Risks of Bensulide Use to Federally Listed
California Red Legged Frog
(Rana aurora draytonii)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
October 18,2007
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Primary Authors
Ibrahim Abdel-Saheb, Environmental Scientist
Fred Jenkins, Biologist
Ron Dean, Biologist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)
Secondary Review
William P. Eckel, Senior Physical Scientist
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)
Dana Spatz, Acting Branch Chief,
Environmental Risk Branch II
Environmental Fate and Effects Division (7507P)
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Table of Contents
Table of Contents
List of Tables
List of Figures
1.0 Executive Summary
2.0 Problem Formulation
2.1 Purpose
2.2 Scope
2.3 Previous Assessments
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Assessment
2.4.2 Environmental Transport Assessment
2.4.3 Mechanism of Action
2.4.4 Use Characterization
2.5 Assessed Species
2.5.1 Distribution
2.5.2 Reproduction
2.5.3 Diet
2.5.4 Habitat
2.6 Designated Critical Habitat
2.7 Action Area
2.8 Assessment Endpoints and Measures of Ecological Effect
2.8.1 Assessment Endpoints for the CRLF
2.8.2 Assessment Endpoints for Designated Critical Habitat
2.9 Conceptual Model
2.9.1 Risk Hypotheses
2.9.2 Diagram
2.10 Analysis Plan
2.10.1 Exposure Analysis
2.10.2 Effects Analysis
2.10.3 Action Area Analysis
3.0 Exposure Assessment
3.1 Label Application Rates and Intervals
3.2 Aquatic Exposure Assessment
3.2.1 Conceptual Model of Exposure
3.2.2 Existing Monitoring Data
3.2.3 Modeling Approach
3.2.3.1 Model Inputs
3.2.3.2 PRZM/EXAMS results
3.2.3.3 Residential Uses
3.2.3.4 Comparison of Modeled EECs with Available Monitoring Data
3.3 Terrestrial Plant Exposure Assessment
4.0 Effects Assessment
4.1 Evaluation of Aquatic Ecotoxicity Studies
4.1.1 Toxicity to Freshwater Fish and Aquatic-Phase Amphibians
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4.1.1.1 Freshwater Fish and Aquatic-Phase Amphibians: Acute Exposure
(Mortality) Studies 58
4.1.1.2 Freshwater Fish and Aquatic-Phase Amphibians: Chronic Exposure
(Early Life Stage and Reproduction) Studies 58
4.1.1.3 Freshwater Fish and Aquatic-Phase Amphibians: Sublethal Effects and
Additional Open Literature Information 59
4.1.2 Toxicity to Freshwater Invertebrates 59
4.1.2.1 Freshwater Invertebrates: Acute Exposure (Mortality) Studies 59
4.1.2.2 Freshwater Invertebrates: Chronic Exposure (Reproduction) Studies 60
4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Open Literature Data.... 60
4.1.3 Toxicity to Aquatic Plants 60
4.1.4 Freshwater Field Studies 60
4.2 Evaluation of Terrestrial Ecotoxicity 60
4.2.1 Toxicity to Terrestrial-Phase Amphibians 60
4.2.1.1 Birds (Terrestrial-Phase Amphibian Surrogate): Acute Exposure
(Mortality) Studies 61
4.2.1.2 Birds (Terrestrial-Phase Amphibian Surrogate): Chronic Exposure
(Reproduction) Studies 61
4.2.2 Toxicity to Mammals 61
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies 61
4.2.2.2 Mammals: Chronic Exposure (Reproduction) Studies 62
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Listed Species Levels of Concern 62
4.4 Incident Database Review 63
5.0 Risk Characterization 64
5.1 Risk Estimation 64
5.1.1 Direct Effects 64
5.1.2 Indirect Effects 67
5.1.2.1 Evaluation of Potential Indirect Effects via Reduction in Food Items 68
5.1.2.2 Evaluation of Potential Indirect Effects via Reduction in Habitat and/or
Primary Productivity (Freshwater Aquatic Plants) 75
5.1.2.3 Evaluation of Potential Indirect Effects via Reduction in Terrestrial Plant
Community (Riparian Habitat) 76
5.2 Risk Description 77
5.2.1 Direct Effects to the CRI.I 78
5.2.1.1 Aquatic Phase 78
5.2.1.2 Terrestrial Phase (Direct Effects) 78
5.2.2 Indirect Effects via Reduction in Food Items 80
5.2.2.1 Aquatic Phase 80
5.2.2.2 Terrestrial Phase 80
5.2.3 Indirect Effects via Reduction in Habitat and/or Primary Productivity
(Freshwater Aquatic Plants) 81
5.2.4 Indirect Effects via Alteration in Terrestrial Plant Community (Riparian
Habitat) 82
5.2.4.1 Importance of Riparian Habitat to the CRLF 82
5.2.4.2 Sensitivity of Riparian Zones to Bensulide 82
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6.0 Uncertainties 82
6.1 Exposure Assessment Uncertainties 82
6.1.1 Modeling Assumptions 82
6.1.2 Impact of Vegetative Setbacks on Runoff 83
6.1.3 PRZM Modeling Inputs and Predicted Aquatic Concentrations 83
6.2 Effects Assessment Uncertainties 84
6.2.1 Age Class and Sensitivity of Effects Thresholds 84
6.2.2 Extrapolation of Long-term Environmental Effects from Short-term
Laboratory Tests 84
6.2.3 Sublethal Effects 84
6.2.4 Location of Wildlife Species 85
6.2.5 Use of avian data as surrogate for amphibian data 85
6.2.6 Assumptions Associated with the Acute LOCs 85
7.0 References 87
APPENDIX A ECOLOGICAL EFFECTS DATA
APPENDIX B PRZM/EXAMS MODELING RESULTS
APPENDIX C. ESTIMATED EXPOSURES AND RISK QUOTIENTS FOR
TERRESTRIAL ANIMALS AND PLANTS (TERRPLANT VI .2.2, T-REX
V. 1.3.1 & T-HERPS V. 1.0)
APPENDIX D BIBLIOGRAPHY OF ECOTOX PAPERS
APPENDIX E. RQ METHOD AND LOCs
APPENDIX F. Probit Analysis Input and Outputs
APPENDIX G. PRODUCT FORMULATIONS CONTAINING MULTIPLE ACTIVE
INGREDIENTS
APPENDIX H. Spatial Summary for Bensulide Uses
Attachment 1: CRLF Life History
Attachment 2: CLRF Baseline Status and Cumulative Effects
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List of Tables
Table 1. California Bensulide Use by Crop: 2002-2005ab 12
Table 2. California Red-legged Frog Recovery Units with Overlapping Core Areas and
Designated Critical Habitat 18
Table 3. Labeled Uses of Concern for Bensulide in California 24
Table 4. California Average Bensulide Use per County 2002-2005* 35
Table 5. Summary of Assessment Endpoints and measures of Ecological Effects for
direct and Indirect Effects of Bensulide on the CRLF 36
Table 6. Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary constituent Elements of Designated Critical Habitat 39
Table 7 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Bensulide CRLF Assessment 51
Table 8 PRZM/EXAMS results 52
Table 9 Bensulide Measurement Endpoints and Values Selected for Use in RQ
Calculations for the Effects Determination 56
Table 10 Specific LOCs Used in this Assessment 58
Table 11. Summary of Acute and Chronic RQs for CRLF Exposed to Bensulide Surface
Water Residues* 65
Table 12. Summary of Acute and Chronic RQs for the CRLF Terrestrial Phase Exposed
to Dietary Residues of Bensulide (based on T-REX V. 1.3.1 model)*1^ 66
Table 13. Summary of Bensulide Indirect Effects RQs for the CRLF Aquatic Phase,
Aquatic Animal Food Items* 68
Table 14. Summary of Bensulide Indirect Effects RQs for the CRLF, Mammalian Food
Items* 70
Table 15. Summary of Acute and Chronic RQs for the CRLF Terrestrial Amphibian Prey
Exposed to Dietary Residues of Bensulide (based on T-HERPS V. 1.0
Model).* n 72
Table 16. Summary of Bensulide Indirect Effects RQs for the CRLF Invertebrate Food
Items.* 73
Table 17. Summary of Bensulide Indirect Effects RQs for the CRLF Aquatic Plant Food
items and Habitat.* 75
Table 18. Summary of Bensulide Indirect Effects RQs for the CRLF Terrestrial and
semi-aquatic plant Habitat.*^ 76
Table 19. Summary of Acute and Chronic RQs for the CRLF Terrestrial Phase Exposed
to Dietary Residues of Bensulide (based on T-HERPS V. 1.0 Model).* ^ *... 79
Table 20 Summary of Direct and Indirect Effects to the CRLF 86
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List of Figures
Figure 1 Bensulide (pc code: 009801) Chemical Structure 8
Figure 2. Bensulide oxon Chemical Structure 9
Figure 3. Benzenesulphonamide Chemical Structure 9
Figure 4. CRLF Reproductive Events by Month 17
Figure 5. Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF 21
Figure 6. Bensulide Initial Area of Concern 25
Figure 7. Bensulide Action Area Maps 27
Figure 8. Conceptual Model for Pesticide Effects on Aquatic Phase of the CRLF 42
Figure 9. Conceptual Model for Pesticide Effects on Terrestrial Phase of the CRLF 43
Figure 10. Conceptual Model for Pesticide Effects on Terrestrial Components of the
CRLF Critical Habitat 44
Figure 11. Conceptual Model for Pesticide Effects on Aquatic Components of CRLF
Critical Habitat 45
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1.0 Executive Summary
The purpose of this assessment is to make an "effects determination" by evaluating the potential
direct and indirect effects of the herbicide, bensulide, on the survival, growth, and reproduction
of the California red legged frog (Rana aurora draytonii). In addition, this assessment evaluates
the potential for bensulide use to result in the modification of designated critical habitat for the
California red legged frog (CRLF). The structure of this risk assessment is based on guidance
contained in U.S. EPA's Guidance for Ecological Risk Assessment (U.S. EPA 1998), the
Services' Endangered Species Consultation Handbook (USFWS/NMFS 1998) and is consistent
with procedures and methodology outlined in the Overview Document (U.S. EPA 2004) and
reviewed by the U.S. Fish and Wildlife Service and National Marine Fisheries Service
(USFWS/NMFS 2004).
Bensulide is a pre-emergent organophosphate herbicide which inhibits meristematic root tissues
and inhibits seedling growth. It is usually applied to bare ground before crops are planted. It is
registered for the control of grasses and broadleaf weeds in agricultural crops, residential grass
lawns, golf courses, turf farms, rights-of-way, and in landscaping applications. Bensulide is used
in a wide variety of different application amounts and is used both as an emulsifiable concentrate
and as a granular application.
Bensulide may move through the environment and be transported away from the site of
application by run-off or spray drift (in the case of the EC formulation). The major degradate,
bensulide oxon is not considered in this assessment because (1) due to the persistence of the
parent, very little of the oxon is expected to form, and (2) no oxon toxicity data is available. A
parent-only exposure assessment is equivalent to a total-toxic-residue assessment because of the
persistence of the parent compound. The oxon is not expected to be more toxic than the parent;
therefore no further assessment is needed.
The initial area of concern for bensulide is limited to those agricultural lands and turf and lawns
where it is applied within the state of California. The initial area of concern represents the
"footprint" of where bensulide could potentially be used based on land cover information. The
initial area of concern is then expanded as necessary based on the potential for direct and indirect
effects above levels of concern (LOCs) which considers the fate and transport properties of the
compound. The action area is defined by the land use classes designated to represent the crops
where bensulide is used in a conservative fashion and account for the fate and transport
characteristics of the pesticide, including transport in streams and rivers, spray drift, and long-
range transport. In general, the action area is defined as the general agricultural cropland and
orchard land classes within the state of California plus those areas beyond this initial area of
concern where effects above Agency levels of concern may occur. For bensulide these areas
beyond the initial area of concern are defined by the distance spray drift exposure to CRLF
habitat components that will exceed the Agency LOC. Based on EFED's spray drift analysis this
distance is a 2792 foot wide buffer around the habitat of the CRLF.
Consistent with the methodology specified in the Agency's Overview Document (U.S. EPA,
2004a), screening-level Estimated Environmental Concentrations (EECs), based on the
PRZM/EXAMS static water body scenario, were used to derive risk quotients (RQs) for all
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relevant agricultural bensulide uses within the action area. RQs based on screening-level EECs
were used to distinguish "no effect" from "may effect" determinations for direct/indirect effects
to the CRLFs and the critical habitat impact analysis.
The assessment endpoints for the CRLF included direct toxic effects on survival, reproduction,
and growth of individual frogs, as well as indirect effects, such as reduction of the food source
and/or modification of habitat. Risk quotients (RQs) for direct acute effects to the CRLF were
calculated using acute toxicity data from the registrant submitted fish (CRLF surrogate species)
acute toxicity data. See table below RQS for direct chronic (reproductive, growth) effects were
calculated using an estimated chronic NOAEC for amphibians based on the acute-to-chronic
ratio for rainbow trout. To assess potential indirect effects to the CRLF via effects to potential
prey (and consequently a reduction of available food items), toxicity data for freshwater fish and
invertebrates as well as birds and mammals were considered. The available registrant submitted
phytotoxicity studies were used to determine the potential risk to primary producers, and in turn,
potential indirect effects to the CRLF.
Federally designated critical habitat has been established for the CRLF. Adverse modifications
to the primary constituent elements of designated critical habitat, as defined in 50 CFR
414.12(b), were also evaluated. PCEs evaluated as part of this assessment include the following:
Breeding aquatic habitat;
Non-breeding aquatic habitat;
Upland habitat; and
Dispersal habitat.
RQs are derived as quantitative estimates of potential high-end risk. Acute and chronic RQs are
compared to the Agency's Levels of Concern (LOCs) to identify instances where bensulide use
within the action area has the potential to adversely affect the CRLF or modify designated
critical habitat. When RQs for a particular type of effect are below LOCs, the pesticide's use is
considered to have "no effect" on the CRLF or its designated critical habitat. Where RQs exceed
LOCs, a potential to cause adverse effects or habitat modification is identified, leading to a
conclusion of "may affect". If bensulide use "may affect" the CRLF, and/or cause modification
to designated critical habitat, the best available information and data are considered to refine the
potential for exposure and effects, and distinguish actions that are Not Likely to Adversely
Affect (NLAA) from those that are Likely to Adversely Affect (LAA). Effects determinations
for direct/indirect effects to the CRLF and the critical habitat impact analysis are summarized
below and presented in Tables 1.1.
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Tahlc 1 1 Siiiiiiii;ii'\ nfcl'kvlsdclciiiiiiKiiK.iis loi dnccl indiicu d'l'ccls lo ihc ( kl.l and lis critical h;ihil;il
\sscsslllClll 1 Jltlpnilll
i: Heels
dclcrminaikHi
liasis lor 1 )elenniii;iik>n
Aquatic Phase
(Eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects
Survival, growth, and
reproduction of CRLF
LAA
All acute RQs are above the listed LOC for surrogate species
(rainbow trout) for all the modeled bensulide uses.
Indirect Effects and Critical Habitat Effects
Reduction or
modification of
invertebrate aquatic prey
base
LAA
The Agency presumed risk of chronic effects to the CRLF aquatic
invertebrate prey for all modeled uses (See Risk Description Sec.
5.2.2.1 for explanation of presumption).
Reduction or
modification of aquatic
vertebrate prey base
NLAA
No LOC exceedance for acute or chronic risks to fish or
amphibian prey base.
Reduction or
modification of aquatic
plant community
No Effect
No LOC Exceedances for any aquatic plant species
Degradation of riparian
vegetation
LAA
The levels of concern for risk to nonlisted plants in semiaquatic
areas (which may include plants inhabiting riparian areas) are
exceeded for bensulide granular and EC formulation uses on turf
and lawn.
Terrestrial Phase
(Juveniles and Adults)
Direct Effects
Survival, growth, and
reproduction of CRLF
LAA
The dietary based RQs calculated by TREX and THERPS (as a
refinement) exceed the acute and chronic LOC for all modeled
bensulide uses.
Indirect Effects and Critical Habitat Effects
Reduction or
modification of
terrestrial prey base
LAA
The level of concern is exceeded for risk to invertebrate,
mammalian and amphibian prey of the CRLF.
Degradation of riparian
vegetation
LAA
The levels of concern for risk to nonlisted plants in semiaquatic
areas (which may include plants inhabiting riparian areas) are
exceeded for bensulide granular and EC formulation uses on turf
and lawn.
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When evaluating the significance of this risk assessment's direct/indirect and adverse habitat
modification effects determinations, it is important to note that pesticide exposures and predicted
risks to the species and its resources (i.e., food and habitat) are not expected to be uniform across
the action area. In fact, given the assumptions of drift and downstream transport (i.e., attenuation
with distance), pesticide exposure and associated risks to the species and its resources are
expected to decrease with increasing distance away from the treated field or site of application.
Evaluation of the implication of this non-uniform distribution of risk to the species would require
information and assessment techniques that are not currently available. Examples of such
information and methodology required for this type of analysis would include the following:
Enhanced information on the density and distribution of CRLF life stages within
specific recovery units and/or designated critical habitat within the action area.
This information would allow for quantitative extrapolation of the present risk
assessment's predictions of individual effects to the proportion of the population
extant within geographical areas where those effects are predicted. Furthermore,
such population information would allow for a more comprehensive evaluation of
the significance of potential resource impairment to individuals of the species.
Quantitative information on prey base requirements for individual aquatic- and
terrestrial-phase frogs. While existing information provides a preliminary picture
of the types of food sources utilized by the frog, it does not establish minimal
requirements to sustain healthy individuals at varying life stages. Such
information could be used to establish biologically relevant thresholds of effects
on the prey base, and ultimately establish geographical limits to those effects.
This information could be used together with the density data discussed above to
characterize the likelihood of adverse effects to individuals.
Information on population responses of prey base organisms to the pesticide.
Currently, methodologies are limited to predicting exposures and likely levels of
direct mortality, growth or reproductive impairment immediately following
exposure to the pesticide. The degree to which repeated exposure events and the
inherent demographic characteristics of the prey population play into the extent to
which prey resources may recover is not predictable. An enhanced understanding
of long-term prey responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and together
with the information described above, a more complete prediction of effects to
individual frogs and potential modification to critical habitat.
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2.0 Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By identifying the
important components of the problem, it focuses the assessment on the most relevant life history
stages, habitat components, chemical properties, exposure routes, and endpoints. The structure
of this risk assessment is based on guidance contained in U.S. EPA's Guidance for Ecological
Risk Assessment {U.S. EPA, 1998), the Services' Endangered Species Consultation Handbook
(USFWS/NMFS, 1998) and is consistent with procedures and methodology outlined in the
Overview Document (U.S. EPA, 2004) and reviewed by the U.S. Fish and Wildlife Service and
National Marine Fisheries Service (USFWS/NMFS, 2004).
2.1 Purpose
The purpose of this listed species assessment is to evaluate potential direct and indirect effects on
individuals of the federally listed "Threatened" California red-legged frog (Rana aurora
draytonii) (CRLF) arising from FIFRA regulatory actions regarding use of Bensulide, which is
registered for the control of grasses and broadleaf weeds in agricultural crops, rights-of-way,
landscaping applications and in lawn care (professional and homeowner) applications. In
addition, this assessment evaluates whether these actions can be expected to result in the
modification of the species' critical habitat. Key biological information for the CRLF is
included in Section 2.5, and designated critical habitat information for the species is provided in
Section 2.6 of this assessment. This ecological risk assessment has been prepared as part of the
Center for Biological Diversity (CBD) vs. EPA et al. (Case No. 02-1580-JSW (JL)) settlement
entered in the Federal District Court for the Northern District of California on October 20, 2006.
In this listed species assessment, direct and indirect effects to the CRLF and potential
modification to its critical habitat are evaluated in accordance with the methods (both screening-
level and species-specific refinements, when appropriate) described in the Agency's Overview
Document (U.S. EPA, 2004). In addition, in accordance with two interim policies, terrestrial
invertebrate LOCs will be used and terrestrial amphibian modeling will be used as a refinement.
Use of such information is consistent with the guidance provided in the Overview Document
(U.S. EPA, 2004), which specifies that "the assessment process may, on a case-by-case basis,
incorporate additional methods, models, and lines of evidence that EPA finds technically
appropriate for risk management objectives" (Section V, page 31 of U.S. EPA, 2004).
In accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of Bensulide are based on an action area. The action area is considered to be the
area directly or indirectly affected by the federal action, as indicated by the exceedance of
Agency Levels of Concern (LOCs) used to evaluate direct or indirect effects. It is acknowledged
that the action area for a national-level FIFRA regulatory decision associated with a use of
bensulide may potentially involve numerous areas throughout the United States and its
territories. However, for the purposes of this assessment, attention will be focused on relevant
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sections of the action area including those geographic areas associated with locations of the
CRLF and its designated critical habitat within the state of California.
As part of the "effects determination," one of the following three conclusions will be reached
regarding the potential for registration of Bensulide at the use sites described in this document to
affect CRLF individuals and/or result in the modification of designated CRLF critical habitat:
"No effect";
"May affect, but not likely to adversely affect"; or
"May affect and likely to adversely affect".
Critical habitat identifies specific areas that have the physical and biological features, (known as
primary constituent elements or PCEs) essential to the conservation of the listed species. The
PCEs for CRLF's are aquatic and upland areas where suitable breeding and non-breeding aquatic
habitat is located, interspersed with upland foraging and dispersal habitat (Section 2.6).
If the results of initial screening-level assessment methods show no direct or indirect effects (no
LOC exceedances) upon individual CRLF's or upon the PCEs of the species' designated critical
habitat, a "no effect" determination is made for the FIFRA regulatory action regarding Bensulide
as it relates to this species and its designated critical habitat. If, however, direct or indirect
effects to individual CRLF's are anticipated and/or effects may impact the PCEs of the CRLF's
designated critical habitat, a preliminary "may affect" determination is made for the FIFRA
regulatory action regarding Bensulide.
If a determination is made that use of Bensulide within the action area(s) associated with the
CRLF "may affect" this species and/or its designated critical habitat, additional information is
considered to refine the potential for exposure and for effects to the CRLF and other taxonomic
groups upon which these species depend (e.g.., aquatic and terrestrial vertebrates and
invertebrates, aquatic plants, riparian vegetation, etc.). Additional information, including spatial
analysis (to determine the geographical proximity of CRLF habitat and Bensulide use sites) and
further evaluation of the potential impact of Bensulide on the PCEs is also used to determine
whether modification to designated critical habitat may occur. Based on the refined information,
the Agency uses the best available information to distinguish those actions that "may affect, but
are not likely to adversely affect" from those actions that "may affect and are likely to adversely
affect" the CRLF and/or the PCEs of its designated critical habitat. This information is presented
as part of the Risk Characterization in Section 5 of this document.
