### 2 

# Problem Formulation for the Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments in Support of the

Registration Review of Mesosulfuron

- methyl

CAS: 208465

- 21

- 8
PC Code: 122009

Environmental Fate and Effects Division Prepared by: Michael Lowit, Ph.D., Ecologist He Zhong , Ph.D., Biologist U.S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division
Environmental Risk Branch I 1200 Pennsylvania Ave., NW
Mail Code 7507P Washington, DC 20460 Reviewed by: Sujatha Sankula, Ph.D., Lead Biologist Faruque Khan, Ph.D., Senior Fate Scientist

### 3 Table of Contents

1. Purpose

................................ ................................ ................................ ................................ ........ 4
2. Problem Formulation

................................ ................................ ................................ .................. 4
2.1. Nature of Regulatory Action

................................ ................................ ................................ 4
2.2. Previous Assessments

................................ ................................ ................................ .......... 4 2.2.1. Ecological Risk Assessments

................................ ................................ ........................ 4 2.2.2. Drinking Water Exposure Assessments

................................ ................................ ........ 4
3. Stressor Source and Distribution

................................ ................................ ................................ 5
3.1. Mechanism of Action

................................ ................................ ................................ .......... 5
3.2. Ove rview of Pesticide Use and Usage

................................ ................................ ................ 5
3.3. Environmental Fate and Transport

................................ ................................ ...................... 6
3.4. Clean Water Act

................................ ................................ ................................ ................ 13 4. Receptors

................................ ................................ ................................ ................................ .. 13
4.1. Effects to Aquatic Organisms

................................ ................................ ........................... 14
4.2. Effects to Terrestrial Organisms

................................ ................................ ....................... 16
4.3. Incident Databases Review

................................ ................................ ............................... 19 5. Risk Hypothesis

................................ ................................ ................................ ....................... 20 6. Analysis Plan

................................ ................................ ................................ ........................... 20
6.1. Stressors of Concern

................................ ................................ ................................ .......... 20 6.2. Measures of Exposure

................................ ................................ ................................ ........ 24
6.3. Measures of Effect

................................ ................................ ................................ ............. 26 6.4. Integration of Exposure and Effects

................................ ................................ .................. 26 6.5. Endangered Species Assessments

................................ ................................ ...................... 26 6.6. Endocrine Disruptor Screening

................................ ................................ .......................... 26 6.7. Drinking Water Assessment

................................ ................................ .............................. 26 6.8. Preliminary Ide ntification of Data Gaps

................................ ................................ ............ 27
6.8.1. Environmental Fate Data

................................ ................................ ............................ 27 6.8.2. Ecological Effects Data

................................ ................................ ............................... 29

7. References

................................ ................................ ................................ ................................ 34
APPENDIX A. Submitted Environmental Fate and Effects Studies

................................ ........... 35 APPENDIX B. SIP v.1.0 Inputs and Outputs

................................ ................................ .............. 40 APPENDIX C. STIR v.1.0 Inputs and Outputs

................................ ................................ ........... 41

### 4 1. Purpose

The purpose of this problem formulation is to provide an understanding o f what is known about the environmental fate, ecological effects, and currently registered uses of mesosulfuron

- methyl

. This document provides a plan for analyzing data relevant to mesosulfuron

- methyl and for conducting environmental fate, ecological risk , endangered species, and drinking water exposure assessments for its registered uses. Additionally, this problem formulation identifies data gaps, uncertainties, and potential assumptions used to address those uncertainties relative to characterizing the potential ecological risk associated with the registered uses of mesosulfuron

methyl

.

2. Problem Formulation

2.1. Nature of Regulatory Action

As part of the implementation of the new Registration Review program 1 

### pursuant to Section 3(g) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the Agency is beginning its
evaluation of mesosulfuron

- methyl to determine whether it continues to meet the FIFRA standard for registration. This problem formula tion in support of the registration review of
mesosulfuron

- methyl will be posted in the initial docket which will open the public phase of the review process.

2.2. Previous Assessments

2.2.1. Ecological Risk Assessments

Mesosulfuron

- methyl ( methyl

- 2

- [3

- (4, 6

- dimethoxypyrimidin

- 2

- yl) ureido

- sulfonyl]

- 4

- methanesulfonamido

- methylbenzoate ) , a sulfonylurea herbicide

, was first registered in the US in
2004 for use as postemergent control and suppress ion of several types of weeds. Wheat and
triticale are the only registered use s of mesosulfuron

- methyl. EFED has conducted one ecological risk assessment (wheat use)

.

The previous risk assessment identified a risk concern for non

- target terrestrial plants (listed and

non

- listed) and aquatic vascular plants (listed) (USEPA, 2004b ).

2.2.2. Drinking Water Exposure Assessments

The drinking water assessment (DWA) for wheat use was conducted using the Tier 1 FQPA Index Reservoir Screening Tool (FIRST) and the Screening Concentration in Ground Water
model (SCIGROW) (USEPA

, 2004 a )

. Three bridge

- intact major degradates ( AE F15 4851, AE
F160459

, and AE F160460) were modeled along with mesosulfuron

- methyl per request of the Health Effect Division (HED) Metabolism Committee Meeting (MARC)



### . The findings from the

DWA are summarized i n Table 1

.

Table 1. Previous Estimat ed Drinking Water Concentrations

Product

Use Peak ( μ g/L, Acute) 1 Annual Average ( μ g/L , Chronic) 1
Parent Only Total Residues Parent Only Total Residues

Surface Water Sources using Tier I FIRST m odel

OSPREY

Winter Wheat 0.7 0.9 0.1 0.2

1 http://www.epa.gov/oppsrrd1/registration_review/

### 5 Product

Use Peak ( μ g/L, Acute) 1 Annual Average ( μ g/L , Chronic) 1
Parent Only Total Residues Parent Only Total Residues

SILVERADO Spring Wheat (including durum) 0.3 0.4 0.05 0.06

Ground Water Sources using Tier I SCIGROW m odel

OSPREY

Winter Wheat 0.01 0.02 0.01 0.02

SILVERADO
Spring Wheat (including durum) 0.01 0.007 0.005 0.007

1 A PCA of0.56 was used for the surface water EDWC



### 3. Stressor Source and Distribution

Mesosulf ur on

- methyl is a sulfonylurea herbicide used to control and suppress several types of
weeds . The formulated water dispersible granules are applied as a post

- emergence ground or aerial spray

. S everal mesosulfuron

- methyl degradates were identified from the submitted
studies ; some are common to other sulfonylurea herbicides. T he major (formed ≥ 10%) degradates are AE F154851, AE F160459, AE F160460, AE F14 0584, AE F147447, AE

F 0 99095, and AE F092944

.

3.1. Mechanism of Action

Mesosulfuron

- methyl belongs to the sulfonylurea herbicide family and more specifically to the pyrimidinylsulfonylurea group. Like all of the su lfonylurea herbicides, it is an acetolactat e synthase inhibitor (ALS

- inhibitor). Inhibition of this enzyme curtails the synthesis of branch ed

chain amino acids (valine, leucine, and isovaline), thus disrupting plant development and causing subsequent death. Valine, leucine, and isov aline are ess ential amino acids but they are not synthesized by higher animals. Sulfonylurea herbicides or other ALS

- inhibitors are not expected to have any direct acute effects on animals b ecause the ALS enzyme i s not present in higher
animals . Nevertheless, chronic effects cannot be ruled out.

3.2. Overview of Pesticide Use and Usage

There are currently eight registered end

- use products containing mesosulfuron

- methyl

. All products are post

- emergence herbicides formulated as water dispersible granules. About
6000 lb mesosulfuron

- methyl is applied annually ( Screening Level Usage Analysis, 1/18/2012) according to the Biological and Economic Analysis Division (BEAD). Uses and application rates are based on the most recent l abel use i nformation s ystem report ( LUIS report)

, provided by BEAD ( 11/8/2012 ). The m aximum application rates and application methods are
list ed in Table 2
, although it should be noted that some labels do not indicate a maximum annual

rate

. To reduce uncertainty in the risk assessment, the Agency requests that the registrant provide additional label information where necessary on the number of applications per year, the total amount applied per year, and the application interval if applicable. The registration review risk

as sessment will be based on current label information at the time of assessment.

### 6 Table 2 . Maximum Rates for Registered Uses of Mesosulfuron

- methyl

Use Method of Application Single Maximum Application Rate (lb ai/A) Maximum Number of Applications per

Year 1 Annual Maximum (lb ai/A) 1

Winter Triticale Ground/Air 0.0134 NS NS

Winter Wheat Ground/Air 0.0134 1 0.0134

Spring Wheat Ground/Air 0.00 36 1 0.00 3

1 Assumes one season /crop of winter or spring wheat per acre per year NS

– not stated on label



### 3.3. Environmental Fate and Transport

The physical, chemical, and environmental fate properties of mesosu lfuron

- methyl and its degradation products are summarized in Table 3

. Mesosulfuron

- methyl , like other sulfonylurea herbicides, has pH

- dependent water solubility (e.g., medium (483 ppm ) at pH 7 to very high (15,390 ppm ) at pH 9 ) and exhibits weak binding to soils ( Koc = 26

- 345 )

. Mesosulfuron

- methyl has the potential to reach surface water by r unoff and leach ing to ground water but has low potenti al to bioaccumulate in fish or volatilize from soil and water.

M esosulfuron

- methyl will enter the environment through direct application onto soil and foliage. It may move off

- site via spray drift, runoff

, and leaching. Biotransformation is the major route of degradation in the environment ( e.g., aerobic soil metabolism t 1/2 

### = 20

- 199 days ; anaerobic aquatic metabolism t 1/2 

### = 6

- 36 days

, and aerobic aquatic metabolism t 1/2 

### = 25

- 100 days )

. M esosulfuron

- methyl breaks down to unique degradates and degradate s common to other sulfonylurea herbicides. B ridge

- intact degradates (AE F154851, AE F160459, and AE F160460) were found more frequently than bridge

- cleavage degradates (AE F140584, AE F147477, AE F099095, AE F119094, and AE F092944 ) although the relative ratios among degradates appear
to vary. There is no evidence from the environmental fate studies that the 4

- methanesulfonamide group in the phenyl ring undergoes transformation for bridge

- intact metabolites and phenyl ring bridge

- cl eavage metabolites

.

Terrestrial field dissipation of mesosulfuron

- methyl was conducted using the highest labeled application rate in bare plots in Florida, Illinois, and California (MRID 45386501). Rainfall was supplemented with irrigation to exceed th e 10

- year average rainfall at the Florida and California test sites; total water input during the study period was approximately 83% of the 10

- year average at the Illinois test site. Under the field conditions, mesosulfuron

- methyl exhibited a biphasic dis sipation pattern, with an initial rapid dissipation phase occurring through approximately 30

- 50 days post treatment. The calculated half

- life values of mesosulfuron

methyl were 58 days (r 2 

### = 0.62), 136 days (r 2 

### = 0.59)

, and 80 days (r 2 

### = 0.75) at the Flor ida,
Illinois

, and California sites

, respectively. In the study, soil samples were not analyzed for transformation products of mesosulfuron

- methyl. However, in a laboratory aerobic soil metabolism study (MRID 45386425), three major and four minor nonvola tile transformation products of mesosulfuron

- methyl were identified as AE F099095 (29.2%), AE F092944 ( 10.9%), AE F154851(16.2%), AE F160459 (8.9%), AE F160460 (8.6%), AE F147447 (7.2%)

, and AE F140584 (7.1%). Volatilized 14 

### CO 2 

### totaled 49.2% of the applie d mesosulfuron

- methyl at termination; volatile [ 14 

### C] organic compounds were <0.1% at all interval s

.

Aerobic aquatic biotransformation of mesosulfuron

- methyl was studied in a gravel pit water

sand sediment system and a river water

- silt lo am sediment system . AE F160459 (21.6%) was a major transformation product in both systems. AE F147447 (16.1%) was a major product only in

### 7 the water

- sand sediment systems

. M inor products (< 10%) were AE F160 460, AE F154851

, AE F092944, AE F140584, AE F099095, and AE F11909 4 . In addition, there were two major unidentified products ( A (Ul, 6.9

- 22%) and D (U3, 6.2

- 13.1%) ) and three minor unidentified products ( C (U2, ≤4.2%), E (U4, ≤1.9%)

, and G (U5, ≤1.9%) )

. In the a naerobic aquatic metabolism study , there were t wo major pr oducts (AE F160459 (25.9%) and AE F160460 (12.6%)) and six minor products ( AE F140584 , AE F147447 , AE F154851 , AE F099095, AE F092944, and AE F119772)

.

