Risks of Prometryn 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
6.17.2009
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Primary Authors:
Jim Hetrick Ph.D., Senior Scientist
Silvia Termes Ph.D, Chemist
Tanja Crk, Biologist
Stephanie Syslo, Environmental Scientist/RAPL
Secondary Review:
Branch Chief, Environmental Risk Assessment Branch 3: Dana Spatz
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Table of Contents
1.0 Executive Summary 4
2.0 Problem Formulation 10
2.1 Purpose 10
2.2 Scope 12
2.3 Previous Assessments 13
2.4 Stressor Source and Distribution 14
2.4.1 Environmental Fate and Physical Chemical Properties 14
2.4.2 Environmental Transport Assessment 17
2.4.3 Mechanism of Action 18
2.4.4 Use Characterization 18
2.5 Assessed Species 25
2.5.1 Distribution 25
2.5.2 Reproduction 28
2.5.3 Diet 28
2.5.4 Habitat 29
2.6 Designated Critical Habitat 30
2.7 Action Area 32
2.8 Assessment Endpoints and Measures of Ecological Effect 33
2.8.1 Assessment Endpoints for the CRLF 33
2.8.2 Assessment Endpoints for Designated Critical Habitat 35
2.9 Conceptual Model 37
2.9.1 Risk Hypotheses 37
2.9.2 Diagram 37
2.10 Analysis Plan 39
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model 40
2.10.1.1 Measures of Exposure 40
2.10.1.2 Measures of Effect 42
2.10.1.3 Integration of Exposure and Effects 43
2.10.1.4 Data Gaps 44
3.0 Exposure Assessment 45
3.1 Label Application Rates and Intervals 45
3.2 Aquatic Exposure Assessment 45
3.2.1 Modeling Approach 45
3.2.2 Model Inputs 47
3.2.3 Results 48
3.2.4 Existing Monitoring Data 49
3.2.4.1 USGS NAWQA Surface Water Data 49
3.2.4.2 USGS NAWQA Groundwater Data 50
3.2.4.3 California Department of Pesticide Regulation (CPR) Data 50
3.2.4.4 Atmospheric Monitoring Data 50
3.2.5 Spray Drift Buffer 51
3.3 Terrestrial Animal Exposure Assessment 53
3.4 Terrestrial Plant Exposure Assessment 54
4.0 Effects Assessment 56
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4.1 Evaluation of Aquatic Ecotoxicity Studies 58
4.1.1 Toxicity to Freshwater Fish 59
4.1.2 Toxicity to Freshwater Invertebrates 61
4.1.3 Toxicity to Aquatic Plants 62
4.2 Toxicity of Prometryn to Terrestrial Organisms 63
4.2.1 Toxicity to Birds 66
4.2.2 Toxicity to Mammals 67
4.2.3 Toxicity to Terrestrial Invertebrates 68
4.2.4 Toxicity to Terrestrial Plants 69
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern 70
4.4 Incident Database Review 71
4.4.1 Terrestrial Animal Incidents 71
4.4.2 Plant Incidents 71
4.4.3 Aquatic Animal Incidents 72
5.0 Risk Characterization 73
5.1 Risk Estimation 73
5.1.1 Exposures in the Aquatic Habitat 73
5.1.2 Exposures in the Terrestrial Habitat 78
5.1.3 Primary Constituent Elements of Designated Critical Habitat 82
5.1.4 Spatial Extent of Potential Effects 83
5.2 Risk Description 87
5.2.1 Direct Effects 92
5.2.2 Indirect Effects (via Reductions in Prey Base) 95
5.2.3 Indirect Effects (via Habitat Effects) 98
5.2.4 Modification to Designated Critical Habitat 101
6.0 Uncertainties 104
6.1 Exposure Assessment Uncertainties 104
6.1.1 Maximum Use Scenario 104
6.1.2 Aquatic Exposure Modeling of Prometryn 104
6.1.3 Potential Groundwater Contributions to Surface Water Chemical
Concentrations 106
6.1.4 Action Area Uncertainties 106
6.1.5 Usage Uncertainties 107
6.1.6 Terrestrial Exposure Modeling of Prometryn 108
6.1.7 Spray Drift Modeling 109
6.2 Effects Assessment Uncertainties 110
6.2.1 Age Class and Sensitivity of Effects Thresholds 110
6.2.2 Use of Surrogate Species Effects Data 110
6.2.3 Sublethal Effects 110
6.2.4 Location of Wildlife Species 110
7.0 Risk Conclusions 112
8.0 References 116
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List of Tables
Table 1-1 Effects Determination Summary for Prometryn Use and the CRLF 6
Table 1-2 Effects Determination Summary for Prometryn Use and CRLF Critical Habitat
Impact Analysis 7
Table 1-3 Prometryn Use-specific Direct Effects Determinations1 for the CRLF 8
Table 1-4 Prometryn Use-specific Indirect Effects Determinations1 Based on Effects to
Prey 8
Table 2-1 Physical and Chemical Properties of Prometryn 16
Table 2-2 Environmental Fate Properties of Prometryn 16
Table 2-3 Labels for Products Containing Prometryn for Uses in States Other Than
California 20
Table 2-4 Labels for Products Containing Prometryn Registered for Use in California..20
Table 2-5 Prometryn Uses Assessed for the CRLF 21
Table 2-6 Summary of California Department of Pesticide Registration (CDPR) Pesticide
Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered
Prometryn Uses 25
Table 2-7 Assessment Endpoints and Measures of Ecological Effects 34
Table 2-8 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitata 36
Table 3-1 Prometryn Use Input Parameters 45
Table 3-2 Physical and Chemical Properties and Environmental Fate Data Used as Input
Parameters for PRZM and EXAMS 47
Table 3-3 Scenarios for PRZM and EXAMS and Application Dates 48
Table 3-4 PRMZ/EXAMS Estimated Exposure Concentrations (ng/L) for Prometryn.. .48
Table 3-5 USGS NAWQA Surface Water Data for Prometryn in California 49
Table 3-6 Input Parameters for Tier I AgDrift Modeling 51
Table 3-7 Tier I Ag Drift Terrestrial and Aquatic EECs from Spray Drift Alone 51
Table 3-8 Terrestrial Plant EECs given aerial and ground spray fractions of the maximum
applied concentration (2.4 Ibs a.i./A on cotton) at 400 feet 52
Table 3-9 Input Paremeters for Tier II AgDisp Modeling 52
Table 3-10 Tier II AgDisp Terrestrial and Aquatic EECs from Aerial Spray Drift
Alone 52
Table 3-11 Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
Prometryn with T-REX 53
Table 3-12 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Prometryn 54
Table 3-13 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Terrestrial Invertebrate Prey Items 54
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Table 3-14 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semi-
aquatic Areas Exposed to Prometryn via Runoff and Drift 55
Table 4-1 Freshwater Aquatic Toxicity Profile for Prometryn 58
Table 4-2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates 59
Table 4-3 Terrestrial Toxicity Profile for Prometryn 63
Table 4-4 Categories of Acute Toxicity for Avian and Mammalian Studies 65
Table 4-5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data 70
Table 5-1 Summary of Direct Effect RQs for the Aquatic-phase CRLF 74
Table 5-2 Summary of 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) 75
Table 5-3 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to the
CRLF via Direct Effects on Aquatic Invertebrates as Dietary Food Items (prey
of CRLF juveniles and adults in aquatic habitats) 76
Table 5-4 Summary of RQs Used to Estimate Indirect Effects to the CRLF via Effects to
Vascular Aquatic Plants (habitat of aquatic-phase CRLF)a 77
Table 5-5 Summary of Chronic RQs* Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (non-granular application) 78
Table 5-6 Summary of Acute and Chronic RQs* Used to Estimate Indirect Effects to the
Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary
Food Items (non-granular application) 80
Table 5-7 RQs* for Monocots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Prometryn via Runoff and Drift 81
Table 5-8 RQs* for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Prometryn via Runoff and Drift 81
Table 5-9 Input Parameters for Tier I AgDrift Modeling 85
Table 5-10 Tier I AgDrift Terrestrial and Aquatic EECs from Spray Drift Alone 85
Table 5-11 Terrestrial Plant RQs given aerial and ground spray fractions of the maximum
applied concentration (2.4 Ibs a.i./A on cotton) at 400 feet 85
Table 5-12 Input Paremeters for Tier II AgDisp Modeling 86
Table 5-13 Tier II AgDisp Terrestrial and Aquatic EECs from Aerial Spray Drift
Alone 86
Table 5-14 Risk Estimation Summary for Prometryn - Direct and Indirect Effects to
CRLF 88
Table 5-15 Risk Estimation Summary for Prometryn - PCEs of Designated Critical
Habitat for the CRLF 89
Table 7-1 Effects Determination Summary for Prometryn Use and the CRLF 113
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Table 7-2 Effects Determination Summary for Prometryn Use and CRLF Critical Habitat
Impact Analysis 114
List of Figures
Figure 2-1. Map of Estimated Annual Agricultural Use of Prometryn in 2002 19
Figure 2-2a Average Annual Prometryn Use in Total Pounds per County 23
Figure 2-2b 2006 Prometryn Use in Total Pounds per County 24
Figure 2-3 Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF 27
Figure 2-4 CRLF Reproductive Events by Month 28
Figure 2-5 Conceptual Model for Pesticide Effects on Terrestrial Phase of the CRLF ..38
Figure 2-6 Conceptual Model for Pesticide Effects on Aquatic Phase of the CRLF 39
Figure 3-1 CDPR PUR Data on Prometryn Applications on Parsley 46
Figure 3-2 Precipitation Data from 1961 to 1964 for Surrogate Parsley Scenario (CA
LettuceScenario) 47
List of Appendices
• Appendix A: Ecological Effects Data
• Appendix B: Multi-ai Product Analysis
• Appendix C:RQ Method and LOCs
• Appendix D: Spatial Analysis of Prometryn
• Appendix E: T-REX Example Output
• Appendix F-l: Excel Spreadsheet of Evalutated ECOTOX Open Literature Data
• Appendix F-2: Bibliography of Evaluated ECOTOX Open Literature Data
• Appendix G: Bibliography of Accepted by ECOTOX but NOT OPP Open
Literature Data
• Appendix H: Bibliography of Rejected ECOTOX Open Literature Data
• Appendix I: Prometryn Incident Data
• Appendix J-1: GENEEC and PRZM/EXAMS Inputs and Outputs
• Appendix J-2: GENEEC Model Inputs and EECs
• Appendix K: T-HERPS Example Output
• Appendix L: Summary of Human Health Effects Data for Prometryn
• Appendix M: TerrPlant Model Inputs and Outputs Example
Attachment 1: Life History of the California Red-legged Frog
Attachment 2: Baseline Status and Cumulative Effects for the California Red-legged Frog
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1.0 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 Federal
Insecticide, Fungicide, Rodenticide Act (FIFRA) regulatory actions regarding use of
prometryn on 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 (U.S. FWS) and National Marine Fisheries Service (NMFS) Endangered Species
Consultation Handbook (U.S. FWS/NMFS 1998) and procedures outlined in the
Agency's Overview Document (U.S. EPA 2004).
The CRLF was listed as a threatened species by U.S. FWS 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 (U.S. FWS 1996) in California.
Prometryn is a symmetric triazine (s-triazine) herbicide. Formulation types registered
include liquids and wettable granules; therefore, all formulations are designed for liquid
application. Currently, labeled uses of prometryn include uses on celery, fennel, dill,
parsley, and cotton. These uses are considered as part of the federal action evaluated in
this assessment.
Prometryn is stable to abiotic hydrolysis and direct photolysis in water and soil.
Biotransformation has been identified as a major dissipation process, albeit slow. There
are no data on the persistence, transformation, or partitioning in water-sediment systems.
It is very mobile to mobile in soils (average Koc = 244 L/kg-OC). Based on the value of
the vapor pressure and Henry's Law Constant it is not expected to volatilize from soil or
water. The low w-octanol-water partition coefficient (Log Kow< 4) of prometryn suggests
low bioaccumulation potential. The major biotransformation product is a hydroxy-
triazine that is potentially a biotransformation product in common with hydroxyl
degradates of other s-triazine herbicides. Based on the persistence and mobility of
prometryn, major routes of transport are likely to be runoff to surface water bodies or to
adjacent fields and leaching to ground water. Prometryn could also reach non-target sites
by drift and/or wind erosion. Water monitoring data from California has identified that
the concentrations of prometryn in surface water range from 0.0054 to 0.621 ug/L.
Although prometryn has been detected in rain and wet deposition, the vapor pressure
suggests low potential for volatility.
Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF, its prey,
and its habitats to prometryn are assessed separately for the two habitats. The
PRZM/EXAMS aquatic exposure model was used to estimate high-end exposures of
prometryn in aquatic habitats resulting from runoff and spray drift from different uses.
The 1-in-10-year peak model-estimated environmental concentrations (EECs) for
selected CA scenarios range from 37.6 to 377.3 |ig/L. This residue accumulation is the
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result of high persistence of prometryn in conjunction with the static hydrology (no flow)
of the standard pond. 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 prometryn reported by NAWQA for
California surface waters with agricultural watersheds is 0.621|ig/L. This value is
approximately 607 times less than the maximum model-estimated environmental
concentration.
The T-REX model is used to estimate prometryn exposures to the terrestrial-phase CRLF
and its potential prey resulting from uses involving prometryn applications. The
AgDRIFT model is also used to estimate deposition of prometryn on terrestrial and
aquatic habitats from spray drift. The TerrPlant model is used to estimate prometryn
exposures to terrestrial-phase CRLF habitat, including plants inhabiting semi-aquatic and
dry areas, resulting from uses involving foliar prometryn applications.
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 effects to the terrestrial habitat are
characterized by available data for terrestrial monocots and dicots.
Degradation products of prometryn in soil metabolism studies are 2,4-
bis(isopropylamino)-6-hydroxy-s-triazine (CS-11526) at 27% of the applied radioactivity
after one year post-treatment and 2-amino-4-isopropylamino-6-methylthio-s-triazine (GS-
11354) at less than 10% after one year post-treatment. There are no available ecotoxicity
data and limited environmental fate data for these degradation products. Based on EPA's
human health assessment conducted to support the prometryn RED (Wassell 1998), the
only residue of concern is prometryn. Therefore, the degradation products of prometryn
are not considered in this assessment.
Risk quotients (RQs) are derived as quantitative estimates of potential high-end risk.
Acute and chronic RQs are compared to the Agency's levels of concern (LOCs) to
identify instances where prometryn use within the action area has the potential to
adversely affect the CRLF and its designated critical habitat via direct effects or
indirectly via 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 each particular type of effect are below
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LOCs, the pesticide is determined to have "no effect" on the CRLF. 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 prometryn use within the action area "may
affect" the CRLF or 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. Similarly for
critical habitat, additional information is considered to refine the potential for exposure
and effects to distinguish those actions that do or do not result in effects to 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 prometryn. Additionally, the Agency has
determined that there is a potential for effects to the CRLF designated critical habitat
from the use of the chemical. A summary of the risk conclusions and effects
determinations for the CRLF and its critical habitat is presented in Table 1-1 and Table
1-2 . Use-specific determinations for direct and indirect effects to the CRLF are provided
in
Table 1-3 and Table 1-4. Further information on the results of the effects determination
is included as part of the Risk Description in Section 5.2. Given the LAA determination
for the CRLF and potential effects to designated critical habitat, a description of the
baseline status and cumulative effects for the CRLF is provided in Attachment 2.
Table 1-1 Effects Determination Summary for Prometryn Use and the CRLF
Assessment
Endpoint
Effects
Determination 1
Basis for Determination
Survival, growth,
and/or reproduction
of CRLF
individuals
LAA1
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Acute risk to freshwater fish LOCs are exceeded for all parsley uses (Spring,
Fall: 2 Ibs a.i./A) and most cotton uses (Fall, pre-emergence ground spray
and pre-emergence aerial spray: 2.4 Ibs a.i./A).
No chronic risk LOCs are exceeded based on the most sensitive toxicity data
for freshwater fish across any of the evaluated uses (Table 5-1).
Terrestrial-phase (Juveniles and Adults):
Prometryn is practically non-toxic to birds on an acute oral and sub-acute
dietary exposure basis and as such, the studies did not provide definitive
toxicity endpoints. No mortality was observed in the acute oral study and
only a single mortality was observed in the sub-acute dietary toxicity study
and the mortality was not considered treatment-related.
There are no chronic risk LOG exceedances for birds consuming small
insects at the maximum annual application rate for prometryn (2.4 Ibs a.i./A
to cotton) in T-REX using dietary-based RQs.
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Assessment
Endpoint
Effects
Determination 1
Basis for Determination
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
Risk to aquatic plant LOG exceedances are observed for non-vascular and
vascular aquatic plants for all uses. For a complete list see Tables 5-2, 5-4.
Acute risk LOG exceedances are not observed for freshwater invertebrates.
The same finding applies here for fish and frog prey items as in the direct
effects (aquatic-phase CRLF) component above.
Terrestrial prey items, riparian habitat
Risk to terrestrial invertebrate LOG exceedances are observed for small
insects at the maximum annual application rate for cotton (2.4 Ibs a.i./A).
Small terrestrial mammals are also potentially affected by prometryn as
acute and chronic risk LOG exceedances are observed for small mammals.
The same description applies here for frog prey items as in the direct effects
(terrestrial-phase CRLF) component above.
Risk to terrestrial plant LOCs are exceeded for monocots in dry and semi-
aquatic areas for cotton uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton uses (aerial: 2.4 Ibs a.i./A).
Dicots are more sensitive as LOG exceedances are estimated in dry and semi-
aquatic areas for both application types on cotton (ground and aerial spray at
2.4 Ibs a.i./A).
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely
affect (LAA)
Table 1-2 Effects Determination Summary for Prometryn Use and CRLF Critical
Habitat Impact Analysis
Assessment
Endpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
Habitat Effects
Risk to terrestrial plant LOCs are exceeded for monocots in dry and semi-
aquatic areas for cotton uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton uses (aerial: 2.4 Ibs
a.i./A). Dicots are more sensitive as LOG exceedances are estimated in dry
and semi-aquatic areas for both application types on cotton (ground and
aerial spray at 2.4 Ibs a.i./A).
Risk to aquatic plant LOG exceedances are observed for non-vascular and
vascular plants for all uses.
Acute risk to freshwater fish LOCs are exceeded for all parsley uses
(Spring, Fall: 2 Ibs a.i./A) and most cotton uses (Fall, pre-emergence
ground spray and pre-emergence aerial spray: 2.4 Ibs a.i./A). No chronic
risk LOCs are exceeded based on the most sensitive toxicity data for
freshwater fish and for any evaluated use.
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Assessment
Eiulpoint
Effects
Determination
Basis for Determination
Modification of
terrestrial-phase
PCE
Acute and chronic risk LOG exceedances are not observed for freshwater
invertebrates.
Risk to terrestrial plant LOCs are exceeded for monocots in dry and semi-
aquatic areas for cotton uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton uses (aerial: 2.4 Ibs
a.i./A). Dicots are more sensitive as LOG exceedances are estimated in dry
and semi-aquatic areas for both application types on cotton (ground and
aerial spray at 2.4 Ibs a.i./A).
No definitive acute RQs could be derived because the acute avian effects
data shows no mortality at the highest test concentrations. Chronic risk LOG
exceedances are not observed for birds consuming small insects when
considering a cotton application (2.4 Ibs a.i./A) in T-REX using dietary
based RQs. This direct effects description applies for frog prey items as an
indirect effect on the CRLF.
Risk to terrestrial invertebrate LOG exceedances are observed for small
insects at the maximum annual application rate for cotton (2.4 Ibs a.i./A).
Small terrestrial mammals are also affected by prometryn as acute and
chronic risk LOG exceedances are observed for small mammals.
Table 1-3 Prometryn Use-specific Direct Effects Determinations1 for the CRLF
Use(s)
Cotton
Aquatic Habitat
Acute
LAA
Chronic
NE
Terrestrial Habitat
Acute
NLAA
Chronic
NLAA
1 NE = No effect; NLAA = May affect, but not likely to adversely affect; LAA = Likely to adversely affect
Table 1-4 Prometryn Use-specific Indirect Effects Determinations1 Based on Effects
to Prey
Use(s)
Cotton
Algae
LAA
Aquatic
Invertebrates
Acute
NE
Chronic
NE
Terrestrial
Invertebrates
(Acute)
LAA
Aquatic-phase
frogs and fish
Acute
LAA
Chronic
NE
Terrestrial-
phase frogs
Acute
NLAA
Chronic
NLAA
Small Mammals
Acute
LAA
Chronic
LAA
NE = No effect; NLAA = May affect, not likely to adversely affect; LAA = Likely to adversely affect
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
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not expected to be uniform across the action area. In fact, given the assumptions of drift
and downstream transport (i.e., attenuation with distance), pesticide exposure and
associated risks to the species and its resources are expected to decrease with increasing
distance away from the treated field or site of application. Evaluation of the implication
of this non-uniform distribution of risk to the species would require information and
assessment techniques that are not currently available. Examples of such information and
methodology required for this type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages
within specific recovery units and/or designated critical habitat within the
action area. This information would allow for quantitative extrapolation
of the present risk assessment's predictions of individual effects to the
proportion of the population extant within geographical areas where those
effects are predicted. Furthermore, such population information would
allow for a more comprehensive evaluation of the significance of potential
resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic-
and terrestrial-phase frogs. While existing information provides a
preliminary picture of the types of food sources utilized by the frog, it
does not establish minimal requirements to sustain healthy individuals at
varying life stages. Such information could be used to establish
biologically relevant thresholds of effects on the prey base, and ultimately
establish geographical limits to those effects. This information could be
used together with the density data discussed above to characterize the
likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the
pesticide. Currently, methodologies are limited to predicting exposures
and likely levels of direct mortality, growth or reproductive impairment
immediately following exposure to the pesticide. The degree to which
repeated exposure events and the inherent demographic characteristics of
the prey population play into the extent to which prey resources may
recover is not predictable. An enhanced understanding of long-term prey
responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and
together with the information described above, a more complete prediction
of effects to individual frogs and potential modification to critical habitat.
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2.0 Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By
identifying the important components of the problem, it focuses the assessment on the
most relevant life history stages, habitat components, chemical properties, exposure
routes, and endpoints. The structure of this risk assessment is based on guidance
contained in U.S. Environmental Protection Agency's (EPA's) Guidance for Ecological
Risk Assessment (U.S. EPA 1998), the Services' Endangered Species Consultation
Handbook (U.S. FWS/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 (U.S. FWS/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
prometryn on celery, fennel, dill, parsley, and cotton. In addition, this assessment
evaluates whether use on these sites is expected to result in effects to 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)) 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 effects 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. Use of such
information is consistent with the methodology described in the Overview Document
(U.S. EPA 2004), which specifies that "the assessment process may, on a case-by-case
basis, incorporate additional methods, models, and lines of evidence that EPA finds
technically appropriate for risk management objectives" (Section V, page 31 of U.S. EPA
2004).
In accordance with the Overview Document, provisions of the Endangered Species Act
(ESA), and the Services' Endangered Species Consultation Handbook, the assessment of
effects associated with registrations of prometryn is based on an action area. The action
area is the area directly or indirectly affected by the federal action. It is acknowledged
that the action area for a national-level FIFRA regulatory decision associated with a use
of prometryn 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 prometryn in accordance with current labels:
10
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• "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 LOG exceedances) upon individual CRLFs or upon the PCEs of the species'
designated critical habitat, a "no effect" determination is made for use of prometryn 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 prometryn.
If a determination is made that use of prometryn 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 prometryn use sites) and further evaluation of the potential impact of
prometryn on the PCEs is also used to determine whether effects to designated critical
habitat may occur. Based on the refined information, the Agency uses the best available
information to distinguish those actions that "may affect, but are not likely to adversely
affect" from those actions that "may affect and are likely to adversely affect" the CRLF
or the PCEs of its designated critical habitat. This information is presented as part of the
Risk Characterization in Section 5 of this document.
The Agency believes that the analysis of direct and indirect effects to listed species
provides the basis for an analysis of potential effects on the designated critical habitat.
Because prometryn is expected to directly impact living organisms within the action area
(defined in Section 2.7), critical habitat analysis for prometryn is limited in a practical
sense to those PCEs of critical habitat that are biological or that can be reasonably linked
to biologically mediated processes (i.e., the biological resource requirements for the listed
species associated with the critical habitat or important physical aspects of the habitat that
may be reasonably influenced through biological processes). Activities that may modify
critical habitat are those that alter the PCEs and appreciably diminish the value of the
habitat. Evaluation of actions related to use of prometryn 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.
11
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2.2 Scope
Prometryn is used nationally as a herbicide on a variety of terrestrial food and feed crops
and terrestrial non-food crops. Currently registered uses of prometryn in California are:
cotton, celery, parsley, dill, and fennel; cotton accounted for approximately 73% of the
total pounds applied in California in 2006, with the remainder used on celery (22%),
parsley (4%), fennel (1%) and dill (<1%).
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 prometryn in accordance with the approved product labels for
California is "the action" relevant to this ecological risk assessment.
Although current registrations of prometryn allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of prometryn 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 and 2.6, respectively.
Degradation products of prometryn in soil metabolism studies are 2,4-
bis(isopropylamino)-6-hydroxy-s-triazine (CS-11526) at 27% of the applied radioactivity
after one year post-treatment and 2-amino-4-isopropylamino-6-methylthio-s-triazine (GS-
11354) at less than 10% after one year post-treatment. There are no available ecotoxicity
data and limited environmental fate data for these degradation products. Based on the
human health assessment (Wassell 1998), the only residue of concern is prometryn.
Therefore, the degradation products of prometryn are not considered further in this
assessment.
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 (e.g., additives such as surfactants). In the
case of the product formulations of active ingredients (i.e., a registered end-use product
containing more than one active ingredient), each active ingredient is subject to an
individual risk assessment for regulatory decision regarding the active ingredient on a
particular use site. If effects data are available for a formulated product containing more
than one active ingredient, they may be used qualitatively or quantitatively in accordance
with the Agency's Overview Document and the Services' Evaluation Memorandum (U.S.
EPA 2004; U.S. FWS/NMFS 2004).
Two registered end-use products (Suprend Herbicide and Prometryne +MSMA) contain
multiple active ingredients. Given that the two formulated products for prometryn do not
have LD50 values with associated 95% confidence intervals, it is not possible to undertake
a quantitative or qualitative analysis for potential interactive effects (for a fuller
description and summary table see Appendix B). Analysis of the available open
12
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literature data for multiple active ingredient products relative to the single active
ingredient is provided in Section 4.0.
