound s

. At termination of the 27

- day experi ment , the bound residue ranged

from 6

- 7% in irradiated samples compared to 3

- 4% in dark control with a maximum evolved

CO2 of nearly 1%.

As stated above, hydrolysis appears to be the only important abiotic transformation/degradation

process that is expec ted to affect rimsulfuron. This is also the case for its

transformation/degradation products. Examination of hydrolysis at pH 7, reveals that the major

degradate IN

- 70941 forms and reaches maximums (13

- 17%) early (3

- 7 days) and then declines

as it transfor ms into the second major degradate IN

- 70942 which reaches maximums (81

- 84%)

at 30

- day (experiment termination) with no decline. The cleavage degradates form as minor

degradates from which IN

- 290 reaches a maximum of 7% within the two weeks followed by a

ve ry slight decline to 6% while IN

- E9260 reaches a maximum of 10% at 30

- day (experiment

termination) with no decline.

Soils

Only one study was submitted on aerobic soil metabolism of rimsulfuron covering only on e soil

using two rimsulfuron labels (pyridine and p yrimidine

- 2

- 14 

## C labels). Calculated half

- lives for

the two labels were the same (21.3 days) indicating relatively low persistence in the soil tested.

The degradation profile for the two labels suggests t hat rimsulfuron transforms into the major

transformation product IN

- 70941 by contraction of the Sulfonurea Bridge. IN

- 70941 appears to

transform further into IN

- 70942. In contrast to hydrolysis, cleavage of the sulfonurea b ridge

appears to be more pronounc ed in aerobic soil conditions resulting in another major degradate ;

IN

- E9260. The minor aerobic soil degradates (IN

- 290 and IN

- T5831) are the result of cleavage

of the sulfonurea b ridge. In this study the maximum amount of un

- characterized bound residue

r eached 28

- 33% @ 9 months and declined slightly into 24

- 27% at the 1

- year study termination.

Evolved CO 2 

## and SO 2 

## reached maximums of 4

- 8% at study termination.

In the one year aerobic soil system, profiles for formation and decline of transformation

produc ts/degradates suggest slow decline of the major degradate IN

- 70941 (reached maximums

of 41

- 55% @ 1⁄2

- 2 months and declined to 30

- 33% at study termination) and very slow decline of

the degradates IN

- E9260 (reached a maximum of 19% @ 6 months and declined to 1 6% at study

termination), IN

- 290 (reached a maximum of 3 % @ 1 month and declined to 1% at study

termination) and IN

- T5831 (reached a maximum of 1% @ 3

- 9 months and declined to 0.5% at

study termination). In contrast

, the major degradate IN

- 70942 shows no decline (reached

maximums of 24

- 30% at the study termination) reflecting its persistence as it form s from the

declining transformation product IN

- 7094 1

. b. Bio

- degradation

Using the same soil, the experiment was repeated with a 10

- day aerobic incubation followed by

60 days of anaerobic incubation. Although anaerobic condition s were not confirmed

(supplemental study), calculated half

- lives were near 19 days

, which is comparable to the aerobic

soil half

- life of 20 days. The degradation profiles under anaerobic conditions sugg ested that the

## 19 degradate IN

- 70941 is less persistent under anaerobic condition than under aerobic condition

, while IN

- 70942 and IN

- E9260 are persistent and relatively persistent, respectively, in both

media

. In the anaerobic profiles

, formation and decline of transformation products/degradates

suggest sharp decline of the major degradate IN

- 70941 , in contrast to the aerobic study (reached

maximums of 30

- 32 % @ 5

- 10 days and declined to 6 % at study termination)

, very slow decline

of the degradates IN

- 290 (rea ched a maximum of 8 % @ 28 days and declined to 6% at study

termination), and no decline for the transformation product IN

- 70942 (same to the aerobic study)

and the degradates IN

- E9260 and IN

- T5831 (Maximums of 47

- 56%, 23%

, and 1%, res pectively,

at terminat ion).

Sediment/Water Systems

The only submitted study was an aerobic aquatic study for pH 7. 9 pond water/sediment system

(MRID 432885

- 02). The study was classified supplemental because of the use of small amount

of the se diment relative to water and the repeated dark/light exposure (experiment should have

been kept in the dark. The study was conducted under sterile/non

- sterile conditions and

incubation temperature s of 25/5 o 

## C. On the assumption of minimal effects of ligh t energy

(MRID 419316

- 08), the results indicated that abiotic hydrolysis is the important degradation

pathway of parent r imsulfur o n . Half

- lives were calculated for the water column and were within

a range of 0.5

- 2 days with shorter half

- lives being associa ted with non

- sterile conditions.

Furthermore, low temperature conditions resulted in a significant de c rease in the rate of

degradation (half

- li ves in the range of 59

- 77 days a t 5 o 

## C ). The degradation pattern in the

aerobic aquatic system was similar to h ydrolysis although biodegradation appeared to affect the

terminal transformation product IN

- 70942 as it showed its relative susceptib ility to

biodegradation /photolysis (reached a maximum of 98% @ day 7 then declined to 65% @ 6

- month study termination coi n c iding with an increase in evolved CO 2 

## from <<1% to 10%). The

pattern of formation and decline for the transformation product IN

- 70941 suggest ed its early

transformation into IN

- 70942 w hile degradate s IN

- E9260/ IN

- J290 form ed at minor amount s

(Maximum s of 8/ 9%) and show ed very small/ no decline within the 6

- month period. This latter

degradation profile was similar to that observed in hydrolysis/aerobic soil studies.

Adsorption/desorption characteristics for rimsulfuron were stu died for four US soils and

coefficients were calculated based on measurements of radioactivity (not parent) associated with

solid/water phases (MRID 413563

- 36). Therefore, the study was considered supplemental as

results represent adsorption/desorption of parent and any degradate that might have been formed

within the 4 + 

## hour’s period of incubation. Based on hydrolysis data and reported soil pH values

(pHs 5.4

- 7.7), the only degradate that might be present within the 4 + 

## hour’s period of incubation

is IN

- 7 0941 at levels << 10%. Therefore, radioactivity data may be taken to largely represent

that of parent along with calculated K

oc 

## ’s. In a separate experiment, mobility of the parent and

its transformation products/degradates were established using the TLC method (MRID 413563

- 37). Although the TLC method is not recommended by the Agency, parent results appeared to

be comparable to results obtained by the recommended method. Therefore, TLC data may be

taken to at least indicate mobility of the transformati on products/degradates relative to parent.

All of the results are included in Table 4

. c. Mobility

## 20 Parent rimsulfuron appears to be highly mobile in tested soils with variable organic carbon ( 0.6

-

2.5 %) and clay contents (4

- 30%) (K

oc 

## 19

- 61 L Kg - 1 

## ) . Examination of par ent data also indicated

that the adsorption affinity of parent rimsulfuron is directly corre lated to organic matter content,

not correlated with clay content, and that it is not affected by change s in concentration (1/n of the

Freundlich isotherms were no t significantly different from 1 for four concentrations: 0.1, 0.5, 1,

and 5 ppm). In comparison, the two contraction transformation products of rimsulfuron (IN

70941/2) and one of the cleavage degradates (IN

- E9260) appear to be similar or slightly less

m obile than their parent (K

oc 

## 06

- 357 L Kg

- 1 

## , with the exception of one soil with a K

oc 

## value of

1,398 L Kg - 1 

## “low mobility”) while medium mobility can be assigned to the cleavage degradates

IN

- J290 (K

oc 

## 284

- 362 L Kg

- 1 

## )

.

d. Field Dissipation

The registrant submitted two terrestrial field dissipation studies which were conducted in steel

lysimeters (MRIDs 419316

- 06/10). In these studies, >80% of the applied radioactivity did not

move below the 6” depth and movement to this dep th was observed only after 2

- 4 months. The

parent degraded with calculated first order half

- lives ranging from 5 days in DE to 18 days in IL.

Long half

- life of parent in the top 0

- 3” of the soil in IL may have resulted from slower

degradation attributed t o cooler climates. In contrast to parent, the main two transformation

products IN

- J70941/2 were identified and their relative amounts appeared to be related to site

characteristics. IN

- J70941 predominated in the acidic soils of DE and cooler soils of IL

( maximums of at days). Comparable amounts of both degradates were observed in the

neutral/alkaline soils of MS and CA. Cleavage degradates were not identified , and a s shown in

aerobic soils, these bridge

- cleavage degradates were usually <10% of the applied radioactivity.

f. Transformation Profiles

Available fate and transport data on rimsulfuron indicate that it transforms by sulfonurea bridge

contraction into the major/non

- persistent transformation product IN

- 70941 . IN

- 7 0941 appears to

transform further into the major/persistent transformation product IN

- 70942. In addition,

cleavage of the sulfonurea bridge produce s three degradates: the minor (major in aerobic soil)

degradate IN

- E9260 and the minor degradates IN

- J920 and IN

- T5831. Registrant’s chemical

codes and IUPAC names for rimsulfuron transformation products/degradates are included in

Table 5

.

Rimsulfuron structure contains a pyridine ring linked with a substituted pyrimidine ring by a

sulfonylurea bridge. The main degradation pathway of the chemical is through bridge contraction

which involves elimination of the sulfonyl and urea g roups followed by re

- bridging. This

process results in the formation of the rim sulfuron transformation product IN

- 70941

, which

further transforms into IN

- 70 9 42. In addition, another minor degradation pathway is observed

and it involves degradation of rimsulfuron through sulfonylurea bridge cleavage resulting in the

formation of the degradate IN

- E9260 from the pyridine ring and IN

- J290 an d IN

- T5831 from the

pyrimidine ring. These two transformation/degradation pathways are illustrated in Figure 4.

## 21 Table 5. Rimsulfuron tra nsformati on products/degradate code/chemical names.

Degradation data suggests that the parent will be relatively short lived in aquatic compartments

of the environment as it hydrolyzes with a half

- life of one week. However, the parent becomes

relatively more pers istent in aerobic/anaerobic soil systems (half

- life of 3 weeks) possibly as a

result of the relative deficiency in water for hydrol ysis and the relative persistence to bio

degradation. In terms of persistence, the transformation product IN

- 70941 appears t o be unstable

and transforms into the persistent transformation product IN

- 70942. From IN

- 70941, hydrolysis

produce s the highest stable maximum of the degradate IN

- 70942 (nearly 80%) while aerobic soil

appear s to slow the transformation resulting in a max imum of IN

- 70942 of nearly 30%. In all

systems, the three cleavage degradates appear to form in minor amounts (except IN

- E9260 in

aerobic soil) and show no or very slow decline.

