Risks of Simazine Use to Federally Threatened
California Red-legged Frog
(Rana aurora draytonii)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
October 17,2007
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Primary Authors:
Anita Pease, Senior Biologist
Mark Corbin, Senior Environmental Scientist
Branch Chief, Environmental Risk Assessment Branch 3:
Karen Whitby, Ph.D.
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Table of Contents
1. Executive Summary 10
2. Problem Formulation 17
2.1 Purpose 17
2.2 Scope 19
2.3 Previous Assessments 21
2.4 Stressor Source and Distribution 22
2.4.1 Environmental Fate Properties 22
2.4.1 Environmental Transport Mechanisms 27
2.4.2 Mechanism of Action 27
2.4.3 Use Characterization 27
2.5 Assessed Species 33
2.5.1 Distribution 33
2.5.2 Reproduction 38
2.5.3 Diet 38
2.5.4 Habitat 39
2.6 Designated Critical Habitat 40
2.7 Action Area 42
2.8 Assessment Endpoints and Measures of Ecological Effect 48
2.8.1 Assessment Endpoints for the CRLF 48
2.8.2 Assessment Endpoints for Designated Critical Habitat 50
2.9 Conceptual Model 51
2.9.1 Risk Hypotheses 51
2.9.2 Diagram 52
2.10 AnalysisPlan 55
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model 55
2.10.1.1 Measures of Exposure 55
2.10.1.2 Measures of Effect 57
2.10.1.3 Integration of Exposure and Effects 58
3.1 Label Application Rates and Intervals 58
3.2 Aquatic Exposure Assessment 61
3.2.1 Modeling Approach 61
3.2.2 Model Inputs 62
3.2.3 Results 63
3.2.4 Existing Monitoring Data 65
3.2.4.1 USGS NAWQA Surface Water Data 66
3.2.4.2 USGS NAWQA Groundwater Data 66
3.2.4.3 California Department of Pesticide Regulation (CPR) Data 66
3.2.4.4 Atmospheric Monitoring Data 67
3.2.5 Spray Drift Buffer Analysis 67
3.2.6 Downstream Dilution Analysis 69
3.3 Terrestrial Animal Exposure Assessment 70
3.3.1 Spray Applications 70
3.3.2 Granular Applications 72
3.4 Terrestrial Plant Exposure Assessment 72
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4. Effects Assessment 73
4.1 Toxicity of Simazine to Aquatic Organisms 76
4.1.1 Toxicity to Freshwater Fish 77
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies 78
4.1.1.2 Freshwater Fish: Chronic Exposure (Growth/Reproduction) Studies 79
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open Literature
Information 80
4.1.2 Toxicity to Freshwater Invertebrates 81
4.1.2.1 Freshwater Invertebrates: Acute Exposure Studies 81
4.1.2.2 Freshwater Invertebrates: Chronic Exposure Studies 82
4.1.2.3 Freshwater Invertebrates: Open Literature Data 82
4.1.3 Toxicity to Aquatic Plants 82
4.1.3.1 Aquatic Plants: Laboratory Data 83
4.1.4 Freshwater Field Studies 83
4.2 Toxicity of Simazine to Terrestrial Organisms 84
4.2.1 Toxicity to Birds 86
4.2.1.1 Birds: Acute Exposure (Mortality) Studies 86
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies 87
4.2.2 Toxicity to Mammals 88
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies 88
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies 88
4.2.3 Toxicity to Terrestrial Invertebrates 89
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies 89
4.2.3.2 Terrestrial Invertebrates: Open Literature Studies 90
4.2.4 Toxicity to Terrestrial Plants 90
4.3 Use of Probit Slope Response Relationship to Provide Information on the Endangered
Species Levels of Concern 92
4.4 Incident Database Review 93
4.4.1 Terrestrial Incidents 93
4.4.2 Plant Incidents 93
4.4.3 Aquatic Incidents 93
5. Risk Characterization 94
5.1 Risk Estimation 94
5.1.1 Exposures in the Aquatic Habitat 95
5.1.1.1 Direct Effects to Aquatic-Phase CRLF 95
5.1.1.2 Indirect Effects to Aquatic-Phase CRLF via Reduction in Prey (non-
vascular aquatic plants, aquatic invertebrates, fish, and frogs) 95
5.1.1.3 Indirect Effects to CRLF via Reduction in Habitat and/or Primary
Productivity (Freshwater Aquatic Plants) 98
5.1.2 Exposures in the Terrestrial Habitat 99
5.1.2.1 Direct Effects to Terrestrial-phase CRLF 99
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in Prey
(terrestrial invertebrates, mammals, and frogs) 101
5.1.2.3 Indirect Effects to CRLF via Reduction in Terrestrial Plant Community
(Riparian and Upland Habitat) 105
5.1.3 Primary Constituent Elements of Designated Critical Habitat 106
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5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-Breeding
Habitat) 106
5.1.3.2 Terrestrial-Phase (Upland Habitat and Dispersal Habitat) 107
5.2 Risk Description 108
5.2.1 Direct Effects 112
5.2.1.1 Aquati c-Phase CRLF 112
5.2.1.2 Terrestrial-Phase CRLF 114
5.2.2 Indirect Effects (via Reductions in Prey Base) 115
5.2.2.1 Algae (non-vascular plants) 115
5.2.2.2 Aquati c Invertebrate s 116
5.2.2.3 Fish and Aquatic-phase Frogs 119
5.2.2.4 Terrestrial Invertebrates 119
5.2.2.5 Mammals 120
5.2.2.6 Terrestrial-phase Amphibians 121
5.2.3.1 Aquatic Plants (Vascular and Non-vascular) 121
5.2.3.2 Terrestrial Plants 122
5.2.4 Modification to Designated Critical Habitat 126
5.2.4.1 Aquatic-Phase PCEs 126
5.2.4.2 Terrestrial-Phase PCEs 127
6. Uncertainties 128
6.1 Exposure Assessment Uncertainties 128
6.1.1 Maximum Use Scenario 128
6.1.2 Aquatic Exposure Modeling of Simazine 128
6.1.3 Action Area 130
6.1.4 Usage Uncertainties 131
6.1.5 Terrestrial Exposure Modeling of Simazine 131
6.2 Effects Assessment Uncertainties 132
6.2.1 Age Class and Sensitivity of Effects Thresholds 132
6.2.2 Use of surrogate species effects data 133
6.2.3 Sublethal Effects 133
7. Risk Conclusions 134
8. References 141
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Appendices
Appendix A Ecological Effects Data
Appendix B Multi-ai Product Analysis
Appendix C RQ Method and LOCs
Appendix D GIS Maps
Appendix E T-REX Example Output
Appendix F TerrPlant Example Output
Appendix G Bibliography of ECOTOX Open Literature Not Evaluated
Appendix H Simazine Aquatic Incidents
Appendix I Terrestrial Chronic Exposure Estimates for Granular Applications
of Simazine (Earthworm Fugacity Model)
Attachment I
Attachment II
Status and Life History of the California Red-Legged Frog
Baseline Status and Cumulative Effects for the California Red-
Legged Frog
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List of Tables
Table 1.1 Effects Determination Summary for Direct and Indirect Effects of Simazine on
the CRI.I 13
Table 1.2 Effects Determination Summary for the Critical Habitat Impact Analysis 15
Table 2.1 Summary of Simazine Environmental Fate Properties 24
Table 2.2 Simazine Uses Assessed for the CRLF1 28
Table 2.3 Summary of California Department of Pesticide Registration (CDPR) Pesticide
Use Reporting (PUR) Data from 2002 to 2005 for Currently Registered
Simazine Uses 31
Table 2.4 California Red-legged Frog Recovery Units with Overlapping Core Areas and
Designated Critical Habitat 35
Table 2.5 Assessment Endpoints and Measures of Ecological Effects 49
Table 2.6 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitata 51
Table 3.1 Simazine Uses, Scenarios, and Application Information for the CRLF risk
assessment1 60
Table 3.2 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Simazine Endangered Species Assessment for the
CRLF 62
Table 3.3 Aquatic EECs ((J-g/L) for Simazine Agricultural and Non-agricultural Uses in
California 64
Table 3.4 Summary of AgDISP Predicted Terrestrial Spray Drift Distances 68
Table 3.5 Summary of AgDRIFT Predicted Aquatic Spray Drift Distances 69
Table 3.6 Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
Simazine with T-REX 70
Table 3.7 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Simazine 71
Table 3.8 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Terrestrial Invertebrate Prey Items 71
Table 3.9 Terrestrial EECs for Granular Uses of Simazine 72
Table 3.10 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semi-
aquatic Areas Exposed to Simazine via Runoff and Drift 73
Table 4.1 Comparison of Acute Toxicity Values for Simazine and Degradates 75
Table 4.2 Freshwater Aquatic Toxicity Profile for Simazine 76
Table 4.3 Categories of Acute Toxicity for Aquatic Organisms 77
Table 4.4 Terrestrial Toxicity Profile for Simazine 85
Table 4.5 Categories of Acute Toxicity for Avian and Mammalian Studies 86
Table 4.6 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data 91
Table 5.2 Summary of Acute RQs Used to Estimate Indirect Effects to the CRLF via
Effects to Non-Vascular Aquatic Plants (diet of CRLF in tadpole life stage
and habitat of aquatic-phase CRLF) 96
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Table 5.3 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to the
CRLF via Direct Effects on Aquatic Invertebrates as Dietary Food Items
(prey of CRLF juveniles and adults in aquatic habitats) 97
Table 5.4 Summary of Acute RQs Used to Estimate Indirect Effects to the CRLF via
Effects to Vascular Aquatic Plants (habitat of aquatic-phase CRLF)a 98
Table 5.5 Summary of Chronic RQs* Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (non-granular application) 100
Table 5.6 Comparison of Granular EECs to Adjusted LD50 Value Used to Estimate
Direct Effects to the Terrestrial-phase CRLF (granular application) 101
Table 5.7 Summary of RQs Used to Estimate Indirect Effects to the Terrestrial-phase
CRLF via Direct Effects on Terrestrial Invertebrates as Dietary Food
Items 102
Table 5.8 Summary of Acute and Chronic RQs* Used to Estimate Indirect Effects to the
Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary
Food Items (non-granular application) 103
Table 5.9 Comparison of Granular EECs to Adjusted LD50 Value Used to Estimate
Indirect Effects to the Terrestrial-phase CRLF via Direct Effects on Small
Mammals as Dietary Food Items (granular application) 104
Table 5.10 RQs* for Monocots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Simazine via Runoff and Drift 105
Table 5.11 RQs* for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Simazine via Runoff and Drift 106
Table 5.12 Preliminary Effects Determination Summary for Simazine - Direct and
Indirect Effects to CRLF 108
Table 5.13 Preliminary Effects Determination Summary for Simazine - PCEs of
Designated Critical Habitat for the CRLF 110
Table 5.14 Summary of RQs Used to Assess Potential Risk to Freshwater Invertebrate
Food Items of the CRLF 118
Table 5.15 Spray Drift Dissipation Distances 125
Table 7.1 Effects Determination Summary for Direct and Indirect Effects of Simazine on
the CRLF 137
Table 7.2 Effects Determination Summary for the Critical Habitat Impact Analysis 139
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List of Figures
Figure 2.1 Simazine and Degradate Structures 26
Figure 2.2 Simazine Use in Total Pounds per County 30
Figure 2.3 Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRI.I 37
Figure 2.5 Initial area of concern, or "footprint" of potential use, for simazine 44
Figure 2.6 Simazine Action Area for the California Red Legged Frog 46
Figure 2.7 Portion of the Action Area that is Relevant for the California Red Legged Frog 47
Figure 2.8 Conceptual Model for Aquatic-Phase of the CRLF 53
Figure 2.9 Conceptual Model for Terrestrial-Phase of the CRLF 54
Figure 2.10 Conceptual Model for Pesticide Effects on Aquatic Component of CRLF
Critical Habitat 54
Figure 2.11 Conceptual Model for Pesticide Effects on Terrestrial Component of CRLF
Critical Habitat 55
Figure 3.1 Summary of Applications of Simazine to Grapes in 2005 from CDPR PUR
data 62
Table 5.1 Summary of Direct Effect RQs for the Aquatic-phase CRLF 95
Figure 7.1 Locations Where Aerial Application of Simazine on Rights-of-Way is Likely
to Adversely Affect the CRLF and Cause Modification to Critical Habitat 135
Figure 7.2 Locations Where Ground Applications of Simazine on Cultivated Crops,
Orchards, Turf, and Forestry is Likely to Adversely Affect the CRLF and
Cause Modification to Critical Habitat 136
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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 simazine as an herbicide 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.
Simazine is a triazine herbicide with currently, labeled uses including several fruit and
nut crops, corn, and a number of non-agricultural uses including homeowner and
recreational turf, Christmas trees, tree plantations and nurseries, shelterbelts, and
nonselective weed control in industrial sites, highway medians, railroad rights-of-way,
lumberyards, petroleum sites, and non crop areas on farms. The following uses are
considered as part of the federal action evaluated in this assessment: almonds, nectarines,
apples, pears, sour cherries, avocados, berries (blueberries, boysenberries, cranberries,
loganberries, and raspberries), citrus (grapefruit, lemons, and oranges), nuts (almonds,
filberts, hazelnuts, almonds, walnuts, macadamia nuts), grapes, olives, peaches, non-
bearing fruit trees (apples, cherries, peaches, and pears), Christmas tree plantations for
lumber, non-crop areas (includes commercial/industrial/institutional
premises/equipment/highway uses), tree plantations, tree nurseries, shelterbelts, and
residential, recreational, and sod farm turf. Simazine can be applied as a liquid via
ground sprayer, banded application, or aerial broadcast, or as granular formulation.
The environmental fate properties of simazine along with available monitoring data
identifying its presence in surface water, air, and in precipitation in California indicate
that runoff, spray drift, volatilization, atmospheric transport and subsequent deposition
represent potential transport mechanisms of simazine to the aquatic and terrestrial
habitats of the CRLF. In this assessment, transport of simazine from initial application
sites through runoff and spray drift are considered in deriving quantitative estimates of
simazine exposure to CRLF, its prey and its habitats. Although volatilization of simazine
from treated areas resulting in atmospheric transport and eventual deposition represent
relevant transport pathways leading to exposure of the CRLF and its habitats, it is
expected that detected simazine concentrations in atmospheric monitoring data are
reflective of near field spray drift and not long range transport, given simazine's low
volatility and a lack of detections at higher elevations. In addition, adequate tools are not
available at this time to quantify exposures through these pathways. Therefore,
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volatilization, and potential atmospheric transport are discussed only qualitatively in this
assessment.
Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF, its prey
and its habitats to simazine are assessed separately for the two habitats. Tier-II aquatic
exposure models are used to estimate high-end exposures of simazine in aquatic habitats
resulting from runoff and spray drift from different uses. Peak model-estimated
environmental concentrations resulting from different simazine uses range from 5.6 to
130.2 |ig/L. These estimates are supplemented with analysis of available California
surface water monitoring data from U. S. Geological Survey's National Water Quality
Assessment (NAWQA) program and the California Department of Pesticide Regulation.
The maximum concentration of simazine reported by NAWQA from 2000-2005 for
California surface waters with agricultural watersheds is 64.5 |ig/L. This value is
approximately two times less than the maximum model-estimated environmental
concentration, but is within the range of environmental concentrations estimated for
different uses. The maximum concentration of simazine reported by the California
Department of Pesticide Regulation surface water database from 2000-2005 (36.1 |ig/L)
is roughly 3.5 times lower than the highest peak model-estimated environmental
concentration.
To estimate simazine exposures to the terrestrial-phase CRLF, and its potential prey
resulting from uses involving simazine applications, the T-REX model is used for both
foliar and granular uses. Terrestrial exposure from granular applications are based on
LD50/ft2 values and an earthworm fugacity model. AgDRIFT and AgDISP are also used
to estimate deposition of simazine on terrestrial habitats from spray drift. The TerrPlant
model is used to estimate simazine exposures to terrestrial-phase habitat, including plants
inhabiting semi-aquatic and dry areas, resulting from uses involving foliar and granular
simazine applications
The assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the CRLF itself, as well as indirect effects, such as reduction
of the prey base or 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.
With respect to simazine degradates, deisopropylatrazine (DIA) and
diaminochloroatrazine (DACT), it is assumed that each degradate is less toxic than the
parent compound for aquatic receptors. Comparison of available toxicity information for
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DIA and DACT indicates lesser aquatic toxicity than the parent for freshwater fish,
invertebrates, and aquatic plants. However, the acute toxicity data for mammals indicates
that DIA is more toxic than parent simazine, with a corresponding LD50 value of 1,240
mg/kg, as compared to > 5,000 mg/kg for simazine. Although the degradate toxicity data
indicate that DIA is more toxic to mammals than parent simazine, indirect effects to
terrestrial-phase CRLFs via direct acute effects to mammals are assessed using toxicity
data for simazine because the available fate data show that DIA does not form and persist
in the environment at any substantial level. Degradate toxicity data are not available for
terrestrial plants; however, lesser toxicity is assumed, given the available
ecotoxicological information for other taxonomic groups including aquatic plants, where
the toxic mode of action is similar, and the likelihood that the simazine degradates are
expected to lose efficacy as an herbicide.
Risk quotients (RQs) are derived as quantitative estimates of potential high-end risk.
Acute and chronic RQs are compared to the Agency's levels of concern (LOCs) to
identify instances where simazine use within the action area has the potential to adversely
affect the CRLF and its designated critical habitat via direct toxicity or indirectly based
on direct effects to its food supply (i.e., freshwater invertebrates, algae, fish, frogs,
terrestrial invertebrates, and mammals) or habitat (i.e., aquatic plants and terrestrial
upland and riparian vegetation). When RQs for a particular type of effect are below
LOCs, the pesticide is determined to have "no effect" on the subject species. Where RQs
exceed LOCs, a potential to cause adverse effects is identified, leading to a conclusion of
"may affect." If a determination is made that use of simazine use within the action area
"may affect" the CRLF and its designated critical habitat, additional information is
considered to refine the potential for exposure and effects, and the best available
information is used to distinguish those actions that "may affect, but are not likely to
adversely affect" (NLAA) from those actions that are "likely to adversely affect" (LAA)
the CRLF and its critical habitat.
The best available data suggest that simazine is not likely to adversely affect the aquatic-
phase CRLF by direct toxic effects or by indirect effects resulting from effects to aquatic
invertebrates, fish, and other aquatic-phase frogs as food items. In addition, direct acute
effects and indirect effects via reduction of terrestrial invertebrates as prey are not
expected for terrestrial-phase CRLFs. However, an "LAA" determination was concluded
for the aquatic-phase CRLF, based on indirect effects related to a reduction in algae as
food items for the tadpole, and on aquatic non-vascular plants and sensitive herbaceous
terrestrial plants that comprise its habitat. For the terrestrial-phase CRLF, an "LAA"
determination was concluded for chronic direct effects and indirect effects related to a
reduction in mammals and terrestrial-phase frogs as food items, and herbaceous terrestrial
plants as habitat. Given these direct and indirect effects to the CRLF, modification of
critical habitat is also expected for both aquatic and terrestrial primary constituent
elements (PCEs). A summary of the risk conclusions and effects determinations for the
CRLF and its critical habitat is presented in Tables 1.1 and 1.2. Further information on
the results of the effects determination is included as part of the Risk Description in
Section 5.2.
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Table 1.1 Effects Determination Summary for Direct and Indirect Effects of Simazine on the
CR.LF
Assessment Endpoint Effects
Determination'
Basis for Determination
Aquatic-Phase CRLF
(Eggs, Larvae, and Adults)
Survival, growth, and reproduction of
CRLF individuals via direct effects on
aquatic phases
No effect
Using freshwater fish as a surrogate, no acute and
chronic LOCs are exceeded.
Survival, growth, and reproduction of
CRLF individuals via effects to food
supply (i.e., freshwater invertebrates,
non-vascular plants, fish, and frogs)
Freshwater
invertebrates: NLAA
Simazine may affect sensitive aquatic invertebrates, such
as the water flea; however, the low probability (<4 %) of
an individual effect to the water flea is not likely to
indirectly affect the CRLF, given the wide range of other
types of freshwater invertebrates that the species
consumes. Based on the non-selective nature of feeding
behavior in the CRLF, the low magnitude of anticipated
acute individual effects to preferred aquatic invertebrate
prey species (<0.1%), simazine is not likely to indirectly
affect the CRLF via reduction in freshwater invertebrate
food items. This finding is based on insignificant effects.
The effects are insignificant because the probability of an
individual effect level to freshwater invertebrates (< 4 %
at predicted levels of exposure) is low and the most
sensitive species of freshwater invertebrate species is
likely to overestimate the sensitivity of the majority of
freshwater invertebrate food items in the CRLF's diet.
Non-vascular aauatic
olants: LAA
Simazine uses related to liquid applications on Christmas
trees (5.94 lb ai/A), non-cropland (5 lb ai/A), berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A), and
granular applications of simazine to non-bearing fruit (8
lb ai/A) and berries (4 lb ai/A) exceed LOCs; therefore,
indirect effects to tadpoles that feed on algae are
possible.
Fish and froes: No
effect
Using freshwater fish as a surrogate, no acute and
chronic LOCs are exceeded.
Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat, cover, and/or primary
productivity (i.e., aquatic plant
community)
Non-vascular
aauatic olants: LAA
LOCs are exceeded for non-vascular aquatic plants for
liquid applications of simazine to Christmas trees (5.94
lb ai/A), non-cropland (5 lb ai/A), berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A);
LOCs are also exceeded for granular applications of
simazine to non-bearing fruit (8 lb ai/A) and berries (4
lb ai/A).
Vascular aauatic
olants: No effect
RQs for vascular plants are less than LOCs for all
simazine use patterns
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
Direct effects to
forested riparian
veeetation: NLAA
Direct effects to
Riparian vegetation may be affected because terrestrial
plant RQs are above LOCs. However, woody plants are
generally not sensitive to environmentally-relevant
concentrations of simazine; therefore, effects on shading,
bank stabilization, and structural diversity of riparian
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species' current range.
erassv/herbaceous
riparian vesetation:
LAA < 184 ft
(ground)
NLAA > 184 ft
(ground)
LAA < 850 ft (aerial);
NLAA > 850 ft
(aerial)
areas in the action area are not expected. Aquatic-phase
CRLFs may be indirectly affected by adverse effects to
sensitive herbaceous vegetation (based on all simazine
non-granular and granular uses), which provides habitat
and cover for the CRLF and attachment sites for its egg
masses.
Terrestrial-Phase CRLF
(Juveniles and adults)
Survival, growth, and reproduction of
CRLF individuals via direct effects on
terrestrial phase adults and juveniles
Acute: No effect
The acute avian effects data (used as a surrogate for the
terrestrial-phase CRLF) show no mortality at the highest
treatment levels of simazine in both the acute oral and
subacute dietary studies. In addition, the predicted
granular EECs in mg ai/ft2 are well below the adjusted
LD50 values for two weight classes that are intended to be
representative of juvenile and adult terrestrial-phase
CRLFs.
Chronic:
LAA (for non-
granular simazine
uses)
NLAA (for granular
simazine uses)
Chronic reproductive effects are possible, based on non-
granular uses of simazine. However, chronic direct
effects to the CRLF exposed to granules are unlikely.
This finding is based on discountable effects (i.e.,
chronic effects to simazine granules are not likely to
occur and/or result in a "take" of a single listed
terrestrial-phase CRLF).
Survival, growth, and reproduction of
CRLF individuals via effects on prey (i.e.,
terrestrial invertebrates, small terrestrial
vertebrates, including mammals and
terrestrial phase amphibians)
Terrestrial
invertebrates: NLAA
Simazine is non-toxic to terrestrial invertebrates at
environmentally relevant concentrations. This finding is
based on discountable effects (i.e., acute effects to
simazine at the expected levels of exposure are not likely
to occur and/or result in a "take" of a single listed CRLF
via a reduction in terrestrial invertebrates as food items).
Mammals: LAA
Chronic RQs for non-granular formulations exceed
LOCs. Chronic effects to insectivorous mammals that
consume invertebrates exposed to simazine granules are
also possible.
Fross: LAA
Chronic risks for terrestrial-phase frogs exposed to non-
granular uses of simazine may occur, although acute
mortality is not likely.
Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat (i.e., riparian vegetation)
Direct effects to
forested riparian
vesetation: NLAA
Direct effects to
erassv/herbaceous
rioarian vesetation:
LAA < 184 ft
(ground)
NLAA > 184 ft
(ground)
LAA < 850 ft (aerial);
NLAA > 850 ft
(aerial)
Riparian vegetation may be affected because terrestrial
plant RQs are above LOCs. However, woody plants are
generally not sensitive to environmentally-relevant
concentrations of simazine; therefore, effects to
woodlands within the action area are not expected.
Terrestrial-phase CRLFs may be indirectly affected by
adverse effects to sensitive herbaceous vegetation (based
on all simazine non-granular and granular uses), which
provides habitat and cover for the CRLF and its prey.
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Table 1.2 Effects Determination Summary for the Critical Habitat Impact Analysis
Assessment Endpoint Effects
Determination
Basis for Determination
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.
Habitat
modification
Sensitive herbaceous riparian vegetation may be
affected based on all granular and non-granular uses
of simazine; therefore, critical habitat may be
modified by an increase in sediment deposition and
reduction in herbaceous riparian vegetation that
provides for shelter, foraging, predator avoidance,
and aquatic dispersal for juvenile and adult aquatic-
phase 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.1
Habitat
modification
Sensitive herbaceous riparian vegetation and non-
vascular aquatic plants may be affected; therefore,
critical habitat may be modified via turbidity and
reduction in oxygen content necessary for normal
growth and viability of juvenile and adult aquatic-
phase CRLFs.
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
No effect to
growth and
viability
Habitat
modification
based on
alteration of
food source
Direct effects to the aquatic-phase CRLF, via
mortality, growth, and/or fecundity, are not
expected. However, critical habitat of the CRLF
may be modified via simazine-related impacts to
non-vascular aquatic plants as food items for
tadpoles. LOCs are exceeded for non-vascular
aquatic plants for liquid applications of simazine to
Christmas trees (5.94 lb ai/A), non-cropland (5 lb
ai/A), berries, tree plantations, tree nurseries, and
avocados (4 lb ai/A); LOCs are also exceeded for
granular applications of simazine to non-bearing
fruit (8 lb ai/A) and berries (4 lb ai/A).
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
Habitat
modification
Based on the results of the effects determinations
for aquatic plants, critical habitat of the CRLF may
be modified via simazine-related impacts to non-
vascular aquatic plants as food items for tadpoles.
LOCs are exceeded for non-vascular aquatic plants
for liquid applications of simazine to Christmas
trees (5.94 lb ai/A), non-cropland (5 lb ai/A),
berries, tree plantations, tree nurseries, and
avocados (4 lb ai/A); LOCs are also exceeded for
granular applications of simazine to non-bearing
fruit (8 lb ai/A) and berries (4 lb ai/A).
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
Habitat
modification
Modification to critical habitat may occur via
simazine-related impacts to sensitive herbaceous
vegetation, which provide habitat and cover for the
terrestrial-phase CRLF and its prey, based on all
assessed uses of simazine. Modification to critical
habitat is not expected to occur in woodland areas
1 Physico-chemical water quality parameters such as salinity, pH, mid hardness are not evaluated because these processes are not
biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.
15
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provides the CRLF shelter, forage, and predator
avoidance
because woody plants are not sensitive to
environmentally relevant concentrations of
simazine.
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
Habitat
modification
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Habitat
modification
Based on the characterization of indirect effects to
terrestrial-phase CRLFs via reduction in the prey
base, critical habitat may be modified via a
reduction in mammals and terrestrial-phase
amphibians as food items.
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
Habitat
modification
Direct acute effects, via mortality, are not expected
for the terrestrial-phase CRLF; however, chronic
reproductive effects are possible for all non-
granular uses of simazine. Therefore, simazine may
adversely critical habitat by altering chemical
characteristics necessary for normal growth and
viability of terrestrial-phase CRLFs and their
mammalian and amphibian food sources.
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
to seek concurrence with the LAA determinations and to determine whether there are
reasonable and prudent alternatives and/or measures to reduce and/or eliminate potential
incidental take.
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.
16
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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.
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
simazine on agricultural crops (i.e., almonds, apples, cherries, pears, nectarines, peaches,
berries, avocado, citrus, grapes, olives, and corn) and non-agricultural commodities (i.e.,
non-bearing apples; Christmas trees; tree plantations and nurseries; homeowner,
recreational and sod farm turf; and non-cropland). In addition, this assessment evaluates
whether these uses are expected to result in modification of the species' critical habitat.
This ecological risk assessment has been prepared consistent with a settlement agreement
in the case Center for Biological Diversity (CBD) us. EPA et al. (Case No. 02-1580-
17
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JSW(JL)) settlement entered in Federal District Court for the Northern District of
California on October 20, 2006.
In this assessment, direct and indirect effects to the CRLF and potential modification to
its critical habitat are evaluated in accordance with the methods described in the
Agency's Overview Document (U.S. EPA 2004). Screening level methods include use of
standard models such as PRZM-EXAMS, T-REX, TerrPlant, AgDRIFT, and AgDISP, all
of which are described at length in the Overview Document. Additional refinements
include an analysis of the usage data, a spatial analysis, and use of an earthworm fugacity
model to predict concentrations of simazine granules in terrestrial invertebrates food
items for terrestrial-phase CRLFs and mammals. Use of such information is consistent
with the methodology described in the Overview Document (U.S. EPA 2004), which
specifies that "the assessment process may, on a case-by-case basis, incorporate
additional methods, models, and lines of evidence that EPA finds technically appropriate
for risk management objectives" (Section V, page 31 of U.S. EPA 2004).
In accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of simazine is based on an action area. The action area is the area directly or
indirectly affected by the federal action, as indicated by the exceedance of the Agency's
Levels of Concern (LOCs). It is acknowledged that the action area for a national-level
FIFRA regulatory decision associated with a use of simazine 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 use of simazine in accordance with current labels:
"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.
If the results of initial screening-level assessment methods show no direct or indirect
effects (no LOC exceedances) upon individual CRLFs or upon the PCEs of the species'
designated critical habitat, a "no effect" determination is made for use of simazine 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
18
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CRLF's designated critical habitat, a preliminary "may affect" determination is made for
the FIFRA regulatory action regarding simazine.
If a determination is made that use of simazine within the action area(s) associated with
the CRLF "may affect" this species or its designated critical habitat, additional
information is considered to refine the potential for exposure and for effects to the CRLF
and other taxonomic groups upon which these species depend (e.g., aquatic and terrestrial
vertebrates and invertebrates, aquatic plants, riparian vegetation, etc.). Additional
information, including spatial analysis (to determine the geographical proximity of CRLF
habitat and simazine use sites) and further evaluation of the potential impact of simazine
on the PCEs is also used to determine whether modification of 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 simazine is expected to directly impact living organisms within the action area
(defined in Section 2.7), critical habitat analysis for simazine is limited in a practical
sense to those PCEs of critical habitat that are biological or that can be reasonably linked
to biologically mediated processes (i.e., the biological resource requirements for the listed
species associated with the critical habitat or important physical aspects of the habitat that
may be reasonably influenced through biological processes). Activities that may modify
critical habitat are those that alter the PCEs and appreciably diminish the value of the
habitat. Evaluation of actions related to use of simazine 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
Simazine is widely used as a selective herbicide to control most annual grasses and
broadleaf weeds (before they emerge or after removal of weed growth). Simazine is
registered for pre-plant use or use in established fields of a variety of food and feed crops
including fruit and nut crops such as apples, oranges, and almonds, in addition to corn.
Simazine can also be applied on Christmas trees and on turfgrass grown commercially for
sod. Nonagricultural uses for simazine include nonselective weed control in industrial
sites, highway medians and shoulders, railroad rights-of-way, lumberyards, petroleum
tank farms, and in noncrop areas on farms, such as around buildings, equipment and fuel
storage areas, along fences, road-sides, and lanes. Simazine is also registered for
residential use on turfgrass including both commercial use on recreational lawns such as
golf courses and commercial or homeowner use on home lawns. There is an additional
registration for simazine as an algaecide in ornamental ponds and aquariums of 1,000
gallons or less. Given that this use is limited to ponds of 1,000 gallons or less, the
19
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Agency believes that this use would pose minimal impact on the environment because
labels include the following statement: "Do not apply or allow discharge to lakes, flowing
water, or ponds with outflow," "Do not contaminate domestic livestock or irrigation
water supply," and "Water treated with this product should not be used as a source of
drinking water." Simazine can be applied as a liquid via ground sprayer, banded
application, or aerial broadcast, or as granular formulation.
The end result of the EPA pesticide registration process {i.e., the FIFRA regulatory
action) is an approved product label. The label is a legal document that stipulates how
and where a given pesticide may be used. Product labels (also known as end-use labels)
describe the formulation type {e.g., liquid or granular), acceptable methods of application,
approved use sites, and any restrictions on how applications may be conducted. Thus, the
use or potential use of simazine in accordance with the approved product labels for
California is "the action" relevant to this ecological risk assessment.
Although current registrations of simazine allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of simazine 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.
Degradates of simazine include deisopropyl-atrazine (DIA), diamino-chlorotriazine
(DACT), and hydroxysimazine (HS). Comparison of available toxicity information for
degradates of simazine indicates lesser toxicity than the parent for fish, aquatic
invertebrates, and aquatic plants. Acute toxicity values for DIA are approximately 2.6-
fold less sensitive than acute toxicity values for simazine in freshwater fish. In addition,
no adverse effects were observed in fish and daphnids for DACT and in daphnids for
DIA at the limit of simazine's solubility. Available aquatic plant degradate toxicity data
for DIA and DACT report EC50 values at concentrations that are at least 69 times higher
than the lowest reported aquatic plant EC50 value for parent simazine. Although toxicity
information is not available for hydroxysimazine, this degradate is also likely to be less
toxic than parent simazine, given that the more toxic chloro group is replaced by a less
toxic hydroxyl group during its formation. Degradate toxicity data are also not available
for terrestrial plants; however, lesser toxicity is assumed, given the available
ecotoxicological information for other taxonomic groups including aquatic plants, where
the toxic mode of action is similar, and the likelihood that degradates may lose efficacy
as an herbicide. Although other taxonomic groups appear to be more sensitive to
simazine than its degradates, acute oral toxicity data for mammals indicates that DIA is
more toxic than parent simazine, with a corresponding LD50 value of 1,240 mg/kg-bw, as
compared to > 5,000 mg/kg-bw for simazine.
Given the lesser aquatic toxicity of degradates, as compared to the parent, concentrations
of the simazine degradates are not assessed for direct and/or indirect effects to aquatic-
phase CRLFs. Although the degradate toxicity data indicates that DIA is more toxic to
mammals than parent simazine, indirect effects to terrestrial-phase CRLFs via direct
acute effects to mammals are assessed using toxicity data for simazine because the
20
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available fate data show that DIA does not form and persist in the environment at any
substantial level. Additional details on available simazine degradate toxicity are provided
in Section 4 and Appendix A.
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).
Simazine has registered products that contain multiple active ingredients. Analysis of the
available open literature and acute oral mammalian LD50 data for multiple active
ingredient products relative to the single active ingredient is provided in Appendix B.
