Risks of Oryzalin 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
6/19/08
-------
Primary Authors:
Sujatha Sankula, Ph.D., Biologist
Faruque Khan, Ph.D., Senior Scientist
Secondary Review:
Paige Doelling, Ph.D., Biologist
Jim Lin, Ph.D., Environmental Scientist
Branch Chief, Environmental Risk Assessment Branch 1
Nancy Andrews, Ph.D.
2
-------
Table of Contents
1. Executive Summary 9
2. Problem Formulation 18
2.1 Purpose 18
2.2 Scope 20
2.3 Previous Assessments 21
2.4 Stressor Source and Distribution 21
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 28
2.5 Assessed Species 35
2.5.1 Distribution 35
2.5.2 Reproduction 40
2.5.3 Diet 40
2.5.4 Habitat 41
2.6 Designated Critical Habitat 42
2.7 Action Area 44
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 52
2.9.1 Risk Hypotheses 52
2.9.2 Diagram 53
2.10 Analysis Plan 55
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model 56
2.10.1.1 Measures of Exposure 56
2.10.1.2 Measures of Effect 57
2.10.1.3 Integration of Exposure and Effects 58
2.10.2 Data Gaps 59
3.0 Exposure Assessment 59
3.1 Label Application Rates and Intervals 59
3.2 Aquatic Exposure Assessment 61
3.2.1 Modeling Approach 61
3.2.2 Model Inputs 62
3.2.2.1. Post-processing of PRZM/EXAMS outputs to develop EECs for non-
cropland areas 63
3.2.3 Results 65
3.2.4 Existing Monitoring Data 66
3.2.4.1 USGS NAWQA Surface Water Data 66
3.2.4.2 USGS NAWQA Groundwater Data 67
3.2.4.3 California Department of Pesticide Regulation (CDPR) Data 67
3.2.4.4 Atmospheric Monitoring Data 67
3.3 Terrestrial Animal Exposure Assessment 68
3.3.1 Spray Applications 68
3
-------
3.3.2 Granular Applications 70
3.4 Terrestrial Plant Exposure Assessment 71
4. Effects Assessment 73
4.1 Toxicity of Oryzalin to Aquatic Organisms 74
4.1.1 Toxicity to Freshwater Fish 76
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies 76
4.1.1.2 Freshwater Fish: Chronic Exposure (Growth/Reproduction)
Studies 76
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open Literature
Information 77
4.1.2 Toxicity to Freshwater Invertebrates 77
4.1.2.1 Freshwater Invertebrates: Acute Exposure Studies 77
4.1.2.2 Freshwater Invertebrates: Chronic Exposure Studies 77
4.1.2.3 Freshwater Invertebrates: Open Literature Data 78
4.1.3 Toxicity to Aquatic Plants 78
4.1.3.1 Aquatic Plants: Acute Exposure Studies 78
4.2 Toxicity of Oryzalin to Terrestrial Organisms 78
4.2.1 Toxicity to Birds 80
4.2.1.1 Birds: Acute Exposure (Mortality) Studies 80
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies 81
4.2.2 Toxicity to Mammals 81
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies 81
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies 82
4.2.3 Toxicity to Terrestrial Invertebrates 82
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies 82
4.2.4 Toxicity to Terrestrial Plants 83
4.2.5 Sublethal Effects 84
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern 85
4.4 Incident Database Review 86
4.4.1 Terrestrial Animal Incidents 86
4.4.2 Terrestrial Plant Incidents 86
4.4.3 Aquatic Incidents 87
5. Risk Characterization 87
5.1 Risk Estimation 87
5.1.1 Exposures in the Aquatic Habitat 87
5.1.1.1 Direct Effects to Aquatic-Phase CRLF 87
5.1.1.2 Indirect Effects to Aquatic-Phase CRLF via Reduction in Prey (non-
vascular aquatic plants, aquatic invertebrates, fish, and frogs) 88
5.1.1.3 Indirect Effects to CRLF via Reduction in Habitat and/or Primary
Productivity (Freshwater Aquatic Plants) 91
5.1.2 Exposures in the Terrestrial Habitat 92
5.1.2.1 Direct Effects to Terrestrial-phase CRLF 92
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in Prey
(Terrestrial Invertebrates, Mammals, and Frogs) 95
4
-------
5.1.2.3 Indirect Effects to CRLF via Reduction in Terrestrial Plant
Community (Riparian and Upland Habitat) 98
5.1.3 Primary Constituent Elements of Designated Critical Habitat 100
5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-
Breeding Habitat) 100
5.1.3.2 Terrestrial-Phase (Upland Habitat and Dispersal Habitat) 100
5.2 Risk Description 105
5.2.1 Direct Effects 105
5.2.1.1 Aquatic-Phase CRLF 105
5.2.1.2 Terrestrial-Phase CRLF 106
5.2.2 Indirect Effects (via Reductions in Prey Base) 108
5.2.2.1 Algae (non-vascular plants) 108
5.2.2.2 Aquatic Invertebrates 109
5.2.2.3 Fish and Aquatic-phase Frogs 110
5.2.2.4 Terrestrial Invertebrates 110
5.2.2.5 Mammals Ill
5.2.2.6 Terrestrial-phase Amphibians Ill
5.2.3 Indirect Effects (via Habitat Effects) 112
5.2.3.1 Aquatic Plants (Vascular and Non-Vascular) 112
5.2.3.2 Terrestrial Plants 112
5.2.4 Modification to Designated Critical Habitat 115
5.2.4.1 Aquatic-Phase PCEs 116
5.2.4.2 Terrestrial-Phase PCEs 117
6.1 Exposure Assessment Uncertainties 118
6.1.1 Maximum Use Scenario 118
6.1.2 Aquatic Exposure Modeling of Oryzalin 118
6.1.3 Usage Uncertainties 120
6.1.4 Terrestrial Exposure Modeling of Oryzalin 120
6.1.5 Spray Drift Modeling 120
6.2 Effects Assessment Uncertainties 121
6.2.1 Age Class and Sensitivity of Effects Thresholds 121
6.2.2 Use of Surrogate Species Effects Data 122
6.2.3 Sublethal Effects 122
6.2.4 Location of Wildlife Species 122
7. Risk Conclusions 123
8. References 130
5
-------
Appendices
Appendix A Oryzalin Ecological Effects Data
Appendix B Oryzalin Multi-AI Product Formulations
Appendix C RQ Method and LOCs
Appendix D Oryzalin GIS Maps
Appendix E T-REX Example Output
Appendix F T-HERPS Example Output
Appendix G TERRPLANT Example Output
Appendix H ECOTOX Bibliography Not Considered for Oryzalin
Appendix I Oryzalin Incidents
Appendix J HED Data to Define Oryzalin Action Area
Appendix K ECOTOX Bibliography Considered for Oryzalin
Attachments
Attachment 1 Life History of CRLF
Attachment 2 Baseline Status and Cumulative Effects for the CRLF
List of Tables
Table 1.1 Effects Determination Summary for Direct and Indirect Effects of
Oryzalin on the CRLF 12
Table 1.2 Effects Determination Summary for the Critical Habitat Impact Analysis 14
Table 1.3 Oryzalin Use-specific Direct Effects Determinations for the CRLF 15
Table 1.4 Oryzalin Use-specific Indirect Effects Determinations for the CRLF 15
Table 2.1 Summary of Oryzalin Environmental Fate Properties 22
Table 2.2 Oryzalin Degradates Identified in Environmental Fate Studes 22
Table 2.3 Summary of Half-Life Determinations for Oryzalin at various Sites 22
Table 2.4 Oryzalin Uses Assessed for the CRLF 22
Table 2.5 Summary of California Department of Pesticide Registration (CDPR)'s
Pesticide Use Reporting (PUR1) Data from 2002 to 2005 for Currently
Registered Oryzalin Uses 34
Table 2.6 California Red-legged Frog Recovery Units with Overlapping Core
Areas and Designated Critical Habitat 37
Table 2.7 Assessment Endpoints and Measures of Ecological Effects 49
Table 2.8 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat 51
Table 3.1 Oryzalin Application Information for Food Uses 63
6
-------
Table 3.2 Oryzalin Application Information for Non-Food Uses 63
Table 3.3 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Oryzalin Endangered Species Assessment for the
CRLF 63
Table 3.4 Aquatic EECs for Oryzalin Uses in California 63
Table 3.5 Input parametres for Foliar Applications Used to Derive Terrestrial
EECS for Oryzalin with T-REX 63
Table 3.6 Upper Bound Kenaga Nomogram EECs for Dietary and Dose-Based
Exposures of the CRLF and its Prey to Oryzalin 63
Table 3.7 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via
Effects to Terrestrial Invertebrate Prey Items 70
Table 3.8 Input Parametres and EECs for Terrestrial Animals for Non-Food
Granular Uses of Oryzalin 71
Table 3.9 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and
Semi-aquatic Areas Exposed to Oryzalin Via Drift and Runoff 72
Table 4.1 Freshwater Aquatic Toxicity Profile for Oryzalin 75
Table 4.2 Categories of Acute Toxicity for Aquatic Organisms 75
Table 4.3 Terrestrial Toxicity Profile for Oryzalin 79
Table 4.4 Categories of Acute Toxicity for Avian and Mammalian Studies 80
Table 4.5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data 84
Table 5.1 Summary of Direct Effect RQs for the Aquatic phase CRLF 88
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) 89
Table 5.3 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to
the CRLF Via Direct Effects to Aquatic Invertebrates as Dietary Food
Items 90
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)1 92
Table 5.5 Summary of Acute RQs1 Used to Estimate Direct Effects to the
Terrestrial-Phase CRLF (Broadcast Spray Application) 93
Table 5.6 Summary of Chronic RQs Used to Estimate Direct Effects to the
Terrestrial-Phase CRLF (Broadcast Spray Application) 94
Table 5.7 Comparison of Granular EECs to Adjusted LDso1 Value Used to Estimate
Direct Effects to the Terrestrial-phase CRLF (Granular Non-Food
Uses) 94
Table 5.8 Summary of RQs Used to Estimate Indirect Effects to the Terrestrial-
phase CRLF via Direct Effects on Terrestrial Invertebrates as Dietary
Food Items 95
Table 5.9 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 (Broadcast Spray Application) 96
7
-------
Table 5.10 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 Non-
Food Uses) 97
Table 5.11 RQs* for Monocots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Oryzalin via Runoff and Drift 98
Table 5.12 RQs1 for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Oryzalin via Runoff and Drift 99
Table 5.13 Preliminary Effects Determination Summary for Oryzalin - Direct and
Indirect Effects to CRLF 102
Table 5.14 Preliminary Effects Determination Summary for Oryzalin - PCEs of
Designated Critical Habitat for the CRLF 104
Table 5.15 Terrestrial Phase Amphibian RQ Values Based on T-Herps for Direct
Effects to the CRLF from Ingestion of Oryzalin Residues On or In
Prey Items 104
Table 5.16 Spray Drift Dissipation Distances for Oryzalin 115
Table 7.1 Effects Determination Summary for Direct and Indirect Effects of
Oryzalin on the CRLF 125
Table 7.2 Effects Determination Summary for the Critical Habitat Impact Analysis 127
List of Figures
Figure 2.1 Oryzalin Use in Total Pounds by County 31
Figure 2.2 Oryzalin Use in California (2002-2005) by County 33
Figure 2.3 Major Uses of Oryzalin in California During 2002 - 2005 33
Figure 2.4 CRLF Recovery Units 39
Figure 2.5 CRLF Reproduction Events by Month 40
Figure 2.6 Initial Area of Concern or Footprint of Oryzalin Uses 47
Figure 2.7 Conceptual Model for Aquatic-Phase of the CRLF 53
Figure 2.8 Conceptual Model for Terrestrial-Phase of the CRLF 54
Figure 2.9 Conceptual Model for Pesticide Effects on Aquatic Component of CRLF
Critical Habitat 54
Figure 2.10 Conceptual Model for Pesticide Effects on Terrestrial Component of
CRLF Critical Habitat 55
Figure 7.1 Oryzalin Uses and CRLF Habitats 124
8
-------
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 oryzalin 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.
Oryzalin is a dinitroaniline herbicide that is registered nationally for the control of annual
grasses and certain broadleaf weeds in fruit and nut crops, vineyards, Christmas tree
plantations, ornamentals, turf, and several other non-crop sites. Its herbicidal action is
through inhibition of microtubule polymerization/function of cell division process
leading to adverse effects on seed germination and cellular respiration. Oryzalin is
formulated as granules (0.4 to 1% ai), wettable powder (75% ai), water dispersible
granules (60 - 85%), emulsifiable concentrate (2.84 to 40.4% ai), flowable concentrate
(40.4%) ai), and formulation intermediate/liquid (40.4% ai). Depending on the
formulation, the registered products are applied to the soil surface prior to the emergence
of weeds as broadcast spray or band treatment for liquid formulations (using low pressure
ground equipment) or broadcast for granular formulations (using spreaders). To facilitate
activation and movement of the chemical to the weed seed germination zone, a single V2
to 1 inch of rainfall or sprinkler irrigation is required.
Depending on the environmental conditions, the major route of oryzalin dissipation is
aqueous photolysis (half-life = 0.06 days), photo-degradation on soil surface (half-life =
3.8 days), and degradation under anaerobic soil condition (half-life =10 days). Oryzalin
appears to degrade slowly under aerobic soil conditions (half-life = 63 days) and is stable
to hydrolysis. Under field conditions oryzalin appeared to be moderately persistent, with
a half-life of about two months. Based on its low vapor pressure (1.0 x 10"7 mm Hg at
25°C) and Henry's Law Constant (1.8 x 10"8 atm-m3/mol), volatilization loss of oryzalin
from soil and water systems is expected to be insignificant compared to dissipation by
abiotic and biotic degradation. For this assessment, transport of oryzalin from initial
application sites via runoff and spray drift are considered in evaluating quantitative
estimates of oryzalin exposure to CRLF, its prey and its habitats.
Several degradates have been identified for oryzalin in various environmental fate
studies. There is no evidence in the Reregi strati on Eligibility Decision (RED) document
or in public literature identified through ECOTOX that any of these degradates are of
9
-------
toxicological concern, and none of them are found in significant amounts (>10.0%)
except 2-ethyl-7-nitro-l-propyl-5-sulfonylaminobenzimidazole 3-oxide (UN-2) at 14% in
an aquatic photodegradation study. Since 2-ethyl-7-nitro-l-propyl-5-sulfonylamino
benzimidazole 3-oxide is a minor (<2.4%) degradate in aerobic soil metabolism study
and not of toxicological concern, this assessment is based on parent oryzalin only.
Since CRLFs exist in both aquatic and terrestrial habitats, exposure of the CRLF, its prey
and its habitats to oryzalin are assessed separately for the two habitats. Due to relatively
low volatility and greater sensitivity to photolytic degradation, oryzalin is not expected to
move by long-range transport. There is also no data for oryzalin in the California
Pesticide Air Monitoring database. Tier-II aquatic exposure models are used to estimate
high-end exposures of oryzalin in aquatic habitats resulting from runoff and spray drift
from different uses. Peak model-estimated environmental concentrations resulting from
different oryzalin uses range from 3.5 to 149.5 |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 oryzalin reported by
NAWQA from 1993 to the present for California surface waters with agricultural
watersheds is 1.51 |ig/L. This value is approximately 99 times lower than the maximum
model-estimated environmental concentration.
To estimate oryzalin exposures to the terrestrial-phase CRLF, and its potential prey
resulting from uses involving oryzalin applications, the T-REX model is used for both
foliar and granular uses. The T-HERPS model is used to allow for further
characterization of dietary exposures of terrestrial-phase CRLFs relative to birds. The
TerrPlant model is used to estimate oryzalin exposures to terrestrial-phase CRLF habitat,
including plants inhabiting semi-aquatic and dry areas, resulting from uses involving
foliar oryzalin applications. AgDRIFT model is also used to estimate deposition of
oryzalin on terrestrial and aquatic habitats from spray drift.
The effects determination 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.
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
10
-------
identify instances where oryzalin 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 oryzalin 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.
Based on the best available information, the Agency makes a "Likely to Adversely
Affect" determination for the CRLF from the use of oryzalin. Oryzalin 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 based on effects to
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, respectively. Further information on
the results of the effects determination is included as part of the Risk Description in
Section 5.2. Oryzalin use-specific direct effects determinations for the CRLF and
indirect effects determinations for the prey items can be found in Tables 1.3 and 1.4,
respectively.
11
-------
Table 1.1 Effects Determination Summary for Direct and Indirect Effects of Oryzalin on the C.R.LF
Assessment Endpoint
Effects
Determination1
Basis for Determination
Aquatic-Phase CRLF
(Eggs, Larvae, and Adults)
Direct Effects:
Survival, growth, and reproduction of
CRLF individuals via direct effects on
aquatic phases
NLAA
Using freshwater fish as a surrogate, no chronic LOCs are exceeded;
acute LOCS are exceeded for 1 use only (rights-of-ways) for which
the probability of individual mortality is very low (1 in 1.9E+33 to
3.05E+26).
Indirect Effects:
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
Oryzalin may affect sensitive aquatic invertebrates, such as the water
flea; however, the low probability (1 in 1.03E+47 to 9.53E+20) 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
and food items that the species consumes during its aquatic phase.
Based on the non-selective nature of feeding behavior in the aquatic-
phase CRLF, the low magnitude of anticipated acute individual
effects to preferred aquatic invertebrate prey species, and low
measured concentrations of oryzalin in California watersheds,
oryzalin is not likely to indirectly affect the CRLF via reduction in
freshwater invertebrate food items.
Non-vascular aauatic
olants: LAA
Oryzalin (in liquid form) uses in avocado, berries, olives, tree nuts,
vineyards, non-bearing fruits, nuts and vineyards, rights-of-ways, and
ornamentals (excluding bulbs) and granular uses in non-bearing
fruits, nuts and vineyards, rights-of-ways, and ornamentals (excluding
bulbs) exceeded LOCs. Indirect effects to tadpoles that feed on algae,
therefore, are possible.
Fish and fross:
NLAA
Using freshwater fish as a surrogate, no chronic LOCs are exceeded;
acute LOCS exceeded for only 1 scenario (rights-of-ways) for which
the probability of individual mortality is very low.
Indirect Effects:
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 broadcast
spray applications of oryzalin in avocado, berries, olives, tree nuts,
vineyards, non-bearing fruits, nuts and vineyards, rights-of-ways,
and ornamentals (excluding bulbs) and granular applications in non-
bearing fruits, nuts and vineyards, rights-of-ways, and ornamentals
(excluding bulbs).
Vascular aauatic
olants: LAA
RQs for vascular plants are higher than LOCs for almost all oryzalin
use patterns except citrus fruits, warm season turf grass, and
residential areas.
Indirect Effects:
Survival, growth, and reproduction of
CRLF individuals via effects to riparian
vegetation, required to maintain
acceptable water quality and habitat in
ponds and streams comprising the
species' current range.
Direct effects to
forested riparian
vesetation: NLAA
Direct effects to
srassv/herbaceous
riparian vesetation:
LAA (ground
applications): <164 ft
(monocots); <79 ft
Riparian vegetation may be affected because terrestrial plant RQs are
above LOCs. However, woody plants (other than species such as
Douglas fir) are generally not sensitive to oryzalin; therefore, effects
of riparian 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 oryzalin liquid spray
and granular uses), which provides habitat and cover for the CRLF
and attachment sites for its egg masses.
12
-------
(dicots)
NLAA (ground
applications): >164 ft
(monocots); >79 ft
(dicots)
Terrestrial-Phase CRLF
(Juveniles and adults)
Direct Effects:
Survival, growth, and reproduction of
CRLF individuals via direct effects on
Acute: NLAA
The acute avian effects data was used as a surrogate for the terrestrial-
phase CRLF. Dose-based acute avian RQs, refined based on
amphibian dietary intake using the T-HERPS model, did not exceed
LOCs for any of the modeled uses.
terrestrial phase adults and juveniles
Chronic: LAA
Chronic reproductive effects are possible based on non-granular uses
of oryzalin.
Indirect Effects:
Survival, growth, and reproduction of
CRLF individuals via effects on prey
(i.e., terrestrial invertebrates, small
Terrestrial
invertebrates: NLAA
Oryzalin is non-toxic to terrestrial invertebrates at environmentally
relevant concentrations. At the expected levels of oryzalin exposure,
the effects on vertebrates are small and thus a reduction in terrestrial
invertebrates as food items is unlikely.
terrestrial vertebrates, including
Mammals: LAA
Chronic RQs for non-granular formulations exceed LOCs.
mammals and terrestrial phase
amphibians)
Fross: LAA
Chronic risks for terrestrial-phase frogs exposed to broadcast spray
applications of oryzalin may occur.
Direct effects to
forested riparian
vesetation: NLAA
Riparian vegetation may be affected because terrestrial plant RQs are
above LOCs. However, woody plants (other than species such as
Douglas fir) are generally not sensitive to oryzalin; therefore, effects
of riparian areas in the action area are not expected.
Indirect Effects:
Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat (i.e., riparian vegetation)
Direct effects to
srassv/herbaceous
riparian vesetation:
LAA (ground
applications): <164 ft
(monocots); <79 ft
(dicots)
NLAA (ground
applications): >164 ft
(monocots); >79 ft
(dicots)
Aquatic-phase CRLFs may be indirectly affected by adverse effects
to sensitive herbaceous vegetation (based on all oryzalin liquid spray
and granular uses), which provides habitat and cover for the CRLF
and attachment sites for its egg masses.
'NE = no effect; NLAA = may affect, but not likely to adversely affect; LAA = likely to adversely affect
13
-------
Table 1.2 Effects Determination Summary for the Critical Habitat Impact Analysis
Assessment Endpoint Effects
Determination1
Basis for Determination
(Aquatic Breeding
Aquatic-Phase CRLF PCEs
; 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
Both liquid and granular formulations of oryzalin may affect
sensitive riparian seedlings. As a result, 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
Both liquid and granular formulations of oryzalin may affect
sensitive seedlings. As a result, 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.
Effects on
growth and
viability of
CRLF
Habitat
modification
based on
alteration of
food source
Direct effects to the aquatic-phase CRLF, via mortality are
expected.
Critical habitat of the CRLF may be modified via oryzalin-
related impacts (both formulations) to non-vascular aquatic
plants as food items for tadpoles.
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
oryzalin-related impacts to non-vascular aquatic plants as food
items for tadpoles.
Terrestrial-Phase CRLF PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
Upland areas within 200 ft of the edge of the
riparian vegetation or dripline surrounding aquatic
and riparian habitat that are comprised of
grasslands, woodlands, and/or wetland/riparian
plant species that provides the CRLF shelter,
forage, and predator avoidance
Habitat
modification
Modification to critical habitat may occur via impacts of
oryzalin on sensitive seedlings which provide habitat and cover
for the terrestrial-phase CRLF and its prey.
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.
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.
14
-------
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 oryzalin. Therefore,
oryzalin may adversely affect critical habitat by altering
chemical characteristics necessary for normal growth and
viability of terrestrial-phase CRLFs and their mammalian and
amphibian food sources.
1 NE = No effect; HM = Habitat modification
Table 1.3 Oryzalin Use-specific Direct Effects Determinations1 for the CRLF
Use(s)
APPLICATION
Aquatic Phase
Terrestrial Phase
Method
Acute
Chronic
Acute
Chronic
Bearing and Nonhealing Avocado, Fig, Olive,
Berries, Citrus Fruits, Pome Fruits, Stone Fruits,
Tree Nuts and Vineyards -
Ground Broadcast
NE
NE
NLAA
LAA
Nonhealing Avocado, Fig, Olive, Berries, Citrus
Fruits, Pome Fruits, Stone Fruits, Tree Nuts and
Ground Broadcast
NE
NE
NLAA
LAA
Vineyards -
Granular
NE
NE
NLAA
-
Ornamentals (Excluding Bulbs)
Ground Broadcast
NE
NE
NLAA
LAA
Granular
NE
NE
NLAA
-
Ornamental Bulbs
Ground Broadcast
NE
NE
NLAA
LAA
Granular
NE
NE
NLAA
-
Christmas Tree Plantations
Ground Broadcast
NE
NE
NLAA
LAA
Granular
NE
NE
NLAA
-
Warm Season Turf
Ground Broadcast
NE
NE
NLAA
LAA
Granular
NE
NE
NLAA
-
Rights-of-ways
Ground Broadcast
NLAA
NE
NLAA
LAA
Granular
NLAA
NE
NLAA
-
Residential areas
Granular
NE
NE
NLAA
LAA
'NE = No effect; NLAA = May affect, but not likely to adversely affect; LAA = Likely to adversely affect
-Not applicable
15
-------
'I'iihie 1.4 Orvzsilin I so-specific Indirect KITocls Dclorniiniitions' linscd on KITccls 1» Prcv
i
V|l|lli>:lliMH
VliMc
Vt|llillit- lll\rllrl>l;llr-
1 i-in-uhil
lllM-Hrl>r;ilr-
i. Wulri
Vt|inilit- pliiiT In.!!*
mill ll-li
1 cnv-lrhil |ih;i-r I'iii"*
^lllilll \hlllllll;ll-
M.HicmI
Willi-
( limiiii
Willi-
( liiMiiii
Willi-
( IllMllir
Wlllr
( liiMiiii
Bearing and Nonbearing Avocado, Fig, Olive,
Ground
Berries, Citrus Fruits, Pome Fruits, Stone Fruits,
Broadcast
LAA
NE
NE
NLAA
NE
NE
NLAA
LAA
NLAA
LAA
Tree Nuts and Vineyards -
Nonbearing Avocado, Fig, Olive, Berries, Citrus
Ground
NLAA
LAA
Fruits, Pome Fruits, Stone Fruits, Tree Nuts and
Broadcast
LAA
NE
NE
NLAA
NE
NE
NLAA
LAA
Vineyards -
Granular
LAA
NE
NE
NLAA
NE
NE
NLAA
-
NLAA
LAA
Ornamentals (Excluding Bulbs)
Ground
Broadcast
LAA
NE
NLAA
NE
NE
NLAA
LAA
NLAA
LAA
Granular
LAA
LAA
NE
NLAA
NE
NE
NLAA
-
NLAA
LAA
Ornamental Bulbs
Ground
Broadcast
NE
NE
NE
NLAA
NE
NE
NLAA
LAA
NLAA
LAA
Granular
NE
NE
NE
NLAA
NE
NE
NLAA
-
NLAA
LAA
Christmas Tree Plantations
Ground
NLAA
LAA
Broadcast
NE
NE
NE
NLAA
NE
NE
NLAA
LAA
Granular
NE
NE
NE
NLAA
NE
NE
NLAA
-
NLAA
LAA
Warm Season Turf
Ground
NLAA
LAA
Broadcast
NE
NE
NE
NLAA
NE
NE
NLAA
LAA
Granular
NE
NE
NE
NLAA
NE
NE
NLAA
-
NLAA
LAA
Rights-of-ways
Ground
NLAA
LAA
Broadcast
LAA
LAA
NE
NLAA
NLAA
NE
NLAA
LAA
Granular
LAA
LAA
NE
NLAA
NLAA
NE
NLAA
-
NLAA
LAA
Residential areas
Granular
NE
NE
NE
NLAA
NE
NE
NLAA
LAA
NLAA
LAA
\K = No effect; NLAA = May affect, but not likely to adversely affect; LAA = Likely to adversely affect
-Not applicable
16
-------
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct/indirect and habitat
modification effects determinations, it is important to note that pesticide exposures and
predicted risks to the species and its resources (i.e., food and habitat) are not expected to
be uniform across the action area. In fact, given the assumptions of drift and downstream
transport (i.e., attenuation with distance), pesticide exposure and associated risks to the
species and its resources are expected to decrease with increasing distance away from the
treated field or site of application. Evaluation of the implication of this non-uniform
distribution of risk to the species would require information and assessment techniques
that are not currently available. Examples of such information and methodology required
for this type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages
within specific recovery units and/or designated critical habitat within the
action area. This information would allow for quantitative extrapolation
of the present risk assessment's predictions of individual effects to the
proportion of the population extant within geographical areas where those
effects are predicted. Furthermore, such population information would
allow for a more comprehensive evaluation of the significance of potential
resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic-
and terrestrial-phase frogs. While existing information provides a
preliminary picture of the types of food sources utilized by the frog, it
does not establish minimal requirements to sustain healthy individuals at
varying life stages. Such information could be used to establish
biologically relevant thresholds of effects on the prey base, and ultimately
establish geographical limits to those effects. This information could be
used together with the density data discussed above to characterize the
likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the
pesticide. Currently, methodologies are limited to predicting exposures
and likely levels of direct mortality, growth or reproductive impairment
immediately following exposure to the pesticide. The degree to which
repeated exposure events and the inherent demographic characteristics of
the prey population play into the extent to which prey resources may
recover is not predictable. An enhanced understanding of long-term prey
responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and
together with the information described above, a more complete prediction
of effects to individual frogs and potential modification to critical habitat.
