Risks of Paraquat 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 10, 2009
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Primary Authors:
Tiffany Mason, Environmental Engineer
Christina Wendel, Biologist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)
Secondary Review:
William P. Eckel, PhD, Senior Physical Scientist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)
Donna Randall, Senior Biologist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)
Jean Holmes, PhD, Risk Assessment Process Leader
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)
Branch Chief, Environmental Risk Branch II:
Tom Bailey, PhD, Branch Chief
Environmental Fate and Effects Division (7507P)
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Table of Contents
1.0 Executive Summary 5
2.0 Problem Formulation 13
2.1 Purpose 13
2.2 Scope 15
2.3 Previous Assessments 16
2.4 Stressor Source and Distribution 18
2.4.1 Environmental Fate Assessment 18
2.4.2 Mechanism of Action 21
2.4.3 Use Characterization 21
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
3.0 Exposure Assessment 51
3.1 Label Application Rates and Intervals 51
3.2 Aquatic Exposure Assessment 52
3.2.1 Modeling Approach 52
3.2.2 Model Inputs 52
3.2.3 Results 53
3.2.4 Existing Monitoring Data 54
3.3 Terrestrial Animal Exposure Assessment 55
3.4 Terrestrial Plant Exposure Assessment 57
4.0 Effects Assessment 58
4.1 Evaluation of Aquatic Ecotoxicity Studies 60
4.1.1 Toxicity to Freshwater Fish 62
4.1.2 Toxicity to Freshwater Invertebrates 63
4.1.3 Toxicity to Aquatic Plants 64
4.2 Toxicity of Paraquat to Terrestrial Organisms 64
4.2.1 Toxicity to Birds 66
4.2.2 Toxicity to Mammals 67
4.2.3 Toxicity to Terrestrial Invertebrates 68
4.2.4 Toxicity to Terrestrial Plants 69
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4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern 70
4.4 Incident Database Review 70
4.4.1 Terrestrial Incidents 71
4.4.2 Plant Incidents 71
4.4.3 Aquatic Incidents 72
5.0 Risk Characterization 73
5.1 Risk Estimation 73
5.1.1 Exposures in the Aquatic Habitat 73
5.1.2 Exposures in the Terrestrial Habitat 77
5.1.3 Primary Constituent Elements of Designated Critical Habitat 81
5.2 Risk Description 83
5.2.1 Direct Effects 89
5.2.2 Indirect Effects (via Reductions in Prey Base) 99
5.2.3 Indirect Effects (via Habitat Effects) 102
5.2.4 Effects to Designated Critical Habitat 104
5.2.5 Spatial Extent of Potential Effects 106
6.0 Uncertainties Ill
6.1 Exposure Assessment Uncertainties Ill
6.1.1 Maximum Use Scenario Ill
6.1.2 Crops Not Grown in California Ill
6.1.3 Aquatic Exposure Modeling of Paraquat Ill
6.1.4 Action Area Uncertainties 114
6.1.5 Usage Uncertainties 115
6.1.6 Terrestrial Exposure Modeling of Paraquat 115
6.1.7 Spray Drift Modeling 116
6.2 Effects Assessment Uncertainties 116
6.2.1 Acute to Chronic Ratio 116
6.2.2 Age Class and Sensitivity of Effects Thresholds 117
6.2.3 Use of Surrogate Species Effects Data 117
6.2.4 Sublethal Effects 117
6.2.5 Location of Wildlife Species 118
7.0 Risk Conclusions 119
8.0 References 124
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List of Tables
Table 1-1 Effects Determination Summary for Paraquat Use and the CRLF 8
Table 1-2 Effects Determination Summary for Paraquat Use and CRLF Critical Habitat
Impact Analysis 10
Table 1-3 Paraquat Use-specific Direct Effects Determinations1 for the CRLF 11
Table 1-4 Paraquat Use-specific Indirect Effects Determinations1 Based on Effects to
Prey 11
Table 2-1 Summary of Paraquat Environmental Fate Properties 19
Table 2-2 Paraquat Uses Assessed for the CRLF1 22
Table 2-3 Summary of California Department of Pesticide Registration (CDPR) Pesticide
Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered
Paraquat Uses 25
Table 2-4 Assessment Endpoints and Measures of Ecological Effects for Direct and
Indirect Effects of Paraquat (in terms of the Paraquat Cation) on the CRLF. 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 Paraquat Uses and Application Information for the CRLF risk assessment1... 51
Table 3-2 Summary of GENEEC2 Environmental Fate Data Used for Aquatic Exposure
Inputs for Paraquat Endangered Species Assessment for the CRLF l Based on
the Paraquat Cation 53
Table 3-3 Aquatic EECs (ug/L) for Paraquat Uses in California 54
Table 3-4 Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
Paraquat with T-REX 56
Table 3-5 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Paraquat 56
Table 3-6 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Terrestrial Invertebrate Prey Items 57
Table 4-1 Freshwater Aquatic Toxicity Profile for Paraquat Dichloride (expressed as the
cation) 61
Table 4-2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates 61
Table 4-3 Terrestrial Toxicity Profile for Paraquat Dichloride (expressed as the cation) 65
Table 4-4 Categories of Acute Toxicity for Avian and Mammalian Studies 66
Table 4-5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data 70
Table 5-1 Summary of Acute Direct Effect RQs* for the Aquatic-phase CRLF 74
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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 (diet of CRLF in tadpole life stage and habitat of
aquatic-phase CRLF) 75
Table 5-3 Summary of Acute RQs* 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) 76
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 77
Table 5-5 Summary of Acute RQs* Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (foliar application) From T-REX 78
Table 5-6 Summary of Chronic RQs* Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (foliar application) From T-REX 78
Table 5-7 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 (foliar application) 80
Table 5-8 Risk Estimation Summary for Paraquat - Direct and Indirect Effects to CRLF
84
Table 5-9 Risk Estimation Summary for Paraquat - PCEs of Designated Critical Habitat
for the CRLF 87
Table 5-10a Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for Dietary-
based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 15 g 90
Table 5-1 Ob Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for Dietary-
based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 35 g 91
Table 5-1 la Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-bw) for Dose-
based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 15 g 91
Table 5-1 Ib Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-bw) for Dose-
based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 35 g 92
Table 5-12a Revised Acute Dietary-based RQs* for CRLF consuming different food
items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 15 g 94
Table 5-12b Revised Acute Dietary-based RQs* for CRLF consuming different food
items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 35 g 94
Table 5-13a Refined Dose-based RQs* for CRLF consuming different food items (RQs
calculated using T-HERPS), the weights of small herbivore and insectivore
mammals are 15 g 95
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Table 5-13b Refined Dose-based RQs* for CRLF consuming different food items (RQs
calculated using T-HERPS), the weights of small herbivore and insectivore
mammals are 35 g 96
Table 5-14a Revised Chronic Dietary-based RQs* for CRLF consuming different food
items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 15 g 98
Table 5-14b Revised Chronic Dietary-based RQs* for CRLF consuming different food
items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 35 g 98
Table 5-15 Summary of AgDrift Predicted Terrestrial Spray Drift Distances Using
Maximum Application Rate 108
Table 5-16 Summary of AgDrift Predicted Aquatic Spray Drift Distances Using
Minimum Application Rate 108
Table 7-1 Effects Determination Summary for Paraquat Use and the CRLF 120
Table 7-2 Effects Determination Summary for Paraquat Use and CRLF Critical Habitat
Impact Analysis 122
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List of Figures
Figure 2-1 Paraquat 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 Paraquat 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
Figure 5-1 Overlap Map: CRLF Habitat and Paraquat Initial Area of Concern 110
Appendices
Appendix A Ecological Effects Data
Appendix B Multi-ai Product Analysis
Appendix C RQ Method and LOCs
Appendix D Spatial Analysis of Paraquat
Appendix E T-REX Example Output
Appendix F Bibliography of Evaluated ECOTOX Open Literature Data
Appendix G Bibliography of ECOTOX Open Literature Data Excluded or Not
Evaluated
Appendix H Paraquat Incident Data
Appendix I GENEEC2 Example Output
Appendix J T-HERPS Example Output
Appendix K Summary of Human Health Effects Data for Paraquat
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 Federal
Insecticide, Fungicide, Rodenticide, Act (FIFRA) regulatory actions regarding use of
paraquat dichloride 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 (U.S. FWS) and National Marine Fisheries Service
(NMFS) Endangered Species Consultation Handbook (U.S. FWS/NMFS 1998) and
procedures outlined in the Agency's Overview Document (U.S. EPA 2004).
The CRLF was listed as a threatened species by U.S. FWS 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 (U.S. FWS 1996) in California.
Paraquat dichloride is a contact herbicide that causes desiccation to the plants. It is
applied as a flowable solution from an emulsifiable concentrate. As a result, paraquat
dichloride is already dissociated into its cation, paraquat, when it is applied. Therefore,
this assessment will focus on the paraquat cation. Currently, labeled uses of paraquat
include various agricultural uses such as apricots, loganberries, corn, peanuts, coffee, and
lettuce, as well as multiple non-agricultural uses such as airport landing fields, and
commercial, industrial and institutional premises. The uses considered as part of the
federal action evaluated in this assessment are listed in Table 2-2.
There are a total of three PC codes associated with paraquat; the PC code for paraquat
dichloride is 061601, 061602 for paraquat bis (methyl sulfate), and 061603 for paraquat.
Paraquat bis (methyl sulfate) is no longer a registered product of paraquat, but data from
ECOTOX and past assessments including all three PC codes were incorporated into the
paraquat cation.
Paraquat is dissipated by rapid adsorption to biological materials and clay particles. Due
to the apparent adsorption strength of paraquat, these bound residues do not appear to be
environmentally available. Paraquat was shown to be very immobile in soil with batch
equilibrium studies conducted on four soils in the laboratory. Adsorption Kds ranged
from 68-50,000. There was no desorption of paraquat from any of these soils (MRID
40762701). Due to high biological toxicity to plants and animals prior to adsorption,
paraquat is subject to spray drift concerns. However, paraquat has such extremely high
adsorption coefficients, it is not expected to volatilize once applied to the soil. In
addition, since it is not expected to volatilize, is not a concern for atmospheric transport.
Paraquat does not hydrolyze, does not photodegrade in aqueous solutions, and is resistant
to biotic degradation. Essentially no aerobic or anaerobic microbial degradation of
paraquat occurred during the laboratory studies. In short and long-term field dissipation
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studies, paraquat residues were shown to be persistent and to accumulate slightly with
repeated applications.
Adsorbed paraquat could potentially be found in surface water systems associated with
soil particles carried by erosion. Paraquat is not expected to be a contaminant of
groundwater.
The only monitoring data available for paraquat was from the California Department of
Pesticide Regulation (CPR) database. Out of 399 samples taken from July 2005 to
October 2006, only one sample contained paraquat. The detection, at 0.24 ppb, was
below the quantification limit of 1 ppb.
Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF, its prey
and its habitats to paraquat are assessed separately for the two habitats. A Tier-I aquatic
exposure model, GENEEC2, was used to estimate high-end exposures of paraquat in
aquatic habitats resulting from spray drift from different uses. Peak model-estimated
environmental concentrations resulting from different paraquat uses ranged from 1.6 to
33 |ig/L. 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.
NAWQA did not have any available monitoring data for paraquat in California surface
waters or ground water. The maximum concentration of paraquat reported by the
California Department of Pesticide Regulation surface water database (0.24 |ig/L) is
roughly 3,717 times lower than the highest peak model-estimated environmental
concentration.
To estimate paraquat exposures to the terrestrial-phase CRLF, and its potential prey
resulting from uses involving paraquat applications, the T-REX model is used for spray
treatment. The AgDRIFT model is also used to estimate deposition of paraquat on
terrestrial and aquatic habitats from spray drift. The T-HERPS model is used as a
refinement tool to explore amphibian-specific food intake on potential exposures to the
terrestrial phase CRLF.
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 effects to 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 effects to the terrestrial habitat are
characterized by available data for terrestrial monocots and dicots.
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QINA (4-carboxyl-l-methylpyridinium) is a degradate formed by paraquat. However, in
the photodegradation in water study the quantity of degradate present was only 6% of the
radioactivity of paraquat after 85 weeks of natural sunlight irradiation. Due to paraquat
degrading very slowly, the minor degradate, QINA, does not pose an important
environmental concern and will not be evaluated in this assessment.
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 paraquat 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 paraquat within the action area "may
affect" the CRLF or 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. Similarly for
critical habitat, additional information is considered to refine the potential for exposure
and effects to distinguish those actions that may or do not result in effects to its critical
habitat.
Based on the best available information, the Agency makes a May Affect, and Likely to
Adversely Affect determination for the CRLF based on the direct effects to the
terrestrial-phase CRLF, and indirect effects to the aquatic- and terrestrial-phase
CRLF. Additionally, the Agency has determined that there is the potential for effects to
CRLF designated critical habitat from the use of paraquat. 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. Use-specific determinations for direct and indirect effects to
the CRLF are provided in Table 1-3 and Table 1-4. The non-agricultural and agricultural
uses with the maximum application rates, along with the agricultural use with the median
application rate, and the agricultural use with the three lowest application rates were used
to bound the potential exposures from all registered uses. Further information on the
results of the effects 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 II.
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Table 1-1 Effects Determination Summary for Paraquat Use and the CRLF
Assessment
Endpoint
Effects
Determination l
Basis for Determination
Survival, growth,
and/or reproduction
of CRLF
individuals
Potential for Direct Effects
NE1
LAA1
Aquatic-phase (Eggs, Larvae, and Adults):
The aquatic phase amphibian acute LOCs for listed species (0.05) are not
exceeded for any uses of paraquat in California. The chronic EECs are all less
than the estimated chronic value derived from the ACR. Therefore, there are no
exceedances of chronic LOCs.
Terrestrial-phase (Juveniles and Adults):
Refined acute dietary-based RQs for CRLFs consuming small insects exceed
the acute listed species LOG (0.1) for all uses of paraquat except melons, RQs
ranged from 1.28 (Airport/public health use/guava) to 0.06 (melons). The
Refined acute dietary-based RQs for CRLFs consuming large insects and 15g
small insectivore mammals resulted in paraquat use on airports/public health
use/guava exceeding the listed species LOG (0.1), with an RQ of 0.14 for both.
The refined acute dietary-based RQs for CRLFs consuming small herbivore
mammals (15g) resulted in all uses exceeding the listed species LOG, RQs
ranged from 2.17 (Airport/public health use/guava) to 0.10 (melons) and for
35g small mammals all uses except melons exceed the listed species LOG, RQs
ranged from 1.50 (Airport/public health use/guava) to 0.77 (melons). There are
no exceedances for CRLFs consuming small terrestrial-phase amphibians.
Refined dose-based RQs for CRLF of varying weights (1.4g, 37g and 238g)
consuming small insects exceed the acute endangered species LOG (0.1) for
only the Airport/public health and Guava uses of paraquat for all weights of
CRLF). There are no exceedances for small sized (1.4g) CRLF consuming
large insects and CRLF this size are too small to consume small mammals or
small terrestrial-phase amphibians. The RQs for small sized (1.4g) CRLF are
0.27 suggesting that small CRLF consuming small insects are potentially
affected by acute exposures to paraquat.
Refined dose-based RQs for medium sized (37g) CRLF consuming small
herbivore mammals (either 15g or 35g) exceed the acute listed species LOG
(0.1) for all uses of paraquat. There were also exceedances in the acute listed
species LOG (0.1) for medium sized CRLF consuming small insectivore (15g)
mammals for the airports/public health, guava, and ginger uses of paraquat. For
medium sized CRLF consuming small insectivore (35g) mammals there were
exceedances in the acute listed species LOG (0.1) for all uses of paraquat except
carrots and melons. There are no exceedances for medium sized (37g) CRLF
consuming large insects or small terrestrial-phase amphibians. Due to
exceedances of LOCs for CRLF consuming small herbivore mammals (either
15g or 35g) for all paraquat uses, and exceedances of LOCs for CRLF
consuming small insectivore mammals (either 15g or 35g) for a majority of
paraquat uses indicate that the medium sized CRLF could potentially be
affected by acute exposures to paraquat.
Refined dose-based RQs for large sized (238g) CRLF consuming small
herbivore mammals (either 15g or 35g) exceed the acute listed species LOG
(0.1) for all uses of paraquat except melons. There were no exceedances for
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Assessment
Endpoint
Effects
Determination 1
Basis for Determination
LAA1
LAA1
large sized (23 8g) CRLF consuming large insects, small insectivore mammals
(15g or 35g), or small terrestrial-phase amphibians. The exceedances of LOCs
for CRLF consuming small herbivore mammals (either 15g or 35g) for all
paraquat uses except melons, indicates that the large sized CRLF could
potentially be affected by acute exposures to paraquat.
Refined chronic dietary-based RQs for CRLFs consuming small insects and
small herbivore mammals (eitherlSg or 35g) using T-HERPS model exceed the
chronic species LOG (1.0) for all uses of paraquat. Refined chronic dietary-
based RQs for CRLFs consuming large insects and small insectivore mammals
(either 15g or 35g) using T-HERPS model exceed the chronic species LOG (1.0)
for Airport/public health, guava, and ginger uses of paraquat. The refined
chronic dietary-based RQs for CRLFs consuming small terrestrial-phase
amphibians using T-HERPS model exceed the chronic species LOG (1.0) for
Airport/public health and guava uses of paraquat (the maximum uses).
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
LOCs for non-vascular plants are exceeded for all uses. The non-vascular plant
RQs range from 138 for airports, commercial/industrial areas, and public health
areas to 4.1 for melons.
LOCs for vascular plants are not exceeded for any uses. The vascular plant RQs
range from 0.77 (airports, commercial/industrial areas, public health areas) to
0.02 (melons).
LOCs for aquatic invertebrates are not exceeded for any uses. The acute RQs
range from 0.730 for airports, commercial/industrial areas, and public health
areas to 0.004 for melons. When comparing chronic indirect effects, the
estimated chronic value at 0.174 ppm is not exceeded for any use.
For fish/frogs none of the uses exceed the LOCs for listed species. The RQs
range from 0.004 for airports, commercial/industrial areas, and public health
areas to < 0.001 for melons. When comparing chronic direct effects, the
estimated chronic value at 1.89 ppm is not exceeded for any use.
Terrestrial prey items, riparian habitat
RQs could not be calculated for terrestrial invertebrates as the endpoint was not
definitive. The calculated EECs were compared to the toxicity endpoint, and it
was determined that terrestrial invertebrates would not likely adversely affect the
CRLF indirectly as food.
For small mammals the acute dose-based RQs exceed the Agency's LOG (0.1)
for all uses of paraquat, the RQs ranged from 7.63 (airports/public health
use/guava) to 0.34 (melons). The chronic dose-based RQs exceed the Agency's
LOG (1.0) for all uses of paraquat, and range from 128.53 (airports/public health
use/guava) to 5.78 (melons). The chronic dietary-based RQs exceed the
Agency's LOG (1.0) for all uses except melons, and range from 14.81
(airports/public health use/guava) to 0.67 (melons).
The RQs for small terrestrial-phase amphibians did not exceed the listed species
LOG (0.1) for any use of paraquat. Reduction in amphibian prey items,
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Assessment
Endpoint
Effects
Determination 1
Basis for Determination
specifically other frogs is not affected from paraquat use.
The RQs for non-target terrestrial monocot and dicot plants inhabiting semi-
aquatic and upland dry areas do not exceed the Agency's LOG (1.0) for any uses.
All aerial applications of paraquat results in spray drift exceedances for dicots
(only). These exceedances range from 3.57 (Agricultural fallow/ideland
maximum aerial application rate) to 1.07 (Melons, minimum aerial application
rate).
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 Paraquat Use and CRLF Critical
Habitat Impact Analysis
Assessment
Endpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
May affect
Due to aquatic non-vascular and terrestrial plant communities being reduced
from a majority of use sites, there is potential for alteration of channel/pond
morphology or geometry and/or increase in sediment deposition within the
stream channel or pond. These plant communities provide shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile and adult CRLFs. In
addition, there is potential for 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.
LOCs are exceeded for terrestrial riparian plants and for aquatic non-vascular
plants from exposure to paraquat from spray drift. LOCs for non-vascular
plants are exceeded for all uses of paraquat.
Modification of
terrestrial-phase
PCE
May affect
The use of paraquat at all sites may create the following effects to PCE:
elimination and/or disturbance of upland habitat; ability of habitat to support
food source of CRLFs, elimination and/or disturbance of dispersal habitat,
reduction and/or modification of food sources for terrestrial phase juveniles and
adults, and alteration of chemical characteristics necessary for normal growth
and viability of juvenile and adult CRLFs and their food source.
The RQs for vascular plants did not exceed the Agency' s LOG (1.0) for any uses
of paraquat in California.
The RQs for non-target terrestrial monocot and dicot plants inhabiting semi-
aquatic and upland dry areas do not exceed the Agency's LOG (1.0) for all uses.
All aerial applications of paraquat results in spray drift exceedances for dicots
(only).
The use of paraquat on most use sites will exceed the revised acute dietary- and
dose-based LOG and chronic LOG for prey food items of small mammals, and
invertebrates. Food sources for the CRLF are reduced, and the CRLF is
indirectly affected from this reduction.
10
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Table 1-3 Paraquat Use-specific Direct Effects Determinations1 for the CRLF
Use(s)
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC HEALTH USE),
NONAGRICULTURAL RIGHTS-OF-
WAY/FENCEROWS/HEDGEROWS
GUAVA
GINGER
BEANS - SUCCULENT (LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER
CORN (SILAGE)
MELONS
Aquatic Habitat
Acute
NE
NE
NE
NE
NE
NE
Chronic
NE
NE
NE
NE
NE
NE
Terrestrial Habitat
Acute
LAA
LAA
LAA
LAA
LAA
NLAA
Chronic
LAA
LAA
LAA
LAA
LAA
LAA
1 NE = No effect; NLAA = May affect, but not likely to adversely affect; LAA = Likely to adversely affect
Table 1-4 Paraquat Use-specific Indirect Effects Determinations1 Based on Effects
to Prey
Use(s)
AIRPORTS/LANDING
FIELDS, COMMERCIAL/
INSTITUTIONAL/
INDUSTRIAL
PREMISES/
EQUIPMENT
(OUTDOOR),
NONAGRICULTURAL
AREAS (PUBLIC
HEALTH USE),
NONAGRICULTURAL
RIGHTS-OF-WAY/
FENCEROWS/
HEDGEROWS
GUAVA
GINGER
BEANS- SUCCULENT
(LIMA/SNAP), CARROT
(INCLUDING TOPS),
PEAS (UNSPECIFIED),
PEPPER
CORN (SILAGE)
MELONS
Algae
LAA
LAA
LAA
LAA
LAA
LAA
Aquatic
Invertebrates
Acute
NE
NE
NE
NE
NE
NE
Chronic
NE
NE
NE
NE
NE
NE
Terrestrial
Invertebrates
(Acute)
NLAA
NLAA
NLAA
NLAA
NLAA
NLAA
Aquatic-phase
frogs and fish
Acute
NE
NE
NE
NE
NE
NE
Chronic
NE
NE
NE
NE
NE
NE
Terrestrial-phase
frogs
Acute
LAA
LAA
LAA
LAA
LAA
NLAA
Chronic
LAA
LAA
LAA
LAA
LAA
LAA
Small Mammals
Acute
LAA
LAA
LAA
LAA
LAA
LAA
Chronic
LAA
LAA
LAA
LAA
LAA
LAA
1 NE = No effect; NLAA = May affect, not likely to adversely affect; LAA = Likely to adversely affect
11
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Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct/indirect and adverse
habitat modification effects determinations, it is important to note that pesticide
exposures and predicted risks to the 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
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.
12
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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. Environmental Protection Agency's (EPA's) Guidance for Ecological
Risk Assessment (U.S. EPA 1998), the Services' Endangered Species Consultation
Handbook (U.S. FWS/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 (U.S. FWS/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
paraquat on a range of uses such as commercial and industrial non-agricultural uses,
fruits, vegetables, feed for livestock, ornamental shrubs, flowers, and trees. 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.
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 GENEEC2, T-REX, and AgDRIFT, all of which are described at
length in the Overview Document. Additional refinements include the use of the T-
HERPS model and PRZM/EXAMS when appropriate based on results of GENEEC2.
The T-HERPS model is used as a refinement tool to explore amphibian-specific food
intake on potential exposures to the terrestrial phase CRLF. 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 paraquat is based on an action area. The action area is the area directly or
indirectly affected by the federal action, as indicated by the exceedance of the Agency's
Levels of Concern (LOCs). It is acknowledged that the action area for a national-level
FIFRA regulatory decision associated with a use of paraquat may potentially involve
numerous areas throughout the United States and its Territories. However, for the
13
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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 paraquat 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 CRLFs 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 CRLFs or upon the PCEs of the species'
designated critical habitat, a "no effect" determination is made for use of paraquat as it
relates to this species and its designated critical habitat. If, however, potential direct or
indirect effects to individual CRLFs 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 paraquat.
If a determination is made that use of paraquat 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
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 paraquat use sites) and further evaluation of the potential impact of paraquat
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 paraquat is expected to directly impact living organisms within the action area
(defined in Section 2.7), critical habitat analysis for paraquat 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
14
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critical habitat are those that alter the PCEs and appreciably diminish the value of the
habitat. Evaluation of actions related to use of paraquat 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
Please see Table 2-2 for a range of currently registered uses of paraquat in CA.