The Agency believes that the analysis of direct and indirect effects to listed species provides the
basis for an analysis of potential effects on the designated critical habitat. Because bensulide is
expected to directly impact living organisms within the action area (defined in Section 2.7),
critical habitat analysis for Bensulide is limited in a practical sense to those PCEs of critical
habitat that are biological or that can be reasonably linked to biologically mediated processes
(i.e., the biological resource requirements for the listed species associated with the critical habitat
or important physical aspects of the habitat that may be reasonably influenced through biological
processes). Activities that may destroy or adversely modify critical habitat are those that alter
the PCEs and appreciably diminish the value of the habitat. Evaluation of actions related to use
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of Bensulide that may alter the PCEs of the CRLF's critical habitat form the basis of the critical
habitat impact analysis. Actions that may affect the CRLF's designated critical habitat have
been identified by the Services and are discussed further in Section 2.6.
2.2 Scope
Bensulide [S-(0,0-Diisopropyl phosphorodithioate) ester of N-(2- mercapto) benzene-
sulfonamide] is a pre-emergent herbicide registered for the control of grasses and broadleaf
weeds in agricultural crops such as kohl crops, cucurbits, leafy vegetables, legume, onion and
garlic. It is also used on residential grass lawns, golf courses, turf farms, rights-of-way and in
landscaping applications. County level usage data for bensulide were obtained from California's
Department of Pesticide Regulation Use Reporting (CDPR PUR) database. Reported usage
information considered in this assessment spans from 2001-2005.
There are a number of uses reported in the CDPR PUR database that either are misuses or entry
errors in the database for they are not supported by past or current state (Section 24c) or national
(Section 3) labels for bensulide. These uses are not part of the FIFRA regulatory action and have
not been included in this assessment but are identified here for completeness. Between 2002-
2005 these combined uses comprised a total of approximately 0.40% of all bensulide applied in
CA: uncultivated non-agricultural (<0.01%), vertebrate control (<0.01%), commodity fumigation
(<0.01%), rangeland (<0.01%),water area (<0.01%), unspecified vegetable (<0.01%), structural
pest control (<0.01%), uncultivated agricultural (0.02%), soil fumigation (0.08%), unknown
(0.09%) and unspecified leafy vegetable (0.14%). Some uses may potentially be emergency uses,
which are federal actions which are typically of limited use and duration. ESA effects would be
considered at the time when the emergency use(s) were granted and are not included in this
assessment. Bensulide was also used in research (i.e. research commodity record) (0.02%); this
research occurred in Fresno, Monterey, San Benito, Solano, Tulare and Yolo Counties. This use
will be excluded as well from this assessment. Experimental use permits are federal actions that
are taken for specific research projects which are typically of limited use and acreage. Each
experimental use is considered on a case-by-case basis, limited to the year that the permit was
granted; ESA effects would be considered at the time when the experimental use permit was
granted.
The end result of the EPA pesticide registration process (the FIFRA regulatory action) is an
approved product label. The label is a legal document that stipulates how and where a given
pesticide may be used. Product labels (also known as end-use labels) describe the formulation
type (e.g., liquid or granular), acceptable methods of application, approved use sites, and any
restrictions on how applications may be conducted. Thus, the use or potential use of bensulide in
accordance with the approved product labels for California is "the action" being assessed.
Although current registrations of bensulide allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of bensulide in portions
of the action area that are reasonably assumed to be biologically relevant to the CRLF and its
designated critical habitat. Further discussion of the action area for the CRLF and its critical
habitat is provided in Section 2.7.
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This assessment concentrates on the parent bensulide (Figure 1) because it is persistent, as is also
its major degradate bensulide oxon (Figure 2) (N-[(2-(diisopropoxyphosphinoylthio)-l-ethyl] -
benzenesulfonamide). The minor degradate benzenesulphonamide (Figure 3) concentrations are
expected to be low. In an aerobic soil metabolism study, bensulide oxon reached a maximum
concentration of 13.8% of the applied at 270 days post treatment and decreased to 10.1% at 360
days, and benzenesulfonamide reached a maximum level of 0.52% at 360 days. Because the
inherent toxicity of the oxon is unknown, the ecological relevance of oxon residues potentially
present in the environment cannot be assessed. It is therefore assumed that the toxicity of the
oxon is equivalent to that of the parent.
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of
active ingredients, either those of multiple active ingredients in product formulations or those
produced by the applicator. With regards to product formulations of active ingredients (that is, a
registered product containing more than one active ingredient), each active ingredient is subject
to an individual risk assessment regarding each active ingredient separately, for use on a
particular site. If effects data are available for a formulated product containing more than one
active ingredient, they may be used qualitatively or quantitatively in accordance with the
Agency's Overview Document and the Services' Evaluation Memorandum (U.S. EPA, 2004;
USFWS/NMFS, 2004). There are two registered products that contain bensulide as one of two
active ingredients. Proturf Goosegrass and Crabgrass Control (EPA Reg. No. 00053800164) and
Anderson's Goose and Crabgrass control (EPA Reg. No. 00919800176) are both mixtures of
bensulide and the oxadiazole herbicide oxadiazon at 5.25% and 1.31% respectively
There are many variables within the landscape covered by this risk assessment that can affect
predicted exposures and effects of bensulide in any given area. Even within contiguous Red-
Legged Frog critical habitats in California there is great variability in land use and cover,
topography, and precipitation.
Figure 1 Bensulide (pc code: 009801) Chemical Structure
T*
8
-------
Figure 2. Bensulide oxon Chemical Structure
HjC
ฆo
ฆNH
Figure 3. Benzenesulphonamide Chemical Structure
-------
2.3 Previous Assessments
Three previously published, relevant risk assessments for Bensulide are the 1998 Bensulide
Reregi strati on Eligibility Document (EPA, 1998), the 2000 Interim Reregi strati on Eligibility
Decision (U.S. EPA, 2000) and the 2000 Addendum to the Bensulide RED: Revised Risk
Assessment and Risk Characterization for Risk to Aquatic Organisms from Use on Turf (U.S.
EPA, 2000). No comparison was made to the labeled usages for the previous assessments to
current ones. This assessment focuses only on current label usage information. For specific
details not mentioned in this assessment, these documents can be consulted.
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Assessment
Although the environmental fate data base for bensulide is not complete, information from
acceptable laboratory studies indicates bensulide is persistent. Neither abiotic hydrolysis nor
photolysis are major degradation processes in water or on soil surfaces. The main route of
dissipation of bensulide appears to be aerobic soil metabolism with a reported half-life of 1 year.
Under aerobic conditions it appears that mineralization of bensulide to carbon dioxide (CO2) and
immobilization as unextractable residues are the major mechanisms of dissipation in the soil.
Under anaerobic soil conditions bensulide did not degrade. Based on the lack of degradation
under laboratory conditions, it is predicted that bensulide will be extremely persistent in
anaerobic terrestrial ecosystems.
Information from acceptable laboratory studies indicates that bensulide is not mobile in the four
soils tested (Koc's ranged from 1,433 to 4,326 ml/g); however, the major degradates bensulide
oxon (N-[(2-(diisopropoxyphosphinoylthio) - 1 -ethyl] - benzenesulfonamide) and
benzenesulphonamide ranged from mobile to highly mobile in the same four test soils. Bensulide
has the potential to be transported dissolved in water and on suspended sediment in runoff to
surface waters where, based on laboratory data, it is expected to persist.
The environmental fate assessment developed from the results of the laboratory studies
has not been confirmed by acceptable field dissipation information. Of eight field dissipation
studies submitted none were acceptable. While half-life of bensulide was reported in these
studies to range from 8-34 days in California and from 91-210 days in Mississippi, these values
are questionable given none of the studies exhibited a consistent decline of parent compound.
Additionally, none of the studies is acceptable because the application rate could not be
confirmed and bare ground plots were not used. The study plots had been planted to turf, and no
mention was made of how the turf and thatch in the samples were separated from the soil or of
any attempt to extract residues from the turf or thatch. In a currently unacceptable but
upgradeable field dissipation study, calculated first order half-lives for bensulide in the top 6
inches of soil was 80.4 days. Bensulide and its major degradate bensulide oxon were found only
in the top 6 inches of the soil.
10
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With a reported fish whole body bioconcentration factor (BCF) of 550 and a whole body
elimination of 98% after 14 days depuration, bensulide does not appear to have the potential to
significantly bioaccumulate in fish.
2.4.2 Environmental Transport Assessment
Ground spray applications may potentially result in transport and loading of bensulide to off-
field soil and foliage via spray drift. Granular ground application methods are not expected to
result in granules being distributed to off-field soil; however on-field bensulide soil residues,
from either ground spray or granular application methods, have the potential to be transported
both dissolved in water and on suspended soil in runoff to off-field terrestrial areas and to surface
waters. Once in the aquatic system it is expected to partition primarily to sediment where it will
be relatively stable. However as discussed in the fate section above, based on results of a fish
bioconcentration study in which the BCF was not significant and the depuration rate was
relatively fast, biomagnification up through the food web is not expected to be a significant
transport pathway. In general deposition of drifting or run-offloads are expected to be greatest
close to the site of application As discussed in the previous fate section, bensulide is not
expected to leach to ground water.
In general, deposition of drifting or volatilized pesticides is expected to be greatest close to the
site of application. Computer models of spray drift (AgDRIFT or AgDISP) are used to
determine if the exposures to aquatic and terrestrial organisms are below the Agency's Levels of
Concern (LOCs). If the limit of exposure that is below the LOC can be determined using
AgDRIFT or AgDISP, longer-range transport is not considered in defining the action area. For
example, if a buffer zone <1,000 feet (the optimal range for AgDRIFT and AgDISP models)
results in terrestrial and aquatic exposures that are below LOCs, no further drift analysis is
required. If exposures exceeding LOCs are expected beyond the standard modeling range of
AgDRIFT or AGDISP, the Gaussian extension feature of AgDISP may be used. In addition to
the use of spray drift models to determine potential off-site transport of pesticides, other factors
such as available air monitoring data and the physicochemical properties of the chemical are also
considered.
Due to model limitations, it may not be possible to provide a quantitative estimate of
exposure with known uncertainty, beyond the range of Ag-Drift v. 2.1 or Ag-DISP.
Cannot model aquatic concentrations resulting from long range transport beyond the range of
the Gaussian extension of Ag-Disp; therefore, analysis will be qualitative if exposures exceed
LOC at the limit of the Gaussian extension range.
2.4.3 Mechanism of Action
Bensulide is a pre-emergent organophosphate herbicide which inhibits meristematic root tissues
(inhibits cell division in root tips) and inhibits seedling growth by conjugation of acetyl co-
11
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enzyme A, specific site unknown (Ware, 1978; Martin, 2000). It is usually applied to bare
ground before crops are planted. It is not translocated from foliage into plants.
The mode of toxic action to non-target organisms (e.g., mammals) is via the inhibition of
cholinesterase and accumulation of acetylcholine at the nerve synapses, resulting in classic
symptoms of organophosphate poisoning.
2.4.4 Use Characterization
The California usages for bensulide are presented in Table 1. California Bensulide Use by Crop:
2002-2005ab.The agricultural use rate is typically 5-6 lbs ai acre, and the 6 ai lb rate is often used.
An exception to this occurs in southwest deserts, where it is usually applied in the fall and again
to a second crop (usually lettuce) about 120 days later. Up to 6 lbs ai/acre can be applied for each
crop for a maximum of 12 lbs ai/acre/year. Sprinkler and chemigation systems are used in
Southwest deserts to deliver bensulide and often use rates as low as 4 lb ai/acre per application.
The highest application rate is a ground application of 32 lb ai/A on golf course turf.
Table 1. California Bensulide Use by Crop: 2002-2005ab.
Crop
Total
Pounds
2002-2005
AVG
Annual
Pounds
Applied
per Year
Mean
Annual
Area
Treated
(acres)
AVG Annual
Pounds Applied
per AVG Annual
Area Treated
(acres)
Grand Total
900200.8
225367.9
81772.63
309.37
LETTUCE,LEAF
263815.17
65953.79
18874.32
3.49
LETTUCE, HEAD
208478.64
52119.66
16271.99
3.20
BROCCOLI
110619.30
27654.83
8433.56
3.28
MUSTARD
53692.27
13423.07
2549.14
5.27
ONION, DRY
49933.00
12483.25
4632.15
2.69
CANTALOUPE
47899.43
11974.86
5203.29
2.30
CABBAGE
20053.50
5013.37
1175.46
4.27
CHINESE CABBAGE
(NAPPA)
19449.96
4862.49
1004.47
4.84
MELON
16112.43
4028.11
2545.79
1.58
LANDSCAPE
MAINTENANCE
14329.29
3582.32
37.56
95.38
PEPPER, FRUITING
12812.80
3203.20
779.03
4.11
BOKCHOY
10341.03
2585.26
554.96
4.66
CILANTRO
7990.42
1997.60
496.04
4.03
WATERMELON
6110.11
1527.53
387.56
3.94
CHINESE GREENS
5579.13
1394.78
276.74
5.04
ENDIVE (ESCAROLE)
5334.52
1333.63
476.65
2.80
COLLARD
4772.29
1193.07
236.53
5.04
GAI LON
4215.62
1371.63
268.35
5.11
CAULIFLOWER
3997.65
999.41
375.29
2.66
KALE
3421.83
855.46
208.15
4.11
FENNEL
3178.09
794.52
141.92
5.60
CHICORY
2678.45
669.61
263.98
2.54
ARRUGULA
2560.02
640.00
137.94
4.64
12
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Crop
Total
Pounds
2002-2005
AVG
Annual
Pounds
Applied
per Year
Mean
Annual
Area
Treated
(acres)
AVG Annual
Pounds Applied
per AVG Annual
Area Treated
(acres)
CUCUMBER
2471.41
617.85
163.40
3.78
MIZUNA
2463.63
615.91
135.42
4.55
RAPPINI
1896.26
474.07
107.06
4.43
SQUASH, SUMMER
1704.42
426.11
144.32
2.95
N-OUTDR FLOWER
1673.81
418.45
76.51
5.47
PARSLEY
1629.79
407.45
78.51
5.19
SQUASH
1412.12
353.03
86.89
4.06
VEGETABLES, LEAFY3
1296.08
324.02
72.99
4.44
CANOLA (RAPE)
1226.46
306.61
94.50
3.24
CELERY
1136.23
284.06
52.08
5.45
PUMPKIN
1115.92
278.98
54.01
5.17
EGGPLANT
547.56
136.89
29.36
4.66
BRUSSELS SPROUT
536.51
134.13
60.42
2.22
PEAS
474.92
118.73
29.75
3.99
KOHLRABI
468.63
117.16
36.13
3.24
CARDOON
432.56
108.14
24.34
4.44
DANDELION GREEN
418.68
104.67
16.39
6.39
PEPPER, SPICE
417.45
104.36
33.18
3.15
SPINACH
382.53
95.63
29.69
3.22
SQUASH, ZUCCHINI
312.32
78.08
26.25
2.97
BEET
208.92
52.23
10.40
5.02
TURF/SOD
100.01
25.00
3.75
6.67
RADISH
80.31
20.08
4.63
4.34
ARTICHOKE, GLOBE
79.32
19.83
5.00
3.97
HERB, SPICE
65.44
16.36
8.25
1.98
VEGETABLE3
60.48
15.12
3.63
4.17
SQUASH, WINTER
55.52
13.88
2.80
4.96
COTTON
44.67
11.17
25.25
0.44
GAI CHOY
40.65
10.16
1.95
5.21
SWISS CHARD
23.80
5.95
1.50
3.97
CORN, HUMAN
CONSUMPTION
19.15
4.79
1.61
2.97
GRAPE, WINE
12.94
3.24
9.38
0.35
N-GRNHS FLOWER"
10.21
2.55
8.73
0.29
ONION, GREEN
4.17
1.04
3.00
0.35
N-OUTDR PLANTS IN
CONTAINERS"
2.73
0.68
0.63
1.09
N-GRNHS PLANTS IN
CONTAINERS"
0.19
0.05
15000.05
0.00
w Use reports in CA DPR PUR that represent misuse or misreporting and are excluded in this assessment
ฎ Use excluded in this assessment because it will not affect CRLF.
Analysis of labeled use information is the critical first step in evaluating the federal action. The
current label for bensulide represents the FIFRA regulatory action; therefore, labeled use and
application rates specified on the label form the basis of this assessment. The assessment of use
13
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information is critical to the development of the action area and selection of appropriate
modeling scenarios and inputs. The use analysis is summarized in Appendix B.
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis of both
national- and county-level usage information (LUIS report, 12/08/2006) using state-level usage
data obtained from USDA-NASS1, Doane (www.doane.com); the full dataset is not provided due
to its proprietary nature), and the California's Department of Pesticide Regulation Pesticide Use
Reporting (CDPR PUR) database2 . CDPR PUR is considered a more comprehensive source of
usage data than USDA-NASS or EPA proprietary databases, and thus the usage data reported for
Bensulide by county in this California-specific assessment were generated using CDPR PUR
data. Usage data are averaged together over the years 2000 to 2005 to calculate average annual
usage statistics by county and crop for Bensulide, including pounds of active ingredient applied
and base acres treated. California State law requires that every pesticide application be reported
to the state and made available to the public. The summary of Bensulide usage for all use sites,
including both agricultural and non-agricultural, is provided in Appendix B.
2.5 Assessed Species
The CRLF was federally listed as a threatened species by USFWS effective June 24, 1996
(USFWS, 1996). It is one of two subspecies of the red-legged frog and is the largest native frog
in the western United States (USFWS, 2002). A brief summary of information regarding CRLF
distribution, reproduction, diet, and habitat requirements is provided in Sections 2.5.1 through
2.5.4, respectively.
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 (See Figure 5).
2.5.1 Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically inhabited 46
counties in California including the Central Valley and both coastal and interior mountain ranges
(USFWS, 1996). Its range has been reduced by about 70%, and the species currently resides in
22 counties in California (USFWS, 1996). The species has an elevation range of near sea level
to 1,500 meters (5,200 feet) (Jennings and Hayes, 1994); however, nearly all of the known CRLF
populations have been documented below 1,050 meters (3,500 feet) (USFWS, 2002).
Populations currently exist along the northern California coast, northern Transverse Ranges
(USFWS 2002), foothills of the Sierra Nevada (5-6 populations), and in southern California
south of Santa Barbara (two populations) (Fellers, 2005a). Relatively larger numbers of CRLF's
are located between Marin and Santa Barbara Counties (Jennings and Hayes, 1994). A total of
1 United States Department of Agriculture (USDA), National Agricultural Statistics Service (NASS) Chemical Use
Reports provide summary pesticide usage statistics for select agricultural use sites by chemical, crop and state. See
http://www.usda.gOv/nass/pubs/estindxl.htm#agchem.
2 The California Department of Pesticide Regulation's Pesticide Use Reporting database provides a census of
pesticide applications in the state. See http://www.cdpr.ca.gov/docs/pur/purmain.htm.
14
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243 streams or drainages are believed to be currently occupied by the species, with the greatest
numbers in Monterey, San Luis Obispo, and Santa Barbara counties (USFWS, 1996). Occupied
drainages or watersheds include all bodies of water that support CRLFs (i.e., streams, creeks,
tributaries, associated natural and artificial ponds, and adjacent drainages), and habitats through
which CRLF's can move (i.e., riparian vegetation, uplands) (USFWS, 2002).
The distribution of CRLF's within California is addressed in this assessment using four
categories of location including recovery units, core areas, designated critical habitat, and known
occurrences of the CRLF reported in the California Natural Diversity Database (CNDDB) that
are not included within core areas and/or designated critical habitat (see Figure 5). Recovery
units, core areas, and other known occurrences of the CRLF from the CNDDB are described in
further detail in this section, and designated critical habitat is addressed in Section 2.6.
Recovery Units
Eight recovery units have been established by USFWS for the CRLF. These areas are
considered essential to the recovery of the species, and the status of the CRLF "may be
considered within the smaller scale of the recovery units, as opposed to the statewide range"
(USFWS 2002). Recovery units reflect areas with similar conservation needs and population
status, and therefore, similar recovery goals. The eight units described for the CRLF are
delineated by watershed boundaries defined by US Geological Survey hydrologic units and are
limited to the elevational maximum for the species of 1,500 m above sea level. The eight
recovery units for the CRLF are listed in Table 2 and shown in Figure 5.
Core Areas
USFWS has designated 35 core areas across the eight recovery units to focus their recovery
efforts for the CRLF (see Table 2). Figure 5 summarizes the geographical relationship among
recovery units, core areas, and designated critical habitat. The core areas, which are distributed
throughout portions of the historic and current range of the species, represent areas that allow for
long-term viability of existing populations and reestablishment of populations within historic
range. These areas were selected because they: 1) contain existing viable populations; or 2) they
contribute to the connectivity of other habitat areas (USFWS, 2002). Core area protection and
enhancement are vital for maintenance and expansion of the CRLF's distribution and population
throughout its range.
For purposes of this assessment, designated critical habitat, currently occupied (post-1985) core
areas, and additional known occurrences of the CRLF from the CNDDB are considered. Each
type of spatial information is evaluated within the broader context of recovery units. For
example, if no labeled uses of Bensulide occur (or if labeled uses occur at predicted exposures
less than the Agency's LOCs) within an entire recovery unit, a "no effect" determination would
be made for all designated critical habitat, currently occupied core areas, and other known
CNDDB occurrences within that recovery unit. Historically occupied sections of the core areas
15
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are not evaluated as part of this assessment because the USFWS Recovery Plan (USFWS, 2002)
indicates that CRLF's are extirpated from these areas. A summary of currently and historically
occupied core areas is provided in Table 2 (currently occupied core areas are bolded). While
core areas are considered essential for recovery of the CRLF, core areas are not federally-
designated critical habitat, although designated critical habitat is generally contained within these
core recovery areas. It should be noted, however, that several critical habitat units are located
outside of the core areas, but within the recovery units. The focus of this assessment is currently
occupied core areas, designated critical habitat, and other known CNDDB CRLF occurrences
within the recovery units. Federally-designated critical habitat for the CRLF is further explained
in Section 2.6.
Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in California.
The CNDDB serves as a repository for historical and current species location sightings.
Information regarding known occurrences of CRLF's outside of the currently occupied core
areas and designated critical habitat is considered in defining the current range of the CRLF.
See: http://www.dfg.ca.gov/bdb/html/cnddb_info.html for additional information on the
CNDDB.