The results of this analysis show that an assessment based on the toxicity of the single
active ingredient of simazine is appropriate.
The results of available toxicity data for mixtures of simazine with other pesticides are
presented in Section A.6 of Appendix A. Based on a review of the available data, other
triazine herbicides may combine with simazine to produce additive toxic effects on
aquatic plants. The variety of chemical interactions presented in the available data set
suggest that the toxic effect of simazine, in combination with other pesticides used in the
environment, can be a function of many factors including but not necessarily limited to:
(1) the exposed species, (2) the co-contaminants in the mixture, (3) the ratio of simazine
and co-contaminant concentrations, (4) differences in the pattern and duration of
exposure among contaminants, and (5) the differential effects of other physical/chemical
characteristics of the receiving waters (e.g. organic matter present in sediment and
suspended water). Quantitatively predicting the combined effects of all these variables
on mixture toxicity to any given taxa with confidence is beyond the capabilities of the
available data. However, a qualitative discussion of implications of the available
pesticide mixture effects data involving simazine on the confidence of risk assessment
conclusions for the CRLF is addressed as part of the uncertainty analysis for this effects
determination.
2.3 Previous Assessments
A Reregi strati on Eligibility Decision (RED) was completed for simazine on April 6, 2006
(U.S. EPA, 2006)2. The results of the Agency's ecological risk assessment for simazine,
which was completed as part of the RED, suggest the potential for adverse acute effects
to non-target terrestrial and aquatic plants, and direct chronic effects to birds and
mammals. In addition, a number of the granular uses resulted in potential direct adverse
2 Available via the internet at: http://www.epa.gov/oppsrrdl/reregistration/REDs/simazine_red.pdf
21
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effects to freshwater invertebrates and fish, although there was a high degree of
uncertainty associated with the freshwater fish data set because exposure concentrations
were not verified in the available acute toxicity tests. Simazine is not likely to be acutely
toxic to estuarine/marine fish and invertebrates, and it is unlikely to cause acute mortality
to birds and mammals, although acute sublethal effects to birds are possible.
The Agency has also completed effects determinations for the Barton Springs salamander
for simazine (U.S. EPA, 2007a) as part of the settlement for the court case Center for
Biological Diversity and Save Our Springs Alliance v. Leavitt, No. 1:04CV00126-CKK
(filed January 26, 2004). The results of this endangered species risk assessment show
that simazine has no effect on the Barton Springs salamander by direct toxic effects
and/or indirect effects resulting from effects to aquatic invertebrates and plants.
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Properties
Simazine is moderately soluble in water at 20°C with a solubility of 3.5 mg/L. Based on
laboratory studies, simazine could persist for several months (ti/2 = 91 days; aerobic soil
metabolism) in the environment and maybe for years in oxygen deprived aquatic systems
(ti/2 = 664 days; anaerobic aquatic metabolism), as it is not easily degraded by soil
microbial organisms. If released on soil surface and under direct sunlight, it will undergo
relatively faster degradation (t V2 ~ 22 days). Simazine is also quite resistant to aqueous
abiotic reactions (stable to hydrolysis at pH 5, 7, and 9 and to photolysis in buffered
solution at pH 7), thus increasing its likelihood to runoff and contaminate surface water.
However, it must be noted that a supplemental aqueous photolysis study showed
simazine degrading with a half-life of 16 hours in the presence of acetone as a sensitizer.
Laboratory adsorption data show low water/soil partitioning for simazine. The
Freundlich Kd-ads constants for the adsorption phase were below 5 for all soils tested.
Organic matter (OM) seems to affect the sorption efficiency of simazine as the adsorption
coefficient was shown to be strongest in a high organic matter clay soil (Kd-ads 4.31, OM
4.8%) and weakest in a low organic matter loam soil (Kd-ads 0.48, OM 0.8%). These data
indicate that simazine is highly mobile, thus having strong potential to leach to ground
water systems, especially in OM poor soil systems, such as loam and sand soils.
Based on its low vapor pressure (6.1 x 10"9 mm Hg at 20°C) and Henry's Law Constant
(3.2 x 10"10 atm-m3/mol at 25°C), volatilization loss of simazine from soil and water
systems is expected to be insignificant compared to dissipation by chemical degradation
and metabolism. Based on laboratory bioaccumulation in rainbow trout, simazine is not
expected to bioaccumulate in fish, which is in concurrence with simazine's low Kow value
of 122. The BCF in all tissue tested ranged from 0.9 (viscera) to 2.3 (muscle).
Elimination of accumulated residues by day 28 of depuration was 52% in viscera and
98%) in muscle.
22
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Based on its persistence and mobility, as demonstrated by the laboratory data, simazine is
expected to reach surface water via transport from soil surfaces during runoff events and
ground water via vertical movement through soil (leaching). Aside from monitoring data,
terrestrial field and aquatic dissipation studies were also submitted for simazine.
Unfortunately, most of the terrestrial field studies did not follow the Subdivision N
Guidelines and were deemed not acceptable to provide information on the behavior of
simazine under actual terrestrial field conditions. Two supplemental studies, however,
indicated that simazine could persist in the fields for over one month to several years
depending on soil texture and soil temperature. In addition, a non-guideline study on
simazine persistence in soil as a function of temperature and soil moisture (MRID
00027881) also indicated that although decreasing soil moisture slows simazine's
metabolism rate in soil, soil temperature exerted the greatest influence in the breakdown
of simazine by microbes: a decrease in soil temperature from 25 to 15°C (with other
factors remaining constant) could increase simazine's half-life by up to 250 to 300%. As
for aquatic field studies, dissipation of simazine is variable, with half lives ranging from
12 days in swimming pool water, to 53 days in surface water man-made ponds, and up to
700 days in a lake in Missouri. The fast degradation of simazine in the swimming pool
water study could be attributed partially to photodegradation, which was seen in
laboratory studies to accelerate in the presence of photosensitizers or chemical species
(such as hydroxyl radicals) capable of inducing photoreactions.
There are three types of degradates/metabolites for simazine. The first type of degradate
is formed via dealkylation of the amino groups, for which mono- and fully dealkylated
degradates are known (G-28279 or DIA and G-28273 or DACT). The second type is
formed by substitution of the chloro group by a hydroxyl group (G-30414 or
hyrdroxy simazine, HA). The third type is formed by substitution of the chloro group by
a hydroxyl group together with partial or complete dealkylation (GS-17791 and GS-
17792). From limited laboratory data, the relative concentrations of the degradates in soil
were generally DIA>DACT~Hydroxysimazine, except for one aerobic soil metabolism
study and one aerobic aquatic metabolism study, where the concentration of
hydroxysimazine was higher than that of DIA towards the end of the studies. The highest
detected concentration of DIA in the laboratory studies was approximately 10% of total
applied radioactivity (aerobic soil metabolism study) and less than 5% on soil surfaces of
two supplemental terrestrial field studies, which indicates that DIA, and subsequently
DACT and hydroxysimazine, may not form and persist in the environment at any
substantial levels.
Like parent simazine, the dealkylated degradates are very mobile in the sand soil and the
loam soil, as shown by their low (<2) adsorption coefficients (Kads). Mobility for these
dealkylated degradates, however, appears to decrease in soil with higher clay content
(Kads in clay soil range from 1.56 to 4.3). Therefore, although laboratory studies indicate
that the dealkylated degradates are as likely (or even more likely) to leach to ground
water as parent simazine, as with simazine, soil characteristics must be taken into account
when assessing the leaching potential of these degradates in a specific region.
Hydroxysimazine, on the other hand, shows the strongest adsorption to soil, with Kads
values of 8 in sand to 480 in clay soil, thus possessing lower leaching potential than its
23
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parent. Acceptable field dissipation studies are not currently available to confirm the
laboratory findings on the mobility of these degradates.
In summary, simazine is somewhat persistent and mobile in soils and has the potential to
reach surface water and ground water via run off and leaching, respectively. When
present in ground water and in surface water, simazine will further persist, especially in
systems with relatively long hydrologic residence times (such as in some reservoirs),
mostly due to its resistance to abiotic hydrolysis and to direct aqueous photolysis, its
susceptibility to biodegradation, and its limited volatilization potential. For simazine
degradates such as DIA and DACT, laboratory and field studies indicate that their
concentrations in the environment are likely to be insignificant compared to parent
simazine.
The relatively low soil/water partitioning of simazine and its chloro degradates
indicates that the concentrations of the degradates in/on suspended and bottom sediment
in equilibrium with the water column will be somewhat comparable to their parent. In
contrast, hydroxysimazine concentration would be much higher. Table 2.1 lists the
environmental fate properties of simazine, along with the major and minor degradates
detected in the submitted environmental fate and transport studies. Structures of
simazine and its principal degradates are included in Figure 2.1.
Table 2.1 Summary of Simazine Environmental Fate Properties
Study
Half-lives, Days
Major Degradates
Minor Degradates
MRID #
Study Status
Hydrolysis
stable at pH 4, 7 , and 9 @ 20C
none
00027856
Acceptable
Direct Aqueous
Photolysis
stable (t Vi >30 days - duration of
study) in sterile, unbuffered water
irradiated with a mercury vapor lamp.
G-28273 (max 11% TAT at
study end)
00143171
Supplemental
t Vi ~ 16 hrs in sterile, unbuffered 1%
aqueous acetone solution irradiated
with artificial light
stable (t Vi -382 days) in sterile
buffered solution, irradiated with
xenon lamp
G-28279 (max 82 % after
98 hr)
G-28273, G-30414 and GS-
17792
none
42503708
Acceptable
Soil Photolysis
22 days (corrected for dark control, 12-
hr irradiation)
none
G-30414, G-28279, G-
28273, and GS-17792.
40614410
Supplemental/
Unacceptable
Aerobic Soil
Metabolism
110 days (silt loam)
G-28279 (max 10% at day
60)
G-30414, G-28273, GS-
17792, G-28516, GS-17791,
and C02
00158638
Supplemental
91 days (sandy loam)
GS-30414 (max 62% at
study end)
43004501
Supplemental
24
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Table 2.1 Summary of Simazine Environmental Fate Properties
Study
Half-lives, Days
Major Dcgradatcs
Minor Degradat.es
MRID #
Study Status
GS-17792 and GS-28279
Anaerobic Soil
Metabolism
56 days (sandy loam)
none
G-28279, G-30414, G-
28273, and GS-17792
00027857
Supplemental
Anaerobic
Aquatic
Metabolism
664 days (sandy clay)
none
G-30414, G-28279, and G-
28273
40614411
Acceptable
Aerobic
Aquatic
Metabolism
61 (sediment), 109 (water), and 71
days (total system)
G-30414 (max 12% day 30)
G-28279, G-30044, and G-
31709
43004502
Acceptable
Kd-ads / Kd-des
(mL/g)
4.3/9.3 (clay), 0.7/2.3 (sand), 1.3/6.2
(sandy loam), and 0.5/0.8 (loam)
NA
41442903
41257903
Acceptable
Koc- ads / Koc-des
(mL/g)
153 / 331 (clay), 123/426 (sand),
114/555 (sandy loam), and
103/167(loam)
Terrestrial
Field
Dissipation
186 days (bareground, MN)
max 0.13 ppm in 12-18" at day 270
149 days (bareground, CA)
0.56 ppm in 6-12" at day 564
G-28279 and G-30414 (6-
12")
G-28279 (max 0.16 ppm 6-
12" day 269) and G-30414
(max 0.57ppm 18-24" day
564)
40614417
40614418
Unacceptable
Unacceptable
33 days (citrus crop, FL) 0-8"
44 days (bareground, FL) 0-8"
G-28279 (max 0.28 ppm 0-
8" day 19) and G-30414
(max O.Olppm 0-8" day 91)
G-28279 (max 0.39 ppm 0-
8" day 18) and G-30414
(max 0.52ppm 0-8" day 30)
40634201
Unacceptable
26 days (citrus crop, FL) 0-8"
15 days (bareground, FL) 0-8"
G-28279 (max 0.24ppm 0-
8" day 15) and G-30414
(max 1.4ppm 0-8" day 15)
G-28279 (max 0.3 lppm 0-
8" day 15) and G-30414
(max 0.83ppm 0-8" day 31)
40634202
Unacceptable
Supplemental
119 days (raspberries, OR) 0-8"
125 days (bareground, OR) 0-8"
G-28279 (max l.lppmO-
8") and G-30414 (max
<0.09ppm 0-8")
40614413
40614414
Unacceptable
110 days (corn plot, MO) 0-8"
101 days (bareground, MO) 0-8"
G-28279 (max <0.2ppm 0-
8") and G-30414 (max
<0.24ppm 0-8")
40614415
40614416
Unacceptable
480 days (Nebraska) 12-24"
Not analyzed
00027863
Supplemental
25
-------
Table 2.1 Summary of Simazine Environmental Fate Properties
Study
Half-lives, Days
Major Degradates
Minor Degradates
mrii) #
Study Status
Aquatic Field
Dissipation
60 to 700 days in lakes
12 days in GA swimming pool water
53 days in IA man-made pond water
G-28279
G-28279 and G-30414
G-28279 and G-30414
00027829
40614420
40614422
Supplemental
Supplemental
Supplemental
G-28279 = DIA/CEAT; G-28273 = DACT; G-30414 = Hydroxysimazine
ci
Simazine
ci
N^N CHa
HJN''''^N N CHj
Desethyl-s-atrazine (DEA)
c
N^N
HaC^N^N^NH;
Desisiporpyl-s-atrazine (DIA)
Diaminochlorotriazine (DACT)
Figure 2.1 Simazine and Degradate Structures
26
-------
2.4.1 Environmental Transport Mechanisms
Potential transport mechanisms include pesticide surface water runoff, spray drift, and
secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or
more distant ecosystems. Surface water runoff and spray drift are expected to be the
major routes of exposure for simazine.
A number of studies have documented atmospheric transport and re-deposition of
pesticides from the Central Valley to the Sierra Nevada Mountains (Fellers et al., 2004,
Sparling et al., 2001, LeNoir et al., 1999, and McConnell et al., 1998). Prevailing winds
blow across the Central Valley eastward to the Sierra Nevada Mountains, transporting
airborne industrial and agricultural pollutants into the Sierra Nevada ecosystems (Fellers
et al., 2004, LeNoir et al., 1999, and McConnell et al., 1998). Several sections of critical
habitat for the CLRF are located east of the Central Valley. The magnitude of transport
via secondary drift depends on the simazine'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. Therefore, physicochemical properties of simazine that
describe its potential to enter the air from water or soil (e.g., Henry's Law constant and
vapor pressure), pesticide use data, modeled estimated concentrations in water and air,
and available air monitoring data from the Central Valley and the Sierra Nevadas are
considered in evaluating the potential for atmospheric transport of simazine to locations
where it could impact the CRLF.
In general, deposition of drifting or volatilized pesticides is expected to be greatest close
to the site of application. Computer models of spray drift (AgDRIFT and AgDISP) are
used to determine potential exposures to aquatic and terrestrial organisms. Vegetative
vigor toxicity studies show that simazine is equally toxic to monocot and dicot terrestrial
plants, thus the distance of potential impact away from the use sites (action area) is
determined by the distance required to fall below the LOC for these non-target plants.
2.4.2 Mechanism of Action
Simazine is part of the triazine herbicide family (including atrazine, cyanazine,
propazine) and is very effective at inhibiting the photosynthetic process in susceptible
plants by binding to specific sites within the plant's chloroplasts. Specifically, simazine
inhibits photosynthesis via competition with plastoquinone II at its binding site in the
process of electron transport in photosystem II.
2.4.3 Use Characterization
Currently, Syngenta Crop Protection, Inc. is the primary manufacturer of simazine;
however, there are an additional 13 registrants with active registrations. Syngenta Crop
Protection, Inc. supports the majority of the uses (Princep Caliber 90ź, Princepź). Other
registrants and products include Atanor S. A. (Simazina Atanor), Chem-Real Investment
Corp., Ciba, Ltd. (Gesastopź, Princepź), Drexel Chemical Co. (Drexelź Simazine),
27
-------
Helm AG, Makhteshim-Agan (Simanexź), Micro-Flo Co., OXON Italia S.P.A., Platte
Chemical Co., Sanachem (Pty) Ltd., Sanonda Co. Ltd., Sostram Corp. (Sim-Trolź),
Terra International, Inc., and Tecomag (Nezitecź).
Table 2.2 presents the simazine application rates and management practices relevant to
the 2007 growing season in California. Environmental exposures are estimated for
assessed uses of simazine according to the label for the 2007 growing season in order to
be conservative; however, several uses will be cancelled {i.e., all non-residential granular
uses and aerial applications) once the mitigation practices resulting from the 2006 RED
are fully implemented in 2010.
Table 2.2 Simazine Uses Assessed for the CRLF1
Use2
Max. Single Appl.
Rate (lb ai/A)
Max. Number of
Applieation per
Year
Almonds and Nectarines
2
1
Apples, Pears, and Sour Cherries
4
1
Avocados
4
1
Blueberries and (blackberries, boysenberries,
loganberries, and raspberries)
4
1
(liquid and granular)
or
2 + 23
2
Citrus - Grapefruit, Lemon, and Orange
4 or
1
2 + 23
2
Cranberry
4
1
4
1
Filberts or Hazlenut
or
2 + 23
2
Grapes
4.8
1
Macadamia Nuts
4
1
Olives
4
1
Peaches
2
1
28
-------
Table 2.2 Simazine Uses Assessed for the CRLF1
Use2
Max. Single Appl.
Rate (lb ai/A)
Max. Number of
Applieation per
Year
Walnuts
4
1
Corn
2 (sand, silt, and
loam w/ low OM)
1
Apple, Sour Cherry, Peach, and Pear Trees (non bearing
or young trees only)
(Granular only)
8
1
Christmas Tree Plantation for Lumber
5.94
1
Non-Cropland
(Aerial application)
5
1
Tree Plantations
4
1
Tree Nurseries
4
1
Shelterbelts
(Granular)
3
1
Turfgrass (Residential)
(Granular and Liquid)
2
or
1 + 1
2
Turfgrass on Golf courses (Fairways)
(Granular and Liquid)
2
or
1 + 1
2
All applications are tank mixed, except as noted
2
All formulations are liquid ground applications unless otherwise noted as granular or aerial
Second notation corresponds to two applications
A national map (Figure 2.2) showing the estimated poundage of simazine uses across the
United States is provided below. The map was downloaded from a U.S. Geological
Survey (USGS), National Water Quality Assessment Program (NAWQA) website. On
the county level, simazine use is heaviest in the Central Valley of CA, where mostly
almonds, nuts, fruits, and citrus are grown, and in Florida on turf and citrus.
29
-------
Sirnazine Use in Total Pounds per County
Figure 2.2 Simazine Use in Total Pounds per County
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis
of both national- and county-level usage information (Kaul and Jones, 2006) using state-
level usage data obtained from USDA-NASS . Doane (www.doane.com; the full dataset
is not provided due to its proprietary nature), and the California's Department of
Pesticide Regulation Pesticide Use Reporting (CDPR PUR) database4. CDPR PUR is
considered a more comprehensive source of usage data than USDA-NASS or EPA
proprietary databases; therefore, CDPR PUR data were used to obtain county-level
simazine usage data for this California-specific assessment. Four years (2002-2005) of
usage data were included in this analysis. Data from CDPR PUR were obtained for every
pesticide application made on every use site at the section level (approximately one
square mile) of the public land survey system. BEAD summarized these data to the
county level by site, pesticide, and unit treated. Calculating county-level usage involved
3 United States Depart of Agriculture (USDA). National Agricultural Statistics Service (NASS) Chemical
Use Reports provide summary pesticide usage statistics for select agricultural use sites by chemical, crop
and state. See http://www.usda.gov/nass/pubs/estindxl,htm#agchem.
4 The California Department of Pesticide Regulation's Pesticide Use Reporting database provides a census
of pesticide applications in the state. See http://www.cdpr.ca.gov/docs/pur/pumiain.htm.
30
-------
summarizing across all applications made within a section and then across all sections
within a county for each use site and for each pesticide. The county level usage data that
were calculated include: average annual pounds applied, average annual area treated, and
average and maximum application rate across all five years. The units of area treated are
also provided where available.
Between 2002 and 2005, simazine was reportedly used in 53 counties in California. The
principal use was on orchard vineyard crops including oranges, grapes, almonds, and
walnuts. In addition, a non-agricultural use site (rights-of-way) had significant amount
of use with the 6th overall amount of pounds applied. The greatest average usage
(average of pounds applied per commodity across all four years) was to oranges in Tulare
county at roughly 112,000 lbs. By far, the greatest usage of simazine in California is to
oranges at an average of approximately 200,000 lbs annually, followed by wine grapes at
approximately 118,000 lbs annually, table grapes at an approximate average of 112,000
lbs annually, almonds at 60,000 lbs annually, walnuts at approximately 48,000 lbs
annually, rights-of-way at 39,000 lbs annually, avocados at 16,000 lbs annually, lemons
at 15,000 lbs annually, olives at 14,000 lbs annually, and peaches at 11,000 lbs annually.
All remaining crops had less than 10,000 lbs applied annually and several uses had less
than 10 lbs annually (some with only one reported application).
A summary of simazine usage for all California use sites is provided below in Table 2.3.
Table 2.3 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 2002 to 2005 for Currently Registered
Simazine Uses
Site Name
Average
Pounds All
Uses
Avg
App
Rate
All
Uses
Avg
95 th %
App
Rate
Avg
99th%
App
Rate
Avg Max App
Rate
ORANGE
197336.1
2.1
3.3
4.2
7.9
GRAPE, WINE
117984.7
1.3
2.5
3.1
6.4
GRAPE
112477.7
1.4
2.4
2.7
5.6
ALMOND
59756.0
0.9
2.0
2.4
4.0
WALNUT
47506.6
1.5
4.0
5.6
8.3
RIGHTS OF WAY
38686.0
3.3
9.0
9.0
9.0
AVOCADO
16188.5
2.3
3.4
5.8
12.0
LEMON
14916.0
2.1
3.2
4.7
8.7
OLIVE
13975.0
1.4
2.3
2.8
4.7
PEACH
10727.2
1.4
2.0
2.2
3.1
LANDSCAPE MAINTENANCE
9690.3
0.5
0.5
0.5
0.5
NECTARINE
8123.1
2.7
3.2
3.6
4.6
GRAPEFRUIT
5021.9
2.0
3.3
3.7
4.5
PEAR
2530.7
1.7
2.5
4.3
4.3
APPLE
2107.5
1.4
2.0
2.1
2.1
31
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Table 2.3 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 2002 to 2005 for Currently Registered
Simazine Uses
Site Name
Average
Pounds All
Uses
Avg
App
Rate
All
Uses
Avg
95 th %
App
Rate
Avg
99th%
App
Rate
Avg Max App
Rate
UNCULTIVATED NON-AG
1184.2
2.2
3.6
3.8
3.8
N-OUTDR PLANTS IN CONTAINERS
851.7
2.2
4.8
6.5
7.0
PLUM
526.1
1.1
1.7
2.4
2.4
CITRUS
495.8
1.6
2.3
2.5
2.5
FOREST, TIMBERLAND
287.2
4.9
6.9
6.9
6.9
N-GRNHS FLOWER
267.0
3.1
3.7
3.8
3.8
TANGERINE
222.7
3.8
4.3
4.3
4.3
CHERRY
194.1
1.1
1.6
1.6
1.6
N-OUTDR FLOWER
183.3
2.3
4.0
4.4
4.4
UNCULTIVATED AG
159.1
2.0
2.6
2.6
2.6
BLUEBERRY
157.2
1.8
2.2
2.2
2.2
PECAN
118.8
0.9
1.4
1.4
1.4
LETTUCE
108.3
17.3
33.8
33.8
33.8
APRICOT
62.4
0.9
1.4
1.4
1.4
CORN
59.0
1.3
1.4
1.5
1.5
N-GRNHS PLANTS IN CONTAINERS
52.1
2.6
4.6
4.6
4.6
CHRISTMAS TREE
47.4
1.7
2.4
2.4
2.4
BOYSENBERRY
26.6
1.0
1.1
1.1
1.1
RANGELAND
20.5
1.4
1.4
1.4
1.4
PRUNE
17.7
1.4
2.2
2.2
2.2
STRAWBERRY
16.8
1.9
1.9
1.9
1.9
ALFALFA
16.1
1.4
1.7
1.7
1.7
N-OUTDR TRANSPLANTS
7.9
1.7
1.7
1.7
1.7
MINT
7.9
1.8
1.8
1.8
1.8
PERSIMMON
5.6
1.4
1.6
1.6
1.6
CAULIFLOWER
4.0
1.6
1.6
1.6
1.6
NUTS
1.4
3.6
3.6
3.6
3.6
PASTURELAND
1.3
0.4
0.4
0.4
0.4
RASPBERRY
0.8
0.4
0.5
0.5
0.5
TANGELO
0.7
1.0
1.0
1.0
1.0
COTTON
0.5
1.8
1.8
1.8
1.8
OAT
0.4
0.0
0.0
0.0
0.0
KIWI
0.3
0.4
0.4
0.4
0.4
BLACKBERRY
0.2
0.9
0.9
0.9
0.9
32
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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
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 2.2). 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
33
-------
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 2.4 and shown
in Figure 2.3.
Core Areas
USFWS has designated 35 core areas across the eight recovery units to focus their
recovery efforts for the CRLF (see Figure 2.3). Table 2.4 summarizes the geographical
relationship among recovery units, core areas, and designated critical habitat. The core
areas, which are distributed throughout portions of the historic and current range of the
species, represent areas that allow for long-term viability of existing populations and
reestablishment of populations within historic range. These areas were selected because
they: 1) contain existing viable populations; or 2) they contribute to the connectivity of
other habitat areas (USFWS 2002). Core area protection and enhancement are vital for
maintenance and expansion of the CRLF's distribution and population throughout its
range.
For purposes of this assessment, designated critical habitat, currently occupied (post-
1985) core areas, and additional known occurrences of the CRLF from the CNDDB are
considered. Each type of locational information is evaluated within the broader context
of recovery units. For example, if no labeled uses of CHEMX 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 2.4 (currently occupied core areas are bolded). While core areas are
considered essential for recovery of the CRLF, core areas are not federally-designated
34
-------
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.
Table 2.4 California Red-legged Frog Recovery Units with Overlapping Core
Areas and Designated Critical Habitat
Recovery Unit1
(Figure 2.a)
Core Areas2'7 (Figure 2.a)
Critical Habitat
Units 3
Currently
Occupied
(post-1985)
4
Historically
Occupied 4
Sierra Nevada
Foothills and Central
Valley (1)
(eastern boundary is
the 1,500m elevation
line)
Cottonwood Creek (partial)
(8)
--
Feather River (1)
BUT-1A-B
Yuba River-S. Fork Feather
River (2)
YUB-1
--
NEV-16
Traverse Creek/Middle Fork
American River/Rubicon (3)
--
Consumnes River (4)
ELD-1
S. Fork Calaveras River (5)
--
Tuolumne River (6)
--
Piney Creek (7)
--
East San Francisco Bay
(partial)(16)
--
North Coast Range
Foothills and
Western Sacramento
River Valley (2)
Cottonwood Creek (8)
--
Putah Creek-Cache Creek (9)
--
Jameson Canyon - Lower
Napa Valley (partial) (15)
--
Belvedere Lagoon (partial)
(14)
--
Pt. Reyes Peninsula (partial)
(13)
--
North Coast and
North San Francisco
Bay (3)
Putah Creek-Cache Creek
(partial) (9)
--
Lake Berryessa Tributaries
(10)
NAP-1
Upper Sonoma Creek (11)
--
Petaluma Creek-Sonoma
Creek (12)
--
Pt. Reyes Peninsula (13)
MRN-1, MRN-2
Belvedere Lagoon (14)
--
Jameson Canyon-Lower
Napa River (15)
SOL-1
South and East San
Francisco Bay (4)
--
CCS-1A6
East San Francisco Bay
(partial) (16)
ALA-1A, ALA-
IB, STC-1B
--
STC-1A6
South San Francisco Bay
SNM-1A
35
-------
(partial) (18)
Central Coast (5)
South San Francisco Bay
(partial) (18)
SNM-1A, SNM-
2C, SCZ-1
Watsonville Slough- Elkhorn
Slough (partial) (19)
SCZ-2 5
Carmel River-Santa Lucia
(20)
MNT-2
Estero Bay (22)
--
--
SLO-86
Arroyo Grande Creek (23)
--
Santa Maria River-Santa
Ynez River (24)
--
Diablo Range and
Salinas Valley (6)
East San Francisco Bay
(partial) (16)
MER-1A-B,
STC-1B
--
SNB-16, SNB-26
Santa Clara Valley (17)
--
Watsonville Slough- Elkhorn
Slough (partial)(19)
MNT-1
Carmel River-Santa Lucia
(partial)(20)
--
Gablan Range (21)
SNB-3
Estrella River (28)
SLO-1A-B
Northern Transverse
Ranges and
Tehachapi Mountains
(7)
--
SLO-86
Santa Maria River-Santa
Ynez River (24)
STB-4, STB-5,
STB-7
Sisquoc River (25)
STB-1, STB-3
Ventura River-Santa Clara
River (26)
VEN-1, VEN-2,
VEN-3
--
LOS-16
Southern Transverse
and Peninsular
Ranges (8)
Santa Monica Bay-Ventura
Coastal Streams (27)
--
San Gabriel Mountain (29)
--
Forks of the Mojave (30)
--
Santa Ana Mountain (31)
--
Santa Rosa Plateau (32)
--
San Luis Rey (33)
--
Sweetwater (34)
--
Laguna Mountain (35)
--
1 Recovery units designated by the USFWS (USFWS, 2000, pg 49).
2 Core areas designated by the USFWS (USFWS, 2000, pg 51).
3 Critical habitat units designated by the USFWS on April 13, 2006 (USFWS, 2006, 71 FR 19244-19346).
4 Currently occupied (post-1985) and historically occupied core areas as designated by the USFWS
(USFWS, 2002, pg 54).
5 Critical habitat unit where identified threats specifically included pesticides or agricultural runoff
(USFWS, 2002).
6 Critical habitat units that are outside of core areas, but within recovery units.
7 Currently occupied core areas that are included in this effects determination are bolded.
36
-------
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
|__| Recovery Unit Boundaries
Currently Occupied Core Areas
| Critical Habitat
| CNDDB Occurence Sections
County Boundaries o
180 Miles
Figure 2.3 Recovery Unit, Core Area, Critical Habitat, and Occurrence
Designations for CRLF
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 Mojava*
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
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Other Known Occurrences from the CNDDB
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 2.4 depicts CRLF annual reproductive timing.
Figure 2.4 CRLF Reproductive Events by Month
J
F
M
A
M
J
J
A
S
o
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter)
Orange =
Adults and juveniles can be present all year
2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied
specifically, it is assumed that their diet is similar to that of other frog species, with the
aquatic phase feeding exclusively in water and consuming diatoms, algae, and detritus
38
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(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
(Sialis cf. californica), pillbugs (Armadilliadrium vulgare), and water striders (Gerris sp).
The preferred prey species, however, was the sowbug (Hayes and Tennant, 1985). This
study suggests that CRLFs forage primarily above water, although the authors note other
data reporting that adults also feed under water, are cannibalistic, and consume fish. For
larger CRLFs, over 50% of the prey mass may 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
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).
39
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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 2.4.
'Critical habitat' is defined in the ESA as the geographic area occupied by the species at
the time of the listing where the physical and biological features necessary for the
conservation of the species exist, and there is a need for special management to protect
the listed species. It may also include areas outside the occupied area at the time of
listing if such areas are 'essential to the conservation of the species.' All designated
critical habitat for the CRLF was occupied at the time of listing. Critical habitat receives
protection under Section 7 of the ESA through prohibition against destruction or adverse
modification with regard to actions carried out, funded, or authorized by a federal
Agency. Section 7 requires consultation on federal actions that are likely to result in the
destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the
conservation of the species.' Critical habitat designations identify, to the extent known
using the best scientific and commercial data available, habitat areas that provide
essential life cycle needs of the species or areas that contain certain primary constituent
elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to,
space for individual and population growth and for normal behavior; food, water, air,
light, minerals, or other nutritional or physiological requirements; cover or shelter; sites
for breeding, reproduction, rearing (or development) of offspring; and habitats that are
protected from disturbance or are representative of the historic geographical and
ecological distributions of a species. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
40
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Breeding aquatic habitat;
Non-breeding aquatic habitat;
Upland habitat; and
Dispersal habitat.
Further 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 simazine 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 modify 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.
(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.
41
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(6) Alteration or elimination of the CRLFs 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 simazine is expected to directly impact living
organisms within the action area, critical habitat analysis for simazine 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 simazine is likely to encompass considerable portions of the
United States based on the large array of agricultural uses. However, the scope of this
assessment limits consideration of the overall action area to those portions that may be
applicable to the protection of the CRLF and its designated critical habitat within the state
of California. Deriving the geographical extent of this portion of the action area is based
on consideration of the types of effects that simazine may be expected to have on the
environment, the exposure levels to simazine that are associated with those effects, and
the best available information concerning the use of simazine 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 simazine. An analysis of labeled uses and review of available product labels was
completed. Several of the currently labeled uses are special local needs (SLN) uses or are
restricted to specific states and are excluded from this assessment. In addition, a
distinction has been made between food use crops and those that are non-food/non-
agricultural uses. For those uses relevant to the CRLF, the analysis indicates that, for
simazine, the following agricultural uses are considered as part of the federal action
evaluated in this assessment:
Almonds
Nectarines
Apples
Pears
Sour cherries
Avocados
Blueberries
Blackberries
Boysenberries
Loganberries
Raspberries
42
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Citrus
Cranberry
Filbert
Hazelnut
Grapes
Macadamia nuts
Olives
Peaches
Walnuts
Corn
In addition, the following non-food and non-agricultural uses are considered:
Non-bearing apple, cherry, peach, and pear trees
Christmas tree plantations
Non-cropland {i.e., commercial/industrial/institutional premises/highways)
Tree plantations
Tree nurseries
Shelterbelt plantings
Turfgrass on sod farms
Turfgrass on golf courses
Homeowner turf
Following a determination of the assessed uses, an evaluation of the potential "footprint"
of simazine use patterns is determined. This "footprint" represents the initial area of
concern, based on an analysis of available land cover data for the state of California.
The initial area of concern is defined as all land cover types that represent the labeled
uses described above. A map representing all the land cover types that make up the
initial area of concern for simazine is presented in Figure 2.5.
43
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Legend
Recovery units
_j County boundaries
| simazine forest
simazine orchard
simazine agriculture
3 simazine turf
| simazine rights of way
i Kilo meters
0 20 40 80 120 160
Figure 2.5 Initial area of concern, or "footprint" of potential use, for simazine
Once the initial area of concern is defined, the next step is to compare the extent of that
area with the results of the screening-level risk assessment. The screening-level risk
assessment identifies which taxa, if any, are predicted to be exposed at concentrations
above the Agency's Levels of Concern (LOC). The screening-level assessment includes
an evaluation of the environmental fate properties of simazine to determine which routes
of transport are likely to have an impact on the CRLF.