2. Measures of Aquatic Exposure for the Ecological Risk Assessment

Tier II linked PRZM/EXAMS

Surface water EECs for rimsulfuron were obtained by modeling using tier I GENE EC2 and

because of exceedances, Tier II linked PRZM/EXAMS was final l y used

. The proposed new use

patterns includ e soybeans and the amended tolerance for field corn , therefore several scenarios

were used to represents these use patterns. Table 6 summarizes the crop use patterns, and

associated scenarios/parameters used for modeling.

Applicant's Code IUPAC Chemical Name



### (01) IN

- 70941 N

- (4, 6

- Dimethoxy

- 2

- pyrimidinyl)

- N

- ((3

- ethylsulfonyl)

- 2

- pyridinyl))Urea

(02) In

- 70942 N

- ((3

- Ethylsulfonyl)

- 2

- pyridinyl)

- 4, 6

- dimethoxy

- 2

- pyrimidineamine)

(03) IN

- E9260 3

- (Ethylsulfonyl)

- 2

- pyridine sulfonamide

(04) IN

- J290 2

- Amino

- 4, 6

- dimethoxy pyrimidine

(05) IN

- T5831 N

- (4, 6

- Dimethoxy

- 2pyrimidinyl) Urea

## 22 N S O

O C H

2 

### C H

3



### S O

O N H

2



## Figure 4 : Transformation/degradation pathways for rimsulfuron in various environmentally

relevant systems. Parent Rimsulfuron

N S O

O C H

2 

### C H

3



### N N O

O C H

3



### C H

3 

### N

C O

N H

2



### IN

- 70941



### N S O

O C H

2 

### C H

3



### N N O

O C H

3



### C H

3 

### N H 

### N N O

O C H

3



### C H

3 

### N H

2



### IN

- J290: Pyrimidine Amine IN

- E9260 : Pyridine Sulfonamide

N N O

O C H

3



### C H

3 

### N H

C O

N H

2 

### Sulfonurea

- Brigde Cleavage ( MINOR

in all systems, Except as indicated)

M AJOR in

Aerobic

Soil Only Sulfonurea

- Brigde Contraction ( MAJOR

i n all systems) Sulfonylurea Bridge

Pyrimidine Ring Pyridine Ring



### N N O

O C H

3



### C H

3 

### N

H N S O

O C H

2 

### C H

3



### N

H S O

O

O

## 23 Table 6

. PRZM/EXAMS modeled crop scenarios/parameters.

Table 6

. PRZM/EXAMS modeled crop scenarios/ para meters.

Use Pattern Representative Scenario Application Date: dd/mm Number of Applications & Intervals



### DUPONTTM

OPTIMUM®

GAT® Corn IL corn 22

- 05

One application three weeks

postemergence for all scenarios (from

Metadata file) MS corn 01

- 05

NC corn 0 5

- 05

OH corn 22

- 05

PA corn 07

- 05

DUPONTTM

OPTIMUM®

GAT® Soybean MS soybean 07

- 05



## Source: See Appendix

Other input values used in modeling based on the above mentioned assumptions/scenarios are

included in Table 7

.

Table 7

. PRZM/EXAMS input param eters for modeling (Aquatic ECO EECs).

Table 7

. PRZM/EXAMS input parameters for modeling.

Input Parameter Value* Reference



### Chemical Name Rimsulfuron

Output file name RIMSULFU

Molecular Weight (g mole

- 1 

### ) 431.44

MRIDs: 413563

- 01 and 419316

- 02 Vapor Pr essure (torr , at 25°C ) 1.1x10

- 8



### Henry's Law Constant (A tm m - 3



### mole

- 1 

### ) 8.56 x10

- 1 3 

### Calculated

Aerobic Soil Metabolism Half

- life

(days) 64 One half

- life x 3 (21.3x3; MRID 413563

- 34)

Water column Half

- life (days)

(Aerobic Aquatic Metabolism half

life) Stab le No aerobic aquatic metabolism data and

there is significant hydrolysis.

Benthic sediment Half

- life (days)

(Anaerobic Aquatic Metabolism

half

- life) Stable No anaerobic aquatic metabolism data and

there is significant hydrolysis.

Application Rate (Kg a .i./ha) 0.0701 0.0626 lb a.i./A

Application Number (Method of

application) One (aerial) Product Label

Depth of Incorporation (cm) 0 Product Label

## 24 Table 7

. PRZM/EXAMS input parameters for modeling.

Input Parameter Value* Reference



### CAM (chemical application

method) 2 L inear foliar based on crop canopy

IPSCND ( disposition of pesticide

re maining on foliage after harvest ) 1 P esticide remaining on foliage is converted

to surface application to the top soil layer

Application Efficiency 0.95 95% application efficiency for aerial

applications

Spray Drift (fraction) 0.05 5% spray drift for aer ial applications

Solubility (ppm) 7 3,000 10X the value at pH 7 and 25°C of 7,300

ppm. MRIDs: 41356301

K OC 

### (L Kg

- 1 

### ) 47.5 Average of four values (MRID 413563

- 36).

K OC 

### model was determined to be

appropriate.

Hydrolysis Half

- life @ pH 7 (days) 7.2 Averag e value at pH 7 (MRID 413563

- 33)

Direct Aqueous Photolysis Half

life(days) Stable Maximum dark control corrected value

(MRID 419316

- 08)

FEXTRC, Foliar extraction 0.5

EFED guidance on input parameters for

PRZM/ EXAMS dated 2/28/02 PLDKRT, Decay rate on foliage 0

PLVKRT, Volatilization rate from

foliage 0

UPTKF, Uptake factor 0

* Fate data values are as per Guidance for Selecting Input Parameters in Modeling the Environmental Fate and

Transport of Pesticides; Version II

, February 28, 2002.



## Resultan t modeling EEC ’s that were used for t he ecological risk assessment are summarized in

Table 8 . For reference, an example of a model run is included in Appendix II I

.

Table 8

. Modeled Ecological EECs (ppb) for Rimsulfuron

Crop Scenario Peak 21

- day 60

- day



### IL corn 0.744 0.326 0.156

MS corn 1.380 0.705 0.291

NC corn 0.459 0.221 0.0930

OH corn 0.578 0.301 0.131

PA corn 0.477 0.238 0.103

MS soybean 1.096 0.513 0.211



## The above stated values represent upper

- bound estimates of the parent c oncentrations tha t might

be found in aquatic systems due to the use of rimsulfuron on field corn and soybeans . Modeling

## 25 is performed using the highest application rates/number and shortest application intervals.

Therefore, these values represent the high est exposure scena rio for the various proposed use

patterns.

b. Ecological Aquatic Exposure from Monitoring Data

Although rimsulfuron was first registered in 1994, it appears that it was not included in the

national monitoring program. No monitoring data were found in the NAWQA database at the

following site.

http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME:2972429206327222289

Monitori ng studies were submitted by the registrant on or around 1998 , but it appears that the

studies have not been reviewed.

3. Measure of Terrestrial Exposure

a.

Measures of exposure for terrestrial and semi

- aquatic plants are inco rporated as part of the model

TerrPlant. This model uses application rate and a runoff value dependent on solubility. The

model generates risk quotients for comparison to LOCs. Terrestrial Exposure Modeling

**C. Ecological Effects Characterization**

In screening

- level ecological risk assessments, effects characterization describes the types of

effects a pesticide can produce in an aquatic or terrestrial organism. This characterization is

based on registrant

- submitted studies that describe acute and chronic effects toxicity information

for various aquatic and terrestrial animals and plants. Toxicity testing reported in this section

does not represent all species of bird, mammal, or aquatic organism. Since not all wildlife

species can ever be tested, representatives from large groups of species must be used. Generally,

only two surrogate species for both freshwater fish and birds are used to represent all freshwater

fish (2000+) and bird (680+) species in the United States. For mammals, acute studies are

usually limited to the Norway ra t or the house mouse. Estuarine/marine testing is usually limited

to a crustacean, a mollusc, and a fish. Also, neither reptiles nor amphibians are tested. The

assessment of risk or hazard makes the assumption that avian and reptilian toxicity are simil ar.

The same assumption is used for fish and amphibians. Generally, the most toxic endpoints for

the technical grade active ingredient (TGAI) are used in the assessment to represent each group

of organism.

Toxicity to Terrestrial Organisms

Rimsulfuro n is considered practically non

- toxic to most terrestrial animals. This includes birds

(mallard LD 50 

## > 2000 mg/kg; bobwhite quail LD 50 

## > 2250 mg/kg; mallard and bobwhite quail

## 26 LC 50 ’ 

## s > 5620 ppm), mammals (rat LD 50 

## > 5000 mg/kg), and bees (LD 50 

## > 100 ug/be e). The

NOAEC in an avian reproduction study with bobwhite quail is 1250 ppm.

In contrast, plants are extremely sensitive to rimsulfuron. For seedling emergence, plant height

was the most sensitive parameter (EC 25 

## = 0.0006 lb ai/A for the most sensiti ve monocot and

0.00013 for the most sensitive dicot). For vegetative vigor, root weight was the most sensitive

parameter (EC 25 

## = 0.00004 lb ai/A for the most sensitive monocot and 0.00003 lb ai/A for the

most sensitive dicot).

Toxicity to Aquatic Organ isms

Rimsulfuron is considered practically non

- toxic to most aquatic animals. This includes

freshwater fish (rainbow trout LC 50 

## > 390 ppm; bluegill sunfish LC 50 

## > 390 ppm), freshwater

invertebrates ( Daphnia magna LC 50 

## > 360 ppm), and estuarine/marine org anisms (sheepshead

minnow LC 50 

## > 110 ppm; mysid shrimp LC 50 

## > 110 ppm; oyster shell deposition EC 50 

## > 120

ppm). In contrast, vascular plants are extremely sensitive to rimsulfuron. The most sensitive

aquatic plant tested is duckweed (EC50 = 11.6 ppb).



