Risks of Methomyl Use to Federally Threatened
Bay Checkerspot Butterfly (Euphydryas editha
bayensis), Valley Elderberry Longhorn Beetle
(Desmocerus californicus dimorphus), California Tiger
Salamander (Ambystoma californiense), Central
California Distinct Population Segment, and Delta
Smelt (Hypomesus transpacificus),
And the Federally Endangered
California Clapper Rail (Rallus longirostris ob so let us),
California Freshwater Shrimp (Syncarispacificus),
California Tiger Salamander (Ambystoma
californiense) Sonoma County Distinct Population
Segment and Santa Barbara County Distinct
Population Segment, San Francisco Garter Snake
(Thamnophis sirtalis tetrataenia), and Tidewater Goby
(Eucyclogobius newberryi)
Pesticide Effects Determinations
PC Code: 090301
CAS Number: 16752-77-5
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
September 28,2012
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Primary Authors:
Tiffany Coleman, Environmental Engineer
Tanja Crk, Biologist
Environmental Risk Branch III
Environmental Fate and Effects Division (7507P)
Secondary Review:
James Hetrick, Ph.D., Senior Scientist
Melissa Panger, Ph.D., Senior Scientist
Rosanna Louie-Juzwiak, Risk Assessment Process Leader
Environmental Risk Branch III
Environmental Fate and Effects Division (7507P)
Branch Chief, Environmental Risk Assessment Branch III:
Dana Spatz
Environmental Fate and Effects Division (7507P)
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Table of Contents
1. EXECUTIVE SUMMARY 14
1.1. Purpose of Assessment 14
1.2. Scope of Assessment 15
1.2.1. Uses Assessed 15
1.2.2. Environmental Fate Properties of Methomyl 16
1.2.3. Evaluation of Degradates and Stressors of Concern 18
1.3. Assessment Procedures 19
1.3.1. Exposure Assessment 19
1.3.2. Toxicity Assessment 19
1.3.3. Measures of Risk 20
1.4. Summary of Conclusions 20
2. PROBLEM FORMULATION 30
2.1. Purpose 30
2.2. Scope 31
2.2.1. Evaluation of Degradates and Other Stressors of Concern 32
2.2.2. Evaluation of Mixtures 33
2.3. Previous Assessments 33
2.4. Environmental Fate Properties 35
2.4.1. Environmental Transport Mechanisms 39
2.4.2. Mechanism of Action 40
2.4.3. Use Characterization 40
2.5. Assessed Species 58
2.6. Designated Critical Habitat 71
2.7. Action Area and LAA Effects Determination Area 74
2.7.1. Action Area 74
2.7.2. LAA Effects Determination Area 74
2.8. Assessment Endpoints and Measures of Ecological Effect 76
2.8.1. Assessment Endpoints 76
2.8.2. Assessment Endpoints for Designated Critical Habitat 81
2.9. Conceptual Model 81
2.9.1. Risk Hypotheses 81
2.9.2. Diagram 82
2.10. Analysis Plan 84
2.10.1. Measures of Exposure 85
2.10.2. Measures of Effect 85
2.10.3. Integration of Exposure and Effects 85
2.10.4. Data Gaps 86
3. EXPOSURE ASSESSMENT 86
3.1. Label Application Rates and Intervals 87
3.2. Aquatic Exposure Assessment 88
3.2.1. Modeling Approach 88
3
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3.2.2. Model Inputs 90
3.2.3. Results 91
3.2.4. Existing Monitoring Data 93
3.3. Terrestrial Aximai. Exposure Assessment 94
3.3.1. Exposure to Residues in Terrestrial Food Items 94
3.3.2. Exposure to Terrestrial Invertebrates Derived Using T-REX 97
3.4. Terrestrial Plant Exposure Assessment 101
4. EFFECTS ASSESSMENT 101
4.1. Ecotoxicity Study Data Sources 101
4.2. Toxicity of Methomyl to Aquatic Organisms 103
4.3. Toxicity of Methomyl to Terrestrial Organisms 106
4.3.1. Toxicity to Terrestrial Plants 108
4.4. Toxicity of Chemical Mixtures 109
4.5. Incident Database Review 109
4.5.1. Terrestrial Incidents 110
4.5.2. Plant Incidents Ill
4.5.3. Aquatic Incidents Ill
4.6. Use of Probit Slope Response Relationship to Provide Information on
the Endangered Species Levels of Concern 112
5. RISK CHARACTERIZATION 115
5.1. Risk Estimation 115
5.1.1. Exposures in the Aquatic Habitat 115
5.1.2. Exposures in the Terrestrial Habitat 120
5.1.3. Primary Constituent Elements ofDesignated Critical Habitat 128
5.2. Risk Description 128
5.2.1. Freshwater Fish and Aquatic-phase Amphibians 133
5.2.2. Freshwater Invertebrates 137
5.2.3. Estuarine/Marine Fish 139
5.2.4. Estuarine/Marine Invertebrates 140
5.2.5. Aquatic vascular/non-vascular plants 140
5.2.6. Birds, reptiles, and terrestrial-phase amphibians 141
5.2.7. Mammals 142
5.2.8. Terrestrial invertebrates 142
5.2.9. Terrestrial plants 143
5.2.10. Modification ofDesignated Critical Habitat 147
5.2.11. Spatial Extent of Potential Effects 148
5.3. Effects Determinations 150
5.3.1. Assessed Species 150
5.3.2. Addressing the Risk Hypotheses 150
6. UNCERTAINTIES 151
6.1. Exposure Assessment Uncertainties 151
6.1.1. Terrestrial Exposure Assessment Uncertainties 151
6.1.2. Aquatic Exposure Modeling of Methomyl 154
6.1.3. Exposure in Estuarine/marine Environments 154
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6.1.4. Modeled Versus Monitoring Concentrations 155
6.2. Effects Assessment Uncertainties 156
6.2.1. Data Gaps and Uncertainties 156
6.2.2. Use of Surrogate Species Effects Data 157
6.2.3. Sublethal Effects 158
6.2.4. Aquatic non-vascular open literature data 158
6.2.5. Scatter bait use 159
7. RISK CONCLUSIONS 159
8. REFERENCES 169
9. MRID LIST 171
161-1 Hydrolysis 171
161-2 Photodegradati on-water 171
161-3 Photodegradati on-soil 171
161-4 Photodegradati on-air 172
162-1 Aerobic soil metabolism 172
162-2 Anaerobic soil metabolism 172
162-4 Aerobic aquatic metab 173
163-1 Leach/adsorp/desorption 173
164-1 Terrestrial field dissipation 173
164-2 Aquatic field dissipation 174
165-0 Accumulation Studies — General 175
71-1 Avian Single Dose Oral Toxicity 176
71-2 Avian Dietary Toxicity 176
71-3 Small and Wild mammal Data 177
71-4 Avi an Reproducti on 177
71-5 Simulated or Actual Field Testing 177
72-1 Acute Toxicity to Freshwater Fish 178
72-2 Acute Toxicity to Freshwater Invertebrates 179
72-3 Acute Toxicity to Estuarine/Marine Organisms 180
72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study 180
72-5 Life cycle fish 181
72-7 Simulated or Actual Field Testing 181
123-2 Aquatic plant growth 181
141-1 Honey bee acute contact 182
141-2 Non Target Beneficial Insect Toxicity 182
142-3 Simulated or Actual Field Testing 183
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Appendices
Appendix A. Multi-Active Ingredients Product Analysis
Appendix B. Verification Memo for Methomyl
Appendix C. Risk Quotient (RQ) Method and Levels of Concern (LOCs)
Appendix D. Example Output from PRZM/EXAMS, ECOSAR
Appendix E. Example Output from T-REX and T-HERPS
Appendix F. Multi-Active Ingredients Bibliography
Appendix G. Summary of Ecotoxicity Data for Methomyl
Appendix H. Bibliography of ECOTOX Open Literature
Appendix I. Accepted ECOTOX Data Table
Appendix J. Acute Toxicity Values for Freshwater Fish and Invertebrates
Appendix K. Description of Spatial Analysis and Maps Showing the Overlap of the
Initial Area of Concern and the Species Habitat and Occurrence Sections
Appendix L. Tidewater Goby Habitat Maps Depicting Potential Use Areas and its
Overlap
Appendix M. Monitoring Data for Methomyl
Appendix N. Schematic for Methomyl Scatter Bait Uses
Appendix O. Methomyl Multi-crop Memo
Attachments
Attachment I. Supplemental Information on Standard Procedures for Threatened and
Endangered Species Risk Assessments on the San Francisco Bay Species
Attachment II: Status and Life History for the San Francisco Bay Species
Attachment III: Baseline Status and Cumulative Effects for the San Francisco Bay
Species
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List of Tables
Table
1-1. Summary of Environmental Chemistry, Fate and Transport Properties of
Methomyl
. 17
Table
1-2 Effects Determination Summary for Effects of Methomyl on the SFGS, CCR,
BCB, VELB, CTS, DS, CFS, and TG
.22
Table
1-3 Effects Determination Summary for the Critical Habitat Impact Analysis....
25
Table
1-4 Use Specific Summary of the Potential for Adverse Effects to Aquatic Taxa
17
Table
1-5 Use Specific Summary of the Potential for Adverse Effects to Terrestrial
Taxa
28
Table
2-1 Summary of Soil Batch Equilibrium Parameters for Methomyl. A
. 36
Table
2-2. Physical-chemical Properties of Methomyl
. 37
Table
2-3. Summary of methomyl Environmental Fate Properties
. 38
Table
2-4. Summary of Current Methomyl Uses
.41
Table
2-5. Currently Registered Methomyl End-Use Products
.41
Table
2-6. Methomyl Uses Assessed for California
.44
Table
2-7. Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 1999 to 2010 for Currently
Registered Methomyl Uses1
. 55
Table
2-8. Summary of Current Distribution, Habitat Requirements, and Life History
Information for the Assessed Listed Species1
. 59
Table
2-9. Designated Critical Habitat PCEs for the BCB, VELB, CTS-CC DPS, DS,
CTS-SB DPS, and TG Species
. 72
Table
2-10. Taxa Used in the Analyses of Direct and Indirect Effects for the Assessed
Listed Species
. 76
Table
2-11. Taxa and Assessment Endpoints Used to Evaluate the Potential for Use of
Methomyl to Result in Direct and Indirect Effects to the Assessed Listed
Species or Modification of Critical Habitat
. 78
Table
3-1. Methomyl Uses, Scenarios, and Application Information
. 87
Table
3-2. Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Methomyl Endangered Species Assessment
. 90
Table
3-3. Aquatic EECs ((J-g/L) for Methomyl Uses in California
. 91
Table
3-4. Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
Methomyl with T-REX and T-HERPS
. 95
Table
3-5. Upper-bound Kenaga Nomogram EECs for Dietary- and Dose-based
Exposures of Birds and Mammals Derived Using T-REX for Methomyl:
Accounting for direct effects with most sensitive size classes for acute
exposure
. 97
Table
3-6. Summary EECs Used for Estimating Risk to Terrestrial Invertebrates and
Derived Using T-REX ver. 1.5. for Methomyl
. 98
Table
3-7. Upper-bound Kenaga Nomogram EECs for Dietary- and Dose-based
Exposures of Amphibians and Reptiles Derived Using T-HERPS for
Methomyl: CTS specific
. 99
Table
3-8. Upper-bound Kenaga Nomogram EECs for Dietary- and Dose-based
Exposures of Amphibians and Reptiles Derived Using T-HERPS for
Methomyl: SFGS specific
100
Table
4-1. Aquatic Toxicity Profile for Methomyl
7
104
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Table 4-2. Categories of Acute Toxicity for Fish and Aquatic Invertebrates 105
Table 4-3. Terrestrial Toxicity Profile for Methomyl 106
Table 4-4. Categories of Acute Toxicity for Avian and Mammalian Studies 107
Table 4-5 Measures of Effects to Plants from Methomyl Efficacy Studies 112
Table 4-6 Individual Effect Probabilities Using the IEC v. 1.1 Model 117
Table 5-1. Acute and Chronic RQs for Freshwater Fish and/or Aquatic-Phase
Amphibians and Reptiles (Surrogate: Channel Catfish) 116
Table 5-2. Summary of Acute and Chronic RQs for Freshwater Invertebrates. (Surrogate:
Daphnia magna) 117
Table 5-3. Summary of RQs for Estuarine/Marine Fish (Surrogate: Sheepshead minnow)
118
Table 5-4. Summary of Acute and Chronic RQs for Estuarine/Marine Invertebrates
(Surrogate: Northern pink shrimp) 119
Table 5-5. Acute and Chronic RQs Derived Using T-REX for Methomyl: Birds
(including CCR), CTS (all DPS), and SFGS consuming short grass 122
Table 5-6 Acute and Chronic RQs Derived Using T-REX for Methomyl: Birds (including
CCR), CTS (all DPS), and SFGS consuming arthropods 125
Table 5-7 Acute and Chronic RQs Derived Using T-HERPS for Methomyl: CTS (all
DPS) Consuming Small Insects and Herbivorous Mammals 126
Table 5-8 Acute and Chronic RQs Derived Using T-HERPS for Methomyl: SFGS
Consuming Small Insects and Herbivorous Mammals 126
Table 5-9. Acute and Chronic RQs Derived Using T-REX for Methomyl and Mammals
126
Table 5-10. Summary of RQs for Terrestrial Invertebrates 127
Table 5-11. Risk Estimation Summary for Methomyl - Direct and Indirect Effects 128
Table 5-12. Risk Estimation Summary for Methomyl - Effects to Designated Critical
Habitat. (PCEs) 130
Table 5-13. Freshwater Fish Genus and Species Mean Acute 96-Hr LC50 Values 135
Table 5-14. Ranked Freshwater Invertebrate Genus Mean Acute Values 138
Table 5-15 Range of Acute and Chronic RQs that Exceed Non-listed Species LOCs for
Prey of Each SF Bay Species 144
Table 5-16. Buffers for Most Sensitive Aquatic and Terrestrial Species using AgDRIFT
148
Table 6-1. Percentage of EEC orRQ for the Specified Dietary Items and Size Classes as
Compared to the EEC or RQ for The Most Sensitive Dietary Items (Short
Grass) and Size Class (Small Bird or Small Mammal) 152
Table 6-2. Percentage of EEC or RQ for the Specified Dietary Class as Compared to the
EEC or RQ for The Most Sensitive Dietary Class (Small Herbivore Mammals)
and Size Class (Medium Amphibian or Snake) 153
Table 7-1. Effects Determination Summary for Effects of Methomyl on the SFGS, CCR,
BCB, VELB, CTS, DS, CFS, and TG 160
Table 7-2. Effects Determination Summary for the Critical Habitat Impact Analysis. 164
Table 7-3. Use Specific Summary of The Potential for Adverse Effects to Aquatic Taxa
165
Table 7-4. Use Specific Summary of The Potential for Adverse Effects to Terrestrial
Taxa 166
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List of Figures
Figure 2-1. Methomyl Usage by Cop Reporting District (2006-2010) 53
Figure 2-2. Bay Checkerspot Butterfly (BCB) (Euphydryas editha bayensis)Critical
Habitat and Occurrence Sections identified in Case No. 07-2794-JCS 64
Figure 2-3. Valley Elderberry Longhorn Beetle (VELB) (Desmocerus californicus
dimorphus) Critical Habitat and Occurrence Sections identified in Case No.
07-2794-JCS 65
Figure 2-4. California Tiger Salamander (CTS) (Ambystoma californiense) Critical
Habitat and Occurrence Sections identified in Case No. 07-2794-JCS 66
Figure 2-5. Delta Smelt (DS) (Hypomesus transpacificus) Critical Habitat and
Occurrence Sections identified in Case No. 07-2794-JCS 67
Figure 2-6. California Clapper Rail (CCR) (Rallus longirostris obsoletus) Critical Habitat
and Occurrence Sections identified in Case No. 07-2794-JCS 68
Figure 2-7. California Freshwater Shrimp (CFWS) (Syncarispacifica) Critical Habitat
and Occurrence Sections identified in Case No. 07-2794-JCS 69
Figure 2-8. San Francisco Garter Snake (SFGS) (Thamnophis sirtalis tetrataenia) Critical
Habitat and Occurrence Sections identified in Case No. 07-2794-JCS 70
Figure 2-9. Tidewater Goby (TG) (Eucyclogobius newberryi) Critical Habitat and
Occurrence Sections identified in Case No. 07-2794-JCS. The critical habitat
and sections are exaggerated here by a buffer applied to the original habitat
polygons. A series of larger scale maps are referenced in Appendix L which
show the actual area of critical habitat and sections 71
Figure 2-10. Conceptual Model Depicting Stressors, Exposure Pathways, and Potential
Effects to Aquatic Organisms from the Use of Methomyl 83
Figure 2-11. Conceptual model depicting stressors, exposure pathways, and potential
effects to terrestrial organisms from the use of methomyl 84
Figure 5-1. Freshwater Fish Species Sensitivity Distribution for Methomyl 136
Figure 5-2. Species Sensitivity Distribution for Freshwater Invertebrates and Methomyl.
139
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List of Commonly Used Abbreviations and Nomenclature
l-ig/kg
Symbol for "micrograms per kilogram"
^g/L
Symbol for "micrograms per liter"
°C
Symbol for "degrees Celsius"
AAPCO
Association of American Pesticide Control Officials
a.i.
Active Ingredient
AIMS
Avian Monitoring Information System
Acc#
Accession Number
amu
Atomic Mass Unit
BCB
Bay Checkerspot Butterfly
BCF
Bioconcentration Factor
BEAD
Biological and Economic Analysis Division
bw
Body Weight
CAM
Chemical Application Method
CARB
California Air Resources Board
AW
Alameda Whipsnake
CBD
Center for Biological Diversity
CCR
California Clapper Rail
CDPR
California Department of Pesticide Regulation
CDPR-PUR
California Department of Pesticide Regulation Pesticide Use
Reporting Database
CFWS
California Freshwater Shrimp
CI
Confidence Interval
CL
Confidence Limit
CTS
California Tiger Salamander
CTS-CC
California Tiger Salamander Central California Distinct
Population Segment
CTS-SB
California Tiger Salamander Santa Barbara County Distinct
Population Segment
CTS-SC
California Tiger Salamander Sonoma County Distinct
Population Segment
DS
Delta Smelt
EC
Emulsifiable Concentrate
ECos
5% Effect Concentration
EC 25
25% Effect Concentration
EC 50
50% (or Median) Effect Concentration
ECOTOX
EPA managed database of Ecotoxicology data
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EEC
Estimated Environmental Concentration
EFED
Environmental Fate and Effects Division
e-g-
Latin exempli gratia ("for example")
EIM
Environmental Information Management System
EPI
Estimation Programs Interface
ESU
Evolutionarily significant unit
et al.
Latin et alii ("and others")
etc.
Latin et cetera ("and the rest" or "and so forth")
EXAMS
Exposure Analysis Modeling System
FIFRA
Federal Insecticide Fungicide and Rodenticide Act
FQPA
Food Quality Protection Act
ft
Feet
GENEEC
Generic Estimated Exposure Concentration model
HPLC
High Pressure Liquid Chromatography
IC05
5% Inhibition Concentration
IC50
50% (or median) Inhibition Concentration
i.e.
Latin for id est ("that is")
IEC V1.1
Individual Effect Chance Model Version 1.1
KABAM
K0w (based) Aquatic BioAccumulation Model
kg
Kilogram(s)
kJ/mole
Kilojoules per mole
km
Kilometer(s)
Kaw
Air-water Partition Coefficient
Kd
Solid-water Distribution Coefficient
KF
Freundlich Solid-Water Distribution Coefficient
Koc
Organic-carbon Partition Coefficient
Kow
Octanol-water Partition Coefficient
LAA
Likely to Adversely Affect
lb a.i./A
Pound(s) of active ingredient per acre
LC50
50% (or Median) Lethal Concentration
LD50
50% (or Median) Lethal Dose
LOAEC
Lowest Observable Adverse Effect Concentration
LOAEL
Lowest Observable Adverse Effect Level
LOC
Level of Concern
LOD
Level of Detection
LOEC
Lowest Observable Effect Concentration
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LOQ
Level of Quantitation
m
Meter(s)
MA
May Affect
MATC
Maximum Acceptable Toxicant Concentration
m2/day
Square Meters per Days
ME
Mi croencap sul ated
mg
Milligram(s)
mg/kg
Milligrams per kilogram (equivalent to ppm)
mg/L
Milligrams per liter (equivalent to ppm)
mi
Mile(s)
mmHg
Millimeter of mercury
MRID
Master Record Identification Number
MW
Molecular Weight
n/a
Not applicable
NASS
National Agricultural Statistics Service
NAWQA
National Water Quality Assessment
NCOD
National Contaminant Occurrence Database
NE
No Effect
NLAA
Not Likely to Adversely Affect
NLCD
National Land Cover Dataset
NMFS
National Marine Fisheries Service
NO A A
National Oceanic and Atmospheric Administration
NOAEC
No Observable Adverse Effect Concentration
NOAEL
No Observable Adverse Effect Level
NOEC
No Observable Effect Concentration
NRCS
Natural Resources Conservation Service
OPP
Office of Pesticide Programs
OPPTS
Office of Prevention, Pesticides and Toxic Substances
ORD
Office of Research and Development
PCE
Primary Constituent Element
pH
Symbol for the negative logarithm of the hydrogen ion activity
in an aqueous solution, dimensionless
pKa
Symbol for the negative logarithm of the acid dissociation
constant, dimensionless
ppb
Parts per Billion (equivalent to |ig/L or |ig/kg)
ppm
Parts per Million (equivalent to mg/L or mg/kg)
12
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PRD
Pesticide Re-Evaluation Division
PRZM
Pesticide Root Zone Model
ROW
Right of Way
RQ
Risk Quotient
SFGS
San Francisco Gaiter Snake
SJKF
San Joaquine Kit Fox
SLN
Special Local Need
SMHM
Salt Marsh Harvest Mouse
TG
Tidewater Goby
T-HERPS
Terrestrial Herpetofaunal Exposure Residue Program
Simulation
T-REX
Terrestrial Residue Exposure Model
UCL
Upper Confidence Limit
USD A
United States Department of Agriculture
USEPA
United States Environmental Protection Agency
USFWS
United States Fish and Wildlife Service
USGS
United States Geological Survey
VELB
Valley Elderberry Longhorn Beetle
WP
Wettable Powder
wt
Weight
13
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1. Executive Summary
1.1. Purpose of Assessment
The purpose of this assessment is to evaluate potential direct and indirect effects on the Bay
Checkerspot Butterfly (BCB, Euphydryas editha bayensis), Valley Elderberry Longhorn Beetle
(VELB, Desmocerus californicus dimorphus), California Tiger Salamander Central California
DPS (CTS-CC DPS, Ambystoma calif orniense), Delta Smelt (DS, Hypomesus transpacificus),
California Clapper Rail (CCR, Rallus longirostris obsoletus), California Tiger Salamander:
Sonoma County DPS (CTS-SC DPS, A. calif or niense), California Tiger Salamander: Santa
Barbara County DPS (CTS-SB DPS, A. californiense), California Freshwater Shrimp (CFWS,
Syncarispacified), San Francisco Garter Snake (SFGS, Thamnophis sirtalis tetrataenia), and
Tidewater Goby (TG, Eucyclogobius newberryi) arising from FIFRA regulatory actions
regarding use of methomyl, a carbamate insecticide, on agricultural and non-agricultural sites. In
addition, this assessment evaluates whether these actions can be expected to result in
modification of designated critical habitat for the Bay Checkerspot Butterfly (BCB, E. editha
bayensis), Valley Elderberry Longhorn Beetle (VELB, D. californicus dimorphus), California
Tiger Salamander Central California DPS (CTS-CC DPS, A. californiense), Delta Smelt (DS, H.
transpacificus), California Tiger Salamander: Santa Barbara County DPS (CTS-SB DPS, A.
californiense), and Tidewater Goby (TG, E. newberryi). This assessment was completed in
accordance with the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries
Service (NMFS) Endangered Species Consultation Handbook (USFWS/NMFS, 1998),
procedures outlined in the Agency's Overview Document (USEPA, 2004), and consistent with a
suit in which methomyl was alleged to be of concern to the BCB, VELB, CTS, DS, CCR, CFS,
SFGS, and TG (Center for Biological Diversity (CBD) vs. EPA et al. (Case No. 07-2794-JCS).
- Bay Checkerspot Butterfly (BCB): The BCB was listed as threatened in 1987 by the
USFWS. The species primarily inhabits native grasslands on serpentine outcrops around
the San Francisco Bay Area in California.
- Valley Elderberry Longhorn Beetle (VELB): The VELB was listed as threatened in
1980 by the USFWS. The species is found in areas with elderberry shrubs throughout
California's Central Valley and associated foothills on the east and the watershed of the
Central Valley on the west.
- California Tiger Salamander (CTS): There are currently three CTS Distinct
Population Segments (DPSs): the Sonoma County(SC) DPS, the Santa Barbara (SB)
DPS, and the Central California (CC) DPS. Each DPS is considered separately in the risk
assessment as they occupy different geographic areas. The main difference in the
assessment will be in the spatial analysis. The CTS-SB and CTS-SC were downlisted
from endangered to threatened in 2004 by the USFWS, however, the downlisting was
vacated by the U.S. District Court. Therefore, the Sonoma and Santa Barbara DPSs are
currently listed as endangered while the CTS-CC is listed as threatened. CTS utilize
vernal pools, semi-permanent ponds, and permanent ponds, and the terrestrial
environment in California. The aquatic environment is essential for breeding and
reproduction and mammal burrows are also important habitat for estivation.
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- Delta Smelt (DS): The DS was listed as threatened on March 5, 1993 (58 FR 12854) by
the USFWS (USFWS, 2007a). DS are mainly found in the Suisun Bay and the
Sacramento-San Joaquin estuary near San Francisco Bay. During spawning DS move
into freshwater.
- CA Clapper Rail (CCR): The CCR was listed by the USFWS as an endangered species
in 1970. The species is found only in California in coastal wetlands along the San
Francisco estuary and Suisun Bay.
- California Freshwater Shrimp (CFS): The CFS was listed as endangered in 1988 by
the USFWS. The CFS inhabits freshwater streams in Central California in the lower
Russian River drainage and westward to the Pacific Ocean and coastal streams draining
into Tomales Bay and southward into the San Pablo Bay.
- San Francisco Garter Snake (SFGS): The SFGS was listed as endangered in 1967 by
the USFWS. The species is endemic to the San Francisco Peninsula and San Mateo
County in California in densely vegetated areas near marshes and standing open water.
- Tidewater Goby (TG): The TG was listed as endangered in 1994 by the USFWS. The
range of the TG is limited to coastal brackish water habitats along the coast of California.
1.2. Scope of Assessment
1.2.1. Uses Assessed
Methomyl is an insecticide currently registered for use on a wide variety of sites including field,
vegetable, and orchard crops; turf (sod farms only); livestock quarters; commercial premises; and
refuse containers. Estimates of methomyl usage indicate that it is used extensively on sweet
corn, lettuce, cotton, and alfalfa (these uses represent 50% of methomyl-use in the United States
and are registered uses in California). All uses are agricultural, industrial, or commercial; there
are no residential uses for methomyl. It is recognized that methomyl is used in many parts of the
U.S.; however, the scope of this assessment limits consideration of the areas of use that may be
applicable to the protection of the SFBay and its designated critical habitat within the state of
California. For a complete list of uses, please see Section 2.
Methomyl is formulated mainly as soluble concentrates, but also includes granular,
pelleted/tableted, and bait/solid formulations. Baited granular formulations are not assessed as
they are expected to primarily occur around buildings in urban areas, removed from areas where
the San Francisco (SF) Bay species being assessed are likely to occur. Application methods for
the agricultural uses of methomyl include aircraft (fixed-wing and helicopter), high and low
volume ground sprayer, ultra low volume sprayer, and granule application. Although most
potential uses are assessed, risks from ground boom and aerial applications are the focus of this
assessment because they are expected to result in the highest off-target concentrations of
methomyl. Runoff associated with large rainfall events is expected to be responsible for the
greatest off-target movement of methomyl.
The end result of the EPA pesticide registration process (the FIFRA regulatory action) is an
approved product label. The label is a legal document that stipulates how and where a given
15
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pesticide may be used. Product labels (also known as end-use labels) describe the formulation
type (e.g., liquid or granular), acceptable methods of application, approved use sites, and any
restrictions on how applications may be conducted. Thus, the use or potential use of methomyl
in accordance with the approved product labels for California is "the action" being assessed.
Although current registrations of methomyl allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of methomyl in portions
of the action area that are reasonably assumed to be biologically relevant to the SF Bay species
and their designated critical habitat. Further discussion of the action area for the SF Bay species
and their critical habitat is provided in Section 2.7.
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of
active ingredients, either those mixtures of multiple active ingredients in product formulations or
those in the applicator's tank. Methomyl has registered products that contain multiple active
ingredients. Analysis of the available acute oral mammalian LD50 data for multiple active
ingredient products relative to the single active ingredient is provided in APPENDIX A. A list
of accepted literature on mixtures is available in APPENDIX F. If effects data are available for
a formulated product containing more than one active ingredient, they may be used qualitatively
or quantitatively in accordance with the Agency's Overview Document and the Services'
Evaluation Memorandum (U.S., EPA 2004; USFWS/NMFS 2004).
1.2.2. Environmental Fate Properties of Methomyl
As noted in the 1998 Reregi strati on Eligibility Decision (RED), methomyl is moderately
persistent and mobile in soil. Methomyl is less persistent in aqueous environments. It is stable
to hydrolysis at lower pHs (neutral to acidic), but it degrades slowly in alkaline conditions (ti/2 =
30 days). Methomyl degradation appears to be dependent on microbially-mediated (aerobic soil
metabolism - ti/2 = 4.3 - 45 d; anaerobic soil metabolism - ti/2 = 14 days; aerobic aquatic
metabolism - ti/2 = 3.5-4.5 d) and abiotic processes (photodegradation in water - ti/2 = 1 d).
Under anaerobic conditions, methomyl degradation is likely to be faster than under aerobic
conditions (Smelt et al., 1983), particularly in the presence of reduced iron (Bromilow et al.,
1986). In laboratory studies, methomyl does not readily adsorb to soil and has the potential to
be mobile (mean Koc = 46 mL/g0C). Table 1-1 summarizes the fate and physical-chemical
properties of methomyl based on information from the registrants.
Field dissipation studies (MRIDs 41623901, 41623902, 42288001, 43217903) show varying
dissipation rates of the chemical in soils (DT50 from 4 to 54 days). Dissipation rates were related
primarily to differences in soil moisture content, which may affect the microbial activity, and
rainfall/irrigation, which could influence leaching. Methomyl was detected in soil as deep as 15
- 90 cm.
16
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Table 1-1.Summary of Environmental Chemistry, Fate and Transport Properties of
Methomyl.
PARAMETER
VALUE
REFERENCE/
COMMENTS
Selected Physical/Chemical Parameters
PC code
090301
CAS No.
16752-77-5
Chemical name
(S-methyl N-((methylcarbamoyl)oxy) thioacetimidate
Chemical formula
C5H10N2O2S
Molecular weight
162.2 g/mol
Product Chemistry
Water solubility (20 °C)
5.5 x 104 mg/L
MRID 41402101
Vapor pressure
5.4 x 10 6torr
MRID 41209701
Henry's law constant
(atm-m3/mol)
2.1 x 10"11 atm-m3/mol
(calculated)
Kow
1.31
MRID 00157991
Persistence
Hydrolysis
pH 5: stable
pH 7: stable
pH 9: 30 d
MRID 00131249
pH2.09-7.11: >413 d pH8.88:14.6d
pH 7.40: 337 d pH 8.89: 16.1 d
pH 7.67: 206 d pH 9.45: 4.77 d
pH 7.92: 123 d pH 9.92: 1.66 d
pH 8.42: 40.8 d
Strathmann and
Stone, 2002 (values
calculated from rate
constants)
Photolysis in water
ti/2 = 1 d
MRID 0161885
Clear water, near
surface
50 d (natural water)
Stable (pH 7 buffer w/ no excess nitrate)
42 days (pH 7 buffer w/ 100 M excess nitrate)
8.5 days (pH 7 buffer w/ 1000 M excess nitrate)
MRID 43823305
Photolysis in soil
ti/2 ~ 33 d
MRID 00163745
Aerobic soil metabolism
Flanagan silt loam
44 days
MRID 00008568
Madera, CA loam
12 days
MRID 43217901
USA (mattapex), Loam
France (nambsheim),
SandyLoam
Germany (speyer 2.2), Sandy
Loam
7.9 days
6.4 days
4.3 days
MRID 45473401
Anaerobic soil
metabolism
Madera, CA loam: 14 d
MRID 432179-02
Aerobic aquatic
metabolism
Auchingilsie clay loam: 4.0 d
Hinchingbrooke silty clam loam: 4.6 d
MRID 433254-01
17
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PAR AMI.UK
\ Al l 1.
Ki i i:ki:\( 1:/
( ommims
Anaerobic aquatic
metabolism
No data
Mobility
Batch equilibrium
Soil Texture
K/
1/N
Koc
MRID 00161884
Sandy loam
0.72
0.86
65
Silt loam
1.0
0.86
45
Silt
1.4
0.86
36
Sandy loam
0.23
0.90
39
Field Dissipation
Terrestrial field
dissipation
54 d (CA sandy loam cropped to cabbage);
leached to deepest sample depth (60-90 cm)
4-6 d (MS loam cropped to cabbage); leached to
15-30 cm sample depth
MRID 41623901/
41623902
MRID 42288001/
43217903
Bioaccumulation
Accumulation in fish,
BCF
No data
Bioaccumulation is not
expected based on low
Kow
1. Units of (mg/kg)/(mg/L)1/N, where 1/N is the Freundlich exponent.
Potential transport mechanisms for methomyl include surface water runoff, spray drift, and
leaching. Secondary drift (atmospheric transport) of volatilized or soil-bound residues leading to
deposition onto nearby or more distant ecosystems is not expected given methomyl's relatively
high solubility in water (5.5 x 104 mg/L), low vapor pressure (5.4 x 10"6 torr) and Henry's law
11 3
constant (2.1 x 10" atm-m /mol).
1.2.3. Evaluation of Degradates and Stressors of Concern
Major degradates include methomyl oxime (S-methyl-N-hydroxythioacetimidate), acetonitrile,
acetamide ,and CO2. There are data demonstrating the formation of methomyl sulfoxide during
disinfection (chlorination) in water treatment (MRID 46210701), although this compound was
not found in any environmental fate studies. According to ECOSAR (See APPENDIX D for
ECOSAR output), the calculated endpoints indicate that the fish and invertebrates are less
sensitive to the oxime than to the parent compound (Fish (LC50) = 76.219 ppm for oxime, Fish
(EC50) = 0.320 ppm for parent; invertebrates (LC50) = 8.436 ppm for oxime, invertebrates
(EC50) = 0.005 ppm for parent). ECOSAR calculated an EC50 for green algae of 8.557 ppm for
the oxime. One open literature study on micro-algae showed an EC50 range from 108-184 ppm.
The aquatic plant data suggest that the oxime may possibly be more toxic to aquatic plants, but
this is based on a single open literature study (Record #: 118717, Pereira el a/.2009)that was
deemed qualitative, and not for quantitative use (i.e., not suitable for RQ calculations See Section
5.l.le). Based on the available data, the oxime appears to be less toxic to aquatic organisms than
the parent compound. Previously, methomyl was deemed to not have any degradates with
toxicological concerns (DP 374952), which also includes the oxime and degradate methomyl
sulfoxide. Therefore, this assessment is based on the parent, methomyl, alone.
18
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1.3. Assessment Procedures
A description of routine procedures for evaluating risk to the SF Bay species are provided in
Attachment I.
1.3.1. Exposure Assessment
1.3.1.a. Aquatic Exposures
Tier-II aquatic exposure models are used to estimate high-end exposures of methomyl in aquatic
habitats resulting from runoff and spray drift from different uses. The models used to predict
aquatic EECs are the Pesticide Root Zone Model coupled with the Exposure Analysis Model
System (PRZM/EXAMS). The AgDRIFT model is also used to estimate deposition of
methomyl on aquatic habitats from spray drift. The peak model-estimated environmental
concentrations resulting from different methomyl uses range from 2.5 |ig/L (sorghum) to 61.9
|ig/L (cole crops, particularly cabbage). These estimates are supplemented with analysis of
available California surface water monitoring data from U. S. Geological Survey's National
Water Quality Assessment (NAWQA) program and the California Department of Pesticide
Regulation (CDPR). There were 19 detections of methomyl reported by NAWQA for California
surface waters out of 394 samples. The maximum concentration reported was 0.67 |ig/L and all
detects were concentrated to four sites. The maximum concentration of methomyl reported by
the CDPR surface water database (5.4 |ig/L) is roughly 11.6 times lower than the highest peak
model-estimated environmental concentration.
1.3.1.b. Terrestrial Exposures
To estimate methomyl exposures to terrestrial species resulting from uses involving methomyl
applications, the T-REX model is used for foliar and granular uses {i.e., on sweet corn). The
AgDRIFT model is also used to estimate deposition of methomyl on terrestrial habitats from
spray drift. The T-HERPS model is used to allow for further characterization of dietary
exposures of terrestrial-phase amphibians relative to birds.
1.3.2. Toxicity Assessment
The assessment endpoints include direct toxic effects on survival, reproduction, and growth of
individuals, as well as indirect effects, such as reduction of the food source and/or modification
of habitat. The Agency evaluated registrant-submitted studies and data from the open literature
(where available) to characterize methomyl toxicity. The most sensitive toxicity value available
from acceptable or supplemental studies for each taxon relevant for estimating potential risks to
the assessed species and/or their designated critical habitat was used.
Methomyl is highly toxic to freshwater and moderately toxic to estuarine/marine fish. It
is very highly toxic to freshwater and marine/estuarine invertebrates on an acute exposure basis.
The compound has growth effects on a chronic basis as well for estuarine/marine fish at a
LOAEC of 0.490 mg a.i./L; the chronic freshwater fish endpoint (NOAEC: 0.012 mg a.i./L) is
based on an acute to chronic ratio (ACR). In addition, methomyl has reproductive effects on a
19
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chronic basis for freshwater invertebrates at a LOAEC of 0.001 mg a.i./L; the chronic
estuarine/marine invertebrate endpoint (NOAEC: 0.0024 mg a.i./L) is based on an acute to
chronic ratio (ACR). Methomyl is highly toxic and slightly toxic on an acute oral and subacute
dietary exposure basis, respectively, to birds. It is highly toxic to mammals on an acute oral
exposure basis. Methomyl has reproductive effects on birds and mammals, affecting number of
eggs and offspring produced as well as pup body weight in subsequent generations at 150 (bird)
and 75 (rat) mg a.i./kg-diet concentrations, respectively. Methomyl is classified as highly toxic to
honey bees on an acute contact exposure basis. Registrant submitted data on aquatic and
terrestrial plants are not available. However, an open literature study on algae was reviewed and
used qualitatively in risk characterization. A review of efficacy studies on terrestrial plants is
available in this document as well.
1.3.3. Measures of Risk
Acute and chronic risk quotients (RQs) are compared to the Agency's Levels of Concern (LOCs)
to identify instances where methomyl use has the potential to adversely affect the assessed
species or adversely modify their designated critical habitat. When RQs for a particular type of
effect are below LOCs, the pesticide is considered to have "no effect" on the species and its
designated critical habitat. Where RQs exceed LOCs, a potential to cause adverse effects or
habitat modification is identified, leading to a conclusion of "may affect". If methomyl use
"may affect" the assessed species, and/or may cause effects to designated critical habitat, the best
available additional information is considered to refine the potential for exposure and effects, and
distinguish actions that are Not Likely to Adversely Affect (NLAA) from those that are Likely to
Adversely Affect (LAA).
1.4. Summary of Conclusions
In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the information
presented in this endangered species risk assessment represents the best data currently available
to assess the potential risks of methomyl to SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG
and the designated critical habitat of BCB, VELB, CTS (CC DPS & SB DPS), DS, and TG.
Based on the best available information, the Agency makes a May Affect, Likely to Adversely
Affect determination for the SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG. The species
critical habitat and/or occurrence sections overlap with the use footprint. Additionally, the
Agency has determined that there is the potential for modification of the designated critical
habitat for the BCB, VELB, CTS (CC DPS & SB DPS), DS, and TG from the use of the
chemical. Given the LAA determination for SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG
and potential modification of designated critical habitat for BCB, VELB, CTS (CC DPS & SB
DPS), DS, and TG, a description of the baseline status and cumulative effects is provided in
Attachment III.
A summary of the risk conclusions and effects determinations for the SFGS, CCR, BCB, VELB,
CTS, DS, CFS, and TG and the critical habitat, given the uncertainties discussed in Section 6 and
20
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Attachment I, is presented in Table 1-2 and Table 1-3. Use specific effects determinations are
provided in Table 1-4 and Table 1-5.
Table 1-2. Effects Determination Summary for Effects of Methomyl on the SFGS, CCR,
BCB, VELB,
CTS, DS, CFS, and TG
Species
Effects
Determination
Basis for Determination
San Francisco
Garter Snake
(Thamnophis
sirtalis tetrataenia)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: dose and dietary-based RQs >0.1 for most assessed uses for small and
medium-sized reptiles (based on toxicity data for birds) consuming
arthropodsand herbivorous mammals
• Chronic: dietary-based RQs >1 for most assessed uses for small and medium-
sized reptiles (based on toxicity data for birds) consuming arthropods and
herbivorous mammals
• Granular (RQs 3.83-14.35) and scatter bait (RQ 5.55) uses exceed LOCs (based
on bird toxicity data)
• Bird (surrogates for reptiles) incident data indicate numerous deaths of various
species by baiting and unknown use patterns
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on bird toxicity data) ranges from 1 in
294,000 to 1 in 1 (at the default slope of 4.5)
Potential for Indirect Effects
• SFGS prey base is affected based on LOC exceedences; SFGS feeds on
invertebrates (freshwater invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86;
terrestrial invert RQs: 42.30-157.12), fish (freshwater fish RQs: acute: 0.13-
0.19; chronic: 1.99-2.67), small mammals (15g mammal RQs: acute: 1.02-7.25;
chronic: 1.80-58.01), reptiles and amphibians (bird RQs: acute: 0.12-27.97;
chronic: 1.44-3.34; 20g reptile: acute: 0.15 -23.29; chronic: 1.10-2.56)
• Granular(RQs 1.58-5.92)andscatterbait(RQ4.91)usesexceedLOCsfor
mammals (prey of SFGS)
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: honey bee, lab rat,
bird, freshwater invertebrate/fish) ranges from 1 in 5.37x 107 to 1 in 1
California Clapper
Rail (Rallus
longirostris
obsoletus)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: dose and dietary-based RQs >0.1 for most assessed uses for small and
medium-sized birds consuming arthropods and herbivorous mammals
• Chronic: dietary-based RQs >1 for most assessed uses for small and medium-
sized birds consuming arthropods and herbivorous mammals
• Granular (RQs 3.83-14.35) and scatter bait (RQ 5.55) uses exceed LOCs (based
on bird toxicity data)
• Bird incident data indicate numerous deaths of various species by baiting and
unknown use patterns
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on bird toxicity data) ranges from 1 in
294,000 to 1 in 1 (at the default slope of 4.5)
Potential for Indirect Effects
• CCR prey base is affected; CCR feeds on aquatic invertebrates, worms, spiders
(freshwater invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86; terrestrial invert
RQs: 42.30-157.12; estuarine/marine invert: acute: 0.13-3.26; chronic: 1.33-
17.75), dead fish (freshwater fish RQs: acute: 0.13-0.19; chronic: 1.99-2.67),
small mammals (15g mammal RQs: acute: 1.02-7.25; chronic: 1.80-58.01),
small birds and amphibians/frogs (bird RQs: acute: 0.12-27.97; chronic: 1.44-
3.34)
21
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Species
Effects
Determination
Basis for Determination
• Granular(RQs 1.58-5.92)andscatterbait(RQ4.91)usesexceedLOCsfor
mammals (prey of CCR)
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: honey bee, lab rat,
bird, freshwater invertebrate/fish, estuarine/marine invertebrate/fish) ranges
from 1 in 8.8 x 1024 to 1 in 1
Bay Checkerspot
Butterfly
(Euphydryas editha
bayensis)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Terrestrial invertebrate/ arthropod RQs > 0.05 (the interim terrestrial
invertebrate LOC) for all uses.
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on honey bee toxicity data) is 1 in 1
Potential for Indirect Effects
• Habitat modification (without terrestrial plant data risk is assumed);
furthermore, incident data on melons indicates damage to terrestrial plants after
ground application possibly due to a methomyl formulation
• The species critical habitat and/or occurrence sections overlap with the use
footprint
Valley Elderberry
Longhorn Beetle
(Desmocerus
californicus
dimorphus)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Terrestrial invertebrate/ arthropod RQs > 0.05 (the interim terrestrial
invertebrate LOC) for all uses.
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on honey bee toxicity data) is 1 in 1
Potential for Indirect Effects
• Habitat modification (without terrestrial plant data risk is assumed);
furthermore, incident data on melons indicates damage to terrestrial plants after
ground application possibly due to a methomyl formulation
• The species critical habitat and/or occurrence sections overlap with the use
footprint
California Tiger
Salamander
(Ambystoma
californiense)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: dose and dietary-based RQs >0.1 for most assessed uses for small and
medium-sized terrestrial-phase amphibians (based on bird toxicity data)
consuming arthropods and herbivorous mammals
• Chronic: dietary-based RQs >1 for most assessed uses for small and medium-
sized terrestrial-phase amphibians (based on bird toxicity data) consuming
arthropods and herbivorous mammals
• Granular (RQs 3.83-14.35) and scatter bait (RQ 5.55) uses exceed LOCs (based
on bird toxicity data)
• Bird (which are surrogates for terrestrial-phase amphibians) incident data
indicate numerous deaths of various species by baiting and unknown use
patterns
• Acute: RQs > 0.05 for most uses assessed including cabbage, turf, anise, alfalfa,
celery, and scatter bait, with respect to freshwater fish (which are a surrogate for
aquatic-phase amphibians)
22
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Species
Effects
Determination
Basis for Determination
• Chronic: RQs >1 for cabbage and scatter bait,, with respect to freshwater fish
(which are a surrogate for aquatic-phase amphibians)
• One large fish kill attributed to methomyl was reported
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on bird and freshwater fish toxicity data)
ranges from 1 in 5.37 x 107 to 1 in 1
Potential for Indirect Effects
• CTS prey base is affected; CTS feeds on algae, aquatic invertebrates/
zooplankton, freshwater snails, terrestrial invertebrates, worms (freshwater
invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86; terrestrial invert RQs:
42.30-157.12; estuarine/marine invert: acute: 0.13-3.26; chronic: 1.33-17.75),
fish (freshwater fish RQs: acute: 0.13-0.19; chronic: 1.99-2.67), small mammals
(15g mammal RQs: acute: 1.02-7.25; chronic: 1.80-58.01), amphibians/frogs
(bird RQs: acute: 0.12-27.97; chronic: 1.44-3.34; 20g amphibian: acute: 0.12-
16.44; chronic: 1.45-3.36)
• Granular(RQs 1.58-5.92) and scatter bait (RQ 4.91)uses exceed LOCs for
mammals (prey of CTS)
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: honey bee, lab rat,
bird, freshwater invertebrate/fish) ranges from 1 in 5.37 x 107 to 1 in 1
Delta Smelt
(Hypomesus
transpacificus)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: RQs > 0.05 for most uses assessed including cabbage, turf, anise, alfalfa,
celery, and scatter bait, with respect to freshwater fish; a single RQ value is at
the listed species LOC of 0.05 for the use on cabbage, with respect to
estuarine/marine fish
• Chronic: RQs >1 for cabbage and scatter bait, with respect to freshwater fish; all
chronic RQs are less than 1 for estuarine/marine fish
• One large fish kill was a reported incident
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on estuarine/marine and freshwater fish
toxicity data) ranges from 1 in 8.8 x 1024 to 1 in 877
Potential for Indirect Effects
• DS prey base is affected; adult DS feeds on planktonic copepods, cladocerans,
amphipods and insect larvae and juvenile DS feed on zooplankton (freshwater
invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86; estuarine/marine invert:
acute: 0.13-3.26; chronic: 1.33-17.75); the DS larvae feed on phytoplankton
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates:estuarine/marine and
freshwater invertebrates) ranges from 1 in 29,900 to 1 in 1
California
Freshwater Shrimp
(Syncaris pacifica)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• With regard to estuarine/marine invertebrate data,
Acute: RQs > 0.05 for all assessed uses
Chronic: RQs >1 for all except one assessed use (i.e., sorghum)
• With regard to freshwater invertebrate data,
Acute: RQs > 0.05 for all assessed uses
Chronic: RQs >1 for all assessed uses
• The species critical habitat and/or occurrence sections overlap with the use
footprint
23
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Species
Effects
Determination
Basis for Determination
• Probability of individual effect (based on freshwater invertebrate toxicity data)
ranges from 1 in 6.69 to 1 in 1
Potential for Indirect Effects
• CFS prey base is affected; CFS feeds on zooplankton (freshwater invert RQs:
acute: 0.50-12.38; chronic: 1.57-60.86), detritus, algae, aquatic macrophyte
fragments, aufwuchs
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: freshwater
invertebrates) ranges from 1 in 6.69 to 1 in 1
Tidewater Goby
(Eucyclogobius
new berryi)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: RQs > 0.05 for most uses assessed including cabbage, turf, anise, alfalfa,
celery, and scatter bait, with respect to freshwater fish; a single RQ value is at
the listed species LOC of 0.05 for the use on cabbage, with respect to
estuarine/marine fish
• Chronic: RQs >1 for cabbage and scatter bait, with respect to freshwater fish; all
chronic RQs are less than 1 for estuarine/marine fish
• One large fish kill was a reported incident
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on estuarine/marine and freshwater fish
toxicity data) ranges from 1 in 8.8 x 1024 to 1 in 877
Potential for Indirect Effects
• TG prey base is affected; adult TG feeds on small benthic invertebrates,
crustaceans, snails, mysids, aquatic insect larvae, juvenile TG feeds on
unicellular zooplankton (freshwater invert RQs: acute: 0.50-12.38; chronic:
1.57-60.86; estuarine/marine invert: acute: 0.13-3.26; chronic: 1.33-17.75) or
phytoplankton
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates:estuarine/marine and
freshwater invertebrates) ranges from 1 in 29,900 to 1 in 1
24
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Table 1-3. Effects Determination Summary for the Critical Habitat Impact Analysis
Designated
Critical Habitat
for:
Effects
Determination
Basis for Determination
Bay Checkerspot
Butterfly
(Euphydryas editha
bayensis)
Habitat
Modification
• Risk to terrestrial plants and thus BCB habitat (esp. dwarf plantain, purple owl's
clover, exserted paintbrush) was assumed. (RQs were not calculated given no
available terrestrial plant data.)
• Incident data on melons indicates damage to terrestrial plants after ground
application possibly due to a methomyl formulation
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
Valley Elderberry
Longhorn Beetle
(Desmocerus
californicus
dimorphus)
Habitat
Modification
• Risk to terrestrial plants and thus VELB habitat (esp. elderberry trees) was
assumed. (RQs were not calculated given no available terrestrial plant data.)
• Incident data on melons indicates damage to terrestrial plants after ground
application possibly due to a methomyl formulation
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
California Tiger
Salamander
(Ambystoma
californiense)
[Central CA, Santa
Barbara County]
Habitat
Modification
• Terrestrial arthropod RQs > 0.05 (the interim terrestrial invertebrate LOC) for
all uses.
• Risk to terrestrial plants and thus CTS habitat was assumed. (RQs were not
calculated given no available terrestrial plant data.)
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
• Mammal acute dose-based RQs >0.5 for all assessed uses; chronic: dose- and/or
dietary-based RQs>0.1 for all assessed uses.
• Bird (surrogate for terrestrial-phase amphibians) acute dose and dietary-based
RQs >0.1 (listed sp.) for most assessed uses for small and medium-sized birds
consuming short grass, arthropods/small insects, and herbivorous mammals;
chronic dietary-based RQs >1 for most assessed uses for small and medium-
sized birds consuming short grass, arthropods/small insects, and herbivorous
mammals
• Fish (surrogate for aquatic-phase amphibians) acute RQs > 0.05 for most uses
assessed including cabbage, turf, anise, alfalfa, celery, and scatter bait; chronic
RQs >1 for cabbage and scatter bait
• Freshwater invertebrate acute RQs >0.1 for all assessed uses; chronic RQs >1
for all assessed uses
Delta Smelt
(Hypomesus
transpacificus)
Habitat
Modification
• Risk to terrestrial plants and thus DS habitat was assumed. (RQs were not
calculated given no available terrestrial plant data.)
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
• Freshwater invertebrate acute RQs >0.1 for all assessed uses; chronic RQs >1
for all assessed uses
• Estuarine/marine invertebrate acute RQs >0.1 for all assessed uses; chronic
RQs >1 for all except one assessed use (i.e., sorghum)
Tidewater Goby
(Eucyclogobius
new berryi)
Habitat
Modification
• Risk to terrestrial plants and thus TG habitat was assumed. (RQs were not
calculated given no available terrestrial plant data.)