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For simazine, the principal routes of transport away from the application site are expected
to be runoff and spray drift due to its mobility and moderate persistence. However,
simazine has also been documented to occur in air monitoring samples, albeit at low
concentrations, and thus, long-range transport away from the area of application cannot
be precluded. Typically, air monitoring studies do not distinguish the route of transport
associated with the detections. The location of the available air monitoring for simazine
(Majewski, 2002) suggest that these detections are related to nearby sources and are more
likely due to spray drift than long-range transport. Furthermore, the vapor pressure of
simazine suggests that volatilization leading to long-range transport is unlikely.
LOC exceedances are used to describe how far effects may be seen from the initial area
of concern. Factors considered include: spray drift, downstream run-off, atmospheric
transport, etc. Typically, this information is incorporated into GIS and a map of the
action area is created.
The AgDRIFT model (Version 2.01) is used to define how far from the initial area of
concern an effect to a given terrestrial species may be expected. The spray drift analysis
for simazine using the most sensitive terrestrial toxicity endpoint {i.e., terrestrial plants)
suggests that the distance for potential effects from the treated area of concern is beyond
the range of the AgDRIFT model {i.e., 1000 feet). Subsequently, the AgDISP model
(Version 8.15) with the Gaussian extension (used for longer range transport because the
limits of the regular AgDISP model were exceeded) was used to define this distance. The
AgDISP model was run in ground mode using default settings (except for wind speed at
10 mph and release height at 4 feet). Using the Gaussian extension, a maximum spray
drift distance of 8,740 feet was derived. Further detail on the spray drift analysis is
provided in Section 3.2.5.
In addition to the buffered area from the spray drift analysis, the final action area also
considers the downstream extent of simazine that exceeds the LOC (discussed in Section
3.2.6). It should be noted that the action area for simazine is based on the endangered
species LOCs for aquatic and terrestrial plants. However, the portion of the action area
that is relevant to the CRLF is based on the non-listed species LOCs for aquatic and
terrestrial plants because the CRLF does not have an obligate relationship w/plants
The action area for simazine, including the full extent (based on the listed species LOC
for terrestrial plants), is depicted in Figure 2.6. The portion of the action area that is
relevant for the CRLF (based on the non-listed LOC for terrestrial plants) is presented in
Figure 2.7.
45
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Legend
AA downstream extent
Action area (8740ft buffer)
Recovery units
County boundaries
i Kilometers
»23 50 75100
Figure 2.6 Simazine Action Area for the California Red Legged Frog
46
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Legend
Relevant portion of AA (3891ft buffer)
Relevant portion of AA (streams)
Recovery units
_| County boundaries
i Kilo meters
«1S> 50 75100
*4
Figure 2.7 Portion of the Action Area that is Relevant for the California Red Legged
Frog
Subsequent to defining the action area, an evaluation of usage information was conducted
to determine the area where use of simazine may impact the CRLF. This analysis is used
to characterize where predicted exposures are most likely to occur, but does not preclude
use in other portions of the action area. A more detailed review of the county-level use
47
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information was also completed. These data suggest that simazine has historically been
used on a wide variety of agricultural and non-agricultural uses.
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."5 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
simazine (e.g., runoff, spray drift, etc.), and the routes by which ecological receptors are
exposed to simazine (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 simazine is provided in Table 2.5.
5 From U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
48
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Tsihlc 2.5 Assessment l.ndpoinls siml Mesisures of Kcologicsil KITecls
Assessment Endpoint
Measures of Ecological Effects6
Aquatic-Phase CRLF
(Eggs, larvae, juveniles, and adults)11
Direct Effects
1. Survival, growth, and reproduction of CRLF
la. Fathead minnow LC50
lb. Fathead minnow chronic NOAEC
Indirect Effects and Critical Habitat Effects
2. Survival, growth, and reproduction of CRLF
individuals via indirect effects on aquatic prey food
supply (i.e., fish, freshwater invertebrates, non-
vascular plants)
2a. Fathead minnow LC50
2b. Fathead minnow chronic NOAEC
2c. Water flea acute TL50
2d. Water flea chronic NOAEC.
2e. Non-vascular plant (freshwater algae) acute
EC50
3. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat, cover,
food supply, and/or primary productivity (i.e.,
aquatic plant community)
3a. Vascular plant acute EC50 (duckweed)
3b. Non-vascular plant acute EC50 (freshwater
algae)
4. Survival, growth, and reproduction of CRLF
individuals via effects to riparian vegetation
4a. Monocot and dicot seedling emergence EC25
4b. Monocot and dicot vegetative vigor EC25
Terrestrial-Phase CRLF
(Juveniles and adults)
Direct Effects
5. Survival, growth, and reproduction of CRLF
individuals via direct effects on terrestrial phase
adults and juveniles
5a. Mallard duck acute LD50b
5b. Bobwhite quail chronic NOAECb
Indirect Effects and Critical Habitat Effects
6. Survival, growth, and reproduction of CRLF
individuals via effects on terrestrial prey
(i.e.,terrestrial invertebrates, small mammals , and
frogs)
6a. Honey bee oral LD50
6b. Rat acute LD50
6b. Rat chronic NOAEC
6b. Mallard duck acute LD50b
6b. Bobwhite quail chronic NOAEC b
7. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian and upland vegetation)
7a. Monocot EC25 (seedling emergence)
7b. Dicot EC25 (seedling emergence)
a Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult
frogs are considered "aquatic" for the purposes of this assessment because exposure pathways in the water
are considerably different that exposure pathways on land.
b Birds are used as surrogates for terrestrial phase amphibians.
6 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix A.
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2.8.2 Assessment Endpoints for Designated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related
to the use of simazine that may alter the PCEs of the CRLF's critical habitat. PCEs for
the CRLF were previously described in Section 2.6. Actions that may modify critical
habitat are those that alter the PCEs and jeopardize the continued existence of the CRLF.
Therefore, these actions are identified as assessment endpoints. It should be noted that
evaluation of PCEs as assessment endpoints is limited to those of a biological nature {i.e.,
the biological resource requirements for the listed species associated with the critical
habitat) and those for which simazine effects data are available.
Adverse modification to the critical habitat of the CRLF includes, but is not limited to,
the following, as specified by USFWS (2006):
1. Alteration of water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal 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 simazine on critical habitat of the
CRLF are described in Table 2.6. 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).
50
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Table 2.6 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat"
Assessment Endpoint
Measures of Ecological Eft'eet
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.
a. Non-vascular plant acute EC50 (freshwater algae)
b. Distribution of EC25 values for terrestrial monocots
c. Distribution of EC25 values for terrestrial dicots
Alteration in water chemistry/quality including
temperature, turbidity, and oxygen content necessary
for normal growth and viability of juvenile and adult
CRLFs and their food source.
a. Non-vascular plant acute EC50 (freshwater algae)
b. Distribution of EC25 values for terrestrial monocots
c. Distribution of EC25 values for terrestrial dicots
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
a. Fathead minnow LC50
b. Fathead minnow chronic NOAEC
c. Water flea acute TL50
d. Water flea chronic NOAEC.
e. Non-vascular plant (freshwater algae) acute EC50
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
a. Non-vascular plant acute EC50 (freshwater 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
a. Distribution of EC25 values for monocots
b. Distribution of EC25 values for dicots
c. Honey bee oral LD50
d. Rat acute LD50
e. Rat chronic NOAEC
f. Mallard duck acute LD50
g. Bobwhite quail chronic NOAEC
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.
a Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these processes are not
biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.
2.9 Conceptual Model
2.9.1 Risk Hypotheses
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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 simazine to the environment.
The following risk hypotheses are presumed for this endangered species assessment:
Labeled uses of simazine within the action area may directly affect the CRLF by
causing mortality or by adversely affecting growth or fecundity;
Labeled uses of simazine within the action area may indirectly affect the CRLF
by reducing or changing the composition of food supply;
Labeled uses of simazine 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 current range of the species
and designated critical habitat, thus affecting primary productivity and/or cover;
Labeled uses of simazine 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 simazine 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 simazine 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 simazine 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 simazine 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 simazine 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.
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the stressor simazine 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 2.8 and 2.9, respectively, and the conceptual
models for the aquatic and terrestrial PCE components of critical habitat are shown in
Figures 2.10 and 2.11, respectively. Exposure routes shown in dashed lines (long-range
52
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atmospheric transport and groundwater) are not quantitatively considered because the
contribution of those potential exposure routes to potential risks to the CRLF and
modification to designated critical habitat is expected to be negligible.
Figure 2.8 Conceptual Model for Aquatic-Phase of the CRLF
53
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| Simazine applied to agricultural and non-agricultural use sites in California |
Stressor
Figure 2.9 Conceptual Model for Terrestrial-Phase of the CRLF
Figure 2.10 Conceptual Model for Pesticide Effects on Aquatic Component of
CRLF Critical Habitat
54
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Figure 2.11 Conceptual Model for Pesticide Effects on Terrestrial Component of
CRLF Critical Habitat
2.10 Analysis Plan
In order to address the risk hypothesis, the potential for adverse direct and indirect effects
to the CRLF, its prey, and its habitat is estimated. In the following sections, the use,
environmental fate, and ecological effects of simazine are characterized and integrated to
assess the risks. This is accomplished using a risk quotient (ratio of exposure
concentration to effects concentration) approach. Although risk is often defined as the
likelihood and magnitude of adverse ecological effects, the risk quotient-based approach
does not provide a quantitative estimate of likelihood and/or magnitude of an adverse
effect. However, as outlined in the Overview Document (U.S. EPA, 2004), the
likelihood of effects to individual organisms from particular uses of simazine is estimated
using the probit dose-response slope and either the level of concern (discussed below) or
actual calculated risk quotient value.
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model
2.10.1.1 Measures of Exposure
The environmental fate properties of simazine along with available monitoring data
indicate that runoff and spray drift are the principle potential transport mechanisms of
simazine to the aquatic and terrestrial habitats of the CRLF. In this assessment, transport
of simazine through runoff and spray drift is considered in deriving quantitative estimates
of simazine exposure to CRLF, its prey and its habitats. Although simazine has been
detected at low concentrations in air monitoring samples, the available data suggest that
55
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detections are related to nearby sources and are more likely due to spray drift than long-
range transport. In addition, the vapor pressure of simazine suggests that volatilization
leading to long-range transport is unlikely.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of simazine 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 is 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 simazine that may occur in surface water bodies
adjacent to application sites receiving simazine 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 simazine. The measure of
exposure for aquatic species is the l-in-10 year return peak or rolling mean concentration.
The l-in-10 year peak is used for estimating acute exposures of direct effects to the
CRLF, as well as indirect effects to the CRLF through effects to potential prey items,
including: algae, aquatic invertebrates, fish, and frogs. The l-in-10-year 60-day mean is
used for assessing chronic exposure to the CRLF and fish and frogs serving as prey items.
The l-in-10-year 21-day mean is used for assessing aquatic invertebrate chronic
exposure, which are also potential prey items.
Exposure estimates for the terrestrial-phase CRLF and terrestrial invertebrates and
mammals (serving as potential prey) assumed to be in the target area or in an area
exposed to spray drift are derived using the T-REX model (version 1.3.1, 12/07/2006).
This model incorporates the Kenega nomograph, as modified by Fletcher et al. (1994),
which is based on a large set of actual field residue data. The upper limit values from the
nomograph represented the 95th percentile of residue values from actual field
measurements (Hoerger and Kenega, 1972). 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 simazine 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
56
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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 simazine are bound by using the dietary based EECs for
small insects and large insects. In addition, terrestrial exposures from granular
applications (mg ai/square foot) for the CRLF are also estimated using T-REX and an
earthworm fugacity model.
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 simazine 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.
2.10.1.2 Measures of Effect
Data identified in Section 2.8 are used as measures of effect for direct and indirect effects
to the CRLF. Data were obtained from registrant submitted studies or from literature
studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched
in order to provide more ecological effects data and in an attempt to bridge existing data
gaps. ECOTOX is a source for locating single chemical toxicity data for aquatic life,
terrestrial plants, and wildlife. ECOTOX was created and is maintained by the Agency's
Office of Research and Development, and the National Health and Environmental Effects
Research Laboratory's Mid-Continent Ecology Division.
The assessment of risk for direct effects to the terrestrial-phase CRLF makes the
assumption that toxicity of simazine to birds is similar to the terrestrial-phase CRLF. The
same assumption is made for fish and aquatic-phase CRLF. Algae, aquatic invertebrates,
fish, and amphibians represent potential prey of the CRLF in the aquatic habitat.
Terrestrial invertebrates, small mammals, and terrestrial-phase amphibians represent
potential prey of the CRLF in the terrestrial habitat. Aquatic, semi-aquatic, and terrestrial
plants represent habitat of CRLF.
The acute measures of effect used for animals in this screening level assessment are the
LD50, LC50 and 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 LC50 is the concentration of a chemical that is
estimated to kill 50% of the test organisms. EC stands for "Effective Concentration" and
the EC50 is the concentration of a chemical that is estimated to produce a specific effect in
50% of the test organisms. Endpoints for chronic measures of exposure for listed and
non-listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for "No
Ob served-Adverse-Effect-Level" and refers to the highest tested dose of a substance that
has been reported to have no harmful (adverse) effects on test organisms. The NOAEC
57
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{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 EC50 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 agricultural and non-agricultural uses of
simazine, 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 simazine 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 Appendix C).
For this endangered species assessment, listed species LOCs are used for comparing RQ
values for acute and chronic exposures of simazine directly to the CRLF. If estimated
exposures directly to the CRLF of simazine resulting from a particular use are sufficient
to exceed the listed species LOC, then the effects determination for that use is "may
affect". When considering indirect effects to the CRLF due to effects to animal prey
(aquatic and terrestrial invertebrates, fish, frogs, and mice), the listed species LOCs are
also used. If estimated exposures to CRLF prey of simazine resulting from a particular
use are sufficient to exceed the listed species LOC, then the effects determination for that
use is a "may affect." If the acute RQ being considered also exceeds the non-listed
species acute risk LOC, then the effects determination is a LAA. If the RQ is between
the listed species LOC and the non-listed species LOC, then further lines of evidence {i.e.
probability of individual effects, species sensitivity distributions) are considered in
distinguishing between a determination of NLAA and a LAA. When considering indirect
effects to the CRLF due to effects to algae as dietary items or plants as habitat, the non-
listed species LOC for plants is used because the CRLF does not have an obligate
relationship with any particular aquatic and/or terrestrial plant. If the RQ being
considered for a particular use exceeds the non-listed species LOC for plants, the effects
determination is LAA.
3. Exposure Assessment
3.1 Label Application Rates and Intervals
Simazine labels may be categorized into two types: labels for manufacturing uses
(including technical grade simazine and its formulated products) and end-use
products. While technical products, which contain simazine of high purity, are not
used directly in the environment, they are used to make formulated products, which
can be applied in specific areas to control weeds. The formulated product labels
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legally limit simazine's potential use to only those sites that are specified on the
labels.
In the April 2006 RED (U.S. EPA, 2006), EPA stipulated a number of changes to the
use of simazine including label restrictions and other mitigation measures designed to
reduce risk to human health and the environment. The label changes include
cancellation of aerial and non-residential granular uses of simazine. In addition, a
number of other mitigation measures, including rate reductions, cancellations of
certain uses, added spray drift language, and buffer restrictions near streams, rivers,
lakes, and reservoirs are proposed. These proposed mitigation measures are expected
to become final in 2010. Of the proposed mitigation measures relevant to this
assessment that are expected to become final in 2010, all aerial applications and non-
residential granular uses will be cancelled in California and spray drift and buffer
restriction language will be added to the labels. The proposed spray drift language
includes specific application restrictions for wind speed (<10 mph), droplet size
(coarse or coarser ASAE standard 572 spray), and release height (nozzle height no
more than 4 feet above ground or crop canopy). The proposed buffer restrictions
prohibit application of simazine within 66 feet of streams and rivers and 200 feet of
lakes and reservoirs.
Currently registered non-agricultural uses of simazine within the CRLF action area
include dormant fruit, tree plantations and nurseries, shelterbelts, Christmas trees, turf
(residential, recreational, and sod farm), and non-cropland areas defined as industrial
sites, highway medians, rights-of-way, lumberyards, tank farms, fuel storage areas,
and fence lines. Agricultural uses within the CRLF action area include fruit and nut
crops such as apples, oranges, grapes, berries, peaches, nectarines, avocados, olives,
almonds, macadamia nuts, and walnuts in addition to corn. The uses being assessed
are summarized in Table 3.1.
Simazine is formulated as liquid, water dispersible granules, wettable powder,
emulsifiable concentrate, and granular formulations. Application equipment for the
agricultural uses includes ground application (the most common application method),
aerial application, band treatment, incorporated treatment, various sprayers (low-
volume, hand held, directed), and spreaders for granular applications. Risks from
ground boom and aerial applications are considered in this assessment because they
are expected to result in the highest off-target levels of simazine due to generally
higher spray drift levels. Ground boom and aerial modes of application tend to use
lower volumes of application applied in finer sprays than applications coincident with
sprayers and spreaders and thus have a higher potential for off-target movement via
spray drift.
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Table 3.1 Simazine Uses, Scenarios, and Application Information for the CRLF risk assessment1
Scenario
Uses Represented
Application Rate2
Number of
Application Interval
by Scenario
Applications
CA almond
Filbert
4 lbs
1
NA
Hazelnut
Macadamia nut
Walnut
CA almond
Almond
2 lbs
1
NA
CA fruit
Apple
4 lbs
1
NA
Cherry
Pear
CA fruit
Nectarine
2 lbs
1
NA
Peach
CA fruit
Non-food on
8 lbs
1
NA
Apple
(granular only)
Cherry
(0 lbs Post-RED)
Peach
Pear
CA strawberry or
Blueberry
4 lbs
1
NA
CA wine grapes
Blackberry
(liquid and granular)
Boysenberry
(0 lbs for granular Post-
Longanberry
RED)
Raspberry
Cranberry
CA avocado
Avocado
4 lbs
1
NA
CA citrus
Grapefruit
4 lbs
1
NA
Lemon
Orange
CA grapes
Grapes
4.8 lbs
1
NA
(4.0 lbs Post-RED)
CA olives
Olives
4 lbs
1
NA
CA corn
Corn
2 lbs
1
NA
CA forestry
Tree plantations
4 lbs
1
NA
CA nursery
Tree nurseries
4 lbs
1
NA
CA forestry
Christmas trees
5.94 lbs
1
(4 lbs Post-RED)
(2 apps Post-RED)
CA fruit
Shelterbelts
3 lbs (granular only)
1
NA
(0 lbs Post-RED)
CAturf
Sod farm
1 lbs (liquid and granular)
2
Assumed 30 days between
Golf course
1 lbs (liquid and granular)
applications
CA residential
Homeowner turf
1 lbs (liquid and granular)
2
Assumed 30 days between
1 lbs (liquid and granular)
applications
CA right of way
Non-cropland
5 lbs (aerial)
1
NA
(0 lbs Post-RED)
1 Uses assessed based on memorandum from SRRD dated August 27, 2007.
2 All uses modeled by ground applications unless otherwise noted as granular or aerial.
60
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3.2 Aquatic Exposure Assessment
For Tier 2 surface-water assessments, two models are used in tandem. PRZM simulates
fate and transport on the agricultural field. The version of PRZM (Carsel et al., 1998)
used was PRZM 3.12 beta, dated May 24, 2001. The water body is simulated with
EXAMS version 2.98, dated July 18, 2002 (Burns, 1997). Tier 2 simulations are run for
multiple (usually 30) years and the reported EECs are the concentrations that are
expected once every ten years based on the thirty years of daily values generated by the
simulation. PRZM and EXAMS were run using the PE4 shell, dated May 14, 2003,
which also summarizes the output. Spray drift was simulated using the AgDRIFT model
version 2.01 dated May 24, 2001.
3.2.1 Modeling Approach
Aquatic exposures are quantitatively estimated for all of assessed uses using scenarios
that represent high exposure sites for simazine use. Each of these sites represents a 10
hectare field that drains into a 1-hectare pond that is 2 meters deep and has no outlet.
Exposure estimates generated using the standard pond are intended to represent a wide
variety of vulnerable water bodies that occur at the top of watersheds including prairie
pot holes, playa lakes, wetlands, vernal pools, man-made and natural ponds, and
intermittent and first-order streams. As a group, there are factors that make these water
bodies more or less vulnerable than the standard surrogate pond. Static water bodies that
have larger ratios of drainage area to water body volume would be expected to have
higher peak EECs than the standard pond. These water bodies will be either shallower or
have large drainage areas (or both). Shallow water bodies tend to have limited additional
storage capacity, and thus, tend to overflow and carry pesticide in the discharge whereas
the standard pond has no discharge. As watershed size increases beyond 10 hectares, at
some point, it becomes unlikely that the entire watershed is planted to a single crop,
which is all treated with the pesticide. Headwater streams can also have peak
concentrations higher than the standard pond, but they tend to persist for only short
periods of time and are then carried downstream.
All of the modeled scenarios assume 100% of the watershed is treated simultaneously,
with the exception of the residential turf uses. In modeling the residential turf scenario, it
is assumed that no more than 50% of a typical residential site is covered in turf; therefore,
the modeled EECs for these uses are reduced by a factor of 50%. Further details on the
rationale for the residential turf modeling assumptions has been described in several
previously conducted assessments (U.S. EPA, 2007a and b).
Crop-specific management practices for all of the assessed uses of simazine were used
for modeling, including application rates, number of applications per year, application
intervals, buffer widths and resulting spray drift values modeled from AgDRIFT and
AgDISP, and the first application date for each crop. The date of first application was
61
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developed based on several sources of information including data provided by BEAD, a
summary of individual applications from the CDPR PUR data, and crop profiles
maintained by the USDA. A sample of the distribution of simazine applications to grapes
from the CDPR PUR data for 2005 used to pick a March 1 application date is shown in
Figure 3.1.
2500
2000
500
j --J
4ml
Figure 3.1 Summary of Applications of Simazine to Grapes in 2005 from CDPR
PUR data.
More detail on the crop profiles and the previous assessments may be found at:
http://pestdata.ncsu.edu/cropprofiles/cropprofiles.cfm
3.2.2 Model Inputs
Simazine is a triazine herbicide used on a wide variety of food and non-food crops.
Simazine environmental fate data used for generating model parameters is listed in Table
2.2. The input parameters for PRZM and EXAMS are in Table 3.2.
Table 3.2 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Simazine Endangered Species Assessment for the CRLF
Fate Property Value MRID (or source)
Molecular Weight 202 g/mole Product Chemistry
62
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Table 3.2 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Simazine Endangered Species Assessment for the CRLF
Fate Property
Value
MRID (or source)
Henry's constant
3.2x 10"10 Pa m3 / mole
Product Chemistry
Vapor Pressure
6.1 x 1(T9 torr
Product Chemistry
Solubility in Water
3.5 ppm
Product Chemistry
Photolysis in Water
stable
00143171
42503708
Aerobic Soil Metabolism Half-lives
ti/2 = 130 days
(upper 90th percentile confidence
bound on mean half-life of 110 and
91 days)
00158638
43004501
Hydrolysis
stable
00027856
Aerobic Aquatic Metabolism (water
column)
Anaerobic Soil Metabolism (benthic)
ti/2 =213 days
(input value is three times the
single laboratory aerobic aquatic
metabolism half-life of 71 days)
ti/2 = 168 days
(input value is three times the
single laboratory anaerobic aquatic
metabolism half-life of 56 days)
43004502
40614411
Koc
123 (average of 152.5, 123.3, 114,
and 102.7)
41442903
41257903
Application Efficiency
Spray Drift Fraction1
95 % for aerial
99 % for ground
5 % for aerial
1 % for ground
default value2
default value2
1 - Spray drift not included in final EEC due to edge-of-field estimation approach
2 - Inputs determined in accordance with EFED "Guidance for Chemistry and Management Practice Input Parameters
for Use in Modeling the Environmental Fate and Transport of Pesticides " dated February 28, 2002
3.2.3 Results
The aquatic EECs for the various scenarios and application practices are listed in Table
3.3. Estimated aquatic exposures are highest for simazine use on Christmas trees with
peak EEC of 130.2 |ig/L. The use with the next highest peak exposure concentration is
based on liquid applications on berries with peak EEC of 108.4 |ig/L, followed by
granular use on berries, tree plantations, tree nurseries, non-cropland, dormant fruit, and
avocados with 103 |ig/L, 88.0 |ig/L, 68.2 |ig/L, 66.0 |ig/L, 61.5 |ig/L, and 53.5 |ig/L
respectively. All other modeled simazine uses yield peak exposure concentrations below
50 |ig/L.
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Table 3.3 Aquatic EECs (jig/L) for Simazine Agricultural and Non-agricultural Uses in California
Scenario1
Application
Rate2
Date of First
Application
Crops
Represented
Peak
EEC
4-dav
average
EEC
21-day
average
EEC
60-dav
average
EEC
90-day
average
EEC
CA almond
(high rate)
4 lbs
December 1
Filbert
Hazelnut
Macadamia nut
Walnut
25.6
25.5
25.0
20.6
20.2
CA almond
(low rate)
2 lbs
December 1
Almond
12.8
12.7
12.5
10.3
10.1
CA fruit
(high rate)
4 lbs
March 1
Apple
Cherry
Pear
11.1
11.1
10.9
10.5
10.2
CA fruit
(low rate)
2 lbs
March 1
Nectarine
Peach
5.6
5.5
5.4
5.3
5.1
CA fruit
(dormant)
8 lbs
(granular)
(0 lbs Post-
RED)
December 1
Non-food on
Apple
Cherry
Peach
Pear
61.5
61.2
59.8
51.5
50.6
CA
strawberry
4 lbs
(granular)
(0 lbs Post-
RED)
December 1
Blueberry
Blackberry
Boysenberry
Longanberry
Raspberry
Cranberry
103.4
102.5
100.5
81.9
79.4
CA
strawberry
4 lbs
(liquid)
December 1
Blueberry
Blackberry
Boysenberry
Longanberry
Raspberry
Cranberry
108.4
107.4
105.4
86.3
83.7
CA avocado
4 lbs
December 1
Avocado
53.5
53.1
51.9
33.5
32.5
CA citrus
4 lbs
December 1
Grapefruit
Lemon
Orange
7.1
7.0
6.9
6.5
6.4
CA grapes
4.8 lbs
(4.0 lbs Post-
RED)
March 1
Grapes
18.2
18.1
17.6
16.7
16.0
CA olives
4 lbs
December 1
Olives
33.9
33.7
29.9
28.9
28.0
CA corn
2 lbs
April 1
Corn
12.3
12.2
11.9
11.3
10.8
CA forestry
4 lbs
December 1
Tree
Plantations
88.0
87.5
85.6
61.6
60.0
CA forestry
5.94 lbs
(4 lbs Post-
RED w/2
apps)
December 1
Christmas trees
130.2
130.1
127.2
91.4
89.1
CA nursery
4 lbs
December 1
Tree nurseries
68.2
67.9
66.3
39.7
38.6
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Table 3.3 Aquatic EECs (jig/L) for Simazine Agricultural and Non-agricultural Uses in California
Scenario1
Application
Rate2
Date of First
Application
Crops
Represented
Peak
EEC
4-dav
average
EEC
21-day
average
EEC
60-dav
average
EEC
90-day
average
EEC
CA fruit
3 lbs
(granular)
(0 lbs Post-
RED)
December 1
Shelterbelts
12.0
11.9
9.3
8.9
8.6
CAturf
libs
(2 liquid apps
w/ 30 day
interval)
March 1
Sod farm
Golf course
8.8
8.7
8.6
8.4
8.3
CAturf
libs
(2 granular
apps w/30
day interval)
March 1
Sod farm
Golf course
6.6
6.6
6.5
6.4
6.2
CA
residential
libs
(2 liquid apps
w/ 30 day
interval)
March 1
Homeowner
turf
5.2
5.2
5.2
5.0
4.9
CA
residential
libs
(2 granular
apps w/30
day interval)
March 1
Homeowner
turf
4.3
4.2
4.2
4.1
4.0
CA right of
way
5 lbs (aerial)
(0 lbs Post-
RED)
March 1
Non-cropland
(commercial,
industrial,
institutional
premises,
equipment,
highways)
66.04
65.41
64.59
62.12
60.57
1 All uses modeled with ground application (unless otherwise noted) based on current labels and do not
include post-RED mitigations
2 All uses modeled with one application unless otherwise noted
3.2.4 Existing Monitoring Data
A critical step in the process of characterizing EECs is comparing the modeled estimates
with available surface water monitoring data. Simazine has a limited set of surface water
monitoring data relevant to the CRLF assessment. Most of this data is non-targeted (i.e.,
study was not specifically designed to capture simazine concentrations in high use areas).
Included in this assessment are simazine data from the USGS NAWQA program
(http://water.usgs.gov.nawqa) and data from the California Department of Pesticide
Regulation (CDPR). In addition, air monitoring data for simazine are summarized.
These monitoring data are characterized in terms of general statistics including number of
samples, frequency of detection, maximum concentration, and mean from all detections,
where that level of detail is available.
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3.2.4.1 USGS NAWQA Surface Water Data
Surface water monitoring data from the United States Geological Survey (USGS)
NAWQA program was accessed on June 28, 2007 and all data for the state of California
were downloaded. A total of 2,004 water samples were analyzed for simazine. Of these
samples, simazine was detected in 1,756 samples (196 were estimated either above or
below the range of quantitation) with a frequency of detection of 88%. The maximum
concentration detected was 64.5 |j,g/L in Mustang Creek near Monpelier in Merced
County in 2004. Two additional samples from the same site (also from the same runoff
event in 2004) were above 50 |_ig/L, while a total of 35 sites (all but one sample collected
since 2000) were above 10 |_ig/L, and 117 samples were above 1 |~ig/L. No clear pattern
in simazine detections from different use sites is evident because simazine was detected
in a number of different types of watersheds (agricultural, urban, mixed and other) as
classified by the USGS land use information. The average concentration of all samples
was 0.67 |j,g/L while the average concentration of all detections was 0.76 |_ig/L.
3.2.4.2 USGS NAWQA Groundwater Data
Groundwater monitoring data from the United States Geological Survey (USGS)
NAWQA program were accessed on June 28, 2007 and all data for the state of California
was downloaded. A total of 674 water samples were analyzed for simazine. Of these
samples, simazine was detected in 288 samples (39 were estimated either above or below
the range of quantitation) with a frequency of detection of 43%. The maximum
concentration detected was 0.5 |j,g/L from a groundwater well in Merced County. As
with the surface water data, there was no clear pattern associated with use sites as the
NAWQA detections were from different types of watersheds (agricultural, urban, mixed
and other) as classified by the USGS land use information. The average concentration of
all samples was 0.024 |j,g/L while the average concentration of all detections was 0.049
Hg/L.
3.2.4.3 California Department of Pesticide Regulation (CPR) Data
Surface water monitoring data was accessed from the California Department of Pesticide
regulation (CDPR) on June 28, 2007 and all data with analysis for simazine were
extracted. A total of 4,053 samples were available. Of these samples, simazine was
detected in 1,988 samples for a frequency of detection of 49%. The maximum
concentration was 36.1 |j,g/L in 2002 from the USGS site at Mustang Creek (this is the
same site as the peak concentration from the USGS NAWQA data). The maximum
concentration from a site not included in the USGS data was 22.7 |j,g/L from the Highline
Spillway in Merced County from 2002. Of all samples, only 68 were detected at
concentrations above 1 |_ig/L and most of these were from Merced, San Joaquin, and
Stanislaus Counties. There was no monitoring data for degradates of simazine from the
CDPR data.
66
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3.2.4.4 Atmospheric Monitoring Data
Available monitoring data for simazine in air and rainfall were evaluated to provide
context to the evaluation of the extent of action area and estimated concentrations in
surface water. Based on the available information (Majewski et al., 2000; Majewski and
Capel, 1995; Capel et al., 1994, McConnell, et al, 2004, Kuang, et al, 2003, Foreman, et
al, 1999, Dubus, et al, 2000), simazine has been detected in rainwater and air samples
across the United States. In general, simazine has been detected in some studies at
variable frequency of detections but in general, detections in rainfall have been below 1
l_ig/L (Makjewski, et al 2002, Kuang, et al, 2003, Dubus, et al, 2000). Often there is a
lack of ancillary data in these studies to determine whether these detections are due to
spray drift or longer-range transport due to volatilization. However, given that most of
the studies focus on major agricultural locations, that simazine has not been detected in
any of the studies conducted at higher elevations, coupled with the relatively low
volatility of simazine, it is expected that many of these detections are reflective of near
field (spray drift) exposure and are not indicative of long-range transport. The
concentrations detected in the reviewed studies suggest that transport of simazine via
atmospheric transport will yield exposures well below those predicted by modeling.
3.2.5 Spray Drift Buffer Analysis
In order to determine terrestrial and aquatic habitats of concern due to simazine
exposures through spray drift, it necessary to estimate the distance that spray applications
can drift from the treated field and still be present at concentrations that exceed levels of
concern. An analysis of spray drift distances was completed using all available tools,
including AgDRIFT, AgDISP, and the Gaussian extension to AgDISP. For simazine use
relative to the terrestrial-phase CRLF, the results of the screening-level risk assessment
indicate that spray drift using the most sensitive endpoints for terrestrial plants exceeds
the 1,000 foot range of the AgDrift model for the Tier I ground mode (no higher tier
modeling for ground applications is available in AgDrift). Subsequently, the AgDISP
model with the Gaussian extension (for longer range transport because the extent of the
regular AgDISP model was exceeded) was used to evaluate potential distances beyond
which exposures would be expected to be below LOC.
The AgDISP model was run in ground mode and aerial mode (for non-cropland use only)
with the following settings beyond the standard default settings.
20 gal/acre spray volume rate (label specific)
4 ft release height (label specific)
15 ft release height for aerial applications (label specific)
10 mph limitation (label specific)
Very fine to fine spectrum (default value)
No canopy
Nonvolatile fraction of 0.075 (for 5.94 lb ai/A), 0.0625 (for 5 lb ai/A), 0.06 (for
4.8 lb ai/A), 0.05 (for 4 lb ai/A), and 0.025 (for 2 lb ai/A)
67
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Volatile fraction of 0.0314 (for 5.94 lb ai/A), 0.0262 (for 5 lb ai/A), 0.0251 (for
4.8 lb ai/A), 0.021 (for 4 lb ai/A), and 0.0105 (for 2 lb ai/A)
For the terrestrial phase, an analysis was conducted using the most sensitive terrestrial
endpoint, the terrestrial plant NOAEC of 0.0018 lbs ai/acre. This distance identifies
those locations where terrestrial landscapes can be impacted by spray drift deposition
alone (no runoff considered) at concentrations above the listed species LOC for terrestrial
plants. The LOC was compared to the highest RQ for aerial applications to non-cropland
at 5.0 lbs ai/acre. In this analysis, the most sensitive endpoint was the NOAEC of 0.0018
lbs ai/A (0.002016 kg/hectare), which yielded a terrestrial spray drift distance of 8,740
feet. Similar analysis was conducted for application rates of 4.8 lbs ai/acre (grapes), 4 lbs
ai/acre (fruit, berries, avocado, citrus, olives, and forestry), and 2 lbs ai/acre (almonds,
fruit, corn, and turf). Each lower application rate yields a lower buffer distance. These
distances represent the maximum extent where effects are possible using the most
sensitive data and the endangered species LOC for plants (1.0).
