Risks of BROMACIL and
BROMACIL LITHIUM Use to the 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 19,2007
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Primary Authors
Kristina Garber, Biologist
Cheryl A. Sutton, Ph. D., Environmental Scientist
Reviewers
Thomas Steeger, Ph.D., Senior Biologist
Marietta Echeverria, RAPL
Branch Chief, Environmental Risk Branch 4
Elizabeth Behl
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Acknowledgement
The bromacil chemical team would like to acknowledge the contribution of the California
Red-Legged Frog Steering Committee in compiling detailed information on the
threatened species. Additionally, the Steering Committee has provided invaluable
guidance toward achieving greater consistency in format and content between chemicals
being assessed. We acknowledge the contribution of Mr. Kurt Pluntke in providing the
Geographic Information System analysis used to define the potential overlap between
California red-legged frog and their designated critical habitat with the action area.
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Table of Contents
ACKNOWLEDGEMENT 3
TABLE OF CONTENTS 4
1. EXECUTIVE SUMMARY 8
2. PROBLEM FORMULATION 14
2.1 PURPOSE 14
2.2 SCOPE 16
2.3 PREVIOUS ASSESSMENTS 18
2.4 STRESSOR SOURCE AND DISTRIBUTION 18
2.4.1 Environmental Fate Assessment 18
2.4.2 Environmental Transport Assessment 21
2.4.3 Mechanism of Action 22
2.4.4 Use Characterization 22
2.5 ASSESSED SPECIES 25
2.5.7 Distribution 25
2.5.2 Reproduction 31
2.5.3 Diet 32
2.5.4 Habitat 32
2.6 DESIGNATED CRITICAL HABITAT 33
2.7 ACTION AREA 35
2.8 ASSESSMENT ENDPOINTS AND MEASURES OF ECOLOGICAL EFFECT 39
2.8.1. Assessment Endpointsfor the CRLF 39
2.8.2. Assessment Endpoints for Designated Critical Habitat 41
2.9 CONCEPTUAL MODEL 43
2.9.1 Risk Hypotheses 43
2.9.2 Diagram 44
2.10 ANALYSIS PLAN 48
2.10.1. Measures to Evaluate the Risk Hypothesis and Conceptual Model 49
2.10.2. Data Gaps 52
3. EXPOSURE ASSESSMENT 54
3.1. AQUATIC EXPOSURE ASSESSMENT 54
3.1.1. Existing Water Monitoring Data for California 54
3.1.2. Modeling Approach 55
3.1.3. Aquatic Modeling Results 60
3.2. TERRESTRIAL EXPOSURE ASSESSMENT 60
3.2.1. Exposure to Plants 60
3.2.2. Exposures to animals 61
3.2.3. Spray Drift Modeling 62
4. EFFECTS ASSESSMENT 64
4.1. EVALUATION OF AQUATIC ECOTOXICITY STUDIES FOR BROMACIL 65
4.1.1. Toxicity to freshwater fish 67
4.1.2. Toxicity to freshwater invertebrates 67
4.1.3. Toxicity to aquatic plants 68
4.2. EVALUATION OF TERRESTRIAL ECOTOXICITY STUDIES FOR BROMACIL 69
4.2.1. Toxicity to birds 72
4.2.2. Toxicity to mammals 73
4.2.3. Toxicity to terrestrial insects 73
4.2.4. Toxicity to terrestrial plants 73
4.3. INCIDENT REPORTS 74
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5. RISK CHARACTERIZATION 78
5.1. RISK ESTIMATION 78
5.7.7. Exposures in the Aquatic Habitat 78
5.1.2. Exposures in the Terrestrial Habitat 80
5.2. RISK DESCRIPTION 82
5.2.1. Direct Effects 83
5.2.2. Indirect Effects (through effects to prey) 88
5.2.3. Indirect Effects (through effects to habitat) 93
5.2.4. Primary Constituent Elements of Designated Critical Habitat 94
5.2.5. Action Area 96
5.2.6. Description of Assumptions, Limitations, Uncertainties, Strengths and Data Gaps 101
5.2.7. Addressing the Risk Hypotheses 109
6. CONCLUSIONS 110
PREFERENCES 112
Appendices
Appendix A. Pesticide Products Formulated with Bromacil and Other Pesticide Active Ingredients
Appendix B. PRZM/EXAMS Inputs and Outputs and results of non-cropland refinements
Appendix C. Outputs from TerrPlant vl.2.2
Appendix D. Outputs from T-REX v. 1.3.1
Appendix E. Outputs from T-HERPS v.1.0
Appendix F. The Risk Quotient Method and Levels of Concern
Appendix G. List of citations accepted and rejected by ECOTOX criteria
Appendix H. Detailed analysis of final bromacil/bromacil lithium action area and overlap of action area
with CRLF core areas and critical habitat
Attachments
Attachment 1: Status and Life History of California Red-legged Frog
Attachment 2: Baseline Status and Cumulative Effects for the California Red-legged Frog
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List of Figures
Figure 1. Historical (2002) extent of bromacil use in agricultural areas 24
Figure 2. Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for CRLF 30
Figure 3. CRLF Reproductive Events by Month 31
Figure 4. Initial action area for crops described by orchard and vineyard landcover which corresponds to
potential bromacil use sites on citrus. This map represents the area potentially directly affected by the
federal action 37
Figure 5. Initial action area for crops described by right-of-way landcover which corresponds to potential
bromacil and bromacil lithium use sites on (some) non-cropland areas. This map represents the area
potentially directly affected by the federal action 38
Figure 6. Conceptual Model for Pesticide Effects on Aquatic Phase of the Red-Legged Frog 45
Figure 7. Conceptual Model for Pesticide Effects on Terrestrial Phase of Red-Legged Frog 46
Figure 8. Conceptual Model for Pesticide Effects on Aquatic Components of Red-Legged Frog Critical
Habitat 47
Figure 9. Conceptual Model for Pesticide Effects on Terrestrial Components of Red-Legged Frog Critical
Habitat 48
Figure 10. Final action area for crops described by the orchard/vineyard landcover which corresponds to
potential bromacil use on citrus. This map represents the area potentially directly and indirectly affected by
the federal action 98
Figure 11. Final action area for crops described by right-of-way landcover which corresponds to potential
bromacil and bromacil lithium use sites on non-cropland areas. This map represents the area potentially
directly and indirectly affected by the federal action 99
List of Tables
Table 1. Effects Determination Summary for the CRLF based on bromacil use on citrus 11
Table 2. Effects Determination Summary for the CRLF based on bromacil and bromacil lithium use on
non-cropland areas 12
Table 3. Chemical identities of bromacil and bromacil lithium 19
Table 4. Summary of environmental chemistry, fate and transport properties of bromacil 20
Table 5. Uses and maximum use rates of bromacil and bromacil lithium 23
Table 6. California Red-legged Frog Recovery Units with Overlapping Core Areas and Designated Critical
Habitat 28
Table 7. Summary of Assessment Endpoints and Measures of Ecological Effects for Direct and Indirect
Effects of bromacil and bromacil lithium on the California Red-legged Frog 40
Table 8. Summary of Assessment Endpoints and Measures of Ecological Effect for Primary Constituent
Elements of Designated Critical Habitat 42
Table 9. Agency risk quotient (RQ) metrics and levels of concern (LOG) per risk class 52
Table 10. NAWQA 1993 - 2005 data for bromacil detections u in CA SURFACE waters. Data are
distinguished by the landcover (e.g. agricultural, urban, etc.) of the watershed of the sampled water bodies.
54
Table 11. NAWQA 1993 - 2005 data for bromacil detections u in CA GROUND waters. Data are
distinguished by the landcover (e.g. agricultural, urban, etc.) of the watershed of the sampled water bodies.
55
Table 12. Chemical specific PRZM/EXAMS Input Parameters for deriving aquatic EECs for bromacil... 58
Table 13. Use-specific PRZM/EXAMS Input Parameters for deriving aquatic EECs for bromacil 58
Table 14. Aquatic EECs from PRZM/EXAMS modeling for maximum application rates of bromacil. EECs
are based on the appropriate PRZM scenario and the standard EXAMS pond 60
Table 15. TerrPlant inputs and resulting EECs for plants inhabiting dry and semi-aquatic areas exposed to
bromacil through runoff and drift 60
Table 16. Input parameters for T-REX used to derive terrestrial EECs for bromacil 61
Table 17. Upper-bound Kenega nomogram EECs for exposures of the CRLF and its prey to bromacil 61
Table 18. Distance away from edge of field where terrestrial animal and plant LOCs are not exceeded by
exposures to bromacil through spray drift 62
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Table 19. Scenario and standard management input parameters for simulation of bromacil in spray drift
using AgDisp with Gaussian farfield extension 63
Table 20. Summary of most sensitive toxicity for assessing direct and indirect effects of bromacil to CRLF
in aquatic habitats 66
Table 21. Categories of Acute Toxicity for Aquatic Animals 66
Table 22. EC50 and NOAEC values from registrant submitted studies involving exposures of bromacil to
unicellular, aquatic plants 69
Table 23. Summary of most sensitive toxicity for assessing direct and indirect effects of bromacil to CRLF
in terrestrial habitats 70
Table 24. Categories for mammalian acute toxicity based on median lethal dose in mg per kilogram body
weight (parts per million) 71
Table 25. Categories of avian acute oral toxicity based on median lethal dose in milligrams per kilogram
body weight (parts per million) 71
Table 26. Categories of avian subacute dietary toxicity based on median lethal concentration in milligrams
per kilogram diet per day (parts per million) 71
Table 27. Comparison of seedling emergence endpoints1 for wheat and rape exposed to bromacil and
bromacil lithium 74
Table 28. Comparison of vegetative vigor endpointsl for wheat and rape exposed separately to bromacil
and bromacil lithium 74
Table 29. Summary of reported incidents involving terrestrial plants in relation to applications of bromacil.
76
Table 3 0. Summary of reported incidents involving fish kills in relation to applications of bromacil 77
Table 31. RQ values for acute and chronic exposures directly to the CRLF in aquatic habitats 79
Table 32. RQ values for exposures to unicellular aquatic plants (diet of CRLF in tadpole life stage) 79
Table 33. Risk Quotient (RQ) values for acute and chronic exposures to aquatic invertebrates (prey of
CRLF juveniles and adults) in aquatic habitats 79
Table 34. RQ values for exposures of aquatic plants to bromacil 80
Table 35. RQ values for exposures of terrestrial-phase CRLF to bromacil. RQs estimated using T-REX.. 80
Table 36. RQ values for exposures of terrestrial animals to bromacil. RQs estimated using T-REX 81
Table 37. RQ values for exposures of terrestrial plants to bromacil. RQs estimated using TerrPlant 82
Table 38. RQ values for acute and chronic exposures directly to the CRLF in aquatic habitats resulting
from applications of bromacil and bromacil lithium to non-cropland areas at the maximum uses allowed by
labels 84
Table 39. Dietary-based and dose-based EECs relevant to direct effects to the CARLF through
consumption of prey contaminated by bromacil. Modeling done with T-HERPS 85
Table 40. Acute and chronic, dietary-based RQs and dose-based RQs for direct effects to the terrestrial-
phase CRLF, based on bromacil exposures resulting from applications to citrus. RQs calculated using T-
HERPS 86
Table 41. Acute and chronic, dietary-based RQs and dose-based RQs for direct effects to the terrestrial-
phase CRLF, based on bromacil exposures resulting from bromacil applications to non-cropland areas (max
rate = 2 applications of 15.4 Ibs a.i./A). RQs calculated using T-HERPS 87
Table 42. Acute and chronic, dietary-based RQs and dose-based RQs for direct effects to the terrestrial-
phase CRLF, from bromacil lithium applications to non-cropland areas (max rate = 1 application of 12 Ibs
a.i./A). RQs calculated using T-HERPS 87
Table 43. Species specific RQs for unicellular aquatic plants 89
Table 44. RQ values for exposures of terrestrial frogs (prey of CRLF) to bromacil. RQs estimated using T-
HERPS 92
Table 45. Quantitative results of spatial analysis of lotic aquatic action area relevant to bromacil 96
Table 46. Overlap between CRLF habitat (core areas and critical habitat) and citrus action area by recovery
unit(RU#) 100
Table 47. Overlap between CRLF habitat (core areas and critical habitat) and non-cropland action area by
recovery unit (RU#) 100
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1. Executive Summary
The purpose of this assessment is to evaluate potential direct and indirect effects on the
California red-legged frog (Rana aurora draytonii; CRLF) arising from FIFRA
regulatory actions regarding use of bromacil and its salt, bromacil lithium, on agricultural
and non-agricultural sites. In addition, this assessment evaluates whether these actions
can be expected to result in modification of the species' designated critical habitat. This
assessment was completed in accordance with the U.S. Fish and Wildlife Service
(USFWS) and National Marine Fisheries Service (NMFS) Endangered Species
Consultation Handbook (USFWS/NMFS, 1998 and procedures outlined in the Agency's
Overview Document (U.S. EPA, 2004).
The CRLF was listed as a threatened species by USFWS in 1996. The species is endemic
to California and Baja California (Mexico) and inhabits both coastal and interior
mountain ranges. A total of 243 streams or drainages are believed to be currently
occupied by the species, with the greatest numbers in Monterey, San Luis Obispo, and
Santa Barbara counties (USFWS 1996) in California.
This assessment considers registrations of bromacil, as well as bromacil lithium, which
dissociates to form bromacil. Bromacil and bromacil lithium are currently registered
herbicides for use on non-cropland areas, including (but not necessarily limited to)
airports, parking lots, industrial areas, rights-of-way (for railroads, highways, pipeline
and utilities), storage areas, lumberyards, tank farms, under asphalt and concrete
pavement and fence rows. These chemicals can also be used in uncultivated portions of
agricultural areas, including farmyards, fuel storage areas, fence rows and barrier strips.
In addition, bromacil is registered for use in citrus orchards and pineapple fields. The
maximum use rates of bromacil and bromacil lithium on non-cropland areas are 2
applications per year of 15.4 Ibs a.i./A and 1 application per year of 12 Ibs a.i./A,
respectively. The maximum use rate of bromacil on citrus orchards is 1 application per
year of 6.4 Ibs a.i./A. All exposure modeling and resulting risk conclusions are made
based on these maximum application rates.
In this assessment, it is assumed that uses of bromacil and bromacil lithium could
potentially result in exposures of bromacil to aquatic and terrestrial habitats of the CRLF.
In this assessment, when uses of non-cropland areas are discussed, bromacil and bromacil
lithium are considered. Since bromacil lithium dissociates in water to form bromacil, this
assessment refers to exposures resulting from non-cropland uses in terms of bromacil.
Fate and effects data for bromacil are considered relevant for both bromacil and bromacil
lithium.
The environmental fate properties of bromacil along with monitoring data identifying its
presence in surface waters and ground waters in California indicate that bromacil has the
potential to be transported to non-target areas. In this assessment, transport of bromacil
from initial application sties through runoff and spray drift are considered in deriving
quantitative estimates of bromacil exposure to CRLF, its prey and its habitats.
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Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF, its prey
and its habitats to bromacil are assessed separately for the two habitats. Tier-II exposure
models (PRZM/EXAMS) are used to estimate high-end exposures of bromacil in aquatic
habitats resulting from runoff and spray drift from different uses. Peak model-estimated
environmental concentrations resulting from maximum label rates of bromacil for citrus
and non-agricultural uses are 0.050 and 2.34 mg/L, respectively, in aquatic habitats.
These estimates are 1-3 orders of magnitude greater than the maximum concentration of
bromacil (0.0075 mg/L) measured in non-targeted monitoring in California surface
waters.
To estimate bromacil exposures to terrestrial-phase CRLF, and its potential prey resulting
from uses involving maximum application rates of bromacil or bromacil lithium, the T-
REX model is used. To further characterize exposures of terrestrial-phase CRLF to
dietary- and dose-based exposures of bromacil, T-HERPS is used. AgDRIFT and
AGDISP are also used to estimate deposition of bromacil on terrestrial habitats from
spray drift. To estimate bromacil exposures to terrestrial-phase habitat, including plants
inhabiting semi-aquatic and dry areas, the TerrPlant model is used.
The assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the aquatic- and terrestrial-phase CRLF itself, as well as
indirect effects, such as reduction of the prey base and/or modification of its habitat.
Direct effects to the CRLF in the aquatic habitat are based on toxicity information for
freshwater fish, which are generally used as a surrogate for aquatic-phase amphibians. In
the terrestrial habitat, direct effects are based on toxicity information for birds, which are
used as a surrogate for terrestrial-phase amphibians. Given that the CRLF's prey items
and designated critical habitat requirements in the aquatic habitat are dependant on the
availability of freshwater aquatic invertebrates and aquatic plants, toxicity information
for these taxonomic groups is also discussed. In the terrestrial habitat, indirect effects
due to depletion of prey are assessed by considering effects to terrestrial insects, small
terrestrial mammals and frogs. Indirect effects due to modification of the terrestrial
habitat are characterized by available data for terrestrial monocots and dicots.
Bromacil is slightly toxic to freshwater fish and practically non-toxic to freshwater
invertebrates on an acute exposure basis. Toxicity categories for aquatic plants have not
been defined. If classification for animals were applied to aquatic plants, bromacil would
be classified very highly toxic to unicellular and vascular plants. The NOAECs for the
fathead minnow and waterflea are 3.0 and 8.2 mg a.i./L, respectively. Bromacil is
practically nontoxic to birds and slightly toxic to mammals on an acute exposure basis.
Chronic exposures to bobwhite quail in reproduction studies indicate reproductive effects
(embryo viability and survival, hatchability and hatchling survival) with a NOAEC of
1500 mg/kg-diet/day. Chronic exposures to rats in a reproduction study indicate a
NOAEL for body weight reductions of 250 mg/kg-diet/day. Seedling emergence and
vegetative vigor studies with wheat (a monocot) result in EC25 values of 0.030 and 0.042
Ibs a.i./A, respectively. Seedling emergence and vegetative vigor studies with rape (a
dicot) result in EC25 values of 0.0047 and 0.0055 Ibs a.i./A, respectively.
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Risk quotients (RQs) are derived as quantitative estimates of potential high-end risk.
Acute and chronic RQs are compared to the Agency's levels of concern (LOCs) for
Federally-listed threatened species to identify if bromacil or bromacil lithium use within
the action area has any direct or indirect effect on the CRLF. Based on estimated
environmental concentrations for the currently registered uses of bromacil or bromacil
lithium, RQ values are above the Agency's LOG for direct acute effects on the CRLF
resulting from applications to citrus and non-cropland areas; this represents a "may
affect" determination. RQs for uses on citrus and non-cropland areas exceed the LOG for
exposures to aquatic unicellular plants. Therefore, there is a potential to indirectly affect
larval (tadpole) CRLF due to effects to the algae forage base in aquatic habitats. The
effects determination for indirect effects to the CRLF due to effects to its prey base is
"may affect." When considering the prey of larger CRLF in terrestrial habitats (e.g. frogs,
fish and small mammals), RQs for some of these taxa also exceed the LOG for acute and
chronic exposures, resulting in a "may affect" determination. RQ values for plants in
aquatic and terrestrial habitats exceed the LOG; therefore, indirect effects to the CRLF
through effects on aquatic and terrestrial habitats result in a "may affect" determination.
All "may affect" determinations are further refined using available evidence to determine
whether they are "not likely to adversely affect" (NLAA) or "likely to adversely affect"
(LAA). Additional evidence is employed to distinguish between NLAA and LAA
determinations. This evidence includes available monitoring data and likelihood of
individual mortality analysis.
Refinement of all "may affect" determinations from bromacil use on citrus results in a
"NLAA" determination for direct effects to the CRLF, a "LAA" determination for
indirect effects to the CRLF based on effects to its prey, specifically algae, and a "LAA"
determination for indirect effects to the CRLF based on effects to aquatic and terrestrial
habitat (Table 1). Consideration of CRLF critical habitat indicates a determination of
"habitat modification" for aquatic and terrestrial habitats based on bromacil use on citrus.
The overall CRLF effects determination for bromacil use on citrus is "LAA."
Refinement of all "may affect" determinations from bromacil and bromacil lithium use
on non-cropland areas result in a "LAA" determination for direct effects to the CRLF, a
"LAA" determination for indirect effects to the CRLF based on effects to its prey,
specifically algae, and a "LAA" determination for indirect effects to the CRLF based on
effects to aquatic and terrestrial habitat (Table 2). Consideration of CRLF critical habitat
indicates a determination of "habitat modification" for aquatic and terrestrial habitats
based on non-cropland uses of bromacil and bromacil lithium. The overall CRLF effects
determination for bromacil and bromacil lithium use on non-cropland areas is
"LAA."
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
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Table 1. Effects Determination Summary for the CRLF based on bromacil use on citrus.
Assessment I ml point
Effects
Determination1
Basis for Determination
Direct effects to CRLF
NLAA
- Acute and chronic RQs for CRLF in aquatic habitats do not exceed the listed species LOG, therefore, the risk of bromacil exposures to CRLF in this habitat is low.
-Dose-based and dietary-based acute RQs for the terrestrial phase CRLF are indiscreet because dose-based and dietary-based studies did not quantify LD50 and LC50
values (respectively), which were greater than the highest concentrations tested.
-Refined RQs (using T-HERPS) indicates a potential LOG exceedance for medium sized (37g) terrestrial-phase CRLF consuming small herbivore mammals (based on
acute, dose based exposures). No other dose-based RQs exceed the LOG for CRLF of other feeding categories. Risk of mortality and sublethal effects to the CRLF is
unlikely since comparison of EECs to the lowest concentration where sublethal effects were observed in an acute oral study with birds indicates that exposure
concentrations are insufficient to reach levels where sublethal effects were observed.
-RQ for acute, dietary-based exposure to the terrestrial phase CRLF does not exceed LOG.
-RQ for chronic exposure of the terrestrial phase CRLF to bromacil does not exceed listed species LOG.
Indirect effects to tadpole
CRLF via reduction of
prey
(i.e., algae)
LAA
-RQ exceeds LOG by>8x.
- According to available toxicity data for 4 species of unicellular aquatic plants, EECs are sufficient to exceed the LOG for 3 of 4 species.
- Non-target monitoring data are at levels sufficient to exceed the LOG for unicellular aquatic plants.
- Exposures of bromacil in aquatic habitats have the potential to affect populations and possibly communities of aquatic algae.
Indirect effects to juvenile
CRLF via reduction of
prey (i.e., invertebrates)
NLAA
- Aquatic Invertebrates: Acute and chronic RQs do not exceed LOG, indicating low risk of mortality to these organisms.
- Terrestrial Invertebrates: RQs for small and large insects potentially exceed the LOG. RQs are indiscreet because the available acute toxicity study did not quantify
LD50. Direct comparison of the level were 1.2% mortality was observed with EECs calculated by T-REX for small and large insects exposed to bromacil applied to
citrus, the EECs are insufficient to reach the level where 1.2% mortality was observed in honey bees. Indirect effects to the CRLF due to effects to terrestrial
invertebrates are insignificant.
Indirect effects to adult
CRLF via reduction of
prey
(i.e., invertebrates, fish,
frogs, mice)
NLAA
- Aquatic Invertebrates: Acute and chronic RQs do not exceed LOG, indicating low risk of mortality to these organisms.
- Terrestrial Invertebrates: RQs for small and large insects potentially exceed the LOG. RQs are indiscreet because the available acute toxicity study did not quantify
LD50. Direct comparison of the level were 1.2% mortality was observed with EECs calculated by T-REX for small and large insects exposed to bromacil applied to
citrus, the EECs are insufficient to reach the level where 1.2% mortality was observed in honey bees. Indirect effects to the CRLF due to effects to terrestrial
invertebrates are insignificant.
- Fish and aquatic-phase frogs: Acute and chronic RQs do not exceed listed species LOG for fish and aquatic-phase amphibians, indicating low risk of mortality to
these organisms.
- Terrestrial-phase frogs: For terrestrial frogs serving as CRLF prey, refined EECs from T-HERPS result in RQs which are insufficient to exceed acute and chronic
listed species LOCs.
- Mice: Acute RQ exceeds listed species LOG by 8.2X for small terrestrial mammals consuming short grass. Exposures up to 23 feet beyond the edge of the citrus
orchard are sufficient to exceed the LOG. The likelihood of individual mortality for mice directly on the field is 34.5%.
-Chronic RQ exceeds listed species LOG by 6.1 to 53X for small terrestrial mammals consuming short grass. Chronic exposures (dose-based) up to 132 feet
beyond the edge of the citrus orchard are sufficient to exceed the LOG. Chronic EECs are sufficient to exceed the LOAEC concentration for the available
chronic mammalian toxicity study.
- Summary: Because the adult CRLF is an opportunistic feeder, it will consume available prey. Since effects are not expected for the majority of its possible prey items
(4 of 5), it is expected that there will be sufficient prey to maintain the adult CRLF. Potential effects to mice are considered insignificant to the adult CRLF, when
considering its entire diet.
Indirect effects to CRLF
via reduction of habitat
and/or primary
productivity
(i.e., plants)
LAA
-RQs for plants inhabiting acute and terrestrial habitats exceed LOG by several orders of magnitude.
-For terrestrial dicots, spray drift exposures up to 4026 feet (0.76 miles) beyond the edge of the citrus orchard are sufficient to exceed the LOG.
-Several ecological incidents have been reported related to effects of runoff of bromacil to non-target plants.
-Bromacil is an herbicide, and is expected to cause effects to plants.
'LAA = likely to adversely affect; NLAA = not likely to adversely affect; NE = no effect
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Table 2. Effects Determination Summary for the CRLF based on bromacil and bromacil lithium use on non-cropland areas.
Assessment I ml point
Effects
Determination1
Basis for Determination
Direct effects to CRLF
LAA
- Acute aquatic RQs for the maximum use rate of bromacil on rights of ways and impervious surfaces exceed the listed species LOG. The likelihood of individual
mortality to a CRLF individual is 1 in 2.17e7. Since the chance of this occurring is approximately 0.000005%, potential direct effects are insignificant. Therefore, the
risk of bromacil exposures to CRLF in this habitat is low.
- Acute aquatic RQs that result from the maximum use rate of bromacil lithium are insufficient to exceed the listed species LOG.
- The chronic aquatic RQ does not exceed listed species LOG.
- Dose-based and dietary-based acute RQs for the terrestrial phase CRLF are indiscreet because dose-based and dietary-based studies did not quantify LD50 and LC50
values (respectively), which were greater than the highest concentrations tested.
- Refined RQs (using T-HERPS) indicates potential LOG exceedances for several feeding categories and body sizes of CRLF when considering applications of
bromacil and bromacil lithium at their respective maximum use rates.
- Comparison of EECs to effects observed in acute tests indicated that EECs exceed levels where sublethal effects and mortality (20%) were observed. Therefore, there
is potential for direct effects to the terrestrial-phase CRLF resulting from acute exposures.
- For chronic exposures of the CRLF in the terrestrial habitat, the LOG is exceeded for applications of bromacil, specifically for CRLF feeding on small insects and on
small herbivore mammals. Chronic RQs for bromacil lithium applications also exceed the LOG. Direct comparison of chronic dietary-based EECs resulting from
bromacil applications to the chronic avian reproduction study LOAEC indicate that EECs are sufficient to exceed the level where reproductive effects were observed in
birds.
- Acute effects directly to terrestrial-phase CRLF resulting from bromacil and bromacil lithium applications at the maximum allowed rates to and to non-cropland areas
cannot be discounted.