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
• Freshwater invertebrate acute RQs >0.1 for all assessed uses; chronic RQs >1
for all assessed uses
• Estuarine/marine invertebrate acute RQs >0.1 for all assessed uses; chronic
RQs >1 for all except one assessed use (i.e., sorghum)
25
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Table 1-4. Use Specific Summary of The Potential for Adverse Effects to Aquatic Taxa
Uses
Potential for Effects to Identified Taxa Found in the Aquatic Environment:
DS, TG
and
DS, TG, CTS-CC, SC,
CFWS and
Estuarinc/Marinc
Vascular
Non-
Estuarinc/Marinc
and SB DPS, and
Freshwater
Invcrtcbi
•atcs
Plants'
vascular
Vertcbr
itcs
Freshwater
Vertebrates2
Invertcb
rates
Plants'
Acute
Chronic
Acute
Chronic
Acute
Chronic
Acute
Chronic
Bulbs
No
No
No
No
Yes
Yes
Yes
Yes
No
No
/Onions
Cereal grains
No
No
No
No
Yes
Yes
Yes
Yes
No
No
/Corn
Cereal grains
No
No
No
No
Yes
Yes
Yes
Yes
No
No
/Corn
Cereal grains
No
No
No
No
Yes
Yes
Yes
No
No
No
(sp.
Sorghum)
Cole crops
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
/Cabbage
Grasses
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
/Turf
Herbs
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
/Anise/Mint
Leguminous
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
forage
(alfalfa)
Non-cole
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
leafy crops
/Celery
Scatter bait
No
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
Avocado
No
No
No
No
Yes
Yes
Yes
Yes
No
No
1 A yes in this column indicates a potential for direct effects to DS and TG and indirect effects to CCR, TG, and DS as a result of an effect to
estuarine/marine fish.
2 A yes in this column indicates a potential for direct effects to DS, TG and indirect effects to SFGS, CCR, TG, and DS. A yes also indicates a potential for
direct and indirect effects for the CTS-CC, CTS-SC, and CTS-SB as a result of an effect to freshwater fish.
3 A yes in this column indicates a potential for direct effects to the CFWS and indirect effects to the CFWS, SFGS, CCR, CTS-CC, CTS-SB, CTS-SC, TG,
and DS as a result of an effect to freshwater invertebrates.
4 A yes in this column indicates a potential for indirect effects to CCR, TG, and DS as a result of an effect to estuarine/marine invertebrates.
5 A yes in this column indicates a potential for indirect effects to SFGS, CCR, CTS-CC, CTS-SC, CTS-SB, TG, DS, and CFWS.
26
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Table 1-5. Use Specific Summary of The Potential for Adverse Effects to Terrestrial Taxa
Uses
Potential for Effects to Identified Taxa Found in the Terrestrial Environment:
Small
CCR and Small
CTS-CC, CTS-SC,
SFGS and
BCB, VELB, and
Dicots6
Monocots6
Mammals1
Birds2
CTS-SB and
Reptiles4
Invertebrates
Amphibians3
(Acute)5
Acute
Chronic
Acute
Chronic
Acute
Chronic
Acute
Chronic
Bulbs
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Onions
Cereal
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
grains /Corn
Cereal
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
grains /Corn
Cereal
Yes
Yes
Yes
No
Yes
No
Yes
No
Yes
Yes
Yes
grains (sp.
Sorghum)
Cole crops
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Cabbage
Grasses
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Turf
Herbs
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Anise/Mint
Leguminous
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
forage
(alfalfa)
Non-cole
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
leafy crops
/Celery
Avocado
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Granular
Yes
N/A
Yes
N/A
Yes
N/A
Yes
N/A
N/A
Yes
Yes
Scatter bait
Yes
N/A
Yes
N/A
Yes
N/A
Yes
N/A
N/A
Yes
Yes
1 A yes in this column indicates a potential for indirect effects to SFGS, CCR, CTS-CC, CTS-SC, CTS, and CTS-SB as a result of an effect to small
mammals.
2 A yes in this column indicates a potential for direct effects to CCR and indirect effects to the CCR, SFGS, CTS-CC, CTS-SC,and CTS-SB as a result of an
effect to small birds.
3 A yes in this column indicates a potential for direct effects to CTS-CC, CTS-SC, CTS-SB, and indirect effects to CTS-CC, CTS-SC, CTS-SB, SFGS, CCR
as a result of an effect to terrestrial-phase amphibians (for which birds serve as surrogate).
27
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4 A yes in this column indicates the potential for direct and indirect effects to SFGS and other reptiles as a result of an effect to reptiles (for which birds
serve as a surrogate).
5 A yes in this column indicates a potential for direct effect to BCB and VELB and indirect effects to SFGS, CCR, CTS-CC, CTS-SC, and CTS-SB as a
result of an effect to terrestrial invertebrates.
6 A yes in this column indicates a potential for indirect effects to BCB, VELB, SFGS, CCR, CTS-CC, CTS-SC, CTS-SB, TG, DS, and CFWS. For the BCB
and VELB this is based on the listed species LOC because of the obligate relationship with terrestrial monocots and dicots. For other species, the LOC
exceedances are evaluated based on the LOC for non-listed species.
N/A - information not available
28
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Based on the conclusions of this assessment, a formal consultation with the U. S. Fish and
Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct/indirect and adverse habitat
modification effects determinations, it is important to note that pesticide exposures and predicted
risks to the listed species and its resources {i.e., food and habitat) are not expected to be uniform
across the action area. In fact, given the assumptions of drift and downstream transport {i.e.,
attenuation with distance), pesticide exposure and associated risks to the species and its resources
are expected to decrease with increasing distance away from the treated field or site of
application. Evaluation of the implication of this non-uniform distribution of risk to the species
would require information and assessment techniques that are not currently available. Examples
of such information and methodology required for this type of analysis would include the
following:
• Enhanced information on the density and distribution of BCB, VELB, SFGS,
CCR, CTS, DS, CFS, and TG life stages within the action area and/or applicable
designated critical habitat. This information would allow for quantitative
extrapolation of the present risk assessment's predictions of individual effects to
the proportion of the population extant within geographical areas where those
effects are predicted. Furthermore, such population information would allow for
a more comprehensive evaluation of the significance of potential resource
impairment to individuals of the assessed species.
• Quantitative information on prey base requirements for the assessed species.
While existing information provides a preliminary picture of the types of food
sources utilized by the assessed species, it does not establish minimal
requirements to sustain healthy individuals at varying life stages. Such
information could be used to establish biologically relevant thresholds of effects
on the prey base, and ultimately establish geographical limits to those effects.
This information could be used together with the density data discussed above to
characterize the likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the pesticide.
Currently, methodologies are limited to predicting exposures and likely levels of
direct mortality, growth or reproductive impairment immediately following
exposure to the pesticide. The degree to which repeated exposure events and the
inherent demographic characteristics of the prey population play into the extent to
which prey resources may recover is not predictable. An enhanced understanding
of long-term prey responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and together
with the information described above, a more complete prediction of effects to
individual species and potential modification to critical habitat.
29
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2. Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By identifying the
important components of the problem, it focuses the assessment on the most relevant life history
stages, habitat components, chemical properties, exposure routes, and endpoints. The structure
of this risk assessment is based on guidance contained in U.S. EPA's Guidance for Ecological
Risk Assessment (USEPA, 1998), the Services' Endangered Species Consultation Handbook
(USFWS/NMFS, 1998) and is consistent with procedures and methodology outlined in the
Overview Document (USEPA, 2004) and reviewed by the U.S. Fish and Wildlife Service and
National Marine Fisheries Service (USFWS/NMFS/NOAA, 2004).
2.1. Purpose
The purpose of this endangered species assessment is to evaluate potential direct and indirect
effects on individuals of the BCB, VELB, CTS, DS, CCR, CFS, SFGS, and TG arising from
FIFRA regulatory actions regarding use of methomyl on a variety of agricultural and on
agricultural uses. This ecological risk assessment has been prepared consistent with a stipulated
injunction in the case Center for Biological Diversity (CBD) us. EPA et al. (Case No. 07-2794-
JCS) entered in Federal District Court for the Northern District of California on May 17, 2010.
In this assessment, direct and indirect effects to the BCB, VELB, CTS, DS, CCR, CFS, SFGS,
and TG and potential modification to designated critical habitat for the BCB, VELB, CTS-CC
DPS, DS, CTS-SB DPS, and TG are evaluated in accordance with the methods described in the
Agency's Overview Document (USEPA, 2004).
- Bay Checkerspot Butterfly (BCB): The PCEs for BCBs are areas on serpentinite-
derived soils that support the primary larval host plant {i.e., dwarf plantain) and at least
one of the species' secondary host plants. Additional BCB PCE's include the presence of
adult nectar sources, aquatic features that provide moisture during the spring drought, and
areas that provide adequate shelter during the summer diapause.
- Valley Elderberry Longhorn Beetle (VELB): The PCEs for the VELBs include areas
that contain its host plant {i.e., elderberry trees).
- California Tiger Salamander (CTS): The PCEs for CTSs are standing bodies of
freshwater sufficient for the species to complete the aquatic portion of its life cycle that
are adjacent to barrier-free uplands that contain small mammal burrows. An additional
PCE is upland areas between sites (as described above) that allow for dispersal of the
species.
- Delta Smelt (DS): The PCEs for DSs are shallow fresh or brackish backwater sloughs
for egg hatching and larval viability, suitable water with adequate river flow for larval
and juvenile transport, suitable rearing habitat, and unrestricted access to suitable
spawning habitat.
- Tidewater Goby (TG): The PCEs for TGs are persistent, shallow aquatic habitats with
salinity from 0.5 parts per thousand (ppt) to 12 ppt, that contain substrates suitable for the
construction of burrows and submerged aquatic plants that provide protection. An
30
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additional PCE is the presence of sandbars that at least partially closes a lagoon or
estuary during the late spring, summer, and fall.
In accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of methomyl is based on an action area. The action area is the area directly or
indirectly affected by the federal action, as indicated by the exceedance of the Agency's Levels
of Concern (LOCs). It is acknowledged that the action area for a national-level FIFRA
regulatory decision associated with a use of methomyl may potentially involve numerous areas
throughout the United States and its Territories. However, for the purposes of this assessment,
attention will be focused on relevant sections of the action area including those geographic areas
associated with locations of the BCB, VELB, CTS-CC DPS, DS, CTS-SB DPS, and TG and
their designated critical habitat within the state of California. As part of the "effects
determination," one of the following three conclusions will be reached separately for each of the
assessed species in the lawsuits regarding the potential use of methomyl in accordance with
current labels:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Additionally, for habitat and PCEs, a "No Effect" or a "Habitat Modification" determination is
made.
A description of routine procedures for evaluating risk to the San Francisco Bay Species are
provided in Attachment I.
2.2. Scope
Methomyl is a carbamate insecticide currently registered for use on a wide variety of sites
including field, vegetable, and orchard crops; turf (sod farms only); livestock quarters;
commercial premises; and refuse containers. Estimates of methomyl usage indicate that it is
used extensively on sweet corn, lettuce, cotton, and alfalfa (these uses represent 50% of
methomyl-use in the United States and are registered uses in California. All uses are
agricultural, industrial, or commercial; there are no residential uses for methomyl. It is
recognized that methomyl is used in many parts of the U.S., however, the scope of this
assessment limits consideration of the areas of use that may be applicable to the protection of the
BCB, VELB, CTS, DS, CCR, CFS, SFGS, TG and its designated critical habitat within the state
of California.
Methomyl is formulated mainly as soluble concentrates, but also includes granular,
pelleted/tableted, and bait/solid formulations. Application methods for the agricultural uses of
methomyl include aircraft (fixed-wing and helicopter), high and low volume ground sprayer,
ultra low volume sprayer, and granule application. Although all potential uses are assessed, risks
from ground boom and aerial applications are focused on in this assessment because they are
expected to result in the highest off-target concentrations of methomyl. Runoff associated with
31
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large rainfall events is expected to be responsible for the greatest off-target movement of
methomyl.
The end result of the EPA pesticide registration process (i.e., the FIFRA regulatory action) is an
approved product label. The label is a legal document that stipulates how and where a given
pesticide may be used. Product labels (also known as end-use labels) describe the formulation
type (e.g., liquid or granular), acceptable methods of application, approved use sites, and any
restrictions on how applications may be conducted. Thus, the use or potential use of methomyl
in accordance with the approved product labels for California is "the action" relevant to this
ecological risk assessment.
Although current registrations of methomyl allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of methomyl in portions
of the action area that are reasonably assumed to be biologically relevant to the BCB, VELB,
CTS, DS, CCR, CFS, SFGS, and TG and their designated critical habitat. Further discussion of
the action area for the BCB, VELB, CTS, DS, CCR, CFS, SFGS, TG species and their critical
habitat is provided in Section 2.7.
2.2.1. Evaluation of Degradates and Other Stressors of Concern
Major degradates include methomyl oxime (S-methyl-N-hydroxythioacetimidate) detected at a
maximum of 44% in the alkaline hydrolysis study; acetonitrile detected at a maximum of 66%,
40% and 27% in the aqueous photolysis, soil photolysis and aerobic aquatic metabolism studies,
respectively; acetamide detected at 14% in the aerobic aquatic metabolism study; and CO2
detected at 22.5-75% in the aerobic soil, anaerobic soil, and aquatic metabolism studies.
Methomyl oxime was detected at high concentrations in the alkaline hydrolysis study, but was
only a minor degradate in the aerobic soil metabolism, anaerobic soil metabolism, photolysis and
aerobic aquatic metabolism studies. There are data demonstrating the formation of methomyl
sulfoxide during disinfection (chlorination) in water treatment (MRU) 46210701), although this
compound was not found in any environmental fate studies.
According to ECOSAR (See APPENDIX D for ECOSAR output), the calculated endpoints
indicate that the fish and invertebrates are less sensitive to the oxime than than to the parent
compound (Fish (LC50) = 76.219 ppm for oxime, Fish (EC50) = 0.320 ppm for parent;
invertebrates (LC50) = 8.436 ppm for oxime, invertebrates (EC50) = 0.005 ppm for parent).
ECOSAR calculated an EC50 for green algae of 8.557 ppm for the oxime. One open literature
study on micro-algae showed an EC50 range from 108-184 ppm. The aquatic plant data suggest
that the oxime may possibly be more toxic to aquatic plants, but this is based on a single open
literature study (Record #: 118717, Pereira el a/.2009)that was deemed qualitative, and not for
quantitative use (i.e., not suitable for RQ calculations See Section 5.1.le). Based on the
available data, the oxime appears to be less toxic to aquatic organisms than the parent compound.
Previously, methomyl was deemed to not have any degradates with toxicological concerns (DP
374952 - Panger, 2010), which also includes the oxime and degradate methomyl sulfoxide.
Therefore, this assessment is based on the parent, methomyl, alone.
32
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2.2.2. Evaluation of Mixtures
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of
active ingredients, either those mixtures of multiple active ingredients in product formulations or
those in the applicator's tank. In the case of the product formulations of active ingredients (that
is, a registered product containing more than one active ingredient), each active ingredient is
subject to an individual risk assessment for regulatory decision regarding the active ingredient on
a particular use site. If effects data are available for a formulated product containing more than
one active ingredient, they may be used qualitatively or quantitatively in accordance with the
Agency's Overview Document and the Services' Evaluation Memorandum (U.S., EPA 2004;
USFWS/NMFS 2004).
Methomyl has registered products that contain multiple active ingredients. Analysis of the
available acute oral mammalian LD50 data for multiple active ingredient products relative to the
single active ingredient is provided in APPENDIX A. The results of this analysis show that the
formulated product (Stimukil fly bait, EPA Reg. No. 53871-3) is more toxic to the laboratory rat
than is the technical grade active ingredient. As a result, scatter bait uses under this formulation
label are modeled with the formulation toxicity data. With regard to scatter bait and remaining
assessed uses, the RQs based on the technical grade active ingredient toxicity data exceed
Agency LOCs; refinement to the endpoint based on the formulated product is not expected to
alter risk conclusions.
2.3. Previous Assessments
Several ecological risk assessments for methomyl have been completed since it was first
registered in 1968. The most encompassing assessment was for the Reregi strati on Eligibility
Decision (RED) process and was completed in 1998 (USEPA 19986). The current risk
assessment builds upon the 1998 risk assessment, which determined that acute and chronic risk
quotients (RQ) exceeded risk levels of concern (LOC) for endangered/threatened birds (and,
thus, reptiles and terrestrial-phase amphibians), mammals, and aquatic vertebrates (and, thus,
aquatic-phase amphibians) and invertebrates.
Following the RED, the following mitigation and Integrated Pest Management (IPM) plans were
added to the labels for all methomyl formulated products:
1) The registrant will revise end use product labels to reduce the maximum seasonal use
rates as noted below;
Crop
Old Season Rate
(lb ai)
New Season Rate
(lb ai)
Percent Decrease
Broccoli
7.2
6.3
12.5
Cabbage
9.0
7.2
20
Cauliflower
9.0
7.2
20
Celery
9.0
7.2
20
Chinese cabbage
8.1
7.2
11.1
Corn, sweet
7.2
6.3
12.5
Lettuce, head
9.0
7.2
20
Tomato
7.2
6.3
12.5
33
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2) The registrant will reduce the single maximum per acre application rate of methomyl by
50% from 1.8 pounds to 0.9 pounds on peaches and commercial sod farms. No methomyl
crop use will exceed a single application rate of 0.9 pounds of methomyl per acre.
3) The following statement supporting the use of an Integrated Pest Management (IPM) plan
must be added to the labels. "This product should be used as part of an Integrated Pest
Management (IPM) program which can include biological, cultural, and genetic practices
aimed at preventing economic pest damage. Application of this product should be based
on IPM principles and practices including field scouting or other detection methods,
correct target pest identification, population monitoring and treating when target pest
populations reach locally determined action thresholds. Consult your state cooperative
extension service, professional consultant or other qualified authorities to determine
appropriate action threshold levels for treating specific pest/crop systems in your area."
4) Based on the environmental risk assessment for methomyl, the following advisories are
required to be on the label for methomyl: a labeling statement for potential ground water
contamination, a labeling statement to minimize the potential for surface water
contamination and labeling statements are required on manufacturing use products and
end use products based on the toxicity to nontarget organisms. A bee hazard statement is
also required.
5) The following spray drift label requirement for products with aerial applications is
required to be on the label for methomyl: "Do not apply by ground equipment within 25
feet, or by air within 100 feet of lakes, reservoirs, rivers, estuaries, commercial fish ponds
and natural, permanent streams, marshes or natural, permanent ponds. Increase the buffer
zone to 450 feet from the above aquatic areas when ultra low volume application is
made."
The Agency consulted with the USFWS in 1989 regarding methomyl impacts on some
endangered species (USFWS 1989). As a result, the USFWS issued a formal Biological Opinion
that identified reasonable and prudent measures and alternatives to mitigate effects of methomyl
use on endangered species.
Subsequent to the RED, the registrant submitted several studies including, but not limited to, two
predatory mite studies (MRID 451255-01, 451255-02); two aphid studies (MRID 451333-01,
451333-02); two earthworm studies (MRID 454592-01, 449693-01); an acute oral and contact
honey bee study (MRID 450930-01), a supplemental aqueous photolysis study (MRID
43823305), an acceptable storage stability study (MRID 43708807), and a supplemental aerobic
soil metabolism study (MRID 45473401). These studies have been reviewed and are
incorporated into the current risk assessment. The current assessment also builds on the previous
RED by incorporating open literature (from the ECOTOX search engine) and assessing indirect
effects, including those effects caused by the potential loss of food items (e.g., terrestrial and
aquatic invertebrates).
On April 1, 2003, the Agency initiated formal consultation with the National Marine Fisheries
Service relative to an effects determination regarding methomyl's potential effects to 26
Environmentally Significant Units (ESUs) of Pacific salmon and steelhead. That assessment
determined that use of methomyl would have no effect (NE) on two ESU's based on lack of use
34
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in proximity to waters supporting these two ESUs and that methomyl was Likely to Adversely
Affect (LAA) 24 ESUs both directly and indirectly based on effects to the aquatic invertebrate
prey base. In response to the Agency's effects determination and consultation, NMFS issued a
Biological Opinion (BO) in 2009 (NMFS, 2009;
http://www.epa.gOv/espp/litstatus/effects/index.htm#methomvn. In the BO NMFS concluded
that the use of methomyl is likely to jeopardize the continued existence of 18 salmonid ESUs and
destroy or adversely modify designated critical habitat for 16 ESUs (USEPA, 2010).
On July 20, 2007, the Agency submitted a risk assessment and effects determination to the
USFWS for the California red-legged frog (Rana aurora draytonii) (CRLF) (and its designated
critical habitat) relative to the use of methomyl in California
(http://www.epa.gOv/espp/litstatus/effects/redleg-frog/index.html#methomvn. A LAA effects
determination was made based on the potential for direct effects to both aquatic- and terrestrial-
phase CRLF and the potential for indirect effects to prey taxa (for both aquatic- and terrestrial-
phase CRLF). Additionally, a 'habitat modification' effects determination was made for CRLF
designated critical habitat based on the potential for effects to prey items for both aquatic- and
terrestrial-phase CRLF.
In 2007, DuPont submitted a voluntary cancelation on strawberries. The use was cancelled in
the fall of 2010. Likewise, in preparation for the N-Methyl Carbamate (NMC) Cumulative, the
individual chemical dietary risk assessment identified grapes as a risk driver and Dupont
responded by submitting a voluntary cancellation for the use on grapes. A final cancellation
order for grapes was published December 8, 2010.
On July 16, 2010, the Agency submitted a Registration Review Problem Formulation for
Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure
Assessments for Methomyl. Subsequent to the problem formulation, the registrant submitted a
passerine acute oral toxicity study waiver (MRID 48736202). The waiver was reviewed by
EFED on May 16, 2012 (USEPA 2012, DP Barcode 400766); EFED continues to believe that an
avian acute oral toxicity study with passerines is a critical data gap. Furthermore, terrestrial and
aquatic plant data were recommended by EFED during the registration review process. A refined
DWA is currently being developed for methomyl.
2.4. Environmental Fate Properties
As noted in the 1998 RED, methomyl is moderately persistent and mobile in soil. Methomyl is
less persistent in aqueous environments. It is stable to hydrolysis at lower pHs (neutral to
acidic), but it degrades slowly in alkaline conditions (ti/2 = 30 days). Methomyl degradation
appears to be dependent on microbially-mediated (aerobic soil metabolism - ti/2 = 4.3 - 44 d;
anaerobic soil metabolism - ti/2 = 14 days; aerobic aquatic metabolism - ti/2 = 4-4.6 d) and
abiotic processes (photodegradation in water - ti/2 = 50 d). Under anaerobic conditions
methomyl degradation is likely to be faster than under aerobic conditions (Smelt et al., 1983),
particularly in the presence of reduced iron (Bromilow et al., 1986). In laboratory studies,
methomyl does not readily adsorb to soil and has the potential to be mobile (mean Koc = 46 ± 13
35
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L/kgoc)- Tables 2-2 and 2-3 summarizes the fate and physical-chemical properties of methomyl
based on information from the registrants.
Major degradates include methomyl oxime (S-methyl-N-hydroxythioacetimidate) detected at a
maximum of 44% in the alkaline hydrolysis study; acetonitrile detected at a maximum of 66%,
40% and 27% in the aqueous photolysis, soil photolysis and aerobic aquatic metabolism studies,
respectively; acetamide detected at 14% in the aerobic aquatic metabolism study; and CO2
detected at 22.5-75% in the aerobic soil, anaerobic soil, and aquatic metabolism studies. The
only non-volatile degradate in the laboratory studies was methomyl oxime (S-methyl-N-
hydroxythioacetimidate). It was present at high concentrations in the alkaline hydrolysis study,
but was only a minor degradate in the aerobic soil metabolism, anaerobic soil metabolism,
photolysis and aerobic aquatic metabolism studies.
Several studies showed that dissipation of methomyl is rapid on foliage (Willis and McDowell,
1987). Of the ten studies for methomyl identified in this review of foliar dissipation, three
measured total residues on the leaves rather than dislodgeable residues. One of these three
studies had significant rainfall during the study. The two remaining studies, one on mint and the
other on Bermuda grass, had half-lives of 0.5 and 2.5 days, respectively. Because these studies
only had rainfall after the pesticide is mostly dissipated and volatilization is likely to be very
small for methomyl (see next section), the dominant route of foliar dissipation is likely aerobic
metabolism on the leaf surface.
Mobility. Methomyl is mobile in soils as demonstrated by soil thin-layer chromatography (TLC;
Rf values 0.64-0.79; MRID 00044306). A batch equilibrium study shows that methomyl has a
low affinity to bind to soil (see Table 2-1 further indicating that the chemical will be mobile
(MRID 00161884). Methomyl binding (which is low) is significantly correlated with soil
organic carbon content, with a mean Koc of 46 ± 13 L/kgoc-
Table 2-1 Summary of Soil Batch Equilibrium Parameters for Methomyl. A
Soil
Fraction of
Organic Carbon
Mean Kd
Koc
Kk
1/n
kfoc
Cecil sandy loam
0.012
0.79
65
0.73
0.85
61
Flanagan silt Loam
0.025
1.1
45
1.0
0.87
41
Keyport silt loam
0.043
1.6
36
1.4
0.86
32
Woodstown sandy loam
0.006
0.24
39
0.23
0.88
37
A Kd is the soil-water partition coefficient. Koc is the organic carbon-normalized partition coefficient based on
meanKd's. KF is the Freundlich coefficient. 1/n is the Freundlich exponent. KF0C is similar to Koc except based
on Freundlich coefficients
Methomyl is a highly soluble chemical in water (5.5 x 104 mg/L; MRID 41402101). Its vapor
pressure (5.4 x 10"6 torr) and Henry's Law Constant (2.1 x 10"11 atm-m3/mol) indicate that it has
a low potential to volatilize (MRID 41209701).
Bioaccumulation. The low octanol/water partition coefficient (Kow) of 1.31 ± 0.02 (mean ± std.
error; MRID 157991) suggests that the chemical will have a low tendency to accumulate in
aquatic biota.
36
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Field Dissipation. Two guideline terrestrial field dissipation studies are available for methomyl
(MRID 41623901/41623902, 42288001/43217903). Dissipation half-lives from the surface soil
of cropped cabbage fields ranged from 4-6 days in Mississippi to 54 days in California. Two
factors may explain the differences in dissipation between the two sites. Soil moisture content,
which may affect the level of biological activity, varied between the two sites (moisture contents
ranged from 2.5% to 17% in the California soils and averaged 16% over the first 15 days in the
Mississippi soils). The Mississippi site received more rainfall, which may have led to more
leaching out of the surface. In both studies most of the methomyl residues were found in the
upper 30 cm of soil.
Prospective Groundwater Study. A small-scale prospective ground-water monitoring study was
conducted for methomyl (MRID 43568301). Lannate L, a formulated product of methomyl, was
applied in August 1992 to a site cropped in sweet corn in Cook County, Georgia. Monitoring
continued until October 1994 when the study was terminated. The study was conducted by DuPont
in a highly vulnerable, high use area of Georgia. Methomyl was applied to the crop at 0.45 lbs
a.i./A 25 times over 63 days for a total of 11.25 lbs a.i./A. Although this rate represents 1,5x the
maximum label rate per crop of sweet corn, the study was conducted to support a potential increase
in the maximum label rate. Groundwater was monitored monthly for a period of 27 months.
Methomyl was not detected in groundwater when detections occurred in 12-foot depth suction
lysimeters at concentrations up to 0.943 |ig/L. Out of the 156 samples taken from six down-
gradient wells in this study, only six samples from five wells contained methomyl residues.
Concentrations ranged from 0.110 to 0.428 |ig/L, using a detection limit of 0.1 |ig/L, at 62 and 117
days after the initial treatment (DAIT). Sampling continued for 789 (DAIT), but no detections were
seen after 117 DAIT.
Table 2-2 and Table 2-3 lists the physical-chemical properties of methomyl. Please see Section
3 for further discussion on the environmental fate and transport properties of methomyl.
Table 2-2. Physical-chemical Properties of Methomyl
Property
Parent Compound
Value and units
MRID or Source
Molecular Weight
162.2 g/mol
Product chemistry (calculated)
Chemical Formula
C5H10N2O2S
Product chemistry
Vapor Pressure
5.4 x 10"6 torr
MRID 41209701
Henry's Law Constant
2.1 x 10"11 atm-m3/mole
Estimated from water solubility
and vapor pressure
Water Solubility
5.5 x 104 mg/L @ 20°C
MRID 41402101
Octanol - water partition coefficient
(Kow)
1.31
MRID 00157991
37
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Table 2-3. Summary of methomyl Environmental Fate Properties
Studv
Value and unit
Major Dcgradatc
Minor 1) circulates
IVI RID # or Citation
Study
Classification,
Comment
Half-life1 =
Abiotic Hydrolysis
pH 5
pH 7
pH 9
stable
stable
36 d;
MHTA: S-methyl-N-
hydroxythioacetimidate
(40-44% in pH 9 solution
only)
pH 2.09-7.11: >413 d
pH 8.88: 14.6 d
pH 7.40: 337 d
pH 8.89: 16.1 d
pH 7.67: 206 d
pH 9.45: 4.77 d
pH 7.92: 123 d
pH 9.92: 1.66 d
pH 8.42: 40.8 d
MRID 00131249;
Strathmann and Stone,
2002 (values calculated
from rate constants)
Acceptable
Direct Aqueous
Photolysis
Half-life -
50 d (natural water)
Stable (pH 7 buffer w/
no excess nitrate)
42 days (pH 7 buffer w/
100 M excess nitrate)
8.5 days (pH 7 buffer
w/ 1000 M excess
nitrate)
Transformation products
were not determined.
MRID 43823305
Half-life1 =
33 day
Supplemental - no
transformation
products were
addressed, no
volatiles were
collected, and a
material balance
could not be
determined .
Dissipation was
observed (40-90%
decrease in 15 days)
Soil Photolysis
Acetonitrile (40% at 30
days)
MRID 00163745
Acceptable
Aerobic Soil
Metabolism
Half-life1 =
Flanagan silt loam: 44
days, Madera, CA
loam: 12 days;
USA (mattapex), Loam:
7.9 days
France (nambshem),
Sandy Loam: 6.4 days
Germany (speyer 2.2),
Sandy Loam: 4.3 days
C02 (75.3%) at 3 months)
MHTA (2.3%);
C02 (51%o at 30 days)
Unextracted Residues
(32.2% at 30 days)
Methomyl oxime (0.8%),
C02 (59.2%o at 30 days)
Unextracted Residues
(25.2% at 30 days)
Methomyl oxime (2.2%),
C02 (51% at 30 days)
Unextracted Residues
(31% at 30 days)
Methomyl oxime (1.4%)
MRID 00008568,
43217901;
MRID 454 73401
Half-life1 =
Acceptable;
Supplemental
Anaerobic Soil
Metabolism
14 days (static), loam
7 days (flowing), loam
C02 (52.9%)
MHTA (0.9%)
MRID 43217902
Half-life"1^
Acceptable
Aerobic Aquatic
Acetonitrile (23.65-
MRID 43325401
Supplemental
38
-------
Study
Value and unit
Major Dcgradatc
Minor 1) circulates
MRID # or Citation
Study
Classification,
Comment
Metabolism
Auchingilsie clay loam:
3.5 days
Hinchingbrooke silty
clam loam: 4.8 days
27.02% in traps, 15.8-
16.9% in water and
sediment)
Acetamide (14.1%) in
water and sediment)
C02 (32.14-46.21% in
trap)
Anaerobic Aquatic
Metabolism
No data
No data
No data
No data
Freundlich solid-
water distribution
coefficient (KF)
K F, 1/n
0.72 L/kg, 0.86, Sandy
Loam
1.0 L/kg, 0.86, Silt
Loam
1.4 L/kg, 0.86, Silt
0.23 L/kg, 0.90, Sandy
Loam
No data on transformation
products
MRID 00161884
Acceptable
Organic-carbon
normalized
distribution
coefficient (Koc)
Koc =
46 ± 13 L/kgoc (n=4)
No data on transformation
products
MRID 00161884
Acceptable
Terrestrial Field
Dissipation
Dissipation Half-life1'2
54 d (CA sandy loam
cropped to cabbage);
leached to deepest
sample depth (60-90
cm)
4-6 d (MS loam
cropped to cabbage);
leached to 15-30 cm
sample depth
MRIDs 41623901,
41623902
42288001,43217903
Aquatic Field
Dissipation
No data
No data
No data
No data
Bioconcentration
Factor (BCF)-
Species Name
No data
No data
No data
Bioaccumulation is
not expected based on
low Kow
Foliar degradation
half-life
0.5 d (mint);
2.5 d (Bermuda grass)
Kiigemagi and Deinzer,
1979;
Sheets et al., 1982
Abbreviations: wt=weight
1 Half-lives were calculated using the single-first order equation and nonlinear regression, unless otherwise
specified.
2The value may reflect both dissipation and degradation processes.
2.4.1. Environmental Transport Mechanisms
Potential transport mechanisms for methomyl include surface water runoff, spray drift, and
leaching. Secondary drift (atmospheric transport) of volatilized or soil-bound residues leading to
deposition onto nearby or more distant ecosystems is not expected given methomyl's relatively
high solubility in water (5.5 x 104 mg/L), low vapor pressure (5.4 x 10"6 torr) and Henry's law
constant (2.1 x 10"11 atm-m3/mol). Air monitoring data reported by CDPR show that methomyl
39
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was not detected in 84 samples taken in 1987 and 20 samples taken in 1989 in Fresno County. In
the Association of American Pesticide Control Officials (AAPCO) 1999 Pesticide Enforcement
Survey (http://aapco.ceris.purdue.edu/doc/survevs/drift99.htmn. state agencies reported that the
number of drift complaints associated with methomyl is low as compared with 2,4-D, atrazine,
dicamba, paraquat and glyphosate, which were the most common. However the survey does not
provide information on the magnitude of exposure, nor does it differentiate between drift and
volatility, and indicates that the most common confirmation technique is visual examination of
drift and residue confirmation.
Air monitoring data collected from the 1960s through the 1980s, and summarized by Majewski
and Capel (1995), do not indicate the presence of methomyl in the atmosphere, due in large part
to the lack of testing for methomyl. The authors' review a single study which tested for
methomyl in ambient air at three residential sites near an agricultural area in Salinas, California
which were sampled during a high pesticide use month. Methomyl was not detected at any of the
air monitoring sites (the level of detection was 35 nanograms per cubic meter).
In general, deposition of drifting or volatilized pesticides is expected to be greatest close to the
site of application. Computer models of spray drift (AgDRIFT) are used to determine potential
exposures to aquatic and terrestrial organisms via spray drift. The distance of potential impact
away from the use sites (action area) is determined by the distance required to fall below the
LOC for the taxonomic group that has the largest RQ to LOC ratio.
2.4.2. Mechanism of Action
Based on its chemical structure, methomyl belongs to the oxime carbamate class of insecticides.
A number of other insecticides included in this chemical class, such as aldicarb, butocarboxin,
and oxamyl are very similar in structure to methomyl.
Carbamate insecticides act by inhibiting acetylcholinesterase and reducing the degradation of the
neurotransmitter acetylcholine. As a result, intersynaptic concentrations of acetylcholine
increase as the neurotransmitter accumulates leading to increased firing of the postsynaptic
neurons. This may ultimately lead to convulsions, paralysis, and death of the organism exposed
to the chemical.
2.4.3. Use Characterization
Analysis of labeled use information is the critical first step in evaluating the federal action. The
current labels for methomyl represent the FIFRA regulatory action; therefore, labeled use and
application rates specified on the label form the basis of this assessment. The assessment of use
information is critical to the development of the action area and selection of appropriate
modeling scenarios and inputs.
Methomyl is currently registered for use on a wide variety of sites including field, vegetable, and
orchard crops; turf (sod farms only); livestock quarters; commercial premises; and refuse
containers (see Table 2-4). There are no residential uses for methomyl. Seven end-use products
containing methomyl are currently registered for use in the United States (see Table 2-5). Three
of the end-use products are for agricultural use and are labeled 'restricted use' (Methomyl 5G
40
-------
Granules, Lannate SP), indicating that only certified pesticide applicators are legally allowed to
apply the product. The other four end-use products are for scatter bait or bait station uses and are
not labeled 'restricted use'.
Table 2-4. Summary of Current Methomyl Uses.
Summary of Current Methomyl Uses.
Use Category
Uses
Agricultural
Alfalfa, anise/fennel, asparagus, barley, beans (succulent and dry), beets,
Bermuda grass (pasture), blueberries, broccoli, broccoli raab, Brussels
sprouts, cabbage, carrot, cauliflower, celery, chicory, Chinese broccoli,
Chinese cabbage, collards (fresh market), corn (sweet, field, popcorn, and
seed), cotton, cucumber, eggplant, endive/escarole, garlic, horseradish, leafy
green vegetables, lentils, lettuce (head and leaf), lupine, melons, mint,
nonbearing nursery stock (field grown), oats, onions (dry and green), peanuts,
peas, peppers, potato, pumpkin, radishes, rye, sorghum, soybeans, spinach,
sugar beet, summer squash, sweet potato, tobacco, tomatillo, tomato, sod,
wheat
Orchard
Apple, avocado, grapefruit, lemon, nectarines, oranges, peaches, pears
(northeastern U.S. only), pecans (southeastern U.S. only), pomegranates,
tangelo, tangerine
Non-
Agricultural
Bakeries, beverage plants, broiler houses, canneries, commercial dumpsters
that are enclosed, commercial use sites (unspecified), commissaries, dairies,
dumpsters, fast food establishments, feedlots, food processing establishments,
hog houses, kennels, livestock barns, meat processing establishments, poultry
houses, poultry processing establishments, restaurants, supermarkets, stables,
warehouses
Tabic 2-5. Currcntlv Registered Methomvl End-Use Products.
FORMULATION
EPA REG.
NO.
(date latest
label)
%
ACTIVE
METHODS OF
APPLICATION
USE RESTRICTIONS
LANNATE SP
There are 14 SLNs; 7
are for CA:
CA770308
CA770431
CA770495
CA780136
CA860059
CA900034
CA910011
352-342
(12/8/2010)
90% by
weight
Ground
Aerial
Chemigation
- Overhead sprinkler chemigation is allowed for alfalfa,
barley, oats, green and dry bulb onion, potatoes, rye,
sugar beets, and wheat. Refer to supplemental, or
Special Local Need (SLN) label or crop specific
sections of this label for direction for chemigation. Do
not apply this product through any other type of
irrigation systems, except those allowed by instructions
provided in supplemental, SLN or this product label.
- Do not apply by ground equipment within 25 ft, or by
air within 100 feet of lakes, reservoirs, rivers, estuaries,
commercial fish ponds, and natural, permanent streams,
marshes, or ponds (increase buffer to 450 ft with ultra
low volume application).
- Use only in commercial and farm plantings (not for
home plantings or after opening for U-Pick operations).
- Use of hand held application equipment is prohibited.
- Pilot must not assist in mixing and loading operations.
METHOMYL 90SP
83100-28
see 352-342
There are no SLNs
(4/5/2011)
41
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Tabic 2-5. Currcntlv Registered Methomvl End-Use Products.
FORMULATION
EPA REG.
NO.
(date latest
label)
%
ACTIVE
METHODS OF
APPLICATION
USE RESTRICTIONS
LANNATE LV
There are 4 SLNs;
none are for CA
352-384
(12/8/2010)
2.41b
ai/gallon
Ground
Aerial
Chemigation
- Overhead sprinkler chemigation is allowed for alfalfa,
barley, succulent and dried beans, oats, green and dry
bulb onion, succulent peas, potatoes, rye, sweet corn
(not in CA), sugar beets, and wheat. Drip chemigation is
allowed for onions. Refer to supplemental, or Special
Local Need (SLN) label or crop specific sections of this
label for direction for chemigation. Do not apply this
product through any other type of irrigation systems,
except those allowed by instructions provided in
supplemental, SLN or this product label.
- Do not apply by ground equipment within 25 ft, or by
air within 100 feet of lakes, reservoirs, rivers, estuaries,
commercial fish ponds, and natural, permanent streams,
marshes, or ponds (increase buffer to 450 ft with ultra
low volume application).
- Use only in commercial and farm plantings (not for
home plantings or after opening for U-Pick operations).
- Use of hand held application equipment is prohibited.
- Pilot must not assist in mixing and loading operations.
METHOMYL 29LV
83100-27
see 352-384
There are no SLNs
(11/23/2011)
GOLDEN MALRIN
RF-128 FLY
KILLER
2724-274
(10/20/2010)
1.0%
Scatter bait
Bait station
- Not to be used inside or around homes, or any other
place where children or pets are likely to be present.
- Place scatterbait in areas inaccessible to livestock.
LURECTRON
SCATTERBAIT
7319-6
(11/15/2011)
1.0%
Scatter bait
Bait station
Brush on paste
Keep children and pets out of treated areas. Do not
place scatterbait around commercial dumpsters that are
not enclosed.
STIMUKIL FLY
BAIT
53871-3
(8/17/2004)
1.0%
Scatter bait
Bait station
Brush on paste
- Bait stations should be at least 4' above ground and in
areas not accessible to children, pets, and livestock.
- Brush paste on outside of structures so that it is
inaccessible to children, pets, and livestock.
METHOMYL 5G
GRANULES
57242-2
(8/21/2011)
5%
Ground, banded
application in corn
whorl
- Do not apply within 25 ft of lakes, reservoirs, rivers,
estuaries, commercial fishponds, and natural, permanent
streams, marshes or natural, permanent ponds.
- Not for use in home plantings or U-Pick operations.
There are a total of 30 products containing methomyl. This includes three technical products
(352-366, 70552-2, and 81598-9) and one manufacturing use product (352-361). These four
products are used only to formulate methomyl end use products and are not reviewed further. Of
the 30 products, 18 are SLNs; however, there are only seven SLN registrations for use in
California. The other 11 SLNs are not reviewed further.
Table 2-5 provides a complete listing of the remaining eight section 3 end-use products and the
seven SLNs. The table includes the formulation, EPA registration number, date of stamped
label, % active ingredient, methods of application, and any relevant use restrictions.
Two of the end-use products are labelled as 'restricted use' chemicals (Lannate® LV and
Lannate® SP), indicating that only licensed pesticide applicators are legally allowed to apply the
42
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product. None of the scatter bait/bait station end-use products are labelled as 'restricted use'
chemicals. Methomyl is registered for use on a wide variety of sites including field, vegetable,
and orchard crops; turf (sod farms only); livestock quarters; commercial premises; and refuse
containers. Low volume aerial applications (a minimum of 1 gallon of tank mixture/acre) are
allowed in CA for a variety of non-orchard agricultural uses (see APPENDIX B). For the
purposes of this assessment 'agricultural uses' refer to all field and vegetable crops and sod
farms. Orchard uses are analyzed separately from other agricultural uses because of their
different use patterns.
For agricultural and orchard uses, the maximum single application rate allowed on the labels is
0.9 lb active ingredient (a.i.)/acre, which is the most common single maximum application rate
for all agricultural uses (see APPENDIX B for a complete list of registered uses and application
rates).
Maximum seasonal labeled application rates (indicated on the label as maximum application
rates per crop) for agricultural uses range from 0.9 lb a.i./acre/crop [i.e., Bermuda grass
(pasture), avocado, lentils, beans (interplanted with trees), sorghum, and soybeans (interplanted
with trees)] to 7.2 lbs a.i./acre/crop [i.e., cabbage, lettuce (head), cauliflower, broccoli raab,
celery, and Chinese cabbage].
All orchard and most agricultural uses involve foliar application. The only granular
agricultural/orchard use is for corn (which also has a foliar use). Since the maximum seasonal
application rate for methomyl use on corn is the same for the foliar and granular formulations,
and no spray drift is expected for granular use, modeling only foliar applications for corn in the
aquatic assessment is expected to be conservative. The granular use on corn and all foliar uses
were also assessed in the terrestrial assessment.
All non-agricultural and non-orchard, outdoor uses for methomyl in CA are limited to bait
stations and scatter bait around agricultural (e.g., animal premises) and commercial structures
and commercial dumpsters. The bait station use involves placing the pesticide within the bait
station and hanging the bait station at least four feet off the ground (as stipulated on the labels);
as a result, no spray drift or runoff is expected from this use. The scatter bait can be mixed with
water to form a paste which can be brushed onto walls, window sills, and support beams. Since
the scatter bait uses are also granular applications, no spray drift exposure is expected but there is
potential for off-site exposure via runoff. Therefore, the scatter bait is modeled in the aquatic
assessment. Scatter bait is also assessed as a granular application in the terrestrial assessment.
Table 2-6 presents the uses and corresponding application rates and methods of application
considered in this assessment.
43
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Table 2-6. M
ethomyl Uses Assessed for California
Use (App.
Method)
Form.
Maximum
Single
A pp. Rate
(lbs
a.i./acrc)
Minimum
Rctrcatmcnt
Interval
(days)
Maximum
A pp. Rate
per Crop
(lbs
a.i./aere)
Maximum
Number
of A pp.
per Crop
Maximum
Number of
Crops per
Year
Maximum
A pp. Rate
per Year
(lbs
a.i./aere)
Alfalfa
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
3.6 lb ai/A
10
1 crop with
multiple
cuttings
3.6 lb a.i./A
Lannate SP
Methomyl
90SP
Anise (Fennel)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb a/A
10
2
9 lb a.i./A
Lannate SP
Methomyl
90SP
Apple
(ground only)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
7
4.5 lb ai/A
5
1
4.5 lb a.i./A
Lannate SP
Methomyl
90SP
Asparagus
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
8
1
4.5 lb a.i./A
Lannate SP
Methomyl
90SP
Avocado
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
0.9 lb ai/A
2
1
0.9 lb a.i./A
Lannate SP
Methomyl
90SP
Barley
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
1.8 lb ai/A
4
1
1.8 lb a.i/.A
Lannate SP
Methomyl
90SP
Beans,
Succulent
(kidney, lima,
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
10
1
4.5 lb a.i/.A
mung, Navy,
pinto, snap, wax,
broad, fava,
asparagus beans,
blackeyed peas,
cowpeas)
Lannate SP
Methomyl
90SP
Sweet Lupine,
White Sweet
Lupine, White
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
10
1
4.5 lb a.i./A
Lupine, Grain
Lupine
Lannate SP
Methomyl
90SP
Beans, Dry
(same as
succulent beans)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
10
1
4.5 lb a.i/.A
44
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Use (App.
Method)
Form.
Maximum
Single
A pp. Rate
(lbs
a.i./aere)
Minimum
Rctrcatmcnt
Interval
(days)
Maximum
A pp. Rate
per Crop
(lbs
a.i./aerc)
Maximum
Number
of A pp.
per Crop
Maximum
Number of
Crops per
Year
Maximum
A pp. Rate
per Year
(lbs
a.i./aere)
Lannate SP
Methomyl
90SP
BeansSLN
(interplanted
with nonbearing
almonds, plums,
prunes, peaches,
and walnuts)
(CA-770431)
Lannate SP
0.45 lb ai/A
5
0.9 lb ai/A
2
1
0.9 lb a.i/.A
Beets (table)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
3.6 lb ai/A
8
2
7.2 lb a.i/.A
Lannate SP
Methomyl
90SP
Bermudagrass
(pasture)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
0.9 lb ai/A
4
1
0.9 lb a.i/.A
Lannate SP
Methomyl
90SP
Blueberries
(ground only)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
3.6 lb ai/A
4
1
3.6 lb a.i./A
Lannate SP
Methomyl
90SP
Broccoli
Lannate LV
Methomyl
29LV
0.9 lb ai/A
2
6.3 lb ai/A
10
Imperial
Valley: 1
Coastal
Valleys: 3
San Joaquin
Valley: 2
6.3 lb a.i./A
18.9 lb a.i./A
12.6 lb a.i./A
Lannate SP
Methomyl
90SP
Broccoli,
ChineseSLN
(CA-860059)
Lannate SP
0.9 lb ai/A
5
4.5 lb ai/A
5
2
9 lb a.i./A
Broccoli
RaabSLN
(CA-900034)
Lannate SP
0.9 lb ai/A
5
7.2 lb ai/A
10
Imperial
Valley: 1
Coastal
Valleys: 3
San Joaquin
Valley: 2
7.2 lb a.i./A
21.6 lb a.i./A
14.4 lb a.i./A
Brussels Sprouts
Lannate LV
Methomyl
29LV
0.9 lb ai/A
2
5.4 lb ai/A
10
1
5.4 lb ai/A
Lannate SP
Methomyl
90SP
Cabbage
Lannate LV
Methomyl
29LV
0.9 lb ai/A
2
7.2 lb ai/A
15
3
21.6 lb a.i./A
Lannate SP
Methomyl
90SP
45
-------
Use (App.
Method)
Form.
Maximum
Single
A pp. Rate
(lbs
a.i./aerc)
Minimum
Rctrcatmcnt
Interval
(days)
Maximum
A pp. Rate
per Crop
(lbs
a.i./aerc)
Maximum
Number
of A pp.
per Crop
Maximum
Number of
Crops per
Year
Maximum
A pp. Rate
per Year
(lbs
a.i./aere)
Carrot
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
6.3 lb ai/A
10
1
6.3 lb a.i./A
Lannate SP
Methomyl
90SP
Cauliflower
Lannate LV
Methomyl
29LV
0.9 lb ai/A
2
7.2 lb ai/A
10
Coastal
Region: 2
San Joaquin
Valley: 1
14.4 lb a.i./A
7.2 lb a.i./A
Lannate SP
Methomyl
90SP
Celery
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
7.2 lb ai/A
10
2.5
18 lb a.i./A
Lannate SP
Methomyl
90SP
Chicory
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
1.8 lb ai/A
2
San Joaquin
Valley: 2
Desert: 1
3.6 lb a.i./A
1.8 lb a.i./A
Lannate SP
Methomyl
90SP
Chinese
Cabbage
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
7.2 lb ai/A
10
3
21.6 lb a.i./A
Lannate SP
Methomyl
90SP
Collards (fresh
market only)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
5.4 lb ai/A
8
3
16.2 lb a.i./A
Lannate SP
Methomyl
90SP
Corn (field and
popcorn)
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
2.5 lb ai/A
10
1
2.5 lb a.i./A
Lannate SP
Methomyl
90SP
Corn (seed)
Lannate SP
Methomyl
90SP
0.45 lb ai/A
5
2.5 lb ai/A
10
1
2.5 lb a.i./A
Corn (sweet)
Lannate LV
Methomyl
29LV
0.45 lb ai/A
1
6.3 lb ai/A
28
3
18.9 lb a.i./A
Lannate SP
Methomyl
90SP
Corn (sweet)
Methomyl
5G
Granules
0.15 lb ai/A
NR
6.3 lb ai/A
10
3
18.9 lb a.i./A
Cotton2
Lannate LV
Methomyl
0.675 lb ai/A
3
1.8 lb ai/A
8
1
1.8 lb a.i./A
46
-------
Use (App.
Method)
Form.
Maximum
Single
A pp. Rate
(lbs
a.i./aerc)
Minimum
Rctrcatmcnt
Interval
(days)
Maximum
A pp. Rate
per Crop
(lbs
a.i./aerc)
Maximum
Number
of A pp.
per Crop
Maximum
Number of
Crops per
Year
Maximum
A pp. Rate
per Year
(lbs
a.i./aere)
29LV
Lannate SP
Methomyl
90SP
Cucumber
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
5.4 lb ai/A
12
1
5.4 lb a.i./A
Lannate SP
Methomyl
90SP
Eggplant
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
10
1
4.5 lb a.i./A
Lannate SP
Methomyl
90SP
Endive, Escarole
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
8
2
(less in
desert)
9 lb a.i./A
Lannate SP
Methomyl
90SP
Garlic
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
2.7 lb ai/A
6
1
2.7 lb a.i./A
Lannate SP
Methomyl
90SP
Grapefruit3
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
2.7 lb ai/A
4
1
2.7 lb a.i./A
Lannate SP
Methomyl
90SP
Horseradish
(ground Only)
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
1.8 lb ai/A
4
1
1.8 lb a.i./A
Lannate SP
Methomyl
90SP
Leafy Green
Vegetables
(beet tops,
dandelions, kale,
mustard greens,
parsley, Swiss
chard, turnip
greens)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
3.6 lb ai/A
8
4
14.4 lb a.i./A
Lannate SP
Methomyl
90SP
Lemon3
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
2.7 lb ai/A
4
1
2.7 lb a.i./A
Lannate SP
Methomyl
90SP
Lentils
Lannate LV
Methomyl
0.9 lb ai/A
5
0.9 lb ai/A
2
1
0.9 lb a.i./A
47
-------
Maximum
Minimum
Maximum
Maximum
Maximum
Number of
Crops per
Year
Maximum
Use (App.
Method)
Form.
