UNITED STATES ENVIRONMENTAL PROTECTION
AGENCY

WASHINGTON, D.C.  20460

OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

Environmental Fate and Ecological Risk Assessment

for the Reregistration of Sulfometuron-methyl: Vegetative Management and
Other Non-crop Uses

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

SULFOMETURON METHYL

PC Code: 122001; CAS Number: 74222-97-2

Note: Appendix A has been slightly revised from the 11/28/07 review (DP
Barcode D346171) per registrant comment.

 Prepared by:

M. Barrett,  Chemist,

Environmental Fate Reviewer, ERB V

K. Sappington, Biologist,

Ecological Effects Reviewer, ERB V

Approved by:

Mah Shamim, PhD, Chief ERB V	February 14, 2008

DP Barcode D334277

United States Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch V

1200 Pennsylvania Ave.

Mail Code 7507P

Washington, D.C. 20460

TABLE OF CONTENTS

  TOC \o "1-4" \h \z \u    HYPERLINK \l "_Toc191187505"  1.	EXECUTIVE
SUMMARY	  PAGEREF _Toc191187505 \h  8

  HYPERLINK \l "_Toc191187506"  1.1.	Nature of Chemical Stressor
PAGEREF _Toc191187506 \h  8

  HYPERLINK \l "_Toc191187507"  1.2.	Conclusions- Exposure
Characterization	  PAGEREF _Toc191187507 \h  8

  HYPERLINK \l "_Toc191187508"  1.3.	Conclusions- Effects
Characterization	  PAGEREF _Toc191187508 \h  9

  HYPERLINK \l "_Toc191187509"  1.4.	Potential Risks to Non-target
Animals and Plants	  PAGEREF _Toc191187509 \h  10

  HYPERLINK \l "_Toc191187510"  1.5.	Conclusions - Endangered Species
PAGEREF _Toc191187510 \h  11

  HYPERLINK \l "_Toc191187511"  1.6.	Identification of Uncertainties and
Their Impact on the Risk Assessment	  PAGEREF _Toc191187511 \h  13

  HYPERLINK \l "_Toc191187512"  1.6.1.	Environmental Fate and Exposure
PAGEREF _Toc191187512 \h  13

  HYPERLINK \l "_Toc191187513"  1.6.2.	Ecological Effects	  PAGEREF
_Toc191187513 \h  14

  HYPERLINK \l "_Toc191187514"  2.	PROBLEM FORMULATION	  PAGEREF
_Toc191187514 \h  15

  HYPERLINK \l "_Toc191187515"  2.1.	Nature of the Regulatory Action
PAGEREF _Toc191187515 \h  15

  HYPERLINK \l "_Toc191187516"  2.2.	Stressor Source and Distribution
PAGEREF _Toc191187516 \h  15

  HYPERLINK \l "_Toc191187517"  2.2.1.	Nature of the Chemical Stressor
PAGEREF _Toc191187517 \h  15

  HYPERLINK \l "_Toc191187518"  2.2.2.	Overview of Pesticide Usage
PAGEREF _Toc191187518 \h  17

  HYPERLINK \l "_Toc191187519"  2.3.	Receptors	  PAGEREF _Toc191187519
\h  17

  HYPERLINK \l "_Toc191187520"  2.3.1.	Aquatic and Terrestrial Effects
PAGEREF _Toc191187520 \h  17

  HYPERLINK \l "_Toc191187521"  2.3.2.	Ecosystems at Risk	  PAGEREF
_Toc191187521 \h  19

  HYPERLINK \l "_Toc191187522"  2.4.	Assessment Endpoints	  PAGEREF
_Toc191187522 \h  19

  HYPERLINK \l "_Toc191187523"  2.5.	Conceptual Model	  PAGEREF
_Toc191187523 \h  20

  HYPERLINK \l "_Toc191187524"  2.5.1.	Risk Hypotheses	  PAGEREF
_Toc191187524 \h  20

  HYPERLINK \l "_Toc191187525"  2.5.2.	Conceptual Diagram	  PAGEREF
_Toc191187525 \h  20

  HYPERLINK \l "_Toc191187526"  2.6.	Analysis Plan	  PAGEREF
_Toc191187526 \h  24

  HYPERLINK \l "_Toc191187527"  2.6.1.	Conclusions from Previous Risk
Assessments	  PAGEREF _Toc191187527 \h  24

  HYPERLINK \l "_Toc191187528"  2.6.2.	Preliminary Identification of
Data Gaps and Analysis Plan	  PAGEREF _Toc191187528 \h  25

  HYPERLINK \l "_Toc191187529"  2.6.3.	Measures of Effect and Exposure
PAGEREF _Toc191187529 \h  25

  HYPERLINK \l "_Toc191187530"  3.	ANALYSIS	  PAGEREF _Toc191187530 \h
27

  HYPERLINK \l "_Toc191187531"  3.1.	USE CHARACTERIZATION	  PAGEREF
_Toc191187531 \h  27

  HYPERLINK \l "_Toc191187532"  3.2.	EXPOSURE CHARACTERIZATION	  PAGEREF
_Toc191187532 \h  33

  HYPERLINK \l "_Toc191187533"  3.2.1.	Environmental Fate and Transport
Characterization	  PAGEREF _Toc191187533 \h  33

  HYPERLINK \l "_Toc191187534"  3.2.2.	Measures of Aquatic Exposure
PAGEREF _Toc191187534 \h  43

  HYPERLINK \l "_Toc191187535"  <IP_ADDRESS>.	Aquatic Exposure Monitoring and
Field Data	  PAGEREF _Toc191187535 \h  43

  HYPERLINK \l "_Toc191187536"  <IP_ADDRESS>.	Aquatic Exposure Modeling
PAGEREF _Toc191187536 \h  43

  HYPERLINK \l "_Toc191187537"  3.2.3.	Measures of Terrestrial  Exposure
  PAGEREF _Toc191187537 \h  51

  HYPERLINK \l "_Toc191187538"  <IP_ADDRESS>.	Terrestrial Exposure Modeling
PAGEREF _Toc191187538 \h  51

  HYPERLINK \l "_Toc191187539"  <IP_ADDRESS>.	Residue Studies	  PAGEREF
_Toc191187539 \h  56

  HYPERLINK \l "_Toc191187540"  3.2.4.	Uncertainties and Limitations for
this Exposure Assessment	  PAGEREF _Toc191187540 \h  56

  HYPERLINK \l "_Toc191187541"  <IP_ADDRESS>.	Limitations In Knowledge Of
Actual Use Patterns	  PAGEREF _Toc191187541 \h  56

  HYPERLINK \l "_Toc191187542"  <IP_ADDRESS>.	Variability In Sulfometuron
Environmental Persistence	  PAGEREF _Toc191187542 \h  57

  HYPERLINK \l "_Toc191187543"  <IP_ADDRESS>.	Exposure To Sulfometuron Methyl
Degradates	  PAGEREF _Toc191187543 \h  57

  HYPERLINK \l "_Toc191187544"  3.3.	ECOLOGICAL EFFECTS CHARACTERIZATION
  PAGEREF _Toc191187544 \h  57

  HYPERLINK \l "_Toc191187545"  3.3.1.	Aquatic Effects Characterization
 PAGEREF _Toc191187545 \h  59

  HYPERLINK \l "_Toc191187546"  <IP_ADDRESS>.	Freshwater Fish, Acute
PAGEREF _Toc191187546 \h  59

  HYPERLINK \l "_Toc191187547"  <IP_ADDRESS>.	Freshwater Invertebrates, Acute
  PAGEREF _Toc191187547 \h  60

  HYPERLINK \l "_Toc191187548"  <IP_ADDRESS>.	Estuarine and marine Fish,
Acute	  PAGEREF _Toc191187548 \h  60

  HYPERLINK \l "_Toc191187549"  <IP_ADDRESS>.	Estuarine and marine
Invertebrates, Acute	  PAGEREF _Toc191187549 \h  61

  HYPERLINK \l "_Toc191187550"  <IP_ADDRESS>.	Freshwater Fish, Chronic
PAGEREF _Toc191187550 \h  62

  HYPERLINK \l "_Toc191187551"  <IP_ADDRESS>.	Freshwater Invertebrate,
Chronic	  PAGEREF _Toc191187551 \h  62

  HYPERLINK \l "_Toc191187552"  <IP_ADDRESS>.	Aquatic Animal Sublethal
Effects: Formulated Product  and Degradate Toxicity	  PAGEREF
_Toc191187552 \h  63

  HYPERLINK \l "_Toc191187553"  <IP_ADDRESS>.	Field Studies	  PAGEREF
_Toc191187553 \h  64

  HYPERLINK \l "_Toc191187554"  <IP_ADDRESS>.	Aquatic Plants	  PAGEREF
_Toc191187554 \h  65

  HYPERLINK \l "_Toc191187555"  3.3.2.	Terrestrial Effects
Characterization	  PAGEREF _Toc191187555 \h  66

  HYPERLINK \l "_Toc191187556"  <IP_ADDRESS>.	Acute Effects on Birds
PAGEREF _Toc191187556 \h  66

  HYPERLINK \l "_Toc191187557"  <IP_ADDRESS>.	Acute Effects on Mammals
PAGEREF _Toc191187557 \h  67

  HYPERLINK \l "_Toc191187558"  <IP_ADDRESS>.	Acute Effects on
Terrestrial-phase Amphibians, Reptiles and Beneficial Insects	  PAGEREF
_Toc191187558 \h  68

  HYPERLINK \l "_Toc191187559"  <IP_ADDRESS>.	Chronic Effects on Birds
PAGEREF _Toc191187559 \h  68

  HYPERLINK \l "_Toc191187560"  <IP_ADDRESS>.	Mammals,  Reproductive Effects
 PAGEREF _Toc191187560 \h  69

  HYPERLINK \l "_Toc191187561"  <IP_ADDRESS>.	Terrestrial Animal Sublethal
Effects, Formulated Product and Degradation Products	  PAGEREF
_Toc191187561 \h  69

  HYPERLINK \l "_Toc191187562"  <IP_ADDRESS>.	Field Studies	  PAGEREF
_Toc191187562 \h  70

  HYPERLINK \l "_Toc191187563"  <IP_ADDRESS>.	Terrestrial Plants	  PAGEREF
_Toc191187563 \h  70

  HYPERLINK \l "_Toc191187564"  4.	RISK CHARACTERIZATION	  PAGEREF
_Toc191187564 \h  73

  HYPERLINK \l "_Toc191187565"  4.1.	Risk Estimation - Integration of
Exposure and Effects Data	  PAGEREF _Toc191187565 \h  73

  HYPERLINK \l "_Toc191187566"  4.1.1.	Non-target Aquatic Animals and
Plants	  PAGEREF _Toc191187566 \h  75

  HYPERLINK \l "_Toc191187567"  <IP_ADDRESS>.	Fish and Aquatic Invertebrates
 PAGEREF _Toc191187567 \h  75

  HYPERLINK \l "_Toc191187568"  <IP_ADDRESS>.	Aquatic Plants	  PAGEREF
_Toc191187568 \h  76

  HYPERLINK \l "_Toc191187569"  4.1.2.	Non-target Terrestrial Animals
PAGEREF _Toc191187569 \h  77

  HYPERLINK \l "_Toc191187570"  <IP_ADDRESS>.	Birds, Acute Risks	  PAGEREF
_Toc191187570 \h  77

  HYPERLINK \l "_Toc191187571"  <IP_ADDRESS>.	Birds, Chronic Risks	  PAGEREF
_Toc191187571 \h  78

  HYPERLINK \l "_Toc191187572"  <IP_ADDRESS>.	Mammals, Acute Risks	  PAGEREF
_Toc191187572 \h  78

  HYPERLINK \l "_Toc191187573"  <IP_ADDRESS>.	Mammals, Chronic Risks
PAGEREF _Toc191187573 \h  79

  HYPERLINK \l "_Toc191187574"  <IP_ADDRESS>.	Non-Target Terrestrial-phase
Amphibians, Reptiles and Terrestrial Invertebrates	  PAGEREF
_Toc191187574 \h  80

  HYPERLINK \l "_Toc191187575"  4.1.3.	Non-target Terrestrial Plants
PAGEREF _Toc191187575 \h  81

  HYPERLINK \l "_Toc191187576"  <IP_ADDRESS>.	Non-Endangered and Endangered
Plant Risks	  PAGEREF _Toc191187576 \h  81

  HYPERLINK \l "_Toc191187577"  4.1.4.	Use of Contaminated Irrigation
Waters	  PAGEREF _Toc191187577 \h  82

  HYPERLINK \l "_Toc191187578"  4.2.	RISK DESCRIPTION	  PAGEREF
_Toc191187578 \h  83

  HYPERLINK \l "_Toc191187579"  4.2.1.	Risk to Aquatic Animals and
Plants	  PAGEREF _Toc191187579 \h  83

  HYPERLINK \l "_Toc191187580"  <IP_ADDRESS>.	Fish and Aquatic Invertebrates
 PAGEREF _Toc191187580 \h  83

  HYPERLINK \l "_Toc191187581"  <IP_ADDRESS>.	Non-target Aquatic-phase
Amphibians	  PAGEREF _Toc191187581 \h  85

  HYPERLINK \l "_Toc191187582"  <IP_ADDRESS>.	Aquatic Plants	  PAGEREF
_Toc191187582 \h  86

  HYPERLINK \l "_Toc191187583"  <IP_ADDRESS>.	Aquatic Toxicity of
Sulfometuron Methyl Degradates	  PAGEREF _Toc191187583 \h  87

  HYPERLINK \l "_Toc191187584"  4.2.2.	Risk to Terrestrial Animals
PAGEREF _Toc191187584 \h  90

  HYPERLINK \l "_Toc191187585"  <IP_ADDRESS>.	Birds	  PAGEREF _Toc191187585
\h  90

  HYPERLINK \l "_Toc191187586"  <IP_ADDRESS>.	Mammals	  PAGEREF _Toc191187586
\h  92

  HYPERLINK \l "_Toc191187587"  <IP_ADDRESS>.	Non-target Terrestrial-phase
Amphibians, Reptiles, and Beneficial Insects	  PAGEREF _Toc191187587 \h
92

  HYPERLINK \l "_Toc191187588"  4.2.3.	Risk to Terrestrial Plants
PAGEREF _Toc191187588 \h  92

  HYPERLINK \l "_Toc191187589"  <IP_ADDRESS>.	Tier 1 Modeling of Runoff and
Spray Drift	  PAGEREF _Toc191187589 \h  92

  HYPERLINK \l "_Toc191187590"  <IP_ADDRESS>.	Field and Greenhouse Studies
PAGEREF _Toc191187590 \h  93

  HYPERLINK \l "_Toc191187591"  <IP_ADDRESS>.	Contaminated Irrigation Water
PAGEREF _Toc191187591 \h  94

  HYPERLINK \l "_Toc191187592"  4.2.4.	Refined Spray Drift Analysis
PAGEREF _Toc191187592 \h  95

  HYPERLINK \l "_Toc191187593"  4.2.5.	Review of Incident Data	  PAGEREF
_Toc191187593 \h  97

  HYPERLINK \l "_Toc191187594"  4.2.6.	Overall Ecological Risk
Conclusions	  PAGEREF _Toc191187594 \h  98

  HYPERLINK \l "_Toc191187595"  4.2.7.	Endocrine Effects	  PAGEREF
_Toc191187595 \h  99

  HYPERLINK \l "_Toc191187596"  4.2.8.	Federally Threatened and
Endangered (Listed) Species	  PAGEREF _Toc191187596 \h  99

  HYPERLINK \l "_Toc191187597"  <IP_ADDRESS>.	Action Area	  PAGEREF
_Toc191187597 \h  99

  HYPERLINK \l "_Toc191187598"  <IP_ADDRESS>.	Taxonomic Groups Potentially at
Risk	  PAGEREF _Toc191187598 \h  100

  HYPERLINK \l "_Toc191187599"  4.3.	Description of Assumptions,
Limitations, Uncertainties, and Data Gaps	  PAGEREF _Toc191187599 \h
105

  HYPERLINK \l "_Toc191187600"  4.3.1.	Assumptions and Limitations
Related to Effects on all Species	  PAGEREF _Toc191187600 \h  105

  HYPERLINK \l "_Toc191187601"  4.3.2.	Assumptions and Limitations
Related to Effects on Aquatic Species	  PAGEREF _Toc191187601 \h  107