17
-------
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
the herbicide oryzalin for both agricultural (for weed control in crops such as avocado,
fig, olives, berries, citrus, stone fruits, pome fruits, tree nuts, wine and table grapes,
ornamentals including bulbs) and non-agricultural (for weed control in Christmas tree
plantations, warm season turf grass, non-cropland and industrial sites including roadsides
and rights-of-ways (referred to together as rights-of-ways) purposes. In addition, this
assessment evaluates whether use on these sites is expected to result in modification of
the species' designated critical habitat. This ecological risk assessment has been
prepared consistent with a settlement agreement in the case Center for Biological
Diversity (CBD) vs. EPA et al. (Case No. 02-1580-JSW (JL)) settlement entered in
Federal District Court for the Northern District of California on October 20, 2006.
In this assessment, direct and indirect effects to the CRLF and potential modification to
its designated 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, and AgDRIFT all of
which are described at length in the Overview Document. Additional refinements
include an analysis of California Pesticide Use Reporting (CA PUR) data and the use of
the T-HERPS model to predict daily dietary intake specifically by the CRLF of oryzalin
residues in terrestrial invertebrates and small mammal dietary items. Use of such
information is consistent with the methodology described in the Overview Document,
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 oryzalin 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
18
-------
FIFRA regulatory decision associated with a use of oryzalin 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 oryzalin in accordance with current labels:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Designated critical habitat identifies specific areas that have the 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 oryzalin as it
relates to this species and its designated critical habitat. If, however, potential direct or
indirect effects to individual CRLFs are anticipated or effects may impact the PCEs of the
CRLF's designated critical habitat, a preliminary "may affect" determination is made for
the FIFRA regulatory action regarding oryzalin.
If a determination is made that use of oryzalin 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 oryzalin use sites) and further evaluation of the potential impact of oryzalin
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 oryzalin is expected to directly impact living organisms within the action area
(defined in Section 2.7), critical habitat analysis for oryzalin 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
19
-------
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 oryzalin 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
Oryzalin, applied to the soil surface prior to the emergence of weeds, is a herbicide used
to control seedling grasses and some annual broadleaf weeds in a variety of food crops
such as avocado, fig, olives, berries, citrus fruits, pome fruits, tree nuts, stone fruits, and
vineyards. Other labeled non-food uses for oryzalin include non-bearing orchards,
vineyards, and berries, ornamentals, Christmas tree plantations, warm season turf grass,
residential and non-croplands such as rights-of-ways.
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 oryzalin in accordance with the approved product labels for
California is "the action" relevant to this ecological risk assessment.
Although current registrations of oryzalin allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of oryzalin 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.
Several degradates have been identified for oryzalin of which the main degradate is 4-
hydroxy-3, 5-dinitrobenzenesulfonamide (OR 20). There is no evidence that any of these
degradates are of toxicological concern, and none of them are found in significant
amounts (>10.0%) except 2-ethyl-7-nitro-l-propyl-5-sulfonylaminobenzimidazole 3-
oxide at 14% in an aquatic photodegradation study. Since 2-ethyl-7-nitro-l-propyl-5-
sulfonylamino benzimidazole 3-oxide is not of toxicological concern and formed in
negligible amount (<2.4%) in an aerobic soil metabolism study, this assessment is based
on parent oryzalin only.
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
multiple 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
20
-------
are available for a formulated product containing more than one active ingredient, they
may be used qualitatively or quantitatively in accordance with the Agency's Overview
Document and the Services' Evaluation Memorandum (U.S., EPA 2004; USFWS/NMFS
2004).
Oryzalin has ten registered products that contain multiple active ingredients (Appendix
B) Based on a review of the available studies on oryzalin mixtures, it appears that the
information presented in the papers pertain to efficacy and phytotoxicity of the mixtures
for weed control. No information is available on the toxicity of individual components of
oryzalin mixtures (Appendix B).
2.3 Previous Assessments
Oryzalin was first registered in the United States in 1974 as a preemergence herbicide in
fruits, nuts, vineyards, orchards, forestry, rights-of-ways, and agricultural crops. A
Registration Standard was issued in 1987 (NTIS# PB89-102396) which evaluated the
studies submitted on oryzalin to that date. Prior to the issuance of the Registration
Standard, several agricultural crops were deleted. The only food crop groups remaining
on oryzalin labels are berries, vine and orchard crops (i.e., citrus fruits, pome fruits, stone
fruits, and tree nuts). In addition, oryzalin has many non-food uses including
ornamentals, Christmas trees, non-bearing fruit and nut trees, non-bearing vineyards and
berries, and established warm season turf and rights-of-ways. A Data Call-In was issued
in 1991 requiring additional phytotoxicity data, plant and animal analytical methods, and
non-dietary exposure data. The Environmental Protection Agency issued the Registration
Eligibility Decision (RED) for oryzalin in September of 1994 by determining that all of
the then registered oryzalin products were eligible for re-registration except for products
labeled for use on residential lawns and turf. The results of the Agency's 1994 ecological
risk assessment for oryzalin, which was conducted as part of the RED, suggest the
potential for adverse acute effects to non-target aquatic animals in shallow waters (6
inches deep) and terrestrial and aquatic plants. No acute or sub-lethal chronic effects to
birds were reported due to exposure to oryzalin. The Tolerance Reassessment Progress
and Risk Management Decision (TRED) for oryzalin, dated 26 May 2006, determined
that the lawn and turf uses for oryzalin are eligible for re-registration based on the
submitted new studies on exposure monitoring on residential lawns and turf.
The Agency also completed an effects determination for the threatened and endangered
Pacific anadromous salmon and steelhead in 2003 based on oryzalin uses in grapes and
almonds in the Pacific Northwest as part of the settlement for the petition filed against
EPA by Washington Toxics Coalition (filed November 26, 2002). The results of this
endangered species risk assessment showed that oryzalin may affect but is not likely to
adversely affect 17 ESUs (Evolutionarily Significant Units) and will have no effect on
nine ESUs. These determinations were based on possible indirect effects to listed
salmonids from loss of aquatic plant cover in spawning and rearing habitats.
21
-------
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Properties
The major route of oryzalin dissipation is aqueous photolysis, photodegradation on soil
surface, and degradation under anaerobic conditions. Oryzalin appears to degrade slowly
under aerobic soil conditions and is stable to hydrolysis. Under field conditions oryzalin
appeared to be moderately persistent, with a half-life of about two months. Based on its
low vapor pressure (1.0 x 10"7 mm Hg at 25°C) and Henry's Law Constant (1.8 x 10"8
atm-m3/mol), volatilization loss of oryzalin from soil and water systems is expected to be
insignificant compared to dissipation by abiotic and biotic degradation. Table 2.1 lists
selected physical, chemical and environmental fate properties of oryzalin.
Table 2.1 Summary of Oryzalin Environmental Fate Properties
Parameter
Value
Major Degradates
Minor Degradates
Source/
MRU) #
Study Status
Common name
Oryzalin
...
U.S. EPA, 1994
...
Chemical name
3,5-dinitro-N4,N4-
dipropylsulfanilamide
...
U.S. EPA, 1994
...
Chemical family
Dinitroaniline
...
U.S. EPA, 1994
...
Empirical
formula
C12H18N4O6S
...
U.S. EPA, 1994
...
Structure
H ? ( CH,—CH.-CH,
NO.
...
U.S. EPA, 1994
...
Molecular mass
346.35
...
U.S. EPA, 1994
Water solubility
(20 °C)
2.5 mg/L
...
MRID 41208101-2
Acceptable
Vapor pressure
(25°C)
1.0 x 10"7 mmHg
...
MRID 40454801
Acceptable
Henry's Law
Constant
1.82 x 10"8 atm m3/mol
...
Calculated1
—
Octanol/water
partition
coefficient (Log
I"Vow)
3.73 atpH 7
...
U.S. EPA, 1994
—
Hydrolysis
Stable
...
MRID 41378401
Acceptable
Direct Aqueous
Photolysis
0.06 days
UN-2, 14.0%
OR-5, 2.9%,
OR-3, 5.7%
MRID 40863401
supplemental
Soil Photolysis
3.8 days
OR-3, 2.6%,
OR-15, 3.2%
OR-21, 4.6%.
MRID 41050001
Acceptable
Aerobic Soil
63 days
OR-20, 4.7 %,
UN-1, UN-2, OR-4,
MRID 41322801
Acceptable
22
-------
Table 2.1 Summary of Oryzalin Environmental Fate Properties
Parameter
Value
Major Degradates
Minor Degradates
Source/
MRID#
Study Status
Metabolism
OR-9, OR-13, OR-15
OR-20 and OR-4, <
2.4%
Anaerobic Soil
Metabolism
10 Days
UN-1, OR-3 and OR-20
MRID 413228-02
Acceptable
Soil Partition
Coefficient Koc)'
840, 700, 933, and 1290 L kg o.c.4
—
MRID 41479802
Acceptable
Terrestrial Field
Dissipation
77-146 days
58-136 days
...
MRID 42138001
Acceptable
Fish
bioconcentration
32x (edible)
105x (viscera)
66x (whole fish)
...
MRID 40787501
Acceptable
Laboratory studies indicate that oryzalin is stable to hydrolysis at pHs 5, 7 and 9. (MRID
41378401) but exhibits susceptibility to rapid direct aqueous photolysis; the aqueous
photolytic half-life is 1.4 hours (MRID 41288701). The degradates of aqueous photolysis
are OR-5 (2.9%), OR-3 (5.7%), and UN-2 (14%). The chemical also readily
photodegrades on the soil surface with an estimated half-life of 3.8 days, and the
degradates are OR-3 (2.6%), OR-15 (3.2%) and OR-21 (4.6) (MRID 41050001).
Oryzalin degrades aerobically with a half-life of 63 days in sandy loam soil (MIRD
41322801). The main degradate is 4-hydroxy-3,5-dinitrobenzenesulfonamide (OR 20),
which accounted for a maximum of 4.7% of radioactivity at 1 month post treatment in the
soil aerobic metabolism study. Eight other degradates were identified, each accounting
for < 2.4%) of the applied radioactivity (Table 2.1). The benzenesulfonamide ring
remained intact in all of the identified metabolites. By the end of the experiment at 6.1
months, 63.1% of the applied radioactivity was nonextractable and 5.7% had been
mineralized to C02. Under anaerobic conditions oryzalin nitro groups undergo reduction
to amines, dealkylation, and ring formation to produce benzimidazoles, with a half-life of
10 days (MRID 41322802). Anaerobic metabolites that accounted for < 0.2% are UN-1,
UN-2, OR-3, and OR-20. Table 2.2 provides names, structures and the occurrence of
various degradates detected in environmental fate studies.
In the field, oryzalin appears to dissipate slowly with a half-life of 68 days in Florida
sand soil and a first phase half-life of 58 days in California loam soil and 77 days in
Michigan silty clay loam soil. The second phase half-lives were 138 days in California
loam soil and 146 days in Michigan silty clay loam soil. Parent oryzalin did not appear to
be mobile under field conditions. The parent was undetectable and always less than
detection limits (i.e., 0.01 ppm; MRID 42138001) below 12 inches of soil depth. Oryzalin
degradates were not monitored in the field dissipation studies submitted. Although
oryzalin does not appear to be mobile under field conditions, the soil partition
23
-------
coefficients (Koc = 700 to 1290 L Kg"1, MRID 41479802 ) indicate that chemical
mobility will vary from moderately mobile to slightly mobile according to FAO
Classification Scheme (FAO 2000) depending on soil type and organic matter content.
Oryzalin has potential to contaminate surface water via spray drift and runoff. Substantial
quantities of oryzalin could be available for runoff for a few days to months post-
application depending on the degree of exposure to sunlight (photodegradation on soil
half-life of 3.8 days; aerobic soil half-life of 63 days; terrestrial field dissipation half-lives
of 77-146 and 58-138 days). The soil partitioning coefficients of oryzalin indicates that
fractions of oryzalin could be transported via both dissolution in runoff water and
adsorption to eroding soil in the event of significant rainfall occurring after application
prior to soil incorporation. Based upon its Koc, significant fractions of the oryzalin in
receiving surface waters should exist both dissolved in the water column and adsorbed to
suspended sediment. The susceptibility of oryzalin to direct photolysis in water (half-life
= 1.4 hours) should limit its persistence in clear shallow waters with low light
attenuation. However, its resistance to abiotic hydrolysis coupled with only a moderate
susceptibility to aerobic biodegradation indicate that it will be somewhat more persistent
in receiving surface waters that are deeper, have high light attenuation, low
microbiological activities and long hydrological resident times.
Oryzalin is less likely to contaminate ground water resources due to reduction in the
anaerobic soil layer. However, in sandy soils under some environmental conditions, such
as excess precipitation, or where soil preferential flow conditions exist and exposure to
sunlight is minimal, oryzalin residues may leach into ground water and undergo reduction
to more polar compounds.
Based solely on the log Kow value of 3.73 of oryzalin, there is some potential for
bioconcentration in aquatic organisms. However, based on a laboratory bioaccumulation
study (MRID 40787501), oryzalin did not significantly bioconcentrate in bluegill sunfish.
The BCFs were 32X in edible tissue, 105X in nonedible tissue, and 66X in whole fish.
Depuration ranged from 79.2 to 80.8% after 24 hours and 88.7 to 95.1% after 14 days.
Nine degradates have been identified for oryzalin in the soil aerobic metabolism study.
Three other degradates were also identified in various fate studies (Table 2.2). The main
degradate is 4-hydroxy-3,5-dinitrobenzenesulfonamide, which accounted for a maximum
of 4.7%) of radioactivity at 1 month post-treatment in the soil aerobic metabolism study.
Eight other degradates were isolated, but each comprised <2.4% of the applied
radioactivity. The available data on degradates of oryzalin are insufficient to assess their
runoff characteristics or persistence in surface waters. The registrant conducted a
mobility/adsorption/desorption study to determine the mobility of nine oryzalin
degradates and whether or not degradate leaching is a major route of dissipation. Out of
nine metabolites formed, three (OR-20, UN-2, and the unidentified compound UN-3;
(MRID 43433202) appeared to be very mobile.
24
-------
Table 2.2 Oryzalin Degradates Identified in Environmental
7ate Studies
Code
Structure
IUPAC Name
Reference
OR-2
SO-NK-;
3,5 -dinitro-4-(propyl-amino)
benzenesulfonamide
MRID 413228011
MRID 413228022
OR-3
N '}
Ir
DE>f i
'O
1
1
UK,
3,5-dinitro-4-amino-
benzenesulfonamide
MRID 412787013
MRID 410500014
OR-4
$0**11,
3-amino-4-(dipropylamino)-
5-nitrobenzenesulfonamide
MRID 41322801
MRID 41322802
OR-5
II '-*B?
sll
I
"lb
3-amino-4-propylamino)- 5-
nitrobenzenesulfonamide
MRID 41278701
OR-9
Nil,
502N"H>
3,4,5-triaminobenzene-
sulfonamide
MRID 41322801
OR-13
StC'\ ^CjH,
~T^
50:SV4
2-ethyl-7-nitro-1 -propyl - 1H-
benzimidazole-5-
sulfonamide
MRID 41322801
MRID 41322802
OR-15
li\.
IP..
mm
2-ethyl-7-nitro-lH-
benzimidazole-5-
sulfonamide
MRID 41322801
MRID 41322802
MRID 41050001
OR-20
• N *>
t
4-hydroxy-3,5-dinitro-
benzenesulfonamide
MRID 41322801
MRID 41322802
OR-21
1
n
: ! >v;i,
1
3,4-dinitro-4-
dipropylamineo-sulfanalic
acid
MRID 41050001
25
-------
Table 2.2 Oryzalin Degradates Identified in Environmental
7ate Studies
Code
Structure
IUPAC Name
Reference
OR-41
OK
f
HtMv
safm,
4-[(2-hydroxypropy-amino)]-
3,5-dinitro-
benzenesulfonamide
MRID 41322801
UN-1
«-£Sv
• ?
• 0 , t To J
Y 0
.•SOjSH,
3,3'-azoxybis[(4-
propylamino]-5-nitro]-
benzenesulfonamide
MRID 41322801
MRID 41322802
UN-2
N— N
i 1.
To •, 0
2-ethyl-7-nitro-1 -propyl -1H-
benzimidazole-5-
sulfonamide-3-oxide
MRID 41322801
MRID 41322802
MRID 41278701
Aerobic soil metabolism; 2Anaerobic soil metabolism; 3Aquatic photolysis; 4Soil photolysis
Field trials were conducted on papaya, banana, and guava to determine the magnitude of
oryzalin residues on crops. Oryzalin residues were not detected in any samples of papaya
or papaya puree (MRIDS 411155-01) as well as banana and guava (MRIDS 416337-00
and 416337-01). Since no residue was detected in crops, the dissipation of transferable
residues of oryzalin on turf was used to determine foliar half-life. The study on the
dissipation of isoxaben and oryzalin transferable residues on residential turf was
conducted at three sites in California, Indiana, and Mississippi (MRID 450407-01). Two
typical end-use formulations containing oryzalin (Surflan® AS as liquid), isoxaben and
oryzalin (Turf Fertilizer contains Gallery® Plus Surflan® as granules) were applied using
a drop granular spreader and a spray boom liquid applicator.
No turf transferable residue (TTR) value of oryzalin was greater than 6.1% of applied
active ingredient, even at DAT 0 (immediately after application). Maximum TTRs were
found at the CA location for all typical end-use products tested. The liquid broadcast
application of Surflan® AS generally demonstrated a higher transfer of residues from the
turf surface than the granular applications (Gallery® Turf Fertilizer and Turf Fertilizer
contains Gallery® Plus Surflan®). The registrant corrected all TTR values using the
average procedural recoveries for the day of analysis. All overall percent field
fortification recoveries were >90%. For TTR values < LOQ (but > LOD), the registrant
reported the values as estimated values. Reviewer used a value of V2 the LOQ for TTR
values < LOQ (D235659). TTR values
-------
Table 2.3 Summary of Half-Life Determinations for Oryzalin at Various Sites
Product
Active Ingredient
Site
HED
Calculated
Registrant
Calculated
Half-Life
(days)
Half-Life
(days)
Surflan AS
Oryzalin
CA
1.5
1.5
IN
6.9
6.6
MS
3.4
3.4
Turf Fertilizer containing
Gallery Plus Surflan
Oryzalin
CA
1.1
1.1
IN
2.1
2.1
MS
NA1
3.7
'NA = Half-life not calculated because active ingredient TTR values dropped below the LOQ (0.003 |ig/cnr)
2.4.1 Environmental Transport Mechanisms
Potential transport mechanisms for oryzalin include 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 oryzalin. Based on its low vapor pressure (1.0 x 10"7 mm Hg
at 25°C) and Henry's Law Constant (1.8 x 10"8 atm-m3/mol), volatilization loss of
oryzalin from soil and water systems is expected to be insignificant compared to
dissipation by abiotic and biotic degradation. Based on low volatility and high sensitivity
to photolytic degradation, oryzalin is not expected to continue long-range transport.
In general, deposition of drifting pesticides is expected to be greatest close to the site of
application. A computer model of spray drift (AgDRIFT) is used to determine potential
exposures to aquatic and terrestrial organisms via spray drift. Seedling emergence
toxicity studies show that oryzalin 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
Oryzalin is a broad spectrum herbicide that is used to control seedling grasses and some
annual broadleaf weeds in both agricultural and non-agricultural settings. Depending on
the formulation, the registered products of oryzalin are applied to the soil surface prior to
the emergence of weeds as broadcast spray or band treatment for liquid formulations
(using low pressure ground equipment) or soil broadcast for granular formulations (using
spreaders). To facilitate activation and movement of the chemical to the weed seed
germination zone, a single V2 to 1 inch of rainfall or sprinkler irrigation is required.
Depending on the rate of application, the soil residual activity of oryzalin ranges between
4 to 10 months.
27
-------
Oryzalin is mainly absorbed by roots, has little or no foliar activity, and is not
translocated within the plant. Thus the primary effect of oryzalin is on root development.
Roots of affected plants are relatively few in number, short, thick, and club shaped. The
inhibited root growth causes tops of plants to be stunted and demonstrate a dark green
color.
Oryzalin, similar to the other members of the chemical family dinitroanilines, acts by
disrupting the assembly of microtubules. As a result, mitosis or cell division of plants,
ranging from single-celled algae to higher plants, is inhibited. Oryzalin, however, is
ineffective against vertebrate and fungal microtubules.
2.4.3 Use Characterization
Analysis of label use information is the critical first step in evaluating the federal action.
The current label for oryzalin represents the FIFRA regulatory action; therefore, use and
application rates specified on the label form the basis of this assessment. The assessment
of use information is critical to the development of the action area and selection of
appropriate modeling scenarios and inputs.
Oryzalin is a dinitroaniline herbicide that is registered nationally for control of annual
grasses and certain broadleaf weeds in fruit and nut crops, vineyards, Christmas tree
plantations, ornamentals, turf, and several other non-crop sites. Oryzalin is formulated as
granules (0.4 to 1% ai), wettable powder (75% ai), water dispersible granules (60 - 85%
ai), emulsifiable concentrate (2.84 to 40.4% ai), flowable concentrate (40.4%), and
formulation intermediate/liquid (40.4% ai). Depending on the formulation, oryzalin is
typically applied using low pressure ground equipment or spreaders. The labels for
oryzalin caution not to apply this herbicide to Douglas fir, slender deutzia, Techny
arborvitae, eastern hemlock, begonia, and coleus due to phytotoxicity on the above
species.
The following current labeled uses for oryzalin are considered as part of the federal
action evaluated in this assessment: avocado, fig, olives, berries, pome fruits, stone fruits,
citrus, tree nuts, wine and table grapes, ornamentals (landscape gardens, containers,
production fields, ornamental bulbs, and ground covers/perennials), Christmas tree
plantations, warm season turf grass, residential areas, and rights-of-ways. There are no
new pending uses for oryzalin which are active at this time.
Table 2.4 presents the uses and corresponding application rates (single and maximum),
application interval, and methods of application considered in this assessment.
28
-------
Table 2.4 Oryzalin Uses Assessed for the CRLF
Use
Formulation
Code1
Application
Method
Maximum
Single
Applicatio
11 Rate
(lb ai/A)
Maximum
Number of
Applications
per Year
(#)
Maximum
Seasonal
Application
Rate
(lb ai/A)
Application
Interval
(days)
Berries
Blackberry, blueberries,
boysenberry, currant,
dewberry, elderberry,
gooseberry, loganberry and
raspberry
Citrus Fruits
Grapefruit, kumquat, kiwi,
lime, lemon, mandarin,
tangerine, orange, pummelo,
nectarine, orange
Pome Fruits
EC/DF
Low pressure
ground sprayer/
Sprinkler
irrigation
/Broadcast/
Chemigation/
Soil broadcast
treatment
6
2
12
75
Apple, apricot, crabapple,
Figs, loquat, mayhaw,
pomegranate, and quince
Tree Nuts
Almonds, chestnut
chinquapin, filbert, hickory
nut, macadamia nut, pecan,
pistachio walnut
Stone Fruits
Avocado, Cherry, Nectarine,
olive, peach, pear, plum,
prune
Vineyards
Wine and table grapes
G
Granules by
Spreader/
Broadcast
4
4
15
60
Non-bearing trees/vineyards
EC/DFAVP/L
Low pressure
ground sprayer/
Sprinkler
irrigation
/Broadcast/
Chemigation/
Soil broadcast
treatment
4
3
12
90
Granular
Granule
applicator
Spreader,
/Broadcast
4
4
15
60
Ornamentals2
EC/DFAVP/L
Low pressure
ground sprayer/
Sprinkler
irrigation
/Broadcast/
Chemigation/
Soil broadcast
treatment
4
3
12
90
29
-------
Table 2.4 Oryzalin Uses Assessed for the CRLF
Use
Formulation
Application
Maximum
Maximum
Maximum
Application
Code1
Method
Single
Applicatio
n Rate
Number of
Applications
per Year
Seasonal
Application
Rate
Interval
(lb ai/A)
(#)
(lb ai/A)
(days)
Granule
G
applicator
Spreader,
/Broadcast
4
4
15
60
Christmas Tree Plantation
Low pressure
EC/DF/L/WP
ground sprayer/
Sprayer/
Spreader
/Broadcast/
Directed spray/
Soil broadcast
treatment
4
2
8
60
Granule
G
applicator
Spreader,
/Broadcast
4
4
15
60
Ornamental bulbs
Low pressure
EC/L
ground sprayer/
Sprayer
1.5
2
2.25
90
Granule
G
applicator
Spreader,
/Broadcast
1.5
2
2.25
90
Warm Season Turf Grass
EC/L
Low pressure
ground sprayer/
Sprayer
2
3
6
90
Granule
G
applicator
Spreader,
/Broadcast
1.5
4
6
90
Rights-of-ways
EC/LAVP
Low pressure
ground sprayer/
Sprayer
6.1
2
12.2
240
Granule
G
applicator
Spreader,
/Broadcast
4
4
15.0
60
Residential areas
Granule
G
applicator
Spreader
2
3
6
56
formulation codes: DF- Water Dispersible Granules (Dry Flowable); EC-Emulsifiable Concentrate; G-Granular; L-Liquid; WP-
Wettable Powder
2Use in landscape gardens, container and field grown ornamentals, drainage areas under shadehouse benches, ground
covers/perennials
30
-------
A national map (Figure 2.1) showing the extent of estimated annual oryzalin uses across
the United States as of 2002 is provided below. The map was downloaded from U.S.