2.3 Previous Assessments
Below is a summary of previous ecological risk assessments for prometryn.
2.3.1 Section 18 CA Department of Pesticide Regulation (December 4,1998)
EFED's Ecological Effects Branch (EEB) reviewed the proposed renewal emergency exemption
for the use of prometryn on parsley in the following eight southern California counties
(Monterey, Orange, Riverside, San Benito, San Luis Obispo, Santa Barbara, Stanislaus, and
Ventura). EEB concluded that the proposed use would not result in acute risks to non-target
birds, mammals, and fish, based on the available toxicity data. The likelihood of adverse chronic
effects on small mammals and birds was unclear, because some studies were incomplete.
Available toxicity data on terrestrial and aquatic plants indicated that prometryn is highly toxic to
some plant species, hence sensitive non-target crops and non-target plants adjacent to parsley
fields might be adversely affected. There is general concern for adverse effects on non-target
plants. The risk quotients for non-target plants near treated-parsley fields from runoff ranged
from less than 1 up to 294 for aquatic species, up to 24 for terrestrial plants, and up to 29 for
wetland plants. Many endangered and threatened plant species had been identified in the eight
parsley-growing counties covered by this petition. Information on the location of parsley fields
with respect to critical habitat for plants were unavailable, hence it was not possible to assess
potential risks for listed plants. The U.S. Fish and Wildlife Service had indicated that a 20 yard
buffer zone should be maintained around listed plant species.
2.3.2 Reregistration Eligibility Document for Prometryn (1996) - EPA
738-R-95-033
The ecological risk assessment was conducted in support of the reregi strati on eligibility
decision for prometryn. Maximum single application rates for use of prometryn on
celery, cotton, dill and pigeon peas ranged from 0.8 Ibs ai/A to 3.2 Ibs ai/A [4.0 Ibs a.i./A
in Hawaii]. Prometryn applications were evaluated as pre- or post-emergent, at plant,
post-plant herbicide applied via ground or aerial spray.
PRZM/EXAMS modeling predicted peak prometryn concentrations from 179.9 to 276.8
|ig/L for single application of 2.8 Ibs ai/a via aerial and ground spray on cotton.
The acute endangered species LOG was exceeded for freshwater fish. Chronic risk to
freshwater fish was not evaluated because of the lack of valid data; therefore, risk to
listed aquatic vertebrate species was presumed. No LOCs were exceeded for acute or
chronic effects to freshwater invertebrates. The restricted LOG was exceeded for
marine/estuarine invertebrates (mollusks) for single applications of 2.8 Ibs ai/A on cotton
and 3.2 Ibs ai/A on celery. Additionally, the endangered species LOG was exceeded for
13
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marine/estuarine invertebrates and fish. Prometryn was expected to cause adverse effects
to non-target aquatic plants.
Terrestrial EECs for prometryn ranged from 22 mg/kg on fruits to 960 mg/kg [Hawaii
application at 4 Ibs ai/A] on short range grasses. No acute LOCs were exceeded for
birds. However, the chronic LOG was exceeded for birds consuming short range grass or
fruit/vegetable leaves using 4 Ib ai/A application rate of prometryn. The endangered
species LOG was exceeded for small mammals consuming grasses within prometryn
treated areas. Terrestrial plant RQs ranged from 19.9 for monocot (vigor) to 533.3 for
dicot (vigor). Therefore, prometryn was expected to cause adverse effects to non-target
terrestrial plants as well.
2.3.3 Effects Determination for Pacific Salmonids
On November 29, 2002, EPA initiated formal consultation with the National Marine
Fisheries Service relative to potential effects of prometryn on listed Pacific salmon and
steelhead. Of the 26 species of salmon and steelhead to which effects were assessed,
EPA found prometryn would have no effects on 17 and may affect 9. On November 5,
2007, a suit was filed against the National Marine Fisheries Service (NMFS) seeking a
judgement that NMFS' failure to complete section 7 consultation on 37 pesticides for
which EPA initiated consultation, violates section 7(b)(l) of the Endangered Species Act
and section 706(1) of the Administrative Procedure Act. On July 30, 2008 a settlement
was filed in that case which among other things, establishes a schedule for issuing
biological opinions for the 37 actions on which EPA initiated consultation. The
biological opinion that will address the consultation initiated for prometryn, is scheduled
to be issued by NMFS in February, 2012.
2.3.4 Special Local Need Registrations
Special Local Need registrations for California were granted for use of Prometryne 4L
Herbicide (EPA Reg. No. 34704-692) on fennel (CA960025); and Caparol 4L Herbicide
(EPA Reg. No. 100-620) on celery (CA980017). While these SLNs have not expired, the
products are now fully registered for use on these crops as of 3/18/1997 and 6/15/1999,
respectively.
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate and Physical-Chemical Properties
Prometryn is a methylthio-(symmetric) triazine. The chemical names (CAS and IUPAC)
are presented below together with the CAS Registry Number and chemical structure:
U.S. EPA PC Code: 080805
CA DPR Chemical Code: 502
IUPAC: 7V2,7V^-diisopropyl-6-methylthio-l,3,5-triazine-2,4-diamine
CAS: 7V2,7V^-diisopropyl-6-methylthio-l,3,5-triazine-2,4-diamine
14
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CAS Reg. No.: 7287-19-6
Chemical Formula: Ci0Hi9N5S
SMILES: CSclnc(NC(C)C)nc(NC(C)C)nl
Chemical Structures:
H3C
HN^^CHj
CH3
NAME: Prometryn [ANSLBSLISO]
RN: 7287-19-6
H3C CH3
H3C ^ , NH
CH3
Name: Prometryn aerobic soil metabolite (27% after one year incubation)
CAS Name: l,3,5-Triazin-2(lH)-one, 4,6-bis((l-methylethyl)amino)-
IUPAC: 2,4-bis(isopropylamino)-6-hydroxy-s-triazine
CAS Reg No. 7374-53-0
N CH3
NH2
Name: Prometryn aerobic soil metabolite (1.1% after one year incubation)
IUPAC: 2-amino-4isopropylamino-6-methylthio-s-triazine (GS-1154)
15
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The physical and chemical properties of prometryn relevant to its environmental fate and
transport behavior appear in Table 2-1. The environmental fate properties of prometryn,
along with the major and minor degradates detected in the submitted environmental fate
and transport studies are presented in Table 2-2.
Table 2-1. Physical and Chemical Properties of Prometryn
Molecular Weight, g/mole
Solubility in Water, mg/L, 25 °c
Vapor Pressure, 2 5 ° c.
Henry's Law Constant*, atm m mole"
w-octanol/water partition coefficient, Log Kow
241.4
33
1.6x 10'6mmHg
1.3x 10'4Pa
9xlO'9
3.46
*EPI Suite (Ver. 4) estimation
Table 2-2 Environmental Fate Properties of Prometryn
Study
Abiotic
Hydrolysis
Direct Aqueous
Photolysis
Soil Photolysis
Aerobic Soil
Metabolism
Anaerobic Soil
Metabolism
Anaerobic
Aquatic
Metabolism
Aerobic Aquatic
Metabolism
163- Mobility in
Soil
Batch-
equilibrium
Adsorption/
Desorption
Value
Stable at pH 5, 7, and 9
Stable
Stable
t -/2 270 days; (One soil)
Sandy Soil
t ./2 90 days
Stable
No data submitted
No data submitted
Freundlich, Adsorpotion
0.86 (agricultural sand) to 3.18
(silty clay loam); add other soils
Major Degradates
Minor Degradates
None
2,4-bis(isopropylamino)-6-
hydroxy-s-triazine (GS-11526,
27% Of the applied radioactivity
after 360 days
2-amino-4isopropylamino-6-
methylthio-s-triazine (Gs-1154)
1.1% at 30 days
No data
No data
GS 1 1526 mobile to very mobile
(FreudlichKads7.1to0.5)
GS-11354 very mobile
(FreudlichKads 0.63-1.9)
MRID#
40573704
40573705
40573706
00148338
41155509
_
-
40573713
41875901
41875902
41875903
41875904
41875905
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
N/A
N/A
Acceptable
16
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Study
163-2 Volatility
from Soil
(Laboratory)
Terrestrial Field
Dissipation
Aquatic Field
Dissipation
Bioaccumulation
in Fish
Value
Sand soil
Volatility was minimal, 0.99%
prometryn volatilized by 30 days
t -/2 Cotton CA, 105 days
t- /2 Cotton CA 71 days
t -/2 Cotton TX 14-30 days
t -/2 Cotton TX 14 days
No data
Residues did not accumulate in
fish even though the Log Kow Of
3.46 is above the Log 3 trigger
value
Major Degradates
Minor Degradates
No
Prometryn was not detected
below 45 cm
CS-11354 detected at 120 cm
soil depth
Not applicable
MRID#
41875906
Not
applicabl
e
Study
Classification
Acceptable
Acceptable
(for flowable
concentrate)
N/A
According to the submitted physical-chemical and environmental fate data, the
degradation of prometryn is driven by microbial (biotic) activity and not by abiotic
processes; however, biotransformation is slow. The major biotransformation product is
GS-11534 (see Table 2-2b). The low Freundlich adsorption coefficient of prometryn
suggests that the chemical has the potential to run off and/or leach to ground water.
Although no guideline studies are available to evaluate the role of indirect photolysis,
indirect photolysis in natural water has been reported for prometryn (Connell et al. 2004;
Cessna 2008; Kontantinous 2001; Garbini 2007).
Other possible transformation products of prometryn have been reported recently (2008-
2009). These transformation products originate through oxidation of the thioether linkage
in the parent compound, in which the sulfide sulfur S(-II) oxidizes to S(IV) and S(VI) and
generates the sulfoxide and/or the sulfone. Some bacteria are capable of oxidizing the
thioether sulphur to form sulfoxide and/or sulfone in prometryn (Harada et al. 2006;
Yamazaki et al. 2008), but their formation in environmental media has not been
established.
Degradation products of prometryn in soil metabolism studies are 2,4-
bis(isopropylamino)-6-hydroxy-s-triazine (CS-11526) at 27% of the applied radioactivity
after one year post-treatment and 2-amino-4-isopropylamino-6-methylthio-s-triazine (GS-
11354) at less than 10% after one year post-treatment. There are no available ecotoxicity
data and limited environmental fate data for these degradation products. Based on the
human health assessment (Wassell 1998), the only residue of concern is prometryn.
Therefore, the degradation products of prometryn are not considered further in this
assessment.
Prometryn is persistent and mobile in terrestrial and aquatic environments.
17
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2.4.2 Environmental Transport Assessment
Potential transport mechanisms include surface water runoff, leaching to ground water,
spray drift, and secondary drift of volatilized or soil-bound residues leading to deposition
onto nearby or more distant ecosystems.
A number of studies have documented atmospheric transport and re-deposition of
pesticides from the Central Valley to the Sierra Nevada Mountains (Fellers et al. 2004;
Sparling et al. 2001; LeNoir et al. 1999; McConnell et al. 1998). Prevailing winds blow
across the Central Valley eastward to the Sierra Nevada Mountains, transporting airborne
industrial and agricultural pollutants into the Sierra Nevada ecosystems (Fellers et al,
2004; LeNoir et al, 1999; McConnell et al, 1998). Several sections of critical habitat for
the CLRF are located east of the Central Valley. The magnitude of transport via
secondary drift depends on prometryn's ability to mobilize into air and its eventual
removal through wet and dry deposition of gases/particles and photochemical reactions in
the atmosphere. Very recently (2008-2009) the US Geological Survey (USGS) has
reported data on the presence of pesticides in rain and wet deposition in four USA
agricultural watersheds. Among other pesticides, prometryn was detected in rain and wet
deposition in California (Vogel et al., 2008)1. The basin studied in California was San
Joaquin -Tulare- Merced River2, which contains habitat for the California RLF.
2.4.3. Mechanism of Action
Prometryn is a systemic herbicide that acts as a photosynthesis inhibitor. Prometryn binds
to the D-l quinone-binding protein (Q8), thereby blocking photosynthetic electron
transport.
2.4.4 Use Characterization
Prometryn is used as an herbicide on a variety of terrestrial food and feed crops and
terrestrial non-food crops. Food crops include: cotton, celery, parsley, dill, fennel, pigeon
peas and parsnips; non-food uses include: crops grown for seed (carrot, parsley, parsnips,
and coriander); and kenaf. Prometryn can be applied at the following times: preplant;
preemergence; post emergence directed; post-transplanting (for celery and fennel); and at
lay-by and for winter weed control (for cotton). As shown in Figure 2-1, U.S. Geological
Survey (USGS) National Water Quality Assessment Program (NAWQA) data indicate
that in 2002, prometryn was used on agricultural crops predominantly in California, west
Texas, the southeastern states, and the Mississippi Delta region. At that time, the use of
prometryn on cotton represented about 98% of the national use.
1 The cropland in West California (samples collected) is dominated by almonds and vineyards. In addition
to the California studies, other studies where conducted in agricultural watersheds in Maryland, Indiana,
and Nebraska. Atrazine was detected in all samples. Simazine was the most frequently detected triazine in
California.
2 For description of the California's Merced River Basin see Vogel et al. (2008) and pertinent references
therein. The environmental setting of the Basin is described in Gronberg & Kratzer (2007).
18
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PROMETRYN - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds par square mile of agricultural
land in county)
CH no estimated use
D 0.001 to 0.055
D 0.056 to 0.284
D 0.285 to 0.994
D 0.995 to 3.177
• >=3.178
Crops
cotton
celery
parsley
Total
Pounds Applied
1688861
25503
2871
Percent
National Use
98.35
1.49
0.17
Figure 2-1. Map of Estimated Annual Agricultural Use of Prometryn in 2002.
Source: http://water.usgs.gov/nawqa/pnsp/usage/maps/show map.php?vear=02&map=ml987
The food use on pigeon peas and parsnips and the non food uses (carrot, parsley,
parsnips, and coriander grown for seed; and kenaf) are not being assessed because the use
on pigeon peas is restricted to Puerto Rico only; the food use on parsnips is a SLN for
Florida only; and the non-food uses of prometryn are geographically restricted to areas
outside of California (Table 2-3). If use patterns indicate that pigeon peas and/or the
non-food crops are grown in California in the future, the conclusions of this assessment
may need to be revisited.
19
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Table 2-3 Labels for Products Containing Prometryn for Uses in States Other Than
California
Registration #
Product name
Crops
Geographical
restriction
NON-FOOD/NON-FEED USES
OR04000200
WA96001400
AR96000600
LA98000500
MS96001300
Caparol 4L
(100-620)
Prometryne 4L
For seed only:
Carrot, Coriander,
Parsley, Parsnip
For seed only:
Carrot, Coriander,
Parsley, Parsnip
Kenaf
OR only
WAonly
AR, LA, MS only
FOOD/FEED USES
FL97001100
100-620
66222-15
Caparol 4L (100-620)
Caparol 4L
Prometrex 4L
Parsnip
Pigeon peas
Pigeon peas
FL only
Puerto Rico only
Puerto Rico only
Table 2-4 Labels for Products Containing Prometryn Registered for Use in
California
Registration #
100-620
100-1163
9779-297
9779-317
10163-94
34704-692
66222-15
66222-116
CA960025
CA980017
Product name
Caparol 4L Herbicide
Suprend Herbicide
Prometryne 4L Herbicide
Prometryne + MSMA
Gowan Prometryne 4L
Herbicide
Prometryne 4L Herbicide
Prometrex 4L
Cotton-Pro
Prometryne 4L Herbicide
Caparol 4L Herbicide
Crops
Cotton, celery
Cotton
Cotton, celery
Cotton
Cotton, dill,
parsley
Cotton, celery,
parsley, dill, fennel
Cotton, celery,
parsley, dill, fennel
Cotton, celery,
parsley
Fennel
Celery
Analysis of labeled use information is the critical first step in evaluating the federal
action. The current label for prometryn represents the FIFRA regulatory action;
therefore, labeled use and application rates specified on the label form the basis of this
assessment. The assessment of use information is critical to the development of the action
area and selection of appropriate modeling scenarios and inputs.
20
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For uses permitted in California, prometryn is formulated as a flowable concentrate (8.4-
45.41% active ingredient), as a wettable granular (79.3% active ingredient), as a liquid
(44-44.4% active ingredient), or as an emulsifiable concentrate (44.4% active ingredient).
Application rates range from 0.5 to 2.4 Ibs active ingredient/acre (or Ibs a.i./A). Labels
have additional requirements in order to reduce spray drift. These include the buffers and
other mitigation actions listed in Section 3.2.5 as well as a requirement for a spray with
medium to coarse droplet size applied at a maximum boom height of 4 ft above the
ground or canopy for ground spray and of 10 ft for aerial spray.
The uses and corresponding application rates and methods considered in this assessment
are presented in Table 2-5.
Table 2-5 Prometryn Uses Assessed for the CRLF
Use
Celery
Cotton
Dill
Fennel
Parsley
Max. Single
Appl. Rate
(Ib ai/A)
2
2.4
1.6
2
2
Max.
Number of
Applications
per Year
1
Varies3
1
1
1
Incorporation
Depth (cm)
4.0
10b
4.0
4.0
4.0
Application Method (s)
Soil broadcast, soil band treatment, soil
incorporated, band treatment, basal spray
treatment, directed spray; sprinkler
irrigation
Aerial // Fixed wing aircraft; sprinkler
irrigation; Soil broadcast, soil band
treatment, soil incorporated, band
treatment, basal spray treatment, directed
spray
Soil broadcast, soil band treatment, soil
incorporated, band treatment, basal spray
treatment, directed spray;
Soil broadcast, soil band treatment, soil
incorporated, band treatment, basal spray
treatment, directed spray;
Preplant broadcast incorporated or
shielded applicator post-transplant
a Can apply up to 5.5 Ibs a.i. /A total per year over the following main application times: Pre-plant (max application of
2.4 Ib a.i. /A); post-emergence (up to 3 applications totaling 2 Ibs a.i./A); lay-by (maximum 1 .6 Ibs a.i./A); and winter
weed control (maximum 2.4 Ibs a.i./A).
b Ground application depth is 4 inches (~10cm); this value was used in modeling
Application equipment includes: fixed wing aircraft (cotton only); band sprayer or
sprayer; ground boom (high volume [cotton only] and low pressure [cotton only] and low
volume [celery and cotton only]); shielded applicator (cotton only); sprinkler irrigation
(celery and cotton only); and low-pressure hand wand or backpack sprayer.
The Agency's Biological and Economic Analysis Division (BEAD) can provide an
analysis of county-level usage using state-level usage data obtained from USDA-NASS3,
3 United States Depart of Agriculture (USDA), National Agricultural Statistics Service (NASS) Chemical
Use Reports provide summary pesticide usage statistics for select agricultural use sites by chemical, crop
and state. See http://www.usda.gov/nass/pubs/estindxl.htnrfagchem.
21
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Doane (www.doane.com: the full dataset is not provided due to its proprietary nature)
and the California's Department of Pesticide Regulation Pesticide Use Reporting (CDPR
PUR) database4. However, for this assessment, no national usage data were provided, so
the usage data reported for prometryn by county in this California-specific assessment
were generated using CDPR PUR data. Eight years (1999-2006) 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 eight years. The units of area treated are also
provided where available.
Based on this analysis, an average of 188,863 Ibs of prometryn was applied in California
to an average of 131,775 acres per year. From 1999-2006, prometryn was used in a total
of 21 counties for the five registered uses (Figure 2-2a). Use was at a maximum of
282,295 Ibs in 2000 and then steadily dropped to less than half that by 2006, to 103,113
Ibs/year. Use on cotton steadily decreased from 1999 to 2006; use on the other crops was
generally uniform over the reporting period. Four counties accounted for 80% of the
total pounds applied per county in 2006 [Fresno (43%), Kern (20%), Ventura (10%),
Monterey (7%)] (Figure 2-2b). Cotton accounted for approximately 73% of the total Ibs
applied in CA in 2006, with celery (22%), parsley (4%), fennel (1%) and dill (<1%).
This analysis may not be entirely representative of current use rates because application
intensity may have changed since the 2006 data were reported, and because it may also
include misreporting.
An evaluation of usage information was conducted to determine the area where use of
prometryn may impact the CRLF. This analysis is used to characterize where predicted
exposures are most likely to occur, but does not preclude use in other portions of the
action area. A more detailed review of the county-level use information was also
completed. These data suggest that prometryn has historically been applied in areas used
by the CRLF (Figures 2-2a and 2-2b), such as in the southern Central Valley (one of the
recovery units) where there is high prometryn use on cotton.
4 The California Department of Pesticide Regulation's Pesticide Use Reporting (CDPR PUR) database
provides a census of pesticide applications in the state. See http://www.cdpr.ca.gov/docs/pur/purmain.htin.
22
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Figure 2-2a Average Annual Prometryn Use in Total Pounds per County
Average Annual Prometryn Usage 1999-2006
County name
FRESNO
KERN
KINGS
MERCED
VENTURA
MONTEREY
TULARE
SANTA BARBARA
RIVERSIDE
IMPERIAL
SAN LUIS OBISPO
SAN BEN I TO
SAN JOAQUIN
MADERA
STANISLAUS
SANTA CLARA
ORANGE
SANTA CRUZ
SAN BERNARDINO
LOS ANGELES
SAN MATED
Average Lbs
89,811
32,254
19,967
10,029
9,568
8,359
7,230
4,750
2,296
1,129
980
708
635
434
318
175
93
76
33
16
1
Prometryn usage
Average Ibs applied
1 -500
501 - 1,000
1,001 -5,000
5,001 -15,000
> 15,000
CA counties
23
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Figure 2-2b 2006 Prometryn Use in Total Pounds per County
Total Prometryn Usage 2006
County name
FRESNO
KERN
VENTURA
'MONTEREY
SANTA BARBARA
MERCED
KINGS
SAN JOAQUIN
TULARE
IMPERIAL
RIVERSIDE
SAN LUIS OBISPO
SAN BENITO
STANISLAUS
SANTA CLARA
ORANGE
•\«L_Z?*s*i^^B«errr-._- j^\ _ ) \
SanFra
Prometryn usage
Total Ibs (2006)
1-500
501 - 1,000
1,001 -5,000
5,001 -15,000
> 15,000
CA counties
Total Ibs
44,787
20,210
10,010
7,042
4,832
4,695
3,638
1,849
1,496
1,291
1,203
977
927
115
39
2
;
24
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A summary of prometryn usage for all California use sites is provided in Table 2-6
Table 2-6 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered
Prometryn Uses
Site Name
Cotton
Celery
Parsley
Fennel
Dill
Average Pounds
All Uses1
161775
22831
3620
573
64
Avg App Rate
All Uses 1
(Ibs per acre)
1.51
1.26
1.42
0.75
1.27
Avg 95th% App
Rate1
(Ibs per acre)
1.94
1.98
1.95
1.80
1.59
Avg 99th% App
Rate1
(Ibs per acre)
2.17
2.07
2.18
1.92
1.72
1 Weighted average
2.5 Assessed Species
The CRLF was federally listed as a threatened species by U.S. FWS effective June 24,
1996 (U.S. FWS 1996). It is one of two subspecies of the red-legged frog and is the
largest native frog in the western United States (U.S. FWS 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 I.
Final critical habitat for the CRLF was designated by U.S. FWS on April 13, 2006 (U.S.
FWS 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 (U.S. FWS 1996). Its range has been reduced by about 70%,
and the species currently resides in 22 counties in California (U.S. FWS 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) (U.S. FWS 2002).
Populations currently exist along the northern California coast, northern Transverse
Ranges (U.S. FWS 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 (U.S. FWS 1996). Occupied drainages or watersheds
25
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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) (U.S. FWS 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 2-3). Recovery units, core areas, and other known occurrences of the CRLF from
the CNDDB are described in further detail in Attachment I, 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 U.S. FWS to be important in the preservation of the species. Designated
critical habitat is generally contained within the core areas, although a number of critical
habitat units are outside the boundaries of core areas, but within the boundaries of the
recovery units. Additional information on CRLF occurrences from the CNDDB is used
to cover the current range of the species not included in core areas and/or designated
critical habitat, but within the recovery units.
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.
26
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Recovery Units
1. Sierra Nevada Foothills and Central Valley
2. North Coast Range Foothills and Western
Sacramento River Valley
3. North Coast and North San Francisco Bay
4. South and East San Francisco Bay
5. Central Coast
6. Diablo Range and Salinas Valley
7. Northern Transverse Ranges and Tehachapi
Mountains
8. Southern Transverse and Peninsular Ranges
Legend
j Recovery Unit Boundaries
|] Currently Occupied Core Areas
^H Critical Habitat
|H CNDDB Occurence Sections
County Boundaries n
90
L_
Core Areas
1. Feather River
2. Yuba River- S. Fork Feather River
3. Traverse Creek/ Middle Fork/ American R. Rubicon
4. Cosumnes River
5. South Fork Calaveras River*
6. Tuolumne River*
7. Piney Creek*
8. Cottonwood Creek
9. Putah Creek - Cache Creek*
10. Lake Berryessa Tributaries
11. Upper Sonoma Creek
12. Petaluma Creek — Sonoma Creek
13. Pt. Reyes Peninsula
14. Belvedere Lagoon
15. Jameson Canyon - Lower Napa River
16. East San Francisco Bay
17. Santa Clara Valley
19. Watsonville Slough-Elkhorn Slough
20. Carmel River — Santa Lucia
21. Gablan Range
22. Estero Bay
23. Arroyo Grange River
24. Santa Maria River — Santa Ynez River
25. Sisquoc River
26. Ventura River — Santa Clara River
27. Santa Monica Bay - Venura Coastal Streams
28. Estrella River
29. San Gabriel Mountain*
30. Forks of the Mojave*
31. Santa Ana Mountain*
32. Santa Rosa Plateau
33. San Luis Ray*
34. Sweetwater*
35. Laguna Mountain*
18. South San Francisco Bay
* Core areas that were historically occupied by the California red-legged frog are not included in the map
Figure 2-3 Recovery Unit, Core Area, Critical Habitat, and Occurrence
Designations for CRLF
27
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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 (U.S. FWS 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,
U.S. FWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b; U.S. FWS 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 (U.S. FWS 2002). Figure 2-4 depicts CRLF annual reproductive
timing.
J
F
M
A
M
J
J
A
S
0
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over- winter)
Orange =
Adults and juveniles can be present all year
Figure 2-4 CRLF Reproductive Events by Month
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
tadpoles feeding exclusively in water and consuming diatoms, algae, and detritus (U.S.