  HYPERLINK \l "_Toc191187602"  4.3.3.	Assumptions and Limitations
Related to Effects on Terrestrial Species	  PAGEREF _Toc191187602 \h
107

  HYPERLINK \l "_Toc191187603"  5.	Literature Cited	  PAGEREF
_Toc191187603 \h  108

  HYPERLINK \l "_Toc191187604"  6.	APPENDICES	  PAGEREF _Toc191187604 \h
 111

  HYPERLINK \l "_Toc191187605"  APPENDIX A: Structures and Chemical
Names of Sulfometuron methyl Metabolites	  PAGEREF _Toc191187605 \h  111

  HYPERLINK \l "_Toc191187606"  APPENDIX B: Environmental Fate Data
Requirements	  PAGEREF _Toc191187606 \h  113

  HYPERLINK \l "_Toc191187607"  APPENDIX C:  Ecological Aquatic Exposure
Modeling	  PAGEREF _Toc191187607 \h  115

  HYPERLINK \l "_Toc191187608"  APPENDIX D:  Terrplant Spreadsheet
PAGEREF _Toc191187608 \h  123

  HYPERLINK \l "_Toc191187609"  APPENDIX E: Adverse Ecological Incidents
Associated with Sulfometuron Methyl Use	  PAGEREF _Toc191187609 \h  125

  HYPERLINK \l "_Toc191187610"  APPENDIX F: T-REX Output	  PAGEREF
_Toc191187610 \h  127

  HYPERLINK \l "_Toc191187611"  APPENDIX G:  Modeling of Terrestrial
plant Exposure from Contaminated irrigation Water	  PAGEREF
_Toc191187611 \h  129

  HYPERLINK \l "_Toc191187612"  APPENDIX H: Ecological Effects Data
Summaries	  PAGEREF _Toc191187612 \h  131

  HYPERLINK \l "_Toc191187613"  APPENDIX I; Ecological Effects Data
Requirements	  PAGEREF _Toc191187613 \h  144

  HYPERLINK \l "_Toc191187614"  APPENDIX J: Ecological Effects Studies
Rejected by OPP	  PAGEREF _Toc191187614 \h  146

LIST OF TABLES

  TOC \h \z \c "Table"    HYPERLINK \l "_Toc191187615"  Table 1.  Listed
Taxonomic Groups Potentially at Risk from Direct or Indirect Effects of
Sulfometuron Methyl Application for Vegetative Management Throughout the
U.S.	  PAGEREF _Toc191187615 \h  12

  HYPERLINK \l "_Toc191187616"  Table 2. Nature and product chemistry of
the chemical stressor - Sulfometuron methyl.	  PAGEREF _Toc191187616 \h
15

  HYPERLINK \l "_Toc191187617"  Table 3.  Taxonomic Groups, Test Species
and Acute Toxicity Classification for Assessing Ecological Risks of
Sulfometuron Methyl to Non-target Organisms.	  PAGEREF _Toc191187617 \h
18

  HYPERLINK \l "_Toc191187618"  Table 4.  Measures of Ecological Effects
and Exposure for Sulfometuron Methyl	  PAGEREF _Toc191187618 \h  26

  HYPERLINK \l "_Toc191187619"  Table 5. Permitted application methods
for sulfometuron methyl, DuPont Products	  PAGEREF _Toc191187619 \h  28

  HYPERLINK \l "_Toc191187620"  Table 6. Permitted application methods
for sulfometuron methyl, Vegetation Management LLC Products	  PAGEREF
_Toc191187620 \h  28

  HYPERLINK \l "_Toc191187621"  Table 7.  States with high sulfometuron
usage (based upon DuPont sales data, 2001-2004).	  PAGEREF _Toc191187621
\h  28

  HYPERLINK \l "_Toc191187622"  Table 8.  Annual usage of sulfometuron
methyl in the US by use site.	  PAGEREF _Toc191187622 \h  29

  HYPERLINK \l "_Toc191187623"  Table 9.  Sulfometuron application rate
ranges by product label and use site.	  PAGEREF _Toc191187623 \h  30

  HYPERLINK \l "_Toc191187624"  Table 10. Key results of sulfometuron
methyl environmental fates studies.	  PAGEREF _Toc191187624 \h  35

  HYPERLINK \l "_Toc191187625"  Table 11.  Models Used to Estimate
Exposure Concentrations for Aquatic Ecosystem.	  PAGEREF _Toc191187625
\h  44

  HYPERLINK \l "_Toc191187626"  Table 12. Aquatic exposure with PRZM –
EXAMS: Modeling scenarios and representative usage pattern summary.
PAGEREF _Toc191187626 \h  45

  HYPERLINK \l "_Toc191187627"  Table 13.  PRZM/EXAMS input parameters
for modeling (Aquatic ecological EECs).	  PAGEREF _Toc191187627 \h  46

  HYPERLINK \l "_Toc191187628"  Table 14.  Estimated environmental
concentrations (µg/L) for aquatic exposure to parent sulfometuron
methyl: scenario-specific results from PRZM-EXAMS modeling.	  PAGEREF
_Toc191187628 \h  48

  HYPERLINK \l "_Toc191187629"  Table 15.  Sulfometuron methyl surface
water EECs used in aquatic risk assessment.	  PAGEREF _Toc191187629 \h
50

  HYPERLINK \l "_Toc191187630"  Table 16. Estimated concentrations of
sulfometuron methyl in ground water (SCI-GROW inputs and results).
PAGEREF _Toc191187630 \h  50

  HYPERLINK \l "_Toc191187631"  Table 17.  Unadjusted Dietary
Terrestrial EECs for Birds and Mammals Following Sulfometuron Methyl
Spray Application For Non-Crop Vegetative Management.	  PAGEREF
_Toc191187631 \h  52

  HYPERLINK \l "_Toc191187632"  Table 18.   EECs for Terrestrial Plants
Located Adjacent to Sulfometuron Methyl (aerial and ground spray
application) Treated Sites.	  PAGEREF _Toc191187632 \h  53

  HYPERLINK \l "_Toc191187633"  Table 19.  Selected AgDRIFT inputs for
high-end exposure from aerial applications of sulfometuron methyl using
best management practices.	  PAGEREF _Toc191187633 \h  54

  HYPERLINK \l "_Toc191187634"  Table 20.  Estimated percentage of
sulfometuron methyl spray drift from ground or aerial applications at
various distances from a treated field.	  PAGEREF _Toc191187634 \h  55

  HYPERLINK \l "_Toc191187635"  Table 21.  Estimated amount of
sulfometuron methyl spray drift from ground or aerial applications at
various distances from a field treated with  the maximum labeled rate of
0.375 lb ai/A.	  PAGEREF _Toc191187635 \h  56

  HYPERLINK \l "_Toc191187636"  Table 22.  The Most Sensitive Endpoints
Used In The Sulfometuron Methyl Screening-Level Risk Estimation.
PAGEREF _Toc191187636 \h  59

  HYPERLINK \l "_Toc191187637"  Table 23.  Freshwater Fish Acute
Toxicity of Sulfometuron Methyl.	  PAGEREF _Toc191187637 \h  60

  HYPERLINK \l "_Toc191187638"  Table 24.  Freshwater Invertebrate Acute
Toxicity of Sulfometuron Methyl.	  PAGEREF _Toc191187638 \h  60

  HYPERLINK \l "_Toc191187639"  Table 25.  Estuarine/Marine Fish Acute
Toxicity of Sulfometuron Methyl.	  PAGEREF _Toc191187639 \h  61

  HYPERLINK \l "_Toc191187640"  Table 26.  Freshwater Invertebrate Acute
Toxicity of Sulfometuron Methyl.	  PAGEREF _Toc191187640 \h  62

  HYPERLINK \l "_Toc191187641"  Table 27.  Freshwater Aquatic
Invertebrate Chronic Toxicity for Sulfometuron Methyl.	  PAGEREF
_Toc191187641 \h  63

  HYPERLINK \l "_Toc191187642"  Table 28.  Non-target Aquatic Plant
Toxicity for Sulfometuron Methyl.	  PAGEREF _Toc191187642 \h  66

  HYPERLINK \l "_Toc191187643"  Table 29.  Avian Acute Oral Toxicity for
Sulfometuron Methyl.	  PAGEREF _Toc191187643 \h  67

  HYPERLINK \l "_Toc191187644"  Table 30.  Avian Subacute Dietary
Studies for Sulfometuron Methyl.	  PAGEREF _Toc191187644 \h  67

  HYPERLINK \l "_Toc191187645"  Table 31.  Mammalian Acute Toxicity for
Sulfometuron Methyl.	  PAGEREF _Toc191187645 \h  68

  HYPERLINK \l "_Toc191187646"  Table 32.  Non-Target Insects - Acute
Contact Toxicity for Sulfometuron Methyl.	  PAGEREF _Toc191187646 \h  68

  HYPERLINK \l "_Toc191187647"  Table 33.  Mammalian Developmental
Toxicity of Sulfometuron Methyl .	  PAGEREF _Toc191187647 \h  69

  HYPERLINK \l "_Toc191187648"  Table 34.  Mammalian Acute Toxicity to
Sulfometuron Methyl in Formulated Product: DPX-T5486-87	  PAGEREF
_Toc191187648 \h  70

  HYPERLINK \l "_Toc191187649"  Table 35.  Summary of Most Sensitive
Tier II Terrestrial Non-target Plant Seedling Emergence and Vegetative
Vigor Toxicity Data for Sulfometuron Methyl.	  PAGEREF _Toc191187649 \h
72

  HYPERLINK \l "_Toc191187650"  Table 36.  Risk Presumptions for Aquatic
Animals.	  PAGEREF _Toc191187650 \h  74

  HYPERLINK \l "_Toc191187651"  Table 37.  Risk Presumptions for
Terrestrial Animals.	  PAGEREF _Toc191187651 \h  74

  HYPERLINK \l "_Toc191187652"  Table 38.  Risk Presumptions for Plants.
  PAGEREF _Toc191187652 \h  74

  HYPERLINK \l "_Toc191187653"  Table 39.  Endpoints Used for Estimating
Risks of Sulfometuron Methyl to Aquatic Animals and Plants.	  PAGEREF
_Toc191187653 \h  75

  HYPERLINK \l "_Toc191187654"  Table 40.  Summary of Acute Aquatic
Plant Risk Quotients for Rights of Way Uses.	  PAGEREF _Toc191187654 \h
76

  HYPERLINK \l "_Toc191187655"  Table 41.  Endpoints Used for Estimating
Risks of Sulfometuron Methyl to Terrestrial Animals.	  PAGEREF
_Toc191187655 \h  77

  HYPERLINK \l "_Toc191187656"  Table 42.  Upper Bound Kenaga, Acute
Avian Dose-Based Risk Quotients (Bounding Analysis Only).	  PAGEREF
_Toc191187656 \h  78

  HYPERLINK \l "_Toc191187657"  Table 43. Upper Bound Kenaga, Subacute
Dietary-Based Risk Quotients (Bounding Analysis Only).	  PAGEREF
_Toc191187657 \h  78

  HYPERLINK \l "_Toc191187658"  Table 44.   Upper Bound Kenaga, Acute
Mammalian Dose-Based  Risk Quotients (Bounding Analysis Only).	  PAGEREF
_Toc191187658 \h  79

  HYPERLINK \l "_Toc191187659"  Table 45.  Upper Bound Kenaga, Chronic
Mammalian Dose-Based Risk Quotients.	  PAGEREF _Toc191187659 \h  79

  HYPERLINK \l "_Toc191187660"  Table 46.  Upper Bound Kenaga, Chronic
Mammalian Dietary-Based Risk Quotients	  PAGEREF _Toc191187660 \h  80

  HYPERLINK \l "_Toc191187661"  Table 47.  Summary of Selected Endpoints
from Terrestrial Plant Toxicity Studies of Sulfometuron Methyl	  PAGEREF
_Toc191187661 \h  81

  HYPERLINK \l "_Toc191187662"  Table 48.  RQ Values For Plants In Dry
And Semi-Aquatic Areas Exposed To Sulfometuron Methyl Through Runoff
And/Or Spray Drift.	  PAGEREF _Toc191187662 \h  81

  HYPERLINK \l "_Toc191187663"  Table 49.  Risk Quotients for Non-target
and Endangered Plants, Resulting From Exposure to Sulfometuron Methyl in
Irrigation Water	  PAGEREF _Toc191187663 \h  82

  HYPERLINK \l "_Toc191187664"  Table 50.  Toxicity of sulfometuron
methyl to the African clawed frog from a study by Fort et al.  (1999).
PAGEREF _Toc191187664 \h  86

  HYPERLINK \l "_Toc191187665"  Table 51.  ECOSAR-predicted toxicity
values for major degradates of sulfometuron methyl.	  PAGEREF
_Toc191187665 \h  88

  HYPERLINK \l "_Toc191187666"  Table 52.  Risks to Terrestrial Plants
from Spray Drift According to Distance Downwind, Application Method, and
Drift Exposure Conditions	  PAGEREF _Toc191187666 \h  95

  HYPERLINK \l "_Toc191187667"  Table 53.  Listed Taxonomic Groups
Potentially at Risk from Direct or Indirect Effects of Sulfometuron
Methyl Application for Vegetative Management Throughout the U.S.
PAGEREF _Toc191187667 \h  104

LIST OF FIGURES

  TOC \h \z \c "Figure"    HYPERLINK \l "_Toc191187668"  Figure 1.
Conceptual model for sulfometuron methyl fate and effects in aquatic
ecosystems.	  PAGEREF _Toc191187668 \h  22

  HYPERLINK \l "_Toc191187669"  Figure 2. Conceptual model for
sulfometuron methyl fate and effects in terrestrial ecosystems.
PAGEREF _Toc191187669 \h  23

  HYPERLINK \l "_Toc191187670"  Figure 3. Chronic Toxicity of
Sulfonylurea Herbicides to Freshwater Fish	  PAGEREF _Toc191187670 \h
84

  HYPERLINK \l "_Toc191187671"  Figure 4. Chronic Avian Toxicity of
Sulfonylurea Herbicides	  PAGEREF _Toc191187671 \h  91

EXECUTIVE SUMMARY  TC \l1 "I.  EXECUTIVE SUMMARY

Nature of Chemical Stressor

Sulfometuron methyl, (2-[[[[(4,6-Dimethyl-2-pyrimidinyl) amino]
carbonyl] amino] sulfonyl] benzoic acid, methyl ester), is a
broad-spectrum pre- and post-emergence herbicide that is currently
registered for weed control in forestry and non-food crop situations,
including vegetative management in right of ways and railroads.  It is
used to control a variety of broad-leaf weeds and grasses.  Similar to
other sulfonylurea herbicides, the mode of action of sulfometuron methyl
involves inhibiting the activity of the enzyme acetolactate synthase
(ALS), which in turn inhibits the synthesis of selected amino acids that
are required for cell proliferation in plants.

Sulfometuron methyl is formulated as a water dispersible granule (WDG)
and applied using a variety of methods including helicopter, fixed-wing
aircraft, ground spray (boom and backpack) and spot treatment.  It is
generally applied once per year for non-crop areas in years that
vegetation management is needed. In some instances (weed escapes) a
second application may be made, but all products limit the total
quantity of sulfometuron methyl that may be applied (from any source) to
6 ounces of active ingredient per acre per year (0.375 lb ai/A).
Therefore, application rates in general forestry, and for site
preparation and/or release in conifer, hardwood and Christmas tree
plantations, will vary significantly depending upon the specific purpose
of the application and the desirable tree species.  In forestry, uses
can be similar to plantation sites, but may also include the maintenance
of access routes and fire breaks.  It is further noted that use rates
can also vary with climate and soil type.

Conclusions- Exposure Characterization

1.2.1.	Environmental Fate

a.	Persistence

Sulfometuron methyl is expected to be relatively persistent in soil and
water (half-life ranging from about 2 weeks to 6 months, depending on
environmental conditions).  The persistence of sulfometuron is likely to
be lowest under low pH conditions in soil and water.

