Risks of Oxydemeton Methyl Use to Federally Listed
California Red Legged Frog
(Rana aurora draytonii)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
October 18,2007
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Primary Authors
Shannon Borges, Biologist
William P. Eckel, Ph.D., Senior Fate Scientist
Secondary Review
Donna Randall, Senior Effects Scientist
Nelson Thurman, Ph.D., Senior Fate Scientist
Branch Chief (Acting), Environmental Risk Assessment Branch 2
Dana Spatz
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Table of Contents
1. Executive Summary 7
2. Problem Formulation 11
2.1 Purpose 11
2.2 Scope 13
2.2.1 Degradates 14
2.3 Previous Assessments 14
2.4 Stressor Source and Distribution 14
2.4.1 Environmental Fate and Transport Assessment 14
2.4.2 Mechanism of Action 17
2.4.3 Use and Usage Characterization 17
2.5 Assessed Species 23
2.5.1 Distribution 23
2.5.2 Reproduction 28
2.5.3 Diet 28
2.5.4 Habitat 29
2.6 Designated Critical Habitat 30
2.6.1 Special Rule Exemption for Routine Ranching Activities 32
2.7 Action Area 33
2.8 Assessment Endpoints and Measures of Ecological Effect 36
2.8.1 Assessment Endpoints for the CRLF 37
2.8.2 Assessment Endpoints for Designated Critical Habitat 38
2.9 Conceptual Model 51
2.9.1 Risk Hypotheses 51
2.9.2 Diagram 51
2.10 Analysis Plan 56
2.10.1 Exposure Analysis 56
2.10.2 Effects Analysis 57
2.10.3 Action Area Analysis 57
3. Exposure Assessment 59
3.1 Label Application Rates and Intervals 59
3.2 Aquatic Exposure Assessment 59
3.2.1 Conceptual Model of Exposure 59
3.2.2 Existing Monitoring Data 60
3.2.3 Modeling Approach 60
3.2.3.1 Model Inputs 61
3.2.3.2 Results 63
3.3 Terrestrial Exposure Assessment 64
3.2.4 Conceptual Model of Exposure 64
3.2.5 Modeling Approach 64
3.2.6 Model Inputs 65
3.2.7 Results 65
3.2.7.1 EECs for Direct Effects to Terrestrial Phase CRLF 65
3.2.7.2 Terrestrial EECs for Indirect Effects to CRLF 66
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4. Effects Assessment 67
4.1 Evaluation of Aquatic Ecotoxicity Data 67
4.1.1 Toxicity to Freshwater Fish 70
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies 70
4.1.1.2 Freshwater Fish: Chronic Exposure (Chronic/Reproduction) Studies 71
4.1.1.3 Freshwater Fish: Sublethal Effects and Open Literature Information 73
4.1.2 Toxicity to Freshwater Invertebrates 73
4.1.2.1 Freshwater Invertebrates: Acute Exposure Studies 73
4.1.2.2 Freshwater Invertebrates: Chronic Exposure Studies 74
4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Additional Open
Literature Information 75
4.1.3 Freshwater Field Studies 75
4.2 Evaluation of Terrestrial Ecotoxicity Data 75
4.2.1 Toxicity to Birds 75
4.2.1.1 Birds: Acute Exposure (Mortality) Studies 75
4.2.1.2 Birds: Chronic Exposure (Chronic/Reproduction) Studies 76
4.2.1.3 Birds: Sublethal Effects and Additional Open Literature Information .... 77
4.2.2 Toxicity to Wild Mammals 77
4.2.2.1 Wild Mammals: Acute Exposure Studies 77
4.2.2.2 Wild Mammals: Chronic Exposure Studies 78
4.2.2.3 Wild Mammals: Sublethal Effects and Open Literature Information 79
4.2.3 Toxicity to Nontarget Insects 81
4.2.4 Terrestrial Field Studies 81
4.3 Toxicity to Aquatic and Terrestrial Plants 82
4.4 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern 82
4.5 Incident Database Review 83
5. Risk Characterization 84
5.1. Risk Estimation 84
5.1.1. Aquatic Direct and Indirect Effects 84
5.1.1.1. Direct Effects 84
5.1.1.2. Indirect Effects 85
5.1.2. Terrestrial Direct and Indirect Effects 86
5.1.2.1. Direct Effects 86
5.1.2.2. Indirect Effects 87
5.1.1. Probability of Individual Mortality for Acute Direct and Indirect Effect to
the CRLF 88
Indirect Effects to the CRLF 88
5.2. Risk Description 89
5.2.1. Direct Effects to the California Red Legged Frog 90
5.2.1.1. Aquatic Phase 90
5.2.1.2. Terrestrial Phase 90
5.2.2. Indirect Effects Due to Reduction in Food Items 93
5.2.2.1. Aquatic Phase 93
5.2.2.2. Terrestrial Phase 93
5.2.3. Effects to Critical Habitat 93
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5.3. Action Area 94
5.3.1. Aquatic Phase 94
5.3.1.1. Spray Perimeter 94
5.3.1.2. Downstream Dilution 94
5.3.2. Terrestrial Phase 95
5.4. Listed Species Effects Determination for the California Red Legged Frog 97
5.4.1. "No Effect" Determination 97
5.4.2. "May Effect" Determination 97
5.4.3. "Adverse Effect" Determination 98
5.5 Risk Hypotheses Revisited 101
6. Uncertainties 103
6.1. Maximum Use Scenario 103
6.2. Usage Uncertainties 103
6.3. Exposure Assessment Uncertainties 103
6.3.1. PRZM Modeling Inputs and Predicted Aquatic Concentrations 104
6.3.2. Aquatic Exposure Estimates 105
6.3.3. Residue Levels Selection 106
6.3.4. Dietary Intake 106
6.4. Effects Assessment Uncertainties 106
6.4.1. Age Class and Sensitivity of Effects Thresholds 106
6.4.2. Extrapolation of Long-term Environmental Effects from Short-term
Laboratory Tests 107
6.4.3. Sublethal Effects 107
6.4.4. Location of Wildlife Species 107
6.5. Use of Surrogate Data for Amphibians 107
6.6. Assumptions Associated with the Acute LOCs 108
6.7. Action Area 108
7. References 109
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Appendices
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
Attachment 1
Attachment 2
PRZM-EXAMS Water Modeling Results
T-REX and T-HERPS Model Output
Papers accepted for ECOTOX-OPP and Included
Papers accepted for ECOTOX-OPP but Not Included
Papers Excluded from ECOTOX (Without Abstracts)
Reviews of ECOTOX Papers Included in Assessment
Toxicity Categories and Levels of Concern
Spatial Summary for Oxydemeton Methyl Uses
Status and Life History of the California Red Legged Frog
Baseline Status and Cumulative Effects for the California Red Legged
Frog
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1. Executive Summary
Background
This assessment evaluates the potential for oxydemeton-methyl (ODM) to adversely affect the
California Red Legged Frog (CRLF). ODM is an organophosphate insecticide. The mode of
action for this class of chemicals is the inhibition of acetylcholinesterase, which is necessary for
completion of neurotransmission. Inhibition of acetylcholinesterase results in disruption to the
central and peripheral nervous system, and can result in mortality as well as sublethal effects.
ODM is currently registered for use on a variety of field, fruit, and vegetable crops as well as on
Christmas trees, ornamental trees, and in forestry. ODM applications to Christmas, ornamental,
and forestry trees are made by tree injection, while ODM applications for other uses in California
are made via spray applications (ground and aerial) and chemigation. Application rates vary
between each use, with one-time application rates ranging from 0.375 - 0.75 lbs ai/acre, number
of applications ranging from 1 to 3, and intervals ranging 7-14 days. Exposure can occur at the
application site; however, ODM is also expected to move through the environment and be
transported away from the site of application by run-off or spray drift.
Tree injection methods are expected to confine ODM within tissues of treated trees. The
potential for seepage of ODM from plant roots as a result of this method of treatment is
unknown, but is not expected to result in exposure at the soil surface. Therefore, terrestrial
organisms are not expected to be exposed, including the CRLF. The potential for runoff is also
expected to be very low, so aquatic organisms are unlikely to be affected. Therefore, uses
requiring this application method are considered to have "no effect" on the CRLF and are not
analyzed further in this assessment. Uses that were included are: alfalfa grown for seed, lima
beans, sugar beets, broccoli, broccoli raab, brussel sprouts, cabbage, cauliflower, clover grown
for seed, sweet corn, cotton, cucurbits (cucumbers, pumpkins, summer squash, winter squash,
watermelons, musk melons [cantaloupes], other melons), non-bearing fruit trees (apples,
apricots, cherries, crab apples, nectarines, peaches, plums, prunes, quinces), non-bearing grapes,
head lettuce, Spanish onions, peppermint, spearmint, safflower, walnuts, and ornamental plants
grown for cut flowers.
There were insufficient monitoring data to support an aquatic evaluation based on concentrations
found in water samples. Therefore, it was necessary to estimate aquatic exposure based on
modeled results. Terrestrial exposure was also estimated through the use of models.
Aquatic Phase
Direct, acute effects to the aquatic phase CRLF are not expected as there are no acute listed LOC
exceedences for freshwater fish, the surrogate test species for the aquatic phase CRLF. Chronic
data for freshwater fish are available; however, the NOAEC calculated for this test is greater than
the LC50. Therefore, an acute-to-chronic ratio determined from other organophosphorus
insecticides was used to estimate chronic toxicity. Based on this value, the RQ for chronic
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reproductive effects exceeds the LOC for cole crops, indicating risk to the aquatic-phase CRLF
resulting from chronic exposure. Indirect effects to the CRLF and its critical habitat due to
effects on aquatic plants are not expected, since ODM was not shown to be toxic to aquatic
plants in Tier I tests. Although acute RQs for aquatic invertebrates exceed the LOC, indirect
effects to CRLF, based on invertebrate food availability are not expected because the effect on
invertebrate food sources is determined to be insignificant. Thus it was determined that ODM
use is likely to adversely affect the aquatic phase CRLF through direct chronic effects and
indirect effects due to chronic effects to fish and amphibian food resources and critical habitat
(fish and invertebrate prey base).
Terrestrial Phase
ODM use is likely to adversely affect the terrestrial phase of the CRLF directly, as determined
by acute and chronic LOC exceedences for birds, the surrogate test species for terrestrial phase
CRLF. Avian reproductive effects indicate direct chronic fecundity effects to CRLF as well.
Toxic effects on the CRLF prey base are likely to adversely affect the terrestrial phase CRLF as
several taxa from the CRLF diet exceed the acute and chronic LOCs. Birds, mammals, insects,
and small amphibians are all part of the terrestrial CRLF diet. Because multiple components of
the diet are expected to be affected, including mammals, birds and insects, a determination of
likely to adversely affect is also made for indirect effects. Plant LOCs were not exceeded, thus
plant-related indirect effects and effects to critical habitat are not expected.
Based on LOC exceedences, the overlap of use sites with frog habitat and core areas, and other
factors, the following table summarizes the effects determination for the CRLF from ODM use.
Table 1-1: Effects Determination Summary for ODM Use and the California Red-Legged
Frog.
Assessment
1 julpoinl
I-fleets
determination
liasis lor Determination
Aquatic Phase
(Eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects and Critical Habitat Effects
1. Survival, growth, and
reproduction of CRLF
May Affect,
Likely to
Adversely Affect
Chronic RQs exceed LOC for surrogate species (rainbow trout)
for 3 cole crops (broccoli, cauliflower, brussel sprouts)
May Affect,
Not Likely to
Adversely Affect
No chronic exceedance for aquatic vertebrates for lettuce. No
chronic exceedance for aquatic vertebrates for lettuce, since
aquatic EEC is essentially equal to the no effect level
No Effect
Exposure not expected from all non-food uses applied via tree
injection due to lack of exposure. Acute and chronic RQs do not
exceed LOCs for food uses other than cole crops.
Indirect Effects
2. Reduction or
modification of aquatic
prey base
May Affect,
Likely to
Adversely Affect
Chronic RQs exceed LOC for fish (rainbow trout) for 3 cole
crops, resulting in impacts to fish and amphibian prey base
May Affect,
Acute LOC is exceeded for aquatic invertebrates for 3 cole crops,
Adversely Affect likelihood of individual effect. No chronic exceedance for
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Assessment
1 julpoinl
1. fleets
dctcrmi nation
liasis lor Determination
aquatic vertebrates for lettuce, since aquatic EEC is essentially
equal to the no effect level
No Effect
Exposure to aquatic organisms not expected from all non-food
uses applied via tree injection. Acute and chronic RQs do not
exceed LOCs for invertebrates with food uses other than cole
crops.
3. Reduction or
modification of aquatic
plant community
No Effect
No LOC exceedences for any plant species
4. Degradation of
riparian vegetation
No Effect
No LOC exceedences for any plant species.
Terrestrial Phase
(Juveniles and Adults)
Direct Effects
5. Survival, growth, and
reproduction of CRLF
May Affect,
Likely to
Adversely Affect
Acute and Chronic LOC exceedences for birds, the surrogate
species for direct effects to frogs, at lowest use rate. Probability
of effect approaches 100% at calculated RQs.
No Effect
Exposure to terrestrial organisms not expected from all non-food
uses applied via tree injection.
Indirect Effects and Critical Habitat Effects
6. Reduction or
modification of
terrestrial prey base
May Affect, Likely
to Adversely Affect
Acute and Chronic LOC exceedences for multiple components of
CRLF prey base (mammals, birds, and terrestrial invertebrates) at
lowest use rate. LAA to terrestrial phase CRLF and its critical
habitat based on acute RQs exceeding 0.5 and chronic RQs over
LOC for mammals, insects, birds. Adverse terrestrial critical
habitat modification is expected.
No Effect
Exposure to terrestrial organisms not expected from all non-food
uses applied via tree injection.
7. Degradation of
riparian vegetation
No Effect
No plant LOC exceedences.
When evaluating the significance of this risk assessment's direct/indirect and adverse habitat
modification effects determinations, it is important to note that pesticide exposures and predicted
risks to the species and its resources (i.e., food and habitat) are not expected to be uniform across
the action area. In fact, given the assumptions of drift and downstream transport (i.e., attenuation
with distance), pesticide exposure and associated risks to the species and its resources are
expected to decrease with increasing distance away from the treated field or site of application.
Evaluation of the implication of this non-uniform distribution of risk to the species would require
information and assessment techniques that are not currently available. Examples of such
information and methodology required for this type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages within
specific recovery units and/or designated critical habitat within the action area.
This information would allow for quantitative extrapolation of the present risk
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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.
Effects on Primary Constituent Elements of the Critical Habitat
Aquatic Breeding and Non-breeding Habitat
Adverse effects on the aquatic critical habitat are not expected, as there is No Effect via aquatic
plants, and the effect on invertebrates is insignificant.
Upland and Dispersal Habitat
There may be effects on these habitats through reduction in prey base (invertebrates, and small
mammals, birds, and amphibians). However, effects are not expected to result from reduction in
plant populations.
Action Area
Based on chronic effects to mammals, a terrestrial buffer zone of 11,338 feet is needed to
delineate the Action Area. This is the distance from the edge of the use site needed to reduce
exposure to below the Level of Concern for all taxa considered. The aquatic Action Area is
based on direct effects to the CRLF as a result of exposure to ODM. Nevertheless, based on the
RQs, terrestrial effects are expected to dominate the Action Area.
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2. Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By identifying the
important components of the problem, it focuses the assessment on the most relevant life history
stages, habitat components, chemical properties, exposure routes, and endpoints. The structure
of this risk assessment is based on guidance contained in U.S. EPA's Guidance for Ecological
Risk Assessment (U.S. EPA 1998), the Services' Endangered Species Consultation Handbook
(USFWS/NMFS 1998) and is consistent with procedures and methodology outlined in the
Overview Document (U.S. EPA 2004) and reviewed by the U.S. Fish and Wildlife Service
(USFWS) and National Marine Fisheries Service (USFWS/NMFS 2004).
2.1 Purpose
The purpose of this endangered species assessment is to evaluate potential direct and indirect
effects on individuals of the federally threatened California red-legged frog (Rana aurora
draytonii) (CRLF) arising from FIFRA regulatory actions regarding use of Oxydemeton methyl
(ODM). This ecological risk assessment has been prepared as part of the Center for Biological
Diversity (CBD) vs. EPA et al. (Case No. 02-1580-JSW(JL)) settlement entered in the Federal
District Court for the Northern District of California on October 20, 2006.
This assessment covers ODM uses on alfalfa grown for seed, lima beans, sugar beets, broccoli,
broccoli raab, brussel sprouts, cabbage, cauliflower, clover grown for seed, sweet corn, cotton,
cucurbits (cucumbers, pumpkins, summer squash, winter squash, watermelons, musk melons
[cantaloupes], other melons), non-bearing fruit trees (apples, apricots, cherries, crab apples,
nectarines, peaches, plums, prunes, quinces), non-bearing grapes, head lettuce, Spanish onions,
peppermint, spearmint, safflower, walnuts, and ornamental plants grown for cut flowers. ODM
is also registered for use in treating ornamental, forest, non-bearing and Christmas trees via
injection. However, these uses are expected to pose little chance of exposure outside of the
treated trees due to the nature of the treatment method, so they are not included in this risk
assessment. In addition, this assessment evaluates whether these actions can be expected to
result in the modification of the species' critical habitat. Key biological information for the
CRLF is included in Section 2.5, and designated critical habitat information for the species is
provided in Section 2.6 of this assessment.
In this endangered species assessment, direct and indirect effects to the CRLF and potential
modification to its critical habitat are evaluated in accordance with the methods (both screening
level and species-specific refinements, when appropriate) described in the Agency's Overview
Document (U.S. EPA 2004).
In accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of ODM are based on an action area. The action area is considered to be the area
directly or indirectly affected by the federal action, as indicated by the exceedance of Agency
Levels of Concern (LOCs) used to evaluate direct or indirect effects. It is acknowledged that the
action area for a national-level FIFRA regulatory decision associated with a use of ODM may
potentially involve numerous areas throughout the United States and its Territories. However,
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for the purposes of this assessment, attention will be focused on relevant sections of the action
area including those geographic areas associated with locations of the CRLF and its designated
critical habitat within the state of California.
As part of the "effects determination," one of the following three conclusions will be reached
regarding the potential for registration of ODM at the use sites described in this document to
affect CRLF individuals and/or result in modification of designated CRLF critical habitat:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Critical habitat identifies specific areas that have the physical and biological features, (known as
primary constituent elements or PCEs) essential to the conservation of listed species. The PCEs
for CRLFs are aquatic and upland areas where suitable breeding and non-breeding aquatic
habitat is located, interspersed with upland foraging and dispersal habitat (Section 2.6).
If the results of initial screening-level assessment methods show no direct or indirect effects (no
LOC exceedances) upon individual CRLFs or upon the PCEs of the species' designated critical
habitat, a "no effect" determination is made for the FIFRA regulatory action regarding ODM as
it relates to this species and its designated critical habitat. If, however, direct or indirect effects
to individual CRLFs are anticipated and/or effects may impact the PCEs of the CRLF's
designated critical habitat, a preliminary "may affect" determination is made for the FIFRA
regulatory action regarding ODM.
If a determination is made that use of ODM within the action area(s) associated with the CRLF
"may affect" this species and/or its designated critical habitat, additional information is
considered to refine the potential for exposure and for effects to the CRLF and other taxonomic
groups upon which these species depend (e.g.., aquatic and terrestrial vertebrates and
invertebrates, aquatic plants, riparian vegetation, etc.). Additional information, including spatial
analysis (to determine the geographical proximity of CRLF habitat and ODM use sites) and
further evaluation of the potential impact of ODM on the PCEs is also used to determine whether
modification to designated critical habitat may occur. Based on the refined information, the
Agency uses the best available information to distinguish those actions that "may affect, but are
not likely to adversely affect" from those actions that "may affect and are likely to adversely
affect" the CRLF and/or the PCEs of its designated critical habitat. This information is presented
as part of the Risk Characterization in Section 5 of this document.
The Agency believes that the analysis of direct and indirect effects to listed species provides the
basis for an analysis of potential effects on the designated critical habitat. Because ODM is
expected to directly impact living organisms within the action area (defined in Section 2.7),
critical habitat analysis for ODM is limited in a practical sense to those PCEs of critical habitat
that are biological or that can be reasonably linked to biologically mediated processes (i.e., the
biological resource requirements for the listed species associated with the critical habitat or
important physical aspects of the habitat that may be reasonably influenced through biological
processes). Activities that may destroy or adversely modify critical habitat are those that alter
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the PCEs and appreciably diminish the value of the habitat. Evaluation of actions related to use
of ODM that may alter the PCEs of the CRLF's critical habitat form the basis of the critical
habitat impact analysis. Actions that may affect the CRLF's designated critical habitat have
been identified by the Services and are discussed further in Section 2.6.
2.2 Scope
ODM is registered for use on a variety of agricultural crops in California, including alfalfa grown
for seed, lima beans, sugar beets, broccoli, broccoli raab, brussel sprouts, cabbage, cauliflower,
clover grown for seed, sweet corn, cotton, cucurbits (cucumbers, pumpkins, summer squash,
winter squash, watermelons, musk melons [cantaloupes], other melons), non-bearing fruit trees
(apples, apricots, cherries, crab apples, nectarines, peaches, plums, prunes, quinces), non-bearing
grapes, head lettuce, Spanish onions, peppermint, spearmint, safflower, walnuts, and ornamental
plants grown for cut flowers. Applications made to these crops via aerial or ground spray are the
focus of this risk assessment. The product registered for these uses may also be applied via
chemigation; however, the range of exposures resulting from this method of application is
expected to be accounted for by the aerial and ground spray applications. Therefore, the focus of
this assessment will be the ground and aerial applications for the above uses, and additional
analyses will not be conducted for chemigation. ODM is also registered for use in treating
ornamental, forest, non-bearing and Christmas trees via tree injection methods. Because these
uses are expected to pose little opportunity for exposure to terrestrial or aquatic organisms, they
are not included in this risk assessment.
The uses considered in this risk assessment represent all currently registered uses according to a
review of all current labels. No other uses are relevant to this assessment. Any other reported
use, such as may be seen in the California's Department of Pesticide Regulation Pesticide Use
Reporting (CDPR PUR) database1, represent either historic uses that have been canceled, mis-
reported uses, or mis-use. Historical uses, mis-reported uses, and misuse are not considered part
of the federal action and, therefore, are not considered in this assessment.
The end result of the EPA pesticide registration process (the FIFRA regulatory action) is an
approved product label. The label is a legal document that stipulates how and where a given
pesticide may be used. Product labels (also known as end-use labels) describe the formulation
type (e.g., liquid or granular), acceptable methods of application, approved use sites, and any
restrictions on how applications may be conducted. Thus, the use or potential use of ODM in
accordance with the approved product labels for California is "the action" being assessed.
Although current registrations of ODM allow for use nationwide, this ecological risk assessment
and effects determination addresses currently registered uses of ODM 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.
1 The California Department of Pesticide Regulation's Pesticide Use Reporting database provides a census of
pesticide applications in the state. See http://www.cdpr.ca.gov/docs/pur/purmain.htm.
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The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of
active ingredients, either those mixtures of multiple active ingredients in product formulations or
those in the applicator's tank. In the case of the product formulations of active ingredients (that
is, a registered product containing more than one active ingredient), each active ingredient is
subject to an individual risk assessment for regulatory decision regarding the active ingredient on
a particular use site. If effects data are available for a formulated product containing more than
one active ingredient, they may be used qualitatively or quantitatively in accordance with the
Agency's Overview Document and the Services' Evaluation Memorandum (U.S., EPA 2004;
USFWS/NMFS 2004).
Oxydemeton-methyl does not have any registered products that contain multiple active
ingredients.
2.2.1 Degradates
ODM has two degradates which two are sufficiently similar to the parent to possibly have similar
toxicity (i.e., both are phosphate esters and have the entire basic structure of ODM). These are
the sulfone (MSRO), an oxidation product containing one extra oxygen atom on sulfur, and the
sulfide (MSI) a reduction product containing one less oxygen atom on sulfur than the parent.
ODM does not form an oxon degradate. The sulfide (MSI) forms only under anaerobic
conditions, and neither compound is a major degradate. It is not believed that addition of either
of these degradates to the exposure assessment will change the outcome of the assessment.
2.3 Previous Assessments
The Agency published an Interim Reregi strati on Eligibility Decision in August 2002 and
identified numerous human health and ecological risks associated with the labeled uses of ODM.
Upon completion of the assessment, the Agency decided on a number of label amendments to
address the occupational worker and ecological concerns. ODM is highly toxic to honey bees on
an acute contact and acute oral basis. Acute and chronic risks to birds and mammals were also
identified as concerns. The document is available on the web, at:
http://www.epa.gov/oppsrrdl/REDs/oxydemeton ired amend and ired.pdf. Numerous
mitigation measures resulted from the IRED assessment, including cancellation of some uses,
precautionary labeling, and the use of buffer zones around areas managed for wildlife or as
wildlife habitat. Currently, new labels reflecting these changes are being reviewed and are
expected to be finalized by August 2007. As a result, this assessment will only incorporate uses
and restrictions confirmed by OPP's Registration Division as of the date of this assessment.
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate and Transport Assessment
Based on acceptable and supplemental data, parent ODM (S-[2-(ethylsulfinyl)ethyl]-0,0-
dimethyl phosphorothioate) degrades rapidly in alkaline (pH 9) aqueous solutions and by
microbial-mediated metabolism. Volatility is not a significant route of dissipation, based on the
Henry's Law Constant of 1.5 x 10"11 atm m3 /mol.
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The metabolites formed in the submitted laboratory studies were desmethyl ODM (S-[2-
(ethylsulfinyl)ethyl]-0-methyl phosphorothioate), ODM Thiol (2-(ethylsulfinyl) ethane sulfonic
acid), 2-(ethylsulfonyl) ethane sulfonic acid, ODM-sulfide [MSI: (S-[2-(ethylthio)ethyl]0,0-
dimethyl phosphorothioate)], ESMSE (l-(ethylsulfinyl)-2-(methylsulfinyl)ethane), and ODM
sulfone (S-[2-(ethylsulfonyl)ethyl] 0,0-dimethylphosphorothioate). These metabolites are
dephosphorylated and/or demethylated ODM. The metabolites ODM Thiol (2-(ethylsulfinyl)
ethane sulfonic acid) and 2-(ethylsulfonyl) ethane sulfonic acid are formed under aerobic
conditions, and are persistent and mobile and are likely to reach water resources where they
would persist and accumulate. The ESMSE metabolite that was formed under anaerobic aquatic
conditions also did not appear to degrade, however, it is not expected to persist in water because
it is not formed under aerobic conditions. All other detected ODM metabolites were non-
persistent in the submitted studies, and are not likely to persist and accumulate in water even if
they reached water resources.
Under anaerobic aquatic conditions, parent ODM degraded rapidly to form S-[2-
(ethylthio)ethyl]0,0-dimethyl phosphorothioate (ODM-sulfide; MSI). MSI in water increased
from 0.1 % of applied at day zero to 53.9 % at 7 days, followed by a decline to non-detectable
levels by six months. The other major metabolite reached a maximum of 17.6 % by 9 months,
and was 12.9 % of applied by 12 months in water. MSI and EMSME were almost exclusively
associated with water in the study. The calculated half-life for MSI in water was 9 days.
