# Risks of Diuron 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

February 18, 2009

### Primary Authors: Ron Dean, Biologist Tiffany Mason, Environmental Engineer Bill Shaughnessy, PhD, E nvironmental Scientist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507C)

Secondary Review: William P. Eckel, PhD, Senior Scientist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)

Jean Holmes, Senior Scientist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)

Branch Chief, Environm ental Risk Branch II: Tom Bailey, Ph D, Branch Chief
Environmental Fate and Effects Division (7507P)

iTable of Contents 1.0 Executive Summary.................................................................................................1

2.0 Problem Formulation .............................................................................................11 2.1 Purpose.................................................................................................................... .......11 2.2 Scope...................................................................................................................... ........13
2.3 Previous Assessments ....................................................................................................14
2.4 Stressor Source and Distribution ...................................................................................15 2.4.1 Environmental Fate Properties...............................................................................15 2.4.2 Environmental Transport Mechanisms..................................................................17
2.4.3 Mechanism of Action.............................................................................................21
2.4.4 Use Characterization..............................................................................................21 2.5 Assessed Species........................................................................................................... .25
2.5.1 Distribution ............................................................................................................2 5 2.5.2 Reproduction..........................................................................................................28
2.5.3 Diet..................................................................................................................... ....28
2.5.4 Habitat.................................................................................................................. ..29 2.6 Designated Critical Habitat............................................................................................30
2.7 Action Area................................................................................................................ ....32 2.8 Assessment Endpoints and Measures of Ecological Effect ...........................................35 2.8.1. Assessment Endpoints for the CRLF.....................................................................36 2.8.2 Assessment Endpoints for Designated Critical Habitat.........................................37 2.9 Conceptual Model..........................................................................................................4 0 2.9.1 Risk Hypotheses.....................................................................................................40 2.9.2 Diagram.................................................................................................................. 40 2.10 Analysis Plan ............................................................................................................. ....44
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model ......................44 2.10.1.1 Measures of Exposure............................................................................ 44
2.10.1.2 Measures of Effect ................................................................................. 46 2.10.1.3 Integration of Exposure and Effects ...................................................... 47
2.10.2 Data Limitations.....................................................................................................48 3.0 Exposure Assessment.............................................................................................48 3.1 Label Application Rates and Intervals...........................................................................49 3.2 Aquatic Exposure Assessment.......................................................................................49 3.2.1 Modeling Approach ...............................................................................................49 3.2.2 Model Inputs ..........................................................................................................49
3.2.3 Results.................................................................................................................. ..50 3.2.4 Existing Monitoring Data ......................................................................................52 3.2.6 Downstream Dilution Analysis..............................................................................53 3.3 Terrestrial Animal Exposure Assessment......................................................................54 3.4 Terrestrial Plant Exposure Assessment..........................................................................57 3.4.1 Spray Drift Buffer Analysis...................................................................................59

4.0 Effects Assessment ................................................................................................61 4.1 Toxicity of Diuron to Aquatic Organisms .....................................................................63 4.1.1 Toxicity to Freshwater Fish ...................................................................................65 4.1.2 Toxicity to Freshwater Invertebrates .....................................................................65

ii4.1.3 Toxicity to Aquatic Plants .....................................................................................65 4.2 Toxicity of Diuron to Terrestrial Organisms .................................................................66 4.2.1 Toxicity to Birds ....................................................................................................67 4.2.2 Toxicity to Mammals.............................................................................................68 4.2.3 Toxicity to Terrestrial Invertebrates ......................................................................68 4.2.4 Toxicity to Terrestrial Plants .................................................................................68 4.3 Use of Probit Slope Response Relationship to Provide Information on the Endangered Species Levels of Concern.........................................................................................................69
4.4 Incident Database Review..............................................................................................70

5.0 Risk Characterization.............................................................................................70

5.1 Risk Estimation............................................................................................................ ..70 5.1.1 Exposures in the Aquatic Habitat ..........................................................................71 5.1.1.1 Direct Effects to Aquatic-Phase CRLF................................................................. 71 5.1.1.2 Indirect Effects to Aquatic-Phase CRL F via Reduction in Prey (non-vascular aquatic plants, aqua tic invertebrates, fish, and frogs)........................................... 79
5.1.1.3 Indirect Effects to CRLF via Reducti on in Habitat and Primary Productivity (Freshwater Aquatic Plants).................................................................................. 86 Table 5.4 Summary of Acute RQs Used to Es timate Indirect Effects to the CRLF via Effects to Vascular Aquatic Plan ts (habitat of aquatic-phase CRLF) a ...............86 5.1.2 Exposures in the Terrestrial Habitat ......................................................................89 5.1.2.1 Direct Effects to Terrestrial-phase CRLF............................................................. 89
5.1.2.2 Indirect Effects to Terre strial-Phase CRLF via Reducti on in Prey (terrestrial invertebrates, mammals, and frogs)...................................................................... 91
5.1.2.3 Indirect Effects to CRLF via Reduc tion in Terrestrial Plant Community (Riparian and Upland Habitat).............................................................................. 93 5.1.3 Primary Constituent Elements of Designated Critical Habitat ..............................94 5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat) ................................................................................................................ 94 5.1.3.2 Terrestrial-Phase (Upland Hab itat and Dispersal Habitat) ................................... 95 5.2 Risk Description........................................................................................................... ..96
5.2.1 Direct Effects .......................................................................................................100 5.2.1.1 Aquatic-Phase CRLF .......................................................................................... 100
5.2.1.2 Terrestrial-Phase CRLF ...................................................................................... 101 5.2.2 Indirect Effects (via Re ductions in Prey Base)....................................................104 5.2.2.1 Algae (non-vascular plants) ................................................................................ 104 5.2.2.2 Aquatic Invertebrates.......................................................................................... 105 5.2.2.3 Fish and Aquatic-phase Frogs............................................................................. 106
5.2.2.4 Terrestrial Invertebrates...................................................................................... 106
5.2.2.5 Mammals............................................................................................................. 107 5.2.2.6 Terrestrial-phase Amphibians............................................................................. 107 5.2.3 Indirect Effects (via Habitat Effects) ...................................................................108 5.2.3.1 Aquatic Plants (Vascular and Non-vascular)...................................................... 108
5.2.3.2 Terrestrial Plants ................................................................................................. 108 5.2.4 Modification to Designa ted Critical Habitat........................................................109 5.2.4.1 Aquatic-Phase PCEs ........................................................................................... 109
5.2.4.2 Terrestrial-Phase PCEs ....................................................................................... 110

iii6.0 Uncertainties ........................................................................................................111 6.1. Exposure Assessment Uncertainties ............................................................................111
6.1.1 Maximum Use Scenario.......................................................................................111 6.1.2 Aquatic Exposure Modeling of Diuron................................................................112
6.1.3 Action Area Uncertainties....................................................................................113 6.1.4 Usage Uncertainties .............................................................................................114 6.1.5 Terrestrial Exposure Modeling of Diuron............................................................114
6.2 Effects Assessment Uncertainties................................................................................115 6.2.1 Age Class and Sensitivity of Effects Thresholds.................................................115 6.2.2 Use of Surrogate Species Effects Data ................................................................116
6.2.3 Sublethal Effects ..................................................................................................117 6.2.4 Location of Wildlife Species ...............................................................................117

7.0 Risk Conclusions .................................................................................................117

8.0 References............................................................................................................122

Appendices

Appendix A Multi-ai Product Analysis Appendix B Chemical Structure of Parent and Degradates Appendix C Use Rates and Methods Appendix D CDPR PUR Usage Data Appendix E RQ Method and LOCs Appendix F Spatial Summary of Diuron Appendix G PRZM/EXAMS Output Appendix H T-REX Example Output Appendix I TerrPlant Example Output Appendix J Bibliography of ECOTOX Open Literature Not Evaluated Appendix K Accepted ECOTOX Data Table Spreadsheet Appendix L Ecological Effects Data Appendix M Diuron Incidents Appendix N T-Herps Example Output

Attachment I. Status and Life Hist ory of the California Red-legged Frog
Attachment II. Baseline Status and Cumu lative Effects for the California Red-legged Frog

ivList of Tables

Table 1.1 Effects Determination Summary for Effects of Diuron on the CRLF............... 5 Table 1.2 Effects Determination Summary for the Critical Habitat Impact Analysis....... 6 Table 1.3 Diuron Use-specific Di rect Effects Determinations 1 for the CRLF .................. 7 Table 1.4 Diuron Use-specific Indi rect Effects Determinations 1 Based on Effects to Prey8 Table 2.1 Summary of Diuron Half-lives ....................................................................... 17 Table 2.2 Active Use Sites for Diuron as Applicable to California................................. 24 Table 3.1 Summary of PRZM/EXAMS Enviro nmental Fate Data Used for Aquatic Exposure Inputs for Diuron Endangered Species Assessment for the CRLF................... 50 Table 3.2 Table Aquatic EECs (ppb) for Diuron Uses in California............................... 51 Table 3.3 T-REX Model Input Parameters...................................................................... 54 Table 3.4 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based Exposures of the CRLF and its Prey to Diuron ................................................................ 55 Table 3.5 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Terrestrial Invertebra te Prey Items ................................................................................... 56 Table 3.6 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semiaquatic Areas Exposed to di uron via Runoff and Drift..................................................... 58 Table 3.7 Summary of AgDRIFT Predicted Spra y Drift Buffer for Terrestrial Plants ... 60 Table 4.1 Freshwater Aquatic To xicity Profile for Diuron.............................................. 63 Table 4.2 Categories of Acute Toxi city for Aquatic Organisms ..................................... 64
Table 4.3 Terrestrial Toxici ty Profile for Diuron ............................................................. 66 Table 4.4 Categories of Acute Toxicity for Avian and Mammalian Studies.................... 67
Table 4.5 Terrestrial Plant T oxicity Profile for Diuron .................................................. 69 Table 5.1. Summary of Direct Effect RQs for the Aquatic-phase CRLF........................ 72 Table 5.2 Summary of Acute 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)* ...................................................................................................... 80 Table 5.3 Summary of Acute and Chronic RQs Us ed to Estimate Indirect Effects to the CRLF via Direct Effects on Aquatic Inverteb rates as Dietary Food Items (prey of CRLF juveniles and adults in aquatic habitats)* ......................................................................... 83 Table 5.4 Summary of Acute RQs Used to Es timate Indirect Effects to the CRLF via Effects to Vascular Aquatic Plan ts (habitat of aquatic-phase CRLF) a ............................. 86 Table 5.5 Summary of Acute RQs Used to Esti mate Direct Effects to the Terrestrialphase CRLF ...................................................................................................................... 90 Table 5.6 Summary of Acute and Chronic RQs* Used to Estimate Indirect Effects to the Terrestrial-phase CRLF via Di rect Effects on Small Mammals as Dietary Food Items .. 92 Table 5.7 RQs* † for Non-Target Plants Inhabiting Dry and Semi-Aquatic Areas Exposed to Diuron via Runoff and Drift........................................................................... 93 Table 5.8 Risk Estimation Summary for Diuron - Direct and Indirect Effects to CRLF . 97 Table 5.9 Risk Estimation Summary for Diur on – PCEs of Designa ted Critical Habitat
for the CRLF..................................................................................................................... 98 Table 5.10. Upper-bound Kenega Nomogram T- HERPS EECs (mg/kg-diet) for Dietarybased Exposures of the CRLF and its Prey to Diuron 1 ................................................... 102

vTable 5.11. Revised Acute Dietary-based RQs for CRLF consuming different food items (RQs calculated using T-HERPS)*................................................................................. 103 Table 7.1 Effects Determination Summary for Effects of Diuron on the CRLF........... 119 Table 7.2 Effects Determination Summary for the Critical Habitat Impact Analysis... 120

viList of Figures

Figure 2.1 Diuron Agricultural Use in Total Pounds per County..................................... 23 Figure 2.2 Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF................................................................................................................................. 27 Figure 2.3 – CRLF Reproductive Events by Month......................................................... 28 Figure 2.4 Initial area of concern, or “foot print” of potential use, for diuron ................. 34 Figure 2.5 Conceptual Model for Aquatic-Phase of the CRLF ....................................... 41 Figure 2.6 Conceptual Model for Te rrestrial-Phase of the CRLF ................................... 42 Figure 2.7 Conceptual Model for Pesticid e Effects on Aquatic Component of CRLF
Critical Habitat.................................................................................................................. 43 Figure 2.8 Conceptual Model for Pesticide Effects on Terrestrial Component of CRLF
Critical Habitat.................................................................................................................. 44

vii

### 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), from FIFRA regulatory actions regarding use of diur on on agricultural and non-agricu ltural sites. In addition,
this assessment evaluates whether these actions can be expected to result in modification of the species’ designated critical habitat. This assessment was completed in accordance with the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) Endangered Species Consultation Handbook (USFWS/NMFS, 1998) and procedures outlined in the Agency’s Overview Document (U.S. EPA, 2004).

The CRLF was listed as a threatened species by USFWS in 1996. The species is endemic to California and Baja California (Mexico) and inhabits both co astal 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 (USF WS, 1996) in California.

Diuron (N-(3,4-dichlorophenyl)-N,N-dimethylur ea) is a systemic substituted phenylurea
herbicide. In the U.S. diuron is used on a variety of fruit and nut crops, grains, cotton, corn, sorghum, mint, gum, asparagus, sugarcan e, seed crops, coffee, hay, cut flowers, and for fallow, idle cropland use, and impervious surfaces such as paved areas. It may be used in irrigation and drainage systems when water is not present. Diuron is available in wettable powder, flowable, liquid suspension, and soluble concentrate formulations for
use in California. Technical diuron is a wh ite, crystalline, and odor less solid. Diuron is registered for pre- and post emergent control using ground and aerial equipment. Diuron is often applied in combination with othe r herbicides such as bromacil, hexazinone, paraquat, thiadiazuron, imazapyr, monosodium, s odium chlorate, sodium metaborate, and copper sulfate (U.S. EPA, 2004a). This asse ssment evaluates only t hose registered uses
which allow use in California.

Diuron is easily taken up by plants and rapi dly translocated. Diur on primarily functions by inhibiting the Hill reacti on in photosynthesis, limiting the production of high-energy compounds such as adenosine triphosphate (ATP ) used for various metabolic processes.

Diuron is generally considered to be both mobile and persistent. It is relatively stable in
neutral water. In addition to aquatic photolysis, microbial degradation is the primary factor in the degradation of di uron in aquatic environments.

Diuron is not expected to concentrate in a quatic organisms. Diuron is regulated as a known ground water contaminant in California, where it has been detected in the 2 to 3 ppb range (online at http://www.cdpr.ca.gov ) . Because diuron has a low Henry’s law constant and a low vapor pressure, volat ilization is considered insignificant.

At sufficient levels diuron residues in soil are toxic to plants. Residue levels are lower in soils with low organic content. Residue half-l ives are from one month to one year for the parent, five months for a major degradate , and one month for a minor degradate.

1Degradate formation is summarized below. Some pineapple fields contained residues three years after the last application.

Diuron degrades in the environment to four major (>10% of the applied parent) and four minor (<10% of the applied parent) metabo lites and impurities. The major metabolites are: carbon dioxide (CO 2 ), N-(3,4-dichlorophenyl)-N-methylurea (DCPMU), N'-(3- chlorophenyl)-N,N-dimethylurea (MCPDMU), and 1,1-dimethyl-3-phenylurea (PDMU).
The minor metabolites include: 4-dichlor ophenylurea (DCPU); 3,4-dichloroaniline (3,4- DCA), N-(3-chlorophenyl)-N -methylurea (CPMU), and 3,3' ,4,4'-tetrachlorobenzene (TCAB).

There were no acceptable toxicity studies on the major degradates identified in the ECOTOX database. As a result, they will be as signed the same toxicity as the parent for purposes of this assessment. Because the c oncentrations of parent diuron exceed levels of concern by themselves (both in modeling and monitoring data), the non-inclusion of degradates does not cause a different outcome for the "may affect" determination. Therefore, this assessment only addresses ecolo gical risks associated with exposures to the parent compound.

Likewise, the minor degradates, 3,4-DCA and TCAB, will not be assessed further. 3,4 DCA is not a significant residue (< 1%) in any metabolism or hydrolysis study, and TCAB is also a minor degradate (0.038 pp m) and is only found in the soil photolysis study which is a minor degradation route for diuron.

Diuron contains two impurities from the manufacturing proce ss, TCAB and 3,3',4,4'- tetrachloroazoxybenzene (TCAOB), both ‘dioxin- like’ substances. TCAB levels between 0.15 and 28 ppm have been found in diuron samp les tested. TCAOB is present at lower levels. Since, these impurities have only b een found at fairly low levels, they are not
residues of concern for diuron and will not be evaluated in this assessment.

Diuron is classified as a 'known/likely' carcinogen. EPA is required under the FFDCA, as amended by FQPA, to develop a screeni ng program to determine whether certain substances (including all pesticid e active and other ingredients) “may have an effect in
humans that is similar to an effect produced by a naturally occurring estrogen, or other such endocrine effects as the Administrator may designate.” Following the recommendations of its Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC), EPA determined that there were scie ntific bases for including, as part of the program, androgen and thyroid hormone system s, in addition to the estrogen hormone system. EPA also adopted EDSTAC’s r ecommendation that the Program include evaluations of potential effects in wildlife. When the appropriate sc reening and/or testing protocols being considered under the Agency ’s Endocrine Disrupter Screening Program (EDSP) have been developed and vetted, diur on may be subjected to additional screening and/or testing to better characterize effects related to endocrine disruption.

As noted in the 2003 Registration Eligib ility Decision (RED), diuron has been characterized as a “known/likely” carcinogen, based on urinary bladder carcinomas in both sexes of the Wistar rat, kidney carcinom as in the male rat (a rare tumor), and

2mammary gland carcinomas in the female NMRI mouse. Because of this, the spatial extent of the action area (i.e., the boundary wh ere exposures and poten tial effects are less than the Agency’s LOC) for diuron cannot be de termined. Therefore, it is assumed that the action area encompasses the entire state of Ca lifornia, regardless of the spatial extent (i.e., initial area of concern or foot print) of the pesticide use(s).

Since CRLFs exist within aquatic and terrestria l habitats, exposure of the CRLF, its prey and its habitats to diuron are assessed separately for the two habitats. Tier-II aquatic exposure models are used to estimate high-e nd exposures of diuron in aquatic habitats resulting from runoff and spray drift from different uses. Peak model-estimated environmental concentrations resulting fr om different diuron uses range from 3.76 to 4911 ppb for use on grasses grown for seed, and paved areas (impervious surfaces), respectively. These estimates are supplemented with analysis of available California surface water monitoring data from U. S. Geological Survey’s National Water Quality Assessment (NAWQA) program and the Califor nia Department of Pesticide Regulation (CDPR). Particularly in the CDPR monitori ng data, diuron is frequently detected and
exceeds levels of concern with values up to 160 ppb.

To estimate on-site diuron dietary exposures to the terrestrial-phase CRLF, and its potential prey resulting from uses involvi ng diuron applications, the T-REX model is used for spray treatment. The AgDRIFT model is also used to estimate deposition of
diuron on off-site terrestrial and aquatic habitats from spray drift. The TerrPlant model is used to estimate diuron exposures to terr estrial-phase CRLF hab itat, including plants inhabiting semi-aquatic and dry areas, from s ite run-off and spray drift. The T-HERPS
model is used to allow for further character ization of dietary expos ures of terrestrialphase CRLFs relative to birds.

The effects determination assessment endpoints for the CRLF include direct toxic effects on the survival, reproduction, and growth of the CRLF itself. 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 that the CRLFs prey items and designa ted critical habitat requirements in the aquatic habitat are dependant on the availabil ity of freshwater aquatic invertebrates and aquatic plants, toxicity information for th ese taxonomic groups is also discussed.

In the terrestrial habitat, indirect effect s due to depletion of prey are assessed by considering effects to terrestrial insects, sm all terrestrial mammals, and frogs. Indirect
effects due to modification of the terrestrial habitat are characterized by available data for terrestrial monocotyledonous (monocot) and dicotyledonous (dicot) plants.

Risk quotients (RQs) are derived as estimates of potential risk. Acute and chronic RQs
for animals and listed and non-lis ted plant RQs are compared to the Agency’s levels of concern (LOCs) to identify instances wher e diuron use within the action area has the

3potential to adversely affect th e CRLF via direct toxicity or indirectly based on effects to its food supply (i.e., freshwater invertebrates, algae, fish, frogs, terr estrial invertebrates, and mammals) or habitat (i.e., aquatic plan ts and terrestrial upland and riparian vegetation) or to modify its cri tical habitat. When RQs for each particular type of effect are below their respective LOCs, the pesticide is determined to have “no effect” on the CRLF or to modify its critical habitat. Where RQs exceed LOCs, a potential to cause adverse effects is identified, leading to a c onclusion of “may affect” for the CRLF and a potential to modify its critical habitat. If a determinati on is made that use of diuron within the action area “may affect” the CRLF, 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 cons idered to refine the potential for exposure and effects to distinguish thos e actions that do or do result in modification of its critical
habitat.

Based on the best available information, the Agency makes a May Affect, and Likely to Adversely Affect determination for diuron exposure to the CRLF based on direct and indirect effects to the aquatic - and terrestrial-phase CRLF. Further, registered uses of diuron are anticipated to result in modificat ion to critical habitat of the CRLF.

A summary of the risk conclusions and e ffects determinations for the CRLF and its critical habitat is presented in Table 1.1 and Table 1.2 . Use-specific determinations for direct and indirect effects to the CRLF are provided in Table 1.3 and Table 1.4 . Further
information on the results of the effects dete rmination is included as part of the Risk Description in Section 5.2. Given the LAA determination for the CRLF and potential modification of designated critical habitat, a description of the baseline status and
cumulative effects for the CRLF is provided in Attachment II.

4Table 1.1 Effects Determination Summary for Effects of Diuron on the CRLF

Assessment

Endpoint Effects
Determination 1 Basis for Determination

Potential for Direct Effects Aquatic-phase (Eggs, La rvae, and Adults) : The aquatic phase amphibian acute LOCs for Listed species (0.05) are exceeded for most
uses of diuron in California. Ac ute RQs that exceed the Agency’s LOC range from 12.28 (paved areas) to 0.06 (papaya and walnut). Chronic RQs that exceed the Agency’s LO C for chronic exposure (1.0) range from 131.85 (paved areas) to 1.26 (banana, plantain). LAA

Terrestrial-phase (Juveniles and Adults) : Refined acute dietary-based RQs for CRLFs consuming large inse cts and small herbivore mammals exceed the acute listed species LOC (0.1) for all uses of diuron except Sorghum and Field Corn. The acute dietary-based RQs for CRLFs consuming large insects exceed the acute listed species LOC for Agricultural Rights-of-Way, Fencerows etc. No acute dietary based
LOCs were exceeded for CLRF cons uming small insectivore mammals
and small terrestrial phase amphibi ans for any diuron use.

Potential for Indirect Effects Aquatic prey items, aquatic habitat, cover and/or primary productivity : LOCs for non-vascular plants are exceeded for all uses. The RQs range from 2046.25 (paved areas) to 1.57 (grasses grown for seed).

Aquatic invertebrates acute LOCs are exceeded. The acute RQs that exceed the LOC range from 30.69 (paved areas) to 0.05 (cotton aerial application). Chronic LOCs are exceeded for several uses. RQs that exceed the Agency’s LOC range from 21.21or paved areas to 1.02 for bermudagrass.

RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses. These range from 460.46 (paved areas) to 1.30 (hazelnut). Survival, growth, and/or reproduction of
CRLF
individuals

LAA

Terrestrial prey items, riparian habitat : For small mammals, chronic dose based RQs exceed the Agency’s LOC (1.0) for most uses (Table 5.6) . The dose based chronic RQs that exceed the LOC range from 8.29 (Agricultural Rights-of-Way, Fencerows, Hedgerows, Airports, etc.) to 1.31 (walnut). The dietary based chronic RQs do not exceed the LOC for any uses. The RQs that
exceed the acute dose based LOC ra nge from 0.41 (Agricultural Rightsof-Way, Fencerows, Hedgerows, Air ports, etc.) to 0.13 (Bermuda grass, Blackberry, Boysenberry, Sp earmint). For terrestrial phase amphibians, the chronic LOC is exceed ed for all uses of diuron and the acute LOCs are exceeded for all uses except sorghum.

LOCs are exceeded for terrestrial riparian plants and for aquatic plants from exposure to diuron from runoff or spray drift. Alteration of riparian and vascular plants may re sult in alteration of temperature, turbidity, and oxygen content. RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses. These range from 460.46 (paved areas) to 1.30 (hazelnut).
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely affect (LAA)

5Table 1.2 Effects Determination Summary fo r the Critical Habitat Impact Analysis

Assessment

Endpoint Effects
Determination 1 Basis for Determination

Modification of aquatic-phase
PCE HM Due to aquatic vascular and terrestrial plant communities being reduced from all 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 for shelter, foraging, predator avoidance, and aquatic dispersal for juvenile and adult CRLFs. In addition, there is potential for alteration in water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal growth and viab ility of juvenile and adult CRLFs
and their food.

LOCs are exceeded for terrestrial riparian plants and for aquatic vascular plants from exposure to diuron from runoff or spray drift. LOCs for non-vascular plants are exceeded for all uses.

Modification of terrestrial-phase
PCE HM The use of diuron at all use sites may create the fo llowing modification
of PCE: elimination and/or disturba nce 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 juven iles and adults, and alteration of chemical characteristics necessary for normal growth and viability of juvenile and adult CRLFs and their food source.

The RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses of diuron in California. RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses. These range from 460.46 (paved areas) to 1.30 (hazelnut). Use of diuron on most use
sites will exceed acute and chronic LOCs for many prey food items of
the CRLF. Food sources are reduced and the CRLF is therefore indirectly affected.

The RQs for non-target terrestrial m onocot and dicot plants inhabiting semi-aquatic and upland dry areas exceed the Agency’s LOC (1.0) for all uses except for monocot plants exposed to sorghum applications ( Table 5.7 ). These exceedances range from 300.00 (semi-aquatic plants exposed to non-agricultural aer ial applications) to 0.19 (dicot plants inhabiting dry areas exposed to sorghum applica tions). Several diuron uses result in plant LOC exceedances from spray drift. These exceedances range from 12.00 (dicot plants exposed to field corn applications) to 1.13 (m onocot plants exposed to cotton applications).