# I V. RISK CHARACTERIZATION

**A. Risk Estimation** 

Since rimsulfuron is considered practically non

- toxic to terrestrial and aquatic animals, the focus

of this risk assessment is on terrestrial and aquatic plants which are highly sensitive.

The model TerrPlant was run t o develop risk quotien ts (RQs) for terrestrial plants

. Emergence

RQ ’ s for areas adjacent to treatment sites (EEC/seedling emergence EC 25 

## ) range from 6.25

–

10.42 for monocots and 28.85

– 48.08 for dicots. Emergence RQs for semi

- aquatic areas

(E EC/seedling emergence EC 25 

## ) range from 53.12

– 57.29 for monocots and 245.19

– 264.42 for

dicots. Drift RQs (drift EEC/vegetat ive vigor EC 25 

## ) range from 15.62

– 78.12 for monocots and

20.83

– 104.17 for dicots. See the TerrPlant printout for further deta ils ( Appendix II ).

The above RQs for terrestrial plants all far exceed the Acute Risk LOC of 1 for ter restrial and

semi

- aquatic non

- endangered plants . Although NOAEC values are not available to develop

specific RQ value s for endangered species, t hey woul d be even further exceeded for endangered

plants. This exceedance can be expected because NOAEC values would be lower than the EC 25



## values that are used for non

- endangered plants

.

To develop risk quotients (RQs) for non

- endangered aquatic plants, the highest peak aquatic

EEC across all crops (1.3 8 ppb, MS corn scenario, PRZM/EXAMS) is compared to the lowest

aquatic plant EC 50 

## (11.6 ppb). This produces an RQ of 0.1 2 . Thus, the LOC of 1 is not

exceeded for non

- endangered aquatic plants. For endangered aquatic plants, this EEC is

compared to the NOAEC (0.09 ppb). Table 9 shows that this comparison results in an RQ of

## 27 15.3 , indicating that the endangered species LOC of 1 is exceeded. All six of the scenarios (see

Exposure Characterization) result in ex ceedance of the aquatic plant endangered species LOC

.

Table 9

. Aquatic Plant Risk Quotients (Endangered Species)

. Crop Scenario Peak EEC (ppb) Risk Quotient



### IL corn 0.744 8.27

MS corn 1.380 15.3

NC corn 0.459 5.10

OH corn 0.578 6.42

PA corn 0.477 5.30

MS soybean 1.096 12.2



## B. **Risk Description**

The risk hypothesis states that the use of rimsulfuron could expose sensitive terrestrial and

aquatic plants, resulting in adverse effects. Based on available ecotoxicity data and predicted

environmental exposures, this ecological risk assessment support s the presumption of risk to

sensitive terrestrial and aquatic plants, including federally

- listed species.

As shown above under Risk Estimation, terrestrial plant risk quotients far exceed LOC ’ s for even

non

- endangered species. This is true for adjacent areas and semi

- aquatic areas (calculation uses

seedling emergence EC 25 

## ), and areas affected by drift (calculation uses vegetative vigor EC 25 

## ),

and is true for both monocots and dicots. As indicated, endan gered species LOCs are considered

exceeded as well, since the threshold for them is lower.

For aquatic plants, rimsulfuron EEC’s do not exceed the LOC for non

- endangered plants.

However, this information is derived from a study with uncertainty around t he measured

concentrations to which Lemna gibba was exposed, thereby introducing uncertainty into the RQ

estimate (MRID 42471308). The RQ derived from this study may underestimate risk to aquatic

vascular plants. In contrast to non

- endangered plant speci es, t he endangered species LOC is

exceeded for all six of the scenarios used t o evaluate the proposed new use in soybean and new

tolerance limit in field corn

.

EFED assesses acute risk but not chronic or reproductive effects to terrestrial and aquatic pla nts.

Rimsulfuron may therefore pose other risks that have not been assessed by EFED. Other

sulfonyl urea herbicides have adversely affected plant reproduction such as seed formation and

the production of viable seed (Chlorsulfuron R egistration E ligibilit y D ecision ). Rimsulfuron is

similar in structure and activity to other sulfonyl urea herbicides. Given this similarity,

rimsulfuron may also inhibit various aspect s of plant reproduction in both endangered and non

endangered plants at realistic environme ntal concentrations.

## 28 EFED’s Ecological Incident Information System (EIIS) was checked for reported incidents of

adverse affect s. As of 4/14/09, there were 25 incidents shown where all incident s involved

effects on plant s . While many were claims of t reated crop damage, there were seven listed as

being due to drift or sp ray drift. Of these seven, three have been categorized as Possible and two

as Probable. The AgDrift model, which EFED currently uses to assess risk from pesticide drift,

confirms the risk posed by pesticide movement offsite to both terrestrial endangered and non

endangered terrestrial plants and endangered aquatic plants, Figure 5

. The application

parameters used in the model, e.g. boom height and spray type, are conservative but with in the

recommendations of the label. According to this screening model, risk to terrestrial non

endangered and endangered plants is above the level of concern (value of 1) beyond 900 ft from

the edge of the field for both aerial and ground applications. However, risk to aquatic

endangered plants is above the level of concern only up to 300 ft beyond the field edge for aerial

applications and 100 ft for ground applications. While EFED’s risk assessment methods assume

that pesticides can move off

- site and p otentially affect off

- site non

- target organisms (in addition

to on

- site affects), reported incidents (when available) can help confirm this risk.

Endocrine Disruption

EPA is required under the FFDCA, as amended by FQPA, to develop a screening program to

determine whether certain substances (including all pesticide active and other ingredients) “may

have an effect in humans that is similar to an effect produced by a naturally occurring estrogen,

or other such endocrine effects as the Administrator may desi gnate.” 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 the appropriate screening and/or testing protocols being considered

under the Agency’s Endocrine Disrupter Screening Program (EDSP) have been developed and

vetted, Rimsulfuron may be subjected to additional screening and/or testing to better characterize

any effects related to endocrine disruption.

**C. Endangered Species Assessment** 

The following section discus ses the screening

- level assessment for federally

- listed threatened

and endangered species.

Listed Species

The Agency’s levels of concern for endangered and threatened species are exceeded for direct

effects to federally

- listed terrestrial and aquatic pl ants. The LOC is also exceeded for non

endangered terrestrial plants. As a result, there is also a concern for potential indirect effects to

listed species that depend on terrestrial and/or aquatic plants.

a. Action Area

For listed species assessment purpo ses, the action area is considered to be the area affected

directly or indirectly by the Federal action and not merely the immediate area involved in the

## 29 action. At the initial screening

- level, the risk assessment considers broadly described taxonomic

gro ups and so conservatively assumes that listed species within those broad groups are

collocated with the pesticide treatment area. This means that terrestrial plants and wildlife are

assumed to be located on or adjacent to the treated site and aquatic orga nisms are assumed to be

located in a surface water body adjacent to the treated site. The assessment also assumes that the

listed species are located within an assumed area which has the relatively highest potential

exposure to the pesticide, and that exp osures are likely to decrease with distance from the

treatment area. Section II.A of this risk assessment presents the pesticide use sites that are

employed to establish initial location of species with treatment areas.

b. Taxonomic Groups Potentially at Ri sk

If the assumptions associated with the screening

- level action area result in RQs that are below

the listed species LOCs, a "no effect" determination conclusion may be made with respect to

listed species in that taxa (for direct effects), and no further refinement of the action area is

necessary (assumptions include a complete data set for that taxa). Furthermore, RQs below the

listed species LOCs for a given taxonomic group indicate no concern for indirect effects upon

listed species that depend upon the taxonomic group covered by the RQ as a resource. However,

in situations where the screening assumptions lead to RQs in excess of the listed species LOCs

for a given taxonomic group, a potential for a "may affect" conclusion exists and may be

associate d with direct effects on listed species belonging to that taxonomic group or may extend

to indirect effects upon listed species that depend upon that taxonomic group as a resource. In

such cases, additional information on the biology of listed species, th e locations of these species,

and the locations of use sites could be considered along with available information on the fate

and transport properties of the pesticide to determine the extent to which screening assumptions

regarding an action area apply to a particular listed organism. These subsequent refinement steps

could 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

pestic ide use site.

c . Indirect Effects Analysis

Pesticides have the potential to exert indirect effects upon the listed organisms by, for example,

perturbing forage or prey availability, altering the extent of nesting habitat, and creating gaps in

the food ch ain. In conducting a screen for indirect effects, direct 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 a s resources

critical to their life cycle . These effects are summarized in Table 10 . Species specific concerns

for rimsulfuron indirect effects to listed organisms will require a determination of the

coincidence of rimsulfuron use with locations of listed species and the biologically based

resources upon which they depend.

## 30 0 5 10 15 20 25

Monocot

Dicot

0 20 40 60 80 100

Monocot

Dicot

0 0.5

1 1.5 2 2.5

3

0 1 2 3 4 5

0 200 400 600 800 1000 

### Terrestrial Scenario Aerial Application Terrestrial Scenario Ground Application

Aquatic Scenario Aerial Application Aquatic Scenario Ground Application



### Distance from Edge of Field (ft)EndangeredPlant RQNon-Endangered Plant RQ

0 5 10 15 20 25

Monocot

Dicot

0 20 40 60 80 100

Monocot

Dicot

0 0.5

1 1.5 2 2.5

3

0 1 2 3 4 5

0 200 400 600 800 1000 

### Terrestrial Scenario Aerial Application Terrestrial Scenario Ground Application

Aquatic Scenario Aerial Application Aquatic Scenario Ground Application



### Distance from Edge of Field (ft)EndangeredPlant RQNon-Endangered Plant RQ



## Figure 5: Risk Quotient (EEC/EC 25 

## for terrestrial scenario, EEC/NOAEC for aquatic scenario)

over distance from the edge of the field by exposure scenario. The exposure concentratio ns are

based on the AgDrift screening tool with an application rate of 0.0625 lbs a.i./acre, boom height

set to high and droplet size of very fine to fine for ground applications, and droplet size of fine to

medium for aerial applications.

## 31 Based on the proposed usage of rinsulfuron, i t appears at present that the principa l risk of

rimsulfuron is direct acute risk to plants and indirect risk to species that depend on plants. T he

screening level risk assessment also shows that there is a concern for indirect effects to listed

species that may depend upon terrestrial and/or aquatic plants for their survival. As described

above, acute RQs for terrestrial and aquatic plants exceed endangered species LOCs. Acute RQs

for terrestrial plants also exceed the LOC for non

- endangered species.