The degradation of parent ODM is dependent on alkaline-induced hydrolysis and microbial-
mediated metabolism. Parent ODM hydrolyzed with half-lives of 93 days, 40 days, and 2.5 days
in pH 5, 7, and 9 buffer solutions, respectively. Photodegradation in water or on soil is not an
important route of dissipation, with calculated half-lives of 137 days (194 days in dark control
pH buffer solutions) and 63 days (53 days in dark control soil). The only major photolytic
transformation product was 2-(ethylsulfonyl) ethane sulfonic acid at a maximum concentration
of 18.4 % of applied by 30 days of irradiation in soil.
ODM is not persistent in aerobic soil and anaerobic aquatic environments. The aerobic soil
metabolism half-life was 3.2 days in sandy loam soil. The major metabolites were ODM Thiol
and 2-(ethylsulfonyl) ethane sulfonic acid at maximum concentrations of 27-31 % of applied.
Both of these metabolites are dephosphorylated and demethylated ODM and both kept increasing
or reached consistent concentrations in laboratory studies. The minor metabolite ODM sulfone
(S-[2-(ethylsulfonyl)ethyl] 0,0-dimethylphosphorothioate) did not exceed 6.3 % of applied by 3
days. Parent ODM also degraded rapidly (ti/2=3.5 days) under anaerobic aquatic sediment/water
conditions (Eh range of -65 to -2 mV for the 0-21 days used for half-life calculations). The
major metabolites in the study were ODM sulfide (S-[2-(ethylthio)ethyl]0,0-dimethyl
phosphorothioate) and ESMSE (1 -(ethylsulfinyl)-2-methylsulfinyl) ethane. ODM sulfide was
almost exclusively associated with water in the study, and degraded with a calculated half-life of
9 days. Non-extractable sediment residues increased to 25.5-26.7 % of applied by 2-3 months,
and then declined to 18.3 % by 12 months.
Batch equilibrium data indicate that parent ODM partitions primarily to the liquid phase and is
potentially very mobile in all tested soils. Parent ODM had Freundlich adsorption coefficients
(Kd's) of 0.01 to 0.89 ml/g in sand, sandy loam, silt loam, and clay loam soils. No desorption
15
-------
coefficients could be calculated for parent ODM and no adsorption or desorption coefficients
could be calculated for ODM sulfone and ODM sulfide due to limited adsorption.
Volatility of parent ODM or any organic metabolite is not expected to be a significant route of
dissipation since no loss of material was observed in a laboratory volatility study. ODM has a
vapor pressure of 2.85 x 10"5 Torr, a Henry's Law Constant of 1.5 x 10"11 atm m3 /mol, and is
miscible in water.
Based on supplemental data, ODM applied at 1 and 4.5 lbs ai/A rapidly dissipated (ti/2's=l.6 to
2.2 days) in field dissipation studies in California that were irrigated and planted to sugar beets.
The short half-lives are consistent with the aerobic soil metabolism half-life of 3.2 days. The
short half-lives and the lack of observed leaching would indicate that degradation was the
primary route of dissipation. Neither ODM nor ODM sulfone were detected past 14 days or
below 6 inches of soil depth.
Potential transport mechanisms include pesticide surface water runoff, spray drift, and secondary
drift of volatilized or soil-bound residues leading to deposition onto nearby or more distant
ecosystems. The magnitude of pesticide transport via secondary drift depends on the pesticide's
ability to be mobilized into air and its eventual removal through wet and dry deposition of
gases/particles and photochemical reactions in the atmosphere. A number of studies have
documented atmospheric transport and redeposition of pesticides from the Central Valley to the
Sierra Nevada mountains (Fellers et al., 2004, Sparling et al., 2001, LeNoir et al., 1999, and
McConnell et al., 1998). Prevailing winds blow across the Central Valley eastward to the Sierra
Nevada mountains, transporting airborne industrial and agricultural pollutants into Sierra Nevada
ecosystems (Fellers et al., 2004, LeNoir et al., 1999, and McConnell et al., 1998). Therefore,
physicochemical properties of the pesticide that describe its potential to enter the air from water
or soil (e.g., Henry's Law constant and vapor pressure), pesticide use, modeled estimated
concentrations in water and air, and available air monitoring data from the Central Valley and the
Sierra Nevadas are considered in evaluating the potential for atmospheric transport of ODM to
habitat for the CRLF.
In general, deposition of drifting or volatilized pesticides is expected to be greatest close to the
site of application. Computer models of spray drift (AgDRIFT or AGDISP) are used to
determine if the exposures to aquatic and terrestrial organisms are below the Agency's Levels of
Concern (LOCs). If the limit of exposure that is below the LOC can be determined using
AgDRIFT or AGDISP, longer-range transport is not considered in defining the action area. For
example, if a buffer zone <1,000 feet (the optimal range for AgDRIFT and AGDISP models)
results in terrestrial and aquatic exposures that are below LOCs, no further drift analysis is
required. If exposures exceeding LOCs are expected beyond the standard modeling range of
AgDRIFT or AGDISP, the Gaussian extension feature of AGDISP may be used. In addition to
the use of spray drift models to determine potential off-site transport of pesticides, other factors
such as available air monitoring data and the physicochemical properties of the chemical are also
considered.
16
-------
2.4.2 Mechanism of Action
ODM is an organophosphorus (OP) compound belonging to a class known as the anti-
cholinesterases. These chemicals act upon target pests through neurotoxic action, in which the
enzyme, acetylcholinesterase (AChE), is inhibited within the central and peripheral nervous
system. The transmission of nerve impulses across nerve synapses and the junctions between
nerves and other tissues is accomplished by the release of a chemical agent, acetylcholine, which
binds to receptors on the post-synaptic membrane. When transmission is complete, acetylcholine
must be removed from its receptors. AChE hydrolyzes acetylcholine, thereby releasing it from
its receptor and allowing the nerve to cease transmission. OPs disrupt this process by
competitively binding to AChE, thereby preventing it from hydrolyzing acetylcholine. The
result is continuous firing of the nerve impulse, which can lead to pulmonary paralysis and death
by asphyxiation. Since the OP-AChE bond can "age" and become irreversible, recovery only
occurs with regeneration of new AChE.
2.4.3 Use and Usage Characterization
Analysis of labeled use information is the critical first step in evaluating the federal action. The
current label for ODM 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.
ODM is nationally registered for use in a variety of agricultural crops including alfalfa grown for
seed, lima beans, sugar beets, broccoli, broccoli raab, brussel sprouts, cabbage, cauliflower,
clover grown for seed, Christmas trees, sweet corn, cotton, cucurbits (cucumbers, pumpkins,
summer squash, winter squash, watermelons, musk melons [cantaloupes], other melons), filberts,
non-bearing fruit trees (apples, apricots, cherries, crab apples, nectarines, peaches, plums,
prunes, quinces), non-bearing grapes, head lettuce, Spanish onions, peppermint, sorghum,
spearmint, safflower, walnuts, and field grown ornamentals and nursery stock, ornamental plants
grown for cut flowers. Applications are made to these crops via aerial or ground spray or
chemigation. Details of the labeled uses are provided in Table 2-1. ODM is also registered for
use in treating ornamental, forest, non-bearing and Christmas trees via tree injection. It is not
registered for use in California on Christmas trees, field grown ornamentals and nursery stock
except by tree injection, and it is not registered for use on filberts or sorghum in California by
any application method.
17
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Table 2-1. Labeled ODM Uses Assessed in this Document.
Registration
Number,
Product
Name,
% AI,
Formulations
Crop
Max. One-
time Appl.
Rate
Max. No.
Appl. per
Crop
Cycle
Max.
Quantity
Applied per
Crop Cycle
Min.
Appl.
Interval
Application
method
10163-220,
MSR Spray
Concentrate,
25%,
Liquid
Alfalfa (grown for
seed)
0.5 lbs ai/A
2
1.0 lbs ai/A
14 days
Aerial, chemigation,
groundboom
Beans, lima
0.5 lbs ai/A
2
1.0 lbs ai/A
7 days
Aerial, chemigation,
groundboom
Beets, sugar
0.5 lbs ai/A
1
0.5 lbs ai/A
NA
Aerial, chemigation,
groundboom
Broccoli
0.5 lbs ai/A
2
1.0 lbs ai/A
7 days
Aerial, chemigation,
groundboom
Brussel sprouts
0.5 lbs ai/A
3
1.5 lbs ai/A
7 days
Aerial, chemigation,
groundboom
Cabbage
0.75 lbs
ai/A
3
2.25 lbs ai/A
7 days
Aerial, chemigation,
groundboom
Cauliflower
0.5 lbs ai/A
2
1.0 lbs ai/A
7 days
Aerial, chemigation,
groundboom
Clover grown for
seed
0.5 lbs ai/A
2
1.0 lbs ai/A
14 days
Aerial, chemigation,
groundboom
Corn, sweet
0.5 lbs ai/A
2
1.0 lbs ai/A
7 days
Aerial, chemigation,
groundboom
Cotton
0.5 lbs ai/A
1
0.5 lbs ai/A
NA
Chemigation and
groundboom
Curcurbits:
cucumbers,
pumpkins,
summer squash,
winter squash,
watermelons,
muskmelons
(canteloupes),
other melons
0.5 lbs ai/A
1
0.5 lbs ai/A
NA
Aerial, chemigation,
groundboom
Fruit trees, non-
bearing: apples,
apricots, cherries,
crab apples,
nectarines,
peaches, plums,
prunes, quinces
0.375 lbs
ai/A
2
0.75 lbs ai/A
7 days
Airblast
Grapes, non-
bearing
0.375 lbs
ai/A
2
0.75 lbs ai/A
7 days
Airblast
Lettuce, head
0.5 lbs ai/A
2
1.0 lbs ai/A
7 days
Aerial, chemigation,
and groundboom
Onions, Spanish
(bulb)
0.5 lbs ai/A
2
1.0 lbs ai/A
14 days
Aerial, chemigation,
and groundboom
Peppermint and
spearment
0.75 lbs
ai/A
2
1.5 lbs ai/A
10 days
Chemigation and
groundboom.
Safflower
0.5 lbs ai/A
2
1.0 lbs ai/A
7 days
Aerial, chemigation,
groundboom
Walnuts
0.375 lbs
ai/A
1
0.375 lbs
ai/A
NA
Airblast.
18
-------
Registration
Number,
Product
Name,
% AI,
Formulations
Crop
Max. One-
time Appl.
Rate
Max. No.
Appl. per
Crop
Cycle
Max.
Quantity
Applied per
Crop Cycle
Min.
Appl.
Interval
Application
method
CA010003,
MSR Spray
Concentrate,
25%,
Liquid
Ornamental plants
grown for cut
flowers
0.375 lbs
ai/A
2
0.75 lbs ai/A
7 days
Groundboom,
Airblast
CA950002,
MSR Spray
Concentrate,
25%,
Liquid
Broccoli raab
0.5 lbs ai/A
2
1.0 lbs ai/A
7 days
Aerial, Chemigation,
Groundboom
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis of both
national- and county-level usage information using state-level usage data obtained from USDA-
NASS2, Doane (www.doane.com; the full dataset is not provided due to its proprietary nature),
and the CDPR PUR database. CDPR PUR is considered a more comprehensive source of usage
data than USDA-NASS or EPA proprietary databases, and thus the usage data reported for ODM
by county in this California-specific assessment were generated using CDPR PUR data. Usage
data are averaged together over the years 2000 to 2005 to calculate average annual usage
statistics by county and crop for ODM, including pounds of active ingredient applied and base
acres treated. California State law requires that every pesticide application be reported to the
state and made available to the public. The summary of ODM usage for all use sites, including
both agricultural and non-agricultural, is provided below.
California PUR Usage Data
The state of California requires that all pesticide applications (excluding private homeowner
uses) be reported. This data is collected in the PUR (pesticide use reporting) database. The
Office of Pesticide Programs' (OPP) Biological and Economic Analysis Division (BEAD)
performed an analysis (S. Semenova, July 19, 2007) of the PUR data for the years 2002 to 2005,
including data for ODM. Use of ODM was reported in a total of 37 California counties over that
time.
According to the PUR database, a total of 96,005.7 lb of ODM were used in California in 2002,
93,744.7 lb in 2003, 102,554.4 lb. in 2004, and 121,500.3 lb. in 2005. The average annual
number of pounds applied over that four-year period was 103,451.3. Table 2-2a below gives the
reported usages that accounted for 95% of the annual average pounds applied, or about 98,279
lb.
2 United States Depart of Agriculture (USDA), National Agricultural Statistics Service (NASS) Chemical Use
Reports provide summary pesticide usage statistics for select agricultural use sites by chemical, crop and state. See
http://www.usda.gOv/nass/pubs/estindxl.htm#agchem.
19
-------
According to this analysis, the heaviest usage is on head lettuce and broccoli in Monterey County
(over 53,000 lb.). The next highest usage was in Santa Barbra County on broccoli, followed by
broccoli in San Luis Obispo County. Ten different use sites are represented in the top 95% of
pounds applied.
Tables 2-2b to 2-2h below give the complete summaries for seven of the ten uses represented in
Table 2-2a (all, or nearly all, of the cotton, rappini, and sugarbeet usage is already reported in
Table 2-2a).
There are twenty counties represented in Tables 2-2b to 2-2h. The agricultural uses on lettuce
and cole crops (broccoli, cabbage, cauliflower, brussel sprouts) are concentrated in 12 counties:
Monterey, Santa Barbara, San Luis Obispo, San Benito, Santa Cruz, Santa Clara, Ventura,
Fresno, Kern, Imperial, Stanislaus, and San Joaquin. The corn use is limited to Contra Costa,
Riverside, and Solano counties. Landscape maintenance includes many counties not included in
the major agricultural uses, such as Los Angeles, Orange, San Diego, Butte, and San Mateo. The
number of pounds applied to corn and landscapes is small compared to the major uses (lettuce
and cole crops).
The information presented in Tables 2-2b to 2-2h show where the heaviest use of ODM occurs in
California, and on which crops or use sites.
Table 2-2a. Reported Applications of ODM that account for 95% of Average Annual Use
in California.
County
Site Name
Total
Pounds
2002
Total
Pounds
2003
Total
Pounds
2004
Total
Pounds
2005
AVG
Annual
Pounds
Applied
CONTRA COSTA
CORN, HUMAN
CONSUMPTION
943.0
780.8
1335.7
1805.3
1216.2
FRESNO
CORN, HUMAN
CONSUMPTION
1921.2
696.0
2565.5
5424.5
2651.8
FRESNO
BROCCOLI
230.7
1942.8
2168.4
1959.6
1575.4
FRESNO
COTTON
644.4
956.5
0.0
0.0
400.2
LOS ANGELES
LANDSCAPE
MAINTENANCE
172.5
325.7
790.3
228.4
379.2
MERCED
SUGARBEET
75.5
144.9
1345.3
719.6
571.3
MONTEREY
LETTUCE, HEAD
29928.0
27373.5
31772.4
34310.3
30846.0
MONTEREY
BROCCOLI
20278.5
21155.4
22043.7
26471.8
22487.3
MONTEREY
CAULIFLOWER
6615.6
6699.3
7031.6
8426.0
7193.1
MONTEREY
CABBAGE
2042.7
2929.9
2090.2
2737.3
2450.0
MONTEREY
RAPPINI
981.4
683.7
1036.8
876.0
894.5
SAN BENITO
LETTUCE, HEAD
1569.4
827.7
888.6
696.8
995.6
SAN LUIS
OBISPO
BROCCOLI
5349.0
6105.8
4737.9
7646.7
5959.9
SAN LUIS
OBISPO
LETTUCE, HEAD
949.7
904.7
1582.6
1860.7
1324.4
SAN MATEO
BRUSSEL SPROUT
370.7
442.2
253.9
482.6
387.4
SANTA
BARBARA
BROCCOLI
11989.5
11282.5
11700.0
16553.5
12881.4
20
-------
County
Site Name
Total
Pounds
2002
Total
Pounds
2003
Total
Pounds
2004
Total
Pounds
2005
AVG
Annual
Pounds
Applied
SANTA
BARBARA
LETTUCE, HEAD
1936.9
1542.2
2618.5
3204.7
2325.6
SANTA
BARBARA
CAULIFLOWER
1942.8
1341.7
1765.7
1755.4
1701.4
SANTA CRUZ
BRUSSEL SPROUT
750.9
850.7
623.7
947.8
793.3
SANTA CRUZ
LETTUCE, HEAD
832.4
744.6
1002.0
422.9
750.5
VENTURA
CABBAGE
608.8
563.4
715.5
354.0
560.5
Table 2-2b. Usage of ODM on Head Lettuce, 20
02 to 2005
County
Total lb.
applied
2002
Total lb.
applied
2003
Total lb.
applied
2004
Total lb.
applied
2005
Annual
Avg. lb.
applied
MONTEREY
29928.0
27373.5
31772.4
34310.3
30846.0
SANTA BARBARA
1936.9
1542.2
2618.5
3204.7
2325.6
SAN LUIS OBISPO
949.7
904.7
1582.6
1860.7
1324.4
SAN BENITO
1569.4
827.7
888.6
696.8
995.6
SANTA CRUZ
832.4
744.6
1002.0
422.9
750.5
SANTA CLARA
209.3
357.0
398.5
267.8
308.1
VENTURA
225.6
135.9
127.9
117.4
151.7
FRESNO
0.0
55.5
0.0
0.0
13.9
Table 2-2c. Usage of ODM on Broccoli, 2002 to 2005
County
Total lb.
applied
2002
Total lb.
applied
2003
Total lb.
applied
2004
Total lb.
applied
2005
Annual
Avg. lb.
applied
MONTEREY
20278.5
21155.4
22043.7
26471.8
22487.3
SANTA BARBARA
11989.5
11282.5
11700.0
16553.5
12881.4
SAN LUIS OBISPO
5349.0
6105.8
4737.9
7646.7
5959.9
FRESNO
230.7
1942.8
2168.4
1959.6
1575.4
SANTA CLARA
141.3
290.2
292.6
276.1
250.0
SAN BENITO
283.9
291.3
182.2
167.9
231.3
VENTURA
288.0
208.3
137.1
71.2
176.2
SANTA CRUZ
136.5
110.5
178.4
101.9
131.8
KERN
67.3
31.8
138.0
157.7
98.7
IMPERIAL
26.8
225.3
0.0
0.0
63.0
STANISLAUS
0.0
25.0
0.0
93.2
29.6
SAN JOAQUIN
0.0
0.0
1.9
87.5
22.3
Table 2-2d. Usage oi
F ODM on Cabbage, 2002 to 2005
County
Total lb.
applied
2002
Total lb.
applied
2003
Total lb.
applied
2004
Total lb.
applied
2005
Annual
Avg. lb.
applied
MONTEREY
2042.7
2929.9
2090.2
2737.3
2450.0
VENTURA
608.8
563.4
715.5
354.0
560.5
SAN BENITO
595.9
378.7
175.0
251.2
350.2
SANTA CRUZ
62.8
82.8
118.4
135.1
99.8
21
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County
Total lb.
applied
2002
Total lb.
applied
2003
Total lb.
applied
2004
Total lb.
applied
2005
Annual
Avg. lb.
applied
SANTA BARBARA
113.8
109.6
61.2
73.2
89.4
SAN LUIS OBISPO
36.6
134.6
80.2
76.1
81.9
KERN
24.1
18.6
21.6
92.7
39.2
SANTA CLARA
1.5
69.0
0.0
0.0
17.6
SAN JOAQUIN
11.1
16.7
0.0
6.9
8.7
IMPERIAL
0.0
15.0
0.0
0.0
3.7
Table 2-2e. Usage o
' ODM on Cauliflower, 2002 to 2005
Total lb.
Total lb.
Total lb.
Total lb.
Annual
applied
applied
applied
applied
Avg. lb.
County
2002
2003
2004
2005
applied
MONTEREY
6615.6
6699.3
7031.6
8426.0
7193.1
SANTA BARBARA
1942.8
1341.7
1765.7
1755.4
1701.4
SAN LUIS OBISPO
344.6
171.2
92.7
107.5
179.0
SANTA CRUZ
153.2
134.2
70.0
39.1
99.2
VENTURA
147.4
96.3
25.7
0.0
67.4
SAN BENITO
86.8
84.6
21.0
24.1
54.1
SANTA CLARA
13.4
0.0
0.0
48.7
15.5
KERN
41.9
0.0
1.5
4.9
12.1
SAN JOAQUIN
4.5
3.0
6.4
0.0
3.5
Table 2-2f. Usage of ODM on Corn for
Human consumption, 2002 to 2005
County
Total lb.
applied
2002
Total lb.
applied
2003
Total lb.
applied
2004
Total lb.
applied
2005
Annual
Avg. lb.
applied
FRESNO
1921.2
696.0
2565.5
5424.5
2651.8
CONTRA COSTA
943.0
780.8
1335.7
1805.3
1216.2
RIVERSIDE
19.5
10.6
78.8
209.5
79.6
SAN JOAQUIN
69.2
99.9
0.0
118.7
72.0
SOLANO
0.0
14.6
54.4
0.0
17.2
VENTURA
5.9
31.2
0.0
0.0
9.3
SANTA BARBARA
33.6
0.0
0.0
0.0
8.4
SANTA CLARA
4.9
0.0
0.0
0.0
1.2
Table 2-2g. Usage of ODM for Landscape Maintenance, 2002 to 2005
(Annual Average 10 lb. or more)
County
Total lb.
applied
2002
Total lb.
applied
2003
Total lb.
applied
2004
Total lb.
applied
2005
Annual
Avg. lb.
applied
LOS ANGELES
172.5
325.7
790.3
228.4
379.2
ORANGE
139.4
139.1
177.0
212.3
167.0
SAN DIEGO
249.0
38.3
32.6
16.4
84.1
BUTTE
59.7
54.7
22.1
8.6
36.3
RIVERSIDE
30.2
50.6
18.2
6.3
26.3
VENTURA
26.5
22.0
0.0
0.0
12.1
22
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Table 2-2h. Usage oi
' ODM on Brussel Sprouts, 2002 to 20
05
County
Total lb.
applied
2002
Total lb.
applied
2003
Total lb.
applied
2004
Total lb.
applied
2005
Annual
Avg. lb.
applied
SANTA CRUZ
750.9
850.7
623.7
947.8
793.3
SAN MATEO
370.7
442.2
253.9
482.6
387.4
MONTEREY
323.9
208.8
59.4
224.5
204.1
SANTA BARBARA
69.4
46.7
64.5
73.7
63.6
SAN LUIS OBISPO
14.1
40.0
15.4
74.8
36.1
2.5 Assessed Species
The CRLF was federally listed as a threatened species by USFWS effective June 24, 1996
(USFWS 1996). It is one of two subspecies of the red-legged frog and is the largest native frog
in the western United States (USFWS 2002). A brief summary of information regarding CRLF
distribution, reproduction, diet, and habitat requirements is provided in Sections 2.5.1 through
2.5.4, respectively. Further information on the status, distribution, and life history of and
specific threats to the CRLF is provided in Attachment 1.
Final critical habitat for the CRLF was designated by USFWS on April 13, 2006 (USFWS 2006;
71 FR 19244-19346). Further information on designated critical habitat for the CRLF is
provided in Section 2.6.
2.5.1 Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically inhabited 46
counties in California including the Central Valley and both coastal and interior mountain ranges
(USFWS 1996). Its range has been reduced by about 70%, and the species currently resides in
22 counties in California (USFWS 1996). The species has an elevational range of near sea level
to 1,500 meters (5,200 feet) (Jennings and Hayes 1994); however, nearly all of the known CRLF
populations have been documented below 1,050 meters (3,500 feet) (USFWS 2002).
Populations currently exist along the northern California coast, northern Transverse Ranges
(USFWS 2002), foothills of the Sierra Nevada (5-6 populations), and in southern California
south of Santa Barbara (two populations) (Fellers 2005a). Relatively larger numbers of CRLFs
are located between Marin and Santa Barbara Counties (Jennings and Hayes 1994). A total of
243 streams or drainages are believed to be currently occupied by the species, with the greatest
numbers in Monterey, San Luis Obispo, and Santa Barbara counties (USFWS 1996). Occupied
drainages or watersheds include all bodies of water that support CRLFs (i.e., streams, creeks,
tributaries, associated natural and artificial ponds, and adjacent drainages), and habitats through
which CRLFs can move (i.e., riparian vegetation, uplands) (USFWS 2002).
The distribution of CRLFs within California is addressed in this assessment using four categories
of location including recovery units, core areas, designated critical habitat, and known
occurrences of the CRLF reported in the California Natural Diversity Database (CNDDB) that
are not included within core areas and/or designated critical habitat (see Figure 2.a). Recovery
23
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units, core areas, and other known occurrences of the CRLF from the CNDDB are described in
further detail in this section, and designated critical habitat is addressed in Section 2.6. Recovery
units are large areas defined at the watershed level that have similar conservation needs and
management strategies. The recovery unit is primarily an administrative designation, and land
area within the recovery unit boundary is not exclusively CRLF habitat. Core areas are smaller
areas within the recovery units that comprise portions of the species' historic and current range
and have been determined by USFWS to be important in the preservation of the species.
Designated critical habitat is generally contained within the core areas, although a number of
critical habitat units are outside the boundaries of core areas, but within the boundaries of the
recovery units. Additional information on CRLF occurrences from the CNDDB is used to cover
the current range of the species not included in core areas and/or designated critical habitat, but
within the recovery units.
Recovery Units
Eight recovery units have been established by USFWS for the CRLF. These areas are
considered essential to the recovery of the species, and the status of the CRLF "may be
considered within the smaller scale of the recovery units, as opposed to the statewide range"
(USFWS 2002). Recovery units reflect areas with similar conservation needs and population
statuses, and therefore, similar recovery goals. The eight units described for the CRLF are
delineated by watershed boundaries defined by US Geological Survey hydrologic units and are
limited to the elevational maximum for the species of 1,500 m above sea level. The eight
recovery units for the CRLF are listed in Table 2-3 and shown in Figure 2.a.
Core Areas
USFWS has designated 35 core areas across the eight recovery units to focus their recovery
efforts for the CRLF (see Figure 2.a). Table 2-3 summarizes the geographical relationship
among recovery units, core areas, and designated critical habitat. The core areas, which are
distributed throughout portions of the historic and current range of the species, represent areas
that allow for long-term viability of existing populations and reestablishment of populations
within historic range. These areas were selected because they: 1) contain existing viable
populations; or 2) they contribute to the connectivity of other habitat areas (USFWS 2002). Core
area protection and enhancement are vital for maintenance and expansion of the CRLF's
distribution and population throughout its range.
For purposes of this assessment, designated critical habitat, currently occupied (post-1985) core
areas, and additional known occurrences of the CRLF from the CNDDB are considered. Each
type of locational information is evaluated within the broader context of recovery units. For
example, if no labeled uses of ODM occur (or if labeled uses occur at predicted exposures less
than the Agency's LOCs) within an entire recovery unit, a "no effect" determination would be
made for all designated critical habitat, currently occupied core areas, and other known CNDDB
occurrences within that recovery unit. Historically occupied sections of the core areas are not
evaluated as part of this assessment because the USFWS Recovery Plan (USFWS 2002)
indicates that CRLFs are extirpated from these areas. A summary of currently and historically
occupied core areas is provided in Table 2-3 (currently occupied core areas are bolded). While
24
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core areas are considered essential for recovery of the CRLF, core areas are not federally-
designated critical habitat, although designated critical habitat is generally contained within these
core recovery areas. It should be noted, however, that several critical habitat units are located
outside of the core areas, but within the recovery units. The focus of this assessment is currently
occupied core areas, designated critical habitat, and other known CNDDB CRLF occurrences
within the recovery units. Federally-designated critical habitat for the CRLF is further explained
in Section 2.6.