1 Habitat Modification (HM) or No effect (NE)

67 Table 1.3 Diuron Use-specific Direct Effects Determinations 1 for the CRLF Aquatic Habitat Terrestrial Habitat Use(s) Acute Chronic Acute Chronic*

AGRICULTURAL RIGHTS-OF-WAY / FENCEROWS/
HEDGEROWS LAA LAA LAA LAA

ALFALFA Ground NE NE LAA LAA
ALFALFA Aerial NE NE LAA LAA

APPLE NE NE LAA LAA

ARTICHOKE LAA NE LAA LAA

ASPARGUS LAA NE LAA LAA

BANANA/PLANTAIN LAA LAA LAA LAA

BLACKBERRY/BOYSENBERRY LAA LAA LAA LAA

BLUEBERRY NE NE LAA LAA

CITRUS NE NE LAA LAA CORN, FIELD NE NE NE LAA

DEWBERRY NE NE LAA LAA FILBERT (HAZELNUT) NE NE LAA LAA

GRAPE NE NE LAA LAA LOGANBERRY, RASPBERRY (BLACK/RED) NE NE LAA LAA

OLIVE NE NE LAA LAA

PAPAYA NE NE LAA LAA

PEPPERMINT NE NE LAA LAA

PEACH NE NE LAA LAA

PEAR NE NE LAA LAA

PECAN LAA NE LAA LAA

SORGHUM NE NE NE LAA

SPEARMINT LAA LAA LAA LAA WALNUT (ENGLISH/BLACK) LAA NE LAA LAA

WHEAT Pre Harvest NE NE LAA LAA

WHEAT Post Harvest NE NE LAA LAA
COTTON Ground NE NE LAA LAA
COTTON Aerial NE NE LAA LAA AIRPORTS/ LANDING FIELDS, DRAINAGE SYSTEMS, INDUSTRIAL AREAS (OUTDOOR),
SEWAGE DISPOSAL AREAS LAA LAA LAA LAA

BERMUDAGRASS LAA LAA LAA LAA

GRASSES GROWN FOR SEED NE NE LAA LAA

IRRIGATION SYSTEMS LAA LAA LAA LAA

ORNAMENTAL HERBACEOUS PLANTS LAA NE LAA LAA
NON-AGRICULTURAL RIGHTS OF WAY Ground LAA LAA LAA LAA
NON-AGRICULTURAL RIGHTS OF WAY Aerial LAA LAA LAA LAA PAVED AREAS (PRIVATE ROADS/SIDEWALKS) LAA LAA LAA LAA

UNCULTIVATED AGRICULTIRAL AREAS Ground LAA LAA LAA LAA

UNCULTIVATED AGRICULTIRAL AREAS Aerial LAA LAA LAA LAA

UNCULTIVATED NON-AGRICULTURAL AREAS LAA LAA LAA LAA

1 NE = No effect; MA/NLAA = May affect, but not likel y to adversely affect; LAA = May affect and likely to adversely affect * No acceptable chronic data are available for amphibian s or their avian surrogates by which to determine chronic direct risks to the CRLF, therefore an LAA dete rmination is made in the absence of these data and because supporting information on linur on, a similar herbicide, exhibits chronic toxicity to these species.Table 1.4 Diuron Use-specific Indirect Effects Determinations1Based on Effects to PreyAquatic InvertebratesAquatic-phase frogsand fishTerrestrial-phase frogsSmall MammalsUse(s)AlgaeAcuteChronicTerrestrialInvertebrates(Acute)AcuteChronicAcuteChronic*AcuteChronicAGRICULTURAL RIGHTS-OFWAY / FENCEROWS/HEDGEROWSLAALAALAANLAALAALAALAALAALAALAAALFALFA GroundLAALAANENLAANENELAALAANELAAALFALFA AerialLAALAANENLAANENELAALAANELAAAPPLELAALAANENLAANENELAALAANELAAARTICHOKELAALAANENLAALAANELAALAANELAAASPARGUSLAALAANENLAALAANELAALAANELAABANANA/PLANTAINLAALAANENLAALAALAALAALAALAALAABLACKBERRY/BOYSENBERRYLAALAANENLAALAALAALAALAALAALAABLUEBERRYLAANENENLAANENELAALAANENECITRUSLAANENENLAANENELAALAANELAACORN, FIELDLAANENENLAANENENELAANENEDEWBERRYLAALAANENLAANENELAALAANELAAFILBERT (HAZELNUT)LAALAANENLAANENELAALAANENEGRAPELAALAANENLAANENELAALAANELAALOGANBERRY,RASPBERRY(BLACK/RED)LAANENENLAANENELAALAANENEOLIVELAANENENLAANENELAALAANENEPAPAYALAALAANENLAALAANELAALAANELAAPEPPERMINTLAANENENLAANENELAALAANELAAPEACHLAALAANENLAANENELAALAANELAAPEARLAALAANENLAANENELAALAANENEPECANLAALAANENLAANENELAALAANELAASORGHUMLAALAANENLAANENENELAANENESPEARMINTLAALAANENLAALAALAALAALAALAALAAWALNUT (ENGLISH/BLACK)LAALAANENLAANENELAALAANELAAWHEAT Pre HarvestLAALAANENLAANENELAALAANENE89Aquatic InvertebratesAquatic-phase frogsand fishTerrestrial-phase frogsSmall MammalsUse(s)AlgaeAcuteChronicTerrestrialInvertebrates(Acute)AcuteChronicAcuteChronic*AcuteChronicWHEAT Post HarvestLAALAANENLAANENELAALAANENECOTTON GroundLAANENENLAANENELAALAANELAACOTTON AerialLAALAANENLAANENELAALAANELAAAIRPORTS/ LANDINGFIELDS, DRAINAGESYSTEMS, INDUSTRIALAREAS (OUTDOOR),SEWAGE DISPOSALAREASLAALAALAANLAALAALAALAALAALAALAABERMUDAGRASSLAALAALAANLAANENELAALAALAALAAGRASSES GROWN FOR SEEDLAANENENLAANENELAALAANENEIRRIGATION SYSTEMSLAALAANENLAALAALAALAALAALAALAAORNAMENTALHERBACEOUS PLANTSLAALAANENLAALAALAALAALAANELAANON-AGRICULTURALRIGHTS OF WAY GroundLAALAALAANLAALAALAALAALAALAALAANON-AGRICULTURALRIGHTS OF WAY AerialLAALAALAANLAALAALAALAALAALAALAAPAVED AREAS (PRIVATEROADS/SIDEWALKS)LAALAALAANLAALAALAALAALAALAALAAUNCULTIVATEDAGRICULTIRAL AREASGroundLAALAALAANLAALAALAALAALAALAALAAUNCULTIVATEDAGRICULTIRAL AREAS AerialLAALAALAANLAALAALAALAALAALAALAAUNCULTIVATED NONAGRICULTURAL AREASLAALAALAANLAALAALAALAALAALAALAA1NE = No effect; NLAA = May affect, but not likely to adversely affect; LAA = May affectand likely to adversely affect* No acceptable chronic data are available for amphibians or their avian surrogates bywhich to determine chronic direct risksto the CRLF, therefore an LAAdetermination is made in the absence of these data and because linuron, a similar herbicide, exhibits chronic toxicity to thesespecies in the range of modeleddiuron surface water levels.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 Spec ies 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.

10

### 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. EPA’s Guidance for Ecological Risk Assessment (U.S. EPA 1998), the
Services’ Endangered Species C onsultation Handbook (USFWS/NMFS 1998) and is consistent with procedures and methodology outlined in the Overview Document (U.S. EPA 2004) and reviewed by the U.S. Fish and Wildlife Service and National Marine Fisheries Service (USFWS/NMFS 2004).

2.1 Purpose

The purpose of this endangered species 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 diuron on terrestrial food, feed, forestry, non- food, and outdoor residential sites. In addition, this assessment evaluates whether diur on use on these crops is expected to result in modification of the species’ designated critical habitat. This ecological risk assessment has been prepared consistent with a settlement agreement in the case Center for Biological Diversity (CBD) vs. EPA et al . (Case No. 02-1580-JSW (JL)) settlement
entered in Federal District Court for the Nort hern District of Calif ornia on October 20,
2006.

Diuron is a broad-spectrum residual herbic ide registered for pre-emergent and postemergent control of both broadleaf and annua l grassy weeds. When diuron is used on pre-emergent weeds, it allows seeds to germ inate normally, but causes them to lose their green color, after which they soon die of st arvation (Ferrell et al., 2004). In the U.S. diuron is used on a variety of fruit and nut crops, grains, cotton, corn, sorghum, mint, gum, asparagus, sugarcane, seed crops, coff ee, hay, cut flowers, and for fallow and idle cropland use. It may be used in irrigati on and drainage systems when water is not present.

It is also used to control weeds on hard surf aces, such as, roads, railway tracks, and paths (at around 3 kg/ha), and to control weeds in crop s, such as, pear and apple trees, forestry, ornamental trees and shrubs, pineapples, s ugar cane, cotton, alfalfa and wheat (at lower rates of around 1.8 kg/ha). It can be us ed for both pre-emergent and knockdown weed
control. Its use in some lo cations is becoming limited due to the development of resistant weed species. In some products it is combin ed with other active ingredients such as glyphosate, bromacil, hexazinone, amitrole and 2,4- D. In some countries diuron is also registered for aquatic weed control, as a co tton defoliant, and for use in home aquaria and fish ponds. It is used as a booster biocid e in antifouling pain ts where its activity enhances the efficacy of copper in these products.

11In this assessment, direct a nd indirect effects to the CRLF and potential modification to its designated critical habitat are evaluated in accordance w ith the methods described in the Agency’s Overview Document (U.S. EP A 2004). Screening level methods include
use of standard models such as PRZM-EXAM S, T-REX, TerrPlant, and AgDRIFT, all of which are described at length in the Over view Document. Additional refinements
include use of the T-HERPS model. Use of such information is consistent with the methodology described in the Overview Docume nt (U.S. EPA 2004), which specifies that “the assessment process may, on a case-by- case basis, incorporate additional methods, models, and lines of evidence that EPA finds technically appropriate for risk management objectives” (Section V, page 31 of U.S. EPA 2004).

In accordance with the Overview Document, provisions of the ESA, and the Services’ Endangered Species Consultation Handbook, the assessment of effects associated with registrations of diuron is base d on an action area. The action area is the area directly or indirectly affected by the federal action, as indicated by the exceedance of the Agency’s LOCs. It is acknowledged that the acti on area for a national-level FIFRA regulatory
decision associated with a use of diur on may potentially involve numerous areas throughout the United States and its Territori es. However, for the purposes of this assessment, attention will be focused on rele vant sections of the action area including those geographic areas associated with locati ons of the CRLF and its designated critical habitat within the state of California. As pa rt of the “effects determination,” one of the following three conclusions will be reached regarding the potential use of diuron 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 diuron 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 CRLFs designated critical habita t, a preliminary “may affect ” determination is made for the FIFRA regulatory action regarding diuron.

If a determination is made that use of diuron within the action area(s) associated with the CRLF “may affect” this species or its designated critical habitat, additional information is considered to refine the potential for e xposure and for effects to the CRLF and other taxonomic groups upon which these species depend (e.g

., aquatic and terrestrial

12vertebrates and invertebrates, aquatic plan ts, riparian vegetation, etc.). Additional information, including spatial analysis (to de termine the geographical proximity of CRLF habitat and diuron use sites) and further eval uation of the potential impact of diuron on
the PCEs is also used to determine whethe r modification of designa ted critical habitat may occur. Based on the refined information, the Agency uses the best available information to distinguish those actions that “may affect, but are not likely to adversely affect” from those actions that “may affect and are likely to adversely affect” the CRLF or the PCEs of its designated cr itical habitat. This informati on is presented as part of the
Risk Characterization in Sec tion 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 diuron is expected to directly im pact living organisms within the action area (defined in Section 2.7), critical habitat anal ysis for diuron is limited in a practical sense
to those PCEs of critical habitat that are bi ological 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
critical habitat are those that alter the PCEs and appreciably diminish the value of the
habitat. Evaluation of actions related to us e of diuron that may alter the PCEs of the CRLFs critical habitat form the basis of the critical habitat impact analysis. Actions that may affect the CRLFs designated critical habi tat have been identifie d by the Services and
are discussed further in Section 2.6.

2.2 Scope

Diuron is registered in California for a vari ety of agricultural a nd non-agricultural uses (see Table 2.2).

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 diur on in accordance with the a pproved product labels for
California is “the action” relevant to this ecol ogical risk assessment.

Although current registrations of diuron allow for use nation wide, this ecological risk
assessment and effects determination addresses currently registered uses of diuron 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 habita t is provided in Section 2.7.

The major route of dissipation for diuron is mi crobial degradation in water. Here the major metabolism degradate is N’-(3-chlorophenyl)-N,N-dimethylurea (MCPDMU). Diuron also degrades through photolysis in both water and soil; here the major degradates

13are CO2 and N’-(3,4-dichlorophenyl)-N-methyl urea (DCPMU), respectively. A more detailed discussion of the major and minor degradates formed in the decomposition of diuron is presented in Section 2.4.

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

Diuron has registered products that contain mu ltiple active ingredient s. However, there are no available data on mixtures containing di uron in the open literature. There are no product LD 50 values, with associated 95% Confiden ce Intervals (CIs) available for diuron among the data submitted to the Agency. The assessment will be based on the toxicity of a single active ingredient of di uron. Analysis of the availa ble open literature and acute mammalian toxicity data for mu ltiple active ingredient products relative to the single active ingredient is provided in Appendix A.

As discussed in USEPA (2000) a quantitati ve component-based evaluation of mixture toxicity requires data of appr opriate quality for each compon ent of a mixture. In this mixture evaluation, an LD50 with associated 95% CI is needed for the formulated product. The same quality of data is also re quired for each component of the mixture. Given that the formulated products for diuron do not have LD50 data available it is not possible to undertake a quantitati ve or qualitative analysis for pot ential interactive effects. However, because the active ingredients are no t expected to have similar mechanisms of action, metabolites, or toxicoki netic behavior, it is reasona ble to conclude that an assumption of dose-addition would be inapprop riate. Consequentl y, an assessment based on the toxicity of diuron is th e only reasonable approach that employs the available data to address the potential acute risks of the formulated products

.

2.3 Previous Assessments

Diuron has been registered in the United States since 1967 for use as an herbicide, mildewcide and algaecide. A Registra tion Standard, titled "Guidance for the Reregistration of Pesticide Products Cont aining Diuron as the Active Ingredient" was released in 1983. The Registration Standard involved a thorough review of the scientific data base underlying pesticid e registrations and an identification of essential but missing studies which may not have been required when the product was initially registered or studies that we re considered insufficient. Subsequent Data Call-Ins (DCIs) were issu ed in 1990, and 1995 for diuron.

14In 2003, the Office of Pesticide Programs (OPP) requested th e initiation of ESA section 7(a) (2) consultation regard ing the potential impact of diuron on the Evolutionary Significant Units (ESU) of the Pacific salmon and steelhead. OPP determined that the use of diuron on certain crops (peaches, wa lnuts, filberts) may affect 10 ESUs at application rates above 3.2 lb ai/A, may affect 7 ESUs at application rates above 2.2 lb ai/A, and will have no effect on 10 ESUs at any labeled agricultural rate. The use of diuron for non-crop sites, especi ally rights-of-way, may affect 25 ESUs, may affect but is not likely to adversely affect one ESU, and will have no effect on one ESU.

To mitigate risks of concern posed by th e use of diuron, EPA in its Reregistration Eligibility Decision (RED) fo r diuron, dated September 2003, noted a number of label amendments identified by EPA or agreed to by the registrant(s) to address the worker, residential and ecological concerns; these included:

• All wettable powder products will be voluntarily canceled.

• Reduction in application rate and increased treatment in tervals, and limit on the number of applications for some crops.

• Use of the backpack sprayer is prohibited.

• Implement use of PPE and engineering controls for some workers.

• Eliminate aerial applications except fo r rights-of-way, alfalfa, cotton, winter barley, winter wheat, sugar cane, and grass seed crops.

• Implement best management prac tices to reduce spray drift.

2.4 Stressor Source and Distribution

2.4.1 Environmental Fate Properties

The environmental fate database for diuron is essentially complete. Diuron is stable in neutral media at normal temperatures, and is hydr olyzed by acid and alkalis. It is stable
towards oxidation and moisture under normal conditions and decomposes at 180-190° C (Helliwell et al., 1998).

Diuron is mobile and has the potential to l each to groundwater and to contaminate surface waters. An upgradable adsorption/deso rption/leaching study (MRID 44490501) showed that diuron has an average K
oc value of 920 and Freundlich K ads s values (7.9-28). Sorption of diuron to soil is highly correlated with soil organic ma tter. In addition, diuron has
relatively low water solubility (42 ppm) and low volatility (6.9 x 10 -8 mm Hg at 25° C).

Although stable to hydrolysis at pH 5, 7, and 9, the minor degradate 3,4-dichloroaniline (3,4-DCA) was identified in all hydrolysis test solutions (0.5% of applied). The
calculated half-lives for diur on in aqueous and soil photolysis studies were found to be 43 and 173 days respectively.

In soil, the photolysis degradate were a ll minor, N'-(3,4-dichlorophenyl)-N-methylurea (DCPMU) at 3.6 percent, demethylated DCPMU (DCMU), 3,4-dichloroaniline (3,4- DCA), and 3,3',4,4'-tetrachlorobenzene (T CAB) at 0.7 percent, 0.370 ppm, and 0.038

15ppm respectively. The calculated half-liv es in aerobic and anaerobic soil metabolism studies were 372 (aerobic) and 1,000 (anaer obic) days. Under aerobic conditions, the major degradate was DCPMU (20.9-22.5 % of the amount applied at 365 days), and minor degradates were DCPU and CO 2 . Under anaerobic conditions, the only major degradate identified was DCPMU, which accoun ted for a maximum of 10.3% of applied (at 45 days).

In contrast to its persistence in laborat ory studies of hydrolysis, aqueous and soil photolysis, and aerobic and anaerobic soil metabo lism, diuron degraded relatively quickly in aquatic metabolism laboratory studies, with a half-life of 33 days under aerobic conditions and of 5 days under anaerobic c onditions. The major metabolism degradate under aerobic conditions was N'-(3-chlorophe nyl)-N,N-dimethylur ea (MCPDMU) which reached 25 % of the applied dose by the end of the study and was evenly distributed between the soil and aqueous phase. Other degradates identified were DCPMU (9.2 percent) and CPMU (8 percent), and were pr imarily associated with the soil phase. The three major degradates unde r anaerobic conditions were MCPDMU which was mainly associated with the aqueous phase, 1,1-di methyl-3-phenylurea (PDMU), and CPMU.

In terrestrial field dissipation studies in FL , MS, and CA with sand, silt loam, and silty clay loam soils, diuron dissipated in bare ground plots with half-lives of 73, 139, and 133 days, respectively. The major degradate DCPMU dissipated in the same plots with half-lives of 217, 1733, and 630 days. In aquatic field dissi pation studies, halflives were 115-177 days and the major degradate was DCPMU. These studies were conducted in drainage channel berms and soil, and thus should be compared quantitatively to soil laboratory studies, not aquatic studies.

The environmental degradates of toxicologi cal concern to humans and other non-target species include 3,4-DCA and TCAB. Howeve r, EPA’s Metabolism Assessment Review Committee (MARC) has conclude d that residues of 3,4-DCA is not a residue of concern for diuron as 3,4-DCA (<1%) was not a signi ficant residue in any metabolism or hydrolysis study. Moreover, TCAB (0.038 pp m) residue was only found in the soil photolysis study which is a minor route of degradation for diuron.

Degradation half-lives for th e parent are presented in Table 2.1 . This table also presents the major and minor degradates of the pare nt compound. The chemical structures of diuron and the metabolites (DCPMU, DCPU , DCA, and MCPDMU) are presented in Appendix B.

16T able 2.1 Summary of Diuron Half-lives

Study Value (units) Major Degradates Minor Degradates MRID #

Hydrolysis Stable at pH 5, 7, 9 3,4-DCA (~2%) 41418804

Direct Aqueous Photolysis T 1⁄2 = 43 days CO 2 41418805

Soil Photolysis T 1⁄2 = 173 days DCPMU (3.6%)
DCMU ( ≤ 0.7%), 3,4- DCA (0.370 ppm), TCAB (0.038 ppm) 41719302

Aerobic Soil
Metabolism T 1⁄2 = 372 days DCPMU (22.5%)
DCPU (3.4%), CO 2 (3.36%) 41719303

Anaerobic
Soil
Metabolism T 1⁄2 = 1,000 days DCPMU (10.3 %) 41418806

Anaerobic Aquatic
Metabolism T 1⁄2 = 5 MCPDMU (83%)
PDMU (13%), mCPMU (23%) 42661901

Aerobic Aquatic
Metabolism T 1⁄2 = 33 MCPDMU (25%)
DCPMU (9.2%), CPMU (8%) 42260501

K d-ads / K d-des (mL/g) 14 Material balances were not reported. 44490501

Terrestrial
Field Dissipation Sand = 73 days Silt Loam = 139 days Silty Clay Loam = 133 days DCPMU (Sand = 217 days, Silt Loam = 1733 days, Silty Clay Loam = 630 days) 44654001

44865001

2.4.2 Environmental Transport Mechanisms

AIR Diuron is applied by broadcast or band sp ray on soil surface using ground or aerial equipment, suggesting that there is a possibi lity of drift. Dr ift is quantitatively considered in the exposure assessment. Howe ver, diuron is non-vola tile, as indicated by its low vapor pressure of 6.90 x10 -8 mm Hg (25o C), and a low Henry’s law constant of
5.10 x 10 -10 atm m 3 mol -1 . These properties indicate that diuron is unlikely to be dispersed in air over a large area and has a lo w tendency to volatilize from water or moist soils. Volatilization is insignificant except when diuron is exposed on the soil surface for several days or weeks under hot, dr y conditions (Hess and Warren, 2002).

17WATER
Diuron’s K OC ( 468-1666) indicates a relatively low tendency to sorb to soils and sediments, while its hydrolysis and aqueous photolysis half-lives are relatively long. Consequently diuron is both mobile and rela tively persistent, and is therefore prone to off-site movement in surface runoff, and migr ation to ground water. As discussed in the field monitoring studies below, diuron in r unoff water is above Agency LOCs for direct effects on the CRLF (fish LC50 of 400 to 710 ppb).

Andrieux et al. (1997) assesse d losses of diuron via runoff from vineyards under natural
Mediterranean climate conditions. Duri ng the growing season of 1994 and 1995, runoff
and diuron concentrations were monitored at two field sites, one tilled and one under notill management. Despite a time lag of greater than 4 months between application and the first runoff event in 1994, diuron concentrations in overland flow exceeded 200 ug/L at the no-till in both year s of investigations. In 1995, th e first strong rainfall following application removed 60% of total diuron runo ff loss at both sites, although it accounted
for 17 and 7% of the total seasonal r unoff volume at the no- till and tilled site, respectively. In 1995, seasonal diuron loss at the no-till sites was 1.71 % and at the tilled
site was 0.68%. No herbicide residues were detected in soil samples collected 1 week prior to chemical spraying in 1994 and 1995. The authors suggested that moderate temperatures and moisture conditions duri ng winter facilitated complete microbial decomposition. In four-months of soil samplin g following herbicide treatment there were no detections below a soil depth of 2 cm at th e no-till plot. However, at the tilled site, pesticides were present in samples at depths of 0-15 cm 17 days after spraying to three months. The authors suggested that infiltration increases attr ibutable to tillage effects accounted for diuron distribution in the soil pr ofile. The authors concluded that the persistence of diuron coupled with tillage may provide the potential for leaching. In contrast, no-till practices have been shown to contribute to ground water
contamination under certain California conditions.

Braun and Hawkins (1991) conducted a rain fall runoff monitoring study in a citrusgrowing region of Tulare County, California, where growers commonly avoid cultivation
of citrus row middles. The row middles unde r such a management practice are typically compacted, with low infiltration rates and a high tendency to yiel d runoff during storm events. One method of disposing of excess runo ff water in the area is to utilize dry wells that allow drainage of run off through the sh allow hard-pan soil layer. This mechanism allows direct introduction of residues to the subsurface and subsequent potential migration to shallow ground water. Although diuron applications had occurred at least 2 months prior to sampling, re latively high concentrations of diuron in runoff water entering dry wells were found, ranging up to 890 μg L -1 . The data provide strong evidence that the widespread regional presence of diuron in ground water is at least partially attributable to contamin ated runoff water entering dry wells.

Spurlock et al. (1997) examined the runoff of diuron, simazine, and bromacil from citrus
orchard middles under simulated rainfall condi tions. Peak diuron runoff concentrations were comparable to those reported by Br aun and Hawkins (1991), ranging from 600 to

181700 μg L -1 . Little difference in runoff concen trations of the three pre-emergent
herbicides was observed indica ting that herbicide substituti on would be an ineffective mitigation measure. They concluded that low soil permeability arising from hardpan layers or compaction drives the runoff pr ocess. These same factors are probably responsible for diuron off-site movement in runoff water from ri ghts-of-way because rights-of-way are generally engineer ed to maximize water run off.

Powell et al. (1996) studied off-site moveme nt of diuron in surface water from a highway shoulder right-of-way applica tion. Diuron was applied in a spray to a 2.4-meter wide strip next to the highway paveme nt, at a rate of 3.59 kg diuron ha -1 . Simulated rain (13 mm in 1 hr) was applied to plots on treated hi ghway shoulders at three sites. Diuron was
detected at two of three sites. Concentr ations of diuron were as high as 1770 μg L -1 in runoff (combined water and sediment), from sampling conducted one day after herbicide application. From 0.2 to 5.4% of the diuron ap plied to highway shoulders moved off-site in runoff during the simulations. Simulated ra in was applied to treated highway shoulder at intervals of 0, 2, and 4 wk after herbicide application. The highest percentages were observed when rain was simulated 1 day after herbicide application. Diuron is typically applied in winter or early sp ring during California’s rainy seas on to control weeds. This practice, coupled with relatively high us e, is one reason why diuron is commonly detected pesticides in Californi a surface water. Diuron was dete cted in more than half of 955 surface water samples analyzed and repor ted in DPR’s surface water database. Typical reporting limits for the diuron analyses are 0.05 - 0.10 μg -1 . While detected concentrations range from 0.01 to 30.6 μg L -1 , the majority of concentrations range from 0.1 to 1 μg L -1 . These concentrations were approximately equal to the 20 th and 80 th percentiles of detected concentrations. Th e highest concentrations and most frequent detections occur during December-March, wh ich coincides with both the rainy season and the peak diuron application season.

Microbes are the primary agents in the degrad ation of diuron in aquatic environments. The aerobic biodegradation pathway for di uron is well established, proceeding by successive demethylation steps to form DCPMU, DCPU [1-(3,4-dichlorophenyl)urea] and DCA (3,4-dichloroaniline). Reductive dechlorination has been observed in anaerobic pond sediments and leads to the formati on of the dechlorinated product, 3-(3- chlorophenyl)-1,1 dimethylurea (F ield et al., 1997). Boule et al. (1997) reported that the major photoproducts observed in the photolys is of diuron [3-(3,4-dichlorophenyl)-1,1- dimethylurea] in aqueous solution resulted from a heterolytic substitution of chlorine by OH. A wavelength effect was observed: at 254 nm the formation of 3-(4-chloro-3- hydroxyphenyl)-1,1-dimethylurea accounted for more than 90% of the conversion,
whereas when the solution was irradiated in 'black light' (85% of photons emitted at 365 nm, about 7% at 344 nm), the major photoproduct was 3-(3-chloro-4-hydroxyphenyl)- 1,1-dimethylurea. However, as noted previous ly, photolysis is not generally a principal route of diuron degradation in aqueous systems.

SOIL Diuron is moderately to highl y persistent and mobile in soils. The commonly reported average field dissipation half-life is 115 da ys (MRID 44654001), although such half-lives

19are typically highly variable. Phytotoxic residues generally dissipate within a season when applied at low selective rates. At hi gher application rates, residues may persist for more than one year (Kidd and James, 1991). Microbial degradation is the primary means of diuron dissipation from soil. Photodegrad ation is not considered a primary dissipation route, but losses can be signi ficant if diuron remains on the soil surface for several days or weeks (Hess and Warren, 2002). Mobility in the soil is related to organic matter and to the type of the residue. The metabolites are less mobile than the parent. Similar to many other pesticides, diuron sorption is high ly correlated with organic matter (Spurlock and Biggar, 1994). Consequently leaching is grea test in low organic matter soils. Other soil conditions that favor diuron leaching include high soil permeability to water, such as
in coarse soils.