In order to characterize the portion of the action area that is relevant to the CRLF and
specific to the area where the effects determination {i.e. NLAA versus LAA) will be
made, a similar analysis was conducted using the most sensitive non-endangered plant
EC25 of 0.009 lbs ai/acre. Typically the NOAEC is used when there is an obligate
relationship between the species being assessed and endangered plants (or other taxa).
However, there is no obligate relationship between the CRLF and any endangered plant;
therefore the LAA/NLAA determination is based on the area defined by the non-listed
species LOC {i.e., EEC/ECso)- Using the same approach described above, the maximum
distance for the aerial use of simazine on non-cropland at 5.0 lbs ai/acre is 3,891 feet with
reductions in distance for lower application rates. A summary of the modeled distances
by application rate is presented in Table 3.4.
Table 3.4 Summary of AgDISP Predicted Terrestrial Spray Drift Distances
Application Rate
(method)
Uses Represented
NOAEC
Distance (ft)
ec2S
Distance (ft)
5.0 (aerial)
Non-cropland
8740
3891
5.94 (ground)
Christmas trees
5770
2765
4.8 (ground)
Grapes
4540
2628
4 (ground)
Apples, Pears, Sour Cherries,
Avocados, Berries, Citrus,
Filberts, Hazelnuts,
Macadamia Nuts, Olives,
Walnuts, Tree Plantations,
and Tree Nurseries
4032
2523
2 (ground)
Almonds, Nectarines,
Peaches, Corn, and Turf
3110
2198
Given that the greatest buffer distance is 8,740 feet for terrestrial plants, this value was
used to define the action area {i.e., this buffer distance is added to the initial area of
concern depicted in Figure 2.5). The action area (based on the buffer distance of 8,740
feet) and the portion of the action area that is relevant to the CRLF (based on impacts to
terrestrial plants at the non-listed LOC and a corresponding buffer distance of 3,891 feet)
68
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is shown in Figure 2.6.
Similar to the analysis described above (except that only AgDRIFT was needed), the
buffer distance needed to get below the most sensitive aquatic LOC was determined.
This distance identifies those locations where water bodies can be impacted by spray drift
deposition alone (no runoff considered) resulting in concentrations above the LOC. The
most sensitive aquatic endpoint is for aquatic non-vascular plants (blue green algae) with
NOAEC and EC50 values of 5.4 and 36 |ig/L, respectively. The analysis yields a much
lower buffer distance than the terrestrial buffer with a distance of 135 feet (based on the
non-listed LOC using the EC50 value). The results of the analysis are presented in Table
3.5.
Table 3.5 Summary of AgDRI FT Predicted Aquatic Spray Drift Distances
Application Rate
(method)
Uses Represented
NOAEC
Distance (ft)
ECS0
Distance (ft)
5.0 (aerial)
Non-cropland
>1,000
135
5.94
Christmas trees
6.56
0
4.8
Grapes
3.28
0
4
Apples, Pears, Sour Cherries,
Avocados, Berries, Citrus,
Filberts, Hazelnuts,
Macadamia Nuts, Olives,
Walnuts, Tree Plantations,
and Tree Nurseries
3.28
0
2
Almonds, Nectarines,
Peaches, Corn, and Turf
0
0
3.2.6 Downstream Dilution Analysis
The final step in defining the action area is to determine the downstream extent of
exposure in streams and rivers where the EEC could potentially be above levels that
would exceed the most sensitive LOC. To complete this assessment, the greatest ratio of
aquatic RQ to LOC was estimated. Using an assumption of uniform runoff across the
landscape, it is assumed that streams flowing through treated areas {i.e. the initial area of
concern) are represented by the modeled EECs; as those waters move downstream, it is
assumed that the influx of non-impacted water will dilute the concentrations of simazine
present. The use of the "RQ to LOC ratio" provides information on the concentration
that must be reached in downstream water to be below the LOC. Therefore, the analysis
defines the point were the percentage of treated area with the watershed would yield
sufficient non-impacted water to dilute the EECs to concentrations below the LOC.
Further details on this approach are provided in Appendix D.
Using a NOAEC for non-vascular aquatic plants (the most sensitive species) of 5.4 ug/L
and a maximum peak EEC for applications to Christmas trees of 130 ug/L yields an
RQ/LOC ratio of 24 (24/1). Using the downstream dilution approach (described in more
detail in Appendix D) yields a target percent crop area (PCA) of 27.8%. This value has
been input into the downstream dilution approach and results in a total of 18,704
kilometers of stream downstream from the initial area of concern (footprint of use). By
69
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way of comparison, there are 199,830 kilometers of streams within the initial area of
concern, all of which are assumed to be at the modeled EEC. Similar to the spray drift
buffer described above, the LAA/NLAA determination is based on the area defined by
the point where concentrations exceed the EC50 value, in this case 36 ug/L (also for non-
vascular aquatic plants). Applying the same approach to downstream extent yields a
RQ/LOC ratio of 3.6 (3.6/1) which equates to a downstream dilution factor of 4.2% and
adds a total of 10,885 kilometers to the initial area of concern.
3.3 Terrestrial Animal Exposure Assessment
T-REX (Version 1.3.1) is used to calculate dietary and dose-based EECs of simazine for
the CRLF and its potential prey (e.g. small mammals and terrestrial insects) inhabiting
terrestrial areas. EECs used to represent the CRLF are also used to represent exposure
values for frogs serving as potential prey of CRLF adults. T-REX simulates a 1-year time
period. For this assessment, spray and granular applications of simazine are considered,
as discussed in Sections 3.3.1 and 3.3.2 below.
3.3.1 Spray Applications
Terrestrial EECs for non-granular formulations of simazine were derived for the uses
summarized in Table 3.4. Given that no data on interception and subsequent dissipation
from foliar surfaces is available for simazine, a default foliar dissipation half-life of 35
days is used based on the work of Willis and McDowell (1987). Use-specific input
values, including number of applications, application rate and application interval are
provided in Table 3.6. An example output from T-REX is available in Appendix E.
Table 3.6 1 nput Parameters lor Koliar Applications I setl to Derive
Terrestrial KKCs lor Simazine with l -UK\
I sc (Application method)
Application r;ilc
(lbs ;ii/.\)
Number of
Applications
Christmas trees (ground)
5.94
1
Non-cropland (aerial)
5
1
Grapes (ground)
4.8
1
Apples, Pears, Sour Cherries, Avocados,
Berries, Citrus, Filberts, Hazelnuts,
Macadamia Nuts, Olives, Walnuts, and Tree
Plantations, Tree Nurseries (ground)
4
1
Almonds, Nectarines, Peaches, and Corn
(ground)
2
1
Turf (ground)
1
2
T-REX is also used to calculate EECs for terrestrial insects exposed to simazine. Dietary-
based EECs calculated by T-REX for small and large insects (units of a.i./g) are used to
bound an estimate of exposure to bees. Available acute contact toxicity data for bees
exposed to simazine (in units of |ig a.i./bee), are converted to |ig a.i./g (of bee) by
70
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multiplying by 1 bee/0.128 g. The EECs are later compared to the adjusted acute contact
toxicity data for bees in order to derive RQs.
For modeling purposes, exposures of the CRLF to simazine through contaminated food
are estimated using the EECs for the small bird (20 g) which consumes small insects.
Dietary-based and dose-based exposures of potential prey are assessed using the small
mammal (15 g) which consumes short grass. Upper-bound Kenega nomogram values
reported by T-REX for these two organism types are used for derivation of EECs for the
CRLF and its potential prey (Table 3.7). Dietary-based EECs for small and large insects
reported by T-REX as well as the resulting adjusted EECs are available in Table 3.8. An
example output from T-REX v. 1.3.1 is available in Appendix E.
Tahlc3.7 Ippcr-houml kcncgn \oino«r;mi KIX's lor Diclsirv- iind Dosc-hsiscd
Kxposurcs of the CUM'' :iihI ils Prcv lo Sinm/inc
r.r.Cs lor ( Rl.l-
I'.r.Cs lor Pro
(sniiill niiiimiiiils)
I SO
l)ic(;ir\-bused
II. ( ippni)
Dnsc-hiiscri I'.IK
(mg/kg-lm)
l)ic(;ir\-bused
I I.( ippni)
Doso-hiisod r.r.c
(in )
Christmas trees
802
913
1,426
1,359
Non-cropland
675
769
1200
1144
Grapes
648
738
1,152
1,098
Apples, Pears, Sour Cherries,
Avocados, Blueberries,
Citrus, Filberts, Hazelnuts,
Macadamia Nuts, Olives,
Walnuts, and Tree
Plantations, and Tree
Nurseries
540
615
960
915
Almonds, Nectarines,
Peaches, and Corn
270
308
480
458
Turf
135
154
240
229
Til hie 3.S KKCs (ppm) lor Indirect KITccls l<> (lie Torreslriiil-Phiiso (Kl.l-
vin KITocls lo Torres! rinl Invcrlohriilc Prcv llcms
I SO
Sill ;i 11 Insect
l.iiriie Insect
Christmas trees
802
89
Non-cropland
675
75
Grapes
648
72
Apples, Pears, Sour Cherries, Avocados, Blueberries,
Citrus, Filberts, Hazelnuts, Macadamia Nuts, Olives,
Walnuts, and Tree Plantations, and Tree Nurseries
540
60
Almonds, Nectarines, Peaches, and Corn
270
30
Turf
135
15
71
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3.3.2 Granular Applications
Terrestrial exposures from granular applications (mg ai/square foot) for the CRLF are
also estimated using the T-REX Version 1.3.1. Broadcast treatment of simazine-treated
granules assumes that 100% of the granules are unincorporated on the ground. Risk to
terrestrial animals from ingesting granules is based on LD50/ft2 values. Although the
habitat of the CRLF and its prey items are not limited to a square foot, there is
presumably a direct correlation between the concentration of a pesticide in the
environment (mg/ft2) and the chance that an animal will be exposed to a concentration
that could adversely affect its survival. Further description of the mg/ft2 index is
provided in U.S. EPA (1992 and 2004).
In order to derive an estimate of the granular exposure per square foot, the granular
application rates for simazine were converted from lb ai/A to mg/ft2in Table 3.9 using
the following equation: mg/ft2 EEC = (application rate in lb ai/A x 453,590 mg/lb) /
4,560 ft2/A). The LD50/ft2 values are calculated using the avian toxicity value (adjusted
LD50 of the assessed animal and its weight classes) as a surrogate for the terrestrial-phase
CRLF and the EEC (mg ai/ft2).
Table 3.9 Terrestrial EECs for Granular Uses of Simazine
Use
Application Rate
(lb ai/A)
Number of
Applications
EEC
(mg/ft2)
Non-bearing Fruit
8
1
83.3
Berries
4
1
41.7
Shelterbelts
3
1
31.2
Turf
1
2
10.4
Uncertainties associated with use of the T-REX model to estimate risk to the terrestrial-
phase of the CRLF based on ingestion of simazine granules are discussed in Section
6.2.4.
3.4 Terrestrial Plant Exposure Assessment
TerrPlant (Version 1.1.2) 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 3.10).
A runoff value of 0.01 is utilized based on simazine's solubility, which is classified by
TerrPlant as <10 mg/L. For aerial, ground, and granular application methods, drift is
assumed to be 5%, 1% and 0%, respectively. Soil incorporation is assumed to be 1 for
both ground and granular applications. EECs relevant to terrestrial plants consider
pesticide concentrations in drift and in runoff. These EECs are listed by use in Table
3.10. An example output from TerrPlant v. 1.2.2 is available in Appendix F.
72
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Tiihle3.IO Terrl'lnnl Inputs ;iihI Resulting KIX s lor Plnnts Inhiihiling Dry ;iikI Semi-;i(|iiiilic
A ions Kxposeri to Simn/ine vi;i KunolTnml Drift
I SO
Application
I'illO
(lbs ii.i./A)
Application
method
Drill
Value
Sprsij «lrill
li.(
(lbs ii.i./A)
l)r\ aivii
II. (
(lbs ii.i./A)
Scini-iKpiiilic
;ircii r.r.c
I Ills ii.i./A)
Christmas trees
5.94
Foliar - ground
1
0.059
0.119
0.653
Non-cropland
5
Foliar - aerial
5
0.25
0.3
0.75
Grapes
4.8
Foliar - ground
1
0.048
0.096
0.528
Apples, Pears, Sour
Cherries, Avocados,
Blueberries, Citrus,
Filberts, Hazelnuts,
Macadamia Nuts,
Olives, Walnuts, Tree
Plantations, and Tree
Nurseries
4
Foliar - ground
1
0.04
0.08
0.44
Almonds, Nectarines,
Peaches, Corn, and
Turf1
2
Foliar - ground
1
0.02
0.04
0.22
Non-bearing Fruit
8
Granular
0
0
0.08
0.8
Berries
4
Granular
0
0
0.04
0.4
Shelterbelts
3
Granular
0
0
0.03
0.3
Turf1
2
Granular
0
0
0.02
0.2
1 The TerrPlant model considers only exposures to plants from single pesticide applications. Although simazine use on turf is
usually applied as two separate applications of 1 lb ai/A, terrestrial plant EECs were derived using a conservative assumption
of one application at 2 lb ai/A.
4. Effects Assessment
This assessment evaluates the potential for simazine to directly or indirectly affect the
CRLF or modify its designated critical habitat. As previously discussed in Section 2.7,
assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of CRLF, as well as indirect effects, such as reduction of the
prey base or modification of its habitat. In addition, potential modification of critical
habitat are assessed by evaluating effects to the PCEs, which are components of the
critical habitat areas that provide essential life cycle needs of the CRLF. Direct effects to
the aquatic-phase of the CRLF are based on toxicity information for freshwater fish,
while terrestrial-phase effects are based on avian toxicity data, given that birds are
generally used as a surrogate for terrestrial-phase amphibians. Because the frog's prey
items and habitat requirements are dependent on the availability of freshwater fish and
invertebrates, small mammals, terrestrial invertebrates, and aquatic and terrestrial plants,
toxicity information for these taxa are also discussed. Acute (short-term) and chronic
(long-term) toxicity information is characterized based on registrant-submitted studies
and a comprehensive review of the open literature on simazine.
As described in the Agency's Overview Document (U.S. EPA, 2004), the most sensitive
endpoint for each taxon is used for risk estimation. For this assessment, evaluated taxa
include aquatic-phase amphibians, freshwater fish, freshwater invertebrates, aquatic
73
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plants, birds (surrogate for terrestrial-phase amphibians), mammals, terrestrial
invertebrates, and terrestrial plants.
Toxicity endpoints are established based on data generated from guideline studies
submitted by the registrant, and from open literature studies that meet the criteria for
inclusion into the ECOTOX database maintained by EPA/Office of Research and
Development (ORD) (U.S. EPA, 2004). Open literature data presented in this assessment
were obtained from 2006 simazine RED as well as ECOTOX information obtained on
September 30, 2006. In order to be included in the ECOTOX database, papers must
meet the following minimum criteria:
(1) the toxic effects are related to single chemical exposure;
(2) the toxic effects are on an aquatic or terrestrial plant or animal species;
(3) there is a biological effect on live, whole organisms;
(4) a concurrent environmental chemical concentration/dose or application
rate is reported; and
(5) there is an explicit duration of exposure.
Data that pass the ECOTOX screen are evaluated along with the registrant-submitted
data, and may be incorporated qualitatively or quantitatively into this endangered species
assessment. In general, effects data in the open literature that are more conservative than
the registrant-submitted data are considered. The degree to which open literature data are
quantitatively or qualitatively characterized is dependent on whether the information is
relevant to the assessment endpoints {i.e., maintenance of CRLF survival, reproduction,
and growth) identified in Section 2.8. For example, endpoints such as behavior
modifications are likely to be qualitatively evaluated, because quantitative relationships
between modifications and reduction in species survival, reproduction, and/or growth are
not available.
Citations of all open literature not considered as part of this assessment because they
were either rejected by the ECOTOX screen or accepted by ECOTOX but not used {e.g.,
the endpoint is less sensitive and/or not appropriate for use in this assessment) are
included in Appendix G. Appendix G also includes a rationale for rejection of those
studies that did not pass the ECOTOX screen and those that were not evaluated as part of
this endangered species risk assessment.
In addition to registrant-submitted and open literature toxicity information, other sources
of information, including use of the acute probit dose response relationship to establish
the probability of an individual effect and reviews of the Ecological Incident Information
System (EIIS), are conducted to further refine the characterization of potential ecological
effects associated with exposure to simazine. A summary of the available aquatic and
terrestrial ecotoxicity information, use of the probit dose response relationship, and the
incident information for simazine are provided in Sections 4.1 through 4.4, respectively.
With respect to simazine degradates, deisopropylatrazine (DIA) and
diaminochloroatrazine (DACT), it is assumed that each of the degradates are less toxic
74
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than the parent compound for aquatic receptors. As shown in Table 4.1, comparison of
available toxicity information for DIA and DACT indicates lesser aquatic toxicity than
the parent for freshwater fish, invertebrates, and aquatic plants. However, the acute
toxicity data for mammals indicates that DIA is more toxic than parent simazine, with a
corresponding LD50 value of 1,240 mg/kg, as compared to > 5,000 mg/kg for simazine.
Although the degradate toxicity data indicates that DIA is more toxic to mammals than
parent simazine, indirect effects to terrestrial-phase CRLFs via direct acute effects to
mammals are assessed using toxicity data for simazine because the available fate data
show that DIA does not form and persist in the environment at any substantial level.
Therefore, indirect effects to terrestrial-phase CRLFs via direct acute effects to mammals
as prey items are evaluated using the acute toxicity data for simazine. Although
degradate toxicity data are not available for terrestrial plants, lesser toxicity is assumed,
given the available ecotoxicological information for other taxonomic groups including
aquatic plants, where the toxic mode of action is similar, and the likelihood that the
simazine degradates are expected to lose efficacy as an herbicide.
Table 4.1 Comparison of Acute Toxicity Values for Simazine and Degradates
Substance Tested
Fish LCso
(Hg/L)
Daphnid EQ0
(ug/L)
Aquatic Plant
ECS0 (n-g/L)
Mammalian LD?o
(mjj/kjj)
Simazine
6,400
1000
36
>5,000
DACT
>100,000
>100,000
No data
No data
DIA
17,000
126,000
2,500
1,240
Therefore, given the lesser aquatic toxicity and fate characteristics of the degradates, as
compared to the parent, concentrations of the simazine degradates are not assessed for
direct and/or indirect effects to aquatic- and terrestrial-phase CRLFs. The available
information also indicates that aquatic organisms are more sensitive to the technical grade
(TGAI) than the formulated products of simazine; however, chronic toxicity data for
freshwater fish and invertebrates are not available for the technical grade of simazine.
Therefore, available chronic toxicity data for the formulated product (adjusted to account
for the percentage of active ingredient) are used as measures of chronic effects for
freshwater fish and invertebrates. A detailed summary of the available ecotoxicity
information for all simazine degradates and formulated products is presented in Appendix
A.
The results of available toxicity data for mixtures of simazine with other pesticides are
presented in Section A.6 of Appendix A. Based on the available information, other
triazine herbicides, such as atrazine, may combine with simazine to produce additive
toxic effects on aquatic plants. The variety of chemical interactions presented in the
available data set suggest that the toxic effect of simazine, in combination with other
pesticides used in the environment, can be a function of many factors including but not
necessarily limited to: (1) the exposed species, (2) the co-contaminants in the mixture, (3)
the ratio of simazine and co-contaminant concentrations, (4) differences in the pattern
and duration of exposure among contaminants, and (5) the differential effects of other
physical/chemical characteristics of the receiving waters (e.g. organic matter present in
sediment and suspended water). Quantitatively predicting the combined effects of all
these variables on mixture toxicity to any given taxa with confidence is beyond the
75
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capabilities of the available data. However, a qualitative discussion of implications of the
available pesticide mixture effects data involving simazine on the confidence of risk
assessment conclusions for the CRLF is addressed as part of the uncertainty analysis for
this effects determination.
4.1 Toxicity of Simazine to Aquatic Organisms
Table 4.2 summarizes the most sensitive aquatic toxicity endpoints for the CRLF, based
on an evaluation of both the submitted studies and the open literature, as previously
discussed. A brief summary of submitted and open literature data considered relevant to
this ecological risk assessment for the CRLF is presented below. Additional information
is provided in Appendix A.
Table 4.2 Freshwater Aquatic Toxicity Profile for Simazine
Assessment Endpoint
Species
Toxicity Value Used in
Risk Assessment
Citation
MRID#
(Author &
Date)
Comment
Acute Direct Toxicity to
Aquatic-Phase CRLF
Fathead
Minnow1
96-hour LC50 = 6,400
(ig/L
(TGAI)
Probit slope unavailable
000333-09
(Sleight, 1971)
Supplemental:
Nominal
concentrations; no
raw data provided
Chronic Direct Toxicity
to Aquatic-Phase CRLF
Fathead
Minnow1
NOAEC = 960 |ig/L2
LOAEC = 2000 |ig/L2
(80% formulated
product)
000436-76
(Mayer &
Sanders, 1976)
Acceptable: 12%
reduction in fry
growth at 2,000
(ig/L2
Indirect Toxicity to
Aquatic-Phase CRLF via
Acute Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Daphnia
magna
48-hour TL50 = 1,000
(ig/L
(TGAI)
Probit slope unavailable
450882-21
(Sanders, 1970)
Supplemental:
Nominal
concentrations; no
raw data provided
Indirect Toxicity to
Aquatic-Phase CRLF via
Chronic Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Daphnia
magna
NOAEC = 2,000 (ig/L2
LOAEC = >2,000 (ig/L2
(80% formulated
product)
000436-76
(Mayer &
Sanders, 1976)
Acceptable: No
adverse effects at
the highest test
concentration
Indirect Toxicity to
Aquatic-Phase CRLF via
Acute Toxicity to Non-
vascular Aquatic Plants
Blue-
green
algae
5-day EC50 = 36 |ig/L
(TGAI)
NOAEC = 5.4 (ig/L
426624-01
(Thompson and
Swigert, 1992a)
Supplemental: A
NOAEC could not
be determined
based on cell
density. Existing
cell density data
was used to
calculate an EC0s
for use as a
76
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NOAEC
Indirect Toxicity to
Aquatic-Phase CRLF via
Acute Toxicity to
Vascular Aquatic Plants
Duckweed
14-day EC50 = 140 |ig/L
NOAEC = 54 (ig/L
425037-04
(Thompson and
Swigert, 1992b)
Acceptable:
LOAEC of 110
|ig/L based on
reduction in frond
number
1 Used as a surrogate for the aquatic-phase CRLF.
2 Data for the TGAI are not available. Concentrations are adjusted for % a.i.
It should be noted that a considerable number of freshwater acute toxicity data and field
studies are available for simazine. Reported acute toxicity values generally exceed the
water solubility limit of simazine (approximately 3.5 mg/L at 20° C). While simazine
concentrations in water would appear to be stable to hydrolysis and photolysis for the
duration of the acute static studies, the actual exposure levels are uncertain because
mean-measured concentrations are not available, and precipitation is frequently reported
in the acute studies. Test concentrations are rarely measured to verify exposure levels;
therefore, a high degree of uncertainty exists for the freshwater toxicity data for simazine.
As such, studies with LC50 values >100 mg/L are highly uncertain. It appears that
simazine is acutely toxic to some freshwater fish and aquatic invertebrates in the range of
1 to 10 mg/L.
Toxicity to aquatic fish and invertebrates is categorized using the system shown in Table
4.3 (U.S. EPA, 2004). Toxicity categories for aquatic plants have not been defined.
Table 4.3 Categories of Acute Toxicity for Aquatic Organisms
LCso (ppm)
Toxicity Category
<0.1
Very highly toxic
>0.1-1
Highly toxic
>1-10
Moderately toxic
>10 - 100
Slightly toxic
> 100
Practically nontoxic
4.1.1 Toxicity to Freshwater Fish
Ecotoxicity data for freshwater fish are generally used as surrogates for aquatic-phase
amphibians when amphibian toxicity data are not available (U.S. EPA, 2004). A
comprehensive search of the open literature provided no toxicity information on lethal or
sublethal effects of simazine to amphibians. However, atrazine, a triazine herbicide in
the same chemical class as simazine, has been associated with endocrine-related effects
{i.e., gonadal abnormalities and laryngeal alterations) in frogs. The Agency review of the
current database of published studies and registrant submitted studies on atrazine lead to
the conclusion that there was sufficient evidence to formulate a hypothesis that atrazine
exposure may impact gonadal development in amphibians, but there was insufficient data
to confirm or refute the hypothesis (transmission of meeting minutes of the Scientific
Advisory Panel (SAP) held June 17-20, 2003;
(http://www.epa.gov/oscpmont/sap/2003/June/iunemeetingreport.pdf). Because atrazine
and simazine share a similar mechanism of herbicidal action and similar degradates,
including DIA and DACT, the current hypothesis regarding potential sublethal effects of
77
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atrazine to amphibians may be applicable to simazine depending on the outcome of future
studies on atrazine. The results of these studies, as well as other recent open literature
data, which focus on the potential effects of atrazine on amphibian gonadal development,
are being reviewed. This information will be presented and discussed as part of a second
SAP to be held in October 2007.
Given that no simazine toxicity data are available for aquatic-phase amphibians,
freshwater fish data were used as a surrogate to estimate direct acute and chronic risks to
the CRLF. Freshwater fish toxicity data were also used to assess potential indirect effects
of simazine to the CRLF. Direct effects to freshwater fish resulting from exposure to
simazine may indirectly affect the CRLF via reduction in available food. As discussed in
Section 2.5.3, over 50% of the prey mass of the CRLF may consist of vertebrates such as
mice, frogs, and fish (Hayes and Tennant, 1985).
A summary of acute and chronic freshwater fish data, including data from the open
literature, is provided below in Sections 4.1.1.1 through 4.1.1.3.
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies
As shown in Table A-10, submitted acute toxicity values for technical grade simazine
exceed its expected water solubility (-3.5 mg/L), with values ranging from 6.4 to >32 mg
ai/L. The solubility of simazine is dependant on the water temperature, with a trend
toward decreasing solubility at lower temperatures (Schwarzenbach etal., 1993). The
following mathematical function describes the relationship between water solubility and
temperature: Log (mg/L) = 0.021(T, K) - 5.5358 (R2 = 0.9862, n = 5), where T =
temperature and K = kelvin. Further examination of the test temperatures for the acute
freshwater studies reveals that all submitted tests were conducted at temperatures < 18°C.
Based on the mathematical relationship between solubility and temperature, the expected
solubility of simazine in water at a temperature of 18°C would be approximately 3.8
mg/L. With respect to technical grade simazine, the reported acute LC50 values for
fathead minnow (MRID 000333-09) and bluegill sunfish (MRID 000254-38) are 6,400
and 16,000 |ig/L, respectively. While both of these LC50 values exceed the predicted
limit of simazine's solubility in water (3,800 |ig/L), a co-solvent was used to increase the
limit of simazine's water solubility, and no observation of precipitate were noted in the
test chambers. Therefore, the fathead minnow LC50 value of 6,400 |ig/L was selected as
the surrogate acute freshwater fish toxicity endpoint and used to assess direct acute
effects of simazine to the CRLF. This test was categorized as supplemental because no
raw data or test concentrations were provided in the study. A no effect level of 2,500
|ig/L was established in the 96-hour fathead minnow study. This no effect level is
consistent with the results of a 28-day subacute rainbow trout study (MRID 000436-68).
Following 28-days of exposure, no mortality or other toxic symptoms were observed at
the 2,500 |ig/L treatment level. The subacute study was classified as supplemental
because the fish were too large (25-40g) and only one treatment level (2,500 |ig/L) was
tested. In the acute bluegill sunfish study, which is classified as core, no mortality was
observed in treatment groups < 5,600 |ig/L, and 40% mortality was observed in the
10,000 |ig/L treatment group.
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There is additional uncertainty in all available acute freshwater studies on the TGAI
regarding dissolved levels of simazine in water because mean-measured test
concentrations were not analyzed. Reported nominal concentration results reflect the
concentration after the application and not necessarily the concentration of simazine in
water during or at the end of the 96-hour test. A number of the acute studies on both the
TGAI and formulated product are classified as invalid because precipitation of the test
substance in the test chambers was reported and LC50 values exceed the water solubility
of simazine by a large margin.
Acute effects data for freshwater fish are available for a number of simazine's formulated
products including Aquazine (80% WP) and a 50% formulation. All ai-adjusted LC50
values for Aquazine (>72,600 |ig/L) and the 50% formulation (13,500 to 55,000 |ig/L)
exceed the lowest LC50 value for the TGAI (6,400 |ig/L). The available data suggests
that Aquazine and the 50% formulation are less toxic to freshwater fish than the TGAI.
Based on the available data, simazine is categorized as moderately toxic to freshwater
fish on an acute basis. No additional data on the acute toxicity of simazine or its
degradates to freshwater fish were located in the open literature.
4.1.1.2 Freshwater Fish: Chronic Exposure (Growth/Reproduction)
Studies
Chronic freshwater fish acute toxicity studies were used to assess potential direct effects
via growth and reproduction to the aquatic-phase of the CRLF. No freshwater fish early
life-stage test using the TGAI was submitted for simazine. Two fish life-cycle tests with
fathead minnow were submitted for Aquazine, an 80% formulation that is typically
applied directly to the water (MRID 000436-76). One test was conducted with steady
concentrations via continuous flow. In the second test, the chemical was applied at the
beginning of the test and allowed to decrease at normal degradation rates. Both tests
were conducted at the same initial test concentrations. The static test where
concentrations decrease over time is intended to be representative of typical use-pattern
exposures of Aquazine. The lowest endpoint values in the continuous and usage-pattern
exposures were increase in percent hatched fry (NOAEC = 130 |ig/L ai) and increased fry
growth (length) (NOAEC = 25 |ig/L ai), respectively. However, neither of these
endpoints are considered as toxicologically relevant for the risk assessment. Therefore, a
NOAEC value of 960 |ig/L ai was selected, based on 12% reduction in growth (length) to
30-day old fry at a continuous exposure treatment level of 2,000 |ig/L ai. The
corresponding LOAEC value, based on reduction in fry growth, is 2,000 |ig/L ai.
Freshwater fish life-cycle studies for the 80% formulation are summarized in Table A-12
of Appendix A.
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4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open
Literature Information
In addition to submitted studies, data were located in the open literature that report
sublethal effect levels to freshwater fish that are less than the selected measures of effect
summarized in Table 4.2. Although these studies report potentially sensitive endpoints,
effects on survival, growth, or reproduction were not observed in the available full life-
cycle studies at concentrations that induced the reported sublethal effects described below
and in Appendix A.
No additional information is available that indicates greater acute freshwater fish
sensitivity to simazine than the submitted data. In addition, no laboratory freshwater fish
early life-stage or life-cycle tests using simazine and/or its formulated products were
located in the open literature. However, one laboratory study on sublethal effects of
simazine to male Atlantic salmon (Salmo salar L.) is available. In a study conducted by
Moore and Lower (2001; ECOTOX# 67727), simazine inhibited in vitro olfactory
function in male Atlantic salmon parr. The results of the this study are summarized in
Table A-13 of Appendix A. Following a 5 day exposure period, the reproductive priming
effect of the female pheromone prostaglandin F2a on the levels of expressible milt in
males was reduced after exposure to simazine at concentrations as low as 0.1 (J,g/L.
Although the hypothesis was not tested, the study authors suggest that exposure of smolts
to simazine during the freshwater stage may potentially affect olfactory imprinting to the
natal river and subsequent homing of adults. Although this study produced a NOAEC
that is lower than the fish full life-cycle test of 960 ppb, this study was not considered
appropriate for RQ calculation for the following reasons:
A negative control was not used; therefore, potential solvent effects cannot
be evaluated;
The study did not determine whether the decreased response of olfactory
epithelium to specific chemical stimuli would likely impair similar
responses in intact fish; and
A quantitative relationship between the magnitude of reduced olfactory
response of male epithelial tissue to the female priming hormone observed
in the laboratory and reduction in salmon reproduction (i.e., the ability of
male salmon to detect, respond to, and mate with ovulating females) in the
wild is not established.
Although these studies raise questions about the potential effects of simazine on
endocrine-mediated functions in anadromous fish, it is not possible to quantitatively link
these sublethal effects to the selected assessment endpoints for the CRLF (i.e., survival,
growth, and reproduction of individuals and modification to designated critical habitat).
Therefore, potential sublethal effects on fish are evaluated qualitatively in Section 5.2 and
not used as part of the quantitative risk characterization. Further detail on sublethal
effects to fish is provided in Sections A.4.3 and Table A-13 of Appendix A.
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4.1.2 Toxicity to Freshwater Invertebrates
Freshwater aquatic invertebrate toxicity data were used to assess potential indirect effects
of simazine to the CRLF. Direct effects to freshwater invertebrates resulting from
exposure to simazine may indirectly affect the CRLF via reduction in available food
items. As discussed in Section 2.5.3, the main food source for juvenile aquatic- and
terrestrial-phase CRLFs is thought to be aquatic invertebrates found along the shoreline
and on the water surface, including aquatic sowbugs, larval alderflies and water striders.
A summary of acute and chronic freshwater invertebrate data, including data published in
the open literature, is provided below in Sections 4.1.2.1 through 4.1.2.3.
4.1.2.1 Freshwater Invertebrates: Acute Exposure Studies
Acute toxicity data for simazine are available for the preferred test species, Daphnia
magna, as well as seven other freshwater invertebrates including the seed shrimp
(Cypridopsis vidua), scud (Gammarus lacustris and G. fasciatus), stonefly (Pteronarcys
californica), sowbug (Asellus brevicaudus), glass shrimp {Palaemonetes kadiakensis),
and crayfish (Orconectes nais). Results of acute toxicity tests with freshwater
invertebrates are tabulated in Table A-14 of Appendix A.
In a comparative analysis of herbicides on six species of freshwater invertebrates, 48-hr
exposure to simazine at concentrations of 1,000 and 3,700 [j,g/L resulted in 50 percent
mortality in daphnia and seed shrimp, respectively (MRID 450882-21). In the same
analysis, simazine did not appear to have any effect on the scud {G. fasciatus), sowbug,
glass shrimp, or crayfish, with 48-hr TL50 values exceeding 100,000 |ig/L, However, as
previously mentioned, toxicity values > 100,000 [j,g/L exceed the water solubility of
simazine by a wide margin; therefore, the validity of the data is uncertain. TL50 values
reported in the study are median tolerance limits, representative of the concentration in
water in which 50 percent of the animals exhibit a specific response {i.e., mortality,
immobilization) at a given time. It should be noted that no test concentrations or raw
data were provided as part of this study; therefore, it was classified as supplemental. In
addition, the slope of the dose-response relationship for daphnia could not be determined
due to a lack of raw data and test concentrations.
Two additional supplemental 96-hr acute toxicity studies on freshwater invertebrates are
available for the technical grade of simazine. In a chemical database of acute toxicity to
freshwater animals maintained by the Columbia National Fisheries Research Laboratory
of the U.S. Fish and Wildlife Service, 96-hr exposure of the stonefly {P. californica) to
simazine resulted in an EC50 of 1,900 [j,g/L (MRID 400980-01). A 96-hr EC50 value of
13,000 [j,g/L was reported for the scud {G. lacustris) (MRID 050092-42) in a study
classified as supplemental because no mortality data were provided and test
concentrations were not specified.
