Risks of Pendimethalin Use to Federally
Threatened California Red-legged Frog
(Rana aurora draytonii)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
June 16,2009
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Primary Authors:
Michael Davy, Agronomist
William P. Eckel, Ph.D., Physical Scientist
Secondary Review:
Jean Holmes, DVM,MPH
Risk Assessment Process Leader
Final Review:
Tom Bailey, Ph.D., Branch Chief
Environmental Risk Assessment Branch 2
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Table of Contents
1.0 Executive Summary 10
2.0 Problem Formulation 15
2.1 Purpose 15
2.2 Scope 17
2.3 Previous Assessments 18
2.4 Stressor Source and Distribution 19
2.4.1 Environmental Fate Assessment 19
2.4.2 Mechanism of Action 21
2.4.3 Use Characterization 22
2.5 Assessed Species 28
2.5.1 Distribution 28
2.5.2 Reproduction 31
2.5.3 Diet 31
2.5.4 Habitat 32
2.6 Designated Critical Habitat 33
2.7 Action Area 35
2.8 Assessment Endpoints and Measures of Ecological Effect 39
2.8.1 Assessment Endpoints for the CRLF 39
2.8.2 Assessment Endpoints for Designated Critical Habitat 41
2.9 Conceptual Model 43
2.9.1 Risk Hypotheses 43
2.9.2 Diagram 43
2.10 Analysis Plan 45
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model 46
2.10.1.1 Measures of Exposure 46
2.10.1.2 Measures of Effect 48
2.10.1.3 Integration of Exposure and Effects 49
3.0 Exposure Assessment 49
3.1 Label Application Rates and Intervals 50
3.2 Aquatic Exposure Assessment 51
3.2.1 Modeling Approach 51
3.2.2 Model Inputs 52
3.2.3 Results 53
3.2.4 Existing Monitoring Data 54
3.2.4.1USGSNAWQA Surface Water Data 54
3.2.4.2 USGS NAWQA Groundwater Data 54
3.2.4.3 California Department of Pesticide Regulati on (CPR) Data 55
3.2.4.4 Atmospheric Monitoring Data 56
3.2.4.5 Spray Drift Buffer and Downstream Dilution Analysis for Action Area. 56
3.3 Terrestrial Animal Exposure Assessment 57
3.4 Terrestrial Plant Exposure Assessment 59
4.0 Effects Assessment 60
4.1 Evaluation of Aquatic Ecotoxicity Studies 62
4.1.1 Toxicity to Freshwater Fish 63
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4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies 63
4.1.1.2 Freshwater Fish: Chronic Exposure (Early Life Stage and Reproduction)
Studies 64
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open Literature
Information 64
4.1.1.4 Aquatic-phase Amphibian: Acute and Chronic Studies 64
4.1.2 Toxicity to Freshwater Invertebrates 65
4.1.2.1 Freshwater Invertebrates: Acute Exposure (Mortality) Studies 65
4.1.2.2 Freshwater Invertebrates: Chronic Exposure (Reproduction) Studies 65
4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Open Literature Data.... 66
4.1.3 Toxicity to Aquatic Plants 66
4.1.3.1 Aquatic Plants: Laboratory Data 66
4.1.3.2 Freshwater Field Studies 67
4.2 Toxicity of Pendimethalin to Terrestrial Organisms 67
4.2.1 Toxicity to Birds 68
4.2.1.1 Birds: Acute Exposure (Mortality) Studies 69
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies 69
4.2.1.3 Birds: Open Literature Studies 69
4.2.2 Toxicity to Mammals 69
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies 70
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies 70
4.2.2.3 Mammals: Open Literature Studies 70
4.2.3 Toxicity to Terrestrial Invertebrates 70
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies 70
4.2.3.2 Terrestrial Invertebrates: Open Literature Studies 71
4.2.4 Toxicity to Terrestrial Plants 71
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern 72
4.4 Incident Database Review 73
4.4.1 Terrestrial Incidents 73
4.4.2 Plant Incidents 74
4.4.3 Aquatic Incidents 74
5.0 Risk Characterization 76
5.1 Risk Estimation 76
5.1.1 Exposures in the Aquatic Habitat 76
5.1.1.1 Direct Effects to Aquatic-Phase CRLF 76
5.1.1.2 Indirect Effects to Aquatic-Phase CRLF via Reduction in Prey (non-
vascular aquatic plants, aquatic invertebrates, fish, and frogs) 78
5.1.1.3 Indirect Effects to CRLF via Reduction in Habitat and/or Primary
Productivity (Freshwater Aquatic Plants) 80
5.1.2 Exposures in the Terrestrial Habitat 80
5.1.2.1 Direct Effects to Terrestrial-phase CRLF 80
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in Prey
(terrestrial invertebrates, mammals, and frogs) 83
5.1.2.3 Indirect Effects to CRLF via Reduction in Terrestrial Plant Community
(Riparian and Upland Habitat) 86
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5.1.3 Primary Constituent Elements of Designated Critical Habitat 88
5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-Breeding
Habitat) 88
5.1.3.2 Terrestrial-Phase (Upland Habitat and Dispersal Habitat) 89
5.2 Risk Description 90
5.2.1 Direct Effects 93
5.2.1.1 Aquatic-Phase CRLF 93
5.2.1.2 Terrestrial-Phase CRLF 94
5.2.2 Indirect Effects (via Reductions in Prey Base) 98
5.2.2.1 Algae (non-vascular plants) 98
5.2.2.2 Aquatic Invertebrates 99
5.2.2.3 Fish and Aquatic-phase Frogs 100
5.2.2.4 Terrestrial Invertebrates 100
5.2.2.5 Mammals 101
5.2.2.6 Terrestrial-phase Amphibians 102
5.2.3 Indirect Effects (via Habitat Effects) 102
5.2.3.1 Aquatic Plants (Vascular and Non-vascular) 102
5.2.3.2 Terrestrial Plants 103
5.2.4 Effects to Designated Critical Habitat 104
5.2.4.1 Aquatic-Phase PCEs 104
5.2.4.2 Terrestrial-Phase PCEs 105
5.2.5 Spatial Extent of Potential Effects 106
5.2.5.1 Spray Drift 106
5.2.5.2 Downstream Dilution Analysis 108
5.2.5.3 Overlap between CRLF habitat and Spatial Extent of Potential Effects 108
6.0 Uncertainties Ill
6.1 Exposure Assessment Uncertainties Ill
6.1.1 Maximum Use Scenario Ill
6.1.2 Aquatic Exposure Modeling of Pendimethalin Ill
6.1.3 Usage Uncertainties 113
6.1.4 Terrestrial Exposure Modeling of Pendimethalin 113
6.1.5 Spray Drift Modeling 114
6.1.6 Volatility 115
6.1.7 Bioaccumulation 115
6.2 Effects Assessment Uncertainties 116
6.2.1 Age Class and Sensitivity of Effects Thresholds 116
6.2.2 Use of Surrogate Species Effects Data 116
6.2.3 Sublethal Effects 116
6.2.4 Location of Wildlife Species 117
7.0 Risk Conclusions 117
8.0 References 121
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List of Tables
Table 1-1 Effects Determination Summary for Pendimethalin Use and the CRLF 13
Table 1-2 Effects Determination Summary for Pendimethalin Use and CRLF Critical
Habitat Impact Analysis 13
Table 2-1 Summary of Pendimethalin Environmental Fate Properties 20
Table 2-2 Pendimethalin Uses Assessed for the CRLF 22
Table 2-3 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 1994 to 2006 for Currently
Registered Pendimethalin Uses: By County 26
Table 2-4 Assessment Endpoints and Measures of Ecological Effects 40
Table 2-5 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitata 42
Table 3-1 Pendimethalin Uses, Scenarios, and Application Information for the CRLF
risk assessment1 50
Table 3-2 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Pendimethalin Endangered Species Assessment for the
CRLF1 52
Table 3-3 Aquatic EECs (ug/L) for Pendimethalin Uses in California 53
Table 3-4 Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
Pendimethalin with T-REX 57
Table 3-5 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Pendimethalin 58
Table 3-6 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Terrestrial Invertebrate Prey Items 58
Table 3-7 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semi-
aquatic Areas Exposed to Pendimethalin via Runoff and Drift 59
Table 4-1 Freshwater Aquatic Toxicity Profile for Pendimethalin 62
Table 4-2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates 63
Table 4-3. Terrestrial Toxicity Profile for Pendimethalin 67
Table 4-4 Categories of Acute Toxicity for Avian and Mammalian Studies 68
Table 4-5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data 71
Table 5-1 Summary of Direct Effect RQsa for the Aquatic-phase CRLF 77
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Table 5-2 Summary of RQs Used to Estimate Indirect Effects to the CRLF via Effects to
Non-Vascular Aquatic Plants a (diet of CRLF in tadpole life stage and habitat
of aquatic-phase CRLF) 78
Table 5-3 Summary of Acute and Chronic RQsa Used to Estimate Indirect Effects to
the CRLF via Direct Effects on Aquatic Invertebrates as Dietary Food
Items (prey of CRLF juveniles and adults in aquatic habitats) 79
Table 5-4 Summary of RQs Used to Estimate Indirect Effects to the CRLF via Effects to
Vascular Aquatic Plants (habitat of aquatic-phase CRLF)a 80
Table 5-5 Summary of Acute RQs* Used to Estimate Direct Effects to the Terrestrial-
phase CRLF 81
Table 5-6 Summary of Chronic RQs* Used to Estimate Direct Effects to the Terrestrial-
phase CRLF 82
Table 5-7 Summary of RQs Used to Estimate Indirect Effects to the Terrestrial-phase
CRLF via Direct Effects on Terrestrial Invertebrates as Dietary Food Items 83
Table 5-8 Summary of Acute and Chronic RQs* Used to Estimate Indirect Effects to the
Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary
Food Items 85
Table 5-9 RQs* for Monocots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Pendimethalin via Runoff and Drift 86
Table 5-10 RQs* for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Pendimethalin via Runoff and Drift 87
Table 5-11 Risk Estimation Summary for Pendimethalin - Direct and Indirect Effects to
CRLF 90
Table 5-12 Risk Estimation Summary for Pendimethalin - PCEs of Designated Critical
Habitat for the CRLF 91
Table 5-13 Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based Risk
Quotients (1 Ibs a.i./acre, 1 application) 96
Table 5-14 Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based Risk
Quotients (1.24 Ibs a.i./acre, 1 application) 96
Table 5-15. Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based Risk
Quotients (1.425 Ibs a.i./acre, 1 application) 96
Table 5-16. Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based Risk
Quotients (6 Ibs a.i./Acre, 1 application) 96
Table 5-17 RQ Comparisons among Weight Class and Applications Rates for CRLF
Consuming Small Herbivore Mammal That Recently Consumed
Contaminated Short Grass 97
Table 5-18. Range of Risk Quotients for Non-Target Terrestrial Plants from
Pendimethalin Usage 103
Table 5-19 Summary of AgDrift Predicted Terrestrial Spray Drift Distances 107
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Table 5-20 Summary of AgDrift Predicted Aquatic Spray Drift Distances 107
Table 7-1 Effects Determination Summary for Pendimethalin Use and the CRLF 118
Table 7-2 Effects Determination Summary for Pendimethalin Use and CRLF Critical
Habitat Impact Analysis 119
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List of Figures
Figure 2.1 Pendimethalin Use in Total Pounds per County 24
Figure 2.2 Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF 30
Figure 2.3 CRLF Reproductive Events by Month 31
Figure 2.4. Initial area of concern, or "footprint" of potential use, for Pendimethalin.... 37
Figure 2.5 Conceptual Model for Pesticide Effects on Terrestrial Phase of the CRLF... 44
Figure 2.6 Conceptual Model for Pesticide Effects on Aquatic Phase of the CRLF 45
Appendices
Appendix A Ecological Effects Data
Appendix B Multi-ai Product Analysis Pendimethalin
Appendix C RQ Method and LOCs
Appendix D CRLF Spatial Summary Pendimethalin
Appendix E T-REX Output
Appendix F TerrPlant Output
Appendix G ECOTOX Bibliography
Appendix H Accepted ECOTOX Data Table
Appendix I FLED Effects Pendimethalin
Appendix J PRZM-EXAMS Output
Appendix K KABAM Model Output
Attachment I. Status and Life History of the California Red-legged Frog
Attachment II. Baseline Status and Cumulative Effects for the California Red-legged
Frog
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1.0 Executive Summary
The purpose of this assessment is to evaluate potential direct and indirect effects on the
California red-legged frog (Rana aurora draytonii) (CRLF) arising from FIFRA
regulatory actions regarding use of pendimethalin on agricultural and non-agricultural
sites. In addition, this assessment evaluates whether these actions can be expected to
result in effects to the species' designated critical habitat. 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 and procedures outlined in the Agency's Overview Document
(U.S. EPA, 2004).
The CRLF was listed as a threatened species by USFWS in 1996. The species is endemic
to California and Baja California (Mexico) and inhabits both coastal and interior
mountain ranges. A total of 243 streams or drainages are believed to be currently
occupied by the species, with the greatest numbers in Monterey, San Luis Obispo, and
Santa Barbara counties (USFWS, 1996) in California.
The following uses are considered as part of the federal action evaluated in this
assessment: alfalfa, lupine for seed, almond, beech nut, brazil nut, butternut, cashew,
chestnut, chinquapin, filbert (hazelnut), hickory nut, macadamia nut (bushnut), mayhaw
(hawthorn), pecan, pistachio, walnut (English/black), calamondin, citron (citrus), citrus,
citrus hybrids other than tangelo, grapefruit, kumquat, lemon, lime, orange, pummelo
(shaddock), tangelo, tangerines, Brassica (head and stem) vegetables, broccoli, broccoli
(Chinese), brussels sprouts, cabbage, cabbage (Chinese), cauliflower, kohlrabi, mustard
cabbage (gai choy - pak-choi), corn (field, pop, sweet), sunflower, cotton, forest trees (all
species), Christmas tree plantations, apple, apricot, cherry, crabapple, fig, loquat,
nectarine, peach, pear, pepino (melon pear), plum, plum (Japanese), pomegranate, prune,
quince, small fruits, garlic, leek, grapes, eggplant, olive, onion (green, scallions, spring),
shallot, potato (white/Irish), nonagricultural rights-of-way/fencerows/hedgerows,
artichoke, asparagus, beans (dry, succulent/lima/snap), carrot (including tops), garbanzos
(including chick peas), legume vegetables, lentils, peanuts, peas (dry, early dwarf,
pigeon, southern/cowpea), pepper, strawberry, tomato, groundcherry (strawberry tomato,
tomatillo), airports/landing fields, commercial/industrial lawns, golf course turf,
industrial areas (outdoor), ornamental and/or shade trees, ornamental ground cover,
ornamental herbaceous plants, ornamental lawns and turf, ornamental nonflowering
plants, ornamental sod farm (turf), ornamental woody shrubs and vines, recreation area
lawns, residential lawns, shelterbelt plantings, sorghum, wheat, and rice.
Ground and aerial spray applications of pendimethalin (including some forms of
chemigation) will potentially result in spray drift onto non-target plants, soil, and water
adjacent to a treated field. Pendimethalin is expected to be persistent in the terrestrial
environment and under the right conditions, may accumulate in the soil with repeated
applications resulting in the potential for pendimethalin to reach the aquatic environment
on suspended soil in runoff water. Laboratory dissipation studies in soil under aerobic
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conditions, demonstrate a half-life of approximately 72-172 days, and field dissipation
studies in the Midwest similarly had half-lives that ranged from 84-147 days. However,
field dissipation studies in Louisiana and Mississippi had half-lives of <20 days,
demonstrating that pendimethalin can be relatively short-lived under some environmental
conditions. Field half-lives less than 20 days may be due to volatilization, which has a
measured half-life of 12.5 days in moist soil. In laboratory studies, pendimethalin can
photodegrade in water with a half-life of approximately 42 days. However, in the
environment, pendimethalin will not be available for photodegradation because the
pendimethalin in water will tend to sorb to soil or sediment particles as indicated by Koc's
which range from 13000-29400 ml/g. Thus, pendimethalin is considered hardly mobile
according to FAO classification.
Pendimethalin may accumulate in fish based on submitted data. Pendimethalin residues
accumulated in bluegill sunfish exposed to 3 ppb of pendimethalin, with BCFs of 1400X
for edible, 5800X for nonedible, and 5100X for whole fish. Depuration was rapid, with
87- 91% of the 14C-residues eliminated from the fish tissues by 14 days of depuration.
The major terminal degradates in terrestrial environments include several compounds
formed at insignificant levels (<10 % of applied). Therefore, no degradates are included
in the definition of the chemical stressor.
Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF and its
prey to pendimethalin are assessed separately for the two habitats. Tier-II aquatic
exposure models are used to estimate high-end exposures of pendimethalin in aquatic
habitats resulting from runoff and spray drift from different uses. Peak model-estimated
environmental concentrations resulting from different pendimethalin uses range from
1.74 ppb (rights-of-way/impervious) to 16.6 |ig/L (forestry) and 48 ppb (rice paddies).
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. The
maximum concentration of pendimethalin reported by NAWQA for California surface
waters with agricultural watersheds is 0.68 |ig/L. This value is approximately 71 times
less than the maximum model-estimated environmental concentration. The maximum
concentration of pendimethalin reported by the California Department of Pesticide
Regulation surface water database (3.5 |ig/L) is roughly 14 times lower than the highest
peak model-estimated environmental concentration.
To estimate pendimethalin exposures to the terrestrial-phase CRLF, and its potential prey
resulting from uses involving pendimethalin applications, the T-REX model is used for
foliar uses. AgDRIFT and AGDISP models are also used to estimate deposition of
pendimethalin on terrestrial and aquatic habitats from aerial and ground spray drift. The
TerrPlant model is used to estimate pendimethalin exposures to terrestrial-phase CRLF
habitat, including plants inhabiting semi-aquatic and dry areas, resulting from uses
involving foliar pendimethalin applications. The T-HERPS model is used to allow for
further characterization of dietary exposures of terrestrial-phase CRLFs relative to birds.
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The effects determination assessment endpoints for the CRLF include direct toxic effects
on the survival, reproduction, and growth of the CRLF itself, as well as indirect effects,
such as reduction of the prey base or modification of its habitat. Direct effects to the
CRLF in the aquatic habitat are based on toxicity information for freshwater fish, which
are generally used as a surrogate for aquatic-phase amphibians. In the terrestrial habitat,
direct effects are based on toxicity information for birds, which are used as a surrogate
for terrestrial-phase amphibians. Given that the CRLF's prey items and designated
critical habitat requirements in the aquatic habitat are dependant on the availability of
freshwater aquatic invertebrates and aquatic plants, toxicity information for these
taxonomic groups is also discussed. In the terrestrial habitat, indirect effects due to
depletion of prey are assessed by considering effects to terrestrial insects, small terrestrial
mammals, and frogs. Indirect effects due to modification of the terrestrial habitat are
characterized by available data for terrestrial monocots and dicots.
Pendimethalin is stable to most of the environmental degradation processes measured,
meaning there is little production of degradates. Thus, no degradates were considered in
the assessment, which was based on parent pendimethalin alone. There was monitoring
data for one possible degradate, 4-hydroxypendamethalin, in the NAWQA data. It was
not detected (less than 0.143 ppb) in 61 ground water samples, and 8 surface water
samples, all taken from the San Joaquin-Tulare Basin.
Risk quotients (RQs) are derived as quantitative estimates of potential high-end risk.
Acute and chronic RQs are compared to the Agency's levels of concern (LOCs) to
identify instances where pendimethalin use within the action area has the potential to
adversely affect the CRLF and its designated critical habitat via direct toxicity or
indirectly based on direct effects to its food supply (i.e., freshwater invertebrates, algae,
fish, frogs, terrestrial invertebrates, and mammals) or habitat (i.e., aquatic plants and
terrestrial upland and riparian vegetation). When RQs for each particular type of effect
are below LOCs, the pesticide is determined to have "no effect" on the CRLF. Where
RQs exceed LOCs, a potential to cause adverse effects is identified, leading to a
conclusion of "may affect." If a determination is made that use of pendimethalin use
within the action area "may affect" the CRLF and its designated critical habitat,
additional information is considered to refine the potential for exposure and effects, and
the best available information is used to distinguish those actions that "may affect, but are
not likely to adversely affect" (NLAA) from those actions that are "likely to adversely
affect" (LAA) the CRLF.
Based on the best available information, the Agency makes a May Affect and Likely to
Adversely Affect determination for the CRLF from the use of pendimethalin.
Additionally, the Agency has determined that there is the potential for effects to CRLF
designated critical habitat from the use of the chemical. There is potential for direct and
indirect effects to the aquatic-phase and terrestrial-phase CRLF from the use of
pendimethalin. Potential effects to the habitat of the aquatic and terrestrial phase CRLF
has been determined due to effects to terrestrial and aquatic non-target plants. A summary
of the risk conclusions and effects determinations for the CRLF and its critical habitat is
presented in Table 1-1 and Table 1-2. Further information on the results of the effects
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determination is included as part of the Risk Description in Section 5.2. Given the LAA
determination for the CRLF and potential effects to designated critical habitat, a
description of the baseline status and cumulative effects for the CRLF is provided in
Attachment 2
Table 1-1 Effects Determination Summary for Pendimethalin Use and the CRLF
Assessment
Endpoint
Survival, growth,
and/or reproduction
of CRLF
individuals
Effects
Determination 1
LAA1
Basis for Determination
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Acute LOCs were exceeded for fish or aquatic-phase amphibians
Terrestrial-phase (Juveniles and Adults):
Acute and chronic LOCs were exceeded for birds. The available toxicity
data suggest that amphibians are less sensitive than birds to pendimethalin,
and considering factors such as lower food intake of terrestrial phase
amphibians relative to birds reduces EECs and RQs, but does not reduce
RQs to levels that are below LOCs. Likely to adversely affect CRLF.
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity:
LOG is exceeded only for non-vascular aquatic plants. RQs are below LOG
for freshwater invertebrates (chronic and acute effects) and fish or frogs
(chronic and acute effects). Pendimethalin could potentially impact
terrestrial and aquatic plants to an extent that could result in indirect effects
to the CRLF or effects to critical habitat.
Terrestrial prey items, riparian habitat:
Chronic LOG is exceeded for mammal and birds (surrogate for frog).
Pendimethalin is practically non-toxic to honeybees with no mortalities observed
in testing. LOG is exceeded for terrestrial invertebrates. Uncertainty in toxicity
to insects from EEC that is above highest bee concentration tested does not
preclude potential risk. Pendimethalin may adversely affect insects. Acute
LOCs were not exceeded for insectivorous amphibians using the T-HERPS
model at the highest rate of application.
LOG is exceeded for non-target terrestrial plants and thereby critical habitat
could be affected as a result of these potential impacts.
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely
affect (LAA)
Table 1-2 Effects Determination Summary for Pendimethalin Use and CRLF
Critical Habitat Impact Analysis
Assessment
Endpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
Habitat effects
Effects to riparian vegetation (terrestrial plants) and aquatic non-vascular and
vascular plants result in LOG exceedances. These effects may indirectly affect
the CRLF via reduction in food supply, changes in available cover, physical
parameters of the waterbody (e.g. increase temperature or turbidity)
LOG is exceeded for effects to non-vascular aquatic plants, freshwater
invertebrates (chronic and acute effects) and fish or frogs (chronic and acute
effects).
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Modification of
terrestrial-phase
PCE
Effects to riparian vegetation (terrestrial plants) result in LOG exceedances.
Effects may result in changes in community composition or relative abundance
of riparian plant species, possibly altering terrestrial - phase CRLF habitat.
Chronic LOG is exceeded for mammal. Although there are NLAA
determinations for other prey items, small mammals constitute up to half of the
food intake for CRLF and reduction in small mammalian populations may be
significant.
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 effects determinations, it is important to note that pesticide exposures and
predicted risks to the 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 CRLF life stages
within specific recovery units and/or designated critical habitat within the
action area. 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 species.
• Quantitative information on prey base requirements for individual aquatic-
and terrestrial-phase frogs. While existing information provides a
preliminary picture of the types of food sources utilized by the frog, 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
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determination of the magnitude and duration of resource impairment, and
together with the information described above, a more complete prediction
of effects to individual frogs and potential modification to critical habitat.
2.0 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 (U.S. EPA 1998), the
Services' Endangered Species Consultation Handbook (USFWS/NMFS 1998) and is
consistent with procedures and methodology outlined in the Overview Document (U.S.
EPA 2004) and reviewed by the U.S. Fish and Wildlife Service and National Marine
Fisheries Service (USFWS/NMFS 2004).
2.1 Purpose
The purpose of this endangered species assessment is to evaluate potential direct and
indirect effects on individuals of the federally threatened California red-legged frog
(Rana aurora draytonii) (CRLF) arising from FIFRA regulatory actions regarding use of
pendimethalin on alfalfa, lupine for seed, almond, beech nut, brazil nut, butternut,
cashew, chestnut, chinquapin, filbert (hazelnut), hickory nut, macadamia nut (bushnut),
mayhaw (hawthorn), pecan, pistachio, walnut (English/black), calamondin, citron
(citrus), citrus, citrus hybrids other than tangelo, grapefruit, kumquat, lemon, lime,
orange, pummelo (shaddock), tangelo, tangerines, Brassica (head and stem) vegetables,
broccoli, broccoli (Chinese), brussels sprouts, cabbage, cabbage (Chinese), cauliflower,
kohlrabi, mustard cabbage (gai choy - pak-choi), corn (field, pop, sweet), sunflower,
cotton, forest trees (all species), Christmas tree plantations, apple, apricot, cherry,
crabapple, fig, loquat, nectarine, peach, pear, pepino (melon pear), plum, plum
(Japanese), pomegranate, prune, quince, small fruits, garlic, leek, grapes, eggplant, olive,
onion (green, scallions, spring), shallot, potato (white/Irish), nonagricultural rights-of-
way/fencerows/hedgerows, artichoke, asparagus, beans (dry, succulent/lima/snap), carrot
(including tops), garbanzos (including chick peas), legume vegetables, lentils, peanuts,
peas (dry, early dwarf, pigeon, southern/cowpea), pepper, strawberry, tomato,
groundcherry (strawberry tomato, tomatillo), airports/landing fields,
commercial/industrial lawns, golf course turf, industrial areas (outdoor), ornamental
and/or shade trees, ornamental ground cover, ornamental herbaceous plants, ornamental
lawns and turf, ornamental nonflowering plants, ornamental sod farm (turf), ornamental
woody shrubs and vines, recreation area lawns, residential lawns, shelterbelt plantings,
sorghum, wheat, and rice. In addition, this assessment evaluates whether use on these
sites is expected to result in effects to the species' designated critical habitat. This
ecological risk assessment has been prepared consistent with a settlement agreement in
the case Center for Biological Diversity (CBD) vs. EPA et al. (Case No. 02-1580-
JSW(JL)) entered in Federal District Court for the Northern District of California on
October 20, 2006.
15
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In this assessment, direct and indirect effects to the CRLF and potential effects to its
designated critical habitat are evaluated in accordance with the methods described in the
Agency's Overview Document (U.S. EPA 2004). Screening level methods include use of
standard models such as PRZM-EXAMS, T-REX, TerrPlant, AgDRIFT, and AGDISP,
all of which are described at length in the Overview Document. Additional refinements
include an analysis of the usage data, consideration of available monitoring data, a spatial
analysis, and use of the T-HERPS model. Use of such information is consistent with the
methodology described in the Overview Document (U.S. EPA 2004), which specifies that
"the assessment process may, on a case-by-case basis, incorporate additional methods,
models, and lines of evidence that EPA finds technically appropriate for risk management
objectives" (Section V, page 31 of U.S. EPA 2004).
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 pendimethalin is based on an action area. The action area is the area
directly or indirectly affected by the federal action. It is acknowledged that the action
area for a national-level FIFRA regulatory decision associated with a use of
pendimethalin 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 CRLF and its designated critical habitat within the state of California. As
part of the "effects determination," one of the following three conclusions will be reached
regarding the potential use of pendimethalin in accordance with current labels:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Designated critical habitat identifies specific areas that have the physical and biological
features, (known as primary constituent elements or PCEs) essential to the conservation
of the listed species. The PCEs for CRLF are aquatic and upland areas where suitable
breeding and non-breeding aquatic habitat is located, interspersed with upland foraging
and dispersal habitat.
If the results of initial screening-level assessment methods show no direct or indirect
effects (no LOG exceedances) upon individual CRLF or upon the PCEs of the species'
designated critical habitat, a "no effect" determination is made for use of pendimethalin
as it relates to this species and its designated critical habitat. If, however, potential direct
or indirect effects to individual CRLF are anticipated or effects may impact the PCEs of
the CRLF's designated critical habitat, a preliminary "may affect" determination is made
for the FIFRA regulatory action regarding pendimethalin.
If a determination is made that use of pendimethalin within the action area(s) associated
with the CRLF "may affect" this species or its designated critical habitat, additional
information is considered to refine the potential for exposure and for effects to the CRLF
16
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and other taxonomic groups upon which these species depend (e.g., aquatic and terrestrial
vertebrates and invertebrates, aquatic plants, riparian vegetation, etc.). Additional
information, including spatial analysis (to determine the geographical proximity of CRLF
habitat and pendimethalin use sites) and further evaluation of the potential impact of
pendimethalin on the PCEs is also used to determine whether effects to designated
critical habitat may occur. Based on the refined information, the Agency uses the best
available information to distinguish those actions that "may affect, but are not likely to
adversely affect" from those actions that "may affect and are likely to adversely affect"
the CRLF or affect the PCEs of its designated critical habitat. This information is
presented as part of the Risk Characterization in Section 5 of this document.
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 pendimethalin is expected to directly impact living organisms within the action
area (defined in Section 2.7), critical habitat analysis for pendimethalin is limited in a
practical sense to those PCEs of critical habitat that are biological or that can be
reasonably linked to biologically mediated processes (i.e., the biological resource
requirements for the listed species associated with the critical habitat or important
physical aspects of the habitat that may be reasonably influenced through biological
processes). Activities that may modify critical habitat are those that alter the PCEs and
appreciably diminish the value of the habitat. Evaluation of actions related to use of
pendimethalin that may alter the PCEs of the CRLF's critical habitat form the basis of the
critical habitat impact analysis. Actions that may affect the CRLF's designated critical
habitat have been identified by the Services and are discussed further in Section 2.6.
2.2 Scope
As described above, the herbicide pendimethalin has a wide variety of outdoor uses,
including both in agricultural and non-agricultural settings.
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), acceptable methods of application, approved
use sites, and any restrictions on how applications may be conducted. Thus, the use of
pendimethalin in accordance with the approved product labels for California is "the
action" relevant to this ecological risk assessment.
Although current registrations of pendimethalin allow for use nationwide, this ecological
risk assessment and effects determination addresses currently registered uses of
pendimethalin in portions of the action area that are reasonably assumed to be
biologically relevant to the CRLF and its designated critical habitat. Further discussion
of the action area for the CRLF and its critical habitat is provided in Section 2.7.
Degradates were not considered, as pendimethalin is relatively stable to all degradation
processes measured. The half-lives used as model inputs reflect this stability and lack of
17
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degradate production. Sixty-nine measurements of one potential degradate (4-
hydroxypendamthalin) in California waters produced no detections.
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).
