Risks of Acephate Use to the Federally
Listed California Red Legged Frog
(Rana aurora draytonii)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
July 19, 2007
l
-------
Primary Authors
Michael Davy, Agronomist
William P. Eckel, Ph.D., Agronomist
Carolyn Hammer, Environmental Scientist
Secondary Review
Donna Randall, Senior Biologist
Nelson Thurman, Senior Science Advisor
Dana Spatz, Acting Branch Chief,
Environmental Risk Assessment Branch 2
2
-------
Table of Contents
1. Executive Summary 6
2. Problem Formulation 10
2.1 Purpose 10
2.2 Scope 12
2.2.1. Degradates 12
2.2.2. Mixtures 13
2.2.3. Other use sites not quantitatively assessed 15
2.3 Previous Assessments 16
2.3.1 Acephate Assessments 16
2.3.2 California Red-legged Frog Assessments 16
2.4 Stressor Source and Distribution 17
2.4.1 Environmental Fate Assessment 17
2.4.2 Environmental Transport Assessment 18
2.4.3 Mechanism of Action 19
2.4.4 Use Characterization 20
2.5 Assessed Species 28
2.5.1 Distribution 28
2.5.2 Reproduction 33
2.5.3 Diet 33
2.5.4 Habitat 34
2.6 Designated Critical Habitat 35
2.6.1. Special Rule Exemption for Routine Ranching Activities 37
2.7 Action Area 38
2.8 Assessment Endpoints and Measures of Ecological Effect 44
2.8.1. Assessment Endpoints for the CRLF 44
2.8.2. Assessment Endpoints for Designated Critical Habitat 46
2.9 Conceptual Model 49
2.9.1 Risk Hypotheses 49
2.9.2 Diagram 50
2.10 Analysis Plan 53
2.10.1 Exposure Analysis 53
2.10.2 Effects Analysis 54
2.10.3 Action Area Analysis 55
3. Exposure Assessment 56
3.1 Label Application Rates and Intervals 56
3.2 Aquatic Exposure Assessment 57
3.2.1. Conceptual Model of Exposure 57
3.2.2 Existing Monitoring Data 57
3.2.3 Modeling Approach 57
3.2.4. Aquatic EEC Results 60
3.3. Terrestrial Exposure Assessment 60
3.3.1 Conceptual Model of Exposure 61
3.3.2. Modeling Approach 61
3.3.3. Model Inputs 62
3
-------
3.3.4 Results 62
4. Effects Assessment 64
4.1 Evaluation of Aquatic and Terrestrial Ecotoxicity Studies 64
4.1.1 Toxicity to Freshwater Aquatic Animals 69
4.1.2 Toxicity to Amphibians - Aquatic Phase 73
4.1.3 Toxicity to Freshwater Invertebrates 74
4.1.4. Toxicity to Birds 75
4.1.5. Toxicity to Mammals 78
4.1.6 Toxicity to Insects 80
4.1.7. Summary of Effects Assessment 81
5. Risk Characterization 86
5.1 Risk Estimation 86
5.1.1 Aquatic Direct and Indirect Effects 86
5.1.2 Terrestrial Phase Direct Effects 89
5.1.3. Individual Effects Calculation for Direct Acute Effect on CRLF 91
5.1.4. Indirect Effects, Terrestrial Phase 93
5.2 Risk Description 94
5.2.1 Direct Effects to the California Red Legged Frog 95
5.2.2. Indirect Effects to the CRLF 100
5.3 Action Area 100
5.3.1. Aquatic Phase 101
5.3.2. Terrestrial Phase 102
5.4 Listed Species Effect Determination for the California Red-Legged Frog 105
5.4.1. "May Affect" Determination 105
5.4.2 "Adverse Effect" Determination 105
5.5 Risk Hypotheses Revisited 108
6. Uncertainties 110
6.1.1 Maximum Use Scenario 110
6.1.2 Usage Uncertainties 110
6.2. Exposure Assessment Uncertainties 110
6.2.1 PRZM Modeling Inputs and Predicted Aquatic Concentrations Ill
6.2.2 Aquatic Exposure Estimates 112
6.3.3 Residue Levels Selection 113
6.3.4 Dietary Intake 113
6.4 Effects Assessment Uncertainties 114
6.4.1 Age Class and Sensitivity of Effects Thresholds 114
6.4.2 Extrapolation of Long-term Environmental Effects from Short-Term
Laboratory Tests 114
6.4.3 Sublethal Effects 114
6.4.4 Location of Wildlife Species 115
6.5. Use of avian data as surrogate for amphibian data 115
6.6. Assumptions Associated with the Acute LOCs 115
6.8. Action Area 115
7. References 117
4
-------
Appendices
Appendix
A
Appendix
B
Appendix
C
Appendix
D
Appendix
D1
Appendix
D2
Appendix
E
Appendix
F
Appendix
F1
Appendix
G
Appendix
H
Appendix
I
Appendix
J
Appendix
K
Appendix
L
Ecological Effects Data
Aquatic Exposure Modeling Runs
Incident Database Information
ECOTOX Database, Accepted
ECOTOX Database, Excluded
ECOTOX Database, Mixures
Toxicity Categories and LOCs
T-REX Model Outputs
T-HERPS Model Outputs
Acephate Label Information
Acephate Mixture Product Names
Fate Properties of Acephate
Usage Data
Geographic Information systems (GIS) maps
Terrestrial Invertebrate Exposure
Attachments
1. Life History of the California Red-Legged Frog
2. Baseline Cumulative Effects
5
-------
1. Executive Summary
Background
Acephate is an organophosphate insecticide currently registered for use on a variety of
field, fruit, and vegetable crops; in food handling establishments; rights-of-ways,
fencerows, sewage disposal areas, drainage systems, and on ornamental plants both in
greenhouses and outdoors (including lawns, turf, and cut flowers). Acephate use in
California entails a variety of application techniques and varies greatly in amounts
applied, number of applications, application intervals, and timing of applications.
Acephate may move through the environment and be transported away from the site of
application by run-off or spray drift. The toxic degradate of acephate, methamidophos, is
also considered in this assessment.
Exposure pathways to the CRLF or its critical habitat were considered non-existent for
indoor uses that remain indoors which includes use in eating establishments, food
processing facilities and other indoor applications. These uses are therefore considered to
have "no effect" on the CRLF or its critical habitat. The following summary addresses
effects to the CRLF and its critical habitat from the remaining labeled uses.
There were insufficient monitoring data to support an aquatic evaluation based on
concentrations found in water samples; specifically there were no targeted monitoring
data on acephate for this region. Therefore, it was necessary to estimate exposure based
on modeled results.
The mode of action for acephate is similar to other organophosphate insecticides in that
the chemical inhibits an enzyme, acetylcholinesterase. This action causes disruption to
the central nervous system.
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. An acute-to-chronic ratio analysis with other organophosphate insecticides
indicated no LOC exceedence for reproductive effects. Indirect effects to the aquatic
phase of the frog, due to effects on critical habitat are not expected, since there were no
LOC exceedences to aquatic plants, nor effects to water quality. Indirect effects to
CRLF, based on food availability are not expected, because the effect on invertebrate
food sources is discountable. Thus it was determined that acephate use is not likely to
adversely affect the aquatic phase CRLF, or its critical habitat.
Terrestrial Phase
Acephate 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
6
-------
effects to CRLF. 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 LOC. 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, an LAA determination was made for indirect effects. An LAA
determination for terrestrial critical habitat was concluded based on adverse modification
of terrestrial food resources.
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 methamidophos use.
Assessment
Endpoint
Effects
determination
Basis for Determination
Aquatic Phase
(Eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects and Critical Habitat Effects
1. Survival, growth,
and reproduction of
CRLF
No Effect
All Acute and Chronic RQ are below the listed LOC for
surrogate species (rainbow trout)
Indirect Effects
2. Reduction or
modification of
aquatic prey base
May Affect,
Not Likely to
Adversely Affect
Acute LOC is exceeded for aquatic invertebrates,
however effect is considered discountable based on
low likelihood of individual effect.
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. No
adverse aquatic critical habitat modification is
expected.
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. Initial
Area of Concern overlaps habitat. Use is widespread
(nearly all counties). Use is documented in all months.
Probability of effect approaches 100% at calculated
RQs.
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). 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.
7
-------
Assessment
Endpoint
Effects
determination
Basis for Determination
7. Degradation of
riparian vegetation
No Effect
No plant LOC exceedences.
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 are is No Effect
via aquatic plants, and the effect on invertebrates is discountable.
Upland and Dispersal Habitat
There may be effects on these habitats through reduction in prey base (invertebrates, and
small mammals, birds, and amphibians).
There may also be a reduction in shelter for the CRLF (small mammal burrows) due to
the effects on mammals.
Action Area
Based on chronic effects to small birds consuming short grass food items, a terrestrial
buffer zone of 2,913 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 effects to prey items (invertebrates) exposed to the
degradate methamidophos. Based on the RQs, terrestrial effects are expected to dominate
the Action Area.
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
8
-------
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 adverse modification to critical
habitat.
9
-------
2. Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By
identifying the important components of the problem, it focuses the assessment on the
most relevant life history stages, habitat components, chemical properties, exposure
routes, and endpoints. The structure of this risk assessment is based on guidance
contained in U.S. EPA's Guidance for Ecological Risk Assessment (U.S. EPA 1998), the
Services' Endangered Species Consultation Handbook (USFWS/NMFS 1998) and is
consistent with procedures and methodology outlined in the Overview Document (U.S.
EPA 2004) and reviewed by the U.S. Fish and Wildlife Service and National Marine
Fisheries Service (USFWS/NMFS 2004)..
2.1 Purpose
The purpose of this endangered species assessment is to evaluate potential direct and
indirect effects on individuals of the federally threatened California red-legged frog
(Rana aurora draytonii) (CRLF) arising from FIFRA regulatory actions regarding use of
acephate on labeled use sites. In addition, this assessment evaluates whether these
actions can be expected to result in the destruction or adverse modification of the species'
critical habitat. Key biological information for the CRLF is included in Section 2.5, and
designated critical habitat information for the species is provided in Section 2.6 of this
assessment. This ecological risk assessment has been prepared as part of the Center for
Biological Diversity (CBD) vs. EPA etal. (Case No. 02-1580-JSW(JL)) settlement
entered in the Federal District Court for the Northern District of California on October
20, 2006.
In this endangered species assessment, direct and indirect effects to the CRLF and
potential adverse 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 acephate 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 acephate may potentially involve numerous areas
throughout the United States and its Territories. However, for the purposes of this
assessment, attention will be focused on relevant sections of the action area including
those geographic areas associated with locations of the CRLF and its designated critical
habitat within the state of California.
As part of the "effects determination," one of the following three conclusions will be
reached regarding the potential for registration of acephate at the use sites described in
10
-------
this document to affect CRLF individuals and/or result in the destruction or adverse
modification of designated CRLF critical habitat:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Critical habitat identifies specific areas that have the physical and biological features,
(known as primary constituent elements or PCEs) essential to the conservation of the
listed species. The PCEs for CRLFs are aquatic and upland areas where suitable breeding
and non-breeding aquatic habitat is located, interspersed with upland foraging and
dispersal habitat (Section 2.6).
If the results of initial screening-level assessment methods show no direct or indirect
effects (no 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 acephate 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 acephate.
If a determination is made that use of acephate 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 geographic proximity of the
CRLF habitat and 175% acephate use sites) and further evaluation of the potential impact
of acephate on the PCEs is also used to determine whether destruction or adverse
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 acephate is expected to directly impact living organisms within the action area
(defined in Section 2.7), critical habitat analysis for acephate 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 the PCEs and appreciably diminish
the value of the habitat. Evaluation of actions related to use of acephate that may alter
11
-------
the PCEs of the CRLFs 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
Acephate (O, S-Dimethyl acetylphosphoramidothioate) is an organophosphate insecticide
currently registered for use on a variety of field, fruit, and vegetable crops; in food
handling establishments; on ornamental plants both in greenhouses and outdoors
(including lawns, turf, and cut flowers); and in and around the home. Acephate was first
registered in 1973 for ornamental uses and in 1974 for food uses (agricultural crops).
Target pests include: Armyworms, aphids, beetles, bollworms, borers, budworms,
cankerworms, crickets, cutworms, fire ants, fleas, grasshoppers, leafhoppers, loopers,
mealybugs, mites, moths, roaches, spiders, thrips, wasps, weevils, and whiteflies.
California's Department of Pesticide Regulation maintains a database of all pesticide
applications throughout the state and provides this information to the public. According
to the Summary of Pesticide Use Reporting Data (2005), the reported pounds of acephate
used have decreased by nearly 60%, from approximately 458,000 lbs in 1995 to 194,000
lbs in 2005. The acreage to which acephate was applied has also decreased during that
time period, from about 490,000 acres in 1995 to 198,000 acres in 2005. Since
California's Department of Pesticide Regulation (CDPR) Pesticide Use Reporting (PUR)
data does not account for residential uses, the actual pounds used could be higher.
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 acephate in accordance with the approved product labels for California is
"the action" being assessed.
Although current registrations of acephate allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of acephate 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.
2.2.1. Degradates
The major degradate of acephate in aerobic soil metabolism studies is methamidophos,
(up to 23%) which is itself a registered insecticide. Methamidophos was also found in
the aqueous photolysis study (maximum formation of 1.6% of the applied amount), the
soil photolysis study (5.3 to 8.4% in both irradiated and control), the anaerobic aquatic
metabolism study (5% at 7 days), and the aerobic aquatic metabolism study (<1.6%).
12
-------
Methamidophos is more toxic to vertebrates and invertebrates than is acephate, so its
effects will be considered in the aquatic risk assessment. Because terrestrial LOCs are
expected to be exceeded based on exposure to the parent acephate alone, methamidophos
exposure will not be considered quantitatively for terrestrial wildlife.
FIFRA methamidophos registered uses are also being assessed for the CRLF. Therefore,
the effects characterization for methamidophos will be found in detail in the
Methamidophos Assessment for CRLF and only summarized within this assessment as
needed.
Since there is information on the maximum formation of methamidophos in soil after
application of acephate (23% at 32 days in a Fresno loam soil, less than 10% in two other
soils), the exposure of aquatic organisms to methamidophos can be quantified in PRZM-
EXAMS modeling by assuming that the starting concentration of methamidophos in the
soil is 23% of the application rate of acephate. The fate and transport properties of
acephate and methamidophos are very similar, thus separate modeling runs are not
necessary.
2.2.2. Mixtures
Product Formulations Containing Multiple Active Ingredients
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).
Formulated Product Data and Aquatic Exposure
The limitation on the quantitative exposure modeling for formulations is based on the
expectation that the varying physical-chemical properties of individual components of
pesticide formulations will result in progressively different formulation constituents in
environmental media over time. As the proportions of formulation components in
environmental media differ from the proportions in the tested formulation, the
assumption that environmental residues are toxicologically equivalent to tested
formulations cannot be supported beyond the time period immediately following
product application. This assumption is especially important in the case of runoff from
treated areas to surface waters. In this case, varying fate and transport properties for
each formulation component will result in a final proportion of the residues of these
components in the receiving surface waters that is significantly different than the
proportion of ingredients that are applied and that were tested in an aquatic organism
13
-------
toxicity study using the formulated product. Therefore available formulated product
data for products directly applied to aquatic environments or that may drift into aquatic
environments were considered, and only for effects resulting from acute exposure to the
formulated product (see Overview Document section V.B.l.b.(2) and Services
Evaluation memorandum).
Formulated Product Data and Terrestrial Exposure
In situations where available toxicity data indicate that a formulated product may be more
toxic to terrestrial wildlife than indicated by active ingredient effects testing, it may be
necessary to consider exposure to the formulation. Exposure modeling in these instances
is limited to dietary exposure to residues for a time period immediately following
pesticide product application.
The limitation on the quantitative exposure modeling for formulations is based on the
expectation that the varying physical-chemical properties of individual components of
pesticide formulations will result in progressively different formulation constituents in
environmental media over time. Because the proportions of formulation components in
environmental media differ from the proportions in the tested formulation, the
assumption that environmental residues are toxicologically equivalent to tested
formulations cannot be supported beyond the time period immediately following
product application. Therefore, available formulated product data for terrestrial
applications were considered only for effects resulting from acute dietary exposure to
the formulated product (see Overview Document section V.B.l.c.(2) and Services
Evaluation memorandum).
Acephate has registered products containing multiple active ingredients. These products,
their product registration numbers, the active ingredient(s) in the product in addition to
acephate, the percentage of each active ingredient in the product, and the available
product formulation data are listed in Table 2.1 below. The ECOTOX search strategy
for public scientific literature identifies studies addressing multiple active ingredients (see
Overview Document and Services Evaluation memorandum). If a multiple active
ingredient study was performed on any of the formulated pesticide products in Table 2.1,
this assessment considers those studies. In addition to public literature, if the registrant
has submitted data on any of the formulated products in Table 2.1, those data as well
have been considered and noted.
The below registered products containing multiple active ingredients are in pressurized
containers used only for residential and greenhouse uses. Exposure pathways from
indoor use to the CRLF are considered unlikely and therefore these uses have "no effect"
on the CRLF. A quantitative risk assessment from mixtures to the CRLF was not done
due to discountable nature of exposure of the mixtures.
14
-------
Table 2.1 Data on Acephate Mixtures with Other Active Ingredients
Formulated
Registrant
Submitted
Public Scientific
Literature
EPA Reg#
Product
Formulation
Studies
Studies*
00023902476
ORTHO SYSTEMIC
ROSE & FLORAL
SPRAY
Acephate (0.25%)
ResmetMn (0.1%)
Triforine (0.1%)
none
See Appendix D2 for
listing of ECOTOX
literature studies.