2.5.2 Reproduction
CRLF's breed primarily in ponds; however, they may also breed in quiescent streams, marshes,
and lagoons (Fellers, 2005a). According to the Recovery Plan (USFWS, 2002), CRLF's breed
from November through late April. Peaks in spawning activity vary geographically; Fellers
(2005b) reports peak spawning as early as January in parts of coastal central California. Eggs
are fertilized as they are being laid. Egg masses are typically attached to emergent vegetation,
such as bulrushes (Scirpus spp.) and cattails (Typha spp.) or roots and twigs, and float on or near
the surface of the water (Hayes and Miyamoto, 1984). Egg masses contain approximately 2000
to 6000 eggs ranging in size between 2 and 2.8 mm (Jennings and Hayes, 1994). Embryos hatch
10 to 14 days after fertilization (Fellers 2005a) depending on water temperature. Egg predation
is reported to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn, 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles (terrestrial-
phase), typically between May and September (Jennings and Hayes, 1994; USFWS, 2002);
tadpoles have been observed to over-winter (delay metamorphosis until the following year)
(Fellers, 2005b; USFWS, 2002). Males reach sexual maturity at 2 years, and females reach
sexual maturity at 3 years of age; adults have been reported to live 8 to 10 years (USFWS, 2002).
Figure 4 depicts CRLF annual reproductive timing.
16
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Figure 4. CRLF Reproductive Events by Month
J
F
M
A
M
J
J
A
S
o
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter)
Orange =
Adults and juveniles can be present all year
2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied specifically, it is
assumed that their diet is similar to that of other frog species, with the aquatic phase feeding
exclusively in water and consuming diatoms, algae, and detritus (USFWS, 2002). Tadpoles filter
and entrap suspended algae (Seale and Beckvar, 1980) via mouthparts designed for effective
grazing of periphyton (Wassersug, 1984, \; Kupferberg et al., 1994; Kupferberg, 1997; Altig and
McDiarmid, 1999).
Juvenile and adult CRLF's forage in aquatic and terrestrial habitats and their diet differs greatly
from that of larvae. The main food source for juvenile aquatic- and terrestrial-phase CRLF's is
thought to be aquatic and terrestrial invertebrates found along the shoreline and on the water
surface. Hayes and Tennant (1985) report, based on a study examining the gut content of 35
juvenile and adult CRLF's, that the species feeds on as many as 42 different invertebrate taxa,
including Arachnida, Amphipoda, Isopoda, Insecta, and Mollusca. The most commonly observed
prey species were larval alderflies (Sialis cf. californica), pillbugs (Armadilliadrium vu/gare),
and water striders (Gerris sp). The preferred prey species, however, was the sowbug (Hayes and
Tennant, 1985). This study suggests that CRLF's forage primarily above water, although the
authors note other data reporting that adults also feed under water, are cannibalistic, and
consume fish. For larger CRLF's, over 50% of the prey mass may consists of vertebrates such as
mice, frogs, and fish, although aquatic and terrestrial invertebrates were the most numerous food
items (Hayes and Tennant, 1985). For adults, feeding activity takes place primarily at night; for
juveniles feeding occurs during the day and at night (Hayes and Tennant, 1985).
2.5.4 Habitat
CRLF's require aquatic habitat for breeding, but also use other habitat types including riparian
and upland areas throughout their life cycle. CRLF use of their environment varies; they may
complete their entire life cycle in a particular habitat or they may utilize multiple habitat types.
Overall, populations are most likely to exist where multiple breeding areas are embedded within
varying habitats used for dispersal (USFWS, 2002). Generally, CRLF's utilize habitat with
perennial or near-perennial water (Jennings et al. 1997). Dense vegetation close to water,
shading, and water of moderate depth are habitat features that appear especially important for
CRLF (Hayes and Jennings, 1988).
17
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Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds,
marshes, sag ponds (land depressions between fault zones that have filled with water), dune
ponds, and lagoons. Breeding adults have been found near deep (0.7 m) still or slow moving
water surrounded by dense vegetation (USFWS, 2002); however, the largest number of tadpoles
have been found in shallower pools (0.26 - 0.5 m) (Reis, 1999). Data indicate that CRLF's do
not frequently inhabit vernal pools, as conditions in these habitats generally are not suitable
(Hayes and Jennings, 1988).
CRLF's 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 CRLF's use dense, shrubby or emergent vegetation closely associated with deep-
water pools bordered with cattails and dense stands of overhanging vegetation
(http://www.fws.gOv/endangered/features/rl_frog/rlfrog.html#where).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability, and life
stage. Adults rely on riparian vegetation for resting, feeding, and dispersal. The foraging quality
of the riparian habitat depends on moisture, composition of the plant community, and presence of
pools and backwater aquatic areas for breeding. CRLF's can be found living within streams at
distances up to 3 km (2 miles) from their breeding site and have been found up to 30 m (100 feet)
from water in dense riparian vegetation for up to 77 days (USFWS, 2002).
During dry periods, the CRLF is rarely found far from water, although it will sometimes disperse
from its breeding habitat to forage and seek other suitable habitat under downed trees or logs,
industrial debris, and agricultural features (UWFWS, 2002). According to Jennings and Hayes
(1994), CRLF's also use small mammal burrows and moist leaf litter as habitat. In addition,
CRLF's may also use large cracks in the bottom of dried ponds as refugia; these cracks may
provide moisture for individuals avoiding predation and solar exposure (Alvarez, 2000).
2.6 Designated Critical Habitat
In a final rule published on April 13, 2006, 34 separate units of critical habitat were designated
for the CRLF by USFWS (USFWS, 2006; FR 51 19244-19346). A summary of the 34 critical
habitat units relative to USFWS-designated recovery units and core areas (previously discussed
in Section 2.5.1) is provided in Table 2.
Table 2. California Red-legged Frog Recovery Units with Overlapping Core Areas and
Designated Critical Habitat
Recovery Unit1
Core Areas 2 7 (Figure 5)
Critical Habitat
Units3
Currently
Occupied
(post-1985)4
Historically
Occupied 4
Sierra Nevada
Foothills and Central
Valley (1)
(eastern boundary is
the 1,500 m elevation
Cottonwood Creek (partial) (8)
--
Feather River (1)
BUT-1A-B
Yuba River-S. Fork Feather River
(2)
YUB-1
NEV-16
18
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Recovery Unit1
Core Areas 2 7 (Figure 5)
Critical Habitat
Units3
Currently
Occupied
(post-1985)4
Historically
Occupied 4
line)
Traverse Creek/Middle Fork
American River/Rubicon (3)
--
Consumnes River (4)
ELD-1
S. Fork Calaveras River (5)
--
Tuolumne River (6)
--
Piney Creek (7)
--
East San Francisco Bay
(partial)(16)
--
North Coast Range
Foothills and Western
Sacramento River
Valley (2)
Cottonwood Creek (8)
--
Putah Creek-Cache Creek (9)
--
Jameson Canyon - Lower Napa
Valley (partial) (15)
Belvedere Lagoon (partial) (14)
Pt. Reyes Peninsula (partial) (13)
North Coast and North
San Francisco Bay (3)
Putah Creek-Cache Creek (partial)
(9)
"
Lake Berryessa Tributaries (10)
NAP-1
Upper Sonoma Creek (11)
--
Petaluma Creek-Sonoma Creek
(12)
--
Pt. Reyes Peninsula (13)
MRN-1, MRN-2
Belvedere Lagoon (14)
--
Jameson Canyon-Lower Napa
River (15)
SOL-1
South and East San
Francisco Bay (4)
--
CCS-1A6
East San Francisco Bay (partial)
(16)
ALA-1A, ALA-
IB, STC-1B
STC-1A6
South San Francisco Bay (partial)
(18)
SNM-1A
Central Coast (5)
South San Francisco Bay (partial)
(18)
SNM-1A, SNM-
2C, SCZ-1
Watsonville Slough- Elkhorn
Slough (partial) (19)
SCZ-2 5
Carmel River-Santa Lucia (20)
MNT-2
Estero Bay (22)
--
--
SLO-86
Arroyo Grande Creek (23)
~
Santa Maria River-Santa Ynez
River (24)
--
Diablo Range and
Salinas Valley (6)
East San Francisco Bay (partial)
(16)
MER-1A-B,
STC-1B
--
SNB-16, SNB-26
Santa Clara Valley (17)
--
Watsonville Slough- Elkhorn
Slough (partial)(19)
MNT-1
19
-------
Recovery Unit1
Core Areas 2 7 (Figure 5)
Critical Habitat
Units3
Currently
Occupied
(post-1985)4
Historically
Occupied 4
Carmel River-Santa Lucia
(partial)(20)
--
Gablan Range (21)
SNB-3
Estrella River (28)
SLO-1A-B
Northern Transverse
Ranges and Tehachapi
Mountains (7)
--
SLO-86
Santa Maria River-Santa Ynez
River (24)
STB-4, STB-5,
STB-7
Sisquoc River (25)
STB-1, STB-3
Ventura River-Santa Clara River
(26)
VEN-1, VEN-2,
VEN-3
LOS-16
Southern Transverse
and Peninsular Ranges
(8)
Santa Monica Bay-Ventura
Coastal Streams (27)
--
San Gabriel Mountain (29)
--
Forks of the Mojave (30)
--
Santa Ana Mountain (31)
--
Santa Rosa Plateau (32)
--
San Luis Rey (33)
--
Sweetwater (34)
--
Laguna Mountain (35)
--
1 Recovery units designated by the USFWS (USFWS, 2000, pg 49).
2 Core areas designated by the USFWS (USFWS, 2000, pg 51).
3 Critical habitat units designated by the USFWS on April 13, 2006 (USFWS, 2006, 71 FR 19244-19346).
4 Currently occupied (post-1985) and historically occupied core areas as designated by the USFWS (USFWS, 2002,
Pg 54).
5 Critical habitat unit where identified threats specifically included pesticides or agricultural runoff (USFWS, 2002).
6 Critical habitat units that are outside of core areas, but within recovery units.
7 Currently occupied core areas that are included in this effects determination are bolded
20
-------
Figure 5. Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF
Legend
| Recovery Unit Boundaries
Currently Occupied Core Areas
Critical Habitat
CNDDB Occurence Sections
County Boundaries
Recovery Units
I . 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
19. Watsonville Slough-EMiorn Slough
2.
Yuba River- S. Fork Feather River
20. Carmel River - Santa Lucia
3.
Traverse Creek/ Middle Fork/ American R. Rubicon
21. Gablan Range
4.
Cosumnes River
22. Estero Bay
5.
South Fork Calaveras River*
23. Arroyo Grange River
6.
Tuolumne River*
24. Santa Maria River - Santa Ynez River
7.
Piney Creek*
25. Sisquoc River
8.
Cottonwood Creek
26. Ventura River - Santa Clara River
9.
Putah Creek - Cache Creek*
27. Santa Monica Bay - Venura Coastal Streams
10.
Lake Berryessa Tributaries
28. Estrella River
11.
Upper Sonoma Creek
29. San Gabriel Mountain*
12.
Petaluma Creek Sonoma Creek
30. Forks of the Mojave*
13.
Pt. Reyes Peninsula
31. Santa Ana Mountain*
14.
Belvedere Lagoon
32. Santa Rosa Plateau
15.
Jameson Canyon - Lower Napa River
33. San Luis Ray*
16.
East San Francisco Bay
34. Sweetwater*
17.
Santa Clara Valley
35. Laguna Mountain*
18.
South San Francisco Bay
* Core areas that were historically occupied by the California red-legged frog are not included in the map
21
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'Critical habitat' is defined in the ESA as the geographic area occupied by the species at the time
of the listing where the physical and biological features necessary for the conservation of the
species exist, and there is a need for special management to protect the listed species. It may
also include areas outside the occupied area at the time of listing if such areas are 'essential to
the conservation of the species.' All designated critical habitat for the CRLF was occupied at the
time of listing. Critical habitat receives protection under Section 7 of the ESA through
prohibition against destruction or adverse modification with regard to actions carried out, funded,
or authorized by a federal Agency. Section 7 requires consultation on federal actions that are
likely to result in the destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the conservation
of the species.' Critical habitat designations identify, to the extent known using the best
scientific and commercial data available, habitat areas that provide essential life cycle needs of
the species or areas that contain certain primary constituent elements (PCEs) (as defined in 50
CFR 414.12(b)). PCEs include, but are not limited to, space for individual and population
growth and for normal behavior; food, water, air, light, minerals, or other nutritional or
physiological requirements; cover or shelter; sites for breeding, reproduction, rearing (or
development) of offspring; and habitats that are protected from disturbance or are representative
of the historic geographical and ecological distributions of a species. The designated critical
habitat areas for the CRLF are considered to have the following PCEs that justify critical habitat
designation:
Breeding aquatic habitat;
Non-breeding aquatic habitat;
Upland habitat; and
Dispersal habitat.
Occupied habitat may be included in the critical habitat only if essential features within the
habitat may require special management or protection. Therefore, USFWS does not include
areas where existing management is sufficient to conserve the species. Critical habitat is
designated outside the geographic area presently occupied by the species only when a
designation limited to its present range would be inadequate to ensure the conservation of the
species. For the CRLF, all designated critical habitat units contain all four of the PCEs, and were
occupied by the CRLF at the time of FR listing notice in April 2006. The FR notice designating
critical habitat for the CRLF includes a special rule exempting routine ranching activities
associated with livestock ranching from incidental take prohibitions. The purpose of this
exemption is to promote the conservation of rangelands, which could be beneficial to the CRLF,
and to reduce the rate of conversion to other land uses that are incompatible with CRLF
conservation.
USFWS has established adverse modification standards for designated critical habitat (USFWS,
2006). Activities that may destroy or adversely modify critical habitat are those that alter the
PCEs and jeopardize the continued existence of the species. Evaluation of actions related to use
of Bensulide that may alter the PCEs of the CRLF's critical habitat form the basis of the critical
habitat impact analysis. According to USFWS (2006), activities that may affect critical habitat
and therefore result in adverse effects to the CRLF include, but are not limited to the following:
22
-------
(1) Significant alteration of water chemistry or temperature to levels beyond the tolerances of
the CRLF that result in direct or cumulative adverse effects to individuals and their life-
cycles.
(2) Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat that could result in elimination or
reduction of habitat necessary for the growth and reproduction of the CRLF by increasing
the sediment deposition to levels that would adversely affect their ability to complete
their life cycles.
(3) Significant alteration of channel/pond morphology or geometry that may lead to changes
to the hydrologic functioning of the stream or pond and alter the timing, duration, water
flows, and levels that would degrade or eliminate the CRLF and/or its habitat. Such an
effect could also lead to increased sedimentation and degradation in water quality to
levels that are beyond the CRLF's tolerances.
(4) Elimination of upland foraging and/or aestivating 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).
As previously noted in Section 2.1, the Agency believes that the analysis of direct and indirect
effects to listed species provides the basis for an analysis of potential effects on the designated
critical habitat. Because bensulide is expected to directly impact living organisms within the
action area, critical habitat analysis for bensulide is limited in a practical sense to those PCEs of
critical habitat that are biological or that can be reasonably linked to biologically mediated
processes.
2.7 Action Area
For listed species assessment purposes, the action area is considered to be the area affected
directly or indirectly by the federal action and not merely the immediate area involved in the
action (50 CFR 402.02). It is recognized that the overall action area for the national registration
of Bensulide is likely to encompass considerable portions of the United States based on the large
array of agricultural and non-agricultural uses. However, the scope of this assessment limits
consideration of the overall action area to those portions that may be applicable to the protection
of the CRLF and its designated critical habitat within the state of California. Deriving the
geographical extent of this portion of the action area is the product of consideration of the types
of effects that bensulide may be expected to have on the environment, the exposure levels to
Bensulide that are associated with those effects, and the best available information concerning
the use of bensulide and its fate and transport within the state of California.
The definition of action area requires a stepwise approach that begins with an understanding of
the federal action. The federal action is defined by the currently labeled uses for bensulide. An
analysis of labeled uses and review of available product labels was completed. This analysis
indicates that, for bensulide, the following uses are considered as part of the federal action
23
-------
evaluated in this assessment. As explained in section 2.2, there are a number of uses reported in
the CDPR PUR database that may be entry errors in the database for they are not supported by
past or current state (Section 2.4.c) or national (Section 3) labels for bensulide. These uses are
not part of the FIFRA regulatory action and have not been included in this assessment. Labeled
uses for bensulide are listed in Table 3.
Table 3. Labeled Uses of Concern
Arugula
Artichoke (globe)
Beet
Bok choy
Broccoli
Brussels Sprouts
Cabbage
Canola
Cantaloupe
Cardoon
Cauliflower
Celery
Chicory
Chinese cabbage (Napa)
Chinese greens
Cilantro
Collard
Corn (human consumption)
for Bensulide in California
Cotton
Cucumber
Dandelion green
Eggplant
Endive
Fennel
Gai Choy
Gai Lon
Grape (wine)
Herbs and spices
Kale
Kohlrabi
Landscape maintenance
Lettuce (head)
Lettuce (leaf)
Melon
Mizuna
Mustard
Ornamentals (field grown)
Onion (dry)
Onion (green)
Parsley
Peas
Pepper (fruiting)
Pepper (spice)
Pumpkin
Radish
Rapini
Rights of way
Spinach
Squash
Summer squash
Swiss chard
Turf/sod
Watermelon
Winter squash
Zucchini squash
After a determination of which uses will be assessed, an evaluation of the potential "footprint" of
the use pattern should be determined. This "footprint" represents the initial area of concern and
is typically based on available land cover data. Local land cover data available for the state of
California were analyzed to refine the understanding of potential Bensulide use. However, no
areas are excluded from the final action area based on usage and land cover data. The initial area
of concern is defined as all land cover types that represent the labeled uses described above. A
map representing all the land cover types that make up the initial area of concern is presented in
Figure 6.
24
-------
Figure 6. Bensulide Initial Area of Concern
Bensulide Initial Area of Concern
Legend
| Bensulide_AII Uses
Initial Streams Effected by Bensulide
~ Counts' boundaries
Kilometers
50 100 150 200
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Service (NASS, 2002)
Gap Anal/sis Program Orchard^ Vineyard Laridcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
September, 2007. Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
25
-------
Once the initial area of concern is defined, the next step is to compare the extent of that area with
the results of the screening level risk assessment. The screening-level risk assessment will
define which taxa, if any, are predicted to be exposed at concentrations above the Agency's
Levels of Concern (LOC). The screening level assessment includes an evaluation of the
environmental fate properties of Bensulide to determine which routes of transport are likely to
have an impact on the CRLF.
Review of the environmental fate data as well as physical-chemical properties of Bensulide
indicate that spray drift and runoff is likely to be the dominant exposure pathway to plants and
animals off the treated site and residues on soil invertebrates is likely to be the dominant
exposure pathway to animals on the treated site. Because this product is applied to bare ground,
residues on foliage onsite is an incomplete pathway as no plants are present. Insects exposed to
bensulide in treated areas may be a significant exposure pathway.
LOC exceedances are then used to describe how far outside the initial area of concern effects
may be seen. For example, Ag-Drift v. 2.1 modeling can be used to define how far from the
initial area of concern an effect to non-target terrestrial plants may be expected. Other processes
considered in expanding the initial area of concern can include downstream distance where
concentrations are expected to be above the LOC, long-range transport, and secondary exposure
through biological vectors. The process of expanding the initial area of concern is repeated for
all taxa where exceedances of the LOC occur, and the greatest expansion of the initial area of
concern is considered the action area.
LOC exceedances are used to describe how far effects may be seen from the initial area of
concern. Factors considered include: spray drift, downstream run-off, atmospheric transport, etc.
This information is incorporated into GIS and a map of the action area is created Figure 7.
26
-------
Figure 7. Bensulide Action Area Maps
Bensulide Use and CRLF Habitat
Legend
~ CNDDB Occurrence Sections
| All Bensulide Uses Buffered 2792ft
| Critical habitat
Core areas
CD Recovery units
~ County boundaries
25 50 100 150 200
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Service (NASS, 2002)
Gap Anat/sis Program Orchard/Vineyard Landcaver (GAP)
National Land Coyer Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Septerrfcier, 2007. Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
27
-------
Action Area and CRLF Habitat Overlap
Legend
Custom layout
Streams Effected in CRLF Habitat
| Terrestrial Action Area overlaped with CRLF
Critical habitat
Core areas
~ Recovery units
~ County boundaries
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Sen/ice (NASS, 2002)
Gap Anal/sis Program Orchard? Vineyard Landctwer (GAP)
National Land Cwer Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
September, 2007. Projection: Albers EqualArea Conic USGS,
North American Datum of 1983 (NAD 1983)
28
-------
Action Area and CRLF Habitat Overlap - RU1
Siskiyou
Shasta
Teham
Vlendoci
Plumas
Glenn
Sierra
Colusa
^Nevada
Kilometers
El Dorad'
Legend
Custom layout
Streams Effected in CRLF Habitat
| Terrestrial Action Area overiaped with CRLF
| Critical habitat
Core areas
CD Recovery units
s County boundaries
Solano
11 * 1"
I ba<
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Sen/ice (NASS, 2002!
Gap Anal/sis Program Orchard? Vineyard Landctwer (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Septerrber, 2007. Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
29
-------
Mendocino
Colusa
Sonoma
Solano
Marin
San i oaquin
Action Area and CRLF Habitat Overlap - RU2
Legend
~ Recovery units
~ County boundaries
Custom layout
Streams Effected in CRLF Habitat
| Terrestrial Action Area overlaped with CRLF
Critical habitat
Core areas
16 24 32 TiedQ.
Alameda
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Sen/ice (NASS, 2002!
Gap Analysis Program Orchard? Vineyard Landccwer (GAP)
National Land Cwer Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
September, 2007. Projection: Albers EqualArea Conic USGS,
North American Datum of 1983 (NAD 1983)
30
-------
San FrangsOT
Santa Clan
San Benito
Legend
Custom layout
Streams Effected in CRLF Habitat "
| Terrestrial Action Area overlaped with CRLF
Critical habitat
Core areas
~ Recovery units
~ County boundaries
ฆ Kilometers
Action Area and CRLF Habitat Overlap - RU3
Stanislaus
-resno
Merced
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Sen/ice (NASS, 2002!
Gap Anal/sis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Septerrber, 2007. Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
31
-------
San Benito
Monterey
ian Luis Obispo
Santa Bai
!ntura
Action Area and CRLF Habitat Overlap - RU4
Legend
Custom layout
Streams Effected in CRLF Habitat
| Terrestrial Action Area overlaped with CRLF
Critical habitat
Core areas
~ Recovery units
~ County boundaries
i Kilometers
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Sen/ice (NASS, 2002)
Gap Anal/sis Program Orchard/Vineyard Landctwer (GAP)
National Land Cower Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
September, 2007. Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
32
-------
intura
Orange
Riverside
Legend
Custom layout
Streams Effected in CRLF Habitat
| Terrestrial Action Area overlaped with CRLF
Critical habitat
Core areas
~ Recovery units
~ County boundaries
Action Area and CRLF Habitat Overlap - RU5
Santa Barbara
San Diego
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Sen/ice (NASS, 2002)
Gap Anal/sis Program Orchard? Vineyard Landctwer (GAP)
National Land Cower Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
September, 2007. Projection: Albers EqualArea Conic USGS,
North American Datum of 1983 (WD 1983)
33
-------
Action Area and CRLF Habitat Overlap - RU6
Nevada
Placei
Dorad'
rcrarnento
Amador
C&averas
Tuolumne
Legend
Custom layout
Streams Effected in CRLF Habitat
Terrestrial Action Area overlaped with CRLF
Critical habitat
Core areas
Recovery units
County boundaries 1 ^
I "
Mariposa
Kilometers"
Madera
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Sen/ice (NASS, 2002!