- At the maximum use rate of bromacil, there is potential for risk directly to the terrestrial-phase CRLF based on chronic exposures.
Indirect effects to tadpole
CRLF via reduction of
prey (i.e., algae)
LAA
-RQ exceeds LOC by>300x.
- According to available toxicity data for 4 species of unicellular aquatic plants, EECs are sufficient to exceed the LOC for 4 of 4 species.
- Non-target monitoring data are at levels sufficient to exceed the LOC for unicellular aquatic plants.
- Exposures of bromacil in aquatic habitats have the potential to affect populations and possibly communities of aquatic algae.
Indirect effects to
juvenile CRLF via
reduction of prey (i.e.,
invertebrates)
NLAA
- Aquatic Invertebrates: Acute and chronic RQs do not exceed LOC, indicating low risk of mortality to these organisms.
- Terrestrial Invertebrates: Direct comparison of the level were 1.2% mortality was observed with EECs calculated by T-REX for large insects, indicates that EECs are
insufficient to reach the level where 1.2% mortality was observed in honey bees. For small insects, EECs are approximately 3x the level where 1.2% mortality was
observed in honey bees. It is expected that beyond the edge of the application site, EECs will be below the level where 1.2% mortality was observed in honey bees.
On application sites, use of bromacil on non-cropland areas could potentially result in mortality to >1.2% of small sized insects. There is potential for effects to some
terrestrial invertebrates (small sized) representing CRLF prey; however, it seems unlikely that large sized terrestrial invertebrates will be affected by bromacil
applications to non-cropland areas, leaving terrestrial invertebrates to serve as prey to terrestrial-phase CRLF.
Indirect effects to adult
CRLF via reduction of
prey (i.e., invertebrates,
fish, frogs, mice)
NLAA
- Aquatic Invertebrates: Acute and chronic RQs do not exceed LOC, indicating low risk of mortality to these organisms.
- Terrestrial Invertebrates: There is potential for effects to some terrestrial invertebrates (small sized) representing CRLF prey; however, it seems unlikely that large
sized terrestrial invertebrates will be affected, leaving terrestrial invertebrates to serve as prey to terrestrial-phase CRLF.
- Fish and aquatic-phase frogs: The likelihood of individual mortality to an individual fish or frog is <0.001%. The chronic LOC is not exceeded.
- Terrestrial-phase frogs: For terrestrial frogs serving as CRLF prey, refined EECs from T-HERPS result in acute and chronic RQs which potentially exceed acute
listed species LOC.
- Mice: Acute RQ exceeds listed species LOC by 35X for small terrestrial mammals consuming short grass. Exposures up to 771 feet beyond the edge of the
application site are sufficient to exceed the LOC. The likelihood of individual mortality for mice directly on the field is approximately 100%.
-Chronic RQ exceeds listed species LOC by 26 to 225X for small terrestrial mammals consuming short grass. Chronic exposures (dose-based) up to 3113 feet
beyond the edge of the site of application are sufficient to exceed the LOC. Chronic EECs are sufficient to exceed the LOAEC concentration for the available
chronic mammalian toxicity study.
- Summary: Because the adult CRLF is an opportunistic feeder, it will consume available prey. Since effects are not expected for the majority of its possible prey items
(3 of 5), it is expected that there will be sufficient prey to maintain the adult CRLF. Potential effects to mice and terrestrial species of prey frogs are considered
insignificant to the adult CRLF, when considering its entire diet.
Indirect effects to CRLF
via reduction of habitat
and/or primary
productivity (i.e., plants)
LAA
-RQs for plants inhabiting acute and terrestrial habitats exceed LOC by several orders of magnitude.
-For terrestrial dicots, spray drift exposures up to 5909 feet (1.12 miles) beyond the edge of the application site are sufficient to exceed the LOC.
-Several ecological incidents have been reported related to effects of runoff of bromacil to non-target plants.
-Bromacil is an herbicide, and is expected to cause effects to plants.
'LAA = likely to adversely affect; NLAA = not likely to adversely affect; NE = no effect
12
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When evaluating the significance of this risk assessment's direct/indirect and habitat
modification 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.
13
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2. Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By
identifying the important components of the problem, it focuses the assessment on the
most relevant life history stages, habitat components, chemical properties, exposure
routes, and endpoints. The structure of this risk assessment is based on guidance
contained in U.S. EPA's Guidance for Ecological Risk Assessment (U.S. EPA 1998), the
Services' Endangered Species Consultation Handbook (USFWS/NMFS 1998) and is
consistent with procedures and methodology outlined in the Overview Document (U.S.
EPA 2004) and reviewed by the U.S. Fish and Wildlife Service and National Marine
Fisheries Service (USFWS/NMFS 2004).
2.1 Purpose
The purpose of this endangered species assessment is to evaluate potential direct and
indirect effects on individuals of the federally threatened California red-legged frog
(Rana aurora draytonii; CRLF) arising from FIFRA regulatory actions regarding use of
bromacil and its lithium salt as an herbicide on citrus and non-cropland areas, including
industrial and right-of-way areas. 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 endangered 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 accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of bromacil and bromacil lithium 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 bromacil and bromacil lithium may
potentially involve numerous areas throughout the United States and its Territories.
However, for the purposes of this assessment, attention will be focused on relevant
sections of the action area including those geographic areas associated with locations of
the CRLF and its designated critical habitat within the state of California.
As part of the "effects determination," one of the following three conclusions will be
reached regarding the potential for registration of bromacil and bromacil lithium at the
14
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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 CRLFs 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 LOG exceedances) upon individual CRLFs or upon the PCEs of the species'
designated critical habitat, a "no effect" determination is made for the FIFRA regulatory
action regarding bromacil and bromacil lithium as it relates to this species and its
designated critical habitat. If, however, direct or indirect effects to individual CRLFs are
anticipated or effects may impact the PCEs of the CRLF's designated critical habitat, a
preliminary "may affect" determination is made for the FIFRA regulatory action
regarding bromacil and bromacil lithium.
If a determination is made that use of bromacil and bromacil lithium 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 bromacil and bromacil lithium use sites) and further
evaluation of the potential impact of bromacil and bromacil lithium on the PCEs are 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 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 bromacil and bromacil lithium are expected to directly impact living organisms
within the action area (defined in Section 2.7), critical habitat analyses for bromacil and
bromacil lithium are limited in a practical sense to those PCEs of critical habitat that are
biological or that can be reasonably linked to biologically mediated processes (i.e., the
biological resource requirements for the listed species associated with the critical habitat
or important physical aspects of the habitat that may be reasonably influenced through
biological processes). Activities that may modify critical habitat are those that alter the
15
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PCEs and appreciably diminish the value of the habitat. Evaluation of actions related to
use of bromacil and bromacil lithium 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
This assessment considers registrations of bromacil, as well as its salt, bromacil lithium,
which dissociates to form bromacil in water. Bromacil and bromacil lithium are currently
registered for use as herbicides on non-cropland areas, including (but not necessarily
limited to) airports, parking lots, industrial areas, rights-of-way (for railroads, highways,
pipeline and utilities), storage areas, lumberyards, tank farms, under asphalt and concrete
pavement and fence rows. These chemicals can also be used as herbicides in uncultivated
portions of agricultural areas, including farmyards, fuel storage areas, fence rows and
barrier strips. In addition, bromacil (but not bromacil lithium) is registered for use in
citrus orchards and pineapple fields. Although labels allow applications of bromacil to
pineapple, this crop is generally not grown in California and is therefore, not relevant to
this assessment (USDA 2007).
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 bromacil and bromacil lithium in accordance with the approved product
labels for California are "the actions" being assessed.
Although current registrations of bromacil and bromacil lithium allow for use
nationwide, this ecological risk assessment and effects determination addresses currently
registered uses of bromacil and bromacil lithium 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.
In this assessment, it is assumed that uses of bromacil and bromacil lithium could
potentially result in exposures of bromacil to aquatic and terrestrial habitats of the CRLF.
In this assessment, when uses of non-cropland areas are discussed, bromacil and bromacil
lithium are considered. Since bromacil lithium dissociates in water to form bromacil, this
assessment refers to exposures resulting from non-cropland uses in terms of bromacil.
Fate and effects data for bromacil are considered relevant for both bromacil and bromacil
lithium.
Consistent with what was done for the environmental fate and ecological risk assessment
in support of the reregi strati on eligibility decision on bromacil, only parent bromacil (and
bromacil lithium) are included in this assessment. Although bromacil photodegrades
16
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rapidly at pH 9, information on photodegradates is not available. In soil, bromacil
degrades slowly (half-life of 275 days), and CC>2 is the only major degradate. Five
aerobic soil minor degradates were identified, but were present at only 0.6-3.4% of total
residues. The major and persistent anaerobic aquatic degradate, 3-sec-butyl-6-
methyluracil (Metabolite F), which represented a maximum of 80.7% of the applied (day
304), was not determined to be of toxicological concern (Linda Taylor, HED/OPP) in the
bromacil RED.
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures
of active ingredients, either those mixtures of multiple active ingredients in product
formulations or those in the applicator's tank. In the case of the product formulations of
active ingredients (that is, a registered product containing more than one active
ingredient), each active ingredient is subject to an individual risk assessment for
regulatory decision regarding the active ingredient on a particular use site. If effects data
are available for a formulated product containing more than one active ingredient, the
data 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).
Bromacil has registered products that contain multiple active ingredients, including
diuron; 2,4-dichlorophenoxyacetic acid; sodium chlorate; sodium metaborate; and 2,4-
dichlorophenoxy)-2,ethylhexyl ester. Analysis of the available acute oral mammalian
LDso data (and available open literature for Bromacil) for multiple active ingredient
products relative to the single active ingredient are provided in Appendix A. The results
of this analysis show that an assessment based on the toxicity of the single active
ingredient of bromacil or bromacil lithium is appropriately conservative since the
technical grade active ingredient is more toxic than the formulated end product.
This assessment considers only the single active ingredients bromacil and bromacil
lithium. However, the assessed species and their environments may be exposed to
multiple pesticides simultaneously. Interactions of other toxic agents with bromacil
could result in additive effects, synergistic effects or antagonistic effects. Evaluation of
pesticide mixtures is beyond the scope of this assessment because of the myriad factors
that cannot be quantified based on the available data. Those factors include identification
of other possible co-contaminants and their concentrations, differences in the pattern and
duration of exposure among contaminants, and the differential effects of other
physical/chemical characteristics of the receiving waters (e.g. organic matter present in
sediment and suspended water). Evaluation of factors that could influence
additivity/synergism is beyond the scope of this assessment and is beyond the capabilities
of the available data to allow for an evaluation. However, it is acknowledged that not
considering mixtures could over- or under-estimate risks depending on the type of
interaction and factors discussed above.
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2.3 Previous Assessments
Bromacil was first registered as an herbicide in the U.S. in 1961. EPA issued a
Registration Standard for bromacil in September 1982 (PB87-110276). In 1996, the
Agency completed a Reregi strati on Eligibility Decision (RED) for bromacil and its
lithium salt (USEPA 1996).
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Assessment
The environmental fate database for bromacil is largely complete. Bromacil is a
persistent and mobile herbicide. The primary routes of dissipation appear to be
photolysis in water under alkaline conditions (pH 9) and microbial degradation under
anaerobic conditions. However, the photodegradates under alkaline conditions have not
been defined, and the rate of degradation under anaerobic conditions has not been
accurately determined.
In laboratory studies, bromacil was stable to hydrolysis, photodegradation in water at
pH's 5 and 7, and photodegradation on soil. At pH 9, where an absorption spectrum shift
occurs, bromacil photodegraded fairly rapidly with a half-life of 4-7 days. However, the
radiolabeled residues in the pH 9 test solution was not further characterized, so
degradates were not identified or quantified.
Microbial degradation of bromacil in aerobic soil is slow, with a half-life of 275 days in a
silty clay loam soil. Carbon dioxide was the major degradate, totaling 40.3% of the
applied at 12 months posttreatment.
Bromacil may be expected to degrade more rapidly under anaerobic than aerobic
conditions. In an open-literature laboratory study, bromacil had an observed half-life of
144 to 198 days in Greenfield sandy loam soil under saturated (anaerobic) soil conditions
(Wolf, 1974). However, since there is no acceptable guideline study a conservative
assumption of "stable to anaerobic microbial degradation" is used in this assessment for
modeling aquatic exposures.
In field studies, bromacil was very persistent, with dissipation half-lives of 124-155 days
in the surface soil of bareground plots in Delaware and California, and detections in the
upper 10 cm of the plots through 538 and 415 days posttreatment, respectively.
Bromacil accumulates only slightly in fish and depurates rapidly. Maximum
bioconcentration factors (BCF) were 4.6X for muscle, 6.8-8.3X for viscera, 2.1-2.2X for
carcass, and 2.5-2.8X for whole fish. Depuration was rapid, with >96% of the
accumulated [14C]residues eliminated from the fish tissues by day 3 of the depuration
period.
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Table 3 summarizes the chemical identities of bromacil and bromacil lithium. Table 4
summarizes the environmental chemistry, fate and transport properties of bromacil.
Table 3. Chemical identities of bromacil and bromacil lithium.
PARAMETER
PC code
CAS No.
Chemical name
Chemical formula
Bromacil
012301
314-40-9
5-bromo-3-sec-butyl-6-methyluracil
C9H13BrN2O2
Bromacil lithium
012302
53404-19-6
5-bromo-3-sec-butyl-6-methyluracil, lithium
salt
C9H13BrN2O2Li+
19
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Table 4. Summary of environmental chemistry, fate and transport properties of bromacil.
PARAMETER
VALUE
REFERENCE/
COMMENTS
Selected Physical/Chemical Parameters
Molecular weight
Water solubility (25 °C)
Vapor pressure (25 °C)
Henry's law constant
Log Kow
pka
261.12g/mol
815 mg/L
3.1xlO"7torr
l.lX10-9atm*m3/mol
2.11
9.1
USEPA, 1996
USEPA, 1996
USEPA, 1996
USEPA, 1996
Hansch & Leo, 1995
bromacil ionizes at pH 9.1;
USEPA, 1996
Persistence
Hydrolysis
Photolysis in water (t1/2j
days)
Photolysis in soil
(t1/2> days)
Aerobic soil metabolism
(t1/2, days)
Anaerobic soil
metabolism
Aerobic aquatic
metabolism
Anaerobic aquatic
metabolism
pH5: stable
pH 7: stable
pH 9: stable
pH5:356
pH 7: 102
pH 9: 7, 4.3
166
275
No data
No data
No data
MRID 4095 1505
MRIDs 40951507, 40951508
Absorption spectrum shift occurs
in alkaline conditions (at pka of
9.1).
MRID 4095 1509
MRID 4095 15 10
No studies submitted.
No studies submitted.
Submitted study is unacceptable.
Mobility
Column Leaching
Soil Texture % of applied bromacil
found in leachate of the
four columns
Sand total residues in leachate =
Sandy loam 91.2-99.6% of the applied;
„, , bromacil in leachate - 89.0-
Clay loam „. 10/ -., ,. ,
94 1% of the applied
Silt loam
MRID 40951512; Koc of 32 used
in assessment is from SCS/ARS
database (only column leaching
data were available from
submitted studies)
Field Dissipation
Terrestrial field
dissipation (ti/2, days)
155 (silty clay loam soil in DE)
124 (loam soil in CA)
MRID 41677101; dissipation
from soil surface of bare ground
plots
Bioaccumulation
Accumulation in fish,
BCF
2.5-2.8X
MRID 4095 15 13
20
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2.4.2 Environmental Transport Assessment
Laboratory mobility data, in addition to groundwater monitoring information, have
clearly demonstrated that bromacil is mobile in soil. However, bromacil's tendency to
leach was not overwhelmingly apparent from the two field dissipation studies. The
timing and amount of rainfall/irrigation in these studies is a possible explanation.
In column leaching studies, bromacil was mobile in columns of sand, sandy loam, clay
1-14
loam, and silt loam soils. [ C]Residues in the leachates of all four soils totaled 91.2-
99.6% of the applied (bromacil comprised 89.0-94.1% of the applied).
Aged (30 days) bromacil residues were also mobile in a column of silt loam soil.
[14C]Residues in the leachate totaled 87.3% of the applied radioactivity. Bromacil was
the only compound identified in the leachate, comprising 82.8% of the applied
radioactivity.
Batch equilibrium data were not submitted for bromacil. For this assessment, the Koc
value of 32 L/kgoc used in modeling aquatic exposures was obtained from the Soil
Conservation Service Agricultural Research Station (SCS/ARS) database. This value is
similar in magnitude to values reported in the open literature. Gerstl (1984) found an
average Koc value of 23 L/kgoc from experimental values determined in 8 soils and 4
sediments. These values indicate that bromacil is mobile in soil, a conclusion which is
consistent with the results observed in the column leaching studies.
In the field, Bromacil was persistent, but did not demonstrate the degree of mobility that
was predicted based on the laboratory studies and the available groundwater monitoring
data. One possible explanation for the limited mobility in the two sites could be the
amount and timing of rainfall/irrigation. However, the average rainfall for the test period
was about or above the 30-year annual average of 43.36 inches for Wilmington,
Delaware, so minimal irrigation was needed. The average rainfall at the second field site
was below the 30-year annual average of 9.84 inches for Fresno, California, so
substantial irrigation was needed. Irrigation was based on common agricultural practice
for the area. Bromacil (Hyvar® X Herbicide, 80% WP), applied at 12 Ib ai/A, dissipated
with half-lives of 155 days from the upper 10 cm of a bare ground plot of silty clay loam
soil located in Delaware, and 124 days from the upper 10 cm of a bare ground plot of
loam soil located in California. Bromacil was detected at the Delaware and California
sites in the upper 10 cm of the plots through 538 and 415 days post treatment,
respectively.
Potential transport mechanisms for bromacil include surface water runoff, spray drift, and
secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or
more distant ecosystems. The magnitude of pesticide transport via secondary drift
depends on the pesticide's ability to be mobilized into air and its eventual removal
through wet and dry deposition of gases/particles and photochemical reactions in the
atmosphere. Based on the vapor pressure and Henry's Law constant of bromacil,
21
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volatilization from treated areas resulting in atmospheric transport and deposition
represent unlikely transport pathways leading to exposure of the CRLF and its habitats.
2.4.3 Mechanism of Action
Bromacil is classified in as a uracil herbicide. Bromacil interferes with the photosynthesis
of a plant by blocking electron transport in photosystem II. Symptoms of plant injury
include chlorosis and death of leaf tissue (Martin 2000).
2.4.4 Use Characterization
Analysis of labeled use information is the critical first step in evaluating the federal
action. The current labels for bromacil and bromacil lithium represent 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. Bromacil and bromacil lithium are currently registered for use on non-cropland
areas, including (but not necessarily limited to) airports, parking lots, industrial areas,
rights-of-way (for railroads, highways, pipeline and utilities), storage areas, lumberyards,
tank farms, under asphalt and concrete pavement and fence rows. These chemicals can
also be used in uncultivated portions of agricultural areas, including farmyards, fuel
storage areas, fence rows and barrier strips. In addition, bromacil (but not bromacil
lithium) is registered for use in citrus orchards and pineapple fields. Although labels
allow applications of bromacil to pineapple, this crop is not grown in California and is
therefore, not relevant to this assessment (USDA 2007). Maximum application rates and
numbers of applications for uses of bromacil and bromacil lithium are presented in Table
5. Products of bromacil and bromacil lithium include granular and liquid formulations.
22
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Table 5. Uses and maximum use rates of bromacil and bromacil lithium.
Use
Citrus
Non-
cropland1
Non-
cropland1
Chemical
Bromacil
Bromacil
Bromacil
lithium
Max. single
application
rate in
Ibs a.i./A
(kg a.i./ha)
6.4
(7.2)
15.4
(17.3)
12
(13.4)
Max.#
applications
per year
1
2
1
Timing of
applications
Any time
(best in late fall to
early winter or
winter to early
summer)
Any time (varies
from pre-
emergence to
establishment of
predominant weed
species)
Any time (varies
from pre-
emergence to
establishment of
predominant weed
species)
Formulation
Type
wettable powder,
dispersible
granules
liquid, granular,
water-emulsifiable
concentrate,
pellet,
wettable powder,
dispersible
granules,
emulsion,
aerosol,
water-soluble
liquid
Liquid,
water-soluble
liquid
Application Type
Broadcast,
soil broadcast,
spot soil treatment,
spray
Broadcast,
spot treatment,
spray,
prepaying treatment,
basal spray
treatment, directed
spray
Broadcast,
spot treatment,
spray,
basal spray
treatment, directed
spray, sprinkle
Non-cropland use includes non-agricultural areas, sewage disposal areas, sewage systems, paved areas, drainage systems.
industrial areas. Examples of non-cropland use include parking lots, around buildings, fence rows, railroad sidings, industrial
yards, pipelines, rights-of-way, lumber yards, highways, under asphalt and concrete pavement, oil refineries, cable coverings,
and substations, vacant lots, waste lagoons, airports, sewage disposal areas, and other similar sites.
urban areas, and outdoor
plants, tank farms, storage
runway lights, utility poles
Estimates of national use of bromacil in agriculture are available; however, national-level
uses of bromacil and bromacil lithium in non-cropland areas are not available.
Approximately 410 thousand pounds of the active ingredient bromacil were used on
citrus in 2002. Bromacil was used on citrus in California, Arizona, Texas and Florida
(Figure 1; USGS 2007). Use data for bromacil-lithium, which has no agricultural uses,
are unavailable.
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BROMACIL - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds par square mile of agricultural
land in county)
EH no estimated use
D 0.001 to 0.013
D 0.014 to 0.116
D 0.117 to 0.681
D 0.682 to 3.172
• >=3.182
Crops
Total
Pounds Applied
Percent
National Use
citrus fruit
410957
100.00
Figure 1. Historical (2002) extent of bromacil use in agricultural areas.
Pesticide use data available from the California Department of Pesticide Regulation
(CDPR 2007a), includes county-level data for various bromacil uses, including both
agricultural and non-agricultural uses. From 2002-2005, an annual average of 54
thousand pounds of bromacil were used in California. The percentage of total bromacil
use in California was highest on oranges (39.9% of total pounds applied), rights-of-way
(36.3%), lemons (8.1%), landscape maintenance (6.7%) and grapefruit (3.4%). Use on
citrus and rights-of-way represent 91.5% of total pounds of bromacil applied in
California during 2002-2005. Applications of bromacil to citrus and rights-of-way
occurred in counties throughout the state, including those also containing CRLF core
areas and critical habitat.
Pesticide use data for bromacil lithium indicates that from 2002-2005, an annual average
of 9.9 thousand pounds of bromacil lithium were used in California. Rights-of-way
represent 98.3% of the total applied pounds, while the remaining 1.7% of bromacil
lithium applied was used for "landscape maintenance." Applications of bromacil lithium
24
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occurred in counties throughout the state, including those also containing CRLF core
areas and critical habitat (CDPR 2007a).
Analysis of CDPR data for bromacil use in California from 2001-2005 (CDPR 2007a)
indicates that, although the majority of single applications for citrus were at rates that fell
below the maximum single application rate of 6.4 Ibs a.i./A, some applications were
possibly above this application rate. Estimated application rates ranged 0.01-20 Ibs a.i./A,
with a 90th percentile of 1.7 Ibs a.i./A (n = 916). Fewer data are available for specific
applications of bromacil to non-cropland areas. Of the available data, application rates
ranged 0.4-14.5 Ibs a.i./A, with a 9(r percentile of 5.1 Ibs a.i./A (n = 20).
The uses considered in this risk assessment represent all currently registered uses
according to a review of all current labels. No other uses are relevant to this assessment.
Any reported use, such as may be seen in the CDPR PUR database, represent either
historic uses that have been canceled, mis-reported uses, or mis-use. Historical uses, mis-
reported uses, and misuse are not considered part of the federal action and, therefore, are
not considered in this assessment.
2.5 Assessed Species
The CRLF was federally listed as a threatened species by USFWS effective June 24,
1996 (USFWS 1996). It is one of two subspecies of the red-legged frog and is the largest
native frog in the western United States (USFWS 2002). A brief summary of information
regarding CRLF distribution, reproduction, diet, and habitat requirements is provided in
Sections 2.5.1 through 2.5.4, respectively. Further information on the status, distribution,
and life history of and specific threats to the CRLF is provided in Attachment 1.
Final critical habitat for the CRLF was designated by USFWS on April 13, 2006
(USFWS 2006; 71 FR 19244-19346). Further information on designated critical habitat
for the CRLF is provided in Section 2.6.
2.5.1 Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically
inhabited 46 counties in California including the Central Valley and both coastal and
interior mountain ranges (USFWS 1996). Its range has been reduced by about 70%, and
the species currently resides in 22 counties in California (USFWS 1996). The species has
an elevational range of near sea level to 1,500 meters (5,200 feet) (Jennings and Hayes
1994); however, nearly all of the known CRLF populations have been documented below
1,050 meters (3,500 feet) (USFWS 2002).
Populations currently exist along the northern California coast, northern Transverse
Ranges (USFWS 2002), foothills of the Sierra Nevada (5-6 populations), and in southern
California south of Santa Barbara (two populations) (Fellers 2005a). Relatively larger
numbers of CRLFs are located between Marin and Santa Barbara Counties (Jennings and
Hayes 1994). A total of 243 streams or drainages are believed to be currently occupied
25
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by the species, with the greatest numbers in Monterey, San Luis Obispo, and Santa
Barbara counties (USFWS 1996). Occupied drainages or watersheds include all bodies
of water that support CRLFs (i.e., streams, creeks, tributaries, associated natural and
artificial ponds, and adjacent drainages), and habitats through which CRLFs can move
(i.e., riparian vegetation, uplands) (USFWS 2002).
The distribution of CRLFs within California is addressed in this assessment using four
categories of location including recovery units, core areas, designated critical habitat, and
known occurrences of the CRLF reported in the California Natural Diversity Database
(CNDDB) that are not included within core areas and/or designated critical habitat (see
Figure 2). 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 are large areas defined at the watershed level
that have similar conservation needs and management strategies. The recovery unit is
primarily an administrative designation, and land area within the recovery unit boundary
is not exclusively CRLF habitat. Core areas are smaller areas within the recovery units
that comprise portions of the species' historic and current range and have been
determined by USFWS to be important in the preservation of the species. Designated
critical habitat is generally contained within the core areas, although a number of critical
habitat units are outside the boundaries of core areas, but within the boundaries of the
recovery units. Additional information on CRLF occurrences from the CNDDB is used
to cover the current range of the species not included in core areas and/or designated
critical habitat, but within the recovery units.
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 statuses, 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 6 and shown
in Figure 2.
Core Areas
USFWS has designated 35 core areas across the eight recovery units to focus their
recovery efforts for the CRLF (see Figure 2). Table 6 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
26
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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 locational information is evaluated within the broader context
of recovery units. For example, if no labeled uses of bromacil or bromacil lithium 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 are not evaluated as part of
this assessment because the USFWS Recovery Plan (USFWS 2002) indicates that CRLFs
are extirpated from these areas. A summary of currently and historically occupied core
areas is provided in Table 6 (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.
27
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Table 6. California Red-legged Frog Recovery Units with Overlapping Core Areas and Designated
Critical Habitat.