Due to the diuron’s persistence and mobilit y, the herbicide is commonly detected in California’s ground water (Troiano et al., 2001). As of June 2004, there were confirmed
detections of diuron in 418 California wa ter wells reported in DPR’s well inventory database (WIDB). Typical diuron repor ting limits in the WIDB are 0.05 μg L -1 , and
detected diuron concentra tions range up to 3.96 μg L -1 . Diuron’s use is regulated under DPR’s ground water protection regulations (online at http://www.cdpr.ca.gov )

.

In a right-of-way runoff study by Powell et al. (1996) post-simulation and end of season
soil cores at the two sites with measurable runoff had detectable diuron residues only in the top 15 cm (0.5 ft). However, cores take n prior to application had diuron down to 0.30 m, presumably from the past year’s applic ation. At a third simulated rainfall site, no runoff left the plots. The absence of detectab le residues in soil to a depth of 3.0 m (10 ft) suggests that much of the herbicide applie d to the shoulder may have leached rapidly through the coarse gravelly soil. The soil data was insufficient to yield definite conclusions about leaching in infiltration areas . However, the levels of diuron found in runoff suggest that dry wells, if present, would provide an important conduit for the transport of diuron to groundwater. The aut hors concluded that ri ghts-of-ways with high percentages of gravel and sa nd in the soil may be of concern, since diuron may be transported rapidly to de pths greater than 0.3 m.

Bogarets et al. (2000) studi ed diuron’s microbial degr adation and ecotoxicology to investigate its fate after application to so ils. Quantitative biodegradation assays were executed with fungal strains, showing that diuron was degraded but not entirely
mineralized. A series of tests were carried out to choose the most efficient fungal strain for diuron degradation. Among the fungal st rains tested, only three were able to transform diuron to any extent (up to 50%) after 7 days of incubation: B. bassiana, C. elegans , and M. isabellina. No degradation occurred using fungal strains : F. oxysporum
and G. candidum . Although C. elegans was the most efficient since there was no diuron remaining after seven days of incubation. Di uron degradation by the three fungal strains
led to the formation of two metabolites obt ained in different ratios according to the microorganism. For the three fungal strains, diuron degradat ion led to the formation of the demethylated products. The identified metabolites were synthesized in sufficient
amounts to confirm their structures and dete rmine their non-target toxicity using four biotests. According to the Microtox test, the metabolites N- (3 ,4-dichlorophenyl)-N20methylurea and N-3, 4-dichlorophenylurea pres ented a three times higher toxicity than
that of diuron.

2.4.3 Mechanism of Action

Diuron is a systemic substituted phenylurea herbicide. Diuron is taken up by plants and rapidly translocated. Diuron primarily f unctions by inhibiting the Hill reaction in photosynthesis, limiting the production of high-energy compounds such as adenosine triphosphate (ATP) used for various metabo lic processes. Diuron binds to the Q B

binding niche on D1 protein of the photosys tem II complex in chloroplast thylakoid membranes, thus blocking electron transport from Q A to Q B . This process prevents CO 2 fixation and the production of ATP and othe r high energy compounds which are needed for plant growth. The inability to reoxidize Q A promotes the formation of triplet state chlorophyll, which interacts with ground state oxygen to form singlet oxygen. Both triplet chlorophyll and singlet oxygen can ex tract hydrogen from unsaturated lipids, producing a lipid radical and in itiating a chain reac tion of lipid peroxidation. Lipids and proteins are attacked and oxidi zed, resulting in loss of chlorophyll and ca rotenoids, and in leaky membranes which cause cells and cell or ganelles to dry and di sintegrate rapidly (Hess and Warren, 2002).

2.4.4 Use Characterization

There are currently 72 product registrations for diuron including two Special Local Needs registrations in California.

Diuron contains two significant impuriti es from the manufacturing process 3,3',4,4'- tetrachloroazobenzene (TCAB) and 3,3',4,4'- tetrachloroazoxyben zene (TCAOB), both
‘dioxin-like’ substances that are known to cause a skin disease known as chloracne. TCAB levels between 0.15 and 28 ppm have been found in diuron samples tested. TCAOB is present at lower levels. Since these residues appear to be present at insignificant levels, they are not asse ssed further in this assessment.

In addition to agricultural uses, diuron al so has widespread us e in non-agricultural applications, especially industrial and right s of way uses, where often in combination with other herbicides it provide s total vegetation control. These applications include along fence lines, pipelines, powerlines, railwa y lines, roads, footpa ths; in timber yards and storage areas; and around co mmercial, industrial and farm buildings, electrical substations, and petroleum storag e tanks. It has some use as an algaecide in ornamental ponds, fountains, and aquaria, but not natural water bodies.

Diuron is one of the most commonly used pest icides in California. Reported statewide use in 2002 was 1,303,745 pounds. Of this reported use, 48 percent was applied to rights of way, followed by 18 percent and 14 percen t on alfalfa and oranges, respectively. Additional 2002 uses in California included grapes (4.3 pe rcent), landscape maintenance (3.7 percent), walnuts (2.6 percent), and co tton (1.6 percent). Diuron use has been reported in all 58 counties in California.

21Diuron is often used in combination with othe r herbicides such as bromacil, hexazinone, paraquat, thiadiazuron, imazapyr monosodium, s odium chlorate, sodium metaborate, and copper sulfate (U.S. EPA, 2004a).

Diuron is available in wettable powder, gr anular, flowable, pelle ted/tableted, liquid suspension, and soluble concentrate formulations . However, true granular applications
are not allowed in California and are therefore not assessed fu rther in this document.

Diuron is applied using the following equi pment: groundboom sprayer, aerial equipment, chemigation, rights-of-way sprayer, high- pressure handwand, low-pressure handwand, tractor-drawn spreader, granular backpack spr eader (since true granular applications are not allowed in California, this applica tion method will not be assessed), push-type spreader, airless sprayer, pa intbrush, shaker-type applicat or, backpack sprayer, belly grinder, and by hand. .

For agricultural uses, labeled single app lication rates range from 0.4 to 12 lbs active ingredient (ai) per acre (A). For non-agricultural uses labe led rates are 12 lbs ai/acre. Diuron may be applied to non-agricultura l areas 1 to 2 times per year.

A national map showing the estimated poundage of diuron used for agricultural purposes in 2002 by county is presented in Figure 2.1 . The map was obtained from the U.S. Geological Survey (USGS), National Wate r Quality Assessment Program (NAWQA)
website (URL: http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=m1991)

.

22Source: USGS, 2002

Figure 2.1 Diuron Agricultural Use in Total Pounds per County

Analysis of labeled use information is the cr itical first step in evaluating the federal action. The current label for diuron represen ts the FIFRA regulatory 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.

Table 2.2 presents the uses allowed in Califor nia that will be focused on in this assessment along with the corresponding scenario s used for the Tier II aquatic modeling. Please see Section 3.0 for further explanation.

23Table 2.2 Active Use Sites for Diur on as Applicable to California

Crop Scenario

AGRICULTURAL RIGHTS-OF-W AY/FENCEROWS/HEDGEROWS CA impervious RLF and CA
residential RLF

ALFALFA CA alfalfa OP

APPLE, PEACH, PEAR CA fruit STD

ARTICHOKE, ASPARGUS CA row crop RLF

BANANA, PLANTAIN, PAPAYA CA avocado RLF

BLACKBERRY, BOYSENBERRY , DEWBERRY, LOGANBERRY, RASPBERRY (BLACK/RED) OR Berries OP

BLUEBERRY CA wine grapes RLF

CITRUS CA citrus STD

CORN, FIELD CA corn OP

FILBERT (HAZELNUT), PECAN, WALNUT (ENGLISH/BLACK) CA almond STD

GRAPE CA grapes STD

OLIVE CAOliveRLF-V2

PEPPERMINT, SPEARMINT OR mint STD

SORGHUM, WHEAT CA wheat RLF

Non-Food/Feed Crops

COTTON CA cotton STD

Non-Crop Land

AIRPORTS/ LANDING FIELDS, DRAINAGE SYSTEMS, INDUSTRIAL AREAS (OUTDOOR), SEWAGE DISPOSAL AREAS. PAVED AREAS (PRIVATE ROADS/SIDEWALKS) CA impervious RLF

BERMUDAGRASS CA rangeland hay RLF

GRASSES GROWN FOR SEED CA turf RLF

IRRIGATION SYSTEMS CA residential RLF

ORNAMENTAL HERBACEOUS PLANTS CA Nursery

NON-AGRICULTURAL RIGHTS OF WAY CA impervious RLF and CA
residential RLF

UNCULTIVATED AG, UNCULTIVATED NON-AG CA Rangeland Hay_V2 RLF

* Uses provided by BEAD – July 23, 2008, Scenarios provided by EFED

24The Agency’s Biological and Economic Analysis Division (BEAD) provides an analysis of both national- and county-l evel usage information (Kaul and Jones, 2006) using statelevel usage data obtained from USDA-NASS 1 , Doane ( www.doane.com ); the full dataset is not provided due to its pr oprietary nature) and the Califor nia’s Department of Pesticide Regulation Pesticide Use Re porting (CDPR PUR) database 2 . CDPR PUR is considered a more comprehensive source of usage da ta than USDA-NASS or EPA proprietary databases, and thus the usage data repor ted for diuron by county in this Californiaspecific assessment were generated using CD PR PUR data. Four years (2002-2005) of usage data were included in this analysis. Available data from CD PR PUR were obtained for every pesticide application made on every use site at the secti on level (approximately one square mile) of the public land survey sy stem. BEAD summarized these data to the county level by site, pesticide, and unit treate d. Calculating county- level usage involved summarizing across all applications made with in a section and then across all sections within a county for each use site and for each pesticide. The county level usage data that were calculated include: average annual pounds applied, average annua l area treated, and average and maximum application rate across all five years. The units of area treated are also provided where available. A summary of diuron usage for all California use sites is provided in Appendix C, and a summary of the CDPR PUR usage data can be found in Appendix D.

2.5 Assessed Species

The CRLF was federally listed as a threaten ed species by USFWS effective June 24, 1996 (USFWS 1996). It is one of two subspecies of the red-legged frog and is the largest native frog in the western United States (U SFWS 2002). A brief summary of information regarding CRLF distribution, repr oduction, diet, and habitat re quirements is provided in Sections 2.5.1 through 2.5.4, respectively. Furt her information on the status, distribution, and life history of and specific threats to the CRLF is provided in Attachment I.
Final critical habitat for the CRLF was designated by USFWS on April 13, 2006 (USFWS 2006; 71 FR 19244-19346). Further information on designated critical habitat for the CRLF is provided in Section 2.6.

2.5.1 Distribution

The CRLF is endemic to California and Baja California (Mexico) and historically
inhabited 46 counties in Ca lifornia including the Central Valley and both coastal and interior mountain ranges (USF WS 1996). Its range has b een reduced by about 70%, and the species currently resides in 22 counties in California (USFWS 1996). The species has an elevational range of near sea level to 1,500 meters ( 5,200 feet) (Jennings and Hayes

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.

251994); however, nearly all of the known CRLF populations have been documented below 1,050 meters (3,500 feet) (USFWS 2002).

Populations currently exist along the northern California coast, northern Transverse Ranges (USFWS 2002), foothills of the Sierra Ne vada (5-6 populations), and in southern California south of Santa Barbara (two populat ions) (Fellers 2005a). Relatively larger
numbers of CRLFs are located between Mari n and Santa Barbara Counties (Jennings and Hayes 1994). A total of 243 streams or draina ges are believed to be currently occupied by the species, with the greatest numbers in Monterey, San Luis Obispo, and Santa Barbara counties (USFWS 1996). Occupied drai nages or watersheds include all bodies of water that support CRLFs (i.e., streams, cr eeks, tributaries, associated natural and artificial ponds, and adjacent drainages), and habitats through which CRLFs can move (i.e., riparian vegetation, uplands) (USFWS 2002).

The distribution of CRLFs 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 Figure 2.2 ). Recovery units, core areas, and other known occurrences of the CRLF from
the CNDDB are described in further detail in Attachment I, and desi gnated critical habitat
is addressed in Section 2.6. Recovery units are large areas defined at the watershed level
that have similar conservation needs and mana gement strategies. The recovery unit is primarily an administrative designation, and land area within the recovery unit boundary is not exclusively CRLF habitat. Core areas are smaller areas within the recovery units that comprise portions of the species’ hi storic and current range and have been determined by USFWS to be important in th e preservation of the species. Designated critical habitat is generally contained within the core ar eas, although a number of critical
habitat units are outside the boundaries of core areas, but within the bound aries of the recovery units. Additional information on CRLF occurrences from the CNDDB is used to cover the current range of the species not included in core areas and/or designated critical habitat, but within the recovery units.

Other Known Occurrences from the CNDBB

The CNDDB provides location and natural history information on species found in California. The CNDDB serves as a 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.

26Recovery 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-l egged 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-l egged frog are not included in the map Figure 2.2 Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for CRLF

27Other 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.

2.5.2 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 (USFWS 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, USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until the following year) (Fellers 2005b, USFWS 200 2). Males reach sexual maturity at 2 years, and females reach sexual maturity at 3 years of age; adults have been reported to live 8 to 10 years (USFWS 2002). Figure 2.3 depicts CRLF annual reproductive timing.

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 Reproductive 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 (USFWS 2002). Tadpoles filter and entrap su spended algae (Seale and Beckvar, 1980)

28via mouthparts designed for effectiv e grazing of periphyton (Wassersug, 1984, Kupferberg et al. ; 1994; Kupferberg, 1997; A ltig 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 examining 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 (USFWS 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 important for CRLF (Hayes and Jennings 1988). Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds, marshes, sag ponds (land depressions between fault zones that have filled with water), dune ponds, and lagoons. Breeding adults have been found n ear deep (0.7 m) still or slow moving water surrounded by dense vegetation (USF WS 2002); however, the largest number of tadpoles have been found in shallower pools (0.26 – 0.5 m) (Reis, 1999). Data indicate that CRLFs do not frequently inhabit vernal pools, as conditions in these habitats generally are not suitable (Hayes and Jennings 1988).

CRLFs also frequently breed in artificial impoundments such as stock ponds, although additional research is needed to identify habitat requirements within artificial ponds (USFWS 2002). Adult CRLFs use dense, shrubby or emergent vegetation closely associated with deep-water pools bordered w ith cattails and dense stands of overhanging vegetation ( http://www.fws.gov/endangered/f eatures/rl_frog/rlfrog.html#where ).

In general, dispersal and habitat use depends on climatic conditions, habitat suitability, and life stage. Adults rely on riparian vege tation for resting, feedi ng, and dispersal. The foraging quality of the riparian habitat depends on moisture, composition of the plant

29community, 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 (USFWS 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 trees or logs, industrial debr is, and agricultural features (UWFWS 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 USFWS (USF WS 2006; FR 51 19244-19346). A summary
of the 34 critical habitat units relative to USFWS-designated recovery units and core areas (previously discussed in Sec tion 2.5.1) is provided in Table 2.4.

‘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 through prohibition against destruction or adverse modification with regard to actions carried out, funded, or authorized by a federal Agency. Section 7 requires consultation on fede ral actions that are likely to result in the
destruction or adverse modifi cation 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

30• Dispersal habitat.

Further description of thes e habitat types is provided in Attachment 1.

Occupied habitat may be include d in the critical habitat only if essential features within the habitat may require special management or protection. Theref ore, USFWS does not include areas where existing management is su fficient to conserve the species. Critical habitat is designated outside the geographic area presently occupied by the species only when a designation limited to its present 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 FR listing notice in April 2006. The FR notice designating critic al habitat for the CRLF includes a special rule exempting routine ranchi ng activities associated with livestock ranching from incidental take prohibitions. The purpose of this exemption is to promote the conservation of rangelands, which could be bene ficial to the CRLF, and to reduce the rate
of conversion to other land uses that are incompatible with CRLF conservation. Please see Attachment 1 for a full explanation on this special rule.

USFWS has established adverse modification standards for designate d critical habitat (USFWS 2006). Activities that may destroy or adversely modify critic al habitat are those that alter the PCEs and jeopardize the continue d existence of the species. Evaluation of actions related to use of diuron that may a lter the PCEs of the CRLF’s critical habitat form the basis of the critical habitat imp act analysis. According to USFWS (2006), activities that may affect critical habitat a nd therefore 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) 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. (3) 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. (4) Elimination of upland foraging and/or aes tivating habitat or dispersal habitat. (5) Introduction, spread, or augmentation of non-native aquatic species in stream segments or ponds used by the CRLF. (6) Alteration or elimination of the CRLF ’s food sources or prey base (also evaluated as indirect effects to the CRLF).

31As 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 di uron is expected to di rectly impact living organisms within the action area, critical habitat analysis for diuron 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.

2.7 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 di uron is likely to encompass c onsiderable 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 (USEPA 2004) cons iders the resu lts of the risk assessment process to establish boundaries for that action area with the understanding that exposures below the Agency’s defined LOCs constitute a no-effect threshold. For the purposes of this assessment, attention will be focused on the footprint of the action (i.e., the area where pesticide application occurs ), plus all areas where offsite transport (i.e., spray drift, downstream dilution, etc.) may result in poten tial exposure within th e state of California that exceeds the Agency’s LOCs.

Deriving the geographical extent of this portion of the action area is based on consideration of the types of effects that diuron may be expected to have on the environment, the exposure levels to diuron that are associated with those effects, and the best available information concerning the use of diuron and its fate and transport within the state of California. Specific measures of ecological effect for the CRLF that define the action area include any direct and indirect toxic effect to the CRLF and any potential
modification of its critical ha bitat, including reduction in su rvival, growth, and fecundity
as well as the full suite of sublethal effects av ailable in the effects lit erature. Therefore, the action area extends to a point where environmental exposures are below any
measured lethal or sublethal effect thres hold for any biological entity at the whole organism, organ, tissue, and cellu lar level of organization. In situations where it is not possible to determine the threshold for an obs erved effect, the action area is not spatially
limited and is assumed to be the entire state of California.

The definition of action area requires a stepwise approach that begins with an understanding of the federal act ion. The federal action is de fined by the currently labeled uses for diuron. An analysis of labeled uses and review of availa ble product labels was completed. Several of the currently labeled us es are special local needs (SLN) uses or are restricted to specific states and are excl uded from this assessment. In addition, a
distinction has been made between food use crops and those that are non-food/nonagricultural uses. For those uses relevant to the CRLF, the analysis indicates that, for

32diuron, agricultural and non-agri cultural uses listed in Table 2.2 are considered part of the
federal action evaluated in this assessment.

Following a determination of the assessed uses , an evaluation of the potential “footprint” of diuron use patterns (i.e., th e area where pesticide applicat ion 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 labeled uses described above. A map represen ting all the land cover types related to agricultural uses that make up the initial ar ea of concern for diuron is presented in Figure
2.4 . Diuron, in fact, is used in all 58 of California’s counties when you consider nonagricultural uses as well.

33Figure 2.4 Initial area of concern, or “foot print” of potential use, for diuron

34Once 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. As stated in the 2003 Registration Eligib ility Decision (RED), diuron has been characterized as a “known/likely” human carcinogen, based on urinary bladder carcinomas in both sexes of the Wistar rat, kidney carcinomas in the male rat (a rare tumor), and mammary gland carcinomas in the female NMRI mouse. Because of this, the spatial extent of the ac tion area (i.e., the boundary wh ere exposures and potential effects are less than the Agency’s LOC) for di uron cannot be determined. Therefore, it is assumed that the action area encompasses the en tire state of California, regardless of the spatial extent (i.e., initial area of concern or footprint) of the pesticide use(s). This determination is supported by the fact that di uron use has been reporte d in all 58 counties
in California.

The AgDRIFT model (Version 2.01) is used to define how far from the initial area of concern an effect to a given species may be expected via spray drift. The spray drift analysis for diuron using the most sensitive endp oint (most sensitive plant toxicity study: Vegetative Vigor - Tomato ( Lycopersicon esculentum )) suggests that a maximum spray drift distance of at least 1,000 feet is necessary. The Tier 1 ground analysis allows users to evaluate off-site deposition and exposur e out to 1,000 ft downwind from the location of the application. Further detail on the spra y drift analysis is pr ovided in Section 3.2.5.

In addition to the buffered area from the spra y drift analysis, the final action area also
considers the downstream extent of diuron th at exceeds the LOC (discussed in Section 3.2.6).

An evaluation of usage information was c onducted to determine the area where use of diuron may impact the CRLF. This analysis is used to charact erize where predicted exposures are most likely to occur, but doe s 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 diuron has historically been used on a wide variety of agricultural and non-ag ricultural uses.

2.8 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 upland and dispersal habitats), the migration pathways of diuron

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

35( e.g., runoff, spray drift, etc.), and the rout es by which ecological receptors are exposed
to diuron (e.g., direct contact, etc.).

2.8.1. Assessment Endpoints for the CRLF

Assessment endpoints for the CRLF include direct toxic effects on the survival, reproduction, and growth of the CRLF, as well as indirect effects, such as reduction of the prey base or modification of its habitat. In addition, potential m odification of critical habitat is assessed by evaluating potential eff ects to PCEs, which are components of the habitat areas that provide essential life cycle needs of the CRLF. Each assessment endpoint requires one or more “measures of ecological effect,” defined as changes in the attributes of an assessment endpoint or cha nges in a surrogate entity or attribute in response to exposure to a pesticide. Specific measures of ecological effect are generally evaluated based on acute and chronic toxicity information from registrant-submitted guideline tests that are performed on a limited number of organisms. Additional ecological effects data from the open literature are also considered. It should be noted that assessment endpoints are limited to dir ect and indirect effects associated with survival, growth, and fecundity, and do not incl ude the full suite of sublethal effects used to define the action area. According th e Overview Document (USEPA 2004), the Agency relies on acute and chronic effects endpoi nts that are either direct measures of impairment of survival, growth, or fec undity or endpoints for which there is a scientifically robust, peer reviewed relationship that ca n quantify the impact of the measured effect endpoint on the assessment endpoi nts 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 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 diuron is provided in Table 2.4.

Table 2.4 Assessment Endpoints and Measures of Ecological Effects 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. Amphibian acute LC 50 (ECOTOX) or most sensitive
fish acute LC 50 (guideline or ECOTOX) if no suitable amphibian data are available 1b. Amphibian chronic NOAEC (ECOTOX) or most sensitive fish chronic NOAEC (guideline or ECOTOX) 1c. Amphibian early-life stage data (ECOTOX) or most sensitive fish early-life stage NOAEC (guideline or ECOTOX) Indirect Effects and Critical Habitat Effects 2. Survival, growth, and reproduction of
CRLF individuals via indirect effects on 2a. Most sensitive fish, aquatic invertebrate, and aquatic plant EC 50 or LC 50 (guideline or ECOTOX)

4 All registrant-submitted and open literature toxicity da ta reviewed for this assessment are included in Appendix J.

36Assessment Endpoint Measures of Ecological Effects 4

aquatic prey food supply ( i.e., fish, freshwater invertebrates, non-vascular plants) 2b. Most sensitive aquatic invertebrate and fish chronic NOAEC (guideline or ECOTOX) 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. Vascular plant acute EC 50 (duckweed guideline test or ECOTOX vascular plant) 3b. Non-vascular plant acute EC 50 (freshwater algae or diatom, or ECOTOX non-vascular)

4. Survival, growth, and reproduction of CRLF individuals via effects to riparian vegetation 4a. Distribution of EC 25 values for monocots (seedling emergence, vegetative vigor, or ECOTOX)
4b. Distribution of EC 25 values for dicots (seedling emergence, vegetative vigor, or ECOTOX)
Terrestrial-Phase CRLF

(Juveniles and adults) Direct Effects

5. Survival, growth, and reproduction of
CRLF individuals via direct effects on terrestrial phase adults and juveniles 5a. Most sensitive bird b or terrestrial-phase amphibian
acute LC 50 or LD 50 (guideline or ECOTOX)
5b. Most sensitive bird b or terrestrial-phase amphibian chronic NOAEC (guideline or ECOTOX) 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. Most sensitive terrestrial invertebrate and vertebrate
acute EC 50 or LC 50 (guideline or ECOTOX) c
6b. Most sensitive terrestrial invertebrate and vertebrate chronic NOAEC (guideline or ECOTOX)

7. Survival, growth, and reproduction of
CRLF individuals via indirect effects on habitat ( i.e., riparian and upland vegetation) 7a. Distribution of EC 25 for monocots (seedling emergence, vegetative vigor, or ECOTOX
7b. Distribution of EC 25 for dicots (seedling emergence, vegetative vigor, or ECOTOX)

a Adult frogs are no longer in the “aquatic phase” of the amphibian life cycle; however, submerged adult frogs are considered “aquatic” for the purposes of 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.

2.8.2 Assessment Endpoints for De signated Critical Habitat

As previously discussed, designa ted critical habitat is assessed to evaluate actions related to the use of diuron that may alter the PCEs of the CRLF’s critical habitat. PCEs for the CRLF were previously described in Section 2.6. Actions that may modify critical habitat are those that alter the PCEs and jeopardi ze 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 diuron effects data are available.

Adverse modification to the critical habitat of the CRLF includes, but is not limited to, the following, as specified by USFWS (2006):

1. Alteration of water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal grow th and viability of juvenile and
adult CRLFs.

372. Alteration of chemical characterist ics necessary for normal growth and viability of juvenile and adult CRLFs.
3. Significant increase in sediment depositi on within the stream channel or pond or disturbance of upland fora ging and dispersal habitat.
4. Significant alteration of channe l/pond morphology or geometry.
5. Elimination of upland foraging and/or aes tivating habitat, as well as 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.

Measures of such possible effects by labeled use of diuron on critical habitat of the CRLF
are described in Table. So me components of these PCEs are associated with physical abiotic features (e.g., presence and/or dept h of a water body, or distance between two sites), which are not expected to be measurab ly altered by use of pe sticides. Assessment endpoints used for the analysis of designate d critical habitat ar e based on the adverse
modification standard es tablished by USFWS (2006).

38Table 2.5 Summary of Assessment Endpoints and Measures of Ecological Effect for Primary
Constituent Elements of De signated Critical Habitat a

Assessment Endpoint Measures of Ecological Effect

Aquatic-Phase CRLF PCEs (Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat) Alteration of channel/pond morphology or geometry and/or increase in sediment deposition within the stream channel or pond: aquatic habitat (including riparian vegetation) provides for shelter, foraging, predator avoidance, and aquatic dispersal for juvenile
and adult CRLFs. a. Most sensitive aquatic plant EC 50 (guideline or ECOTOX)
b. Distribution of EC 25 values for terrestrial monocots (seedling emergence, vegetative vigor, or ECOTOX)
c. Distribution of EC 25 values for terrestrial dicots (seedling emergence, vegetative vigor, or ECOTOX)

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. a. Most sensitive EC 50 values for aquatic plants (guideline or ECOTOX)
b. Distribution of EC 25 values for terrestrial monocots (seedling emergence or vegetative vigor, or ECOTOX)
c. Distribution of EC 25 values for terrestrial dicots (seedling emergence, vegetative vigor, or ECOTOX)

Alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their
food source. a. Most sensitive EC 50 or LC 50 values for fish or aquaticphase amphibians and aquatic invertebrates (guideline or ECOTOX) b. Most sensitive NOAEC values for fish or aquatic-phase amphibians and aquatic invertebrates (guideline or ECOTOX)

Reduction and/or modification of aquatic-based food sources for pre-metamorphs ( e.g., algae) a. Most sensitive aquatic plant EC 50 (guideline or ECOTOX)

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. a. Distribution of EC 25 values for monocots (seedling emergence, vegetative vigor, or ECOTOX)
b. Distribution of EC 25 values for dicots (seedling emergence, vegetative vigor, or ECOTOX)
c. Most sensitive food source acute EC 50 /LC 50 and NOAEC values for terrestrial vertebrates (mammals) and invertebrates, birds or terrestrial-phase amphibians, and
freshwater fish.

a Physico-chemical water quality parameters such as sa linity, pH, and hardness are not evaluated because these processes are not biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.