Table 2-3. California Red-legged Frog Recovery Units with Overlapping Core Areas and
Designated Critical Habitat
Recovery Unit1
(Figure 2.a)
Core Areas2'7 (Figure 2.a)
Critical Habitat
Units3
Currently
Occupied
(post-1985)4
Historically
Occupied4
Sierra Nevada Foothills
and Central Valley (1)
(eastern boundary is the
1,500m elevation line)
Cottonwood Creek (partial) (8)
--
Feather River (1)
BUT-1A-B
Yuba River-S. Fork Feather
River (2)
YUB-1
--
NEV-16
Traverse Creek/Middle Fork
American River/Rubicon (3)
--
Consumnes River (4)
ELD-1
S. Fork Calaveras River (5)
--
Tuolumne River (6)
--
Piney Creek (7)
--
East San Francisco Bay
(partial)(16)
--
North Coast Range
Foothills and Western
Sacramento River
Valley (2)
Cottonwood Creek (8)
--
Putah Creek-Cache Creek (9)
--
Jameson Canyon - Lower Napa
Valley (partial) (15)
--
Belvedere Lagoon (partial) (14)
--
Pt. Reyes Peninsula (partial)
(13)
--
North Coast and North
San Francisco Bay (3)
Putah Creek-Cache Creek (partial)
(9)
--
Lake Berryessa Tributaries (10)
NAP-1
Upper Sonoma Creek (11)
--
Petaluma Creek-Sonoma Creek
(12)
--
Pt. Reyes Peninsula (13)
MRN-1, MRN-2
Belvedere Lagoon (14)
--
Jameson Canyon-Lower Napa
River (15)
SOL-1
South and East San
Francisco Bay (4)
--
CCS-1A6
East San Francisco Bay (partial)
(16)
ALA-1A, ALA-
IB, STC-1B
--
STC-1A6
South San Francisco Bay
(partial) (18)
SNM-1A
25
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South San Francisco Bay
SNM-1A, SNM-
(partial) (18)
2C, SCZ-1
Watsonville Slough- Elkhorn
Slough (partial) (19)
SCZ-2 5
Central Coast (5)
Carmel River-Santa Lucia (20)
MNT-2
Estero Bay (22)
--
--
SLO-86
Arroyo Grande Creek (23)
--
Santa Maria River-Santa Ynez
River (24)
East San Francisco Bay (partial)
MER-1A-B, STC-
(16)
1B
--
SNB-16, SNB-26
Diablo Range and
Salinas Valley (6)
Santa Clara Valley (17)
--
Watsonville Slough- Elkhorn
Slough (partial)(19)
MNT-1
Carmel River-Santa Lucia
(partial)(20)
Gablan Range (21)
SNB-3
Estrella River (28)
SLO-1A-B
--
SLO-86
Santa Maria River-Santa Ynez
STB-4, STB-5,
Northern Transverse
River (24)
STB-7
Ranges and Tehachapi
Sisquoc River (25)
STB-1, STB-3
Mountains (7)
Ventura River-Santa Clara
River (26)
VEN-1, VEN-2,
VEN-3
--
LOS-16
Santa Monica Bay-Ventura
Coastal Streams (27)
San Gabriel Mountain (29)
--
Southern Transverse
Forks of the Mojave (30)
--
and Peninsular Ranges
Santa Ana Mountain (31)
--
(8)
Santa Rosa Plateau (32)
--
San Luis Rey (33)
--
Sweetwater (34)
--
Laguna Mountain (35)
--
1 Recovery units designated by the USFWS (USFWS 2000, pg 49).
2 Core areas designated by the USFWS (USFWS 2000, pg 51).
3 Critical habitat units designated by the USFWS on April 13, 2006 (USFWS 2006, 71 FR 19244-19346).
4 Currently occupied (post-1985) and historically occupied core areas as designated by the USFWS (USFWS 2002,
Pg 54).
5 Critical habitat unit where identified threats specifically included pesticides or agricultural runoff (USFWS 2002).
6 Critical habitat units that are outside of core areas, but within recovery units.
Currently occupied core areas that are included in this effects determination are bolded.
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Recovery Units
Sierra Nevada Foothills and Central Valley
North Coast Range Foothills and Western
Sacramento River Valley
North Coast and North San Francisco Bay
South and East San Francisco Bay
Central Coast
Diablo Range and Salinas Valley
Northern Transverse Ranges and Tehachapi
Mountains
Southern Transverse and Peninsular Ranges
Legend
] Recovery Unit Boundaries
Currently Occupied Core Areas
| Critical Habitat
| CNDDB Occurence Sections
County Boundaries
Core Areas
1. Feather River
2. Yuba River- S. Fork Feather River
3. Traverse Creek/ Middle Fork/ American R. Rubicon
4. Cosumnes River
5. South Fork Calaveras River*
6. Tuolumne River*
7. Piney Creek*
8. Cottonwood Creek
9. Putah Creek - Cache Creek*
10. Lake Berryessa Tributaries
11. Upper Sonoma Creek
12. Petaluma Creek - Sonoma Creek
13. Pt. Reyes Peninsula
14. Belvedere Lagoon
15. Jameson Canyon - Lower Napa River
16. East San Francisco Bay
17. Santa Clara Valley
18. South San Francisco Bay
19. Watsonville Slough-Elkhom Slough
20. Carmel River - Santa Lucia
21. Gablan Range
22. Estero Bay
23.
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*
3 5. Laguna Mountain*
Arroyo Grange River
* Core areas that were historically occupied by the California red-legged frog are not included in the map
Figure 2a. Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF 27
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Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in California.
The CNDDB serves as a repository for historical and current species location sightings.
Information regarding known occurrences of CRLFs outside of the currently occupied core areas
and designated critical habitat is considered in defining the current range of the CRLF. See:
http://www.dfg.ca.gov/bdb/html/cnddb info.html for additional information on the CNDDB.
2.5.2 Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams, marshes,
and lagoons (Fellers 2005a). According to the Recovery Plan (USFWS 2002), CRLFs breed
from November through late April. Peaks in spawning activity vary geographically; Fellers
(2005b) reports peak spawning as early as January in parts of coastal central California. Eggs
are fertilized as they are being laid. Egg masses are typically attached to emergent vegetation,
such as bulrushes (Scirpus spp.) and cattails (Typha spp.) or roots and twigs, and float on or near
the surface of the water (Hayes and Miyamoto 1984). Egg masses contain approximately 2000
to 6000 eggs ranging in size between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch
10 to 14 days after fertilization (Fellers 2005a) depending on water temperature. Egg predation
is reported to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles (terrestrial-
phase), typically between May and September (Jennings and Hayes 1994, USFWS 2002);
tadpoles have been observed to over-winter (delay metamorphosis until the following year)
(Fellers 2005b, USFWS 2002). Males reach sexual maturity at 2 years, and females reach sexual
maturity at 3 years of age; adults have been reported to live 8 to 10 years (USFWS 2002). Figure
2b depicts CRLF annual reproductive timing.
Figure 2b. - <
RU I
Reproductive Events by Monl
h
J
F
M
A
M
J
J
A
S
o
N
D
Light Blue =
Green = Tadpoles (except those that over-winter)
Orange = Young Juvenile®
Adults and juveniles can be present all year
2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied specifically, it is
assumed that their diet is similar to that of other frog species, with the aquatic phase feeding
exclusively in water and consuming diatoms, algae, and detritus (USFWS 2002). Tadpoles filter
and entrap suspended algae (Seale and Beckvar, 1980) via mouthparts designed for effective
28
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grazing of periphyton (Wassersug, 1984, Kupferberg el al.; 1994; Kupferberg, 1997; Altig and
McDiarmid, 1999).
Juvenile and adult CRLFs forage in aquatic and terrestrial habitats, and their diet differs greatly
from that of larvae. The main food source for juvenile aquatic- and terrestrial-phase CRLFs is
thought to be aquatic and terrestrial invertebrates found along the shoreline and on the water
surface. Hayes and Tennant (1985) report, based on a study examining the gut content of 35
juvenile and adult CRLFs, that the species feeds on as many as 42 different invertebrate taxa,
including Arachnida, Amphipoda, Isopoda, Insecta, and Mollusca. The most commonly observed
prey species were larval alderflies (Sialis cf. californica), pillbugs (Armadilliadrium vulgare),
and water striders (Gerris sp). The preferred prey species, however, was the sowbug (Hayes and
Tennant, 1985). This study suggests that CRLFs forage primarily above water, although the
authors note other data reporting that adults also feed under water, are cannibalistic, and
consume fish. For larger CRLFs, over 50% of the prey mass may consists of vertebrates such as
mice, frogs, and fish, although aquatic and terrestrial invertebrates were the most numerous food
items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at night; for
juveniles feeding occurs during the day and at night (Hayes and Tennant 1985).
2.5.4 Habitat
CRLFs require aquatic habitat for breeding, but also use other habitat types including riparian
and upland areas throughout their life cycle. CRLF use of their environment varies; they may
complete their entire life cycle in a particular habitat or they may utilize multiple habitat types.
Overall, populations are most likely to exist where multiple breeding areas are embedded within
varying habitats used for dispersal (USFWS 2002). Generally, CRLFs utilize habitat with
perennial or near-perennial water (Jennings et al. 1997). Dense vegetation close to water,
shading, and water of moderate depth are habitat features that appear especially important for
CRLF (Hayes and Jennings 1988).
Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds,
marshes, sag ponds (land depressions between fault zones that have filled with water), dune
ponds, and lagoons. Breeding adults have been found near deep (0.7 m) still or slow moving
water surrounded by dense vegetation (USFWS 2002); however, the largest number of tadpoles
have been found in shallower pools (0.26 - 0.5 m) (Reis, 1999). Data indicate that CRLFs do
not frequently inhabit vernal pools, as conditions in these habitats generally are not suitable
(Hayes and Jennings 1988).
CRLFs also frequently breed in artificial impoundments such as stock ponds, although additional
research is needed to identify habitat requirements within artificial ponds (USFWS 2002). Adult
CRLFs use dense, shrubby, or emergent vegetation closely associated with deep-water pools
bordered with cattails and dense stands of overhanging vegetation
(http://www.fws.gov/endangered/features/rl frog/rlfrog.html#where).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability, and life
stage. Adults rely on riparian vegetation for resting, feeding, and dispersal. The foraging quality
of the riparian habitat depends on moisture, composition of the plant community, and presence of
29
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pools and backwater aquatic areas for breeding. CRLFs can be found living within streams at
distances up to 3 km (2 miles) from their breeding site and have been found up to 30 m (100 feet)
from water in dense riparian vegetation for up to 77 days (USFWS 2002).
During dry periods, the CRLF is rarely found far from water, although it will sometimes disperse
from its breeding habitat to forage and seek other suitable habitat under downed trees or logs,
industrial debris, and agricultural features (UWFWS 2002). According to Jennings and Hayes
(1994), CRLFs also use small mammal burrows and moist leaf litter as habitat. In addition,
CRLFs may also use large cracks in the bottom of dried ponds as refugia; these cracks may
provide moisture for individuals avoiding predation and solar exposure (Alvarez 2000).
2.6 Designated Critical Habitat
In a final rule published on April 13, 2006, 34 separate units of critical habitat were designated
for the CRLF by USFWS (USFWS 2006; FR 51 19244-19346). A summary of the 34 critical
habitat units relative to USFWS-designated recovery units and core areas (previously discussed
in Section 2.5.1) is provided in Table 2-3.
'Critical habitat' is defined in the Endangered Species Act (ESA) as the geographic area
occupied by the species at the time of the listing where the physical and biological features
necessary for the conservation of the species exist, and there is a need for special management to
protect the listed species. It may also include areas outside the occupied area at the time of
listing if such areas are 'essential to the conservation of the species.' All designated critical
habitat for the CRLF was occupied at the time of listing. Critical habitat receives protection
under Section 7 of the ESA through prohibition against 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 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.
Please note that a more complete description of these habitat types is provided in Attachment 1.
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Occupied habitat may be included in the critical habitat only if essential features within the
habitat may require special management or protection. Therefore, USFWS does not include
areas where existing management is sufficient to conserve the species. Critical habitat is
designated outside the geographic area presently occupied by the species only when a
designation limited to its present range would be inadequate to ensure the conservation of the
species. For the CRLF, all designated critical habitat units contain all four of the PCEs, and were
occupied by the CRLF at the time of FR listing notice in April 2006. The FR notice designating
critical habitat for the CRLF includes a special rule exempting routine ranching activities
associated with livestock ranching from incidental take prohibitions. The purpose of this
exemption is to promote the conservation of rangelands, which could be beneficial to the CRLF,
and to reduce the rate of conversion to other land uses that are incompatible with CRLF
conservation. Please see Attachment 1 for a full explanation on this special rule.
USFWS has established adverse modification standards for designated critical habitat (USFWS
2006). Activities that may destroy or adversely modify critical habitat are those that alter the
PCEs and jeopardize the continued existence of the species. Evaluation of actions related to use
of ODM that may alter the PCEs of the CRLF's critical habitat form the basis of the critical
habitat impact analysis. According to USFWS (2006), activities that may affect critical habitat
and therefore result in adverse effects to the CRLF include, but are not limited to the following:
(1) Significant alteration of water chemistry or temperature to levels beyond the tolerances
of the CRLF that result in direct or cumulative adverse effects to individuals and their
life-cycles.
(2) Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat that could result in elimination or
reduction of habitat necessary for the growth and reproduction of the CRLF by
increasing the sediment deposition to levels that would adversely affect their ability to
complete their life cycles.
(3) Significant alteration of channel/pond morphology or geometry that may lead to changes
to the hydrologic functioning of the stream or pond and alter the timing, duration, water
flows, and levels that would degrade or eliminate the CRLF and/or its habitat. Such an
effect could also lead to increased sedimentation and degradation in water quality to
levels that are beyond the CRLF's tolerances.
(4) Elimination of upland foraging and/or aestivating habitat or dispersal habitat.
(5) Introduction, spread, or augmentation of non-native aquatic species in stream segments
or ponds used by the CRLF.
(6) Alteration or elimination of the CRLF's food sources or prey base (also evaluated as
indirect effects to the CRLF).
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 ODM is expected to directly impact living organisms within the action
area, critical habitat analysis for ODM 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.
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2.6.1 Special Rule Exemption for Routine Ranching Activities
As part of the critical habitat designation, the Service promulgated a special rule exemption
regarding routine ranching activities where there is no Federal nexus from take prohibitions
under Section 9 of the ESA. (USFWS 2006, 71 FR 19285-19290). The Service's reasoning
behind this exemption is that managed livestock activities, especially the creation of stock ponds,
provide habitat for the CRLF. Maintenance of these areas as rangelands, rather than conversion
to other uses should ranching prove to be economically infeasible is, overall, of net benefit to the
species.
Several of the specific activities exempted include situations where pesticides may be used in
accordance with labeled instructions. In this risk assessment, the Agency has assessed the risk
associated with these practices using the standard assessment methodologies. Specific
exemptions, and the reasoning behind each of the exemptions is provided below. The rule
provides recommended best management practices, but does not require adherence to these
practices by the landowner.
1. Stock Pond Management and Maintenance
a. Chemical control of aquatic vegetation. These applications are allowed primarily
because the Service felt "it is unlikely that vegetation control would be needed
during the breeding period, as the primary time for explosive vegetation control is
during the warm summer months." The Service recommends chemical control
measures be used only "outside of the general breeding season (November
through April) and juvenile stage (April through September) of the CRLF."
Mechanical means are the preferred method of control.
b. Pesticide applications for mosquito control. These applications are allowed
because of concerns associated with human and livestock health. Alternative
mosquito control methods, primarily introduction of nonnative fish species, are
deemed potentially more detrimental to the CRLF than chemical or bacterial
larvicides. The Service believes "it unlikely that [mosquito] control would be
necessary during much of the CRLF breeding season," and that a combination of
management methods, such as manipulation of water levels, and/or use of a
bacterial larvicide will prevent or minimize incidental take.
2. Rodent Control. The Service notes "we believe the use of rodenticides present a low risk
to CRLF conservation." In large part, this is due to the fact that "it is unknown the extent
to which small mammal burrows are essential for the conservation of CRLF."
a. Toxicant-treated grains. No data were available to evaluate the potential effects
of these compounds (primarily anti-coagulants) on the CRLF. Grain is not a
typical food item for the frog, but individuals may be indirectly exposed by
consuming invertebrates which have ingested treated grain. There is a possibility
of dermal contact, especially when the grain is placed in the burrows. Placing
treated grain into the burrows is not prohibited, but should this method of rodent
control be used, the Service recommends bait-station or broadcast application
methods to reduce the probability of exposure.
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b. Burrow fumigants. Use of burrow fumigants is not prohibited, but the Service
recommends "not using burrow fumigants within 0.7 mi (1.2 km) in any direction
from a water body" suitable as CRLF habitat.
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 ODM is likely to encompass considerable portions of the United States based on the large
array of agricultural uses for which it is registered. However, the scope of this assessment limits
consideration of the overall action area to those portions that may be applicable to the protection
of the CRLF and its designated critical habitat within the state of California. Deriving the
geographical extent of this portion of the action area is the product of consideration of the types
of effects that ODM may be expected to have on the environment, the exposure levels to ODM
that are associated with those effects, and the best available information concerning the use of
ODM and its fate and transport within the state of California.
The definition of action area requires a stepwise approach that begins with an understanding of
the federal action. The federal action is defined by the currently labeled uses for ODM. An
analysis of labeled uses and review of available product labels was completed. This analysis
indicates that, for ODM, the following uses are considered as part of the federal action evaluated
in this assessment:
Alfalfa grown for seed
Broccoli raab
Clover grown for seed
Pumpkins
Musk melons (cantaloupes)
Cherries
Plums
Head lettuce
Safflower
Beans (lima)
Brussel sprouts
Sweet corn
Summer squash
Other melons
Crab apples
Prunes
Spanish onions
Walnuts
Sugar beets
Cabbage
Cotton
Winter squash
Apples
Nectarines
Quinces
Peppermint
Broccoli
Cauliflower
Cucumbers
Watermelons
Apricots
Peaches
Grapes
Spearmint
Ornamental plants grown for cut flowers.
The analysis indicates that the following uses: ornamental, forest, non-bearing tree, and
Christmas tree uses for which applications are made by injection do not need to be considered in
this assessment. Tree injection methods of application are expected to pose little opportunity for
exposure to the CRLF and other organisms upon which it depends. Tree injection methods are
expected to confine ODM within tissues of treated trees. The potential for passive export of
ODM from plant roots as a result of this method of treatment is unknown, but is not expected to
result in exposure at the soil surface. ODM residues will be available to insects that consume
leaves or sap; however, most of these are expected to be present on the trees while they are alive.
Further, California PUR database usage data between 2002 and 2005 indicate that tree injection
applications of ODM are minor compared to other types of applications. Most applications of
this type were made to trees in landscape maintenance and rights of way. In most instances
fewer than four instances of application occurred, and less than one pound was applied per year.
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These applications are expected to occur in urban and suburban areas, which is reflected in the
fact that usage is highest in San Diego, Orange, and Los Angeles Counties, which have large
urban areas. Therefore, exposure to terrestrial organisms is not expected to be significant. The
potential for runoff is also expected to be very low, so aquatic organisms are unlikely to be
affected. Thus, tree injection uses are concluded to have "No Effect" on the CRLF and are not
analyzed further in this assessment.
After determination of which uses will be assessed, an evaluation of the potential "footprint" of
the use pattern should be determined. This "footprint" represents the initial area of concern and
is typically based on available land cover data. Local land cover data available for the state of
California were analyzed to refine the understanding of potential ODM use. The overall
conclusion of this analysis is that all uses listed above have the potential to overlap with CRLF
habitat. The initial area of concern is defined as all land cover types that represent the labeled
uses described above. A map representing all the land cover types that make up the initial area
of concern is presented in Figure 2c.
34
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Oxydemeton-methyl All Uses - Initial Area of Concern
Legend
Custom layout
~ Recovery units
| ODM All Uses Overlap
| CA counties
| CNDDB occurrence sections
| Critical habitat
Core areas
ODM All Uses
0 25 50 100 150 200
Compiled from California County boundaries (ESRI, 2002), Map created by US Environmental Protection Agency, Office
USDA National Agriculture Statistical Service (NASS, 2002) of pesticides Programs, Environmental Fate and Effects Division.
Gap Analysis Program Ore bard/Vineyard Landcover (GAP) September, 2007. Projection: Albers Equal Area Conic USGS,
National Land Cover Database (NLCD) (MRLC, 2001) North American Datum of 1983 (NAD 1983)
Figure 2c. Initial Area of Concern Map for ODM Uses in Proximity to the CRLF.
Once the initial area of concern is defined, the next step is to compare the extent of that area with
the results of the screening level risk assessment. The screening level risk assessment will define
which taxa, if any, are predicted to be exposed at concentrations above the Agency's Levels of
Concern (LOC). The screening level assessment includes an evaluation of the environmental
fate properties of ODM to determine which routes of transport are likely to have an impact on
the CRLF.
35
-------
Based on the low sorption potential and low volatility of ODM and its degradates, exposure in
water bodies will be primarily in the water column. Exposure may occur in the soil at sites of
application, through run-off to water bodies, and through spray drift to terrestrial environments.
LOC exceedances are used to describe how far effects may be seen from the initial area of
concern. Factors considered include: spray drift, downstream run-off, atmospheric transport, etc.
This information is incorporated into GIS and a map of the action area is created.
For ODM and the CRLF, the screening-level assessment indicated that exceedances are expected
for birds (surrogate for the CRLF), mammals, and terrestrial invertebrates as a result of all uses.
Further refinement of this assessment using the spreadsheet model, T-HERPS, which is more
specific to analyses for CRLF exposure, resulted in the same findings. Fish and aquatic
invertebrates also demonstrate RQs that exceed aquatic LOCs as a result of ODM aerial and
ground applications to cole crops (broccoli, cauliflower, cabbage), and aerial applications to
lettuce. Plants in terrestrial and riparian areas and aquatic plants are excluded from this
assessment because toxicity tests available in guideline and ECOTOX studies demonstrated that
ODM is not toxic to plants. Furthermore, no incidents involving plants have been reported in
OPPs Ecological Incident Information System (EIIS). Based on this information, we believe that
plants can be safely excluded from consideration in this risk assessment. Therefore, it is
concluded that there is "No Effect" on the CRLF via plant-related endpoints. Discussion of plant
effects is discussed further in Section 4: Effects Assessment.
Based on the RQ determined for all uses (i.e., RQs exceed for all terrestrial taxa under all uses
analyzed in this risk assessment), and the extent of spray drift expected as a result of the highest
application rate to cabbage, the initial area of concern is expected to be expanded beyond its
perimeter by the addition of a 11,338-fit zone. It is also expanded due to runoff into moving
water from areas of which at least 27% of cropped land contains ODM-treated crops. As a result
the action area is larger than the initial area of concern. This area encompasses between 22.1%
and 62.8% of CRLF habitat within the eight recovery units. The action area and analyses used to
derive this area is given in the Risk Estimation Section, where the action area is depicted in
Figure 5a. Detailed GIS results and maps are provided in Appendix G.
2.8 Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental value that
is to be protected."3 Selection of the assessment endpoints is based on valued entities (e.g.,
CRLF, organisms important in the life cycle of the CRLF, and the PCEs of its designated critical
habitat), the ecosystems potentially at risk (e.g,. waterbodies, riparian vegetation, and upland and
dispersal habitats), the migration pathways of ODM (e.g., runoff, spray drift, etc.), and the routes
by which ecological receptors are exposed to ODM-related contamination (e.g., direct contact,
etc).
3 From U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
36
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2.8.1 Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival, reproduction,
and growth of the CRLF, as well as indirect effects, such as reduction of the prey base and/or
modification of its habitat. In addition, potential modification of critical habitat is assessed by
evaluating potential effects to PCEs, which are components of the habitat areas that provide
essential life cycle needs of the CRLF. Each assessment endpoint requires one or more
"measures of ecological effect," defined as changes in the attributes of an assessment endpoint or
changes in a surrogate entity or attribute in response to exposure to a pesticide. Specific
measures of ecological effect are generally evaluated based on acute and chronic toxicity
information from registrant-submitted guideline tests that are performed on a limited number of
organisms. Additional ecological effects data from the open literature are also considered.
A complete discussion of all the toxicity data available for this risk assessment, including
resulting measures of ecological effect selected for each taxonomic group of concern, is included
in Section 4 of this document. A summary of the assessment endpoints and measures of
ecological effect selected to characterize potential assessed direct and indirect CRLF risks
associated with exposure to ODM is provided in Table 2-4. At this time, data on the toxicity of
ODM to amphibians are not available; therefore, data for other taxa will be used as a surrogate
for the CRLF.
Table 2-4 Summary of Assessment Endpoints and Measures of Ecological Effects for Direct and
Indirect Effects of Oxydemeton Methyl on the California Red-legged Frog
Assessment Endpoint Measures of Ecological Effects4
Aquatic Phase
(eggs, larvae, tadpoles, juveniles, and adults)*
1. Survival, growth, and reproduction of CRLF
individuals via direct effects on aquatic phases
la. Most sensitive fish acute LC50 (guideline)
lb. Most sensitive fish early-life stage NOAEC (guideline
or ECOTOX)
2. Survival, growth, and reproduction of CRLF
individuals via effects to food supply (i.e.,
freshwater invertebrates, non-vascular plants)
2a. Most sensitive fish and aquatic invertebrate EC50 or
LC50 (guideline) (see below about aquatic plants)
2b. Most sensitive aquatic invertebrate (guideline)and fish
chronic NOAEC (determined with ACR)
3. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat, cover,
and/or primary productivity (i.e., aquatic plant
community)
3. Non-vascular plant EC50 (freshwater algae, guideline)
(Resulted in No-Effect determination, so aquatic plants are
excluded from further analysis)
4. Survival, growth, and reproduction of CRLF
individuals via effects to riparian vegetation,
required to maintain acceptable water quality and
habitat in ponds and streams comprising the
species' current range.
4. Distribution of EC25 values for monocots (ECOTOX)
(Resulted in No-Effect determination, so terrestrial plants
are excluded from further analysis)
Terrestrial Phase (Juveniles and adults)
5. Survival, growth, and reproduction of CRLF
individuals via direct effects on terrestrial phase
adults and juveniles
5a. Most sensitive birdb acute LC50 or LD50 (guideline)
5b. Most sensitive birdb chronic NOAEC (guideline)
6. Survival, growth, and reproduction of CRLF
individuals via effects on prey (i.e., terrestrial
invertebrates, small terrestrial vertebrates, including
6a. Most sensitive terrestrial invertebrate and vertebrate
acute EC50 or LC50 (guideline)0
6b. Most sensitive terrestrial invertebrate and vertebrate
4 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in Section 4.
37
-------
mammals and terrestrial phase amphibians)
chronic NOAEC (guideline)
7. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian vegetation)
7a. Distribution of EC25 values for monocots (ECOTOX)
(Resulted in No-Effect determination, so terrestrial plants
are excluded from further analysis)
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 Although the most sensitive toxicity value is initially used to evaluate potential indirect effects, sensitivity
distribution is used (if sufficient data are available) to evaluate the potential impact to food items of the CRLF.
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 ODM 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 destroy or adversely modify critical
habitat are those that alter the PCEs. Therefore, these actions are identified as assessment
endpoints. It should be noted that evaluation of PCEs as assessment endpoints is limited to those
of a biological nature (i.e., the biological resource requirements for the listed species associated
with the critical habitat) and those for which ODM effects data are available.