Pendimethalin has registered products that contain multiple active ingredients. Analysis
of the available open literature and acute oral mammalian LD50 data for multiple active
ingredient products relative to the single active ingredient is provided in Appendix B.
The results of this analysis show that an assessment based on the toxicity of the single
active ingredient of pendimethalin is appropriate.
2.3 Previous Assessments
A Reregi strati on Eligibility Decision (RED) ecological risk chapter was completed in
1997. The RED concluded that pendimethalin would not represent a high acute risk to
birds or a high acute or chronic risk to mammals. The chronic risk to birds could not be
determined because avian reproduction studies had not been submitted. Chronic risk
Levels of Concern (LOCs) for fish were exceeded by a small margin. But it was
presumed that overall, pendimethalin did not represent a high risk to aquatic animals and
plants, including estuarine organisms. The use of pendimethalin may adversely affect
endangered species of terrestrial and semi-aquatic plants, aquatic plants and invertebrates
including mollusks, fish, and birds (specifically grazers). The risk to nontarget terrestrial
and semi-aquatic plants was expected to be moderate.
On December 1, 2004, EPA initiated consultation with the National Marine Fisheries
Service (NMFS) requesting concurrence in a determination relative to potential effects
from pendimethalin uses to Pacific salmon and steelhead. In the assessment supporting
that consultation, EPA concluded that pendimethalin has moderate to high laboratory
toxicity to fish and aquatic invertebrates and somewhat less toxicity on aquatic plants.
OPP determined that any effects of concern would be directly on listed salmon and
steelhead and would vary for different uses and species. It was further determined that
pendimethalin would not affect salmon and steelhead food or cover, nor adversely
modify their Critical Habitat from any of the registered uses except a single aerial use -
aerial application to corn. OPP's conclusions relative to 26 listed Pacific salmon and
steelhead was that uses of pendimethalin were not likely to adversely affect four species
and would have no effect on twenty-two species reviewed. A response to this request is
anticipated from NMFS in 2012.
18
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2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Assessment
The environmental fate properties of pendimethalin indicate that it is persistent, with
half-lives in relevant compartments of 172 days (soil) and 208 to 330 days (anaerobic and
aerobic aquatic systems). Only the aqueous photolysis half-life is relatively short (42
days) but photolysis may not occur because of the strong tendency of pendimethalin to
sorb to sediment (log Kow = 5.18, average Koc = 17,040 mL/g O.C.). Pendimethalin
may be bioaccumulative in aquatic organisms. A whole-body bioconcentration factor
(BCF) of 5100 from a 35-day exposure was measured in bluegill sunfish. BCFs were
lower in catfish (about 1600) and negligible in guppy. The most rapid dissipation process
for pendimethalin appears to be volatilization from moist soil (half-life about 12.5 days).
Thus, pendimethalin may be transported away from the site of application before it
degrades, making atmospheric transport a potentially important exposure mechanism.
However, EPISuite v4.0 (http://www.epa.gov/oppt/exposure/pubs/episuite.htm), an
EPA-sponsored environmental fate estimation program, estimates of atmospheric half-
life (4.2 hours due to reaction with hydroxyl radical, AOPWin program) and sorption to
airborne particles (1 to 7%, AERO Win program) indicate that long-range transport may
not be a concern. The tendency of pendimethalin to partition to sediment, and its long
half-life there, make transport by movement of sediment in flowing water systems a
concern.
Table 2.1 lists the environmental fate properties of pendimethalin, along with the major
and minor degradates detected in the submitted environmental fate and transport studies.
19
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Table 2-1 Summary of Pendimethalin Environmental Fate Properties
Study
Hydrolysis
Direct Aqueous
Photolysis
Soil Photolysis
Aerobic Soil
Metabolism
Anaerobic Soil
Metabolism
Anaerobic
Aquatic
Metabolism
Aerobic Aquatic
Metabolism
Kd-ads / Kd.des
(mL/g)
TV" / "K"
-"-oc- ads ' -"-oc-des
(mL/g)
Laboratory
Volatility
Fish
Bioaccumulation
Value (units)
Stable
Dark corrected, continuous irradiation
half-life 21 days; 12-hour light/dark
half-life 42 days.
16.5-day half-life
Stable
172 day (Deviation from IPG, as
explained in 1997 RED)
Range 42-1322 days
Stable
98% parent at 60 days
208-day half-life
(upper 90th %ile confidence bound on
mean)
330 days (single value)
30 - 854 (U.S. soils)
61 - 285 (Japanese soils)
17,040 mL/gO.C. (U.S. soils)
(avg of 5 values, 13000 - 29400)
7011- 43863 mL/g o.c. (Japanese
soils)
Volatilization half-life 12.5 days from
moist loam soil
Bioconcentration factor BCF = 5 100,
35-day exposure
Major Degradates
Minor Degradates
None
37 minor, unidentified
degradates
2,6-dinitro-3,4-
dimethylaniline (9.3% of
applied)
None
2, 6-dinitro3,4-xylidine
4-[(l -ethylpropyl) aminoJ-2-
methyl-3, 5-dinitrobenzyl
alcohol
4-[(l -ethylpropyl) aminoJ-2-
methyl3, 5-dinitro-o-toluic
acid
2, 6-dinitro3,4-xylidine
4-[(l -ethylpropyl) aminoJ-2-
methyl-3, 5-dinitrobenzyl
alcohol
4-[(l -ethylpropyl) aminoJ-2-
methyl3, 5-dinitro-o-toluic
acid
None
None
n.a.
None measured
4-[(l -ethylpropyl) aminoJ-2-
methyl-3, 5-dinitrobenzyl
alcohol (3.1%)
MRID#
00106777
00153763
43808201
00153764
40185104
40185105
40813501
43154702
47385201
00153765
43041901
00153766
00156726
00158235
Study Status
acceptable
acceptable
acceptable
acceptable
acceptable
acceptable
acceptable
acceptable
acceptable
20
-------
Study
Terrestrial Field
Dissipation
Aquatic Field
Dissipation
Value (units)
34-day half-life in California almond
orchard, sandy loam soil. No leaching
below 6 inches.
No data
Major Degradates
Minor Degradates
MRID#
41722504
Study Status
acceptable
2.4.2 Environmental Transport Assessment
Potential transport mechanisms include pesticide surface water runoff, spray drift, and
secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or
more distant ecosystems. Surface water runoff and spray drift are expected to be the
major routes of exposure for pendimethalin.
A number of studies have documented atmospheric transport and re-deposition of
pesticides from the Central Valley to the Sierra Nevada Mountains (Fellers et al., 2004,
Sparling et al., 2001, LeNoir et al., 1999, and McConnell et al., 1998). Prevailing winds
blow across the Central Valley eastward to the Sierra Nevada Mountains, transporting
airborne industrial and agricultural pollutants into the Sierra Nevada ecosystems (Fellers
et al., 2004, LeNoir et al., 1999, and McConnell et al., 1998). Several sections of critical
habitat for the CLRF are located east of the Central Valley. The magnitude of transport
via secondary drift depends on the pendimethalin's ability to be mobilized into air and its
eventual removal through wet and dry deposition of gases/particles and photochemical
reactions in the atmosphere. Therefore, physicochemical properties of pendimethalin that
describe its potential to enter the air from water or soil (e.g., Henry's Law constant and
vapor pressure), pesticide use data, modeled estimated concentrations in water and air,
and available air monitoring data from the Central Valley and the Sierra Nevadas are
considered in evaluating the potential for atmospheric transport of pendimethalin to
locations where it could impact the CRLF.
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 and/or AGDISP)
are used to determine potential exposures to aquatic and terrestrial organisms via spray
drift.
2.4.2
Mechanism of Action
Pendimethalin is a selective herbicide registered for control of broadleaf weeds and
grassy weed species on a variety of agricultural crops, turf, and ornamentals.
Pendimethalin disrupts the process of mitosis in the growth of shoots and roots. It acts as
a microtubule disrupter by inhibiting cell division and cell elongation in plants, and is
generally applied early in the growing season. Absorption of the herbicide takes place at
the roots and the shoots. Very little translocation occurs from the site of intake.
21
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2.4.3
Use Characterization
Pendimethalin is applied as a liquid spray formulation. Pendimethalin can be applied
either by aerial equipment or using ground equipment to a variety of row crops, orchard
crops, vineyards, sod, seed, and to rice. It can be broadcasted by air or ground, and be
banded as a directed spray or applied by irrigation equipment in various crops. It can
also be left on the soil surface or incorporated.
Approximately 27 million pounds of pendimethalin were applied in 2002 according to the
National Center for Food and Agriculture, and the majority was applied to soybeans
(39.6%), cotton (20.22 %), and corn (19.4 %) (Fig. 2.1). Together, soybeans, cotton, and
corn account for 79 % of the applied pendimethalin nationwide. This existing use
information is provided as a basis for considering background exposures from existing
use.
Table 2.2 presents the uses and corresponding application rates and methods of
application considered in this assessment.
Table 2-2 Pendimethalin Uses Assessed for the CRLF
Use
walnut (english/black), tangerines, tangelo, small fruits, pummelo
(shaddock), pomegranate, pistachio, pecan, orange, macadamia
nut (bushnut), lime, lemon, kumquat, hickory nut, grapefruit,
filbert (hazelnut), citrus hybrids other than tangelo, citron
(citrus), chinquapin, chestnut, cashew, calamondin, butternut,
brazil nut, beech nut, almond, grapes.
Prune, plum, pear, peach, olive, nectarine, fig, cherry, apricot,
apple, ornamental and/or shade trees, nonagricultural rights-of-
way, fencerows, hedgerows, mulch, industrial areas (outdoor),
forest trees (all or unspecified), Christmas tree plantations,
recreation area lawns, loquat, shelterbelt plantings, quince,
mayhaw, crabapple, alfalfa
Asparagus, artichoke
golf course turf, airports/landing fields
residential lawns
Shallot, onion, com (sweet, pop, field)
Carrot
Sunflower
Tomato, tomatillo, tobacco, sorghum, potato (white/Irish), lupine
(grain), garlic, garbanzos (including chick peas) beans, succulent
(snap or lima) beans, dried-type beans, cotton, cowpea (southern
pea, black-eyed bean),
Max. Single
Appl. Rate
(Ib ai/A)
6.0
4.0
3.9
3.5
3.0
2.0
1.9
1.73
1.485
Max.
Number of
Application
per Year
1
1
1
1
1
1
1
1
1
Application
Method
ground
ground, aerial
ground, aerial
ground, aerial
ground, aerial
ground, aerial
ground, aerial
ground, aerial
ground, aerial
22
-------
Use
Wheat, pepper, pepino (melon pear), groundcherry, eggplant
Strawberry
Legume vegetables
Rice, mustard cabbage (gai choy, pak-choi), kohlrabi,
cauliflower, cabbage (Chinese), cabbage, brussels sprouts,
broccoli (Chinese), broccoli, Brassica (head and stem) vegetables
Max. Single
Appl. Rate
(Ib ai/A)
1.425
1.485
1.24
1.0
Max.
Number of
Application
per Year
1
2
1
1
Application
Method
ground, aerial
ground, aerial
ground, aerial
ground, aerial
23
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The figure below summarizes pendimethalin use nationwide in 2002. Pendimethalin is
used primarily on soybeans, cotton, corn, sugarcane, peanuts, rice, sunflower, potatoes,
tobacco, and onions. Most use is apparently outside of California. Non-agricultural
uses, which predominate in California, are not represented on this map. The map was
downloaded from a U.S. Geological Survey (USGS), National Water Quality Assessment
Program (NAWQA) website.
PENDIMETHALIN - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds par square mile of agricultural
land in county)
O no estimated use
D 0.001 to 0.113
D 0.114 to 0.746
D 0.747 to 2.459
D 2.46 to 5.677
• >= 5.678
Crops
soybeans
cotton
corn
sugarcane
peanuts
rice
sunflower seed
potatoes
tobacco
dry onions
Total
pounds applied
5128074
2619139
2510653
819146
426157
245003
230464
227553
162376
111265
Percent
national use
39.59
20.22
19.38
6.32
3.29
1.89
1.78
1.76
1.25
0.86
http://water.usgs. gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=ml629
Figure 2.1 Pendimethalin Use in Total Pounds per County
Analysis of labeled use information is the critical first step in evaluating the federal
action. The current label for pendimethalin represents 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.
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis
of both national- and county-level usage information (Kaul and Jones, 2006) using state-
24
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level usage data obtained from USDA-NASS1, 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) database2. 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 pendimethalin by county in this
California-specific assessment were generated using CDPR PUR data. Eight years
(1999-2006) of usage data were included in this analysis. Data from CDPR PUR were
obtained for every pesticide application made on every use site at the section level
(approximately one square mile) of the public land survey system. 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 five years. The units
of area treated are also provided where available.
Some uses reported in the CDPR PUR database may be different than those considered in
the assessment. 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 other reported use, such as may be seen in the CDPR PUR database,
represent either historic uses that have been canceled, 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.
Table 2.3 below gives the total number of pounds of pendimethalin used in California
counties from 1994 to 1998 and 1999 to 2006. The figures represent the sum of the
average number of pounds used in each year of the two periods, as reported in the
Pesticide use Reporting database (PUR). Summaries of the data were provided by OPP's
Biological and Economic Analysis Division (BEAD). The data indicate that the largest
amounts were used in Kings, Fresno, and Kern counties, all of which exceeded 150,000
pounds. Thirteen counties (Santa Barbara through Glenn) showed use of between 10,000
and 100,000 pounds during the period. Twenty-two counties (Contra Costa through El
Dorado) had usage of between 1,000 and 10,000 pounds. Overall, 54 of 58 California
counties had reported usage of pendimethalin, indicating that use of the compound is
geographically widespread. This is a strong line of evidence that the CRLF is potentially
exposed to pendimethalin.
1 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.usda.gov/nass/pubs/estindxl.htm#agchem.
2 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.
25
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Table 2-3 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 1994 to 2006 for Currently Registered
Pendimethalin Uses: By County
County
KINGS
FRESNO
KERN
SANTA BARBARA
TULARE
LOS ANGELES
IMPERIAL
STANISLAUS
RIVERSIDE
MERCED
SAN JOAQUIN
MADERA
BUTTE
SANTA CLARA
GLENN
CONTRA COSTA
ORANGE
SACRAMENTO
SAN DIEGO
SOLANO
SONOMA
ALAMEDA
YOLO
PLACER
SAN BERNARDINO
MONTEREY
COLUSA
SAN LUIS OBISPO
SUTTER
TEHAMA
YUBA
SAN MATEO
VENTURA
SAN BENITO
CALAVERAS
SHASTA
EL DORADO
NAPA
LAKE
MARIN
TUOLUMNE
LAS SEN
MODOC
1994-
1998
99690
74212
90122
820
16738
4671
15584
9128
15279
10480
6801
7660
5758
5717
4865
3222
5272
5571
6588
2211
2897
1810
1322
1309
2339
2328
1149
1761
1109
1148
371
798
824
809
609
593
466
418
367
563
239
169
84
1999-
2006
95429
77816
59505
83486
33549
41639
24149
24623
14997
9747
11203
10086
5974
5838
6202
6083
3634
3030
1854
4261
3546
3288
3640
3167
2073
2052
2985
1610
1857
1212
1368
854
809
753
665
642
611
411
261
46
361
309
389
Total
195119
152028
149627
84306
50287
46310
39733
33751
30276
20227
18004
17746
11732
11555
11067
9305
8906
8601
8442
6472
6443
5098
4962
4476
4412
4380
4134
3371
2966
2360
1739
1652
1633
1562
1274
1235
1077
829
628
609
600
478
473
26
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MENDOCINO
AMADOR
SISKIYOU
NEVADA
SANTA CRUZ
SAN FRANCISCO
MONO
HUMBOLDT
INYO
MARIPOSA
TRINITY
158
272
138
307
148
85
149
53
49
24
0
293
145
250
74
131
116
39
19
11
4
1
451
417
388
381
279
201
188
72
60
28
1
Table 2.3b below shows the number of pounds of pendimethalin applied by crop and use
site, during the periods 1994 to 1998, and 1999 to 2006. The figures are aggregated
across counties, and are ranked by total numbers of pounds applied in the entire period.
Only crops or use sites with at least 1,000 pounds usage are shown in the table.
Cotton is the major use, with nearly two million pounds applied from 1994 to 2006. Six
use sites (landscape, almond, rights-of-way, garlic, onions, pistachio, and alfalfa) each
totaled over 100,000 pounds applied. A further 18 uses (nursery through nectarine) each
had from 10,000 to 100,000 pounds of usage.
It is notable that non-agricultural uses (landscape and rights-of-way) are among the
highest uses of pendimethalin. Based on the county rankings, it is concluded that these
uses represent the greatest part of the usage in urban counties.
Table 2.3b. Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 1994 to 2006 for Currently Registered
Pendimethalin Uses: By Crop/Use Site
CROP/USE SITE
COTTON
LANDSCAPE MAINTENANCE
ALMOND
RIGHTS OF WAY
GARLIC
ONION, DRY & GREEN
PISTACHIO
ALFALFA
NURSERY - ALL
GRAPE, WINE
POTATO
GRAPE
CORN, HUMAN CONSUMPTION
BEAN, DRIED
UNCULTIVATED AG / nonag
WALNUT
1994-1998 Ibs
1198354
213421
124150
40510
100657
49023
28480
3327
43897
39711
41086
34005
29757
14529
8370
17340
1999-2006 Ibs
787909
224903
88858
146505
70532
93909
93363
99865
44167
45880
35707
25160
28782
38200
42817
29352
TOTAL Ibs
1986263
438324
213008
187015
171189
142932
121843
103192
88064
85591
76793
59165
58539
52729
51187
46692
27
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CORN (FORAGE - FODDER)
SUNFLOWER
ORANGE
PEACH
RICE
BEAN, UNSPECIFIED
SOIL FUMIGATION/PREPLANT
PRUNE
BEAN, SUCCULENT
NECTARINE
WHEAT
PLUM
CHERRY
SAFFLOWER
STRUCTURAL PEST CONTROL
TOMATO
CELERY
LEMON
APPLE
TURF/SOD
WATER(INDUSTRIAL)
SUGARCANE
TANGERINE
SORGHUM/MILO
13629
8257
2317
3572
1237
11229
6852
12351
2817
2529
7703
594
0
180
2204
796
3354
817
2369
1624
0
72
174
892
22894
12354
17988
13534
15149
4922
8718
3213
7853
8053
1143
6954
6913
3853
1685
2863
15
2288
594
1013
1429
1307
1178
281
36523
20611
20305
17106
16386
16151
15570
15564
10670
10582
8846
7548
6913
4033
3889
3659
3369
3105
2963
2637
1429
1379
1352
1173
2.5 Assessed Species
The CRLF was federally listed as a threatened species by USFWS effective June 24,
1996 (USFWS 1996). It is one of two subspecies of the red-legged frog and is the largest
native frog in the western United States (USFWS 2002). A brief summary of information
regarding CRLF distribution, reproduction, diet, and habitat requirements is provided in
Sections 2.5.1 through 2.5.4, respectively. Further information on the status, distribution,
and life history of and specific threats to the CRLF is provided in Attachment 1.
Final critical habitat for the CRLF was designated by USFWS on April 13, 2006
(USFWS 2006; 71 FR 19244-19346). Further information on designated critical habitat
for the CRLF is provided in Section 2.6.
2.5.1
Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically
inhabited 46 counties in California including the Central Valley and both coastal and
interior mountain ranges (USFWS 1996). Its range has been reduced by about 70%, and
the species currently resides in 22 counties in California (USFWS 1996). The species has
an elevational range of near sea level to 1,500 meters (5,200 feet) (Jennings and Hayes
1994); however, nearly all of the known CRLF populations have been documented below
1,050 meters (3,500 feet) (USFWS 2002).
28
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Populations currently exist along the northern California coast, northern Transverse
Ranges (USFWS 2002), foothills of the Sierra Nevada (5-6 populations), and in southern
California south of Santa Barbara (two populations) (Fellers 2005a). Relatively larger
numbers of CRLFs are located between Marin and Santa Barbara Counties (Jennings and
Hayes 1994). A total of 243 streams or drainages are believed to be currently occupied
by the species, with the greatest numbers in Monterey, San Luis Obispo, and Santa
Barbara counties (USFWS 1996). Occupied drainages or watersheds include all bodies
of water that support CRLFs (i.e., streams, creeks, tributaries, associated natural and
artificial ponds, and adjacent drainages), and habitats through which CRLFs can move
(i.e., riparian vegetation, uplands) (USFWS 2002).
The distribution of CRLFs within California is addressed in this assessment using four
categories of location including recovery units, core areas, designated critical habitat, and
known occurrences of the CRLF reported in the California Natural Diversity Database
(CNDDB) that are not included within core areas and/or designated critical habitat (see
Figure 2.2). Recovery units, core areas, and other known occurrences of the CRLF from
the CNDDB are described in further detail in Attachment I, and designated critical habitat
is addressed in Section 2.6. Recovery units are large areas defined at the watershed level
that have similar conservation needs and management strategies. The recovery unit is
primarily an administrative designation, and land area within the recovery unit boundary
is not exclusively CRLF habitat. Core areas are smaller areas within the recovery units
that comprise portions of the species' historic and current range and have been
determined by USFWS to be important in the preservation of the species. Designated
critical habitat is generally contained within the core areas, although a number of critical
habitat units are outside the boundaries of core areas, but within the boundaries of the
recovery units. Additional information on CRLF occurrences from the CNDDB is used
to cover the current range of the species not included in core areas and/or designated
critical habitat, but within the recovery units.
Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in
California. The CNDDB serves as a repository for historical and current species location
sightings. Information regarding known occurrences of CRLFs outside of the currently
occupied core areas and designated critical habitat is considered in defining the current
range of the CRLF. See: http://www.dfg.ca.gov/bdb/html/cnddb_info.html for additional
information on the CNDDB.
29
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Recovery Units
1. Sierra Nevada Foothills and Central Valley
2. North Coast Range Foothills nd Western
Sacramento River Valley
3. North Coast and North San Francisco Bay
4. South and East San Francisc Bay
5. Central Coast
6. Diablo Range and Salinas Valley
7. Northern Transverse Rang nd Tehachapi
Mountains
8. Southern Transverse and Peninsular Ranges
Legend
] Recovery Unit Boundaries
|] Currently Occupied Core Areas
^B Critical Habitat
I CNDDB Occurence Sections
_! County Boundaries
45
Core Areas
1. Feather River
Yuba River- S. Fork Feather River
Traverse Creek/ Middle Fork/ American R. Rubicon
Cosumnes River
South Fork Calaveras River*
Tuolumne River*
Piney Creek*
Cottonwood Creek
Putah Creek - Cache Creek*
9.
10. Lake Berryessa Tributaries
11. Upper Sonoma Creek
12. Petaluma Creek — Sonoma Creek
13. R. Reyes Peninsula
14. Belvedere Lagoon
15. Jameson Canyon - Lower Napa River
16. East San Francisco Bay
17. Santa Clara Valley
18. South San Francisco Bay
* Core areas that were historically occupied by the California red-legged frog are not included in the map
19. Watsonville Slough-Elkhorn Slough
20. Carmel River — Santa Lucia
21. Gab Ian Range
22. Estero Bay
23. Arroyo Grange River
24. Santa Maria River - Santa Ynez River
25. Sisquoc River
26. Ventura River - Santa Clara River
27. Santa Monica Bay - Venura Coastal Streams
28. Estrella River
29. San Gabriel Mountain*
30. Forks of the Mojave*
31. Santa Ana Mountain*
32. Santa Rosa Plateau
33. San Luis Ray*
Sweetwater*
Laguna Mountain*
Figure 2.2 Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF
30
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2.5.2 Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams,
marshes, and lagoons (Fellers 2005a). According to the Recovery Plan (USFWS 2002),
CRLFs breed from November through late April. Peaks in spawning activity vary
geographically; Fellers (2005b) reports peak spawning as early as January in parts of
coastal central California. Eggs are fertilized as they are being laid. Egg masses are
typically attached to emergent vegetation, such as bulrushes (Scirpus spp.) and cattails
(Typha spp.) or roots and twigs, and float on or near the surface of the water (Hayes and
Miyamoto 1984). Egg masses contain approximately 2000 to 6000 eggs ranging in size
between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch 10 to 14 days after
fertilization (Fellers 2005a) depending on water temperature. Egg predation is reported
to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles
(terrestrial-phase), typically between May and September (Jennings and Hayes 1994,
USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b, USFWS 2002). Males reach sexual maturity at 2
years, and females reach sexual maturity at 3 years of age; adults have been reported to
live 8 to 10 years (USFWS 2002). Figure 2.3 depicts CRLF annual reproductive timing.
J
F
M
A
M
J
J
A
S
o
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter)
Orange =
Adults and juveniles can be present all year
Figure 2.3 CRLF Reproductive Events by Month
2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied
specifically, it is assumed that their diet is similar to that of other frog species, with the
aquatic phase feeding exclusively in water and consuming diatoms, algae, and detritus
(USFWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar, 1980)
via mouthparts designed for effective grazing of periphyton (Wassersug, 1984,
Kupferberg et al; 1994; Kupferberg, 1997; Altig and McDiarmid, 1999).
Juvenile and adult CRLFs forage in aquatic and terrestrial habitats, and their diet differs
greatly from that of larvae. The main food source for juvenile aquatic- and terrestrial-
phase CRLFs is thought to be aquatic and terrestrial invertebrates found along the
shoreline and on the water surface. Hayes and Tennant (1985) report, based on a study
examining the gut content of 35 juvenile and adult CRLFs, that the species feeds on as
many as 42 different invertebrate taxa, including Arachnida, Amphipoda, Isopoda,
Insecta, and Mollusca. The most commonly observed prey species were larval alderflies
-------
(Stalls cf. californicd)., pillbugs (Armadilliadrium vulgare), and water striders (Gerris sp).
The preferred prey species, however, was the sowbug (Hayes and Tennant, 1985). This
study suggests that CRLFs forage primarily above water, although the authors note other
data reporting that adults also feed under water, are cannibalistic, and consume fish. For
larger CRLFs, over 50% of the prey mass may consists of vertebrates such as mice, frogs,
and fish, although aquatic and terrestrial invertebrates were the most numerous food
items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at
night; for juveniles feeding occurs during the day and at night (Hayes and Tennant 1985).
2.5.4 Habitat
CRLFs require aquatic habitat for breeding, but also use other habitat types including
riparian and upland areas throughout their life cycle. CRLF use of their environment
varies; they may complete their entire life cycle in a particular habitat or they may utilize
multiple habitat types. Overall, populations are most likely to exist where multiple
breeding areas are embedded within varying habitats used for dispersal (USFWS 2002).
Generally, CRLFs utilize habitat with perennial or near-perennial water (Jennings et al.
1997). Dense vegetation close to water, shading, and water of moderate depth are habitat
features that appear especially important for CRLF (Hayes and Jennings 1988).
Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds,
marshes, sag ponds (land depressions between fault zones that have filled with water),
dune ponds, and lagoons. Breeding adults have been found near deep (0.7 m) still or slow
moving water surrounded by dense vegetation (USFWS 2002); however, the largest
number of tadpoles have been found in shallower pools (0.26 - 0.5 m) (Reis, 1999). Data
indicate that CRLFs do not frequently inhabit vernal pools, as conditions in these habitats
generally are not suitable (Hayes and Jennings 1988).
CRLFs also frequently breed in artificial impoundments such as stock ponds, although
additional research is needed to identify habitat requirements within artificial ponds
(USFWS 2002). Adult CRLFs use dense, shrubby, or emergent vegetation closely
associated with deep-water pools bordered with cattails and dense stands of overhanging
vegetation (http://www.fws.gov/endangered/features/rl_frog/rlfrog.html#where).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability,
and life stage. Adults rely on riparian vegetation for resting, feeding, and dispersal. The
foraging quality of the riparian habitat depends on moisture, composition of the plant
community, and presence of pools and backwater aquatic areas for breeding. CRLFs can
be found living within streams at distances up to 3 km (2 miles) from their breeding site
and have been found up to 30 m (100 feet) from water in dense riparian vegetation for up
to 77 days (USFWS 2002).
During dry periods, the CRLF is rarely found far from water, although it will sometimes
disperse from its breeding habitat to forage and seek other suitable habitat under downed
trees or logs, industrial debris, and agricultural features (UWFWS 2002). According to
Jennings and Hayes (1994), CRLFs also use small mammal burrows and moist leaf litter
as habitat. In addition, CRLFs may also use large cracks in the bottom of dried ponds as
32
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refugia; these cracks may provide moisture for individuals avoiding predation and solar
exposure (Alvarez 2000).
2.6 Designated Critical Habitat
In a final rule published on April 13, 2006, 34 separate units of critical habitat were
designated for the CRLF by USFWS (USFWS 2006; FR 51 19244-19346). A summary
of the 34 critical habitat units relative to USFWS-designated recovery units and core
areas (previously discussed in Section 2.5.1) is provided in Attachment I.
'Critical habitat' is defined in the ESA as the geographic area occupied by the species at
the time of the 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.' All designated
critical habitat for the CRLF was occupied at the time of listing. Critical habitat receives
protection under Section 7 of the ESA (Section 7) through prohibition against destruction
or adverse modification with regard to actions carried out, funded, or authorized by a
federal Agency. Section 7 requires consultation on federal actions that are likely to result
in the destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be '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)). PCEs include, but are not limited to,
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. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
• Breeding aquatic habitat;
• Non-breeding aquatic habitat;
• Upland habitat; and
• Dispersal habitat.
Further description of these habitat types is provided in Attachment I.
Occupied habitat may be included in the critical habitat only if essential features within
the habitat may require special management or protection. Therefore, USFWS does not
include areas where existing management is sufficient to conserve the species. Critical
habitat is designated outside the geographic area presently occupied by the species only
when a designation limited to its present range would be inadequate to ensure the
conservation of the species. For the CRLF, all designated critical habitat units contain all
33
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four of the PCEs, and were occupied by the CRLF at the time of FR listing notice in
April 2006. The FR notice designating critical habitat for the CRLF includes a special
rule exempting routine ranching activities associated with livestock ranching from
incidental take prohibitions. The purpose of this exemption is to promote the
conservation of rangelands, which could be beneficial to the CRLF, and to reduce the rate
of conversion to other land uses that are incompatible with CRLF conservation. Please
see Attachment I for a full explanation on this special rule.
USFWS has established adverse modification standards for designated critical habitat
(USFWS 2006). 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 pendimethalin that may alter the PCEs of the CRLF's critical
habitat form the basis of the critical habitat impact analysis. According to USFWS
(2006), activities that may affect critical habitat and therefore result in adverse effects to
the CRLF include, but are not limited to the following:
(1) Significant alteration of water chemistry or temperature to levels beyond the
tolerances of the CRLF that result in direct or cumulative adverse effects to
individuals and their life-cycles.
(2) Alteration of chemical characteristics necessary for normal growth and viability
of juvenile and adult CRLFs.
(3) Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat that could result in
elimination or reduction of habitat necessary for the growth and reproduction of
the CRLF by increasing the sediment deposition to levels that would adversely
affect their ability to complete their life cycles.
(4) Significant alteration of channel/pond morphology or geometry that may lead to
changes to the hydrologic functioning of the stream or pond and alter the timing,
duration, water flows, and levels that would degrade or eliminate the CRLF
and/or its habitat. Such an effect could also lead to increased sedimentation and
degradation in water quality to levels that are beyond the CRLF's tolerances.