Table 3 . Physical, Chemical, and Environmental Fate Properties of Mesosulfuron

- methyl and Degradation Products

Parameter Value Reference Comments

Chemical Mesosulfuron

- methyl (AE F 130060)

Chemical Name (IUPAC ) methyl

- 2

- [3

- (4,6

- dimethoxypyrimidin

- 2

- yl) ureido

sulfonyl]

- 4

- methanesulfonamido

methylbenzoate MRID 45386202

Chemical Family sulfonylurea herbicide
Empirical Formula C 17 H 21 N 5 O 9 S 2 MRID 45386202 Product Chemistry

SMILES c1(ccc(cc1S(=O)(=O)NC(=O)Nc1nc (cc(OC)n1)OC)CNS(=O)(=O)C)C(= O)OC EPI V4.10 1

CAS Number 208465

- 21

- 8 MRID 45386202 Product Chemistry

Structure http://www.chemsp
ider.com/Structure Search.aspx Product Chemistry

Select Physical/Chemical Parameters

Molecular mass 503.55 MRID 45386202 Product Chemistry
Solubility (20oC), mg/L 7.2 (pH 5) 483 (pH 7) 15,390 (pH 9) MRID 45386215 Product Chemistry

Log Kow 1.39 (pH 5)

- 0.48 (pH 7)

- 2.06 (pH 9) MRID 45386219 Product Chemistry

Vapor pressure in Pascals (Pa) 3.5 x 10 - 12 (20 ° C)
1.1 x 10 - 11 (25 ° C)

3.3 x 10 - 11 (30 ° C) MRID 45386217 Product Chemistry
Henry’s law constant (25°C, pH 7) 6.17 x10 - 18 atm·m 3 /mol EPI 4.1

Persistence

### 8 Parameter Value Reference Comments

Hydrolysis (25oC) pH 4 pH 7 pH 9 Major Degradates : AE F092944 (38.4%, pH 4) AE F140584 (50.3%, pH 4) AE F092944 (37.4&32.1%, pH 7&9) AE F147447 (45.2&46.8%, pH 7&9)

Minor Degradate:

AE F154851 (3.8%, pH9) 3.5 days 253.1 days 318.5 days MRID 45386418 Acceptable

Aqueous Photolysis (t 1⁄2 )

Minor Degradates (≤3.7%) : AE F 147447
AE F 160459
AE F 140584 197 days 385 days MRID 45386419
MRID 45386420 Supplemental Supplemental

Soil Photolysis (t 1⁄2 ) Stable MRID 45386421 Supplemental

Aerobic Soil Metabolism (t 1⁄2 )

Major Degradates : AE F092944(10.9%,MRID 45386425) AE F154851(16.2%,MRID 45386425) AE F099095(29.2%, MRID 45386425)

Minor Degradates : AE F160459 (8.9%,MRID 45386424)
AE F160460 (8.6%,MRID 45386424) AE F099095 (3.1%,MRID 45386422) AE F147447 (7.2%,MRID 45386423) AE F140584 (7.1%,MRID 45386423) 74 days (German loamy sand) 76 days (German loamy sand) 32 days (Illinois sandy loam) 86 days (German sandy loam) 100 days (German loamy sa nd)

20 days (German silt loam) 29 days (France loam) 82 days (UK loam) 199 days (North Dakota Clay) MRID 45386422
MRID 45386423
MRID 45386424

MRID 45386425 Acceptable Acceptable Acceptable

Acceptable

Anaerobic Aquatic Metabolism (t 1⁄2 )

Major Degradates : AE F160459(25.9%,MRID 45386427) AE F160460 (12.6%,MRID 45386429)

Minor Degradates : AE F140584 (2.5%,MRID 45386427) AE F147447 (6.8%,MRID 45386427) AE F154851 (6.6%,MRID 45386429) AE F099095 (0.7%,MRID 45386427) AE F092944 (5.7%,MRID 45386429) AE F119772 (5.7%,MRID 45386429) 23

- 29 days (Water)
32

- 48 days (Sediment)

27

- 36 days (Total system)

5.4 days (Water) 8.0 days (Sediment) 6.2 days (Total system) MRID 45386427

MRID 45386429 Supplemental

Supplemental

### 9 Parameter Value Reference Comments
Aerobic Aquatic Metabolism (t 1⁄2 )

Major Degradates : AE F160459 (21.6%)
AE F147447 ( 16.1 %)
Unknown A (U1) (6.9

- 22%)
Unknown D (U3) (6.2

- 13.1%)

Minor Degradates : AE F160460 (8.4%) AE F154851 ( 4.9 %)
AE F092944 (4.4 %) AE F140584 (1.9%) AE F099095 ( ≤ 0. 9%) AE F119094 ( 1.5 %)
Unknown C (U2) (≤4.2%)
Unknown E (U4) (≤1.9%)
Unknown G (U5) (≤1.9%) Gravel pit water

- sand sediment from Germany [Phenyl

- U

14 C]

- label 97.2 days (Water) 108.7 days (Sediment) 99.8 days (Total system)

[Pyrimidyl

- 2

- 14 C]

- label 82.3 days (Water)
84. 0 days (Sediment)
83.6 days (Total system)

River water

- silt loam sediment from Germany Phenyl

- U

14 C]

- label 26.2 days (Water) 70.0 days (Sediment) 35.7 days (Total system)

[Pyrimidyl

- 2

- 14 C]

- label 14.9 days (Water) 42.3 days (Sediment) 24.9 days (Total system) MRID 45386430

MRID 45386431 Supplemental

Supplemental (Kinetic Evaluation of MRID 45386430)

Bioconcentration/ Depuration (t 1⁄2 ) N/A N/A N/A
Mobility

Koc ( mL/g) 345 (Sand , pH 5.8 ) 137 (Sandy clay loam , pH7.9 ) 37 (Münster loamy sand , pH 6.3 )
31 (Speyer loamy sand , pH 6.6 ) 92 (Millington sandy loam , pH 7.6 ) 26 (Schwanheim sandy loam , pH
7.1 ) 36 (Clay loam , pH 7.9 ) 85 (Loam , pH 8.0 ) 48 (Silt loam , pH 7.9 ) MRID 45386432 Acceptable

Field Dissipation
Terrestrial Field Dissipation (t 1⁄2 ) 58days (Florida) 136 days (Illinois) 80 days (California) MRID 45386501 Supplemental

Mesosulfuron

- methyl Degradates



### Parameter Value 

### Reference Comments

Bridge

- intact Metabolites of Mesosulfuron

- methyl (Unique to Mesosulfuron

- methyl )
Company Code AE F154851 MRID 45386425 Mesosulfuron

Chemical Name 2

- [3

- (4,6

- dimethoxypyrimidine

- 2

- yl)ureidosulfonyl]

- 4

- methanesulfonamidomethyl benzoic
acid MRID 45386425

Empirical Formula 

### C 16 

### H 19 

### N 5 

### O 9 

### S 2 EPI 4.1

### 10 Parameter Value Reference Comments

SMILES O=C(Nc1nc(OC)cc(OC)n1)NS(=O)( =O)c2cc(ccc2C(=O)O)CNS(=O)(=O )C EPI 4.1

CAS Number 400852

- 66

- 6

Molecular mass 489.48 EPI 4.1

Structure http://www.chemsp
ider.com/Structure Search.aspx

Koc ( mL/g) 119 (Minnesota clay loam) 66 (Hattersheim silt loam) 50 (Münster sandy loam) MRID 45386433 (Acceptable)

Company Code AE F160459 MRID 45386427
MRID 45386429

Chemical Name Methyl 2

- [3

- (4

- hydroxy

- 6

- methoxypyrimidine

- 2

- yl)ureidosulfonyl]

- 4

- methanesulfonamido

- methyl
benzoate MRID 45386427
MRID 45386429

Empirical Formula 

### C 16 

### H 19 

### N 5 

### O 9 

### S 2 EPI 4.1

SMILES C(=O)(c1c(S(=O)(=O)NC(=O)Nc2n c(O)cc(OC)n2)cc(CNS(C)(=O)=O)c c1)OC EPI 4.1

Molecular mass 489.48 EPI 4.1

Structure http://www.chemsp
ider.com/Structure Search.aspx

Company Code AE F160460 MRID 45386429

Chemical Name 2

- [3

- (4

- hydroxy

- 6

-

m ethoxypyrimidin

- 2

- yl) ureidosulfonyl]

- 4

- methanesulfonamidomethyl

- benzoic
acid MRID 45386429

Empirical Formula 

### C 15 

### H 17 

### N 5 

### O 9 

### S 2 EPI 4.1

SMILES C(=O)(O)c1c(S(=O)(=O)NC(=O)Nc 2nc(O)cc(OC)n2)cc(CNS(C)(=O)=O )cc1 EPI 4.1

### 11 Parameter Value Reference Comments

Molecular mass 475.45 EPI 4.1

Structure http://www.chemsp
ider.com/Structure Search.aspx

Phenyl Ring Bridge

- cleavage Metabolites of Mesosulfuron

- methyl (Unique to Mesosulfuron

- methyl )
Company Code AE F140584 MRID 45386418

Chemical Name M ethyl 4

- methanesulfonamidomethyl

- 2

- sulfamoylbenzoate MRID 45386418

Empirical Formula C 10 H 14 N 2 O 6 S 2 EPI 4.1

SMILES C(=O)(c1c(S(N)(=O)=O)cc(CNS(C)( =O)=O)cc1)OC EPI 4.1

Molecular mass 322.35 EPI 4.1

Structure http://www.chemsp
ider.com/Structure Search.aspx

Company Code AE F147447 MRID 45386418

Chemical Name 6

- M ethanesulfonamidomethyl

- 1,2

- benzisothiazol

- 3(2H)

- one 1,l dioxide MRID 45386418

Empirical Formula C 9 H 10 N 2 O 5 S 2 EPI 4.1

SMILES C1(=O)c2c(cc(CNS(C)(=O)=O)cc2) S(=O)(=O)N1 EPI 4.1

Molecular mass 290.31 EPI 4.1

Structure http://www.chemsp
ider.com/Structure Search.aspx

Pyrimidine Ring Bridge

- cleavage Metabolites of Mesosulfuron

- methyl (Common to Other Sulfonylurea Herbicides)
Company Code AE F099095 MRID 45386434

Chemical Name (CAS) 4,6

- dimethoxypyrimidin

- 2

- yl

- urea MRID 45386434

Empirical Formula C 7 H 10 N 4 O 3 EPI 4.1

SMILES c1(OC)cc(OC)nc(NC(N)=O)n1 EPI 4.1

### 12 Parameter Value Reference Comments

Molecular mass 198.18 EPI 4.1

Structure http://www.chemsp
ider.com/Structure Search.aspx

Koc ( mL/g) 3856 (Minnesota clay loam) 365 (Hattersheim silt loam) 206 (Münster sandy loam) MRID 45386434 (Acceptable)

Company Code AE F119094

Chemical Name (CAS) 4

- Hydroxy

- 6

- methoxypyrim i din

- 2

- yl

- urea Empirical Formula C 6 H 8 N 4 O 3 EPI 4.1

SMILES c1(O)cc(OC)nc(NC(N)=O)n1 EPI 4.1

Molecular mass 184.16 EPI 4.1

Structure http://www.chemsp
ider.com/Structure Search.aspx

Company Code AE F092944 MRID 45386418
MRID 45386425

Chemical Name (CAS) 2

- Amino

- 4,6

- dimethoxypyrimidine MRID 45386418
MRID 45386425
Empirical Formula C 6 H 9 N 3 O 2 EPI 4.1

SMILES c1(OC)cc(OC)nc(N)n1 EPI 4.1

CAS Number 36315

- 01

- 2 CSID:106290

Molecular mass 155.16 EPI 4.1

### 13 Parameter Value Reference Comments

Structure http://www.chemsp
ider.com/Structure Search.aspx

1 http://www.epa.gov/oppt/exposure/pubs/episuite.htm



### 3.4. Clean Water Act

Mesosulfuron

- methyl is not identified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act 2 

### . In addition, no Total Maximum Daily Loads (TMDL) have been developed 3 

### . The Impaired Waters and Total Maximum Daily Loads
website can be consulted for more information 4 

### . The Agency invites submission of water quality
data for m esosulfuron

- methyl . To the extent possible, data should conform to the quality
standards in the OPP Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and Management

Process 5 

### , in order to ensure they can be used quantitatively or qual itatively in pesticide risk

assessments.