Assessment endpoints and measures of ecological effect selected to characterize potential
modification to designated critical habitat associated with exposure to ODM are provided in
Table 2-7. Adverse modification to the critical habitat of the CRLF includes the following, as
specified by USFWS (2006) and previously discussed in Section 2.6:
1. Alteration of water chemistry/quality including temperature, turbidity, and oxygen
content necessary for normal growth and viability of juvenile and adult CRLFs.
2. Alteration of chemical characteristics necessary for normal growth and viability of
juvenile and adult CRLFs.
3. Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat.
4. Significant alteration of channel/pond morphology or geometry.
5. Elimination of upland foraging and/or aestivating habitat, as well as dispersal habitat.
6. Introduction, spread, or augmentation of non-native aquatic species in stream
segments or ponds used by the CRLF.
7. Alteration or elimination of the CRLF's food sources or prey base.
Measures of such possible effects by labeled use of ODM on critical habitat of the CRLF are
described in Table 2-5. Some components of these PCEs are associated with physical abiotic
features (e.g., presence and/or depth of a water body, or distance between two sites), which are
not expected to be measurably altered by use of pesticides. Assessment endpoints used for the
analysis of designated critical habitat are based on the adverse modification standard established
by USFWS (2006).
38
-------
Table 2-5. Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat
Ass
M
ess
ea
me
su
nt
re
End
s
poi
of
nt
E
CO
lo
gi
ca
1
Ef
fe
ct
s
Aquatic Phase PCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alte
a.
rati
M
on
OS
of
t
cha
se
nnel
ns
/pon
iti
d
ve
mor
aq
phol
ua
ogy
tic
or
Pi
geo
an
met
t
iy
E
and/
c5
or
0
incr
(g
ease
ui
in
de
sedi
lin
men
e
t
or
dep
E
ositi
C
on
0
with
T
in
0
the
X)
stre
b.
am
Di
cha
str
nnel
ib
5 All toxicity data reviewed for this assessment are included in Section 4.
39
-------
or
uti
pon
on
d:
of
aqu
E
atic
c2
habi
5
tat
va
(inc
lu
ludi
es
ng
fo
ripa
r
rian
ter
veg
re
etati
str
on)
ial
pro
m
vide
on
s
oc
for
ot
shel
s
ter,
(S
fora
ee
ging
dli
ng
pred
e
ator
m
avoi
er
dan
ge
ce,
nc
and
e,
aqu
ve
atic
ge
disp
tat
ersa
iv
1 for
e
juve
vi
nile
go
and
r,
adul
or
t
E
CR
C
LFs
0
T
0
X)
c.
Di
str
ib
uti
on
of
E
c2
5
va
40
-------
lu
es
fo
r
ter
re
str
ial
di
CO
ts
(S
ee
dli
ng
e
m
er
(TP
ge
nc
e,
ve
ge
tat
iv
e
vi
go
r,
or
E
C
0
T
0
X)
Alte
a.
rati
M
on
OS
in
t
wat
se
er
ns
che
iti
mist
ve
ry/q
E
ualit
c5
y
0
incl
va
udin
lu
g
es
tem
fo
pera
r
ture
aq
ua
turb
tic
41
-------
idit
Pi
y,
an
and
ts
oxy
(g
gen
ui
cont
de
ent
lin
nec
e
essa
or
iy
E
for
C
nor
0
mal
T
gro
0
wth
X)
and
b.
viab
Di
ility
str
of
ib
juve
uti
nile
on
and
of
adul
E
t
c2
CR
5
LFs
va
and
lu
thei
es
r
fo
foo
r
d
ter
sour
re
ce.6
str
ial
m
on
oc
ot
s
(S
ee
dli
ng
e
m
er
(TP
nc
e
or
ve
ge
tat
6 Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these
processes are not biologically mediated and are not relevant to the endpoints included in this assessment.
42
-------
iv
e
vi
go
r,
or
E
C
O
T
O
X)
c.
Di
str
ib
uti
on
of
E
C2
5
va
lu
es
fo
r
ter
re
str
ial
di
CO
ts
(S
ee
dli
ng
e
m
er
ge
nc
e,
ve
ge
tat
iv
e
vi
go
r,
or
E
C
O
43
-------
T
0
X)
Alte
a.
rati
M
on
OS
of
t
othe
se
r
ns
che
iti
mic
ve
al
E
char
c5
acte
0
risti
or
cs
L
nec
c5
essa
0
iy
va
for
lu
nor
es
mal
fo
gro
r
wth
fis
and
h
viab
or
ility
aq
of
ua
CR
tic
LFs
-
and
ph
thei
as
r
e
foo
a
d
m
sour
ph
ce.
ibi
an
s
an
d
aq
ua
tic
in
ve
rte
br
at
es
(g
ui
de
lin
e
or
44
-------
E
C
O
T
O
X)
b.
M
OS
t
se
ns
iti
ve
N
O
A
E
C
va
lu
es
fo
r
fis
h
or
aq
ua
tic
ph
as
e
a
m
ph
ibi
an
s
an
d
aq
ua
tic
in
ve
rte
br
at
es
(g
ui
de
lin
e
45
-------
or
E
C
0
T
0
X)
Red
a.
ucti
M
on
OS
and/
t
or
se
mod
ns
ifica
iti
tion
ve
of
aq
aqu
ua
atic-
tic
base
Pi
d
an
foo
t
d
E
sour
c5
ces
0
for
(g
pre-
ui
met
de
amo
lin
rphs
e
{e.g.
or
E
alga
C
e)
0
T
0
X)
Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Eli
a.
min
Di
atio
str
n
ib
and/
uti
or
on
dist
of
urba
E
nee
c2
of
5
upla
va
nd
lu
habi
es
tat;
fo
abili
r
ty
m
of
on
46
-------
habi
oc
tat
ot
to
s
sup
(S
port
ee
foo
dli
d
ng
sour
e
ce
m
of
er
CR
ge
LFs
nc
e,
Upl
ve
and
ge
area
tat
s
iv
with
e
in
vi
200
go
ft of
r,
the
or
edg
E
e of
C
the
0
ripa
T
rian
0
veg
X)
etati
b.
on
Di
or
str
drip
ib
line
uti
surr
on
oun
of
ding
E
aqu
c2
atic
5
and
va
ripa
lu
rian
es
habi
fo
tat
r
that
di
are
CO
com
ts
pris
(S
ed
ee
of
dli
gras
ng
slan
e
ds,
m
woo
er
dlan
ge
ds,
nc
and/
e,
47
-------
or
ve
wetl
ge
and/
tat
ripa
iv
rian
e
plan
vi
t
go
spec
r,
ies
or
that
E
pro
C
vide
0
s
T
the
0
CR
X)
LF
c.
shel
M
ter,
OS
fora
t
ge,
se
and
ns
pred
iti
ator
ve
avoi
fo
dan
od
ce
so
Eli
ur
min
ce
atio
ac
n
ut
and/
e
or
E
dist
c5
urba
o/
nee
L
of
c5
disp
0
ersa
an
1
d
habi
N
tat:
0
Upl
A
and
E
or
C
ripa
va
rian
lu
disp
es
ersa
fo
1
r
habi
ter
tat
re
with
str
in
ial
desi
ve
gnat
rte
ed
br
48
-------
unit
at
s
es
and
(
bet
m
wee
a
n
m
occ
m
upie
al
d
s)
loca
an
tion
d
s
in
with
ve
in
rte
0.7
br
mi
at
of
es,
eac
bi
h
rd
othe
s
r
or
that
ter
alio
re
w
str
for
ial
mov
-
eme
ph
nt
as
bet
e
wee
a
n
m
sites
ph
incl
ibi
udin
an
g
s,
both
an
natu
d
ral
fr
and
es
alter
h
ed
w
sites
at
whi
er
ch
fis
do
h.
not
cont
ain
barr
iers
to
disp
ersa
1
Red
ucti
49
-------
on
and/
or
mod
ifica
tion
of
foo
d
sour
ces
for
terr
estri
al
pha
se
juve
nile
s
and
adul
_ts
Alte
rati
on
of
che
mic
al
char
acte
risti
cs
nec
essa
iy
for
nor
mal
gro
wth
and
viab
ility
of
juve
nile
and
adul
t
CR
LFs
and
thei
r
50
-------
foo
d
sour
ce.
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 ODM to the environment. The following risk hypotheses are
presumed for this endangered species assessment:
• Labeled uses of ODM within the action area may directly affect the CRLF by causing
mortality or by adversely affecting growth or fecundity;
• Labeled uses of ODM within the action area may indirectly affect the CRLF by reducing
or changing the composition of food supply;
• Labeled uses of ODM within the action area may indirectly affect the CRLF and/or
modify designated critical habitat by reducing or changing the composition of the terrestrial plant
community (i.e., riparian habitat) required to maintain acceptable water quality and habitat in the
ponds and streams comprising the species' current range and designated critical habitat;
• Labeled uses of ODM within the action area may modify the designated critical habitat of
the CRLF by reducing or changing breeding and non-breeding aquatic habitat (via modification
of water quality parameters, habitat morphology, and/or sedimentation);
• Labeled uses of ODM within the action area may modify the designated critical habitat of
the CRLF by reducing the food supply required for normal growth and viability of juvenile and
adult CRLFs;
• Labeled uses of ODM within the action area may modify the designated critical habitat of
the CRLF by reducing or changing upland habitat within 200 ft of the edge of the riparian
vegetation necessary for shelter, foraging, and predator avoidance.
• Labeled uses of ODM within the action area may modify the designated critical habitat of
the CRLF by reducing or changing dispersal habitat within designated units and between
occupied locations within 0.7 mi of each other that allow for movement between sites including
both natural and altered sites which do not contain barriers to dispersal.
• Labeled uses of ODM within the action area may modify the designated critical habitat of
the CRLF by altering chemical characteristics necessary for normal growth and viability of
juvenile and adult CRLFs.
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment. It
specifies the stressor (ODM), release mechanisms, biological receptor types, and effects
endpoints of potential concern. The conceptual models for aquatic and terrestrial phases of the
51
-------
CRLF are shown in Figures 2c and 2d, and the conceptual models for the aquatic and terrestrial
PCE components of critical habitat are shown in Figures 2e and 2f. Exposure routes shown in
dashed lines are not quantitatively considered because the resulting exposures are expected to be
so low as not to cause adverse effects to the CRLF.
Long-range atmospheric transport is not expected due to the non-volatility and non-persistent
nature of ODM. Likewise, groundwater transport is considered unlikely due to the low
persistence of ODM, even when its mobility in soil is considered. The operative routes of
exposure will be spray drift at the time of application, and run-off due to precipitation.
Figure 2d. Conceptual Model for Pesticide Effects on Aquatic Phase of the Red-Legged
Frog
52
-------
Figure 2e. Conceptual Model for Pesticide Effects on Terrestrial Phase of Red-Legged Frog
53
-------
Figure 2f. Conceptual Model for Pesticide Effects on Aquatic Components of Red-Legged
Frog Critical Habitat
54
-------
Figure 2g. Conceptual Model for Pesticide Effects on Terrestrial Components of Red-
Legged Frog Critical Habitat
55
-------
2.10 Analysis Plan
Analysis of ODM risks to the California Red-Legged Frog (both direct and indirect) and to its
critical habitat will be assessed according to the Overview Document (EPA, 2004) and Agency
guidance for ecological risk assessments.
2.10.1 Exposure Analysis
Aquatic. Risks (direct effects) to the aquatic phase CRLF will be assessed by comparing
modeled surface water exposure concentrations of ODM to acute and chronic effect
concentrations for aquatic phase amphibians (surrogate freshwater fish) from laboratory studies
(see the Effects Analysis section below). Risks (indirect effects) to aquatic dietary food
resources (aquatic invertebrates) of the aquatic phase CRLF or risks (indirect effects) to aquatic
habitat that support the CRLF will also be assessed by comparing modeled surface water
exposure concentrations of total ODM residues to laboratory established effect levels appropriate
for the taxa.
For the screening assessment, the standard EXAMS water body of 2 meters maximum depth, and
20,000 cubic meters volume, will be used. Since ODM is applied by numerous application
methods, the model accounts for loading into the surface water via spray drift, run-off and
erosion (Figure 2d and 2f). Agricultural scenarios appropriate for labeled ODM uses will be
used to account for local soils, weather and growing practices which impact the magnitude and
frequency of ODM loading to the surface water. Maximum labeled application rates, with
maximum number of applications and shortest intervals, will be used to help define (1) the
Action Area within California for the Federal Action and (2) for evaluating effects to the CRLF.
Concentrations of ODM estimated by PRZM-EXAMS represent loading in water bodies adjacent
to any treated field and assume that the concentration applies to any water body within the
treated area.
Terrestrial. Risks to the terrestrial phase CRLF will be assessed by comparing modeled
exposure to effect concentrations from laboratory studies. Exposure in the terrestrial phase will
be quantified using the TREX model, which automates the calculation of dietary exposure
according to the Hoerger-Kenaga nomogram, as modified by Fletcher et al. (1994). The
nomogram tabulates the 90th and 50th percentile exposure expected on various classes of food
items, and scales the exposure (in dietary terms) to the size and daily food intake of several size
classes of birds and mammals. Birds are also used as surrogates to represent reptiles and
terrestrial-phase amphibians. A foliar decay half-life of 35 days will be used. This is the default
value used in EFED when the foliar dissipation half-life is not known and no data exist from
which to estimate it.
The LOC is expected to be exceeded for ODM for birds (the surrogate organism for the CRLF).
Therefore, the T-HERPS model will be used to characterize direct risks to the CRLF. This
model utilizes the same principles as in TREX, except that the estimated daily food intake is
adjusted for herpetofauna given that they consume less food per day than homeotherms.
56
-------
Effects to terrestrial invertebrates will be estimated by using the dose-based EEC obtained from
TREX for 20g birds consuming large insects (in mg/kg bw) multiplied by an estimated value for
bee bodyweight (0.128g) to obtain a dose in (j,g/bee, which can then be divided by the toxicity
value (also in (j,g/bee) to calculate an RQ.
2.10.2 Effects Analysis
As previously discussed, assessment endpoints for the frog include direct toxic effects on
survival, reproduction, and growth of the species itself, as well as indirect effects, such as
reduction of the prey base and/or modification of its habitat. Direct effects to the red-legged frog
are based on toxicity information for freshwater fish and birds, which are generally used as a
surrogate for aquatic and terrestrial phase amphibians, respectively. The open literature will be
screened also for available frog toxicity data. Indirect effects to the red legged frog are assessed
by looking at available toxicity information of the frog's prey items and habitat requirements
(freshwater invertebrates, freshwater vertebrates, terrestrial invertebrates, and terrestrial
vertebrates).
2.10.3 Action Area Analysis
The Action Area for the federal action is the geographic extent of exceedence of listed species
Levels of Concern (LOCs) for any taxon or effect (acute or chronic, direct or indirect) resulting
from the maximum label-allowed use of ODM. To define the extent of the Action Area for
ODM with respect to the CRLF and its habitat, the following exposure assessment tools will be
used: PRZM-EXAMS, TREX, THERPS, AgDrift, AgDISP, and ArcGIS, a geographic
information system (GIS) program. Other tools may be used as required if these are inadequate
to define the maximum extent of the Action Area.
Terrestrial. To determine the terrestrial extent of the Action Area for terrestrial effects, a
distance around the initial area of concern over which effects are potentially extended by spray
drift must be estimated. To estimate this distance, the rate (in lb ai/acre) needed to bring all RQs
below their respective LOC (0.1 for acute, non-endangered birds and mammals, and 1.0 for
chronic) is calculated by dividing the LOC by the RQ, and multiplying the result by the highest
single application rate (0.75 lb/acre):
Rate below LOC (lb ai/acre) = (LOC/RQ)*(application rate, lb ai/acre).
The AgDrift or AgDISP model is then used to calculate the buffer distance needed to reduce the
rate to below LOCs. If the result is beyond the range of these models, then the Gaussian
extension to AgDISP is used.
Aquatic. To determine the downstream extent of the Action area for any aquatic effects, ODM
residues will also estimated for downstream from the treated areas by assuming dilution with
stream water (derived from land area) from unaffected sources propagating downstream, until a
point is reached beyond which there are no relevant LOC exceedances. Once the distribution of
predicted stream water concentrations is obtained, it is further processed using a model that
57
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calculates expected dilution in the stream according to contributing land area. As the land area
surrounding the field on which ODM is applied is enlarged, it encompasses a progressively
greater drainage area; in effect, a progressively larger 'sub-watershed' is created, with a
concomitant increase in dilution at the drainage point. This drainage point moves down-gradient
along the stream channel as the sub-watershed is expanded. At a certain point the predicted
stream concentrations will fall below the LOC. The area below this point is then assumed not to
be at risk, with the upstream areas (up to the initial application area) assumed to present the
potential for (direct and indirect) impact on the RLF. Additional ODM inputs within the same
watershed will cause the area bounded by the LOC to increase, extending the length of stream
that is likely to be impacted.
In order to determine the extent of the action area downstream from the initial area of concern,
the Agency will need to complete the screening level risk assessment. Once all aquatic risk
quotients (RQs) are calculated, the Agency determines which RQ to level of concern (LOC) ratio
is greatest for all aquatic organisms (plant and animal). For example, if fish have an acute RQ of
1 and aquatic invertebrates have an acute RQ of 2, the invertebrate RQ to LOC ratio (2/0.05)
would be greater than for plants (1/0.05). Therefore, the Agency would identify all stream
reaches downstream from the initial area of concern where the percent catchment area (PCA) for
the land uses identified for ODM are greater than 1/40, or 2.5%. All streams identified as
draining upstream catchments greater than 2.5% of the land class of concern, will be considered
part of the action area.
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3. Exposure Assessment
3.1 Label Application Rates and Intervals
Application rates and application intervals for ODM uses analyzed in this risk assessment are
presented in Table 3-1.
Table 3-1. Label Use Rates
'or ODM in California.
Use
Max. One-Time
Max No.
Min. Appl.
Application. Rate
Applications
Interval
Cabbage
0.75 lbs ai/A
3
7 days
Peppermint and spearmint
0.75 lbs ai/A
2
10 days
Brussel sprouts
0.5 lbs ai/A
3
7 days
Beans, lima
0.5 lbs ai/A
2
7 days
Broccoli
0.5 lbs ai/A
2
7 days
Broccoli raab
0.5 lbs ai/A
2
7 days
Cauliflower
0.5 lbs ai/A
2
7 days
Corn, sweet
0.5 lbs ai/A
2
7 days
Lettuce, head
0.5 lbs ai/A
2
7 days
Safflower
0.5 lbs ai/A
2
7 days
Alfalfa (grown for seed)
0.5 lbs ai/A
2
14 days
Clover grown for seed
0.5 lbs ai/A
2
14 days
Onions, Spanish (bulb)
0.5 lbs ai/A
2
14 days
Beets, sugar
0.5 lbs ai/A
1
N/A
Cotton
0.5 lbs ai/A
1
N/A
Curcurbits
0.5 lbs ai/A
1
N/A
Fruit trees, non-bearing1
0.375 lbs ai/A
2
7 days
Grapes, non-bearing
0.375 lbs ai/A
2
7 days
Ornamental plants grown
for cut flowers
0.375 lbs ai/A
2
7 days
Walnuts
0.375 lbs ai/A
1
N/A
Apples, apricots, cherries, crab apples, nectarines, peaches, plums, prunes, quinces
2Cucumbers, pumpkins, summer squash, winter squash, watermelons, muskmelons (canteloupes), other melons
3.2 Aquatic Exposure Assessment
As discussed in section 2.5.4, the CRLF occupies a variety of shallow, static and flowing aquatic
habitats in the aquatic phase of its life cycle (egg to tadpole). The current range of the CRLF is
represented by the core areas, critical habitat and occurrence sections in Figure 2a.
3.2.1 Conceptual Model of Exposure
Aquatic exposure of the CRLF within the action area is estimated with the PRZM (Pesticide
Root Zone Model) and EXAMS (Exposure Analysis Modeling System) model (EPA, 2004).
Screening-level exposures (estimated environmental concentrations, EEC) are produced using
the standard farm pond of 20,000 cubic meters volume. Watersheds where ODM is used are
59
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assumed to have 100% cropped area. The downstream extent of streams with exposures above
the Level of Concern (LOC) is estimated (using GIS methods) by expanding the watershed
considered until uncontaminated stream flow dilutes the initial pond concentration to below the
LOC. For the ODM application rates listed in Table 3-1 above, this results in a downstream
extent into areas containing >27% of areas containing crops associated with ODM.
Standard assumptions of 1% spray drift for ground application and 5% drift for aerial application
are used. If the pond concentration from PRZM-EXAMS exceeds the LOC, a spray drift buffer
is calculated (using AgDrift model) that will reduce the pond concentration to below the LOC. If
a spray drift buffer cannot be used to reduce the pond concentration to below the LOC, then a
separate spray drift buffer (neglecting run-off) is calculated with AgDrift to ensure that pond
concentrations are below the LOC (see section 2.10.3 above).
3.2.2 Existing Monitoring Data
The state of California performed monitoring for ODM in Sacramento county in 1991 (Aug 26,
Oct 25, and Oct 26) and 1992 (Feb 9 and 10). There were no detections in 180 samples with a
detection limit of 0.1 or 1.0 ppb. The general areas monitored included the American River,
Chicken/Strong Ranch Slough, City of Folsom urban runoff, and the Sacramento River. These
data are not considered sufficient for the exposure assessment, so modeling will be used instead.
3.2.3 Modeling Approach
The Tier 2 model, PRZM-EXAMS, was used to estimate aquatic exposures to ODM in the
absence of adequate monitoring data in the areas of interest. PRZM scenarios were chosen to
represent the registered crop uses (see Table 3-2 below). Model input parameters were chosen in
accordance with the Input Parameter Guidance of Feb. 28, 2002.
Use sites and the PRZM scenarios used to represent them are given in Table 3-2.
Risk quotients (RQs) were initially based on EECs derived using the Pesticide Root Zone
Model/Exposure Analysis Modeling System (PRZM/EXAMS) standard ecological pond
scenario according to the methodology specified in the Overview Document (U.S. EPA, 2004).
Where LOCs for direct/indirect effects and/or adverse habitat modification are exceeded based
on the modeled EEC using the static water body (i.e., "may affect"), refined modeling may be
used to differentiate "may affect, but not likely to adversely affect" from "may affect and likely
to adversely affect" determinations for the CRLF and its designated critical habitat.
The general conceptual model of exposure for this assessment is that the highest exposures are
expected to occur in the headwater streams adjacent to agricultural fields. Many of the streams
and rivers within the action area defined for this assessment are in close proximity to agricultural
use sites. Twenty-eight California scenarios were used in this assessment, 16 of which were
developed for the CRLF assessment. Each scenario is intended to represent a high-end exposure
setting for a particular crop. Each scenario location is selected based on various factors
including crop acreage, runoff and erosion potential, climate, and agronomic practices. Once a
location is selected, a scenario is developed using locally specific soil, climatic, and agronomic
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data. Each PRZM scenario is assigned a specific climatic weather station providing 30 years of
daily weather values.
Specific California PRZM scenarios were chosen for this assessment (Table 3-2), plus a scenario
for mint from Oregon. All scenarios were used within the standard framework of
PRZM/EXAMS modeling using the standard graphical user interface (GUI) shell, PE4v01.pl.
Table 3-2. Application Parameters for Modeled Crops
PRZM
Crop
Rate
Number of
Interval
First
Scenario1
lb/acre
applications
(days)
Application
Date
Cole crop
Broccoli, cauliflower, broccoli
raab
0.5
2
7
Feb. 1
Brussel sprouts
0.5
3
7
Feb. 1
Cabbage
0.75
3
7
Feb. 1
Oregon
Peppermint, spearmint
0.75
2
10
Apr. 20
mint
Row
Lima Beans
0.5
2
14
Mar. 1
Crop
Corn
Sweet Corn
0.5
2
7
Apr. 15
Lettuce
Head Lettuce
0.5
2
7
Mar. 1
Alfalfa
Alfalfa, clover (both grown for
seed)
0.5
2
14
Mar 1
Onion
Spanish Onion (bulb)
0.5
2
14
Mar. 1
Sugarbeet
Sugarbeet
0.5
1
n/a
Mar. 1
Cotton
Cotton
0.5
1
n/a
May 10
Melons
Curcubits (cucumbers,
pumpkins, summer and winter
squash, watermelons,
muskmelons, canteloupes
0.5
1
n/a
May 20
Fruit
Non-bearing apples, apricots,
cherries, crab apples,
nectarines, peaches, plums,
prunes, quinces
0.375
2
7
Mar. 1
Nursery
Ornamental plants grown for
flowers
0.375
2
7
Mar. 1
Almond
Walnut
0.375
1
n/a
Mar. 1
'Where applicable, both ground and aerial applications were modeled. Aerial applications are
prohibited for cotton, fruit trees, grapes, mint, walnuts, nurseries.
3.2.3.1 Model Inputs
The estimated water concentrations from surface water sources were calculated using Tier 2
PRZM/EXAMS. PRZM is used to simulate pesticide transport as a result of runoff and erosion
from a standardized watershed, and EXAMS estimates environmental fate and transport of
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pesticides in surface waters. The linkage program shell (PE4v01.pl) that incorporates the site-
specific scenarios was used to run these models.
The PRZM/EXAMS model was used to calculate concentrations using the standard ecological
water body scenario in EXAMS. Weather and agricultural practices were simulated over 30
years so that the 1 in 10 year exceedance probability at the site was estimated for the standard
ecological water body.
Models to estimate the effect of setbacks on load reduction for runoff are not currently available.
It is well documented that vegetated setbacks can result in a substantial reduction in pesticide
load to surface water (USDA, NRCS, 2000). Therefore, the aquatic EECs presented in this
assessment are likely to over-estimate exposure in areas with well-vegetated setbacks. While the
extent of load reduction cannot be accurately predicted through each relevant stream reach in the
action area, data from USD A (USD A, 2000) suggest reductions could range from 11 to 100%.
The appropriate PRZM input parameters (Table 3-3) were selected from the environmental fate
data submitted by the registrant and in accordance with US EPA-OPP EFED water model
parameter selection guidelines, Guidance for Selecting Input Parameters in Modeling the
Environmental Fate and Transport of Pesticides, Version 2.3, February 28, 2002.
Table 3-3. PRZM-EXAMS Input Parameters
Input Parameter
Value
Source/Comment
Molecular Weight
246.29 g/mol
EFGWB one-liner
Aerobic Soil half-life
9.6 days (3 times single value
of 3.2 days)
MRID 42830501
Freundlich constant, Kf
0.01
MRID 40884202
Aqueous Solubility
1,000,000 ppm (miscible)
EFGWB one-liner
Vapor Pressure
2.85 E-5 torr
EFGWB one-liner
Hydrolysis half-life
41 days (pH 7)
MRID 00143057
Aqueous photolysis half-life
136 days
MRID 40781501
Benthic half-life
10.5 days (3 times single value
of 3.5 days)
MRID 42901801
Aerobic aquatic half-life
19.2 days
2 times soil input value as per
Input Parameter guidance
Chemical Application Method
(CAM)
2 (foliar spray)
Pesticide Labels
Incorporation Depth
0 cm
Appropriate for foliar spray
Application Efficiency
0.99 (ground spray)
0.95 (aerial spray)
as per Input Parameter
guidance
Spray Drift
1% (ground)
5% (aerial)
as per Input Parameter
guidance
Table 3-2 provides details of the application parameters utilized in each scenario modeled. The
date of first application was set at March 1, because most uses for which there are data (PUR)
show use in California in most months of the year, and March corresponds to both a rainy part of
the year (thereby capturing higher run-off values), and the reproductive season of the frog. Other
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dates were used where the PRZM scenario emergence, maturation and harvest dates for the crop
made March 1 inappropriate. Safflower was not modeled, because there was no appropriate
PRZM scenario to use as a surrogate.