The end result of the EPA pesticide registration process (i.e.., the FIFRA regulatory
action) is an approved product label. The label is a legal document that stipulates how
and where a given pesticide may be used. Product labels (also known as end-use labels)
describe the formulation type (e.g.., liquid or granular), acceptable methods of application,
approved use sites, and any restrictions on how applications may be conducted. Thus, the
use or potential use of paraquat in accordance with the approved product labels for
California is "the action" relevant to this ecological risk assessment.
Although current registrations of paraquat allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of paraquat 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.
There are three PC codes associated with paraquat; 061601 for paraquat dichloride,
061602 for paraquat bis (methyl sulfate), and 061603 for paraquat. Paraquat bis (methyl
sulfate) is no longer a registered product of paraquat, and the PC code for paraquat alone
its unclear if it is the cation or not. Since paraquat dichloride and the paraquat cation are
used interchangeably within the literature and in past assessments. For our assessment,
data from all three PC codes and chemicals were incorporated, and converted to the
paraquat cation.
QINA (4-carboxyl-l-methylpyridinium) is a minor photodegradate of paraquat.
However, in the photodegradation in water study the quantity of degradate present was
only 6% of the radioactivity of paraquat after 85 weeks of natural sunlight irradiation.
Due to paraquat degrading very slowly, the minor degradate, QINA, does not pose as an
important environmental concern and will not be evaluated in this assessment.
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
15
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Document and the Services' Evaluation Memorandum (U.S., EPA 2004; USFWS/NMFS
2004).
Paraquat has registered products that contain multiple active ingredients. The results of
available toxicity data for mixtures of paraquat with other pesticides are presented in
Appendix B; however, there are no toxicity data for paraquat Multi-AI products. There
are available open literature data from ECOTOX and three studies which contained
information examining toxicity effects of paraquat when mixed with other chemicals.
According to the available open literature data, other pesticides may combine with
paraquat to produce additive, and/or antagonistic toxic effects. Mixtures included
paraquat with linuron, and paraquat with copper sulfate.
2.3 Previous Assessments
Paraquat was discovered in 1882 and was registered in England in 1962 prior to being
registered in the United States in 1964 for use as a contact herbicide to control or
suppress a broad spectrum of emerged weeds under the name paraquat dichloride. The
Agency classified paraquat dichloride as a restricted use pesticide due to high acute
toxicity to animals and people in 1978 (February 9, 1978 (43 FR 5782)). Under the
restricted use classification, only certified applicators or applicators working under their
direct supervision, are authorized to apply paraquat dichloride end-use products.
Also in 1978, paraquat dichloride was accepted as a candidate for the Special Review
board process because it was believed to exceed the risk criteria under 40 CFR 162.11:
teratogenicity, lack of emergency treatment, chronic effects, reproductive effects,
oncogenicity (data gap), mutagenicity (data gap), and acute effects. Other areas of
concern included mammalian toxicity and avian reproductive effects.
In October 1982 (43 FR 30613), the Agency issued a Final Position Document which
concluded that the available data did not support paraquat dichloride being placed into
the Special Review status since the risk criteria identified in 1978 had not been exceeded.
As a result, a Data Call-In (DCI) was issued requesting additional dermal and inhalation
data, and more precise information to assess the potential acute effects to applicators.
In June 1987, a Registration Standard for paraquat dichloride was issued (NTIS#PB88-
217005) in which the Agency evaluated the studies submitted as a result of the previous
DCI. In 1991, additional data were requested and evaluated for use in the 1997
Reregi strati on Eligibility Decision (RED). In the 1997 RED, the Agency requested
additional data in order to establish tolerances on taro foliage, corn and soybean aspirated
grain fractions, wheat and hay, cotton and gin byproducts, and processed grapes, as well
as data to confirm that the existing tolerance for field corn was adequate to cover the
specialized use of paraquat as a harvest aid.
To mitigate risks of concern posed by the use of paraquat, the Agency noted a number of
label amendments to address the worker, and ecological concerns.
• The maximum application rate for all paraquat dichloride products will be
lowered from 1.6 Ib cation/A to 1.0 Ib cation/A.
16
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o Broadcast applications with backpack sprayers (non-spot) should not
exceed the application rate 0.625 Ib cation/A and the application volume
should be no less than 20 gallons/A.
o The maximum application rate for spot spraying on all paraquat labels will
be no more than 0.0195 Ibs cation/gallon.
• Remove the plastic acid bottle and tree injection directions for use from the resin
soaking sections of all paraquat dichloride labels.
• Include the hazard statement "Paraquat dichloride is toxic to non-target crops and
plants if off-target movement occurs. Extreme care must be taken to ensure that
off-target drift is minimized to the greatest extent possible."
• For sole-active-ingredients end-use products that contain paraquat, the product
labeling must be revised to adopt the handler personal protective
equipment/engineering control requirements and remove any conflicting PPE
requirements.
o For multiple-active-ingredient end-use products that contain paraquat, the
handler personal protective equipment/engineering control requirements
set forth in this section must be compared to the requirements on the
current labeling and the more protective must be retained.
• Implement best management practices (BMPs) to reduce spray drift, including
BMPs for controlling droplet size, boom length, application height, swath
adjustment, wind, temperature and humidity, temperature inversions, and
sensitive areas.
• Implement use of PPE and engineering controls for workers.
A drinking water assessment was performed March 15, 2000, which determined paraquat
under most circumstances was unlikely to infiltrate past the first few centimeters of soil,
or to move off-field dissolved in runoff. Yet, monitoring data has demonstrated that
despite its apparent immobility, paraquat can reach ground water. Paraquat was reported
in 11 out of 971 wells sampled between 1983 and 1990 (USEPA Pesticides in
Groundwater Database, 1992) with 65 samples taken from private drinking water wells
having concentrations greater than 100 ug/L. These wells were located in coarse-grained
glacial soils that are extremely permeable, with saturated hydraulic conductivities on the
order of 20,000 ft/day (T.Mesko, USGS, personal communication). Detections were also
reported in household wells at concentrations ranging up to 1.52 ug/L (Mostaghimi et al.
1998). Data in Smith and Mayfield (1978) suggests that the application of fertilizer may
enhance the mobility of paraquat. The extremely slow breakdown of sorbed paraquat also
suggests the possibility that saturation and breakthrough may occur after years of
repeated application on some soils. Because of its strong cation-exchange sorption to
soils, runoff modeling is not appropriate for paraquat dichloride. In most circumstances,
the levels of paraquat residues in surface or ground water are expected to be insignificant.
Because it should sorb to suspended sediment, coagulation and flocculation processes in
drinking water treatment plants are likely to remove any paraquat residues present in the
raw water. Residues of paraquat in drinking water derived from surface supplies can
therefore be assumed to be negligible. For residues in ground water it was recommended
to use the value of 1.52 ug/L for human exposure assessment.
17
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On March 30, 2006, a risk assessment for proposed new uses of paraquat dichloride on
cantaloupe, cucumber, summer squash, ginger, okra, onion, tanier, and wheat was
performed. With the exception of wheat (where aerial and/or ground spray was to be
allowed), the proposed new uses are for ground spray only. In most cases no more than
2.0 Ibs a.i./A per season will be allowed. The exception is for the proposed use on
ginger, for which a maximum of 6.0 Ibs a.i./A per year is directed. The 2006 risk
assessment concluded that these new uses are expected to have acute toxicological effects
to terrestrial aquatic wildlife, aquatic plants, and terrestrial plants, and chronic
toxicological effects on terrestrial wildlife. Likewise, the assessment determined that
sub-lethal effects include lung damage in rats and oxidative stress in all organisms, which
can lead to premature aging as well as early demise.
On July 31, 2006, uses on ginger and okra were proposed, and the uses on soybeans,
wheat, cotton, cucurbits, onions, and tanier were amended. In this Human Health Risk
Assessment (HED):
• Tolerances were established or amended for the uses
• The registrant requested amended registration for use on cotton, soybean, wheat,
ginger, dry bulb onion, okra, and tanier (March 30, 2006 EFED assessment). In
this assessment, the registrant proposed to cancel the addition of those uses, but
did propose an amended use on cucurbits.
• Registrant needs to propose maximum seasonal rates for cotton, cucurbits, ginger,
soybeans, and wheat, minimal retreatment intervals for multiple post emergence
applications, and the directions for tanier needs to be modified to specify its
geological restrictions in Florida.
• Crop field trials for certain uses were requested.
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Assessment
The primary route of environmental dissipation of paraquat is adsorption to soil clay
particles. Paraquat does not hydrolyze, does not photodegrade in aqueous solutions, and
is resistant to microbial degradation under aerobic and anaerobic conditions. Essentially
no microbial degradation of paraquat was seen after 180 days of aerobic incubation or
after 60 days of anaerobic incubation following a 30 day aerobic incubation.
Paraquat was shown to be very immobile in soil with batch equilibrium studies conducted
on four soils in the laboratory. High rates of paraquat were added because at realistic field
application rates, paraquat was below detection in the batch equilibrium adsorption
solution. Adsorption Kds ranged from 68-50,000, and there was no detectable
desorption.
In laboratory studies with radiolabeled paraquat, no radioactivity volatilized from the soil
surface to adsorb to glass or to collect in volatile traps. With low vapor pressure and
extremely high adsorption coefficients, paraquat would not be expected to volatilize once
18
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applied to the soil, but spray drift could potentially be an issue since paraquat is
extremely biologically active and toxic to plants and animals.
In short and long term field dissipation studies, paraquat residues were extractable only
by acid reflux and were shown to be persistent and to accumulate slightly with repeated
applications. Paraquat is dissipated by rapid adsorption to clay particles. Due to the
apparent adsorption strength of paraquat for soil clays, these bound residues do not
appear to be environmentally available. Adsorbed radiolabeled paraquat did undergo
isotopic exchange when soil samples were shaken with a highly concentrated, non-
labeled paraquat solution (7440 ppm paraquat in water), so the potential for desorption
does exist; however, since there was no apparent exchange with calcium chloride in the
batch equilibrium study, this exchange will probably not affect the environmental
behavior of paraquat.
Paraquat is very persistent and is more likely to enter surface waters systems associated
with soil particles carried by erosion that will most likely be found sorbed onto eroded
particles at or near the application site rather than dissolved in the water column.
Therefore, this chemical is expected to be transported primarily along with soil particles
and subsequently redeposited onto the beds of surface water bodies or lowland areas that
receive eroded sediments from uplands (e.g., riparian zones, wetlands). The primary
route for dissipation of paraquat in the environment is through sorption onto solids; once
sorbed, paraquat is very difficult to extract. As a result, paraquat is not expected to be a
contaminant of groundwater, except in soils with very low clay content.
In previous reviews (reviews by Jordan, 2/14/1986), a minor photodegradate, 4-carboxyl-
1-methylpyridinium (QINA) which comprised 6% of applied radioactivity after 85 weeks
of natural sunlight irradiation, was determined to be mobile. According to the field data
reviewed in this submission which showed that paraquat degraded very slowly, QINA
would apparently not be an important environmental concern.
Table 2-1 lists the environmental fate properties of paraquat, along with the major and
minor degradates detected in the submitted environmental fate and transport studies.
Table 2-1 Summary of Paraquat Environmental Fate Properties
Study
Hydrolysis
Direct Aqueous
Photolysis
Soil Photolysis
Value (units)
Stable at pH 5, 7, 9
Stable
Stable
Major Degradates
Minor Degradates
No degradates reported
No degradates reported
CO2(0.15%)
4-carboxyl-l-
methylpyridinium (QINA)
(6%)
No degradates reported
MRID#
Upton et
al., 1985
MPJD
40562301
(Jordan,
1986)
MPJD
146807
Study Status
Acceptable
Acceptable
Supplemental
Acceptable
19
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Study
Aerobic Soil
Metabolism
Anaerobic Soil
Metabolism
Anaerobic
Aquatic
Metabolism
Aerobic
Aquatic
Metabolism
Kd-ads / Kd-des
(mL/g)
J^oc- ads ' J^oc-des
(mL/g)
Terrestrial
Field
Dissipation
Aquatic Field
Dissipation
Value (units)
Stable
Stable
No Study
<2 weeks (only represents water phase.
Did not measure amount of paraquat
sorbed to the soil)
68 - 50,000 (no measureable
correlation with % OC)
15,473 to 1,000,000
Half-life not calculated; however, cited
reference indicates a half-life of > 10
years
No Study
Major Degradates
Minor Degradates
Did not degrade. No
degradates reported.
No degradates reported.
0.29% uncharacterized
radioactivity.
No Study
No degradates reported
No degradates reported
No degradates reported.
No Study
MRID#
MRID
41319301
MRID
41319302
No Study
MRID
00055093
MRID
40762701
http://www
.ermanz.go
vt.nz/consu
Itations/cei
r/t.pdf
MRID
41293202
42802101
42738701
42738702
42802102
No Study
Study Status
Acceptable
Acceptable
No Study
Supplemental
Acceptable
Supplemental
Acceptable
No Study
2.4.2 Environmental Transport Assessment
Potential transport mechanisms include pesticide spray drift, and secondary drift of soil-
bound residues leading to deposition onto nearby or more distant ecosystems. Spray drift
is expected to be the major route of exposure for paraquat.
In general, deposition of drifting pesticides is expected to be greatest close to the site of
application. A computer model of spray drift (AgDRIFT) is used to determine potential
exposures to aquatic and terrestrial organisms via spray drift. The distance of potential
impact away from the use sites (action area) is determined by the distance required to fall
below the LOG for airports/commercial/public health areas (non-agricultural use) and
guava (agricultural use). These uses have the greatest application rate, greatest number
of applications per season, and the least amount of time between applications.
Due to model limitations, it may not be possible to provide a quantitative estimate of
exposure with known uncertainty, beyond the range of AgDRIFT.
20
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2.4.2 Mechanism of Action
Paraquat dichloride is a quaternary nitrogen compound widely used for broadleaf weed
control. It is a fast-acting contact herbicide used to suppress or eradicate a wide spectrum
of post-emergent weeds. It also functions as a defoliant and desiccant and is most
effective on growing plants with abundant green tissue. It is highly toxic (EPA toxicity
class I) but readily immobilized. Paraquat is quickly absorbed by living (esp. healthy)
plant tissue and produces superoxides during photosynthesis, which destroy plant cells. It
is less effective on dry, drought-stressed, woody, or fully mature plants.
2.4.3 Use Characterization
Analysis of labeled use information is the critical first step in evaluating the federal
action. The current label for paraquat 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.
There are a few uses that are not being assessed because they are either restricted in
California or the crop is not grown in California. The following uses will not be assessed
because they are not grown in California: cocoa, coffee, banana, plantain, pineapple, and
soybeans. If the use patterns indicate that these crops are grown in CA in the future, the
conclusions of this assessment may need to be revisited. The following uses, listed with
their respective labels, will not be assessed because they are restricted in California:
• Label 100-1217, Label 48273-00027: asparagus, broad beans, dried beans, moth
beans, mung beans, rice beans, lima beans, snap beans, tepary beans, urd beans,
catjang, cowpea/blackeyed pea, garbanzos, guar, lentils, lupine, pastures, and
dried and southern peas.
• Label 66222-00130 and Label 74530-00032: asparagus, broad beans, dried
beans, moth beans, mung beans, rice beans, lima beans, tepary beans, urd beans,
catjang, cocoa, cowpea/blackeyed pea, garbanzos, guar, lentils, lupine, pastures,
dried and southern peas, and persimmon.
• Label 82542-00003 and Label 82557-00001: asparagus, broad beans, dried
beans, moth beans, mung beans, rice beans, lima beans, tepary beans, urd beans,
catjang, cocoa, cowpea/blackeyed pea, garbanzos, guar, lentils, lupine, pastures,
and dried and southern peas.
The labels listed below are Section 24c labels for paraquat in other states and do not
apply to California. As a result, they will not be assessed in this assessment.
• Label CO06000700: alfalfa.
• Label ID08000900 and WY08000600: clover.
• Label MS05002100: agricultural crops/soils.
• Label NC06000400: sage.
• Label NJ06000100 and VA06000200: unspecified vegetables.
• Label TX06001700, TX08001900, and TX08002000: cotton
21
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Table 2-2 presents the uses and corresponding application rates and methods of
application considered in this assessment.
Table 2-2 Paraquat Uses Assessed for the CRLF1
Use (Application Method)
ACEROLA (WEST INDIES CHERRY),
APRICOT, CHERRY, NECTARINE, PEACH,
PLUM, KIWI FRUIT
DECIDUOUS FRUIT TREES (UNSPECIFIED),
FOREST TREES (SOFTWOODS - CONIFERS)
AGRICULTURAL FALLOW/IDLELAND
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE), NONAGRICULTURAL
RIGHTS-OF-WAY/FENCEROWS/HEDGEROWS
ALFALFA, BROCCOLI, ENDIVE (ESCAROLE),
LETTUCE
RHUBARB
ALMOND, BEECH NUT, BRAZIL NUT,
BUTTERNUT, CASHEW, CHESTNUT,
CHINQUAPIN, FILBERT (HAZELNUT),
HICKORY NUT, MACADAMIA NUT
(BUSHNUT), PECAN, PISTACHIO, WALNUT
(ENGLISH/BLACK), APPLE, FIG, ORCHARDS
(UNSPECIFIED), PEAR, PRUNE,
ARBORVITAE/ ASH /ELM /FIR /OAK /PINE
(FOREST/SHELTERBELT), AVOCADO,
CALAMONDIN, CITRON (CITRUS),
GRAPEFRUIT, KUMQUAT, LEMON, LIME,
ORANGE, PAPAYA, PUMMELO (SHADDOCK),
GRAPES, ORNAMENTAL AND/OR SHADE
TREES, WOODY SHRUBS AND VINES
ARTICHOKE
CABBAGE, CABBAGE - CHINESE,
COLLARDS,
ASPARAGUS, RICE, BARLEY, SAFFLOWER
(UNSPECIFIED), SMALL GRAINS
(UNSPECIFIED), SORGHUM, WHEAT,
CAULIFLOWER, CORN (UNSPECIFIED)/
SWEET/ FIELD/ POP, SUNFLOWER, COTTON
(UNSPECIFIED)
Max. Single
Appl. Rate
(Ib ai/A)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Max. Number of
Application per
Year
3
5
10
2
5
3
3
Application
Method
Ground
Aircraft
Ground
Ground
Aircraft
Ground
Ground
Ground
Ground
Aircraft
Ground
Aircraft
Ground
22
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Use (Application Method)
BEANS - SUCCULENT (LIMA/SNAP),
CARROT (INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER, CHAYOTE,
CUCUMBER, GOURD (WAX) - CHINESE,
GOURDS, MELONS - BITTER (BALSAM
PEAR)/ CANTALOUPE/ CITRON MUSK
/WATER, PEPINO (MELON PEAR), PUMPKIN,
SQUASH (ALL OR UNSPECIFIED),
EGGPLANT, GROUNDCHERRY
(STRAWBERRY TOMATO/TOMATILLO),
TOMATILLO, TOMATO, TURNIP (GREENS)
GARLIC, ONION
BLACKBERRY, BOYSENBERRY,
ELDERBERRY, GOOSEBERRY,
HUCKLEBERRY, LOGANBERRY,
RASPBERRY (BLACK - RED), BLUEBERRY,
CURRANT
BRUSSELS SPROUTS, KALE, VEGETABLES
(UNSPECIFIED), KOHLRABI
CITRUS HYBRIDS OTHER THAN TANGELO,
TANGELO, CRABAPPLE, LOQUAT, QUINCE,
MAYHAW (HAWTHORN)
CORN (SILAGE), STRAWBERRY
GUAR
PASTURES, POTATO - WHITE/IRISH
GHERKIN, SUGAR BEET
GRASSES GROWN FOR SEED
GINGER
GUAVA
MELONS
MINT/PEPPERMTNT/SPEARMINT
OKRA
OLIVE
Max. Single
Appl. Rate
(Ib ai/A)
1.0
1.0
1.0
1.0
0.5
1.0
1.0
1.0
0.3
0.8
1.0
1.0
Max. Number of
Application per
Year
1
5
3
5
3
3
6
10
1
2
1
4
Application
Method
Ground
Aircraft
Ground
Ground
Aircraft
Ground
Ground
Ground
Aircraft
Ground
Aircraft
Ground
Ground
Ground
Ground
Aircraft
Ground
Aircraft
Ground
Ground
Ground
23
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Use (Application Method)
PASSION FRUIT (GRANADILLA)
PEANUTS (UNSPECIFIED)
PERSIMMON
Max. Single
Appl. Rate
(Ib ai/A)
1.0
0.3
0.9
Max. Number of
Application per
Year
10
1
5
Application
Method
Ground
Ground
Ground
Uses assessed based on memorandum from SRRD dated February 5, 2009
Provided below, Figure 2-1 shows the estimated poundage of paraquat uses across the
United States. The map was downloaded from a U.S. Geological Survey (USGS),
National Water Quality Assessment Program (NAWQA) website.
PARAQUAT - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds par square mile of agricultural
land in county)
LJ no estimated use
D 0.001 to 0.017
D 0.018 to 0.102
D 0.103 to 0.383
D 0.384 to 1.13
• >= 1.131
Total
Cr°Ps pounds applied
corn
cotton
soybeans
alfalfa hay
grapes
cropland in summer fallow
almonds
wheat for grain
apples
peanuts
907815
696264
530939
362471
221792
157644
149748
117677
90627
66431
Percent
national use
23.13
17.74
13.53
9.23
5.65
4.02
3.82
3.00
2.31
1.69
Figure 2-1 Paraquat Use in Total Pounds per County
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis
of both national- and county-level usage information (Memo: County-Level Usage for
Propanil, Paraquat Dichloride, Pendimehtalin, Myclobutanil, Prometryn, Dicofol,
Alachlor, and Endosulfan in California in Support of a Red Legged Frog Endangered
24
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Species Assessment, 04 February 2009) using state-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 paraquat 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 eight years. The units of area treated are also provided where
available.