ORTHENEX
none
INSECT &
DISEASE
Acephate (4%)
Fenbutatinoxide
CONTROL
(0.75%)
00023902594
FORMULA III
Triforine (3.25%)
ISOTOX INSECT
none
KILLER FORMULA
Acephate (8%)
00023902595
IV
Fenbutatinoxide (0.5%)
00049900441
WHITMIRE TC 136
Acephate (1.5%)
Fenpropathrin(l%)
none
As summarized in Appendix H there are no product LD50 values, with associated 95%
Confidence Intervals (CIs) available.
As discussed in U.S. EPA (2000), a quantitative component-based evaluation of mixture
toxicity requires data of appropriate quality for each component of a mixture. In this
mixture evaluation, an LD50 with associated 95% CI is needed for the formulated
product. The same quality of data is also required for each component of the mixture.
Given that the formulated products for acephate do not have LD50 data available, it is not
possible to undertake a quantitative or qualitative analysis for potential interactive effects.
However, because the active ingredients are not expected to have similar mechanisms of
action, metabolites, or toxicokinetic behavior, it is reasonable to conclude that an
assumption of dose-addition would be inappropriate. Consequently, an assessment based
on the toxicity of acephate is the only reasonable approach that employs the available
data to address the potential acute risks of the formulated products in Appendix H.
2.2.3. Other use sites not quantitatively assessed
Structural pest control applications, while a significant contribution to the total pounds of
acephate reportedly applied each year, are not considered as likely exposure pathways to
the CRLF or its critical habitat and are therefore considered to have "no effect" on the
CRLF or its critical habitat. Indoor uses for eating establishments, food processing
facilities and other indoor applications are not considered further in this assessment as the
products are to be used indoors, in small amounts and disposed of according to the label
instructions which will not result in exposure to the CRLF or its critical habitat.
Therefore these indoor uses are also considered to have "no effect" on the CRLF or its
critical habitat.
15
-------
2.3 Previous Assessments
2.3.1 Acephate Assessments
The Agency published an Interim Reregi strati on Eligibility Decision for Acephate in
September 2001 which identified numerous human health and ecological risks associated
with the labeled uses of acephate. Upon completion of the assessment, the Agency
decided on a number of label amendments to address the worker, residential, and
ecological concerns. Acephate and its degradate methamidophos are highly toxic to
honey bees and beneficial predatory insects on an acute contact basis. Acute and chronic
risks to birds and chronic risk to mammals were also of concern. The document is
available on the web, at: http://www.epa.gov/oppsrrdl/REDs/acephate ired.pdf.
Numerous mitigation requirements (label amendments) resulted from the IRED
assessment. However, at this time only those label amendment changes that are reflected
by the current labels were assessed as the product user will follow the label rather than
the IRED.
Some changes include requiring labeling to protect honeybees and to reduce the potential
for spray drift. Also, aerial applications to turf have been deleted as have residential
indoor uses also been deleted.
On March 31, 2004 EPA released an assessment of the potential effects of acephate to 26
listed Environmentally Significant Units (ESUs) of Pacific salmon and steelhead. That
assessment concluded that acephate would have no effect on the species under
consideration. While acephate was noted to have significant toxicity to aquatic
invertebrates, as does this assessment, the minimal usage, the size of the watersheds
under consideration and the volume of the water bodies serving as habitat to these species
taken together, resulted in the determination of no effect to the listed salmon and
steelhead.
2.3.2 California Red-legged Frog Assessments
The Agency is currently developing a number of risk assessments for the CLRF, each
addressing different pesticide active ingredients. A total of 66 chemicals will be
assessed. Metolachlor is among the first group of ten chemicals to be completed. For
information regarding the other chemicals in this group1 please see the relevant
document.
1 Other chemicals assessed in the first group include methamidaphos, methomyl, azinphos-methyl,
acephate, imazpyr, aldicarb, metam sodium, diazinon and chloropicrin
16
-------
2.4
Stressor Source and Distribution
Acephate technical is a colorless to white solid with a melting point of 81-91° C.
Acephate is highly soluble in water (79 g/100 ml), acetone (151 g/100 ml), and ethanol
(>100 g/100 ml), and is soluble in methanol (57.5 g/100 ml), ethyl acetate (35.0 g/100
ml), benzene (16.0 g/100 ml), and hexane (<0.1g/100 ml) at 25° C. Acephate degrades to
another, registered organophosphate insecticide, methamidophos.
Case number: 0042
CAS registry number: 30560-19-1
OPP chemical code: 103301
Empirical formula: C4H10NO3PS
Molecular weight: 183.16 g/mol
Vapor Pressure: 1.7 x lO-emm Hg at 24°C
Trade and other names: Orthene®
Technical registrants: Valent U.S.A. Corporation; Micro-Flo Company LLC; United
Phosphorous Ltd.; Drexel Chemical Corporation
2.4.1 Environmental Fate Assessment
Aerobic soil metabolism is the main degradation process for acephate. Observed half-
lives are less than two days under the nominal or expected use conditions, producing the
intermediate degradate methamidophos, which is also an insecticidally active compound.
Methamidophos is itself rapidly metabolized by soil microorganisms to carbon dioxide
and microbial biomass (half-lives of < 10 days). Acephate is stable against hydrolysis
except at high pH (half-life at pH 9 of 18 days) and does not photodegrade. Acephate is
not persistent in anaerobic clay sediment: creek water systems in the laboratory, with a
half-life of 6.6 days. The major degradates under anaerobic conditions were carbon
dioxide and methane, comprising > 60% of the applied acephate after 20 days of
anaerobic incubation. No other anaerobic degradates were present at > 10% during the
incubation. There are no acceptable data for the aerobic aquatic metabolism of acephate;
supplemental information indicates that acephate degrades more rapidly in aquatic
systems when sediment is present. Appendix I describes the fate properties of acephate
in greater detail.
Acephate is very soluble (80.1-83.5g/100 mL) and very mobile (Koc = 2.7) in the
laboratory. Only one Koc value is available, because acephate was adsorbed in only one of
the five soils (a clay loam) used in the batch equilibrium studies. When tested in the same
soils, methamidophos was determined to be more mobile than acephate; again, only one
Koc value is available (Koc= 0.9 in the clay loam soil). Because acephate is not persistent
under aerobic conditions, very little acephate is expected to leach to groundwater. If any
acephate does reach ground water, it would not be expected to persist, due to its short
anaerobic half-life. Volatilization from soil or water is not expected to be a route of
dissipation for either acephate or methamidophos.
17
-------
Field studies conducted in Mississippi (tobacco on silt loam soil), California (bell peppers
on silt loam soil), Florida (cauliflower on sand soil) and Iowa (soybeans on loam soil)
produced dissipation half-lives of 2 days or less with no detections of parent or the
degradate methamidophos below a depth of 50 cm. Laboratory studies showed that
bioaccumulation of acephate in bluegill sunfish was insignificant. A maximum
bioaccumulation factor of lOx occurred after 14 days' exposure to acephate at 0.007 and
0.7 ppm.
2.4.2 Environmental Transport Assessment
Batch equilibrium studies
Batch equilibrium studies using acephate and methamidophos were conducted using four
soils ranging in texture from sand to clay loam. In three of the soils, acephate and
methamidophos were not adsorbed in sufficient quantities to permit the calculation of
Freundlich adsorption coefficients (Freundlich Kads). For the clay loam soil, the reported
adsorption values for parent acephate and its degradate, methamidophos, are listed in the
following table:
Soil
pH
CEC
(meq/lOOg)
%clay
%organic
matter
Acephate
Methamidophos
Clay
loam
5.8
20.2
32
3.3
K
1/n
r2
K
1/n
r2
0.090
1.06
0.96
0.029
0.64
0.93
Calculated Koc for acephate and methamidophos in this clay loam soil were 2.7 and 0.9,
respectively. Because of the minimal adsorption of the chemicals in the adsorption phase
of the study, it was not possible to determine desorption values in the soils. Based on the
values listed above, it appears that acephate and methamidophos are very mobile in soils.
Volatility
Based on the vapor pressure of acephate (pure active: 1.7 x 10"6mm Hg/Torr [MRID
40390601]) and its calculated Henry's constant (5.1 x 10"13 atm mole / m3), it is not
expected that acephate will volatilize from either soil or water in significant quantities.
Therefore it is not expected that volatilization will be a significant route of dissipation for
acephate.
Long Range Transport
Potential transport mechanisms generally 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
18
-------
(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 acephate 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.
2.4.3 Mechanism of Action
Some of the information for the mode of action below comes from Davies et. al., 1981.
Organophosphate insecticides (such as acephate) act upon target pests through a
neurotoxic action, which affects the central nervous system. Specifically, the mechanism
of action is known to be acetylcholinesterase inhibition. The transmission of nerve
impulses across synapses and the junctions between nerve and an organ (gland, muscle,
nerve) is accomplished by the release of a chemical agent, acetylcholine. Acetylcholine
must be rapidly destroyed or inactivated at or near the site of its release to continue
transmission of new impulses. The destruction of acetylcholine at such sites is
accomplished by an enzyme, acetylcholinesterase. Acetylcholinesterase is located at the
neurosynaptic junctions and breaks the acetylcholine into acetyl and choline fragments.
Acetylcholinesterase functions to increase the precision of nerve firing, enabling some
nerve cells to fire as rapidly as 1,000 times per second without overlap of the of the
neural impulses. Acetylcholinesterase inhibitors prevent the acetylcholinesterase from
removing the acetylcholine and thereby causing disruption to the central nervous system.
At a high enough concentration of the inhibitors, the muscles may not contract the
diaphragm and breathing ceases and death results.
Depending on the organophosphate involved, the dose received, and the duration of
exposure; the period for regeneration of the acetylcholinesterase to occur varies among
organisms.
19
-------
2.4.4 Use Characterization
2.4.4.1 Use Profile
Acephate is a an organophosphate insecticide currently registered for use on a variety of
field, fruit, and vegetable crops; in food handling establishments; on ornamental plants
both in greenhouses and outdoors (including lawns, turf, and cut flowers); and in and
around the home. The use profile is based on the current, federally registered uses
(Section 3 and 24c for California). There are well over 100 registered labels for
acephate, with products ranging from 0.25% to 97.4% ai. Section 3 (nation-wide) and
section 24(c) (California) registered uses for acephate are presented in Table 2.2. with the
label maximum one time application, maximum annual application rate, and the
minimum time between treatments. A complete list of product names and registration
numbers is in Appendix G.
Table 2.2. Labeled uses assessed in this document.
Crop/Site (a)
Registration
Number
Equipment
Max
Application
Rate Qty
Max App
Rate
Unit/Area
Seasonal
Max
Dose/Crop
Cycle
Minimum
Interval
Between
Retreatment
(days)
Bean and fruiting
vegetable (1)
019713-00400
Aircraft; Ground
1.00
Lb ai /A
2.07 lb
AN; 3
Bermuda grass
CA79013800
Aircraft; Ground
1.00
Lb ai /A
NS
NS
Celery
019713-00400
Aircraft; Ground
1.00
Lb ai /A
2.07 lb
NS; 3
Christmas Tree
Plantations
053883-00133
Aircraft; Ground
0.50
Lb ai /A
NS
NS; 28
066330-00354
Ground
0.50
lb/100 gal/A
NS
NS
066330-00354
Aircraft
0.50
lb/2 gal
NS
NS
Citrus (non-bearing)
034704-00903
Ground
0.76
Lb ai/ A
NS
AN; 7
019713-00400
Sprinkler can
0.0012
gal mound
NS
7
059639-00026
Drencher
0.01
lb ai/mound
(4 ft diameter)
NS
NS
Cole Crops (2)
019713-00400
Aircraft; Ground
1.00
Lb ai /A
2.07 lb
AN; 7
Cotton (Unspecified)
019713-00400
Aircraft; Ground
1.00
Lb ai /A
61b
AN; 3
019713-00400
Soil in-furrow
treatment
1.13
Lb ai /A
NS
an; 3
019713-00408
Seed treatment
Hopper box;
Slurry-type seed
treater; Sprayer
0.39(0.117)
lb cwt (Lb
ai/acre)
NS
NS
Cranberry
059639-00026
Aircraft; Ground
1.00
Lb ai /A
0.9975 lb
NS; 7
Drainage Systems
019713-00400
Aircraft; Ground
0.25
Lb ai /A
NS
NS
070506-00001
Drencher
0.01
lb mound
NS
NS
070506-00002
Spoon
1.50
Tsp mound
NS
NS
Outdoor Facilities/
Premises (3 and 12)
059639-00026
Aircraft; Ground
0.25
Lb ai /A
NS
AN
019713-00495
Sprinkler can
0.01
lb mound
NS
NS
019713-00495
Spoon
1.50
Tsp mound
NS
NS
070506-00001
Paintbrush
0.08
lb nest
NS
NS
070506-00001
Sprayer
0.08
lb nest
NS
NS
20
-------
Seasonal
Max
Dose/Crop
Cycle
Minimum
Crop/Site (a)
Registration
Number
Equipment
Max
Application
Rate Qty
Max App
Rate
Unit/Area
Interval
Between
Retreatment
(days)
081964-00002
Ground
0.25
lb/3.3 gal
NS
NS
Aircraft;
Ground;
Fencerows/
Hydraulic
Hedgerows (4)
066330-00356
Sprayer
0.25
Lb ai /A
NS
NS
053883-00133
Spoon
0.002
gal mound
NS
NS
053883-00133
Sprinkler
0.01
lb mound
NS
NS
053883-00133
Spoon
1.50
Tsp mound
NS
NS
Golf Course Turf
059639-00087
Ground
0.11
lb IK sq.ft
NS
NS; 7
066330-00356
Granule
073614-0001
applicator
5.0
Lb ai /A
NS
7
Lettuce
019713-00400
Aircraft; Ground
1.00
Lb ai /A
2.01b
AN; 7
Mint/Peppermint/Spe
armint
019713-00400
Aircraft; Ground
1.00
Lb ai /A
2.01b
AN; 7
Onion (24 C)
CA87007100
Ground
1.00
Lb ai /A
NS
AN
gal in. trunk
Ornamentals (5)
070506-00001
Paintbrush
0.01
diam
NS
NS
059639-00087
Spoon
0.00015
gal pot
NS
NS
000239-02453
Shaker can
0.00011
gal sq.ft
NS
AN
070506-00008
Paintbrush
0.0038
gal tree
NS
NS
000499-00421
Aerosol can
0.50
lb IK sq.ft
NS
NS
066330-00358
Sprayer
1.13
tbsp/1.5 gal
NS
7
oz 1.5K sq.ft
000499-00421
Aerosol can
4.00
(L)
NS
NS
Mist blower;
019713-00544
Hydraulic
sprayer
1.20
lb/100 gal/A
NS
NS
000239-02461
Sprayer
0.01
lb/1 gal
NS
7
000239-02453
Shaker can
0.001
lb sq.ft
NS
30
Mist blower;
081964-00003
Hydraulic
sprayer
1.20
Lb ai /A
NS
NS
Aircraft;
Ground;
059639-00033
Hydraulic
Sprayer
0.45
Lb ai /A
NS
NS
059639-00028
Hydraulic
sprayer
0.75
lb IK sq.ft
NS
AN
Granule
059639-00087
applicator
0.06
lb IK sq.ft
NS
NS
000239-02472
Shaker can
0.00011
gal sq.ft
NS
AN
059639-00087
Spoon
0.00015
gal pot
NS
NS
059639-00033
Aircraft; Ground
1.00
Lb ai /A
NS
3
Peanuts
019713-00400
Aircraft; Ground
1.00
Lb ai /A
3.9975 lb
AN; 7
059639-00033
Hopper box;
Planter/seed box
0.20
lb cwt
3.9975 lb
AN; 7
Sewage Disposal
Areas
019713-00544
Aircraft; Ground
0.13
Lb ai /A
NS
NS
Soybeans
(Unspecified)
059639-00026
Aircraft; Ground
1.00
Lb ai /A
1.51b
7
21
-------
Crop/Site (a)
Registration
Number
Equipment
Max
Application
Rate Qty
Max App
Rate
Unit/Area
Seasonal
Max
Dose/Crop
Cycle
Minimum
Interval
Between
Retreatment
(days)
Stone Fruit (6)
059639-00091
Aircraft; Ground
0.97
Lb ai /A
NS
AN
Pome Fruit (7)
059639-00091
Aircraft; Ground
0.97
Lb ai /A
NS
AN
Tree Nut (8)
059639-00091
Aircraft; Ground
0.97
Lb ai /A
NS
AN
Turf (9)
000239-02632
Granule
applicator
4.95
Lb ai /A
NS
7
000239-02632
Hose-end
sprayer
6.75
tbsp IK sq.ft
NS
AN
000239-02632
Sprayer
0.11
lb IK sq.ft
NS
14
059639-00026
Sprinkler can
0.01
lb mound
NS
14
059639-00026
Sprinkler can
0.15
gal mound
NS
14
059639-00026
Spoon
1.80
Tsp mound
NS
NS
Uncultivated Land
(10)
059639-00026
Aircraft; Ground
0.25
Lb ai /A
NS
NS
059639-00031
Product
container
0.01
lb mound
NS
AN
059639-00031
Ground
1.80
Tsp mound
NS
NS
066330-00356
Spoon
0.00
gal mound
NS
NS
066330-00360
Ground
0.11
lb IK sq.ft
NS
NS
Vine Crop (11)
059639-00091
Aircraft; Ground
0.97
Lb ai /A
NS
AN
Source: LUIS Report, Updated November 2006.
(a) Similar use sites were combined into one category.