3.2.3.2 Results
The following results were obtained from PRZM-EXAMS (Table 3-4); output from PRZM-
EXAMS is provided in Appendix A. The highest peak exposures were for the cole crops
(broccoli, cauliflower, cabbage, brussel sprouts) because the crop emergence date for the PRZM
scenario dictated a first application date in early February, which is a particularly rainy period.
The higher rainfall results in higher run-off, and therefore higher exposure. These uses also have
some of the highest application rates with the shortest application interval.
Table 3-4. PRZM-EXAMS Mode
ed Exposure to C
>DM.
Crop
Application
Method
Peak Cone,
(ppb)
21-Day Cone,
(ppb)
60-Day Cone, (ppb)
Cabbage
Ground
33.11
26.22
17.19
Aerial
34.52
28.09
18.49
Mint
Ground
0.49
0.39
0.26
Brussel sprouts
Ground
22.07
17.26
11.32
Aerial
23.01
18.71
12.32
Lima beans
Ground
3.32
2.44
1.54
Aerial
5.00
3.69
2.47
Broccoli,
Ground
20.31
15.04
9.46
Cauliflower
Aerial
21.52
15.94
10.06
Corn
Ground
0.74
0.56
0.34
Aerial
2.74
1.96
1.23
Lettuce
Ground
9.60
7.33
4.55
Alfalfa
Ground
5.40
4.13
2.58
Aerial
6.76
5.24
3.29
Onion
Ground
1.00
0.79
0.49
Aerial
2.66
1.94
1.36
Sugar beets
Ground
2.82
2.04
1.21
Aerial
3.53
2.55
1.62
Cotton
Ground
0.43
0.27
0.18
Melons
Ground
0.28
0.19
0.11
Aerial
1.40
0.94
0.49
Fruit
Airblast
3.06
2.23
1.45
Grapes
Airblast
2.93
2.27
1.47
Nursery
Ground
3.84
2.90
1.77
Aerial
4.68
3.81
2.36
Walnuts
Ground
0.80
0.61
0.42
Airblast
1.61
1.17
0.78
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3.3 Terrestrial Exposure Assessment
As discussed in section 2.5.4, adult CRLF occupy a variety of terrestrial dispersal habitats. The
current range of the CRLF is represented by the core areas, critical habitat and occurrence
sections in Figure 2a.
3.2.4 Conceptual Model of Exposure
Terrestrial exposure of the CRLF on agricultural fields within the action area is estimated with
the T-REX model, which automates exposure analysis according to the Hoerger-Kenaga
nomogram modified by Fletcher et al (1994). The nomogram relates the pesticide application
rate to residues measured on crops in numerous field studies. T-REX utilizes the nomogram to
estimate initial residue values on the day of application, and automates the calculation of daily
residue decay. T-REX then calculates both a diet-based exposure value and a dose-based
exposure value for birds and mammals. This model is a screening-level tool with which to
determine effects to the CRLF, and is also a tool used to estimate on-field exposure to
mammalian and terrestrial invertebrate food items. In the event that the RQ exceeds the listed-
species LOC for birds, which is the surrogate organism for the terrestrial-phase CRLF, the T-
HERPS model is used to obtain a more refined estimate of exposure to the CRLF for exposure
characterization. This model provides a dose-based estimate of exposure by taking into account
a more realistic estimate of food intake for the CRLF given that they are poikilotherms and
consume less food. Off-field exposure of animals is estimated with the AgDrift and AgDISP
models. Where the estimated travel distance of ODM drift exceeds the limit within the AgDrift
model, the Gaussian extension of the AgDISP model is used to estimate the distance to which
terrestrial animals are exposed as a result of spray drift.
T-REX and T-HERPS estimate the daily decay of ODM residues using a first-order degradation
model that requires an input for the foliar dissipation half-life. The default half-life value is 35
days, which is used when no other information is available. Willis and McDowell (1987)
provide foliar dissipation half-life values for many active ingredients, and is primarily consulted
to obtain this value. Alternatively, guideline magnitude of residue studies (171-4) submitted to
the Agency may be consulted. Willis and McDowell (1987) does not list a half-life value for
ODM, and the available magnitude of residue studies do not provide adequate information with
which to estimate a half-life. Therefore, the default 35-day value will be used, but the effect of
the half-life will be explored by substituting hypothetical values for risk characterization.
3.2.5 Modeling Approach
On-field exposures of the CRLF and its prey were estimated with T-REX. In order to bracket the
possible risks, the lowest and highest rates of ODM application (walnuts and cabbage,
respectively) were first modeled. Walnuts receive a one-time treatment of 0.375 lbs ai/acre
while cabbage can receive 3 treatments of 0.75 lbs ai/acre spaced at 7-day intervals. The default
35-day half-life was used to model exposure to foliar residues, since there was no further
information regarding the actual half-life. This may be an overestimation of the half-life, since
ODM is not particularly persistent in the environment; however, it would result in a conservative
estimate of exposure. Direct risk to the CRLF was bounded using 20-gram and 100-gram avian
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weight classes within T-REX, since the weight of young adult frog falls in in this range. The
CRLF was assumed to consume the broadleaf plant/small insect food category, since the bulk of
its diet is invertebrates, and the small insect food category provides a higher dose. In addition,
large CRLF also consumes other frogs and mice.
Dose-based RQs for the combination of weight class and food item categories for birds within T-
REX exceeded the listed-species LOC when modeled using the application rate for walnuts
(Table 3-5). Therefore, T-HERPS was also run in order to characterize the potential daily dose
of ODM to the CRLF with a more refined estimate.
Indirect risks to the CRLF through effects on its prey base were estimated in two ways.
First, indirect effects via losses of larger prey items (for example, Pacific tree frog and California
mouse) were estimated conservatively using the 37-gram weight class for amphibians within T-
HERPS and the 15-gram weight class for mammals within TREX. For amphibian prey, the 37-
gram/small herbivorous mammal class provided the most conservative estimate. The short-grass
food category were used for the mammals, since it provides the highest dose estimate for that
taxon and is included in its diet. Diet-based EECs were used to estimate chronic effects.
Indirect effects via losses of smaller prey items (terrestrial invertebrates) were estimated using
the LD50 data for the honey bee, and an assumed body weight of 0.128 grams. The dose was
calculated by multiplying the dose-based EEC for 20-gram birds consuming large insects (given
in mg/kg bw, which is identical to (_ig/g bw) by an estimate of the body weight of a bee (0.128 g).
This provides an estimated exposure value for the bee in units of (J,g/bee, which can be directly
compared to the LD50 for honeybees to derive an RQ.
3.2.6 Model Inputs
TREX and T-HERPS model inputs included the lowest and highest application rates (0.375 to
0.75 lb ai/acre), number of applications (1-3), application interval (7 days), and default foliar
dissipation rate (35 days).
3.2.7 Results
See Appendix B for details of the T-REX and T-HERPS EEC calculations. Summaries of the
results are provided in the following sections.
3.2.7.1 EECs for Direct Effects to Terrestrial Phase CRLF
Table 3-5 presents the EECs for birds (surrogate for terrestrial phase CRLF) calculated with T-
REX. The values presented are for uses involving the lowest and highest application rates and
are based on the upper bound estimate of exposure from the Kenaga nomogram. The lowest
application rate used in the model is for applications on walnuts in which the maximum one-time
rate is 0.375 lbs ai/acre and only one application is allowed. The highest application rate is
based on the use in cabbage, in which up to 3 applications of 0.75 lbs ai/acre may be made, each
at 7 day intervals. Values from the T-REX model will be used to calculate RQs and determine
direct effects to the CRLF.
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Table 3-5. Upper Bound Kenaga Residues for 20-g and 100-g Birds (surrogates for CRLF)
from T-REX
Weight Class
Exposure Type
EECs1
Small Insects
Large Insects
Low
High
Low
High
20 g
Dose-based
57.66
303.09
6.41
33.68
O
o
Dose-based
32.88
172.84
3.65
19.20
(no size class distinction)
Diet-based
50.63
266.13
5.63
29.57
'"Low " and "High" refer to EECs determined for the lowest application rate and the highest application rate (see
text).
3.2.7.2 Terrestrial EECs for Indirect Effects to CRLF
EECs are determined for amphibian, mammalian, and insect prey items in order to estimate the
risk of indirect effects to the CRLF as a result of the loss of these prey items. EECs for
amphibians (using birds) and mammals were estimated using T-REX (Tables 3-6 and 3-7).
These EECs are based on the same scenarios upon which the direct effects assessment are based.
The smallest weight classes (20-g birds and 15-g mammals) are used. The short grass foraging
class will be used to make determinations, since EECs are highest for this class and provide a
protective assessment of exposure. Other foraging classes are included for further
characterization.
Amphibians (Birds)
Table 3-6 provides EECs for potential amphibian prey items. These values were calculated
using T-REX and represent a 20-g animal.
Table 3-6. Upper Bound Kenaga, Dose- and Diet-Based EECs for Amphibian prey items.
Exposure Type
EECs1
Short Grass
Tall Grass
Broadleaf Plants/
Small Insects
Fruits/Pods/
Seeds/
Large Insects
Low
High
Low
High
Low
High
Low
High
Dose-based
102.50
538.83
46.98
246.96
57.66
303.09
6.41
33.68
Diet-based
90.00
473.11
41.25
216.84
50.63
266.13
5.63
29.57
'"Low " and "High" refer to EECs determined for the lowest application rate and the highest application rate for
ODM.
Mammals
EECs for mammalian prey are presented below (Table 3-7), based on T-REX output for the
lowest and highest application scenarios.
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Table 3-7. Upper Bound Kenaga, Dose- and Diet-Based EECs for 15-g Mammalian Prey.
EECs1
Broadleaf
Fruits/Pods/
Seeds/
Large
Insects
Exposure Type
Short Grass
Tall Grass
Plants/
Small Insects
Granivore
Low
High
Low
High
Low
High
Low
High
Low
High
Dose-based
85.81
451.08
39.33
206.74
48.27
253.73
5.36
28.19
1.19
6.26
Diet-based
90.00
473.11
41.25
216.84
50.63
266.13
5.63
29.57
N/A
N/A
'"Low " and "High" refer to EECs determined for the lowest application rate and the highest application rate for
ODM.
Terrestrial Invertebrates
Using the approach to estimating the EEC for terrestrial invertebrates described above, the dose
estimated to terrestrial invertebrates for the walnut scenario (low value) is 0.82 [j,g/bee and for
the cabbage scenario (high value) is 4.31 [j,g/bee.
4. Effects Assessment
This assessment evaluates the potential for ODM to directly or indirectly affect the CRLF and/or
modify its designated critical habitat. As previously discussed, assessment endpoints for the
CRLF include direct toxic effects on the survival, reproduction, and growth, as well as indirect
effects, such as reduction of the prey base and/or modification of its habitat. In addition,
potential modification of critical habitat 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.
Toxicity data used to evaluate direct effects, indirect effects, and modification to critical habitat
in this risk assessment for ODM are summarized in Table 4-1.
Information on the toxicity of ODM to selected taxa is characterized based on registrant-
submitted studies and a comprehensive review of the open literature on ODM. Values used for
each measurement endpoint identified in Table 2-7 are selected from these data. Currently, no
FIFRA data requirements exist for aquatic-phase or terrestrial-phase frogs and are therefore not
part of typical registrant submitted data packages. A summary of the available ecotoxicity
information; the selected individual, population, and community-level endpoints for
characterizing risks; and interpretation of the LOC, in terms of the probability of an individual
effect based on probit dose response relationship are provided in Sections 4.1 through 4.3,
respectively.
4.1 Evaluation of Aquatic Ecotoxicity Data
Toxicity measurement endpoints are selected from data from guideline studies submitted by the
registrant, and from open literature studies that meet the criteria for inclusion into the ECOTOX
database maintained by EPA/Office of Research and Development (ORD) (U.S. EPA, 2004).
Open literature data presented in this assessment were obtained from a search of the ECOTOX
database (February 2007). Table 4-1 summarizes the most sensitive results for each
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measurement endpoint, 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 is presented below. Additional
information is provided in Appendices C-E.
In order to be included in the ECOTOX database, papers must meet the following minimum
criteria:
(1) the toxic effects are related to single chemical exposure;
(2) the toxic effects are on an aquatic or terrestrial plant or animal species;
(3) there is a biological effect on live, whole organisms;
(4) a concurrent environmental chemical concentration/dose or application rate is
reported; and
(5) there is an explicit duration of exposure.
Data that pass the ECOTOX screen are further evaluated for use in the assessment 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, matching
measurement endpoints listed in Table 2-7, that are more conservative than the registrant-
submitted data and that are found to be scientifically sound based on a review of the paper are
used quantitatively. The degree to which open literature data are used quantitatively or
qualitatively is dependent on whether the information is scientifically sound and whether it is
quantitatively linked to the assessment endpoints (e.g., maintenance of California Red-Legged
Frog survival, reproduction, and growth) identified in Table 2-7). For example, endpoints such
as behavior modifications are likely to be qualitatively evaluated, because quantitative
relationships between degree and type of behavior modifications and reduction in species
survival, reproduction, and/or growth are usually not available.
Where possible, the most sensitive values from studies using the technical grade active
ingredient (TGAI) were selected for this assessment. In some cases, however (e.g., acute
toxicity tests to birds), only tests with the technical formulation intermediate Metasystox-R (50%
ai) containing methyl isobutyl ketone are available. This compound has minimal toxicity to
mammals, fish, and birds (Toxnet, U.S. National Library of Medicine, available at:
http://toxnet.nlm.nih.gov/). so when the test material has been clearly identified, the toxicity
value may be adjusted for purity. In many cases, however, the reports do not state whether
adjustment has already been done, and toxicity values are expressed in terms of active ingredient
where possible. Further, Metasystox-R is also the name of emulsifiable concentrate products
containing ODM (25% ai) that are no longer in use; some studies refer to Metasystox-R 50% EC
while others refer to "technical" material with 50% ai without further clarification. Therefore,
use of tests in which the test material is clearly defined as TGAI with high purity is preferred
when possible.
Table 4-1. Summary of ODM Toxicity Data Used to Assess Direct Effects, Indirect Effects,
and Modification to Critical Habitat for the CRLF.
68
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Assessment
Endpoints
Measures of
Effect
Species
Toxicity Value
and Slope
(where
applicable)
Study
classification
(Selection
basis)
Reference
Survival and
reproduction of
individuals and
communities of
freshwater fish in
close proximity to
sites
Freshwater fish
acute 96-hr LC50
Rainbow trout
(Oncorhynchu
s mykiss)
0.73 ppm ai
Reliable
estimate of
slope not
available
Acceptable
(most sensitive
value)
MRID
40269001
(USEPA 1978)
Freshwater fish
early life-stage
NOAEC
Rainbow trout
(Oncorhynchu
s mykiss)
0.005 ppm ai
Value was
estimated using
ACR derived
from dichlorvos
N/A
Survival and
reproduction of
individuals and
communities of
freshwater
invertebrates in close
proximity to sites
Freshwater
invertebrate acute
96-h LC5o (for
scud 48-h LC50 or
EC5o where the
effect measured is
surrogate)
Scud
(Gammarus
lacustris)
0.19 ppm
Probit slope not
available
Acceptable
(most sensitive
value)
MRID
00097842
(Sanders 1969)
Freshwater
invertebrate
reproductive
NOAEC
Waterflea
(Daphnia
magna)
0.046 ppm ai
Acceptable
(only value
available)
40986601
Burgess 1991
Abundance (i.e.,
survival,
reproduction, and
growth) of
individuals and
populations of birds
in close proximity to
sites.
Avian (single
dose) acute oral
LD5o
Rock pigeon
{Columbia
livia)
7 mg ai/kg bw
Probit slope not
available
Supplemental
(most sensitive
value)
MRID
00160000
(Hudson et al.
1984)
MRID
05000975
(Tucker and
Haegele 1971)
Avian subacute
5-day dietary
LC50
Northern
bobwhite
(Colinus
virginianus)
434 ppm ai
Probit slope not
available
Acceptable
(most sensitive
value)
MRID
00022923
(Hill et al.
1975)
Avian
reproduction
NOAEC
Northern
bobwhite
(Colinus
virginianus)
1.8 ppmai
Acceptable
(most sensitive
value)
MRID
40747202
(Beavers et al.
1988)
Abundance (i.e.,
survival,
reproduction, and
growth) of
individuals and
populations of
mammals in close
proximity to sites
Mammalian acute
oral (single dose)
LD5o
Laboratory rat
(Rattus
norvegicus)
48 mg ai/kg bw
(females)
Probit slope =
8.2
Acceptable
(most sensitive
value)
MRID
40779801
(Eigenberg
1990)
Mammalian
reproductive
NOAEC or
NOAEL
Laboratory rat
(Rattus
norvegicus)
0.05 mg ai/kg
bw/day (1 ppm)
Acceptable
(most sensitive
value based on
reproductive
paramet
MRIDs
00155396
00260513
00256926
Kroetlinger
and Kaliner
(1985)
69
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Assessment
Endpoints
Measures of
Effect
Species
Toxicity Value
and Slope
(where
applicable)
Study
classification
(Selection
basis)
Reference
Survival of
beneficial insect
populations in close
proximity to sites
Honey bee acute
contact LD50
Honey Bee
(Apis mellifera
0.31 ug/bee
Probit slope not
available
Supplemental
(most sensitive
value)
MRID
05001991
(Stevenson
1978)
4.1.1 Toxicity to Freshwater Fish
No aquatic phase amphibian studies are available for ODM. Therefore toxicity studies with
freshwater fish are used as surrogates for assessing direct acute and chronic effects to the aquatic
phase CRLF as well as indirect acute and chronic effects to its food sources. Fish toxicity
studies for two freshwater species using the TGAI are required to establish the acute toxicity of
ODM to fish. The preferred test species are rainbow trout (a coldwater fish) and bluegill sunfish
(a warm water fish).
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies
Two studies with the ODM TGAI are available. Based on these studies, ODM is moderately to
highly toxic to freshwater fish on an acute basis (Table 4-2).
Table 4-2. Acute Toxicity of Technical Grat
e ODM to Freshwater Fish.
Species
% ai
96-hour LC50
Toxicity category
MRID (Author, Year)
Status
Bluegill sunfish
(Lepomis macrochirus)
97.9
1.22 ppmai
Moderately toxic
40269002 (USEPA, 1978)1
Acceptable
Rainbow trout
(Oncorhynchus mykiss)
97.9
0.73 ppm ai
Highly toxic
40269001 (USEPA, 1978)1
Acceptable
1 Static test
Other studies (Table 4-3) are also available with the 50% technical grade product or liquid
concentrate (as stated). In some cases it is unclear whether the value presented is corrected for
the purity of the test material. In all cases, however, the 96-hour LC50s using the high purity
TGAI provide more sensitive values whether they are adjusted or not. It should be noted that in
the studies by Shellenberger (1970, MRID 00060635) the positive toxicity test with DDT
resulted in higher toxicity values than normal for the test lab, which may explain the relatively
higher values obtained for ODM. Data obtained from MRIDs 00003503 and 40098001 have
been determined to be supplemental until such time that the raw data from these studies have
been reviewed and the results verified. At this time, these data have not been reviewed for
ODM.
70
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Table 4-3. Acute Toxicity of 50% Technical Material ODM to Freshwater Fish.
Species
% ai
96-hour
LC50
Toxicity
category
MRID (Author, Year)
Status
Goldfish
(Carassius auratus)
50
82.5 ppmai1
Slightly toxic
00060635 (Shellenberger 1970)
Supplemental
Rainbow trout
(Oncorhynchus mykiss)
50
4.3 ppmai1
Moderately toxic
00060635 (Shellenberger 1970)
Supplemental
Channel catfish
(Ictalurus punctatus)
50
23.0 ppmai1
Slightly toxic
00060635 (Shellenberger 1970)
Supplemental
Bluegill sunfish
(Lepomis macrochirus)
50
1.9 ppm2
Moderately toxic
00060639 (Lamb and Roney 1973)
Supplemental
Rainbow trout
(iOncorhynchus mykiss)
50
6.4 ppm3
Moderately toxic
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental
Channel catfish
{Ictalurus punctatus)
50
< 18.0 ppm3
N/A
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental
Bluegill sunfish
(Lepomis macrochirus)
50
13.0 ppm3
Slightly toxic
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental
Largemouth bass
(Micropterus salmoides)
50
31.5 ppm3
Slightly toxic
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental
Walleye
(Sander vitreus vitreus)
50
18.0 ppm3
Slightly toxic
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental
Whether the test was static or flow-through or whether mean measured value were used is not described
2Nominal concentrations used, flow-through or static conditions not reported.
3Static test, use of nominal or mean measured concentrations not described.
Three additional studies (Table 4-4) with the 25% formulated product Metasystox-R Concentrate
are also available. The registrant submitted studies are acceptable for studies with a formulated
product. The additional study with Tilapia was obtained from the ECOTOX database (Reference
#12184), and is classified as supplemental.
Table 4-4. Toxicity of Metasystox-R (25% ai) Formulated Product to Freshwater Fish.
Species
% ai
96-hour LC50
Toxicity category
MRID (Author, Year)
Status
Rainbow trout
0Oncorhynchus mykiss)
25
26.0 ppm
Slightly toxic
00074349 (Nelson etal. 1977)
Acceptable
Bluegill sunfish
(Lepomis macrochirus)
25
23.0 ppm
Slightly toxic
00074349 (Nelsonetal. 1977)
Acceptable
Tilapia
(Tilapia mossambica)
25
6.85 ppm
Moderately toxic
ECOTOX #12184 (Moses et al. 1985)
Supplemental
4.1.1.2 Freshwater Fish: Chronic Exposure (Chronic/Reproduction) Studies
A freshwater fish early life-stage test using the TGAI is required for ODM because the end-use
product is expected to be transported to water from the intended use site, and the following
conditions are met: (1) the pesticide is intended for use such that its presence in water is likely
to be continuous or recurrent regardless of toxicity, and (2) any aquatic acute LC50 or EC50 is
71
-------
less than 1 mg/1 (rainbow trout LC50 = 0.73 mg/L). The results of this study are presented in
Table 4-5.
Table 4-5. Freshwater Fish Early Life Stage Toxicity of ODM Under Flow-Through
Conditions.
Species
% ai
NOAEC/LOAEC
Endpoints
Affected
MRID (Author, Year)
Status
Rainbow trout
(Oncorhynchus mykiss)
97.7
NOAEC = 2.6 ppm ai
LOAEC =4.9 ppm ai
Fry survival and
growth
41054501
43635701 (Cohle 1989)
Acceptable
Uncertainty is associated with the use of this value in risk assessment, since the NOAEC for this
species is higher than the LC50. Therefore, a chronic value will be estimated using the highest
acute-to-chronic ratio for rainbow trout from among all organophosphates that have LC50 and
fish early life stage data for rainbow trout. Nineteen organophosphates were found that have
both an acute and chronic study for rainbow trout (Table 4-6). The ACR ranged from 5.4 for
Terbufos to 144.0 for Dichlorvos. In order to provide the most conservative estimate for the
chronic freshwater fish NOEC for ODM, the ACR of 144 will be used to estimate the NOAEC
for rainbow trout. The estimated chronic NOAEC for rainbow trout as derived from the ACR of
144 and LC50 of 0.73 ppm is 0.005 ppm or 5 ppb. This value was derived as follows. The
(ODM) rainbow trout LC50 used in this assessment is 0.73 ppm ai. The largest acute-to-chronic
ratio from the organophosphates is 144 for Dichlorvos. This ratio is used to calculate the final
NOEC for ODM.
0.750 ppm ai (acute)/0.0052 ppm ai (chronic) = 144 = ACR ratio for Dichlorvos
Estimated NOAEC for ODM = LCsn = 0.73 ppm ai = 144
NOEC est. NOAEC
Estimated NOAEC for ODM = 0.73/144 = 0.005 ppm ai
The table below (4-6) shows the inputs for the organophosphates that were considered for the
ODM ACR.
Table 4-6. ODM Acute to Chronic Ratio for Rainbow
96-hr
ODM
LC50
NOAEC
NOEC
Chemical
(ppm ai)
MRIDs
(ppm ai)
MRIDs
ACR
(ppm ai)
Azinphos methyl
0.0088
03125193
0.00029
00145592
30.344
0.024
Coumaphos
0.890
40098001
0.0117
43066301
76.068
0.010
Dichlorvos
0.750
43284702
0.0052
43788001
144.23
0.005
Dimethoate
7.500
TN 1069*
0.430
43106303
17.441
0.042
Disulfoton
1.850
40098001
0.220
41935801
8.4090
0.089
Fenamiphos
0.068
40799701
0.0038
41064301
17.894
0.041
Fenitrothion
2.000
40098001
0.046
40891201
43.478
0.017
Fenthion
0.830
40214201
0.0075
40564102
110.66
0.007
rout NOEC
72
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96-hr
ODM
LC50
NOAEC
NOEC
Chemical
(ppm ai)
MRIDs
(ppm ai)
MRIDs
ACR
(ppm ai)
Fonofos
0.050
00090820
0.0047
40375001
10.638
0.069
Isofenphos
1.800
00096659
0.153
00126777
11.764
0.062
Phosmet
0.105
40098001
0.0032
40938701
32.812
0.022
terbufos
0.0076
40098001
0.0014
41475801
5.4285
0.134
* TN 1069 is test number for EPA's Animal Biology Lab, McCann, 1977
4.1.1.3 Freshwater Fish: Sublethal Effects and Open Literature Information
No other studies were available for ODM in the ECOTOX database or elsewhere in which
sublethal effects to freshwater fish are described.
4.1.2 Toxicity to Freshwater Invertebrates
Toxicity studies on freshwater invertebrates were evaluated to assess the potential for ODM to
induce indirect effects to the aquatic phase CRLF via a reduction in invertebrate prey. Acute
studies with several species and a chronic study with waterflea (Daphnia magna) are available.
The results of these studies are presented in the sections below.
4.1.2.1 Freshwater Invertebrates: Acute Exposure Studies
A freshwater aquatic invertebrate toxicity test using the TGAI is required to establish the toxicity
of ODM to aquatic invertebrates. The preferred test species is Daphnia magna; however, two
studies are also available with the scud (Gammarus lacustris). Results of studies using the
technical grade material or technical material dissolved in acetone or water (Sanders 1969 and
1972 studies) are presented in Table 4-7. Studies involving the scud (Sanders 1969, 1972;
MRID 00097842 and 05017538, respectively) were scientifically sound, but were determined to
be supplemental because the purity of the test compound is not provided, it is unknown whether
the results presented are adjusted for purity, mature scuds were used instead of immature scuds,
and because the study did not follow guidelines. The test material was reported as technical
grade material. The value from MRID 00097842 is a more sensitive value than that obtained
from the study with Daphnia; therefore, it will be used in this risk assessment.
Table 4-7. Acute Toxicity of Technical ODM to Waterflea ant
Scud.
Species
% ai
48-hour LC50
Toxicity
category
MRID (Author, Year)
Status
Waterflea
{Daphnia magna)
94.6
0.24 ppm ai
Highly toxic
40286801 (Forbis, 1987)
Acceptable
Scud
(Gammarus lacustris)
Tech.
0.190 ppm
Highly toxic
00097842 (Sanders 1969)
Supplemental
Scud
('Gammarus lacustris)
Tech.