4. Receptors

Consistent with the process described in the Overview Document (USEPA, 2004 c ), the risk
assessment for m esosulfuron

- methyl relies on a surrogate species approach. Toxicological data generated from sur rogate test species, which are intended to be representative of broad taxonomic groups, are used to extrapolate the potential effects on a variety of species (receptors) included under these taxonomic groupings.

A cute and chronic toxicity data from studie s submitted by pesticide registrants along with the available open literature will be used to evaluate the potential direct and indirect effects of

m esosulfuron

- methyl to aquatic and terrestrial receptors. This includes toxicity on the technical grade act ive ingredient, degradates, and when available, formulated products ( e.g. , “Six

- Pack” studies). Open literature studies will be identified through EPA’s ECOTOXicology (ECOTOX)
database 6 

### , which use s a literature search engine for locating chemical toxicity data.

A summary of data representing non

- target organisms exposed to m esosulfuron

- methyl and its degradation products in aquatic and terrestrial habitats is provided in Sections 4.1 and 4.2 . A summary of ecological incidents associated with m esosulfuron

- methyl is provided in Section
4.3

. Studies submitted by the registrant are listed in Appendix A . The ECOTOX database will
be searched when the risk assessment for m esosulfuron

- methyl is prepare d. At that time,

2 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

3 http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_ group_name=PESTICIDES

4 http://www.epa.gov/owow/tmdl/

5 http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1

- sop.pdf

6 http://cfpub.epa.gov/ecotox/

### 14 endpoints more sensitive than available guideline studies will be reviewed from the open
literature studies.

4.1. Effects to Aquatic Organisms

Table 4 . Summary of Toxicity of Mesosulfuron

- methyl (TGAI) to Aquatic Animal s
Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Rainbow Trout ( Oncorhynchus mykiss ) 96 hr 94.6 LC 50 > 91.5 mg total
ai/L

NOAEC ≥ 91.5 mg
total ai/L 45386231 NA Supplemental

Bluegill sunfish ( Lepomis
macrochirus ) 96 hr 94.6 LC 50 > 96.4 mg total
ai/L

NOAEC ≥ 96.4 mg
total ai/L 45386230 NA Supplemental

Rainbow Trout ( Oncorhynchus mykiss ) 28 day 1 94.6 NO A EC ≥ 29. 6 mg ai/L

LO A EC > 29. 6 45386232 NA Supplemental

Waterflea (Daphnia magna) 48 hr 94.6 EC 50 > 90.2 mg ai/L

NOAEC ≥ 90.2 mg ai/L 45386233 NA Acceptable (“Core”)

Waterflea (Daphnia magna) Life

Cycle 94.6 NOAEC = 1.7 mg ai/L

LOAEC = 3.0 mg ai/L based on dry weight 45386305 NA Acceptable (“Core”)

Sheepshead
minnow ( Cyprinodon variegatus ) 96 hr 95.7 LC 50 > 105 mg ai/L

NOAEC ≥ 105 mg ai/L 45386301 Practically

non

- toxic Supplemental

Mysid shrimp ( Americamysis
bahia ) 96 hr 95.7 LC 50 > 111 mg ai/L

NOAEC ≥ 111mg ai/L 45386303 Practically

non

- toxic Acceptable (“Core”)

Eastern oyster ( Crassostrea virginica ) 96 hr 95.6 EC 50 > 100 mg ai/L

NOAEC ≥ 100mg ai/L 45386302 Practically

non

- toxic Acceptable (“Core”)

1 OECD 28

- day sub

- chronic study with 2 month old fish. NA = not applicable



### Table 5 . Summary of Toxicity of Mesosulfuron

- methyl Degradation Products (TGAI) to Aquatic Animal s
Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Rainbow Trout ( Oncorhynchus mykiss ) 96 hr Unknown
AE F092944 LC 50 = 97 mg ai/L IUPAC footprint 1 Slightly
toxic NA

Waterflea (Daphnia magna) 48 hr Unknown
AE F092944 EC 50 > 100 mg
ai/L IUPAC footprint 1 Practically

non

- toxic NA

### 15 Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Waterflea (Daphnia magna) 21 day Unknown
AE F092944 NOAEC = 24 mg
ai/L IUPAC footprint 1 NA NA

1 IUPAC footprint database studies are not reviewed by the Agency and the toxicity endpoints are used at face value. http://sitem.herts.ac.uk/aeru/iupac/441.htm NA = not applicable



### Table 6 . Summary of Toxicity of Mesosulfuron

- methyl (TGAI) to Aquatic Plants

Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Marine Diatom (Skeletonema costatum) 96 hr 95.7 IC 50 = 98000 (91000

- 110000) 1 μg ai/L

NO A EC = 37800 μg ai/L

Based on reduced biomass (area under the growth curve) 45386314 NA Acceptable (“Core”)

Cyanobacteria (Anabaena flosaquae 96 hr 95.7 IC 50 = 2400 (1700

- 3300) 1
μg ai/L

NO A EC = 1100 μg ai/L

Based on reduced cell density 45386315 NA Acceptable (“Core”)

Freshwater
Diatom (Navicula pelliculosa ) 96 hr 94.6 IC 50 > 70800 μg ai/L

NO A EC ≥ 70.8 μg ai/L 45386307 NA Acceptable (“Core”)

Duckweed (Lemma gibba ) 7 day 95.3 IC 50 = 0.64 (0.56

- 0.73) 1 μg ai/L

NO A EC = 0.19 μg ai/L

Based on reduced number
of fronds 45386310 NA Acceptable (“Core”)

1 Range is 95% confidence interval. NA = not applicable



### Table 7 . Summary of Toxicity of Mesosulfuron

- methyl Degradation Products (TGAI) to Aquatic Plants

Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Freshwater Green Algae (Pseudokirchneriella subcapitata) 96 hr 93.1

AE
F147447 IC 50 > 92000 μg ai/L

NO A EC ≥ 92000 μg ai/L 45386308 NA Acceptable (“Core”)

### 16 Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Freshwater Green Algae (Pseudokirchneriella subcapitata) 96 hr 96.8

AE
F160459 IC 50 = 98000 μg
ai/L

NO A EC = 54600 μg ai/L

Based on reduced biomass (area under the growth curve) 45386309 NA Acceptable (“Core”)

Freshwater Green Algae (Pseudokirchneriella subcapitata) 72 hr Unknown

AE
F092944 IC 50 = 120000 μg
ai/L IUPAC footprint 2 NA NA

Duckweed (Lemma gibba ) 7 day 93.1

AE
F147447 IC 50 > 90900 μg ai/L

NO A EC ≥ 90900 μg ai/L 45386313 NA Acceptable (“Core”)

Duckweed (Lemma gibba ) 7 day 96.8

AE
F160459 IC 50 = 1500 (1100

- 2000) 1 μg ai/L

NO A EC = 290 μg ai/L

Based on reduced
number of fronds 45386311 NA Acceptable (“Core”)

Duckweed (Lemma gibba ) 7 day 96.1

AE
F160460 IC 50 > 94710 μg ai/L

NO A EC ≥ 94710 μg ai/L 45386312 NA Acceptable (“Core”)

Duckweed (Lemma gibba ) 7 day Unknown

AE
F092944 IC 50 > 100000 μg ai/L IUPAC footprint 2 NA NA

1 Range is 95% confidence interval.

2 IUPAC footprint database studies are not reviewed by the Agency and the toxicity endpoints are used at face value. http://sitem.herts.ac.uk/aeru/iupac/441.htm NA = not applicable



### 4.2. Effects to Terrestrial Organisms

Table 8 . Summary of Toxicity of Mesosulfuron

- methyl (TGAI) to Terr estrial Animal s
Species Exposure
Scenario %
AI Toxicity MRID Toxicity Category Classification

Northern Bobwhite Quail ( Colinus virginianus ) Single oral dose, birds
observed for 14 days 94.6 LD 50 >2000 mg/kg

NO A EL < 2000 mg/kg

LO A EL ≤ 2000 based

on reduced consumption

No mortality 45386224 Practically

non

- toxic Acceptable (“Core”)

### 17 Species Exposure
Scenario %
AI Toxicity MRID Toxicity Category Classification

Mallard Duck ( Anas platyrhynchos ) Single oral dose, birds
observed for 14 days 94.6 LD 50 >2000 mg/kg

No mortality or
sublethal effects
observed 45386225 Practically

non

- toxic Acceptable (“Core”)

Northern Bobwhite Quail ( Colinus virginianus ) 8 days (5 days
treatment and 3 days observation) 94.6 LC 50 >4800 ppm ai

NO A EC < 297 ppm ai

LO A EC ≤ 297 based on reduced consumption

No mortality 45386226 NA Acceptable (“Core”)

Mallard Duck ( Anas platyrhynchos ) 8 days (5 days
treatment and 3 days observation) 94.6 LC 50 >4750 ppm ai

NO A EC < 309 ppm ai

LO A EC ≤ 309 based on reduced consumption

No mortality 45386227 NA Acceptable (“Core”)

Northern Bobwhite Quail ( Colinus virginianus ) One

generation Reproduction Study 94.6 NOAEC ≥ 1000 ppm ai 45386228 NA Supplemental

Mallard Duck ( Anas platyrhynchos ) One

generation Reproduction Study 94.6 NOAEC ≥ 990 ppm ai 45386229 NA Supplemental

Honeybee ( Apis mellifera ) Acute contact 95.9 LD 50 > 13 μg ai/bee 45386319 Practically
nontoxic Acceptable (“Core”)

Rat Acute Oral 95.6 LD 50 > 5000 mg/kg 45386321 Practically
nontoxic Acceptable

Rat 2

- year chronic 94.6 NOAEL ≥ 16,000 ppm (1175 mg/kg bw/day

– males; 1388 mg/kg bw/day

– females)

Parental systemic, offspring, and reproductive 45430405 NA Acceptable

NA = not applicable

### 18 Table 9 . Summary of Toxicity of Mesosulfuron

- methyl Degradation Products (TGAI) to
Terrestrial Animal s
Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Rat Acute
Oral Unknown
AE F099095 LD 50 = 677 mg/kg (males) 47305223 Slightly
toxic NA

Rat Acute
Oral Unknown
AE F092944 LD 50 = 737 mg/kg (males) IUPAC footprint 1 Slightly
toxic NA

1 IUPAC footprint database studies are not reviewed by the Agency and the toxicity endpoints are used at face

value. http://sitem.herts.ac.uk/aeru/iupac/441.htm NA = not applicable



### Table 10 . Summary of Toxicity of Mesosulfuron

- methyl Formulations to Terrestrial
Animal s
Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Rat Acute
Oral 2.26
Silverado Wild
Oat Herbicide LD 50 > 2000 mg/kg 46034702 Practically
nontoxic 1 Acceptable

Rat Acute
Oral 4.84 Osprey LD 50 > 2000 mg/kg 46034602 Practically
nontoxic 1 Acceptable

Rat Acute
Oral 4.5 Olympus Flex

( plus 6.8% propoxycarbazone

- sodium) LD 50 > 2000 mg/kg 46038502 Practically
nontoxic 1 Acceptable

Rat Acute
Oral 3.08 (plus 0.61% iodosulfuron) LD 50 > 2000 mg/kg 47756302 Practically
nontoxic 1 Acceptable

1 On a formulation basis



### Table 11 . Summary of Toxicity of Mesosulfuron

- methyl Formulations to Terrestrial Plants

Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Terrestrial
Plants Vegetative Vigor,

21

- day 4.81 Osprey 4.5
WG Most sensitive monocot

46688201 NA Under Review Oat (dry weight)
IC 25 = 0.42 (0.36

- 0.49) 1
g ai/ha

NO A EC = 0.33 g ai/ha

LO A EC = 1 g ai/ha

Most sensitive dicot

Soybean (dry weight)
IC 25 = 0.16 (0.14

- 0.19) 1
g ai/ha

NO A EC = 0.04 g ai/ha

LO A EC = 0.11 g ai/ha

### 19 Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Seedling Emergence,
14

- day 74.73 (TGAI plus adjuvant) Most sensitive monocot

45745702

NA Supplemental Onion (shoot length)
IC 25 = 8.4 (5.4

- 13) 1 g ai/ha

NO A EC = 7.5 g ai/ha

LO A EC = 15 g ai/ha

50% (TGAI plus
iodosulfuron
and adjuvant) Most sensitive dicot

45386316 Lettuce (shoot length)
IC 25 = 0.92 (0.34

- 2.5) 1 g ai/ha

NO A EC = 0.81 g ai/ha

LO A EC = 1.63 g ai/ha

1 Range is 95% confidence interval. NA = not applicable



### Table 12 . Summary of Toxicity of Mesosulfuron

- methyl Degradation Products (TGAI) to
Terrestrial Plants

Species Exposure
Scenario % AI Toxicity MRID Toxicity Category Classification

Variable Flatsedge ( Cyperus difformis )

Barnyard Grass ( Echinochloa crus

galli )

Kidneyleaf Mudplantain ( Heteranthera reniformis ) Vegetative Vigor,

21

- day 1 Unknown
AE F099095 NO A EC ≥ 350 g ai/ha 4 6588504 NA Unreviewed

Japonica Rice ( Oryza sativa ) Unknown
AE F099095 NO A EC ≥ 750 g ai/ha 4 6588501 NA Unreviewed

1 EPPO guideline n o 135 studies on rice and rice weeds NA = not applicable



### 4.3. Incident Databases Review

I ncidents involving m esosulfuron

- methyl were reported in the Ecological Incident Information System ( EIIS, v 2.1.1 ) and the Aggregate Incident Data System as of November 8 , 2012 . No incidents were reported in the Avian Incident Monitoring System (AIMS) 7



### .

All 29 reported incidents (2004

- 2011) reported in EIIS involved damage to wheat and all but one were considered possibly or probably caused by direct application of mesosulfuron

- methyl

. Thirty

- seven incidents, all of minor plant

- damage attributed to mesosulfuron

- methyl products, were reported in the Aggregate Incident Data System

.