392.9 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 th e stressor is the release of di uron to the environment. The following risk hypotheses are presumed fo r this endangered species assessment:

The labeled use of diuron 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 pl ant community in the ponds and streams comprising the species’ current range and desi gnated critical habita t, 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;

• Modify the designated critical habita t of the CRLF by reducing or changing breeding and non-breeding aquatic habitat (via modification of water quality parameters, habitat morphology, and/or sedimentation);

• Modify 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;

• Modify the designated critical habita t 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.

• Modify the designated critical habita t of the CRLF by reducing or changing dispersal habitat within designa ted units and between occupied locations within 0.7 mi of
each other that allow for movement between si tes including both natural and altered sites which do not contain barriers to dispersal.

• Modify the designated critical habi tat of the CRLF by altering chemical characteristics necessary for normal growth a nd viability of juven ile and adult CRLFs.

2.9.2 Diagram

The conceptual model is a graphic representation of the structure of the risk assessment. It specifies the diuron release mechanisms , biological receptor types, and effects endpoints of potential concern. The conceptual models for aquatic and terrestrial phases
of the CRLF are shown in Figure 2.5 and Figure 2.6 , respectively, and the conceptual models for the aquatic and terrestrial PCE comp onents of critical ha bitat are shown in

40Figure 2.7 and Figure 2.8 , respectively. Exposure routes shown in dashed lines are not quantitatively considered because the contribu tion of those potential exposure routes to potential risks to the CRLF and modification to designated critical ha bitat is expected to be negligible.

Stre ssor

Source

Receptors

Attribute Change S p ra y drift

Red-legged Frog Eggs Juveniles

Individual organisms Reduced survival Reduced g rowth

Food sources Reduction in algae Reduction in pre y Habitat quality and channel/pond morphology or geometry
A dverse water quality changes Increased sedimentation Reduced shelter Surface water/ Sediment Runoff

Aquatic Animals Invertebrates Vertebrates Exposure Media

Uptake/gills

or

Ingestion Ingestion Long range atmospheric

trans p ort
Wet/dry Soil

Uptake/gills

or

A quatic Plants Non-vascular Vascula r Uptake/cell, roots,

Riparian and Upland plants terrestrial exposure pathways and PCEs

Community Reduced seedling
emergence or

ve g etative vi g or

Other chemical characteristics Adversely modified chemical characteristics Population
Y ield Reduced yield Individual organisms Reduced survival Reduced g rowth Groundwa ter diuron applied to use site

Habitat PCEs

Figure 2.5 Conceptual Model fo r Aquatic-Phase of the CRLF

41Stre ssor

Sourc e

Attribute Change

Habitat PCEs Direct application S p ra y drift

Red-legged Frog Juvenile/Adult Terrestrial

insects

Food resources Reduction in food

sources Elimination and/or disturbance of upland or dispersal habitat Reduction in primary productivity Reduced shelter Restrict movement Terrestrial plants grasses/forbs, fruit, seeds (trees, shrubs) Runoff

Mammals Exposure Soil

Ingestion Ingestion

Ingestion In g estion Dermal Long range atmospheric

transport

Root Wet/dry

Individual organisms Reduced survival Reduced growth

Other chemical characteristics Adversely modified chemical characteristics Population Reduced survival Reduced growth Reduced reproduction Community Reduced seedling emergence or vegetative vigor (Distribution) Media and diuron applied to use site

Figure 2.6 Conceptual Model fo r Terrestrial-Phase of the CRLF

42Stre ssor

Source

Receptor

Attribute Change diuron applied to use site

S p ra y drift

Red-legged Frog Eggs/Juveniles Larvae/Adult Tadpoles

Individual organisms Reduced survival Reduced g rowth

Food sources Reduction in algae Reduction in pre y Habitat quality and channel/pond morphology or geometry
A dverse water quality changes Increased sedimentation Reduced shelter Surface water/ Sediment Runoff

Aquatic Animals Invertebrates Vertebrates Exposure Media

Uptake/gills

or

Ingestion Ingestion Long range atmospheric

trans p ort
Wet/dry Soil

Uptake/gills

or

A quatic Plants Non-vascular Vascula r Uptake/cell, roots,

Riparian and Upland plants terrestrial exposure pathways and PCEs

Community Reduced seedling
emergence or

ve g etative vi g or

Habitat PCEs Other chemical characteristics Adversely modified chemical characteristics Population
Y ield Reduced yield Individual organisms Reduced survival Reduced g rowth Groundwate r

Figure 2.7 Conceptual Model for Pesticide Eff ects on Aquatic Component of CRLF
Critical Habitat

43Figure 2.8 Conceptual Model for Pesticid e Effects on Terrestrial Component of
CRLF Critical Habitat

Stressor

Source

Attribute Change

Habitat PCEs Direct application S p ra y drift

Red-legged Frog Juvenile/Adult Terrestrial

insects

Food resources Reduction in food

sources Elimination and/or disturbance of upland or dispersal habitat Reduction in primary productivity Reduced shelter Restrict movement Terrestrial plants grasses/forbs, fruit, seeds (trees, shrubs) Runoff

Mammals Exposure Media and Soil

Ingestion Ingestion

Ingestion In g estion Dermal Long range atmospheric

transport

Root Wet/dry

Individual organisms Reduced survival Reduced growth

Other chemical characteristics Adversely modified chemical characteristics Population Reduced survival Reduced growth Reduced reproduction Community Reduced seedling emergence or vegetative vigor (Distribution) diuron applied to use site

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 diuron 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 Overview Document (U.S. EPA, 2004), the
likelihood of effects to individua l organisms from particular uses of diuron is estimated using the probit dose-response sl ope and either the level of concern (discussed below) or actual calculated risk quotient value.

2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model

2.10.1.1 Measures of Exposure

The environmental fate properties of diuron al ong with available monitoring data indicate that runoff and spray drift are the principle potential trans port mechanisms of diuron to the aquatic and terrestrial habitats of the CRLF. In this assessment, transport of diuron

44through runoff and spray drift is considered in deriving quantitative estimates of diuron exposure to CRLF, its prey and its habitats. The reported vapor pre ssure of diuron is 6.9
x 10 -8 torr at 25°C; therefore, volatilization is not considered a probable route of dissipation.

Measures of exposure are based on aquatic and terrestrial models that predict estimated environmental concentrations (EECs) of di uron using maximum labeled application rates and methods of application. The models used to predict aquatic EECs are the Pesticide Root Zone Model coupled with the Exposur e Analysis Model System (PRZM/EXAMS). T-REX is used to predict terrestrial EECs on food items. TerrPlant is used to derive
EECs relevant to terrestrial and wetland plants. These models are parameterized using relevant reviewed registrant-submitted environmental fate data.

PRZM (v3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are screening simulation models coupled with the input shell pe5.pl (Aug 2007) to generate daily exposures and 1-in-10 year EECs of diur on that may occur in surface water bodies adjacent to application sites receiving di uron through runoff and spray drift. PRZM simulates pesticide application, movement a nd transformation on an agricultural field and the resultant pesticide loadings to a recei ving water body via runoff, erosion and spray drift. EXAMS simulates the fate of the pesticide and resulting concentrations in the water body. The standard scenario used 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 aquati c organisms to diuron. The measure of exposure for aquatic species is the 1-in-10 year return peak or rolling 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 effects to the CRLF through effects to potential prey items, including: algae, aquatic inve rtebrates, 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 us ed for assessing chronic exposure for aquatic invertebrates, which are al so potential prey items.

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 diuron through contaminated food 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

45for the CRLF and one of its prey items. Es timated exposures of terrestrial insects to diuron are bound by using the dietary based EECs for small insects and large insects.

Birds are currently used as surrogates for te rrestrial-phase CRLF. However, amphibians are poikilotherms (body temperat ure varies with environmenta l temperature) while birds are homeotherms (temperature is regulate d, constant, and largely independent of environmental temperatures). Therefore, am phibians tend to have much lower metabolic
rates and lower caloric intake requirements than birds or mammals. As a consequence, birds are likely to consume more food than amphibians on a daily dietary intake basis, assuming similar caloric content of the food items. Therefore, the use of avian food intake allometric equation as a surrogate to amphibians is likely to result in an overestimation of exposure and risk for reptiles a nd terrestrial-phase amphibians. Therefore, T-REX (version 1.3.1) has been refined to th e T-HERPS model (v. 1.0), which allows for an estimation of food intake for poikilotherms using the same basic procedure as T-REX
to estimate avian food intake.

EECs for terrestrial plants inhabiting dry 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.

Spray drift model, AgDRIFT is used to assess exposures of terrestrial phase CRLF and its prey to diuron deposited on terres trial habitats by spray drift. In addition to the buffered area from the spray drift analysis, the downstr eam extent of diuron that exceeds the LOC
for the effects determination is also considered.

2.10.1.2 Measures of Effect

Data identified in Section 2.8 are used as measur es 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 USEPA, Office of Research and Deve lopment, and the National Health and
Environmental Effects Research Labora tory's Mid-Continent Ecology Division.

The assessment of risk for direct effect s to the terrestrial-phase CRLF makes the assumption that toxicity of diur on to birds is similar to or le ss 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.

46The 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.

2.10.1.3 Integration 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 diuron, and the likelihood of dir ect and indirect effects to CRL F in aquatic and terrestrial habitats. The exposure and toxi city effects data are integrat ed in order to evaluate the risks of adverse ecological e ffects on non-target species. For the assessment of diuron risks, the risk quotient (RQ) method is used to compare exposure and measured toxicity values. EECs are divided by acute and chr onic toxicity values. The resulting RQs are then compared to the Agency’s levels of concern (LOCs) (USEPA, 2004) (see Appendix E).

For this endangered species assessment, listed species LOCs are used for comparing RQ values for acute and chronic exposures of di uron directly to the CRLF. If estimated exposures directly to the CRLF of diuron resulting from a part icular use are sufficient to exceed the listed species LOC, th en the effects determination for that use is “may affect”. When considering indirect effects to the CRLF due to effects to animal prey (aquatic and terrestrial invertebrates, fis h, frogs, and mice), the listed speci es LOCs are also used. If estimated exposures to CRLF prey of diuron resulting from a particular use are sufficient to exceed the listed species LOC, then the e ffects determination for that use is a “may affect.” If the RQ being considered also exceeds the non-listed species acute risk LOC,
then the effects determination is a LAA. If the acute RQ is betw een the listed species

47LOC and the non-listed acute risk species LOC, then further lines of evidence ( i.e

. probability of individual effects, species se nsitivity distributions) are considered in distinguishing between a determ ination 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 nonlisted species LOC for plants is used b ecause the CRLF does not have an obligate relationship with any particular aquatic and/ or terrestrial plant. If the RQ being considered for a particular use exceeds the non-listed species LOC fo r plants, the effects determination is “may affect”. Further in formation on LOCs is provided in Appendix E.

2.10.2 Data Limitations

No acceptable toxicity studies have submitted to the Agency, nor were any acceptable studies found in the open literature for th e chronic effects of diuron on avian or amphibian species. Linuron, a similar chemical of the same class, has acceptable chronic avian data. The avian reproductive studies for linuron (MRID 42541801, 42541802) using mallard duck and bobwhite quail found re productive effects at 300 ppm ai with an NOAEL being established at 100 ppm.

The endpoints affected for mallard duck reproduction are egg production, adult body weight, feed consumption, viable embryos of eggs set, number of viable embryos, and number of live embryos. For the Bobwhite Quail the endpoints affected are hatchability and offspring survivability. The LC 50 for the Bobwhite Quail exposed to linuron was 1700ppm, where the LC 50 for the Bobwhite Quail exposed to linuron was almost identical at 1730 ppm (MRID 00022923). Therefore it is assumed that linuron and diuron have a
similar mode of action and therefore chroni c effects from diuron are assumed to be similar to those observed from linuron exposure. Chronic risks are therefore assumed to amphibian species and their avian surroga tes for uses of diuron in California.

3.0 Exposure Assessment

Diuron is a broad-spectrum residual herbic ide registered for pre-emergent and postemergent control of both broadleaf and annual gr assy weeds. In the U.S. diuron is used on a variety of fruit and nut crops, grains, cotton, corn, sorghum, mint, gum, asparagus, sugarcane, seed crops, coffee, hay, cut flowers, and for fallow and idle cropland use. It may be used in irrigation and drainage systems when water is not present.

It is also used to control weeds on hard surf aces, such as, roads, railway tracks, and paths (at around 3 kg/ha), and to control weeds in crop s, such as, pear and apple trees, forestry, ornamental trees and shrubs, pineapples, s ugar cane, cotton, alfalfa and wheat (at lower rates of around 1.8 kg/ha). Its use in some locations is becoming limited due to the development of resistant weed species. In some products it is formulated with other active ingredients such as glyphosate, brom acil, hexazinone, amitrole and 2,4-D. This assessment evaluates only those registered uses which allow use in California.

483.1 Label Application Rates and Intervals

Currently registered agricultu ral and non-agricultural uses of diuron within California include agricultural and non-agricultural crops, as well as industrial and paved areas. The uses and applicable PRZM/EXAMS s cenarios being assessed were summarized in Table 2.2. For a list of the applicati on rates and intervals used, please refer to
Table 3.2 below.

3.2 Aquatic Exposure Assessment

3.2.1 Modeling Approach

As discussed in Section 2.10.1.1, the models used to predict a quatic EECs are the
Pesticide Root Zone Model coupled with the Exposure Analysis Model System (PRZM/EXAMS). Using PRZM/EXAMS, aquatic exposures are quantitatively estimated
for all of the assessed uses w ith scenarios that represent hi gh exposure sites for diuron use. Each of these sites repr esents a 10 hectare field that dr ains into a 1-hectare pond that is 2 meters deep and has no outlet. Exposur e estimates generated us ing the standard pond are intended to represent a wide variety of vulne rable water bodies that occur at the top of watersheds including prairie pot holes, playa lakes, wetla nds, vernal pools, man-made and natural ponds, and intermittent and first-or der streams. As a group, there are factors
that make these water bodies more or less vulnerable than the sta ndard surrogate pond.
Static water bodies that have larger ratios of drainage area to water body volume would be expected to have higher peak EECs than the standard pond. These water bodies will be either shallower or have large drainage ar eas (or both). Shallow water bodies tend to have limited additional storage capacity, and t hus, tend to overflow a nd carry pesticide in the discharge whereas the sta ndard pond has no discharge. As watershed size increases beyond 10 hectares, at some point, it become s unlikely that the entire watershed is planted to a single crop, which is all treated with the pesticide. Headwater streams can also have peak concentrations higher than the standard pond, but they tend to persist for only short periods of time and are then carried downstream.

Crop-specific management practices for all of the assessed uses of diuron were used for modeling, including application rates, number of applica tions per year, application intervals, and the first applic ation date for each crop. The date of first application was developed based on several sources of inform ation including data provided by BEAD, a summary of individual app lications from the CDPR PUR data, and Crop Profiles maintained by the USDA.

3.2.2 Model Inputs

The input parameters for PRZM and EXAMS are presented in Table 3.1

.

49Table 3.1 Summary of PRZM/EXAMS Enviro nmental Fate Data Used for Aquatic Exposure Inputs for Diuron Endangered Species Assessment for the CRLF

Fate Property Value (unit) MRID (or source)

Molecular Weight 233.1 g/mol Product Chemistry

Henry’s constant 5.1E-10 atm-m -3 /mol MRID 00017763

Vapor Pressure 6.9E-8 torr (25°C) MRID 43762901, Herbicide
Handbook 7 th Edition, WSSA,
1994

Solubility in Water 420 mg/l (42 mg/l x 10 per input guidance) Product Chemistry, Input
Parameter Guidance

Photolysis in Water 43 days MRID 41418805

Aerobic Soil Metabolism Half-lives 372 days MRID 41719303

Hydrolysis Stable at pH7 (>500 hrs) MRID 41418804

Aerobic Aquatic Metabolism (water column) 99 days (33 days x 3 per input guidance) MRID 42260501, Input
Parameter Guidance

Anaerobic Aquatic Metabolism (benthic) 15 days (5 days x 3 per input guidance) MRID 42661901, Input
Parameter Guidance

Koc 920 (avg. of 468, 626, and 1666) MRID 44490501

Application rate and frequency Various (see Table 3.2) Per Label Instructions

Application intervals Various (see Table 3.2) Per Label Instructions

Chemical Application Method (CAM) 1 Label; Input Guidance for Eco
Assessments

Application Efficiency 0.99 Ground
0.95 Aerial Per Input Guidance for Eco
Assessments

Spray Drift Fraction 1 0.01 Ground
0.05 Aerial Per Input Guidance for Eco
Assessments Inputs determined in ac cordance with EFED “ Guidance for Chemistry and Managemen t Practice Input Parameters for Use in Modeling the Environmental Fate and Transport of Pesticides” dated February 28, 2002

3.2.3 Results

The PRZM/EXAMS model estimated aquatic EECs for the various scenarios and application practices are listed in Table 3.2. See Appendix G for a summary of the outputs. Peak EECs ranged from 3.76 to 4911 ppb for use on grasses grown for seed and paved areas (impervious su rfaces), 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 applications allowed per season, and/or th e interval between applications. The assumptions were as follows:

50• For the application intervals that were not stated, the most conservative (minimum) known application interval wa s used (21 days for cotto n). 21 days was chosen
because it was the minimum known in terval that was registered.

• If the maximum number of applications was also missing, the maximum number of intervals a year was determine by taking th e maximum allowable application of active ingredient per year (12 lb ai/yr) and divi ding it by the maximum application rate for the use in question. The following is an example of a calculation to determine the maximum number of applications per year for the use of di uron on blackberries:

Max No. of Appl.Yr -1 = 12 lb ai. acre -1 yr -1 ÷ 2.4 lb ai. acre -1 appl. -1 = 5 appl. yr -1

Table 3.2 Aquatic EECs (ppb) for Diuron Uses in California

Max # of Applications Interval
Between

Apps Application
method Crop Application
Rate (lbs/A) (Apps/yr) (Days) Peak
EEC ppb 96
Hour EEC pbb 21 Day EEC pbb 60 Day EEC pbb

AGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 12 2 21 Ground 688 672 584 457

Ground 10.6 10.4 9.1 7.2 ALFALFA 2.4 1 0 Aircraft 13.7 13.3 11.7 9.4

APPLE 3.2 2 90 Ground 11.7 11.2 9.6 7.8

ARTICHOKE 3.2 1 0 Ground 32.0 31.1 27.4 25.1

ASPARGUS 3.2 1 0 Ground 37.0 35.5 30.2 22.9 BANANA, PLANTAIN 4.8 2 42 Ground 54.2 52. 0 44.3 32.8
BLACKBERRY, BOYSENBERRY 2.4 5 21 Ground 140 136 121 103

BLUEBERRY 1.6 2 112 Ground 4.65 4.48 4.05 3.21

CITRUS 3.2 2 60 Ground 6.83 6.57 5.65 4.88
CORN, FIELD 0.8 1 0 Ground 7.24 6.95 6.13 4.68

DEWBERRY 2.4 3 60 Ground 19.7 19.3 16.8 14.3
FILBERT (HAZELNUT) 2.2 2 150 Ground 18.9 18.4 15.9 12.2

GRAPE 3.2 2 90 Ground 9.71 9.32 8.10 6.37 LOGANBERRY, RASPBERRY (BLACK/RED) 2.4 1 0 Ground 5.13 4.95 4.31 3.02

OLIVE 1.6 2 168 Ground 7.17 6.90 5.97 4.86

PAPAYA 4 1 0 Ground 25.2 24.6 21.2 15.7

PEPPERMINT 2.4 1 0 Ground 4.17 4.05 3.55 2.79

PEACH 3 1 0 Ground 11.0 10.5 9.0 7.3

PEAR 3.2 1 0 Ground 11.7 11.2 9.6 7.8

PECAN 3.2 1 0 Ground 27.0 26.3 22.8 17.3

SORGHUM 0.4 2 21 Ground 5.87 5.67 5.44 4.52

SPEARMINT 2.4 5 21 Ground 107 104 97.1 82.0 WALNUT (ENGLISH/BLACK) 3 2 150 Ground 25.8 25.1 21.8 16.6

18.0 17.3 14.9 12.0 WHEAT 1.6 1 0 Ground 12.8 12.3 11.9 10.3 Non-Food/Feed Crops

Ground 8.36 8.13 7.42 5.72 COTTON 1.6 3 21 Aircraft 14.2 13.9 12.9 10.2 Non-Crop Land AIRPORTS/ LANDING FIELDS, DRAINAGE SYSTEMS,
INDUSTRIAL AREAS (OUTDOOR), SEWAGE DISPOSAL
AREAS 12 2 21 Ground

2190 2115 1825 1382

BERMUDAGRASS 2.4 5 21 Ground 226 219 204 168

GRASSES GROWN FOR SEED 1.6 1 0 Ground 3.76 3.62 3.20 2.89

51Interval Max # of Application Between Applications method Apps

IRRIGATION SYSTEMS 12 2 21 Ground 52.6 50.7 45.0 37.5

ORNAMENTAL HERBACEOUS
PLANTS 4 1 0 Ground 36.5 35.5 30.7 23.6

Ground 630 619 560 476 NON-AGRICULTURAL RIGHTS
OF WAY 12 2 90 Aircraft 627 616 552 468 PAVED AREAS (PRIVATE

ROADS/SIDEWALKS) 12 1 0 Ground 4911 4725 4241 3428

Ground 1130 1099 1023 840 UNCULTIVATED AG 12 1 0 Aircraft 1169 1130 1063 891

UNCULTIVATED NON-AG 12 2 21 Ground 285 276 252 203

3.2.4 Existing Monitoring Data

3.2.4.1 USGS NAWQA Surface Water Data

A critical step in the process of characteri zing EECs is comparing the modeled estimates with available surface water monitoring data. The USGS has collected 347 surface water samples from four river basins in Califor nia (Sacramento, San Joaquin-Tulare, Santa Ana, and Nevada) with a detection limit of 0.01 ppb. Out of these samples, 232 (69%) were positive for diuron. The maximum concentration observed was 23.3 ppb in the Santa Ana River Basin in San Bernardino County.

3.2.4.2 USGS NAWQA Groundwater Data

The USGS collected 428 ground water samples where 75 (17.5%) of these samples
contained diuron. The three river basins looke d at were Sacramento, San Joaquin-Tulare,
and Santa Ana. The maximum concentrati on observed was 1.8 ppb in the San JoaquinTulare water basins in Kings County.

Similar to the most recent analysis of US GS data, an “Analysis of Diuron Monitoring Data with [an] emphasis on the USGS N AQWA Surface Water Sampling” in February 1999, observed the San Joaquin-Tulare basin as well. It was c oncluded that diuron concentrations reached their peaks in the wint er and spring seasons (January to June).
USGS concluded that runoff was more efficient than irrigation return flows in transporting pesticides, in this case diuron, into surface water. Although USGS detected diuron in more than 10% of the ground water samples, the concentrations were generally less than 0.1 ppb.

. 3.2.4.3 California Department of Pesticide Regulation Data

The California Department of Pesticide Regul ation (CDPR) has been collecting surface
water data on diuron since 1992. In a me mo sent to the Special Review and Reregistration Division (SRRD) from the E nvironmental Fate and Effects Division (EFED) in 2003, titled “Surface Water Monitoring Data for Diuron”, summarized surface water monitoring data for diuron collected by CDPR over the period December 2000 to
March 2001. There were three locations (82 samples) in the Sacramento River, and two locations (54 samples) in the San Joaquin River. One-hundred percent of the samples

52taken from the San Joaquin River had detect able diuron, with a maximum concentration of 8.45 ppb. The average concentration at th e San Joaquin River stations was 1.7 ppb. About seventy-five percent of the samples in the Sacramento River had detectable diuron with a maximum concentration of 1.42 ppb. The average concentrati on, assuming that all non-detects were equal to the detection limit of 0.05 ppb, was 0.16 ppb.

Currently, the monitoring data available at CD PR has expanded to include data collected from 2004, 2005, and 2006. Between 2004 and 2006, the data indicates that diuron concentrations range from non-detect to 160 ppb (San Joaquin County, January 3, 2005, and Tulare County, February 21, 2005). Ou t of 156 sampling locations, 152 locations (97.4%) were located within 0.5 miles or less of an agricultural ar ea. The four other
locations were 8 miles or more from the nearest agricultural area.

Sixteen percent of the 705 samples collect ed from 2004 to 2006 were greater than the detection limit. The majority of the highe r concentrations of diuron came from San Joaquin County, and occurred between the end of December and the beginning of January. The year 2005, for San Joaquin C ounty, yielded the greatest concentrations overall with an average concentr ation of 10.9 ppb for the year.

Diuron’s concentrations being greatest in, and mainly only showing up in the monitoring data during the winter months is consiste nt with the labeled use for pre-emergence application. In addition, during the winter months, high concen trations may be detected due to transport from rainfall runoff. Runoff during the winter in the San Joaquin Valley may include large amounts of non-agricultu ral runoff from coastal ranges. When comparing this monitoring data to the results from PRZM/EXAMS, the CDPR data further supports that spray drift is a major route of off site movement.

3.2.4.4 Atmospheric Monitoring Data

The California Air Review Board has not c onducted ambient air monitoring of diuron. Therefore, no atmospheric monitoring data is available.

3.2.6 Downstream 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 modeled EECs; as those waters move downstr eam, it is assumed that the influx of nonimpacted water will dilute the conc entrations of diuron present.

Using the LC50 for Selenastrum capricornutum (the most sensitive species) of 2.40 ppb and a maximum peak EEC for applicatio ns to non-agricultural rights-ofway/fencerows/hedgerows of 341.6 ug/L yields an RQ/LOC ratio of 142.33. Using the downstream dilution approach (described in mo re detail in Appendix F) yields a target percent crop area (PCA). This value has been input into the downstream dilution approach resulting in a total of 285 kilometers of stream downs tream from the initial area

53of concern (footprint of use). Similar to the spray drift buffer described above, the
LAA/NLAA determination is based on the area defined by the point where concentrations exceed the LC50 value, in this case 2.40 ppb.

See Appendix F for the spatial summary of diuron used to determine the downstream
dilution.

3.3 Terrestrial Animal Exposure Assessment

T-REX (Version 1.3.1) is used to calculate dietary and dose-based EECs of diuron 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, ground spray applications of diur on are considered, as
discussed in below.

Terrestrial EECs for ground spray applicati ons of diuron were derived for the uses registered in California. Given that no da ta on interception and s ubsequent dissipation from foliar surfaces is available for diuron, a de fault foliar dissipation half-life of 35 days
is used based on the work of Willis and Mc Dowell (1987). Use specific input values, including number of applications, and application rate are shown in Table 3.3 . An example output from T-REX is available in Appendix H.