The usage data reported by CDPR PUR summarizing paraquat's usage for all California
use sites is provided below in Table 2-3. The uses range from commercial and industrial
non-agricultural uses to agricultural uses such as fruits, vegetables, feed for livestock, and
ornamental shrubs, flowers, and trees. The uses considered in this risk assessment
represent all currently registered uses according to a review of all current labels. No
other uses are relevant to this assessment. Any reported use, such as may be seen in the
CDPR PUR database, represent either historic uses that have been canceled, 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 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered
Paraquat Uses
Site Name
ALFALFA
ALMOND
APPLE
APRICOT
ARTICHOKE, GLOBE
ASPARAGUS
AVOCADO
Average
Pounds All
Uses
3,034.6
8,778.1
234.2
79.6
432.8
189.8
31.1
Avg
App
Rate All
Uses
0.7
0.9
0.8
0.9
0.9
1.0
0.9
Avg
95th%
App
Rate
1.0
1.4
1.6
1.4
1.1
1.3
2.0
Avg
99th%
App
Rate
1.3
2.2
2.5
2.1
1.1
1.3
2.4
Avg Max App
Rate
2.4
5.5
3.2
3.0
2.5
1.3
2.4
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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Site Name
BARLEY
BEAN, DRIED
BEAN, SUCCULENT
BEAN, UNSPECIFIED
BLACKBERRY
BLUEBERRY
BOYSENBERRY
BROCCOLI
BRUSSELS SPROUT
BUILDINGS/NON-AG OUTDROOR
CABBAGE
CANTALOUPE
CARROT
CAULIFLOWER
CHERRY
CHESTNUT
CHINESE CABBAGE (NAPPA)
CHRISTMAS TREE
CITRUS
COLLARD
CORN (FORAGE - FODDER)
CORN, HUMAN CONSUMPTION
COTTON
CUCUMBER
DITCH BANK
EGGPLANT
ENDIVE (ESCAROLE)
FIG
FORAGE HAY/SILAGE
GARLIC
GRAIN
GRAPE
GRAPE, WINE
GRAPEFRUIT
GRASS, SEED
INDUSTRIAL SITE
KALE
KIWI
Average
Pounds All
Uses
21.2
43.4
46.6
11.9
18.1
317.0
8.8
59.3
0.2
2.9
9.6
57.6
46.7
20.5
439.4
16.3
21.5
2.2
24.9
8.5
576.1
26.6
15,389.3
48.6
9.7
19.5
2.2
56.6
7.4
27.2
7.4
4,519.4
2,574.0
22.6
23.1
0.2
0.4
95.0
Avg
App
Rate All
Uses
0.7
0.9
1.1
1.0
0.8
0.9
0.7
0.9
1.3
1.3
1.1
0.8
1.1
1.1
0.9
0.7
1.0
0.9
0.8
1.0
1.0
1.5
0.5
1.0
2.3
1.1
1.4
0.8
0.7
1.0
0.6
0.9
0.7
0.8
1.0
0.9
1.2
1.8
Avg
95th%
App
Rate
0.8
1.1
1.5
1.8
1.0
2.2
1.2
1.2
1.3
1.3
1.5
1.1
1.1
1.2
1.6
1.3
1.1
0.9
1.1
1.0
1.3
1.6
1.0
1.8
4.8
1.6
1.4
1.1
0.9
1.0
0.6
1.3
1.2
1.2
1.0
0.9
1.2
3.9
Avg
99th%
App
Rate
0.8
1.1
2.5
1.8
4.2
2.6
1.2
1.2
1.3
1.3
1.5
1.1
1.1
2.2
2.3
1.3
1.1
0.9
1.3
1.0
1.4
1.6
1.1
2.0
4.8
1.6
1.4
1.3
0.9
1.0
0.6
1.5
1.6
3.1
1.0
0.9
1.2
5.2
Avg Max App
Rate
0.8
1.1
2.9
1.8
4.2
2.6
1.2
1.2
1.3
1.3
1.5
1.1
1.1
2.2
3.5
1.3
1.1
0.9
1.3
1.0
2.4
1.6
2.6
2.0
4.8
1.6
1.4
1.3
0.9
1.0
0.6
2.9
2.6
3.1
1.0
0.9
1.2
5.2
26
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Site Name
KOHLRABI
LANDSCAPE MAINTENANCE
LEMON
LETTUCE, HEAD
LETTUCE, LEAF
MELON
MINT
NECTARINE
N-GRNHS FLOWER
N-GRNHS PLANTS IN CONTAINERS
N-OUTDR FLOWER
N-OUTDR PLANTS IN CONTAINERS
N-OUTDR TRANSPLANTS
OLIVE
ONION, DRY
ONION, GREEN
ORANGE
ORCHARD FLOOR
PASTURELAND
PEACH
PEANUT
PEAR
PEAS
PECAN
PEPPER, FRUITING
PEPPER, SPICE
PERSIMMON
PISTACHIO
PLUM
POTATO
PRUNE
PUMPKIN
RANGELAND
RASPBERRY
REGULATORY PEST CONTROL
RESEARCH COMMODITY
RHUBARB
RICE
Average
Pounds All
Uses
0.6
6.6
96.8
320.1
57.4
41.8
373.6
894.2
2.8
5.0
10.7
28.5
15.1
132.8
86.1
11.9
575.9
2.7
15.2
747.5
1.3
139.0
8.8
26.1
125.1
411.3
3.3
1,511.7
727.8
46.3
515.7
1.3
27.3
67.7
5.1
9.7
3.1
58.8
Avg
App
Rate All
Uses
1.3
1.7
0.9
1.3
1.1
0.9
0.7
0.7
1.2
14.6
0.8
1.4
0.9
0.9
1.1
1.1
1.1
0.9
0.8
0.9
1.2
0.8
1.2
1.1
1.0
1.0
0.9
0.8
0.7
1.0
0.8
0.9
0.6
1.1
0.7
0.8
1.3
1.3
Avg
95th%
App
Rate
1.3
2.2
1.5
1.9
1.5
1.0
0.9
1.2
1.5
28.0
1.1
2.2
3.0
1.9
1.4
1.4
1.6
1.1
1.1
1.5
1.2
1.3
1.6
2.8
2.1
1.8
1.2
1.3
1.1
1.2
1.3
0.9
0.6
1.5
0.7
1.5
1.3
2.0
Avg
99th%
App
Rate
1.3
2.2
3.7
2.5
1.5
1.0
2.6
1.9
1.6
28.0
2.7
2.8
3.5
2.2
1.5
1.4
3.0
1.1
1.1
1.8
1.2
2.6
1.6
2.8
2.3
1.8
1.2
2.1
1.3
1.7
2.1
0.9
0.6
2.3
0.7
2.4
1.3
2.0
Avg Max App
Rate
1.3
2.2
3.7
3.9
1.5
1.0
2.9
2.8
1.6
28.0
2.7
2.8
3.5
2.5
1.5
1.4
4.9
1.1
1.1
3.2
1.2
3.2
1.6
2.8
2.4
2.4
1.2
4.8
2.5
1.7
3.3
0.9
0.6
3.7
0.7
2.4
1.3
2.0
27
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Site Name
RIGHTS OF WAY
SAFFLOWER
SORGHUM (FORAGE - FODDER/ MILO)
SOYBEAN
SQUASH
SQUASH, SUMMER
SQUASH, WINTER
SQUASH, ZUCCHINI
STRAWBERRY
STRUCTURAL PEST CONTROL
SUDANGRASS
SUGARBEET
SUNFLOWER
TANGELO
TOMATO
UNCULTIVATED AG
UNCULTIVATED NON-AG
VEGETABLE
VERTEBRATE CONTROL
WALNUT
WATERMELON
WHEAT
Average
Pounds All
Uses
407.3
98.1
10.6
9.4
14.1
9.9
2.6
6.5
75.1
1.4
10.2
61.2
326.7
15.9
270.0
394.1
60.8
4.8
3.2
796.6
43.1
41.2
Avg
App
Rate All
Uses
0.9
0.9
0.4
0.5
1.1
1.6
0.8
0.9
0.9
0.5
0.7
1.0
0.8
1.1
0.9
1.0
1.3
0.7
0.2
0.8
1.2
0.8
Avg
95th%
App
Rate
1.0
1.2
0.5
0.5
1.3
4.3
0.9
1.0
1.6
0.5
0.8
1.2
1.9
1.7
1.2
1.9
1.9
0.9
0.5
1.3
2.4
1.0
Avg
99th%
App
Rate
1.0
1.9
0.5
0.5
1.3
4.3
0.9
1.0
2.5
0.5
0.8
1.2
2.7
1.7
1.7
2.4
4.8
0.9
0.5
1.9
2.4
1.0
Avg Max App
Rate
1.0
1.9
0.5
0.5
1.3
4.3
0.9
1.0
2.9
0.5
0.8
1.2
2.7
1.7
1.8
2.7
4.9
0.9
0.5
4.0
2.4
1.0
2.5 Assessed Species
The CRLF was federally listed as a threatened species by U.S. FWS effective June 24,
1996 (U.S. FWS 1996). It is one of two subspecies of the red-legged frog and is the
largest native frog in the western United States (U.S. FWS 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 I.
Final critical habitat for the CRLF was designated by U.S. FWS on April 13, 2006 (U.S.
FWS 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
28
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interior mountain ranges (U.S. FWS 1996). Its range has been reduced by about 70%,
and the species currently resides in 22 counties in California (U.S. FWS 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) (U.S. FWS 2002).
Populations currently exist along the northern California coast, northern Transverse
Ranges (U.S. FWS 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 (U.S. FWS 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) (U.S. FWS 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
Attachment I). 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 U.S. FWS 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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Legend
Recovery Units
1. Sierra Nevada Foothills and Central Valley
2. North Coast Range Foothills and Western
Sacramento River Valley
North Coast and North San Francisco Bay
South and East San Francisco Bay
Central Coast
Diablo Range and Salinas Valley
7. Northern Transverse Ranges and Tehachapi
Mountains
Southern Transverse and Peninsular Ranges
I Recovery Unit Boundaries ^
Currently Occupied Core Areas
| Critical Habitat
| CNDDB Occurence Sections
County' Boundaries Q
Core Areas
1. Feather River
2. Yuba River- S. Fork Feather River
3. Traverse Creek/ Middle Fork/ American R. Rubicon
4. Cosumnes River
5. South Fork Calaveras River*
6. Tuolumne River*
7. Pmey Creek*
8. Cottonwood Creek
9. Putah Creek - Cache Creek*
10. Lake Berryessa Tributaries
11. Upper Sonoma Creek
12. Petaluma Creek - Sonoma Creek
13. Pt. 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-
Watsonville S lough-Elkhorn Slough
Carmel River - Santa Lucia
Gablan Range
Estero Bay
Arroyo Grange River
Santa Maria River - Santa Ynez River
Sisquoc River
Ventura River - Santa Clara River
Santa Monica Bay - Venura Coastal Streams
Estrella River
San Gabriel Mountain*
Forks of the Mojave*
Santa Ana Mountain*
Santa Rosa Plateau
San Luis Ray*
Sweetwater*
Laguna Mountain*
•-legged frog are not included in the map
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 (U.S. FWS 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,
U.S. FWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b; U.S. FWS 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 (U.S. FWS 2002). Figure 2-3 depicts CRLF annual reproductive
timing.
J
F
M
A
M
J
J
A
S
0
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over- winter)
Orange = Young Juveniles
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
(U.S. FWS 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 andMcDiarmid 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
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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 (U.S. FWS 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 (U.S. FWS 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 (U.S.
FWS 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://ecos.fws.gov/speciesProfile/SpeciesReport.do?spcode=D02D).
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 (U.S. FWS 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
32
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trees or logs, industrial debris, and agricultural features (U.S. FWS 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
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 U.S. FWS (U.S. FWS 2006; FR 51 19244-19346). A
summary of the 34 critical habitat units relative to U.S. FWS-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, U.S. FWS does not
include areas where existing management is sufficient to conserve the species. Critical
33
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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
four of the PCEs, and were occupied by the CRLF at the time of the Final Rule (FR)
listing notice in April 2006 (71 FR 19243, 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.
U.S. FWS has established adverse modification standards for designated critical habitat
(U.S. FWS 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 paraquat that may alter the PCEs of the CRLF's
critical habitat form the basis of the critical habitat impact analysis. According to U.S.
FWS (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 paraquat is expected to directly impact living
organisms within the action area, critical habitat analysis for paraquat 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.
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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 paraquat is likely to encompass considerable portions of the
United States based on the large array of 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 (U.S. EPA 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 paraquat may be expected to have on the
environment, the exposure levels to paraquat that are associated with those effects, and
the best available information concerning the use of paraquat 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 paraquat. An analysis of labeled uses and review of available product labels was
completed. Several of the currently labeled uses are special local needs (SLN) uses or are
restricted to specific states other than California and are excluded from this assessment.
In addition, a distinction has been made between food use crops and those that are non-
food/non-agricultural uses. The agricultural uses as well as the non-agricultural and non-
food uses relevant to the CRLF can be found in Table 2-2.
Following a determination of the assessed uses, an evaluation of the potential "footprint"
of paraquat 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 represent the
35
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labeled uses described above. A map representing all the land cover types that make up
the initial area of concern for paraquat is presented in Figure 2-4.
The uses represented by paraquat are depicted by the following land cover types:
cultivated crops (51%), developed/high intensity (0.83%), developed/low intensity
(1.7%), developed/open space (0.83%), forest (9.9%), orchards/vineyards (33%), and
pasture/hay (2.5%). Cultivated crops are areas used for the production of annual crops,
such as corn, soybeans, vegetables, and cotton. This class also includes all land being
actively tilled. Developed/high intensity areas are where people reside, or work in high
numbers. The impervious surfaces account for 80-100% of the total cover.
Developed/low intensity areas include a mixture of constructed materials and vegetation
with impervious surfaces accounting for 20-40% of total cover. Developed/open space
includes areas with a mixture of constructed materials, but mainly vegetation in the form
of lawn grasses. Impervious surfaces account for lass than 20% of total cover. Forest
represents deciduous, evergreen, and mixed vegetation. These areas are dominated by
trees that are generally greater than 5 meters tall, and greater than 20% of total vegetation
cover. Orchards/vineyards represent areas used for the cultivation of crops, such as fruits
and nuts, which grow on vines or trees. Lastly, pasture/hay represents areas of grasses,
legumes, or grass-legume mixtures planted for livestock grazing or the production of seed
or hay crops. Typically, pasture/hay vegetation accounts for greater than 20% of total
vegetation. For more information regarding which specific uses are represented by each
land cover type, see Appendix D.
Paraquat appears to be applied in 55 out of 58 counties in California per the CAPUR
database. In addition, paraquat has both a wide range of agricultural and non-agricultural
uses throughout the state. Likewise, when modeling with AgDRTFT, the buffer zone
needed to prevent ecological effects from spray drift is greater than 1,000 feet. As a
result, the entire state of California will be the action area.
36
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Paraquat Use - Initial Area of Concern
I Forest use
Developed-open space
Developed-low density
Developed-medium density
Developed-high density
Pasturehay use
Orchard vineyard use
Cultivated crop use
County boundaries
i Kilometers
02040 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 Pesticides Programs, Environmental Fate and Effects Division.
Projection: Albers Equal Area Conic USGS, North American
Datum of 1983 (MAD 1983).
6/1/2009
Figure 2-4 Initial area of concern, or "footprint" of potential use, for Paraquat
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 primary route of environmental dissipation of paraquat dichloride is adsorption to
biological material and soil clay particles. Paraquat dichloride has been shown to adsorb
to clay crystalline lattices with no apparent correlation between organic matter content
and paraquat adsorption. Paraquat does not hydrolyze, does not photodegrade in aqueous
solutions, and is resistant to microbial degradation under aerobic and anaerobic
conditions. Paraquat is also very immobile in soil and is not expected to volatilize once
applied. However, spray drift could potentially be a problem because paraquat is very
biologically active and toxic to plants and animals before it becomes adsorbed to soil clay
particles.
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 uses the most sensitive endpoint. The cocklebur (£€25 = 0.014 Ib cation/A) was
used to represent the non-listed plant species. The AgDRIFT results suggest that ground
applications for non-listed plants need a spray drift buffer distance of approximately 361
feet. However, aerial applications yielded a spray drift buffer distance that was out of
range for the AgDRIFT model (1,000 feet). Therefore, a maximum spray drift distance
of greater than 1,000 feet was derived. Further detail on the spray drift analysis is
provided in Section 5.1.4.1.
In addition to the buffered area from the spray drift analysis, the final action area also
considers the downstream extent of paraquat that exceeds the LOG (discussed in Section
5.1.4.2). An evaluation of usage information was conducted to determine the area where
use of paraquat 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 paraquat has historically been used on a wide variety
of agricultural and non-agricultural uses in approximately 55 counties in California. As a
result, since paraquat has both agricultural and non-agricultural uses, it is applied in 55 of
58 counties, and has a buffer zone greater than 1,000 feet for aerial application, with such
widespread use the action area is the entire state of California.
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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
paraquat (e.g., runoff, spray drift, etc.), and the routes by which ecological receptors are
exposed to paraquat (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 effects to its habitat. In addition, potential effects to 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 (U.S. EPA 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 paraquat is provided in Table 2-4.
3 U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
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Table 2-4 Assessment Endpoints and Measures of Ecological Effects for Direct and
Indirect Effects of Paraquat (in terms of the Paraquat Cation) on the CRLF.
Assessment Endpoint | Measures of Ecological Effects4
Aquatic-Phase CRLF
(Eggs, larvae, juveniles, and adults)3
Direct Effects
1. Survival, growth, and reproduction of
CRLF
la. Rainbow trout (Oncorhynchus mykiss) LCso
Ib. No Chronic Fish Data
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. Algae (Navicula pelliculosa) ECso
2b. No Chronic Invertebrate Data
2c. Water flea (Daphnia magna) ECso
3a. Duckweed (Lemna gibba) EC50
3b. Algae (Navicula pelliculosa) ECso
4a. Monocots: Seedling Emergence, Vegetative Vigor EC25
4b. Dicots: Seedling Emergence, Vegetative Vigor EC25
Terrestrial-Phase CRLF
(Juveniles and adults)b
Direct Effects
5. Survival, growth, and reproduction of
CRLF individuals via direct effects on
terrestrial phase adults and juveniles
5a. Japanese Quail (Coturnix coturnixjaponica) LC50
5b. Mallard duck (Anas platyrhynchos) NOEAC
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. Laboratory rat (Rattus norvegicus) Female LD50
6b. Wistar Derived Rats-Alderley Park Strain NOAEL
6c. Honey bee (Apis me I lifer a) LD50
6d. Northern Bobwhite Quail (Colinus virginianus) LD50
6e. Japanese Quail (Coturnix coturnixjaponica) LCso
6f . Mallard duck (Anas platyrhynchos) NOEAC
7a. Monocots: Seedling Emergence, Vegetative Vigor EC25
7b. Dicots: Seedling Emergence, Vegetative Vigor EC25
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.
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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 paraquat 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 affect 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 paraquat effects data are available. Adverse modification to
the critical habitat of the CRLF includes, but is not limited to, those PCEs listed in
Section 2.6.
Measures of such possible effects by labeled use of paraquat on critical habitat of the
CRLF are described in Table 2-5. 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 U.S. FWS (2006).
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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 Effect4
Aquatic-Phase CRLF 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.
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)
la. Algae (Navicula pelliculosa) ECso
Ib. Duckweed (Lemna gibba) ECso
Ic. Monocots: Seedling Emergence, Vegetative Vigor EC25
Id. Dicots: Seedling Emergence, Vegetative Vigor EC25
2a. Algae (Navicula pelliculosa) ECso
2b. Duckweed (Lemna gibba) EC50
2c. Monocots: Seedling Emergence, Vegetative Vigor EC25
2d. Dicots: Seedling Emergence, Vegetative Vigor EC25
3a. Water flea (Daphnia magna) EC50
3b. Rainbow trout (Oncorhynchus mykiss) LCso
3c. No chronic fish or aquatic-phase amphibians or aquatic
invertebrates data
4a. Algae (Navicula pelliculosa) ECso
Terrestrial-Phase CRLF 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.
5a. Monocots: Seedling Emergence, Vegetative Vigor EC25
5b. Dicots: Seedling Emergence, Vegetative Vigor EC25
5c. Laboratory rat (Rattus norvegicus) Female LD50
5d. Wistar Derived Rats-Alderley Park Strain NOAEL
5e. Honey bee (Apis mellifera) LD50
5f. Northern Bobwhite Quail (Colinus virginianus) LD50
5g. Japanese Quail (Coturnix coturnixjaponica) LCso
5h. Mallard duck (Anas platyrhynchos) NOEAC
" 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.
4 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix A.
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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 paraquat to the environment.
The following risk hypotheses are presumed for this endangered species assessment:
The labeled use of paraquat 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; or
• 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 paraquat 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
43
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conceptual models for the aquatic and terrestrial PCE components of critical habitat.
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 effects
to designated critical habitat is expected to be negligible.
Stressor
Source
Exposure
Media
Paraquat applied to use site
Long range
atmospheric
transport
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Wet/dry deposition-*'
Receptors
Attribute
Change
Birds/terrestrial-
phase
amphibians/
reptiles/mammals
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Food chain
Reduction in prey
Effects to PCEs
related to prey
availability
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Effects to PCEs related to habitat
Figure 2-5 Conceptual Model for Pesticide Effects on Terrestrial Phase of the
CRLF
44
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Stressor
Source
Exposure
Media
Paraquat applied to use site
t
| Spray drift] |"Runoff"l I Soil \
^
*• Groundwater •
Surface water/
Sediment
T
T.
Long range
atmospheric
transport
•Wet/dry deposition
Uptake/gills
or integument
Uptake/gills
or integument
Receptors
Attribute
Change
Aquatic Animals
Invertebrates
Vertebrates
Uptake/cell,
roots, leaves
Aquatic Plants
Non-vascular
Vascular
Fish/aquatic-
phase amphibians
"Piscivorous
mammals and
birds
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Food chain
Reduction in algae
Reduction in prey
Effects to PCEs
related to prey
availability
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Effects to 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 paraquat 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 paraquat 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 paraquat along with available monitoring data
indicate that runoff and spray drift are the principle potential transport mechanisms of
paraquat to the aquatic and terrestrial habitats of the CRLF. In this assessment, transport
of paraquat through runoff and spray drift is considered in deriving quantitative estimates
of paraquat exposure to CRLF, its prey and its habitats. Paraquat is not expected to
volatilize once applied to soil due to its extremely high adsorption coefficients. As a
result, atmospheric transport is unlikely. See Section 3.2.4 for an explanation of existing
monitoring data.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of paraquat using maximum labeled application
rates and methods of application. The model used to predict aquatic EECs was the
GENeric Estimated Environmental Concentration Model (GENEEC2) which mimics the
Tier II models the Pesticide Root Zone Model coupled with the Exposure Analysis Model
System (PRZM/EXAMS). The model used to predict terrestrial EECs on food items is
T-REX. These models are parameterized using relevant reviewed registrant-submitted
environmental fate data.
GENEEC2 (v2.0, August 2001) is a Tier I computer program, that uses the soil/water
partition coefficient and degradation kinetic data to estimate runoff from a ten hectare
field into a one hectare by two meter deep "standard" pond. This first tier is designed as a
coarse screen and estimates conservative pesticide concentrations in surface water from a
few basic chemical parameters and pesticide label use and application information. Tier I
is used to screen chemicals to determine which ones potentially pose sufficient risk to
warrant higher level modeling. It calculates acute as well as longer-term estimated
environmental concentration (EEC) values. It considers reduction in dissolved pesticide
concentration due to adsorption of pesticide to soil or sediment, incorporation,
degradation in soil before runoff to a water body, direct deposition of spray drift into the
water body, and degradation of the pesticide within the water body. It is designed to
mimic a PRZM-EXAMS simulation.
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 paraquat that may occur in surface water bodies
adjacent to application sites receiving paraquat 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 paraquat. The measure of
46
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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 1-in-10-year 60-day mean is
used for assessing chronic exposure to the CRLF and fish and frogs serving as prey
items; the 1-in-10-year 21-day mean is used for assessing chronic exposure for aquatic
invertebrates, which are also potential prey items.
Chemicals failing to pass the GENEEC2 program move on to the Tier II
(PRZM/EXAMS) modeling. However, in the case of paraquat, all direct aquatic, indirect
aquatic, and vascular aquatic plant EECs do not result in an exceedance. The non-
vascular aquatic plant EECs result in an exceedance, but paraquat is an herbicide and
exceedances for plants is expected.
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
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 paraquat 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
paraquat are bound by using the dietary based EECs for small insects and large insects.
For an additional refinement of terrestrial-phase CLRF dose and dietary-based exposures
the T-HERPS model is employed. The T-HERPS is used as a refinement tool to explore
amphibian-specific food intake on potential exposures to the terrestrial phase CRLF. It
incorporates the same inputs as T-REX with equations adjusted for poikilotherm 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, application rate and
minimum incorporation depth.
The spray drift model, AgDRIFT, is used to assess exposures of terrestrial phase CRLF
and its prey to paraquat deposited on terrestrial habitats by spray drift. In addition to the
buffered area from the spray drift analysis, the downstream extent of paraquat that
exceeds the LOG for the effects determination is also considered.
47
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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 U.S. EPA,
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 paraquat 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, LC50 and EC50. 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 EC50 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,
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.
48
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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
paraquat, 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 paraquat 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) (U.S. EPA
2004) (see Appendix C).
For this endangered species assessment, listed species LOCs are used for comparing RQ
values for acute and chronic exposures of paraquat directly to the CRLF. If estimated
exposures directly to the CRLF of paraquat 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 paraquat 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.
2.10.1.4 Data Gaps
The long-term stability of sediment-bound paraquat under various conditions (such as
changes in pH, Eh, etc.) is unknown. There is insufficient data to determine to what
extent paraquat will accumulate at the same site with successive applications, and what
the effects of accumulation might be. Likewise, paraquat is expected to adsorb to soils
with high clay content. Therefore, a batch equilibrium study using soils with varying
percents of clay content as well as soils with low clay content would be beneficial to
better understand which types of soils paraquat may not adsorb to and possibly leach to
ground water.
The effect of consuming soil-bound paraquat on organisms is unknown. The fate of
paraquat dichloride residues in desiccated plant material (that is, how tightly bound to
biological material does it remain relative to clay-bound paraquat) is unknown.
49
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Therefore, conservative assumptions were made when running the models to determine
the effects. Please see Section 3 and Section 5 for further explanation on assumptions
made for modeling.
Paraquat is likely to reach the aquatic environment via erosion and runoff, and persist in
the aquatic sediment resulting in exposure to benthic dwelling freshwater invertebrates
and fish. Currently, however no chronic toxicity studies for freshwater invertebrates or
fish have been submitted to the Agency. Therefore, there is a data gap for chronic
freshwater invertebrates and fish toxicity. Due to this data gap we used the chemical
diquat, which is similar in structure to calculate an acute to chronic ratio (ACR). Only
the freshwater invertebrate data were used as two different species offish were studied
and an ACR could not be calculated across species.
There is only one multi-active ingredient product containing paraquat and Carfentrazone-
ethyl as Cyclone Star (EPA Reg Number 00010001316). There is no toxicity data
relative to this compound (Carfentrazone-ethyl) in the literature or in the assessment
provided by Human Helath and Effects Division (HED). Therefore, no difnitive
statement can be made as to whether this product poses any toxic risk greater or less than
paraquat product alone. The best available information suggests that the assessment
based on paraquat alone is adequate to understand risk to non-target receptors.
50
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3.0 Exposure Assessment
Paraquat is formulated as an emulsifiable concentrate. Application methods include
ground, aerial, and by various sprayers (band, hooded, low-pressure, and shielded). Risks
from ground boom and aerial applications are expected to result in the highest off-target
levels of paraquat 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
Paraquat labels may be categorized into two types: labels for manufacturing uses
(including technical grade paraquat and its formulated products) and end-use products.
While technical products, which contain paraquat of high purity, are not used directly in
the environment, they are used to make formulated products. The formulated product
labels legally limit paraquat's potential use to only those sites that are specified on the
labels.
Currently registered agricultural and non-agricultural uses of paraquat within California
are listed in Table 2-2. The uses being assessed are summarized in Table 3-1 below. The
uses assessed were the non-agricultural use and agricultural use with the maximum
application rate/largest number of applications per year/smallest application interval, the
median agricultural use, and the agricultural use with smallest application rate/the least
number of applications per year /largest application interval.
Table 3-1 Paraquat Uses and Application Information for the CRLF risk
assessment1
Uses Represented by Scenario
AGRICULTURAL FALLOW/IDLELAND
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE), NONAGRICULTURAL
RIGHTS-OF-WAY/FENCEROWS/HEDGEROWS
GUAVA, PASSION FRUIT (GRANADILLA)
MELONS, PEANUTS (ground only)
Application
Rate (Ib
cation/A)
1.0
1.0
1.0
0.3
Number of
Applications
5
10
10
1
Application
Interval
5
5
5
1
Application
Method
Aircraft
Ground
Ground
Ground
Aircraft
Ground
Uses assessed based on memorandum from SRRD dated February 5, 2009
51
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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 paraquat 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 paraquat were used for
modeling, including application rates, number of applications per year, application
intervals, and the first application date for each crop.