FWS 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
28
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examining the gut content of 35 juvenile and adult CRLFs, that the species feeds on as
many as 42 different invertebrate taxa, including Arachnida, Amphipoda, Isopoda,
Insecta, and Mollusca. The most commonly observed prey species were larval alderflies
(Stalls cf californicd)., pillbugs (Armadilliadrium vulgare), and water striders (Gerris sp).
The preferred prey species, however, was the sowbug (Hayes and Tennant 1985). This
study suggests that CRLFs forage primarily above water, although the authors note other
data reporting that adults also feed under water, are cannibalistic, and consume fish. For
larger CRLFs, over 50% of the prey mass may consists of vertebrates such as mice, frogs,
and fish, although aquatic and terrestrial invertebrates were the most numerous food
items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at
night; for juveniles feeding occurs during the day and at night (Hayes and Tennant 1985).
2.5.4 Habitat
CRLFs require aquatic habitat for breeding, but also use other habitat types including
riparian and upland areas throughout their life cycle. CRLF use of their environment
varies; they may complete their entire life cycle in a particular habitat or they may utilize
multiple habitat types. Overall, populations are most likely to exist where multiple
breeding areas are embedded within varying habitats used for dispersal (U.S. FWS 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 (U.S. FWS 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 (U.S.
FWS 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://ecos.fws.gov/speciesProfile/SpeciesReport.do?spcode=D02D).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability,
and life stage. Adults rely on riparian vegetation for resting, feeding, and dispersal. The
foraging quality of the riparian habitat depends on moisture, composition of the plant
community, and presence of pools and backwater aquatic areas for breeding. CRLFs can
be found living within streams at distances up to 3 km (2 miles) from their breeding site
and have been found up to 30 m (100 feet) from water in dense riparian vegetation for up
to 77 days (U.S. FWS 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
29
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trees or logs, industrial debris, and agricultural features (U.S. FWS 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 U.S. FWS (U.S. FWS 2006; FR 51 19244-19346). A
summary of the 34 critical habitat units relative to U.S. FWS-designated recovery units
and core areas (previously discussed in Section 2.5.1) is provided in Attachment I.
'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 (Section 7) through prohibition against destruction
or adverse modification with regard to actions carried out, funded, or authorized by a
federal Agency. Section 7 requires consultation on federal actions that are likely to result
in the destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the
conservation of the species.' Critical habitat designations identify, to the extent known
using the best scientific and commercial data available, habitat areas that provide
essential life cycle needs of the species or areas that contain certain primary constituent
elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to,
space for individual and population growth and for normal behavior; food, water, air,
light, minerals, or other nutritional or physiological requirements; cover or shelter; sites
for breeding, reproduction, rearing (or development) of offspring; and habitats that are
protected from disturbance or are representative of the historic geographical and
ecological distributions of a species. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
Breeding aquatic habitat;
Non-breeding aquatic habitat;
Upland habitat; and
Dispersal habitat.
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, U.S. FWS does not
include areas where existing management is sufficient to conserve the species. Critical
30
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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 the Final Rule (FR)
listing notice in April 2006 (71 FR 19243, 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 I for a full explanation on this special rule.
U.S. FWS has established adverse modification standards for designated critical habitat
(U.S. FWS 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 prometryn that may alter the PCEs of the CRLF's
critical habitat form the basis of the critical habitat impact analysis. According to U.S.
FWS (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) 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 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.
(4) 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.
(5) Elimination of upland foraging and/or aestivating habitat or 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 (also
evaluated as indirect effects to the CRLF).
As previously noted in Section 2.1, the Agency believes that the analysis of direct and
indirect effects to listed species provides the basis for an analysis of potential effects on
the designated critical habitat. Because prometryn is expected to directly impact living
organisms within the action area, critical habitat analysis for prometryn 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 prometryn 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 (U.S. EPA 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 occurs), 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 prometryn may be expected to have on the
environment, the exposure levels to prometryn that are associated with those effects, and
the best available information concerning the use of prometryn 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 prometryn. 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 particular,
the food use on pigeon peas and parsnips and the non food uses (carrot, parsley, parsnips,
and coriander grown for seed, and kenaf) are not being assessed because the use on
pigeon peas is restricted to Puerto Rico only; the food use on parsnips is restricted to
Florida only; and the non-food uses of prometryn are geographically restricted to areas
outside of California (Table 2-3). For those uses relevant to the CRLF, the analysis
indicates that, for prometryn, the following agricultural food uses are considered as part
of the federal action evaluated in this assessment: cotton, celery, parsley, dill, and fennel.
Due to the lack of a defined no effect concentration for given studies in the ECOTOX
data (October 31, 2008), the spatial extent of the action area (i.e., the boundary where
32
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exposures and potential effects are less than the Agency's LOG) for prometryn 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). The following ECOTOX studies reported LOAELs without a
corresponding NOAEL: Kozlowski & Torrie 1965 (Ref. #41006) on Norway pine, Isakeit
& Lockwood 1989 (Ref. #70027) on fungi, El-Abyad et al. 1988 (Ref. #104611) on
fungi, Osman & El-Khadem 1989 (Ref. #106174) on fungi, and Tezak et al. 1992 (Ref.
#105506) on the Norway rat.
2.8 Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental
value that is to be protected."5 Selection of the assessment endpoints is based on valued
entities (e.g., CRLF, organisms important in the life cycle of the CRLF, and the PCEs of
its designated critical habitat), the ecosystems potentially at risk (e.g., waterbodies,
riparian vegetation, and upland and dispersal habitats), the migration pathways of
prometryn (e.g., runoff, spray drift, etc.), and the routes by which ecological receptors are
exposed to prometryn (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 effects to its habitat. In addition, potential effects to 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. 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 (U.S. EPA 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.
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 4.0 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 prometryn is provided in Table 2-7.
5 U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
33
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Table 2-7 Assessment Endpoints and Measures of Ecological Effects
Assessment Endpoint0
Measures of Ecological Effects6
Aquatic-Phase CRLF
(Eggs, larvae, juveniles, and adults)*
Direct Effects
1. Survival, growth, and reproduction of CRLF
la. Rainbow Trout (Oncorhynchus mykiss) LCso,
Ib. Fathead Minnow (Pimephales promelas) NOAEC
Indirect Effects and Critical Habitat Effects
1. Survival, growth, and reproduction of CRLF
individuals via indirect effects on aquatic prey
food supply (i.e., fish, freshwater invertebrates,
non-vascular plants)
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)
4. Survival, growth, and reproduction of CRLF
individuals via effects to riparian vegetation
2a. Rainbow Trout LC50, Waterflea (Daphnia magna)
ECso, Freshwater diatom (Naviculla pelliculosa) ECso,
Duckweed (Lemna gibba) ECso
2b. Fathead Minnow NOAEC, Waterflea NOAEC
3 a. Duckweed EC50
3b. Freshwater diatom EC50
4a. Oat EC2s (seedling emergence); Onion EC25
(vegetative vigor)
4b. Cabbage EC25 (seedling emergence); Cucumber EC25
(vegetative vigor)
Terrestrial-Phase CRLF
(Juveniles and adults)
Direct Effects
5. Survival, growth, and reproduction of CRLF
individuals via direct effects on terrestrial phase
adults and juveniles
5a. Mallard Duckb (Anas platyrhynchos) LD50, Northern
Bobwhite Quail (Colunus virginianus) LC50
5b. Mallard Duck 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)
7. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian and upland vegetation)
6a. Honey bee (Apis mellifera) LD50, Rat (Ratus
norvegicus) LD50
6b. None, Rat NOAEC
7a. Oat EC25 (seedling emergence); Onion EC25
(vegetative vigor)
7b. Cabbage EC25 (seedling emergence); Cucumber EC25
(vegetative vigor)
a Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult frogs
are considered "aquatic" for the purposes of this assessment because exposure pathways in the water are
considerably different that exposure pathways on land.
b Birds are used as surrogates for terrestrial phase amphibians.
0 All endpoints are based on guideline studies
6 All registrant-submitted toxicity data reviewed for this assessment are included in Appendix A. Reviewed
open literature data is included in Appendices F-l and F-2.
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2.8.2 Assessment Endpoints for Designated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related
to the use of prometryn that may alter the PCEs of the CRLF's critical habitat. PCEs for
the CRLF were previously described in Section 2.6. Actions that may modify critical
habitat are those that alter the PCEs and jeopardize the continued existence of the CRLF.
Therefore, these actions are identified as assessment endpoints. It should be noted that
evaluation of PCEs as assessment endpoints is limited to those of a biological nature (i.e.,
the biological resource requirements for the listed species associated with the critical
habitat) and those for which prometryn effects data are available.
Measures of such possible effects by labeled use of prometryn 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 U.S. FWS (2006).
35
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Table 2-8 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat3
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.
Alteration in water chemistry /quality including
temperature, turbidity, and oxygen content necessary
for normal growth and viability of juvenile and adult
CRLFs and their food source.
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
a. Freshwater diatom EC50
b. Oat EC2s (seedling emergence); Onion EC25 (vegetative
vigor)
c. Cabbage EC25 (seedling emergence); Cucumber EC25
(vegetative vigor)
a. Freshwater diatom EC50
b. Oat EC25 (seedling emergence); Onion EC25 (vegetative
vigor)
c. Cabbage EC25 (seedling emergence); Cucumber EC25
(vegetative vigor)
a. Rainbow Trout LC50, Waterflea. EC50
b. Fathead Minnow NOAEC, Waterflea NOAEC
a. Freshwater diatom EC50
Terrestrial-Phase CRLFPCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian
habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
Elimination and/or disturbance of dispersal habitat:
Upland or riparian dispersal habitat within designated
units and between occupied locations within 0.7 mi of
each other that allow for movement between sites
including both natural and altered sites which do not
contain barriers to dispersal
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
a. Oat EC25 (seedling emergence); Onion EC25 (vegetative
vigor)
b. Cabbage EC25 (seedling emergence); Cucumber EC25
(vegetative vigor)
c. Rat LD50, Rat NOAEC, Honey Bee LD50, Mallard Duck
LD50, Northern Bobwhite Quail LC50, Mallard Duck
NOAEC, Rainbow Trout LC50, Fathead Minnow NOAEC
a Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these processes are not biologically
mediated and, therefore, are not relevant to the endpoints included in this assessment.
36
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2.9 Conceptual Model
2.9.1 Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in
assessment endpoints) and may be based on theory and logic, empirical data,
mathematical models, or probability models (U.S. EPA 1998). For this assessment, the
risk is stressor-linked, where the stressor is the release of prometryn to the environment.
The following risk hypotheses are presumed for this endangered species assessment:
The labeled use of prometryn 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 affect 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 affect 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;
• affect 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);
• affect the designated critical habitat of the CRLF by reducing the food supply
required for normal growth and viability of juvenile and adult CRLFs;
• affect 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;
• affect 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; or
• affect the designated critical habitat of the CRLF by altering chemical
characteristics necessary for normal growth and viability of juvenile and adult
CRLFs.
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the prometryn release mechanisms, biological receptor types, and effects
endpoints of potential concern. The conceptual models for terrestrial and aquatic
exposures are shown in Figure 2-5 and Figure 2-6, respectively, which include the
conceptual models for the aquatic and terrestrial PCE components of critical habitat.
37
-------
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 effects
to designated critical habitat is expected to be negligible.
Stressor
Source
Exposure
Media
Prometryn applied to use site
\ Spray drift|
| Runoff |
Terrestrial-phase
amphibians
, ,—Dermal uptake/lnqestiorr*—
Root
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Ingestion
Receptors
Ingestion
Birds/terrestrial-
phase amphibians/
reptiles/mammals
Attribute
Change
Individual
organisms
Reduced survival
Reduced growth
Reduced reproduction
uptake .4! f
Wet/dry deposition-*
Long range
atmospheric
transport
Food chain
Reduction in prey
Modification of PCEs
related to prey availability
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Modification of PCEs related to
habitat
Figure 2-5 Conceptual Model for Prometryn Effects on Terrestrial-Phase of the
CRLF
38
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Stressor
Prometryn applied to
1 1
use site
^
Source | Spray drift ] | Runoff | I Soil H
Groundwater|
Exposure
Media
Surface water/
Sediment
T
.Wet/dry deposition
Long range
atmospheric
transport
Receotors
Uptake/gills
or integument
1
Uptake/gills
or integument
Aquatic Animals
Invertebrates
Vertebrates
Fish/aquatic-phase
amphibians
"Piscivorous mammals
and birds
T
Inqeption
Attribute
Change
Individual
organisms
Reduced survival
Reduced growth
Reduced reproduction
Uptake/cell,
roots^ leaves
Aquatic Plants
Non-vascular
Vascular
t
Inqestion
Food chain
Reduction in algae
Reduction in prey
Modification of PCEs
related to prey availability
1
Habitat integrity
Reduction in primary
productivity
Reduced cover
ommunity change
Modification of PCEs related to
habitat
** Route of exposure includes only ingestion of aquatic fish and invertebrates
Figure 2-6 Conceptual Model for Prometryn Effects on Aquatic-Phase of the CRLF
2.10 Analysis Plan
In order to address the risk hypothesis, the potential for direct and indirect effects were
estimated for the CRLF, its prey, and its habitat. In the following sections, the use,
environmental fate, and ecological effects of prometryn are characterized and integrated
to assess the risks. This is accomplished using a risk quotient (or RQ, 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 prometryn is estimated using
the probit dose-response slope and either the level of concern (discussed below) or actual
calculated risk quotient value.
39
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2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model
2.10.1.1 Measures of Exposure
The environmental fate and physical-chemical properties of prometryn along with
available monitoring data indicate that runoff and leaching to ground water (surface
water/ground water interactions) are the principal potential transport mechanisms of
prometryn to the aquatic and terrestrial habitats of the CRLF. In this assessment,
transport of prometryn through runoff and spray drift is considered in deriving
quantitative estimates of prometryn exposure to the CRLF, its prey, and its habitat. The
laboratory volatility study (MRTD 41875906) as well as the vapor pressure (product
chemistry data) and Henry's Law constant (estimated from EPI Suite7) suggest low
volatilization potential. However, recent data have shown the presence of prometryn in
rain and wet deposition (Vogel et al. 2008), which suggests that atmospheric transport
can occur.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of prometryn using maximum labeled application
rates, target crop, time of application, and methods of application. The model used to
predict aquatic EECs is a 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 (version 3.12.2, May 2005) and EXAMS (version 2.98.4.6, 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 prometryn that may occur in surface water
bodies adjacent to application sites receiving prometryn through runoff and spray drift for
specific scenarios. 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
prometryn. 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 aquatic phase of the CRLF, as well as indirect effects to
the CRLF through effects to potential prey items, including: algae, aquatic invertebrates,
fish and frogs. The 1-in-10-year 60-day mean is used for assessing chronic exposure to
the CRLF and fish and frogs serving as prey items; the 1-in-10-year 21-day mean is used
for assessing chronic exposure for aquatic invertebrates, which are also potential prey
items. In addition, GENEEC (Version 2.0, August 2001) estimates pesticide
7 Estimation Programs Interface (EPI) Suite TM, Version 4.0
40
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concentrations immediately after application followed by a single run-off event (peak
concentration) as well as the concentration in water (pond) as a function of time (21 day
average for chronic exposure concentration to aquatic invertebrates and 60 day average
chronic exposure concentration for fish).
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, December 7,
2006). This model incorporates the Kenega nomograph, as modified by Fletcher et al.
(1994), which is based on a large set of actual field residue data. The upper limit values
from the nomograph represent the 95th percentile of residue values from actual field
measurements (Hoerger and Kenega 1972). For modeling purposes, direct exposures of
the CRLF to prometryn 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
prometryn 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 1.4.1, October 8, 2008) has been refined to the T-HERPS model (version
1.0, May 15, 2007), 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 AgDRIFT model (Ver. 2.1.03) is used to assess exposures of terrestrial phase CRLF
and its prey to prometryn deposited on terrestrial habitats by spray drift. AGDISP
(version 8.13; dated 12/14/2004) (Teske and Curbishley 2003) is used to simulate aerial
and ground applications using the Gaussian far-field extension. In addition to the
buffered area from the spray drift analysis, the downstream extent of prometryn that
exceeds the LOG for the effects determination is also considered.
41
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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 (OPP 2004)8. 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 U.S. EPA, Office of Research and Development, and the National
Health and Environmental Effects Research Laboratory's Mid-Continent Ecology
Division.
The assessment of risk for direct effects to the terrestrial-phase CRLF makes the
assumption that toxicity of prometryn to birds is similar to or less than 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, LCso and ECso- LD stands for "Lethal Dose", and LD50 is the amount of a material,
given all at once, that is estimated to cause the death of 50% of the test organisms. LC
stands for "Lethal Concentration" and LCso is the concentration of a chemical that is
estimated to kill 50% of the test organisms. EC stands for "Effective Concentration" and
the ECso is the concentration of a chemical that is estimated to produce a specific effect in
50% of the test organisms. Endpoints for chronic measures of exposure for listed and
non-listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for "No
Ob served-Adverse-Effect-Level" and refers to the highest tested dose of a substance that
has been reported to have no harmful (adverse) effects on test organisms. The NOAEC
(i.e., "No-Observed-Adverse-Effect-Concentration") is the highest test concentration at
which none of the observed effects were statistically different from the control. The
NOEC is the No-Observed-Effects-Concentration. For non-listed plants, only acute
exposures are assessed (i.e.., EC25 for terrestrial plants and ECso for aquatic plants).
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 to 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.
8 Office of Pesticide Programs, U.S. EPA. July 16, 2004. Interim Guidance of the Evaluation Criteria for
Ecological Toxicity Data in the Open Literature: Phases I and II. Procedures for Identifying, Selecting, and
Acquiring Toxicity Data Published in the Open Literature For Use in Ecological Risk Assessments.
42
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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 uses of prometryn, 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 prometryn 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) (U.S. EPA 2004) (see Appendix C)
For this endangered species assessment, listed species LOCs are used for comparing RQ
values for acute and chronic exposures of prometryn directly to the CRLF. If estimated
exposures directly to the CRLF of prometryn resulting from a particular use are sufficient
to exceed the listed species LOG, 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 prometryn resulting from a particular
use are sufficient to exceed the listed species LOG, then the effects determination for that
use is a "may affect." If the RQ being considered also exceeds the non-listed species
acute risk LOG, then the effects determination is a LAA. If the acute RQ is between the
listed species LOG and the non-listed acute risk species LOG, 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 LOG 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 LOG for plants, the
effects determination is "may affect". Further information on LOCs is provided in
Appendix C
43
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2.10.1.4 Data Gaps
Environmental Fate
Anaerobic and aerobic aquatic metabolism studies are not available for prometryn. The
aerobic aquatic metabolism half-life of a chemical is an important input parameter in
PRZM-EXAMS simulations. The aerobic soil metabolism was used to estimate the
aerobic aquatic metabolism rate in accordance with the PRZM-EXAMS Input Parameters
Selection Guidelines (February 28, 2001).
Environmental Effects
Environmental effects data gaps that are identified do not affect the CRLF assessment.
The following studies are required for future risk assessments where it is expected that
marine/estuarine ecosystems are likely to be affected by prometryn use:
• 850.1350 Aquatic invertebrate life cycle (saltwater): mysid shrimp (Mysidopsis
bahia)
• 850.1400 Fish early-life stage (saltwater): recommended sheepshead minnow
(Cyprinodon variegatus)
44
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3.0 Exposure Assessment
Prometryn is formulated as liquid, emulsifiable concentrate, flowable concentrate, and
water dispersible granules. Application equipment includes ground and aerial spray
applications.
3.1 Label Application Rates and Intervals
Prometryn labels may be categorized into two types: labels for manufacturing uses
(including technical grade prometryn and its formulated products) and end-use products.
While technical products, which contain prometryn of high purity, are not used directly in
the environment, they are used to make formulated products, which can be applied in
specific areas to control weeds. The formulated product labels legally limit prometryn's
potential use to only those crops and sites that are specified on the labels.
Prometryn is used only on agricultural crops. Currently registered agricultural uses of
prometryn within California include celery, fennel (anise, sweet anise), dill, parsley, and
cotton. The uses being assessed are summarized in Table 3-1.
Table 3-1 Prometryn Use Input Parameters1
Agricultural
Commodity
Celery
Fennel
Parsley
Dill
Cotton
Number
of crop
cycles per
year
2.52
22
I3
1J
1
Maximum
Single
application
rate, Ib
a.i./acre
2
2
2
1.6
2.4
Number of
Applications
per crop cycle
1
1
1
1
1-3*
Interval
between
applications
n/a
n/a
n/a
n/a
Maximum
Application
per crop/year
Ib a.i./acre
5
4
2
1.6
5.5
Method of
Application
Ground
Ground
Ground
Ground
Ground/Aerial
1 Product label for Caparol® 4L; 44.4% prometryn; liquid; EPA Reg No. 100-620 is representative of typical
application instructions for prometryn herbicide use on cotton in California.
2 U.S. EPA. 2007. Memo from Monisha Kaul (BEAD) to Melissa Panger (EFED). Subject: Maximum Number of Crop Cycles Per
Year in California for Methomyl Use Sites. Dated February 28.
Number of crop cycles per year as assumed by EFED
* Applications on cotton were modeled using single applications for pre-plant and post-harvest. Also, the labels allow
3 applications: as an aerial spray application of 2.4 Ibs ai/A at pre-plant; ground spray application of 0.7 Ibs ai/A at
post-plant; and ground spray application of 2.4 Ibs ai/A at post-harvest.
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 prometryn 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.
45
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Exposure estimates generated using the standard pond are intended to represent a wide
variety of vulnerable water bodies that occur at the top of watersheds including prairie
pot holes, playa lakes, wetlands, vernal pools, man-made and natural ponds, and
intermittent and first-order streams. As a group, there are factors that make these water
bodies more or less vulnerable than the standard surrogate pond. Static water bodies that
have larger ratios of drainage area to water body volume would be expected to have
higher peak EECs than the standard pond. These water bodies will be either shallower or
have large drainage areas (or both). Shallow water bodies tend to have limited additional
storage capacity, and thus, tend to overflow and carry pesticide in the discharge whereas
the standard pond has no discharge. As watershed size increases beyond 10 hectares, at
some point, it becomes unlikely that the entire watershed is planted to a single crop,
which is all treated with the pesticide. Headwater streams can also have peak
concentrations higher than the standard pond, but they tend to persist for only short
periods of time and are then carried downstream.
Crop-specific management practices for all of the assessed uses of prometryn were used
for modeling, including application rates, number of applications per year, application
intervals, application methods and the first application date for each crop. The date of
first application was developed based on several sources of information including data
provided by BEAD, a summary of individual applications from the CDPR PUR data, and
Crop Profiles maintained by the USDA. Additionally, seasonal high rainfall distribution
patterns were used to select pesticide application dates when CDPR PUR data did not
indicate any clear seasonal trend in prometryn application timing. This situation was
observed for prometryn applications to fennel, parsley, and celery. A sample distribution
of prometryn applications to parsley is shown in Figure 3-1.
Figure 3-1: CDPR PUR Data on Prometryn Applications on Parsley. Application rate
in Ibs/A is on the y-axis and date is on the x-axis.
46
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Because there is no temporal pattern for prometryn use on parsley, a spring and fall
application timing was selected to provide a conservative aquatic exposure assessment
for prometryn. These application timings correspond with seasonal high events (Figure
3-2).
•8
•a
o 2
O
O
T T
\
,• •y T v 11
30 60 90 120 150 180 210 240 270 300 330 360 390
Julian Day
Figure 3-2: Precipitation Data from 1961 to 1964 for Surrogate Parsley Scenario
(CA Lettuce Scenario)
3.2.2 Model Inputs
PRZM and EXAMS
Prometryn environmental fate and physical-chemical data used as PRZM/EXAMS input
parameters are listed in Table 3-2.
Table 3-2 Physical and Chemical Properties and Environmental Fate Data Used as
Input Parameters for PRZM and EXAMS 1
Physical-chemical Properties and
Environmental Fate Input parameters (PRZM -
EXAMS)
Molecular Weight, grams/mole
Solubility in Water, mg/L
Vapor Pressure
Henry's Law Constant, atm-m3-mole-l
[Abiotic] Hydrolysis Half-life, days
[Direct] Photolysis in Water, days
Available Data
241.35
33
1.0 xlO"3 ton-
No; Estimated
Stable
Stable
Selected Value
241.35
33
1.0xlO"3torr
9.1xl(r9
0
0
Source
Product
chemistry
Product
chemistry
Product
chemisty
Estimated
(EPIWin,
Version 4.0)
161-1
MPJD495737-
04
161-2
MPJD495737-
04
47
-------
Aerobic Soil Metabolism Half-life. Days
Anaerobic Aquatic Metabolism Half-life
Aerobic Aquatic Metabolism Half-life
Sorption Coefficients,
Koc
Dependent
270 days (1-soil)
No
No
Sand 246
Loamy sand 169
Silt loam 117
Silty clay loam 448
3x270
810
0
2x810
1620
244
162-1
MRID00148338
Not applicable
Not applicable
163-1 MRID
00148338
1 Inputs determined in accordance with EFED "Guidance for Chemistry and Management Practice Input
Parameters for Use in Modeling the Environmental Fate and Transport of Pesticides" dated February 28,
2002
The rationale for PRZM/EXAMS scenarios selection is shown in Table 3-3. When
available, scenarios developed for the California RLF were used. Otherwise, standard
scenarios for California were used. For each agricultural commodity, spring and fall
applications were considered in the assessment to account for seasonal precipitation
patterns.
Table 3-3. Scenarios for PRZM and EXAMS and Application Dates
Agricultural Commodity
Celery /Fennel
Parsley
Dill
Cotton
Selected Scenario
CA RLF, Row Crop
CA Lettuce STD
CA RLF Row Crop
CA Cotton STD
Meteorological Station
Monterrey (Santa Maria)
Monterrey
(Santa Maria)
See celery
Bakersfield
Metflle
W23234
W23273
See celery
W23155
3.2.3 Results
Aquatic EECs for the various scenarios and application practices are listed in Table 3-4.
Inputs and outputs for PRZM-EXAMS are contained in Appendix J-l. Inputs and
outputs for GENEEC are also contained in Appendix J-l as well as Appendix J-2.