Table 3.3 T-REX Model Input Parameters

Crop Application Rate per Crop
Scenario (lbs/A) Number of Applications Application
interval (days)

Agricultural Rights-of-Way, Fencerows, Hedgerows, Airports, landing Fields, Drainage

Systems, Outdoor Industrial Areas, Irrigation

Systems, Non-Agricultural Rights of Way,Sewage Disposal Areas, Uncultivated NonAgricultural Areas 12 2 21

Alfalfa, Peppermint 2.4 1 n/a
Apple, Grape 3.2 2 90

Citrus 3.2 2 60
Artichoke, Asparagus 3.2 1 n/a

Banana, Plantain 4.8 2 42 Bermuda grass, Blackberry, Boysenberry, Spearmint 2.4 5 21

Blueberry 1.6 2 112

Field Corn 0.8 1 n/a

Cotton 1.6 3 21
Dewberry 2.4 3 60

Filbert (Hazelnut) 2.2 2 150

Grass Seed, Wheat 1.6 1 n/a

54Application

Crop Rate per Application Number of Crop interval Applications Scenario (days) (lbs/A)

Loganberry, Raspberry 2.4 1 n/a

Olive 1.6 2 168

Pecan, Pear 3.2 1 n/a
Ornamental Herbaceous Plants, Papaya 4 1 21
Uncultivated Agricultural Areas, Paved Areas 12 1 n/a

Peach 3 1 n/a
Sorghum 0.4 1 n/a

Walnut 3 2 150

T-REX is also used to calculate EECs for te rrestrial insects exposed to diuron. Dietarybased EECs calculated by T-REX for small and larg e insects (units of a.i. /g) are used to bound an estimate of exposure to bees. Available acute contact toxicity data for bees exposed to diuron (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 later compared to the adjusted acute contact toxicity data for bees in order to derive RQs.

For modeling purposes, exposures of the CRLF to diuron 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 3.4 ). Dietary-based EECs for small and large insects reported by T-REX as well as the resu lting adjusted EECs are available in Table 3.5

.

Table 3.4 Upper-bound Kenega Nomogram EE Cs for Dietary- and Dose-based Exposures of the CRLF and its Prey to Diuron

EECs for CRLF EECs for Prey (small mammals)

Use Dietarybased EEC (ppm) Dose-based EEC (mg/kg-bw) Dietarybased EEC (ppm) Dose-based EEC(mg/kgbw)Agricultural Rights-ofWay, Fencerows, Hedgerows, Airports, landing Fields, Drainage Systems, Outdoor Industrial Areas, Irrigation Systems, Non-Agricultural Rights of Way, Sewage Disposal Areas,
Uncultivated Non2688.80 3062.28 4780.09 5444.05

55EECs for CRLF EECs for Prey (small mammals)

Use Dietarybased EEC (ppm) Dose-based EEC (mg/kg-bw) Dose-basedDietarybased EEC (ppm) EEC(mg/kgbw) Agricultural Areas Alfalfa, Peppermint, 324.00 369.00 576.00 549.17 Apple, Grape 504.68 574.78 897.21 855.42 Artichoke, Asparagus 432.00 874.68 768.00 732.23 Banana, Plantain 930.06 1059.24 1653.44 1576.43 Bermuda grass, Blackberry, Boysenberry, Spearmint 833.22 948.95 1481.28 1412.29

Blueberry 239.50 272.77 425.79 405.95 Citrus, 563.65 641.94 1002.05 955.38
Field Corn 108.00 123.00 192.00 183.06
Cotton 452.53 515.38 804.49 767.02 Dewberry 452.83 515.73 805.03 767.54 Filbert (Hazelnut) 312.23 355.60 555.07 529.22 Grass Seed, Wheat 216.00 246.00 384.00 366.11 Loganberry, Raspberry 324.00 369.00 576.00 549.17
Olive 223.75 254.83 397.78 379.26
Ornamental Herbaceous plants, Papaya 540.00 615.01 960.00 915.29

Uncultivated Agricultural Areas, Paved Areas 1620.00 1845.02 2880.00 2745.86

Peach 461.25 461.25 720.00 686.46 Pear, Pecan 432.00 492.00 768.00 737.23 Sorghum 54.00 61.50 96.00 91.53
Walnut 425.76 484.9 756.92 721.66

Table 3.5 EECs (ppm) for Indirect Effect s to the Terrestrial-Phase CRLF via Effects to Terrestrial Invertebrate Prey Items

Use Small Insect Large Insect

Agricultural Rights-of-Wa y, Fencerows, Hedgerows, Airports, landing Fields, Dr ainage Systems, Outdoor Industrial Areas, Irrigation Sy stems, Non-Agricultural Rights of Way, Sewage Dis posal Areas, Uncultivated Non-Agricultural Areas 2688.80 298.76 Alfalfa, Peppermint, 324.00 36.00 Apple, Grape 504.68 56.08 Citrus, 563.65 62.63

56Use Small Insect Large Insect

Artichoke, Asparagus 432.00 48.00 Banana, Plantain 930.06 103.34 Bermuda grass, Blackberry, Boysenberry, Spearmint 833.22 92.58 Blueberry 239.50 26.61
Field Corn 108.00 12.00
Cotton 452.53 50.28 Dewberry 452.83 50.31 Filbert (Hazelnut) 312.23 34.69 Grass Seed, Wheat 216.00 24.00 Loganberry, Raspberry 324.00 36.00
Olive 223.75 24.86 Pecan, Pear 432.00 48.00 Ornamental Herbaceous plants, Papaya 540.00 60.00 Uncultivated Agricultural Areas, Paved Areas 1620.00 180.00
Peach 461.25 51.25 Sorghum 54.00 6.00
Walnut 425.76 47.31

3.4 Terrestrial Plant Ex posure Assessment

TerrPlant (version 1.2.2) is used to calculat e EECs for non-target plants inhabiting dry and semi-aquatic areas. Parameter values for application rate, drift assumption and incorporation depth are based upon the use a nd related application method. A runoff
value of 0.02 was selected based on diuron’s so lubility of between 10-100 mg/L. Drift was assumed to be 5% for aerial applica tions and 1% for ground applications.

TerrPlant was used to model EECs from soil and foliar applications relevant to terrestrial plants. These EECs are presented in Table 3.6 . An example output from TerrPlant v.1.2.2 is available in Appendix I

.

57Table 3.6 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semi-aquatic Areas Exposed to diuron via Runoff and Drift

Application

rate Spray
drift
EEC Dry

area EEC Semiaquatic

area EEC

Use (lbs a.i./A) Application
method Drift
Value

(%) (lbs a.i./A) (lbs a.i./A) (lbs a.i./A) Agricultural Rights-of-Way,

Fencerows, Hedgerows, Airports, landing Fields, Drainage Systems, Outdoor Industrial Areas, IrrigationSystems, NonAgricultural Rights of Way, Sewage Disposal Areas,
Uncultivated Non-Agricultural
Areas 12 Foliar/Ground 1 0.12 0.36 2.52

Alfalfa, Peppermint, Spearmint, Bermudagrass,

Blackberry, Boysenberry, Loganberry, Raspberry, Dewberry 2.4 Foliar/Ground 1 0.02 0.07 0.50

Apple, Citrus,

Pear, Grape,

Artichoke, Asparagus, Pecan 3.2 Foliar/Ground 1 0.03 0.10 0.67

Asparagus

(Aerial) 3.2 Foliar/Ground 5 0.16 0.22 0.80

Banana, Plantain 4.8 Foliar/Ground 1 0.05 0.14 1.01

Blueberry, Cotton, Grass Seed, Olive,
Wheat 1.6 Foliar/Ground 1 0.02 0.05 0.34

58Application

rate Spray
drift
EEC Dry

area EEC Semiaquatic

area EEC Drift Application Value
Use (lbs a.i./A) method (%) (lbs a.i./A) (lbs (lbs a.i./A) a.i./A)

Field Corn 0.8 Foliar/Ground 1 0.01 0.02 0.17

Filbert (Hazelnut) 2.2 Foliar/Ground 1 0.02 0.07 0.46

Non-agricultural 12 Aerial 5 0.60 0.84 3.00

Ornamental
Herbaceous Plants, Papaya 4 Foliar/Ground 1 0.04 0.12 0.84

Uncultivated Agricultural Areas, Paved
Areas 12 Foliar/Ground 1 0.12 0.36 2.52

Peach, Walnut 3 Foliar/Ground 1 0.03 0.09 0.63

Sorghum 0.4 Foliar/Ground 1 0.00 0.01 0.08

3.4.1 Spray Drift Buffer Analysis In order to determine terrestrial and aquatic habitats of concern due to diuron 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 spray drift distan ces was completed using AgDRIFT and can be
found in Table 3.7.

AgDRIFT was run for terrestrial analysis onl y, and due to uncertainties default values were used to determine the aquatic analysis. The default values for PRZM/EXAMS (used for the aquatic analysis) assumed the mo st conservative scenario, that a buffer was not present.

For the terrestrial assessment, the AgDRIFT model was run as a Tier I ground analysis, as well as Tier I, and II aerial analyses focusing on determining a buffer zone for nonlisted and listed plant species. The fo llowing settings beyond the standard default settings were implemented:

• 12 lb ai/A

• EC 25 = 0.002 lb ai/A

• EC 05 = 0.001 lb ai/A

• Nonvolatile Rate (Tier II aerial only) = 25 lb/a

59• Spray Volume Rate (Tier II aerial only) = 3 gal/a

• Active Rate (Tier II aerial only) = 4 lb/a

The AgDRIFT model was used to evaluate potential distances beyond which exposures would be expected to be be low LOC. However, due to the limitations imposed by the Tier 1 ground analysis, and Tier s I and II aerial analyses, wh ich allow users to evaluate off-site deposition and exposure out to 1,000 ft downwind from the location of the application, the exact buffer needed for exposur es to be below the LOC is uncertain.

Table 3.7 Summary of AgDRIFT Predic ted Spray Drift Buffer for Terrestrial
Plants

Tier I Ground Application

Risk
Class Risk Description Application
Rate Toxicity
Value
Used Fraction
of applied Nonvolatile Rate (lb/a) Minimum Spray
Volume

Rate (gal/a) Active
Rate (lb ai/a) Distance

NonListed
Plants Potential for
effects to nontarget, non-listed

plants from

exposures EC 25 = 0.002 lb

ai/A 0.0002

Listed
Plants Potential for
effects to nontarget, listed plants from

exposures 12

EC 05 = 0.001 lb

ai/A 0.0001 Does not apply Does not apply Does

not apply > 1,000
ft

Tier I Aerial Application

Risk
Class Risk Description Application
Rate Toxicity
Value
Used Fraction
of applied Nonvolatile Rate (lb/a) Minimum Spray
Volume

Rate (gal/a) Active
Rate (lb ai/a) Distance

NonListed
Plants Potential for
effects to nontarget, non-listed

plants from

exposures EC 25 = 0.002 lb

ai/A 0.0002

Listed
Plants Potential for
effects to nontarget, listed plants from

exposures 12

EC 05 = 0.001 lb

ai/A 0.0001 Does not apply Does not apply Does

not apply > 1,000
ft

Tier II Aerial Application

Risk
Class Risk Description Application
Rate Toxicity
Value
Used Fraction
of applied Nonvolatile Rate (lb/a) Minimum Spray
Volume

Rate (gal/a) Active
Rate (lb ai/a) Distance

NonListed
Plants Potential for
effects to nontarget, non-listed

plants from

exposures EC 25 = 0.002 lb

ai/A 0.0002

Listed
Plants Potential for
effects to nontarget, listed plants from

exposures 12

EC 05 = 0.001 lb

ai/A 0.0001 25 3 4 > 1,000
ft

604.0 Effects Assessment

This assessment evaluates the potential for diuron to directly or indirectly affect the CRLF or modify its designated critical habitat. As previously disc ussed 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 modification of its habitat. In addition, potential
modification of critical habitat is assessed by evaluating effects to the PCEs, which are components of the critical habitat areas that provide essential 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 e ffects are based on avian toxicity data, given that birds are generally used as a surrogate for terrestrial-phase am phibians. Because the frog’s prey items and habitat requirements are dependent on the availability of freshwater fish and invertebrates, small mammals, te rrestrial invertebrates, and aquatic and terrestrial plants, toxicity information for these taxa are also di scussed. Acute (shortterm) and chronic (long-term) toxicity inform ation is characterized based on registrantsubmitted studies and a comprehensive revi ew of the open literature on diuron.

As described in the Agency’s Overview Document (U.S. EPA, 2004), the most sensitive endpoint for each taxon is used for risk estimation. For this assessment, evaluated taxa include aquatic-phase amphibians, freshwater fish, freshwater 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 l iterature data presented in this assessment
were obtained from as well as ECOTOX inform ation obtained on [11/30/2007]. In order to be included in the ECOTOX database, papers must meet th e following minimum
criteria:

(1) the toxic effects are related to single chemical exposure; (2) the toxic effects are on an aquatic or terrestrial plant or animal species; (3) there is a biological effect on live, whole organisms; (4) a concurrent environmental chemical concentration/dose or application rate is reported; and (5) there is an explicit duration of exposure.

Data that pass the ECOTOX screen are 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 the registrant-submitted data are considered. The degree to which open literature data are quantitatively or qualitatively characterized for the effects determination is dependent on
whether the information is releva nt to the assessment endpoints ( i.e. , maintenance of CRLF survival, reproduction, and growth) identified in Section 2.8. For example,

61endpoints 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 diuron.

Citations of all open literature not considered as part of this assessment because they were either rejected by the ECOTOX screen or accepted by ECOTOX but not used (e.g., the endpoint is less sensitive) are included in Appendix J. This section also includes a rationale for rejection of t hose studies that did not pass the ECOTOX screen and those that were not evaluated as part of th is endangered species risk assessment.

A detailed spreadsheet of the available EC OTOX open literature data, including the full suite of lethal and sublethal endpoints is presented in Appendix J. This section also includes a summary of the human health effects data for diuron.

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 diuron. A summary of the av ailable aquatic and terrestrial ecotoxicity inform ation, use of the probit dose response relationship, and the incident information for diuron are provide d in Sections 4.1 through 4.4, respectively.

The terminal residues of concern in plan ts and animals are diuron (parent) and metabolites convertible to 3, 4-DCA including desmethoxy-linuron, norlinuron, desmethyl diuron, and hydroxy-norlinuron. The Agency determined that 3, 4-DCA was not of regulatory concern in connection with th e registered use of diuron due to the very
low levels at which the chemical is dete cted in plants and animals (<0.01ppm). The Agency concluded that with the possibl e exception of 3,4-DCA itself, metabolites convertible to 3,4-DCA are not likely to be more toxic than the parent compound. This
risk assessment considers the to tal residues of diuron as parent diuron for purposes of risk

assessment

A detailed summary of the available ecotoxicity information for all di uron degradates and formulated products are pr esented in Appendix L.

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 ta nk. 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

62are available for a formulated product contai ning more than one active ingredient, they may be used qualitatively or quantitatively 5 6

.
There are no product LD 50 values, with associated 95% Confidence Intervals (CIs)
available for diuron.

As discussed in USEPA (2000) a quantitati ve component-based evaluation of mixture toxicity requires data of appr opriate quality for each compon ent of a mixture. In this mixture evaluation, an LD 50 with associated 95% CI is needed for the formulated product. The same quality of data is also re quired for each component of the mixture. Given that the formulated produc ts for diuron do not have LD 50 data available it is not possible to undertake a quantitati ve or qualitative analysis for pot ential interactive effects. However, because the active ingredients are no t expected to have similar mechanisms of action, metabolites, or toxicoki netic behavior, it is reasona ble to conclude that an assumption of dose-addition would be inappropriate.

4.1 Toxicity of Diuron to Aquatic Organisms

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 L.

Table 4.1 Freshwater Aquatic Toxicity Profile for Diuron

Assessment Endpoint Species Toxicity Value
Used in Risk
Assessment Citation MRID # or ECOTOX # Comment

Acute Direct Toxicity to Aquatic-Phase
CRLF Striped Bass ( Morone
saxatili s) 96h LC 50 = 400 ppb ECOTOX
102151 Supplemental 1

Chronic Direct Toxicity to Aquatic-Phase
CRLF Fathead
Minnows ( Pimephales promelas ) NOAEC = 26 ppb
ai MRID
00141636 Acceptable (Based on No. of Survivors)

Indirect Toxicity to Aquatic-Phase Scud ( Gammmarus fasciatus ) 48h EC 50 = 160 ppb
ai MRID
40094602 Acceptable

5 Overview of the Ecological Risk Assessment Proces s in the Office of Pesticid e Programs, Environmental Protection Agency (January 2004) (Overview Document).

6 Memorandum to Office of Preventio n, Pesticides and Toxic Substance, US EPA conveying an evaluation by the U.S. Fish and Wildlife Service and National Mari ne Fisheries Service of an approach to assessing the ecological risks of pesticide products (January 2004).

63Table 4.1 Freshwater Aquatic Toxicity Profile for Diuron

Assessment Endpoint Species Toxicity Value
Used in Risk
Assessment Citation Comment MRID # or ECOTOX #
CRLF via Acute Toxicity
to Freshwater
Invertebrates (i.e. prey items)
Indirect Toxicity to Aquatic-Phase
CRLF via
Chronic Toxicity to
Freshwater
Invertebrates (i.e. prey items) Water Flea ( Daphnia

magna ) 28d NOAEC = 200 ppb ai MRID
TN2418 Supplemental 1

Indirect Toxicity to Aquatic-Phase
CRLF via Acute Toxicity
to Non-vascular Aquatic Plants Green Algae ( Selenastrum capricornutu

m ) EC 50 = 2.40 ppb ai MRID
42218401 Acceptable

Indirect Toxicity to Aquatic-Phase
CRLF via Acute Toxicity
to Vascular Aquatic Plants Duckweed ( Lemna perpusilla ) 7d EC 50 = 15 ppb ECOTOX
8628 Supplemental 1

1 This study is considered to be supplemental due to lack of raw data and replicates.

Toxicity to aquatic fish a nd invertebrates is categorized using the system shown in Table
4.2 (U.S. EPA, 2004). Diuron falls in the rang e of “highly toxic” ( 0.1 to 1 ppm or 100 to 1000 ppb for fish and invertebrates. Toxicity categories for a quatic plants have not been
defined.

Table 4.2 Categories of Acute Toxicity for Aquatic Organisms

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

644.1.1 Toxicity to Freshwater Fish

Given that no diuron toxicity data are availa ble for aquatic-phase amphibians; freshwater fish data were used as a surrogate to estimat e direct acute and chronic risks to the CRLF. Freshwater fish toxicity data were also used to assess potenti al indirect effects of diuron
to the CRLF. Effects to freshwater fish resulting from exposure to diuron could indirectly affect the CRLF via reduction in available food. As discussed in Section 2.5.3, over 50% of the prey mass of the CRLF may c onsist of vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).

Diuron is highly toxic to both warm water a nd cold water freshwater fish on an acute exposure basis. The most sensitive freshwater species tested was the warm water Striped Bass species, which exhibited a 96-hour LC 50 value of 400 ppb (ECOTOX 102151). Another acute study accepted by the Agency showed the co ld water Cutthroat Trout having an acute 96h LC 50 of 710 ppb ai (MRID 40098001). The Fathead Minnow exhibited a chronic toxicity NOAEC of 26 ppb based on number of survivors (MRID 00141636).

4.1.2 Toxicity to Freshwater Invertebrates

Freshwater aquatic invertebrate toxicity data were used to as sess potential indirect effects
of diuron to the CRLF. Effects to freshwat er invertebrates resulting from exposure to diuron could indirectly affect the CRLF vi a reduction in available food items. As discussed in Section 2.5.3, the main food s ource 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.

Diuron is highly acutely toxic to freshwater invertebrates based on acceptable studies on the Scud. This species exhibited a 48-hour EC 50 value of 160 ppb (MRID: 40094602). Chronic toxicity studies showed the Wate r Flea as exhibiting a 28d NOAEC of 200 ppb (MRID: TN2418).

4.1.3 Toxicity to Aquatic Plants

Aquatic plant toxicity studies were used as one of the measures of effect to evaluate whether diuron may affect primary production an d 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.

Two types of studies were used to evaluate the potential of diuron to a ffect aquatic plants. Laboratory and field studies were used to determine whether diuron may cause direct effects to aquatic plants. A summary of the laboratory data and freshwater field studies for aquatic plants is provided in Sections 4.1.3.1 and 4.1.4.

The Green Alga Selenastrum capricornutum exhibited the most sensitive non-vascular plant acute endpoint with an EC 50 of 2.40 ppb. The aquatic vascular plant Lemna

65perpusilla exhibited the most sensitive vasc ular acute endpoint with a 7d EC 50 of 15 ppb ai (ECOTOX 8628).

4.2 Toxicity of Diuron to Terrestrial Organisms

Table 4.3 summarizes the most sensitive terrestr ial 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.

Table 4.3 Terrestrial Toxici ty Profile for Diuron

Endpoint Species Toxicity Value Used in
Risk Assessment Citation
MRID# Comment

Acute Direct Toxicity to
TerrestrialPhase CRLF (LD 50 ) Mallard Duck
( Anas platyrhynchos ) 14d LD 50 = >2000 mg/kg-bw MRID
00160000 Acceptable
No mortality reported. Ataxia persisted for 11d after study

Acute Direct Toxicity to
TerrestrialPhase CRLF (LC 50 ) Northern Bobwhite Quail
( Colinus virgianus ) 9d LC 50 = 1730 ppm ai MRID
00022923 Acceptable

Chronic
Direct Toxicity to
TerrestrialPhase CRLF No Acceptable Study Available -- -- --

Indirect Toxicity to
TerrestrialPhase CRLF (via acute toxicity to
mammalian prey items) Laboratory Rat ( Rattus norvegicus ) LD 50 = ♂ 5000 mg/kg-bw ♀ 10000 mg/kg-bw MRID
00146145 Acceptable

Indirect Toxicity to
TerrestrialPhase CRLF (via chronic toxicity to
mammalian prey items) Laboratory Rat ( Rattus norvegicus ) NOAEC = 250 ppm MRID
00146145 Acceptable

Indirect Toxicity to
TerrestrialPhase CRLF (via acute toxicity to
terrestrial
invertebrate prey items) Honey Bee
( Apis mellifera ) LD 50 >145 μg/bee (1133.05 ppm) MRID
00036935 Acceptable

(Only 2.7% mortality observed at highest level tested)

Indirect Dicot Seedling EC 25 = 0.075 lb ai/A MRID Acceptable

66Endpoint Species Toxicity Value Used in
Risk Assessment Citation Comment
MRID# Emergence
Tomato ( Lycopersicon
esculentum ) 44113401

Dicot Vegetative Vigor Tomato ( Lycopersicon
esculentum ) EC 25 = 0.002 lb ai/A MRID
44113401 Acceptable

Monocot Seedling Emergence
Onion ( Allium cepa ) EC 25 = 0.099 lb ai/A MRID

44113401 Acceptable Toxicity to
Terrestrialand AquaticPhase CRLF (via toxicity
to terrestrial plants)

Monocot Vegetative Vigor
Wheat ( Triticum
aestivum ) EC 25 = 0.021 lb ai/A MRID

44113401 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 to xicity data are not available (U.S. EPA, 2004). No terrestrial-phase amphibian data ar e available for diuron; therefore, acute and chronic avian toxicity data ar e used to assess the potential direct effects of diuron to terrestrial-phase CRLFs.

There are no data by which to assess chronic toxicity to avia n species (surrogates for the terrestrial phase frog) either submitted by the registrants or in the public literature. Linuron, a similar chemical of the same cla ss, has acceptable chronic avian data. The avian reproductive studies for linur on (MRID 42541801, 42541802) using mallard duck and bobwhite quail found reproductive eff ects at 300 ppm ai with an NOAEL being established at 100 ppm. The endpoints affect ed for mallard duck reproduction are egg production, adult body weight, feed consumption, viable embryos of eggs set, number of viable embryos, and number of live embryos . For the bobwhite quail the endpoints

67affected are hatchability and offspring surviv ability. This suggests that diuron may have chronic effects to avian species, but these ri sks cannot be quantified in the absence of
data. 4.2.2 Toxicity to Mammals

Mammalian toxicity data are used to assess potential indirect eff ects of diuron to the terrestrial-phase CRLF. Effects to small mammals resulting from exposure to diuron could also indirectly affect the CRLF via re duction in available f ood. As discussed in Section 2.5.3, over 50% of the pr ey mass of the CRLF may consist of vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).

An acute oral LD 50 of 5000 mg/kg-bw was observed in the Laboratory Rat (MRID 00146145). The Laboratory Rat NOAEC is 250 ppm (MRID 00146145).

4.2.3 Toxicity to Terrestrial Invertebrates

Terrestrial invertebrate toxicity data are used to assess potenti al indirect effects of diuron to the terrestrial-phase CRLF. Effects to te rrestrial invertebrates resulting from exposure to diuron could also indirectly affect the CRLF via reduction in available food. Diuron is classified as practically non-toxi c to the Honey Bee. The acute LD 50 for Honey Bee is >145.03 μg/bee (MRID 00036935). Only 2.7% mort ality was observed in this study at the highest level tested. The test was th erefore not definitive and RQs were not calculated. There were no additional acceptabl e terrestrial invertebrate data from registrant submitted studies or from the open literature by which to calculate RQ values.

4.2.4 Toxicity to Terrestrial Plants

Terrestrial plant toxicity data are used to evaluate the potential for diuron to affect riparian zone and upland vegetation within the action area for the CRLF. Impacts to riparian and upland (i.e., gra ssland, woodland) vegetation coul d result in indirect effects to both aquatic- and terrestri al-phase CRLFs, as well as modification to designated
critical habitat PCEs via increased sedi mentation, alteration in water quality, and reduction in of upland and riparian habitat that provides shelter, foraging, predator avoidance and dispersal for j uvenile 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.

68Commercial 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 diuron, is largely unknow n. 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 endpoints reported for diuron exposure to dicot plants are a vegetative vigor EC 25 value of 0.002 lb ai/A and a seedling emergence EC 25 value of 0.075 lb ai/A as expressed by tomato plants (MRID 44113401). The most sensitive endpoints reported for diuron exposure to monocot pl ants are a vegetative vigor EC 25 value of 0.021 lb ai/A as expressed by Wheat, and a seedling emergence EC 25 value of 0.099 lb ai/A as expressed by Onion (MRID 44113401). The results of the Tier II seedling emergence and vegetative vigor toxic ity tests on non-target plants are summarized below in Table
4.5

.

Table 4.5 Terrestrial Plant T oxicity Profile for Diuron

Endpoint Species Toxicity Value Used
in Risk Assessment Citation
MRID# Comment

Dicot Seedling Emergence
Tomato ( Lycopersicon
esculentum ) EC 25 = 0.075 lb ai/A MRID
44113401 Acceptable

Dicot Vegetative Vigor Tomato ( Lycopersicon
esculentum ) EC 25 = 0.002 lb ai/A MRID
44113401 Acceptable

Monocot Seedling Emergence
Onion ( Allium cepa ) EC 25 = 0.099 lb ai/A MRID

44113401 Acceptable Indirect Toxicity to
Terrestrialand AquaticPhase CRLF (via toxicity
to terrestrial plants)

Monocot Vegetative Vigor
Wheat ( Triticum
aestivum ) EC 25 = 0.021 lb ai/A MRID

44113401 Acceptable

4.3 Use of Probit Slope Response Relati onship 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 the 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 diuron on par with the acute toxicity endpoint selected for RQ calculation. To accomplish this interpretati on, the Agency uses the slope of the dose

69response 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 ecologi cal incidents involving diuron was completed on 12/18/08. Thirty highly probable, proba ble or possible incide nts involving diuron have been reported. These uses were either re gistered uses or undetermined uses. One of these incidents resulted in a bird kill, 22 resu lted in plant damage and seven resulted in fish kills. A detailed description of incidents relating to diuron use is presented in Appendix M. These incidents will be used in addition to other lines of evidence to draw conclusions regarding the ri sks of diuron to the CRLF.

The absence of additional documented incidents does not necessarily mean that such incidents did not occur. Mortality incidents must be seen, reported, investigated, and submitted to the Agency in order to be record ed in the incident database. Incidents may not be noticed because the carcasses decayed, were removed by scavengers, or were in out-of-the-way or hard-to-see locations. Due to the voluntary nature of incident reporting, an incident may not be reported to appropria te authorities capable of investigating it.