Geological Survey (USGS), National Water Quality Assessment Program (NAWQA)
website. As of 2002, over 93% of total agricultural uses for oryzalin are in the crops
listed in Figure 2.1. The highest poundage (142,601 lbs) of oryzalin was applied to
citrus fruits. Grapes (74,753 lbs) and apples (39,855 lbs) represented the second and third
highest total pounds of oryzalin applied.
Figure 2.1 Oryzalin Use in Total Pounds per
County
ORYZALIN - herbicide
2002 estimated annual agricultural use
Crops
Total
Percent
pounds applied
national use
citrus fruit
142601
38.65
grapes
74753
20.26
apples
39856
10.80
pistachios
36762
9.96
almonds
21803
5.91
cherries
13972
3.79
peaches
10544
2.86
plums and prunes
6678
1.81
pecans
6077
1.65
blueberries
5105
1.38
Average annual use of
active ingredient
(pounds par square mile of agricultural
land in county)
G no estimated use
~ 0.001 to 0.002
~ 0.003 to 0.006
~ 0.007 to 0.019
~ 0.02 to 0.095
¦ >=0.096
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis
of both national- and county4evel usage information (Kaul and Jones, 2006) using state-
level usage data obtained from USDA-NASS2, 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) database3 . CDPR PUR is considered
a more comprehensive source of usage data than USDA-NASS or proprietary databases,
2United States Depart of Agriculture (USD A), 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.
3The 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/punnain.htm.
31
-------
and thus the usage data reported for oryzalin by county in this California-specific
assessment were generated using CDPR PUR data. 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 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 four years. The units of area treated are also
provided where available.
During the period 2002 to 2005 oryzalin was reportedly used in 54 counties in California.
Of the 54 counties, 36 counties listed in Figure 2.2 used more than 1000 pounds of
oryzalin during 2002-2005. The principal use was on orchard and vineyard crops
including almonds, pistachio, grapes, apples, apricots, cherries, citrus, lemon, nectarine,
orange, peach, pear, plum, prune, quince, avocado, figs, olive and walnuts. Non-orchard
uses included berries. In addition, non-agricultural applications were reported as rights-of
ways, nursery and ornamentals, landscape maintenance, Christmas trees, greenhouse
flowers, structural pest control as well as several applications as research commodities
(also limited to a few counties for each use).
During 2002 - 2005, the percentage of total oryzalin use in California was highest on tree
nuts (42.5% of total use) followed by grapes (24.8%), right-of ways (10.7%), stone fruits
(8.7%>), landscape maintenance (5.8%>), pome fruits (2.9%), citrus (2.5%) and other uses
(2.1%>) (Figure 2.3). The total annual average for reported uses over this four-year period
was 465,153 lbs. The greatest average usage (average of pounds applied per commodity
across all four years) was to almonds in Stanislaus county at 17,580 lbs. Use data from
2002 - 2005 for California indicate that oryzalin is applied throughout the year, with the
majority of applications occurring during the late winter to early spring months
(December -March). A summary of oryzalin usage for all California use sites is provided
in Table 2.5.
32
-------
Figure 2.2 Oryzalin Usage in California (2002 - 2005) by County
£ 80x103
Io
CM
o
U)
c
3
Q
O)
3
ro
N
rc
3
C
C
<
i
<
60x103
40x103 -
20x103
California Counties
Figure 2.3 Major Uses of Oryzalin in California During 2002 - 2005
~ Tree Nuts (42.8%)
¦ Grapes (24.8%)
~ Stone Fruits (8.7%)
~ Pome Fruits (2.9%)
¦ Citrus (2.5%)
~ Rights of way (10.7%)
¦ Landscape Maintances (5.8%)
~ Others (2.1%)
33
-------
Table 2.5 Summary of California Department of Pesticide Regulation (CDPR)'s Pesticide Use
Reporting (PUR1) Data from 2002 to 2005 for Currently Registered Oryzalin Uses
Site Name1
Average
Pounds
All Uses
Average
Application
Rate
All Uses
Average
95th %
Application
Rate
Average
99th %
Application
Rate
Average
Maximum
Application
Rate
Tree nut (almond, chestnut, pecan,
pistachio, and walnut
197,607
2.04
3.42
4.01
5.90
Grape (table and wine)
115,123
1.79
3.32
4.26
5.96
Rights-of Way
49,941
NA2
NA
NA
NA
Stone fruits (avocado, cherry,
nectarine, olive, peach, plum, prune,
42,043
2.21
3.45
3.84
4.43
Landscape maintenance
26,970
NA
NA
NA
NA
Pome fruits (apple, apricot, figs, pear
pomegranate, quince
13,311
2.09
3.41
3.80
3.80
Citrus (citrus, kiwi, lemon, orange,
tangerine, tangelo,
11,711
2.37
3.17
3.76
3.82
Outdoor container
5,792
1.58
2.00
2.05
2.05
Structural pest control3
732
NA
NA
NA
NA
Berries (blueberry,
725
2.02
2.61
2.61
2.61
Non-outdoor transplants
668
2.53
2.98
2.98
2.98
Uncultivated Agriculture
290
3.03
4.38
4.38
4.38
Non-Greenhouse plants in container
266
2.38
4.55
4.85
5.90
Non outdoor flowers
197
2.23
5.59
5.87
5.87
Uncultivated non-agriculture
122
1.69
2.22
2.22
2.22
Research Commodity3
94
NA
NA
NA
NA
Christmas Plantation
87
1.58
2.00
2.05
2.05
Non-greenhouse flower and
transplants
85
3.38
4.49
11.82
11.82
*Use reports in CDPR PUR that represent misuse or misreporting are not included in this table
2Not available
3Uses excluded in this assessment because they will not affect CRLF
34
-------
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
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
35
-------
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 2.2.
Core Areas
USFWS has designated 35 core areas across the eight recovery units to focus their
recovery efforts for the CRLF (see Figure 2.4). Table 2.6 summarizes the geographical
relationship among recovery units, core areas, and designated critical habitat. The core
areas, which are distributed throughout portions of the historic and current range of the
species, represent areas that allow for long-term viability of existing populations and
reestablishment of populations within historic range. These areas were selected because
they: 1) contain existing viable populations; or 2) they contribute to the connectivity of
other habitat areas (USFWS 2002). Core area protection and enhancement are vital for
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. 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 2.6 (currently occupied core areas are bolded). While core
areas are considered essential for recovery of the CRLF, core areas are not federally-
designated critical habitat, although designated critical habitat is generally contained
within these core recovery areas. It should be noted, however, that several critical habitat
units are located outside of the core areas, but within the recovery units. The focus of this
assessment is currently occupied core areas, designated critical habitat, and other known
CNDDB CRLF occurrences within the recovery units. Federally-designated critical
habitat for the CRLF is further explained in Section 2.6.
36
-------
Table 2.6 California Red-legged Frog Recovery Units with Overlapping Core
Areas and Designated Critical Habitat
Recovery Unit1
(Figure 2.a)
Core Areas 2,1 (Figu re 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
(partial) (18)
SNM-1A
Central Coast (5)
South San Francisco Bay
(partial) (18)
SNM-1A, SNM-
2C, SCZ-1
Watsonville Slough- Elkhorn
Slough (partial) (19)
SCZ-2 5
Carmel River-Santa Lucia
(20)
MNT-2
37
-------
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)
--
Recovery units designated by the USFWS (USFWS 2000, pg 49).
2Core areas designated by the USFWS (USFWS 2000, pg 51).
3Critical habitat units designated by the USFWS on April 13, 2006 (USFWS 2006, 71 FR 19244-19346).
4Currently occupied (post-1985) and historically occupied core areas as designated by the USFWS
(USFWS 2002, pg 54).
5Critical habitat unit where identified threats specifically included pesticides or agricultural runoff (USFWS
2002).
6Critical habitat units that are outside of core areas, but within recovery units.
'Currently occupied core areas that are included in this effects determination are bolded.
38
-------
Legend
| Recovery Unit Boundaries
Currently Occupied Core Areas
| Critical Habitat
| CNDDB Occurence Sections
County Boundaries q 45
I I 1 L_
180 Miles
_l
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
Core Areas
1.
Feather River
23.
Arroyo Grange River
2.
Yuba River- S. Fork Feather River
24.
Santa Maria River - Santa Ynez River
3.
Traverse Creek/ Middle Fork/ American R. Rubicon
25.
Sisquoc River
4.
Cosumnes River
26.
Ventura River - Santa Clara River
5.
South Fork Calaveras River*
27.
Santa Monica Bay - Venura Coastal Streams
6.
Tuolumne River*
28.
Estrella River
7.
Piney Creek*
29.
San Gabriel Mountain*
8.
Cottonwood Creek
30.
Forks of the Mojave*
9.
Putah Creek - Cache Creek*
31.
Santa Ana Mountain*
10.
Lake Berryessa Tributaries
32.
Santa Rosa Plateau
11.
Upper Sonoma Creek
33.
San Luis Ray*
12.
Petaluma Creek - Sonoma Creek
34.
Sweetwater*
13.
Pt. Reyes Peninsula
35.
Laguna Mountain*
14.
Belvedere Lagoon
15.
Jameson Canyon - Lower Napa River
* Core areas that were historically occupied by the California
16.
East San Francisco Bay
red-legged frog are not included in the map
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
39
-------
Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in
California. The CNDDB serves as a repository for historical and current species location
sightings. Information regarding known occurrences of CRLFs outside of the currently
occupied core areas and designated critical habitat is considered in defining the current
range of the CRLF. See: http://www.dfg.ca.gov/bdb/html/cnddb info.html for additional
information on the CNDDB.
2.5.2 Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams,
marshes, and lagoons (Fellers 2005a). According to the Recovery Plan (USFWS 2002),
CRLFs breed from November through late April. Peaks in spawning activity vary
geographically; Fellers (2005b) reports peak spawning as early as January in parts of
coastal central California. Eggs are fertilized as they are being laid. Egg masses are
typically attached to emergent vegetation, such as bulrushes (Scirpus spp.) and cattails
(Typha spp.) or roots and twigs, and float on or near the surface of the water (Hayes and
Miyamoto 1984). Egg masses contain approximately 2000 to 6000 eggs ranging in size
between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch 10 to 14 days after
fertilization (Fellers 2005a) depending on water temperature. Egg predation is reported
to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles
(terrestrial-phase), typically between May and September (Jennings and Hayes 1994,
USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b, USFWS 2002). Males reach sexual maturity at 2
years, and females reach sexual maturity at 3 years of age; adults have been reported to
live 8 to 10 years (USFWS 2002). Figure 2.5 depicts CRLF annual reproductive timing.
Figure 2.5 - CRLF J
reproductive Events by Mont
h
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
40
-------
(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).
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
41
-------
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 2.6.
'Critical habitat' is defined in the ESA as the geographic area occupied by the species at
the time of the listing where the physical and biological features necessary for the
conservation of the species exist, and there is a need for special management to protect
the listed species. It may also include areas outside the occupied area at the time of
listing if such areas are 'essential to the conservation of the species.' All designated
critical habitat for the CRLF was occupied at the time of listing. Critical habitat receives
protection under Section 7 of the ESA through prohibition against destruction or adverse
modification with regard to actions carried out, funded, or authorized by a federal
Agency. Section 7 requires consultation on federal actions that are likely to result in the
destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the
conservation of the species.' Critical habitat designations identify, to the extent known
using the best scientific and commercial data available, habitat areas that provide
essential life cycle needs of the species or areas that contain certain primary constituent
elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to,
space for individual and population growth and for normal behavior; food, water, air,
light, minerals, or other nutritional or physiological requirements; cover or shelter; sites
for breeding, reproduction, rearing (or development) of offspring; and habitats that are
protected from disturbance or are representative of the historic geographical and
ecological distributions of a species. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
• Breeding aquatic habitat;
• Non-breeding aquatic habitat;
42
-------
• 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 oryzalin that may alter the PCEs of the CRLF's critical habitat
form the basis of the critical habitat impact analysis. According to USFWS (2006),
activities that may affect critical habitat and therefore result in adverse effects to the
CRLF include, but are not limited to the following:
(1) Significant alteration of water chemistry or temperature to levels beyond the
tolerances of the CRLF that result in direct or cumulative adverse effects to
individuals and their life-cycles.
(2) Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat that could result in
elimination or reduction of habitat necessary for the growth and reproduction of
the CRLF by increasing the sediment deposition to levels that would adversely
affect their ability to complete their life cycles.
(3) Significant alteration of channel/pond morphology or geometry that may lead to
changes to the hydrologic functioning of the stream or pond and alter the timing,
duration, water flows, and levels that would degrade or eliminate the CRLF
and/or its habitat. Such an effect could also lead to increased sedimentation and
degradation in water quality to levels that are beyond the CRLF's tolerances.
(4) Elimination of upland foraging and/or aestivating habitat or dispersal habitat.
(5) Introduction, spread, or augmentation of non-native aquatic species in stream
segments or ponds used by the CRLF.
(6) Alteration or elimination of the CRLF's food sources or prey base (also
evaluated as indirect effects to the CRLF).
43
-------
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 oryzalin is expected to directly impact living
organisms within the action area, critical habitat analysis for oryzalin 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 oryzalin 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. The Agency's approach to defining the action area under the provisions of
the Overview Document (USEPA 2004) considers the results of the risk assessment
process to establish boundaries for that action area with the understanding that exposures
below the Agency's defined Levels of Concern (LOCs) constitute a no-effect threshold.
For the purposes of this assessment, attention will be focused on the footprint of the
action (i.e., the area where pesticide application could occur), plus all areas where offsite
transport (i.e., spray drift, downstream dilution, etc.) may result in potential exposure
within the state of California that exceeds the Agency's LOCs.
Deriving the geographical extent of this portion of the action area is based on
consideration of the types of effects that oryzalin may be expected to have on the
environment, the exposure levels to oryzalin that are associated with those effects, and
the best available information concerning the use of oryzalin and its fate and transport
within the state of California. Specific measures of ecological effect for the CRLF that
define the action area include any direct and indirect toxic effect to the CRLF and any
potential modification of its critical habitat, including reduction in survival, growth, and
fecundity as well as the full suite of sublethal effects available in the effects literature.
Therefore, the action area extends to a point where environmental exposures are below
any measured lethal or sublethal effect threshold for any biological entity at the whole
organism, organ, tissue, and cellular level of organization. In situations where it is not
possible to determine the threshold for an observed effect, the action area is not spatially
limited and is assumed to be the entire state of California.
The definition of action area requires a stepwise approach that begins with an
understanding of the federal action. The federal action is defined by the currently labeled
uses for oryzalin. 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
44
-------
oryzalin, the following agricultural uses are considered as part of the federal action
evaluated in this assessment:
• Berries
o Blackberries
o Blueberries
o Boysenberries
o Current
o Dewberry
o Elderberry
o Gooseberry
o Loganberries
o Raspberries
o Kiwi
• Citrus
o Grapefruit
o Kumquat
o Lime
o Lemon
o Mandarin
o Tangerine
o Orange
o Pummelo
o Orange
• Grapes
o Grapes (wine)
o Grape (table)
• Pome Fruits
o Apples
o Apricot
o Crabapple
o Figs
o Loquat
o Mayhaw
o Pear
• Stone Fruits
o Avocados
o Cherries
o Nectarine
o Olive
o Peach
o Plum
45
-------
o Prune
o Pomegranate
o Quince
• Tree nuts
o
Almonds
o
Chestnut
o
Chinquapin
o
Filbert
o
Macadamia nut
o
Pecan
o
Pistachio
o
Walnut
In addition, the following non-food and non-agricultural uses are considered:
• Christmas Tree Plantations
• Landscape maintenance
• Non-bearing trees/vineyards
• Rights-of-ways
• Residential areas/lawns
• Ornamentals
• Ornamentals bulbs
• Warm Season Turf Grass
Following a determination of the assessed uses, an evaluation of the potential "footprint"
of oryzalin use patterns (i.e., the area where pesticide application could occur) is
determined. This "footprint" represents the initial area of concern, based on an analysis
of available land cover data for the state of California. The initial area of concern is
defined as all land cover types and the stream reaches within the land cover areas that
represent the labeled uses described above. A map representing all the land cover types
that make up the initial area of concern for oryzalin is presented in Figure 2.6. Additional
GIS maps and related details are presented in Appendix D.
46
-------
Figure 2.6 Initial area of concern or "footprint" of potential uses for Oryzalin
Turf use
Developed-open space
Developed-low density
Developed-medium density
Developed-high density
Orchard/v ineyard use
Cultivated crop use
| CA_Right_of_Way
County boundaries
Kilometers
0 20 40 80 120 160
Compiled from California County boundaries (ESRI, 2002),
USEW Gap Analysis Program Orchard/ Vineyard Landcover (GAP)
National Land Cewer Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Erwinonmental Fate and Effects Division.
Projection: Albers Equal Area Conic USGS, North American
Datum of 1983 (NAD 1983).
Oryzalin Uses - Initial Area of Concern
Once the initial area of concern is defined, the next step is to define the potential
boundaries of the action area by determining the extent of offsite transport via spray drift
and runoff where exposure of one or more taxonomic groups to the pesticide exceeds the
listed species LOCs.
47
-------
As previously discussed, the action area is defined by the most sensitive measure of
direct and indirect ecological toxic effects including reduction in survival, growth,
reproduction, and the entire suite of sublethal effects from valid, peer-reviewed studies.
Due to the positive results in both the carcinogenicity and mutagenicity tests [HED's
Risk Assessment for Tolerance Reassessment Eligibility Decision (TRED) dated
5/18/2004, D300962; Appendix J], the spatial extent of the action area (i.e., the
boundary where exposures and potential effects are less than the Agency's LOC) for
oryzalin cannot be determined. Therefore, it is assumed that the action area encompasses
the entire state of California, regardless of the spatial extent (i.e., initial area of concern
or footprint) of the pesticide use(s).
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."4 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., water bodies,
riparian vegetation, and upland and dispersal habitats), the migration pathways of
oryzalin (e.g., runoff, spray drift, etc.), and the routes by which ecological receptors are
exposed to oryzalin (e.g., direct contact, etc.).
2.8.1. Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the CRLF, as well as indirect effects, such as reduction of
the prey base or modification of its habitat. In addition, potential 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 (Appendix K and H).
It should be noted that assessment endpoints are limited to direct and indirect effects
associated with survival, growth, and fecundity, and do not include the full suite of
sublethal effects used to define the action area. According the Overview Document
(USEPA 2004), the Agency relies on acute and chronic effects endpoints that are either
direct measures of impairment of survival, growth, or fecundity or endpoints for which
there is a scientifically robust, peer reviewed relationship that can quantify the impact of
the measured effect endpoint on the assessment endpoints of survival, growth, and
fecundity.
4FromU.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
48
-------
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 oryzalin is provided in Table 2.7.
Table 2.7 Assessment l.ndpoinls and Measures of Ideological l-TTecls
Assessment Endpoint
Measures of Ecological Effects5
Aquatic-Phase CRLF
(Eggs, larvae, juveniles, and adults)l
Direct Effects
1. Survival, growth, and reproduction of CRLF
la. Bluegill sunfish 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. Bluegill sunfish LC50
2b. Fathead minnow chronic NOAEC
2c. Water flea LC50
2d. Water flea NOAEC
2e. Non-vascular plant (green algae) 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 (green algae)
4. Survival, growth, and reproduction of CRLF
individuals via effects to riparian vegetation
4a. Monocot and dicot EC25 values
4b. Monocot and dicot NOAEC values
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. Bobwhite quail2 acute LC50 and LD50
5b. Bobwhite quail chronic NOAEC
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 acute LD50
6b. Rat acute LD50
6c. Rat chronic NOAEC
6d. Bobwhite quailb acute LC50 and LD50
6e. Bobwhite quail chronic NOAEC
7. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian and upland vegetation)
7a. Monocot EC25 values (seedling emergence)
7b. Dicot EC25 values (seedling emergence)
1 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; 2Birds are used as surrogates for terrestrial phase
amphibians.
5A11 registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix A.
49
-------
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 oryzalin that may alter the PCEs of the CRLFs 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 oryzalin 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 oryzalin on critical habitat of the
CRLF are described in Table 2.8. Some components of these PCEs are associated with
physical abiotic features (e.g., presence and/or depth of a water body, or distance between
two sites), which are not expected to be measurably altered by use of pesticides.
Assessment endpoints used for the analysis of designated critical habitat are based on the
adverse modification standard established by USFWS (2006).
50
-------
Table 2.8 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat1
Assessment Endpoint
Measures of Ecological Effect
Aquatic-Phase CRLFPCEs
(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 green algae EC50
b. EC25 values for terrestrial monocots
c. 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 green algae EC50
b. EC25 values for terrestrial monocots
c. EC25 values for terrestrial dicots
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
a. Bluegill sunfish LC50
b. Fathead minnow chronic NOAEC
c. Water flea LC50
d. Water flea NOAEC
e. Non-vascular plant (green algae) EC50
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
a. Non-vascular green algae EC50
Terrestrial-Phase CRLF PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian
habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
a. EC25 values for monocots
b. EC25 values for dicots
c. Honey bee oral acute LD50
d. Rat acute LD50
e. Rat chronic NOAEC
f. Bobwhite quail acute LC50 and 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.
1 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.
51
-------
2.9 Conceptual Model
2.9.1 Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects {i.e.,changes in
assessment endpoints) and may be based on theory and logic, empirical data,
mathematical models, or probability models (U.S. EPA, 1998). For this assessment, the
risk is stressor-linked, where the stressor is the release of oryzalin to the environment.
The following risk hypotheses are presumed for this endangered species assessment:
The labeled use of oryzalin within the action area may:
• directly affect the CRLF by causing mortality or by adversely affecting growth or
fecundity;
• indirectly affect the CRLF by reducing or changing the composition of food
supply;
• indirectly affect the CRLF or modify designated critical habitat by reducing or
changing the composition of the aquatic plant community in the ponds and streams
comprising the species' current range and designated critical habitat, thus affecting
primary productivity and/or cover;
• indirectly affect the CRLF or modify designated critical habitat by reducing or
changing the composition of the terrestrial plant community (i.e., riparian habitat)
required to maintain acceptable water quality and habitat in the ponds and streams
comprising the species' current range and designated critical habitat;
• 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);
• modify the designated critical habitat of the CRLF by reducing the food supply
required for normal growth and viability of juvenile and adult CRLFs;
• 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.
• 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.
• modify the designated critical habitat of the CRLF by altering chemical
characteristics necessary for normal growth and viability of juvenile and adult CRLFs.
52
-------
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the oryzalin 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 2.7 and 2.8, respectively, and the conceptual models
for the aquatic and terrestrial PCE components of critical habitat are shown in Figures
2.9 and 2.10, respectively. Exposure routes shown in dashed lines are not quantitatively
considered because the contribution of those potential exposure routes to potential risks
to the CRLF and modification to designated critical habitat is expected to be negligible.
Figure 2.7 Conceptual Model for Aquatic-Phase of the CRLF
53
-------
Figure 2.8 Conceptual Model for Terrestrial-Phase of the CRLF
Figure 2.9 Conceptual Model for Pesticide Effects on Aquatic Component of CRLF
Critical Habitat
54
-------
Figure 2.10 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 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 oryzalin 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 oryzalin is estimated
using the probit dose-response slope and either the level of concern (discussed below) or
actual calculated risk quotient value.
55
-------
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model
2.10.1.1 Measures of Exposure
The environmental fate properties of oryzalin along with available monitoring data
indicate that runoff and spray drift are the principle potential transport mechanisms of
oryzalin to the aquatic and terrestrial habitats of the CRLF. Based on the relatively low
volatility and greater sensitivity to photolytic degradation, oryzalin has low potential for
long-range transport. There is also no data for oryzalin in the California Pesticide Air
Monitoring database. Therefore, in this assessment, transport of oryzalin through runoff
and spray drift is considered in deriving quantitative estimates of oryzalin exposure to
CRLF, its prey and its habitats.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of oryzalin using maximum labeled application
rates and methods of application. The models used to predict aquatic EECs are the
Pesticide Root Zone Model coupled with the 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 (v3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are screening
simulation models coupled with the input shell pe5.pl (Aug 2007) to generate daily
exposures and l-in-10 year EECs of oryzalin that may occur in surface water bodies
adjacent to application sites receiving oryzalin 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, 2-meters deep (20,000 m3 volume) with no outlet. PRZM/EXAMS was used to
estimate screening-level exposure of aquatic organisms to oryzalin. 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 1-in-10-year 21-day mean is used for assessing chronic exposure for aquatic
invertebrates, 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 Kenaga 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
56
-------
nomograph represented the 95th percentile of residue values from actual field
measurements (Hoerger and Kenaga, 1972). For modeling purposes, direct exposures of
the CRLF to oryzalin 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 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
oryzalin are bound by using the dietary based EECs for small insects and large insects.
Birds are currently used as surrogates for terrestrial-phase CRLF. However, amphibians
are poikilotherms (body temperature varies with environmental temperature) while birds
are homeotherms (temperature is regulated, constant, and largely independent of
environmental temperatures). Therefore, amphibians tend to have much lower metabolic
rates and lower caloric intake requirements than birds or mammals. As a consequence,
birds are likely to consume more food than amphibians on a daily dietary intake basis,
assuming similar caloric content of the food items. Therefore, the use of avian food
intake allometric equation as a surrogate to amphibians is likely to result in an over-
estimation of exposure and risk for reptiles and terrestrial-phase amphibians. Therefore,
T-REX (version 1.3.1) has been refined to the T-HERPS model (v. 1.0), which allows for
an estimation of food intake for poikilotherms using the same basic procedure as T-REX
to estimate avian food intake.
EECs for terrestrial plants inhabiting dry and wetland areas are derived using TerrPlant
(version 1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in
spray drift to calculate EECs. EECs are based upon solubility, application rate and
minimum incorporation depth.
The spray drift model AgDRIFT was used to assess exposures of terrestrial phase CRLF
and its prey to oryzalin deposited on terrestrial habitats by spray drift. In addition to the
buffered area from the spray drift analysis, the downstream extent of oryzalin that
exceeds the LOC for the effects determination is also considered.
2.10.1.2 Measures of Effect
Data identified in Section 2.8 are used as measures of effect for direct and indirect effects
to the CRLF. Data were obtained from registrant submitted studies or from literature
studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched
in order to provide more ecological effects data and in an attempt to bridge existing data
gaps. ECOTOX is a source for locating single chemical toxicity data for aquatic life,
terrestrial plants, and wildlife. ECOTOX was created and is maintained by the USEPA,
Office of Research and Development, and the National Health and Environmental Effects
Research Laboratory's Mid-Continent Ecology Division.