(5) Elimination of upland foraging and/or aestivating habitat or dispersal habitat.
(6) Introduction, spread, or augmentation of non-native aquatic species in stream
segments or ponds used by the CRLF.
(7) Alteration or elimination of the CRLF's food sources or prey base (also
evaluated as indirect effects to the CRLF).
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 pendimethalin is expected to directly impact
living organisms within the action area, critical habitat analysis for pendimethalin is
limited in a practical sense to those PCEs of critical habitat that are biological or that can
be reasonably linked to biologically mediated processes.
34
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2.7 Action Area
For listed species assessment purposes, the action area is considered to be the area
affected directly or indirectly by the federal action and not merely the immediate area
involved in the action (50 CFR 402.02). It is recognized that the overall action area for
the national registration of pendimethalin is likely to encompass considerable portions of
the United States based on the large array of agricultural and its 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 CRLF and its designated
critical habitat within the state of California. The Agency's approach to defining the
action area under the provisions of the Overview Document (USEPA 2004) considers the
results of the risk assessment process to establish boundaries for that action area with the
understanding that exposures below the Agency's defined Levels of Concern (LOCs)
constitute a no-effect threshold. For the purposes of this assessment, attention will be
focused on the footprint of the action (i.e., the area where pesticide application occurs),
plus all areas where offsite transport (i.e., spray drift, downstream dilution, etc.) may
result in potential exposure within the state of California that exceeds the Agency's
LOCs.
Deriving the geographical extent of this portion of the action area is based on
consideration of the types of effects that pendimethalin may be expected to have on the
environment, the exposure levels to pendimethalin that are associated with those effects,
and the best available information concerning the use of pendimethalin and its fate and
transport within the state of California. Specific measures of ecological effect that define
the action area include any direct and indirect toxic effect 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. Therefore, the action area
extends to a point where environmental exposures are below any measured lethal or
sublethal effect threshold for any biological entity at the whole organism, organ, tissue,
and cellular level of organization. In situations where it is not possible to determine the
threshold for an observed effect, the action area is not spatially limited and is assumed to
be the entire state of California.
The definition of action area requires a stepwise approach that begins with an
understanding of the federal action. The federal action is defined by the currently labeled
uses for pendimethalin. An analysis of labeled uses and review of available product
labels was completed. Several of the current labels are special local needs (SLN) labels
for other states and some uses on other labels are restricted to specific states other than
California and are, therefore, excluded from this assessment. The agricultural and
nonagricultural uses that are considered as part of the federal action evaluated in this
assessment can be found in Table 2.2.
Following a determination of the assessed uses, an evaluation of the potential "footprint"
of pendimethalin use patterns (i.e., the area where pesticide application occurs) 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
35
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represent the labeled uses described above. A map representing all the land cover types
that make up the initial area of concern for pendimethalin is presented in
Pendimethalin Use - Initial Area of Concern
Forest use
Turf use
Developed-open space
Developed- low density
Developed-medium density
Developed-high density
Pasturehay use
Orchard vineyard use
Cultivated crop use
County boundaries
iKilorneters
0 2040 80 120 160
Compiled from California County boundaries(ESRI, 2002),
USDA Cap Analysis Program Orchard/Vineyard Landcover (CAP)
National Land Cover Database (NLCD) (MRLC. 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Dwision.
Projection: A Ibers Equal Area Conic USGS, North American
Datum of 1983 (NAD 1983).
Wlv
;-t- -' -•-
5/26/2009
Figure 2.4.
More information regarding which specific uses are represented for each land cover types
can be found in Appendix D.
36
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Pendimethalin Use - Initial Area of Concern
| Forest use
| Turf use
Developed-open space
Developed-low density
Developed-medium density
Developed-high density
Pasturehay use
Orchard vineyard use
Cultivated crop use
County boundaries
iKilorneters
0 2040 80 120 160
Compiled from California County boundaries(ESRI, 2002),
USDA Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of P e st ic id es P rocj rams, E nv i ro nrnental F ate an d Effe ct s Dw i sio n.
Projection: Alb ers Equal Area Conic USGS, North American
Datum of 1983 (NAD 1983).
5/26/2009
Figure 2.4. Initial area of concern, or "footprint" of potential use, for
Pendimethalin
37
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Once the initial area of concern is defined, the next step is to define the potential
boundaries of the action area by determining the extent of offsite transport via spray drift
and runoff where exposure of one or more taxonomic groups to the pesticide exceeds the
listed species LOCs.
As previously discussed, the action area is defined by the most sensitive measure of
direct and indirect ecological toxic effects including reduction in survival, growth,
reproduction, and the entire suite of sublethal effects from valid, peer-reviewed studies.
The action area is determined by the footprint of the action plus all offsite areas where
exposure of one or more taxonomic groups to pendimethalin exceeds the Agency's
LOCs. The spatial extent at which the Agency's LOCs are not exceeded is based on the
potential exposure level and the most sensitive effects endpoints The most sensitive for
terrestrial environments was the plant EC25 of 0.01 Ib/acre for ryegrass seedling
emergence, Table 4.5). The most sensitive endpoints for aquatic environments were the
duckweed EC50 of 12.5 ppb and the diatom EC50 of 5.2 ppb (section 4.1.3.1).
The routes of exposure that determine the extent of the action area are run-off in
stormwater or irrigation water (mostly in the sorbed phase) and spray drift. Volatilization
and redeposition (eg., via rainwater) may also contribute to the extent of the action area,
bur this could not be quantified. A paper by Vogel et al. (2008) found pendimethalin in
rainwater in Merced County at a concentration of 0.143 ppb maximum. This is an
additional line of evidence that pendimethalin may be transported by air outside the
immediate use site.
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. The spray drift
analysis for pendimethalin using the most sensitive endpoint (ryegrass seedling
emergence EC25 of 0.01 Ib/acre) suggests that effects are expected beyond 1,000 feet
from the edge of pendimethalin treated areas
In addition to the buffered area from the spray drift analysis, the final action area also
considers the downstream extent of pendimethalin that exceeds the LOG. Based on this
analysis, the action area includes streams as far as 272 kilometers downstream from
forestry use areas.
An evaluation of usage information was conducted to determine the area where use of
pendimethalin may impact the CRLF. This analysis is used to characterize where
predicted exposures 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 pendimethalin is widely used both in agricultural and
non-agricultural settings in 54 of 58 California counties. Thus, it is likely that
pendimethalin use sites and CRLF habitat areas intersect.
38
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Based on these considerations, the action area is considered to be the entire state of
California.
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."3 Selection of the assessment endpoints is based on valued
entities (e.g., CRLF, organisms important in the life cycle of the CRLF, 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
pendimethalin (e.g., runoff, spray drift, etc.), and the routes by which ecological receptors
are exposed to pendimethalin (e.g., direct contact, etc.).
2.8.1 Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the CRLF, 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 potential effects to PCEs, which are components of the
habitat areas that provide essential life cycle needs of the CRLF. Each assessment
endpoint requires one or more "measures of ecological effect," defined as changes in the
attributes of an assessment endpoint or changes in a surrogate entity or attribute in
response to exposure to a pesticide. Specific measures of ecological effect are generally
evaluated based on acute and chronic toxicity information from registrant-submitted
guideline tests that are performed on a limited number of organisms. Additional
ecological effects data from the open literature are also considered. It should be noted
that assessment endpoints are limited to direct and indirect effects associated with
survival, growth, and fecundity, and do not include the full suite of sublethal effects used
to define the action area. According the Overview Document (USEPA 2004), the
Agency relies on acute and chronic effects endpoints that are either direct measures of
impairment of survival, growth, or fecundity or endpoints for which there is a
scientifically robust, peer reviewed relationship that can quantify the impact of the
measured effect endpoint on the assessment endpoints of survival, growth, and fecundity.
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 4.0 of this document. A summary of the assessment endpoints and
measures of ecological effect selected to characterize potential assessed direct and
indirect CRLF risks associated with exposure to pendimethalin is provided in table 2-4
below.
3 U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
39
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Table 2-4 Assessment Endpoints and Measures of Ecological Effects
Assessment Endpoint
Measures of Ecological Effects4
Aquatic-Phase CRLF
(Eggs, larvae, juveniles, andadultsf
Direct Effects
1. Survival, growth, and reproduction of CRLF
la. Most sensitive fish acute LC50 (guideline or
ECOTOX) if no suitable amphibian data are
available
Ib. Most sensitive fish chronic NOAEC (guideline
or ECOTOX) if no suitable amphibian data are
available
Indirect Effects and Critical Habitat Effects
1. Survival, growth, and reproduction of CRLF
individuals via indirect effects on aquatic prey food
supply (i.e., fish, freshwater invertebrates, non-
vascular plants)
3. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat, cover,
food supply, and/or primary productivity (i.e.,
aquatic plant community)
4. Survival, growth, and reproduction of CRLF
individuals via effects to riparian vegetation
2a. Most sensitive fish, aquatic invertebrate, and
aquatic plant EC50 or LC50 (guideline or ECOTOX)
2b. Most sensitive aquatic invertebrate and fish
chronic NOAEC (guideline or ECOTOX)
3 a. Vascular plant acute EC50 (duckweed guideline
test or ECOTOX vascular plant)
3b. Non-vascular plant acute EC50 (freshwater algae
or diatom, or ECOTOX non-vascular)
4a. Distribution of EC25 values for monocots
(seedling emergence, vegetative vigor, or
ECOTOX)
4b. Distribution of EC25 values for dicots (seedling
emergence, vegetative vigor, or ECOTOX)
Terrestrial-Phase CRLF
(Juveniles and adults)
Direct Effects
5. Survival, growth, and reproduction of CRLF
individuals via direct effects on terrestrial phase
adults and juveniles
5a. Most sensitive birdb or terrestrial-phase
amphibian acute LC50 or LD50 (guideline or
ECOTOX)
5b. Most sensitive birdb or terrestrial-phase
amphibian chronic NOAEC (guideline or
ECOTOX)
Indirect Effects and Critical Habitat Effects
6. Survival, growth, and reproduction of CRLF
individuals via effects on terrestrial prey
(i.e., terrestrial invertebrates, small mammals , and
frogs)
7. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian and upland vegetation)
6a. Most sensitive terrestrial invertebrate and
vertebrate acute EC50 or LC50 (guideline or
ECOTOX)C
6b. Most sensitive terrestrial invertebrate and
vertebrate chronic NOAEC (guideline or ECOTOX)
7a. Distribution of EC25 for monocots (seedling
emergence, vegetative vigor, or ECOTOX
7b. Distribution of EC25 for dicots (seedling
emergence, vegetative vigor, or ECOTOX)
a Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult
frogs are considered "aquatic" for the purposes of this assessment because exposure pathways in the water
are considerably different that exposure pathways on land.
b Birds are used as surrogates for terrestrial phase amphibians.
4 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix A.
40
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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 pendimethalin that may alter the PCEs of the CRLF's critical habitat. PCEs
for the CRLF 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 CRLF.
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 pendimethalin effects data are available. Adverse
modification to the critical habitat of the CRLF includes, but is not limited to, those listed
in Section 2.6.
Measures of such possible effects by labeled use of pendimethalin on critical habitat of
the CRLF are described in Table 2-55. 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.
Assessment endpoints used for the analysis of designated critical habitat are based on the
adverse modification standard established by USFWS (2006).
41
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Table 2-5 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat3
Assessment Endpoint
Measures of Ecological Effect
Aquatic-Phase CRLFPCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or geometry
and/or increase in sediment deposition within the
stream channel or pond: aquatic habitat (including
riparian vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile
and adult CRLFs.
Alteration in water chemistry /quality including
temperature, turbidity, and oxygen content necessary
for normal growth and viability of juvenile and adult
CRLFs and their food source.
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
a. Most sensitive aquatic plant EC50 (guideline or
ECOTOX)
b. Distribution of EC25 values for terrestrial monocots
(seedling emergence, vegetative vigor, or ECOTOX)
c. Distribution of EC25 values for terrestrial dicots
(seedling emergence, vegetative vigor, or ECOTOX)
a. Most sensitive EC50 values for aquatic plants (guideline
or ECOTOX)
b. Distribution of EC25 values for terrestrial monocots
(seedling emergence or vegetative vigor, or ECOTOX)
c. Distribution of EC25 values for terrestrial dicots
(seedling emergence, vegetative vigor, or ECOTOX)
a. Most sensitive EC50 or LC50 values for fish or aquatic-
phase amphibians and aquatic invertebrates (guideline or
ECOTOX)
b. Most sensitive NOAEC values for fish or aquatic -phase
amphibians and aquatic invertebrates (guideline or
ECOTOX)
a. Most sensitive aquatic plant EC50 (guideline or
ECOTOX)
Terrestrial-Phase CRLFPCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian
habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
Elimination and/or disturbance of dispersal habitat:
Upland or riparian dispersal habitat within designated
units and between occupied locations within 0.7 mi of
each other that allow for movement between sites
including both natural and altered sites which do not
contain barriers to dispersal
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
a. Distribution of EC25 values for monocots (seedling
emergence, vegetative vigor, or ECOTOX)
b. Distribution of EC25 values for dicots (seedling
emergence, vegetative vigor, or ECOTOX)
c. Most sensitive food source acute EC50/LC50 and NOAEC
values for terrestrial vertebrates (mammals) and
invertebrates, birds or terrestrial-phase amphibians, and
freshwater fish.
a Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these processes are not
biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.
42
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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 (U.S. EPA, 1998). For this assessment, the
risk is stressor-linked, where the stressor is the release of pendimethalin to the
environment. The following risk hypotheses are presumed for this endangered species
assessment:
The labeled use of pendimethalin within the action area may:
• directly affect the CRLF by causing mortality or by adversely affecting growth or
fecundity;
• indirectly affect the CRLF by reducing or changing the composition of food
supply;
• indirectly affect the CRLF or modify designated critical habitat by reducing or
changing the composition of the aquatic plant community in the ponds and
streams comprising the species' current range and designated critical habitat, thus
affecting primary productivity and/or cover;
• indirectly affect the CRLF or modify designated critical habitat by reducing or
changing the composition of the terrestrial plant community (i.e., riparian habitat)
required to maintain acceptable water quality and habitat in the ponds and streams
comprising the species' current range and designated critical habitat;
• affect the designated critical habitat of the CRLF by reducing or changing
breeding and non-breeding aquatic habitat (via modification of water quality
parameters, habitat morphology, and/or sedimentation);
• affect the designated critical habitat of the CRLF by reducing the food supply
required for normal growth and viability of juvenile and adult CRLFs;
• affect the designated critical habitat of the CRLF by reducing or changing upland
habitat within 200 ft of the edge of the riparian vegetation necessary for shelter,
foraging, and predator avoidance.
• affect the designated critical habitat of the CRLF by reducing or changing
dispersal habitat within designated units and between occupied locations within
0.7 mi of each other that allow for movement between sites including both natural
and altered sites which do not contain barriers to dispersal.
• affect the designated critical habitat of the CRLF by altering chemical
characteristics necessary for normal growth and viability of juvenile and adult
CRLFs.
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the pendimethalin release mechanisms, biological receptor types, and effects
endpoints of potential concern. The conceptual models for terrestrial and aquatic
exposures are shown in Figure 2.5 and Figure 2.6, respectively, which include the
conceptual models for the aquatic and terrestrial PCE components of critical habitat.
43
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Exposure routes shown in dashed lines are not quantitatively considered because the
contribution of those potential exposure routes to potential risks to the CRLF and
modification to designated critical habitat is expected to be negligible.
Stressor
Source
Pendimethalin applied to use site
Exposure
Media
1—Dermal uptake/lnqestiorr*—
.T.
Long range
atmospheric
transport
Terrestrial-phase
amphibians
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Root uptake.4!
Wet/dry deposition-*1
Ingestion
Receptors
Ingestion
Birds/terrestrial-
phase amphibians/
reptiles/mammals
Attribute
Change
Individual
organisms
Reduced survival
Reduced growth
Reduced reproduction
Food chain
Reduction in prey
Modification of PCEs
related to prey availability
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Modification of PCEs related to
habitat
Figure 2.5 Conceptual Model for Pesticide Effects on Terrestrial Phase of the
CRLF
44
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Stressor
Pendimethalin applied to use site
Source
Spray drift and
vnlatili7atinn
Exposure
Media
tlll7f
|| Runoff |
:_£:
*• Groundwater:
Surface water/
Sediment
T
.T.
Long range
atmospheric
transport
.Wet/dry deposition .
Receptors
Uptake/gills
or integument
1
Uptake/gills
or integument
Aquatic Animals
Invertebrates
Vertebrates
Fish/aquatic-phase
amphibians
"Piscivorous mammals
and birds
Inqe^tion
Attribute Individual
Change
organisms
Reduced survival
Reduced growth
Reduced reproduction
Uptake/cell,
roots^ leaves
Aquatic Plants
\lon-vascular
Vascular
t
Inqestion
Food chain
Reduction in algae
Reduction in prey
Modification of PCEs
related to prey availability
1
Habitat integrity
Reduction in primary
productivity
Reduced cover
ommunity change
Modification of PCEs related to
habitat
** Route of exposure includes only ingestion of aquatic fish and invertebrates
Figure 2.6 Conceptual Model for Pesticide Effects on Aquatic Phase of the CRLF
2.10 Analysis Plan
In order to address the risk hypothesis, the potential for direct and indirect effects to the
CRLF, its prey, and its habitat is estimated. In the following sections, the use,
environmental fate, and ecological effects of pendimethalin 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 (U.S. EPA, 2004), the
likelihood of effects to individual organisms from particular uses of pendimethalin is
estimated using the probit dose-response slope and either the level of concern (discussed
below) or actual calculated risk quotient value.
45
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2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model
2.10.1.1 Measures of Exposure
The environmental fate properties of pendimethalin along with available monitoring data
indicate that runoff and spray drift are the principle potential transport mechanisms of
pendimethalin to the aquatic and terrestrial habitats of the CRLF. In this assessment,
transport of pendimethalin through runoff and spray drift is considered in deriving
quantitative estimates of pendimethalin exposure to CRLF, its prey and its habitats.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of pendimethalin 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 Tier 1 Rice model is used to estimate pendimethalin
concentrations in rice paddy water on the day of application. The model used to predict
terrestrial EECs on food items is T-REX. 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.
PRZM (v3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are screening
simulation models coupled with the input shell pe5.pl (Aug 2007) to generate daily
exposures and l-in-10 year EECs of pendimethalin that may occur in surface water
bodies adjacent to application sites receiving pendimethalin through runoff and spray
drift. PRZM simulates pesticide application, movement and transformation on an
agricultural field and the resultant pesticide loadings to a receiving water body via runoff,
erosion and spray drift. EXAMS simulates the fate of the pesticide and resulting
concentrations in the water body. The standard scenario used for ecological pesticide
assessments assumes application to a 10-hectare agricultural field that drains into an
adjacent 1-hectare water body, 2-meters deep (20,000 m3 volume) with no outlet.
PRZM/EXAMS was used to estimate screening-level exposure of aquatic organisms to
pendimethalin. The measure of exposure for aquatic species is the l-in-10 year return
peak or rolling mean concentration. The l-in-10 year peak is used for estimating acute
exposures of direct effects to the CRLF, as well as indirect effects to the CRLF through
effects to potential prey items, including: algae, aquatic invertebrates, fish and frogs. The
l-in-10-year 60-day mean is used for assessing chronic exposure to the CRLF and fish
and frogs serving as prey items; the l-in-10-year 21-day mean is used for assessing
chronic exposure for aquatic invertebrates, which are also potential prey items.
Exposure in aquatic environments via bioaccumulation and foodchain exposure was
quantified with the KABAM (Kow-based bioaccumulation) model (documented at
http://www.epa.gov/oppefedl/models/water/kabam/kabam_user_guide.html).
Exposure estimates for the terrestrial-phase CRLF and terrestrial invertebrates and
mammals (serving as potential prey) assumed to be in the target area or in an area
46
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exposed to spray drift are derived using the T-REX model (version 1.3.1, 12/07/2006).
This model incorporates the Kenega nomograph, as modified by Fletcher et al. (1994),
which is based on a large set of actual field residue data. The upper limit values from the
nomograph represented the 95th percentile of residue values from actual field
measurements (Hoerger and Kenega, 1972). For modeling purposes, direct exposures of
the CRLF to pendimethalin through contaminated food are estimated using the EECs for
the small bird (20 g) which consumes small insects. Dietary-based and dose-based
exposures of potential prey (small mammals) are assessed using the small mammal (15 g)
which consumes short grass. The small bird (20g) consuming small insects and the small
mammal (15g) consuming short grass are used because these categories represent the
largest RQs of the size and dietary categories in T-REX that are appropriate surrogates
for the CRLF and one of its prey items. Estimated exposures of terrestrial insects to
pendimethalin are bound by using the dietary based EECs for small insects and large
insects.
Birds are currently used as surrogates for terrestrial-phase CRLF. However, amphibians
are poikilotherms (body temperature varies with environmental temperature) while birds
are homeotherms (temperature is regulated, constant, and largely independent of
environmental temperatures). Therefore, amphibians tend to have much lower metabolic
rates and lower caloric intake requirements than birds or mammals. As a consequence,
birds are likely to consume more food than amphibians on a daily dietary intake basis,
assuming similar caloric content of the food items. Therefore, the use of avian food
intake allometric equation as a surrogate to amphibians is likely to result in an over-
estimation of exposure and risk for reptiles and terrestrial-phase amphibians. Therefore,
T-REX (version 1.3.1) has been refined to the T-HERPS model (v. 1.0), which allows for
an estimation of food intake for poikilotherms using the same basic procedure as T-REX
to estimate avian food intake.
EECs for terrestrial plants inhabiting dry and wetland areas are derived using TerrPlant
(version 1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in
spray drift to calculate EECs. EECs are based upon solubility and application rate.
Spray drift models, AGDISP and/or AgDRIFT are used to assess exposures of terrestrial
phase CRLF and its prey to pendimethalin deposited on terrestrial habitats by spray drift.
AGDISP (version 8.13; dated 12/14/2004) (Teske and Curbishley, 2003) is used to
simulate aerial and ground applications. In addition to the buffered area from the spray
drift analysis, the downstream extent of pendimethalin that exceeds the LOG for the
effects determination is also considered.
Although volatility is a potential route of exposure, volatility and subsequent deposition
will not be quantified because there are currently no valid models that would be useful to
quantify this potential route of exposure to terrestrial environments. Pendimethalin is a
semi-volatile compound that may be lost from moist soil. The volatilization half-life
from moist soil was found to be 12.5 days (MRID 00153766). Pendimethalin has been
observed at low concentrations (0.143 ppb maximum) in rainwater in California (Vogel
et al., 2008). This effect was accounted for in the PRZM-EXAMS modeling by invoking
47
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the PRZM volatilization routine, thus allowing volatilization to compete with runoff and
metabolism as a dissipation route. Comparison of the highest EEC scenario (forestry)
shows that the effect is small (16.6 ppb with volatility invoked and 18.1 ppb without).
The relatively slow volatilization rate from even moist soil is not believed to result in as
large or immediate an aquatic exposure as spray drift at the time of application. Thus,
airborne exposure is adequately quantified by the spray drift analysis. Terrestrial
exposure of plants and animals is accounted for by the AgDrift and AgDISP effect area
analysis.
2.10.1.2 Measures of Effect
Data identified in Section 2.8 are used as measures of effect for direct and indirect effects
to the CRLF. Data were obtained from registrant submitted studies or from literature
studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched
in order to provide more ecological effects data and in an attempt to bridge existing data
gaps. ECOTOX is a source for locating single chemical toxicity data for aquatic life,
terrestrial plants, and wildlife. ECOTOX was created and is maintained by the USEPA,
Office of Research and Development, and the National Health and Environmental Effects
Research Laboratory's Mid-Continent Ecology Division.
The assessment of risk for direct effects to the terrestrial-phase CRLF makes the
assumption that toxicity of pendimethalin to birds is similar to or less than the toxicity to
the terrestrial-phase CRLF. The same assumption is made for fish and aquatic-phase
CRLF. Algae, aquatic invertebrates, fish, and amphibians represent potential prey of the
CRLF in the aquatic habitat. Terrestrial invertebrates, small mammals, and terrestrial-
phase amphibians represent potential prey of the CRLF in the terrestrial habitat. Aquatic,
semi-aquatic, and terrestrial plants represent habitat of CRLF.
The acute measures of effect used for animals in this screening level assessment are the
LD50, LCso and ECso- LD stands for "Lethal Dose", and LD50 is the amount of a material,
given all at once, that is estimated to cause the death of 50% of the test organisms. LC
stands for "Lethal Concentration" and LCso is the concentration of a chemical that is
estimated to kill 50% of the test organisms. EC stands for "Effective Concentration" and
the ECso is the concentration of a chemical that is estimated to produce a specific effect in
50% of the test organisms. Endpoints for chronic measures of exposure for listed and
non-listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for "No
Ob served-Adverse-Effect-Level" and refers to the highest tested dose of a substance that
has been reported to have no harmful (adverse) effects on test organisms. The NOAEC
(i.e., "No-Observed-Adverse-Effect-Concentration") is the highest test concentration at
which none of the observed effects were statistically different from the control. The
NOEC is the No-Observed-Effects-Concentration. For non-listed plants, only acute
exposures are assessed (i.e., EC25 for terrestrial plants and ECso for aquatic plants).
It is important to note that the measures of effect for direct and indirect effects to the
CRLF and its designated critical habitat are associated with impacts to survival, growth,
48
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and fecundity, and do not include the full suite of sublethal effects used to define the
action area. According the Overview Document (USEPA 2004), the Agency relies on
effects endpoints that are either direct measures of impairment of survival, growth, or
fecundity or endpoints for which there is a scientifically robust, peer reviewed
relationship that can quantify the impact of the measured effect endpoint on the
assessment endpoints of survival, growth, and fecundity.
2.10.1.3 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
pendimethalin, and the likelihood of direct and indirect effects to CRLF in aquatic and
terrestrial habitats. The exposure and toxicity effects data are integrated in order to
evaluate the risks of adverse ecological effects on non-target species. For the assessment
of pendimethalin risks, 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).
For this endangered species assessment, listed species LOCs are used for comparing RQ
values for acute and chronic exposures of pendimethalin directly to the CRLF. If
estimated exposures directly to the CRLF of pendimethalin resulting from a particular use
are sufficient to exceed the listed species LOG, then the effects determination for that use
is "may affect". When considering indirect effects to the CRLF due to effects to animal
prey (aquatic and terrestrial invertebrates, fish, frogs, and mice), the listed species LOCs
are also used. If estimated exposures to CRLF prey of pendimethalin resulting from a
particular use are sufficient to exceed the listed species LOG, then the effects
determination for that use is a "may affect." If the RQ being considered also exceeds the
non-listed species acute risk LOG, then the effects determination is a LAA. If the acute
RQ is between the listed species LOG and the non-listed acute risk species LOG, then
further lines of evidence (i.e. probability of individual effects, species sensitivity
distributions) are considered in distinguishing between a determination of NLAA and a
LAA. When considering indirect effects to the CRLF due to effects to algae as dietary
items or plants as habitat, the non-listed species LOG for plants is used because the CRLF
does not have an obligate relationship with any particular aquatic and/or terrestrial plant.
If the RQ being considered for a particular use exceeds the non-listed species LOG for
plants, the effects determination is "may affect". Further information on LOCs is
provided in Appendix C.
3.0 Exposure Assessment
Pendimethalin is formulated as granules and emulsifiable concentrate. Application
equipment includes ground application, and aerial application. Risks from ground boom
49
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and aerial applications are expected to result in the highest off-target levels of
pendimethalin 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.
3.1 Label Application Rates and Intervals
Pendimethalin labels may be categorized into two types: labels for manufacturing uses
(including technical grade pendimethalin and its formulated products) and end-use
products. While technical products, which contain pendimethalin 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 grasses and certain broadleaf weeds in agricultural
crops, orchards, landscapes and rights-of-way. The formulated product labels legally
limit pendimethalin's potential use to only those sites that are specified on the labels.
There are no known pending mitigations that would influence the exposure assessment.
Currently registered agricultural and non-agricultural uses of pendimethalin within
California are summarized in Table 3-1.
Table 3-1 Pendimethalin Uses, Scenarios, and Application Information for the
CRLF risk assessment1
Scenario
Scenario
CAalfalfa WirrigOP
CAalmond WirrigSTD
CAalmond WirrigSTD
Cacitrus WirrigSTD
Cacitrus WirrigSTD
CAcolecropRLF
CAcornOP
Cacotton WirrigSTD
CAForestryRLF
Cafruit WirrigSTD
CAgarlicRLF
Cagrapes WirrigSTD
Cagrapes WirrigSTD
CAmelonsRLF
CAOliveRLF
CAOnion WirrigSTD
CApotatoRLF
CArowcropRLF
CAStrawberry-
noplasticRLF
Uses Represented
by Scenario
Uses Represented
alfalfa
nut trees
nut trees
citrus crops
citrus crops
cole crops
field corn, sweet
corn, popcorn
cotton
forestry
fruit trees
garlic
grapes
grapes
eggplant
olives
onion
potato, white/Irish
artichoke/asparagus
strawberry
Application Rate
Application rate
(Ib/acre)
3.98
5.985
3.96
5.985
3.96
0.99
1.98
1.98
3.96
3.96
1.485
5.845
3.96
1.485
3.96
1.98
1.485
3.895
1.485
Application Method
Application method
air
ground
air
ground
air
air
air
air
air
air
air
ground
air
air
air
air
air
air
air
50
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Scenario
Catomato WirrigSTD
CAtomatoSTD
CARightofWayfRLF,
CAImperviousRLF
CAwheatRLF
Tier 1 Rice Model
Uses Represented
by Scenario
tomato, tomatillo
groundcherry
rights-of-way
wheat
rice
Application Rate
1.485
1.485
3.96
1.485
0.99
Application Method
ground
air
air
air
air
1 Uses assessed based on memorandum from SRRD (Verification Memorandum for Pendimethalin for
Red Legged Frog Assessment) dated 2/17/2009.
3.2 Aquatic Exposure Assessment
3.2.1 Modeling Approach
Aquatic exposures are quantitatively estimated for all of assessed uses using scenarios
that represent high exposure sites for pendimethalin use. Each of these sites represents a
10 hectare field that drains into a 1-hectare pond that is 2 meters deep and has no outlet.
Exposure estimates generated using the standard pond are intended to represent a wide
variety of vulnerable water bodies that occur at the top of watersheds including prairie
pot holes, playa lakes, wetlands, vernal pools, man-made and natural ponds, and
intermittent and first-order streams. As a group, there are factors that make these water
bodies more or less vulnerable than the standard surrogate pond. Static water bodies that
have larger ratios of drainage area to water body volume would be expected to have
higher peak EECs than the standard pond. These water bodies will be either shallower or
have large drainage areas (or both). Shallow water bodies tend to have limited additional
storage capacity, and thus, tend to overflow and carry pesticide in the discharge whereas
the standard pond has no discharge. As watershed size increases beyond 10 hectares, at
some point, it becomes unlikely that the entire watershed is planted to a single crop,
which is all treated with the pesticide. Headwater streams can also have peak
concentrations higher than the standard pond, but they tend to persist for only short
periods of time and are then carried downstream.
Crop-specific management practices for all of the assessed uses of pendimethalin were
used for modeling, including application rates, number of applications per year,
application intervals, and the first application date for each crop.