Single
A pp. Rate
(lbs
a.i./aerc)
Rctrcatmcnt
Interval
(days)
A pp. Rate
per Crop
(lbs
a.i./aerc)
Number
of A pp.
per Crop
A pp. Rate
per Year
(lbs
a.i./aere)
29LV
Lannate SP
Methomyl
90SP
Lettuce (head
Lannate LV
0.9 lb ai/A
2
7.2 lb ai/A
15
Central
varieties)
Methomyl
29LV
Coast: 2
Central
14.4 lb a.i./A
Lannate SP
Valley: 2
14.4 lb a.i./A
Methomyl
90SP
Other
Regions: 1
7.2 lb a.i./A
Lettuce (leaf
Lannate LV
0.9 lb ai/A
2
3.6 lb ai/A
8
Desert: 1
3.6 lb a.i./A
varieties)
Methomyl
29LV
Other
Regions: 2
7.2 lb a.i./A
Lannate SP
Methomyl
90SP
Melons
Lannate LV
0.9 lb ai/A
5
5.4 lb ai/A
12
1
5.4 lb a.i./A
(cantaloupe,
casaba, Santa
Methomyl
29LV
Claus,
Lannate SP
Crenshaw,
honeydew,
honey balls,
Persian, golden
pershaw, mango
melon, pinapple
melon, snake,
Methomyl
90SP
watermelon)
Mint
Lannate LV
0.9 lb ai/A
5
1.8 lb ai/A
4
Peppermint:
(peppermint,
spearmint)
Methomyl
29LV
1*
Spearmint:
1.8 lb a.i./A
Lannate SP
2*
3.6 lb a.i./A
Methomyl
90SP
Nectarine4
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
2.7 lb ai/A
3
1
2.7 lb a.i./A
Lannate SP
Methomyl
90SP
Nonbearing
Lannate SP
0.9 lb ai/A
5
4.5 lb ai/A
5
1
4.5 lb a.i./A
Fruit, Grape, and
Nut Nursery
Stock (field
grown)SLN
(CA-770308)
Oats
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
1.8 lb ai/A
4
1
1.8 lb a.i./A
Lannate SP
Methomyl
90SP
Onions (green)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
5.4 lb ai/A
8
3
16.2 lb a.i./A
Lannate SP
48
-------
Maximum
Minimum
Maximum
Maximum
Maximum
Number of
Crops per
Year
Maximum
Use (App.
Method)
Form.
Single
A pp. Rate
(lbs
a.i./aerc)
Rctrcatmcnt
Interval
(days)
A pp. Rate
per Crop
(lbs
a.i./aerc)
Number
of A pp.
per Crop
A pp. Rate
per Year
(lbs
a.i./aere)
Methomyl
90SP
Onions (dry
Lannate LV
0.9 lb ai/A
5
3.6 lb ai/A
8
1
3.6 lb a.i./A
bulb)
Methomyl
29LV
Lannate SP
Methomyl
90SP
Oranges3
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
2.7 lb ai/A
4
1
2.7 lb a.i./A
Lannate SP
Methomyl
90SP
Peaches
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
5.4 lb ai/A
6
1
5.4 lb a.i./A
Lannate SP
Methomyl
90SP
Peas, succulent
Lannate LV
0.9 lb ai/A
3
2.7 lb ai/A
6
1
2.7 lb a.i./A
(pigeon peas,
chick, garbanzo,
Methomyl
29LV
dwarf peas,
garden peas,
Lannate SP
Methomyl
green peas,
English peas,
Field peas,
edible pod peas)
90SP
Peppers (bell,
Lannate LV
0.9 lb ai/A
5
4.5 lb ai/A
10
1
4.5 lb a.i./A
hot, pimentos,
sweet)
Methomyl
29LV
Lannate SP
Methomyl
90SP
Pomegranates
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
1.8 lb ai/A
2
1
1.8 lb a.i./A
Lannate SP
Methomyl
90SP
Potato
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
10
1
4.5 lb a.i./A
Lannate SP
Methomyl
90SP
PumpkinsSLN
Lannate SP
0.9 lb ai/A
5
2.7 lb ai/A
3
1
2.7 lb a.i./A
(CA-910011)
(San Joaquin,
Stanislaus,
Merced,
Sacramento, and
Riverside
Counties)
RadishesSLN
Lannate SP
0.9 lb ai/A
5
1.8 lb ai/A
2
5
9 lb a.i./A
49
-------
Use (App.
Method)
Form.
Maximum
Single
A pp. Rate
(lbs
a.i./aere)
Minimum
Rctrcatmcnt
Interval
(days)
Maximum
A pp. Rate
per Crop
(lbs
a.i./aerc)
Maximum
Number
of A pp.
per Crop
Maximum
Number of
Crops per
Year
Maximum
A pp. Rate
per Year
(lbs
a.i./aere)
(CA-770495)
Rye
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
1.8 lb ai/A
4
1
1.8 lb a.i./A
Lannate SP
Methomyl
90SP
Sorghum
(except sweet
sorghum)
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
0.9 lb ai/A
2
1
0.9 lb a.i./A
Lannate SP
Methomyl
90SP
Soybeans
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
1.35 lb ai/A
3
1
1.35 lb a.i./A
Lannate SP
Methomyl
90SP
Soybeans SLN
(interplanted
with nonhealing
almonds, plums,
prunes, peaches,
and walnuts)
(CA-770431)
Lannate SP
0.45 lb ai/A
5
0.9 lb ai/A
2
1
0.9 lb a.i./A
Spinach
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
3.6 lb ai/A
8
3
10.8 lb a.i./A
Lannate SP
Methomyl
90SP
Sugar Beet
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
10
1
4.5 lb a.i./A
Lannate SP
Methomyl
90SP
Summer Squash
(crookneck,
straightneck,
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
5.4 lb ai/A
12
1
5.4 lb a.i./A
scallop,
vegetable
marrow,
spaghetti,
hyotan, cucuzza,
hechima,
Chinese okra,
bitter melon,
balsam pear,
balsam apple,
Chinese
cucumber)
Lannate SP
Methomyl
90SP
Sweet
PotatoesSNL
Lannate SP
0.9 lb ai/A
5
2.7 lb ai/A
3
1
2.7 lb a.i./A
50
-------
Use (App.
Method)
Form.
Maximum
Single
A pp. Rate
(lbs
a.i./aerc)
Minimum
Rctrcatmcnt
Interval
(days)
Maximum
A pp. Rate
per Crop
(lbs
a.i./aerc)
Maximum
Number
of A pp.
per Crop
Maximum
Number of
Crops per
Year
Maximum
A pp. Rate
per Year
(lbs
a.i./aere)
(Aerial only)
(CA-780136)
Tangelo,
Tangerine3
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
2.7 lb ai/A
4
1
2.7 lb a.i./A
Lannate SP
Methomyl
90SP
Tomato
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
6.3 lb ai/A
16
1
6.3 lb a.i./A
Lannate SP
Methomyl
90SP
Tomatillo
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
4.5 lb ai/A
5
1
4.5 lb a.i./A
Lannate SP
Methomyl
90SP
Turf (sod farms
only)
Lannate LV
Methomyl
29LV
0.9 lb ai/A
5
3.6 lb ai/A
4
2
7.2 lb a.i./A
Lannate SP
Methomyl
90SP
Wheat
Lannate LV
Methomyl
29LV
0.45 lb ai/A
5
1.8 lb ai/A
4
1
1.8 lb a.i./A
Lannate SP
Methomyl
90SP
Feedlots,
livestock
housing,
kennels, food
processing
Golden
Malrin
Scatterbait
0.22 lb ai/A
(4 oz
prod/500 ft2)
1
NR
NR
N/A
Lucreton
Scatterbait
plants, fenced
dumpsters
(outside)
Stimukil
Fly Bait
Feedlots,
livestock
housing,
kennels, food
processing
Golden
Malrin
Bait Station
0.22 lb ai/A
(1 oz
1
NR
NR
N/A
plants, fenced
dumpsters
(outside)
Lucreton
Scatterbait
prod/bait
station with
4 bait
Stimukil
Fly Bait
stations/500
ft2)
Livestock
housing
Lucreton
Scatterbait
Brush on
paste
1
NR
NR
N/A
51
-------
Maximum
Minimum
Maximum
Maximum
Maximum
Number of
Crops per
Year
Maximum
Use (App.
Method)
Form.
Single
App. Rate
(lbs
a.i./aere)
Rctrcatmcnt
Interval
(days)
App. Rate
per Crop
(lbs
a.i./aerc)
Number
of App.
per Crop
App. Rate
per Year
(lbs
a.i./aere)
(outside)
Stimukil
Fly Bait
Mix w/
water (4 oz
product + 4
oz water)
and brush on
structures
Walkways in
Golden
Scatterbait
1
NR
NR
N/A
caged poultry
layer houses
Malrin
0.22 lb ai/A
(inside)
Lurcreton
Scatterbait
(4 oz
prod/500 ft2)
Stimukil
Fly Bait
Walkways in
Golden
Bait Station
1
NR
NR
N/A
caged poultry
layer houses
(inside)
Malrin
0.22 lb ai/A
(1 oz
prod/bait
station with
4 bait
stations/500
ft2)
Lurcreton
Scatterbait
Stimukil
Fly Bait
Abbreviations: App. = applications; Form. = formulation; N/A = not applicable; NR = not reported on label
1 5 days was used unless otherwise stated on the label.
2 Different rates depending on geographic region; the listed rates are for CA
3 Limited to use in CA, AZ, and HI
SLN = CA Special Local Needs 24(c)
4 Limited to use in CA, and AZ
* For perennial crops, we used the number of cuttings per year
Of all of the registered uses of methomyl (excluding non-CA Special Local Needs [SLN]
registrations), the following uses are excluded from our assessment because they are not
registered for use in or applicable to CA:
peanuts (not grown in CA)
pears (methomyl is registered for use on pears in the Northeastern U.S. only)
pecans (methomyl is registered for use on pecans in the Southeastern U.S. only)
- tobacco (not grown in CA).
Several methomyl crops can be grown more than one time per year in CA (i.e., they have
multiple crop cycles). Most methomyl product labels specify application rates on a per crop
cycle basis (not on a per year basis). Information from BEAD indicates that many crops can be
grown more than one time/year in California (U.S. EPA 2007). Since standard PRZM scenarios
only consist of one crop per year, applications to only one crop per year were modeled. For uses
where methomyl is applied for multiple cropping cycles within a year, EECs presented in this
assessment may underpredict exposures. For all other labeled uses, it was assumed that a
maximum seasonal application specified on the label was equivalent to a maximum annual
52
-------
application. 1 . For the labeled application rates and information from EPA's Office of Pesticide
Programs' Benefits and Economic Analysis Division (BEAD) on the number of times each crop
for which methomyl is registered for use can be grown in CA see APPENDIX B.
According to the the Agency's Biological and Economic Analysis Division (BEAD),
California's average pounds per 1,000 acres of farmland range from a maximum of 27.3 lbs of
methomyl down to < 1 lb (Figure 2-1).
Figure 2-1. Methomyl Usage by Cop Reporting District (2006-2010)2
1 ( SI'I'. I. 2007. Maximum Number of Crop Cycles Per Year in California for Methomyl Use Sites, Memo from
Monisha Kaul (BEAD) to Melissa Panger (SPED), Dated 27 February 2007.
2 '
This is a map of agricultural pesticide usage at the Crop Reporting District (CRD) level. CRDs are boundaries created by I 'SDA NASS which
are aggregates of counties (1 SDA. 2010). Pesticide usage is displayed as average pounds (for the years 2006-2010) per 1,000 acres offarmland in
a CRD to normalize for the variation in farmland between CRDs. Farmland acreage was obtained from USDA (2007).
.Usage is based on private market surveys of pesticide use in agriculture (Proprietary Data, 2006-2010). The" survey data are limited to the states;
that represent the top 80-90% of acreage for the individual crops, therefore, use may be occurring in regions outside the scope of the survey.
CRDs showing no usage of pesticides may be due to either the lack of pesticide use to the region or non-participation in the agricultural surveys.
In addition, across the years, there may be variations in the specific crops included in the eRD survey. This may result in a lower annual average
for the CRD.
53
-------
BEAD provided an analysis of both national- and county-level usage information (Kaul, 2012)
using state-level usage data obtained from USDA-NASS3, Doane (www.doane.com; the full
dataset is not provided due to its proprietary nature) and the California's Department of Pesticide
Regulation Pesticide Use Reporting (CDPR PUR) database4. CDPR PUR is considered a more
comprehensive source of usage data than USDA-NASS or EPA proprietary databases, and thus
the usage data reported for methomyl by county in this California-specific assessment were
generated using CDPR PUR data. Eleven years (1999-2010) of usage data were included in this
analysis. Data from CDPR PUR were obtained for every agricultural pesticide application made
on every use site at the section level (approximately one square mile) of the public land survey
system.5 BEAD summarized these data to the county level by site, pesticide, and unit treated.
Calculating county-level usage involved summarizing across all applications made within a
section and then across all sections within a county for each use site and for each pesticide. The
county level usage data that were calculated include: average annual pounds applied, average
annual area treated, and average and maximum application rate across all eleven years. The
units of area treated are also provided where available.
It is important to note that the uses considered in this risk assessment represent all currently
registered uses according to a review of all current labels. No other uses are relevant to this
assessment. Any reported use, such as may be seen in the CDPR PUR database, represent either
historic uses that have been canceled (see Section 2.3), mis-reported uses, or mis-use. Historical
uses, mis-reported uses, and misuse are not considered part of the federal action and, therefore,
are not considered in this assessment.
CDPR PUR data for all methomyl uses in CA can be found in Table 2-7. All uses that were
misuses, unknown uses, or uses that have been cancelled were not included in the table below.
The use sites stating animal premises, poultry, chicken, etc were left in the table because it is
believed this may be due to the bait use which is a methomyl registered use. The maximum
average annual pounds of methomyl applied between 1999 to 2010 belonged to lettuce with
49,370.05 lbs, then alfalfa (43,070.94 lbs), and corn (37,441.15).
3 United States Depart of Agriculture (USDA), National Agricultural Statistics Service (NASS) Chemical Use
Reports provide summary pesticide usage statistics for select agricultural use sites by chemical, crop and state. See
http://www.pestmanagement.info/nass/app usage.cfm.
4 The California Department of Pesticide Regulation's Pesticide Use Reporting database provides a census of
pesticide applications in the state. See http://www.cdpr.ca.gov/docs/pur/purmain.htm.
5 Most pesticide applications to parks, golf courses, cemeteries, rangeland, pastures, and along roadside and railroad
rights of way, and postharvest treatments of agricultural commodities are reported in the database. The primary
exceptions to the reporting requirement are home-and-garden use and most industrial and institutional uses
(http://www.cdpr.ca.gov/docs/pur/purmain.htni).
54
-------
Table 2-7. Summary of California Department of Pesticide Registration (CDPR) Pesticide
Use Reporting (PUR) Data from 1999 to 2010 for Currently Registered Methomyl Uses1
Site Name
Average
Annual
Pounds
Applied
Average
Application
Rate
(lbs
a.i./unit
area)
Maximum Application
Rate
(lbs a.i./unit area)
Reported Unit Area
Per Site
ALFALFA
43,070.94
0.5
4.6
Acres
ALMOND
11.37
0.9
1.5
Acres
ANIMAL PREMISE
0.01
0.0
0.0
Thousand cubic
feet
ANIMAL PREMISE
0.92
0.0
0.0
Square feet
ANIMAL PREMISE
0.01
0.0
0.0
Cubic feet
ANIMAL PREMISE
0.11
0.1
0.4
Not stated
ANIMAL PREMISE
1.11
0.0
0.2
Acres
ANIMAL PREMISE
15.88
0.1
1.6
Misc. unit
APPLE
127.07
0.7
0.9
Acres
ASPARAGUS
1,353.89
0.8
9.1
Acres
AVOCADO
25.13
0.8
0.9
Acres
BEAN, DRIED
4,780.43
0.6
4.5
Acres
BEAN, SUCCULENT
2,578.03
0.6
2.7
Acres
BEAN, UNSPECIFIED
884.36
0.6
6.8
Acres
BEET
167.82
0.6
0.9
Acres
BERMUDAGRASS
1,277.70
0.6
0.9
Acres
BLUEBERRY
411.18
0.7
1.4
Acres
BROCCOLI
0.00
0.0
0.0
Square feet
BROCCOLI
4,614.16
0.7
9.0
Acres
BRUSSELS SPROUT
155.87
0.9
1.0
Acres
CABBAGE
0.00
0.0
0.0
Square feet
CABBAGE
1,529.94
0.7
3.4
Acres
CABBAGE
0.04
0.6
0.6
Misc. unit
CANTALOUPE
6,417.69
0.6
9.0
Acres
CARROT
1,841.80
0.6
4.5
Acres
CARROT
1.80
0.6
0.6
Square feet
CARROT (FORAGE - FODDER)
0.15
0.9
0.9
Acres
CAULIFLOWER
1,169.24
0.7
4.5
Acres
CELERY
7,610.29
0.8
9.0
Acres
CELERY
1.96
0.9
0.9
Square feet
CHICKEN
0.20
0.0
0.0
Misc. unit
CHICORY
18.42
0.8
0.9
Acres
CHINESE CABBAGE (NAPPA)
315.17
0.8
17.3
Acres
-------
Site Name
Average
Annual
Pounds
Average
Application
Rate
(lbs
a.i./unit
area)
Maximum Application
Rate
(lbs a.i./unit area)
Reported Unit Area
Per Site
CHINESE GREENS
3.94
1.0
1.8
Acres
CILANTRO
0.02
0.3
0.3
Acres
CITRUS
53.44
5.8
47.7
Acres
COLLARD
58.00
0.5
0.9
Acres
CORN (FORAGE - FODDER)
3,123.69
0.4
4.7
Acres
CORN, HUMAN CONSUMPTION
37,441.15
0.4
6.8
Acres
CORN, HUMAN CONSUMPTION
2.76
0.9
0.9
Not stated
CORN, HUMAN CONSUMPTION
3.41
0.3
0.5
Square feet
COTTON
1,899.94
0.6
4.5
Acres
COTTON (FORAGE - FODDER)
1.35
0.5
0.5
Acres
EGGPLANT
118.19
0.9
18.0
Acres
ENDIVE (ESCAROLE)
335.56
0.7
9.0
Acres
FORAGE HAY/SILAGE
16.11
0.4
0.5
Acres
GARLIC
765.99
0.4
1.7
Acres
GRAPEFRUIT
14.86
0.8
0.9
Acres
LETTUCE, HEAD
49,370.05
0.7
7.2
Acres
LETTUCE, HEAD
0.87
0.5
0.6
Square feet
LETTUCE, LEAF
0.50
0.5
0.5
Square feet
LETTUCE, LEAF
28,727.72
0.6
10.8
Acres
MELON
2,379.84
0.6
4.5
Acres
MINT
21.70
0.7
2.9
Acres
NECTARINE
5,625.51
0.8
9.1
Acres
OAT
14.37
0.9
6.8
Acres
OAT (FORAGE - FODDER)
69.31
0.4
1.2
Acres
ONION, DRY
13,035.65
0.7
12.2
Acres
ONION, GREEN
368.37
0.6
1.8
Acres
ORANGE
2,027.40
0.8
11.3
Acres
PEACH
845.90
0.9
9.6
Acres
PEAS
2,144.44
0.8
9.0
Acres
PEAS (FORAGE - FODDER)
0.23
0.9
0.9
Acres
POMEGRANATE
3,222.28
0.8
1.8
Acres
POTATO
3,905.84
0.7
9.2
Acres
POULTRY
0.02
0.0
0.0
Square feet
Thousand cubic
POULTRY
0.00
0.0
0.0
feet
POULTRY
0.82
0.1
0.2
Acres
POULTRY
2.08
0.0
0.2
Misc. unit
-------
Site Name
Average
Annual
Pounds
0.03
Average
Application
Rate
(lbs
a.i./unit
area)
0.0
Maximum Application
Rate
(lbs a.i./unit area)
0.0
Reported Unit Area
Per Site
POULTRY
PUMPKIN
581.99
0.6
11.5
Acres
RADISH
21.36
0.8
2.0
Acres
RYE
2.37
0.4
0.5
Acres
RYEGRASS
5.44
0.5
0.5
Acres
SORGHUM (FORAGE - FODDER)
502.73
0.5
4.5
Acres
SORGHUM/MILO
126.03
0.4
0.7
Acres
SPINACH
2,725.94
0.7
7.7
Acres
SQUASH
0.19
0.5
0.5
Square feet
SQUASH
447.15
0.6
5.9
Acres
SQUASH, SUMMER
104.55
0.7
1.1
Acres
SQUASH, WINTER
1.58
0.9
1.4
Acres
SQUASH, ZUCCHINI
5.61
0.5
0.7
Acres
STRUCTURAL PEST CONTROL
20.72
Not Stated
Not Stated
Not stated
STRUCTURAL PEST CONTROL
1.64
0.7
0.7
Acres
SUGARBEET
16,205.26
0.6
5.4
Acres
SUGARBEET (FORAGE - FODDER)
114.98
0.5
0.9
Acres
SWEET POTATO
1,515.80
0.8
2.7
Acres
TANGELO
3.95
0.6
0.9
Acres
TANGERINE
126.17
0.7
0.9
Acres
TOMATILLO
18.16
0.6
2.7
Acres
TOMATO
9,810.11
0.7
9.4
Acres
TOMATO
0.01
0.0
0.0
Square feet
TOMATO, PROCESSING
12.86
0.5
0.5
Square feet
TOMATO, PROCESSING
21,532.56
0.6
8.1
Acres
TURF/SOD
0.56
0.5
0.5
Acres
TURKEY
0.07
0.0
0.0
Misc. unit
UNCULTIVATED AG
21.73
0.5
0.7
Acres
UNCULTIVATED AG
3.95
0.3
0.5
Square feet
UNCULTIVATED NON-AG
4.13
3.3
4.5
Acres
VEGETABLES, LEAFY
13.78
0.8
0.9
Acres
VERTEBRATE CONTROL
5.65
0.7
0.9
Acres
VERTEBRATE CONTROL
0.04
Not Stated
Not Stated
Not stated
WATERMELON
2,864.38
0.7
4.5
Acres
WHEAT
79.43
0.5
0.9
Acres
WHEAT (FORAGE - FODDER)
48.54
0.4
0.5
Acres
1- Based on data supplied by BEAD (February 23, 2012).
-------
2.5. Assessed Species
Table 2-8 provides a summary of the current distribution, habitat requirements, and life history
parameters for the listed species being assessed. More detailed life-history and distribution
information can be found in Attachment III. See Figure 2-2 through Figure 2-9 for maps of
the current range and designated critical habitat, if applicable, of the assessed listed species.
- Bay Checkerspot Butterfly (BCB): The BCB was listed as threatened in 1987 by the
USFWS. The species primarily inhabits native grasslands on serpentine outcrops around
the San Francisco Bay Area in California.
- Valley Elderberry Longhorn Beetle (VELB): The VELB was listed as threatened in
1980 by the USFWS. The species is found in areas with elderberry shrubs throughout
California's Central Valley and associated foothills on the east and the watershed of the
Central Valley on the west.
- California Tiger Salamander (CTS): There are currently three CTS Distinct
Population Segments (DPSs): the Sonoma County(SC) DPS, the Santa Barbara (SB)
DPS, and the Central California (CC) DPS. Each DPS is considered separately in the risk
assessment as they occupy different geographic areas. The main difference in the
assessment will be in the spatial analysis. The CTS-SB and CTS-SC were downlisted
from endangered to threatened in 2004 by the USFWS, however, the downlisting was
vacated by the U.S. District Court. Therefore, the Sonoma and Santa Barbara DPSs are
currently listed as endangered while the CTS-CC is listed as threatened. CTS utilize
vernal pools, semi-permanent ponds, and permanent ponds, and the terrestrial
environment in California. The aquatic environment is essential for breeding and
reproduction and mammal burrows are also important habitat for estivation.
- Delta Smelt (DS): The DS was listed as threatened on March 5, 1993 (58 FR 12854) by
the USFWS (USFWS, 2007a). DS are mainly found in the Suisun Bay and the
Sacramento-San Joaquin estuary near San Francisco Bay. During spawning DS move
into freshwater.
- CA Clapper Rail (CCR): The CCR was listed by the USFWS as an endangered species
in 1970. The species is found only in California in coastal wetlands along the San
Francisco estuary and Suisun Bay.
- California Freshwater Shrimp (CFS): The CFS was listed as endangered in 1988 by
the USFWS. The CFS inhabits freshwater streams in Central California in the lower
Russian River drainage and westward to the Pacific Ocean and coastal streams draining
into Tomales Bay and southward into the San Pablo Bay.
- San Francisco Garter Snake (SFGS): The SFGS was listed as endangered in 1967 by
the USFWS. The species is endemic to the San Francisco Peninsula and San Mateo
County in California in densely vegetated areas near marshes and standing open water.
- Tidewater Goby (TG): The TG was listed as endangered in 1994 by the USFWS. The
range of the TG is limited to coastal brackish water habitats along the coast of California.
58
-------
Table 2-8. Summary of Current Distribution, Habitat Requirements, and Life History
Information
'or the Assessed Listed Species1
Designated
Critieal
Habitat?
Assessed
Size
Current Range
Habitat
Reproductive
Diet
Species
Type
Cycle
Bay
Adult
Santa Clara and
1) Primary
Yes
Larvae hatch
Obligate with
Checkerspot
butterfly -
San Mateo
habitat -
in March -
dwarf plantain.
Butterfly
5 cm in
Counties [Because
native
May and grow
Primary diet is
(BCB)
length
the BCB
grasslands on
to the 4th
dwarf plantain
(Euphydryas
distribution is
large
instar in about
plants (may
editha
considered a
serpentine
two weeks.
also feed on
bayensis)
metapopulation,
outcrops;
The larvae
purple owl's-
any site with
2) Secondary
enter into a
clover or
appropriate habitat
habitat -
period of
exserted
in the vicinity of
'islands' of
dormancy
paintbrush if
its historic range
smaller
(diapause)
the dwarf
(Alameda, Contra
serpentine
that lasts
plantains
Costa, San
outcrops
through the
senesce before
Francisco, San
with native
summer. The
the larvae
Mateo, and Santa
grassland;
larvae resume
pupate).
Clara counties)
3) Tertiary
activity with
Adults feed on
should be
habitat -
the start of the
the nectar of a
considered
non-
rainy season.
variety of
potentially
serpentine
Larvae pupate
plants found in
occupied by the
areas where
once they
association
butterfly (USFWS
larval food
reach a weight
with
1998, p. 11-177)].
plants occur
of 300 - 500
milligrams.
Adults emerge
within 15 to
30 days
depending on
thermal
conditions,
feed on
nectar, mate
and lay eggs
during a flight
season that
lasts 4 to 6
weeks from
late February
to early May
serpentine
grasslands
Valley
Males:
Central Valley of
Completely
Yes
The larval
Obligates with
Elderberry
1.25-
California (from
dependent on
stage may last
elderberry
Longhorn
2.5 cm
Shasta County to
its host plant,
2 years living
trees
Beetle (VELB)
length
Fresno County in
elderberry
within the
(Sambucus
(Desmocerus
Females:
the San Joaquin
(Sambucus
stems of an
sp). Adults
californicus
1.9-
Valley)
species),
elderberry
eat the
dimorphus)
2.5 cm
which is a
plant. Then
elderberry
length
common
component
of the
remaining
riparian
larvae enter
the pupal
stage and
transform into
adults. Adults
foliage until
about June
when they
mate. Upon
hatching the
59
-------
Designated
Critieal
Habitat?
Assessed
Size
Current Range
Habitat
Reproductive
Diet
Species
Type
Cycle
forests and
emerge and
larvae tunnel
adjacent
are active
into the tree
upland
from March to
where they
habitats of
June feeding
will spend 1-2
California's
and mating,
years eating
Central
when the
the interior
Valley
elderberry
produces
flowers.
wood which is
their sole food
source.
California
Adult
CTS-SC are
Freshwater
Yes
Emeree from
Aauatic Phase:
Tiger
14.2-80.5
primarily found on
pools or
burrows and
algae, snails,
Salamander
g4
the Santa Rosa
ponds
breed: fall and
zooplankton,
(CTS)
Plain in Sonoma
(natural or
winter rains
small
(Ambystoma
County.
man-made,
Eees: laid in
crustaceans,
californiense)
vernal pools,
pond Dec. -
and aquatic
CTS-CC occupies
ranch stock
Feb., hatch:
larvae and
the Bay Area
ponds, other
after 10 to 14
invertebrates,
(central and
Ashless
days
smaller
southern Alameda,
ponds);
Larval staee:
tadpoles of
Santa Clara,
Grassland or
3-6 months,
Pacific tree
western Stanislaus,
oak savannah
until the
frogs, CRLF,
western Merced,
communities,
ponds dry out,
toads;
and the majority of
in low
metamorphose
Terrestrial
San Benito
foothill
late spring or
Phase:
Counties), Central
regions;
early summer,
terrestrial
Valley (Yolo,
Small
migrate to
invertebrates,
Sacramento,
mammal
small
insects, frogs,
Solano, eastern
burrows
mammal
and worms
Contra Costa,
burrows
northeast
Alameda, San
Joaquin,
Stanislaus,
Merced, and
northwestern
Madera Counties),
southern San
Joaquin Valley
(portions of
Madera, central
Fresno, and
northern Tulare
and Kings
Counties), and the
Central Coast
Range (southern
Santa Cruz,
Monterey,
northern San Luis
Obispo, and
portions of
western San
Benito, Fresno,
60
-------
Assessed
Species
Size
Current Range
Habitat
Type
Designated
Critieal
Habitat?
Reproductive
Cycle
Diet
and Kern
Counties).
CTS-SB are found
in Santa Barbara
County.
Delta Smelt
(DS)
(Hypomesus
transpacificus)
Up to 120
mm in
length
Suisun Bay and
the Sacramento-
San Joaquin
estuary (known as
the Delta) near San
Francisco Bay, CA
The species
is adapted to
living in
fresh and
brackish
water. They
typically
occupy
estuarine
areas with
salinities
below 2 parts
per thousand
(although
they have
been found
in areas up to
18ppt). They
live along
the
freshwater
edge of the
mixing zone
(saltwater-
freshwater
interface).
Yes
They spawn in
fresh or
slightly
brackish water
upstream of
the mixing
zone.
Spawning
season usually
takes place
from late
March
through mid-
May, although
it may occur
from late
winter (Dec.)
to early
summer (July-
August).
Eggs hatch in
9-14 days.
They primarily
planktonic
copepods,
cladocerans,
amphipods,
and insect
larvae. Larvae
feed on
phytoplankton;
juveniles feed
on
zooplankton.
California
Clapper Rail
(CCR)
(Rallus
longirostris
obsoletus)
250 - 350
g
Juveniles
-50 g3
Alameda, Contra
Costa, Marin,
Napa, San
Francisco, San
Mateo, Santa
Clara, Solano, and
Sonoma counties
Tidal marsh
habitat
No
Breeding:
Feb. - August
Nesting: mid-
March-Aug.
Lav Eggs:
March - July
Incubation: 23
to 29 days;
Leave nest: 35
to 42 days
after hatch;
Juveniles
fledge at ten
weeks and can
breed during
the spring
after they
hatch
Opportunistic
feeders:
freshwater and
estuarine
invertebrates,
seeds, worms,
mussels,
snails, clams,
crabs, insects,
and spiders;
occasionally
consume small
birds and
mammals,
dead fish, up
to 15% plant
material
California
Freshwater
Shrimp
Up to 50
mm
postorbital
Marin, Napa, and
Sonoma Counties,
CA
Freshwater,
perennial
streams; they
No
Breed once a
year, typically
in Sept. Eggs
Feed on
detritus (algae,
aquatic
61
-------
Designated
Critieal
Habitat?
Assessed
Size
Current Range
Habitat
Reproductive
Diet
Species
Type
Cycle
(CFWS)
length
prefer quiet
adhere to the
macrophyte
(Syncaris
(from the
portions of
pleopods and
fragments,
pacified)
eye orbit
tree-lined
are cared for
zooplankton,
to tip of
streams with
for 8 - 9
and aufwuchs)
tail)
underwater
vegetation
and exposed
tree roots
months;
embryos
emerge during
May or early
June.
San Francisco
Adult
San Mateo County
Densely
No
Oviparous
Juveniles:
Garter Snake
(46-131
vegetated
Reoroduction-
frogs (Pacific
(SFGS)
cm in
freshwater
Breedins:
tree frog,
(Thamnophis
length),
ponds near
Spring (Mar.
CRLF, and
sirtalis
Females -
open grassy
and Apr.) and
bullfrogs
tetrataenia)
227 g,
hillsides;
Fall (Sept. to
depending on
Males -
emergent
Nov.)
size) and
113 g;
vegetation;
Ovulation and
insects
Juveniles
rodent
Preenancv:
Adults:
- 2 g
burrows
Late spring
primarily frogs
(Cover Jr.
and early
(mainly
and
summer
CRLFs; also
Boyer,
Youns: Born
bullfrogs,
1988)
3-4 months
toads); to a
(18-20
after mating
lesser extent
cm in
newts;
length)
freshwater fish
and
invertebrates;
insects and
small
mammals
Tidewater
50 mm in
Along the coast in
Coastal
Yes
They are
They are
Goby (TG)
length
California (from 3
brackish
typically an
generalists that
(Eucyclogobius
miles south of the
water
annual
eat a wide
newberryi)
CA/OR border to
habitats,
species.
variety of
44 miles north of
primarily
Spawning has
invertebrates
the US/Mexico
coastal
been observed
[small benthic
border -there are
lagoons,
in every
invertebrates,
gaps in the
estuaries,
month of the
crustaceans,
geographic
river mouths,
year except
snails, mysids,
distribution where
and marshes.
Dec. Females
and aquatic
lagoons and/or
They are
may lay more
insect larvae).
estuaries are
typically
than 1 clutch
Juveniles
absent)
found in
water less
than 1 m
deep with
salinities of
less than 12
parts per
thousand.
in a year.
Eggs take
from 9 to 11
days to hatch.
probably feed
on unicellular
phytoplankton
or
zooplankton.
For more detailed information on the distribution, habitat requirements, and life history information of the
assessed listed species, see Attachment II.
62
-------
2 Oviparous = eggs hatch within the female's body and young are born live.
3 No data on juvenile CCR body weights are available at this time. As a surrogate for CCR juveniles, data on captive
21-day king rails were averaged for the juvenile body weight. King rails make an appropriate proxy for the CCR in
the absence of information. The birds were once considered the same species by taxonomists, are members of the
same genus (.Rallus), and occasionally interbreed where habitats overlap.
4 See Page 369 of Trenham el al. (Trenham el al.. 2000).
63
-------
Bay Checkerspot Butterfly Habitat
' r
Legend
a Bay Checkerspot Butterfly RP
|| Bay Checkerspot Butterfly CH
Bay Checkerspot Btfly sections
NHD waterbody
CAStreams and Rivers
CAcounties
.; ' San Benito
Sac:faifip!9!g
Contra Costa a.
Alameda
1:517,774
Map created by US EPA on 1 QI7/2009. Projection: AlbersEqual
Area Conic LJSGS, North American Datum of 1983 (NAD 1983).
County boundaries and streams from ESRI (2002), Water bodies
from NHDPIus (2006). Occurrence section data obtained from
Case No. 07-2794-JCS, critical habitat data obtained from
http://crithab.fws.gov/, point data obtained from USFWS Recovery
Plan (RP) 1998. Landctwerfrom USDA Cap Analysis Program
Orchard/Vineyard, National Land Cover Database (MRLC, 2001)
and derivative products.
i Kilometers
01.53 6 9 1 2
Figure 2-2. Bay Checkerspot Butterfly (BCB) (Euphydrycts editha bciyensis)Critical Habitat and
Occurrence Sections identified in Case No. 07-2794-JCS
64
-------
Valley Elderberry Longhorn Beetle Habitat
Figure 2-3 Valley Elderberry Longhorn Beetle (VELB) (Desmocerus californicus dimorphus)
Critical Habitat and Occurrence Sections identified in Case No. 07-2794-JCS
65
-------
Son om a
County
DPS
\ jp s
/¦ 'A
M *... \ J
Mann U^S-
t lr
O
msta f
*
j§§jffi48j
^ «lr
A
- '*
5 ">
<
o
$>
' >
2
>k
r *
Legend
CATiger Salamander CH
CATiger Salamander sections
Counties
I Kilometers
0 10 20
40 60 80
1:1,934,159
Santa
Baitoara
DPS
Map Created by USEPA on 2/17C010. Projection: Alters Equal
Area Conic USGS, North American Datum 1983.
Compiled from ESRI county boundaries and streams (2002).
CTS occurrence section data from Case No. 07-2794-JCS,
critical habitat data from http://crithab.fws.gov.
o
Figure 2-4. California Tiger Salamander (CTS) (Ambystomci cciliforniense) Critical Habitat and
Occurrence Sections identified in Case No. 07-2794-JCS
66
-------
Delta Smelt Habitat
Figure 2-5. Delta Smelt (DS) (Hypomesus transpacificus) Critical Habitat and Occurrence
Sections identified in Case No. 07-2794-JCS
67
-------
California Clapper Rail Habitat
Sarifa
Alameda
10/2009
Contra Costa
o Calif Clapper Rail from RP
Calif Clapper Rail (sections)
NHD water bodies
Streams and Rivers
CAcounties
Sari Mateo
l Kilometers
1:459,989 /
Map created by US EPA on 1 Q'6/2009. Projection: Albers Equal
Area Conic USGS, Worth American Datum of 1983 (NAD 1983).
River data from 2004 ESRI data, county boundaries from 2002 ESRI data.
CA Clapper Rail section information obtained from Case No. 07-2794-JCS.
Point habitat data obtained from USFWS Recovery Plan, 1 984.
S
Legend
Figure 2-6. California Clapper Rail (CCR) (Ral/iis longirostris obsoletus) Critical Habitat and
Occurrence Sections identified in Case No. 07-2794-JCS
68
-------
California Freshwater Shrimp Habitat
Ki I o in ete r s
0 2 4 8 12 16
1:490,782
S5
Map created by US EPA on 10/6/2009. Projection: Albers Equal
Area Conic USGS, North American Datum of 1983 (NAD 1983).
County boundaries and streams from ESRI (2002). Water bodies
from NHDPIus (2006).
CA Freshwater Shrimp section information from Case No. 07-2794-JCS,
river habitat segments obtained from USFWS Recovery Plan (RP) 1998.
/
Legend
CAFreshwater Shrimp sections
CAFreshwater Shrimp habitat (RP)
NHD Area
CA Streams and Rivers
CAcounties
Figure 2-7. California Freshwater Shrimp (CFWS) (Syncarispacified) Critical Habitat and
Occurrence Sections identified in Case No. 07-2794-JCS
69
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SF Garter Snake Habitat
/
/
o
Legend
SF Garter Snake distribution from RP
| SF Garter Snake occurrence sections
NHD waterbody
CAStreams and Rivers
CAcounties
l Kilometers
0 1 2
4 6 8
1:282,367
Map created by US EPA on 1Q/7/2009. Projection: Albers Equal
Area Conic USGS, North American Datum of 1983 (NAD 1983).
County boundaries and streams from ESRI (2002). Water bodies
from NHDPIus (2006), section data obtained from Case No.
07-279 4-JCS, SFGS distribution data obtained from USFWS
Recovery Plan (RP) 1985.
San Francisco ^
Alarnetya
San
Francisco
Bay
v
\ f
/r
San Mateo
Santa Clara
Figure 2-8. San Francisco Garter Snake (SFGS) (Thamnophis sirtalis tetrataenia) Critical
Habitat and Occurrence Sections identified in Case No. 07-2794-JCS
70
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Tidewater Goby Critical Habitat Areas
Figure 2-9. Tidewater Goby (TG) (Eucyclogobius newberryi) Critical Habitat and Occurrence
Sections identified in Case No. 07-2794-JCS. The critical habitat and sections are exaggerated
here by a buffer applied to the original habitat polygons. A series of larger scale maps are
referenced in Appendix L which show the actual area of critical habitat and sections.
2.6. Designated Critical Habitat
Critical habitat has been designated for the BCB, VELB, CTS-CC DPS, DS, CTS-SB DPS, and
TG. Risk to critical habitat is evaluated separately from risk to effects on the species. 'Critical
habitat' is defined in the ESA as the geographic area occupied by the species at the time of the
71
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listing where the physical and biological features necessary for the conservation of the species
exist, and there is a need for special management to protect the listed species. It may also
include areas outside the occupied area at the time of listing if such areas are 'essential to the
conservation of the species. Critical habitat designations identify, to the extent known using the
best scientific and commercial data available, habitat areas that provide essential life cycle needs
of the species or areas that contain certain primary constituent elements (PCEs) (as defined in 50
CFR 414.12(b)). Table 2-9 describes the PCEs for the critical habitats designated for the BCB,
VELB, CTS-CC DPS, DS, CTS-SB DPS, and TG.
Table 2-9. Designated Critical Habitat PCEs for the BCB, VELB, CTS-CC DPS, DS, CTS-
SB DPS, and TG Species1.
Species
PCEs
Reference
California tiger
salamander
Standing bodies of fresh water, including natural and man-made
(e.g., stock) ponds, vernal pools, and dune ponds, and other
ephemeral or permanent water bodies that typically become
inundated during winter rains and hold water for a sufficient length
of time (i.e., 12 weeks) necessary for the species to complete the
aquatic (egg and larval) portion of its life cycle2
FR Vol. 69 No. 226
CTS, 68584, 2004
Barrier-free uplands adjacent to breeding ponds that contain small
mammal burrows. Small mammals are essential in creating the
underground habitat that juvenile and adult California tiger
salamanders depend upon for food, shelter, and protection from the
elements and predation
Upland areas between breeding locations (PCE 1) and areas with
small mammal burrows (PCE 2) that allow for dispersal among such
sites
Valley
Elderberry
Longhorn
Beetle
Areas that contain the host plant of this species [i.e., elderberry trees
(Sambucus sp.)] (a dicot)
43 FR 35636 35643,
1978
Bay
Checkerspot
Butterfly
The presence of annual or perennial grasslands with little to no
overstory that provide north/south and east/west slopes with a tilt of
more than 7 degrees for larval host plant survival during periods
of atypical weather (e.g., drought).
66 FR 21449 21489,
2001
The presence of the primary larval host plant, dwarf plantain
(Plantago erecta) (a dicot) and at least one of the secondary host
plants, purple owl's-clover or exserted paintbrush, are required for
reproduction, feeding, and larval development.
The presence of adult nectar sources for feeding.
Aquatic features such as wetlands, springs, seeps, streams, lakes, and
ponds and their associated banks, that provide moisture during
periods of spring drought; these features can be ephemeral, seasonal,
or permanent.
Soils derived from serpentinite ultramafic rock (Montara, Climara,
Henneke, Hentine, and Obispo soil series) or similar soils
(Inks, Candlestick, Los Gatos, Fagan, and Barnabe soil series)
that provide areas with fewer aggressive, normative plant species for
larval host plant and adult nectar plant survival and reproduction.2
The presence of stable holes and cracks in the soil, and surface rock
outcrops that provide shelter for the larval stage of the bay
checkerspot butterfly during summer diapause.2
Tidewater Goby
Persistent, shallow (in the range of about 0.1-2 m), still-to-slow-
moving, aquatic habitat most commonly ranging in salinity from less
65 FR 69693 69717,
2000
72
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Species
PCEs
Reference
than 0.5 ppt to about 10-12 ppt, which provides adequate space for
normal behavior and individual and population growth
Substrates (e.g., sand, silt, mud) suitable for the construction of
burrows for reproduction
Submerged and emergent aquatic vegetation, such as Potamogeton
pectinatus and Ruppia maritima, that provides protection from
predators
Presence of a sandbar(s) across the mouth of a lagoon or estuary
during the late spring, summer, and fall that closes or partially closes
the lagoon or estuary, thereby providing relatively stable water levels
and salinity.
Delta Smelt
Spawning Habitat—shallow, fresh or slightly brackish backwater
sloughs and edgewaters to ensure egg hatching and larval viability.
Spawning areas also must provide suitable water quality (i.e., low
"concentrations of pollutants) and substrates for egg attachment
(e.g., submerged tree roots and branches and emergent vegetation).
59 FR 65256 65279,
1994
Larval and Juvenile Transport—Sacramento and San Joaquin Rivers
and their tributary channels must be protected from physical
disturbance and flow disruption. Adequate river flowjs necessary to
transport larvae from upstream spawning areas to rearing habitat in
Suisun Bay. Suitable water quality must be provided so that
maturation is not impaired by pollutant concentrations.
Rearing Habitat—Maintenance of the 2 ppt isohaline and suitable
water quality (low concentrations of pollutants) within the Estuary is
necessary to provide delta smelt larvae and juveniles a shallow
protective, food-rich environment in which to mature to adulthood.
Adult Migration— Unrestricted access to suitable spawning habitat
in a period that may extend from December to July. Adequate flow
and suitable water quality_may need to be maintained to
attract migrating adults in the Sacramento and San Joaquin River
channels and their associated tributaries. These areas also should be
protected from physical disturbance and flow disruption during
migratory periods.
These PCEs are in addition to more general requirements for habitat areas that provide essential life cycle needs of
the species such as, space for individual and population growth and for normal behavior; food, water, air, light,
minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction,
rearing (or development) of offspring; and habitats that are protected from disturbance or are representative of the
historic geographical and ecological distributions of a species.
2 PCEs that are abiotic, including, physical-chemical water quality parameters such as salinity, pH, and hardness are
not evaluated.
More detail on the designated critical habitat applicable to this assessment can be found in
Attachment II. Activities that may destroy or adversely modify critical habitat are those that
alter the PCEs and jeopardize the continued existence of the species. Evaluation of actions
related to use of methomyl that may alter the PCEs of the designated critical habitat for BCB,
VELB, CTS-CC DPS, DS, CTS-SB DPS, and TG form the basis of the critical habitat impact
analysis.
As previously noted in Section 2.1, the Agency believes that the analysis of direct and indirect
effects to listed species provides the basis for an analysis of potential effects on the designated
critical habitat. Because methomyl is expected to directly impact living organisms within the
action area, critical habitat analysis for methomyl is limited in a practical sense to those PCEs of
73
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critical habitat that are biological or that can be reasonably linked to biologically mediated
processes.
2.7. Action Area and LAA Effects Determination Area
2.7.1. Action Area
The action area is used to identify areas that could be affected by the Federal action. The Federal
action is the authorization or registration of pesticide use or uses as described on the label(s) of
pesticide products containing a particular active ingredient. The action area is defined by the
Endangered Species Act as, "all areas to be affected directly or indirectly by the Federal action
and not merely the immediate are involved in the action" (50 CFR §402.2). Based on an analysis
of the Federal action, the action area is defined by the actual and potential use of the pesticide
and areas where that use could result in effects. Specific measures of ecological effect for the
assessed species that define the action area include any direct and indirect toxic effect to the
assessed species and any potential modification of its critical habitat, including reduction in
survival, growth, and fecundity as well as the full suite of sublethal effects available in the
effects literature. It is recognized that the overall action area for the national registration of
methomyl is likely to encompass considerable portions of the United States based on the large
array of agricultural and non-agricultural uses. However, the scope of this assessment limits
consideration of the overall action area to those portions that may be applicable to the protection
of the BCB, VELB, CTS, DS, CCR, CFS, SFGS, and TG and their designated critical habitat
within the state of California. For this assessment, the entire state of California is considered the
action area. The purpose of defining the action area as the entire state of California is to ensure
that the initial area of consideration encompasses all areas where the pesticide may be used now
and in the future, including the potential for off-site transport via spray drift and downstream
dilution that could influence the San Francisco Bay Species. Additionally, the concept of a state-
wide action area takes into account the potential for direct and indirect effects and any potential
modification to critical habitat based on ecological effect measures associated with reduction in
survival, growth, and reproduction, as well as the full suite of sublethal effects available in the
effects literature.
It is important to note that the state-wide action area does not imply that direct and/or indirect
effects and/or critical habitat modification are expected to or are likely to occur over the full
extent of the action area, but rather to identify all areas that may potentially be affected by the
action. The Agency uses more rigorous analysis including consideration of available land cover
data, toxicity data, and exposure information to determine areas where BCB, VELB, CTS, DS,
CCR, CFS, SFGS, and TG and their designated critical habitat may be affected or modified via
endpoints associated with reduced survival, growth, or reproduction.
2.7.2. LAA Effects Determination Area
A stepwise approach is used to define the Likely to Adversely Affect (LAA) Effects
Determination Area. An LAA effects determination applies to those areas where it is expected
that the pesticide's use will directly or indirectly affect the species and/or modify its designated
critical habitat using EFED's standard assessment procedures (see Attachment I) and effects
74
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endpoints related to survival, growth, and reproduction. This is the area where the "Potential
Area of LAA Effects" (initial area of concern + drift distance or downstream dilution distance)
overlaps with the range and/or designated critical habitat for the species being assessed. If there
is no overlap between the potential area of LAA effects and the habitat or occurrence areas, a no
effect determination is made. The first step in defining the LAA Effects Determination Area is
to understand the federal action. The federal action is defined by the currently labeled uses for
methomyl. An analysis of labeled uses and review of available product labels was completed.
Labeled uses that are special local needs (SLN) uses not specified for use in California or
restricted to specific states were excluded from this assessment. In addition, a distinction has
been made between food use crops and those that are non-food/non-agricultural uses. For those
uses relevant to the assessed species, the analysis indicates that, for methomyl, there is a
multitude of agricultural, orchard, and non-agricultural uses that are considered as part of the
federal action evaluated in this assessment. For a summary of uses, please see Table 2-6.
Following a determination of the assessed uses, an evaluation of the potential "footprint" of
methomyl use patterns {i.e., the area where pesticide application may occur) is determined. This
"footprint" represents the initial area of concern, based on an analysis of available land cover
data for the state of California. The initial area of concern is defined as all land cover types and
the stream reaches within the land cover areas that represent the labeled uses described above.
For methomyl, these land cover types include cultivated crops; developed high, low, medium
intensity; developed open space; forest; open water; orchards; pasture/hay; and wetlands. Since
there are a large number of uses covering a high number of land cover types, in this case, an
initial area of concern map was not developed. Since the chemical may be used over a wide
area, an initial area of concern map may under represent potential use.
Once the initial area of concern is defined, the next step is to define the potential boundaries of
the Potential Area of LAA Effects by determining the extent of offsite transport via spray drift
and runoff where exposure of one or more taxonomic groups to the pesticide will result in
exceedances of the listed species LOCs.
The AgDRIFT model (Version 2.01) is used to define how far from the initial area of concern an
effect to a given species may be expected via spray drift {e.g., the drift distance). The spray drift
analysis for methomyl uses the most sensitive endpoint for aquatic exposure, and terrestrial
exposure. The terrestrial exposure spray drift analysis was further broken down into
invertebrates versus non-invertebrates. The most sensitive endpoints for spray drift were: 5 |ig
a.i./L (acute, aquatic assessment), 0.7 |ig a.i./L (chronic, aquatic assessment), 24.2 mg/kg-bw
(acute non-invertebrate, terrestrial assessment), 75 mg/kg-bw (chronic non-invertebrate,
terrestrial assessment), 0.16|ig a.i./bee (acute invertebrate, terrestrial assessment). Further
details on the spray drift analysis are provided in Section 5.2.11.a.
In addition to the buffered area from the spray drift analysis, the Potential Area of LAA Effects
area also considers the downstream extent of methomyl that exceeds the LOC based on
downstream dilution analysis (discussed in Section 5.2.11.b).
An evaluation of usage information was conducted to determine the area where use of methomyl
may impact the assessed species. This analysis is used to characterize where predicted exposures
75
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are most likely to occur, but does not preclude use in other portions of the action area. A more
detailed review of the county-level use information was also completed. These data suggest that
methomyl has historically been used on a wide variety of agricultural and non-agricultural uses.
2.8. Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental value that
is to be protected."6 Selection of the assessment endpoints is based on valued entities (e.g., CTS,
organisms important in the life cycle of the CTS, and the PCEs of its designated critical habitat),
the ecosystems potentially at risk (e.g,. waterbodies, riparian vegetation, and upland and
dispersal habitats), the migration pathways of methomyl (e.g., runoff, spray drift, etc.), and the
routes by which ecological receptors are exposed to methomyl-related contamination (e.g., direct
contact, etc.).
2.8.1. Assessment Endpoints
A complete discussion of all the toxicity data available for this risk assessment, including
resulting measures of ecological effect selected for each taxonomic group of concern, is included
in Section 4 of this document. Table 2-10 identifies the taxa used to assess the potential for
direct and indirect effects from the uses of methomyl for each listed species assessed here. The
specific assessment endpoints used to assess the potential for direct and indirect effects to each
listed species are provided in Table 2-11.
Table 2-10. Taxa Used in the Analyses of Direct and Indirect Effects for the Assessed Listed
Species.
Listed
Birds
Mammals
Terr.
Terr.
FW Fish
FW
Estuarine
Estuarine
Aquatic
Species
Plants
Inverts.
Inverts.
/Marine
/Marine
Plants
Fish
Inverts.