3.2.2 Model Inputs
Paraquat is an herbicide used on various crops such as apricots, loganberries, corn,
peanuts, coffee, lettuce, and non-crop areas such as airport landing fields, and
commercial, industrial and institutional premises. Paraquat's environmental fate data
used for generating model parameters is listed in Table 2-2. The input parameters for the
GENEEC2 model are in Table 3-2.
Most of the inputs used in the GENEEC2 model followed the Input Parameter Guidance;
however, since paraquat's adsorption Kds ranged from 68-50,000 (mobile to highly
immobile), the average Kd would not necessarily be an accurate depiction of paraquat's
mobility. Paraquat is an interesting chemical due to its high affinity to clay (negatively
charged particles) as a result of its cationic charge in the molecule. Therefore, paraquat
may be more mobile in soil that is less charged, such as sand, and will become
increasingly less mobile in soils with higher percentages of clay. The Kd was determined
by plotting the Kds along with their corresponding concentrations (Ib cation/A) in order
to determine the linear regression. Once this was established, the maximum allowable
application rate (1 Ib cation/A) was plugged into the equation given by the regression to
determine the corresponding Kd. This was done for all four soils in the study (MRTD
40762701). Then, the average Kd was determined and used as the input. Determining
52
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Kd in this manner is believed to be very conservative because the Kd value calculated by
this method assumes paraquat to be more mobile than expected.
Table 3-2 Summary of GENEEC2 Environmental Fate Data Used for Aquatic
Exposure Inputs for Paraquat Endangered Species Assessment for the CRLF1
Based on the Paraquat Cation
Fate Property
Value (unit)
MRID (or source)
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)
Kd
Application rate and frequency
Application intervals
186 g/mol
1.9xlO-9atmm3mor1
7,000,000 mg/1 (700,000* mg/1 x
10 per input guidance)
0 (Stable)
0 (Stable)
0 (Stable)
0 (0.5 x Aerobic Soil Metabolism
study)
0 (0.5 x Anaerobic Soil
Metabolism study)
295
Various (see Table 3.3)
Various (see Table 3.3)
http ://toxnet.nlm. nih. gov
http ://toxnet.nlm. nih. gov
http ://toxnet.nlm. nih. gov
*http://www.inchem.org/docu
ments/icsc/icsc/eics0005 .htm
Per Input Parameter Guidance
MRID 40562301
MRID 41319301
MRID 41319302
Per Input Parameter Guidance
Per Input Parameter Guidance
MRID 40762701
Per Label Instructions
Per Label Instructions
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 application practices using the GENEEC2 model are
listed in Table 3-3. The maximum non-agricultural and agricultural application
rate/interval/applications per year were calculated, along with the median use application
rate/interval/applications per year, and minimum use application rate/interval/applications
per year. See Appendix I for a summary of the outputs. Peak EECs ranged from 1.6 ppb
to 55 ppb for use on melons, and airports/commercial/public health areas (impervious
areas) and guava/passion fruit respectively.
Since some of the application data needed for modeling were not stated on the labels,
assumptions were made by EFED analysts regarding the maximum number of
53
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applications allowed per season, and/or the interval between applications. The
assumptions were as follows:
• For the application intervals that were not stated, the most conservative
(minimum) known application interval was used (5 days). Five days was chosen
because it was the minimum known interval that was registered.
• If the maximum number of applications was not stated, the most conservative
(maximum) known number of applications was used (10 applications). Ten
applications were chosen because 10 was the maximum known number of
applications allowed that was registered.
• If the maximum number of applications was not stated, but the uses had an
application timing of pre-emergence or pre-plant, and was not listed as having
multiple crop seasons per year in California, per a table created by the Biological
and Economic Analysis Division (BEAD), the maximum application number was
assumed to be one.
Table 3-3 Aquatic EECs (ug/L) for Paraquat Uses in California
Application
Rate (1kg
cation/ha)
1.0
1.0
1.0
0.3
Crops Represented
AGRICULTURAL FALLOW/IDLELAND
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE), NONAGRICULTURAL
RIGHTS-OF-WAY/FENCEROWS/HEDGEROWS
GUAVA, PASSION FRUIT (GRANADILLA)
MELONS, PEANUTS (ground only)
Peak
EEC
33
27
55
55
2.0
1.6
21-day
average EEC
20
17
34
34
1.2
1.0
60-day
average
EEC
10
8.5
17
17
0.62
0.51
3.2.4 Existing Monitoring Data
Whenever it is available, monitoring data is included in assessments in order to better
characterize the EECs calculated in the modeled estimates. In this assessment,
monitoring data was sought from the following sources: the USGS NAWQA program
(http ://water.usgs.gov/nawqa), the California Department of Pesticide Regulation
(CDPR), and the California Air Review Board.
3.2.4.1 USGS NAWQA Surface Water Data
The USGS has not looked for any samples containing paraquat. Therefore, no surface
water data are available.
54
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3.2.4.2 USGS NAWQA Groundwater Data
The USGS has not collected any samples looking for paraquat. Therefore, no ground
water data are available.
3.2.4.3 California Department of Pesticide Regulation (CDPR) Data
The California Department of Pesticide Regulation (CDPR) has been collecting surface
water data on paraquat for many years. Out of 399 samples, 398 of the samples did not
contain paraquat. One sample showed a detection of paraquat at 0.24 ppb; the detection
limit was 1 ppb.
The positive sample was taken on May 16, 2006 in the Merced River. 99.7 % of the
samples did not detect any paraquat from July 2005 to October 2006. The samples were
taken in the Summer, Spring, and Fall seasons.
3.2.4.4 Atmospheric Monitoring Data
The California Air Review Board has not conducted ambient air monitoring of paraquat.
Therefore, no atmospheric monitoring data are available.
3.3 Terrestrial Animal Exposure Assessment
T-REX (Version 1.3.1) is used to calculate dietary and dose-based EECs of paraquat 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 paraquat were considered, as discussed
below.
Instead of running all of the uses, the maximum non-agricultural use, the maximum
agricultural use, the median agricultural use, and the minimum agricultural use were run
using T-Rex in order to get an upper and lower bound for the terrestrial effects.
Maximum is defined as the use with the largest application rate, the shortest intervals,
and the most applications.
Terrestrial EECs for foliar formulations of paraquat were derived for the uses
summarized in Table 3-4. The non-agricultural and agricultural uses with the maximum
application rates, along with the agricultural use with the median application rate, and the
agricultural use with the lowest application rate were all modeled. The third and second
lowest application rates were also modeled, to determine the lowest rates in which there
were no exceedances. Given that no data on interception and subsequent dissipation from
foliar surfaces was available for paraquat, a default foliar dissipation half-life of 35 days
was used based on the work of Willis and McDowell (1987). Use specific input values,
including number of applications, application rate and application interval are provided in
Table 3-4. An example output from T-REX is available in Appendix E.
55
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Table 3-4 Input Parameters for Foliar Applications Used to Derive Terrestrial
EECs for Paraquat with T-REX
Use (Application method)
Airports (Maximum, Non-agricultural)
Guava (Maximum, Agricultural)
Ginger (Median, Agricultural)
Corn (Third lowest, Agricultural)
Carrots (Second lowest, Agricultural)
Melons (Lowest, Agricultural)
Application
rate
(Ibs ai/A)
1
1
1
0.5
1
0.3
Number of
Applications
10
10
6
o
J
1
1
Intervals Between
Applications
(Days)
5
5
30
5
1
1
T-REX is also used to calculate EECs for terrestrial insects exposed to paraquat. 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 toxicity data
for bees exposed to paraquat (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 paraquat 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.
Any RQs that exceed the LOG for listed species will be analyzed in T-HERPS. The T-
HERPS model will therefore be employed as a refinement tool to explore amphibian-
specific food intake on potential exposures to the terrestrial phase CRLF. The T-HERPS
model incorporates the same inputs as T-REX with equations adjusted for poikilotherm
food intake. An example output from T-HERPS is available in Appendix J.
Table 3-5 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Paraquat
Use
Airports
Guava
Ginger
Corn
Carrots
Melons
EECs for CRLF
(Avian, 20 g)
Dietary-based
EEC (ppm)
900
900
293
184
135
41
Dose-based EEC
(mg/kg-bw)
1025
1025
333
209
154
46
EECs for Prey
(small mammals, 15 g)
Dietary-based
EEC (ppm)
1600
1600
520
327
240
72
Dose-based EEC
(mg/kg-bw)
1530
1530
500
175
229
69
56
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Table 3-6 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via
Effects to Terrestrial Invertebrate Prey Items
Use
Airports
Guava
Ginger
Corn
Carrots
Melons
Small Insect
900
900
293
184
135
41
Large Insect
100
100
33
20
15
4.5
3.4 Terrestrial Plant Exposure Assessment
AgDRIFT (Version 2.01) is used to calculate spray drift; it was also used to estimate
terrestrial plant exposure. The spray drift analysis uses the most sensitive endpoint. See
section 5.2.5.1 for the spray drift analysis.
57
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4.0 Effects Assessment
This assessment evaluates the potential for paraquat to directly or indirectly affect the
CRLF or modify its designated critical habitat. As previously 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 effects to its habitat. In addition, potential effects to critical
habitat are 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 paraquat.
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 aquatic-phase amphibians, freshwater fish, 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 RED 1997, the EFED and FLED new use chapters 2006 as well as
ECOTOX information obtained on December 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;5
(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
5 The studies that have information on mixtures are listed in the bibliography as rejected due to the
presence of mixtures. These studies are evaluated by EFED when applicable to the assessment; however,
the data is not used quantitatively in the assessment.
58
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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, unless
quantitative relationships between modifications and reduction in species survival,
reproduction, and/or growth are 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 paraquat.
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 Appendices F and G. Both Appendix F and
G also include 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 bibliography of the available ECOTOX open literature data,
including the full suite of lethal and sublethal endpoints are presented in Appendices F
and G. A summary of the human health effects data for paraquat is found in Appendix K.
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 paraquat (Appendix H). A summary of the available
aquatic and terrestrial ecotoxicity information, use of the probit dose response
relationship, and the incident information for paraquat are provided in Sections 4.1
through 4.4, respectively.
Paraquat has registered products that contain multiple active ingredients. The results of
available toxicity data for mixtures of paraquat with other pesticides are presented in
Appendix B; however, there is no toxicity data for paraquat Multi-AI products. There is
available open literature data from ECOTOX and three studies contained information
examining toxicity effects of paraquat when mixed with other chemicals. The
bibliographic information of these studies is presented in Appendix F. According to the
available open literature data, other pesticides may combine with paraquat to produce
additive, and/or antagonistic toxic effects. Mixtures included paraquat with linuron, and
paraquat with copper sulfate.
If chemicals that show additive effects with paraquat are present in the environment in
combination with paraquat, the toxicity of paraquat may be increased, offset by other
environmental factors, or even reduced by the presence of antagonistic contaminants if
they are also present in the mixture. The variety of chemical interactions presented in the
available data set suggest that the toxic effect of paraquat, in combination with other
pesticides used in the environment, can be a function of many factors including but not
59
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necessarily limited to (1) the exposed species, (2) the co-contaminants in the mixture, (3)
the ratio of paraquat and co-contaminant concentrations, (4) differences in the pattern and
duration of exposure among contaminants, and (5) the differential effects of other
physical/chemical characteristics of the receiving waters (e.g., organic matter present in
sediment and suspended water). Quantitatively predicting the combined effects of all
these variables on mixture toxicity to any given taxa with confidence is beyond the
current abilities of ecotoxicology. However, a qualitative discussion of implications of
the available pesticide mixture effects data involving paraquat on the confidence of risk
assessment conclusions for the freshwater vascular plant (duckweed, Lemna minor vs L.
gibba), and mammals is part of the uncertainty analysis for this effects determination.
Paraquat plus copper sulfate mixture was found to exhibit both an antagonistic and
additive relationship in the vascular aquatic plant Lemna minor (E 102140). In the
presence of both paraquat and copper sulfate there was a reduction in the percent
inhibition of Fv/Fm> a measurement of the efficiency of Photosystem II (PSII), indicating
an antagonistic relationship. An additive relationship was observed in two other
parameters; 62 evolution and the fraction of inhibited centers (FIC). This study was
completed in 48h, whereas guideline studies on vascular plants range from 7-14 days,
therefore the effects observed with this mixture may potentially change over time.
The mixture of paraquat plus linuron (formulations used for potatoes) was found to not be
genotoxic, but was found to be cytotoxic to adult wistar rats (E104633). However, this
mixture (paraquat plus linuron) would not be found in California as linuron is not
registered for use on potatoes in California. The final mixture study in ECOTOX was a
field study that examined the impacts of herbicides on species found in a field that was
treated with herbicides (E147983). Other studies examine impacts to non-target
organisms off the pesticide treated field as a result of runoff or spray drift. The
treatments examined compared herbicide treatments to other cultural practices (tillage),
which showed impacts to the "native field species" from tilling alone. This paper is only
mentioned and will not be used quantitatively or qualitatively, it is simply an additional
reference that demonstrates the potential impacts of cultural practices on the reduction in
CRLF food sources. Bibliographic information is presented in Appendix F.
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.
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Table 4-1 Freshwater Aquatic Toxicity Profile for Paraquat Bichloride (expressed
as the cation)
Assessment
Endpoint
Species
Toxicity Value
Used in Risk
Assessment
Describe effect
(i.e. mortality,
growth,
reproduction)
Citation MRID
# (Author &
Date)
Study
Classification
Direct Toxicity to Aquatic-Phase CRLF
Acute
Chronic
Bluegill
sunfish
96hLC50= 13
mg/L
Mortality
40098001
(Mayer &
Ellersieck 1986)
Acceptable
Estimated - See Section 5
Indirect Toxicity to Aquatic-Phase CRLF
via Acute
Toxicity to
Freshwater
Invertebrates
(i.e. prey items)
via Chronic
Toxicity to
Freshwater
Invertebrates
(i.e. prey items)
via Acute
Toxicity to
Freshwater Fish
(i.e. prey items)
via Chronic
Toxicity to
Freshwater Fish
(i.e. prey items)
via Toxicity to
Non-vascular
Aquatic Plants
via Toxicity to
Vascular
Aquatic Plants
Daphnia
magna
48hEC50=1.2
mg/L
Mortality
00114473
(Wheeler 1978)
Acceptable
Estimated - See Section 5
Bluegill
sunfish
96hLC50=13
mg/L
Mortality
40098001
(Mayer &
Ellersieck 1986)
Acceptable
Estimated - See Section 5
Navicula
pelliculosa
(freshwater
diatom)
Lemna gibba
(Duckweed)
4dEC50 = 0.396
ug/L
14dEC50 = 71
ug/L
Growth
Growth and
Reproduction
42601006
(Smyth et al.
1992)
42601003
(Smyth et al.
1992)
Acceptable
Acceptable
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
LC50 (ppm)
<0.1
>0.1-1
>1-10
> 10 - 100
>100
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically nontoxic
61
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4.1.1 Toxicity to Freshwater Fish
No scientifically valid data are available for aquatic-phase amphibians, and therefore,
freshwater fish data were used as a surrogate to estimate direct chronic risks to the CRLF.
Freshwater fish toxicity data were also used to assess potential indirect effects of
Paraquat to the CRLF. Effects to freshwater fish resulting from exposure to Paraquat
may 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
Freshwater fish data were used as a surrogate to estimate direct acute risks to the CRLF.
Effects to freshwater fish from direct exposure to Paraquat could also indirectly affect the
CRLF from reduction in available food.
Paraquat is classified as slightly toxic to warm and cold freshwater fish on an acute
exposure basis. The most sensitive freshwater species was the bluegill sunfish, with a
96h LC50 of 13 mg/L (MRID 40098001 Mayer and Ellersieck 1986). Freshwater fish
acute toxicity values range from a 96h LC50 of 13 mg/L to 156 mg/L (both endpoints are
bluegill sunfish, MRID 40098001 Mayer and Ellersieck 1986). Other species within that
range include the rainbow trout (15, 29, and 38.68 mg/L) (MRIDs 40098001, 00162738,
and 00162736). These studies were completed using formulated products that contained
21.2% to 29% of the paraquat cation. In general, the toxicity of these formulated
products are similar in toxicity to a range of different species of freshwater fish.
4.1.1.2 Freshwater Fish: Chronic Exposure (Early Life Stage and
Reproduction) Studies
There are no available freshwater fish chronic exposure toxicity studies conducted with
Paraquat. The direct chronic toxicity values for the CRLF were calculated using an acute
to chronic ratio (ACR) using a similar chemical compound, diquat dibromide (Section
5.1.1).
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open
Literature Information
There were numerous studies found within the ECOTOX database, however they were
not integrative in the measurements of growth and reproduction. Potential sublethal
effects on fish are evaluated qualitatively and not used as part of the quantitative risk
characterization. One study did provide some information regarding different
biochemical factors influenced by exposures to paraquat (E104191). Further details on
62
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ECOTOX studies are provided in Appendix F, which also contains the rejection codes
and other information as to why studies from ECOTOX were not used.
4.1.1.4 Aquatic-phase Amphibian: Acute and Chronic Studies
Studies were found in ECOTOX that used aquatic-phase amphibians as study organisms.
However, there were some fatal flaws with all the frog studies that were reviewed and
they were therefore, not used in this risk assessment. In particular there were concerns
with the husbandry of the organisms (i.e., the amount of individuals per treatment
replicate), as well as the lack of detailed information within the published literature. Also
of concern was the presence of the solvent dimethyl sulfoxide (DMSO) as a co-solvent,
which confounds the experiment as the solvent could be resulting in increased toxicity,
and not the chemical being tested. In general there was an overall lack of information
within the studies, especially in regards to the controls and the chemical solutions that
were used within the experiments. There is also some concern with the testing methods
used, Frog Embryo Teratogenesis Assay-Xenopus (FETAX). The study conditions do
not provide the ability to deduce the chronic endpoints of the frogs, and the age of
organisms used in this type of assay results in inherent variability. There are problems
with the rearing of the frogs out past stage 54 as mortality levels are too high, resulting
from the loading rate within the containers, and the feeding on the yolk until further
development. Appendix F contains information as to why these studies and others from
ECOTOX were not used within the assessment.
4.1.2 Toxicity to Freshwater Invertebrates
Freshwater aquatic invertebrate toxicity data were used to assess potential indirect effects
of paraquat to the CRLF. Effects to freshwater invertebrates resulting from exposure to
paraquat 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
Paraquat is classified as moderately toxic to freshwater invertebrates based on acceptable
studies of the water flea (Daphnia magna). This species exhibited a 48h ECso value of
1.2 mg/L (MRID 0014473 Wheeler 1973).
4.1.2.2 Freshwater Invertebrates: Chronic Exposure (Reproduction)
Studies
There are no available freshwater invertebrate chronic exposure toxicity studies
conducted with Paraquat. The indirect chronic toxicity values for the CRLF were
63
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calculated using an acute to chronic ratio (ACR) using a similar chemical compound,
diquat dibromide (Section 5.1.1).
4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Open
Literature Data
There were numerous studies found within the ECOTOX database, however they were
not integrative in the measurements of growth and reproduction. The studies instead
provided information on the sublethal effects observed. Additionally, the studies were
not usable in this Risk Assessment. Further details on ECOTOX studies are provided in
Appendix F, which also contains the rejection codes and other information as to why
studies from ECOTOX were not used.
4.1.3 Toxicity to Aquatic Plants
Aquatic plant toxicity studies were used as one of the measures of effect to evaluate
whether paraquat 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.
Laboratory studies were used to determine whether paraquat may cause direct effects to
aquatic plants. A summary of the laboratory data and freshwater field studies for aquatic
plants is provided in Sections 4.1.3.2 and 4.1.3.2.
4.1.3.1 Aquatic Plants: Laboratory Data
Both the vascular and non-vascular aquatic plant studies that include the most sensitive
species are Tier II toxicity tests. The freshwater diatom (Naviculapelliculosd) was the
most sensitive non-vascular plant with a 4d ECso of 0.396 ug/L (MRID 42601006 Smyth
et al. 1992). The vascular plant Lemna gibba was the most sensitive vascular plant with a
14d EC50 of 71 ug/L (MRID 42601003 Smyth et al. 1992).
4.1.3.2 Freshwater Field Studies
There were no submitted field studies.
4.2 Toxicity of Paraquat to Terrestrial Organisms
Table 4-3 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.
64
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Table 4-3 Terrestrial Toxicity Profile for Paraquat Bichloride (expressed as the
cation)
Assessment
Endpoint
Species
Toxicity Value
Used in Risk
Assessment
Describe
effect (i.e.
mortality,
growth,
reproduction)
Citation
MRID#
(Author &
Date)
Study
Classification
Direct Toxicity to Terrestrial-phase CRLF
Acute Dose-
based
Acute
Dietary-based
Chronic
Colinus
virginianus
(Northern
Bobwhite)
Coturnix
coturnix
japonica
(Japanese
Quail)
Anas
platyrhynchos
(Mallard
Duck)
LD50= 128.1
mg/kg bw
5dLC50 = 703
ppm
NOAEC = 30
ppm
Mortality
Mortality
% viable eggs,
eggs set,
normality of
hatchlings and
# of 14d old
survival
00029001
(Fink et al.
1979)
00022923
(Hill et al.
1975)
00110455
(Fink et al.
1982)
Acceptable
Supplemental
Acceptable
Indirect Toxicity to Terrestrial-phase CRLF
via acute
toxicity to
mammalian
prey items
via chronic
toxicity to
mammalian
prey items
via acute
toxicity to
terrestrial
invertebrate
prey items
via acute
toxicity to
terrestrial
invertebrate
prey items
via acute
toxicity to
terrestrial
invertebrate
prey items
Rat
Wistar
Derived Rats-
Alderley Park
Strain
Apis mellifera
(Honey bee)
Colinus
virginianus
(Northern
Bobwhite)
Coturnix
coturnix
japonica
(Japanese
Quail)
LD50 = 90 mg/kg
bw(F)
NOAEL= 7.5
mg/kg-bw
NOAEC = 108
ppm
48hLD50>34.8
ug/bee
LD50= 128.1
mg/kg bw
5dLC50 = 703
ppm
Mortality
Reproductive
Toxicity- 3
generation
study
Reproduction
Mortality
Mortality
Mortality
00054573
(Rittenhouse
1977)
00126783
00149748
00149749
05001991
(Stevenson
1978)
00029001
(Fink et al.
1979)
00022923
(Hill et al.
1975)
Acceptable
Acceptable
(HED 2006)
Acceptable
Acceptable
Supplemental
65
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Assessment
Endpoint
via chronic
toxicity to
terrestrial
invertebrate
prey items
via toxicity to
terrestrial
plants
Species
Anas
platyrhynchos
(Mallard
Duck)
Seedling
Emergence
Monocots
Seedling
Emergence
Dicots
(Cocklebur)
Vegetative
Vigor
Monocots
(Corn)
Vegetative
Vigor
Dicots
(Cocklebur )
Toxicity Value
Used in Risk
Assessment
NOAEC = 30
ppm
EC25 = 0.84 Ibs
cation/A (using
most sensitive
species (dicot
data))
EC25 = 0.84 Ibs
cation/A
EC25 = 0.16 Ibs
cation/A
EC25 = 0.0141bs
cation/A
Describe
effect (i.e.
mortality,
growth,
reproduction)
% viable eggs,
eggs set,
normality of
hatchlings and
# of 14d old
survival
Growth
Growth
Growth
Growth
Citation
MRID#
(Author &
Date)
00110455
(Fink et al.
1982)
42639601
(Canning and
White 1992)
42639601
(Canning and
White 1992)
42601001
(Canning and
White 1992)
42601001
(Canning and
White 1992)
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
Acute toxicity to terrestrial animals is categorized using the classification system shown
in Table 4-4 (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 LCSO
< 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 paraquat; therefore, acute
and chronic avian toxicity data are used to assess the potential direct effects of paraquat
to terrestrial-phase CRLFs.
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4.2.1.1 Birds: Acute Exposure (Mortality) Studies
There were two acute avian oral studies that were submitted, one classified as acceptable,
and the other classified as supplemental (MRID 00029001 Fink et al. 1979, & 00160000
Hudson et al. 1984). The most sensitive species was the Northern Bobwhite quail with
an acute oral LD50 value of 128.1 mg/kg (MRID 00029001 Fink et al. 1979). The
mallard duck acute oral toxicity classification to paraquat ranges from moderately toxic
(144.8 mg/kg) to slightly toxic (436.8 mg/kg), both studies are supplemental (Fink et al.
1979). Paraquat is classified as being moderately toxic to birds on an acute oral basis.
Subacute dietary tests are required to establish toxicity of paraquat to birds. The
preferred test species are the mallard duck and the bobwhite quail. The most sensitive
subacute dietary 5d LC50 value was 703 ppm for the Japanese quail (a non-guideline test
species, indicating that the study was supplemental MRID 00022923 Hill et al. 1975).
However, the Japanese quail is believed to be an acceptable representative of avain
subacute dietary toxicity. Acceptable studies (from guideline bird species, the mallard
duck and bobwhite quail) resulted in 5d LC50 values of 711 ppm for the northern
bobwhite quail, and 2914.6 ppm for the mallard duck. Paraquat is classified as being
moderately toxic to slightly toxic to birds on a subactue dietary basis.
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies
Avian reproductive toxicity endpoints were submitted for two species, the northern
bobwhite quail (MRID 00110453 Fink et al. 1981) and the mallard duck (MRID
00110455 Fink et al. 1982). The northern bobwhite quail appeared to be the less
sensitive of the two species with an 8d NOAEC value of 100 ppm with adult mortality as
the endpoint. The mallard duck was the most sensitive species with an 18 week NOAEC
of 30 ppm, and a LOAEC value of 100 ppm (the highest concentration tested).