7 http://www.abcbirds.org/abcprograms/policy/ toxins /aims/aims/index.cfm

### 20 The total number of actual incidents associated with the use of mesosulfuron

- methyl may be higher than what is reported to the Agency. Incidents may go unreported since effects may not be immediately apparent or readily attributed to the use of a chemical. As such, the absence of incident reports cannot be construed as the absence of incidents.

5. Risk Hypothesis

Mesosulfuron

- methyl , when used in accordance with current labels, can result in offsite movement of the compound via spray drift, runoff, and leaching to ground water, leading to exposure of non

- target plants and animals. Application of m esosulfuron

- methyl to wheat and
triticale fields may serve as a major source of m esosulfuron

- methyl exposure to wildlife. When used in accordance with the labels, m esosulfuron

- methyl use will cause adverse effects upon the survival, growth, and reproduction of non

- target terrestrial and aquatic organisms. These non

target organisms i nclude federally

- listed threatened and endangered species.

6. Analysis Plan

In order to address the risk hypothesis, the potential for adverse effects on the environment is estimated. The use, environmental fate, and ecological effects of m esosulfuron

- m ethyl will be characterized and integrated to assess risk. This will be accomplished using a risk quotient (ratio of exposure concentration to effects concentration) approach. Although risk is often defined as the likelihood and magnitude of adverse ecol ogical effects, the risk quotient

- based approach does not provide a quantitative estimate of likelihood or magnitude of an adverse effect. However, as outlined in the Overview Document (USEPA, 2004 c ), the likelihood of effects to individual organisms from particular uses of m esosulfuron

- methyl will be estimated using the probit dose

response slope and either the level of concern or actual calculated risk quotient value.

This analysis plan will be revisited and may be revised depending upon a full review o f the data available in the open literature and the information submitted by the public in response to the opening of the Registration Review docket.

6.1. Stressors of Concern

The stressors of concern will be mesosulfuron

- methyl and in some cases the majo r degradation products ( Table 1 3 )

.

The Agency is seeking clarification on two unknown degradates from the submitted aerobic metabolism study (MRID 45386430 and 4538643 1 ) and requesting an ECM/ILV method that is capable of identif y ing the major degradates ( see Section 6.8 ).

Table 1 3 . Summary of the Major and Minor Mesosulfuron

- methyl D egradates

Company Code (Maximum %

Formation) Chemical Name Mechanism of Formation Comments

AE F154851 (16.2%)
MRID 45386425 2

- [3

- (4,6

- dimethoxypyrimidine

- 2

- yl)ureidosulfonyl]

- 4

- methanesulfonamidomethyl benzoic acid Methyl ester hydrolysis Bridge

- intact degradates (unique to
mesosulfuron

methyl) AE F160459 (25. 9%)
MRID 45386427 Methyl 2

- [3

- (4

- hydroxy

- 6

- methoxypyrimidine

- 2

- yl)ureidosulfonyl]

- 4

- methanesulfonamido

- methyl benzoate Demethoxyfication at the 4

- position of the pyrimidinyl

group

### 21 AE F160460 (12.6%)
MRID 45386429 2

- [3

- (4

- hydroxy

- 6

- m ethoxypyrimidin

- 2

- yl) ureidosulfonyl]

- 4

- methanesulfonamidomethyl

- benzoic acid Demethoxyfication at the 4

- position of the pyrimidinyl group, Methyl ester hydrolysis

AE F140584 (50.3%, pH 4 )
MRID 45386418 Methyl 4

- methanesulfonamidomethyl

- 2

- sulfamoylbenzoate Cleavage of the sulfonylurea bridge Phenyl ring bridge

- cleav ed ( u nique to

m esosulfuron

methyl ) AE F147447 (45.2 at pH 7, 46.8% at pH 9)
MRID 45386418 6

- Methanesulfonamidomethyl

- 1,2

- benzisothiazol

- 3(2H)

- one 1,l dioxide Cleavage of the sulfonylurea bridge, Methyl ester hydrolysis, Isothiazole ring formation

AE F099095 (29.2%)
MRID 45386425 4,6

- dimethoxypyrimidin

- 2

- yl

- urea Cleavage of the sulfonylurea bridge Pyrimidine ring bridge

- cleaved ( c ommon to
other

s ulfonylurea

h erbicides) AE F119094 (1.5%)
MRID 45386430 4

- Hydroxy

- 6

- methoxypyrimdin

- 2

- yl

- urea Cleavage of the sulfonylurea bridge, Demethoxyfication at
the 4

- position

AE F092944 (38.4% at pH 4, 37.4% at pH 7,
3 2.1% at pH 9)
MRID 45386418 2

- Amino

- 4,6

- dimethoxypyrimidine Cleavage of the sulfonylurea bridge, Elimination of the

– NH 2 CO

- group



### Residues of Concern for Drinking Water Consumed by Humans

The only drinking water assessment for mesosulfuron

- methyl was completed in 2004 ( USEPA,
2004a ). Mesosulfuron

- methyl and three bridge

- intact majo r degradates ( AE F15 4851, AE F160459, and AE F160460) were modeled per req uest of the HED’s MARC (01/28/2004 meeting ). R esidues of concern for human health drinking water may be revisited.

Residues of Concern for Ecological Risk Assessment

In the absence of degradate data, the major degradates will be considered stressors of concern when assessing risk to aquatic organisms; however, data are more likely to impact the assessment of aquatic vascular plants.

Limited aquatic toxicity data were available for the major degradation products; however, for most endpoints information w as available from Ecological Structure Activity Relationship (ECOSAR) methods 8 

### or the IUPAC footprint database 9 

### ( Table 1 4 ). The most toxic value was selected for this screening unless indicated otherwise. Some degradates may be more toxic than
mesosulfur on

- methyl to fish and invertebrates. For aquatic plants, available information suggests that some degradates are equal in toxicity to mesosulfuron

- methyl and others are much
less toxic.

Although some degradates may be more toxic than mesosulfuron

- methyl to fish and invertebrates, preliminary estimates of exposure are much lower than would trigger a risk concern ( Table 1 5 ). Exposure for this analysis was based on the highest application rate and
mesosulfuron

- methyl EECs assuming no degradation.

8 ECOSAR predictive software is available publically though the Epi SuiteTM program

. http://www.epa.gov/oppt/exposure/pubs/episuite.htm

9 http://sitem.herts.ac.uk/aeru/iupac/577.htm

### 22 The lack of information on toxicity of two degradates (AE F154851 and AE F140584) to vascular plants could impact risk conclusions

. Listed plants are anticipated to be a risk concern
based on mesosulfuron

- methyl alone. Non

- listed plants may be a risk concern as well if a total toxic residue ( TTR ) approach is used (preliminary EEC = 2.69 μg/L, as reported in Table 1 5 ) ; however, this m ay not be the case if all degradates are clearly less toxic than mesosulfuron

methyl and EECs are based on mesosulfuron

- methyl alone (preliminary EEC = 0.31 μg/L as reported in USEPA, 2004b). One of the degradates, AE F154851, is a SU bridge

- intact

compou nd; thus it will be assumed equal in toxicity to mesosulfuron

- meth yl in the absence of
data and a TTR approach will be used to estimate EECs. The other degradate, AE F140584

, would only need to be slightly more toxic than mesosulfuron

- methyl to trigger a risk concern (listed and non

- listed species) based on its own preliminary EECs 10 

### . On the other hand, ECOSAR estimates suggest that AE F140584 is not more toxic than mesosulfuron

- methyl to

non

- vascular plants which may or may not be representative of the po tential toxicity to vascular plants ( Table 1 4 ). AE F140584 toxic ity will be assumed equal to me s osulfuron

- methyl in the
absence of data and a TTR approach will be used to estimate EECs.

10 Preliminary EEC for AE F140584 (0.18 μg/L ) was calculated by adjusting the maximum application rate of
mesosulfuron

- methyl (lb AE F140584/A = lb ai/A * maximum percent formation of AE F140584 in fate studies * (MW AE F140584/MW ai) and assuming that AE F140584 is stable to degradation.

### 23 Table 1 4 . Comparative Aquatic Toxicity of Mesosulfuron

- methyl and Major Degradation Products Compound FW fish
96

- hr

acute
LC 50 

### (mg/L) FW fish
chronic
NO A EC (mg/L) 1 

### FW
invertebrate
48

- hr acute
EC 50 

### (mg/L) FW
invertebrate
chronic
NO A EC (mg/L) 1 

### ME fish
96

- hr

acute
LC 50 

### (mg/L) ME
invertebrate
96

- hr acute
LC 50 

### (mg/L) Vascular plant 7

- day EC 50



### (μg/L) Non

vascular plant 96

- hr EC 50



### (μg/L)

Mesosulfuron

methyl > 91.5 ≥ 29.6 2 

### > 90.2 1.7 > 105.0 > 111.0 0.64 56.0

AE F154851 20367.7 3 

### 155.0 4 

### 7284.6 3 

### 96.0 4
, 5



### - - - 547.0

AE F160459 97.0 4 

### 0.02 5.5 6.8 5 

### 1314.1 3 

### 2739.4 3 

### 1500.0 98000.0

AE F160460 2023.2 3 

### 0.15 73.6 101.8 235000.0 3



### - > 94700.0 532.0

AE F140584 731.0 4 

### 12.0 548.2 7.2 5 

### 1360.9 4 

### 3249.3 4



### - 2792.0

AE F147447 6.1 0.54 5 

### 7.6 0.7 5



### - - > 90900.0 > 92000.0

AE F099095 337.6 1.9 116.5 1.5 5



### - - 2.5

- 200.0 6 

### 147.0

AE F092944 97.0 89.6 7 

### > 100.0 24.0

- - >100000.0 120000.0

1 ECOSAR estimated c hronic value is defined as the geometric mean of the no observed effect concentration (NOEC) and the lowest observed effect concentration (LOEC).

2 OECD 28

- day sub chronic study

3 Endpoint exceeds predicted water solubility of compound by 10x

– no effects at saturation are predicted if the compound is solid.

4 Endpoint exceeds predicted water solubility of compound.

5 Value is b ased on acute

- to

- chronic ratio . O ther ECOSAR classes predict lower toxicity (i.e., higher values)

. 6 AE F099095 is a urea

- type compound. Urea herbicides ( e.g. , linuron) are less toxic than mesosulfuron

- methyl to vascular plants (EC 50 = 2.5

- 200 μg/L). Data are reported in the problem formulation for ortho sulfamuron (DP 390068).