The Tier 1 Rice Model calculates the water column concentration in a flooded rice paddy
on the day of application, accounting only for sorption to sediment as a dissipation
mechanism.
KABAM is used to estimate potential bioaccumulation of hydrophobic organic pesticides
in freshwater aquatic ecosystems and risks to mammals and birds consuming aquatic
organisms which have bioaccumulated these pesticides. This tool can also be used to
estimate pesticide concentrations in fish tissues consumed by humans (i.e., filets). The
bioaccumulation portion of KABAM is based upon work by Arnot and Gobas (2004)
who parameterized a bioaccumulation model based on PCBs and some pesticides (e.g.,
51
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lindane, DDT) in freshwater aquatic ecosystems. KABAM relies on a chemical's octanol-
water partition coefficient (KOW) to estimate uptake and elimination constants through
respiration and diet of organisms in different trophic levels. Pesticide tissue residues are
calculated for different levels of an aquatic food web. The model then uses pesticide
tissue concentrations in aquatic animals to estimate dose- and dietary-based exposures
and associated risks to mammals and birds consuming aquatic organisms, using an
approach that is similar to the TREX model (USEPA 2008). Input parameters for
KABAM are given in Appendix K.
3.2.2 Model Inputs
Pendimethalin is a herbicide used on a wide variety of food, non-food crops, and non-
agricultural sites. Pendimethalin environmental fate data used for generating model
parameters is listed in Table 2.1 in Section 2.4.1. The input parameters for PRZM and
EXAMS are in Table 3-2. Application dates were generally one to two weeks before the
crop emergence date in the PRZM scenario, as pendimethalin is a pre-emergence/pre-
plant herbicide.
Table 3-2 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Pendimethalin Endangered Species Assessment for the CRLF1
Fate Property
Molecular Weight
Henry's constant
Vapor Pressure
Solubility in Water
Photolysis in Water
Aerobic Soil Metabolism Half-lives
Hydrolysis
Aerobic Aquatic Metabolism (water
column)
Anaerobic Aquatic Metabolism
(benthic)
Koc
Application rate and frequency
Application intervals
Chemical Application Method (CAM)
Value (unit)
281.31
8.6E-7 atm-m3/mol
3.0E-5 mmHg
3.0mg/Lat25°C
42 day half -life (12 hours
light/dark)
172 days
Stable
330 day half-life (total system)
3x factor not used due to long half-
life from single study
208 day half-life
17040 mL/g o.c.
MRID (or source)
VP/solubility
00153766
00153762; lOx actual value as
per Input Parameter Guidance
(IPG)
00153763
40185 104; deviation from IPG
as explained in 1997 RED
00106777
47385201
40813501; upper 90th %ile
confidence bound
43041901 (average of 5
values)
See table 3.1
Soil appl;ied
52
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Fate Property
Application Efficiency
Spray Drift Fraction
Air Diffusion coefficient
Enthalpy of Vaporization
Value (unit)
0.99 ground
0.95 aerial
0.01 ground
0.05 aerial
3427 cm2/day
20 kcal/mol
MRID (or source)
IPG
IPG
= 1.55/(MW)A0.65
PRZM default
1 - Inputs determined in accordance with EFED "Guidance for Chemistry and Management Practice Input
Parameters for Use in Modeling the Environmental Fate and Transport of Pesticides" dated February 28,
2002
3.2.3 Results
The aquatic EECs for the various scenarios and application practices are listed in Table
3-3. Most peak exposures were 16 ppb or below. Most exposures were dominated by
spray drift.
Table 3-3 Aquatic EECs (ug/L) for Pendimethalin Uses in California
PRZM Scenario
CAcolecropRLF
Cacitrus WirrigSTD a
Cagrapes_WirrigSTD,
CAwinegrapesRLF
CApotatoRLF
CAtomatoSTD
CAmelonsRLF
CAgarlicRLF
CAStrawberry-
noplasticRLF
CAOnion WirrigSTD
Cacotton WirrigSTD
CAwheatRLF
CAalmond WirrigSTD
CAcornOP
Cacitrus WirrigSTD a
CAOliveRLF
Cafruit WirrigSTD b
CAalfalfa WirrigOP
Cagrapes_WirrigSTD,
CAwinegrapesRLF
CAalmond WirrigSTD c
CArowcropRLF d
Application
Rate (Ib/A)
0.99
5.985
5.845
1.485
1.485
1.485
1.485
1.485
1.98
1.98
1.485
5.985
1.98
3.96
3.96
3.96
3.98
3.96
3.96
3.895
Aerial/
Ground
A
G
G
A
A
A
A
A
A
A
A
G
A
A
A
A
A
A
A
A
Specific Crop
Several cole
crops
Several citrus
crops
grapes
potato,
white/Irish
groundcherry
eggplant
garlic
strawberry
onion
cotton
wheat
several
several
several
olives
several
alfalfa
grapes
several
artichoke/asp
aragus
Peak
EEC
(ppb)
3.16
3.42
4.06
4.14
4.21
4.22
4.31
4.74
5.55
5.75
6.10
6.56
6.84
11.06
11.16
11.18
11.28
11.44
11.71
11.92
21 -day
EEC
(ppb)
1.29
0.94
1.31
0.99
1.10
1.04
1.15
1.92
1.35
1.54
2.81
2.38
2.00
2.65
2.78
3.03
3.11
2.94
3.68
4.04
60-day
EEC
(ppb)
0.98
0.58
0.95
0.57
0.66
0.62
0.73
1.36
0.80
0.99
2.13
1.61
1.54
1.52
1.70
1.85
1.95
1.83
2.30
2.86
53
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CAForestryRLF e
Tier 1 Rice Model
CARightofWayfRLF,
CAImperviousRLF f
3.96
0.99
3.96
A
A
A
several
rice
several
16.60
48
1.74
6.41
—
0.55
4.93
—
0.36
a This scenario represents calamondin, citron (citrus), citrus hybrids other than tangelo, grapefruit,
kumquat, lemon, lime, orange, pummelo (shaddock), and tangelo.
b This scenario represents apple, apricot, cherry, crabapple, fig, loquat, nectarine, peach, pear, pepino
(melon pear), plum, pomegranate, prune, quince, and small fruits.
0 This scenario represents almond, beech nut, brazil nut, butternut, cashew, chestnut, chinquapin, filbert
(hazelnut), hickory nut, macadamia nut (bushnut), mayhaw (hawthorn), pecan, pistachio, walnut (English
or black).
d This scenario represents artichoke, asparagus, beans, carrot (including tops), garbanzos (including chick
peas), legume vegetables, peanuts (unspecified), peas, and pepper.
e This scenario represents forestry and Christmas tree plantations.
f These combined scenarios represents airports/landing fields, commercial/industrial lawns, golf course
turf, industrial areas (outdoor), mulch, ornamental and/or shade trees, ornamental ground cover, ornamental
herbaceous plants, ornamental lawns and turf, ornamental non-flowering plants, ornamental sod farm (turf),
ornamental woody shrubs and vines, paved areas (private roads/sidewalks), Rights-of-way, fencerows,
hedges recreation area lawns, residential lawns, and shelterbelt plantings. Combined EEC is 50%
Impervious scenario with 1% of application rate and no drift, and 50% Rights-of-way scenario.
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
pendimethalin data from the USGS NAWQA program (http://water.usgs.gov/nawqa) and
data from the California Department of Pesticide Regulation (CDPR).
3.2.4.1 USGS NAWQA Surface Water Data
Data for pendimethalin and its degradate hydroxypendamethalin were downloaded from
the NAWQA Data Warehouse site on March 30, 2009. The data was restricted to
California sampling stations. There were 604 measurements of pendimethalin in the
Sacramento River and San Joaquin-Tulare River basins. There was measureable
pendimethalin in 319 of the 604 samples (53% positive).
The highest concentration recorded (0.679 ppb) was at a station called "Highline Cn Spill
Nr Hilmar Ca" in the San Joaquin-Tulare River Basin. All 9 measurements at this site
were positive for pendimethalin, with a range of 0.262 to 0.679 ppb.
All 8 measurements of hydroxypendimethalin in surface water were in the San Joaquin-
Tulare basin. All were non-detect (<0.143 ppb).
3.2.4.2 USGS NAWQA Groundwater Data
54
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There were 589 measurements of pendimethalin in the NAWQA data for the Sacramento
River and San Joaquin-Tulare River Basins. There was only one positive result (0.0138
ppb) in Stanislaus County (San Joaquin-Tulare basin).
All 61 measurements of pendimethalin in ground water were in the San Joaquin-Tulare
basin. All were non-detect (<0.143 ppb).
3.2.4.3 California Department of Pesticide Regulation (CPR) Data
Data for pendimethalin were downloaded from the California surface water monitoring
database on March 19, 2009. There were 565 measurements of pendimethalin in the
Sacramento River valley (33 were positive), and 1802 measurements (326 were positive)
in the San Joaquin River valley. The maximum concentration in the Sacramento River
valley was 0.7 ppb, and it was 3.5 ppb in the San Joaquin valley. The data for all stations
in the two valleys are given in Figure 3.1 below.
0.8 i
0.7
0.6
0.5
£ 0.4
0- 0.3
0.2
0.1
Pendimethalin [ug/L] in Sacramento Valley Streams
5/7/1990
1/31/1993 10/28/1995 7/24/1998 4/19/2001
date
1/14/2004 10/10/2006
7/6/2009
55
-------
Pendimethalin [ug/L] in San Joaquin Valley Streams
imethalin
|v
o c
ppb Pend
n I-
4»
•
•
•
•
» . . ':
. !'»i :«i.ijiii-
5/7/1990 1/31/1993 10/28/1995 7/24/1998 4/19/2001 1/14/2004 10/10/2006
date
• Cone [ug/L]
Figure 3.1 California DPR surface water monitoring data
3.2.4.4 Atmospheric Monitoring Data
Pendimethalin has been detected in air in an agricultural setting (Merced River basin
downstream from McSwain dam) in California (Vogel et al. 2008). Of 23 rainwater
samples taken, 78% were positive, with a maximum concentration of 0.143 |ig/L, and a
median of 0.021 |ig/L. Sampling was conducted in 2003 and 2004.
As explained above in section 2.10.1.1, volatilization and redeposition is not quantifiable
with currently approved models. However, analysis of water modeling results with and
with soil volatilization routines invoked indicate that the volatilization effect is small for
pendimethalin, and airborne exposure is dominated by spray drift at the time of
application.
3.2.4.5 Spray Drift Buffer and Downstream Dilution Analysis for
Action Area
Because pendimethalin use is documented in 54 of 58 California counties, and because it
is semi-volatile and has been detected in rainwater, the Action Area is considered to be
the entire state. Spray drift and downstream dilution analysis for the Action Area were
therefore not conducted.
56
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3.3 Terrestrial Animal Exposure Assessment
T-REX (Version 1.3.1) is used to calculate dietary and dose-based EECs of
pendimethalin for the CRLF and its potential prey (e.g. small mammals and terrestrial
insects) inhabiting terrestrial areas. EECs used to represent the CRLF are also used to
represent exposure values for frogs serving as potential prey of CRLF adults. T-REX
simulates a 1-year time period. For this assessment, spray applications of pendimethalin
are considered, as discussed in below.
Terrestrial EECs for foliar formulations of pendimethalin were derived for the uses
summarized in Table 3.4. Given that no data on interception and subsequent dissipation
from foliar surfaces is available for pendimethalin, a default foliar dissipation half-life of
35 days is used based on the work of Willis and McDowell (1987). Use of specific input
values, including number of applications, application rate and application interval are
provided in Table 3.4. Outputs from T-REX is available in Appendix E.
Table 3-4 Input Parameters for Foliar Applications Used to Derive Terrestrial
EECs for Pendimethalin with T-REX
Use Sites
walnut (english/black), tangerines, tangelo, small fruits, pummelo
(shaddock), pomegranate, pistachio, pecan, orange, macadamia nut
(bushnut), lime, lemon, kumquat, hickory nut, grapefruit, filbert
(hazelnut), citrus hybrids other than tangelo, citron (citrus), chinquapin,
chestnut, cashew, calamondin, butternut, brazil nut, beech nut, almond,
grapes.
Prune, plum, pear, peach, olive, nectarine, fig, cherry, apricot, apple,
ornamental and/or shade trees, nonagricultural rights-of-way,
fencerows, hedgerows, mulch, industrial areas (outdoor), forest trees
(all or unspecified), Christmas tree plantations, recreation area lawns,
loquat, shelterbelt plantings, quince, mayhaw, crabapple, alfalfa
Asparagus, artichoke
golf course turf, airports/landing fields
residential lawns
Shallot, onion, corn (sweet, pop, field)
Carrot
Sunflower
Tomato, tomatillo, tobacco, sorghum, potato (white/Irish), lupine
(grain), garlic, garbanzos (including chick peas) beans, succulent (snap
or lima) beans, dried-type beans, cotton, cowpea (southern pea, black-
eyed bean),
Wheat, pepper, pepino (melon pear), groundcherry, eggplant
Strawberry
Legume vegetables
Rice, mustard cabbage (gai choy, pak-choi), kohlrabi, cauliflower,
cabbage (Chinese), cabbage, brussels sprouts, broccoli (Chinese),
broccoli, Brassica (head and stem) vegetables
Application rate
(Ibs ai/A)
6.0
4.0
3.9
3.5
3.0
2.0
1.9
1.73
1.485
1.425
1.485
1.24
1.0
Number of
Applications
1
1
1
1
2 (30 day interval)
1
1
T-REX is also used to calculate EECs for terrestrial insects exposed to pendimethalin.
Dietary-based EECs calculated by T-REX for small and large insects (units of a.i./g) are
used to bound an estimate of exposure to terrestrial insects. Available acute contact
57
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toxicity data for bees exposed to pendimethalin (in units of jig a.i./bee), are converted to
jig a.i./g (of bee) by multiplying by 1 bee/0.128 g. The EECs are later compared to the
adjusted acute contact toxicity data for bees in order to derive RQs.
For modeling purposes, exposures of the CRLF to pendimethalin through contaminated
food are estimated using the EECs for the small bird (20 g) which consumes small
insects. Dietary-based and dose-based exposures of potential prey are assessed using the
small mammal (15 g) which consumes short grass. Upper-bound Kenega nomogram
values reported by T-REX for these two organism types are used for derivation of EECs
for the CRLF and its potential prey (Table 3.5). Dietary-based EECs for small and large
insects reported by T-REX as well as the resulting adjusted EECs are available in Table
3.6. An example output from T-REX v. 1.3.1 is available in Appendix E.
Table 3-5 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Pendimethalin
Application rate
6.0
4.0
3.9
3.5
3.0
2.0
1.9
1.73
1.485
1.425
1.485 (2 applications)
1.24
1.0
EECs for CRLF (including other
frog prey)
Dietary-based
EEC (ppm)
810
540
526
472
405
270
256
234
200
192
301
167
135
Dose-based EEC
(mg/kg-bw)
922
615
600
538
461
307
292
267
228
219
342
191
154
EECs for Prey
(small mammals)
Dietary-based
EEC (ppm)
1,440
960
936
840
720
480
456
415
356
242
535
298
240
Dose-based EEC
(mg/kg-bw)
1374
915
892
801
686
458
435
396
340
326
510
284
229
Table 3-6 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via
Effects to Terrestrial Invertebrate Prey Items
Application Rate
6.0
4.0
3.9
3.5
3.0
2.0
1.9
1.73
Small Insect
810
540
527
473
405
270
257
234
Large Insect
90
60
59
53
45
30
29
26
58
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1.485
1.425
1.485 (2 applications)
1.24
1.0
200
192
342
167
135
22
21
38
19
15
3.4 Terrestrial Plant Exposure Assessment
TerrPlant (Version 1.1.2) is used to calculate EECs for non-target plant species inhabiting
dry and semi-aquatic areas. Parameter values for application rate and drift assumption
are based upon the use and related application method (Table 3.7). A runoff value of
0.01 is utilized based on pendimethalin's solubility, which is 0.28 mg/L. For aerial and
ground application methods, drift is assumed to be 5% and 1%, respectively. EECs
relevant to terrestrial plants consider pesticide concentrations in drift and in runoff.
These EECs are listed by use in Table 3.7. An example output from TerrPlant v.1.2.2 is
available in Appendix F.
Table 3-7 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and
Semi-aquatic Areas Exposed to Pendimethalin via Runoff and Drift
Application
rate
(Ibs a.i./A)
6.0
4.0
4.0
3.9
3.9
3.5
3.5
3.0
3.0
2.0
2.0
1.9
1.9
1.73
1.73
1.485
1.485
1.24
1.24
1.0
1.0
Application
method
Foliar - ground
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Drift
Value
(%)
1
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
Spray
drift
EEC
(Ibs
a.i./A)
0.060
0.040
0.200
0.039
0.195
0.035
0.175
0.030
0.150
0.020
0.100
0.019
0.095
0.017
0.087
0.015
0.074
0.012
0.062
0.010
0.050
Dry area
EEC
(Ibs
a.i./A)
0.120
0.080
0.24
0.078
0.234
0.070
0.210
0.060
0.180
0.040
0.120
0.038
0.114
0.035
0.104
0.030
0.089
0.025
0.074
0.020
0.060
Semi-aquatic
area EEC
(Ibs a.i./A)
0.660
0.440
0.600
0.429
0.585
0.385
0.525
0.330
0.450
0.220
0.300
0.209
0.285
0.190
0.260
0.163
0.223
0.136
0.186
0.110
0.150
59
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4.0 Effects Assessment
This assessment evaluates the potential for pendimethalin to directly or indirectly affect
the CRLF or affect its designated critical habitat. As discussed in Section 2.7, assessment
endpoints for the CRLF effects determination include direct toxic effects on the survival,
reproduction, and growth of CRLF, 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 the CRLF. Direct effects to the
aquatic-phase of the CRLF are based on toxicity information for freshwater fish, while
terrestrial-phase effects are based on avian toxicity data, given that birds are generally
used as a surrogate for terrestrial-phase amphibians. Because the frog's prey items and
habitat requirements are dependent on the availability of freshwater fish and
invertebrates, small mammals, terrestrial invertebrates, and aquatic and terrestrial plants,
toxicity information for these taxa are also discussed. Acute (short-term) and chronic
(long-term) toxicity information is characterized based on registrant-submitted studies
and a comprehensive review of the open literature on pendimethalin.
As described in the Agency's Overview Document (U.S. EPA, 2004), the most sensitive
endpoint for each taxon is used for risk estimation. For this assessment, evaluated taxa
include freshwater fish (also as a surrogate for aquatic-phase amphibians), freshwater
invertebrates, aquatic plants, birds (surrogate for terrestrial-phase amphibians), mammals,
terrestrial invertebrates, and terrestrial plants.
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) (U.S. EPA, 2004). Open literature data presented in this assessment
were obtained from ECOTOX on 10/31/2008. In order to be included in the ECOTOX
database, papers must meet the following minimum criteria:
(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.
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., maintenance of
CRLF survival, reproduction, and growth) identified in Section 2.8. For example,
endpoints such as behavior modifications are likely to be qualitatively evaluated, because
60
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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 to define the action area for pendimethalin.
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 G. Appendix G 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.
A detailed spreadsheet of the available ECOTOX open literature data, including the full
suite of lethal and sublethal endpoints is presented in Appendix G. Appendix I also
includes a summary of the human health effects data for pendimethalin.
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 the Ecological Incident Information
System (EIIS), are conducted to further refine the characterization of potential ecological
effects associated with exposure to pendimethalin. A summary of the available aquatic
and terrestrial ecotoxicity information, use of the probit dose response relationship, and
the incident information for pendimethalin are provided in Sections 4.1 through 4.4,
respectively.
There are no available toxicity information on the degradates of pendimethalin.
A detailed summary of the available ecotoxicity information for all pendimethalin
formulated products are presented in Appendix A.
In regards to mixtures of other products containing pendimethalin, only three products
(EPA Reg. Nos. 241-331, 241-376 and 5905-495) have definitive product LD50 values
with associated confidence intervals. Although there are no 95% confidence intervals
associated with the pendimethalin technical, an evaluation of the three products listed
above show that for EPA Reg. Nos. 241-331 and 241-376, the product LDso values can be
attributed solely to the toxicity of pendimethalin. When these product LD50s (3506 and
2500 mg/kg, respectively) and associated confidence intervals (892-1223 and 504-800
mg/kg, respectively) are adjusted for the percent pendimethalin (30.24% and 25.4%,
respectively), the adjusted LD50 values for EPA Reg. No. 241-331 (1060 mg/kg, CI:
892-1223) and EPA Reg. No. 241-376 (635 mg/kg, CI: 504-800) are not lexicologically
distinct from the LDso of pendimethalin (1050 mg/kg). Similarly, for EPA Reg. No.
5905-495, the toxicity can be attributed to propanil. When the LD50 for this product
(1110 mg/kg) and its confidence interval (913-1360 mg/kg) are adjusted for the percent
propanil (33.7%), the adjusted LD50 value of 374 mg/kg (CI: 308-458 mg/kg) is within a
factor of two of the confidence interval for propanil (1080 mg/kg; CI: 868-1343 mg/kg)
and the difference is not considered to be lexicologically significant.
61
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Because the active ingredients are not expected to have similar mechanisms of action,
metabolites, or toxicokinetic behavior, it is reasonable to conclude that an assumption of
dose-addition would be inappropriate. Consequently, an assessment based on the toxicity
of pendimethalin is the only reasonable approach that employs the available data to
address the potential acute risks of the formulated products. Additional information can
be found in Appendix B.
4.1 Evaluation of Aquatic Ecotoxicity Studies
Table 4-1 summarizes the most sensitive aquatic toxicity endpoints for the CRLF, 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 CRLF is presented below. Additional information
is provided in Appendix A.
Table 4-1 Freshwater Aquatic Toxicity Profile for Pendimethalin
Assessment
Endpoint
Acute Direct
Toxicity to Aquatic-
Phase CRLF
Chronic Direct
Toxicity to Aquatic-
Phase CRLF
Indirect Toxicity to
Aquatic -Phase
CRLF via Acute
Toxicity to
Freshwater
Invertebrates (i.e.
prey items)
Indirect Toxicity to
Aquatic -Phase
CRLF via Chronic
Toxicity to
Freshwater
Invertebrates (i.e.
prey items)
Indirect Toxicity to
Aquatic -Phase
CRLF via Toxicity
to Non-vascular
Aquatic Plants
Indirect Toxicity to
Aquatic -Phase
CRLF via Toxicity
to Vascular Aquatic
Species
Rainbow
trout
Fathead
minnow
Daphnia
magna
Waterflea
(Daphnia
magna)
Marine
diatom
Skeletonem
a costatum
Duckweed
(Lemna
gibba)
Toxicity Value
Used in Risk
Assessment
LC50 =138 ppb
NOAEC = 6.3
ppb
EC50 = 280 ppb
NOAEC = 14.5
ppb
EC50 = 5.2 ppb
EC50=12..5
ppb
Describe effect
(i.e. mortality,
growth,
reproduction)
mortality
reduction of egg
production
mortality
reduced
production of
Daphnia young
growth
growth
Citation
MRID#
(Author &
Date)
00046291
Sleight,
1972
00037940
EG&G
Bionomics,
1975
00059738
LeBlanc,
1976
00100504
Graney,
1981
42372205
Hughes,
1992
42137101
Hughes,
1992
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
62
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Assessment
Endpoint
Plants
Species
Toxicity Value
Used in Risk
Assessment
Describe effect
(i.e. mortality,
growth,
reproduction)
Citation
MRID#
(Author &
Date)
Study
Classification
Toxicity to aquatic fish and invertebrates is categorized using the system shown in Table
4-2 (U.S. EPA, 2004). Toxicity categories for aquatic plants have not been defined.
Table 4-2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates
LCSO (ppm)
<0.1
>0.1-1
>1-10
> 10 - 100
>100
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically nontoxic
4.1.1 Toxicity to Freshwater Fish
Given that no pendimethalin toxicity data are available for aquatic-phase amphibians;
freshwater fish data were used as a surrogate to estimate direct acute and chronic risks to
the CRLF. Freshwater fish toxicity data were also used to assess potential indirect effects
of pendimethalin to the CRLF. Effects to freshwater fish resulting from exposure to
pendimethalin could indirectly affect the CRLF via reduction in available food. As
discussed in Section 2.5.3, over 50% of the prey mass of the CRLF may consist of
vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).
A summary of acute and chronic freshwater fish data, including data from the open
literature, is provided below in Sections 4.1.1.1 through 4.1.1.3.
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies
Three acute freshwater studies using the technical pendimethalin and seven using
formulations were submitted to the Agency. For the technical pendimethalin studies, the
LCso for the three species offish range from 138 ppb to 418 ppb. For the formulated
product studies, three species offish range from 520 ppb formulation to 86,600 ppb
formulation.
The species for the three technical pendimethalin studies are bluegill sunfish, rainbow
trout, and channel catfish. The LCso for the species are 199 ppb, 138 ppb, and 418 ppb,
respectively.
The species for the seven formulated product studies are bluegill sunfish, rainbow trout,
and channel catfish. The LCSO for the formulation studies are listed below:
AI1
LCsn (ppm
formulation)
LCsn (ppm a.i.
calculated) MPJD
63
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Bluegill sunfish Prowl 3E
Lepomis macrochims 34.4% 1.04 ppm 0.358ppm 00037927
Rainbow trout Prowl 3E
Oncorhynchus mykiss 34.4% 1.0 ppm 0.344 ppm 00037927
Bluegill sunfish Prowl 4E
Lepomis macrochims 42.3% 0.92 ppm 0.389 ppm 00037927
Rainbow trout Prowl 4E
Oncorhynchus mykiss 42.3% 0.52 ppm 0.220 ppm 00037927
Bluegill sunfish Avenge 2AS
Lepomis macrochims 31.8% 90.4 ppm 28.747 ppm 00037927
Rainbow trout Avenge 2AS
Oncorhynchus mykiss 31.8% 86.6 ppm 27.539 ppm 00037927
Channel catfish Prowl 4E
Ictaluruspunctatus 42.3% 1.9 ppm 0.804 ppm 00131773
1 AI refers to active ingredient percentage. The formulated product is also displayed.
The endpoint selected for the assessment is the rainbow trout study using technical grade
pendimethalin and it had an LCso of 138 ppb (C.I. 110-170) since it is the most sensitive
of the freshwater fish. The MRID number is 00046291.
4.1.1.2 Freshwater Fish: Chronic Exposure (Early Life Stage and
Reproduction) Studies
One chronic freshwater fish study (MRID00037940) was submitted to the Agency. This
study is a Fathead minnow (Pimephalespromelets) full life cycle study using a technical
grade pendimethalin. The 288-day NOAEC is 6.3 ppb (0.0063 ppm). The NOAEC is
based on reduction of egg production. The LOAEC = 9.8 ppb (0.0098 ppm) based on
reduction of egg production. Reduced hatchability was also observed at 22 and 43 ppb.
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open
Literature Information
The ecotoxicity studies from the ECOTOX database provided endpoints that are less
sensitive than the submitted rainbow trout study (MRID 00046291) which had an LCso of
138 ppb. No useful chronic freshwater invertebrate studies were found in the ECOTOX
database with NOAEC more sensitive than the submitted fathead minnow study (MRID
00037940).
4.1.1.4 Aquatic-phase Amphibian: Acute and Chronic Studies
No studies are available.
64
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4.1.2 Toxicity to Freshwater Invertebrates
Freshwater invertebrate toxicity data were used to assess potential indirect effects of
pendimethalin to the CRLF. Effects to freshwater invertebrates resulting from exposure
to pendimethalin could indirectly affect the CRLF via reduction in available food items.
As discussed in Section 2.5.3, the main food source for juvenile aquatic- and terrestrial-
phase CRLFs is thought to be aquatic invertebrates found along the shoreline and on the
water surface, including aquatic sowbugs, larval alderflies and water striders.
A summary of acute and chronic freshwater invertebrate data, including data published in
the open literature, is provided below in Sections 4.1.2.1 through 4.1.2.3.
4.1.2.1 Freshwater Invertebrates: Acute Exposure (Mortality) Studies
Three acute freshwater invertebrate studies were submitted to the Agency: two studies
using the waterflea Daphnia magna and one using crayfish, Procambarus simulans.
A Daphnia magna study using technical grade pendimethalin had an ECso of 280 ppb
(C.I. 230-330) and is considered to be an acceptable study. The other Daphnia magna
study used the formulation containing 45.6% active ingredient with the EC50 = 5.1 ppm
(5100 ppb) formulation. This study is considered to be acceptable for formulated study.
The crayfish study is categorized as supplemental due to the precipitate being observed in
concentrations of 1.0 ppm and more; the dissolved O2 concentration is less than 40% of
saturation; and DMSO was used as a solvent which tends to increase mortalities rather
than decrease them. This ECso for this study is greater than 1.0 ppm (1000 ppb).
Acute toxicity of pendimethalin technical to freshwater invertebrates is categorized as
highly toxic and moderately toxic. Pendimethalin formulation is categorized as
moderately toxic.
The most sensitive freshwater invertebrate species tested is Daphnia magna, with a 48-
hour ECso value of 280 |ig/L (MRTD: 00059738), is used for deriving risk quotients for
the CRLF prey.
4.1.2.2 Freshwater Invertebrates: Chronic Exposure (Reproduction)
Studies
One chronic freshwater invertebrate study (MRID 00100504) was submitted to the
Agency. This study is a Daphnia magna life cycle study using a technical grade
pendimethalin. The 21-day NOAEC is 14.5 ppb (0.0145 ppm). The NOAEC is based on
reduced production of Daphnia. LOAEC = 0.0172 ppm (17.2 ppb). Mortality was
observed in the study with 100% mortality at the 2 highest dose levels of 35.8 and 74.2
ppb. No appreciable mortality observed at 3 lowest concentration levels of 4.3, 8.2, and
14.5 ppb. Reduction of productivity of 50% occurred at 22.1 and 17.5 ppb concentration
levels.
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4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Open
Literature Data
The ecotoxicity studies from the ECOTOX database provided endpoints that are less
sensitive than the submitted Daphnia magna study (MRID 00059738) which had an
of 280 ppb. No useful chronic freshwater invertebrate studies were found in the
ECOTOX database with NOAEC more sensitive than the submitted Daphnia magna
study (MRID 00100504).
4.1.3 Toxicity to Aquatic Plants
Aquatic plant toxicity studies were used as one of the measures of effect to evaluate
whether pendimethalin may affect primary production and the availability of aquatic
plants as food for CRLF tadpoles. Primary productivity is essential for indirectly
supporting the growth and abundance of the CRLF.
Only laboratory studies were used to determine whether pendimethalin may cause direct
effects to aquatic plants since there are no available field studies to evaluate the effects of
pendimethalin to aquatic plants. A summary of the laboratory data for aquatic plants is
provided in Sections 4.1.3.1 and 4.1.3.2 .