57
-------
The assessment of risk for direct effects to the terrestrial-phase CRLF makes the
assumption that toxicity of oryzalin to birds is similar to the toxicity 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 EC50. 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
(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).
It is important to note that the measures of effect for direct and indirect effects to the
CRLF and its designated critical habitat are associated with impacts to survival, growth,
and fecundity, and do not include the full suite of sublethal effects used to define the
action area. According the Overview Document (USEPA 2004), the Agency relies on
effects endpoints that are either direct measures of impairment of survival, growth, or
fecundity or endpoints for which there is a scientifically robust, peer reviewed
relationship that can quantify the impact of the measured effect endpoint on the
assessment endpoints of survival, growth, and fecundity.
2.10.1.3 Integration of Exposure and Effects
Risk characterization is the integration of exposure and ecological effects characterization
to determine the potential ecological risk from agricultural and non-agricultural uses of
oryzalin, 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 oryzalin 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 oryzalin directly to the CRLF. If estimated
58
-------
exposures directly to the CRLF of oryzalin 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 oryzalin resulting from a particular use are
sufficient to exceed the listed species LOC, then the effects determination for that use is a
"may affect." If the RQ being considered also exceeds the non-listed species acute risk
LOC, then the effects determination is a LAA. If the acute RQ is between the listed
species LOC and the non-listed acute risk 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 "may affect". Further information on LOCs is provided in Appendix C.
2.10.2 Data Gaps
A major data gap in this assessment is the lack of toxicity data on amphibians. No studies
are identified in the open literature that documented the acute or chronic exposure effects
of oryzalin on amphibians. Therefore, acute and chronic toxicity data on fish and birds
(which served as surrogate species for aquatic and terrestrial phase amphibians,
respectively) were used. No other data gaps were identified for oryzalin in this
assessment.
3. Exposure Assessment
Oryzalin is formulated as liquid, granular, water dispersible granules, wettable powder,
and emulsifiable concentrate. Formulated products of oryzalin are applied pre-
emergence to weeds as liquid spray (broadcast and band treatment using low pressure
ground equipment or through irrigation water) or granular applications (using spreaders).
Risks from both broadcast spray and granular applications are considered in this
assessment because they are expected to result in greatest off-target levels of oryzalin due
to spray drift and runoff. Broadcast spray applications made to ground tend to have a
higher potential for off-target movement via spray drift compared to granular
applications. Therefore, it is expected that direct and indirect effects to aquatic and
terrestrial-phase CRLF will be greater from broadcast spray applications (i.e., liquid
formulations) compared to granular applications of oryzalin.
3.1 Label Application Rates and Intervals
Oryzalin labels may be categorized into two types: labels for manufacturing uses
(including technical grade oryzalin and its formulated products) and end-use
products. While technical products, which contain oryzalin of high purity, are not
used directly in the environment, they are used to make formulated products, which
59
-------
can be applied in specific areas to control weeds. The formulated product labels
legally limit oryzalin's potential use to only those sites that are specified on the
labels. Currently registered uses for oryzalin within California include agricultural
(Table 3.1) and non-agricultural uses (Table 3.2). The uses being assessed are
summarized in Table 3.1 and Table 3.2.
Table 3.1. Orv/aliii Application Inl'onnnlion 1-0r Koori I ses1
I SO
Hearing and Nun-
Iharinii
1 rees/\ iHoards
Non-lh'arinii
Trees/\ inejards - -
Non-ISearin^
1 rees/\ incvards -
ISroadcast Spraj
Application
Granular
Application
ISi'oadcasI Spraj
Application
Berries
Blackberry, blueberries,
boysenberry, currant, dewberry,
elderberry, gooseberry, loganberry,
raspberry, and kiwi
Citrus Fruits
Grapefruit, kumquat, lime, lemon,
mandarin, tangerine, orange,
pummelo, nectarine, orange
Pome Fruits
Apple, apricot, crabapple, figs,
loquat, mayhaw, pomegranate, and
quince
6 lb aiA,
2 applications,
75-day interval,
12 lb ai/A/year
4 lb ai/A,
4 applications,
60-day interval,
15 lb ai/A/year
4 lb ai/A,
3 applications,
90-day interval,
12 lb ai/A/year
Tree Nuts
Almonds, chestnut chinquapin,
filbert, hickory nut, macadamia
nut, pecan, pistachio walnut
Stone Fruits
Avocado, Cherry, nectarine, olive,
peach, pear, plum, prune
Vineyards
Wine and table grapes
^ses assessed based on memorandum from SRRD dated 12/19/2007
60
-------
Table 3.2. Orv/alin Application Infoi'malion lor Non-hood I ses1
I se
(iranular Application
ISi'oadcasI Spr;i\
Application
Ornamentals*
4 lb ai/A,
4 applications,
60-day interval,
15.03 lb aiA/year
4 lb ai/A,
3 applications,
90-day interval,
12 lb ai/A/ year
Christmas Tree Plantation
4 lb ai/A,
2 applications,
60-day interval,
8 lb ai/A/ year
Ornamental bulbs
1.5 lb ai/A,
2 application,
90-day interval,
2.25 lb ai/A/yr
1.5 lb ai/A,
2 application,
90-day interval,
2.25 lb ai/A/yr
Warm Season Turf Grass
1.5 lb ai/A,
4 applications,
90-day interval,
6 lb ai/A/ year
2 lb ai/A,
3 applications,
90-day interval,
6 lb ai/A/ year
Rights-of-ways
4 lb ai/A,
4 applications,
60-day interval,
15.03 lb ai/A/year
6.1 lb ai/A,
2 applications,
8-month interval,
12.2 lb ai/A/yr
Residential areas
2 lb ai/A,
3 applications,
56-day interval,
6 lb ai/A/ year
^ses assessed based on memorandum from SRRD dated 12/19/2007
*Use in landscape gardens, container and field grown ornamentals, drainage areas under shadehouse
benches, ground covers/perennials
3.2 Aquatic Exposure Assessment
3.2.1 Modeling Approach
Aquatic exposures are quantitatively estimated for all of assessed uses using scenarios
that represent high exposure sites for oryzalin 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
61
-------
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.
Crop-specific management practices for all of the assessed uses of oryzalin were used for
modeling, including application rates, number of applications per year, application
intervals and the first application date for each crop. Since oryzalin is a pre-emergence
herbicide to control annual grasses and certain broadleaf weeds, the date of first
application was based on late winter (January 1st) to accommodate multiple applications
and extended periods between application intervals for all crop and non-crop scenarios.
3.2.2 Model Inputs
The physical, chemical and environmental fate data of oryzalin used for generating model
parameters are listed in Table 2.1. The input parameters used in simulating PRZM and
EXAMS are listed in Table 3.3.
The CA rights-of-ways and CA impervious scenarios are used in tandem in order to
model EECs resulting from use of oryzalin on non-cropland areas. The rights-of-ways
scenario was developed specifically for the San Francisco Bay region using the
conceptual approach developed for the Barton Springs salamander atrazine endangered
species risk assessment (U.S. EPA, 2006). The San Francisco area was selected to be
representative of urbanized areas with CRLF habitat present in the general vicinity. The
impervious scenario was developed to represent the paved areas within a watershed. The
EECs derived by PRZM/EXAMS for the two scenarios are further refined to be more
representative of non-cropland areas, specifically rights-of-ways. These refinements,
termed "post-processing" are described below.
62
-------
Table 3.3 Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Oryzalin Endangered Species Assessment for the CRLF
Fate Property
Value (unit)
MRID (or source)
Molecular Weight
346.35
Registrant data
Henry's constant
1.82 x 10"8 atmm3/mol
Calculated from solubility and
vapor pressure
Vapor Pressure
1 x 10"7 mm Hg at 25 °C
MRID 40454801
Solubility in Water1
2.5 mg/1 at 25 °C x 10
MRID 41208101-2
Photolysis in Water
0.06 days
MRID 41278701
Aerobic Soil Metabolism Half-lives2
189 days (63x3)
MRID 41322801
Hydrolysis
Stable
MRID 41378401
Aerobic Aquatic Metabolism3
378 days
See comments below
Anaerobic Aquatic Metabolism4
60 days
See comments below
Koc
941 L kg o.c."1 (mean of 4 values)
MRID 41479802
Application rate and frequency
Variable
Table 3.1 and Table 3.2
Application intervals
Variable
Table 3.1 and Table 3.2
Chemical Application Method (CAM)
1 (Soil application)
According to oryzalin labels
Application Efficiency
Spray Drift Fraction5
99% for ground application
100% for granular application
1% for ground application
Non for granular application
Default, EFED guidance
Default, EFED guidance
'Water solubility was multiplied by 10 according to Guidance for selecting input parameters in modeling for environmental
fate and transport of pesticides Version II. February 27, 2002.
2Multiplied by 3, according to Guidance for selecting input parameters in modeling for environmental fate and transport of
pesticides Version II. February 27,2002.
3Assumed 2X of aerobic soil metabolism input value, according to Guidance for selecting input parameters in modeling for
environmental fate and transport of pesticides Version II. February 27, 2002
4Assumed 2X anaerobic soil metabolism half-life multiplied by three (T1/2 = 10 days, MRID 41322802), according to
Guidance for selecting input parameters in modeling for environmental fate and transport of pesticides Version II.
February 27, 2002.
5Spray drift not included in final EEC due to edge-of-field estimation approach
3.2.2.1. Post-processing of PRZM/EXAMS outputs to develop EECs
for non-cropland areas
Available data for California indicate that use of oryzalin on rights-of-ways represents a
significant portion of the past (2002 - 2005) use of oryzalin (10.7% of total use). Of uses
of oryzalin on non-cropland areas, 81.0% was applied to rights-of-ways (CPUR 2007a).
Rights-of-ways include roads, highways, railroads, utilities and pipelines. These areas
contain both impervious (i.e. cement, asphalt, metal surfaces) and pervious surfaces. It is
63
-------
assumed that oryzalin will be applied to the pervious surfaces, where weeds are expected
to grow. It is also assumed that oryzalin is not applied to impervious surfaces in rights-of
ways, but that there is a 1% incidental spray and 0.5% granular release onto impervious
surfaces in the right-of-ways. Further details on how these values were derived and
characterization of alternative assumptions are provided in the Barton Springs salamander
endangered species risk assessment for atrazine (U.S. EPA, 2006).
In a standard PRZM scenario, it is assumed that an entire 10 ha field is composed only of
the identified crop, and that the field has uniform surface properties throughout the field.
In a right-of-way, this is not a reasonable assumption, since a right-of-way contains both
impervious and pervious surfaces. Since the two surfaces have different properties
(especially different curve numbers influencing the runoff from the surfaces) and
different masses of applied oryzalin, the standard approach for deriving aquatic EECs is
revised using the following approach:
1 Aquatic EECs are derived for the pervious portion of the right-of-way, using the
maximum use rate of oryzalin on the CArightofway scenario. At this point, it is
assumed that 100% of the right-of-way is composed of pervious surface. Specific
inputs for this modeling are defined below.
2 Aquatic EECs are derived for the impervious portion of the right-of-way, using
1% for liquid formulation and 0.5% for granular formulation of the maximum use
rate of oryzalin on the CAimpervious scenario. At this point, it is assumed that
100%) of the right-of-way is composed of impervious surface.
3 The daily aquatic EECs (contained in the PRZM/EXAMS output file with the
suffix "TS") are input into a Microsoft® Excel® worksheet.
4 Daily aquatic EECs for the impervious surface are multiplied by 50%. Daily
aquatic EECs for the pervious surface are multiplied by 50%. The resulting EECs
for impervious and pervious surfaces are added together to get an adjusted EEC
for each day of the 30-year simulation period (Equation 1).
Equation 1: Revised EEC = (imperviousEEC * 50%)+(perviousEEC * 50%)
5 Rolling averages for the relevant durations of exposure (21-day, and 60-day
averages) are calculated. The l-in-10 year peak, 21-day and 60-day values are
used to define the acute and chronic EECs for the aquatic habitat.
In this approach, it is assumed that rights-of-way are composed of equal parts pervious
and impervious surfaces (i.e. in steps 4, the EECs of both surfaces are multiplied by
50%>). This is more likely to be representative of a highway or road rights-of-way. It is
likely that rights-of-way contain different ratios of the two surfaces. In general,
incorporation of impervious surfaces into the exposure assessment results in increasing
runoff volume in the watershed, which tends to reduce overall pesticide exposure (when
assuming 1% and 0.5% overspray to the impervious surface).
64
-------
3.2.3 Results
The aquatic EECs for the various scenarios and application practices are listed in Table
3.4. Oryzalin use resulted in both the highest and lowest estimated aquatic exposures for
non-food uses. The calculated highest peak oryzalin exposure concentration was 149.5
ppb for rights-of-ways and the lowest exposure concentration was 3.5 ppb for residential
areas, both using granular formulations. Among the food uses modeled, oryzalin use
resulted in highest peak exposure concentration of 53 ppb in berries and wine grapes and
lowest peak exposure concentration of 9.7 ppb in citrus fruits. Only liquid oryzalin
formulations are labeled for food uses where as both liquid and granular formulations are
labeled for non-food uses. With liquid formulations, oryzalin use resulted in the highest
estimated aquatic exposures for rights-of-ways (141.9 ppb) and lowest exposures for
warm season turf grass (5.42 ppb).
Table 3.4 Aquatic EECs for Oryzalin Uses in California
Crops
Represented
PRZM/EXAMS
Scenarios
Single
Application
Rate1
Application
Interval
Peak
EEC
21-day
Average
EEC
60-Day
Average
EEC
(lb ai/A) |
(days)
|
llg/Lj
Food Uses
Avocado
CAavocado V2
6 (L)
2
39.10
19.1
9.59
Berries
Blackberry, blueberries,
boysenberry, currant,
dewberry, elderberry,
gooseberry, loganberry
kiwi, and raspberry
CAwinegrapes
RLFV2
6 (L)
2
52.98
29.24
15.87
Citrus Fruits
CAcitrusSTD
Grapefruit, kumquat,
lime, lemon, mandarin,
6 (L)
9.74
5.39
2.68
tangerine, orange,
pummelo, nectarine,
orange
A
Pome Fruits
CAfruitsSTD
Apple, pear, apricot,
crabapple, Fig, loquat,
mayhaw, pomegranate,
and quince
Stone Fruits
6 (L)
2
22.85
12.48
6.23
Cherry, Nectarine,
peach, plum, prune
Olive
CA01iveRLF_V2
6 (L)
2
21.65
11.98
6.39
Tree Nuts
CAalmondSTD
Almonds, chestnut
chinquapin, filbert,
hickory nut, macadamia
nut, pecan, pistachio
walnut
6 (L)
2
49.36
26.28
14.15
65
-------
Table 3.4 Aquatic EECs for Oryzalin Uses in California
Crops
PRZM/EXAMS
Single
Application
Peak
21-day
60-Day
Represented
Scenarios
Application
Rate1
Interval
EEC
Average
EEC
Average
EEC
(lb ai/A) |
(days)
1
llg/Lj
Vineyards
Table Grapes
Wine Grapes
CAGrapesSTD
CAwinegrapesRLF_V2
6 (L)
6 (L)
2
2
21.45
52.98
11.34
29.24
5.84
15.87
Non-Food Uses
All non-bearing fruits,
nuts, and vineyards
CANurserySTD
4 (L)
4(G)
3
4
47.64
72.61
26.27
36.73
15.03
21.03
crops2
Christmas Tree
CA forestry RLF
4 (L)
2
33.5
19.37
9.90
Plantation
4(G)
4
33.58
19.72
11.27
Rights-of-ways
CArightofways
RLF V2
6.1 (L)
4(G)
2
4
141.89
149.48
84.92
83.47
38.52
37.69
Ornamentals3
CANursery STD
4 (L)
3
47.64
26.27
15.03
4(G)
4
72.61
36.73
21.03
Ornamental Bulbs
CANursery STD
1.5 (L)
2
16.44
8.48
4.37
1.5 (G)
2
16. 32
8.49
4.31
Warm Season Turf
CAturfRLF
2 (L)
3
5.42
2.75
1.65
Grass
1.5 (G)
4
8.21
4.16
1.92
Residential Areas
CA Residential RLF
2(G)
3
3.5
1.82
1.21
'G = Granular formulation; L = liquid formulation
Non-bearing fruit and nut trees and non-bearing vineyards are defined as plants that will not bear fruit for
at least one year after treatment
Use in landscape gardens, containers and field grown ornamentals, and ground covers/perennials
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. Most of this data is non-targeted (i.e., study
was not specifically designed to capture oryzalin concentrations in high use areas).
Included in this assessment are oryzalin data from the USGS NAWQA program
(http://water.usgs.gov.nawqa) and data from the California Department of Pesticide
Regulation (CDPR). Typically, sampling frequencies employed in monitoring studies are
insufficient to document peak exposure values. This coupled with the fact that these data
are not temporally or spatially correlated with pesticide application times and/or areas
limit the utility of these data in estimating exposure concentrations for risk assessment.
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.
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 February 10, 2008 and all data for the State of
California were downloaded. A total of 347 water samples were analyzed for oryzalin. Of
these samples, 27 (7.82%) had positive detections of oryzalin. The maximum
66
-------
concentration detected was 1.51 |ig/L in the Arcade Creek near Del Paso Heights,
Sacramento and the Warm Creek near San Bernardino, CA. Oryzalin was detected in the
Arcade Creek in 7 samples with concentrations ranging 0.08 -1.51 |ig/L and in the Warm
Creek in 5 samples with concentrations ranging from 0.05 -1.51 |ig/L. Oryzalin was also
detected in the Merced residential Area River Road Bridge near Newman, CA (8 samples
ranging in concentration 0.13- 0.57 |ig/L). Seven more samples were detected at various
areas with concentrations ranging 0.02 -0,71 |ig/L. No clear pattern in oryzalin detections
from different use sites is evident because oryzalin was detected in a number of different
types of watersheds (agricultural, urban, mixed and other) as classified by the USGS land
use information.
3.2.4.2 USGS NAWQA Groundwater Data
Groundwater monitoring data from the United States Geological Survey (USGS)
NAWQA program were accessed on February 10, 2008 and all data for the state of
California was downloaded. A total of 450 water samples were analyzed for oryzalin.
Of these samples, oryzalin was not detected in any samples (below the range of
quantitation).
3.2.4.3 California Department of Pesticide Regulation (CDPR)
Data
Pesticide monitoring studies in surface water were primarily carried out by the
California Department of Pesticide Regulation (CDPR), Environmental Hazard
Assessment Program (EHAP), United States Geological Survey (USGS), and the Central
Valley Regional Water Quality Control Board. Data from these and other studies are
documented in EHAP's surface water database (SURF). Surface water monitoring data
was accessed from the CDPR on June 28, 2007 and all data with analysis for oryzalin
were extracted. A total of 174 samples were available. Of these samples, oryzalin was
detected in 5 samples for a frequency of detection of <3.0 %. The maximum
concentration was 1.51 |j,g/L at Arcade Creek near Norwood, Sacramento, CA. All
oryzalin residues were detected at the same site in Sacramento County at concentrations
ranging between 0.08 -1.51|ig/L.
3.2.4.4 Atmospheric Monitoring Data
Based on its low vapor pressure (1.0 x 10"7 mm Hg at 25°C) and Henry's Law Constant
(1.8 x 10"8 atm-m3/mol), volatilization loss of oryzalin from soil and water systems is
expected to be insignificant. Based on relatively low volatility and high sensitivity to
photolytic degradation, oryzalin is not expected to continue long-range transport. There is
also no data for oryzalin in the California Pesticide Air Monitoring database.
67
-------
3.3 Terrestrial Animal Exposure Assessment
T-REX (Version 1.3.1) is used to calculate dietary and dose-based EECs of oryzalin 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, both broadcast spray and granular applications of oryzalin
are considered, as discussed in Section 3.3.1 and 3.3.2 below.
3.3.1 Spray Applications
Terrestrial EECs for broadcast spray formulations of oryzalin were derived for the uses
summarized in Tables 3.1 and 3.2. A foliar dissipation half-life period could not be
established from the papaya, banana, and guava studies submitted for oryzalin as no
residues were detected throughout the study periods. Furthermore, non-detection of
residues at zero days after application rendered these studies invalid. However, based on
the study entitled "Dissipation of Transferable Residues of Isoxaben and Oryzalin on Turf
Treated with Formulations of the Pesticides" (MRID 450407-01), the calculated 90th
percentile of half-life is 4.6 days. Since the above half-life period is very close to the soil
photolysis half-life of 3.8 days, this value (4.6 days) is used in T-REX calculations. The
T-REX default foliar dissipation half-life period of 35 days was also used to bound the
estimates for risk.
Use specific input values, including number of applications, application rate and
application interval are provided in Table 3.5. An example output from T-REX is
available in Appendix E.
Table 3.5 Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for Oryzalin
wit
\i T-REX
Use Category
Application
Number of
Maximum
Application
Rate
(lb ai/A)
Applications
(#)
Application Rate
(lb ai/A/vcar)
Interval
(Days)
Food Uses
Bearing and Nonbearing Avocado,
Fig, Olive, Berries, Citrus Fruits,
6
2
12
75
Pome Fruits, Stone Fruits, Tree
Nuts and Vineyards
Non-Food Uses
Nonbearing Avocado, Fig, Olive,
Berries, Citrus Fruits, Pome Fruits,
4
3
12
90
Stone Fruits, Tree Nuts and
Vineyards and Ornamentals
(Excluding Bulbs)
Ornamental Bulbs
1.5
2
2.25
90
Christmas Tree Plantations
4
2
8
60
Warm Season Turf
2
3
6
90
Rights-of-ways
6.1
2
12.2
240
68
-------
T-REX is also used to calculate EECs for terrestrial insects exposed to oryzalin. 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 oryzalin (in units of |ig a.i./bee), are converted to |ig a.i./g (of bee) by
multiplying by 1 bee/0.128 g (i.e., dividing |ig a.i./g (of bee) by 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 oryzalin 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 Kenaga 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 3.6). Dietary-based EECs for small and large insects
reported by T-REX as well as the resulting adjusted EECs are available in Table 3.7.
Table 3.6 I pper-bonnd kenaga Nomogram KIX s lor Dietary-and Dose-based
Kxposnres of 1 lie ( Rl.T and its Prev lo Orv/alin
r.r.Cs lor cm.i-
i:i.( s
lor Pre\
(Slllilll lllilllllllills)
I SO
Dieliin-hiised
Dose-hiised I I.(
l)iel;in-l>iised
Dose-hiised I I.(
I I.( ippni)
(mg/kg-lm)
I I.( ippni)
(mg/kg-lm)
Food Uses
Bearing and Nonbearing
Avocado, Fig, Olive, Berries,
Citrus Fruits, Pome Fruits,
Stone Fruits, Tree Nuts and
Vineyards
810
923
1440
1373
Non-Food Uses
Nonbearing Avocado, Fig,
Olive, Berries, Citrus Fruits,
Pome Fruits, Stone Fruits,
Tree Nuts and Vineyards and
Ornamentals (Excluding
Bulbs)
540
615
960
915
Ornamental Bulbs
203
231
360
343
Christmas Tree Plantations
540
615
960
915
Warm Season Turf
270
308
480
458
Rights-of-ways
826
941
1469
1400
69
-------
1 able 3.7 KKC's (ppm) lor Indirect K fleets to the Terrestrial-Phase (UI.I- via KITects
to Terrestrial Invertebrate Prev Items
I SO
Sniiill Insect
l.iirjie Insert
Food Uses
Bearing and Nonbearing Avocado, Fig, Olive, Berries, Citrus
Fruits, Pome Fruits, Stone Fruits, Tree Nuts and Vineyards
810
90
Non-Food Uses
Nonbearing Avocado, Fig, Olive, Berries, Citrus Fruits, Pome
Fruits, Stone Fruits, Tree Nuts and Vineyards and Ornamentals
(Excluding Bulbs)
540
60
Ornamental Bulbs
203
23
Christmas Tree Plantations
540
60
Warm Season Turf
270
30
Rights-of-ways
826
92
The upper bound Kenaga Nomogram-based EECs for terrestrial phase CRLF and small
mammal prey items suggests that exposure concentrations (both dose and dietary-based)
were lowest and highest for non-food uses of oryzalin. Specifically, terrestrial EECs
were lowest for ornamental bulbs (Table 3.6). This is due to oryzalin's lowest use
rate/application and lowest use rate/A/year for ornamental bulbs compared to the other
modeled uses. Highest exposure concentrations, on the other hand, were noted for
oryzalin use on rights-of-ways. A similar trend was also noted for terrestrial invertebrate
exposure concentrations (Table 3.7).
3.3.2 Granular Applications
Estimated environmental concentrations from granular applications (mg ai/square foot)
fortheCRLF are also estimated using T-REX (1.3.1). T-REX assumes that 100% of the
applied oryzalin granules are left on the ground unincorporated. Additionally, T-REX
also assumes that no residual exposure is associated with granular applications and thus
calculates EECs based on single application of oryzalin.
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).
70
-------
In order to derive an estimate of the granular exposure per square foot, the granular
application rates for oryzalin were converted from lb ai/A to mg/ft2 in Table 3.8 using the
following equation: EEC in mg/ft2 = (application rate in lb ai/A x 453,590 mg/lb) /
43,560 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. Risk quotients were calculated by comparing the granular EECs (mg ai/ft2) with
adjusted avian toxicity values.
Table 3.8 Input Parameters and Estimated Environmental Concentrations (EECs) for
Terrestrial Animals for Non-Food Granular Uses of Oryzalin
Use Category
Application Rate
(lb ai/A)
EEC
(mjj/ft2)
Nonbearing Avocado, Fig, Olive, Berries, Citrus Fruits, Pome
Fruits, Stone Fruits, Tree Nuts and Vineyards and
Ornamentals (Excluding Bulbs)
4
41.7
Ornamental Bulbs
1.5
15.6
Christmas Tree Plantations
4.01
41.7
Warm Season Turf
1.5
15.6
Rights-of-ways
4.01
41.7
Residential Areas
2
20.8
Estimated environmental concentrations for terrestrial animals from granular uses of
oryzalin are lowest for ornamental bulbs and warm season turf (15.6 mg/ft2 for both). All
other modeled uses, except residential areas (20.8 mg/ft2), resulted in terrestrial EECs of
41.7 mg/ft2.
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 application method (Table 3.9). A runoff
value of 0.01 is utilized based on oryzalin's solubility, which is classified by TerrPlant as
<10 mg/L. For ground broadcast and granular application methods, drift is assumed to be
1% and 0%, respectively. EECs relevant to terrestrial plants consider pesticide
concentrations in drift and in runoff. These EECs are listed by use in Table 3.9. An
example output from TerrPlant v. 1.2.2 is available in Appendix G.
Spray drift EECs are calculated for liquid formulations of oryzalin only as no drift is
associated with granular formulations and were highest (0.06 lb ai/A) for all food uses
and 1 non-food use (rights-of-ways) (Table 3.9). Runoff EECs, in general, were greater
for semi-aquatic areas compared to dry areas. Also, runoff EECs were lower for granular
applications compared to broadcast spray applications.