7 Neutral organic estimates are reported because N

- substituted anilines are less toxic than estimated by the aniline ECOSAR class.
BOLD values are ECOSAR (v1.00) toxicity estimates (lowest toxicity value of multiple ECOSAR classes i s shown , i.e., the most toxic ). BOLD
Italic values are from the footprint database (reported when toxicity value is lower than ECOSAR estimate). Non

- bolded values are toxicity values
from available studies.
FW = freshwater and ME = marin e/estuarine

### 24 Table 1 5 . Preliminary Aquatic RQs for Mesosulfuron

- methyl and Major Degradation
Products 1,2

Compound FW fish
96

- hr

acute
LC 50 (mg/l) RQ FW fish
chronic
NO A EC

(mg/l) RQ FW
invertebrate
48

- hr acute
EC 50 (mg/l) RQ FW
invertebrate

chronic
NO A EC

(mg/l) RQ

Mesosulfuron

- methyl 91.5 0.000029 29.6 0.000091 90.2 0.000030 1.7 0.001582

AE F154851 20367.7 0.000000 155.0 0.000017 7284.6 0.000000 96 .0 0.000028

AE F160459 97.0 0.000028 0.02 0.134000 5.5 0.000489 6.8 0.00039 6

AE F160460 2023.2 0.000001 0.15 0.017867 73.6 0.000037 101.8 0.000026

AE F140584 731.0 0.000004 12 .0 0.000223 548.2 0.000005 7.2 0.00037 4

AE F147447 6.1 0.000441 0.54 0.004926 7.6 0.000354 0.7 0.003 843

AE F099095 337.6 0.000008 1.9 0.001411 116.5 0.000023 1.5 0.0017 93

AE F092944 97 0.000028 89.6 0.000030 100 .0 0.000027 24 0.000112

1 Toxicity based on data in Table 1 4 (marine

- estuarine fish/invertebrates RQs are not presented because available toxicity data suggests that they are no t more sensitive than freshwater fish/invertebrates )

. RQs are not typically
calculated for non

- definitive endpoints; h owever, they are presented here for comparative purposes only. RQs based

on non

- definitive endpoints are higher (overestimate risk) than if based on actual toxicity. RQs based on toxicity endpoints greater than the predicted solubility limit ( i.e., ECOSAR estimates of some of the degradates ) have limited meaning

. Nonetheless, risk is low in these cases given that (1) the preliminary EECs are ≥ 11,000 X lower than the

ECOSAR

- estimated solubility limit (s) of the pertinent degradate (s) and (2) ECOSAR

- estimate d toxicity suggest s that there is less than a 50% acute effect and no adverse chronic effect at the solubility limit (s) of the pertinent degradate (s)

. 2 RQs calculated using mesosulfuron

- methyl EECs based on the highest application rate and assuming no degradation (Peak, 21

- day, and 60

- day EEC = 2.69 μg/l).



### Limited terrestrial toxicity data were available for the major degradation products ( Table 9 and
12 ). However, the degradation products are not likely a risk concern for birds or mammals given that they would need to be at least two to three orders of magnitude more toxic than
mesosulfuron

- methyl to exceed levels of concern (LOC) . Preliminary degradate EECs were calculated based on the highest acute (3.66 mg/kg bw ) and subacute/ chronic ( 3.22 mg/kg diet)
mesosulfuron

- methyl EEC calculated in T

- REX. Each degradate EEC was calculated as follows:

EEC = mesosulfuron

- methyl EEC * max % of degradate formed in fate studies * (MW degradate
/ MW mesosulfuron

- methyl)

There are limited degradate toxicity data for terrestrial plants. SU bridge

- intact degradates (AE F154851, AE F160459, and AE F160460) and mesos ulfuron

- methyl will be assumed equal in toxicity to terrestrial plants in the absence of data. AE F09 9095 , a urea

- type compound, is a potentially herbicidally

- active non

- SU degradate. Limited data for AE F099095 suggests that it
is not more toxic than me sosulfuron

- methyl. Furthermore, m esosulfuron

- methyl is more toxic than urea herbicides ( see orthosulf am uron problem formulation for toxicity comparison; DP 390068); thus, AE F09 9095 is likely not more toxic than mesosulfuron

- methyl assuming its toxicity i s similar to that of the urea herbicides.

6.2. Measures of Exposure

Mesosulfuron

- methyl concentrations in aquatic and terrestrial environments will be modeled using the ma ximum labeled application rates and n umber s of applications, the minimum

### 25 applicati on intervals, and application methods that have the greatest potential for off

- site
transport.

Spray Drift

The AgDRIFT spray drift model (v2.01; May, 2001) or AgDISP model 11 

### will be used to assess

exposure of non

- target organisms to mesosulfuron

- methyl through off

- site spray drift. The models also function as tools for evaluating potential buffer zones.

Aquatic Exposure

T ier II models PRZM ( P esticide R oot Z one M odel, v3.12.2; May , 200 5 ) and EXAMS ( EX posure A nalysis M odeling S ystem, version 2.98.04. 06, April 2005) in the PE5 shell 12 

### will be used to estimate environmental concentrations (EECs) of mesosulfuron

- methyl and degradation products (as appropriate) in surface waters.

If available, monitoring data will be evaluated and used for characterizing the distribution of
mesosulfuron

- methyl and degradation products

.

Terrestrial Exposure

There is potential exposure to non

- target organisms through consumption of contaminated food items ( e.g. , insects or vegetation)

, drinking water , direct application, inhalation, runoff, and spray drift.

T

- REX (v 1.5) 13 

### will be used to estimate exposure of birds and mammal to m esosulfuron

- methyl

. For input into T

- REX, the default foliar dissipation half

- life of 35 days will be used in the absence of acceptable foliar dissipation rate data (if labels allow multiple applications)

.

TerrPlant (v 1.2.2) 13 

### will be used to calculate EECs for characterizing exposure to terrestrial and
semi

- aquatic plants.

Screening Imbibition Program

The Screenin g Imbibition Program (SIP v.1.0 ) 13 

### was used to calculate an upper bound estimate of bird and mammal exposure to mesosulfuron

- methyl in drinking water.

Although the model identifies a p otential concern for birds (acute and chronic) and mammals (acute and chronic )

, the model prediction has limited meaning because toxicity was based on

non

- definitive endpoints from studies with no observed mortality ( Table 8 )

. That is, the potential concern is unquantifiable and less than suggested by the model.

Although conclusion s about risk from drinking water exposure alone are uncertain , drinking water may contribute to a total exposure (dietary food sources, dermal, and inhalation) that has

11 http://w ww.epa.gov/pesticides/science/models_pg.htm#atmospheric

12 http:// www.epa.gov /oppefed1/models/water

13 http:// www.epa.gov/oppef ed1/models/terrestrial

### 26 potential for effects on non

- target animals and should be explored further. Appendix B provides
model results.

Screening Tool for Inhalation Risk

The Screening Tool for Inhalation Risk (STIR v. 1.0) 13 

### was used to provide an upper bound estimate of exposure of birds and mammals to pesticides through inhalation of spray drift or

vapor.

The screening suggests that mesosulfuron

- methyl exposure is not likely significant enough for an
inhalation risk concern

. Appendix C provides model results.

6.3. Measures of Effect

Toxicity effects data will be used as measures of direct and indirect eff ects to biological receptors (USEPA, 2004 c ). As discussed previously, data will be obtained from registrant

submitted studies and from literature studies identified in ECOTOX.

Quantitative assessment of risks will be based on study endpoints that can b e directly linked to the Agency’s assessment endpoints of impaired survival, growth, and reproduction. Sub

- lethal effects ( e.g. , lethargy and changes in coloration) will be evaluated qualitatively. Available
incident data will be used to further characte rize risk.

6.4. Integration of Exposure and Effects

The e xposure and effects data will be integrated in order to evaluate potential adverse ecological
effects on non

- target species. The risk quotient (RQ) method will be used to compare exposure
and measu red toxicity values. EECs will be divided by acute and chronic toxicity values. The resulting RQs will be compared to the Agency’s LOC (USEPA, 2004 c ).

6.5. Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to Federally

- listed threatened and endangered (listed) species from registered uses of m esosulfuron

- methyl . This assessment will be conducted i n accordance with the Overview Document (USEPA, 2004 c ), provis ions of the ESA, and the Services’ Endangered Species Consultation Handbook (USFWS and NMFS, 1998).

6.6. Endocrine Disruptor Screening

As required by Federal Food, Drug and Cosmetic Act (FFDCA) section 408(p), m esosulfuron

methyl is subject to the endocrine screening part of the Endocrine Disruptor Screening Program (EDSP) 14



### . Mesosulfuron

- methyl is not in the first or second group of pesticide active ingredients to be screened under the EDSP.

6.7. Drinking Water Assessment

A new DWA may be conducted for m esosulfuron

- methyl based on new or revised label
information at the time of risk assessment. T hree bridge

- intact major degradates ( AE F154 851,
AE F160459

, and AE F160460) will be included based on the past HED MARC m eeting

14 http://www.epa.gov/endo/

### 27 (01 /28/2004)

. R esidue s in surface waters will be estimated using PRZM/EXAMS and residues
in ground water will be estimated using the Tier I SCI

- GROW model and the Tier II PRZM/EXAM ground water model

. 15 

### EECs will be adjusted by p ercent c ropped a rea (PCA) factors to account for the maximum fractional area within a watershed that may be planted

. 16



### 6.8. Preliminary Identification of Data Gaps

Available studies submitted to fulfill environmental fate and ecological effects guideline requirements are presented i n Sections 6.8.1 and 6.8.2 , respectively. D ata gaps are identified and discussed in regard to impacts on risk assessment.

6.8.1. Environmental Fate Data

Data gaps for mesosulfuron

- methyl remain ( Table 1 6 )

. The following data are recommended to reduce uncertaint y in the ecological risk assessment.

• Aerobic Aquatic Metabolism (OPPTS Guideline 835.4300)

– ( mesosulfuron

- methyl )

• Aquatic Field Dissipation Study (OPPTS Guideline 835.6200)

– ( mesosulfuron

- methyl )

• Environmental Chemistry Methods for Soil and Plant Material (OCSPP Guideline 850.6100)

- ( mesosulfuron

- methyl and major degradates AE F160459, AE F160460, AE F154851, AE F140458, AE F147447, AE F099095

, and AE F092944 )

Aerobic Aquatic Metabolism (mesosulfuron

- methyl)

Two major metabolites (“unknown A and D”) were not identified in the submitted stud ies
(MRID 45386430 and 45385431). Data are needed that identifies all major transformation products ( i.e., formed >10%).

Aquatic field dissipation (mesosulfuron

- methyl)

No aquatic field diss ipation data are available. Mesosulfuron

- methyl is a very water soluble and persisten t chemical in aquatic environment s . It is very likely that the compound will be introduced into the aquatic environment via run

- off and leaching.

EC M/ILV method for plant and soil (mesosulfuron

- methyl and major degradates)

Studies are needed for mesosulfuron

- methyl and major degradation products. Mesosulfuron

methyl, l ike most sulfonylureas, exhibits long term phytotoxicity. Whether this is due to sorption on soil or toxicity of degradates cannot be resolved with available information. It leaves open the possibility of soil mediated transport due to windborne dust or other pathways. The lack of analytical methods with a limit of quantitation (LOQ) at levels of eco logical concern for plants will leave this question unresolved. ECM/ILV for soil will be used to confirm the submitted terrestrial field dissipation data

. Therefore, the ECM/ILV methods are required for soil and plants to mediate the uncertainties.

15 http://www.epa.gov/oppefed1/models/water

16 http://www.epa.gov/oppefed1/models/water/pca_adjustment_dwa.html

### 28 Othe r data gaps , “Yes” without bold font in Table 1 6 , are not likely to change risk conclusion s; therefore, studies are not recommended at this time.

Table 1 6 . Environmental Fate Data Gaps for Mesosulfuron

- methyl

Guideline Description MRID Classification Data Gap Comments

835.2120 Hydrolysis 45386418 Acceptable No 1 Data gaps exist for aquatic photolysis at pH

5 and 9 ; however, available data at pH 7
will be sufficient for modeling purposes.

2 Study is not required because of low vapor

pressure.

3 Study can be substituted by Anaerobic Aquatic Metabolism (835.4400)

4 Addtional data are
needed to identify two major unknown
metabolites

5 Study w aiver was

g ranted DP Barcode(s):
297232

, 12/08/03

6 The terrestrial field dissipation study was
not conducted with the typical end use products nor does it appear that attempts were made to identify degradates.

7 Additional data will
not be needed i f the
available data are deemed acceptable

. 835.2240 Photodegradation in

Water 45386419

45386420 Supplemental Supplemental Yes 1

835.2410 Soil Photolysis 45386421 Supplemental No

835.2370 Photodegradation in Air

-- -- Yes 2

835.4100 Aerobic Soil Metabolism 45386422

45386423

45386424

45386425 Acceptable Acceptable Acceptable Acceptable No

835.4200 Anaerobic Soil

Metabolism -- -- Yes 3

835.4300 Aerobic Aquatic

Metabolism 45386430

45385431 Supplemental Supplemental Yes 4

835.4400 Anaerobic Aquatic

Metabolism 45386427

45386428 Supplemental Supplemental No

835.1230

835.1240 Leaching Adsorption/Desorption 45386432

45386433

45386434 Acceptable Acceptable Acceptable N o

835.1410 Laboratory Volatility

-- -- Yes 5

835.8100 Field Volatility

-- -- No 2

835.6100 Terrestrial Field Dissipation 45386501

45386502

46948901 Supplemental

In Review Yes 6

, 7

835.6200 Aquatic Field Dissipation

-- -- Yes

850.6100 ECM/ILV
(Water) 45386522

45386523

46451701

46451702 In Review

In Review

In Review

In Review Yes 7

850.6100 ECM/ILV
(Soil) -- -- Yes

850.1730 Bioa ccumulation in Fish

-- -- Yes 5

### 29 6.8.2. Ecological Effects Data

Several data gaps for mesosulfuron

- methyl remain ( Tables 1 7
, 1 8 , and 1 9 ). After review, some studies have been reclassified and no longer meet a given data requirement. Studies are not recommended at this time for some data gaps (“Yes” with out bold font in Tables 17, 18, and 19 ) because risk conclusions are unlikely to change.