Recovery Unit 1
(Figure 2)
Sierra Nevada
Foothills and Central
Valley (1)
(eastern boundary is
the 1,500m elevation
line)
North Coast Range
Foothills and
Western Sacramento
River Valley (2)
North Coast and
North San Francisco
Bay (3)
South and East San
Francisco Bay (4)
Central Coast (5)
Core Areas 2'7 (Figure 2)
Cottonwood Creek (partial)
(8)
Feather River (1)
Yuba River-S. Fork Feather
River (2)
—
Traverse Creek/Middle Fork
American River/Rubicon (3)
Consumnes River (4)
S. Fork Calaveras River (5)
Tuolumne River (6)
Piney Creek (7)
East San Francisco Bay
(partial)(16)
Cottonwood Creek (8)
Putah Creek-Cache Creek (9)
Jameson Canyon - Lower
Napa Valley (partial) (15)
Belvedere Lagoon (partial)
(14)
Pt. Reyes Peninsula (partial)
(13)
Putah Creek-Cache Creek
(partial) (9)
Lake Berryessa Tributaries
(10)
Upper Sonoma Creek (11)
Petaluma Creek-Sonoma
Creek (12)
Pt. Reyes Peninsula (13)
Belvedere Lagoon (14)
Jameson Canyon-Lower
Napa River (15)
—
East San Francisco Bay
(partial) (16)
—
South San Francisco Bay
(partial) (18)
South San Francisco Bay
(partial) (18)
Watsonville Slough- Elkhorn
Slough (partial) (19)
Carmel River-Santa Lucia
(20)
Estero Bay (22)
~
Critical Habitat
Units 3
~
BUT-1A-B
YUB-1
NEV-16
~
ELD-1
—
—
—
~
~
~
~
~
~
~
NAP-1
—
~
MRN-1, MRN-2
—
SOL-1
CCS-1A6
ALA-1A, ALA-
IB, STC-1B
STC-1A6
SNM-1A
SNM-1A, SNM-
2C, SCZ-1
SCZ-2 5
MNT-2
~
SLO-86
Currently
Occupied
(post-
1985) 4
•/
S
S
•/
•/
•/
•/
S
S
•/
•/
•/
•/
•/
•/
•/
•/
•/
•/
•/
•/
S
Historically
Occupied 4
•/
•/
•/
•/
•/
28
-------
Diablo Range and
Salinas Valley (6)
Northern Transverse
Ranges and
Tehachapi Mountains
(7)
Southern Transverse
and Peninsular
Ranges (8)
Arroyo Grande Creek (23)
Santa Maria River-Santa
Ynez River (24)
East San Francisco Bay
(partial) (16)
~
Santa Clara Valley (17)
Watsonville Slough- Elkhorn
Slough (partial)(19)
Carmel River-Santa Lucia
(partial)(20)
Gablan Range (21)
Estrella River (28)
~
Santa Maria River-Santa
Ynez River (24)
Sisquoc River (25)
Ventura River-Santa Clara
River (26)
~
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)
—
~
MER-1A-B,
STC-1B
SNB-16, SNB-26
~
MNT-1
~
SNB-3
SLO-1A-B
SLO-86
STB-4, STB-5,
STB-7
STB-1, STB-3
VEN-1, VEN-2,
VEN-3
LOS-16
~
~
~
~
~
~
~
~
•/
S
s
s
s
s
s
s
•/
•/
•/
s
s
s
s
s
s
s
s
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.
29
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Recovery Units
Sierra Nevada Foothills and Central Valley
North Coast Range Foothills and Western
Sacramento River Valley
North Coast and North San Francisco Bay
South and East San Francisco Bay
Central Coast
Diablo Range and Salinas Valley
Northern Transverse Ranges and Tehachapi
Mountains
Southern Transverse and Peninsular Ranges
Legend
I I Recovery Unit Boundaries
| Currently Occupied Core Areas
^^| Critical Habitat
• CNDDB Occurence Sections
County Boundaries
45
Core Areas
1. Feather River
2. Yuba River- S. Fork Feather River
3. Traverse Creek/ Middle Fork/ American R. Rubicon
4. Cosumnes River
5. South Fork Calaveras River*
6. Tuolumne River*
7. Piney Creek*
8. Cottonwood Creek
9. Putah Creek - Cache Creek*
10. Lake Berryessa Tributaries
11. Upper Sonoma Creek
12. Petaluma Creek - Sonoma Creek
13. Pt. Reyes Peninsula
14. Belvedere Lagoon
15. Jameson Canyon - Lower Napa River
16. East San Francisco Bay
17. Santa Clara Valley
18. South San Francisco Bay
19. Watsonville Slough-Elkhorn Slough
20. Carmel River - Santa Lucia
21. Gablan Range
22. Estero Bay
23. Arroyo Grange River
24. Santa Maria River - Santa Ynez River
25. Sisquoc River
26. Ventura River - Santa Clara River
27. Santa Monica Bay - Venura Coastal Streams
28. Estrella River
29. San Gabriel Mountain*
30. Forks of the Mojave*
31. Santa Ana Mountain*
32. Santa Rosa Plateau
33. San Luis Ray*
34. Sweetwater*
35. Laguna Mountain*
* Core areas that were historically occupied by the California red-legged frog are not included in the map
Figure 2. Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for CRLF.
30
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Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in
California. The CNDDB serves as a repository for historical and current species location
sightings. Information regarding known occurrences of CRLFs outside of the currently
occupied core areas and designated critical habitat is considered in defining the current
range of the CRLF. See: http://www.dfg.ca.gov/bdb/html/cnddb_info.html for additional
information on the CNDDB.
2.5.2 Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams,
marshes, and lagoons (Fellers 2005a). According to the Recovery Plan (USFWS 2002),
CRLFs breed from November through late April. Peaks in spawning activity vary
geographically; Fellers (2005b) reports peak spawning as early as January in parts of
coastal central California. Eggs are fertilized as they are being laid. Egg masses are
typically attached to emergent vegetation, such as bulrushes (Scirpus spp.) and cattails
(Typha spp.) or roots and twigs, and float on or near the surface of the water (Hayes and
Miyamoto 1984). Egg masses contain approximately 2000 to 6000 eggs ranging in size
between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch 10 to 14 days after
fertilization (Fellers 2005a) depending on water temperature. Egg predation is reported
to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles
(terrestrial-phase), typically between May and September (Jennings and Hayes 1994,
USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b, USFWS 2002). Males reach sexual maturity at 2
years, and females reach sexual maturity at 3 years of age; adults have been reported to
live 8 to 10 years (USFWS 2002). Figure 3 depicts CRLF annual reproductive timing.
Month
Breeding/Egg
Masses
Adults and
Juveniles
Figure 3. CRLF Reproductive Events by Month.
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2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied
specifically, it is assumed that their diet is similar to that of other frog species, with the
aquatic phase feeding exclusively in water and consuming diatoms, algae, and detritus
(USFWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar, 1980)
via mouthparts designed for effective grazing of periphyton (Wassersug, 1984,
Kupferberg et al.; 1994; Kupferberg, 1997; Altig and McDiarmid, 1999).
Juvenile and adult CRLFs forage in aquatic and terrestrial habitats, and their diet differs
greatly from that of larvae. The main food source for juvenile aquatic- and terrestrial-
phase CRLFs is thought to be aquatic and terrestrial invertebrates found along the
shoreline and on the water surface. Hayes and Tennant (1985) report, based on a study
examining the gut content of 35 juvenile and adult CRLFs, that the species feeds on as
many as 42 different invertebrate taxa, including Arachnida, Amphipoda, Isopoda,
Insecta, and Mollusca. The most commonly observed prey species were larval alderflies
(Stalls cf californicd)., pillbugs (Armadilliadrium vulgare), and water striders (Gerris sp).
The preferred prey species, however, was the sowbug (Hayes and Tennant, 1985). This
study suggests that CRLFs forage primarily above water, although the authors note other
data reporting that adults also feed under water, are cannibalistic, and consume fish. For
larger CRLFs, over 50% of the prey mass may consists of vertebrates such as mice, frogs,
and fish, although aquatic and terrestrial invertebrates were the most numerous food
items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at
night; for juveniles feeding occurs during the day and at night (Hayes and Tennant 1985).
2.5.4 Habitat
CRLFs require aquatic habitat for breeding, but also use other habitat types including
riparian and upland areas throughout their life cycle. CRLF use of their environment
varies; they may complete their entire life cycle in a particular habitat or they may utilize
multiple habitat types. Overall, populations are most likely to exist where multiple
breeding areas are embedded within varying habitats used for dispersal (USFWS 2002).
Generally, CRLFs utilize habitat with perennial or near-perennial water (Jennings et al.
1997). Dense vegetation close to water, shading, and water of moderate depth are habitat
features that appear especially important for CRLF (Hayes and Jennings 1988).
Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds,
marshes, sag ponds (land depressions between fault zones that have filled with water),
dune ponds, and lagoons. Breeding adults have been found near deep (0.7 m) still or slow
moving water surrounded by dense vegetation (USFWS 2002); however, the largest
number of tadpoles have been found in shallower pools (0.26 - 0.5 m) (Reis, 1999). Data
indicate that CRLFs do not frequently inhabit vernal pools, as conditions in these habitats
generally are not suitable (Hayes and Jennings 1988).
CRLFs also frequently breed in artificial impoundments such as stock ponds, although
additional research is needed to identify habitat requirements within artificial ponds
(USFWS 2002). Adult CRLFs use dense, shrubby, or emergent vegetation closely
32
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associated with deep-water pools bordered with cattails and dense stands of overhanging
vegetation (http://www.fws.gov/endangered/features/rl frog/rlfrog.html#where).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability,
and life stage. Adults rely on riparian vegetation for resting, feeding, and dispersal. The
foraging quality of the riparian habitat depends on moisture, composition of the plant
community, and presence of pools and backwater aquatic areas for breeding. CRLFs can
be found living within streams at distances up to 3 km (2 miles) from their breeding site
and have been found up to 30 m (100 feet) from water in dense riparian vegetation for up
to 77 days (USFWS 2002).
During dry periods, the CRLF is rarely found far from water, although it will sometimes
disperse from its breeding habitat to forage and seek other suitable habitat under downed
trees or logs, industrial debris, and agricultural features (UWFWS 2002). According to
Jennings and Hayes (1994), CRLFs also use small mammal burrows and moist leaf litter
as habitat. In addition, CRLFs may also use large cracks in the bottom of dried ponds as
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.
'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
33
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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.
Please note that a more complete description of these habitat types is provided in
Attachment 1.
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. Please
see Attachment 1 for a full explanation on this special rule.
USFWS has established adverse modification standards for designated critical habitat
(USFWS 2006). Activities that may destroy or adversely modify critical habitat are those
that alter the PCEs and jeopardize the continued existence of the species. Evaluation of
actions related to use of bromacil and bromacil lithium that may alter the PCEs of the
CRLF's critical habitat form the basis of the critical habitat impact analysis. According
to USFWS (2006), activities that may affect critical habitat and therefore result in adverse
effects to the CRLF include, but are not limited to the following:
(1) Significant alteration of water chemistry or temperature to levels beyond the
tolerances of the CRLF that result in direct or cumulative adverse effects to
individuals and their life-cycles.
(2) 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.
34
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(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 bromacil and bromacil lithium is expected to
directly impact living organisms within the action area, critical habitat analysis for
bromacil and bromacil lithium 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 bromacil and bromacil lithium is likely to encompass
considerable portions of the United States based on the uses on citrus and the large array
of uses on non-cropland areas. 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 bromacil and bromacil lithium may be expected
to have on the environment, the exposure levels to bromacil that are associated with those
effects, and the best available information concerning the use of bromacil 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 bromacil and bromacil lithium. An analysis of labeled uses and review of
available product labels was completed. This analysis indicates that for bromacil and
bromacil lithium, the following uses are considered as part of the federal action evaluated
in this assessment:
. Citrus (oranges, lemons, tangerines, tangelos, grapefruit, etc.)
. Non-cropland areas (airports, parking lots, industrial areas, rights-of-way (for
railroads, highways, pipeline and utilities), storage areas, lumberyards, tank farms,
under asphalt and concrete pavement and fence rows, etc.)
The analysis indicates that pineapple, which is a registered use of bromacil, is not
considered in this assessment, since the crop is not grown in California and therefore, the
use is not expected to result in exposure to the CRLF.
35
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After the determination of which uses will be assessed, an evaluation of the potential
"footprint" of the use pattern is 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
bromacil and bromacil lithium uses. The initial area of concern is defined as all land
cover types that represent the labeled uses described above. The initial area of concern is
represented by 1) orchard and vineyard landcovers which are assumed to be
representative of citrus and 2) rights-of-way which are assumed to be representative of
non-cropland areas. Maps representing the land cover types that make up the initial areas
of concern for citrus and non-cropland areas are presented in Figures 4 and 5,
respectively. These maps represent the areas directly affected by the federal action.
It should be noted that the initial action area map for non-cropland areas is defined only
by rights-of-way, and does not include several other potential non-cropland uses of
bromacil and bromacil lithium (e.g. parking lots, fence rows, tank farms, storage yards,
etc.). The initial action area for non-cropland areas is actually larger than what is depicted
in Figure 5; however, spatial data are unavailable at this time to define the extent of these
additional non-cropland areas where bromacil and bromacil lithium can be applied. Since
rights-of-way areas make up the majority of past use of bromacil (81.0%) and bromacil
lithium (98.3%) on non-cropland areas, rights-of-way are relevant for defining the spatial
extent of non-cropland areas.
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. In this assessment, transport
of bromacil through runoff and spray drift is considered in deriving quantitative estimates
of bromacil exposure to CRLF, its prey and its habitats.
Since this screening level risk assessment defines taxa that are predicted to be exposed
through runoff and drift to bromacil at concentrations above the Agency's Levels of
Concern (LOG), there is need to expand the action area to include areas that are affected
indirectly by this federal action. Two methods are employed to define the areas
indirectly affected by the federal action, and thus the total action area. These are the
down stream dilution assessment for determining the extent of the affected lotic aquatic
habitats (flowing water) and the spray drift assessment for determining the extent of the
affected terrestrial habitats. In order to define the final action areas relevant to uses of
bromacil and bromacil lithium on citrus and non-cropland areas, it is necessary to
combine areas directly affected, as well as aquatic and terrestrial habitats indirectly
affected by the federal action. It is assumed that lentic (standing water) aquatic habitats
(e.g. ponds, pools, marshes) overlapping with the terrestrial areas are also indirectly
affected by the federal action The analysis of areas indirectly affected by the federal
action, as well as the determination of the final action area for bromacil and
bromacil lithium is described in the risk discussion (Section 5.2.5). Additional
analysis related to the intersection of the bromacil and bromacil lithium action area and
CRLF habitat used in determining the final action area is described in Appendix H.
36
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N
Legend
| | County Boundary
90
45
90 Miles
Compiled from California County boundaries (ESRI, 2002),
USDA National Agriculture Statistical Service (MASS, 2002)
Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC.2001)
Map created by U.S. Environmental Protection Agency,
Office of Pesticides Programs, Environmental Fate and
Effects Division. April 11, 2007.
Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
Figure 4. Initial action area for crops described by orchard and vineyard landcover which
corresponds to potential bromacil use sites on citrus. This map represents the area potentially
directly affected by the federal action.
37
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Legend
| | County Boundary
• CA_Right_of_Way
\
JL
90
45
90 Miles
Compiled from California County boundaries (ESRI, 2002),
USDANationalAgriculture Statistical Service (MASS,2002)
Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC.2001)
Map created by U.S. Environmental Protection Agency,
Office of Pesticides Programs, Environmental Fate and
Effects Division. April 11, 2007.
Projection: Albers Equal Area Conic US6S,
North American Datum of 1983 (NAD 1983)
Figure 5. Initial action area for crops described by right-of-way landcover which corresponds to
potential bromacil and bromacil lithium use sites on (some) non-cropland areas. This map represents
the area potentially directly affected by the federal action.
38
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2.8 Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental
value that is to be protected" (USEPA 1992). 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 bromacil and bromacil lithium (e.g., runoff, spray drift, etc.), and the routes
by which ecological receptors are exposed to bromacil and bromacil lithium -related
contamination (e.g., direct contact, etc).
2.8.1. Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the CRLF, as well as indirect effects, such as reduction of
the prey base 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 bromacil and bromacil lithium is
provided in Table 7.
39
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Table 7. Summary of Assessment Endpoints and Measures of Ecological Effects for Direct and
Indirect Effects of bromacil and bromacil lithium on the California Red-legged Frog.
Assessment Endpoint
Measures of Ecological Effects
Aquatic Phase (eggs, larvae, tadpoles, juveniles, and adults)1
1. Survival, growth, and reproduction of
CRLF individuals via direct effects on
aquatic phases
2. Survival, growth, and reproduction of
CRLF individuals via effects to food
supply (i.e., freshwater invertebrates, non-
vascular plants)
3. Survival, growth, and reproduction of
CRLF individuals via ndirect 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.
la. most sensitive fish2 96-h LCso = 36 mg/L (Rainbow
trout)
Ib. most sensitive fish2 chronic NOAEC = 3.0 mg/L
(Rainbow trout)
2a. most sensitive fish 96-h LCso = 36 mg/L (Rainbow trout)
2b. most sensitive fish chronic NOAEC = 3.0 mg/L
(Rainbow trout)
2c. Most sensitive aquatic invertebrate 48-hEC50= 121 mg/L
(waterflea)
2d. Most sensitive aquatic invertebrate chronic NOAEC =
8.2 mg/L (waterflea)
2e. Most sensitive aquatic unicellular plant EC50 = 0.0068
mg/L (green algae)
3a. Most sensitive aquatic unicellular plant EC50= 0.0068
mg/L (green algae)
3b. Vascular aquatic plant EC50 = 0.045 mg/L (duckweed)
4a. Most sensitive EC25 for monocots = 0.030 Ibs a.i./A
(wheat)
4b. Most sensitive EC25 for dicots = 0.0047 Ibs a.i./A (rape)
Terrestrial Phase (Juveniles and adults)
5. Survival, growth, and 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)
5a. Most sensitive bird3 acute LD50 >2250 mg/kg (Northern
bobwhite quail)
5b. Most sensitive bird3 sub-acute LC50>10,000 mg/kg-diet
(Northern bobwhite quail)
5c. Most sensitive bird3 chronic NOAEC = 1550 mg/kg-diet
(Northern bobwhite quail)
6a. Most sensitive terrestrial invertebrate LD50>1209 ug
a.i./g (honey bee)
6b. Most sensitive terrestrial mammal acute LD50 = 812
mg/kg (laboratory rat)
6c. Most sensitive terrestrial mammal chronic NOAEL = 250
mg/kg-diet/day (laboratory rat)
6d. Most sensitive bird3 acute LD50 >2250 mg/kg (Northern
bobwhite quail)
6e. Most sensitive bird3 sub-acute LC50>10,000 mg/kg-diet
(Northern bobwhite quail)
6f. Most sensitive bird3 chronic NOAEC = 1550 mg/kg-diet
(Northern bobwhite quail)
7a. Most sensitive EC25 for monocots = 0.030 Ibs a.i./A
(wheat)
7b. Most sensitive EC25 for dicots = 0.0047 Ibs a.i./A (rape)
'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.
Frogs are used as surrogates for aquatic-phase CRLF and aquatic-phase frog species which are prey to CRLF.
3 Birds are used as surrogates for terrestrial phase CRLF and terrestrial-phase frog species which are prey to CRLF.
40
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2.8.2. Assessment Endpoints for Designated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related
to the use of bromacil and bromacil lithium that may alter the PCEs of the CRLF's
critical habitat. PCEs for the CRLF were previously described in Section 2.6. Actions
that may modify critical habitat are those that alter the PCEs. 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 bromacil and bromacil lithium effects data are available.
Assessment endpoints and measures of ecological effect selected to characterize potential
modification to designated critical habitat associated with exposure to bromacil and
bromacil lithium are provided in Table 8. 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 CRLFs.
2. Alteration of chemical characteristics necessary for normal growth and
viability of juvenile and adult CRLFs.
3. Significant increase in sediment deposition within the stream channel or pond
or disturbance of upland foraging and dispersal habitat.
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.
Measures of such possible effects by labeled use of bromacil and bromacil lithium on
critical habitat of the CRLF are described in Table 8. Some components of these PCEs
are associated with physical abiotic features (e.g., presence and/or depth of a water body,
or distance between two sites), which are not expected to be measurably altered by use of
pesticides. Assessment endpoints used for the analysis of designated critical habitat are
based on the adverse modification standard established by USFWS (2006).
41
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Table 8. Summary of Assessment Endpoints and Measures of Ecological Effect for Primary
Constituent Elements of Designated Critical Habitat.
Assessment Endpoint
Measures of Ecological Effect
Aquatic Phase PCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or geometry
and/or increase in sediment deposition within the
stream channel or pond: aquatic habitat (including
riparian vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile
and adult CRLFs.
Alteration in water chemistry /quality including
temperature, turbidity, and oxygen content necessary
for normal growth and viability of juvenile and adult
CRLFs and their food source. :
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
la. Most sensitive aquatic unicellular plant EC50= 0.0068
mg/L (green algae)
Ib. Vascular aquatic plant EC50 = 0.045 mg/L (duckweed)
Ic. Most sensitive EC2s for monocots = 0.030 Ibs a.i./A
(wheat)
Id. Most sensitive EC25 for dicots = 0.0047 Ibs a.i./A (rape)
2a. Most sensitive aquatic unicellular plant EC50= 0.0068
mg/L (green algae)
2b. Vascular aquatic plant EC50 = 0.045 mg/L (duckweed)
2c. Most sensitive EC25 for monocots = 0.030 Ibs a.i./A
(wheat)
2d. Most sensitive EC25 for dicots = 0.0047 Ibs a.i./A (rape)
3a. most sensitive fish2 96-h LC50 = 36 mg/L (Rainbow trout)
3b. most sensitive fish2 chronic NOAEC = 3.0 mg/L
(Rainbow trout)
3c. Most sensitive aquatic invertebrate 48-hEC50= 121 mg/L
(waterflea)
3d. Most sensitive aquatic invertebrate chronic NOAEC = 8.2
mg/L (waterflea)
3e. Most sensitive aquatic unicellular plant EC50 = 0.0068
mg/L (green algae)
4a. Most sensitive aquatic unicellular plant EC50= 0.0068
mg/L (green algae)
Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian
habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
Elimination and/or disturbance of dispersal habitat:
Upland or riparian dispersal habitat within designated
units and between occupied locations within 0.7 mi of
each other that allow for movement between sites
including both natural and altered sites which do not
contain barriers to dispersal
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
5a. Most sensitive EC2s for monocots = 0.030 Ibs a.i./A
(wheat)
5b. Most sensitive EC25 for dicots = 0.0047 Ibs a.i./A (rape)
5c. Most sensitive terrestrial invertebrate LD50>1209 ug a.i./g
(honey bee)
6d. Most sensitive terrestrial mammal acute LD50 = 812
mg/kg (laboratory rat)
5e. Most sensitive terrestrial mammal chronic NOAEL = 250
mg/kg-diet/day (laboratory rat)
5f. Most sensitive bird3 acute LD50 >2250 mg/kg (Northern
bobwhite quail)
5g. Most sensitive bird3 sub-acute LC50>10,000 mg/kg-diet
(Northern bobwhite quail)
5h. Most sensitive bird3 chronic NOAEC = 1550 mg/kg-diet
(Northern bobwhite quail)
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.
2 Frogs are used as surrogates for aquatic-phase CRLF and aquatic-phase frog species which are prey to CRLF.
Birds are used as surrogates for terrestrial phase CRLF and terrestrial-phase frog species which are prey to CRLF.
42
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2.9 Conceptual Model
2.9.1 Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in
assessment endpoints) and may be based on theory and logic, empirical data,
mathematical models, or probability models (U.S. EPA, 1998). For this assessment, the
risk is stressor-linked, where the stressor is the release of bromacil and bromacil lithium
to the environment. The following risk hypotheses are presumed for this endangered
species assessment:
• Labeled uses of bromacil and bromacil lithium within the action area may directly
affect the CRLF by causing mortality or by adversely affecting growth or
fecundity;
• Labeled uses of bromacil and bromacil lithium within the action area may
indirectly affect the CRLF by reducing or changing the composition of food
supply;
• Labeled uses of bromacil and bromacil lithium within the action area may
indirectly affect the CRLF or modify designated critical habitat by reducing or
changing the composition of the aquatic plant community in the ponds and
streams comprising the species' current range and designated critical habitat, thus
affecting primary productivity and/or cover;
• Labeled uses of bromacil and bromacil lithium within the action area may
indirectly affect the CRLF or modify designated critical habitat by reducing or
changing the composition of the terrestrial plant community (i.e., riparian habitat)
required to maintain acceptable water quality and habitat in the ponds and streams
comprising the species' current range and designated critical habitat;
• Labeled uses of bromacil and bromacil lithium 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);
• Labeled uses of bromacil and bromacil lithium within the action area may modify
the designated critical habitat of the CRLF by reducing the food supply required
for normal growth and viability of juvenile and adult CRLFs;
• Labeled uses of bromacil and bromacil lithium within the action area may modify
the designated critical habitat of the CRLF by reducing or changing upland habitat
within 200 ft of the edge of the riparian vegetation necessary for shelter, foraging,
and predator avoidance.
• Labeled uses of bromacil and bromacil lithium within the action area may modify
the designated critical habitat of the CRLF by reducing or changing dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal.
• Labeled uses of bromacil and bromacil lithium within the action area may modify
the designated critical habitat of the CRLF by altering chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs.
43
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2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the stressor (bromacil and bromacil lithium), 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 Figures 6 and 7, and the
conceptual models for the aquatic and terrestrial PCE components of critical habitat are
shown in Figures 8 and 9. Exposure routes shown in dashed lines are not quantitatively
considered because the resulting exposures are expected to be so low as not to cause
adverse effects to the CRLF.
The environmental fate properties of bromacil, along with monitoring data identifying its
presence in surface water and groundwater in California, indicate that runoff and spray
drift represent potential transport mechanisms of bromacil to the aquatic and terrestrial
habitats of the CRLF. In this assessment, transport of bromacil through runoff/ leaching
and spray drift is considered in deriving quantitative estimates of bromacil exposure to
CRLF, its prey and its habitats. Based on the vapor pressure and Henry's Law constant of
bromacil, volatilization from treated areas resulting in atmospheric transport and
deposition represent unlikely transport pathways leading to exposure of the CRLF and its
habitats. Therefore, exposure of the CRLF and its habitat to bromacil through runoff and
spray drift to surface waters, and leaching to groundwater with subsequent interaction of
groundwater to surface waters are the exposure pathways considered in this assessment.
The exposure route from groundwater interacting with runoff is implicitly accounted for
in exposure modeling which relies on the curve number method which is based on stream
response (whether overland or subsurface) to a rain event. Both overland and subsurface
flows are driven by rain events. Also, acute exposure concentrations from ground water
are likely to be lower than those estimated for surface water.
44
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Stressor
Source
Exposure
Media
Pesticide applied to use site
Spray drift 1
|
Surface wate
Sediment
Runoff 1 1 So!l 1 H Groundwater |
r/
4 ..Wet/
dry deposition
T.
Long range
atmospheric
transport
Uptake/gills
or integument
Uptake/cell,
roots, leaves
Uptake/gill*
or integument
Receptors
Attribute
Change
Aquatic Animals
Invertebrates
Vertebrates
Ingestion
Red-legged Frog
Eggs Juveniles
Larvae Adult
Tadpoles
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Aquatic Plants
Non-vascular
Vascular
t
Ingestion
Food chain
Reduction in algae
Reduction in prey
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Figure 6. Conceptual Model for Pesticide Effects on Aquatic Phase of the Red-Legged Frog.