Gap Analysis Program Orchard; Vineyard Landccwer (GAP)
National Land Cower Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Septerrber, 2007. Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
34
-------
Subsequent to defining the action area, an evaluation of usage information was conducted to
determine area where use of Bensulide may impact the CRLF. This analysis is used to
characterize where predicted exposures are most likely to occur but does not preclude use in
other portions of the action area. A more detailed review of the county-level use information
was also completed and is represented in Table 4. More information may be found in Appendix
H.
Table 4. California Average Bensulide Use per County 2002-2005*.
County
AVG
Annual
Pounds
Applied
County
AVG
Annual
Pounds
Applied
IMPERIAL
110576.50
MONTEREY
42955.34
ORANGE
105.49
SAN BENITO
20316.03
SOLANO
101.95
RIVERSIDE
16291.57
EL DORADO
65.32
SAN BERNARDINO
7600.48
SAN DIEGO
63.88
VENTURA
7548.35
PLACER
63.29
STANISLAUS
5304.86
TUOLUMNE
49.22
SANTA BARBARA
3823.24
TULARE
42.47
FRESNO
3045.66
YOLO
35.51
SANTA CLARA
2740.15
CALAVERAS
35.51
SAN LUIS OBISPO
1128.65
TEHAMA
31.21
SACRAMENTO
1071.46
GLENN
19.29
KERN
746.42
COLUSA
15.08
LOS ANGELES
480.86
SAN FRANCISCO
11.02
SANTA CRUZ
455.01
SISKIYOU
10.02
ALAMEDA
225.99
SAN MATEO
7.39
MERCED
213.43
NEVADA
4.96
SAN JOAQUIN
199.38
MENDOCINO
3.13
BUTTE
183.48
SUTTER
2.38
SHASTA
152.57
NAPA
1.36
MADERA
134.28
HUMBOLDT
1.12
CONTRA COSTA
108.98
PLUMAS
0.70
"There are no data listed in the PUR data base for Alpine, Amador, Del Norte, Inyo, Kings, Lake, Lassen, Marin, Mariposa,
Modoc, Mono, Sierra, Sonoma, Trinity and Yuba Counties.
2.8 Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental value that
is to be protected."3 Selection of the assessment endpoints is based on valued entities (e.g.,
CRLF, organisms important in the life cycle of the CRLF, and the PCEs of its designated critical
habitat), the ecosystems potentially at risk (e.g., waterbodies, riparian vegetation, and upland and
dispersal habitats), the migration pathways of Bensulide (e.g., runoff, spray drift, etc.), and the
routes by which ecological receptors are exposed to bensulide-related contamination (e.g., direct
contact, etc).
'From U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
35
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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 and/or
modification of its habitat. In addition, potential modification of critical habitat is assessed by
evaluating potential effects to PCEs, which are components of the habitat areas that provide
essential life cycle needs of the CRLF. Each assessment endpoint requires one or more
"measures of ecological effect," defined as changes in the attributes of an assessment endpoint or
changes in a surrogate entity or attribute in response to exposure to a pesticide. Specific
measures of ecological effect are generally evaluated based on acute and chronic toxicity
information from registrant-submitted guideline tests that are performed on a limited number of
organisms. Additional ecological effects data from the open literature are also considered.
A complete discussion of all the toxicity data available for this risk assessment, including
resulting measures of ecological effect selected for each taxonomic group of concern, is included
in Section 4 of this document. A summary of the assessment endpoints and measures of
ecological effect selected to characterize potential assessed direct and indirect CRLF risks
associated with exposure to bensulide is provided in Table 5.
Table 5. Summary of Assessment Endpoints and measures of Ecological Effects for direct
and Indirect Effects of Bensulide on the CRLF
Assessment Endpoint Measures of Ecological Effects
reproduction of CRLF
individuals via direct
effects on aquatic phases
Aquatic Phase
(eggs, larvae, tadpoles, juveniles, and adults)*
1. Survival, growth, and la. Most sensitive amphibian acute
LC50 or if no suitable amphibian data
are available, fish acute LC50 (source:
guideline or ECOTOX data)
lb. Most sensitive amphibian chronic
NOAEC or if no suitable amphibian
data are available, fish chronic NOAEC
(source: guideline or ECOTOX)
lc. Most sensitive amphibian early-life
NOAEC or if no suitable amphibian
data are available, fish early-life stage
NOAEC (source: guideline or
ECOTOX)
2. Survival, growth, and 2a. Most sensitive (1) fishLC50; (2)
reproduction of CRLF aquatic invertebrate LC50 or EC50; and
individuals via effects to (3) aquatic plant EC50 (source:
food supply (i.e., guideline or ECOTOX))
freshwater invertebrates,
non-vascular plants)
Toxicity Endpoint (see effects
table for endpoint selection,
Section 4)
la. Rainbow trout (Oncorrhynchus
my kiss) acute 96-hr LC\0 = 0.72
ppm a.i.
lb. Fathead minnow (Pimephales
promelas) early life-stage NOAEC
= 0.374 ppm a.i.
lc. Same as lb.
2a 1. Rainbow trout (Oncorrhynchus
mykiss) acute 96-hr LC50 = 0.72
ppm a.i.
2a2. Water flea (Daphnia magna)
Acute 48-hr EC50 = 0.58
ppm ai.
4 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in Appendix A.
36
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Assessment Endpoint Measures of Ecological Effects
3. Survival, growth, and
reproduction of CRLF
individuals via indirect
effects on habitat, cover,
and/or primary
productivity (i.e., aquatic
plant community)
4. Survival, growth, and
reproduction of CRLF
individuals via effects to
riparian vegetation,
required to maintain
acceptable water quality
and habitat in ponds and
streams comprising the
species' current range.
2b. Most sensitive (1) aquatic
invertebrate chronic NOAEC; and (2)
fish chronic NOAEC (source: guideline
or ECOTOX)
3a. Most sensitive vascular plant EC50
(source: duckweed guideline test or
ECOTOX vascular plant)
3b. Most sensitive non-vascular plant
EC50 (source: guideline test or
ECOTOX reference no. is 2478)
4a. Distribution of monocot (1)
seedling emergence EC25 values and (2)
vegetative vigor EC25 values (source:
guidelines and ECOTOX)
4b. Distribution of dicot (1) seedling
emergence EC25 values; and (2)
vegetative vigor EC25 values (source:
guidelines or ECOTOX)5
Terrestrial Phase (Juveniles and adults)
5. Survival, growth, and 5a. Most sensitive terrestrial-phase
amphibian acute LC50 or LD50 or if no
suitable amphibian data are available,
birdb acute LC50 or LD50 (source:
guideline or ECOTOX)
5b. Most sensitive terrestrial-phase
amphibian chronic NOAEL or if no
suitable amphibian data are available,
birdb chronic NOAEC (source:
guideline or ECOTOX)
6a. Most sensitive (1) terrestrial
invertebrate LD50 or ED50; and (2)
terrestrial vertebrate acute LD50 or LC50
(source: guideline or ECOTOX)0
reproduction of CRLF
individuals via direct
effects on terrestrial
phase adults and
juveniles
6. Survival, growth, and
reproduction of CRLF
individuals via effects on
prey (i.e., terrestrial
invertebrates, small
terrestrial vertebrates,
including mammals and
terrestrial phase
amphibians)
7. Survival, growth, and
reproduction of CRLF
individuals via indirect
effects on habitat (i.e.,
riparian vegetation)
6b. Most sensitive (I) terrestrial
invertebrate chronic NOAEL; and (2)
terrestrial vertebrate chronic NOAEC
(source: guideline or ECOTOX)
7a. Distribution of monocot (1)
seedling emergence EC25 values; and
(2) vegetative vigor EC25 values
(source: guidelines or ECOTOX)
Toxicity Endpoint (see effects
table for endpoint selection,
Section 4)
2a. 3. Green Alga,
(Pseudokirchneriella subcapitata)
EC50 =1.5 ppma.i.
2b 1. No Data Available
2b2. Fathead minnow (Pimephales
promelas) early life-stage NOAEC
= 0.374 ppm a.i.
3 a. No aquatic plant vascular data
available
3b. Green Alga,
(Pseudokirchneriella subcapitata)
72 hr EC50 value of 1.5 ppm
4a 1. Monocot Seedling emergence
EC25 range from2.1 lb a.i./Ato >
6.0 lb a.i./A
4a2. All monocots tested
vegetative EC25 > 6.0 lb a.i./A
4b 1. All dicots tested
EC25 > 6 lb a.i./A
4b2. Dicot Vegetative vigor EC25
range from 1.3 lb a.i./A > 6 lb a.i./A
5a. Northern Bobwhite quail
(Colinus virginianus) Avian (single
dose) acute oral LD50 = 13 86
mg/kg-bw
5b. Mallard duck (Anas
platyrhynchos) Reproductive study
NOAEL = 2.5 ppm a.i.
6al. Honey bee (Apis sp.) Acute
contact LD50 = 1.6 ug a.i./bee
6a2. Rat (Rattus norvegicus) acute
oral (single dose) LD50 value = 270
mg/kg-bw
6b 1. No Data Available
6b2. Rat (Rattus norvegicus) F2 pup
survival: NOAEL = 150 ppm a.i
7al. Monocot Seedling emergence
EC25 range from 2.1 lb a.i./A to > 6
lb a.i./A
7a2. All monocots tested
vegetative EC25 > 6.0 lb a.i./A
' The available information indicates that the California red-legged frog does not have any obligate relationships.
37
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Assessment Endpoint Measures of Ecological Effects
Toxicity Endpoint (see effects
table for endpoint selection,
Section 4)
7b 1. All dicots tested
EC25 > 6 lb a.i./A
7b2. Dicot seedling emergence
EC25 ranges from 1.3 lb a.i./A to > 6
lb a.i./A
11 Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult frogs are
considered "aquatic" for the purposes of this assessment because exposure pathways in the water are considerably
different that exposure pathways on land.
b Birds are used as surrogates for terrestrial phase amphibians.
0 Although the most sensitive toxicity value is initially used to evaluate potential indirect effects, sensitivity
distribution is used (if sufficient data are available) to evaluate the potential impact to food items of the CRLF.
7b. Distribution of dicot (1) seedling
emergence EC25 values, and (2)
vegetative vigor EC25 values (source:
guidelines or ECOTOX)5
2.8.2 Assessment Endpoints for Designated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related to the
use of Bensulide that may alter the PCEs of the CRLFs critical habitat. PCEs for the CRLF
were previously described in Section 2.6. Actions that may destroy or adversely modify critical
habitat are those that alter the PCEs. Therefore, these actions are identified as assessment
endpoints. It should be noted that evaluation of PCEs as assessment endpoints is limited to those
of a biological nature {i.e., the biological resource requirements for the listed species associated
with the critical habitat) and those for which Bensulide effects data are available.
Assessment endpoints and measures of ecological effect selected to characterize potential
modification to designated critical habitat associated with exposure to Bensulide are provided in
Table 6. Adverse modification to the critical habitat of the CRLF includes the following, as
specified by USFWS (2006) and previously discussed in Section 2.6:
1. Alteration of water chemistry/quality including temperature, turbidity, and oxygen
content necessary for normal growth and viability of juvenile and adult CRLF's.
2. Alteration of chemical characteristics necessary for normal growth and viability of
juvenile and adult CRLF's.
3. Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat.
4. Significant alteration of channel/pond morphology or geometry.
5. Elimination of upland foraging and/or aestivating 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.
Some components of these PCEs are associated with physical abiotic features {e.g., presence
and/or depth of a water body, or distance between two sites), which are not expected to be
measurably altered by use of pesticides. Assessment endpoints used for the analysis of
designated critical habitat are based on the adverse modification standard established by USFWS
(2006).
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Table 6. Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary constituent Elements of Designated Critical Habitat
Assessment Endpoint
Measures of Ecological Effect
Toxicity Endpoint (see effects table
for endpoint selection, Section 4)
Aquatic Phase PCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond
morphology or geometry
and/or increase in sediment
deposition within the stream
channel or pond: aquatic
habitat (including riparian
vegetation) provides for
shelter, foraging, predator
avoidance, and aquatic
dispersal for juvenile and
adult CRLF's.
a. Most sensitive aquatic plant EC50
(source: guideline orECOTOX)
b. Distribution of terrestrial monocot^/;
seedling emergence EC25 values; and (2)
vegetative vigor EC25 values (source:
guidelines or ECOTOX)
c. Distribution of terrestrial dicot (I)
seedling emergence EC25 values; and (2)
vegetative vigor EC25 values (source:
guidelines or ECOTOX)
a. Green Alga, (Pseudokirchneriella
subcapitata) EC50 =1.5 ppm a.i.
bl. Monocot Seedling emergence
EC25 ranges from 2.1 lb a.i./A to > 6
lb a.i./A
b2. All monocots tested vegetative
EC25 > 6.0 lb a.i./A
cl. All dicots tested
EC25 > 6 lb a.i./A
c2. Dicot seedling emergence EC25
ranges from 1.3 lb a.i./A to > 6 lb
a.i./A
Alteration in water
chemistry/quality including
temperature, turbidity, and
oxygen content necessary for
normal growth and viability
of juvenile and adult CRLF's
and their food source.7
a. Most sensitive EC50 value for aquatic
plants (source; guideline or ECOTOX)
b. Distribution of terrestrial monocot (1)
seedling emergence EC25 values; and (2)
vegetative vigor EC25 values (source:
guidelines or ECOTOX)
c. Distribution of terrestrial dicot (I)
seedling emergence EC25 values; and (2)
vegetative vigor EC25 values (source:
guidelines or ECOTOX)
a. Green Alga, (Selenastrum
capriconutum) EC50 =1.8 ppm a.i.
bl. Monocot Seedling emergence
EC25 values range from 2.1 lb a.i./A
> 6 lb a.i./A
b2. All monocots tested Vegetative
EC25 > 6.0 lb a.i./A
cl. All dicots tested
EC25 > 6 lb a.i./A
c2. Dicot vegetative vigor EC25
values ranges from 1.3 lb a.i./A to >
6 lb a.i.A
Alteration of other chemical
characteristics necessary for
normal growth and viability
of CRLF's and their food
source.
Reduction and/or
modification of aquatic-based
food sources for pre-
metamorphosis (e.g., algae)
a. Most sensitive (1) LC50 values for fish
or aquatic-phase amphibians; and (2)
LC50 or EC50 values for aquatic
invertebrates (source: guidelines or
ECOTOX)
b. Most sensitive NOAEC values for (1)
fish or aquatic-phase amphibians; and (2)
aquatic invertebrates (source: guideline or
ECOTOX)
a. Most sensitive aquatic plant EC50
(source: guideline orECOTOX)
al. Rainbow trout acute 96-hr LC50
(Oncorrhynchus mykiss)LC50 0.72
ppm a.i.
a2. Water flea (Daphnia magna)
Acute 48-hr EC50 = 0.58
ppm ai.
bl. Fathead minnow early life-stage
(Pimephales promelas) NOAEC =
0.374 ppm a.i.
b2. No Data Available
a. Green Alga, (Pseudokirchneriella
subcapitata ) EC50 =1.5 ppm a.i.
All toxicity data reviewed for this assessment are included in Appendix A.
7 Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these
processes are not biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.
39
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Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or
disturbance of upland habitat;
ability of habitat to support
food source of CRLF's:
Upland areas within 200 ft of
the edge of the riparian
vegetation or dripline
surrounding aquatic and
riparian habitat that are
comprised of grasslands,
woodlands, and/or
wetland/riparian plant species
that provides the CRLF
shelter, forage, and predator
avoidance
Elimination and/or
disturbance of dispersal
habitat: Upland or riparian
dispersal habitat within
designated units and between
occupied locations within 0.7
mi of each other that allow
for movement between sites
including both natural and
altered sites which do not
contain barriers to dispersal
Reduction and/or
modification of food sources
for terrestrial phase juveniles
and adults
Alteration of chemical
characteristics necessary for
normal growth and viability
of juvenile and adult CRLF's
and their food source.
a. Distribution of terrestrial monocot (1)
seedling emergence EC25 values; and (2)
vegetative vigor EC25 values (source:
guidelines or ECOTOX)
b. Distribution of terrestrial dicot (I)
seedling emergence EC25 values; and
vegetative vigor EC25 values (source:
guidelines or ECOTOX)
c. Most sensitive terrestrial food
source^ acute LC50 or LD50 and
chronic NOAEL values for mammals; (2)
acute LC50 or LD50 and chronic NOAEL
for terrestrial-phase amphibians or birds;
(3) acute LC50 or LD50 and chronic
NOAEL for terrestrial invertebrates; (4)
acute LC50 and chronic NOAEC for
freshwater fish; and (5) acute LC50 or
EC50 and chronic NOAEC for aquatic
invertebrates
al. Monocot seedling emergence
EC25 values ranges from 2.1 lb a.i./A
to > 6 lb a.i./A
a2. All dicots tested vegetative vigor
study EC25 > 6 lbs a.i./acre
bl. All dicots tested seedling
emergence EC25 > 6 lbs a.i./acre
b2. Dicot vegetative EC25 values
ranges from 1.3 lb a.i./A to > 6 lb
a.i./A
cl. Rat (Rattus norvegicus) acute
oral (single dose) LD50 value = 270
mg/kg
c2. Northern Bobwhite quail
(Colinus virginianus) Avian (single
dose) acute oral LD50 = 1386 mg/kg
Mallard duck (Anas platyrhynchos)
Reproductive study NOAEL = 2.5
ppm a.i.
c3. Honey bee {Apis sp.) Acute
contact LD50 = 1.6 ug a.i./bee
No terrestrial invertebrate chronic
toxicity data Available
c4. . Rainbow trout acute 96-hr
LC50 (Oncorrhynchus mykiss) LC50
0.72 ppm a.i.
Fathead minnow early life-stage
(Pimephales promelas) NOAEC =
0.374 ppm a.i.
c5. Water flea (Daphnia magna)
Acute 48-hr EC50 = 0.58
ppm ai.
No aquatic invertebrate chronic
toxicity data available
40
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2.9 Conceptual Model
2.9.1 Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects {i.e., changes in
assessment endpoints) and may be based on theory and logic, empirical data, mathematical
models, or probability models (U.S. EPA, 1998). For this assessment, the risk is stressor-linked,
where the stressor is the release of Bensulide to the environment. The following risk hypotheses
are presumed for this listed species assessment:
Labeled uses of Bensulide within the action area may directly affect the CRLF by causing
mortality or by adversely affecting growth or fecundity;
Labeled uses of Bensulide within the action area may indirectly affect the CRLF by
reducing or changing the composition of food supply;
or modify designated critical habitat by reducing or changing the composition of the
aquatic plant community in the ponds and streams comprising the species' current range and
designated critical habitat, thus affecting primary productivity and/or cover;
or modify designated critical habitat by reducing or changing the composition of the
terrestrial plant community {i.e., riparian habitat) required to maintain acceptable water quality
and habitat in the ponds and streams comprising the species' current range and designated
critical habitat;
Labeled uses of Bensulide within the action area may modify the designated critical
habitat of the CRLF by reducing or changing breeding and non-breeding aquatic habitat (via
modification of water quality parameters, habitat morphology, and/or sedimentation);
or by reducing the food supply required for normal growth and viability of juvenile and
adult CRLF's;
or by reducing or changing upland habitat within 200 ft of the edge of the riparian
vegetation necessary for shelter, foraging, and predator avoidance.
or by reducing or changing dispersal habitat within designated units and between
occupied locations within 0.7 mi of each other that allow for movement between sites including
both natural and altered sites which do not contain barriers to dispersal.
or by altering chemical characteristics necessary for normal growth and viability of
juvenile and adult CRLF's.
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment. It
specifies the stressor (bensulide), 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 8, Figure 9, Figure 10 and Figure 11.
41
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Figure 8. Conceptual Model for Pesticide Effects on Aquatic Phase of the CRLF
Stressor
Long range
atmospheric
transport
>| Groundwater
Source
Exposure
Media
Wet/dry deposition *
Uptake/gills
or integument
Uptake/cell,
roots leaves
Uptake/gills
or integument
Ingestion
Ingestion
Receptors
S T.
Attribute
Change
Soil
Runoff
Spray drift'
Aquatic Plants
Non-vascular
Vascular
Aquatic Animals
Invertebrates
Vertebrates
Red-legged Frog
Eggs Juveniles
Larvae Adult
Tadpoles
Food chain
Reduction in algae
Reduction in prey
Riparian plant
terrestrial
exposure
pathways see
Figure 2.c
Surface water/
Sediment
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Bensulide Applied as Ground Spray or Granular
*: Not applicable for granular formulation
42
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Figure 9. Conceptual Model for Pesticide Effects on Terrestrial Phase of the CRLF
Stressor
Long range
atmospheric
Source
n
Dermal uptake/I ngestion-
Exposure
Media
Root uptake
Terrestrial
insects
Wet/dry deposition*
Ingestion
Ingestion
Ingestion
.h Ingestion^
Ingestion
Receptors
XI
Attribute
Change
Runoff
Mammals
Spray drift'
Amphibians
Soil
Direct
application
Food chain
Reduction in prey
Red-legged Frog
Juvenile
Adult
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Bensulide Applied as Ground Spray or Granular
Not applicable for granular formulation
43
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Figure 10. Conceptual Model for Pesticide Effects on Terrestrial Components of the CRLF
Critical Habitat
Stressor
Long range
atmospheric
Source
S~L
Dermal uptake/lngestion-
Exposure
Media and
Receptors
Root uptake
Terrestrial
insects
Wet/dry deposition-*-
Ingestion
Ingestion
Ingestion
ฆ j- Ingestion^
.rR
s~l
Attribute
Change
Habitat
PCEs
Not applicable for granular formulation
Runoff
Mammals
Soil
Spray drift'
Direct
application
Red-legged Frog
Juvenile
Adult
Food resources
Reduction in food
sources
Population
Reduced survival
Reduced growth
Reduced reproduction
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Other chemical
characteristics
Adversely modified
chemical characteristics
Terrestrial plants
grasses/forbs, fruit,
seeds (trees, shrubs)
Community
Reduced seedling emergence
or vegetative vigor
(Distribution)
Elimination and/or disturbance of
upland or dispersal habitat
Reduction in primary productivity
Reduced shelter
Restrict movement
Bensulide Applied as Ground Spray or Granular
44
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Figure 11. Conceptual Model for Pesticide Effects on Aquatic Components of CRLF
Critical Habitat
Stressor
Long range
atmospheric
+j Groundwater
Source
Exposure
Media
Wet/dry deposition *
Uptake/gills
or integument
Uptake/cell,
roots, leaves
Uptake/gills
or integument
Receptors
Ingestion
Ingestion
Community
Reduced seedling
emergence or vegetative
vigor (Distribution)
Population
Yield
Reduced yield
Attribute
Change
Habitat
PCEs
Soil
Runoff
Spray drift*
Aquatic Animals
Invertebrates
Vertebrates
Aquatic Plants
Non-vascular
Vascular
Surface water/
Sediment
Food sources
Reduction in algae
Reduction in prey
Red-legged Frog
Eggs Juveniles
Larvae Adult
Tadpoles
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Riparian and
Upland plants
terrestrial exposure
pathways and PCEs
see Figure 2.d
Other chemical
characteristics
Adversely modified
chemical characteristics
Bensulide Applied as Ground Spray or Granular
Habitat quality and channel/pond
morphology or geometry
Adverse water quality changes
Increased sedimentation
Reduced shelter
*: Not applicable for granular formulation
2.10 Analysis Plan
Analysis of risks to the California Red-Legged Frog (both direct and indirect) and to its critical
habitat will be assessed according to the Overview Document (EPA, 2004) and Agency guidance
for ecological risk assessments.