1.1 ppm
Moderately toxic
05017538 (Sanders 1972)
Supplemental
73
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Five studies are also available that utilize test material with 50% ai. Based on the study by
Nelson et al. (1977; MRID 00074350), the 50% technical product is very highly toxic to
waterflea on an acute basis (Table 4-8). All studies are supplemental for reasons provided in the
table footnotes. A more sensitive value is obtained in the study with 50% Metasystox-R
technical by Nelson et al. (1977, MRID 00074350) compared to the studies above; however, the
value is very inconsistent with others for Daphnia and the report does not contain information
about parameters related to survival. In all of the other studies, it is not known whether the
toxicity value presented is adjusted for purity.
Table 4-8. Acute Toxicity of 50% ai Technical Product Metasystox-R to Waterflea.
Species
%
ai
LC50
Toxicity
category
MRID (Author, Year)
Status
Waterflea
{Daphnia magna)
50
0.0033 ppm ai (48-
hr)
Very highly toxic
00074350 (Nelson etal. 1977)
Supplemental1
Waterflea
{Daphnia magna)
50
0.16 ppm (48-hr)
Highly toxic
00165007 (Heimbach 1985)
Supplemental2
Scud
{Gammarus lacustris)
50
1.0 ppm (96-hr)
Highly toxic
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental3
Scud
{Gammarus lacustris)
50
1.2 ppm (96-hr)
Moderately toxic
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental3
Aquatic sowbug
(Asellus brevicauclus)
50
1.4 ppm (96-hr)
Moderately toxic
00003503 (Johnson and Finley 1980)
40098001 (Mayer and Ellersieck 1986)
Supplemental3
1 First and second instars were used in the study, and dissolved oxygen was not reported.
Classified as supplemental because TGAI not used but was submitted in response to a DCI for a study with TGAI.
Study is otherwise scientifically sound.
3A11 data from these studies have been classified as supplemental until raw data are obtained to verify the results.
4.1.2.2 Freshwater Invertebrates: Chronic Exposure Studies
A freshwater aquatic invertebrate life-cycle test using the TGAI is required for ODM since the
end-use product is expected to be transported to water from the intended use site, and the
following conditions are met: (1) the pesticide is intended for use such that its presence in
water is likely to be continuous or recurrent regardless of toxicity, and (2) aquatic acute
LC50 or EC50 is less than 1 mg/1 (rainbow trout LC50 = 0.73 mg/L and daphnia EC50 = 0.23
Mg/L). The preferred test species is Daphnia magna. Results of the test are presented in Table
4-9.
Table 4-9. 21-Day Renewal Chronic Toxicity Test to Waterflea.
Species
% ai
21-Day NOAEC
Endpoints Affected
MRID (Author, Year)
Status
Waterflea
{Daphnia magna)
97.7
0.046 ppm ai
Adult mean length, survival,
and young/adult/day
40986601 (Burgess 1991)
Acceptable
74
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4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Additional Open
Literature Information
Additional studies with ODM in freshwater aquatic invertebrates are not available.
4.1.3 Freshwater Field Studies
No field studies on freshwater plants or animals are available for ODM.
4.2 Evaluation of Terrestrial Ecotoxicity Data
Data collected on birds, mammals, terrestrial plants, and terrestrial insects are utilized in this risk
assessment to estimate direct effects to the terrestrial phase CRLF resulting from acute and
chronic exposure, indirect effects to the CRLF resulting from loss of prey and loss/disturbance of
riparian, upland, and dispersal habitat, and modification of Critical Habitat PCEs. Toxicity
endpoints available for this assessment and the endpoints actually selected for quantitative
assessment of direct and indirect effects to the CRLF are summarized in the sections below.
4.2.1 Toxicity to Birds
4.2.1.1 Birds: Acute Exposure (Mortality) Studies
No terrestrial phase amphibian studies are available for ODM. Therefore birds are used as a
surrogate for the terrestrial phase CRLF. An oral toxicity study using the technical grade of the
active ingredient (TGAI) is required to establish the acute toxicity of ODM to birds. Two dietary
studies using the TGAI are also required to establish the subacute toxicity to birds. The
preferred guideline test species is mallard (a waterfowl) or Northern bobwhite (an upland
gamebird). For ODM, acute exposure studies are available for the guideline species and several
others, including a passerine and "near-passerine" species. Only studies with the 50% technical
product are available. These data do indicate that on an acute oral basis, ODM ranges from
moderately to very highly toxic to birds; on a subacute dietary basis, ODM is practically non-
toxic to highly toxic (Table 4-10).
We note here that in the EFED RED Chapter the subacute dietary LC50 values presented for birds
from the Hill et al. (1975) study (MRID 00022923) were adjusted for the purity of the test
substance. However, it is stated in that reference that the LC50 values are presented as ppm of
active ingredient, so they have been corrected below.
Table 4-10. Avian Acute Oral and Subacute Dietary Toxicity Data for ODM from
Acceptable and Supplemental Studies
Species
%
ai
Endpoint
Toxicity
category1
MRID (Author, Year)
Status
Acute Oral
Northern bobwhite
(Colinus virginianus)
50
LD50 = 17 mg ai/kg 0)
LD5o = 18.5 mg ai/kg (§)
Highly
toxic
00060636 (Lamb et al. 1972)
Acceptable
Chukar
(Alectoris graeca)
50
LD50 = 60 mg ai/kg
Moderately
toxic
00160000 (Hudson etal. 1984)
Supplemental'
California quail
50
LD50 = 24 mg ai/kg
Highly
75
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Species
%
ai
Endpoint
Toxicity
category1
MRID (Author, Year)
Status
(Callipepla californica)
toxic
Chukar
(Alectoris graeca)
50
LD50 = 57 mg ai/kg
Moderately
toxic
05000975 (Tucker and Haegele 1971)
Supplemental2'3
Rock pigeon
0Columbia livia)
50
LD50 = 7.5 mg ai/kg
Very highly
toxic
Mallard
(Anas platyrhynchos)
50
LD50 = 27 mg ai/kg
Highly
toxic
00160000 (Hudson et al. 1984)
05000975 (Tucker and Haegele 1971)
Supplemental2'3
Japanese quail
(Coturnix coturnix
japonica)
50
LD50 = 42 mg ai/kg
Highly
toxic
Ring-necked pheasant
(Phasianus colchicus)
50
LD50 = 21 mg ai/kg
Highly
toxic
House sparrow
(Passer domesticus)
50
LD50 = 35 mg ai/kg
Highly
toxic
Rock pigeon
0Columbia livia)
50
LD50 = 7 mg ai/kg
Very highly
toxic
Subacute Dietary
Northern bobwhite
(Colinus virginianus)
50
LC50 = 434 ppm ai
Highly
toxic
00022923 (Hill et al. 1975)
Acceptable2
Mallard
(Anas platyrhynchos)
50
LC50 >5000 ppm ai
Practically
non-toxic
Japanese quail
(Coturnix coturnix
japonica)
50
LC50 = 1309 ppmai
Slightly
toxic
Ring-necked pheasant
(Phasianus colchicus)
50
LC50 = 1497 ppm ai
Slightly
toxic
Category for material tested. It is unclear whether values reported under MRID 00160000 and 05000975 are
adjusted for % active ingredient, so toxicity categories may be different for technical material with high purity.
2Mallard and Northern bobwhite are preferred guideline species.
3Methods are not well described.
4.2.1.2 Birds: Chronic Exposure (Chronic/Reproduction) Studies
Avian reproduction studies using the TGAI were required because the CRLF may be subject to
repeated or continuous exposure to ODM. The preferred test species are mallard duck and
bobwhite quail. Acceptable studies are available for both species (Table 4-11). Adverse effects
were observed in the bobwhite study (MRID 40747202) in which 14-day old survivor weights
were significantly reduced in the 6.9 ppm ai and higher treatment group. The number of eggs
laid and number of eggs set were also significantly affected, but these were increased in
treatment groups compared to controls. In the mallard study (MRID 40747202), reduced food
consumption was observed in adults in the 17.3 ppm ai treatment, but no affects on reproduction
were observed.
76
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Table 4-11. Avian
Acceptable and Su
\cute Oral and Subacute Dietary Toxicity Data for ODM from
pplemental Studies
Species
% ai
NOAEC/LOAEC
NOAEC
Endpoints
MRID (Author, Year)
Status
Northern bobwhite
(Colinus virginianus)
92.4
1.8 ppm ai / 6.9 ppm ai
14-day old survivor
weight1
40747202 (Beavers et al. 1988)
Acceptable
Mallard
(Anas platyrhynchos)
92.4
17.3 ppm ai / 54.0 ppm ai
Reduced adult food
consumption
40747201 (Beavers et al. 1988)
Acceptable
dumber of eggs laid and set per hen were also significantly higher in the 6.9 ppm ai and higher treatment groups.
4.2.1.3 Birds: Sublethal Effects and Additional Open Literature Information
A search in the ECOTOX open literature database provided one teratogenicity study with
domestic chickens (Gallus domesticus) in which chick embryos were exposed to ODM (technical
grade, 89% purity) at doses ranging from 0.01 mg to 2.00 mg via direct injection into the egg
(Lenselink et al. 1993, ECOTOX # 88893). Survival to later stages was significantly reduced at
0.50 mg and higher doses (p<0.001), with none of the embryos surviving at the highest dose
level of 2.00 mg. The percentage of animals showing developmental anomalies was
significantly greater at dose levels > 0.05; however they did not show a clear dose-response
relationship as the 1.00 mg dose group did not show a significant percentage of affected animals.
These included the musculoskeletal effects of wry neck, absent or malformed limbs, eye
abnormalities, and thoracogastroschisis; and cardiovascular effects such as ventricular septal
defects and aortic arch anomalies. The study does not report whether the dose values used in the
study are corrected for percentage of active ingredient, so these values may be lower. Whether
these effects occur in wild birds is questionable because it is not known whether injection into
the egg represents potential exposure that would occur in the field. However, this study does
demonstrate that ODM has the potential to affect birds during development within the egg. How
this may apply to amphibians is unknown, but may indicate some potential for teratogenicity.
4.2.2 Toxicity to Wild Mammals
4.2.2.1 Wild Mammals: Acute Exposure Studies
Toxicity studies on mammals were evaluated to assess the potential for ODM to induce indirect
effects to the terrestrial phase CRLF via a reduction in prey base. In most cases, rat or mouse
toxicity values obtained from the Agency's Health Effects Division (HED) substitute for wild
mammal testing. One study with a Peromyscus species was also submitted (MRID 00060626);
however, the report submitted consists of raw data and no description of the study design and
therefore is not valid for use.
The majority of acute oral studies for ODM involving mammals were conducted with the 25%
active ingredient formulation (Metasystox-R) or with this formulation given in combination with
other compounds. One study using technical grade material is available, and based on the LD50
value for females in this study, ODM is categorized as highly toxic to small mammals on an
acute oral basis (Table 4-12).
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A search in the ECOTOX database resulted in one study that reported a mouse acute oral LD50 of
118 mg/kg bw (Kumari et al. 1995 [ECOTOX #88896]); however, the source of this information
was not reported and the study itself cannot be evaluated. Nevertheless, the value is greater than
that estimated for the rat in registrant submitted studies.
Table 4-12. Acute C
)ral Toxicity of ODM to the Laboratory Rat.
Species
% ai
LDso
Toxicity category
MRID (Author, Year)
Status
Laboratory rat
(Rattus norvegicus)
93.3
61 mg ai/kg (3)
48 mg ai/kg (?)
Highly toxic1
40779801 (Eigenberg 1990;
also listed as Sheets 1988)
Acceptable
toxicity category for wild mammals. Male LD50 value would be categorized as moderately toxic.
4.2.2.2 Wild Mammals: Chronic Exposure Studies
Chronic toxicity data for mammals are needed to assess the potential for ODM to induce indirect
effects to the terrestrial phase CRLF via a reduction in prey base due to chronic effects of prey
items. Chronic tests are not conducted on wild mammals, so the two-generation rat reproduction
study required by HED is used as a substitute. Two acceptable reproduction studies are
available, and the most sensitive reproductive NOAEL/LOAEL is presented in Table 4-13.
The 1999 EFED RED Chapter and its revisions utilized data from the study by Eigenberg (1990)
(MRID 41461901); however, a study with a more sensitive endpoint is presented for the rat in
the HED RED Chapter for ODM. In this study, significant reproductive effects that were
observed included decreased parental body weight, decreased parental testes weight, decreased
fertility index, vacuolation of the epithelial cells of the corpus epididymus, decreased pup weight
and increased pup mortality (Kroetlinger and Kaliner 1985, primary MRID 00155396).
In the Eigenberg (1990) study, similar effects were observed, including decreases in male and
female fertility were also observed in the P and Fi generations, epididymal vacuolation, body
weight reduction, testes weight reduction, ovarian weight reduction, and nominally increased
estrous cycle length in females. Based on cholinesterase inhibition in adults, a NOAEC of < 1.0
ppm (NOAEL < 0.043 mg/kg-bw/day) and a LOAEC of 1.0 ppm can be established as chronic
values for wild mammals. The parental NOAEL is less than that established by the Kroetlinger
and Kaliner (1985) study. However, there is uncertainty associated with the NOAEL value from
the Eigenberg study based on ChE activity, and the other parameters measured produce higher
NOAEC values. Since the ChE NOAEL represents effects on a critical biological variable, this
value should be considered in the risk assessment. Therefore, values from both studies will be
modeled where necessary to bracket the chronic risk.
A search in the ECOTOX database did not find studies with lower LOAEL/NOAEL values than
the studies presented below.
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Table 4-13. Chronic/Reproductive Toxicity of ODM to the Laboratory Rat.
Species
% ai
NOAEL/LOAEL
NOAEL/LOAEL
Endpoints
MRID (Author,
Year)
Status
Laboratory rat
(Rattus norvegicus)
52.5
Parental, reproductive and
oflsDri nu:
LOAEL = 0.5 mg a.i./kg-
bw/day (10 ppm)
NOAEL = 0.05 mg a.i./kg-
bw/day (1 ppm)
Parental systemic: male and
female body weight, female
gestation weight
Reproductive: absolute testes
weight, vacuolation in the
corpus epididymus
Offspring: viability index
(mortality), pup weight
during lactation
00155396
00260513
00256926
Kroetlinger and
Kaliner (1985)
Acceptable
Laboratory rat
(Rattus norvegicus)
50
Parental svstemic:
LOAEL = 2.1 mg a.i./kg-
bw/day (50 ppm)
NOAEL = 0.38 mg a.i./kg-
bw/day (9 ppm)
Parental ChE:
LOAEL = 0.043 mg a.i./kg-
bw/day (1 ppm)
NOAEL < 0.043 mg a.i./kg-
bw/day (1 ppm)
OffsDrine:
LOAEL = 2.1 mg a.i./kg-
bw/day (50 ppm)
NOAEL = 0.38 mg a.i./kg-
bw/day (9 ppm)
OffsDrine ChE:
LOAEL = 0.38 mg a.i./kg-
bw/day (9 ppm)
NOAEL = 0.13 mg a.i./kg-
bw/day (3 ppm)
Parental systemic: male and
female fertility
Parental ChE: brain, plasma,
and RBC ChE activity
Offspring: Litter size, pup
weight during lactation
Offspring ChE: brain,
plasma, RBC ChE activity
41461901
Eigenberg
(1990)
Acceptable
4.2.2.3 Wild Mammals: Sublethal Effects and Open Literature Information
A search in the ECOTOX database provided several studies detailing sublethal effects of
exposure to ODM in laboratory mammals. These studies are described below.
Tayyaba et al. (1981) (ECOTOX ref. # 89144) studied nucleic acid metabolism alterations in the
brain due to exposure to Metasystox-R (25% ODM) in laboratory rats. Injections of 4 mg/kg-bw
were given to the rats daily for 10 days. Mortality was not observed in any of the rats; however,
sublethal effects that were observed included unconsciousness, muscular fasciculations,
hyperexcitability to tactile stimuli, convulsions, and ataxia. Further, the authors found that the
test material altered the concentration of nucleic acids in the brain and also the functional activity
of lysosomal enzymes in the brain. This study provides some additional information on
sublethal effects of ODM in mammals, although the exposure route in the study is not
necessarily relevant to a field situation.
In a study in which female laboratory rats were exposed dermally to ODM as Metasystox-R,
Raizada et al. (1993) (ECOTOX ref. # 89143) alone and in combination with
hexachlorocyclohexane (lindane), which is a broad-spectrum insecticide. Rats were exposed
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dermally to 125 mg/kg-bw/day ODM alone and in combination with 100 mg/kg-bw/day HCH
for 7, 15, and 30 days (the study does not report whether the dose is corrected for percentage ai
in the test material). Mortality was observed in all test groups, but further details are not
provided. Exposure to ODM alone for 30 days produced severe sublethal effects, including
tremor, dyspnea, salivation, convulsion, and diarrhea. ODM also produced severe necrosis in
liver cells and changes in the granular and molecular layer of the cerebellum. Further,
significant reductions in brain AChE activity occurred by 15 and 30 days of exposure in the
ODM group. The degree of inhibition was >20% in all cases, indicating sufficient AChE
depression to cause sublethal effects and behavioral changes. Inhibition was also observed in
erythrocyte ChE on all days examined. Effects observed in the ODM-only group were more
pronounced in the group receiving the combination of pesticides. This study demonstrates that
severe sublethal effects and some mortality may result from dermal exposure to ODM in the
field. However, it is not known how this study represents levels of actual exposure, except that
rats were tested at the same concentration for varying lengths of time. Currently there is no
methodology that adequately quantifies dermal exposure, so how well this study represents
effects that would be observed in the field is not known.
Kumari et al. (1995) (ECOTOX #88896) administered sublethal doses of 28, 56, and 80 mg/kg
Metasystox-R orally to Swiss albino mice (7-8 weeks old). Cells from animals were observed
for signs of mutagenicity. The study reports effects based on statistical significance; however,
the significance may be misleading because of batches of cells from multiple animals were
combined and each cell was considered to be the experimental unit. However, the study does
report observations of mutagenicity based on chromosomal aberration and abonormal sperm
cells. The authors also note induction of micronuclei, potentially indicating DNA damage. The
data from this study requires a revised analysis, but does demonstrate the potential for mutagenic
effects that may affect fertility and reproductive success in mammals.
In contrast to the studies described above, Clemens et al (1990) (ECOTOX #88987)
demonstrated few effects with repeated oral exposure during gestation in female laboratory rats.
In a one-generation reproduction study, the authors dosed female rats with 0.0 to 4.5 mg/kg of
ODM (90.6% purity) orally from Days 6 to 16 of gestation. Females were studied from Day 16
of gestation through Day 21 postpartum to observe body weight, food consumption, and blood
and brain ChE activity. Abnormalities were observed in fetuses, and offspring that were
delivered were observed for neurobehavioral function with a series of behavioral challenges
(e.g., time to righting after being dropped from 38 cm, degree of negative geotaxis, reaction to
auditory startle, performance in a maze, activity in an open field, olfactory discrimination, and
visual placing). Tremor and reduced food consumption was observed in dams at the highest test
dose, but reproductive parameters were not affected. Brain AChE activity was significantly
affected in all test groups, and in the two highest test groups brain AChE was depressed to >50%
on Day 16 and in the highest test group on Day 20. No significant effects were observed in the
offspring. The authors conclude that limited effects occurred as a result of repeated exposures
during gestation; however, the AChE effects observed in the brain indicate the potential for
sublethal effects and mortality to occur.
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4.2.3 Toxicity to Nontarget Insects
Toxicity studies on terrestrial invertebrates are utilized to assess the potential for ODM to induce
indirect effects to the terrestrial phase CRLF via a reduction in invertebrate prey base. The acute
contact LD50, using the honey bee, Apis mellifera, is an acute contact, single-dose laboratory
study designed to estimate the quantity of toxicant required to cause 50% mortality in a test
population of bees. One acute oral and three acute contact studies provide data for adult and
larval honey bees (Table 4-14). Based on the most sensitive values, ODM is classified as highly
toxic to honey bees on an acute oral and acute contact basis.
Table 4-14. Acute Contact and Acute Oral Toxicity of ODM
to Honey Bees.
Species
Test Type
% ai
LD50
Toxicity
category
MRID (Author, Year)
Status
Honey bee
(Apis mellifera)
Acute contact
Tech.
3.0 ug/bee
Moderately
toxic
00036935 (Atkins et al. 1975)
Acceptable
Honey bee
(Apis mellifera)
Acute contact
Tech.
2.2 ug/larva
Moderately
toxic
00074486 (Atkins and Kellum 1980)
Supplemental1
Honey bee
(Apis mellifera)
Acute contact
Tech.
0.54 ug/bee
Highly toxic
05001991 (Stevenson 1978)
Acceptable
Honey bee
(Apis mellifera)
Acute oral
Tech.
0.31 ug/bee
Highly toxic
05001991 (Stevenson 1978)
Acceptable
'No guideline exists for study on bee larvae. Larvae were 3-4 days old.
Another study submitted to the Agency provides additional information for toxicity to honey
bees and other nontarget insects. Johansen and Eves (1965, MRID 00060628) estimated the
toxicity of residual ODM applied at 0.5 lbs ai/acre on foliage to honey bees and alkali bees
(Nomia melanderi), and showed that ODM had short-lived toxicity to both species exposed to
foliar residues. Hand treatments of ODM formulated product (25% ai) were made to small plots
of alfalfa and bees were housed with the vegetation at 3 hours post application. Mortality was
observed after 24 hours, and residues resulted in 2% and 20% mortality in honey bees and alkali
bees, respectively, indicating low to moderate toxicity via exposure to foliar residues.
No other useful or valid toxicity values were found in the ECOTOX literature database for
honeybees or other nontarget insects for ODM.
4.2.4 Terrestrial Field Studies
A simulated field study with House sparrows (Passer domesticus), Northern bobwhite (Colinus
virginianus), and New Zealand rabbits (Oryctolagus cuniculus) was conducted to assess the
potential effects of ODM to wildlife in the field (Lamb and Jones 1973, MRID 00060638). This
study was submitted in order to fulfill the guideline requirement (71-5) for a simulated or actual
field study, and was rated as supplemental. The animals were exposed to both treated and
untreated alfalfa at an application rate of 2.25 lb ai/A, applied three times with a two week
application interval. One pair of each species was placed in a metal cage, and the cage was
placed on either a control plot or treatment plot of alfalfa. Each plot had six cages of each
species. The commercial feed for half of the cages for each species was withheld for 6 hours
after each application so that only natural food was available for the animals. Cages were moved
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on days 6, 13, 20, 27, and 34 to fresh alfalfa that had received previous applications. Animals
were observed daily for toxic signs, and dead animals were replaced.
There was no treatment-related mortality of quail during the 42 day study. Weight losses for
both treated and control birds were equivalent. The treated rabbits had no toxic symptoms or
deaths, although one control rabbit died. There were high mortalities of control and treated
sparrows, particularly during the last week of the study. The high death rate was attributed to
stress due to being caged over an extended period of time.
The data indicate that a formulated product of Metasystox-R was not significantly hazardous to
caged bobwhite, house sparrows, and New Zealand rabbits. However, issues such as repellency
were not considered, and the study does not provide adequate information (e.g., cage size) to
evaluate exposure. Therefore, the study does have deficiencies that limit its usefulness for
estimating risk.
4.3 Toxicity to Aquatic and Terrestrial Plants
Aquatic Plants - A Tier I aquatic plant study with green algae (Scenedesmus subspicatus) showed
no significant effects on population growth at test concentrations up to 100 ppm ai (MRID
44657701). A study is not available with a vascular aquatic plant species; however, effects are
expected to be minimal.
Terrestrial Plants - Tier I and II seedling emergence and vegetative vigor tests for terrestrial
plants have not been submitted for ODM and were not requested by EFED in its RED Chapter.
Some plant data are available in the ECOTOX database that demonstrate the effects of ODM on
seed germination and growth. Based on information from Panda (1983), barley seeds soaked in
water containing 100 ppm ai ODM for 6 hours did not demonstrate significant decreases in
germination rate compared to controls. This value can be related to the highest one-time
application rate currently registered for ODM (0.75 lbs ai/acre) by estimating the concentration
of ODM in a 1-cm zone saturated with water at the soil surface. Assuming a soil bulk density of
1.3 g/cm3, the application rate of 0.75 lbs ai/acre would result in a soil concentration of 6.5 ppm,
which is well below the NOAEC value derived from the Panda (1983) study. A NOAEC value
for growth was determined to be 1500 ppm ai in this study based on seedling height after one
week. Another study using similar test methods with onion showed a NOAEC for seed
germination rate of 2000 ppm (Pandita 1986). Based on this information, effects on terrestrial
plants are expected to be minimal.
4.4 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 the CRLF and aquatic and terrestrial
animals that may indirectly affect the CRLF (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 ODM on par with the
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acute toxicity endpoint selected for RQ calculation. To accomplish this interpretation, the
Agency uses the slope of the dose-response relationship available from the toxicity study used to
establish the acute toxicity measures of effect for each taxonomic group that is relevant to this
assessment. The individual effects probability associated with the acute RQ is based on the
mean estimate of the slope and an assumption of a probit dose response relationship. In addition
to a single effects probability estimate based on the mean, upper and lower estimates of the
effects probability are also provided to account for variance in the slope, if available. The upper
and lower bounds of the effects probability are based on available information on the 95%
confidence interval of the slope. A statement regarding the confidence in the estimated event
probabilities is also included. Studies with good probit fit characteristics (i.e., statistically
appropriate for the data set) are associated with a high degree of confidence. Conversely, a low
degree of confidence is associated with data from studies that do not statistically support a probit
dose response relationship. In addition, confidence in the data set may be reduced by high
variance in the slope (i.e., large 95% confidence intervals), despite good probit fit characteristics.
In the event that dose response information is not available to estimate a slope, a default slope
assumption of 4.5 (95% C.I.: 2 to 9) (Urban and Cook, 1986) is used.
Individual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.1
(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental
Fate and Effects Division (June 22, 2004). The model allows for such calculations by entering
the mean slope estimate (and the 95% confidence bounds of that estimate) as the slope parameter
for the spreadsheet. In addition, the acute RQ is entered as the desired threshold.
For ODM, mortality was observed in acute toxicity studies for freshwater fish, freshwater
invertebrates, birds, mammals, and honey bees. Where probit slopes are provided, they are used
along with their upper and lower confidence limits (if available) to estimate the probability of
individual morality and its potential variability. In cases where they are unavailable, the default
slope assumption of 4.5 with default upper and lower slope bounds of 2 and 9 are used as per
original Agency assumptions of a typical slope cited in Urban and Cook (1986). The chance of
individual mortality will be determined using the listed species LOC as the threshold of concern
and also the RQ determined for each taxon. These analyses are presented below in the Risk
Characterization along with calculations of RQs for each taxon.
4.5 Incident Database Review
The Ecological Incident Information System (EIIS) was searched for incidents involving ODM.
Only one incident (1002680-001) was recorded involving ODM. This incident occurred in
October 1987 in Monterey County, California, and is associated with its use in broccoli. In this
case, four California quail were found dead in a farm yard adjacent to a broccoli field. Several of
the birds had broccoli leaves in their crops, and residues of ODM and methamidophos (another
organophosphate insecticide) were detected in these crop contents. The causal relationship
between ODM and the birds' deaths was determined to be possible, although the degree to which
methamidophos contributed is unknown.
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5. Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations to determine
the potential ecological risk from the assessed ODM use scenarios within the action area and
likelihood of direct and indirect effects on the California Red Legged Frog. The risk
characterization provides estimation and description of the likelihood of adverse effects;
articulates risk assessment assumptions, limitations, and uncertainties; and synthesizes an overall
conclusion regarding the effects determination (i.e., "no effect," "likely to adversely affect," or
"may affect, but not likely to adversely affect") for the California Red Legged Frog.