The Agency’s levels of concern for endan gered and threatened species are exceeded for direct

effects to federally

- listed terrestrial and aquatic plants. The LOC is also exceeded for non

endangered terrestrial plants. As a result, there is also a concern for potential indirect effects to

all sp ecies that depend on plants. The Program LOCATES was run to identify those species that

are located in counties with potential rimsulfuron use, and that could be affected either directly

or indirectly ( summarized in Tables 11

– 1 4

, listed in Appendix III )

.

d . Data Related to Under

- represented Taxa

No data are currently available in EFED that would indicate that taxa under

- represented among

those used for risk quotient calculations are more sensitive to rimsulfuron.

Table 10. Pot ential Effects to Federally Listed Taxa Associated with Direct or Indirect Effects from the

Proposed Application of Rimsulfuron on Soybeans and Field Corn.

Listed Taxon Direct

Effects Uses of Concern Indirect

Effects Uses of Concern

Terrestrial and semi

aquatic plants

-

monocots Yes Soybeans and Field Corn No None

Terrestrial and semi

aquatic plants

- dicots Yes Soybeans and Field Corn No None

Terrestrial invertebrates No None Yes 1 

### Soybeans and Field Corn

Birds No None Yes 1 

### Soybeans and Field Corn

Terrestrial phase

amphibians No None Yes 1 

### Soybeans and Field Corn

Reptiles No None Yes 1 

### Soybeans and Field Corn

Mammals No None Yes 1 

### Soybeans and Field Corn

Aquatic vascular plants Yes Soybeans and Field Corn No None

Freshwater fish No None Yes 1 

### Soyb eans and Field Corn

Aquatic phase

amphibians No None Yes 1 

### Soybeans and Field Corn

Freshwater crustaceans No None Yes 1 

### Soybeans and Field Corn

Mollusks No None Yes 1 

### Soybeans and Field Corn

Marine/estuarine fish No None Yes 1 

### Soybeans and Field Corn

Mari ne/estuarine

invertebrates No None Yes 1 

### Soybeans and Field Corn

Potential indirect effects on a taxon attributable to:

1 

### direct effects on terrestrial and aquatic plants

## 32 Table 11. Tabulation by State an d Taxonomic Group of Listed Species that Occur in Rimsulfuron

Use Areas for Corn for silage or greenchop.

No species exclusions corn for silage or greenchop

Minimum of 1 Acre All Medium Types ReportedAmphibianArachnidBirdBivalveConf/cycdsCrustaceanDicotFernsFishGastropodInsectLichenMammalMarineMonocotReptile

AL 2 0 3 26 0 1 10 3 14 10 0 0 4 0 3 5

AR 0 0 2 4 0 1 2 0 2 0 0 0 2 0 0 0

AZ 2 0 7 0 0 0 8 0 15 0 0 0 8 0 2 1

CA 5 0 14 0 0 9 118 0 25 0 13 0 19 1 12 7

CO 0 0 2 0 0 0 8 0 5 0 1 0 2 0 1 0

CT 0 0 2 1 0 0 1 0 1 0 1 0 1 0 1 1

DE 0 0 1 0 0 0 0 0 1 0 0 0 1 0 2 1

FL 1 0 8 7 1 1 38 0 3 0 1 1 8 1 2 9

GA 1 0 2 15 1 0 10 2 11 0 1 0 2 1 6 1

HI 0 0 12 0 0 0 87 7 0 38 0 0 1 1 7 2

IA 0 0 2 2 0 0 3 1 2 1 0 0 1 0 2 0

ID 0 0 1 0 0 0 1 0 7 6 0 0 3 0 0 0

IL 0 0 2 7 0 1 7 0 1 1 2 0 2 0 2 0

IN 0 0 2 11 0 0 4 0 0 0 2 0 2 0 1 1

KS 0 0 3 0 0 0 1 0 4 0 1 0 2 0 1 0

KY 0 0 6 22 0 1 9 0 5 0 1 0 3 0 0 0

LA 0 0 2 1 0 0 1 1 2 0 0 0 1 1 0 2

MA 0 0 3 0 0 0 1 0 1 0 3 0 1 0 2 2

MD 0 0 1 1 0 0 4 0 2 0 2 0 2 0 2 1

ME 0 0 2 0 0 0 1 0 2 0 0 0 1 0 2 0

MI 0 0 2 2 0 0 4 1 0 0 4 0 3 0 3 1

MN 0 0 1 2 0 0 2 0 1 0 1 0 2 0 2 0

MO 0 0 2 6 0 1 6 0 7 0 2 0 2 0 1 0

MS 0 0 3 9 0 0 2 1 3 0 0 0 2 0 0 7

MT 0 0 3 0 0 0 2 0 4 0 0 0 3 0 0 0

NC 0 1 1 7 0 0 18 0 4 1 1 1 4 1 4 2

ND 0 0 3 0 0 0 0 0 1 0 0 0 0 0 1 0

NE 0 0 3 0 0 0 2 0 2 0 1 0 1 0 1 0

NH 0 0 0 1 0 0 1 0 0 0 1 0 1 0 1 0

NJ 0 0 1 0 0 0 2 0 1 0 0 0 1 0 3 1

NM 1 0 6 0 0 2 10 0 13 5 0 0 5 0 0 1

NV 0 0 0 0 0 0 8 0 14 0 2 0 0 0 1 1

NY 0 0 2 1 0 0 4 1 1 1 1 0 1 0 1 1

OH 0 0 1 6 0 0 4 0 1 0 4 0 2 0 2 2

OK 0 0 5 2 0 0 0 0 4 0 1 0 3 0 1 0

OR 0 0 4 0 0 1 9 0 19 0 2 0 1 0 2 0

PA 0 0 1 2 0 0 0 0 0 0 0 0 2 0 2 1

RI 0 0 1 0 0 0 1 0 1 0 1 0 1 0 1 0

SC 1 0 4 1 0 0 11 1 1 0 0 0 1 3 3 5

SD 0 0 3 0 0 0 0 0 2 0 1 0 1 0 1 0

TN 0 1 2 36 0 1 16 1 16 3 0 1 3 0 1 0

TX 4 10 12 0 0 1 14 0 5 1 9 0 4 0 2 6

UT 0 0 2 0 0 0 19 0 8 0 0 0 2 0 2 1

VA 1 0 2 21 0 2 13 0 7 1 3 0 5 0 4 1

VT 0 0 0 1 0 0 1 0 0 0 0 0 1 0 1 0

WA 0 0 4 0 0 0 5 0 19 0 0 0 4 0 0 0

WI 0 0 3 2 0 0 4 0 0 0 2 0 2 0 2 0

WV 1 0 0 5 0 0 4 0 0 1 0 0 5 0 1 0

WY 0 0 0 0 0 0 2 0 0 0 0 0 4 0 0 0

## 33 Table 12. Tabulation by State and Taxonomic Group of Listed Species that Occur in Rimsulfuron

Use Areas for Corn for Grain.

No species exclusio ns Corn for grain

Minimum of 1 Acre All Medium Types ReportedAmphibianArachnidBirdBivalveConf/cycdCrustaceanDicotFernsFishGastropodInsectLichenMammalMarineMonocotReptile

AL 2 0 3 30 0 1 10 3 15 10 0 0 4 0 3 5

AR 0 0 2 6 0 0 3 0 2 1 1 0 1 0 0 0

AZ 2 0 6 0 0 0 12 0 15 1 0 0 9 0 2 2

CA 6 0 12 0 1 8 102 0 24 1 12 0 16 2 12 7

CO 0 0 2 0 0 0 4 0 5 0 0 0 2 0 1 0

CT 0 0 2 1 0 0 1 0 1 0 0 0 1 0 1 1

DE 0 0 1 0 0 0 0 0 1 0 0 0 1 0 2 1

FL 1 0 8 7 1 1 40 0 4 0 1 1 7 1 2 9

GA 1 0 4 16 1 0 11 2 11 0 1 0 3 1 6 2

HI 0 1 26 0 0 1 200 11 0 39 1 0 1 1 19 2

IA 0 0 2 2 0 0 3 1 2 1 0 0 1 0 2 0

ID 0 0 0 0 0 0 1 0 8 6 0 0 3 0 0 0

IL 0 0 2 7 0 1 7 0 1 1 2 0 2 0 2 0

IN 0 0 2 11 0 0 4 0 0 0 2 0 2 0 1 1

KS 0 0 3 0 0 0 1 0 4 0 1 0 2 0 1 0

KY 0 0 6 22 0 1 10 0 5 0 1 0 3 0 0 0

LA 0 0 5 3 0 0 2 1 2 0 0 0 1 1 0 7

MA 0 0 3 0 0 0 0 0 1 0 1 0 1 0 2 2

MD 0 0 1 1 0 0 4 0 2 0 2 0 2 0 2 1

ME 0 0 2 0 0 0 1 0 2 0 0 0 1 0 2 0

MI 0 0 2 2 0 0 4 1 0 0 4 0 3 0 3 1

MN 0 0 1 2 0 0 2 0 1 0 1 0 2 0 2 0

MO 0 0 2 6 0 1 7 0 7 1 2 0 2 0 1 0

MS 1 0 5 9 0 0 2 1 3 0 0 0 3 0 0 7

MT 0 0 3 0 0 0 2 0 3 0 0 0 3 0 0 0

NC 0 1 4 8 0 0 21 0 4 1 1 1 4 1 5 5

ND 0 0 3 0 0 0 0 0 1 0 0 0 0 0 1 0

NE 0 0 3 0 0 0 2 0 2 0 1 0 1 0 1 0

NH 0 0 0 1 0 0 1 0 0 0 1 0 1 0 1 0

NJ 0 0 2 0 0 0 2 0 1 0 0 0 1 0 3 1

NM 1 0 6 0 0 1 7 0 7 2 0 0 5 0 0 1

NV 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0

NY 0 0 2 1 0 0 4 1 1 1 1 0 1 0 1 1

OH 0 0 1 6 0 0 4 0 1 0 4 0 2 0 2 2

OK 0 0 6 2 0 0 0 0 4 0 1 0 3 0 2 0

OR 0 0 3 0 0 0 6 0 20 0 0 0 1 0 0 0

PA 0 0 1 2 0 0 0 0 0 0 0 0 2 0 2 1

RI 0 0 1 0 0 0 1 0 1 0 1 0 0 0 0 0

SC 1 0 4 1 0 0 12 1 1 0 0 1 1 3 6 5

SD 0 0 3 0 0 0 0 0 2 0 1 0 1 0 1 0

TN 0 1 3 38 0 1 16 1 16 3 0 1 3 0 2 0

TX 4 10 12 0 0 1 25 0 7 1 9 0 5 0 2 6

UT 0 0 1 0 0 0 15 0 6 0 0 0 2 0 2 1

VA 1 0 2 21 0 2 13 0 7 1 3 0 5 0 4 1

VT 0 0 0 1 0 0 1 0 0 0 0 0 1 0 1 0

WA 0 0 2 0 0 0 4 0 12 0 0 0 3 0 0 0

WI 0 0 3 2 0 0 4 0 0 0 2 0 2 0 2 0

WV 1 0 0 5 0 0 4 0 0 1 0 0 5 0 1 0

WY 0 0 0 0 0 0 2 0 0 0 0 0 4 0 0 0

## 34 Table 13. Tabulation by Stat e and Taxonomic Group of Listed Species that Occur in Rimsulfuron Use Areas

for Soybeans for Beans.