5.0 Risk Characterization

Risk characterization is the integration of the exposure and effects characterizations.
Risk characterization is used to determine the potential for direct and/or indirect effects to the CRLF or for modification to its designated critical habitat from the use of diuron in CA. The risk characterization provides an estimation (Section 5.1) and a description (Section 5.2) of the likel ihood of adverse effects; articula tes 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

70concern (LOCs) for each category evaluated (A ppendix E). 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 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 diuron usage scenarios summarized in Table 3.2 and the appropriate aquatic toxicity endpoi nt from Table 4.1. Risks to the terrestrial-phase CRLF and its prey ( e.g . terrestrial insects, small mammals and terrestrial-phase frogs) ar e estimated based on exposures resulting from applications of diuron (Tables 3.5 through 3.6) and the appr opriate toxicity endpoint from Table 4.6. Exposures are also derived for terrestrial plants, as discussed in Section 3.3 and summarized in Table 3.7, based on the highest application rates of diuron use within the
action area.

5.1.1 Exposures in the Aquatic Habitat

5.1.1.1 Direct Effects to Aquatic-Phase CRLF

Direct effects to the aquatic -phase CRLF are based on peak EECs in the standard pond and the lowest acute toxicity value for freshwat er fish. In order to assess direct chronic risks to the CRLF, 60-day EECs and the lowest chronic toxicity value for freshwater fish are used. The RQs for diuron uses results in acute and chronic exceedances of the Agency’s LOC for freshwater fish which are surrogates for the aquatic phase for amphibians.

The aquatic phase amphibian acute LOCs for lis ted species (0.05) are exceeded for most uses of diuron in California. Acute RQs that exceed the Agency’s LOC range from 12.28 (paved areas) to 0.06 (papaya and walnut). Chronic RQs that exceed the Agency’s LOC for chronic exposure (1.0) range from 131.85 (pav ed areas) to 1.26 (banana, plantain). A probit slope value for the acute fathead minnow t oxicity test is not available; therefore, the individual effect probability was estimat ed 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). The estimated probability of an individual effect for treatments that exceeded the Agency’s acute RQs for listed species ranged from a pproximately 1 in 1 for paved areas to approximately 1 in 1.64 E+4 for banana/p lantain (upper and lower 95% confidence
intervals of 1 in 2.28 E+ 01 to 1 in 1.29 E+14). Based on these exceedances, diuron May Affect the aquatic-phase of the CRLF. Results are presented in Table 5.1.

71Table 5.1. Summary of Direct Effect RQs for the Aquatic-phase CRLF

Use Direct
Effects

to CRLF a Surrogate Species Toxicity
Value ( μ g/L) EEC
Peak/60d ( μ g/L) RQ Probability
of Individual
Effect* LOC
Exceedance
and Risk Interpretation

Acute
Direct Toxicity Striped
Bass LC 50 = 400 687.59 1.72 1 in 1.17 (1
in 1.47 to 1 in 1.07) b Yes c AGRICULTURAL
RIGHTS-OFWAY/FENCEROWS/
HEDGEROWS Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 456.81 17.57 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 10.63 0.03 1 in 2.75E+11 (1
in 1.00 E+16
to 1 in 8.63 E+02) b No ALFALFA

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 7.20 0.28 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 13.69 0.03 1 in 2.75E+11 (1
in 1.00 E+16
to 1 in 8.63 E+02) b No ALFALFA(Aerial)

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 9.40 0.36 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 11.68 0.03 1 in 2.75E+11 (1
in 1.00 E+16
to 1 in 8.63 E+02) b No APPLE

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 7.80 0.30 Not applicable for chronic endpoints No

ARTICHOKE Acute
Direct Toxicity Striped
Bass LC 50 = 400 32.00 0.08 1 in 2.51E+06 (1
in 1.00 E+16
to 1 in 7.08 E+1) b Yes c

72Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 25.08 0.96 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 36.99 0.09 1 in 7.90 E+05 (1 in
1.00 E+16 to
1 in 1.00 E+06) b Yes c ASPARGUS

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 22.92 0.88 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 54.21 0.14 1 in 1.64 E+4 (1 in
2.28 E+01 to
1 in 1.29 E+14) b Yes c BANANA,
PLANTAIN

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 32.78 1.26 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 139.70 0.35 1 in 4.98E+01 (1
in 5.53 to 1
in 4.91 E+4) b Yes c BLACKBERRY,
BOYSENBERRY

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 102.90 3.96 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 4.65 0.01 <1 in 1.00E+16 (1
in 3.16 E+04
to <1 in 1.00E+16) b No BLUEBERRY

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 3.21 0.12 Not applicable for chronic endpoints No

CITRUS Acute
Direct LC 50 = 400 6.83 0.02 1 in 9.48 E+13 (1 in No

73Toxicity 2.95 E+3 to
<1 in 1.00 E+16) b

Chronic
Direct Toxicity Rainbow
Trout NOAEC =
26 4.88 0.19 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 7.24 0.02 1 in 9.48 E+13 (1 in
2.95 E+3 to
<1 in 1.00 E+16) b No CORN, FIELD

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 4.68 0.18 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 19.71 0.05 1 in 4.17 E+08 (1 in
2.16 E+02
to <1 in 1.00 E+16) b No DEWBERRY

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 14.29 0.55 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 18.90 0.05 1 in 4.17 E+08 (1 in
2.16 E+02
to <1 in 1.00 E+16) b No FILBERT (HAZELNUT)

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 12.16 0.47 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 9.71 0.02 1 in 9.48 E+13 (1 in
2.95 E+3 to
<1 in 1.00 E+16) b No GRAPE

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 6.37 0.24 Not applicable for chronic endpoints No

LOGANBERRY,
RASPBERRY Acute
Direct Striped
Bass LC 50 = 400 5.13 0.01 <1 in 1.00E+16 (1 No

74Toxicity in 3.16 E+04
to <1 in 1.00E+16) b (BLACK/RED)

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 3.02 0.12 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 7.17 0.02 1 in 9.48 E+13 (1 in
2.95 E+3 to
<1 in 1.00 E+16) b No OLIVE

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 4.86 0.19 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 25.21 0.06 1 in 5.20 E+07 (1 in
1.38 E+02 to
<1 in 1.00 E+16) b Yes c PAPAYA

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 15.72 0.60 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 4.17 0.01 <1 in 1.00E+16 (1
in 3.16 E+04
to <1 in 1.00E+16) b No PEPPERMINT

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 2.79 0.11 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 10.95 0.03 1 in 2.75E+11 (1
in 1.00 E+16
to 1 in 8.63 E+02) b No PEACH

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 7.31 0.28 Not applicable for chronic endpoints No

PEAR Acute
Direct Toxicity Striped
Bass LC 50 = 400 11.66 0.03 1 in 2.75E+11 (1
in 1.00 E+16
to 1 in 8.63 E+02) b No

75Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 7.79 0.30 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 27.04 0.07 1 in 9.86 E+06 (1 in
9.57 E+1 to
<1 in 1.00 E+16) b Yes c PECAN

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 17.33 0.67 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 5.87 0.01 <1 in 1.00E+16 (1
in 3.16 E+04
to <1 in 1.00E+16) b No SORGHUM

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 4.52 0.17 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 106.70 0.27 1 in 1.90E+02 (1
in 7.83 to 1
in 6.46 E+06) b Yes c SPEARMINT

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 81.95 3.15 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 25.78 0.06 1 in 5.20 E+07 (1 in
1.38 E+02 to
<1 in 1.00 E+16) b Yes c WALNUT (ENGLISH/BLACK)

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 16.58 0.64 Not applicable for chronic endpoints No

WHEAT (preharvest) Acute
Direct Toxicity Striped
Bass LC 50 = 400 18.03 0.05 1 in 4.17 E+08 (1 in
2.16 E+02
to <1 in 1.00 E+16) b No

76Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 12.02 0.46 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 12.82 0.03 1 in 2.75E+11 (1
in 1.00 E+16
to 1 in 8.63 E+02) b No WHEAT (post- harvest)

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 10.29 0.40 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 8.36 0.02 1 in 9.48 E+13 (1 in
2.95 E+3 to
<1 in 1.00 E+16) b No COTTON (ground)

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 5.72 0.22 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 14.25 0.04 1 in 6.30 E+09 (1 in
3.86 E+02 to
<1 in 1.00 E+16) b No COTTON(aerial)

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 10.24 0.39 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 2190.00 5.48 ~1 in 1 b Yes c AIRPORTS/ LANDING FIELDS,
DRAINAGE SYSTEMS,
INDUSTRIAL
AREAS (OUTDOOR),
SEWAGE
DISPOSAL AREAS Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 1382.00 53.15 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 226.00 0.57 1 in 7.35 (1
in 3.20 to 1
in 7.14 E+01) b Yes c BERMUDAGRASS

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 167.90 6.46 Not applicable for chronic endpoints Yes d

77Acute
Direct Toxicity Striped
Bass LC 50 = 400 3.76 0.01 <1 in 1.00E+16 (1
in 3.16 E+04
to <1 in 1.00E+16) b No GRASSES GROWN
FOR SEED

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 2.89 0.11 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 52.56 0.13 1 in 2.99E+04 (1
in 2.62 E+01
to 1 in 1.29 E+15) b Yes c IRRIGATION
SYSTEMS

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 37.45 1.44 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 36.55 0.09 1 in 7.90 E+05 (1 in
5.48 E+01 to
<1 in 1.00 E+16) b Yes c ORNAMENTAL
HERBACEOUS
PLANTS

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 23.56 0.91 Not applicable for chronic endpoints No

Acute
Direct Toxicity Striped
Bass LC 50 = 400 629.91 1.57 1 in 1.23. (1
in 1.53 to 1 in 1.04) b Yes cNONAGRICULTURAL
RIGHTS OF WAY (ground) Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 476.35 18.32 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 626.91 1.57 1 in 1.23. (1
in 1.53 to 1 in 1.04) b Yes cNONAGRICULTURAL
RIGHTS OF WAY (aerial) Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 468.16 18.01 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 4911.00 12.28 ~1 in 1 b Yes c PAVED AREAS

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 3428.00 131.85 Not applicable for chronic endpoints Yes d

78Acute
Direct Toxicity Striped
Bass LC 50 = 400 1130.00 2.83 ~1 in 1 b Yes c UNCULTIVATED
AG

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 840.40 32.32 Not applicable for chronic endpoints Yes d

Acute
Direct Toxicity Striped
Bass LC 50 = 400 284.80 0.71 1 in 3.97 (1
in 2.61 to 1
in 1.11 E+01) b Yes c UNCULTIVATED
NON-AG

Chronic
Direct Toxicity Fathead
Minnow NOAEC =
26 202.50 7.79 Not applicable for chronic endpoints Yes d

a RQs associated with acute and chronic direct toxicity to the CRLF are also used to assess potential indirect effects to the CRLF based on a reduction in freshwater fish and frogs as food items.

b A probit slope value for the acute fathead minnow toxicity test is not available; th erefore, the effect probability was calcul ated based on a default slope assumption of 4.5 with upper and lowe r 95% confidence intervals of 2 and 9 (Urban and Cook, 1986).

c RQ > acute endangered species LOC of 0.05.

d RQ > chronic LOC of 1.0.

5.1.1.2 Indirect Effects to Aquatic-Pha se CRLF via Reduction in Prey (non-vascular aquatic plants, aquatic invertebrates, fish, and frogs)

Non-vascular Aquatic Plants

Indirect effects of diuron to the aquatic-phase CRLF (tadpoles) via reduction in nonvascular aquatic plants in its diet are ba sed on peak EECs from the standard pond and the lowest acute toxicity value fo r aquatic non-vascular plants. The Agency’s LOC (1.0) is
exceeded for all current uses of diuron in California. The RQs range from 2046.25 (paved areas) to 1.57 (grasses grown for seed). Results are presented in Table 5.2

. Based on these exceedances, diuron May Affect the CRLF via reduction of nonvascular plants.

79Table 5.2 Summary of Acute RQs Used to Es timate Indirect Effe cts to the CRLF via Effects to Non-Vascular Aquatic Plants (diet of CRLF in tadpole life stage and habitat of aquatic-phase CRLF)*

Uses Application rate (lb ai/A) Application
Method Peak EEC (μg/L) Indirect effects RQ* (food and habitat)

AGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 12 Ground 687.59 286.50

2.4 Ground 10.63 4.43 ALFALFA
2.4 Aircraft 13.69 5.71

APPLE 3.2 Ground 11.68 4.87

ARTICHOKE 3.2 Ground 32.00 13.33

ASPARGUS 4.8 Ground 36.99 15.41

BANANA, PLANTAIN 2.4 Ground 54.21 22.59

BLACKBERRY, BOYSENBERRY 1.6 Ground 139.70 58.21

BLUEBERRY 2.4 Ground 4.65 1.94

CITRUS 3.2 Ground 6.83 2.85

CORN, FIELD 0.8 Ground 7.24 3.02

DEWBERRY 2.4 Ground 19.71 8.21

FILBERT (HAZELNUT) 2.2 Ground 18.90 7.87

80Peak Indirect effects RQ* Application Application Uses rate (lb ai/A) Method EEC (food and habitat) (μg/L)

GRAPE 3.2 Ground 9.71 4.04

LOGANBERRY, RASPBERRY (BLACK/RED) 2.4 Ground 5.13 2.14

OLIVE 1.6 Ground 7.17 2.99

PAPAYA 4 Ground 25.21 10.50

PEPPERMINT 2.4 Ground 4.17 1.74

PEACH 3 Ground 10.95 4.56

PEAR 3.2 Ground 11.66 4.86

PECAN 3.2 Ground 27.04 11.27

SORGHUM 4.8 Ground 5.87 2.45

SPEARMINT 2.4 Ground 106.70 44.46

WALNUT (ENGLISH/BLACK) 0.4 Ground 25.78 10.74

2.4 Pre-Harvest 18.03 7.51
WHEAT

3 PostHarvest 12.82 5.34

Ground 8.36 3.48
COTTON 1.6 Aircraft 14.25 5.94

81Peak Indirect effects RQ* Application Application Uses rate (lb ai/A) Method EEC (food and habitat) (μg/L)

AIRPORTS/ LANDING FIELDS, DRAINAGE SYSTEMS,
INDUSTRIAL AREAS (OUTDOOR), SEWAGE DISPOSAL
AREAS 12 Ground 2190.00 912.50

BERMUDAGRASS 2.4 Ground 226.00 94.17

GRASSES GROWN FOR SEED 12 Ground 3.76 1.57

IRRIGATION SYSTEMS 1.6 Ground 52.56 21.90

ORNAMENTAL HERBACEOUS
PLANTS 12 Ground 36.55 15.23

12 Ground 629.91 262.46 NON-AGRICULTURAL RIGHTS
OF WAY 4 Aircraft 626.91 261.21

PAVED AREAS (PRIVATE

ROADS/SIDEWALKS) 12 Ground 4911.00 2046.25

12 Ground 1130.00 470.83
UNCULTIVATED AG

12 Ground 1169.00 487.08

UNCULTIVATED NON-AG 12 Ground 284.80 118.67

82Peak Indirect effects RQ* Application Application Uses rate (lb ai/A) Method EEC (food and habitat) (μg/L)

* LOC exceedances (RQ > 1.0) are bolded and shaded. RQ = use-specific peak EEC/ [ Selenastrum capricornutum
EC 50 = 2.40 ppb].

Aquatic Invertebrates

Indirect acute effects to the aquatic-phase CRLF via effects to prey (invertebrates) in aquatic habitats are based on peak EECs in the standard pond and the lowest acute toxicity value for freshwater invertebrates. For chronic risk s, 21-day EECs and the lowest chronic toxicity value for invertebrates are used to derive RQs. The Agency’s acute Listed LOC (0.05) is exceeded for most uses of diuron in California. The acute RQs that exceed the LOC range from 30.69 (Paved Ar eas) to 0.06 (grape). The chronic RQs exceed the Agency’s LOC for several used. Th e chronic values that exceeded range from 21.21 (Paved Areas) to 1.02 (Bermudagrass). A summary of the acute and chronic RQ values for exposure to aquatic invertebrates (as prey items of aquatic-phase CRLFs) is provided in Table 5.3. Based on acute Listed LOC exceedances for chronic and acute aquatic invertebrates from most use sites, diuron May Affect the CRLF indirectly via reduction in freshwater invertebrate prey items.

Table 5.3 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to the CRLF via Direct Effects on Aquatic Inve rtebrates as Dietary Food Items (prey of CRLF juveniles and adults in aquatic habitats)*

Uses Application rate (lb

ai/A) Application
Method Peak
EEC (μg/L) 21 Day
EEC ppb Indirect
Effects
Acute RQ* Indirect
Effects
Chronic

RQ**

AGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 12 Ground 687.59 672.03 4.30 2.92

2.4 Ground 10.63 10.37 0.07 0.05 ALFALFA 2.4 Aircraft 13.69 13.29 0.09 0.06

83APPLE 3.2 Ground 11.68 11.22 0.07 0.05

ARTICHOKE 3.2 Ground 32.00 31.15 0.20 0.14

ASPARGUS 4.8 Ground 36.99 35.46 0.23 0.15

BANANA, PLANTAIN 2.4 Ground 54.21 51.95 0.34 0.22

BLACKBERRY, BOYSENBERRY 1.6 Ground 139.70 135.80 0.87 0.60

BLUEBERRY 2.4 Ground 4.65 4.48 0.03 0.02

CITRUS 3.2 Ground 6.83 6.57 0.04 0.03

CORN, FIELD 0.8 Ground 7.24 6.95 0.05 0.03

DEWBERRY 2.4 Ground 19.71 19.25 0.12 0.08

FILBERT (HAZELNUT) 2.2 Ground 18.90 18.41 0.12 0.08

GRAPE 3.2 Ground 9.71 9.32 0.06 0.04

LOGANBERRY, RASPBERRY (BLACK/RED) 2.4 Ground 5.13 4.95 0.03 0.02

OLIVE 1.6 Ground 7.17 6.90 0.04 0.03

PAPAYA 4 Ground 25.21 24.56 0.16 0.11

PEPPERMINT 2.4 Ground 4.17 4.05 0.03 0.02

PEACH 3 Ground 10.95 10.51 0.07 0.05

PEAR 3.2 Ground 11.66 11.20 0.07 0.05

PECAN 3.2 Ground 27.04 26.33 0.17 0.11

SORGHUM 4.8 Ground 5.87 5.67 0.04 0.03

SPEARMINT 2.4 Ground 106.70 103.70 0.67 0.49

84WALNUT (ENGLISH/BLACK) 0.4 Ground 25.78 25.11 0.16 0.11

2.4 Pre-Harvest 18.03 17.34 0.11 0.07
WHEAT

3 PostHarvest 12.82 12.34 0.08 0.06

Ground 8.36 8.13 0.05 0.04
COTTON 1.6

Aircraft 14.25 13.88 0.09 0.06

AIRPORTS/ LANDING FIELDS, DRAINAGE SYSTEMS,
INDUSTRIAL AREAS (OUTDOOR), SEWAGE DISPOSAL
AREAS 12 Ground 2190.00 2115.00 13.69 9.13

BERMUDAGRASS 2.4 Ground 226.00 218.80 1.41 1.02

GRASSES GROWN FOR SEED 12 Ground 3.76 3.62 0.02 0.02

IRRIGATION SYSTEMS 1.6 Ground 52.56 50.67 0.33 0.23

ORNAMENTAL HERBACEOUS
PLANTS 12 Ground 36.55 35.45 0.23 0.15

12 Ground 629.91 619.12 3.94 2.80 NON-AGRICULTURAL RIGHTS
OF WAY 4 Aircraft 626.91 615.83 3.92 2.76

PAVED AREAS (PRIVATE

ROADS/SIDEWALKS) 12 Ground 4911.00 4725.00 30.69 21.21

12 Ground 1130.00 1099.00 7.06 5.12

UNCULTIVATED AG

12 Ground 1169.00 1130.00 7.31 5.31

UNCULTIVATED NON-AG 12 Ground 284.80 275.70 1.78 1.26

85* LOC exceedances (acute RQ > 0.05, chronic RQ > 1.0) are bolded and shaded. RQ = use-specific peak EEC/ [ Selenastrum capricornutum EC 50 = 2.40 ppb].

Fish and Frogs

Fish and frogs also represent potential prey items of adult aquatic-phase CRLFs. RQs
associated with acute and chronic direct to xicity to the CRLF (Table 5.1) are used to assess potential indirect effects to the CRLF based on a reduction in freshwater fish and frogs as food items. Based on chronic and acute LOC exceedances, diuron May Affect the CRLF indirectly vi a reduction in freshwater fish and frogs as food items.

5.1.1.3 Indirect Effects to CRLF via Reduction in Habitat and 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. A summary of acute RQs used to estimate indirect effects to the CRL F via effects to vascular aquatic plants is presented in Table 5.4. The RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses of diuron in California . These range from 327.40 (paved areas) to 1.26 (Filbert/Hazelnut). Because of this, and in addition to the LOC exceedances for all uses of diuron to non-vascular aquatic plants, it is determined that diuron May Affect the CRLF indirectly via reduction in vascular aquatic plants.

Table 5.4 Summary of Acute RQs Used to Es timate Indirect Effe cts to the CRLF via Effects to Vascular Aquatic Plants (habitat of aquatic-phase CRLF) a

Uses Application rate (lb

ai/A) Application
Method Peak
EEC (μg/L) Indirect Effects Acute RQ*

AGRICULTURAL RIGHTS-OFWAY/FENCEROWS/HEDGEROWS 12 Ground 687.59 45.84

2.4 Ground 10.63 0.71 ALFALFA
2.4 Aircraft 13.69 0.91

86APPLE 3.2 Ground 11.68 0.78

ARTICHOKE 3.2 Ground 32.00 2.13

ASPARGUS 4.8 Ground 36.99 2.47

BANANA, PLANTAIN 2.4 Ground 54.21 3.61

BLACKBERRY, BOYSENBERRY 1.6 Ground 139.70 9.31

BLUEBERRY 2.4 Ground 4.65 0.31

CITRUS 3.2 Ground 6.83 0.46

CORN, FIELD 0.8 Ground 7.24 0.48

DEWBERRY 2.4 Ground 19.71 1.31

FILBERT (HAZELNUT) 2.2 Ground 18.90 1.26

GRAPE 3.2 Ground 9.71 0.65

LOGANBERRY, RASPBERRY (BLACK/RED) 2.4 Ground 5.13 0.34

OLIVE 1.6 Ground 7.17 0.48

PAPAYA 4 Ground 25.21 1.68

PEPPERMINT 2.4 Ground 4.17 0.28

PEACH 3 Ground 10.95 0.73

PEAR 3.2 Ground 11.66 0.78

PECAN 3.2 Ground 27.04 1.80

87SORGHUM 4.8 Ground 5.87 0.39

SPEARMINT 2.4 Ground 106.70 7.11

WALNUT (ENGLISH/BLACK) 0.4 Ground 25.78 1.72

2.4 Pre-Harvest 18.03 1.20
WHEAT

3 PostHarvest 12.82 0.85

Ground 8.36 0.56
COTTON 1.6 Aircraft 14.25 0.95

AIRPORTS/ LANDING FIELDS, DRAINAGE SYSTEMS,
INDUSTRIAL AREAS (OUTDOOR), SEWAGE DISPOSAL
AREAS 12 Ground 2190.00 146.00

BERMUDAGRASS 2.4 Ground 226.00 15.07

GRASSES GROWN FOR SEED 12 Ground 3.76 0.25

IRRIGATION SYSTEMS 1.6 Ground 52.56 3.50

ORNAMENTAL HERBACEOUS
PLANTS 12 Ground 36.55 2.44

12 Ground 629.91 41.99 NON-AGRICULTURAL RIGHTS
OF WAY 4 Aircraft 626.91 41.79

88PAVED AREAS (PRIVATE ROADS/SIDEWALKS) 12 Ground 4911.00 327.40

12 Ground 1130.00 75.33

UNCULTIVATED AG

12 Ground 1169.00 77.93

UNCULTIVATED NON-AG 12 Ground 284.80 18.99

a LOC exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC/ [ Lemna major EC 50 = 2.40 ppb].

5.1.2 Exposures in the Terrestrial Habitat

5.1.2.1 Direct Effects to Terrestrial-phase CRLF

As discussed in Section 3.3, potential direct effect determinations to terrestrial-phase CRLFs are based on foliar applications of diur on. Potential direct acute effects to the terrestrial-phase CRLF are derived by c onsidering dose- and dietary-based EECs modeled in T-REX for a small bird (20 g) c onsuming small invertebrates (Table 3.5) and acute oral and subacute dietary toxicity e ndpoints for avian species. The Bobwhite Quail exhibited the greatest acute sensitivity to di uron and was therefore se lected to serve as a surrogate for the CRLF.

Potential direct chronic eff ects of diuron to the terrestri al-phase CRLF are derived by considering dietary-based expos ures modeled in T-REX for a small bird (20g) consuming
small invertebrates. Chronic effects are estimat ed using the lowest av ailable toxicity data for birds. EECs are divided by toxicity valu es to estimate chronic dietary-based RQs.

As mentioned, there are no acceptable data for chronic or dose based acute toxicity of diuron to amphibians or their avian surrogates. Therefore, no RQs were calculated for these values. Linuron, a similar chemical of the same class, has acceptable chronic avian data. The avian reproductive studi es for linuron (MRID 42541801, 42541802) using mallard duck and bobwhite quail found reprodu ctive effects at 300 ppm ai with an NOAEL being established at 100 ppm. Th e endpoints affected for mallard duck reproduction are egg production, adult body weight , feed consumption, viable embryos of eggs set, number of viable embryos, and number of live embryos. For the bobwhite quail the endpoints affected are hatchability and offspring su rvivability. This suggests that diuron may have chronic e ffects to avian species, but these risks cannot be quantified

89in the absence of data. As a result, chronic risks are assu med to avian surrogates for all
uses of diuron in California.

The most sensitive dose based LD 50 was >2000 ppm ai as exhi bited by the Mallard Duck (MRID 00160000). It is important to note that although no mortality was observed in this study, ataxia persisted for 11d after study c oncluded. This sublethal effect could potentially result in the animals being more su sceptible to predation as a result of being both conspicuous to predators and by having a diminished ability to avoid capture. The calculated acute dietary RQs for the terres trial phase CRLF exceed the Agency’s LOC (0.1) for all uses except sorghum. The RQ s in Table 5.5 below are based on the 5-day dietary LC 50 of 1730 ppm for bobwhite quail.

The acute dietary based RQs exceed the LOC for all uses except Field Corn and Sorghum. The exceedances range from 1.55 (A gricultural Rights-of-Way, Fencerows, Hedgerows, Airports, etc.) to 0.12 (grass for s eed, wheat). These results are summarized
in Table 5.5

. Based on acute dietary LOC exceeda nces for the listed bird surrogate for amphibians, diuron May Affect the te rrestrial-phase of the CRLF directly.