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Based on the available data, simazine is categorized as highly to slightly toxic to
freshwater invertebrates on an acute basis. No additional data on the acute toxicity of
simazine or its degradates to freshwater invertebrates were located in the open literature.
4.1.2.2 Freshwater Invertebrates: Chronic Exposure Studies
No freshwater invertebrate life-cycle test using the TGAI was submitted for simazine. A
freshwater aquatic invertebrate life-cycle test using the formulated product Aquazine
(80% formulation) was submitted for simazine (MRID 000436-76) using the preferred
species D. magna. The results of this test are summarized in Table A-16 of Appendix A.
No treatment-related adverse effects to parental mortality and production of offspring
occurred during the 21-day study at the highest test concentration of 2,000 (J,g/L. The
only treatment-related effect was a significant increase in production of offspring
produced at the 80 [j,g/L test concentration. Therefore, the NOAEC value is 2,000 (J,g/L.
4.1.2.3 Freshwater Invertebrates: Open Literature Data
Only one chronic toxicity study on freshwater invertebrates is available from the open
literature. It appears that D. pulex fed a diet of green alga are less sensitive to the effects
of simazine, as compared with those that are fed mixed bacterial cultures. Similar to the
results reported in the registrant submitted studies, simazine concentrations at the highest
treatment level (5,000 |ig/L) were shown to enhance reproduction and growth in I). pulex
that were fed green alga following 14 days of exposure. Conversely, reproduction was
significantly reduced at simazine concentrations of 5,000 and 1,000 [j,g/L when mixed
bacterial cultures were used as the food source. However, no significant differences in
the number of offspring per adult were observed at treatment levels of 100, 200, or 2,000
[j,g/L; therefore, the results are erratic and not dose-dependant. Given the variability in
reproductive responses in D. pulex fed mixed bacterial cultures and issues of
comparability between chronic freshwater invertebrate guidelines (where invertebrates
are not fed mixed bacterial cultures), the data from this study are addressed qualitatively.
The results of this study are described in further detail in Section A.4.7 and Table A. 17 of
Appendix A.
4.1.3 Toxicity to Aquatic Plants
Aquatic plant toxicity studies were used as one of the measures of effect to evaluate
whether simazine may affect primary production and the availability of aquatic plants as
food for CRLF tadpoles. Primary productivity is essential for indirectly supporting the
growth and abundance of the CRLF.
Two types of studies were used to evaluate the potential of simazine to affect aquatic
plants. Laboratory and field studies were used to determine whether simazine may cause
direct effects to aquatic plants. A summary of the laboratory data and freshwater field
studies for aquatic plants is provided in Sections 4.1.3.1 and 4.1.4.
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4.1.3.1 Aquatic Plants: Laboratory Data
A summary of acute toxicity of simazine to aquatic plants is provided in Table A-21 of
Appendix A. Tier II toxicity data for technical grade simazine is available for vascular
duckweed (Lemna gibba) and the following non-vascular plants: blue-green algae
(Anabaena jlos-aquae), marine diatom (Skeletonema costatum and Phaeodactylum
tricornutum), freshwater alga (Selenastrum capricornutum), freshwater diatom (Navicula
pelliculosa), marine algae (Isochrysis galbana), and marine green algae (Chlorococcum
sp. and Dunaliella tertiolecta).
One Tier II study of the freshwater aquatic vascular plant, duckweed, was completed
using the TGAI of simazine (MRID 425037-04). Frond number was the most sensitive
endpoint with an EC50 value of 140 (^g/L. NOAEC and LOAEC values, based on
reduction in frond number and growth rate inhibition were 54 and 110 |ig/L, respectively.
Growth was reduced by 9.1% in plants in the 110 [j,g/L treatment group. By days 6-9 and
onward, there was an increase in colony breakup, smallness of frond, and root destruction
in test solutions of > 230 (J,g/L.
The Tier II results indicate that freshwater blue-green algae {Anabaena) is the most
sensitive non-vascular plant to simazine (MRID 426624-01). The EC50 for Anabaena is
36 |ig/L, as compared to EC50 values ranging from 90 to 100 [j,g/L for other freshwater
non-vascular plants. The Tier II aquatic plant study with the freshwater alga, Anabaena,
was scientifically valid, but could not be classified as acceptable because a NOAEC value
was not determined. In an Agency 1993 memo, dated October 18, 1993, EPA agreed that
existing growth data be used to derive an EC10 value for use as the NOAEC. However,
current Agency policy specifies that the EC05 be used to derive the NOAEC in order to
protect listed species that have obligate relationships with non-vascular plants. The
resulting NOAEC value based on the EC05 is 5.4 (J,g/L. Reduction in growth rates of
36.8, 80.1, 97.6, and 107% were observed by day 5 at respective test concentrations of
78, 170, 320, and 660 (J,g/L. In addition, a 28% reduction in cell density was observed at
the lowest test concentration of 20 (J,g/L.
4.1.4 Freshwater Field Studies
A number of field studies are available in the open literature that evaluate adverse effects
to freshwater organisms resulting from single and multiple applications of simazine to
freshwater ponds to remove noxious growths of aquatic macrophytes. Generally, direct
application of simazine to ponds results in a die-off of macrophytes, which consequently
results in a decrease of dissolved oxygen (DO). In many of the studies, adverse effects to
freshwater fish in field studies following simazine application are attributed to indirect
effects including a combination of low DO and reduced food resources, rather than direct
toxicity of simazine. Available data from aquatic field studies are inadequate to
determine whether simazine applications to aquatic habitats at levels of approximately
1,000 [j,g/L (1 ppm) result in adverse effects to non-target aquatic organisms either by
direct toxicity or indirect effects such as low DO, lost food/habitat resources, and/or
decreased ecosystem productivity in the absence of macrophytes. The available field
83
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data indicate that benthic macroinvertebrates are generally not adversely impacted by
simazine concentrations of 1,000 (J,g/L, although one study reported a reduction in
zooplankton biomass in the post-treatment period. In most of the studies, the fish are
older life stages such as fingerlings and/or adults, which are not normally as sensitive to
pesticides as larval and fry stages. In addition to indirect effects associated with low DO,
the results of one field study suggest a possible direct effect of simazine on the feeding
response of channel catfish, following direct application of 1,300 [j,g/L to earthen channel
catfish ponds infested with stonewort. The reviewed field studies are qualitatively
evaluated in this risk assessment because observed adverse effects associated with
simazine exposure are likely the result of a complex interaction of several parameters
rather than simazine concentration alone. Further discussion of the open literature field
studies for freshwater fish and invertebrates is provided in Section A.4.8 and summarized
in Table A-18 of Appendix A.
The open literature contains a large amount of information on the toxicity of simazine to
aquatic plants; however, the majority of data report toxicity values that are higher (i.e.,
not as sensitive) than the endpoints reported in the submitted studies. A number of open
literature papers, which characterize unique endpoints to aquatic plants, present data with
endpoint values that are more sensitive than the submitted endpoints, or discuss aquatic
plant succession and recovery following simazine application are discussed below.
Tables A-23 and A-18 of Appendix A provide a summary of the open literature
laboratory and in situ studies, respectively, on the effects of simazine to aquatic plants.
Based on the results of the in situ and laboratory studies, it appears that simazine results
in a reduction of chlorophyll a in periphyton and phytoplankton at simazine levels
between 500 and 1,000 (J,g/L. Other studies show increased chlorophyll a production at
simazine concentrations of <0.05 ug/L. In addition, despite the apparent sensitivity of the
blue-green algae Anabaena flos-aquae to simazine, the results of one open literature
study suggest possible resistance and shifts in the aquatic periphytic plant community to
blue-green alga at the higher simazine treatment levels of 5,000 (J,g/L. Simazine
resistance has also been reported in seeds and tubers of Potamogeton foliosus. There is
evidence to suggest that recovery occurs in algae upon removal of simazine from the site
of action, with the recovery inversely proportional to the prior exposure level. In one
study, recovery of macrophytes was noted within two to three months following
application of simazine granules at 25 lb doses (% ai was not reported). Further detail on
the open literature data for aquatic plants is discussed in Section A.5.3.
4.2 Toxicity of Simazine to Terrestrial Organisms
Table 4.4 summarizes the most sensitive terrestrial toxicity endpoints for the CRLF,
based on an evaluation of both the submitted studies and the open literature. A brief
summary of submitted and open literature data considered relevant to this ecological risk
assessment for the CRLF is presented below.
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Table 4
.4 Terrestrial Toxicity Profile for Simazine
Endpoint
Species
Toxicity Value Used
in Risk Assessment
Citation
IMRID#
(Author &
Date)
Comment
Acute Direct
Toxicity to
Terrestrial-Phase
CRLF (LD50)
Mallard duck1
LD50 = >4,640 mg
ai/kg-bw
000727-98
(Fink, 1976)
Supplemental: No mortality at the
highest test concentration; however,
reduced reaction to external stimuli, wing
droop, and depression were observed at
concentrations as low as 1,000 mg ai/kg-
bw one hour after dosing. Birds were 14
days old rather than required age of 14-16
weeks; therefore, there is uncertainty
associated with the reported sublethal
effects.
Acute Direct
Toxicity to
Terrestrial-Phase
CRLF (LC5o)
Mallard duck
and Bobwhite
quail1
LC50 = >5,000 mg
ai/kg-diet
000229-23
(Hill et al.,
1975)
Acceptable: No mortality at the highest
test concentration
Chronic Direct
Toxicity to
Terrestrial-Phase
CRLF
Bobwhite
quail1
NOAEC = 100 mg
ai/kg
LOAEC = 500 mg
ai/kg
001631-34
(Beavers,
1986)
Acceptable: Reduction in number of eggs
laid, viable embryos, live embryos,
hatchlings, and 14-day old chick
survivors at 500 mg ai/kg
Indirect Toxicity to
Terrestrial-Phase
CRLF (via acute
toxicity to
mammalian prey
items)
Rat
Simazine LD50 =
>5,000 mg ai/kg-bw
001488-97
(Rosenfeld,
1985)
Acceptable: At 5,000 mg ai/kg-bw, 3/10
animals died
Indirect Toxicity to
Terrestrial-Phase
CRLF (via chronic
toxicity to
mammalian prey
items)
Rat
NOAEC = 10 mg
ai/kg
LOAEC = 100 mg
ai/kg
418036-01
(Epstein et al.,
1991)
Acceptable: Reduction in body weight
gain
Indirect Toxicity to
Terrestrial-Phase
CRLF (via acute
toxicity to
terrestrial
invertebrate prey
items)
Honey bee
LD50 = >96.7 (ig
ai/bee
000369-35
(Atkins et al.,
1975)
Acceptable: 6.5% mortality in the 96.7
|ig ai/bee treatment group
Indirect Toxicity to
Terrestrial- and
Aquatic-Phase
CRLF (via toxicity
to terrestrial plants)
Seedlins
Emersence
Monocots
(Onions)
EC25 = 0.02 lb ai/A
426346-03
(Chetram,
1993a)
Acceptable: Onion shoot height
Seedlins
Emersence
Dicots
EC25 = 0.009 lb ai/A
426346-03
(Chetram,
1993a)
Acceptable: Lettuce dry weight
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(Lettuce)
Veeetative
Visor
Monocots
(Oats)
EC25 = 0.033 lb ai/A
426346-04
(Chetram,
1993b)
Acceptable: Oats dry weight
Veeetative
Visor
Dicots
(Lettuce)
EC25 = 0.033 lb ai/A
426346-04
(Chetram,
1993b)
Acceptable: Lettuce dry weight
1 Used as a surrogate for the terrestrial-phase CRLF.
Acute toxicity to terrestrial animals is categorized using the classification system shown
in Table 4.5 (U.S. EPA, 2004). Toxicity categories for terrestrial plants have not been
defined.
Table 4.5 Categories of Acute Toxicity for Avian and Mammalian Studies
Toxicity Category
Oral LD50
Dietary LC50
Very highly toxic
<10 mg/kg
< 50 ppm
Highly toxic
10-50 mg/kg
50 - 500 ppm
Moderately toxic
51 -500 mg/kg
501 - 1000 ppm
Slightly toxic
501 - 2000 mg/kg
1001 - 5000 ppm
Practically non-toxic
> 2000 mg/kg
> 5000 ppm
4.2.1 Toxicity to Birds
As specified in the Overview Document, the Agency uses birds as a surrogate for
terrestrial-phase amphibians when amphibian toxicity data are not available (U.S. EPA,
2004). No terrestrial-phase amphibian data are available for simazine; therefore, acute
and chronic avian toxicity data are used to assess the potential direct effects of simazine
to terrestrial-phase CRLFs.
4.2.1.1 Birds: Acute Exposure (Mortality) Studies
Acute oral toxicity data are available for a number of avian species; this data is
summarized in Table A-l of Appendix A. Simazine is classified as practically non-toxic
to birds on an acute exposure basis. The acute oral toxicity of simazine is based on a 14-
day study to 14-day old mallard ducks (Anasplatyrhynchos) (MRID 000727-98); the
LD50 exceeded the highest dose tested (>4640 mg ai/kg bw). There was no mortality
during the study. However, reduced reaction to external stimuli (sound and movement),
wing droop, and depression were observed at the 1,000, 2,150, and 4,640 mg/kg doses
one hour after dosing, as compared to the control group. As a result, the mallard NOAEC
is 464 mg/kg. It should be noted that this study is classified as supplemental because it
deviates from the guideline protocol in that the birds were 14 days old rather than 14 to
16 weeks.
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The results of the subacute dietary studies for the preferred test species, bobwhite quail
(Colinus virginianus) and mallard duck (A. platyrhynchos), are summarized in Table A-3
of Appendix A. Subacute avian dietary toxicity values for the technical grade and a 80%
formulation indicate that simazine is practically non-toxic. Hill et al. reported no
mortality in four species of birds at the highest concentrations of technical simazine
tested (MRID 000229-23). Corresponding LC50 values for the mallard duck, bobwhite
quail, and ring-necked pheasant (Phasianus colchicus) are > 5,000 mg/kg; the LC50 value
for the Japanese quail (Coturnix coturnix japonica) is >3,720 mg/kg. Mortalities were
observed in bobwhite quail and mallard duck acute dietary tests with the formulated
product of simazine (Simazine 80 WP). In the bobwhite test (MRID 000233-18),
mortality was 40% at 8800 mg/kg ai, beginning on Day 4 through Day 9. The bobwhite
NOAEL of <4000 mg/kg ai is based on a 90% reduction in body weight gain and a 37%
reduction in food consumption over the exposure period (Day 1 through Day 7). In the
mallard test (MRID 000233-19), 30% mortality occurred at 25,600 mg/kg ai, with all
deaths occurring between Days 5 and 8. The mallard NOAEL of <800 mg/kg ai is based
on a 48 to 59% reduction in body weight gain and a 24% reduction in food consumption
during the exposure period.
Based on a review of the open literature, no additional information on the acute and
subacute toxicity of simazine to birds is available that indicates greater avian sensitivity
than the registrant-submitted studies.
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies
Two avian reproduction studies for simazine are available, which are summarized in
Table A-4 and Section A. 1.3 of Appendix A. The primary reproductive effect of
simazine on avian reproduction appears to be reduction in the number of eggs laid.
The most sensitive reproductive endpoint is based on the bobwhite quail study (MRID
001631-34), where the NOAEC was determined to be 100 mg/kg, based on reduction in
the number of eggs laid, viable embryos, live embryos, hatchlings, and 14-day old chick
survivors. The primary reproductive effect of simazine on avian reproduction appears to
be reduction in the number of eggs laid. The number of eggs laid was reduced by 20% at
the highest treatment level of 500 mg/kg. Adverse reproductive effects increased by
approximately 13% at the embryo viability stage and remained constant throughout the
study, also affecting the number hatched and survival of 14-day chicks. The LOAEC was
the highest concentration tested of 500 mg/kg.
In the mallard duck reproduction study (MRID 435769-01), simazine technical had a
significant adverse effect on egg production and female weight gain at the 450 mg/kg ai
test concentration. The reduced number of hatchlings and 14-day old survivors at that
level, as compared to the control group, can be attributed to the reduced number of eggs
laid. The number of eggs laid was reduced by approximately 50% at the highest
treatment level of 450 mg/kg. The NOAEC was determined to be 150 mg/kg, based on
reduction in the number of eggs laid and female body weight; the LOAEC was 450
mg/kg.
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Based on a review of the open literature, no additional information on the chronic toxicity
of simazine to birds is available that suggests greater sensitivity than the registrant-
submitted data.
4.2.2 Toxicity to Mammals
Mammalian toxicity data are used to assess potential indirect effects of simazine to the
terrestrial-phase CRLF. Direct effects to small mammals resulting from exposure to
simazine may also indirectly affect the CRLF via reduction in available food. As
discussed in Section 2.5.3, over 50% of the prey mass of the CRLF may consist of
vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies
The acute mammalian toxicity data for simazine is summarized in Table A-5 and Section
A.2.1 of Appendix A. Rats exposed to technical grade simazine showed no mortality at
the highest doses tested. The corresponding LD50 value for the TGAI is >5,000 mg/kg-
bw, classifying technical grade simazine as practically non-toxic (MRID 001488-97) to
mammals on an acute basis. In this study, one out of five males and two out of five
females died. Therefore, the LD50 value of >5,000 mg/kg for simazine is based on a 30%
mortality rate at the highest test concentration of 5,000 mg/kg.
Acute mammalian oral toxicity data are also available for one of the degradates of
simazine, DIA, and are summarized in Table A-6 and Section A.2.1 of Appendix A.
Both the female and male LD50 values are more toxic to laboratory rats than technical
grade values for the parent simazine with respective values of 810 and 2,290 mg/kg
(MRID 430123-01). The combined LD50 value for males and females is 1,240 mg/kg.
Based on a review of the open literature, no additional information on the acute toxicity
of simazine or its degradates to mammals is available that indicates greater sensitivity
than the studies discussed above.
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies
Reproductive and developmental mammalian toxicity values for simazine are reported in
Table A-7 and Section A.2.2. These studies provide adequate toxicity data on chronic
developmental and reproductive effects of simazine. Chronic studies using laboratory
rats show consistent reductions in adult body weight gain and adult body weight at
simazine concentrations of 100 mg/kg-diet. The corresponding NOAEC value for these
studies is 10 mg/kg-diet (MRIDs 418036-01 and 406144-05). In addition, reproductive
effects including increased abortions, reduced fetal weight, and increased skeletal
variations have been observed in New Zealand white rabbits at a concentration of 200
mg/kg/day, with a corresponding NOAEL value of 75 mg/kg/day (MRID 001614-07).
88
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In March 2002, the Agency's Health Effects Division (HED) evaluated the available
scientific evidence for determining whether a common mechanism of toxicity exists
among certain triazine-containing pesticides, including simazine, atrazine, propazine,
tribenuron-methyl (Express) and the 2-hydroxyatrazine, DEA, DIA, and DACT (EPA,
2002). Treatment of laboratory animals with these chemicals results in toxic
neuroendocrine effects such as mammary gland tumors in only female rats, attenuation of
the lutenizing hormone (LH) surge, alteration of the estrous cycle, altered pregnancy
maintenance, and delayed pubertal development. The development of mammary gland
tumors in female rates is postulated to be associated with disruption of the hypothalamic-
pituitary-gonadal (HPG) axis. Altered secretory activity of the HPG axis begins with a
decrease in the release of gonadotropin releasing hormone (GnRH) by the hypothalamus
followed by a consequent attenuation of the LH surge during the estrous cycle. As a
result, ovulation does not occur and the estrous cycle is prolonged, thereby increasing
exposure to estrogen. Increased exposure to estrogen is conducive to the development of
mammary gland tumors. Based on the available weight-of-evidence, HED determined
that atrazine, simazine, propazine, and the degradates DEA, DIA, and DACT can be
grouped by a common mechanism of toxicity for disruption of the HPG axis. Therefore,
equivalent mammalian toxicity is assumed for the parent compound and degradates of
simazine. Submitted studies provide evidence that administration of these compounds to
female SD rats leads to increased incidence and/or early onset of benign and mammary
gland tumors. Simazine at dose levels of 100 ppm (5.3 mg/kg/day) and 1000 ppm (45.8
mg/kg/day) resulted in a statistically-significant dose-related trend in mammary gland
carcinomas (MRID 406144-05). The corresponding NOAEC value for this study was 10
ppm or 0.47 mg/kgBW/day.
Based on a review of the open literature, no additional information on the chronic toxicity
of simazine or its degradates to mammals is available that suggests greater sensitivity
than the submitted data.
4.2.3 Toxicity to Terrestrial Invertebrates
Terrestrial invertebrate toxicity data are used to assess potential indirect effects of
simazine to the terrestrial-phase CRLF. Direct effects to terrestrial invertebrates resulting
from exposure to simazine may also indirectly affect the CRLF via reduction in available
food.
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies
The use of simazine on corn and other crops that require pollination may result in
exposure to non-target beneficial insects, such as the honey bee. The results of acute
contact toxicity testing of simazine on the honey bee (Apis mellifera) are summarized in
Table A-8 and Section A.3.1. By 48 hours in the contact test, 6.5% mortality was
observed in the 96.7 |ig/bee treatment group (MRID 000369-35); therefore, the LD50
value for the contact test is >96.7 |ig/bee. As a result, simazine is categorized as
practically non-toxic to honeybees on an acute contact basis. The acute contact honey
89
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bee LD50 = >96.7 |ig/bee (converted to 754 ppm based on Mayer and Johansen, 1990) is
used to assess potential indirect effects to the terrestrial-phase CRLF.
4.2.3.2 Terrestrial Invertebrates: Open Literature Studies
Three open literature studies on simazine effects to non-target insects including
earthworms and beetles were located and are summarized in Table A-9 and Section A.3.2
of Appendix A. All studies are classified as qualitative because no effects were observed
at the highest test concentrations.
The results of two earthworm studies (Martin, 1982: ECOTOX #58170; Lydy and Linck,
2003; ECOTOX #71459) showed no adverse effects to mortality and growth, following
96-hours of exposure at 10 ug/cm2 and 7 days of exposure at 100 ppm, the highest
simazine concentrations tested. Samsoe-Peterson (1987; ECOTOX # 70278) evaluated
the effects of simazine (50% a.i.) on the rove beetle, Aleochara bileneata. Following 5
days of exposure, no mortality or reduction in egg production were observed in the
simazine-treated adult female beetles at an application rate of 600 L/ha (assuming that the
density of water is 8.35 lbs/gallon, an application rate of 600 L/ha is roughly equivalent
to 534 lb/A). Although this application rate was intended to be the "maximum
recommended practical use", it is well above the current maximum registered labeled use
for simazine of 5.94 lb ai/A. According to the standard used by the International
Organization of Biological Control (IOBC) working group "Pesticides and Beneficial
Organisms", simazine was classified as "harmless" to the rove beetle.
4.2.4 Toxicity to Terrestrial Plants
Terrestrial plant toxicity data are used to evaluate the potential for simazine to affect
riparian zone and upland vegetation within the action area for the CRLF. Impacts to
riparian and upland {i.e., grassland, woodland) vegetation may result in indirect effects to
both aquatic- and terrestrial-phase CRLFs, as well as modification to designated critical
habitat PCEs via increased sedimentation, alteration in water quality, and reduction in of
upland and riparian habitat that provides shelter, foraging, predator avoidance and
dispersal for juvenile and adult CRLFs.
Plant toxicity data from both registrant-submitted studies and studies in the scientific
literature were reviewed for this assessment. Registrant-submitted studies are conducted
under conditions and with species defined in EPA toxicity test guidelines. Sub-lethal
endpoints such as plant growth, dry weight, and biomass are evaluated for both monocots
and dicots, and effects are evaluated at both seedling emergence and vegetative life
stages. Guideline studies generally evaluate toxicity to ten crop species. A drawback to
these tests is that they are conducted on herbaceous crop species only, and extrapolation
of effects to other species, such as the woody shrubs and trees and wild herbaceous
species, contributes uncertainty to risk conclusions.
Commercial crop species have been selectively bred, and may be more or less resistant to
particular stressors than wild herbs and forbs. The direction of this uncertainty for
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specific plants and stressors, including simazine, is largely unknown. Homogenous test
plant seed lots also lack the genetic variation that occurs in natural populations, so the
range of effects seen from tests is likely to be smaller than would be expected from wild
populations.
Based on the results of the tests, it appears that emerged seedlings are more sensitive to
simazine via soil/root uptake exposure than emerged plants via foliar routes of exposure.
However, all tested plants, with the exception of corn, exhibited adverse effects in both
the seedling emergence and vegetative vigor toxicity tests, following exposure to Princep
4L at 4 lb ai/A. The results of the Tier II seedling emergence and vegetative vigor
toxicity tests on non-target plants are summarized below in Table 4.6 and also in
Appendix A (Tables A-19 and A-20).
In Tier II seedling emergence toxicity tests, the most sensitive monocot and dicot species
are onion and lettuce, respectively. EC25 values for lettuce and onions, which are based
on a reduction in dry weight, are 0.009 lb ai/A and 0.02 lb ai/A, respectively. In the Tier
II vegetative vigor test, lettuce (a dicot) and oat (a monocot) were determined to be
equally sensitive to treatment, based on dry weight, with an EC25 of 0.033 lb ai/A for
both species; the NOAEC for both was 0.016 lb ai/A.
Based on a review of the open literature, no additional information is available that
indicates greater non-target terrestrial plant sensitivity to simazine than the registrant-
submitted studies discussed above.
Table 4.6 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data
Crop
Tvpc of Study
Species
NOAEC
(lb ai/A)
EC25
(lb ai/A)
Most sensitive
parameter
Slope
Seedling Emergence
Monocots
Corn
4.0
>4.0
None
NA
Oats
0.016
0.031
Dry Weight
3.82
Onion
0.0017
0.02
Shoot Height
0.901
Ryegrass
0.15
0.045
Dry Weight
3.18
Dicots
Radish
0.049
>0.049
Dry Weight
0.344
Soybean
<0.049
0.057
Dry Weight
1.92
Lettuce
0.0018
0.009
Dry Weight
1.88
Tomato
0.016
0.038
Dry Weight
3.85
Cucumber
0.016
0.046
Dry Weight
2.56
Cabbage
0.049
0.034
Dry Weight
1.95
Vegetative Vigor
Monocots
Corn
4.0
>4.0
None
NA
Oats
0.016
0.033
Dry Weight
3.75
Onion
0.016
0.039
2.19
Ryegrass
0.049
0.26
Shoot Height
3.36
Dicots
0.049
0.063
Dry Weight
2.19
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Radish
Soybean
0.049
0.085
Dry Weight
2.86
Lettuce
0.016
0.033
Dry Weight
3.08
Tomato
0.031
0.037
Dry Weight
4.18
Cucumber
0.016
0.036
Dry Weight
1.38
Cabbage
0.016
0.041
Dry Weight
1.89
In addition, a report on the toxicity of simazine to woody plants (Wall, 2007) was
reviewed by the Agency. A total of 79 species were tested at application rates ranging
from 0.5 to 12 lb ai/A. The species were exposed to simazine in a direct application,
which represents a worst case exposure scenario. It is expected that woody plant species
adjacent to treated areas would not be exposed to simazine at the tested rates. In addition,
simazine is labeled for use around numerous woody species including citrus, tree nuts,
grapes, and woody shrubs and vines. Based on the available data, it is unlikely that
simazine will cause adverse effects to non-target woody plant species. A summary of the
woody plant data is provided in Table A-20b of Appendix A.
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern
The Agency uses the probit dose response relationship as a tool for providing additional
information on the potential for acute direct effects to individual listed species and
aquatic animals that may indirectly affect the listed species of concern (U.S. EPA, 2004).
As part of the risk characterization, an interpretation of acute RQ for listed species is
discussed. This interpretation is presented in terms of the chance of an individual event
(i.e., mortality or immobilization) should exposure at the EEC actually occur for a species
with sensitivity to simazine on par with the acute toxicity endpoint selected for RQ
calculation. To accomplish this interpretation, the Agency uses the slope of the dose
response relationship available from the toxicity study used to establish the acute toxicity
measures of effect for each taxonomic group that is relevant to this assessment. The
individual effects probability associated with the acute RQ is based on the mean estimate
of the slope and an assumption of a probit dose response relationship. In addition to a
single effects probability estimate based on the mean, upper and lower estimates of the
effects probability are also provided to account for variance in the slope, if available.
Based on a review of the acute toxicity for simazine, no dose response information is
available to estimate a slope for this analysis; therefore, a default slope assumption of 4.5
(with lower and upper bounds of 2 to 9) (Urban and Cook, 1986) is used.
Individual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.1
(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP,
Environmental Fate and Effects Division (June 22, 2004). The model allows for such
calculations by entering the mean slope estimate (and the 95% confidence bounds of that
estimate) as the slope parameter for the spreadsheet. In addition, the acute RQ is entered
as the desired threshold.
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4.4
Incident Database Review
A review of the EIIS database for ecological incidents involving simazine was completed
on May 22, 2006. The results of this review for terrestrial, plant, and aquatic incidents
are discussed below in Sections 4.4.1 through 4.4.3, respectively.
4.4.1 Terrestrial Incidents
Only two simazine incidents have been reported involving terrestrial organisms. The first
incident entailed two quail found dead in an area in Yosemite National Park treated with
granular simazine to control weeds. Chemical analysis of the crop and gizzard contents
was conducted, and 0.5 ppm simazine was detected. The reported certainty index for the
quail incident (# 1005754-015) was categorized as "unlikely" because the detected
concentrations of simazine were "not enough to cause a kill." In the second incident,
which occurred on June 26, 1998, five Canada geese were found dead in a corn field in
Rockingham County, Virginia, following spray application of Princep 4L (#1008168-
001). Soil and vegetative samples were collected along the bank near the creek in which
the dead geese were found. Substantial concentrations of simazine and atrazine were
found in the samples. Simazine detections ranged from 0.16 to 2.3 ppm in soil and 8.5 to
20.5 ppm in foliage. The certainty index for the corn field incident is "probable."
4.4.2 Plant Incidents
Three simazine incidents have been reported for terrestrial plants. In the first incident,
water from a simazine-treated swimming pool affected a section of lawn grass. The
certainty index for the lawn incident (# 1003567-001) is "highly probable." Both of the
remaining two incidents occurred on May 9, 2000, in a corn field in Virginia (#1012366-
022 and #112366-023). Following aerial broadcast application of simazine and atrazine,
plant damage was observed to approximately 130 acres of corn. Reported observations
of corn plant damage included shortened internodes, and reduced root structure, plant
height and ear production, which led to a reduction in the final yield of corn. The
certainty index for both incidents was reported as "unlikely."
4.4.3 Aquatic Incidents
Nine freshwater aquatic incidents involving fish kills have been reported for simazine
between the years of 1976 and 1995. Six incidents have a certainty index of "highly
probable" or "probable," and the other three have certainty indices of "possible" and
"unlikely." Six incidents resulted from treatment of a lake, pond, or lagoon; two
incidents were associated with simazine use on corn and from simazine use along railroad
tracks; and the treatment site for the other incident was not reported. In a number of the
incidents involving direct application of simazine to lakes, ponds, and lagoons, the
legality of use was listed as "misuse" or "undetermined." For those incidents where the
legality of use is reported as "registered use," the volume of the water bodies is not
provided; therefore, it is unclear whether simazine was applied in accordance with its
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intended use. The six incidents involving direct application of simazine to water are
summarized in Appendix H. All occurred prior to 1996, when label language was
clarified to restrict direct applications to ornamental ponds and aquaria greater than 1,000
gallons. It is important to note that in a number of the incidents involving direct
application of simazine to water, low DO, caused by decaying aquatic vegetation, is
attributed as an indirect effect related to the fish kills. The certainty index associated
with the remaining three incidents (those resulting from use on corn, railroad tracks, and
an unspecified treatment site) was reported as "unlikely."
Of the nine reported incidents, three were reported in California, two were reported in
Nebraska, two were reported in South Carolina and one was reported in Michigan and in
Tennessee. Fish species listed in these kills include smelt, bullheads, stickleback, striped
bass, bluegills, channel catfish, croaker, menhaden, mullet, northern pike, pinfish, yellow
perch, sea trout, black bullhead, and fathead minnows. A complete list of the aquatic
incidents involving simazine is included as Appendix H.
5. Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations to
determine the potential ecological risk from varying simazine use scenarios within the
action area and likelihood of direct and indirect effects on the CRLF and its designated
critical habitat. The risk characterization provides an estimation (Section 5.1) and a
description (Section 5.2) of the likelihood of adverse effects; articulates risk assessment
assumptions, limitations, and uncertainties; and synthesizes an overall conclusion
regarding the likelihood of adverse effects to the CRLF or its designated critical habitat
(i.e., "no effect," "likely to adversely affect," or "may affect, but not likely to adversely
affect").
5.1 Risk Estimation
Risk is estimated by calculating the ratio of exposure to toxicity. This ratio is the risk
quotient (RQ), which is then compared to pre-established acute and chronic levels of
concern (LOCs) for each category evaluated (Appendix C). For acute exposures to the
CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the LOC
is 0.05. For acute exposures to the CRLF and mammals, the LOC is 0.1. The LOC for
chronic exposures to CRLF and its prey, as well as acute exposures to plants is 1.0.
Risk to the aquatic-phase CRLF is estimated by calculating the ratio of exposure to
toxicity using l-in-10 year EECs based on the label-recommended simazine usage
scenarios summarized in Table 3.3 and the appropriate aquatic toxicity endpoint from
Table 4.2. Risks to the terrestrial-phase CRLF and its prey (e.g. terrestrial insects, small
mammals and terrestrial-phase frogs) are estimated based on exposures resulting from
foliar and granular applications of simazine (Tables 3.5 through 3.7) and the appropriate
toxicity endpoint from Table 4.4. Exposures are also derived for terrestrial plants, as
discussed in Section 3.3 and summarized in Table 3.8, based on the highest application
rates of simazine use within the action area.
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5.1.1 Exposures in the Aquatic Habitat
The highest screening-level aquatic EEC (based on non-granular use of simazine on
Christmas trees at 5.94 lbs ai/A) was initially used to derive risk quotients. In cases
where LOCs were not exceeded based on this use pattern, additional RQs were not
derived because it was assumed that RQs for lower EECs would also not exceed LOCs.
However, if LOCs were exceeded based on the highest EECs, use-specific RQs were also
derived.
5.1.1.1 Direct Effects to Aquatic-Phase CRLF
Direct effects to the aquatic-phase CRLF are based on peak EECs in the standard pond
and the lowest acute toxicity value for freshwater fish. In order to assess direct chronic
risks to the CRLF, 60-day EECs and the lowest chronic toxicity value for freshwater fish
are used. As shown in Table 5.1, all acute and chronic RQs are well below their
respective LOCs; therefore, direct effects associated with acute and chronic exposure to
simazine are not expected to occur for the aquatic-phase CRLF. RQs were calculated
only for the use that resulted in the highest EEC (foliar use on Christmas trees at 5.94 lb
ai/A) because none of the acute or chronic LOCs were exceeded. These RQs are further
characterized in Section 5.2.1.1.