Abiotic and microbially-mediated hydrolysis / degradation are both major
routes of transformation of sulfometuron methyl in water, soil, and
water-sediment systems. The degradation in soil and water appears to be
enhanced in the presence of an active microbial population (aerobic and
anaerobic degradation both proceed more slowly under sterile
conditions).

b.	Transport and Bioaccumulation

Sulfometuron has a low potential to volatilize from soil or water or to
bioaccumulate. Off-site  transport of sulfometuron methyl occurs via
spray drift, and the wind erosion of soil particulates containing
sulfometuron  methyl.

Sulfometuron methyl does not sorb strongly to soils and has the
potential to leach to ground water and/or reach surface water during
runoff events.  Sulfometuron methyl is a weak acid (pKa of 5.2).  The
mobility of sulfometuron methyl is expected to increase with increasing
pH based upon available data submitted to EPA for related sulfonylurea
herbicides and published studies; however direct, definitive evidence of
this for sulfometuron methyl has not been produced.

Conclusions- Effects Characterization

Available acute toxicity data for freshwater fish and invertebrates
indicate that sulfometuron methyl is practically non-toxic on an acute
exposure basis.  All EC50s/ LC50s are >100 mg/L. For marine and
estuarine fish and invertebrates, available acute toxicity data indicate
that sulfometuron methyl is at most slightly toxic on an acute exposure
basis (EC50/ LC50s range from >38 to >45 mg ai/L).

No acceptable studies were available for evaluating the effects of
chronic exposure to sulfometuron methyl on freshwater, estuarine or
marine fish.  Chronic NOAEC for freshwater fish was therefore estimated
to be >21 mg ai/L using an acute-chronic ratio derived from
flazasulfuron, another sulfonylurea herbicide with the same mode of
action.  The aquatic invertebrate NOAEC is 97 mg ai/L (highest
concentration tested) at which survival and reproduction were not
significantly different from controls.  Estimated chronic effects for
estuarine/marine fish and invertebrates are uncertain because no chronic
data on saltwater species were submitted by the registrant.  However,
comparison of freshwater and saltwater species acute toxicity values
does not suggest considerable differences in sensitivity between
freshwater and saltwater species.

Aquatic vascular plants are more sensitive than any of the aquatic
nonvascular plants tested.  The 14-day EC50 and NOAEC for the freshwater
vascular plant (duckweed) for frond count (the most sensitive endpoint
tested) was 0.48 and 0.21 μg/L, respectively.  The green-algae was the
most sensitive non-vascular plant tested with EC50 and NOAEC values of
4.6 and 0.63 μg/L, respectively, based on cell density.

Sulfometuron methyl is practically non-toxic to birds (LD50 >4,650
mg/kg-bw; LC50 >4,600 mg/kg-diet), mammals (LD50 >5000 mg/kg-bw), and
bees (LD50 >100 ug/bee) on an acute toxicity basis.  No sublethal
effects were observed from the acute toxicity studies of birds and
mammals.  Data on reproductive effects of sulfometuron methyl to birds
were not available.  Acceptable data on mammalian reproductive effects
were also not available.  Data on the effects of gestational exposure to
sulfometuron methyl were available from a rabbit developmental toxicity
study which resulted in a NOAEL of 300 mg ai/kg-bw/d (highest dose
tested).

Seedling emergence and vegetative vigor studies in terrestrial plants
were submitted by the registrant.  Based on the most sensitive species
and endpoints reported, sulfometuron methyl is slightly more toxic to
terrestrial plants in the vegetative vigor study compared to seedling
emergence.  The seedling emergence EC25 for the most sensitive dicot
(sugar beet) and monocot (sorghum) are 3.2 x 10 -5 and 1.9 x 10 -4 lb
ai/A, respectively.  The vegetative vigor EC25 for the most sensitive
dicot (soybean) and monocot (corn) are 1.8 x 10 -5 and 3.7 x 10 -5 lb
ai/A, respectively. The guideline seedling emergence and vegetative
vigor studies reported non-lethal effects of sulfometuron methyl
exposure on plants such as chlorosis, growth retardation, necrosis, and
unusual pigmentation.

Potential Risks to Non-target Animals and Plants

Potential risks to aquatic and terrestrial plants are indicated by this
risk assessment, as LOCs are widely exceeded for terrestrial and aquatic
plants at the maximum application rate.  For terrestrial plants, RQs
calculated at the edge of a treated field resulting from spray drift
alone were as high as 22,000 for non-endangered plants and 400,000 for
endangered plants.  Terrestrial plant RQs dropped substantially 50 ft
from the edge of a treated field but still exceeded Agency LOCs at 900
ft (700 to 12,000 for non-endangered and endangered plants,
respectively.  The impact of spray drift practices recommended by the
label did not reduce RQ values below LOCs for terrestrial plants (RQs
were reduced only by a factor of three compared to ‘high end’
exposure assumptions).  Potential risks to terrestrial plants from
irrigation with sulfometuron methyl contaminated surface water were also
evident (RQ = 3.9 and 71 for non-endangered and endangered species,
respectively).

 model (e.g., 90-d EEC of 16 μg/L), the ability of duckweed and other
vascular aquatic plants to recover from predicted long-term exposure
concentrations of sulfometuron methyl in adjacent, static aquatic
systems appears unlikely under the exposure conditions modeled.

Although use of ‘typical’ application rates would result in RQs of
up to one order of magnitude lower than the maximum application rate,
RQs would still exceed Agency LOCs for terrestrial and aquatic plants.
The conclusion of potential risks to aquatic and terrestrial plants from
sulfometuron methyl application in non-crop uses is consistent with
findings from other sulfonylurea herbicide risk assessments and
ecological incident reports associated with sulfometuron methyl usage.
Wind-driven erosion and drift of sulfometuron was implicated in one of
the largest ecological incidents reported following its application (as
Oust) to fire-damaged rangeland (crop damage estimated at $72 million).
Although LOCs were not exceeded for terrestrial or aquatic animals,
animals that depend on plants for survival or reproduction (presumably
all taxa at the screening level) are also potentially at risk from
indirect effects resulting from direct effects of sulfometuron to
aquatic or terrestrial plants.

An analysis of the of the effects of various spray drift management
practices (using the AgDRIFT model; see   HYPERLINK
"http://www.agdrift.com/AgDRIFt2/DownloadAgDrift2_0.htm"
http://www.agdrift.com/AgDRIFt2/DownloadAgDrift2_0.htm  ) demonstrates
that a substantial reduction in off-site exposure is possible with the
implementation of application methods known to reduce drift.  Droplet
size is important in controlling spray drift. Using larger droplet
sizes, such as coarse or extremely coarse spraying, reduces the downwind
drift to adjacent areas compared to when medium or fine spraying is
used. Thus, this assessment suggests that by placing drift management
practices on labels such as specifying coarse or extremely coarse sprays
(based on the ASAE standard), risks to non-target plants would not
extend as far from the treated area. Reducing boom height during
application and applying when wind speeds are between 3 and 10 mph are
other examples of practices that control drift.  Many of these practices
are recommended, but not required by the product labels (see Section
REF _Ref179644072 \w \h  \* MERGEFORMAT  <IP_ADDRESS>  and   REF
_Ref179645835 \w \h  \* MERGEFORMAT  <IP_ADDRESS>  for more details).

In addition, in regions where sulfometuron methyl has been used
regularly, sulfometuron methyl concentrations in surface irrigation
water may result in damage to agricultural crops that are sensitive to
sulfometuron methyl.

Conclusions - Endangered Species

Direct effects LOCs were exceeded for endangered aquatic and terrestrial
plants.  In addition, there is potential for indirect effects to all
animal taxa that depend on plants for survival, growth, or reproduction,
which are presumably all animal taxa at the screening level. Therefore,
listed species from all taxonomic groups are potentially at risk from
sulfometuron methyl uses.

The results of this screening risk assessment indicate that direct
effects to plant species could present an indirect risk at the higher
levels of organization (i.e. population, trophic level, community, and
ecosystem).  The distance from the treated area that risks could extend
is greater than 900 ft, which is the maximum distance that EFED’s Tier
2 spray drift model (AgDRIFT; information on this model is available at
 HYPERLINK "http://www.agdrift.com/AgDRIFt2/DownloadAgDrift2_0.htm"
http://www.agdrift.com/AgDRIFt2/DownloadAgDrift2_0.htm  ) can estimate.
Due to the wide geographic distribution of potential application areas
for non-crop uses of sulfometuron methyl, an action area for endangered
species cannot be defined at this time for this assessment.  A model is
available for extending predictions of deposition from spray drift
beyond 1000 feet (AgDISP with Gaussian extension; see Teske and Thistle,
2004; and Thistle et al., 2005).  However, the trends observed in
modeling of drift out to 900 feet downwind from treated areas imply that
potential risks to the most sensitive species (non-target terrestrial
plants) are likely to extend well beyond 1000 feet given the currently
available information for our Tier II assessment. Field studies are not
available to quantify actual risk to plant and animal communities in
forest/edge and wetland/riparian habitats.  However, in terrestrial and
shallow-water aquatic communities, plants are the primary producers upon
which the succeeding trophic levels depend.  If the available plant
material is impacted due to the effects of sulfometuron methyl, this may
have negative effects not only on the herbivores, but also throughout
the food chain.  Also, depending on the severity of impacts to the plant
communities [i.e., forests, wetlands, ecotones (edge and riparian
habitats)], community assemblages and ecosystem stability may be altered
(i.e. reduced bird populations in edge habitats; reduced riparian
vegetation resulting in increased light penetration and temperature in
aquatic habitats, loss of cover and food for fish).  In addition,
riparian vegetation, which is a significant component of the food supply
for aquatic herbivores and detritivores provides habitat (i.e. leaf
packs, materials for case-building for invertebrates) may also be
affected.

The following table provides listed taxonomic groups that may be at risk
from direct or indirect effects due to applications of sulfometuron
methyl for vegetative management uses nationwide.

Table   SEQ Table \* ARABIC  1 .  Listed Taxonomic Groups Potentially at
Risk from Direct or Indirect Effects of Sulfometuron Methyl Application
for Vegetative Management Throughout the U.S.

Listed Taxon	Direct Effects	Basis for Direct Effects Concern	Indirect
Effects	Basis for Indirect Effects Concern

Terrestrial and Semi-Aquatic Plants – monocots and dicots	Yes	The
endangered and non-endangered species LOCs are exceeded for terrestrial
plants. 	Yes	Potential concerns from shifts in plant community structure
and function due to from selective impacts on plant species.

Terrestrial Invertebrates	No	Sulfometuron methyl is practically nontoxic
to honeybees, suggesting no direct effect concerns for terrestrial
invertebrates.	Yes	Potential concerns for terrestrial invertebrates that
use plants for habitat, feeding, or cover requirements.

Birds and Reptiles1	No	The LOC is not exceeded	Yes	Potential concerns
for birds and reptiles that use plants for habitat, feeding, or cover
requirements.

Terrestrial-phase Amphibians(1)	No	The LOC is not exceeded 	Yes
Potential concerns for terrestrial-phase amphibians that use plants for
habitat, feeding, or cover requirements.

Mammals

	No	The LOC is not exceeded 	Yes	Potential concerns for mammals that use
plants for habitat, feeding, or cover requirements.

Aquatic Vascular Plants and Nonvascular Plants	Yes	The endangered and
non-endangered species LOCs are exceeded for aquatic vascular and
nonvascular plants. 	Yes	Potential concerns from shifts in plant
community structure and function due to from selective impacts on plant
species.

Freshwater and Marine/Estuarine fish and Aquatic-phase Amphibians(2)	No
The LOC is not exceeded	Yes	Potential concerns for fish and
aquatic-phase amphibians that use plants for habitat, feeding, or cover
requirements.

Freshwater and Marine/Estuarine Crustaceans	No	The LOC is not exceeded
Yes	Potential concerns for crustaceans that use plants for habitat,
feeding, or cover requirements.

Mollusks	No	The LOC is not exceeded	Yes	Potential concerns for mollusks
that use plants for habitat, feeding, or cover requirements.

(1) Birds are used as surrogate species for terrestrial-phase amphibians
and reptiles; therefore, potential direct and indirect effects to
endangered avian, terrestrial-phase amphibians and reptilian species are
considered equivalent.

(2) Fish are used as a surrogate for aquatic phase amphibians;
therefore, potential direct and indirect effects to endangered fish and
aquatic-phase amphibian species are considered equivalent.

Identification of Uncertainties and Their Impact on the Risk Assessment

Environmental Fate and Exposure

Limitations In Knowledge Of Actual Use Patterns

Specific regions of use are not known.  The use pattern of sulfometuron
methyl does not lend itself to easy characterization geographically:
There are a variety of vegetation management uses on sites that are less
clearly defined than agricultural crops and have disjoint or unusual
treatment area configurations (e.g., as with rights of way and railroad
uses, or industrial site grounds)

Practical limits on usage rates long-term at particular sites may
different from legally allowable use levels (e.g., usage is highly
unlikely to occur every year at a particular site even though this is
allowable under the label language)

Variability In Sulfometuron Environmental Persistence

Sulfometuron methyl persistence is significantly affected by soil or
water chemistry and may not always be easy to predict from typically
available soil / water property data alone.  A clearer picture of the
range of variability in sulfometuron methyl persistence in the
environment would require environmental fate studies on a greater
variety of soils / waters / sediments with a greater range of pH levels
and other soil properties. This is particularly true for the aerobic
soil and anaerobic aquatic metabolism studies

Insufficient Data And Methods Are Currently Available For Predicting
Exposure To Sulfometuron Methyl Degradates.

The total residues of sulfometuron methyl including environmentally
significant degradates were not modeled with PRZM-EXAMS because of data
and model limitations.

Limitations in environmental fate data for the degradates constrains the
modeling. The data on individual degradates, environmental persistence
and mobility is insufficient to model each compound separately.
Furthermore, total residue modeling with the currently available
receiving water body assumes residues concentrate in that body (pond)
since:

 available data require assumptions of total stability of sulfometuron
total residues (because insufficient decline data are available from the
laboratory studies);

The existing surface water exposure scenario assumes these stable
residues do not migrate from the pond and simply concentrate in the pond
as applications of sulfometuron methyl are applied to the watershed.

Data on sulfometuron effects on plants implies that low levels of
sulfometuron methyl in soil and water may adversely affect the growth of
sensitive terrestrial or aquatic species. For some sulfonylurea
herbicides concentrations below 1ug/L in water or 1ug/kg in soil have
been shown to affect the growth of sensitive plant species.

Ecological Effects

Indirect Effects to Animals. In this screening-level risk assessment,
aquatic and terrestrial plants were found to be at potential risk from
the modeled sulfometuron methyl uses.  Therefore, the potential exists
for indirect effects on aquatic and terrestrial animals that depend on
plants adversely affected by exposure to sulfometuron methyl.  These
indirect effects on aquatic and terrestrial animals could be expressed
at the organism, population, community or ecosystem level of
organization.  No acceptable field studies were available to quantify
the indirect effects of sulfometuron methyl to aquatic or terrestrial
animals.  Because risks associated with indirect effects on aquatic and
terrestrial animals could not be assessed, ecological risks to animals
could be underestimated to the extent that such indirect effects occur.

Ecological Risk of Sulfometuron Methyl Degradation Products.  In this
screening level ecological risk assessment, ecological risks associated
with the major degradates of sulfometuron methyl (e.g., pyrimidine
amine, pyrimidine-ol, saccharin, sulfonamide) could not be reliably
assessed.  Reasons for this limitation are two-fold.  First, the vastly
different chemistries of the degradates (and likely correspondent
differences in toxicological profiles) essentially precluded a
meaningful application of the total residue approach in the exposure
assessment.  Second, acceptable ecotoxicity data were not available for
the degradates.  Because the chemical structure and environmental
behavior of the major degradates differ substantially from the parent
molecule (i.e., degradation involves cleavage of the sulfonylurea
bridge, essentially splitting the molecule in half), it could not be
assumed with reasonable confidence that the degradates are equivalent in
toxicity to the parent compound.

Toxicity Data Quality and Data Gaps. Acceptable or supplemental toxicity
data were not available for assessing the chronic toxicity of
sulfometuron methyl to freshwater fish or the reproductive toxicity to
birds and mammals.  A bounding analysis suggests that the risk
assessment results are not likely to be sensitive to the lack of chronic
toxicity data for fish, given the large difference between EECs and
extrapolated toxicity limits.  For mammals, the NOAEL of 300 mg
ai/kg-bw/d was used from a developmental toxicity study to rabbits.
While providing some information on the effect of sulfometuron methyl on
mammalian development during gestational exposure, results from this
study do not capture the potential effects of sulfometuron methyl on
reproductive endpoints including courtship, mating, sex ratios and
offspring survival, growth and development.  Diet and dose-based RQs
based on this NOAEL were 0.01 or lower, thus indicating that
reproductive toxicity would have to occur at exposures that are
approximately two orders of magnitude lower than developmental effects.

