# 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

### 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, Environm ental Risk Branch II: Tom Bailey, PhD, Branch Chief
Environmental Fate and Effects Division (7507P)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 ........................................................................ 694.3 Use of Probit Slope Response Relation ship 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 Redu ctions 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.................................................................................................. 111 6.1 Exposure Assessment Uncertainties ............................................................... 111
6.1.1 Maximum Use Scenario.............................................................................. 111 6.1.2 Crops Not Grown in California................................................................... 111 6.1.3 Aquatic Exposure Modeling of Paraquat.................................................... 111
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...................................................................................................... 124List of Tables

Table 1-1 Effects Determination Summa ry for Paraquat Use and the CRLF..................... 8

Table 1-2 Effects Determination Summary fo r Paraquat Use and CRLF Critical Habitat Impact Analysis .............................................................................................. 10

Table 1-3 Paraquat Use-specific Direct Effects Determinations 1 for the CRLF .............. 11

Table 1-4 Paraquat Use-specific In direct Effects Determinations 1 Based on Effects to Prey ................................................................................................................. 11
Table 2-1 Summary of Paraquat En vironmental Fate Properties ..................................... 19

Table 2-2 Paraquat Uses Assessed for the CRLF 1 ............................................................ 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 Eff ects for Direct and Indirect Effects of Paraquat (in term s 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 Habitat a ...................... 42

Table 3-1 Paraquat Uses and Application Information for the CRLF risk assessment 1 ... 51

Table 3-2 Summary of GENEEC 2 Environmental Fate Data Used for Aquatic Exposure Inputs for Paraquat Endangered Species Assessment for the CRLF 1 Based on the Paraquat Cation......................................................................................... 53

Table 3-3 Aquatic EECs ( μ g/L) for Paraquat Uses in California ..................................... 54

Table 3-4 Input Parameters for Foliar Applic ations 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 Invertebra te 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 Pa raquat 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 Eff ect RQs* for the Aquatic-phase CRLF ............. 74Table 5-2 Summary of RQs* Used to Estimate I ndirect Effects to the CRLF via Effects to Non-Vascular Aquatic Plants (diet of CRLF in tadpole li fe 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 Invertebrate s as Dietary Food Items (prey of CRLF juveniles and adults in aquatic habitats) ......................................................... 76

Table 5-4 Summary of RQs* Used to Estimate I ndirect Effects to the CRLF via Effects to Vascular Aquatic Plants (hab itat of aquatic-phase CRLF) a ............................ 77
Table 5-5 Summary of Acute RQs* Used to Es timate Direct Effects to the Terrestrialphase CRLF (foliar application) From T-REX............................................... 78

Table 5-6 Summary of Chronic RQs* Used to Estimate Direct Effects to the Terrestrialphase 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 E ffects on Small Mammals as Dietary Food Items (foliar application) ....................................................................... 80

Table 5-8 Risk Estimation Summary for Paraqua t - Direct and Indirect Effects to CRLF
......................................................................................................................... 84
Table 5-9 Risk Estimation Summary for Para quat – PCEs of Designa ted Critical Habitat
for the CRLF................................................................................................... 87

Table 5-10a Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for Dietarybased Exposures of the CRLF and its Prey to Paraquat, the weights of small herbivore and insectivore mammals are 15 g. ................................................ 90

Table 5-10b Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for Dietarybased Exposures of the CRLF and its Prey to Paraquat, the weights of small herbivore and insectivore mammals are 35 g. ................................................ 91

Table 5-11a Upper-bound Kene ga Nomogram T-HERPS EE Cs (mg/kg-bw) for Dosebased Exposures of the CRLF and its Prey to Paraquat, the weights of small herbivore and insectivore mammals are 15 g. ................................................ 91

Table 5-11b Upper-bound Kenega NomogramT-HERPS EECs (mg/kg-bw) for Dosebased 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. .......................................................................................... 95Table 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 CRL F 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 CRL F 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 Predicte d Aquatic Spray Drift Distances Using Minimum Application Rate .......................................................................... 108

Table 7-1 Effects Determination Summa ry for Paraquat Use and the CRLF................. 120

Table 7-2 Effects Determination Summary for Paraquat Use and CRLF Critical Habitat Impact Analysis ............................................................................................ 122List of Figures

Figure 2-1 Paraquat Use in Total Pounds per County ...................................................... 24

Figure 2-2 Recovery Unit, Core Area, Critic al Habitat, and Occu rrence Designations for
CRLF............................................................................................................... 30
Figure 2-3 CRLF Reproductive Events by Month........................................................... 31

Figure 2-4 Initial area of c oncern, or “footprint” of pot ential 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 Pesticid e Effects on Aquatic Phase of the CRLF ...... 45

Figure 5-1 Overlap Map: CRLF Habitat a nd 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 Evaluate d 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 Hea lth Effects Data for Paraquat

Attachment I Status and Life Hist ory of the California Red-legged Frog
Attachment II Baseline Status and Cumulati ve Effects for the California Red-legged Frog

### 1.0 Executive Summary

The purpose of this assessment is to evaluate potential direct and i ndirect effects on the California red-legged frog (Rana aurora draytonii ) (CRLF) arising from Federal Insecticide, Fungicide, Roden ticide, Act (FIFRA) regulator y actions regarding use of paraquat dichloride on agricultural and non-ag ricultural 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 Mari ne 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 speci es by U.S. FWS in 1996. The species is endemic to California and Baja California (Mex ico) 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. FW S 1996) in California.

Paraquat dichloride is a contact herbicide that causes desiccation to the plants. It is applied as a flowable solution from an emulsi fiable 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 ca tion. Currently, labeled uses of paraquat include various agricultural uses such as apri cots, loganberries, corn, peanuts, coffee, and lettuce, as well as multiple non-agricultural uses such as airport landing fields, and commercial, industrial and inst itutional premises. The uses considered as part of the
federal action evaluated in this asse ssment are listed in Table 2-2.

There are a total of three PC codes associat ed with paraquat; the PC code for paraquat dichloride is 061601, 061602 for pa raquat bis (methyl sulfate) , and 061603 for paraquat. Paraquat bis (methyl sulfate) is no longer a regi stered product of paraquat, but data from ECOTOX and past assessments including all thr ee PC codes were incorporated into the paraquat cation.

Paraquat is dissipated by rapid adsorption to bi ological materials and clay particles. Due to the apparent adsorption st rength of paraquat, these bound residues do not appear to be environmentally available. Paraquat was show n to be very immobile in soil with batch equilibrium studies conducted on four soil s in the laboratory. Adsorption Kds ranged from 68-50,000. There was no desorption of pa raquat from any of these soils (MRID 40762701). Due to high biological toxicity to plants and animals prior to adsorption, paraquat is subject to spray dr ift concerns. However, paraquat has such extremely high adsorption coefficients, it is not expected to volatilize on ce 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 photodegrad e in aqueous solutions, and is resistant to biotic degradation. Essentially no aer obic or anaerobic microbial degradation of paraquat occurred during the labo ratory studies. In short a nd long-term field dissipation

5studies, paraquat residues were shown to be pe rsistent 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 paraqu at was from the California Department of Pesticide Regulation (CPR) database. Ou t of 399 samples taken from July 2005 to October 2006, only one sample contained pa raquat. The detection, at 0.24 ppb, was below the quantification limit of 1 ppb.

Since CRLFs exist within aquatic and terrestria l habitats, exposure of the CRLF, its prey and its habitats to paraquat are assessed sepa rately for the two habitats. A Tier-I aquatic exposure model, GENEEC2, was used to es timate 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 μg/L. These estimates are supplemented with analysis of available California surface water monitoring data from U. S. Geol ogical Survey’s National Water Quality Assessment (NAWQA) program and the Califor nia Department of Pesticide Regulation. NAWQA did not have any available monitoring data for paraquat in California surface waters or ground water. The maximum c oncentration of paraquat reported by the California Department of Pesticide Regulat ion surface water database (0.24 μg/L) is roughly 3,717 times lower than the highest peak model-estimated environmental
concentration.

To estimate paraquat exposures to the terres trial-phase CRLF, and its potential prey resulting from uses involving paraquat applic ations, the T-REX model is used for spray treatment. The AgDRIFT model is also used to estimate deposition of paraquat on terrestrial and aquatic habita ts from spray drift. The T-HERPS model is used as a refinement tool to explore amphibian-specifi c food intake on potenti al 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 th e 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 informati on for birds, which are used as a surrogate for terrestrial-phase amphibians. Given th at the CRLF’s prey items and designated critical habitat requirements in the aquatic habitat are dependant on the availability of freshwater aquatic invertebrates and aquati c plants, toxicity information for these taxonomic groups is also discussed. In the te rrestrial habitat, indi rect effects due to depletion of prey are assessed by considering eff ects 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.

6QINA (4-carboxyl-1-methylpyridinium) is a degr adate formed by paraquat. However, in the photodegradation in water study the quantity of degradate present was only 6% of the radioactivity of paraqua t after 85 weeks of natural sunli ght irradiation. Due to paraquat degrading very slowly, the minor degrad ate, QINA, does not pose an important
environmental concern and will not be evaluated in this assessment.

Risk quotients (RQs) are derived as quantita tive 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 habi tat via direct toxicity or indirectly based on direct effects to its food supply (i.e., fres hwater invertebrates, algae, fish, frogs, terrestrial invertebrates, and mammals) or ha bitat (i.e., aquatic plants and terrestrial upland and riparian vegetation). When RQs fo r 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 habi tat, 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 adve rsely affect” (LAA) the CRLF. Similarly for critical habitat, additional information is c onsidered to refine th e potential for exposure and effects to distinguish thos e 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 th e CRLF and its critical habitat is presented
in Table 1-1 and Table 1-2 . Use-specific determinations fo r direct and indirect effects to the CRLF are provided in Table 1-3 and Table 1-4 . The non-agricultura l and agricultural uses with the maximum application rates, al ong with the agri cultural 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 regi stered 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

.

7Table 1-1 Effects Determination Summary for Paraquat Use and the CRLF

Assessment

Endpoint Effects
Determination 1 Basis for Determination

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 Ca lifornia. The chronic EECs are all less
than the estimated chronic value derived fr om the ACR. Theref ore, there are no
exceedances of chronic LOCs. Survival, growth, and/or reproduction
of CRLF
individuals NE 1

LAA 1 Terrestrial-phase (Juveniles and Adults) :

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 in all uses ex ceeding 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 mel ons 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 acu te endangered speci es 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. Th e 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 CRL F consuming small insectivore (15g) mammals for the airports/public health, guav a, and ginger uses of paraquat. For medium sized CRLF consuming small in sectivore (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 ex ceedances for medium sized (37g) CRLF consuming large insects or small terre strial-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 medi um 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

8Assessment Endpoint Effects Basis for Determination
Determination 1 large sized (238g) CRLF consuming larg e 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, indicat es 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 (either15g or 35g) using T-HERPS model exceed the chronic species LOC (1.0) for all uses of paraquat. Refined chronic dietarybased 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).
Potential for Indirect Effects Aquatic prey items, aquatic habitat, cover and/or primary productivity

LOCs for non-vascular plants are exceede d for all uses. The non-vascular plant RQs range from 138 for airports, commer cial/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/indu strial 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 comp aring chronic indire ct 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 co mparing chronic direct effects, the
estimated chronic value at 1.89 ppm is not exceeded for any use. LAA 1

LAA 1 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 invertebra tes would not likely adversely affect the CRLF indirectly as food.

For small mammals the acute dose-base d RQs exceed the Agency’s LOC (0.1) for all uses of paraquat, the RQs ranged from 7.63 (airports/public health use/guava) to 0.34 (melons). The ch ronic dose-based RQs exceed the Agency’s LOC (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 LOC (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 amphi bians did not exceed the listed species LOC (0.1) for any use of paraquat. Reduction in amphibian prey items,

9Assessment Endpoint Effects Basis for Determination
Determination 1 specifically other frogs is not affected from paraquat use.

The RQs for non-target terrestrial monocot and dicot plants inhabiting semiaquatic and upland dry areas do not exceed the Agency’s LOC (1.0) for any uses. All aerial applications of paraquat results in spray drift exc eedances 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 cont ent necessary for normal growth and viability of juvenile and adult CRLFs and their food.

LOCs are exceeded for terrestrial ripari an 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 char acteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food source. The RQs for vascular plants did not exce ed the Agency’s LOC (1.0) for any uses of paraquat in California.

The RQs for non-target terrestrial monocot and dicot plants inhabiting semiaquatic 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 exc eedances for dicots (only).

The use of paraquat on most use sites w ill exceed the revised acute dietary- and dose-based LOC and chronic LOC 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.

10Table 1-3 Paraquat Use-specific Direct Effects Determinations 1 for the CRLF

Aquatic Habitat Terrestrial Habitat Use(s) Acute Chronic Acute Chronic AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE),
NONAGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS NE NE LAA LAA

GUAVA NE NE LAA LAA

GINGER NE NE LAA LAA BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER NE NE LAA LAA

CORN (SILAGE) NE NE LAA LAA

MELONS NE NE NLAA 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 Determinations 1 Based on Effects to Prey

Aquatic
Invertebrates Aquatic-phase frogs and fish Terrestrial-phase frogs Small Mammals Use(s) Algae

Acute Chronic Terrestrial
Invertebrates (Acute) Acute Chronic Acute Chronic Acute Chronic

AIRPORTS/LANDING FIELDS, COMMERCIAL/

INSTITUTIONAL/

INDUSTRIAL
PREMISES/
EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC HEALTH USE),
NONAGRICULTURAL

RIGHTS-OF-WAY/

FENCEROWS/
HEDGEROWS LAA NE NE NLAA NE NE LAA LAA LAA LAA

GUAVA LAA NE NE NLAA NE NE LAA LAA LAA LAA

GINGER LAA NE NE NLAA NE NE LAA LAA LAA LAA

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED),
PEPPER LAA NE NE NLAA NE NE LAA LAA LAA LAA

CORN (SILAGE) LAA NE NE NLAA NE NE LAA LAA LAA LAA

MELONS LAA NE NE NLAA NE NE NLAA LAA LAA LAA

1 NE = No effect; NLAA = May affect, not likely to adversely affect; LAA = Likely to adversely affect

11Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Sect ion 7 of the Endangered Specie s Act should be initiated. When evaluating the significance of this ri sk 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 ar ea. In fact, given the assumptions of drift and downstream transport (i.e., attenuation with distance), pes ticide exposure and associated risks to the species and its resour ces 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 re quire information and assessment techniques that are not currently avai lable. Examples of such information and methodology required for this type of an alysis 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 pred ictions of individual effects to the proportion of the population extant with in geographical areas where those effects are predicted. Furthermore, such population information would allow for a more comprehensive eval uation of the significance of potential resource impairment to individuals of the species.

• Quantitative information on prey base requirements for individual aquaticand terrestrial-phase frogs. Wh ile existing information provides a preliminary picture of the types of food sources util ized by the frog, it does not establish minimal requirements to sustain healthy individuals at varying life stages. Such informa tion could be used to establish biologically relevant thresholds of ef fects 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 mortalit y, 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 ex tent to which prey resources may recover is not predictable. An e nhanced 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 descri bed above, a more complete prediction
of effects to individual frogs and potential modificati on to critical habitat.

12

### 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 st ages, habitat components, chemical properties, exposure routes, and endpoints. The structure of th is risk assessment is based on guidance
contained in U.S. Environmental Protecti on Agency's (EPA’s) Guidance for Ecological Risk Assessment (U.S. EPA 1998), the Se rvices’ Endangered Species Consultation Handbook (U.S. FWS/NMFS 1998) and is consis tent with procedures and methodology outlined in the Overview Document (U.S. EP A 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 assessme nt is to evaluate potential direct and
indirect effects on individuals of the fede rally threatened California red-legged frog ( Rana aurora draytonii ) (CRLF) arising from FIFRA regul atory actions regarding use of paraquat on a range of uses such as commer cial 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 eco logical risk assessment has been prepared consistent with a settlement agreement in the case Center for Biol ogical 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 a nd indirect effects to the CRLF and potential effects to its designated critical habitat ar e 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, an d AgDRIFT, all of which are described at length in the Overview Document. Additi onal refinements include the use of the THERPS model and PRZM/EXAMS when appropr iate 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 eviden ce that EPA finds technically appropriate for risk management objectives” (Sec tion 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 a ssessment of effects associated with registrations of paraquat is ba sed on an action area. The actio n 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 acknowle dged 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

13purposes of this assessment, attention will be focused on relevant sections of the action area including those geographic areas associat ed with locations of the CRLF and its designated critical habitat within the stat e 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 phys ical and biological features, (known as primary constituent elem ents or PCEs) essential to the conservation of the listed species. The PCEs for CRLFs ar e aquatic and upland areas where suitable breeding and non-breeding aquatic habitat is located, interspe rsed with upland foraging and dispersal habitat.

If the results of initial scr eening-level assessment methods show no direct or indirect effects (no LOC exceedances) upon individual CRL Fs or upon the PCEs of the species’ designated critical habitat, a “no effect” determination is ma de for use of paraquat as it relates to this species and its designated critic al habitat. If, however, potential direct or indirect effects to individual CRLFs are anticip ated or effects may impact the PCEs of the CRLF’s designated critical habita t, a preliminary “may affect” determination is made for the FIFRA regulatory acti on regarding paraquat.

If a determination is made that use of para quat 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 poten tial for exposure and fo r effects to the CRLF and other taxonomic groups upon which these species depend ( e.g. , aquatic and terrestrial vertebrates and invertebrates, aquatic plan ts, riparian vegetation, etc.). Additional information, including spatial analysis (to de termine the geographical proximity of CRLF habitat and paraquat use sites) and further ev aluation of the potential impact of paraquat
on the PCEs is also used to determine whethe r effects to designated critical habitat may occur. Based on the refined information, the Agency uses the best available information to distinguish those actions th at “may affect, but are not likely to adve rsely 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 di rect and indirect eff ects to listed species provides the basis for an analys is of potential effects on the designated critical habitat. Because paraquat is expected to directly im pact 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 bi ological resource requirements for the listed species associated with the cri tical habitat or impo rtant physical aspects of the habitat that may be reasonably influenced through biological processes). Activities that may modify

14critical habitat are those that alter the PCEs and appreciably diminish the value of the
habitat. Evaluation of actions related to us e 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 ha bitat have been iden tified by the Services
and are discussed further in Section 2.6

.

2.2 Scope

Please see Table 2-2 for a range of current ly 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 la bel 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), accepta ble methods of application, approved use sites, and any rest rictions on how applications may be conducted. Thus, the use or potential use of para quat in accordance with the approved product labels for
California is “the action” relevant to this ecol ogical risk assessment.

Although current registrations of paraquat allow for use nationw ide, 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 a ssociated with paraquat; 061601 for paraquat dichloride, 061602 for paraquat bis (methyl sulfate), and 061603 for paraquat. Paraquat bis (methyl sulfate) is no longer a register ed product of paraquat, and th e 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 a nd in past assessments. For our assessment,
data from all three PC codes and chemical s were incorporated, and converted to the paraquat cation.

QINA (4-carboxyl-1-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 afte r 85 weeks of natural su nlight 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 mixtur es 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 mo re than one active ingredient), each active ingredient is subj ect 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 contai ning more than one active ingredient, they may be used qualitatively or quantitatively in accordance with the Agency’s Overview

15Document and the Services’ Evaluation Memorandum (U.S., EPA 2004; USFWS/NMFS 2004).

Paraquat has registered products that contain multiple active i ngredients. The results of available toxicity data for mi xtures 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 pa raquat when mixed with other chemicals. According to the available open literature data, other pesticides may combine with paraquat to produce additive, and/or antagoni stic toxic effects. Mixtures included paraquat with linuron, and para quat with copper sulfate.

2.3 Previous Assessments

Paraquat was discovered in 1882 and was regist ered in England in 1962 prior to being registered in the United Stat es in 1964 for use as a cont act herbicide to control or suppress a broad spectrum of emerged weed s under the name paraquat dichloride. The Agency classified paraquat dichloride as a restricted use pestic ide due to high acute toxicity to animals and people in 1978 (February 9, 1978 (43 FR 5782)). Under the restricted use classification, only certified a pplicators or applicators working under their direct supervision, are author ized to apply paraquat dich loride end-use products.

Also in 1978, paraquat dichloride was accepte d 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 treatmen t, chronic effects, reproductive effects, oncogenicity (data gap), mutage nicity (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 sin ce 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 th e potential acute effects to applicators.

In June 1987, a Registration Standard for pa raquat dichloride wa s issued (NTIS#PB88- 217005) in which the Agency evaluated the stud ies submitted as a result of the previous DCI. In 1991, additional data were reque sted and evaluated for use in the 1997 Reregistration 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 gi n 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 lb cation/A to 1.0 lb cation/A.