45
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Stressor
Pesticide applied to use site
4
SonrrP Direct — ~±_
application / J
Exposure I 1 T*1
Terrestrial jer
insects gra
Ingestion
1
Ingestion
1 ,.
Receptors Red-legged Frog .
Juvenile
Adult 4.
^ r
Attribute Individual organisms
Change Reduced survival
Reduced growth
Reduced reproduction
i '
__f "^—Dermal uptake/Inge
^-
sses/forbs, fruit, seeds
(trees, shrubs)
U Inaestion ^
r
tt
i r ^ '
Food chain
Reduction in prey
| ^
;stion ^_ Soil
— - Root uptake -^J
Ingestion 1
|
i
Habitat inte(
Reduction in
Community c
K
r
ry deposition -4-
r
jrity
primary productivity
er
hange
Figure 7. Conceptual Model for Pesticide Effects on Terrestrial Phase of Red-Legged Frog.
46
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Stressor
Source
Exposure
Media
Receptors
Attribute
Change
Habitat
PCEs
^
1 Spray drift 1
Surfac
Sed
1
Pesticide
+
1 Runoff 1
ment [^
41
ills
or integument
applied to use site
z_
Soil |
Uptake/cell,
1
• Wet/dry deposition
.T.
Long range
atmospheric
transport
Uptake/gills
or integument
roots, leaves
Red-legged Frog
Eggs Juveniles
Larvae Adult
Tadpoles
Aquatic Animals
nvertebrates
Vertebrates
Aquatic Plants
Non-vascular
Vascular
^ Ingestion
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Other chemical
characteristics
Adversely modified
chemical characteristics
T
Ingestion
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Riparian and Upland
plants terrestrial
exposure pathways and
PCEs see Figure 7
Population
Yield
Reduced yield
Food sources
Reduction in algae
Reduction in prey
I
I
Community
Reduced seedling
emergence or vegetative
vigor (Distribution)
Habitat quality and channel/pond
morphology or geometry
Adverse water quality changes
Increased sedimentation
Reduced shelter
Figure 8. Conceptual Model for Pesticide Effects on Aquatic Components of Red-Legged Frog
Critical Habitat.
47
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Stressor
Source
Exposure
Media and
Receptors
Pesticide applied
1
i
to use site
\ Spray drift
Runoff
.J.
Long range
atmospheric
transport
Dermal uptake/lngestion
Terrestrial plants
grasses/forbs, fruit,
seeds (trees, shrubs)
Root uptake -4!
Wet/dry deposition
^•Ingestion
Ingestion
Red-legged Frog
Juvenile
Adult
Attribute
Change
Habitat
PCEs
Ingestion
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Other chemical
characteristics
Adversely modified chemical
characteristics
Hngest
Ll
Mammals
Population
Reduced survival
Reduced growth
Reduced reproduction
Food resources
Reduction in food
sources
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
Figure 9. Conceptual Model for Pesticide Effects on Terrestrial Components of Red-Legged Frog
Critical Habitat.
2.10 Analysis Plan
In order to address the risk hypothesis, the potential for adverse effects on the CRLF, its
prey and its habitat is estimated. In the following sections, the use, environmental fate,
and ecological effects of bromacil and its lithium salt are characterized and integrated to
assess the risks to the CRLF. This is accomplished using a risk quotient (ratio of
exposure concentration to effects concentration) approach. Although risk is often defined
as the likelihood and magnitude of adverse ecological effects, the risk quotient-based
approach does not provide a quantitative estimate of likelihood and/or magnitude of an
adverse effect. However, as outlined in the Overview Document (USEPA 2004), the
likelihood of effects to individual organisms from particular uses of a pesticide such as
bromacil is estimated using the probit dose-response slope and either the level of concern
(discussed below) or actual calculated risk quotient value.
48
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2.10.1. Measures to Evaluate the Risk Hypothesis and Conceptual Model
2.10.1.1. Measures of Exposure
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of bromacil using maximum labeled application
rates and methods. The models used to predict aquatic EECs are the Pesticide Root Zone
Model coupled with the Exposure Analysis Model System (PRZM/EXAMS). The model
used to predict terrestrial EECs on food items is T-REX. The model used to derive EECs
relevant to terrestrial and wetland plants was TerrPlant. These models are parameterized
using relevant reviewed registrant-submitted environmental fate data.
PRZM (v3.12beta, May 24, 2001) and EXAMS (V2.98.04, Aug. 18, 2002) are screening
simulation models coupled with the input shell pe4v01.pl (Aug.8, 2003) to generate daily
exposures and l-in-10 year EECs of bromacil that may occur in surface water bodies
adjacent to application sites receiving bromacil through runoff and spray drift. PRZM
simulates pesticide application, movement and transformation on an agricultural field and
the resultant pesticide loadings to a receiving water body via runoff, erosion and spray
drift. EXAMS simulates the fate of the pesticide and resulting concentrations in the
water body. The standard scenario used for ecological pesticide assessments assumes
application to a 10-hectare agricultural field that drains into an adjacent 1-hectare water
body that is 2 meters deep (20,000 m3 volume) with no outlet. PRZM/EXAMS is used to
estimate screening-level exposure of aquatic organisms to bromacil. The measures of
exposure for aquatic species are the l-in-10 year return peak or rolling mean
concentration. The l-in-10 year peak is used for estimating acute exposures of direct
effects to the CRLF, as well as indirect effects to the CRLF through effects to potential
prey items, including: algae, aquatic invertebrates, fish and frogs. The 1-in-10-year 60-
day mean is used for assessing chronic exposure to the CRLF and fish and frogs serving
as prey items. The 1-in-10-year 21-day mean is used for assessing aquatic invertebrate
chronic exposure, which are also potential prey items.
Exposure estimates for terrestrial phase CRLF and terrestrial invertebrates and mammals
(serving as potential prey) assumed to be in the target area or in an area exposed to spray
drift are derived using the T-REX model (version 1.3.1, 12/07/2006). This model
incorporates the Kenega nomograph, as modified by Fletcher et al. (1994), which is
based on a large set of actual field residue data. The upper limit values from the
nomograph represented the 95th percentile of residue values from actual field
measurements (Hoerger and Kenega, 1972). The Fletcher et al. (1994) modifications to
the Kenega nomograph are based on measured field residues from 249 published research
papers, including information on 118 species of plants, 121 pesticides, and 17 chemical
classes. These modifications represent the 95th percentile of the expanded data set. For
modeling purposes, direct exposures of the CRLF to bromacil through contaminated food
are estimated using the EECs for the small bird (20 g) which consumes small insects.
Dietary-based and dose-based exposures of potential prey (small mammals) are assessed
using the small mammal (15 g) which consumes short grass. The small bird (20g)
consuming small insects and the small mammal (15g) consuming short grass are used
49
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because these categories represent the largest RQs of the size and dietary categories in T-
REX that are appropriate surrogates for the CRLF and one of its prey items. Estimated
exposures of terrestrial insects to bromacil are bound by using the dietary based EECs for
small insects and large insects.
Birds are currently used as surrogates for terrestrial-phase CRLF. However, amphibians
are poikilotherms (body temperature varies with environmental temperature) while birds
are homeotherms (temperature is regulated, constant, and largely independent of
environmental temperatures). Therefore, amphibians tend to have much lower metabolic
rates and lower caloric intake requirements than birds or mammals. As a consequence,
birds are likely to consume more food than amphibians on a daily dietary intake basis,
assuming similar caloric content of the food items. Therefore, the use of avian food
intake allometric equation as a surrogate to amphibians is likely to result in an over-
estimation of exposure and risk for reptiles and terrestrial-phase amphibians. Therefore,
T-REX (version 1.3.1) has been refined to the T-HERPS model (v. 1.0), which allows for
an estimation of food intake for poikilotherms using the same basic procedure as T-REX
to estimate avian food intake.
EECs for terrestrial plants inhabiting dry and wetland areas are derived using TerrPlant
(version 1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in
spray drift to calculate EECs. EECs are based upon solubility, application rate and
minimum incorporation depth.
Two spray drift models, AGDisp and AgDRIFT are used to assess exposures of terrestrial
phase CRLF and its prey to bromacil deposited on terrestrial habitats by spray drift.
AGDisp (version 8.13; dated 12/14/2004) (Teske and Curbishley 2003) is used to
simulate aerial and ground applications using the Gaussian farfield extension. AgDrift
(version 2.01; dated 5/24/2001) is used to simulate spray blast applications to orchard
crops.
2. W.I.2. Measures of Effect
Data identified in Section 2.8 are used as measures of effect for direct and indirect effects
to the CRLF. Data were obtained from registrant submitted studies or from literature
studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched
in order to provide more ecological effects data and in an attempt to bridge existing data
gaps. ECOTOX is a source for locating single chemical toxicity data for aquatic life,
terrestrial plants, and wildlife. ECOTOX was created and is maintained by the USEPA,
Office of Research and Development, and the National Health and Environmental Effects
Research Laboratory's Mid-Continent Ecology Division (ECOTOX, 2006).
The assessment of risk for direct effects to the CRLF makes the assumption that toxicity
of bromacil to birds is similar to terrestrial-phase CRLF. The same assumption is made
for fish and aquatic-phase CRLF. Algae, aquatic invertebrates, fish and amphibians
represent potential prey of the CRLF in the aquatic habitat. Terrestrial invertebrates,
50
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small mammals, and terrestrial phase amphibians represent potential prey of the CRLF in
the terrestrial habitat. Aquatic plants and semi-aquatic plants represent habitat of CRLF.
The acute measures of effect used for animals in this screening level assessment are the
LD50, LCso and ECso- LD stands for "Lethal Dose", and LD50 is the amount of a material,
given all at once, that is estimated to cause the death of 50% of the test organisms. LC
stands for "Lethal Concentration" and LCso is the concentration of a chemical that is
estimated to kill 50% of the test organisms. EC stands for "Effective Concentration" and
the ECso is the concentration of a chemical that is estimated to produce a specific effect in
50% of the test organisms. Endpoints for chronic measures of exposure for listed and
non-listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for "No
Ob served-Adverse-Effect-Level" and refers to the highest tested dose of a substance that
has been reported to have no harmful (adverse) effects on test organisms. The NOAEC
(i.e., "No-Observed-Adverse-Effect-Concentration") is the highest test concentration at
which none of the observed effects were statistically different from the control. The
NOEC is the No-Observed-Effects-Concentration. For non-listed plants, only acute
exposures are assessed (i.e., EC25 for terrestrial plants and ECso for aquatic plants).
2.10.1.3. Integration of Exposure and Effects
Risk characterization is the integration of exposure and ecological effects characterization
to determine the potential ecological risk from the use of bromacil on citrus and non-
cropland areas, and the likelihood of direct and indirect effects to CRLF in aquatic and
terrestrial habitats. The exposure and toxicity effects data are integrated in order to
evaluate the risks of adverse ecological effects on non-target species. For the assessment
of bromacil risks, the risk quotient (RQ) method is used to compare exposure and
measured toxicity values. EECs are divided by acute and chronic toxicity values. The
resulting RQs are then compared to the Agency's levels of concern (LOCs) (USEPA,
2004) (see Table 9). These criteria are used to indicate when bromacil's and bromacil
lithium's uses, as directed on the label, have the potential to cause adverse direct or
indirect effects to the CRLF.
51
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Table 9. Agency risk quotient (RQ) metrics and levels of concern (LOG) per risk class.
Risk Class
Description
RQ
LOC
Aquatic Habitats
Acute Listed
Species
Chronic Listed
and Non-Listed
Species
Non-Listed
CRLF may be potentially affected by use by direct or indirect
effects.
Potential for chronic risk to CRLF through direct or indirect
effects. Indirect effects represented by effects to invertebrates, fish
or amphibians, which represent potential prey.
Potential for effects in non-listed plants.
Peak EEC/ECso1
60-day EEC/NOEC
(CRLF)
21 -day EEC/NOEC
(invertebrates)
Peak EEC/ EC50
0.05
1
1
Terrestrial Habitats
Acute Listed
Species
Acute Listed
Species
Acute Non-
Listed Species
Chronic Listed
Species
Non-Listed
CRLF may be potentially affected by use by direct or indirect
effects.
Potential effects to terrestrial invertebrates. CRLF may be
potentially affected by use by direct or indirect effects.
CRLF may be potentially affected by use by indirect effects
through effects to animal prey (i.e. mice and terrestrial-phase
amphibians).
Potential for chronic risk to CRLF through direct or indirect
effects. Indirect effects represented by effects to small mammals,
which represent potential prey.
Potential for effects in non-listed plants.
Dietary EEC 2/LC50
Or
Dose EEC 2/LD50
EEC 2/LD50
Dietary EEC 2/LC50
Or
Dose EEC 2/LD50
EEC 2/NOAEC
Peak EEC/ EC25
0.1
0.05
0.5
1
1
2 Based on upper-bound Kenaga values.
2.10.2. Data Gaps
Environmental Fate
Degradate information is not available for aqueous photodegradation at pH 9 (at which an
absortion spectrum shift occurs relative to more acidic pHs), where bromacil is relatively
rapidly degraded.
Additionally, the half-life for anaerobic aquatic metabolism has not been accurately
determined. Because OPP does not find the reported half-life to be valid, an assumption
of stability had to be used in the aquatic exposure modeling for this assessment in lieu of
data.
Mobility data are only available for column leaching studies; batch equilibrium studies
have not been submitted, so Kd and Koc values are lacking. For aquatic exposure
modeling, the Koc value was obtained from the SCS/ARS database, and indicates a high
level of mobility that is in agreement with the mobility observed in the column leaching
studies (in which [14C]residues in the leachates of all four soil columns totaled 91.2-
99.6% of the applied).
While two terrestrial field dissipation studies have been submitted, both were on bare
ground plots. A citrus field dissipation study on soils in California is not available.
52
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Effects characterization
No data are available for defining the toxicity of bromacil to amphibians. As a result,
direct effects to the CRLF in aquatic habitats are based on toxicity information for
freshwater fish, which serves as a surrogate for aquatic amphibians. Also, direct effects
to the CRLF in terrestrial habitats are based on toxicity information for birds, which serve
as a surrogate for terrestrial-phase amphibians.
Data are unavailable to define the sub-acute (dietary) exposure of technical bromacil to
birds. In place of this gap, data are used from a study involving dietary exposures of birds
to a formulated product containing bromacil.
53
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3. Exposure Assessment
3.1. Aquatic Exposure Assessment
3.1.1. Existing Water Monitoring Data for California
Surface and groundwater monitoring data are available for California waters. These data
include United States Geological Survey's (USGS) National Water Quality Assessment
(NAWQA) and the California Department of Pesticide Regulation (CDPR) Surface
Water Database. These data are described below.
3.1.1.1. NAWQA Data (1993-2005) for California
NAWQA monitoring data are available for bromacil from California surface waters
(USGS 2007) (Table 10). Samples were analyzed using HPLC. Although NAWQA
monitoring does not target specific chemicals, bromacil was detected in 6.6% of 347
samples from 1993-2005, with a maximum concentration of 1.9 |ig/L. Bromacil was
detected in a total of 23 samples collected from 5 different sites in 5 counties in
California. These counties (Sacramento, Merced, Stanislaus, San Joaquin and Orange)
also contain CRLF core areas and critical habitat. NAQWA data include information on
the landcover composition of the watershed of the waters from which samples were
taken. Detection rates and maximum detections of bromacil in surface water samples are
differentiated in Table 10 by watershed landcover categories. The sample containing the
maximum concentration of bromacil was collected in January, 1994 in an area receiving
runoff from a landcover classified "mixed."
Table 10. NAWQA 1993 - 2005 data for bromacil detections u in CA SURFACE waters. Data are
distinguished by the landcover (e.g. agricultural, urban, etc.) of the watershed of the sampled water
bodies.
Statistics
Number of samples
Number Detections
% Detects
Maximum Concentration (jig/L)
Agricultural
96
4
4.2%
0.0373
Mixed
179
17
9.5%
1.9
Urban
11
0
0%
0.035
Other
61
2
3.3%
1.43
Total
347
23
6.6%
1.9
Excludes samples identified by "<", which signify non-detections.
2Method detection limit = 0.035 ug/L
Groundwater NAWQA monitoring data are also available for bromacil from California
(USGS 2007) (Table 11). Samples were analyzed using HPLC. From 1993-2005,
bromacil was detected in 5.0% of 402 samples, with a maximum concentration of 0.545
|ig/L. Bromacil was detected in a total of 20 samples collected from 19 different sites in
10 counties in California. These counties (Colusa, Fresno, Madera, Merced, Orange,
Riverside, Sacramento, San Bernardino, Stanislaus, and Tulare) also contain CRLF core
areas and critical habitat. The sample containing the maximum concentration of bromacil
was collected in May 2000 in an area receiving runoff from a landcover classified
"mixed."
54
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Table 11. NAWQA 1993 - 2005 data for bromacil detections u in CA GROUND waters. Data are
distinguished by the landcover (e.g. agricultural, urban, etc.) of the watershed of the sampled water
bodies.
Statistics
Number of samples
Number Detections
% Detects
Maximum Concentration (u,g/L)
Agricultural
209
7
3.3%
0.190
Mixed
89
9
10.1%
0.545
Urban
63
1
1.6%
0.0.026
Other
41
3
7.3%
0.081
Total
402
20
5.0%
0.545
Excludes samples identified by "<", which signify non-detections.
2Method detection limit = 0.035 ug/L
3.1.1.2. California Department of Pesticide Regulation Surface Water
Database
CDPR maintains a database of monitoring data of pesticides in CA surface waters. The
sampled water bodies include rivers, creeks, urban streams, agricultural drains, the San
Francisco Bay delta region and storm water runoff from urban areas. The database
contains data from 51 different studies by federal state and local agencies as well as
groups from private industry and environmental interests. Some data reported in this
database are also reported by USGS in NAWQA; therefore, there is some overlap
between these two data sets (CDPR 2007).
From 1992-2002, 1008 samples from CA surface waters were analyzed for bromacil. Of
these, bromacil was detected in 7.7%, with a maximum concentration of 7.5 |ig/L, which
was detected in 1992 in San Joaquin County. These samples included 65 different sites
from 16 counties; including counties where CRLF core areas and critical habitat are
located.
3.1.2. Modeling Approach
As stated above, the Tier II models used to calculate aquatic EECs are PRZM and
EXAMS. For this modeling effort, PRZM scenarios designed to represent different crops
and geographic areas of CA are used in conjunction with the standard pond environment
in EXAMS. Use-specific and chemical-specific parameters for the PE4 shell as well as
PRZM scenarios are described below. The PRZM/EXAMS output files generated by this
modeling approach are located in Appendix B.
3.1.2.1. PRZM scenarios
For modeling aquatic exposures resulting from applications of bromacil use on citrus, the
CA citrus scenario is used.
The CA right-of-way and CA impervious scenarios are used in tandem in order to model
EECs resulting from use of bromacil on non-cropland areas. The rights-of-way scenario
was developed specifically for the San Francisco Bay region using the conceptual
approach developed for the Barton Springs salamander atrazine endangered species risk
assessment (U.S. EPA, 2006). The San Francisco area was selected to be representative
55
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of urbanized areas with CRLF habitat present in the general vicinity. The impervious
scenario was developed to represent the paved areas within a watershed. The EECs
derived by PRZM/EXAMS for the two scenarios are further refined to be more
representative of non-cropland areas, specifically rights-of-way. These refinements,
termed "post-processing" are described below.
3.1.2.2. Post-processing of PRZM/EXAMS outputs to develop EECs for
non-cropland areas
Although the non-cropland classification includes a wide variety of areas (see Use
Characterization, Section 2.4.4), rights-of-way are used to represent these areas.
Available data for California indicate that use of bromacil on rights-of-way represents a
significant portion of the past (2002-2005) use of bromacil (36.3% of total use). Of uses
of bromacil on non-cropland areas, 81.0% was applied to rights-of-way (CPUR 2007a).
Rights-of-way are roads, highways, railroads, utilities and pipelines. These areas contain
both impervious (i.e. cement, asphalt, metal surfaces) and pervious surfaces. It is
assumed that bromacil will be applied to the pervious surfaces, where weeds are expected
to grow. It is also assumed that bromacil is not applied to impervious surfaces in rights-of
way, but that there is a 1% incidental spray onto impervious surfaces in the right-of-way.
Further details on how the 1% value was derived and characterization of alternative
assumptions are provided in the Barton Springs salamander endangered species risk
assessment for atrazine (U.S. EPA, 2006).
In a standard PRZM scenario, it is assumed that an entire 10 ha field is composed only of
the identified crop, and that the field has uniform surface properties throughout the field.
In a right-of-way, this is not a reasonable assumption, since a right-of-way contains both
impervious and pervious surfaces. Since the two surfaces have different properties
(especially different curve numbers influencing the runoff from the surfaces) and
different masses of applied bromacil, the standard approach for deriving aquatic EECs is
revised using the following approach:
1) Aquatic EECs are derived for the pervious portion of the right-of-way, using the
maximum use rate of bromacil on the CArightofway scenario. At this point, it is
assumed that 100% of the right-of-way is composed of pervious surface. Specific
inputs for this modeling are defined below.
2) Aquatic EECs are derived for the impervious portion of the right-of-way, using
1% of the maximum use rate of bromacil on the CAimpervious scenario. At this
point, it is assumed that 100% of the right-of-way is composed of impervious
surface.
3) The daily aquatic EECs (contained in the PRZM/EXAMS output file with the
suffix "TS") are input into a Microsoft® Excel® worksheet.
4) Daily aquatic EECs for the impervious surface are multiplied by 50%. Daily
aquatic EECs for the pervious surface are multiplied by 50%. The resulting EECs
for impervious and pervious surfaces are added together to get an adjusted EEC
for each day of the 30-year simulation period (Equation 1).
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Equation 1: Revised EEC = (imperviousEEC * 50%) + (perviousEEC * 50%)
5) Rolling averages for the relevant durations of exposure (21-day, and 60-day
averages) are calculated. The l-in-10 year peak, 21-day and 60-day values are
used to define the acute and chronic EECs for the aquatic habitat.
In this approach, it is assumed that a right-of-way is composed of equal parts pervious
and impervious surfaces (i.e. in step 4, the EECs of both surfaces are multiplied by 50%).
This is more likely to be representative of a highway or road right-of-way. It is likely that
right-of-way contain different ratios of the two surfaces. In general, incorporation of
impervious surfaces into the exposure assessment results in increasing runoff volume in
the watershed, which tends to reduce overall pesticide exposure (when assuming 1%
overspray to the impervious surface).
3.1.2.3. Input Parameters
The appropriate chemical-specific PRZM/EXAMS input parameters are selected from
reviewed environmental fate data submitted by the registrant (Table 4) and in accordance
with EFED water model input parameter selection guidance (U.S. EPA 2002). A
summary of the chemical specific model inputs used in this assessment are provided in
Table 12
PRZM/EXAMS input parameters specific to uses of bromacil and bromacil lithium on
citrus and non-cropland areas are described below and are summarized in Table 13.
Parameters for these uses are determined based on label recommendations.
57
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Table 12. Chemical specific PRZM/EXAMS Input Parameters for deriving aquatic EECs for
bromacil.
Input Parameter
Koc (L/kgoc)
Henry's Law Constant (atm-m3/mol)
Hydrolysis Half -life (days)
Aerobic Soil Metabolism Half-life (days)
Aerobic Aquatic Metabolism Half-life
(days)
Anaerobic Aquatic Metabolism Half-life
(days)
Aqueous Photolysis Half -life (days; pH 7)
Vapor pressure (torr at 25°C)
Solubility in water
(mg/L @ pH 7, 25°C)
Molecular Wt. (g/mol)
Value
32
i.ixio-9
0 (stable)
825
1650
0 (stable)
102
S.lxlO'7
8150
261.12
Source/Comments
Value obtained from SCS/ARS
database; only column leaching data
were available from submitted studies
bromacil RED
MRID 4095 1505
MRID 40951510; input is 3X the
measured half -life value (275 days) to
account for uncertainty in using a
single value, per EFED guidance
default input value of 2X aerobic soil
input, per EFED guidance
conservative assumption in lieu of
data, per EFED guidance
MRIDs 4095 1507
40951508
bromacil RED
10X measured solubility of 815 ppm,
per EFED guidance
bromacil RED
Table 13. Use-specific PRZM/EXAMS Input Parameters for deriving aquatic EECs for bromacil.
Input Parameter
Single Application Rate (kg a.i./ha)
Number of applications per year
Application Interval (days)
CAM
Spray Drift
Application Efficiency
Application Date
Citrus
7.2
1
NA
1
0.01
0.99
January 25
Non-cropland areas:
Rights of Way
17.3
2
14
1
0.01
0.99
January 25
Non-cropland areas:
Impervious
0.1731
2
14
1
0
1
January 25
1 As noted above, it is assumed that 1% of bromacil applied to the pervious portion of a right-of-way is
incidentally sprayed onto the pervious surface.
58
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Citrus
According to current labels, the maximum single application rate of bromacil on citrus is
6.4 Ibs a.i./A (7.2 kg a.i./ha). Labels indicate that one maximum application should be
made per year (registrations 352-287, 352-505, 70506-83 and 81927-4).
Labels indicate that bromacil applications should be made beneath and/or between trees.
In PRZM, application methods are defined by the CAM (Chemical Application Method)
values; a CAM value of 1 is used to represent applications to soil with no incorporation.
This value is selected for representing applications of bromacil to the areas between
citrus trees.
The labels also indicate that contact of the product with tree foliage should be avoided.
Based on this, as well as instructions that applications should be made beneath and/or
between trees, it is unlikely that aerial methods would be employed for applications of
bromacil to citrus. Therefore, the spray drift assumption for ground applications, 1%, is
used in modeling aquatic EECs. The accompanying application efficiency of 99% is
used.
The application date is chosen based on label directions which indicate that applications
made in late fall or early winter will have the best results in terms of weed control. The
label also indicates that applications should be made at a time when rainfall (or irrigation)
would occur. Consideration of the meteorological data associated with the CA citrus
scenario indicates that the largest rainfall events occur in January. Based on this
information, an application date of January 25 was chosen. In actuality, applications of
bromacil can be made any time of the year, and according to available pesticide use data
for California, applications of bromacil to citrus have been made throughout the year.
Non-cropland
According to current labels, the maximum single application rate of bromacil on non-
cropland areas is 15.4 Ibs a.i./A (17.3 kg a.i./ha), with 2 maximum applications allowed
per year (registration 10088-68).
The minimum application interval is not indicated on this label. It is assumed that the
pesticide user would apply the pesticide and then wait to see results. After two weeks, the
pesticide user may then reapply bromacil to the treatment site. Therefore, it is assumed
that a second application may be made 14 days after the other.
To represent applications of bromacil to rights-of way and to impervious surfaces, a
CAM of 1 is used to represent applications directly to the ground.
The label with the maximum use rate for non-cropland areas (registration 10088-68)
clearly prohibits applications by aerial methods. Therefore, the spray drift assumption for
ground applications, 1% and the accompanying application efficiency of 99% are used in
modeling aquatic EECs.
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Label instructions indicate that applications of bromacil to non-cropland areas can be
made any time during the year. Consideration of the meteorological data associated with
the CA rightofway and CA impervious scenarios indicates that the largest rainfall events
occur in January. In general, the greater amount of rainfall in a single event, the greater
the EEC in the receiving aquatic habitat. In order to select an application date resulting in
a conservative estimate of exposure of aquatic habitats to bromacil, an application date of
January 25 was chosen.
3.1.3. Aquatic Modeling Results
PRZM/EXAMS EECs representing l-in-10 year peak, 21-day, and 60-day concentrations
of bromacil in the aquatic environment are located in Table 14.