No species exclusions. Soybeans for bean

Minimum of 1 Acre All Medium Types ReportedAmphibianArachnidBirdBivalveConf/cycdCrustaceanDicotFernsFishGastropodInsectLichenMammalMarineMonocotReptile

AL 2 0 3 29 0 1 9 2 15 10 0 0 4 2 3 8

AR 0 0 2 5 0 1 3 0 3 1 1 0 1 0 0 0

CO 0 0 1 0 0 0 0 0 1 0 0 0 1 0 0 0

CT 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 6

DE 0 0 1 0 0 0 0 0 1 0 0 0 1 3 2 6

FL 1 0 7 7 1 0 23 0 2 0 0 1 4 5 1 8

GA 1 0 4 15 1 0 9 2 11 0 0 0 2 4 4 6

HI 0 1 13 0 0 1 72 2 0 1 0 0 1 2 11 4

IA 0 0 2 2 0 0 3 1 2 1 0 0 1 0 2 0

IL 0 0 2 7 0 1 7 0 1 1 2 0 2 0 2 0

IN 0 0 2 11 0 0 4 0 0 0 2 0 2 0 1 1

KS 0 0 3 0 0 0 1 0 4 0 1 0 2 0 1 0

KY 0 0 6 22 0 1 10 0 5 0 1 0 3 0 0 0

LA 0 0 5 3 0 0 2 0 2 0 0 0 1 3 0 6

MA 0 0 2 0 0 0 0 0 1 0 1 0 1 2 1 5

MD 0 0 1 1 0 0 4 0 2 0 2 0 2 3 2 5

ME 0 0 2 0 0 0 1 0 1 0 0 0 1 3 2 1

MI 0 0 2 2 0 0 3 0 0 0 4 0 3 0 3 1

MN 0 0 1 2 0 0 2 0 1 0 1 0 2 0 2 0

MO 0 0 2 6 0 1 7 0 7 1 2 0 2 0 1 0

MS 0 0 5 9 0 0 2 1 3 0 0 0 3 2 0 9

MT 0 0 3 0 0 0 0 0 1 0 0 0 3 0 0 0

NC 0 1 4 8 0 0 20 0 3 0 1 1 2 4 5 5

ND 0 0 3 0 0 0 0 0 1 0 0 0 0 0 1 0

NE 0 0 3 0 0 0 1 0 2 0 1 0 1 0 1 0

NH 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1

NJ 0 0 2 0 0 0 2 0 1 0 0 0 1 3 3 5

NM 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0

NY 0 0 2 1 0 0 4 1 1 1 1 0 1 3 1 6

OH 0 0 1 6 0 0 4 0 1 0 4 0 2 0 2 2

OK 0 0 6 2 0 0 0 0 4 0 1 0 3 0 2 0

PA 0 0 1 2 0 0 0 0 0 0 0 0 2 0 2 1

RI 0 0 1 0 0 0 1 0 1 0 1 0 0 3 0 4

SC 1 0 3 1 0 0 12 1 1 0 0 1 1 4 6 6

SD 0 0 3 0 0 0 0 0 2 0 1 0 1 0 1 0

TN 0 1 3 37 0 1 16 1 15 3 0 1 3 0 2 0

TX 3 7 12 0 0 1 14 0 3 0 6 0 4 2 2 6

VA 1 0 2 16 0 2 12 0 6 1 2 0 5 3 4 5

VT 0 0 0 1 0 0 1 0 0 0 0 0 1 0 0 0

WI 0 0 3 2 0 0 4 0 0 0 2 0 2 0 2 0

WV 1 0 0 1 0 0 3 0 0 1 0 0 4 0 1 0

## 35 e . Critical Habitat

In the evaluation of pesticide effects on designated critical habitat, consideration is given to the

physical and biological features (constituent elements) of a critical 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 consideration s or protection. The

evaluation of impacts for a screening level pesticide risk assessment focuses on the biological

features t hat are constituent elements. It is accomplished using the screening

- level taxonomic

analysis (RQs) and listed species levels of concern that are used to evaluate direct and indirect

effects to listed organisms.

The screening

- level risk assessment has identified potential concerns for indirect effects on listed

species for those organisms dependant upon terrestrial and/or aquatic plants. 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 habitat ca n occur in either of two ways. First, the agencies could determine

whether the action area overlaps critical habitat or the occupied range of any listed species. If so,

EPA would examine whether the pesticide's potential impacts on non

- endangered species would

affect the listed species indirectly or directly affect a constituent element of the critical habitat.

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 impacted by

the pesticide. Then EPA would determine whether use of the pesticide overlaps the critical

habitat or the occupied range of those listed species.

At present, the information reviewed by EPA does not permit use of either analytical approach to

make a definitive identification of species that are potentially impacted indirectly or critical

habitats that is potentially impacted directly by the use of the pesticide. EPA and the Service(s)

are working tog ether to conduct the necessary analysis.

**C. Uncertainties**

In this ecological risk assessment, the uncertainties are listed as follows:

(1) Environmental Fate data availability

Table 14. Tabulation by State and Taxonomic Group of Listed Species

that Occur in Rimsulfuron Use Areas for Soybeans for Beans.

No species exclusions corn (PR)

Minimum of 1 Acre All Medium Types Reported

Puerto Rico

Amphibian Bird Dicot Ferns Marine Monocot Reptile

PR 3 7 28 7 1 4 7

## 36 In a review dated March 14 , 2007 (D326660), EFED requested the new studies i ndicated below.

Base d on the current status for rimsulfuron, data gaps exist

, and the registrant is requested to

satisfy them by conducting new studies as follows:

**•** One aerobic soil metabolism study, using two US soils from relevant use areas

(§835.4100)

**•** One anaerobic aquatic metabolism (relevant natural water sediment system) (§835.4400)

**•** One aerobic aquatic metabolism (relevant natural water sediment system) (§835.4300)

The above stated fate and transpo rt studies are needed because it is necessary to rep resent soils

from the wide use areas of the US

. One aerobic soil metabolism is available (MRID 41356334,

Acceptable), which was conducted in one soil. Since rimsulfuron use areas are extensive, studies

conducted in two relevant US soils were requested. N o anaerobic aquatic metabolism study has

been submitted, and light exposure was used in a previously submitted aerobic aquatic

metabolism study , which was deemed supplemental (MRID 43288502)

. A new study is

required.

( 2 ) Ecotoxicity data availability/qua lity

Data on the ecotoxicity of degradates is not available, including phytotoxicity. The following

studies on the tra nsformation product/degradate IN

- 70942 have not been submitted but are

needed for ecological risk assessment:

**•** Freshwater fish early life

- stage ( § 850.1400)

**•** aquatic invertebrate life

- cycle ( § 850.1300)

Since the EFED LOC ’ s for plants are based on acute risk, the plant risk assessment is also based

on acute risk (to parent rimsulfuron). While studies of the toxicity of the degradates IN

- 709 41,

IN

- 70942, and IN

- E9260 to both terrestrial and aquatic plants have been submitted, they have

not yet been reviewied. However, if the degradates are similarly phytotoxic, the period of

phytotoxicity in the field (in both terrestrial and aquatic environ ments) would be longer.

(3) Lack of developed risk evaluation methods

The Agency currently does not perform assessments for chronic risk to plants. EFED uses

adverse effect incident data in evaluating the chemical’s risk.

## 37 

# REFERENCES

Environmental Fate

DER (data evaluation report) for MRID: 41931602

Citation: Brennan, D. (1990) DPX

- E9636: Physical and Chemical Characteristics : Room

Temperature Storage Stability: Lab Project Number: AMR

- 1816

- 90. Unpublished study

prepared by E. I. du Pont de Nemours and Co. 16 p.

DER for MRID: 41356301

Citation: Brennan, D. (1989) DPX

- E9636: Product Identity and Composition, Analysis and

Certification of Product Ingredients and Physical and Chemical Characteristics: Lab Project

Number: E 9636.A. Unpublished study prepared by E. I. du Pon t de Nemours and Co., Inc. 193 p.

DER for MRID: 41356333

Citation: Horne, P.; Boucher, C. (1989) Hydrolysis of [Pyridine

- 2

- Cardon 14] DPX

- E9636 and

[Pyrimidine

- 2

- Carbon 14]DPX

- E9636 in Buffer Solu

- tions of 5, 7, and 9: Lab Project Number:

AMR

- 1221

- 88. Unpub

- lished study prepared by E. I. du Pont de Nemours & Co., Inc. 46 p.

DER for MRID: 41931606

Citation: Naidu, M. (1991) Field Soil Dissipation Study of ?Pyridine

- 2

- 14C| DPX

- E9636 and

?Pyrimidine

- 2

- 14C|DPX

- E9636: Lab Project Number: AMR

- 1451

- 89. Unpublished study

prepared by E. I du Pont de Nem

- ours and Co. 142 p.