Concentrations of the paraquat cation for the one generation mallard duck toxicity test
were 0, 10, 30, and 100 ppm. Adverse affect endpoints were the reduction in the %
viable eggs, the number of eggs set, the number of 14d old survivors, and normality of
hatchlings (MRID 00110455 Fink et al. 1982).
4.2.1.3 Terrestrial-phase Amphibian Acute and Chronic Studies
There were no terrestrial-phase amphibian acute or chronic studies submitted or available
in the open literature.
4.2.2 Toxicity to Mammals
Mammalian toxicity data are used to assess potential indirect effects of paraquat to the
terrestrial-phase CRLF. Effects to small mammals resulting from exposure to paraquat
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).
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4.2.2.1 Mammals: Acute Exposure (Mortality) Studies
Paraquat is classified as moderately toxic on an acute oral basis to mammals. This is
based on an acute oral LD50 value of 90.98 mg/kg-bw (MRID 00054573 Rittenhouse
1977). See the HED Table from the most recent HED Human Health Risk Assessment in
Appendix K.
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies
In a 3-generation reproduction and fertility study in rats, paraquat was administered to
Wistar Derived Rats-Alderley Park Strain (MRIDs 00126783, 00149748, & 00149749).
The offspring and reproductive NOAEL were both 7.5 mg/kg-bw, and the both NOAECs
were 108 ppm (MRIDs 00149748 & 00149749). Reproductive NOAEC was used to
calculate RQ values. This study is classified as acceptable/guideline and satisfies the
guideline for a reproduction toxicity study, OPPTS 870.3800. The parental NOAEL was
0.9 mg/kg-bw, and the parental NOAEC was 18 ppm (MRID 00126783 Lindsay et al.
1982). The parental LOAEL was 2.7 mg/kg-bw, and the parental LOAEC was 54 ppm
(MRID 00126783 Lindsay et al. 1982). Parental toxicity endpoints were mortality and
lung damage (particularly increased incidences of alveolar histiocytes), indicating a
sublethal impact lower than the acute oral endpoints. HED determined that paraquat
dichloride was not a mutagen or a carcinogen (HED 2006). Paraquat was found to be
weakly positive in the mouse lymphoma assay and human lymphocyte cytogenetic assay
and was positive in the sister chromatid exchange assay (HED 2006). Paraquat was not
mutagenic in the bacterial gene mutation assay, not genotoxic in the unscheduled DNA
synthesis assay in vitro or in vivo, was negative for chromosomal aberration in the bone
marrow test, and no evidence was found for suppressed fertility or dominant lethal
mutagenicity in mice. There was also no evidence of carcinogenicity in animal studies,
and paraquat was classified as a Group E chemical (evidence of non-carcinogenicity in
humans) (Cancer Peer Review Committee and the Science Advisory Committee 1989,
HED 2006). See the HED Table from the most recent HED Human Health Risk
Assessment in Appendix K.
4.2.3 Toxicity to Terrestrial Invertebrates
Terrestrial invertebrate toxicity data are used to assess potential indirect effects of
paraquat to the terrestrial-phase CRLF. Effects to terrestrial invertebrates resulting from
exposure to paraquat could also indirectly affect the CRLF via reduction in available
food.
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies
A honeybee acute contact study (TGAI) resulted in a 48h LD50 > 34.8 ug/bee (MRID
05001991 Stevenson 1978). Paraquat is classified as practically non-toxic to honeybees.
68
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4.2.3.2 Terrestrial Invertebrates: Open Literature Studies
There were no terrestrial invertebrate studies available in the open literature.
4.2.4 Toxicity to Terrestrial Plants
Terrestrial plant toxicity data are used to evaluate the potential for paraquat 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 effects to designated critical habitat
PCEs via increased sedimentation, alteration in water quality, and reduction in 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 paraquat, 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 most sensitive results of the Tier II seedling emergence and vegetative vigor toxicity
tests on non-target plants are summarized below in Table 4-5. For seedling emergence
only one of four monocot species had scientifically sound results, and it was higher than
dicot values. Therefore, it was assumed that monocots were as sensitive as the most
sensitive dicot. An addendum DER to MRID 42601001 (Canning and White 1992) was
made as the statistics for the non-target plants vegetative vigor phytotoxicity study were
recalculated using the NUTHATCH statistical program.
69
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Table 4-5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data
Crop
Type of
Study
Species
NOAEC
(Ib cation/A)
EC25
(Ib cation/A)
Most sensitive
parameter
Seedling Emergence
Monocots
Dicots
Assumed as sensitive as dicots
Cocklebur
0.423
0.85
Dry weight
Vegetative Vigor
Monocots
Dicots
Corn
Cockelbur
0.064
EC05 = 0.0065
(95% CI 0.0040-0.01)
0.16
(95% CI 0.073-0.36)
0.014
(95% CI 0.01-0.019)
Dry weight
Dry weight
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 paraquat 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
estimate) as the slope parameter for the spreadsheet. In addition, the acute RQ is entered
as the desired threshold.
4.4 Incident Database Review
A review of the EIIS database for ecological incidents involving paraquat and paraquat
dichloride, which are used interchangeably, was completed on April 17, 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 total of 4 incidents involving paraquat (PC
code 061603) were reported, and a total of 26 incidents involving paraquat di chloride (PC
70
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code 061601) were reported. There were no incidents reported for paraquat bis (methyl
sulfate) (PC code 061602). A complete list of the incidents involving paraquat and
paraquat dichloride including associated uncertainties is included as Appendix H.
4.4.1 Terrestrial Incidents
There were no reported terrestrial incidents for paraquat (PC code 061603). There were
three reported terrestrial incidents for paraquat dichloride (PC code 061601). Two
incidents resulted in the mortality of birds, and the other reported both bird mortality and
plant damage (1008168-001,1000097-015, and 1007334-001). Two of the incidents
occurred in Virginia one was a formulation with a registered use on corn that resulted in
the mortality of 5 Canadian geese where paraquat dichloride was the probable cause of
the incident in June 1998 (1008168-001). The other incident was from the consumption
of granules resulting in the death of approximately 12 birds. However, paraquat
dichloride was unlikely the cause of the incident on May 1989 (1000097-015), as there
are no granular forms of paraquat. Paraquat was reported since it was applied within the
area of the observed incident. The other incident occurred in Illinois resulting in plant
damage on 18 of 103 acres of corn, and the death of 4 unknown species of birds in June
1998 from drift/spray exposure (1007334-001), the legal classification was that paraquat
was of probable cause for the incident.
4.4.2 Plant Incidents
There were a total of four plant incidents listed for paraquat (PC code 061603). Plant
damage was sustained to three non-target species; radishes, apples, and ornamentals
(1014409-001,1013884-038, and 1013884-014), while plant mortality was reported for
alfalfa (1014409-024). All incidents reported were from Washington, one from a
registered use on peas where ornamentals were affected, and paraquat was the probable
cause of plant damage; one from a misuse (alfalfa) where paraquat was a possible cause
of mortality; and the other two the use was of undetermined legality, and paraquat was a
possible cause of plant damage. All exposures occurred from drift, with apples also
being exposed from direct spray. The total magnitude of exposure was not reported.
There were a total of 17 plant incidents listed for paraquat dichloride (PC code 061601).
Two accidental misuse incidents occurred in an agricultural area in Wisconsin resulting
in plant damage to alfalfa, ash, and ornamentals (1005660-005), and ash, oats and
discoloration to alfalfa (1005880-005) from drift exposure. Paraquat was the probable
cause of these incidents. Three accidental misuse incidents on corn resulted in plant
damage to grass (1007371-033,1007371-034, and 1007371-035) on June 17, 1997, and
paraquat was the propable cause of these incidents. 120 acres of a corn field was
damaged after undetermined legality of broadcast application occurred May 9, 2000, and
paraquat was a possible cause of this incident (1012366-023). Plant damage to 181 acres
of peppermint occurred after registered use May 1, 1996, and paraquat was a possible
cause of this incident (1013636-029). Undetermined legality use of paraquat dichloride
application was the possible cause of 150 (75% of 200) acres of corn damaged on May
11, 1999 in Alabama (1009573-009). After the registered use application of paraquat
71
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dichloride 10 acres of peanuts were damaged June 19, 2001 in North Carolina, and
paraquat was a possible cause of this incident (1011838-055). Carryover from the
broadcast application of paraquat di chloride was the probable cause of damage to 1040
acres of corn May 24, 2002 in Illinois (1013554-040). The registered use application of
paraquat di chloride was a possible cause of the damage to 60 acres of pasture grass April
23, 2003 in Georgia (1014034-009). The registered application of paraquat dichloride on
peanuts was a possible cause of plant damage to 5 acres of peanuts in Virginia May 23,
2001 (1012684-010). Undetermined legality use of paraquat dichloride on peanuts was a
possible cause of plant damage to 80 acres of peanuts in Oklahoma (1011838-091) and all
25 acres in Georgia (1011838-038). Registered use of broadcast application of paraquat
dichloride to soybeans was a possible cause of plant damage to an unknown tree as a
result of drift June 27, 1994 in Arkansas (1001131-001). It is highly probable that the
accidental misuse of paraquat dichloride on soybeans resulted in plant damage to
unknown amounts of soybeans as the result of drift May 20, 1997 in Pennsylvania
(1007371-008). Intentional misuse of paraquat dichloride by spray application on wheat
was the probable cause of plant damage to 120 of 184 acres from drift January 26, 2005
in California (1016940-005).
4.4.3 Aquatic Incidents
There were no reported aquatic incidents listed for paraquat (PC code 061603). There
were six reported aquatic incidents listed for paraquat dichloride (PC code 061601).
Undetermined legality use of paraquat dichloride on an agricultural area was a possible
cause of the mortality of 54 fish (1 largemouth bass, and 53 sunfish) due to runoff June 4,
1981 in Virginia (BOOOO-502-18). Registered usage of paraquat dichloride application on
an agricultural area in North Carolina was unlikely the cause of the mortality to unknown
amount of unknown fish November 29, 1993 (1003654-012). Registered use of paraquat
dichloride on corn was unlikely the cause of the mortality of numerous unknown fish
from runoff in Kentucky April 1, 1992 (B000175-001). The application of paraquat
dichloride on a field was a possible cause of the mortality offish (bass, bluegill, and
crappie) in Indiana June 2, 1997 (1009314-005). An undetermined legality application of
paraquat dichloride was a possible cause of the mortality of an unknown amount of bass,
bluegill, and crappie to die in Indiana January 1, 1997 (1005805-001). Paraquat
dichloride was was a possible cause of the 200 bass and bluegills that were found dead
after an undetermined legality application of paraquat dichloride June 3, 1999 (1008768-
007).
72
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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 effects to its designated critical habitat from the use of paraquat in CA.
The risk characterization provides an estimation (Section 5.1) and a description (Section
5.2) of the likelihood of adverse effects; articulates risk assessment assumptions,
limitations, and uncertainties; and synthesizes an overall conclusion regarding the
likelihood of adverse effects to the 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 in its terrestrial environment and mammals, the
LOG is 0.1. The LOG for chronic exposures to CRLF and its prey, as well as acute
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 paraquat 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 paraquat (Table 3-5 and Table 3-6) and the appropriate toxicity endpoint
from Table 4-3. Exposures are also derived for terrestrial plants, as discussed in Section
3.4 and toxicity summarized in Section 4.2.4, based on the highest application rates of
paraquat use within the action area.
Due to Paraquat being a cation, the risk estimated may be more conservative for soils
with higher clay contents due to paraquat's ability to dissipate by rapid adsorption to
biological materials and clay particles. The bound residues do not appear to be
environmentally available because they are so strongly adsorbed. Paraquat is also very
immobile in soil with adsorption Kds ranging from 68-50,000. Paraquat has such
extremely high adsorption coefficients, it is not expected to desorb from the soil.
5.1.1 Exposures in the Aquatic Habitat
5.1.1.1 Direct Effects to Aquatic-Phase CRLF
Direct acute 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. However, since freshwater fish chronic toxicity values are not
73
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available at this time, the direct chronic toxicity values for the CRLF were calculated
using an acute to chronic ratio. The acute to chronic ratio (ACR) was completed using a
similar chemical compound, diquat dibromide. However, the ACR could not be
calculated for freshwater fish (direct effects to the CRLF) using the same method as the
indirect effects, as the species offish were different in the diquat acute and chronic
studies for the direct effects. There is greater uncertainty when using two different
species offish, in addition to the general uncertainty related with comparing toxicity of
two different compounds. The ACR for invertebrates was completed and the estimated
indirect chronic toxicity of paraquat to the CRLF was approximately 0.174 ppm (174
ppb). For qualitative purposes, although it is not general practice, the chronic direct
effect was calculated using the calculated chronic ratio from the invertebrates divided by
the acute LC50 value from the freshwater fish. Because these species are different, it
increases the uncertainty, but can provide valuable information in helping to discuss the
possible toxicity to the aquatic phase CRLF directly. The ACR for freshwater fish and
the estimated direct chronic toxicity of paraquat to the CRLF was found to be
approximately 1.89 ppm (1890 ppb). As seen in Table 5-1, none of the EECs exceed 1,
890 ppb. As a result, it appears that paraquat is determined to have no direct effect on
the aquatic-phase of the CRLF on a chronic basis.
Based on the data presented in Table 5-1, it appears that paraquat has no acute direct
affects on the aquatic-phase CRLF since there are no LOC exceedences.
Table 5-1 Summary of Acute Direct Effect RQs* for the Aquatic-phase CRLF
Use
AGRICULTURAL FALLOW/IDLELAND
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDU
STRIAL PREMISES/EQUIPMENT
(OUTDOOR), NONAGRICULTURAL
AREAS (PUBLIC HEALTH USE),
NONAGRICULTURAL RIGHTS-OF-
WAY/FENCEROWS/HEDGEROWS
GUAVA, PASSION FRUIT
(GRANADILLA)
MELONS, PEANUTS (ground only)
EEC
(Jig/L)b
33
27
55
55
2.0
1.6
RQ
0.003
0.002
0.004
0.004
O.001
O.001
Probability of
Individual
Effect at
RQC
No exceedance
No exceedance
No exceedance
No exceedance
No exceedance
No exceedance
LOC
Exceedance
and Risk
Interpretation
NO
NO
NO
NO
NO
NO
a RQs associated with acute 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. No chronic data is available.
b The highest EEC based on maximum application rate per use (see Table 3-3).
0 A probit slope value for the acute bluegill sunfish 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). (Only calculated when there was an exceedance).
RQ < acute endangered species LOC of 0.05.
A The most sensitive species used to determine the acute direct effects (surrogate species) was the bluegill
Sunfish (96h LC50 = 13000 ppb).
74
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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 paraquat 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. RQ's exceed the modeled
EECs (Table 5-2); therefore, paraquat may affect the aquatic-phase CRLF
indirectly via effects to non-vascular aquatic plants.
Table 5-2 Summary of RQs* Used to Estimate Indirect Effects to the CRLF via
Effects to Non-Vascular Aquatic Plants (diet of CRLF in tadpole life stage and
habitat of aquatic-phase CRLF)
Use
AGRICULTURAL FALLOW/IDLELAND
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS
(PUBLIC HEALTH USE), NONAGRICULTURAL RIGHTS-OF-
WAY/FENCEROWS/HEDGEROWS
GUAVA, PASSION FRUIT (GRANADILLA)
MELONS, PEANUTS (ground only)
Peak
EEC
(HS/L)
33
27
55
55
2.0
1.6
Indirect effects RQa
(food and habitat)
82
69
138
138
4.9
4.1
a RQs used to estimate indirect effects to the CRLF via toxicity to vascular aquatic plants are summarized in Table 5-4
* LOG exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC/ most sensitive non- vascular
aquatic plant endpoint (Acute: Navicula pelliculosa EC50= 0.396 ppb).
b) Aquatic Invertebrates
As mention in Section 5.1.1.1, in the absence of chronic data, the acute to chronic ratio
(ACR) between diquat and paraquat was calculated. The ACR for invertebrates and the
estimated indirect chronic toxicity of paraquat to the CRLF was found to be
approximately 174 ppb (0.174 ppm). As seen in Table 5-3, RQs do not exceed the LOC
and therefore, paraquat has no indirect effects on the CRLF via reduction in
freshwater invertebrate prey items on a chornic basis.
A summary of the acute RQ values for exposure to aquatic invertebrates (as prey items of
aquatic-phase CRLFs) is provided in Table 5-3. As described above for Table 5-1, probit
slope analysis was not performed because there were no exceedances for any use. Based
on the data presented in Table 5-3 paraquat has no indirect effect on the CRLF via
reduction in freshwater invertebrate prey items on an acute basis.
75
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Table 5-3 Summary of Acute RQs* 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)
Use
AGRICULTURAL FALLOW/IDLELAND
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC HEALTH
USE), NONAGRICULTURAL RIGHTS-OF-
WAY/FENCEROWS/HEDGEROWS
GUAVA, PASSION FRUIT (GRANADILLA)
MELONS, PEANUTS (ground only)
Peak EEC
(Hg/L)
33
27
55
55
2.0
1.6
Indirect
Effects
Acute
RQ*
0.025
0.021
0.042
0.042
0.002
0.001
Probability of
Individual Effect at
RQa
No exceedance
No exceedance
No exceedance
No exceedance
No exceedance
No exceedance
* = LOG exceedances (acute RQ > 0.05) are bolded and shaded. Acute RQ = use-specific peak EEC / acute freshwater
invertebrate endpoint (Daphnia magna EC50 =1200 ppb). No chronic data is available.
a 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).
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. However, since freshwater fish chronic toxicity values are not
available at this time, the indirect chronic toxicity values for the CRLF were estimated
using the ACR of freshwater invertebrates exposed to diquat. Based on Table 5-1 it can
be concluded that paraquat will have no indirect effects on the aquatic-phase of the
CRLF on an acute or chronic basis from fish or other aquatic-phase frogs as prey
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 the data
presented in Tables 5-2 and 5-4, paraquat may affect the CRLF via reduction in non-
vascular plants, but will have no indirect effect via reduction in vascular plants.
76
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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
Use
AGRICULTURAL FALLOW/IDLELAND
AIRPORTS/LANDING FIELDS, COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE), NONAGRICULTURAL RIGHTS-OF-
WAY/FENCEROWS/HEDGEROWS
GUAVA, PASSION FRUIT (GRANADILLA)
MELONS, PEANUTS (ground only)
Peak EEC
(Hg/L)
33
27
55
55
2.0
1.6
Indirect effects
RQa
(food and
habitat)
0.46
0.38
0.77
0.77
0.03
0.02
a RQs used to estimate indirect effects to the CRLF via toxicity to non- vascular aquatic plants are summarized in Table 5-2
* = LOG exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC / vascular aquatic plant endpoint (Lemna
gibba EC50= 71 ppb).
5.1.2 Exposures in the Terrestrial Habitat
5.1.2.1 Direct Effects to Terrestrial-phase CRLF
As previously discussed in Section 3.3, potential direct effects to terrestrial-phase CRLFs
are based on broadcast foliar (ground and aerial) application of paraquat. Potential direct
acute effects of paraquat 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. Acute effects are estimated using the lowest available toxicity data for birds.
EECs are divided by toxicity values to estimate acute dietary-based RQs (Table 5-5).
The Japanese quail was the most sensitive to paraquat on a subacute dietary basis (LCso =
703ppm), and the Northern bobwhite quail was the most sensitive on an acute dietary
basis (LD50 = 128.1 mg/kg-bw) were therefore selected to serve as a surrogate for the
CRLF. Resulting acute dietary and dose-based RQs for all but one use (melons with the
lowest application rate) of paraquat exceed the Agency's acute endangered species LOG
of 0.1 for the CRLF (Table 5-5). The probability of individual effect at the endangered
species LOC (0.1) ranges from 1 in 1.46 with a 95% CI of 1 in 1.71 to 1 in 1.20 (for
airports) to 1 in 1.71*103 with a 95% CI of 1 in 1.34*101 to 1 in 2.35* 1010 (for carrots).
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).
Potential direct chronic effects of paraquat to the terrestrial-phase CRLF are derived by
considering dietary-based exposures modeled in T-REX for a small bird (20g) consuming
small invertebrates (Table 3-5). Chronic effects are estimated using the lowest available
toxicity data for birds. EECs are divided by toxicity values to estimate chronic dietary-
based RQs (Table 5-6). Chronic reproductive effects for the Mallard duck were observed
77
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with a NOAEC of 30 ppm. The chronic dietary-based RQs for the terrestrial phase CRLF
exceed the Agency's chronic LOG of 1.0 for all uses of paraquat (Table 5-6). The
probability of individual effect probit slope analysis is not applicable for chronic
endpoints Based on the potential for both acute and chronic effects (Tables 5-5 and
5-6) paraquat 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 (foliar application) From T-REX
Use
Application Rate (Ib cation/acre)
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC HEALTH USE)
(1 Ib cation/acre; 10 times/yr; 5 day intervals) (maximum-
non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5 day intervals)
(maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30 day intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3 times/year; 5 day
intervals)
BEANS - SUCCULENT (LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER
(1 Ib cation/acre; 1 time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1 day intervals)
(minimum-ag)
Dietary-based
Acute RQ1
1.28
1.28
0.42
0.26
0.19
0.06
Probability of
Individual Effect at
RQa
1 in 1.46
(1 in 1.71 to 1 in 1.20)a
1 in 1.46
(1 in 1.71 to 1 in 1.20)a
lin2.22E+01
(lin4.43E+01to 1 in
2.87E+03)a
lin2.36E+02
(1 in 8.27 to 1 in 1.43
E+07)a
1 in 1.71 E+03
(1 in 1.34E+01 to 1 in
2.35E+10)a
No exceedance
* = LOG exceedances (Acute RQ > 0. 1) are bolded and shaded.
1 Based on Japanese quail LC50 = 703 ppm.
a A probit slope value for the acute avian 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).
Table 5-6 Summary of Chronic RQs* Used to Estimate Direct Effects to the
Terrestrial-phase CRLF (foliar application) From T-REX
Use
(Application Rate)
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC HEALTH
USE) (1 Ib cation/acre; 10 times/yr; 5 day intervals)
(maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5 day intervals)
(maximum- ag)
Dietary-based Chronic RQ1
30.00
30.00
78
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Use
(Application Rate)
Ginger (1 Ib cation/acre; 6 times/yr; 30 day intervals
(ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3 times/year; 5 day
intervals)
BEANS - SUCCULENT (LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS (UNSPECIFIED),
PEPPER (1 Ib cation/acre; 1 time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1 day intervals)
(minimum-ag)
Dietary-based Chronic
RQ1
9.76
6.13
4.50
1.35
* = LOG exceedances (Chronic RQ > 1 ) are bolded and shaded.
1 Based on Mallard duck NOAEC = 30 ppm.
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in
Prey (terrestrial invertebrates, mammals, and frogs)
a) Terrestrial Invertebrates
In order to assess the risks of paraquat 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 > 34.6|ig cation/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 > 270.3 jig cation/g of bee, to calculate RQs. Indirect effects
cannot be precluded from available data because the LD50 exceeds the levels tested even
though pesticide related mortality was observed Therefore, it is determined that
paraquat may indirectly affect the CRLF via reduction in terrestrial invertebrate
prey items.
b) 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 (LD50 = 90.98 mg/kg-bw). EECs are divided by
the toxicity value to estimate acute and chronic dose-based RQs as well as chronic
dietary-based RQs (Table 5-7). RQs representing acute and chronic exposures of small
mammals consuming short grass on the treated field contaminated with paraquat exceed
endangered species LOG of 0.1 (acute) and 1 (chronic) for all uses except melons (Table
5-7). Melons chronic dietary based RQ does not exceed the endangered species LOG of
0.1. The probability of individual effect at the endangered species LOG (0.1) is 1 in
2.94*105 (95%CI: 1 in 4.40*101 to 8.86*1018). 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).
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The probability of individual effect probit slope analysis is not applicable for chronic
endpoints. HED determined that paraquat dichloride was not a mutagen or a carcinogen
(HED 2006). Paraquat was found to be weakly positive in the mouse lymphoma assay
and human lymphocyte cytogenetic assay and was positive in the sister chromatid
exchange assay (HED 2006). Paraquat was not mutagenic in the bacterial gene mutation
assay, not genotoxic in the unscheduled DNA synthesis assay in vitro or in vivo, was
negative for chromosomal aberration in the bone marrow test, and not evidence was
found for suppressed fertility or dominant lethal mutagenicity in mice. There was also no
evidence of carcinogenicity in animal studies, and paraquat was classified as a Group E
chemical (evidence of non-carcinogenicity in humans) (Cancer Peer Review Committee
and the Science Advisory Committee 1989, HED 2006). Based on the acute and
chronic LOC exceedances of paraquat on small mammal prey (Table 5-7), paraquat
may indirectly affect the CRLF via reduction in small mammal prey items.