San Francisco
Direct/
Indirect
Indirect
Indirect
Indirect
Indirect
n/a
n/a
Indirect
garter
Indirect
(prey/
(habitat)
(prey)
(prey)
(prey)
(habitat)
snake**
(prey)
habitat)
No data
Acute onlv:
Acute:
Acute/
Open lit
Acute/
Acute/
available
Honey bee
Channel
Chronic:
and other
Chronic:
Chronic:
catfish
Waterflea
carbamate
Bobwhite
Lab rat
Chronic:
data
quail
Fathead
available
minnow
California
Direct/
Indirect
Indirect
Indirect
Indirect
Indirect
Indirect
Indirect
Indirect
clapper rail**
Indirect
(prey)
(food/
(prey)
(prey)
(prey)
(prey)
(prey)
(food/
(prey)
Acute/
habitat)
Acute onlv:
Acute:
Acute/
Acute/
Acute/
habitat)
Acute/
Chronic:
No data
Honey bee
Channel
Chronic:
Chronic:
Chronic:
Open lit
Chronic:
Lab rat
available
catfish
Waterflea
Sheepshead
Northern
and other
Bobwhite
Chronic:
minnow
pink
carbamate
quail
Fathead
shrimp
data
minnow
available
Bay
n/a
n/a
Indirect
Direct
n/a
n/a
n/a
n/a
n/a
checkerspot
(food/
Acute onlv:
butterfly
habitat)*
Honey bee
No data
available
6FromU.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
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Listed
Birds
Mammals
Terr.
Terr.
FW Fish
FW
Estuarinc
Estuarinc
Aquatic
Species
Plants
Inverts.
Inverts.
/Marine
Fish
/Marine
Inverts.
Plants
Valley
elderberry
longhorn
beetle
n/a
n/a
Indirect(f
ood/
habitat)*
No data
available
Direct
Acute onlv:
Honey bee
n/a
n/a
n/a
n/a
n/a
California
Direct/
Indirect
Indirect
Indirect
Direct /
Indirect
n/a
Indirect
Indirect
tiger
salamander
Indirect
Acute/
Chronic:
(prey/
habitat)
Acute/
(habitat)
No data
available
(prey)
Acute onlv:
Honey bee
Indirect
(prey)
Acute:
(prey)
Acute/
Chronic:
(prey)
Acute/
Chronic:
(food/
habitat)
Open lit
Bobwhite
Chronic:
Channel
Waterflea
Northern
and other
quail
Lab rat
catfish
Chronic:
Fathead
minnow
pink
shrimp
carbamate
data
available
Tidewater
n/a
n/a
Indirect
n/a
Direct***
Indirect
Direct***
Indirect
Indirect
goby
(habitat)
No data
Acute:
Channel
(prey)
Acute/
Acute/
Chronic:
(prey)
Acute/
(habitat)
Open lit
available
catfish
Chronic:
Fathead
minnow
Chronic:
Waterflea
Sheepshead
minnow
Chronic:
Northern
pink
shrimp
and other
carbamate
data
available
Delta smelt
n/a
n/a
Indirect
n/a
Direct***
Indirect
Direct***
Indirect
Indirect
(habitat)
No data
Acute:
Channel
(prey)
Acute/
Acute/
Chronic:
(prey)
Acute/
(food/
habitat)
available
catfish
Chronic:
Fathead
minnow
Chronic:
Waterflea
Sheepshead
minnow
Chronic:
Northern
pink
shrimp
Open lit
and other
carbamate
data
available
California
n/a
n/a
Indirect
n/a
n/a
Direct/
n/a
Direct
Indirect
freshwater
shrimp
(food/
habitat)
No data
available
Indirect
(prey)
Acute/
Chronic:
Waterflea
Acute/
Chronic:
Northern
pink
shrimp
(food/
habitat)
Open lit
and other
carbamate
data
available
Abbreviations: n/a = Not applicable; Terr. = Terrestrial; Invert. = Invertebrate; FW = Freshwater
* obligate relationship
** Consumption of residues of methomyl in aquatic organisms may result in direct effects to the San Francisco
Garter Snake and the Clapper Rail.
***The most sensitive fish species across freshwater and estuarine/marine environments is used to assess effects for
these species because they may be found in freshwater or estuarine/marine environments. Note, however, that both
sets of RQs were calculated, one for the freshwater and the other for the estuarine/marine environment.
77
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Table 2-11. Taxa and Assessment Endpoints Used to Evaluate the Potential for Use of
Methomyl to Result in Direct and Indirect Effects to the Assessed Listed Species or
Modification of Critical Habitat.
Taxa Used to Assess
Direct and Indirect
Effects to Assessed
Species and/or
Modification to
Critical Habitat or
Habitat
Assessed Listed
Species
Assessment Endpoints
Measures of Ecological Effects
1. Freshwater Fish and
Aquatic-Phase
Amphibians
Direct Effect -
-Tidewater Goby*
-Delta Smelt*
-California Tiger
Salamander
Survival, growth, and
reproduction of individuals
via direct effects
la. Most sensitive fish acute 96-hr LC50
(0.32 mg a.i./L) for channel catfish
(Ictalurus punctatus, MRID 40098001)
lb. Most sensitive fish chronic NOAEC
(0.012 mg a.i./L) for channel catfish (I.
punctatus, based on an ACR calculation)
lc. Most sensitive fish early-life stage
NOAEC (0.057 mg/L, based on larval
survival) for fathead minnow
(Pimephalespromelas, MRID 00131255).
A fish life cycle test NOAEC (0.076
mg/L, based on growth) for fathead
minnow (P. promelas, MRID 43072101).
Indirect Effect (orcy)
-SF Garter Snake
-CA Clapper Rail
-[CA Tiger
Salamander?]
Survival, growth, and
reproduction of individuals
or modification of critical
habitat/habitat (CTS-SB
DPS) via indirect effects on
aquatic prey food supply
(i.e., fish and aquatic-phase
amphibians)
2. Freshwater
Invertebrates
Direct Effect -
-CA FW Shrimp
Survival, growth, and
reproduction of individuals
via direct effects
2a. Most sensitive freshwater
invertebrate 48-hr EC50 (0.005 mg a.i./L)
for waterflea (Daphnia magna, MRID
40098001).
2b. Most sensitive freshwater
invertebrate chronic NOAEC (0.0007 mg
a.i./L) for waterflea (D. magna, MRID
1312541)
Indirect Effect (orcy)
-CA FW shrimp
-SF Garter Snake
-CA Clapper Rail
- CA Tiger Salamander
-Tidewater Goby
-Delta Smelt
Survival, growth, and
reproduction of individuals
or modification of critical
habitat/habitat (CTS-SB
DPS, TG, and DS) via
indirect effects on aquatic
prey food supply (i.e.,
freshwater invertebrates)
3. Estuarine/Marine Fish
Direct Effect -
-Tidewater Goby*
- Delta Smelt*
Survival, growth, and
reproduction of individuals
via direct effects
3a. Most sensitive estuarine/marine fish
96-hr LC50 (1.16 mg a.i./L) for
sheepshead minnow (Cyprinodon
variegatus, MRID 41441202)
3b. Most sensitive estuarine/marine fish
chronic NOAEC (0.260 mg a.i./L) for
sheepshead minnow (C. variegatus,
MRID 45013202)
3c. Most sensitive estuarine/marine fish
early-life stage NOAEC (0.26 mg a.i./L,
for total length and wet weight) for
sheepshead minnow (C. variegatus,
MRID 45013202)
Indirect Effect (orcy)
-CA Clapper Rail
Survival, growth, and
reproduction of individuals
via indirect effects on
aquatic prey food supply
(i.e., estuarine/marine fish)
4. Estuarine/Marine
Invertebrates
Indirect Effect (orcy)
-CA Clapper Rail
-Tidewater Goby
-Delta Smelt
Survival, growth, and
reproduction of individuals
or modification of critical
habitat/habitat (TG and DS)
via indirect effects on
4a. Most sensitive estuarine/marine
invertebrate 96-hr LC50 (0.019 mg a.i./L)
for northern pink shrimp (Penaeus
duorarum, MRID 00009134)
4b. Most sensitive estuarine/marine
78
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Taxa Used to Assess
Direct and Indirect
Effects to Assessed
Species and/or
Modification to
Critical Habitat or
Habitat
Assessed Listed
Species
Assessment Endpoints
Measures of Ecological Effects
aquatic prey food supply
(i.e., estuarine/marine
invertebrates)
invertebrate chronic NOAEC (0.0024 mg
a.i./L) for northern pink shrimp (P.
duorarum, based on an ACR calculation)
5. Aquatic Plants
(freshwater/marine)
Indirect Effect
(food/habitat)
-SF Garter Snake (fw)
-CA Clapper Rail (fw)
-CA Tiger Salamander
(fw)
-Tidewater Goby
(fw/em)
-Delta Smelt (fw/em)
-CA FW Shrimp (fw)
Survival, growth, and
reproduction of individuals
or modification of critical
habitat/habitat (CTS-SB
DPS, TG, DS) via indirect
effects on habitat, cover,
food supply, and/or primary
productivity (i.e., aquatic
plant community)
5a. Vascular plant acute EC50 data not
available for methomyl; toxicity data
available from other carbamates
5b. Non-vascular plant acute EC50 (108-
184 mg a.i./L) for Pseudokirchneriella
subcapitata (a microalgae) from the open
literature (Record # 118717, Pereira et al.
2009), but endpoints are for qualitative
use only. Toxicity data available from
other carbamates.
6. Birds
Direct Effect
-SF Garter Snake
-CA Clapper Rail
-CA Tiger Salamander
Survival, growth, and
reproduction of individuals
via direct effects
6a. Most sensitive bird" or terrestrial-
phase amphibian acute LC50 (1,100
mg/kg-diet, MRID 00022923) or LD50
(24.2 mg/kg-bw, MRID 00161886) for
bobwhite quail (Colinus virginianus)
6b. Most sensitive bird" or terrestrial-
phase amphibian chronic NOAEC (150
mg/kg-diet) for bobwhite quail (C.
virginianus, MRID 41898602)
Indirect Effect
(orev/rearine sites)
-SF Garter Snake
-CA Clapper Rail
-CA Tiger Salamander
Survival, growth, and
reproduction of individuals
or modification of critical
habitat/habitat (CTS-SB
DPS) via indirect effects on
terrestrial prey (birds)
7. Mammals
Direct Effect
None.
Survival, growth, and
reproduction of individuals
via direct effects
7a. Most sensitive laboratory mammalian
acute LC50 or LD50 (30 mg a.i./kg-bw) for
the laboratory rat (Rattus norvegicus,
MRID 42140101)
7b. Most sensitive laboratory mammalian
chronic NOAEL (75 mg a.i./kg-diet or
3.75 mg a.i./kg/day) for the laboratory rat
(R. norvegicus, MRIDs 43250701,
43769401)
Indirect Effect
(d rev/habitat from
burrows/rearine sites)
-SF Garter Snake
-CA Clapper Rail
-CA Tiger Salamander
Survival, growth, and
reproduction of individuals
or modification of critical
habitat/habitat (CTS-SB
DPS) via indirect effects on
terrestrial prey (mammals)
and/or burrows/rearing sites
8. Terrestrial
Invertebrates
Direct Effect
-Bay Checkerspot
Butterfly
-Valley elderberry
longhorn beetle
Survival, growth, and
reproduction of individuals
via direct effects
8a. Most sensitive terrestrial invertebrate
acute contact LD50 (0.16 |.ig a.i./bee) for
the honey bee (Apis mellifera, MRID
45093001); in the same study an acute
oral LD50 was determined to be 0.28 |.ig
a.i./bee
8b. Most sensitive terrestrial invertebrate
chronic NOAEC not available
Indirect Effect (orev)
-SF Garter Snake
-CA Clapper Rail
-CA Tiger Salamander
Survival, growth, and
reproduction of individuals
or modification of critical
habitat/habitat (CTS-SB
DPS) via indirect effects on
terrestrial prey (terrestrial
invertebrates)
9. Terrestrial Plants
Indirect Effect
Survival, growth, and
9a. Distribution of EC25 formonocots
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Taxa Used to Assess
Direct and Indirect
Effects to Assessed
Species and/or
Modification to
Critical Habitat or
Habitat
Assessed Listed
Species
Assessment Endpoints
Measures of Ecological Effects
(food/habitat) (11011-
oblisate relationship
-SF Garter Snake
-CA Clapper Rail
-CA Tiger Salamander
-Tidewater Goby
-Delta Smelt
-CA Freshwater Shrimp
reproduction of individuals
or modification of critical
habitat/habitat (CTS-SB
DPS, TG, DS, BCB, VELB)
via indirect effects on food
and habitat (i.e., riparian
and upland vegetation)
not available
9b. Distribution of EC25 (EC05 or
NOAEC for the BCB and the VELB) for
dicots not available
Indirect Effect
(food/habitat) (obligate
relationship
-Bay Checkerspot
Butterfly
-Valley Elderberry
Longhorn Beetle
Abbreviations: SF=San Francisco
*The most sensitive fish species across freshwater and estuarine/marine environments is used to assess effects for
these species because they may be found in freshwater or estuarine/marine environments.
** Birds are used as a surrogate for terrestrial-phase amphibians and reptiles.
Methomyl has registered products containing multiple active ingredients. The only methomyl
products that contain multiple active ingredients involve the scatter bait/bait station uses {i.e.,
STIMUKIL® FLY BAIT, LURECTRON® SCATTERBAIT, GOLDEN MALRIN® RF-128 FLY
KILLER). As noted in APPENDIX A, of the formulated products, two products (EPA Reg. No.
2724-274 and 53871-3) have an LD50 value and associated confidence intervals. When these
product LD50S and associated confidence intervals are adjusted for the percent methomyl (1.1
and 1%, respectively) the adjusted LD50 value of 34.2 mg a.i./kg-bw (CI range of 27.8 to 42 mg
a.i./kg, MRID 41950001 for the Golden Marlin formulation with EPA Reg. No. 2724-274) is not
statistically distinct from the female rat 14-day LD50 of methomyl (30 mg a.i./kg-bw; CI range of
23 - 40 mg a.i./kg, MRID 42140101); however, the LD50 value of 14 mg a.i./kg-bw (CI range of
11.7-16.8 mg a.i./kg, MRID 44933202 for the Stimukil fly bait with EPA Reg. No. 53871-3)
suggests that the formulation is more toxic than the active ingredient alone. Thus, it is
reasonable to conclude that an assumption of dose-addition would be appropriate. As a result,
the scatter bait use is assessed for the terrestrial environment using the Stimukil fly bait
formulation label and formulation-based rat laboratory data.
The remaining methomyl formulations only contain a single active ingredient {i.e., methomyl).
Available toxicity data for aquatic freshwater animals did not show any significant differences
between formulated commercial products and the technical active ingredient. For species in
which comparative data are available, the confidence intervals of the toxicity endpoints for
freshwater fish and invertebrates exposed to the TGAI and formulated methomyl overlap,
indicating that the toxicity of methomyl TGAI and formulated methomyl are very similar, if not
the same, for freshwater animals (see APPENDIX J). Toxicity data for birds are only available
for the TGAI. For terrestrial invertebrates (as of the CRLF 2007 assessment) there were not
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enough comparative data to determine the relative toxicity between the TGAI and formulated
methomyl. Since methomyl is the only active ingredient in the formulated products tested, and
the primary route of exposure for terrestrial invertebrates is expected to be deposition via spray
drift, toxicity data from both the TGAI and formulated methomyl products (from products
similar to those currently registered) are appropriate for assessing potential acute risks to
terrestrial invertebrates. As a result, the risk analyses were conducted using the most sensitive
endpoint determined from toxicity studies using either formulated commercial products,
corrected for active ingredient, or technical active ingredient.
2.8.2. Assessment Endpoints for Designated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related to the
use of methomyl that may alter the PCEs of the assessed species' designated critical habitat.
PCEs for the assessed species were previously described in Section 2.6. Actions that may
modify critical habitat are those that alter the PCEs and jeopardize the continued existence of the
assessed species. Therefore, these actions are identified as assessment endpoints. It should be
noted that evaluation of PCEs as assessment endpoints is limited to those of a biological nature
{i.e., the biological resource requirements for the listed species associated with the critical
habitat) and those for which methomyl effects data are available.
Assessment endpoints used to evaluate potential for direct and indirect effects are equivalent to
the assessment endpoints used to evaluate potential effects to designated critical habitat. If a
potential for direct or indirect effects is found, then there is also a potential for effects to critical
habitat. Some components of these PCEs are associated with physical abiotic features {e.g.,
presence and/or depth of a water body, or distance between two sites), which are not expected to
be measurably altered by use of pesticides.
2.9. Conceptual Model
2.9.1. Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects {i.e., changes in
assessment endpoints) and may be based on theory and logic, empirical data, mathematical
models, or probability models (USEPA, 1998). For this assessment, the risk is stressor-linked,
where the stressor is the release of methomyl to the environment. The following risk hypotheses
are presumed in this assessment:
The labeled use of methomyl within the action area may:
• directly affect SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TGby causing mortality or
by adversely affecting growth or fecundity;
• indirectly affect SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG and/or modify their
designated critical habitat by reducing or changing the composition of food supply;
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• indirectly affect SFGS, CCR, CTS, DS, CFS, and TG and/or modify their designated
critical habitat by reducing or changing the composition of the aquatic plant community
in the species' current range, thus affecting primary productivity and/or cover;
• indirectly affect SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG and/or modify their
designated critical habitat by reducing or changing the composition of the terrestrial plant
community in the species' current range;
• indirectly affect SFGS, CCR, CTS, DS, CFS, and TG and/or modify their designated
critical habitat by reducing or changing aquatic habitat in their current range (via
modification of water quality parameters, habitat morphology, and/or sedimentation);
• indirectly affect CTS and/or modify their designated critical habitat by reducing or
changing terrestrial habitat in their current range (via reduction in small burrowing
mammals leading to reduction in underground refugia/cover).
2.9.2. Diagram
The conceptual model is a graphic representation of the structure of the risk assessment. It
specifies the methomyl release mechanisms, biological receptor types, and effects endpoints of
potential concern. The conceptual models for BCB, VELB, CTS, DS, CCR, CFS, SFGS, and
TG species and the conceptual models for the aquatic and terrestrial PCE components of critical
habitat are shown in Figure 2-10 and Figure 2-11 . Although the conceptual models for
direct/indirect effects and modification of designated critical habitat PCEs are shown on the
same diagrams, the potential for direct/indirect effects and modification of PCEs will be
evaluated separately in this assessment. Exposure routes shown in dashed lines are not
quantitatively considered because the contribution of those potential exposure routes to potential
risks to BCB, VELB, CTS, DS, CCR, CFS, SFGS, and TG and modification to designated
critical habitat is expected to be negligible.
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Figure 2-10. Conceptual Model Depicting Stressors, Exposure Pathways, and Potential
Effects to Aquatic Organisms from the Use of Methomyl.
Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological risk.
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Figure 2-11. Conceptual model depicting stressors, exposure pathways, and potential
effects to terrestrial organisms from the use of methomyl.
Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological risk.
2.10. Analysis Plan
In order to address the risk hypothesis, the potential for direct and indirect effects to the assessed
species, prey items, and habitat is estimated based on a taxon-level approach. In the following
sections, the use, environmental fate, and ecological effects of methomyl are characterized and
integrated to assess the risks. This is accomplished using a risk quotient (ratio of exposure
concentration to effects concentration) approach. Although risk is often defined as the likelihood
and magnitude of adverse ecological effects, the risk quotient-based approach does not provide a
quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as outlined
in the Overview Document (USEPA, 2004), the likelihood of effects to individual organisms
from particular uses of methomyl is estimated using the probit dose-response slope and either the
level of concern (discussed below) or actual calculated risk quotient value.
Descriptions of routine procedures for evaluating risk to the San Francisco Bay Species are
provided in Attachment I.
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2.10.1. Measures of Exposure
The environmental fate properties of methomyl along with available monitoring data indicate
that water and sediment runoff and spray drift are the principle potential transport mechanisms of
methomyl to the aquatic and terrestrial habitats. Methomyl has the potential to persist in pH's 7
and below.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of methomyl using maximum labeled application rates and
methods of application. The models used to predict aquatic EECs are the Pesticide Root Zone
Model coupled with the Exposure Analysis Model System (PRZM/EXAMS). The model used to
predict terrestrial EECs on food items is Terrestrial Residue Exposure (T-REX) model. When
terrestrial plant data is available, the model used to derive EECs relevant to terrestrial and
wetland plants is TerrPlant. These models are parameterized using relevant reviewed registrant-
submitted environmental fate data. More information on these models is available in Attachment
I.
2.10.1.a. Estimating Exposure in the Aquatic Environment
The measure of exposure for aquatic species is the estimated environmental concentration (EEC)
expected once every ten years based on 30 years of simulations. The l-in-10 year peak
concentration is used for estimating acute effects to aquatic vertebrate and invertebrate species;
the l-in-10 year 21-day mean concentration is used for assessing aquatic invertebrate chronic
exposure; and thel-in-10 year 60-day mean concentration is used for assessing chronic exposure
for fish (and aquatic-phase amphibians).
2.10.1.b. Estimating Exposure in the Terrestrial Environment
For the foliar uses, the terrestrial measure of exposure for vertebrate and invertebrate animals is
based on the upper bound concentration of residues normalized for application rates on various
dietary items. For the granular uses on corn whorls, the exposures for terrestrial vertebrates are
based on the LD50/ft2 values.
2.10.2. Measures of Effect
Data identified in Section 2.8 are used as measures of effect for direct and indirect effects. Data
were obtained from registrant submitted studies or from literature studies identified by
ECOTOX. More information on the ECOTOXicology (ECOTOX) database and how
toxicological data is used in assessments is available in Attachment I.
2.10.3. Integration of Exposure and Effects
Risk characterization is the integration of exposure and ecological effects characterization to
determine the potential ecological risk from agricultural and non-agricultural uses of methomyl,
and the likelihood of direct and indirect effects to the assessed species in aquatic and terrestrial
habitats. The exposure and toxicity effects data are integrated in order to evaluate the risks of
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adverse ecological effects on non-target species. The risk quotient (RQ) method is used to
compare exposure and measured toxicity values. EECs are divided by acute and chronic toxicity
values. The resulting RQs are then compared to the Agency's levels of concern (LOCs)
(USEPA, 2004)(see Appendix C). More information on standard assessment procedures is
available in Attachment I.
2.10.4. Data Gaps
The studies submitted to fulfill environmental fate data requirements for methomyl are not
sufficient for exposure assessment. The submitted aqueous photolysis studies either have poor
material balances or did not analyze for transformation products of methomyl. The submitted
aerobic aquatic metabolism (MRID 43325401) and anaerobic aquatic metabolism (MRID 73214)
studies have poor material balances, and therefore, do not describe the fate of methomyl in
surface water bodies down gradient from terrestrial use sites. Also, since there isn't any
anaerobic aquatic metabolism data, two times the anaerobic soil metabolism data is used for
modeling. This is believed to be a conservative approach; however, it is an uncertainty without
the actual data.
The studies submitted to fulfill environmental effects data requirements for methomyl are also
not sufficient. Although many submissions have been made to provide data on the effects of
methomyl to aquatic and terrestrial organisms, data gaps still exist. Data gaps include the
following: avian acute oral toxicity (850.2100), avian reproduction (850.2300), terrestrial plant
(850.4100, 850.4150), and aquatic plant (850.5400, 850.4400) toxicity studies. The specific data
gaps are described in full in Registration Review Preliminary Problem Formulation for
Methomyl (DP Barcode 374952, 2010). An update of this data since the problem formulation is
that the registrant (E.I. DuPont de Nemours and Company, Inc.) requested a data waiver (MRID
48736202, DuPont project ID: 34679) for an avian (passerine) acute oral toxicity study
(850.2100), which was identified as an additional data need in support of registration review of
2010. After carefully reviewing the registrant's waiver request, EFED still identifies the avian
acute oral toxicity study with passerines as a critical data gap (see Response to Waiver Request
memo, DP Barcode 400766, May 16, 2012).
3. Exposure Assessment
Methomyl is formulated as mainly soluble concentrates, but also includes granular,
pelleted/tableted, and bait/solid formulations. Application methods for the agricultural uses of
methomyl include aircraft (fixed-wing and helicopter), high and low volume ground sprayer,
ultra low volume sprayer, and granule application. Risks from ground boom and aerial
applications are considered in this assessment because they are expected to result in the highest
off-target levels of methomyl due to generally higher spray drift levels. Ground boom and aerial
modes of application tend to use lower volumes of application applied in finer sprays than
applications coincident with sprayers and spreaders and thus have a higher potential for off-
target movement via spray drift. Runoff associated with large rainfall events is expected to be
responsible for the greatest off-target movement of methomyl.
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3.1. Label Application Rates and Intervals
Methomyl labels may be categorized into two types: labels for manufacturing uses (including
technical grade methomyl and its formulated products) and end-use products. While
technical products, which contain methomyl of high purity, are not used directly in the
environment, they are used to make formulated products, which can be applied in specific
areas to control insects. The formulated product labels legally limit methomyl's potential use
to only those sites that are specified on the labels.
Currently, there are refinements being discussed for the methomyl registration which may
lead to proposed mitigation measures. Due to the fact these are still under review, the
influence of any changes are not being included in this effects determination.
Currently registered agricultural and non-agricultural uses of methomyl within California
include a multitude of agricultural and non-agricultural uses. Please see Section 2.4.3 for a
full list of uses. The uses being assessed are summarized in Table 3-1. The uses modeled
below encompass the range of uses; the highest, median, and lowest application rates; and the
uses where methomyl is applied the most based on information provided by BEAD.
Table 3-1. Methomyl Uses, Scenarios, and Application Information
Uses
Represented
bv Scenario
Scenario
Application
Method/
Formulation
Application
Rate
Maximum
Number of
Applications
Application
Interval
Date of
First
Application
Alfalfa
C Aalfalfa_W irrigOP
Aerial/ soluble
concentrate
0.9
4*
5
28-Dec
Avocado
CAAvocadoRLF_V2
Aerial/ soluble
concentrate
0.9
1
NA
21-Nov
Cabbage
(encompasses
cauliflower,
Chinese
broccoli,
Chinese
cabbage,
collards, leafy
green
vegetables,
Broccoli,
Broccoli raab,
Brussels
sprouts)
CAColeCropRLF_V2
Aerial/ soluble
concentrate
0.9
8*
2
22-Feb
Celery
(encompasses
endive/escarole,
leafy green
vegetables,
lettuce,
spinach)
CA lettuce STD
Aerial/ soluble
concentrate
0.9
8*
5
1-Apr
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Uses
Represented
bv Scenario
Scenario
Application
Method/
Formulation
Application
Rate
Maximum
Number of
Applications
Application
Interval
Date of
First
Application
Corn2
(encompasses
barley, oats,
rye, sorghum,
wheat)
CAcornOP
Aerial/ soluble
concentrate
0.45
14 (due to max
lbs a.i./year
when divided
by max rate. )
1
27-Jul
Corn2
CAcornOP
Aerial/ soluble
concentrate
0.24
26 (Can apply
at a lower rate
28 times -26 is
all
PRZM/EXAMS
can handle)
1
27-Jul
mint
CARowCropRLF_V2
Aerial/ soluble
concentrate
0.9
5*
5
1-Apr
onions
(encompasses
Garlic)
CAonion_WirrigSTD
Aerial/ soluble
concentrate
0.9
6*
5
1-Jun
Scatter bait
CA
residential/impervious
Ground/
granular
0.22
26 (label
doesn't specify
how many apps
are allowed,
this is max
PRZM/EXAMs
can handle)
5
1-Jan
Sorghum *
lowest
methomyl use
rate
CAcornOP
Aerial/ soluble
concentrate
0.45
2
5
27-Jul
Turf - sod
farms only
(encompasses
bermuda grass)
CATurfRLF
Aerial/ soluble
concentrate
0.9
4
5
2-Jan
1 Uses assessed based on memorandum from Pesticide Re-evaluation Division (PRD) dated May 31,2012 and EFED Label
Data report and associated Label Use Information Reports prepared on April 13, 2012.
2: Corn was run twice to show if EECs generated would be higher applying methomyl at the maximum number of times allowed
on the label at a lower rate in order to not exceed the yearly maximum, or apply methomyl at the maximum application rate with
fewer applications to not exceed the yearly maximum application rate.
*It was found from running corn as explained in footnote 2, that running the crops at the maximum application rate fewer times
than allowed on the label in order to not exceed the yearly maximum application rate resulted in higher EECs. As a result, the
crops with the * after the maximum number of applications denotes crops run with fewer applications in order to not exceed the
yearly rate.
"Grouping crops results in some crops receiving a more conservative EEC.
a. Cole Crops - Chinese cabbage, collards and broccoli Raab RTI=5 days, brussels sprouts max rate 5.4 lbs ai/A/yr.
b. Lettuce - endive max rate 4.5 lbs ai/A/yr. Head Lettuce RH = 2 days.
c. Corn - sweet corn has RH of 1 day, while others have RTI of 5 days. Barley, oats, rye, and wheat max rate is 1.8
lb/A/yr. Remove sorghum (covered in Table later).
d. Row crop for mint - modeled 5 apps at 0.9 lbs ai/A, or 4.5 lbs ai/A/yr. Table 2-6 indicates that for mint you would
expect a max of 3.6 lbs ai/A/yr.
e. Onions - garlic has a max rate of 0.45 lbs ai/A w/ a total annual of 2.7 lbs ai/A/yr.
3.2. Aquatic Exposure Assessment
3.2.1. Modeling Approach
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The EECs (Estimated Environmental Concentrations) are calculated using the EPA Tier II
PRZM (Pesticide Root Zone Model) and EXAMS (Exposure Analysis Modeling System) with
the EFED Standard Pond environment. PRZM is used to simulate pesticide transport as a result
of runoff and erosion from an agricultural field, and EXAMS estimates environmental fate and
transport of pesticides in surface water. Aquatic exposure is modeled for the parent alone.
The most recent PRZM/EXAMS linkage program (PE5, PE Version 5, dated Nov. 15, 2006) was
used for all surface water simulations. Linked crop-specific scenarios and meteorological data
were used to estimate exposure resulting from use on crops and turf.
California-specific PRZM crop scenarios, which consist of location-specific soils, weather, and
cropping practices, were used in the simulations to represent labeled agricultural uses of
methomyl. These scenarios were developed to represent high-end exposure sites in terms of
vulnerability to runoff and erosion and subsequent off-site transport of pesticide. Methomyl is
registered on a wide variety of field, vegetable and orchard crops (see APPENDIX B).
Registered uses were grouped into categories according to similarity of growth, morphology,
product use and cropping area and representative PRZM scenarios for each category were used
for modeling. Particular attention was given to grouping crops according to the areas in which
they are grown because rainfall is understood to be a driving variable in the PRZM model. A
summary of the output files used to estimate methomyl concentrations in the aquatic systems for
ecological risk assessment can be found in APPENDIX D.
For the scatter bait use pattern, a conceptual model was developed and the impervious and
residential scenarios were post-processed to obtain the EECs. The conceptual model includes the
assumption that 50% of the modeled area is impervious, and 3% of the impervious area is
treated, while the remaining 50% of the residential area was treated. Details of the conceptual
model are in APPENDIX N. This approach is consistent with the approach taken in the
California Red Legged Frog Litigation Assessment (USEPA 2007).
PRZM/EXAMS modeling was completed using the maximum seasonal use pattern for each
category. Methomyl product labels, however, specify application rates on a per crop basis and
not on a per annual basis. Information from BEAD indicates that many crops can be grown more
than one time/year in California (APPENDIX O). Since standard PRZM scenarios consist of
one crop per year, applications to one crop per year were modeled (discussed further in Section
2.4.3). Even though methomyl is short-lived in water, it is moderately persistent in soils. Any
carry-over in the soil from a previous crop may be available for runoff and may result in runoff
loadings that are larger than EECs modeled in this assessment (See Section 6.1.2).
Use-specific management practices for all of the assessed uses of methomyl were used for
modeling, including application rates, number of applications per year, application intervals,
buffer widths and resulting spray drift values modeled from AgDRIFT, and the first application
date for each use. Application-specific and chemical-specific input parameters are listed in
Tables 3.1 and 3.2, respectively. Modeling inputs were selected according to EFED's Input
Parameter Guidance (USEPA 2009). Pesticide applications were simulated as aerial spray
applications or ground spray as prescribed by product labels. Foliar applications (PRZM
chemical application method, CAM = 2) were simulated and spray drift estimates were
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calculated with AgDRIFT corresponding to the label-required buffers of 100 ft and 25 ft for
aerial and ground spray applications, respectively. Tier I aerial and ground models were run
assuming ASAE Very Fine to Fine droplet size distribution and a high boom assumption for
ground spray to determine the spray drift values. The date of first application was developed
based on several sources of information including data provided by BEAD, a summary of
individual applications from the CDPR PUR data, and Crop Profiles maintained by the USD A.
More detail on the crop profiles and the previous assessments may be found at:
http://www.ipmcenters.org/CropProfiles/
The first day of application was chosen to correspond to the wetter portion of the year, which
tends to be winter/early spring.
3.2.2. Model Inputs
The appropriate PRZM and EXAMS input parameters for methomyl and related compounds
were selected from the environmental fate data submitted by the registrant and in accordance
with US EPA-OPP EFED water model parameter selection guidelines, Guidance for Selecting
Input Parameters in Modeling the Environmental Fate and Transport of Pesticides. Version 2.7,
October 22, 2009 and PE5 User's Manual. (P)RZM (E)XAMS Model Shell, Version (5),
November 15, 2006. Input parameters can be grouped by physical-chemical properties and other
environmental fate data, application information, and use scenarios. Physical and chemical
properties relevant to assess the behavior of methomyl and related compounds in the
environment are presented in Table 2-2 and Table 2-3 and application information from the
label in Table 2-6 and Table 3-1. The input parameters for PRZM and EXAMS are in Table
3-2. Appendix D contains example model output files and tables showing the data used to
calculate input values.
Table 3-2. Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Methomyl Endangered Species Assessment1
Fate Property
Value (unit)
MRID (or source)
Molecular Weight
162.2 g/mol
(calculated)
Henry's constant
2.1 x 10"11 atm-m3/mol
(calculated)
Vapor Pressure
5.4 x 10"6 torr
MRID 41209701
Solubility in Water
5.5 x 104 mg/L
MRID 41402101
Photolysis in Water
50 days
MRID 43823305
Aerobic Soil Metabolism Half-lives
26.1 days
Upper 90% confidence bound
on the mean of 5 half-life
values. MRIDs 00008568,
43217901, 45473401
Hydrolysis Half-lives
Stable
MRID 00131249
Aerobic Aquatic Metabolism Half-life
(water column)
5.2 days
Upper 90% confidence bound
on the mean of 2 half-life
values. MRID 43325401
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Fate Property
Value (unit)
MRID (or source)
Anaerobic Aquatic Metabolism Half-
life (benthic)
28 days
2X anaerobic soil metabolism
single value of 14 days,
(calculated from MRID
43217902)
Organic-carbon water partition
coefficient (Koc, L/kg OC)
46 L/kgoc
Mean of four Koc values.
MRID 00161884
Application rate and frequency
See Table 3.1
See Table 3.1
Application intervals
See Table 3.1
See Table 3.1
Chemical Application Method (CAM)
2
Input Parameter Guidance
Application Efficiency
0.99 (scatter bait)
0.95 aerial
Input Parameter Guidance
Spray Drift Fraction
0.01 (scatter bait)
0.0511 aerial
Draft Guidance on Modeling
Offsite Deposition of
Pesticides via Spray Drift for
Ecological and Drinking
Water Assessments for the
Environmental Fate and
Effects Division
Incorporation Depth
NA
NA
Foliar degradation rate (1/day)
0.309 (1/day)
Upper 90% confidence bound
on the mean of two rate
constants. Kiigemagi and
Deinzer, 1979, Sheets et al.,
1982
1 - Inputs determined in accordance with EFED " Guidance for Selecting Input Parameters in Modeling the
Environmental Fate and Transport of Pesticides. Version 2.1" dated October 22, 2009.
3.2.3. Results
The aquatic EECs for the various scenarios and application practices are listed in Table 3-3. The
example output from PRZM-EXAMS is provided in APPENDIX D. The maximum peak, 21
day average, and 60 day average EECs are associated with cole crops, specifically cabbage for
the peak and 21 day average (61.9 (J,g/L, 42.6 [j,g/L respectively) with scatter bait having the
highest EECs for the 60 day average (32.0 (J,g/L) and sorghum having the lowest EECs for all
EEC categories (2.5 (J,g/L, 1.1 (J,g/L, 0.4 [j,g/L respectively). Please see Table 3-3 for a list of all
EECs and modeled methomyl uses.
Table 3-3. Aquatic EECs (iig/L) for Methomyl Uses in California
Scenario
(Application
Method/
Formulation)
C ,'rops/l iscs
Represented
Application
Kate (Ih
a.i./A)
Number of
Applications
Application
Interval
(days)
Date of
l'irst
Application
l'eak
EEC
(Pg/L)
21-day
average
EEC
(Ug/L)
60-dav
average
EEC
Og/L)
CAalfalfaWirrigOP
(Aerial/ soluble
concentrate)
Alfalfa
0.9
4
5
28-Dec
26.5
20.1
11.4
CAAvocadoRLFV 2
(Aerial/ soluble
concentrate)
Avocado
0.9
1
NA
21-Nov
5.6
3.2
1.5
91
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Scenario
(Application
Method/
Formulation)
C j'ops/l ses
Represented
Application
Kate (Ih
a.i./A)
Number of
Applications
Application
Interval
(days)
Date of
l'i rst
Application
Peak
EEC
(fxg/L)
21-day
average
EEC
(Ug/L)
60-dav
average
EEC
(W?/L)
CAColeCropRLF_V2
(Aerial/ soluble
concentrate)
Cabbage
(encompasses
cauliflower,
Chinese
broccoli,
Chinese
cabbage,
collards, leafy
green
vegetables,
Broccoli,
Broccoli raab,
Brussels
sprouts)
0.9
8
2
22-Feb
61.9
42.6
23.9
CA lettuce STD
(Aerial/ soluble
concentrate)
Celery
(encompasses
endive/esc arole,
leafy green
vegetables,
lettuce,
spinach)
0.9
8
5
1-Apr
21.4
16.8
10.4
CAcornOP
(Aerial/ soluble
concentrate)
Corn
(encompasses
barley, oats,
rye, sorghum,
wheat)
0.45
14
1
27-Jul
10.2
6.6
3.1
CAcornOP
(Aerial/ soluble
concentrate)
Corn **
0.24
26
1
27-Jul
6.7
5.5
3.0
C ARowCropRLFV 2
(Aerial/ soluble
concentrate)
mint
0.9
5
5
1-Apr
14.6
11.8
7.2
CAonion WirrigSTD
(Aerial/ soluble
concentrate)
onions
(encompasses
Garlic)
0.9
6
5
1-Jun
9.1
4.7
2.5
CA residential
/impervious
(Ground/ granular)
Scatter bait
0.22
262
5
1-Jan
42.9
36.3
32.0
CAcornOP
(Aerial/ soluble
concentrate)
Sorghum *
lowest
methomyl use
rate
0.45
2
5
27-Jul
2.5
1.1
0.4
CATurfRLF
(Aerial/ soluble
concentrate)
Turf - sod
farms only
(encompasses
bermuda grass)
0.9
4
5
2-Jan
19.3
14.2
8.9
1 Drift values calculated with AgDRIFT according to 100 ft and 25 ft buffers for aerial and ground spray applications as directed by product
labels
2 Not specified on the label. 26 applications per year is the most PRZM can process.
*See Table 3-1 for more information.
92
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3.2.4. Existing Monitoring Data
A critical step in the process of characterizing EECs is comparing the modeled estimates with
available surface water monitoring data. Included in this assessment are methomyl data from the
USGS NAWQA program (http://water.usgs.gov/nawqa) and data from the California
Department of Pesticide Regulation (CDPR). In addition, air monitoring data for methomyl was
looked for, but no data was found. For a summary of all monitoring data on methomyl, please
see APPENDIX M
3.2.4.a. USGS NAWQA Surface Water Data
The USGS NAWQA surface water database
((http://infotrek.er.usgs.gov/apex/f?p=136:l:0::NQ:::) was evaluated for available monitoring
data. A total of 394 water samples were analyzed for methomyl in California alone. Of these
samples, 19 (21%) had positive detections of methomyl. The maximum concentration detected
was 0.67 |ig/L in the Salt Slough at Highway 165 near Stevinson, California. Methomyl was
detected in the Salt Slough in four samples with concentrations ranging 0.13 -0.67 |ig/L.
Methomyl was also detected in the San Joaquin River near Vernalis, California (three samples
ranging in concentration 0.0052 - 0.0723 |ig/L), the Orestimba Creek at River Road near Crows
Landing, California (10 samples ranging in concentration 0.0043 - 0.33 |ig/L) and at Merced
River at River Road bridge new Newman, California (one sample at 0.01 |ig/L).
3.2.4.b. USGS NAWQA Groundwater Data
The USGS NAWQA groundwater database
(http://infotrek.er.usgs.gov/nawqa queries/isp/gwmaster.isp) was evaluated for available
monitoring data in California. One sample was taken looking for the degradate methomyl oxime,
and 459 samples from 339 sites were taken for the parent methomyl. No detects were found of
methomyl or the methomyl oxime in groundwater in California. However, there are detections of
methomyl in groundwater at concentrations up to 20 |ig/L from other sources in other states. For
national groundwater information, please see APPENDIX M which has a summary of all
monitoring data for methomyl. This assessment focuses on the state of California.
3.2.4.C. California Department of Pesticide Regulation (CDPR) Data
The CDPR surface water database (http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm)
was evaluated for available monitoring data. CDPR focuses on monitoring data just for the state
of CA. A total of 1,118 water samples were analyzed for methomyl. Of these, 191 samples
(17%) had positive detections of methomyl. The maximum concentration reported was 5.4 |ig/L
in the Ingram/Hospital Creek (tributary to the San Joaquin River). Methomyl was detected at 21
sites (out of a total of 84) in Imperial, Merced, Stanislaus, and Yolo Counties at concentrations
ranging between 0.05 - 5.4 |ig/L.
93
-------
3.2.4.d. Atmospheric Monitoring Data
The January 2008 report by the Western Contaminants Assessment Project (WACAP) yielded no
detects of methomyl in the atmosphere or evidence of long range transport. A copy of the report
can be found at http://www.nature.nps.gov/air/studies/air toxics/wacap.cfm.
A report generated by Daly et al. and published by the American Chemical Society in 2007 titled
Pesticides in Western Canada Mountain Air and Soil did not sample for methomyl which is
expected since long range transport and volatilization of methomyl are not expected to be major
pathways of concern.
3.3. Terrestrial Animal Exposure Assessment
3.3.1. Exposure to Residues in Terrestrial Food Items
T-REX (Version 1.5) is used to calculate dietary and dose-based EECs of methomyl for birds
(including terrestrial-phase amphibians and reptiles), mammals, and terrestrial invertebrates. T-
REX simulates a 1-year time period. T-HERPS is used as a refinement of dietary and dose-based
EECs for snakes and amphibians when risk quotients from T-REX are higher than LOCs. T-
HERPS was also set up to simulate a 1-year time period. For this assessment, spray, granular,
and scatter bait applications of methomyl are considered. Terrestrial EECs were derived for the
uses previously summarized in Table 2-6. Exposure estimates generated using T-REX and T-
HERPS are for the parent alone.
Granular applications to corn whorls using methomyl 5G Granules formulation were calculated
using the LDso/ft option in T-REX v. 1.5 for birds and mammals. Additional information is
provided in the risk characterization section for each taxonomic group.
Similarly, scatter bait applications using Stimukil fly bait formulation were calculated using the
LD5o/ft option in T-REX v. 1.5 for birds and mammals. According to the Stimukil fly bait label,
the scatterbait is applied at a rate of Vi lb per 500 ft2, which is 21.78 lb of formulation/Acre and
0.2178 lbs a.i./A. Although the bait may be reapplied at 3-5day intervals, the T-REX model
analysis for LD50/ft2 which is used to calculate the RQs, estimates exposure based on only a
single application of the product. Furthermore, the RQ represents an area confined by one square
foot and is not intended to represent the dispersal of the product across an acre. Further
discussion of uncertainties about this use is located in Section 50.2.5.
Terrestrial EECs for foliar formulations of methomyl were derived for the uses summarized in
Table 3-4. A foliar dissipation half-life of 2.5 days is used based on the submitted foliar
degradation data (Sheets et al. 1982) on Bermuda grass. In order to be consistent with the CA
red-legged frog assessment, a foliar dissipation half-life of 3 days would have been used. A
recalculation of RQs (using 3 days instead of 2.5 days) for a subset of data (the 20g bird
consuming arthropods - i.e., values with the least number of acute and chronic dietary LOC
exceedances for the given uses) indicated that although the RQs increased slightly, risk
conclusions did not change. Use specific input values, including number of applications,
94
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application rate, foliar half-life and application interval are provided in Table 3-4. An example
output from T-REX and T-HERPS is available in APPENDIX E.
Table 3-4. Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
Methomyl with T-REX and T-HERPS
Use (Application
method)
Max. Single
A pp. Rate
(lbs a.i./A)
Number of
Applications
per Year
Application
Interval
(days)
Max. Annual
A pp. Rate
(lbs a.i./A)
Foliar Dissipation
Half-Life
Bulbs3
0.9
6
5
5.4
2.5 days
Cereal grains'3
0.45
14h
1
6.3
2.5 days
Cereal grains'3
0.225
28h
1
6.3
2.5 days
Cereal grains (sp.
sorghum)0
0.45
2
5
0.9
2.5 days
Cole crops'1
0.9
8
2
7.2
2.5 days
Grasses6
0.9
4
5
3.6
2.5 days
Herbsf
0.9
5
5
4.5
2.5 days
Leguminous forage
(alfalfa)
0.9
4
5
3.6
2.5 days
Non-cole leafy crops8
0.9
8
5
7.2
2.5 days
Avocado
0.9
1
N/A
0.9
2.5 days
Corn (sweet) - granular
0.15
1
N/A
N/A
N/A
Scatter bait - as
granularJ
0.2178
1
N/A
N/A
N/A
n/a = Not applicable
n/s = Not specified in label
aOnions (encompasses garlic)
bCorn (encompasses barley, oats, rye, sorghum, wheat) is the highest methomyl rate
°Sorghum is the lowest methomyl rate
d Cabbage (cauliflower, Chinese broccoli, Chinese cabbage, collards, leafy green vegetables, broccoli, broccoli raab,
Brussels sprouts)
eSod (encompasses Bermuda grass)
fAnise (encompasses mint)
8Celery (encompasses endive/escarole, leafy green vegetables, lettuce, spinach)
hThe compound can be applied at two rates: 14 times at a higher rate of 0.45 lbs a.i./A or 28 times at a lower rate of
0.225 lbs a.i./A . Since PRZM/EXAMS can only account for 26 applications, the third option is to apply the
pesticide 26 times at 0.24 lbs a.i./A in order to maintain consistency with the aquatic exposure model run. However,
the third option is not run for terrestrial exposure as the terrestrial models can account for 28 applications.
1 This use is a granular application on corn whorls using Methomyl 5G Granules. Reapplication is 10 times and a
maximum application rate per year is reported as 18.9 lbs a.i./A in the verification memo (Appendix B). However,
the T-REX model analysis for LD50/ft2could only capture a single application of the product
J This use was modeled as a broadcast granular application using Stimukil fly bait formulation. The bait may be
reapplied at 3-5day intervals, but the T-REX model analysis for LD50/ft2could only capture a single application of
the product.
Organisms consume a variety of dietary items and may exist in a variety of sizes at different life
stages. T-REX estimates exposure for the following dietary items: short grass, tall grass,
broadleaf plants, fruits/pods/seeds, and arthropods. Birds, including the CCR, and mammals,
consume all of these items. The size classes of birds represented in T-REX are small (20 g),
medium (100 g), and large (1000 g). The size classes for mammals are small (15 g), medium (35
g), and large (1000 g). EECs are calculated for the most sensitive dietary item and size class for
95
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birds (surrogate for amphibians and reptiles) and mammals. For mammals and birds, the most
sensitive EECs are for the smallest size class consuming short grass.
For foliar applications of liquid formulations, T-HERPS estimates exposure for the following
dietary items: broadleaf plants/small insects, fruits/pods/seeds/large insects, small herbivore
mammals, small insectivore mammals, and small amphibians. Snakes and amphibians may
consume all of these items. The default size classes of amphibians represented in T-HERPS are
small (2 g), medium (20 g), and large (200 g). The default vertebrate prey size that the medium
and large amphibians can consume is 13 g and 133 g, respectively (small amphibians are not
expected to eat vertebrate prey). The default size classes for snakes are small (2 g), medium (20
g), and large (800 g). The default vertebrate prey size that medium and large snakes can
consume is 25 g and 1286 g, respectively (small snakes are not expected to eat vertebrate prey).
EECs are calculated for the most sensitive dietary item and size class for amphibians and snakes.
For both amphibians and reptiles, the most sensitive EECs and RQs are for a 20-gram animal
that consumes small herbivore mammals. If dietary RQs are more sensitive than acute dose
based RQs for acute exposures they are shown as well. Dietary based EECs and RQs are used to
characterize risk from chronic exposure. The percentages of the EECs for the different dietary
items are discussed in the discussion on uncertainties (see Section 6.1.1 .b).
3.3.1.a. Dietary Exposure to Mammals, Birds, and Amphibians
Derived Using T-REX
For the foliar uses, upper-bound Kenaga nomogram values reported by T-REX are used for
derivation of dietary EECs for the CTS, CCR, SFGS, and their potential prey (Table 3-5).
EECs in T-REX that are applicable to direct effects to the CCR are for small (20 g, juveniles)
and medium (100 g, adult) birds consuming a variety of dietary items. The most conservative
EEC for the CCR is for the small bird consuming short grass. EECs in T-REX that are
applicable to assess direct effect to the terrestrial-phase CTS, SFGS, and AW are for small birds
(20g) consuming short grass7. For birds (surrogates for amphibians and reptiles), EECs and for
acute dose based and chronic dietary based exposure are calculated as these are the most
conservative values. If the LC50 is lower than the LD50, the highest acute dietary EECs are
shown as well. For mammals, EECs for acute dose based and chronic dose based exposure are
calculated as these are typically the most conservative values.
7 The short grass EECs and RQs are used for reptiles and amphibians to represent a conservative screen. It is not
being assumed that amphibians and snakes eat short grass, the result of modeling the 20 gram bird consuming short
grass is more conservative than modeling an alternative diet for amphibians and snakes and is therefore, a valid
conservative screen and is protective of these species. If the short grass assessment does not result in LOC
exceedances, there is a high confidence that effects are unlikely to occur.
96
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Table 3-5. Upper-bound Kenaga Nomogram EECs for Dietary- and Dose-based Exposures
of Birds and Mammals Derived Using T-REX for Methomyl: Accounting for direct effects
with most sensitive size classes for acute exposure
Use(s),
Type of
Application"
App Rate
(lb a.i./A, #
Apps,
Interval in
days)
EECs for CCR, CTS (all
(small birds ot'20g con
arthroj
DPS), SFGS, and Birds
turning short grass &
lods)
EECs for Mammals
(small mammals of 15 g consuming short grass)
Dictary-b
(mg/k
ascd EEC
4-dict)
Dosc-bascd EEC
(mg/kg-bw)
Dictarv-bascd EEC
(mg/kg-dict)
Dosc-bascd EEC
(mg/kg-bw)
Short
grass
Arthropod
Short
grass
Arthropod
Bulbs
0.9, 6, 5
287.93
112.77
327.92
128.44
287.93
274.52
Cereal grains
0.45, 14, 1
436.82
171.09
497.50
194.85
436.82
416.48
Cereal grains
0.225, 28, 1
222.92
87.31
253.88
99.44
222.92
212.53
Cereal grains
(sp. sorghum)
0.45, 2, 5
135.00
52.88
153.75
60.22
135.00
128.71
Cole crops
0.9, 8, 2
501.45
196.40
571.10
223.68
501.45
478.09
Grasses
0.9, 4, 5
286.88
112.36
326.72
127.97
286.88
273.51
Herbs
0.9, 5, 5
287.72
112.69
327.68
128.34
287.72
274.32
Leguminous
forage
(alfalfa)
0.9, 4, 5
286.88
112.36
326.72
127.97
286.88
273.51
Non-cole
leafy crops
0.9, 8, 5
288.00
112.80
328.00
128.47
288.00
274.58
Avocado
0.9, 1, NA
216.00
84.60
246.00
96.35
216.00
205.94
a See Table 3-4 for details on the uses.
3.3.2. Exposure to Terrestrial Invertebrates Derived Using T-REX
T-REX is also used to calculate EECs for terrestrial invertebrates exposed to methomyl from
foliar uses. Available acute contact toxicity data for bees exposed to methomyl (in units of |ig
a.i./bee), are converted to |ig a.i./g (of bee) by multiplying 1 bee by 0.128 g (the average weight
on an adult honey bee). In this case, the acute contact LD50 is 0.16 |Lxg a.i./bee for the honey bee
(Apis mellifera, MRID 45093001), which results in an adjusted toxicity value of 1.25|ag a.i./g of
bee. Dietary-based EECs calculated by T-REX for arthropods (units of |ag a.i./g of bee) are used
to estimate exposure to terrestrial invertebrates. The EECs are compared to the adjusted acute
contact toxicity data for bees in order to derive RQs.