Table 14. Aquatic EECs from PRZM/EXAMS modeling for maximum application rates of bromacil.
EECs are based on the appropriate PRZM scenario and the standard EXAMS pond.
Use
Citrus
Non-cropland
Scenario
CA citrus
CA rightofway and
CA impervious
Peak EEC
(mg/L)
0.056
2.34
21-day EEC
(mg/L)
0.056
2.33
60 -day EEC
(mg/L)
0.056
2.32
3.2. Terrestrial Exposure Assessment
3.2.1. Exposure to Plants
TerrPlant is used to calculate EECs for non-target plant species inhabiting dry and semi-
aquatic areas. Parameter values for application rate, drift assumption and incorporation
depth are based upon the use and related application method (Table 15). A runoff value
of 0.5 is utilized based on bromacil's solubility, which is classified by TerrPlant as >100
mg/L. For ground application methods, a drift assumption of 1% is selected. EECs
relevant to terrestrial plants consider pesticide concentrations in drift and in runoff.
These EECs are listed by use in Table 15. Output from TerrPlant v.1.2.2 are available in
Appendix C.
Table 15. TerrPlant inputs and resulting EECs for plants inhabiting dry and semi-aquatic areas
exposed to bromacil through runoff and drift.
Use
Citrus
Non-cropland
Application
rate
(Ibs a.i./A)
6.4
15.4
Application
method
ground
ground
Drift
Value
(%)
0.01
0.01
Spray drift
EEC
(Ibs a.i./A)
0.064
0.154
Dry area
EEC
(Ibs a.i./A)
0.32
0.924
Semi-
aquatic
area EEC
(Ibs a.i./A)
3.2
7.85
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3.2.2. Exposures to animals
3.2.2.1. Modeling Approach
T-REX is used to calculate dietary and dose-based EECs of bromacil for the CRLF and
its potential prey (e.g. terrestrial invertebrates, small mammals, terrestrial-phase frogs)
inhabiting terrestrial areas. EECs used to represent CRLF are also used to represent
exposure values for frogs serving as potential prey of CRLF adults. T-REX simulates a 1-
year time period. Foliar dissipation data are unavailable for estimating a half-life for
bromacil. As a result, the default value of 35 days is used. Use specific input values,
including number of applications, application rate and application interval are located in
Table 16. Outputs for T-REX v. 1.3.1 are available in Appendix D.
Table 16. Input parameters for T-REX used to derive terrestrial EECs for bromacil.
Use
Citrus
Non-cropland
Number of
applications
1
2*
Application rate
(Ibs a.i./A)
6.4
15.4
*Application interval of 14 days.
3.2.2.2. Terrestrial Animal Exposure Modeling Results
For modeling purposes, exposures of the CRLF to bromacil through contaminated food
are estimated using the EECs for the small bird (20 g) which consumes small insects.
Dietary-based EECs calculated by T-REX for small and large insects (units of jig a.i./g)
are used to bound an estimate of exposure to terrestrial invertebrates. Dietary-based and
dose-based exposures of potential prey are assessed using the small mammal (15 g)
which consumes short grass. Upper-bound Kenega nomogram values reported by T-REX
for these two organism types are used for derivation of EECs for the CRLF and its
potential prey (Table 17).
Table 17. Upper-bound Kenega nomogram EECs for exposures of the CRLF and its prey to
bromacil.
Organism
CRLF
small insects (prey)
large insects (prey)
small mammals (prey)
small frogs (prey)
Exposure
Dietary
Dose
Contact
Contact
Dietary
Dose
Dietary
Dose
Units
ppm
mg/kg-bw
ug a.i./g (of insect)
ug a.i./g (of insect)
ppm
mg/kg-bw
ppm
mg/kg-bw
Citrus
EEC*
864
984
864
96.0
1536
1464
864
984
Non-cropland
EEC*
3655
4162
3655
406
6497
6194
3655
4162
*based on a default foliar dissipation half-life of 35 days.
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3.2.3. Spray Drift Modeling
In order to determine the extent of terrestrial habitats of concern beyond application sites,
it is necessary to estimate the distance spray applications can drift from the treated field
and still be greater than the level of concern. Spray drift modeling was done for animals
and plants to determine the farthest distance required to not exceed the LOG for
exposures to bromacil drifted to non-target areas. This assessment requires the use of the
spray drift model, AgDrift (version 2.01; dated 5/24/2001). In cases where estimates of
drift exceed the limits of the AgDrift model, the AGDisp (version 8.13; dated
12/14/2004) (Teske and Curbishley, 2003) is used to simulate aerial and ground
applications using the Gaussian farfield extension.
The Tier I version of AgDrift was used for simulating applications of bromacil to citrus
and non-cropland areas by ground methods. It was assumed that a high boom height
would be used for ground applications. Given that labels did not describe any spray drift
mitigations, the most conservative assumption for spray drop size distributions, "ASAE
very fine to fine" was used to determine the range of possible depositions of bromacil.
The maximum single application rate for citrus (6.4 Ibs a.i./A) and non-cropland areas
(15.4 Ibs a.i./A) was used to determine the farthest distance from the edge of field where
there are no LOG exceedances for animals or plants (based on point deposition) (Table
18). AgDrift is useful for estimating point deposition out to 990 feet from the edge of a
field. In cases where estimates of exposure at 990 feet estimated by AgDrift were
sufficient to exceed the LOG for a taxonomic group, AGDisp was used. The parameters
used for AGDisp are defined in Table 19, with results in Table 18.
Table 18. Distance away from edge of field where terrestrial animal and plant LOCs are not
exceeded by exposures to bromacil through spray drift.
Organism
CRLF
Terrestrial
invertebrates
Terrestrial
mammals
Terrestrial
plants
Exposure
dose-acute
dietary-acute
dietary chronic
acute small
acute large
dose-acute
dose-chronic
dietary -chronic
monocots -drift
dicots -drift
LOC
0.1
0.1
1
0.05
0.05
0.1
1
1
1
1
Point deposition
that does not
exceed LOC
(Ibs a.i./A)
>1.1
>7.5
11
>0.44
>4.0
0.75
0.12
1.04
0.03
0.0047
Distance (in feet) from edge of field
where LOC is not exceeded-results
differ based on Use
Citrus
<16
NA
NA
<39
<3
23
132
17
437
40261
(0.76 mile)
Non-cropland areas
<36
<7
NA
<89
<13
52
292
39
810
59091
(1.12 mile)
NA = not applicable
:990 feet represents the range of AgDRIFT. Any value beyond this distance was calculated using AGDISP.
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Table 19. Scenario and standard management input parameters for simulation of bromacil in spray
drift using AgDisp with Gaussian farfield extension.
Parameter Description
Application Method
Nozzle type1
Boom Pressure1
Release height
Spray lines
Nozzles
Droplet Size Distribution
(DSD)
Swath Width
Wind Speed
Wind direction
Air temperature
Relative Humidity
Spray Material
Fraction of active solution that
is non-volatile
Fraction of additive solution
that is non-volatile
Upslope angle
Side slope angle
Canopy type
Surface roughness
Transport
Height for wind peed
measurement
Maximum comp. Time
Maximum downwind distance
Vortex decay rate OGE
Vortex decay rate IGE
Aircraft drag coefficient
Propeller efficiency
Ambient pressure
Ground reference
Evaporation rate
Specific Gravity (non-
volatile)
Parameter Value
for Citrus
Ground
Flat fan
60 Ib
4 feet
20
42
Fine to very fine
60ft
15 mph
-90°
65° F
50%
Water
0.08
0.1
0°
0°
none
0.0246 ft
Oft
6.56 ft
600 sec
2608.24 ft
0.3355
1.25
0.1
0.8
29.91
Oft
84.76 ug-(K-s)'1
1.0
Parameter Value for
Non-cropland
Aerial
NA
NA
15 feet
20
42
Fine to very fine
60ft
15 mph
-90°
65° F
50%
Water
0.0098
1
0°
0°
none
0.0246 ft
Oft
6.56 ft
600 sec
2608.24 ft
0.3355
1.25
0.1
0.8
29.91
Oft
84.76 ug-(K-s)'1
0.939
Comments
Product Labels
Program default
Program default
Program default
Program default
None available
Default; draft guidance
Program default
Default; draft guidance
Default
Program default
Program default
Program default
Product labels
Product labels
Assume flat surface
Assume flat surface
Default from guidance
Program default, none
provided
Program default
Program default
Program default
Program default
Program default
Program default
Program default
Program default
Program default
Program default
Program default
For citrus, assume that
product is dissolved in
water.
1 parameter for ground spray only
NA = Not Applicable
63
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4. Effects Assessment
This assessment evaluates the potential for bromacil to adversely affect the CRLF. As
previously discussed in Section 2.7, assessment endpoints for the CRLF include direct
toxic effects on the survival, reproduction, and growth of the CRLF itself, as well as
indirect effects, such as reduction of the prey base and/or modification of its habitat.
Direct effects to the CRLF in aquatic habitats are based on toxicity information for
freshwater vertebrates, specifically fish, which are generally used as a surrogate for
amphibians. Direct effects to the CRLF in terrestrial habitats are based on toxicity
information for birds, which are generally used as a surrogate for terrestrial-phase
amphibians.
Given that the CRLF's prey items and habitat requirements are dependent on the
availability of freshwater aquatic invertebrates and aquatic plants, fish, frogs, terrestrial
invertebrates and terrestrial mammals, toxicity information for these organisms is also
discussed.
Acute (short-term) and chronic (long-term) toxicity information is characterized based on
registrant-submitted studies and a comprehensive review of the open literature on
bromacil. A summary of the available freshwater and terrestrial ecotoxicity data relevant
to this assessment is discussed below.
The focus of this assessment is on the technical grade active ingredient (TGAI) of
bromacil. Data available for exposures of organisms to formulated products are not used
for deriving RQs, with the exception of instances where no suitable data are available for
exposures of organisms to the TGAI. Effects data are available for exposures of animals
and plants to formulated products containing bromacil or bromacil lithium. Some of these
data are described in Appendix A.
Toxicity endpoints are established based on data generated from guideline studies
submitted by the registrant, and from open literature studies that meet the criteria for
inclusion into the ECOTOX database maintained by EPA/Office of Research and
Development (ORD) (U.S. EPA, 2004). Open literature data presented in this assessment
were obtained from ECOTOX in May 2007, from a search which included all open
literature data for bromacil and its salts (including lithium, sodium and dimethylamine),
only one of which (lithium) is still registered for use. In order to be included in the
ECOTOX database, papers must meet the following minimum criteria:
• the toxic effects are related to single chemical exposure;
• the toxic effects are on an aquatic or terrestrial plant or animal species;
• there is a biological effect on live, whole organisms;
• a concurrent environmental chemical concentration/dose or application rate is
reported;
• and there is an explicit duration of exposure.
64
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Data that pass the ECOTOX screen are evaluated along with the registrant-submitted
data, and may be incorporated qualitatively or quantitatively into this endangered species
assessment. In general, effects data in the open literature that are more conservative than
the registrant-submitted data are considered. A list of citations accepted and rejected by
ECOTOX and the rational for rejection is available in Appendix G.
This section also includes information related to reported incidents of ecological effects
associated with bromacil. Available incidents include effects to terrestrial and wetland
plants, as well as effects to fish.
4.1. Evaluation of Aquatic Ecotoxicity Studies for Bromacil
As described in the Agency's Overview Document (U.S. EPA, 2004), the most sensitive
endpoint for each taxa is evaluated. For this assessment, evaluated taxa relevant to the
aquatic habitat of the CRLF include freshwater fish, freshwater aquatic invertebrates, and
freshwater aquatic plants. Currently, no guideline tests exist for frogs. Therefore,
surrogate species (fish) are used as described in the Overview Document (U.S. EPA,
2004) to represent direct exposures to the CRLF in the aquatic habitat. No ecotoxicity
data for amphibians exposed to bromacil are available from the open literature. Table 20
summarizes the most sensitive aquatic, ecological toxicity endpoints for the CRLF, its
prey and its habitat, based on an evaluation of both the submitted studies and the open
literature, as previously discussed. The values presented in Table 20 are used for
deriving quantitative RQs for this risk assessment. A brief summary of submitted and
open literature data considered relevant to this ecological risk assessment is presented
below.
65
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Table 20. Summary of most sensitive toxicity for assessing direct and indirect effects of bromacil to
CRLF in aquatic habitats.
Assessment Endpoint
Species
(common name)
End-point
Mean
concentration
(mg/L)
Study
Classification
Ref.
(MRID)
Measures of Direct Effects
Acute toxicity to CRLF
Chronic toxicity to CRLF
Oncorhyncus mykiss
(Rainbow Trout)
Oncorhyncus mykiss
(Rainbow Trout)
LCso
NOAEC
36
3.0
Acceptable
Supplemental
40951503
44566101
Measures of Indirect Effects
Toxicity to unicellular
plants composing aquatic
habitat and representing
prey for tadpole CRLF
Toxicity to multicellular
plants composing aquatic
habitat
Acute toxicity to
invertebrates (prey)
Chronic toxicity to
invertebrates (prey)
Acute toxicity to fish and
frogs representing prey
Acute toxicity to fish and
other species of frogs (prey)
Pseudokirchneriella
subcapitatum
(green algae)
Lemna gibba
(duckweed)
Daphnia magna
(Water Flea)
Daphnia magna
(Water Flea)
Oncorhyncus mykiss
(Rainbow Trout)
Oncorhyncus mykiss
(Rainbow Trout)
ECso
ECso
EC50
NOAEC
LC50
NOAEC
0.0068
0.045
121
8.2
36
3.0
Supplemental
Acceptable
Acceptable
Acceptable
Acceptable
Supplemental
42516401
46095401
40951504
44566401
40951503
44566101
Acute toxicity to aquatic fish and invertebrates is categorized using the system shown in
Table 21 (U.S. EPA, 2004). Based on thesecategories bromacil is classified slightly
toxic to practically nontoxic to freshwater fish and invertebrates, respectively, on an acute
exposure basis. Toxicity categories for aquatic plants have not been defined. If
classification for animals were applied to aquatic plants, bromacil would be classified
very highly toxic to unicellular and vascular plants.
Table 21. Categories of Acute Toxicity for Aquatic Animals.
LC50 (mg/L)
<0.1
>0.1-1
>1-10
> 10 - 100
>100
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically nontoxic
66
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4.1.1. Toxicity to freshwater fish
Acute exposures
Registrant submitted studies are available for acute exposures of rainbow trout
(Onchoryhnchus mykiss) and bluegill sunfish (Lepomis macrochirus) to bromacil. One
data point is available in ECOTOX for acute exposure of a freshwater fish to bromacil.
This value, which is reported as a 96-h LCso of 186 mg/L for fathead minnows
(Pimephales promelas) (Geiger et al. 1988), represents a less conservative value than
registrant-submitted data. Therefore, this value is not considered further in this
assessment.
The available registrant-submitted study involving rainbow trout was a static, 96-h
exposure, resulting in a LCso of 36 mg/L (95% confidence interval: 30-40 mg/L). This
LC50 value represents the most sensitive endpoint available for acute exposures offish to
bromacil. Sublethal effects observed in surviving fish exposed to 22.5 mg/L bromacil and
higher included loss of equilibrium, swollen appearance and sinking to the bottom of test
vessels. No effects were described at 16.9 mg/L (MRID 40951503).
The registrant-submitted study involving bluegill sunfish was a static, 96-h exposure,
resulting in a LCso of 127 mg a.i./L. Sublethal effects observed in surviving fish exposed
to 95 mg/L bromacil and higher included loss of equilibrium. No effects were described
at 71 mg/L (MRID 409515-02).
Chronic exposures
Data are available from a registrant-submitted study where rainbow trout were exposed to
bromacil for 90 days in a flow-though study. The NOAEC and LOAEC values for this
study were 3.0 and 7.2 mg a.i./L, respectively, based on treatment-related effects to mean
wet weight, which was the only measured endpoint that was affected. At the highest test
concentration (7.2 mg a.i./L), measured wet weights of juvenile fish were 32.4% lower
than controls. No treatment related effects on survival were observed in any of the
treatment groups (maximum of 7.2 mg a.i./L). This study is scientifically sound, but is
classified supplemental, due to excessive variation in measured concentrations of
bromacil in the treatment levels (MRID 44566101).
No data are available in ECOTOX for chronic exposures offish to bromacil.
4.1.2. Toxicity to freshwater invertebrates
Acute exposures
A registrant-submitted study is available for acute exposures of freshwater invertebrates
to bromacil. Data are also available in ECOTOX for acute exposures of freshwater
invertebrates to bromacil.
67
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The available registrant-submitted study involving waterflea (Daphnia magnd) was a
static, 48-h exposure, resulting in an ECso of 121 mg/L (95% confidence interval: 111-
148 mg/L), based on immobility. Effects were observed at 111 and 148 mg/L (20% and
100% immobility, respectively, with no effects described at 83 mg/L (MRID 409515-04).
This ECso value is used in this risk assessment for quantifying RQ values for acute
exposures of aquatic invertebrates to bromacil.
ECOTOX includes data for a study involving 48-h exposures of waterfleas
(Ceriodaphnia dubid) to bromacil. Resulting ECsovalues, based on immobility, were 65
mg a.i./L (95% confidence interval: 56-75 mg a.i./L) for exposures in laboratory water
and 75 mg a.i./L (95% confidence interval: 63-88 mg a.i./L) for exposures in field-
collected water (Foster et al. 1998). Due to insufficient data available in the publication,
(including raw data) the acceptability of this study could not be evaluated. Therefore,
these data are not utilized for quantifying RQ values representing acute exposures of
aquatic invertebrates to bromacil. As published, these EC50 values represent lower values
than the value used for deriving RQs, so, these data are used at face value to characterize
potential risk of aqueous exposures of bromacil to aquatic invertebrates (see section
5.2.2).
Chronic exposures
Data are available from a registrant-submitted study where waterfleas (D. magnd) were
exposed to bromacil for 21 days. The NOAEC and LOAEC values for this study were
8.2 and 21 mg a.i./L, respectively, based on treatment-related effects to reproduction and
growth. In the 21 mg a.i./L treatment level, adults did not produce offspring. Also, at that
treatment level, adults had significantly reduced body lengths and dry weights in
comparison to organisms in the negative control (13% and 45% decreases, respectively;
MRID 44566401).
No data are available in ECOTOX for chronic exposures of freshwater invertebrates to
bromacil.
4.1.3. Toxicity to aquatic plants
Unicellular plants
Data relevant to exposures of unicellular, aquatic plants to bromacil are available from
several registrant submitted studies. No data are available in ECOTOX for exposures of
aquatic, unicellular plants to technical bromacil.
Registrant-submitted studies for algae and diatoms (unicellular plants) include
values ranging 6.8-69.9 jig a.i./L, based on decreased cell density. Effects were observed
at exposures of green algae at the lowest bromacil concentrations tested, i.e., 1.1 ng a.i./L
(Table 22)
68
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Table 22. EC50 and NOAEC values from registrant submitted studies involving exposures of
bromacil to unicellular, aquatic plants.
Species
(common name)
Pseudokirchneriella
subcapitatum (green algae)
Navicula pelliculosa
(Freshwater diatom)
Skeletonema cosatum
(marine diatom)
Anabaena flos-aquae
(Blue-green algae)
EC50*
units: jig a.i./L
(95% C.I.)
6.8 (5.9-7.8)
6.91 (5.59-8.54)
12.1(8.3-17.6)
69.9(54.2-90.1)
NOAEC
Oiga.i./L)
<1.1
3.39
5.5
11.2
Study
Classification
Supplemental
Acceptable
Acceptable
Acceptable
Ref. (MRID)
42516401
44218501
44218503
44218502
*Effects based on decreased cell density.
Vascular plants
Data are available from a registrant-submitted study where duckweed (Lemna gibba) was
exposed to bromacil for 14 days. The NOAEC and EC50 values based on decrease in
frond number were 17 and 45 ug a.i./L, respectively. Effects to dry weight were also
observed during this study (MRID 46095401) albeit at higher concentrations. No data are
available in ECOTOX for exposures of aquatic vascular plants to bromacil.
4.2. Evaluation of Terrestrial Ecotoxicity Studies for Bromacil
As described in the Agency's Overview Document (U.S. EPA, 2004), the most sensitive
endpoint for each taxa is evaluated. For this assessment, evaluated taxa relevant to the
terrestrial habitat of the CRLF include birds, terrestrial insects, mammals and terrestrial
plants. Currently, no guideline tests exist for terrestrial-phase amphibians. Therefore,
surrogate species (birds) are used as described in the Overview Document (U.S. EPA,
2004) to represent direct exposures to the CRLF in the terrestrial habitat. No ecotoxicity
data for amphibians exposed to bromacil are available from the open literature. Table 23
summarizes the most sensitive terrestrial, ecological toxicity endpoints for the CRLF, its
prey and its habitat, based on an evaluation of both the registrant-submitted studies and
the open literature, as previously discussed. The values presented in Table 23 are used
for deriving quantitative RQs for this risk assessment. A brief summary of registrant-
submitted and open literature data considered relevant to this ecological risk assessment
is presented below.
69
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Table 23. Summary of most sensitive toxicity for assessing direct and indirect effects of bromacil to
CRLF in terrestrial habitats.
Assessment Endpoint
Species
(common name)
End-
point
Mean
concentration
Study
Classification
Ref.
(MRID)
Measures of Direct Effects
Acute toxicity to CRLF
Sub-acute toxicity to CRLF
Chronic toxicity to CRLF
Colinus virginianus
(Northern bobwhite
quail)
Colinus virginianus
(Northern bobwhite
quail)
Colinus virginianus
(Northern bobwhite
quail)
LD50
LC50
NOAEC
>2250 mg/kg
>10,000 mg/kg-
diet
1550 mg/kg-diet
Acceptable
Supplemental
Acceptable
40951501
00013295
44844801
Measures of Indirect Effects
Acute toxicity to
invertebrates (prey)
Acute toxicity to mammals
(prey)
Chronic toxicity to
mammals (prey)
Acute toxicity to frogs
representing prey
Sub-acute toxicity to frogs
representing prey
Chronic toxicity to other
species of frogs (prey)
Toxicity to monocot plants
composing wetland and
terrestrial habitat
Toxicity to dicot plants
composing wetland and
terrestrial habitat
Apis mellifera
(Honey bee)
Rattus norvegicus
(laboratory rat)
Rattus norvegicus
(laboratory rat)
Colinus virginianus
(Northern bobwhite
quail)
Colinus virginianus
(Northern bobwhite
quail)
Colinus virginianus
(Northern bobwhite
quail)
Triticum aestivum
(wheat)
Brassica napus
(rape)
LD50
LD50
NOAEL
LD50
LD50
NOAEC
EC25
EC25
>1209
uga.i./g(ofbee)
8 12 mg/kg
250 mg/kg-
diet/day
>2250 mg/kg
>10,000 mg/kg-
diet
1550 mg/kg-diet
0.030 Ibs ai./A1
0.042 Ibs a.i./A2
0.0047 Ibs ai./A1
0.0055 Ibs a.i./A2
Supplemental
Acceptable
Acceptable
Acceptable
Supplemental
Acceptable
Supplemental
Supplemental
00018842
44196209
41804601
40951501
00013295
44844801
44488307
44488307
1 based on effects to seedling emergence
2based on effects to vegetative vigor
Similar to toxicity categories for aquatic organisms, categories of acute toxicity ranging
from "practically nontoxic" to "very highly toxic" have been established for terrestrial
organisms based on LDso values (Table 24), and avian species based on LDso values
(Table 25). Subacute dietary toxicity for avian species is based on the LCso values
70
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(Table 26). Based on these categories, bromacil is practically nontoxic to birds and
slightly toxic to mammals on an acute exposure basis.
Table 24. Categories for mammalian acute toxicity based on median lethal dose in mg per kilogram
body weight (parts per million).
LD50 (mg a.i./kg)
<10
10-50
51-500
501-2000
>2000
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
Table 25. Categories of avian acute oral toxicity based on median lethal dose in milligrams per
kilogram body weight (parts per million).
LD50 (ppm)
<10
10-50
51-500
501-2000
>2000
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
Table 26. Categories of avian subacute dietary toxicity based on median lethal concentration in
milligrams per kilogram diet per day (parts per million).
LC50 (ppm)
<50
50-500
501-1000
1001-5000
>5000
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
71
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4.2.1. Toxicity to birds
Acute
Data are available from a registrant-submitted study, where bobwhite quail (Colinus
virginianus) were given acute, oral doses of bromacil. No mortalities were observed
during the 14-day study period, which resulted in a LDso >2250 mg/kg (highest dose
tested). Between days 0 and 3, reduced body weight gains in relation to the control were
observed at the two highest test doses, resulting in a NOAEL of 810 mg/kg. At 1350
mg/kg, body weight gains in female birds were 5.1% lower than controls. At 2250 mg/kg,
body weight gains in female and male birds were decreased 4.7 and 5.4%, respectively,
when compared to controls. By the end of the study, body weight gains of females and
males were similar in all treatment groups, including controls (MRID 40951501).
No data are available for sub-acute dietary exposures of birds to technical bromacil. In
lieu of toxicity data for technical grade bromacil, available data from a study involving
dietary-based exposures of birds to a formulated product (Hyvar® X Bromacil Weed
Killer, 80% a.i.) of bromacil are used in this assessment. In this study, mallard ducks
(Anas platyrhynchos) and bobwhite quail were exposed to a formulated product of
bromacil (83.4% a.i.) through dietary exposures. The resulting 8-d LC50 values for both
species exceeded the highest concentration tested, i.e., >10,000 mg/kg-diet/day (of
bromacil). No mortalities were observed in exposures involving mallard ducks.
Bobwhite quail mortalities were observed in exposures involving several different
treatment levels; however, the mortalities were less than 50% of individuals in each
treatment group. In the test, 6.8% mortality was observed in controls, 10% mortality was
observed in the 464 and 4640 mg/kg-diet/day treatment levels and 20% mortality was
observed in the 2150 and 10,000 mg/kg-diet/day treatment levels (MRID 00013295).
This study is classified acceptable for a formulated product, but supplemental for use in
this assessment, since the test material was not technical bromacil.
No toxicity data are available in ECOTOX for acute exposures of birds to bromacil.
Chronic
Data are available from two registrant-submitted studies, where bobwhite quail and
mallard ducks were given chronic (21 weeks), dietary exposures of bromacil. In the
study involving Northern bobwhite quail, effects to hatchability, embryo viability,
embryo survival and hatching survival were observed at 3100 mg/kg-diet/day, resulting
in a NOAEC of 1550 mg a.i./kg-diet/day (MRID 44844801). In the study involving
mallard ducks, significant effects were observed in egg shell thickness at the 3100 mg
a.i./kg-diet/day treatment level. Significant effects to hatchability of mallards were
observed at the 6200 mg a.i./kg-diet/day treatment level. The NOAEC for this study was
also 1550 mg a.i./kg-diet/day (MRID 44844601).
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4.2.2. Toxicity to mammals
Acute
Data are available from a registrant-submitted study, where laboratory rats (Rattus
norvegicus) were given acute oral doses of technical grade bromacil. Mortalities were
observed in animals dosed with 1000 and 2000 mg/kg, which resulted in an acute oral
LD50 of 812 mg/kg for females and 1682 mg/kg for males. Sublethal effects that were
observed included: hunched posture, ataxia, lethargy, decreased respiration, hemorrhagic
lungs, and dark liver and kidneys (MRID 44196209). No data are available in ECOTOX
for acute exposures of mammals to bromacil.