The following stud ies are recommended:

• Aquatic plant growth (850. 45 00)

- freshwater green alga (Mesosulfuron

- methyl )

• Aquatic plant growth (850.4400)

- vascular plant (AE F15485 1 and AE F140584)

Mesosulfuron

- methyl

Acute freshwater fish toxicity

Available data for freshwater fish are supplemental in part because samples were not filtered or centrifuged prior to analysis given the presence of precipitate in the test chambers. The amount
of mesosulfuron

- methyl that was freely dissolved and bioavailable cannot be determined without centrifugation or filtration. As such, toxicity may be underestimated. However, uncertainty is minimal in regard to the risk conclu sions. Effects were not observed (mortality or sublethal) and there is no risk concern as long as about 0.05% of the mesosulfuron

- methyl was in solution ( i.e.

, dissolved) 17 

### . Furthermore, there is no risk concern based on the lowest ECOSAR estimate (LC 50 

### = 332 mg ai/L). Repeat testing is unlikely to change risk conclusions unless aquatic EECs are substantially higher in the future ( e.g. , higher application rates are requested).

Freshwater fish early life stage

Data are available for sub

- chronic (28 day ) toxicity to rainbow trout (two months of age) but not for early life stage (ELS) toxicity. No effects (mortality or growth) were observed in the 28

- day study (NO A EC ≥ 29.6 mg ai/L). The potential for chronic effects on fish reproduction remains

uncerta in without an early life stage study. However, there is a large margin of safety based on the current application rates and available toxicity information. ELS toxicity would need to be ≥ four orders of magnitude more toxic than the sub

- chronic NO A EC (29 .6 mg ai/L) to have a risk concern. Additionally, ELS toxicity would need to be ≥ three orders of magnitude greater than the lowest ECOSAR estimate (most toxic, NOEC = 3.4 mg ai/L) to have a chronic risk concern. An ELS study is unlikely to change risk c onclusions at this time given the margin of safety. However, additional data could be important in the future if aquatic EECs approach the ECOSAR estimate ( e.g. , higher application rates are requested) or new information suggests reproductive effects at e nvironmentally relevant concentrations of mesosulfuron

- methyl

.

Passerine acute oral toxicity

Data are not available for a passerine species, which are potentially more sensitive than larger birds due to their smaller size and higher metabolic rates. The available acute oral studies with

17 Percentage not precise and would be lower because EECs were calculated using a TTR approach and toxicity endpoints are non

- definitive.

### 30 bobwhite quail and mallard duck showed no mortality at a concentration of 2000 mg/kg. A passerine species (ca. 25 g) would need to be > 50 X more sensitive than the quail and duck to exceed the listed species LOC at the highest registered application rate. Additionally, no mortality was observed at 4800 ppm in the available avian acute dietary studies. At the current application rates, the value of a passerine study would be confirmatory in nature.

Avian reproduction

A non

- definitive NOAEC was established in the available studies (MRID 45386228 and 45386229) based on no adverse effects at the highest dose tested. Requesting additional data to
establish a definitive NOAEC has little value at this time because terrestri al EECs for currently registered uses are more than 300 X lower than the non

- definitive NOAEC. However, additional data could be important in the future if terrestrial EECs approach the highest concentration tested in the available studies ( e.g. , higher a pplication rates are requested).

Terrestrial plants

– seedling emergence

Available data are supplemental because the observation period was 14 days post

- application instead of 21 days post

- emergence of control plants. Additionally, the test material was TGAI plus adjuvant instead of a TEP (including inert materials) plus adjuvant. Available data suggest that repeat testing would likely result in minimal impact on risk conclusions.

Risk from spray drift is likely to be impacted more by foliar applicat ions. Toxicity was greater for foliar application (vegetative vigor) than for application to seeds (seedling emergence) in studies conducted with the same test material and duration. The value of repeat testing would be confirmatory in this regard.

Seedling emergence data will have a greater impact on assessing risk from runoff. However, little may be gained from repeat testing considering the results of the available vegetative vigor studies. Vegetative vigor data show little difference in toxicit y for studies conducted for 21 days using a TEP (MRID 46688201, under review) and 14 days using TGAI plus adjuvant (MRID
45386317 and 45745701 ). The general risk picture would change little if effects to seedling emergence, like vegetative vigor, are min imally impacted by extending the study duration and testing with a TEP.

Aquatic plant growth

- freshwater green alga

Acceptable data are available for three of four recommended test species. Green alga data are
needed to assess risk to non

- vascular plan ts because different species are likely to show a range of sensitivity to mesosulfuron

- methyl . The most sensitive species will be used to assess risk. Data are of value in reducing uncertainty of risk to non

- vascular plants. Other means of addressing ri sk will be used to reduce uncertainty in the absence of a study. For instance, toxicity may be estimated based on the lowest ECOSAR estimate ( IC 50 

### = 56 μg ai/L) or data
from other SU herbicides.

Non

- Guideline

– Special study for non

- target plant reprod uctive toxicity with TEP

EFED's Plant Technical Team (PTT) conducted an analysis of available SU plant reproduction data from the open literature and the registrant

- submitted data for chlorsulfuron and concluded

### 31 that data from the 850.4150 vegetative vigor guideline study are sufficiently protective of potential impacts to plant reproduction. Acetolactate synthase (ALS) inhibitors primarily affect metabolically

- active meristem tissues. When plants are exposed at a young, vigorously growing
life

- stage, effects are expressed primarily as inhibition of vegetative growth ( i.e. biomass, shoot length). As plants mature these effects are less pronounced. However, as plants enter their reproductive life

- stage, the metabolically

- active tissue will include flow er and seed production. Plants exposed to SU herbicides during the reproductive life stage are likely to exhibit adverse effects on reproduction, generally expressed as reduced seed number or reduced seed weight. Based on the latest data analysis, these effects are expected to occur at similar concentrations to those effects determined in the guideline vegetative vigor studies (850.4150). Therefore, fulfilling this DCI has a low potential to add value to the risk assessment and a study is not
recommended

.

Degradation Products

Fish and aquatic invertebrates (acute and chronic toxicity)

Data are not requested at this time because risk conclusions are unlikely to change based on the currently labeled rates ( see Section 6.1 ). ECOSAR estimates suggest that some degradates may be more acutely or chronically toxic than mesosulfuron

- methyl to fish and invertebrates. However, LOCs are not exceeded even when the lowest ECOSAR estimates ( i.e. , most toxic for each degradate) are compared to preliminary mesosulfur on

- methyl EECs (maximum application rate) calculated with the assumption of no degradation. EECs of individual degradates would be lower. Other means of addressing risk will be used to reduce uncertainty in the absence of studies. A TTR approach will b e used to calculate EECs and toxicity may be based on ECOSAR estimates or analogous compounds. However, studies could be important in the future if aquatic EECs are expected to be higher ( e.g. , higher application rates are requested).

Avian (acute and ch ronic toxicity)

Data are not requested at this time because risk conclusions are unlikely to change based on the currently labeled rates ( see Section 6.1 ). Degradates would need to be at least two to three orders of magnitude more toxic than mesosulfur on

- methyl to be a risk concern. However, data could be important in the future if EECs are expected to be higher ( e.g. , higher application rates are requested).

Aquatic plant gro wth

– vascular plant (AE F15485 1 and AE F140584 )

Data are recommended to reduce potential uncertainty in risk conclusions for non

- listed species ( see Section 6.1) . AE F15485 1 ( SU bridge

- intact compound ) and AE F140584 toxicity will be assumed equal to mesosulfuron

- methyl in the absence of data and a TTR approach will be used
to calculate EECs.

Aquatic plant growth

– non

- vascular plants

Data are not requested at this time because available information suggests that the degradation products are not more toxic than mesosulfuron

- methyl ( see Section 6.1 ). In the absence of submitted data, those degradates will be assumed as toxic as mesosulfuron

- methyl and a TTR

### 32 approach will be used to calculate EECs. However, as discussed above, an acceptable study is
needed to establish mesosulfuron

- methyl toxicity to green algae.

Terrestrial plants

Data are not requested at this time; however, SU bridge

- intact degradates will be assumed equal in toxicity to mesosulfuron

- methyl in the absence of data ( see Section 6.1 ).

Table 1 7 . Ecological Effects Data (TGAI) for Aquatic Animal s Exposed to Mesosulfuron

methyl and Data Gaps

Guideline Description MRID Classification Data Gap? Comments

850.1075 Acute freshwater fish toxicity (cold water species) 45386231 Supplemental Yes 1,2 1 EFED does not recommend requesting a new study because little will be gained from submission of a new study.

2 See text above Table 1 7

. Acute freshwater fish toxicity (warm water species) 45386230 Supplemental Yes 1,2

Acute estuarine/ marine fish toxicity 45386301 Supplemental Yes 1

850.1010 Acute toxicity to
freshwater
invertebrates 45386233 Acceptable (“Core”) No

850.1025 Acute estuarine/
marine mollusk toxicity 45386302 Acceptable (“Core”) No

850.1035 Acute estuarine/
marine invertebrate toxicity 45386303 Acceptable (“Core”) No

850.1300 Freshwater invertebrate life cycle 45386305 Acceptable (“Core”) No

850.1400 Freshwater fish early life stage 45386232 Supplemental Yes 1,2

### 33 Table 1 8 . Ecological Effects Data (TGAI) for Terrestrial Animals Exposed to
Mesosulfuron

- methyl and Data Gaps

Guideline Description MRID Classification Data Gap? Comments

850.2100 Avian acute oral toxicity (upland game or waterfowl species) 45386224
45386225 Acceptable (“Core”) No 1 These data are required under 40 CFR part 158 for terrestrial
outdoor uses. However,
EFED does not recommend requesting a study at this time.

2 See text above Table 1 7

3 EFED does not recommend requesting a new study because little will be gained
from submission of a new study. Avian acute oral toxicity (passerine species) None Not applicable Yes 1,2

850.2200 Avian dietary toxicity (upland game species) 45386226 Acceptable (“Core”) No

Avian dietary toxicity

(waterfowl species) 45386227 Acceptable (“Core”) No

850.2300 Avian reproduction (upland game species) 45386228 Supplemental Yes 2,3

Avian reproduction (waterfowl species) 45386229 Supplemental Yes 2,3

850.3020 Honeybee acute contact toxicity 45386319 Acceptable (“Core”) No



### Table 1 9 . Ecological Effects Data for Plants Exposed to Mesosulfuron

- methyl and Data Gaps

Guideline Description MRID Classification Data Gap? Comments

850.4100 A Terrestrial plant toxicity (Tier I&II seedling emergence) 45745702
45386316 Supplemental Supplemental Yes 1,2 1 EFED does not recommend requesting a new study because little will be gained from submission of a new study.

2 See text above Table 1 7

3 These data are required under 40 CFR part 158 for terrestrial outdoor uses. Data are of value in reducing uncertainty of risk to non

- vascular plants.