Table 5-7 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 (foliar application)
Use
(Application Rate)
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDU
STRIAL PREMISES/EQUIPMENT
(OUTDOOR), NONAGRICULTURAL
AREAS (PUBLIC HEALTH USE) (1 Ib
cation/acre; 10 times/yr; 5 day intervals)
(maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30
day intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3
times/year; 5 day intervals)
BEANS - SUCCULENT (LIMA/SNAP),
CARROT (INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib
cation/acre; 1 time/yr; 1 day intervals)
Chronic RQ
Dose-based
Chronic RQ1
128.53
128.53
41.82
26.28
19.28
Dietary-based
Chronic RQ2
14.81
14.81
4.82
3.03
2.22
Acute RQ
Dose-based
Acute RQ3
7.63
7.63
2.48
1.56
1.14
Probability of
% Effect at
Acute RQa
100%
1 in 1 (1 in
1 04 to 1 in l)a
100%
1 in 1 (1 in
1.04tolinl)a
96%
1 in 1.04 ( 1 in
1.27tolinl)a
81%
1 in 1.24 (1 in
1.54 to lin
1.04)a
60%
1 in 1.66 (1 in
1 83 to 1 in
1.44)a
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Melons (0.3 Ib cation/acre; 1 time/yr; 1 day
intervals) (minimum-ag)
5.78
0.67
0.34
1.75%
1 in 57.1 (lin
5.73 to 1 in
8.07E+04) a
* = LOG exceedances (acute RQ > 0.1 and chronic RQ > 1) are bolded and shaded.
1 Based on dose-based EEC and paraquat rat NOAEL = 5.4 mg/kg-bw.
Based on dietary-based EEC and paraquat rat NOAEC = 108 mg/kg-diet.
3 Based on dose-based EEC and paraquat rat acute oral LD50 = 90.98 mg/kg-bw.
a A probit slope value for the acute avian 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).
c) 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 table (Table 5-5 and 5-6) for results. The acute LOG is exceeded
for all uses of paraquat except Melons, and the chronic LOG is exceeded for all uses of
paraquat. Based on the acute and chronic LOC exceedances, paraquat 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 the most sensitive terrestrial plant data, in this case
vegetative vigor EC25 data, as a screen. The vegetative vigor endpoint is EC25 = 0.014 Ib
cation/acre. To determine the reduction in terrestrial plants, a spray drift analysis using
AgDRIFT was performed. Please see Section 5.2.5.1 for an explanation of the effects of
spray drift.
Paraquat may indirectly affect the CRLF via reduction in terrestrial plants from
both aerial and ground application for vegetation that is located between the site of
application to the border of where plant exposure is expected. The distance of effect
is expected to be 1,000 feet or possibly greater.
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:
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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, paraquat is likely to affect aquatic-
phase PCEs of designated habitat related to effects on aquatic and terrestrial plants.
Reduction of aquatic based food sources may occur from most use sites.
Because reduction of aquatic based food sources may occur from most use sites, paraquat
may be likely to indirectly affect the CRLF. Likewise, due to paraquat's ability to reduce
aquatic non-vascular plants used as food source and habitat for CRLF, paraquat may be
likely to indirectly affect the CRLF. Since there are LOG exceedances on non-target
terrestrial dicot plants from spray drift at the minimum application rate, paraquat may
indirectly affect the CRLF via reduction in terrestrial plants from aerial application as
well. As a result, due to aquatic vascular and terrestrial plant communities being reduced
from most use sites, there is potential for alteration of channel/pond morphology or
geometry and/or increase in sediment deposition within the stream channel or pond and
for 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.
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 paraquat on this PCE (i.e., alteration of food sources), acute and chronic
freshwater fish and invertebrate toxicity endpoints, as well 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 acute LOC exceedances for aquatic plants,
paraquat may result in effects to aquatic-phase PCEs.
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
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• 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. These results will inform the
effects determination for effects to designated critical habitat for the CRLF. There were
no LOG exceedances for non-target monocot plants (inhabiting upland dry, semi-dry
areas) or resulting from spray drift. Although there were no LOG exceedances for non-
target dicot plants inhabititing upland dry and semi-dry area RQ's, there was an
exceedance for spray drift. The buffer determined from AgDRIFT (Section 5.2.5.1)
yielded a buffer of at least 1,000 feet. Therefore, any plants with in a 1,000 foot radious
from the application site may potentially be affected. Based on the results paraquat
may affect the first and second terrestrial-phase PCEs.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of paraquat 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 5.1.2.2.
Based on acute and chronic LOC exceedances for CRLF prey items of small
mammals, terrestrial invertebrates and other frogs, paraquat may result in effects
to the third terrestrial-phase PCE.
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. Direct acute and chronic RQs for terrestrial-phase CRLFs are presented in
Section 5212 Due to acute and chronic LOC exceedances at all but one use sites
(acute only) to terrestrial-phase CRLFs, paraquat may result in effects to the fourth
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.
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A summary of the risk estimation results are provided in Table 5-8 for direct and indirect
effects to the CRLF and in Table 5-9 for the PCEs of designated critical habitat for the
CRLF.
Table 5-8 Risk Estimation Summary for Paraquat - 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
No
The aquatic phase amphibian acute LOCs for listed species
(0.05) are not exceeded for any uses of paraquat in California.
The RQs range from 0.004 for airports, commercial/industrial
areas, and public health areas to < 0.001 for melons.
When comparing chronic direct effects, the estimated chronic
value at 1.89 ppm is not exceeded for any use.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects to
food supply (i.e., freshwater
invertebrates, non-vascular plants)
Yes
LOCs for aquatic invertebrates are not exceeded for any uses.
The acute RQs range from 0.042 for airports,
commercial/industrial areas, and public health areas to < 0.01 for
melons.
When comparing chronic indirect effects, the estimated chronic
value at 0.174 ppm is not exceeded for any use.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
habitat, cover, and/or primary
productivity (i.e., aquatic plant
community)
Yes
RQs for vascular aquatic plants do not exceed the Agency's
LOC (1.0) for any uses. These range from 0.77 (airports,
commercial/industrial areas, public health areas) to 0.02
(melons).
LOCs for non-vascular plants are exceeded for all uses. The
RQs range from 138 (airports, commercial/industrial areas, and
public health areas) to 4.1 (melons).
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.
Yes
RQs for non-target terrestrial monocot and dicot plants
inhabitating semi-aquatic and upland dry areas do not exceed
the Agency's LOC for any uses except for dicot plants exposed
to agricultural follow/ideland, and melon applications for spray
drift. Spray drift RQs for these applications range from 3.57 to
1.07 respectively.
Terrestrial Phase
(Juveniles and adults)
Direct Effects
Survival, growth, and reproduction
of CRLF individuals via direct
effects on terrestrial phase adults and
juveniles
yes
Refined acute dietary-based RQs for CRLFs consuming small
insects exceed the acute listed species LOC (0.1) for all uses of
paraquat except melons, RQs ranged from 1.28 (Airport/public
health use/guava) to 0.06 (melons). The Refined acute dietary-
based RQs for CRLFs consuming large insects and 15g small
insectivore mammals resulted in paraquat use on airports/public
health use/guava exceeding the listed species LOC (0.1), with
an RQ of 0.14 for both. The refined acute dietary-based RQs
for CRLFs consuming small herbivore mammals (15g) resulted
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Assessment Endpoint
LOC
Exceedances
(Y/N)
Description of Results of Risk Estimation
in all uses exceeding the listed species LOC, RQs ranged from
2.17 (Airport/public health use/guava) to 0.10 (melons) and for
35g small mammals all uses except melons exceed the listed
species LOC, RQs ranged from 1.50 (Airport/public health
use/guava) to 0.77 (melons). There are no exceedances for
CRLFs consuming small terrestrial-phase amphibians.
Refined dose-based RQs for CRLF of varying weights (1.4g,
37g and 238g) consuming small insects exceed the acute
endangered species LOC (0.1) for only the Airport/public
health and Guava uses of paraquat for all weights of CRLF).
There are no exceedances for small sized (1.4g) CRLF
consuming large insects and CRLF this size are too small to
consume small mammals or small terrestrial-phase amphibians.
The RQs for small sized (1.4g) CRLF are 0.27 suggesting that
small CRLF consuming small insects are potentially affected by
acute exposures to paraquat.
Refined dose-based RQs for medium sized (37g) CRLF
consuming small herbivore mammals (either 15g or 35g)
exceed the acute listed species LOC (0.1) for all uses of
paraquat. There were also exceedances in the acute listed
species LOC (0.1) for medium sized CRLF consuming small
insectivore (15g) mammals for the airports/public health,
guava, and ginger uses of paraquat. For medium sized CRLF
consuming small insectivore (35g) mammals there were
exceedances in the acute listed species LOC (0.1) for all uses of
paraquat except carrots and melons. There are no exceedances
for medium sized (37g) CRLF consuming large insects or small
terrestrial-phase amphibians. Due to exceedances of LOCs for
CRLF consuming small herbivore mammals (either 15g or 35g)
for all paraquat uses, and exceedances of LOCs for CRLF
consuming small insectivore mammals (either 15g or 35g) for a
majority of paraquat uses indicate that the medium sized CRLF
could potentially be affected by acute exposures to paraquat.
Refined dose-based RQs for large sized (238g) CRLF
consuming small herbivore mammals (either 15g or 35g)
exceed the acute listed species LOC (0.1) for all uses of
paraquat except melons. There were no exceedances for large
sized (23 8g) CRLF consuming large insects, small insectivore
mammals (15g or 35g), or small terrestrial-phase amphibians.
The exceedances of LOCs for CRLF consuming small
herbivore mammals (either 15g or 35g) for all paraquat uses
except melons, indicates that the large sized CRLF could
potentially be affected by acute exposures to paraquat.
Refined chronic dietary-based RQs for CRLFs consuming small
insects and small herbivore mammals (eitherl5g or 35g) using
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Assessment Endpoint
LOC
Exceedances
(Y/N)
Description of Results of Risk Estimation
T-HERPS model exceed the chronic species LOC (1.0) for all
uses of paraquat. Refined chronic dietary-based RQs for
CRLFs consuming large insects and small insectivore mammals
(either 15g or 35g) using T-HERPS model exceed the chronic
species LOC (1.0) for Airport/public health, guava, and ginger
uses of paraquat. The refined chronic dietary-based RQs for
CRLFs consuming small terrestrial- phase amphibians using T-
HERPS model exceed the chronic species LOC (1.0) for
Airport/public health and guava uses of paraquat (the maximum
uses).
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
prey (i.e., terrestrial invertebrates,
small terrestrial mammals and
terrestrial phase amphibians)
yes
The acute-dose based RQs for small mammals exceed the
endangered species LOC for all uses except Melons, and ranged
from 7.63 (Airports/public health use, maximum application
rate) to 0.34 (Melons). These results are summarized in Table
5-7.
The chronic dietary-based RQs for small mammals exceed the
endangered species LOC for all uses except Melons, and ranged
from 14.81 (Airports/public health use, maximum application
rate) to 0.67 (Melons). The chronic dose-based RQs for small
mammals exceed the endangered species LOC for all uses, and
ranged from 128.53 (Airports/public health use) to 5.78
(Melons). These results are summarized in Table 5-7.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
habitat (i.e., riparian vegetation)
yes
The RQs for non-target terrestrial monocot and dicot plants
inhabiting semi-aquatic and upland dry areas do not exceed the
Agency's LOC (1.0) for all uses. All aerial applications of
paraquat results in spray drift exceedances for dicots (only).
These exceedances range from 3.57 (Agricultural
fallow/ideland maximum aerial application rate) to 1.07
(Melons, minimum aerial application rate).
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Table 5-9 Risk Estimation Summary for Paraquat - 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.
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)
Yes
Yes
Yes
Yes
LOCs are exceeded for terrestrial riparian plants
and for aquatic non-vascular plants from exposure
to paraquat from spray drift.
LOCs are exceeded for terrestrial riparian plants
and for aquatic plants from exposure to paraquat
from spray drift. Alteration of riparian and non-
vascular plants may result in alteration of
temperature, turbidity, and oxygen content.
LOG is exceeded for indirect effects on terrestrial
phase CRLF from most paraquat applications.
LOCs for non-vascular plants are exceeded for all
uses.
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
feet 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
yes
yes
The AgDRIFT model was used to evaluate
potential distances beyond which exposures would
be expected to be below the LOG. The Tier I
ground application output for the maximum
application rate of paraquat indicated a buffer zone
of >1,000 feet for non-listed plants to be below the
LOG. For the minimum application rate, the output
indicated a buffer zone of of > 1,000 feet for non-
listed species.
Both the Tier I and Tier II aerial application output
for the maximum and minimum application rates of
paraquat indicated that the buffer zone required
would be greater than 1,000 feet for non-listed
plants. Since the model is restricted to accurately
discerning a buffer within 1,000 feet of the
application, the exact distance needed for a buffer
to protect listed and non-listed plants is unknown.
Effects are expected to non-target plants over 1,000
feet from the use site from aerial application of
paraquat at the maximum application use rate.
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Assessment Endpoint
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.
Habitat Effects
(Y/N)
yes
yes
Description of Results of Risk Estimation
Acute RQs for small mammals and birds exceed the
endangered species LOG for all uses of paraquat
except Melons.
Chronic dietary RQs for birds exceed the endangered
species LOG for all uses of paraquat. For small
mammals the chronic dietary -based RQs exceed the
endangered species LOG for all uses of paraquat
except Melons. The chronic dose-based RQs for
small mammals exceed the endangered species LOG
for all uses of paraquat.
All aerial applications of paraquat results in spray
drift exceedances for non-target terrestrial plants
inhabiting semi-aquatic and upland dry areas.
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.
The criteria used to make determinations that the effects of an action are "not likely to
adversely affect" the CRLF include the following:
• Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where "take"
occurs for even a single individual. "Take" in this context means to harass or
harm, defined as the following:
• Harm includes significant habitat modification or degradation that
results in death or injury to listed species by significantly impairing
behavioral patterns such as breeding, feeding, or sheltering.
• Harass is defined as actions that create the likelihood of injury to listed
species to such an extent as to significantly disrupt normal behavior
patterns which include, but are not limited to, breeding, feeding, or
sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are
extremely unlikely to occur.
• 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 is provided in Sections 5.2.1 through 5.2.3.
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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 spray drift
containing paraquat.
Paraquat is considered "moderately toxic" to the freshwater fish, which are surrogates for
the aquatic phase CRLF. The aquatic animal acute LOCs for listed species (0.05) was
not exceeded for any of the uses. The RQ's ranged from 0.004 for airports to <0.001 for
melons.
As discussed in Section 5.1.1.1, the acute to chronic ratio (ACR) was used to estimate
chronic exposure to aquatic animals. With this method, the chronic exposure values are
estimated to be at levels far less than 0.05 LOG for listed species. It is important to note
that since there isn't any actual data from paraquat to determine the actual chronic
exposure to aquatic animals, the estimated chronic exposure determined using the ACR
contains uncertainty.
Of the aquatic animal incidents that were reported for paraquat, and in all of the reported
incidents the certainty of paraquat being responsible was either unlikely or possible.
Three were from registered uses of paraquat, and three were from the undetermined
legality use of paraquat dichloride. Two of the incidents related to the registered use of
paraquat di chloride believed that paraquat di chloride was the unlikely cause of mortality
seen; the total mortality of the unknown fish was also unknown in 1993 and 1992
(1003654-012 and B000175-001 respectively). The other incident related to the
registered use of paraquat was possibly responsible for the deaths of unknown amounts of
bass, bluegill sunfish, and crappie in 1997 (1009314-005). The other three paraquat
incidents were the possible result of undertermined legality usage of paraquat. A total of
54 dead fish (1 largemouth bass, and 53 sunfish) were observed in 1981 (BOOOO-502-18),
an unknown amount of dead bass, bluegill, and crappie were observed in 1997 (1005805-
001), and a total of 400 dead fish (200 each of bass and bluegill) were observed in 1999
(1008768-007).
Because there are no LOC exceedances from registered uses of paraquat to the
CRLF surrogate species (freshwater fish), because monitored concentrations in
surface water are far below modeled estimates, and because the non-target incidents
resulting from paraquat use are judged to be unlikely to possible, the Agency
concludes that paraquat will have no direct effects on aquatic-phase CRLF.
5.2.1.2 Terrestrial-Phase CRLF
The RQs representing acute dietary-based exposures exceed the Agency's LOC (0.1) for
all uses of paraquat except melon (Section 5.1.2.1.). The RQs ranged from 1.28
89
-------
(Airport/public health use) to 0.06 (Melons) (Table 5-5). The chronic dietary-based RQs
all exceed the Agency's LOG (1.0) for all uses of paraquat (Section 5.1.2.1.). The RQs
ranged from 30.0 (Airports/public health use) to 1.35 (Melons) (Table 5-6). These RQs
were derived using the T-REX model, which estimates exposures that are specific to food
intake equations for birds. RQs generated for birds are used as surrogates to represent
RQs for the terrestrial-phase CRLF. Based on these exceedances to the terrestrial-phase
CRLF, a "May Affect" determination was made.
The T-HERPS model was therefore employed as a refinement tool to explore amphibian-
specific food intake on potential exposures to the terrestrial phase CRLF. The T-HERPS
model incorporates the same inputs as T-REX with equations adjusted for poikilotherm
food intake. The dietary-based and dose-based EECs generated by T-HERPS are found
in Tables 5-10a & b and 5-1 la & b, respectively. An example output from T-HERPS is
available in Appendix J.
Table 5-10a Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for
Dietary-based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 15 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/IN
DUSTRIAL PREMISES/EQUIPMENT
(OUTDOOR), NONAGRICULTURAL
AREAS (PUBLIC HEALTH USE) (1
Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30
day intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3
times/year; 5 day intervals)
BEANS - SUCCULENT
(LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib
cation/acre; 1 time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1
day intervals) (minimum-ag)
Small
Insects
899.99
899.99
292.84
184.01
135.00
40.50
Large
Insects
100.00
100.00
32.54
20.45
15.00
4.50
Small
Herbivore
Mammals
1525.46
1525.46
496.36
311.89
228.82
68.65
Small
Insectivore
Mammals
95.34
95.34
31.02
19.49
14.30
4.29
Small
Terrestrial
Phase
Amphibians
31.24
31.24
10.16
6.39
4.69
1.41
90
-------
Table 5-1 Ib Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for
Dietary-based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 35 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/IN
DUSTRIAL PREMISES/EQUIPMENT
(OUTDOOR), NONAGRICULTURAL
AREAS (PUBLIC HEALTH USE) (1
Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30
day intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3
times/year; 5 day intervals)
BEANS - SUCCULENT
(LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib
cation/acre; 1 time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1
day intervals) (minimum-ag)
Small
Insects
899.99
899.99
292.84
184.01
135.00
40.50
Large
Insects
100.00
100.00
32.54
20.45
15.00
4.50
Small
Herbivore
Mammals
1054.30
1054.30
343.05
215.56
158.15
47.44
Small
Insectivore
Mammals
65.89
65.89
21.44
13.47
9.88
2.97
Small
Terrestrial
Phase
Amphibians
31.24
31.24
10.16
6.39
4.69
1.41
Table 5-12a Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-bw) for
Dose-based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 15 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/IN
DUSTRIAL PREMISES/EQUIPMENT
(OUTDOOR), NONAGRICULTURAL
AREAS (PUBLIC HEALTH USE) (1
Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30
day intervals (ag))
CRLF
Size (g)
1.4
37
238
1.4
37
238
1.4
37
238
Small
Insects
34.97
34.36
22.52
34.97
34.36
22.52
11.38
11.18
7.33
Large
Insects
3.89
3.82
2.50
3.89
3.82
2.50
1.26
1.24
0.81
Small
Herbivore
Mammals
N/A
618.43
96.14
N/A
618.43
96.14
N/A
201.23
31.28
Small
Insectivore
Mammals
N/A
38.65
6.01
N/A
38.65
6.01
N/A
12.58
1.96
Small
Terrestrial
Phase
Amphibians
N/A
1.19
0.78
N/A
1.19
0.78
N/A
0.39
0.25
91
-------
CORN (SILAGE) (0.5 Ib cation/acre; 3
times/year; 5 day intervals)
BEANS- SUCCULENT
(LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib
cation/acre; 1 time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1
day intervals) (minimum-ag)
1.4
37
238
1.4
37
238
1.4
37
238
7.15
7.03
4.60
5.24
5.15
3.38
1.57
1.55
1.01
0.79
0.78
0.51
0.58
0.57
0.38
0.17
0.17
0.11
N/A
126.44
19.66
N/A
92.77
14.42
N/A
27.83
4.33
N/A
7.90
1.23
N/A
5.80
0.90
N/A
1.74
0.27
N/A
0.24
0.16
N/A
0.18
0.12
N/A
0.05
0.04
Table 5-131b Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-bw) for
Dose-based Exposures of the CRLF and its Prey to Paraquat, the weights of small
herbivore and insectivore mammals are 35 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/IN
DUSTRIAL PREMISES/EQUIPMENT
(OUTDOOR), NONAGRICULTURAL
AREAS (PUBLIC HEALTH USE) (1
Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30
day intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3
times/year; 5 day intervals)
BEANS- SUCCULENT
(LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib
cation/acre; 1 time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1
day intervals) (minimum-ag)
CRLF
Size (g)
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
Small
Insects
34.97
34.36
22.52
34.97
34.36
22.52
11.38
11.18
7.33
7.15
7.03
4.60
5.24
5.15
3.38
1.57
1.55
1.01
Large
Insects
3.89
3.82
2.50
3.89
3.82
2.50
1.26
1.24
0.81
0.79
0.78
0.51
0.58
0.57
0.38
0.17
0.17
0.11
Small
Herbivore
Mammals
N/A
997.31
155.04
N/A
997.31
155.04
N/A
324.50
50.45
N/A
203.91
31.70
N/A
149.60
23.26
N/A
44.88
6.98
Small
Insectivore
Mammals
N/A
62.33
9.69
N/A
62.33
9.69
N/A
20.28
3.15
N/A
12.74
1.98
N/A
9.35
1.45
N/A
2.80
0.44
Small
Terrestrial
Phase
Amphibians
N/A
1.19
0.78
N/A
1.19
0.78
N/A
0.39
0.25
N/A
0.24
0.16
N/A
0.18
0.12
N/A
0.05
0.04
92
-------
Acute Exposures
Refined acute dietary-based RQs for CRLFs consuming small insects and small herbivore
mammals exceed the acute listed species LOG (0.1) for all uses of paraquat except
Melons (only small insects when the small mammals weigh 15g). The acute dietary-
based RQs for CRLFs consuming large insects exceed the acute listed species LOG for
Airports/public health uses and Guava for both the 15g and 35g small mammals. The
acute dietary-based RQs for CRLFs consuming small insectivore mammals exceed the
acute listed species LOG for Airports/public health uses and Guava for the 15g small
herbivore mammal only. No acute dietary based LOCs were exceeded for CLRF
consuming small terrestrial phase amphibians for any paraquat use. Results are presented
in Tables 5-12a and 5-12b
Refined dose-based RQs for CRLF of varying weights (1.4g, 37g and 238g) consuming
small insects exceed the acute endangered species LOG (0.1) for only the Airport/public
health and Guava uses of paraquat for all weights of CRLF (Table 5-13a and Table 5-
13b). There are no exceedances for small sized (1.4g) CRLF consuming large insects
(Table 5-13a), and CRLF this size are too small to consume small mammals or small
terrestrial-phase amphibians. The RQs for small sized (1.4g) CRLF are 0.27 suggesting
that small CRLF consuming small insects are potentially affected by acute exposures to
paraquat.
Refined dose-based RQs for medium sized (37g) CRLF consuming small herbivore
mammals (either 15g or 35g) exceed the acute listed species LOG (0.1) for all uses of
paraquat (Table 5-13a and Table 5-13b). There were also exceedances the acute listed
species LOG (0.1) for medium sized CRLF consuming small insectivore (15g) mammals
for the airports/public health, guava, and ginger uses of paraquat (Table 15-13a). For
medium sized CRLF consuming small insectivore (35g) mammals there were
exceedances in the acute listed species LOG (0.1) for all uses of paraquat except carrots
and melons (Table 5-13b). There are no exceedances for medium sized (37g) CRLF
consuming large insects or small terrestrial-phase amphibians (Table 15-13a and Table
15-13b). Due to exceedances of LOCs for CRLF consuming small herbivore mammals
(either 15g or 35g) for all paraquat uses, and exceedances of LOCs for CRLF consuming
small insectivore mammals (either 15g or 35g) for a majority of paraquat uses indicate
that the medium sized CRLF could potentially be affected by acute exposures to
paraquat.
Refined dose-based RQs for large sized (23 8g) CRLF consuming small herbivore
mammals (either 15g or 35g) exceed the acute listed species LOG (0.1) for all uses of
paraquat except melons (Table 5-13a and Table 5-13b). There were no exceedances for
large sized (238g) CRLF consuming large insects, small insectivore mammals (15g or
35g), or small terrestrial-phase amphibians (Table 15-13a and Table 15-13b). Due to
exceedances of of LOCs for CRLF consuming small herbivore mammals (either 15g or
35g) for all paraquat uses except melons, indicate that the large sized CRLF could
potentially be affected by acute exposures to paraquat.