2.10.1 Exposure Analysis
Risks (direct effects) to the aquatic phase CRLF will be assessed by comparing modeled surface
water exposure concentrations of bensulide and its degradates to acute and chronic (early life
stage hatching success and growth) effect concentrations for aquatic phase amphibians (or
surrogate freshwater fish) from laboratory studies (see the Effects Analysis section below).
Risks (direct effects) to aquatic dietary food resources (aquatic invertebrates, algae) of the
aquatic phase CRLF or risks (direct effects) to aquatic habitat that support the CRLF will also be
assessed by comparing modeled surface water exposure concentrations of total bensulide
residues to laboratory established effect levels appropriate for the taxa.
45
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Surface water concentrations of bensulide residues will be quantified using a model, PRZM-
EXAMS. For the screening assessment, the standard EXAMS water body of 2 meters maximum
depth, and 20,000 cubic meters volume, will be used. Agricultural scenarios appropriate for
labeled bensulide uses will be used to account for local soils, weather and growing practices
which impact the magnitude and frequency of bensulide loading to the surface water. Maximum
labeled application rates, with maximum number of applications and shortest intervals, will be
used to help define (1) the Action Area within California for the Federal Action and (2) for
evaluating effects to the CRLF.
Risks to the terrestrial phase CRLF will be assessed by comparing modeled exposure to effect
concentrations from laboratory studies. Exposure in the terrestrial phase will be quantified using
the T-REX V. 1.3.1 model, which automates the calculation of dietary exposure according to the
Hoerger-Kenaga nomogram, as modified by Fletcher el al., 1994. The nomogram tabulates the
90th and 50th percentile exposure expected on various classes of food items, and scales the
exposure (in dietary terms) to the size and daily food intake of several size classes of birds and
mammals. Birds are also used as surrogates to represent reptiles and terrestrial-phase
amphibians.
2.10.2 Effects Analysis
Bensulide Toxicity (Including Major Toxic Degradates):
As previously discussed in Section 2.8.1 and 2.8.2, assessment endpoints for the CRLF include
direct toxic effects on survival, reproduction, and growth of the species itself, as well as indirect
effects, such as reduction of the prey base and/or modification of its habitat. Direct effects to the
CRLF are based on toxicity information for freshwater fish and birds, which are generally used
as a surrogate for aquatic and terrestrial phase amphibians, respectively. The open literature will
be screened also for available amphibian toxicity data. Indirect effects to the CRLF are assessed
by looking at available toxicity information of the frog's prey and habitat requirements
(freshwater invertebrates, freshwater vertebrates, aquatic plants, terrestrial invertebrates,
terrestrial vertebrates, and terrestrial plants).
Acute (short-term) and chronic (long-term) toxicity information for bensulide and its degradates
is characterized based on registrant-submitted studies and an updated review of the open
literature. A summary of the available freshwater and terrestrial ecotoxicity information, the
community-level endpoints, species' sensitivity distributions and the incident information for
bensulide are provided in Sections 4.1 through 4.4.
Toxicity studies for bensulide degradates (where available) will be discussed for exposure to the
aquatic phase of the CRLF and incorporated into this risk assessment.
Product Formulations Containing Multiple Active Ingredients:
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of
active ingredients, either those mixtures of multiple active ingredients in product formulations or
46
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those in the applicator's tank. In the case of the product formulations of active ingredients (that
is, a registered product containing more than one active ingredient), each active ingredient is
subject to an individual risk assessment for regulatory decision regarding the active ingredient on
a particular use site. If effects data are available for a formulated product containing more than
one active ingredient, they may be used qualitatively or quantitatively in accordance with the
Agency's Overview Document and the Services' Evaluation Memorandum (U.S., EPA, 2004;
USFWS/NMFS, 2004). See Appendix G.
2.10.3 Action Area Analysis
The Action Area for the federal action is the geographic extent of exceedance of Listed species
Levels of Concern (LOC) for any taxon or effect (plant or animal, acute or chronic, direct or
indirect) resulting from the maximum label-allowed use of bensulide. To define the extent of the
Action Area, the following exposure assessment tools will be used where appropriate: PRZM-
EXAMS, T-REX V. 1.3.1, Ag-Driftv. 2.1, T-Herps v. 1.0, TerrPlantv. 1.2.2 and ArcGIS (a
geographic information system [GIS] program). Other tools may be used as required if these are
inadequate to define the maximum extent of the Action Area.
In order to determine the extent of the action area downstream from the initial area of concern,
the Agency will need to complete the screening level risk assessment. Once all aquatic risk
quotients (RQs) are calculated, the Agency determines which RQ to level of concern (LOC) ratio
is greatest for all aquatic organisms (plant and animal).
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3.0 Exposure Assessment
3.1 Label Application Rates and Intervals
Analysis of labeled use information is the critical first step in evaluating the federal action. The
current label for bensulide represents the FIFRA regulatory action; therefore, labeled use and
application rates specified on the label form the basis of this assessment. The assessment of use
information is critical to the development of the action area and selection of appropriate
modeling scenarios and inputs.
Currently, labeled uses of bensulide include turf, ornamentals, and vegetable crops. There are 17
active Section 3 labels of products containing bensulide. The EPA registration numbers for these
labels are 538-26, 538-155, 538-164, 869-212, 2217-696, 2217-778, 2217-838, 9798-172, 9798-
176, 10163-196, 10163-198, 10163-199, 10163-200, 10163-201, 10163-204, 10163-205.
A comprehensive list of these uses, along with the methods and rates associated with
applications of bensulide are available in Appendix B. Crops are grouped based on similar forms
and application practices.
3.2 Aquatic Exposure Assessment
3.2.1 Conceptual Model of Exposure
Aquatic exposure of the CRLF is estimated with the PRZM-EXAMS model (EPA, 2004).
Estimated environmental concentrations (EEC) are produced using the standard screening-level
20,000 cubic meters surface water body. Watersheds where bensulide is used are assumed to have
100% cropped area. The downstream extent of streams with exposures above the Level of
Concern (LOC) is estimated (using GIS methods) by expanding the watershed considered until
uncontaminated stream flow dilutes the initial pond concentration to below the LOC.
Standard assumptions of 1% spray drift for ground application are used. If the pond
concentration from PRZM-EXAMS exceeds the LOC, a spray drift buffer is calculated (using
Ag-Drift v. 2.1 model) that will reduce the pond concentration to below the LOC. If a spray drift
buffer cannot be used to reduce the pond concentration to below the LOC, then a separate spray
drift buffer (neglecting run-off) is calculated with Ag-Drift v. 2.1 to ensure that pond
concentrations are below the LOC (see Section 2.10.3 above).
3.2.2 Existing Monitoring Data
The California Department of Pesticide Regulation Surface Water Database and the USGS
National Water Quality Assessment program (NAWQA) database were searched for bensulide.
No monitoring data for either ground or surface water were available; therefore, modeling alone
was used to estimate the aquatic exposure for bensulide. Above, it was stated that data are
available
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3.2.3 Modeling Approach
Use sites and the PRZM scenarios used to represent them are given in Table 7.
Risk quotients (RQs) were initially based on EECs derived using the Pesticide Root Zone
Model/Exposure Analysis Modeling System (PRZM/EXAMS) standard ecological pond scenario
according to the methodology specified in the Overview Document (U.S. EPA, 2004). Where LOCs
for direct/indirect effects and/or adverse habitat modification are exceeded based on the modeled
EEC using the static water body (i.e., "may affect"), refined modeling may be used to differentiate
"may affect, but not likely to adversely affect" from "may affect and likely to adversely affect"
determinations for the CRLF and its designated critical habitat.
The general conceptual model of exposure for this assessment is that the highest exposures are
expected to occur in the headwater streams adjacent to agricultural fields. Many of the streams
and rivers within the action area defined for this assessment are in close proximity to agricultural
use sites.
California PRZM scenarios were chosen for this assessment, include: lettuce, row crop
(representing beans, celery, and peppers), melon, cotton, turf (representing Bermuda grass for
seed and landscape maintenance), almond (representing nut trees), fruit (representing various
fruit trees)garlic, onion, and cole crops (broccoli, cauliflower).
Structural pest control was not modeled due to lack of an appropriate PRZM scenario, and the
low likelihood of exposure. All scenarios were used within the standard framework of
PRZM/EXAMS modeling using the standard graphical user interface (GUI) shell, PE4v01.pl.
3.2.3.1 Model Inputs
The estimated water concentrations from surface water sources were calculated using Tier 2 PRZM
(Pesticide Root Zone Model) and EXAMS (Exposure Analysis Modeling System). PRZM is used to
simulate pesticide transport as a result of runoff and erosion from a standardized watershed, and
EXAMS estimates environmental fate and transport of pesticides in surface waters. The linkage
program shell (PE4v01.pl) that incorporates the site-specific scenarios was used to run these models.
The PRZM/EXAMS model was used to calculate concentrations using the standard ecological water
body scenario in EXAMS. Weather and agricultural practices were simulated over 30 years so that
the 1 in 10 year exceedance probability at the site was estimated for the standard ecological water
body.
Models to estimate the effect of setbacks on load reduction for runoff are not currently available.
It is well documented that vegetated setbacks can result in a substantial reduction in pesticide
load to surface water (USDA, NRCS, 2000). Therefore, the aquatic EECs presented in this
assessment are likely to over-estimate exposure in areas with well-vegetated setbacks. While the
49
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extent of load reduction cannot be accurately predicted through each relevant stream reach in the
action area, data from USDA (USDA, 2000) suggest reductions could range from 11 to 100%.
The date of first application was set at March 1 in all PRZM/EXAMS model runs, because most uses,
for which there are use reporting data (PUR), in California show applications of bensulide occur in
most months of the year, and March corresponds to both a rainy part of the year (thereby capturing
higher run-off values), and the reproductive season of the frog.
PRZM input parameters were selected from the environmental fate data submitted by the registrant
and in accordance with US EPA-OPP EFED water model parameter selection guidelines, Guidance
for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides,
Version 2.3, February 28, 2002.
This product may only be applied by chemigation in Arizona and California. Bensulide is
applied through sprinkler, including center pivot, lateral move, end tow, side (wheel) roll,
traveler, big gun, solid set or hand move; or drip (trickle), including surface and subsurface drip
irrigation systems. Bensulide should not be through any other type of irrigation system.
50
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Table 7 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic Exposure
Inputs for Bensulide CRLF Assessment
Input variable (Units)
Input value and
calculations
Source/Quality of data
Crop name
See table 8
EPA Reg. No. 10163-222
Application method
See table 8
EPA Reg. No. 10163-222
application rate (lb ai/acre)
See table 8
EPA Reg. No. 10163-222
Interval between appl. (d)
See table 8
EPA Reg. No. 10163-222
Application efficiency
0.99
Input parameters guideline (2/28/2002)
Spray drift fraction
0.01
Input parameters guideline (2/28/2002)
Aerobic soil met. ti/2(day)
363
MRID# 40460302
Hydrolysis ti/2(day)
220
MRID# 00160074
Aerobic aquatic met. ti/2(day)
693
No data; soil aerobic met. rate multiplied by
0.5; Input parameters guideline
Solubility @ 25 ฐC (mg/L)
56
MRID# 41532001
Vapor pressure (torr)
8.2 x 10-7
MRID# 41532001
tv- (mL/g)
1VOC
2943
MRID# 43180701 (avg of 4 values.); Input
parameters guideline
Henry's Law Const.
(atm.m3/mole)
7.7 x 10"8
MRID# 41532001
Aquatic photolysis ti/2 (day)
200
MRID# 40513401
MWT (g/mole)
397.5
RED (1998)
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3.2.3.2 PRZM/EXAMS results
Table 8 PRZM/EXAMS results
(Crop/Use) PRZM Scenario Formulation
golf course turf CA turf RLF
Ornamental1 CA nursery
Granular
EC
EC
Application
Rate (lb/acre)
32
13.5
9
Number of
Applications (i
interval (day)
2(120)
2(120)
1
Peak EEC
(PPb)
87.54
51.9
168
21-day avg 0-day avg
EEC (ppb) ppb)
73.7
49.2
138
6.9
7.8
15
Residential
lawns
Broccoli2
Granular 6
CA residential Granular 32
RLF EC 13.5
CA cole crop RLF EC 9
1
2(120)
2(120)
1
231
192
52.1
112
191
185
50.1
100.0
60
81
9.1
8.1
Broccoli raab, CA cole crop RLF EC
broccoli,
Chinese,
Lettuce3 CA lettuce no-irrg. EC
chard (Swiss)4 CA lettuce no-irrg. EC
Celery, pepper, CA row crop RLD EC
cardoon, dock
(sorrel)
Celtuce5 CA row crop RLF EC
Melon6 CA melon RLF EC
1
1
2(120)
2(120)
2(120)
71.0
135
89.7
85.84
58.3
64.0
113.3
75.3
79.4
53.7
71.8
2.1
9.0
5.8
7.8
4.8
3.0
Eggplant7
CA melon RLF
EC
2(120)
59.2
47.9
2.0
Garlic
Tomatillo
okra (Chinese)
Onion8
CA garlic RLF
CA tomato no-
irrg.
EC
EC
EC
CA onion no-irrg. EC
Radish/daikon CA onion no-irrg. EC
Chinese
2(120)
2(120)
4(120)
3(120)
41.9
84.0
126
67.8
83.9
33.0
71.7
108
54.5
62.8
7.4
6.2
9.3
6.5
2.8
a. Ornamental, herbaceous plants, Ornamental and/or shade trees, Ornamental ground cover, Ornamental woody shrubs and vines
b. Broccoli, cabbage, cauliflower, collards, cress (garden), kale, kohlrabi, leafy vegetables.
c. Lettuce (head, leaf), Brussels sprout, endive, parsley, spinach
d. chard (Swiss), chicory, corn salad, dandelion, fennel, roquette (arugula)
e. Celtuce, chervil,, chrysanthemum (garland), pimento, orach, pepper (chili)
f. Melon , cucumber, chayote, gherkin, gourds, gourd (wax) Chinese, bitter melons (balsam pear), melons (cantaloupe, mango, musk,
water, pineapple), winter melons (casaba, Crenshaw, honeydew, Persian), pumpkin, cucuzzi (spaghetti squash)
g. Eggplant, gourd cherry (strawberry tomato/tomatillo), pepino (melon pear).
h. Onion , orach (mountain spinach), shallot
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3.2.3.3 Residential Uses
It is likely that some overspray may reach impervious surfaces in the residential setting. In order
to account for overspray, the impervious surface was modeled using three separate assumptions.
For the purposes of risk assessment, it is assumed that 1% of the application rate could reach the
impervious surfaces surrounding each residential lot, it is also assumed that 50% of the Vi acre
lot is treated with bensulide. In addition to the footprint of the typical house, it is also assumed
that a typical house has a driveway of approximately 25 by 30 feet or 750 square feet and
roughly 250 square feet of sidewalk.
The first assumption may result in an underestimation of exposure, given that more overspray of
impervious surfaces is possible. In order to account for the variability in overspray, the
residential scenario was modeled assuming two alternate scenarios of 0% and 10% overspray to
impervious surfaces. The alternate assumptions are intended to provide a bound on the 1%
assumption. Because both the residential and rights-of-way scenarios were modeled using the
paired pervious/impervious approach, the alternate scenarios were modeled for both scenarios
(residential was modeled for both granular and liquid formulations). The conservativeness of
these assumptions is unknown, given a lack of data on this phenomenon. However, given that the
impervious scenario is intended to represent nontarget surfaces such as roads, parking lots and
buildings, it is seems reasonable to assume that 10% overspray is an over-estimation of what
would likely occur to these off-site areas, while 0% may be an under-estimation.
In order to model the overspray, the binding coefficient was set to zero and the aerobic soil
metabolism half-life was set to stable in lieu of actual data for the impervious scenario. It is
assumed that non-binding would occur on these surfaces and that limited degradation would
occur. The percentage overspray was then multiplied by the total application rate to yield an
effective application rate for the overspray to impervious surfaces. Without actual data on these
processes, it is impossible to determine whether these exposures reflect reality, especially given
that no monitoring data is available
This impact of a decrease in impervious surface will hold only with the assumption of limited
overspray. This assumption was explored by comparing the impact of the change in percentage
of impervious surface on the 10% overspray scenario discussed above. In this case, peak EECs
increase by roughly 50% while the averages are only slightly increased.
Finally, in this assessment it is assumed that 50% of the ]A acre lot is treated. In order to test the
significance of this assumption, the exposure scenario was re-run using a different assumption of
10%) treatment of the Vi acre lot. As expected, peak EECs are reduced by roughly a factor of five,
while the longer term exposures are reduced by a factor of two to three times.
Note that this scenario represents general impervious surfaces within a watershed not part of the
Vi acre lot and includes roads, parking lots, and buildings among others where overspray from
residential lots is expected to be minimal. The Vi acre lot, by comparison, was developed with a
curve number reflective of the fact that the lot is covered with both pervious surfaces (grass and
landscaped gardens) and impervious surfaces (driveways, sidewalks, and buildings). In this case,
the assumption that 50% of the lot is treated likely overestimates the amount of landscaped area
53
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treated, but underestimates unintentional overspray of driveways and sidewalks. The impact of
this assumption is also evaluated in Section 3.2.7. Overall, these are simplifying assumptions that
are likely to provide a reasonable high-end estimate of exposure, given the limitations of
modeling approach. The combined edge of field concentrations are estimated using the *.zts
output from PRZM as described above. In this paired scenario approach, the *.zts output from
both the impervious and residential scenarios are weighted and added together to provide an
overall estimate of exposure.
Two categories of formulations are currently registered for bensulide use on residential sites,
including granular and liquid formulations. Both formulations were modeled separately because
application rates are different and the standard assumption for modeling granular formulations is
different from liquid formulations. Granular formulations are typically modeled as soil applied
(CAM is set to 8 with a minimized incorporation depth of 1 cm and 0% spray drift), which
assumes the standard spray drift of 1% for ground applications. However, because spray drift is
not assumed to contribute to the loadings in the spring and some overspray is expected to
impervious surfaces, both residential scenarios (liquid and granular) were modeled assuming that
1% of the application rate is applied to the impervious surface.
3.2.3.4 Comparison of Modeled EECs with Available Monitoring Data
There is no available monitoring data from California to allow a meaningful comparison with
modeled EECs
3.3 Terrestrial Plant Exposure Assessment
TerrPlant v. 1.2.2 (v. 1.2.2) was used to estimate loading to off-site soils, which includes both a
terrestrial plant upland (dry) habitat model and a semi-aquatic area habitat model, to evaluate
effects on seedling emergence. For liquid formulations, loading is determined based on both run-
off and spray drift inputs. For granular formulations, only loading to soils due to run-off is
estimated. Additionally TerrPlant v. 1.2.2 models loading to foliage (on lb a.i./A basis) due to
spray drift to evaluate effects on vegetative vigor. For exposure estimates TerrPlant v. 1.2.2
input parameters include: (1) application rate; (2) runoff, based on chemical solubility; and (3)
soil incorporation depth. A detailed explanation of the model as well as the modeling inputs and
outputs for estimating terrestrial and semi-aquatic plant exposure risks to bensulide are
summarized in Appendix C.
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4.0 Effects Assessment
This assessment evaluates the potential for bensulide to adversely affect the California Red-
Legged Frog (CRLF). As previously discussed in Section 2.8, selected assessment endpoints for
the CRLF include assessment of direct toxic effects on the survival, reproduction, and growth of
the frog itself, as well as indirect effects, such as reduction of the prey base and/or modification
of its habitat (Table 4). Taxa selected as measurement endpoints include freshwater fish as a
prey item and also as a surrogate for aquatic phase of CRLF (since no amphibian toxicity data
are available); freshwater aquatic invertebrates (prey item); birds as surrogates for terrestrial
phase of CRLF and other amphibians (prey item) (since no terrestrial amphibian toxicity data are
available); small mammals (prey item); terrestrial invertebrates (prey item); aquatic plants, and
terrestrial plants (essential component CRLF habitat). Toxicity data for freshwater fish and birds
are used as surrogate data for aquatic-phase and terrestrial-phase amphibians (U.S. EPA, 2004).
Information on the toxicity of bensulide to selected taxa is characterized based on registrant-
submitted studies and a comprehensive review of the open literature on bensulide (obtained from
the ECOTOX database). Values used for each measurement endpoint identified in Table 9 are
selected from this data. A summary of the available ecotoxicity information; the selected
individual, population, and community-level endpoints for characterizing risks; and
interpretation of the LOC, in terms of the probability of an individual effect based on probit dose
response relationship are provided in Sections 4.1 through 4.3, respectively.
4.1 Evaluation of Aquatic Ecotoxicity Studies
Toxicity measurement endpoints are selected from data from guideline studies submitted by the
registrant, and from open literature studies that meet the criteria for inclusion into the ECOTOX
database maintained by EPA/Office of Research and Development (ORD) (U.S. EPA, 2004).
Open literature data presented in this assessment were obtained from a search of the ECOTOX
database (5/31/2007). Table 9 summarizes the most sensitive results for each measurement
endpoint, based on an evaluation of both the submitted studies and the open literature, as
previously discussed. Table 10 summarizes the agency's LOCs. A brief summary of submitted
and open literature data considered relevant to this ecological risk assessment is presented below.
55
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Table 9 Bensulide Measurement Endpoints and Values Selected for Use in RQ Calculations
for the Effects Determination
Assessment Endpoint Mcasu res of Effect Species
Survival, growth, and
reproduction of CRLF
individuals via direct
effects on aquatic
phases
Survival, growth, and
reproduction of CRLF
individuals via effects
to freshwater
invertebrates prey.