4 No data gap for me sosulfuron

methyl; however, data are
recommended for two degradation products (AE F154851 and AE F140584). 850.4150 B Terrestrial plant toxicity (Tier I&II vegetative vigor) 46688201 Under Review TBD

850. 45 00 C Aquatic plant growth (freshwater green alga) 45386306 Invalid Yes 3

Aquatic plant growth (freshwater diatom) 45386307 Acceptable (“Core”) No

Aquatic plant growth

(saltwater diatom) 45386314 Acceptable (“Core”) No

850.45 5 0 C Aquatic plant growth (Cyanobacteria) 45386315 Acceptable (“Core”) No

850.4400 Aquatic plant growth (vascular plants) 45386310 Acceptable (“Core”) No 2 ,4

A As of July 2012 the Final Guideline 850.4100 contains both Tier I and Tier II test guidance (formerly 850.4 100
and 850.4 225 , respectively)

. B As of July 2012 the Final Guideline 850.4150 contains both Tier I and Tier II test guidance (formerly 850.4 1 50
and 850.4 2 50, respectively)

. C Formerly 850. 54 00

### 34 7. References

USEPA. 2004a. Dri nking Water Assessment for Mesosulfuron

- m ethyl and Its Major Metabolites New
Chemical

- Uses on Winter Wheat (OSPREY; 4.5% mesosulfuron

- methyl) and Spring Wheat, Including Dumm (SILVERADO, 2.0% mesosulfuron

- methyl). DP Barcode: D 295662

USEPA. 2004 b

. Mesosulfu ron Methyl Section 3

- Uses on Winte r Wheat (OSPREY; 4.5%
mesosulfuron

- methyl) and Spring Wheat, Including Durum (SILVERADO, 2.0% mesosulfuron

methyl). DP Barcodes: D284053, D284719, D295614, D295656, D296 120, D297232

USEPA. 2004c. Overview of the Ecological Risk Assessment Process in t he Office of Pesticide Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington DC.

, January 23, 2004.

USFWS and NMFS. 1998. Endangered Species Consultation Handbook: Procedures for Conducting Consultation and Conference Activities Under Section 7 of the Endangered Species Act. Final
Draft. March 1998.

### 35 

## APPENDIX A. Submitted Environmental Fate and Effects Studies

MRID Citation Reference

Fate
Studies

45386418 Burri, R. (2000) Hydrolysis of (Carbon 14)

- AE F130060 at Different pH Values: Lab Project Number: 738090: C008110. Unpublished study prepared by RCC Ltd. 70 p. {OPPTS 835.2110 and 835.2130}

45386419 Schmidt, W.; Buerkle, W. (2000) Aqueous Photol ysis Under Laboratory Conditions: (U

- (Carbon 14)

- AE F130060: Lab Project Number: CP97/040: C008008. Unpublished study prepared by Aventis CropScience. 58 p.

45386420 Buerkle, W. (2000) Real Half

- Lives of the Aqueous Photolysis: AE F130060: Lab Project Nu mber: C009998: OE00/118. Unpublished study prepared by Aventis CropScience. 6 p. {OPPTS 835.2210}

45386421 Burri, R. (2000) Photolysis of (Carbon 14)

- AE F130060 on Soil Surface Under Laboratory Conditions: Lab Project Number: 738088: C006911. Unpublished study prepared by RCC Ltd. 51 p.

45386422 Tarara, G. (2000) Kinetics and Metabolism in Soil LS 2.2 at 10C and 20C Under Aerobic Conditions: (2

- (Carbon 14)

- Pyrimidyl)AE F130060: Lab Project Number: CB96/011: C009871. Unpublished study prepared by Aventis CropScience. 82 p.

45386423 Tarara, G. (2000) Kinetics and Metabolism in Soil LS 2.2 at 10C and 20C Under Aerobic Conditions: (2

- (Carbon 14)

- Phenyl)AE F130060: Lab Project Number: CB97/053: C009873. Unpublished study prepared by Aventis CropScience. 60 p.

45386424 Tarara, G. (2000) Degradation in Three Soils at 20C Under Aerobic Conditions: AE F130060: Lab Project Number: CB96/056: C009874. Unpublished study prepared by Aventis CropScience. 80 p.

45386425 Tarara, G. (2000) Degradation in Four Soils at 20C Under Ae robic Conditions: (2

- (Carbon 14)

- Pyrimidinyl)AE F130060: Lab Project Number: CB96/140: C009870. Unpublished study prepared by Aventis CropScience. 96 p.

45386426 Schafer, D. (2000) Kinetic Evaluation of AE F130060 Aerobic Soil Degradation Studies Using T opFit 2.0: Lab Project Number: C009951: OE00/105. Unpublished study prepared by Aventis CropScience GmbH. 121 p. {OPPTS 835.4100}

45386427 Tarara, G. (2000) Kinetics and Metabolism in Soil LS 2.2 at 20C Under Anaerobic Soil Conditions: (U

- (Carbon 14)AE F 130060 and (2

- (Carbon 14)

- Pryrimidinyl)AE F130060: Lab Project Number: CB98/136: C009872. Unpublished study prepared by Aventis CropScience GmbH. 71 p.

45386428 Schafer, D. (2000) Kinetic Evaluation of AE F130060 Anaerobic Soil Degradation Studies Using TopFit 2.0: Lab Project Number: C010057: OE00/122. Unpublished study prepared by Aventis CropScience GmbH. 33 p. {OPPTS 835.4200}

45386429 Gildemeister, H. (2001) Degradation in a Water/Sediment

- System at Different Temperatures Under Anaerobic Conditions in the Laboratory (2

- (Carbon 14)

- Pyrimidinyl)

- and (U

- (Carbon 14)

- Phenyl)

- AE F130060: Lab Project Number: CB97/143: C011868. Unpublished stud y prepared by Aventis CropScience. 76 p.

45386430 Steinfuhrer, T.; Zumdick, A. (2000) Aerobic Degradation in Two Water/Sediment

- System at 20C (Carbon 14)

- AE F130060: Lab Project Number: CB97/082: C009416. Unpublished study prepared by Aventis CropScience . 218 p. {OPPTS 835.4300}

45386431 Schafer, D. (2000) Kinetic Evaluation of AE F130060 Aerobic Water/Sediment

- System Using TopFit

### 36 2.0: Lab Project Number: C009952: OE00/115. Unpublished study prepared by Aventis CropScience GmbH. 97 p. {OPPTS 835.4300}

45386432 Allan, J.; Pate, M. (2000) The Adsorption/Desorption of (Carbon 14)

- AE F130060 on Nine Soils: Lab Project Number: 500CK: C003710: CK96E500. Unpublished study prepared by Aventis CropScience. 84 p.

45386433 Rosenwald, J. (2000) AE F154851: Adsor ption in Three Soils: Final Report: Lab Project Number:
1490

- 017: C007785. Unpublished study prepared by Covance Labs., GmbH. 79 p.

45386434 Rosenwald, J. (2000) AE F099095: Adsorption in Three Soils: Final Report: Lab Project Number:
1490

- 016: C007786. Unpublished study prepared by Covance Labs., GmbH. 79 p.

45386501 Cole, M. (2001) Dissipation of AE F115008 and AE F130060 in Soil Following Application of AE
F115008 WDG and AE F122006 WDG or AE F130060 WDG and AE F107982 WDG to a Bare Plot
at the Maxim um Proposed Rates, USA, 1998: Lab Project Number: BY98R004: B003218. Unpublished study prepared by Aventis CropScience. 256 p.

46948901 Lenz, M. (2006) Terrestrial Field Dissipation of Mesosulfuron

- methyl in North Dakota Soil, 2004. Project Number: MEMMY 002. Unpublished study prepared by Agvise Inc and Bayer Corp. 109 p.

45386502 Wrede, A. (2000) Stability of AE F130060 in Soil During Deep Freeze Storage of 24 Months. Unpublished Study Performed and Submitted by Aventis CropScienceGmbH, Frankfurt, Federa l Republic of Germany. Study ID. CR 97/037. Experiment Imitation August 12, 1997 and Completion August 12, 1999 p. 10. Final Report Issued August 21, 2000.

45386504 Frey, J.; Harrison, C.; Buerkle, L. (2000) Residues in Rotated Crops Sown 31 Days after Application to Bare Soil at a Rate of 15 g a.s./ha: (2

- (Carbon

- 14)

- Pyrimidyl)

- AE F130060: Lab Project Number: CM97/044: C008238. Unpublished study prepared by Aventis C ropScience. 32 p.

45386505 Frey, J.; Harrison, C.; Buerkle, L. (2000) Residues in Rotated Crops Sown 32 Days after Application to Bare Soil at a Rate of 15 g a.s./ha: (U

- (Carbon

- 14)

- Phenyl)

- AE F130060: Lab Project Number: CM97/046: C008240. Unpublished s tudy prepared by Aventis CropScience. 32 p.

45386506 Frey, J.; Harrison, C. (2000) Residues in Rotated Crops Sown 4 Months after Application to Bare Soil at a Rate of 15 g a.s./ha: (2

- (Carbon

- 14)

- Pyrimidyl)

- AE F130060: Lab Project Number: CM97/163:
C0082 42. Unpublished study prepared by Aventis CropScience. 26 p.

45386507 Frey, J.; Harrison, C. (2000) Residues in Rotated Crops Sown 4 Months after Application to Bare Soil at a Rate of 15 g a.s./ha: (U

- (Carbon

- 14)

- Phenyl)

- AE F130060: Lab Project Number: C M97/164: C008243. Unpublished study prepared by Aventis CropScience. 26 p.

45386508 Frey, J.; Harrison, C. (2000) Residues in Rotated Crops Sown 1 Year after Application to Bare Soil at a Rate of 15 g a.s./ha: (2

- (Carbon

- 14)

- Pyrimidyl)

- AE F130060: Lab Pr oject Number: CM97/045: C008239. Unpublished study prepared by Aventis CropScience. 26 p.

45386509 Frey, J.; Harrison, C. (2000) Residues in Rotated Crops Sown 1 Year after Application to Bare Soil at a Rate of 15 g a.s./ha: (U

- (Carbon

- 14)

- Phenyl)

- AE F13 0060: Lab Project Number: CM97/047: C008241. Unpublished study prepared by Aventis CropScience. 26 p.

45386522 Wrede, A. (2000) Enforcement Method for Surface and Drinking Water by HPLC

- UV: AE F130060: Lab Project Number: EM F15/99

- 0: C008689. Unpublishe d study prepared by Aventis CropScience GmbH. 35 p. {OPPTS 860.1340}

45386523 Wrede, A. (2000) Validation of the Enforcement Method EM F15/99

- 0 for Surface and Drinking Water by HPLC

- UV: AE F130060: Lab Project Number: CR 00/008: C008686: EM F15/99

- 0. Unpublished study prepared by Aventis CropScience GmbH. 68 p. {OPPTS 860.1340}

4 5386532 Phillips, J.; Ramanarayanan, T. (2001) Tier One Chronic Dietary Exposure Analysis for
Mesosulfuron

- Methyl Including Drinking Water Estimated Concentration (DWEC) Comparison to Drinking Water Level of Comparison (DWLOC): Lab Project Number: MESOSULF URON

- 01

- 01: B003220. Unpublished study prepared by Aventis CropScience. 25 p.

### 37 46451701 Wrede, A. (2002) Validation of the Enforcement Method EM F04/00

- 0 for Surface Water by LC

MS/MS: Amidosulfuron, Mesosulfuron

- Methyl and Foramsulfuron. Project Number: 02F026, C024802. Unpublished study prepared by Bayer Cropscience Gmbh. 56 p.

46451702 Reichert, N.; Klimmek, S. (2003) Independent Laboratory Validation of the Analytical Method for the Residue Analysis of Amidosulfuron, Mesosulfuron

- Methyl and Foramsulfu ron in Surface Water. Project Number: IF/02/000105070, C/030823. Unpublished study prepared by Institut Fresenius Chemische und Biologische. 47 p.



### Effects
Studies

45386224 Ebert, E. (1998) Bobwhite Quail Acute Oral Toxicity Test: AE F130060; Substance, Technical: Lab Project Number: 98.0450: C0002332. Unpublished study prepared by Hoechst Marion Roussel Deutschland GmbH. 34 p.

45386225 Ebert, E. (1998) Mallard Duck Acute O ral Toxicity Test: AE F130060; Substance, Technical: Lab Project Number: A67403: 98.0047. Unpublished study prepared by Hoechst Marion Roussel Deutschland GmbH. 33 p.

45386226 Ebert, E. (1999) Bobwhite Quail Dietary LC(50) Study: AE F130060; Substance, T echnical: Lab Project Number: 98.0964: C002392. Unpublished study prepared by Hoechst Marion Roussel Deutschland GmbH. 36 p.

45386227 Ebert, E. (1998) Mallard Duck Dietary LC(50) Study: AE F130060; Substance, Technical: Lab Project Number: 98.0436: C0008 41. Unpublished study prepared by Hoechst Marion Roussel Deutschland GmbH. 37 p.

45386228 Ebert, E. (2000) Bobwhite Quail Dietary Reproduction Study: AE F130060; Substance, Technical: Lab Project Number: 2000.0138: C009084: 97.0745. Unpublished study pre pared by Aventis Pharma Deutschland GmbH. 186 p.

45386229 Frey, L.; Beavers, J.; Jaber, M. (1999) Mallard Duck Dietary Reproduction Toxicity Study: AE F130060; Substance, Technical: Lab Project Number: C005103: 312

- 115. Unpublished study prepared by Wild life International Ltd. 152 p.