16o Broadcast applications with backpa ck sprayers (non-spot) should not exceed the application rate 0.625 lb 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 lbs cation/gallon.

• Remove the plastic acid bottle and tree inj ection directions for use from the resin soaking sections of all pa raquat dichloride labels.

• Include the hazard statement “Paraquat dich loride is toxic to non-target crops and plants if off-target movement occurs. Ex treme 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 requireme nts and remove any conflicting PPE requirements.

o For multiple-active-ingredient end-use products that contain paraquat, the handler personal protective equipmen t/engineering cont rol requirements
set forth in this section must be compared to the requirements on the current labeling and the more pr otective must be retained.

• Implement best management practices (B MPs) to reduce spray drift, including BMPs for controlling droplet size, bo om length, application height, swath adjustment, wind, temperature and humi dity, temperature inversions, and
sensitive areas.

• Implement use of PPE and engineering controls for workers.

A drinking water assessment was performe d March 15, 2000, which determined paraquat under most circumstances was unlikely to infiltra te past the first few centimeters of soil,
or to move off-field dissolved in runoff. Yet, monitoring data has demonstrated that despite its apparent immobili ty, paraquat can reach ground wate r. 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 μ g/L. These wells were located in coarse-grained glacial soils that are extremely permeable, with saturate d hydraulic condu ctivities on the order of 20,000 ft/day (T.Mesko, USGS, personal communication). Detections were also reported in household wells at c oncentrations ra nging up to 1.52 μ g/L (Mostaghimi 

### et al. 1998). Data in Smith and Mayfield (1978) suggest s that the applicati on of fertilizer may enhance the mobility of paraquat. The extremel y 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 appropr iate for paraquat dichloride. 

### In most circumstances, the levels of paraquat residues in surface or gr ound 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 para quat residues present in the raw water. Residues of paraquat in dri nking 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 μ g/L for human exposure assessment.

17On March 30, 2006, a risk assessment for propo sed new uses of paraquat dichloride on cantaloupe, cucumber, summer squash, gi nger, okra, onion, tanier, and wheat was performed. With the exception of wheat (whe re 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 lbs a.i./A per season will be allowed. The exception is for the proposed use on ginger, for which a maximum of 6.0 lbs a.i. /A per year is dire cted. The 2006 risk
assessment concluded that these new uses are e xpected to have acute toxicological effects to terrestrial aquatic wildlife, aquatic pl ants, 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 regist ration 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 dissipati on of paraquat is adsorption to soil clay particles. Paraquat does not hydrolyze, doe s not photodegrade in aqueous solutions, and is resistant to microbial degradation under ae robic and anaerobic c onditions. Essentially no microbial degradation of paraquat was s een after 180 days of aerobic incubation or after 60 days of anaerobic incubatio n following a 30 day aerobic incubation.

Paraquat was shown to be very immobile in so il with batch equilibrium studies conducted on four soils in the laboratory. High rates of pa raquat 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 paraqua t, 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, para quat would not be expe cted to volatilize once

18applied to the soil, but spray drift could potentially be an issu e since paraquat is extremely biologically active and toxic to plants and animals.

In short and long term field dissipation studies, paraquat re sidues 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 undergoisotopic exchange when soil samples were shaken with a highly concentrated, nonlabeled 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 ca rried 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 envi ronment 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 so ils with very low clay content.

In previous reviews (reviews by Jordan, 2/14/1986), a minor photodegradate, 4-carboxyl1-methylpyridinium (QINA) which comprised 6% of applied radioac tivity 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 im portant environmental concern.

Table 2-1 lists the environmental fa te 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 Value (units) Major Degradates Minor Degradates MRID # Study Status

Hydrolysis Stable at pH 5, 7, 9 No degradates reported Upton et al., 1985 Acceptable

Direct Aqueous Photolysis Stable No degradates reported

CO 2 (0.15%)

4-carboxyl-1- methylpyridinium (QINA) (6%) MRID
40562301

(Jordan, 1986) Acceptable

Supplemental

Soil Photolysis Stable No degradates reported MRID
146807 Acceptable

19Study Value (units) Major Degradates Minor Degradates MRID # Study Status

Aerobic Soil
Metabolism Stable Did not degrade. No degradates reported. MRID
41319301 Acceptable

Anaerobic Soil
Metabolism Stable No degradates reported. 0.29% uncharacterized radioactivity. MRID
41319302 Acceptable

Anaerobic Aquatic
Metabolism No Study No Study No Study No Study

Aerobic Aquatic
Metabolism <2 weeks (only represents water phase. Did not measure amount of paraquat sorbed to the soil) No degradates reported MRID 00055093 Supplemental

K d-ads / K d-des (mL/g)

K oc- ads / K oc-des (mL/g) 68 – 50,000 (no measureable correlation with % OC)

15,473 to 1,000,000 No degradates reported MRID
40762701

http://www

.ermanz.go vt.nz/consu
ltations/cei r/t.pdf Acceptable

Supplemental

Terrestrial
Field Dissipation Half-life not calculated; however, cited
reference indicates a half-life of > 10

years No degradates reported. MRID
41293202

42802101

42738701

42738702

42802102 Acceptable

Aquatic Field Dissipation No Study No Study No Study No Study

2.4.2 Environmental Transport Assessment

Potential transport mechanisms include pesticid e spray drift, and sec ondary drift of soilbound 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 drif t (AgDRIFT) is used to determine potential exposures to aquatic and terres trial organisms via spray drift. The distance of potential impact away from the use sites (action area) is determined by the distance required to fall below the LOC for airports/commercial/public health areas (non-agricultural use) and guava (agricultural use). These uses have th e greatest application rate, greatest number of applications per season, and the leas t amount of time between applications.

Due to model limitations, it may not be possi ble to provide a quantitative estimate of exposure with known uncertainty, beyond the range of AgDRIFT.

202.4.2 Mechanism of Action

Paraquat dichloride is a quate rnary nitrogen compound widely used for broadleaf weed
control. It is a fast -acting contact herb icide 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 gree n tissue. It is highl y toxic (EPA toxicity class I) but readily immobilized. Paraquat is quickly absorbed by living (esp. healthy) plant tissue and produces superoxi des during photosynthesis, whic h destroy plant cells. It is less effective on dry, drought-stresse d, woody, or fully mature plants.

2.4.3 Use Characterization

Analysis of labeled use information is the cr itical first step in evaluating the federal action. The current label for paraquat represen ts the FIFRA regulator y action; therefore, labeled use and application rates specified on th e 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 m odeling scenarios and inputs.

There are a few uses that are not being asse ssed because they are e ither restricted in California or the crop is not grown in Californi a. The following uses will not be assessed because they are not grown in California: co coa, 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 beca use 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, garban zos, 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, garban zos, guar, lentils, lupine, pastures, and dried and southern peas.

The labels listed below are Section 24c labe ls for paraquat in ot her 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

21Table 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 CRLF 1

Use (Application Method) Max. Single Appl. Rate

(lb ai/A) Max. Number of Application per
Year Application
Method

ACEROLA (WEST INDIES CHERRY), APRICOT, CHERRY, NECTARINE, PEACH, PLUM, KIWI FRUIT DECIDUOUS FRUIT TREES (UNSPECIFIED), FOREST TREES (SOFTWOODS - CONIFERS) 1.0 3 Ground

Aircraft

AGRICULTURAL FALLOW/IDLELAND 1.0 5 Ground AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE), NONAGRICULTURAL
RIGHTS-OF-WAY/FENCEROWS/ HEDGEROWS 1.0 10 Ground

Aircraft ALFALFA, BROCCOLI, ENDIVE (ESCAROLE),
LETTUCE Ground

RHUBARB 1.0 2 Ground 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 1.0 5 Ground

ARTICHOKE Ground

Aircraft CABBAGE, CABBAGE - CHINESE, COLLARDS, 1.0 3 Ground

Aircraft ASPARAGUS, RICE, BARLEY, SAFFLOWER (UNSPECIFIED), SMALL GRAINS (UNSPECIFIED), SORGHUM, WHEAT, CAULIFLOWER, CORN (UNSPECIFIED)/ SWEET/ FIELD/ POP, SUNFLOWER, COTTON (UNSPECIFIED) 1.0 3 Ground

22Use (Application Method) Max. Single Appl. Rate

(lb ai/A) Max. Number of Application Application per Method
Year

Ground 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) Aircraft

GARLIC, ONION 1.0 1 Ground BLACKBERRY, BOYSENBERRY, ELDERBERRY, GOOSEBERRY, HUCKLEBERRY, LOGANBERRY, RASPBERRY (BLACK - RED), BLUEBERRY,
CURRANT 1.0 5 Ground

Aircraft BRUSSELS SPROUTS, KALE, VEGETABLES (UNSPECIFIED), KOHLRABI 1.0 3 Ground CITRUS HYBRIDS OTHER THAN TANGELO, TANGELO, CRABAPPLE, LOQUAT, QUINCE,
MAYHAW (HAWTHORN) 1.0 5 Ground

CORN (SILAGE), STRAWBERRY

GUAR Ground

Aircraft

PASTURES, POTATO - WHITE/IRISH 0.5 3 Ground

Aircraft

GHERKIN, SUGAR BEET Ground

GRASSES GROWN FOR SEED 1.0 3 Ground

GINGER 1.0 6 Ground

GUAVA 1.0 10 Ground

Aircraft

MELONS 0.3 1 Ground

Aircraft

MINT/PEPPERMINT/SPEARMINT 0.8 2 Ground

OKRA 1.0 1 Ground

OLIVE 1.0 4 Ground

23Use (Application Method) Max. Single Appl. Rate

(lb ai/A) Max. Number of Application Application per Method
Year

PASSION FRUIT (GRANADILLA) 1.0 10 Ground

PEANUTS (UNSPECIFIED) 0.3 1 Ground

PERSIMMON 0.9 5 Ground

1 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 fr om a U.S. Geological Survey (USGS), National Water Quality Assessment Program (NAWQA) website.

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, Pendimeh talin, Myclobutanil, Prometryn, Dicofol, Alachlor, and Endosulfan in California in Support of a Red Legged Frog Endangered

24Species Assessment, 04 February 2009) usi ng state-level usage data obtained from
USDA-NASS 1 , Doane ( www.doane.com ; the full dataset is not provided due to its proprietary nature) and the Ca lifornia’s Department of Pes ticide Regulation Pesticide Use Reporting (CDPR PUR) database 2 . CDPR PUR is consider ed 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 th is California-specific assessment were generated using CDPR PUR data. Eight year s (1999-2006) of usage data were included in this analysis. Data from CDPR PUR we re 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-lev el 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 leve l usage data that were calculated include: average annual pounds applied, average annua l 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 usag e for all California use sites is provided below in Table 2-3 . The uses range from commercial and industrial non-agricultural uses to agricultu ral uses such as fruits, vege tables, feed for livestock, and ornamental shrubs, flowers, and trees. Th e uses considered in this risk assessment represent all currently registered uses accordi ng 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 ei ther historic uses that ha ve been canceled, mis-reported uses, or mis-use. Historical uses, mis-repor ted uses, and misuse are not considered part of the federal action and, th erefore, are not considered in this assessment.

Table 2-3 Summary of California Departme nt of Pesticide Registration (CDPR) Pesticide Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered Paraquat Uses

Site Name Average
Pounds All
Uses Avg App
Rate All

Uses Avg
95th%

App
Rate Avg
99th%

App
Rate Avg Max App
Rate

ALFALFA 3,034.6 0.7 1.0 1.3 2.4

ALMOND 8,778.1 0.9 1.4 2.2 5.5

APPLE 234.2 0.8 1.6 2.5 3.2

APRICOT 79.6 0.9 1.4 2.1 3.0

ARTICHOKE, GLOBE 432.8 0.9 1.1 1.1 2.5

ASPARAGUS 189.8 1.0 1.3 1.3 1.3

AVOCADO 31.1 0.9 2.0 2.4 2.4

1 United States Depart of Agriculture (USDA), Natio nal Agricultural Statistics Service (NASS) Chemical Use Reports provide summary pesticide usage statistic s for select agricultural use sites by chemical, crop
and state. See http://www.usda.gov/nass/pubs/estindx1.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

.

25Site Name Average
Pounds All
Uses Avg App
Rate All

Uses Avg Avg
95th% 99th%

App
Rate App Avg Max App
Rate Rate

BARLEY 21.2 0.7 0.8 0.8 0.8

BEAN, DRIED 43.4 0.9 1.1 1.1 1.1

BEAN, SUCCULENT 46.6 1.1 1.5 2.5 2.9

BEAN, UNSPECIFIED 11.9 1.0 1.8 1.8 1.8

BLACKBERRY 18.1 0.8 1.0 4.2 4.2

BLUEBERRY 317.0 0.9 2.2 2.6 2.6

BOYSENBERRY 8.8 0.7 1.2 1.2 1.2

BROCCOLI 59.3 0.9 1.2 1.2 1.2

BRUSSELS SPROUT 0.2 1.3 1.3 1.3 1.3

BUILDINGS/NON-AG OUTDROOR 2.9 1.3 1.3 1.3 1.3

CABBAGE 9.6 1.1 1.5 1.5 1.5

CANTALOUPE 57.6 0.8 1.1 1.1 1.1

CARROT 46.7 1.1 1.1 1.1 1.1

CAULIFLOWER 20.5 1.1 1.2 2.2 2.2

CHERRY 439.4 0.9 1.6 2.3 3.5

CHESTNUT 16.3 0.7 1.3 1.3 1.3
CHINESE CABBAGE (NAPPA) 21.5 1.0 1.1 1.1 1.1

CHRISTMAS TREE 2.2 0.9 0.9 0.9 0.9

CITRUS 24.9 0.8 1.1 1.3 1.3

COLLARD 8.5 1.0 1.0 1.0 1.0
CORN (FORAGE - FODDER) 576.1 1.0 1.3 1.4 2.4

CORN, HUMAN CONSUMPTION 26.6 1.5 1.6 1.6 1.6

COTTON 15,389.3 0.5 1.0 1.1 2.6

CUCUMBER 48.6 1.0 1.8 2.0 2.0

DITCH BANK 9.7 2.3 4.8 4.8 4.8

EGGPLANT 19.5 1.1 1.6 1.6 1.6
ENDIVE (ESCAROLE) 2.2 1.4 1.4 1.4 1.4

FIG 56.6 0.8 1.1 1.3 1.3

FORAGE HAY/SILAGE 7.4 0.7 0.9 0.9 0.9

GARLIC 27.2 1.0 1.0 1.0 1.0

GRAIN 7.4 0.6 0.6 0.6 0.6

GRAPE 4,519.4 0.9 1.3 1.5 2.9

GRAPE, WINE 2,574.0 0.7 1.2 1.6 2.6

GRAPEFRUIT 22.6 0.8 1.2 3.1 3.1

GRASS, SEED 23.1 1.0 1.0 1.0 1.0

INDUSTRIAL SITE 0.2 0.9 0.9 0.9 0.9

KALE 0.4 1.2 1.2 1.2 1.2

KIWI 95.0 1.8 3.9 5.2 5.2

26Site Name Average
Pounds All
Uses Avg App
Rate All

Uses Avg Avg
95th% 99th%

App
Rate App Avg Max App
Rate Rate

KOHLRABI 0.6 1.3 1.3 1.3 1.3

LANDSCAPE MAINTENANCE 6.6 1.7 2.2 2.2 2.2

LEMON 96.8 0.9 1.5 3.7 3.7

LETTUCE, HEAD 320.1 1.3 1.9 2.5 3.9

LETTUCE, LEAF 57.4 1.1 1.5 1.5 1.5

MELON 41.8 0.9 1.0 1.0 1.0

MINT 373.6 0.7 0.9 2.6 2.9

NECTARINE 894.2 0.7 1.2 1.9 2.8

N-GRNHS FLOWER 2.8 1.2 1.5 1.6 1.6

N-GRNHS PLANTS IN CONTAINERS 5.0 14.6 28.0 28.0 28.0

N-OUTDR FLOWER 10.7 0.8 1.1 2.7 2.7

N-OUTDR PLANTS IN CONTAINERS 28.5 1.4 2.2 2.8 2.8

N-OUTDR TRANSPLANTS 15.1 0.9 3.0 3.5 3.5

OLIVE 132.8 0.9 1.9 2.2 2.5

ONION, DRY 86.1 1.1 1.4 1.5 1.5

ONION, GREEN 11.9 1.1 1.4 1.4 1.4

ORANGE 575.9 1.1 1.6 3.0 4.9

ORCHARD FLOOR 2.7 0.9 1.1 1.1 1.1

PASTURELAND 15.2 0.8 1.1 1.1 1.1

PEACH 747.5 0.9 1.5 1.8 3.2

PEANUT 1.3 1.2 1.2 1.2 1.2

PEAR 139.0 0.8 1.3 2.6 3.2

PEAS 8.8 1.2 1.6 1.6 1.6

PECAN 26.1 1.1 2.8 2.8 2.8

PEPPER, FRUITING 125.1 1.0 2.1 2.3 2.4

PEPPER, SPICE 411.3 1.0 1.8 1.8 2.4

PERSIMMON 3.3 0.9 1.2 1.2 1.2

PISTACHIO 1,511.7 0.8 1.3 2.1 4.8

PLUM 727.8 0.7 1.1 1.3 2.5

POTATO 46.3 1.0 1.2 1.7 1.7

PRUNE 515.7 0.8 1.3 2.1 3.3

PUMPKIN 1.3 0.9 0.9 0.9 0.9

RANGELAND 27.3 0.6 0.6 0.6 0.6

RASPBERRY 67.7 1.1 1.5 2.3 3.7

REGULATORY PEST CONTROL 5.1 0.7 0.7 0.7 0.7

RESEARCH COMMODITY 9.7 0.8 1.5 2.4 2.4

RHUBARB 3.1 1.3 1.3 1.3 1.3

RICE 58.8 1.3 2.0 2.0 2.0

27Site Name Average
Pounds All
Uses Avg App
Rate All

Uses Avg Avg
95th% 99th%

App
Rate App Avg Max App
Rate Rate

RIGHTS OF WAY 407.3 0.9 1.0 1.0 1.0

SAFFLOWER 98.1 0.9 1.2 1.9 1.9
SORGHUM (FORAGE - FODDER/ MILO) 10.6 0.4 0.5 0.5 0.5

SOYBEAN 9.4 0.5 0.5 0.5 0.5
SQUASH 14.1 1.1 1.3 1.3 1.3
SQUASH, SUMMER 9.9 1.6 4.3 4.3 4.3
SQUASH, WINTER 2.6 0.8 0.9 0.9 0.9
SQUASH, ZUCCHINI 6.5 0.9 1.0 1.0 1.0

STRAWBERRY 75.1 0.9 1.6 2.5 2.9

STRUCTURAL PEST CONTROL 1.4 0.5 0.5 0.5 0.5

SUDANGRASS 10.2 0.7 0.8 0.8 0.8

SUGARBEET 61.2 1.0 1.2 1.2 1.2

SUNFLOWER 326.7 0.8 1.9 2.7 2.7

TANGELO 15.9 1.1 1.7 1.7 1.7

TOMATO 270.0 0.9 1.2 1.7 1.8

UNCULTIVATED AG 394.1 1.0 1.9 2.4 2.7

UNCULTIVATED NON-AG 60.8 1.3 1.9 4.8 4.9

VEGETABLE 4.8 0.7 0.9 0.9 0.9

VERTEBRATE CONTROL 3.2 0.2 0.5 0.5 0.5

WALNUT 796.6 0.8 1.3 1.9 4.0

WATERMELON 43.1 1.2 2.4 2.4 2.4

WHEAT 41.2 0.8 1.0 1.0 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 subspe cies of the red-legged frog and is the largest native frog in the western United St ates (U.S. FWS 2002). A brief summary of information regarding CRLF distribution, repr oduction, 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 speci fic threats to the CRLF is provided in
Attachment I.

Final critical habitat for the CRLF was de signated by U.S. FWS on April 13, 2006 (U.S. FWS 2006; 71 FR 19244-19346). Further informa tion on designated cri tical 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 Ca lifornia including the Central Valley and both coastal and

28interior mountain ranges (U.S. FWS 1996). It s range has been reduced by about 70%, and the species currently resides in 22 c ounties 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 Si erra Nevada (5-6 populations), and in
southern California south of Santa Barbara (two populations) (Felle rs 2005a). Relatively larger numbers of CRLFs are located be tween Marin and Santa Barbara Counties (Jennings and Hayes 1994). A total of 243 st reams or drainages are believed to be currently occupied by the sp ecies, with the greatest numbers in Monterey, San Luis Obispo, and Santa Barbara counties (U.S. FWS 1 996). 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 with in California is addressed in this assessment using four categories of location including r ecovery units, core areas, desi gnated critical habitat, and
known occurrences of the CRLF reported in the California Natural Diversity Database (CNDDB) that are not included within core ar eas and/or designated critical habitat (see Attachment I). Recovery units, core ar eas, and other known occurrences of the CRLF
from the CNDDB are described in further deta il 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 conserva tion needs and management strategies. The recovery unit is primarily an administra tive 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 genera lly contained within th e core areas, although
a number of critical habitat units are outside the boundaries of core areas, but within the boundaries of the recovery units. Additiona l 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 r ecovery 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 repositor y for historical and current species location sightings. Information regarding known occurrences of CRLFs outside of the currently occupied core areas and designated critical ha bitat 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.