Vascular Plant Reproduction.  Terrestrial and aquatic plants appear most
sensitive to sulfometuron methyl exposure.  While toxicity data were
available for endpoints related to systemic growth, seedling emergence
and visual injury, these guideline studies are not designed to capture
reproductive endpoints.  There is some evidence to suggest plant
reproduction may be affected by sulfonylurea herbicides at levels below
effects on vegetative growth or visual injury (Fletcher et al., 1993).
Therefore, to the extent that terrestrial and aquatic plant reproduction
are more sensitive to sulfometuron methyl than growth endpoints, risks
to aquatic and terrestrial plants may be underestimated in this risk
assessment.

PROBLEM FORMULATION

The purpose of problem formulation is to provide the foundation for the
ecological risk assessment being conducted for sulfometuron methyl.  It
sets the objectives for the risk assessment, evaluates the nature of the
problem, and provides a plan for analyzing the data and characterizing
the risk (US EPA, 1998).

Nature of the Regulatory Action

Under section 4 of the Federal Insecticide, Fungicide, and Rodenticide
Act (FIFRA), EPA is reevaluating existing pesticides to ensure that they
meet current scientific and regulatory standards. With this document,
EPA has completed its baseline environmental fate and ecological effects
risk assessment to support a Reregistration Eligibility Decision (RED)
for the

herbicide, sulfometuron methyl.  Sulfometuron methyl was first
registered for use in 1982 by E.I. du Pont de Nemours and Company
(DuPont); all registered uses then and now have been for vegetation
control in non-agricultural areas.  Currently, both DuPont and
Vegetation Management, LLC have registered end-use products containing
sulfometuron methyl.

Stressor Source and Distribution

Nature of the Chemical Stressor

Sulfometuron methyl, a broad-spectrum pre- and post-emergence herbicide,
is currently registered for weed control in forestry and non-food crop
situations, including vegetative management in rights-of-ways and
railroads.  It is used to control a variety of broad-leaf weeds and
grasses.  Similar to other sulfonylurea herbicides, the mode of action
of sulfometuron methyl involves inhibiting the activity of the enzyme
acetolactate synthase (ALS), which in turn inhibits the synthesis of
selected amino acids that are required for cell proliferation in plants.
 A brief summary of the product chemistry data on sulfometuron methyl is
provided in   REF _Ref184022003 \h  Table 2 .

Table   SEQ Table \* ARABIC  2 . Nature and product chemistry of the
chemical stressor - Sulfometuron methyl.

Common name	Sulfometuron methyl

IUPAC Chemical Name	2-(4,6-Dimethylpyrimidin-2-ylcarbamoylsulfamoyl)
benzoic acid, methyl ester

OR

2-[3-(4,6-dimethylpyrimidin-2-yl)ureidosulfonyl] benzoic acid, methyl
ester

CAS Chemical Name	2-[[[[(4,6-Dimethyl-2-pyrimidinyl) amino] carbonyl]

Pesticide type	Herbicide

Chemical class	Sulfonylurea herbicide

CAS number	74222-97-2

Empirical formula	C15H16N4SO5

Molecular Mass (g/mol)	364.38

Vapor pressure at 20o C	5.4 x10-16 Torr

Henry’s Law Constant at 20o C

(atm m3/mol)	1.1 x 10-18, calculated

from vapor pressure

Solubility in water (mg/L)at 200C	pH 5 buffer...... 6.42 ppm

pH 7 buffer ...... 244 ppm

pH 8.6 buffer.. 12,500 ppm

Log Kow 	pH 5 = 1.03

pH 7 = -0.46

pH 9 = -1.87

pKa at 25°C	5.2

Sulfometuron methyl may be persistent and mobile and may have a
significant impact on ground water and surface water resources.
Degradation half-lives in soil and water range from about 2 weeks to 6
months due to aerobic metabolism, anaerobic aquatic, aerobic aquatic,
and hydrolysis (except in acidic solution the half-life is only about 1
week).  Parent persistence is similar under anaerobic and aerobic
conditions. Complete degradation / mineralization is more rapid under
aerobic conditions and is generally enhanced substantially when microbes
are present. The primary route of degradation is by the following
pathway involving cleavage of the sulfonylurea bridge:

Hydrolytic cleavage generating a sulfonamide plus the aminopyrimidine
(resulting in elimination of a carbon dioxide molecule)

The sulfonamide (produced by hydrolysis of the sulfonylurea) is further
cyclized with the carbomethoxy group in the ortho position, yielding a
saccharin.

Degradation by this same pathway occurs at a slower rate under sterile
conditions.

Sulfometuron methyl is considered “mobile” according to the
classification system of the Food and Agricultural Organization,
Agriculture and Consumer Protection Department’s “Assessing Soil
Contamination: A Reference Manual” (see:   HYPERLINK
"http://www.fao.org/DOCREP/003/X2570E/X2570E06.htm"
http://www.fao.org/DOCREP/003/X2570E/X2570E06.htm  ).  Sulfometuron
methyl mobility is

“high” to “very high” based upon the classification system of
McCall et al. (1981; see also   HYPERLINK
"http://www.epa.gov/oppefed1/ecorisk_ders/terrestrial_field_dissipation.
htm"
http://www.epa.gov/oppefed1/ecorisk_ders/terrestrial_field_dissipation.h
tm  for a description). Soil persistence is sufficient such that
vulnerable aquifers may be expected to be impacted.  Sulfometuron methyl
concentrations in surface waters may be relatively high when significant
runoff events occur after application and / or spray drift to water
bodies in close proximity to the treatment area occurs.

Overview of Pesticide Usage

Sulfometuron methyl is formulated as a water dispersible granule (WDG)
and applied using a variety of methods including helicopter, fixed-wing
aircraft, ground spray (boom and backpack) and spot treatment.
Sulfometuron methyl is registered for non-crop agricultural and
vegetative management uses throughout the United States.  The most
significant uses include forestry and tree nurseries (weed control to
promote seedling growth), vegetative management in utility
right-of-ways, roadsides and railroads, industrial sites (e.g., to
maintain bare ground in utility substations), under asphalt and concrete
prior to paving and for broadleaf weed control in unimproved turf and on
non-crop restoration sites. The highest use areas are believed to be in
Pacific Coast states and the southeastern United States.

The application rates and frequency varies widely depending on use and
the specific pest situation, but all uses are restricted to an annual
maximum application of 6 oz ai./acre.

Receptors

Aquatic and Terrestrial Effects

The receptor is the biological entity that is exposed to the stressor
(US EPA, 1998).  Aquatic receptors potentially at risk include (but are
not limited to): fish, amphibians, invertebrates (e.g., aquatic insects,
mollusks, crustaceans, and worms), vascular plants and algae.
Terrestrial receptors potentially at risk include (but are not limited
to): birds, mammals, reptiles, amphibians, terrestrial invertebrates
(e.g., insects, worms, arachnids), and plants.

Consistent with the process described in the Overview Document (US EPA,
2004), this risk assessment uses a surrogate species approach in its
evaluation of sulfometuron methyl.  T  SEQ CHAPTER \h \r 1 oxicological
data generated from surrogate test species, that are intended to be
representative of broad taxonomic groups, are used to extrapolate to
potential effects on a variety of species (receptors) included under
these taxonomic groupings.

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

  REF _Ref177716963 \h  \* MERGEFORMAT  Table 3  provides a summary of
the taxonomic groups and the surrogate species tested to help understand
potential acute ecological effects of pesticides to these non-target
taxonomic groups.  In addition, the table provides a preliminary
overview of the potential acute toxicity of sulfometuron methyl by
providing the acute toxicity classifications.  Based on a preliminary
review of the ecological effect data, sulfometuron methyl is, for the
most part, practically non-toxic to freshwater fish, freshwater
invertebrates, birds, mammals, and honeybees under acute exposure
conditions.  Acute toxicity to estuarine/marine fish and invertebrates
was not observed at the highest concentrations tested, which fell into
the slightly toxic category. Under chronic exposure conditions, the
sulfometuron methyl inhibited reproduction of both fathead minnow
(Pimephales promelas) and water fleas (Daphnia magna).  Acceptable
chronic reproductive toxicity data were not available for birds or
mammals.  As expected, aquatic and terrestrial plants show the greatest
sensitivity to the parent compound.

Major environmental degradates of sulfometuron methyl most commonly
include: the sulfometuron sulfonamide, the sulfometuron pyrimidine
amine, and saccharin; other degradates occur less commonly (see   REF
_Ref184020399 \h  Table 10  and   REF _Ref177717834 \h  \* MERGEFORMAT
APPENDIX A: Structures and Chemical Names of Sulfometuron methyl
Metabolites ). Other than deesterification from sulfometuron methyl to
the free acid, the degradates are formed from cleavage of the sulfonyl
urea bridge between the phenyl and pyrimidine ring structures.  The
latter compounds are not expected to be substantially phytotoxic,
however, information is requested from the registrant to confirm this.

Table   SEQ Table \* ARABIC  3 .  Taxonomic Groups, Test Species and
Acute Toxicity Classification for Assessing Ecological Risks of
Sulfometuron Methyl to Non-target Organisms.

Taxonomic Group	Example(s) of Surrogate Species	Acute Toxicity
Classification

Birds1	  SEQ CHAPTER \h \r 1 Mallard duck (Anas platyrhynchos)

Bobwhite quail (Colinus virginianus)	Practically non-toxic

  SEQ CHAPTER \h \r 1 Mammals	  SEQ CHAPTER \h \r 1 Laboratory rat
(Rattus norvegicus)	Practically non-toxic

  SEQ CHAPTER \h \r 1 Insects	  SEQ CHAPTER \h \r 1 Honey bee (Apis
mellifera L.)	Practically non-toxic

  SEQ CHAPTER \h \r 1 Freshwater fish2		  SEQ CHAPTER \h \r 1 Bluegill
sunfish (Lepomis macrochirus)

Rainbow trout (Oncorhynchus mykiss)	Practically non-toxic

Practically non-toxic

  SEQ CHAPTER \h \r 1 Freshwater invertebrates	  SEQ CHAPTER \h \r 1
Water flea (Daphnia magna)	Practically non-toxic

  SEQ CHAPTER \h \r 1 Estuarine/marine fish	  SEQ CHAPTER \h \r 1
Sheepshead minnow (Cyprinodon variegatus)	> Slightly toxic4

Estuarine/marine invertebrates	Mysid shrimp (Mysidopsis bahia)

Eastern oyster (Crassostrea virginica)	> Slightly toxic4

> Slightly toxic4

  SEQ CHAPTER \h \r 1 Terrestrial plants3	  SEQ CHAPTER \h \r 1 Monocots
– corn (Zea mays)

Dicots – soybean (Glycine max)	Not classified

  SEQ CHAPTER \h \r 1 Aquatic plants and algae	  SEQ CHAPTER \h \r 1
Duckweed (Lemna gibba)

Green algae (Selenastrum capricornutum)

Bluegreen algae (Anabaena flos-aquae)

Diatom (Navicula pelliculosa)

	Not classified

  SEQ CHAPTER \h \r 1 1 In absence of data, birds are used as surrogates
for terrestrial-phase amphibians and reptiles.

2 In absence of data, freshwater fish may be surrogates for
aquatic-phase amphibians.

3 Data required for 4 species of monocots from 2 families (must include
corn) and 6 species of dicots from 4 families (must include soybean).

4 Toxicity endpoint was greater than the highest concentration tested,
which fell in the slightly toxic category.

Ecosystems at Risk

The ecosystems at potential risk from sulfometuron methyl are extensive
in scope due to the wide geographic distribution of potential
sulfometuron methyl application sites.  As a result, it is not possible
to identify specific ecosystems at risk during the development of this
baseline risk assessment.  However, in general terms, terrestrial
ecosystems potentially at risk could include the treatment areas
directly and adjacent areas that may receive herbicide drift or runoff.
This could include the treatment area itself as well as other cultivated
fields, fencerows and hedgerows, meadows, fallow fields or grasslands,
woodlands, riparian habitats and other uncultivated areas. Within these
ecosystems, available toxicity data indicate terrestrial plants are
highly sensitive to sulfometuron methyl and thus, they could be directly
affected.  Organisms dependent on sensitive terrestrial plants could be
affected indirectly, which could result in subsequent effects at the
community and ecosystem levels.  Birds and mammals appear to be much
less sensitive to the direct exposure of sulfometuron methyl compared to
plants, although they could be affected indirectly to the extent they
depend on affected plants for food and habitat.

Aquatic ecosystems potentially at risk include water bodies adjacent to,
or down stream from, the treatment area and might include impounded
bodies such as ponds, lakes, reservoirs and wetland areas, or flowing
waterways such as streams and rivers. For uses in coastal areas, aquatic
habitat also includes marine ecosystems, including estuaries and salt
marshes.  Similar to the terrestrial ecosystems, available toxicity data
indicate aquatic plants are highly sensitive to sulfometuron methyl
exposure and thus could be directly affected.  Other organisms dependent
on aquatic plants could be affected indirectly.  Aquatic animals appear
to be much less sensitive to direct exposure to sulfometuron methyl
compared to plants, although they could be affected indirectly to the
extent they depend on affected plants for food and habitat.

Assessment Endpoints

Assessment endpoints represent the actual environmental value that is to
be protected, defined by an ecological entity (species, community, or
other entity) and its attribute or characteristics (US EPA, 1998).
For sulfometuron methyl, the ecological entities may include the
following:  birds, mammals, freshwater fish and invertebrates,
estuarine/marine fish and invertebrates, terrestrial plants, insects,
and aquatic plants and algae. The attributes for each of these entities
may include growth, reproduction, and survival and are discussed further
in the Analysis Plan (Section   REF _Ref178558153 \r \h  2.6 ).

Conceptual Model

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

A conceptual model is used in this risk assessment to provide a written
and visual description of the predicted relationships between
sulfometuron methyl, potential routes of exposure, and the predicted
effects for the assessment endpoint. A conceptual model consists of two
major components: risk hypotheses and a conceptual diagram (US EPA,
1998).

Risk Hypotheses

	Risk hypotheses are specific assumptions about potential adverse
effects (i.e., changes in assessment endpoints) and may be based on
theory and logic, empirical data, mathematical models, or probability
models (EPA 1998a).  For sulfometuron methyl, the following ecological
risk hypothesis is being employed for this baseline risk assessment:

Given persistence and mobility of sulfometuron methyl and some of its
degradates, there is a likelihood that terrestrial and/or aquatic
organisms will be exposed when sulfometuron methyl is used in accordance
with the label.  Consequently, considering the mode of action, direct
toxicity and potential indirect effects, labeled uses of sulfometuron
methyl have the potential to cause adverse effects upon the survival,
growth, and reproduction of non-target terrestrial and aquatic plants
and animals.

Conceptual Diagram

Based on the iterative process of examining the usage information, fate
and effects data, the risk hypotheses described previously, conceptual
diagrams are shown in   REF _Ref179505907 \h  Figure 1  and   REF
_Ref179505925 \h  Figure 2  for aquatic and terrestrial ecosystems,
respectively.  These conceptual models illustrate: (1) the most likely
stressors/exposure pathways, and (2) the organisms that are most
relevant and applicable to this assessment.

The dominant sources/transport pathways of sulfometuron methyl to
aquatic ecosystems include spray drift, runoff and erosion from treated
areas to surface waters and aquatic sediments.  Sulfometuron methyl also
has the potential to leach to groundwater which can serve as inputs to
surface water, although this is not explicitly modeled for ecological
effects in this risk assessment due to modeling and data limitations.
Once in surface water and sediments, sulfometuron methyl may be directly
toxic to aquatic vascular plants (rooted macrophytes) and nonvascular
plants (algae) via uptake through the roots or cell membrane.
Sulfometuron methyl exposure in surface water and sediments may also
cause direct toxicity to aquatic animals, although the generally low
toxicity to aquatic animals renders this pathway less of a concern
compared to aquatic plants.  Indirect effects on aquatic animals via
impacts on aquatic plants is also a concern, but is not explicitly
modeled in this risk assessment due to model and data limitations.