Table 5.5 Summary of Acute RQs Used to Esti mate Direct Effects to the Terrestrialphase CRLF

Use (Application Rate) Dietary -based Acute RQ 2

Agricultural Rights-of-Way, Fe ncerows, Hedgerows, Airports, landing Fields, Drainage System s, Outdoor Industrial Areas, Irrigation Systems, Non-Agricultural Rights of Way, Sewage Disposal Areas, Uncultivated Non-Agricultural Areas 1.55

Alfalfa, Peppermint, 0.19 Apple, Grape 0.29 Citrus, 0.33 Artichoke, Asparagus 0.25 Banana, Plantain 0.54 Bermuda grass, Blackberry, Boysenberry, Spearmint 0.48 Blueberry 0.14 Field Corn 0.06
Cotton 0.26 Dewberry 0.26 Filbert (Hazelnut) 0.18 Grass Seed, Wheat 0.12 Loganberry, Raspberry 0.19 Olive 0.13 Pear, Pecan 0.25 Ornamental Herbaceous plants, Papaya 0.31 Uncultivated Agricultural Areas, Paved Areas 0.94 Peach 0.23 Sorghum 0.03

90Use Dietary -based Acute (Application Rate) RQ 2

Walnut 0.25
* = LOC exceedances (acute RQ > 0.1) are bolded and shaded.

2 Based on Bobwhite Quail LC 50 =1730 ppm].

5.1.2.2 Indirect Effects to Terrestrial -Phase CRLF via Reduction in Prey (terrestrial invertebrates, mammals, and frogs)

5.1.2.2.1 Terrestrial Invertebrates

In order to assess the risks of diuron to terrestrial inverteb rates, which are considered prey of CRLF in terrestrial habitats, the hone ybee 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 of >145.03 μg a.i. /bee by 1 bee/0.128g, which is based on the weight of an adult honey bee. The toxicity value for terrestrial invertebrates is calculated to be >1133.05 ppm, but only 2.77% mortality was obser ved at the highest levels tested. Therefore, this test is not definitive and acute RQ s were not calculated. However, because the terrestrial EEC’s excee d the highest levels tested for several uses, it is determined that diuron May A ffect the CRLF indirectly via reduction in terrestrial invertebrate prey items.

5.1.2.2.2 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. EECs are divided by the toxicity value to estimate acute and chronic dose-based RQs as well as chronic dietary-based RQs.

Chronic dose based RQs exceed the Agency’s LOC (1.0) for most uses (
Table 5.6 ). The dose based chronic RQs that exceed the LOC range from 8.29 (Agricultural Rights-of-Way, Fencerows, Hedge rows, Airports, etc.) to 1.31 (walnut). The dietary based chronic RQs do not exceed the LOC for any uses. The RQs that exceed the acute dose based LOC range from 0.41 (Agricultural Rights-of-Way, Fencerows, Hedgerows, Airports, etc.) to 0.13 (Bermuda grass, Blackberry, Boysenberry, Spearmint). Based on acute and chronic LOC exceedances on sm all mammal prey items, diuron May Affect the CRLF indirect ly via reduction in small mammal prey
items.

91Table 5.6 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
Chronic RQ 1 Acute RQ Use

Dose-based Chronic RQ Dietary-based Chronic RQ Dose-based Acute RQ 2
Agricultural Rights-of-Way, Fencerows, Hedgerows, Airports, landing Fields, Drainage Systems, Outdoor Industrial Areas, Irrigation System s, Non-Agricultural Rights of Way, Sewage Disposal Areas, Uncultivated Non-Agricultural Areas 8.29 0.96 0.41

Alfalfa, Peppermint 1.00 0.12 0.05
Apple, Grape 1.56 0.18 0.08
Artichoke, Asparagus 1.33 0.15 0.07

Banana, Plantain 2.87 0.33 0.14 Bermuda grass, Blackberry, Boysenberry, Spearmint 2.57 0.30 0.13 Blueberry 0.74 0.09 0.04

Citrus 1.74 0.20 0.09

Field Corn 0.33 0.04 0.02

Cotton 1.40 0.16 0.07
Dewberry 1.40 0.16 0.07
Filbert (Hazelnut) 0.96 0.11 0.05 Grass Seed, Wheat 0.67 0.08 0.03 Loganberry, Raspberry 1.00 0.12 0.05 Olive 0.69 0.08 0.03 Ornamental Herbaceous Plants, Papaya 1.67 0.19 0.08 Uncultivated Agricultural Areas, Paved
Areas 5.00 0.58 0.25 Peach 1.25 0.14 0.06 Pear, Pecan 1.33 0.15 0.07 Sorghum 0.17 0.02 0.01 Walnut 1.31 0.15 0.07
* = LOC exceedances (acute RQ > 0.1 and chronic RQ > 1) are bolded and shaded.

1 Based on dose-based EEC and diur on rat NOAEC = 250.00 mg/kg-bw.

2 Based on dose-based EEC and diuron rat acute oral LD 50 = 5000.00 mg/kg-bw.

5.1.2.2.3 Frogs

An additional prey item of the adult terrestrial -phase CRLF is other species of frogs. In order to assess risks to these organisms, di etary-based and dose-based exposures modeled

92in T-REX for a small bird (20g) consuming small invertebrates are used. See Section
5.1.2.1 for results. The chronic LOC is exceeded for all uses of diuron and the acute LOCs are exceeded for all uses except sorghum. Based on acute and chronic LOC exceedances on the prey item of small frogs , diuron May Affect the CRLF indirectly via reduction in small frog prey items.

5.1.2.3 Indirect Effects to CRLF via Reduction in Terrestrial Plant Community (Riparian and Upland Habitat)

Potential indirect effects to the CRLF resul ting from direct effects on riparian and upland vegetation are assessed using RQs from te rrestrial plant seedling emergence and vegetative vigor EC 25 data as a screen. Diuron is a systemic herbicide.

The RQs for non-target terrestri al monocot and dicot plants inhabiting semi-aquatic and upland dry areas exceed the Agency’s LOC (1.0) for all uses except for monocot plants exposed to sorghum applications ( Table 5.7 ). These exceedances range from 300.00 (semi-aquatic plants exposed to non-agricultura l aerial applications) to 0.19 (dicot plants inhabiting dry areas exposed to sorghum applications).

Several diuron uses result in LOC exceedances from spray drift. These exceedances range from 12.00 (dicot plants exposed to field corn applications) to 1.13 (monocot plants exposed to cotton applications). Based on LOC exceedances on the non-target terrestrial plants at all use sites, di uron May Affect the terrestrial phase CRLF indirectly via effects to ripa rian and upland habitat.

Table 5.7 RQs* † for Non-Target Plants Inhabi ting Dry and Semi-Aquatic Areas Exposed to Diuron via Runoff and Drift

Use Application rate (lbs

a.i./A) Application
method Drift
Value

(%) Group Spray drift RQ Dry area RQ Semiaquatic area RQ

Monocot 3.64 25.45 5.71Agricultural Rights-ofWay, Fencerows, Hedgerows, Airports, landing Fields, Drainage Systems, Outdoor Industrial Areas, Irrigation Systems, Non-Agricultural Rights of Way, Sewage Disposal Areas,
Uncultivated NonAgricultural Areas 12.0 Foliar/Ground 1

Dicot 4.80 33.60 60.00

Monocot 0.73 5.09 1.14 Alfalfa, Peppermint, Spearmint, Bermudagrass,

Blackberry, Boysenberry, Loganberry, Raspberry, Dewberry 2.4 Foliar/Ground 1

Dicot 0.96 6.72 12.00

93Application Drift Semi- Application Spray drift Dry Use rate (lbs a.i./A) method Value (%) Group aquatic RQ area RQ area RQ

Monocot 0.97 6.79 1.52 Apple, Citrus, Pear, Grape, Artichoke, Asparagus, Pecan 3.2 Foliar/Ground 1

Dicot 1.28 8.96 16.00

Monocot 2.26 8.08 7.62
Asparagus (Aerial) 3.2 Foliar/Ground 1 Dicot 2.99 10.67 80.00

Monocot 1.45 10.18 2.29

Banana, Plantain 4.8 Foliar/Ground 1 Dicot 1.92 13.44 24.00

Monocot 0.48 3.39 0.76 Blueberry, Grass Seed,

Olive, Pear, Wheat 1.6 Foliar/Ground 1 Dicot 0.64 4.48 8.00

Monocot 0.24 1.70 0.38 Field Corn 0.8 Foliar/Ground 1 Dicot 12.00 84.00 4.00

Monocot 1.13 4.04 3.81 Cotton 3 Aerial 5 Dicot 1.49 5.33 40.00

Monocot 0.48 3.39 0.76
Cotton 3 Ground 1 Dicot 24.0 168.0 8.00

Monocot 0.67 4.67 1.05 Filbert (Hazelnut) 2.2 Foliar/Ground 1 Dicot 0.88 6.16 11.00

Monocot 8.48 30.30 28.57
Non-agricultural 12 Aerial 5 Dicot 11.20 40.00 300.00

Monocot 1.21 8.48 1.90

Ornamental Herbaceous Plants, Papaya 4 Foliar/Ground 1

Dicot 1.60 11.20 20.00

Monocot 3.64 25.45 5.71 Uncultivated Agricultural Areas,
Paved Areas 12 Foliar/Ground 1 Dicot 4.80 33.60 60.00

Monocot 0.91 6.36 1.43

Peach, Walnut 3 Foliar/Ground 1 Dicot 1.20 8.40 15.00

Monocot 0.12 0.85 0.19

Sorghum 0.4 Foliar/Ground 1 Dicot 0.16 1.12 2.00
* LOC Exceedances (RQ > 1.0) are bolded and shaded. † Spray drift RQs consider only spray drift alone, dry area a nd semi-aquatic RQs consider spra y drift as well as runoff.

5.1.3 Primary Constituent Elements of Designated Critical Habitat

5.1.3.1 Aquatic-Phase (Aquatic Breed ing 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:

94• 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 vascular and non-vascular aquatic and terrestrial plants provided in Sections 5.1.1.2, 5.1.1.3, and 5.1.2.3, diuron may result in Habitat Modification of aquatic-phase PCEs of designated habitat related to effects on aquatic and/or terrestrial plants.

• Aquatic non-vascular plants used as food source and habitat for CRLF may be potentially affected from all diuron uses.

• Reduction of aquatic based food sources may occur from most use sites.

• Due to aquatic vascular and terrestria l plant communities being reduced from most use sites, there is potential for alteration of cha nnel/pond morphology or geometry and/or increase in sediment deposition within the stream channel or pond.

• Due to aquatic vascular and terrestria l plant communities being reduced from most use sites, there is potential for alteration in water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal growth and viability of juvenile and adult CRLFs and their food.

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 diuron on this PCE, acute and chronic freshwater fish and invertebrate toxicity endpoints, as well endpoints for aqua tic non-vascular plants are used as measures of effects. RQs for these endpoints we re calculated in Sections 5.1.1.1 and 5.1.1.2. Based on acute and chronic LOC exceedances for freshwater fish and aquatic invertebrates, diuron may result in Habi tat Modification of aquatic-phase PCEs
related to effects of alteration of other ch emical characteristics necessary for normal growth and viability of CRL Fs and their food source.

5.1.3.2 Terrestrial-Phase (Upland Hab itat and Dispersal Habitat)

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 dripline surroundi ng aquatic and riparian ha bitat that are comprised

95of 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

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 modification of 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 diuron on this PCE, acute and chronic toxicity endpoints for birds, mammals, and terrestrial invertebrates are used as measures of effects. RQs for thes e endpoints were calcula ted 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, diuron may result in Habitat
Modification of the first three terrestrial phase PCEs.

The fourth terrestrial-phase PC is based on alteration of chemi cal 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 use sites to terrestrial-phase CRLFs, diuron may result in Habitat Modification of 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.

If the RQs presented in the Risk Estimati on (Section 5.1) show no direct or indirect effects for the CRLF, and no modification to PCEs of the CRLF’s designated critical habitat, a “no effect” determination is ma de, based on diuron’s use within the action area. However, if direct or indirect effect s LOCs are exceeded, or if effects may modify the PCEs of the CRLF’s critical habitat, the Agency concludes a preliminary “may
affect” determination for the FIFRA regulatory action regarding diuron. Based on direct and indirect LOC exceedances for CRLF, the Agency concludes a preliminary May Affect determination for the CRLF and critical habitat. A summary of the results of th e risk estimation is provided in Table 5.8 for direct and indirect effects to the CRLF and in Table 5.9 for the PCEs of designated critical habitat
for the CRLF.

96Table 5.8 Risk Estimation Summary for Di uron - 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 YES The aquatic phase amphibian acute LOCs for Listed species (0.05) are exceeded for most uses of diuron in California. Acute RQs that exceed the Agency’s LOC range from 12.28 (paved areas) to 0.06 (papaya and walnut). Chronic RQs that exceed the Agency’s LOC for chronic exposure (1.0) range from 131.85 (paved areas) to 1.26 (banana, plantain).

Indirect Effects Survival, growth, and reproduction of
CRLF individuals via effects to food supply ( i.e., freshwater invertebrates, non-vascular plants) YES LOCs for non-vascular plants are exce eded for all uses. The RQs range from 2046.25 (paved areas) to 1.57 (grasses grown for seed).

Aquatic invertebrates acute a LOC are exceeded. The acute RQs that exceed the LOC range from 30.69 (paved areas) to 0.05 (cotton aerial application). Chronic LOCs are exceeded for several uses. RQs that exceed the Agency’s LOC range from 21.21or paved areas to 1.02 for bermudagrass.
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 exceed the Agency’s LOC (1.0) for most uses. These range from 460.46 (paved areas) to 1.30 (hazelnut).

Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects to riparian vegetation, required to maintain acceptable water quali ty and habitat in ponds and streams comprising the species’ current range. YES RQs for non-target terrestrial monocot and dicot plants inhabiting semiaquatic and upland dry areas exceed the Agency’s LOC for all uses except for monocot plants exposed to sorghum applications. RQs range from 300.00 (semi-aquatic plants e xposed to non-agricultural aerial applications) to 0.19 (dicot plants inhabiting dry areas exposed to sorghum applications).

Terrestrial Phase (Juveniles and adults)
Direct Effects Survival, growth, and reproduction of
CRLF individuals via direct effects on terrestrial phase adults and juveniles YES The acute dietary based RQs that exceed the LOC range from 1.55 (Agricultural Rights-of-Way, Fencerow s, Hedgerows, Airports, etc.) to 0.12 (grass for seed, wheat). These results are summarized in Table 5.5

.

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 Chronic dose based RQs exceed the Agency’s LOC (1.0) for most uses (

Table 5.6 ). The dose based chronic RQs that exceed the LOC range from 8.29 (Agricultural Rights-o f-Way, Fencerows, Hedgerows, Airports, etc.) to 1.31 (walnut). The dietary based chronic RQs do not exceed the LOC for any uses. The RQs that exceed the acute dose based LOC range from 0.41 (Agricultu ral Rights-of-Way, Fencerows, Hedgerows, Airports, et c.) to 0.13 (Bermuda grass, Blackberry, Boysenberry, Spearmint).

Indirect Effects Survival, growth, and reproduction of
CRLF individuals via effects on habitat ( i.e., riparian vegetation) YES The RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses of diuron in California. These range from 373.33 (paved areas) to 1.01 (alfalfa aerial).

The RQs for non-target terrestrial m onocot and dicot plants inhabiting semi-aquatic and upland dry areas exceed the Agency’s LOC (1.0) for all

97uses except for monocot plants e xposed to sorghum applications ( Table

5.7 ). These exceedances range from 300.00 (semi-aquatic plants exposed to non-agricultural aerial applications) to 0.19 (dicot plants inhabiting dry areas exposed to sorghum applications ). Several diuron uses result in plant LOC exceedances from spray drift. These exceedances range from 12.00 (dicot plants exposed to field corn applications) to 1.13 (monocot plants exposed to cotton applications).

Table 5.9 Risk Estimation Summary for Di uron – PCEs of Designated Critical
Habitat for the CRLF

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

Aquatic Phase PCEs (Aquatic Breeding Habitat and A quatic 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 vascular plants from exposure to diuron from runoff or 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 diuron from runoff or spray drift. Alteration of riparian and vascular 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 indirect effects on terrestrial and aquatic-phase CRLF from most diuron applications.

Reduction and/or modifica tion of aquatic-based 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 distur bance 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 habita t 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 LOC. However, due to the limitations imposed by the Tier 1 ground analysis (allo ws users to evaluate off-site deposition and exposure out to 1,000 ft downwind from the location of the application), the exact buffer needed for exposures to be below the LOC is uncertain.

The output from AgDRIFT indicated that the buffer zone required would be greater than 1,000 feet. Since the model is restricted to accurately di scerning a buffer within 1,000 feet of the application, the exact distance needed for a buffer to protect non-listed and listed plants is unknown. However, as seen in Table 3.7 , the calculated risk quotient (RQ) is significantly larger than the level of concern (LOC) for non-listed and listed plant species (LOC = 1).

98LOC Exceedances Assessment Endpoint Description of Results of Risk Estimation (Y/N)

This comparison provides awareness to approximately how much greater than 1,000 feet the buffer needs to be.

Elimination and/or dist urbance 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 YES Effects are expected to non-ta rget terrestrial plants over 1000 ft from use site from ground application.

Reduction and/or modification of food sources for terrestrial phase juveniles and adults YES LOC is exceeded for indirect effects on terrestrial and aquatic-phase CRLF from diuron application

Alteration of chemical characteristics necessary for normal growth and viab ility of juvenile and
adult CRLFs and their food source. YES LOC is exceeded for direct effects on terrestrial and aquatic-phase CRLF from diuron applications.

Following a preliminary “may affect” or “hab itat modification” dete rmination, additional information is considered to refine the potenti al for exposure at the predicted levels based on the life history characteristics ( i.e. , habitat range, feeding pr eferences, etc.) of the
CRLF. Based on the best available informa tion, the Agency uses the refined evaluation to distinguish those actions th at “may affect, but are not likely to adve rsely affect” from those actions that are “likely to adversely affect” the CRLF and its designated critical
habitat.

The criteria used to make determinations that the effects of an acti on are “not likely to adversely affect” the CRLF and its designated critical habitat 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 and its designated crit ical habitat is provided in Sections 5.2.1 through 5.2.3.

995.2.1 Direct Effects

5.2.1.1 Aquatic-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 runoff and spray drift containing diuron.

Diuron is considered “highly toxic” to the fr eshwater fish, which are surrogates for the aquatic phase CRLF. The aquatic animal acute LOCs for Listed species (0.05) are exceeded for most uses of diuron in California. Acute RQs that exceed the Agency’s LOC range from 12.28 (paved areas) to 0.06 (papaya). The probability of an individual effect to the aquatic-phase CRLF is based on the slope of the dose re sponse curve for the acute endpoint used to derive the RQ. The probability, based on th e default slope of 4.5 is one in 4.18E+08. Because the upper and lower 95% confidence interval of the slope is not known, a plausible range of slopes of 2 to 9 were used to obtain reasonable upper and lower bounds. The resulting probability of an individual effect to the aquatic-phase CRLF range between one in 215.83 and one in 1.75E+31.

Chronic RQs that exceed the Agency’s LOC for chronic exposure (1.0) range from 131.85 (paved areas) to 1.26 (banana, plantain ). The aquatic chr onic animal LOC for listed species (1.0) is exceeded for most uses of diuron in California.

The USGS collected 422 positive ground water samples containing Diuron. The three
river basins looked at were Sacramento, San Joaquin-Tu lare, and Santa Ana. The maximum concentration observed was 1.8 ppb in the San Joaquin-Tulare water basins in Kings County.

Monitoring data from CDPR indicate thatdiuron concentrations range from nondetectable to 160 ppb. The majority of the la rge concentrations of Diuron came from San Joaquin County, and occurred between the end of December and the beginning of January. The year 2005, for San Joaquin C ounty, yielded the greatest concentrations
overall.

Moreover, the CDPR monitoring data showed that eleven samp les (1.56% of the 705 samples), ranging from 31 ppb to 160 ppb, detected levels of diuron that would result in
chronic direct effects to the CRLF. Likewi se, four samples (0.57%), ranging from 9.5 ppb to 15 ppb, detected diuron at levels that woul d result in chronic indirect effects to the CRLF. These detects occurred during the mont hs of December, January, and February in years 2005 and 2006, and in March for the 2006 year. The San Joaquin County had 5 detects (3.38% of samples) resulting in chr onic direct effects and 1 detect (0.68% of samples) resulting in chronic indirect effe cts, Tulare County ha d 1 detect (2.22% of samples) resulting in a chronic direct effect, and Stanislaus County had 5 detects (6.94% of samples) resulting in chr onic direct effects and 2 detect s (2.78% of samples) resulting

100in chronic indirect effects. Consequen tly, almost 10% of the samples taken from Stanislaus County, just over 4% from San Joaquin County, a little over 2% from Tulare County contained detects at leve ls that would cause chronic or indirect effects to the
CRLF.

Seven reported incidents resulted in fish kills. Five of these fish kills resulted from direct application of diuron to water bodies which is not allowed in California. However, three
incidents were from drift or runoff of diuron from applications made adjacent to water
bodies. This demonstrates that diuron ma y pose a threat to aquatic organisms through labeled uses (Appendix J). It is also important to note th at the absence of additional documented incidents does not necessarily m ean that such incidents did not occur. Mortality incidents must be seen, reported, investigated, and submitted to the Agency in
order to be recorded in the incident databa se. Incidents may not be noticed because the carcasses decayed, were removed by scavengers, or were in ou t-of-the-way or hard-to-see locations. Due to the voluntary nature of incident reporting, an incident may not be reported to appropriate authoritie s capable of inve stigating it. Based on these exceedances to the aquatic-phase CRLF, repor ted diuron incidents resulting in fish kills and its monitored pres ence in surface water, a “M ay Affect and Likely to Adversely Affect (LAA)” determination is made for diuron use in California.

5.2.1.2 Terrestrial-Phase CRLF

The RQs representing acute dietary-based e xposures exceed the Agency’s LOC for all uses except sorghum (Section 5.1.2.1.). Th ese RQs were derived using the T-REX model, which estimates exposures that are sp ecific to food intake equations for birds. RQs generated for birds are used as surrogate s to represent RQs for the terrestrial-phase
CRLF. Based on these exceedances to the te rrestrial-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 EECs generated by T-HE RPS are found in Table 5.10. An example output from T-HERPS is av ailable in Appendix K.

101Table 5.10. Upper-bound Kenega Nomogram T-HERPS EECs (mg/kg-diet) for Dietary-based Exposures of the CRLF and its Prey to Diuron 1

.

Scenario Small
Insects Large
Insects Small
Herbivore
Mammals Small
Insectivore
Mammals Small
Terrestrial

Phase Amphibians
Agricultural Rights-of-Way, Fencerows, Hedgerows, Airports, landing Fields, Drainage Systems, Outdoor Industrial Areas,Irrigation Systems, NonAgricultural Rights of Way, Sewage Disposal Areas, Uncultivated Non-Agricultural
Areas 2113.70 234.86 2476.10 154.76 73.37

Alfalfa, Peppermint, 324.00 36.00 379.55 23.72 11.25 Apple, Grape 504.68 56.08 591.21 36.95 17.52

Citrus

Artichoke, Asparagus 432.00 48.00 506.07 31.36 15.00

Banana, Plantain 930.06 103.34 1089.52 68.10 32.28 Bermuda grass, Blackberry, Boysenberry, Spearmint 951.44 105.72 114.57 69.66 33.03

Blueberry 239.50 23.61 280.57 17.54 8.31

Field Corn 108.00 12.00 126.52 7.91 3.75

Cotton 452.53 50.28 530.11 33.13 15.71 Dewberry 452.83 50.31 530.47 33.15 15.72 Filbert (Hazelnut) 312.23 34.69 365.76 22.86 10.84
Grass Seed, Wheat 216.00 24.00 253.03 15.81 7.50 Loganberry, Raspberry 324.00 36.00 379.55 23.72 11.25

Olive 223.75 24.86 262.12 16.38 7.77
Pear, Pecan 432.00 48.00 506.07 31.63 15.00 Ornamental Herbaceous Plants, Papaya 540.00 60.00 632.59 39.54 18.74

Uncultivated Agricultural Areas,
Paved Areas 1620.00 180.00 1897.76 118.61 56.23

Peach 405.00 45.00 474.44 29.65 14.06 Sorghum 54.00 6.00 63.26 3.95 1.87

Walnut 425.76 47.31 498.76 31.17 14.78

1 weights of small herbivore an d insectivore mammals are 35g

102Acute exposures

Refined acute dietary-based RQs for CRLFs c onsuming large insects and small herbivore mammals exceed the acute listed species LO C (0.1) for all uses of diuron except Sorghum and Field Corn. The acute diet ary-based RQs for CRLFs consuming large insects exceed the acute listed species LO C for Agricultural Rights-of-Way, Fencerows etc. No acute dietary based LOCs were ex ceeded for CLRF consum ing small insectivore mammals and small terrestrial phase amphi bians for any diuron use. Results are presented in Table 5.11.

Table 5.11. Revised Acute Dietary-based RQ s for CRLF consuming different food items (RQs calculated using T-HERPS)*.

Scenario Small
Insects Large
Insects Small
Herbivore
Mammals Small Insectivore
Mammals Small
Terrestrial

Phase Amphibians
Agricultural Rights-ofWay, Fencerows, Hedgerows, Airports, landing Fields, Drainage Systems, Outdoor Industrial Areas, Irrigation Systems, Non-Agricultural Rights of Way, Sewage Disposal Areas,
Uncultivated NonAgricultural Areas 1.22 0.14 1.43 0.09 0.04

Alfalfa, Peppermint, 0.19 0.02 0.22 0.01 0.01 Apple, Grape 0.29 0.03 0.34 0.02 0.01

Citrus 0.33 0.04 0.38 0.02 0.01

Artichoke, Asparagus 0.25 0.03 0.29 0.02 0.01

Banana, Plantain 0.54 0.06 0.63 0.04 0.02 Bermuda grass, Blackberry, Boysenberry, Spearmint 0.55 0.06 0.64 0.04 0.02

Blueberry 0.14 0.02 0.16 0.01 <0.01

Field Corn 0.06 0.01 0.07 <0.01 <0.01

Cotton 0.26 0.03 0.31 0.02 <0.01 Dewberry 0.26 0.03 0.31 0.02 0.01 Filbert (Hazelnut) 0.18 0.02 0.21 0.01 0.01
Grass Seed, Wheat 0.12 0.01 0.15 0.01 <0.01

103Loganberry, Raspberry 0.19 0.02 0.22 0.01 0.01

Olive 0.13 0.01 0.15 0.01 <0.01
Ornamental Herbaceous plants, Papaya 0.31 0.03 0.37 0.02 0.01

Uncultivated Agricultural Areas, Paved Areas 0.94 0.10 1.10 0.07 0.03

Peach 0.23 0.03 0.27 0.02 0.01
Pear, Pecan 0.25 0.03 0.29 0.02 0.01 Sorghum 0.03 <0.01 0.04 <0.01 <0.01

Walnut 0.25 0.03 0.29 0.02 0.01
*RQs exceeding the Listed LOC (0.10) are bolded and shaded

Based on the dietary probit dose-response slope of 7.22 the chance of individual mortality for which RQs exceed the Listed LOC range from approximately one in 6.75E+10 at an RQ of 0.12 (Grass Seed and Wheat uses) to a pproximately one in one at an RQ of 1.22 (Agricultural Rights-of-Way, etc.). Therefore, based on th ese refined dietary based acute risk quotients and their exceedan ces of the Agency’s LOC a Likely to Adversely Affect (LAA) determination is made for diuron use in California.

5.2.2 Indirect Effects (via Reductions in Prey Base)

5.2.2.1 Algae (non-vascular plants)

Indirect effects of diuron to the aquatic-phase CRLF (tadpoles) via reduction in nonvascular aquatic plants in its diet are ba sed on peak EECs from the standard pond and the lowest acute toxicity value fo r aquatic non-vascular plants. The Agency’s LOC (1.0) is
exceeded for all current uses of diuron in California. The RQs range from 2331.67 for Paved Areas to 1.82 for Sorghum (Section 5.1.1.2).