4.1.3.1 Aquatic Plants: Laboratory Data
Aquatic plant toxicity data submitted to the Agency show a range of EC50 values from 5.2
ppb to > 174 ppb. The most sensitive species tested are the green algae and marine
diatom and the least sensitive species is the cyanobacteria (blue-green algae). Below is a
listing of the species tested and their toxicity value:
Green algae (Selenastrum capricornutum)
Marine diatom (Skeletonema costatum)
Freshwater diatom (Navicula pelliculosa)
Blue-green algae (Anabaena flos-aquae)
Duckweed (Lemna gibba)
EC.n (PPb)
5.4 ppb
5.2 ppb
6.7 ppb
>174 ppb
12.5 ppb
NOAEL
3.0
0.7
3.2
98
5.6
MRID
42372204
42372205
42372206
42372207
42137101
The endpoint selected for the assessment is the marine diatom study using technical grade
pendimethalin had an ECso of 5.2 ppb since it is most sensitive of the aquatic plants
tested. In addition, the duckweed is the only vascular aquatic plant tested and will be
used for assessing aquatic habitat. The ECso for the duckweed is 12.5 ppb.
66
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4.1.3.2 Freshwater Field Studies
No studies are available.
4.2 Toxicity of Pendimethalin to Terrestrial Organisms
Table 4.3 below summarizes the most sensitive terrestrial toxicity endpoints for the
CRLF, based on an evaluation of both the submitted studies and the open literature. A
brief summary of submitted and open literature data considered relevant to this ecological
risk assessment for the CRLF is presented below.
Table 4-3. Terrestrial Toxicity Profile for Pendimethalin
Assessment
Endpoint
Acute Dose-
based Direct
Toxicity to
Terrestrial-
Phase CRLF
Acute Dietary-
based Direct
Toxicity to
Terrestrial-
Phase CRLF
Chronic Direct
Toxicity to
Terrestrial-
Phase CRLF
Indirect
Toxicity to
Terrestrial-
Phase CRLF
(via acute
toxicity to
mammalian
prey items)
Indirect
Toxicity to
Terrestrial-
Phase CRLF
(via chronic
toxicity to
mammalian
prey items)
Indirect
Toxicity to
Terrestrial-
Species
Mallard
duck
Bobwhite
quail
Mallard
duck
Rat
Rat
Honey bee
Toxicity
Value Used in
Risk
Assessment
LD50=1421
mg/kg-bw
LC50 = 4187
ppm
NOAEC=141
ppm
LD50 = 1050
mg/kg-bw
NOAEL = 25
mg/kg-bw
(500 ppm)
LD50 = >49.8
ugm/bee
Describe effect
(i.e. mortality,
growth,
reproduction)
mortality
mortality
14-day survivor
bodyweight
mortality
decreases in the
number of pups
born and pup
weights
mortality
Citation
MRID#
(Author &
Date)
00059739
Fink, 1976
00026675
Fink, 1973
44907601
Beavers, 1996
00026657
41725203
00099890
Atkins,
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
67
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Assessment
Endpoint
Phase CRLF
(via acute
toxicity to
terrestrial
invertebrate
prey items)
Indirect
Toxicity to
Terrestrial- and
Aquatic -Phase
CRLF (via
toxicity to
terrestrial
plants)
Species
Emergence
Monocots
Seedling
Emergence
Dicots
Vegetative
Vigor
Monocots
Vegetative
Vigor
Dicots
Toxicity
Value Used in
Risk
Assessment
Ryegrass EC25
= 0.01 Ib ai/A
Lettuce EC25 =
0.09 Ibai/A
Ryegrass
EC25 = 0.034
Ibai/A
Lettuce
EC25 = 0.10 Ib
ai/A
Describe effect
(i.e. mortality,
growth,
reproduction)
Dry weight
Dry weight
Dry weight
Dry weight
Citation
MRID#
(Author &
Date)
42372201
Chetram, 1992
42372201
Chetram, 1992
42372203
Chetram, 1992
42372203
Chetram, 1992
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
Acute toxicity to terrestrial animals is categorized using the classification system shown
in Table 4-44 (U.S. EPA, 2004). Toxicity categories for terrestrial plants have not been
defined.
Table 4-4 Categories of Acute Toxicity for Avian and Mammalian Studies
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
Oral LD50
< 10 mg/kg
10-50 mg/kg
51 -500 mg/kg
501 -2000 mg/kg
> 2000 mg/kg
Dietary LC50
< 50 ppm
50 - 500 ppm
501 - 1000 ppm
1001 - 5000 ppm
> 5000 ppm
4.2.1 Toxicity to Birds
As specified in the Overview Document, the Agency uses birds as a surrogate for
terrestrial-phase amphibians when amphibian toxicity data are not available (U.S. EPA,
2004). No terrestrial-phase amphibian data are available for pendimethalin; therefore,
acute and chronic avian toxicity data are used to assess the potential direct effects of
pendimethalin to terrestrial-phase CRLFs.
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4.2.1.1 Birds: Acute Exposure (Mortality) Studies
Two subacute LCso dietary avian studies and one acute LD50 oral acute avian study using
the technical pendimethalin were submitted to the Agency. For the LCso dietary studies,
the LC50 for the bobwhite quail is 4187 ppm and the mallard duck is >4640 ppm. For the
acute LD50 for the mallard, the LD50 is 1421 mg/kg-bw.
The endpoint selected for the assessment is the bobwhite quail's LCso of 4187 ppm
(MRID 00026674) and the mallard's LD50 of 1421 mg/kg-bw (00059739).
Pendimethalin technical is categorized as slightly toxic on subacute dietary and acute oral
basis to birds. No avian studies using pendimethalin formulated product have been
submitted to the Agency.
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies
Two avian reproduction studies were submitted to the Agency. No treatment related
effects were observed in the bobwhite quail and the LOAEL is greater than 1410 ppm.
The mallard duck study (MRID 44907601) showed the parameter of 14-day survivor
bodyweight was reduced at 1410 ppm. The NOAEL for the mallard study is 410 ppm.
No other treatment related effects were observed. This study is classified as acceptable.
4.2.1.3 Birds: Open Literature Studies
No studies more sensitive than the submitted avian studies were found in the ECOTOX
database.
4.2.2 Toxicity to Mammals
Mammalian toxicity data are used to assess potential indirect effects of pendimethalin to
the terrestrial-phase CRLF. Effects to small mammals resulting from exposure to
pendimethalin could also indirectly affect the CRLF via reduction in available food. As
discussed in Section 2.5.3, over 50% of the prey mass of the CRLF may consist of
vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).
Most recent data and information on mammalian toxicity comes from Registration
Division document entitled "Pendimethalin. Human Health Risk Assessment for the
Proposed Food Uses of the Herbicide on Artichoke, Globe; Asparagus; Brassica Head
and Stem Vegetables, Subgroup 5A; and Grape (PP#6E7129)", dated August 22, 2007.
The document was authored by Debra Rate, Ph.D., Biologist, Alternative Risk Integration
and Assessment (ARIA), Risk Integration, Minor Use, and Emergency Response Branch
(RIMUERB), Registration Division (RD) (7505P) to Barbara Madden/ Susan Stanton
RIMUERB/RD (7505P). This is found in Appendix I.
69
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4.2.2.1 Mammals: Acute Exposure (Mortality) Studies
The Agency's rat acute oral assessment endpoint for risk assessment purpose shows the
LD50 to be 1250 mg/kg (male) and 1050 mg/kg (female) (MRID 00026657).
Pendimethalin is considered to be slightly toxic to mammals on an acute oral basis.
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies
A 2-generation reproduction study (MRID 41725203) with pendimethalin was reviewed
by HED. The parental systemic NOAEL was 25 mg/kg/day (500 ppm), based on
decreased body weight gain and food consumption at the LOAEL of 125 mg/kg/day
(2500 ppm). The reproductive/offspring NOAEL is 25 mg/kg/day (500 ppm), based on
decreases in the number of pups born and pup weight at the LOAEL of 125 mg/kg/day
(2500 ppm). Parental and reproductive NOAELs and LOAELs were based on a generic
ratio (1:20) of dietary intake of chemical.
The HED Cancer Peer Review Committee classified pendimethalin as a "Group C"
(possible human) carcinogen, based on thyroid follicular cell adenomas in rats. The
committee recommended a non-quantitative approach (non-linear, RfD approach) since
mode of action studies are available that demonstrate that the thyroid tumors are due to a
thyroid-pituitary imbalance, and also since pendimethalin was shown to be non-
mutagenic in mammalian somatic cells and germ cells.
4.2.2.3 Mammals: Open Literature Studies
No studies more sensitive than the submitted mammalian studies were found in the
ECOTOX database.
4.2.3 Toxicity to Terrestrial Invertebrates
Terrestrial invertebrate toxicity data are used to assess potential indirect effects of
pendimethalin to the terrestrial-phase CRLF. Effects to terrestrial invertebrates resulting
from exposure to pendimethalin may also indirectly affect the CRLF via reduction in
available food.
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies
Only one acute oral bee toxicity study (MRID ) was submitted to the Agency. This study
was authored by Dr. Atkins in 1974. The species tested is the honey bee, Apis mellifera.
The LD50 acute oral is greater than 49.8 jig/bee with no mortality observed at the highest
tested dose. Pendimethalin is classified as practically non-toxic to the honey bee.
70
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4.2.3.2 Terrestrial Invertebrates: Open Literature Studies
No studies more sensitive than the submitted bee study were found in the ECOTOX
database.
4.2.4 Toxicity to Terrestrial Plants
Terrestrial plant toxicity data are used to evaluate the potential for pendimethalin to affect
riparian zone and upland vegetation within the action area for the CRLF. Impacts to
riparian and upland (i.e., grassland, woodland) vegetation may result in indirect effects to
both aquatic- and terrestrial-phase CRLFs, as well as modification to designated critical
habitat PCEs via increased sedimentation, alteration in water quality, and reduction in of
upland and riparian habitat that provides shelter, foraging, predator avoidance and
dispersal for juvenile and adult CRLFs.
Plant toxicity data from both registrant-submitted studies and studies in the scientific
literature were reviewed for this assessment. Registrant-submitted studies are conducted
under conditions and with species defined in EPA toxicity test guidelines. Sub-lethal
endpoints such as plant growth, dry weight, and biomass are evaluated for both monocots
and dicots, and effects are evaluated at both seedling emergence and vegetative life
stages. Guideline studies generally evaluate toxicity to ten crop species. A drawback to
these tests is that they are conducted on herbaceous crop species only, and extrapolation
of effects to other species, such as the woody shrubs and trees and wild herbaceous
species, contributes uncertainty to risk conclusions.
Commercial crop species have been selectively bred, and may be more or less resistant to
particular stressors than wild herbs and forbs. The direction of this uncertainty for
specific plants and stressors, including pendimethalin, is largely unknown. Homogenous
test plant seed lots also lack the genetic variation that occurs in natural populations, so the
range of effects seen from tests is likely to be smaller than would be expected from wild
populations.
The results of the Tier II seedling emergence and vegetative vigor toxicity tests on non-
target plants are summarized below in Table 4-55.
Table 4-5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data
Crop
Species
NOAEC
(Ib ai/A)
EC25
(Ib ai/A)
Most sensitive
parameter
Seedling Emergence
Monocots
Oat, Avena sativa
0.25
1.0
Plant height
71
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Crop
Dicots
Species
Ryegrass, Lolium perenne
Corn, Zea mays
Onion, Allium cepa
Soybean, Glycine max
Lettuce, Lactuca saliva
Radish, Rhaphanus sativus
Tomato, Lycopersicon
esculentum
Cucumber, Cucumis sativus
Cabbage, Brassica oleracea
NOAEC
(Ib ai/A)
0.065 1
0.5
0.06
2.0
0.063
0.13
0.13
0.25
0.25
EC25
(Ib ai/A)
0.01
0.68
0.08
4.7
0.09
0.86
0.2
2.4
0.44
Most sensitive
parameter
Dry weight
Plant height
Dry weight
Dry weight
Dry weight
Plant height
Dry weight
Plant height
Plant height
Vegetative Vigor
Monocots
Dicots
Oat, Avena sativa
Ryegrass, Lolium perenne
Corn, Zea mays
Onion, Allium cepa
Soybean, Glycine max
Lettuce, Lactuca sativa
Radish, Rhaphanus sativus
Tomato, Lycopersicon
esculentum
Cucumber, Cucumis sativus
Cabbage, Brassica oleracea
0.5
0.0008
2.0
0.50
0.13
0.003
>4.0
0.13
>4.0
2.0
0.78
0.034
2.8
0.56
0.27
0.10
>4.0
0.5
>4.0
4.8
Dry weight
Dry weight
Plant height
Plant height
Dry weight
Dry weight
n/a
Dry weight
n/a
Dry weight
1 EC05 was used in lieu of NOEAC since study was unable to determine NOAEC value
4.3 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 (U.S. EPA, 2004).
As part of the risk characterization, an interpretation of acute RQ 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 pendimethalin 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 IECV1.1
(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
72
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estimate) as the slope parameter for the spreadsheet. In addition, the acute RQ is entered
as the desired threshold.
4.4 Incident Database Review
EPA maintains an incident database system (Ecological Incident Information System or
EIIS) to track and evaluate accidental kills associated with pesticide use. The likelihood
that a particular pesticide caused the incident is classified as "highly probable",
"probable", "possible", or "unlikely", based on the information contained in the incident
report.
A review of the EIIS database for ecological incidents involving pendimethalin was
completed on April 16, 2009. The results of this review for terrestrial, plant, and aquatic
incidents are discussed below in Sections 4.4.1 through 4.4.3, respectively. A complete
list of the incidents involving pendimethalin including associated uncertainties is
included as Appendix H.
In the years since EPA has maintained the database, a total of 69 incidents were reported,
of which 65 related to terrestrial plants.
4.4.1 Terrestrial Incidents
There were two incidents involving pendimethalin with alleged adverse effects to
terrestrial animals (American Robin, Rock dove, Ground squirrel, and an "unknown"
bird.)
In a 1998 Kansas incident (1007495-001) twelve robins and rock doves were killed. It is
not known as to what site the pendimethalin was applied but was applied nearby. No
toxicological analysis was reportedly taken; therefore no confirmation was made as to
whether pendimethalin was responsible for the deaths of the 12 birds. Pendimethalin is
slightly toxic on an acute oral and subacute dietary basis to birds. It is uncertain that
pendimethalin was responsible for the bird deaths.
There was also an incomplete incident report (1002343-001) involving surface application
of pendimethalin and fertilizer granules to turf with mortality of unknown numbers of
ground squirrel and an "unknown" bird. The corpses were analyzed for
organophosphates (OP) but not for pendimethalin. No OPs were found. Pendimethalin is
slightly toxic on an acute oral and subacute dietary basis to birds and small mammals. It
is uncertain and not likely that pendimethalin is responsible for the deaths of the squirrels
and the bird.
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4.4.2 Plant Incidents
Most of these plant incidents related to the treated crop itself, including corn, soybean,
potatoes, lawns, azalea bushes, and peanuts. Some of the incidents occur from spray drift
and runoff. Of the 65 reported alleged incidents involving pendimethalin, four of the
incidents were from spray drift to nearby non-target plants. The severity of these plant
incidents ranged from plant damage (most incidents) to mortality. The following
reported alleged incidents are from spray drift or runoff from treated sites to non-target
plants:
1014702-053 - In Wisconsin, pendimethalin was applied with clomazone to soybean.
The two herbicides drifted over to raspberry plants and trees causing some damage to
these plants. The damage symptoms observed were more consistent with clomazone
damage than pendimethalin. Pendimethalin may have contributed to plant damage but
the symptoms of plant damage to non-target plants are more consistent with clomazone.
It is probable that pendimethalin may be involved with non-target plant damage.
B000621-001 - In 1986 in Illinois, pendimethalin was applied with clomazone to
soybean field. The two herbicides drifted over to damage nearby lawns, fruit trees, and
vegetable gardens. The damage symptoms observed were more consistent with
clomazone damage than pendimethalin. Pendimethalin may have contributed to plant
damage but the symptoms of plant damage to non-target plants are more consistent with
clomazone. It is probable that pendimethalin may be involved with non-target plant
damage.
10009262-054 - In 1996 in California, a greenhouse floor was sprayed with
pendimethalin. Vapor from the spray drifted onto potted azaleas plants sitting on the
benches above the floor. 172,636 potted azaleas were unmarketable. It is likely that
pendimethalin contributed to damage to azaleas from volatility.
1013587-052 - In 1999 in Washington State, pendimethalin was applied to residential
ornamentals. Large tree limbs were observed dying. Pendimethalin was analyzed and
found present in the foliage of the trees.
4.4.3 Aquatic Incidents
There are two aquatic incidents reported involving mortality of 300 and 996 fish,
respectively. The fish involved were bass and bluegill (300 fish) and minnow (996 fish),
but the incident reports considered pendimethalin involvement "unlikely."
In 1998 in Ohio, (incident 1007677-001) pendimethalin and Lorsban were applied to a
corn field. One inch of rain fell shortly afterwards and runoff from the corn field ran into
a pond. The distance from the field to the pond is from 14-70 feet. Approximately 300
bass and bluegills were later found dead. Fish and water samples were taken but findings
74
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were not submitted. Lorsban (chlorpyrifos) is much more toxic to aquatic animals than
pendimethalin by three orders of magnitude and is more soluble in water. It is more
likely that Lorsban is the cause of the mortality to the fish. Pendimethalin is not expected
to kill fish outright from runoff from one inch of rain on a corn field based on its EEC
and toxicity.
In 1993 in Minnesota, an incident involving the deaths of 996 minnows was reported.
There is very little information in this report which indicated that "250 -300 gallons
yellow weed killer, Prowl" contributed to the deaths of the minnows in the Schwerin
Creek. This information comes from a Minnesota Department of Natural Resources
report showing a table of various spill incidents involving pesticides reported to
Minnesota. It is likely that a significant spill of concentrated pendimethalin is the cause
of deaths of the minnow in the creek.
75
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5.0 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
the CRLF or for modification to its designated critical habitat from the use of
pendimethalin 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 CRLF or its designated critical habitat (i.e., "no
effect," "likely to adversely affect," or "may affect, but not likely to adversely affect").
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
CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the LOG
is 0.05. For acute exposures to the CRLF and mammals, the LOG is 0.1. The LOG for
chronic exposures to CRLF and its prey, as well as exposures to plants is 1.0.
Risk to the aquatic-phase CRLF is estimated by calculating the ratio of exposure to
toxicity using l-in-10 year EECs based on the label-recommended pendimethalin usage
scenarios summarized in Table 3-3 and the appropriate aquatic toxicity endpoint from
Table 4-1. Risks to the terrestrial-phase CRLF and its prey (e.g. terrestrial insects, small
mammals and terrestrial-phase frogs) are estimated based on exposures resulting from
applications of pendimethalin (Tables 3.5 - 3.6) and the appropriate toxicity endpoint
from Table 4.3. Exposures are also derived for terrestrial plants, as discussed in Section
3.7 and toxicity summarized in Section 4.2.4, based on the highest application rates of
pendimethalin use within the action area.
5.1.1 Exposures in the Aquatic Habitat
5.1.1.1 Direct Effects to Aquatic-Phase CRLF
Direct effects to the aquatic-phase CRLF are based on peak EECs in the standard pond
and the lowest acute toxicity value for freshwater fish. In order to assess direct chronic
risks to the CRLF, 60-day EECs and the lowest chronic toxicity value for freshwater fish
are used. Based on exceedances of the acute LOG (0.05) for listed species,
pendimethalin may directly affect the aquatic-phase of the CRLF. The results of the RQ
calculations are in Table 5.1 below.
76
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Table 5-1 Summary of Direct Effect RQsa for the Aquatic-phase CRLF
EEC Scenario
CAForestryRLF
(forest trees and
Christmas tree
plantations)
CArowcropRLF 8
Rice model
(Rice)
Cagrapes_WirrigSTD,
CAwinegrapesRLF
(grapes)
CAalmond_WirrigSTDh
CATurfRLF J
CAalfalfa_WirrigOP
(alfalfa, lupine)
Cafruit_WirrigSTD '
CAOliveRLF
(olives)
Cacitrus_WirrigSTD K
CAcornOP
(corn and sunflower)
Peak
EEC
(Hg/L)"
16.6
11.9
48
11.4
11.7
11.5
11.3
11.2
11.2
11.1
6.8 d
60-day
EEC
(Hg/L) b
4.9
2.9
Not
available
1.8
2.3
1.9
2.0
1.9
1.7
1.5
1.5
Acute
RQ
0.12
0.09
0.35
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.05
Chronic
RQ
0.8 e
<1.0e
Not
applicable
<1.0e
<1.0e
<1.0e
<1.0e
<1.0e
<1.0e
<1.0e
<1.0e
Probability of
Individual
Effect at ES
LOC
4.18E+08
Probability of
Individual
Effect at RQ
1 in 5.85E+04
(1 in 30.5
tolinl.73E+16)c
lin7.91E+05
(1 in 54.8 to 1 in
4.10E+20)C
1 in 49. 8
(1 in 5. 53 to 1 in
4.91E+04 )c
lin2.51E+06
(1 in 70.8 tolin
3.64E+22 )c
lin2.51E+06
(1 in 70.8 tolin
3.64E+22 )c
lin2.51E+06
(1 in 70.8 tolin
3.64E+22 )c
lin2.51E+06
(1 in 70.8 to 1 in
3.64E+22 )c
lin2.51E+06
(1 in 70.8 to 1 in
3.64E+22 )c
lin2.51E+06
(1 in 70.8 tolin
3.64E+22 )c
lin2.51E+06
(1 in 70.8 tolin
3.64E+22 )c
lin4.18E+08
(1 in 216 to 1 in
1.75E+31 )c
a RQs associated with acute and chronic direct toxicity to the CRLF are also used to assess potential
indirect effects to the CRLF based on a reduction in freshwater fish and frogs as food items. The toxicity
value used as surrogate species is rainbow trout LC50 of 138 ppb (ug/L) and Fathead minnow NOAEC of
6.3 ppb (ug/L).
b The highest EEC based on foliar use of pendimethalin on forestry at 4.0 Ib ai/A (see Table 3-3).
0 A probit slope value for the acute rainbow trout toxicity test is not available; therefore, the effect
probability was calculated based on a default slope assumption of 4.5 with upper and lower 95%
confidence intervals of 2 and 9 (Urban and Cook, 1986). Not calculated for chronic endpoints.
d Peak EEC below 6.8 ppb will result in RQ < acute endangered species LOC of 0.05.
e RQ< chronic LOC of 1.0.
8 This scenario represents artichoke, asparagus, beans, carrot (including tops), garbanzos (including chick
peas), legume vegetables, peanuts (unspecified), peas, and pepper.
h This scenario represents almond, beech nut, brazil nut, butternut, cashew, chestnut, chinquapin, filbert
(hazelnut), hickory nut, macadamia nut (bushnut), mayhaw (hawthorn), pecan, pistachio, walnut (English
or black)
1 This scenario represents apple, apricot, cherry, crabapple, fig, loquat, nectarine, peach, pear, pepino
(melon pear), plum, pomegranate, prune, quince, and small fruits.
J This scenario represents commercial/industrial lawns, golf course turf, ornamental lawns and turf,
ornamental sod farm (turf), recreation area lawns, and residential lawns.
77
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K This scenario represents calamondin, citron (citrus), citrus hybrids other than tangelo, grapefruit,
kumquat, lemon, lime, orange, pummelo (shaddock), and tangelo.
5.1.1.2 Indirect Effects to Aquatic-Phase CRLF via Reduction in Prey
(non-vascular aquatic plants, aquatic invertebrates, fish, and
frogs)
a) Non-vascular Aquatic Plants
Indirect effects of pendimethalin to the aquatic-phase CRLF (tadpoles) via reduction in
non-vascular aquatic plants in its diet are based on peak EECs from the standard pond
and the lowest toxicity value (ECso) for aquatic non-vascular plants. Based on
exceedances of the acute LOG (1.0) for aquatic plants, pendimethalin is likely to
indirectly affect the CRLF via reduction in non-vascular plants. The results of the RQ
calculations are in Table 5.2 below.
Table 5-2 Summary of RQs Used to Estimate Indirect Effects to the CRLF via
Effects to Non-Vascular Aquatic Plants a (diet of CRLF in tadpole life stage and
habitat of aquatic-phase CRLF)
Uses
Rice model (Rice)
CAForestryRLF (forest trees and
Christmas tree plantations)
CArowcropRLF e
CAalrnond_WirrigSTD'
CATurfRLF h
Cagrapes_WirrigSTD,
CAwinegrapesRLF (grapes)
CAalmond_WirrigSTD '
CAalfalfa_WirrigOP (alfalfa, lupine)
Cafruit_WirrigSTD g
CAOliveRLF (olives)
Cacitrus_WirrigSTD '
CAcornOP (corn and sunflower)
CAwheatRLF (sorghum and wheat)
CAcotton_WirrigSTD (cotton)
CAOnion_WirrigSTD (onion and
shallot)
Application rate (Ib
ai/A) and type
1 Ib ai/A (aerial)
4 Ib ai/A (aerial)
4 Ib ai/A (aerial)
4 Ib ai/A (aerial)
4 Ib ai/A (aerial)
4 Ib ai/A (aerial)
6 Ib ai/A (ground)
4 Ib ai/A (aerial)
4 Ib ai/A (aerial)
4 Ib ai/A (aerial)
4 Ib ai/A (aerial)
2 Ib ai/A (aerial)
1.5 Ib ai/A (aerial)
2 Ib ai/A (aerial)
2 Ib ai/A (aerial)
Peak EEC
(Hg/L)
48
16.6 b
11.9
11.7
11.5
11.4
6.6
11.3
11.2
11.2
11.1
6.8
6.1
5.8
5.6 c
Indirect effects RQ*
(food and habitat)
9.2
3.2
2.3
2.3
2.2
2.2
1.3
2.2
2.2
2.2
2.1
1.3
1.2
1.1
1.1
* LOG exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC/ marine diatom
(Skeletonema costatum) ECso of 5.2 ppb.
a The toxicity value used as surrogate species is marine diatom (Skeletonema costatum) EC50 of 5.2 ppb
(ug/L).
b The highest EEC based on foliar use of pendimethalin is on forestry at 4.0 Ib ai/A (see Table 3-3).
c Peak EEC below 5.2 ppb will result in RQ < acute LOC of 1.0.
78
-------
e This scenario represents artichoke, asparagus, beans, carrot (including tops), garbanzos (including chick
peas), legume vegetables, peanuts (unspecified), peas, and pepper.
f This scenario represents almond, beech nut, brazil nut, butternut, cashew, chestnut, chinquapin, filbert
(hazelnut), hickory nut, macadamia nut (bushnut), mayhaw (hawthorn), pecan, pistachio, walnut (English
or black)
8 This scenario represents apple, apricot, cherry, crabapple, fig, loquat, nectarine, peach, pear, pepino
(melon pear), plum, pomegranate, prune, quince, and small fruits.
h This scenario represents commercial/industrial lawns, golf course turf, ornamental lawns and turf,
ornamental sod farm (turf), recreation area lawns, and residential lawns.
1 This scenario represents calamondin, citron (citrus), citrus hybrids other than tangelo, grapefruit, kumquat,
lemon, lime, orange, pummelo (shaddock), and tangelo.
b) Aquatic Invertebrates
Indirect acute effects to the aquatic-phase CRLF via effects to prey (invertebrates) in
aquatic habitats are based on peak EECs in the standard pond and the lowest acute
toxicity value for freshwater invertebrates. For chronic risks, 21-day EECs and the lowest
chronic toxicity value for invertebrates are used to derive RQs. A summary of the acute
and chronic RQ values for exposure to aquatic invertebrates (as prey items of aquatic-
phase CRLFs) is provided in Table 5-3. Based on the acute LOG (0.5) and chronic LOG
(1.0) not being exceeded, pendimethalin has no effect, indirectly on the CRLF based on
effects to aquatic invertebrates. The table shows only the use sites that exceed the LOG
plus the highest EEC that does not exceed the LOG.
Table 5-3 Summary of Acute and Chronic RQsa Used to Estimate Indirect Effects to
the CRLF via Direct Effects on Aquatic Invertebrates as Dietary Food Items (prey
of CRLF juveniles and adults in aquatic habitats)
EEC Scenario
Rice model
(Rice)
CAForestryRLF
(Forest trees and
Christmas tree
plantations)
CArowcropRLF h
( artichoke/asparagus)
Peak
EEC
(Jig/L)b
48
16.6
11.9
21-day
EEC
(Hg/L)b
Not
available
6.4
4.0
Acute
RQ
0.17'
0.06 b
0.04'
Chronic
RQ
Not
applicable
0.4 e
<1.0e
Probability of
Individual
Effect at ES
LOC
Probability of
Individual Effect at
RQ
1 in 3,740 (1 in 16.2 to
lin4.62E+ll)c
lin5.22E+07(lin
138tolin5.04E+27)c
Not applicable
a RQs associated with acute and chronic direct toxicity to the CRLF are also used to assess potential
indirect effects to the CRLF based on a reduction in freshwater fish and frogs as food items. The toxicity
value used as surrogate species is Daphnia magna EC50 of 280 ppb (ug/L) and Daphnia magna NOAEC of
14.5 ppb (ug/L).
b The highest EEC based on foliar use of pendimethalin on forestry and Christmas trees at 4.0 Ib ai/A (see
Table 3-3).
0 A probit slope value for the acute Daphnia magna toxicity test is not available; therefore, the effect
probability was calculated based on a default slope assumption of 4.5 with upper and lower 95%
confidence intervals of 2 and 9 (Urban and Cook, 1986). Not calculated for chronic endpoints.
d Peak EEC below 5.2 ppb will result in RQ < acute endangered species LOC of 0.05.
e RQ< chronic LOC of 1.0.
f RQ< acute LOC of 0.5.
79
-------
h This scenario represents artichoke, asparagus, beans, carrot (including tops), garbanzos (including chick
peas), legume vegetables, peanuts (unspecified), peas, and pepper.
c) Fish and Frogs
Fish and frogs also represent potential prey items of adult aquatic-phase CRLFs. RQs
associated with acute and chronic direct toxicity to the CRLF (Table 5.1) are used to
assess potential indirect effects to the CRLF based on a reduction in freshwater fish and
frogs as food items. Based on listed species LOG exceedances using the surrogate
rainbow trout acute LCso toxicity endpoint and the fathead minnow chronic NOAEC
endpoint, pendimethalin may indirectly affect the CRLF via reduction in freshwater fish
and frogs as food items.
5.1.1.3 Indirect Effects to CRLF via Reduction in Habitat and/or
Primary Productivity (Freshwater Aquatic Plants)
Indirect effects to the CRLF via direct toxicity to aquatic plants are estimated using the
most sensitive non-vascular and vascular plant toxicity endpoints. Because there are no
obligate relationships between the CRLF and any aquatic plant species, the most sensitive
ECso values, rather than NOAEC values, were used to derive RQs. Based on vascular
aquatic plant LOG (1.0) exceedances, pendimethalin may indirectly affect the CRLF via
reduction in vascular plants from uses on forestry and Christmas tree plantations and
from rice use. Table 5-4 shows only the use sites that exceed the LOG plus the highest
EEC that does not exceed the LOG.
Table 5-4 Summary of RQs Used to Estimate Indirect Effects to the CRLF via
Effects to Vascular Aquatic Plants (habitat of aquatic-phase CRLF)a
Uses
Rice model (Rice)
CAForestryRLF (forest trees and
Christmas tree plantations)
Application rate (Ib
ai/A) and type
1 Ib ai/A (aerial)
4 Ib ai/A (aerial)
Peak EEC
(Hg/L)
48
16.6
Indirect effects RQ*
(food and habitat)
3.8
1.3
a RQs used to estimate indirect effects to the CRLF via toxicity to vascular aquatic plants are summarized in
Table 5.2. The toxicity value used as surrogate species is duckweed (Lemna gibba) EC50 of 12.5 ppb (ug/L).
b The highest EEC based on foliar use of pendimethalin on forestry at 4.0 Ib ai/A (see Table 3-3).
c Peak EEC below 12.5 ppb will result in RQ < acute LOC of 1.0.