29Recovery Units 1. Sierra Nevada Foothills and Central Valley 2. North Coast Range Foothills and Western Sacramento River Valley 3. North Coast and North San Francisco Bay 4. South and East San Francisco Bay
5. Central Coast 6. Diablo Range and Salinas Valley 7. Northern Transverse Ranges and Tehachapi
Mountains 8. Southern Transverse and Peninsular Ranges

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. Piney 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 19. Watsonville Slough-Elkhorn Slough
20. Carmel River – Santa Lucia 21. Gablan Range 22. Estero Bay 23. Arroyo Grange River
24. Santa Maria River – Santa Ynez River 25. Sisquoc River
26. Ventura River – Santa Clara River 27. Santa Monica Bay – Venura Coastal Streams
28. Estrella River
29. San Gabriel Mountain* 30. Forks of the Mojave*
31. Santa Ana Mountain*
32. Santa Rosa Plateau 33. San Luis Ray*
34. Sweetwater* 35. Laguna Mountain*

* Core areas that were historically occupied by the California red-legged frog are not included in the map Recovery Units 1. Sierra Nevada Foothills and Central Valley 2. North Coast Range Foothills and Western Sacramento River Valley 3. North Coast and North San Francisco Bay 4. South and East San Francisco Bay
5. Central Coast 6. Diablo Range and Salinas Valley 7. Northern Transverse Ranges and Tehachapi
Mountains 8. Southern Transverse and Peninsular Ranges

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. Piney 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 19. Watsonville Slough-Elkhorn Slough
20. Carmel River – Santa Lucia 21. Gablan Range 22. Estero Bay 23. Arroyo Grange River
24. Santa Maria River – Santa Ynez River 25. Sisquoc River
26. Ventura River – Santa Clara River 27. Santa Monica Bay – Venura Coastal Streams
28. Estrella River
29. San Gabriel Mountain* 30. Forks of the Mojave*
31. Santa Ana Mountain*
32. Santa Rosa Plateau 33. San Luis Ray*
34. Sweetwater* 35. Laguna Mountain*

* Core areas that were historically occupied by the California red-legged frog are not included in the map

Figure 2-2 Recovery Unit, Core Are a, Critical Habitat, and Occurrence Designations for CRLF

302.5.2 Reproduction

CRLFs breed primarily in ponds; however, they may also breed in quiescent streams, marshes, and lagoons (Fellers 2005a). Accord ing to the Recovery Plan (U.S. FWS 2002), CRLFs breed from November through late April. Peaks in spawning activity vary geographically; Fellers (2005b) re ports peak spawning as early as January in parts of coastal central California. Eggs are fertili zed 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 appr oximately 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 re quire 11 to 28 weeks to me tamorphose into juveniles (terrestrial-phase), typica lly between May and Septem ber (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.

D N O S A J J M A M F J

Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter) Orange = Adults and juveniles can be present all year Young Juveniles D N O S A J J M A J F M

Light Blue = Breeding/Egg Masses
Green = Orange = Adults and juveniles can be present all year Tadpoles (except those that over-winter) Young Juveniles

Figure 2-3 CRLF Reproduc tive Events by Month

2.5.3 Diet

Although the diet of CRLF aquatic-phase la rvae (tadpoles) has not been studied specifically, it is assumed that their diet is si milar to that of other frog species, with the aquatic phase feeding exclusiv ely 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 and McDiarmid 1999).

Juvenile and adult CRLFs forage in aquatic a nd terrestrial habitats, and their diet differs greatly from that of larvae. The main food source for juvenile aquatic- and terrestrialphase CRLFs is thought to be aquatic a nd terrestrial invert ebrates found along the shoreline and on the water surface. Hayes a nd Tennant (1985) report, based on a study

31examining the gut content of 35 juvenile a nd adult CRLFs, that the species feeds on as many as 42 different invertebrate taxa , including Arachnida, Amphipoda, Isopoda, Insecta, and Mollusca. The most commonly obs erved prey species were larval alderflies ( Sialis cf. californica ), 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 c onsists of vertebrates such as mice, frogs, and fish, although aquatic and terrestrial inve rtebrates were the most numerous food items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at night; for juveniles feeding o ccurs during the day and at ni ght (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 lif e cycle. CRLF use of their environment varies; they may complete their entire life cycl e 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 ha bitats 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, shadin g, and water of modera te depth are habitat features that appear especially impor tant for CRLF (Hayes and Jennings 1988). Breeding sites include streams, deep pools, b ackwaters 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 be en 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 sh allower pools (0.26 – 0.5 m) (Reis 1999). Data
indicate that CRLFs do not fre quently 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 requirement s within artificial ponds (U.S. FWS 2002). Adult CRLFs use dense, shrubby, or emergent vegetation closely associated with deep-water pools bordered with cattail s and dense stands of overhanging vegetation ( http://ecos.fws.gov/speciesProfi le/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 resti ng, feeding, and dispersal. The foraging quality of the riparian habitat depends on moisture, composition of the plant community, and presence of pools and backwa ter 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 hab itat to forage and seek othe r suitable habitat under downed

32trees or logs, industrial debr is, and agricultural features (U.S. FWS 2002). According to Jennings and Hayes (1994), CRLFs also use sm all mammal burrows and moist leaf litter as habitat. In addition, CRLFs may also use larg e cracks in the bottom of dried ponds as refugia; these cracks may provide moisture for individuals avoidi ng predation and solar exposure (Alvarez 2000).

2.6 Designated Critical Habitat

In a final rule published on April 13, 2006, 34 se parate 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 rela tive to U.S. FWS-desi gnated 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 th e geographic area occupi ed by the species at the time of the listing where the physical and biological features necessary for the conservation of the species exis t, and there is a need for special management to protect the listed species. It may also include ar eas outside the occupied area at the time of listing if such areas are ‘essential to the c onservation of the species.’ All designated critical habitat for the CRLF was occupied at the time of listing. Cr itical habitat receives protection under Section 7 of the ESA (Section 7) through prohibition against destruction
or adverse modification with regard to actions carried ou t, 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 desi gnation, the habitat must be ‘essential to the conservation of the species.’ Critical hab itat designations identify, to the extent known using the best scientific a nd commercial data available, habitat areas that provide essential life cycle needs of the species or areas that contai n 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 a nd for normal behavior; food, water, air, light, minerals, or other nutritional or physiolo gical requirements; cove r or shelter; sites for breeding, reproduction, rearing (or developmen t) of offspring; a nd habitats that are protected from disturbance or are represen tative of the histor ic geographical and ecological distributions of a species. The de signated 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 thes e habitat types is provided in Attachment I.

Occupied habitat may be include d 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 su fficient to conserve the species. Critical

33habitat is designated outside the geographic area presently occupied by the species only when a designation limited to its present ra nge would be inadequa te to ensure the conservation of the species. For the CRLF, all designated critical habi tat units contain all four of the PCEs, and were occupied by th e 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 ru le exempting routine ranching activities
associated with livestock ranc hing from incidental take prohi bitions. The purpose of this exemption is to promote the conservation of ra ngelands, 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 fo r a full explanation on this special rule.

U.S. FWS has established adverse modificati on standards for designated critical habitat (U.S. FWS 2006). Activities that may destr oy or adversely modify critical habitat are those that alter the PCEs and jeopardize th e continued existence of the species. Evaluation of actions related to use of para quat 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 critic al habitat and theref ore result in adverse effects to the CRLF include, but are not limited to the following:

(1) Significant alteration of water chemistr y or temperature to levels beyond the
tolerances of the CRLF that result in di rect or cumulative adverse effects to individuals and their life-cycles. (2) Alteration of chemical characteristics n ecessary 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 fora ging 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 deposit ion to levels that would adversely affect their ability to co mplete their life cycles. (4) Significant alteration of ch annel/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 coul d 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 aes tivating 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 para quat is expected to directly impact living organisms within the action area, critical ha bitat 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 biological ly mediated processes.

342.7 Action Area

For listed species assessment purposes, the action area is considered to be the area affected directly or indirec tly by the federal action and not merely the immediate area involved in the action (50 CFR 402.02). It is recognized th at 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 agri cultural uses. However, the scope of this
assessment limits considerati on of the overall action area to those portions that may be applicable to the protection of the CRLF and its designated critical ha bitat within the state of California. The Agency’s approach to defining the action area unde r the provisions of the Overview Document (U.S. EPA 2004) cons iders 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, attenti on will be focused on the footprint of the action (i.e., the area where pesticide applica tion occurs), plus all areas where offsite transport (i.e., spray drift, downstream dilu tion, etc.) may result in potential exposure
within the state of California th at 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 m easures of ecological e ffect that define the action area include any direct a nd indirect toxic effect and any potential modification of its critical habitat, including reduction in su rvival, growth, and fec undity as well as the
full suite of sublethal effects available in the effects literature. Th erefore, the action area extends to a point where environmental expos ures are below any m easured lethal or sublethal effect threshold for any biological entity at the whole organism, organ, tissue,
and cellular level of or ganization. In situations where it is not possible to determine the threshold for an observed effect, the action ar ea is not spatially limite d 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 act ion. The federal action is de fined by the currently labeled uses for paraquat. An analysis of labeled us es and review of avai lable product labels was completed. Several of the currently labeled us es are special local needs (SLN) uses or are restricted to specific states other than Califor nia and are excluded from this assessment. In addition, a distinction has been made be tween food use crops a nd those that are nonfood/non-agricultural uses. The agricultural uses as well as the non-agricultural and nonfood uses relevant to the CRL F 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 applic ation 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 with in the land cover areas that represent the

35labeled uses described above. A map represen ting 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 depict ed by the following land cover types: cultivated crops (51%), developed/high in tensity (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 ar eas used for the production of annual crops, such as corn, soybeans, vegetables, and cott on. This class also in cludes all land being actively tilled. Developed/high intensity areas are where people reside, or work in high numbers. The impervious surfaces acc ount for 80-100% of the total cover. Developed/low intensity areas include a mixture of construc ted materials and vegetation with impervious surfaces accounting for 20-40% of total cover. Developed/open space
includes areas with a mixture of constructed ma terials, but mainly vegetation in the form of lawn grasses. Impervious surfaces account for lass than 20% of to tal cover. Forest represents deciduous, evergreen, and mixed ve getation. 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, past ure/hay represents areas of grasses, legumes, or grass-legume mixtures planted for livestock grazing or the production of seed or hay crops. Typically, past ure/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 applie d in 55 out of 58 counties in California per the CAPUR database. In addition, paraquat has both a wi de range of agricultu ral and non-agricultural uses throughout the state. Likewise, when modeling with AgDRIFT, 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.

36Figure 2-4 Initial area of concern, or “f ootprint” of potential use, for Paraquat

37Once the initial area of concern is defined, the next step is to define the potential boundaries of the action area by determining the ex tent of offsite tran sport via spray drift and runoff where exposure of one or more ta xonomic groups to the pe sticide 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 re duction in survival, growth, reproduction, and the entire suite of sublethal effects from va lid, peer-reviewed studies.

The primary route of environmental dissipati on of paraquat dichloride is adsorption to biological material and soil clay particles. Paraquat dichlori de has been shown to adsorb to clay crystalline lattices with no appare nt 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 potential ly be a problem because paraquat is very biologically active and to xic 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 (EC 25 = 0.014 lb cation/A) was used to represent the non-liste d plant species. The AgDRIF T results suggest that ground applications for non-listed plants need a sp ray drift buffer distance of approximately 361 feet. However, aerial applic ations yielded a spray drift bu ffer 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. Furt her detail on the spray drift analysis is provided in Section 5.1.4.1.

In addition to the buffered area from the spra y drift analysis, the final action area also considers the downstream extent of paraquat that exceeds the LOC (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 ha s historically been us ed on a wide variety of agricultural and non-agricultural uses in approximately 55 counties in California. As a result, since paraquat has both agri cultural and non-agricultural uses, it is applied in 55 of 58 counties, and has a buffer zone greater than 1,000 feet for aerial a pplication, with such widespread use the action area is th e entire state of California.

382.8 Assessment Endpoints and Measures of Ecological Effect

Assessment endpoints are defined as “explicit expressions of the ac tual 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 upla nd 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 a ddition, potential effects to critical habitat is assessed by evaluating potential effects to PCEs, which are compone nts of the habitat areas that provide essential life cycle ne eds of the CRLF. Each assessment endpoint requires one or more “measures of ecological e ffect,” 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 ar e 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 indi rect 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 endpoint s for which there is a scientif ically 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 ecologica l effect selected for each ta xonomic 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 po tential assessed direct and indirect CRLF risks associated with expos ure to paraquat is pr ovided in Table 2-4.

3 U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.

39Table 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 Effects 4 Aquatic-Phase CRLF (Eggs, larvae, juveniles, and adults) a Direct Effects 1. Survival, growth, and reproduction of
CRLF 1a. Rainbow trout ( Oncorhynchus mykiss ) LC 50 1b. No Chronic Fish Data Indirect Effects and Critical Habitat Effects 2. Survival, growth, and reproduction of
CRLF individuals via indirect effects on aquatic prey food supply ( i.e., fish, freshwater invertebrates, non-vascular plants) 2a. Algae ( Navicula pelliculosa ) EC 50 2b. No Chronic Invertebrate Data 2c. Water flea ( Daphnia magna ) EC 50 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) 3a. Duckweed ( Lemna gibba ) EC 50 3b. Algae ( Navicula pelliculosa ) EC 50

4. Survival, growth, and reproduction of CRLF individuals via effects to riparian vegetation 4a. Monocots: Seedling Emergence, Vegetative Vigor EC 25 4b. Dicots: Seedling Emergence, Vegetative Vigor EC 25

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 coturnix japonica ) LC 50 5b. Mallard duck ( Anas platyrhynchos ) NOEAC

Indirect Effects and Critical Habitat Effects

6. Survival, growth, and reproduction of
CRLF individuals via ef fects on terrestrial prey ( i.e., terrestrial invertebrates, small mammals , and frogs) 6a. Laboratory rat ( Rattus norvegicus ) Female LD 50 6b. Wistar Derived Rats-Alderley Park Strain NOAEL 6c. Honey bee ( Apis mellifera ) LD 50 6d. Northern Bobwhite Quail ( Colinus virginianus ) LD 50 6e. Japanese Quail ( Coturnix coturnix japonica ) LC 50 6f. Mallard duck ( Anas platyrhynchos ) NOEAC 7. Survival, growth, and reproduction of
CRLF individuals via indirect effects on habitat ( i.e., riparian and upland vegetation) 7a. Monocots: Seedling Emergence, Vegetative Vigor EC 25 7b. Dicots: Seedling Emergence, Vegetative Vigor EC 25

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 th is 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 da ta reviewed for this assessment are included in Appendix A.

402.8.2 Assessment Endpoints for Desi gnated Critical Habitat

As previously discussed, designa ted critical habitat is assessed to evaluate actions related to the use of paraquat that ma y 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 jeopa rdize the continued existence of the CRLF. Therefore, these actions are id entified as assessment endpoints. It should be noted that evaluation of PCEs as assessment endpoints is lim ited to those of a biological nature (i.e., the biological resource requirements for the list ed species associated with the critical habitat) and those for which paraquat effects da ta 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 labele d use of paraquat on cri tical 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 exp ected to be measurably alte red by use of pesticides. Assessment endpoints used for the analysis of designated critical ha bitat are based on the adverse modification standard established by U.S. FWS (2006).

41Table 2-5 Summary of Assessment Endpoints and Measures of Ecological Effect for Primary Constituent Elements of Designated Critical Habitat a

Assessment Endpoint Measures of Ecological Effect 4

Aquatic-Phase CRLF PCEs (Aquatic Breeding Habitat an d 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. 1a. Algae ( Navicula pelliculosa ) EC 50 1b. Duckweed ( Lemna gibba ) EC 50 1c. Monocots: Seedling Emergence, Vegetative Vigor EC 25 1d. Dicots: Seedling Emergence, Vegetative Vigor EC 25

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. 2a. Algae ( Navicula pelliculosa ) EC 50 2b. Duckweed ( Lemna gibba ) EC 50 2c. Monocots: Seedling Emergence, Vegetative Vigor EC 25 2d. Dicots: Seedling Emergence, Vegetative Vigor EC 25 Alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their
food source. 3a. Water flea ( Daphnia magna ) EC 50 3b. Rainbow trout ( Oncorhynchus mykiss ) LC 50 3c. No chronic fish or aquatic-phase amphibians or aquatic
invertebrates data Reduction and/or modification of aquatic-based food sources for pre-metamorphs ( e.g., algae) 4a. Algae ( Navicula pelliculosa ) EC 50

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 ch aracteristics necessary for normal growth and viability of juvenile and adult
CRLFs and their food source. 5a. Monocots: Seedling Emergence, Vegetative Vigor EC 25 5b. Dicots: Seedling Emergence, Vegetative Vigor EC 25 5c. Laboratory rat ( Rattus norvegicus ) Female LD 50 5d. Wistar Derived Rats-Alderley Park Strain NOAEL 5e. Honey bee ( Apis mellifera ) LD 50 5f. Northern Bobwhite Quail ( Colinus virginianus ) LD 50 5g. Japanese Quail ( Coturnix coturnix japonica ) LC 50 5h. Mallard duck ( Anas platyrhynchos ) NOEAC

a Physico-chemical water quality parameters such as salinity, pH , and hardness are not evaluated because these processes are not biologically mediated and, therefore, are not releva nt 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.

422.9 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 mortal ity or by adversely a ffecting 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 rang e and designated critic al 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 qual ity and habitat in the ponds and streams comprising the species’ current range and designated critical habitat;

• affect the designated critical habita t of the CRLF by reducing or changing breeding and non-breeding aqua tic habitat (via modifi cation of water quality parameters, habitat morphology, and/or sedimentation);

• affect the designated critical habita t of the CRLF by reducing the food supply required for normal growth and viabili ty 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 habita t 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 moveme nt between sites including both natural
and altered sites which do not c ontain barriers to dispersal; or

• affect the designated critical habi tat 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 rele ase mechanisms, biological re ceptor types, and effects endpoints of potential concern. The concep tual models for terre strial and aquatic exposures are shown in Figure 2-5 and Figure 2-6 , respectively, which include the

43conceptual models for the aquatic and terrestr ial 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.

Stresso r

Source

Receptors

Attribute Change Paraquat applied to use site

Direct deposition Spra y drift

Birds/terrestrialphase amphibians/ reptiles/mammals

Terrestrial

insects

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 Terrestrial/riparian plants grasses/forbs, fruit, seeds (trees, shrubs) Runoff

Mammals

/ Birds Exposure Media Soil

Ingestion Ingestion

Ingestion Ingestion Dermal Long range atmospheric

transport

Root
Wet/dry deposition

Terrestrialphase

am p hibians Ingestion

Figure 2-5 Conceptual Mode l for Pesticide Effects on Terrestrial Phase of the
CRLF

44** Route of exposure includes only ingesti on of aquatic fish and invertebrates Stresso r

Source

Receptors

Attribute Change Paraquat applied to use site

Spray drift

Fish/aquaticphase 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 Surface water/ Sediment Runoff

Aquatic Animals Invertebrates Vertebrates Uptake/gills or integument

Ingestion Ingestion Uptake/gills or integument

A quatic Plants Non-vascular Vascular Uptake/cell, roots, leaves Riparian plant terrestrial
exposure pathways see

Figure 2-5 Long range atmospheric

transport

Wet/dry deposition Groundwate r Soil

Exposure Media

Figure 2-6 Conceptual Mode l for Pesticide Effects on Aquatic Phase of the CRLF

2.10 Analysis Plan

In order to address the risk hypot hesis, the potential for direct and indirect effects to the CRLF, its prey, and its habitat is estimat ed. In the following sections, the use, environmental fate, and ecological effects of pa raquat are characterized and integrated to assess the risks. This is accomplished us ing a risk quotient (ratio of exposure
concentration to effects concen tration) approach. Although ri sk is often defined as the likelihood and magnitude of adve rse ecological effects, the ri sk quotient-based approach does not provide a quantitative estimate of lik elihood and/or magnitude of an adverse effect. However, as outlined in the Over view 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.