Chronic
Data are available from a 2-generation dietary exposure reproduction study in rats. The
reported NOAEL was 250 mg/kg-diet/day, with a LOAEC of 2500 mg/kg-diet/day.
Observed effects included decreased growth (body weight reductions) in parent and first
and second generation offspring (MRID 41804601). The results of this study (i.e. the
NOAEL) are used to derive RQs for mammals representing prey of the terrestrial phase
CRLF.
ECOTOX includes data from a study in which laboratory rats were exposed to bromacil
in the diet for 2 years. The reported NOAEL was 250 mg/kg-diet/day. The LOAEL of
1250 mg/kg-diet/day was based on observed decrease in body weight gains and food
consumption (Sherman and Kaplan 1975). These results are consistent with those
included in MRID 41804601.
4.2.3. Toxicity to terrestrial insects
Data are available on the acute toxicity of bromacil to honey bees (Apis melliferd). In an
acute contact toxicity study, the LDso was higher than the highest dose tested, i.e., >11 jig
a.i./bee (MRID 00251374). In another study involving 96-h acute contact exposures of
honeybees to a formulated product containing bromacil (Hyvar® X Bromacil Weed
Killer, 80% a.i.), the LC50 was >193.38 |ig/bee (MRID 00018842). At this level, 1.2%
mortality was observed. Adjustment of this value for the % a.i. of the test substance
results in an LD50 >155 jig a.i./bee. This toxicity value is converted to units of jig a.i./g
(of bee) by multiplying by 1 bee/0.128 g thereby resulting in an LD50 >1209 jig a.i./g.
No data are available in ECOTOX for exposures of insects to technical grade bromacil.
4.2.4. Toxicity to terrestrial plants
Toxicity data were submitted from seedling emergence and vegetative vigor studies
involving separate exposures of wheat (monocot) and rape (dicot) to technical bromacil
and technical bromacil lithium.
73
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In the seedling emergence tests involving bromacil and bromacil lithium, percent
survival, dry weight and plant height were significantly affected in both wheat and rape.
The % inhibition in seedling emergence in the treated species as compared to the control
ranged from -11 to 5% for bromacil and from -5 to 13% for bromacil lithium. The most
sensitive endpoint for wheat and rape in the seedling emergence tests was dry weight.
The following abnormalities were noted for bromacil: slight growth retardation,
malformations, chlorosis and necrosis. The following abnormalities were noted for
bromacil lithium: slight to moderate chlorosis, slight to severe growth retardation, slight
unusual pigmentation and slight to severe burn or necrosis. NOAEC, £€25 and ECso
values for bromacil and bromacil lithium exposures t indicate that the two chemicals are
of similar toxicities to wheat and to rape (MRTD 444883-07; Table 27).
Table 27. Comparison of seedling emergence endpoints1 for wheat and rape exposed to bromacil and
bromacil lithium.
Endpoint
NOAEC
EC25
EC50
Wheat
Bromacil
0.020
0.030
0.085
Bromacil Lithium
0.020
0.034
0.087
Rape
Bromacil
0.006
0.0047
0.013
Bromacil Lithium
0.006
0.010
0.013
:Based on decreased dry weight.
In the vegetative vigor tests, the plant dry weight and plant height were affected by
exposures to bromacil and bromacil lithium. The most sensitive endpoint for wheat and
rape in the vegetative vigor tests was dry weight. The following abnormalities were noted
in tests where plants were exposed to bromacil or bromacil lithium: chlorosis, necrosis
and growth retardation. NOAEC, £€25 and ECso values for bromacil and bromacil
lithium exposures indicate that the two chemicals are of similar toxicities to wheat and to
rape (MRID 444883-07; Table 28).
Table 28. Comparison of vegetative vigor endpointsl for wheat and rape exposed separately to
bromacil and bromacil lithium.
Endpoint
NOAEC
EC25
EC50
Wheat
Bromacil
0.020
0.042
0.068
Bromacil Lithium
0.001
0.028
0.065
Rape
Bromacil
0.006
0.0055
0.010
Bromacil Lithium
0.003
0.0060
0.010
:Based on decreased dry weight.
4.3. Incident Reports
A search of the EIIS (Environmental Incident Information System) database for
ecological incidents (run on September 21, 2007) identified are a total of 32 incidents
associated with bromacil that were reported from 1992-2005. No incidents are identified
in EIIS in association with bromacil lithium. Incidents included in EIIS are defined by a
certainty index associated with the likelihood that the pesticide application described
resulted in the observed incident. The certainty index defines incidents as unrelated,
unlikely, possible, probable and highly probable. One notable source of uncertainty
74
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associated with the EIIS database is the nature of reporting of incidents. Many more
incidents may have occurred due to bromacil exposures but may not have been reported
due to various factors, such as a lack of reporting, or a lack of witnessing of effects.
Therefore, the lack of an incident report does not necessarily indicate a lack of an
incident.
The majority (27) of the incidents associated with bromacil involve damage to terrestrial
plants. These incidents are summarized in Table 29. These incidents involved
applications classified as "misuse" and as "registered use." The certainty index associated
with all of the incidents was defined as either "possible," "probable" or "highly
probable." These incidents reported observed effects to individual plants, including trees,
effects to lawns, and effects to crops covering areas greater than 100 acres. In some cases,
other herbicides where applied along with bromacil (e.g. diuron, atrazine, metolachlor).
Reports indicated that bromacil exposures occurred through direct treatment of areas,
spray drift, runoff and carryover from one season to the next.
In addition, 5 of the incidents associated with bromacil involved mortalities of fish
(Table 30). Of these 5 incidents reporting fish kills, 3 reported combined exposures of
fish to 2,4-D and bromacil, 1 reported combined exposures offish to copper and bromacil
and 1 reported exposures of fish to bromacil only. This last report (# 1008956-001)
involved an incident where bromacil was dumped into a storm drain, which discharged to
a local river. The certainty of this incident in relation to bromacil was "probable."
However, this incident was classified as misuse which is not a component of the federal
action under review in this assessment.
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Table 29. Summary of reported incidents involving terrestrial plants in relation to applications of bromacil.
Incident ID
1013884-004
1010837-045
1008184-001
1010837-055
1012457-012
1012684-012
1010837-020
1012457-017
1012457-013
1008441-001
1010837-048
10144700-001
1016569-001
1010837-030
1015360-001
1013850-001
1014409-062
1014177-001
1012457-019
1013587-020
1015382-001
1012708-001
1010837-031
1005972-001
1005075-001
1006010-003
1016610-001
Use Site
Home,
exterior
N/R
N/R
N/R
Peanut
Peanut
corn
N/R
Peanut
Fence row
corn
Right-of-
way, utility
Residential
N/R
Driveway
Right-of-
way, rail
N/R
Citrus
Peanut
Right-of-way
Residential
area
Plants
N/R
PLANT
SITE
PASTURE
Utility plant
lawn
Plants affected
yard
corn
trees
soybeans
peanuts
peanuts
corn
peanuts
peanuts
Trees and turf
corn
sod
Willow trees
sunflowers
Trees (pine and
deciduous)
Back yard
Trees and
shrubs
Bell peppers
peanut
Evergreen trees
Trees and grass
Oaks (mature),
shrubs, plants
sunflower
Mature oaks
Alfalfa, oats,
hay
Pasture grass
and bullrush
Trees (pine,
cottonwood,
willow) and
grass
Date
4/22/98
7/13/00
8/19/98
6/19/00
5/28/01
5/29/01
6/7/00
5/20/01
5/29/01
1 1/6/98
7/10/00
5/1/04
7/25/05
6/27/00
8/24/04
5/24/02
7/3/92
3/15/02
6/4/01
3/2/98
6/25/04
6/1/01
6/27/00
9/1/97
8/19/97
9/1/03
Legality
Registered use
Undetermined
Undetermined
Undetermined
Undetermined
Registered use
Undetermined
Undetermined
Undetermined
Undetermined
Undetermined
Registered use
Undetermined
Undetermined
Misuse
(accidental)
Registered use
Undetermined
Registered use
Undetermined
Registered use
Undetermined
Undetermined
Undetermined
Registered use
Misuse
(accidental)
Misuse
(accidental)
Misuse
(intentional)
Certainty
Highly
Probable
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Possible
Probable
Probable
Probable
Probable
Probable
Probable
Probable
State
WA
NY
PA
VA
PA
OK
GA
KY
NY
OK
NM
SD
OR
MI
WA
CA
GA
WA
WY
FL
SD
TX
TX
MS
ID
County
Grant
Wyoming
Huntington
Isle of
Wight
Sussex
Bradford
Beckham
Mitchell
Mason
Steuben
Carter
San Juan
Douglas
Grant
Washtenaw
Benton
Riverside
Grady
Adams
Polk
Douglas
Elaine
Total Magnitude
Not given
ALL
UNKNOWN
35 ACRES
52.5 acres
40 acres
ALL
30 acres
102.7 acres
unknown
ALL
Not given
45 (number)
ALL
3 (number)
1/3 of backyard
Not given
30 acres
88.7 acres
N/R
N/R
40 trees
ALL
3 (number)
3 Acres
unknown
Various
Appl. Rate
N/R
N/R
N/R
N/R
N/R
N/R
N/R
N/R
N/R
N/R
N/R
12 LB/
acre
N/R
N/R
8 Ibs/acre
N/R
N/R
N/R
N/R
N/R
N/R
N/R
N/R
N/A
N/R
N/R
4 pounds
Exposure route
Drift and runoff
Treated directly
Drift
Treated directly
Treated directly
Treated directly
Treated directly
Treated directly
Treated directly
Runoff
Treated directly
runoff
Spray
carryover
N/R
Spray
N/R
carryover
Treated directly
drift
runoff
Direct treatment
carryover
runoff
unknown
runoff
Direct treatment
Other pesticides
diuron
atrazine, metolachlor
NR
atrazine, metolachlor
s-metolachlor,
flumioxazin
s-metolachlor,
flumioxazin
atrazine, metolachlor
flumioxazin
flumioxazin
NR
atrazine, metolachlor
diruon
diuron
Dicamba, 2,4-D,
primisulfuron-methyl
diuron
2,4-D, dimethylamine,
diuron, glyphosate,
isopropylamine salt
Diuron, oryzalin
diuron
Ethalfluralin, flumioxazin
diuron
diuron
Dicamba, 2,4-D,
primisulfuron-methyl
Diuron, sulfometuron,
imazapyr
diuron
Diuron, glyphosate,
isopropylamine salt,
sulfometuron
diuron
N/R = not reported
76
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Table 30. Summary of reported incidents involving fish kills in relation to applications of bromacil.
Incident ID
1004875-001
1007154-001
1008956-001
1004668-001
1003601-001
Use Site
N/R
Utility plant
Sewer disposal
N/R
stream
Type of Fish
N/R
N/R
N/R
N/R
White sucker,
minnow, eel,
dace
Date
3/10/96
3/18/98
1/1/94
3/10/96
6/22/93
Legality
Misuse
(intentional)
Registered use
Misuse
(intentional)
Misuse
(accidental)
Registered use
Certainty
Highly
Probable
Possible
Probable
Probable
Probable
State
LA
MS
IA
LA
DE
County
East
Baton
Rouge
East
Baton
Rouge
New
Castle
# fish killed
Hundreds
(along 1.6
mile stretch
of creek)
some
Unknown
600
1000
Appl.
Method
Leaking
drum
Soil
incorporation
Dumped into
drain
spill
Surface
application
Other
pesticides
2, 4-D
Diuron, copper
sulfate
N/R
2,4-D
2, 4-D
Product
KROVAR I DF
FENOCIL III
N/R
N/R = not reported
77
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5. Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations to
determine the potential ecological risk from varying bromacil and bromacil lithium use
within the action area and to determine likelihood of direct and indirect effects on the
CRLF. The risk characterization provides estimation and description of the likelihood of
adverse effects; it articulates risk assessment assumptions, limitations, and uncertainties;
and synthesizes 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.
5.1. Risk Estimation
Risk is estimated by calculating the ratio of exposure to toxicity. This ratio is the risk
quotient (RQ), which is then compared to pre-established acute and chronic risk levels of
concern (LOCs) for each category evaluated (Appendix F). For acute exposures to the
CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the acute
risk to endangered species LOG is 0.05. For acute exposures to the CRLF and mammals,
the acute risk to endangered species LOG is 0.1. The LOG for chronic risk to CRLF and
its prey, as well as acute risk to plants is 1.0. As discussed in the analysis plan of the
problem formulation (specifically, section 2.10.1.3), the acute risk to non-listed species
LOG value for animal prey, which is 0.5, is also used for evaluating RQs.
Screening-level RQs are based on the most sensitive endpoints and modeled EECs from
the following scenarios for bromacil:
• Use on citrus @ 6.4 Ibs a.i./A; 1 application per year
• Use on non-cropland areas @ 15.4 pound a.i./A; 2 applications per year
For exposures of terrestrial plants inhabiting dry and semi-aquatic habitats, single
maximum applications of use on citrus and non-cropland areas were modeled, based on
the application rates listed above.
5.1.1. Exposures in the Aquatic Habitat
5.1.1.1. Direct Effects to CRLF
For assessing acute risks of direct effects to the larval and juvenile and adult CRLF
inhabiting water, l-in-10 year peak EECs in the standard pond are used with the lowest
acute toxicity value for fish. For chronic risks, l-in-10 year peak 60-day EECs and the
lowest chronic toxicity value for fish are used. Resulting RQs exceed the acute risk to
listed species LOG (RQ>0.05) for applications to non-cropland areas. RQs do not exceed
the acute or chronic risk LOCs for applications to citrus or the chronic risk LOG for
applications to non-cropland areas (Table 31).
78
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Table 31. RQ values for acute and chronic exposures directly to the CRLF in aquatic habitats.
Use
Citrus
Non-cropland
Peak EEC
(mg/L)
0.056
2.34
60-d EEC
(mg/L)
0.056
2.32
Acute CRLF
RQ1
0.01
0.0653
Chronic
CRLF RQ2
0.02
0.77
'Calculated using LC50=36 mg/L.
Calculated using NOAEC = 3 mg/L.
3Exceeds acute, listed species LOC (0.05).
5.1.1.2 Indirect Effects to CRLF through effects to organisms composing
diet (i.e. prey)
For assessing risks of indirect effects of bromacil to the aquatic-phase CRLF (tadpoles)
through effects to its diet, l-in-10 year peak EECs from the standard pond are used with
the lowest acute toxicity value for aquatic unicellular plants to derive RQs. Resulting
RQs exceed the acute risk LOC (RQ>1.0) for aquatic plants from bromacil applications
citrus and non-cropland areas (Table 32).
Table 32. RQ values for exposures to unicellular aquatic plants (diet of CRLF in tadpole life stage).
Use
Citrus
Non-cropland
Peak EEC
(mg/L)
0.056
2.34
Unicellular
Plant RQ1
8.242
3442
'Calculated using EC50=0.0068 mg/L.
2 Exceeds aquatic plant LOC (1.0).
For assessing risks of indirect acute effects to the aquatic-phase CRLF through effects to
prey (invertebrates) in aquatic habitats, l-in-10 year peak EECs in the standard pond are
used with the lowest acute toxicity value for invertebrates. For chronic risks, l-in-10 year
peak 21-day EECs and the lowest chronic toxicity value for invertebrates are used to
derive RQs. Resulting RQs do not exceed the acute and chronic risk to listed species
LOC (RQ>0.05 and >1.0, respectively) for applications to citrus and non-cropland areas
(Table 33)
Table 33. Risk Quotient (RQ) values for acute and chronic exposures to aquatic invertebrates (prey
of CRLF juveniles and adults) in aquatic habitats.
Use
Citrus
Non-cropland
Peak EEC
(mg/L)
0.056
2.34
21-d EEC
(mg/L)
0.056
2.33
Acute Invert
RQ1
O.01
0.02
Chronic
Invert RQ2
0.01
0.28
'Calculated using EC50=121 mg/L.
Calculated using NOAEC = 8.2 mg/L.
Fish and frogs also represent prey of CRLF. These RQs are represented by those used for
direct effects to the CRLF in aquatic habitats (Table 31). RQs for non-cropland areas
exceed the acute risk LOC for listed animals (RQ>0.05), but not for non-listed animals
(RQ>0.5). The chronic risk LOC for non-listed and listed animals (RQ>1.0) is not
79
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exceeded for non-cropland areas. RQs for citrus do not exceed the acute or chronic risk
LOCs for non-listed and listed fish and frogs.
5.1.2.3. Indirect Effects to CRLF through effects to habitat (plants)
For assessing risks of indirect effects of bromacil to the aquatic habitat (plants) the 1-in-
10 year peak EECs from the standard pond are used with the lowest acute toxicity value
for aquatic unicellular plants and for aquatic vascular plants to derive RQs. Resulting
RQs exceed the LOG (RQ>1.0) for both unicellular and vascular aquatic plants from
bromacil applications to citrus and non-cropland areas (Table 34).
Table 34. RQ values for exposures of aquatic plants to bromacil.
Use
Citrus
Non-cropland
Peak EEC
(mg/L)
0.056
2.34
Unicellular
Plant RQ1
8.23
3443
Vascular
Aquatic Plant
RQ2
1.23
523
'Calculated using EC50=0.0068 mg/L.
Calculated using EC50=0.045 mg/L.
3 Exceeds aquatic plant LOC (1.0).
5.1.2. Exposures in the Terrestrial Habitat
5.1.2.1. Direct Effects to CRLF
As described above, to assess risks of bromacil to terrestrial-phase CRLF, dietary-based
and dose-based exposures modeled in T-REX for a small bird (20g) consuming small
invertebrates are used. Acute, subacute and chronic effects are estimated using the lowest
available toxicity data for birds. EECs are divided by toxicity values to estimate acute
and chronic dietary-based RQs as well as dose-based RQs.
For use on citrus, indiscreet, dose-based RQs potentially exceed the LOC. Acute and
chronic, dietary-based RQs for use on citrus do not exceed the LOC. For use on non-
cropland areas, the LOC is potentially exceeded by RQs for dose-based and dietary-based
exposures (Table 35).
Table 35. RQ values for exposures of terrestrial-phase CRLF to bromacil. RQs estimated using T-
REX.
Exposure
Dose-acute
Dietary-acute
Dietary -chronic
Toxicity Value
LD50>2250 mg/kg
LC50>10,000 mg/kg-diet
NOAEC = 1550 mg/kg-diet
Citrus
RQ
O.611
O.09
0.56
Non-cropland
RQ
<2.6'
O.371
2.362
1 since this RQ is indiscreet, it potentially exceeds the acute listed species LOC of 0.1
2exceeds chronic, listed species LOC (1.0)
80
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5.1.2.2. Indirect Effects to CRLF through effects to prey
In order to assess the risks to terrestrial invertebrates, which are considered prey of CRLF
in terrestrial habitats, the honey bee is used as a surrogate for terrestrial invertebrates. As
described earlier, the toxicity value for terrestrial invertebrates is calculated by
multiplying the lowest available acute contact LD50 of >155 jig a.i./bee by 1 bee/0.128 g,
which is based on the weight of an adult honey bee. EECs (jig a.i./g of bee) calculated by
T-REX for small and large insects are divided by the calculated toxicity value for
terrestrial invertebrates, which is >1209 jig a.i./g of bee. The resulting RQ values for
large insect and small insect exposures bound the potential range of exposures for
terrestrial insects from the use of bromacil. For all uses, RQ values potentially exceed the
LOC (RQ>0.05) for both large and small terrestrial insects (Table 36).
Table 36. RQ values for exposures of terrestrial animals to bromacil. RQs estimated using T-REX.
Organism
small insects
(prey)
large insects
(prey)
small mammals
(prey)
small frogs
(prey)
Exposure
Acute Contact
Acute Contact
Dose-acute
Dose-chronic
Dietary-chronic
Dose-acute
Dietary-acute
Dietary-chronic
Toxicity Value
LD50>1209 ug a.i./g
LD50>1209 ug a.i./g
LD50=812mg/kg
NOAEC = 12.5 mg/kg-bw
NOAEL = 250 mg/kg-diet/day
LD50>2250 mg/kg
LC50>10,000 mg/kg-diet
NOAEC = 1550 mg/kg-diet
Citrus
RQ
O.711
<0.0791
0.822
533
6.13
<0.614
O.09
0.56
Non-
cropland RQ
<3.01
<0.341
3.52
2253
26.03
<2.64
<0.374
2.363
1 since this RQ is indiscreet, it potentially exceeds the LOC for terrestrial invertebrates (0.05)
2exceeds the acute listed species LOC of 0.1
3exceeds chronic, listed species LOC (1.0)
4since this RQ is indiscreet, it potentially exceeds the acute listed species LOC of 0.1
As described above, to assess risks of bromacil to prey (small mammals) of larger
terrestrial-phase CRLF, dietary-based and dose-based exposures modeled in T-REX for a
small mammal (15g) consuming short grass are used. Acute, subacute and chronic effects
are estimated using the most sensitive mammalian toxicity data. EECs are divided by the
toxicity value to estimate acute and chronic dietary-based RQs as well as acute dose-
based RQs. For all uses on citrus and non-cropland, acute RQ values exceed the acute
risk to listed species and non-listed species LOCs (RQ>0.1 and 0.5, respectively) and
chronic dose-based and dietary-based RQ values exceed the chronic risk LOC (RQ>1.0)
for mammals considered as potential prey species for CRLF (Table 36).
An additional prey item of the adult CRLF is other species of frogs. In order to assess
risks to these organisms, dietary-based and dose-based exposures modeled in T-REX for
a small bird (20g) consuming small invertebrates are used. These are the same EECs,
toxicity values and RQs used to assess direct effects to the CRLF. For use on citrus, dose-
based RQs potentially exceed the LOC. Acute and chronic, dietary-based RQs for use on
citrus do not exceed the LOC. For use on non-cropland areas, the LOC is potentially
exceeded by RQs for dose-based and dietary-based exposures (Table 36).
81
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5.1.2.3. Indirect Effects to CRLF through effects to habitat (plants)
For use on citrus and non-cropland areas, RQs exceed the LOG for monocots and dicots
exposed to bromacil through runoff and drift (Table 37).
Table 37. RQ values for exposures of terrestrial plants to bromacil. RQs estimated using TerrPlant.
Plant type
Monocot1
Dicot2
Exposure
Dry Areas
(runoff and drift)
Semi-Aquatic Areas
(runoff and drift)
Spray Drift only
Dry Areas
(runoff and drift)
Semi-Aquatic Areas
(runoff and drift)
Spray Drift only
Citrus
RQ
133
1093
2.13
823
6943
143
Non-cropland
RQ
313
2623
5.13
1973
16713
333
:based on EC2s = 0.03 Ibs a.i./A (effects on seedling emergence)
2based onEC25 = 0.0047 Ibs a.i./A (effects on seedling emergence)
3exceeds LOG (1.0) for non-listed terrestrial plants
5.2. Risk Description
The risk description synthesizes an overall conclusion regarding the likelihood of adverse
impacts leading to an effects determination (i.e., "no effect," "may affect, but not likely
to adversely affect," or "likely to adversely affect") for the CRLF.
If the RQs presented in the Risk Estimation (Section 5.1) show no indirect effects and
LOCs for the CRLF are not exceeded for direct effects, a "no effect" determination is
made, based on use of bromacil and bromacil lithium 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. 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"
82
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occurs for even a single individual. "Take" in this context means to harass or
harm, defined as the following:
o 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.
o 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.
5.2.1. Direct Effects
5.2.1.1. Aquatic-phase
Citrus
Acute and chronic RQ values representing uses of bromacil on citrus are insufficient to
exceed the LOCs for direct effects to the CRLF in aquatic habitats. Therefore, the
determination for direct effects to the CRLF in aquatic habitats is "No Effect" for uses of
bromacil on citrus.
Non-cropland
For bromacil and bromacil lithium uses on non-cropland areas, the acute risk LOG is
exceeded for direct effects to the CRLF in aquatic habitats. The chronic risk LOG is not
exceeded for direct effects to the CRLF in aquatic habitats, indicating that chronic
exposures to the CRLF in aquatic habitats are not of concern. Therefore, the
determination is "May Affect" based on acute exposures resulting from applications of
bromacil and bromacil lithium.
In this assessment, it is assumed that modeling the highest rate possible for bromacil (2
applications of 15.4 Ibs a.i./A per year) is a conservative representation of applications of
both bromacil and bromacil lithium, the latter of which has a lower maximum application
rate of 12 Ibs a.i./A (1 application per year). Modeling the highest application scenario
results in higher aquatic EECs. In this case, aquatic EECs resulting from the maximum
83
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use of bromacil are sufficient to exceed the listed species LOG for acute exposures.
However, aquatic EECs resulting from applications of bromacil lithium at its maximum
use rate are insufficient to exceed the listed species LOG (Table 38). Therefore, for
bromacil lithium, the determination for acute exposures of bromacil to the CRLF is "Not
Likely to Adversely Affect."
Table 38. RQ values for acute and chronic exposures directly to the CRLF in aquatic habitats
resulting from applications of bromacil and bromacil lithium to non-cropland areas at the maximum
uses allowed by labels.
Chemical
Bromacil
Bromacil lithium
Max single
application rate
(number of
applications/year)
(in Ibs a.i./A)
15.4 (2)
12(1)
Peak
EEC
(mg/L)
2.34
0.83
60-d EEC
(mg/L)
2.32
0.83
Acute CRLF
RQ1
0.0653
0.023
Chronic
CRLF RQ2
0.77
0.28
'Calculated using LC50=36 mg/L.
Calculated using NOAEC = 3 mg/L.
3Exceeds acute, listed species LOG (0.05).
Estimates of acute exposure of CRLF to bromacil from uses in rights-of-way result in
RQs that exceed the acute risk LOG by a factor of 1.3X. An analysis of the likelihood of
individual direct mortality is conducted using the LCso of 36 mg/L and the default slope
of 4.5. For non-cropland areas, the likelihood of individual mortality is 1 in 2.17e7, which
is equivalent to a 0.00005% chance.
Based the above information, acute effects directly to aquatic-phase CRLF resulting from
bromacil applications at the maximum allowed rate to non-cropland areas although
possible, are insignificant. Therefore, the determination for effects to the aquatic-phase
CRLF resulting from bromacil and bromacil lithium use on non-cropland areas is "Not
Likely to Adversely Affect."
5.2.1.2. Terrestrial-phase
Although dietary-based RQ values are considerably lower than dose-based RQ values
(Table 35), the former do not take into account that different sized animals consume
differing amounts of food and that depending on the forage item, an animal has to
consume varying amounts due to differing nutrition levels in the food item. If dietary-
based RQ values are adjusted to account for differential food consumption, the adjusted
RQ value would likely approximate the dose-based RQ value.
Exposure modeling with T-REX results in some LOG exceedances for RQs representing
bromacil exposures to the terrestrial-phase CRLF. As discussed above (Section 2.10.1.1),
the use of avian food intake allometric equation as a surrogate to amphibians is likely to
result in an over-estimation of exposure and risk for reptiles and terrestrial-phase
amphibians. The T-HERPS model was used to account for amphibian-specific
exposures.