5.1. Risk Estimation
Risk was estimated by calculating the ratio of estimated environmental concentrations (EECs;
see Tables 3-4 through 3-7) and the appropriate toxicity endpoint (see Tables 4-1 through 4-14).
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 (Table 5-1). Appendix F describes the
categories of toxicity.
Table 5-1. Levels of Concern for Listed Terrestrial and Aquatic Organisms
Taxa
Acute LOC
Chronic LOC
Avian1 (terrestrial phase amphibians)
0.1
1
a
Mammalian
0.1
1
Terrestrial plants3
1
Aquatic Animals4 (aquatic phase amphibians)
0.05
1
Insects 5
0.05
1
Used in RQ calculations:
1 LD50 and estimated NOEL
2 LD50 and NOEC
3 EC25
4 LC/EC50 and estimated and reproductive NOEC
5 LD50 per EFED's CRLF Steering Committee
5.1.1. Aquatic Direct and Indirect Effects
5.1.1.1. Direct Effects
Aquatic exposure estimates from PRZM-EXAMS were compared to fish acute and chronic
toxicity endpoints, and Risk Quotients were calculated. Peak and 60-day EECs used in these
calculations are presented above in the Exposure Characterization section. In the absence of
amphibian data, the fish represents the CRLF. For ground and aerial applications, all RQs were
below the LOC of 0.05 for acute risk and exceeded the LOC of 1.0 for chronic risk for broccoli
and cauliflower, brussel sprouts, and cabbage (Table 5-2). The chronic RQ for aerial
applications to lettuce is essentially equal to the no effect level, so chronic effects are expected to
be unlikely as a result of applications to lettuce. Therefore, direct effects to the aquatic phase
CRLF is expected as a result of chronic exposure due to applications to the cole crops listed
above.
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Table 5-2. Acute and Chronic Freshwater Fish RQs Resulting from Ground and Aerial or
Airblast Applications of ODM. RQs that Exceed the LOCs are Presented in Bold.
Ground Applications
Aerial or Airb
ast Applications
Crop
Fish acute
Fish Chronic
Fish acute
Fish Chronic
RQ1
RQ2
RQ1
RQ2
Cabbage
0.045
3.438
0.047
3.698
Mint
0.001
0.053
N/A
N/A
Brussel sprouts
0.030
2.263
0.032
2.464
Lima beans
0.005
0.308
0.007
0.494
Broccoli, Cauliflower
0.028
1.892
0.029
2.013
Corn
0.001
0.068
0.004
0.245
Lettuce
0.013
0.910
0.015
1.064
Alfalfa
0.007
0.516
0.009
0.658
Onion
0.001
0.098
0.004
0.273
Sugar beets
0.004
0.243
0.005
0.324
Cotton
0.001
0.036
N/A
N/A
Melons
<0.001
0.023
0.002
0.097
Fruit (airblast)
N/A
N/A
0.004
0.290
Grapes (airblast)
N/A
N/A
0.004
0.293
Nursery
0.005
0.354
0.006
0.473
Walnuts
0.001
0.083
0.002
0.157
Calculated using rainbow trout LC50 of 730 ppb.
Calculated using estimated freshwater fish NOAEC of 5 ppb.
5.1.1.2. Indirect Effects
Aquatic phase CRLFs may be indirectly affected through losses of aquatic plant and invertebrate
food items. However, since ODM has been demonstrated to have low toxicity to aquatic plants,
indirect effects are not expected to occur via this route. They can also occur through losses of
aquatic invertebrates.
To determine the potential for losses to aquatic invertebrates that can cause indirect effects to the
aquatic phase CRLF, peak and 21-day aquatic exposure estimates from PRZM-EXAMS were
compared to aquatic invertebrate toxicity endpoints to calculate acute and chronic RQs (Table 5-
3). Acute RQs were above the LOC of 0.05 for cole crops and lettuce for both ground and aerial
or airblast applications, indicating that toxic effects on invertebrates are expected for those uses.
All other acute RQs were below this LOC and all chronic RQs were below the LOC of 1.0.
Table 5-3. Acute and chronic freshwater invertebrate RQs resulting from ground and
Ground Applications
Aerial or Airblast Applications
Crop
Invertebrate
Invertebrate
Invertebrate
Invertebrate
Acute RQ1
Chronic RQ2
Acute RQ1
Chronic RQ2
Cabbage
0.174
0.570
0.182
0.611
Mint
0.003
0.008
N/A
N/A
Brussel sprouts
0.116
0.375
0.121
0.407
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Ground Applications
Aerial or Airblast Applications
Crop
Invertebrate
Invertebrate
Invertebrate
Invertebrate
Acute RQ1
Chronic RQ2
Acute RQ1
Chronic RQ2
Lima beans
0.017
0.053
0.026
0.080
Broccoli,
Cauliflower
0.107
0.327
0.113
0.347
Corn
0.004
0.012
0.014
0.043
Lettuce
0.051
0.159
0.057
0.185
Alfalfa
0.028
0.090
0.036
0.114
Onion
0.005
0.017
0.014
0.042
Sugar beets
0.015
0.044
0.019
0.056
Cotton
0.002
0.006
N/A
N/A
Melons
0.001
0.004
0.007
0.020
Fruit (airblast)
N/A
N/A
0.016
0.049
Grapes
(airblast)
N/A
N/A
0.015
0.049
Nursery
0.020
0.063
0.025
0.083
Walnuts
0.004
0.013
0.008
0.026
Calculated using the scud LC50 of 190 ppb.
Calculated using the Daphnia (waterflea) NOAEC of 46 ppb.
5.1.2. Terrestrial Direct and Indirect Effects
5.1.2.1. Direct Effects
Using the T-REX tool for estimating exposure to the CRLF, dose- and diet-based acute and
chronic RQs exceed the listed species LOCs of 0.1 (acute) and 1.0 (chronic) for CRLF
consuming small insects (Table 5-4). This is true for the lowest and highest application rates.
For CRLF consuming large insects, only the diet-based acute RQs did not exceed the LOC.
Based on these findings, direct effects to the terrestrial phase CRLF are expected following
application of ODM in all uses assessed.
Table 5-4. Upper Bound Kenaga Residues for 20-g and 100-g Birds (surrogates for CRLF)
from T-REX.
Weight Class
Exposure Type
RQs
Small Insects
Large Insects
Low
High
Low
High
20 g2
Dose-based Acute
8.23
43.30
0.92
4.81
O
o
Dose-based Acute
4.70
24.70
0.52
2.74
(no size class distinction)3
Diet-based Acute
0.12
0.61
0.01
0.07
(no size class distinction)4
Diet-based Chronic
28.13
147.85
3.13
16.43
'"Low " and "High" refer to RQs determined for the lowest application rate (to walnuts) and the highest application
rate (to cabbage).
Calculated using rock pigeon LD50 of 7 mg/kg bw.
Calculated using Northern bobwhite LC50 of 434 ppm.
Calculated using Northern bobwhite NOAEC of 1.8 ppm.
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5.1.2.2. Indirect Effects
Terrestrial food sources are mainly accounted for by terrestrial insects, but as described above,
the terrestrial phase CRLF also consumes small mammals, other frogs, and may consume fish.
Indirect effects are expected due to losses of other amphibians, as evidenced by the direct effects
to the CRLF described above. Indirect effects can occur to the terrestrial phase CRLF through
losses of aquatic (fish) and terrestrial prey items (terrestrial invertebrates, small mammals, other
amphibians) and also riparian and upland plants. Since ODM has low toxicity to terrestrial
plants, indirect effects due to losses of terrestrial vegetation are not expected to occur. RQ
calculations for fish were described above in Section 5.5.1.2 and RQs for amphibians were
described above in Section 5.5.2.1 for direct effects on the aquatic and terrestrial phase CRLF,
respectively. Findings in these analyses also apply to the analysis of indirect effects on fish and
other amphibians as prey items, so these analyses will not be reiterated here. Therefore, this
section contains analyses for mammalian and terrestrial invertebrates that can be food items for
the terrestrial phase CRLF.
Mammals
RQs for mammals were also examined using the T-REX spreadsheet model (Table 5-5). Dose-
based acute RQs calculated for 15-g mammals exceed the LOC for the lowest application rate
assessed (for walnuts) except for those that consume large insects and for granivores. At the
highest application rate, all feeding classes exceed mammal LOCs. For both dose- and diet-
based RQs, chronic RQs exceed the LOC in all cases.
Table 5-5. Upper Bound Kenaga, Acute and Chronic Mammalian Dose- and Diet-Based
Risk Quotients
RQ Type
RQs1
Short Grass
Tall Grass
Broadleaf Plants/
Small Insects
Fruits/Pods/
Seeds/
Large Insects
Granivore
Low
High
Low
High
Low
High
Low
High
Low
High
Dose-based
acute2
0.81
4.28
0.37
1.96
0.46
2.41
0.05
0.27
0.01
0.06
Dose-based
chronic3
907.96
4772.97
416.15
2187.61
510.73
2684.79
56.75
298.31
12.61
66.29
Diet-based
chronic4
90.00
473.11
41.25
216.84
50.63
266.13
5.63
29.57
N/A
N/A
'"Low" and "High" refer to EECs determined for the lowest (walnuts) and highest (cabbage) application rates for
ODM.
Calculated with adjusted rat LD50 of 105.5 mg/kg bw.
Calculated with adjusted rat NOAEL of 0.09 mg/kg bw/day.
Calculated using rat NOAEC of 1.0 ppm.
87
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Terrestrial Invertebrates
For terrestrial insects, the RQs determined using EECs converted to [j,g/bee were determined to
be 2.65 for the lowest application rate (walnuts) and 13.90 for the highest application rate. Both
of these values exceed the terrestrial invertebrate LOC on 0.05. Details of the calculations used
to arrive at these numbers are provided above in Section 3.3.2.
5.1.1. Probability of Individual Mortality for Acute Direct and Indirect Effect to
the CRLF
The risk of mortality to the CRLF is based on acute RQs derived for fish (representing the
aquatic phase) and birds (representing the terrestrial phase). Chances of individual effects for
CRLF prey items are derived from their respective RQs as well. The individual chance of effect
is calculated using the probit-slope determined from acute toxicity studies and a specified
threshold of effect. If the slope is not available from the toxicity study, then a default value of
4.5 (CI 2.0 - 9.0) is used (Urban and Cook, 1986). The threshold of effect is designated as the
LOC, which is used to derive a general estimate of the chance of mortality for each taxon, or the
RQ, which is used to derive an estimate based on the effects observed on that taxon. These
probabilities are calculated using the Excel spreadsheet developed by Ed Odenkirchen, OPP
(IEC vl.l, June 22, 2004). Results of these analyses for taxa concerning direct and indirect
effects are provided below.
Direct Effects to the CRLF
Acute RQs for fish did not exceed the listed-species LOC, so no direct effects resulting from
acute mortality to the aquatic-phase CRLF are expected. Therefore, the chance of individual
mortality is not determined for the aquatic-phase CRLF. Acute RQs did exceed for the birds,
representing the terrestrial-phase CRLF. The slope for the rock pigeon LD50 study is not
available, so the default value would be used to estimate the chance of individual terrestrial-
phase CRLF mortality. As a result, the chance of individual mortality, using the LOC of 0.1 as
the threshold of effect, would be 1 in 2.94 x 105, with variability ranging from 1 in 8.86 x 1018to
1 in 44. Using the highest RQ calculated above (42.13), the probability of individual mortality is
1 in 1 or approaching 100%. These findings also apply to the assessment of indirect effects.
Indirect Effects to the CRLF
Aquatic vertebrates - The chance of individual effect is not determined for fish or aquatic-phase
amphibians in this assessment because RQs based on the fish LC50 did not exceed the acute
listed species LOC.
Aquatic invertebrates - The slope for the LC50 study with the scud is not available, so the default
value would be used to estimate the chance of individual mortality to an aquatic invertebrate
food item for the CRLF. As a result, the chance of individual mortality is 1 in 4.18 x 108, with
variability ranging from 1 in 1.75 x 1031 to 1 in 216 when the threshold of effect is the LOC of
0.05. If the highest acute RQ calculated above (0.182) is used as the threshold, then the chance
88
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of individual mortality is actually 1 in 2,300 with variability ranging from 1 in 7.27 x 1010to 1 in
14.
Mammals - The probit slope determined from the rat LD50 used to estimate acute RQs was 8.2.
Confidence intervals were not provided in the study report, so the reliability cannot be evaluated.
However, based on this slope, and using the listed species LOC for terrestrial vertebrates, the
chance of individual mortality in mammals as a result of ODM use is 1 in 8.32 x 1015. If the
highest acute RQ calculated above (4.28) is used as the threshold, the chance is actually 1 in 1 or
100%.
Birds/Amphibians — The assessment for direct effects to the CRLF (above) is applicable. At the
calculated RQ, the individual chance of effect approaches 100%.
Terrestrial Invertebrates - The slope for the LC50 study with the honeybee is not available, so the
default value would be used to estimate the chance of individual mortality to terrestrial
invertebrates. Since the same LOC is used, the findings based on the default would be the same,
which were the chance of individual mortality is 1 in 4.18 x 108, with variability ranging from 1
in 1.75 x 1031 to 1 in 216. However, if the highest acute RQ calculated above (13.90) is used as
the threshold, then the chance of individual mortality is actually 1 in 1 (100%), with variability
ranging from 1 in 1.01 (99%) to 1 in 1 (100%).
5.2. Risk Description
The risk description synthesizes an overall conclusion regarding the likelihood of adverse
impacts leading to an effects determination (i.e., "no effect," "may affect, but not likely to
adversely affect," or "likely to adversely affect") for the California Red Legged frog.
If the RQs presented in the Risk Estimation (Section 5.1.2) show no indirect effects, and LOCs
for the CRLF are not exceeded for direct effects (Section 5.1.1), a "no effect" determination is
made based on ODM's use within the action area. If, however, indirect effects are anticipated
and/or exposure exceeds the LOCs for direct effects, the Agency concludes a preliminary "may
affect" determination for the CRLF. Following a "may affect" determination, additional
information is considered to refine the potential for exposure at the predicted levels based on the
life history characteristics (i.e., habitat range, feeding preferences, etc) of the CRLF and potential
community-level effects to aquatic plants and terrestrial plants growing in semi-aquatic areas.
Based on the best available information, the Agency uses the refined evaluation to distinguish
those actions that "may affect, but are not likely to adversely affect" from those actions that are
"likely to adversely affect" the CRLF.
The criteria used to make determinations that the effects of an action are "not likely to adversely
affect" the CRLF include the following:
• Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where "take" occurs
for even a single individual. "Take" in this context means to harass or harm, defined as
the following:
89
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• "Harm" includes significant habitat modification or degradation that results in
death or injury to listed species by significantly impairing behavioral patterns
such as breeding, feeding, or sheltering.
• "Harass" is defined as actions that create the likelihood of injury to listed
species to such an extent as to significantly disrupt normal behavior patterns
which include, but are not limited to, breeding, feeding, or sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are extremely
unlikely to occur. For example, use of dose-response information to estimate the
likelihood of effects can inform the evaluation of some discountable effects.
• Adverse Nature of Effect: Effects that are wholly beneficial without any adverse
effects are not considered adverse.
A description of the risk and effects determination for each of the established assessment
endpoints for the CRLF is provided in Sections 5.6.1 through 5.6.3.
5.2.1. Direct Effects to the California Red Legged Frog
The federal action is all labeled uses. In order to compare the location of the labeled uses with
the areas important to the frog, the potential use areas in California were overlaid with the core
areas, critical habitat and known occurrence areas of the CRLF. The result of this layering is the
ability to discern areas of overlap between potential use and the CRLF life-cycle.
5.2.1.1. Aquatic Phase
Risk Quotients for freshwater fish (surrogates for the CRLF) are below LOC for acute effects for
all uses (Table 5-2). RQs exceed the LOC for chronic effects for broccoli, cauliflower, cabbage,
and aerial applications to lettuce (Table 5-2). Chronic RQs range from 1.9 to 3.4 for CRLF for
ground applications to these crops and from 1.1 to 3.7 for aerial applications. Applications made
to these crops have the highest rates (0.5 - 0.75 lbs ai/acre), have multiple applications (2-3), and
have the shortest application interval (7 days) compared to the other crops for which RQs did not
exceed. Therefore, risk to the aquatic phase CRLF due to adverse reproductive and other chronic
effects is anticipated resulting from these labeled uses of ODM. Whether this results in a LAA
determination depends on whether aquatic phase CRLFs co-occur in areas with these crops and
areas affected downstream by aquatic residues resulting from applications to these crops. This
analysis is discussed in Section 5.7.1.2 below.
5.2.1.2. Terrestrial Phase
Risk Quotients for terrestrial-phase CRLF, as represented by 20-gram and 100-gram birds,
exceed LOC for both acute and chronic (reproductive) effects (Table 5-4). Dose-based acute
RQs range from 0.5 to 8.2 for CRLF minimum exposure resulting from applications to walnuts
(1 application of 0.375 lbs ai/acre) and from 2.7 to 43.3 for maximum exposure from
applications made to cabbage (3 applications of 0.75 lbs ai/acre made 7 days apart). Only diet-
90
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based RQs for the large insect food source are below LOC (0.1). Chronic RQs range from 3.1 to
28.1 for CRLF for minimum exposure and 16.4 to 147.9 for maximum exposure. Based on this
analysis, both mortality and adverse reproductive effects to the terrestrial-phase CRLF (from a
diet including both small and large insects) are anticipated from all labeled uses of ODM
assessed in this document.
Refinement ofRQfor CRLF terrestrial phase (T-HERPS analysis)
Birds are currently used as surrogates for reptiles and terrestrial-phase amphibians. However,
reptiles and amphibians are poikilotherms (body temperature varies with environmental
temperature) while birds are homeotherms (temperature is regulated, constant, and largely
independent of environmental temperatures). Therefore, reptiles and amphibians (collectively
referred to as herptiles hereafter) 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 or reptiles on a daily dietary intake basis, assuming similar caloric content
of the food items. This can be seen when comparing the estimated caloric requirements for free
living iguanid lizards (Iguanidae) (EQ 1) to passerines (song birds) (EQ 2) (U.S. EPA, 1993):
iguanid FMR (kcal/day)= 0.0535 *(bw in g)0'799 (EQ 1)
passerine FMR (kcal/day) = 2.123 *(bw in g)0'749 (EQ 2)
With relatively comparable exponents (slopes) to the allometric functions, one can see that,
given a comparable body weight, the free living metabolic rate of birds can be 40 times higher
than reptiles, though the requirement differences narrow with high body weights. Consequently,
use of avian food intake allometric equation as a surrogate to herptiles is likely to result in an
over-estimation of exposure for reptiles and terrestrial-phase amphibians.
Because of the need to evaluate dietary exposure to the CRLF, the T-REX model (version 1.3.1.)
has been altered to allow for an estimation of food intake for herptiles T-HERPS using the same
basic procedure that T-REX uses to estimate avian food intake. This tool is thus used to make a
refined estimate of exposure and risk based on body weights, food items, and daily food intake
rates that are more appropriate for the CRLF. A comparison is made below between the results
for the CRLF obtained with the T-REX model and results obtained from the T-HERPS model.
Table 5-6 presents the EECs for herptiles calculated with the T-HERPS model. The values
presented are for uses involving the lowest and highest application rates as above for T-REX.
91
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Table 5-6. Upper Bound Kenaga, Acute Terrestrial Herpetofauna Dose-Based and Diet-
Based EECs from T-HERPS
Dose-Based EECs,
Amphibian Size Class
(grams)
EECs1 (mg/kg bw)
Broadleaf
Plants/
Small Insects
Fruits/Pods/
Seeds/
Large Insects
Small
Herbivore
Mammals
Small
Insectivore
Mammal
Small
Amphibians
Low
High
Low
High
Low
High
Low
High
Low
High
1.4
1.97
10.34
0.22
1.15
N/A
N/A
N/A
N/A
N/A
N/A
37
1.93
10.13
0.21
1.13
56.10
294.9
3.51
18.43
0.07
0.35
238
1.27
6.66
0.14
0.74
8.72
45.85
0.55
2.87
0.04
0.23
Diet-Based EECs
EECs1 (ppm)
(no size class distinction)
50.63
266.13
5.63
29.57
59.30
311.75
3.71
19.48
1.76
9.24
'"Low " and "High" refer to EECs determined for the lowest application rate and the highest application rate (see
text).
RQs from the T-HERPS modeling are presented in Table 5-7. Although dose-based EECs and
RQs for herptiles are lower based on this analysis compared to those from T-REX, LOCs are still
exceeded for the low application rate three of the five feeding categories and for the high
application rate in all but the small amphibian feeding class. Diet-based RQs (and EECs above)
are the same for the small and large insect food categories; they are retained below for
comparison to other feeding categories. Based on this analysis, diet-based RQs exceed the
chronic LOC for both the low and high application rate in all feeding classes. The exception is
for the small amphibian feeding class under the low application rate scenario; however, this
value does approach the LOC. Therefore, based on this refined analysis, acute and chronic risk
is still anticipated for the CRLF.
Table 5-7. Upper Bound Kenaga, Acute and Chronic Terrestrial Herpetofauna Dose-Based
and Diet-Based RQs
Dose-Based Acute RQ,
Amphibian Size Class
(grams)2
RQs1
Broadleaf
Plants/
Small Insects
Fruits/Pods/
Seeds/
Large Insects
Small
Herbivore
Mammals
Small
Insectivore
Mammal
Small
Amphibians
Low
High
Low
High
Low
High
Low
High
Low
High
1.4
0.28
1.48
0.03
0.16
N/A
N/A
N/A
N/A
N/A
N/A
37
0.28
1.45
0.03
0.16
8.01
42.13
0.50
2.63
0.01
0.05
238
0.18
0.98
0.02
0.11
1.25
6.55
0.08
0.41
0.01
0.03
Diet-Based RQs (Acute and Chronic)
Acute3
0.12
0.61
0.01
0.07
0.14
0.72
0.01
0.04
<0.01
0.02
Chronic4
28.13
147.85
3.13
16.43
32.95
173.20
2.06
10.82
0.98
5.13
'"Low " and "High" refer to RQs determined for the lowest application rate (to walnuts) and the highest application
rate (to cabbage).
Calculated using rock pigeon LD50 of 7 mg/kg bw.
Calculated using Northern bobwhite LC50 of 434 ppm.
Calculated using Northern bobwhite NOAEC of 1.8 ppm.
92
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5.2.2. Indirect Effects Due to Reduction in Food Items
5.2.2.1. Aquatic Phase
Sub-adult and adult CRLF consume invertebrates. Acute RQs for freshwater invertebrates range
up to 0.18 (Table 5-3), so there is a "May Affect" finding. However, since the RQ is below the
Acute Risk LOC (0.5), other factors must be considered in determining if this constitutes a
"Likely to Adversely Affect" or "Not Likely to Adversely Affect" finding, as explained below in
section 5.4.2. Based on the likelihood of individual effects on aquatic invertebrates (Section
5.5.3), indirect risk to the CRLF via effects on aquatic invertebrates is considered "NLAA."
5.2.2.2. Terrestrial Phase
Risk quotients for two common prey animals (small mammals and frogs [represented by bird
RQs]) greatly exceed both acute and chronic LOC (Tables 5-4 and 5-5) at even the lowest
labeled application rate. These prey animals are thus anticipated to suffer adverse effects
(mortality and reproductive effects) from all labeled ODM uses. The acute RQ for a terrestrial
invertebrate (honey bee), representing the bulk of the terrestrial phase CRLF diet, ranges from
2.7 to 13.9. Thus, adverse indirect effects to the CRLF, mediated via reduction in prey base, are
anticipated.
5.2.3. Effects to Critical Habitat
Activities that may destroy or adversely modify critical habitat are those that alter the CRLF's
PCEs and jeopardize its continued existence. Evaluation of actions related to ODM use that may
alter these PCEs form the basis of the critical habitat impact analysis. As previously discussed in
the Problem Formulation, PCEs that are identified as assessment endpoints are limited to those
that are of a biological nature and those PCEs for which ODM effects data are available.
Adverse modification of designated critical habitat via actions that may directly impact aquatic
and terrestrial plants are associated with those characteristics necessary for normal behavior,
growth, and viability of all CRLF life stages. However, effects on terrestrial and aquatic plants
were not assessed, since ODM has been demonstrated to be of low toxicity to plants. Therefore,
adverse modifications to critical habitat are not expected to occur as a result of losses of aquatic
and terrestrial plants. As a result, major alterations of the normal sedimentation, water
chemistry, water temperatures, and hydrologic functioning of aquatic habitats are not expected as
a result of aquatic or riparian plant losses occurring after applications of ODM. Further,
elimination or alteration of riparian, dispersal, and/or upland habitat is also not expected.
Aquatic. Indirect effects due to reduction of invertebrate food based were determined to be
insignificant, and this conclusion also applies to effects to critical habitat as a result in losses in
prey base.
Terrestrial. Indirect effects were also predicted to occur to all terrestrial species as a result of
applications of ODM to all uses included in this analysis. These losses would affect the
terrestrial prey base for the terrestrial phase CRLF. Further, community and ecosystem
93
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functioning could also be altered. For example, losses of insects could affect the pollination rate
for flowering plants, which would indirectly affect riparian, dispersal, and upland vegetation.
Similarly, losses of birds and mammals could affect seed dispersal, thus indirectly affecting
plants. Perturbations of populations within the community could also disrupt normal community
function.
5.3. Action Area
The Action Area for listed species from the labeled use of a pesticide is defined by the degree to
which the screening level RQs exceed the listed species LOC for any taxon. If necessary,
standard modeling assumptions are changed to determine the limits of LOC exceedence. For
example, the spray drift assumption for aerial application can be lowered from the standard 5%
until the RQ no longer exceeds the LOC. The distance at which this occurs beyond the boundary
of a treated field is used to define the action area. This analysis does assume, however, that no
secondary poisoning occurs due to movement of contaminated animals.
5.3.1. Aquatic Phase
The Action Area for effects on aquatic species consists of two parts. One is a spray drift
perimeter around the use site, and the other is a downstream dilution factor. Both parts are
intended to find the geographic extent of Listed species LOC exceedance.
5.3.1.1. Spray Perimeter
The estimate of the spray perimeter around aquatic habitats for determining the aquatic species
action area is based on chronic effects to listed aquatic vertebrates (fish). RQs for aquatic
invertebrates exceed the listed species acute LOC. However, the likelihood of an individual
effect on scud at its highest RQ is very low (Section 5.5.3); thus, this effect is insignificant.
In order to be below the chronic LOC for listed aquatic vertebrates (1.0), the 60-day
concentration in the EXAMS pond would need to 5 ppb (chronic LOC [1.0] * NOAEC [5 ppb]).
With the standard drift assumption for ground application of 1%, the lettuce 60-day
concentration is below the LOC (5 ppb) for lettuce. However, for the broccoli and cauliflower
scenario, the 60-day EEC is 8.8 ppb, which is not low enough. Since the cabbage application
rate is higher than that of broccoli and cauliflower, concentrations are expected to be higher.
Therefore, a buffer to reduce exposure to below LOC cannot be established for any of the cole
crops.
5.3.1.2. Downstream Dilution
The downstream dilution analysis calculates how far downstream the EEC remains above the
listed species LOC, given flow contributions from both contaminated and uncontaminated
streams in the watersheds of potential ODM use. The initial area of concern was defined by
Figure 2B., which shows all agricultural land in all counties in California where ODM is used.