Survival, growth, and
reproduction of CRLF
individuals via indirect
effects on habitat,
cover, and/or primary
productivity (i.e.,
aquatic plant
community)
Most sensitive
amphibian acute
LC50 or if no suitable
amphibian data are
available, fish acute
LC50 (source:
guideline or
ECOTOX data)
lb. Most sensitive
amphibian chronic
NOAEC or if no
suitable amphibian
data are available,
fish chronic NOAEC
(source: guideline or
ECOTOX)
Freshwater
invertebrate acute
96-h LC50 (for
cladocerans 48-h
LC50 or EC50 where
the effect measured
is surrogate)
Freshwater
invertebrate
reproductive
NOAEC
Freshwater green
algae, cyanobacteria
or diatom 96-h IC50
for biomass.
Freshwater green
algae, cyanobacteria
or diatom 96-h
NOAEC (orECos)
for biomass
Rainbow trout
(Oncorhynchus
mykiss)
Fathead minnow
(Pimephales
promelas)
Water flea
(Daphnia magna)
No Data Available
Green Alga,
(Pseudokirchneriella
subcapitata)
Green Alga,
(Selenastrum
capriconutum)
Toxicity
Value
0.72 ppm a.i.
Study classification Reference
(Selection basis)
Supplemental
(Most sensitive)
NOAEC=
0.374 ppm
a.i.
Acute 48-hr
EC50 = 0.58
ppm a.i.
No Data
Available
Acceptable
(Only fish early life-
stage study
available)
Supplemental1
(Most sensitive)
No Data
Available
72 hr EC50 = Pending Review
1.5ppma.i. (Most sensitive)
120hrEC05 Acceptable
= 0.93 ppm (Most sensitive)
a.i.
Survival, growth, and Avian (single dose) Northern Bobwhite LD50= 1386 Acceptable
reproduction of CRLF
individuals via direct
effects on terrestrial
phase adults and
juveniles
acute oral LDS
Avian subacute
5-day dietary LC50
quail
(Colinus virginianus)
Northern bobwhite
quail
(Colinus virginianus)
and Mallard duck
(Anas platyrhynchos)
mg/kg-bw
LCso > 5620
ppm a.i.
40098001
(Mayer and
Ellersiek,
1986)
MRID 447204-08
Kranzfelder, 1998
MRID 47116601
(McCann, 1978)
(Only avian acute
oral study available)
Acceptable
(Only studies
available and most
sensitive endpoints)
No Data available
ECOTOX
Open Literature
Reference: no.
2478
MRID 447204-02
(Kranfelder, 1998)
MRID 158455
(Grimes, 1986)
MRID 158456
(Grimes, 1986)
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Assessment Endpoint Measures of Effect Species
Avian reproduction Mallard duck
NOAEL
Survival, growth, and
reproduction of CRLF
individuals via effects
on terrestrial vertebrate reproductive
Mammalian acute
oral (single dose)
LD50
Mammalian
Rat (Rattus
norvegicus)
Rat
prey
Survival, growth, and
reproduction of CRLF
individuals via effects
on terrestrial
invertebrate prey
Survival, growth, and
reproduction of CRLF
individuals via effects
to riparian vegetation,
required to maintain
acceptable water
quality and habitat in
ponds and streams
comprising the species'
current range.
Survival, growth, and
reproduction of CRLF
individuals via indirect
effects on habitat (i.e.,
riparian vegetation)
NOAEC or NOAEL
Honey bee acute Honey bee
contact LD50
6a. Seedling
emergence EC25
Ryegrass
6b. Seedling Ryegrass
emergence NOAEC
6c. Vegetative vigor Cucumber
EC25
6d. Vegetative vigor Cucumber
NOAEC
Toxicity
Value
Reproductive
study
NOAEL=
2.5 ppm a.i.
LD50 value =
270 mg/kg-
bw
F2 pup
survival:
NOAEL=
150 ppm a.i.;
Acute
contact LD50
= 1.6
ug a.i./bee
Study classification Reference
(Selection basis)
Acceptable
(Most sensitive)
MRID 44486901
(Mansell, 1998)
Acceptable
(Most sensitive
endpoint)
Acceptable
(Most sensitive)
Acceptable
(Most sensitive)
EC25:1.91b
a.i./A
a.i./A
NOAEL:
0.38 lb.
a.i./A
MRID 92005011
(Velez, 1990)
MRID 00146585
Acceptable
(Most sensitive
endpoint of multiple
species tested)
NOAEC: Acceptable
0.38 lb a.i./A (Most sensitive
endpoint of multiple
species tested)
EC25: 1.3 lb Acceptable
(Most sensitive
endpoint of multiple
species tested)
MRID 00036935
(Atkins et al,
1975)
MRID No.
447463-01
(Schwab, 1998)
MRID No.
447463-01
(Schwab, 1998)
MRID 447463-01
(Schwab, 1998)
Note 1: The dissolved oxygen at the four highest test concentrations were unacceptably low (27.2%-48.9%)
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Table 10 Specific LOCs Used in this Assessment
Taxa
Listed
Acute LOC
Nonlisted
Acute
LOC
Listed and Nonlisted
Chronic LOC
Avian1 (terrestrial phase
amphibians)
0.1
0.2
1
Mammalian^
0.1
0.2
1
Terrestrial plantsJ
1
1
Aquatic animals 4
0.05
0.1
1
Aquatic plants 5
1
1
Terrestrial insects 6
0.05*
*The Agency has not established LOCs for terrestrial insects. This assessment will use the ratio of 0.05 as a cut-off value for
making effects determinations.
Toxicity values used in RQ calculations:
1 LD50 and estimated NOAEL, respectively.
2 LD50 and NOAEL, respectively.
3 EC50 for non-listed species and NOAEC for listed species.
4 LC/EC50 and estimated and reproductive NOAEC, respectively (the acute designation is not applicable for plants).
5 EC05/EEC or NOAEC/EEC for the listed LOC and EC25/EEC for non-listed LOC.
4.1.1 Toxicity to Freshwater Fish and Aquatic-Phase Amphibians
4.1.1.1 Freshwater Fish and Aquatic-Phase Amphibians: Acute Exposure
(Mortality) Studies
There are three registrant submitted freshwater fish acute toxicity studies (MRID 157315, MRID
400980-01, and MRID 400980-01). There are no acceptable fish acute or amphibian toxicity
studies available in the open literature. The 96-h LC50 values for freshwater fish among the
available registrant submitted studies range from 0.72 ppm a.i. to 1.1 ppm a.i. Based on this
data, bensulide is categorized as moderately to highly toxic to freshwater fish. The most
sensitive endpoint value among all the studies was a 96-h LC50 of 0.72 ppm a.i. for rainbow trout,
Oncorhynchus mykiss, (MRID 400980-01). This endpoint is selected as the measurement
endpoint for characterizing: 1) the acute direct effects of bensulide to the aquatic phase of the
CRLF and 2) acute effects of bensulide to the aquatic phase CLRF prey including other frogs and
fish.
4.1.1.2 Freshwater Fish and Aquatic-Phase Amphibians: Chronic Exposure
(Early Life Stage and Reproduction) Studies
Similar to the acute data, chronic freshwater fish toxicity studies are used to assess potential
direct effects to the CRLF because direct chronic toxicity bensulide data for frogs do not exist.
There is one acceptable fish chronic toxicity study available to access the potential risk to the
CRLF (Table 4.1; Acc. No. 447204). This study is an "Early Life-Stage Toxicity Test of the
Fathead, Pimephalespromelas, Under Flow-through Conditions". The results of the study
demonstrate a NOEAC of 0.374 ppm a.i. based on larval growth and survival. The NOAEC
produced in this study is used as the measurement endpoint for characterizing: 1) the chronic
direct effects of bensulide to the aquatic phase of the CRLF and 2) chronic effects of bensulide to
the aquatic phase CLRF prey including other frogs and fish.
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4.1.1.3 Freshwater Fish and Aquatic-Phase Amphibians: Sublethal Effects and
Additional Open Literature Information
There are no reported sublethal effects in any of the registrant submitted fish acute toxicity
studies. There are no acceptable fish or aquatic-phase amphibian acute toxicity studies testing
bensulide available in the open literature. The registrant submitted chronic toxicity study
reported a significant decrease in larval growth at a NOAEC of 0.374 a.i ppm as a sublethal
effect to the fish. No other sublethal effects were noted at concentrations at or below this
NOAEC.
4.1.2 Toxicity to Freshwater Invertebrates
Freshwater aquatic invertebrate toxicity data are used to assess potential effects of bensulide to
freshwater invertebrate prey of the CRLF. Effects to freshwater invertebrates resulting from
exposure to bensulide may affect the CRLF via reduction in available food. Aquatic-phase is
presumed to be algae grazers but there is some uncertainty in that assumption. Therefore,
aquatic invertebrates are also assumed to be a food source for CRLF aquatic-phase.
A summary of acute and chronic freshwater invertebrate data is provided below in Sections
4.1.2.1 through 4.1.2.2.
4.1.2.1 Freshwater Invertebrates: Acute Exposure (Mortality) Studies
There are two supplemental registrant submitted freshwater invertebrate acute toxicity studies.
One study tested the acute toxicity of bensulide on the water flea, Daphnia magna, (Acc.
No. 159322) and the other study tested the acute toxicity of bensulide on the amphipod,
Gammarus fasciatus (MRID 400980-01). The study testing Daphnia magna demonstrated the
most sensitive EC50 value of the two studies.
The toxicity endpoint values were a 48-hr. LC50 of 0.58 and 3.3 ppm a.i. for the water flea and
the amphipod, respectively. These studies indicate that bensulide is moderately to highly toxic to
freshwater invertebrates. There are no acceptable freshwater invertebrate acute toxicity studies
testing bensulide available in the public literature.
The 48 hr LC50 value of 0.58 ppm a.i. is used to evaluate whether bensulide will pose an acute
risk to CRLF freshwater invertebrate dietary sources. This value is used because it is the most
sensitive acute invertebrate toxicity endpoint available. The study was deemed supplemental
because the dissolved oxygen at the four highest test concentrations was unacceptably low
(27.2%-48.9%).
Further details regarding the available acute freshwater invertebrate toxicity data are provided in
Appendix A.
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4.1.2.2 Freshwater Invertebrates: Chronic Exposure (Reproduction) Studies
Currently there are no valid registrant submitted freshwater invertebrate chronic toxicity studies
available. Additionally according to the ECOTOX database there are no acceptable aquatic
invertebrate chronic toxicity data available in the public literature.
4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Open Literature Data
None of the registrant submitted freshwater acute invertebrate studies reported any sublethal
effects.
4.1.3 Toxicity to Aquatic Plants
The registrant has submitted two acceptable freshwater plant studies testing the technical grade
active ingredient of bensulide. The species tested in these studies include the cyanobacteria
(formerly classified as blue-green algae), Anabaena floss-aquae, and the freshwater green algae,
Pseudokirchneriella subcapitata (formerly Selenastrum capriconutum) (MRID 447204-03 and
447204-02 respectively). The endpoint values for the cyanobacteria study are a 120 hr. EC50 >
3.58 ppm a.i. and a 120 hr NOEAC of 3.58 ppm. The endpoint values for the green algae study
are a 120 hr. EC50 of 1.8 ppm a.i. and an EC05 of 0.93 ppm a.i.. Appendix A provides further
details regarding these studies. The ECOTOX database lists 10 open literature aquatic plant
studies testing bensulide toxicity to the green algae species, Pseudokirchneriella subcapitata.
Only one of endpoints produced by the ECOTOX data demonstrate an EC50 value that is more
sensitive more than the EC50 values produced in the registrant submitted study. This value is a
72 hr EC50 value of 1.5 ppm for Pseudokirchneriella subcapitata. Appendix A provides further
details regarding these studies listed in ECOTOX. The green algae EC50 of 1.5 ppm a.i.
(ECOTOX Reference no. 2748) and an EC05 of 0.93 ppm a.i for green algae study (447204-02)
will be used to assess the risk of indirect of effects of bensulide to the aquatic phase of the
CRLF. This endpoint is selected because it is the most sensitive endpoint among all the
available aquatic plant toxicity data.
4.1.4 Freshwater Field Studies
No freshwater field studies with bensulide are available..
4.2 Evaluation of Terrestrial Ecotoxicity
4.2.1 Toxicity to Terrestrial-Phase Amphibians
No information on bensulide toxicity to terrestrial-phase amphibians was found in the open
literature. Therefore, birds will be used as a surrogate species for effects to terrestrial-phase
amphibians (U.S. EPA, 2004). Avian toxicity acute and chronic endpoint values for bensulide
from open literature are generally less sensitive than the registrant submitted avian studies with
bensulide. A summary of acute and chronic avian data, including sublethal effects, is provided
below.
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4.2.1.1 Birds (Terrestrial-Phase Amphibian Surrogate): Acute Exposure
(Mortality) Studies
Avian acute toxicity studies are used to assess potential direct effects to the CRLF because direct
acute toxicity data on amphibians are unavailable (See Section 6.2.5 for an explanation of the
extrapolation between birds and amphibians). Bensulide acute oral and acute dietary toxicity has
been evaluated by two registrant submitted studies. The registrant submitted avian acute oral
toxicity study demonstrated a LD50 of 1386 mg a.i./kg-bw for bobwhite quail (MRID 158455).
This study classifies bensulide as slightly toxic to birds on an acute oral basis. Both registrant
submitted avian dietary toxicity studies demonstrated no mortality or overt signs of toxicity at
the highest test concentration of 5620 ppm (MRID 158456 and MRID 158457). Since the LC50,
is greater than 5000 ppm as demonstrated by avian dietary studies, bensulide is practically
nontoxic to birds on a subacute dietary basis. There are no bensulide avian acute toxicity data
available in the public literature. The endpoints produced in these studies will be used to assess
the acute effects of bensulide to the terrestrial phase of the CRLF.
4.2.1.2 Birds (Terrestrial-Phase Amphibian Surrogate): Chronic Exposure
(Reproduction) Studies
There are three registrant submitted avian reproduction studies. The submitted studies test the
chronic toxicity of bensulide to the Mallard duck, and the Northern bobwhite quail. The
reproduction NOAEL values were produced in two of the studies. They include a NOAEL of 2.5
ppm a.i. for the Mallard duck study (MRID 4486901) and a NOAEL of 250 ppm a.i. for the
Northern bobwhite quail study (MRID 43616001). Affected endpoints in the studies include
eggshell thickness, hatching success, and survival of chicks. The other study did not determine a
NOAEL. Further details of these studies are provided in Appendix A. The NOAEL value of 2.5
ppm will be used to assess the chronic risk of bensulide to the terrestrial phase of the CRLF.
This endpoint is used because it is the most sensitive endpoint among all the registrant submitted
bird reproduction studies.
4.2.1.3 Avians: Sublethal Effects and Additional Open Literature Information
None of the bird acute or chronic toxicity studies reported any sublethal effects lower than any
concentrations lower than those selected as measurement endpoints.
4.2.2 Toxicity to Mammals
Rat or mouse toxicity values are obtained from the Agency's Health Effects Division (HED) as
substitute for wild mammal testing. Toxicity data on small mammals are used in this assessment
to assess the effect of bensulide exposure on their availability as food items for the CRLF.
Additional information regarding the available data can be found in Appendix A.
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies
There is one acute oral rat toxicity available to the Agency (MRID 00097921). The results of
this study indicate that bensulide is characterized as moderately toxic to small mammals on an
61
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acute oral basis. The most sensitive endpoint value obtained in this study was an LD50 of 270
mg/kg-bw (MRID 920050-11). Further details regarding this study are presented in Appendix A.
4.2.2.2 Mammals: Chronic Exposure (Reproduction) Studies
A single rat multigenerational reproductive toxicity study was performed with bensulide. The
endpoints for reproductive toxicity were aNOAEL of 150 ppm a.i. (15.4 mg/kg/day) and a
LOAEL of 900 ppm a.i. (93.2 mg/kg/day) based on pup survival. Plasma cholinesterase activity
was significantly reduced compared to control at dietary concentrations as low as 25 ppm a.i.(2.3
mg/kg/day). Further details regarding this study are presented in Appendix A.
a) Mammals: Sublethal Effects and Additional Open Literature
Information
The mammal acute oral toxicity study (MRID 00097921) demonstrated treatment related
sublethal effects inclulding: convulsions or ataxia at higher doses (1500, 389, 322, or 320
mg/kg/day), exophthalmus, diarrhea, yellow stains in ano-genital region, red stains about face,
and depression. All survivors appeared normal by day 6.
As previously mentioned the rat multigenerational reproductive toxicity study (MRID 43948701)
demonstrated sublethal effects which entailed reduced plasma cholinesterase activity compared
to control at dietary concentrations as low as 25 ppm a.i. (2.3 mg/kg/day).
4.2.3. Terrestrial Plants: Vegetative Vigor and Seedling Emergence Toxicity
There are two acceptable registrant submitted terrestrial plant toxicity studies. These include a
vegetative vigor study (MRID 447463) and seedling emergence study (MRID 447463-01). The
most sensitive endpoints produced in the vegetative vigor study was an EC25 of 1.3 lbs a.i. /A
and a NOEAC of 0.38 lbs a.i./A. Appendix A provides a detailed account of the vegetative vigor
toxic effects exhibited to the other less sensitive plant species tested in this study. The most
sensitive endpoints produced in the seedling emergence study was an EC25 of 1.9 lb a.i./A and a
NOEAC of 0.38 lb a.i./A. Appendix A provides a detailed account of the seedling emergence
toxic effects exhibited to the other less sensitive plant species tested in this study. In addition to
the registrant submitted terrestrial plant toxicity studies, there are several terrestrial plant studies
listed in ECOTOX. However, none of these studies produced endpoints that were any more
sensitive than the endpoints produced in the registrant submitted studies. Thus, the most
sensitive endpoints produced in the registrant submitted studies will be utilized to determine the
risk of indirect effects posed to the CRLF.
4.3 Use of Probit Slope Response Relationship to Provide Information on the Listed
Species Levels of Concern
The Agency uses the probit dose response relationship as a tool for providing additional
information on the potential for acute direct effects to individual listed species and aquatic
animals that may indirectly affect the listed species of concern (U.S. EPA, 2004). As part of the
risk characterization, an interpretation of acute RQ for listed species is discussed. This
62
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interpretation is presented in terms of the chance of an individual event {i.e., mortality or
immobilization) should exposure at the EEC actually occur for a species with sensitivity to
bensulide on par with the acute toxicity endpoint selected for RQ calculation. To accomplish
this interpretation, the Agency uses the slope of the dose response relationship available from the
toxicity study used to establish the acute toxicity measures of effect for each taxonomic group
that is relevant to this assessment. The individual effects probability associated with the acute
RQ is based on the mean estimate of the slope and an assumption of a probit dose response
relationship. In addition to a single effects probability estimate based on the mean, upper and
lower estimates of the effects probability are also provided to account for variance in the slope, if
available. The upper and lower bounds of the effects probability are based on available
information on the 95% confidence interval of the slope. A statement regarding the confidence
in the estimated event probabilities is also included. Studies with good probit fit characteristics
{i.e., statistically appropriate for the data set) are associated with a high degree of confidence.
Conversely, a low degree of confidence is associated with data from studies that do not
statistically support a probit dose response relationship. In addition, confidence in the data set
may be reduced by high variance in the slope {i.e., large 95% confidence intervals), despite good
probit fit characteristics. In the event that dose response information is not available to estimate
a slope, a default slope assumption of 4.5 (lower and upper bounds of 2 to 9) (Urban and Cook,
1986) is used.
Individual effect probabilities are calculated using an Excel spreadsheet tool IECV1.1
(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental
Fate and Effects Division (June 22, 2004). The model allows for such calculations by entering
the mean slope estimate (and the 95% confidence bounds of that estimate) as the slope parameter
for the spreadsheet. In addition, the acute RQ is entered as the desired threshold. Results of the
probit slope analyses are described in Section 5.2.
4.4 Incident Database Review
According to the Agency's Ecological Incident Information System (EIIS) currently there are no
reported ecological incidents for bensulide.
63
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5.0 Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations to determine
the ecological risk from bensulide labeled uses (Sections 3 and 24(c) on the CRLF and its critical
habitat. The risk characterization provides an estimation of risks (RQ method) relative to
established LOCs and the results are then interpreted through a risk description and synthesized
into an overall conclusion regarding the effects determination {i.e., "no effect," "likely to
adversely affect," or "may affect, but not likely to adversely affect") for the CRLF. The risk
characterization includes a description of the assumptions, limitations and uncertainties
associated with the risk estimates and the impact to the effect determination.
A "may effect" will be concluded when at least one LOC is exceeded. In cases where the RQ
exceeds one or more LOCs (i.e., "may affect"), additional factors including the biology and life
history characteristics of the assessed species are considered and used to characterize the
potential of Bensulide to adversely affect the CRLF and its designated critical habitat.
5.1 Risk Estimation
Risk was estimated by calculating the ratio of estimated environmental concentrations (EECs)
and the appropriate toxicity endpoint. This ratio is the risk quotient (RQ), which is then
compared to pre-established acute and chronic levels of concern (LOCs). Risk quotients used to
evaluate potential direct and indirect effects to the CRLF and to designate critical habitat are in
Sections 5.1.1. and 5.1.2. RQs are described and interpreted in Section 5.2 (risk description).
5.1.1 Direct Effects
Direct effects to the CRLF associated with acute and chronic exposure to Bensulide residues in
surface water (table in 3.2.3.2) are based on the most sensitive toxicity data available for fish
(surrogate for aquatic phase amphibians). RQs for assessing these direct effects for all labeled
uses of bensulide exceeded the agency's level of concern for acute exposure for all uses. These
results are presented in Table 11. Direct effects to CRLF associated with acute and chronic
exposure to Bensulide residues on dietary items and the most sensitive toxicity data available for
birds (surrogate for terrestrial phase amphibians). Detailed T-REX V. 1.3.1 determination of
dietary item RQs for all uses are included in Appendix B.
The dietary item assessment in the T-REX V. 1.3.1 model uses avian intake rates, because
amphibian dietary intake rates are lower than avian rates this model will overestimate risks to
amphibians. Because acute and chronic RQ values exceeded LOC values, risk estimates for the
dietary exposure pathway were refined by using amphibian dietary intake rates using the T-
HERPS V. 1.0 model. Acute and chronic RQ values calculated using T-HERPS V. 1.0 exceeded
the agency's level of concern for acute exposure for all uses. These results are presented in
Table 12.