(b) AN = as needed; NS = not specified
1) Bean: Bean- Dried Type; Succulent-Lima; Succulent-Snap; Fruiting Vegetables; Pepper
2) Cole: Brussels Sprouts; Cauliflower
3) Outdoor Facilities/Premises: Commercial/Industrial/Industrial Premises/Equipment (Outdoor
Household/Domestic Dwellings Outdoor Premises; Industrial Areas (Outdoor); Meat Processing Plant
Premises (Nonfood Contact); Nonagricultural Outdoor Buildings/Structures; Paths/Patios; Paved Areas
(Private Roads/Sidewalks); Refuse/Solid Waste Sites (Outdoor)
4) Fencerows/Hedgerows: agricultural rights of way/fencerows/hedgerows; nonagricultural rights of
way/fencerows/hedgerows
5) Ornamentals: Crabapple; ornamental and/or shade trees; ornamental ground cover; ornamental herbaceous
plants; ornamental nonflowering plants; ornamental woody shrubs and vines
6) Stone Fruit: Apricot; Cherry; Plum; Prune
7) Tree Fruit: Apple; Pear
8) Tree Nut: Almond; Pistachio; Walnuts (English/Black)
9) Turf: Commercial/industrial lawns; ornamental lawns and turf; ornamental sod farm (turf); recreation area
lawns; residential lawns
10) Uncultivated Land; agricultural fallow/idleland; agricultural uncultivated areas; nonagricultural uncultivated
areas/soils; recreational areas
11) Vine Crop: kiwi fruit; grapes
12) The following uses do not result in exposure of the CRLF or essential habitat because they are solely indoor
uses and associated maximum application rates are not included in this table : Commercial
Storages/Warehouses Premises; Commercial Transportation Facihties-Nonfeed/Nonfood;
Commercial/Industrial/Industrial Premises/Equipment (Indoor);); Eating Establishments; Food Processing
Plant Premises (Nonfood Contact); Food Stores/Markets/Supermarkets Premises;
Food/Grocery/Marketing/Storage/Distribution Facility Premise; Hospitals/Medical Institutions Premises
(Human/Veterinary); Household/Domestic Dwellings; Household/Domestic Dwelling Contents;
Household/Domestic Dwellings Indoor Food Handling Areas; Household/Domestic Dwellings Indoor
Premises; Poultry Processing Plant Premises (Nonfood Contact); Refuse Solid Waste Containers (Garbage
Cans); Refuse/Solid Waste Sites (Indoor);
22
-------
Acephate was first registered in 1973 for ornamental uses, and in 1974 for food uses
(agricultural crops). Use data from 1988 to 1997 indicate that approximately 4 to 5
million pounds of active ingredient (ai) are used domestically each year (USEPA, 2001).
Based on California Department of Pesticide Regulation (Cal DPR) Pesticide Use
Reporting (PUR) annual reports, annual use of acephate in California ranged from
approximately 194,000 to 259,000 pounds a.i. from 2001 through 2005 (Table 2.3)2.
Table 2.3. Summary of annual acephate use in California from 2001 through 2005.
Number of
Year
Pounds a.i. Applied
Applications
2001
240,109
21,098
2002
258,955
20,177
2003
223,749
18,676
2004
201,816
18,624
2005
194,365
16,009
Source: CAL DPR PUR Annual Reports for 2001-2005, viewed April 2007
Food. Acephate is registered for use on beans (green and lima), Brussels sprouts,
cauliflower, celery, cottonseed, cranberries, lettuce, peanuts, peppermint, peppers (bell
and non-bell), citrus, fruit trees, nut trees, soybeans, and spearmint.
Other Agriculture, Non-food: Acephate is also registered for use on cotton, and as seed
treatment on cotton and peanuts (seed for planting), on non-bearing fruit trees, such as
ornamental citrus, and on tobacco.
Residential: Acephate is registered for use outdoors around residential buildings, homes,
and apartments, for the control of roaches, wasps, fire ants, and crickets, among other
pests. It is also registered for outdoor use on home lawns, trees, shrubs and ornamentals.
Public Health. Acephate is registered for use in and around industrial, institutional
and commercial buildings, including restaurants, food handling establishments,
warehouses, stores, hotels, manufacturing plants, and ships for the control of
roaches and fire ants.
Other Nonfood. Acephate is registered for use on sod, golf course turf, field borders,
fence rows, roadsides, ditch banks, borrow pits, wasteland, and greenhouse and
horticultural nursery floral and foliage plants.
Target pests include: Army worms, aphids, beetles, bollworms, borers, budworms,
cankerworms, crickets, cutworms, fire ants, fleas, grasshoppers, leafhoppers,
loopers, mealybugs, mites, moths, roaches, spiders, thrips, wasps, weevils,
whiteflies, and others (EPA IRED, 2001).
Formulation types: Wettable Powder, Soluble Powder, Soluble Extruded Pellets,
Granular, and Liquid. All forms, except for granular, are mixed with water prior to
application and are applied in a liquid form.
2 http://www.cdpr.ca.gov/docs/pur/purmain.htm (April 2007)
23
-------
Analysis of labeled use information is the critical first step in evaluating the federal
action. The current label for acephate 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.
Equipment for agriculture, greenhouse, nursery, and turf uses: Granular acephate can be
applied by belly grinder, hand, tractor-drawn spreader, push-type spreader, and shaker
can. Liquid acephate (formulated from soluble powders or soluble extruded pellets) may
be applied by aircraft, airblast sprayer, backpack sprayer, chemigation, hydraulic
sprayers, groundboom spray, handgun, high pressure sprayer, hopper box (seed
treatment), low-pressure handwand, slurry (seed treatment), sprinkler can, transplanting
in water (tobacco), or by an aerosol generator (greenhouses).
Equipment for residential and public health uses: Residential applications can be made
by aerosol can, backpack sprayer, hose-end sprayer, and low-pressure handwand.
Residential granular applications can be made by shaker can or by hand. Residential
soluble powder applications may be made by sprinkler can or compressed air sprayers.
Method. Acephate may be applied on seed before planting, in-furrow at planting, or as a
foliar spray, it may be applied to float beds, plant beds, or as a transplant (tobacco)
treatment. For use against fire ants it may be applied directly on their soil mound (drench
and dry methods). Acephate is also used indoors as spot, crack and crevice, and bait
treatments.
Rates: Rates vary according to method of application and pest. The highest registered
maximum one time application rate is 5 lbs ai/A on commercial/residential turf. The
highest seasonal application rate is 6 lb ai/A/year (1 lb ai/A at 6 applications per season)
for cotton.
2.4.4.2. Use and Useage in California, 2000-2005
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-NASS3, Doane (www.doane.com; the full dataset is not provided
due to its proprietary nature), and the California's Department of Pesticide Regulation
Pesticide Use Reporting (CDPR PUR) database4 . CDPR PUR is considered a more
comprehensive source of usage data than USDA-NASS or EPA proprietary databases,
and thus the usage data reported for acephate by county in this California-specific
assessment were generated using CDPR PUR data. Usage data are averaged together
3 United States Depart of Agriculture (USDA), National Agricultural Statistics Service (NASS) Chemical
Use Reports provide summary pesticide usage statistics for select agricultural use sites by chemical, crop
and state. See http://www.usda.gov/nass/pubs/estindxl,htm#agchem.
4 The California Department of Pesticide Regulation's Pesticide Use Reporting database provides a census
of pesticide applications in the state. See http://www.cdpr.ca.gov/docs/pur/purmain.htm.
24
-------
over the years 2002 to 2005 to calculate average annual usage statistics by county and
crop for acephate, including pounds of active ingredient applied (Table 2.4). California
State law requires that every pesticide application be reported to the state and made
available to the public.
Table 2.4. Average Annual Pounds of Acephate Applied in California by Counties and
Uses. Only the major uses are included. (2002-2005). Information on the remaining uses
County
Average Annual
Pounds Applied
Lettuce
Cotton
Bean
Celery
Non Food
Outdoor
Structural Pest
Control
Pepper
Landscape
Maintenance
Greenhouse
Cauliflower
Mint
Citrus
Average
Annual
Pounds
Applied
211,133
83,897
50,215
16,409
15,438
14,329
10,979
5,866
5,038
3,961
1,662
1,370
906
Monterey
61,958
50,144
NR
1,280
7,146
310
45
319
707
770
1,188
NR
NR
Fresno
34,299
14,427
16,893
1,301
NR
75
169
1,302
2
63
4
NR
28
Kern
14,189
129
10,949
996
NR
72
1,031
648
6
1
NR
NR
233
Imperial
14,021
5,450
8,287
19
39
50
37
27
NR
NR
40
NR
6
Santa
Barbara
11,014
6,087
NR
32
1,691
2,414
98
105
33
172
358
NR
NR
Ventura
10,894
99
NR
1,153
4,991
1,285
2,738
103
56
204
NR
NR
NR
Kings
6,616
226
6,309
13
NR
NR
29
NR
NR
NR
NR
NR
NR
Riverside
6,190
76
4,156
36
93
426
337
81
794
58
7
NR
40
Stanislaus
4,839
NR
NR
1,982
NR
2,633
60
36
53
51
NR
NR
NR
San Benito
4,586
1,984
NR
NR
632
62
6
1,858
4
11
5
NR
NR
San Diego
4,444
NR
NR
49
NR
1,858
697
44
749
918
NR
2
NR
San Luis
Obispo
4,314
3,149
NR
5
714
166
7
60
87
101
25
NR
NR
Merced
3,692
NR
2,220
1,405
NR
2
36
NR
0
9
19
NR
NR
Santa
Clara
3,247
382
NR
7
61
109
430
1,249
713
273
NR
NR
NR
San
Joaquin
3,156
NR
139
2,011
NR
890
19
NR
6
77
NR
NR
NR
Sutter
2,798
NR
11
2,705
NR
69
8
NR
0
NR
NR
NR
NR
Los
Angeles
2,774
NR
NR
NR
NR
769
1,369
NR
516
86
NR
NR
NR
Santa
Cruz
2,488
1,731
NR
4
72
164
30
NR
39
442
3
NR
NR
Orange
2,175
NR
NR
14
NR
1,322
400
16
271
151
NR
NR
NR
Source: CDPR PUR 2007
The uses considered in this risk assessment represent all currently registered uses
according to a review of all current labels. No other uses are relevant to this assessment.
Any reported use, such as may be seen in the CDPR PUR database, represent either
historic uses that have been canceled, mis-reported uses, or mis-use. Historical uses, mis-
reported uses, and misuse are not considered part of the federal action and, therefore, are
not considered in this assessment.
25
-------
County
Figure 2. A. Percent Contribution of Each County to the Total Pounds Acephate Applied
Annually in California source: cdpr pur 2007
Figure 2. A shows useage for the top eight use sites, limited to the top nineteen counties,
in terms of pounds applied in 2004. Monterey county is a major use area for acephate.
Note that the following counties not included in the figure each contributed less than 1%
of the total annual acephate use in California, between 2003-2005: Tulare, San Francisco,
Colusa, Madera, Glenn, Solano, San Mateo, Yolo, Contra Costa, Siskiyou, San
Bernardino, Sacramento, Sonoma, Butte, Alameda, Modoc, Shasta, Lassen, Marin,
Tehama, Placer, Humboldt, Napa, Plumas, Del Norte, Sierra, Tuolumne, Nevada,
Mendocino, El Dorado, Mono, Lake, Yuba, Mariposa, Inyo, Amador, Calaveras, Trinity.
Figure 2B shows the data for 2003-2005 broken down by month of application, for the
top eight uses.
26
-------
40,000 n
35,000
30,000
25,000
c.
% 20,000
Vl
*o
§ 15,000
o
Cu
10,000
5,000
0 4
~ 2003
~ 2004
~ 2005
c<3
S—i
CD
Ph
¦c
<
3
GO
3
CD
03
rm
> o
o w
£ Q
Month
Figure 2.B. Pounds of A.I. applied per month to the following sites in 2003, 2004, 2005: Bean Celery,
Citrus, Cotton, Landscape Maintenance, Lettuce, Pepper, Pistachio. Source: cdpr pur 2007
J
F
M
A
M
J
J
A
S
O
N
D
Figure 2.C - CRLF Reproductive Events by Month
Light Blue =
Green = Tadpoles (except those that over-winter)
Orange =
Adults and juveniles can be present all year
Above, Figure 2.C represents the CRLF reproductive cycle over time, and is presented in
parallel to Figure 2.B, depicting the timing of acephate application to illustrate the
temporal co-occurrence of reproductive events with acephate usage. The months when
there are egg masses and tadpoles present (November to May) correspond to high usage
on lettuce, celery and cotton. While this does not account for spatial differences between
the location of the frog habitat and timing of reproductive events, it does show that there
is general overlap between the timing of acephate applications and CRLF reproduction.
27
-------
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 elevation 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.D). Recovery units, core areas, and other known occurrences of the CRLF from
the CNDDB are described in further detail in this section, and designated critical habitat
is addressed in Section 2.6. Recovery units are large areas defined at the watershed level
that have similar conservation needs and management strategies. The recovery unit is
primarily an administrative designation, and land area within the recovery unit boundary
is not exclusively CRLF habitat. Core areas are smaller areas within the recovery units
that comprise portions of the species' historic and current range and have been
determined by USFWS to be important in the preservation of the species. Designated
28
-------
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 status, 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 2.5 and shown
in Figure 2.D.
Core Areas
USFWS has designated 35 core areas across the eight recovery units to focus their
recovery efforts for the CRLF (see Figure 2.D). Table 2.5 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 acephate 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 2.5 (currently occupied core areas are bolded). While core areas are
considered essential for recovery of the CRLF, core areas are not federally-designated
critical habitat, although designated critical habitat is generally contained within these
core recovery areas. It should be noted, however, that several critical habitat units are
located outside of the core areas, but within the recovery units. The focus of this
29
-------
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 2.5. 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
Occupied 4
Sierra Nevada
Foothills and Central
Valley (1)
(eastern boundary is
the 1,500m elevation
line)
Cottonwood Creek (partial)
(8)
--
Feather River (1)
BUT-1A-B
Yuba River-S. Fork Feather
River (2)
YUB-1
--
NEV-16
Traverse Creek/Middle Fork
American River/Rubicon (3)
--
Consumnes River (4)
ELD-1
S. Fork Calaveras River (5)
--
Tuolumne River (6)
--
Piney Creek (7)
--
East San Francisco Bay
(partial)(16)
--
North Coast Range
Foothills and
Western Sacramento
River Valley (2)
Cottonwood Creek (8)
--
Putah Creek-Cache Creek (9)
--
Jameson Canyon - Lower
Napa Valley (partial) (15)
--
Belvedere Lagoon (partial)
(14)
--
Pt. Reyes Peninsula (partial)
(13)
--
North Coast and
North San Francisco
Bay (3)
Putah Creek-Cache Creek
(partial) (9)
--
Lake Berryessa Tributaries
(10)
NAP-1
Upper Sonoma Creek (11)
--
Petaluma Creek-Sonoma
Creek (12)
--
Pt. Reyes Peninsula (13)
MRN-1, MRN-2
Belvedere Lagoon (14)
--
Jameson Canyon-Lower
Napa River (15)
SOL-1
South and East San
Francisco Bay (4)
--
CCS-1A6
East San Francisco Bay
(partial) (16)
ALA-1A, ALA-
IB, STC-1B
--
STC-1A6
South San Francisco Bay
(partial) (18)
SNM-1A
Central Coast (5)
South San Francisco Bay
(partial) (18)
SNM-1A, SNM-
2C, SCZ-1
30
-------
Table 2.5. 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
Occupied 4
Watsonville Slough- Elkhorn
Slough (partial) (19)
SCZ-2 5
Carmel River-Santa Lucia
(20)
MNT-2
Estero Bay (22)
--
--
SLO-86
Arroyo Grande Creek (23)
--
Santa Maria River-Santa
Ynez River (24)
--
Diablo Range and
Salinas Valley (6)
East San Francisco Bay
(partial) (16)
MER-1A-B,
STC-1B
--
SNB-16, SNB-26
Santa Clara Valley (17)
--
Watsonville Slough- Elkhorn
Slough (partial)(19)
MNT-1
Carmel River-Santa Lucia
(partial)(20)
--
Gablan Range (21)
SNB-3
Estrella River (28)
SLO-1A-B
Northern Transverse
Ranges and
Tehachapi Mountains
(7)
--
SLO-86
Santa Maria River-Santa
Ynez River (24)
STB-4, STB-5,
STB-7
Sisquoc River (25)
STB-1, STB-3
Ventura River-Santa Clara
River (26)
VEN-1, VEN-2,
VEN-3
--
LOS-16
Southern Transverse
and Peninsular
Ranges (8)
Santa Monica Bay-Ventura
Coastal Streams (27)
--
San Gabriel Mountain (29)
--
Forks of the Mojave (30)
--
Santa Ana Mountain (31)
--
Santa Rosa Plateau (32)
--
San Luis Rey (33)
--
Sweetwater (34)
--
Laguna Mountain (35)
--
1 Recovery units designated by the USFWS (USFWS 2000, pg 49).
2 Core areas designated by the USFWS (USFWS 2000, pg 51).
3 Critical habitat units designated by the USFWS on April 13, 2006 (USFWS 2006, 71 FR 19244-19346).
4 Currently occupied (post-1985) and historically occupied core areas as designated by the USFWS
(USFWS 2002, pg 54).
5 Critical habitat unit where identified threats specifically included pesticides or agricultural runoff
(USFWS 2002).
6 Critical habitat units that are outside of core areas, but within recovery units.
7 Currently occupied core areas that are included in this effects determination are bolded.
31
-------
CRLF Habitat Areas
Sierra Neva
Foothills
> * Ofc
N. Transverse
hapi Mountains
S. Transverse Range
& Peninsular Ranges
North Coast Foothills &
Western Sacramento River
N. San Francisc
Bay/North Coast
South & East San 4
Francisco Bay
Central Coast
hhzzh Kilometers
01530 60 90 1 20
Core Areas
Legend
Occurrence sections
| Critical habitat
Core areas
Recovery units (labeled)
County boundaries
Compiled from California County boundaries (ESRI, 2002),
US DA National Agriculture Statistical Service (NASS, 2002)
Gap Anal/sis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
June 15, 2007. Projection: Albers Equal Area Conic USGS, North
American Datum of 1983 (MAD 1983!