452.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model

2.10.1.1 Measure s of Exposure

The environmental fate properties of para quat along with available monitoring data indicate that runoff and spra y drift are the principle poten tial 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 c onsidered in deriving quantitative estimates of paraquat exposure to CRLF, its prey and it s 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 fo r 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 m odel used to predict aquatic EECs was the GENeric Estimated Environmental Concentration Model (GENEEC2) which mimics the
Tier II models the Pesticide Root Zone M odel coupled with the E xposure Analysis Model System (PRZM/EXAMS). The model used to predict terrestrial EECs on food items is T-REX. These models are parameterized us ing relevant reviewed registrant-submitted
environmental fate data.

GENEEC2 (v2.0, August 2001) is a Tier I comput er program, that us es the soil/water partition coefficient and degrad ation kinetic data to estima te runoff from a ten hectare field into a one hectare by two meter deep “sta ndard” pond. This first ti er is designed as a coarse screen and estimates conservative pest icide concentrations in surface water from a few basic chemical parameters and pesticide label use and applicati on information. Tier I
is used to screen chemicals to determine which ones potentially pos e sufficient risk to warrant higher level modeling. It calculat es acute as well as longer-term estimated environmental concentration (EEC) values. It considers reduction in dissolved pesticide concentration due to adsorption of pestic ide 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 1-in-10 year EECs of paraquat that may occur in surface water bodies adjacent to application sites receiving paraqu at through runoff and spray drift. PRZM simulates pesticide application, movement a nd transformation on an agricultural field and the resultant pesticide loadi ngs to a receiving water body via runoff, erosion and spray drift. EXAMS simulates the fate of the pe sticide and resulting concentrations in the water body. The standard scenario used fo r ecological pesticide assessments assumes application to a 10-hectare agri cultural field that drains in to an adjacent 1-hectare water body, 2-meters deep (20,000 m 3 volume) with no outlet. PRZM/EXAMS was used to estimate screening-level exposure of aquatic organisms to paraquat. The measure of

46exposure for aquatic species is the 1-in-10 year return peak or rolli ng mean concentration. The 1-in-10 year peak is used for estimati ng acute exposures of direct effects to the CRLF, as well as indirect e ffects to the CRLF through effect s 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 al so potential prey items.

Chemicals failing to pass the GENEEC 2 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 nonvascular aquatic plant EECs result in an ex ceedance, but paraquat is an herbicide and exceedances for plants is expected.

Exposure estimates for the terrestrial-phase CRLF and terrestria l invertebrates and mammals (serving as potential prey) assumed to be in the target area or in an area exposed to spray drift are derived usi ng 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 95t h percentile of residue values from actual field measurements (Hoerger and Ke nega 1972). For modeling pur poses, direct exposures of the CRLF to paraquat through contaminated fo od are estimated using the EECs for the small bird (20 g) which consumes small inse cts. Dietary-based a nd dose-based exposures of potential prey (small mammals) are assesse d 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 categ ories represent the largest RQs of the size and dietary categorie s in T-REX that are appropriate surrogates for the CRLF and one of its prey items. Es timated 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 expo sures 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 a nd wetland areas are derived using TerrPlant (version 1.2.2, 12/26/2006). This model uses es timates 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 deposit ed on terrestrial habitats by sp ray drift. In addition to the buffered area from the spray drift analysis , the downstream extent of paraquat that
exceeds the LOC for the effects dete rmination is also considered.

472.10.1.2 Measure s 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 regi strant 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 Devel opment, and the National Health and Environmental Effects Research Laboratory's Mid- Continent Ecology Division.

The assessment of risk for direct effect s 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 amphi bians represent potent ial prey of the CRLF in the aquatic habitat. Terrest rial invertebrates, small mammals, and terrestrial-phase amphibians represent potential pr ey of the CRLF in the terrestrial habitat. Aquatic, semiaquatic, and terrestrial plants represent habitat of CRLF.

The acute measures of effect used for animal s in this screening level assessment are the
LD 50 , LC 50 and EC 50 . LD stands for "Lethal Dose", and LD 50 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 LC 50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. EC stands for “Effective Concentration” and
the EC 50 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 an d NOEC. NOAEL stands for “No
Observed-Adverse-Effect-Level” and refers to the highest tested dose of a substance that has been reported to have no harmful (adve rse) 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 statis tically different from the control. The
NOEC is the No-Observed-Effects-Concentra tion. For non-listed plants, only acute exposures are assessed ( i.e. , EC 25 for terrestrial plants and EC 50 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 as sociated 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 Docu ment (USEPA 2004), the Agency relies on effects endpoints that are either direct measures of impairme nt 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.

482.10.1.3

2.10.1.4 Integra tion of Exposure and Effects

Risk characterization is the integration of exposure and ecological e ffects characterization to determine the potential ecolo gical 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 expos ure 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 Agen cy’s levels of con cern (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 pa raquat directly to the CRLF. If estimated exposures directly to the CRLF of paraquat re sulting from a particular use are sufficient to exceed the listed species LOC, then the e ffects determination for that use is “may affect”. When considering i ndirect 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 pr ey of paraquat resulting from a particular
use are sufficient to exceed the listed species LOC, then the effects determination for that use is a “may affect.” If the RQ being considered also exceed s the non-listed species acute risk LOC, then the effects determination is a LAA. If the acute RQ is between the listed species LOC and the non-listed acute ri sk species LOC, then further lines of evidence ( i.e . probability of individual effects, species sensitivity distributions) are considered in distinguishing between a de termination 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 LOC for pl ants is used because the CRLF does not have an obligate relationship with any particular aq uatic and/or terrestrial plant. If the RQ being considered for a particular use exceed s the non-listed species LOC for plants, the effects determination is “may affect”. Further information on LOCs is provided in Appendix C.

Data Ga ps

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 batc h equilibrium study usi ng soils with varying percents of clay content as well as soils w ith low clay content w ould 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 paraqua t 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 re lative to clay-bound pa raquat) is unknown.

49Therefore, conservative assumptions were ma de when running the models to determine
the effects. Please see Sec tion 3 and Section 5 for furthe r explanation on assumptions made for modeling.

Paraquat is likely to reach the aquatic envir onment via erosion and runoff, and persist in the aquatic sediment resulting in exposure to benthic dwelling fres hwater invertebrates and fish. Currently, however no chronic toxici ty studies for freshwater invertebrates or fish have been submitted to the Agency. Therefore, there is a data gap for chronic
freshwater invertebrates and fi sh toxicity. Due to this data gap we used the chemical diquat, which is similar in structure to calcu late an acute to chr onic ratio (ACR). Only
the freshwater invertebrate data were used as two different species of fish were studied
and an ACR could not be cal culated across species.

There is only one multi-active ingredient product containing paraquat and Carfentrazoneethyl as Cyclone Star (EPA Reg Numb er 00010001316). There is no toxicity data relative to this compound (Car fentrazone-ethyl) in the lite rature or in the assessment provided by Human Helath and Effects Di vision (HED). Therefore, no difnitive statement can be made as to whether this produ ct 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

### 3.0 Exposure Assessment

Paraquat is formulated as an emulsifiable concentrate. Application methods include ground, aerial, and by various sprayers (band, ho oded, low-pressure, and shielded). Risks from ground boom and aerial applications are exp ected to result in the highest off-target levels of paraquat due to generally highe r spray drift levels. Ground boom and aerial modes of application tend to use lower volum es of application app lied in finer sprays than applications coincident with sprayers and spreaders an d 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 tw o types: labels for manufacturing uses (including technical grade pa raquat and its formulated pr oducts) and end-use products. While technical products, which contain paraqua t 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 agricultu ral 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 Applicat ion Information for the CRLF risk

assessment 1

Uses Represented by Scenario Application Rate (lb cation/A) Number of Applications Application
Interval Application
Method

Aircraft

AGRICULTURAL FALLOW/IDLELAND 1.0 5 5 Ground AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE), NONAGRICULTURAL
RIGHTS-OF-WAY/FENC EROWS/HEDGEROWS 1.0 10 5 Ground

GUAVA, PASSION FRUIT (GRANADILLA) 1.0 10 5 Ground

Aircraft

MELONS, PEANUTS (ground only) 0.3 1 1 Ground

1 Uses assessed based on memorandum from SRRD dated February 5, 2009

513.2 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 mete rs deep and has no outlet. Exposure estimates generated using the sta ndard pond are intended to represent a wide variety of vulnerable water bodi es 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 standa rd surrogate pond. Stat ic 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 te nd to have limited additional storage capacity, and thus, tend to overflow a nd carry pesticide in the discharge whereas the standard pond has no discharge. As wa tershed size increases beyond 10 hectares, at some point, it becomes unlikely that the enti re 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 th e assessed uses of paraquat were used for modeling, including application rates, number of applica tions per year, application intervals, and the first app lication date for each crop.

3.2.2 Model Inputs

Paraquat is an herbicide used on various cr ops such as apricots, loganberries, corn, peanuts, coffee, lettuce, and non-crop ar eas such as airport landing fields, and commercial, industrial and inst itutional 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 m odel followed the Input Parameter Guidance; however, since paraquat’s adsorption Kd s ranged from 68-50,000 (mobile to highly immobile), the average Kd would not necessari ly 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 mo lecule. Therefore, paraquat may be more mobile in soil that is le ss 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 correspond ing concentrations (l b cation/A) in order to determine the linear regression. Once th is was established, the maximum allowable application rate (1 lb cati on/A) was plugged into the equa tion given by the regression to determine the corresponding Kd. This was done for all four soils in the study (MRID 40762701). Then, the average Kd was determined and used as the input. Determining

52Kd 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 Enviro nmental Fate Data Used for Aquatic Exposure Inputs for Paraquat Endangered Species Assessment for the CRLF 1 Based on the Paraquat Cation

Fate Property Value (unit) MRID (or source)

Molecular Weight 186 g/mol http://toxnet.nlm.nih.gov

Henry’s constant 1.9 x 10 -9 atm m 3 mol -1 http://toxnet.nlm.nih.gov

Vapor Pressure 0 http://toxnet.nlm.nih.gov

Solubility in Water 7,000,000 mg/l (700,000* mg/l x 10 per input guidance) * http://www.inchem.org/docu
ments/icsc/icsc/eics0005.htm Per Input Parameter Guidance

Photolysis in Water 0 (Stable) MRID 40562301

Aerobic Soil Metabolism Half-lives 0 (Stable) MRID 41319301

Hydrolysis 0 (Stable) MRID 41319302

Aerobic Aquatic Metabolism (water column) 0 (0.5 x Aerobic Soil Metabolism study) Per Input Parameter Guidance

Anaerobic Aquatic Metabolism (benthic) 0 (0.5 x Anaerobic Soil Metabolism study) Per Input Parameter Guidance

Kd 295 MRID 40762701

Application rate and frequency Various (see Table 3.3) Per Label Instructions

Application intervals Various (see Table 3.3) 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 applicati on practices using the GENEEC2 model are
listed in Table 3-3

. The maximum non-agricultural and agricultural application rate/interval/applications per year were calcu lated, along with the me dian use application rate/interval/applications per year, and minimu m 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/co mmercial/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 analys ts regarding the ma ximum number of

53applications allowed per season, and/or th e interval between applications. The assumptions were as follows:

• For the application intervals that were not stated, the most conservative (minimum) known application in terval 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 Califo rnia, 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 ( μ g/L) for Paraquat Uses in California

Application

Rate (lkg cation/ha) Crops Represented Peak EEC 21-day average EEC 60-day

average

EEC

33 20 10

1.0 AGRICULTURAL FALLOW/IDLELAND 27 17 8.5

1.0 AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE), NONAGRICULTURAL
RIGHTS-OF-WAY/FENCEROW S/HEDGEROWS 55 34 17

1.0 GUAVA, PASSION FRUIT (GRANADILLA) 55 34 17

2.0 1.2 0.62

0.3 MELONS, PEANUTS (ground only) 1.6 1.0 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 m odeled estimates. In this assessment, monitoring data was sought from the fo llowing 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 N AWQA Surface Water Data The USGS has not looked for any samples c ontaining paraquat. Th erefore, no surface
water data are available.

543.2.4.2

3.2.4.3

3.2.4.4 USGS N AWQA Groundwater Data The USGS has not collected any samples l ooking for paraquat. Therefore, no ground
water data are available.

Califo rnia Department of Pestic ide Regulation (CDPR) Data The California Department of Pesticide Regul ation (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 de tection 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, Sp ring, and Fall seasons.

Atmosp heric Monitoring Data

The California Air Review Board has not conduc ted 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 th e 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, sp ray applications of paraquat we re considered, as discussed
below.

Instead of running all of the uses, the ma ximum non-agricultural use, the maximum agricultural use, the median agricultural us e, 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 larges t 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 agricu ltural uses with the maximum application rates, along with th e agricultural us e with the median appl ication rate, and the agricultural use with th e 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 de fault 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 applicat ion interval are provided in
Table 3-4 . An example output from T-REX is available in Appendix E.

55Table 3-4 Input Parameters for Foliar A pplications Used to Derive Terrestrial EECs for Paraquat with T-REX

Use (Application method) Application

rate (lbs ai/A) Number of Applications Intervals Between Applications (Days) Airports (Maximum, Non-agricultural) 1 10 5 Guava (Maximum, Agricultural) 1 10 5 Ginger (Median, Agricultural) 1 6 30 Corn (Third lowest, Agricultural) 0.5 3 5 Carrots (Second lowest, Agricultural) 1 1 1 Melons (Lowest, Agricultural) 0.3 1 1

T-REX is also used to calculate EECs for te rrestrial insects exposed to paraquat. Dietarybased EECs calculated by T-REX for small and la rge insects (units of a.i./g) are used to bound an estimate of exposure to terrestrial in sects. Available acute contact toxicity data for bees exposed to paraquat (in units of μg a. i./bee), are converted to μg a.i./g (of bee) by multiplying by 1 bee/0.128 g. The EECs are la ter compared to the adjusted acute contact toxicity data for bees in order to derive RQs.

For modeling purposes, exposures of the CRL F 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 pot ential 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 type s 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 resu lting 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 LOC for listed spec ies will be analyzed in T-HERPS. The THERPS model will therefore be employed as a refinement tool to explore amphibianspecific food intake on potential exposures to the terrestrial phase CRLF. The T-HERPS model incorporates the same inputs as T-RE X 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

EECs for CRLF

(Avian, 20 g) EECs for Prey (small mammals, 15 g) Use Dietary-based EEC (ppm) Dose-based EEC (mg/kg-bw) Dietary-based EEC (ppm) Dose-based EEC (mg/kg-bw)

Airports 900 1025 1600 1530

Guava 900 1025 1600 1530 Ginger 293 333 520 500

Corn 184 209 327 175

Carrots 135 154 240 229

Melons 41 46 72 69

56Table 3-6 EECs (ppm) for Indirect Effe cts to the Terrestrial-Phase CRLF via Effects to Terrestrial Invertebrate Prey Items

Use Small Insect Large Insect

Airports 900 100

Guava 900 100 Ginger 293 33

Corn 184 20

Carrots 135 15

Melons 41 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 th e most sensitiv e endpoint. See section 5.2.5.1 for the spray drift analysis.

57

### 4.0 Effects Assessment

This assessment evaluates the potential for paraquat to directly or indirectly affect the CRLF or modify its designated critical habita t. As previously discussed in Section 2.7

, assessment endpoints for the CRLF effects dete rmination include dir ect 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, poten tial effects to critical habitat are assessed by evaluating effects to the PCEs, which are components of the critical habitat areas that provide essential lif e 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 invert ebrates, and aquatic a nd terrestrial plants, toxicity information for these taxa are also discussed. Acute (short-term) and chronic (long-term) toxicity information is characte rized based on registrant-submitted studies and a comprehensive review of th e open literature on paraquat.

As described in the Agency’s Overview Do cument (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 i nvertebrates, aquatic plants, birds (surrogate for terrestria l-phase amphibians), mammals, terrestrial invertebrates, and te rrestrial plants.

Toxicity endpoints are esta blished based on data gene rated 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 lite rature data presented in this assessment were obtained from RED 1997, the EFED and HED 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 ev aluated 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 mo re 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.

58the 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 releva nt to the assessment endpoints ( i.e. , maintenance of CRLF survival, reproduction, and gr owth) identified in Section 2.8 . For example, endpoints such as behavior modifications are likely to be qualitatively evaluated, unless quantitative relationships between modificat ions and reduction in species survival, reproduction, and/or growth are available. Although the effects de termination relies on endpoints that are re levant to the assessment endpoints of survival, growth, or reproduction, it is important to note that the full suite of subletha l endpoints potentially available in the effects literature (regardle ss of their significance to the assessment endpoints) are considered to defi ne the action area for paraquat.

Citations of all open literature not considered as part of this a ssessment because they were either rejected by the ECOTOX scr een 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 di d 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 subl ethal endpoints are pres ented in Appendices F and G. A summary of the human health effect s data for paraquat is found in Appendix K.

In addition to registrant-submitted and open lite rature toxicity information, other sources of information, including use of the acute pr obit dose response rela tionship to establish the probability of an individual effect and re views of the Ecological Incident Information System (EIIS), are conducted to further refi ne the characterization of potential ecological effects associated with exposure to paraquat (Appendix H). A summ ary of the available aquatic and terrestrial ecotoxicity info rmation, use of the probit dose response relationship, and the incide nt information for paraquat are provided in Sections 4.1 through 4.4 , respectively.

Paraquat has registered products that contain multiple active i ngredients. The results of available toxicity data for mi xtures 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 ECOT OX 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 da ta, other pesticides may combine with paraquat to produce additive, and/or antagonistic toxic effects. Mixtures in cluded 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, th e toxicity of paraquat may be increased, offset by other environmental factors, or even reduced by th e presence of antagonistic contaminants if they are also present in the mixture. The vari ety of chemical interact ions presented in the available data set suggest that the toxic eff ect of paraquat, in co mbination with other pesticides used in the environment, can be a function of many f actors including but not

59necessarily limited to (1) the exposed species, (2) the co-contaminants in the mixture, (3) the ratio of paraquat an d co-contaminant concentrations, (4 ) differences in the pattern and duration of exposure among contaminants, a nd (5) the differential effects of other physical/chemical characteristic s of the receiving waters (e .g., organic matter present in sediment and suspended water). Quantitative ly predicting the combined effects of all
these variables on mixture t oxicity 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 fres hwater 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 th e vascular aquatic plant Lemna minor (E 102140). In the presence of both paraquat and copper sulf ate there was a reduc tion in the percent
inhibition of F
v /F m, a measurement of the efficiency of Photosystem II (PSII), indicating an antagonistic relationship. An additive relationship was observed in two other parameters; O 2 evolution and the fraction of inhib ited 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 mi xture may potentially change over time.

The mixture of paraquat plus linuron (formulati ons used for potatoes) was found to not be genotoxic, but was found to be cytotoxic to adult wistar rats (E 104633). 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 herb icides on species found in a field that was treated with herbicides (E147983). Other studies examine imp acts to non-target organisms off the pesticide treated field as a result of runoff or spray drift. The treatments examined compared herbicide treatm ents to other cultural practices (tillage), which showed impacts to the “native field sp ecies” 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 imp acts of cultural practices on the reduction in CRLF food sources. Bibliographic informa tion is presented in Appendix F.

4.1 Evaluation of Aquati c 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.

60Table 4-1 Freshwater Aquatic Toxicity Prof ile for Paraquat Dichloride (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 Bluegill
sunfish 96h LC 50 = 13 mg/L Mortality 40098001 (Mayer & Ellersieck 1986) Acceptable

Chronic Estimated – See Section 5
Indirect Toxicity to Aquatic-Phase CRLF
via Acute Toxicity to
Freshwater
Invertebrates (i.e. prey items) Daphnia

magna 48h EC 50 = 1.2 mg/L Mortality 00114473 (Wheeler 1978) Acceptable

via Chronic Toxicity to
Freshwater
Invertebrates (i.e. prey items) Estimated – See Section 5

via Acute Toxicity to
Freshwater Fish (i.e. prey items) Bluegill
sunfish 96h LC 50 = 13 mg/L Mortality 40098001 (Mayer & Ellersieck 1986) Acceptable

via Chronic Toxicity to
Freshwater Fish (i.e. prey items) Estimated – See Section 5

via Toxicity to
Non-vascular Aquatic Plants Navicula pelliculosa (freshwater diatom) 4d EC 50 = 0.396

μ g/L Growth 42601006 (Smyth et al. 1992) Acceptable

via Toxicity to
Vascular Aquatic Plants Lemna gibba (Duckweed) 14d EC 50 = 71

μ g/L Growth and Reproduction 42601003 (Smyth et al. 1992) Acceptable

Toxicity to aquatic fish a nd 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

LC 50 (ppm) Toxicity Category
< 0.1 Very highly toxic
> 0.1 - 1 Highly toxic
> 1 - 10 Moderately toxic
> 10 – 100 Slightly toxic
> 100 Practically nontoxic

614.1.1 Toxicity to Freshwater Fish

No scientifically valid data are available for aquatic-phase amphibi ans, and therefore, freshwater fish data were used as a surrogate to estimate direct chronic risks to the CRLF. Freshwater fish toxicity data were also us ed 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 ma y consist of vertebrates such as mice, frogs, and fish (Hayes and Tennant 1985).