The exposure values are applicable to direct effects to the VELB and BCB and in estimating
indirect effects based on reduction in prey to the CCR, SFGS, and CTS. An example output from
T-REX v. 1.5 is available in APPENDIX E.
97
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Table 3-6. Summary EECs Used for Estimating Risk to Terrestrial Invertebrates and
Derived Using T-REX ver. 1.5. for Methomyl
Use,
Method of Application11
Application Rate (lbs a.i./acrc), # of
app, App interval (days)
Arthropod EEC
(in a.i./g of bee, or ppm)
Bulbs
0.9, 6, 5
112.77
Cereal grains
0.45, 14, 1
171.09
Cereal grains
0.225, 28, 1
87.31
Cereal grains (sp. sorghum)
0.45,2, 5
52.88
Cole crops
0.9, 8, 2
196.40
Grasses
0.9, 4, 5
112.36
Herbs
0.9, 5, 5
112.69
Leguminous forage (alfalfa)
0.9, 4, 5
112.36
Non-cole leafy crops
0.9, 8, 5
112.80
Avocado
0.9, 1, NA
84.60
a See Table 3-4 for details on the uses.
3.3.2.a. Dietary Exposure to Amphibians and Reptiles Derived Using T-
HERPS
Birds were used as surrogate species for terrestrial-phase CTS and SFGS. Terrestrial-phase
amphibians and reptiles are poikilotherms indicating that their body temperature varies with
environmental temperature. Birds are homeotherms indicating that their temperature is
regulated, constant, and largely independent of environmental temperatures. As a consequence,
the caloric requirements of terrestrial-phase amphibians and reptiles are markedly lower than
birds. Therefore, on a daily dietary intake basis, birds consume more food than terrestrial-phase
amphibians. This can be seen when comparing the caloric requirements for free living iguanid
lizards (used in this case as a surrogate for terrestrial phase amphibians) to song birds (USEPA,
1993):
iguanid FMR (kcal/day) = 0.0535 (bw g)0'7"
passerine FMR (kcal/day) = 2.123 (bw g)0'749
With relatively comparable slopes to the allometric functions, one can see that, given a
comparable body weight, the free-living metabolic rate (FMR) of birds can be 40 times higher
than reptiles, though the requirement differences narrow with high body weights.
Because the existing risk assessment process is driven by the dietary route of exposure, a finding
of safety for birds, with their much higher feeding rates and, therefore, higher potential dietary
exposure is reasoned to be protective of terrestrial-phase amphibians consuming similar dietary
items. For this not to be the case, terrestrial-phase amphibians would have to be 40 times more
sensitive than birds for the differences in dietary uptake to be negated. However, existing dietary
toxicity studies in terrestrial-phase amphibians for methomyl are lacking. To quantify the
potential differences in food intake between birds and terrestrial-phase CTS and amphibians,
food intake equations for the iguanid lizard were used to replace the food intake equation in T-
98
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REX for birds, and additional food items of the CTS and amphibians were evaluated. These
functions were encompassed in a model called T-HERPS. T-HERPS is available at:
http://www.epa.gov/oppefedl/models/terrestrial/index.htm. EECs calculated using T-HERPS
are shown in this Section and potential risk is further discussed in the risk characterization.
EECs in T-HERPS that are applicable to the CTS are small (2 g, juveniles) amphibians
consuming small and large insects and medium (20 g) amphibians consuming small and large
insects, small herbivorous and insectivorous mammals, and amphibians. The dietary item that
results in the highest EEC for CTS (all DPS) is the small herbivore mammal. EECs calculated
using T-HERPS for the CTS are shown in Table 3-7.
Table 3-7. Upper-bound Kenaga Nomogram EECs for Dietary- and Dose-based Exposures
Use(s),
Type of
Application"
App Rate
(lb a.i./A), #
App,
Interval
(days)
EEC for Small CTS (2g)
(small birds 2g consuming small
insects)
EEC for Medium CTS (20g)
(medium birds 20g consuming
small/medium herbivorous mammals
of 1.33g/13.33)
Dietary-based
EEC (mj^kg-diet)
Dose-based EEC
(mg/kg-lm)
Dietary-based
EEC (mg/kg-
diet)b
Dose-based EEC
(mg/kg-bw)
Bulbs
0.9, 6, 5
161.96
8.99
288.98
192.66
Cereal grains
(corn-14x)
0.45, 14, 1
245.71
13.65
438.42
292.28
Cereal grains
(corn-28x)
0.225, 28, 1
125.39
6.96
223.73
149.15
Cereal grains
(sp.
sorghum)
0.45, 2, 5
75.94
4.22
135.49
90.33
Cole crops
0.9, 8, 2
282.07
15.66
503.29
335.52
Grasses
0.9, 4, 5
161.37
8.96
287.93
191.95
Herbs
0.9, 5, 5
161.84
8.99
288.77
192.52
Leguminous
forage
(alfalfa)
0.9, 4, 5
161.37
8.96
287.93
191.95
Non-cole
leafy crops
0.9, 8, 5
162.00
9.00
289.05
192.70
Avocado
0.9, 1, NA
121.50
6.75
216.79
144.53
a See Table 3-4 for details on the uses.
bEEC for medium-sized herbivorous mammal (of 13.33g)
T-REX may underestimate exposure to snakes when birds are used as a surrogate and are
assumed to eat similar dietary items because of the large meal size a snake may consume on a
o
single day. That is why birds consuming short grass in T-REX are used as the screen to
determine whether further refinement in T-HERPS is needed for snakes. T-HERPS was
8 When examining the same application rates and types, RQs calculated in T-REX for small birds consuming short
grass are higher than or equal to the highest RQs estimated in T-HERPs for medium snakes consuming small
herbivore mammals. Therefore, RQs calculated in T-REX for the small birds consuming short grass may be used as
a screen for examining risk to snakes.
99
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modified (version 1.1) to estimate exposure to snakes based on the maximum size prey item they
could consume and is used to refine a risk estimate when LOCs are exceeded for small birds
consuming short grass based on RQs estimated in T-REX. The following allometric equation
was used to estimate the maximum size prey items for snakes (King, 2002).
Prey Size = Snake Mass1015
The 95% confidence limits on the coefficient are 0.959 and 1.071 (King, 2002). The upper limit
was used in T-HERPS to estimate exposure to snakes.
EECs in T-HERPS that are applicable to the SFGS are small (2 g, juveniles) snakes consuming
small and large insects and medium (20 g) snakes consuming small and large insects, small
herbivorous and insectivorous mammals, and amphibians. The most sensitive EECs and RQs for
SFGS are for the medium animal consuming small herbivorous mammals. EECs calculated
using T-HERPS for the SFGS are shown in Table 3-8.
Table 3-8. Upper-bound Kenaga Nomogram EECs for Dietary- and Dose-based Exposures
of Amphibians and Reptiles Derived Using T-HERPS for Methomyl: SFGS specific
Use(s),
Type of
Application"
App Rate
(lb a.i./A), #
App,
Interval
(days)
EEC for Small SFGS (2g)
(small bird 2g consuming small
insects)
EEC for Medium SFGS (20g)
(medium bird 20g consuming
small/medium herbivorous mammals of
2.10g/24.74g)
Dietary-based
EEC (mg/kg-
diet)
Dose-based
EEC
(mg/kg-l»v)
Dietary-based
EEC (mg/kg-
diet)b
Dose-based EEC
(mg/kg-bw)
Bulbs
0.9, 6, 5
161.96
8.99
220.71
273.02
Cereal grains
(corn-14x)
0.45, 14, 1
245.71
13.65
334.85
414.21
Cereal grains
(corn-28x)
0.225, 28, 1
125.39
6.96
170.87
211.37
Cereal grains
(sp. sorghum)
0.45,2, 5
75.94
4.22
103.48
128.01
Cole crops
0.9, 8, 2
282.07
15.66
384.38
475.49
Grasses
0.9, 4, 5
161.37
8.96
219.90
272.02
Herbs
0.9, 5, 5
161.84
8.99
220.55
272.82
Leguminous
forage
(alfalfa)
0.9, 4, 5
161.37
8.96
219.90
272.02
Non-cole
leafy crops
0.9, 8, 5
162.00
9.00
220.76
273.08
Avocado
0.9, 1, NA
121.50
6.75
165.57
204.82
a See Table 3-4 for details on the uses.
bEEC for medium-sized herbivorous mammal (of 24.74g)
100
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3.4. Terrestrial Plant Exposure Assessment
TerrPlant (Version 1.1.2) is typically used to calculate EECs for non-target plant species
inhabiting dry and semi-aquatic areas. However, the TerrPlant model was not run because no
acceptable studies {i.e., a vegetative vigor and seedling emergence studies) are available for
methomyl. Although there are no acceptable terrestrial plant guideline toxicity studies available
for methomyl, several efficacy studies that were conducted to test the effects of methomyl on a
variety of target and non-target invertebrate pests also supplied information on effects to plants
after methomyl applications. Due to a lack of information on study design and data analyses,
these efficacy studies are classified as 'supplemental' and are not adequate for plant (or
terrestrial invertebrate) RQ calculation.
4. Effects Assessment
This assessment evaluates the potential for methomyl to directly or indirectly affect SFGS, CCR,
BCB, VELB, CTS, DS, CFS, and TG or modify their designated critical habitat. Assessment
endpoints for the effects determination for each assessed species include direct toxic effects on
the survival, reproduction, and growth, as well as indirect effects, such as reduction of the prey
base or modification of its habitat. In addition, potential modification of critical habitat is
assessed by evaluating effects to the PCEs, which are components of the critical habitat areas
that provide essential life cycle needs of each assessed species. Direct effects to the aquatic-
phase CA tiger salamander are based on toxicity information for freshwater fish, while
terrestrial-phase amphibian effects (CA tiger salamander) and reptiles (San Francisco garter
snake) are based on avian toxicity data, given that birds are generally used as a surrogate for
terrestrial-phase amphibians and reptiles.
As described in the Agency's Overview Document (USEPA, 2004), the most sensitive endpoint
for each taxon is used for risk estimation. For this assessment, evaluated taxa include freshwater
fish (used as a surrogate for aquatic-phase amphibians), freshwater invertebrates,
estuarine/marine fish, estuarine/marine invertebrates, birds (used as a surrogate for terrestrial-
phase amphibians and reptiles), mammals, and terrestrial invertebrates. No registrant-submitted
data for the aquatic and terrestrial plants are available. However, an open literature study and
registrant submitted data on other carbamates are available to inform risk characterization for
aquatic plants (see Section 5.l.le). Acute (short-term) and chronic (long-term) toxicity
information is characterized based on registrant-submitted studies and open literature (where
available) on methomyl. This section summarizes the ecotoxicity data available on methomyl.
4.1. Ecotoxicity Study Data Sources
Toxicity endpoints are established based on data generated from guideline studies submitted by
the registrant, and from open literature studies that meet the criteria for inclusion into the
ECOTOX database maintained by EPA/Office of Research and Development (ORD) (USEPA,
2004). Open literature data presented in this assessment were obtained from ECOTOX
information originally compiled Oct. 13, 2004 and refreshed Jan. 2010. In order to be included in
the ECOTOX database, papers must meet the following minimum criteria:
101
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(1) the toxic effects are related to single chemical exposure;
(2) the toxic effects are on an aquatic or terrestrial plant or animal species;
(3) there is a biological effect on live, whole organisms;
(4) a concurrent environmental chemical concentration/dose or application rate is
reported; and
(5) there is an explicit duration of exposure.
Open literature toxicity data for other 'target' insect species (not including bees, butterflies,
beetles, and non-insect invertebrates including soil arthropods and worms), which include
efficacy studies, are not currently considered in deriving the most sensitive endpoint for
terrestrial insects. Efficacy studies do not typically provide endpoint values that are useful for
risk assessment (e.g., NOAEC, EC50, etc.), but rather are intended to identify a dose that
maximizes a particular effect (e.g., EC 100). Therefore, efficacy data and non-efficacy
toxicological target insect data are not included in the ECOTOX open literature summary table
provided in APPENDIX I. For the purposes of this assessment, 'target' insect species are
defined as all terrestrial insects with the exception of bees, butterflies, beetles, and non-insect
invertebrates (i.e., soil arthropods, worms, etc.) which are included in the ECOTOX data
presented in APPENDIX I.
Data that pass the ECOTOX screen are evaluated along with the registrant-submitted data, and
may be incorporated qualitatively or quantitatively into this endangered species assessment. In
general, effects data in the open literature that are more conservative than the registrant-
submitted data are considered. The degree to which open literature data are quantitatively or
qualitatively characterized for the effects determination is dependent on whether the information
is relevant to the assessment endpoints (i.e., survival, reproduction, and growth) identified in
Section 2.8. For example, endpoints such as behavior modifications are likely to be qualitatively
evaluated, because quantitative relationships between modifications and reduction in species
survival, reproduction, and/or growth are not available. Although the effects determination relies
on endpoints that are relevant to the assessment endpoints of survival, growth, or reproduction, it
is important to note that the full suite of sublethal endpoints potentially available in the effects
literature (regardless of their significance to the assessment endpoints) are considered, as they are
relevant to the understanding of the area with potential effects, as defined for the action area.
Citations of all open literature not considered as part of this assessment because they were either
rejected by the ECOTOX screen or accepted by ECOTOX but not used (e.g., the endpoint is less
sensitive) are included in APPENDIX H. Appendix H also includes a rationale for rejection of
those studies that did not pass the ECOTOX screen and those that were not evaluated as part of
this endangered species risk assessment.
In addition to registrant-submitted and open literature toxicity information, other sources of
information, including use of the acute probit dose response relationship to establish the
probability of an individual effect and reviews of ecological incident data, are considered to
further refine the characterization of potential ecological effects associated with exposure to
methomyl. A summary of the available aquatic and terrestrial ecotoxicity information and the
incident information for methomyl are provided in Sections 4.1 through 4.4.
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4.2. Toxicity of Methomyl to Aquatic Organisms
Table 4-1 summarizes the most sensitive aquatic toxicity endpoints, based on an evaluation of
both the submitted studies and the open literature, as previously discussed. A brief summary of
submitted and open literature data considered relevant to this ecological risk assessment for the
SFGS, CCR, CTS, DS, CFS, and TG is presented below. Additional information is provided in
APPENDIX G
Based on the available data, methomyl is characterized as very highly toxic to freshwater fish
and invertebrates (freshwater and estuarine/marine) and moderately toxic to estuarine/marine fish
on an acute exposure basis. An open literature study (Record #: 118717, Pereira el al.2009)
quantifying the growth inhibition in Pseudokirchneriella subcapitata (a microalgae) after
Lannate (200g a.i./L methomyl formulation) and methomyl (99.5% purity) exposure indicates a
96-hour EC50 of 184 mg a.i./L (95% CI of 164-206 mg a.i./L for Lannate) and a 96-hour EC50 of
108 mg a.i./L (95% CI of 87-126 mg a.i./L for methomyl a.i.). For additional discussion, refer to
Section 5.1.I.e.
Regarding chronic exposure, toxicity data for methomyl are available for freshwater fish,
estuarine/marine fish, freshwater invertebrates, and estuarine/marine invertebrates. No toxicity
data from chronic exposure to methomyl are available for the most acutely sensitive freshwater
fish species, the channel catfish (Ictaluruspunctatus) (LC50 = 0.320 mg a.i./L). Therefore, an
acute-to-chronic ratio (ACR) is used to calculate a chronic freshwater fish endpoint using acute
and chronic data from the fathead minnow (for which both acute and chronic toxicity data are
available). The most sensitive no observed adverse effect concentration (NOAEC) and lowest
observed adverse effect concentration (LOAEC) for freshwater fish [fathead minnows
(Pimephalespromelas)\ are 0.057 and 0.117 mg a.i./L, respectively, based on reduced survival
(MRID 131255). The ACR for fathead minnow, i.e. ACR = 26.3, results in a NOAEC of 0.012
mg a.i./L for the channel catfish [(1.5 mg/L)/(0.057 mg/L) = (0.320 mg/L)/(x mg/L)].
For estuarine/marine fish, an early life-stage toxicity study (MRID: 450132-02) with sheepshead
minnows resulted in a NOAEC of 0.26 mg a.i./L, and a LOAEC of 0.49 mg a.i./L, based on both
reduction in total length and wet weight. Fish with deformed bodies and lethargy/erratic
swimming were noted at 1.0 mg a.i./L. No other sub-lethal effects (other than length and weight
reductions) were noted at any other time or concentration.
A 21-day life-cycle toxicity study of Daphnia magna resulted in a NOAEC of 0.0007 mg. a.i./L
and a LOAEC of 0.001 mg a.i./L based on delayed reproduction (MRID 131254). The NOAEC
and LOAEC are 0.0016 and 0.0035 mg a.i./L, respectively, based on the number of young
produced. No other sub-lethal effects were noted at any other concentration.
For estuarine/marine invertebrates, the most acutely sensitive species tested is the northern pink
shrimp (Penaeus duorarum) (LC50 = 0.019 mg a.i./L). Since no toxicity data from chronic
exposure to methomyl are available for the northern pink shrimp, an ACR is used to calculate a
chronic estuarine/marine endpoint using acute and chronic data from mysid shrimp
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(Americamysis bahia) (for which both acute and chronic data are available). The most sensitive
no observed adverse effect concentration (NOAEC) and lowest observed adverse effect
concentration (LOAEC) for mysid shrimp are 0.0291 and 0.0591 mg a.i./L, respectively, based
on reduced number of young per surviving female (MRID 450132-03). The ACR for mysid
shrimp, i.e. ACR = 8.07, results in a NOAEC of 0.0024 mg a.i./L for the northern pink shrimp
[(0.234 mg/L)/(0.029 mg/L) = (0.019 mg/L)/(x (ig/L)].
An outdoor microcosm study (MRID 437444-02) was conducted with the formulated methomyl
product Lannate L [24% a.i. (methomyl)] to evaluate the fate in tank water and hydrosoil and
assess the effects on populations of phytoplankton, zooplankton, macroinvertebrates, and bluegill
sunfish (Lepomis macrochirus). Applications were performed over a period of 22 days (22 daily
applications) to 28 days (4 applications with a 7-day reapplication interval); the total length of
the study was 35 days. Treatment groups were defined by the amount of test substance added at
each application (0.48 or 0.048 g a.i.; test vessel volume = 5,900 L; nominal treatment
concentrations were not provided) and by the interval between test substance applications [1 day
(total of 22 applications), 3 days (total of 8 applications), or 7 days (total of 4 applications)].
Before the start of the study, each of the 56 tanks used in the study was stocked with bluegill
sunfish and inoculated with aquatic plants and animals (invertebrates) from an untreated, pre-
existing pond on site, colonized by native invertebrates.
At the end of the study, phytoplankton showed no apparent methomyl-related effects.
Zooplankton showed mixed results; the abundance of adult copepods and rotifers generally
increased following methomyl applications, however, cladoceran abundance was reduced (to less
than 1% of the abundance of the control group) in the methomyl-treated groups and their
numbers did not recover during the study period. Bluegill survival was not affected in any of the
microcosm treatment levels. Body length and body weight at harvest, however, were
significantly reduced (up to 18.5%) at all methomyl treatment levels when compared with
controls. The size reductions were attributed to a decrease in food resources, particularly
cladocerans.
Table 4-1. Aquatic Toxicity Profile for Methomy
Species
Taxa Represented
Tovieitv Value
MRID#
Classification
Comment
Channel catfish
(Ictalurus
punctatus)
Freshwater fish and
aquatic-phase
amphibians
96-hr LC50 =
0.320 mg a.i./L
40098001
Supplemental
Slope = 4.2 (2.3 -
6.2)
Channel catfish
{Ictalurus
punctatus)
NOAEC = 0.012
mg a.i./L
N/A
N/A
Based an acute to
chronic ratio (ACR)1
using acute and
chronic data from the
fathead minnow and
acute data from the
channel catfish.
Daphnid
(Daphnia
magna)
Freshwater
invertebrates
48-hr EC50 =
0.005 mg a.i./L
40098001
Supplemental
A slope could not be
determined
NOAEC = 0.0007
mg a.i./L
1312541
Acceptable
The LOAEC is 0.001
mg a.i./L based on
delayed reproduction.
Sheepshead
minnow
Estuarine/marine
fish
96-hr LC50= 1.16
mg a.i./L
41441202
Acceptable
Slope = 8.0
104
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(Cyprinodon
variegatus)
NOAEC = 0.260
mg a.i./L
45013202
Acceptable
The LOAEC is 0.490
mg a.i./L based on
reduced growth
Eastern oyster
(Crassostrea
virginica)
EC50 >140 mg
a.i./L
42074601
Acceptable
Shell deposition
study; NOAEC =
0.12 mg a.i./L
96-hr LC50 =
0.019 mg a.i./L
00009134
Acceptable
A slope could not be
determined
Northern pink
shrimp
(Penaeus
duorarum)
Estuarine/marine
invertebrates
NOAEC = 0.0024
mg a.i./L
N/A
N/A
Based an acute to
chronic ratio (ACR)2
using acute and
chronic data from
mysid and acute data
from the Northern
pink shrimp
Non-vascular aquatic plants
(Pseudokirchneriellla subcapitata)
96-hr EC50= 184
mg a.i./L
(Lannate form.)
96-hour EC50 =
108 mg a.i./L
(methomyl a.i.)
Record #:
118717,
Pereira et
al. 2009
Qualitative
(Open lit.)3
Raw effects data and
health of organisms
prior to initiation not
reported.
Lannate (200 g a.i./L)
Methomyl (99.5%
purity)
95% CI of 164-206
mg a.i./L for
Lannate;
95% CI of 87-126
mg a.i./L for
methomyl a.i.
Vascular aquatic plants
No data available
N/A
N/A
N/A
1 Fathead minnow LC50 (1.5 mg/L) divided by the NOAEC (0.057 mg/L) yields an ACR of 26.3; ACR of 26.3 in
turn divided into the channel catfish LC50 (0.320 mg/L) yields an estimated chronic NOAEC (0.102 mg/L) for
channel catfish.
2 Mysid shrimp LC50 (0.234 mg/L) divided by the NOAEC (0.029 mg/L) yields an ACR of 8.07; ACR of 8.07 in
turn divided into the northern pink shrimp LC50 (0.019 mg/L) yields an estimated chronic NOAEC (0.0024 mg/L)
for northern pink shrimp.
3 Open literature data are under a different classification scheme (quantitative, qualitative, invalid) than registrant
submitted data (acceptable, supplemental, invalid). Under the qualitative categorization, this data is being used in
risk characterization only and is not intended to calculate a risk quotient.
1-ECOTOX references are designated with an E followed by the ECOTOX reference number.
Toxicity to fish and aquatic invertebrates is categorized using the system shown in Table 4.2
(USEPA, 2004). Toxicity categories for aquatic plants have not been defined.
Table 4-2. Categories of Acute Toxicity for Fish and Aquatic Invertebrates
LCso (m»/L)
Toxicity Category
<0.1
Very highly toxic
>0.1 - 1
Highly toxic
>1-10
Moderately toxic
> 10 - 100
Slightly toxic
> 100
Practically nontoxic
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4.3. Toxicity of Methomyl to Terrestrial Organisms
Table 4-3 summarizes the most sensitive terrestrial toxicity endpoints, based on an evaluation of
both the submitted studies and the open literature. A brief summary of submitted data
considered relevant to this ecological risk assessment is presented below. Additional
information is provided in Appendix G.
Methomyl is classified as highly toxic to birds, mammals, and honey bees on an acute exposure
basis. There are currently no methomyl vegetative vigor or seedling emergence toxicity data
available for terrestrial plants (see Section 4.3.1).
An avian reproduction study was performed on methomyl with the northern bobwhite quail
(Colinus virginianus). In this study, the LOAEC is 500 mg/kg-diet based on fewer eggs laid and
eggs set and the NOAEC is 150 mg a.i./kg-diet (MRID: 41898602). In a 2-generation
reproduction study with rats (Rattus norvegicus), the NOAEL for parental systemic toxicity is
3.75 mg/kg-bw and the LOAEL is 30 mg/kg-bw based on decreased growth (body weight) and
food consumption and altered hematology parameters. The NOAEL for offspring toxicity is also
3.75 mg/kg-bw and the LOAEL is 30 mg/kg-bw based on decreases in both survival (the mean
number of live pups) and growth (mean body weights of offspring) (MRIDs: 43250701,
43769401).
Table 4-3. Terrestrial Toxicity Profile for Methomyl
Species
Taxa
Represented
Toxicity Value
MRID#
Classification
Comment
Bobwhite quail
0Colinus
virginianus)
Birds, reptiles,
and terrestrial-
phase
amphibians
LD50 = 24.2 mg/kg-bw
00161886
Acceptable
None
LC50 = 1,100 mg/kg-
diet
22923
Acceptable
None
NOAEC = 150 mg/kg-
diet
41898602
Acceptable
LOAEC = 500 mg
a.i./kg-diet, based
on reduction in
number of eggs
laid/hen
Laboratory rat
(Rattus norvegicus)
Mammals
LD50 = 30 mg a.i./kg-
bw (female)
42140101
Acceptable
None
Laboratory rat
NOAEL = 75 mg
a.i./kg-diet (3.75 mg
a.i./kg/day)
LOAEL = 600 mg
a.i./kg-diet (30 mg
a.i./kg/day)
43250701,
43769401
Acceptable
NOAEL based on
decreases in both
the mean number
of live pups and
mean body weights
of offspring
106
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Species
Taxa
Represented
Toxicity Value
IMRID #
Classification
Comment
Honey bee
(Apis mellifera)
LD50 = 0.28 ng a.i./bee
45093001
Acceptable
Acute oral;
NOAEL = 0.09 ng
a.i./bee
LD50 = 0.16 ng a.i./bee
Acute contact;
NOAEL = 0.08 ng
a.i./bee
Wasp (Aphidius
rhopalosiphi)
Terrestrial
invertebrates
48-hr LC50 =0.00022
lbs a.i./acre
45133301
Supplemental
(not adequate
forRQ
calculation)
Scientifically
sound, but a non-
guideline study and
not adequate for
RQ calculation (it
involves a product
not currently
registered in the
U.S.)
Terrestrial Plants
No data available
N/A
N/A
N/A
n/a: not applicable; ND = not determined; bw = body weight
Acute toxicity to terrestrial animals is categorized using the classification system shown in Table
4-4 (USEPA, 2004). Toxicity categories for terrestrial plants have not been defined.
Table 4-4. Categories of Acute Toxicity for Avian and Mammalian Studies
Toxicity Category
Oral LD50
Dietary LCj#
Very highly toxic
<10 mg/kg
< 50 mg/kg-diet
Highly toxic
10-50 mg/kg
50 - 500 mg/kg-diet
Moderately toxic
51 - 500 mg/kg
501 - 1000 mg/kg-diet
Slightly toxic
501 - 2000 mg/kg
1001 - 5000 mg/kg-diet
Practically non-toxic
> 2000 mg/kg
> 5000 mg/kg-diet
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4.3.1. Toxicity to Terrestrial Plants
There are no acceptable or supplemental terrestrial plant guideline toxicity studies available for
methomyl; however, several efficacy studies testing the effects of methomyl on a variety of
target and non-target invertebrate pests also supplied information on effects to plants after
methomyl applications. Due to a lack of information on study design and data analyses, these
efficacy studies are classified as 'supplemental' and are not adequate for plant (or terrestrial
invertebrate) RQ calculation. None of the studies showed adverse effects to plants at the highest
treatment levels tested (most of which were at or above the maximum allowable single
application rate for methomyl of 0.9 lbs a.i./acre) and the NOAEC from the studies represented
the highest treatment rates examined (see Table 4-5). However, because none of the studies
addressed potential risks to monocots, or effects on seedling emergence and some N-methyl
carbamates are plant auxins and are used to thin fruit (e.g., carbaryl), risks to plants from the use
of methomyl cannot be precluded using the available data. Furthermore, incident reports on
melons indicate damage to older, treated leaves as a result of ground application of a methomyl
formulation (see Section 4.5.2. Plant Incidents).
TABLE 4-5. Measures of Effects to Plants from Methomyl E
'ficacy Studies.
Plant Species
NOAEL
Highest level
tested?1
Effect
measured2
ECOTOX NO./Reference
Alfalfa
>0.9 lbs a.i./acre
Yes
Growth
88088/Laub etal. (1999)
(Medicago sativa)
Eggplant
>3.6 lbs a.i./acre
Yes
Growth
74745/Morale and Kurundkar (1989)
(Solanum melongena)
Injury
>1,000 ppm
Yes
Growth
89394/Sharma etal. (1997)
Common Bean
>0.9 lbs a.i./acre
Yes
Injury
88838/Ghidiu (1988)
(Phaseolus vulgaris)
Bell pepper
>946 ml/acre
Yes
Growth
82231/Stansly and Cawley (1993)
{Capsicum annuum)
>0.9 lbs a.i./acre
Yes
Growth
82730/Schuster (1994)
>0.9 lbs a.i./acre
Yes
Biomass
82246/Zehnder and Speese (1992)
Cabbage
(Brassica oleracea)
>0.9 lbs a.i./acre
Yes
Injury
88084/Edelson etal. (1999)
Hybrid strawberry
(Fragaria x ananassa)
>0.9 lbs a.i./acre
Yes
Photosynthesis
88792/Carson etal. (1986)
Lettuce
>1 lbs a.i./acre
Yes
Abundance
82237/Palumbo etal. (1991)
(Lactuca sativa)
Peony
>20.0 lbs a.i./acre
Yes
Abundance
89251/Schmittetal. (1974)
(Paeonia lactiflora)
Peach
>0.23 lbs a.i./lOO
Yes
Injury
88091/Hull (1999)
(Prunus persica)
gallon
Pigeonpea
>0.53 lbs a.i./acre
Yes
Abundance
82560/Giraddi etal. (2002)
(Cajanus cajan)
Potato
>1.0 lbs a.i./acre
Yes
Injury
77263/Raman and Palacios (1986)
{Solanum tuberosum)
Tomato
>0.45 lbs a.i./acre
Yes
Injury
74169/Walgenbach etal. (1991)
{Solanum lycopersicum)
>0.9 lbs a.i./acre
Yes
Injury
88062/Carson etal. (1999)
>0.9 lbs a.i./acre
Yes
Injury
88089/Kund etal. (1999)
>0.9 lbs a.i./acre
Yes
Injury
88089/Kund etal. (1999)
>0.45 lbs a.i./acre
Yes
Injury
88269/Stansly etal. (1999)
>4.0 lbs a.i./acre
Yes
Biomass
89472/McLeod (1972)
Wild celery
{Apium graveolens)
>0.9 lbs a.i./acre
Yes
Injury
82728/Carson etal. (1994)
'Highest Level Tested' refers to whether the NOAEL represents the highest level tested.
2 'Effect Measured' refers to the effect that was measured in the study. Because the NOAELs represent the highest
level tested in each study, no adverse effects to plants were observed in any of the studies.
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4.4. Toxicity of Chemical Mixtures
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of
active ingredients, either those mixtures of multiple active ingredients in product formulations or
those in the applicator's tank. In the case of the product formulations of active ingredients (that
is, a registered product containing more than one active ingredient), each active ingredient is
subject to an individual risk assessment for regulatory decision regarding the active ingredient on
a particular use site. If effects data are available for a formulated product containing more than
one active ingredient, they may be used qualitatively or quantitatively in accordance with the
Agency's Overview Document and the Services' Evaluation Memorandum (U.S., EPA 2004;
USFWS/NMFS 2004).
Methomyl has registered products that contain multiple active ingredients. Analysis of the
available acute oral mammalian LD50 data for multiple active ingredient products relative to the
single active ingredient is provided in APPENDIX A. The results of this analysis show that the
formulated product (Stimukil fly bait, EPA Reg. No. 53871-3) is more toxic to the laboratory rat
than is the technical grade active ingredient. As a result, scatter bait uses under this formulation
label are modeled with the formulation toxicity data. With regard to scatter bait and remaining
assessed uses, the RQs based on the technical grade active ingredient toxicity data exceed
Agency LOCs; refinement to the endpoint based on the formulated product is not expected to
alter risk conclusions.
A List of accepted literature on mixtures is available in APPENDIX F.
4.5. Incident Database Review
Preliminary reviews of the Ecological Incident Information System (EIIS, version 2.1) and the
Avian Incident Monitoring System (AIMS)9 were conducted on February 17, 2010 and again on
July 23, 2012. A total of 12 EIIS incidents associated with methomyl use (not including those
classified as 'unlikely' due to methomyl use) have been reported (10 involving terrestrial
organisms - birds, opossums, and plants -and 2 involving aquatic organisms - all fish). The
reported incidents occurred between 1978 and 2010. The certainty in which these incidents were
a result of methomyl use was described as highly probable in three incidents, highly likely in two
incidents, probable in four incidents, and possible in three incidents. Two of the incidents were
the result of registered use, five were the result of misuse (intentional baiting); however, it is
unknown if the other five incidents resulted from misuse or registered uses. Two additional
cases were reported in AIMS. Specific details of the incidents are described below.
In addition to the incidents recorded in EIIS and AIMS, additional incidents have been reported
to the Agency in aggregated incident reports, within the US EPA Office of Pesticide Programs
Incident Data System. Pesticide registrants report certain types of incidents to the Agency as
aggregate counts of incidents occurring per product per quarter. Ecological incidents reported in
aggregate reports include those categorized as 'minor fish and wildlife' (W-B), 'minor plant' (P-
B), and 'other non-target' (ONT) incidents. 'Other non-target' incidents include reports of
9 http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm
109
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adverse effects to insects and other terrestrial invertebrates. For methomyl, as of July 23, 2012
registrants have reported 7 minor fish and wildlife incidents, all of which occurred between 1999
and 2011. The number of individual organisms affected in these incidents was not specified.
Unless additional information on these aggregated incidents become available, they are assumed
to be representative of registered uses of methomyl in the risk assessment.
Due to limitations with data in the EIIS, a low number or lack of reported incidents in the
database cannot be construed as evidence that additional incidents have not occurred. Incident
reports for non-target plants and animals typically provide information on mortality events only.
Reports for other adverse effects, such as reduced growth or impaired reproduction, are rarely
received. EPA's changes in the registrant reporting requirements of incidents may also account
for the reduced number of reported incidents. Registrants are now only required to submit
detailed information on 'major' incidents. Minor incidents are generally reported aggregately
and are not included in EIIS. In addition, there have been reductions in state monitoring efforts
due to lack of resources.
4.5.1. Terrestrial Incidents
Five of the terrestrial incidents (one from New York, one from Maine, two from Florida, and one
from Greece) were the result of intentional baiting and involved mortality in the following birds:
rock dove (Columba livia), egret (species not provided), crow (Corvis sp.), red-tailed hawk
(Buteo jamaicensis), American kestrel (Falco sparverius), Eleanora's falcon (Falco eleonorae),
and grackle (Quiscalus spp.) [Incident #/Event ID: (EIIS) 1009064-001,1011181-001, and
1017139-001; (AIMS) 1841 and 1953], The legality of use for another of the incidents, which
occurred in the British Virgin Islands and involved the death of 13 laughing gulls (Larus
articilla) and one cattle egret (Bubulcus ibis), was undetermined (Incident #: 1018980-010).
Oxamyl, which is classified as very highly toxic to birds on an acute exposure basis, was also
suspected in this incident. Two of the incidents occurred in France and involved the registered
use (in France) of methomyl on cabbage (methomyl is also registered for use on cabbage in the
United States). Incident # 1006382-001 occurred in 1989 from a foliar spray of methomyl at a
rate of 0.225 lbs a.i./acre. This incident, which was classified as 'probable', resulted in the
mortality of at least 52 finches. The other French incident (1006382-002; 1992) was also
classified as 'probable' and involved the registered use of methomyl (foliar spray) on cabbage.
This incident involved the incapacitation of 31 birds and mortality in 35 birds (finches and
linnets) after the birds were observed drinking dew from the cabbage field the day after
methomyl application. An incident (1021455-003) occurred in Florida and was reported by the
National Wildlife Health Center (NWHC), USGS, on 12/05/2009. The report indicates that 31
vultures and 3 Virginia opossums were found sick or dead. Diagnostic evaluation found
methomyl toxicosis making methomyl as a 'highly probable' cause. There was 82% ChE
inhibition with complete reversal upon incubation. Report states that no bait or human presence
was found. The use site and application- whether legal or not- is unknown.
The AIMS reports indicate a couple of incidents resulted from abuse of product. An incident
(Case 03-0206; Event #1953; 2003) in Hancock County, ME (East Orland) indicated that
methomyl was highly likely to be responsible for the deaths of an unknown number of crows and
110
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red-tailed hawks. The other incident (Case 00-0152; Event #1841; 2000) in Seminole County, FL
indicated that methomyl was highly likely to be responsible for the death of one egret. These
determinations were made on the basis of a chemical residue analysis on carcasses and
circumstances clearly indicative of poisoning.
4.5.2. Plant Incidents
An incident on melons was reported twice for Yuma County, AZ, once by Bayer Crop Science
on 9/7/2010 (Incident # 1022338-002) and again by DuPont Crop Protection on 10/21/2010
(Incident # 1022338-001). On September 7, 2010 and Aug 30, 2010 a fall melon crop suffered
damage to older, treated leaves after a tank mix application of the following products DuPont
Lannate® S (a.i. methomyl, PC Code 090301) and Valent Danitol (a.i. Fenpropathrin, PC Code
127901) insecticides. The older leaves on the melon plants suffered very light speckling and
symptoms were observed two days after the ground application. The incidents classified
methomyl as a 'possible'cause and legality of the application was undetermined.
4.5.3. Aquatic Incidents
In a report from the California Fish and Game Department (Incident # 1013436-001), there was a
large fish kill, i.e., several thousand threadfin shad (Dorosoma petenense) and catfish (Ictalurus
spp.), in the San Joaquin River near the town of Lathrop, California on October 16, 2001. The
treatment site is unknown, and it is unknown if the kill was the result of misuse or registered use.
The certainty that the kill resulted from methomyl was listed as 'possible'. However, upon
further review of the incident, it was acknowledged by California Fish and Game that un-ionized
ammonia was the cause of the fish kill. Analyses of composited gill samples found the presence
of several pesticides (i.e., dioxathion = 121.1 ppm; carbaryl = 1.75 ppm; carbofuran = 4.51 ppm;
fenuron = 0.78 ppm; methomyl = 5.08 ppm; monuron = 5.83 ppm). However, these pesticides
were not detected in the water samples and no mention was made in the California Fish and
Game report that these pesticides may have been important factors in the fish kill.
A fish kill incident occurred in Seminole County, Georgia, on June 16, 1992 (Incident # 100108-
001). The treatment site was corn, and it is unknown if the kill was the result of misuse or
registered use. Also, the certainty that the kill resulted from methomyl was listed as 'probable'.
Upon further review of the incident report, it was assumed that runoff from a 200-acre plot of
sweet corn treated with fertilizer and insecticides killed 125 bluegill, bowfin (Amia calva), and
carp (Cyprinus spp). During a rainy two week period prior to the fish kill, the corn plot had been
treated with 5 applications of methomyl (aerial, 1.5 pints/acre), 4 applications of chlorpyrifos, 4
applications of fertilizer, and 2 applications of borax. The suspected cause of the fish kill was
methomyl, as Lannate LV, toxicosis. Measured concentrations of methomyl were found in water
samples taken from the pond and pond-overflow area.
Ill
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4.6. Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern
The Agency uses the probit dose response relationship as a tool for providing additional
information on the potential for acute direct effects to individual listed species and aquatic
animals that may indirectly affect the listed species of concern (USEPA, 2004). As part of the
risk characterization, an interpretation of acute RQs for listed species is discussed. This
interpretation is presented in terms of the chance of an individual event {i.e., mortality or
immobilization) should exposure at the EEC actually occur for a species with sensitivity to
methomyl on par with the acute toxicity endpoint selected for RQ calculation. To accomplish
this interpretation, the Agency uses the slope of the dose response relationship available from the
toxicity study used to establish the acute toxicity measures of effect for each taxonomic group
that is relevant to this assessment. The individual effects probability associated with the acute
RQ is based on the mean estimate of the slope and an assumption of a probit dose response
relationship. In addition to a single effects probability estimate based on the mean, upper and
lower estimates of the effects probability are also provided to account for variance in the slope, if
available.
Individual effect probabilities are calculated based on an Excel spreadsheet tool IEC vl.l
(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental
Fate and Effects Division (June 22, 2004). The model allows for such calculations by entering
the mean slope estimate (and the 95% confidence bounds of that estimate) as the slope parameter
for the spreadsheet. In addition, the acute RQ is entered as the desired threshold.
112
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1 Table 4-6. Individual Effect Probabilities Using the IEC v 1.1 Model
Taxa
Su novate
Endpoint
MRID
Uses1
Slope2
Chance of
Chance of
SF Bav
SF Bav
represented
species (most
(LCS0 or
(RQ)
Individual
Individual
Species
Species
senstitive)
LDS0)
effect (~1
in...) for
Min RQ3
effect (~1
in...) for
Max RQ3
(direct
effect)
(indirect
effect)
Freshwater fish
and aquatic-phase
amphibians
Channel
96-hr
40098001
Anise (0.05), turf,
celery, alfalfa, scatter
bait, cabbage (0.19)
4.23
5.37x10'
877
catfish
LC50 =
2.32
787
21.2
TG, DS,
SFGS, CCR,
(Ictalurus
punctatus)
0.320 mg
a.i.lL
6.15
1.62 x 1015
218,000
CTS
CTS
Daphnid
40098001
Sorghum (0.50),
3.45
6.69
1
(Daphnia
48-hr
avocado, corn, onion,
1.12
2.72
1.12
CFS, SFGS,
CCR, CTS,
TG, DS
Freshwater
invertebrates
magna)
ec50 =
0.005 mg
a.i./L
corn at higher app,
anise, turf, celery,
alfalfa, scatter bait,
cabbage (12.38)
5.79
24.6
1
CFS
Sheepshead
96-hr
41441202
8.0
8.8 x 1024
8.8 x 1024
Estuarine/marine
minnow
r
0
0
II
Cabbage (0.05)
5.16
1.05 x 10u
1.05x10"
TG, DS
CCR
fish
(Cyprinodon
variegatus)
1.16 mg
a.i./L
10.83
4.58 x 1044
4.58 x 1044
Northern pink
00009134
Sorghum (0.13),
4.5
29,900
1.01
shrimp
96-hr
avocado, corn, onion,
2
26.2
1.18
Estuarine/marine
invertebrates
(Penaeus
duorarum
LC50 =
0.019 mg
corn at higher app,
anise, turf, celery,
1.31 x 1015
1
—
CCR, TG,
DS
a.i./L
alfalfa, scatter bait,
cabbage (3.26)
y
Birds, Reptiles,
Bobwhite
00161886
4.5
58,500
1
and Terrestrial-
quail
Sorghum (0.12,
dietary-based), cole
crops (27.97, dose-
based)
2
30.5
1
Phase
Amphibians
(T-REX, 20g bird
consuming short
grass)
(Colinus
virginianus)
LD50 =
24.2
mg/kg-bw
9
1.73 x 1016
1
SFGS,
CCR, CTS
SFGS, CCR,
CTS
Birds, Reptiles,
Bobwhite
00161886
4.5
294,000
1
and Terrestrial-
quail
Bulbs, grasses, herbs,
2
44
1.02
Phase
Amphibians
(T-REX, 20g bird
consuming
arthropods)
{Colinus
virginianus)
LD50 =
24.2
mg/kg-bw
alfalfa, non-cole leafy
crops (0.10, dietary-
based), cole crops
(10.96, dose-based)
9
8.86 x 1018
1
SFGS,
CCR, CTS
SFGS, CCR,
CTS
113
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Birds, Reptiles,
and Terrestrial-
Phase
Amphibians
(T-HERPS, 20g)
Bobwhite
quail
(Colinus
virginianus)
ld50 -
24.2
mg/kg-bw
00161886
Sorghum (0.12,
dietary-based), cole
crops (16.44, dose
based)
4.5
58,500
1
CTS
[refinement]
CTS
[refinement]
2
30.5
1.01
9
1.73 x 1016
1
Birds, Reptiles,
and Terrestrial-
Phase
Amphibians
(T-HERPS, 20g)
Bobwhite
quail
(iColinus
virginianus)
ld50 =
24.2
mg/kg-bw
00161886
Avocado (0.15,
dietary-based), cole
crops (23.29 dose-
based)
4.5
9,560
1
SFGS
[refinement]
SFGS
[refinement]
2
20.1
1
9
1.65 xlO13
1
Mammals
(T-REX, 15g)
Laboratory rat
(Rattus
norvegicus)
LD50 = 30
mg
a.i./kg-bw
42140101
Sorghum (1.95, dose-
based), cole crops
(7.25, dose-based)
4.5
1.11
1
—
SFGS, CCR,
CTS
2
1.39
1.04
9
1
1
Terrestrial
Invertebrates
Honey bee
(Apis
mellifera)
ld50 =
0.16 (ig
a.i./bee
45093001
Sorghum (42.30), cole
crops (157.12)
4.33
1
1
BCB,
VELB
SFGS, CCR,
CTS
3.37
1
1
5.30
1
1
1 Uses for which the acute RQ exceeds the listed species LOC for the given taxon category. The lowest exceeded RQ and the highest exceeded RQ is in brackets.
2 Default value for slope is 4.5, with upper and lower bounds of 2 and 9
3 Acute RQs provide a min/max range and depend on uses that exceeded acute listed species LOC of 0.05 for aquatic organisms and 0.1 for terrestrial organisms
114
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5. Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations. Risk
characterization is used to determine the potential for direct and/or indirect effects to SFGS,
CCR, BCB, VELB, CTS, DS, CFS, and TG or for modification to their designated critical
habitat from the use of methomyl in CA. The risk characterization provides an estimation
(Section 5.1) and a description (Section 5.2) of the likelihood of adverse effects; articulates risk
assessment assumptions, limitations, and uncertainties; and synthesizes an overall conclusion
regarding the likelihood of adverse effects to the assessed species or their designated critical
habitat {i.e., "no effect," "likely to adversely affect," or "may affect, but not likely to adversely
affect"). In the risk estimation section, risk quotients are calculated using standard EFED
procedures and models. In the risk description section, additional analyses may be conducted to
help characterize the potential for risk.
5.1. Risk Estimation
Risk is estimated by calculating the ratio of exposure to toxicity. This ratio is the risk quotient
(RQ), which is then compared to pre-established acute and chronic levels of concern (LOCs) for
each category evaluated (Appendix C). For acute exposures to the aquatic animals, as well as
terrestrial invertebrates, the LOC is 0.05. For acute exposures to the birds (and, thus, reptiles and
terrestrial-phase amphibians) and mammals, the LOC is 0.1. The LOC for chronic exposures to
animals, as well as acute exposures to plants is 1.0.
Acute and chronic risks to aquatic organisms are estimated by calculating the ratio of exposure to
toxicity using l-in-10 year EECs in Table 3-3 based on the label-recommended methomyl usage
scenarios summarized in Table 3-1 and the appropriate aquatic toxicity endpoint from Table
4-1. Acute and chronic risks to terrestrial animals are estimated based on exposures resulting
from applications of methomyl (Table 3-4), corresponding EECs (Tables 3-5, 3-6, 3-7, and 3-8)
and the appropriate toxicity endpoint from Table 4-3. Exposures, however, were not derived for
terrestrial plants, given the lack of toxicity data.
5.1.1. Exposures in the Aquatic Habitat
5.1.1.a. Freshwater Fish and Aquatic-phase Amphibians
Acute risk to fish and aquatic-phase amphibians and reptiles is based on 1 in 10 year peak EECs
in the standard pond and the lowest acute toxicity value for freshwater fish. Chronic risk is
based on the 1 in 10 year 60-day EECs and the lowest chronic toxicity value for freshwater fish.
Risk quotients for freshwater fish are shown in Table 5-1.
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Table 5-1. Acute and Chronic RQs for Freshwater Fish and/or Aquatic-Phase Amphibians
and Reptiles (Surrogate: Channel Catfish)
Uses/Application Rate (in lbs a.i./A)/
Frequency (per year) / Interval (in days)
Peak EEC
(mg/L)
60-day EEC
(mg/L)
Acute
RQ*
Chronic
RQ*
Onions/O.9/6/5
0.0091
0.0025
0.03
0.21
Corn/0.45/14/1
0.0102
0.0031
0.03
0.26
Corn/0.24/ 26/1
0.0067
0.0030
0.02
0.25
Sorghum/0.45/2/5
0.0025
0.0004
0.01
0.03
Cabbage/0.9/8/2
0.0619
0.0239
0.19
1.99
Turf/0.9/4/5
0.0193
0.0089
0.06
0.74
Anise/0.9/5/5
0.0146
0.0072
0.05
0.60
Alfalfa/0.9/4/5
0.0265
0.0114
0.08
0.95
Celery/0.9/8/5
0.0214
0.0104
0.07
0.87
Scatter bait/0.22/26/5
0.0429
0.0320
0.13
2.67
Avocado/ 0.9/1/NA
0.0056
0.0015
0.02
0.13
* = LOC exceedances (acute listed species RQ > 0.05; chronic RQ > 1.0) are bolded. For some uses the non-
listed LOCs (0.5 for acute, 0.1 acute restricted use) are exceeded.
Acute RQ = use-specific peak EEC /LC50, where LC50 = 0.320 mg a.i./L (MRID 40098001)
Chronic RQ = use-specific 60-day EEC /NOAEC, where NOAEC = 0.012 mg a.i./L (based on ACR)
Based on the acute and chronic RQs calculated for freshwater fish (and/or aquatic-phase
amphibians), methomyl has the potential to directly affect the CTS, DS, and TG for the
following uses: cabbage, turf, anise, alfalfa, celery, and scatter bait. Additionally, since the acute
and chronic RQs are exceeded (see values in bold for specific uses), there is also potential for
indirect effects to those listed species that rely on fish (and/or aquatic-phase amphibians) during
at least some portion of their life-cycle {i.e., SFGS, CCR, CTS).
5.1.l.b. Freshwater Invertebrates
Acute risk to freshwater invertebrates is based on 1 in 10 year peak EECs in the standard pond
and the lowest acute toxicity value for freshwater invertebrates. Chronic risk is based on 1 in 10
year 21-day EECs and the lowest chronic toxicity value for freshwater invertebrates. Risk
quotients for freshwater invertebrates are shown in Table 5-2.
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Table 5-2. Summary of Acute and Chronic RQs for Freshwater Invertebrates. (Surrogate:
Daphttia magna)
Uses/Application Rate (in lbs a.i./A)/
Frequency (per year) / Interval (in days)
Peak EEC
(mg/L)
21-day EEC
(mg/L)
Acute
RQ*
Chronic
RQ*
Onions/O.9/6/5
0.0091
0.0047
1.82
6.71
Corn/0.45/14/1
0.0102
0.0066
2.04
9.43
Corn/0.24/ 26/1
0.0067
0.0055
1.34
7.86
Sorghum/0.45/2/5
0.0025
0.0011
0.50
1.57
Cabbage/0.9/8/2
0.0619
0.0426
12.38
60.86
Turf/0.9/4/5
0.0193
0.0142
3.86
20.29
Anise/0.9/5/5
0.0146
0.0118
2.92
16.86
Alfalfa/0.9/4/5
0.0265
0.0201
5.30
28.71
Celery/0.9/8/5
0.0214
0.0168
4.28
24.00
Scatter bait/0.22/26/5
0.0429
0.0363
8.58
51.86
Avocado/ 0.9/1/NA
0.0056
0.0032
1.12
4.57
* = LOC exceedances (acute listed species RQ > 0.05; chronic RQ > 1.0) are bolded. For some uses the non-
listed LOCs (0.5 for acute, 0.1 acute restricted use) are exceeded.
Acute RQ = use-specific peak EEC /EC50, where EC50 = 0.005 mg a.i./L (MRID 40098001)
Chronic RQ = use-specific 21-day EEC /NOAEC, where NOAEC = 0.0007 mg a.i./L (MRID 01312541)
Based on the acute and chronic RQs calculated for freshwater invertebrates, methomyl (all uses)
has the potential to directly affect the CFS. Additionally, since the acute and chronic LOCs are
exceeded (see values in bold for specific uses), there is also potential for indirect effects to those
listed species that rely on freshwater invertebrates during at least some portion of their life-cycle
{i.e., SFGS, CCR, CTS, DS, CFS, and TG).
5.1.I.e. Estuarine/Marine Fish
Acute risk to estuarine/marine fish is based on 1 in 10 year peak EECs in the standard pond and
the lowest acute toxicity value for estuarine/marine fish. Chronic risk is based on 1 in 10 year
60-day EECs and the lowest chronic toxicity value for estuarine/marine fish is used. Risk
quotients are shown in Table 5-3.