Figure 2.D Recovery Unit and Core Area Designations for CRLF
32
-------
Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in
California. The CNDDB serves as a repository for historical and current species location
sightings. Information regarding known occurrences of CRLFs outside of the currently
occupied core areas and designated critical habitat is considered in defining the current
range of the CRLF. See: http://www.dfg.ca.gov/bdb/html/cnddb info.html for additional
information on the CNDDB.
2.5.2 Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams,
marshes, and lagoons (Fellers 2005a). According to the Recovery Plan (USFWS 2002),
CRLFs breed from November through late April. Peaks in spawning activity vary
geographically; Fellers (2005b) reports peak spawning as early as January in parts of
coastal central California. Eggs are fertilized as they are being laid. Egg masses are
typically attached to emergent vegetation, such as bulrushes (Scirpus spp.) and cattails
(Typha spp.) or roots and twigs, and float on or near the surface of the water (Hayes and
Miyamoto 1984). Egg masses contain approximately 2000 to 6000 eggs ranging in size
between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch 10 to 14 days after
fertilization (Fellers 2005a) depending on water temperature. Egg predation is reported
to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles
(terrestrial-phase), typically between May and September (Jennings and Hayes 1994,
USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b, USFWS 2002). Males reach sexual maturity at 2
years, and females reach sexual maturity at 3 years of age; adults have been reported to
live 8 to 10 years (USFWS 2002). Figure 2.E depicts CRLF annual reproductive timing.
Figure 2.E -
CRLF Reproductive Events by Monl
th
J
F
M
A
M
J
J
A
S
o
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter)
Orange =
Adults and juveniles can be present all year
2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied
specifically, it is assumed that their diet is similar to that of other frog species, with the
aquatic phase feeding exclusively in water and consuming diatoms, algae, and detritus
(USFWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar, 1980)
33
-------
via mouthparts designed for effective grazing of periphyton (Wassersug, 1984,
Kupferberg et al.\ 1994; Kupferberg, 1997; Altig and McDiarmid, 1999).
Juvenile and adult CRLFs forage in aquatic and terrestrial habitats, and their diet differs
greatly from that of larvae. The main food source for juvenile aquatic- and terrestrial-
phase CRLFs is thought to be aquatic and terrestrial invertebrates found along the
shoreline and on the water surface. Hayes and Tennant (1985) report, based on a study
examining the gut content of 35 juvenile and adult CRLFs, that the species feeds on as
many as 42 different invertebrate taxa, including Arachnida, Amphipoda, Isopoda,
Insecta, and Mollusca. The most commonly observed prey species were larval alderflies
(Sialis cf. californica), pillbugs (Armadilliadrium vulgare), and water striders (Gerris sp).
The preferred prey species, however, was the sowbug (Hayes and Tennant, 1985). This
study suggests that CRLFs forage primarily above water, although the authors note other
data reporting that adults also feed under water, are cannibalistic, and consume fish. For
larger CRLFs, over 50% of the prey mass may consists of vertebrates such as mice, frogs,
and fish, although aquatic and terrestrial invertebrates were the most numerous food
items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at
night; for juveniles feeding occurs during the day and at night (Hayes and Tennant 1985).
2.5.4 Habitat
CRLFs require aquatic habitat for breeding, but also use other habitat types including
riparian and upland areas throughout their life cycle. CRLF use of their environment
varies; they may complete their entire life cycle in a particular habitat or they may utilize
multiple habitat types. Overall, populations are most likely to exist where multiple
breeding areas are embedded within varying habitats used for dispersal (USFWS 2002).
Generally, CRLFs utilize habitat with perennial or near-perennial water (Jennings et al.
1997). Dense vegetation, shading water of moderate depth is a habitat feature that
appears 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
34
-------
community, and presence of pools and backwater aquatic areas for breeding. CRLFs can
be found living within streams at distances up to 3 km (2 miles) from their breeding site
and have been found up to 30 m (100 feet) from water in dense riparian vegetation for up
to 77 days (USFWS 2002).
During dry periods, the CRLF is rarely found far from water, although it will sometimes
disperse from its breeding habitat to forage and seek other suitable habitat under downed
trees or logs, industrial debris, and agricultural features (USFWS 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.D.
'Critical habitat' is defined in the ESA as the geographic area occupied by the species at
the time of the listing where the physical and biological features necessary for the
conservation of the species exist, and there is a need for special management to protect
the listed species. It may also include areas outside the occupied area at the time of
listing if such areas are 'essential to the conservation of the species.' All designated
critical habitat for the CRLF was occupied at the time of listing. Critical habitat receives
protection under Section 7 of the ESA through prohibition against destruction or adverse
modification with regard to actions carried out, funded, or authorized by a federal
Agency. Section 7 requires consultation on federal actions that are likely to result in the
destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the
conservation of the species.' Critical habitat designations identify, to the extent known
using the best scientific and commercial data available, habitat areas that provide
essential life cycle needs of the species or areas that contain certain primary constituent
elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to,
space for individual and population growth and for normal behavior; food, water, air,
light, minerals, or other nutritional or physiological requirements; cover or shelter; sites
for breeding, reproduction, rearing (or development) of offspring; and habitats that are
protected from disturbance or are representative of the historic geographical and
ecological distributions of a species. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
• Breeding aquatic habitat;
• Non-breeding aquatic habitat;
• Upland habitat; and
35
-------
• Dispersal habitat.
Please note that a more complete description of these habitat types is provided in
Attachment 1.
Occupied habitat may be included in the critical habitat only if essential features within
the habitat may require special management or protection. Therefore, USFWS does not
include areas where existing management is sufficient to conserve the species. Critical
habitat is designated outside the geographic area presently occupied by the species only
when a designation limited to its present range would be inadequate to ensure the
conservation of the species. For the CRLF, all designated critical habitat units contain all
four of the PCEs, and were occupied by the CRLF at the time of FR listing notice in
April 2006. The FR notice designating critical habitat for the CRLF includes a special
rule exempting routine ranching activities associated with livestock ranching from
incidental take prohibitions. The purpose of this exemption is to promote the
conservation of rangelands, which could be beneficial to the CRLF, and to reduce the rate
of conversion to other land uses that are incompatible with CRLF conservation. Please
see Attachment 1. for a full explanation on this special rule.
USFWS has established adverse modification standards for designated critical habitat
(USFWS 2006). Activities that may destroy or adversely modify critical habitat are those
that alter the PCEs and jeopardize the continued existence of the species. Evaluation of
actions related to use of acephate 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 may 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).
36
-------
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 acephate is expected to directly impact living
organisms within the action area, critical habitat analysis for acephate is limited in a
practical sense to those PCEs of critical habitat that are biological or that can be
reasonably linked to biologically mediated processes.
2.6.1. 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
37
-------
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.
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 acephate is likely to encompass considerable portions of the
United States based on the large array of agricultural uses and non-agricultural uses.
However, the scope of this assessment limits consideration of the overall action area to
those portions that may be applicable to the protection of the CRLF and its designated
critical habitat within the state of California. Deriving the geographical extent of this
portion of the action area is the product of consideration of the types of effects that
acephate may be expected to have on the environment, the exposure levels to acephate
that are associated with those effects, and the best available information concerning the
use of acephate 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 acephate. An analysis of labeled uses and review of available product labels was
completed. This analysis indicates that, for acephate, the following uses are considered
as part of the federal action evaluated in this assessment:
All outdoor uses that result in spray drift or run-off exposure are included in the initial
area of concern. Indoor uses are not considered part of the Action Area since exposure of
the CRLF is unlikely.
After a 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 based on available land cover data for labeled outdoor uses. Local
land cover data available for the state of California were analyzed to refine the
understanding of potential acephate use. The initial area of concern is defined as all land
38
-------
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 2.F.
39
-------
Acephate Initial Area of Concern
Compiled from California County boundaries (ESRi, 2002),
USEW National Agriculture Statistical Service (NASS, 2002)
Gap Analysis Program Orchard/Vineyard Landccwer (GAP)
National Land Ctwer Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
June 2007. Projection: Alters Equal Area Conic USGS, North
American Datum of 1983 (NAD 1 983)
Figure 2.F. Initial Area of Concern
40
-------
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 acephate to determine which routes
of transport are likely to have an impact on the CRLF.
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.
Based on the environmental fate assessment, the dominant routes of exposure to acephate
and its degradate methamidophos are believed to be run-off and spray drift. Transport
through groundwater is not considered to be a route of exposure due to the low
persistence of both compounds. Volatilization and long-range transport are not
considered to be a route of exposure due to the low vapor pressure and Henry's Law
constant of both compounds. Based on its low log Kow (-0.85) bioaccumulation is not
expected to be a concern.
41
-------
Acephate Action Area
Legend
Aquatic ActionArea
!¦ Terrestrial Action Area
County boundaries
V
Kilometers
01530 60 90 120
Compiled from California County boundaries (ESRI, 2002),
USDA National Agriculture Statistical Sen/ice (NASS, 2002)
Gap Analysis Program Orchard)'Vineyard Landcwer (GAP)
National Land Ctwer Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate arid Effects Division.
June XX, 2007. Projection: Albers Equal Area Conic USGS, North
American Datum of 1983 (WD 1983)
Figure 2.G Acephate Action Area
42
-------
Subsequent to defining the action area, an evaluation of usage information was conducted
to determine area where use of acephate may impact the CRLF. This analysis is used to
characterize where predicted exposures are most likely to occur but does not preclude use
in other portions of the action area. A more detailed review of the county-level use
information was also completed. These data suggest that, as presented in Figures 2A,
exposure is likely to be greatest in the counties of highest reported usage. Most of the
acephate usage in California is concentrated in a few counties.
Action Area Calculation
The Action Area for acephate will be dominated by its effects on terrestrial species, due
to the much higher RQ values in the terrestrial analysis. The highest risk quotient for any
animal was for birds (avian) chronic risk based on dietary analysis (RQ = 167).
The dose (lb/acre) that results in an RQ below the chronic level of concern is 0.006 lb
ai/A (1 lb/acre^ 167), No adjustment is needed for LOC, since it is 1 for chronic risk.
The AgDISP model with the far-field Gaussian extension was used to calculate the spray
drift buffer needed to reduce exposures to below 0.006 lb/acre. The following inputs
were used; 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 2,913 feet
(about 0.55 mile).
Table 2.6. AgDISP Input Parameters
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
0.032 (1.33 lb product in 5 gal = 42 lb
water)
Active Fraction
0.024 (nonvol frac x % a.i. = 75%)
Canopy
None
Specific gravity (Carrier)
1
Initial Average Deposition
0.006 lb/acre
43
-------
2.8 Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental
value that is to be protected."5 Selection of the assessment endpoints is based on valued
entities (e.g., CRLF, organisms important in the life cycle of the CRLF, and the PCEs of
its designated critical habitat), the ecosystems potentially at risk (e.g,. waterbodies,
riparian vegetation, and upland and dispersal habitats), the migration pathways of
acephate (e.g., runoff, spray drift, etc.), and the routes by which ecological receptors are
exposed to acephate-related contamination (e.g., direct contact, etc).
2.8.1. Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the CRLF, as well as indirect effects, such as reduction of
the prey base and/or modification of its habitat. In addition, potential destruction and/or
adverse 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 acephate is provided in Table 2.7.
Table 2.7 Summary of Assessment Endpoints and Measures of Ecological Effects for Direct
and Indirect Effects of acephate on the California Red-legged Frog
Assessment Endpoint
Measures of Ecological Effects6
Toxicity Endpoint (see effects
table for endpoint selection,
Section 4)
Aquatic Phase
(eggs, larvae, tadpoles, juveniles, and adults)11
1. Survival, growth, and
reproduction of CRLF
individuals via direct
effects on aquatic phases
la. Most sensitive fish acute LC50
lb. Most sensitive fish chronic
NOAEC
lc. Most sensitive fish early-life stage
NOAEC
la. Rainbow trout acute 96-hr LC50
832 ppm ai
lb. none available
lc. Rainbow trout 0.215 ppm ai
5 From U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
6 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix A.
44
-------
Table 2.7 Summary of Assessment Endpoints and Measures of Ecological Effects for Direct
and Indirect Effects of acephate on the California Red-legged Frog
Assessment Endpoint
Measures of Ecological Effects6
Toxicity Endpoint (see effects
table for endpoint selection,
Section 4)
(Acute-Chronic-Ratio)
2. Survival, growth, and
reproduction of CRLF
individuals via effects to
food supply (i.e.,
freshwater invertebrates,
non-vascular plants)
2a. Most sensitive fish (1), aquatic
invertebrate (2), and aquatic plant (3-)
EC50 or LC50 (guideline)
2b. Most sensitive aquatic invertebrate
(1 -) and fish (2) chronic NOAEC
(guideline or ECOTOX)
2al. Rainbow trout acute 96-hr LC50
832 ppm ai
2a2. -Daphnia magna acute 48-hr
EC50 =1.1 ppmai
2a3. Skeletonema costatum algae 5-
day EC50 >50 ppm ai
2b 1. Daphnia magna NOAEC =
0.015 ppmai
2b2. none available
3. Survival, growth, and
reproduction of CRLF
individuals via indirect
effects on habitat, cover,
and/or primary
productivity (i.e., aquatic
plant community)
3a. Vascular plant EC50 (duckweed
guideline test or ECOTOX vascular
plant)
3b. Non-vascular plant EC50 ()
3 a. none available
3b. Skeletonema costatum algae 5-
day EC50 >50 ppm ai
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.
4a. Distribution ofEC25 values for
monocots (seedling emergence,
vegetative vigor, or ECOTOX)
4b. Distribution ofEC25 values for
dicots (seedling emergence, vegetative
vigor, or ECOTOX)7
4a. EC25 and NOEC values are
greater than 4.5 lb/acre
4b. EC25 and NOEC values are
greater than 4.5 lb/acre
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 () or terrestrial-
phase amphibian acute LC50 or LD50
(guideline)
5b. Most sensitive birdb () or
terrestrial-phase amphibian chronic
NOAEC (guideline or ECOTOX)
5a. Dark eyed junko acute oral LD50
= 106 mg ai/kg-bw
5b. Mallard duck Reproductive
study NOEL = 5 ppm ai
6. Survival, growth, and
reproduction of CRLF
individuals via effects on
prey (i.e., terrestrial
invertebrates, small
terrestrial vertebrates,
including mammals and
terrestrial phase
amphibians)
6a. Most sensitive terrestrial
invertebrate (1-) and vertebrate (2-)
acute EC50 or LC50 (guideline or
ECOTOX)0
6b. Most sensitive terrestrial
invertebrate(l) and vertebrate(2-)
chronic NOAEC (guideline or
ECOTOX)
6al. Honey bee acute contact LD50
= 1.20 ug ai/bee
6a2. Rat Acute oral LD50 = 866 mg
ai/kgbw
6b 1. None available
6b2. Rat 3- generation reproductive
study NOAEL = 50 mg ai/kg bw-
day diet4
7. Survival, growth, and
reproduction of CRLF
individuals via indirect
7a. Distribution of EC25 for monocots
(seedling emergence, vegetative vigor,
or ECOTOX
7a. All monocot EC25 and NOEC
values are greater than 4.5 lb/acre
7 The available information indicates that the California red-legged frog does not have any obligate
relationships.
45
-------
Table 2.7 Summary of Assessment Endpoints and Measures of Ecological Effects for Direct
and Indirect Effects of acephate on the California Red-legged Frog
Assessment Endpoint
Measures of Ecological Effects6
Toxicity Endpoint (see effects
table for endpoint selection,
Section 4)
effects on habitat (i.e.,
riparian vegetation)
7b. Distribution of EC25 for dicots
(seedling emergence, vegetative vigor,
or ECOTOX)5
7b. All dicot EC25 and NOEC
values are greater than 4.5 lb/acre
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 acephate 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 and may jeopardize the
continued existence of the CRLF. Therefore, these actions are identified as assessment
endpoints. It should be noted that evaluation of PCEs as assessment endpoints is limited
to those of a biological nature (i.e., the biological resource requirements for the listed
species associated with the critical habitat) and those for which acephate effects data are
available.
Assessment endpoints and measures of ecological effect selected to characterize potential
modification to designated critical habitat associated with exposure to acephate 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.
46
-------
Measures of such possible effects by labeled use of acephate on critical habitat of the
CRLF are described in Table 2.7. 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).
47
-------
Table 2.8. Summary of Assessment Endpoints and Measures of Ecological Effect for Primary
Constituent Elements of Designated Critical Habitat
Assessment Endpoint
Measures of Ecological Effect8
Aquatic Phase PCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or geometry
and/or increase in sediment deposition within the
stream channel or pond: aquatic habitat (including
riparian vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile
and adult CRLFs.
a. Most sensitive aquatic plant
EC50 (guideline or
ECOTOX)
b. Distribution of EC25 values
for terrestrial monocots
(seedling emergence,
vegetative vigor, or
ECOTOX)
c. Distribution of EC25 values
for terrestrial dicots (seedling
emergence, vegetative vigor,
or ECOTOX)
a. Skeletonema costatum
algae 5-day EC50 >50 ppm ai
b. All monocot EC25 and
NOEC values are greater than
4.5 lb/acre
c. All dicot EC25 and NOEC
values are greater than 4.5
lb/acre
Alteration in water chemistry/quality including
temperature, turbidity, and oxygen content necessary
for normal growth and viability of juvenile and adult
CRLFs and their food source.9
a. Most sensitive EC50 values
for aquatic plants (guideline or
ECOTOX)
b. Distribution of EC25 values
for terrestrial monocots
(seedling emergence or
vegetative vigor, or
ECOTOX)
c. Distribution of EC25 values
for terrestrial dicots (seedling
emergence, vegetative vigor,
or ECOTOX)
a. Skeletonema costatum
algae 5-day EC50 >50 ppm ai
b. All monocot EC25 and
NOEC values are greater than
4.5 lb/acre
c. All dicot EC25 and NOEC
values are greater than 4.5
lb/acre
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
a. Most sensitive EC50 or LC50
values for fish or aquatic-
phase amphibians and aquatic
invertebrates (guideline or
ECOTOX)
b. Most sensitive NOAEC
values for fish or aquatic-
phase amphibians and aquatic
invertebrates (guideline or
ECOTOX)
a. Skeletonema costatum
algae 5-day EC50 >50 ppm ai
b. All monocot EC25 and
NOEC values are greater than
4.5 lb/acre
c. All dicot EC25 and NOEC
values are greater than 4.5
lb/acre
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
a. Most sensitive aquatic plant
EC50 (guideline or
ECOTOX)
a. Skeletonema costatum
algae 5-day EC50 >50 ppm ai
Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
a. Distribution of EC25 values
for monocots (seedling
emergence, vegetative vigor,
or ECOTOX)
a. Skeletonema costatum
algae 5-day EC50 >50 ppm ai
b. All monocot EC25 and
Upland areas within 200 ft of the edge of the riparian
vegetation or drinline surrounding agnatic and riparian. , , .