A summary of acute and chr onic freshwater fish data, including data from the open literature, is provide d below in Sections 4.1.1.1 through 4.1.1.3

.

4.1.1.1

4.1.1.2

4.1.1.3 Freshw ater 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 exposur e 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 freshwat er species was the bluegill sunfish, with a
96h LC 50 of 13 mg/L (MRID 40098001 Mayer and E llersieck 1986). Freshwater fish acute toxicity values range from a 96h LC 50 of 13 mg/L to 156 mg/L (both endpoints are bluegill sunfish, MRID 40098001 Mayer and Ellersi eck 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 us ing formulated products that contained 21.2% to 29% of the paraquat cation. In ge neral, the toxicity of these formulated products are similar in toxicity to a range of different specie s of freshwater fish.

Freshw ater Fish: Chronic Exposure (Early Life Stage and Reproduction) Studies

There are no available freshwater fish chr onic exposure toxicity studies conducted with Paraquat. The direct chronic toxicity values for the CRLF we re calculated using an acute to chronic ratio (ACR) using a similar chemical compound, diquat dibromide (Section 5.1.1).

Freshw ater 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 gr owth 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

62ECOTOX 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

4.1.2.1

4.1.2.2 Aquati c-phase Amphibian: Ac ute and Chronic Studies

Studies were found in ECOTOX that used aqua tic-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 info rmation within the published literature. Also of concern was the presence of the solvent di methyl sulfoxide (DMSO) as a co-solvent, which confounds the experiment as the solven t could be resulting in increased toxicity, and not the chemical being tested. In genera l 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 chroni c 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 informati on as to why these studies and others from
ECOTOX were not used w ithin the assessment.

4.1.2 Toxicity to Freshwater Invertebrates

Freshwater aquatic invertebrate toxicity data were used to as sess potential indirect effects of paraquat to the CRLF. Effects to freshwat er 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 terrestrialphase CRLFs is thought to be aquatic inve rtebrates found along the shoreline and on the water surface, including aquatic sowbugs, larval alderf lies 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

.

Freshw ater 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 EC 50 value of 1.2 mg/L (MRID 0014473 Wheeler 1973).

Freshw ater Invertebrates: Chronic Exposure (Reproduction)
Studies

There are no available freshwater inverteb rate chronic exposure toxicity studies conducted with Paraquat. The indirect ch ronic toxicity values for the CRLF were

63calculated using an acute to chronic rati o (ACR) using a similar chemical compound, diquat dibromide (Section 5.1.1).

4.1.2.3

4.1.3.1

4.1.3.2 Freshw ater 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 effect s observed. Additionall y, the studies were
not usable in this Risk Assessment. Furt her details on ECOTOX studi es are provided in Appendix F, which also contains the rejec tion codes and other information as to why
studies from ECOTOX we re 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 indi rectly 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 da ta and freshwater field studies for aquatic plants is provided in Sections 4.1.3.2 and 4.1.3.2

.
Aquati c Plants: Laboratory Data

Both the vascular and non-vasc ular aquatic plant studies that include the most sensitive species are Tier II toxicity te sts. The freshwater diatom ( Navicula pelliculosa ) was the most sensitive non-vascular plant with a 4d EC 50 of 0.396 μ g/L (MRID 42601006 Smyth et al. 1992). The vascular plant Lemna gibba was the most sensitive vascular plant with a
14d EC 50 of 71 μ g/L (MRID 42601003 Smyth et al. 1992).

Freshw ater Field Studies

There were no submitted field studies.

4.2 Toxicity of Paraquat to Terrestrial Organisms

Table 4-3 summarizes the most sensitive terr estrial 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 co nsidered relevant to this ecological risk assessment for the CRLF is presented below.

64Table 4-3 Terrestrial Toxicity Profile for Paraquat Dichloride (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 Dosebased Colinus virginianus (Northern Bobwhite) LD 50 = 128.1 mg/kg bw Mortality 00029001 (Fink et al. 1979) Acceptable

Acute Dietary-based Coturnix
coturnix japonica (Japanese Quail) 5d LC 50 = 703

ppm Mortality 00022923 (Hill et al. 1975) Supplemental

Chronic Anas platyrhynchos (Mallard Duck) NOAEC = 30

ppm % viable eggs, eggs set, normality of hatchlings and
# of 14d old
survival 00110455 (Fink et al. 1982) Acceptable

Indirect Toxicity to Terrestrial-phase CRLF

via acute toxicity to
mammalian prey items Rat LD 50 = 90 mg/kg bw (F) Mortality 00054573 (Rittenhouse 1977) Acceptable

via chronic toxicity to
mammalian prey items Wistar
Derived RatsAlderley Park
Strain NOAEL= 7.5 mg/kg-bw

NOAEC = 108

ppm Reproductive Toxicity- 3 generation study Reproduction 00126783

00149748

00149749 Acceptable
(HED 2006)

via acute toxicity to
terrestrial
invertebrate prey items Apis mellifera (Honey bee) 48h LD 50 > 34.8

μ g/bee Mortality 05001991 (Stevenson 1978) Acceptable

via acute toxicity to
terrestrial
invertebrate prey items Colinus virginianus (Northern Bobwhite) LD 50 = 128.1 mg/kg bw Mortality 00029001 (Fink et al. 1979) Acceptable

via acute toxicity to
terrestrial
invertebrate prey items Coturnix
coturnix japonica (Japanese Quail) 5d LC 50 = 703

ppm Mortality 00022923 (Hill et al. 1975) Supplemental

65Assessment Endpoint Species Toxicity Value
Used in Risk
Assessment Describe effect (i.e. mortality, growth, reproduction) Citation Study
MRID # Classification (Author & Date)

via chronic toxicity to
terrestrial
invertebrate prey items Anas platyrhynchos (Mallard Duck) NOAEC = 30

ppm % viable eggs, eggs set, normality of hatchlings and
# of 14d old
survival 00110455 (Fink et al. 1982) Acceptable

Seedling Emergence
Monocots EC 25 = 0.84 lbs cation/A (using
most sensitive species (dicot data)) Growth 42639601 (Canning and White 1992) Acceptable

Seedling Emergence
Dicots
(Cocklebur) EC 25 = 0.84 lbs
cation/A Growth 42639601 (Canning and White 1992) Acceptable

Vegetative Vigor
Monocots (Corn) EC 25 = 0.16 lbs
cation/A Growth 42601001 (Canning and White 1992) Acceptable via toxicity to

terrestrial

plants

Vegetative Vigor
Dicots (Cocklebur ) EC 25 = 0.014lbs
cation/A Growth 42601001 (Canning and White 1992) Acceptable

Acute toxicity to terrestrial animals is categ orized using the classi fication 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 Oral LD 50 Dietary LC 50 Very highly toxic < 10 mg/kg < 50 ppm Highly toxic 10 - 50 mg/kg 50 - 500 ppm Moderately toxic 51 - 500 mg/kg 501 - 1000 ppm

Slightly toxic 501 - 2000 mg/kg 1001 - 5000 ppm Practically non-toxic > 2000 mg/kg > 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 para quat; therefore, acute and chronic avian toxicity data are used to assess the potential direct effects of paraquat to terrestrial-phase CRLFs.

664.2.1.1

4.2.1.2

4.2.1.3 Birds: Acute Exposure (Mortality) Studies

There were two acute avian oral studies that were submitted, one classified as acceptable, and the other classified as supplem ental (MRID 00029001 Fink et al. 1979, & 00160000 Hudson et al. 1984). The most sensitive speci es was the Northern Bobwhite quail with
an acute oral LD 50 value of 128.1 mg/kg (MRID 00029001 Fink et al. 1979). The mallard duck acute oral toxicity classificati on to paraquat ranges from moderately toxic (144.8 mg/kg) to slightly toxi c (436.8 mg/kg), both studies ar e supplemental (Fink et al. 1979). Paraquat is classified as being moderate ly toxic to birds on an acute oral basis.

Subacute dietary tests are re quired to establish toxicity of paraquat to birds. The preferred test species are the mallard duck a nd the bobwhite quail. The most sensitive subacute dietary 5d LC 50 value was 703 ppm for the Japa nese quail (a non-guideline test species, indicating that the study was suppl emental 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 LC 50 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.

Birds: Chronic Exposure (Growth, Reproduction) Studies

Avian reproductive toxicity endpoints we re 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 bobwhi te 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).

Terres trial-phase Amphibian Ac ute and Chronic Studies

There were no terrestrial-phase amphibian acut e or chronic studies submitted or available in the open literature.

4.2.2 Toxicity to Mammals

Mammalian toxicity data are used to assess po tential indirect effects of paraquat to the terrestrial-phase CRLF. Eff ects to small mammals resulti ng from exposure to paraquat could also indirectly affect the CRLF via re duction in available f ood. 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).

674.2.2.1

4.2.2.2

4.2.3.1 Mammal s: Acute Exposure (Mortality) Studies

Paraquat is classified as mode rately toxic on an acute oral basis to mammals. This is
based on an acute oral LD 50 value of 90.98 mg/kg-bw (MRID 00054573 Rittenhouse 1977). See the HED Table from the most r ecent HED Human Health Risk Assessment in Appendix K.

Mammal s: Chronic Exposure (Growth, Reproduction) Studies

In a 3-generation reproduction and fertility st udy in rats, paraquat was administered to Wistar Derived Rats-Alderley Pa rk 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 classifi ed 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 wa s 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 inciden ces of alveolar histiocytes), indicating a sublethal impact lower than the acute oral endpoints. HED determined that paraquat dichloride was not a mutagen or a carci nogen (HED 2006). Paraquat was found to be weakly positive in the mouse lymphoma assa y 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 evid ence of carcinogenicity in animal studies, and paraquat was classified as a Group E ch emical (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 toxici ty data are used to assess pot ential indirect effects of paraquat to the terrestrial-phase CRLF. Effect s to terrestrial invertebrates resulting from exposure to paraquat could also indirectly affect the CRL F via reduction in available
food.

Terres trial Invertebrates: Acut e Exposure (Mortality) Studies

A honeybee acute contact study (TGAI) resulted in a 48h LD 50 > 34.8 μ g/bee (MRID 05001991 Stevenson 1978). Paraquat is classifi ed as practically non-toxic to honeybees.

684.2.3.2 Terres trial Invertebrates: Open Literature Studies

There were no terrestrial invertebrate st udies 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., grassl and, woodland) vegetation may resu lt in indirect effects to both aquatic- and terrestrial-phase CRLFs, as well as effects to designated critical habitat PCEs via increased sedimentation, alterati on in water quality, and reduction in upland and riparian habitat that provi des shelter, foraging, predator avoidance and dispersal for juvenile and adult CRLFs.

Plant toxicity data from both registrant-subm itted 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 gui delines. Sub-lethal endpoints such as plant growt h, 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 ar e conducted on herbaceous crop species only, and extrapolation of effects to other species, such as th e woody shrubs and trees and wild herbaceous species, contributes uncertainty to risk conclusions.

Commercial crop species have b een selectively bred, and may be more or less resistant to particular stressors than wild herbs and forb s. The direction of this uncertainty for specific plants and stressors, including pa raquat, is largely unknown. Homogenous test plant seed lots also lack th e 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 seed ling 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 scien tifically 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 pl ants vegetative vigor phytotoxicity study were recalculated using the NUTH ATCH statistical program.

69Table 4-5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor Toxicity (Tier II) Data

Crop Type of Study Species NOAEC (lb cation/A) EC 25 (lb cation/A) Most sensitive parameter

Seedling Emergence
Monocots Assumed as sensitive as dicots

Dicots Cocklebur 0.423 0.85 Dry weight
Vegetative Vigor

Monocots Corn 0.064 0.16
(95% CI 0.073–0.36) Dry weight

Dicots Cockelbur EC 05 = 0.0065
(95% CI 0.0040–0.01) 0.014
(95% CI 0.01–0.019) Dry weight

4.3 Use of Probit Slope Response Relation ship to Provide Information on the Endangered Species Levels of Concern

The Agency uses the probit dose response rela tionship 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 th e listed species of concern (U.S. EPA 2004). As part of the risk characterization, an inte rpretation 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 expos ure at the EEC actually occur for a species with sensitivity to paraquat on par with th e acute toxicity endpoi nt selected for RQ calculation. To accomplish this interpretati on, 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 relationshi p. In addition to a single effects probability es timate based on the mean, upper and lower estimates of the effects probability are also pr ovided to account for variance in the slope, if available.

Individual effect probabilitie s are calculated based on an Ex cel spreadsheet tool IECV1.1 (Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental Fate and Effects Division (J une 22, 2004). The model allows for such calculations by entering the mean slope esti mate (and the 95% confidence bounds of that estimate) as the slope parameter for the spread sheet. In addition, the acute RQ is entered
as the desired threshold.

4.4 Incident Database Review

A review of the EIIS database for ecologica l incidents involving paraquat and paraquat dichloride, which are used interchangeab ly, was completed on April 17, 2009. The
results of this review for terr estrial, 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 in cidents involving para quat dichloride (PC

70code 061601) were reported. There were no in cidents 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 terrest rial incidents for paraquat (PC code 061603). There were three reported terrestrial in cidents for paraquat dichloride (PC code 061601). Two incidents resulted in the mortality of birds, and the other reported bot h bird mortality and plant damage (I008168-001, I000097-015, and I007334-001). 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 para quat dichloride was the probable cause of the incident in June 1998 (I008168-001). The other incident was from the consumption of granules resulting in the death of a pproximately 12 birds. However, paraquat dichloride was unlikely the cause of th e incident on May 1989 (I000097-015), as there are no granular forms of paraquat. Paraquat was reported since it was applied within the
area of the observed incident. The other inci dent occurred in Illinois resulting in plant damage on 18 of 103 acres of corn, and the de ath of 4 unknown species of birds in June 1998 from drift/spray exposure (I007334-001), the legal classificati on 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 sp ecies; radishes, apples, and ornamentals (I014409-001, I013884-038, and I013884-014), while plant mortality was reported for alfalfa (I014409-024). All incidents repor ted were from Washington, one from a registered use on peas where ornamentals we re affected, and paraquat was the probable cause of plant damage; one from a misuse (alfalfa) where paraqua t 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 sp ray. The total magnitude of exposure was not reported.

There were a total of 17 plan t incidents listed for paraqua t dichloride (PC code 061601).
Two accidental misuse incidents occurred in an agricultural area in Wisconsin resulting in plant damage to alfalfa, ash, and ornamentals (I005660-005), and ash, oats and discoloration to alfalfa (I005880-005) from drift exposure. Paraquat was the probable cause of these incidents. Three accidental misuse incidents on corn resulted in plant damage to grass (I007371-033, I007371- 034, and I007371-035) 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 broa dcast application occurred May 9, 2000, and paraquat was a possible cause of this incide nt (I012366-023). Plant damage to 181 acres of peppermint occurred after registered use May 1, 1996, and paraquat was a possible cause of this incident (I013636-029). Undeterm ined 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 (I009573-009). After the re gistered use application of paraquat

71dichloride 10 acres of peanuts were damaged June 19, 2001 in North Carolina, and paraquat was a possible cause of this in cident (I011838-055). Carryover from the broadcast application of paraquat dichloride was the pr obable cause of damage to 1040 acres of corn May 24, 2002 in Illinois (I013554- 040). The registered use application of paraquat dichloride was a possible cause of th e damage to 60 acres of pasture grass April 23, 2003 in Georgia (I014034-009). 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 (I012684-010). Undetermined legality use of paraquat dichloride on peanuts was a possible cause of plant damage to 80 acres of peanuts in Oklahoma (I011838-091) and all 25 acres in Georgia (I 011838-038). 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 (I 001131-001). It is highl y 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 (I007371-008). Intentional misuse of paraqua t 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 (I016940-005).

4.4.3 Aquatic Incidents

There were no reported aquatic incidents li sted 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 largemout h bass, and 53 sunfish) due to runoff June 4, 1981 in Virginia (B0000-502-18). Registered usag e of paraquat dichlo ride application on an agricultural area in North Carolina was un likely the cause of the mortality to unknown amount of unknown fish November 29, 1993 (I0 03654-012). 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 of fish (bass, bluegill, and crappie) in Indiana June 2, 1997 (I009314-005). 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 Indi ana January 1, 1997 (I005805-001). Paraquat dichloride was was a possible cause of the 200 bass and bluegills that were found dead after an undetermined legality application of paraquat di chloride June 3, 1999 (I008768- 007).

72

### 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 critic al habitat from the use of paraquat in CA. The risk characterization provides an estima tion (Section 5.1) and a description (Section 5.2) of the likelihood of adverse effects; articulates risk assessment assumptions, limitations, and uncertainties; and synthesi zes an overall conclusion regarding the
likelihood of adverse effects to the CRLF or its designated critic al 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 e xposure to toxicity. Th is ratio is the risk quotient (RQ), which is then compared to pr e-established acute a nd chronic levels of concern (LOCs) for each category evaluated (A ppendix C). For acute exposures to the CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the LOC is 0.05. For acute exposures to the CRLF in its terrestrial environment and mammals, the LOC is 0.1. The LOC 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 1-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 terres trial-phase CRLF and its prey ( e.g . terrestrial insects, small mammals and terrestrial-phase frogs) are es timated 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 fo r terrestrial plants, as discussed in Section 3.4 and toxicity summarized in Section 4.2.4, based on the highest ap plication rates of paraquat use within the action area.

Due to Paraquat being a cation, the risk esti mated may be more c onservative 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 fr eshwater fish. In or der to assess direct chronic risks to the CRLF, 60-day EECs and the lowest chronic toxicity value for freshwater fish are used. However, since fres hwater fish chronic toxicity values are not

73available 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 dibromid e. However, the ACR could not be calculated for freshwater fish (direct effect s to the CRLF) using the same method as the indirect effects, as the speci es of fish were different in the diquat acute and chronic studies for the direct effects. There is gr eater uncertainty when using two different species of fish, in addition to the general un certainty related with comparing toxicity of two different compounds. The ACR for inve rtebrates was complete d 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 ch ronic ratio from the i nvertebrates divided by
the acute LC 50 value from the freshwater fish. B ecause these species are different, it increases the uncertainty, but can provide valuable informati on in helping to discuss the possible toxicity to the aquatic phase CRLF di rectly. 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 Ta ble 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 Effe ct RQs* for the Aquatic-phase CRLF

Use EEC ( μ g/L) b RQ Probability of
Individual
Effect at

RQ C LOC
Exceedance

and Risk Interpretation

33 0.003 No exceedance NO

AGRICULTURAL FALLOW/IDLELAND 27 0.002 No exceedance NO
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDU STRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE),
NONAGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 55 0.004 No exceedance NO

GUAVA, PASSION FRUIT (GRANADILLA) 55 0.004 No exceedance NO

2.0 <0.001 No exceedance NO

MELONS, PEANUTS (ground only) 1.6 <0.001 No exceedance NO

a RQs associated with acute direct toxicity to the CRLF ar e also used to assess potential indirect effects to the
CRLF based on a reduction in freshwater fish and fr ogs as food items. No chr onic data is available.

b The highest EEC based on maximu m application rate per use (see Table 3-3 ).

c A probit slope value for the acute bluegi ll sunfish toxicity test is not availabl e; 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 calc ulated when there was an exceedance).

* RQ < acute endangered species LOC of 0.05. ^ The most sensitive species used to determine the acute direct effects (surrogate species) was the bluegill Sunfish (96h LC 50 = 13000 ppb).

745.1.1.2 Indire ct Effects to Aquatic-Phas e CRLF via Reduction in Prey (non-vascular aquatic plants, a quatic invertebrates, fish, and frogs)

a) Non-vascular Aquatic Plants

Indirect effects of paraquat to the aquatic-phase CRLF (t adpoles) via reduction in nonvascular aquatic plants in its diet are ba sed on peak EECs from the standard pond and the lowest toxicity value EC 50 for aquatic non-vascular plants. RQ’s exceed the modeled EECs (Table 5-2); therefore, paraqua t may affect the aquatic-phase CRLF indirectly via effects to no n-vascular aquatic plants.