The dominant sources/transport pathways of sulfometuron methyl to
terrestrial ecosystems include direct spray on terrestrial food items,
spray drift, runoff and erosion from herbicide treated areas, and
leaching to groundwater.  Wind-driven erosion of treated soils is also a
potential source of concern, particularly to non-target plants but is
not modeled in this risk assessment due to data and modeling
limitations.  Volatilization of sulfometuron methyl is also a potential
source of exposure for terrestrial animals via inhalation, but is of
less concern given its low volatility and low inhalation toxicity based
on mammalian data (MRID 430892-03).  Once sorbed onto food items,
terrestrial animals (birds, mammals) may be exposed to sulfometuron
methyl via diet and dermal absorption, although its low toxicity to
birds and mammals suggest that effects from this exposure pathway are
much less likely than effects on terrestrial plants.  Adverse effects on
non-target terrestrial plants may occur through exposure to herbicide
spray drift, contaminated runoff and groundwater, erosion of herbicide
treated soil via direct contact and root uptake, and irrigation with
contaminated ground water or surface water sources.  Indirect impacts
may occur on animals that depend on affected terrestrial plants for food
or habitat.

Figure   SEQ Figure \* ARABIC  1 . Conceptual model for sulfometuron
methyl fate and effects in aquatic ecosystems.

1 Bold lines and text boxes represent exposure pathways and effects that
were assessed quantitatively in this risk assessment.  Dashed lines
indicate potential exposure pathways or effects that were not assessed
quantitatively.

Figure   SEQ Figure \* ARABIC  2 . Conceptual model for sulfometuron
methyl fate and effects in terrestrial ecosystems.

1 Solid lines and text boxes represent exposure pathways and effects
that were assessed quantitatively in this risk assessment.  Dashed lines
indicate potential exposure pathways or effects that were not assessed
quantitatively.

Analysis Plan  tc \l2 "E.        Analysis Plan

This document characterizes the environmental fate and effects of
sulfometuron methyl to assess whether existing label uses for
reregistration of this compound result in potential risk to non-target
organisms above the Agency’s levels of concern (LOCs). Available
environmental fate, ecotoxicity, and physicochemical property data were
taken from studies submitted previously to EPA and where available, the
open scientific literature.  At or near the time of their submission to
EPA, environmental fate and effect studies underwent formal data
evaluation review (DER) to determine their acceptability relative to
published EPA guidelines.  For the ecotoxicity data, the studies and/or
DERs were re-reviewed to ensure that studies met current acceptability
guidelines.  For the environmental fate studies, new data or information
or new studies were submitted in response to Agency reviews of earlier
data submissions; most of these new study addendums or replacements for
older studies were submitted in the early 1990s but were not previously
subject to formal review by the Agency.  Any literature studies used in
this risk assessment were evaluated according to EPA/OPP/EFED review
guidelines in place at the time of submission and accepted if deemed
scientifically valid; however, test conditions deviate in some ways from
the current OECD Guidelines (See   HYPERLINK
"http://www.epa.gov/oppefed1/ecorisk_ders/toera_analysis_exp.htm#WSAN2"
http://www.epa.gov/oppefed1/ecorisk_ders/toera_analysis_exp.htm#WSAN2
and   HYPERLINK
"http://www.oecd.org/department/0,3355,en_2649_34377_1_1_1_1_1,00.html"
http://www.oecd.org/department/0,3355,en_2649_34377_1_1_1_1_1,00.html
).

Conclusions from Previous Risk Assessments

No previous environmental fate and ecological risk assessment was
available for sulfometuron methyl that was comparable to current OPP
practices.  However, comprehensive ecological risk assessments were
available from two other Federal sources: US Forest Service (USDA, 2004)
and the Bureau of Land Management (BLM, 2005).  In many cases, the
overall methodology and data used in these assessments was similar to
that used by OPP, although some differences in the models,
interpretation of data, and associated assumptions were evident.

Results from the US Forest Service Ecological Risk assessment (USDA,
2004) indicate that risk of direct toxicity to aquatic and terrestrial
animals is unlikely, due to exposure via contaminated diet, dermal
contact, and inhalation.  Risks were evident to terrestrial and aquatic
plants, with hazard quotients (equivalent to Agency RQ values) up to 4
for aquatic plants (peak concentrations) and up to 15,000 for
terrestrial plants based on the NOAEC for vegetative vigor.  The US
Forest Service assessment considered only ground applications, which
would likely result in lower RQs compared to aerial applications that
are modeled in the OPP ecological risk assessment.

Results from the BLM ecological risk assessment (BLM, 2005) are similar
to those of the US Forest Service.  No risks from direct spray, drift,
or surface runoff of sulfometuron methyl were identified for terrestrial
animals, fish or aquatic invertebrates.  Risks to terrestrial and
aquatic plants from off site drift and surface runoff were evident, with
RQs up to 2,500 associated with aerial application 100ft from the
treated area and up to 40 for aquatic plants from surface runoff to a
model pond.  Results from modeling wind-driven erosion did not indicate
risk to terrestrial plants, although results depended largely on the
treatment area size and may underestimate risks from larger scale
applications.

Preliminary Identification of Data Gaps  tc \l3 "1.         Preliminary
Identification of Data Gaps and Methods and Analysis Plan

Data from registrant-submitted studies and the open literature were used
to assess the potential effects of sulfometuron methyl and its major
metabolites on non-target organisms.  For aquatic and terrestrial
plants, a re-review of the toxicity data indicated that the ecological
effect studies meet basic guideline requirements and no data gaps were
identified for terrestrial and freshwater aquatic plants.  For aquatic
animals, a re-review of the toxicity data indicates that no acceptable
data were available for chronic toxicity to fish (freshwater, or
marine/estuarine). For birds, no data were available to assess effects
on avian growth or reproduction.  Similarly for mammals, no acceptable
data were available on reproductive effects of sulfometuron methyl.
Thus, for ecological effects, the following data gaps are identified
along with associated uncertainties:

Avian Reproduction Study (71-4)

Fish Early Life Stage Study for Freshwater or Estuarine/Marine Species
(72-4)

2-generation reproduction study with rat (83-4)

There are no outstanding environmental fate data gaps.

In accordance with OPP practices for conducting baseline ecological risk
assessments of pesticides (see the “Overview Document; US EPA, 2004),
the primary method used to assess risk in this screening-level
assessment is the risk quotient (RQ).  The RQ is the result of comparing
measures of exposure to measures of effect.  A commonly used measure of
exposure is the estimated exposure concentration (EEC) and commonly used
measures of effect include toxicity values such as the LD50 or NOAEC.
The resulting RQ is then compared to a specified LOC.  If the RQ exceeds
an LOC, then risks are identified.

Measures of Effect and Exposure

Considering the previous discussion of data gaps and risk assessment
procedures, the following measures of effects and exposure presented in
 REF _Ref178576262 \h  Table 4  are selected for this baseline risk
assessment.

Table   SEQ Table \* ARABIC  4 .  Measures of Ecological Effects and
Exposure for Sulfometuron Methyl

Assessment Endpoint

Surrogate Species and Measures of Ecological Effect1

Measures of Exposure

Birds2	Survival

	Bobwhite acute oral LD50

Bobwhite and mallard subacute dietary LC50

Maximum residues on food items (foliar)

	Reproduction and growth	Bobwhite and mallard chronic reproduction NOAEC
and LOAEC

 (no studies available)

	Mammals	Survival	Laboratory rat acute oral LD50

Reproduction and growth	Laboratory rat oral reproduction chronic NOAEC
and LOAEC

(no acceptable studies available)

	Freshwater fish3

	Survival	Rainbow trout and bluegill sunfish acute LC50 	Peak EEC4

	Reproduction and growth	Fathead minnow

        chronic (early life-stage) NOAEC and LOAEC

(no acceptable studies available)	60-day average EEC4

Freshwater invertebrates	Survival	Water flea acute EC50	Peak EEC4

	Reproduction and growth	Water flea chronic (life cycle) LOAEC	21-day
average EEC4

Estuarine/marine fish

	Survival	Sheepshead minnow acute LC50 	Peak EEC4

	Reproduction and growth	Sheepshead minnow chronic (early life-stage)
NOAEC and LOAEC

(No studies available)	60-day average EEC4

Estuarine/marine invertebrates	Survival	Eastern oyster acute EC50 and
mysid acute LC50	Peak EEC4

	Reproduction and growth	Mysid chronic NOAEC and LOAEC

(no data available)	21-day average EEC4

Terrestrial plants5	Survival and growth	Monocot and dicot seedling
emergence and vegetative vigor EC25, EC05, and NOAEC values	Estimates of
runoff and spray drift to non-target areas

Insects

	Survival (not quantitatively assessed)	Honeybee acute contact LD50
Maximum application rate

Aquatic plants and algae	Survival and growth	Algal and vascular plant
(i.e., duckweed) EC50 and NOAEC values for growth rate and biomass
measurements	Peak EEC

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

2 Birds may be used as surrogates for amphibians (terrestrial phase) and
reptiles.

3 Freshwater fish may be used as surrogates for amphibians (aquatic
phase).

4 One in 10-year return frequency.

 5 Data required for 4 species of monocots from 2 families (must include
corn) and 6 species of dicots from 4 families (must include soybean).
LD50 = Lethal dose to 50% of the test population; NOAEC = No observed
adverse effect concentration; LOAEC = Lowest observed adverse effect
concentration; LC50 = Lethal concentration to 50% of the test
population; EC50/EC25 = Effect concentration to 50%/25% of the test
population.

ANALYSIS

USE CHARACTERIZATION

Information in this section is taken from the “Sulfometuron Methyl Use
Closure Memo” from John Pates, Special Review and Reregistration
Division (dated January 30, 2007). In addition, some data submitted to
the Agency by DuPont Corp. is used by permission.

Sulfometuron methyl is a broad-spectrum sulfonylurea herbicide (numerous
other herbicides in this class are also registered for various uses in
the United States).  There are no agricultural uses for sulfometuron
methyl, but it is used on a wide variety of non-crop situations for
vegetation management (railroad, highway, power line, and other
rights-of-way; suppression of vegetation at utility substations,
unimproved turf in industrial areas, in preparation of ground for
asphalt or concrete paving, etc.) and in forestry plantings. It is
applied either post-emergent or pre-emergent.  It works by blocking the
active growing regions of stem and root tips. Sulfometuron methyl is
formulated as a water dispersible granule (WDG) and applied using a
variety of methods including helicopter, fixed-wing aircraft, ground
spray (boom and backpack) and spot treatment (  REF _Ref184020171 \h
Table 5  and   REF _Ref184020188 \h  Table 6 ).

Sulfometuron methyl is generally applied once per year for non-crop
areas.  In some instances (weed escapes) a second application may be
made, but all products limit the total quantity of sulfometuron methyl
that may be applied (from any source) to 6 ounces of active ingredient
per year.  Therefore, application rates in general forestry, and for
site preparation and/or release in conifer, hardwood and Christmas tree
plantations, will vary significantly depending upon the specific purpose
of the application and the desirable tree species.  In forestry, uses
can be similar to plantation sites, but may also include the maintenance
of access routes and fire breaks.  It is further noted that use rates
can also vary with climate and soil type.  Ranges of application rates
by use are summarized in   REF _Ref177866558 \h  Table 9 .

Considering all types of uses, regions of the U.S. where sulfometuron
methyl appears to have the greatest use include the southeast and west
coast states. Data from DuPont (used by permission) indicate that OR and
TX are the highest use states overall (  REF _Ref177654603 \h  Table 7
).  However, Vegetation Management LLC also markets sulfometuron methyl
products and the geographical distribution of the use of its products
could be somewhat different.  The total amount used annually is
estimated to be close to 250,000 pounds active ingredient   REF
_Ref177740523 \h  Table 8 .

Table   SEQ Table \* ARABIC  5 . Permitted application methods for
sulfometuron methyl, DuPont Products

Forestry/ Plantations	Aerial (fixed wing, helicopter), ground (closed
cab), and backpack (spot spray).

Vegetative Management	Aerial (helicopter) and ground (closed and open
cab).

Railroad	Aerial (helicopter) and ground (closed and open cab).

Table   SEQ Table \* ARABIC  6 . Permitted application methods for
sulfometuron methyl, Vegetation Management LLC Products

SFM	Ground (broadcast, directed), air (helicopter- only), backpack
sprayers (forestry applications include banded or spot hand
applications).

SFM Extra	Ground (broadcast, directed), air (helicopter or fixed wing
aircraft, backpack sprayers (forestry applications include banded or
spot hand applications).

Table   SEQ Table \* ARABIC  7 .  States with high sulfometuron usage
(based upon DuPont sales data, 2001-2004).

	Thousands of Pounds A.I. Applied Annually Statewide

Use Site	1 to 5 	5 to 10	10 to 20	> 20

Forestry	OR, TX, LA, GA, VA	AR, MS, AL	 ---	 ---

Vegetation Management	WA, OK, LA, MS, AL, GA, SC, VA, PA	CA, TX	OR	 ---

Railroad	WA, OR, CA, NM, ND, NE, KS, TX, IL, MS, OH, FL, MA	TN, WV	---
---

Total Uses (sales)	MT, CO, NM, ND, NE, KS, OK, MN, IL, OH, PA, VA, SC,
FL, MA	OR, CA, AR, LA, TN, MS, AL, GA, WV	TX	OR

Table   SEQ Table \* ARABIC  8 .  Annual usage of sulfometuron methyl in
the US by use site.

Use Site	Low Estim.	High Estim.

	Annual Usage,

Lbs ai

 (Commercial Christmas Trees - Nurseries) 	50	830

 Forestry 	89,000	100,000

 Non-crop Vegetative Management (VM - includes Roadway, Utility &
Pipeline) 	80,000	100,000

 Railroad (RR) 	50,000	71,000

 Total 	230,000	261,000

 Estimates reflect ranges from combined registrant and OPP-BEAD
generated estimates. Registrant estimates are combined for DuPont and
Vegetation Management for any and all years of reported data.  BEAD
estimates reflect multiple data sources from 1999 to 2003 period.

Table   SEQ Table \* ARABIC  9 .  Sulfometuron application rate ranges
by product label and use site.

Product Name	Type of Formulation	Additional Active Ingredient(s)	Use
Site(s)	Single App.  Low Rate (pounds a.i.)	Single App.  High Rate
(pounds a.i.)

DuPont™ Oust®

Herbicide

Or “Sulfometuron methyl 75”	Dispersible granules	None (may be tank
mixed)	Forestry

Non-Crop	0.047

0.047	0.375

0.375

DuPont™ Oust® XP Herbicide	Dispersible granules	None (may be tank
mixed)	Forestry

Non-Crop	0.023

0.047	0.375

0.375

DuPont™

Oust®  Extra Herbicide	Dispersible granules	Metsulfuron Methyl	Conifer
Plantations

Non-Crop	0.023

0.016	0.281

0.188

DuPont™ Oustar®

Herbicide	Dispersible granules	Hexazinone

	Forestry	0.075

	0.175

DuPont™ Westar®

Herbicide	Dispersible granules	Hexazinone

	Christmas Trees

Forestry

Non-Crop	0.025

0.100

0.131	0.100

0.131

0.194

DuPont™ Landmark® MP Herbicide	Dispersible granules	Chlorsulfuron
Non-Crop 	0.023	0.281

DuPont™ Landmark® II MP Herbicide	Dispersible granules	Chlorsulfuron
Non-Crop 	0.035	0.350

DuPont™ Landmark® XP Herbicide	Dispersible granules	Chlorsulfuron
Non-Crop 	0.023	0.281

DuPont™ Landmark® II XP Herbicide	Dispersible granules	Chlorsulfuron
Non-Crop 	0.035	0.350

DuPont™

Throttle™ MP Herbicide	Dispersible granules	Sulfentrazone

Chlorsulfuron	Non-Crop **	0.141	0.141

DuPont™

Throttle™ XP

Herbicide	Dispersible granules	Sulfentrazone

Chlorsulfuron	Non-Crop	0.141	0.141

SFM 75, SFM Extra	Dispersible granules	Only in  tank mixes	Conifer Site
Preparation (pre-plant)	0.063	0.250

SFM 75, SFM Extra	Dispersible granules	Only in  tank mixes	Conifer
Release (post-transplant)	0.125	0.188

SFM 75, SFM Extra	Dispersible granules	Only in  tank mixes	Conifer Site
Preparation or Post-transplant for specific weeds (e.g., Kudzu)	0.281
0.375

SFM 75, SFM Extra	Dispersible granules	Only in  tank mixes	Hardwoods
(seedlings or transplants in dormancy)	0.023	0.234

SFM 75, SFM Extra	Dispersible granules	Only in  tank mixes	Non-Crop:

“Non-Agricultural”*	0.035	0.375

SFM 75, SFM Extra	Dispersible granules	Only in  tank mixes	Non-Crop:

Under asphalt and concrete pavements (before paving)	0.188	0.375

SFM 75, SFM Extra	Dispersible granules	Only in  tank mixes	Non-crop:

Turf (unimproved)	0.023	0.188

** Non-Crop lumps together uses such as rights-of-way, industrial site
weed management, applications prior to concrete or asphalt paving,
unimproved turf, etc.