64
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Table 11. Summary of Acute and Chronic RQs for CRLF Exposed to Bensulide Surface
Water Residues*
Scenario
Anile RO'
Chronic K
-------
Table 12. Summary of Acute and Chronic RQs for the CRLF Terrestrial Phase Exposed to
Dietary Residues of Bensulide (based on T-REX V. 1.3.1 model)*1^
Scenario
Acute Dose RQ ' (Kinulsiliiiblc
( oiHTiilnilions) iiiul l.l)ซ/rt:
((ii'iinuhir Applications)
Chronic Dietary
UQ"
20ซ Bird
IOOป liiril
Golf course, residential lawn, turf (gran)
16.69
2.62
Golf course, residential lawn, turf (EC)
2.27
1.02
796.71
Ornamental (gran)
6.52
1.02
Ornamental, broccoli, cabbage, cauliflower,
collards, cress (garden), kale, kohlrabi, leafy
vegetables, Lettuce (head, leaf), Brussels
sprout, chard (Swiss), chicory, corn salad,
dandelion, endive, fennel, parsley, roquette
(arugula), spinach
1.39
0.62
486
Broccoli raab, broccoli, Chinese, chard
(Swiss), chicory, corn salad, dandelion,
fennel, roquette (arugula), Garlic,
0.92
0.41
324
Celery, pepper, cardoon, dock (sorrel),
melon, cucumber, chayote, gherkin, gourds,
gourd (wax) Chinese, bitter melons (balsam
pear), melons (cantaloupe, mango, musk,
water, pineapple), winter melons (casaba,
Crenshaw, honeydew, Persian), pumpkin,
cucuzzi (spaghetti squash), tomatillo
1.51
0.68
531.14
66
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Scenario
Acute Dose RQ' (Kimilsiliithle
C oiiceiili ittions) mill l.l);/l'l:
((ii itiiuhti- Applications)
Chronic Dieliirv
UQ"
20ป Hi rd
I00ป Bird
Celtuce, chervil, chrysanthemum (garland),
pimento, orach, pepper (chili), eggplant,
gourd cherry (strawberry tomato/tomatillo),
pepino (melon pear), okra (Chinese)
1.01
0.45
354.09
Onion, orach (mountain spinach), shallot
1.02
0.46
357.15
Radish/daikon Chinese
1.53
0.68
535.33
* Bolded acute RQ values exceed the acute listed species LOC (0.1) and bolded chronic RQ values exceed the
chronic LOC (1)
aBased on Northern Bobwhite quail (Colinus virginianus Avian (single dose) acute oral LD50 = 1386 mg/kg-bw) as
amphibian surrogate.
b Based on Mallard duck (Anas platyrhynchos) Reproductive study Toxicity Value NOAEL = 2.50 ppm ppb a.i.) as
amphibian surrogate.
0 Chronic dietary RQ's for granular applications are not typically assessed.
1 Unable to calculate acute dietary RQ's as avian 5-day LC50 = >5620 ppm a.i. (Table 6). However, application
highest application rates yielded EEC's less than 5620 ppm a.i..
5.1.2 Indirect Effects
Pesticides have the potential to exert indirect effects upon listed species by inducing changes in
structural or functional characteristics of affected communities. Perturbation of forage or prey
availability and alteration of the extent and nature of habitat are examples of indirect effects.
In conducting a screen for indirect effects, direct effects LOCs for each taxonomic group
(freshwater and terrestrial vertebrates, freshwater and terrestrial invertebrates, terrestrial plants)
are employed to make inferences concerning the potential for indirect effects upon listed species
that rely upon non-listed organisms in these taxonomic groups as resources critical to their life
cycle (U.S. EPA, 2004). This approach used to evaluate indirect effects to listed species is
67
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endorsed by the Services (USFWS/NMFS, 2004b). If no direct effect listed species LOCs are
exceeded for non-listed organisms that are critical to the California Red Legged Frog's life cycle,
the concern for indirect effects to the CRLF is expected to be minimal. As an herbicide,
bensulide has a potential to negatively impact vegetation in CRLF habitat areas.
5.1.2.1 Evaluation of Potential Indirect Effects via Reduction in Food Items
Potential indirect effects from direct effects on animal food items were evaluated by considering
the diet of the California Red Legged frog and the sensitivity distribution of aquatic prey
organisms. Aquatic phase CRLF larvae consume algae, diatoms, and detritus. The green alga
Selenastrum capriconutum data was used to assess potential indirect effects on the larval stage of
the CRLF; no other aquatic plant data are available for an indirect effects analysis of the aquatic
phase of the CRLF. Terrestrial phase CRLFs feed on a wide range of freshwater and terrestrial
invertebrates, and freshwater and terrestrial vertebrates, including water striders, sow bugs, fish,
other frogs, salamanders, and small mice. While aquatic and terrestrial invertebrates comprise
the most numerous food items, 50% of the prey mass in larger adult CRLFs consists of
vertebrates such as mice, frogs, and fish. The RQs used to characterize potential indirect effects
to the terrestrial and aquatic phase of the CRLF from direct acute and chronic effects on
freshwater vertebrate and invertebrate as well as terrestrial vertebrate and invertebrate food
sources are provided in Table 13, Table 14,
Table 15 and Table 16.
Based on these RQ calculations, there are acute LOC exceedances for fish and aquatic
invertebrate prey of the CRLF for all the modeled uses of bensulide (Table 13). There are acute
and chronic LOC exceedances for mammalian prey of the CRLF for all the modeled uses (Table
14). The RQ calculations for terrestrial amphibian prey of the CRLF indicate the LOC is
exceeded for chronic risk for all the modeled uses (Table 15). There are acute LOC exceedances
for terrestrial invertebrate prey of the CRLF for all the proposed uses.
Table 13. Summary of Bensulide Indirect Effects RQs for the CRLF Aquatic Phase,
Aquatic Animal Food Items*
l-ish
Invertebrates
Acute
Scenario
UQ"
Chronic UQh
Acute UQ'
68
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Kisli
liiYcrlchmlcs
Scenario
Acute
UQ"
Chronic KQh
Acute UQ'
Golf course turf (gran)
0.12
0.18
0.15
Golf course turf (ec)
0.07
0.13
0.09
Residential lawns (gran)
0.12
0.18
0.15
Residential lawns (ec)
0.27
0.48
0.33
Ornamental
0.07
0.13
0.09
Ornamental (gran)
0.32
0.43
0.40
Broccoli, cabbage, cauliflower,
collards, cress (garden), kale,
kohlrabi, leafy vegetables
0.16
0.24
0.19
Broccoli raab, broccoli, Chinese,
0.10
0.14
0.12
Lettuce (head, leaf), Brussels
sprout, chard (Swiss), chicory, corn
salad, dandelion, endive, fennel,
parsley, roquette (arugula), spinach
0.19
0.26
0.23
Chard (Swiss), chicory, corn salad,
dandelion, fennel, roquette
(arugula),
0.12
0.18
0.15
Celery, pepper, cardoon, celtuce,
chervil,, chrysanthemum (garland),
dock (sorrel), pimento, orach,
pepper (chili)
0.12
0.18
0.15
Celtuce, chervil,, chrysanthemum
(garland), pimento, orach, pepper
(chili)
0.08
0.12
0.10
Melon, cucumber, chayote, gherkin,
gourds, gourd (wax) Chinese, bitter
melons (balsam pear), melons
(cantaloupe, mango, musk, water,
pineapple), winter melons (casaba,
Crenshaw, honeydew, Persian),
pumpkin, cucuzzi (spaghetti squash)
0.12
0.18
0.15
Eggplant, gourd cherry (strawberry
tomato/tomatillo), pepino (melon
pear)
0.08
0.12
0.10
Garlic
0.12
0.17
0.15
Tomatillo
0.08
0.11
0.10
Okra (Chinese)
0.06
0.07
0.07
Onion, orach (mountain spinach),
shallot
0.12
0.18
0.14
Radish/daikon Chinese
0.18
0.27
0.22
69
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* Bolded values exceed LOC of > 0.05 for acute exposure. No values exceeded the LOC of >1.00 for chronic
exposure.
" Based on Rainbow trout (Oncorrhynchus mykiss) Toxicity Value LC50 720 ppb a.i.
b Based on Fathead minnow (Pimephalespromelas) Toxicity Value NOAEC = 374 ppb a.i.
0 Based on Water Flea {Daphnia magna) Toxicity Value LC50 580 ppb a.i.
Table 14. Summary of Bensulide Indirect Effects RQs for the CRLF, Mammalian Food
Items*
.Mammal KQ
Scenario
Acute Dose RQ'
(Kmulsiriithlc
CoiHTiilnitious) iiiul
Ll);,i/lr ((ii'iinuhir
Applications)
Chronic Dose UQh
Chronic Dietary
KQ"
ISg
Mammal
35g
.Mammal
15g
.Mammal
35g
.Mammal
Golf course, residential lawn, turf
(gran)c
37.43
19.83
Golf course, residential lawn, turf
(EC)
5.69
4.86
204.81
174.95
23.61
Ornamental (gran)0
14.62
7.75
Ornamental, Broccoli, cabbage,
cauliflower, collards, cress
(garden), kale, kohlrabi, leafy
vegetables, Lettuce (head, leaf),
Brussels sprout, chard (Swiss),
chicory, corn salad, dandelion,
endive, fennel, parsley, roquette
(arugula), spinach
3.47
2.96
124.93
106.72
14.4
Broccoli raab, broccoli, Chinese,
chard (Swiss), chicory, corn salad,
dandelion, fennel, roquette
(arugula), Garlic
2.31
1.98
83.29
71.15
9.6
70
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Miiinm:il KQ
Scciiiirio
Acute Dose KQ'
(Kinulsiliiihle
( ouceiilnitioiis) iinil
Ll);,i/lr ((ii'iinuhir
Applications)
Chronic Dose KQ1'
Chronic Dicliirv
UQh
\ 1 ;i in in ;i 1
35g
Mil in in ill
Mil in in ill
35g
\ 1il111 lllil1
Celery, pepper, cardoon, dock
(sorrel), Melon, cucumber,
chayote, gherkin, gourds, gourd
(wax) Chinese, bitter melons
(balsam pear), melons
(cantaloupe, mango, musk, water,
pineapple), winter melons (casaba,
Crenshaw, honeydew, Persian),
pumpkin, cucuzzi (spaghetti
squash), Tomatillo
3.47
2.96
124.93
106.72
14.4
celtuce, chervil, chrysanthemum
(garland), pimento, orach, pepper
(chili), eggplant, gourd cherry
(strawberry tomato/tomatillo),
pepino (melon pear), okra
(Chinese)
2.55
2.18
91.81
78.42
10.58
Celery, pepper, cardoon, celtuce,
chervil,, chrysanthemum
(garland), dock (sorrel), pimento,
orach, pepper (chili)
3.79
3.24
136.54
116.63
15.74
Onion, orach (mountain spinach),
shallot
2.55
2.18
91.81
78.42
10.58
Radish/daikon Chinese
3.82
3.27
137.62
117.55
15.86
* Bolded RQ values exceed LOC values
a Based on Rat {Rattus norvegicus) Toxicity Value LC50 270 mg/kg-bw.
b Based on Rat (Rattus norvegicus) Toxicity Value NOAL 150 ppm
0 Chronic dietary RQ's for granular applications are not typically assessed.
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Table 15. Summary of Acute and Chronic RQs for the CRLF Terrestrial Amphibian Prey
Exposed to Dietary Residues of Bensulide (based on T-HERPS V. 1.0 Model).* ^
AciiU" Dose Uy'
Chronic
Dicliin RQ1'
Sceiiiirio
1.4 ป
l-'roii
3^ ป
l-'mii
Golf Course Turf (EC)
0.06
0.05
796.91
Ornamental Crops, Lettuce (head, leaf), Brussels sprout, chard (), chicory, corn salad,
dandelion, endive, fennel, parsley, roquette (Arugula), spinach
0.03
0.03
864.00
Broccoli raab, broccoli, Chinese, chard (Swiss), chicory, corn salad, dandelion, fennel,
roquette (arugula), Garlic, celtuce, chervil,, chrysanthemum (garland), pimento, orach,
pepper (chili), eggplant, gourd cherry (strawberry tomato/tomatillo), pepino (melon
pear), okra (Chinese), Onion, orach (mountain spinach), shallot
0.02
0.02
324.00
Celery, pepper, cardoon, celtuce, chervil,, chrysanthemum (garland), dock (sorrel),
pimento, orach, pepper (chili)
0.04
0.04
531.14
Melon, cucumber, chayote, eggplant, gherkin, gourds, gourd cherry, melon (bitter)
cantaloupe, citron, honeydew, musk, water, pineapple), pear, pumpkin, squash
0.03
0.03
486.00
Garlic
0.02
0.02
324.00
Tomatillo
0.02
0.02
324.00
Okra (Chinese)
0.03
0.03
486.00
Onion, orach (mountain spinach)
0.02
0.02
324.00
* Bolded RQ values meet or exceed LOC values for listed aquatic animals
a Based on Northern Bobwhite quail (Colinus virginianus) Avian (single dose) acute oral Toxicity Value LD50 =
1386 mg/kg -bw.
b Based on Mallard duck (Anas platyrhynchos) Reproductive study Toxicity Value NOAEL = 2500 ppm ppb a.i..
t Unable to calculate acute dietary RQ's as avian 5-day LC50 = >5620 ppm a.i.. However, application highest
application rates yielded EEC's less than 5620 ppm a.i..
J Granular applications could not be refined via T-HERPS V. 1.0 model.
72
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Table 16. Summary of Bensulide Indirect Effects RQs for the CRLF Invertebrate Food
Items.*
Invertebrate A
Scenario
rule UQ
Aquatic11
Terrestrial1'
Large Small
golf course, residential lawn, turf (gran)0
0.06
41.97
377.70
golf course, residential lawn, turf (EC)
0.03
0.16
17.70
Ornamental (gran)0
0.06
0.38
41.97
Ornamental, Broccoli, cabbage, cauliflower, collards,
cress (garden), kale, kohlrabi, leafy vegetables, Lettuce
(head, leaf), Brussels sprout, chard (Swiss), chicory, corn
salad, dandelion, endive, fennel, parsley, roquette
(arugula), spinach
0.13
0.16
17.70
Broccoli raab, broccoli, Chinese, chard (Swiss), chicory,
corn salad, dandelion, fennel, roquette (arugula), Garlic
0.03
0.10
10.80
Celery, pepper, cardoon, dock (sorrel), Melon, cucumber,
chayote, gherkin, gourds, gourd (wax) Chinese, bitter
melons (balsam pear), melons (cantaloupe, mango, musk,
water, pineapple), winter melons (casaba, Crenshaw,
honeydew, Persian), pumpkin, cucuzzi (spaghetti squash),
Tomatillo
celtuce, chervil,, chrysanthemum (garland), pimento,
orach, pepper (chili), eggplant, gourd cherry (strawberry
tomato/tomatillo), pepino (melon pear), okra (Chinese)
0.15
0.06
7.20
Celery, pepper, cardoon, celtuce, chervil,,
chrysanthemum (garland), dock (sorrel), pimento, orach,
pepper (chili)
Onion, orach (mountain spinach), shallot
0.07
0.10
10.80
Radish/daikon Chinese
0.05
0.06
7.20
golf course, residential lawn, turf (gran)0
0.09
0.10
10.80
golf course, residential lawn, turf (EC)
0.06
0.06
7.20
Ornamental (gran)0
0.06
0.11
11.80
73
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liiYcrk'hi'iiU' Acute UQ
ToiToslrisil1'
Ornamental, Broccoli, cabbage, cauliflower, collards,
cress (garden), kale, kohlrabi, leafy vegetables, Lettuce
(head, leaf), Brussels sprout, chard (Swiss), chicory, corn
salad, dandelion, endive, fennel, parsley, roquette
(arugula), spinach
0.04
0.07
7.87
Melon, cucumber, chayote, gherkin, gourds, gourd (wax)
Chinese, bitter melons (balsam pear), melons (cantaloupe,
mango, musk, water, pineapple), winter melons (casaba,
Crenshaw, honeydew, Persian), pumpkin, cucuzzi
(spaghetti squash)
0.06
0.11
11.80
Broccoli raab, broccoli, Chinese, chard (Swiss), chicory,
corn salad, dandelion, fennel, roquette (arugula), Garlic
0.04
0.07
7.87
Garlic
0.06
0.06
7.20
Celery, pepper, cardoon, dock (sorrel), Melon, cucumber,
chayote, gherkin, gourds, gourd (wax) Chinese, bitter
melons (balsam pear), melons (cantaloupe, mango, musk,
water, pineapple), winter melons (casaba, Crenshaw,
honeydew, Persian), pumpkin, cucuzzi (spaghetti squash),
Tomatillo
0.04
0.11
11.80
celtuce, chervil,, chrysanthemum (garland), pimento,
orach, pepper (chili), eggplant, gourd cherry (strawberry
tomato/tomatillo), pepino (melon pear), okra (Chinese)
0.03
0.07
7.87
Celery, pepper, cardoon, celtuce, chervil,,
chrysanthemum (garland), dock (sorrel), pimento, orach,
pepper (chili)
0.06
0.07
7.94
Onion, orach (mountain spinach), shallot
0.06
0.11
11.90
* Bolded RQ values exceed LOC values
a Based on Water Flea (Daphnia magna) Toxicity Value LC50 580 ppb a.i. and 21 day peak EEC.
b Based on Honey Bee (Apis sp.) Toxicity Value 1.6 ug/individual, assuming an average fresh weight per honey bee of 128
milligrams. The LD50 of honey bees was multiplied by 7.8 to determine the ppm toxicity.
0 Chronic dietary RQ's for granular applications are not typically assessed.
74
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5.1.2.2 Evaluation of Potential Indirect Effects via Reduction in Habitat and/or
Primary Productivity (Freshwater Aquatic Plants)
Potential indirect effects on habitat and/or primary productivity were assessed using the RQs
from a green alga (Selenastrum capriconutum). This species will only provide insight into a
small part of the sensitivity spectrum of freshwater plants. Risk quotients used to estimate
potential indirect effects to the CRLF from effects on aquatic and terrestrial plants primary
productivity are summarized in Table 17.
None of the use scenarios led to LOC exceedances for freshwater aquatic plants and terrestrial
plants, or for terrestrial plants growing in semi-aquatic areas. Both aquatic plant and terrestrial
plant RQs were <1.0 and do not exceed the LOC.
Table 17. Summary of Bensulide Indirect Effects RQs for the CRLF Aquatic Plant Food
items and Habitat.*
Scenario
Golf course turf (gran)
Golf course turf (ec)
Residential lawns (gran)
Residential lawns (ec)
Ornamental
Ornamental (gran)
Broccoli, cabbage, cauliflower, collards, cress (garden), kale,
kohlrabi, leafy vegetables
Broccoli raab, broccoli, Chinese,
Lettuce (head, leaf), Brussels sprout, chard (Swiss), chicory, corn
salad, dandelion, endive, fennel, parsley, roquette (arugula), spinach
chard (Swiss), chicory, corn salad, dandelion, fennel, roquette
(arugula),
Celery, pepper, cardoon, pepper (chili)
Celtuce, chervil,, chrysanthemum (garland), pimento, orach, pepper
(chili)
Melon, cucumber, chayote, gherkin, gourds, gourd (wax) Chinese,
bitter melons (balsam pear), melons (cantaloupe, mango, musk,
water, pineapple), winter melons (casaba, Crenshaw, honeydew,
Persian), pumpkin, cucuzzi (spaghetti squash)
Eggplant, gourd cherry (strawberry tomato/tomatillo), pepino (melon
pear)
Garlic
Tomatillo
Okra (Chinese)
Onion, orach (mountain spinach), shallot
Radish/daikon Chinese
\on-
I.Ncd
0.06
0.03
0.06
0.13
0.03
0.15
0.07
0.05
0.09
0.06
0.06
0.04
0.06
0.04
0.06
0.04
0.03
0.06
0.06
l.isial
0.07
0.05
0.07
0.19
0.05
0.17
0.09
0.06
0.11
0.07
0.07
0.05
0.07
0.05
0.07
0.05
0.03
0.07
0.06
* Bolded RQ values exceed LOC values
a Based on Green Algae {Selenastrum. capriconutum) Toxicity Value 72h LC501.5 ppm.
b Based on Green Algae (
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5.1.2.3 Evaluation of Potential Indirect Effects via Reduction in Terrestrial Plant
Community (Riparian Habitat)
Bensulide is an herbicide, therefore it may pose indirect risks to the CRLF by impacting the
terrestrial plant communities in which it depends. Bensulide RQs exceed the Agency's LOC's
for all monocot plants in turf and lawn applications for both granular and EC formulations.
Listed monocot RQs are exceeded for all other application scenarios. No data exist for
dicotyledonous plants. These risks are summarized in Table 18.
Table 18. Summary of Bensulide Indirect Effects RQs for the CRLF Terrestrial and Semi-
aquatic Plant Habitat.*1^
Smi;iriป
I'liinl
1 > |H'
l.islod Shiius
l)n
Si'ini-A(|iiiilic
Spr.ij Drill
Turf and Lawn Granular
Monocot
non-listed
0.30
3.05
<0.1
listed
1.68
16.84
<0.1
Dicot
non-listed
0.11
1.07
<0.1
listed
0.43
4.27
<0.1
Turf and Lawn EC
Monocot
non-listed
0.19
1.35
<0.1
listed
1.07
7.46
0.36
Dicot
non-listed
<0.1
0.47
0.10
listed
0.27
1.89
0.36
Ornamental (gran)
Monocot
non-listed
<0.1
0.57
<0.1
listed
0.32
3.16
<0.1
Dicot
non-listed
<0.1
0.20
<0.1
listed
<0.1
0.80
<0.1
Broccoli raab, broccoli, Chinese, chard (),
chicory, corn salad, dandelion, fennel,
roquette (arugula), Garlic, celtuce, chervil,,
chrysanthemum (garland), pimento, orach,
pepper (chili), eggplant, gourd cherry
(strawberry tomato/tomatillo), pepino (melon
pear), okra (Chinese), Onion, orach (mountain
spinach), shallot
Monocot
non-listed
<0.1
0.60
<0.1
listed
0.47
3.32
0.16
Dicot
non-listed
<0.1
0.21
<0.1
listed
0.12
0.84
0.16
Ornamental, Broccoli, cabbage, cauliflower,
collards, cress (garden), kale, kohlrabi, leafy
vegetables, Lettuce (head, leaf), Brussels
sprout, chard (Swiss), chicory, corn salad,
dandelion, endive, fennel, parsley, roquette
(arugula), spinach, celery, pepper, cardoon,
dock (sorrel), Melon, cucumber, chayote,
gherkin, gourds, gourd (wax) Chinese, bitter
melons (balsam pear), melons (cantaloupe,
mango, musk, water, pineapple), winter
melons (casaba, Crenshaw, honeydew,
Persian), pumpkin, cucuzzi (spaghetti squash),
Tomatillo, Radish/daikon Chinese
Monocot
non-listed
0.13
0.90
<0.1
listed
0.71
4.97
0.24
Dicot
non-listed
<0.1
0.32
<0.1
listed
0.18
1.26
0.24
* Bolded RQ values exceed LOC values
' Monocot seedling emergence values based on Ryegrass (EC25 = 2.1 ppm, NOEAC = 0.38ppm). Monocot
vegetative vigor values based on Ryegrass (EC25 = >6.00 ppm, NOEAC = 0.75 ppm). Dicot seedling emergence
values based on Cucumber (EC25 = >6.00ppm, NOEAC =1.50 ppm). Dicot vegetative vigor values based on
Cucumber (EC25 =1.30 ppm, NOEAC = 0.38 ppm).