Table 3-4: PRZM/EXAMS Estimated Exposure Concentrations (jig/L) for
Prometryn
Crop
Celery/
Fennel
Parsley
Cotton
Application Timing
Spring (April 1)
Fall (December 1)
Spring( April 1)
Fall (December 1)
Spring (April l)-Ground Spray
Spring (April l)-Aerial Spray
Fall (December 1) - Ground
Premg(grd spray)-Post Ememg-Post Har1
Premg(air spray)-Post Ememg-Post Har1
Incorporation
Depth (cm)
4.0
4.0
4.0
4.0
4.0
10.2
4.0
10.2-4.0-4.0
10.2-4.0-4.0
l-in-10-Year
Peak
102.9
152.9
209.7
377.3
49.2
88.8
93.2
187.0
240.0
21-Day
102
142.8
208.8
370.0
48.4
88.2
88.8
182.4
235.4
60- Day
101.9
142.5
206.9
368.7
47.3
87.7
86.3
176.9
231.7
^re-emergent application date = April 1; Post-emergent application date = May 1; Post harvest application
date = December 1
It is important to note that the l-in-10 year estimated environmental concentrations
represent accumulated concentrations over a 27 year period. Because of the year to year
48
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accumulation in the standard pond, the l-in-10 year EEC has no probabilistic meaning
regarding return frequency of concentrations. However, the reported EECs are highly
conservative due to the extensive residue accumulation in the pond.
3.2.4 Existing Surface Water Monitoring Data
A critical step in the process of characterizing EECs is comparing the modeled estimates
with available surface water monitoring data. Monitoring data were evaluated to assess
measured concentrations of prometryn in surface water and ground water. Monitoring
data were obtained from USGS NAWQA (http://water.usgs.gov/nawqa) and the
California Department of Pesticide Regulation (CDPR).
3.2.4.1 USGS NAWQA Surface Water Data
The USGS surface water monitoring data for prometryn in CA are based on 14 sampling
sites in 5 counties. The minimum reporting limit (MRL) for prometryn ranged from
0.0054 to 0.011 ug/L with a median MRL of 0.0054 ug/L. The detection frequency of
prometryn among surface water monitoring sites is 32.6% (105 detects/322 total
samples). The maximum prometryn concentration detected was 0.621 ug/L (Table 3-5).
The maximum average prometryn concentration is 0.032593 ug/L. The sampling site
with the highest prometryn concentrations (Site # 11274538) was identified as Stanislaus
County with a watershed size of 1,276 square miles. The land use in the watershed is
classified as mixed.
Table 3-5: USGS NAWQA Surface Water Data for Prometryn in California
County
MERCED
MERCED
MERCED
MERCED
MERCED
MERCED
MERCED
MERCED
RIVERSIDE
SACRAMENTO
SACRAMENTO
SAN JOAQUIN
STANISLAUS
STANISLAUS
STANISLAUS
USGS Station ID
11273500
372323120481700
372829120420801
372839120413901
373012120393401
373020120385201
373112120382901
373115120382801
11074000
11447360
11447650
11303500
11274538
374111121000301
374115120591601
Number of
Samples
38
5
7
19
4
1
23
26
30
30
52
57
28
1
1
Maximum Cone.
(Ug/L)
0.006
0.014
0.023
0.010
0.012
0.005
0.014
0.013
0.006
0.008
0.006
0.285
0.621
0.005
0.005
49
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3.2.4.2 USGS NAWQA Groundwater Data
The USGS ground water monitoring data for prometryn in CA are based on 247 sample
sites in Fresno, Kern, Kings, Madera, Merced, Orange, and Sacramento Counties. The
minimum reporting limit (MRL) for prometryn ranged from 0.0059 to 0.054 ug/L. There
were no detections of prometryn in ground water. The land use in the ground water
recharge areas were classified as cropland, mixed, orchard/vineyard, and
resident! al/commerical.
3.2.4.3 California Department of Pesticide Regulation (CDPR) Data
The CDPR surface water monitoring data for prometryn is based on samples from Butte,
Colusa, Sacramento, Solano, Sutler, Tehama, Yolo, Yuba, and Shasta Counties. The
limit of quantification (LOQ) was 0.5 ug/L. The CDPR data for surface water shows no
detections of prometryn. All samples had prometryn concentrations below the LOQ.
3.2.4.4 Atmospheric Monitoring Data
The US Geological Survey (USGS) has reported the presence of pesticides in rain and
wet deposition in four USA agricultural watersheds (Maryland, Indiana, Nebraska and
California) at a 0.05 ug/L laboratory reporting limit (Vogel etal, 2008)9 during the
2003-2004 sampling period.
In California, prometryn was detected in rain in the San Joaquin -Tulare- Merced River10
basin, where a wide variety of crops are grown. Wet depositions were related to storm
events during the rainy season (December-March). Of 13 detections, a maximum
concentration of 0.031 ug/L was detected in rain on December 11, 2003 and a maximum
wet deposition of 0.735 ug/m2 on December 16, 2003. Because data on detection of
prometryn in rain and wet deposition is limited, spray drift estimates are used as high-end
estimates for potential atmospheric transport contributions.
9 The cropland in West California (samples collected) is dominated by almonds and vineyards. In addition
to the California studies, other studies where conducted in agricultural watersheds in Maryland, Indiana,
and Nebraska. Atrazine was detected in all samples. Simazine was the most frequently detected triazine in
California.
10 For description of the California's Merced River Basin see Vogel et al. (2008) and pertinent references
therein. The environmental setting of the Basin is described in Gronberg & Kratzer (2007).
50
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3.2.5 Spray Drift Buffer
Aerial and ground spray application are recommended for prometryn [Caparol (EPA Reg
No. 100-620), Cotton Pro (EPA Reg No. 1812-274), Prometryn 4L Herbicide (EPA Reg.
No. 9779-297), and Prometryne + MSMA (EPA Reg, No. 9779-317). There are limited
mitigation measures for ground spray applications. For aerial applications, spray drift
management options are as follows:
• Applications should be made a maximum height of 10 feet.
• Applications should not be made at wind speeds exceeding 10 mph
• A 400-feet upwind spray drift buffer should be employed when sensitive non-
target plants are near the application site
• Coarse to Medium Droplet Size Spectrum should be used.
Tier 1 AgDrift (ver 2.1.03) modeling was used to estimate the impact of the 400 feet
buffer on terrestrial and aquatic EECs. Input parameters for Tier I AgDrift spray drift
modeling are shown in Table 3-6. Spray drift deposition concentrations for Tier I
AgDrift modeling are shown in Table 3-7. Provided the pesticide travels a distance of
400 ft from a point source, a 0.011 spray fraction of the applied concentration is expected
for aerial applications and a 0.0021 spray fraction of applied concentration is expected for
ground applications (according to Tier 1 AgDrift). The terrestrial plant EECs calculated
in TerrPlant based on the given aerial and ground spray fractions at 400 ft are shown in
Table 3-8.
Table 3-6: Input Parameters for Tier I AgDrift Modeling
Parameter
Droplet Spectrum
Application Rate
Input Value
Coarse to Medium
2.4 Ibs/A
Table 3-7: Tier 1 AgDrift Terrestrial and Aquatic EECs from Spray Drift Alone
Buffer Distance
(feet)
0
400
997
0
400
997
Spray
Method
Aerial
Aerial
Aerial
Ground
Ground
Ground
Maximum
Application Rate
(Ibs ai/A)
2.4
2.4
2.4
2.4
2.4
2.4
EECs
Terrestrial
(Ibs ai/A)
1.200
0.026
0.013
2.43
0.005
0.002
Aquatic
(HS/L)
11.993
1.207
0.699
2.218
0.227
0.092
51
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Table 3-8: Terrestrial Plant EECs given aerial and ground spray fractions of the
maximum applied concentration (2.4 Ibs a.i./A on cotton) at 400 feet
Use
Cotton
Cotton
Application
rate
(Ibs a.i./A)
2.4
2.4
Application
method
Aerial1
Ground2
Spray
Fractions
at 400 ft
0.011
0.0021
Spray
drift
EEC
(Ibs
a.i./A)
0.0264
0.005
Dry
area
EEC
(Ibs
a.i./A)
0.0384
0.053
Semi-
aquatic
area EEC
(Ibs a.i./A)
0.1464
0.485
Incorporation depth is 4 inches (10.2 cm) based on the label.
2 Incorporation depth is 1 .6 inches (4 cm) based on PRZM/EXAMS default. The TerrPlant default value of 1
was used.
Tier II AgDisp (ver 8.13) modeling was conducted to assess the impact of spray drift
mitigation recommendations for aerial spray applications. Input parameters for Tier II
AgDisp spray drift modeling are shown in Table 3-9. Spray drift deposition
concentrations from Tier II AgDisp modeling are shown in Table 3-10.
Table 3-9: Input Parameters for Tier II AgDisp Modeling
Parameter
Aircraft
Release Height
DSD
Wind Speed
Temp
Relative Humidity
Spray Volume Rate
Active Fraction
Nonvol. Fraction
Input Value
Air tractor AT-401
10ft
Coarse to Medium
lOmph
650F
50%
5 gal/A
0.1056
0.24
Table 3-10: Tier II AgDisp Terrestrial and Aquatic EECs from Aerial Spray Drift
Alone
Buffer Distance
(feet)
0
400
1000
Spray
Method
Aerial
Aerial
Aerial
Maximum
Application Rate
(Ibs ai/A)
2.4
2.4
2.4
EECs
Terrestrial
(Ibs ai/A)
6.1
0.04
0.0094
Aquatic
(HS/L)
3.546
0.611
0.083
52
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3.3 Terrestrial Animal Exposure Assessment
T-REX (Version 1.4.1) is used to calculate dietary and dose-based EECs of prometryn 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, ground and aerial spray applications of prometryn are
considered, as discussed below.
Terrestrial EECs for foliar formulations of prometryn were derived for the uses
summarized in Table 3-4. Given that no data on interception and subsequent dissipation
from foliar surfaces is available for prometryn, a default foliar dissipation half-life of 35
days is used based on the work of Willis and McDowell (1987). Although prometryn can
be applied to cotton at pre-plant (2.4 Ibs a.i./A), post-emergence (0.7 Ibs a.i./A), and post
harvest (2.4 Ibs a.i./A), all three uses were not included in T-REX because the model
does not account for variable application rates during the year. Therefore, the highest
application rate (2.4 Ibs a.i./A) on cotton at pre-plant incorporation (Reg No. 100-620,
9779-297, 10163-94, 34704-692, 66222-15) was used in T-REX to calculate the most
conservative estimates of the risk quotients and the lowest application rate (0.7 Ibs a.i./A)
on cotton was used to bracket the risk quotient estimates at the lower bound values.
Celery, fennel, parsley and dill all have application rates below the highest application
rate on cotton. Therefore, the risk quotient calculations on the highest application rate on
cotton are representative of the upper bound estimates of risk to the CRLF. Use specific
input values, including number of applications, application rate and application interval
are provided in Table 3-11. An example output from T-REX is available in Appendix
E.
Table 3-11 Input Parameters for Foliar Applications Used to Derive Terrestrial
EECs for Prometryn with T-REX
Use (Application method)
Cotton
Cotton
Celery /Fennel/Parsley
Dill
Application rate
(Ibs ai/A)
2.4
0.7
2.0
1.6
Number of Applications
1
1
1
1
T-REX is also used to calculate EECs for terrestrial insects exposed to prometryn.
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 terrestrial insects. Available acute contact
toxicity data for bees exposed to prometryn (in units of jig a.i./bee), are converted to jig
a.i./g (of bee) by multiplying by 1 bee/0.128 g. The EECs are later compared to the
adjusted acute contact toxicity data for bees in order to derive RQs.
For modeling purposes, exposures of the CRLF to prometryn 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
53
-------
mammal (15 g) which consumes short grass. Upper-bound Kenega nomogram values
reported by T-REX for these two organism types are used for derivation of EECs for the
CRLF and its potential prey (Table 3-12). Dietary-based EECs for small and large insects
reported by T-REX as well as the resulting adjusted EECs are available in Table 3-13.
An example output from T-REX v. 1.4.1 is available in Appendix E.
Table 3-12 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Prometryn
Use
Cotton
Cotton
Celery /Fennel/Parsley
Dill
Application
Rate
(Ibs a.i./A)
2.4
0.7
2.0
1.6
EECs for CRLF
(small avian, 20g)
Residues on small insects
Dietary-based
EEC (ppm)
324
94.5
270
216
Dose-based
EEC
(mg/kg-bw)
369
107.6
307.5
246
EECs for Prey
(small mammals, 15g)
Residues on short grass
Dietary-based
EEC (ppm)
576
168
480
384
Dose-based
EEC
(mg/kg-bw)
549.2
160.2
457.6
366.1
Table 3-13 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via
Effects to Terrestrial Invertebrate Prey Items
Use
Cotton
Cotton
Celery /Fennel/Parsley
Dill
Application
Rate
(Ibs a.i./A)
2.4
0.7
2.0
1.6
Small Insect
324
94.5
270
216
Large Insect
36
10.5
30
24
3.4 Terrestrial Plant Exposure Assessment
TerrPlant (Version 1.2.2) is used to calculate EECs for non-target plant species inhabiting
dry and semi-aquatic areas. Parameter values for application rate, drift assumption and
incorporation depth are based upon the use and related application method (Table 3-14).
A runoff value of 0.02 is utilized based on prometryn's solubility in water (33 mg/L),
which is classified by TerrPlant. For aerial and ground application methods, drift is
assumed to be 5% and 1%, respectively. EECs relevant to terrestrial plants consider
pesticide concentrations in drift and in runoff. These EECs are listed by use in Table
3-14. An example output from TerrPlant v. 1.2.2 is available in Appendix M.
54
-------
Table 3-14 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and
Semi-aquatic Areas Exposed to Prometryn via Runoff and Drift
Use
Cotton
Cotton
Cotton
Cotton
Celery /Fennel/Parsley
Dill
Application
rate
(Ibs a.i./A)
2.4
2.4
0.7
0.7
2.0
1.6
Application method
Aerial (Winter)1
Ground Spray (Spring)2
Aerial (Winter)1
Ground Spray (Spring)2
Ground Spray2
Ground Spray2
Drift
Value
(%)
5
1
5
1
1
1
Spray
drift
EEC
(Ibs
a.i./A)
0.12
0.024
0.035
0.007
0.02
0.016
Dry
area
EEC
(Ibs
a.i./A)
0.132
0.072
0.038
0.021
0.06
0.048
Semi-
aquatic
area EEC
(Ibs a.i./A)
0.24
0.504
0.07
0.147
0.42
0.336
Incorporation depth is 4 inches (10.2 cm) based on the label.
Incorporation depth is 1 .6 inches (4 cm) based on PRZM/EXAMS default. The TerrPlant default value of 1 was used.
55
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4.0 Effects Assessment
This assessment evaluates the potential for prometryn to directly or indirectly affect the
CRLF or its designated critical habitat. As 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 effects to its habitat. In addition, potential effects to critical habitat are
assessed by evaluating effects to the PCEs, which are components of the critical habitat
areas that provide essential life cycle needs of the CRLF. Direct effects to the aquatic-
phase of the CRLF are based on toxicity information for freshwater fish, while terrestrial-
phase effects are based on avian toxicity data, given that birds are generally used as a
surrogate for terrestrial-phase amphibians. Because the frog's prey items and habitat
requirements are dependent on the availability of freshwater fish and invertebrates, small
mammals, terrestrial invertebrates, and aquatic and terrestrial plants, toxicity information
for these taxa are also discussed. Acute (short-term) and chronic (long-term) toxicity
information is characterized based on registrant-submitted studies and a comprehensive
review of the open literature on prometryn.
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 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 ECOTOX information obtained on October 31, 2008. 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;n
(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
11 The studies that have information on mixtures are listed in the bibliography as rejected due to the
presence of mixtures. These studies are evaluated by EFED when applicable to the assessment; however,
the data is not used quantitatively in the assessment.
56
-------
CRLF survival, reproduction, and growth) identified in Section 2.8. For example,
endpoints such as behavior modifications are likely to be qualitatively evaluated, because
quantitative relationships between modifications and reduction in species survival,
reproduction, and/or growth are not available. 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 to define the action area for prometryn.
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 Appendices G and 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.
A detailed spreadsheet of the available ECOTOX open literature data, including the full
suite of lethal and sublethal endpoints is presented in Appendix F-l. Appendix F-2
represents the available ECOTOX open literature data as a bibliographic listing with
rationale for use or rejection in the risk assessment. Appendix L also includes a summary
of the human health effects data for prometryn.
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 prometryn. A summary of the available aquatic and
terrestrial ecotoxicity information, use of the probit dose-response relationship, and the
incident information for prometryn are provided in Sections 4.1 through 4.4, respectively.
Degradation products of prometryn in soil metabolism studies are 2,4-
bis(isopropylamino)-6-hydroxy-s-triazine (CS-11526) at 27% of the applied radioactivity
after one year post-treatment and 2-amino-4-isopropylamino-6-methylthio-s-triazine (GS-
11354) at less than 10% after one year post-treatment. There are no available ecotoxicity
data and limited environmental fate data for these degradation products. Based on EPA's
human health assessment conducted to support the prometryn RED (Wassell 1998), the
only residue of concern is prometryn. Therefore, the degradation products of prometryn
are not considered in this assessment.
Two acceptable ecotoxicity studies on mixtures are available for two freshwater fish
species using Primaze SOW, which contains 40% prometryn a.i. and 38% atrazine a.i. The
acute toxicity study (MRID 00040692) on the warmwater fish bluegill sunfish (Lepomis
macrochirus) yielded a 96-hour LCso of 21 mg/L, which indicates that the formulated
product is slightly toxic to bluegill. The acute toxicity study (MRID 00024738) on the
coldwater fish rainbow trout (Oncorhynchus mykiss) yielded a 96-hour LCso of 9.6 mg/L,
which indicates that the formulated product is moderately toxic to rainbow trout.
57
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4.1 Evaluation of Aquatic Ecotoxicity Studies
Table 4-1 summarizes the most sensitive aquatic toxicity endpoints for the CRLF, based
on an evaluation of both the submitted studies and the open literature, as previously
discussed. A brief summary of submitted and open literature data considered relevant to
this ecological risk assessment for the CRLF is presented below. Additional information
is provided in Appendix A.
Table 4-1 Freshwater Aquatic Toxicity Profile for Prometryn
Assessment
Endpoint
Acute Direct
Toxicity to
Aquatic -Phase
CRLF
Chronic Direct
Toxicity to
Aquatic -Phase
CRLF
Indirect Toxicity
to Aquatic-Phase
CRLF via Acute
Toxicity to
Freshwater
Invertebrates (i.e.
prey items)
Indirect Toxicity
to Aquatic-Phase
CRLF via Chronic
Toxicity to
Freshwater
Invertebrates (i.e.
prey items)
Indirect Toxicity
to Aquatic-Phase
CRLF via
Toxicity to Non-
vascular Aquatic
Plants
Species
Rainbow
Trout1
Fathead
Minnow1
Daphnia
magna
Daphnia
magna
Navicula
pelliculosa
(freshwater
diatom)
Toxicity Value
Used in Risk
Assessment
LC50= 2.9 mg
a.i./L
Slope = 3. 4 (95%
C.I. 1.99-4.83)
TGAI, 99% a.i.
NOAEC= 0.62
mg a.i./L
TGAI, 98.4%
EC50 = 18.59 mg
a.i./L
Slope = 5.24
(95% C.I. 3.34-
7.14)
TGAI, 98.9% a.i.
NOAEC = 1.0
mg a.i./L
TGAI, 98.1% a.i.
EC50 = 0.001 mg
a.i./L
TGAI, 98.4 % a.i.
Describe effect
(i.e. mortality,
growth,
reproduction)
Mortality
Most sensitive
endpoint is growth
(specifically, dry
and wet weight)
Mortality
Most sensitive
biological
parameter is
daphnid length
Mortality (percent
inhibition) based
on cell count data
(or, mean standing
crop, cells/mL) on
day 5
Citation
MRID#
(Author &
Date)
00070686
(Beliles,
Scott, &
Knott 1965)
43801702
(Graves,
Mank, &
Swigert
1995)
00070146
(Vilkas
1977)
40573720
(Surprenant
1988)
42620201
(Hughes &
Alexander
1992a)
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
58
-------
Indirect Toxicity
to Aquatic-Phase
CRLF via
Toxicity to
Vascular Aquatic
Plants
Lemna
gibba
EC50 = .0118 mg
a.i./L
TGAI, 98.4 % a.i.
Mortality (percent
inhibition) based
on mean frond
counts on day 14
42520901
(Hughes &
Alexander
1992b)
Acceptable
1 Used as surrogate for the aquatic -phase CRLF
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 Fish and Aquatic Invertebrates
LC50 (ppm)
<0.1
>0.1-1
>1-10
> 10 - 100
>100
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically nontoxic
4.1.1 Toxicity to Freshwater Fish
Ecotoxicity data for freshwater fish are generally used as surrogates for aquatic-phase
amphibians when amphibian toxicity data are not available (U.S. EPA, 2004). A
comprehensive search of the open literature provided no valid toxicity information on
lethal or sublethal effects of prometryn to amphibians.
Given that no prometryn toxicity data are available for aquatic-phase amphibians,
freshwater fish data are used as a surrogate to estimate direct acute and chronic risks to
the CRLF. Freshwater fish toxicity data are also used to assess potential indirect effects
of prometryn to the CRLF. Effects to freshwater fish resulting from exposure to
prometryn 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
The acute freshwater fish, rainbow trout (Onchorynchus mykiss formerly Salmo
gairdneri), study (MRID 00070686) reports a LCso of 2.9 mg a.i./L based on mortality
over a 96 hour period. The endpoint is based on six nominal concentration levels (8.73,
4.88, 2.78, 1.57, 0.87, and 0.56 ppm), a solvent (acetone) control, and negative control.
The water temperature varied quite a bit starting from 12.8 to 17.2°C. The study did not
indicate if the concentration of the solvent control is the same concentration used in the
test levels. The outcome of the positive control (DDT) gave an LCso estimate that was
59
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lOx higher than a previous study estimate. Assuming that the difference in the two
studies may come as a result of differing methodologies, the latter suggests that the
endpoint cited from this study, which is used in this assessment, may be underestimating
toxicity of prometryn to freshwater fish. Despite these and several minor guideline
deviations, the study is considered acceptable for 99% a.i. prometryn.
Based on the available data, prometryn is categorized as moderately toxic to freshwater
fish on an acute exposure basis.
In addition, two acceptable ecotoxicity studies on formulations are available for two
freshwater fish species using Caparol SOW, containing 80% prometryn a.i. The acute
toxicity study (MRID 00121155) on the warmwater fish bluegill sunfish (L. macrochirus)
yielded a 96-hour LCso of 10 mg/L (i.e., the lowest concentration tested) (8 mg a.i./L),
which indicates that the formulated product is moderately toxic to bluegill. The acute
toxicity study (MRID 00121154) on the coldwater fish rainbow trout (O. mykiss) yielded
a 96-hour LC50 of 7.2 mg/L (5.8 mg a.i./L), which indicates that the formulated product is
moderately toxic to rainbow trout. The endpoints generated by the formulation studies
were not lower than those obtained from the technical study. As a result, the endpoints
generated by the formulated product studies are not used in risk estimation.
Additional acute effects data for freshwater fish were not available for degradates of
prometryn from either the registrant-submitted guideline studies or the open literature. No
additional open literature studies were available which would provide effects information
based on the parent compound.
4.1.1.2 Freshwater Fish: Chronic Exposure (Early Life Stage and
Reproduction) Studies
The chronic freshwater fish, fathead minnow (Pimephalespromelas\ early life-stage
study (MRID 43801702) reports a NOAEC of 0.62 mg a.i./L based on decreased growth
(17% reduced wet weight at 2.4 mg a.i./L relative to the average of the negative and
solvent controls; 16.7% reduced dry weight at 1.2 mg a.i./L relative to the average of the
negative and solvent controls) over a 28-day period. The endpoint is based on six mean-
measured concentration levels (2.4, 1.2, 0.62, 0.31, 0.16, and 0.081 mg a.i./L), a solvent
(acetone) control, and negative control. All fish appeared normal throughout the test. The
most sensitive endpoint was growth, specifically dry and wet weight. The study is
considered acceptable for 98.4% a.i. prometryn.
Additional chronic effects data for freshwater fish were not available for formulated
products or degradates of prometryn from either the registrant-submitted guideline
studies or the open literature. No additional open literature studies were available which
would provide effects information based on the parent compound.
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4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open
Literature Information
No additional information is available that indicates greater acute freshwater fish
sensitivity to prometryn than the submitted data. In addition, no laboratory freshwater
fish early life-stage or life-cycle tests using prometryn and/or its formulated products or
degradates 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 prometryn to the CRLF. Effects to freshwater invertebrates resulting from exposure to
prometryn 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 (Mortality) Studies
The acute freshwater invertebrate, water flea (Daphnia magnet), study (MRID 00070146)
reports an ECso of 18.59 mg a.i./L based on mortality over a 48 hour period. The endpoint
is based on five nominal concentration levels (100, 56, 32, 18, and 10 ppm), a solvent
(acetone) control, and negative control. Despite several minor guideline deviations, the
study is considered acceptable for the 98.9% a.i. prometryn.
Based on the available data, prometryn is categorized as slightly toxic to freshwater
invertebrates on an acute exposure basis. Additional acute effects data for freshwater
invertebrates were not available for formulated products or degradates of prometryn from
either the registrant-submitted guideline studies or the open literature. No additional
open literature studies using the parent compound were available which would provide
more sensitive effects information than the current registrant-submitted studies.
4.1.2.2 Freshwater Invertebrates: Chronic Exposure (Reproduction)
Studies
The chronic freshwater invertebrate, water flea (Daphnia magna), life-cycle study
(MRID 40573720) reports a NOAEC of 1.0 mg a.i./L based on decreased growth (16.7%
reduced body length at 2.0 mg a.i./L from the control) over a 21-day exposure period.
The endpoint is based on five mean-measured concentration levels (2, 1, 0.46, 0.27, and
0.10 mg a.i./L) and a dilution water control. There was no significant effect of prometryn
concentration on daphnid survival, the number of days to first brood, or the number of
offspring produced. Despite several minor guideline deviations, the study is considered
acceptable for the 98.1% a.i. prometryn.
61
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Additional chronic effects data for freshwater invertebrates were not available for
formulated products or degradates of prometryn from either the registrant-submitted
guideline studies or the open literature. No additional open literature studies were
available which would provide effects information based on the parent compound.
4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Open
Literature Data
No additional information is available that indicates greater acute freshwater invertebrate
sensitivity to prometryn than the submitted data. In addition, no laboratory freshwater
invertebrate life-cycle tests using prometryn and/or its formulated products or degradates
were located in 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 prometryn 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.