* “Non-agricultural” is a term on Vegetation Management LLC labels
that includes most of the non-crop uses not otherwise specifically
listed.

EXPOSURE CHARACTERIZATION

Environmental Fate and Transport Characterization

The body of environmental fate data submitted demonstrates sulfometuron
is mobile and persistent in the environment (  REF _Ref184020399 \h
Table 10 ). Sulfometuron methyl is more soluble in neutral and alkaline
water than in acidic water. The major route of dissipation for
sulfometuron methyl is believed to be aerobic and anaerobic degradation
/ metabolism in soil and water (pseudo first-order degradation
half-lives generally around 2 to 6 months), with hydrolysis potentially
dominant under acidic conditions. First-order rate aerobic soil
metabolism half lives range from 52 to 58 days in two laboratory studies
(technically both with the same soil type, but measured in two
independent studies several years apart).  In comparison, lump
dissipation half-lives in the field ranged from 44 to 128 days at four
sites (when considering only the residues remaining in the upper 15 cm
of topsoil and calculating a lumped pseudo first-order rate including
all residue data during the entire ca. 350 to 500 days of each study).
At all four field study sites, about 99 % of the applied sulfometuron
methyl had dissipated from the upper six inches of the soil profile
within 3 to 6 months after application, but dissipation of the small
amount of sulfometuron methyl remaining in the topsoil a few months
after application was much slower. Sulfometuron methyl is subject to
hydrolysis at environmental pHs; with significantly more rapid
hydrolysis occurring under acidic conditions (e.g., a hydrolysis
half-life of 9 days at pH 5 and 139 days at pH 7).  None of the
laboratory and field studies in soil or sediment / water environments,
albeit all at measured pHs somewhat greater than 5, show as rapid
degradation as measured in the pH 5 hydrolysis study.

.

Metabolism in the aquatic environment is variable, ranging from
half-life of 17 to 104 days in anaerobic conditions and 9 to 187 days
for aerobic conditions (the more rapid degradation with a 9-day total
system half-life took place in a test system with sediment pH of 5.4 and
water pH of 7.6).  Although sulfometuron methyl persistence is expected
to generally increase with higher soil pH (rotational crop restrictions
for many other sulfonylureas, which are all weak acids, reflect this), a
consistent trend was not found in the available studies.

Soil retention of sulfometuron methyl is low, with Freundlich adsorption
KF values ranging between 0.15 and 2.1 (mg/kg)/(mg/L)n in four test
soils with soil organic carbon content ranging between 0.6 and 2.6
percent.

Sorption was not found to be strongly dependent on any of the major
properties of the tested soils in the registrant-submitted studies. The
pKa of sulfometuron methyl is 5.4, and theoretically, adsorption may
increase in very acidic soils where the methyl ester form of
sulfometuron would predominate.  However, the pH range of the four test
soils in the batch equilibrium adsorption / desorption study was only
6.7 to 7.7 . The published literature do seem to show more of a
relationship of sulfometuron methyl and other sulfonylureas to mobility
in soil; Weber et al. (2004) have reviewed the literature and concluded
that there is consistent relationship between pH and mobility of
sulfonylureas (“NHSO2 acid herbicides” means sulfonylurea
herbicides):

OM and pH were also the primary soil properties in best-fit Kd equations
obtained for five of the six NHSO2 acid herbicides, with all three soil
properties utilized in the Kd equation for sulfometuron-methyl. Cl was
also one component of the Kd equation for sulfometuron-methyl, but Cl
and pH were also related soil properties. As was the case for the COOH
acid herbicides, sorption increased as OM increased or as pH decreased.

Other abbreviations used in the above excerpt from the Weber et al.
article:

OM = Soil organic mater content

Cl = Chloride ion concentration

COOH acid herbicides = Herbicides with a carboxy acid functional group
such as 2,4-D and Imazethapyr

Weber et al. developed the following specific equation for predicting
sulfometuron adsorption from soil properties:

Kd = 3.0 + 0.49(OM) – 0.03(Cl) – 0.47(pH) ± 2.3

In general, sulfonylureas were found to have the strongest correlation
between soil pH and the measured pesticide Kd of any of ten families of
pesticides tested; the correlation of soil percent OM and Kd was second
to “OH acid” (uracil) herbicides such as bromacil. Similarly, soil
pH and % OM together accounted for more of the variability in soil Kd
for these two classes of herbicides (54% for sulfonylureas and 67% for
uracils) than for any of the other pesticide families evaluated.

Based on the of McCall et al. (1981) mobility classification system
sulfometuron methyl is mobile to highly mobile in each of the test
soils.

In terrestrial field dissipation studies at four US sites, leaching of
parent sulfometuron methyl  occurred at measurable concentrations;  (>10
 ppb in depth increments from 15 to 90 cm) was noted at each test site.
Consistent with the terrestrial field dissipation and the aged leaching
results, minimal levels (but possibly still high enough to be
phytotoxic) of sulfometuron methyl residues were estimated for ground
water (0.33 ug/L for vulnerable aquifers) using the SCI-GROW model.
Leaching of the degradates was not evaluated in the field dissipation
studies.

Sulfometuron persistence in water indicates that if, either via spray
drift or any runoff event, sulfometuron methyl reaches surface water, it
may persist for a few weeks to several months and present some concern
to surface water resources.  The fairly low use rate (maximum annual
rate of 0.375 lb ai/A) and the apparent typical use pattern of applying
in only one or two years out of a several year period should limit the
actual exposure of sulfometuron methyl parent residues in surface water
(however, note that sulfometuron methyl could negatively affect certain
sensitive plants at very low exposure levels because it is such a potent
herbicide with respect to many plant species).

Aquatic modeling at the highest application rate applied every year
results in a peak surface water estimated environmental concentration
(EEC) of 31.5 µg/L; additional assumptions for this modeling are
discussed in “Section   REF _Ref178226314 \r \h  \* MERGEFORMAT
<IP_ADDRESS> ,   REF _Ref178226222 \h  \* MERGEFORMAT  Aquatic Exposure
Modeling ”. Note that sulfometuron methyl was not predicted to
accumulate in the receiving pond so the effect of sulfometuron methyl on
EECs determined only was significant for the chronic (not acute)
exposure estimates.

Volatility studies were not reported.  However, based its chemical
properties, volatilization is not expected to be a route of dissipation
of sulfometuron methyl in water or soils.

Sulfometuron methyl degrades to CO2 under aerobic, non-sterile
conditions (relatively little mineralization occurs under sterile
conditions), but with significant accumulation of intermediate
degradates, including a sulfonamide and saccharin from the phenyl ring
part of the parent molecule and a pyrimidine amine from the pyrimidine
ring portion (see “  REF _Ref178038010 \h  \* MERGEFORMAT  APPENDIX A:
Structures and Chemical Names of Sulfometuron methyl Metabolites ”).
For the phenyl ring labeled studies, CO2 was up to 28 to 44 % of applied
at study termination whereas for the pyrimdine-ring labeled studies CO2
was up to 53% of applied at study termination (see   REF _Ref184020399
\h  Table 10 , aerobic soil metabolism studies, for further
information). Additional details on the accumulation of sulfometuron
methyl degradates in the various studies will be provided in a Drinking
Water Assessment for Sulfometuron Methyl.

The only submitted studies directly evaluating the fate of sulfometuron
methyl degradates were adsorption / desorption studies on the pyrimidine
amine and saccharin. The soil retention characteristics of two of the
sulfometuron methyl degradates were studied in batch equilibrium
adsorption / desorption studies: saccharin Kfs were 0.03 to 0.27 and the
pyrimidine amine Kfs were 0.17 to 3.70 in the four test soils (  REF
_Ref184020399 \h  Table 10 ). This means saccharin would be slightly
more mobile and the pyrimidine amine slightly less mobile than parent
(Kfs of 0.15 to 2.12 in the same four soils)

Table   SEQ Table \* ARABIC  10 . Key results of sulfometuron methyl
environmental fates studies.

Parameter

[Guideline #]	Value1	MRID(s)

Hydrolysis

[161-1]

	t½= 8.8 days @ 25 oC, pH 5;

t½=139 days @ 25 oC, pH 7;

t½= 224 days @ 25 oC, pH 9.

Major degradates (from cleavage of the sulfonylurea bridge):

Sulfonamide – only in acidic water

Saccharin – all pH levels

Pyrimidine amine – all pH levels

42715201

Direct photolysis in water

[161-2]	Combined labels results:

t½= 428 days @ 24 oC, pH 5;

t½= stable @ 24 oC, pH 7;

t½= stable @ 24 oC, pH 9.

(calculated by the difference in degradation rates between irradiated
and dark controls and adjusting for typical light levels on sunny days)

Major degradates (irradiated water):

pH 5:  sulfonamide, pyrimidine amine;

pH 7:  none;

pH 9:  none.

42182401

43174101

Photolysis on soil

[161-3]	t½= 72.1 days @ 25 oC,

Study duration was 33 days, substantial degradation occurred in dark
controls and the calculated photolysis half-life represents the
difference in the dissipation rate in the irradiated and the dark
control samples.

Major degradates (from cleavage of the sulfonylurea bridge):

Saccharin reached a maximum of 48.4% of the applied at 33 days (study
termination.)

Pyrimidine amine reached a maximum of 53.1% at 33 days (study
termination.)

There was no substantial difference in the degradation pathway of
sulfometuron methyl between the irradiated- and the dark control soil.

No other degradate accounted for >4% of the applied radioactivity
regardless of whether the phenyl ring or the pyrimidine ring was
14C-labeled.

41420601

Aerobic soil metabolism

[162-1]

	Study with [pyrimidine-2-14C] Sulfometuron Methyl

Soil: Keyport Silt loam (pH 6.3, 1.6% O.C.) from Delaware

First Order t½:			57.8 days (r2 = 0.9239).

Observed DT50:		23 days.

Observed DT90:		110 days.

Sterile soil First Order t½: 	364 days

Major transformation products:

Pyrimidine amine (maximum 41.0% of the applied)

Pyrimidine-ol (maximum 10.5% of the applied).

	CO2 (maximum 53.1% of applied).

Minor transformation products:

Free acid sulfometuron methyl.

Pyrimidine urea.

42091401

Aerobic soil metabolism

[162-1]

	Study with U- 14C-phenyl-labeled Sulfometuron Methyl

Soil: Keyport Silt loam (pH 6.4, 1.6 % O.C.) from Delaware (0.12 mg
a.i./kg).

First Order t½:		52.5 days (r2 = 0.9239).

Observed DT50:	29 days.

Observed DT90:	162 days.

Major transformation products:

Sulfonamide.

Saccharin.

Free acid sulfonamide plus urea (1.0 mg a.i./Kg only).

	CO2.

Minor transformation products:

Free acid sulfonamide plus urea (0.12 mg a.i./Kg only)

43174102 and 245375

Anaerobic aquatic metabolism

[162-3]	Study  performed with [pyrimidine-2-14C] Sulfometuron Methyl

Matrix: Bradenton Pond water-sand sediment.

First Order t½:			37.4 days (r2 = 0.6125).

Observed total system DT50:	22 to 61 days (inconsistent decline data).

Observed total system DT90:	102 days.

Matrix: Landenberg Pond water-sandy loam sediment.

First Order t½; total system:	17.1 days (r2 = 0. 0.6394).

Observed total system DT50:	6.1 days.

Observed total system DT90:	21.7 days.

Major transformation products (both systems):

free acid sulfometuron methyl.

pyrimidine amine.

Minor identified transformation products:

pyrimidine-ol.

CO2.

42091402 and 43188601

Anaerobic aquatic metabolism

[162-3]	Study with [phenyl-U-14C] Sulfometuron Methyl

Matrix: Pond water-sandy loam sediment from Bradenton, Florida.

(water pH 5.5 .  Sediment: pH 5.1; O.C. = 5.9 %).

First Order t½; total system:	104 days (r2 = 0.4883)*.

Observed DT50 in total system:	ca. 21 days.

Sterile t½; total system:	44 days

* Based upon limited and inconsistent data.

Matrix: Pond water-silt loam sediment from Landenberg, Pennsylvania.

(water pH 5.8 .  Sediment: pH 5.6; O.C. = 2.1 %).

First Order t½; total system:	87 days (r2 = 0.3577).

Observed DT50 in total system:	ca. 28 days.

Sterile t½; total system:	175 days

Matrix: Pond water-loam sediment from Saskatoon, Canada. (water pH 8.3 .
  Sediment: pH 7.8; O.C. = 0.9 %).

First Order t½; total system:	77 days (r2 = 0.5853).

Observed DT50 in total system:	ca. 70 days.

Sterile t½; total system:	399 days

Matrix: Pond water-silt loam sediment from Walnut Grove, Tennessee.
(water pH 5.5 .   Sediment: pH 5.1; O.C. = 0.5 %).

First Order t½; total system:	73 days (r2 = 0.5691).

Observed DT50 in total system:	ca. 28 days.

Sterile t½; total system:	95 days

Major transformation products:

	saccharin.

	free acid sulfonamide.

Minor identified transformation products:

	Methyl-2-aminocarbonyl(aminosulfonyl)benzoate.

4413010-20 (143540)

Aerobic aquatic metabolism

[162-4]	Study  performed with [pyrimidine-2-14C] Sulfometuron Methyl

Matrix used: Pond water-silt loam sediment (Landenberg, acidic system).

First Order t½; total system:	9.2 days (r2 = 0.94).

Observed DT50 in total system:	15 days.

Observed DT90 in total system:	31 days (extrapolated).

Major transformation products:

Pyrimidine amine (pyrimidine label).

Hydroxymethyl-pyrimidine sulfometuron methyl.

Free acid sulfonamide (phenyl label).

Sulfonamide (phenyl label).

Minor identified transformation products:

CO2.

Matrix used: Pond water-sand sediment (Bradenton, alkaline system).

First Order t½; total system:	187.3 days (r2 = 0.5713).

Observed DT50 in total system:	>39 days.

Major transformation products:

Pyrimidine amine (pyrimidine label).

Free acid sulfonamide (phenyl label).

Minor identified transformation products:

Hydroxymethyl-pyrimidine sulfometuron methyl.

Sulfonamide (phenyl label).

CO2.

42091403 and 43174103

Adsorption/

Desorption

(Kd and

Koc in L Kg-1)

	Parent sulfometuron methyl:

Soil type:  Chino Sandy loam; pH 7.1, organic carbon 1.0%.

Adsorption Kd:			0.35.

Adsorption Koc:			35.

Freundlich adsorption KF:	0.153.

Freundlich adsorption KFoc:	14.7.

1/N				0.504

Soil type:  Fargo silt loam ; pH 7.7, organic carbon 2.6%.

Adsorption Kd:			2.07.

Adsorption Koc:			79.6.

Freundlich adsorption KF:	2.12.

Freundlich adsorption KFoc:	83.2.

1/N				1.23

Soil type:  Miaka Sand ; pH 7.0, organic carbon 0.6%.

Adsorption Kd:			Not applicable.

Adsorption Koc:			Not applicable.

Freundlich adsorption KF:	0.508.

Freundlich adsorption KFoc:	87.6.

1/N				1.61

Soil type:  Tama Silt loam ; pH 6.7, organic carbon 1.5%.

Adsorption Kd:			0.79.

Adsorption Koc:			52.7.

Freundlich adsorption KF:	0.974.

Freundlich adsorption KFoc:	67.2.