71
-------
Table 3.9 Terr Plant Inputs and Resulting EECs for Plants
Exposed to Oryzalin via Runofl
Inhabiting Dry and Semi-aquatic Areas
'and Drift
Use Category
Type of
Application
Single
Application
Rate
(lb ai/A)
Drift
Value
(%)
Spray
drift
EEC
(lb ai/A)
Dry area EEC
(lb ai/A)
Semi-
aquatic
area EEC
(lb ai/A)
Food Uses
Bearing and
Nonbearing Avocado,
Fig, Olive, Berries,
Citrus Fruits, Pome
Fruits, Stone Fruits,
Tree Nuts and
Vineyards -
Ground
Broadcast
6
1
0.06
0.12
0.66
Non-Food Uses
Nonbearing Avocado,
Fig, Olive, Berries,
Citrus Fruits, Pome
Fruits, Stone Fruits,
Tree Nuts and
Vineyards and
Ornamentals
(Excluding Bulbs)
Ground
Broadcast
4
1
0.04
0.08
0.44
Granular
4
0
0
0.04
0.4
Ornamental Bulbs
Ground
Broadcast
1.5
1
0.02
0.03
0.17
Granular
1.5
0
0
0.02
0.15
Christmas Tree
Plantations
Ground
Broadcast
4
1
0.04
0.08
0.44
Granular
4
0
0
0.04
0.40
Warm Season Turf
Ground
Broadcast
2
1
0.02
0.04
0.22
Granular
1.5
0
0
0.02
0.15
Rights-of-ways
Ground
Broadcast
6.1
1
0.06
0.12
0.67
Granular
4
0
0
0.04
0.4
Residential areas
Granular
2
0
0
0.02
0.2
72
-------
4. Effects Assessment
This assessment evaluates the potential for oryzalin 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 effects determination 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 is 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 oryzalin.
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
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 Reregi strati on Eligibility Decision document for oryzalin as well as
ECOTOX information obtained on 30 September, 2007. 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 for the effects determination is dependent on
whether the information is relevant to the assessment endpoints (i.e., maintenance of
73
-------
CRLF survival, reproduction, and growth) identified in Section 2.8. For example,
endpoints such as behavior modifications are likely to be qualitatively evaluated, unless
quantitative relationships between modifications and reduction in species survival,
reproduction, and/or growth are available. Although the effects determination relies on
endpoints that are relevant to the assessment endpoints of survival, growth, or
reproduction, it is important to note that the full-suite of sublethal endpoints potentially
available in the effects literature (regardless of their significance to the assessment
endpoints) are considered for oryzalin.
Citations of all open literature not considered as part of this assessment because they
were either rejected by the ECOTOX screen or accepted by ECOTOX but not used (e.g.,
the endpoint is less sensitive) are included in Appendix H. Appendix H 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.
Open literature studies deemed relevant but classified invalid for use in this assessment
and the rationale for their exclusion are presented in Table A-10 of Appendix A.
Appendix A also includes a summary of the human health effects data for oryzalin.
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 oryzalin. A summary of the available aquatic and
terrestrial ecotoxicity information, use of the probit dose response relationship, and the
incident information for oryzalin are provided in Sections 4.1 through 4.4, respectively.
No ecotoxicity information is available for oryzalin degradates, formulated products, or
mixtures.
4.1 Toxicity of Oryzalin to Aquatic Organisms
Table 4.1 summarizes the most sensitive aquatic toxicity endpoints for the CRLF, based
on an evaluation of the registrant-submitted studies. No valid open literature studies were
identified for oryzalin for use in the current assessment. A brief summary of submitted
data considered relevant to this ecological risk assessment for the CRLF is presented in
Table 4.1 below and also in Appendix A (Table A-l).
74
-------
Table 4.1 Freshwater Aquatic r
'oxicity Profile for Oryzalin
Assessment Endpoint
Species
Toxicity Value Used in
Risk Assessment
Citation IMRID
# (Author &
Date)
Comment
Acute Direct Toxicity to
Aquatic-Phase CRLF
Bluegill
sunfish
96-hour LC50 = 2.88 mg/L
NOAEC = 1 mg/L
Slope = 9.3
00072595
Sleight, 1971
Core
TGAI
Chronic Direct Toxicity
to Aquatic-Phase CRLF
Fathead
minnow
NOAEC = 0.22 mg/L
LOAEC = 0.43 mg/L
00126841
Lilly Research
Lab, 1982
Core
TGAI
Mean larval weight is the
most sensitive endpoint
Indirect Toxicity to
Aquatic-Phase CRLF via
Acute Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Water flea
48-hour EC50 =1.5 mg/L
NOAEC = 1 mg/L
Slope = 9.5
00072596
Carter et al.,
1980
Core
TGAI
Indirect Toxicity to
Aquatic-Phase CRLF via
Chronic Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Water flea
NOAEC = 0.358 mg/L
LOAEC = 0.608 mg/L
43986901
Kirk et al., 1996
Core
TGAI
Most sensitive endpoint is
the dry weight of the first
generation daphnid
Indirect Toxicity to
Aquatic-Phase CRLF via
Acute Toxicity to Non-
vascular Aquatic Plants
Green
algae
5-day EC50 = 42 ppb
NOAEC = 13.8 ppb
43136901
Hughes and
Williams. 1994
Core
TGAI
Indirect Toxicity to
Aquatic-Phase CRLF via
Acute Toxicity to
Vascular Aquatic Plants
Duckweed
14-day EC50 = 15.4 ppb
NOAEC = 5.48 ppb
43136905
Hughes and
Williams. 1994
Core
TGAI
Toxicity to aquatic fish and invertebrates is categorized using the system shown in Table
4.2 (U.S. EPA, 2004). Toxicity categories for aquatic plants have not been defined.
Table 4.2 Categories of Acute Toxicity for Aquatic Organisms
LQo (mjj/L or ppm)
Toxicity Category
<0.1
Very highly toxic
>0.1-1
Highly toxic
>1-10
Moderately toxic
> 10 - 100
Slightly toxic
> 100
Practically nontoxic
75
-------
4.1.1 Toxicity to Freshwater Fish
Given that no oryzalin 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 oryzalin to the CRLF. Effects to freshwater fish resulting from exposure to oryzalin
could indirectly affect the CRLF via reduction in available food. As discussed in Section
2.5.3, over 50% of the prey mass of the CRLF may consist of vertebrates such as mice,
frogs, and fish (Hayes and Tennant, 1985).
A summary of acute and chronic freshwater fish data is provided below in Sections
4.1.1.1 through 4.1.1.3.
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies
Three freshwater fish studies (two on rainbow trout and one on bluegill sunfish), as
shown in Appendix A (Table A-2), are available to document the acute exposure effects
of oryzalin on freshwater fish. Based on these studies, the 96-hour acute toxicity of
oryzalin to the rainbow trout (MRID TNI078), rainbow trout (MRID 00072595) and the
bluegill sunfish (MRID 00072595) were 3.45, 3.26 (NOAEC = 3.2 mg/L), and 2.88
(NOAEC = 1 mg/L) mg/L, respectively. The acute toxicity values for the above
freshwater fish exceeded the expected water solubility for oryzalin of 2.5 mg/L at 20 C.
The above three studies tested the technical grade active ingredient, concluded that
oryzalin is moderately toxic to both fish species, and were classified as Core.
The bluegill sunfish LC50 of 2.88 mg/L was selected as the surrogate freshwater fish
toxicity endpoint to assess the direct acute effects of oryzalin to the CRLF as it is the
most sensitive endpoint. No additional valid data on the acute toxicity of oryzalin
degradates to freshwater fish were located in the open literature.
4.1.1.2 Freshwater Fish: Chronic Exposure (Growth/Reproduction)
Studies
Two scientifically sound freshwater fish chronic toxicity tests, conducted using technical
grade oryzalin, were submitted (Appendix A, Table A-3). Species tested were rainbow
trout (MRID 00126842) and fathead minnow (MRID 00126841). The rainbow trout study
was a 66-day early life stage test whereas the fathead minnow study was a 34-day early
life stage study. The reported NOAEC/LOAEC values were >0.46/>0.46 and 0.22/0.43
mg/L for rainbow trout and fathead minnow, respectively, suggesting that fathead
minnow is more sensitive to oryzalin than rainbow trout. Both studies were classified as
Core.
No adverse effects were noted at any concentration tested in the rainbow trout study. As
a result, a definitive NOAEC value could not be established in the study. In the chronic
76
-------
exposure study using fathead minnow, mean larval weights were affected at the highest
oryzalin dose tested. The NOAEC value (0.22 |ig/L) reported in the fathead minnow
study was used in this assessment as this is the definitive and the most sensitive endpoint.
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open
Literature Information
No valid studies were located in the open literature that report endpoints on sublethal
effects to freshwater fish that are less sensitive than the selected measures of effect
summarized in Table 4.2. In addition, no laboratory freshwater fish early life-stage or
life-cycle tests using oryzalin and/or its formulated products were located in the open
literature.
4.1.2 Toxicity to Freshwater Invertebrates
Freshwater aquatic invertebrate toxicity data were used to assess potential indirect effects
of oryzalin to the CRLF. Effects to freshwater invertebrates resulting from exposure to
oryzalin could indirectly affect the CRLF via reduction in available food items. As
discussed in Section 2.5.3, the main food source for juvenile aquatic- and 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 is provided below in
Sections 4.1.2.1 through 4.1.2.3.
4.1.2.1 Freshwater Invertebrates: Acute Exposure Studies
Data on the acute exposure effects of oryzalin on aquatic invertebrates are available for
the water flea {Daphnia magna) (MRID 00072596). Oryzalin toxicity to other freshwater
invertebrates is not available. Results of acute toxicity tests with freshwater invertebrates
are tabulated in Appendix A (Table A-2).
The 48-hr test on water flea reported an EC50 of 1.5 mg/L and a slope of 9.5. At test
concentrations greater thanl.6 mg/L, hypoactivity, prostration, and immobility were the
effects noted. Reported NOAEC value was 0.62 mg/L based on immobility (mortality).
Based on this data, oryzalin is categorized as moderately toxic to freshwater invertebrates
on an acute basis. No additional data on the acute toxicity of oryzalin or its degradates to
freshwater invertebrates were located in the open literature.
4.1.2.2 Freshwater Invertebrates: Chronic Exposure Studies
An aquatic invertebrate (Daphnia magna) lifecycle study (MRID 43986901) submitted
for oryzalin (Appendix A, Table A-3) reported a NOAEC value of 0.358 mg/L and a
LOAEC value of 0.608 mg/L. The above endpoints were based on the dry weights of the
first generation daphnid. This study was classified as Core.
77
-------
4.1.2.3 Freshwater Invertebrates: Open Literature Data
No freshwater invertebrate studies, based on acute or chronic exposure, were located for
oryzalin from the open literature.
4.1.3 Toxicity to Aquatic Plants
Aquatic plant toxicity studies were used as one of the measures of effect to evaluate
whether oryzalin 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.
4.1.3.1 Aquatic Plants: Acute Exposure Studies
Tier II toxicity data for technical grade oryzalin is available for the vascular plant
duckweed (Lemna gibba) and the following four non-vascular plants: blue-green algae
(Anabaena jlos-aquae), marine diatom (Skeletonema costatum), freshwater alga
{Selenastrum capricornutum), and freshwater diatom (Navicula pelliculosa). A summary
of acute toxicity of oryzalin to aquatic plants is provided in Appendix A (Table A-4).
In the 14-day acute toxicity study with the aquatic vascular plant duckweed, the EC50 and
NOAEC were determined to be >15.4 and 5.48 ppb a.i., respectively. The above
endpoints were based on mean frond counts.
Results for non-vascular plants indicate that the marine diatom, Skeletonema costatum.
is the most sensitive plant to oryzalin (MRID 43136904). Cell density or growth-based
EC50 values for the non-vascular plants were 42 ppb for green algae, 24,000 ppb for blue-
green algae, 72 ppb for freshwater diatom, and 41 ppb for marine diatom. The respective
NOAEC values for the above non-vascular plant species were 13.8 ppb, 8100 ppb, 15.4
ppb, and 30.6 ppb.
Due to the non-obligatory relationship between the CRLF and the aquatic non-vascular
plants, the EC50 values are used as measurement endpoints to determine risk. The EC50
values for Selenastrum capricorutum and Lemna gibba of 42 ppb and 15.4 ppb,
respectively, were used to assess indirect effects to CRLF. The endpoint for green algae
was used in this assessment as it is a freshwater non-vascular plant on which CRLF feeds.
No valid aquatic plant studies were located for oryzalin in the open literature that
reported an endpoint less than the selected measures of effect summarized in Table 4.2.
4.2 Toxicity of Oryzalin to Terrestrial Organisms
Table 4.3 summarizes the most sensitive terrestrial toxicity endpoints for the CRLF,
based on an evaluation of the submitted studies. No studies on terrestrial organisms were
identified for oryzalin in the open literature. A brief summary of submitted data
considered relevant to this ecological risk assessment for the CRLF is presented below.
78
-------
Table 4.3 1
'errestrial Toxicity Profile for Oryza
in
Endpoint
Species
Toxicity Value Used
in Risk Assessment
Citation
MRID#
(Author & Date)
Comment
Acute Direct Toxicity to
Terrestrial-Phase CRLF
(LD50)
Bobwhite quail
LD5o= 506.7 mg
ai/kg-bw
Slope = 4.5
00098462
Cochrane et al.,
1982
Core
Effects noted include lethargy,
ataxia, ruffled appearance,
emaciation, and yellow colored
loose feces; dose-related decline in
food consumption and body weight
loss were also noted
Acute Direct Toxicity to
Terrestrial-Phase CRLF
(LC50)
Bobwhite
quail/mallard
duck
LC50 = >5000 mg
ai/kg-diet
00072593/
00072594
Lilly Research Lab,
1980
Supplemental
Chronic Direct Toxicity
to Terrestrial-Phase CRLF
Bobwhite quail
NOAEC = 132 mg
ai/kg
LOAEC = 311 mg
ai/kg
44162201
Gallagher et al.,
1996
Core
Female body weight
Indirect Toxicity to
Terrestrial-Phase CRLF
(via acute toxicity to
mammalian prey items)
Rat
LD50 = >10 g ai/kg
00026592
Lilly Research Lab,
1975
Core
Indirect Toxicity to
Terrestrial-Phase CRLF
(via chronic toxicity to
mammalian prey items)
Rat
NO A F.I. = 13.8 mg
ai/kg bw
I.OAF.I. = 42.89 mg
ai/kg/day
00026779
Elanco Products
Company, 1979
00044332
Carter etal., 1980
00070569
Todd, 1981
Core
Females more sensitive than males;
decreased body weight gain,
decreased hematology parameters,
and increased microscopic findings
in the thyroid were the noted
effects
Indirect Toxicity to
Terrestrial-Phase CRLF
(via acute toxicity to
terrestrial invertebrate
prey items)
Honey bee
LD5o = >H ng/bee
00066220
A summary study that evaluated
toxicity of various pesticides to
honey bees
Indirect Toxicity to
Terrestrial- and Aquatic-
Phase CRLF (via toxicity
to terrestrial plants)
Seedline
Emergence
Monocots
Dicots
EC25= 0.0285 lb ai/A
EC25= 0.0506 lb ai/A
42602401
Feutz, 1992
Core
TEP
ryegrass shoot length
tomato shoot length
Vesetative Visor
Monocots
Dicots
EC25= 0.174 lb ai/A
EC25= 0.0828 lb ai/A
42602401
Feutz, 1992
Core
TEP
ryegrass shoot length
tomato shoot length
79
-------
Acute toxicity to terrestrial animals is categorized using the classification system shown
in Table 4.4 (U.S. EPA, 2004). Toxicity categories for terrestrial plants have not been
defined.
Table 4.4 Categories of Acute Toxicity for Avian and Mammalian Studies
Toxicity Category
Oral LD5o
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 oryzalin; therefore, acute
and chronic avian toxicity data are used to assess the potential direct effects of oryzalin to
terrestrial-phase CRLFs.
4.2.1.1 Birds: Acute Exposure (Mortality) Studies
Acute oral toxicity data (MRID 00098462) available on a single avian species, bobwhite
quail (Colinus virginianus), is summarized in Appendix A (Table A-5). Based on the
LD50 of 506.7 mg ai/kg bw reported in this study, oryzalin is classified as slightly toxic to
birds on an acute exposure basis. Toxic effects noted include lethargy, ataxia, ruffled
appearance, emaciation, and yellow colored loose feces. Dose-related decline in food
consumption and body weight loss were also noted. This study was classified as Core.
The results of the subacute dietary studies for the preferred test species, bobwhite quail
and mallard duck (A. platyrhynchos), are summarized in Appendix A (Table A-5).
Subacute avian dietary toxicity values indicate that oryzalin is practically non-toxic to
birds. Dietary studies on both the bobwhite quail (MRID# 00072593) and the mallard
duck (MRID# 00072594) reported LCsos > 5000 ppm (the highest concentration tested).
In the bobwhite quail study, there was one mortality at the 5000 ppm concentration but it
was attributed to mechanical injury and was not considered a toxicant-related death. Even
though there was no mortality observed, the bobwhite quail study did show reduced food
consumption and reduction in body weight gain at all concentrations tested including the
lowest concentration of 625 ppm. In the mallard duck study, there were no mortalities
and no observable effects at any of the concentrations tested.
Based on a review of the open literature, no additional information on the acute and
subacute toxicity of oryzalin to birds is available that indicates greater avian sensitivity
than the registrant-submitted studies.
80
-------
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies
Four avian reproduction studies, two on bobwhite quail (MRID 00129050 and MRID
44162201) and two on mallard duck (MRID 00126843 and MRID 44162202), are
submitted for oryzalin. These studies are summarized in Appendix A (Table A-6).
The bobwhite quail (MRID 00129050) and the mallard duck (MRID 00126843) studies
submitted in 1982 were classified as supplemental. While the bobwhite quail study did
not fulfill guideline requirements due to mortality of birds in the control treatment, the
mallard duck study determined a NOAEC of 1000 ppm, which is the highest dose tested
in the study. The mallard duck study was classified as core at the time the study was first
reviewed in 1982; however, it was classified as supplemental in the RED because the
application rates for a single application have increased 4-fold from 1.5 lbs a.i./A to 6.0
lb a.i./A. To bridge this data gap and to satisfy the data requirements for avian
reproduction, two new studies were submitted in 1996.
The most sensitive avian reproductive endpoint used in this assessment is based on the
bobwhite quail study submitted in 1996 (MRID 44162201). The NOAEC was determined
to be 132 mg/kg, based on reduction in the female body weight. No other reproductive
effects were noted in this study. The reported LOAEC was 311 mg/kg.
In the mallard duck reproduction study of 1996 (MRID 44162202), oryzalin did not cause
adverse effect on any of the endpoints evaluated even at the highest dose tested. The
NOAEC/LOAEC values were determined to be >311 mg/kg. This study was classified
as supplemental as mallard ducks were exposed to treatment for only 8 weeks prior to
egg-hatching period, as opposed to the 10 week period stipulated in the guidelines.
Based on a review of the open literature, no additional information on the chronic toxicity
of oryzalin 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 oryzalin to the
terrestrial-phase CRLF. Effects to small mammals resulting from exposure to oryzalin
could 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 terrestrial phase 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 oryzalin is summarized in Appendix A (Table A-
7). Rats exposed orally to technical grade oryzalin showed no mortality at the highest
doses tested (MRID 00026592). The corresponding LD50 value for the TGAI is >10,000
mg/kg-bw, which classifies technical grade oryzalin as practically non-toxic to mammals
on an acute basis.
81
-------
Based on a review of the open literature, no additional information on the acute toxicity
of oryzalin to mammals is available that indicates greater sensitivity than the study
discussed above.
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies
Data on chronic developmental and reproductive effects of oryzalin on mammals are
reported in Appendix A (Table A-7). Chronic studies (MRID 000026779, 00044332,
00070569) that tested oryzalin toxicity on laboratory rats reported a NOAEL/LOAEL
value of 13.82/42.89 mg/kg/day based on symptoms in females. The studies showed
consistent reductions in body weight gain, decreased hematology parameters, increased
microscopic findings in the thyroid in females, decreased survival, increased thyroid
weight, increased incidence of skin lesions, follicular cell thyroid tumors in both sexes,
skin tumors in both sexes, and mammary gland tumors in females. Overall, female rats
were more sensitive to oryzalin than males.
Based upon female rat thyroid follicular cell combined adenoma and carcinoma tumor
rates of 7.79 x 10-3 in human equivalents, oryzalin is classified as "Likely to be
Carcinogenic to Humans" [HED's Risk Assessment for Tolerance Reassessment
Eligibility Decision (TRED) dated 5/18/2004, D300962; Appendix J], Oryzalin is
mutagenic in the sister chromatid exchange by intraperitoneal injection, but not
oral intubation, and is also positive in the DNA repair test, but negative in the Ames
assay and UDS assay. Based on the above, HED classified oryzalin as a mutagen
(D300962; Appendix J).
Based on a review of the open literature, no additional information on the chronic toxicity
of oryzalin 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
oryzalin to the terrestrial-phase CRLF. Effects to terrestrial invertebrates resulting from
exposure to oryzalin could also indirectly affect the CRLF via reduction in available
food.
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies
Non-target beneficial insects, such as the honey bee (Apis mellifera), could be exposed to
oryzalin due to applications in crops such as citrus fruits and certain tree nuts and stone
fruits that are frequented and pollinated by bees. The results of acute contact toxicity test
(MRID 00066220) using formulated oryzalin on the honey bee are summarized in
Appendix A (Table A-8). The LD50 value for the contact test is >11 |ig/bee. As a result,
oryzalin is categorized as practically non-toxic to honeybees on an acute contact basis.
82
-------
The acute contact honey bee LD50 of >11 |ig/bee is used to assess potential indirect
effects to the terrestrial-phase CRLF.
No open literature studies that documented adverse effects on non-target insects were
located for oryzalin.
4.2.4 Toxicity to Terrestrial Plants
Terrestrial plant toxicity data are used to evaluate the potential for oryzalin 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 the registrant-submitted studies were only reviewed as no valid
plant studies were found in the scientific literature. 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
specific plants and stressors, including oryzalin, 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.
The results of the Tier II seedling emergence and vegetative vigor toxicity tests (MRID
42602401) on non-target plants (four monocots including corn, oats, onion, and ryegrass
and six dicots including cabbage, cucumber, lettuce, tomato, soybean, and radish) are
summarized in Table 4.5 and also in Appendix A (Table A-9). In both the seedling
emergence and vegetative vigor tests, technical grade oryzalin was evaluated at 0.008,
0.025, 0.074, 0.222, 0.667, 2.0, and 6.0 lb a/i/A on the above plants. Shoot length was
found to be the most sensitive endpoint in both the tests.
In both the seedling emergence and vegetative vigor tests, the most sensitive monocot
and dicot species were ryegrass and tomato, respectively. The EC25 values for ryegrass
and tomato, which are based on a reduction in shoot length, were 0.0285 lb ai/A and
0.0506 lb ai/A, respectively, in the seedling emergence test and 0.174 lb ai/A and 0.0828
lb ai/A, respectively, in the vegetative vigor test. The NOAEC values for ryegrass and
83
-------
tomato in the seedling emergence study were 0.008 lb ai/A and undetermined (as the
NOAEC value was the lowest dose tested), respectively. The NOAEC values for
ryegrass and tomato in the vegetative vigor study were 0.0253 and 0.0740 lb ai/A,
respectively.
Table 4.5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data
Crop
Type of Study
Species
NOAEC
(lb ai/A)
EC2S
(lb ai/A)
Most sensitive parameter
Seedling Emergence
Monocots
Oats
0.222
0.278
Shoot length
Corn
>6.0
ND
-
Ryegrass
0.008
0.0285
Shoot length
Onion
0.222
0.318
Shoot length
Dicots
Cabbage
0.222
0.656
Shoot length
Cucumber
0.667
1.7
Shoot length
Lettuce
0.222
0.152
Shoot length
Tomato
l~ND
0.0506
Shoot length
Soybean
>6.0
ND
-
Radish
>6.0
ND
-
Vegetative Vigor
Monocots
Corn
0.222
0.244
Shoot length
Oats
0.222
0.445
Shoot length
Ryegrass
0.0253
0.174
Shoot length
Onion
>6.0
ND
-
Dicots
Lettuce
0.0740
0.144
Shoot length
Tomato
0.0740
0.0828
Shoot length
Cabbage
>6.0
ND
-
Cucumber
>6.0
ND
-
Radish
>6.0
ND
-
Soybean
>6.0
ND
-
'ND = not determined due to significant inhibition at all treatment levels; ND = not determined due to
no significant inhibition at any treatment level
Based on a review of the open literature, no additional information is available that
indicates greater non-target terrestrial plant sensitivity to oryzalin than the registrant-
submitted studies discussed above.
4.2.5 Sublethal Effects
No valid studies on aquatic and terrestrial organisms were located in the open literature
that documented sub-lethal effects (other than the assessment endpoints: growth, survival,
and reproduction) associated with exposure to oryzalin.
84
-------
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 (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 oryzalin 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.
As presented in the Appendix A, slope information is available for the acute toxicity
tests on fresh water fish, freshwater invertebrates, and birds. A review of the reported
slopes available for bluegill sunfish, water flea, and bobwhite quail indicates a range of
4.5 (not a default value) to 9.3 (Table 4.6). In general, the reported slope for aquatic
organisms is high compared to the terrestrial organisms.
Table 4.6 Probit Slope Information for Acute Toxicity Studies on Oryzalin
Species Name
mg/L or
mg/kg ai
Confidence
Limits
Slope of the Dose-
Response Curve
MRID and Study
Classification
Bluegill sunfish
Lepomis
macrochirus
2.88
2.23-3.7
9.3 at 95% CI1
00072595
Core
Water flea
Daphnia magna
1.5
14-1.6
9.5 at 95% CI
00072596
Core
Bobwhite quail
Colinus virginianus
506.7
391 -656
4.5 at 95% CI
(not a default value)
00098462
Core
!CI = confidence interval
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.
85
-------
4.4 Incident Database Review
A review of the EIIS database for ecological incidents involving oryzalin was completed
on 28 February 2008. The results of this review for terrestrial wildlife, terrestrial plant,
and aquatic incidents are discussed below in Sections 4.4.1 through 4.4.3, respectively.
Associated uncertainties are included in Appendix I.
4.4.1 Terrestrial Animal Incidents
No ecological incidents involving terrestrial animals were reported for oryzalin.
4.4.2 Terrestrial Plant Incidents
The Washington Department of Agriculture reported that 13 acres of merlot wine grapes
in Grant county were damaged on April 3, 1998 due to direct application of oryzalin.
The legality of use for this incident was listed as "registered use". The certainty index for
this incident (1013884-027) is UNLIKELY as oryzalin is a registered pesticide in grape.
The damage to grapes is possibly due to the application of norflurazon, the legality of
which was listed as "misuse".
A plant incident (7/3/1992) that resulted in damage to trees and shrubs (specific plants
not reported) was reported from Benton county, Washington in 1992. The incident
resulted due to applicator error of mixing oryzalin with bromacil/diuron. The legality of
this use was reported as "undetermined". The certainty index for this incident (1014409-
062) is POSSIBLE.