Laboratory studies were used to determine whether prometryn may cause direct effects to
aquatic plants. A summary of the laboratory data for aquatic plants is provided in Section
4.1.3.1.
4.1.3.1 Aquatic Plants: Laboratory Data
Non-vascular plants
The non-vascular freshwater diatom (Naviculapelliculosd) toxicity test (MRID
42620201) reports an ECso of 0.001 mg a.i./L based on the percent inhibition of plant
cell count (in cells/mL) on the final day (i.e., the fifth day) of exposure. The endpoint is
based on mean-measured concentration levels of 8.02, 3.85, 1.87, 0.962, 0.562, and 0.288
|j,g a.i./L), a solvent (dimethylformamide) control, and a negative control. Increasing
amounts of prometryn technical had an increasingly inhibitory effect on cell growth.
Five-day responses ranged from 19.6 to 98.9% inhibition across the concentrations tested.
Despite a couple minor guideline deviations, the study is considered acceptable for the
98.4% a.i. prometryn.
Further examination of toxicity data for other non-vascular plants indicated ECso values
for green algae (Pseudokirchneriella subcapitata formerly Selenastrum capricornutum)
of 0.012 mg a.i./L, marine diatom (Skeletonema costatum) of 0.0076 mg a.i./L,
freshwater cyanobacteria (Anabaena flos-aquae) of 0.0401 mg a.i./L; these other
62
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nonvascular plant test species are approximately seven to forty times less sensitive to
prometryn than the freshwater diatom. Additional effects data for non-vascular plants
were not available for formulated products or degradates of prometryn from either the
registrant-submitted guideline studies or the open literature. No additional open literature
studies using the parent compound were available which would provide more sensitive
effects information than the current registrant-submitted studies.
Vascular plants
The vascular aquatic plant, duckweed (Lemna gibba G3) toxicity test (MRID 42520901)
reports an ECso of 0.0118 mg a.i./L based on mortality (i.e., percent inhibition) via mean
frond counts on the final day (i.e., the fourteenth day) of exposure. The endpoint is based
on mean-measured concentration levels of 40.2, 18.1, 8.42, 3.99, 1.76, and 1.01 |j,g a.i./L,
a solvent (dimethylformamide) control, and a negative control Percent inhibition of
frond formation across treatment concentrations ranged from 1.29 to 91.9%. Fronds in
the two highest concentration solutions appeared smaller in size and lighter in color than
in the controls. Root length also appeared reduced for plants exposed to the highest
concentration solution. Despite several minor guideline deviations, the study is
considered acceptable for the 98.4% a.i. prometryn.
Additional effects data for vascular plants were not available for formulated products or
degradates of prometryn from either the registrant-submitted guideline studies or the
open literature. No additional open literature studies were available which would provide
effects information based on the parent compound.
4.2 Toxicity of Prometryn to Terrestrial Organisms
Table 4-3 summarizes the most sensitive terrestrial toxicity endpoints for the CRLF,
based on an evaluation of the registrant-submitted studies. A brief summary of
registrant-submitted data considered relevant to this ecological risk assessment for the
CRLF is presented below.
Table 4-3 Terrestrial Toxicity Profile for Prometryn
Assessment
Endpoint
Acute Dose-
based Direct
Toxicity to
Terrestrial-
Phase CRLF
Species
Mallard
Duck
Toxicity Value
Used in Risk
Assessment
LD50 > 4640 mg/kg
Slope = N.A.
TGAI, 98.8 % a.i.
Describe effect
(i.e. mortality,
growth,
reproduction)
There was no
mortality at any
dosage level.
Reduction in
feed
consumption and
body weight gain
at the 4640
mg/kg dose level
(highest of five)
Citation
MRID#
(Author &
Date)
00082966
(Fink,
Beavers &
Brown
1977)
Study
Classification
Acceptable
63
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Assessment
Endpoint
Afntp
-iiX^Lllt
Dietary-based
Direct
Toxicity to
Terrestrial-
Phase CRLF
Chronic
Toxicity to
Terrestrial-
Phase CRLF
Indirect
Toxicity to
Terrestrial-
Phase CRLF
(via acute
toxicity to
mammalian
prey items)
Indirect
Toxicity to
Terrestrial-
Phase CRLF
(via chronic
toxicity to
mammalian
prey items)
Indirect
Toxicity to
Terrestrial-
Phase CRLF
(via acute
toxicity to
terrestrial
invertebrate
prey items)
Species
Northern
Bobwhite
Quail
Mallard
Duck
Rat
Rat
Honey bee
Toxicity Value
Used in Risk
Assessment
LC50 > 5000 mg/kg
diet
Slope = N.A.
TGAI, 98.1% a.i.
NOAEC = 500 mg
/kg diet
TGAI, 98.1% a.i.
LD50 = 1802 mg/kg
bw
NOAEC = 10
mg/kg diet
NOAEL = 0.65
mg/kg bw
TGAI
LD50 > 96.69
ug/bee
FTI/'-t A T
1 \J Al
Describe effect
(i.e. mortality,
growth,
reproduction)
Only one out of
10 individuals
was observed
dead at the 5000
mg/kg diet
concentration
(highest of five)
on day 6 (out of
8 days).
Reduction in
body weight gain
and food
consumption at
two highest
treatment levels.
Only one adult
mortality at the
250 mg/kg diet
level. No other
measures were
statistically
significant from
the control
Oral toxicity
Reproductive
endpoints based
on decreased pup
weight
10% mortality at
the tested limit
dose
Citation
MRID#
(Author &
Date)
40457502
(Fletcher
1984)
41035901
(Fletcher &
Pedersen
1989)
00060314
(Kapp 1975)
41445101
(Giknis &
Yau 1990)
00036935
(Atkins,
Greywood
&
Macdonald
1975)
Study
Classification
Acceptable
Acceptable
—
Acceptable
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Assessment
Endpoint
Indirect
Toxicity to
Terrestrial-
and Aquatic-
Phase CRLF
(via toxicity
to terrestrial
plants)
Species
QppHllTK*
k-jCCUllli&,
Emergence
Monocots
(Oat)
Emergence
Dicots
(Cabbage)
Vegetative
Vigor
Monocots
(Onion)
Vegetative
Vigor
Dicots
(Lettuce*)
Toxicity Value
Used in Risk
Assessment
EC25 = 0.049 Ibs
NOAEC = 0.011§
Ibs a.i./A
TGAI, 98.1% a.i.
EC25 = 0.02 Ibs
a.i./A
NOAEC = 0.008t
Ibs a.i./A
TGAI, 98.1% a.i.
EC25 = 0.18 Ibs
NOAEC = 0.1 Ibs
3.1./A
TGAI, 98.1% a.i.
EC25 = 0.01 Ibs
NOAEC = 0.003§
Ibs a.i./A
TGAI, 98.1% a.i.
Describe effect
(i.e. mortality,
growth,
reproduction)
Oat: decreased
dry weight
Cabbage:
decreased dry
weight
Onion: decreased
dry weight
Lettuce:
decreased dry
weight
Citation
MRID#
(Author &
Date)
41035904
(Canez
1988a)
41035904
(Canez
1988a)
41035903
(Canez
1988b)
41035903
(Canez
1988b)
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
§ The original NOAEC is undefined; the NOAEC cited is the EC05
T The original NOAEC > EC25 ; the NOAEC cited is the EC05
* The cucumber is potentially the more sensitive dicot tested; however, the endpoint values
obtained for it are considered invalid.
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
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
Oral LD50
< 10 mg/kg
10 - 50 mg/kg
51 -500 mg/kg
50 1-2000 mg/kg
> 2000 mg/kg
Dietary LCSO
< 50 ppm
50 - 500 ppm
501- 1000 ppm
1001 - 5000 ppm
> 5000 ppm
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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 prometryn; therefore, acute
and chronic avian toxicity data are used to assess the potential direct effects of prometryn
to terrestrial-phase CRLFs.
4.2.1.1 Birds: Acute Exposure (Mortality) Studies
The avian acute dose-based (gavage) study with mallard duck (Anasplatyrhynchos)
(MRID 00082966) reports a LD50 of >4640 mg/kg-bw over an 8-day period. The
endpoint is based on five nominal concentration levels (4640, 2150, 1000, 464, and 215
mg/kg-bw) a negative control and a positive control (dieldren) were also used. However,
prometryn did not cause any signs of toxicity at the dosage levels tested. Instead,
reductions in feed consumption and body weight gain were observed at the 4640 mg/kg-
bw dose level. Several guideline deviations were observed in this study. The birds were
only 14 days old instead of the recommended 16 weeks and the observation period lasted
8 days instead of the recommended 14 days. In addition, the mean body weight food
consumption was only measured on the first and last days. Despite these and a couple
other minor guideline deviations, the study is considered acceptable for 98.8% a.i.
prometryn.
The avian subacute dietary study with, Northern bobwhite quail (Colinus virginianus)
(MRID 40457502) reports a LC50 of >5000 mg/kg-diet over an 8-day exposure period.
The endpoint is based on five nominal dietary exposure levels (5000, 2500, 1250, 625,
and 312 mg/kg-diet) and a negative control. A single mortality was observed in the 5000
mg/kg-diet level on the sixth day. Birds receiving prometryn displayed concentration-
related food avoidance during the test period. There was a reduction in body weight gain
and food consumption at the two highest treatment levels compared to the controls. Yet,
body weight measurements were not made on day 5, the final day of the fasting phase of
the test. After receiving plain feed for days 6-8, feeding resumed to normal. Although
failure to obtain day 5 body weights may lead to a masking of toxicological effects, the
reductions in body weight at day 8 are evidence of a treatment effect at the two highest
test concentrations. Despite this and a couple other minor guideline deviations, the study
is considered acceptable for 98.1% a.i. prometryn.
Based on the available data, prometryn is categorized as practically non-toxic to avian
species tested on an acute oral and sub-acute dietary exposure basis. Additional acute
effects data for avian species were not available for formulated products or degradates of
prometryn from either the registrant-submitted guideline studies or the open literature. No
additional open literature studies were available which would provide effects information
based on the parent compound.
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4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies
A chronic avian reproduction study (MRID 41035901) with 26.5 week old mallard ducks
reports a NOAEC of 500 mg/kg-diet based on adult mortality over a 20 week period. The
endpoint is based on three nominal concentration levels (500, 250, and 50 mg/kg-diet)
and a negative control. Mortality was observed in one adult female duck at the 250
mg/kg-diet level. Necropsy revealed clotted blood present in the lungs, oral cavity,
esophagus, and around the heart. A nodule was found on the lobe of the right lung. There
were no abnormal behavioral effects noted during the study. Gross pathological
examinations conducted on half of the birds surviving to terminal sacrifice revealed
abnormalities in 7 birds. Measures of adult body weight, food consumption, reproductive
parameters, and egg shell thickness were not significantly different between the control
and treatment groups. Inconsistent differences in offspring body weights were not
considered to be treatment-related. Despite a small series of guideline deviations, the
study is considered acceptable for 98.1% a.i. prometryn.
Additional chronic effects data for avian species were not available for formulated
products or degradates of prometryn from either the registrant-submitted guideline
studies or the open literature. No additional open literature studies were available which
would provide effects information based on the parent compound.
4.2.1.3 Terrestrial-phase Amphibian Acute and Chronic Studies
No additional information is available on terrestrial-phase amphibian acute and/or
chronic sensitivity to prometryn. In addition, no laboratory acute or chronic tests using
prometryn and/or its formulated products or degradates were located in the open
literature.
4.2.2 Toxicity to Mammals
Mammalian toxicity data are used to assess potential indirect effects of prometryn to the
terrestrial-phase CRLF. Effects to small mammals resulting from exposure to prometryn
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 CRLF may consist of vertebrates such as
mice, frogs, and fish (Hayes and Tennant 1985). Sections 4.2.2.1 and 4.2.2.2 contain
additional information on the mammalian acute and chronic guideline studies,
respectively, used in the assessment.
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies
The available data indicate that prometryn is slightly toxic to small mammals on an acute
oral basis (MRID 00060314). The endpoint used in the assessment is based on the results
from male rats (LDso = 1802 mg/kg-bw). The study is classified as category III.
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Additional acute effects data for small mammal species were not available for formulated
products or degradates of prometryn from either the registrant-submitted guideline
studies or the open literature. No additional open literature studies were available which
would provide effects information based on the parent compound.
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies
In a two generation reproductive toxicity study (MRID 41445101), prometryn technical
was administered in the diet to groups of 30 male and 30 female Sprague-Dawley rats at
levels of 0, 10 ppm (0.6 mg/kg-bw/day in males, 0.7 mg/kg-bw/day in females), 750 ppm
(47.8 mg/kg-bw/day in males, 53.6 mg/kg-bw/day in females) or 1500 ppm (96.7 mg/kg-
bw/day in males, 105.6 mg/kg-bw/day in females). Body weight gain in FO males
decreased significantly at 1500 ppm (11-40%) and 750 ppm (11-18%). Body weight gain
decreased in FO females by up to 50% at 1500 ppm and 750 ppm. Similar changes in
body weight gain were seen in Fl males. Corresponding decreases in food consumption
were also observed. The Parental Systemic Toxicity NOAEC was 10 ppm; the LOAEC
was 750 ppm, based on decreased food consumption, body weight and body weight gain.
Statistically significant decreases in Fl pup body weights were observed at 1500 and 750
ppm (up to 12%) during lactation. A similar, though less marked, profile was seen in F2
generation pups. While actual weight loss was small (5-12%), and may be artifactual to
maternal weight losses, it is considered of toxicological significance because of its
potential negative impact on postnatally developing systems such as the neuro- and
immune systems. Reproductive NOAEC was 10 ppm (0.65 mg/kg-bw/day); the LOAEC
was 750 ppm (-50 mg/kg-bw/day), based on decreased pup weight.
Additional chronic effects data for small mammal species were not available for
formulated products or degradates of prometryn from either the registrant-submitted
guideline studies or the open literature. No additional open literature studies were
available which would provide effects information based on the parent compound.
4.2.3 Toxicity to Terrestrial Invertebrates
Terrestrial invertebrate toxicity data are used to assess potential indirect effects of
prometryn to the terrestrial-phase CRLF. Effects to terrestrial invertebrates resulting
from exposure to prometryn could also indirectly affect the CRLF via reduction in
available food.
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies
The use of prometryn on cotton and other crops that require pollination may result in
exposure to non-target beneficial insects, such as the honey bee (Apis melliferd). The
results of a laboratory acute contact toxicity test (MRID 00036935) of prometryn on the
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honey bee indicate 10 % mortality after direct treatment at a limit test dose of 96.69
jig/bee; therefore, the LD50 value for the contact test is greater than 96.69 jig/bee. As a
result, prometryn is categorized as practically non-toxic to honeybees on an acute contact
exposure basis.
Additional acute effects data for terrestrial invertebrate species were not available for
formulated products or degradates of prometryn from either the registrant-submitted
guideline studies or the open literature. No additional open literature studies using the
parent compound were available which would provide more sensitive effects information
than the current registrant-submitted studies.
4.2.4 Toxicity to Terrestrial Plants
Terrestrial plant toxicity data are used to evaluate the potential for prometryn to affect
riparian zone and upland vegetation within the action area for the CRLF. Impacts to
riparian and upland (i.e., grassland, woodland) vegetation could result in indirect effects
to both aquatic- and terrestrial-phase CRLFs, as well as effects to designated critical
habitat PCEs via increased sedimentation, alteration in water quality, and reduction in
upland and riparian habitat that provides shelter, foraging, predator avoidance and
dispersal for juvenile and adult CRLFs.
Plant toxicity data from registrant-submitted studies were reviewed for this assessment.
One open literature terrestrial plant study was reviewed for determining effects to woody
plants. The study was not used in risk estimation but is summarized in the risk description
(Section 5.2.3.2). 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 monocotyledonous (monocots)
and dicotyledonous (dicots) species, and effects are evaluated at both seedling emergence
and vegetative life stages.
The results of the Tier II seedling emergence and vegetative vigor toxicity tests on non-
target plants are summarized below in Table 4-5.
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Table 4-5 Non-target Terrestrial Plant Seedling Emergence and Vegetative Vigor
Toxicity (Tier II) Data
Crop
Type of Study
Species
NOAEC
(Ib ai/A)
EC25
(Ib ai/A)
Most sensitive parameter*
Seedling Emergence
Monocots
Dicots
Oat
Ryegrass
Corn
Onion
Soybean
Lettuce
Carrot
Tomato
Cucumber
Cabbage
0.011§
0.07T
0.2
0.038
0.043T
0.001T
0.063T
0.004§
0.008f
0.049
0.18
0.35
0.08
0.23
0.025
0.173
0.18
0.026
0.02
Dw
Ht
Dw
Ht
Dw
dw
pe
dw
dw
dw
Vegetative Vigor
Monocots
Dicots
Oat
Ryegrass
Corn
Onion
Soybean
Lettuce
Carrot
Tomato
Cucumber4
Cabbage
0.8
>1.6
0.4
0.1
0.044§
0.003§
>1.6
0.051§
0.019
0.05
1.4
>1.6
0.79
0.18
0.17
0.01
>1.6
0.12
0.1
0.10
Dw
dw, ht, su
Dw
Dw
Dw
Dw
dw, ht, su
Dw
Ht
Dw
* Sensitive parameters: ht - plant height measurements, pe - percentage of seedlings emerged, dw - dry
weight determination, su - survival
f The original NOAEC > EC25 ; the NOAEC cited is the EC05
§ The original NOAEC is undefined; the NOAEC cited is the EC05
A The cucumber dry weight is potentially the more sensitive parameter; however, the endpoint values
obtained for it are considered invalid.
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern
The Agency uses the probit dose-response relationship as a tool for providing additional
information on the potential for acute direct effects to individual listed species and
aquatic animals that may indirectly affect the listed species of concern (U.S. EPA 2004).
As part of the risk characterization, an interpretation of acute RQ for listed species is
discussed. This interpretation is presented in terms of the chance of an individual event
(i.e., mortality or immobilization) should exposure at the EEC actually occur for a species
with sensitivity to prometryn 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
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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.
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.
4.4 Incident Database Review
A review of the EIIS database for ecological incidents involving prometryn was
completed on March 25, 2009. The results of this review for terrestrial, plant, and
aquatic incidents are discussed below in Sections 4.4.1 through 4.4.3, respectively. A
complete list of the incidents involving prometryn including associated uncertainties is
included as Appendix I.
4.4.1 Terrestrial Animal Incidents
No prometryn incidents have been reported involving terrestrial organisms.
4.4.2 Plant Incidents
Six prometryn incidents have been reported involving terrestrial plants. The first incident
(#1019130-056) is on corn (Zea mays) where prometryn was classified as a 'probable'
cause via broadcast application on 86 acres in New Madrid County, Missouri (date
7.31.2007). The route of exposure was through carryover, or the presence of residues
from an application made in a previous growing season, that resulted in plant damage.
The remaining five incidents involve applications to cotton (Gossypium). One incident
(#1007796-005) classified as 'possibly' attributable to prometryn included 600 acres of
cotton in Hale County, Texas (date 8.25.1998). The chemical was applied directly to
cotton and resulted in the loss of all the treated cotton plants. The next incident
(#1007796-006) is also classified as 'possibly' attributable to prometryn resulted in the
loss of 1,424 acres of cotton in Hale County, Texas (date 8.17.1998). As in the previous
incident involving cotton, the chemical was applied directly to the cotton plants. The
legality of each of the aforementioned uses is not specified in the incident report. Another
incident (#1009573-014) that is classified as 'probably' attributable to prometryn
occurred as a result of a broadcast application to 48 acres in Caldwell County, Texas
(date 11.12.1999). The chemical (formulation code 'F') was applied directly to the cotton
plants and resulted in plant damage in the form of chlorotic yellowing. The following
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incident (#1016903-008) is classified as 'possibly' attributable to prometryn occurred
following a band application to 60 acres of cotton in Uvalde County, Texas (date
7.21.2005). The chemical (formulation code 'EC') was applied directly to the cotton field
and resulted in plant damage; the herbicide caused chlorotic yellowing of the cotton plant
leaves. The final incident (#1016903-009) is classified as 'possibly' attributable to
prometryn and occurred as a result of a band application to 26 acres of cotton in Evans
County, Georgia (date 9.8.2005). The chemical (formulation code 'EC') was applied
directly to cotton fields and resulted in plant damage; the herbicide caused chlorotic
yellowing, necrotic browning, and death of the leaves. Each of the latter three incidents
was categorized as a 'registered use' of prometryn.
4.4.3 Aquatic Animal Incidents
Three freshwater aquatic incidents involving fish kills have been reported for prometryn
in August 1996 in Richland County, Louisiana; it is possible that the three incidents are
related. However, prometryn is classified as an 'unlikely' cause; instead, exposure to
profenofos and/or azinphos-methyl as well as low dissolved oxygen levels brought on by
death of oxygen producing plants may have contributed to the multiple fish deaths. The
incidents (dated 8.6.1996) include runoff from a 'registered use' of prometryn on cotton
on land adjacent to surface water and resulted in the loss of "thousands" of common carp
(Cyprinus carpio) and 25 shad (Clupeidae) in Crew Lake (#1004021-004) and a use of
'unknown' legality killed "hundreds" of buffalo (Catostomidae) and "thousands" of shad
in Little Lake LaFourche (#1004021-005). The third incident (dated 8.7.1996) is
classified as a 'registered use' on cotton that killed hundreds of buffalo, gar (Lepisosteus
spp.), and shad in Dave's Bayou, south of Charlieville (#1004668-011).
72
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5.0 Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations.
Risk characterization is used to determine the potential for direct and/or indirect effects to
the CRLF or for modification to its designated critical habitat from the use of prometryn
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 LOG
is 0.05. For acute exposures to the CRLF and mammals, the LOG is 0.1. The LOG is 1.0
for chronic exposures to CRLF and its prey, as well as acute exposures to plants.
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 prometryn 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
applications of prometryn (Table 3-11 and Table 3-12) and the appropriate toxicity
endpoint from Table 4-3. Exposures are also derived for terrestrial plants, as discussed in
Section 3.4 and toxicity summarized in Section 4.2.4, based on the highest application
rates of prometryn 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 potential direct
chronic risks to the CRLF, 60-day EECs calculated via the PRZM/EXAMS model and
the lowest chronic toxicity value for freshwater fish are used. The Agency's acute LOCs
are exceeded for all parsley, a fall celery/fennel, and two pre-emergence cotton uses
(Table 5-1). Based on these results, prometryn may directly affect the aquatic-phase of
the CRLF.
73
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Table 5-1 Summary of Direct Effect RQs for the Aquatic-phase CRLF
Use Type
Celery /Fennel
(Spring, Apr 1)
Celery /Fennel
(Fall, Dec 1)
Parsley (Spring,
Aprl)
Parsley (Fall,
Decl)
Cotton (Spring,
Apr 1 )-Ground
spray
Cotton (Spring,
Apr 1 )- Aerial
spray
Cotton (Fall,
Decl)
Cotton (Pre-
emergence)-
ground spray
Cotton (Pre-
emergence)-
Aerial spray
Application rate
(Ib ai/A) and type
2 (liquid)
2 (liquid)
2 (liquid)
2 (liquid)
2.4 (liquid)
2.4 (liquid)
2.4 (liquid)
Seasonal 5.51 (liquid)
Single App 2.4
(liquid)
Seasonal 5.51
(liquid)
Single App 2.4
(liquid)
Peak
EEC
(H8/L)a
102.9
152.9
209.7
377.3
49.2
88.8
93.2
187.0
240.0
60-Day EEC
(H8/L)a
101.9
142.5
206.9
368.7
47.3
87.7
86.3
176.9
231.7
Direct
Effects
Acute
RQs"
0.04C
0.05
0.07
0.13
0.02
0.03
0.03
0.06
0.08
Probability
of Individual
Effect at RQ
(confidence
interval)
1 in 9. 98 x
105(lin370
to 1 in 1.37
xlO11)
1 in 2.06 x
105 (1 in
208 to 1 in
6.06 x 109)
1 in 2.32 x
104(lin93
to 1 in 8.23
xlO7)
1 in 772(1
in 26 to 1 in
1.07xl05)
1 in 2.62 x
108(lin
2.77 x 103 to
1 in 8.75 x
1015)
1 in 8. 91 x
106 (1 in
819 to lin
1.05 x 1013)
1 in 8. 91 x
106 (1 in
819 to lin
1.05 x 1013)
lin 6.13 x
104 (1 in
133 to 1 in
5.55 x 108)
1 in 1.04 x
104(lin69
to 1 in 1.71
xlO7)
Direct
Effects
Chronic
RQs"
0.16d
0.23
0.33
0.59
0.08
0.14
0.14
0.29
0.37
a The highest EEC (acute) and 60-day EEC (chronic) based on given use type of prometryn (see Table 3-4). The
exposure estimates are based on PRZM/EXAMS model.
b RQs associated with acute (LC50 = 2.9 mg/L, rainbow trout) and chronic (NOAEC = 0.62 mg/L, fathead minnow)
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.
0 RQ < acute risk to endangered species LOG of 0.05. The LOG exceedances are in bold.
d RQ< chronic LOG of 1.0.
Note: The probability of individual effect at ES LOC for acute direct toxicity is 1 in 2.06 x 105 (95% C.I. 1 in 208 to 1
in6.06x!09)
74
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5.1.1.2 Indirect Effects to Aquatic-Phase CRLF via Reduction in Prey (non-
vascular aquatic plants, aquatic invertebrates, fish, and frogs)
5.1.1.2.1 Non-vascular Aquatic Plants
Indirect effects of prometryn 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 (i.e.,
calculated via the PRZM/EXAMS model) and the lowest toxicity value (ECso) for aquatic
non-vascular plants. In this case the lowest ECso (0.001 mg a.i./L) was based on toxicity
to N. pelliculosa. The Agency's non-listed plant LOCs are exceeded for all prometryn
uses (Table 5-2). Based on these results, prometryn may indirectly affect the CRLF via
reduction in non-vascular aquatic plants.