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"able 5-3. Summary of RQs for Estuarine/Marine Fis
i (Surrogate: Sheepshead minnow)
Uses/Application Rate (in lbs a.i./A)/
Frequency (per year) / Interval (in days)
Peak EEC
(mg/L)
60-day EEC
(m»/L)
Acute
RQ*
Chronic
RQ*
Onions/O.9/6/5
0.0091
0.0025
0.01
0.01
Corn/0.45/14/1
0.0102
0.0031
0.01
0.01
Corn/0.24/ 26/1
0.0067
0.0030
0.01
0.01
Sorghum/0.45/2/5
0.0025
0.0004
0.00
0.00
Cabbage/0.9/8/2
0.0619
0.0239
0.05
0.09
Turf/0.9/4/5
0.0193
0.0089
0.02
0.03
Anise/0.9/5/5
0.0146
0.0072
0.01
0.03
Alfalfa/0.9/4/5
0.0265
0.0114
0.02
0.04
Celery/0.9/8/5
0.0214
0.0104
0.02
0.04
Scatter bait/0.22/26/5
0.0429
0.0320
0.04
0.12
Avocado/ 0.9/1/NA
0.0056
0.0015
0.00
0.01
* = LOC exceedances (acute listed species RQ > 0.05; chronic RQ > 1.0) are bolded.
Acute RQ = use-specific peak EEC /LC50, where LC50 = 1.16 mg a.i./L (MRID 41441202)
Chronic RQ = use-specific 60-day EEC /NOAEC, where NOAEC = 0.260 mg a.i./L (MRID 45013202)
Based on the acute and chronic RQs calculated for estuarine/marine fish, methomyl has a low
potential to directly affect the DS and TG from the assessed uses. Additionally, since the acute
and chronic RQs are not exceeded (a single RQ for the cabbage use is at the acute listed species
LOC, however), there is also low potential for indirect effects to those listed species that rely on
estuarine/marine fish during at least some portion of their life-cycle {i.e., CCR).
5.1.l.d. Estuarine/Marine Invertebrates
Acute risk to estuarine/marine invertebrates is based on peak EECs in the standard pond and the
lowest acute toxicity value for estuarine/marine invertebrates. Chronic risk is based on 21-day
EECs and the lowest chronic toxicity value for estuarine/marine invertebrates. Risk quotients are
shown in Table 5-4.
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Table 5-4. Summary of Acute and Chronic RQs for Estuarine/Marine Invertebrates
(Surrogate: Northern pink shrimp)
Uses/Application Rate (in lbs a.i./A)/
Frequency (per year) / Interval (in days)
Peak EEC
(mg/L)
21-day EEC
(mg/L)
Acute
RQ*
Chronic
RQ*
Onions/O.9/6/5
0.0091
0.0047
0.48
1.96
Corn/0.45/14/1
0.0102
0.0066
0.54
2.75
Corn/0.24/ 26/1
0.0067
0.0055
0.35
2.29
Sorghum/0.45/2/5
0.0025
0.0011
0.13
0.46
Cabbage/0.9/8/2
0.0619
0.0426
3.26
17.75
Turf/0.9/4/5
0.0193
0.0142
1.02
5.92
Anise/0.9/5/5
0.0146
0.0118
0.77
4.92
Alfalfa/0.9/4/5
0.0265
0.0201
1.39
8.38
Celery/0.9/8/5
0.0214
0.0168
1.13
7.00
Scatter bait/0.22/26/5
0.0429
0.0363
2.26
15.13
Avocado/ 0.9/1/NA
0.0056
0.0032
0.29
1.33
* = LOC exceedances (acute RQ > 0.05; chronic RQ > 1.0) are bolded and shaded. For some uses the non-
listed LOCs (0.5 for acute, 0.1 acute restricted use) are exceeded.
Acute RQ = use-specific peak EEC /LC50, where LC50 = 0.019 mg a.i./L (MRID 00009134)
Chronic RQ = use-specific 21-day EEC /NOAEC, where NOAEC = 0.0024 mg a.i./L (based on ACR)
Based on the acute and chronic RQs calculated for estuarine/marine invertebrates, methomyl (all
uses) has the potential to directly affect estuarine/marine invertebrates. As a result, there is
potential for indirect effects to those listed species that rely on estuarine/marine invertebrates
during at least some portion of their life-cycle {i.e., CCR, DS, and TG).
5.1.I.e. Non-vascular and Vascular Aquatic Plants
An open literature study (Record #: 118717, Pereira el al.2009) quantifying the growth inhibition
in P. subcapitata (a microalgae) after Lannate (200g a.i./L methomyl formulation) and methomyl
(99.5% purity) exposure indicates a 96-hour EC50 of 184 mg a.i./L (95% CI of 164-206 mg a.i./L
for Lannate) and a 96-hour EC50 of 108 mg a.i./L (95% CI of 87-126 mg a.i./L for methomyl
a.i.). Additional 96-hour EC50 values are available for a different species, Selenastrum
capricornutum from the following carbamates: thiodicarb (EC50 >8.3 mg a.i./L, MRID
42324801) and pirimicarb (EC50: 120 mg a.i./L, 95% CI: 110-120 mg a.i./L, MRID 44883925).
Growth and cell density inhibition were the observed effects in these studies. The definitive
endpoint for the active ingredient pirimicarb is comparable to that of methomyl a.i. and falls
within the confidence interval reported in the open literature study. Over a longer exposure
period and with a different non-vascular species, however, sensitivity to carbamates increases.
For example, 5-day EC50 values for Navicula sp. are 0.60 mg a.i./L (MRID 42431601) for
carbaryl and 0.12 mg a.i./L (MRID 45546104) for oxamyl based on an effect to cell density.
A similar effect of study duration is observed in the vascular species, Lemna gibba (or
duckweed), whereby a 7-day aldicarb study yielded an EC50 of 110 mg a.i./L (an extrapolated
119
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value, MRID 47904402) based on an effect on dry weight and two 14-day studies indicated a
greater sensitivity (based on reduced number of fronds) to carbamates, carbaryl (1.5 mg/L,
MRID 42372102) and oxamyl (30 mg a.i./L, MRID 45546103).
PRZM/EXAMS modeled peak EECs range from 0.0025-0.0619 mg a.i./L, which are 4 orders of
magnitude lower than the concentrations at which the effect on the non-vascular plants was
observed in the methomyl open literature study and the pirimicarb study and 1 to 4 orders of
magnitude lower than the the concentrations at which the effect on the vascular plants and 5-day
non-vascular plants was observed for the remaining carbamates. Based on the available lines of
evidence from the open literature and data submitted for other carbamate insecticides with
similar modes of action, methomyl is unlikely to result in direct effects to non-vascular and
vascular plants and, by extension, indirect effects to species that rely on non-vascular plants
during at least some portion of their life-cycle (i.e., SFGS, CCR, CTS, DS, CFS, and TG).
5.1.2. Exposures in the Terrestrial Habitat
5.1.2.a. Birds (surrogate for Reptiles and Terrestrial-phase
Amphibians)
As previously discussed in Section 3.3, potential direct effects to terrestrial species are based on
foliar, granular, and scatter bait applications of methomyl. Granular applications to corn whorls
using methomyl 5G Granules formulation were calculated using the LD50/ft2 option in T-REX v.
1.5. Similarly, scatter bait applications using Stimukil fly bait formulation were calculated using
the LDso/ft2 option in T-REX v. 1.5.
Potential risks to birds and, thus, terrestrial-phase amphibians are evaluated using T-REX, acute
and chronic toxicity data for the most sensitive bird species for which data are available, and the
most sensitive dietary item and size class for that species. For terrestrial-phase amphibians, the
most conservative RQ in T-REX is for the small bird consuming small insects. For birds the
most conservative RQ in T-REX is for the small bird consuming short grass.
The LD50/ft analysis for granular application to sweet corn whorls was done for the 20g bird,
assuming the following: a maximum single application rate of 0.15 lbs a.i./A with 0%
incorporation. Four combinations of the row spacing (15 and 30 inches) and bandwidth (8 and
12 inches) were used under the rows/band/in-furrow granular application option; the range of
RQs is 4.78-14.35 for a 20g bird, with the 30in row spacing and 8in bandwith contributing the
highest RQ estimates. In addition, the broadcast granular application option, yieleded an RQ of
3.83 for a 20g bird. All RQs exceed the listed species LOC (0.1) as well as the acute and acute
restricted use LOCs (0.5 and 0.2, respectively).
The LDso/ft analysis for scatter bait application to areas outside of certain commercial
establishments (e.g., feed lots, poultry houses, livestock barns, canneries, beverage plants, meat
and poultry processing establishments, commercial refuse dumpsters, and food processing
plants) was also done for the 20g bird assuming the following: a maximum single application
rate of 0.2178 lbs a.i./A applied only once at 0% incorporation. The broadcast granular
120
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application option yieleded an RQ of 5.55 for a 20g bird. This RQ exceeds the listed species
LOC (0.1) as well as the acute and acute restricted use LOCs (0.5 and 0.2, respectively).
T-HERPS is used to assess potential risk to snakes and as a refinement to RQs for amphibians if
T-REX indicates potential risk to amphibians. Small snakes and amphibians only consume
insects while medium and large snakes and amphibians consume small and large insects,
mammals, and amphibians. The most sensitive RQ for snakes and amphibians are for medium
snakes consuming small herbivore mammals.
Potential direct acute effects to the CCR, CTS (all DPS), and SFGS are evaluated using dose-
and dietary-based EECs modeled in T-REX for small (20 g, juveniles) birds consuming short
grass (Table 3-5) and acute oral and subacute dietary toxicity endpoints for avian species (Table
4-3).
Potential direct acute effects to the CTS and SFGS are evaluated by considering dose- and
dietary-based EECs modeled in T-HERPS for medium amphibians and/or snakes consuming
small herbivorous mammals (Tables 3-7 and 3-8) and acute oral and subacute dietary toxicity
endpoints for avian species (Table 4-3).
Potential indirect effects to the CCR, SFGS, and CTS may result from direct acute effects to
birds and/or amphibians due to a reduction in prey. RQs for indirect effects are calculated in the
same manner as those for direct effects; however, the indirect effect RQs are compared to the
non-listed LOC (acute and acute restricted use LOCs, 0.5 and 0.2, respectively). The most
conservative EEC calculated in T-REX is for small birds consuming short grass.
Potential direct chronic effects to the birds (including CCR), CTS (all DPS), and SFGS are
evaluated by considering dietary-based EECs modeled in T-REX and T-HERPS consuming a
variety of dietary items. The specific EECs for each species are for the same size birds and same
dietary items as those considered for acute exposure. Chronic effects are estimated using the
lowest available NOAEC from a chronic study for birds. Dietary-based EECs are divided by
toxicity values to estimate chronic dietary-based RQs.
Acute and chronic RQs for the birds (including CCR), CTS (all DPS), and SFGS derived using
T-REX are shown in Table 5-5.
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Table 5-5. Acute and Chronic RQs Derived Using T-REX for Methomyl: Birds (including
CCR), CTS (all DPS), and SFGS consuming short grass
RQs for Birds (including CCR), CTS (all DPS) and SFGS
Use Type
(small bird 20" consuming
short grass)
Aeutc Dosc-
Acute Dictarv
Chronic Dictarv
Bascd1
Based2
Based3
Bulbs
16.06
0.26
1.92
Cereal grains (corn-14x)
24.37
0.40
2.91
Cereal grains (corn-28x)
12.44
0.20
1.49
Cereal grains (sp. sorghum)
7.53
0.12
0.9
Cole crops
27.97
0.46
3.34
Grasses
16.00
0.26
1.91
Herbs
16.05
0.26
1.92
Leguminous forage (alfalfa)
16.00
0.26
1.91
Non-cole leafy crops
16.07
0.26
1.92
Avocado
12.05
0.20
1.44
*LOC exceedances (acute listed species RQ > 0.1 and chronic RQ > 1.0) are bolded. For some uses
the non-listed LOCs (0.5 for acute, 0.2 acute restricted use) are exceeded.
1 Based on dose-based EEC and Northern bobwhite quail acute oral LD50 = 24.2 mg/kg-bw (MRID
00161886)
2Based on dietary-based EEC and Northern bobwhite quail subacute dietary LC50 = 1,100 mg/kg-diet
(MRID 00022923).
3Based on dietary-based EEC and Northern bobwhite quail NOAEC =150 mg/kg-diet (MRID
41898602)
Table 5-6. Acute and Chronic RQs Derived Using T-REX for Methomyl: Birds (including
CCR), CTS (all DPS), and SFGS consuming arthropods
RQs for Birds (including CCR), CTS (all DPS) and SFGS
Use Type
(small bird 20g consuming arthropods)
Acute Dose-
Acute Dictarv
Chronic Dictarv
Based1
Based2
Based3
Bulbs
6.29
0.10
0.75
Cereal grains (corn-14x)
9.54
0.16
1.14
Cereal grains (corn-28x)
4.87
0.08
0.58
Cereal grains (sp. sorghum)
2.95
0.05
0.35
Cole crops
10.96
0.18
1.31
Grasses
6.27
0.10
0.75
Herbs
6.29
0.10
0.75
Leguminous forage (alfalfa)
6.27
0.10
0.75
Non-cole leafy crops
6.29
0.10
0.75
Avocado
4.72
0.08
0.56
*LOC exceedances (acute RQ > 0.1 and chronic RQ > 1.0) are bolded. For some uses the non-listed
LOCs (0.5 for acute, 0.2 acute restricted use) are exceeded.
Based on dose-based EEC and Northern bobwhite quail acute oral LD50 = 24.2 mg/kg-bw (MRID
00161886)
2Based on dietary-based EEC and Northern bobwhite quail subacute dietary LC50 = 1,100 mg/kg-diet
(MRID 00022923).
3Based on dietary-based EEC and Northern bobwhite quail NOAEC =150 mg/kg-diet (MRID
41898602)
Based on the calculated acute and chronic RQs for 20g birds consuming short grass and
arthropods, methomyl has the potential to directly affect the CCR, CTS (all DPS) and the SFGS
for all uses including the granular use on sweet corn whorls and scatter bait. Additionally, since
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the acute and chronic RQs are exceeded, there is a potential for indirect effects to those listed
species that rely on birds (and, thus, reptiles and/or terrestrial-phase amphibians) during at least
some portion of their life-cycle (i.e., CCR, CTS (all DPS), and the SFGS).
A refinement of the RQs for the CTS and SFGS using T-HERPS is provided below Table 5-7
and Table 5-8. The amphibian CTS default weights are 2, 20, and 200g; the reptile SFGS default
weights were 2, 20, and 800g. The maximum size mammal that can be consumed by the three
amphibian size classes are 1.33, 13.33, and 133.33g, respectively [based on the default
assumption that an amphibian can eat 2/3 of its body weight, Cook 1997]; the maximum size
amphibian/reptile that can be consumed by the three reptile size classes are 2.10, 24.74, and
1285.91g, respectively [based on the equation: BW of assessed species1'071, King 2002], The
percent water content for all herptile size classes was assumed to be 80%.
Table 5-7. Acute and Chronic RQs Derived Using T-HERPS for Methomyl: CTS (all DPS)
consuming small insects and herbivorous mammals
RQs for Small CTS (2g)
RQs for Medium CTS (20g)
(small bird 2
« consuming small inseets)
(medium bird 20g consuming
small/medium herbivorous mammals of
Use Type
1.33^/13.33")
Acute
Aeute
Chronie
Aeute
Aeute
Chronic
Dose-
Dietarv
Dietary
Based5
Dose-
Dietarv
Dietarv
Based1
Based2
Based1
Based2'"
Based3"
Bulbs
0.53
0.15
1.08
9.44
0.26
1.93
Cereal grains (corn-14x)
0.80
0.22
1.64
14.32
0.40
2.92
Cereal grains (corn-28x)
0.41
0.11
0.84
7.31
0.20
1.49
Cereal grains (sp.
sorghum)
0.25
0.07
0.51
4.42
0.12
0.90
Cole crops
0.92
0.26
1.88
16.44
0.46
3.36
Grasses
0.53
0.15
1.08
9.40
0.26
1.92
Herbs
0.53
0.15
1.08
9.43
0.26
1.93
Leguminous forage
(alfalfa)
0.53
0.15
1.08
9.40
0.26
1.92
Non-cole leafy crops
0.53
0.15
1.08
9.44
0.26
1.93
Avocado
0.40
0.11
0.81
7.08
0.20
1.45
*LOC exceedances (acute RQ > 0.1 and chronic RQ > 1.0) are bolded. For some uses the non-listed LOCs (0.5 for
acute, 0.2 acute restricted use) are exceeded.
1 Based on dose-based EEC and Northern bobwhite quail acute oral LD50 = 24.2 mg/kg-bw (MRID 00161886)
2Based on dietary-based EEC and Northern bobwhite quail subacute dietary LC50 = 1,100 mg/kg-diet (MRID
00022923).
3Based on dietary-based EEC and Northern bobwhite quail NOAEC =150 mg/kg-diet (MRID 41898602)
aRQ for medium-sized herbivorous mammal (of 13.33g)
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Table 5-8. Acute and Chronic RQs Derived Using T-HERPS for Methomyl: SFGS
consuming small insects and herbivorous mammals
Use Type
RQs for Small SFGS (2g)
(small bird 2g eonsuming small inseets)
RQs for Medium SFGS (20$
(medium bird 20g eonsuming
small/medium herbivorous mammals of
2.10g/24.74g)
Aeute
Dose-
Based1
Aeute
Dietary
Based5
Chronie
Dietary
Based5
Aeute
Dose-
Based1
Aeute
Dietary
Based21'
Chronie
Dietary
Based3"'
Bulbs
0.53
0.15
1.08
13.37
0.20
1.47
Cereal grains (corn-14x)
0.80
0.22
1.64
20.29
0.30
2.23
Cereal grains (corn-28x)
0.41
0.11
0.84
10.35
0.16
1.14
Cereal grains (sp.
sorghum)
0.25
0.07
0.51
6.27
0.09
0.69
Cole crops
0.92
0.26
1.88
23.29
0.35
2.56
Grasses
0.53
0.15
1.08
13.32
0.20
1.47
Herbs
0.53
0.15
1.08
13.36
0.20
1.47
Leguminous forage
(alfalfa)
0.53
0.15
1.08
13.32
0.20
1.47
Non-cole leafy crops
0.53
0.15
1.08
13.38
0.20
1.47
Avocado
0.40
0.11
0.81
10.03
0.15
1.10
*LOC exceedances (acute RQ > 0.1 and chronic RQ > 1.0) are bolded. For some uses the non-listed LOCs (0.5 for
acute, 0.2 acute restricted use) are exceeded.
1 Based on dose-based EEC and Northern bobwhite quail acute oral LD50 = 24.2 mg/kg-bw (MRID 00161886)
2Based on dietary-based EEC and Northern bobwhite quail subacute dietary LC50 = 1,100 mg/kg-diet (MRID
00022923).
3Based on dietary-based EEC and Northern bobwhite quail NOAEC =150 mg/kg-diet (MRID 41898602)
aRQ for medium-sized herbivorous mammal (of 24.74g)
Based on the calculated acute and chronic RQs for small 2g CTS/SFGS and medium 20g
CTS/SFGS consuming small insects and herbivorous mammals, T-HERPS calculations further
confirm that methomyl does have the potential to directly affect the CTS (all DPS) and the SFGS
for all assessed uses. Additionally, since the acute and chronic RQs are exceeded, there is a
potential for indirect effects to those listed species that rely on reptiles and terrestrial-phase
amphibians during at least some portion of their life-cycle {i.e., CTS (all DPS), and the SFGS).
5.1.2.b. Mammals
Potential risks to mammals are evaluated using T-REX, acute and chronic mammalian toxicity
data, and a variety of body-size and dietary categories. As previously discussed in Section 3.3,
potential direct effects to terrestrial species are based on foliar, granular, and scatter bait
applications of methomyl. Granular applications to corn whorls using methomyl 5G Granules
formulation were calculated using the LD5o/ft option in T-REX v. 1.5. Similarly, scatter bait
applications using Stimukil fly bait formulation were calculated using the LD50/ft2 option in T-
REXv. 1.5
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2
The LDso/ft analysis for granular application to sweet corn whorls was done for the 15g
mammal, assuming the following: a maximum single application rate of 0.15 lbs a.i./A with 0%
incorporation. Four combinations of the row spacing (15 and 30 inches) and bandwidth (8 and
12 inches) were used under the rows/band/in-furrow granular application option; the range of
RQs is 1.97-5.92 for a 15g mammal, with the 30in row spacing and 8in bandwith contributing
the highest RQ estimates. In addition, the broadcast granular application option, yieleded an RQ
of 1.58 for a 15g mammal. All RQs exceed the listed species LOC (0.1) as well as the acute and
acute restricted use LOCs (0.5 and 0.2, respectively).
The LD50/ft analysis for scatter bait application to areas outside of certain commercial
establishments (e.g., feed lots, poultry houses, livestock barns, canneries, beverage plants, meat
and poultry processing establishments, commercial refuse dumpsters, and food processing
plants) was also done for the 15g mammal assuming the following: a maximum single
application rate of 0.2178 lbs a.i./A applied only once at 0% incorporation. The broadcast
granular application option yieleded an RQ of 4.91 for a 20g mammal. The formulation based
endpoint (LD50) of 14 mg a.i./kg-bw for the laboratory rat was used for the RQ calculation.
When the active ingredient endpoint was used for the calculation, the RQ was 2.29. Both of these
RQs exceed the listed species LOC (0.1) as well as the acute and acute restricted use LOCs (0.5
and 0.2, respectively).
Potential for indirect effects to the SFGS, CCR, and CTS may result from direct effects to
mammals due to a reduction in prey. Potential indirect effects to the SFGS and CTS may result
from direct effects to mammals due effects to habitat or a reduction in rearing sites. RQs for
indirect effects are calculated in the same manner as those for direct effects. The most sensitive
EECs calculated in T-REX are for small mammals consuming short grass.
Potential direct chronic effects to the mammals are evaluated by considering dietary-based EECs
modeled in T-REX consuming a variety of dietary items. The specific EECs for each species are
for the same size mammals and same dietary items as those considered for acute exposure.
Chronic effects are estimated using the lowest available NOAEC from a chronic reproductive
study for mammals. Dietary-based EECs are divided by toxicity values to estimate chronic
dietary-based RQs.
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Table 5-9. Acute and Chronic RQs Derived Using T-REX for Methomyl and Mammals
Use Type
RQs for Small Mammals (15g)
(small mammals consuming short grass)
RQs for Large Mammals (lOOOg)
(large mammal consuming short grass)
Acute Dose-
Based
Chronic
Dietary
Based
Chronic
Dose
Based
Acute Dose-
Based
Chronic
Dietary
Based
Chronic
Dose
Based
Bulbs
4.16
3.84
33.31
1.91
3.84
15.25
Cereal grains (corn-
14x)
6.32
5.82
50.53
2.89
5.82
23.14
Cereal grains (corn-
28x)
3.22
2.97
25.79
1.48
2.97
11.81
Cereal grains (sp.
sorghum)
1.95
1.80
15.62
0.89
1.80
7.15
Cole crops
7.25
6.69
58.01
3.32
6.69
26.56
Grasses
4.15
3.83
33.19
1.90
3.83
15.20
Herbs
4.16
3.84
33.28
1.90
3.84
15.24
Leguminous forage
(alfalfa)
4.15
3.83
33.19
1.90
3.83
15.20
Non-cole leafy crops
4.16
3.84
33.32
1.91
3.84
15.25
Avocado
3.12
2.88
24.99
1.43
2.88
11.44
*LOC exceedances (acute RQ > 0.1 and chronic RQ > 1.0) are bolded. For some uses the non-listed LOCs (0.5
for acute, 0.2 acute restricted use) are exceeded.
1 Based on dose-based EEC and laboratory rat acute oral LD50 = 30 mg/kg-bw (MRID 42140101)
2Based on dietary-based EEC and laboratory rat NOAEL =75 mg a.i./kg-diet (MRIDs 43250701, 43769401)
3Based on dose-based EEC and laboratory rat NOAEL =75 mg a.i./kg-diet (MRIDs 43250701, 43769401)
Based on calculated acute and chronic RQs for 15g and lOOOg mammals consuming short grass,
methomyl does have the potential to directly affect listed mammals of the sizes modeled given
all the uses assessed, including the granular use on sweet corn whorls and scatter bait.
Additionally, since the acute and chronic RQs are exceeded, there is potential for indirect effects
to those listed species that rely on mammals during at least some portion of their life-cycle {i.e.,
CCR, CTS (all DPS), and the SFGS).
5.I.2.C. Terrestrial Invertebrates
In order to assess the risks of methomyl to terrestrial invertebrates, the honey bee (acute contact
LD50 of 0.16 |Lxg a.i./bee; MRID 45093001) is used as a surrogate for terrestrial invertebrates.
The toxicity value for terrestrial invertebrates is calculated by multiplying the lowest available
acute contact LD50 of 0.16 |ig a.i./bee by 1 bee/0.128g, which is based on the weight of an adult
honey bee. EECs (|ig a.i./g of bee) calculated by T-REX for arthropods are divided by the
calculated toxicity value for terrestrial invertebrates, which is 1.25 |ig a.i./g of bee. Risk
quotients are shown in Table 5-10.
Potential for indirect effects to the SFGS, CCR, and CTS may result from direct acute effects to
terrestrial invertebrates due to a reduction in prey. RQs for indirect effects are calculated in the
same manner as those for direct effects.
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Table 5-10. Summary of RQs for Terrestrial Invertebrates.
Use
Arthropod RQ*
Bulbs
90.22
Cereal grains (corn-14x)
136.87
Cereal grains (corn-28x)
69.85
Cereal grains (sp. sorghum)
42.30
Cole crops
157.12
Grasses
89.89
Herbs
90.15
Leguminous forage (alfalfa)
89.89
Non-cole leafy crops
90.24
Avocado
67.68
* LOC exceedances (RQ > 0.05) are bolded.
Based on the RQs generated from arthropod EECs, methomyl does have the potential to directly
affect the BCB and VELB for all assessed uses. Additionally, since these RQs exceed the
Agency's interim terrestrial invertebrate LOC, there is a potential for indirect effects to those
listed species that rely on terrestrial invertebrates during at least some portion of their life-cycle
(i.e., CCR, CTS (all DPS), and the SFGS).
5.1.2.d. Terrestrial Plants
Generally, for indirect effects, potential effects on terrestrial vegetation are assessed using RQs
from terrestrial plant seedling emergence and vegetative vigor EC25 data as a screen. Since the
BCB and the VELB have an obligate relationship with specific dicot plant species, the seedling
emergence and vegetative vigor EC05 or the NOAEC for dicots are typically used to calculate
RQs for indirect effects to these species via potential effects to dicots. However, no terrestrial
plant data are available for RQ calculation. Although there are no acceptable terrestrial plant
guideline toxicity studies available for methomyl, several efficacy studies that were conducted to
test the effects of methomyl on a variety of target and non-target invertebrate pests also supplied
information on effects to plants after methomyl applications. Due to a lack of information on
study design and data analyses, these efficacy studies are classified as 'supplemental' and are not
adequate for plant (or terrestrial invertebrate) RQ calculation. None of the studies showed any
adverse effects to plants at the highest treatment levels tested (most of which were at or above
the maximum allowable single application rate for methomyl of 0.9 lbs a.i./acre) and the
NOAEL from the studies represented the highest treatment rates examined (see Table 4-5).
However, because none of the studies addressed potential risks to monocots, or effects on
seedling emergence and some N-methyl carbamates are plant auxins and are used to thin fruit
(e.g., carbaryl), risks to plants from the use of methomyl cannot be precluded using the available
data. Furthermore, incident reports on melons indicate damage to older, treated leaves as a result
of ground application of a methomyl formulation (see Section 4.5.2. Plant Incidents). Given the
lack of toxicity data and the results of incident reports, risk to terrestrial plants cannot be
precluded. Therefore, there is a potential for indirect effects to those listed species that rely on
terrestrial plants (for food, habitat, etc.) during at least some portion of their life-cycle (i.e., BCB,
VELB, SFGS, CCR, CTS, DS, CFS, and TG).
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5.1.3. Primary Constituent Elements of Designated Critical Habitat
For methomyl use, the assessment endpoints for designated critical habitat PCEs involve the
same endpoints as those being assessed relative to the potential for direct and indirect effects to
the listed species assessed here. Therefore, the effects determinations for direct and indirect
effects are used as the basis of the effects determination for potential modification to designated
critical habitat.
5.2. Risk Description
The risk description synthesizes overall conclusions regarding the likelihood of adverse impacts
leading to a preliminary effects determination (i.e., "no effect," "may affect, but not likely to
adversely affect," or "likely to adversely affect") for the assessed species and the potential for
modification of their designated critical habitat based on analysis of risk quotients and a
comparison to the Level of Concern. The final No Effect/May Affect determination is made
after the spatial analysis is completed at the end of the risk description, Section 5.2.11. In
Section 5.2.11, a discussion of any potential overlap between areas where potential usage may
result in LAA effects and areas where species are expected to occur (including any designated
critical habitat) is presented. If there is no overlap of the species habitat and occurrence sections
with the Potential Area of LAA Effects a No Effect determination is made.
If the RQs presented in the Risk Estimation (Section 5.1) show no direct or indirect effects for
the assessed species, and no modification to PCEs of the designated critical habitat, a
preliminary "no effect" determination is made, based on methomyl's use within the action area.
However, if LOCs for direct or indirect effect are exceeded or effects may modify the PCEs of
the critical habitat, the Agency concludes a preliminary "may affect" determination for the
FIFRA regulatory action regarding methomyl. A summary of the risk estimation results (a
preliminary effects determination of "no effect" or "may affect") are provided in Table 5-11 for
direct and indirect effects to the listed species assessed here and in Table 5-12 for the PCEs of
their designated critical habitat.
Table 5-11. Risk
Estimation Summary for Methomyl - Direct and Indirect Effects
Taxa
LOC Excccdanccs (Yes/No)
Description of Results of Risk
Estimation
Assessed Species Potentially
Affected
Freshwater Fish and
Aquatic-phase
Amphibians
Non-listed Species (Yes)
Acute: RQs >0.1 for cabbage and
scatter bait
Chronic: RQs >1 for cabbage and
scatter bait
Indirect Effects: SFGS. CCR.
CTS
Listed Species (Yes)
Acute: RQs > 0.05 for most uses
assessed including cabbage, turf,
anise, alfalfa, celery, and scatter
bait.
Chronic: RQs >1 for cabbage and
scatter bait
Direct Effects: CTS. DS. TG
Freshwater
Invertebrates
Non-listed Species (Yes)
Acute: RQs >0.1 for all assessed
uses
Chronic: RQs >1 for all assessed
uses
Indirect Effects: SFGS. CCR.
CTS, DS, CFS, TG
Listed Species (Yes)
Acute: RQs > 0.05 for all assessed
uses
Direct Effects: CFS
128
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Taxa
LOC Excccdanccs (Yes/No)
Description of Results of Risk
Estimation
Assessed Species Potentially
Affected
Chronic: RQs >1 for all assessed
uses
Estuarine/Marine
Fish
Non-listed Species (No)
Acute: RQs are less than 0.1 for
all assessed uses
Chronic: RQs are less than 1 for
all assessed uses
Indirect Effects: None
expected.
Listed Species (No)
Acute: A single RQ value is at the
listed species LOC of 0.05 for the
use on cabbage
Chronic: RQs are less than 1 for
all assessed uses
Direct Effects: None
expected.
Non-listed Species (Yes)
Acute: RQs >0.1 for all assessed
uses
Chronic: RQs >1 for all except
one assessed use (i.e., sorghum)
Indirect Effects: CCR. DS.
TG
Estuarine/Marine
Invertebrates
Listed Species (Yes)
Acute: RQs > 0.05 for all assessed
uses
Chronic: RQs >1 for all except
one assessed use (i.e., sorghum)
Direct Effects: None
expected, as no SF Bay
species for this assessment is
an estuarine/marine
invertebrate.
Vascular Aquatic
Plants
Non-listed Species (Yes)
RQs were not calculated given no
available vascular plant data.
However, a review of toxicity data
using other carbamates and
calculated EECs for methomyl
suggests that vascular plants will
likely not be exposed to
concentrations at which an effect
is expected.
Indirect Effects: None
expected.
Non-Vascular
Aquatic Plants
Non-listed Species (No)
RQs were not calculated given
that the open literature study was
classified as qualitative. However,
a comparison of endpoints (96-hr
EC50: 108-184 mg a.i./L) and
peak EECs (0.0025-0.0619 mg
a.i./L) indicates that non-vascular
plants will likely not be exposed
to concentrations at which an
effect is expected.
Indirect Effects: None
expected.
Birds, Reptiles, and
Terrestrial-Phase
Amphibians
Non-listed Species (Yes)
Acute: dose-based RQs >0.5 for
most if not all assessed uses for
small birds consuming short grass,
arthropods/small insects, and
herbivorous mammals
Chronic: dietary-based RQs >1 for
most assessed uses (except
consistently sorghum) small and
medium-sized birds consuming
short grass, arthropods/small
insects, and herbivorous mammals
Granular: 3.83-14.35
Scatter bait: 5.55
Indirect Effects: CCR. CTS.
SFGS
Listed Species (Yes)
Acute: dose and dietary-based
RQs >0.1 for most assessed uses
for small and medium-sized birds
consuming short grass,
Direct Effects: CCR. CTS.
SFGS
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Taxa
LOC Exccedances (Yes/No)
Description of Results of Risk
Estimation
Assessed Species Potentially
Affected
arthropods/small insects, and
herbivorous mammals
Chronic/granular/scatter bait:
Same as for non-listed (above
cell)
Mammals
Non-listed Species (Yes)
Acute: dose-based RQs >0.5 for
all assessed uses.
Chronic: dose- and/or dietary-
based RQs>0.1 for all assessed
uses.
Granular: 1.58-5.92
Scatter bait: 4.91
Indirect Effects: CCR. CTS.
SFGS
Listed Species (Yes)
Acute: dose-based RQs >0.1 for
all assessed uses.
Chronic/ granular/scatter bait:
Same as for non-listed (above
cell)
Direct Effects: None as no SF
Bay species for this
assessment is a mammal
Terrestrial
Invertebrates
Listed Species (Yes)
Arthropod RQs > 0.05 (the
interim terrestrial invertebrate
LOC) for all uses.
Direct/Indirect Effects: BCB.
VELB (direct); CCR, CTS,
SFGS (indirect)
Terrestrial Plants -
Monocots
Non-listed Species (Yes)
RQs were not calculated given no
available terrestrial plant data.
Risk was assumed.
Indirect Effects: BCB.
VELB, SFGS, CCR,
CTS, DS, CFS, and TG
Terrestrial Plants -
Dicots
Non-listed Species (Yes)
RQs were not calculated given no
available terrestrial plant data.
Risk was assumed.
Indirect Effects: BCB.
VELB, SFGS, CCR,
CTS, DS, CFS, and TG
Listed Species (Yes)
RQs were not calculated given no
available terrestrial plant data.
Risk was assumed.
Indirect Effects: BCB.
VELB, SFGS, CCR,
CTS, DS, CFS, and TG
Table 5-12. Risk Estimation Summary for Methomyl - Effects to Designated Critical
Habitat. (PCEs)
Taxa
LOC Exceedances
(Yes/No)
Description of Results of
Risk Estimation
Species Associated with a
Designated Critical Habitat
that May Be Modified by
the Assessed Action
Freshwater Fish and
Aquatic-phase
Amphibians
Non-listed Species (Yes)
Acute: RQs >0.1 for cabbage and
scatter bait
Chronic: RQs >1 for cabbage and
scatter bait
CTS (SB-DPS & CC DPS),
DS, TG
Listed Species (Yes)
Acute: RQs > 0.05 for most uses
assessed including cabbage, turf,
anise, alfalfa, celery, and scatter
bait.
Chronic: RQs >1 for cabbage and
scatter bait
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Taxa
LOC Exceedances
(Yes/No)
Description of Results of
Risk Estimation
Species Associated with a
Designated Critical Habitat
that May Be Modified by
the Assessed Action
Freshwater
Invertebrates
Non-listed Species (Yes)
Acute: RQs >0.1 for all assessed
uses
Chronic: RQs >1 for all assessed
uses
CTS (SB-DPS & CC DPS),
DS, TG
Estuarine/Marine
Fish
Non-listed Species (No)
Acute: RQs are less than 0.1 for
all assessed uses
Chronic: RQs are less than 1 for
all assessed uses
None expected.
Listed Species (No)
Acute: A single RQ value is at the
listed species LOC of 0.05 for the
use on cabbage
Chronic: RQs are less than 1 for
all assessed uses
Estuarine/Marine
Invertebrates
Non-listed Species (Yes)
Acute: RQs >0.1 for all assessed
uses
Chronic: RQs >1 for all except
one assessed use (i.e., sorghum)
CTS (SB-DPS & CC DPS),
DS, TG
Vascular Aquatic
Plants
Non-listed Species (Yes)
RQs were not calculated given no
available vascular plant data.
However, a review of toxicity data
using other carbamates and
calculated EECs for methomyl
suggests that vascular plants will
likely not be exposed to
concentrations at which an effect
is expected.
None expected.
Non-Vascular
Aquatic Plants
Non-listed Species (No)
RQs were not calculated given
that the open literature study was
classified as qualitative. However,
a comparison of endpoints (96-hr
EC50: 108-184 mg a.i./L) and
peak EECs (0.0025-0.0619 mg
a.i./L) indicates that non-vascular
plants will likely not be exposed
to concentrations at which an
effect is expected.
None expected.
Birds, Reptiles, and
Terrestrial-Phase
Amphibians
Non-listed Species (Yes)
Acute: dose-based RQs >0.5 for
most if not all assessed uses for
small birds consuming short grass,
arthropods/small insects, and
herbivorous mammals
Chronic: dietary-based RQs >1 for
most assessed uses for small and
medium-sized birds consuming
short grass, arthropods/small
insects, and herbivorous mammals
Granular: 3.83-14.35
Scatter bait: 5.55
CTS (SB-DPS & CC DPS)
Listed Species (Yes)
Acute: dose and dietary-based
RQs >0.1 for most assessed uses
for small and medium-sized birds
consuming short grass,
arthropods/small insects, and
herbivorous mammals
Chronic/granular/scatter bait:
Same as for non-listed (above
CTS (SB-DPS & CC DPS)
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Taxa
LOC Exceedances
(Yes/No)
Description of Results of
Risk Estimation
Species Associated with a
Designated Critical Habitat
that May Be Modified by
the Assessed Action
cell)
Mammals
Non-listed Species (Yes)
Acute: dose-based RQs >0.5 for
all assessed uses.
Chronic: dose- and/or dietary-
based RQs>0.1 for all assessed
uses.
Granular: 1.58-5.92
Scatter bait: 4.91
CTS (SB-DPS & CC DPS)
Terrestrial
Invertebrates
Listed Species (Yes)
Arthropod RQs > 0.05 (the
interim terrestrial invertebrate
LOC) for all uses.
BCB, VELB, CTS (SB-DPS
& CC DPS)
Terrestrial Plants -
Monocots
Non-listed Species (Yes)
RQs were not calculated given no
available terrestrial plant data.
Risk was assumed.
BCB, VELB, CTS (SB-
DPS & CC DPS), DS, and
TG
Non-listed Species (Yes)
RQs were not calculated given no
available terrestrial plant data.
Risk was assumed.
BCB, VELB, CTS (SB-
DPS & CC DPS), DS, and
TG
Terrestrial Plants -
Dicots
Listed Species (Yes)
RQs were not calculated given no
available terrestrial plant data.
Risk was assumed.
BCB, VELB
Following a preliminary "may affect" determination, additional information is considered to
refine the potential for exposure at the predicted levels based on the life history characteristics
{i.e., habitat range, feeding preferences, etc) of the assessed species. Based on the best available
information, the Agency uses the refined evaluation to distinguish those actions that "may affect,
but are not likely to adversely affect" from those actions that are "likely to adversely affect" the
assessed species and its designated critical habitat.
The criteria used to make determinations that the effects of an action are "not likely to adversely
affect" the assessed species or modify its designated critical habitat include the following:
• Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where "take" occurs
for even a single individual. "Take" in this context means to harass or harm, defined as
the following:
¦ Harm includes significant habitat modification or degradation that results in
death or injury to listed species by significantly impairing behavioral patterns
such as breeding, feeding, or sheltering.
¦ Harass is defined as actions that create the likelihood of injury to listed species
to such an extent as to significantly disrupt normal behavior patterns which
include, but are not limited to, breeding, feeding, or sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are extremely
unlikely to occur.
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• Adverse Nature of Effect: Effects that are wholly beneficial without any adverse effects
are not considered adverse.
A description of the risk and effects determination for each of the established assessment
endpoints for the assessed species and their designated critical habitat is provided in Sections
5.2.1 through 5.2.10. The effects determination section for each listed species assessed will
follow a similar pattern. Each will start with a discussion of the potential for direct effects,
followed by a discussion of the potential for indirect effects. In the instance where a direct effect
is not supported by the evidence, but indirect effects are, then the indirect effects will be
described in the direct effects section (where appropriate). Additional indirect effects are
enumerated in the indirect effects section. These discussions do not consider the spatial analysis.
For those listed species that have designated critical habitat, the section will end with a
discussion on the potential for modification to the critical habitat from the use of methomyl.
Finally, in Section 5.2.11, a discussion of any potential overlap between areas of concern and the
species (including any designated critical habitat) is presented. If there is no overlap of the
species habitat and occurrence sections with the Potential Area of LAA Effects a No Effect
determination is made.
5.2.1. Freshwater Fish and Aquatic-phase Amphibians
5.2.1.a. Direct Effects
The acute RQs (0.05-0.19) and chronic RQs (1.99-2.67) for freshwater fish and aquatic-phase
amphibians exceed listed species LOCs (acute: 0.05; chronic: 1). The peak model-estimated
environmental concentrations resulting from different methomyl uses range from 2.5 |ig/L
(sorghum) to 61.9 |ig/L (cole crops, particularly cabbage). The maximum concentration reported
from the USDA NAWQA database for surface water was 0.67 |ig/L. The maximum
concentration of methomyl reported by the CDPR surface water database was 5.4 |ig/L and is
roughly 11.6 times lower than the highest peak model-estimated environmental concentration.
As a result, it is believed that PRZM/EXAMS EECs provide a conservative measure of exposure.
However, one aquatic incident (100108-001) was reported in 1992 with regard to a large fish kill
as a result of methomyl runoff from a 200 acre treated corn field; 125 bluegill, bowfin, and carp
were killed.
Using the lowest and highest RQs (0.05-0.19) that exceed the acute listed LOC for aquatic
animals (0.05), the chance of an individual mortality for freshwater fish and aquatic phase
amphibians is 1 in 5.37 x 107 to 1 in 877 for slope of 4.23 and ranges from 1 in 787 to 1 in 21.2
and 1 in 1.62 x 1015 to 218,000 for the 95% confidence limits of 2.32 and 6.15, respectively.
Furthermore, spatial distribution maps for freshwater dwelling species indicates overlap between
habitat and the methomyl use footprint (APPENDIX K).
Lastly, because freshwater fish are being used as surrogates for aquatic-phase CTS and the most
sensitive acute toxicity value for methomyl is being used, an analysis of the sensitivity of
freshwater fish to methomyl on an acute exposure basis was completed. Therefore, a species
sensitivity distribution (SSD) for the eight freshwater fish for which acute toxicity data are
available was calculated. The eight genus mean 96-h LC50 values used to calculate the acute
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SSD for freshwater fish are listed in Table 5-13. This calculation is consistent with the Office of
Water's approach for generating SSDs for Ambient Water Quality Criteria (AWQC). For a
specific species with multiple tests available, the geometric species mean LC50 value for the
specific species was calculated first, and then the genus mean LC50 was calculated.
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Table 5-13. Freshwater Fish Genus and Species Mean Acute 96-Hr LC50 Values.
GENUS MEAN
ACUTE VALUE
(Hg/L)
SPECIES
NUMBER OF ACUTE
VALUES USED TO
CALCULATE THE
SPECIES MEAN
VALUE
SPECIES MEAN
ACUTE VALUE
(Hg/L)
1,996
Pimephales promelas
Fathead minnow
4
1,996
1,590
Salvelinus fontinalis
Brook trout
3
1,590
1,504
Oncorhynchus mykiss
Rainbow trout
18
1,504
1,070
Tilapia nilotica
Tilapia
1
1,070
975
Micropterus salmoides
Largemouth bass
2
975
964
Salmo salar
Atlantic salmon
10
964
831
Lepomis macrochirus
Bluegill sunfish
21
831
587
Ictalurus punctatus1
Channel catfish
5
587
The genus log LC50 values are used to calculate a SSD using a Student's t-distribution (a t-
distribution was used because toxicity values were only available for eight freshwater fish
genera). Therefore, a t- distribution of genus mean log LC50 values and log SD values was
assumed in extrapolating 5th, 50th, and 95th percentile LC50 values for freshwater fish. All
caculations were done using Excel 2003. Using this approach, the 5th percentile LC50 is 526
[j,g/L, the 50th or median percentile LC50 value is 1,112 (J,g/L, and the 95th is 2,352 [j,g/L (Figure
5-1). Assuming that the genera tested represent the full range of freshwater fish sensitivity to
methomyl, these results indicate that 5% of freshwater fish will have an LC50 value less than or
equal to 526 (J,g/L, 50% less than or equal to 1,112 (J,g/L, and 95% less than or equal to 2,352
[j,g/L. Relative to this sensitivity distribution, the channel catfish LC50 value (320 (J,g/L) is a
conservative estimate with over 95% of the fish being less sensitive. Even relative to the genus
mean for catfish (Ictalurus spp. LC5o=587 (J,g/L), the value used in this assessment is
conservative.
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0 H i i i i i
0 500 1000 1500 2000 2500
Methomyl (ug/L)
Figure 5-1. Freshwater Fish Species Sensitivity Distribution for Methomyl.
The highest 1 in ten year aquatic peak EEC for all of the agricultural, non-agricultural, and
orchard scenarios for methomyl is 61.9 [j,g/L (for the cole crops scenario). At this EEC, and as
discussed above, the Agency's acute risk to listed species LOC is exceeded using the most
sensitive acute toxicity value for freshwater fish (i.e., 320 (J,g/L). If RQs were calculated based
on this EEC and the 5th percentile (i.e., LC50 = 526 (J,g/L), the median percentile (i.e., LC50 =
1,112 (J,g/L), and the 95n percentile (i.e., LC50 = 2,352 (J,g/L) LC50 for freshwater fish, the RQs
would equal 0.12, 0.06, and 0.03, respectively. Therefore, according to this analysis, unless
aquatic-phase CTS, the DS, and TG are less sensitive to methomyl than approximately half of all
freshwater fish tested, the potential for direct adverse effects (mortality) on aquatic-phase CTS,
the DS, and TG from methomyl use (at maximum seasonal application rates) exists. The
aquatic-phase considers life stages of the CTS that are obligatory aquatic organisms, including
eggs and larvae. It also considers submerged terrestrial-phase juveniles and adults, which spend
a portion of their time in water bodies that may receive runoff and spray drift containing
methomyl. The remaining organisms (DS and TG) are aquatic and are directly exposed to
methomyl concentrations found in water. Although aquatic-phase amphibians (including the
CTS) may be less sensitive to methomyl than freshwater fish, until comparative toxicity data on
amphibians are available, conclusions regarding their relative sensitivity to methomyl are
uncertain; therefore, it is assumed that they are as sensitive to methomyl as freshwater fish.
Based on the above analyses, there is the potential for risk of direct effects to aquatic-phase
CTS, the DS, and TG from acute and/or chronic exposure to methomyl from most registered
agricultural uses of methomyl (i.e., cabbage, turf, anise, alfalfa, celery, and scatter bait).
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5.2.2. Freshwater Invertebrates
5.2.2.a. Direct Effects
The acute RQs (0.50-12.38) and chronic RQs (1.57-60.86) for freshwater invertebrates exceed
listed species LOCs (acute: 0.05; chronic: 1) for all assessed uses. Aquatic incident data are not
available for freshwater invertebrates; however, invertebrate incident data are rarely reported.
Using the lowest and highest RQs (0.5-12.38) that exceed the acute listed LOC for aquatic
animals (0.05), the chance of an individual mortality for freshwater invertebrates is 1 in 6.69 to 1
in 1 for slope of 3.45 and ranges from 1 in 2.72 to 1 in 1.12 and 1 in 24.6 to 1 in 1 for the 95%
confidence limits of 1.12 and 5.79, respectively. Furthermore, spatial distribution maps for
freshwater dwelling species indicates overlap between habitat and the methomyl use footprint
(APPENDIX K)
The six genus mean EC50 values used to calculate the acute SSD for freshwater invertebrates are
listed in Table 5-14. For a specific species with multiple tests available, the geometric species
mean EC50 value for the specific species was calculated first, and then the mean EC50 for the
genus was calculated. The log EC50 values for available genera are assumed to be from a normal
distribution and are used to calculate the parameters of this distribution, i.e., mean and standard
deviation (SD).
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Table 5-6. Ranked Freshwater Invertebrate Genus Mean Acute Values.
RANK
(IliM S MEAN
AC I I K VALUE
(Total fig/L)
SPECIES
NUMHEUOK ACUTE
VALUES USED TO
CALCULATE THE SPECIES
MEAN VALUE
6
886
Gammarus pseudolimnaeus[
Scud
3
5
99.7
Isogenus sp.2
Stonefly
2
4
64.3
Pteronarcella sp.2
Stonefly
2
3
53.1
Chironomus plumosus1
Midge
2
2
31.4
Skwala sp.2
Stonefly
2
1
15.7
Daphnia magna1
Daphnid
4
Endpoints are from a 48-hr study.
2 Endpoints are from a 96-hr study.
The genus log LC50 values are used to calculate a SSD using a Student's t-distribution (a t-
distribution was used because toxicity values were only available for six freshwater invertebrate
genera). Therefore, a t-distribution of genus mean log LC50 values and log SD values was
assumed in extrapolating 5th, 50th, and 95th percentile LC50 values for freshwater invertebrates.
All calculations were done using Excel 2003. Since there was a relatively small sample size,
data from 48-hr and 96-hr studies were combined. This may alter the shape of the distribution
curve and may result in underestimating the effects, however, the information provided by the
SSD was still considered useful. Using this approach, the 5th percentile LC50 is 4.5 (J,g/L, the 50th
or median percentile LC50 value is 73 (J,g/L, and the 95th is 1,174 (J,g/L. The cumulative EC50
SSD with concentration-response curves for the 5th, 50th, and 95th percentile generic species are
presented in Figure 5-2.
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Figure 5-2. Species Sensitivity Distribution for Freshwater Invertebrates and Methomyl.
The highest 1 in ten year aquatic peak EEC for all of the agricultural, non-agricultural, and
orchard scenarios for methomyl is 61.9 [j,g/L (for the cole crops scenario). At this EEC the
Agency's acute risk to listed species LOC is exceeded using the most sensitive acute toxicity
value for freshwater invertebrates (i.e., 5 (J,g/L). The acute sensitivity distribution for freshwater
aquatic invertebrates indicates that 5% of the freshwater invertebrate genera have an EC 50 value
of 4.5 [j,g/L or less, 50% have an EC 50 value of 73 [j,g/L or less, and 95% have an EC50 value of
1,174 [j,g/L or less (assuming the invertebrates tested exhibit a full range of sensitivity to
methomyl). The modeled scenarios for methomyl predict peak EECs ranging from 2.5 [j,g/L
(sorghum) to 61.9 [j,g/L (cole crops). The predicted peak EECs for only one of the scenarios
modeled (sorghum) is below 4.5 (J,g/L; 10 of the 11 modeled uses have EEC values that range
from >4.5 [j,g/L to 73 (J,g/L. Therefore, based on available data and this analysis, estimated
environmental concentrations of methomyl may result in 50% mortality of sensitive freshwater
invertebrates for most of the modeled uses at their maximum methomyl application rates in the
assessment area.
Based on the above analyses, there is the potential for risk of direct effects to the CFS from
acute and chronic exposure to methomyl from all registered agricultural and scatter bait uses
assessed for methomyl.
5.2.3. Estuarine/Marine Fish
5.2.3.a. Direct Effects
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The only acute RQ for estuarine/marine fish that approaches or exceeds the acute listed species
LOC is for the cabbage use. The remaining acute RQs and all the chronic RQs for
estuarine/marine fish are below the listed species LOCs. Aquatic incident data were not
submitted and are not available for estuarine/marine fish. This does not mean, however, that an
estuarine/marine fish kill did not occur, but that it was potentially not reported.
Using an RQ of 0.05, the chance of an individual mortality for estuarine/marine fish is 1 in 8.8 x
1024 for slope of 8 and ranges from 1 in 1.05 x 1011 to 1 in 4.58 x 1044 for the 95% confidence
limits of 5.16 and 10.83, respectively. Nevertheless, given all lines of evidence including that
the RQs do not exceed LOCs and that there is potential for dilution in the presumably larger
estuarine/marine environment, methomyl does not have the potential to directly affect the DS
and TG via the marine environment.