93
-------
Table 5-14a Revised Acute Dietary-based RQs* for CRLF consuming different food
items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 15 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE) (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30 day
intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3 times/year;
5 day intervals)
BEANS - SUCCULENT (LIMA/SNAP),
CARROT (INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib cation/acre; 1
time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1 day
intervals) (minimum-ag)
Small
Insects
1.28
1.28
0.42
0.26
0.19
0.06
Large
Insects
0.14
0.14
0.05
0.03
0.02
0.01
Small
Herbivore
Mammals
2.17
2.17
0.71
0.44
0.33
0.10
Small
Insectivore
Mammals
0.14
0.14
0.04
0.03
0.02
0.01
Small
Terrestrial
Phase
Amphibians
0.04
0.04
0.01
0.01
0.01
<0.01
*RQs exceeding the Listed LOG (0. 10) are bolded and shaded
Table 5-15b Revised Acute Dietary-based RQs* for CRLF consuming different food
items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 35 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRI
AL PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE) (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30 day
intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3
times/year; 5 day intervals)
BEANS - SUCCULENT (LIMA/SNAP),
CARROT (INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib cation/acre; 1
time/yr; 1 day intervals)
Small
Insects
1.28
1.28
0.42
0.26
0.19
Large
Insects
0.14
0.14
0.05
0.03
0.02
Small
Herbivore
Mammals
1.50
1.50
0.49
0.31
0.22
Small
Insectivore
Mammals
0.09
0.09
0.03
0.02
0.01
Small
Terrestrial
Phase
Amphibians
0.04
0.04
0.01
0.01
0.01
94
-------
Melons (0.3 Ib cation/acre; 1 time/yr; 1 day
intervals) (minimum-ag)
0.06
0.01
0.07
<0.01
<0.01
*RQs exceeding the Listed LOG (0. 10) are bolded and shaded
Table 5-16a Refined Dose-based RQs* for CRLF consuming different food items
(RQs calculated using T-HERPS), the weights of small herbivore and insectivore
mammals are 15 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL
/INDUSTRIAL
PREMISES/EQUIPMENT
(OUTDOOR),
NONAGRICULTURAL AREAS
(PUBLIC HEALTH USE) (1 Ib
cation/acre; 10 times/yr; 5 day
intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr;
5 day intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr;
30 day intervals (ag))
CORN (SILAGE) (0.5 Ib
cation/acre; 3 times/year; 5 day
intervals)
BEANS- SUCCULENT
(LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib
cation/acre; 1 time/yr; 1 day
intervals)
Melons (0.3 Ib cation/acre; 1
time/yr; 1 day intervals) (minimum-
ag)
CRLF
Size (g)
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
Small
Insects
0.27
0.27
0.18
0.27
0.27
0.18
0.09
0.09
0.06
0.06
0.05
0.04
0.04
0.04
0.03
0.01
0.01
0.01
Large
Insects
0.03
0.03
0.02
0.03
0.03
0.02
0.01
0.01
0.01
0.01
0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
Small
Herbivore
Mammals
N/A
4.83
0.75
N/A
4.83
0.75
N/A
1.57
0.24
N/A
0.99
0.15
N/A
0.72
0.11
N/A
0.22
0.03
Small
Insectivore
Mammals
N/A
0.30
0.05
N/A
0.30
0.05
N/A
0.10
0.02
N/A
0.06
0.01
N/A
0.05
0.01
N/A
0.01
<0.01
Small
Terrestrial
Phase
Amphibians
N/A
0.01
0.01
N/A
0.01
0.01
N/A
<0.01
<0.01
N/A
<0.01
<0.01
N/A
<0.01
<0.01
N/A
<0.01
<0.01
*RQs exceeding the Listed LOG (0.10) are bolded and shaded
95
-------
Table 5-17b Refined Dose-based RQs* for CRLF consuming different food items
(RQs calculated using T-HERPS), the weights of small herbivore and insectivore
mammals are 35 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAMNSTITUTIONA
MNDUSTRIAL
PREMISES/EQUIPMENT
(OUTDOOR),
NONAGRICULTURAL AREAS
(PUBLIC HEALTH USE) (1 Ib
cation/acre; 10 times/yr; 5 day
intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10
times/yr; 5 day intervals)
(maximum- ag)
Ginger (1 Ib cation/acre; 6
times/yr; 30 day intervals (ag))
CORN (SILAGE) (0.5 Ib
cation/acre; 3 times/year; 5 day
intervals)
BEANS- SUCCULENT
(LIMA/SNAP), CARROT
(INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib
cation/acre; 1 time/yr; 1 day
intervals)
Melons (0.3 Ib cation/acre; 1
time/yr; 1 day intervals)
(minimum-ag)
CRLF
Size (g)
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
1.4
37
238
Small
Insects
0.27
0.27
0.18
0.27
0.27
0.18
0.09
0.09
0.06
0.06
0.05
0.04
0.04
0.04
0.03
0.01
0.01
0.01
Large
Insects
0.03
0.03
0.02
0.03
0.03
0.02
0.01
0.01
0.01
0.01
0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
Small
Herbivore
Mammals
N/A
7.79
1.21
N/A
7.79
1.21
N/A
2.53
0.39
N/A
1.59
0.25
N/A
1.17
0.18
N/A
0.35
0.05
Small
Insectivore
Mammals
N/A
0.49
0.08
N/A
0.49
0.08
N/A
0.16
0.02
N/A
0.10
0.02
N/A
0.07
0.01
N/A
0.02
<0.01
Small
Terrestrial
Phase
Amphibians
N/A
0.01
0.01
N/A
0.01
0.01
N/A
<0.01
<0.01
N/A
<0.01
<0.01
N/A
<0.01
<0.01
N/A
<0.01
<0.01
*RQs exceeding the Listed LOG (0.10) are bolded and shaded
A probit slope value for the acute avian toxicity test was 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). For all uses
with RQs that exceed the endangered species LOCs the probability of individual effects
were conducted to determine the probability that one individual could be impacted by
exposure to paraquat. Using the revised acute dietary-based RQs for CRLF consuming
different food items the chance of individual mortality for which the RQs exceed the
LOC (0.1) range from approximately 1 in 2.94* 105 (95 % CI: 1 in 4.4* 101 to 1 in
8.86*1018) (<1%) at an RQ 0.10 (Melons, small herbivore mammals weighing 15g) to
approximately 1 in 1 (95 % CI: 1 in 1.33 to 1 in 1) (100%) at an RQ of 2.17
(Airports/public health use/Guava, small herbivore mammals weighing 15g) (Table 5-
96
-------
12a). This range of RQs is relevant to CRLF consuming small and large insects, and
small herbivore and insectivore mammals. This range is not relevant to CRLF consuming
small terrestrial-phase amphibians modeled for any use scenario since there was no LOG
exceedance.
Since the CRLF also consumes larger sizes of mammals RQs were also calculated for
small herbivore and insectivore mammals weighing 35g. Using the revised acute dietary-
based RQs for CRLF consuming different food items the chance of individual mortality
for which the RQs exceed the LOG (0.1) range from approximately 1 in 1.64*104 (95 %
CI: 1 in 2.28* 101 to 1 in 1.31*1014) (<1 %) at an RQ 0.14 (Airports/public health use/
Guava, large insects) to approximately 1 in 1.27 (95 % CI: 1 in 1.57 to 1 in 1.06) (86%)
at an RQ of 1.50 (Airports/public health use/Guava, small herbivore mammals weighing
35g) (Table 5-12b). This range of RQs is relevant to CRLF consuming small and large
insects, and small herbivore mammals. This range is not relevant to CRLF consuming
small insectivore mammals or small terrestrial-phase amphibians modeled for any use
scenario since there was no LOG exceedance.
Using the revised acute dose-based RQs for CRLF consuming different food items the
chance of individual mortality for which the RQs exceed the LOG (0.1) range from
approximately 1 in 2.94* 105 (95 % CI: 1 in 4.4* 101 to 1 in 8.86*1018) (<1%) at an RQ
0.10 (Ginger, small herbivore mammals weighing 15g, 37g CRLF) to approximately 1 in
1 (95 % CI: 1 in 1.09 to 1 in 1) (100%) at an RQ of 4.83 (Airports/public health
use/Guava, small herbivore mammals weighing 15g, 37g CRLF) (Table 5-13a). This
range of RQs is relevant to all sizes of CRLF consuming small insects, and small
herbivore and insectivore mammals. This range is not relevant to CRLF (of any size)
consuming large insects or small terrestrial-phase amphibians modeled for any use
scenario since there were no LOG exceedances.
Using the revised acute dose-based RQs for CRLF consuming different food items the
chance of individual mortality for which the RQs exceed the LOG (0.1) range from
approximately 1 in 2.94* 105 (95 % CI: 1 in 4.4* 101 to 1 in 8.86*1018) (<1%) at an RQ
0.10 (Corn, small insectivore mammals weighing 35g, 37g CRLF) to approximately 1 in
1 (95 % CI: 1 in 1.04 to 1 in 1) (100%) at an RQ of 7.79 (Airports/public health
use/Guava, small herbivore mammals weighing 35g, 37g CRLF) (Table 5-13b). This
range of RQs is relevant to all sizes of CRLF consuming small insects, and small
herbivore and insectivore mammals. This range is not relevant to CRLF (of any size)
consuming large insects or small terrestrial-phase amphibians modeled for any use
scenario since there were no LOG exceedances.
Chronic Exposures
Refined chronic dietary-based RQs for CRLFs consuming small insects and small
herbivore mammals (either 15g or 35g) using T-HERPS model exceed the chronic
species LOG (1.0) for all uses of paraquat (Table 5-14a and 5-14b). Refined chronic
dietary-based RQs for CRLFs consuming large insects and small insectivore mammals
(either 15g or 35g) using T-HERPS model exceed the chronic species LOG (1.0) for
Airport/public health, guava, and ginger uses of paraquat (Table 5-14b). The refined
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chronic dietary-based RQs for CRLFs consuming small terrestrial- phase amphibians
using T-HERPS model exceed the chronic species LOG (1.0) for Airport/public health
and guava uses of paraquat (the maximum uses) (Table 5-14a and 5-14b).
Table 5-18a Revised Chronic Dietary-based RQs* for CRLF consuming different
food items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 15 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE) (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30 day
intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3 times/year;
5 day intervals)
BEANS - SUCCULENT (LIMA/SNAP),
CARROT (INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib cation/acre; 1
time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1 day
intervals) (minimum-ag)
Small
Insects
30.0
30.0
9.76
6.13
4.50
1.35
Large
Insects
3.33
3.33
1.08
0.68
0.50
0.15
Small
Herbivore
Mammals
50.85
50.85
16.55
10.40
7.63
2.29
Small
Insectivore
Mammals
3.18
3.18
1.03
0.65
0.48
0.14
Small
Terrestrial
Phase
Amphibians
1.04
1.04
0.34
0.21
0.16
0.05
*RQs exceeding the Listed LOG (1 .0) are bolded and shaded
Table 5-194b Revised Chronic Dietary-based RQs* for CRLF consuming different
food items (RQs calculated using T-HERPS), the weights of small herbivore and
insectivore mammals are 35 g.
Scenario
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL
PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC
HEALTH USE) (1 Ib cation/acre; 10 times/yr; 5
day intervals) (maximum- non-ag)
Guava (1 Ib cation/acre; 10 times/yr; 5 day
intervals) (maximum- ag)
Ginger (1 Ib cation/acre; 6 times/yr; 30 day
intervals (ag))
CORN (SILAGE) (0.5 Ib cation/acre; 3 times/year;
5 day intervals)
Small
Insects
30.0
30.0
9.76
6.13
Large
Insects
3.33
3.33
1.08
0.68
Small
Herbivore
Mammals
35.14
35.14
11.43
7.19
Small
Insectivore
Mammals
2.20
2.20
0.71
0.45
Small
Terrestrial
Phase
Amphibians
1.04
1.04
0.34
0.21
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BEANS - SUCCULENT (LIMA/SNAP),
CARROT (INCLUDING TOPS), PEAS
(UNSPECIFIED), PEPPER (1 Ib cation/acre; 1
time/yr; 1 day intervals)
Melons (0.3 Ib cation/acre; 1 time/yr; 1 day
intervals) (minimum-ag)
4.50
1.35
0.50
0.15
5.27
1.58
0.33
0.10
0.16
0.05
*RQs exceeding the Listed LOG (1 .0) are bolded and shaded
In the available chronic study where Mallard duck were exposed to paraquat, the NOAEC
was 30 ppm and the LOAEC was 100 ppm, based on effects to % viable egs, eggs set,
normality of hatchlings, and number of 14-day old survivors. In comparing the LOAEC
to the chronic dietary-based EECs for CRLF small insects and small herbivore mammals
indicate that the EECs for all uses except melons exceed the concentration where
reproductive effects were observed within the laboratory. For CRLF consuming large
insects (except airport/public health/guava use), small insectivore mammals (15g or 35g),
and small terrestrial-phase amphibians all uses except those previously listed have EECs
which do not exceed the LOAEC. Therefore, some CRLF feeding categories, paraquat
EECs are at levels were reproductive effects were observed in birds, which serve as
surrogates for the CRLF.
Of the terrestrial animal incidents that were reported paraquat was not the only chemical
that was present in the field. Only one incident was from the registered use of paraquat,
and paraquat was considered as being probably responsible, for the death of
approximately 5 Canadian geese, as it had the highest acute toxicity to birds of the
pesticides applied in the mix tank (the others were Atrazine, Simazine, Cyanazine, and
Esfenvalerate) (1008168-001). With the other two incidents, paraquat was considered to
be unlikely or possibly responsible for the incident (1000097-015,1007334-001).
Avian dietary and dose-based toxicity is very different, based upon the chemical
properties of paraquat. This is a conservative estimate as paraquat's toxicity may vary
due to it binding to the food residue and maybe less biologically available to the
organism.
Based on the line of evidence, and on these refined acute and chronic risk quotients
(RQs) and their exceedances of the Agency's LOC a May Affect and is Likely to
Adversely Affect (LAA) determination is made for paraquat use in California.
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. Indirect effects of
paraquat 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 acute
toxicity value for aquatic non-vascular plants. The Agency's LOC (1.0) is exceeded for
all uses of paraquat in California. The RQs range from 2213 for airports,
commercial/industrial areas, and public health areas to 11 for melons (Section 5.1.1.2).
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The fate characteristics indicate that paraquat is expected to be persistent in aquatic
environments. As a result, the primary food source for the aquatic-phase CRLF (non-
vascular aquatic plants) is expected to be adversely affected.
Because of non-vascular LOC exceedance from registered uses of paraquat the
Agency concludes that there is a potential of indirect impact to the aquatic-phase of
the CRLF from reduction of food items (algae). Therefore, paraquat May Affect
and is Likely to Adversely Affect (LAA) the CRLF.
5.2.2.2 Aquatic Invertebrates
The potential for paraquat 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.
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.
The fate properties of paraquat suggest that paraquat is expected to be transported
primarily along with soil particles and subsequently redeposited onto the beds of surface
water bodies or lowland areas that receive eroded sediments from uplands, such as
riparian zones.
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. The acute RQs range from 0.042 for airports,
commercial/industrial areas, and public health areas to 0.001 for melons.
Since there are not any aquatic chronic data values for paraquat, the chronic risk to
aquatic animals is estimated using the ACR as described in Section 5.1.1.1. There is
believed to be no risk to invertebrates using this method due to the ACR being much
higher than the EECs calculated using GENEEC2 for the invertebrates.
Because there are no LOC exceedances from registered uses of paraquat to the
CRLF surrogate species (freshwater invertebrates), because monitored
concentrations in surface water are far below modeled estimates, and because the
non-target incidents resulting from paraquat use are judged to be unlikely to
possible, the Agency concludes that paraquat will not indirectly affect the CRLF.
5.2.2.3 Fish and Aquatic-phase Frogs
As discussed in Section 2.5.3, the diet of CRLF also includes small fish and other
aquatic-phase frogs. Direct effects to the aquatic-phase CRLF are based on peak EECs in
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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 would be used. However, since there are not any aquatic
chronic data values, the chronic RQs could not be calculated. Therefore, the chronic
exposure to CRLF is uncertain.
Because there are no LOC exceedances from registered uses of paraquat to the
CRLF surrogate species (freshwater fish), the Agency concludes that paraquat will
not indirectly affect the aquatic-phase of the CRLF on an acute or chronic basis
from fish or other aquatic-phase frogs as prey items.
5.2.2.4 Terrestrial Invertebrates
When the terrestrial-phase CRLF reaches juvenile and adult stages, its diet is mainly
composed of terrestrial invertebrates. Terrestrial invertebrate toxicity data is used to
assess potential indirect effects of paraquat to the terrestrial-phase CRLF. Effects to
terrestrial invertebrates resulting from exposure to paraquat may also indirectly affect the
CRLF via reduction in available food.
Because the LD50 was not definitive, and there was little incidence of mortality, RQs
were not calculated. However, EECs were compared to the highest concentration tested.
All of estimated EEC's the level tested for all uses for small insects and all of the uses
greater than 6 applications per year with 30 day intervals at 1 Ib cation/acre per
application for large insects; therefore, a preliminary "May Affect" determination was
made. However, the calculated EEC's for Airports/public health use/Guava (899.99 ppm
small insects and 100.00 ppm large insects) were 26 and 2.9 times the level of paraquat
tested (>34.6 ug cation/bee), at which there was a low incidence of mortality. Therefore,
it is reasonable to assume that the effects to terrestrial invertebrate populations will be
negligible for the uses of paraquat in California. Therefore, based on the weight-of-
evidence, the Agency concludes that there is a negligible potential impact to
terrestrial invertebrates that the CRLF consumes, and therefore paraquat May
Affect but is Not Likely to Adversely Affect (NLAA) the CRLF.
5.2.2.5 Mammals
Life history data for terrestrial-phase CRLFs indicate that large adult frogs consume
terrestrial vertebrates, including mice. Acute dose based RQs exceed the Agency's
endangered species LOC (0.1) for all uses of paraquat. The dose based RQs that exceed
the LOC range from 0.34 (Melons) to 7.63 (Airports/public health uses/Guava) (Table 5-
7). Chronic dose based RQs exceed the Agency's LOC (1.0) for all uses and range from
5.78 (Melons) to 128.53 (Airports/public health use/Guava) (Table 5-7). The dietary
based chronic RQs exceed the Agency's LOC for all uses except melons and range from
3.03 (Corn) to 14.81 (Airports/public health use/Guava) (Table 5-7).
Based on the mammalian dose-based acute RQs and a probit dose-response default slope
of 4.5 the estimated mammalian prey item population reduction for which RQs exceed
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the Listed (endangered species) LOCs are approximately 1 in 1 for all uses except melon
(no exceedance) (Table 5-7). The acute dose-based EECs are well above the levels
mortality was documented at. The chronic dose-based and dietary-based EECs are also
well above the levels that were tested, and showed mortality and sublethal effects (lung
damage). Because environmental exposure levels are estimated to be much higher than
the level which may cause acute effects to mammals, the CRLF may be indirectly
affected by acute exposure to paraquat.
Reproductive and sublethal effects (lung damage) were observed in chronic mammalian
studies, and resulted in RQ values that exceeded the LOG (1.0) for all uses (chronic dose-
based) and all uses except melons (chronic dietary-based). The RQs ranged from 128.53
to 5.78 for the dose-based, and 14.81 to 0.67 for the dietary-based (Table 5-7). Paraquats
toxicity, when combined in the diet is lower than the gavage (dose) based treatment,
indicating that the toxicity may be reduced in combination with the diet. Chronic
exposure to paraquat is likely.
Based on effects to small mammals, there is a potential indirect impact to the CRLF
via reduction in small mammal prey items, and therefore paraquat May Affect and
is Likely to Adversely Affect (LAA) the CRLF.
5.2.2.6 Terrestrial-phase Amphibians
Terrestrial-phase adult CRLFs also consume frogs. RQ values representing direct
exposures of paraquat to terrestrial-phase CRLFs are used to represent exposures of
paraquat to frogs in terrestrial habitats. The T-FLERPS model was therefore employed as a
refinement tool to explore amphibian-specific food intake on potential exposure to
terrestrial-phase amphibian food items for the CRLF. The T-FLERPS model incorporates
the same inputs as T-REX with equations adjusted for poikilotherm food intake. As
described in Section 5.2.1.2, the RQs for small terrestrial-phase amphibians did not
exceed the listed species LOG (0.1) for any use of paraquat. Reduction in amphibian
prey items, specifically other frogs is not affected from paraquat use. Other items in the
prey base all had RQs that exceeded the listed species LOG for numerous uses of
paraquat.
Based on this evidence, a May Affect and is Likely to Adversely Affect (LAA)
determination is made for indirect effects via reductions in prey base to the
terrestrial-phase CRLF.
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
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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.
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. Indirect effects of paraquat to the aquatic-phase CRLF (tadpoles) are present
in the reduction of non-vascular aquatic plants in the aquatic-phase CRLFs diet. The
Agency's LOG (1.0) for non-vascular plants is exceeded for all uses of paraquat in
California. The non-vascular aquatic plant RQs range from 138 for airports,
commercial/industrial/public health uses to 4.1 for use on melon (Section 5.1.1.2).
Indirect effects of paraquat to the aquatic-phase CRLF (tadpoles) are also found via the
reduction in vascular aquatic plants in the aquatic-phase CRLFs diet. The Agency's LOG
(1.0) for vascular plants is exceeded for all uses of paraquat in California. The acute RQs
range from 0.77 for airports, commercial/industrial areas, and public health areas to 0.02
for melons (Section 5.1.1.2).
An analysis of the fate characteristics of paraquat indicates that paraquat is expected to be
persistent in aquatic environments. As a result, the primary food source for the aquatic-
phase CRLF (both vascular and non-vascular aquatic plants) is expected to be adversely
affected.
Because of the non-vascular aquatic plant LOC exceedances for registered uses of
paraquat, and verified non-target incidents resulting from paraquat use, the Agency
concludes that there is a potential of indirect impact to the aquatic-phase of the
CRLF from reduction of food items (algae). Therefore, paraquat May Affect and is
Likely to Adversely Affect (LAA) the CRLF.
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.
Potential indirect effects to the CRLF based on impacts to habitat and/or primary
production were assessed using RQs from monocot and dicot plant data. The RQs for
monocots were below the Agency's LOC, whereas the dicot spray drift RQ exceeded the
Agency's RQ (1.0), for all aerial applications of paraquat (Tables 5-15 and 5-16).
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Twenty-one incidents have been reported for paraquat, listed under paraquat and paraquat
dichloride, but they are one in the same. There were nine incidents from the misuse of
paraquat that resulted in plant damage, with one incident of plant mortality (1014409-
024), and one incident of plant discoloration (1005880-005). Of the reported misuses of
paraquat; two from general misuse, six from accidental misuse, and one from the
intentional misuse of paraquat (1014409-024,1013554-040,1005660-005,1005880-005,
1007371-033,1007371-034,1007371-035,1007371-008, and 1016940-005 respectively).
There were a total of six incidents from the registered use of paraquat and all resulted in
plant damage (1013884-038,1013636-029,1011838-055,1014034-099,1012684-010,
1001131-001). The remaining six incidents were from undetermined legality of paraquat
use and resulted in plant damage (1014409-001,1013884-014,1012366-023,1009573-
009,101183 8-091, and 101183 8-03 8).
Based on LOC exceedances in spray drift RQs for dicots, and the twenty-one
reported incidents that resulted in plant damage a variety of monocots, paraquat
May Affect and is Likely to Adversely Affect (LAA) the CRLF indirectly via habitat
degradation through reduction in terrestrial plants. Of particular concern is the
risk from spray drift during/after aerial application.
5.2.4 Effects to Designated Critical Habitat
5.2.4.1 Aquatic-Phase PCEs
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.
LOCs are exceeded for terrestrial riparian plants and for aquatic plants from exposure to
paraquat from spray drift. Alteration of riparian and vascular plants may result in
alteration of temperature, turbidity, and oxygen content.
Aquatic non-vascular plants used as a food source and habitat for CRLF may be
potentially affected from all paraquat uses. A reduction in these aquatic based food
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sources may occur from most use sites. Likewise, due to aquatic vascular and terrestrial
plant communities being reduced from most use sites, there is potential for alteration of
channel/pond morphology or geometry and/or increase in sediment deposition within the
stream channel or pond.
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.
Based on acute LOC exceedances for aquatic plants paraquat may result in effects
to aquatic-phase PCEs of designated critical habitat related to effects of alteration of
other chemical characteristics necessary for normal growth and viability of CRLFs
and their food source.
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 (Section
5.2.3.2) from paraquat use (aerial applications only).
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. These results will inform the
effects determination for effects to designated critical habitat for the CRLF.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of paraquat on this PCE,
acute and chronic toxicity endpoints for terrestrial invertebrates, mammals, and
terrestrial-phase frogs are used as measures of effects. RQs for these endpoints were
calculated in Section 5.1.2.2. There is potential for habitat effects via indirect effects
to terrestrial-phase CRLFs via reduction in prey base (Section 5.2.2.4 for terrestrial
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invertebrates, Section 5.2.2.5 for mammals, and 5.2.2.6 for frogs) from paraquat
use.
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. Direct acute and chronic RQs for terrestrial-phase CRLFs are presented in
Section 5.2.1.2. There is potential for habitat effects 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
from paraquat use. Paraquat use may result in habitat effects based on effects to
the terrestrial PCE related to alteration of chemical characteristics necessary for
normal growth and viability.
5.2.5 Spatial Extent of Potential Effects
A May Affect 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 paraquat's use pattern is identified, using land
cover data that correspond to paraquat's use pattern. The spatial extent of the effects
determination also includes areas beyond the initial area of concern that may be impacted
by spray drift. The identified direct and indirect effects 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
1,000 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 downstream dilution extent analysis results in a
distance of 300 kilometers for forest land cover, 285 kilometers for cultivated crop,
orchard/vineyard, and pasture/hay land cover and 88.7 kilometers for developed land
cover. 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 paraquat sufficient to
result in a May Affect 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 Paraquat 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 AgDrift with the most
sensitive endpoints for terrestrial plants.