A nursery in the Washington county of Oregon reported on February 2, 2002 that six
acres of tulips were damaged by exhibiting twisting of leaves. The certainty index for this
incident (1013636-027) is POSSIBLE. The legality of this use was reported as
"registered use". The report mentions that isoxaben was used along with glyphosate,
diclofop-methyl, fenhexamid, iprodione, and oryzalin and that diclofop-methyl was used
previously in the sprayer.
Dow Elanco reported an incident in 1994 that 676,000 Douglas fir seedlings treated with
Snapshot herbicide (a mixture of isoxaben and oryzalin) had to be discarded as they
turned chlorotic and swollen. The certainty index for this incident (1001485-001) is
Possible and the legality was reported as "undetermined". The incident report noted that
little information was provided to determine which herbicide in the mixture caused the
damage.
An acre of Idaho strain fir trees experienced loss of turgidity, necrosis, stem brittleness,
fissures, and death in Washington state in 1989/90. Pesticide application history indicated
use of oxyfluorfen at planting, napropamide one month after planting, oxyfluorfen five
months after planting, and oryzalin eleven months after planting. The legality of use for
this incident was listed as "intentional misuse" as the label for Surflan (oryzalin) clearly
states "do not apply to Douglas fir". The certainty index for this incident (1001734-001)
is PROBABLE.
86
-------
4.4.3 Aquatic Incidents
Approximately 450 bluegill sunfish and largemouth bass were killed between April 6 and
13, 2001 in Georgia, following the application of a formulated product of oryzalin
(Surflan) on March 31. Rain fell on 4 April and it is possible that the pond was
contaminated by either spray drift or runoff. The legality of use for this incident was
listed as "misuse". Residues in fish tissue were not measured. The certainty index for
this incident (1011444-011) is POSSIBLE.
5. Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations.
Risk characterization is used to determine the potential for direct and/or indirect effects to
the CRLF or for modification to its designated critical habitat from the use of oryzalin in
CA. 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 in the terrestrial habitat, 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 oryzalin usage
scenarios summarized in Table 3.4 and the appropriate aquatic toxicity endpoint from
Table 4.1. 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
broadcast spray and granular applications of oryzalin (Tables 3.6, 3.7, and 3.8) and the
appropriate toxicity endpoint from Table 4.3. Exposures are also derived for terrestrial
plants, as summarized in Table 3.9, based on the highest application rates of oryzalin use
within the action area.
5.1.1 Exposures in the Aquatic Habitat
5.1.1.1 Direct Effects to Aquatic-Phase CRLF
Direct effects to the aquatic-phase CRLF are based on peak EECs in the standard pond
and the lowest acute toxicity value for freshwater fish. In order to assess direct chronic
87
-------
risks to the CRLF, 60-day EECs and the lowest chronic toxicity value for freshwater fish
are used.
Acute RQs exceeded the endangered species LOC of 0.05 only from use on rights-of-
ways (Table 5.1). Risk quotients for all other modeled uses that did not exceed Agency
LOC were not presented in the Table 5.1 below. Direct effects associated with acute
exposure are expected to occur for the aquatic-phase CRLF based on the highest yearly
oryzalin use rate. Chronic RQs, on the other hand, are well below the Agency's LOC of
1.0 for all the modeled uses. Direct effects associated with chronic exposure to oryzalin
are not expected to occur for the aquatic-phase CRLF. Chronic RQs were calculated only
for the use that resulted in the highest EEC (non-food use - rights-of-ways at 12.2 lb
ai/A/year). The preliminary effect determination is "may affect" based on direct acute
effects to aquatic phase CRLF from rights-of-way uses only.
Table 5.1 Summary of f
)irect Effect RQs1 for the Aquatic-phase CRLF
Use Scenario
Surrogate
Species
Toxicity
Value
(Hg/L)
EEC
(Hg/L)2
RQ
Probability of
Individual
Effect3
LOC
Excccdancc
and Risk
Interpretation
Acute Direct Toxicity
Rights-of-
ways (granular
at 15.0 lb
ai/A/year)
Bluegill
sunfish
LC50 = 2,880
Peak: 149.5
0.052
1 in 2.77E+32
Yes4
Rights-of-
ways
(broadcast
spray at 12.2
lb ai/A/year)
Bluegill
sunfish
LC50 = 2,880
Peak: 141.9
0.05
1 in 1.88E+33
Yes4
Chronic Direct Toxicity
Rights-of-
ways
(broadcast
spray at 12.2
lb ai/A/year)
Fathead
minnow
NOAEC =
220
60-day:
51.38
0.23
Not calculated
for chronic
endpoints
No5
1 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.
2The highest EEC based on oryzalin use on rights-of-ways (see Table 3.3).
3The probit slope value for the acute bluegill sunfish toxicity test is 9.3.
4RQ > acute endangered species LOC of 0.05.
5RQ < 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 oryzalin 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. Risk quotients exceeded the
non-endangered/endangered risk LOC (RQ >1.0) for aquatic plants due to liquid
88
-------
broadcast spray applications of oryzalin to some food crops such as avocado, berries, tree
nuts, olives, and wine grapes (Table 5.2). Regarding non-food uses, acute risk quotients
exceeded the Agency's LOC from applications to non-bearing fruits, tree nuts, vineyards,
rights-of-ways, and ornamentals (excluding bulbs) for both liquid and granular
formulations. Regardless the formulation type, no acute risk LOCs were exceeded for
warm season turf grass, ornamental bulbs, residential areas, and Christmas tree
plantations. Thus, the preliminary effects determination is "may affect", based on
indirect effects to aquatic-phase CRLFs through a reduction in non-vascular aquatic
plants as food items.
'I'iihie 5.2 Siiiniiiiirv of Acute UQs I sed lo Kslimnle Indirect l-TTecls
lo (lie ( KIT via
KITecls lo N»n-\ iisculnr Aqunlic Pliiuls (diet of ( KIT in tadpole life singe mid
hiihilnl of ii(|iiiilic-phiise ( KIT)
I SOS
Single
Application
Kiile1
(II) 1) are bolded; RQ = use-specific peak EEC/42 ppb (most sensitive endpoint for
non-vascular aquatic plant (green algae)
89
-------
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.
Table 5.3 Siimmarv of Acute and Chronic KQs I sed to Kslimale Indirect KITects lo (lie
CUM'' via Direct KITecls on Aquatic Invertebrates as Dietary hood Items (prev of ( KM-
juveniles and adults in aquatic habitats)
I SOS
Application
Kiile1
(II) iii/A)
Pciik r.r.c
ifiji/i.)
2i-d;i\ r.r.c
uiii/i.i
Indirccl
ll'lccls
Acule UQ
Indirccl I'.ITccls
( lirnnic RQ
Food Uses
Avocado
6 (L)
39.1
76.17
0.03
0.05
Berries
6 (L)
52.48
29.24
0.04
0.08
Citrus fruits
6 (L)
9.74
5.39
0.01
0.02
Pome and stone fruits
6 (L)
22.85
12.48
0.02
0.03
Olives
6 (L)
21.65
11.98
0.01
0.03
Tree nuts
6 (L)
49.36
26.28
0.03
0.07
Vineyards
6 (L)
21.45
(table grapes)
52.98
(wine grapes)
11.34
(table grapes)
29.24
(wine grapes)
0.01
0.04
0.03
0.08
Non-Food Uses
Non-bearing fruits,
nuts, and vineyards
and ornamentals
excluding bulbs
4 (L)
4(G)
47.64
72.61
26.27
36.73
0.03
0.05
0.07
0.1
Christmas tree
plantations
4 (L)
4.01 (G)
33.5
33.6
19.37
19.72
0.02
0.02
0.05
0.06
Rights-of-ways
6.12 (L)
4.01 (G)
141.9
149.5
115.97
90.79
0.09
0.1
0.24
0.23
Ornamental bulbs
1.5 (L)
1.5 (G)
16.4
16.3
8.48
8.49
0.01
0.01
0.02
0.02
Warm season turf
grass
2 (L)
1.5 (G)
5.4
8.2
2.75
4.16
0.004
0.01
0.01
0.01
Residential areas
2(G)
3.5
1.82
0.002
0.01
1L = liquid formulation; G = granular formulation
*LOC exceedances (acute RQ > 0.05; chronic RQ > 1.0) are bolded. Acute RQ = use-specific peak EEC/1500 ppb
(most sensitive acute freshwater invertebrate endpoint). Chronic RQ = use-specific 21-day EEC/358 ppb (most
sensitive chronic freshwater invertebrate endpoint)
Acute RQs for various modeled oryzalin uses ranged between 0.002 and 0.1 and were
less than LOCs (RQ = 0.5) for non-listed species. However, acute RQs exceeded the
90
-------
LOCs for listed species (RQ > 0.05) due to broadcast spray applications of oryzalin in
rights-of-ways and granular applications in nonhealing fruits, ornamentals (excluding
bulbs), and rights-of-ways. Regardless the type of formulation, acute RQs exceeded the
listed species LOC for rights-of-ways. Chronic RQs are less than the chronic LOC (RQ
> 1.0) for aquatic invertebrates for all modeled oryzalin uses. The preliminary effects
determination is "may affect" 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.
Fish and Frogs
Fish and frogs also represent potential prey items of adult aquatic-phase CRLFs. RQs
associated with acute and chronic direct toxicity to the CRLF (Table 5.1) are used to
assess potential indirect effects to the CRLF based on a reduction in freshwater fish and
frogs as food items. Given that acute RQs for direct toxicity to the CRLF exceeded the
Agency's LOCs for oryzalin uses on rights-of-ways, indirect effects based on a reduction
of fish and frogs as prey items are 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.
Except for oryzalin application in citrus fruits (liquid formulation), warm season turf
grass (both liquid and granular formulations), and residential areas (granular
formulations), endangered/non-endangered species RQs exceeded the LOC of 1 for
vascular aquatic plants for all other modeled scenarios (Table 5.4). Therefore, the
preliminary effects determination is "may affect", based on indirect effects to habitat
and/or primary productivity for the aquatic-phase CRLF.
91
-------
Table 5.4 Summary of Acute UQs I sed lo Kslimalc Indirect Kfl'ecls lo (lie ( KM- via
KITecls lo Vascular Aquatic Plants (habilal of aquatic-phase ( Kl.l- )1
I SOS
Application K;ilc:(ll>
;ii/.\)
Pciik r.r.c
uiii/i.i
Indirccl cllccls U 1) are bolded. RQ
= use-specific peak EEC/15.4 ppb (most sensitive endpoint for vascular aquatic plant)
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 broadcast spray and granular applications of oryzalin. Though two foliar
half-life periods (4.6 and 35 days) were modeled in T-REX, results were presented for the
analysis that utilized 4.6 days only as risk conclusions were similar for both.
92
-------
5.1.2.1.1
Broadcast Spray Applications
Potential direct acute effects to the terrestrial-phase CRLF are derived by considering
dose- and dietary-based EECs modeled in T-REX for a small bird (20 g) consuming
small invertebrates (Table 3.6) and acute oral and subacute dietary toxicity endpoints for
avian species.
Risk quotients calculated using the bobwhite quail oral LD50 value of 506.7 mg/kg ai
suggests that acute RQs exceeded the LOCs for listed species (RQ > 0.1) for all use
categories (Table 5.5). The range for dose-based avian acute RQs is 0.6 to 2.6. On the
other hand, definitive dietary-based 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, showed no mortality to both the mallard duck and bobwhite
quail at the highest tested level of oryzalin (LC50 >5,000 mg/kg-diet). Since the predicted
dietary-based EECs (which ranged between 270 and 1101 ppm) were several fold lower
than the avian LC50 value of >5,000 mg/kg-diet, dietary-based acute avian and terrestrial-
phase CRLF mortality is unlikely. The preliminary effects determination for direct acute
effects to the terrestrial-phase CRLF is "may affect" based on exposure to oryzalin doses.
Tabic 5.5 Summary of Acute KQs1 I setl to Kstimalc Direct K ITects to the 1
CUM'' (Broadcast Spray Application)
errest rial-Phase
I se Category
Dose-based
i:i:c
Dose-based
Acute UQ2
Probability of
Individual
i: fleet'
Food Uses
Bearing and Nonbearing Avocado, Fig, Olive,
Berries, Citrus Fruits, Pome Fruits, Stone Fruits,
Tree Nuts and Vineyards
923
2.5
1 in 104
Non-Food Uses
Nonbearing Avocado, Fig, Olive, Berries, Citrus
Fruits, Pome Fruits, Stone Fruits, Tree Nuts and
Vineyards and Ornamentals (Excluding Bulbs)
615
1.7
1 in 118
Ornamental Bulbs
231
0.6
1 in 629
Christmas Tree Plantations
615
1.7
1 in 118
Warm Season Turf
308
0.8
1 in 302
Rights-of-ways
941
2.6
1 in 103
1 LOG' exceedances (acute RQ > 0.5 and acute endangered species RQ > 0.1) are bolded.
2Based on bobwhite quail oral LD50 of 506.7 ppm; 3The probit slope value for the acute bobwhite quail toxicity test
is 4.5 (not a default value)
Potential direct chronic effects of oryzalin 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 5.6, chronic RQs, which ranged from 1.5 to 6.3, exceed LOCs for all
modeled broadcast spray applications of oryzalin. Therefore, the preliminary effects
determination is "may affect" for direct chronic effects to the terrestrial-phase CRLF.
93
-------
Table 5.6 Summary of Chronic KQs I setl to Kslimale Direct K fleet s lo (lie Terrestrial-
Phase ( KM- (Broadcast Spray Application)
I SO
(Application Rale)
Diclan-hascd I I.(
Diclan-hascd Chronic UQ1
Food Uses
Bearing and Nonbearing Avocado, Fig, Olive,
Berries, Citrus Fruits, Pome Fruits, Stone Fruits,
Tree Nuts and Vineyards
810
6.1
Non-Food Uses
Nonbearing Avocado, Fig, Olive, Berries, Citrus
Fruits, Pome Fruits, Stone Fruits, Tree Nuts and
Vineyards and Ornamentals (Excluding Bulbs)
540
4.1
Ornamental Bulbs
203
1.5
Christmas Tree Plantations
540
4.1
Warm Season Turf
270
2.1
Rights-of-ways
826
6.3
1 LOG' exceedances (chronic RQ > 1) are bolded and are based on bobwhite quail NOAEC of 132 ppm.
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 oryzalin granules are derived based on LD50/ft2 values. A comparison of
EECs derived for granular applications of oryzalin with adjusted avian LD50 values for
two weight classes of 20g and lOOg (representative of juvenile and adult terrestrial-phase
CRLFs) suggests that the predicted granular EECs (mg ai/ft2) do not exceed or approach
the adjusted LD50 values for any of the uses (Table 5.7).
Table 5.7 Comparison of Granular EECs to Adjusted LDso1 Value Used to Estimate Direct
Effects to the Terrestrial-phase CRLF (Granular Non-Food Uses)
Use
Application Rate
EEC
RQ2
(lb ai/A)
(mg/ft2)
20 g (juvenile)
lOOg (adult)
Nonbearing Avocado, Fig, Olive, Berries,
4
41.7
0.11
0.09
Citrus Fruits, Pome Fruits, Stone Fruits,
Tree Nuts and Vineyards and Ornamentals
(Excluding Bulbs)
Ornamental Bulbs
1.5
15.6
0.04
0.03
Christmas Tree Plantations
4.01
41.8
0.11
0.09
Warm Season Turf
1.5
15.6
0.04
0.03
Rights-of-ways
4.01
41.8
0.11
0.09
Residential areas
2
20.8
0.06
0.04
1 Adjusted Avian LD50 = LD50 (AW/TW)'"'" 1 ; Actual Avian (bobwhite quail) LD50 = 507 mg/kg-bw; Weight of tested
species (TW) (bobwhite quail) = 178 gm; Assessed weight of juvenile and adult frogs (AW) = 20 and 100 g, respectively;
Adjusted LD50 Value (mg/kg-bw) for 20 g juvenile and 100 g adult was calculated to be 365 and 466, respectively
2LOC exceedances (acute RQ > 0.5 and acute endangered species RQ > 0.1) are bolded.
With acute RQs ranging between 0.04 and 0.11, endangered species acute risk (0.1) was
exceeded for granular applications for juvenile CRLF. None of the modeled scenarios'
94
-------
RQs exceeded endangered species risk LOCs for the adult CRLF. Overall, the
preliminary effects determination for direct effects to the terrestrial-phase CRLF via
granular application of oryzalin is "may affect". Further qualitative discussion of
potential acute risks to birds associated with exposure to granular oryzalin is provided in
Section 5.2.1.2.
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in
Prey (terrestrial invertebrates, mammals, and frogs)
5.1.2.2.1 Terrestrial Invertebrates
In order to assess the risks of oryzalin 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 >ll|ig a.i./beeby 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 > 86|ig a.i./g of bee.
As the toxicity endpoint for honey bee 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 oryzalin (Table 5.8).
Table 5.S Summary of UQs I sed to Kslimale Indirect K fleet s lo (lie Tcrrcslrial-pliasc
( KIT via Direct K ITcd s on Terrestrial Invertebrates as Dietary hood Items
I so
Sniiill Insecl RQ1
l.siific Insecl UQ1
Food Uses
Bearing and Nonbearing Avocado, Fig, Olive, Berries, Citrus
Fruits, Pome Fruits, Stone Fruits, Tree Nuts and Vineyards
<9.4
<1.0
Non-Food Uses
Nonbearing Avocado, Fig, Olive, Berries, Citrus Fruits, Pome
Fruits, Stone Fruits, Tree Nuts and Vineyards and Ornamentals
(Excluding Bulbs)
<6.3
<0.7
Ornamental Bulbs
Christmas Tree Plantations
<6.3
<0.7
Warm Season Turf
<3.1
<0.3
Rights-of-ways
<12.8
<1.4
1 LOG' exceedances (RQ > 0.05) are bolded. Because a definitive endpoint was not established for terrestrial
invertebrates (/'. e., the value is greater than the highest test concentration), the RQ represents an upper bound
value.
95
-------
Table 5.8 suggests that the acute RQ values, which range from < 0.7 to <12.8, may
exceed the LOC (RQ > 0.05) for both large and small terrestrial insects for all modeled
scenarios. These exceedances refer to on-site residue exposures for terrestrial insects and
would be expected to decline with distance from the site of application. The preliminary
effects determination for indirect effects to terrestrial-phase CRLFs via reduction in
terrestrial invertebrates as dietary food items is "may affect".
5.1.2.2.2 Mammals
Risks associated with the 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. EECs are divided by the toxicity value to
estimate acute and chronic dose-based RQs as well as chronic dietary-based RQs.
Definitive acute dose-based RQ values could not be derived because the mammalian
LD50 value is >10,000 mg/kg-bw. Therefore, the acute dose-based RQ values are
representative of upper bound values (Table 5.9). The upper bound acute dose-based
RQs did not exceed LOCs for any of the use categories modeled using T-REX.
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
oryzalin (Table 5.9). Therefore, the preliminary effects determination for indirect effects
to terrestrial-phase CRLFs via reduction in small mammals (exposed to broadcast spray
applications of oryzalin) as dietary food items is "may affect".
Table 5.9 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
(Broadcast Spray Application)
Use
Chronic RQ1
Acute RQ1
(Application Rate)
Dose-based Chronic RQ1
Dietary-based
Chronic RQ2
Dose-based Acute RQ3
Food Uses
Bearing and Nonbearing Avocado, Fig,
Olive, Berries, Citrus Fruits, Pome Fruits,
45.2
5.2
<0.06
Stone Fruits, Tree Nuts and Vineyards
Non-Food Uses
Nonbearing Avocado, Fig, Olive, Berries,
Citrus Fruits, Pome Fruits, Stone Fruits,
30.1
3.5
<0.04
Tree Nuts and Vineyards and
Ornamentals (Excluding Bulbs)
Ornamental Bulbs
11.3
1.3
<0.02
Christmas Tree Plantations
30.1
3.5
<0.04
Warm Season Turf
15.1
1.7
<0.02
Rights-of-ways
46.1
5.3
<0.06
1 LOC exceedances (acute RQ > 0.1 and chronic RQ > 1) are bolded; 2Based on dose-based EEC and oryzalin rat
NOAEL of 13.82 mg/kg-bw; 3Based on dietary-based EEC and oryzalin rat NOAEC of 276.4 mg/kg-diet; 4Based on
dose-based EEC and oryzalin rat acute oral LD50 of >10,000 mg/kg-bw.
96
-------
5.1.2.2.2a
Mammals (Granular Applications)
Indirect effects to terrestrial-phase CRLFs via ingestion of small mammals that may
consume oryzalin granules are based on LD50/ft2 values. However, a definitive LD50/ft2
value could not be derived because the mammalian LD50 value was reported as >10,000
mg/kg-bw {i.e., 50% mortality was not observed in the highest treatment levels of
oryzalin). 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 performed (Table 5.10).
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 < 4.0 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 oryzalin) as dietary food items is "no effect".
Table 5.10 Comparison of Granular EECs to Adjusted LD5o Value Used to
Estimate Indirect Effects to the Terrestrial-phase CRLF via Direct Effects on Small
Mammals as Dietary Food Items (Granular Non-Food Uses)
Use
Application Rate
(lb ai/A)
EEC
(mjj/t't2)
Adjusted LDjo Value
(mg/kg-bw)1
Nonbearing Avocado, Fig,
Olive, Berries, Citrus Fruits,
4
41.7
>4,472
Pome Fruits, Stone Fruits, Tree
Nuts and Vineyards and
Ornamentals (Excluding Bulbs)
Ornamental Bulbs
1.5
15.6
Christmas Tree Plantations
4.01
41.8
Warm Season Turf
1.5
15.6
Rights-of-ways
4.01
41.8
Residential areas
2
20.8
'Adjusted Mammalian LD50 = LD50 (TW/AW)(0 2;>)
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 (dose-based) (RQs = 0.6 - 2.6) and chronic
(RQs = 1.5 - 6.3) effects to frogs are likely, based on the available avian acute and
chronic toxicity data. 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".
97
-------
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 both monocot and dicot plants are more sensitive to
applications of oryzalin at the seedling emergence stage than at the vegetative stage.
Seedling emergence of corn, soybean, and radish and vegetative vigor of onion, cabbage,
cucumber, radish, and soybean were not affected following exposure to oryzalin. The
results of these tests indicate that a variety of terrestrial plants that may inhabit riparian
and upland zones may be sensitive to oryzalin exposure.
Table 5.11 RQs* for Monocots Inhabiting Dry and Semi-Aquatic Areas Exposed to Oryzalin via Runoff and
Drift
Use Category
Tvpc of
Application
Application
Rate
(lb ai/A)
Drift Value
(%)
Drv area
RQ
Semi-aquatic
area RQ
Sprav drift
RQ
Food Uses
Bearing and Nonbearing Avocado, Fig,
Olive, Berries, Citrus Fruits, Pome Fruits,
Stone Fruits, Tree Nuts and Vineyards -
Ground
Broadcast
6
1
4.2
23.2
2.11
Non-Food Uses
Nonbearing Avocado, Fig, Olive, Berries,
Citrus Fruits, Pome Fruits, Stone Fruits,
Tree Nuts and Vineyards and Ornamentals
(Excluding Bulbs)
Ground
Broadcast
4
1
2.8
15.4
1.4
Granular
4
0
1.4
14.0
<0.1
Ornamental Bulbs
Ground
Broadcast
1.5
1
1.1
5.8
0.5
Granular
1.5
0
0.5
5.3
<0.1
Christmas Tree Plantations
Ground
Broadcast
4
1
2.8
15.4
1.4
Granular
4
0
1.4
14.1
<0.1
Warm Season Turf
Ground
Broadcast
2
1
1.4
7.7
0.7
Granular
1.5
0
0.5
5.3
<0.1
Rights-of-ways
Ground
Broadcast
6.1
1
4.3
23.6
2.2
Granular
4
0
1.4
14.1
<0.1
Residential areas
Granular
2
0
0.7
7.0
<0.1
1 LOG' exceedances (RQ > 1) are bolded
98
-------
The LOC (RQ > 1.0) is exceeded for exposures resulting from single applications of all
liquid and granular uses of oryzalin for both monocot and dicot plants inhabiting semi-
aquatic areas (Tables 5.11 and 5.12). Dry area RQs did not exceed LOC for monocots
from granular applications of oryzalin in ornamental bulbs, warm season turf, and
residential areas only where as LOC is exceeded for several granular uses and non-
granular uses for dicots. Spray drift RQs, on the other hand, exceeded for oryzalin non-
granular uses in bearing trees, non-bearing trees, ornamentals (excluding bulbs),
Christmas tree plantations, and rights-of-ways for monocots and bearing trees and rights-
of-ways for dicots. 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 5.12 RQs1 for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to Oryzalin via Runoff and
Drift
Use Category
Type of
Application
Application
Rate
(lbs ai/A)
Drift Value
(%)
Drv Area
RQ
Semi-Aquatic
Area RQ
Sprav Drift
RQ
Food Uses
Bearing and Nonbearing
Avocado, Fig, Olive, Berries,
Citrus Fruits, Pome Fruits, Stone
Fruits, Tree Nuts and Vineyards
Ground
Broadcast
6
1
2.4
13.0
1.2
Non-Food Uses
Nonbearing Avocado, Fig,
Olive, Berries, Citrus Fruits,
Pome Fruits, Stone Fruits, Tree
Nuts and Vineyards and
Ornamentals (Excluding Bulbs)
Ground
Broadcast
4
1
1.6
8.7
0.8
Granular
4
0
0.8
7.9
<0.1
Ornamental Bulbs
Ground
Broadcast
1.5
1
0.6
3.3
0.3
Granular
1.5
0
0.3
3.0
<0.1
Christmas Tree Plantations
Ground
Broadcast
4
1
1.6
8.7
0.8
Granular
4
0
0.8
7.9
<0.1
Warm Season Turf
Ground
Broadcast
2
1
0.8
4.4
0.4
Granular
1.5
0
0.3
3.0
<0.1
Rights-of-ways
Ground
Broadcast
6.1
1
2.4
13.3
1.2
Granular
4
0
0.8
7.9
<0.1
Residential areas
Granular
2
0
0.4
4.0
<0.1
1 LOC exceedances (RQ > 1) are bolded
99
-------
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:
• 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 "habitat modification",
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 oryzalin 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 "habitat
modification" (see Section 5.1.1.1). 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 "habitat modification" (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 n 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
100
-------
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 "habitat modification", 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 oryzalin on this PCE,
acute and chronic toxicity endpoints for birds, mammals, and terrestrial invertebrates are
used as measures of effects. RQs for these endpoints, calculated in Section 5.1.2.2.
exceed the LOCs for all oryzalin non-granular broadcast spray uses. Granular uses of
oryzalin, however, are not expected to cause direct effects to frog prey items of the
terrestrial-phase CRLF. The preliminary effects determination for this PCE via impacts
of non-granular uses of oryzalin to terrestrial-phase CRLF food items is "habitat
modification".