5.2.4. Estuarine/Marine Invertebrates
5.2.4.a. Direct Effects
The acute RQs (0.13-3.26) and chronic RQs (1.33-17.75) for estuarine/marine invertebrates
exceed listed species LOCs (acute: 0.05; chronic: 1) for nearly all assessed uses. No incident
data are available for estuarine/marine invertebrates. This does not mean, however, that an
invertebrate kill did not occur, but that it was potentially not reported.
Using the lowest and highest RQs (0.13-3.26) that exceed the acute listed LOC for aquatic
animals (0.05), the chance of an individual mortality for estuarine/marine invertebrates is 1 in
29,900 to 1 in 1.01 for the default slope of 4.5 and ranges from 1 in 26.2 to 1 in 1.18 and 1 in
1.31 x 1015 to 1 in 1 for the default 95% confidence limits of 2 and 9, respectively. Should
modeled concentrations reach the estuarine/marine environment there is potential for indirect
effects to the CCR, DS, and TG from all registered agricultural and scatter bait uses assessed
for methomyl; no direct effects are expected to the assessed species because none belong to
the marine/estuarine invertebrate taxonomic group.
5.2.5. Aquatic vascular/non-vascular plants
5.2.5.a. Direct Effects
PRZM/EXAMS modeled peak EECs range from 0.0025-0.0619 mg a.i./L, which are 4 orders of
magnitude lower than the concentrations at which the effect on the non-vascular plants was
observed in the methomyl open literature study and the pirimicarb study and 1 to 4 orders of
magnitude lower than the the concentrations at which the effect on the vascular plants and 5-day
non-vascular plants was observed for the remaining carbamates reviewed (see Section 5.1.1 .e).
Based on the available lines of evidence from the open literature and data submitted for other
carbamate insecticides with similar modes of action, methomyl is unlikely to result in direct
effects to non-vascular and vascular plants and, by extension, indirect effects to species that rely
on non-vascular plants during at least some portion of their life-cycle {i.e., SFGS, CCR, CTS,
DS, CFS, and TG).
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5.2.6. Birds, reptiles, and terrestrial-phase amphibians
5.2.6.a. Direct Effects
The acute RQs (dose based: 3.93-27.97; dietary based: 0.12-0.46) and chronic RQs (dietary
based: 1.44-3.34) for birds, reptiles, and terrestrial-phase amphibians exceed listed species LOCs
(acute: 0.1; chronic: 1) for all uses when modeling is based on consumption of short grass. The
acute RQs (dose based: 1.54-10.96; dietary based: 0.10-0.18) and chronic RQs (dietary based:
1.14-1.31) for birds, reptiles, and terrestrial-phase amphibians exceed listed species LOCs (acute:
0.1; chronic: 1) for nearly all uses when modeling is based on consumption of arthropods. In
either case, there is potential for direct effects to the CCR, CTS (all DPS), and SFGS from
all assessed agricultural uses of methomyl, including the granular use on sweet corn whorls
(RQs: 3.83-14.35 for a 20g bird) and scatter bait (RQ of 5.55).
A refinement of the RQs for the CTS and SFGS using T-HERPS indicates LOC exceedances for
most if not all uses. On a chronic basis, the sorghum use does not lead to LOC exceedances for
the CTS and SFGS; for additional exceptions that are not consistent across the size classes
assessed see Table 5-9 and Table 5-10. The acute RQs (dose based: 0.13-0.92; dietary-based:
0.11-0.26) and chronic RQs (dietary based: 1.08-1.88) for a small 2g bird (surrogate for small
CTS) consuming small insects exceed listed species LOCs (acute: 0.1; chronic: 1). The acute
RQs (dose based: 2.31-16.44; dietary-based: 0.12-0.46) and chronic RQs (dietary based: 1.45-
3.36) for a medium 20g bird (surrogate for CTS) consuming herbivorous mammals of 1.33 to
13.3g exceed listed species LOCs (acute: 0.1; chronic: 1). The acute RQs (dose based: 0.13-
0.92; dietary-based: 0.11-0.26) and chronic RQs (dietary based: 1.08-1.88) for a small 2g bird
(surrogate for small SFGS) consuming small insects exceed listed species LOCs (acute: 0.1;
chronic: 1). The acute RQs (dose based: 6.27-23.29; dietary-based: 0.15-0.35) and chronic RQs
(dietary based: 1.10-2.56) for a medium 20g bird (surrogate for SFGS) consuming herbivorous
mammals of 2.10 to 24.7g exceed listed species LOCs (acute: 0.1; chronic: 1). T-HERPS
calculations further confirm that methomyl does have the potential to directly affect the
CTS (all DPS) and the SFGS from all assessed agricultural uses of methomyl.
Bird incident data indicate death by intentional baiting of the rock dove (Columba livia), egret
(species not provided), crow (Corvis sp.), red-tailed hawk (Buteo jamaicensis), American kestrel
(Falco sparverius), Eleanora's falcon (Falco eleonorae), and grackle (Quiscalus spp.) (Incident
#/Event ID: (EIIS) 1009064-001,1011181-001, and 1017139-001; (AIMS) 1841 and 1953). The
AIMS reports (Event ID #: 1953, 1841) indicate deaths of crows, red-tailed hawks, and an egret
resulting from abuse of product. Deaths in laughing gulls (Larus articilla), cattle egret (Bubulcus
ibis), finches, linnets, and vultures were also observed from uknown use patterns, foliar spray, or
drinking contaminated dew (Incident#: 1018980-010,1006382-001,1006382-002,1021455-003).
Using the lowest and highest RQs (0.10-27.97) that exceed the acute listed LOC for terrestrial
animals (0.10), the chance of an individual mortality for birds, reptiles, and terrestrial-phase
amphibians is 1 in 294,000 to 1 in 1 for the default slope of 4.5 and ranges from 1 in 44 to 1 in 1
18
and 1 in 8.86 x 10 to 1 in 1 for the default 95% confidence limits of 2 and 9, respectively.
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Furthermore, spatial distribution maps for CCR, CTS, and SFGS species indicates overlap
between habitat and the methomyl use footprint.
5.2.7. Mammals
5.2.7.a. Direct Effects
The acute RQs (dose based: 1.02-7.25) and chronic RQs (dietary based: 1.80-6.69; dose based:
8.14-58.01) for small 15g mammals consuming short grass exceed listed species LOCs (acute:
0.1; chronic: 1) for all uses. The acute RQs (dose based: 0.47-3.32) and chronic RQs (dietary
based: 1.80-6.69; dose based: 3.73-26.56) for large lOOOg mammals consuming short grass
exceed listed species LOCs (acute: 0.1; chronic: 1) for all uses. Based on calculated acute and
chronic RQs for 15g and lOOOg mammals consuming short grass, methomyl does have the
potential to directly affect listed mammals of the sizes modeled given the modeled uses. Using
the lowest and highest RQs (1.95-7.25) that exceed the acute listed LOC for terrestrial animals
(0.10), the chance of an individual mortality for mammals is 1 in 1.11 to 1 in 1 for the default
slope of 4.5 and ranges from 1 in 1.39 to 1 in 1.04 and 1 in 1 (for low and high RQ range) for the
default 95% confidence limits of 2 and 9, respectively. Mammalian incident data is sparse since
only a single incident (#:I021455-003) is available, which indicates death of three Virginia
opossums as a result of an unknown use site and application in Florida.
Potential direct effects to the eight species assessed for methomyl does not apply as none of the
SF Bay species for this assessment is a mammal. However, since the acute and chronic RQs
are exceeded, there is potential for indirect effects to those listed species that rely on
mammals during at least some portion of their life-cycle (ie., CCR, CTS (all DPS), and the
SFGS) all assessed agricultural uses of methomyl, including the granular use on sweet corn
whorls (RQs: 1.58-5.92 for a 15g mammal) and scatter bait (RQ of 4.91).
5.2.8. Terrestrial invertebrates
5.2.8.a. Direct Effects
Based on the RQs (42.30-157.12) generated from arthropod EECs, methomyl does have the
potential to directly affect the BCB and VELB from all assessed agricultural uses of
methomyl. Additionally, since these RQs exceed the Agency's interim terrestrial invertebrate
LOC (0.05), there is a potential for indirect effects to those listed species that rely on terrestrial
invertebrates during at least some portion of their life-cycle (i.e., CCR, CTS (all DPS), and the
SFGS). Incident data were not submitted and are not available for terrestrial invertebrates. This
does not mean, however, that an invertebrate kill did not occur, but that it was potentially not
reported. Using the lowest and highest RQs (42.30-157.12) that exceed the interim terrestrial
invertebrate LOC (0.05), the chance of an individual mortality for terrestrial inverterates is 1 in 1
for slope of 4.33 and for the 95% confidence limits of 3.37 and 5.30. Furthermore, spatial
distribution maps for BCB and VELB species indicates overlap between habitat and the
methomyl use footprint.
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5.2.9. Terrestrial plants
5.2.9.a. Direct Effects
Although there are no acceptable terrestrial plant guideline toxicity studies available for
methomyl, several efficacy studies that were conducted to test the effects of methomyl on a
variety of target and non-target invertebrate pests also supplied information on effects to plants
after methomyl applications. Due to a lack of information on study design and data analyses,
these efficacy studies are classified as 'supplemental' and are not adequate for plant (or
terrestrial invertebrate) RQ calculation. None of the studies showed any adverse effects to plants
at the highest treatment levels tested (most of which were at or above the maximum allowable
single application rate for methomyl of 0.9 lbs a.i./acre) and the NOAEL from the studies
represented the highest treatment rates examined (see Table 4-5). However, because none of the
studies addressed potential risks to monocots, or effects on seedling emergence and some N-
methyl carbamates are plant auxins and are used to thin fruit (e.g., carbaryl), risks to plants from
the use of methomyl cannot be precluded using the available data. Given the lack of data, risk to
terrestrial plants cannot be precluded. Plant incident data are available for melons as a result of a
tank mix application of the following products DuPont Lannate® S (a.i. methomyl, PC Code
090301) and Valent Danitol (a.i. Fenpropathrin, PC Code 127901) insecticides in Arizona
(Incident #: 1022338-002,1022338-001). The older leaves on the melon plants suffered very light
speckling and symptoms were observed two days after the ground application. Furthermore,
spatial distribution maps for BCB, VELB, SFGS, CCR, CTS, DS, CFS, and TG indicate overlap
between habitat and the methomyl use footprint. Since effects to terrestrial plants are assumed
and these species rely on plants for shelter and/or food, there is a potential for indirect effects
to those listed species that rely on terrestrial plants (for food, habitat, etc.) during at least
some portion of their life-cycle (i.e., BCB, VELB, SFGS, CCR, CTS, DS, CFS, and TG)
presumably from all assessed uses.
5.2.9.b. Indirect Effects
i. Potential Loss of Prey
For indirect effects, since RQs exceed the acute non-listed species LOC, methomyl is likely to
indirectly affect the SFGS, CCR, CTS, DS, CFS, and TG for most if not all uses. For specific
uses that exceed the acute non-listed species LOC (0.5) or the acute restricted use LOC (0.1 for
aquatic organisms, 0.2 for terrestrial animals) see the Risk Estimation section. Risk quotients
were not calculated for aquatic and terrestrial plants given limited available data, however, risk
was assumed for terrestrial plants. Therefore, indirect effects to the BCB and VELB are
expected.
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Table 5-7. Range of acute1 and chronic RQs that exceed non-listed species LOCs for prey of
each SF Bay Species.
SF Bay Species
Aquatic
Organisms
Aquatic RQs
Terrestrial
Organisms
Terrestrial RQs
SFGS*
(eats invertebrates,
fish, small
mammals, reptiles,
amphibians)
Freshwater fish
Acute: 0.13-0.19
Chronic: 1.99-2.67
Mammals2
Acute (sm): 1.02-
7.25
Acute (lg): 0.47-3.32
Chronic (sm): 1.80-
58.01
Chronic (lg): 1.80 -
26.56
Granular: 1.58-5.92
Scatter bait: 4.91
Freshwater inverts.
Acute: 0.50-12.38
Chronic: 1.57-60.86
Birds / Terrestrial-
phase Amphibians
Acute3: 0.12-27.97
Chronic: 1.44-3.34
Acute4 *: 0.15 -23.29
Chronic*: 1.10-2.56
Granular: 3.83-14.35
Scatter bait: 5.55
Aquatic plants
RQs were not
calculated. However,
a comparison of
available endpoints
to peak EECs
indicates that non-
vascular and
vascular plants will
likely not be
exposed to
concentrations at
which an effect is
expected.
Terrestrial inverts.
42.30-157.12
Terrestrial plants
No data. Risk
presumed.
CCR
(eats dead fish,
frogs, aquatic
inverts., aquatic
plants, seeds,
worms, spiders,
small birds and
mammals, terrestrial
plants)
Freshwater fish
Acute: 0.13-0.19
Chronic: 1.99-2.67
Mammals2
Acute (sm): 1.02-
7.25
Acute (lg): 0.47-3.32
Chronic (sm): 1.80-
58.01
Chronic (lg): 1.80 -
26.56
Granular: 1.58-5.92
Scatter bait: 4.91
Freshwater inverts.
Acute: 0.50-12.38
Chronic: 1.57-60.86
Birds
Acute3: 0.12-27.97
Chronic: 1.44 -3.34
Granular: 3.83-14.35
Scatter bait: 5.55
E/M fish
Acute: <0.1
Chronic: <1.0
Terrestrial inverts.
42.30-157.12
E/M inverts.
Acute: 0.13-3.26
Chronic: 1.33-17.75
Terrestrial plants
No data. Risk
presumed.
Aquatic plants
RQs were not
calculated. However,
a comparison of
available endpoints
to peak EECs
indicates that non-
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vascular and
vascular plants will
likely not be
exposed to
concentrations at
which an effect is
expected.
CTS*
(eats freshwater
snails, aquatic
invertebrates, fish,
frogs, algae,
zooplankton,
terrestrial
invertebrates,
worms, small
mammals)
Freshwater fish
Acute: 0.13-0.19
Chronic: 1.99-2.67
Mammals
Acute (sm): 1.02-
7.25
Acute (lg): 0.47-3.32
Chronic (sm): 1.80-
58.01
Chronic (lg): 1.80 -
26.56
Granular: 1.58-5.92
Scatter bait: 4.91
Freshwater inverts.
Acute: 0.50-12.38
Chronic: 1.57-60.86
Birds / Terrestrial-
phase amphibians
Acute3: 0.12-27.97
Chronic: 1.44 -3.34
Acute5 *: 0.12-16.44
Chronic*: 1.45-3.36
Granular: 3.83-14.35
Scatter bait: 5.55
Aquatic plants
RQs were not
calculated. However,
a comparison of
available endpoints
to peak EECs
indicates that non-
vascular and
vascular plants will
likely not be
exposed to
concentrations at
which an effect is
expected.
Terrestrial inverts.
42.30-157.12
Terrestrial plants
No data. Risk
presumed.
DS
(eats primarily
planktonic
copepods,
cladocerans,
amphipods, and
insect larval; larvae
feed on
phytoplankton;
juveniles on
zooplankton)
Freshwater inverts.
Acute: 0.50-12.38
Chronic: 1.57-60.86
Terrestrial plants
No data. Risk
presumed.
E/M inverts.
Acute: 0.13-3.26
Chronic: 1.33-17.75
Aquatic plants
RQs were not
calculated. However,
a comparison of
available endpoints
to peak EECs
indicates that non-
vascular and
vascular plants will
likely not be
exposed to
concentrations at
which an effect is
expected.
CFS
(eats detritus -
algae, aquatic
Freshwater inverts.
Acute: 0.50-12.38
Chronic: 1.57-60.86
Terrestrial plants
No data. Risk
presumed.
Aquatic plants
RQs were not
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macrophyte
fragments,
zooplankton,
aufwuchs)
calculated. However,
a comparison of
available endpoints
to peak EECs
indicates that non-
vascular and
vascular plants will
likely not be
exposed to
concentrations at
which an effect is
expected.
TG
(eats small benthic
invertebrates,
crustaceans, snails,
mysids, aquatic
insect larvae;
juveniles may feed
on unicellular
phytoplankton or
zooplankton)
Freshwater inverts.
Acute: 0.50-12.38
Chronic: 1.57-60.86
Terrestrial plants
No data. Risk
presumed.
E/M inverts.
Acute: 0.13-3.26
Chronic: 1.33-17.75
Aquatic plants
RQs were not
calculated. However,
a comparison of
available endpoints
to peak EECs
indicates that non-
vascular and
vascular plants will
likely not be
exposed to
concentrations at
which an effect is
expected.
BCB / VELB
N/A
N/A
Terrestrial plants
No data. Risk
presumed.
E/M = estuarine/marine; N/A = not applicable
*T-HERPS was run for this SF Bay species
1 Acute restricted use LOC (0.1) and Acute LOC (0.5) were both considered as non-listed LOCs for aquatic
organisms. Acute restricted use LOC (0.2) and Acute LOC (0.5) were both considered as non-listed LOCs for
terrestrial organisms.
2 Acute and chronic values for small 15g mammals (sm); acute and chronic values for large lOOOg mammals (lg);
chronic values include both dose-based and dietary based RQs. All values are based on consumption of short grass.
3Acute values include both dose-based and dietary based RQs based on consumption of short grass
4 Acute values include both dose-based and dietary based RQs, and both acute and chronic RQ values are based on
medium sized SFGS (20g) consuming small/medium herbivorous mammals of 2.10 to 24.74g
5 Acute values include both dose-based and dietary based RQs, and both acute and chronic RQ values are based on
medium sized CTS (20g) consuming small/medium herbivorous mammals of 1.33 to 13.3g
ii. Potential Modification of Habitat
Aquatic plants serve several important functions in aquatic ecosystems. Non-vascular aquatic
plants are primary producers and provide the autochthonous energy base for aquatic ecosystems.
Vascular plants provide structure, rather than energy, to the system, as attachment sites for many
aquatic invertebrates, and refugia for juvenile organisms, such as fish and frogs. Emergent
plants help reduce sediment loading and provide stability to nearshore areas and lower
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streambanks. In addition, vascular aquatic plants are important as attachment sites for egg
masses of aquatic species.
PRZM/EXAMS modeled peak EECs range from 0.0025-0.0619 mg a.i./L, which are 4 orders of
magnitude lower than the concentrations at which the effect on the non-vascular plants was
observed in the methomyl open literature study and the pirimicarb study and 1 to 4 orders of
magnitude lower than the the concentrations at which the effect on the vascular plants and 5-day
non-vascular plants was observed for the remaining carbamates (see Section 5.1.1 .e). With some
uncertainty in the open literature study results, including lack of reporting of raw effects data to
verify the calculated endpoints, minimal availability of data for other carbamates with a similar
mode of action, methomyl is unlikely to result in modification to the aquatic plant habitat.
Terrestrial plants serve several important habitat-related functions for the listed assessed species.
In addition to providing habitat and cover for invertebrate and vertebrate prey items of the listed
assessed species, terrestrial vegetation also provides shelter and cover from predators while
foraging. Upland vegetation including grassland and woodlands provides cover during dispersal.
Riparian vegetation helps to maintain the integrity of aquatic systems by providing bank and
thermal stability, serving as a buffer to filter out sediment, nutrients, and contaminants before
they reach the watershed, and serving as an energy source.
Although there are no acceptable terrestrial plant guideline toxicity studies available for
methomyl, several efficacy studies that were conducted to test the effects of methomyl on a
variety of target and non-target invertebrate pests also supplied information on effects to plants
after methomyl applications (see Table 4-5). However, because none of the studies addressed
potential risks to monocots, or effects on seedling emergence and some N-methyl carbamates are
plant auxins and are used to thin fruit (e.g., carbaryl), risks to plants from the use of methomyl
cannot be precluded using the available data. In addition, incident reports on melons indicate
damage to older, treated leaves as a result of ground application of a methomyl formulation (see
Section 4.5.2. Plant Incidents). Given the lack of toxicity data and the available incidents
reports, risk to terrestrial plants cannot be precluded. Furthermore, spatial distribution maps for
BCB, VELB, SFGS, CCR, CTS, DS, CFS, and TG indicate overlap between habitat and the
methomyl use footprint. Since effects to terrestrial plants are assumed and these species rely on
plants for shelter and/or food, there is a potential for indirect effects to those listed species
that rely on terrestrial plants (for food, habitat, etc.) during at least some portion of their
life-cycle (i.e., BCB, VELB, SFGS, CCR, CTS, DS, CFS, and TG).
5.2.10. Modification of Designated Critical Habitat
Based on the weight-of-evidence and particularly the output of the RQ calculations whereby
direct and indirect effects are expected for certain species (see the table above), there is a
potential for the modification designated critical habitat (i.e., particularly in reference to the
species with a designated critical habitat designation including BCB, VELB, CTS (CC DPS &
SB DPS), DS, and TG.)
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5.2.11. Spatial Extent of Potential Effects
Since LOCs are exceeded, analysis of the spatial extent of potential LAA effects is needed to
determine where effects may occur in relation to the treated site. If the potential area of usage
and subsequent Potential Area of LAA Effects overlaps with SFGS, CCR, BCB, VELB, CTS,
DS, CFS, and TG habitat or areas of occurrence and/or critical habitat, a likely to adversely
affect determination is made. If the Potential Area of LAA Effects and the SFGS, CCR, BCB,
VELB, CTS, DS, CFS, and TG habitat and areas of occurrence and/or critical habitat do not
overlap, a no effect determination is made.
To determine this area, the footprint of methomyl's use pattern is identified, using corresponding
land cover data, see Section 2.7. The land cover classes used to determine the use footprint
include cultivated orchard, vineyard, pasture, hay, turf, and all urban NLCD categories based on
potential uses on bulbs, cereal grians, cole crops, grasses, herbs, leguminous forage, non-cole
leafy crops, avocado, and scatter bait. Actual usage is expected to occur in a smaller area as the
chemical is only expected to be used on a portion of the identified area. The spatial extent of the
effects determination also includes areas beyond the initial area of concern that may be impacted
by runoff and/or spray drift (Use Footprint + distance down stream or down wind from use sites
where organisms relevant to the assessed species may be affected). The determination of the
buffer distance and downstream dilution for spatial extent of the effects determination is
described below.
5.2.11.a. Spray Drift
In order to determine terrestrial and aquatic habitats of concern due to methomyl exposures
through spray drift, it is necessary to estimate the distance that spray applications can drift from
the treated area and still be present at concentrations that exceed levels of concern. Ground
applications of methomyl granular formulations are not expected to result in any spray drift. For
the flowable uses, a quantitative analysis of spray drift distances was completed using AgDRIFT
(v. 2.01) using default inputs for aerial applications {i.e., ASABE Very Fine to Fine). The most
sensitive acute and chronic endpoints for aquatic and terrestrial exposure were utilized. For
terrestrial exposure, a buffer was determined for invertebrates and vertebrates.
Table 5-8. Buffers for Most Sensitive Aquatic and Terrestrial Species using AgDRIFT
Endpoint
Species
Max
Application
Rate
Fraction of
Applied
Type of
Assessment
Buffer1
Acute: EC50
(at 48 hrs) =
0.005 mg
a.i.lL
Daphnia
Magna
(MRID
40098001)
0.90 lb a.i./A
NA
Aquatic (Tier I)
120 feet
Chronic:
NOAEC =
0.0007 mg
a.i.lL
Daphnia
Magna
(MRID
1312541)
0.90 lb a.i./A
NA
Aquatic (Tier I)
753 feet
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Acute: LD50
= 24.2
mg/kg-bw
Bobwhite
quail (MRID
00161886)
(Non-
invertebrate)
0.90 lb a.i./A
LOC/RQ = 0.004
Terrestrial
(Tier 1)
>1000 feet
Chronic:
NOAEL =
75 mg
a.i./kg-diet
(equivalent
to 3.75 mg
a.i./kg/day)
Lab rat
(MRID
43250701,
43769401)
(Non-
invertebrate)
0.90 lb a.i./A
LOC/RQ = 0.15
Terrestrial
(Tier 1)
162.3 feet
Acute: LD50
= 0.16 ug
a.i./bee
Honey Bee
(acute contact
study - MRID
45093001)
(Invertebrate)
0.90 lb a.i./A
LOC/RQ = 0.0003
Terrestrial
(Tier 1)
>1000 feet
All aerial applications already have a 100 foot buffer taken into account and was added to the buffer values determined by
AgDRIFT. Therefore, the values seen in the table is the total buffer distance including the 100 foot buffer that is already on the
label.
5.2.1 l.b. Downstream Dilution Analysis
The downstream extent of exposure in streams and rivers where the EEC could potentially be
above levels that would exceed the most sensitive LOC is calculated using the downstream
dilution model. To complete this assessment, the greatest ratio of aquatic RQ to LOC was
estimated. Using an assumption of uniform runoff across the landscape, it is assumed that
streams flowing through treated areas {i.e., the Initial Area of Concern) are represented by the
modeled EECs; as those waters move downstream, it is assumed that the influx of non-impacted
water will dilute the concentrations of methomyl present. The highest RQ/LOC ratio and the
land cover class are used as inputs into the downstream dilution model.
Using a 48-hr LC50 value of 5 |ig/L for Daphnia magna, an LOC of 0.05, and a maximum peak
EEC of 61.9 |ig/L for cole crops from the Tier IIPE5 model yields an RQ/LOC ratio of 247.6
((61.9/5)/0.05). The downstream dilution approach is described in more detail in Appendix K.
This value has been input into the downstream dilution model and results in a distance of 258.5
kilometers which represents the maximum continuous distance of downstream dilution from the
edge of the Initial Area of Concern where LOCs may be exceeded in the aquatic environment. It
is also important to note that this chemical has wide usage {e.g., applied in almost all land
classes, showing that the chemical can be used practically everywhere.) As a result, giving a
distance may result in a limitation since it does not capture the likelihood that the stream reaches
will run into adjacent land cover classes that may also have usage.
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5.2.1 I.e. Overlap of Potential Areas of LAA Effect and Habitat and
Occurrence of SFGS, CCR, BCB, VELB, CTS, DS, CFS, and
TG
The spray drift and downstream dilution analyses help to identify areas of potential effect to the
SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG from registered uses of methomyl. The
Potential Area of LAA effects on survival, growth, and reproduction for the SFGS, CCR, BCB,
VELB, CTS, DS, CFS, and TG from methomyl spray drift extend from the site of application to
120 feet or greater than 1000 feet from the site of application. For exposure to runoff and spray
drift, the area of potential LAA effects extends up to 258.5 km downstream from the site of
application. The maps presented in APPENDIX K indicate overlap between the habitat space in
all SF Bay species assessed and the use footprint area without the downstream dilution distance
incorporated into the use footprint space. However, should these distances be added to the
footprint of the Initial Area of Concern (which represents potential methomyl use sites) and
compared to SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG habitat, it is likely that the area
of overlap will increase. The overlap between the areas of LAA effect and SFGS, CCR, BCB,
VELB, CTS, DS, CFS, and TG habitat, including designated critical habitat, indicates that
methomyl use in California has the potential to affect the SFGS, CCR, BCB, VELB, CTS, DS,
CFS, and TG. More information on the spatial analysis is available in APPENDIX K.
5.3. Effects Determinations
5.3.1. Assessed Species
Overall, each species includes a habitat location that overlaps with the methomyl area of effects
{i.e., a combination of methomyl uses assessed in this risk assessment that is represented by the
2001 NLCD data). All listed species (SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG) have
the potential for direct and indirect effects as a result of methomyl exposure at the registered use
rates.
Therefore, the Agency makes a may affect, and likely to adversely affect determination for all
species (SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG) and a habitat modification
determination for their designated critical habitat {i.e., particularly in reference to the species
with a designated critical habitat designation including BCB, VELB, CTS (CC DPS & SB DPS),
DS, and TG.) based on the potential for direct and indirect effects and effects to the PCEs of
critical habitat.
5.3.2. Addressing the Risk Hypotheses
In order to conclude this risk assessment, it is necessary to address the risk hypotheses defined in
Section 2.9.1. Based on the conclusions of this assessment, none of the hypotheses can be
rejected, meaning that the stated hypotheses represent concerns in terms of direct and indirect
effects of methomylon the SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG and their
designated critical habitat {i.e., that of BCB, VELB, CTS (CC DPS & SB DPS), DS, and TG.)
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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 (USEPA, 1998). For this assessment, the risk is stressor-linked,
where the stressor is the release of methomyl to the environment. The following risk hypotheses
are confirmed in this assessment:
The labeled use of methomyl within the action area may:
• directly affect SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TGby causing mortality or
by adversely affecting growth or fecundity;
• indirectly affect SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG and/or modify their
designated critical habitat by reducing or changing the composition of food supply;
• indirectly affect SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG and/or modify their
designated critical habitat by reducing or changing the composition of the terrestrial plant
community in the species' current range;
• indirectly affect SFGS, CCR, CTS, DS, CFS, and TG and/or modify their designated
critical habitat by reducing or changing aquatic habitat in their current range (via
modification of water quality parameters, habitat morphology, and/or sedimentation);
• indirectly affect CTS and/or modify their designated critical habitat by reducing or
changing terrestrial habitat in their current range (via reduction in small burrowing
mammals leading to reduction in underground refugia/cover).
6. Uncertainties
Uncertainties that apply to most assessments completed for the San Francisco Bay Species
Litigation are discussed in Attachment I. This section describes additional uncertainties specific
to this assessment.
6.1. Exposure Assessment Uncertainties
6.1.1. Terrestrial Exposure Assessment Uncertainties
6.1.1.a. T-REX
Organisms consume a variety of dietary items and may exist in a variety of sizes at different life
stages. For foliar applications of liquid formulations, T-REX estimates exposure for the
following dietary items: short grass, tall grass, broadleaf plants, fruits/pods/seeds, arthropods,
and seeds for granivores. Birds (used as a surrogate for amphibians and reptiles), including the
CCR, and mammals consume all of these items. The size classes of birds represented in T-REX
are the small (20 g), medium (100 g), and large (1000 g). The size classes for mammals are
small (15 g), medium (35 g), and large (1000 g). EECs are calculated for the most sensitive
dietary item and size class for birds (surrogate for amphibians and reptiles) and mammals. Table
6-1 shows the percentages of the EECs and RQs of the various dietary classes for each size class
as compared to the most sensitive dietary class (short grass) and size class (small mammal or
151
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bird). This information could be used to further characterize potential risk that is specific to the
diet of birds and mammals. For example, if a mammal only consumes broadleaf plants and small
insects and the RQ was 100 for small mammals consuming short grass, the RQ for small
mammals that only consumed broadleaf plants would be 56 (100 x 0.56).
Table 6-1. Percentage of EEC or RQ for the Specified Dietary Items and Size Classes as
Compared to the EEC or RQ for The Most Sensitive Dietary Items (Short Grass) and Size
Dioliin llems
Percenlasic of FFCs or HQs lor (lie Specified Dielan llems ;iihI
Si/e ( hiss :is compared lo (lie FFC or RQ lor Sniiill ISirtls1 or
Sniiill M;imm;ils Consuming Sliorl Crass
IJials IW liased LLCsaiid RQs
Si/e Class
Small. 2ii u
Mid. lull u
Larue. 1
EEC
RQ
EEC
RQ
EEC
RQ
Short Grass
100%
100%
57%
50%
26%
19%
Tall Grass
46%
46%
26%
23%
12%
9%
Broadleaf plants
56%
56%
32%
28%
14%
11%
Fruits/pods/seeds
6%
6%
4%
3%
2%
1%
Arthropods
39%
39%
22%
20%
10%
7%
(iianiN ores
1".,
1".,
() -,r„
()
() "o".,
()
Mammals I)nsc-I3;iscd LI.( sand RQs
Si/e Class
Small. 15 u
Mid. '5 u
I.arue. 1
LLC
RQ
LLC
RQ
LLC
RQ
Short Grass
100%
100%
69%
85%
16%
46%
Tall Grass
46%
46%
32%
39%
7%
21%
Broadleaf plants
56%
56%
39%
48%
9%
26%
Fruits/pods/seeds
6%
6%
4%
5%
1%
3%
Arthropods
39%
39%
27%
34%
6%
18%
Granivores
1%
1%
0.96%
1%
0.22%
0.64%
Mammals and Birds: Dicta.ry-ba.scd EECs and RQs for all Size Classes"
Short Grass
100%
Tall Grass
46%
Broadleaf plants
56%
Fruits/pods/seeds
6%
Arthropods
39%
methomyl (Mineau el al. 1996).
2 Percentages for dose-based chronic EECs and RQs for mammals are equivalent to the acute dose-based EECs and
RQs.
In the risk assessment, RQs were only calculated for the most sensitive dietary class relevant to
the organisms assessed. For most organisms, not enough data is available to conclude that birds
or mammals may not exclusively feed on a dietary class for at least some time period. However,
most birds and mammals consume a variety of dietary items and thus the RQ will overestimate
risk to those organisms. For example, the CCR is estimated to consume only 15% plant material
(USFWS, 2003). Additionally, some organisms will not feed on all of the dietary classes. For
example, many amphibians would only consume insects and not any plant material.
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6.1.l.b. T-HERPS
For foliar applications of liquid formulations, T-HERPS estimates exposure for the following
dietary items: broadleaf plants/small insects, fruits/pods/seeds/large insects, small herbivore
mammals, small insectivore mammals, and small amphibians. Snakes and amphibians may
consume all of these items. The default size classes of amphibians represented in T-HERPS are
small (2 g), medium (20 g), and large (200 g). The default vertebrate prey size that the medium
and large amphibians can consume is 13 g and 133 g, respectively (small amphibians are not
expected to eat vertebrate prey). The default size classes for snakes are small (2 g), medium (20
g), and large (800 g). The default vertebrate prey size that medium and large snakes can
consume is 25 g and 1,286 g, respectively (small snakes are not expected to eat vertebrate prey).
EECs are calculated for the most sensitive dietary item and size class for amphibians and snakes.
Table 6-2 shows the percentages of the EECs and RQs of the various dietary classes for each
size class as compared to the most sensitive dietary class (herbivorous mammal) and size class
[medium (20 g) amphibian or snake]. This information could be used to further characterize
potential risk that is specific to the diet of amphibians and snakes.
Table 6-2. Percentage of EEC or RQ for the Specified Dietary Class as Compared to the
EEC or RQ for The Most Sensitive Dietary Class (Small Herbivore Mammals) and Size
Class (Medium Amphibian or Snake)
Dicliin llems
Pmvnliiiic of r.l'.Cs or HQs lor (ho Specified Dieliin llems ;ind
Si/e ( hiss ;is compared lo I lie l-'.l-'.C or RQ lor Medium
Amphihiiins or Snakes' Consuming Sm;dl llcrl>i\orc
\mphihiaiis \ciilc Dose IJased IK sand RQs
Si/c ( lass
Small. 2 u
\iid. : u
Larue, sou u
i:i:c
RQ
i:i:c
RQ
i:i:c
RQ
Broadleaf plants/sm Insects
3%
4%
2%
2%
i%
1%
Fruits/pods/seeds/lg insects
0.4%
0.4%
0.2%
0.2%
0.1%
0.1%
Small herbivore mammals
N/A
N/A
100%
100%
23%
17%
Small insectivore mammals
N/A
N/A
6%
6%
1%
1%
Small amphibians
N/A
N/A
2%
2%
1%
1%
Amphibians a nd Snakes: Acute and Chronic Dieta ry-based EECs and RQs for a ll Size Classes
Amphibians
Snakes
Broadleaf plants/sm Insects
21%
25%
Fruits/pods/seeds/lg insects
2%
3%
Small herbivore mammals
100%
100%
Small insectivore mammals
Small amphibians
6%
6%
1%
1%
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1 The percents of the maximum RQ shown here for amphibians and reptiles are based on the specific scaling factor
of 1.0778 for methomyl (Mineau et al. 1996).
In the risk assessment, RQs were only calculated for the most sensitive dietary class relevant to
the organisms assessed. For most organisms, not enough data are available to conclude that
amphibians or snakes may not exclusively feed on a dietary class for at least some time period.
However, most amphibians and snakes consume a variety of dietary items and thus the RQ will
overestimate risk to those organisms. Additionally, some organisms will not feed on all of the
dietary classes. For example, many amphibians would only consume insects and not any plant
material.
6.1.2. Aquatic Exposure Modeling of Methomyl
Several methomyl crops can be grown more than one time per year in CA (i.e., they have
multiple crop cycles). Most methomyl product labels specify application rates on a per crop
cycle basis (not on a per year basis). Since standard PRZM scenarios only consist of one crop per
year, applications to only one crop per year were modeled. For uses where methomyl is applied
for multiple cropping cycles within a year, EECs presented in this assessment may underpredict
exposures.
For the scatter bait use pattern, a conceptual model was developed and the impervious and
residential scenarios which assume that 50% of the modeled area is impervious, and 3% of the
impervious area is treated. Although this is believed to be a conservative assumption, it is
possible that aquatic exposure for the scatter bait use pattern may be over or underestimated
based on where the scatter bait is being applied.
In addition, Methomyl is expected to be unstable in the presence of ferrous iron, as well as
degradate more rapidly in environments where the pH is more alkaline. Therefore, in aquatic
environments with a pH greater than 7 and/or environments that are iron-rich, may result more
rapid degradation of methomyl. Likewise, if the pH is below 7 and the environment is iron-poor,
methomyl is more stable. As a result, based on the actual aquatic conditions, the calculated
EECs may be over or underestimating depending on the respective situations mentioned above.
6.1.3. Exposure in Estuarine/marine Environments
PRZM-EXAMS modeled EECs are intended to represent exposure of aquatic organisms in
relatively small ponds and low-order streams. Therefore, it is likely that EECs generated from
the PRZM-EXAMS model will over-estimate potential concentrations in larger receiving water
bodies such as estuaries, embayments, and coastal marine areas because chemicals in runoff
water (or spray drift, etc.) should be diluted by a much larger volume of water than would be
found in the 'typical' EXAMS pond. However, as chemical constituents in water draining from
freshwater streams encounter brackish or other near-marine-associated conditions, there is
potential for important chemical transformations to occur. Many chemical compounds can
undergo changes in mobility, toxicity, or persistence when changes in pH, Eh (redox potential),
salinity, dissolved oxygen (DO) content, or temperature are encountered. For example,
desorption and re-mobilization of some chemicals from sediments can occur with changes in
salinity (Jordan et al., 2008; Means, 1995; Swarzenski et al., 2003), changes in pH (e.g., Wood
154
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and Baptista 1993; Parikh et al. 2004; Fernandez et al. 2005), Eh changes (Velde and Church,
1999; Wood and Baptista, 1993), and other factors. Thus, although chemicals in discharging
rivers may be diluted by large volumes of water within receiving estuaries and embayments, the
hydrochemistry of the marine-influenced water may negate some of the attenuating impact of the
greater water volume; for example, the effect of dilution may be confounded by changes in
chemical mobility (and/or bioavailability) in brackish water. In addition, freshwater
contributions from discharging streams and rivers do not instantaneously mix with more saline
water bodies. In these settings, water will commonly remain highly stratified, with fresh water
lying atop denser, heavier saline water - meaning that exposure to concentrations found in
discharging stream water may propagate some distance beyond the outflow point of the stream
(especially near the water surface). Therefore, it is not assumed that discharging water will be
rapidly diluted by the entire water volume within an estuary, embayment, or other coastal aquatic
environment. PRZM-EXAMS model results should be considered consistent with
concentrations that might be found near the head of an estuary unless there is specific
information - such as monitoring data - to indicate otherwise. Conditions nearer to the mouth of
a bay or estuary, however, may be closer to a marine-type system, and thus more subject to the
notable buffering, mixing, and diluting capacities of an open marine environment. Conversely,
tidal effects (pressure waves) can propagate much further upstream than the actual estuarine
water, so discharging river water may become temporarily partially impounded near the mouth
(discharge point) of a channel, and resistant to mixing until tidal forces are reversed.
The Agency does not currently have sufficient information regarding the hydrology and
hydrochemistry of estuarine aquatic habitats to develop alternate scenarios for assessed listed
species that inhabit these types of ecosystems. The Agency acknowledges that there are unique
brackish and estuarine habitats that may not be accurately captured by PRZM-EXAMS modeling
results, and may, therefore, under- or over-estimate exposure, depending on the aforementioned
variables.
6.1.4. Modeled Versus Monitoring Concentrations
In order to account for uncertainties associated with modeling, available monitoring data were
compared to PRZM/EXAMS estimates of peak EECs for the different uses. As discussed above,
several data values were available from NAWQA and CDPR for methomyl concentrations
measured in surface waters receiving runoff from agricultural areas. The specific use patterns
(e.g., application rates and timing, crops) associated with the agricultural areas are unknown,
however, they are assumed to be representative of potential methomyl use areas. The peak
model-estimated environmental concentrations resulting from different methomyl uses range
from 2.5 |ig/L (sorghum) to 61.9 |ig/L (cole crops, particularly cabbage). The maximum
concentration reported from the USGA NAWQA database for surface water was 0.67 |ig/L. The
maximum concentration of methomyl reported by the CDPR surface water database was 5.4
|ig/L and is roughly 11.6 times lower than the highest peak model-estimated environmental
concentration. As a result, it is believed that PRZM/EXAMS EECs provide a conservative
measure of exposure.
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6.2. Effects Assessment Uncertainties
6.2.1. Data Gaps and Uncertainties
Although many submissions have been made to provide data on the effects of methomyl to
aquatic and terrestrial organisms, data gaps still exist. Noted data gaps since the problem
formulation (USEPA 2010) include the following: avian acute oral toxicity (850.2100), avian
reproduction (850.2300), terrestrial plant (850.4100, 850.4150), and aquatic plant (850.5400,
850.4400) toxicity studies. The specific data gaps are described in full in Registration Review
Preliminary Problem Formulation for Methomyl (DP Barcode 374952, 2010). An update of this
data since the problem formulation is that the registrant (E.I. DuPont de Nemours and Company,
Inc.) requested a data waiver (MRID 48736202, DuPont project ID: 34679) for an avian
(passerine) acute oral toxicity study (850.2100), which was identified as an additional data need
in support of registration review of 2010. After carefully reviewing the registrant's waiver
request, EFED still identifies the avian acute oral toxicity study with passerines as a critical data
gap (see Response to Waiver Request memo, DP Barcode 400766, May 16, 2012). No additional
data were submitted since the problem formulation (USEPA 2010).
Avian Acute Oral and Reproduction Toxicity
Acceptable acute avian oral toxicity data were submitted for exposures of bobwhite quail and
mallard duck to methomyl; however, data are not available for passerines, which are required
under the new 40 CFR Part 158 (Jul. 1, 2010) data requirements for conventional pesticides. The
new Part 158 data requirements specify that acute avian oral toxicity data be submitted for either
a mallard duck or bobwhite quail and a passerine species. Therefore, an avian oral toxicity test
(OCSPP Guideline 850.2100) is required for passerine birds.
Under the 40 CFR Part 158 (Jul. 1, 2010) data requirements for conventional pesticides, avian
reproduction data are required on waterfowl and upland game species (OCSPP 850.2300).
Currently acceptable data for methomyl are only available for an upland game species (Bobwhite
quail). Data from another N-methylcarbamate {i.e., thiodicarb) suggest that mallard ducks may
be more sensitive than Bobwhite quail on a chronic-exposure basis. The chronic toxicity data
available for birds indicate that mallard ducks (NOAEC = 500 mg a.i./kg-diet; LOAEC = 1,000
mg a.i./kg-diet, based on a reduction in number of eggs laid) (MRID 43313004) are more
sensitive to thiodicarb than bobwhite quail (no reproductive effects seen at any concentration
tested; highest concentration tested = 1,000 mg a.i./kg-diet) (MRID 43313003). Additionally,
bobwhite quail appear more sensitive to methomyl than to thiodicarb based on chronic exposure
(for methomyl, NOAEC = 150 mg a.i./kg-diet; LOAEC = 500 mg a.i./kg-diet, based on fewer
eggs laid and eggs set) (MRID 41898602). Therefore, based on available data, it is reasonable to
assume that mallard ducks may be more sensitive to methomyl than bobwhite quail on a chronic
exposure basis. Therefore, since additional avian reproduction data for methomyl could result in
a more sensitive avian reproductive endpoint, and, thus, could alter the estimated level of risk for
birds (and by extension to terrestrial-phase amphibians and reptiles) from the use of methomyl,
we recommend requesting these data for methomyl at this time.
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Terrestrial Plant Studies
Terrestrial plant toxicity studies and associated risk analysis of plants are required for
registration of pesticides with outdoor uses (CFR Part 158). For terrestrial plants, Tier II studies
are required when potential concerns are triggered {i.e., when there is some indication that there
may be significant toxicity to plants). These indicators may be an herbicidal mode of action or
statements on the label indicating toxicity to plants. None of these indicators are present for
methomyl.
Several efficacy studies that were conducted to test the effects of methomyl on a variety of target
and non-target invertebrate pests supplied information on effects to plants after methomyl
applications (see Table 4-5). However, because none of the studies addressed potential risks to
monocots, or effects on seedling emergence and some N-methyl carbamates are plant auxins and
are used to thin fruit {e.g., carbaryl), risks to plants from the use of methomyl cannot be
precluded using the available data. In addition, incident reports on melons indicate damage to
older, treated leaves as a result of ground application of a methomyl formulation (see Section
4.5.2. Plant Incidents). Finally, a Tier I seedling emergence study on another carbamate, aldicarb
(MRID 47904401), indicated >25% effects on shoot length and weight to ryegrass (monocot)
and tomato (dicot), triggering the need for a tier II study for this chemical. It is uncertain what
quantifiable toxicological effect methomyl application will have on terrestrial plants given that
guideline studies for methomyl are not available.
Vascular and Non-vascular Aquatic Plant Studies
Aquatic plant toxicity studies and associated risk analysis of plants are required for registration
of pesticides with outdoor uses (40 CFR Part 158). Toxicity data for both vascular and non-
vascular aquatic plants (Tier I, OCSPP Guidelines 850.4400 and 850.5400) are required but are
not available for methomyl. With some uncertainty in the available open literature study results,
including lack of reporting of raw effects data to verify the calculated endpoints, minimal
availability of data for other carbamates with a similar mode of action (see Section 5.1.1.e),
methomyl is unlikely to result in modification to the aquatic plant habitat.
6.2.2. Use of Surrogate Species Effects Data
Guideline toxicity tests and open literature data on methomyl are not available for aquatic-phase
amphibians; therefore, freshwater fish are used as surrogate species for aquatic-phase amphibians
and the CTS. Endpoints based on freshwater fish ecotoxicity data are assumed to be protective
of potential direct effects to aquatic-phase amphibians including the CTS. Efforts are made to
select the organisms most likely to be affected by the type of compound and usage pattern;
however, there is an inherent uncertainty in extrapolating across phyla. In addition, the
Agency's LOCs are intentionally set very low, and conservative estimates are made in the
screening level risk assessment to account for these uncertainties.
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6.2.3. Sublethal Effects
When assessing acute risk, the screening risk assessment relies on the acute mortality endpoint as
well as a suite of sublethal responses to the pesticide, as determined by the testing of species
response to chronic exposure conditions and subsequent chronic risk assessment. Consideration
of additional sublethal data in the effects determination t is exercised on a case-by-case basis and
only after careful consideration of the nature of the sublethal effect measured and the extent and
quality of available data to support establishing a plausible relationship between the measure of
effect (sublethal endpoint) and the assessment endpoints. However, the full suite of sublethal
effects from valid open literature studies is considered for the characterization purposes.
To determine effects of carbamates on channel catfish, Carter (1971; ref #: 14034) observed
brain cholinesterase inhibition and other signs of poisoning. In a static 48-h exposure to
methomyl at concentrations ranging from 100 to 1,000 (J,g/L, inhibition of brain cholinesterase
was proportional to the concentration of methomyl and maximum inhibition occurred within 2
hours with little or no recovery in 48 hours. Sequential signs of poisoning included
hyperactivity, lethargy, paralysis, scoliosis, loss of equilibrium, and opercular and mouth
paralysis. Another study by Coppage (1977; ref #: 7669) in which estuarine/marine fishes
(pinfish, sheepshead minnow, and sailfin molly) were exposed to methomyl, acetylcholinesterase
inhibition was similar (77-89%) regardless of the species or period of exposure (4 to 48 h), when
a near-median kill occurred. In the wild, effects such as those noted in the previous tests could
be manifested as reduced foraging efficiency, and/or lowered predator avoidance. Alternatively,
fish may sense and avoid the contaminated area. Extrapolation of these measurement endpoints
to the assessment endpoints of reduced survival, growth and reproduction of individual fish in
the wild is highly uncertain and because currently accepted methods are unavailable to
quantitatively estimate risk (EPA 2004, USFWS/NMFS 2004), they are summarized
qualitatively.
6.2.4. Aquatic non-vascular open literature data
An open literature study (Record #: 118717, Pereira el al.2009) quantifying the growth inhibition
in P. subcapitata (a microalgae) after Lannate (200g a.i./L methomyl formulation) and methomyl
(99.5% purity) exposure indicates a 96-hour EC50 of 184 mg a.i./L (95% CI of 164-206 mg a.i./L
for Lannate) and a 96-hour EC50 of 108 mg a.i./L (95% CI of 87-126 mg a.i./L for methomyl
a.i.). Elements of the protocol that are discussed in the article closely follow the OCSPP 850
guidelines for the species. (Indeed, the authors indicate that OECD guidelines were followed.)
However, there are several guideline deviations. Although there are at least five test
concentrations in each trial (i.e., formulation and active ingredient), these concentrations are not
in geometric progression of twofold (a minimum requirement for all toxicity studies submitted to
EFED). The health of organisms prior to study initiation was not reported. The temperature was
maintained at 20±2°C under permanent illumination, whereas OCSPP guideline 850.4500
dictates 24±2°C under continuous illumination. Three replicates instead of a minimum of four
were used in this study; vials were 100 mL instead of the guideline 125-500 mL flasks. Other
elements were in line with the guideline requirements: 96 hr test duration, static design, initial
cell density of 104 cells/mL, shaker speed of 100 rpm, and age of organisms was within guideline
range. Growth inhibition was a calculated endpoint in this study; however, guideline
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recommends endpoints (NOAEC, LOAEC) for biomass yield, growth rate, and area under the
curve. Furthermore, the raw effects data were not reported; this would limit verification of the
cited endpoint values. However, confidence in the results is high given the consistency between
formulation-based versus active ingredient-based endpoint values for a given species.
6.2.5. Granular and Scatter bait uses
Aquatic exposure for the scatter bait use pattern was assessed using a conceptual model and the
impervious and residential scenarios which assume that 50% of the modeled area is impervious,
and 3% of the impervious area is treated. Although this is believed to be a conservative
assumption, it is possible that aquatic exposure for the scatter bait use pattern may be over or
underestimated based on where the scatter bait is being applied. Furthermore, the label does not
specify how many applications are allowed; therefore, 26 was used as the maximum number of
applications in PRZM/EXAMS because this is the maximum number that the program can
process.
Terrestrial exposure to scatter bait was assessed for birds and mammals based on information in
the label for Stimukil fly bait (EPA Reg. No. 53871-3). This product is a versatile multi-a.i.
formulation (1% methomyl a.i.; 0.04% (Z)-9-tricosene) which includes uses on bait stations, as
scatter bait, and brush. In addition, acute mammalian oral data (MRID 44933202) are available
using this formulation as a test compound. Based on submitted toxicological data, this
formulation is more toxic (14 mg a.i./kg-bw) to the laboratory rat than is the technical grade
active ingredient (30 mg a.i./kg-bw, MRID 42140101; see Appendix A). According to the label,
the scatterbait is applied at a rate of Vi lb per 500 ft2, which is 21.78 lb of formulation/Acre and
0.2178 lbs a.i./A. The bait may be reapplied at 3-5day intervals, but the T-REX model analysis
for LD50/ft2 which was used to calculate the RQs, could only capture a single application of the
product. Furthermore, the RQ represents an area confined by one square foot and is not intended
to represent the dispersal of the product across an acre. The limitations of the LD50/ft2 analysis
for the scatter bait uses also apply for the granular uses on sweet corn whorls.
7. Risk Conclusions
In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the information
presented in this endangered species risk assessment represents the best data currently available
to assess the potential risks of methomyl to SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG
and the designated critical habitat of BCB, VELB, CTS (CC DPS & SB DPS), DS, and TG.
Based on the best available information, the Agency makes a May Affect, Likely to Adversely
Affect determination for the SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG. Additionally,
the Agency has determined that there is the potential for modification of the designated critical
habitat for the BCB, VELB, CTS (CC DPS & SB DPS), DS, and TG from the use of the
chemical. Given the LAA determination for SFGS, CCR, BCB, VELB, CTS, DS, CFS, and TG
and potential modification of designated critical habitat for BCB, VELB, CTS (CC DPS & SB
DPS), DS, and TG, a description of the baseline status and cumulative effects is provided in
Attachment III.