DER for MRID: 41931608

Citation: Horne, P.; Boucher, C. (1989) Photodegradation of ?Pyridine

- 2

- 14C| DPX

- E9636 and

?Pyrimidine

- 2

- 1 4C| in Water(Conducted in Sunlight) : Lab Project Number: AMR

- 1220

- 88.

Unpublished study prepared by E. I. du Pont de Nemours and Co. 59 p.

DER for MRID: 41931609

Citation: Brown, A.; Young, G. (1989) Photodegradation of ?Pyridine

- 2

- 14C|DPX

- E9636 an d

?Pyrimidine

- 2

- 14C|DPX

- E9636 on Soil: Lab Project Num

- ber: AMR

- 1219

- 88. Unpublished

study prepared by E. I du Pont de Nemours and Co. 54 p.

DER for MRID: 41931610

Citation: Naidu, M. (1990) Field Soil Dissipation Study of ?Pyridine

- 2

- 14C| DPX

- E9636 and

?Pyrimidine

- 14C|DPX

- E9636 at Newark, Delaware: Lab Project Number: AMR

- 1225

- 88.

Unpublished study prepared by E. I du Pont de Nemours and Co. 51 p.

DER for MRID: 41356334

Citation: Naidu, M. (1989) Aerobic Soil Metabolism of [Pyridine

- 2

- carbon 1 4] DPX

- E9636 and

[Pyrimidine

- 2

- carbon 14]DPX

- E9636: Lab Project Number: AMR

- 1218

- 88. Unpublished study

prepared by E. I. du Pont de Nemours and Co., Inc. 49 p.

## 38 DER for MRID: 41356335

Citation: Naidu, M.; Fogiel, A. (1989) Anaerobic Soil Metabolism of [Pyri

- dine

- 2

- carbon

14]DPX

- E9636 and [Pyrimidine

- 2

- carbon 14]DPX

- E9636 Laboratory Project Number: AMR

1217

- 88. Unpublished study pre

- pared by E. I. du Pont de Nemours and Co., Inc. 53 p.

DER for MRID: 41356336

Citation: Naidu, M. (1989) Batch E quilibrium (Adsorption/Desorption) Studies of DPX

- E9636:

Lab Project Number: AMR

- 1204

- 88. Unpublished study prepared by E. I. du Pont de Nemours

& Co., Inc. 38 p.

DER for MRID: 41356337

Citation: Naidu, M.; Fogiel, A. (1989) Soil Mobility of DPX

- E96 36 and Its Soil Degradates by

Soil TLC: Lab Project Number: AMR

- 1327

- 88. Unpublished study prepared by E. I. du Pont de

Nemours & Co., Inc. 21 p.

DER for MRID: 43288502

Citation: Naidu, M. (1991) Aerobic Aquatic Metabolism of (Pyridine

- 2

- (carbon 14)) DPX

E9636 and (Pyrimidin

- 2

- (carbon 14)) DPX

- E9636: Lab Project Number: AMR/1407/89.

Unpublished study prepared by E.I. du Pont de Nemours and Co. 76 p.

Ecological Effects

Chlorsulfuron Registration Eligibility Decision. 2004. Docket Title: Chlorsulf uron Risk

Assessments and Preliminary Risk Reduction Options (Phase 3 of 4 Phase Process); Notice of

Availability . ID: EPA

- HQ

- OPP

- 2004

- 0219

- 0008

.

DER for MRID: 42471308

Citation: Hoberg, J. et al. (1992) Acute Toxicity of DPX

- E9636 to Lemna gibba G3: Lab Project

Number: 92

- 4

- 4236: 97.0991.6128.410. Unpublish ed study prepared by Springborn Laboratories

Inc. 62 p.

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the

EPA food

- chain (Kenaga) nomogram, an instrum ent for estimating pesticide residues on plants.

Environ. Tox. Chem. 13:1383

- 1391.

Hoerger, F., and E.E. Kenaga. 1972. Pesticide residues on plants: Correlation of representative

data as a basis for estimation of their magnitude in the environment. In F. Coulston and F. Korte,

eds., Environmental Quality and Safety: Chemistry, Toxicology, and Technology, Georg Thieme

Publ, Stuttgart, West Germany, pp. 9

- 28.

Kenega, E.E. 1977. In Pesticide Management and Insecticide Resistance, Academic Press, NY,

pp. 51

- 9 4.

## 39 

# APPENDIX I. Ecological Effects Information

Summary:

This herbicide was practically non

- toxic to both terrestrial avian species

- (subacutely) and

mammalian (acutely and chronically) species

. Rimsulfuron is also practically non

- toxic to both

freshwa ter and saltwater animals on an acute basis. However, both aquatic and terrestrial

vascular plants are highly susceptible to rimsulfuron.

Toxicity to Terrestrial Animal

The results of acute/subacute toxicity testing indicate that rimsulfuron is pract ically nontoxic to

avian species on both a sub acute dietary basis and an acute oral basis. Results of avian toxicity

testing with rimsulfuron are tabulated below.

Avian Acute/Subacute Toxicity

Species %

ai LC 50 (ppm)/

LD 50 (ppm) Toxicity Category MRID No.

Author/Year Study Classification

Northern bobwhite quail

(Colinus virginianus) 98.8 LD 50 >2250 Practically non

- toxic 4 1356304

J. Grimes

and M. Jaber

(1988 ) Core

Northern bobwhite quail

(Colinus virginianus) 98.8 LC 50 >5620 P ractically non

- toxic 43414531

A.G. Murray

(1992 ) Core

Mallard duck

(Anas platyrhynchus) 98.8

Formulated

Product LD 50 >2000 Practicall y non

- toxic 41931630

J.S. Culotta

et al (1993) Core

Mallard duck

(Anas platyrhynchus) 98.8 LC 50 > 1378 Slightly toxic 41931633

J. Grimes

and M. Jaber

(1989) Supplemental

Mallard duck

(Anas platyrhynchus) 98.8 LC 50 >5620 practically non

- toxic 41356306

J. Grimes

and M. Jaber

(1989) Core



### Avian Reproduction

Species % ai NOAEC/LOAEC

(ppm) Endpoints Affected MRID No.

Author/Year Study

Classification

Northern bobwhite quail

(Colinus virginianus) 99 1250 / > 1 25 0 N/A 43277201

J. B. Beavers et al

(199 4 ) Core



## Mammals, Acute and Chronic

Wild mammal testing is required on a case

- by

- case basis, depending on the results of lower tier

laboratory mammalian studies, intended use pattern

, and pertinent environmental fate

characteristi cs. In most cases, rat or mouse toxicity values obtained from the Agency's Health

Effects Division (HED) substitute for wild mammal testing. Based on a laboratory rat LD 50

## 40 value of >5000 mg/kg, rimsulfuron is practically nontoxic to small mammals on an a cute oral

basis. These toxicity values are reported below.

Mammalian acute toxicity

Species % ai Test Type Toxicity

Value Affected

Endpoints MRID

Rat

(Rattus norvegicus) 98.8 O ral LD 50 >5000 mg/kg None 47091007

Rat

(Rattus norvegicus) 98.8 Acute Inhalation LC 50 >5.0 mg/L None 41356314



## Terrestrial Invertebrates

Insects

Based on a honey bee acute contact test, rimsulfuron is practically non

- toxic to bees. The results

of rimsulfuron testing using the honeybee are tabulated below:

N on

- target insect toxicity

Species

% ai Results Toxicity Category/effects MRID Study

Classification

Honey bee

(Apis mellifera) 98.8 % >100 μ g a

. i

. /bee Practically non

- toxic 41356331

K. Hoxter and M. Jaber

(1989) Core



## Toxicity to Aquatic Animals

The results of acute testing show that rimsulfuron is categorized as practically non

- toxic to cold

water freshwater fish, freshwater invertebrates, and warm

- water freshwater fish. Results of

freshwater animal acute toxicity testing are tabulated b elow.

Freshwater Animal Acute Toxicity

Species % ai EC 50 /

LC 50 (ppm) Toxicity Category MRID No.

Author/Year Study

Classification

Bluegill sunfish

(Lepomis macrochirus) 98.8 EC 50 >390 practically non

- toxic 41356308

D.G. Hutton (1989) Core

Waterflea

(Daphnia magna) 98.8 EC 50 =1000 Practically non

- toxic 41931621

K.N. Baer (1990) Supplemental

Waterflea

(Daphnia magna) 98.8 E C 50 >360 Practically non

- toxic 41356309

D.G. Hutton (1989) Core

Rainbow trout

(Oncorhynchus mykiss) 98.8 LC 50 >390 Practically non

- toxic 41356307

D.G. Hutton (1989 ) Core

Bluegill sunfish

(Lepomis macrochirus) 98.8 LC 50 >390 Practically non

- toxic 41931620

D.G. Hutton (1990) Core

## 41 Rimsulfuron is also categorized as practically non

- toxic to estuarine/marine fish and

estuarine/marine invertebrates on an acute basis. The results of acute toxicity testing with

estuarine/marine species are tabulated below.

Estuarine/Marine Acute Toxicity

Species % ai. LC50/EC50 (ppm) Toxicity Categor y MRID No.

Author/Year Study

Classification

Sheepshead minnow

( Cypridon variegatus ) 99 LC 50 > 110 Practically non

- toxic 42471303

W.C. Graves and J.P.

Swigert Core

Eastern oyster (shell

deposition or embryo

- larvae)

(Crassostrea virginica) 99 EC 50 >120 Practically non

- toxic 42471301

W.C. Graves and J.P.

Swigert (1992) Core

Mysid

(Americamysis bahia) 99 LC 50 >110 Practically non

- toxic 42471302

W.C. Graves and J.P.

Swigert (1992) Core



## The results indicate that rimsulfuron is hig hly toxic to both aquatic and terrestrial vascular plants

. A quatic and terrestrial plant testing results are tabulated below.

Nontarget Plant Toxicity

Species %a.i. EC 25 NOAEC MRID No.