1/N				0.851

	42789301

Adsorption/

Desorption

Of Degradates

  SEQ CHAPTER \h \r 1 Pyrimidine amine

Although the registrant conducted adsorption / desorption studies for
the pyrimidine amine degradate, the results were insufficiently
documented to verify their calculations of adsorption coefficients (and
furthermore, they only reported Freundlich adsorption “KF” and
“KFoc” values without 1/N values (or sufficient data for the
reviewer to calculate them) and Kd values were also not reported.

For rimsulfuron, a structurally similar pyrimidine amine degradate (but
with 4-, 6-dimethoxy rather than 4-, 6-dimethyl substitution of the
pyrmidine amine) was reported to have Kd values of 0.23 to 1.52 and Koc
values of 19 to 61 in four test soils. See DP Barcode D326660, EFED
review of rimsulfuron methyl new uses dated 3/14/07 for more details.

  SEQ CHAPTER \h \r 1 Saccharin

Although the registrant conducted adsorption / desorption studies for
saccharin, the results were insufficiently documented to verify their
calculations of adsorption coefficients (and furthermore, they only
reported Freundlich adsorption “KF” and “KFoc” values without
1/N values and Kd values were also not reported.

Saccharin has been reported elsewhere to be quite mobile, e.g.:

When tested as a degradate of metsulfuron methyl (  HYPERLINK
"http://ec.europa.eu/food/plant/protection/evaluation/existactive/list1-
13_en.pdf"
http://ec.europa.eu/food/plant/protection/evaluation/existactive/list1-1
3_en.pdf  )

42789301

Terrestrial Field/Lysimeter

Dissipation 2	Greenville, MS silty clay loam soil: pH 6.7, 0.6% O.C.

Half-life: 49.2 days (based on 0- to 359-day data);

12.2 days (based on 0- to 91-day data).

DT90:	32 days

Major transformation products detected (>0.01 ppm):

Sulfometuron free acid (SFA)

Pyrimdine amine (PYA)

Sulfonamide IN-D5803 (SFN)

Saccharin IN-581 (SCC)

Rochelle, IL silty clay loam soil: pH 6.8, 1.0% O.C.

Half-life: 128 days (based on 0- to 723-day data, residues in 0-15 cm
depth only);

14.4 days (based on 0- to 90-day data).

DT90:	35 days

Major transformation products detected (>0.01 ppm):

PYA, SFN, and SCC

Uvale, TX clay soil: pH 7.9, 1.3% O.C.

Half-life:  53.3 days (based on 0- to 447-day data);

13.0 days (based on 0- to 90-day data).

DT90:	25 days

Major transformation products detected (>0.01 ppm):

PYA, SFN, and SCC

Maldera, CA sandy loam soil: pH 7.8, 0.7% O.C.

Half-life: 44.1 days (based on 0- to 420-day data);

22.9 days (based on 0- to 180-day data).

DT90:	55 days

Major transformation products detected (>0.01 ppm):

PYA, SFN, and SCC	Numbers 43212101 and 43637101

1 Unless otherwise specified, half-lives were derived with a
“Log-linear” degradation rate calculation; a process of calculating
degradation rates and half-lives from linear regression of
log-transformed concentration measurements over time. This provides a
first-order type of measurement of pesticide decline.

2 For these field dissipation studies, differences between half-lives
measured over various time durations apparently reflect both slowing of
degradation at lower temperatures and a large variability in measured
concentrations; also, a 2-compartment degradation model for adsorbed and
dissolved sulfometuron is quite possibility more appropriate (little
dissipation of the remaining residues in the topsoil occurred during the
second year of these studies, for example). A 2-compartment model was
not used to represent dissipation rate here because the data are not
sufficient robust (e.g., very high variability between replicate
measurements), the effects of weather changes on degradation rate cannot
easily be isolated, and the amount of residues lost through dissipation
out of the topsoil also cannot be separated from the amount lost to
degradation. At all four of these field study sites about 99% of the
applied sulfometuron methyl dissipated from the topsoil within 3 to 6
months.

Measures of Aquatic Exposure

Aquatic Exposure Monitoring and Field Data

A few surface-water monitoring studies are available for sulfometuron
methyl. In streams, most recently Michael (2003) found, after
application of sulfometuron methyl at 0.42 kg/ha to watersheds of
unspecified area (reflecting a forestry planting usage) that
concentrations of sulfometuron methyl in runoff water collected at the
edge of the field reached a maximum of 49 ug/L (24-hour average).
However, samples taken approximately 150 meters downstream never
exceeded the minimum detection limit of 1 ug/L (a fairly high MDL given
the potency of this herbicide) reported in this study (stream flow data
were not supplied).

In the most widespread monitoring survey available, sulfometuron methyl
was detected only rarely (2 of 132 samples from 52 sites – mostly
Midwestern US streams and rivers, but including some reservoirs as
well); see Battaglin et al. (2000).  The maximum concentration of
sulfometuron methyl detected was 0.018 ug/L; but it is not known how
much sulfometuron methyl usage was associated with the watersheds
included in this monitoring survey.

Blomquist et al. (2001) in a monitoring study of 12 reservoir systems
across the United States found sulfometuron occurred above the minimum
reporting limit of 0.05 ug/L in 12% of the samples collected with a
maximum concentration of 0.16 ug/L and a 95th percentile concentration
of 0.10 ug/L.  This study focused on drinking water supplies and may not
represent the most vulnerable water bodies for ecological exposure.

Aquatic Exposure Modeling

EFED’s PRZM (Pesticide Root Zone Model) and EXAMS (EXposure Analysis
Modeling System) models (  REF _Ref178047312 \h  Table 11 ) were used in
this assessment to estimate the exposure of sulfometuron methyl residues
to the aquatic environment as a result of the proposed uses in forestry
and various non-crop land vegetation control uses.  PRZM simulates
pesticide transport as a result of runoff and erosion from an 10-hectare
agricultural field and EXAMS considers environmental fate and transport
of pesticides in surface water and predicts EECs in a standard pond
(10,000-m2 pond, 2-m deep), with the assumption that the small field is
cropped at 100%.  Calculations are carried out with the linkage program
shell – PE5.pl - which incorporates the standard scenarios developed
by EFED.  (For additional information see   HYPERLINK
"http://www.epa.gov/oppefed1/models/water/index.htm"
http://www.epa.gov/oppefed1/models/water/index.htm ).  Potential
exposure from ground-water (for, example, via contaminated irrigation
water) was also estimated using the SCI-GROW model.

Table   SEQ Table \* ARABIC  11 .  Models Used to Estimate Exposure
Concentrations for Aquatic Ecosystem.

Exposure Estimate Type	Models Used

Aquatic ecosystems

Surface water (Tier II)

PE v5.0, PRZM v3.12.2, EXAMS v<IP_ADDRESS>

Details of executables:

PRZM 3.12.2, named przm3122.exe (dated May 12, 2005)

EXAMS <IP_ADDRESS>, executable file named EXAMS.EXE (dated April 12, 2005)

PE v5.0,  Executable file PE5.pl (dated July 24, 2006)

Ground water (Tier I)	SCI-GROW v2.3

Executable file sg23.exe (dated May 16, 2006)

The estimated environmental concentrations (EECs) were predicted
assuming 1 aerial or ground application at the maximum allowable single
application rate of 0.375 lbs. a.i./A (which also represents the maximum
annual application amount permitted on all labels). Applications were
broadcast without incorporation, according the uses endorsed by the
label.  None of the available modeling scenarios as currently set up
represents a clear match for the sulfometuron methyl use pattern as
described in Section   REF _Ref177973597 \w \h  3.1  . Nonetheless, a
combination of scenarios which represent usage patterns and locations
that can reasonably be expected to represent a range of conditions for
the forestry planting and non-crop uses of sulfometuron methyl were able
to be selected from the suite of available standard scenarios and, with
slight adjustments, the available regional scenarios  (see   REF
_Ref177973831 \h  Table 12 ).  The major adjustments to the standard
scenario modeling were:

1.  Specific regional scenario adjustments. The rights-of-way regional
scenarios were selected for this national assessment because they are
the only scenarios currently approved in EFED for specific modeling of
this type of use.  However, they were run with both their native
meteorological files as the source of weather data and with alternate
weather data files believed to represent more runoff-prone climates that
may represent areas with significant use of sulfometuron methyl

2.  Modeling with multiple application dates.  The multiple PRZM –
EXAMS runs with multiple application dates were used for final
development of EECs for the highest exposure scenarios because the
product labels frequently refer to uses that are recommended for spring,
summer, fall, and even winter application (although only spring, summer,
and fall dates were tested with our modeling, as they were judged to be
significantly more common than winter applications).

The most important reason for modeling with multiple application dates
is that there is significant variability in the results (calculated
EECs) of the modeling that can arise strictly as a factor of the
application date chosen. In fact, when, for example, the Texas
Right-of-Way scenario (using Port Arthur, Texas meteorological data) was
rerun with 28 different application dates, the acute (peak daily value)
EECs (a distribution of 1 in 10-year return frequency values) ranged
from 8.5 to 49.5 ug/L and the 90-day EECs  ranged from 5.5 to 27.2 ug/L.
This is quite a significant difference when it is considered that this
variability is solely for the 1 in 10 year return frequency exposure
levels, not for all of the year-to-year differences in EECs from the
modeling.

Sulfometuron methyl product labels allow for flexibility in when
sulfometuron methyl is applied and there is not as much consistency in
the optimal application season as there would be, for example, with most
agricultural crops.  In this case, the 90th percentile application date
model results were chosen for risk calculations.

Both aerial and ground applications were simulated, but ground
applications were only simulated for a few scenarios since the ground
application assumption yielded lower EEC estimates for sulfometuron
methyl than aerial applications at the same site.

The pesticide-specific input parameters for this modeling (summarized in
  REF _Ref177972956 \h  Table 13 ) were selected from the environmental
fate studies submitted by the registrant, and in accordance with the US
EPA-OPP EFED water model parameter selection guidelines, Guidance for
Selecting Input Parameters in Modeling the Environmental Fate and
Transport of Pesticides, Version II, February 28, 2002.

We considered modeling total residues of sulfometuron methyl (including
sulfometuron methyl, sulfometuron free acid, the sulfonamide, saccharin,
and the pyrimidine amine) as well, since the Health Effects Division has
made a preliminary call that they might contribute to toxicity in
mammals (electronic mail message from Larry Chitlik, HED dated /7/2007).
However, with the available data total residue model inputs would be
different from assumptions for the parent compound (  REF _Ref177972956
\h  \* MERGEFORMAT  Table 13 ) in that stability to hydrolysis, aerobic
aquatic metabolism, and anaerobic aquatic metabolism hand to be assumed
(only aerobic soil metabolism had a measurable total residue half-life:
136 days).  This would lead to an assumption of no degradation in the
pond represented by EXAMS, which is set up for a pond with no turnover
in ecological risk assessments (an additional conservative assumption).
Further details on the limitations of the modeling and uncertainties
regarding exposure to sulfometuron methyl degradates are provided in
Section   REF _Ref178575384 \r \h  \* MERGEFORMAT  <IP_ADDRESS> .

Table   SEQ Table \* ARABIC  12 . Aquatic exposure with PRZM – EXAMS:
Modeling scenarios and representative usage pattern summary.

Scenario ID1	WBAN (met. file)2	appl. meth.	CAM3	applictn. dates (MM-DD)
Use(s) represented

PA Apples (std)	W14751	Aerial	2	03-15	Forestry, Conifer Plantations

FL Citrus (std)	W12844	Ground	1	03-01	Forestry, Conifer Plantations

FL Citrus (std)	W12844	Aerial	1	03-01	Forestry, Conifer Plantations

FL Turf (std)	W12834	Ground	1	03-01	Non-crop (e.g., unimproved turf &
rights of way)

FL Turf (std)	W12834	Aerial	2	03-01	Unimproved turf, non-crop

PA Turf (std)	W14751	Aerial	2	03-01	Unimproved turf, non-crop

OR Xmas Trees (std)	W24232	Ground	1	03-01	Christmas Trees, Forestry,
Conifer Plantations

OR Xmas Trees (std)	W24232	Aerial	2	03-01	Christmas Trees, Forestry,
Conifer Plantations

CA right of way (RLF)	W23234	Aerial 	2	03-01	Non-Crop (rights of way,
unimproved turf, railroads, etc.)

CA right of way (RLF)	W94224	Aerial	2	03-01	Non-Crop (rights of way,
unimproved turf, railroads, etc.)

CA right of way (RLF)	W94224	Aerial	2	Feb to Oct4 	Non-Crop (rights of
way, unimproved turf, railroads, etc.)

TX right of way (BSS)	W13958	Aerial	2	03-01	Non-Crop (rights of way,
unimproved turf, railroads, etc.)

TX right of way (BSS)	W12917	Aerial	2	03-01	Non-Crop (rights of way,
unimproved turf, railroads, etc.)

TX right of way (BSS)	W12917	Aerial	2	Feb to Oct4 	Non-Crop (rights of
way, unimproved turf, railroads, etc.)

TX right of way (BSS)	W12917	Ground	2	Feb to Oct4 	Non-Crop (rights of
way, unimproved turf, railroads, etc.)

1 Native scenario designation state and use site.  Native scenario
target in parenthesis, where: std = std scenario used in nationwide
assessments; RLF = scenario originally developed for regional
assessments related to the California red-legged frog; and BSS =
scenario originally developed for regional assessments related to the
Barton Springs salamander.

2 The Weather Bureau Automated Network (WBAN) meteorological station
used for weather inputs in the runoff modeling.

3 CAM = Chemical application method. CAM 1 is application direct to
soil, although a 4 cm incorporation depth is

automatically assumed, to account for surface roughness. CAM 2 is linear
foliar decay based on crop canopy, default soil incorporation depth for
non-foliar intercepted chemical is 4 cm.

4 Only one application per year in each model run.  PRZM-EXAMS was
separately run for application dates between February 1 and October 29,
increasing the application date by 10 Julian days with each successive
model run (2/1, 2/11, 2/21, etc.).

 Table   SEQ Table \* ARABIC  13 .  PRZM/EXAMS input parameters for
modeling (Aquatic ecological EECs).

Input Parameter	Value*	Reference

Molecular Weight (gram mole -1)	364.38	MRID: 416728-02

Vapor Pressure (torr)	5.4x10-16

	Aerobic Soil Metabolism Half-life (days)	60.9	90% Upper Confidence
Limit of the mean of measured values  (MRIDs 42091401; 43174102 and
245375)

Water column Half-life (days)

(Aerobic Aquatic Metabolism half-life)	292	90% Upper Confidence Limit of
the mean of measured values  (MRIDs 42091403 and 43174103 )

Benthic sediment Half-life (days)

(Anaerobic Aquatic Metabolism half-life)	76	90% Upper Confidence Limit
of the mean of measured values  (MRIDs 43174102, 245375, 42091402, and
43188601)

Application Rate (Kg a.i./ha)	0.41	Efficiency= 0.99 for ground spray,
0.95 for aerial.

Application Number (Method of application)	    One	Product Label;
typical use.

Application method; Depth of Incorporation (cm)	Aerial or ground;

0	CAM=1 or CAM=2 depending on the use.

Spray Drift (fraction)	0.01 (GS), 0.05 (aerial)	Default values per
guidance document. (GS= ground spray)

Solubility (ppm)	244	Highest solubility was recorded for alkaline water
(12,500 ppm at pH 8.6).  However, experience from other studies
indicates these experimental values are too high (Therefore, this value
was not multiplied by 10 as normally recommended).

Koc (L Kg-1)	47.5	Average of four values (MRID 42789301).

Koc model was determined to be appropriate.

Hydrolysis Half-life @ pH 7 (days)	139 days

MRID 42715201.

Direct Aqueous Photolysis Half-life(days)	Stable	Maximum dark control
corrected value (MRIDs 42182401 and 43174101)

Fate data values are as per Guidance for Selecting Input Parameters in
Modeling the Environmental Fate and Transport of Pesticides; Version II
February 28, 2002.