Table 5-2 Summary of 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). RQs based on EECs from PRZM/EXAMS and a
freshwater non-vascular plant EC50 of 0.001 mg a.i./L
Uses
Celery /Fennel (Spring, Apr 1 )
Celery /Fennel (Fall, Dec 1)
Parsley (Spring, Apr 1)
Parsley (Fall, Dec 1)
Cotton (Spring, Apr l)-Ground spray
Cotton (Spring, Apr 1)- Aerial spray
Cotton (Fall, Dec 1)
Cotton (Pre-emergence)- Ground spray
Cotton (Pre-emergence)-Aerial spray
Application rate (Ib
ai/A) and type
2 (liquid)
2 (liquid)
2 (liquid)
2 (liquid)
2.4 (liquid)
2.4 (liquid)
2.4 (liquid)
Seasonal 5. 5 (liquid)
Single App 2.4 (liquid)
Seasonal 5. 5 (liquid)
Single App 2.4 (liquid)
Peak EEC
(Hg/L)
102.9
152.9
209.7
377.3
49.2
88.8
93.2
187.0
240.0
Indirect effects RQ*
(food and habitat)
102.9
152.9
209.7
377.3
49.2
88.8
93.20
187.0
240.0
* LOG exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC/ 0.001 mg/L.
'The labels allow 3 applications as an aerial/ground spray application of 2.4 Ibs ai/A at pre-plant, ground spray
application of 0.7 Ibs ai/A at post-plant, and ground spray application of 2.4 Ibs ai/A at post-harvest.
5.1.1.2.2 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 (i.e., calculated via the
PRZM/EXAMS model) and the lowest acute toxicity value for freshwater invertebrates,
i.e., waterflea ECso = 18.6 mg a.i./L. For chronic risks, 21-day EECs and the lowest
chronic toxicity value for invertebrates, i.e., waterflea NOAEC =1.0 mg a.i./L, 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. However,
no LOG exceedances were observed. Based on acute and chronic RQ values that are
below the Agency's LOCs as well as supporting low values (i.e., on the order of
75
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approximately 1 in a quintillion to over 1 in a septillion) for the probability of individual
effect (based on acute data only), prometryn is expected to have no indirect effect on the
CRLF via reduction in freshwater invertebrate prey items.
Table 5-3 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to
the CRLF via Direct Effects on Aquatic Invertebrates as Dietary Food Items (prey
of CRLF juveniles and adults in aquatic habitats) RQs based on EECs from
PRZM/EXAMS. Acute and chronic toxicity endpoints are based on waterflea data
at 18.6 and 1.0 mg a.i./L, respectively.
Uses
Celery /Fennel (Spring,
Aprl)
Celery /Fennel (Fall, Dec
1)
Parsley (Spring, Apr 1)
Parsley (Fall, Dec 1)
Cotton (Spring, Apr 1)-
Ground spray
Cotton (Spring, Apr 1)-
Aerial spray
Cotton (Fall, Dec 1)
Cotton (Pre-emergence)-
Ground spray
Cotton (Pre-emergence)-
Aerial spray
Application
rate (Ib ai/A)
and type
2 (liquid)
2 (liquid)
2 (liquid)
2 (liquid)
2.4 (liquid)
2.4 (liquid)
2.4 (liquid)
Seasonal 5.51
(liquid)
Single App
2.4 (liquid)
Seasonal 5.51
(liquid)
Single App
2.4 (liquid)
Peak
EEC
(Hg/L)
102.9
152.9
209.7
377.3
49.2
88.8
93.2
187.0
240.0
21-day
EEC
(Hg/L)
102.0
142.8
208.8
370.0
48.4
88.2
88.8
182.4
235.4
Indirect
Effects
Acute
RQ*
0.01
0.01
0.01
0.02
O.01
O.01
0.01
0.01
0.01
Probability of
Individual Effect
atRQ
(confidence
interval)
Iinl.87xl025(l
in8.37xl010tol
in6.86x!045)
Iinl.87xl025(l
in8.37xl010tol
in6.86x!045)
Iinl.87xl025(l
in8.37xl010tol
in6.86x!045)
Iin3.67xl018(l
inl.44xl08tol
in2.75x!033)
—
—
Iinl.87xl025(l
in8.37xl010tol
in6.86x!045)
Iinl.87xl025(l
in8.37xl010tol
in6.86x!045)
Iinl.87xl025(l
in8.37xl010tol
in6.86x!045)
Indirect
Effects
Chronic
RQ*
0.10
0.14
0.21
0.37
0.05
0.09
0.09
0.18
0.24
* Risk to listed species LOG exceedances (acute RQ > 0.05; chronic RQ > 1.0) are not observed for aquatic invertebrates
(indirect effects to CRLF). Acute RQ = use-specific peak EEC / 18.6 mg a.i. per liter. Chronic RQ = use-specific 21-day
EEC / 1 .0 mg a.i. per liter.
'The labels allow 3 applications as an aerial/ground spray application of 2.4 Ibs ai/A at pre-plant, ground spray
application of 0.7 Ibs ai/A at post-plant, and ground spray application of 2.4 Ibs ai/A at post-harvest.
NOTE: Probability of Individual Effect at ES acute LOC is 1 in 2.16 x 1011 (95% C.I. 1 in 1.44 x 105 to 1 in 1.29 x 1020)
5.1.1.2.3 Fish and Frogs
Fish and frogs also represent potential prey items of adult aquatic-phase CRLFs. RQs
associated with direct acute and chronic risk 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
76
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food items. Based on LOG exceedances observed in all parsley, a fall celery/fennel, and
two pre-emergence cotton uses (Table 5-1) for acute mortality, prometryn may indirectly
affect the CRLF via reduction in freshwater fish and frogs as food items.
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 peak
EECs from the standard pond (i.e., calculated via the PRZM/EXAMS model) and the
most sensitive vascular and non-vascular plant toxicity endpoints. Because there are no
obligate relationships between the CRLF and any aquatic plant species, the most sensitive
ECso value (0.012 mg a.i./L), rather than NOAEC values, were used to derive RQs. RQs
for non-vascular plants are presented in Section 5.1.1.2.1 and Table 5-2. The Agency's
non-listed plant LOCs are exceeded for all prometryn uses (Table 5-4). Based on these
results and those of section 5.1.1.2.1, prometryn may indirectly affect the CRLF via
reduction in both vascular and non-vascular aquatic plants.
Table 5-4 Summary of RQs Used to Estimate Indirect Effects to the CRLF via
Effects to Vascular Aquatic Plants (habitat of aquatic-phase CRLF)a RQs based on
EECs from PRZM/EXAMS and a freshwater vascular plant EC50 of 0.012 mg a.i./L.
Uses
Celery /Fennel (Spring, Apr 1 )
Celery /Fennel (Fall, Dec 1)
Parsley (Spring, Apr 1)
Parsley (Fall, Dec 1)
Cotton (Spring, Apr l)-Ground spray
Cotton (Spring, Apr 1)- Aerial spray
Cotton (Fall, Dec 1)
Cotton (Pre-emergence)- Ground spray
Cotton (Pre-emergence)-Aerial spray
Application rate (Ib
ai/A) and type
2 (liquid)
2 (liquid)
2 (liquid)
2 (liquid)
2.4 (liquid)
2.4 (liquid)
2.4 (liquid)
Seasonal 5.51 (liquid)
Single App 2.4 (liquid)
Seasonal 5.51 (liquid)
Single App 2.4 (liquid)
Peak EEC
(Mg/L)
102.9
152.9
209.7
377.3
49.2
88.8
93.2
187.0
240.0
Indirect effects RQ*
(food and habitat)
8.7
12.9
17.8
32.0
4.2
7.5
7.9
15.8
20.3
a RQs used to estimate indirect effects to the CRLF via toxicity to non- vascular aquatic plants are summarized in Table
5-2
* Risk to non-listed species LOG exceedances (RQ > 1) are bolded and shaded. RQ = use-specific peak EEC/ 0.012
mg/L.
'The labels allow 3 applications as an aerial/ground spray application of 2.4 Ibs ai/A at pre-plant, ground spray
application of 0.7 Ibs ai/A at post-plant, and ground spray application of 2.4 Ibs ai/A at post-harvest.
77
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5.1.2 Exposures in the Terrestrial Habitat
5.1.2.1 Direct Effects to Terrestrial-phase CRLF
As discussed in Section 3.3, potential direct effects to terrestrial-phase CRLFs are based
on ground spray and aerial applications of prometryn.
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 3-11) and acute oral and subacute dietary toxicity endpoints
for avian species. The acute avian effects data show no mortality in the acute oral toxicity
study (LD50 > 4,640 mg/kg-bw) and a single mortality in the highest treatment level of
prometryn in the subacute dietary toxicity study (LCso > 5,000 mg/kg-diet). As a result,
the calculated RQs (not reported) are indefinite (see discussion in the risk description
section 5.2.1.2 below).
Potential direct chronic risk from prometryn use to the terrestrial-phase CRLF are derived
by considering dietary-based exposures modeled in T-REX for a small bird (20g)
consuming small invertebrates (Table 5-5). Chronic risks are estimated using the lowest
available toxicity data for birds. EECs are divided by toxicity values to estimate chronic
dietary-based RQs. The chronic RQ calculated in T-REX does not exceed the Agency's
chronic risk LOG. Although prometryn is classified as practically non-toxc to birds on an
acute oral and subacute dietary exposure basis, there is uncertainty associated with the
indefinite acute oral LD50 and the subacute dietary LCso values; as such there is
uncertainty regarding the extent to which prometryn may directly affect the terrestrial-
phase of the CRLF. Further discussion is provided in the Risk Description (Section
5.2.1.2).
Table 5-5 Summary of Chronic RQs* Used to Estimate Direct Effects to the
Terrestrial-phase CRLF (non-granular application). Based on a Mallard Duck
NOAEC of 500 mg/kg-diet.
Use
Cotton
Cotton
Celery/ Fennel /Parsley
Dill
Application Rate (Ibs a.i./A)
2.4
0.7
2.0
1.6
Dietary-based Chronic RQ1
0.65
0.19
0.54
0.43
* Chronic risk LOG exceedances (chronic RQ > 1) are bolded and shaded.
1 Based on NOAEC = 500 ppm
78
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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 prometryn 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 (> 96.7 jig a.i./bee at which 10% mortality was
reported) by 1 bee/0.128g, which is based on the weight of an adult honey bee. EECs (jig
a.i./g of bee or ppm) calculated by T-REX for small and large insects are divided by the
calculated toxicity value for terrestrial invertebrates, which is >755|ig a.i./g bee. A probit
slope value for the acute honey bee toxicity test is not available; therefore, the effect
probability was calculated based on a default slope assumption of 4.5 with upper and
lower 95% confidence intervals of 2 and 9 (Urban and Cook, 1986). Since the LD50is an
indeterminate endpoint, however, the calculated effect probability and associated RQs
(not reported) are indefinite (see discussion in the risk description section 5.2.2.4). As a
result, indirect effects to the CRLF via reduction in terrestrial invertebrate prey items is
uncertain
5.1.2.2.2 Mammals
Risks associated with ingestion of small mammals by large terrestrial-phase CRLFs are
derived for dose-based exposures modeled in T-REX for a small mammal (15g)
consuming short grass. Potential acute and chronic risks 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. A probit slope
value for the acute oral toxicity in rat test is not available; therefore, the effect probability
was calculated based on a default slope assumption of 4.5 with upper and lower 95%
confidence intervals of 2 and 9 (Urban and Cook, 1986). Table 5-6 provides a summary
of acute and chronic RQs. Based on acute and chronic risk LOG exceedances, prometryn
may indirectly affect the CRLF via reductions in small mammal prey items.
79
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Table 5-6 Summary of Acute and Chronic RQs* Used to Estimate Indirect Effects
to the Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary
Food Items (non-granular application). Based on the maximum annual application
rate to cotton.
Use
Cotton
Cotton
Celery/
Fennel/
Parsley
Dill
Application
Rate (Ibs
a.i./A)
2.4
0.7
2.0
1.6
Chronic RQ
Dose-based
Chronic RQ1
384.4
112.1
320.4
256.3
Dietary-based
Chronic RQ2
57.6
16.8
48
38.4
Acute RQ
Dose-based
Acute RQ3
0.14
0.04
0.12
0.09
Probability of
Individual Effect
atRQ
Iinl.64xl04
(1 in 23 to 1 in
1.31 xlO14)
Iin6.33xl09
(1 in 386 to 1 in
7.49 x 1035)
Iin5.85xl04
(1 in 30.5 to 1 in
1.73 x 1016)
Iin7.91xl05
(1 in 54.8 to 1 in
4.10xl020)
* LOG exceedances (acute RQ > 0.1 and chronic RQ > 1) are bolded and shaded.
1 Based on dose-based EEC and prometryn rat NOAEL = 0.65 mg/kg-bw.
2 Based on dietary-based EEC and prometryn rat NOAEC = 10 mg/kg-diet.
3Based on dose-based EEC and prometryn rat acute oral LD50 = 1802 mg/kg-bw.
NOTE: Probability of Individual Effect at risk to ES acute LOC is 1 in 2.94 x 105 (95% C.I. 1 in 44 to 1
in8.86x!018).
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. See Section
5.1.2.1 and associated table (Table 5-5) for results. Based on the uncertainty associated
with the indefinite LDso/LCso values in the avian acute oral and subacute dietary studies,
prometryn may indirectly affect the CRLF via reduction in frogs as prey items. Further
discussion is provided in the Risk Description (Section 5.2.1.2).
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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 terrestrial plant seedling emergence and vegetative vigor
EC25 data. See Table 5-7 and Table 5-8, respectively, for monocot and dicot RQs. Based
on terrestrial plant risk LOG exceedances observed in both monocots and dicots,
prometryn may indirectly affect the CRLF via reduction in terrestrial plants.
Example output from TerrPlant v. 1.2.2 is provided in Appendix M.
Table 5-7 RQs* for Monocots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Prometryn via Runoff and Drift
Use
Cotton
Cotton
Cotton
Cotton
Celery/
Fennel/
Parsley
Dill
Application
rate
(Ibs a.i./A)
2.4
2.4
0.7
0.7
2.0
1.6
Application
method
Aerial1
Ground Spray2
Aerial1
Ground Spray2
Ground Spray2
Ground Spray2
Drift
Value
(%)
5
1
5
1
1
1
Spray drift
RQ
Non-Listed
2.45
0.49
0.71
0.14
0.41
0.33
Dry area
RQ
Non-Listed
2.69
1.47
0.79
0.43
1.22
0.98
Semi-aquatic
area RQ
Non-Listed
4.90
10.29
1.43
3.00
8.57
6.86
* Risk to non-listed terrestrial plant LOG exceedances (RQ > 1) are bolded and shaded.
Incorporation depth is 4 inches (10.2 cm) based on the label.
Incorporation depth is 1 .6 inches (4 cm) based on PRZM/EXAMS default. The TerrPlant default value of 1 was used.
Table 5-8 RQs* for Dicots Inhabiting Dry and Semi-Aquatic Areas Exposed to
Prometryn via Runoff and Drift
Use
Cotton
Cotton
Cotton
Cotton
Celery/
Fennel/
Parsley
Dill
Application
rate
(Ibs a.i./A)
2.4
2.4
0.7
0.7
2.0
1.6
Application
method
Aerial1
Ground Spray2
Aerial1
Ground Spray2
Ground Spray2
Ground Spray2
Drift
Value
(%)
5
1
5
1
1
1
Spray drift
RQ
Non-Listed
12
2.40
3.50
0.70
2
1.6
Dry area
RQ
Non-Listed
6.6
3.60
1.93
1.05
3
2.4
Semi-aquatic
area RQ
Non-Listed
12
25.2
3.50
7.35
21
16.8
* Risk to non-listed terrestrial plant LOG exceedances (RQ > 1) are bolded and shaded.
Incorporation depth is 4 inches (10.2 cm) based on the label.
Incorporation depth is 1 .6 inches (4 cm) based on PRZM/EXAMS default. The TerrPlant default value of 1 was used.
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5.1.3 Primary Constituent Elements of Designated Critical Habitat
5.1.3.1 Aquatic-Phase CRLF (Aquatic Breeding Habitat and Aquatic Non-
Breeding Habitat)
Three of the four assessment endpoints for the primary constituent elements (PCEs) of
designated critical habitat for the aquatic-phase 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 (aquatic-phase) and adult (terrestrial-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.
• Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
Based on the risk estimation for potential effects to aquatic non-vascular and vascular
plants as well as terrestrial plants provided in Sections 5.1.1.2.1, 5.1.1.3, and 5.1.2.3,
respectively, where plant risk LOG exceedances are observed in all aquatic non-vascular
plant scenarios (Table 5-2), aquatic vascular plant scenarios (Table 5-4), and terrestrial
plants (Tables 5-7, 5-8) prometryn may affect aquatic-phase CRLF PCEs of designated
habitat related to effects on aquatic and terrestrial plants.
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 prometryn on this PCE (i.e.., alteration of food sources), acute and chronic
freshwater fish and invertebrate toxicity endpoints, as well as endpoints for aquatic non-
vascular plants, are used as measures of potential effects. RQs for these endpoints were
calculated in Sections 5.1.1.1, 5.1.1.2, and 5.1.1.3. Based on exceedences observed for
most acute freshwater fish scenarios (Table 5-1) and all non-vascular plant scenarios
(Table 5-2), prometryn may affect aquatic-phase PCEs of designated habitat related to
effects of alteration of other chemical characteristics necessary for normal growth and
viability of CRLFs and their food source.
5.1.3.2 Terrestrial-Phase (Upland Habitat and Dispersal Habitat)
The first two assessment endpoints for PCEs of designated critical habitat for the
terrestrial-phase CRLF are related to potential effects to terrestrial plants:
• Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of terrestrial-phase CRLFs: Upland areas within 200 ft of the edge of the
riparian vegetation or dripline surrounding aquatic and riparian habitat that are
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comprised of grasslands, woodlands, and/or wetland/riparian plant species that
provides the CRLF shelter, forage, and predator avoidance
• Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal
The risk estimation for terrestrial-phase PCEs of designated habitat related to potential
effects on terrestrial plants is provided in Section 5.1.2.3. Based on risk to terrestrial plant
LOG exceedances observed in monocots and dicots (Tables 5-8, 5-9), prometryn may
affect the first and second terrestrial-phase CRLF PCEs.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the potential impact of prometryn on
this PCE, acute and chronic toxicity endpoints for birds, mammals, and terrestrial
invertebrates are used as measures of effects. RQs for these endpoints were calculated in
Section 5.1.2. Based on LOG exceedances observed for small mammals (Table 5-6) and
small insects (not reported), prometryn may affect the third terrestrial-phase CRLF PCE.
The fourth terrestrial-phase CRLF PCE is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. Direct chronic RQs for terrestrial-phase CRLFs are presented in Section 5.1.2.1.
Based on acute and chronic LOG exceedances estimated for small mammal RQs (Table
5-6) and potential effect on frogs as prey items (Section 5.1.2.2.3), prometryn may affect
the forth terrestrial-phase CRLF PCE.
5.1.4 Spatial Extent of Potential Effects
An LAA effects determination applies to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat.
To determine this area, the footprint of prometryn's use pattern is identified, using land
cover data that correspond to prometryn's use pattern. The spatial extent of the effects
determination also includes areas beyond the initial area of concern that may be impacted
by runoff and/or spray drift. The identified direct and indirect effects and/or effects to
critical habitat are anticipated to occur only for those currently occupied core habitat
areas, CNDDB occurrence sections, and designated critical habitat for the CRLF that
overlap with the initial area of concern plus a distance of 997 ft for aerial spray
applications (and 190 ft for ground spray applications) from its boundary. It is assumed
that non-flowing waterbodies (or potential CRLF habitat) are included within this area.
In addition to the spray drift buffer, the results of the downstream dilution extent analysis
result in a distance of 285 km which represents the maximum continuous distance of
downstream dilution from the edge of the initial area of concern. If any of these streams
reaches flow into CRLF habitat, there is potential to affect either the CRLF or affect its
habitat. These lotic aquatic habitats within the CRLF core areas and critical habitats
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potentially contain concentrations of prometryn sufficient to result in LAA determination
or effects to critical habitat.
The determination of the buffer distance and downstream dilution for spatial extent of the
effects determination is described below.
5.1.4.1 Spray Drift
In order to determine terrestrial and aquatic habitats of concern due to prometryn
exposures through spray drift, it is necessary to estimate the distance that spray
applications can drift from the treated area and still be present at concentrations that
exceed levels of concern. An analysis of spray drift distances was completed using all
available tools, including AgDrift, AGDISP, and the Gaussian extension to AGDISP.
Aerial and ground spray application are recommended for prometryn [Caparol (EPA Reg
No. 100-620), Cotton Pro (EPA Reg No. 1812-274), Prometryn 4L Herbicide (EPA Reg.
No. 9779-297) Prometryne + MSMA (EPA Reg, No. 9779-317). There are limited
mitigation measures for ground spray applications. For aerial applications, spray drift
management options are as follows:
• Applications should be made a maximum height of 10 feet.
• Applications should not be made at wind speeds exceeding 10 mph
• A 400-feet upwind spray drift buffer should be employed when sensitive non-
target plants are near the application site
• Coarse to Medium Droplet Size Spectrum should be used.
Tier 1 AgDrift (ver 2.1.03) modeling was used to estimate the impact of the 400 feet
buffer on terrestrial and aquatic EECs. Input parameters for Tier I AgDrift spray drift
modeling are shown in Table 5-9. Spray drift deposition concentrations for Tier I
AgDrift modeling are shown in Table 5-10. Provided the pesticide travels a distance of
400 ft from a point source, a 0.011 spray fraction of the applied concentration is expected
for aerial applications and a 0.0021 spray fraction of applied concentration is expected for
ground applications (according to Tier 1 AgDrift). The terrestrial plant RQs calculated in
TerrPlant based on the given aerial and ground spray fractions at 400 ft are shown in
Table 5-11. Non-listed terrestrial plant (dicot) LOCs are exceeded (for spray drift only)
for aerial spray applications of the maximum applied concentration (2.4 Ibs a.i./A) at 400
ft. Non-listed terrestrial plant LOCs are exceeded (for dry and semi-aquatic areas given
spray drift and runoff) for both aerial spray and ground spray applications of the
maximum applied concentration (2.4 Ibs a.i./A) at 400 ft. Given the most sensitive
terrestrial plant endpoint (0.01 Ibs a.i./A), the spray drift buffers beyond which LOG
exceedences are not expected are 997 ft for aerial spray applications and 190 ft for
ground spray applications. The calculated aerial spray buffer distance (997 ft) exceeds the
currently prescribed buffer distance (400 ft).
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Table 5-9: Input Parameters for Tier I AgDrift Modeling
Parameter
Droplet Spectrum
Application Rate
Input Value
Coarse to Medium
2.4 Ibs/A
Table 5-10: Tier 1 AgDrift Terrestrial and Aquatic EECs from Spray Drift Alone
Buffer Distance
(feet)
0
400
997
0
400
997
Spray
Method
Aerial
Aerial
Aerial
Ground
Ground
Ground
Maximum
Application Rate
(Ibs ai/A)
2.4
2.4
2.4
2.4
2.4
2.4
EECs
Terrestrial
(Ibs ai/A)
1.200
0.026
0.013
2.43
0.005
0.002
Aquatic
(HS/L)
11.993
1.207
0.699
2.218
0.227
0.092
Table 5-11: Terrestrial Plant RQs given aerial and ground spray fractions of the
maximum applied concentration (2.4 Ibs a.i./A on cotton) at 400 feet
Use
Cotton
Cotton
Cotton
Cotton
Application
rate
(Ibs a.i./A)
2.4
2.4
2.4
2.4
Application
method
Aerial1
Aerial1
Ground2
Ground2
Spray
Fractions
at 400 ft
0.011
0.011
0.0021
0.0021
Plant
Type
Monocot
Dicot
Monocot
Dicot
Spray
drift
RQ
0.54
2.64
0.10
0.50
Dry
area
RQ
0.78
1.92
1.08
2.65
Semi-
aquatic
area RQ
2.99
7.32
9.90
24.25
* Risk to non-listed terrestrial plant LOG exceedances (RQ > 1) are bolded and shaded.
Incorporation depth is 4 inches (10.2 cm) based on the label.
Incorporation depth is 1 .6 inches (4 cm) based on PRZM/EXAMS default. The TerrPlant default value of 1
was used.
Note: see Table 3-8 for EECs
Tier II AgDisp (ver 8.13) modeling was conducted to assess the impact of spray drift
mitigation recommendations for aerial spray applications. Input parameters for Tier II
AgDisp spray drift modeling are shown in Table 5-12. Spray drift deposition
concentrations from Tier II AgDisp modeling are shown in Table 5-13.
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Table 5-12: Input Parameters for Tier II AgDisp
Parameter
Aircraft
Release Height
DSD
Wind Speed
Temp
Relative Humidity
Spray Volume Rate
Active Fraction
Nonvol. Fraction
Input Value
Air tractor AT-401
10ft
Coarse to Medium
lOmph
650F
50%
5 gal/A
0.1056
0.24
Modeling
Table 5-13: Tier II AgDisp Terrestrial and Aquatic EECs from Aerial Spray Drift
Alone
Buffer Distance
(feet)
0
400
1000
Spray
Method
Aerial
Aerial
Aerial
Maximum
Application Rate
(Ibs ai/A)
2.4
2.4
2.4
EECs
Terrestrial
(Ibs ai/A)
6.1
0.04
0.0094
Aquatic
(HS/L)
3.546
0.611
0.083
5.1.4.2 Downstream Dilution Analysis
The downstream extent of exposure in streams and rivers is where the EEC could
potentially be above levels that would exceed the most sensitive LOG. To complete this
assessment, the greatest ratio of aquatic RQ to LOG was estimated. Using an assumption
of uniform runoff across the landscape, it is assumed that streams flowing through treated
areas (i.e. the initial area of concern) are represented by the modeled EECs; as those
waters move downstream, it is assumed that the influx of non-impacted water will dilute
the concentrations of prometryn present.
Using a ECso value of 1 ug/L for non-vascular aquatic plants (the most sensitive species)
and a maximum peak EEC of 377.3 ug/L for fall application to parsley yields an
RQ/LOC ratio of 377.3 (377.3/1). Using the downstream dilution approach (described in
more detail in Appendix D) yields a target percent crop area (PCA) of 0.27. This value
has been input into the downstream dilution approach and results in a distance of
kilometers which represents the maximum continuous distance of downstream dilution
from the edge of the initial area of concern. Similar to the spray drift buffer described
above, the LAA/NLAA determination is based on the area defined by the point where
concentrations exceed the ECso value.
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5.1.4.3 Overlap between CRLF habitat and Spatial Extent of Potential
Effects
An LAA effects determination is made to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat
and the area overlaps with the core areas, critical habitat and available occurrence data
for CRLF.