* = LOC exceedances (RQ > 1) are bolded. RQ = use-specific peak EEC / duckweed EC50 of 12.5 ppb.
5.1.2 Exposures in the Terrestrial Habitat
5.1.2.1 Direct Effects to Terrestrial-phase CRLF
80
-------
Potential direct acute effects to the terrestrial-phase CRLF are derived by considering
dose- and dietary-based EECs modeled in T-REX for a small bird (20 g) consuming
small invertebrates (Table 3.5) and acute oral and subacute dietary toxicity endpoints for
avian species.
Potential direct chronic effects of pendimethalin to the terrestrial-phase CRLF are derived
by considering dietary-based exposures modeled in T-REX for a small bird (20g)
consuming small invertebrates. Chronic effects are estimated using the lowest available
toxicity data for birds. EECs are divided by toxicity values to estimate chronic dietary-
based RQs.
Based on RQ exceedances of listed species acute LOG (0.1) and chronic LOG (1.0) from
all use sites, pendimethalin may directly affect the terrestrial-phase of the CRLF.
Table 5-5 Summary of Acute RQs* Used to Estimate Direct Effects to the
Terrestrial-phase CRLF
Use Site
walnut (english/black), tangerines, tangelo, small fruits,
pummelo (shaddock), pomegranate, pistachio, pecan, orange,
macadamia nut (bushnut), lime, lemon, kumquat, hickory nut,
grapefruit, filbert (hazelnut), citrus hybrids other than tangelo,
citron (citrus), chinquapin, chestnut, cashew, calamondin,
butternut, brazil nut, beech nut, almond, grapes.
Prune, plum, pear, peach, olive, nectarine, fig, cherry, apricot,
apple, ornamental and/or shade trees, nonagricultural rights-of-
way, fencerows, hedgerows, mulch, industrial areas (outdoor),
forest trees (all or unspecified), Christmas tree plantations,
recreation area lawns, loquat, shelterbelt plantings, quince,
mayhaw, crabapple, alfalfa
Asparagus, artichoke
golf course turf, airports/landing fields
residential lawns
Shallot, onion, com (sweet, pop, field)
Carrot
Sunflower
Tomato, tomatillo, tobacco, sorghum, potato (white/Irish),
lupine (grain), garlic, garbanzos (including chick peas) beans,
succulent (snap or lima) beans, dried-type beans, cotton,
Application rate
(Ibs ai/A)
6.0
4.0
3.9
3.5
3.0
2.0
1.9
1.73
1.485
Dietary-based
Acute RQ1
0.2
0.1
0.1
0.1
0.1
<0.1
<0.1
<0.1
<0.1
Dose-
based
Acute RQ1
1.25
0.8
0.8
0.7
0.6
0.4
0.4
0.4
0.3
Probability of Individual Effect at
RQ
Dose-based:
1 in 1.5(1 in 1.73 to 1 in 1.24 )2
Dietary-based:
1 in 1.5(1 in 1.73 to 1 in 1.24 )2
Dose-based:
1 in 3.02 (1 in 2. 36 to 1 in 5.22 )2
Dietary-based:
1 in 2.94E+05 (1 in 44 to 8.86E+18)2
Dose-based:
1 in 3.02 (1 in 2. 36 to 1 in 5.22 )2
Dietary-based:
1 in 2.94E+05 (1 in 44 to 8.86E+18)2
Dose-based:
1 in 4. 12 (1 in 2. 64 to 1 in 12.2 )2
Dietary-based:
1 in 2.94E+05 (1 in 44 to 8.86E+18)2
Dose-based:
1 in 1.5(1 in 1.73 to 1 in 1.24 )2
Dietary-based:
1 in 2.94E+05 (1 in 44 to 8.86E+18)2
Dose-based:
1 in 27.3 (1 in 4.69 to 1 in 5.85E+03)2
Dietary-based: n/a
Dose-based:
1 in 27.3 (1 in 4.69 to 1 in 5.85E+03)2
Dietary-based: n/a
Dose-based:
1 in 27.3 (1 in 4.69 to 1 in 5.85E+03)2
Dietary-based: n/a
Dose-based:
1 in 107 (1 in 6.76 to 7.91E+05)2
Dietary-based: n/a
81
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Use Site
cowpea (southern pea, black-eyed bean),
Wheat, pepper, pepino (melon pear), groundcherry, eggplant
Strawberry
Legume vegetables
Rice, mustard cabbage (gai choy, pak-choi), kohlrabi,
cauliflower, cabbage (Chinese), cabbage, brussels sprouts,
broccoli (Chinese), broccoli, Brassica (head and stem)
vegetables
* = LOG exceedances (acute RQ > 0. 1) are bolded and sh<
1 Based on mallard LD50 of 1421 mg/kg-bw and bobwhite
2 A probit slope value for the acute mallard duck and bobwhite
default slope assumption of 4.5 with upper and lower 95% confi
Application rate
(Ibs ai/A)
1.425
1.485(2
applications w/
30-day interval)
1.24
1.0
Dietary-based
Acute RQ1
<0.1
<0.1
0.1
<0.1
Dose-
based
Acute RQ1
0.3
0.5
0.3
0.2
Probability of Individual Effect at
RQ
Dose-based:
1 in 107 (1 in 6.76 to 7.91E+05)2
Dietary-based: n/a
Dose-based:
1 in 15. 5(1 in 4 to 1 in 832)2
Dietary-based: n/a
Dose-based:
1 in 107 (1 in 6.76 to 7.91E+05)2
Dietary-based: n/a
Dose-based:
1.21E+03 (1 in 12.3 to 6.33E+09)2
Dietary-based: n/a
ided.
;LC50of4187ppm.
}uail toxicity test is not available; therefore, the effect probability was calculated based on a
ience intervals of 2 and 9 (Urban and Cook, 1986). Not calculated for chronic endpoints.
Table 5-6 Summary of Chronic RQs* Used to Estimate Direct Effects to the
Terrestrial-phase CRLF
Use Site
walnut (english/black), tangerines, tangelo, small
fruits, pummelo (shaddock), pomegranate, pistachio,
pecan, orange, macadamia nut (bushnut), lime,
lemon, kumquat, hickory nut, grapefruit, filbert
(hazelnut), citrus hybrids other than tangelo, citron
(citrus), chinquapin, chestnut, cashew, calamondin,
butternut, brazil nut, beech nut, almond, grapes.
Prune, plum, pear, peach, olive, nectarine, fig,
cherry, apricot, apple, ornamental and/or shade trees,
nonagricultural rights-of-way, fencerows,
hedgerows, mulch, industrial areas (outdoor), forest
trees (all or unspecified), Christmas tree plantations,
recreation area lawns, loquat, shelterbelt plantings,
quince, mayhaw, crabapple, alfalfa
Asparagus, artichoke
golf course turf, airports/landing fields
residential lawns
Shallot, onion, corn (sweet, pop, field)
Carrot
Sunflower
Tomato, tomatillo, tobacco, sorghum, potato
(white/Irish), lupine (grain), garlic, garbanzos
(including chick peas) beans, succulent (snap or
lima) beans, dried-type beans, cotton, cowpea
(southern pea, black-eyed bean),
Wheat, pepper, pepino (melon pear), groundcherry,
eggplant
Application rate
(Ibs ai/A)
6.0
4.0
3.9
3.5
3.0
2.0
1.9
1.73
1.485
1.425
Dietary-based Chronic
RQ1
5.7
3.8
3.7
3.35
2.9
1.9
1.8
1.7
1.4
1.4
82
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Use Site
Strawberry
Legume vegetables
Rice, mustard cabbage (gai choy, pak-choi),
kohlrabi, cauliflower, cabbage (Chinese), cabbage,
brussels sprouts, broccoli (Chinese), broccoli,
Brassica (head and stem) vegetables
Application rate
(Ibs ai/A)
1.485 (2 applications w/ 30-
day interval)
1.24
1.0
Dietary-based Chronic
RQ1
2.1
1.2
1.0
* = LOG exceedances (chronic RQ > 1) are bolded and shaded.
1 Based on bobwhite NOAEC of 141 ppm.
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in
Prey (terrestrial invertebrates, mammals, and frogs)
5.1.2.2.1 Terrestrial Invertebrates
In order to assess the risks of pendimethalin to terrestrial invertebrates, which are
considered prey of CRLF in terrestrial habitats, the honey bee 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 greater than 49.8 jig a.i./bee by 1
bee/0.128g, which is based on the weight of an adult honey bee. EECs (jig a.i./g of bee)
calculated by T-REX for small and large insects are divided by the calculated toxicity
value for terrestrial invertebrates, which is >388.4 jig a.i./g of bee. Based on RQ ranges
from 2.09 to 0.05, pendimethalin may indirectly affect the CRLF via reduction in
terrestrial invertebrate prey items
Table 5-7 Summary of RQs Used to Estimate Indirect Effects
phase CRLF via Direct Effects on Terrestrial Invertebrates as
to the Terrestrial-
Dietary Food Items
Use
walnut (english/black), tangerines, tangelo, small
fruits, pummelo (shaddock), pomegranate,
pistachio, pecan, orange, macadamia nut
(bushnut), lime, lemon, kumquat, hickory nut,
grapefruit, filbert (hazelnut), citrus hybrids other
than tangelo, citron (citrus), chinquapin, chestnut,
cashew, calamondin, butternut, brazil nut, beech
nut, almond, grapes. (6.0 Ib ai/A)
Prune, plum, pear, peach, olive, nectarine, fig,
cherry, apricot, apple, ornamental and/or shade
trees, nonagricultural rights-of-way, fencerows,
hedgerows, mulch, industrial areas (outdoor),
forest trees (all or unspecified), Christmas tree
plantations, recreation area lawns, loquat,
shelterbelt plantings, quince, mayhaw, crabapple,
alfalfa (4.0 Ib ai/A)
Asparagus, artichoke (3.9 Ib ai/A)
Small Insect
RQ*
2.09
1.39
1.36
Large
Insect RQ*
0.23
0.15
0.15
Probability of
Individual Effect at RQ
of Small Insect
1 in 1.08(1 in 1.35 to 1
in 1.0 )a
1 in 1.35(1 in 1.11 to 1
in 1.63 )a
1 in 1.38(1 in 1.13 to 1
in 1.65)a
83
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golf course turf, airports/landing fields (3.5 Ib
ai/A)
residential lawns (3.0 Ib ai/A)
Shallot, onion, com (sweet, pop, field) (2.0 Ib
ai/A)
Carrot (1.91bai/A)
Sunflower (1. 73 Ib ai/A)
Tomato, tomatillo, tobacco, sorghum, potato
(white/Irish), lupine (grain), garlic, garbanzos
(including chick peas) beans, succulent (snap or
lima) beans, dried-type beans, cotton, cowpea
(southern pea, black-eyed bean), (1.485 Ib ai/A)
Wheat, pepper, pepino (melon pear),
groundcherry, eggplant
(1. 425 Ib ai/A)
Strawberry (1 .485 Ib ai/A (2 applications w/ 30-
day interval))
Legume vegetables (0.124 Ib ai/A)
Rice, mustard cabbage (gai choy, pak-choi),
kohlrabi, cauliflower, cabbage (Chinese),
cabbage, brussels sprouts, broccoli (Chinese),
broccoli, Brassica (head and stem) vegetables
(l.Olbai/A)
1.22
1.04
0.70
0.66
0.60
0.51
0.49
0.88
0.43
0.35
0.14
0.12
0.08
0.07
0.07
0.06
0.05
0.10
0.05
0.04
1 in 1.54(1 in 1.28 to 1
in 1.76)a
1 in 1.88(1 in 1.78 to 1
in 1.95)a
1 in 4. 12(1 in 2.64 to 1
in 12.2)a
1 in 4. 8(1 in 2.78 to 1 in
19.2)a
1 in 6.29(1 in 3. 04 to 1
in43.6)a
1 in 10.6(1 in 3. 58 to 1
in236)a
1 in 12.2(1 in 3.73 to 1
in 377)a
1 in 249(1 in 2. 19 to 1
in3.24)a
1 in 20.2(1 in 4.31 to 1
in2,060)a
1 in 49.8(1 in 5.53 to 1
in4.91E+04)a
* = LOG exceedances (RQ > 0.05) are bolded and shaded. Because a definitive endpoint was not
established for terrestrial invertebrates (i.e., the value is greater than the highest test concentration), the
RQ represents an upper bound value.
a A probit slope value for the acute honey bee toxicity test is not available; therefore, the effect
probability was calculated based on a default slope assumption of 4.5 with upper and lower 95%
confidence intervals of 2 and 9 (Urban and Cook, 1986). Probability of Individual Effect at RQ of 0.05
is 1 in4.18E+08 (1 in 216 to 1 in 1.75E+31).
5.1.2.2.2
Mammals
Risks associated with ingestion of small mammals by large terrestrial-phase CRLFs are
derived for dietary-based and dose-based exposures modeled in T-REX for a small
mammal (15g) consuming short grass. Acute and chronic effects are estimated using the
most sensitive mammalian toxicity data. EECs are divided by the toxicity value to
estimate acute and chronic dose-based RQs as well as chronic dietary-based RQs. Based
on RQ ranges from 25.0 to 6.2 for chronic effects, pendimethalin is likely to indirectly
affect the CRLF via reduction in small mammal prey items.
84
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Table 5-8 Summary of Acute and Chronic RQs* Used to Estimate Indirect Effects
to the Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary
Food Items
Use
(Application Rate)
walnut (english/black), tangerines, tangelo, small
fruits, pummelo (shaddock), pomegranate,
pistachio, pecan, orange, macadamia nut
(bushnut), lime, lemon, kumquat, hickory nut,
grapefruit, filbert (hazelnut), citrus hybrids other
than tangelo, citron (citrus), chinquapin,
chestnut, cashew, calamondin, butternut, brazil
nut, beech nut, almond, grapes. (6.0 Ib ai/A)
Prune, plum, pear, peach, olive, nectarine, fig,
cherry, apricot, apple, ornamental and/or shade
trees, nonagricultural rights-of-way, fencerows,
hedgerows, mulch, industrial areas (outdoor),
forest trees (all or unspecified), Christmas tree
plantations, recreation area lawns, loquat,
shelterbelt plantings, quince, mayhaw, crabapple,
alfalfa (4.0 Ib ai/A)
Asparagus, artichoke (3.9 Ib ai/A)
golf course turf, airports/landing fields (3.5 Ib
ai/A)
residential lawns (3.0 Ib ai/A)
Shallot, onion, corn (sweet, pop, field) (2.0 Ib
ai/A)
Carrot (1.91bai/A)
Sunflower (1. 73 Ib ai/A)
Tomato, tomatillo, tobacco, sorghum, potato
(white/Irish), lupine (grain), garlic, garbanzos
(including chick peas) beans, succulent (snap or
lima) beans, dried-type beans, cotton, cowpea
(southern pea, black-eyed bean), (1 .485 Ib ai/A)
Wheat, pepper, pepino (melon pear),
groundcherry, eggplant
(1. 425 Ib ai/A)
Strawberry (1.485 Ib ai/A (2 applications w/ 30-
day interval))
Legume vegetables (0.124 Ib ai/A)
Rice, mustard cabbage (gai choy, pak-choi),
kohlrabi, cauliflower, cabbage (Chinese),
Chronic RQ
Dose-
based
Chronic
RQ1
25.0
16.7
16.2
14.6
12.5
8.3
7.9
7.2
6.2
5.9
9.3
5.2
4.2
Dietary-
based
Chronic
RQ2
2.9
1.9
1.9
1.7
1.4
1.0
0.9
0.8
0.7
0.7
1.1
0.6
0.5
Acute RQ
Dose-
based
Acute
RQ3
0.6
0.4
0.4
0.35
0.3
0.2
0.2
0.2
0.2
0.1
0.2
0.1
0.1
Probability of Individual
Effect at RQ
Dose-based:
1 in 6.29 (1 in 1.73 to 1 in 1. 24 )2
Dose-based:
1 in 27.3 (1 in 4.69 to 1 in
5.85E+03)2
Dose-based:
1 in 27.3 (1 in 4.69 to 1 in
5.85E+03)2
Dose-based:
1 in 49.8(1 in 5. 53 to 1 in
4.91E+04)2
Dose-based:
1 in 107(1 in 6.76 to 1 in
7.91E+05)2
Dose-based:
1 in 1.21E+03 (1 in 12.3 to 1
in6.33E+09)2
Dose-based:
1 in 1.21E+03 (1 in 12.3 to 1
in6.33E+09)2
Dose-based:
1 in 1.21E+03 (1 in 12.3 to 1
in6.33E+09)2
Dose-based:
1 in 1.21E+03 (1 in 12.3 to 1
in6.33E+09)2
1 in 2.94E+05 (1 in 44 to 1 in
8.86E+18)2
Dose-based:
1 in 1.21E+03 (1 in 12.3 to 1
in6.33E+09)2
lin2.94E+05(lin44to 1 in
8.86E+18)2
lin2.94E+05(lin44to 1 in
8.86E+18)2
85
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cabbage, brussels sprouts, broccoli (Chinese),
broccoli, Brassica (head and stem) vegetables
(l.Olbai/A)
Chronic RQ
Acute RQ
* = LOG exceedances (acute RQ > 0.1 and chronic RQ > 1) are bolded and shaded.
1 Based on dose-based EEC and pendimethalin rat NOAEL = 25 mg/kg-diet/day (500 ppm).
2 Based on dietary -based EEC and pendimethalin rat NOAEC = 25 mg/kg-diet/day (500 ppm).
Based on dose-based EEC and pendimethalin rat acute oral LD50 = 1050 mg/kg-bw.
5.1.2.2.3 Frogs
An additional prey item of the adult terrestrial-phase CRLF is other species of frogs. In
order to assess risks to these organisms, dietary-based and dose-based exposures modeled
in T-REX for a small bird (20g) consuming small invertebrates are used. See Section
5.1.2.1 and associated tables (Table 5-65 and 5.6) for results. Based on dose-based acute
RQs the range from 1.25 to 0.2 and chronic RQs that range from 5.7 to 1.0,
pendimethalin may indirectly affect the CRLF via reduction in frogs as prey items.
5.1.2.3 Indirect Effects to CRLF via Reduction in Terrestrial Plant
Community (Riparian and Upland Habitat)
Potential indirect effects to the CRLF resulting from direct effects on riparian and upland
vegetation are assessed using RQs from terrestrial plant seedling emergence and
vegetative vigor EC25 data as a screen. Based on LOG exceedances from all use sites,
pendimethalin may indirectly affect the CRLF via reduction in terrestrial plants.
Example output from TerrPlant v. 1.2.2 is provided in Appendix F.
Table 5-9 RQs* for Monocots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Pendimethalin via Runoff and Drift
Use
walnut (english/black), tangerines,
tangelo, small fruits, pummelo
(shaddock), pomegranate, pistachio,
pecan, orange, macadamia nut
(bushnut), lime, lemon, kumquat,
hickory nut, grapefruit, filbert
(hazelnut), citrus hybrids other than
tangelo, citron (citrus), chinquapin,
chestnut, cashew, calamondin,
butternut, brazil nut, beech nut,
almond, grapes.
Prune, plum, pear, peach, olive,
nectarine, fig, cherry, apricot, apple,
ornamental and/or shade trees,
nonagricultural rights-of-way,
fencerows, hedgerows, mulch,
Application
rate
(Ibs a.i./A)
6.0 Ib ai/A
4.0 Ib ai/A
Application
method
ground
ground
Drift
Value
(%)
1
1
Spray drift
RQ
6.0
4.0
Dry area
RQ
12.0
8.0
Semi-aquatic
area RQ
66.0
44.0
86
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Use
industrial areas (outdoor), forest trees
(all or unspecified), Christmas tree
plantations, recreation area lawns,
loquat, shelterbelt plantings, quince,
mayhaw, crabapple, alfalfa
Asparagus, artichoke
golf course turf, airports/landing fields
residential lawns
Shallot, onion, com (sweet, pop, field)
Carrot
Sunflower
Tomato, tomatillo, tobacco, sorghum,
potato (white/Irish), lupine (grain),
garlic, garbanzos (including chick
peas) beans, succulent (snap or lima)
beans, dried-type beans, cotton,
cowpea (southern pea, black-eyed
bean)
Wheat, pepper, pepino (melon pear),
groundcherry, eggplant, strawberry
Legume vegetables
Rice, mustard cabbage (gai choy, pak-
choi), kohlrabi, cauliflower, cabbage
(Chinese), cabbage, brussels sprouts,
broccoli (Chinese), broccoli, Brassica
(head and stem) vegetables
Application
rate
(Ibs a.i./A)
3.91bai/A
3.51bai/A
3.01bai/A
2.0 Ib ai/A
1.91bai/A
1.731bai/A
1.485 Ib ai/A
1.425 Ib ai/A
1.241bai/A
l.Olbai/A
Application
method
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
Drift
Value
(%)
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
Spray drift
RQ
20.0
3.9
19.5
3.5
17.5
3.0
15.0
2.0
10.0
1.9
9.5
1.7
8.7
1.5
7.4
1.4
7.12
1.2
6.2
1.0
5.0
Dry area
RQ
24.0
7.8
23.4
7.0
21.0
6.00
18.0
4.0
12.0
3.8
11.4
3.5
10.4
3.0
8.9
2.9
8.6
2.5
7.4
2.0
6.0
Semi-aquatic
area RQ
60.0
42.9
58.5
38.5
52.5
33.0
43.0
22.0
30.0
20.9
28.5
19.0
26.0
16.3
22.3
15.7
21.4
13.6
18.6
11.0
15.0
* = LOG exceedances (RQ > 1) are bolded and shaded.
Table 5-10 RQs* for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Pendimethalin via Runoff and Drift
Use
walnut (english/black), tangerines,
tangelo, small fruits, pummelo
(shaddock), pomegranate, pistachio,
pecan, orange, macadamia nut
(bushnut), lime, lemon, kumquat,
hickory nut, grapefruit, filbert
(hazelnut), citrus hybrids other than
tangelo, citron (citrus), chinquapin,
chestnut, cashew, calamondin,
butternut, brazil nut, beech nut,
almond, grapes.
Application
rate
(Ibs a.i./A)
6.0 Ib ai/A
Application
method
ground
Drift
Value
(%)
1
Spray drift
RQ
0.7
Dry area
RQ
1.3
Semi-aquatic
area RQ
7.3
87
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Use
Prune, plum, pear, peach, olive,
nectarine, fig, cherry, apricot, apple,
ornamental and/or shade trees,
nonagricultural rights-of-way,
fencerows, hedgerows, mulch,
industrial areas (outdoor), forest trees
(all or unspecified), Christmas tree
plantations, recreation area lawns,
loquat, shelterbelt plantings, quince,
mayhaw, crabapple, alfalfa
Asparagus, artichoke
golf course turf, airports/landing fields
residential lawns
Shallot, onion, com (sweet, pop, field)
Carrot
Sunflower
Tomato, tomatillo, tobacco, sorghum,
potato (white/Irish), lupine (grain),
garlic, garbanzos (including chick
peas) beans, succulent (snap or lima)
beans, dried-type beans, cotton,
cowpea (southern pea, black-eyed
bean)
Wheat, pepper, pepino (melon pear),
groundcherry, eggplant, strawberry
Legume vegetables
Rice, mustard cabbage (gai choy, pak-
choi), kohlrabi, cauliflower, cabbage
(Chinese), cabbage, brussels sprouts,
broccoli (Chinese), broccoli, Brassica
(head and stem) vegetables
Application
rate
(Ibs a.i./A)
4.0 Ib ai/A
3.91bai/A
3. 5 Ib ai/A
3.01bai/A
2.0 Ib ai/A
1.91bai/A
1.731bai/A
1.485 Ib ai/A
1.425 Ib ai/A
1.241bai/A
l.Olbai/A
Application
method
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
ground
aerial
Drift
Value
(%)
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
1
5
Spray drift
RQ
0.4
2.2
0.4
2.2
0.4
1.9
0.3
1.7
0.2
1.1
0.2
1.1
0.2
1.0
0.2
0.8
0.2
0.8
0.1
0.7
0.1
0.6
Dry area
RQ
0.9
2.7
0.9
2.6
0.8
2.3
0.7
2.0
0.4
1.3
0.4
1.3
0.4
1.2
0.3
1.0
0.3
1.0
0.3
0.8
0.2
0.7
Semi-aquatic
area RQ
5.9
6.7
4.8
6.5
4.3
5.8
3.7
5.0
2.4
3.3
2.3
3.2
2.1
2.9
1.8
2.5
1.7
2.4
1.5
2.1
1.2
1.7
* = LOG exceedances (RQ > 1) are bolded and shaded.
5.1.3 Primary Constituent Elements of Designated Critical Habitat
5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-
Breeding Habitat)
Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
88
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• Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
• Alteration in water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
• Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
Based on the risk estimation for potential effects to aquatic and/or terrestrial plants
provided in Sections 5.1.1.2, 5.1.1.3, and 5.1.2.3, pendimethalin may affect aquatic-phase
PCEs of designated habitat related to effects on aquatic and/or terrestrial plants.
The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." To assess
the impact of pendimethalin on this PCE (i.e., alteration of food sources), acute and
chronic freshwater fish and invertebrate toxicity endpoints, as well as endpoints for
aquatic non-vascular plants, are used as measures of effects. RQs for these endpoints
were calculated in Sections 5.1.1.1 and 5.1.1.2. Based on RQ exceedances of LOG,
pendimethalin may affect aquatic-phase PCEs of designated habitat related to effects of
alteration of other chemical characteristics necessary for normal growth and viability of
CRLFs and their food source.
5.1.3.2 Terrestrial-Phase (Upland Habitat and Dispersal Habitat)
The first two assessment endpoints for the terrestrial-phase PCEs of designated critical
habitat for the CRLF are related to potential effects to terrestrial plants:
• Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian habitat that are comprised
of grasslands, woodlands, and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
• Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal
The risk estimation for terrestrial-phase PCEs of designated habitat related to potential
effects on terrestrial plants is provided in Section 5.1.2.3. Based on exceedances of LOG
for non-target terrestrial plants, all use sites of pendimethalin may affect the first and
second terrestrial - phase PCEs.
89
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The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of pendimethalin on this
PCE, acute and chronic toxicity endpoints for birds, mammals, and terrestrial
invertebrates are used as measures of effects. RQs for these endpoints were calculated in
Section 5.1.2.3. Based on RQ exceedances of LOG from all use sites, pendimethalin may
affect the third terrestrial - phase PCE.
The fourth terrestrial-phase PC is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. Direct acute and chronic RQs for terrestrial-phase CRLFs are presented in
Section 5.1.2.1. Based on RQ exceedances of LOG from all use sites, pendimethalin may
affect the forth terrestrial - phase PCE.
5.2 Risk Description
The risk description synthesizes an overall conclusion regarding the likelihood of adverse
impacts leading to an effects determination (i.e., "no effect," "may affect, but not likely
to adversely affect," or "likely to adversely affect") for the CRLF and its designated
critical habitat.
Based on the RQs presented in the Risk Estimation (Section 5.1) a preliminary effects
determination is "may affect" for the CRLF and critical habitat.
The direct or indirect effect LOCs are exceeded and effects may modify the PCEs of the
CRLF's critical habitat, the Agency concludes a preliminary "may affect" determination
for the FIFRA regulatory action regarding pendimethalin. A summary of the results of
the risk estimation results are provided in Error! Not a valid bookmark self-
reference. 1 for direct and indirect effects to the CRLF and in Table 5-122 for the PCEs
of designated critical habitat for the CRLF.
Table 5-11 Risk Estimation Summary for Pendimethalin - Direct and Indirect
Effects to CRLF
Assessment Endpoint
LOC
Exceedances
(Y/N)
Description of Results of Risk Estimation
Aquatic Phase
(eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects
Survival, growth, and reproduction
of CRLF individuals via direct
effects on aquatic phases
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects to
food supply (i.e., freshwater
invertebrates, non-vascular plants)
Indirect Effects
Survival, growth, and reproduction
Yes
Yes
Yes
There are acute LOC exceedances for fish,
aquatic -phase CRLF.
the surrogate for the
There are LOC exceedances for non-target aquatic non-vascular
plants. There are no acute and chronic LOC exceedances for
aquatic invertebrates.
There are exceedances of the LOC for both vascular and non-
vascular aquatic plants.
90
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Assessment Endpoint
of CRLF individuals via effects on
habitat, cover, and/or primary
productivity (i.e., aquatic plant
community)
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects to
riparian vegetation, required to
maintain acceptable water quality
and habitat in ponds and streams
comprising the species' current
range.
LOC
Exceedances
(Y/N)
Yes
Description of Results of Risk Estimation
There are LOC exceedances for non-target aquatic vascular and
terrestrial plants. Effects are possible for riparian vegetation.
Terrestrial Phase
(Juveniles and adults)
Direct Effects
Survival, growth, and reproduction
of CRLF individuals via direct
effects on terrestrial phase adults and
juveniles
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
prey (i.e., terrestrial invertebrates,
small terrestrial mammals and
terrestrial phase amphibians)
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
habitat (i.e., riparian vegetation)
Yes
Yes
Yes
There are acute and chronic LOC exceedances to birds, the
surrogate for the terrestrial-phase CRLF.
There are acute and chronic LOC exceedances to birds, the
surrogate for the terrestrial-phase amphibians.
There are LOC exceedances (>0.05) for terrestrial invertebrates.
There are acute and chronic LOC exceedances for small
mammals.
There are LOC exceedances for non-target aquatic vascular and
terrestrial plants. Effects are possible for riparian vegetation.
Table 5-12 Risk Estimation Summary for Pendimethalin - PCEs of Designated
Critical Habitat for the CRLF
Assessment Endpoint
Habitat Effects
(Y/N)
Description of Results of Risk Estimation
Aquatic Phase PCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or
geometry and/or increase in sediment
deposition within the stream channel or
pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal
for juvenile and adult CRLFs.
Yes
There are LOC exceedances for non-target aquatic
vascular and terrestrial plants. Effects are possible to
non-target terrestrial and aquatic vascular plants
inhabiting riparian areas.
91
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Assessment Endpoint
Alteration in water chemistry /quality
including temperature, turbidity, and oxygen
content necessary for normal growth and
viability of juvenile and adult CRLFs and
their food source.
Alteration of other chemical characteristics
necessary for normal growth and viability of
CRLFs and their food source.
Reduction and/or modification of aquatic-
based food sources for pre-metamorphs
(e.g., algae)
Habitat Effects
(Y/N)
Yes
Yes
Yes
Description of Results of Risk Estimation
There are LOG exceedances for non-target aquatic
vascular and terrestrial plants. Alteration in water
chemistry /quality is possible due to effects on
aquatic/terrestrial plant communities in riparian
areas.
Due to potential effects on non-target aquatic plants
and terrestrial riparian plant species, alteration in
chemical characteristics of aquatic habitat (e.g.
dissolved oxygen) may occur.
There are LOG exceedances for non-vascular aquatic
plants (i.e. algae).
Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland
habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200
ft of the edge of the riparian vegetation or
dripline surrounding aquatic and riparian
habitat that are comprised of grasslands,
woodlands, and/or wetland/riparian plant
species that provides the CRLF shelter,
forage, and predator avoidance
Elimination and/or disturbance of dispersal
habitat: Upland or riparian dispersal habitat
within designated units and between
occupied locations within 0.7 mi of each
other that allow for movement between sites
including both natural and altered sites
which do not contain barriers to dispersal
Reduction and/or modification of food
sources for terrestrial phase juveniles and
adults
Alteration of chemical characteristics
necessary for normal growth and viability of
juvenile and adult CRLFs and their food
source.
Yes
Yes
Yes
Yes
There are LOG exceedances for non-target
terrestrial plants.
There are LOG exceedances for non-target
terrestrial plants. These effects may alter plant
communities necessary for dispersal habitat.
Acute and chronic effects are possible on amphibians
and mammal that serve as prey for CRLFs
Changes in aquatic vegetation and riparian
communities may alter the chemical characteristic of
CRLF habitat
Following a "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 CRLF. 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 CRLF and its designated critical habitat.
The criteria used to make determinations that the effects of an action are "not likely to
adversely affect" the CRLF and its designated critical habitat include the following:
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• 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.
• 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 CRLF and its designated critical habitat is provided in Sections 5.2.1
through 5.2.4.
5.2.1 Direct Effects
5.2.1.1 Aquatic-Phase CRLF
The aquatic-phase considers life stages of the frog 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 pendimethalin.
This assessment used the most sensitive acute and chronic toxicity values across fish
species tested since there was no amphibian data available. RQs were based on acute
studies in rainbow trout (LC50 = 138 ug/L, MRID 00046291) and a chronic NOAEC in
fathead minnow (NOAEC = 6.3 ug/L, MRID 00037940).
The highest acute RQ was 0.12 which exceeds the Agency's listed species acute LOG of
0.05. Based on a default probit slope value of 4.5 for the rainbow trout with 95%
confidence intervals of 2 to 9, the associated probability of an individual effect would be
approximately 1 in 5.85E+04.
The most sensitive chronic toxicity value is based on a life cycle study in fathead
minnow. The chronic RQ (0.8) was based on a NOAEC of 6.3 ug/L which does not
exceed the Agency's chronic LOG of 1.0. The NOAEC is from an acceptable life-cycle
fathead minnow study (MRID 00024377). Most sensitive endpoint was reduction in egg
production that was observed at LOAEC of 44 ug/L
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Eleven aquatic EEC scenarios when compared to the acute toxicity for fish as a surrogate
for aquatic-phase CRLF have acute RQs that exceeded the listed species LOG (0.05).
None of the use sites has exceeded the chronic LOG for the CRLF. For the scenarios that
exceeded the acute LOG for listed species, the probability of individual effect at acute
RQ ranges from 1 in 5.85E+04 to 1 in 2.51E+06. The acute and chronic RQs are
presented in Section 5.1.1.1. Direct effects to the aquatic-phase CRLF are based on peak
EECs in the standard pond and the lowest acute toxicity value for freshwater fish. In
order to assess direct chronic risks to the CRLF, 60-day EECs and the lowest chronic
toxicity value for freshwater fish are used. Based on exceedances of the acute LOG for
listed species (0.05), pendimethalin is likely to directly affect the aquatic-phase of the
CRLF (LAA).
Incident data provided to the Agency indicate that there are two alleged fish kill incidents
that involve pendimethalin. However, these incidents do not show that pendimethalin
registered use contributed to the alleged fish kill incidents. One of the alleged incidents
is a spill in which an up to an estimated 300 gallons of undiluted Prowl was spilled into a
creek. Another alleged incident involved pendimethalin applied as part of a mixture with
Chlorpyrifos, which is highly toxic to fish. Further information on the pendimethalin
incidents are provided in Appendix H.
Monitoring data indicate that EECs modeled in PRZM-EXAMS are conservative. The
highest detected pendimethalin is 0.679 ppb in San Joaquin-Tulare River Basin. The
peak EECs range from 16.6 ppb to 6.8 ppb for those scenarios that exceed the listed
species acute LOG (0.05).
Based on the acute listed species LOG exceedances for CRLF and the widespread use
sites that exceed the acute listed species LOG, pendimethalin is Likely to Adversely
Affect (LAA) the aquatic-phase CRLF directly.
5.2.1.2 Terrestrial-Phase CRLF
Acute and chronic LOCs were exceeded for birds (surrogate for terrestrial-phase CRLF).
Dose-based acute RQs ranged from 1.25 (6.0 Ib ai/A application rate) to 0.2 (1.0 Ib ai/A
application rate). Dietary-based acute RQs ranged from 0.2 (6.0 Ib ai/A application rate)
to <0.1 (less than 2 Ib ai/A application rate). The RQs that exceed the endangered species
LOG (0.1) are associated with a probability of an individual effect of approximately 1 in
1.5 to 1.21E+03 based on a default probit slope of 4.5.
Avian chronic RQs ranged from 1.0 (1 Ib ai/A) to 5.7 (6.0 Ib ai/A). No treatment related
effects were observed in the bobwhite quail and the LOAEL is greater than 1410 ppm.
The mallard duck study (MRID 44907601) showed the parameter of 14-day survivor
bodyweight was reduced at 1410 ppm (LOAEL). The NOAEL for the mallard study is
410 ppm. No other treatment related effects were observed. Avian body weight
reduction may not necessary be a good parameter to measure effects to frog due to
different physiological and caloric requirements. Therefore it is uncertain as to whether
94
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there is a potential chronic risk to CRLF. Since the chronic LOG is exceeded for birds
which are surrogates for CRLF, chronic risk can not be precluded to CRLF. Therefore,
the direct effects determination from chronic effects to CRLF is LAA.
Birds were used as surrogate species for terrestrial phase CRLFs. Terrestrial phase
amphibians are poikilotherms, which mean that their body temperature varies with
environmental temperature; while birds are homeotherms (temperature is regulated,
constant, and largely independent of environmental temperatures). As a consequence, the
caloric requirements of terrestrial phase amphibians 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 (U.S. EPA, 1993):
iguanid FMR (kcal/day)= 0.0535 (bw g)°7"
passerine FMR (kcal/day) = 2.123 (bw g)0749
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.
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 amphibians are lacking. To quantify the potential differences
in food intake between birds and terrestrial phase CRLF, food intake equations for the
iguanid lizard replaced the food intake equation in T-REX for birds, and additional food
items of the CRLF 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.
Results of this analysis are presented in Table 5.13 (use pattern (1.0 Ib ai/A) with lowest
EECs and RQs) through Table 5.16 (use pattern (6.0 Ib ai/A) with highest EECs and
RQs).
95
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Table 5-13 Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based
Risk Quotients (1 Ibs a.i./acre, 1 application)
Size
Class
(grams)
1.4
37
238
Adjusted
LD50
1421.00
1421.00
1421.00
EECs and RQs
Broadleaf
Plants/
Small Insects
EEC
5.24
5.15
3.38
RQ
0.00
0.00
0.00
Fruits/Pods/
Seeds/
Large Insects
EEC
0.58
0.57
0.38
RQ
0.00
0.00
0.00
Small
Herbivore
Mammals
EEC
N/A
92.77
14.42
RQ
N/A
0.07
0.01
Small
Insectivore
Mammal
EEC
N/A
5.80
0.90
RQ
N/A
0.00
0.00
Small
Amphibians
EEC
N/A
0.18
0.12
RQ
N/A
0.00
0.00
Table 5-14 Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based
Risk Quotients (1.24 Ibs a.i./acre, 1 application)
Size
Class
(grams)
1.4
37
238
Adjusted
LD50
1421.00
1421.00
1421.00
EECs and RQs
Broadleaf
Plants/
Small Insects
EEC
6.50
6.39
4.19
RQ
0.00
0.00
0.00
Fruits/Pods/
Seeds/
Large Insects
EEC
0.72
0.71
0.47
RQ
0.00
0.00
0.00
Small Herbivore
Mammals
EEC
N/A
115.03
17.88
RQ
N/A
0.08
0.01
Small
Insectivore
Mammal
EEC
N/A
7.19
1.12
RQ
N/A
0.01
0.00
Small
Amphibians
EEC
N/A
0.22
0.15
RQ
N/A
0.00
0.00
Table 5-15. Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based
Risk Quotients (1.425 Ibs a.i./acre, 1 application)
Size
Class
(grams)
1.4
37
238
Adjusted
LD50
1421.00
1421.00
1421.00
EECs and RQs
Broadleaf
Plants/
Small Insects
EEC
7.79
7.65
5.02
RQ
0.01
0.01
0.00
Fruits/Pods/
Seeds/
Large Insects
EEC
0.87
0.85
0.56
RQ
0.00
0.00
0.00
Small Herbivore
Mammals
EEC
N/A
137.76
21.42
RQ
N/A
0.10
0.02
Small
Insectivore
Mammal
EEC
N/A
8.61
1.34
RQ
N/A
0.01
0.00
Small
Amphibians
EEC
N/A
0.27
0.17
RQ
N/A
0.00
0.00
Table 5-16. Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based
Risk Quotients (6 Ibs a.i./Acre, 1 application)
Size
Class
(grams)
Adjusted
LD50
EECs and RQs
Broadleaf
Plants/
Small Insects
EEC
RQ
Fruits/Pods/
Seeds/
Large Insects
EEC
RQ
Small Herbivore
Mammals
EEC
RQ
Small
Insectivore
Mammal
EEC
RQ
Small
Amphibians
EEC
RQ
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1.4
37
238
1421.00
1421.00
1421.00
31.47
30.93
20.27
0.02
0.02
0.01
3.50
3.44
2.25
0.00
0.00
0.00
N/A
556.59
86.53
N/A
0.39
0.06
N/A
34.79
5.41
N/A
0.02
0.00
N/A
1.07
0.70
N/A
0.00
0.00
These data suggest that dietary exposures from consumption of insects by terrestrial
phase CRLFs is likely to result in exposures that do not exceed LOCs. However, the
endangered species LOG was exceeded for large terrestrial phase CRLFs that consume
small herbivorous mammals in use sites that receive only 1.425 Ibs a.i./acre or more of
pendimethalin applications. The California mouse is a prey item of the CRLF, and this
mouse reportedly eats grasses. However, some assumptions included in the assessment
of small mammals as a food item are conservative because the CRLF eats a variety of
food items and LOCs were not exceeded for CRLFs that eat insectivorous mammals.
The RQs for a 37-gram and a 238-gram CRLF that consumes a small herbivore mammal
that recently consumed contaminated short grass are found below in Table 5.17.
Table 5-17 RQ Comparisons among Weight Class and Applications Rates for
CRLF Consuming Small Herbivore Mammal That Recently Consumed
Contaminated Short Grass
Use site
application rate
6.0
6.0
.425
.425
.24
.24
.0
.0
CRLF weight class
37 gram
238 gram
37 gram
238 gram
37 gram
238 gram
37 gram
238 gram
Dose-based RQ for
small herbivorous
mammals
0.39
0.06
0.10
0.02
0.08
0.01
0.07
0.01
RQs remain above the endangered species LOG for CRLFs that consume herbivorous
mammals for all uses except where applications are less than 1.425 Ib ai/A. Refinements
incorporating dietary habits of CRLFs did not preclude potential risks for CRLFs that
consume herbivorous mammals.
Current assessment methods of potential risks from chronic exposures for birds do not
consider food intake levels. Therefore, T-HERPS does not quantify potential effects of
reduced food intake of terrestrial phase CRLFs relative to birds for chronic risk
assessments. However, chronic RQs would be expected to be reduced by a similar
magnitude seen in the acute analysis.
Incident data provided to the Agency indicate that there are two alleged terrestrial
incidents in which birds and squirrels were killed. In both of these incidents there was no
chemical analysis for pendimethalin made of the corpses. Therefore, the allegation that
pendimethalin was responsible for the deaths of the birds and squirrels was not confirmed
but yet pendimethalin can not be precluded.
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Acute and chronic LOCs were exceeded for birds (as surrogate for CRLF). The available
toxicity data suggest that amphibians are less sensitive than birds to pendimethalin, and
considering factors such as lower food intake of terrestrial phase amphibians relative to
birds reduces EECs and RQs, but does not reduce RQs to levels that are below LOCs.
Potential effects to CRLFs that consume herbivorous mammals cannot be precluded.
Based on the weight-of-evidence, there is a potential direct impact to the terrestrial-phase
of the CRLF based on the avian acute and chronic toxicity endpoints as a surrogate for
terrestrial-phase CRLF. The effects determination of likely to adversely affect (LAA)
terrestrial-phase CRLF from direct effects is based on acute and chronic listed species
LOG exceedances for birds.
5.2.2 Indirect Effects (via Reductions in Prey Base)
5.2.2.1 Algae (non-vascular plants)
As discussed in Section 2.5.3, the diet of CRLF tadpoles is composed primarily of
unicellular aquatic plants (i.e., algae and diatoms) and detritus. Because the aquatic
nonvascular plant RQs exceed the LOG for 15 out of 25 pendimethalin use sites,
pendimethalin is considered likely to indirectly affect the aquatic-phase CRLF via effects
on aquatic nonvascular plants.
There were 604 measurements of pendimethalin in the Sacramento River and San
Joaquin-Tulare River basins. There was measurable pendimethalin in 319 of the 604
samples (53% positive). The highest concentration recorded (0.679 ppb) in the San
Joaquin-Tulare River Basin. All 9 measurements at this site were positive for
pendimethalin, with a range of 0.262 to 0.679 ppb. LOCs that were exceeded have EECs
from the modeled PRZM_EXAMS ranging from peak of 48 ppb (rice model scenario) to
5.6 ppb. EECs that fall below 5.2 ppb did not exceed the LOG for aquatic plants. The
lowest LOG exceedance which has a peak EEC of 5.6 also has a 60-day EEC of 0.8 ppb
which is similar to the peak monitoring concentration detected in surface water in
California.
There are four aquatic non-vascular plant studies submitted to the Agency. The ECso
results of these studies range from 5.2 ppb to >174 ppb. Three of the four species have
similar results. The ECso data on the species are below:
Species tested EC^n
Green algae (Selenastmm capricornutum) 5.4 ppb
Marine diatom (Skeletonema costatum) 5.2 ppb
Freshwater diatom (Navicula pelliculosa) 6.7 ppb
Bluegreen algae (Anabaena flos-aquae) >174 ppb
MRID Source
42372204
42372205
42372206
42372207
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Based on the Agency's LOG for aquatic plants being exceeded and that 3 out of 4 species
have sensitive ECso similarities; there is a potential indirect impact to the CRLF from
reduction of aquatic food items. The effects determination for the CRLF based on
potential reductions in algae is "likely to adversely affect" (LAA).
5.2.2.2 Aquatic Invertebrates
The potential for pendimethalin to elicit indirect effects to the CRLF via effects on
freshwater invertebrate food items is dependent on several factors including: (1) the
potential magnitude of effect on freshwater invertebrate individuals and populations; and
(2) the number of prey species potentially affected relative to the expected number of
species needed to maintain the dietary needs of the CRLF. Together, these data provide a
basis to evaluate whether the number of individuals within a prey species is likely to be
reduced such that it may indirectly affect the CRLF.
There are no aquatic invertebrate's chronic (1.0) or acute (0.5) exceedances of LOG
found in section 5.1.1.2. There are two scenarios (rice and forestry) in which the RQ lies
between the listed species LOG of 0.05 and the acute LOG of 0.5. The probability of
individual effect at RQ for RQ of 0.17 is 1 in 3740 and for the listed species of 0.06 is 1
in 5.22E+07. The scenario with an RQ of 0.17 used a conservative scenario (Rice
model) which is a direct instantaneous deposition to a water column. It does not take into
account runoffs, dilution, or holding patterns before releasing into the environment. Thus
the EEC may be an overestimation of the amount of pendimethalin concentration found
waters from rice fields that are released into environs. The probability of individual
effect at RQ analysis indicates that the chance of adverse effect to the aquatic invertebrate
population is not significant.
Other aquatic invertebrate acute toxicity studies were submitted to the Agency. Another
waterflea {Daphnia magna) study tested with a formulation of 45.6% active ingredient of
pendimethalin. This study showed an ECso of 5.1 ppm formulated product. A submitted
crayfish (Procambarus simulans) study showed an ECso greater than 1.0 ppm (1,000
ppb). This study is considered to be supplemental due to precipitation was seen of
concentrations over 1 ppm, the dissolved 62 concentration is less than 40% of saturation,
and DMSO was used as a solvent which tends to increase mortalities rather than decrease
them. Both studies show that other aquatic invertebrates have orders of magnitude less
sensitivity than the Daphnia magna surrogate.
There were 604 measurements of pendimethalin in the Sacramento River and San
Joaquin-Tulare River basins. There was measurable pendimethalin in 319 of the 604
samples (53% positive). The highest concentration recorded (0.679 ppb) in the San
Joaquin-Tulare River Basin. All 9 measurements at this site were positive for
pendimethalin, with a range of 0.262 to 0.679 ppb which is well below the toxicity level
of Daphnia magna ECso of 280 ppb by three orders of magnitude.
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Based on the weight-of-evidence of chronic and acute LOG not being exceeded for
aquatic invertebrates; the probit slope analysis showing probability of effect being
insignificant; and species sensitivity among other aquatic invertebrates being less
sensitive than the surrogate invertebrate; the effects determination for the CRLF based on
potential reductions in aquatic invertebrates is "not likely to adversely affect" (NLAA).
5.2.2.3 Fish and Aquatic-phase Frogs
In the absence of toxicity data for amphibians, the most sensitive acute and chronic
toxicity values across fish species tested. RQs were based on acute studies in rainbow
trout (LC50 =138 ug/L, MRID 00046291) and a chronic NOAEC in fathead minnow
(NOAEC = 6.3 ug/L, MRID 00037940).
The highest acute RQ from the rice model was 0.0.35. The acute LOG is 0.5. Based on a
default probit slope value of 4.5 for the rainbow trout with 95% confidence intervals of 2
to 9, the associated probability of an individual effect would be approximately 1 in 49.8.
The scenario with an RQ of 0.12 used a conservative scenario (Rice model) which is a
direct instantaneous deposition to a water column. It does not take into account runoffs,
dilution, or holding patterns before releasing into the environment. Thus the EEC may be
an overestimation of the amount of pendimethalin concentration found waters from rice
fields that are released into environs.
The next highest RQ is 0.12 from a forestry and Christmas tree use sites. The associated
probability of an individual effect would be approximately 1 in 5.85E+04. Eleven
scenarios have LOCs that are between the acute LOG (0.5) and the listed species LOG
(0.05) and their RQs range from 0.12 to 0.05. The probability of individual effect at RQ
for RQs of 0.17 to 0.05 is 1 in 5.85E+04 to 1 in 4.18E+08. The probability of individual
effect at RQ analysis indicates that the chance of adverse effect to the aquatic invertebrate
population is not be significant.
The most sensitive chronic toxicity value is based on a life cycle study in fathead
minnow. The chronic RQ (0.8) is based on a NOAEC of 6.3 ug/L from an acceptable
life-cycle study (MRID 00024377). Most sensitive endpoint was reduction in egg
production that was observed at LOAEC of 44 ug/L.
Based on no acute or chronic exceedances and the low probability of an individual effect;
the effects determination for the CRLF based on potential reductions in fish and other
amphibians as food items of the aquatic-phase CRLF is "not likely to adversely affect"
(NLAA).
5.2.2.4 Terrestrial Invertebrates
When the terrestrial-phase CRLF reaches juvenile and adult stages, its diet is mainly
composed of terrestrial invertebrates.
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Toxicity data from honey bee study (MRID 00099890) show the LD50 to be greater than
49.8 jig/Bee. No mortalities were observed at the highest concentration.
Based upon an average fresh weight per honey bee of 128 milligrams, the LD50 of honey
bees (jig /bee) can be multiplied by 7.8 to determine the ppm toxicity. The toxicity
equivalence in ppm would be 388 ppm. According to the Hoerger, Kenaga5 nomogram
modified by Fletcher6, the highest EEC exposure from 6 Ib ai/A application to large
insects would be 90 ppm and to small insects would be 810 ppm. The EEC of small
insects is about 2X more than the highest dose tested. The EEC of the largest insect is
less than 2X the dose tested. Although there are no mortalities of the honey bee at the
highest dose tested and that under the Agency's guidelines, pendimethalin is considered
to be practically non-toxic to honey bee; the honey bee study did not test up to the highest
dose that could be expected from 6 Ib ai/A directly onto small insects at the site of
application.
There is some uncertainty due to the highest concentration dose tested on the bee was
well below the equivalent of 6 Ib ai/A maximum application. There was no mortality at
the highest dose tested, yet it is uncertain if mortality will exist if a higher dose was used
in the bee study that would reflect the maximum application rate. Therefore, potential
risk can not be precluded to terrestrial invertebrates as a food item. Because potential
risk can not be precluded to terrestrial invertebrates as a food item; the effects
determination for the CRLF based on potential reductions in terrestrial invertebrates as
prey items is "likely to adversely affect" (LAA).
5.2.2.5 Mammals
Terrestrial phase CRLFs consume small mammals. This assessment used a 15-gram
herbivorous mammal to determine if there could be a potential reduction in mammal
abundance. Acute dose-based RQs for a 15-gram mammal ranged from 0.1 to 0.6
depending on the use pattern. Assuming a probit slope of 4.5, the probability of an
individual effect would be approximately 1 in 6.9. Assuming that probability of an
individual effect provides insight into the potential for reductions in a local population of
small mammals, a probability of 1 in 6.9 (15.9%) would result in a measurable impact to
mammal abundance and would, therefore, constitute a significant effect.
Reproduction RQs ranged from 5.2 to 25.0. The toxicity endpoint used in the RQs was
based on a parental systemic and reproductive NOAEL of 25 mg/kg-bw/day. The
5 Hoerger, F. and E.E. Kenaga. 1972. Pesticide residues on plants: correlation of representative data as a
basis for estimation of their magnitude in the environment. IN: F. Coulston and F. Corte, eds.,
Environmental Quality and Safety: Chemistry, Toxicology and Technology. Vol 1. Georg Theime
Publishers, Stuttgart, Germany, pp. 9-28
6 Fletcher, J.S., J.E. Nellesson and T. G. Pfleeger. 1994. Literature review and evaluation of the EPA food-
chain (Kenaga) nomogram, an instrument for estimating pesticide residues on plants. Environ. Tox. and
Chem. 13(9):1383-1391
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parental systemic endpoint was based on decreased body weight gain and food
consumption at the LOAEL of 125 mg/kg/day (500 ppm). The reproductive/offspring
NOAEL is 25 mg/kg/day (500 ppm), based on decreases in the number of pups born and
pup weight at the LOAEL of 125 mg/kg/day (2500 ppm) which may be a significant
population effect. The RQs indicate that potential exposures exceed the NOAEL for all
uses. Due to the chronic LOG being exceeded for small mammal prey and the
reproductive endpoint is based on decreasing numbers of pups born and pup weight, the
effects determination for the potential for pendimethalin to indirectly affect the CRLF
from potential impacts to mammalian prey is likely to adversely affect (LAA).
5.2.2.6 Terrestrial-phase Amphibians
The effects determination for terrestrial phase CRLF consuming small mammalian prey
was "likely to adversely affect" (LAA). This determination was based solely on frogs
that consume potentially contaminated herbivore mammals. Terrestrial amphibian prey
of the CRLF includes small amphibians such as tree frogs that do not prey on mammals.
Therefore, the mammalian food group is not relevant in the evaluation of potential
reductions in amphibian prey abundance.
Avian (as surrogate for frog and CRLF) listed species RQs exceeded LOCs (0.1) (Section
5.1). Acute LOCs (0.5) were not exceeded for insectivorous amphibians using the T-
HERPS model (Table 5.16) at the highest rate of application (6 Ib ai/A). Therefore,
reductions from acute effects in amphibian prey as a food item at levels likely to affect
the CRLF are not likely to occur, and the effects determination for the CRLF based on
potential reductions in terrestrial amphibians is "not likely to adversely affect" (NLAA).
Since the chronic LOG have been exceeded, the effects determination for the CRLF
based on potential reductions in terrestrial-phase amphibians as food item is "likely to
adversely affect" (LAA) from chronic LOG exceedances.
5.2.3 Indirect Effects (via Habitat Effects)
5.2.3.1 Aquatic Plants (Vascular and Non-vascular)
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 as attachment sites and refugia for
many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In
addition, vascular plants also provide primary productivity and oxygen to the aquatic
ecosystem. Rooted plants help reduce sediment loading and provide stability to
nearshore areas and lower streambanks. In addition, vascular aquatic plants are important
as attachment sites for egg masses of CRLFs.
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Potential indirect effects to the CRLF based on impacts to habitat and/or primary
production were assessed using RQs from freshwater aquatic vascular and non-vascular
plant data. Section 5.2.2.1 indicates that pendimethalin is likely to adversely impact non-
target aquatic plants.
LOCs are exceeded for aquatic vascular plants and algae from exposure to pendimethalin
from runoff or spray drift. The non-vascular RQs that exceed LOG range from 1.1 to 9.2
and exceed the LOG for 15 out of 25 pendimethalin aquatic model scenarios. The
vascular plant LOG is exceeded for 2 of the 25 aquatic model scenarios with the RQs of
1.3 and 3.8.
There were 604 measurements of pendimethalin in the Sacramento River and San
Joaquin-Tulare River basins. There was measurable pendimethalin in 319 of the 604
samples (53% positive). The highest concentration recorded (0.679 ppb) were found in
the San Joaquin-Tulare River Basin. All 9 measurements at this site were positive for
pendimethalin, with a range of 0.262 to 0.679 ppb. LOCs that were exceeded have EECs
from the modeled PRZM_EXAMS ranging from peak of 48 ppb (rice model scenario) to
5.6 ppb. EECs that fall below 5.2 ppb did not exceed the LOG for aquatic nonvascular
plants and 12.5 ppb for the aquatic vascular plants.
Potential indirect effects to the CRLF based on impacts to habitat and/or primary
production were assessed using RQs from freshwater aquatic vascular and non-vascular
plant data. Based on the LOG exceedances, there is a potential indirect impact to the
aquatic-phase-CRLF from aquatic habitat degradation. The effects determination for the
aquatic-phase CRLF is "likely to adversely affect" (LAA).
5.2.3.2 Terrestrial Plants
Terrestrial plants serve several important habitat-related functions for the CRLF. In
addition to providing habitat and cover for invertebrate and vertebrate prey items of the
CRLF, terrestrial vegetation also provides shelter for the CRLF and cover from predators
while foraging. Terrestrial plants also provide energy to the terrestrial ecosystem through
primary production. 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.
The terrestrial non-target plant LOG is exceeded for all use sites. The RQs are variable
according to the method of application used (aerial or ground application) and the amount
of active ingredient used. Table 5.18 below shows the range of RQs from different
application methods.
Table 5-18. Range of Risk Quotients for Non-Target Terrestrial Plants from
Pendimethalin Usage
| Application | Spray | Runoff to Low-Lying | Runoff to dry
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Application Rate
6.0 Ib ai/A
4.0 Ib ai/A
3.5 Ib ai/A
2.0 Ib ai/A
1.485 Ib ai/A
1.0 Ib ai/A
4.0 Ib ai/A
3. 5 Ib ai/A
2.0 Ib ai/A
1. 485 Ib ai/A
l.Olbai/A
Method
ground
ground
ground
ground
ground
ground
aerial
aerial
aerial
aerial
aerial
Drift RQ
6.0
4.0
3.5
2.0
1.5
1.0
20.0
17.5
10.0
7.4
5.0
semi-aquatic areas
66.0
44.0
38.5
22.0
16.3
11.0
60.0
52.5
30.0
22.3
15.0
adjacent areas
12.0
8.0
7.0
4.0
3.0
2.0
24.0
21.0
12.0
8.9
6.0
Bold denotes that the RQ has exceeded the LOC.
Although the endpoint used for runoff (seedling emergence) is 3X more sensitive than the
spray drift toxicity endpoint (vegetative vigor), there is more LOC exceedances from
aerial application than from runoff. This is due to the fate characteristics of
pendimethalin. Pendimethalin binds more closely to the soil and is usually carried with
soil during a runoff event rather than with water.
The most sensitive monocot appears to be more sensitive than the most sensitive dicot
tested by an order of magnitude. Differences of responses between the dicots and
monocots are mixed and do overlap. Overall, monocots and dicots are both sensitive to
pendimethalin. The herbicidal mode of action of pendimethalin is that it disrupts the
process of mitosis in the growth of shoots and roots. It acts as a microtubule disrupter by
inhibiting cell division and cell elongation in plants. Absorption of the chemical into
plant is via roots and shoots.
Based on the weight-of-evidence, the Agency concludes that there is a potential indirect
impact to CRLF by terrestrial habitat degradation from pendimethalin exposure and
therefore pendimethalin is Likely to Adversely Affect (LAA) the CRLF both riparian and
upland vegetation.
If aerial application was to be eliminated at least 1000 feet of CRLF habitat, potential risk
would be reduced.
5.2.4 Effects to Designated Critical Habitat
Risk conclusions for the designated critical habitat are the same as those for indirect
effects. Agency concludes that there is a potential indirect impact to CRLF by terrestrial
and aquatic habitat degradation from pendimethalin exposure.
5.2.4.1 Aquatic-Phase PCEs
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Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
• Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
• Alteration in water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
• Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
Conclusions for potential indirect effects to the CRLF via direct effects to aquatic and
terrestrial plants are used to determine whether modification to critical habitat may occur.
There is a potential for habitat effects via impacts to aquatic plants (Sections 5.2.2.1 and
5.2.3.1) and terrestrial plants (5.2.3.2)
The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." Other than
impacts to algae as food items for tadpoles (discussed above), this PCE is assessed by
considering direct and indirect effects to the aquatic-phase CRLF via acute and chronic
freshwater fish and invertebrate toxicity endpoints as measures of effects. There is a
potential for habitat effects via impacts to aquatic-phase CRLFs (Sections 5.2.1.1) and
effects to freshwater invertebrates and fish as food items (Sections 5.2.2.2 and 5.2.2.3).
5.2.4.2 Terrestrial-Phase PCEs
Two of the four assessment endpoints for the terrestrial-phase PCEs of designated critical
habitat for the CRLF are related to potential effects to terrestrial plants:
• Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or drip line surrounding aquatic and riparian habitat that are comprised
of grasslands, woodlands, and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance.
• Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal.
There is a potential for habitat effects via impacts to terrestrial plants (5.2.3.2).
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The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of pendimethalin on this
PCE, acute and chronic toxicity endpoints for terrestrial invertebrates, mammals, and
terrestrial-phase frogs are used as measures of effects. There is a potential for habitat
effects via indirect effects to terrestrial-phase CRLFs via reduction in prey base (Section
5.2.2.4 for terrestrial invertebrates, Section 5.2.2.5 for mammals, and 5.2.2.6 for frogs).
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. There is a potential for habitat modification via direct (Section 5.2.1.2) and
indirect effects (Sections 5.2.2.4, 5.2.2.5, and 5.2.2.6) to terrestrial-phase CRLFs.
5.2.5 Spatial Extent of Potential Effects
An LAA effects determination applies to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat.