The fate characteristics indicate that diuron is expected to be persistent in aquatic environments with EECs after 60 days being above the Agency’s LOC for non-vascular aquatic plants, a primary food source for aqua tic-phase CRLF. The application of diuron in California is anticipated to be in late winter and early spring. The timing of the application would coincide with reproduction of CRLF in aquatic environments as well as for the tadpoles to feed on non-vascular aquatic plants.

Because of non-vascular LOC exceedances from registered uses of diuron, its monitored presence in surface water and v erified non-target incidents resulting from diuron use, based on multiple lines of evidence, the Agency concludes that there is a potential indirect impact to the aquatic-phase of the CRLF from reduction of food items (algae) and th erefore diuron is Likely to Adversely Affect (LAA) the
CRLF.

.

1045.2.2.2 Aquatic Invertebrates

As discussed in Section 2.5.3, the diet of CRL F also includes aquatic invertebrates. The potential for diuron to elic it indirect effects to the CRL F 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 application of diuron in Ca lifornia is anticipated to be in late winter and early spring. The timing of the application would coincide with juvenile aquatic- and terrestrial-phase CRLFs that would be feeding on aquatic and terrestrial invertebrates.

Indirect acute effects to the aquatic-phase CRLF via effects to prey (invertebrates) in aquatic habitats are based on peak EECs in the standard pond and the lowest acute toxicity value for freshwater invertebrates. For chronic risk s, 21-day EECs and the lowest chronic toxicity value for invertebrates are used to derive RQs. The Agency’s acute Listed LOC (0.05) is exceeded for most uses of diuron in California. The acute RQs that exceed the LOC range from 30.69 (Paved Ar eas) to 0.06 (grape). The chronic RQs exceed the Agency’s LOC for several used. Th e chronic values that exceeded range from 21.21 (paved areas) to 1.02 (bermudagrass). A summary of the acute and chronic RQ values for exposure to aquatic invertebrates (as prey items of aquatic-phase CRLFs) is provided in Table 5.3 . Based on acute Listed LOC exceedances for chronic and acute aquatic invertebrates from mo st use sites, diuron May A ffect the CRLF indirectly via
reduction in freshwater inve rtebrate prey items.

Based on the aquatic invertebrate RQs and a probit dose-response default slope of 4.5 the estimated reduction in aquatic invertebrate populations for which RQs exceed the Listed LOC range from <0.01% to approximately 100%. To further inves tigate the estimated reduction in aquatic invertebrate populations, a plausible rang e of slopes of 2 to 9 were selected to investigate the upper and lower bounds of this estimate. Using a slope of 2 led to a range of possible reduction in populat ions from less than 0.10% to approximately 100%. Employing a slope of 7 led to a range of possible reduction in aquatic invertebrate populations from less than 1.0% to approximately 100%.

Because aquatic invertebrate populations are expected to be impacted from registered uses of diuron in California, and because diuron’s presence has been
observed in monitored surface water in Ca lifornia, the Agency concludes that there is a potential indirect impact to the aqua tic-phase of the CRLF from a reduction of aquatic invertebrate food items and therefor e diuron is Likely to Adversely Affect (LAA) the CRLF.

1055.2.2.3 Fish and Aquatic-phase Frogs

As discussed in Section 2.5.3, the diet of CRLF also includes small fish and other aquatic-phase frogs. Direct effects to the aquatic-phase CRLF are based on peak EECs in the standard pond and the lowest acute toxicity value for freshwater fish. In order to assess direct chronic risks to the CRLF, 60- day EECs and the lowest chronic toxicity value for freshwater fish are used. The RQs for diuron uses results in acute and chronic exceedances of the Agency’s LOC for freshw ater fish which are surrogates for the aquatic phase for amphibians.

The aquatic phase amphibian acute LOCs for Li sted species (0.05) ar e exceeded for most uses of diuron in California. Acute RQs that exceed the Agency’s LOC range from 13.99 (paved areas) to 0.053 (papaya). Based on th ese RQs and a probit dose-response default slope of 4.5 the estimated aquatic vertebra te prey item population reduction for which RQs exceed the Listed LOC range from approximately 10.0% to approximately 100%. To further investigate the es timated aquatic vertebrate prey item population reduction, a plausible range of slopes of 2 to 9 were selected to investig ate the upper and lower bounds of this estimate. Using a slope of 2 led to a range of estimated population reduction of approximately 30.0% to approxima tely 100%. Employing a slope of 9 led to a range of possible population reduction of approximately 3.0% to approximately 100%.

The aquatic phase amphibian acute LOCs for lis ted species (0.05) are exceeded for most uses of diuron in California. Acute RQs that exceed the Agency’s LOC range from 12.28 (paved areas) to 0.06 (papaya and walnut). Chronic RQs that exceed the Agency’s LOC for chronic exposure (1.0) range from 131.85 (pav ed areas) to 1.26 (banana, plantain).

The application of diuron in Ca lifornia is anticipated to be in late winter and early spring. The timing of the application would coincide with juvenile aquatic- and terrestrial-phase CRLFs that would be feeding on sm all fish, small frogs or tadpoles. Because fish and aquatic phase amphibian populations are ex pected to be impacted from registered uses of diuron in California, and because diuron’s presence has been observed in monitored surface water in California, the Agency concludes that there is a potential indirect impact to the aquatic-pha se of the CRLF from a reduction of fish and aquatic phase amphibian food items and therefore diuron is Likely to Adversely Affect (LAA) the CRLF.

5.2.2.4 Terrestrial 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 are used to assess potential indirect eff ects of diuron to the terrestri al-phase CRLF. Effects to
terrestrial invertebrates result ing from exposure to diuron may also indirectly affect the
CRLF via reduction in available food.

Because the estimated EEC’s exceed the highest level tested for th ree uses for diuron, a preliminary “May Affect” determination was made. However, the calculated EEC’s for

106Agricultural Rights-of-Way etc (2688.80 ppm) was only roughly twice the highest level tested (>1305) at which only a 2.7% mortality was observed. Therefore, it is reasonable
to assume that the effects to terrestrial i nvertebrate populations will be negligible for
these uses of diuron in California. Therefore, based on the weight-of-evidence, the Agency concludes that there is a neglig ible potential impact to terrestrial invertebrates that the CRLF consumes, and therefore diuron May Affect but is Not Likely to Adversely Aff ect (NLAA) the CRLF.

5.2.2.5 Mammals

Life history data for terres trial-phase CRLFs indicate that large adult frogs consume terrestrial vertebrates, incl uding mice. Small mammals can make up to 50% of the CRLF food intake. Acute dose based RQs exceed the Agency’s LOC (1.0) for most uses. The dose based RQs that exceed the LOC range from 0.41 (Agricultural Areas, Rights-ofWay, fencelines etc.) to 0.13 (Bermudagrass, Blackberry, Boysenberry, Spearmint). The dose based chronic RQs that exceed the LO C range from 8.29 (Agricultural Areas, Rights-of-Way, fencelines etc.) to 1.33 (Ar tichoke, Asparagus, Pear, Pecan).. The dietary based chronic RQs do not exceed the LOC for any uses.

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 the Listed LOC range from <0.01% to approx imately 4.00%. To fu rther investigate the estimated reduction in these populations, a pl ausible range of slopes of 2 to 9 were selected to investigate the upper and lower bounds of this es timate. Employing a slope of 9 led to an estimated population reduction of <0.01% for all RQs. Using a slope of 2 led to a range of possible population reduction from approximately 4.00% to approximately
22.00%. Because mammalian populations are expected to be impacted from registered uses of diuron in California, the Agency concludes that there is a potential indirect impact to the terrestrial phase of the CRLF from a reduction of
mammalian food items and therefore diuron is Likely to Adversely Affect (LAA) the
CRLF.

5.2.2.6 Terrestrial-phase Amphibians

Terrestrial-phase adult CRLFs also consume frogs. RQ values representing direct exposures of diuron to terrestri al-phase CRLFs are used to re present exposures of diuron to frogs in terrestrial habitats. The T- HERPS model was therefore employed as a refinement tool to explore amphibian-speci fic food intake on potential exposures to terrestrial phase amphibian food items for th e CRLF. The T-HERPS model incorporates the same inputs as T-REX with equations adjusted for poikilotherm food intake.

Acute exposures

Refined acute dietary-based RQs for terr estrial phase amphibians consuming small
insects and small herbivore mammals exceed the acute listed species LOC (0.1) for all uses of diuron except Sorghum and Field Corn. The acute dietary-based RQ for

107terrestrial phase amphibians consuming larg e insects exceeds the acute listed species LOC for Agricultural Rights- of-Way, Fencerows etc. Based on these refined dietary based risk quotients, terrestrial phase amphi bian populations are expected to be impacted from registered uses of diur on in California. Therefore the Agency concludes that there is a potential indirect impact to the terrestrial phase of the CRLF from a reduction of terrestrial pha se amphibian food items and therefore diuron is Likely to Adversely Affect (LAA) the CRLF.

5.2.3 Indirect Effects (via Habitat Effects)

5.2.3.1 Aquatic 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. In addition to ener gy, vascular plants provide structure as attachment sites and refugia for many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In addition, vascular plants also provide primary productivity and oxygen to the aquatic ecosystem. Rooted plants help reduce sediment loading and provide stability to nearshore areas and lower streambanks. In addition, vascular aquatic plants are important as attachment sites for egg masses of CRLFs.

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 diuron to the aquatic-phase CRLF (tadpoles) via reduction in nonvascular aquatic plants in its diet are ba sed on peak EECs from the standard pond and the lowest acute toxicity value fo r aquatic non-vascular plants. The Agency’s LOC (1.0) is
exceeded for all current uses of diuron in California. The RQs range from 2331.67 (paved areas) to 1.82 (sorghum).

Indirect effects to the CRLF vi a direct toxicity to aquatic plants are estimated using the
most sensitive non-vascular and vascular plant toxicity endpoi nts. The RQs for vascular aquatic plants exceed the Agen cy’s LOC (1.0) for most uses of diuron in California. These range from 373.33 (paved ar eas) to 1.01 (alfalfa aerial). Based on LOC exceedances in vascular and non-vascular pl ants, diuron is Likely to Adversely Affect (LAA) the CRLF indirectly via habi tat degradation through reduction in vascular and non-vascular aquatic plants.

5.2.3.2 Terrestrial 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

108cover 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.

Twenty-two incidents have been reported that were either registered use or of undetermined legality that resu lted in plant damage. The RQs for non-target terrestrial monocot and dicot plants inhabiting semi-aquatic and upland dry areas exceed the Agency’s LOC (1.0) for all uses except for monocot plants exposed to sorghum applications. These exceedances range from300.00 (semi-aquatic plants exposed to nonagricultural aerial applications) to 0.19 (dicot plants inhabiting dry areas exposed to sorghum applications). Several diuron uses result in LOC exceedances from spray drift. These exceedances range from 12.00 (dicot plan ts exposed to field corn applications) to 1.13 (monocot plants exposed to cotton applications). Based on LOC exceedances in vascular and non-vascular plants, and twen ty-two reported incidents that resulted in plant damage, diuron is Likely to Ad versely Affect (LAA) the CRLF indirectly via habitat degradation through reduction terrestrial plants.

5.2.4 Modification to Designated Critical Habitat

Risk conclusions for the designated critical habitat are the same as those for indirect effects. Agency concludes that there is a pot ential indirect impact to CRLF by terrestrial habitat degradation from diuron exposure.

5.2.4.1 Aquatic-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).

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, diuron will result in habitat modification based on effects to aquatic-phase PCEs of designated critical habitat.

• Aquatic non-vascular plants used as food source and habitat for CRLF may be potentially affected from all diuron uses.

109• Reduction of aquatic based food sources may occur from most use sites.

• Due to aquatic vascular and terrestria l plant communities being reduced from most use sites, there is potential for alteration of cha nnel/pond morphology or geometry and/or increase in sediment deposition within the stream channel or pond.

• Due to aquatic vascular and terrestria l plant communities being reduced from most use sites, there is potential for alteration in water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal growth and viability of juvenile and adult CRLFs and their food.

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 diuron on this PCE, acute and chronic freshwater fish and invertebrate toxicity endpoints, as well endpoints for aqua tic non-vascular plants are used as measures of effects. RQs for these endpoints we re calculated in Sections 5.1.1.1 and 5.1.1.2. Based on acute and chronic LOC exceedances for freshwater fish and aquaticinvertebrates, diuron will result in habitat modification based on effects to aquaticphase PCEs of designated critical habitat re lated to effects of alteration of other chemical characteristics necessary for no rmal growth and viability of CRLFs and
their food source.

5.2.4.2 Terrestrial-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 modificati on via impacts to terrestrial plants (Section 5.2.3.2).

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 modification of 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 diuron on this PCE, acute

110and chronic toxicity endpoints for birds, mammals, and terrestrial invertebrates are used as measures of effects. RQs for thes e endpoints were calcula ted in Section 5.1.2.2. Based on acute and chronic LOC exceedances for CRLF prey items of small mammals, terrestrial invertebrates and other frogs, diuron will result in habitat
modification based on effects to the terr estrial PCE relative to reduction in food

sources.

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 use sites to terrestrial-phase CRLFs, diuron will result in habitat modification based on effects
to the terrestrial PCE related to alteration of chemical characteristics necessary for normal growth and viability.

5.2.5.1 Downstream Dilution

The downstream extent of exposure in streams and rivers where the EEC could potentially be above levels that would exceed the most sensitive LOC. 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 represente d by the modeled EECs; as those waters move downstream, it is assumed that the influx of non-impacted water will dilute
the concentrations of diuron present.

Using a EC 50 value of 2.40 ug/L for non-vascular a quatic plants (the most sensitive species) and a maximum peak EEC for appl ications to Agricultural Rights-of-Way, Fencerows, etc. of 688 ug/L yields an RQ/LOC ratio of 142 (142/1). Using the downstream dilution approach (described in more detail in Appendix F) yields a distance of 285 kilometers which represents the maximum continuous distance of downstream dilution from the edge of the initial area of concern. Similar to the spray drift buffer described above, the LAA/NLAA determination is based on the area defined by the point
where concentrations exceed the EC 50 value.

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.

1116.1.2 Aquatic Exposure Modeling of Diuron

The standard ecological water body scenario (EXAMS pond) used to calculate potential aquatic exposure to pesticides is intended to represent conservative estimates, and to avoid underestimations of the actual exposure. The standard scenario consists of application to a 10-hectare field border ing a 1-hectare, 2-meter deep (20,000 m 3 ) pond with no outlet. Exposure estimates genera ted using the EXAMS pond are intended to represent a wide variety of vulnerable water bodies that occur at the top of watersheds including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural ponds, and intermittent and lower order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the EXAMS pond. Static water bodies that have larger ratios of pesticide-treate d drainage area to water body volume would be expected to have higher peak EECs than the EXAMS pond. These water bodies will be
either smaller in size or have larger drainage areas. Sm aller water bodies have limited storage capacity and thus may overflow and carry pesticide in the discharge, whereas the EXAMS pond has no discharge. As waters hed size increases beyond 10-hectares, it becomes increasingly unlikely that the entire watershed is planted w ith a single crop that is all treated simultaneously with the pesticid e. Headwater streams can also have peak concentrations higher than the EXAMS pond, but they likely persist for only short periods of time and are then car ried 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 pesticid es (USFWS/NMFS 2004).

In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone Model is a process or “simulation” model that calculates what happens to a pesticide in an agricultural field on a day-to-day basis. It considers factors such as rainfall and plant transpiration of water, as well as how and when the pesticide is applied. It has two major components: hydrology and chemical transport. Water movement is simulated by the use of generalized soil parameters, including fi eld capacity, wilting point, and saturation water content. The chemical transport com ponent can simulate pesticide application on the soil or on the plant foliage. Dissolved, adsorbed, and vapor-phase concentrations in the soil are estimated by simultaneously cons idering the processes of pesticide uptake by

112plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection, dispersion, and retardation.

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 likely 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 uncertainties associ ated with modeling, available monitoring data were compared to PRZM/EXAMS estimates of peak EECs for the different uses. As discussed above, several data values were available from NAWQA for diuron
concentrations measured in surface waters receiving runoff from agricultural areas. The specific use patterns (e.g. a pplication rates and timing, crops) associated with the agricultural areas are unknown, however, they are assumed to be representative of potential diuron use areas.

The monitoring data available are below th e PZM-EXAMS predictions by an order of magnitude. The monitoring data indicated th at the time weighted mean concentration ranged from below the 0.001 ppb to 0.86 ppb w ith a mean concentration of 0.21 ppb. PRZM-EXAMS prediction (not including the scenarios for impervious surfaces)
estimated diuron to be in the surface waters at peak concentrations from 27.5 ppb to 2.6 ppb and 60 day EEC from 18.3 ppb to 1.8.

6.1.3 Action Area Uncertainties

The action area is considered to be the whole State of Califor nia since diuron is considered to be an animal carcinogen and can not be spatially de fined. Diuron use has been reported in all 58 counties.

1136.1.4 Usage Uncertainties

County-level usage data were obtained from California’s Department of Pesticide Regulation Pesticide Use Reporti ng (CDPR PUR) database. F our years of data (2002 – 2005) 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 there were discrepancies, the most conservative
information was used.

6.1.5 Terrestrial Exposure Modeling of Diuron

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. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is
formulated to maximize assimilative efficien cy (e.g., a value of 85%), a potential for underestimation of exposure may exist by assu ming that consumption of food in the wild is comparable with consumption during labora tory testing. In th e screening process,

114exposure may be underestimated because me tabolic rates are not related to food consumption.

For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal was assumed to occupy either the treated field or adjacent areas receiving a treatment rate on the field. Actual habitat requirements of any particular terrestrial species were not considered, and it was assumed that species occupy, exclusively and permanently, the modeled treatment area. Spray drift model predictions sugges t that this assumption leads to an overestimation of exposure to species that do not occupy the treated field exclusively and permanently.

6.1.6 Spray Drift Modeling

It is unlikely that the same organism woul d be exposed to the maximum amount of spray drift from every application made. In orde r for an organism to receive the maximum concentration of diuron from multiple appl ications, each application of diuron would have to occur under identical atmospheric conditions (e.g., same wind speed and same wind direction) and (if it is an animal) the animal being exposed would have to be located in the same location (which receives the maximum amount of spray drift) after each application. Additionally, othe r factors, including variati ons in topography, cover, and meteorological conditions over the trans port 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 AgDRIF T may overestimate exposure, especially as the distance increases from the site of application, si nce the model does not account for potential obstructions ( e.g ., large hills, berms, buildings, trees, etc .). Furthermore, conservative assumptions are made regarding the droplet size distributions being modeled (was set to the default ‘ASAE Very Fine to Fine’), the application method ( i.e ., aerial), release heights and wind speeds (also set to the de fault values of 10 ft and 10 mph respectively for aerial application; the height for ground applic ation was set to the default ‘high boom’). Altera tions in any of these input s would decrease the area of potential effect.

6.2 Effects Assessment Uncertainties

6.2.1 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 daphnids, 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

115so 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.

6.2.2 Use of Surrogate Species Effects Data

CRLF Guideline toxicity tests and open literature da ta on diuron are not available for frogs or any other aquatic-phase amphibian; therefore, freshwater fish are used as surrogate species for aquatic-phase amphibians. Ther efore, endpoints based on freshwater fish ecotoxicity data are assumed to be protective of potential direct e ffects to aquatic-phase amphibians including the CRLF, and extrapolati on of the risk conclusions from the most sensitive tested species to the aquatic-phase CRLF is likely to overestimate the potential risks to those species. Efforts are made to se lect the organisms most likely to be affected by the type of compound and usage pattern; howev er, there is an inherent uncertainty in extrapolating across phyla. In addition, the Agency’s LOCs are intentionally set very low, and conservative estimates are made in the screening level risk assessment to
account for these uncertainties.

Terrestrial Plants 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 diuron, is largely unknow n. 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.

1166.2.3 Sublethal Effects

When assessing acute risk, the screening risk assessment relies on the acute mortality endpoint as well as a suite of sublethal 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 t is exercised on a case-by-case basis and only after careful consideration of the nature of the
sublethal effect measured and the extent and quality of available data to support establishing a plausible relationship between the measure of effect (sublethal endpoint) and the assessment endpoints. However, the fu ll suite of sublethal effects from valid open literature studies is considered for the purposes of defining the action area.

6.2.4 Location of Wildlife Species

For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal was assumed to occupy either the treated field or adjacent areas receiving a treatment rate on the field. Actual habitat requirements of any particular terrestrial species were not considered, and it was assumed that species occupy, exclusively and permanently, the modeled treatment area. Spray drift model predictions sugges t that this assumption leads to an overestimation of exposure to species that do not occupy the treated field exclusively and permanently.

7.0 Risk Conclusions

In fulfilling its obligations unde r 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 ri sks of diuron to the CRLF and its designated
critical habitat.

The Agency makes a Likely to Adversely Affect determination for the CRLF from the use of diuron. The Agency has determined th at there is the potential for modification of CRLF designated critical habitat from the use of the chemical. The direct effects and
habitat modification effects dete rminations are summarized in Table 7.1 and Table 7.2 respectively. Given the LAA determination for the CRLF an d potential modification of designated critical habitat, a description of the baseline stat us and cumulative effects for the CRLF is provided in Attachment II.

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 ir on’s use pattern is iden tified, using land cover data that correspond to iron’ s use pattern. The spatial extent of the LAA effects
determination also includes ar eas beyond the initial area of c oncern that may be impacted by runoff and/or spray drift. The identified di rect and indirect eff ects and modification to critical habitat are anticipated to occur onl y for those currently o ccupied core habitat areas, CNDDB occurrence sections, and designa ted critical habitat for the CRLF that overlap with the initial area of concern. The AgDRIFT m odel was used to evaluate

117potential distances beyond which exposures would be expected to be below LOC. However, due to the limitations imposed by th e Tier 1 ground analys is (allows users to evaluate off-site deposition and exposure out to 1,000 ft downwind from the location of the application), the exact buffer needed for exposures to be below the LOC is uncertain.

The output from AgDRIFT indicated that the bu ffer zone required would be greater than 1,000 feet. Since the model is restricted to accurately discerning a buffer within 1,000 feet of the application, the exact distance needed for a bu ffer to protect non-listed and listed plants is unknown. However, as seen in Table 3.7 , the calculated risk quotient (RQ) is significantly larger than the level of concern (LOC ) for non-listed a nd listed plant species (LOC = 1). This comparison provi des awareness to approximately how much greater than 1,000 feet the buffe r needs to be. It is assumed that non-flowing water bodies (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 285 kilometers which represents the maximum continuous distance of downstream dilution from the edge of th e initial area of concern. If any of these streams reaches flow into CRLF habitat, there is potential to affect either the CRLF or modify its habitat. These lotic aquatic habi tats within the CRLF core areas and critical habitats potentially contain concentrations of diuron sufficient to result in LAA
determination or modificati on of critical habitat.

Appendix F provides maps of the initial area of concern, along with CRLF habitat areas, including currently occupied core areas, CNDDB occurrence sections, and designated critical habitat. It is expected that any additional areas of CRLF habitat that are located 285 kilometers of stream distance (to account for downstream dilution) outside the initial area of concern may also be impacted and ar e part of the full sp atial extent of the
LAA/modification of critical habitat effects determination.

118Table 7.1 Effects Determination Summary for Effects of Diuron on the CRLF

Assessment

Endpoint Effects
Determination 1 Basis for Determination

Potential for Direct Effects Aquatic-phase (Eggs, La rvae, and Adults) : The aquatic phase amphibian acute LOCs for Listed species (0.05) are exceeded for most uses of diuron in California. Acute RQs that exceed the Agency’s LOC range from 13.99 (paved areas) to 0.053 (papaya). Chronic RQs that exceed the Agency’s LOC for chronic exposure (1.0) range from 188.58 (paved areas) to 1.0003 (banana, plantain).

Terrestrial-phase (Juveniles and Adults) : Refined acute dietary-based RQs for CRLFs consuming large insects and small herbivore mammals exceed the acute listed species LOC (0.1) for all uses of diuron except Sorghum and Field Corn. The acute dietary-based RQs for CRLFs consuming large insects exceed the acute listed species LOC for Agricultural Rights-of-Way, Fencerows etc. and Ornamental Herbaceous Plants. No acute dietary based
LOCs were exceeded for CLRF consum ing small insectivore mammals and small terrestrial phase amphibi ans for any diuron use.

Refined chronic dietary-based RQs for CRLFs consuming insects and mammals exceed the chronic listed species LOC for all uses of diuron across all food item groups.
Potential for Indirect Effects Aquatic prey items, aquatic habitat, cover and/ or primary productivity : LOCs for non-vascular plants are exce eded for all uses. The RQs range from 2331.67 (paved areas) to 1.82 (sorghum).

Aquatic invertebrates acute a LOC are exceeded. The acute RQs that exceed the LOC range from 34.98 (paved areas) to 0.06 (post-harvest wheat). Chronic LOCs are exceeded for paved area applications (RQ=1.50).

RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses. These range from 373.33 (paved areas) to 1.01 (alfalfa aerial). Survival, growth,
and/or reproduction
of CRLF
individuals LAA

Terrestrial prey items, riparian habitat : For small mammal, chronic dose based RQs exceed the Agency’s LOC (1.0) for most uses. The dose based chronic RQs that exceed the LOC range from 5.00 (paved areas) to1.31 (walnut). The acute RQs exceed the Agency’s LOC for several uses. The RQs that exceed the acute dose based LOC range from 0.25 (paved areas) to 0.12 (Agricultural Rights-of-Way, Fencerows, Hedgerows, Airports, etc.).

LOCs are exceeded for terrestrial riparian plants and for aquatic plants from exposure to diuron from runoff or spray drift. Alteration of riparian and vascular plants may result in alteration of temperature, turbidity, and oxygen content. RQs for vascular aquatic plants exceed the Agency’s LOC (1.0) for most uses. These range from 373.33 (paved areas) to 1.01 (alfalfa aerial).
1 No effect (NE); May affect, bu t not likely to adversely affect (NLAA); May affect, likely to adversely affect (LAA)

119Table 7.2 Effects Determination Summary fo r the Critical Habitat Impact Analysis

Assessment

Endpoint Effects
Determination 1 Basis for Determination

Modification of aquatic-phase PCE HM Due to aquatic vascular and terrestrial plant communities being reduced from all use sites, there is potential for alte ration of channel/pond morphology or geometry and/or increase in sediment deposition within the stream channel or pond. These plant commun ities provide for shelter, foraging, predator avoidance, and aquatic dispersal for juvenile and adult CRLFs. In addition, there is potential for alteration in water chemistry/quality including temperature, turbidity, and oxygen content necessary for normal growth and viability of juvenile and adult CRLFs and their food.

LOCs are exceeded for terrestrial riparian plants and for aquatic vascular plants from exposure to diuron from runoff or spray drift. LOCs for non-vascular plants are exceeded for all uses.
Modification of terrestrial-phase
PCE HM The use of diuron at all use sites may create the following modification of 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 aquatic plants ex ceed the Agency’s LOC (1.0) for most uses of diuron in California. These range from 373.33 (paved areas) to 1.01 (alfalfa aerial). Use of diuron on most use sites will exceed acute dietary- and dose-based LOC and chronic LOC for prey food items of small mammals, frogs, and invertebrates. Food source for CRLF is reduced and CRLF is indirectly
affected.

1 Habitat Modification (HM) or No effect (NE)

Based on the conclusions of this assessment, a formal consultation with the U. S.
Fish and Wildlife Service under Section 7 of the Endangered Species Act should be
initiated.

When evaluating the significance of this 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

120proportion 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.

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