84
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In order to explore influences of amphibian-specific food intake equations on potential
dose-based and dietary-based exposures of the terrestrial-phase CRLF to bromacil, T-
HERPS was used. With T-REX, applications of bromacil to citrus and non-cropland
areas, results in dietary-based exposures of 864 and 3655 ppm, respectively. Dietary-
based EECs for CRLF modeled using T-HERPS range 704-1536 ppm for citrus, and 421-
6728 ppm for non-cropland areas, depending upon the food source. With T-REX, dose-
based EECs of 984 and 4162 mg/kg-bw, were derived for citrus and non-cropland areas,
respectively. Dose-based EECs for CRLF modeled using T-HERPS range 2.40-957
mg/kg-bw for citrus and 10.5-4194 for non-cropland areas (Table 39). Outputs from T-
HERPS are available in Appendix E.
Table 39. Dietary-based and dose-based EECs relevant to direct effects to the CARLF through
consumption of prey contaminated by bromacil. Modeling done with T-HERPS.
Food
Dietary
Based EEC
(ppm)
Dose Based
EEC
(mg/kg-bw)
1.4 g CRLF
Dose Based
EEC
(mg/kg-bw)
37 g CRLF
Dose Based
EEC
(mg/kg-bw)
238 g CRLF
Citrus
Small Insects
Large Insects
Small Herbivore mammals
Small Insectivore mammals
Small Terrestrial Phase
Amphibians
1536
704
864
96.0
1012
59.7
27.4
33.6
3.73
N/A
58.7
26.9
33.0
3.67
957
38.4
17.6
21.6
2.40
149
Non-cropland areas
Small Insects
Large Insects
Small Herbivore mammals
Small Insectivore mammals
Small Terrestrial Phase
Amphibians
6728
3084
3784
421
4433
261
120
147
16.3
N/A
257
118
145
16.1
4194
168
77.2
94.7
10.5
652
Acute dose-based and dietary-based RQs are based upon indiscreet toxicity endpoints,
where the LD50 and LCso values, (defined as >2250 mg/kg and > 10,000 mg/kg-diet,
respectively), were not quantified. In the available LDso study for birds, no mortality was
observed in any of the treatment groups. In the LC50 study with quail, mortalities were
observed in several of the treatment groups; however, mortality in each treatment group
was <50%. Therefore, acute RQ values are indiscreet, and, in cases where LOG
exceedances are observed, there is only the potential for an exceedance, i.e., RQ values
are actually less than the calculated value; however, the extent to which they are lower is
uncertain. Because LD50 and LCso values were not defined, likelihood of individual
mortality could not be determined for direct acute affects to the terrestrial phase CRLF.
Citrus
For citrus, the acute dose-based RQ potentially exceeds the LOG, resulting in a "may
affect" determination for acute exposures of the CRLF to bromacil. For acute and chronic
dietary-based exposures resulting from bromacil use on citrus, RQs do not exceed the
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LOCs. Therefore, dietary-based exposures of CRLF to bromacil are not considered in
determining risk.
Amphibian-specific refinement of dose-based exposure modeling using T-HERPS
indicates that the LOG is potentially exceeded for 37 g CRLF consuming small
herbivorous mammals (Table 40). Since there is uncertainty associated with this RQ,
available sublethal effects information are used to further characterize the risk to this size
of CRLF feeding on mammals. In the avian acute oral toxicity study (MRID 40951501),
sublethal effects (5.1% reductions in body weight gains) were observed as low as 1350
mg/kg. Direct comparison of this value to dose-based EECs calculated by T-HERPS for
citrus (Table 39) indicates that estimated exposure concentrations are insufficient to
reach the levels where these effects were observed, indicating that sublethal effects would
be unlikely from dose-based acute exposures. Since sublethal effects are unlikely to
occur, it follows that lethal effects would also be unlikely to occur resulting from
applications of bromacil to citrus.
Table 40. Acute and chronic, dietary-based RQs and dose-based RQs for direct effects to the
terrestrial-phase CRLF, based on bromacil exposures resulting from applications to citrus. RQs
calculated using T-HERPS.
Food
Small Insects
Large Insects
Small Herbivore mammals
Small Insectivore mammals
Small Terrestrial-phase
Amphibians
Dietary
Based
Acute RQ
0.09
<0.01
0.10
O.01
O.01
Dietary
Based
Chronic
RQ
0.56
0.06
0.65
0.04
0.02
Dose Based
RQ
1.4 g CRLF
0.01
O.01
N/A
N/A
N/A
Dose Based
RQ
37 g CRLF
0.01
O.01
0.431
O.03
O.01
Dose Based
RQ
238 g CRLF
0.01
O.01
0.01
O.01
O.01
NA = not applicable
1 since this RQ is indiscreet, it potentially exceeds the acute listed species LOG (0.1)
Based the above information, acute and chronic effects directly to terrestrial-phase CRLF
resulting from bromacil applications at the maximum allowed rates to citrus are unlikely
to occur. Therefore, the determination for effects to the terrestrial-phase CRLF resulting
from bromacil use on citrus is "Not Likely to Adversely Affect."
Non-Cropland
For non-cropland areas, RQs for acute dose-based and dietary-based exposures
potentially exceed the LOG. Also, RQs for chronic dietary-based exposures exceed the
LOG. Therefore, a "may affect" determination is made for direct effects to the CRLF
resulting from bromacil exposures from use on non-cropland areas.
Amphibian-specific refinement of exposure modeling using T-HERPS indicates that RQs
representing exposures of CRLF to bromacil from applications non-cropland areas still
exceed the LOG for some feeding categories and exposure types. Dietary-based RQs for
bromacil uses exceed the acute and chronic risk LOCs for direct effects to CRLF
consuming small insects and small herbivorous mammals. RQs for dose-based exposures
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resulting from bromacil applications to non-cropland areas potentially exceed the LOG
for 37-g CRLF consuming small herbivorous and insectivorous mammals and 238-g
CRLF consuming small herbivorous mammals (Table 41).
Table 41. Acute and chronic, dietary-based RQs and dose-based RQs for direct effects to the
terrestrial-phase CRLF, based on bromacil exposures resulting from bromacil applications to non-
cropland areas (max rate = 2 applications of 15.4 Ibs a.i./A). RQs calculated using T-HERPS.
Food
Small Insects
Large Insects
Small Herbivore mammals
Small Insectivore mammals
Small Terrestrial-phase
Amphibians
Dietary
Based
Acute RQ
O.381
<0.04
<0.441
0.03
0.01
Dietary
Based
Chronic
RQ
2.442
0.27
2.862
0.18
0.08
Dose Based
RQ
1.4 g CRLF
O.07
O.01
N/A
N/A
N/A
Dose Based
RQ
37 g CRLF
O.06
O.01
<1.861
0.121
0.01
Dose Based
RQ
238 g CRLF
O.04
O.01
<0.291
0.02
0.01
NA = not applicable
1 since this RQ is indiscreet, it potentially exceeds the acute listed species LOG (0.1)
2exceeds chronic, listed species LOG (1.0)
Consideration of the lower maximum application rate of bromacil lithium (i.e. 1
application of 12 Ibs a.i./A/year) results in acute dose-based EECs sufficient to
potentially exceed the LOG for 37-g and 238-g CRLF consuming small herbivorous
mammals. Acute dietary-based EECs are sufficient to potentially exceed the LOG for
CRLF consuming small insects and small herbivore mammals. Chronic dietary-based
EECs are sufficient to exceed the LOG for CRLF consuming small insects and small
herbivore mammals (Table 42).
Table 42. Acute and chronic, dietary-based RQs and dose-based RQs for direct effects to the
terrestrial-phase CRLF, from bromacil lithium applications to non-cropland areas (max rate = 1
application of 12 Ibs a.i./A). RQs calculated using T-HERPS.
Food
Small Insects
Large Insects
Small Herbivore mammals
Small Insectivore mammals
Small Terrestrial-phase
Amphibians
Dietary
Based
Acute RQ
0.161
0.02
<0.191
O.01
O.01
Dietary
Based
Chronic
RQ
1.052
0.12
1.222
0.08
0.04
Dose Based
RQ
1.4 g CRLF
0.03
0.01
N/A
N/A
N/A
Dose Based
RQ
37 g CRLF
0.03
0.01
o.so1
O.05
O.01
Dose Based
RQ
238 g CRLF
0.02
0.01
<0.121
O.01
O.01
NA = not applicable
1 since this RQ is indiscreet, it potentially exceeds the acute listed species LOG (0.1)
2exceeds chronic, listed species LOG (1.0)
In the avian acute oral toxicity study (MRID 40951501), sublethal effects (5.1%
reductions in body weight gains) were observed as low as 1350 mg/kg. For non-cropland
areas, direct comparison of the NOAEL of 1350 mg/kg to EECs (Table 39) indicates that
exposure levels for only one feeding category (37 g CRLF consuming small herbivore
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mammals) is sufficient to exceed the level where sublethal effects were observed in the
available acute oral study with birds.
In the avian subacute dietary toxicity study (MRID 00013295), mortality was observed in
treatment levels as low as 464 mg/kg-diet/day (10% mortality), while 20% mortality was
observed in treatment levels as low as 2150 mg/kg-diet/day. Direct comparison of refined
acute dietary-based EECs (from T-HERPS; Table 39) indicates that EECs for some
feeding categories (CRLF consuming small insects and small herbivore mammals)
exceed the levels where 10% and 20% mortality was observed in this laboratory study. It
should be noted that there is uncertainty regarding the significance of these results in
comparison to controls, where 6.8% mortality was observed.
In the chronic toxicity studies involving birds, the NOAEC was 1550 mg/kg-diet/day.
This value is used for deriving RQs in the risk estimation of this assessment. In this
study, the lowest level where effects were observed (i.e. the LOAEC) was 3100 mg/kg-
diet/day. Direct comparison of chronic dietary-based EECs resulting from bromacil
applications to the LOAEC indicate that EECs are sufficient to exceed the level where
reproductive effects were observed in birds. Direct comparisons of chronic dietary-based
EECs resulting from applications of bromacil lithium are insufficient to exceed the LOG
indicating that there is uncertainty associated with the chronic effects of bromacil on the
CRLF resulting from applications of bromacil lithium.
Acute effects directly to terrestrial-phase CRLF resulting from bromacil and bromacil
lithium applications at the maximum allowed rates to non-cropland areas cannot be
discounted. At the maximum use rate of bromacil, there is also potential for risk directly
to the terrestrial-phase CRLF based on chronic exposures. Therefore, the determination
for effects to the terrestrial-phase CRLF resulting from bromacil and bromacil lithium
uses non-cropland areas is "Likely to Adversely Affect.".
5.2.2. Indirect Effects (through effects to prey)
As discussed in section 2.5.3, the diet of tadpole CRLF is composed primarily of
unicellular aquatic plants and detritus. Juvenile CRLF consume primarily aquatic and
terrestrial invertebrates. The diet of adult CRLF is composed of aquatic and terrestrial
invertebrates, fish, frogs and mice. These prey groups are considered in determining
indirect effects to the CRLF caused by direct effects to its prey.
Unicellular plants
Based on LOG exceedances of RQs for algae (Table 32), applications of bromacil to
citrus and bromacil and bromacil lithium to non-cropland areas result in potential effects
to this food source. Therefore, a "may affect" determination is also made for indirect
effects to the CRLF through reductions to a food source resulting from bromacil
exposures from use on citrus and non-cropland areas.
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Available effects data for green algae (ECso=6.8 |ig/L; MRID 42516401) represent the
most sensitive data for unicellular aquatic plants. Toxicity data are available for other
unicellular aquatic plants exposed to bromacil (Table 22). Comparison of peak aquatic
EECs resulting from bromacil use on citrus is sufficient to result in RQ values that would
exceed the LOG for 3 of 4 unicellular aquatic plant species for which toxicity data exist.
Comparison of peak aquatic EECs resulting from bromacil use on non-cropland areas is
sufficient to result in RQ values that would exceed the LOG for 4 of 4 unicellular aquatic
plant species (Table 43).
Table 43. Species specific RQs for unicellular aquatic plants.
Use
Citrus
Non-cropland
Green
Algae RQ
8.21
3441
FW Diatom
RQ
8.11
3391
Marine
Diatom RQ
4.61
1931
Blue Green
Algae RQ
0.8
341
exceeds LOG (1.0) for non-listed aquatic plants
A source of uncertainty in the derivation of RQs is the estimation of exposure. Peak
EECs are several orders of magnitude above the highest measured concentration of
bromacil in California surface waters (0.0075 mg/L); however, the highest measured
concentration of bromacil is sufficient to exceed the LOG for aquatic unicellular plants.
Based on this information, exposures of bromacil in aquatic habitats have the potential to
affect populations and even communities of aquatic algae.
Aquatic invertebrates
Acute and chronic RQ values representing uses of bromacil on citrus and non-cropland
areas are insufficient to exceed the LOCs for effects to invertebrates in aquatic habitats.
Even if RQs were derived using more conservative endpoints for acute toxicity available
in the literature (48-h ECso = 65 mg a.i./L; Foster et al. 1998), these values would not
exceed the LOG. Therefore, aquatic invertebrates are unlikely to be directly affected due
to exposures to bromacil in aquatic habitats.
Terrestrial invertebrates
Because the LDso used in deriving RQs for terrestrial invertebrates is not quantified, RQs
for acute exposures of bromacil to small and large terrestrial invertebrates potentially
exceed the LOG of 0.05 for citrus and non-cropland areas (Table 36). This results in a
"may affect" determination for indirect effects to the CRLF due to acute exposures of
terrestrial invertebrates to bromacil.
In the one of the available toxicity studies with honey bees, 1.2% mortality was observed
at 1209 jig a.i./g (MRID 00018842). Direct comparison of the level were 1.2% mortality
was observed with EECs calculated by T-REX for small and large insects exposed to
bromacil applied to citrus, the EECs are insufficient to reach the level where 1.2%
mortality was observed in honey bees. Therefore, for bromacil applications to citrus,
mortality to terrestrial invertebrates is insignificant.
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For large insects, EECs for non-cropland areas are also below the level where 1.2%
mortality was observed in honey bees, indicating that EECs directly on the application
site resulting from applications of bromacil to non-cropland areas are insufficient to cause
1.2% mortality in bees. For small insects, EECs for non-cropland areas are
approximately 3x the level where 1.2% mortality was observed in honey bees, indicating
that applications of bromacil to non-cropland areas could potentially result in mortality to
>1.2% of small sized insects. It is expected that beyond the edge of the application site,
EECs will be below the level where 1.2% mortality was observed in honey bees.The
intent of estimating exposures and subsequent risks to two size classes of insects is to
bound potential effects to this prey class. There is potential for effects to some terrestrial
invertebrates (small) representing CRLF prey; however, it seems unlikely that large sized
terrestrial invertebrates will be affected significantly by bromacil applications to non-
cropland areas, leaving terrestrial invertebrates to serve as prey to terrestrial-phase CRLF.
Based this information, indirect effects to terrestrial-phase CRLF from acute effects to
terrestrial invertebrates resulting from bromacil applications to non-cropland areas are
insignificant.
Fish and aquatic-phase amphibians
RQ values representing direct exposures of bromacil to aquatic-phase CRLF can also be
used to represent exposures of bromacil to fish and frogs in aquatic habitats. Therefore,
the conclusions made above for direct effects to the CRLF (section 5.2.1.1) also apply to
effects to fish and aquatic amphibians representing prey for the CRLF. Acute and chronic
effects are unlikely for fish and aquatic amphibians exposed to bromacil after
applications to citrus. Acute and chronic effects are insignificant for fish and aquatic
amphibians exposed to bromacil after applications of bromacil and bromacil lithium to
non-cropland areas.
Small terrestrial mammals
Estimates of acute exposure of small mammals (consuming grass) to bromacil from uses
in citrus and non-cropland areas result in RQs that exceed the acute risk LOG by factors
of 8.2X and 35X, respectively. Estimates of bromacil exposures resulting from bromacil
lithium applications to non-cropland areas result in RQs that exceed the acute risk LOG
by 15.4X. Where bromacil or bromacil lithium is applied, exposures are sufficient to
exceed the LOG for up to 23 and 52 feet beyond the edge of the field of citrus and non-
cropland areas, respectively (Table 18).
An analysis of the likelihood of individual acute mortality for mice on the site of
application is conducted using the LD50 of 812 mg/L and the default slope of 4.5. For
citrus, the likelihood of individual mortality is estimated as 1 in 2.9, or 34.5%. For non-
cropland areas, the likelihood of individual mortality is approximately 1 in 1, or 100%.
As the distance from the edge of the field increases, the exposure decreases, and along
with that, the likelihood of individual mortality decreases.
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For chronic exposures of bromacil resulting from use on citrus, dietary-based and dose-
based RQs exceed the LOG by factors of 6.1 and 53, respectively. For chronic exposures
of bromacil resulting from use on non-cropland areas, dietary-based and dose-based RQs
exceed the LOG by factors of 26 and 225, respectively. Estimates of bromacil exposures
resulting from bromacil lithium applications to non-cropland areas result in dietary-based
and dose-based RQs that exceed the acute risk LOG by 11.5X and 100X, respectively. If
RQs were derived using the LOAEC (2500 mg/kg-diet/day) from the available study
involving chronic exposures of rats to bromacil, chronic RQs would still be sufficient to
exceed the LOG for uses on citrus and on non-cropland areas. Where bromacil or
bromacil lithium is applied, exposures are sufficient to exceed the LOG for up to 132 and
292 feet beyond the edge of the field of citrus and non-cropland areas, respectively. As
the distance from the edge of the field increases, the exposure decreases, and along with
that, the likelihood of effects decreases.
Therefore, on the site of applications of bromacil and bromacil lithium as well as some
distance beyond the edge of the field, there is potential for effects to small mammals.
Small terrestrial-phase amphibians
An additional prey item of the adult CRLF is other species of terrestrial-phase frogs. In
order to assess risks to these organisms, dietary-based and dose-based exposures modeled
in T-REX for a small bird (20g) consuming small invertebrates are used. For use on
citrus, dose-based RQs potentially exceed the LOG. Acute and chronic, dietary-based
RQs for use on citrus do not exceed the LOG. For use on non-cropland areas, the LOG is
potentially exceeded by RQs for dose-based and dietary-based exposures (Table 36).
Therefore, for bromacil use on citrus and bromacil and bromacil use on non-cropland
areas, there is potential for effects to terrestrial-phase amphibians which are potential
prey to CRLF. Where bromacil or bromacil lithium is applied, exposures are sufficient to
exceed the LOG for up to 16 and 36 feet beyond the edge of the field of citrus and non-
cropland areas, respectively (Table 18).
In order to explore influences of amphibian-specific food intake equations on potential
dose-based and dietary-based exposures of amphibians (prey of CRLF) to bromacil, T-
HERPS is used. The Pacific tree frog is used to represent amphibian prey species. The
weight of the animal is assumed to be 2.3 g, and its diet is assumed to be composed of
small and large insects. A range of RQs is presented in Table 44 for each use
corresponding to EECs resulting from bromacil exposures to frogs consuming large (low
RQ) and small insects (high RQ).
For Pacific tree frogs consuming small and large insects, acute dietary-based exposures
as well as dose based exposures of bromacil resulting from applications to citrus are
insufficient to exceed the acute or chronic LOCs (Table 44). Therefore, acute and
chronic effects are unlikely for terrestrial-phase amphibians exposed to bromacil after
applications to citrus.
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Table 44. RQ values for exposures of terrestrial frogs (prey of CRLF) to bromacil. RQs estimated
using T-HERPS.
Exposure
Dose-acute
Dietary-acute
Dietary-chronic
Toxicity Value
LD50>2250 mg/kg
LC50>10,000 mg/kg-diet
NOAEC = 1550 mg/kg-diet
Citrus
RQ
<0.01
0.01-0.09
0.06-0.56
Non-cropland RQs
Bromacil
O.01-0.06
0.04-0.381
0.27-2.442
Bromacil
lithium
O.01-0.02
0.02-0.161
0.12-1.051
'Potentially exceeds acute, listed species LOG (0.1).
2exceeds chronic, listed species LOG (1.0).
For applications of bromacil and bromacil lithium to non-cropland areas, the acute,
dietary-based RQ for Pacific tree frogs potentially exceeds the listed species LOG (Table
44). In the sub-acute dietary study used to define acute dietary-based RQs for frogs, less
than 50% mortality was observed at bromacil exposures of 10,000 mg/kg-diet (MRID
00013295). Direct comparison of bromacil EECs for the Pacific tree frog resulting from
applications to non-cropland areas indicates that EECs are below the level where less
than 50% mortality was observed in this laboratory study. In this study, 20% mortality
was observed in treatment levels as low as 2150 mg/kg-diet/day. Direct comparisons of
acute dietary-based EECs for the Pacific tree frog indicate that EECs for frogs consuming
large invertebrates are insufficient to exceed this level while EECs for small invertebrates
exceed this level where 20% mortality was observed.
For applications of bromacil and bromacil lithium to non-cropland areas, chronic dietary-
based RQs exceed the LOG for frogs consuming small insects but not for those
consuming large insects (Table 44). Since frogs would be expected to consume both
small and large insects, it seems likely that the actual EEC should fall somewhere
between the extreme EECs representing diets composed only of small insects and diets
composed only of large insects.
Summary of indirect effects to the CRLF based on effects to prey
Based on the above information, there is potential for applications of bromacil or
bromacil lithium to citrus and non-cropland areas to cause effects to aquatic algae. Since
CRLF rely upon aquatic algae as a food source during the tadpole stage, decreased
availability of algae biomass could indirectly affect the CRLF during this life stage.
Effects to aquatic and terrestrial invertebrates, which compose the diet of the juvenile
CRLF, are not expected from bromacil or bromacil lithium applications to citrus or to
non-cropland areas. Because the adult CRLF is an opportunistic feeder, it will consume
available prey. Potential prey includes aquatic and terrestrial invertebrates, fish, aquatic
frogs, terrestrial frogs and mice. Although there is potential for effects to mice and near
the site of application, indirect effects to the CRLF based on decreased availability of
prey are not expected. It is expected that there will be sufficient prey to maintain the adult
CRLF.
For applications of bromacil or bromacil lithium to citrus and non-cropland areas, the
determination for indirect effects to the tadpole-phase of the CRLF, based on decreased
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availability of prey, is "Likely to Adversely Affect." For the juvenile and adult life
stages of the CRLF, the determination is "Not Likely to Adversely Affect."
5.2.3. Indirect Effects (through effects to habitat)
Aquatic habitat
The aquatic habitat of the CRLF is composed of unicellular and vascular aquatic plants,
as well as riparian vegetation. Citrus and non-cropland RQs for all three groups exceed
the LOG (Tables 34 and 37), resulting in a "may affect" determination for indirect
effects to the CRLF based on effects to its aquatic habitat.
Available effects data for green algae (ECso=6.8 ng/L; MRID 42516401) represent the
most sensitive data for unicellular aquatic plants. Comparison of peak aquatic EECs
resulting from bromacil use on citrus is sufficient to result in RQ values that would
exceed the LOG for 3 of 4 unicellular aquatic plant species for which toxicity data exist.
Comparison of peak aquatic EECs resulting from bromacil use on non-cropland areas is
sufficient to result in RQ values that would exceed the LOG for 4 of 4 unicellular aquatic
plant species. Therefore, EECs are at levels sufficient to decrease populations of algae by
>50% in multiple species of algae. This indicates concern for alteration of algal
communities by decreasing overall algal biomass and altering dominant species.
EECs are also sufficient to exceed concentrations where frond numbers were
significantly decreased in duckweed. This indicates that at estimated exposure
concentrations, bromacil has the potential to decrease populations of vascular aquatic
plants.
Concentrations of bromacil reaching riparian vegetation through runoff and spray drift
are at levels where reduced dry weight was observed in monocots and dicots. This
indicates that exposures of bromacil could result in reduced biomass in riparian
vegetation.
Loss of aquatic and riparian vegetation could result in alteration of physical and chemical
characteristics of the aquatic habitat of the CRLF. These potentially include: alteration of
the morphology of channels and ponds, alterations of geometry of channels and ponds,
increases in sediment depositions, loss of shelter for CRLF, alteration in water chemistry
(including temperature, turbidity, and oxygen content). These changes could potentially
alter the conditions necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
Therefore, the determinations for indirect effects to the CRLF caused by effects to
aquatic and riparian plants resulting from bromacil and bromacil lithium uses on citrus
and non-cropland areas are "Likely to Adversely Affect."
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Terrestrial habitat
The terrestrial habitat of the CRLF is composed of vascular plants, including monocots
and dicots. Citrus and non-cropland RQs for these plants exceed the LOG (Table 37),
resulting in a "may affect" determination for indirect effects to the CRLF based on effects
to its terrestrial habitat.
Exposures to plants inhabiting terrestrial habitats could come from both runoff and spray
drift from the treatment site. EECs calculated by TerrPlant indicate that each exposure
pathway by itself is sufficient to exceed the LOG for non-listed plants, including both
monocots and dicots. Refined modeling of bromacil exposures of plants through spray
drift indicate that exposures exceed the EC25s for monocots and dicots up to 437 and
4026 feet, respectively, from the edge of citrus fields where bromacil is applied. Also, for
bromacil and bromacil lithium applications to non-cropland areas, spray drift exposures
exceed the EC25S for monocots and dicots up to 810 and 5909 feet, respectively, from the
edge of the treatment area (Table 18).
As discussed in section 4.3, there are a number of reported incidents associated with
bromacil involving damage to terrestrial plants. These incidents reported observed effects
to individual plants, including trees, effects to lawns, and effects to crops covering areas
greater than 100 acres. In some cases, other herbicides where applied along with bromacil
(e.g. diuron, atrazine, metolachlor). Reports indicated that bromacil exposures occurred
through direct treatment of areas, spray drift, runoff and carryover from one season to the
next.
Loss of vegetation in the terrestrial habitat of the CRLF could impact the ability of that
habitat to support the food source of the CRLF. Loss of this vegetation could also reduce
available shelter for CRLF.
Therefore, the determinations for indirect effects to the CRLF caused by effects to
terrestrial plants resulting from bromacil and bromacil lithium uses on citrus and non-
cropland areas are "Likely to Adversely Affect."
5.2.4. Primary Constituent Elements of Designated Critical Habitat
5.2.4.1. Aquatic-Phase (Aquatic breeding habitat and aquatic non-breeding
habitat)
Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
• Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
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• Alteration in water chemistry /quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
• Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae)
Due to RQ exceedances for several species of algae, as well as for aquatic vascular
plants, bromacil use on citrus and bromacil and bromacil lithium use on non-cropland
areas use results in a determination of "habitat modification."
The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." As stated
previously, RQs for algae, which represent a food source for larval CRLF (tadpoles),
exceed the LOG. Therefore, the determination for this endpoint is also "habitat
modification."
5.2.4.2. Terrestrial-Phase (upland habitat and dispersal habitat)
Similar to the aquatic-phase PCEs, three of the four assessment endpoints for the
terrestrial-phase PCEs of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
• Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or drip line surrounding aquatic and riparian habitat that are comprised
of grasslands, woodlands, and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
• Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal
• Alteration of chemical characteristics necessary for normal growth and viability
of juvenile and adult CRLFs and their food source.
Due to RQ exceedances for exposures of plants inhabiting dry areas to bromacil
contained in runoff and in drift, bromacil use on citrus and bromacil and bromacil lithium
use on non-cropland areas use results in a determination of "habitat modification."
The remaining terrestrial-phase PCE is "reduction and/or modification of food sources
for terrestrial phase juveniles and adults." Acute and chronic RQs for mice, which
represent a food source for terrestrial phase CRLF, exceed the LOG for bromacil uses on
citrus and bromacil and bromacil lithium uses on non-cropland areas. Therefore, the
determination for this endpoint is "habitat modification."