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A summary of the risk conclusions and effects determinations for the SFGS, CCR, BCB, VELB,
CTS, DS, CFS, and TG and critical habitat, given the uncertainties discussed in Section 6 and
Attachment I, is presented in Table 7-1 and Table 7-2. Use specific effects determinations are
provided in Table 7-3 and Table 7-4
Table 7-1. Effects Determination Summary for Effects of Methomyl on the SFGS, CCR,
BCB, VELB,
CTS, DS, CFS, and TG
Species
Effects
Determination
Basis for Determination
San Francisco
Garter Snake
(Thamnophis
sirtalis tetrataenia)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: dose and dietary-based RQs >0.1 for most assessed uses for small and
medium-sized reptiles (based on toxicity data for birds) consuming
arthropodsand herbivorous mammals
• Chronic: dietary-based RQs >1 for most assessed uses for small and medium-
sized reptiles (based on toxicity data for birds) consuming arthropods and
herbivorous mammals
• Granular (RQs 3.83-14.35) and scatter bait (RQ 5.55) uses exceed LOCs (based
on bird toxicity data)
• Bird (surrogates for reptiles) incident data indicate numerous deaths of various
species by baiting and unknown use patterns
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on bird toxicity data) ranges from 1 in
294,000 to 1 in 1 (at the default slope of 4.5)
Potential for Indirect Effects
• SFGS prey base is affected based on LOC exceedences; SFGS feeds on
invertebrates (freshwater invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86;
terrestrial invert RQs: 42.30-157.12), fish (freshwater fish RQs: acute: 0.13-
0.19; chronic: 1.99-2.67), small mammals (15g mammal RQs: acute: 1.02-7.25;
chronic: 1.80-58.01), reptiles and amphibians (bird RQs: acute: 0.12-27.97;
chronic: 1.44-3.34; 20g reptile: acute: 0.15 -23.29; chronic: 1.10-2.56)
• Granular(RQs 1.58-5.92)andscatterbait(RQ4.91)usesexceedLOCsfor
mammals (prey of SFGS)
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: honey bee, lab rat,
bird, freshwater invertebrate/fish) ranges from 1 in 5.37x 107 to 1 in 1
California Clapper
Rail (Rallus
longirostris
obsoletus)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: dose and dietary-based RQs >0.1 for most assessed uses for small and
medium-sized birds consuming arthropods and herbivorous mammals
• Chronic: dietary-based RQs >1 for most assessed uses for small and medium-
sized birds consuming arthropods and herbivorous mammals
• Granular (RQs 3.83-14.35) and scatter bait (RQ 5.55) uses exceed LOCs (based
on bird toxicity data)
• Bird incident data indicate numerous deaths of various species by baiting and
unknown use patterns
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on bird toxicity data) ranges from 1 in
294,000 to 1 in 1 (at the default slope of 4.5)
Potential for Indirect Effects
160
-------
Species
Effects
Determination
Basis for Determination
• CCR prey base is affected; CCR feeds on aquatic invertebrates, worms, spiders
(freshwater invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86; terrestrial invert
RQs: 42.30-157.12; estuarine/marine invert: acute: 0.13-3.26; chronic: 1.33-
17.75), dead fish (freshwater fish RQs: acute: 0.13-0.19; chronic: 1.99-2.67),
small mammals (15g mammal RQs: acute: 1.02-7.25; chronic: 1.80-58.01),
small birds and amphibians/frogs (bird RQs: acute: 0.12-27.97; chronic: 1.44-
3.34)
• Granular(RQs 1.58-5.92)andscatterbait(RQ4.91)usesexceedLOCsfor
mammals (prey of CCR)
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: honey bee, lab rat,
bird, freshwater invertebrate/fish, estuarine/marine invertebrate/fish) ranges
from 1 in 8.8 x 1024 to 1 in 1
Bay Checkerspot
Butterfly
(Euphydryas editha
bayensis)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Terrestrial invertebrate/ arthropod RQs > 0.05 (the interim terrestrial
invertebrate LOC) for all uses.
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on honey bee toxicity data) is 1 in 1
Potential for Indirect Effects
• Habitat modification (without terrestrial plant data risk is assumed);
furthermore, incident data on melons indicates damage to terrestrial plants after
ground application possibly due to a methomyl formulation
• The species critical habitat and/or occurrence sections overlap with the use
footprint
Valley Elderberry
Longhorn Beetle
(Desmocerus
californicus
dimorphus)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Terrestrial invertebrate/ arthropod RQs > 0.05 (the interim terrestrial
invertebrate LOC) for all uses.
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on honey bee toxicity data) is 1 in 1
Potential for Indirect Effects
• Habitat modification (without terrestrial plant data risk is assumed);
furthermore, incident data on melons indicates damage to terrestrial plants after
ground application possibly due to a methomyl formulation
• The species critical habitat and/or occurrence sections overlap with the use
footprint
California Tiger
Salamander
(Ambystoma
californiense)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: dose and dietary-based RQs >0.1 for most assessed uses for small and
medium-sized terrestrial-phase amphibians (based on bird toxicity data)
consuming arthropods and herbivorous mammals
• Chronic: dietary-based RQs >1 for most assessed uses for small and medium-
sized terrestrial-phase amphibians (based on bird toxicity data) consuming
arthropods and herbivorous mammals
• Granular (RQs 3.83-14.35) and scatter bait (RQ 5.55) uses exceed LOCs (based
on bird toxicity data)
161
-------
Species
Effects
Determination
Basis for Determination
• Bird (which are surrogates for terrestrial-phase amphibians) incident data
indicate numerous deaths of various species by baiting and unknown use
patterns
• Acute: RQs > 0.05 for most uses assessed including cabbage, turf, anise, alfalfa,
celery, and scatter bait, with respect to freshwater fish (which are a surrogate for
aquatic-phase amphibians)
• Chronic: RQs >1 for cabbage and scatter bait,, with respect to freshwater fish
(which are a surrogate for aquatic-phase amphibians)
• One large fish kill attributed to methomyl was reported
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on bird and freshwater fish toxicity data)
ranges from 1 in 5.37 x 107 to 1 in 1
Potential for Indirect Effects
• CTS prey base is affected; CTS feeds on algae, aquatic invertebrates/
zooplankton, freshwater snails, terrestrial invertebrates, worms (freshwater
invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86; terrestrial invert RQs:
42.30-157.12; estuarine/marine invert: acute: 0.13-3.26; chronic: 1.33-17.75),
fish (freshwater fish RQs: acute: 0.13-0.19; chronic: 1.99-2.67), small mammals
(15g mammal RQs: acute: 1.02-7.25; chronic: 1.80-58.01), amphibians/frogs
(bird RQs: acute: 0.12-27.97; chronic: 1.44-3.34; 20g amphibian: acute: 0.12-
16.44; chronic: 1.45-3.36)
• Granular(RQs 1.58-5.92) and scatter bait (RQ 4.91)uses exceed LOCs for
mammals (prey of CTS)
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: honey bee, lab rat,
bird, freshwater invertebrate/fish) ranges from 1 in 5.37 x 107 to 1 in 1
Delta Smelt
(Hypomesus
transpacificus)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: RQs > 0.05 for most uses assessed including cabbage, turf, anise, alfalfa,
celery, and scatter bait, with respect to freshwater fish; a single RQ value is at
the listed species LOC of 0.05 for the use on cabbage, with respect to
estuarine/marine fish
• Chronic: RQs >1 for cabbage and scatter bait, with respect to freshwater fish; all
chronic RQs are less than 1 for estuarine/marine fish
• One large fish kill was a reported incident
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on estuarine/marine and freshwater fish
toxicity data) ranges from 1 in 8.8 x 1024 to 1 in 877
Potential for Indirect Effects
• DS prey base is affected; adult DS feeds on planktonic copepods, cladocerans,
amphipods and insect larvae and juvenile DS feed on zooplankton (freshwater
invert RQs: acute: 0.50-12.38; chronic: 1.57-60.86; estuarine/marine invert:
acute: 0.13-3.26; chronic: 1.33-17.75); the DS larvae feed on phytoplankton
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates:estuarine/marine and
freshwater invertebrates) ranges from 1 in 29,900 to 1 in 1
California
May Affect,
Potential for Direct Effects
162
-------
Species
Effects
Determination
Basis for Determination
Freshwater Shrimp
(Syncaris pacifica)
Likely to
Adversely
Affect (LAA)
• With regard to estuarine/marine invertebrate data,
Acute: RQs > 0.05 for all assessed uses
Chronic: RQs >1 for all except one assessed use (i.e., sorghum)
• With regard to freshwater invertebrate data,
Acute: RQs > 0.05 for all assessed uses
Chronic: RQs >1 for all assessed uses
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on freshwater invertebrate toxicity data)
ranges from 1 in 6.69 to 1 in 1
Potential for Indirect Effects
• CFS prey base is affected; CFS feeds on zooplankton (freshwater invert RQs:
acute: 0.50-12.38; chronic: 1.57-60.86), detritus, algae, aquatic macrophyte
fragments, aufwuchs
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates: freshwater
invertebrates) ranges from 1 in 6.69 to 1 in 1
Tidewater Goby
(Eucyclogobius
new berryi)
May Affect,
Likely to
Adversely
Affect (LAA)
Potential for Direct Effects
• Acute: RQs > 0.05 for most uses assessed including cabbage, turf, anise, alfalfa,
celery, and scatter bait, with respect to freshwater fish; a single RQ value is at
the listed species LOC of 0.05 for the use on cabbage, with respect to
estuarine/marine fish
• Chronic: RQs >1 for cabbage and scatter bait, with respect to freshwater fish; all
chronic RQs are less than 1 for estuarine/marine fish
• One large fish kill was a reported incident
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on estuarine/marine and freshwater fish
toxicity data) ranges from 1 in 8.8 x 1024 to 1 in 877
Potential for Indirect Effects
• TG prey base is affected; adult TG feeds on small benthic invertebrates,
crustaceans, snails, mysids, aquatic insect larvae, juvenile TG feeds on
unicellular zooplankton (freshwater invert RQs: acute: 0.50-12.38; chronic:
1.57-60.86; estuarine/marine invert: acute: 0.13-3.26; chronic: 1.33-17.75) or
phytoplankton
• The species critical habitat and/or occurrence sections overlap with the use
footprint
• Probability of individual effect (based on prey surrogates:estuarine/marine and
freshwater invertebrates) ranges from 1 in 29,900 to 1 in 1
163
-------
Table 7-2. Effects Determination Summary for the Critical Habitat Impact Analysis
Designated
Critical Habitat
for:
Effects
Determination
Basis for Determination
Bay Checkerspot
Butterfly
(Euphydryas editha
bayensis)
Habitat
Modification
• Risk to terrestrial plants and thus BCB habitat (esp. dwarf plantain, purple owl's
clover, exserted paintbrush) was assumed. (RQs were not calculated given no
available terrestrial plant data.)
• Incident data on melons indicates damage to terrestrial plants after ground
application possibly due to a methomyl formulation
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
Valley Elderberry
Longhorn Beetle
(Desmocerus
californicus
dimorphus)
Habitat
Modification
• Risk to terrestrial plants and thus VELB habitat (esp. elderberry trees) was
assumed. (RQs were not calculated given no available terrestrial plant data.)
• Incident data on melons indicates damage to terrestrial plants after ground
application possibly due to a methomyl formulation
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
California Tiger
Salamander
(Ambystoma
californiense)
[Central CA, Santa
Barbara County]
Habitat
Modification
• Terrestrial arthropod RQs > 0.05 (the interim terrestrial invertebrate LOC) for
all uses.
• Risk to terrestrial plants and thus CTS habitat was assumed. (RQs were not
calculated given no available terrestrial plant data.)
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
• Mammal acute dose-based RQs >0.5 for all assessed uses; chronic: dose- and/or
dietary-based RQs>0.1 for all assessed uses.
• Bird (surrogate for terrestrial-phase amphibians) acute dose and dietary-based
RQs >0.1 (listed sp.) for most assessed uses for small and medium-sized birds
consuming short grass, arthropods/small insects, and herbivorous mammals;
chronic dietary-based RQs >1 for most assessed uses for small and medium-
sized birds consuming short grass, arthropods/small insects, and herbivorous
mammals
• Fish (surrogate for aquatic-phase amphibians) acute RQs > 0.05 for most uses
assessed including cabbage, turf, anise, alfalfa, celery, and scatter bait; chronic
RQs >1 for cabbage and scatter bait
• Freshwater invertebrate acute RQs >0.1 for all assessed uses; chronic RQs >1
for all assessed uses
Delta Smelt
(Hypomesus
transpacificus)
Habitat
Modification
• Risk to terrestrial plants and thus DS habitat was assumed. (RQs were not
calculated given no available terrestrial plant data.)
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
• Freshwater invertebrate acute RQs >0.1 for all assessed uses; chronic RQs >1
for all assessed uses
• Estuarine/marine invertebrate acute RQs >0.1 for all assessed uses; chronic
RQs >1 for all except one assessed use (i.e., sorghum)
Tidewater Goby
(Eucyclogobius
new berryi)
Habitat
Modification
• Risk to terrestrial plants and thus TG habitat was assumed. (RQs were not
calculated given no available terrestrial plant data.)
• Area of overlap between species habitat/critical habitat/ or occurrence sections
and the initial area of concern or use footprint
• Freshwater invertebrate acute RQs >0.1 for all assessed uses; chronic RQs >1
for all assessed uses
• Estuarine/marine invertebrate acute RQs >0.1 for all assessed uses; chronic
RQs >1 for all except one assessed use (i.e., sorghum)
164
-------
Table 7-3. Use Specific Summary of The Potential for Adverse Effects to Aquatic Taxa
Uses
Potential for Effects to Identified Taxa Found in the Aquatic Environment:
DS, TG
and
DS, TG, CTS-CC, SC,
CFWS and
Estuarinc/Marinc
Vascular
Non-
Estuarinc/Marinc
and SB DPS, and
Freshwater
Invcrtcbi
•atcs
Plants'
vascular
Vertcbr
itcs
Freshwater
Vertebrates2
Invertcb
rates
Plants'
Acute
Chronic
Acute
Chronic
Acute
Chronic
Acute
Chronic
Bulbs
No
No
No
No
Yes
Yes
Yes
Yes
No
No
/Onions
Cereal grains
No
No
No
No
Yes
Yes
Yes
Yes
No
No
/Corn
Cereal grains
No
No
No
No
Yes
Yes
Yes
Yes
No
No
/Corn
Cereal grains
No
No
No
No
Yes
Yes
Yes
No
No
No
(sp.
Sorghum)
Cole crops
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
/Cabbage
Grasses
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
/Turf
Herbs
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
/Anise/Mint
Leguminous
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
forage
(alfalfa)
Non-cole
No
No
Yes
No
Yes
Yes
Yes
Yes
No
No
leafy crops
/Celery
Scatter bait
No
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
Avocado
No
No
No
No
Yes
Yes
Yes
Yes
No
No
1 A yes in this column indicates a potential for direct effects to DS and TG and indirect effects to CCR, TG, and DS as a result of an effect to
estuarine/marine fish.
2 A yes in this column indicates a potential for direct effects to DS, TG and indirect effects to SFGS, CCR, TG, and DS. A yes also indicates a potential for
direct and indirect effects for the CTS-CC, CTS-SC, and CTS-SB as a result of an effect to freshwater fish.
3 A yes in this column indicates a potential for direct effects to the CFWS and indirect effects to the CFWS, SFGS, CCR, CTS-CC, CTS-SB, CTS-SC, TG,
and DS as a result of an effect to freshwater invertebrates.
4 A yes in this column indicates a potential for indirect effects to CCR, TG, and DS as a result of an effect to estuarine/marine invertebrates.
5 A yes in this column indicates a potential for indirect effects to SFGS, CCR, CTS-CC, CTS-SC, CTS-SB, TG, DS, and CFWS.
165
-------
Table 7-4. Use Specific Summary of The Potential for Adverse Effects to Terrestrial Taxa
Uses
Potential for Effects to Identified Taxa Found in the Terrestrial Environment:
Small
CCR and Small
CTS-CC, CTS-SC,
SFGS and
BCB, VELB, and
Dicots6
Monocots6
Mammals1
Birds2
CTS-SB and
Reptiles4
Invertebrates
Amphibians3
(Acute)5
Acute
Chronic
Acute
Chronic
Acute
Chronic
Acute
Chronic
Bulbs
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Onions
Cereal
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
grains /Corn
Cereal
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
grains /Corn
Cereal
Yes
Yes
Yes
No
Yes
No
Yes
No
Yes
Yes
Yes
grains (sp.
Sorghum)
Cole crops
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Cabbage
Grasses
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Turf
Herbs
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
/Anise/Mint
Leguminous
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
forage
(alfalfa)
Non-cole
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
leafy crops
/Celery
Avocado
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Granular
Yes
N/A
Yes
N/A
Yes
N/A
Yes
N/A
N/A
Yes
Yes
Scatter bait
Yes
N/A
Yes
N/A
Yes
N/A
Yes
N/A
N/A
Yes
Yes
1 A yes in this column indicates a potential for indirect effects to SFGS, CCR, CTS-CC, CTS-SC, CTS, and CTS-SB as a result of an effect to small
mammals.
2 A yes in this column indicates a potential for direct effects to CCR and indirect effects to the CCR, SFGS, CTS-CC, CTS-SC,and CTS-SB as a result of an
effect to small birds.
3 A yes in this column indicates a potential for direct effects to CTS-CC, CTS-SC, CTS-SB, and indirect effects to CTS-CC, CTS-SC, CTS-SB, SFGS, CCR
as a result of an effect to terrestrial-phase amphibians (for which birds serve as surrogate).
166
-------
4 A yes in this column indicates the potential for direct and indirect effects to SFGS and other reptiles as a result of an effect to reptiles (for which birds
serve as a surrogate).
5 A yes in this column indicates a potential for direct effect to BCB and VELB and indirect effects to SFGS, CCR, CTS-CC, CTS-SC, and CTS-SB as
aresult of an effect to terrestrial invertebrates.
6 A yes in this column indicates a potential for indirect effects to BCB, VELB, SFGS, CCR, CTS-CC, CTS-SC, CTS-SB, TG, DS, and CFWS. For the BCB
and VELB this is based on the listed species LOC because of the obligate relationship with terrestrial monocots and dicots. For other species, the LOC
exceedances are evaluated based on the LOC for non-listed species.
167
-------
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish and
Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct/indirect and adverse habitat
modification effects determinations, it is important to note that pesticide exposures and predicted
risks to the listed species and its resources {i.e., food and habitat) are not expected to be uniform
across the action area. In fact, given the assumptions of drift and downstream transport {i.e.,
attenuation with distance), pesticide exposure and associated risks to the species and its resources
are expected to decrease with increasing distance away from the treated field or site of
application. Evaluation of the implication of this non-uniform distribution of risk to the species
would require information and assessment techniques that are not currently available. Examples
of such information and methodology required for this type of analysis would include the
following:
• Enhanced information on the density and distribution of BCB, VELB, SFGS,
CCR, CTS, DS, CFS, and TG life stages within the action area and/or applicable
designated critical habitat. This information would allow for quantitative
extrapolation of the present risk assessment's predictions of individual effects to
the proportion of the population extant within geographical areas where those
effects are predicted. Furthermore, such population information would allow for
a more comprehensive evaluation of the significance of potential resource
impairment to individuals of the assessed species.
• Quantitative information on prey base requirements for the assessed species.
While existing information provides a preliminary picture of the types of food
sources utilized by the assessed species, it does not establish minimal
requirements to sustain healthy individuals at varying life stages. Such
information could be used to establish biologically relevant thresholds of effects
on the prey base, and ultimately establish geographical limits to those effects.
This information could be used together with the density data discussed above to
characterize the likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the pesticide.
Currently, methodologies are limited to predicting exposures and likely levels of
direct mortality, growth or reproductive impairment immediately following
exposure to the pesticide. The degree to which repeated exposure events and the
inherent demographic characteristics of the prey population play into the extent to
which prey resources may recover is not predictable. An enhanced understanding
of long-term prey responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and together
with the information described above, a more complete prediction of effects to
individual species and potential modification to critical habitat.
168
-------
8. References
A bibliography of ECOTOX references, identified by the letter E followed by a number, is
located in APPENDIX H
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Fellers, G. M., McConnell, L. L., Pratt, D., & Datta, S. 2004. Pesticides in Mountain Yellow-
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Jordan, T. E., Cornwell, J. C., Walter, R. B., & Anderson, J. T. 2008. Changes in phosphorus
biogeochemistry along an estuarine salinity gradient. Limnology and Oceanography
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King, R. B. 2002. Predicted and observed maximum prey size - snake size allometry. Functional
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LeNoir, J. S., McConnell, L. L., Fellers, G. M., Cahill, T. M., & Seiber, J. N. 1999. Summertime
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Means, J. C. 1995. Influence of salinity upon sediment-water partitioning of aromatic
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Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure
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Sparling, D. W., Fellers, G. M., & McConnell, L. L. 2001. Pesticides and amphibian population
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169
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USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide
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170
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9.
MRID List
161-1
Hydrolysis
MRID
Citation Reference
8844
2056782
2056783
Harvey, J. (1964?) Exposure of S-Methyl N-?(methylcarbamoyl)oxy|- thioacetimidate in
Sunlight, Water, and Soil. (Unpublished study received Dec 28, 1968 under 8F0671;
submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.; CDL091179-V)
73256
See 2056841
McCann, J.A. (1979) Study of the Degradation Rate of Aqueous Solu- tions of Methomyl.
(U.S. Environmental Protection Agency, Chemical and Biological Investigations Branch,
unpublished study)
131249
2056797
Friedman, P. (19??) Hydrolysis of 1-14C-methomyl: Document No. AMR- 109-83.
(Unpublished study received Oct 3, 1983 under 352-366; submitted by E.I. du Pont de
Nemours & Co., Inc., Wilmington, DE; CDL251424-B)
45473403
DER not
located
Pedersen, C. (2001) Hydrolysis of ?1-(Carbon 14)U Methomyl (DPX-X1179) Technical in pH
4, 5, and 6 Buffer Solutions at High Temperatures: Lab Project Number: DUPONT-5772.
Unpublished study prepared by E.I. du Pont de Nemours and Company. 34 p.
161-2
Photodegradation-water
MRID
Citation Reference
161885
2056803
2056804
Harvey, J. (19??) Photolysis of[1-Carbon 14] Methomyl: Document No. AMR-121-83.
Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc. 14 p.
43823305
DER not
located
Armbrust, K.; Reilly, D. (1995) Indirect Photodegredation of Methomyl in Aqueous Solutions:
Lab Project Number: AMR 2975-94. Unpublished study prepared by DuPont Agricultural
Products. 103 p.
22439
Harvey, J., Jr. (1949?) Decomposition of 14-C-Methomyl in Aerated River Water Exposed to
Sunlight. (Unpublished study received May 6, 1976 under 352-342; submitted by E.I. du Pont
de Nemours & Co., Wilmington, Del.; CDL224073-AJ)
38327
See 22439
Harvey, J., Jr. (19??) Decomposition of 14-C-Methomyl in Aerated River Water Exposed to
Sunlight. (Unpublished study received May 5, 1977 under 352-342; submitted by E.I. du Pont
de Nemours & Co., Wilmington, Del.; CDL229712-P)
161-3
Photodegradation-soil
MRID
Citation Reference
8568
2056779
2056780
Harvey, J., Jr. (1977) Degradation of 14C-Methomyl in Flanagan Silt Loam in Biometer
Flasks. (Unpublished study received Feb 28, 1977 under 352-342; prepared in cooperation
with Univ. of Delaware, Soil Testing Laboratory, submitted by E.I. du Pont de Nemours &
Co., Wilmington, Del.; CDL096026-B)
133184
Harvey, J. (19??) Stability of S-methyl N-?(methylcarbamoyl)oxy|- thioacetimidate in
Sunlight. (Unpublished study received Jun 29, 1977 under 352-342; submitted by E.I. du
Pont de Nemours & Co., Inc., Wilmington, DE; CDL:115397-A)
163745
2056835
2056805
2056806
2056807
Swanson, M. (1986) Photodegradation of [1-Carbon 14]Methomyl on Soil: Document No.
AMR-611-86. Unpublished study prepared by E.I. du Pont de Nemours and Co., Inc. 25 p.
171
-------
161885
2056803
2056804
Harvey, J. (19??) Photolysis of[1-Carbon 14] Methomyl: Document No. AMR-121-83.
Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc. 14 p.
161-4 Photodegradation-air
MRID
Citation Reference
8844
2056782
2056783
Harvey, J. (1964?) Exposure of S-Methyl N-?(methylcarbamoyl)oxy|- thioacetimidate in
Sunlight, Water, and Soil. (Unpublished study received Dec 28, 1968 under 8F0671;
submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.; CDL091179-V)
162-1 Aerobic soil metabolism
MRID
Citation Reference
8568
2056779
2056780
Harvey, J., Jr. (1977) Degradation of 14C-Methomyl in Flanagan Silt Loam in Biometer
Flasks. (Unpublished study received Feb 28, 1977 under 352-342; prepared in cooperation
with Univ. of Delaware, Soil Testing Laboratory, submitted by E.I. du Pont de Nemours &
Co., Wilmington, Del.; CDL096026-B)
8262
2056775
E.I. du Pont de Nemours and Company (1972) Summary of studies 093330-B through
093330-H. (Unpublished study received Mar 10, 1972 under 1F1021; CDL093330-A)
155756
5012954
2056800
2056820
Harvey, J.; Pease, H. (1973) Decomposition of methomyl in soil. J. Agr. Food Chem.
21 (5): 10-12.
43217901
2056830
Malik, N.; Zwick, T. (1990) Aerobic Metabolism of (1-carbon 14) Methomyl in Madera,
California Soil: Final Report: Lab Project Number: SC890027: AMR/1543/89. Unpublished
study prepared by Battelle Memorial Institute. 40 p.
43325402
Open lit
Smelt, J.; Dekker, A.; Leistra, M.; et al. (1983) Conversion of four carbamoyloximes in soil
samples from above and below the soil water table. Pesticide Science 14:173-181.
45473401
DER not
located
Shaw, D. (2001) (Carbon 14)-Methomyl: Rate of Degradation in Three Aerobic Soils: Lab
Project Number: DUPONT-5511: DPT/583: Unpublished study prepared by Huntingdon Life
Sciences Ltd. 76 p.
45473402
DER not
located
Shaw, D. (2001) (Carbon 14)-Methomyl Oxime: Rate of Degradation in Three Aerobic Soils:
Lab Project Number: DUPONT-5512: DPT/584. Unpublished study prepared by Huntingdon
Life Sciences Ltd. 60 p.
8567
2056778
2056777
Harvey, J., Jr. (1977) Decomposition of 14C-Methomyl in a Sandy Loam Soil in the
Greenhouse. (Unpublished study received Feb 28, 1977 under 352-342; prepared in
cooperation with Univ. of Delaware, Soil Testing Laboratory, submitted by E.I. du Pont de
Nemours & Co., Wilmington, Del.; CDL:096026-A)
162-2 Anaerobic soil metabolism
MRID
Citation Reference
43217902
2056832
Malik, N.; Zwick, T. (1990) Anaerobic Metabolism of (1-carbon 14) Methomyl in Madera,
California Soil: Final Report: Lab Project Number: SC890028: AMR/1544/89. Unpublished
study prepared by Battelle Memorial Institute. 45 p.
43325403
Open lit
Bromilow, R.; Briggs, G.; Williams, M. et al. (1986) The role of ferrous ions in the rapid
degradation of oxamyl, methomyl, and aldicarb in anaerobic soils. Pesticide Science
17:535-547.
73214
2056796
2056772
Harvey, J., Jr. (1977) Decomposition of A14IC-Methomyl in Flooded Anaerobic Soils.
(Unpublished study received Mar 27, 1979 under 352-342; submitted by E.I. du Pont de
172
-------
Nemours & Co., Wilmington, Del.; CDL237906-A)
162-4 Aerobic aquatic metab.
MRID
Citation Reference
43325401
2056831
Mayo, B. (1994) Degradability and Fate of (1-(carbon 14))Methomyl in Water/Sediment
Systems: Lab Project Number: DPT/295/932544: AMR/2590/92. Unpublished study prepared
by Huntingdon Research Centre, Ltd. 112 p.
163-1 Leach/adsorp/desorption
MRID
Citation Reference
8259
Registrant summary
E.I. du Pont de Nemours and Company (1971) Environmental Safety of Lannate Methomyl
Insecticide. Summary of studies 095024-B through 095024-K. (Unpublished study received
Apr 9, 1971 under 1F1021; CDL095024-A)
8844
2056782
2056783
Harvey, J. (1964?) Exposure of S-Methyl N-?(methylcarbamoyl)oxy|- thioacetimidate in
Sunlight, Water, and Soil. (Unpublished study received Dec 28, 1968 under 8F0671;
submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.; CDL091179-V)
9324
Or 155756
2056786
2056800
Harvey, J., Jr.; Pease, H.L. (1971?) Decomposition of Methomyl in Soil. (Unpublished study
received May 5, 1977 under 352-342; submitted by E.I. du Pont de Nemours & Co.,
Wilmington, Del.; CDL229711-D)
9325
2056787
2056788
Harvey, J., Jr. (19??) Decomposition of 14C-Methomyl in a High Organic Matter Soil in the
Laboratory. (Unpublished study re- ceived May 5, 1977 under 352-342; submitted by E.I. du
Pont de Nemours & Co., Wilmington, Del.; CDL:229711-E)
44306 or
161884
2056795
Khasawinah, A.M.; Holsing, G.C. (1976) UC 51762 Pesticide: Mobility on Soil Thin-Layer
Chromatograms: File No. 22754. (Unpub- lished study received Sep 10, 1980 under 264-
341; submitted by Union Carbide Agricultural Products Co., Ambler, Pa.; CDL: 099602-J)
133186
See 2056855 - not
reviewed- dupe of
8844
Harvey, J. (19??) Disappearance of the S-methyl N-?(methylcar- bamoyl)oxy|-
thioacetimidate from Soil in the Laboratory. (Un- published study received Jun 29, 1977
under 352-342; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL:
115397-C)
161884
2056802
2056770
2061311
Priester, T. (19??) Batch Equilibrium (Adsorption/desorption) and Soil Thin-layer
Chromatography Studies with Methomyl: Document No. AMR-174-84. Unpublished study
prepared by E.I. du Pont de Nemours and Co., Inc. 44 p.
42201605
Open lit
Karickhoff, S.; Morris, K. (1984) Sorption dynamics of hydrophobic pollutants in sediment
suspensions. Environmental Toxicology and Chemistry 4(1985):469-479.
133187
2056800
E.I. du Pont de Nemours & Co., Inc. (1964) Disappearance of S- methyl 1-C14-N-
?(methylcarbamoyl)oxy|-thioacetimidate in Three Soils in the Laboratory. (Unpublished study
received Jun 29, 1977 under 352-342; CDL115397-D)
5010422
2056818
164-1 Terrestrial field dissipation
MRID
Citation Reference
8844
2056782
2056783
Harvey, J. (1964?) Exposure of S-Methyl N-?(methylcarbamoyl)oxy|- thioacetimidate in
Sunlight, Water, and Soil. (Unpublished study received Dec 28, 1968 under 8F0671;
submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.; CDL091179-V)
9324
2056786
Harvey, J., Jr.; Pease, H.L. (1971?) Decomposition of Methomyl in Soil. (Unpublished study
173
-------
received May 5, 1977 under 352-342; submitted by E.I. du Pont de Nemours & Co.,
Wilmington, Del.; CDL229711-D)
05012954
2056820
Similar to above title
9326
2056789
2056791
E.I. du Pont de Nemours & Company (1971) Methomyl Decomposition in Muck Soil-A Field
Study. (Unpublished study received May 5, 1977 under 352-342; CDL229711-F)
51093
Letter
Pease, H.L. (1970) Letter sent to H.M. Baker dated Aug 19, 1970: Run-off studies with
Methomyl. (Unpublished study received Apr9, 1971 under 1F1021; submitted by E.I. du
Pont de Nemours & Co., Inc., Wilmington, Del.; CDL:095024-E)
51134
Letter
Harvey, J., Jr. (1976) Letter sent to D.C. Drake dated Jul 28, 1976 ?Methomyl in soil|.
(Unpublished study received May 5, 1977 under 352-342; submitted by E.I. du Pont de
Nemours & Co., Wilm- ington, Del.; CDL:229725-A)
92960
See 2056855 pg 6 -
study not reviewed -
no methomyl data
Burkhardt, C.C.; Fairchild, M.L. (1967) Bioassay of field-treated soils to determine bioactivity
and movement of insecticides. Journal of Economic Entomology 60(6):1602-1610.
(Also~ln~un- published submission received Sep 8, 1970 under unknown admin, no.;
submitted by American Cyanamid Co., Princeton, N.J.; CDL: 120350-C)
133188
2056799
Harvey, J. (1964) Disappearance of S-methyl 1-C14-N-?(methylcar-
bamoyl)oxy|thioacetimidate in Field Soil. (Unpublished study received Jun 29, 1977 under
352-342; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL115397-
E)
41623901
2056828
Kennedy, S. (1989) Field Soil Dissipation of Lannate L Insecticide: Lab Project Number:
ML88/0078/DUP. Unpublished study prepared by Morse laboratories, Inc. 84 p.
41623902
2056828
2056849
Kennedy, S. (1989) Field Soil Dissipation of Lannate L insecticide: Lab Project Number:
ML88/0078/DUP. Unpublished study prepared by Morse Laboratories, Inc. 41 p.
42288001
2056829
2056833
Kennedy, C. (1991) Field Soil Dissipation of Lannate L Insecticide-a 1991 Study: Lab
Project Number: AMR-1921-91: ML91-0242-DUP: 9100135. Unpublished study prepared by
Morse Labs and Harris Environmental Technologies, Inc. 64 p.
42345601
Same as 42288001
Kennedy, C. (1991) Field Soil Dissipation of Lannate L Insecticide-A 1991 Study: Lab
Project Number: AMR-1921-91: ML91-0242-DUP: 9100135. Unpublished study prepared by
Morse Laboratories, Inc. 64 p.
43217903
Supplement to
42288001
Kennedy, C. (1992) Field Soil Dissipation of Lannate L Insecticide: A 1991 Study:
Supplement: Lab Project Number: AMR/1921/91: ML91/02420DUP: 9100135. Unpublished
study prepared by Morse Lab., Inc.; Harris Environmental Technologies, Inc. 34 p.
8260
2056775
Pease, H.L. (1968) Methomyl Residue Analyses-Soils. (Unpublished study received Apr 9,
1971 under 1F1021; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.;
CDL095024-D)
8836
2056776
Harvey, J., Jr.; Buchanan, J.B. (1967?) Absence of S-Oxide and S, S Dioxide as Potential
Metabolites of Methomyl in Soil, Tobacco and Rats. (Unpublished study received Dec 28,
1968 under 8F0671; submitted by E.I. du Pont de Nemours & Co., Inc., Wil- mington, Del.;
CDL091179-F)
9325
2056787
Harvey, J., Jr. (19??) Decomposition of 14C-Methomyl in a High Organic Matter Soil in the
Laboratory. (Unpublished study re- ceived May 5, 1977 under 352-342; submitted by E.I. du
Pont de Nemours & Co., Wilmington, Del.; CDL:229711-E)
9326
2056791
E.I. du Pont de Nemours & Company (1971) Methomyl Decomposition in Muck Soil-A Field
Study. (Unpublished study received May 5, 1977 under 352-342; CDL229711-F)
164-2 Aquatic field dissipation
MRID
Citation Reference
43325401
2056831
Mayo, B. (1994) Degradability and Fate of (1-(carbon 14))Methomyl in Water/Sediment
Systems: Lab Project Number: DPT/295/932544: AMR/2590/92. Unpublished study prepared
by Huntingdon Research Centre, Ltd. 112 p.
174
-------
165-0 Accumulation Studies -
General
MRID
Citation Reference
73215
Not reviewed -see
2056855
E.I. du Pont de Nemours & Company (1979) Ecosystem Study. (Unpub- lished study
received Mar 27, 1979 under 352-342; CDL237906-B)
131250
Not reviewed -see
2056855
E.I. du Pont de Nemours & Co., Inc. (1979) Ecosystem Residue Study: Spruce/Fir Forest
and Cedar Swamp, Princeton, Maine, 1978. (Compilation; unpublished study received Oct 3,
1983 under 352- 366; CDL251424-D)
131251
2056798
E.I. du Pont de Nemours & Co., Inc. (1972) ?Residues: Lannate in Rainbow Trout (Salmo
gairdneri)|. (Compilation; unpublished study received Oct 3, 1983 under 352-366;
CDL251424-E)
Non Guideline
43568301
2084132 pg 13-
summary and
2057033
Russell, M.; Hiscock, A.; DeMartinis, J.; et al. (1995) A Small-Scale Prospective
Groundwater Monitoring Study for Methomyl: Final Report: Lab Project Number:
AMR/2311/92: ML92/0335/DUP: 423/04. Unpublished study prepared by Blasland, Bouck &
Lee, Inc. and other facilities. 619 p.
43599801
2057033
2056838
Russell, M.; Bergstrom, L. (1995) Modeling of the Results from a Small-Scale Prospective
Groundwater Study for Methomyl: Lab Project Number: 423.13: AMR 3405-95. Unpublished
study prepared by Blasland, Bouck & Lee, Inc. and DuPont Agricultural Products. 136 p.
43099601
2057025- interim
report
Rigsby, D.; Hiscock, A.; DeMartinis, J. et al. (1993) A Small-Scale Prospective Groundwater
Study for Methomyl: Lab Project Number: AMR 2311-92: 423-04. Unpublished study
prepared by Blasland & Bouck Engineers, P. C., in association with Hickey's Agri-Service,
Harris Laboratories, A&L Mid West Labs, and others. 483 p.
19947
2056794
Harvey, J., Jr. (1977?) Crop Rotation Study with 14C-Methomyl in the Greenhouse.
(Unpublished study received Jan 19, 1978 under 352-342; submitted by E.I. du Pont de
Nemours & Co., Wilmington, Del.; CDL:232720-A)
43708803
2057034
Armbrust, K. (1995) An Aquatic Residue Monitoring Study of Methomyl in and Around
Cucurbit Fields in California: Lab Project Numbers: AMR 2469-92: 92195: ML93-0445-DUP.
Unpublished study prepared by DuPont Agricultural Products; Morse Labs.; and ABC Labs.,
Inc. 432 p.
43708805
2057034
Ruehl, J. (1995) Dissipation of Methomyl on Plastic Ground Cover Following Multiple
Applications of Lannate L Insecticide to Tomato: Lab Project Number: AMR 2346-92.
Unpublished study prepared by DuPont Agricultural Products. 189 p.
43708804
2057034
Leva, S.; McKelvey, S. (1995) An Aquatic Residue Monitoring Study of Methomyl in and
Around Lettuce Fields in Florida: Lab Project Numbers: AMR 2512-92: ML93-0423-DUP:
112-333. Unpublished study prepared by DuPont Agricultural Products; Morse Labs.; and
Wildlife Int'l, Inc. 475 p.
43708801
2057034
Naylor, M.; Palmer, D.; Krueger, H. (1994) An Aquatic Residue Monitoring Study of
Methomyl in and Around Apple Orchards in Michigan: Lab Project Numbers: 112-292: AMR
2278-92: 91-4-3722. Unpublished study prepared by DuPont Agricultural Products; Morse
Labs.; and Wildlife Int'l. Ltd. 555 p.
43744401
2057034
Leva, S.; McKelvey, S. (1995) An Aquatic Residue Monitoring Study of Methomyl in and
Around a Sweet Corn Field in Georgia: Lab Project Number: AMR 2513-92: ML93-0424:
112-335. Unpublished study prepared by Morse Labs and Wildlife International Ltd. 395 p.
42271701
2056851
Eble, J.; Tomic, D. (1991) Foliar Half-life of Methomyl in Cotton Leaves: Lab Project Number:
AMR 1871-90: 907005. 0-1,2,3,4. Unpublished study prepared by Siemer Analytical
Laboratory 90 p.
7684
2056774
Pease, H.L. (1971 ?) Rapid Loss of Surface Residues of Methomyl on Treated Plants.
(Unpublished study received Sep 2, 1972 under 2F1247; submitted by E.I. du Pont de
Nemours & Co., Inc., Wil- mington, Del.; CDL091771-E)
8581
2056781
Peeples, J.L. (1977) Effect of Methomyl on Soil Microorganisms. (Unpublished study
received Mar 24, 1977 under 352-342; sub- mitted by E.I. du Pont de Nemours & Co.,
Wilmington, Del.; CDL: 228749-A)
175
-------
9327
2056790
Belasco, I.J. (19??) Effect of Methomyl on the Activity of Sewage Microorganisms.
(Unpublished study received May 5, 1977 under 352-342; submitted by E.I. du Pont de
Nemours & Co., Wilmington, Del.; CDL229711-G)
157991
2056801
Collins, R.; Kenney, F. (1986) Octanol-water Partition Coefficient of Nudrin Insecticide, Code
5-8-0-0: RIR-25-009-86. Unpublished study prepared by Shell Development Co. 9 p.
5008165
2056808
Citation not found in OPPIN
5008174
2056809
Citation not found in OPPIN
5008203
2056810
Citation not found in OPPIN
5008448
2056814
Citation not found in OPPIN
5009351
2056816
Citation not found in OPPIN
5018583
2056825
Citation not found in OPPIN
71 -1 Avian Single Dose Oral Toxicity
MRID
Citation Reference
7174
DER not
located
Holsing, G.C. (1969) Final Report: Acute Oral-Coturnix Quail: Project No. 201-242.
(Unpublished study received Jan 12, 1971 under 352-342; prepared by Hazleton
Laboratories, Inc., submit- ted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:
106655-D)
9184
E.I. du Pont de Nemours & Company (1972) Carbamic acid, Methyl ester with Oxime
Function of Thiolacetohydroxamic acid, S-Methyl ester (5% Granules): (INX-1179-211):
Haskell Laboratory Report No. 332-72. (Unpublished study received Jul 29, 1976 under 352-
342; CDL224800-H)
161886
2045980
Beavers, J. (1983) An Acute Oral Toxicity Study in the Bobwhite with H-15,000: Final Report:
Project No.: 112-142. Unpublished study prepared by Wildlife International Ltd. 15 p.
160000
2045963
Hudson, R.; Tucker, R.; Haegele, M. (1984) Handbook of toxicity of pesticides to wildlife:
Second edition. US Fish and Wildlife Service: Resource Publication 153. 91 p.
ACC 233993
2046011
Oral Tox to Starling. Chukar, Pidgeon and Japanese Quail, may be the same studies as
summarized in 160000 above
71-2 Avian Dietary Toxicity
MRID
Citation Reference
7016
2057859
Kinzer, D. (1977) Methomyl Fly Bait: Feed Preference Study for Ground Feeding Birds
(Bobwhite Quail): Report No. TR-442. (Un- published study received Apr 20, 1977 under
2724-274; submitted by Zoecon Industries, Inc., Dallas, Tex.; CDL:229392-B)
7819
2045953
Holsing, G.C. (1969) Final Report: Dietary Administration-Coturnix Quail: Project No. 201-
245. (Unpublished study received Sep 10, 1969 under 352-342; prepared by Hazleton
Laboratories, Inc., submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.;
CDL003008-A)
7820
2057845
thru
2057849
Busey, W.M. (1967) Final Report: Acute Aqueous Exposure-Goldfish, Bluegill, and Rainbow
Trout: Acute Dietary Administration-Pekin Ducks and Bobwhite Quail: Project No. 20-
175. (Unpublished study received Jul 23, 1968 under 352-342; prepared by Hazleton
Laboratories, Inc., submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.;
CDL002998-A)
9231
DER not
located
E.I. du Pont de Nemours & Company, Incorporated (1969) Methomyl Di- etary Administration
to Bobwhite Quail. (Unpublished study in- eluding letter dated Mar 25, 1965 from D.E. Rosen
to Harold G. Alford, received May 5, 1977 under 352-342; CDL229723-A)
176
-------
45299801
2082590
Medlicott, B.; Harris, T. (2000) Methomyl (DPX-X1179) Technical: Avian Acute Dietary
Toxicity Test with Northern Bobwhite (Colinus virginianus): Lab Project Number: DUPONT-
4378: 00022. Unpublished study prepared by Genesis Laboratories, Inc. 51 p.
45299802
2082591
Medlicott, B.; Harris, T. (2000) Methomyl (DPX-X1179) Technical: Avian Acute Dietary
Toxicity Test with the Mallard Duck (Anas platyrhynchos): Lab Project Number: DUPONT-
4379: 00023. Unpublished study prepared by Genesis Laboratories, Inc. 51 p.
00022923
2045966
Hill, E.F.; Heath, R.G.; Spann, J.W.; et al. (1975) Lethal Dietary Toxicities of Environmental
Pollutants to Birds: Special Scientific Report-Wildlife No. 191. (U.S. Dept. of the Interior,
Fish and Wildlife Service, Patuxent Wildlife Research Center; unpublished report)
ACC 232017
2017812
Methomyl/Tricosene Mixture tests with Bobwhite and Mallard
62189
Or 10330?
See
Page 4 of
2056939
Heath, R.G.; Spann, J.W.; Hill, E.F.; et al. (1972) Comparative Di- etary Toxicities of
Pesticides to Birds. By U.S. Fish and Wild- life Service, Patuxent Wildlife Research Center.
Washington, D.C.: USFWS. (Special scientific report-wildlife no. 152; Chemagro report no.
33423; available from: U.S. Government Printing Office, Washington, D.C.; 1971 O--460-
531; published study; CDL092011-V
71-3 Small and Wild mammal Data
TNM 015 and TNM
021
See Fed Lab
Data
Rat Dietary Studies at USEPA Beltsville Lab Test Numbers 015 and 021
0160000
2045963
Hudson, R.; Tucker, R.; Haegele, M. (1984) Handbook of toxicity of pesticides to wildlife:
Second edition. US Fish and Wildlife Service: Resource Publication 153. 91 p. Mule deer
- oral test
71-4 Avian Reproduction
MRID
Citation Reference
41898601
2045986
Beavers, J.; Hawrot, R.; Lynn, S.; et al. (1991) H-17940: A One- Generation Reproduction
Study with the Mallard (Anas platyrhyn- chos): Lab Project Number: 112-228. Unpublished
study prepared by Wildlife International Ltd. 166 p.
41898602
2045987
Beavers, J.; Hawrot, R.; Lynn, S.; et al. (1991) H-17940: A One- Generation Reproduction
Study with the Northern Bobwhite (Coli- nus virginianus): Lab Project No: 112/227.
Unpublished study prepared by Wildlife International Ltd. 168 p.
71-5 Simulated or Actual Field Testing
MRID
Citation Reference
7170
2045954
2057850
2057854
Wright, P.L. (1971) Report to E.I. du Pont de Nemours & Company: Field Wildlife Study with
Lannate Methomyl Insecticide in Quail and Rabbits: IBT No. J9836. (Unpublished study
received Jun 24, 1971 under 352-342; prepared by Industrial Bio-Test Labora- tories, Inc.,
submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL007040-A)
10331
Not a Tox
study it would
appear
Aftosmis, J.G. (1973) Carbamic acid, Methyl ester with Oxime Func- tion of
Thiolacetohydroxamine acid, S-Methyl ester (25% Active Ingredient): (LannateAR)l I
Methomyl Insecticide): Haskell Lab- oratory Report No. 354-73. (Unpublished study received
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48324
Summary- no
DER located
Pearce, P.A. (1970) Summary of Canadian Wildlife Service Supported Projects-1970 New
Brunswick Spruce Budworm Control Program: Re- port No. 28788. (Canada, Wildlife
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177
-------
CDL226511-P)
89148
No DER
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Hinkle, S.; Cameron, J.T. (1980) Final Report: Simulated Field Trial in Bobwhite Quail:
Project No. 20-531. (Hazleton Labora- tories, Inc.; unpublished study)
9183
Sherman, H.; Aftosmis, J.G. (1972) Effect of Methomyl-Treated Bait on Bobwhite Quail:
Haskell Laboratory Report No. 405-72. (Un- published study received Jul 29, 1976 under
352-342; submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 224800-F)
8829
2045956
Treated bait with BWQ
72-1 Acute Toxicity to Freshwater Fish
MRID
Citation Reference
69574
Open lit
El-Refai, A.; Fahmy, F.A.; Abdel-Lateef, M.F.A.; et al. (1976) Toxicity of three insecticides
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78426
DER not locatec
Smith, E.J. (1978) 96-hour LC50to Bluegill Sunfish: Haskell Labo- ratory Report No. 55-
78. (Unpublished study received Aug 28, 1981 under 1E2556; submitted by E.I. du Pont
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79175
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79176
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131251
Residue study
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135772
Range test
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5010817
2045981
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7820
2057845
thru
2057849
Busey, W.M. (1967) Final Report: Acute Aqueous Exposure-Goldfish, Bluegill, and
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40098001
2049421
Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Inter- pretation and Data Base
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9007
2045957
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9061
2045958
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9132 or 38324
Summary
E.I. du Pont de Nemours & Company (1968?) LCI50A Values (p.p.b.). (Unpublished study
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178
-------
9133 or 38325
In citations see
2056855
Sleight, B.H., III (1971) Research Report: Continuous Exposure of Rainbow Trout
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9226
2045961
McCain, J.C. (1971) Final Report: Acute Fish Toxicity Study-Static Freshwater: Project
No. 201-254. (Unpublished study received May 5, 1977 under 352-342; prepared by
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20053
DER not located
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(Unpublished study received Apr 21, 1978 under 270-133; prepared by EG&G, Bionomics,
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20054
DER no located
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60949
2045969
TN 1114 in Fed
Lab data in SAN
McCann, J.A. (1977) Methomyl (Lannate): Toxicity to Bluegill (?~Lepomis macrochirus~?):
Test # 1114. (U.S. Environmental Protection Agency, Animal Biology Laboratory,
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60950
2045970
TN 1034 in Fed
Lab data in SAN
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73256
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73793
2045972
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77271
Same as 73793
see Fed Lab
Data in SAN
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77272
2045973
TN 427 in Fed
Lab Data in SAN
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77273
2045974
TN 351 in Fed
Lab data
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9226
2045961
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19978
2046011
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ACC 106658
TN 257 see Fed
Lab Data in SAN
TN 257 USEPA Beltsville Lab MRID not located
72-2 Acute Toxicity to Freshwater Invertebrates
MRID
Citation Reference
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38326
2057857
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72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study
MRID
Citation Reference
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2045977
Muska, C.; Brittelli, M. (1982) Chronic Toxicity of Methomyl to Daphnia magna: Haskell
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-------
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131254
2045979
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72-5 Life cycle fish
MRID
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72-7 Simulated or Actual Field
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MRID
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Citation Reference
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-------
43679310
Open lit
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Atkins, E.L.; Greywood-Hale, E.A.; Macdonald, R.L.; et al. (1974) Effect of Pesticides on
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40602
Johansen, C.; Mayer, D.; Baird, C. (1973) Bee Research Investiga-tions, 1973. (Incomplete,
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79174
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preliminary
test
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(Translation; un- published study, including German text, received Jun 25, 1981 under
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2029428
Sakamoto, S.S.; Johansen, C.A. (1971) Toxicity of Orthene to Honey Bees (?~Apis
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ACC 224800
2057851
Honeybee acute contact with formulation -Possibly MRID 9180?
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2029430
Open lit
Johansen, C.A. (1972) Toxicity of field-weathered insecticide residues to four kinds of bees.
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9129
2029420
Johansen, C.; Retan, A.H. (1973) Insecticide Toxicity to Alfalfa- Pollinating Bees. Rev.
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2057851
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2029443
141-2 Non Target Beneficial Insect Toxicity
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Open lit
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2029433
Open lit
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Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Inter- pretation and Data Base for
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Aquatic insect larvae
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2029431
Open lit
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2029446
Open lit
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5010807
2029451
Open lit
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142-3 Simulated or Actual Field Testing
MRID
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Asquith, D.; Colburn, R. (1973) 1973 Laboratory Evaluation of Vari- ous Pesticides
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9041
DER not
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Efficacy
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9042
2029415
Burkhardt, C.C.; Puterka, G.J.; Michels, G.J., Jr. (1977) Impact of Insecticides on Beneficial
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14038
Efficacy
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5008360
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summary pg 1
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Summary see
2029469
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9023
2029407
Welch, A. (1978) Numbers of Selected Beneficial Insects Found, be- fore and at Various
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2045960
2057852
Sherman, H.; Aftosmis, J.G. (1972) Effect of Methomyl-Treated Bait on Bobwhite Quail:
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Pg 5 of
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ES-VII-
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Drake, D.C.; Woodward, D.F. (1978) Acute Toxicity Studies: Cut- Throat Trout and Stonefly
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Johansen, C.A. (1971) How To Reduce Poisoning of Bees from Pesti- cides. Pullman,
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same study?
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50459
E.I. du Pont de Nemours & Company (1971) Environmental and Wildlife Information Relating
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Check ENS
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5009819
2029446
pg 2
Open lit
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Open lit
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43823301
2057034
Registrant
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43823303
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43961101
Open lit
See small
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44041401
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AMR 3945-96: DUPONT AMR 3945-96. Unpublished study prepared by Waterborne
Environmental, Inc. (WEI). 75 p.
44969301
2045991
Wachter, S. (1999) Methomyl Technical: Acute Toxicity to Earthworm, Eisenia foetida
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47090703
Giddings, J.; Kemman, R. (2007) Methomyl: Summary of Ecotoxicity Data from Ecotox, The
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47090705
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47164600
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186
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