Flow contributions from streams in the corresponding watersheds are included in a Geographic
Information System (GIS) analysis, until the pesticide concentrations (initially the EXAMS pond
94
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peak EEC) from contaminated and uncontaminated streams, weighted for flow, fall below the
Listed species LOC.
The downstream dilution factor that must be achieved is defined by the maximum ratio between
an RQ and its corresponding LOC. In the case of ODM, this is the chronic RQ for fish from
aerial applications to cabbage (3.7), divided by the chronic LOC (1.0), which gives a dilution
factor of 3.7.
5.3.2. Terrestrial Phase
The Action Area due to effects on listed species is also defined by the geographic extent of LOC
exceedence. Quantitative estimates of exposure of avian (including reptiles and terrestrial
amphibians) and mammal species is done with the TREX model, which automates exposure
analysis according to the Hoerger-Kenaga nomogram, as modified by Fletcher (1994).
The lowest ratio between the LOC for listed terrestrial avian and mammalian species (0.1 for
acute effects and 1.0 for chronic effects) and the RQ, times the maximum single application rate,
is used to determine the exposure (in lb/acre) that is below LOC, as shown in Table 5-8.
Exposure below LOC = (LOC/RQ )*(max application rate [lb/acre]).
The Action Area for ODM is dominated by its effects on terrestrial species, due to the much
higher RQs in the terrestrial analysis and exceedances for all uses included in the assessment.
The highest risk quotient for any terrestrial animal was for mammals, in which the chronic RQ
based on the estimated daily dose from the modeling for applications to cabbage was 4,773.
Based on this RQ, the dose (in lb/acre) that results in an RQ below the chronic level of concern is
then 1/4773*0.75 = 0.0002 lb ai/acre. Using the AgDISP model with the far-field Gaussian
extension to calculate the spray drift buffer needed to reduce exposures to below 0.0002 lb
ai/acre for aerial applications. The inputs used in the analysis are presented in Table 5-8; all
other inputs were default values. This analysis indicates that the required spray drift buffer
needed to define the Action Area for terrestrial effects is 11,338 feet (about 2.15 miles).
Table 5-8. AgDISP Input Parameters for
Estimation of Action Area Size
Input parameter
Value
Release height
15 feet
Wind Speed
15 mph
Drop Size Distribution
ASAE Very fine to Fine
Spray volume rate
5 gallons per acre
Non-volatile fraction
0.075
Active Fraction
0.019
Canopy
None
Specific gravity (Carrier)
0.97
Initial Average Deposition
0.0002 lb/acre
95
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The figure below shows the full extent of the Action Area, based on the terrestrial effects
distance of 11,338 feet and the downstream dilution factor of 3.7.
Oxydemeton-methyl Action Area
?
Compiled from California County boundaries (ESRi, 2002),
USQA National Agriculture Statistical Service (NASS, 2002)
Gap Analysis Program Orchard;'Vineyard Landcwer (GAP)
National Land Cwer Database (NLCD) (MRLC, 2001)
Map created by US Environmental ProtectionAgency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
September, 2007. Projection: Albers Equal Area Conic USGS,
North American Datum of 1983 (NAD 1983)
96
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5.4. Listed Species Effects Determination for the California Red Legged Frog
5.4.1. "No Effect" Determination
As stated in the Problem Formulation (Section 2), uses on ornamental, forest, non-bearing trees,
and Christmas trees for which applications are made by injection are expected to pose little
opportunity for exposure to the CRLF and other organisms upon which it depends. Thus, these
uses are concluded to have "No Effect" on the CRLF.
Available data indicate that plants inhabiting aquatic, terrestrial, and semi-aquatic environments
are not sensitive to exposure to ODM at residue concentrations above those expected for aquatic
and terrestrial habitats for the assessed uses of ODM in California. Therefore, it is concluded
that there is "No Effect" on the CRLF via plant-related endpoints. These represent indirect
effects due to reduction or modification of the aquatic and terrestrial plant community as well as
effects on Critical Habitat PCEs related to plants.
5.4.2. "May Effect" Determination
When the action area overlaps (spatially) the designated Core Areas and Critical Habitats a "May
Affect" determination is made. Upon a "May Affect" determination the probability of effect is
considered and a "Likely to Adversely Affect" or "Not Likely to Adversely Affect"
determination is made.
Based on the action area for ODM use in California, the use of ODM "May Effect" the aquatic-
and terrestrial-phase CRLF. Table 5-9 displays the proportion of the core area within each
recovery unit that overlaps with the potential use areas.
Table 5-9. Terrestrial Spatial Summary Results for ODM Uses with 11,338-ft Buffer.
Measure
RU1
RU2
RU3
RU4
RU5
RU6
RU7
RU8
Total
Initial Area of
3
56
16
36
126
333
375
326
1271
Concern (no
buffer, sq km)
Established
3.054
| J
--J
1 J
1.320
3.27S
3.M7
5,307
4.^10
3.320
28.190
species range
area (sq km)
Overlapping
1,092
607
321
1,730
2,289
2,243
2,611
1,185
12,078
area (sq km)
Percent area
29.9
22.1
24.3
52.8
62.8
42.3
53.1
35.6
42.8
affected
# Occurrence
3
0
32
225
249
84
80
28
701
Sections1
'30 occurrence sections occur outside of Recovery Units.
Table 5-10 displays the kilometers of streams that are affected within the CRLF habitat. Within
the initial area of concern, there are 49,130 kilometers of stream waters that are potentially
affected. Using the downstream dilution model adds 843 kilometers to this area, giving a total of
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49,973 potentially affected streams. Since cole crops were the only ones to affect the aquatic-
phase CRLF, only these crops were included in the analysis.
Table 1-10. Stream miles affecting habitat where Cole Crops are used
Recovery Unit
Stream Length (km)
1
269
2
179
3
130
4
484
5
772
6
788
7
891
8
373
5.4.3. "Adverse Effect" Determination
Risk Quotients for direct chronic effects to the aquatic-phase CRLF are above the LOC for four
uses of ODM, including ground and aerial applications to broccoli, cauliflower, cabbage, and
aerial applications to lettuce. Acute RQs for aquatic invertebrates exceed the acute LOC for
these uses as well; however, the effect is considered insignificant based on low likelihood of
individual effect. Nonetheless, since chronic effects are predicted for fish and amphibians,
indirect effects could occur due to the losses of fish and amphibian food items. Based on this
information, and since there is overlap of streams that may contain ODM with CRLF habitat, it is
thus concluded that direct adverse effects to the aquatic-phase CRLF are anticipated for
these four uses.
Risk Quotients for direct acute and chronic effects to the terrestrial-phase CRLF (Tables 5-4 and
5-7) are well above their respective LOCs for all uses assessed. RQs also exceed for acute and
chronic effects to mammals, amphibians (birds), and terrestrial invertebrates for all uses as well.
Furthermore, chronic effects to fish are anticipated as a result of applications to broccoli,
cauliflower, cabbage, and lettuce. Overlap of areas that potentially contain ODM residues and
CRLF habitat are demonstrated. Therefore, indirect effects are anticipated for the terrestrial-
phase CRLF due to impacts on fish species that are part of the CRLF diet. As a result of these
effects, it is concluded that both direct and indirect adverse effects to the terrestrial-phase
CRLF and its critical habitat are anticipated for all assessed uses.
Based on this analysis, it is concluded that the labeled uses of ODM in California "may affect,
and are likely to adversely effect" the California Red-Legged Frog, where the Action area
overlaps its habitat, due to terrestrial and aquatic effects.
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Table 5-11. Effects Determination Summary for ODM Use and the California Red-Legged
Frog.
Assessment
IjkI point
1. fleet s
delei'mi nation
liiisis lor Deteiminiition
Aquatic Phase
(Eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects and Critical Habitat Effects
1. Survival, growth, and
reproduction of CRLF
May Affect,
Likely to
Adversely Affect
Chronic RQs exceed LOC for surrogate species (rainbow trout)
for 3 cole crops (broccoli, cauliflower, brussel sprouts)
May Affect,
Not Likely to
Adversely Affect
No chronic exceedance for aquatic vertebrates for lettuce. No
chronic exceedance for aquatic vertebrates for lettuce, since
aquatic EEC is essentially equal to the no effect level
No Effect
Exposure not expected from all non-food uses applied via tree
injection due to lack of exposure. Acute and chronic RQs do not
exceed LOCs for food uses other than cole crops.
Indirect Effects
2. Reduction or
modification of aquatic
prey base
May Affect,
Likely to
Adversely Affect
Chronic RQs exceed LOC for fish (rainbow trout) for 3 cole
crops, resulting in impacts to fish and amphibian prey base
May Affect,
Not Likely to
Adversely Affect
Acute LOC is exceeded for aquatic invertebrates for 3 cole crops,
however effect is considered insignificant based on low
likelihood of individual effect. No chronic exceedance for
aquatic vertebrates for lettuce, since aquatic EEC is essentially
equal to the no effect level
No Effect
Exposure to aquatic organisms not expected from all non-food
uses applied via tree injection. Acute and chronic RQs do not
exceed LOCs for invertebrates with food uses other than cole
crops.
3. Reduction or
modification of aquatic
plant community
No Effect
No LOC exceedences for any plant species
4. Degradation of
riparian vegetation
No Effect
No LOC exceedences for any plant species.
Terrestrial Phase
(Juveniles and Adults)
Direct Effects
5. Survival, growth, and
reproduction of CRLF
May Affect,
Likely to
Adversely Affect
Acute and Chronic LOC exceedences for birds, the surrogate
species for direct effects to frogs, at lowest use rate. Probability
of effect approaches 100% at calculated RQs.
No Effect
Exposure to terrestrial organisms not expected from all non-food
uses applied via tree injection.
Indirect Effects and Critical Habitat Effects
6. Reduction or
modification of
terrestrial prey base
May Affect, Likely
to Adversely Affect
Acute and Chronic LOC exceedences for multiple components of
CRLF prey base (mammals, birds, and terrestrial invertebrates) at
lowest use rate. LAA to terrestrial phase CRLF and its critical
habitat based on acute RQs exceeding 0.5 and chronic RQs over
LOC for mammals, insects, birds. Adverse terrestrial critical
habitat modification is expected.
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Assessment
1 julpoinl
1. fleets
dclcrmi nation
liasis lor Determination
No Effect
Exposure to terrestrial organisms not expected from all non-food
uses applied via tree injection.
7. Degradation of
riparian vegetation
No Effect
No plant LOC exceedences.
When evaluating the significance of this risk assessment's direct/indirect and adverse habitat
modification effects determinations, it is important to note that pesticide exposures and predicted
risks to the species and its resources (i.e., food and habitat) are not expected to be uniform across
the action area. In fact, given the assumptions of drift and downstream transport (i.e., attenuation
with distance), pesticide exposure and associated risks to the species and its resources are
expected to decrease with increasing distance away from the treated field or site of application.
Evaluation of the implication of this non-uniform distribution of risk to the species would require
information and assessment techniques that are not currently available. Examples of such
information and methodology required for this type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages within
specific recovery units and/or designated critical habitat within the action area.
This information would allow for quantitative extrapolation of the present risk
assessment's predictions of individual effects to the proportion of the population
extant within geographical areas where those effects are predicted. Furthermore,
such population information would allow for a more comprehensive evaluation of
the significance of potential resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic- and
terrestrial-phase frogs. While existing information provides a preliminary picture
of the types of food sources utilized by the frog, it does not establish minimal
requirements to sustain healthy individuals at varying life stages. Such
information could be used to establish biologically relevant thresholds of effects
on the prey base, and ultimately establish geographical limits to those effects.
This information could be used together with the density data discussed above to
characterize the likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the pesticide.
Currently, methodologies are limited to predicting exposures and likely levels of
direct mortality, growth or reproductive impairment immediately following
exposure to the pesticide. The degree to which repeated exposure events and the
inherent demographic characteristics of the prey population play into the extent to
which prey resources may recover is not predictable. An enhanced understanding
of long-term prey responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and together
with the information described above, a more complete prediction of effects to
individual frogs and potential modification to critical habitat.
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5.5 Risk Hypotheses Revisited
Table 5-11 below revisits the risk hypotheses presented in section 2.9.1. The risk hypotheses
were accepted or rejected in accordance with the "No Effect," "May Affect," and "Likely to
Adversely Affect," or "Not Likely to Adversely Affect" findings in this assessment.
Table 5-12 Risk Hypotheses Revisited
Risk Hypothesis
Conclusions
Labeled uses of ODM within the action
area may directly affect the CRLF by
causing mortality or by adversely affecting
growth or fecundity.
Accepted for aquatic phase. "Likely to
Adversely Affect" finding.
Accepted for terrestrial phase. "Likely to
Adversely Affect" finding.
Labeled uses of ODM within the action
area may indirectly affect the CRLF by
reducing or changing the composition of
food supply.
Rejected for aquatic phase. "Not Likely to
Adversely Affect" finding.
Accepted for terrestrial phase. "Likely to
Adversely Affect" finding.
Labeled uses of ODM within the action
area may indirectly affect the CRLF and/or
modify designated critical habitat by
reducing or changing the composition of
the terrestrial plant community (i.e.,
riparian habitat) required to maintain
acceptable water quality and habitat in the
ponds and streams comprising the species'
current range and designated critical
habitat.
Rejected. "No Effect" finding for
terrestrial plants.
Labeled uses of ODM within the action
area may modify the designated critical
habitat of the CRLF by reducing or
changing breeding and non-breeding
aquatic habitat.
Rejected. "No Effect" finding for aquatic
plants.
Labeled uses of ODM within the action
area may modify the designated critical
habitat of the CRLF by reducing the food
supply required for normal growth and
viability of juvenile and adult CRLFs.
Rejected for aquatic phase. "Not Likely to
Adversely Affect" for indirect effects via
invertebrates.
Accepted for terrestrial phase. "Likely to
Adversely Affect" finding for indirect
effects via terrestrial prey losses.
Labeled uses of ODM within the action
area may modify the designated critical
habitat of the CRLF by reducing or
changing upland habitat within 200 ft of
the edge of the riparian vegetation
necessary for shelter, foraging, and
Rejected for terrestrial phase. "Not Likely
to Adversely Affect" finding for indirect
effect via effects on plants.
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predator avoidance.
Labeled uses of ODM within the action
area may modify the designated critical
habitat of the CRLF by reducing or
changing dispersal habitat within
designated units and between occupied
locations within 0.7 mi of each other that
allow for movement between sites
including both natural and altered sites,
which do not contain barriers to dispersal
Rejected for terrestrial phase. "Not Likely
to Adversely Affect" finding for indirect
effect via effects on plants.
Labeled uses of ODM within the action
area may modify the designated critical
habitat of the CRLF by altering chemical
characteristics necessary for normal growth
and viability of juvenile and adult CRLFs.
Accepted. Presence of ODM in terrestrial
habitat is believed to have direct and
indirect effects on CRLF.
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6. Uncertainties
6.1. 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 dependent on
insecticide resistance, timing of applications, cultural practices, and market forces.
6.2. Usage Uncertainties
County-level usage data were obtained from California's Department of Pesticide Regulation
Pesticide Use Reporting (CDPR PUR) database. Four years of data (2002 - 2005) were included
in this analysis because statistical methodology for identifying outliers, in terms of area treated
and pounds applied, was provided by CDPR for these years only. No methodology for removing
outliers was provided by CDPR for 2001 and earlier pesticide data; therefore, this information
was not included in the analysis because it may misrepresent actual usage patterns. CDPR PUR
documentation indicates that errors in the data may include the following: a misplaced decimal;
incorrect measures, area treated, or units; and reports of diluted pesticide concentrations. In
addition, it is possible that the data may contain reports for pesticide uses that have been
cancelled. The CPDR PUR data does not include home owner applied pesticides; therefore,
residential uses are not likely to be reported. As with all pesticide use data, there may be
instances of misuse and misreporting. The Agency made use of the most current, verifiable
information; in cases where there were discrepancies, the most conservative information was
used.
6.3. Exposure Assessment Uncertainties
Due to lack of appropriate PRZM scenarios for California, not all labeled uses were modeled for
aquatic exposure. However, it is likely that the cabbage use (3 applications of 0.75 lbs ai/acre
with a 7-day application interval) provides the highest aquatic exposure estimate, including those
not modeled, all of which have lower maximum one-time application rates, fewer applications,
and/or shorter application intervals.
All exposure estimates were done with maximum application rates, minimum intervals, and
maximum number of applications, to define the Action Area for the Federal action. Actual
exposures will depend on actual use rates, which may be lower. However, due to the length of
the growing season in California, some crops may be grown multiple times in one year. The
approach of this risk assessment was to only model exposure based on per crop-cycle exposures,
but multiple crop cycles may result in exposure that is greater than what has been estimated.
This could cause LOCs to be exceeded for more uses; however, this would not materially change
the risk conclusion or the action area.
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Chronic RQs for fish exceed the LOC, which is unexpected given that ODM is not persistent.
One explanation could be related to the aquatic exposure assessment and its limits related to lack
of data. Aquatic exposure modeling inputs were based on the available guideline data. Some
inputs (e.g., soil metabolism half-life = 3.2 days) were based on a single value, which by EFED
policy is multiplied by 3 to account for uncertainty, and because there was no aquatic
metabolism half-life study, that value was multiplied by 2. Because there are no additional
studies to estimate variability in degradation rates, this value may or may not overestimate
persistence (and, thus, chronic concentrations). However, it is likely that this approach results in
a conservative estimate.
Spray drift estimates were set at 1% for ground application and 5% for aerial application, per
EFED policy. Actual spray drift from aerial application may be higher.
The decay half-life of ODM on foliage and other food items for the T-REX and T-HERPS
analysis was set at the default value of 35 days. No other values were available for use in this
assessment, and this value is expected to be lower. However, since acute and chronic RQs for
terrestrial animals were very high, reducing this value is not expected to affect the risk
conclusions. For example, the chronic RQ for mammals under the cabbage scenario is 2765 if a
foliar half-life of 5 days is used. This value would result in an estimate of 9,600 feet (1.8 miles)
for the terrestrial action area buffer distance.
6.3.1. PRZM Modeling Inputs and Predicted Aquatic Concentrations
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
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regarding the hydrology of these aquatic habitats to develop a specific alternate scenario for the
CRLF. As previously discussed in Section 2.X and Attachment 1, CRLFs prefer habitat with
perennial (present year-round) or near-perennial water and do not frequently inhabit vernal
(temporary) pools because conditions in these habitats are generally not suitable (Hayes and
Jennings 1988). Therefore, the EXAMS pond is assumed to be representative of exposure to
aquatic-phase CRLFs. In addition, the Services agree that the existing EXAMS pond represents
the best currently available approach for estimating aquatic exposure to pesticides
(USFWS/NMFS 2004).
6.3.2. Aquatic Exposure Estimates
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations that are
expected to be exceeded once within a ten-year period. The Pesticide Root Zone Model is a
process or "simulation" model that calculates what happens to a pesticide in a farmer's field on a
day-to-day basis. It considers factors such as rainfall and plant transpiration of water, as well as
how and when the pesticide is applied. It has two major components: hydrology and chemical
transport. Water movement is simulated by the use of generalized soil parameters, including
field capacity, wilting point, and saturation water content. The chemical transport component
can simulate pesticide application on the soil or on the plant foliage. Dissolved, adsorbed, and
vapor-phase concentrations in the soil are estimated by simultaneously considering the processes
of pesticide uptake by plants, surface runoff, erosion, decay, volatilization, foliar wash-off,
advection, dispersion, and retardation.
Uncertainties associated with each of these individual components add to the overall uncertainty
of the modeled concentrations. Additionally, model inputs from the environmental fate
degradation studies are chosen to represent the upper confidence bound on the mean values that
are not expected to be exceeded in the environment approximately 90 percent of the time.
Mobility input values are chosen to be representative of conditions in the environment. The
natural variation in soils adds to the uncertainty of modeled values. Factors such as application
date, crop emergence date, and canopy cover can also affect estimated concentrations, adding to
the uncertainty of modeled values. Factors within the ambient environment such as soil
temperatures, sunlight intensity, antecedent soil moisture, and surface water temperatures can
cause actual aquatic concentrations to differ for the modeled values.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a vegetative
setback on runoff and loadings. The effectiveness of vegetative setbacks is highly dependent on
the condition of the vegetative strip. For example, a well-established, healthy vegetative setback
can be a very effective means of reducing runoff and erosion from agricultural fields.
Alternatively, a setback of poor vegetative quality or a setback that is channelized can be
ineffective at reducing loadings. Until such time as a quantitative method to estimate the effect
of vegetative setbacks on various conditions on pesticide loadings becomes available, the aquatic
exposure predictions are likely to overestimate exposure where healthy vegetative setbacks exist
and underestimate exposure where poorly developed, channelized, or bare setbacks exist.
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6.3.3. Residue Levels Selection
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.
6.3.4. Dietary Intake
It was assumed that ingestion of food items in the field occurs at rates commensurate with those
in the laboratory. Although the screening assessment process adjusts dry-weight estimates of
food intake to reflect the increased mass in fresh-weight wildlife food intake estimates, it does
not allow for gross energy differences. Direct comparison of a laboratory dietary concentration-
based effects threshold to a fresh-weight pesticide residue estimate would result in an
underestimation of field exposure by food consumption by a factor of 1.25 - 2.5 for most food
items.
Differences in assimilative efficiency between laboratory and wild diets suggest that current
screening assessment methods do not account for a potentially important aspect of food
requirements. Depending upon species and dietary matrix, bird assimilation of wild diet energy
ranges from 23 - 80%, and mammal's assimilation ranges from 41 - 85% (U.S. Environmental
Protection Agency, 1993). If it is assumed that laboratory chow is formulated to maximize
assimilative efficiency (e.g., a value of 85%), a potential for underestimation of exposure may
exist by assuming that consumption of food in the wild is comparable with consumption during
laboratory testing. In the screening process, exposure may be underestimated because metabolic
rates are not related to food consumption.
6.4. Effects Assessment Uncertainties
6.4.1. Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test organism age may have a significant impact on the observed
sensitivity to a toxicant. The acute toxicity data for fish are collected on juvenile fish between
0.1 and 5 grams. Aquatic invertebrate acute testing is performed on recommended immature age
classes (e.g., first instar for daphnids, second instar for amphipods, stoneflies, mayflies, and third
instar for midges).
Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients, such as ODM, 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
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surrogate aquatic animals, and is therefore, considered as protective of the California Red
Legged Frog.
6.4.2. Extrapolation of Long-term Environmental Effects from Short-term
Laboratory Tests
The influence of length of exposure and concurrent environmental stressors to the California Red
Legged Frog (i.e., urban expansion, habitat modification, decreased quantity and quality of water
in CRLF habitat, predators, etc.) will likely affect the species' response to ODM. Additional
environmental stressors may decrease the CRLF's sensitivity to the insecticide, although there is
the possibility of additive/synergistic reactions. Timing, peak concentration, and duration of
exposure are critical in terms of evaluating effects, and these factors will vary both temporally
and spatially within the action area. Overall, the effect of this variability may result in either an
overestimation or underestimation of risk. However, as previously discussed, the Agency's
LOCs are intentionally set very low, and conservative estimates are made in the screening level
risk assessment to account for these uncertainties.
6.4.3. Sublethal Effects
For an acute risk assessment, the screening risk assessment relies on the acute mortality endpoint
as well as a suite of sublethal responses to the pesticide, as determined by the testing of species
response to chronic exposure conditions and subsequent chronic risk assessment. Consideration
of additional sublethal data in the assessment is exercised on a case-by-case basis and only after
careful consideration of the nature of the sublethal effect measured and the extent and quality of
available data to support establishing a plausible relationship between the measure of effect
(sublethal endpoint) and the assessment endpoints.
6.4.4. Location of Wildlife Species
For this baseline terrestrial risk assessment, a generic bird or mammal was assumed to occupy
either the treated field or adjacent areas receiving a treatment rate on the field. Actual habitat
requirements of any particular terrestrial species were not considered, and it was assumed that
species occupy, exclusively and permanently, the modeled treatment area. Spray drift model
predictions suggest that this assumption leads to an overestimation of exposure to species that do
not occupy the treated field exclusively and permanently.
6.5. Use of Surrogate Data for Amphibians
Toxicity data for terrestrial phase amphibians was not available for use in this assessment.
Therefore, avian and freshwater fish toxicity data were used as a surrogate for risk estimation for
the terrestrial- and aquatic-phase CRLF, respectively. There is uncertainty regarding the relative
sensitivity of herptiles, birds, and fish to ODM. If birds are substantially more or less sensitive
than the California Red Legged Frog, then risk would be over- or underestimated, respectively.
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6.6. Assumptions Associated with the Acute LOCs
The risk characterization section of this endangered species assessment includes an evaluation of
the potential for individual effects. The individual effects probability associated with the acute
RQ is based on the mean estimate of the slope and an assumption of a probit dose response
relationship for the effects study corresponding to the taxonomic group for which the LOCs are
exceeded.
6.7. Action Area
An example of an important simplifying assumption that may require future refinement is the
assumption of uniform runoff characteristics throughout a landscape. It is well documented that
runoff characteristics are highly non-uniform and anisotropic, and become increasingly so as the
area under consideration becomes larger. The assumption made for estimating the aquatic
Action Area (based on predicted in-stream dilution) was that the entire landscape exhibited
runoff properties identical to those commonly found in agricultural lands in this region.
However, considering the vastly different runoff characteristics of: a) undeveloped (especially
forested) areas, which exhibit the least amount of surface runoff but the greatest amount of
groundwater recharge; b) suburban/residential areas, which are dominated by the relationship
between impermeable surfaces (roads, lots) and grassed/other areas (lawns) plus local drainage
management; c) urban areas, that are dominated by managed storm drainage and impermeable
surfaces; and d) agricultural areas dominated by Hortonian and focused runoff (especially with
row crops), a refined assessment should incorporate these differences for modeled stream flow
generation. As the zone around the immediate (application) target area expands, there will be
greater variability in the landscape; in the context of a risk assessment, the runoff potential that is
assumed for the expanding area will be a crucial variable (since dilution at the outflow point is
determined by the size of the expanding area). Thus, it important to know at least some
approximate estimate of types of land use within that region. Runoff from forested areas ranges
from 45 - 2,700% less than from agricultural areas; in most studies, runoff was 2.5 to 7 times
higher in agricultural areas (e.g., Okisaka et al., 1997; Karvonen et al., 1999; McDonald et al.,
2002; Phuong and van Dam 2002). Differences in runoff potential between urban/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.
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The buffer used to estimate action area based on terrestrial effects was determined to be 11,338
ft, due to chronic effects in mammals that result in indirect effects to the CRLF. This value is
consistent with EFED's current methodology for estimating the action area. However, the actual
distance at which CRLF may be affected is expected to be shorter than this distance, thus the
action area may actually be smaller. For instance, the AgDISP model cannot account for the
effects of topography and vegetation that would interfere with drift. Since the buffer was
determined using the RQ determined from the highest application rate (0.75 lbs ai applied 3
times with 7-day intervals), the methodology also assumes that wind blows in exactly the same
direction over the buffer distance each time applications are made and for the duration that ODM
remains in the air. These assumptions are not entirely realistic, but further information to refine
these aspects of the methodology is not available. Nonetheless, the action area is expected to be
large enough to be protective to the CRLF.
7. References
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Alvarez, J. 2000. Letter to the U.S. Fish and Wildlife Service providing comments on
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Clemens, G. R., R. E. Hartnagel, J. J. Bare, and J. H. Thyssen. 1990. Teratological,
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Harvey & Associates, Alviso, California. 22 pp.
Karvonen, T., Koivusalo, H., Jauhiainen, M., Palko, J. and Weppling, K. 1999. A hydrological
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