To determine this area, the footprint of pendimethalin's use pattern is identified, using
land cover data that correspond to pendimethalin's use pattern. 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. The identified direct/indirect effects and/or
modification to critical habitat are anticipated to occur only for those currently occupied
core habitat areas, CNDDB occurrence sections, and designated critical habitat for the
CRLF that overlap with the initial area of concern plus at least 1000 feet from its
boundary. It is assumed that non-flowing waterbodies (or potential CRLF habitat) are
included within this area.
In addition to the spray drift buffer, the results of the downstream dilution extent analysis
result in a distance of 272 kilometers which represents the maximum continuous distance
of downstream dilution from the edge of the initial area of concern (based on the forestry
use; see Appendix D). If any of these streams reaches flow into CRLF habitat, there is
potential to affect either the CRLF or modify its habitat. These lotic aquatic habitats
within the CRLF core areas and critical habitats potentially contain concentrations of
pendimethalin sufficient to result in LAA determination or effects to critical habitat.
The determination of the buffer distance and downstream dilution for spatial extent of the
effects determination is described below.
5.2.5.1 Spray Drift
In order to determine terrestrial and aquatic habitats of concern due to pendimethalin
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. An analysis of spray drift distances was completed using the
AgDrift model.
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In order to characterize the spatial extent of the effects determination that is relevant to
the CRLF (i.e. NLAA versus LAA), an analysis was conducted using the most sensitive
non-endangered plant £€25 of 0.01 Ibs ai/acre (ryegrass seedling emergence). Typically
the NOAEC is used when there is an obligate relationship between the species being
assessed and endangered plants (or other taxa). However, there is no obligate
relationship between the CRLF and any endangered plant; therefore the LAA/NLAA
determination is based on the area defined by the non-listed species LOG (i.e.,
EEC/EC5o).
The most sensitive effect of concern was the lowest EC25 for seedling emergence, 0.01
Ib/acre for ryegrass. Tier 1 ground spray analysis (terrestrial assessment) was performed
with the AgDrift model. The following settings were used: High boom, ASAE very fine
to fine spray, point deposition, and an application rate of 6 Ib/acre. The resulting buffer
distance for ground spray was 899 feet.
A similar analysis was performed using AgDrift, using the Tier 1 aerial (terrestrial)
assessment with ASAE very fine to fine spray, point deposition, and an application rate
of 4 Ib/acre. The resulting buffer exceeds the limit of the AgDrift model (approximately
1000 feet). A Tier 2 AgDrift aerial analysis was also conducted, with the same result
(over 1000 feet). A summary of the modeled distances by application rate is presented in
Table 5.19.
Table 5-19 Summary of AgDrift Predicted Terrestrial Spray Drift Distances
Application Rate
(method)
6.0 (ground)
4.0 (aerial)
Uses Represented
EC25
Distance (ft)
899
Over 1000
Given that the greatest buffer distance is 1,000 feet for terrestrial plants, this value was
used to define the spatial extent of the effects determination (i.e., this buffer distance is
added to the initial area of concern).
Similar to the analysis described above, the buffer distance needed to get below the most
sensitive aquatic LOG was determined. This distance identifies those locations where
water bodies can be impacted by spray drift deposition alone (no runoff considered)
resulting in concentrations above the LOG. The most sensitive aquatic endpoint is for
aquatic non-vascular plants (Skeletonema) with an ECso value of 5.2 |ig/L. The analysis
yields a much lower ground-spray buffer distance than the terrestrial buffer with a
distance of 79 feet (based on the non-listed LOG using the ECso value). However, the
Tier 1 and 2 aerial analysis again yields a distance of over 1,000 feet. The results of the
analysis are presented in Table 5.20.
Table 5-20 Summary of AgDrift Predicted Aquatic Spray Drift Distances
Application Rate
(method)
Uses Represented
107
EC50
Distance (ft)
-------
Application Rate
(method)
6.0 (ground)
4.0 (aerial)
Uses Represented
EC50
Distance (ft)
79
Over 1000
5.2.5.2 Downstream Dilution Analysis
The downstream extent of exposure in streams and rivers is where the EEC could
potentially be above levels that would exceed the most sensitive LOG. To complete this
assessment, the greatest ratio of aquatic RQ to LOG 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 pendimethalin present.
Using an EC50 value of 5.2 ug/L for non-vascular aquatic plants (the most sensitive
species is Skeletonema costatum) and a maximum peak EEC for applications to rice of 48
ug/L yields an RQ/LOC ratio of 9.2 (9.2/1), which is applied to the pasture/hay and
cultivated crop land cover class. RQ/LOC ratios for other use categories range from 2.3
to 3.2. Using the downstream dilution approach (described in more detail in Appendix
D) yields a target percent crop area (PCA) of 11% for the ratio of 9.2. This value has
been input into the downstream dilution approach and results in a distance of 47
kilometers. However, the forestry RQ/LOC ratio of 3.2 yields a downstream dilution
distance of 272 kilometers, which represents the maximum continuous distance of
downstream dilution from the edge of the initial area of concern, for the forestry land
cover class. Similar to the spray drift buffer described above, the LAA/NLAA
determination is based on the area defined by the point where concentrations exceed the
value.
5.2.5.3 Overlap between CRLF habitat and Spatial Extent of Potential
Effects
An LAA effects determination is made to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat
and the area overlaps with the core areas, critical habitat and available occurrence data
for CRLF.
For pendimethalin, the use patterns fall into the following land cover classes:
Cultivated Crops; Developed, High Intensity; Developed, Low Intensity; Developed,
Medium Intensity; Developed, Open Space; Forest; Open Water; Orchards and
vineyards; Pasture/Hay; Wetlands; Turf; and Rights-of-way. The overlap area also
includes areas beyond the initial area of concern that may be impacted by runoff and/or
spray drift, where it overlaps with CRLF habitat. Appendix D provides maps of the
initial area of concern, along with CRLF habitat areas, including currently occupied core
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areas, CNDDB occurrence sections, and designated critical habitat. It is expected that
any additional areas of CRLF habitat that are located at least 1000 ft (to account for
offsite migration via spray drift) and 272 kilometers of stream reach (to account for
downstream dilution) outside the initial area of concern may also be impacted and are
part of the full spatial extent of the LAA and effects to critical habitat determination.
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Figure 2.6. Overlap Map: CRLF Habitat and Pendimethalin Initial Area of
Concern
Pendimethalin Use & CRLF Habitat Overlap
Pendimethalin use & CRLF overlap
CNDDB occurrence sections
Critical habitat
Core areas
County1 boundaries
i Kilo meters
02040 80 120 180
Compiled from California County boundaries (ESRI, 2002),
USDA Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cower Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Dwision.
Projection: Albers Equal Area Conic USGS, North American
Datum of 1983(I\1AD1983).
5/26/2009
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In order to confirm that uses of pendimethalin have the potential to affect CRLF through
direct applications to target areas and runoff and spray drift to non-target areas, it is
necessary to determine whether or not the spatial extent of potential effects based on
agricultural and orchard crops and turf use of pendimethalin overlap with CRLF habitats.
Spatial analysis using ArcGIS 9.1 indicates that lotic aquatic habitats within the CRLF
core areas and critical habitats potentially contain concentrations of pendimethalin
sufficient to result in RQ values that exceed LOCs. In addition, terrestrial habitats (and
potentially lentic aquatic habitats) of the final action areas for agricultural, forestry,
rights-of ways, ornamental, and turf uses of pendimethalin overlap with the core areas,
critical habitat and available occurrence data for CRLF (Figure 2.6). Thus, uses of
pendimethalin on agricultural and orchard crops and turf use could result in exposures of
the CRLF to pendimethalin in aquatic and terrestrial habitats.
6.0 Uncertainties
6.1 Exposure Assessment Uncertainties
6.1.1 Maximum Use Scenario
The screening-level risk assessment focuses on characterizing potential ecological risks
resulting from a maximum use scenario, which is determined from labeled statements of
maximum application rate and number of applications with the shortest time interval
between applications. The frequency at which actual uses approach this maximum use
scenario may be dependant on pest resistance, timing of applications, cultural practices,
and market forces.
6.1.2 Aquatic Exposure Modeling of Pendimethalin
The standard ecological water body scenario (EXAMS pond) used to calculate potential
aquatic exposure to pesticides is intended to represent conservative estimates, and to
avoid underestimations of the actual exposure. The standard scenario consists of
application to a 10-hectare field bordering a 1-hectare, 2-meter deep (20,000 m3) pond
with no outlet. Exposure estimates generated using the EXAMS pond are intended to
represent a wide variety of vulnerable water bodies that occur at the top of watersheds
including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural
ponds, and intermittent and lower order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the EXAMS pond. Static water bodies
that have larger ratios of pesticide-treated drainage area to water body volume would be
expected to have higher peak EECs than the EXAMS pond. These water bodies will be
either smaller in size or have larger drainage areas. Smaller water bodies have limited
storage capacity and thus may overflow and carry pesticide in the discharge, whereas the
EXAMS pond has no discharge. As watershed size increases beyond 10-hectares, it
becomes increasingly unlikely that the entire watershed is planted with a single crop that
is all treated simultaneously with the pesticide. Headwater streams can also have peak
concentrations higher than the EXAMS pond, but they likely persist for only short
periods of time and are then carried and dissipated downstream.
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The Agency acknowledges that there are some unique aquatic habitats that are not
accurately captured by this modeling scenario and modeling results may, therefore,
under- or over-estimate exposure, depending on a number of variables. For example,
aquatic-phase CRLFs may inhabit water bodies of different size and depth and/or are
located adjacent to larger or smaller drainage areas than the EXAMS pond. The Agency
does not currently have sufficient information regarding the hydrology of these aquatic
habitats to develop a specific alternate scenario for the CRLF. CRLFs prefer habitat with
perennial (present year-round) or near-perennial water and do not frequently inhabit
vernal (temporary) pools because conditions in these habitats are generally not suitable
(Hayes and Jennings 1988). Therefore, the EXAMS pond is assumed to be representative
of exposure to aquatic-phase CRLFs. In addition, the Services agree that the existing
EXAMS pond represents the best currently available approach for estimating aquatic
exposure to pesticides (USFWS/NMFS 2004).
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations
that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone
Model is a process or "simulation" model that calculates what happens to a pesticide in
an agricultural field on a day-to-day basis. It considers factors such as rainfall and plant
transpiration of water, as well as how and when the pesticide is applied. It has two major
components: hydrology and chemical transport. Water movement is simulated by the use
of generalized soil parameters, including field capacity, wilting point, and saturation
water content. The chemical transport component can simulate pesticide application on
the soil or on the plant foliage. Dissolved, adsorbed, and vapor-phase concentrations in
the soil are estimated by simultaneously considering the processes of pesticide uptake by
plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection,
dispersion, and retardation.
Uncertainties associated with each of these individual components add to the overall
uncertainty of the modeled concentrations. Additionally, model inputs from the
environmental fate degradation studies are chosen to represent the upper confidence
bound on the mean values that are not expected to be exceeded in the environment
approximately 90 percent of the time. Mobility input values are chosen to be
representative of conditions in the environment. The natural variation in soils adds to the
uncertainty of modeled values. Factors such as application date, crop emergence date,
and canopy cover can also affect estimated concentrations, adding to the uncertainty of
modeled values. Factors within the ambient environment such as soil temperatures,
sunlight intensity, antecedent soil moisture, and surface water temperatures can cause
actual aquatic concentrations to differ for the modeled values.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a
vegetative setback on runoff and loadings. The effectiveness of vegetative setbacks is
highly dependent on the condition of the vegetative strip. For example, a well-
established, healthy vegetative setback can be a very effective means of reducing runoff
and erosion from agricultural fields. Alternatively, a setback of poor vegetative quality
or a setback that is channelized can be ineffective at reducing loadings. Until such time
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as a quantitative method to estimate the effect of vegetative setbacks on various
conditions on pesticide loadings becomes available, the aquatic exposure predictions are
likely to overestimate exposure where healthy vegetative setbacks exist and
underestimate exposure where poorly developed, channelized, or bare setbacks exist.
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 for pendimethalin
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 pendimethalin use areas.
The monitoring data available are within same order of magnitude as the PRZM-EXAMS
predictions, or slightly lower, for the agricultural and forestry scenarios. The monitoring
data indicated that the maximum observed concentration in Sacramento River valley
streams was 0.7 ppb, and in San Joaquin Valley streams it was 3.5 ppb. PRZM-EXAMS
prediction (not including the scenarios for impervious surfaces) estimated pendimethalin
to be in the surface waters at peak concentrations from 3 to 16 ppb. The impervious
scenario was much higher at 143 ppb.
6.1.3 Usage Uncertainties
County-level usage data were obtained from California's Department of Pesticide
Regulation Pesticide Use Reporting (CDPR PUR) database. Thirteen years of data (1994
- 2006) were included in this analysis. Because statistical methodology for identifying
outliers, in terms of area treated and pounds applied, was not provided by CDPR for
years before 2002, these data are less accurate. No methodology for removing outliers
was provided by CDPR for 2001 and earlier pesticide data; therefore, this information
was included separately in the analysis because it may misrepresent actual usage patterns.
CDPR PUR documentation indicates that errors in the data may include the following: a
misplaced decimal; incorrect measures, area treated, or units; and reports of diluted
pesticide concentrations. In addition, it is possible that the data may contain reports for
pesticide uses that have been cancelled. The CPDR PUR data does not include home
owner applied pesticides; therefore, residential uses are not likely to be reported. As with
all pesticide usage data, there may be instances of misuse and misreporting. The Agency
made use of the most current, verifiable information; in cases where there were
discrepancies, the most conservative information was used.
6.1.4 Terrestrial Exposure Modeling of Pendimethalin
The Agency relies on the work of Fletcher et al. (1994) for setting the assumed pesticide
residues in wildlife dietary items. These residue assumptions are believed to reflect a
realistic upper-bound residue estimate, although the degree to which this assumption
reflects a specific percentile estimate is difficult to quantify. It is important to note that
the field measurement efforts used to develop the Fletcher estimates of exposure involve
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highly varied sampling techniques. It is entirely possible that much of these data reflect
residues averaged over entire above ground plants in the case of grass and forage
sampling.
It was assumed that ingestion of food items in the field occurs at rates commensurate
with those in the laboratory. Although the screening assessment process adjusts dry-
weight estimates of food intake to reflect the increased mass in fresh-weight wildlife food
intake estimates, it does not allow for gross energy differences. Direct comparison of a
laboratory dietary concentration- based effects threshold to a fresh-weight pesticide
residue estimate would result in an underestimation of field exposure by food
consumption by a factor of 1.25 - 2.5 for most food items.
Differences in assimilative efficiency between laboratory and wild diets suggest that
current screening assessment methods do not account for a potentially important aspect of
food requirements. Depending upon species and dietary matrix, bird assimilation of wild
diet energy ranges from 23 - 80%, and mammal's assimilation ranges from 41 - 85%
(U.S. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is
formulated to maximize assimilative efficiency (e.g., a value of 85%), a potential for
underestimation of exposure may exist by assuming that consumption of food in the wild
is comparable with consumption during laboratory testing. In the screening process,
exposure may be underestimated because metabolic rates are not related to food
consumption.
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
considered, and it was assumed that species occupy, exclusively and permanently, the
modeled treatment area. Spray drift model predictions suggest that this assumption leads
to an overestimation of exposure to species that do not occupy the treated field
exclusively and permanently.
6.1.5 Spray Drift Modeling
Although there may be multiple pendimethalin applications at a single site, it is unlikely
that the same organism would be exposed to the maximum amount of spray drift from
every application made. In order for an organism to receive the maximum concentration
of pendimethalin from multiple applications, each application of pendimethalin would
have to occur under identical atmospheric conditions (e.g., same wind speed and - for
plants - same wind direction) and (if it is an animal) the animal being exposed would
have to be present directly downwind at the same distance after each application.
Although there may be sites where the dominant wind direction is fairly consistent (at
least during the relatively quiescent conditions that are most favorable for aerial spray
applications), it is nevertheless highly unlikely that plants in any specific area would
receive the maximum amount of spray drift repeatedly. It appears that in most areas
(based upon available meteorological data) wind direction is temporally very changeable,
even within the same day. Additionally, other factors, including variations in
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topography, cover, and meteorological conditions over the transport distance are not
accounted for by the AgDRIFT/AGDISP model (i.e., it models spray drift from aerial and
ground applications in a flat area with little to no ground cover and a steady, constant
wind speed and direction). Therefore, in most cases, the drift estimates from
AgDRIFT/AGDISP may overestimate exposure even from single applications, especially
as the distance increases from the site of application, since the model does not account for
potential obstructions (e.g., large hills, berms, buildings, trees, etc.). Furthermore,
conservative assumptions are often made regarding the droplet size distributions being
modeled ('ASAE Very Fine to Fine' for orchard uses and 'ASAE Very Fine' for
agricultural uses), the application method (e.g., aerial), release heights and wind speeds.
Alterations in any of these inputs would change the area of potential effect.
6.1.6 Volatility
Pendimethalin is a semi-volatile compound that may be lost from moist soil. The
volatilization half-life from moist soil was found to be 12.5 days (MRID 00153766).
Pendimethalin has been observed in rainwater in California (Vogel et al., 2008). This
effect was accounted for in the PRZM-EXAMS modeling by invoking the PRZM
volatilization routine, thus allowing voltilization to compete with runoff and metabolism
as a dissipation route. Comparison of the highest EEC scenario (forestry) shows that the
effect is small (16.6 ppb with volatility invoked and 18.1 ppb without). The relatively
slow volatilization rate from even moist soil is not believed to result in as large or
immediate an aquatic exposure as spray drift at the time of application. Terrestrial
exposure of plants and animals is accounted for at least in part by the AgDrift and
AgDISP effect area analysis.
6.1.7 Bioaccumulation
Pendimethalin is believed to be bioaccumulative, as it has a logKow of 5.18, and a
whole-body BCF of 5100x in bluegill sunfish (MRID 00156726). PRZM-EXAMS
modeling indicates that pendimethalin may accumulate in sediments as well. Thus, food-
chain exposure via accumulation in aquatic organisms may be a completed exposure
pathway. However, several factors indicate that such exposure may not be a concern.
First, additional bioaccumulation data in catfish (approximate BCF = 1600x), guppies (no
accumulation, with metabolism) (MRID 00046293) and crayfish (MRID 00071124)
whole body BCF = 1.5x) indicate that bioaccumulation is not the only response of aquatic
organisms to pendimethalin. Second, the bluegill sunfish exposed to pendimethalin
accumulated 15 ppm body burden with no ill effects, followed by depuration.
KABAM modeling (Appendix K) indicated some marginal chronic risk for large river
otters (chronic dose-based RQ 1.3, but dietary-based RQ 0.169) and marginal acute risk
for small CRLF (acute dose-based RQ 0.14 to 0.38, but dietary-based RQ 0.007 to 0.008.
However, the assumption of no metabolism in aquatic organisms is probably incorrect, so
the results from KABAM showing marginal risks are therefore discountable.
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6.2 Effects Assessment Uncertainties
6.2.1 Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test organism age may have a significant impact on the
observed sensitivity to a toxicant. The acute toxicity data for fish are collected on
juvenile fish between 0.1 and 5 grams. Aquatic invertebrate acute testing is performed on
recommended immature age classes (e.g., first instar for daphnids, second instar for
amphipods, stoneflies, mayflies, and third instar for midges).
Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients that act directly without metabolic transformation because younger age
classes may not have the enzymatic systems associated with detoxifying xenobiotics. In
so far as the available toxicity data may provide ranges of sensitivity information with
respect to age class, this assessment uses the most sensitive life-stage information as
measures of effect for surrogate aquatic animals, and is therefore, considered as
protective of the CRLF.
6.2.2 Use of Surrogate Species Effects Data
Guideline toxicity tests and open literature data on pendimethalin are not available for
frogs or any other aquatic-phase amphibian; therefore, freshwater fish are used as
surrogate species for aquatic-phase amphibians. Therefore, endpoints based on
freshwater fish ecotoxicity data are assumed to be protective of potential direct effects to
aquatic-phase amphibians including the CRLF, and extrapolation of the risk conclusions
from the most sensitive tested species to the aquatic-phase CRLF is likely to overestimate
the potential risks to those species. 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.
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)
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and the assessment endpoints. However, the full suite of sublethal effects from valid
open literature studies is considered for the purposes of defining the action area.
To the extent to which sublethal effects are not considered in this assessment, the
potential direct and indirect effects of pendimethalin on CRLF may be underestimated.
6.2.4 Location of Wildlife Species
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
considered, and it was assumed that species occupy, exclusively and permanently, the
modeled treatment area. Spray drift model predictions suggest that this assumption leads
to an overestimation of exposure to species that do not occupy the treated field
exclusively and permanently.
6.2.5 Toxicity to Honeybees.
Pendimethalin is rated as practically non-toxic to honeybees. The honeybee contact
toxicity data is used as a surrogate assessment endpoint for all terrestrial invertebrates.
Because the calculated exposure (TREX EEC for large and small insects) exceeds the
highest tested dose, even though there were no mortalities at the highest dose, there is
some residual uncertainty about potential effects to terrestrial invertebrates. This results
in a May Affect determination, however, it is considered discountable.
7.0 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 pendimethalin to the CRLF and its
designated critical habitat.
Based on the best available information, the Agency makes a Likely to Adversely
Affect/May Affect, determination for the CRLF from the use of pendimethalin. The
Agency has determined that there is the potential for effects to CRLF designated critical
habitat from the use of the chemical. All of the uses might affect the frog or its critical
habitat. The LAA determination is from direct and indirect effects to CRLF from the
use of pendimethalin. Given the LAA determination for the CRLF and potential effects
to designated critical habitat, a description of the baseline status and cumulative effects
for the CRLF is provided in Attachment 2.
The LAA effects determination applies to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat.
To determine this area, the footprint of pendimethalin's use pattern is identified, using
land cover data that correspond to pendimethalin's use pattern. The spatial extent of the
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LAA effects determination also includes areas beyond the initial area of concern that may
be impacted by runoff and/or spray drift. The identified direct and indirect effects and
modification to critical habitat are anticipated to occur only for those currently occupied
core habitat areas, CNDDB occurrence sections, and designated critical habitat for the
CRLF that overlap with the initial area of concern plus at least 1000 feet from its
boundary (refer to analysis in Section 5.1.4). It is assumed that non-flowing waterbodies
(or potential CRLF habitat) are included within this area.
In addition to the spray drift buffer, the results of the downstream dilution extent analysis
result in a distance of 272 kilometers which represents the maximum continuous distance
of downstream dilution from the edge of the initial area of concern (refer to analysis in
Section 5.1.4). If any of these streams reaches flow into CRLF habitat, there is potential
to affect either the CRLF or affect its habitat. These lotic aquatic habitats within the
CRLF core areas and critical habitats potentially contain concentrations of pendimethalin
sufficient to result in LAA determination or effects to critical habitat.
Appendix K provides maps of the initial area of concern, along with CRLF habitat areas,
including currently occupied core areas, CNDDB occurrence sections, and designated
critical habitat. It is expected that any additional areas of CRLF habitat that are located at
least 1000 ft (to account for offsite migration via spray drift) and 272 kilometers of
stream distance (to account for downstream dilution) outside the initial area of concern
may also be impacted and are part of the full spatial extent of the LAA and critical habitat
effects determination.
A summary of the risk conclusions and effects determinations for the CRLF and its
critical habitat, given the uncertainties discussed in Section 6, is presented in Table 7.0-1
and Table 7-2.
Table 7-1 Effects Determination Summary for Pendimethalin Use and the CRLF
Assessment
Endpoint
Survival, growth,
and/or reproduction
of CRLF
individuals
Effects
Determination 1
LAA1
Basis for Determination
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Acute LOCs were exceeded for fish or aquatic-phase amphibians
Terrestrial-phase (Juveniles and Adults):
Acute and chronic LOCs were exceeded for birds. The available toxicity
data suggest that amphibians are less sensitive than birds to pendimethalin,
and considering factors such as lower food intake of terrestrial phase
amphibians relative to birds reduces EECs and RQs, but does not reduce
RQs to levels that are below LOCs. Likely to adversely affect CRLF.
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity:
LOG is exceeded only for non-vascular aquatic plants. RQs are below LOG
for freshwater invertebrates (chronic and acute effects) and fish or frogs
(chronic and acute effects). Pendimethalin could potentially impact
terrestrial and aquatic plants to an extent that could result in indirect effects
to the CRLF or modification of critical habitat.
Terrestrial prey items, riparian habitat:
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Assessment
Eiulpoint
Effects
Determination 1
Basis for Determination
Chronic LOG is exceeded for mammal and birds (surrogate for frog).
Pendimethalin is practically non-toxic to honeybees with no mortalities observed
in testing. LOG is exceeded for terrestrial invertebrates. Uncertainty in toxicity
to insects from EEC that is above highest bee concentration tested does not
preclude potential risk. Pendimethalin may adversely affect insects. Acute
LOCs were not exceeded for insectivorous amphibians using the T-HERPS
model at the highest rate of application.
LOG is exceeded for non-target terrestrial plants and thereby critical habitat
could be affected as a result of these potential impacts.
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely
affect (LAA)
Table 7-2 Effects Determination Summary for Pendimethalin Use and CRLF
Critical Habitat Impact Analysis
Assessment
Endpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
Habitat Effects
Effects to riparian vegetation (terrestrial plants) and aquatic non-vascular and
vascular plants result in LOG exceedances. These effects may indirectly affect
the CRLF via reduction in food supply, changes in available cover, physical
parameters of the waterbody (e.g. increase temperature or turbidity)
LOG is exceeded for effects to non-vascular aquatic plants, freshwater
invertebrates (chronic and acute effects) and fish or frogs (chronic and acute
effects).
Modification of
terrestrial-phase
PCE
Effects to riparian vegetation (terrestrial plants) result in LOG exceedances.
Effects may result in changes in community composition or relative abundance
of riparian plant species, possibly altering terrestrial - phase CRLF habitat.
Chronic LOG is exceeded for mammal. Although there are NLAA
determinations for other prey items, small mammals constitute up to half of the
food intake for CRLF and reduction in small mammalian populations may be
significant.
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 habitat
effects determinations, it is important to note that pesticide exposures and predicted risks
to the 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 CRLF life stages within
specific recovery units and/or designated critical habitat within the action area.
This information would allow for quantitative extrapolation of the present risk
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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 species.
Quantitative information on prey base requirements for individual aquatic- and
terrestrial-phase frogs. While existing information provides a preliminary picture
of the types of food sources utilized by the frog, 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 frogs and potential modification to critical habitat.
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8.0 References
Alvarez, J. 2000. Letter to the U.S. Fish and Wildlife Service providing comments on
the Draft California Red-legged Frog Recovery Plan.
Crawshaw, GJ. 2000. Diseases and Pathology of Amphibians and Reptiles in:
Ecotoxicology of Amphibians and Reptiles; ed: Sparling, D.W., G. Linder, and
C.A. Bishop. SETAC Publication Series, Columbia, MO.
Fellers, G. M., et al. 2001. Overwintering tadpoles in the California red-legged frog
(Rana aurora draytonif). Herpetological Review, 32(3): 156-157.
Fellers, G.M, L.L. McConnell, D. Pratt, S. Datta. 2004. Pesticides in Mountain Yellow-
Legged Frogs (Rana Mucosa) from the Sierra Nevada Mountains of California,
USA. Environmental Toxicology & Chemistry 23 (9):2170-2177.
Fellers, Gary M. 2005a. Rana draytonii Baird and Girard 1852. California Red-legged
Frog. Pages 552-554. hr. M. Lannoo (ed.) Amphibian Declines: The Conservation
Status of United States Species, Vol. 2: Species Accounts. University of
California Press, Berkeley, California, xxi+1094 pp.
(http://www.werc.usgs.gov/pt-reves/pdfs/Rana%20draytonii.PDF)
Fellers, Gary M. 2005b. California red-legged frog, Rana draytonii Baird and Girard.
Pages 198-201. In: L.L.C. Jones, et al (eds.) Amphibians of the Pacific Northwest.
xxi+227.
Hayes, M.P. and M.M. Miyamoto. 1984. Biochemical, behavioral and body size
differences between Rana aurora aurora and R. a. draytonii. Copeia 1984(4):
1018-22.
Hayes and Tennant. 1985. Diet and feeding behavior of the California red-legged frog.
The Southwestern Naturalist 30(4): 601-605.
Jennings, M.R. and M.P. Hayes. 1985. Pre-1900 overharvest of California red-legged
frogs (Rana aurora draytonii): The inducement for bullfrog (Rana catesbeiand)
introduction. Herpetological Review 31(1): 94-103.
Jennings, M.R. and M.P. Hayes. 1994. Amphibian and reptile species of special concern
in California. Report prepared for the California Department of Fish and Game,
Inland Fisheries Division, Rancho Cordova, California. 255 pp.
LeNoir, J.S., L.L. McConnell, G.M. Fellers, T.M. Cahill, J.N. Seiber. 1999.
Summertime Transport of Current-use pesticides from California's Central Valley
to the Sierra Nevada Mountain Range,USA. Environmental Toxicology &
Chemistry 18(12): 2715-2722.
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McConnell, L.L., J.S. LeNoir, S. Datta, J.N. Seiber. 1998. Wet deposition of current-use
pesticides in the Sierra Nevada mountain range, California, USA. Environmental
Toxicology & Chemistry 17(10):1908-1916.
Rathburn, G.B. 1998. Rana aurora draytonii egg predation. Herpetological Review,
29(3): 165.
Reis, D.K. Habitat characteristics of California red-legged frogs {Rana aurora draytonii}:
Ecological differences between eggs, tadpoles, and adults in a coastal brackish and
freshwater system. M.S. Thesis. San Jose State University. 58 pp.
D.W. Sparling, G.M. Fellers, L.L. McConnell. 2001. Pesticides and amphibian
population declines in California, USA. Environmental Toxicology & Chemistry
20(7): 1591-1595.
U.S. Environmental Protection Agency (U.S. EPA). 1998. Guidance for Ecological Risk
Assessment. Risk Assessment Forum. EPA/630/R-95/002F, April 1998.
U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of
Pesticide Programs. Office of Prevention, Pesticides, and Toxic Substances.
Office of Pesticide Programs. Washington, D.C. January 23, 2004.
U.S. Fish and Wildlife Service (USFWS). 1996. Endangered and threatened wildlife and
plants: determination of threatened status for the California red-legged frog.
Federal Register 61(101):25813-25833.
USFWS. 2002. Recovery Plan for the California Red-legged Frog (Rana aurora
draytonii). Region 1, USFWS, Portland, Oregon.
(http://ecos.fws.gov/doc/recovery_plans/2002/020528.pdf)
USFWS. 2006. Endangered and threatened wildlife and plants: determination of critical
habitat for the California red-legged frog. 71 FR 19244-19346.
USFWS. Website accessed: 30 December 2006.
http://www.fws.gov/endangered/features/rl_frog/rlfrog.html #where
U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service
(NMFS). 1998. Endangered Species Consultation Handbook: Procedures for
Conducting Consultation and Conference Activities Under Section 7 of the
Endangered Species Act. Final Draft. March 1998.
USFWS/NMFS. 2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act
Section 7 Consultation Regulations; Final Rule. FR 47732-47762.
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Vogel, J.R., Majewski, M.S., and Capel, P.O. (2008) Pesticides in Rain in Four
Agricultural Watersheds in the United States. J. Environ. Qual. V. 37 May-June
2008, pp. 1101-1115.
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