Ait toxicity data reviewea iot tms assessment are included in Appendix A.
9 Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because
these processes are not biologically mediated and, therefore, are not relevant to the endpoints included in
this assessment.
48
-------
habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
Elimination and/or disturbance of dispersal habitat:
Upland or riparian dispersal habitat within designated
units and between occupied locations within 0.7 mi of
each other that allow for movement between sites
including both natural and altered sites which do not
contain barriers to dispersal
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
b. Distribution of EC25 values
for dicots (seedling
emergence, vegetative vigor,
or ECOTOX)
c. Most sensitive food source
acute EC50/LC50 and NOAEC
values for terrestrial
vertebrates (mammals) and
invertebrates, birds or
terrestrial-phase amphibians,
and freshwater fish.
NOEC values are greater than
4.5 lb/acre
c. All dicot EC25 and NOEC
values are greater than 4.5
lb/acre
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 acephate to the environment.
The stressor is defined to be acephate and its degradate methamidophos. The following
risk hypotheses are presumed for this endangered species assessment:
• Labeled uses of acephate within the action area may directly affect the CRLF by
causing mortality or by adversely affecting growth or fecundity;
• Labeled uses of acephate within the action area may indirectly affect the CRLF by
reducing or changing the composition of food supply;
• Labeled uses of acephate within the action area may indirectly affect the CRLF
and/or adversely modify designated critical habitat by reducing or changing the
composition of the aquatic plant community in the ponds and streams comprising the
species' current range and designated critical habitat, thus affecting primary productivity
and/or cover;
• Labeled uses of acephate within the action area may indirectly affect the CRLF
and/or adversely 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;
Based on the results of the submitted terrestrial plant toxicity tests, it appears that
seedlings and emerged plants may not be sensitive to acephate.
There are two Tier II multiple dose phytotoxicity tests for acephate (seedling emergence
and vegetative vigor) that were submitted by the registrant. The EC25 is greater than 4.5
lb ai/A and the NOEC is 4.5 lb ai/A. A typical application rate for acephate is 1.0 lb/A.
49
-------
Based on the results of the submitted terrestrial plant toxicity tests, it appears that
seedlings and emerged plants are not sensitive to acephate and therefore acepahte No
Effect on the CRLF based on these endpoints.
• Labeled uses of acephate within the action area may adversely 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 acephate within the action area may adversely 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 acephate within the action area may adversely 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 acephate within the action area may adversely 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 acephate within the action area may adversely 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 (acephate and methamidophos), release mechanisms, biological
receptor types, and effects endpoints of potential concern. The conceptual models for
aquatic and terrestrial phases of the CRLF are shown in Figures 2.H and 2.1, and the
conceptual models for the aquatic and terrestrial PCE components of critical habitat are
shown in Figures 2. J and 2.K. 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 acephate. Likewise, groundwater transport is considered unlikely due
to the non-persistence of acephate, 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 within a few days of application.
50
-------
Figure 2.H. Conceptual Diagram for Terrestrial Phase Effects on CRLF
Figure 2.1. Conceptual Diagram for Effects on Aquatic Phase CRLF
51
-------
Figure 2. J . Conceptual Diagram for Effects Terrestrial Critical Habitat
Figure 2.K . Conceptual Diagram for Effects on Aquatic Critical Habitat
52
-------
2.10 Analysis Plan
Analysis of risks to the California Red-Legged Frog (both direct and indirect) and to its
critical habitat will be assessed consistent with the Overview Document (USEPA, 2004)
and Agency guidance for ecological risk assessments (USEPA 1998).
There are a number of labeled uses for acephate for indoor applications. Indoor uses
include: Commercial Storages/Warehouses Premises; Commercial Transportation
Facilities-Nonfeed/Nonfood; Commercial/Industrial/Industrial Premises/Equipment
(Indoor); Eating Establishments; Food Processing Plant Premises (Nonfood Contact);
Food Stores/Markets/Supermarkets Premises; Food/Grocery/Marketing/Storage/
Distribution Facility Premise; Hospitals/Medical Institutions Premises
(Human/Veterinary); Household/Domestic Dwellings; Household/Domestic Dwelling
Contents; Household/Domestic Dwellings Indoor Food Handling Areas;
Household/Domestic Dwellings Indoor Premises; Poultry Processing Plant Premises
(Nonfood Contact); Refuse Solid Waste Containers (Garbage Cans); Refuse/Solid Waste
Sites (Indoor).
These applications have been considered. There is no exposure pathway from indoor
applications to the CRLF or its habitat and therefore, indoor applications are determined
to have No Effect on the CRLF.
2.10.1 Exposure Analysis
Direct effects to the aquatic phase CRLF will be assessed by comparing modeled surface
water exposure concentrations of acephate and its degradate methamidophos to acute and
chronic (early life stage hatching success and growth) effect concentrations for aquatic
phase amphibians (surrogate freshwater fish) from laboratory studies (see the Effects
Analysis section below). Effects to aquatic dietary food resources (aquatic invertebrates,
algae) of the aquatic phase CRLF or effects to aquatic habitat that support the CRLF will
also be assessed by comparing modeled surface water exposure concentrations of total
acephate residues to laboratory established effect levels appropriate for the taxa.
A Tier 1 analysis (GENEEC 2.0) will be done first, since the toxicity endpoints for
acephate are all above 1 ppm, and it is not anticipated that any LOCs will be exceeded,
with the possible exception of invertebrates. As a refinement step, surface water
concentrations of acephate and methamidophos will be quantified using the Tier 2 model,
PRZM-EXAMS, if any LOCs are exceeded at the Tier 1 level. The definitive Tier 2
assessment of methamidophos is given in the methamidophos CRLF assessment
document.
For the screening assessment, the standard EXAMS water body of 2 meters maximum
depth, and 20,000 cubic meters volume, will be used. Since acephate is applied by
numerous application methods, the model accounts for loading of acephate into the
surface water via spray drift, run-off and erosion (Figure 2. J). Agricultural scenarios
appropriate for labeled acephate uses will be used to account for local soils, weather and
53
-------
growing practices which impact the magnitude and frequency of acephate 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.
Methamidophos is a major degradate of acephate. Methamidophos is also a registered
organophosphate insecticide, and is registered for use in the U.S. on cotton, potatoes, and
tomatoes and alfalfa grown for seed. Risks from acephate use, which includes its major
degradate methamidophos, are assessed in this effects determination. The Agency is
evaluating the risks to the CRLF posed by registered methamidophos uses separately.
Concentrations of acephate estimated by PRZM-EXAMS represent acephate loading in
water bodies adjacent to any treated field and assume that the concentration applies to
any water body within the treated area.
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 (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 8.2 days, the
maximum for acephate found in Willis and McDowell (1987) will be substituted for the
default 35-day value. Effects from methamidophos are not considered quantitatively as
LOC is expected to be exceeded for parent acephate.
2.10.2 Effects Analysis
As previously discussed in Section 2.8.1 and 2.8.2, 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 CRLF
habitat. Direct effects to the CRLF 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 CRLF are assessed by looking at available toxicity
information relative to the frog's prey items and habitat requirements (freshwater
invertebrates, freshwater vertebrates, aquatic plants, terrestrial invertebrates, terrestrial
vertebrates, and terrestrial plants). Both guideline and open literature toxicity data will
be identified and evaluated for use in determining RQ values.
Acephate's toxicity dataset is incomplete; chronic fish studies are lacking. Other
organophosphates will be screened for available chronic fish data that can be used to
derive acute to chronic ratio (ACR) for acephate.
54
-------
Toxicity studies for acephate degradates (where available) will be discussed for exposure
to the aquatic phase of the CRLF and incorporated into this risk assessment.
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 (LOC) for any taxon or effect (plant or animal, acute or
chronic, direct or indirect) resulting from the maximum label-allowed use of acephate.
To define the extent of the Action Area, the following exposure assessment tools will be
used: PRZM-EXAMS, TREX, AgDrift, 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.
To determine the downstream extent of the Action area for any aquatic effects, acephate
residues are 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 calculates expected dilution in the stream
according to contributing land area. As the land area surrounding the field on which
acephate 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 acephate inputs
within the same watershed will cause the area bounded by (that is, within) 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 both fish and aquatic plants have the same RQ of 1, the fish RQ to LOC ratio
(1/0.05) would be greater than for plants (1/1). Therefore, the Agency would identify all
stream reaches downstream from the initial area of concern where the PCA (percent
cropped area) for the land uses identified for acephate are greater than 1/20, or 5%. All
streams identified as draining upstream catchments greater than 5% of the landclass of
concern, will be considered part of the action area.
55
-------
3. Exposure Assessment
3.1 Label Application Rates and Intervals
The registered uses of acephate in California include cotton, lettuce, citrus, celery,
peppers, beans, mint, Bermuda grass for seed, landscape maintenance, pistachio,
structural pest control, greenhouses, plants in containers, transplants, flowers, and others
(see Table 2.2).
The application rates, intervals, and frequency are summarized in Table 3.1.
Table 3.1. La
)el Use Rates for Acephate in California
Use
Application
Rate (lb
ai/acre)
Number of
applications
allowed
Application
Interval
Application
Type
Beans & Lima
beans - dry
and succulent
1 lb a.i.
2
7 days
air or ground
forms
Celery
1 lb a.i.
2
3 days
Air or ground
Cole Crops -
Brussels
1 lb a.i.
2
not specified
sprouts and
cauliflower
Cotton
1 lb a.i.
6
3, 5, 7 days or
as necessary
Air, ground, in-
furrow
Head lettuce -
crisphead type
1 lb a.i.
2
Not specified
Air or ground
Mint-
1 lb a.i.
2
10 days
Air or ground
peppermint and
spearmint
Non-bearing
Citrus
0.75 lb a.i.
Not specified
7 days or as
necessary
Ground or soil
drench
Non-crop areas
- field borders,
0.25 lb a.i.
Not specified
Not specified
Ground or air
fencerows,
roadsides,
ditchbanks,
borrowpits
Non-crop area
- wastelands
0.125 lb a.i.
1
Not applicable
Ground or air
Peanuts
1 lb a.i.
4
Not specified
Air or ground
Peppers - bell
1 lb a.i.
2
As necessary
Air or ground
Bermuda grass
for seed
1 lb a.i.
Not specified
Not specified
Air or ground
Nursery stock,
non-bearing
deciduous fruit
1 lb a.i.
Not specified
As needed
Air or ground
trees, nut trees,
and vines in
nursery fields
or non-baring
orchards
56
-------
The largest number of applications with the shortest interval between applications will be used whenever
the label does not specify the number of applications or application interval.
3.2 Aquatic Exposure Assessment
As discussed in section 2.5, 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 2.D.
3.2.1. Conceptual Model of Exposure
Aquatic exposure of the CRLF within the action area is estimated with the PRZM-
EXAMS 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 acephate is used are 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.
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
There is very little useful water monitoring data for acephate, due to its non-persistent
nature. There were no data for acephate or methamidophos in the California surface
water database or in the USGS NAWQA surface water monitoring program. The
assessment will therefore be based on modeled concentrations as described in section
3.2.1.
3.2.3 Modeling Approach
Use sites and the PRZM scenarios used to represent them are given in Table 3.4.
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
57
-------
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-six California scenarios 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 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, including citrus,
lettuce, row crop (representing beans, celery, and peppers), cotton, turf (representing
bermudagrass for seed and landscape maintenance), almond (representing nut trees),
fruit (representing various fruit trees) and cole crops (broccoli, cauliflower). Non-crop
areas were not modeled because the application rates are lower than the agricultural uses,
and agricultural scenarios are believed to represent non-agricultural exposures
adequately. Structural pest control was not modeled due to lack of an appropriate PRZM
scenario, and the low likelihood of exposure. All scenarios were used within the standard
framework of PRZM/EXAMS modeling using the standard graphical user interface
(GUI) shell, PE4v01.pl.
3.2.3.1 Model Inputs
A Tier 1 assessment (GENEEC 2.0) was run because the toxicity endpoints for acephate
are in the part-per-million range, and it was not deemed likely that any LOCs would be
exceeded. Tier 2 analysis (PRZM-EXAMS) was run if any LOCs were exceeded at the
Tier 1 level.
The estimated water concentrations from surface water sources were calculated using
Tier 2 PRZM (Pesticide Root Zone Model) and EXAMS (Exposure Analysis Modeling
System). 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 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.
58
-------
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 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.
The appropriate PRZM input parameters 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.
Exposures for the toxic degradate methamidophos were calculated by applying two
correction factors: 0.77 for the molecular weight difference, and 0.23 for the maximum
amount of methamidophos formed in an acephate soil metabolism study (MRID
0014991). Thus, methamidophos exposures are (0.77)*(0.23) = 0.18 times the acephate
exposures.
Table 3.2. Summary of PRZM/EZAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Acephate CRLF Assessment
Fate Property
Value
MRID (or sourec)
Comments
Molecular Weight
Henry's constant
Vapor Pressure
183.16
5.1 E-13 atm-m3/mole
1.7 E-6 torr
calculated from
structure
Acephate IRED
Acephate IRED
none
Calculated from vapor
pressure and solubility
MRID 40390601;
40645901
Solubility in Water
801000 mg/L
Acephate IRED
MRID 40390601
Photolysis in Water
Stable
Acephate IRED
MRID 41081603
Aerobic Soil Metabolism
Half-lives
Hydrolysis
2.3 days
163 days
Acephate IRED
Acephate IRED
MRID 00014991
3 times single value of
14 hours, as per Input
Parameter Guidance
MRID 41081603
Aerobic Aquatic
Metabolism (water
column)
Anaerobic Aquatic
Metabolism (benthic)
Kd
4.6 days
4.6 days
0.09
Acephate IRED
Acephate IRED
Acephate IRED
2 time soil input value
as per Input Parameter
Guidance
2 time soil input value
as per Input Parameter
Guidance
MRID 40504811
59
-------
Fate Property
Value
MRID (or sourec)
Comments
Application Efficiency
Spray Drift Fraction13
95 % for aerial
99 % for ground
5 % for aerial
1 % for ground
Default value0
Default value
as per Input Parameter
Guidance
as per Input Parameter
Guidance for ecological
assessments
Application method
(CAM)
2
Foliar spray
none
Incorporation depth
0 cm
Foliar spray
none
Inputs determined in accordance with EFED "Guidance for Chemistry and Management Practice Input Parameters for
Use in Modeling the Environmental Fate and Transport of Pesticides" dated February 28, 2002.
3.2.4. Aquatic EEC Results
The tables (3.3, 3.4) below present the results of the GENEEC and PRZM-EXAMS
modeling. Details of the results are found in Appendix B.
Table 3.3. GENEEC M
odeled Exposure to Acephate for Maximum Use Rate (Cotton)
Crop/Use
Peak, ppb
21-day average, ppb
60-day average, ppb
Cotton, aerial, 6
applications of 1 lb/acre
spaced at 3 days
85.4
43.6
18.4
Table 3.4. PRZM
[-EXAMS
Modeled Exposures to Acephate
PRZM Scenario
(Crop/Use)
Air or
Ground
Application
Rate (lb/acre)
Number of
Applications @
interval (day)
Peak
EEC
(ppb)
21-day avg
EEC (ppb)
60-day avg
(ppb)
Citrus
G
0.5
1
0.55
0.33
0.20
Cotton
A
1
6 @3
19.2
12.8
6.7
G
1
6 @3
13.4
7.5
3.5
Lettuce
A
1
2 (ail
16.7
10.7
5.0
G
1
2 (ail
15.0
9.0
4.1
Row Crop (beans,
celery, peppers)
A
1
2(ai3
9.7
5.3
2.4
G
1
2(ai3
5.9
3.3
1.5
Turf
(Bermudagrass
for seed)
A
1
1
4.5
2.7
1.3
G
1
1
2.5
1.6
0.76
Almond
(pistachio)
A
1
1
18.1
13.6
7.5
G
1
1
12.9
8.1
4.0
Fruit trees
A
1
1
14.0
9.7
5.0
G
1
1
7.3
4.6
2.1
Cole crops
A
1
2 (ail
13.4
9.0
4.4
G
1
2 (ail
11.3
7.1
3.4
3.3. Terrestrial Exposure Assessment
As discussed in section 2.5, 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 2.D.
60
-------
3.3.1 Conceptual Model of Exposure
Terrestrial exposure of the CRLF on agricultural fields within the Action Area is
estimated with the TREX model, which automates exposure analysis according to the
Hoerger-Kenaga nomogram. Exposure to animals off the field is estimated with the
AgDrift and AgDISP models.