The highest exposures were determined to occur with aerial applications
at rights of way sites; the southeast Texas (using Port Arthur, Texas
weather) scenario and a scenario for Pacific Coastal areas utilizing
Astoria, Oregon weather).  The Florida citrus scenario also yielded
relatively high EEC estimates, and it provides some representation of
forestry planting and other uses in the southeastern US (  REF
_Ref178047777 \h  Table 14 ).  Chosen EEC values for the aquatic risk
assessments are provided in   REF _Ref178044350 \h  Table 15 . Note that
whereas in the modeling sulfometuron methyl applications were simulated
for every year of a 30-year simulation period for each scenario
(standard EFED practices if the product labels do not expressly prohibit
this), in most cases sulfometuron does not appear to be repeatedly used
from year to year at a particular site. However, in this modeling,
sulfometuron methyl was not predicted to accumulate in the receiving
pond so the effect of sulfometuron methyl on EECs determined only was
significant (e.g., if the 30 applications simulated were to be spread
over 150 years, the acute EECs would remain about the same, but the
chronic EECs estimated would be lower).

Table   SEQ Table \* ARABIC  14 .  Estimated environmental
concentrations (µg/L) for aquatic exposure to parent sulfometuron
methyl: scenario-specific results from PRZM-EXAMS modeling.

(all values are listed as ppb or ug/L)

Scenario Description	Site1 	Peak	96 hr	21 Day	60 Day	90 Day	Yearly
Lifetime	Applictn. Date, mm-yy	App-Type3

PA Apple	Fr	2.28	2.23	2.05	1.61	1.39	0.45	0.31	3-15	aerial

FL Citrus	Fr	9.39	9.09	7.97	6.03	4.93	1.48	0.72	3-01	aerial

FL Citrus	Fr	7.32	7.08	6.19	4.71	3.81	1.14	0.43	3-01	ground

FL Turf	NC	1.47	1.43	1.27	1.01	0.86	0.29	0.20	3-01	aerial

FL Turf	NC	0.46	0.44	0.39	0.30	0.25	0.09	0.05	3-01	ground

PA Turf	NC	1.22	1.20	1.12	0.96	0.84	0.29	0.26	3-01	aerial

OR Xmas	Fr	1.57	1.53	1.42	1.21	1.06	0.40	0.29	3-01	aerial

OR(Astoria) Xmas	Fr	2.87	2.82	2.61	2.18	1.91	0.73	0.42	3-01	aerial

OR(Astoria) Xmas	Fr	1.78	1.74	1.58	1.29	1.13	0.43	0.35	9-01	aerial

CA RightsWay	NC	8.33	8.15	7.47	6.17	5.35	2.00	0.84	3-01	aerial

CA(As-OR) 4 RightsWay	NC	13.64	13.37	12.39	10.35	9.04	3.42	1.34	3-01
aerial

CA(As-OR) RightsWay 90th date5	NC	11.01	10.83	10.10	8.46	6.73	2.73	1.44
various 6	aerial

TX RightsWay	NC	6.96	6.74	5.99	4.72	3.94	1.22	0.64	3-01	aerial

TX(PtAr) 7 RightsWay	NC	11.87	11.55	10.66	8.84	7.41	2.30	1.06	3-01
aerial

TX(PtAr) RightsWay 50th date	NC	21.75	20.93	18.33	13.51	10.99	3.39	1.97
Various	aerial

TX(PtAr) RightsWay 90th date	NC	31.45	30.34	26.24	20.45	16.49	5.26	3.14
Various	aerial

TX(PtAr) RightsWay 90th date	NC	26.08	25.20	21.64	15.51	12.48	3.92	2.05
Various	ground

1 Fr = forestry plantings uses.  NC = Non-crop uses on rights of way,
industrial land with unimproved turf, on ground prior to paving,
railroads, etc.

2 CAF = crop area factor.

3 App-Type = application type.

4 As-OR = Astoria, Oregon meteorological weather substituted for the
original San Francisco, CA weather data for this regional scenario.

5 90th Date or 50th Date = For the specified exposure distribution the
90th percentile of the 10th percentile exceedence probability (1 in 10
year return frequency) values were sorted for each model run with
different Julian day application dates (single application per year).
Then each of the 1 in 10 year values were sorted and the concentration
exceeded for 1 in 10 of the possible application dates was selected to
be representative for the scenario.

6 Pt-Ar = Port Arthur, Texas meteorological weather substituted for the
original Austin, TX weather data for this regional scenario.

7 Only one application per year in each model run.  PRZM-EXAMS was
separately run for application dates between February 1 and October 29,
increasing the application date by 10 Julian days with each successive
model run (2/1, 2/11, 2/21, etc.).

Table   SEQ Table \* ARABIC  15 .  Sulfometuron methyl surface water
EECs used in aquatic risk assessment.

Surface Water EECs in ug/L1

Application method	Peak	96-hr	21-day	60-day	90-day	Annual Average	Yearly
Average

Aerial	31.45	30.34	26.24	20.45	16.49	5.26	3.14

Ground	26.08	25.20	21.64	15.51	12.48	3.92	2.05

1 Results based on PRZM/EXAMS modeling described in Section   REF
_Ref178562606 \r \h  \* MERGEFORMAT  <IP_ADDRESS>  using the maximum annual
application rate of 0.375 lb ai/A.

Since some exposure to sensitive terrestrial plants is possible from
contaminated ground water as well as from ground-water entering surface
waters during base flow periods, a Tier I estimate of ground-water
exposure was conducted using SCI-GROW 2.3 (executable file dated
5/16/2006).  The estimate of 0.33 ug/L concentrations in vulnerable
ground water (defined as aquifers where the water table is about 10 to
30 feet in depth and the overlying soil layers are permeable) would
indicate that contributions from ground water into surface waters would
not reach levels estimated to enter surface waters from direct runoff
and spray drift in the PRZM – EXAMS modeling .  However, the levels of
sulfometuron methyl in contaminated well water used for irrigation could
be phytotoxicologically significant.

Table   SEQ Table \* ARABIC  16 . Estimated concentrations of
sulfometuron methyl in ground water (SCI-GROW inputs and results).

Input Parameter	Value*	Reference

Aerobic Soil Metabolism Half-life (days)	55.2	Mean of measured values
(MRIDs 42091401; 43174102 and 245375)

Application Rate (Kg a.i./ha)	0.41	Maximum permitted single (and annual)
rate.

Application Number (Method of application)	    One	Typical use.

Koc (L Kg-1)	73.4	Median of four values (MRID 42789301).

SCI-GROW Modeling Results

Acute Exposure EEC, ug/L 	0.33

	Chronic Exposure EEC, ug/L	0.33

Measures of Terrestrial  Exposure

Terrestrial Exposure Modeling

Terrestrial Animals. Estimates of terrestrial wildlife exposure to
pesticides are typically evaluated for the dietary pathway for birds and
mammals (USEPA, 2004).  Birds are used as surrogates for reptiles and
terrestrial phase amphibians when specific data are unavailable for
these taxonomic groups.  Consistent with this practice and with the
conceptual model for sulfometuron in Section   REF _Ref177796826 \r \h
2.5 , a screening-level risk assessment was conducted for spray
applications of sulfometuron methyl for estimating wildlife exposure to
sulfometuron methyl via dietary uptake.  Specifically, pesticide
residues on food items of wildlife (birds and mammals) were estimated
based on the assumption that animals are exposed to a single pesticide
residue (sulfometuron methyl) in a given exposure scenario.  For this
terrestrial exposure assessment, only spray application methods for
sulfometuron methyl are considered, since labeling does not permit
granular applications.

Estimating sulfometuron methyl concentrations on wildlife food items
focuses on quantifying possible dietary ingestion of residues on
vegetative matter and insects.  No field residue data or field study
information is available for sulfometuron methyl except for lump
dissipation rates from the application of sulfometuron methyl to two
forest sites (MRIDs 42091404 and 43174104), therefore, the residue
estimates were based on a nomogram that relates food item residues to
pesticide application rate.  The residue EECs were generated from a
spreadsheet-based model (T-REX Version 1.3.1) that calculates the decay
of a chemical applied to foliar surfaces for single or multiple
applications and is based on the methods of Hoerger and Kenaga (1972) as
modified by Fletcher et al. (1994).  Residue EECs were calculated for an
application rate at 0.375 lbs a.i./A (i.e., the maximum annual
application rate allowed according to the label) applied one time over a
single year.  As discussed in Section   REF _Ref177797625 \r \h  3.1 ,
the typical application frequency of sulfometuron methyl is not well
documented and expected to be highly variable depending on site
conditions and the type of vegetation to be controlled.  However,
because application of sulfometuron methyl is limited to an annual
maximum rate of no more than 0.375 lb a.i./A for its registered uses, a
one-time application at the maximum rate was chosen to represent a
conservative estimate of the EEC for wildlife dietary exposure. Residue
data supporting a specific value for foliar dissipation half-life were
not available for sulfometuron (e.g., total magnitude of residue
[171-4], reduction of residue [171.5], and foliar dissipation [132-1]).
Although the default foliar dissipation default half-life of 35 days
(Willis and McDowell, 1987) would apply to sulfometuron methyl, a foliar
dissipation half-life was not used since only one application event was
modeled.

The EECs on terrestrial food items may be compared directly with dietary
toxicity data or converted to an oral dose and compared to dose-based
toxicity data. This screening-level risk assessment for sulfometuron
methyl uses estimated upper bound (i.e., 90th percentile) residues as
the initial measure of exposure.  For comparisons with avian and
mammalian dietary-based toxicity data, the maximum predicted upper bound
residues of sulfometuron methyl are used directly without adjustment (
REF _Ref177798194 \h  Table 17 ).  For a single application season,
these EECs are considered to represent an estimate of the upper bound
exposure following sulfometuron methyl application at the maximum label
rate.  For comparisons with dose-based toxicity data, EECs are adjusted
to an average daily dose (mg/kg-bw/d) using standard allometric
relationships.  Additional information on the modeling of sulfometuron
methyl exposure to terrestrial animals is provided in   REF
_Ref179708540 \h  APPENDIX F: T-REX Output

Table   SEQ Table \* ARABIC  17 .  Unadjusted Dietary Terrestrial EECs
for Birds and Mammals Following Sulfometuron Methyl Spray Application
For Non-Crop Vegetative Management.

Uses	# of App. x App. Rate

(application method)	Food Items	Upper Bound EECs

(ppm)

Non-Crop Vegetative Management 1	1 x 0.375 lb a.i./A

(ground broadcast)	Short Grass

Tall Grass

Sm. Insects, Broadleaf Plants

Lg. Insects, Fruits, Pods	90.0

41.3

50.6

5.6

1 Includes uses on unimproved turf, forestry (Christmas trees & other
conifer plantations), non-crop vegetative management including
roadsides, railroads and industrial sites

Terrestrial Plants. For non-target plants, exposures to sulfometuron
methyl are considered most likely to occur as a result of spray drift
and/or runoff from aerial and ground applications.  Spray drift and
runoff are important factors in characterizing the risk of sulfometuron
methyl to non-target plants, which is assumed to reach off-site areas.
Two different models were used to evaluate impacts on terrestrial
plants:

TerrPlant, which focuses more on selection of the environmental setting
for exposure and the combined contributions from runoff and spray drift;
and

AgDRIFT, which focused on evaluation of the effects of different
application procedures on spray drift; only environmental concentrations
from spray drift are measured. AgDRIFT is designed to provide
quantification of spray drift amounts at distances of less than 1000
feet from the treatment area.

The TerrPlant model (Ver.1.2.2) predicts EECs for terrestrial plants
located in dry and semi-aquatic areas adjacent to the treated areas.
The EECs are based on the application rate, solubility of the pesticide
in water and drift characteristics, which depend on application method.
Different loading ratios are used for runoff to dry and semi-aquatic
areas.  For dry areas, pesticide runoff exposure is estimated as sheet
runoff.  In the model, sheet runoff is defined as the amount of
pesticide in water that runs off of the soil surface of a treated field
which is equal in size to the non-target area (1:1 ratio of areas).  For
semi-aquatic areas, runoff exposure is estimated as channelized runoff.
In the model, channelized runoff is the amount of pesticide that runs
off of a treated field 10 times the size of the area adjacent to the
treated field (10:1 ratio of areas).

	According to the TerrPlant model, t  SEQ CHAPTER \h \r 1 he amount of
sulfometuron methyl that runs off is a proportion of the application
rate and is assumed to be 5% based on a solubility of >100 mg/L for
sulfometuron methyl in water (pH 7 or above).  Drift from aerial
applications is assumed to be 5% of the application rate, whereas drift
from ground spray applications is assumed to be 1% (this differs from
AgDRIFT, for which spray drift is not predefined).  Predicted
terrestrial plant EECs (expressed as a fraction of the application rate)
following single, aerial and ground spray application at the maximum
application rate of sulfometuron methyl are summarized in   REF
_Ref177801664 \h  Table 18 . Details on inputs and outputs from the
TerrPlant model are provided in “  REF _Ref179701993 \h  APPENDIX D:
Terrplant Spreadsheet ”.

Table   SEQ Table \* ARABIC  18 .   EECs for Terrestrial Plants Located
Adjacent to Sulfometuron Methyl (aerial and ground spray application)
Treated Sites.

Terrestrial Use	Application Method

(Non-granular)	EEC (lbs ai/A)

Total Loading to Dry Areas Adjacent to Treated Areas2	Total Loading to
Semi-Aquatic Areas Adjacent to Treated Areas3	Drift to Adjacent Areas4

Vegetative management1

(1 x 0.375 lb ai/A)	Aerial	0.038	0.21	0.019

	Ground (unincorporated)	0.023	0.19	0.0038

1 Includes uses on unimproved turf, forestry (Christmas trees & other
conifer plantations), non-crop vegetative management including
roadsides, railroads and industrial sites

2 EEC = Sheet Runoff + Drift (5% for aerial or 1% for ground) assuming
1:1 runoff loading ratio

3 EEC = Channelized Runoff + Drift (5% for aerial or 1% for ground)
assuming 10:1 runoff loading ratio

4 EEC for aerial (appl. rate x 5% drift) or ground application (appl.
rate x 1% drift)

Because sulfometuron methyl is an herbicide, a more in-depth spray drift
exposure assessment utilizing Tier I and II AgDRIFT® (version 2.01)
modeling is also provided to better characterize potential exposure of
terrestrial plants.  AgDRIFT® utilizes empirical data to estimate
off-site deposition of aerial and ground applied pesticides, and acts as
a tool for evaluating the potential of buffer zones to protect sensitive
habitats from undesired exposures.    REF _Ref178147274 \h  Table 20
contains EECs at several distances from the edge of the field.

A total of four different application scenarios were modeled (Columns
labeled [A] through [D]) to illustrate predicted spray deposition of
sulfometuron at various distances from the edge of the field under:

what may be characterized as typical applications that mostly follow
best management practices (that are recommended on the sulfometuron
label) – columns A and C.

Reasonable worst case assumptions following use scenarios that are not
necessarily typical or recommended, but are plausible and permitted on
the label.  See columns B and D.

For ground applications, there is only a “Tier 1” module in AgDRIFT,
but there are some input options still available to vary.  For this
assessment, only the boom height was varied between the ground spray
scenario [A] (0.51 meter height) and the scenario [C] (1.27 m height).
Other key assumptions in the ground application spray drift modeling
include:

Drop Size Distribution: ASAE very fine to fine classification (ASAE is
now ASABE: the American Society of Agricultural and Biological
Engineers)

Number of swaths = 20

Swath Width = 45 feet

Application Efficiency (20 rows): 97.96 %

Use of the 90 %ile upper bound numbers from the empirical data set which
is the basis of AgDRIFT spray drift estimates.

Aerial applications were simulated with the AgDRIFT tier 2 module, which
allowed incorporation of some the best management practices to minimize
spray drift recommended (but not mandated) on product labels.  The more
high-end exposure use condition assumptions for aerial applications in
scenario [B] are given in   REF _Ref178145865 \h  Table 19 .  Factors
varied for the more typical-use scenario [D] with some best-management
practices  include:

Wind speed of 10 mph

ASAE droplet size of fine to medium

Temperature = 86 deg F

Relative Humidity = 75 percent

Boom Height = 10 feet

The model results demonstrate a several fold to 30-fold difference in
the percentage and amount of sulfometuron deposited off-site (the
percentage difference between estimates with each scenario increases
with increasing distance from the targeted field); see   REF
_Ref178147274 \h  Table 20  and   REF _Ref178147279 \h  Table 21 .

Table   SEQ Table \* ARABIC  19 .  Selected AgDRIFT inputs for high-end