Table 5-2 Summary of RQs* Used to Es timate 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 Peak EEC ( μ g/L) Indirect effects RQ a (food and habitat)

33 82

AGRICULTURAL FALLOW/IDLELAND 27 69

AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS(PUBLIC HEALTH USE), NONAGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 55 138

GUAVA, PASSION FRUIT (GRANADILLA) 55 138

2.0 4.9

MELONS, PEANUTS (ground only) 1.6 4.1

a RQs used to estimate indirect effects to the CRLF via toxi city to vascular aquatic plants are summarized in Table 5-4 * LOC exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC/ most sensitive non-vascular aquatic plant endpoint (Acute: Navicula pelliculosa EC 50 = 0.396 ppb).

b) Aquatic Invertebrates

As mention in Section 5.1.1.1, in the absence of chronic data, the acu te to chronic ratio (ACR) between diquat and para quat 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 ther e 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.

75Table 5-3 Summary of Acute RQs* Used to Estimate Indirect Effects to the CRLF via Direct Effects on Aquatic Invertebrate s as Dietary Food Items (prey of CRLF juveniles and adults in aquatic habitats)

Use Peak EEC ( μ g/L) Indirect
Effects
Acute RQ* Probability of
Individual Effect at RQ a

33 0.025 No exceedance

AGRICULTURAL FALLOW/IDLELAND 27 0.021 No exceedance
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTHUSE), NONAGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 55 0.042 No exceedance

GUAVA, PASSION FRUIT (GRANADILLA) 55 0.042 No exceedance

2.0 0.002 No exceedance

MELONS, PEANUTS (ground only) 1.6 0.001 No exceedance
* = LOC exceedances (acute RQ > 0.05) are bolded and shaded. Acute RQ = use-specific peak EEC / acute freshwater invertebrate endpoint ( Daphnia magna EC 50 =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 sl ope 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 freshwat er 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 e xposed to diquat. Ba sed 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 fi sh or other aquatic-phase frogs as prey
items.

5.1.1.3 Indire ct Effects to CRLF via Reduction in Habitat and/or Primary Productivity (Freshwater Aquatic Plants)

Indirect effects to the CRLF vi a direct toxicity to aquatic plants are estimated using the
most sensitive non-vascular and vascular plant toxicity endp oints. Because there are no obligate relationships between the CRLF and any aquatic plant species, the most sensitive
EC 50 values, rather than NOAEC values, were us ed to derive RQs. Based on the data presented in Tables 5-2 and 5-4, paraquat may affect the CRLF via reduction in nonvascular plants, but will have no indirect effect via reduction in vascular plants.

76Table 5-4 Summary of RQs* Used to Es timate Indirect Effects to the CRLF via Effects to Vascular Aquatic Plants (habitat of aquatic-phase CRLF) a

Use Peak EEC ( μ g/L) Indirect effects RQ a (food and habitat)

33 0.46

AGRICULTURAL FALLOW/IDLELAND 27 0.38

AIRPORTS/LANDING FIELDS, COMME RCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLICHEALTH USE), NONAGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 55 0.77

GUAVA, PASSION FRUIT (GRANADILLA) 55 0.77

2.0 0.03

MELONS, PEANUTS (ground only) 1.6 0.02

a RQs used to estimate indirect effects to the CRLF via toxicity to non-vascular a quatic plants are summarized in Table 5-2 * = LOC exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC / vascular aq uatic plant endpoint ( Lemna gibba EC 50 = 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, potenti al direct effects to terrestrial-phase CRLFs are based on broadcast foliar (g round and aerial) application of paraquat. Potential direct acute effects of paraquat to the terrestria l-phase CRLF are derived by considering doseand dietary-based EECs modeled in T-REX fo r a small bird (20 g) consuming small invertebrates ( Table 3-5 ) and acute oral and subacute di etary 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 (LC 50 = 703ppm), and the Northern bobwhite quail was the most sensitive on an acute dietary basis (LD 50 = 128.1 mg/kg-bw) were ther efore 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 e ndangered species LOC of 0.1 for the CRLF (Table 5-5). The probabili ty of individual eff ect 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*10 3 with a 95% CI of 1 in 1.34*10 1 to 1 in 2.35*10 10 (for carrots). The effect probability was calculated based on a default slope assumption of 4.5 with upper and lower 95% confidence interval s of 2 and 9 (Urban and Cook, 1986).

Potential direct chronic eff ects of paraquat to the terres trial-phase CRLF are derived by considering dietary-based expos ures modeled in T-REX for a small bird (20g) consuming small invertebrates ( Table 3-5 ). Chronic effects are estimat ed using the lowest available toxicity data for birds. EECs are divided by toxicity values to estimate chronic dietarybased RQs (Table 5-6). Chronic reproductive effects for the Mallar d duck were observed

77with a NOAEC of 30 ppm. The chronic diet ary-based RQs for the terrestrial phase CRLF exceed the Agency’s chronic LOC 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 acut e 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 (lb cation/acre) Dietary-based Acute RQ 1 Probability of
Individual Effect at RQ a
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE)(1 lb cation/acre; 10 times/yr; 5 day intervals) (maximumnon-ag) 1.28 1 in 1.46 (1 in 1.71 to 1 in 1.20) a

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 1.28 1 in 1.46 (1 in 1.71 to 1 in 1.20) a

Ginger (1 lb cation/acre; 6 times/yr; 30 day intervals (ag)) 0.42 1 in 2.22 E+01 (1 in 4.43 E+01 to 1 in 2.87 E+03) a

CORN (SILAGE) (0.5 lb cat ion/acre; 3 times/year; 5 day intervals) 0.26 1 in 2.36 E+02 (1 in 8.27 to 1 in 1.43 E+07) a BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 0.19 1 in 1.71 E+03 (1 in 1.34E+01 to 1 in 2.35 E+10) a Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 0.06 No exceedance

* = LOC exceedances (Acute RQ > 0.1) are bolded and shaded.

1 Based on Japanese quail LC 50 = 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) Dietary-based Chronic RQ 1

AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 30.00

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 30.00

78Use Dietary-based Chronic RQ 1 (Application Rate)

Ginger (1 lb cation/acre; 6 times/yr; 30 day intervals (ag)) 9.76

CORN (SILAGE) (0.5 lb cat ion/acre; 3 times/year; 5 day intervals) 6.13

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 4.50

Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 1.35

* = LOC exceedances (Chronic RQ > 1) are bolded and shaded.

1 Based on Mallard duck NOAEC = 30 ppm.

5.1.2.2 Indire ct Effects to Terrestria l-Phase CRLF via Reduction in Prey (terrestrial invertebrates, mammals, and frogs)

a) Terrestrial Invertebrates

In order to assess the risks of paraquat to terrestrial invert ebrates, 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 LD 50 > 34.6μg cation/bee by 1 bee/0.128g, which is based on the weight of an adult honey bee. EECs (μg 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 μg cation/g of bee, to calculate RQs. Indirect effects cannot be precluded from ava ilable data because the LD 50 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 a nd dose-based exposures modeled in T-REX for a small mammal (15g) consuming short grass. Acute and chronic effects ar e estimated using the most sensitive mammalian toxicity data (LD 50 = 90.98 mg/kg-bw). EECs are divided by the toxicity value to estimate acute and ch ronic dose-based RQs as well as chronic dietary-based RQs (Table 5-7). RQs represen ting acute and chronic exposures of small mammals consuming short grass on the treated field contaminated with paraquat exceed endangered species LOC of 0.1 (acute) and 1 (c hronic) for all uses except melons (Table 5-7). Melons chronic dietary based RQ doe s not exceed the endangered species LOC of 0.1. The probability of individual effect at the endangered species LOC (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 (U rban and Cook, 1986).

79The probability of individual effect probit slope analysis is not applicable for chronic endpoints. HED determined that paraquat dich loride was not a mutagen or a carcinogen (HED 2006). Paraquat was found to be weak ly positive in the mouse lymphoma assay and human lymphocyte cytogenetic assay a nd 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 s ynthesis assay in vi tro or in vivo, was negative for chromosomal aberration in th e 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 re duction in small mammal prey items.

Table 5-7 Summary of Acute and Chronic RQ s* Used to Estimate Indirect Effects to the Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary Food Items (foliar application)

Chronic RQ Acute RQ Use

(Application Rate) Dose-based Chronic RQ 1 Dietary-based Chronic RQ 2 Dose-based Acute RQ 3 Probability of
% Effect at Acute RQ a

AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDU STRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 128.53 14.81 7.63 100%

1 in 1 (1 in 1.04 to 1 in 1) a

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 128.53 14.81 7.63 100%

1 in 1 (1 in 1.04 to 1 in 1) a

Ginger (1 lb cati on/acre; 6 times/yr; 30 day intervals (ag)) 41.82 4.82 2.48 96%

1 in 1.04 ( 1 in 1.27 to 1 in 1) a

CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 26.28 3.03 1.56 81%

1 in 1.24 (1 in

1.54 to 1 in 1.04) a

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 19.28 2.22 1.14 60%

1 in 1.66 (1 in

1.83 to 1 in 1.44) a

80Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 5.78 0.67 0.34 1.75%

1 in 57.1 (1 in

5.73 to 1 in
8.07E+04) a

* = LOC exceedances (acute RQ > 0.1 and chronic RQ > 1) are bolded and shaded.

1 Based on dose-based EEC and pa raquat rat NOAEL = 5.4 mg/kg-bw.

2 Based on dietary-based EEC and para quat rat NOAEC = 108 mg/kg-diet.

3 Based on dose-based EEC a nd paraquat rat acute oral LD 50 = 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% conf idence 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, di etary-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 LOC is exceeded for all uses of paraquat except Melons, and th e chronic LOC 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

5.1.3.1 Indire ct Effects to CRLF via Reduction in Terrestrial Plant Community (Riparian and Upland Habitat)

Potential indirect effects to the CRLF resul ting from direct effects on riparian and upland vegetation are assessed using the most sensiti ve terrestrial plant data, in this case vegetative vigor EC 25 data, as a screen. The ve getative vigor endpoint is EC 25 = 0.014 lb
cation/acre. To determine the reduction in terr estrial 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.

P araquat may indirectly affect the CRLF via reduction in terrestrial plants from both aerial and ground application for vegeta tion 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

Aquati c-Phase (Aquatic Breedin g Habitat and Aquatic NonBreeding Habitat)

Three of the four assessment endpoints for the aquatic-phase primary constituent elements (PCEs) of designated critical ha bitat for the CRLF are related to potential effects to aquatic and/or terrestrial plants:

81• Alteration of channel/pond morphology or ge ometry and/or increase in sediment deposition within the stream channel or pond: aquatic ha bitat (including riparian vegetation) provides for shelter, fora ging, 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-b ased 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 aquaticphase 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. Si nce there are LOC exceedances on non-target terrestrial dicot plants from spray drift at the minimum application rate, paraquat may indirectly affect the CRLF via reduction in terr estrial plants from ae rial 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 depos ition within the str eam channel or pond and for alteration in water chemistry/qualit y including temperature, turbidity, and oxygen content necessary for normal growth and viabil ity of juvenile and adult CRLFs and their
food.

The remaining aquatic-phase PCE is “altera tion 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 sour ces), acute and chronic freshwater fish and invertebrate toxicity endpoints, as well endpoints for aquatic nonvascular plants are used as measures of ef fects. 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 Terres trial-Phase (Upland Habita t and Dispersal Habitat)

The first two assessment endpoints for the terr estrial-phase PCEs of designated critical habitat for the CRLF are related to poten tial effects to terrestrial plants:

• Elimination and/or disturbance of upland ha bitat; ability of hab itat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or dripline surroundi ng aquatic and riparian ha bitat that are comprised of grasslands, woodlands, and/or wetland/r iparian plant species that provides the CRLF shelter, forage, and predator avoidance

82• Elimination and/or disturbance of dispersa l habitat: Upland or riparian dispersal habitat within designated un its and between occupied locations within 0.7 mi of
each other that allow for movement be tween sites including both natural and
altered sites which do not cont ain 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 LOC exceedances for non-target monocot plants (inhabiting upland dry, semi-dry areas) or resulting from spray drift. A lthough there were no LOC exceedances for nontarget 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 ma y potentially be affected. Based on the results paraquat may affect the first and second terrestrial-phase PCEs.

The third terrestrial-phase PCE is “reducti on 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 e ndpoints 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 oth er 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 5.2.1.2

. Due to acute and chronic LOC exceedances at all but one use sites (acute only) to terrestrial-phase CRLFs, para quat may result in effects to the fourth terrestrial-phase PCE.

5.2 Risk Description

The risk description synthesizes an overall conclusion regarding th e likelihood of adverse impacts leading to an effects determination ( i.e ., “no effect,” “may affect, but not likely to adversely affect,” or “likely to advers ely 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.

83A summary of the risk estimation results are pr ovided 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 no t 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 sp ecies LOC (0.1) for all uses of paraquat except melons, RQs ranged from 1.28 (Airport/public health use/guava) to 0.06 (mel ons). The Refined acute dietarybased RQs for CRLFs consuming large insects and 15g small insectivore mammals resulted in paraquat use on airports/public health use/guava exceeding the lis ted 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

84LOC Assessment Endpoint Exceedances Description of Results of Risk Estimation (Y/N)

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 sma ll 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 fo r 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. Du e 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 (238g) CRLF consuming la rge 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 (either15g or 35g) using

85LOC Assessment Endpoint Exceedances Description of Results of Risk Estimation (Y/N)

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/pub lic health, guava, and ginger uses of paraquat. The refined chronic dietary-based RQs forCRLFs consuming small terrestrial- phase amphibians using THERPS model exceed the chr onic 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).

86Table 5-9 Risk Estimation Summary for Pa raquat – PCEs of Designated Critical
Habitat for the CRLF

Assessment Endpoint Habitat Effects (Y/N) Description of Results of Risk Estimation

Aquatic Phase PCEs (Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat) Alteration of channel/pond morphology or geometry and/or increase in sediment deposition within the stream channel or pond: aquatic habitat (including riparian vegetation) provides for shelter, foraging, predator avoidance, and aquatic dispersal for juvenile and adult CRLFs. Yes LOCs are exceeded for terrestrial riparian plants and for aquatic non-vascular plants from exposure to paraquat from spray drift.

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. Yes LOCs are exceeded for terrestrial riparian plants and for aquatic plants from exposure to paraquatfrom spray drift. Alteration of riparian and nonvascular plants may result in alteration of temperature, turbidity, and oxygen content.

Alteration of other chemical characteristics necessary for normal growth and viability of
CRLFs and their food source. Yes LOC is exceeded for indir ect effects on terrestrial phase CRLF from most paraquat applications.

Reduction and/or modification of aquaticbased food sources for pre-metamorphs (e.g., algae) Yes 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 yes The AgDRIFT model was used to evaluate potential distances beyond which exposures would be expected to be below the LOC. 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 LOC. For the minimum application rate, the output
indicated a buffer zone ofof >1,000 feet for nonlisted species.

Both the Tier I and Tier II aerial application output for the maximum and minimum application rates of paraquat indicated that th e buffer zone required would be greater than 1,000 feet for non-listed plants. Since the model is restricted to accurately discerning a buffer with in 1,000 feet of the application, the exact distance needed for a buffer to protect listed and non-listed plants is unknown.

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 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.

87Habitat Effects Assessment Endpoint Description of Results of Risk Estimation (Y/N)

which do not contain barriers to dispersal
Reduction and/or modification of food sources for terrestrial phase juveniles and
adults

yes Acute RQs for small mammals and birds exceed the endangered species LOC for all uses of paraquat except Melons.

Chronic dietary RQs for bi rds exceed the endangered species LOC for all uses of paraquat. For small
mammals the chronic dietar y-based RQs exceed the endangered species LOC for all uses of paraquat except Melons. The chronic dose-based RQs for small mammals exceed the endangered species LOC for all uses of paraquat.
Alteration of chemical characteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food

source. yes 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, additio nal information is considered to refine the potential for exposure at th e predicted levels based on th e life history characteristics ( i.e. , habitat range, feedi ng preferences, etc.) of the CRLF. Based on the best available information, the Agency uses the refined ev aluation to distinguish those actions that “may affect, but are not likely to adversely a ffect” from those actions that are “likely to adversely affect” the CRLF.

The criteria used to make determinations that the effects of an acti on 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 c ontext of a level of effect where “take” occurs for even a single individual. “T ake” in this context means to harass or harm, defined as the following:

 Harm includes significant habitat m odification or degradation that results in death or injury to listed species by significantly impairing behavioral patterns such as br eeding, feeding, or sheltering.

 Harass is defined as actions that crea te the likelihood of injury to listed species to such an extent as to significantly disrupt normal behavior patterns which include, but are no t limited to, breeding, feeding, or sheltering.

• Likelihood of the Effect Occurring : Discountable effect s are those that are extremely unlikely to occur.

• Adverse Nature of Effect : Effects that are wholly be neficial without any adverse
effects are not considered adverse.

A description of the risk and effects determ ination for each of the established assessment endpoints for the CRLF is provided in Sections 5.2.1 through 5.2.3

.

885.2.1 Direct Effects

5.2.1.1

5.2.1.2 Aquati c-Phase CRLF

The aquatic-phase considers life stages of th e frog that are obligatory aquatic organisms, including eggs and larvae. It also considers submerged te rrestrial-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, wh ich 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 ch ronic 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 LOC 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 re ported for paraquat, and in all of the reported incidents the certainty of paraquat being res ponsible 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 re gistered use of paraquat dichloride believed that paraquat di chloride was the unlikel y cause of mortality seen; the total mortality of the unknow n fish was also unknown in 1993 and 1992 (I003654-012 and B000175-001 respectively). Th e other incident related to the registered use of paraquat was possibly res ponsible for the deaths of unknown amounts of bass, bluegill sunfish, and crappie in 1997 (I009314-005). The ot her three paraquat incidents were the possible result of undertermined legality us age of paraquat. A total of 54 dead fish (1 largemouth bass, and 53 sunfish) were observed in 1981 (B0000-502-18), an unknown amount of dead bass, bluegill, and crappie were obs erved in 1997 (I005805- 001), and a total of 400 dead fish (200 each of bass and bluegill) were observed in 1999 (I008768-007).

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 estimate s, 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 di rect effects on aquatic-phase CRLF.

Terres trial-Phase CRLF

The RQs representing acute dietary-based expos ures exceed the Agency’s LOC (0.1) for all uses of paraquat except melon (S ection 5.1.2.1.). The RQs ranged from 1.28

89(Airport/public health use) to 0.06 (Melons) (Table 5-5). Th e chronic dietary-based RQs all exceed the Agency’s LOC (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 es timates exposures that are specific to food intake equations for birds. RQs generated fo r 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 amphibianspecific food intake on potential exposures to the terrestrial phase CRLF. The T-HERPS model incorporates the same inputs as T-RE X with equations adjusted for poikilotherm food intake. The dietary-based and dose-b ased EECs generated by T-HERPS are found in Tables 5-10a & b and 5-11a & b, respectiv ely. An example output from T-HERPS is available in Appendix J.