Selection of Foliar Half-life Value for T-REX
Willis and McDowell (1987) was consulted for data on acephate persistence on foliage to
replace the default value of 35 days. The default value was not believed to be reasonable
for a non-persistent pesticide like acephate. Table III (p. 35) of this reference gives eight
values for acephate, five of which are for dislodgeable residues (range 0.7 to 8.2 days),
and three of which are for total residues (range 2.8 to 3.5 days). Normally, total residue
values would be used for acephate, since it has a low Koc and is taken up through the
roots (i.e., acts systemically). This rule is applied because it is believed that residues will
be higher and more persistent if the pesticide is taken up into the plant, rather than just
being on the surface of the foliage (which is measured by dislodgeable residue). Of the
eight values, only one was measured on a crop in California (lemons), and it was
measured as dislodgeable residue. This value was also the longest, and therefore most
conservative of the values, at 8.2 days. The next longest value was 3.5 days (total
residue) on citrus in Florida. Since the crops are similar (lemon and citrus) and the
dislodgeable value exceeds the total value, contrary to what is expected, the value of 8.2
days was selected as the input to T-REX.
3.3.2. Modeling Approach
On-field exposure of the CRLF and its prey was estimated with TREX, using both
maximum label rates of 1 lb/acre, 6 applications spaced at 3 day intervals (cotton). A
low-rate scenario (0.25 lb/acre) was also done to bound possible risks. The decay rate
used on foliage and other food items was 8.2 days (Willis & McDowell, 1987, p. 35),
which was measured for acephate on lemons in California. Direct risk to the CRLF was
bounded using 20-gram and 100-gram avian weight classes, since the weight of young
adult frogs falls 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.
The T-HERPS model was used to characterize risk to the CRLF, by applying food intake
rates and prey items appropriate to frogs, in place of the bird food intake rates assumed in
T-REX.
Indirect risks to the CRLF through effects on its prey base were estimated in two ways.
First, indirect effects via larger prey (Pacific tree frog and California mouse) were
estimated conservatively using the 20-gram weight class for the Pacific tree frog and the
61
-------
15-gram weight class for the mouse. The short-grass food category was used since it
provides the highest dose and is eaten by the mouse.
Indirect effects via smaller prey (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 as the large insect EEC in ppm (avian, dose-based, 20-gram animal), divided
by the body weight of the bee. The LD50 (ppm) was calculated as the LD50
(micrograms per bee) divided by the body weight. The RQ was then the dose divided by
the LD50 (ppm).
To define the Action Area, the dose (in lb/acre) needed to bring all RQs below their
respective LOC (0.1 for acute, non-endangered birds and mammals, and 1.0 for chronic)
was calculated by dividing the LOC by the RQ, and multiplying the result by the single
application rate (1 lb/acre):
Dose below LOC (lb/acre) = (LOC/RQ)*(application rate, lb/acre).
The AgDrift or AgDISP model was then used to calculate the buffer distance needed to
reduce the dose to below the LOC. If the result was beyond the range of these models,
then the Gaussian extension to AgDISP was used.
3.3.3. Model Inputs
TREX and T-HERPS model inputs included application rate (1 lb/acre) number of
applications (6), application interval (3 days), and foliar decay rate (8.2 days).
3.3.4 Results
See Appendix F and Appendix F1 for T-REX and T-Herps details of EEC calculations.
Summaries are given here.
3.3.4.1 EECs for Direct Effects to CRLF
Tables 3.5 to 3.6. present the results of the TREX analysis. The EECs in Table 3.5 are
based on the maximum exposure (cotton scenario) of 6 applications of 1 lb a.i./acre,
spaced at 3 day intervals. The EECs in Table 3.6. are based on the lowest labeled
application rate of 0.13 lb a.i./acre (for sewage disposal areas) and an assumption of one
application.
Table 3.5. Summary of EEC for Direct Effects to CRLF (Maximum exposure)
Frog
EEC, ppm
size, g
Small
Large
insects
Insects
20
536.5
59.6
100
306
34
62
-------
Table 3.6 Summary of EEC Direct Effects to CRLF (lowest exposure)
Frog
EEC, ppm
size, g
Small
Large
insects
Insects
20
20
2.2
100
11.4
1.3
3.3.4.2. EECs for Indirect Effects to CRLF
The EECs in Table 3.7. are based on the maximum exposure (cotton scenario) of 6
applications of 1 lb a.i./acre, spaced at 3 day intervals, and those in Table 3.8. on the low
exposure scenario of 0.13 lb a.i./acre. The lowest weight classes (15-20 g) and highest
residue (short grass) categories were used to provide a protective assessment of exposure.
Table 3.7. Summary of EEC for Indirect Effects on CRLF (Maximum exposure)
Avian, 20 gram body weight
Food Item Category
Dose-Based EEC, mg/kg-bw
Short Grass
954
Tall Grass
437
Broadleaf Plants/small Insects
536
Fruits/pods/seeds/large insects
59.6
Mammal, 15-gram Body Weight
Food Item Category
Dose-Based EEC, mg/kg-bw
Short Grass
798
Tall Grass
366
Broadleaf Plants/small Insects
449
Fruits/pods/seeds/large insects
49.9
Table 3.8. Summary of EEC for Indirect Effects on CRLF (lowest exposure)
Food Item Category
Dose-Based EEC, mg/kg-bw
Avian, 20-gram body weight
Short Grass
35.5
Tall Grass
16.3
Broadleaf Plants/small Insects
20
Fruits/pods/seeds/large insects
2.2
Mammal, 15-gram Body Weight
Food Item Category
Dose-Based EEC, mg/kg-bw
Short Grass
29.75
Tall Grass
13.6
Broadleaf Plants/small Insects
16.7
Fruits/pods/seeds/large insects
1.9
63
-------
4. Effects Assessment
This assessment evaluates the potential for acephate to adversely affect the California
Red-Legged Frog (CRLF). As previously discussed in Section 2.7, selected assessment
endpoints for the CRLF include assessment of direct toxic effects on the survival,
reproduction, and growth of the frog itself, as well as indirect effects, such as reduction of
the prey base and/or modification of its habitat (Tables 2.7 and 2.8). Taxa selected as
measurement endpoints include freshwater fish as a prey item and also as a surrogate for
aquatic phase of CRLF, if no amphibian toxicity data are available; freshwater aquatic
invertebrates (prey item); birds as surrogates for terrestrial phase of CRLF and other
amphibians (prey item); small mammals (prey item); terrestrial invertebrates (prey item);
aquatic plants, and terrestrial plants (Tables 2.7 and 2.8). Toxicity data for freshwater
fish and birds are used as surrogate data for aquatic-phase and terrestrial-phase
amphibians (U.S. EPA, 2004).
Information on the toxicity of acephate to selected taxa is characterized based on
registrant-submitted studies and a comprehensive review of the open literature on
acephate. Values used for each measurement endpoint identified in Tables 2.7 and 2.8
are selected from this 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. However, some aquatic-phase frog survival data for acephate are
available from open literature (Table 4.1), these data were reviewed for use in the risk
determination. 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.
In addition, toxicity data on acephate's relevant degradate methamidophos, are discussed
briefly and cross-referenced to the methamidophos effects determination document for
the CRLF (USEPA, 2007).
4.1 Evaluation of Aquatic and Terrestrial Ecotoxicity Studies
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 (12/29/2006). Table 4.1 summarizes the most
sensitive results for each 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 Appendix A.
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;
64
-------
(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 Tables 2.7 and 2.8, 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. In addition, effects data for taxa that are
directly relevant to the California Red-Legged Frog (i.e., aquatic-phase and terrestrial-
phase amphibian data) were also considered over the use of surrogate taxa effects data, if
available. 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 Section 2.7 (Tables
2.7 and 2.8). 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.
65
-------
Table 4.1. Acephate measurement endpoints and values selected for use in RQ
calculations for the effects determination.
Assessment
Endpoint50 ppm ai
NOEC = 5.0
ppm ai
Supplemental
(Most sensitive)
MRID
40228401
(Mayer, 1986)
Freshwater green
algae,
cyanobacteria or
diatom 96-h
NOAEC (orECos)
for biomass
Abundance (i.e.,
survival,
Avian (single
dose) acute oral
LD5o
Dark eyed
junco
106 mg
ai/kg-bw
Supplemental
(Most sensitive)
MRID
00093911
(Zinkl, 1981)
reproduction, and
growth) of
individuals and
Avian subacute
5-day dietary LC50
Japanese quail
dietary sub-
acute LC50 =
718 ppmai
Supplemental
(Most sensitive)
Smith, G.J.,
1987.
populations of birds
in close proximity to
sites, (b)
Avian reproduction
NOAEL
Mallard duck
Reproductive
study NOEL
= 5 ppm ai
(e)
Acceptable
(Most sensitive)
MRID
00029691
(Beavers,
1979)
66
-------
Assessment
Endpoint3.96 lb ai/A
Acceptable
Porch, J.R., et
al., 2003;
MR1D
46173203
6b. Seedling
emergence
NOAEC
3.96 lb ai/A
6c. Vegetative
vigor EC25
>3.96 lb ai/A
Acceptable
Porch, J.R., et
al., 2003;
MR1D
46173204
6d. Vegetative
vigor NOAEC
3.96 lb ai/A
(a) Assessment endpoints and measures of effect from Table 2.7 and 2.8.
(b)Note: Since, acute toxicity studies in birds demonstrated acute toxicity (LC50 orLD50) values higher than
the highest concentrations tested and resulted in no mortalities, acute risk quotients will not be derived for
birds.
(c) As compared to other mammalian toxicity values when adjusted for body weight using allometric
equations.
(d) Parental and pup weight, food consumption, litter size, mating performance and viability are all most
sensitive measured effects.
Cs")
Based on reduced number viable embryos, live 3-week embryos.
67
-------
Table 4.2. Methamidophos measurement endpoints and values selected for use in
RQ calculations in this effects determination.
Assessment
Endpoint50
ppm ai
NOEC = 5.0 ppm
ai
Supplemental
(Most sensitive)
MRID
40228401
(Mayer,
1986)1
Freshwater green
algae,
cyanobacteria or
diatom 96-h
NOAEC (orECos)
for biomass
Abundance (i.e.,
survival,
reproduction, and
growth) of
individuals and
populations of birds
in close proximity to
sites, (b)
Avian (single
dose) acute oral
LD5o
Common
grackle
4.1 mg ai/kg-bw
Supplemental
(Most sensitive)
MRID
00144428
(Lamb, 1972)
Avian subacute
5-day dietary LC50
Bobwhite
quail
dietary sub-acute
LC50 = 42 ppm ai
Supplemental
(Most sensitive)
MRID
00093904
(Beavers &
Fink, 1979)
Avian reproduction
NOAEL
Mallard duck
Reproductive study
NOEL = 3 ppm ai3
Acceptable
(Most sensitive)
MRID
00014114
(Beavers &
Fink, 1978)
68
-------
Assessment
Endpoint4.0 lb ai/A
Acceptable
MRID
46655802
Christ and
Lam, 2005
6b. Seedling
emergence
NOAEC
4.0 lb ai/A
6c. Vegetative
vigor EC25
>4.0 lb ai/A
Acceptable
MRID
46655802
Christ and
Lam, 2005
6d. Vegetative
vigor NOAEC
4.0 lb ai/A
1 Most sensitive measure of effect in study that NOAEC is based on
2 Most sensitive measure of effect in study that NOAEC is based on.
3 Most sensitive measure of effect in study that NOAEC is based on.
4 Since there are no aquatic plant studies for methamidophos, acephate RED was used to provide information on
aquatic plant endpoint.
5 Decrease in number of births, pup viability and body weight. There does not appear to be a palatability problem in
the studies (personal communication Nancy McCarroll, HED, 2/10/98).
4.1.1 Toxicity to Freshwater Aquatic Animals
In the following sections relative acute toxicity of acephate and its major degradate,
methamidophos, to aquatic animals is categorized using the scheme listed in Table 4.3.
Table 4.3. Categories of Toxicity for Aquatic Organisms
LC50 (ppm)
Toxicity Category
<0.1
Very highly toxic
>0.1-1
Highly toxic
>1-10
Moderately toxic
>10 - 100
Slightly toxic
> 100
Practically nontoxic
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies
Acute fish testing with acephate fulfilled data requirements (§72-1). There are no data
from fish early life stage chronic testing (§72-4).
69
-------
Parent acephate
Acephate technical grade active ingredient (TGAI) acute toxicity results exist for several
cold water and warm water freshwater fish species, including Rainbow Trout, Bluegill
Sunfish, Brook Trout, Atlantic Salmon, Cutthroat Trout, Yellow Perch, Channel Catfish,
and Fathead Minnow. A complete list of all the acute freshwater fish toxicity data for
acephate is provided in Appendix A. For twelve studies, the acute freshwater fish 96-h
LC50 values for technical grade acephate range from >50 to >1,000 ppm ai (Appendix A)
and of these twelve studies only one had definitive 96-h LC50 values (Rainbow trout
values 96-h LC50 = 832 ppm (Mayer, 1986)). Data from the Mayer study was reviewed
and the LC50 was calculated. There is another more sensitive LC50 for trout from
Mayer, but a definitive 96-h LC50 value above 100 ppm ai for a pesticide is not required
unless exposure concentrations above 100 ppm are expected to occur under actual use
conditions, which it does not for acephate labeled uses (Section 3.2.3). Based on this
data, acephate is categorized at most as slightly toxic acutely to freshwater fish to
practically non-toxic (Table 4.3). The most sensitive freshwater fish acute 96-h LC50
value of 832 ppm ai with rainbow trout (Oncorhynchus mykiss) (MRID 40098001,
Mayer, 1986) was selected as the measurement endpoint for characterizing acute risks to
freshwater vertebrate prey of the CRLF and for characterizing acute direct risks to the
CRLF aquatic-phase (Table 4.1). No sublethal effects were reported as part of this study.
This study is considered to be supplemental because of a lack of raw data to run a
statistical analysis and only 5 fishes per concentration level was tested (no replicates).
Acephate formulation (75% wettable powder) acute toxicity test results were also
available for several cold water and warm water freshwater species including Rainbow
Trout, Bluegill Sunfish, Brook Trout, Largemouth Bass, Cutthroat Trout, Goldfish,
Yellow Perch, Channel Catfish, Fathead Minnow, and Mosquito Fish (Appendix A). For
these fourteen studies the 96-h LC50 values range from >100 to 6,000 ppm ai. Like the
studies with acephate TGAI, most of these LC50 values were not definitive values.
However, based on the limited data it does not appear that acephate as the 75% wettable
powder formulation is more toxic than the TGAI.
Methamidophos, major degradate
There is only a single acute 96-h LC50 study with a freshwater fish and the major
degradate, methamidophos TGAI, which was with a warm water carp (Cyprinus carpio)
(Appendix A). The definitive 96-h LC50 value of 68 ppm methamidophos for the carp is
more toxic than the definitive 96-h LC50 value observed for acephate freshwater fish
(1,100 ppm ai). Acute test results of formulations with methamidophos are also more
toxic than acephate TGAI or acephate formulations. Methamidophos 96-h LC50 values
for formulations ranged from 12 to 38 ppm for two species, Rainbow Trout and Bluegill
Sunfish, whereas for these same species the acephate TGAI results ranged from >50 to
1,100 ppm ai and for acephate formulations >150 to 2,050 ppm ai.
70
-------
4.1.1.2 Freshwater Fish: Chronic Exposure (Growth/Reproduction) Studies
Parent Acephate
Similar to the acute data, chronic freshwater fish toxicity studies would be used to assess
potential direct effects to the CRLF because direct chronic toxicity guideline data for
frogs do not exist. Since there are no chronic data for freshwater fish, an acute to chronic
ratio (ACR) was determined. Acephate is an organophosphate insecticide. The EFED
toxicity database was accessed to derive an acute to chronic ratio of all organophosphate
insecticides that have an acute LC50 and an early life stage fish study for rainbow trout.
Rainbow trout is usually the most sensitive fish species among pesticides and is the most
sensitive fish acute endpoint for acephate. Nineteen organophosphates were found that
have both an acute and chronic study for rainbow trout. 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 acephate, the ACR of 144 will be used to estimate
the NOEC for rainbow trout. The estimated chronic NOEC for rainbow trout as derived
from and ACR of 144 and a LC50 of 832 ppm is 5.76 ppm or 5760 ppb.
The following section presents the methodology used in deriving an avian ACR for
organophosphates, the group to which acephate belongs, that was used to extrapolate a
chronic fish NOAEC for acephate. The resulting early life stage for freshwater fish
NOAEL was used as a surrogate for the aquatic-phase amphibian (U.S. EPA 2006). Of
the organophosphates, 12 were evaluated for this extrapolation Table 4.4. The EFED
toxicity database was accessed to derive an acute to chronic ratio of all organophosphate
insecticides that have an acute LC50, an early life stage fish study for rainbow trout, and
have been reviewed previously for scientific soundness. Rainbow trout is usually the
most sensitive fish species among pesticides and is the most sensitive fish acute endpoint
for acephate. A species and chemical specific ACR would ideally be determined which
will then be used in the final organophosphate ACR derivation.
The estimated fish (aquatic phase amphibians) chronic NOAEC for acephate is derived as
follows. The (acephate) rainbow trout LC50 used in this assessment is 832 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 acephate.
750(acute)/5.2(chronic) = 144 = ACR ratio for Dichlorvos
Estimated NOEC for acephate = LC50 = 832 ppm = 144
NOEC est. NOEC
Estimated Trout NOEC for acephate = 832/144 = 5.8 ppm ai
The table below (4.4) shows the inputs for the organophosphates that were considered for
the acephate ACR.
71
-------
Methamidophos degradate
As with acephate, methamidophos does not have a chronic fish study. Therefore an ACR
was also done to determine the estimated Trout NOEC for methamidophos.
Estimated NOEC for methamidophos =
LC50 = 25 ppm = 144
NOEC est. NOEC
Estimated Trout NOEC for methamidophos = 25/144 = 0.1736 ppm ai
The table below shows the inputs for the organophosphates that were considered for the
acephate ACR.