For prometryn, the use pattern in the land cover classes including cotton, celery, fennel,
parsley, and dill also includes areas beyond the initial area of concern that may be
impacted by runoff and/or spray drift overlaps with CRLF habitat. Appendix D provides
maps of the initial area of concern, along with CRLF habitat areas, including currently
occupied core areas, CNDDB occurrence sections, and designated critical habitat. It is
expected that any additional areas of CRLF habitat that are located 997 ft for aerial spray
applications (and 190 ft for ground spray applications) from boundary (to account for
offsite migration via spray drift) and 285 kilometers of stream reach (to account for
downstream dilution) outside the initial area of concern may also be impacted and are
part of the full spatial extent of the LAA/effects to critical habitat effects determinations.
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.
Based on the RQs presented in the Risk Estimation (Section 5.1) a preliminary overall
effects determination is "may affect" for the CRLF and "may affect" critical habitat.
The direct or indirect risk LOCs are exceeded or use may modify the PCEs of the
CRLF's critical habitat, the Agency concludes a preliminary "may affect" determination
for the FIFRA regulatory action regarding prometryn. A summary of the risk estimation
results are provided in Table 5- for direct and indirect effects to the CRLF and in Table
5-1 for the PCEs of designated critical habitat for the CRLF.
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Table 5-14 Risk Estimation Summary for Prometryn - Direct and Indirect Effects to
CRLF
Assessment Endpoint
LOC
Exceedances
(Y/N)
Description of Results of Risk Estimation
A qu atic-Ph use
(eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects
Survival, growth, and
reproduction of CRLF
individuals via direct effects
on aquatic phases
Acute: Y
Chronic: N
Acute risk to freshwater fish (and by extension to
aquatic-phase amphibians ) LOCs are exceeded
based on exposure estimates in all parsley uses
(Spring, Fall: 2 Ibs a.i./A) and most cotton uses
(Fall, pre-emergence ground spray and pre-
emergence aerial spray: 2.4 Ibs a.i./A).
No chronic risk LOCs are exceeded based on the
most sensitive toxicity data for freshwater fish
across any of the uses evaluated (Table 5-1).
Indirect Effects
Survival, growth, and
reproduction of CRLF
individuals via effects to food
supply (i.e., freshwater
invertebrates, non-vascular
plants)
Non-vascular
plants: Y
Risk to aquatic plant LOC are exceeded for non-
vascular aquatic plants in all uses. For a complete
list see Table 5-2.
Freshwater
invertebrates:
N
No acute nor chronic risk LOC exceedances are
observed for freshwater invertebrates.
Fish and
frogs: Y
The same description applies here for fish and frog
prey items as in the direct effects (aquatic-phase
CRLF) component above.
Indirect Effects
Survival, growth, and
reproduction of CRLF
individuals via effects on
habitat, cover, and/or primary
productivity (i.e., aquatic
plant community)
Y
Risk to aquatic plant LOCs are exceeded for
vascular aquatic plants in all uses. For a complete
list see Table 5-4.
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.
Y
Risk to terrestrial plant LOCs are exceeded for
monocots in dry and semi-aquatic areas for cotton
uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton
uses (aerial: 2.4 Ibs a.i./A). Dicots are more
sensitive as LOC exceedances are estimated in dry
and semi-aquatic areas for both application types on
cotton (ground and aerial spray at 2.4 Ibs a.i./A).
Terrestrial-Ph use
(Juveniles and adults)
Direct Effects
Survival, growth, and
reproduction of CRLF
individuals via direct effects
Acute: N
No definitive acute RQs could be derived because
the acute avian effects data shows no mortality at
the highest test concentrations.
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Assessment Endpoint
LOC
Exceedances
(Y/N)
Description of Results of Risk Estimation
on terrestrial phase adults and
juveniles
Chronic: N
Chronic risk LOC exceedances are not observed for
birds consuming small insects when considering the
maximum annual application rate to cotton (2.4 Ibs
a.i./A) in T-REX using dietary based RQs.
Y
Indirect Effects
Survival, growth, and
reproduction of CRLF
individuals via effects on
prey (i.e., terrestrial
invertebrates, small terrestrial
mammals and terrestrial
phase amphibians)
Acute risk to terrestrial invertebrate LOC
exceedances are observed for small insects for
cotton use (2.4 Ibs a.i./A). Small terrestrial
mammals may also be affected by prometryn as
acute and chronic risk LOC exceedances are
observed for small mammals serving as prey.
The same description applies here for frog prey
items as in the direct effects (terrestrial-phase
CRLF) component above.
Indirect Effects
Survival, growth, and
reproduction of CRLF
individuals via effects on
habitat (i.e., riparian
vegetation)
Y
The same description applies here as in the indirect
effects to riparian vegetation for the aquatic-phase
CRLF component above.
Table 5-15 Risk Estimation Summary for Prometryn - PCEs of Designated Critical
Habitat for the CRLF
Assessment Endpoint
Habitat Effects
(Y/N)
Description of Results of Risk Estimation
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
Non-vascular
aquatic plants:
Y
Risk to aquatic plant LOC exceedances are
observed for non-vascular aquatic plants in all uses.
For a complete list see Table 5-2.
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Assessment Endpoint
avoidance, and aquatic
dispersal for juvenile and
adult CRLFs.
Alteration in water
chemistry /quality including
temperature, turbidity, and
oxygen content necessary for
normal growth and viability
of juvenile and adult CRLFs
and their food source.
Alteration of other chemical
characteristics necessary for
normal growth and viability
of CRLFs and their food
source.
Reduction and/or
modification of aquatic-based
food sources for pre-
metamorphs (e.g., algae)
Habitat Effects
(Y/N)
Terrestrial
plants: Y
Same as above
Acute: Y
Chronic: N
Freshwater
Invertebrates:
N
Non-vascular
plants: Y
Description of Results of Risk Estimation
Risk to terrestrial plant LOCs are exceeded for
monocots in dry and semi-aquatic areas for cotton
uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton
uses (aerial: 2.4 Ibs a.i./A). Dicots are more
sensitive as LOG exceedances are estimated in dry
and semi-aquatic areas for both application types on
cotton (ground and aerial spray at 2.4 Ibs a.i./A).
Same as above
Acute risk to freshwater fish LOCs are exceeded for
all parsley uses (Spring, Fall: 2 Ibs a.i./A) and most
cotton uses (Fall, pre-emergence ground spray and
pre-emergence aerial spray: 2.4 Ibs a.i./A).
No chronic risk LOCs are exceeded based on the
most sensitive toxicity data for freshwater fish and
for any use type (Table 5-1).
Invertebrate risk LOG exceedances are not observed
for freshwater invertebrates.
Risk to aquatic plant LOG exceedances are
observed for non-vascular aquatic plants in all uses.
For a complete list see Table 5-2.
Terrestrial-Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or
disturbance of upland habitat;
ability of habitat to support
food source of CRLFs:
Upland areas within 200 ft of
the edge of the riparian
vegetation or dripline
surrounding aquatic and
riparian habitat that are
comprised of grasslands,
woodlands, and/or
wetland/riparian plant species
that provides the CRLF
shelter, forage, and predator
avoidance
Elimination and/or
disturbance of dispersal
habitat: Upland or riparian
Terrestrial
plants: Y
Same as
above
Risk to terrestrial plant LOCs are exceeded for
monocots in dry and semi-aquatic areas for cotton
uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton
uses (aerial: 2.4 Ibs a.i./A). Dicots are more
sensitive as LOG exceedances are estimated in dry
and semi-aquatic areas for both application types on
cotton (ground and aerial spray at 2.4 Ibs a.i./A).
Same as above
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Assessment Endpoint
Habitat Effects
(Y/N)
Description of Results of Risk Estimation
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
Y
Acute risk LOG exceedances are observed for small
insects for cotton use (2.4 Ibs a.i./A).
Alteration of chemical
characteristics necessary for
normal growth and viability
of juvenile and adult CRLFs
and their food source.
Y
Acute and chronic risk LOG exceedances are
observed (Table 5-6) for small mammals serving as
prey.
Following a "may affect" determination, additional information is considered to refine
the potential for exposure at the predicted levels based on the life history characteristics
(i.e., habitat range, feeding preferences, etc.) of the CRLF. Based on the best available
information, the Agency uses the refined evaluation to distinguish those actions that
"may affect, but are not likely to adversely affect" from those actions that are "likely to
adversely affect" the CRLF and its designated critical habitat.
The criteria used to make determinations that the effects of an action are "not likely to
adversely affect" the CRLF and its designated critical habitat include the following:
• Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where "take"
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.
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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 includes life stages of the frog that are obligatory aquatic organisms,
including eggs and larvae. It also includes submerged terrestrial-phase juveniles and
adults, which spend a portion of their time in water bodies that may receive runoff and
spray drift containing prometryn.
As shown in Table 5-1, acute RQs based on the highest modeled EECs for prometryn use
on all parsley (2.0 Ibs a.i./A), a fall celery/fennel (2.0 Ibs a.i./A), and two pre-emergence
cotton uses (2.4 Ib a.i./A) and the most sensitive acute freshwater fish data (i.e.., rainbow
trout; used as a surrogate for aquatic-phase amphibians) exceed the Agency's acute risk
to listed species LOG. Acute RQs for other modeled uses did not exceed Agency's acute
risk to listed species LOG. Similarly, chronic RQs based on parallel information (using
data on another aquatic-phase amphibian surrogate, i.e., the fathead minnow) are well
below the Agency's chronic risk LOG. The RQs are based on PRZM/EXAMS EECs.
Comparison of the highest modeled surface water EEC (peak = 377 |ig/L on parsley fall
application representing acute effects) with available NAWQA surface water monitoring
data from California indicates that the peak modeled EEC is approximately 607 times
higher than the maximum concentration of prometryn (0.621 ug/L) detected in Stanislaus
County. The lowest level at which the acute risk to listed species LOG exceedances were
observed was at a peak (acute effects) of 152.9 ug/L, which is 246 times higher than the
maximum concentration detected. Therefore, use of modeled EECs is assumed to provide
a conservative measure of prometryn exposures for aquatic-phase CRLFs.
The probability of an individual effect to aquatic-phase CRLFs was calculated based on
the acute rainbow trout study (MRID 00070686) reported slope, 3.4 (95% C.I. 1.99-4.83).
The corresponding estimated chance of an individual acute mortality to the aquatic-phase
CRLF at the highest RQ level of 0.13, for example, is 1 in 772 (with respective lower and
upper bounds of 1 in 26 to 1 in 1.07 x 105). Given the relatively high probability of an
individual mortality occurrence and acute RQs that are above the Agency's acute risk
LOG, prometryn is likely to cause direct adverse effects to aquatic-phase CRLFs.
There were no acceptable amphibian studies available in the ECOTOX open literature for
prometryn. Three freshwater aquatic incidents involving fish kills (carp, shad, buffalo,
and car) have been reported in 1996 in Richland County of Louisiana for which
prometryn is an 'unlikely' cause; additional chemicals were detected with presumably
higher toxicity to freshwater fish.
In summary, the Agency concludes a "likely to adversely affect" or "LAA" determination
for direct acute effects to the aquatic-phase CRLF, based on risk of acute mortality and
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all available lines of evidence. A "no effect" determination applies to direct chronic
effects to the aquatic-phase CRLF, via growth, based on all available lines of evidence.
5.2.1.2 Terrestrial-Phase CRLF
As stated in the risk estimation section (Section 5.1.2.1), the avian acute oral and
subacute dietary RQs were not estimated because the LDso and LCso values exceed the
maximum limit concentrations tested. The data indicate that prometryn is practically
non-toxic to birds on both an acute oral and subacute dietary exposure basis with no
mortalities at acute oral doses up to and including 4,640 mg/kg-bw (highest level tested)
in the acute oral study with mallard ducks (MRID 00082966) and one mortality at the
highest concentration level of 5,000 mg/kg-diet in the subacute dietary study with
Northern bobwhite quail (MRID 40457502). Observed sublethal effects for these studies
include reductions in feed consumption and body weight gain at the highest dose level of
the acute oral study (4,640 mg/kg-bw; NOAEL: 2,150 mg/kg-bw) and at the two highest
concentration levels (2,500 mg/kg-diet and 5,000 mg/kg-diet; NOAEC: 1,250 mg/kg-
diet) in the subacute dietary study.
Using the terrestrial model, T-REX (v. 1.4.1) and the highest dose level tested in the
acute oral study (4,640 mg/kg-bw with mallard ducks), the adjusted dose for a 20 g bird
would be 2,409 mg/kg-bw. For the use on cotton with a single application rate of 2.4 Ibs
a.i./A, the dose-based EEC for small birds feeding on small insects is 369 mg/kg-bw.
Comparing the two values, the highest dose tested in the acute oral avian study is 6.5
times higher than the estimated dose-based EEC for cotton (e.g., an estimated upper
bound RQ would be 0.15). The acute risk to listed birds LOG is 0.1. Therefore, on a
dose-basis, there is an uncertainty associated with potential mortality to endangered
species at levels above 2,409 mg/kg-bw for a 20 g bird consuming small insects. For the
uncertainty to be diminished (e.g.., for the upper bound RQ to be less than the acute risk
to listed species LOG of 0.1), either the highest dose level tested or the acute LD50 in the
acute oral study would have to be greater than 7,000 mg/kg-bw (3,635 mg/kg-bw for a 20
g bird).
In an effort to refine the acute dose-based risk estimates, the T-REX model was modified
to account for the lower metabolic rate and lower caloric requirement of amphibians
(compared to birds). Acute dose-based RQs were recalculated using the T-HERPS
(Version 1.0) model for small (1 g), medium (37 g), and large (238 g) frogs. For sample
T-HERPS output refer to Appendix K. Using this refinement, the highest acute dose-
based RQ is 0.05 for 37 g frogs eating small herbivorous mammals. This is less than the
acute LOG of 0.1 for listed species.
The T-REX model was used again to interpret potential sublethal effects. For sublethal
effects on a dose-basis, the NOAEL is 2,150 mg/kg-bw. This corresponds to an adjusted
dose of 1,116.3 mg/kg-bw for a 20 g bird. The dose-based EEC is 369 mg/kg-bw, which
is 3 times lower than the NOAEL for sublethal effects. Therefore, sublethal effects on a
dose-basis are not expected.
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In the subacute dietary study of Bobwhite quail, one mortality was observed at the
highest concentration level of 5,000 mg/kg-diet. The estimated dietary-based EEC for
cotton is 324 mg/kg, which is roughly 15 times lower than 5,000 mg/kg (e.g., the upper
bound subacute dietary based RQ would be 0.06). This value is less than the avian acute
risk to listed species LOG of 0.1. Sublethal effects were observed at concentration levels
of 2,500 mg/kg-diet and above with a NOAEC of 1,250 mg/kg-diet. It was noted in the
study that food avoidance was observed at the two highest concentration levels. The
dietary-based EEC is nearly 4 times less than the NOAEC for sublethal effects.
Therefore, based on the reported food avoidance at the levels with decreased body weight
and the fact that the EEC is 4 times lower than the NOAEC, sublethal effects on a sub-
acute dietary exposure basis are not considered likely.
The probabilities of an individual effect to terrestrial-phase CRLFs were not calculated
for the same reasons that RQs were not calculated.
The chronic toxicity study (MRID 41035901) with mallard ducks had one adult (parental)
mortality at the 250 mg/kg-diet level. Since this mortality did not appear to be dose-
related, it is not considered to be treatment-related. As stated in the risk estimation
section, the chronic RQ for birds following use on cotton is 0.65, which does not exceed
the Agency's avian chronic risk LOG of 1.
There were no acceptable amphibian studies available in the ECOTOX open literature for
prometryn. Similarly, no prometryn incidents have been reported involving terrestrial
organisms.
In summary, the Agency concludes a "may effect, not likely to adversely affect" or
"NLAA" determination for acute and chronic direct effects to the terrestrial-phase CRLF,
via mortality, growth, and fecundity, based on all available lines of evidence. The effects
are insignificant for the following reasons:
• There were no mortalities at the highest dose level tested in the avian acute oral
toxicity study. Using the highest dose tested in the model, T-HERPS, provides an
upper bound RQ that does not exceed the acute avian LOG for listed species.
• There was one mortality at the highest dietary concentration in the avian subacute
dietary toxicity study. Using the highest concentration tested to estimate an upper
bound RQ provides an RQ that does not exceed the acute risk to listed species
LOC for birds.
• Observed sublethal effects related to growth in both the acute oral study and the
subacute dietary study were observed at significantly higher dose and
concentration levels than the EECs provided in the T-REX model following use at
the maximum annual application rate used on cotton.
• The chronic RQ for birds following use on cotton does not exceed the chronic risk
to birds LOC.
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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. RQs were calculated
using the most sensitive non-vascular plant ECso (0.001 mg a.i./L) taken from a
freshwater diatom study (MRID 42620201) and EECs generated from PRZM/EXAMS.
Further examination of toxicity data for other non-vascular plants: green algae (0.012 mg
a.i./L), diatom (0.0076 mg a.i./L), and blue-green algae (0.0401 mg a.i./L) indicates that
they are approximately seven to forty times less sensitive to prometryn than the
freshwater diatom. As shown in Table 5-2, non-vascular plant RQs based on N.
pelliculosa exceed the Agency's risk to non-listed aquatic plants LOG for all uses.
Therefore, prometryn is likely to indirectly affect the CRLF via reduction in non-vascular
aquatic plants.
Not unlike the outcome for the direct effect to the aquatic-phase CRLF, comparison of
the highest modeled surface water EEC (peak = 377 jig/L on parsley fall application)
with available NAWQA surface water monitoring data from California indicates that the
peak modeled EEC is approximately 607 times higher than the maximum concentration
of prometryn (0.621 ug/L) detected in Stanislaus County. The lowest modeled surface
water EEC (peak = 49.2 ug/L on fall application on celery/fennel) is 79 times higher than
the maximum concentration. LOG exceedences were observed at all modeled EEC levels.
Therefore, use of modeled EECs is assumed to provide a conservative measure of
prometryn exposures for aquatic non-vascular plants.
Open literature data were not suitable for use in this assessment. No prometryn incidents
have been reported involving aquatic non-vascular plants.
In summary, based on all available lines of evidence the Agency concludes a "likely to
adversely affect" determination for indirect effects of prometryn to CRLF tadpoles, via
reductions in non-vascular plants.
5.2.2.2 Aquatic Invertebrates
The potential for prometryn 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.
RQs were calculated using the most sensitive freshwater invertebrate ECso (18.59 mg
a.i./L) and NOAEC (1.0 mg a.i./L) values taken from an acute toxicity to D. magna study
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(MRID 00070146) and a chronic toxicity to D. magna study (MRID 40573720),
respectively, as well as EECs generated from PRZM/EXAMS. The probability of an
individual effect to aquatic-phase CRLFs was calculated despite low RQs for all uses
modeled in PRZM/EXAMS (Table 5-3). The slope, 5.24 (95% C.I. 3.34-7.14), of the
dose-response curve used in calculating the probability was based on the acute toxicity
study with daphnids. Given that RQs were far below Agency's acute and chronic risk
LOCs as well as the low probabilities of individual effect, prometryn is not likely to
indirectly affect the CRLF via reduction in aquatic invertebrate prey items.
The range of EECs modeled for acute effects on aquatic invertebrates is 49.2-377.3 ug/L;
the range of EECs modeled for chronic effects is 48.4- 370 ug/L. These concentrations
are far above the maximum concentration found in surface water data (0.621 ug/L) and
yet no acute risk LOG exceedances were observed.
In summary, based on all available lines of evidence, the Agency concludes a "no effect"
determination for indirect effects to the CRLF via direct acute (mortality) and chronic
(growth, reproductive and/or survival) effects on freshwater invertebrates as prey.
5.2.2.3 Fish and Aquatic-phase Frogs
No endangered species chronic risk LOCs were exceeded for freshwater fish, which are
used as a surrogate for aquatic-phase amphibians. However, acute risk to listed species
LOCs is exceeded for freshwater fish. Given the relatively high probability of an
individual mortality occurrence and exceedance of acute RQs (refer to Section 5.2.1.1),
prometryn is likely to cause direct acute mortality to aquatic-phase CRLFs. Therefore,
indirect effects to the CRLF via a reduction in freshwater fish and other aquatic-phase
frog species as prey items may occur, and the effects determination for indirect acute
effects is "likely to adversely affect" or "LAA" while the determination for indirect
chronic effects is "no effect".
5.2.2.4 Terrestrial Invertebrates
When the terrestrial-phase CRLF reaches juvenile and adult stages, its diet is mainly
composed of terrestrial invertebrates. As previously discussed in Section 5.1.2.2, indirect
effects to the CRLF via reduction in terrestrial invertebrate prey items is uncertain
because the LD50is an indeterminate endpoint (i.e., >96.7 ug a.i./bee). The reported
mortality is 10% at this concentration. The indefinite RQs calculated for small insects
indicate exceedances of the Agency's LOG for terrestrial invertebrates for all modeled
uses (cotton 2.4 Ibs a.i./L; cotton 0.7; celery/fennel/parsley 2.0; dill 1.6) from <0.13 to <
0.43; the upper bound RQ for large insects is less than the LOG of 0.05. Small insects
are, therefore, more likely to be affected by prometryn as the probability of individual
effect for the highest application rate modeled (cotton 2.4 Ibs a.i./A) is relatively high (1
in 20.2, with respective lower and upper bounds of 1 in 4 to 1 in 2,060); the lowest
application rate modeled (cotton 0.7 Ibs a.i./A) yielded a lower probability of individual
effect (1 in 29,900, with respective lower and upper bounds of 1 in 26 to 1 in 1.31 x
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1015). A probit slope value for the acute honey bee toxicity test was not available;
therefore, the effect probability was calculated based on a default slope assumption of 4.5
with upper and lower 95% confidence intervals of 2 and 9 (Urban and Cook, 1986).
Given LOG exceedance and high probability of individual effect, especially for small
insects, prometryn is likely to indirectly affect the terrestrial-phase CRLF via reduction in
terrestrial invertebrate prey items.
No prometryn incidents have been reported involving terrestrial invertebrates.
Given that upper bound RQs for large insects do not exceed Agency's LOG for terrestrial
invertebrates and that the probabilities of individual effect are low (on the order of 108 for
the highest application rate modeled), a "may affect, not likely to adversely affect"
determination is given for large insects. However, given that RQs for small insects
exceed Agency's LOG for terrestrial invertebrates and that the probabilities of individual
effect are high (especially for the highest application rate modeled), a "likely to adversely
effect" determination is given for small insects, with uncertainty associated with potential
mortality at LCso- In summary, based on available lines of evidence the Agency
concludes a "likely to adversely affect" or "LAA" determination for indirect effects to the
CRLF, via a reduction in terrestrial invertebrates.
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 in Section 5.1.2.2.2,
indirect effects to the CRLF via reduction in terrestrial mammal prey items that are
exposed to prometryn are expected. Both chronic dose-based and dietary-based RQs
greatly exceed the Agency's chronic risk LOG for terrestrial mammals for all uses (Table
5-7). Similarly, the acute dose-based RQ exceeds the Agency's acute risk LOG for cotton
(2.4 Ibs a.i./A) and celery/fennel/parsley (2.0 Ibs a.i./A). In addition, the probability of
individual effect is relatively high for the highest application rate modeled (i.e., 1 in 1.64
x 104, with respective lower and upper bounds of 1 in 23 to 1 in 1.31 x 1014). A probit
slope value for the acute rat toxicity test was not available; therefore, the effect
probability was calculated based on a default slope assumption of 4.5 with upper and
lower 95% confidence intervals of 2 and 9 (Urban and Cook, 1986). Given the LOG
exceedances for acute and chronic effects and the relatively high probability of individual
effect, prometryn is likely to indirectly affect the CRLF via reduction in terrestrial
mammal prey items.
No prometryn incidents have been reported involving mammals.
In summary, based on available lines of evidence the Agency concludes a "likely to
adversely affect" or "LAA" determination for indirect effects to the terrestrial-phase
CRLF via reduction in small mammals as prey through acute and chronic exposure.
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5.2.2.6 Terrestrial-phase Amphibians
Terrestrial-phase adult CRLFs also consume frogs. RQ values representing direct
exposures of prometryn to terrestrial-phase CRLFs are used to represent exposures of
prometryn to frogs in terrestrial habitats. Based on estimated exposures resulting from
ground spray and aerial use of prometryn, acute and chronic risks to frogs are not likely
(refer back to section 5.2.1.2 for a more detailed discussion). In light of the lack of risk to
listed species LOG exceedances for the avian acute oral endpoint (T-HERPS) and the
subacute and chronic dietary endpoints (T-REX), 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 prometryn, is "may effect, not likely to adversely affect" or
"NLAA".
5.2.3 Indirect Effects (via Habitat Effects)
5.2.3.1 Aquatic Plants (Non-vascular and 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 as attachment sites and refugia for
many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In
addition, vascular plants also provide primary productivity and oxygen to the aquatic
ecosystem. Rooted plants help reduce sediment loading and provide stability to
nearshore areas and lower streambanks. In addition, vascular aquatic plants are important
as attachment sites for egg masses of CRLFs.
Potential indirect effects to the CRLF based on impacts to habitat and/or primary
production were assessed using RQs from freshwater aquatic vascular and non-vascular
plant data. As discussed in Section 5.2.2.1, non-vascular plant RQs based onN.
pelliculosa toxicity to prometryn and EEC estimates from PRZM/EXAMS exceed the
Agency's risk to aquatic plant LOG for all uses. Similarly, vascular plant RQs (Table 5-4)
based on the sensitivity of L. gibba to prometryn and EEC estimates from
PRZM/EXAMS exceed the Agency's risk to aquatic plant LOG for all uses. Therefore,
prometryn is likely to indirectly affect the CRLF via reduction in both non-vascular and
vascular aquatic plants.
Not unlike the outcome for the direct effect to the aquatic phase CRLF, comparison of the
highest modeled surface water EEC (peak = 377.3 |ig/L on parsley fall application) with
available NAWQA surface water monitoring data from California indicates that the peak
modeled EEC is approximately 607 times higher than the maximum concentration of
prometryn (0.621 ug/L) detected in Stanislaus County. The lowest modeled surface
water EEC (peak = 49.2 ug/L on fall application on celery/fennel) is 79 times higher than
the maximum concentration. LOG exceedences were observed at all modeled EEC levels
for both aquatic vascular and non-vascular plants. Therefore, use of modeled EECs is
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assumed to provide a conservative measure of prometryn exposures for aquatic vascular
and non-vascular plants.
No prometryn incidents have been reported involving aquatic vascular and non-vascular
plants.