Tab
e 5.1 Summary of Direct Effect RQs for the Aquatic-phase CRLF
Direct Effects
to CRLF'1
Su novate
Species
Toxicity
Value
(Jig/L)
EEC
(Hg/L)b
RQ
Probability of
Individual
Effect
LOC
Excccdancc
and Risk
Interpretation
Acute Direct
Toxicity
Fathead
minnow
LC50 = 6,400
Peak: 130.2
0.02
1 in 9.6E+13
(1 in 2,950 to 1
in 2.3E+52)0
Nod
Chronic Direct
Toxicity
NOAEC =
960
60-day:
91.4
0.10
Not calculated
for chronic
endpoints
Noe
a RQs associated with acute and chronic direct toxicity to the CRLF are also used to assess potential indirect
effects to the CRLF based on a reduction in freshwater fish and frogs as food items.
b The highest EEC based on foliar use of simazine on Christmas trees at 5.94 lb ai/A (see Table 3.3).
0 A probit slope value for the acute fathead minnow toxicity test is not available; therefore, the effect
probability was calculated based on a default slope assumption of 4.5 with upper and lower 95% confidence
intervals of 2 and 9 (Urban and Cook, 1986).
d RQ < acute endangered species LOC of 0.05.
e RQ < chronic LOC of 1.0.
5.1.1.2 Indirect Effects to Aquatic-Phase CRLF via Reduction in Prey
(non-vascular aquatic plants, aquatic invertebrates, fish, and frogs)
Non-vascular Aquatic Plants
Indirect effects of simazine to the aquatic-phase CRLF (tadpoles) via reduction in non-
vascular aquatic plants in its diet are based on peak EECs from the standard pond and the
lowest acute toxicity value for aquatic non-vascular plants. As shown in Table 5.2, RQs
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exceed the acute risk LOC (RQ >1.0) for aquatic plants for liquid applications of
simazine to Christmas trees (5.94 lb ai/A), non-cropland (5 lb ai/A), berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A), and granular applications of
simazine to non-bearing fruit (8 lb ai/A) and berries (4 lb ai/A) with RQ values ranging
from 1.49 to 3.62. The preliminary effects determination is "may effect", based on
indirect effects to aquatic-phase CRLFs based on a reduction in non-vascular aquatic
plants as food items.
Table 5.2 Summary of Acute RQs Used to Estimate Indirect Effects to the CRLF via
Effects to Non-Vascular Aquatic Plants (diet of CRLF in tadpole life stage and
habitat of aquatic-phase CRLF)
Uses
Application rate (lb
ai/A) and type*
Peak EEC
(fig/L)
Indirect effects
RQ**
(food and habitat)
Christmas trees
5.94 (liquid)
130.2
3.62
Berries1
4 (liquid)
108.4
3.01
4 (granular)
103.4
2.87
Tree plantations
4 (liquid)
88.0
2.44
Tree nurseries
4 (liquid)
68.2
1.89
Non-cropland2
5 (liquid)
66.04
1.83
Non-bearing fruit3
8 (granular)
61.5
1.71
Avocados
4 (liquid)
53.5
1.49
Olives
4 (liquid)
33.9
0.94
Nuts (high rate)4
4 (liquid)
25.6
0.71
Grapes
4.8 (liquid)
18.2
0.51
Nuts (low rate)5
2 (liquid)
12.8
0.36
Corn
2 (liquid)
12.3
0.34
Shelterbelts
3 (granular)
12.0
0.33
Fruit (low and high rates)6
2 and 4 (liquid)
5.6-11.1
0.04-0.31
Citrus7
4 (liquid)
7.1
0.20
Turf (residential, recreational, and
sod farm)
1 (2 liquid and granular
applications w/30 day
interval)
4.3-8.8
0.03-0.06
* Simazine is applied once/season via ground application, unless otherwise noted.
** = LOC exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC / blue green algae
EC50 value of 36 |ig/L (MRID 426624-01).
1 Specifically: blueberries, blackberries, boysenberries, loganberries, raspberries, and cranberries
2 Specifically: commercial, industrial, institutional premises, equipment, highways, and rights-of-way
3 Specifically: apples, cherries, peaches, and pears
4 Specifically: filberts, hazelnuts, macadamia nuts, and walnuts
5 Specifically: almonds
6 Specifically: apples, cherries, pears, nectarines, and peaches
7 Specifically: grapefruits, lemons, and oranges
96
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Aquatic Invertebrates
Indirect acute effects to the aquatic-phase CRLF via effects to prey (invertebrates) in
aquatic habitats are based on peak EECs in the standard pond and the lowest acute
toxicity value for freshwater invertebrates. For chronic risks, 21-day EECs and the lowest
chronic toxicity value for invertebrates are used to derive RQs. A summary of the acute
and chronic RQ values for exposure to aquatic invertebrates (as prey items of aquatic-
phase CRLFs) is provided in Table 5.3. Acute RQs exceed the LOCs for listed species
(RQ > 0.05) for liquid applications of simazine to Christmas trees (5.94 lb ai/A), non-
cropland (5 lb ai/A), and berries, tree plantations, tree nurseries, and avocados (4 lb ai/A);
LOCs are also exceed for granular applications of simazine to non-bearing fruit (8 lb
ai/A) and berries (4 lb ai/A). Although the range of acute RQs exceeding LOCs is from
0.05 to 0.13, all acute RQs are less than LOCs for non-listed species (RQ = 0.5).
Resulting chronic RQs are less than the chronic LOC (RQ > 1.0) for aquatic invertebrates
for all modeled simazine uses. The preliminary effects determination is "may effect" for
indirect effects to aquatic-phase CRLFs based on a reduction of freshwater invertebrates
as prey (via direct acute toxicity to freshwater invertebrates). However, reduction in the
freshwater invertebrate prey base via chronic toxicity is not expected.
'I'iihie 5.3 Siimmarv of Acute and Chronic KQs I sod to Kstimale Indirect K fleets to the
CUM'" via Direct Kfleets on Aquatic Invertebrates as Dietary l-'ood Items (prev of
CUM''juveniles and adults in aquatic habitats)
I SOS
Application r;Mc
(II) iii/A) iiiul
(\ pc
iv;ik r.r.c
uiii/i.i
21-chij
i:i.(
ifiji/i.)
Inriirccl
r.nvcis
Acute UQ
Indiivcl
r.lTecls
Chronic UQ
Christmas trees
5.94 (liquid)
130.2
127.2
0.13
0.06
Berries1
4 (liquid)
108.4
105.4
0.11
0.05
4 (granular)
103.4
100.5
0.10
0.05
Tree plantations
4 (liquid)
88.0
85.6
0.09
0.04
Tree nurseries
4 (liquid)
68.2
66.3
0.07
0.03
Non-cropland2
5 (liquid)
66.0
64.6
0.07
0.03
Non-bearing fruit3
8 (granular)
61.5
59.8
0.06
0.03
Avocados
4 (liquid)
53.5
51.9
0.05
0.03
Olives
4 (liquid)
33.9
29.9
0.03
0.01
Nuts (high rate)4
4 (liquid)
25.6
25.0
0.03
0.01
Grapes
4.8 (liquid)
18.2
17.6
0.02
0.01
Nuts (low rate)5
2 (liquid)
12.8
12.5
0.01
0.01
Corn
2 (liquid)
12.3
11.9
0.01
0.01
Shelterbelts
3 (granular)
12.0
9.3
0.01
<0.01
Fruit (low and high
rates)6
2 and 4 (liquid)
5.6-11.1
5.4-10.9
0.01
<0.01
Citrus7
4 (liquid)
7.1
6.9
0.01
<0.01
Turf (residential,
1 (2 liquid and
4.3-8.8
4.2-8.6
<0.01
<0.01
97
-------
recreational, and sod
farm)
granular
applications w/30
day interval)
* Simazine is applied once/season via ground application, unless otherwise noted.
** = LOC exceedances (acute RQ > 0.05; chronic RQ > 1.0) are bolded and shaded. Acute RQ = use-specific
peak EEC / daphnia TL50 value of 1,000 |ig/L (MRID 000436-76). Chronic RQ = use-specific 21-day EEC /
daphnia NOAEC value of 2,000 |ig/L (MRID 000436-76).
1 Specifically: blueberries, blackberries, boysenberries, loganberries, raspberries, and cranberries
2 Specifically: commercial, industrial, institutional premises, equipment, highways, and rights-of-way
3 Specifically: apples, cherries, peaches, and pears
4 Specifically: filberts, hazelnuts, macadamia nuts, and walnuts
5 Specifically: almonds
6 Specifically: apples, cherries, pears, nectarines, and peaches
7 Specifically: grapefruits, lemons, and oranges
Fish and Frogs
Fish and frogs also represent prey of the CRLF. RQs associated with acute and chronic
direct toxicity to the CRLF (Table 5.1) are used to assess potential indirect effects to the
CRLF based on a reduction in freshwater fish and frogs as food items. Given that acute
and chronic RQs for direct toxicity to the CRLF are less than LOCs, indirect effects
based on a reduction of fish and frogs as prey items are not expected.
5.1.1.3 Indirect Effects to CRLF via Reduction in Habitat and/or
Primary Productivity (Freshwater Aquatic Plants)
Indirect effects to the CRLF via direct toxicity to aquatic plants are estimated using the
most sensitive non-vascular and vascular plant toxicity endpoints. Because there are no
obligate relationships between the CRLF and any aquatic plant species, the most sensitive
EC50 values, rather than NOAEC values, were used to derive RQs. As shown in Table
5.4, none of the RQs exceed the LOC of 1 for vascular aquatic plants. However, as
previously discussed in Section 5.1.2.2 and summarized in Table 5.2, LOCs are exceeded
for non-vascular aquatic plants for liquid applications of simazine to Christmas trees
(5.94 lb ai/A), non-cropland (5 lb ai/A), berries, tree plantations, tree nurseries, and
avocados (4 lb ai/A), and granular applications of simazine to non-bearing fruit (8 lb
ai/A) and berries (4 lb ai/A). Therefore, the preliminary effects determination is "may
effect", based on indirect effects to habitat and/or primary productivity for the aquatic-
phase CRLF.
Table 5.4 Summary of Acute UQs I sed lo l.slimale Indirect K fleets lo (lie ( KM- via
KITects lo Vascular Aquatic Plants (habitat of aquatic-phase CUM' )11
I SOS
Application r;ilo (II)
|H'
iv;ik r.r.c
(uii/i.i
Imlirccl effects
HQ
(rood iind hiihiiiii)
Christmas trees
5.94 (liquid)
130.2
0.93
Berries1
4 (liquid)
108.4
0.77
98
-------
4 (granular)
103.4
0.74
Tree plantations
4 (liquid)
88.0
0.63
Tree nurseries
4 (liquid)
68.2
0.49
Non-cropland2
5 (liquid)
66.0
0.47
Non-bearing fruit3
8 (granular)
61.5
0.44
Avocados
4 (liquid)
53.5
0.38
Olives
4 (liquid)
33.9
0.24
Nuts (high rate)4
4 (liquid)
25.6
0.18
Grapes
4.8 (liquid)
18.2
0.13
Nuts (low rate)5
2 (liquid)
12.8
0.09
Corn
2 (liquid)
12.3
0.09
Shelterbelts
3 (granular)
12.0
0.09
Fruit (low and high rates)6
2 and 4 (liquid)
5.6-11.1
0.08
Citrus7
4 (liquid)
7.1
0.05
Turf (residential, recreational, and
sod farm)
1 (2 liquid and granular
applications w/30 day
interval)
4.3-8.8
0.03-0.06
a RQs used to estimate indirect effects to the CRLF via toxicity to non-vascular aquatic plants are
summarized in Table 5.2.
* Simazine is applied once/season via ground application, unless otherwise noted.
** = LOC exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC / duckweed EC50
value of 140 |ig/L (MRID 425037-04).
1 Specifically: blueberries, blackberries, boysenberries, loganberries, raspberries, and cranberries
2 Specifically: commercial, industrial, institutional premises, equipment, highways, and rights-of-way
3 Specifically: apples, cherries, peaches, and pears
4 Specifically: filberts, hazelnuts, macadamia nuts, and walnuts
5 Specifically: almonds
6 Specifically: apples, cherries, pears, nectarines, and peaches
7 Specifically: grapefruits, lemons, and oranges
5.1.2 Exposures in the Terrestrial Habitat
5.1.2.1 Direct Effects to Terrestrial-phase CRLF
As previously discussed in Section 3.3, potential direct effects to terrestrial-phase CRLFs
are based on liquid spray {i.e., foliar) and granular applications of simazine.
5.1.2.1.1 Foliar (non-granular liquid spray applications)
Definitive acute RQ values for terrestrial-phase CRLFs could not be derived because the
acute avian effects data, which are used as a surrogate for terrestrial-phase amphibians,
show no mortality to both the mallard duck and bobwhite quail at the highest tested level
of simazine (LC50 >5,000 mg/kg-diet). In addition, the LD50 value for the mallard duck
(>4,640 mg/kg-bw) also indicates no mortality at the highest test concentration. None of
the predicted dose- and dietary-based EECs (Table 3.7) exceed or approach the respective
5,000 mg/kg-diet and 4,640 mg/kg-bw test levels, suggesting that acute avian and
99
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terrestrial-phase CRLF mortality is unlikely. The preliminary effects determination for
direct acute effects to the terrestrial-phase CRLF is "no effect".
Potential direct chronic effects of non-granular simazine applications to the terrestrial-
phase CRLF are derived by considering dietary-based exposures modeled in T-REX for a
small bird (20g) consuming small invertebrates. Chronic effects are estimated using the
lowest available toxicity data for birds. EECs are divided by toxicity values to estimate
chronic dietary-based RQs. As shown in Table 5.5, chronic RQs, which range from 1.35
to 8.02, exceed LOCs for all modeled non-granular uses of simazine. Therefore, the
preliminary effects determination is "may effect" for direct chronic effects to the
terrestrial-phase CRLF.
Table 5.5 Summary ol C hronic UQs- I sod to Kslimalc Direct K fleets lo (lie
Terrestrial-phase CUM'' (non-granular application)
I so
(Application Rii(o)
I)icl;in-I> 1) are bolded and shaded.
2 Based onbobwhite quail chronic reproduction NOAEC = 100 mg/kg-diet (MRID 001631-34).
5.1.2.1.2 Granular applications
As previously discussed in Section 3.3.2, direct effects to the terrestrial-phase CRLF via
exposure to simazine granules are derived based on LD50/ft2 values. However, definitive
LD50/ft2 values could not be derived because avian LD50 values were reported as greater
than the highest treatment level of simazine {i.e., 50% mortality was not observed in the
highest treatment levels of simazine). Therefore, a comparison of granular EECs with
adjusted avian LD50 values for two weight classes of 20g and lOOg (representative of
juvenile and adult terrestrial-phase CRLFs) was completed. As shown in Table 5.6, the
predicted granular EECs in mg ai/ft2 do not exceed or approach the adjusted LD50 value,
which is based on a mallard duck study where no mortality was observed at the highest
test level of simazine. Further qualitative discussion of potential acute risks to birds
associated with exposure to granular simazine is provided in Section 5.2.1.2. The
100
-------
preliminary effects determination for direct effects to the terrestrial-phase CRLF via
granular application of simazine is "no effect".
Table 5.6 Comparison of Granular EECs to Adjusted LD50 Value Used to Estimate
Direct Effects to the Terrestrial-phase CRLF (granular application)
Use
Application Rate
EEC
Adjusted LDS0 Value (mg/kg-bw)1
(lb ai/A)
(mg/ft2)
20 g (juvenile)
lOOg (adult)
Non-bearing Fruit
8
83.3
2,409
3,067
Berries
4
41.7
Shelterbelts
3
31.2
Turf
1
10.4
1 Adjusted Avian LD50 = LD50(AW/TW)(1
.15-1)
Terrestrial chronic exposure estimates and risks for granular applications of simazine
were derived according to the methodology presented in Appendix I. Exposure
estimates and predicted chronic risks are based on direct ingestion of soil invertebrates
that have bioaccumulated simazine residues of granules in soil. Chronic risks to birds
associated with ingestion of earthworms that have bioaccumulated simazine granules are
not expected because the estimated earthworm residue (4.74 mg ai/kg at an application
rate of 8 lb ai/A) is well below the avian chronic endpoint (100 mg/kg-diet).
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in
Prey (terrestrial invertebrates, mammals, and frogs)
5.1.2.2.1a Terrestrial Invertebrates (non-granular applications)
In order to assess the risks of foliar applications of simazine to terrestrial invertebrates,
which are considered prey of CRLF in terrestrial habitats, the honey bee is used as a
surrogate for terrestrial invertebrates. The toxicity value for terrestrial invertebrates is
calculated by multiplying the lowest available acute contact LD50 of >96.7 |ig a.i./bee by
1 bee/0.128g, which is based on the weight of an adult honey bee. EECs (|ig 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 >755 |ig a.i./g of bee. Given that the
toxicity endpoint is non-definitive (i.e., the LD50 value is greater than the highest test
concentration), the reported RQ values represent an upper bound. The resulting non-
definitive RQ values for large insect and small insect exposures bound the potential range
of exposures for terrestrial insects to simazine. With the exception of the 1 and 2 lb ai/A
simazine use rates (for almonds, nectarines, peaches, corn, and turf) on large insects, RQ
values may exceed the LOC (RQ > 0.05) for both large and small terrestrial insects for all
non-granular uses (Table 5.7). The preliminary effects determination for indirect effects
to terrestrial-phase CRLFs via reduction in terrestrial invertebrates as dietary food items
is "may affect".
101
-------
Table 5.7 Summary of RQs Used to Estimate Indirect Effects to the Terrestrial-
phase CRLF via Direct Effects on Terrestrial Invertebrates as Dietary Food
Items
Use
Small Insect RQ*
Large Insect RQ*
Christmas trees
(5.94 lb ai/A)
<1.06
<0.11
Non-cropland
(5 lb ai/A)
<0.89
<0.10
Grapes
(4.8 lb ai/A)
<0.86
<0.10
Apples. Pears. Sour Cherries. Avocados.
Blueberries. Citrus. Filberts. Ha/.clnuls.
Macadamia Nuts. Olives. Walnuts. Tree
Plantations, and Tree Nurseries
(4.0 lb ai/A)
<0.72
<0.08
Almonds. Nectarines. Peaches, and Corn
(2.0 lb ai/A)
<0.35
0.04
Turf
(1.0 lb ai/A; 2 apps)
<0.17
0.02
* = LOC exceedances (RQ > 0.05) are bolded and shaded. Because a definitive endpoint was not
established for terrestrial invertebrates (i.e., the value is greater than the highest test concentration), the
RQ represents an upper bound value.
5.1.2.2.1b Terrestrial Invertebrates (granular applications)
In order to assess the risks of granular applications of simazine to terrestrial invertebrates,
the earthworm fugacity model (Appendix I) is used to calculate simazine concentrations
in soil (mg/kg) and earthworms, which are used as a surrogate for terrestrial invertebrates
that may be consumed by a terrestrial-phase CRLF. The concentration of simazine in soil
from granular application rates associated with non-bearing fruit (8 lb ai/A) is 4.6 mg/kg
(based on a soil depth of 15 cm). The estimated concentration of simazine in bulk soil is
used to estimate simazine concentrations in a terrestrial invertebrate (i.e., earthworm).
Simazine is assumed to partition between soil organic carbon, the interstitial pore water,
and air occupying the residual pore space not occupied by interstitial water. Earthworms
dwelling in soil are assumed to be exposed to both soil pore-water and via the ingestion
of soil (Belfroid et al., 1994). The concentration of simazine in earthworms (4.74 mg
ai/kg) is calculated as a combination of uptake from soil pore water and ingested soil
across the gastro-intestinal tract, based on information presented in Appendix I.
Comparison of the acute oral LD50 value for the honey bee (>755 |ig a.i./g of bee) with
the estimated concentration of simazine in terrestrial insects (4.74 mg ai/kg) shows that
adverse effects to terrestrial invertebrates are unlikely at the predicted level of simazine
exposure. Therefore, terrestrial-phase CRLFs are not likely to be indirectly affected via
reduction in terrestrial invertebrates (exposed to simazine granules) as a food source.
102
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5.1.2.2.2a
Mammals (Non-granular applications)
Risks associated with ingestion of small mammals by large terrestrial-phase CRLFs are
derived for dietary-based and dose-based exposures modeled in T-REX for a small
mammal (15g) consuming short grass. Acute and chronic effects are estimated using the
most sensitive mammalian toxicity data for simazine. EECs are divided by the toxicity
value to estimate acute and chronic dose-based RQs as well as chronic dietary-based
RQs. As previously discussed in Section 4.1, indirect effects to terrestrial-phase CRLFs
via direct acute effects to small mammals as prey items are evaluated using the acute
toxicity data for simazine, rather than the more toxic DIA degradate, because DIA is not
expected to form and persist in the environment at any substantial level. Definitive acute
dose-based RQ values, based on toxicity data for parent simazine, could not be derived
because the simazine LD50 value is >5,000 mg/kg-bw, and 30 percent mortality was
observed at the highest test concentration. Therefore, the acute dose-based RQ values are
representative of upper bound values. For the simazine, upper bound acute dose-based
RQs exceed LOCs for only the highest application rate to Christmas trees (5.94 lb ai/A).
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 for all modeled uses of
simazine (Table 5.8). Therefore, the preliminary effects determination for indirect effects
to terrestrial-phase CRLFs via reduction in small mammals (exposed to non-granular
applications of simazine) as dietary food items is "may affect".
Table 5.8 Summary of Acute and Chronic RQs* Used to Estimate Indirect Effects to
the Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary Food
Items (non-granular application)
Use
Chronic RQs
Dose-based Acute RQ3
(Application Rate)
Dose-based Chronic RQ1
Dictarv-bascd
Chronic RQ2
Christmas trees
883
143
<0.12
(5.94 lb ai/A)
Non-cropland
744
120
<0.10
(5 lb ai/A)
Grapes
(4.8 lb ai/A)
714
115
<0.10
Apples, Pears, Sour Cherries,
595
96
<0.08
Avocados, Blueberries, Citrus,
Filberts, Hazelnuts, Macadamia
Nuts, Olives, Walnuts, Tree
Plantations, and Tree Nurseries
(4.0 lb ai/A)
Almonds, Nectarines, Peaches,
297
48
<0.04
and Corn
(2.0 lb ai/A)
Turf
149
24
<0.02
(1.0 ai/A; 2 apps)
* = LOC exceedances (acute RQ
>0.1 and chronic RQ > 1) are bolded and shaded.
Based on dose-based EEC and simazine rat NOAEL = 0.7 mg/kg/day (MRID 418036-01).
2 Based on dietary-based EEC and simazine rat NOAEC = 10 mg/kg-diet (MRID 418036-01).
3 Based on dose-based EEC and simazine rat acute oral LD50 = >5,000 mg/kg-bw (MRID 001488-97).
103
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Because a definitive endpoint was not established for mammals (i.e.. the value is greater than the highest test
concentration), the acute RQ represents an upper bound value.
5.1.2.2.2a Mammals (granular applications)
Indirect effects to terrestrial-phase CRLFs via ingestion of small mammals that may
consume simazine granules are based on LD50/ft2 values. However, definitive LD50/ft2
values could not be derived because the mammalian LD50 value was reported as > 5,000
mg/kg-bw {i.e., 50% mortality was not observed in the highest treatment levels of
simazine). Comparison of granular EECs with the adjusted mammalian LD50 value for
the smallest weight class of 15g (representative of a small mammal that an adult
terrestrial-phase CRLF could consume) was completed (Table 5.9). For mammals, the
adjusted LD50 value is based on the converted dose at which 30% mortality occurred.
Because the predicted EECs are well below the adjusted LD50 values for mammals, there
is a low likelihood of acute mortality to mammals consuming granules at application
rates < 8 lb ai/A. Therefore, the preliminary effects determination for indirect effects to
terrestrial-phase CRLFs via an acute reduction in small mammals (exposed to granular
applications of simazine) as dietary food items is "no effect".
Table 5.9 Comparison of Granular EECs to Adjusted LD?o Value Used to Estimate
Indirect Effects to the Terrestrial-phase CRLF via Direct Effects on Small
Mammals as Dietary Food Items (granular application)
Use
Application Rate
(lb ai/A)
EEC
(m«/ft2)
Adjusted LD50 Value (mg/kg-bw)1
Non-bearing Fruit
8
83.3
>10,989
Berries
4
41.7
Shcllcrbclls
3
31.2
Turf
i
10.4
' Adjusted Mammalian LD, = LD5(TW/AW)l";"
Although the Agency has no standard methodology for assessing chronic risk to
mammals from ingestion of granules, it is possible to estimate chronic granular exposure
for mammals via direct ingestion of soil invertebrates that have bioconcentrated pesticide
residues of granules in soil. Terrestrial chronic exposure estimates and risks for granular
applications of simazine were derived according to the methodology presented in
Appendix I. Based on the dietary method and a granular simazine application rate of 8 lb
ai/A, chronic LOCs are not exceeded for insectivorous mammals because the respective
earthworm residue concentration (4.74 mg ai/kg) is less than the mammalian NOAEC (10
mg/kg). However, chronic doses for insectivorous mammals, based on the two highest
granular application rates of simazine (4 and 8 lb ai/A) and adjusted NOAEL for the
smallest size class of mammals (15 g) exceeds chronic LOCs with RQ values ranging
from 1.83 to 3.66 (see Appendix I). Therefore, the preliminary effects determination for
indirect effects to terrestrial-phase CRLFs via a chronic reduction in small mammals
(exposed to granular applications of simazine) as dietary food items is "may affect".
104
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5.1.2.2.3
Frogs
An additional prey item of the adult terrestrial-phase CRLF is other species of frogs. In
order to assess risks to these organisms, dietary-based and dose-based exposures modeled
in T-REX for a small bird (20g) consuming small invertebrates are used. As previously
discussed in Section 5.1.2.1, direct acute effects to frogs are unlikely, based on the
available avian acute toxicity data. However, dietary-based chronic RQ values exceed
the LOC for all modeled non-granular uses of simazine (Table 5.5). Therefore, the
preliminary effects determination for indirect effects to terrestrial-phase CRLFs via
reduction in other species of frogs as dietary food items is "may affect".
5.1.2.3 Indirect Effects to CRLF via Reduction in Terrestrial Plant
Community (Riparian and Upland Habitat)
Potential indirect effects to the CRLF resulting from direct effects on riparian and upland
vegetation are assessed using RQs from terrestrial plant seedling emergence and
vegetative vigor EC25 data as a screen. Based on the results of the submitted terrestrial
plant toxicity tests, it appears that dicot plants are more sensitive in the emerged seedling
test than the vegetative vigor test. However, all tested plants, with the exception of corn,
exhibited adverse effects in both the seedling emergence and vegetative vigor test,
following exposure to simazine. The results of these tests indicate that a variety of
terrestrial plants that may inhabit riparian and upland zones may be sensitive to simazine
exposure.
For monocot and dicot plants inhabiting dry and semi-aquatic areas, the LOC (RQ > 1.0)
is exceeded for exposures resulting from single applications of all non-granular and
granular uses of simazine (Tables 5.10 and 5.11). In addition, spray drift RQs exceed
LOCs for all non-granular uses of simazine for both monocot and dicot plants. Example
output from TerrPlant v. 1.2.2 is provided in Appendix F. The preliminary effects
determination for indirect effects to terrestrial- and aquatic-phase CRLFs via reduction in
the terrestrial plant community is "may affect".
Table 5.10 UQs- for Monocols Inhabiting l)rv and Semi-Aquatic Areas Kxposed lo Simazine via
UiinolTand Drift
I SO
Application
nilo
(lbs ii.i./A)
Application
method
Drill
Yiiluc
Spr;i\ (1 rill
no
l)n iircii
HQ
Scmi-iupiiilic
iircii UO
Christmas trees
5.y4
Foliar - ground
1
2.97
5.94
32.67
Non-cropland
5
Foliar - aerial
5
12.5
15
37.5
Grapes
4.8
Foliar - ground
1
2.40
4.80
26.40
Apples, Pears, Sour
Cherries, Avocados,
Blueberries, Citrus,
Filberts, Hazelnuts,
Macadamia Nuts,
Olives, Walnuts, Tree
4
Foliar - ground
1
2.0
4.0
22.0
105
-------
Plantations, and Tree
Nurseries
Almonds, Nectarines,
Peaches, Corn, and
Turf
2
Foliar - ground
1
1.0
2.0
11.0
Rights-of-Way and
Non-bearing Fruit
8
Granular
0
NA
4.0
40.0
Berries
4
Granular
0
NA
2.0
20.0
Shelterbelts
3
Granular
0
NA
1.5
15.0
Turf
2
Granular
0
NA
1.0
10.0
* = LOC exceedances (RQ > 1) are bolded and shaded.
Table 5.11 RQs* for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to Simazine via
Runoff and Drift
Use
Application
rate
(lbs a.i./A)
Application
method
Drift
Value
(%)
Sprav drift
RQ
Drv area
RQ
Semi-aquatic
area RQ
Christmas trees
5.94
Foliar - ground
1
6.60
13.20
72.60
Non-cropland
5
Foliar - aerial
5
27.78
33.33
83.33
Grapes
4.8
Foliar - ground
1
5.33
10.67
58.67
Apples, Pears, Sour
Cherries, Avocados,
Blueberries, Citrus,
Filberts, Hazelnuts,
Macadamia Nuts,
Olives, Walnuts, Tree
Plantations, and Tree
Nurseries
4
Foliar - ground
1
4.44
8.89
48.89
Almonds, Nectarines,
Peaches, Corn, and
Turf
2
Foliar - ground
1
2.22
4.44
24.44
Rights-of-Way and
Non-bearing Fruit
8
Granular
0
NA
8.89
88.89
Berries
4
Granular
0
NA
4.44
44.44
Shelterbelts
3
Granular
0
NA
3.33
33.33
Turf
2
Granular
0
NA
2.22
22.22
* = LOC exceedances (RQ > 1) are bolded and shaded.
5.1.3 Primary Constituent Elements of Designated Critical Habitat
5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-
Breeding Habitat)
Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
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Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
Alteration in water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
The preliminary effects determination for aquatic-phase PCEs of designated habitat
related to potential effects on aquatic and/or terrestrial plants is "may affect", based on
the risk estimation provided in Sections 5.1.1.2, 5.1.1.3, and 5.1.2.3.
The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." To assess
the impact of simazine on this PCE, acute and chronic freshwater fish and invertebrate
toxicity endpoints, as well endpoints for aquatic non-vascular plants, are used as
measures of effects. RQs for these endpoints were calculated in Sections 5.1.1.1 and
5.1.1.2. Based on these results, the preliminary effects determination for alteration of
characteristics necessary for normal growth and viability of the CRLF is "no effect" (see
Section 5.1.1.1). However, aquatic invertebrate and non-vascular aquatic plant food
items of the CRLF may be affected; therefore the preliminary effects determination for
potential impacts to these food items is "may affect" (see Section 5.1.1.2).
5.1.3.2 Terrestrial-Phase (Upland Habitat and Dispersal Habitat)
Two of the four assessment endpoints for the terrestrial-phase PCEs of designated critical
habitat for the CRLF are related to potential effects to terrestrial plants:
Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or 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.
The preliminary effects determination for terrestrial-phase PCEs of designated habitat
related to potential effects on terrestrial plants is "may affect", based on the risk
estimation provided in Section 5.1.2.3.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of simazine on this PCE,
acute and chronic toxicity endpoints for birds, mammals, and terrestrial invertebrates are
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used as measures of effects. RQs for these endpoints, which were calculated in Section
5.1.2.2, exceed the LOCs for all simazine non-granular uses. Granular uses of simazine
are not expected to cause direct effects to terrestrial invertebrate and frog prey items of
the terrestrial-phase CRLF; however, chronic effects to small insectivorous mammals that
ingest granules may occur. The preliminary effects determination for adverse habitat
modification via impacts of non-granular uses of simazine to terrestrial-phase CRLF food
items is "may affect".
The fourth terrestrial-phase PC is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. Direct acute effects, via mortality, are not expected for the terrestrial-phase
CRLF (see Section 5.2.1.2); however, chronic reproductive effects are possible for all
non-granular uses of simazine. Therefore the preliminary effects determinations for
adverse habitat modification is "no effect" via direct acute effects to terrestrial-phase
CRLFs and "may affect" based on chronic exposures to non-granular applications of
simazine.
5.2 Risk Description
The risk description synthesizes an overall conclusion regarding the likelihood of adverse
impacts leading to an effects determination (i.e., "no effect," "may affect, but not likely
to adversely affect," or "likely to adversely affect") for the CRLF and its designated
critical habitat.
If the RQs presented in the Risk Estimation (Section 5.1) show no direct or indirect
effects for the CRLF, and no modification to PCEs of the CRLF's designated critical
habitat, a "no effect" determination is made, based on simazine's use within the action
area. However, if direct or indirect effect LOCs are exceeded or effects may modify the
PCEs of the CRLF's critical habitat, the Agency concludes a preliminary "may affect"
determination for the FIFRA regulatory action regarding simazine. A summary of the
results of the risk estimation (i.e., "no effect" or "may affect" finding) is provided in
Table 5.12 for direct and indirect effects to the CRLF and in Table 5.13 for the PCEs of
designated critical habitat for the CRLF.
Table 5.12 Preliminary Effects Determination Summary for Simazine - Direct and Indirect
Effects to CRLF
Assessment Endpoint
Preliminary
Effects
Determination
Basis For Preliminary Determination
Aquatic-Phase CRLF
(eggs, larvae, juveniles, and adults)
Survival, growth, and reproduction
of CRLF individuals via direct
effects on aquatic phases
No effect
Using freshwater fish as a surrogate, no acute and chronic
LOCs are exceeded (Table 5.1).
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Survival, growth, and reproduction
of CRLF individuals via effects to
food supply (i.e., freshwater
invertebrates, non-vascular plants)
Freshwater
invertebrates
and aauatic
non-vascular
olants : Mav
affect
Acute freshwater invertebrate and aquatic non-vascular plant
RQs exceed LOCs for liquid applications of simazine to
Christmas trees (5.94 lb ai/A), non-cropland (5 lb ai/A), and
berries, tree plantations, tree nurseries, and avocados (4 lb
ai/A); acute LOCs are also exceeded for granular applications
of simazine to non-bearing fruit (8 lb ai/A) and berries (4 lb
ai/A) (Tables 5.2 and 5.3).
Fish and fross:
No effect
No acute and chronic LOCs are exceeded based on the most
sensitive toxicity data for freshwater fish (Table 5.1).
Survival, growth, and reproduction
of CRLF individuals via indirect
effects on habitat, cover, and/or
primary productivity (i.e., aquatic
plant community)
May affect
LOCs are exceeded for non-vascular aquatic plants for liquid
applications of simazine to Christmas trees (5.94 lb ai/A), non-
cropland (5 lb ai/A), and berries, tree plantations, tree
nurseries, and avocados (4 lb ai/A); LOCs are also exceeded
for granular applications of simazine to non-bearing fruit (8 lb
ai/A) and berries (4 lb ai/A) (Table 5.2).
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.
May affect
LOCs are exceeded for both monocots and dicots for all
modeled uses of simazine (Tables 5.10 and 5.11).