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. Direct acute and chronic RQs for terrestrial-phase CRLFs are presented in
Section 5.2.1.2. Both direct acute effects (via mortality) and chronic reproductive effects
are possible with all the spray and granular applications of oryzalin for the terrestrial-
phase CRLF (see Section 5.2.1.2). Therefore the preliminary effects determination for
this PCE is "habitat modificaiton" due to direct acute effects to terrestrial-phase CRLFs
and "habitat modification" based on chronic exposures to liquid spray applications of
oryzalin.
101
-------
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 oryzalin'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 oryzalin. A summary of the
results of the risk estimation (i.e., "no effect" or "may affect" finding) is provided in
Table 5.13 for direct and indirect effects to the CRLF and in Table 5.14 for the PCEs of
designated critical habitat for the CRLF.
Table 5.13 Preliminary Effects Determination Summary for Oryzalin - Direct and Indirect Effects to
CRLF
Assessment Endpoint
Preliminary
Effects
Determination
Basis For Preliminary Determination
Aquatic Phase
'eggs, larvae, tadpoles, juveniles, and adults)
Survival, growth, and reproduction of
CRLF individuals via direct effects on
aquatic phases
Fish: May affect
Using the bluegill sunfish (a freshwater fish) as a surrogate, no
chronic LOCs are exceeded for any use (Table 5.1). However,
acute LOCs are exceeded for 1 non-food use (rights-of-ways)
only for both liquid and granular uses.
Survival, growth, and reproduction of
CRLF individuals via effects to food supply
(i.e., freshwater invertebrates, non-vascular
plants)
Freshwater
invertebrates and
aquatic non-
vascular plants:
May affect
Except for citrus, pome and stone fruits, table grapes,
Christmas tree plantations, ornamental bulbs, residential areas,
and warm season turf grass, endangered/non-endangered
aquatic non-vascular plant RQs exceeded LOCs for all other
modeled scenarios (Tables 5.2 and 5.3). Acute invertebrate
RQs exceeded LOCS for nonbearing fruits, nuts, and vineyards
(granular), rights-of-ways (liquid and granular) and
ornamentals (excluding bulbs) (granular). Chronic aquatic
invertebrate RQs did not exceed Agency's LOC for any of the
modeled scenarios for either liquid or granular formulations.
Fish and frogs: May
affect
Dose-based acute LOCs are exceeded for rights-of-ways only
based on the most sensitive toxicity data for freshwater fish
(Table 5.1). No chronic LOC exceedances were noted for
freshwater fish with any of the modeled scenarios.
Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat, cover, and/or primary productivity
(i.e., aquatic plant community)
Aquatic plants:
May affect
LOCs are exceeded for non-vascular aquatic plants (all
scenarios except citrus, pome and stone fruits, table grapes,
ornamental bulbs, warm season turf grass, residential areas, and
Christmas tree plantations) and vascular plants (all scenarios
102
-------
except citrus, warm season turf, and residential areas) (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.
Aquatic and
terrestrial plants:
May affect
Most uses are likely to adversely affect CRLF via effects to
riparian vegetation. Both upland and aquatic plants are
expected to be significantly impacted by oryzalin use (Tables
5.2, 5.4, 5.10, and 5.11)
Terrestrial Phase
(Juveniles and adults)
Survival, growth, and reproduction of CRLF
individuals via direct effects on terrestrial phase
adults and juveniles
Acute avian:
May affect
Based on the available avian acute toxicity data, which is used
as a surrogate for terrestrial-phase amphibians, predicted EECs
for liquid formulation of oryzalin are above the reported dose-
based acute avian toxicity value for all modeled scenarios
(Table 5.6). Therefore, direct adverse effects are expected on
terrestrial phase adults and juveniles. Endangered species
acute avian risk is also expected for granular applications of
oryzalin for all scenarios except ornamental bulbs, warm
season turf, and residential areas.
Chronic avian:
May affect
Dietary-based chronic RQs exceeded the LOC for all modeled
broadcast spray applications (food uses) of oryzalin (Tables
5.5).
Survival, growth, and reproduction of CRLF
individuals via effects on prey (i.e., terrestrial
invertebrates, small terrestrial mammals and
terrestrial phase amphibians)
Acute
terrestrial
invertebrates:
May affect
Chronic birds
and mammals:
May affect
All uses are likely to adversely affect CRLF via effects on
terrestrial invertebrates that are prey items of the frog's diet.
Dietary-based chronic RQs for mammals and birds exceed the
LOCs for all modeled non-granular uses of oryzalin (Tables 5.5
and 5.8). However, acute RQs for mammals did not exceed
LOCs for either formulation (Table 5.8).
Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian vegetation)
Terrestrial
plants: May
affect
LOCs are exceeded for both monocots and dicots for all
modeled uses of oryzalin (Tables 5.10 and 5.11).
103
-------
Table 5.14 Preliminary Effects Determination Summary for Oryzalin - PCEs of Designated Critical Habitat
for the CRL.F
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.
Habitat modification
LOCs are exceeded for both monocots and dicots
for all modeled uses of oryzalin (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.
Habitat modification
LOCs are exceeded for both monocots and dicots
for all modeled uses of oryzalin (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:
Habitat modification
Food source:
Habitat modification
Acute LOCs exceeded for freshwater fish for rights-
of-ways only.
Acute freshwater invertebrate and aquatic non-
vascular plant RQs exceed LOCs for both
formulations for most uses (Tables 5.2 and 5.3).
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
Habitat modification
Acute LOCs are exceeded for non-vascular aquatic
plants for most uses.
Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat; ability of
habitat to support food source of CRLFs: Upland areas
within 200 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
LOCs are exceeded for both monocots and dicots
for all modeled uses of oryzalin (Tables 5.10 and
5.11).
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
LOCs are exceeded for both monocots and dicots
for all modeled uses of oryzalin (Tables 5.10 and
5.11).
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Habitat modification
Based on likely effects to small mammals,
amphibians, and terrestrial invertebrates reduction in
food sources is expected (Tables 5.5, 5.7, and 5.8).
Alteration of chemical characteristics necessary for normal
growth and viability of juvenile and adult CRLFs and their
food source.
Habitat modification
Chronic RQs for mammals and birds exceed the
LOCs for all modeled granular and non-granular uses
of oryzalin (Tables 5.5 and 5.8). Therefore, chronic
effects are possible for small insectivorous mammals
that are food items of the CRLF. Acute RQs for
small terrestrial invertebrates exceed the LOC for all
modeled uses of oryzalin (Table 5.7).
104
-------
Following a preliminary "may affect" or "habitat modification" 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"
occurs for even a single individual. "Take" in this context means to harass or
harm, defined as the following:
¦ Harm includes significant habitat modification or degradation that
results in death or injury to listed species by significantly impairing
behavioral patterns such as breeding, feeding, or sheltering.
¦ Harass is defined as actions that create the likelihood of injury to listed
species to such an extent as to significantly disrupt normal behavior
patterns which include, but are not limited to, breeding, feeding, or
sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are
extremely unlikely to occur.
• 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 and larvae. 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 oryzalin. Based on the highest modeled EECs for oryzalin use on
rights-of-ways (6.1 lb ai/A) and the most sensitive freshwater fish (bluegill sunfish for
acute toxicity and fathead minnow for chronic toxicity) (both used as surrogates for
aquatic-phase amphibians), acute RQs are above the Agency's risk LOCs for oryzalin
uses on rights-of-ways only (for both liquid and granular formulations) (Table 5.1).
However, chronic toxicity did not exceed the risk LOC for any of the modeled scenarios.
105
-------
Model-estimated peak environmental concentrations resulting from different oryzalin
uses ranged from 3.5 to 149.5 |ig/L. Comparison of the highest modeled surface water
EEC (peak = 149.5 |ig/L) with available NAWQA surface water monitoring data from
California (1.51 |ig/L) indicates that the peak modeled EEC is approximately 99 times
higher than the maximum concentration of oryzalin detected in Arcade Creek near
Norwood, Sacramento. Therefore, use of modeled EECs is assumed to provide a
conservative measure of oryzalin exposures for aquatic-phase CRLFs.
While the acute RQ for mortality effects for the aquatic-phase CRLF exceeded the listed
species LOC for only one non-food use (rights-of-ways), the probability of individual
effects was low enough that the likelihood of measuring such an effect was considered
improbable. The bluegill sunfish study reported a slope of 9.3. Calculated RQs ranged
between 0.05 (liquid spray) and 0.052 (granular) for applications on rights-of-ways. The
corresponding estimated chance of an individual acute mortality to the aquatic-phase
CRLF is 1 in 1.88E+33 and 1 in 2.77E+32. Given the low probability of an individual
mortality occurrence based on acute exposure and in view of chronic RQs that are well
below LOCs, oryzalin is not likely to cause direct adverse effects to aquatic-phase
CRLFs.
The CDPR (California Department of Pesticide Registration's pesticide use reporting
data for the period 2002 to 2005 indicates that oryzalin use in rights-of-ways accounted
for only 11% of the total use in California. Since most of the oryzalin used in California
is applied in tree nuts (43%) and grapes (25%), it is unlikely that direct and indirect
effects would result to the aquatic phase CRLF based on acute LOC exceedances for
rights-of-ways.
Only one freshwater aquatic incident involving fish (bluegill sunfish and largemouth
bass) kills were reported for oryzalin. The incident, which happened in 2001 in Georgia,
was classified as misuse as it resulted possibly from either spray drift or run off following
a rain event. More details on the incident can be found in Appendix I.
In summary, the Agency concludes a "not likely to adversely effect (NLAA)"
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
Acute mortality is expected for the terrestrial-phase CRLF (based on avian toxicity data)
via exposure to spray and granular applications of oryzalin. The acute avian dose-based
EEC values are above the dose-based LD50 values for most uses for the non-granular
formulations of oryzalin suggesting concerns for risk. Endangered species LOCs are
exceeded for juvenile frogs with most uses for granular formulations of oryzalin.
Therefore, direct effects to the terrestrial-phase CRLF via ingestion of terrestrial
invertebrate food items are expected.
106
-------
Before concluding LAA or NLAA for acute direct effects to the terrestrial-phase CRLF, a
refinement of the risks posed to the terrestrial-phase CRLF from ingestion of residues on
small insects was performed. As the avian acute RQs exceeded the listed species acute
LOC (0.1) when calculated with T-REX, the likelihood of the risk should be considered
in light of the results of the T-HERPS model. This refinement was performed because
the avian acute dose-based RQ values in Table 5.5, used as screening surrogates for
terrestrial-phase amphibians, likely overestimated risks to amphibians. Overestimation is
due to the higher energy requirements of birds over amphibians of the same body weight,
which results in a higher daily food intake rate value and a resultant higher dose-based
exposure for birds than would occur for an amphibian of the same body weight. The T-
HERPS model refines the RQ values based on dietary intake rate of an amphibian, rather
than a dietary intake rate of an avian. Results of the analysis performed with T-HERPS
are presented in Table 5.15. An example T-HERPS output is presented in Appendix F.
Table 5.15 Terrestrial-Phase Amphibian RQ1 Values Based on T-HERPS for Direct
Effects to the CRLF from Ingestion of Oryzalin Residues on or in Prey Items (Based
on Broadcast Spray Applications)
Use Category
Dose-
based
EEC
Dose-based
Acute RQ
Dietary-
based
EEC
Dietary-
based Acute
RQ2
Dietary-based
Chronic RQ3
Food Uses
Bearing and Nonbearing
Avocado, Fig, Olive, Berries,
Citrus Fruits, Pome Fruits, Stone
Fruits, Tree Nuts and Vineyards
31.5
0.06
810
<0.16
6.1
Non-Food Uses
Nonbearing Avocado, Fig, Olive,
Berries, Citrus Fruits, Pome
Fruits, Stone Fruits, Tree Nuts
and Vineyards and Ornamentals
(Excluding Bulbs)
20.98
0.04
540
<0.11
4.1
Ornamental Bulbs
7.87
0.02
203
<0.04
1.5
Christmas Tree Plantations
20.98
0.04
540
<0.11
4.1
Warm Season Turf
10.49
<0.01
270
<0.05
2.1
Rights-of-ways
32.1
0.01
826
<0.17
6.3
Residential areas
10.49
0.02
270
<0.05
2.1
' Based on the daily food ingestion rate for a small sized amphibian of 1.4 g for which the exposure
concentrations and RQs represent conservative estimates.
2
Dietary-based acute RQs did not exceed the avian acute endangered species LOC of 0.1 as the avian LC50 of
>5000 mg/kg-diet is greater than the predicted dietary-based EECs.
3LOC exceedances (chronic RQ > 1) are bolded.
Dose-based acute risk quotients for all the modeled use scenarios (based on broadcast
spray applications) dropped below acute endangered species LOCs (0.1) using T-HERPS.
Dose-based acute risk quotients for terrestrial phase amphibians from ingestion of
residues on or in prey items ranged between <0.01 and 0.08. However, dietary-based
chronic RQs exceeded listed species LOCs for all uses modeled using T-HERPS (dietary-
based RQs calculated by T-HERPS and T-REX are the same).
107
-------
Dietary-based chronic RQs exceed the Agency's LOCs for all of the non-granular uses of
oryzalin. With chronic dietary-based RQ values ranging from approximately 1.5 to 6.3,
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 132 mg/kg-diet, which is based on
reduction in female body weight. No reproductive effects were noted at this NOAEC
level. Based on the bobwhite quail NOAEC value of 132 mg/kg-diet, chronic LOCs are
exceeded for terrestrial-phase CRLFs that consume small insects for all modeled
scenarios and application rates (1.5 to 6.1 lb ai/A per application or 2.25 to 12.2 lb
ai/A/year). An application rate of 0.9 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 85% less than the maximum spray (liquid formulation) application rate for
oryzalin of 6.1 lb ai/A.
T-REX is not a bioaccumulation model. Because CRLF ingests small mammals another
refinement included in the T-HERPS model was a conservative bioaccumulation model
for residues in small herbivorous and insectivorous mammals. The bioaccumulation
model assumes that the animal ingests 100% of its daily intake instantaneously and that
there is no metabolism or elimination of the pesticide residues before being consumed.
Additionally, the diet of the herbivorous small mammal is modeled as short grass, which
has the highest chemical residues after a pesticide exposure of any of the plant residues
modeled. This scenario is highly improbable and also not relevant for oryzalin because
of its short half-life period and low bioaccumulation potential. Therefore, oryzalin is not
likely to be bioavailable for a secondary poisoning type exposure once consumed by the
small mammal. Therefore this refinement was not conducted for oryzalin.
No ecological incidents involving birds were reported for oryzalin.
In summary, the Agency concludes a "likely to adversely affect" or "LAA" effects
determination based on chronic direct effects to the terrestrial-phase CRLF via current
liquid spray (non-granular) uses of oryzalin.
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. Risk quotients for non-
vascular plants were calculated based on the EC50 value of 42 |ig/L for freshwater green
algae {Selenastrum capricornutum). Risk quotients exceeded acute aquatic plant risk
LOCs for all the modeled scenarios except citrus fruits, pome and stone fruits, Christmas
tree plantations, ornamental bulbs, and warm season turf grass for liquid formulations and
Christmas tree plantations, ornamental bulbs, warm season turf grass, and residential
areas for granular formulations (Table 5.2).
108
-------
Toxicity values for freshwater non-vascular plants (other than marine diatom of 41 ppb)
are 42, 72, and 24,000 ppb for green algae, freshwater diatom, and bluegreen algae,
respectively. Thus, all the freshwater non-vascular plant endpoints are above the peak
measured concentrations of oryzalin in California watersheds (<1.5 (J,g/L). The range of
toxic endpoints for the above aquatic non-vascular plants suggests that the endpoint
values for green algae and freshwater diatoms fall within the range of peak modeled
oryzalin concentrations for the use patterns mentioned above (3.5 to 149.5 (J,g/L) and
therefore are at risk from oryzalin applications. Bluegreen algae, on the other hand, do
not appear to be adversely affected by oryzalin uses.
Based on the above, oryzalin may affect sensitive aquatic non-vascular plants such as
green algae and diatoms (freshwater and marine) but is not likely to affect others such as
bluegreen algae. Even though the CRLF consumes a wide range of other types of non-
vascular plants, it is possible that several species other than those tested would be
adversely impacted due to herbicidal nature of oryzalin. Though the measured peak
concentration of oryzalin in California watersheds (1.5 ppb) is lower than the above
toxicity endpoints, it is expected that oryzalin concentrations in the environment may
exceed the 1.5 ppb levels at times, such as the periods that soon follow the application.
Thus, it is likely that oryzalin could indirectly affect the CRLF via reduction in aquatic
non-vascular plants as food items.
The effects determination for indirect effects of oryzalin to CRLF tadpoles via reductions
in non-vascular plants is "likely to adversely affect" or "LAA" for oryzalin uses in
avocado, berries, olives, tree nuts, vineyards, non-bearing fruits, nuts and vineyards,
rights-of-ways, and ornamentals excluding bulbs for liquid formulation and non-bearing
fruits, nuts and vineyards, rights-of-ways, and ornamentals excluding bulbs for granular
formulations. Oryzalin uses in citrus fruits, pome and stone fruits, Christmas tree
plantations, ornamental bulbs, warm season turf grass, and residential areas 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 2.5, the highest oryzalin
usage in California is reported for tree nuts, grapes, rights-of-ways, stone fruits,
landscape maintenance, pome fruits, citrus fruits, and outdoor container ornamentals.
Based on this statistic, the overall effects determination for indirect effects of oryzalin to
CRLF tadpoles via reductions in non-vascular plants is "likely to adversely affect" or
"LAA".
5.2.2.2 Aquatic Invertebrates
Acute RQs exceeded the LOCs for listed species (RQ > 0.05) due to broadcast spray
applications of oryzalin on rights-of-ways and granular applications in nonbearing fruits,
ornamentals (excluding bulbs), and rights-of-ways (Table 5.3). Regardless the type of
formulation, acute RQs exceeded the listed species LOC for rights-of-ways due to highest
oryzalin application rates for this use. Although acute RQs exceeded the acute listed
species LOC of 0.05 for the above uses, they are less than the non-listed acute LOC of
109
-------
0.5. Chronic RQs for aquatic invertebrates, on the other hand, are less than the chronic
LOC (RQ > 1.0) for aquatic invertebrates for all modeled oryzalin uses.
Predicted chance of individual effect using probit dose-response curve slope from the
daphnid study (slope = 9.5) and median lethal estimate (LC50 = 1500 ppb) to a freshwater
invertebrate at an RQ level of 0.1 (highest calculated RQ) is 1 in 9.53E+20. 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 1.03E+47.
The potential for oryzalin 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.
Oryzalin may affect sensitive aquatic invertebrates, such as the water flea; however, the
low probability 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, and the measured low concentrations of oryzalin in California watersheds (-1.5
ppb), oryzalin 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 "not likely to
adversely affect" or "NLAA".
5.2.2.3 Fish and Aquatic-phase Frogs
The Agency concluded a "NLAA" determination for direct effects to the aquatic-phase
CRLF, via mortality, growth, or fecundity. Therefore, indirect effects to the CRLF via a
reduction in freshwater fish and other aquatic-phase frog species as prey items are not
expected.
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 the broadcast spray applications of oryzalin are expected. RQ values
representing acute exposures to terrestrial invertebrates (Table 5.8) indicate that all non-
granular uses of oryzalin may potentially result in adverse effects to small invertebrates.
However, the acute RQ values are non-definitive {i.e., "less than" values). The extent to
which the acute RQs, ranging from <0.3 to <12.8, may fall below the terrestrial
invertebrate LOC of 0.05 is uncertain. Therefore, the effects determination for indirect
110
-------
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 at the expected levels of exposure are not likely to occur 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. As previously discussed, definitive acute RQ
values could not be derived because the mammalian LD50 value is >10,000 mg/kg-bw.
Dose-based acute risk quotients ranged from <0.02 to <0.06 and risk do not appear to
exist based on all modeled oryzalin uses (Table 5.9). Granular formulations of oryzalin
are also not expected to cause acute mortality to mammals because predicted EECs (15.6
to 41.8 mg/sq ft) are well below the adjusted LD50 values for mammals (>4,472 mg/kg-
bw) (Table 5.10). On the other hand, chronic RQs (1.3 to 69.5) representing oryzalin
exposures to rats (small mammals) indicate risks resulting from all broadcast spray (non-
granular) uses.
Based on the available toxicity data, chronic exposure of laboratory rats to oryzalin
resulted in consistent reductions in adult body weight and hematology parameters and
increased microscopic findings in the thyroid in females at 42.89 mg/kg/day and
decreased survival, decreased weight gain and hematology parameters, increased thyroid
weight, incidence of skin lesions, and microscopic findings in males at 112.5 mg/kg/day.
The corresponding NOAEC was 13.8 and 36.9 mg/kg-diet for males and females,
respectively, suggesting that females were most sensitive to oryzalin than males.
Overall, indirect effects are possible for large CRLF adults through decreases in
mammalian prey via chronic exposure to non-granular uses of oryzalin. 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 modeled uses. The
maximum application rate of non-granular uses of oryzalin would have to be reduced to
1.1 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 oryzalin to terrestrial-phase CRLFs are used to represent exposures of
oryzalin to frogs in terrestrial habitats. Based on estimated exposures resulting from non-
granular uses of oryzalin, both acute (dose-based) and chronic risks to frogs are possible.
Therefore, the effects determination for indirect effects to large CRLF adults that feed on
other species of frogs as prey, via acute and chronic exposure to oryzalin, is "likely to
adversely affect" or "LAA."
Ill
-------
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 near shore areas and lower stream banks. In addition, vascular aquatic plants
are important as attachment sites for egg masses of CRLFs.
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 oryzalin to avocado, berries, olives, tree nuts, non-bearing fruits, nuts, and vineyards,
ornamentals excluding bulbs, and rights-of-ways. Similar to liquid formulations, non-
vascular plant RQs did not exceed LOCs for Christmas tree plantations, ornamental
bulbs, and warm season turf grass for granular applications. Vascular plant RQs are less
than the LOC of 1 for citrus fruits (liquid formulation), warm season turf grass (both
liquid and granular formulations) and residential uses (granular formulation) only (Table
5.4). Therefore, indirect effects to the CRLF via direct effects to vascular plants as
habitat are expected.
As previously discussed in Section 5.2.2.1, the range of toxic endpoints for three out of
the four non-vascular plants and the vascular plant included in this assessment fell with
the range of peak modeled oryzalin concentrations (3.5 to 149.5 (J,g/L). Even though the
CRLF depends on a wide range of non-vascular and vascular plants, it is expected that
oryzalin, being a herbicide, would elicit adverse impacts on other vascular and no-
vascular plants resulting in indirect effects to CRLFs via direct habitat-related impacts to
non-vascular and vascular plants. Therefore, the effects determination for indirect effects
of oryzalin to CRLFs via impacts to habitat and/or primary production through direct
effects to non-vascular plants is "likely to adversely affect" or "LAA".
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.
112
-------
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.
Oryzalin is a systemic herbicide that is absorbed mainly through the roots of developing
plants. It has little or no foliar activity and is not translocated within the plant. Thus the
primary effect of oryzalin is on root development of emerging plants. Roots of affected
plants are relatively few in number, short, thick, and club shaped. The inhibited root
growth causes tops of plants to be stunted and demonstrate a dark green color. Based on
the available toxicity data for terrestrial plants, it appears that emerged monocot and dicot
seedlings are more sensitive to oryzalin in the seedling emergence test than in the
vegetative vigor test. This is demonstrated by the difference in both monocot and dicot
plant response to the two guideline studies. The monocot (ryegrass) EC25 values for the
seedling emergence and vegetative vigor tests are 0.029 lb ai/A and 0.174 lb ai/A,
respectively, representing almost a six-fold difference in sensitivity. The dicot (tomato)
EC25 values for the seedling emergence and vegetative vigor tests are 0.0506 lb ai/A and
0.0828 lb ai/A, respectively.
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 water bodies with dense riparian vegetation including
willows (Salix sp.). Upland habitat includes grassland and woodlands, as well as
scrub/shrub habitat. No guideline data are available on the toxicity of oryzalin to woody
plants. However, as oryzalin is labeled for use around numerous woody species
including citrus, tree nuts, and grapes, as well as uses associated with tree plantations and
nurseries, toxicity to woody plants (except for species such as Douglas fir as specified in
the label) is not expected. Furthermore, the label for oryzalin recommends its use on
numerous shrubs and trees including Salix species (willows) to which CRLF exhibits
preference.
As shown in Tables 5.11 and 5.12, RQs exceed LOCs for monocots and dicots
inhabiting dry and semi-aquatic areas exposed to liquid formulations of oryzalin via
runoff and drift. Spray drift RQs did not exceed LOCs for granular formulations. In
general, it appears that monocots are more sensitive than dicots to oryzalin in dry and
semi-aquatic areas.
113
-------
In summary, based on exceedance of the terrestrial plant LOCs for all oryzalin 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:
• Oryzalin may enter riparian areas via runoff and/or spray drift where it may be
taken up by the roots of sensitive emerging seedlings.
• Based on Oryzalin's mode of action and a comparison of seedling emergence
EC25 values to EECs estimated using TerrPlant, emerging or developing
seedlings may be affected. Furthermore, based on the residual nature of
oryzalin, it is expected to impact germinating seedlings and emerging plants
for several months after application. 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.
• Because 7 out of 10 species tested in the seedling emergence studies and five
out of 10 species tested in the vegetative vigor studies were affected, it is
likely that many species of herbaceous plants may be potentially affected by
exposure to oryzalin via runoff and spray drift.
A review of the oryzalin incidents for terrestrial plants revealed 5 incidents. Photo-
toxicity or plant death reported in almost all of these incidents was due to the use of other
herbicides that have the potential to cause injury either in mixture or use before/after the
oryzalin applications. Although the reported number of oryzalin incidents for terrestrial
plants is low, 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 reported by a registrant.
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 oryzalin 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 oryzalin use patterns.
The distance required to dissipate spray drift to below the LOC was determined using
AgDrift based on the EC25 levels for terrestrial plants. Input parameters for AgDrift
included a high boom, screens no finer than 50 mesh (365 |im) for nozzles specified in
the labels, and the spray droplet size distribution of "ASAE medium to coarse (DVo.5=
340.87 |im). Theoretically, dissipation to the no effect level should be modeled in order
114
-------
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
oryzalin. 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).
Since the seedling emergence endpoint (EC25 for ryegrass and tomato = 0.0285 and
0.0506 lb ai/A, respectively) is more sensitive than the vegetative vigor endpoint (EC25
for ryegrass and tomato = 0.174 and 0.0828 lb ai/A, respectively) and as oryzalin is a
preemergence herbicide that inhibits roots of emerging/developing plants with no activity
against existing vegetation, spray drift distances are derived using the seedling emergence
endpoint for both monocots and dicots. For comparison purposes, spray drift dissipation
distances were also calculated using the vegetative vigor endpoint for monocots and
dicots.
Spray drift dissipation distances for typical oryzalin use rates are presented in Table 5.16.