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5.2.5. Action Area
5.2.5.1. Areas indirectly affected by the federal action
The initial action area for bromacil was previously discussed in Section 2.7 and depicted
in Figures 4 and 5 of the problem formulation. In order to determine the extent of the
action area in lotic (flowing) aquatic habitats, the greatest ratios of the RQ to the LOG for
any endpoint for aquatic organisms for each use is used to determine the distance
downstream for concentrations to be diluted below levels that would be of concern (i.e.
result in RQs above the LOG). For this assessment, this applies to RQs for algae. The
action area is determined based on risks to all listed species based on bromacil exposures
resulting from applications of bromacil or bromacil lithium. Therefore, RQs for listed
unicellular aquatic species are used, which are derived by dividing the peak aquatic EEC
by the NOAEC for unicellular aquatic species (<1.1 |ig a.i./L; MRID 42516401). Also,
the LOG of 1.0 is used. The final RQ/LOC ratios are: 51 for bromacil use on citrus, and
2127 for bromacil and bromacil lithium use on non-cropland areas. The total stream
kilometers within the action area that are at levels of concern are defined in Table 45.
Table 45. Quantitative results of spatial analysis of lotic aquatic action area relevant to bromacil.
Measure
Total Streams in CA
Streams within initial area of concern
Downstream distance added
Streams in aquatic action area
Distance (km)
Citrus Areas
332,962
17,283
2,019
19,302
Non-
cropland
Areas
332,962
87,867
14,655
102,522
When considering the terrestrial habitats of the CRLF, spray drift from use sites onto
non-target areas could potentially result in exposures of the CRLF, its prey and its habitat
to bromacil. Therefore, it is necessary to estimate the distance from the application site
where spray drift exposures do not result in LOG exceedances for organisms within the
terrestrial habitat. To account for this, first, the bromacil application rate which does not
result in an LOG exceedance is calculated for each terrestrial taxa of concern (Table 18).
The farthest distance where no LOG is exceeded applies to non-listed species of dicots
(terrestrial plants). As mentioned above, the action area is determined based on risks to
all listed species based on bromacil exposures resulting from applications of bromacil or
bromacil lithium. Since effects thresholds for listed terrestrial plants are defined by the
NOAEC of available seedling emergence and vegetative vigor data, the lowest NOAEC
from terrestrial dicots (0.006 Ibs a.i./A; MRID 44488307) is used to determine the
farthest distance from the edge of the target area where there are no LOG exceedances for
listed species. AgDISP was then used to determine the distance required to reach the
NOAEC value. For bromacil use on citrus, this distance is 4167 feet. For bromacil and
bromacil lithium use on non-cropland areas, this value is 5315 feet.
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To understand the area indirectly affected by the federal action due to spray drift from
application areas, the citrus (Figure 4) and non-cropland (Figure 5) landcovers are
considered as potential application areas. These areas are "buffered" using ArcGIS 9.2.
In this process, the original landcover is modified by expanding the border of each
polygon representing a field out to a designated distance, which in this case, is the
distance estimated where bromacil in spray drift does not exceed any LOCs. This
effectively expands the action area relevant to terrestrial habitats so that it includes the
area directly affected by the federal action, and the area indirectly affected by the federal
action.
5.2.5.2. Final action area
In order to define the final action areas relevant to uses of bromacil and bromacil lithium
on citrus and non-cropland areas, it is necessary to combine areas directly affected, as
well as aquatic and terrestrial habitats indirectly affected by the federal action. This is
done separately for citrus and non-cropland uses using ArcGIS 9.2. Landcovers
representing areas directly affected by bromacil and bromacil lithium applications are
overlapped with indirectly affected aquatic habitats (determined by down stream dilution
modeling) and with indirectly affected terrestrial habitats (determined by spray drift
modeling). It is assumed that lentic (standing water) aquatic habitats (e.g. ponds, pools,
marshes) overlapping with the terrestrial areas are also indirectly affected by the federal
action. The result is a final action area for bromacil uses on citrus (Figure 10) and a final
action area for bromacil and bromacil lithium uses on non-cropland areas (Figure 11).
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-L
-v.
fVN\ '
$ *f-
Legend
County Boundary
Terrestrial and lentic action area
Lotic action area
90 45 0
90 Miles
Compiled from California County boundaries (ESRI, 2002),
USDA National Agriculture Statistical Service (NASS.2002)
Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC.2001)
Map created by U.S. Environmental Protection Agency,
Office of Pesticides Programs, Environmental Fate and
Effects Div ision. April! 1, 2007.
Projection: Albers Equal Area Conic USGS,
North American Datum of 19S3 (NAD 1983)
Figure 10. Final action area for crops described by the orchard/vineyard landcover which
corresponds to potential bromacil use on citrus. This map represents the area potentially directly and
indirectly affected by the federal action.
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Legend
_L
County Boundary
Terresrial and lentic action area
Lotic action area
90 45 0
90 Miles
Compiled from California County boundaries (ESRI, 2002),
USDA National Agriculture Statistical Service (NASS.2002)
Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC.2001)
Map created by U.S. Environmental Protection Agency,
Office of Pesticides Programs, Environmental Fate and
Effects Div ision. April! 1, 2007.
Projection: Albers Equal Area Conic USGS,
North American Datum of 19S3 (NAD 1983)
Figure 11. Final action area for crops described by right-of-way landcover which corresponds to
potential bromacil and bromacil lithium use sites on non-cropland areas. This map represents the
area potentially directly and indirectly affected by the federal action.
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5.2.5.3. Overlap between CRLF habitat and final action area
In order to confirm that uses of bromacil and bromacil have the potential to affect CRLF
through direct applications to target areas and runoff and spray drift to non-target areas, it
is necessary to determine whether or not the final action areas for citrus and non-cropland
uses overlap with CRLF habitats. Spatial analysis using ArcGIS 9.2 indicates that lotic
aquatic habitats within the CRLF core areas and critical habitats potentially contain
concentrations of bromacil sufficient to result in RQ values that exceed LOCs. In
addition, terrestrial habitats (and potentially lentic aquatic habitats) of the final action
areas overlap with the core areas, critical habitat and available occurrence data for CRLF
(Tables 46-47). Thus, uses of bromacil use on citrus and bromacil and bromacil lithium
use on non-cropland areas could result in exposures of bromacil to CRLF in aquatic and
terrestrial habitats. Additional analysis related to the intersection of the bromacil and
bromacil lithium action areas and CRLF habitat is described in Appendix H.
Table 46. Overlap between CRLF habitat (core areas and critical habitat) and citrus action area by
recovery unit (RU#).
Measure
CRLF habitat (km2)*
Overlapping area of CRLF
habitat and terrestrial/lentic
aquatic action area (km2)
% CRLF habitat overlapping
with terrestrial/lentic aquatic
Action Area
# Occurrences overlapping
with terrestrial/lentic aquatic
action area
RU1
3654
7
0%
2
RU2
2742
14
1%
0
RU3
1323
2
0%
0
RU4
3279
50
2%
15
RU5
3650
27
1%
1
RU6
5306
159
3%
3
RU7
4917
435
9%
10
RU8
3326
497
15%
0
Total
28,197
1191
4%
31
*Area occupied by core areas and/or critical habitat.
Table 47. Overlap between CRLF habitat (core areas and critical habitat) and non-cropland action
area by recovery unit (RU#).
Measure
CRLF habitat (km2)*
Overlapping area of CRLF
habitat and terrestrial/lentic
aquatic action area (km2)
% CRLF habitat overlapping
with terrestrial/lentic aquatic
Action Area
# Occurrences overlapping
with terrestrial/lentic aquatic
action area
RU1
3654
1990
54%
6
RU2
2742
1220
44%
1
RU3
1323
768
58%
45
RU4
3279
1632
50%
191
RU5
3650
1661
46%
174
RU6
5306
1777
33%
63
RU7
4917
2069
42%
73
RU8
3326
1643
49%
21
Total
28,197
12,760
45%
574
*Area occupied by core areas and/or critical habitat.
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5.2.6. Description of Assumptions, Limitations, Uncertainties, Strengths and
Data Gaps
5.2.6.1. Exposure Assessment
Aquatic habitat
The standard ecological water body scenario (EXAMS pond) used to calculate potential
aquatic exposure to pesticides is intended to represent conservative estimates, and to
avoid underestimations of the actual exposure. The standard scenario consists of
application to a 10-hectare field bordering a 1-hectare, 2-meter deep (20,000 m3) pond
with no outlet. Exposure estimates generated using the EXAMS pond are intended to
represent a wide variety of vulnerable water bodies that occur at the top of watersheds
including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural
ponds, and intermittent and lower order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the EXAMS pond. Static water bodies
that have larger ratios of pesticide-treated drainage area to water body volume would be
expected to have higher peak EECs than the EXAMS pond. These water bodies will be
either smaller in size or have larger drainage areas. Smaller water bodies have limited
storage capacity and thus may overflow and carry pesticide in the discharge, whereas the
EXAMS pond has no discharge. As watershed size increases beyond 10-hectares, it
becomes increasingly unlikely that the entire watershed is planted with a single crop that
is all treated simultaneously with the pesticide. Headwater streams can also have peak
concentrations higher than the EXAMS pond, but they likely persist for only short
periods of time and are then carried and dissipated downstream.
The Agency acknowledges that there are some unique aquatic habitats that are not
accurately captured by this modeling scenario and modeling results may, therefore,
under- or over-estimate exposure, depending on a number of variables. For example,
aquatic-phase CRLFs may inhabit water bodies of different size and depth and/or are
located adjacent to larger or smaller drainage areas than the EXAMS pond. The Agency
does not currently have sufficient information regarding the hydrology of these aquatic
habitats to develop a specific alternate scenario for the CRLF. As previously discussed in
Section 2 and in Attachment 1, CRLFs prefer habitat with perennial (present year-round)
or near-perennial water and do not frequently inhabit vernal (temporary) pools because
conditions in these habitats are generally not suitable (Hayes and Jennings 1988).
Therefore, the EXAMS pond is assumed to be representative of exposure to aquatic-
phase CRLFs. In addition, the Services agree that the existing EXAMS pond represents
the best currently available approach for estimating aquatic exposure to pesticides
(USFWS/NMFS 2004a).
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations
that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone
Model is a process or "simulation" model that calculates what happens to a pesticide in 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
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components: hydrology and chemical transport. Water movement is simulated by the use
of generalized soil parameters, including field capacity, wilting point, and saturation
water content. The chemical transport component can simulate pesticide application on
the soil or on the plant foliage. Dissolved, adsorbed, and vapor-phase concentrations in
the soil are estimated by simultaneously considering the processes of pesticide uptake by
plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection,
dispersion, and retardation.
There is uncertainty in the PRZM/EXAMS application timing relative to rainfall/runoff
events. Label instructions indicate that applications of bromacil can be made any time
during the year. Consideration of the meteorological data associated with the California
PRZM scenarios indicates that the largest rainfall events occur in January. In general, the
greater amount of rainfall in a single event, the greater the EEC in the receiving aquatic
habitat. In order to select an application date resulting in a conservative estimate of
exposure of aquatic habitats to bromacil, an application date of January 25 was chosen.
Pesticide use data associated with bromacil (CPUR 2007) indicates that past applications
of bromacil have been made throughout the year. Applications made at times where there
is less rainfall could potentially result in less runoff and with that, lower concentrations of
bromacil in aquatic habitats.
A source of uncertainty in the derivation of RQs is the estimation of exposure. The peak
EEC for bromacil in aquatic environments 2.34 mg/L based on modeling for rights-of-
way. As discussed above (section 3.1.1), concentrations of bromacil have been detected
in non-target monitoring at a frequency of approximately 7% in California surface waters
at levels over 500 times below these estimated concentrations (the maximum detected
concentration was 0.0075 mg/L). Because the results of the monitoring data are based
upon non-targeted monitoring, it is uncertain of whether or not available data represent
high-end acute exposure concentrations in California surface waters.
There is uncertainty in this assessment associated with the environmental fate data gaps.
Most significantly, there is some uncertainty in the EECs due to an assumption made in
the aquatic exposure modeling with regard to the degradation of bromacil in anaerobic
environments. While it is evident that the compound degrades in anaerobic
soil/sediment, an accurate half-life value was not available, and the reported half-life (39
days) in the submitted study was not considered to be valid. In lieu of other data, the
anaerobic half-life for bromacil using as an input in the Tier II modeling is 0 days (i.e.,
stable). While the use of the "0 days" as the input value would increase the EECs relative
to using a value that more accurately depicts the more rapid degradation rate which could
be expected in the environment, it is not clear whether this would result in significantly
different risk conclusions. In a laboratory study reported in the literature, bromacil was
persistent in a saturated sandy loam soil, with an observed half-life of 144 to 198 days
(Wolf, 1974). Also, in the environment, bromacil would more likely be associated with
the water column than with sediment since it does not have a tendency to sorb to
soil/sediment particles.
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There is no evidence of bromacil degradation in aquatic environments. As such,
bromacil was assumed stable in the ecological pond used to estimate aquatic exposure
concentrations. Since the ecological pond (used in our modeling) has no outlet, there was
a modeled accumulation of bromacil in the pond throughout the 30 year simulations. In
the case of persistent compounds, a l-in-10 year EEC does not reflect varying
meteorological conditions that are expected once every ten years, since the yearly peaks
are not independent but are actually correlated to the previous year's peak concentration.
This results in acute and chronic exposure concentrations that are very similar (i.e, < 2%
difference between peak and 90-day average EECs). Based on this, EECs used for
deriving RQs for aquatic organisms are potentially an overestimate of exposures in the
aquatic habitats that do not accumulate bromacil.
Uncertainties associated with each of these individual components add to the overall
uncertainty of the modeled concentrations. Additionally, model inputs from the
environmental fate degradation studies are chosen to represent the upper confidence
bound on the mean values that are not expected to be exceeded in the environment
approximately 90 percent of the time. Mobility input values are chosen to be
representative of conditions in the environment. The natural variation in soils adds to the
uncertainty of modeled values. Factors such as application date, crop emergence date,
and canopy cover can also affect estimated concentrations, adding to the uncertainty of
modeled values. Factors within the ambient environment such as soil temperatures,
sunlight intensity, antecedent soil moisture, and surface water temperatures can cause
actual aquatic concentrations to differ for the modeled values.
As discussed in the Use Characterization (section 2.4.4), uses of bromacil and bromacil
lithium on non-cropland areas apply to a wide variety of areas, including: airports,
parking lots, industrial areas, rights-of-way (for railroads, highways, pipeline and
utilities), storage areas, lumberyards, tank farms, under asphalt and concrete pavement
and fence rows. In this assessment, aquatic EECs were derived using rights-of-way to
conceptualize the land area where these herbicides are applied. Given the difference in
surface characteristics, use of one of these other types of non-cropland areas for defining
the conceptual model of the use area could potentially result in different estimates of
exposure. Since historical data for bromacil supports the idea that rights-of-way represent
the major non-cropland use of bromacil in California, it was determined that the rights-
of-way conceptual approach was suitably representative of bromacil exposures in aquatic
habitats resulting from applications to non-cropland areas.
Right-of-way areas were represented by assuming that 50% of the surface of the
watershed is impervious, while 50% is pervious. This is generally representative of a
highway or road right-of-way, where bromacil is expected to be applied to the shoulder
area of the roadway. In this case, it is assumed that runoff from the roadway and shoulder
would be transported directly into the water body of concern (perhaps through drainage
ditches emptying into the water body). Given the diversity of types of rights-of-way to
which bromacil and bromacil lithium could be applied, it is expected that the relative
percentages of impervious and pervious surfaces varies greatly. In deriving aquatic EECs
using this approach, increase in the proportion of impervious surface of a watershed,
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results in a decrease in EEC. EECs included in this risk assessment result in an LOG
exceedance for direct acute effects to the aquatic-phase CRLF. If the right-of-way surface
were modeled as being composed of 60% impervious and 40% pervious, there would be
no LOG exceedance. Using a conceptual approach assuming that 100% of a right-of-way
surface is composed of pervious surface is relevant to utility rights-of-way which would
be expected to have little impervious surface; however, it is unlikely that the entire
watershed of a water body would be composed of this right-of-way. It would be more
likely that the right-of-way would cut through a watershed, leaving only part of the
watershed treated with bromacil or bromacil lithium. The use of a PRZM scenario
assumes that the entire watershed of an area is treated with the pesticide of concern.
Therefore, it is assumed that highway and road rights-of-way would result in higher end
estimates of exposure due to applications of bromacil and bromacil lithium to non-
cropland areas.
In this assessment, it is assumed that applications of bromacil and bromacil to non-
cropland areas are made by ground methods. The label with the highest application rate
(2 applications per year of 15.4 Ibs a.i./A) prohibits aerial applications (registration
10088-68). However, other labels exist which allow for applications of bromacil at lower
rates. Applications by aerial methods result in greater spray drift when compared to
those made by ground methods. When compared to the spray drift exposure estimation
included in this assessment, there is potential for greater exposures of bromacil resulting
from aerial applications of lower application rates.
Model runs are conducted without irrigation. Given that it is unlikely that rights-of-ways
and impervious surfaces will be irrigated, this is a reasonable approach. Although there is
potential for citrus orchards to be irrigated, this is not captured in the current modeling
approach due to limitations of PRZM.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a
vegetative setback on runoff and loadings. The effectiveness of vegetative setbacks is
highly dependent on the condition of the vegetative strip. For example, a well-
established, healthy vegetative setback can be a very effective means of reducing runoff
and erosion from agricultural fields. Alternatively, a setback of poor vegetative quality
or a setback that is channelized can be ineffective at reducing loadings. Until such time
as a quantitative method to estimate the effect of vegetative setbacks on various
conditions on pesticide loadings becomes available, the aquatic exposure predictions are
likely to overestimate exposure where healthy vegetative setbacks exist and
underestimate exposure where poorly developed, channelized, or bare setbacks exist.
Terrestrial habitat
The Agency relies on the work of Fletcher et al. (1994) for setting the assumed pesticide
residues in wildlife dietary items. These residue assumptions are believed to reflect a
realistic upper-bound residue estimate, although the degree to which this assumption
reflects a specific percentile estimate is difficult to quantify. It is important to note that
the field measurement efforts used to develop the Fletcher estimates of exposure involve
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highly varied sampling techniques. It is entirely possible that much of these data reflect
residues averaged over entire above ground plants in the case of grass and forage
sampling.
It was assumed that ingestion of food items in the field occurs at rates commensurate
with those in the laboratory. Although the screening assessment process adjusts dry-
weight estimates of food intake to reflect the increased mass in fresh-weight wildlife food
intake estimates, it does not allow for gross energy differences. Direct comparison of a
laboratory dietary concentration- based effects threshold to a fresh-weight pesticide
residue estimate would result in an underestimation of field exposure by food
consumption by a factor of 1.25 - 2.5 for most food items.
Differences in assimilative efficiency between laboratory and wild diets suggest that
current screening assessment methods do not account for a potentially important aspect of
food requirements. Depending upon species and dietary matrix, bird assimilation of wild
diet energy ranges from 23 - 80%, and mammal's assimilation ranges from 41 - 85%
(U.S. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is
formulated to maximize assimilative efficiency (e.g., a value of 85%), a potential for
underestimation of exposure may exist by assuming that consumption of food in the wild
is comparable with consumption during laboratory testing. In the screening process,
exposure may be underestimated because metabolic rates are not related to food
consumption.
For 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.
Mixtures
This assessment considers only the single active ingredients of bromacil or bromacil
lithium. However, the assessed species and its environments may be exposed to multiple
pesticides simultaneously. Interactions of other toxic agents with bromacil could result in
additive effects, synergistic effects or antagonistic effects. Evaluation of pesticide
mixtures is beyond the scope of this assessment because of the myriad factors that cannot
be quantified based on the available data. Those factors include identification of other
possible co-contaminants and their concentrations, differences in the pattern and duration
of exposure among contaminants, and the differential effects of other physical/chemical
characteristics of the receiving waters (e.g. organic matter present in sediment and
suspended water). Evaluation of factors that could influence additivity/synergism is
beyond the scope of this assessment and is beyond the capabilities of the available data to
allow for an evaluation. However, it is acknowledged that not considering mixtures
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could over- or under-estimate risks depending on the type of interaction and factors
discussed above.
5.2.6.2. Effects Assessment
As previously discussed, direct effects to aquatic-phase CRLF are based on freshwater
fish data, which are used as a surrogate for aquatic-phase amphibians. Toxicity data for
terrestrial-phase amphibians are not available for use in this assessment. Therefore, avian
toxicity data are used as a surrogate for terrestrial-phase CRLF. There is uncertainty
regarding the relative sensitivity of amphibians and their surrogates to bromacil. If the
selected surrogate species are substantially more or less sensitive than the CRLF, then
risk would be over or under estimated, respectively. In addition, given the small data set
for freshwater fish species (3 acute toxicity values), the potential range of sensitivities of
fish (and thus, aquatic amphibians) to bromacil.
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.
It is generally recognized that test organism age may have a significant impact on the
observed sensitivity to a toxicant. The acute toxicity data for fish are collected on
juvenile fish between 0.1 and 5 grams. Aquatic invertebrate acute testing is performed on
recommended immature age classes (e.g., first instar for daphnids, second instar for
amphipods, stoneflies, mayflies, and third instar for midges).
Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients that act directly without metabolic transformation because younger age
classes may not have the enzymatic systems associated with detoxifying xenobiotics. In
so far as the available toxicity data may provide ranges of sensitivity information with
respect to age class, this assessment uses the most sensitive life-stage information as
measures of effect for surrogate aquatic animals, and is therefore, considered as
protective of the California Red Legged Frog.
5.2.6.3. Action Area
An example of an important simplifying assumption that may require future refinement is
the assumption of uniform runoff characteristics throughout a landscape. It is well
documented that runoff characteristics are highly non-uniform and anisotropic, and
become increasingly so as the area under consideration becomes larger. The assumption
made for estimating the aquatic Action Area (based on predicted in-stream dilution) was
that the entire landscape exhibited runoff properties identical to those commonly found in
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agricultural lands in this region. However, considering the vastly different runoff
characteristics of: a) undeveloped (especially forested) areas, which exhibit the least
amount of surface runoff but the greatest amount of groundwater recharge; b)
suburban/residential areas, which are dominated by the relationship between
impermeable surfaces (roads, lots) and grassed/other areas (lawns) plus local drainage
management; c) urban areas, that are dominated by managed storm drainage and
impermeable surfaces; and d) agricultural areas dominated by Hortonian and focused
runoff (especially with row crops), a refined assessment should incorporate these
differences for modeled stream flow generation. As the zone around the immediate
(application) target area expands, there will be greater variability in the landscape; in the
context of a risk assessment, the runoff potential that is assumed for the expanding area
will be a crucial variable (since dilution at the outflow point is determined by the size of
the expanding area). Thus, it important to know at least some approximate estimate of
types of land use within that region. Runoff from forested areas ranges from 45 -
2,700% less than from agricultural areas; in most studies, runoff was 2.5 to 7 times higher
in agricultural areas (e.g., Okisaka et al., 1997; Karvonen et al., 1999; McDonald et al.,
2002; Phuong and van Dam 2002). Differences in runoff potential between
urban/suburban areas and agricultural areas are generally less than between agricultural
and forested areas. In terms of likely runoff potential (other variables - such as
topography and rainfall - being equal), the relationship is generally as follows (going
from lowest to highest runoff potential):
Three-tiered forest < agroforestry < suburban < row-crop agriculture < urban.
There are, however, other uncertainties that should serve to counteract the effects of the
aforementioned issue. For example, the dilution model considers that 100% of the
agricultural area has the chemical applied, which is almost certainly a gross over-
estimation. Thus, there will be assumed chemical contributions from agricultural areas
that will actually be contributing only runoff water (dilutant); so some contributions to
total contaminant load will really serve to lessen rather than increase aquatic
concentrations. In light of these (and other) confounding factors, Agency believes that
this model gives us the best available estimates under current circumstances.
5.2.6.4. Use Data
County-level usage data were obtained from California's Department of Pesticide
Regulation Pesticide Use Reporting (CDPR PUR) database. Four years of data (2002 -
2005) were included in this analysis because statistical methodology for identifying
outliers, in terms of area treated and pounds applied, was provided by CDPR for these
years only. No methodology for removing outliers was provided by CDPR for 2001 and
earlier pesticide data; therefore, this information was not included in the analysis because
it may misrepresent actual usage patterns. CDPR PUR documentation indicates that
errors in the data may include the following: a misplaced decimal; incorrect measures,
area treated, or units; and reports of diluted pesticide concentrations. In addition, it is
possible that the data may contain reports for pesticide uses that have been cancelled.
The CPDR PUR data does not include home owner applied pesticides; therefore,
residential uses are not likely to be reported. As with all pesticide use data, there may be
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instances of misuse and misreporting. The Agency made use of the most current,
verifiable information; in cases where there were discrepancies, the most conservative
information was used.
5.2.6.5. General Uncertainties
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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5.2.7. Addressing the Risk Hypotheses
In order to conclude this risk assessment, it is necessary to address the risk hypotheses
defined in section 2.9.1. Based on the conclusions of this assessment, none of the
hypotheses can be rejected, meaning that the stated hypotheses represent concerns in
terms of effects of bromacil on the CRLF.
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6. Conclusions
Based on estimated environmental concentrations for the currently registered uses of
bromacil or bromacil lithium, RQ values are above the Agency's LOG for direct acute
effects on the CRLF resulting from applications to citrus and non-cropland areas; this
represents a "may affect" determination. RQs for uses on citrus and non-cropland areas
exceed the LOG for exposures to aquatic unicellular plants. Therefore, there is a potential
to indirectly affect larval (tadpole) CRLF due to effects to the algae forage base in
aquatic habitats. The effects determination for indirect effects to the CRLF due to effects
to its prey base is "may affect." When considering the prey of larger CRLF in terrestrial
habitats (e.g. frogs, fish and small mammals), RQs for some of these taxa also exceed the
LOG for acute and chronic exposures, resulting in a "may affect" determination. RQ
values for plants in aquatic and terrestrial habitats exceed the LOG; therefore, indirect
effects to the CRLF through effects on aquatic and terrestrial habitats result in a "may
affect" determination.
Refinement of all "may affect" determinations from bromacil use on citrus results in a
"NLAA" determination for direct effects to the CRLF, a "LAA" determination for
indirect effects to the CRLF based on effects to its prey, specifically algae, and a "LAA"
determination for indirect effects to the CRLF based on effects to aquatic and terrestrial
habitat (Table 1). Consideration of CRLF critical habitat indicates a determination of
"habitat modification" for aquatic and terrestrial habitats based on bromacil use on citrus.
The overall CRLF effects determination for bromacil use on citrus is "LAA."
Refinement of all "may affect" determinations from bromacil and bromacil lithium use
on non-cropland areas result in a "LAA" determination for direct effects to the CRLF, a
"LAA" determination for indirect effects to the CRLF based on effects to its prey,
specifically algae, and a "LAA" determination for indirect effects to the CRLF based on
effects to aquatic and terrestrial habitat (Table 2). Consideration of CRLF critical habitat
indicates a determination of "habitat modification" for aquatic and terrestrial habitats
based on non-cropland uses of bromacil and bromacil lithium. The overall CRLF effects
determination for bromacil and bromacil lithium use on non-cropland areas is
"LAA."
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
Attachment 2, which includes information on the baseline status and cumulative effects
for the CRLF, can be used during this consultation to provide background information on
past US Fish and Wildlife Services biological opinions associated with the CRLF.
When evaluating the significance of this risk assessment's direct/indirect and habitat
modification 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
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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.
Ill
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