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5.2 Risk Description
The risk description synthesizes an overall conclusion regarding the likelihood of adverse
impacts leading to an effects determination (i.e., "no effect," "may affect, but not likely to
adversely affect," or "likely to adversely affect") for the California Red Legged frog.
If the RQs presented in the Risk Estimation (Section 5.1.2) show no indirect effects, and LOCs
for the CRLF are not exceeded for direct effects (Section 5.1.1), a "no effect" determination is
made based on bensulide's use within the action area. If, however, indirect effects are
anticipated and/or exposure exceeds the LOCs for direct effects, the Agency concludes a
preliminary "may affect" determination for the CRLF. Following a "may affect" determination,
additional information is considered to refine the potential for exposure at the predicted levels
based on the life history characteristics (i.e., habitat range, feeding preferences, etc) of the CRLF
and potential community-level effects to aquatic plants and terrestrial plants growing in semi-
aquatic areas. Based on the best available information, the Agency uses the refined evaluation to
distinguish those actions that "may affect, but are not likely to adversely affect" from those
actions that are "likely to adversely affect" the CRLF.
The criteria used to make determinations that the effects of an action are "not likely to adversely
affect" the CRLF include the following:
Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where "take" occurs
for even a single individual. "Take" in this context means to harass or harm, defined as
the following:
Harm includes significant habitat modification or degradation that results in
death or injury to listed species by significantly impairing behavioral patterns
such as breeding, feeding, or sheltering.
Harass is defined as actions that create the likelihood of injury to listed species
to such an extent as to significantly disrupt normal behavior patterns which
include, but are not limited to, breeding, feeding, or sheltering.
Likelihood of the Effect Occurring: Discountable effects are those that are extremely
unlikely to occur. For example, use of dose-response information to estimate the
likelihood of effects can inform the evaluation of some discountable effects.
Adverse Nature of Effect: Effects that are wholly beneficial without any adverse
effects are not considered adverse.
A description of the risk and effects determination for each of the established assessment
endpoints for the CRLF is provided in Sections 5.2.1 through 5.2.3.
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5.2.1 Direct Effects to the CRLF
The federal action is all labeled uses. In order to compare the location of the labeled uses with
the areas important to the frog, the potential use areas in California were over laid with the core
areas, critical habitat and known occurrence areas of the CRLF. The result of this layering is the
ability to discern areas of overlap between potential use and the CRLF life-cycle.
5.2.1.1 Aquatic Phase
The fish (surrogate species to the CRLF) acute RQ calculations indicate that the Agency level of
concern (LOC = 0.05) is exceeded for acute effects to the aquatic phase of the CRLF for all
modeled bensulide uses. The primary driver of these acute LOC exceedances is bensulide's EC
formulation use on residential lawns. These acute LOC exceedances indicate that the aquatic
phase of the CRLF is LAA by all the modeled uses of bensulide. The chronic RQ calculations
indicate that the LOC is not exceeded for risk of chronic effects of bensulide to the aquatic phase
of the CRLF.
Because of the fish acute LOC exceedances, mortality effects to the CRLF are anticipated based
on all modeled uses of bensulide. To provide additional information, the probability of an
individual mortality to the CRLF was calculated using the probit slope analysis described in
Section 4.3. A probit slope value for the acute fish toxicity test is not available; therefore, the
effect probability was calculated using a default slope assumption of 4.5. Based on the default
dose response curve slope of 4.5, the corresponding estimated chance of an individual acute
mortality to the aquatic-phase CRLF is 1 in 4.18x10s.
5.2.1.2 Terrestrial Phase (Direct Effects)
Based on the T-REX V. 1.3.1 model, acute dose RQs and chronic RQs for terrestrial phase
CRLF exceed for all modeled bensulide uses (Table 2). The acute dose LOC exceedances range
from 0.41-16.69 for small and large terrestrial phase CRLF, and the chronic RQs ranged from
324 - 797. The LOCs for the chronic dietary RQs exceed the Agency level of concern for risk
to the terrestrial phase of the CRLF for all the modeled uses.
The T-HERPS V.1.0 model was conducted to refine the assessment of bensulide's risk to the
terrestrial phase of the CRLF (Table 19). Based on this refinement, there are no acute LOC
exceedances for bensulide. There are chronic LOC exceedances for all the proposed uses of
bensulide. The chronic dietary RQs range from 354.09- 535.33. Based on these LOC
exceedances the terrestrial phase of the CRLF is LAA by all the modeled uses of bensulide.
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Table 19. Summary of Acute and Chronic RQs for the CRLF Terrestrial Phase Exposed to
Dietary Residues of Bensulide (based on T-HERPS V. 1.0 Model).* ^
Sceiiiirio
Anile Dose RQ'
C lironic Diclnrv RQ
1.4 ป l"i'oป
37 ป I Yoป
Golf Course Turf (EC)
0.06
0.05
796.91
Ornamental Crops, Lettuce (head, leaf),
Brussels sprout, chard (Swiss), chicory, corn
salad, dandelion, endive, fennel, parsley,
roquette (Arugula), spinach
0.03
0.03
864.00
Broccoli raab, broccoli, Chinese, chard
(Swiss), chicory, corn salad, dandelion, fennel,
roquette (arugula), Garlic, celtuce, chervil,,
chrysanthemum (garland), pimento, orach,
pepper (chili), eggplant, gourd cherry
(strawberry tomato/tomatillo), pepino (melon
pear), okra (Chinese), Onion, orach (mountain
spinach), shallot
0.02
0.02
324.00
Celery, pepper, cardoon, celtuce, chervil,,
chrysanthemum (garland), dock (sorrel),
pimento, orach, pepper (chili)
0.04
0.04
531.14
Melon, cucumber, chayote, eggplant, gherkin,
gourds, gourd cherry, melon (bitter)
cantaloupe, citron, honeydew, musk, water,
pineapple), pear, pumpkin, squash
0.03
0.03
486.00
Garlic
0.02
0.02
324.00
Tomatillo,
0.02
0.02
324.00
Okra (Chinese)
0.03
0.03
486.00
Onion, orach (mountain spinach)
0.02
0.02
324.00
* Bolded RQ values meet or exceed LOC values for listed aquatic animals
a Based on Northern Bobwhite quail (Colinus virginianus) Avian (single dose) acute oral Toxicity Value LD50 =
1386 mg/kg -bw.
b Based on Mallard duck {Anas platyrhynchos) Reproductive study Toxicity Value NOAEL = 2500 ppm ppb a.i.
t Unable to calculate acute dietary RQs as avian 5-day LC50 = >5620 ppm a.i. However, application highest
application rates yielded EEC's less than 5620 ppm a.i.
J Granular applications could not be refined via T-HERPS V. 1.0 model.
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5.2.2 Indirect Effects via Reduction in Food Items
Indirect effects on the CRLF in the terrestrial phase or aquatic phase of its life cycle might be
due to loss of prey (terrestrial or aquatic invertebrates, small mammals, small frogs, and fish) or
effects on terrestrial or aquatic plants that provide habitat.
5.2.2.1 Aquatic Phase
Aquatic invertebrates and fish are the animal prey of the CRLF. Based on the RQ calculations,
the LOC is exceeded for all the modeled uses for risk of acute effects to fish, and aquatic
invertebrate prey of the CRLF. The acute RQs range from 0.07-0.40 for freshwater invertebrate
prey and from 0.07 to 0.32 for fish prey. . These acute LOC exceedances indicate that bensulide
"May Affect" fish and aquatic invertebrate prey of the CRLF. The primary driver for these LOC
exceedances is bensulide's use on residential lawn. The acute freshwater invertebrate LOC
exceedances were based upon a supplemental water flea acute toxicity study (MRID 159322).
The study is supplemental because the dissolved oxygen at the four highest test concentrations
was unacceptably low. Thus, the low dissolved oxygen may have contributed to the lethality
effects demonstrated in this study. Therefore, there is some uncertainty regarding the validity of
the endpoints produced in this study.
There are no chronic LOC exceedances for fish prey of the CRLF. Currently, no valid aquatic
invertebrate data is available to access the chronic risk of aquatic invertebrate prey of the CRLF.
Thus, the Agency cannot calculate chronic RQs for CRLF aquatic invertebrate prey items.
Although there are no aquatic invertebrate chronic toxicity data available, EFED assumes that
bensulide will Likely Adversely Affect (LAA) aquatic invertebrate prey of the CRLF. This
assumption is a based on the presumption of chronic risk in the absence of corresponding data.
The probability of an individual mortality to fish prey and aquatic invertebrate prey of the CRLF
was calculated using the probit slope analysis described in Section 4.3. Based on the probit slope
for the most sensitive fish acute toxicity test (rainbow trout acute LC50 = 0.72 ppm MRID
40098001) with a default slope of 4.5, the corresponding estimated chance of an individual acute
mortality to the fish prey of the CRLF at the highest LOC exceedance of 0.32islin77.
Based on the probit slope for the most sensitive freshwater invertebrate acute toxicity test
(Waterflea acute LC50 = 0.58 ppm MRID 159322) with a slope of 3.8, the corresponding
estimated chance of an individual acute mortality to the aquatic invertebrate of the CRLF at the
highest LOC exceedance of 0.40 is 1 in 15 (Appendix F). Based on this probit analysis, these
effects are considered insignificant, therefore acute effects to the CRLF via aquatic prey are
considered NLAA.
5.2.2.2 Terrestrial Phase
a) 5.2.2.3.1 Terrestrial Vertebrate Food Items
The RQ calculations indicate that the LOC (0.1 for acute and 1 for chronic) is exceeded for all
modeled uses of bensulide for acute and chronic risk of effect to small mammal food items of the
CRLF. The RQ values ranged from 1.98 to 37.43 for acute dose based RQs for 15 gram
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mammals and 35 gram mammals, from 83.29 to 204.81 for chronic dose RQs for 15 gram
mammals and 35 gram mammals and from 9.6 to 15.86 for chronic dietary based RQs. The
primary driver of all these RQ exceedances is bensulide's liquid application to golf course turf,
residential lawn, and turf. Table 19 gives a detailed explanation of the LOC exceedances.
Additionally, the probability of an individual mortality to mammal prey of the CRLF was
calculated using the probit slope analysis described in Section 4.3. Based on the probit slope
analysis for the most sensitive acute rat toxicity test (LD50 = 13 86 mg/kg) with a slope of 2.92,
the corresponding estimated chance of an individual acute mortality to the 15 gm and 35 gm
mammal prey of the CRLF at the highest LOC exceedance of 37 and 19.83 respectively
approaches 100%. Thus, effects to the CRLF via reduction in terrestrial prey are considered
LAA.
The terrestrial-phase CRLF uses small mammal burrows for shelter. If populations of small
mammals are reduced, as is anticipated from the acute and chronic RQs, then there may be fewer
burrows for the CRLF to exploit. This effect is considered to be LAA to the CRLF.
Based on the T-HERPS V. 1.0 model, acute dose RQs for of terrestrial amphibian prey
(surrogate species bird) of the terrestrial phase CRLF are not exceeded for any of the modeled
uses (Table 6). The LOCs for the chronic dietary RQs exceed the Agency level of concern for
risk to the amphibian prey of the CRLF for all the modeled uses. The chronic dietary RQs range
from 324 - 864.
Based on these LOC exceedances, EFED expects all the modeled uses of bensulide to be LAA
terrestrial amphibian prey of CRLF.
b) 5.2.3.2 Terrestrial Invertebrate Food Items
The LOC for risk to terrestrial invertebrate food items of the CRLF is exceeded for all modeled
bensulide uses. The LOC exceedances for large terrestrial invertebrate range from 7.87- 41.97.
The LOC exceedances for small terrestrial invertebrates range from 0.1 - 377.70. The primary
driver of these LOC exceedances is bensulide's use on golf course turf. Table 16 provides a
detailed list the LOC exceedances for risk to terrestrial invertebrate food items of the CRLF for
all modeled bensulide uses. Because of these LOC exceedances all the modeled uses are LAA
the terrestrial invertebrate food items of the CRLF.
5.2.3 Indirect Effects via Reduction in Habitat and/or Primary Productivity
(Freshwater Aquatic Plants)
The RQ calculations for freshwater aquatic plants indicate that there are no LOC exceedances for
risk to fresh aquatic plants that may support the habitat of the CRLF.
Table 17 demonstrates the RQ calculations for freshwater aquatic plants.
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5.2.4 Indirect Effects via Alteration in Terrestrial Plant Community (Riparian
Habitat)
5.2.4.1 Importance of Riparian Habitat to the CRLF
As discussed in section 2.5.4, the habitat of the CRLF varies during its life cycle, with the CRLF
surviving in aquatic, riparian and upland areas. Adults rely on riparian vegetation for resting,
feeding, and dispersal. 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).
5.2.4.2 Sensitivity of Riparian Zones to Bensulide
The only RQ exceedances that indicate a risk to riparian habitats are bensulide's granular and
formulation product uses on turf and lawns. The RQs for these uses (range 1.07- 16.84; LOC >
1) demonstrate an LOC exceedance that plants inhabiting semi-aquatic habitat are at risk of
being adversely affected from bensulide's use on turf. Riparian habitats are largely composed of
semiaquatic plants. Because of these LOC exceedances EFED expects bensulide's turf and lawn
uses to be LAA to riparian habitats of the CRLF.
6.0 Uncertainties
6.1 Exposure Assessment Uncertainties
Overall, the uncertainties inherent in the exposure assessment tend to result in overestimation of
exposures. Factors influencing the over-estimation of exposure include the assumption of no
degradation, dilution, or mixing in the subsurface transport from edge of field. The modeling exercise
conservatively assumes that the surface water and bensulide application site are adjacent. In reality,
there are likely to be processes at work which cannot be accounted for in the modeling that will
reduce the predicted exposures. In addition, the impact of setbacks on runoff estimates has not been
quantified, although these buffers, especially those that are well-vegetated, are likely to result in
significant reduction in runoff loading of bensulide.
Landscape maintenance is known to be a major use of bensulide. This exposure is described for
the aquatic environment using the PRZM turf scenario. All exposure estimates were done with
maximum application rates, minimum intervals, and maximum number of applications, to define
the Action Area for the Federal action. Actual exposures will depend on actual use rates, which
may be lower. Spray drift estimates were set at 1% for ground application, per EFED policy.
6.1.1 Modeling Assumptions
Overall, the uncertainties addressed in this assessment cannot be quantitatively characterized.
However, given the available data and the tendency to rely on conservative modeling
assumptions, it is expected that the modeling results in an over-prediction in exposure. In
general, the simplifying assumptions used in this assessment appear to be reasonable especially
in light of the analysis completed and the absence of monitoring data. There are also a number of
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assumptions that tend to result in exposure over-estimation that cannot be quantified, but can be
qualitatively described. For instance, modeling for each use site assumes that the entire 10-
hectare watershed is taken up by the respective use pattern. The assessment assumes that all
applications have occurred concurrently on the same day at the exact same application rate. This
is unlikely to occur in reality, but is a reasonable conservative assumption in lieu of actual data.
6.1.2 Impact of Vegetative Setbacks on Runoff
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a vegetative
setback on runoff and loadings. The effectiveness of vegetative setbacks is highly dependent on
the condition of the vegetative strip. For example, a well-established, healthy vegetative setback
can be a very effective means of reducing runoff and erosion from agricultural fields.
Alternatively, a setback of poor vegetative quality or a setback that is channelized can be
ineffective at reducing loadings. Until such time as a quantitative method to estimate the effect of
vegetative setbacks of various conditions on pesticide loadings becomes available, the aquatic
exposure predictions are likely to overestimate exposure where healthy vegetative setbacks exist
and underestimate exposure where poorly developed, channelized, or bare setbacks exist.
6.1.3 PRZM Modeling Inputs and Predicted Aquatic Concentrations
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 (PRZM)
is a process or "simulation" model that calculates what happens to a pesticide in a farmer's field
on a day-to-day basis. It considers factors such as rainfall and plant transpiration of water, as
well as how and when the pesticide is applied. It has two major components: hydrology and
chemical transport. Water movement is simulated by the use of generalized soil parameters,
including field capacity, wilting point, and saturation water content. The chemical transport
component simulates pesticide application on the soil or on the plant foliage.
Dissolved, adsorbed, and vapor-phase concentrations in the soil are estimated by simultaneously
considering the processes of pesticide uptake by plants, surface runoff, erosion, decay,
volatilization, foliar wash-off, advection, dispersion, and retardation.
Uncertainty associated with each of these individual components adds 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 open environment 90 percent of the time. Mobility input
values are chosen to be representative of conditions in the open environment. The natural
variation in soils adds to the uncertainty of modeled values. Factors such as application date,
crop emergence date, and canopy cover can also affect estimated concentrations, adding to the
uncertainty of modeled values. Factors within the ambient environment such as soil
temperatures, sunlight intensity, antecedent soil moisture, and surface water temperatures can
cause actual aquatic concentrations to differ for the modeled values.
Additionally, the rate at which bensulide is applied, the percent of a watershed that is cropped,
and the percent of crops in that watershed that are actually treated with bensulide may be lower
than the Agency's default assumptions including use of the maximum allowable application rate,
treatment of the entire crop, and the estimated area within a watershed planted with agricultural
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crops. The geometry of a watershed and limited meteorological data sets also add to the
uncertainty of estimated aquatic concentrations.
6.2 Effects Assessment Uncertainties
6.2.1 Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test organism age may have a significant impact on the observed
sensitivity to a toxicant. The acute toxicity data for fish are collected on juvenile fish between
0.1 and 5 grams. Aquatic invertebrate acute testing is performed on recommended immature age
classes (e.g., first instar for daphnids, second instar for amphipods, stoneflies, mayflies, and third
instar for midges).
Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients, such as bensulide, that act directly without metabolic transformation because
younger age classes may not have the enzymatic systems associated with detoxifying
xenobiotics. In so far as the available toxicity data may provide ranges of sensitivity information
with respect to age class, this assessment uses the most sensitive life-stage information as
measures of effect for surrogate aquatic animals, and is therefore, considered as protective of the
California Red Legged Frog.
6.2.2 Extrapolation of Long-term Environmental Effects from Short-term
Laboratory Tests
The influence of length of exposure and concurrent environmental stressors to the California Red
Legged Frog (i.e., urban expansion, habitat modification, decreased quantity and quality of water
in CRLF habitat, predators, etc.) will likely affect the species' response to bensulide. Additional
environmental stressors may decrease the CRLF's sensitivity to the insecticide, although there is
the possibility of additive/synergistic reactions. Timing, peak concentration, and duration of
exposure are critical in terms of evaluating effects, and these factors will vary both temporally
and spatially within the action area. Overall, the effect of this variability may result in either an
overestimation or underestimation of risk. However, as previously discussed, the Agency's
LOCs are intentionally set very low, and conservative estimates are made in the screening level
risk assessment to account for these uncertainties.
6.2.3 Sublethal Effects
For an acute risk assessment, the screening risk assessment relies on the acute mortality endpoint
as well as a suite of sublethal responses to the pesticide, as determined by the testing of species
response to chronic exposure conditions and subsequent chronic risk assessment. Consideration
of additional sublethal data in the assessment 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.
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6.2.4 Location of Wildlife Species
For this baseline terrestrial risk assessment, a generic bird or mammal was assumed to occupy
either the treated field or adjacent areas receiving a treatment rate on the field. Actual habitat
requirements of any particular terrestrial species were not considered, and it was assumed that
species occupy, exclusively and permanently, the modeled treatment area. Spray drift model
predictions suggest that this assumption leads to an overestimation of exposure to species that do
not occupy the treated field exclusively and permanently.
6.2.5 Use of avian data as surrogate for amphibian data
Toxicity data for terrestrial phase amphibians was not available for use in this assessment.
Therefore, avian toxicity data were used as a surrogate for risk estimation. There is uncertainty
regarding the relative sensitivity of reptiles and birds to bensulide. If birds are substantially more
or less sensitive than the California red legged frog, then risk would be over or under estimated,
respectively.
6.2.6 Assumptions Associated with the Acute LOCs
The risk characterization section of this listed species assessment includes an evaluation of the
potential for individual effects. The individual effects probability associated with the acute RQ
is based on the mean estimate of the slope and an assumption of a probit dose response
relationship for the effects study corresponding to the taxonomic group for which the LOCs are
exceeded.
Additionally the acute freshwater invertebrate LOC exceedances were based upon a
supplemental water flea acute toxicity study (MRID 159322). The study is supplemental
because the dissolve oxygen at the four highest test concentrations was unacceptably low. Thus,
the low dissolved oxygen may have contributed to the lethality effects demonstrated in this
study. Thus, there is some uncertainty regarding the use of the endpoints produced in this study.
However, in order to ensure adequate protection to the CRLF, the data produced in the study was
used as a conservative approach to assessing the risk of bensulide to freshwater aquatic
invertebrate.
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Table 20 Summary of Direct and Indirect Effects to the CRLF
lahle 1 1 Siiiiiiii;ii\ ol'eireclsdelemniialioiis I'oidiiecl indirect effects In 1 lie ( kl.l' and lis critical h;ihil;il
\ssessiiieiil 1 iiidpniiil
~Tecls
delerminaikHi
liasis lor 1 )eleiiiiiiialK
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Evaluation of the implication of this non-uniform distribution of risk to the species would require
information and assessment techniques that are not currently available. Examples of such
information and methodology required for this type of analysis would include the following:
Enhanced information on the density and distribution of CRLF life stages within
specific recovery units and/or designated critical habitat within the action area.
This information would allow for quantitative extrapolation of the present risk
assessment's predictions of individual effects to the proportion of the population
extant within geographical areas where those effects are predicted. Furthermore,
such population information would allow for a more comprehensive evaluation of
the significance of potential resource impairment to individuals of the species.
Quantitative information on prey base requirements for individual aquatic- and
terrestrial-phase frogs. While existing information provides a preliminary picture
of the types of food sources utilized by the frog, it does not establish minimal
requirements to sustain healthy individuals at varying life stages. Such
information could be used to establish biologically relevant thresholds of effects
on the prey base, and ultimately establish geographical limits to those effects.
This information could be used together with the density data discussed above to
characterize the likelihood of adverse effects to individuals.
Information on population responses of prey base organisms to the pesticide.
Currently, methodologies are limited to predicting exposures and likely levels of
direct mortality, growth or reproductive impairment immediately following
exposure to the pesticide. The degree to which repeated exposure events and the
inherent demographic characteristics of the prey population play into the extent to
which prey resources may recover is not predictable. An enhanced understanding
of long-term prey responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and together
with the information described above, a more complete prediction of effects to
individual frogs and potential modification to critical habitat.
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