Table 5-10a Upper-bound Kenega Nomogr am 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 Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians

AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTI TUTIONAL/IN DUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 899.99 100.00 1525.46 95.34 31.24

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 899.99 100.00 1525.46 95.34 31.24

Ginger (1 lb cati on/acre; 6 times/yr; 30 day intervals (ag)) 292.84 32.54 496.36 31.02 10.16

CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 184.01 20.45 311.89 19.49 6.39

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 135.00 15.00 228.82 14.30 4.69

Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 40.50 4.50 68.65 4.29 1.41

90Table 5-11b Upper-bound Kenega Nomogr am 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 Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians

AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTI TUTIONAL/IN DUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 899.99 100.00 1054.30 65.89 31.24

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 899.99 100.00 1054.30 65.89 31.24

Ginger (1 lb cati on/acre; 6 times/yr; 30 day intervals (ag)) 292.84 32.54 343.05 21.44 10.16

CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 184.01 20.45 215.56 13.47 6.39

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 135.00 15.00 158.15 9.88 4.69

Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 40.50 4.50 47.44 2.97 1.41

Table 5-12a Upper-bound Kenega Nomogr am 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 CRLF Size (g) Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians

1.4 34.97 3.89 N/A N/A N/A

37 34.36 3.82 618.43 38.65 1.19 AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTI TUTIONAL/IN DUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 238 22.52 2.50 96.14 6.01 0.78

1.4 34.97 3.89 N/A N/A N/A

37 34.36 3.82 618.43 38.65 1.19 Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag)

238 22.52 2.50 96.14 6.01 0.78

1.4 11.38 1.26 N/A N/A N/A

37 11.18 1.24 201.23 12.58 0.39 Ginger (1 lb cati on/acre; 6 times/yr; 30 day intervals (ag))

238 7.33 0.81 31.28 1.96 0.25

911.4 7.15 0.79 N/A N/A N/A

37 7.03 0.78 126.44 7.90 0.24 CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals)

238 4.60 0.51 19.66 1.23 0.16

1.4 5.24 0.58 N/A N/A N/A

37 5.15 0.57 92.77 5.80 0.18 BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 238 3.38 0.38 14.42 0.90 0.12

1.4 1.57 0.17 N/A N/A N/A

37 1.55 0.17 27.83 1.74 0.05 Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag)

238 1.01 0.11 4.33 0.27 0.04

Table 5-131b Upper-bound Kenega Nom ogram 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 CRLF Size (g) Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians

1.4 34.97 3.89 N/A N/A N/A

37 34.36 3.82 997.31 62.33 1.19 AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTI TUTIONAL/IN DUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 238 22.52 2.50 155.04 9.69 0.78

1.4 34.97 3.89 N/A N/A N/A

37 34.36 3.82 997.31 62.33 1.19 Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag)

238 22.52 2.50 155.04 9.69 0.78

1.4 11.38 1.26 N/A N/A N/A

37 11.18 1.24 324.50 20.28 0.39 Ginger (1 lb cati on/acre; 6 times/yr; 30 day intervals (ag))

238 7.33 0.81 50.45 3.15 0.25

1.4 7.15 0.79 N/A N/A N/A

37 7.03 0.78 203.91 12.74 0.24 CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals)

238 4.60 0.51 31.70 1.98 0.16

1.4 5.24 0.58 N/A N/A N/A

37 5.15 0.57 149.60 9.35 0.18 BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 238 3.38 0.38 23.26 1.45 0.12

1.4 1.57 0.17 N/A N/A N/A
37 1.55 0.17 44.88 2.80 0.05 Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag)

238 1.01 0.11 6.98 0.44 0.04

92Acute Exposures

Refined acute dietary-based RQs for CRLFs c onsuming small insects and small herbivore mammals exceed the acute listed species LOC (0.1) for all uses of paraquat except Melons (only small insects when the sma ll mammals weigh 15g). The acute dietarybased RQs for CRLFs consuming large insect s exceed the acute listed species LOC for Airports/public health uses and Guava for both the 15g and 35g small mammals. The acute dietary-based RQs for CRLFs consumi ng small insectivore mammals exceed the acute listed species LOC 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 fo r any paraquat use. Results are presented
in Tables 5-12a and 5-12b

Refined dose-based RQs for CRLF of vary ing weights (1.4g, 37g and 238g) consuming small insects exceed the acute endangered sp ecies LOC (0.1) for onl y 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 li sted species LOC (0.1) for all uses of paraquat (Table 5-13a and Table 5-13b). Th ere were also exceedances the acute listed species LOC (0.1) for medium sized CRLF consuming small insectivore (15g) mammals for the airports/public health, guava, and ginge r uses of paraquat (Table 15-13a). 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 (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 fo r 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 potential ly 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 li sted species LOC (0.1) for all uses of paraquat except melons (Table 5-13a and Ta ble 5-13b). There were no exceedances for large sized (238g) CRLF consuming large inse cts, small insectivore mammals (15g or 35g), or small terrestrial-phase amphibians (Table 15-13a and Tabl e 15-13b). Due to
exceedances of of LOCs for CRLF consumi ng small herbivore mammals (either 15g or 35g) for all paraquat uses except melons, i ndicate that the large sized CRLF could potentially be affected by acute exposures to paraquat.

93Table 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 Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 1.28 0.14 2.17 0.14 0.04

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 1.28 0.14 2.17 0.14 0.04

Ginger (1 lb cation/acre; 6 times/yr; 30 day intervals (ag)) 0.42 0.05 0.71 0.04 0.01

CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 0.26 0.03 0.44 0.03 0.01

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 0.19 0.02 0.33 0.02 0.01

Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 0.06 0.01 0.10 0.01 <0.01

*RQs exceeding the Listed LOC (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 Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians

AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRI AL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 1.28 0.14 1.50 0.09 0.04

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 1.28 0.14 1.50 0.09 0.04

Ginger (1 lb cation/acre; 6 times/yr; 30 day intervals (ag)) 0.42 0.05 0.49 0.03 0.01

CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 0.26 0.03 0.31 0.02 0.01

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 0.19 0.02 0.22 0.01 0.01

94Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 0.06 0.01 0.07 <0.01 <0.01

*RQs exceeding the Listed LOC (0.10) are bolded and shaded

Table 5-16a Refined Dose-based RQs* fo r CRLF consuming different food items (RQs calculated using T-HERPS), the weig hts of small herbivore and insectivore mammals are 15 g.

Scenario CRLF Size (g) Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians

1.4 0.27 0.03 N/A N/A N/A

37 0.27 0.03 4.83 0.30 0.01 AIRPORTS/LANDING FIELDS,
COMMERCIAL/INS TITUTIONAL
/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 238 0.18 0.02 0.75 0.05 0.01

1.4 0.27 0.03 N/A N/A N/A
37 0.27 0.03 4.83 0.30 0.01 Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag)

238 0.18 0.02 0.75 0.05 0.01

1.4 0.09 0.01 N/A N/A N/A

37 0.09 0.01 1.57 0.10 < 0.01 Ginger (1 lb cati on/acre; 6 times/yr; 30 day intervals (ag))

238 0.06 0.01 0.24 0.02 < 0.01

1.4 0.06 0.01 N/A N/A N/A
37 0.05 0.01 0.99 0.06 < 0.01 CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 238 0.04 < 0.01 0.15 0.01 <0.01

1.4 0.04 < 0.01 N/A N/A N/A

37 0.04 < 0.01 0.72 0.05 < 0.01 BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 238 0.03 < 0.01 0.11 0.01 < 0.01

1.4 0.01 < 0.01 N/A N/A N/A
37 0.01 < 0.01 0.22 0.01 < 0.01 Melons (0.3 lb cation/acre; 1time/yr; 1 day intervals) (minimumag) 238 0.01 < 0.01 0.03 < 0.01 < 0.01 *RQs exceeding the Listed LOC (0.10) are bolded and shaded

95Table 5-17b Refined Dose-based RQs* for CRLF consuming different food items (RQs calculated using T-HERPS), the weig hts of small herbivore and insectivore mammals are 35 g.

Scenario CRLF Size (g) Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians

1.4 0.27 0.03 N/A N/A N/A

37 0.27 0.03 7.79 0.49 0.01 AIRPORTS/LANDING FIELDS,
COMMERCIAL/INS TITUTIONA
L/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR),
NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 238 0.18 0.02 1.21 0.08 0.01

1.4 0.27 0.03 N/A N/A N/A

37 0.27 0.03 7.79 0.49 0.01 Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 238 0.18 0.02 1.21 0.08 0.01

1.4 0.09 0.01 N/A N/A N/A

37 0.09 0.01 2.53 0.16 < 0.01 Ginger (1 lb cation/acre; 6 times/yr; 30 day intervals (ag))

238 0.06 0.01 0.39 0.02 < 0.01

1.4 0.06 0.01 N/A N/A N/A

37 0.05 0.01 1.59 0.10 < 0.01 CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 238 0.04 < 0.01 0.25 0.02 < 0.01

1.4 0.04 < 0.01 N/A N/A N/A

37 0.04 < 0.01 1.17 0.07 < 0.01 BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 238 0.03 < 0.01 0.18 0.01 < 0.01

1.4 0.01 < 0.01 N/A N/A N/A

37 0.01 < 0.01 0.35 0.02 < 0.01 Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 238 0.01 < 0.01 0.05 < 0.01 < 0.01
*RQs exceeding the Listed LOC (0.10) are bolded and shaded

A probit slope value for the acute avian toxic ity 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 a nd 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*10 5 (95 % CI: 1 in 4.4*10 1 to 1 in
8.86*10 18 ) (<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-

9612a). 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 fo r any use scenario since there was no LOC
exceedance.

Since the CRLF also consumes larger size s of mammals RQs were also calculated for
small herbivore and insectivore mammals we ighing 35g. Using the revised acute dietarybased 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 1.64*10 4 (95 %
CI: 1 in 2.28*10 1 to 1 in 1.31*10 14 ) (<1 %) at an RQ 0.14 (Air ports/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/publ ic 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 LOC exceedance.

Using the revised acute dose-based RQs fo r 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*10 5 (95 % CI: 1 in 4.4*10 1 to 1 in 8.86*10 18 ) (<1%) at an RQ 0.10 (Ginger, small herbivore mammals weig hing 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 (Air ports/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 terrestri al-phase amphibians modeled for any use
scenario since there were no LOC exceedances.

Using the revised acute dose-based RQs fo r 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*10 5 (95 % CI: 1 in 4.4*10 1 to 1 in 8.86*10 18 ) (<1%) at an RQ 0.10 (Corn, small insectivore mammals weighi ng 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 (Air ports/public health use/Guava, small herbivore mammals we ighing 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 terrestri al-phase amphibians modeled for any use
scenario since there were no LOC exceedances.

Chronic Exposures

Refined chronic dietary-based RQs for CRL Fs consuming small insects and small herbivore mammals (either 15g or 35g) us ing T-HERPS model exceed the chronic species LOC (1.0) for all uses of paraquat (Table 5-14a and 5-14b) . Refined chronic dietary-based RQs for CRLFs consuming larg e insects and small insectivore mammals (either 15g or 35g) using T-HERPS model ex ceed the chronic species LOC (1.0) for Airport/public health, guava, and ginger us es of paraquat (Table 5-14b). The refined

97chronic dietary-based RQs for CRLFs cons uming small terrestrial- phase amphibians using T-HERPS model exceed the chronic spec ies LOC (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-HERP S), the weights of small herbivore and insectivore mammals are 15 g.

Scenario Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 30.0 3.33 50.85 3.18 1.04

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 30.0 3.33 50.85 3.18 1.04

Ginger (1 lb cation/acre; 6 times/yr; 30 day intervals (ag)) 9.76 1.08 16.55 1.03 0.34

CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 6.13 0.68 10.40 0.65 0.21

BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 4.50 0.50 7.63 0.48 0.16

Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 1.35 0.15 2.29 0.14 0.05

*RQs exceeding the Listed LOC (1.0) are bolded and shaded

Table 5-194b Revised Chronic Dietary-ba sed RQs* for CRLF consuming different food items (RQs calculated using T-HERP S), the weights of small herbivore and insectivore mammals are 35 g.

Scenario Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial
Phase Amphibians
AIRPORTS/LANDING FIELDS,
COMMERCIAL/INSTITUTIONAL/INDUSTRIAL PREMISES/EQUIPMENT (OUTDOOR), NONAGRICULTURAL AREAS (PUBLIC HEALTH USE) (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- non-ag) 30.0 3.33 35.14 2.20 1.04

Guava (1 lb cation/acre; 10 times/yr; 5 day intervals) (maximum- ag) 30.0 3.33 35.14 2.20 1.04

Ginger (1 lb cation/acre; 6 times/yr; 30 day intervals (ag)) 9.76 1.08 11.43 0.71 0.34

CORN (SILAGE) (0.5 lb cation/acre; 3 times/year; 5 day intervals) 6.13 0.68 7.19 0.45 0.21

98BEANS - SUCCULENT (LIMA/SNAP), CARROT (INCLUDING TOPS), PEAS (UNSPECIFIED), PEPPER (1 lb cation/acre; 1 time/yr; 1 day intervals) 4.50 0.50 5.27 0.33 0.16

Melons (0.3 lb cation/acre; 1 time/yr; 1 day intervals) (minimum-ag) 1.35 0.15 1.58 0.10 0.05

*RQs exceeding the Listed LOC (1.0) are bolded and shaded

In the available chronic study where Mallar d duck were exposed to paraquat, the NOAEC was 30 ppm and the LOAEC was 10 0 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 th e laboratory. For CRLF consuming large insects (except airport/public health/guava use), small ins ectivore mammals (15g or 35g), and small terrestrial-phase am phibians 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 repr oductive effects were observed in birds, which serve as surrogates for the CRLF.

Of the terrestrial animal incidents that we re reported paraquat was not the only chemical that was present in the field. Only one incide nt was from the regist ered 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 othe rs were Atrazine, Si mazine, Cyanazine, and Esfenvalerate) (I008168-001). With the other tw o incidents, paraquat was considered to be unlikely or possibly responsible for the incident (I000097-015, I007334-001).

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 base d on peak EECs from the standa rd 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).

99The fate characteristics indicat e that paraquat is expected to be persistent in aquatic environments. As a result, the primary food source for the aquatic-phase CRLF (nonvascular aquatic plants) is expected to be adversely affected.

Because of non-vascular LOC exceedance fr om 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 (a lgae). Therefore, paraquat May Affect and is Likely to Adversely Affect (LAA) the CRLF.

5.2.2.2

5.2.2.3 Aquati c Invertebrates

The potential for paraquat to elicit indirect effects to the CRLF via effects on freshwater invertebrate food items is dependent on seve ral factors including: (1) the potential magnitude of effect on freshwater inverteb rate individuals and populations; and (2) the number of prey species potenti ally affected relative to th e 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 a nd terrestrial-phase CRLFs is thought to be aquatic and terrestrial invertebrates found al ong 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 subs equently 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 us ing this method due to the ACR being much higher than the EECs calculated usin g 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 para quat use are judged to be unlikely to possible, the Agency concludes that paraquat will not indirectly affect the CRLF.

Fish a nd 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

100the 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 chr onic RQs could not be calculate d. 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), th e Agency concludes that paraquat will not indirectly affect the aqua tic-phase of the CRLF on an acute or chronic basis from fish or other aquatic- phase frogs as prey items.

5.2.2.4

5.2.2.5 Terres trial Invertebrates

When the terrestrial-phase CRLF reaches juveni le and adult stages, its diet is mainly composed of terrestrial inverteb rates. Terrestrial invertebrate toxicity data is used to assess potential indirect effect s 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 LD 50 was not definitive, and there was little incidence of mortality, RQs were not calculated. However, EECs were comp ared to the highest c oncentration tested.
All of estimated EEC’s the level tested for all uses for small insects and all of the uses greater than 6 applic ations per year with 30 day inte rvals at 1 lb cation/acre per application for large insects; therefore, a preliminary “M ay 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 μ g cation/bee), at which there was a low incidence of mortality. Therefore,
it is reasonable to assume that the effects to terrestrial in vertebrate populations will be negligible for the uses of paraquat in California. Therefore, based on the weight-ofevidence, 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 Ad versely Affect (NLAA) the CRLF.

Mammal s

Life history data for terres trial-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 (Air ports/public health us es/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/p ublic health use/Guava) (T able 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 h ealth 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

101the Listed (endangered species) LOCs are approx imately 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 dos e-based and dietary-based EECs are also well above the levels that were tested, and showed mortality and s ublethal 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 dama ge) were observed in chronic mammalian studies, and resulted in RQ values that exceed ed the LOC (1.0) for all uses (chronic dosebased) 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 th e dietary-based (Table 5-7). Paraquats toxicity, when combined in the diet is lowe r than the gavage (dos e) based treatment, indicating that the toxicity may be reduced in combinati on 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 item s, and therefore paraquat May Affect and is Likely to Adversely Affect (LAA) the CRLF.

5.2.2.6

5.2.3.1 Terres trial-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. Th e T-HERPS model was therefore employed as a refinement tool to explore amphibian-sp ecific food intake on potential exposure to terrestrial-phase amphibian f ood items for the CRLF. The T-HERPS model incorporates the same inputs as T-REX with equations ad justed for poikilotherm food intake. As described in Section 5.2.1.2, the RQs for sm all terrestrial-phase amphibians did not exceed the listed species LOC (0.1) for any use of paraquat. Reduction in amphibian prey items, specifically other fr ogs is not affected from para quat use. Other items in the prey base all had RQs that exceeded the listed species LOC for numerous uses of paraquat.

Based on this evidence, a May Affect a nd is Likely to Adversely Affect (LAA)
determination is made for indirect effe cts via reductions in prey base to the terrestrial-phase CRLF.

5.2.3 Indirect Effects (via Habitat Effects)

Aquati c Plants (Vascular and Non-vascular)

Aquatic plants serve several important functi ons in aquatic ecosystems. Non-vascular aquatic plants are primary producers and pr ovide the autochthonous energy base for aquatic ecosystems. Vascular plants provide structure as at tachment sites and refugia for many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In

102addition, vascular plants al so provide primary productivity and oxygen to the aquatic ecosystem. Rooted plants help reduce se diment loading and provide stability to
nearshore areas and lower streambanks. In a ddition, vascular aquatic plants are important as attachment sites for egg masses of CRLFs.

Potential indirect effects to the CRLF ba sed on impacts to habitat and/or primary production were assessed using RQs from fres hwater aquatic vascul ar and non-vascular plant data. Indirect effects of paraquat to the aquatic-phase CRLF (tadpoles) are present in the reduction of non-vascular aquatic plan ts in the aquatic-phase CRLFs diet. The Agency’s LOC (1.0) for non-vascular plants is exceeded for all us es of paraquat in
California. The non-vascul ar 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 (t adpoles) are also found via the reduction in vascular aquatic plants in the aquatic-phase CRLFs diet. The Agency’s LOC (1.0) for vascular plants is ex ceeded for all uses of paraquat in California. The acute RQs range from 0.77 for airports, commercial/industr ial areas, and public health areas to 0.02 for melons (Section 5.1.1.2).

An analysis of the fate charac teristics of paraquat indicates th at paraquat is expected to be persistent in aquatic environments. As a result, the primary food source for the aquaticphase CRLF (both vascular and non-vascular aquatic plants) is expected to be adversely
affected.

Because of the non-vascular aquatic plan t LOC exceedances for registered uses of paraquat, and verified non-target incident s resulting from paraquat use, the Agency concludes that there is a potential of indi rect 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 Terres trial Plants

Terrestrial plants serve several important ha bitat-related functions for the CRLF. In addition to providing habitat and cover for inve rtebrate and vertebrate prey items of the CRLF, terrestrial vegetation also provides sh elter for the CRLF and cover from predators while foraging. Terrestrial plan ts also provide energy to th e terrestrial ecosystem through primary production. Upland vegetation incl uding grassland and woodlands provides cover during dispersal. Riparian vegetation he lps 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 r each the watershed, and serving as an energy

source.

Potential indirect effects to the CRLF ba sed on impacts to habitat and/or primary production were assessed using RQs from m onocot and dicot plant data. The RQs for monocots were below the Agency’s LOC, wher eas the dicot spray dr ift RQ exceeded the Agency’s RQ (1.0), for all aerial applica tions of paraquat (Tables 5-15 and 5-16).

103Twenty-one incidents have been reported fo r paraquat, listed under paraquat and paraquat dichloride, but they are one in the same. Th ere were nine incidents from the misuse of paraquat that resulted in plant damage, w ith one incident of plant mortality (I014409- 024), and one incident of plant discolorati on (I005880-005). Of the reported misuses of paraquat; two from general misuse, six from accidental misuse, and one from the intentional misuse of paraqua t (I014409-024, I013554-040, I005660-005, I005880-005, I007371-033, I007371-034, I007371-035, I007371-008, and I016940-005 respectively).
There were a total of six incidents from the re gistered use of paraqua t and all resulted in plant damage (I013884-038, I013636-029, I011838-055, I014034-099, I012684-010, I001131-001). The remaining six incidents were from undetermined legality of paraquat use and resulted in plant dama ge (I014409-001, I013884-014, I012366-023, I009573- 009, I011838-091, and I011838-038).

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 Affe ct (LAA) the CRLF indirectly via habitat degradation through reduction in terrestrial plants. Of particular concern is the risk from spray drift during/a fter aerial application.

5.2.4 Effects to Designated Critical Habitat

5.2.4.1 Aquati c-Phase PCEs

Three of the four assessment endpoints for the aquatic-phase primary constituent elements (PCEs) of designated critical ha bitat for the CRLF are related to potential effects to aquatic and/or terrestrial plants:

• Alteration of channel/pond morphology or ge ometry and/or increase in sediment deposition within the stream channel or pond: aquatic ha bitat (including riparian vegetation) provides for shelter, fora ging, 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-b ased food sources for pre-metamorphs ( e.g., algae).

Conclusions for potential indire ct effects to the CRLF via di rect effects to aquatic and terrestrial plants are used to determine whet her modification to critical habitat may occur. LOCs are exceeded for terrestrial riparian plan ts and for aquatic plants from exposure to paraquat from spray drift. A lteration of riparian and vasc ular 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

104sources may occur from most use sites. Like wise, 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 “altera tion 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 Terres trial-Phase PCEs

Two of the four assessment endpoints for the te rrestrial-phase PCEs of designated critical habitat for the CRLF are related to poten tial effects to terrestrial plants:

• Elimination and/or disturbance of upland ha bitat; ability of hab itat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or drip line surr ounding aquatic and riparian ha bitat that are comprised of grasslands, woodlands, and/or wetland/r iparian plant species that provides the CRLF shelter, forage, and predator avoidance.