Acute to Chronic Table for Organophosphates
Table 4.4. Acephate Acute to Chronic Ratio for Rainbow Trout ]S
Acephate
96-hr LC50
NOAEC
NOEC
Chemical
(ppm ai)
MRIDs
(ppm ai)
MRIDs
ACR
(PPM ai)
Azinphos methyl
0.0088
03125193
0.00029
00145592
30.344
27.41
Coumaphos
0.890
40098001
0.0117
43066301
76.068
10.93
Dichlorvos
0.750
43284702
0.0052
43788001
144.23
5.76
Dimethoate
7.500
TN
1069*
0.430
43106303
17.441
47.70
Disulfoton
1.850
40098001
0.220
41935801
8.4090
98.94
Fenamiphos
0.068
40799701
0.0038
41064301
17.894
46.49
Fenitrothion
2.000
40098001
0.046
40891201
43.478
19.13
Fenthion
0.830
40214201
0.0075
40564102
110.66
7.518
Fonofos
0.050
00090820
0.0047
40375001
10.638
78.20
Isofenphos
1.800
00096659
0.153
00126777
11.764
70.72
Phosmet
0.105
40098001
0.0032
40938701
32.812
25.35
terbufos
0.0076
40098001
0.0014
41475801
5.4285
153.26
OEC
* TN 1069 is test number for EPA's Animal Biology Lab, McCann, 1977
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open Literature
Information
In addition to submitted studies, data were located in the open literature that report
sublethal effect levels to freshwater fish that are less than the selected measures of effect
summarized in Table 4.1.
Some sublethal effects to fish were found in open literature for acephate.
One study (Zinkl, 1987) found that the percentage of ChE inhibition that suggests
poisoning by acephate or methamidophos is greater than 70% since brain ChE inhibition
is at least this much in some trout that did not die. There is persistent ChE depression
72
-------
(Brain ChE activity remains depressed 8 days after a 24-hour exposure to 25 mg/L of
methamidophos and 15 days after exposure to 400 mg/L of acephate) which suggests
sublethal effects such as inability to sustain physical activity in search of food, eluding
predators, and maintaining position in flowing water would occur. However, additional
studies are needed to conclude whether these sublethal effects do occur.
Several studies (Geen, 1981; Schoettger,1976, MRID 14861; Boscor, 1975, MRID
14637; Rabeni, 1979, MRID 14547) indicate no significant adverse effects on fish and
benthic invertebrates from acephate applications.
The above field studies and laboratory data suggest that acephate and other
organophosphate insecticides may not directly cause mortality to fish or benthic
invertebrates. The amount of ChE inhibition that may cause mortality to fish (excess of
70% inhibition) suggests fish species may be somewhat resistant to adverse effects from
acephate. Data are inconclusive as to whether there are behavior modifications to aquatic
organisms from acephate or other organophosphate exposure.
4.1.2 Toxicity to Amphibians - Aquatic Phase
Amphibian toxicity data were used to assess potential direct and indirect effects to the
CRLF. Direct effects to amphibians other than CRLF resulting from exposure to
acephate may indirectly affect the CRLF via reduction in available food.
A summary of acute and chronic amphibian data, including published data in ECOTOX
is provided below in Sections 4.1.3.1 through 4.1.3.3.
4.1.2.1 Amphibians: Acute Exposure Studies
The most sensitive study (MRIDs 00093943, 05019255, Lyons, 1976) found the Green
Frog larvae/tadpole (Rani clamitans) 24 hr. LC50 to be 6433 ppm (5857-6775). This
study is categorized as supplemental because of lack of raw data, dose-response data was
not reported, ten tadpoles per treatment level was tested, with only one test vessel per
treatment level (no replicates), and this study being a non-guideline study. Although the
study was run for 96-hour period, only a 24-hour toxicity endpoint was derived because a
linear dose-response pattern was not obtained. A behavior bioassay suggested that
concentrations up to 500 ppm produced no observable differences between the treatment
and control groups.
Another study of green frog larvae/tadpole was tested with acephate (MRID 4404290,
Hall, 1980) up to 5 ppm for bio-concentration. Neither bio-accumulation nor toxicity
was noted at 5 ppm concentration level.
A study (ECOTOX 11134, Geen, 1984) tested an amphibian, salamander, with acephate
and found a 96-hour LC50 to be 8816 ppm. Exposure of egg masses to acephate
concentrations of 798 ppm did not show any significant differences with the control to
the time of hatching.
73
-------
Acephate is classified as practically non-toxic to aquatic-phase amphibians on an acute
basis.
Additional information can be found in Appendix A.
4.1.3 Toxicity to Freshwater Invertebrates
Freshwater aquatic invertebrate toxicity data were used to assess potential indirect effects
of acephate to the CRLF. Direct effects to freshwater invertebrates resulting from
exposure to acephate may indirectly affect the CRLF via reduction in available food. As
discussed in Section A.5.1 of Attachment A, CRLF aquatic-phase is presumed to be algae
grazers but there is some uncertainty in that assumption. Therefore, aquatic invertebrates
are also assumed to be a food source for CRLF aquatic-phase.
A summary of acute and chronic freshwater invertebrate data, including published data in
ECOTOX is provided below in Sections 4.1.3.1 through 4.1.3.3.
4.1.3.1 Freshwater Invertebrates: Acute Exposure Studies
The most sensitive acceptable study (MRID 47116601, McCann, 1978) found the
Daphnia magna LC50 to be 1.11 ppm ai (0.65-1.88). The probit slope is 1.62. The
range of LC50 toxicity for freshwater invertebrates is 1.11 to >1,000 ppm. One other
Daphnia magna was tested and the LC50 is 71.8 ppm.
A complete list of all the acute freshwater invertebrate toxicity data for acephate is
provided in Appendix A.
Acephate classification ranges from moderately toxic to practically non-toxic to
freshwater invertebrates on an acute basis.
4.1.3.2. Freshwater Invertebrates: Chronic Exposure Studies
A submitted freshwater invertebrate life-cycle study (MRID 44466601, McCann, 1978)
using Daphnia magna was reviewed. The control had 35% mortality of the adults and
the treatments range from 10% to 35% mortality for adults with the highest concentration
level having 10% mortality. Since this is a 21 day static test, it is assumed that the
mortalities come from handling the organisms. There is a dose response trend of
offspring per adult per day. With the dose response trend and because methamidophos
daphnia life study has a more sensitive NOEC of 4.5 ppb, it was decided to make this
study supplemental and not invalid since there is some useful information in this study.
The NOEC is found to be 150 jig ai/L (0.150 ppm) for 21-day test. The NOEC is based
on reduction in numbers of young at 375 ppb and higher.
4.1.3.3. Freshwater Invertebrates: Open Literature Data
74
-------
In addition to submitted studies, data were located in the open literature that report
sublethal effect levels to freshwater invertebrates; however, they are less sensitive than
the selected measures of effect summarized in Table 4.1 and 4.2.
4.1.4. Toxicity to Birds
As previously discussed, no guideline tests exist for frogs; therefore, birds are used as
surrogate species for amphibians including frogs (U.S. EPA, 2004). The available open
literature has no information on acephate toxicity to terrestrial-phase amphibians. Avian
toxicity from open literature shows that acute and chronic ecotoxicity endpoints are
generally less sensitive than the registrant submitted avian studies. A summary of acute
and chronic avian data, including sublethal effects, is provided below.
4.1.4.1 Birds: Acute Exposure (Mortality) Studies
Avian acute toxicity studies were used to assess potential direct effects to the CRLF
because direct acute toxicity guideline data on frogs are unavailable. Acephate toxicity
has been evaluated in some avian species, including mallard duck, bobwhite quail, dark-
eyed junco, common grackle, starling, redwing blackbird, and Japanese quail and the
results of these studies demonstrate a moderate range of sensitivity. The range of acute
oral LD50 values for acephate ranges from 106 mg a.i./kg-bw to 350 mg a.i./kg bw. The
range of subacute dietary LC50 is from 718 ppm to >5000ppm; therefore, acephate is
categorized as moderately toxic to avian species on an acute oral basis to birds and as
practically non-toxic to moderately toxic to avian species on a subacute dietary basis.
Acute Oral LDsn and Avian sub acute dietary endpoint analysis
The most sensitive acute oral LD50 value is 106 mg/kg-bw for the dark eyed junco
(MRID 00093911, Zinkl, 1981). However, there are uncertainties in using this value for
risk assessment for the California Red-Legged Frog (CRLF). There were 5 dose groups
with a geometric progression of 1.4X (EPA recommends 2X progression between doses).
Only 4 birds were tested in each dose group (EPA recommends 10 birds per dose group).
The 106 mg/kg-bw dose group had 2 birds out of 4 that died. No confidence interval and
no probit slope were calculated. This study compared the LD50 value of birds fed larvae
laced with acephate with birds that were given acephate by gavage. The birds initially
refused to ingest larvae that contained 16 |ig acephate/larvae; however, the birds were
willing to consume larvae containing five |ig acephate. The study found that acephate
given by gavage without larvae produced more inhibition than the larvae-fed birds. The
study also concludes that the higher the dose, the more ChE inhibition is found in the
birds. Increased time of exposure may prolong the time for recovery from ChE
inhibition. Feeding the birds larvae containing acephate may decrease the activity of the
acephate when compared to the gavage. The birds fed for five days recovered in 12 to 22
days.
75
-------
The next lowest LD50 value is 109 mg/kg-bw (86-139 mg ai/kg-bw)for bobwhite quail
(MRID 43939301, Campbell, 1992). This study was conducted with a granular
formulation (15% ai). The probit slope is 5.4. The formulation LD50 = 73 4 mg/kg (86-
139 mg/kg formulation). This study followed EPA guidelines and is an acceptable study
for the formulation. The LD50 value (109 mg/kg-bw) from this bobwhite study will be
used in the T-REX model for assessing effects to CRLF (terrestrial-phase).
There are a total of six acute oral studies with acephate using four different species, with
the range of LD50 being from 106 mg/kg-bw to 350 mg/kg-bw. Additional information
may be found in Appendix A.
4.1.4.2. Birds: Chronic Exposure (Reproduction) Studies
Avian reproduction studies indicate that when parents are fed between 5 and 20 ppm
technical grade acephate, the survival of embryos and chicks are adversely affected.
Effects seen in a study on northern bobwhite quail at 80 ppm include reduced body
weight, number of eggs laid, eggs set, viable embryos, number of embryos alive at 3
weeks, number of normal hatchlings, and 14-day old survivors. The NOEL is 20 ppm for
the bobwhite quail (MRID 00029692, Beavers, 1979).
Effects seen in a study on mallard ducks at 20 ppm include a reduced number of viable
embryos and live 3 week embryos. The NOEL for the mallard is 5 ppm (MRID
00029691, Beavers, 1979).
4.1.4.3. Avians: Sublethal Effects and Additional Open Literature
Information
Vyas (ECOTOX 40313) reported that acephate (representing all organophosphates)
affected adult migratory white-throated sparrows {Zonotrichia albicollis). Adult birds
exposed to 256 ppm acephate a.i. were not able to establish a preferred migratory
orientation and exhibited random activity. All juvenile treatment groups displayed a
seasonally correct southward migratory orientation. The author hypothesized that
acephate may have produced aberrant migratory behavior by affecting the memory of the
adult's migratory route and wintering ground. The "experiment reveals that an
environmentally relevant concentration" (similar to 0.5 lb ai/A application) of an OP
such as acephate "can alter migratory orientation, but its effect is markedly different
between adult and juvenile sparrows. Results suggest that the survival of free-flying
adult passerine migrants may be compromised following organophosphorus pesticide
exposure." Although birds are surrogate species for frogs, it is uncertain as to whether
this aberrant behavior in birds can translate over to another aberrant behavior with frogs
in the absence of additional data.
ECOTOX 40343, Vyas, 1996. The effects of a 14-day dietary exposure of acephate on
cholinesterase activity in three regions; basal ganglia, hippocampus, and hypothamulus
were examined in the brain of the white-throated sparrow, Zonotrichia albicollis. All
76
-------
three regions experienced depressed cholinesterase activity between 0.5-2 ppm ai
acephate. The regions exhibited cholinesterase recovery at 2-16 ppm ai acephate;
however, cholinerase activity dropped and showed no recovery at higher dietary levels (>
16 ppm acephate) which suggests that each region maintains its own ChE activity level
integrity until the brain is saturated so that the differences of the regions is nil. Each
region of the brain is responsible for different survival areas such as a foraging and
escaping predators, memory and spatial orientation, food and water intake, reproduction
and several others. Evidence indicated that the recovery is initiated by the magnitude of
depression, not the duration. In general, as acephate concentration increased, depression
in ChE activity among brain regions increased and differences of ChE activity among the
three brain regions decreased. The pattern of ChE depression in different regions of the
brain following low level exposure may prove to be a critical factor in the survival of the
bird. The authors hypothesized that adverse effects to birds in the field may occur at
pesticide exposure levels customarily considered negligible.
Zinkl, 1978. Several large acreages of forest were sprayed with acephate at 0.5, 1.0 or
2.0 lb. ai/A application rates. There was no brain ChE inhibition on day zero after
application. Birds collected from the 2 lb ai/A plots from day one thru six post spray
showed ChE inhibition. Brain ChE inhibition was shown in birds 33 days after treatment
but not 89 days after treatment. Birds seemed to have more inhibition of ChE in summer
application when compared to the fall application in the 1 lb. ai/A plots (30-50% and 25-
40% depression, respectively). The greatest ChE inhibition occurred in dark-eyed juncos
(65%) collected 15 days after treatment. In the 2 lb. ai/A plots, dark-eyed j uncos and
golden-crowned kinglets had 54% ChE inhibition. Of the 14 species collected, only pine
siskins (Siinuspinus) did not show any ChE inhibition. Symptoms of organophosate
poisoning were observed such as a warbling vireo salivating profusely, an American
robin having difficulty maintaining a perching position, and a mountain chickadee having
visible tremors. All of these observations were made in the 1 lb. ai/A plots. The authors
concluded that since marked ChE inhibition did not occur on day zero, but was evident
up to 33 days after application, there was either an accumulative effect that was detected
later or acephate was converted to a more potent ChE inhibitor such as methamidophos.
Spraying the forest with 0.5, 1.0 or 2.0 lb. ai/A caused marked and widespread, and
prolonged ChE depression in passerine birds.
ECOTOX 39518, MRID 40329701. Zinkl, 1980, Zinkl, 1979. Acephate was sprayed in
a forest at 0.5 lb ai/A. Eleven species of birds had ChE inhibition that ranged on average
from 20 to 40%. The maximum depression of ChE found in chipping sparrows was 57%
at day six. Western tanager species was found to have significant inhibition up to 26
days after application. Brain residue analysis of a western tanager collected on day three
contained 0.318 ppm of acephate and 0.055 ppm of methamidophos.
MRID 05014922 and 00163173. (Bart, 1979). Acephate was applied in this study on
June 13 at 0.55 kg/ha (0.5 lb ai/A) on two 200 hectare plots. Authors measured the
presence of the red-eyed vireos by the number of their particular songs. Significant
(P<0.05) decline in number of red-eyed vireos was observed. The decline was
concentrated in the interior of the treated plots rather than spread throughout. This would
77
-------
conclude that acephate affected the decline of the number of red-eyed vireos. No birds
were tested and it is not known whether the declines in vireos were due to direct effects
or indirect effects such as killing off the food items.
MRID 00141694. (Rudolph, 1984) Kestrels were dosed with 50 mg/kg of 75% acephate
formulation. Serum ChE was 37% inhibited and returned to predosed levels eight days
later. Then the birds were dosed again and the serum ChE activity was inhibited at 42%;
brain ChE was at 26% inhibition. The kestrel prey-catching activity was not altered from
the acephate at 50 mg/kg-bw dose level.
MRID 40644802. (Richmond, 1979) Site: Wallowa-Whitman National Forest.
Applications of 1.12 (1.0 lb ai/A) and 2.24 (2.0 lb ai/A) kg/ha were made on forest plots
in Oregon. Extensive inhibition of brain ChE activity (commonly at 30-50%) for up to
33 days for 11 of the 12 species of birds that were collected was observed. The highest
frequency of ChE inhibition was observed on day two post spray. Two species of birds
had observable population decreases. Some birds on the plots treated with 1.12 kg/ha had
65%) ChE inhibition which is thought to be fatal. At both plots, birds were found with
coordination problems, salivating profusely, and inability to fly. These behaviors were
observed up to 20 days after application in the 2.24 kg/ha plot. It was also observed that
breeding pairs for the warbling vireo and yellow-rumpled warbler were decreased. The
authors hypothesized that application of acephate at rates of 1.12 and 2.24 kg/ha can
cause sickness and death to forest birds.
MRID 00093909. (McEwen, 1981) Site:WY, UT and AZ rangeland. In 1979 and 1980,
the birds and small mammals collected up to 24 days after application had reduced ChE
activity. Reduction of 20% or more is indicative of exposure to brain ChE inhibitor. Of
the birds collected in AZ, 24.5% had reduced ChE activity >20%. The birds with the
most ChE inhibition were the last ones collected (21-24 days post treatment). In 1981,
horned larks and lark buntings were collected in WY on a 12,000 acre plot that was
treated with acephate at the rate of 0.105 kg/ha. More than 20% ChE inhibition was
found in 19% of the horned larks and 25% of the lark buntings. Deer mice were also
collected in WY. They were found to have ChE inhibition that ranged from 12.1% to
14.6%.