Terrestrial-Phase CRLF
(Juveniles and adults)
Survival, growth, and reproduction
of CRLF individuals via direct
effects on terrestrial phase adults and
juveniles
Acute: No
effect
Based on the available avian acute toxicity data, which is used
as a surrogate for terrestrial-phase amphibians, no mortality
was reported at the highest test concentrations of simazine.
Predicted EECs, based on non-granular and granular uses of
simazine, are well below reported non-definitive acute avian
toxicity values for simazine (Section 5.1.2.1 and Table 5.6).
Chronic: May
affect for non-
granular uses;
No effect for
granular uses
Using birds as a surrogate, chronic RQs exceed the LOC for all
modeled non-granular uses of simazine (Tables 5.5). However,
chronic risks to birds associated with ingestion of earthworms
that have bioaccumulated simazine granules are not expected
(Section 5.1.2.1.2).
Survival, growth, and reproduction
of CRLF individuals via effects on
prey (i.e., terrestrial invertebrates,
small terrestrial mammals and
terrestrial phase amphibians)
May affect
Chronic RQs for mammals and birds exceed the LOCs for all
modeled non-granular uses of simazine (Tables 5.5 and 5.8).
Acute RQs for mammals also exceed LOCs for liquid
applications of simazine to Christmas trees (5.94 lb ai/A)
(Table 5.8). Acute RQs for small terrestrial invertebrates
exceed the LOC for all modeled uses of simazine (Table 5.7).
Non-granular uses of simazine are not expected to cause direct
effects to terrestrial invertebrate and frog food items of the
terrestrial-phase CRLF (Tables 5.6 and 5.9); however, chronic
effects are possible for small insectivorous mammals that are
food items of the CRLF.
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Survival, growth, and reproduction
of CRLF individuals via indirect
effects on habitat (i.e., riparian
vegetation)
LOCs are exceeded for both monocots and dicots for all
modeled uses of simazine (Tables 5.10 and 5.11).
Table 5.13 Preliminary Effects Determination Summary for Simazine - PCEs of Designated
Critical Habitat for the CRLF
Assessment Endpoint
Preliminary Effects
Determination
Basis For Preliminary Determination
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.
May affect
LOCs are exceeded for both monocots and dicots
for all modeled uses of simazine (Tables 5.10 and
5.11).
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.
May affect
LOCs are exceeded for both monocots and dicots
for all modeled uses of simazine (Tables 5.10 and
5.11).
Alteration of other chemical characteristics
necessary for normal growth and viability of
CRLFs and their food source.
Growth and viability
of CRLF: No effect
Using freshwater fish as a surrogate, no acute and
chronic LOCs are exceeded (Table 5.1).
Food source: Mav
affect
Acute freshwater invertebrate and aquatic non-
vascular plant RQs exceed LOCs for liquid
applications of simazine to Christmas trees (5.94 lb
ai/A), non-cropland (5 lb ai/A), and berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A);
acute LOCs are also exceeded for granular
applications of simazine to non-bearing fruit (8 lb
ai/A) and berries (4 lb ai/A) (Tables 5.2 and 5.3).
Reduction and/or modification of aquatic-
based food sources for pre-metamorphs
(e.g., algae)
May affect
LOCs are exceeded for non-vascular aquatic plants
for liquid applications of simazine to Christmas trees
(5.94 lb ai/A), non-cropland (5 lb ai/A), and berries,
tree plantations, tree nurseries, and avocados (4 lb
ai/A); LOCs are also exceeded for granular
applications of simazine to non-bearing fruit (8 lb
ai/A) and berries (4 lb ai/A) (Table 5.2).
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,
May affect
LOCs are exceeded for both monocots and dicots
for all modeled uses of simazine (Tables 5.10 and
5.11).
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Table 5.13 Preliminary Effects Determination Summary for Simazine- PCEs of Designated
Critical Habitat for the CRLF
Assessment Endpoint
Preliminary Effects
Determination
Basis For Preliminary Determination
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
May affect
LOCs are exceeded for both monocots and dicots
for all modeled uses of simazine (Tables 5.10 and
5.11).
Reduction and/or modification of food
sources for terrestrial phase juveniles and
adults
May affect
Chronic RQs for mammals and birds exceed the
LOCs for all modeled non-granular uses of simazine
(Tables 5.5 and 5.8). Acute RQs for mammals also
exceed LOCs for liquid applications of simazine to
Christmas trees (5.94 lb ai/A) (Table 5.8). Acute
RQs for small terrestrial invertebrates exceed the
LOC for all modeled uses of simazine (Table 5.7).
Non-granular uses of simazine are not expected to
cause direct effects to terrestrial invertebrate and frog
food items of the terrestrial-phase CRLF (Tables 5.6
and 5.9); however, chronic effects are possible for
small insectivorous mammals that are food items of
the CRLF.
Alteration of chemical characteristics
necessary for normal growth and viability of
juvenile and adult CRLFs and their food
source.
May affect
Chronic RQs for mammals and birds exceed the
LOCs for all modeled non-granular uses of simazine
(Tables 5.5 and 5.8). Acute RQs for mammals also
exceed LOCs for liquid applications of simazine to
Christmas trees (5.94 lb ai/A) (Table 5.8). Acute
RQs for small terrestrial invertebrates exceed the
LOC for all modeled uses of simazine (Table 5.7).
Non-granular uses of simazine are not expected to
cause direct effects to terrestrial invertebrate and frog
food items of the terrestrial-phase CRLF (Tables 5.6
and 5.9); however, chronic effects are possible for
small insectivorous mammals that are food items of
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. 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 and its designated critical habitat.
The criteria used to make determinations that the effects of an action are "not likely to
adversely affect" the CRLF and its designated critical habitat include the following:
Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where "take"
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occurs for even a single individual. "Take" in this context means to harass or
harm, defined as the following:
Š 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.
Š Harass is defined as actions that create the likelihood of injury to listed
species to such an extent as to significantly disrupt normal behavior
patterns which include, but are not limited to, breeding, feeding, or
sheltering.
Likelihood of the Effect Occurring: Discountable effects are those that are
extremely unlikely to occur.
Adverse Nature of Effect: Effects that are wholly beneficial without any adverse
effects are not considered adverse.
A description of the risk and effects determination for each of the established assessment
endpoints for the CRLF and its designated critical habitat is provided in Sections 5.2.1
through 5.2.3.
5.2.1 Direct Effects
5.2.1.1 Aquatic-Phase CRLF
The aquatic-phase considers life stages of the frog that are obligatory aquatic organisms,
including eggs, larvae, and tadpoles. It also considers submerged terrestrial-phase
juveniles and adults, which spend a portion of their time in water bodies that may receive
runoff and spray drift containing simazine. As shown in Table 5.1, acute and chronic
RQs based on the highest modeled EECs for simazine use on Christmas trees (5.94 lb
ai/A) and the most sensitive freshwater fish data (used as a surrogate for aquatic-phase
amphibians) are well below the Agency's acute and chronic risk LOCs. Comparison of
the highest modeled surface water EEC (peak = 130 |ig/L) with available NAWQA
surface water monitoring data from California indicates that the peak modeled EEC is
approximately two times higher than the maximum concentration of simazine (64.5 |ig/L)
detected in Mustang Creek in Merced County. Therefore, use of modeled EECs is
assumed to provide a conservative measure of simazine exposures for aquatic-phase
CRLFs.
Because raw data was not provided as part of the acute toxicity study for the fathead
minnow used as a surrogate for the aquatic-phase CRLF, information is unavailable to
estimate a slope for the dose response curve. Therefore, the probability of an individual
effect to aquatic-phase CRLFs was calculated based on a default assumption of 4.5 (with
lower and upper bounds of 2 and 9) (Urban and Cook, 1986). The corresponding
estimated chance of an individual acute mortality to the aquatic-phase CRLF at an RQ
level of 0.02 is 1 in 19.6 trillion (with respective upper and lower bounds of 1 in 2,950 to
1 in 2.3E+52). Given the low probability of an individual mortality occurrence and acute
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and chronic RQs that are well below LOCs, simazine is not likely to cause direct adverse
effects to aquatic-phase CRLFs.
No toxicity information on lethal and/or sublethal effects of simazine to aquatic-phase
amphibians is available, based on a comprehensive search of the open literature. As
discussed in Section 4.1.1.3, one open literature study raises questions about sublethal
effects of simazine on endocrine-mediated olfactory functions in anadromous fish.
Consideration of the sublethal data indicates that effects associated with endocrine-
mediated olfactory functions may occur in anadromous fish including salmon at simazine
concentrations as low as 0.1 |j,g/L (Moore and Lower, 2001). However, there are a
number of limitations in the design of this study, which are addressed in detail in Section
A.4.3 of Appendix A, that preclude quantitative use of the data in this risk assessment.
For example, Moore and Lower (2001) exposed epithelial tissue (after removal of skin
and cartilage) and not intact fish to simazine, and potential solvent effects could not be
reconciled (i.e., no negative control was tested). Furthermore, no quantitative
relationship is established between reduced olfactory response (measured as
electrophysiological response) of epithelial tissue to the priming hormone in the
laboratory and reduction in salmon reproduction (i.e., the ability of male salmon to
detect, respond to, and mate with ovulating females) in the wild. In summary, it is not
possible to quantitatively link the sublethal effects to the selected endpoints for the CRLF
(i.e., survival, growth, and reproduction of individuals). Also, effects to reproduction,
growth, and survival were not observed in the full life cycle studies at levels that
produced the reported sublethal effects (Appendix A). Finally, the limitations in the
study design (described further in Section A.4.3 of Appendix A) preclude the quantitative
use of this data.
A number of freshwater microcosm, mesocosm, and field studies are available for
simazine, although the lowest concentration of simazine tested in these studies was 1,000
[j,g/L, well above environmentally relevant concentrations. In many of the studies
(summarized in Section A.4.8 of Appendix A) , adverse effects to freshwater fish in field
studies following simazine application are attributed to indirect effects including a
combination of low DO and reduced food resources, rather than direct toxicity of
simazine. Therefore, the available field study data are inadequate to determine whether
simazine applications to aquatic habitats at levels of approximately 1,000 [j,g/L result in
adverse effects to freshwater fish either by direct toxicity or indirect effects such as low
DO, lost food/habitat resources, and/or decreased ecosystem productivity in the absence
of macrophytes. In addition to indirect effects associated with low DO, the results of a
field study by Tucker and Boyd (1978) suggest a possible direct effect of simazine on the
feeding response of channel catfish, following direct application of 1,300 [j,g/L to earthen
channel catfish ponds infested with stonewort. However, the application rate of simazine
used in this study is approximately three times higher than current labels allow and direct
applications to water are restricted to ornamental ponds and aquariums of 1,000 gallons
or less.
Although a number of freshwater aquatic incidents involving fish kills were reported for
simazine between the years of 1980 and 1995, the majority of these incidents were the
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result of direct application of simazine to water bodies not in accordance with the current
label restrictions for direct applications to ornamental ponds and aquaria less than 1,000
gallons. A complete list of all the aquatic incidents involving simazine is included in
Appendix H.
In summary, the Agency concludes a "no effect" determination for direct effects to the
aquatic-phase CRLF, via mortality, growth, or fecundity, based on all available lines of
evidence.
5.2.1.2 Terrestrial-Phase CRLF
Based on acute avian toxicity data as a surrogate for the terrestrial-phase amphibians,
direct acute mortality is not expected for the terrestrial-phase CRLF via exposure to non-
granular and granular simazine applications. The acute avian effects data show no
mortality at the highest treatment levels of simazine in both the acute oral (LD50 > 4,640
mg/kg-bw) and subacute dietary (LC50 > 5,000 mg/kg-diet) studies. In addition, the
predicted granular EECs in mg ai/ft2 are well below the adjusted LD50 values for two
weight classes that are intended to be representative of juvenile and adult terrestrial-phase
CRLFs. Therefore, direct effects to the terrestrial-phase CRLF via ingestion of terrestrial
invertebrate food items are not expected.
It should be noted that sublethal effects were observed in the acute mallard duck gavage
test at simazine concentrations ranging from 1,000 to 4,640 mg/kg-bw one hour after
dosing. Observed sublethal effects included reduced reaction to external stimuli (sound
and movement), wing droop, and depression. Although sublethal effects were noted,
there is a high level of uncertainty associated with the mallard duck gavage study because
the birds were 14 days old rather than 14 to 16 weeks when tested, and age is a
significant factor in the sensitivity of birds. In addition, it is unclear whether the same
types of sublethal effects, such as reduced reaction to sound and movement, would be
observed in terrestrial-phase amphibians at similar levels of simazine exposure. In order
to evaluate potential sublethal effects associated with acute exposure to simazine, the
lowest simazine concentration where sublethal effects were observed (1,000 mg/kg-bw)
is compared to predicted terrestrial-phase CRLF doses on small insect food residues
following application of non-granular simazine at 5.94 lb ai/A (913 mg/kg-bw from
Table 3.7). Because the predicted dose on food residues, based on the highest non-
granular application rate, is less than the lowest avian sublethal effects value, sublethal
effects are also unlikely for the terrestrial-phase CRLF. With respect to granular
applications, predicted EECs (< 83.3 mg ai/ft2; see Table 3.9) are less than the avian
sublethal effects value of 1,000 mg/kg-bw; therefore, sublethal effects are unlikely to be
associated with exposure to simazine granules.
In summary, the Agency concludes a "no effect" determination for acute direct effects to
the terrestrial-phase CRLF, via acute mortality, based on all available lines of evidence.
Chronic RQs exceed the Agency's LOCs for all of the non-granular uses of simazine
based on the T-REX modeled dietary residues and avian chronic toxicity data. With
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chronic dietary-based RQ values ranging from approximately 1.35 to 8.02, terrestrial-
phase CRLFs foraging on small insects may result in reduction in offspring survival via
reproductive effects. Chronic risks to the terrestrial-phase CRLF were evaluated using a
bobwhite quail NOAEC value of 100 mg/kg-diet, based on reproductive effects including
reduction in the number of eggs laid, viable embryos, live embryos, hatchlings, and 14-
day old chick survivors. The primary reproductive effect of simazine on avian
reproduction appears to be reduction in the number of eggs laid. The number of eggs laid
was reduced by 20% at the highest treatment level of 500 mg/kg-diet. Based on the
bobwhite quail NOAEC value of 100 mg/kg-diet, chronic LOCs are exceeded for
terrestrial-phase CRLFs that consume small insects for all modeled scenarios and
application rates (1 to 5.94 lb ai/A). A non-granular simazine application rate of 0.7 lb
ai/A would be required to achieve chronic RQ values for terrestrial-phase CRLFs that are
less than chronic LOCs. This value is approximately 8.5 times less than the maximum
non-granular application rate for simazine of 5.94 lb ai/A. The 5.94 lb ai/A application
rate would have to be reduced by approximately 88% in order to achieve an application
rate less than the chronic LOCs for birds, which are used as a surrogate for the terrestrial-
phase CRLF.
One incident has been reported for birds. On June 26, 1998, five Canada geese were
found dead in a corn field in Rockingham County, Virginia, following spray application
of simazine as Princep 4L (#1008168-001). Soil and vegetative samples were collected
along the bank near the creek in which the dead geese were found. Substantial
concentrations of simazine and atrazine were found in the samples. Simazine detections
ranged from 0.16 to 2.3 ppm in soil and 8.5 to 20.5 ppm in foliage. Although the
certainty index for the corn field incident was reported as probable, it is uncertain
whether geese mortality was due to simazine, given the relatively low concentrations of
simazine detected in the soil and foliage.
Chronic risks to birds associated with ingestion of earthworms that have bioaccumulated
simazine granules are not expected (see Appendix I for further details) because the
estimated earthworm residue (4.74 mg ai/kg at a maximum granular application rate of 8
lb ai/A) is well below the avian chronic endpoint (100 mg/kg-diet).
Therefore, a "likely to adversely affect" or "LAA" effects determination is concluded for
chronic direct effects to the terrestrial-phase CRLF via current non-granular uses of
simazine. However, the effects determination for chronic direct effects to the CRLF
exposed to granules is "may affect, but not likely to adversely affect" or "NLAA". This
finding is based on discountable effects (i.e., chronic effects to simazine granules are not
likely to occur and/or result in a "take" of a single listed terrestrial-phase CRLF).
5.2.2 Indirect Effects (via Reductions in Prey Base)
5.2.2.1 Algae (non-vascular plants)
As discussed in Section 2.5.3, the diet of CRLF tadpoles is composed primarily of
unicellular aquatic plants (i.e., algae and diatoms) and detritus. Based on RQs for algae
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(Table 5.2), liquid applications of simazine to Christmas trees (5.94 lb ai/A), non-
cropland (5 lb ai/A), berries, tree plantations, tree nurseries, and avocados (4 lb ai/A), and
granular applications of simazine to non-bearing fruit (8 lb ai/A) and berries (4 lb ai/A)
may affect this food source. RQs for non-vascular plants were based on the most
sensitive EC50 value of 36 |ig/L for freshwater blue-green algae (Anabaena). Further
examination of toxicity data for other freshwater non-vascular plants (diatoms and
Selenastrum) indicates that they are approximately three times less sensitive to simazine
than blue-green algae with EC50 values ranging from 90 to 100 (J,g/L. However, the range
of toxic endpoints for freshwater non-vascular plants falls within the range of peak
modeled simazine concentrations for the use patterns mentioned above (48 to 130 (J,g/L),
as well as peak measured concentrations of simazine in available monitoring data (< 65
(j,g/L). The concentration of simazine in water would have to be < 36 [j,g/L to achieve RQ
values for freshwater non-vascular aquatic plants that are less than LOCs.
Typically, algal populations are relatively dynamic, although the presence of simazine in
the water may result in an overall reduction in biomass, and/or a shift in community
composition as more sensitive species are eliminated. There is evidence to suggest that
recovery occurs in algae upon removal of simazine from the site of action, with recovery
inversely proportional to the prior exposure level. Although recovery of algal
populations has been shown to occur, if the timing of simazine applications co-occur with
the presence of tadpole life stages of the CRLF (from December to March), a reduction in
algae as a food source for the tadpole may occur.
Therefore, the effects determination for indirect effects of simazine to CRLF tadpoles via
reductions in non-vascular plants is "likely to adversely affect" or "LAA" for simazine
uses related to liquid applications simazine to Christmas trees (5.94 lb ai/A), non-
cropland (5 lb ai/A), berries, tree plantations, tree nurseries, and avocados (4 lb ai/A), and
granular applications of simazine to non-bearing fruit (8 lb ai/A) and berries (4 lb ai/A).
As previously mentioned, the aerial non-cropland and non-residential granular uses of
simazine will be cancelled in 2010. In addition, simazine use on olives, nuts, grapes,
corn, apples, cherries, pears, citrus, nectarines, peaches, and turf are not expected to
indirectly impact CRLF tadpoles (via a reduction in non-vascular plants as food) because
all RQs for these uses are below LOCs. According to the 2002-2005 CA PUR data
described in Section 2.4.3 and summarized in Table 2.3, the highest simazine useage in
California is reported for oranges and lemons (citrus), grapes, almonds and walnuts
(nuts), avocados, olives, and peaches, which are not expected to direct effects to non-
vascular plants as food for CRLF tadpoles.
5.2.2.2 Aquatic Invertebrates
As previously discussed in Section 5.1.1.2, acute RQs (ranging from 0.05 to 0.13; Table
5.3) calculated using modeled peak aquatic EECs and the 48-hour TL50 for the water flea,
Daphnia magna, exceed the acute LOC for simazine uses related to liquid applications
simazine to Christmas trees (5.94 lb ai/A), non-cropland (5 lb ai/A), berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A), and granular applications of
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simazine to non-bearing fruit (8 lb ai/A) and berries (4 lb ai/A). Although acute RQs for
these simazine uses exceed the acute listed species LOC of 0.05, they are less than the
non-listed acute LOC of 0.5.
Chronic RQs for invertebrates were less than the Agency's LOC, based on the highest
21-day modeled EECs for all simazine uses and a Daphnia NOAEC value of 2,000 [j,g/L
for the 80% formulated product of simazine. As previously discussed in Section 4.1.2.2,
chronic toxicity data for freshwater invertebrates using the TGAI are not available,
although acute data for freshwater fish show that the formulated products of simazine are
less toxic than the TGAI. Therefore, use of the formulated product chronic toxicity for
freshwater invertebrates may underestimate potential effects, given the available data for
freshwater fish. In addition, there is uncertainty associated with the NOAEC value of
2,000 [j,g/L because no adverse effects to parental mortality or production of offspring
were observed at this highest test concentration, despite an acute TL50 value (1,000 |ig/L)
for the same genus of freshwater invertebrate (Daphnia) that is two times lower than the
chronic NOAEC. In order to characterize this uncertainty, the highest 21-day modeled
EEC for simazine is compared to the lower TL50 value; based on this comparison, the 21-
day modeled EEC (127 (J,g/L) is well below the TL50 value of 1,000 (J,g/L. Chronic
effects for freshwater invertebrates would have to be more than 7 times lower than the
acute freshwater invertebrate endpoint to result in a level of effect that exceeds the LOC
for freshwater invertebrates at the predicted levels of simazine exposure. Therefore,
chronic risks to freshwater invertebrates and potential indirect effects to aquatic-phase
CRLFs that consume them as prey are not expected.
Raw data was not provided as part of the acute toxicity study for Daphnia; therefore, the
probability of an individual effect to freshwater invertebrates was calculated based on a
default assumption of 4.5 (with lower and upper bounds of 2 and 9) (Urban and Cook,
1986). The corresponding estimated chance of an individual acute
mortality/immobilization to a freshwater invertebrate at an RQ level of 0.13 is 1 in
29,900 (with respective upper and lower bounds of 1 in 26 and 1 in 1.31E+15). At the
lower RQ range of 0.05, the corresponding estimated chance of an individual acute
mortality/immobilization to a freshwater invertebrate is 1 in 4.18E+08 (with bounds of 1
in 216 and 1 in 1.75E+31). Even at the highest probability of an individual effect (1 in
26), assuming that the CRLF consumes aquatic invertebrates that are equally as sensitive
as the most sensitive water flea, potential reduction in abundance of aquatic invertebrates
as food would be approximately 3.7 percent.
Further information on the diet of the CRLF indicates that the preferred prey species is
the sowbug (Hayes and Tennant, 1985). Based on the available freshwater invertebrate
toxicity data, simazine has no effect on the sowbug (Asellus brevicaudus) with a
corresponding 48-hour TL50 value of >100,000 (J,g/L. In addition, acute TL50 and EC50
values for other freshwater invertebrate food items, including the stonefly (Pteronarcys
californica), range from 1,900 to >100,000 (J,g/L. As previously mentioned, acute
toxicity values that are >100,000 |ig/L are uncertain because they exceed the level of
simazine's solubility in water (-3,500 (J,g/L) by a wide margin. However, given that no
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adverse effects were observed at these concentrations, it is reasonable to assume that
simazine is not toxic to the sowbug at the limit of its water solubility.
The potential for simazine to elicit indirect effects to the CRLF via effects on freshwater
invertebrate food items is dependent on several factors including: (1) the potential
magnitude of effect on freshwater invertebrate individuals and populations; and (2) the
number of prey species potentially affected relative to the expected number of species
needed to maintain the dietary needs of the CRLF. Together, these data provide a basis
to evaluate whether the number of individuals within a prey species is likely to be
reduced such that it may indirectly affect the CRLF. Table 5.14 presents acute RQs and
the probability of individual effects for other freshwater invertebrate dietary items of the
CRLF, including the sowbug and stonefly.
Table 5.14 Summary of RQs Used to Assess Potential Risk to Freshwater Invertebrate
Food Items of the CRLF
CRLF Aquatic
Invertebrate Food
Item Species
Range of
Acute
Toxicity
Values (fij^L)
(No. of
Studies)1
RQ Range
(based on
an EEC of
130 jig/L)
Probability of
Individual
Effect2
Risk Interpretation
Stonefly
1,900 - 3,500
(2)
0.04 - 0.07
Up to 1 in
9.88E+06
(1.0E-05%)
(1 in 96 to 1 in
7.58E+24)
Simazine may affect sensitive food
items, such as the stonefly; however
the low probability of an individual
effect to the stonefly is not likely to
indirectly affect the CRLF via
reduction in freshwater invertebrate
prey items.
Sowbug
3,500 (1)
0.04
1 in 6.3E+09
(1 in 386 to 1
in 7.49E+35)
RQ is less than the acute LOC,
which is interpreted to represent no
direct effect; therefore, simazine is
not likely to indirectly affect the
CRLF via reduction in its preferred
food item.
1 Given the uncertainties associated with toxicity values >100,000 |ig/L. the solubility limit of simazine (3,500
|ig/L) is used as a surrogate acute toxicity value
2 The probability of an individual effect was calculated using a default probit slope of 4.5 (and lower and upper
bounds of 2 and 9).
As shown in Table 5.14, the listed species LOC, based on use of simazine on Christmas
trees at 5.94 lb ai/A, is exceeded for the stonefly (RQ = 0.07), based on the LC50 value of
1,900 (J,g/L. However, the acute RQ (based on the limit of simazine's solubility in water
as a surrogate for the acute toxicity data for the preferred sowbug food item) is 0.04, less
than the acute endangered species LOC. Based on the default probit slope of 4.5, the
probability of an individual mortality/immobilization to aquatic invertebrate food items
of the CRLF ranges from 1 in 9.9 million to 1 in 6.3 trillion at respective RQ values of
0.07 and 0.04.
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Simazine may affect sensitive aquatic invertebrates, such as the water flea; however, the
low probability (<4%) of an individual effect to the water flea is not likely to indirectly
affect the CRLF, given the wide range of other types of freshwater invertebrates that the
species consumes. Based on the non-selective nature of feeding behavior in the CRLF,
the low magnitude of anticipated acute individual effects to preferred aquatic invertebrate
prey species (<0.1%), simazine is not likely to indirectly affect the CRLF via reduction in
freshwater invertebrate food items. Therefore, the effects determination for indirect
effects to the CRLF via direct acute effects on freshwater invertebrates as prey is "may
affect, but not likely to adversely affect" or "NLAA". This finding is based on
insignificant effects. The effects are insignificant because the probability of an individual
effect level to freshwater invertebrates (< 4% at predicted levels of exposure) is low and
use of toxicity data from the most sensitive species of freshwater invertebrate species is
likely to overestimate the sensitivity of the majority of freshwater invertebrate food items
in the CRLF's diet. Therefore, any predicted effects are expected to be insignificant in
the context of a "take" of a single CRLF via direct acute effects on prey {i.e., freshwater
invertebrates).
5.2.2.3 Fish and Aquatic-phase Frogs
No endangered species acute or chronic LOCs were exceeded for freshwater fish, which
are used as a surrogate for aquatic-phase amphibians. Therefore, indirect effects to the
CRLF via a reduction in freshwater fish and other aquatic-phase frog species as prey
items is not expected, and the effects determination for this assessment endpoint is "no
effect".
5.2.2.4 Terrestrial Invertebrates
When the terrestrial-phase CRLF reaches juvenile and adult stages, its diet is mainly
composed of terrestrial invertebrates. As previously discussed in Section 5.1.2.2.1b,
indirect effects to the CRLF via reduction in terrestrial invertebrates prey items that are
exposed to simazine granules are not expected.
RQ values representing acute exposures to terrestrial invertebrates (Table 5.7) indicate
that all non-granular uses of simazine may potentially result in adverse effects to small
invertebrates. However, the acute RQ values are non-definitive {i.e., "less than" values)
because the acute contact toxicity value for the honey bee is >96.7 [j,g/bee (based on 6.5
percent mortality in the highest treatment group of 96.7 |ig/bee). The extent to which the
acute RQs, ranging from <0.17 to <1.06, may fall below the terrestrial invertebrate LOC
of 0.05 is uncertain. Further examination of the open literature data on simazine effects
to non-target insects including earthworms and beetles indicates that simazine is non-
toxic to terrestrial insects at concentrations well above environmentally-relevant levels.
Based on the maximum application rate of non-granular simazine (5.94 lb ai/A), the
concentration of simazine in soil (conservatively assuming a depth of 1 cm) is 68.5
mg/kg. In a study by Martin (1982), no adverse effects to mortality or growth of juvenile
earthworms were observed following a 7 day exposure to 100 mg/kg simazine in soil. In
addition, no mortality or reduction in egg production were observed in simazine-treated
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adult female beetles at an application rate (>500 lb ai/A) well above the maximum
current rate (Samsoe-Peterson, 1987). The IOBC classifies simazine as "harmless to the
rove beetle", and the Agency classifies simazine as practically non-toxic to honeybees on
an acute contact basis. Based on the available toxicity data, which shows that simazine is
non-toxic to terrestrial invertebrates at environmentally relevant concentrations, the
effects determination for indirect effects to the CRLF via a reduction in terrestrial
invertebrates is "may affect, but not likely to adversely affect" or "NLAA". This finding
is based on discountable effects {i.e., acute effects to simazine at the expected levels of
exposure are not likely to occur and/or result in a "take" of a single listed CRLF via a
reduction in terrestrial invertebrates as food items).
5.2.2.5 Mammals
Life history data for terrestrial-phase CRLFs indicate that large adult frogs consume
terrestrial vertebrates, including mice. RQs representing exposures of simazine to mice
(small mammals) indicate chronic risks resulting from all foliar (non-granular) uses of
simazine. In addition, acute risks are also possible, based on foliar uses of simazine to
Christmas trees (5.94 lb ai/A).
With respect to acute risks from non-granular applications, dose-based RQs, which range
from <0.02 to <0.12, are based on acute toxicity data for simazine. As previously
discussed, definitive acute RQ values could not be derived because the simazine LD50
value is >5,000 mg/kg-bw, and 30 percent mortality was observed at the highest test
concentration. Although the acute RQ for foliar simazine use on Christmas trees (< 0.12)
may exceed the LOC of 0.1, the level and/or extent of the exceedance is uncertain, given
the non-definitive value. Based on an analysis of the likelihood of individual mortality
using the highest RQ value for small mammals (RQ=0.12) and an assumed probit dose-
response slope of 4.5 (with lower and upper confidence intervals of 2 and 9), the
likelihood of an individual mortality to a mammal is 1 in 58,500 (<0.1%) with upper and
lower confidence intervals of 1 in 30 (3%) to 1 in 1.73E+16 (<0.1%). Granular
formulations of simazine are not expected to cause acute mortality to mammals because
predicted EECs are well below the adjusted LD50 values for mammals.
Simazine may affect small mammals at the highest foliar application rate of 5.94 lb ai/A;
however, the low probability (<0.1 to 3%) of an acute effect to small mammals is not
likely to affect adult terrestrial-phase CRLFs, given the wide range of other terrestrial
prey items, including terrestrial invertebrates, that the species consumes. Based on the
non-selective nature of feeding behavior in the CRLF, the low magnitude of anticipated
acute individual effects to mammals (< 3%), simazine is not likely to indirectly affect the
CRLF via acute reduction in mammalian food items. Therefore, the effects determination
for indirect effects to the CRLF via direct acute effects on mammals as prey is "may
affect, but not likely to adversely affect" or "NLAA". This finding is based on
insignificant effects because the probability of an effect to mammals is low (<3%) and
any predicted effects are expected to be insignificant in the context of a "take" of a single
terrestrial-phase CRLF via direct acute effects on mammalian prey.
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With respect to chronic risks associated with non-granular applications of simazine, dose-
based and dietary-based RQs are well above the Agency's LOCs, with dose-based values
ranging from 149 to 883 and dietary-values ranging from 24 tol43. Based on the
available toxicity data, chronic exposure of simazine to laboratory rats results in
consistent reductions in adult body weight at 100 mg/kg-diet, with a corresponding
NOAEC of 10 mg/kg-diet.
Chronic toxicity to small insectivorous mammals that ingest soil invertebrates that have
bioconcentrated pesticide residues of granules in soil is possible (see Appendix I). The
results of the assessment indicate that, when growth effect risks for mammals are
assessed on the basis of a daily ingested dose, the accumulation of simazine in terrestrial
invertebrates may represent, by itself, a biologically significant pathway for exposure for
insectivorous mammals. It should be noted, however, that chronic LOCs are exceeded
only for the two highest granular application rates of simazine (4 and 8 lb ai/A), which
will both be cancelled as part of the RED mitigation in 2010.
In summary, indirect effects are possible for large CRLF adults through decreases in
mammalian prey via chronic exposure to non-granular and granular uses of simazine.
Therefore, the effects determination for indirect effects to terrestrial-phase CRLFs via
reduction in small mammals as prey is "likely to adversely affect" or "LAA" for all
simazine uses. The maximum application rate of non-granular uses of simazine would
have to be reduced to < 0.1 lb ai/A to eliminate potential chronic risks to mammals and
associated indirect dietary effects to terrestrial-phase CRLFs.
5.2.2.6 Terrestrial-phase Amphibians
Terrestrial-phase adult CRLFs also consume frogs. RQ values representing direct
exposures of simazine to terrestrial-phase CRLFs are used to represent exposures of
simazine to frogs in terrestrial habitats. Based on estimated exposures resulting from
granular and non-granular use of simazine, chronic risks to frogs are possible, although
acute mortality is not expected. Therefore, the effects determination for indirect effects
to large CRLF adults that feed on other species of frogs as prey, via chronic exposure to
simazine, is "likely to adversely affect" or "LAA."
5.2.3 Indirect Effects (via Habitat Effects)
5.2.3.1 Aquatic Plants (Vascular and Non-vascular)
Aquatic plants serve several important functions in aquatic ecosystems. Non-vascular
aquatic plants are primary producers and provide the autochthonous energy base for
aquatic ecosystems. Vascular plants provide structure, rather than energy, to the system
as attachment sites for many aquatic invertebrates, and refugia for juvenile organisms,
such as fish and frogs. Emergent plants help reduce sediment loading and provide
stability to nearshore areas and lower streambanks. In addition, vascular aquatic plants
are important as attachment sites for egg masses of CRLFs.
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Potential indirect effects to the CRLF based on impacts to habitat and/or primary
production are assessed using RQs from freshwater aquatic vascular and non-vascular
plant data. Based on RQs for non-vascular plants (previously described in Section
5.2.2.1 and summarized in Table 5.2), LOCs are exceeded for RQs for liquid applications
of simazine to Christmas trees (5.94 lb ai/A), non-cropland (5 lb ai/A), berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A), and granular applications of
simazine to non-bearing fruit (8 lb ai/A) and berries (4 lb ai/A). RQs for vascular plants
are less than the LOC of 1 because the maximum peak EEC of 130 [j,g/L is less than the
most sensitive duckweed EC50 value of 140 (J,g/L. Therefore, indirect effects to the
CRLF via direct effects to vascular plants as habitat are not expected.
With respect to indirect effects to CRLFs via direct habitat-related impacts to non-
vascular plants, concentrations of simazine in aquatic systems near use sites could be
high enough to affect sensitive algal species. As previously discussed in Section 5.2.2.1,
the range of toxic endpoints for non-vascular plants falls with the range of peak modeled
simazine concentrations and available monitoring data. Simazine concentrations in water
would need to be < 36 [j,g/L to be below the LOC for non-vascular aquatic plants. In
addition, it should be noted that recovery from the effects of simazine and the
development of resistance to the effects of simazine in some vascular and non-vascular
aquatic plants have been reported and may add uncertainty to these findings.