• Elimination and/or disturbance of dispersa l habitat: Upland or riparian dispersal habitat within designated un its and between occupied locations within 0.7 mi of
each other that allow for movement be tween sites including both natural and
altered sites which do not cont ain barriers to dispersal.

There is a potential for habitat effects vi a 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 “reducti on 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 i nvertebrates, 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

105invertebrates, 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 ch aracteristics necessary for normal growth and viability.

5.2.5 Spatial Extent of Potential Effects

A May Affect determination applies to t hose 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 pa raquat’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 ar eas beyond the initial area of c oncern that may be impacted by spray drift. The identified direct and indi rect effects are anticip ated 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 downs tream 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 in to CRLF habitat, there is potential to affect either the CRLF or modify its habitat. Thes e lotic aquatic habitats within the CRLF core areas and critical habitats pot entially contain concentrati ons 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 estim ate 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 spra y drift distances was completed using AgDrift with the most sensitive endpoints for terrestrial plants.

For paraquat use with the maximum applicati on rate relative to the terrestrial-phase CRLF, the results of the screening-level risk assessment indicate that spray drift for aerial

106applications, using both the Tier I and Tier II mode, exceeds the 1,000 foot range of the AgDrift model . For the Tier I groun d mode (no higher tier modeling for ground applications is available in AgDrift), the sp ray drift buffer distance is found to be >1,000 feet for non-listed plants as well. A summar y 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 fo r comparison purposes.
For the Tier I and Tier II mode for the aeria l 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 di stance was found to be >1,000 f eet 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 spat ial extent of the effects determination that is relevant to the CRLF (i.e. NLAA versus LAA), an analys is was conducted using the most sensitive non-listed terrestrial plant EC 25 of 0.014 lbs cation/acre. Typically the NOAEC is used when there is an obligate relationship betw een the species being assessed and endangered plants (or other taxa). However, there is no obligate relationshi p between the CRLF and any endangered plant; therefore the LAA/NLAA determin ation is based on the area defined by the non-listed species LOC (i.e., EEC/EC 50 ).

107Table 5-20 Summary of AgDrift Predicted Terrestrial Spray Drift Distances Using Maximum Application Rate

Risk Class Risk Description Application Rate (lb cation/acre) Toxicity
Value
Used Fraction o f applied Nonvolatile Rate (lb/a) Minimum Spray Volume Rate (gal/a) Active Rate (lb ai/a) Distance

Non-Listed Plants Potential for effects to nontarget, non-listed plants from

exposures 1 EC 25 = 0.014 lb
cation/A 0.000004 Does not apply Does not apply Does not apply >1,000 feet

Risk Class Risk Description Application Rate (lb cation/acre) Toxicity
Value
Used Fraction o f applied Nonvolatile Rate (lb/a) Minimum Spray Volume Rate (gal/a) Active Rate (lb ai/a) Distance

Non-Listed Plants Potential for effects to nontarget, non-listed plants from

exposures 1 EC 25 = 0.014 lb
cation/A 0.000004 Does not apply Does not apply Does not apply >1,000 feet

Risk Class Risk Description Application Rate (lb cation/acre) Toxicity
Value
Used Fraction o f applied Nonvolatile Rate (lb/a) Minimum Spray Volume Rate (gal/a) Active Rate (lb ai/a) Distance

Non-Listed Plants Potential for effects to nontarget, non-listed plants from

exposures 1 EC 25 = 0.014 lb
cation/A 0.000004 0.683 0.317 1 >1,000 feet Tier II Aerial A pp lication Tier I Aerial A pp lication Tier I Ground A pp lication

Table 5-21 Summary of AgDrift Predicte d Aquatic Spray Drift Distances Using Minimum Application Rate

Risk Class Risk Descri p tion Application Rate (lb
cation/acre ) Toxicity
Value
Used Fraction of

a pp lied Nonvolatile

Rate ( lb/a ) Minimum Spray Volume

Rate (g al/a ) Active Rate ( lb ai/a ) Distance

Non-Listed Plants Potential for effects to nontarget, non-listed plants from

ex p osures 0.3 EC 25 =
0.014 lb
cation/A 0.000012 Does not

a pp l y Does not

a pp l y Does not

a pp l y >1,000 feet

Risk Class Risk Descri p tion Application Rate (lb
cation/acre ) Toxicity
Value
Used Fraction of

a pp lied Nonvolatile

Rate ( lb/a ) Minimum Spray Volume

Rate (g al/a ) Active Rate ( lb ai/a ) Distance

Non-Listed Plants Potential for effects to nontarget, non-listed plants from

ex p osures 0.3 EC 25 =
0.014 lb
cation/A 0.000012 Does not

a pp l y Does not

a pp l y Does not

a pp l y >1,000 feet

Risk Class Risk Descri p tion Application Rate (lb
cation/acre ) Toxicity
Value
Used Fraction of

a pp lied Nonvolatile

Rate ( lb/a ) Minimum Spray Volume

Rate (g al/a ) Active Rate ( lb ai/a ) Distance

Non-Listed Plants Potential for effects to nontarget, non-listed plants from

ex p osures 0.3 EC 25 =
0.014 lb
cation/A 0.000012 0.683 0.317 0.3 >1,000 feet Tier II Aerial Application Tier I Ground Application

Tier I Aerial Application

5.2.5.2 Downst ream Dilution Analysis

To complete this assessment, the greatest ratio of aquatic RQ to LOC was estimated. Using an assumption of uniform runoff across the landscape, it is assumed that streams flowing through treated areas (i .e. the initial area of concern) are represented by the

108modeled EECs; as those waters move downstr eam, it is assumed that the influx of nonimpacted water will dilute the concen trations 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 applicat ions to airports/commercial/public health areas (non-agricultural use) of 892 ug/L yiel ds 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/vine yard, 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 base d on the area defined by the point where
concentrations exceed the EC 50 value.

5.2.5.3 Overla p between CRLF habitat and Spatial Extent of Potential
Effects

An LAA effects determination is made to t hose 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, crit ical habitat and available occurrence data
for CRLF.

For paraquat, the use pattern in the followi ng land cover classes (forest land cover, cultivated crop, orchard/vineya rd, pasture/hay land cover, an d developed land cover) also include areas beyond the initial area of con cern that may be impacted by spray drift overlaps with CRLF habitat. Appendix D provide s maps of the initia l area of concern, along with CRLF habitat areas, including cu rrently occupied core areas, CNDDB occurrence sections, and designated critical habi tat. It is expected that any additional
areas of CRLF habitat that are located at l east 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 crit ical habitat effects determination.

109Figure 5-1. Overlap Map: CRLF Habitat and Paraquat Initial Area of Concern

110

### 6.0 Uncertainties

6.1 Exposure Assessment Uncertainties

6.1.1 Maximum Use Scenario

The screening-level risk assessment focuses on characterizing poten tial ecological risks resulting from a maximum use scenario, which is determined from labeled statements of maximum application rate and number of appli cations with the shortest time interval between applications. The frequency at whic h 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 gr own 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 Calif ornia 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: co coa, 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 es timate runoff from a ten hectar e field into a one hectare by two meter deep “standard” pond. This first ti er is designed as a coarse screen and estimates conservative pesticide concentrations in surface water from a few basic chemical parameters and pesticide label use an d application information. Tier I is used to screen chemicals to determine which ones pot entially pose sufficient risk to warrant higher level modeling. It calcula tes acute as well as longer-term estimated environmental concentration (EEC) values. It considers redu ction in dissolved pe sticide concentration due to adsorption of pesticide to soil or sediment, incorporation, degradation in soil before washoff to a water body, direct deposi tion of spray drift in to the water body, and degradation of the pesticid e 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 repres ent conservative estimates, and to avoid
underestimations of the actual e xposure. The standard scenario consists of application to a 10-hectare field bordering a 1-he ctare, 2-meter deep (20,000 m 3 ) pond with no outlet. Exposure estimates generated using the pond are intended to represent a wide variety of
vulnerable water bodies that oc cur at the top of watersheds including prairie pot holes, playa lakes, wetlands, vernal pools, man-ma de and natural ponds, and intermittent and lower order streams. As a group, there are fact ors that make these water bodies more or

111less vulnerable than the pond. Static water bodies that have larger ratios of pesticidetreated drainage area to wa ter 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 th e pond has no discharge. As watershed size increases beyond 10-hectares, it becomes increas ingly 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 so me unique aquatic habitats that are not accurately captured by this modeling scenar io 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 a nd depth and/or are located adjacent to larger orsmaller drainage areas than the EXAMS pond. The Agency does not currently have sufficient informa tion regarding the hydrology of these aquatic habitats to develop a specific alternate scenar io 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 addi tion, 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 thes e 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. M obility input values are chosen to be representative of conditions in the environment. The natural va riation in soils adds to the uncertainty of modeled values. Factors such as application date, crop emergence date, and canopy cover can also affect estimated c oncentrations, adding to the uncertainty of
modeled values. Factors within the ambien t environment such as soil temperatures, sunlight intensity, antecedent soil moistu re, and surface water temperatures can cause actual aquatic concentrations to differ for the modeled values.

Unlike spray drift, tools are currently not av ailable to evaluate th e effectiveness of a vegetative setback on runoff and loadings. Th e effectiveness of vegetative setbacks is highly dependent on the condition of the vegetative strip. For example, a wellestablished, healthy vegetative setback can be a very eff ective means of reducing runoff and erosion from agricultural fields. Alternatively, a setbac k of poor vegetative quality
or a setback that is channelized can be ine ffective 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 aqua tic exposure predictions are

112likely to overestimate exposure where h ealthy vegetative setbacks exist and underestimate exposure where poorly developed, channelized, or bare setbacks exist.

In order to account for uncerta inties 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 agricu ltural use areas. Yet, th e 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 pa raquat, it is believed that the larger the clay content in the soil, the greater the likelihood that paraquat will ad sorb 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 shoul d be noted that, in some ar eas 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 pest icide is applied to highly permeable soils overlying shallow unconfined ground water, an d rainfall is sufficient to drive the chemical through the soil to ground water. So luble chemicals that are primarily subject to photolytic degradation will be very likel y to persist in ground water, and can be transportable over long distances. Simila rly, many chemicals degrade slowly under anaerobic conditions (co mmon in aquifers) and are thus mo re 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 ba seflow (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 subs equent 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 occurr ed prior to discharge. Nevertheless, where paraquat is applied to highly permeable soil s over shallow ground wa ter where there is a net recharge to adjacent str eams, ground water could still be a consistent source of chronic background concentrations in surface water, and may also add to surface runoff

113during storm events (as a result of e nhanced 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 characteri stics throughout a lands cape. It is well
documented that runoff characteristics ar e 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 (b ased on predicted in-stream dilution) was that the entire landscape exhi bited runoff properties identical to those commonly found in agricultural lands in this re gion. 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 do minated by the relationship between impermeable surfaces (roads, lots) and grasse d/other areas (lawns) plus local drainage management; c) urban areas, that are do minated by managed storm drainage and impermeable surfaces; and d) agricultural areas dominated by Hortonian and focused runoff (especially with row crops), a re fined assessment should incorporate these differences for modeled stream flow ge neration. As the z one 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 th e 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. R unoff from forested areas ranges from 45 – 2,700% less than from agricultural areas; in mo st studies, runoff was 2.5 to 7 times higher in agricultural areas (Okisaka et al. 1997; Karvonen et al. 1999; McDonald et al. 2002; Phuong and van Dam 2002). Differences in runoff potential between urban/suburban areas and agricultural areas are generally le ss 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 counter act the effects of the aforementioned issue. For example, the di lution model considers that 100% of the agricultural area has the chemical applied, which is almost certainly a gross overestimation. Thus, there will be assumed chemic al 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 ot her) confounding factors, Agency believes that this model gives us the best available estimates under current circumstances.]

1146.1.5 Usage Uncertainties

County-level usage data were obtained from California’s Department of Pesticide Regulation Pesticide Use Reporti ng (CDPR PUR) database. Ei ght years of data (1999 – 2006) were included in this analysis b ecause 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 out liers was provided by CDPR for 2001 and earlier pesticide data; therefore, this inform ation 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 c oncentrations. 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 pesticid e usage data, there may be instances of misuse and misreporting. The Agency made use of the most current, verifiable information; in cases where ther e 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 it ems. These residue assumptions are believed to reflect a realistic upper-bound residue estimate, alt hough 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 devel op 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 pl ants 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 laborato ry. Although the screening a ssessment process adjusts dryweight 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 concentrati on- 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 betw een laboratory and wild diets suggest that current screening assessment me thods 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 mamm al’s assimilation ranges from 41 – 85% (U.S. EPA 1993). If it is assumed that labo ratory 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.

115For 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 sugges t 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 applicati ons 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 appl ication 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 afte r 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 re peatedly. It appears that in most areas (based upon available meteorological data) wind direction is temporal ly very changeable, even within the same day. Additionally, other factors, includi ng variations in topography, cover, and meteorological conditions over the transpor t distance are not accounted for by the AgDRIFT model ( i.e ., it models spray drift from aeria l and ground applications in a flat area with little to no ground cover and a st eady, constant wind speed and direction). Therefore, in most cases, th e drift estimates from AgDR IFT 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), th e application method ( e.g. , aerial), release hei ghts and wind speeds. Alterations in any of these inputs would cha nge 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 speed s 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 risk s, 21-day EECs and the lowest chronic toxicity value for invertebrates ar e used to derive RQs. However, since freshwater invertebrate chronic toxicity values are not available at th is time, the indirect

116chronic toxicity values for the CRLF were unabl e 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 orga nism 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. Aqua tic invertebrate acute testing is performed on recommended immature age classes ( e.g. , first instar for daphni ds, second instar for amphipods, stoneflies, mayflies, and third instar for midges).

Testing of juveniles may overe stimate toxicity at older age classes for pesticide active ingredients that act directly without me tabolic transformation because younger age classes may not have the enzymatic systems a ssociated 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 th e most sensitive life-stage information as measures of effect for surrogate aquatic an imals, and is therefore, considered as protective of the CRLF.

6.2.3 Use of Surrogate Species Effects Data

Guideline toxicity tests and open literature da ta 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, endpoint s based on freshwater fish ecoto xicity 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 th e potential risks to those species. Efforts are made to select the organisms most likel y to be affected by the type of compound and usage pattern; however, there is an inherent uncertainty in extrapol ating across phyla. In addition, the Agency’s LOCs are intentionally set very low, and conservative estimates are made in the screening level risk a ssessment to account fo r 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 respon ses to the pesticide, as determined by the testing of species response to chronic expos ure conditions and subsequent chronic risk
assessment. Consideration of additional sublet hal 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 fu ll suite of sublethal effects from valid open literature studies is considered for the purposes of defining the action area.

117There 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 quantit ative risk characterization. Although one study did provide some informati on regarding different biochemical factors influenced by exposures to paraquat (E 104191). Further details on ECOTOX studies are provided in Appendix G, and c ontain the rejection codes and other information as to why
studies from ECOTOX we re not used.

To the extent to which sublethal effects ar e not considered in this assessment, the potential direct and indir ect 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 sugges t that this assumption leads to an overestimation of exposure to species that do not occupy the treated field exclusively and permanently.

118

### 7.0 Risk Conclusions

In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the information presented in this endangered specie s risk assessment represents the best data currently available to assess the potential risk s 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. Th e 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 cumu lative effects for the CRLF is provided in
Attachment II.

There are three exceptions to this determinati on. 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 LOC (0.05). Second, for the indirect effects to the CRLF, the aquatic invertebrates, a No Effect (NE) determination was also made, as no ne of the EECs for any of the uses exceeded the listed species LOC (0.05). Third, al so 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 consum es. Likewise, none of the EECs for any of
the uses exceeded the listed species LOC (0.05). All of th e other direct and indirect
effects to the CRLF were determined to Likely to Adversely Affect (LAA) the CRLF.

The LAA effects determination applies to t hose 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 pa raquat’s use pattern is identified, using land cover data that correspond to paraquat’s us e 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, CNDD B occurrence sections, and designated critical habitat for the CRLF that ove rlap with the initial area of concern plus at least 1,000 feet from its boundary, see S ection 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 resu lts 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. Pl ease see Section 5.2.5 for a more detailed description. If any of these streams reaches flow into CRLF habitat, there is

119potential to affect either th e CRLF or modify its habitat. These lotic aquatic habitats
within the CRLF core areas and critical hab itats potentially contai n 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 a dditional areas of CRLF hab itat 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 maxi mum 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 L AA/effects to critical
habitat effects determination.

A summary of the risk conclusions and e ffects determinations for the CRLF and its critical habitat, given the uncertainties discussed in Section 6, is presented in Table
7-1 and Table 7-2

. Table 7-1 Effects Determination Summary for Paraquat Use and the CRLF

Assessment

Endpoint Effects
Determination 1 Basis for Determination

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 Ca lifornia. The chronic EECs are all less
than the estimated chronic value derived fr om the ACR. Theref ore, there are no
exceedances of chronic LOCs. Survival, growth, and/or reproduction
of CRLF
individuals NE 1

LAA 1 Terrestrial-phase (Juveniles and Adults) :

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 in all uses ex ceeding 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 mel ons 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 acu te endangered speci es 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. Th e 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.

120Refined 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 CRL F consuming small insectivore (15g) mammals for the airports/public health, guav a, and ginger uses of paraquat. For medium sized CRLF consuming small in sectivore (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 ex ceedances for medium sized (37g) CRLF consuming large insects or small terre strial-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 medi um 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 (238g) CRLF consuming larg e 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, indicat es 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 (either15g or 35g) using T-HERPS model exceed the chronic species LOC (1.0) for all uses of paraquat. Refined chronic dietarybased RQs for CRLFs consuming large insects and small insectivore mammals (either 15g or 35g) us ing T-HERPS model exceed the chronic species LOC (1.0) for Airport/public health, guava, an d 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).

Potential for Indirect Effects

LAA 1 Aquatic prey items, aquatic habitat, cover and/or primary productivity

LOCs for non-vascular plants are exceede d for all uses. The non-vascular plant RQs range from 138 for airports, commer cial/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/indu strial 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 comp aring chronic indire ct 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 co mparing chronic direct effects, the
estimated chronic value at 1.89 ppm is not exceeded for any use.

121LAA 1 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 invertebra tes would not likely adversely affect the CRLF indirectly as food.

For small mammals the acute dose-base d RQs exceed the Agency’s LOC (0.1) for all uses of paraquat, the RQs ranged from 7.63 (airports/public health use/guava) to 0.34 (melons). The ch ronic dose-based RQs exceed the Agency’s LOC (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 LOC (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 amphi bians did not exceed the listed species LOC (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 semiaquatic and upland dry areas do not exceed the Agency’s LOC (1.0) for any uses. All aerial applications of paraquat results in spray drift exc eedances 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 (NLA A); May affect, likely to adversely affect (LAA)

Table 7-2 Effects Determination Summa ry 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 cont ent necessary for normal growth and viability of juvenile and adult CRLFs and their food.

LOCs are exceeded for terrestrial ripari an 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 char acteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food source. The RQs for vascular plants did not exce ed the Agency’s LOC (1.0) for any uses of paraquat in California.

122The RQs for non-target terrestrial monocot and dicot plants inhabiting semiaquatic 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 exc eedances for dicots (only).

The use of paraquat on most use sites w ill exceed the revised acute dietary- and dose-based LOC and chronic LOC 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 Sect ion 7 of the Endangered Specie s Act should be initiated. When evaluating the significance of this ri sk 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 ar ea. In fact, given the assumptions of drift and downstream transport (i.e., attenuation with distance), pes ticide exposure and associated risks to the species and its resour ces 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 re quire information and assessment techniques that are not currently avai lable. Examples of such information and methodology required for this type of an alysis 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 quantitat ive extrapolation of the present risk assessment’s predictions of individual effects to the proportion of the population extant within geographical areas where t hose effects are predicted. Furthermore, such population information would allow fo r a more comprehensive evaluation of the significance of potential resource impa irment to individuals of the species.

• Quantitative information on prey base requirements for individual aquatic- and terrestrial-phase frogs. While existing in formation provides a preliminary picture of the types of food sources utilized by the frog, it does not establish minimal requirements to sustain healthy individua ls at varying life stages. Such
information could be used to establish bi ologically relevant thresholds of effects on the prey base, and ultimately establis h geographical limits to those effects. This information could be used together with the density data discussed above to
characterize the likelihood of a dverse effects to individuals.

• Information on population responses of prey base organisms to the pesticide. Currently, methodologies are limited to pr edicting exposures and likely levels of direct mortality, growth or reproduct ive impairment immediately following exposure to the pesticide. The degree to which repeated exposure events and the inherent demographic characte ristics 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 pesticid e exposure would allow for a more refined determination of the magnitude and durati on of resource impairment, and together with the information described above, a more complete prediction of effects to individual frogs and potential modi fication to critical habitat.

123

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