Author/Year Study

Classification



### Vascular Plants

6 Dicots/4 monocots 98.8 0.0006 lb a.i./A SE monocot

0.00013 SE dicot

0.00004 VV monocot

0.00003 VV dicot N/A 42471304

R.A. McKelvey and

H. Kuratle III (1992) Supplemental

2 Dicots 98.1 0.025 oz a.i./A Slope=2.1 0.016 oz

a.i./A 43539201

R.A. McKelvey

(1994) Core

Duckweed

Lemna gibba 98.57 EC 50 =11.6 ppb Slope=1.2 0.09 42471308

J.R. Hoberg (1992) Core



### Nonvascular Plants

Green algae

Selenastrum

capricornutum 98.57 > 29 ppb 29 ppb 42471305

J.S. Hughes (1992) Core

Marine diatom

Skeletonema costatum 98.8 > 48 ppb 48 ppb 43043601

S.G. Thompson

(1993) Core

Freshwater diatom

Navicula pelliculosa 98.57 N/A <30 ppb 42471307

J.S. Hughes (1992) Core

Blue

- green algae

Anabaena flos

- aquae 98.57 >35 ppb 35.9 ppb 42471306

J.S. Hughes (1992) Core

SE = Seedling Emergence, VV = Vegetative Vigor

## 42 

# Appendix II. TerrPlant Spreadsheet

TerrPlant output for ground applications.

Table 1. Chemical Identity

.

Chemical Name Rimsulfuron

PC code 129009

Use Field Corn and Soybeans

Application Method Ground Broadcast

Application Form Spray

Solubility in Water

(ppm) 7300

Table 2. Input parameters used to derive EECs.

Input Parame ter Symbol Value Units

Application Rate A 0.0625 lbs a.i./acre

Incorporation I 1 none

Runoff Fraction R 0.05 none

Drift Fraction D 0.01 none

Table 3. EECs for Rimsulfuron. Units in lbs a.i./acre.

Description Equation EEC

Ru noff to dry areas (A/I)*R 0.003125

Runoff to semi

- aquatic areas (A/I)*R*10 0.03125

Spray drift A*D 0.000625

Total for dry areas ((A/I)*R)+(A*D) 0.00375

Total for semi

- aquatic areas ((A/I)*R*10)+(A*D) 0.031875

Table 4. Plant surviv al and growth data used for RQ derivation. Units are in lbs a.i./acre.

Seedling Emergence Vegetative Vigor

Plant type EC 25 

### NOAEC EC 25 

### NOAEC

Monocot 0.0006 N/A 0.00004 N/A

Dicot 0.00013 N/A 0.00003 N/A

Table 5. RQ values for plants in dr y and semi

- aquatic areas exposed to Rimsulfuron through runoff

and/or spray drift.*

Plant Type Listed Status Dry Semi

- Aquatic Spray Drift

Monocot non

- listed 6.25 53.13 15.63

Monocot listed

-- -- --

Dicot non

- listed 28.85 245.19 20.83

Dicot listed

-- -- --

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group.

## 43 TerrPlant output for aerial application.

Table 1. Chemical Identity.

Chemical Name Rimsulfuron

PC code 129009

Use Field Corn and Soybeans

Applic ation Method Aerial

Application Form Spray

Solubility in Water

(ppm) 7300

Table 2. Input parameters used to derive EECs.

Input Parameter Symbol Value Units

Application Rate A 0.0625 lbs a.i./acre

Incorporation I 1 none

Run off Fraction R 0.05 none

Drift Fraction D 0.05 none

Table 3. EECs for Rimsulfuron. Units in lbs a.i./acre.

Description Equation EEC

Runoff to dry areas (A/I)*R 0.003125

Runoff to semi

- aquatic areas (A/I)*R*10 0.03125

Spray dri ft A*D 0.003125

Total for dry areas ((A/I)*R)+(A*D) 0.00625

Total for semi

- aquatic areas ((A/I)*R*10)+(A*D) 0.034375

Table 4. Plant survival and growth data used for RQ derivation. Units are in lbs a.i./acre.

Seedling Emergence Veget ative Vigor

Plant type EC 25 

### NOAEC EC 25 

### NOAEC

Monocot 0.0006 N/A 0.00004 N/A

Dicot 0.00013 N/A 0.00003 N/A

Table 5. RQ values for plants in dry and semi

- aquatic areas exposed to Rimsulfuron through runoff

and/or spray drift.*

Plant Type Li sted Status Dry Semi

- Aquatic Spray Drift

Monocot non

- listed 10.42 57.29 78.13

Monocot listed

-- -- --

Dicot non

- listed 48.08 264.42 104.17

Dicot listed

-- -- --

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group.

## 44 

# Appendix I II

. Ecological Aquatic Exposure Modeling

Sample of Model Output

IL Corn

stored as RIMSULFU.out

Chemical: Rimsulfuron

PRZM environment: ILCornSTD.txt modified Tueday, 29 May 2007 at 11:55:34

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 15:33:30

Metfile: w14842.dvf modified Wedday, 3 July 2002 at 08:04:38

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.1752 0.1453 0.07489 0.05012 0.0361 0.008953

1962 0.7862 0.6645 0.3635 0.1579 0.106 0.02619

1963 0.3312 0.2747 0.144 0.08782 0.06432 0.01598

1964 0.3656 0.3082 0.1593 0.08977 0.06177 0.01527

1965 0.2353 0.2081 0.1255 0.05596 0.03804 0.009401

1966 0.6163 0.5113 0.2679 0.1151 0.07955 0.01973

1967 0.1923 0.1594 0.1249 0.07101 0.04882 0.01208

1968 0.3175 0.2633 0.1432 0.07446 0.05062 0.01248

1969 0.1752 0.1453 0.108 0.05564 0.0381 0.009419

1970 0.1842 0.1528 0.09906 0.06718 0.04557 0.01126

1971 0.3571 0.2961 0.1637 0.07518 0.05287 0.01309

1972 0.2085 0.1832 0.1222 0.07404 0.04999 0.01232

1973 0.2108 0.1748 0.1074 0.04523 0.03031 0.007483

1974 0.2478 0.2206 0.1566 0.07909 0.05316 0.01313

1975 0.4803 0.4021 0.2374 0.1007 0.06751 0.01667

1976 0.6953 0.5767 0.2974 0.1615 0.1111 0.02742

1977 0.1752 0.1453 0.0775 0.04234 0.03175 0.007905

1978 0.51 0. 4229 0.23 0.1133 0.07644 0.01889

1979 0.1752 0.1453 0.07969 0.03636 0.0255 0.006316

1980 1.17 0.9704 0.5226 0.2301 0.1548 0.03811

1981 0.1752 0.1453 0.07475 0.04097 0.02764 0.006827

1982 0.3651 0.3027 0.1744 0.08079 0.05452 0.01347

1983 0.177 0.1468 0.0878 2 0.04193 0.02843 0.007025

1984 0.3538 0.2958 0.1912 0.08212 0.05507 0.01356

1985 0.2855 0.2381 0.1477 0.06434 0.04323 0.01068

1986 0.3486 0.2891 0.1736 0.09358 0.06311 0.01559

1987 0.516 0.4279 0.2203 0.1085 0.07327 0.01811

1988 0.2251 0.1867 0.097 0.0396 3 0.02653 0.006706

1989 0.1752 0.1498 0.08243 0.03376 0.02413 0.006

1990 0.7497 0.6217 0.3287 0.1411 0.09464 0.02337

Sorted results

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

0.032258064516129 1.17 0.9704 0.5226 0.2301 0.1548 0.03811

0.064516129032258 1 0.7862 0.6645 0.3635 0.1615 0.1111 0.02742

0.0967741935483871 0.7497 0.6217 0.3287 0.1579 0.106 0.02619

0.129032258064516 0.6953 0.5767 0.2974 0.1411 0.09464 0.02337

0.161290322580645 0.6163 0.5113 0.2679 0.1151 0.07955 0.01973

0.193548387096774 0.516 0. 4279 0.2374 0.1133 0.07644 0.01889

0.225806451612903 0.51 0.4229 0.23 0.1085 0.07327 0.01811

0.258064516129032 0.4803 0.4021 0.2203 0.1007 0.06751 0.01667

0.290322580645161 0.3656 0.3082 0.1912 0.09358 0.06432 0.01598

0.32258064516129 0.3651 0.3027 0.1744 0.08977 0.06311 0.01559

0.354838709677419 0.3571 0.2961 0.1736 0.08782 0.06177 0.01527

## 45 0.387096774193548 0.3538 0.2958 0.1637 0.08212 0.05507 0.01356

0.419354838709677 0.3486 0.2891 0.1593 0.08079 0.05452 0.01347

0.451612903225806 0.3312 0.2747 0.1566 0.07 909 0.05316 0.01313

0.483870967741936 0.3175 0.2633 0.1477 0.07518 0.05287 0.01309

0.516129032258065 0.2855 0.2381 0.144 0.07446 0.05062 0.01248

0.548387096774194 0.2478 0.2206 0.1432 0.07404 0.04999 0.01232

0.580645161290323 0.2353 0.2081 0.1255 0.07101 0 .04882 0.01208

0.612903225806452 0.2251 0.1867 0.1249 0.06718 0.04557 0.01126

0.645161290322581 0.2108 0.1832 0.1222 0.06434 0.04323 0.01068

0.67741935483871 0.2085 0.1748 0.108 0.05596 0.0381 0.009419

0.709677419354839 0.1923 0.1594 0.1074 0.05564 0.0380 4 0.009401

0.741935483870968 0.1842 0.1528 0.09906 0.05012 0.0361 0.008953

0.774193548387097 0.177 0.1498 0.097 0.04523 0.03175 0.007905

0.806451612903226 0.1752 0.1468 0.08782 0.04234 0.03031 0.007483

0.838709677419355 0.1752 0.1453 0.08243 0.04193 0.0284 3 0.007025

0.870967741935484 0.1752 0.1453 0.07969 0.04097 0.02764 0.006827

0.903225806451613 0.1752 0.1453 0.0775 0.03963 0.02653 0.006706

0.935483870967742 0.1752 0.1453 0.07489 0.03636 0.0255 0.006316

0.967741935483871 0.1752 0.1453 0.07475 0.03376 0.02 413 0.006

0.1 0.74426 0.6172 0.32557 0.15622 0.104864 0.025908

Average of yearly averages: 0.0141145

Inputs generated by pe5.pl

- Novemeber 2006

Data used for this run:

Output File: RIMSULFU

Metfile: w14842.dvf

PRZM scenario: ILCornSTD.txt

EXAMS en vironment file: pond298.exv

Chemical Name: Rimsulfuron

Description Variable Name Value Units Comments

Molecular weight mwt 431.44 g/mol

Henry's Law Const. henry 8.56e

- 13 atm

- m^3/mol

Vapor Pressure vapr 1.1e

- 8 torr

Solubility sol 73000 mg/L

Kd Kd mg/L

Koc Koc 47.5 mg/L

Photolysis half

- life kdp 0 days Half

- life

Aerobic Aquatic Metabolism kbacw 0 days Halfife

Anaerobic Aquatic Metabolism kbacs 0 days Halfife

Aerobic Soil Metabolism asm 64 days Halfife

Hydrolysis: pH 7 7.2 days Half

- life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate: TAPP 0.0701 kg/ha

Application Efficiency: APPEFF 0.95 fraction

Spray Drift DRFT 0.05 fraction of application rate applied to pond

Application Date Date 22

- 05 dd/mm or dd/mmm or dd

- mm or dd

- mm m

Record 17: FILTRA

IPSCND 1

UPTKF 0

Record 18: PLVKRT 0

PLDKRT 0

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)

## 46 Selected Information from METADATA Files

ILLINOIS CO RN

The field used to represent corn production in Illinois is located in McLean County,

although the crop is grown extensively throughout the state. According to the 1997 Census of

Agriculture, Illinois is ranked 2 nd 

## among the m ajor corn producing states in the U.S. The crop is

generally planted the early Spring (April) in the south, early May in the north and harvested

beginning in August. Continuous corn is practice is much of the region (approximately 30

percent is continuous ), however, rotation with other crops such as soybean, wheat, sorghum, and

alfalfa is the dominant practice. Most of the corn is planted for feed grain, but may also be

planted for oil, sweetener, and for export. Planting depth and row spacing (generally 30 inches)

follows general practices for the U.S. Conservation tillage practices are regularly used for field

corn with no

- till practiced on about 20 percent of the corn acreage annually. About 50 percent of

the acreage is cultivated with a row cultivat or and an estimated 40 percent is rotary hoed

annually. The crop is rarely grown under irrigation. The soil selected to simulate the field is an

Adair clay loam. Adair clay loam is a fine, smectitic, mesic Aquertic Argiudolls. More than 50

percent of t he soil is used for the production of grains with the balance in meadow and pasture.

Adair clay loam is a deep, somewhat poorly drained, medium to rapid runoff, slowly permeable

soil formed on uplands in a thin mantle of loess or loess and pedisediments a nd a paleosol

formed in glacial till. They are on convex summits of narrow interfluves and on convex side

slopes at slightly lower elevations. Slopes are generally between 2 to 18 percent, but may range

to 30 percent. The soils are extensive in MLRA 10 8 and found in many MLRA in the region.

Adair clay loam is a Hydrologic Group C soil.

MISSISSIPPI CORN

The field used to represent corn production in Mississippi is located in the Southern

Mississippi Valley Uplands. According to the 1997 Census of Agriculture, Mississippi is not a

major corn producing state in the U.S. (not among the top 20 states) with approximately 600,000

acres in production. The crop is generally planted in the early Spring (April) and harveste d

beginning in August . Continuous corn is practiced in much of the region, however, rotation with

ot her crops such as soybean is practiced as well. Most of the corn is planted for feed grain.

Planting depth and row spacing (generally 30 inches) follows g eneral practices for the U.S.

Conventional tillage dominates with more than 50 percent of the practice, followed by

conservation tillage, no

- tillage, and ridge tillage. The crop is rarely grown under irrigation. The

soil selected to simulate the field i s a benchmark soil, Grenada silt loam. Grenada silt loam is a

fine

- silty, mixed, active, thermic Oxyaquic Fraglossudalfs. Most of the soil is used for the

production of row crops such as corn, cotton, and soybeans, the principal crops. Grenada silt

loam is a very deep, moderately well drained, medium to slow runoff, moderately permeable

above a fragipan and slow in the fragipan soil. The fragipan is at a depth of about two feet. The

soils formed in loess. They are located on uplands and stream terrac es of low relief in the

Southern Mississippi Valley Silty Uplands. Slopes are generally between 0 to 8 percent, but may

range to 12 percent. The soils are extensive throughout the region. Grenada silt loam is a

Hydrologic Group C soil.

## 47 NORTH CAROLINA CORN (Eastern)

The field used to represent corn production in Eastern North Carolina is located in Pitt

County in the Piedmont. According to the 1997 Census of Agriculture, North Carolina is ranked

9 th 

## among major c orn producing states in the U.S. Corn is produced throughout the state with

the largest production located in the coastal plain and tidewater regions. Sweet corn is produced

mainly on the coastal plain (MLRA 153 A and B). The crop is generally planted in the early

Spring (April) and harvested beginning in August. Continuous corn is practice d in much of the

region, especially the Piedmont. However, rotation with other crops such as soybean is practiced

on the coastal plain. Most of the corn is planted for feed grain. Planting depth and row spaci ng

(generally 30 inches) follow general practices for the U.S. Conventional tillage dominates

management practices, followed by no

- tillage. However, conservation tillage is continuing to

grow. The crop is rar ely grown under irrigation, except for sweet corn. The soil selected to

simulate the field is a Craven silt loam. Craven silt loam is a fine, mixed, subactive, thermic

Aquic Hapludults. Approximately one

- half of the series is used for the production of row crops

such as corn, tobacco, cotton, small grain, peanuts and pasture. Craven silt loam is a deep,

moderately well drained, medium to rapid runoff, slowly permeable soil formed in clayey

Pleistocene sediments. They are located on nearly level to slop ing Coastal Plain Uplands.

Slopes are generally between 0 to 12 percent. The soils are extensive throughout the Coastal

Plain region. Craven silt loam is a benchmark soil and a Hydrologic Group C soil.

OHIO CORN

The field used to represent corn production in Ohio is located in Darke and/or Pickaway

Counties, although the crop is grown extensively throughout the state. According to the 1997

Census of Agriculture, Ohio is ranked 6 th 

## among the major corn producing states in the U.S. and

Darke and Pickaway are ranked among the highest in Ohio. The crop is generally planted in

early Spring (April 15 to May 10) in the north and from April 10 to May 10 in the south. Corn is

harvested beginning in September depending on kernel moisture a nd may extend into late

November. Continuous corn is practice d in the region (approximately 30 percent is continuous),

however, rotation with mainly soybean is the most common. Rotation promotes weed control

and has been shown to increase yields as much a s 10 percent over continuous corn operations.

Most of the corn is planted for feed grain, but may also be planted for oil, sweetener, and for

export. Planting depth (1

- 1.5 inches) and row spacing (generally 30 inches, but may be as

narrow as 15 to 22 i nches) follows general practices for the U.S. Seeding rates in Ohio range

from 20,000 to 30,000 plants/acre for corn grown for grain and 22,000 to 34,000 plants/acre for

corn grown for silage. Conservation tillage practices are regularly used for field co rn with no

- till

practiced on a small percentage of the corn acreage annually. Corn is generally cultivated with a

row cultivator or rotary hoed. The crop is rarely grown under irrigation. The soil selected to

simulate the field is a Cardington silt loam . Cardington silt loam is a fine, illitic, mesic Aquic

Haplaudalfs. Most of the area is planted in row crops including production of grains with the

balance in pasture and woodland. Cardington silt loam is a very deep, moderately well drained,

negligibl e to very high runoff, slowly permeable soil with an intermittent perched water table at

1

- 2 feet between November and April. These soils formed in loamy till of medium calcium

carbonate content. These soils are on summits, shoulders, and backslopes on Wi sconsin Age

ground moraines and end moraines. Slopes are generally between 0 to 25 percent. The soils are

extensive in MLRA 111 and 139. Cardington silt loam is a Hydrologic Group C soil.

## 48 PENNSYLVANIA CORN

The field used to r epresent corn production in Pennsylvania is located in Lancaster

County in the south

- east portion of the state. According to the 1997 Census of Agriculture,

Pennsylvania is ranked 15 th 

## among major producers of corn in the U.S. The crop is generally

plant ed in the Spring (April) and harvested beginning in September. Continuous corn is practice d

in much of the region. However, rotation with other crops such as soybeans is also practiced.

Most of the corn is planted for feed grain. Planting depth and row spacing (generally 30 inches)

follows general practices for the U.S. Conventional tillage dominates management practices,

followed by no

- tillage. However, conservation tillage is continuing to grow. The soil selected to

simulate the field is a benchmark soil, Hagerstown s ilt loam. Hagerstown silt loam is a fine,

mixed, semiactive, mesic Typic Hapl udalfs. These soils are used f o r general crops, pastures,

orchards

, and truck crops. Large portions are in non

- farm uses. Hagerstown silt loam is a very

dee p, well drained, moderately permeable soil with moderate to rapid runoff. These soils formed

in materials weathered from hard grey limestone of rather high purity. They are found on valley

floors and the adjacent hills. In some areas rock outcrops are co mmon surface features. Slopes

are generally less than 15 percent, but may range up to 45 percent. Hagerstown silt loam is a

Hydrologic Group C soil.

MISSISSIPPI SOYBEANS

The field used to represent soybean production in Mi ssissippi is located in Yazoo County.

According to the 1997 Census of Agriculture, Mississippi harvested more than 2 million acres of

soybeans and ranks 12 th 

## in production in the U.S. The crop is generally planted in Spring (late

April) and harvested beg inning in September. Row spacing is generally 30 to 38

- inches, but

spacing could be a little as 7 inches. Field canopies tend to be very close to 100 percent early in

the season and less as harvest nears. The crop may be grown under irrigation by furrow or canal

systems. Most crops are planted by con ventional tillage, but no

- till or conservation methods are

employed as well. The soil selected to simulate the field is a Loring silt loam. Loring silt loam is

a fine

- silty, mixed, active, thermic, Qxyaquic Fragiudalfs. Nearly all soils are cleared and used

to grow cotton, small grains, soybeans, hay and pasture. Loring silt loam is a moderately well

drained with a fragipan, medium to rapid runoff, moderate permeability above the fragipan and

moderately sl owly permeable in the fragipan soils formed in loess. They are located on level to

strongly sloping uplands and stream terraces. Slopes are generally between 0 to 20 percent. The

soils are extensive in the lower Mississippi drainage basin. Loring silt loam is a Hydrologic

Group C soil.