46392501 Ortego, L. (2004) Proposed NOEC and LOEC for the Avian Reproduction Study: "Mallard Duck Dietary Reproduction Toxicity Study AE F130060; Substance Technical (Code: AE F130060 00 1C95 0001)". Project Number: C005103, B004809. Unpublished study prepared by Bayer Cropscience LP. 8 p.

45386230 Heusel, R.; Weller, O.; Gosch, H. (1999) Acute Toxicity to Bluegill Sunfish (Lepomis macrochirus): AE F130060; Substance, Technical: Lab Project Number: CE97/025. Unpublished study prepared by Hoechst Schering AgrEvo GmbH. 26 p.

45386231 Sowig, P.; Welle r, O.; Gosch, H. (1999) Acute Toxicity to Rainbow Trout (Oncorhynchus mykiss): AE F130060; Substance, Technical: Lab Project Number: CE97/026: C003718. Unpublished study prepared by Hoechst Schering AgrEvo GmbH. 27 p.

45386233 Sowig, P.; Weller, O.; Gosc h, H. (1999) Acute Toxicity to Waterflea (Daphnia magna): AE F130060; Substance, Technical: Lab Project Number: CE97/027: C003741. Unpublished study prepared by Hoechst Schering AgrEvo GmbH. 29 p.

45386301 Abedi, J.; Stachura, B.; Young, B. (2001) 96 Hou r Acute Toxicity to the Sheepshead Minnow, Cyprinodon variegatus, in Static System: AE F130060 Technical 95.7% w/w: Lab Project Number: CK99W506: B003157. Unpublished study prepared by Aventis CropScience. 39 p.

45386302 Dionne, E. (2000) AE 130060 00 1C 96 0004: Acute Toxicity to Eastern Oysters (Crassostrea virginica) Under Flow

- Through Conditions: Lab Project Number: B003104: CK 99W508: 13726. 6125. Unpublished study prepared by Springborn Labs., Inc. 60 p. {OPPTS 850.1025}

45386303 Abedi, J.; Stachur a, B.; Young, B. (2001) 96 Hour Acute Toxicity to the Mysid Shrimp, Mysidopsis bahia, in a Static System: AE F130060 Technical 95.7% w/w: Lab Project Number: CK99W507:

### 38 B003158. Unpublished study prepared by Aventis CropScience. 36 p.

45386232 Sowig, P.; Weller, O.; Gosch, H. (2000) Effects on Juvenile Growth of Rainbow Trout (Oncorhynchus mykiss) in a 28 Days Static Renewal System: AE F130060; Substance, Technical: Lab Project Number: CE97/097: C004237. Unpublished study prepared by Aventis Cro pScience GmbH. 62 p. {OPPTS 850.1075}

45386304 Sowig, P.; Gosch, H.; Weller, O. (2000) Effects on Growth and Reproduction of Daphnia magna (Waterflea): AE F130060; Substance, Technical: Lab Project Number: CE97/098: C008780:
CE97/098

- 1. Unpublished study prepared by Aventis CropScience GmbH. 62 p.

45386305 Sowig, P.; Gosch, H.; Weller, O. (2000) First Amendment to Report CE97/098

- 1; C008780: Effects on Growth and Reproduction of Daphnia magna (Waterflea): AE F130060; Substance, Technical: Lab Project Nu mber: CE97/098: C009791: CE97/098

- 2. Unpublished study prepared by Aventis CropScience GmbH. 64 p.

45386316 Christ, M.; Abedi, J. (2001) Effect on Seedling Emergence of Non

- Targeting Terrestrial Plants (Tier II) AE F130060 + AE F115008: Water Dispersible Granule 50 + 10% w/w: Including a Representative Adjuvant: Lab Project Number: 01CK27636: B003211. Unpublished study prepared by Aventis CropScience GmbH. 170 p.

45386317 Christ, M.; Abedi, J. (2001) Effect on Vegetative Vigor of Non

- Target Terrestrial Plants (Tier II) AE F130060 + AE F115008: Water Dispersible Granule 50 + 10% w/w: Including a Representative Adjuvant: Lab Project Number: 01CK27635: B003212. Unpublished study prepared by Aventis CropScience GmbH. 170 p.

45745701 Christ, M.; Abedi, J. ( 2002) Effect on Vegetative Vigor of Non

- Target Terrestrial Plants (Tier 2) AE F130060+ (Inert Ingredient); Water Dispersible Granule (75.3% w/w) Including a Representative Adjuvant: Lab Project Number: CK99W504: B003969. Unpublished study prepared by Avent is CropScience. 112 p.

45745702 Christ, M.; Abedi, J. (2002) Effect on Seedling Emergence of Non

- Target Terrestrial Plants (Tier 2) AE F130060+ (Inert Ingredient); Water Dispersible Granule (75.3% w/w) Including a Representative Adjuvant: Lab Project Num ber: CK99W505: B003970. Unpublished study prepared by Aventis CropScience. 114 p.

46688201 Christ, M.; Lam, C. (2005) Vegetative Vigor Nontarget Terrestrial Plant Study Using Osprey. Project Number: EBMMY002. Unpublished study prepared by Bayer Corp. 66 p.

45386306 Heusel, R.; Weller, O.; Gosch, H. (1998) AE F130060; Substance, Technical 94.6%: Algal Growth
Inhibition

-- Pseudokirchneriella: Lab Project Number: CE97/024: A59843. Unpublished study prepared by Hoechst Schering AgrEvo GmbH. 46 p.

45386307 S owig, P.; Weller, O.; Gosch, H. (2000) Algal Growth Inhibition

-- Navicula pelliculosa: AE F130060; Substance, Technical: Lab Project Number: CE98/090: C004457. Unpublished study prepared by Aventis CropScience GmbH. 34 p.

45386308 Sowig, P.; Weller, O.; G osch, H. (2000) Algal Growth Inhibition

-- Pseudokirchneriella subcapitata: AE F147447; Substance, Technical (Metabolite of AE F130060): Lab Project Number: CE00/082: C009927. Unpublished study prepared by Aventis CropScience GmbH. 38 p.

45386309 Sowig, P. ; Weller, O.; Gosch, H. (2000) Algal Growth Inhibition

-- Pseudokirchneriella subcapitata: AE F160459; Substance, Pure (Metabolite of AE F130060): Lab Project Number: CE00/081: C010060. Unpublished study prepared by Aventis CropScience GmbH. 38 p.

45386310 Sowig, P.; Weller, O. (2000) Duckweed (Lemna gibba G3) Growth Inhibition Test Substance, Technical, 95.3%: Lab Project Number: CE97/029: C007190. Unpublished study prepared by Aventis CropScience GmbH. 42 p.

45386311 Sowig, P.; Weller, O. (2000) Duckwee d (Lemna gibba G3) Growth Inhibition Test AE F160459, Substance, Pure (Metabolite of AE F130060): Lab Project Number: CE00/058: C009078. Unpublished study prepared by Aventis CropScience GmbH. 41 p.

### 39 45386312 Sowig, P.; Weller, O. (2000) Duckweed (Lemna gibba G3) Growth Inhibition Test AE F160460, Substance, Pure (Metabolite of AE F130060): Lab Project Number: CE00/059: C009792. Unpublished study prepared by Aventis CropScience GmbH. 41 p.

45386313 Sowig, P.; Weller, O. (2000) Duckweed (Lemna gibba G3) Growth Inhibition Test AE F147447, Substance, Technical (Metabolite of AE F130060): Lab Project Number: CE00/057: C009245. Unpublished study prepared by Aventis CropScience GmbH. 41 p.

45386314 Young, B.; Abed i, J. (2001) Effect to Skeletonema costatum (Marine Diatom)in a Growth Inhibition Test AE F130060 Technical 95.7% w/w: Lab Project Number: CK99W502: B003156. Unpublished study prepared by Aventis CropScience GmbH. 59 p.

45386315 Abedi, J.; Christ, M.; Yo ung, B. (2000) Effect to Anabaena flos

- aqua (Blue

- Green Alga) in a Growth Inhibition Test AE F130060 Technical 95.7% w/w: Lab Project Number: CK99W503: B003222. Unpublished study prepared by Aventis CropScience GmbH. 57 p.

45386318 Waltersdorfer, A. (199 6) Oral Toxicity (LD 50) to Honey Bees (Apis mellifera L.): AE F130060: Lab Project Number: CW 96/032: A58014. Unpublished study prepared by Hoechst Schering AgrEvo GmbH. 13 p.

45386319 Waltersdorfer, A. (1997) Contact Toxicity (LD 50) to Honey Bees (Api s mellifera L.): AE F13006 00 1C96 0002: Lab Project Number: CW97/129: A59434. Unpublished study prepared by Hoechst Schering AgrEvo GmbH. 14 p. {OPPTS 850.3020}

45386331 Rosinger, C. (1999) Evaluation of Herbicidal Potential of Metabolites of AE F130060: Lab Project Number: C002929. Unpublished study prepared by Hoechst Schering AgrEvo GmbH. 11 p. {OPPTS 850.4250}

46767101 Ortego, L.; Priester, T.; Kemman, R.; et. al. (2 006) Mesosulfuron: An Assessment of Possible Risk to Endangered Species Associated with Wheat. Project Number: CS1/06704. Unpublished study prepared by Compliance Services International. 51 p.

### 40 

## APPENDIX B . SIP v.1.0 Inputs and Outputs

Table 1. Inputs

Parameter Value

Chemical name Mesosulfuron
Solubility (in water at 25 o C; mg/L) 15390

Mammalian LD 50 (mg/kg

- bw) 5000 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg

- bw) 1175 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Avian LD 50 (mg/kg

- bw) 2000 Avian test species northern bobwhite quail Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg

- diet) 990 Bobwhite quail NOAEC (mg/kg

- diet) 1000 NOAEC (mg/kg

- diet) for other bird species 0 Body weight (g) of other avian species 0 NOAEC (mg/kg

- diet) for 2nd other bird species 0 Body weight (g) of 2nd other avian species 0

Table 2. Mammalian Results

Parameter Acute Chronic Upper bound exposure (mg/kg

- bw) 2647.0800 2647.0800 Adjusted toxicity value (mg/kg

- bw) 3845.8028 903.7637 Ratio of exposure to toxicity 0.6883 2.9290

Conclusion* Exposure through drinking water alone is a

potential concern for
mammals Exposure through drinking water alone is a

potential concern for
mammals

Table 3. Avian Results

Parameter Acute Chronic Upper bound exposure (mg/kg

- bw) 12465.9000 12465.9000 Adjusted toxicity value (mg/kg

- bw) 1440.8590 49.1164 Ratio of exposure to acute toxicity 8.6517 253.8030

Conclusion* Exposure through drinking water alone is a

potential concern for
birds Exposure through drinking water alone is a

potential concern for
birds

### 41 

## APPENDIX C. STIR v.1.0 Inputs and Outputs



# Input

Application and Chemical Information

Enter Chemical Name Mesosulfuron

Enter Chemical Use Outdoor Is the Application a Spray? (enter y or n) y If Spray What Type (enter ground or air) air Enter Chemical Molecular Weight (g/mole) 503.5 Enter Chemical Vapor Pressure (mmHg) 8.25E

- 14 Enter Application Rate (lb ai /acre) 0.013

Toxicity Properties

**Bird**

Enter Lowest Bird Oral LD 50 (mg/kg bw) 10 Enter Mineau Scaling Factor 1.15 Enter Tested Bird Weight (kg) 0.025

**Mammal**

Enter Lowest Rat Oral LD 50 (mg/kg bw) 5000

Enter Lowest Rat Inhalation LC 50 (mg/L) 1.33 Duration of Rat Inhalation Study (hrs) 4 Enter Rat Weight (kg) 0.35



# Output

Results Avian (0.020 kg ) Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 2.24E

- 09

Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 2.81E

- 10

Adjusted Inhalation LD 50 1.99E

- 02

Ratio of Vapor Dose to Adjusted Inhalation LD 50 1.41E

- 08 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) 1.25E

- 03 Ratio of Droplet Inhalation Dose to Adjusted Inhalation
LD 50 6.27E

- 02 Exposure not Likely Significant



### Results Mammalian (0.015 kg ) Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 2.24E

- 09

Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 3.53E

- 10

Adjusted Inhalation LD 50 7.92E+01

Ratio of Vapor Dose to Adjusted Inhalation LD 50 4.46E

- 12 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) 1.57E

- 03 Ratio of Droplet Inhalation Dose to Adjusted Inhalation
LD 50 1.98E

- 05 Exposure not Likely Significant