In summary, the effects determination for indirect effects of simazine to CRLFs via
impacts to habitat and/or primary production through direct effects to non-vascular plants
is "likely to adversely affect" or "LAA" for uses related to liquid applications simazine to
Christmas trees (5.94 lb ai/A), non-cropland (5 lb ai/A), berries, tree plantations, tree
nurseries, and avocados (4 lb ai/A), and granular applications of simazine non-bearing
fruit (8 lb ai/A) and berries (4 lb ai/A). However, the aerial non-cropland and non-
residential granular uses of simazine will be cancelled in 2010.
5.2.3.2 Terrestrial Plants
Terrestrial plants serve several important habitat-related functions for the CRLF. In
addition to providing habitat and cover for invertebrate and vertebrate prey items of the
CRLF, terrestrial vegetation also provides shelter for the CRLF and cover from predators
while foraging. Upland vegetation including grassland and woodlands provides cover
during dispersal. Riparian vegetation helps to maintain the integrity of aquatic systems by
providing bank and thermal stability, serving as a buffer to filter out sediment, nutrients,
and contaminants before they reach the watershed, and serving as an energy source.
Loss, destruction, and alteration of habitat were identified as a threat to the CRLF in the
USFWS Recovery Plan (USFWS, 2002). Herbicides can adversely impact habitat in a
number of ways. In the most extreme case, herbicides in spray drift and runoff from the
site of application have the potential to kill (or reduce growth and/or biomass in) all or a
substantial amount of the vegetation, thus removing or impacting structures which define
the habitat, and reducing the functions (e.g., cover, food supply for prey base) provided
by the vegetation.
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Simazine is a systemic herbicide that is absorbed by the plant through both the leaves and
the roots. It acts by inhibiting photosynthesis within the targeted plant. Based on the
available toxicity data for terrestrial plants, it appears that emerged dicot seedlings are
more sensitive to simazine in the seedling emergence test than dicot plants in the
vegetative vigor test. This is demonstrated by the difference in dicot response to the two
guideline studies. The dicot EC25 values for the seedling emergence and vegetative vigor
tests are 0.009 lb ai/A and 0.033 lb ai/A, respectively, representing almost a four-fold
difference in sensitivity. Monocots show similar levels of sensitivity in the seedling
emergence and vegetative vigor toxicity tests, and dicots and monocots show similar
sensitivity in the vegetative vigor tests.
Riparian vegetation typically consists of three tiers of vegetation, which include a
groundcover of grasses and forbs, an understory of shrubs and young trees, and an
overstory of mature trees. Frogs spend a considerable amount of time resting and feeding
in riparian vegetation; the moisture and cover of the riparian plant community provides
good foraging habitat, and may facilitate dispersal in addition to providing pools and
backwater aquatic areas for breeding (USFWS, 2002). According to Hayes and Jennings
(1988), the CRLF tends to occupy waterbodies with dense riparian vegetation including
willows (Salix sp.). Upland habitat includes grassland and woodlands, as well as
scrub/shrub habitat. While no guideline data are available on the toxicity of woody
plants, the available toxicity information indicates that simazine is not likely to cause
adverse effects to non-target woody plants (Wall, 2007). In addition, simazine is labeled
for use around numerous woody species including citrus, tree nuts, and grapes, as well as
uses associated with forestry, tree plantations/nurseries, woody shrubs, and shelterbelts.
Therefore, simazine is generally not toxic to woody plants. Woody trees and shrubs in
both upland and riparian habitats are expected to intercept some of the simazine that
might otherwise be deposited on the more sensitive herbaceous species. Additionally, in
natural systems, older plants, fallen leaves, and other debris often provide a litter layer,
which may serve to protect newly emerging herbaceous plants.
As shown in Tables 5.10 and 5.11, RQs exceed LOCs for monocots and dicots inhabiting
dry and semi-aquatic areas exposed to simazine via runoff and drift. In general, it
appears that dicots are more sensitive than monocots to simazine in semi-aquatic areas.
Dicots in semi-aquatic and dry areas are approximately 2 times more sensitive than
monocots in similar areas; however, dicots and monocots show similar sensitivity to
simazine in spray drift. Further examination of the terrestrial plant species sensitivity to
simazine shows that for the tested species of monocots and dicots, 9 out of 10 species (all
tested species with the exception of corn) are sensitive to simazine at maximum granular
and non-granular application rates.
In summary, based on exceedance of the terrestrial plant LOCs for all simazine use
patterns following runoff and spray drift to semi-aquatic and dry areas, the following
general conclusions can be made with respect to potential harm to riparian habitat:
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Simazine may enter riparian areas via runoff and/or spray drift where it may
be taken up by the plant by the leaves and roots of sensitive plants.
Comparison of seedling emergence EC25 values to EECs estimated using
Terrplant suggests that existing vegetation may be affected or inhibition of
new growth may occur. Inhibition of new growth could result in degradation
of high quality riparian habitat over time because as older growth dies from
natural or anthropogenic causes, plant biomass may be prevented from being
replenished in the riparian area. Inhibition of new growth may also slow the
recovery of degraded riparian areas that function poorly due to sparse
vegetation because simazine deposition onto bare soil would be expected to
inhibit the growth of new vegetation. As stated previously, simazine is
persistent and mobile; therefore, it is likely to be transported from soil
surfaces during runoff events.
Because LOCs were exceeded for 9 out of 10 species tested in the seedling
emergence and vegetative vigor studies, it is likely that many species of
herbaceous plants may be potentially affected by exposure to simazine via
runoff and spray drift.
Based on a review of the simazine incidents for terrestrial plants, only three have been
reported. In the first incident, a section of lawn grass was damaged following application
of simazine to a swimming pool. In the remaining two incidents, both of which occurred
on May 9, 2000, 130 acres of corn was damaged following aerial application of simazine
and atrazine to corn, although both incidents were reported as "unlikely". Although the
reported number of simazine incidents for terrestrial plants is low, and due to uses either
not relevant for this assessment {i.e. application to swimming pools) or cancelled (aerial
application to corn), an absence of reports does not necessarily provide evidence of an
absence of incidents. The only plant incidents that are reported are those that are alleged
to occur on more than 45 percent of the acreage exposed to the pesticide. Therefore, an
incident could impact 40% of an exposed crop and not be included in the EIIS database
(unless it is reported by a non-registrant, such as a state agency, where data are not
systemically collected.
In summary, terrestrial plant RQs are above LOCs; therefore, upland and riparian
vegetation may be affected. However, woody plants are generally not sensitive to
environmentally-relevant simazine concentrations; therefore, effects on shading, bank
stabilization, structural diversity (height classes) of vegetation, and woodlands are not
expected. Given that both upland and riparian areas are comprised of a mixture of both
non-sensitive woody (trees and shrubs) and sensitive grassy herbaceous vegetation,
CRLFs may be indirectly affected by adverse effects to herbaceous vegetation which
provides habitat and cover for the CRLF and its prey. Therefore, the effects
determination for this assessment endpoint is "likely to adversely affect" or "LAA" for
all assessed simazine use patterns.
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As previously described in Section 3.2.5, downwind spray drift buffers were developed to
determine the distance required to dissipate spray drift to below the LOC, based on both
NOAEC and EC25 levels for terrestrial plants. Dissipation to the no effect level was
modeled in order to provide potential buffer distances that are protective of endangered
terrestrial plant species; this distance beyond the site of application is considered as the
action area for simazine. However, because no obligate relationship exists between the
CRLF and terrestrial plants, the portion of the action area that is relevant to the CRLF is
defined by the dissipation distance to the EC25 level (i.e., the potential buffer distance
required to protect non-endangered terrestrial plant species). The spray drift distances
presented in Table 3.4 were derived based on the most sensitive EC25 value for dicots in
the seedling emergence test (0.009 lb ai/A). Based on the maximum simazine aerial
application rate of 5 lb ai/A (for non-cropland uses), a spray drift buffer of 3,891 feet
from the site of application is required to dissipate to levels below the LOC (for the
portion of the action area that is relevant to the CRLF). Although the seedling emergence
endpoint is more sensitive, the Agency anticipates adverse effects that could reasonably
measured to terrestrial plants via drift exposures are better defined by the vegetative vigor
endpoint. The vegetative vigor toxicity test is intended to assess the potential effects on
plants following deposition of simazine on the leaves and above-ground portions of
plants, which are more likely to receive exposure via spray drift. Therefore, spray drift
distances are derived for the vegetative vigor endpoint, as well as the seedling emergence
endpoint, for both monocots and dicots, in Table 5.15. As discussed in Section 3.2.5, the
drift buffers for the more sensitive seedling emergence endpoint for dicots were derived
using the AgDISP model with the Gaussian extension because the 1,000 foot limit of the
AgDrift model was exceeded. However, spray drift dissipation distances reported for the
vegetative vigor endpoints and for the monocot seedling emergence endpoint were based
on the Agdrift model because the limits of the model were not exceeded using the spray
drift parameters provided in Section 3.2.5. As shown in Table 5.15, adverse effects to
terrestrial plants might reasonably be expected to occur up to 850 feet from the use site
for aerial applications and 184 feet from the use site for ground applications of simazine.
This distance is expected to decrease when the label changes cancelling aerial
applications and incorporating spray drift language are implemented in 2010. The
proposed spray drift language will result in smaller dissipation distances because
restrictions on droplet size, to more coarse drops (ASAE standard 572 spray), will result
in less drift. In some cases, topography (such as an intervening ridge) or weather
conditions (such as prevailing winds towards or away from the frog habitat) could affect
the estimates presented in Table 5.15. However, analysis of these site-specific details is
beyond the scope of this assessment.
Table 5.15 Spray Drift Dissipation Distances
Use
Application
Dissipation Distance (ft)
Rate (lb
Seedling Emergence
Vegetative Vigor
ai/A)
Monocot
Dicot
(Monocots and Dicots)
Ground Applications
Christmas trees
5.94
315
2765
184
Grapes
4.8
253
2628
144
Apples, Pears, Sour Cherries,
4
207
2523
118
Avocados, Berries, Citrus,
Filberts, Hazelnuts,
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Macadamia Nuts, Olives,
Walnuts, and Tree Plantations
and Nurseries
Almonds, Nectarines,
Peaches, Corn, and Turf
2
95
2198
56
Aerial Applications
Non-cropland
5
2,890*
3,891*
850
* = Derived using the Gaussian extension in the AgDISP model.
5.2.4 Modification to Designated Critical Habitat
5.2.4.1 Aquatic-Phase PCEs
Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
Alteration in water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
The effects determinations for indirect effects to the CRLF via direct effects to aquatic
and terrestrial plants are used to determine whether modification to critical habitat may
occur. Based on the results of the effects determinations for aquatic plants (see Sections
5.2.2.1 and 5.2.3.1), critical habitat of the CRLF may be modified via simazine-related
impacts to non-vascular aquatic plants as food items for tadpoles and habitat for aquatic-
phase CRLFs. Critical habitat may be modified by an increase in sediment deposition
and associated turbidity (via impacts to herbaceous riparian vegetation), potential
reduction in oxygen (via impacts to the aquatic plant community and primary
productivity), and reduction in herbaceous riparian vegetation that provides for shelter,
foraging, predator avoidance, and aquatic dispersal for juvenile and adult aquatic-phase
CRLFs. Simazine uses that may result in modification to critical habitat via direct effects
to non-vascular plants include liquid applications simazine to Christmas trees (5.94 lb
ai/A), non-cropland (5 lb ai/A), berries, tree plantations, tree nurseries, and avocados (4
lb ai/A), and granular applications of simazine to non-bearing fruit (8 lb ai/A) and berries
(4 lb ai/A). Based on the results of the effects determination for terrestrial plants (see
Section 5.2.3.2), simazine-related effects on shading (i.e., temperature), bank
stabilization, and structural diversity (height classes) of vegetation are not expected
because woody plants are generally not sensitive to environmentally-relevant
concentrations of simazine. However, modification to critical habitat may occur via
simazine-related impacts to sensitive herbaceous vegetation, which provide habitat and
cover for the CRLF and its prey, based on all assessed uses of simazine.
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The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." Other than
impacts to algae as food items for tadpoles (discussed above), this PCE was assessed by
considering direct and indirect effects to the aquatic-phase CRLF via acute and chronic
freshwater fish and invertebrate toxicity endpoints as measures of effects. As discussed
in Section 5.2.1.1, direct effects to the aquatic-phase CRLF, via mortality, growth, and/or
fecundity, are not expected. In addition, simazine-related effects to freshwater
invertebrates and freshwater fish as food items are also not likely to occur (see Sections
5.2.2.2 and 5.2.2.3). Therefore, simazine is not likely to adversely critical habitat by
altering chemical characteristics necessary for normal growth and viability of aquatic-
phase CRLFs and their non-plant food sources.
5.2.4.2 Terrestrial-Phase PCEs
Two of the four assessment endpoints for the terrestrial-phase PCEs of designated critical
habitat for the CRLF are related to potential effects to terrestrial plants:
Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or drip line surrounding aquatic and riparian habitat that are comprised
of grasslands, woodlands, and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance.
Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal.
As discussed above, modification to critical habitat may occur via simazine-related
impacts to sensitive herbaceous vegetation, which provides habitat, cover, and a means of
dispersal for the terrestrial-phase CRLF and its prey, based on all assessed uses of
simazine. Modification to critical habitat is not expected to occur in woodland areas
because woody plants are not sensitive to environmentally relevant concentrations of
simazine.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of simazine on this PCE,
acute and chronic toxicity endpoints for terrestrial invertebrates, mammals, and
terrestrial-phase frogs are used as measures of effects. Based on the characterization of
indirect effects to terrestrial-phase CRLFs via reduction in the prey base (see Section
5.2.2.4 for terrestrial invertebrates, Section 5.2.2.5 for mammals, and 5.2.2.6 for frogs),
critical habitat may be modified via a reduction in mammals and terrestrial-phase
amphibians as food items.
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
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source. As discussed in Section 5.2.1.2, direct acute effects, via mortality, are not
expected for the terrestrial-phase CRLF; however, chronic reproductive effects are
possible for all non-granular uses of simazine. Therefore, simazine may adversely
critical habitat by altering chemical characteristics necessary for normal growth and
viability of terrestrial-phase CRLFs and their mammalian and amphibian food sources.
6. Uncertainties
6.1 Exposure Assessment Uncertainties
6.1.1 Maximum Use Scenario
The screening-level risk assessment focuses on characterizing potential ecological risks
resulting from a maximum use scenario, which is determined from labeled statements of
maximum application rate and number of applications with the shortest time interval
between applications. The frequency at which actual uses approach this maximum use
scenario may be dependant on insecticide resistance, timing of applications, cultural
practices, and market forces.
6.1.2 Aquatic Exposure Modeling of Simazine
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
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habitats to develop a specific alternate scenario for the CRLF. CRLFs prefer habitat with
perennial (present year-round) or near-perennial water and do not frequently inhabit
vernal (temporary) pools because conditions in these habitats are generally not suitable
(Hayes and Jennings 1988). Therefore, the EXAMS pond is assumed to be representative
of exposure to aquatic-phase CRLFs. In addition, the Services agree that the existing
EXAMS pond represents the best currently available approach for estimating aquatic
exposure to pesticides (USFWS/NMFS 2004).
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations
that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone
Model is a process or "simulation" model that calculates what happens to a pesticide in a
farmer's field on a day-to-day basis. It considers factors such as rainfall and plant
transpiration of water, as well as how and when the pesticide is applied. It has two major
components: hydrology and chemical transport. Water movement is simulated by the use
of generalized soil parameters, including field capacity, wilting point, and saturation
water content. The chemical transport component 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.
Uncertainties associated with each of these individual components add to the overall
uncertainty of the modeled concentrations. Additionally, model inputs from the
environmental fate degradation studies are chosen to represent the upper confidence
bound on the mean values that are not expected to be exceeded in the environment
approximately 90 percent of the time. Mobility input values are chosen to be
representative of conditions in the environment. The natural variation in soils adds to the
uncertainty of modeled values. Factors such as application date, crop emergence date,
and canopy cover can also affect estimated concentrations, adding to the uncertainty of
modeled values. Factors within the ambient environment such as soil temperatures,
sunlight intensity, antecedent soil moisture, and surface water temperatures can cause
actual aquatic concentrations to differ for the modeled values.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a
vegetative setback on runoff and loadings. The effectiveness of vegetative setbacks is
highly dependent on the condition of the vegetative strip. For example, a well-
established, healthy vegetative setback can be a very effective means of reducing runoff
and erosion from agricultural fields. Alternatively, a setback of poor vegetative quality
or a setback that is channelized can be ineffective at reducing loadings. Until such time
as a quantitative method to estimate the effect of vegetative setbacks on various
conditions on pesticide loadings becomes available, the aquatic exposure predictions are
likely to overestimate exposure where healthy vegetative setbacks exist and
underestimate exposure where poorly developed, channelized, or bare setbacks exist.
In order to account for uncertainties associated with modeling, available monitoring data
were compared to PRZM/EXAMS estimates of peak EECs for the different uses. As
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discussed above, several data values were available from NAWQA for simazine
concentrations measured in surface waters receiving runoff from agricultural areas. The
specific use patterns (e.g. application rates and timing, crops) associated with the
agricultural areas are unknown, however, they are assumed to be representative of
potential simazine use areas. Peak EECs resulting from different simazine uses ranged
5.6-130.2 |ig/L. The maximum concentration of simazine reported by NAWQA (2000-
2005) for California surface waters with agricultural watersheds (64.5 |ig/L) was two
times less than the maximum EEC, but within the range of EECs estimated for different
uses. The maximum concentration of simazine reported by the California Department of
Pesticide Regulation surface water database (2000-2005) (36,1 |ig/L) is roughly four
times less than the highest peak EEC. Therefore, use of the PRZM/EXAMS EECs is
assumed to represent a conservative measure of exposure.
6.1.3 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
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/sub urban 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.
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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.
6.1.4 Usage Uncertainties
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
instances of misuse and misreporting. The Agency made use of the most current,
verifiable information; in cases where there were discrepancies, the most conservative
information was used.
6.1.5 Terrestrial Exposure Modeling of Simazine
The Agency relies on the work of Fletcher et al. (1994) for setting the assumed pesticide
residues in wildlife dietary items. These residue assumptions are believed to reflect a
realistic upper-bound residue estimate, although the degree to which this assumption
reflects a specific percentile estimate is difficult to quantify. It is important to note that
the field measurement efforts used to develop the Fletcher estimates of exposure involve
highly varied sampling techniques. It is entirely possible that much of these data reflect
residues averaged over entire above ground plants in the case of grass and forage
sampling.
It was assumed that ingestion of food items in the field occurs at rates commensurate
with those in the laboratory. Although the screening assessment process adjusts dry-
weight estimates of food intake to reflect the increased mass in fresh-weight wildlife food
intake estimates, it does not allow for gross energy differences. Direct comparison of a
laboratory dietary concentration- based effects threshold to a fresh-weight pesticide
residue estimate would result in an underestimation of field exposure by food
consumption by a factor of 1.25 - 2.5 for most food items.
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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 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.
Using the TREX model to estimate risk to the terrestrial-phase of the CRLF may
overestimate risk because the CRLF is not expected to readily ingest as many granules as
a foraging bird (as simulated by the TREX model) which may either: 1) mistakenly select
a simazine granule to consume instead of grit that will aid in digestion, or 2) incidentally
consume simazine granules while ingesting other food items on the ground. The CRLF
does not intentionally ingest grit; therefore, it is unlikely it would mistakenly ingest a
simazine granule for grit. However, the CRLF may incidentally ingest simazine granules
that are attached to a prey item such as a mammal, frog, or terrestrial insect. Because
amphibians typically have a slower metabolism than avian species, they also have lower
feeding rates than birds. Therefore, the CRLF is not expected to consume as many
granules as a bird. Consequently, the TREX model may overestimate the risk of
simazine granule exposure to the CRLF. It should be noted, however, that the CRLF may
potentially be exposed to simazine via other routes such as thru the skin or via ingestion
of drinking water contaminated with simazine. However, there are no approved methods
or models available to the Agency for characterizing these routes of exposure. The TREX
model is assumed to provide a reasonable representation of exposure and risk, given the
best available information and associated uncertainties that may lead to an overestimation
and an underestimation of risk.
6.2 Effects Assessment Uncertainties
6.2.1 Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test organism age may have a significant impact on the
observed sensitivity to a toxicant. The acute toxicity data for fish are collected on
juvenile fish between 0.1 and 5 grams. Aquatic invertebrate acute testing is performed on
recommended immature age classes (e.g., first instar for daphnids, second instar for
amphipods, stoneflies, mayflies, and third instar for midges).
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Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients that act directly without metabolic transformation because younger age
classes may not have the enzymatic systems associated with detoxifying xenobiotics. In
so far as the available toxicity data may provide ranges of sensitivity information with
respect to age class, this assessment uses the most sensitive life-stage information as
measures of effect for surrogate aquatic animals, and is therefore, considered as
protective of the CRLF.
6.2.2 Use of surrogate species effects data
Guideline toxicity tests and open literature data on simazine are not available for frogs or
any other aquatic-phase amphibian; therefore, freshwater fish are used as surrogate
species for aquatic-phase amphibians. Although no data is available for simazine, the
available open literature information on atrazine (a closely related triazine herbicide)
toxicity to aquatic-phase amphibians shows that acute and chronic ecotoxicity endpoints
for aquatic-phase amphibians are generally about 3 to 4 times less sensitive than
freshwater fish. Given that atrazine and simazine share a similar mode of action, it is
assumed that same relationship in toxicity between freshwater fish and aquatic-phase
amphibians would apply to simazine. Therefore, endpoints based on freshwater fish
ecotoxicity data are assumed to be protective of potential direct effects to aquatic-phase
amphibians including the CRLF, and extrapolation of the risk conclusions from the most
sensitive tested species to the aquatic-phase CRLF is likely to overestimate the potential
risks to those species. Efforts are made to select the organisms most likely to be affected
by the type of compound and usage pattern; however, there is an inherent uncertainty in
extrapolating across phyla. In addition, the Agency's LOCs are intentionally set very
low, and conservative estimates are made in the screening level risk assessment to
account for these uncertainties.
6.2.3 Sublethal Effects
For an acute risk assessment, the screening risk assessment relies on the acute mortality
endpoint as well as a suite of sublethal responses to the pesticide, as determined by the
testing of species response to chronic exposure conditions and subsequent chronic risk
assessment. Consideration of additional sublethal data in the assessment is exercised on a
case-by-case basis and only after careful consideration of the nature of the sublethal
effect measured and the extent and quality of available data to support establishing a
plausible relationship between the measure of effect (sublethal endpoint) and the
assessment endpoints.
Open literature is useful in identifying sublethal effects associated with exposure to
simazine. These effects in freshwater fish include, but are not limited to, decreased
response from olfactory epithelium and effects on endocrine-mediated processes.
However, no data are available to link the sublethal measurement endpoints to direct
mortality or diminished reproduction, growth and survival that are used by OPP as
assessment endpoints. While the study by Moore and Lower (2001) attempted to relate
the results of olfactory perfusion assays to decreased predator avoidance and homing
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response in salmon, there a number of uncertainties associated with the study that limit its
utility. OPP acknowledges that sublethal effects have been associated with simazine
exposure in aquatic systems; however, at this point there are insufficient data to
definitively link the measurement endpoints to assessment endpoints. To the extent to
which sublethal effects are not considered in this assessment, the potential direct and
indirect effects of simazine on CRLF may be underestimated.
7. Risk Conclusions
In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the
information presented in this endangered species risk assessment represents the best data
currently available to assess the potential risks of simazine to the CRLF and its
designated critical habitat. The best available data suggest that simazine may affect and
is likely to adversely affect the CRLF, based on direct chronic effects to terrestrial-phase
CRLF and indirect effects to both aquatic- and terrestrial phase CRLFs (via reduction in
algae, mammals, and frogs as food and habitat modification based on effects to non-
vascular aquatic plants and herbaceous terrestrial vegetation). In addition, these effects
also constitute modification to critical habitat. These effects are anticipated to occur only
for those occupied core habitat areas, CNDDB occurrence sections, and designated
critical habitat for the CRLF that are located < 850 feet from legal use sites where
simazine is applied aerially and <184 feet from use sites where simazine is applied with
ground-based equipment. Given the LAA determination for the CRLF and potential
modification of designated critical habitat, a description of the baseline status and
cumulative effects for the CRLF is provided in Attachment II.
Using ARCGIS9, the National Land-Cover Dataset (NLCD, 2001), and the CRLF habitat
information provided by the USFWS, the Agency has identified the areas where indirect
effects to the CRLF and modification to designated critical habitat are anticipated to
occur. These areas are depicted for aerial application of simazine on rights-of-way in
Figure 7.1 and for ground-based application of simazine on other uses (i.e., Christmas
trees, cultivated crops, orchards, and turf) in Figure 7.2. Indirect effects (habitat
modification based on effects to the herbaceous terrestrial plant community) could
potentially occur in 52% of the CRLF range assessed (approximately 3.63 million out of
6.97 million acres). The percentage of "LAA" habitat was derived by dividing the sum
of the "LAA area" for the eight recovery units by the total CRLF habitat within the eight
recovery units; the CRLF habitat and "LAA" area values are provided on page 9 of
Appendix D. Modification to CRLF designated critical habitat could potentially occur in
58% (approximately 260,202 out of 450,300 acres) of the currently designated habitat
area. Based on the results of this effects determination, the CRLF may be indirectly
affected within various portions of all of the core areas within the eight recovery units. In
addition, modification of designated critical habitat is likely to occur in 36 out of the 37
critical habitat units (all critical habitat units with the exception of ALA-IB in Recovery
Unit 4). According to the information provided in Appendix D, 37 counties within
California include CRLF habitat that may be adversely affected by simazine use.
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\
/ \
Legend
j Areas where LAA applies
( -^y >,**Ł; \
Downstream extent of A A
CNDDB occurrence sections
| Critical habitat
Core areas
Recovery units
_| County boundaries
hh=h Kilometers ^ "* j V_.
01530 60 90 120 ' t \
Figure 7.1 Locations Where Aerial Application of Simazine on Rights-of-Way is
Likely to Adversely Affect the CRLF and Cause Modification to Critical Habitat
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cmHk jI5}C \
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Table 7.1 Effects Determination Summary for Direct and Indirect Effects of Simazine on the
CR.LF
Assessment Endpoint Effects
Determination1
Basis for Determination
A quatic-Ph aseCRLF
(Eggs, Larvae, Adults)
Survival, growth, and reproduction of
CRLF individuals via direct effects on
aquatic phases
No effect
Using freshwater fish as a surrogate, no acute and
chronic LOCs are exceeded.
Survival, growth, and reproduction of
CRLF individuals via effects to food
supply (i.e., freshwater invertebrates,
non-vascular plants, fish, and frogs)
Freshwater
invertebrates: NLAA
Simazine may affect sensitive aquatic invertebrates, such
as the water flea; however, the low probability (<4%) of
an individual effect to the water flea is not likely to
indirectly affect the CRLF, given the wide range of other
types of freshwater invertebrates that the species
consumes. Based on the non-selective nature of feeding
behavior in the CRLF, the low magnitude of anticipated
acute individual effects to preferred aquatic invertebrate
prey species (<0.1%), simazine is not likely to indirectly
affect the CRLF via reduction in freshwater invertebrate
food items. This finding is based on insignificant effects.
The effects are insignificant because the probability of an
individual effect level to freshwater invertebrates (< 4%
at predicted levels of exposure) is low and the most
sensitive species of freshwater invertebrate species is
likely to overestimate the sensitivity of the majority of
freshwater invertebrate food items in the CRLF's diet.
Non-vascular aauatic
olants: LAA
Simazine uses related to liquid applications on Christmas
trees (5.94 lb ai/A), non-cropland (5 lb ai/A), berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A), and
granular applications of simazine to non-bearing fruit (8
lb ai/A) and berries (4 lb ai/A) exceed LOCs; therefore,
indirect effects to tadpoles that feed on algae are
possible.
Fish and froes: No
effect
Using freshwater fish as a surrogate, no acute and
chronic LOCs are exceeded.
Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat, cover, and/or primary
productivity (i.e., aquatic plant
community)
Non-vascular
aauatic olants: LAA
LOCs are exceeded for non-vascular aquatic plants for
liquid applications of simazine to Christmas trees (5.94
lb ai/A), non-cropland (5 lb ai/A), berries, tree
plantations, tree nurseries, and avocados (4 lb ai/A);
LOCs are also exceeded for granular applications of
simazine to non-bearing fruit (8 lb ai/A) and berries (4
lb ai/A).
Vascular aauatic
olants: No effect
RQs for vascular plants are less than LOCs for all
simazine use patterns
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.
Direct effects to
forested riparian
veeetation: NLAA
Direct effects to
erassv/herbaceous
riparian veeetation:
Riparian vegetation may be affected because terrestrial
plant RQs are above LOCs. However, woody plants are
generally not sensitive to environmentally-relevant
concentrations of simazine; therefore, effects on shading,
bank stabilization, and structural diversity of riparian
areas in the action area are not expected. Aquatic-phase
CRLFs may be indirectly affected by adverse effects to
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LAA < 184 ft
(ground)
NLAA > 184 ft
(ground)
LAA < 850 ft (aerial);
NLAA > 850 ft
(aerial)
sensitive herbaceous vegetation (based on all simazine
non-granular and granular uses), which provides habitat
and cover for the CRLF and attachment sites for its egg
masses.
Terrestrial-Phase CRLF
(Juveniles and adults)
Survival, growth, and reproduction of
CRLF individuals via direct effects on
terrestrial phase adults and juveniles
Acute: No effect
The acute avian effects data (used as a surrogate for the
terrestrial-phase CRLF) show no mortality at the highest
treatment levels of simazine in both the acute oral and
subacute dietary studies. In addition, the predicted
granular EECs in mg ai/ft2 are well below the adjusted
LD50 values for two weight classes that are intended to be
representative of juvenile and adult terrestrial-phase
CRLFs.
Chronic:
LAA (for non-
granular simazine
uses)
NLAA (for granular
simazine uses)
Chronic reproductive effects are possible, based on non-
granular uses of simazine. However, chronic direct
effects to the CRLF exposed to granules are unlikely.
This finding is based on discountable effects (i.e.,
chronic effects to simazine granules are not likely to
occur and/or result in a "take" of a single listed
terrestrial-phase CRLF).
Survival, growth, and reproduction of
CRLF individuals via effects on prey (i.e.,
terrestrial invertebrates, small terrestrial
vertebrates, including mammals and
terrestrial phase amphibians)
Terrestrial
invertebrates: NLAA
Simazine is non-toxic to terrestrial invertebrates at
environmentally relevant concentrations. This finding is
based on discountable effects (i.e., acute effects to
simazine at the expected levels of exposure are not likely
to occur and/or result in a "take" of a single listed CRLF
via a reduction in terrestrial invertebrates as food items).
Mammals: LAA
Chronic RQs for non-granular formulations exceed
LOCs. Chronic effects to insectivorous mammals that
consume invertebrates exposed to simazine granules are
also possible.
Fross: LAA
Chronic risks for terrestrial-phase frogs exposed to non-
granular uses of simazine may occur, although acute
mortality is not likely.
Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat (i.e., riparian vegetation)
Direct effects to
forested riparian
veeetation: NLAA
Direct effects to
erassv/herbaceous
rioarian veeetation:
LAA < 184 ft
(ground)
NLAA > 184 ft
(ground)
LAA < 850 ft (aerial);
NLAA > 850 ft
(aerial)
Riparian vegetation may be affected because terrestrial
plant RQs are above LOCs. However, woody plants are
generally not sensitive to environmentally-relevant
concentrations of simazine; therefore, effects to
woodlands within the action area are not expected.
Terrestrial-phase CRLFs may be indirectly affected by
adverse effects to sensitive herbaceous vegetation (based
on all simazine non-granular and granular uses), which
provides habitat and cover for the CRLF and its prey.
138
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Table 7.2 Effects Determination Summary for the Critical Habitat Impact Analysis
Assessment Endpoint
Effects
Determination
Basis for Determination
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.
Habitat
modification
Sensitive herbaceous riparian vegetation may be
affected based on all granular and non-granular uses
of simazine; therefore, critical habitat may be
modified by an increase in sediment deposition and
reduction in herbaceous riparian vegetation that
provides for shelter, foraging, predator avoidance,
and aquatic dispersal for juvenile and adult aquatic-
phase 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.7
Habitat
modification
Sensitive herbaceous riparian vegetation and non-
vascular aquatic plants may be affected; therefore,
critical habitat may be modified via turbidity and
reduction in oxygen content necessary for normal
growth and viability of juvenile and adult aquatic-
phase CRLFs.
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
No effect to
growth and
viability
Habitat
modification
based on
alteration of
food source
Direct effects to the aquatic-phase CRLF, via
mortality, growth, and/or fecundity, are not
expected. However, critical habitat of the CRLF
may be modified via simazine-related impacts to
non-vascular aquatic plants as food items for
tadpoles. LOCs are exceeded for non-vascular
aquatic plants for liquid applications of simazine to
Christmas trees (5.94 lb ai/A), non-cropland (5 lb
ai/A), berries, tree plantations, tree nurseries, and
avocados (4 lb ai/A); LOCs are also exceeded for
granular applications of simazine to non-bearing
fruit (8 lb ai/A) and berries (4 lb ai/A).
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
Habitat
modification
Based on the results of the effects determinations
for aquatic plants, critical habitat of the CRLF may
be modified via simazine-related impacts to non-
vascular aquatic plants as food items for tadpoles.
LOCs are exceeded for non-vascular aquatic plants
for liquid applications of simazine to Christmas
trees (5.94 lb ai/A), non-cropland (5 lb ai/A),
berries, tree plantations, tree nurseries, and
avocados (4 lb ai/A); LOCs are also exceeded for
granular applications of simazine to non-bearing
fruit (8 lb ai/A) and berries (4 lb ai/A).
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
Habitat
modification
Modification to critical habitat may occur via
simazine-related impacts to sensitive herbaceous
vegetation, which provide habitat and cover for the
terrestrial-phase CRLF and its prey, based on all
assessed uses of simazine. Modification to critical
habitat is not expected to occur in woodland areas
because woody plants are not sensitive to
environmentally relevant concentrations of
7
Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these processes are not
biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.
139
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Elimination and/or disturbance of dispersal habitat:
Upland or riparian dispersal habitat within
designated units and between occupied locations
within 0.7 mi of each other that allow for movement
between sites including both natural and altered sites
which do not contain barriers to dispersal
Habitat
modification
simazine.
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Habitat
modification
Based on the characterization of indirect effects to
terrestrial-phase CRLFs via reduction in the prey
base, critical habitat may be modified via a
reduction in mammals and terrestrial-phase
amphibians as food items.
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
Habitat
modification
Direct acute effects, via mortality, are not expected
for the terrestrial-phase CRLF; however, chronic
reproductive effects are possible for all non-
granular uses of simazine. Therefore, simazine may
adversely critical habitat by altering chemical
characteristics necessary for normal growth and
viability of terrestrial-phase CRLFs and their
mammalian and amphibian food sources.
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.
140
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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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