Based on the endpoints derived for seedling emergence, adverse effects to terrestrial
plants might reasonably be expected to occur up to 164 feet for monocots and up to 79
feet for dicots from the use site for ground applications of oryzalin. Vegetative vigor-
based dissipation distances were only 12 and 54% of those calculated based on seedling
emergence endpoints for monocots and dicots, respectively. The dissipation distance is
expected to increase based on a decrease in droplet size as fine drops will result in more
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 5.16.
Table 5.16 Spray Drift Dissipation Distances for Oryzalin
Oryzalin Application
Rate
(lb ai/A)
Dissipation
distance (ft)
Seedling Emergence
Vegetative Vigor
Monocot
Dicot
Monocot
Dicot
6
164
79
20
43
4
98
49
13
26
2
43
20
7
13
1.5
30
16
7
10
In addition to the spray drift dissipation distance, the distance which represents the
maximum continuous downstream dilution from the edge of the initial area of concern
where direct/indirect effects and/or critical habitat modification may occur from oryzalin
applications was also calculated. The downstream dilution analysis is based on the
greatest ratio of aquatic RQ to LOC, which was calculated to be 9.7 for oryzalin. This
value was estimated using the NOAEC value for the most sensitive aquatic plant species,
duckweed in this case, of 15.4 ppb and maximum peak EEC from oryzalin applications to
rights-of-ways of 149 ppb. Downstream dilution analysis for oryzalin suggests that 51
kilometers is the furthest distance that could be added downstream (Appendix D).
115
-------
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 oryzalin-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. Oryzalin uses may result in modification to critical habitat via direct effects to
non-vascular plants for both liquid and granular applications.
Based on the results of the effects determination for terrestrial plants (see Section
5.2.3.2), oryzalin-related effects on shading (i.e., temperature), bank stabilization, and
structural diversity (height classes) of vegetation are not expected because woody plants
(other than plants such as Douglas fir) are generally not sensitive to environmentally-
relevant concentrations of oryzalin. However, modification to critical habitat may occur
via oryzalin-related impacts to sensitive herbaceous vegetation, which provide habitat
and cover for the CRLF and its prey, based on all assessed uses of oryzalin.
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 are expected.
Therefore, oryzalin is likely to adversely affect critical habitat by altering chemical
116
-------
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 oryzalin-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
oryzalin. Modification to critical habitat is not expected to occur in woodland areas
because most woody plants are not sensitive to environmentally relevant concentrations
of oryzalin.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of oryzalin 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
source. As discussed in Section 5.2.1.2, direct acute effects, via mortality, are expected
for the terrestrial-phase CRLF. Furthermore, chronic reproductive effects are also
possible for all non-granular uses of oryzalin. Therefore, oryzalin 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.
117
-------
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 pest resistance, timing of applications, cultural practices,
and market forces.
6.1.2 Aquatic Exposure Modeling of Oryzalin
The standard ecological water body scenario (EXAMS pond) used to calculate potential
aquatic exposure to pesticides is intended to represent conservative estimates, and to
avoid underestimations of the actual exposure. The standard scenario consists of
application to a 10-hectare field bordering a 1-hectare, 2-meter deep (20,000 m3) pond
with no outlet. Exposure estimates generated using the EXAMS pond are intended to
represent a wide variety of vulnerable water bodies that occur at the top of watersheds
including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural
ponds, and intermittent and lower order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the EXAMS pond. Static water bodies
that have larger ratios of pesticide-treated drainage area to water body volume would be
expected to have higher peak EECs than the EXAMS pond. These water bodies will be
either smaller in size or have larger drainage areas. Smaller water bodies have limited
storage capacity and thus may overflow and carry pesticide in the discharge, whereas the
EXAMS pond has no discharge. As watershed size increases beyond 10-hectares, it
becomes increasingly unlikely that the entire watershed is planted with a single crop that
is all treated simultaneously with the pesticide. Headwater streams can also have peak
concentrations higher than the EXAMS pond, but they likely persist for only short
periods of time and are then carried and dissipated downstream.
The Agency acknowledges that there are some unique aquatic habitats that are not
accurately captured by this modeling scenario and modeling results may, therefore,
under- or over-estimate exposure, depending on a number of variables. For example,
aquatic-phase CRLFs may inhabit water bodies of different size and depth and/or are
located adjacent to larger or smaller drainage areas than the EXAMS pond. The Agency
does not currently have sufficient information regarding the hydrology of these aquatic
habitats to develop a specific alternate scenario for the CRLF. 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
118
-------
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
an agricultural field on a day-to-day basis. It considers factors such as rainfall and plant
transpiration of water, as well as how and when the pesticide is applied. It has two major
components: hydrology and chemical transport. Water movement is simulated by the use
of generalized soil parameters, including 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
discussed above, several data values were available from NAWQA for oryzalin
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 oryzalin use areas. The maximum concentration of oryzalin reported by
119
-------
NAWQA (2000-2005) for California surface waters with agricultural watersheds is 1.51
|ig/L. This is roughly 198 times lower than the highest peak EEC estimated for rights-of-
ways (3.5 - 149.5 ppb) using PRZM/EXAMS. Therefore, use of the PRZM/EXAMS
EECs is assumed to represent a conservative measure of exposure.
6.1.3 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 homeowner-applied pesticides; therefore,
residential uses are not likely to be reported. As with all pesticide usage data, there may
be instances of misuse and misreporting. The Agency made use of the most current,
verifiable information; in cases where there were discrepancies, the most conservative
information was used.
6.1.4 Terrestrial Exposure Modeling of Oryzalin
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.
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%
120
-------
(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 the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
considered, and it was assumed that species occupy, exclusively and permanently, the
modeled treatment area. Spray drift model predictions suggest that this assumption leads
to an overestimation of exposure to species that do not occupy the treated field
exclusively and permanently.
6.1.5 Spray Drift Modeling
It is unlikely that the same organism would be exposed to the maximum amount of spray
drift from every application made. In order for an organism to receive the maximum
concentration of oryzalin from multiple applications, each application of oryzalin would
have to occur under identical atmospheric conditions (e.g., same wind speed and same
wind direction) and (if it is an animal) the animal being exposed would have to be located
in the same location (which receives the maximum amount of spray drift) after each
application. Additionally, other factors, including variations in topography, cover, and
meteorological conditions over the transport distance are not accounted for by the
AgDRIFT model (i.e., it model spray drift from aerial and ground applications in a flat
area with little to no ground cover and a steady, constant wind speed and direction).
Therefore, in most cases, the drift estimates from AgDRIFT may overestimate exposure,
especially as the distance increases from the site of application, since the model does not
account for potential obstructions (e.g., large hills, berms, buildings, trees, etc.).
Furthermore, conservative assumptions are made regarding the droplet size distributions
being modeled ('ASAE Medium to Course " for agricultural and non-agriculture uses),
and 'the application method (i.e., ground), release heights and wind speeds. Alterations
in any of these inputs would decrease the area of potential effect.
6.2 Effects Assessment Uncertainties
6.2.1 Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test 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).
121
-------
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 oryzalin are not available for frogs or
any other aquatic-phase amphibian; therefore, freshwater fish are used as surrogate
species for aquatic-phase amphibians. 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
When assessing acute risk, 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 effects determination t is
exercised on a case-by-case basis and only after careful consideration of the nature of the
sublethal effect measured and the extent and quality of available data to support
establishing a plausible relationship between the measure of effect (sublethal endpoint)
and the assessment endpoints. However, the full suite of sublethal effects from valid
open literature studies is considered for the purposes of defining the action area.
No studies were identified in the submitted studies or open literature that documented
sublethal effects (other than the assessment endpoints such as growth, survival, and
reproduction) associated with exposure to oryzalin. To the extent to which sublethal
effects are not considered in this assessment, the potential direct and indirect effects of
oryzalin on CRLF may be underestimated.
6.2.4 Location of Wildlife Species
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
considered, and it was assumed that species occupy, exclusively and permanently, the
122
-------
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.
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 oryzalin to the CRLF and its designated
critical habitat.
Based on the results of the Agency's endangered species risk assessment for oryzalin, a
Likely to Adversely Affect (LAA) and modification to critical habitat determination was
concluded for the CRLF. The spatial extent of the effects determination is based on the
initial area of concern for application of oryzalin on cultivated crops, orchards/vineyards,
turf, rights of way, and developed, open space, low, medium, and high densities, and
expanded to include the total area where there is potential for direct or indirect effects to
occur via off-site transport mechanisms. The extent of potential off-site transport is
determined by deriving the spray drift area and the run-off area based on downstream
dilution. The identified direct and indirect effects are anticipated to occur only for those
currently occupied core areas, CNDDB occurrence sections, and areas of designated
critical habitat for the CRLF that are located 164 feet from legal use sites where oryzalin
is applied to the use sites listed above. Downstream extent analysis (which is based on the
greatest ratio of aquatic RQ to LOC of 9.7 that was estimated using the NOAEC value for
the vascular aquatic plant duckweed (the most sensitive species) of 15.4 ppb and a
maximum peak EEC for applications to rights-of-ways of 149 ppb) shows that 51
kilometers is the furthest distance that could be added downstream. This distance
represents the maximum continuous downstream dilution from the edge of the initial area
of concern where direct/indirect effects and/or critical habitat modification may occur.
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 (Figure 7.1). Additional details on the GIS maps can be obtained from Appendix D.
A summary of the risk conclusions and effects determinations for the CRLF and its
critical habitat, given the uncertainties discussed in Section 6, is presented in Tables 7.1
and 7.2.
123
-------
Figure 7.1
Oryzalin Uses & CRLF Habitat
US DA Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Projection: Albers Equal Area Conic USGS, North American
Datum of 1983 (NAD 19831 Produced 05/13)2006
124
-------
Table 7.1 Effects Determination Summary for Direct and Indirect Effects of Oryzalin on the CRLF
Assessment Endpoint
Effects
Determination1
Basis for Determination
Aquatic-Phase CRLF
(Eggs, Larvae, and Adults)
Direct Effects:
Survival, growth, and reproduction of CRLF
individuals via direct effects on aquatic phases
NLAA
Using freshwater fish as a surrogate, no chronic LOCs
are exceeded; acute LOCS are exceeded for 1 use only
(rights-of-ways) for which the probability of individual
mortality is very low (1 in 1.9E+33 to 3.05E+26).
Indirect Effects:
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
Oryzalin may affect sensitive aquatic invertebrates, such
as the water flea; however, the low probability (1 in
1.03E+47 to 9.53E+20) 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 and food items that the species consumes
during its aquatic phase. Based on the non-selective
nature of feeding behavior in the aquatic-phase CRLF,
the low magnitude of anticipated acute individual effects
to preferred aquatic invertebrate prey species, and low
measured concentrations of oryzalin in California
watersheds, oryzalin is not likely to indirectly affect the
CRLF via reduction in freshwater invertebrate food
items.
Non-vascular aauatic
olants: LAA
Oryzalin (in liquid form) uses in avocado, berries, olives,
tree nuts, vineyards, non-bearing fruits, nuts and
vineyards, rights-of-ways, and ornamentals (excluding
bulbs) and granular uses in non-bearing fruits, nuts and
vineyards, rights-of-ways, and ornamentals (excluding
bulbs) exceeded LOCs. Indirect effects to tadpoles that
feed on algae, therefore, are possible.
Fish and froes:
NLAA
Using freshwater fish as a surrogate, no chronic LOCs
are exceeded; acute LOCS exceeded for only 1 scenario
(rights-of-ways) for which the probability of individual
mortality is very low.
Indirect Effects:
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
broadcast spray applications of oryzalin in avocado,
berries, olives, tree nuts, vineyards, non-bearing fruits,
nuts and vineyards, rights-of-ways, and ornamentals
(excluding bulbs) and granular applications in non-
bearing fruits, nuts and vineyards, rights-of-ways, and
ornamentals (excluding bulbs).
Vascular aauatic
olants: LAA
RQs for vascular plants are higher than LOCs for
almost all oryzalin use patterns except citrus fruits,
warm season turf grass, and residential areas.
Indirect Effects:
Survival, growth, and reproduction of CRLF
individuals via effects to riparian vegetation,
required to maintain acceptable water quality
and habitat in ponds and streams comprising
the species' current range.
Direct effects to
forested riparian
veeetation: NLAA
Direct effects to
erassv/herbaceous
Riparian vegetation may be affected because terrestrial
plant RQs are above LOCs. However, woody plants
(other than species such as Douglas fir) are generally not
sensitive to oryzalin; therefore, effects of riparian areas
in the action area are not expected.
Aquatic-phase CRLFs may be indirectly affected by
adverse effects to sensitive herbaceous vegetation (based
125
-------
riparian vesetation:
LAA (ground
applications): <164 ft
(monocots); <79 ft
(dicots)
NLAA (ground
applications): >164 ft
(monocots); >79 ft
(dicots)
on all oryzalin liquid spray and granular uses), which
provides habitat and cover for the CRLF and attachment
sites for its egg masses.
Terrestrial-Phase CRLF
(Juveniles and adults)
Direct Effects:
Survival, growth, and reproduction of CRLF
individuals via direct effects on terrestrial
phase adults and juveniles
Acute: NLAA
The acute avian effects data was used as a surrogate for
the terrestrial-phase CRLF. Dose-based acute avian
RQs, refined based on amphibian dietary intake using the
T-HERPS model, did not exceed LOCs for any of the
modeled uses.
Chronic: LAA
Chronic reproductive effects are possible based on non-
granular uses of oryzalin.
Indirect Effects:
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
Oryzalin is non-toxic to terrestrial invertebrates at
environmentally relevant concentrations. At the
expected levels of oryzalin exposure, the effects on
vertebrates are small and thus a reduction in terrestrial
invertebrates as food items is unlikely.
Mammals: LAA
Chronic RQs for non-granular formulations exceed
LOCs.
Fross: LAA
Chronic risks for terrestrial-phase frogs exposed to
broadcast spray applications of oryzalin may occur.
Direct effects to
forested riparian
vesetation: NLAA
Riparian vegetation may be affected because terrestrial
plant RQs are above LOCs. However, woody plants
(other than species such as Douglas fir) are generally not
sensitive to oryzalin; therefore, effects of riparian areas
in the action area are not expected.
Indirect Effects:
Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian vegetation)
Direct effects to
srassv/herbaceous
rioarian vesetation:
LAA (ground
applications): <164 ft
(monocots); <79 ft
(dicots)
NLAA (ground
applications): >164 ft
(monocots); >79 ft
(dicots)
Aquatic-phase CRLFs may be indirectly affected by
adverse effects to sensitive herbaceous vegetation (based
on all oryzalin liquid spray and granular uses), which
provides habitat and cover for the CRLF and attachment
sites for its egg masses.
'NE = no effect; NLAA = may affect, but not likely to adversely affect; LAA = likely to adversely affect
126
-------
Table 7.2 Effects Determination Summary for the Critical Habitat Impact Analysis
Assessment Endpoint
Effects
Determination1
Basis for Determination
Aquatic-Phase CRLFPCEs
(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
Both liquid and granular formulations of oryzalin may
affect sensitive riparian seedlings. As a result, 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.6
Habitat
modification
Both liquid and granular formulations of oryzalin may
affect sensitive seedlings. As a result, 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.
Effects on
growth and
viability of
CRLF
Direct effects to the aquatic-phase CRLF, via mortality
are expected.
Habitat
modification
based on
alteration of
food source
Critical habitat of the CRLF may be modified via
oryzalin-related impacts (both formulations) to non-
vascular aquatic plants as food items for tadpoles.
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 oryzalin-related impacts to non-vascular
aquatic plants as food items for tadpoles.
Terrestrial-Phase CRLF PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat; ability of
habitat to support food source of CRLFs: Upland areas within
200 ft of the edge of the riparian vegetation or dripline
surrounding aquatic and riparian habitat that are comprised of
grasslands, woodlands, and/or wetland/riparian plant species
that provides the CRLF shelter, forage, and predator
avoidance
Habitat
modification
Modification to critical habitat may occur via impacts
of oryzalin on sensitive seedlings which provide habitat
and cover for the terrestrial-phase CRLF and its prey.
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
Habitat
Direct acute effects, via mortality, are not expected for
6 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.
127
-------
growth and viability of juvenile and adult CRLFs and their
food source.
modification
the terrestrial-phase CRLF; however, chronic
reproductive effects are possible for all non-granular
uses of oryzalin. Therefore, oryzalin may adversely
affect critical habitat by altering chemical
characteristics necessary for normal growth and
viability of terrestrial-phase CRLFs and their
mammalian and amphibian food sources.
1 NE = No effect; HM = Habitat modification
Based on the above, the Agency makes a "Likely to Adversely Affect" determination for
the CRLF from the use of oryzalin. Oryzalin 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.
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this 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
128
-------
effects are predicted. Furthermore, such population information would
allow for a more comprehensive evaluation of the significance of potential
resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic-
and terrestrial-phase frogs. While existing information provides a
preliminary picture of the types of food sources utilized by the frog, it
does not establish minimal requirements to sustain healthy individuals at
varying life stages. Such information could be used to establish
biologically relevant thresholds of effects on the prey base, and ultimately
establish geographical limits to those effects. This information could be
used together with the density data discussed above to characterize the
likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the
pesticide. Currently, methodologies are limited to predicting exposures
and likely levels of direct mortality, growth or reproductive impairment
immediately following exposure to the pesticide. The degree to which
repeated exposure events and the inherent demographic characteristics of
the prey population play into the extent to which prey resources may
recover is not predictable. An enhanced understanding of long-term prey
responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and
together with the information described above, a more complete prediction
of effects to individual frogs and potential modification to critical habitat.
129
-------
8. References
Altig, R. and R.W. McDiarmid. 1999. Body Plan: Development and Morphology. In
R.W. McDiarmid and R. Altig (Eds.), Tadpoles: The Biology of Anuran
Larvae.University of Chicago Press, Chicago, pp. 24-51.
Alvarez, J. 2000. Letter to the U.S. Fish and Wildlife Service providing comments on
the Draft California Red-legged Frog Recovery Plan.
Atkins. E.L., E.A. Greywood, and R.L. MacDonald. 1975. Toxicity of pesticides and
other agricultural chemicals to honey bees. Laboratory studies. Univ. of Calif.,
Div. Agric. Sci. Leaflet 2287. 38 pp. (MRID# 000369-35).
Burns, L.A. 1997. Exposure Analysis Modeling System (EXAMSII) Users Guide for
Version 2.97.5, Environmental Research Laboratory, Office of Research and
Development, U.S. Environmental Protection Agency, Athens, GA.
Carsel, R.F. , J.C. Imhoff, P.R. Hummel, J.M. Cheplick and J.S. Donigian, Jr. 1997.
PRZM-3, A Model for Predicting Pesticide and Nitrogen Fate in Crop Root and
Unsaturated Soil Zones: Users Manual for Release 3.0; Environmental Research
Laboratory, Office of Research and Development, U.S. Environmental Protection
Agency, Athens, GA.
Crawshaw, G.J. 2000. Diseases and Pathology of Amphibians and Reptiles in:
Ecotoxicology of Amphibians and Reptiles; ed: Sparling, D.W., G. Linder, and
C.A. Bishop. SETAC Publication Series, Columbia, MO.
Fellers, G. M., et al. 2001. Overwintering tadpoles in the California red-legged frog
{Rana aurora draytonii). Herpetological Review, 32(3): 156-157.
Fellers, G.M, L.L. McConnell, D. Pratt, S. Datta. 2004. Pesticides in Mountain Yellow-
Legged Frogs (Rana Mucosa) from the Sierra Nevada Mountains of California,
USA. Environmental Toxicology & Chemistry 23 (9):2170-2177.
Fellers, Gary M. 2005a. Rana draytonii Baird and Girard 1852. California Red-legged
Frog. Pages 552-554. hr. M. Lannoo (ed.) Amphibian Declines: The Conservation
Status of United States Species, Vol. 2: Species Accounts. University of
California Press, Berkeley, California, xxi+1094 pp.
(http://www.werc.usgs.gov/pt-reves/pdfs/Rana%20dravtonii.PDF)
Fellers, Gary M. 2005b. California red-legged frog, Rana draytonii Baird and Girard.
Pages 198-201. hr. L.L.C. Jones, et al (eds.) Amphibians of the Pacific Northwest.
xxi+227.
Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation
of the EPA food-chain (Kenaga) nomogram, and instrument for estimating
130
-------
pesticide residues on plants. Environmental Toxicology and Chemistry 13
(9): 1383-1391.
Hayes, M.P. and M.R. Jennings. 1988. Habitat correlates of distribution of the
California red-legged frog (Rana aurora draytonii) and the foothill yellow-legged
frog (Rana boylii): Implications for management. Pp. 144-158. In Proceedings
of the symposium on the management of amphibians, reptiles, and small
mammals in North America. R. Sarzo, K.E. Severson, and D.R. Patton (technical
coordinators). USDA Forest Service General Technical Report RM-166.
Hayes, M.P. and M.M. Miyamoto. 1984. Biochemical, behavioral and body size
differences between Rana aurora aurora and R. a. draytonii. Copeia 1984(4):
1018-22.
Hayes and Tennant. 1985. Diet and feeding behavior of the California red-legged frog.
The Southwestern Naturalist 30(4): 601-605.
Hoerger, F., and E.E. Kenaga. 1972. Pesticide residues on plants: Correlation of
representative data as a basis for estimation of their magnitude in the
environment. In F. Coulston and F. Korte, eds., Environmental Quality and
Safety: Chemistry, Toxicology, and Technology, Georg ThiemePubl, Stuttgart,
West Germany, pp. 9-28.
Jennings, M.R. and M.P. Hayes. 1985. Pre-1900 overharvest of California red-legged
frogs (Rana aurora draytonii): The inducement for bullfrog (Rana catesbeiana)
introduction. Herpetological Review 31(1): 94-103.
Jennings, M.R. and M.P. Hayes. 1994. Amphibian and reptile species of special concern
in California. Report prepared for the California Department of Fish and Game,
Inland Fisheries Division, Rancho Cordova, California. 255 pp.
Jennings, M.R., S. Townsend, and R.R. Duke. 1997. Santa Clara Valley Water District
California red-legged frog distribution and status - 1997. Final Report prepared
by H.T. Harvey & Associates, Alviso, California. 22 pp.
Karvonen, T., Koivusalo, H., Jauhiainen, M., Palko, J. and Weppling, K. 1999. A
hydrological model for predicting runoff from different land use areas, Journal of
Hydrology, 217(3-4): 253-265.
Kuhn, J.O. 1991. Acute Oral Toxicity Study in Rats. CIBA-GEIGY Corporation,
Agricultural Division, Greensboro, NC. Study Number 7803-91.
Kupferberg, S. 1997. Facilitation of periphyton production by tadpole grazing:
Functional differences between species. Freshwater Biology 37:427-439.
Kupferberg, S.J., J.C. Marks and M.E. Power. 1994. Effects of variation in natural
131
-------
algal and detrital diets on larval anuran (Hyla regilla) life-history traits. Copeia
1994:446-457.
LeNoir, J.S., L.L. McConnell, G.M. Fellers, T.M. Cahill, J.N. Seiber. 1999.
Summertime Transport of Current-use pesticides from California's Central Valley
to the Sierra Nevada Mountain Range,USA. Environmental Toxicology &
Chemistry 18(12): 2715-2722.
Majewski, M.S. and P.D. Capel. 1995. Pesticides in the atmosphere: distribution, trends,
and governing factors. Ann Arbor Press, Inc. Chelsea, MI.
McConnell, L.L., J.S. LeNoir, S. Datta, J.N. Seiber. 1998. Wet deposition of current-use
pesticides in the Sierra Nevada mountain range, California, USA. Environmental
Toxicology & Chemistry 17(10): 1908-1916.
McDonald M.A.I; Healey J.R.; Stevens P. A. 2002. The effects of secondary forest
clearance and subsequent land-use on erosion losses and soil properties in the
Blue Mountains of Jamaica. Agriculture, Ecosystems & Environment, Volume
92, Number 1: 1-19.
Okisaka S.; Murakami A.; Mizukawa A.; Ito J.; Vakulenko S.A.; Molotkov I.A.; Corbett
C.W.; Wahl M.; Porter D.E.; Edwards D.; Moise C. 1997. Nonpoint source runoff
modeling: A comparison of a forested watershed and an urban watershed on the
South Carolina coast. Journal of Experimental Marine Biology and Ecology,
Volume 213, Number 1: 133-149.
Phuong V.T. and van Dam J. Linkages between forests and water: A review of research
evidence in Vietnam. In. Forests, Water and Livelihoods European Tropical
Forest Research Network. ETFRN NEWS (3pp).
Rathburn, G.B. 1998. Rana aurora draytonii egg predation. Herpetological Review,
29(3): 165.
Reis, D.K. Habitat characteristics of California red-legged frogs (Rana aurora draytonii):
Ecological differences between eggs, tadpoles, and adults in a coastal brackish
and freshwater system. M.S. Thesis. San Jose State University. 58 pp.
Seale, D.B. andN. Beckvar. 1980. The comparative ability of anuran larvae (genera:
Hyla, Bufo and Rana) to ingest suspended blue-green algae. Copeia 1980:495-
503.
Sparling, D.W., G.M. Fellers, L.L. McConnell. 2001. Pesticides and amphibian
population declines in California, USA. Environmental Toxicology & Chemistry
20(7): 1591-1595.
Teske, Milton E., and Thomas B. Curbishley. 2003. AgDisp ver 8.07 Users Manual.
USD A Forest Service, Morgantown, WV.
132
-------
U.S. Environmental Protection Agency (U.S. EPA). 1998. Guidance for Ecological Risk
Assessment. Risk Assessment Forum. EPA/630/R-95/002F, April 1998.
U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of
Pesticide Programs. Office of Prevention, Pesticides, and Toxic Substances.
Office of Pesticide Programs. Washington, D.C. January 23, 2004.
U.S. Fish and Wildlife Service (USFWS). 1996. Endangered and threatened wildlife and
plants: determination of threatened status for the California red-legged frog.
Federal Register 61(101):25813-25833.
USFWS. 2002. Recovery Plan for the California Red-legged Frog (Rana aurora
draytonii). Region 1, USFWS, Portland, Oregon.
(http://ecos.fws.gov/doc/recovery plans/2002/020528.pdf)
USFWS. 2006. Endangered and threatened wildlife and plants: determination of critical
habitat for the California red-legged frog. 71 FR 19244-19346.
USFWS. Website accessed: 30 December 2006.
http://www.fws.gov/endangered/features/rl frog/rlfrog.html#where
U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service
(NMFS). 1998. Endangered Species Consultation Handbook: Procedures for
Conducting Consultation and Conference Activities Under Section 7 of the
Endangered Species Act. Final Draft. March 1998.
USFWS/NMFS. 2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act
Section 7 Consultation Regulations; Final Rule. FR 47732-47762.
Willis, G.H. and L.L. McDowell. 1987. Pesticide Persistence on Foliage in Reviews of
Environmental Contamination and Toxicology. 100:23-73.
Wassersug, R. 1984. Why tadpoles love fast food. Natural History 4/84.
133
------- |