In summary, based on all available lines of evidence, the Agency concludes a "likely to
adversely affect" or "LAA" determination for indirect effects of prometryn to the CRLF
via impacts to habitat and/or primary production through direct effects to non-vascular
and vascular aquatic plants.
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. Terrestrial plants also provide energy to the terrestrial ecosystem through
primary production. Upland vegetation including grassland and woodlands provides
cover during dispersal. Riparian vegetation helps to maintain the integrity of aquatic
systems by providing bank and thermal stability, serving as a buffer to filter out sediment,
nutrients, and contaminants before they reach the watershed, and serving as an energy
source.
Loss, destruction, and alteration of habitat were identified as a threat to the CRLF in the
USFWS Recovery Plan (USFWS, 2002). Herbicides can adversely impact habitat in a
number of ways. In the most extreme case, herbicides in spray drift and runoff from the
site of application have the potential to kill (or reduce growth and/or biomass in) all or a
substantial amount of the vegetation, thus removing or impacting structures which define
the habitat, and reducing the functions (e.g., cover, food supply for prey base) provided
by the vegetation.
Risk to terrestrial plant LOCs are exceeded for monocots in dry and semi-aquatic areas
for highest application cotton uses (ground: 2.4 Ibs a.i./A) and in dry and semi-aquatic
areas as well as spray drift alone for highest application cotton uses (aerial: 2.4 Ibs a.i./A;
Table 5-7). Dicots are more sensitive as LOG exceedances are estimated in dry and semi-
aquatic areas for both application types on cotton (ground and aerial spray at 2.4 Ibs
a.i./A; Table 5-8). Therefore, based on LOG exceedances observed for both monocots
and dicots, prometryn is likely to indirectly affect the CRLF via reduction in terrestrial
plants.
Based on the available toxicity data for terrestrial plants, it appears that emerged monocot
seedlings are more sensitive to prometryn in the seedling emergence test than monocot
plants in the vegetative vigor test. This is demonstrated by the difference in monocot
response in the two guideline studies. For example, the oat (a monocot) EC25 values for
the seedling emergence and vegetative vigor tests are 0.049 Ibs a.i./A and 1.4 Ibs a.i./A,
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respectively, representing almost a 26-fold difference in sensitivity (Table 4-5). Dicots
show reverse levels of sensitivity in the seedling emergence versus the vegetative vigor
toxicity tests. For example, the lettuce (a dicot) £€25 values for seedling emergence and
vegetative vigor tests are 0.025 Ibs a.i./A and 0.01 Ibs a.i./A, respectively, representing
over a 2-fold difference in sensitivity (Table 4-5). In addition, it is likely the case that the
cucumber is a more sensitive dicot tested in the vegetative vigor study. However, the
endpoint values obtained for this species are considered invalid and were not used in the
assessment. Nevertheless, LOG exceedances were observed at the highest concentration
(use on cotton at 2.4 Ibs a.i./A) with the next most sensitive dicot species (lettuce) based
on the results of the vegetative vigor study.
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 a canopy
of mature trees. Frogs spend a considerable amount of time resting and feeding in
riparian vegetation; the moisture and cover of the riparian plant community provides
good foraging habitat, and may facilitate dispersal in addition to providing pools and
backwater aquatic areas for breeding (USFWS, 2002). According to Hayes and Jennings
(1988), the CRLF tends to occupy waterbodies with dense riparian vegetation including
willows (Salix sp.). Upland habitat includes grassland and woodlands, as well as
scrub/shrub habitat. While no guideline data are available on the toxicity of woody
plants, the available toxicity information from the open literature (Ref # 41006,
Kozlowski & Torrie 1965) indicates prometryn has a greater effect on red pine (Pinus
resinosa Ait.) seedling survival and dry-weight production than it does on seedling
germination. The effect of prometryn (incorporation into soil) on percent germination did
not differ greatly from the control at the given time steps for which germination was
observed (i.e., 33, 43, and 73 days). The effect of prometryn (incorporation into soil) on
survival and dry-weight production was more severe; prometryn killed all seedlings by
110 days after planting at the highest doses (8 and 16 Ibs/A) tested and only 14.1% and
10.9% of seedlings survived in the 2 and 4 Ibs/A treatments, respectively. Sublethal
effects included slight needle curling, chlorosis, and growth inhibition. Prometryn led to
significant reductions in total dry-weight production of seedlings relative to controls. In
addition to the negative effect on seedling survival and dry-weight production, the study
suggests that, soil incorporated prometryn is more toxic than surface-applied prometryn.
Therefore, prometryn may potentially have a negative effect on terrestrial woody plant
species.
Six prometryn incidents have been reported for terrestrial plants. An incident on 86 acres
of corn lists prometryn as a 'probable' cause of plant damage via carryover, or the
presence of residues from an application made in a previous growing season, of a
broadcast application. The remaining five incidents are on cotton. Two incidents list
prometryn as a 'possible' cause of cotton plant loss on 600 and 1,424 acres via direct
treatment. One incident lists prometryn as a 'probable' cause of plant damage on 48 acres
of cotton via direct treatment using broadcast application. Two remaining incidents list
prometryn as a 'possible' cause of plant damage on 26 and 60 acres of cotton via direct
treatment using band application. The latter three cotton incidents utilizing broadcast and
band applications were all 'registered uses' of the compound.
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In summary, based on all available lines of evidence the Agency concludes a "likely to
adversely affect" or "LAA" determination for indirect effects of prometryn to the CRLF
via adverse, direct effects to herbaceous terrestrial vegetation, which provides habitat and
cover for the CRLF and its prey.
5.2.4 Effects to Designated Critical Habitat
5.2.4.1 Aquatic-Phase PCEs
Three of the four assessment endpoints for the primary constituent elements (PCEs) of
designated critical habitat for the aquatic-phase 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).
Conclusions for potential indirect effects to the CRLF via direct effects to aquatic and
terrestrial plants are used to determine whether effects 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 affected via prometryn-related impacts
to non-vascular and vascular aquatic plants as food items for tadpoles and habitat for
aquatic-phase CRLFs. Prometryn uses that may result in effects to critical habitat via
direct effects to non-vascular (Section 5.1.1.2.1) and vascular aquatic plants (Section
5.1.1.3) include applications on celery/fennel (2.0 Ibs a.i./A), parsley (2.0 Ibs a.i./A), and
cotton (2.4 Ibs a.i./A). In addition, based on ground spray and aerial applications of
prometryn on cotton (Section 5.1.2.3) critical habitat may be affected by a reduction in
herbaceous riparian vegetation (Section 5.2.3.2) that provides for shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile and adult aquatic-phase CRLFs.
Therefore, there is a potential for habitat effects via impacts to aquatic and terrestrial
plants.
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 is 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 potential effects. As
discussed in Section 5.2.1.1, direct effects to the aquatic-phase CRLF are expected for
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certain prometryn uses. In addition, prometryn-related effects to freshwater fish as food
items are also likely to occur (see Sections 5.2.2.3) even though prometryn-related effects
to freshwater invertebrates as food items are not likely to occur (see Section 5.2.2.2).
Therefore, prometryn may affect critical habitat by altering chemical characteristics
necessary for normal growth and viability of aquatic-phase CRLFs along with potential
effects on the availability of some of their non-plant food sources.
5.2.4.2 Terrestrial-Phase PCEs
Two of the four assessment endpoints for the PCEs of designated critical habitat for the
terrestrial-phase 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, effects to critical habitat may occur via prometryn-related impacts to
sensitive herbaceous terrestrial vegetation (Section 5.2.3.2), which provides habitat,
cover, and a means of dispersal for the terrestrial-phase CRLF and its prey, based on
ground spray and aerial applications of prometryn at the maximum annual application
rate used on cotton.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of prometryn 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 affected via a reduction in small insects and mammals as food
items.
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics that are
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 to the terrestrial-phase CRLF
are possible but not likely and chronic reproductive effects are not expected. As
discussed in Sections 5.2.2.4, 5.2.2.5, and 5.2.2.6, indirect effects to the terrestrial-phase
CRLF are expected via potential reduction in small insect and mammalian species as
food items. Therefore, the ability of prometryn to affect critical habitat by altering
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chemical characteristics that are necessary for normal growth and viability of terrestrial-
phase CRLF directly is not likely. However, prometryn may affect critical habitat by
altering chemical characteristics that are necessary for normal growth and viability of
small insect and mammalian food sources.
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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 Prometryn
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
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of exposure to aquatic-phase CRLFs. In addition, the Services agree that the existing
EXAMS pond represents the best currently available approach for estimating aquatic
exposure to pesticides (U.S. FWS/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 prometryn
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
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potential prometryn use areas. A comparison of NAWQA monitoring data and
PRZM/EXAMS modeling indicate the modeling estimates are approximately 600 X
greater than the available monitoring data.
PRZM/EXAMS modeling indicates accumulation of prometyrn in the pond due to the
high persistence of prometyrn and the static hydrology in the standard pond. This
accumulation limits the ability to define reliable 1 in 10 year EECs because of temporal
autocorrelation. However, the use of 1-in-10-year EEC provides a conservative estimate
of exposure because it represents -27 years of accumulation.
6.1.3 Potential Groundwater Contributions to Surface Water Chemical
Concentrations
Although the potential impact of discharging groundwater on CRLF populations is not
explicitly delineated, it should be noted that groundwater could provide a source of
pesticide to surface water bodies - especially low-order streams, headwaters, and
groundwater-fed pools. This is particularly likely if the chemical is persistent and
mobile. Soluble chemicals that are primarily subject to photolytic degradation will be
very likely to persist in groundwater, and can be transportable over long distances.
Similarly, many chemicals degrade slowly under anaerobic conditions (common in
aquifers) and are thus more persistent in groundwater. Much of this groundwater will
eventually be discharged to the surface - often supporting stream flow in the absence of
rainfall. Continuously flowing low-order streams in particular are sustained by
groundwater discharge, which can constitute 100% of stream flow during baseflow (no
runoff) conditions. Thus, it is important to keep in mind that pesticides in groundwater
may have a major (detrimental) impact on surface water quality, and on CRLF habitats.
SciGrow may be used to determine likely 'high-end' groundwater vulnerability, with the
assumption (based upon persistence in sub- and anoxic conditions, and mobility) that
much of the compound entering the groundwater will be transported some distance and
eventually discharged into surface water. Although concentrations in a receiving water
body resulting from groundwater discharge cannot be explicitly quantified, it should be
assumed that significant attenuation and retardation of the chemical will have occurred
prior to discharge. Nevertheless, groundwater could still be a significant consistent
source of chronic background concentrations in surface water, and may also add to
surface runoff during storm events (as a result of enhanced groundwater discharge
typically characterized by the 'tailing limb' of a storm hydrograph).
6.1.4 Action Area Uncertainties
An example of an important simplifying assumption that may require future refinement is
the assumption of uniform runoff characteristics throughout a landscape. It is well
documented that runoff characteristics are highly non-uniform and anisotropic, and
become increasingly so as the area under consideration becomes larger. The assumption
made for estimating the aquatic action area (based on predicted in-stream dilution) was
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that the entire landscape exhibited runoff properties identical to those commonly found in
agricultural lands in this region. However, considering the vastly different runoff
characteristics of: a) undeveloped (especially forested) areas, which exhibit the least
amount of surface runoff but the greatest amount of groundwater recharge; b)
suburban/residential areas, which are dominated by the relationship between
impermeable surfaces (roads, lots) and grassed/other areas (lawns) plus local drainage
management; c) urban areas, that are dominated by managed storm drainage and
impermeable surfaces; and d) agricultural areas dominated by Hortonian and focused
runoff (especially with row crops), a refined assessment should incorporate these
differences for modeled stream flow generation. As the zone around the immediate
(application) target area expands, there will be greater variability in the landscape; in the
context of a risk assessment, the runoff potential that is assumed for the expanding area
will be a crucial variable (since dilution at the outflow point is determined by the size of
the expanding area). Thus, it important to know at least some approximate estimate of
types of land use within that region. Runoff from forested areas ranges from 45 -
2,700% less than from agricultural areas; in most studies, runoff was 2.5 to 7 times higher
in agricultural areas ( Okisaka et al. 1997; Karvonen et al. 1999; McDonald et al. 2002;
Phuong and van Dam 2002). Differences in runoff potential between urban/suburban
areas and agricultural areas are generally less than between agricultural and forested
areas. In terms of likely runoff potential (other variables - such as topography and
rainfall - being equal), the relationship is generally as follows (going from lowest to
highest runoff potential):
Three-tiered forest < agroforestry < suburban < row-crop agriculture < urban.
There are, however, other uncertainties that should serve to counteract the effects of the
aforementioned issue. For example, the dilution model considers that 100% of the
agricultural area has the chemical applied, which is almost certainly a gross over-
estimation. Thus, there will be assumed chemical contributions from agricultural areas
that will actually be contributing only runoff water (dilutant); so some contributions to
total contaminant load will really serve to lessen rather than increase aquatic
concentrations. In light of these (and other) confounding factors, Agency believes that
this model gives us the best available estimates under current circumstances.
6.1.5 Usage Uncertainties
County-level usage data were obtained from California's Department of Pesticide
Regulation Pesticide Use Reporting (CDPR PUR) database. Eight years of data (1999 -
2006) 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.
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The CPDR PUR data does not include home owner 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.
6.1.6 Terrestrial Exposure Modeling of Prometryn
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%
(U.S. EPA 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.
Given that no data on interception and subsequent dissipation from foliar surfaces is
available for prometryn, a default foliar dissipation half-life of 35 days was used based on
the work of Willis and McDowell (1987). In addition, the highest application rate (2.4
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Ibs a.i./A) on cotton at pre-plant incorporation (Reg No. 100-620, 9779-297, 10163-94,
34704-692, 66222-15) was used in T-REX to calculate the most conservative estimates of
the risk quotients. Dill, parsley, celery/fennel, and even other cotton uses all have
application rates below this value. Therefore, the risk quotient calculations are
representative of the upper bound estimates of risk to the CRLF. It should be noted,
however, that the CRLF may potentially be exposed to prometryn via other routes such as
through the skin or via ingestion of drinking water contaminated with prometryn.
However, there are no approved methods or models available to the Agency for
characterizing these routes of exposure. The T-REX model is assumed to provide a
reasonable representation of exposure and risk, given the best available information and
associated uncertainties that may lead to an overestimation and an underestimation of
risk.
Guideline studies generally evaluate toxicity to ten agricultural 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 prometryn, 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.
6.1.7 Spray Drift Modeling
Although there may be multiple prometryn applications at a single site, 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
prometryn from multiple applications, each application of prometryn would have to occur
under identical atmospheric conditions (e.g., same wind speed and - for plants - same
wind direction) and (if it is an animal) the animal being exposed would have to be present
directly downwind at the same distance after each application. Although there may be
sites where the dominant wind direction is fairly consistent (at least during the relatively
quiescent conditions that are most favorable for aerial spray applications), it is
nevertheless highly unlikely that plants in any specific area would receive the maximum
amount of spray drift repeatedly. It appears that in most areas (based upon available
meteorological data) wind direction is temporally very changeable, even within the same
day. Additionally, other factors, including variations in topography, cover, and
meteorological conditions over the transport distance are not accounted for by the
AgDRIFT/AGDISP model (i.e.., it models 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/AGDISP may
overestimate exposure even from single applications, especially as the distance increases
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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 often made regarding the droplet size distributions being modeled ('ASAE Very Fine
to Fine' for orchard uses and 'ASAE Very Fine' for agricultural uses), the application
method (e.g.., aerial), release heights and wind speeds. Alterations in any of these inputs
would change 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).
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 or open literature studies on prometryn are not available for frogs
or any other aquatic-phase amphibian; therefore, freshwater fish are used as surrogate
species for aquatic-phase amphibians. Therefore, endpoints based on freshwater fish
ecotoxicity data are assumed to be protective of potential direct effects to aquatic-phase
amphibians including the CRLF, and extrapolation of the risk conclusions from the most
sensitive tested species to the aquatic-phase CRLF is likely to overestimate the potential
risks to those species. Efforts are made to select the organisms most likely to be affected
by the type of compound and usage pattern; however, there is an inherent uncertainty in
extrapolating across phyla. In addition, the Agency's LOCs are intentionally set very
low, and conservative estimates are made in the screening level risk assessment to
account for these uncertainties.
6.2.3 Sublethal Effects
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 is
exercised on a case-by-case basis and only after careful consideration of the nature of the
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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. To the extent to which sublethal effects are not considered
in this assessment, the potential direct and indirect effects of prometryn 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
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.
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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 prometryn to the CRLF and its
designated critical habitat.
Based on the best available information, the Agency makes a "Likely to Adversely
Affect" determination for the CRLF from the use of prometryn. The Agency has
determined that there is a potential for effects to CRLF designated critical habitat from
the use of the chemical. A description of the baseline status and cumulative effects for
the CRLF is provided in Attachment 2.
The LAA effects determination applies to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat.
To determine this area, the footprint of prometryn's use pattern is identified, using land
cover data that correspond to prometryn's use pattern. The spatial extent of the LAA
effects determination also includes areas beyond the initial area of concern that may be
impacted by runoff and/or spray drift. The identified direct and indirect effects and
modification to critical habitat are anticipated to occur only for those currently occupied
core habitat areas, CNDDB occurrence sections, and designated critical habitat for the
CRLF that overlap with the initial area of concern plus 997 ft for aerial spray applications
(and 190 ft for ground spray applications) from its boundary (refer to analysis in Section
5.1.4). It is assumed that non-flowing waterbodies (or potential CRLF habitat) are
included within this area.
In addition to the spray drift buffer, the results of the downstream dilution extent analysis
result in a distance of 285 km which represents the maximum continuous distance of
downstream dilution from the edge of the initial area of concern (refer to analysis in
Section 5.1.4). If any of these streams reaches flow into CRLF habitat, there is potential
to affect either the CRLF or modify its habitat. These lotic aquatic habitats within the
CRLF core areas and critical habitats potentially contain concentrations of prometryn
sufficient to result in LAA determination or effects to critical habitat.
Appendix D provides maps of the initial area of concern, along with CRLF habitat areas,
including currently occupied core areas, CNDDB occurrence sections, and designated
critical habitat. It is expected that any additional areas of CRLF habitat that are located
997 ft for aerial spray applications (and 190 ft for ground spray applications) (to account
for offsite migration via spray drift) and 285 km of stream distance (to account for
downstream dilution) outside the initial area of concern may also be impacted and are
part of the full spatial extent of the LAA/effects to critical habitat determinations.
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 Error!
Reference source not found, and Error! Reference source not found..
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Table 7-1. Effects Determination Summary for Prometryn Use and the CRLF
Assessment
Endpoint
Survival, growth,
and/or reproduction
of CRLF
individuals
Effects
Determination 1
LAA1
Basis for Determination
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Acute risk to freshwater fish LOCs are exceeded for all parsley uses (Spring,
Fall: 2 Ibs a.i./A) and most cotton uses (Fall, pre-emergence ground spray
and pre-emergence aerial spray: 2.4 Ibs a.i./A).
No chronic risk LOCs are exceeded based on the most sensitive toxicity data
for freshwater fish across any of the evaluated uses (Table 5-1).
Terrestrial-phase (Juveniles and Adults):
Prometryn is practically non-toxic to birds on an acute oral and sub-acute
dietary exposure basis and as such, the studies did not provide definitive
toxicity endpoints. No mortality was observed in the acute oral study and
only a single mortality was observed in the sub-acute dietary toxicity study
and the mortality was not considered treatment-related.
There are no chronic risk LOG exceedances for birds consuming small
insects at the maximum annual application rate for prometryn (2.4 Ibs a.i./A
to cotton) in T-REX using dietary-based RQs.
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
Risk to aquatic plant LOG exceedances are observed for non-vascular and
vascular aquatic plants for all uses. For a complete list see Table 5-2, 5-4.
Acute risk LOG exceedances are not observed for freshwater invertebrates.
The same finding applies here for fish and frog prey items as in the direct
effects (aquatic-phase CRLF) component above.
Terrestrial prey items, riparian habitat
Risk to terrestrial invertebrate LOG exceedances are observed for small
insects at the maximum annual application rate for cotton (2.4 Ibs a.i./A).
Small terrestrial mammals are also potentially affected by prometryn as
acute and chronic risk LOG exceedances are observed for small mammals.
The same description applies here for frog prey items as in the direct effects
(terrestrial-phase CRLF) component above.
Risk to terrestrial plant LOCs are exceeded for monocots in dry and semi-
aquatic areas for cotton uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton uses (aerial: 2.4 Ibs a.i./A).
Dicots are more sensitive as LOG exceedances are estimated in dry and semi-
aquatic areas for both application types on cotton (ground and aerial spray at
2.4 Ibs a.i./A).
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely
affect (LAA)
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Table 7-2. Effects Determination Summary for Prometryn Use and CRLF Critical
Habitat Impact Analysis
Assessment
Endpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
Habitat Effects
Modification of
terrestrial-phase
PCE
Risk to terrestrial plant LOCs are exceeded for monocots in dry and semi-
aquatic areas for cotton uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton uses (aerial: 2.4 Ibs
a.i./A). Dicots are more sensitive as LOG exceedances are estimated in dry
and semi-aquatic areas for both application types on cotton (ground and
aerial spray at 2.4 Ibs a.i./A).
Risk to aquatic plant LOG exceedances are observed for non-vascular and
vascular plants for all uses.
Acute risk to freshwater fish LOCs are exceeded for all parsley uses
(Spring, Fall: 2 Ibs a.i./A) and most cotton uses (Fall, pre-emergence
ground spray and pre-emergence aerial spray: 2.4 Ibs a.i./A). No chronic
risk LOCs are exceeded based on the most sensitive toxicity data for
freshwater fish and for any evaluated use.
Acute and chronic risk LOG exceedances are not observed for freshwater
invertebrates.
Risk to terrestrial plant LOCs are exceeded for monocots in dry and semi-
aquatic areas for cotton uses (ground: 2.4 Ibs a.i./A) and in dry and semi-
aquatic areas as well as spray drift alone for cotton uses (aerial: 2.4 Ibs
a.i./A). Dicots are more sensitive as LOG exceedances are estimated in dry
and semi-aquatic areas for both application types on cotton (ground and
aerial spray at 2.4 Ibs a.i./A).
No definitive acute RQs could be derived because the acute avian effects
data shows no mortality at the highest test concentrations. Chronic risk LOG
exceedances are not observed for birds consuming small insects when
considering a cotton application (2.4 Ibs a.i./A) in T-REX using dietary
based RQs. This direct effects description applies for frog prey items as an
indirect effect on the CRLF.
Risk to terrestrial invertebrate LOG exceedances are observed for small
insects at the maximum annual application rate for cotton (2.4 Ibs a.i./A).
Small terrestrial mammals are also affected by prometryn as acute and
chronic risk LOG exceedances are observed for small mammals.
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
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distance away from the treated field or site of application. Evaluation of the implication
of this non-uniform distribution of risk to the species would require information and
assessment techniques that are not currently available. Examples of such information and
methodology required for this type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages within
specific recovery units and/or designated critical habitat within the action area.
This information would allow for quantitative extrapolation of the present risk
assessment's predictions of individual effects to the proportion of the population
extant within geographical areas where those effects are predicted. Furthermore,
such population information would allow for a more comprehensive evaluation of
the significance of potential resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic- and
terrestrial-phase frogs. While existing information provides a preliminary picture
of the types of food sources utilized by the frog, it does not establish minimal
requirements to sustain healthy individuals at varying life stages. Such
information could be used to establish biologically relevant thresholds of effects
on the prey base, and ultimately establish geographical limits to those effects.
This information could be used together with the density data discussed above to
characterize the likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the pesticide.
Currently, methodologies are limited to predicting exposures and likely levels of
direct mortality, growth or reproductive impairment immediately following
exposure to the pesticide. The degree to which repeated exposure events and the
inherent demographic characteristics of the prey population play into the extent to
which prey resources may recover is not predictable. An enhanced understanding
of long-term prey responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and together
with the information described above, a more complete prediction of effects to
individual frogs and potential modification to critical habitat.
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8 References
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the Draft California Red-legged Frog Recovery Plan.
Altig, R.; R.W. McDiarmid. 1999. Body Plan: Development and Morphology. In R.W.
McDiarmid and R. Altig (Eds.), Tadpoles: The Biology ofAnuran Larvae.
University of Chicago Press, Chicago, pp. 24-51.
Cessna, AJ. 2008. Nonbiological Degradation ofTriazine Herbicides: Photolysis and
Hydrolysis. Chapter 23 in Triazine Herbicides , edited by Janis McFarland and
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Connell, LL., Harman-Fetch and Hagy, L.D. 2004. Measured Concentrations of
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Crawshaw, GJ. 2000. Diseases and Pathology of Amphibians and Reptiles in:
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El-Abyad M.S., H. Attaby and K.M. Abu-Aisha. 1988. Effect of the Herbicide Prometryn
on Metabolic Activities of Two Fusarium Wilt Fungi. Trans Br Mycol Soc 90(3):
351-358
Fellers, G. M., etal. 2001. Overwintering tadpoles in the California red-legged frog
(Rana aurora draytonii). Herpetological Review, 32(3): 156-157.
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(http://www.werc.usgs.gov/pt-reves/pdfs/Rana%20draytonii.PDF)
Fellers, G. M. 2005b. California red-legged frog, Rana draytonii Baird and Girard. Pages
198-201. In: L.L.C. Jones, et al (eds.) Amphibians of the Pacific Northwest.
xxi+227.
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Fletcher J.S.; I.E. Nellessen; T.G. Pfleeger. 1994. Literature Review and Evaluation of
the EPA Food-chain (Kenaga) Nomogram, an Instrument for Estimating Pesticide
Residues on Plants. Environmental Toxicology and Chemistry, 13:9 (13 83-1391).
Garbini, J.R., Milori, D., Simoes, M.L., Wilson, T.L. and Martin, N. 2007 Influence if
humic substances on the photolysis of aqueous pesticide residues.Chemosphere,
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Gronberg, J.A. and C.R. Kratzer. 2007. Environmental Setting of the Lower Merced
River Basin, California. U.S. Geological Service, Scientific Investigations Report
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Harada, H., Tagaki, K., Fujii, K. and Iwasaki, A. 2006. Transformation ofmetilito-s-
triazines via sulfur oxidation, by strain JUN7, a Bacillus cereus species Soil
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Hayes, M. P.; M. R. Jennings. 1988. Habitat correlates of distribution of the California
redlegged frog (Rana aurora draytonii) and the foothill yellow-legged frog (Rana
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