For paraquat use with the maximum application rate relative to the terrestrial-phase
CRLF, the results of the screening-level risk assessment indicate that spray drift for aerial
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applications, using both the Tier I and Tier II mode, exceeds the 1,000 foot range of the
AgDrift model . For the Tier I ground mode (no higher tier modeling for ground
applications is available in AgDrift), the spray drift buffer distance is found to be > 1,000
feet for non-listed plants as well. A summary of the modeled distances by application
method is presented in Table 5-15.
Since the maximum application rate resulted in distances exceeding the range allowed by
the AgDRIFT model, the lowest application rate was also run for comparison purposes.
For the Tier I and Tier II mode for the aerial application, the spray drift buffer distance
was found to be >1,000 feet for non-listed plants. For the Tier I ground application
mode, the spray drift buffer distance was found to be > 1,000 feet for the non-listed plants
(no higher tier modeling for ground applications is available in AgDrift). See Table 5-16
for a summary of the modeled distances by application method.
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-listed terrestrial plant £€25 of 0.014 Ibs cation/acre. 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/ECso).
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Table 5-20 Summary of AgDrift Predicted Terrestrial Spray Drift Distances Using
Maximum Application Rate
Tier I Ground Application
Risk Glass
Non-Listed Plants
Risk Description
Potential for effects to non-
target, non-listed plants from
exposures
Application
Rate (Ib
cation/ acre)
1
Toxicity
Value
Used
EC25 =
0.014 Ib
cation/A
Fraction of
applied
0.00000^
Nonvolatile
Rate (Ib/a)
Does not
apply
Minimum
Spray Volume
Rate (gal/a)
Does not
apply
Active Rate
(Ib ai/a)
Does not
apply
Distance
> 1,000 feet
Tier I Aerial Application
Risk Glass
Non-Listed Plants
Risk Description
Potential for effects to non-
target, non-listed plants from
exposures
Application
Rate (Ib
cation/ acre)
1
Toxicity
Value
Used
EG25 =
0.014 Ib
cation/A
Fraction of
applied
0.00000^
Nonvolatile
Rate flb/a)
Does not
apply
Minimum
Spray Volume
Rate (gal/a)
Does not
apply
Active Rate
(Ib ai/a)
Does not
apply
Distance
> 1,000 feet
Tier II Aerial Application
Risk Glass
Non-Listed Plants
Risk Description
Potential for effects to non-
target, non-listed plants from
exposures
Application
Rate (Ib
cation/ acre)
1
Toxicity
Value
Used
EG25 =
0.014 Ib
cation/A
Fraction of
applied
0.00000^
Nonvolatile
Rate (Ib/a)
0.683
Minimum
Spray Volume
Rate (gal/a)
0.317
Active Rate
(Ib ai/a)
1
Distance
> 1,000 feet
Table 5-21 Summary of AgDrift Predicted Aquatic Spray Drift Distances Using
Minimum Application Rate
Tier I Ground Application
Kiak Class
A on-Listed Plants
Risk Description
Potential for effects to non-
target, non-listed plants from
exposures
Application
Kate (Ib
cation/acre)
0.3
Toxicitv
Value
l.sed
EC25 =
0.014 Ib
cation/A
Fraction of
applied
0.000012
JNonvolatile
Kate (Ib/a)
Does not
applv
Minimum
Sprav Volume
Kate (gal/a)
Does not
applv
Active Kate
(Ib ai/a)
Does not
applv
Distance
> 1,000 feet
Tier I Aerial Application
Kiak Class
A on-Listed Plants
Risk Description
Potential for effects to non-
target, non-listed plants from
exposures
Application
Kate (Ib
cation/acre)
0.3
Toxicitv
Value
l.sed
EC25 =
0.014 Ib
cation/A
Fraction of
applied
0.000012
JNonvolatile
Kate (Ib/a)
Does not
applv
Minimum
Sprav Volume
Kate (gal/a)
Does not
applv
Active Kate
(Ib ai/a)
Does not
applv
Distance
> 1,000 feet
Tier II Aerial Application
Kiak Class
A on-Listed Plants
Risk Description
Potential for effects to non-
target, non-listed plants from
exposures
Application
Kate (Ib
cation/acre)
0.3
Toxicitv
Value
l.sed
EC25 =
0.014 Ib
cation/A
Fraction of
applied
0.000012
JNonvolatile
Kate (Ib/a)
0.683
Minimum
Sprav Volume
Kate (gal/a)
0.317
Active Kate
(Ib ai/a)
0.3
Distance
> 1,000 feet
5.2.5.2 Downstream Dilution Analysis
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
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modeled EECs; as those waters move downstream, it is assumed that the influx of non-
impacted water will dilute the concentrations of paraquat present.
Using a NOAEC value of 0.158 ug/L for vascular aquatic plants (the most sensitive
species) and a maximum peak EEC for applications to airports/commercial/public health
areas (non-agricultural use) of 892 ug/L yields an RQ/LOC ratio of 5424 (5424/1), and
guava (agricultural use) of 26 ug/L yields an RQ/LOC ratio of 158 (158/1). Using the
downstream dilution approach (described in more detail in Appendix J) results in a
distance of 300 kilometers for forest land cover (which represents the maximum
continuous distance of downstream dilution from the edge of the initial area of concern),
285 kilometers for cultivated crop, orchard/vineyard, and pasture/hay land cover and
88.7 kilometers for developed land cover. 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 ECso 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 paraquat, the use pattern in the following land cover classes (forest land cover,
cultivated crop, orchard/vineyard, pasture/hay land cover, and developed land cover) also
include areas beyond the initial area of concern that may be impacted by spray drift
overlaps with CRLF habitat. Appendix D 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 1,000 ft (to account for offsite migration
via spray drift) and 300 kilometers for forest land cover (to account for the maximum
continuous distance of downstream dilution from the edge of the initial area of concern)
outside the initial area of concern may also be impacted and are part of the full spatial
extent of the LAA/effects to critical habitat effects determination.
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Paraquat Use & CRLF Overlap
Paraquat & CRLF overlap
CNDDB occurrence sections
Critical habitat
Core areas
County boundaries
i Kilometers
02040 80 120 160
Compiled from California County boundaries (ESRI, 2002),
USDA Gap Analysis Program Orchard^ Vineyard Landcover (GAP)
National Land Ccwer Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Projection: Albers Equal Area Conic USGS, North American
Datum ofl 983 (NAD 1983).
.
.>> J.
6/1/2009
Figure 5-1. Overlap Map: CRLF Habitat and Paraquat Initial Area of Concern
110
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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 Crops Not Grown in California
Crops that are not currently grown in California according to CDPR PUR data, as well as
the USDA NASS database, are listed on current labels. As these crops are not currently
grown in California and are not expected to be grown in California in the future, use of
paraquat was not assessed for these crops. The following uses will not be assessed
because they are not grown in California: cocoa, coffee, banana, plantain, pineapple, and
soybeans. If the use patterns indicate that these crops are grown in CA in the future, the
conclusions of this assessment may need to be revisited.
6.1.3 Aquatic Exposure Modeling of Paraquat
GENEEC2 is a Tier I computer program, that uses the soil/water partition coefficient and
degradation kinetic data to estimate runoff from a ten hectare field into a one hectare by
two meter deep "standard" pond. This first tier is designed as a coarse screen and
estimates conservative pesticide concentrations in surface water from a few basic
chemical parameters and pesticide label use and application information. Tier I is used to
screen chemicals to determine which ones potentially pose sufficient risk to warrant
higher level modeling. It calculates acute as well as longer-term estimated environmental
concentration (EEC) values. It considers reduction in dissolved pesticide concentration
due to adsorption of pesticide to soil or sediment, incorporation, degradation in soil
before washoff to a water body, direct deposition of spray drift into the water body, and
degradation of the pesticide within the water body. It is designed to mimic a
PRZM-EXAMS simulation.
The standard ecological water body scenario (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 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
111
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less vulnerable than the 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 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 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 pond, but they
likely persist for only short periods of time and are then carried and dissipated
downstream.
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 (U.S. FWS/NMFS 2004).
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
as a quantitative method to estimate the effect of vegetative setbacks on various
conditions on pesticide loadings becomes available, the aquatic exposure predictions are
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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, it is preferred to compare
available monitoring data to GENEEC2 estimates of peak EECs for the different uses.
However, as discussed above, only CDPR had looked for paraquat, and only detected one
positive concentration of approximately 1 ppb. It is believed the positive detection was a
result of runoff from agricultural use areas. Yet, the specific use patterns (e.g. application
rates and timing, crops) associated with the agricultural areas are unknown, but they are
assumed to be representative of potential paraquat use areas.
Due to the lack of detections from the CDPR data, 399 samples and only one detect, it is
believed that the GENEEC2 EECs provide a conservative measure of exposure.
Moreover, due to the chemical properties of paraquat, it is believed that the larger the
clay content in the soil, the greater the likelihood that paraquat will adsorb to the clay
surface and will remain. Therefore, paraquat would become decreasingly mobile in areas
with increased clay content, and this would decrease the probability of paraquat finding
its way to water bodies due to run-off If paraquat is found in aquatic environments,
paraquat will bind quickly to clay found within the water body due to its cationic
properties; it is a double charged cation.
Although the potential impact of discharging ground water on CRLF populations is not
explicitly delineated, it should be noted that, in some areas of the country, ground water
could provide a source of pesticide to surface water bodies - especially low-order
streams, headwaters, and ground water-fed pools. This is particularly likely if the
chemical is persistent and mobile, the pesticide is applied to highly permeable soils
overlying shallow unconfmed ground water, and rainfall is sufficient to drive the
chemical through the soil to ground water. Soluble chemicals that are primarily subject
to photolytic degradation will be very likely to persist in ground water, and can be
transportable over long distances. Similarly, many chemicals degrade slowly under
anaerobic conditions (common in aquifers) and are thus more persistent in ground water.
Under the right hydrologic conditions, this ground water may eventually be discharged to
the surface - often supporting stream flow in the absence of rainfall. Continuously
flowing low-order streams in particular are sustained by ground water discharge, which
can constitute 100% of stream flow during baseflow (no runoff) conditions. Thus, it is
important to keep in mind that pesticides in ground water may impact surface water
quality during base flow conditions with subsequent impact on CRLF habitats. However,
many smaller streams in CA are net dischargers of water to ground water that go dry
during portions of the year and are not supplied by baseflow from ground water.
Although concentrations in a receiving water body resulting from ground water discharge
cannot be explicitly quantified, it should be assumed that significant attenuation and
retardation of the chemical will have occurred prior to discharge. Nevertheless, where
paraquat is applied to highly permeable soils over shallow ground water where there is a
net recharge to adjacent streams, ground water could still be a consistent source of
chronic background concentrations in surface water, and may also add to surface runoff
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during storm events (as a result of enhanced ground water discharge typically
characterized by the 'tailing limb' of a storm hydrograph).
6.1.4 Action Area Uncertainties
An example of an important simplifying assumption that may require future refinement is
the assumption of uniform runoff characteristics throughout a landscape. It is well
documented that runoff characteristics are highly non-uniform and anisotropic, and
become increasingly so as the area under consideration becomes larger. The assumption
made for estimating the aquatic action area (based on predicted in-stream dilution) was
that the entire landscape exhibited runoff properties identical to those commonly found in
agricultural lands in this region. However, considering the vastly different runoff
characteristics of: a) undeveloped (especially forested) areas, which exhibit the least
amount of surface runoff but the greatest amount of groundwater recharge; b)
suburban/residential areas, which are dominated by the relationship between
impermeable surfaces (roads, lots) and grassed/other areas (lawns) plus local drainage
management; c) urban areas, that are dominated by managed storm drainage and
impermeable surfaces; and d) agricultural areas dominated by Hortonian and focused
runoff (especially with row crops), a refined assessment should incorporate these
differences for modeled stream flow generation. As the zone around the immediate
(application) target area expands, there will be greater variability in the landscape; in the
context of a risk assessment, the runoff potential that is assumed for the expanding area
will be a crucial variable (since dilution at the outflow point is determined by the size of
the expanding area). Thus, it important to know at least some approximate estimate of
types of land use within that region. Runoff from forested areas ranges from 45 -
2,700% less than from agricultural areas; in most studies, runoff was 2.5 to 7 times higher
in agricultural areas (Okisaka et al. 1997; Karvonen et al. 1999; McDonald etal. 2002;
Phuong and van Dam 2002). Differences in runoff potential between urban/suburban
areas and agricultural areas are generally less than between agricultural and forested
areas. In terms of likely runoff potential (other variables - such as topography and
rainfall - being equal), the relationship is generally as follows (going from lowest to
highest runoff potential):
Three-tiered forest < agroforestry < suburban < row-crop agriculture < urban.
There are, however, other uncertainties that should serve to counteract the effects of the
aforementioned issue. For example, the dilution model considers that 100% of the
agricultural area has the chemical applied, which is almost certainly a gross over-
estimation. Thus, there will be assumed chemical contributions from agricultural areas
that will actually be contributing only runoff water (dilutant); so some contributions to
total contaminant load will really serve to lessen rather than increase aquatic
concentrations. In light of these (and other) confounding factors, Agency believes that
this model gives us the best available estimates under current circumstances.]
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6.1.5 Usage Uncertainties
County-level usage data were obtained from California's Department of Pesticide
Regulation Pesticide Use Reporting (CDPR PUR) database. Eight years of data (1999 -
2006) were included in this analysis because statistical methodology for identifying
outliers, in terms of area treated and pounds applied, was provided by CDPR for these
years only. No methodology for removing outliers was provided by CDPR for 2001 and
earlier pesticide data; therefore, this information was not included 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.
6.1.6 Terrestrial Exposure Modeling of Paraquat
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
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. EPA 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.
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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.
6.1.7 Spray Drift Modeling
Although there may be multiple paraquat 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
paraquat from multiple applications, each application of paraquat 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 topography, cover, and
meteorological conditions over the transport distance are not accounted for by the
AgDRIFT 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 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' 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. However,
since these input values were not provided in the labels, the default values for the droplet
size, release heights, and wind speeds were used for this assessment.
6.2 Effects Assessment Uncertainties
6.2.1 Acute to Chronic Ratio
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. However, since
freshwater invertebrate chronic toxicity values are not available at this time, the indirect
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chronic toxicity values for the CRLF were unable to be calculated. As a result, there is
uncertainty as to what degree paraquat may have chronic indirect effects on the CRLF.
6.2.2 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.
6.2.3 Use of Surrogate Species Effects Data
Guideline toxicity tests and open literature data on paraquat are not available for frogs or
any other aquatic-phase amphibian; therefore, freshwater fish are used as surrogate
species for aquatic-phase amphibians. The open literature that was available is not
applicable as the quality of the experiments is not sound to include in the analysis of
toxicity. 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.
6.2.4 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 is
exercised on a case-by-case basis and only after careful consideration of the nature of the
sublethal effect measured and the extent and quality of available data to support
establishing a plausible relationship between the measure of effect (sublethal endpoint)
and the assessment endpoints. However, the full suite of sublethal effects from valid
open literature studies is considered for the purposes of defining the action area.
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There were numerous studies found within the ECOTOX database that reported on the
sublethal effects observed after paraquat exposure. Potential sublethal effects on fish are
evaluated qualitatively and not used as part of the quantitative risk characterization.
Although one study did provide some information regarding different biochemical factors
influenced by exposures to paraquat (E104191). Further details on ECOTOX studies are
provided in Appendix G, and contain the rejection codes and other information as to why
studies from ECOTOX were not used.
To the extent to which sublethal effects are not considered in this assessment, the
potential direct and indirect effects of paraquat on CRLF may be underestimated.
6.2.5 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.
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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 paraquat to the CRLF and its designated
critical habitat.
Based on the best available information, the Agency makes a May Affect and Likely to
Adversely Affect (LAA) determination for the CRLF from the use of paraquat. The
Agency has determined that there is the potential for effects to CRLF designated critical
habitat from the use of the chemical. The direct effects and habitat modification
determinations are summarized in Table 7.1 and Table 7.2 respectively. 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 II.
There are three exceptions to this determination. First, for the direct affects to the CRLF,
the aquatic-phase CRLF (from surrogate fish species), a No Effect (NE) determination
was made, as none of the EECs for any of the uses exceeded the listed species LOG
(0.05). Second, for the indirect effects to the CRLF, the aquatic invertebrates, a No
Effect (NE) determination was also made, as none of the EECs for any of the uses
exceeded the listed species LOG (0.05). Third, also for the indirect effects to the CRLF,
the terrestrial invertebrates were determined to May Affect, But Not Likely to
Adversely Affect (NLAA) the CRLF, as there is a negligible potential impact to
terrestrial invertebrates that the CRLF consumes. Likewise, none of the EECs for any of
the uses exceeded the listed species LOG (0.05). All of the other direct and indirect
effects to the CRLF were determined to Likely to Adversely Affect (LAA) the CRLF.
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 paraquat's use pattern is identified, using land
cover data that correspond to paraquat's use pattern. The spatial extent of the LAA
effects determination also includes areas beyond the initial area of concern that may be
impacted by spray drift. The identified direct and indirect effects 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 1,000 feet from its boundary, see Section 5.2.5 for further information. 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 300 kilometers for forest land cover (which represents the
maximum continuous distance of downstream dilution from the edge of the initial area of
concern), 285 kilometers for cultivated crop, orchard/vineyard, and pasture/hay land
cover and 88.7 kilometers for developed land cover. Please see Section 5.2.5 for a more
detailed description. If any of these streams reaches flow into CRLF habitat, there is
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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
paraquat sufficient to result in LAA determination or effects to critical habitat.
Appendix D 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 1,000 ft (to account for offsite migration via spray drift) and 300 kilometers for
forest land cover (to account for the maximum continuous distance of downstream
dilution from the edge of the initial area of concern) outside the initial area of concern
may also be impacted and are part of the full spatial extent of the LAA/effects to 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-land Table 7-2.
Table 7-1 Effects Determination Summary for Paraquat Use and the CRLF
Assessment
Endpoint
Effects
Determination 1
Basis for Determination
Survival, growth,
and/or reproduction
of CRLF
individuals
NE1
LAA1
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
The aquatic phase amphibian acute LOCs for listed species (0.05) are not
exceeded for any uses of paraquat in California. The chronic EECs are all less
than the estimated chronic value derived from the ACR. Therefore, there are no
exceedances of chronic LOCs.
Terrestrial-phase (Juveniles and Adults):
Refined acute dietary-based RQs for CRLFs consuming small insects exceed
the acute listed species LOG (0.1) for all uses of paraquat except melons, RQs
ranged from 1.28 (Airport/public health use/guava) to 0.06 (melons). The
Refined acute dietary-based RQs for CRLFs consuming large insects and 15g
small insectivore mammals resulted in paraquat use on airports/public health
use/guava exceeding the listed species LOG (0.1), with an RQ of 0.14 for both.
The refined acute dietary-based RQs for CRLFs consuming small herbivore
mammals (15g) resulted in all uses exceeding the listed species LOG, RQs
ranged from 2.17 (Airport/public health use/guava) to 0.10 (melons) and for
35g small mammals all uses except melons exceed the listed species LOG, RQs
ranged from 1.50 (Airport/public health use/guava) to 0.77 (melons). There are
no exceedances for CRLFs consuming small terrestrial-phase amphibians.
Refined dose-based RQs for CRLF of varying weights (1.4g, 37g and 238g)
consuming small insects exceed the acute endangered species LOG (0.1) for
only the Airport/public health and Guava uses of paraquat for all weights of
CRLF). There are no exceedances for small sized (1.4g) CRLF consuming
large insects and CRLF this size are too small to consume small mammals or
small terrestrial-phase amphibians. The RQs for small sized (1.4g) CRLF are
0.27 suggesting that small CRLF consuming small insects are potentially
affected by acute exposures to paraquat.
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LAA1
Refined dose-based RQs for medium sized (37g) CRLF consuming small
herbivore mammals (either 15g or 35g) exceed the acute listed species LOG
(0.1) for all uses of paraquat. There were also exceedances in the acute listed
species LOG (0.1) for medium sized CRLF consuming small insectivore (15g)
mammals for the airports/public health, guava, and ginger uses of paraquat. For
medium sized CRLF consuming small insectivore (35g) mammals there were
exceedances in the acute listed species LOG (0.1) for all uses of paraquat except
carrots and melons. There are no exceedances for medium sized (37g) CRLF
consuming large insects or small terrestrial-phase amphibians. Due to
exceedances of LOCs for CRLF consuming small herbivore mammals (either
15g or 35g) for all paraquat uses, and exceedances of LOCs for CRLF
consuming small insectivore mammals (either 15g or 35g) for a majority of
paraquat uses indicate that the medium sized CRLF could potentially be
affected by acute exposures to paraquat.
Refined dose-based RQs for large sized (238g) CRLF consuming small
herbivore mammals (either 15g or 35g) exceed the acute listed species LOG
(0.1) for all uses of paraquat except melons. There were no exceedances for
large sized (23 8g) CRLF consuming large insects, small insectivore mammals
(15g or 35g), or small terrestrial-phase amphibians. The exceedances of LOCs
for CRLF consuming small herbivore mammals (either 15g or 35g) for all
paraquat uses except melons, indicates that the large sized CRLF could
potentially be affected by acute exposures to paraquat.
Refined chronic dietary-based RQs for CRLFs consuming small insects and
small herbivore mammals (eitherlSg or 35g) using T-HERPS model exceed the
chronic species LOG (1.0) for all uses of paraquat. Refined chronic dietary-
based RQs for CRLFs consuming large insects and small insectivore mammals
(either 15g or 35g) using T-HERPS model exceed the chronic species LOG
(1.0) for Airport/public health, guava, and ginger uses of paraquat. The refined
chronic dietary-based RQs for CRLFs consuming small terrestrial-phase
amphibians using T-HERPS model exceed the chronic species LOG (1.0) for
Airport/public health and guava uses of paraquat (the maximum uses).
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
LOCs for non-vascular plants are exceeded for all uses. The non-vascular plant
RQs range from 138 for airports, commercial/industrial areas, and public health
areas to 4.1 for melons.
LOCs for vascular plants are not exceeded for any uses. The vascular plant RQs
range from 0.77 (airports, commercial/industrial areas, public health areas) to
0.02 (melons).
LOCs for aquatic invertebrates are not exceeded for any uses. The acute RQs
range from 0.730 for airports, commercial/industrial areas, and public health
areas to 0.004 for melons. When comparing chronic indirect effects, the
estimated chronic value at 0.174 ppm is not exceeded for any use.
For fish/frogs none of the uses exceed the LOCs for listed species. The RQs
range from 0.004 for airports, commercial/industrial areas, and public health
areas to < 0.001 for melons. When comparing chronic direct effects, the
estimated chronic value at 1.89 ppm is not exceeded for any use.
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LAA1
Terrestrial prey items, riparian habitat
RQs could not be calculated for terrestrial invertebrates as the endpoint was not
definitive. The calculated EECs were compared to the toxicity endpoint, and it
was determined that terrestrial invertebrates would not likely adversely affect the
CRLF indirectly as food.
For small mammals the acute dose-based RQs exceed the Agency's LOG (0.1)
for all uses of paraquat, the RQs ranged from 7.63 (airports/public health
use/guava) to 0.34 (melons). The chronic dose-based RQs exceed the Agency's
LOG (1.0) for all uses of paraquat, and range from 128.53 (airports/public health
use/guava) to 5.78 (melons). The chronic dietary-based RQs exceed the
Agency's LOG (1.0) for all uses except melons, and range from 14.81
(airports/public health use/guava) to 0.67 (melons).
The RQs for small terrestrial-phase amphibians did not exceed the listed species
LOG (0.1) for any use of paraquat. Reduction in amphibian prey items,
specifically other frogs is not affected from paraquat use.
The RQs for non-target terrestrial monocot and dicot plants inhabiting semi-
aquatic and upland dry areas do not exceed the Agency's LOG (1.0) for any uses.
All aerial applications of paraquat results in spray drift exceedances for dicots
(only). These exceedances range from 3.57 (Agricultural fallow/ideland
maximum aerial application rate) to 1.07 (Melons, minimum aerial application
rate).
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 Paraquat Use and CRLF Critical
Habitat Impact Analysis
Assessment
Endpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
May affect
Due to aquatic non-vascular and terrestrial plant communities being reduced
from a majority of use sites, there is potential for alteration of channel/pond
morphology or geometry and/or increase in sediment deposition within the
stream channel or pond. These plant communities provide shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile and adult CRLFs. In
addition, there is potential for 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.
LOCs are exceeded for terrestrial riparian plants and for aquatic non-vascular
plants from exposure to paraquat from spray drift. LOCs for non-vascular
plants are exceeded for all uses of paraquat.
Modification of
terrestrial-phase
PCE
May affect
The use of paraquat at all sites may create the following effects to PCE:
elimination and/or disturbance of upland habitat; ability of habitat to support
food source of CRLFs, elimination and/or disturbance of dispersal habitat,
reduction and/or modification of food sources for terrestrial phase juveniles and
adults, and alteration of chemical characteristics necessary for normal growth
and viability of juvenile and adult CRLFs and their food source.
The RQs for vascular plants did not exceed the Agency' s LOG (1.0) for any uses
of paraquat in California.
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The RQs for non-target terrestrial monocot and dicot plants inhabiting semi-
aquatic and upland dry areas do not exceed the Agency's LOG (1.0) for all uses.
All aerial applications of paraquat results in spray drift exceedances for dicots
(only).
The use of paraquat on most use sites will exceed the revised acute dietary- and
dose-based LOG and chronic LOG for prey food items of small mammals, and
invertebrates. Food sources for the CRLF are reduced, and the CRLF is
indirectly affected from this reduction.
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct/indirect and adverse
habitat modification effects determinations, it is important to note that pesticide
exposures and predicted risks to the 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
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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