4.1.5. Toxicity to Mammals
Rat or mouse toxicity values are obtained from the Agency's Health Effects Division
(HED) as substitute for wild mammal testing. Toxicity data on small mammals are used
in this assessment to assess the effect of acephate exposure on their availability as food
items for the CRLF. While the relative percent composition of mammal in the frog's diet
is uncertain, gut content studies have found the CRLF gut to contain 50% mammal
content (USFWS, 2002). It is necessary to consider the affect of acephate on this
potentially significant food source, as population level effects to mammals may result in
indirect effects to the CRLF. Additional information can be found in Appendix A.
4.1.5.1. Mammals: Acute Exposure (Mortality) Studies
78
-------
Mammalian toxicity studies reviewed by the Agency indicate that acephate is
characterized as moderately toxic to small mammals on an acute oral basis (LD50=866
mg/kg bw, rat, MRID 00014675; LD50=321 mg/kg bw, meadow vole, Rattner and
Hoffman, 1984). However, for the degradate, toxicity studies indicate that
methamidophos is highly toxic to small mammals on an acute oral and dermal basis
(MRID 00014044, 00014047, 00014048).
The meadow vole appears (by numbers alone) to be more sensitive than the rat. In order
to provide the vole toxicity input into the T-REX exposure model, the LD50 value needs
to be adjusted. Below are the steps to compute the adjusted value.
In order for the terrestrial exposure and the LD50 toxicity value for mammals to be
imputed into the T-REX model for determination of RQ to mammals, the LD50 value of
the meadow vole must be converted to an adjusted LD50. The dose-based LD50 (mg/kg-
bw) or NOAEL (mg/kg-bw) values from acceptable or supplemental toxicity studies are
adjusted for the size of the animal tested compared with the size of the animal being
assessed (e.g., 350-gram rat) are relative to the animal's body weight (mg residue/kg bw)
because consumption of the same mass of pesticide residue results in a higher body
burden in smaller animals compared with larger animals. Adjusted mammalian LD50s
(mg/kg-bw) are used to calculate dose-based acute risk quotients for 15-, 35-, and 1000-
gram mammals. The following equations are used for the adjustment (U.S. EPA 1993):
Adjusted mammalian LD50 where:
( TW) (a2S)
Adj. NOAEL or LDS0 = NOAEL or LD5oy-j^J
Adj. LD50 = adjusted NOAEL or LD50 (mg/kg-bw)
LD50 = endpoint reported from mammal study (mg/kg-bw)
TW= body weight of tested animal (35g vole)
AW= body weight of assessed animal (350 g rat)
Thus, the meadow vole LD50 of 321 mg/kg-bw x (35g/350)0'25 = 180.5 mg/kg-bw =
adjusted LD50 for meadow vole input for T-Rex exposure model.
The meadow vole adjusted LD50 is more sensitive than the rat LD50 (866 mg/kg-bw).
Therefore the meadow vole LD50 will be the value use in the T-REX terrestrial exposure
model.
4.1.5.2. Mammals: Chronic Exposure (Reproduction) Studies
Laboratory data indicate that acephate and its degradate, methamidophos, may pose
chronic risk to mammals by affecting the reproductive capacity of mammals. Acephate
fed to female rats at 500 ppm were found to have significant adverse effects when
compared to controls of parental and pup body weight, food consumption, litter size, and
mating performance and viability. The NOEL for the rat reproductive study is 50 ppm
(MRID 40323401, MRID 40605701).
79
-------
4.1.5.3 Mammals: Sublethal Effects and Additional Open Literature
Information
ECOTOX 39518, MRID 40329701. (Zinkl, 1980,). There is a marked inhibition of brain
ChE activity in squirrels after aerial treatment of forests at rates of 0.57 kg/ha (0.51 lb/A)
of Orthene but no mortality noted.
ECOTOX 35459, Stehn, 1976. Increased ingestion of arthropods by insectivorous
mammals has been reported following acephate application. This signifies a direct
pathway for substantial exposure to acephate due to consumption of dead and dying
insects.
4.1.6 Toxicity to Insects
Toxicity data on insects are used in this assessment to assess the effect of acephate
exposure on their availability as food items for the CRLF. Insect toxicity from open
literature shows that acute ecotoxicity endpoints are generally less sensitive than the
registrant submitted bee studies. Additional information can be found in Appendix A.
4.1.6.1. Acute toxicity to bees
Analysis of the results of honey bee acute contact studies indicate that acephate is highly
toxic to bees and beneficial insects on an acute contact basis (MRID 00014714, MRID
44038201). The study indicated an LDsoof 1.2 ug/honey bee. Further studies indicated
that acephate is highly toxic to bees from two hours to 96 hours after foliar application at
rates of 1 lb/A and from 2 hours to 24 hours at 0.5 lb ai/A rate (Appendix A).
EPA also reviewed a study (MRID 05004012) that tried to determine a toxicity ratio of
acephate. By comparing the sensitivity of beneficial predator insects to that of the pest
tobacco budworm, one would be able to determine the selectivity of toxicity to the
beneficial or pest insect. The ratio is calculated using the LC50 values for the pest divided
by the LC50 values for the beneficial insect; a ratio greater than 1 represents that acephate
is more toxic to the predator than to the pest. Green lacewing had a calculated ratio of
6.4 and the ratio for the parasitic wasp was 10.0. Acephate is more toxic to these two
beneficial predators than it is to the pest.
An acute contact toxicity study for methamidophos, a degradate of acephate, on bees
indicates that methamidophos is highly toxic to bees on an acute contact basis (MRID
00036935). The LDsowas 1.37 ug/bee.
4.1.6.2 Insects: Sublethal Effects and Additional Open Literature
Information
80
-------
ECOTOX 35475. Stoner,1985. All bee colonies that were fed 10 ppm acephate lost
queens early in the study and the affected colonies were unable to rear new queens.
Acephate appears to be systemic in nurse bees, causing glandular secretions fed to queens
to be toxic. The study implied infrequent encounters by honey bee foragers with
acephate on crops at levels of 1 ppm (1 ppm is NOAEC level) or less should be harmless.
However, foragers may be expected to encounter levels greater than 1 ppm in the field
because of 6-9 day residue persistence and residual systemic activity of acephate in plants
for up to 15 days. Acephate fed to worker bees via sugar syrup showed up in the royal
jelly for the queen, indicating that acephate is systemic to bees. Although these
concentrations of 1 ppm or less were harmless to the worker bees, levels at 0.1 ppm
showed significant reduction of the surviving brood. Consequently, the study concluded
that acephate is a hazard to honey bees because of its high contact toxicity, and because
of its systemic nature.
MRID 00099762. (Johansen, 1977). Orthene was found to be more detrimental to honey
bee populations than carbaryl. Brood cycles of some colonies were found to be
permanently broken, and all of the bees were dead within 45-48 days after exposure.
Depression in the numbers of wild foraging bees at all treated plots was apparent.
Measured seed and fruit production of northern bluebells (Mertensiapaniculata) were
significantly reduced from lack of pollination due to acephate when compared to control.
MRID 00099763. (Johansen, 1977). Severe impacts on yellow jacket wasps and ants at
rates of application of 1 and 2 lb ai/A sprayed on forest. Temperature seems to affect the
exposure of wasps in that cooler temperature (39°F) causes wasps not to forage out of
nests and therefore not be exposed as much, whereas warmer temperatures (59°F)
increases the activity of wasps and the exposure to acephate.
4.1.7. Summary of Effects Assessment
Of the numerous studies evaluated, the lowest, and therefore most sensitive, toxicity
endpoint was chosen to assess the possibility of direct or indirect effect to the frog, as
determined by calculation of the RQ.
4.1.7.1 Direct Effects
The acute mortality endpoint for the rainbow trout, with a 96-hr LC50 = 1 lOppm ai, is the
most sensitive value of the available data, and will be used as a surrogate (measurement
endpoint) for calculating direct effects (risk) to the aquatic-phase frog. Because there
were no data available for chronic toxicity associated with long term (relative to life-
cycle) exposure, an acute to chronic ratio was calculated using the relationship between
the acute and chronic toxicity of other organophosphate pesticides, as described above.
The chronic exposure endpoint for the aquatic phase of the frog life-cycle is estimated to
be 0.150 ppm for the rainbow trout.
81
-------
There are three avian toxicity tests used to calculate the risk to the terrestrial phase of the
CRLF. For acute exposure, the mortality endpoint for dark eyed junco, LD50=106
mg/kg-bw was used. Dietary effects were calculated based on data from tests with the
Japanese quail, LC50=718 ppm. Finally, risks due to chronic exposure were calculated
using the exposure level where no effects to embryo mortality were observed for chronic
exposure of the mallard duck to acephate, NOAEL= 5 ppm.
4.1.7.2. Indirect Effects
Based on the life history of the frog, impacts to CRLF prey or habitat could indirectly
affect the CRLF. To assess the risk of indirect effects from prey, the toxicity endpoints
for small mammals, birds (other frogs as food item), terrestrial arthropods, and aquatic
invertebrates were used.
The most sensitive acute mammal endpoint is mortality of the rat upon acute exposure to
acephate, LD50=866 mg/kg-bw. The most sensitive mammalian reproduction endpoint is
adverse affects to parental and pup weight, food consumption, litter size, mating
performance and viability upon chronic exposure of a rat to acephate, NOAEL=50
mg/kg-bw.
The most sensitive acute endpoint is mortality of the dark eyed junco, LD50=106 mg/kg-
bw was used. Dietary effects were calculated based on data from tests with the Japanese
quail, LC5o=71 8 ppm. Finally, risks due to chronic exposure were calculated using the
exposure level where no effects to embryo mortality were observed for chronic exposure
of the mallard duck to acephate, NOAEL= 5 ppm.
The most sensitive acute aquatic invertebrate endpoint is the daphnid 48-hr EC5o=l .l
ppm a.i. and the chronic endpoint used to estimate risk to aquatic prey items is the
daphnid NOAEC= 0.015 ppm.
Acephate is highly toxic to bees up to 96 hours after foliar application. Comparative
toxicity between beneficial and non-beneficial insects shows that Acephate may be more
harmful to beneficial insects than insect pests.
4.1.7.3. Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern
The Agency uses the probit dose response relationship as a tool for providing additional
information on the potential for acute direct effects to individual listed species and
aquatic animals that may indirectly affect the listed species of concern (U.S. EPA, 2004).
As part of the risk characterization, an interpretation of acute RQ for listed species is
discussed. This interpretation is presented in terms of the chance of an individual event
(i.e., mortality or immobilization) should exposure at the EEC actually occur for a species
with sensitivity to acephate on par with the acute toxicity endpoint selected for RQ
calculation. To accomplish this interpretation, the Agency uses the slope of the dose
response relationship available from the toxicity study used to establish the acute toxicity
82
-------
measures of effect for each taxonomic group that is relevant to this assessment (i.e.,
freshwater fish used as a surrogate for aquatic-phase amphibians and freshwater
invertebrates). 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.
Individual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.1
(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP,
Environmental Fate and Effects Division (June 22, 2004). The model allows for such
calculations by entering the mean slope estimate (and the 95% confidence bounds of that
estimate) as the slope parameter for the spreadsheet. In addition, the acute RQ is entered
as the desired threshold.
4.1.7.4. Review of Ecological Incident Information System (EIIS)
In general, although there are many reported incidents of toxic effects to non-target plants
and animals from acephate, the majority of these reports are not clearly documented or
else acephate was applied in combination with other pesticides and it is not possible to
determine which pesticide primarily caused the undesirable effect. A more detailed
account of these reports can be found in Appendix C. The majority of acephate specific
incidents reported were associated with bee kills. Some reports were also associated with
bird and fish kills, and damage to plants, but the exact causes of the reported incidents are
uncertain.
The EIIS database show the following reported incidents that are associated with
acephate use. More details of the incidents can be found in Appendix C. The two avian
incidents have a probable certainty incident. The plant incidents are localized residential
uses with a mixture of other active ingredients and in an aerosol container. Fish incidents
are not reported below but can be found in Appendix C. In each of the incidents, the fish
kills resulted from a mixture of other active ingredients that are known to be more toxic
to fish than acephate.
Avians -
1998 in SC - 24 dead boat-tailed grackles collected and methamidophos residues found
within them attributed to acephate use on fire ants
83
-------
2005 in GA - 50 boat-tailed grackles were found dead. Acephate residues found within
some of them. Acephate was used to control fire ants.
Plant Injury -
There are no data or information available to ascertain the extent of the damage or the
type of damage for the plants. Thus it is not known whether acephate caused the damage.
There are some alleged mortalities for plants from the use of a rose and spray mixture. It
is not certain as to whether the mixture caused the mortalities since the data reported to
EPA is very sparse.
1994 in PA - Orthenex Rose and Flower Spray (aerosol) is alleged to have cause damage
to ornamentals and/or flowers.
1998 in FL - There was an allegation of plant damage from the use of Ortho Systemic
Rose and Floral Spray on ornamentals.
1998 in PA - There was an allegation of plant damage from the use of Ortho Orthenex™
Insect and Disease Control Formula III on ornamentals.
1999 in DC - There was an allegation of plant damage from the use of Isotox Insect
Killer Formula IV. Product was sprayed on a dwarf Alberta pine with the results that the
pine is dying.
1999 in IN - There was an allegation of plant damage from the use of Ortho Orthenex™
Insect and Disease Control Formula III on ornamentals. The report indicated that the
flowering almond and hibiscus were dying.
1999 in TX - There was an allegation of plant damage from the use of Ortho Orthenex™
Insect and Disease Control Formula III on ornamentals. There was an allegation of plant
damage from the use of Ortho Orthenex™ Insect and Disease Control Formula III on
ornamentals. The report indicated that the homeowner applied this product on 40 - 50
bushes used as hedge per recommendation of county extension agent. About 95% of the
bushes died.
1999 in GA - There was an allegation of plant damage from the use of Ant-Stop
Orthene™ Fire Ant Kill. Product was applied on spots of the lawn resulting in "burnt
spots".
Bee Kills
Washington State reported 7 incidents of bee kills from 1992 to 2002. Most of the
incidents indicate that 40 to 60 colonies were killed off per incident.
84
-------
85
-------
5. Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations to
determine the potential ecological risk from varying acephate 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 3.3 through 3.8) and the appropriate toxicity endpoint (see Tables 2.7,
4.1, 4.2). 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 E describes the categories of toxicity.
Table 5.1. Levels of Concern for Terrestrial and Aquatic Organisms
Taxa
Acute LOC
Chronic LOC
Avian1 (terrestrial phase amphibians)
0.1
1
Mammalian2
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
2LD50andNOEC
3 EC25
4 LC/EC50 and estimated and reproductive NOEC
5 LD50 per EFED's CRLF Steering Committee
Aquatic screening level RQs are based on the most sensitive endpoints and modeled
surface water concentrations from the following scenarios of acephate: citrus, cotton,
lettuce, row crops (beans, celery, peppers), turf (landscape maintenance), almond
(surrogate for pistachio), fruit trees, and cole crops (broccoli, cauliflower, Brussels
sprouts).
5.1.1 Aquatic Direct and Indirect Effects
5.1.1.2 Direct Effects
There is no direct acute risk to CRLF aquatic-phase from the use of acephate. Tier 1
EECs (Table 3.3) were below the LOC. The very low RQs (Tables 5.2, 5.3) for direct
effects to fish (surrogate for CRLF) indicate that direct effects are not expected even for
86
-------
applications much higher than the maximum labeled rate. Therefore, a Tier 2 analysis
was not conducted for fish.
5.1.1.3 Indirect Effects
Indirect risk to aquatic phase CRLF is driven by acephate use on cotton and almond with
an acute RQ of 0.13 for prey items (aquatic invertebrates, Table 5.5).
The only acute RQs above the LOC in the aquatic phase were for invertebrates exposed
to methamidophos as a degradate of acephate (estimated as 18% of the modeled acephate
EEC). This suggests that the CRLF may be at indirect risk in the aquatic phase due to
reduction in prey base (invertebrates). Aquatic plant RQ were also below LOC, therefore
no indirect effects mediated via aquatic plants are expected, either as they affect food
supply or habitat.
Chronic effects to all aquatic taxa were below LOC for both parent acephate and
its degradate methamidophos.
Table 5.2. Tier 1 Acute Risk Quotients for Acephate
Use
EEC
RQs for Direct
and Indirect
Effects,
Rainbow trout,
LC50 = 832,000
ppb
RQs Indirect
Effects, Prey
Item: Daphnia
magna, ECS0 =
1,110 ppb
RQs Direct
Effects, Green
JrogLDso =
6,433,000 ppb
Cotton, Aerial,
6 applications
of 1 lb/acre
spaced at 3
days
Peak, 85.4 ppb
<0.05
0.08 *
<0.05
* Exceeds LOC of 0.05
Table 5.3. Tier 1 Chronic Risk Quotients for Acephate
Use
Chronic RQ
Cotton, Aerial, 6
applications of 1 lb/acre
spaced at 3 days
EEC
RQs for Direct and
Indirect Effects,
Rainbow trout, NOAEC
= 5,800 ppb
RQs Indirect Effects,
Prey Item: Daphnia
magna, NOAEC =150
ppb
21-day, 43.6 ppb
60-day, 18.4 ppb
<0.05
2.9 *
* Exceeds LOC of 1.0
87
-------
Table 5.
Risk Quotients: Acute Aquatic Acephate Exposure (Tier 2)
Crop/Use
Application
Method (Air/
Acephate
Peak
RQs for
Direct and
RQs
Indirect
RQs
Direct
Ground)
EEC
Indirect
Effects,
Effects,
(PPb)
Effects,
Rainbow
trout, LCS0
= 832,000
ppb
Prey Item:
Daphnia
magna, ECS0
= 1,110 ppb
Green frog
ld50 =
6,433,000
ppb
Citrus
G
0.55
Cotton
A
19.2
G
13.4
Lettuce
A
16.7
G
15.0
Row Crop (beans,
A
9.7
celery, peppers)
G
5.9
Turf
(Bermudagrass
for seed)
A
4.5
<0.05
<0.05
<0.05
G
2.5
Almond
A
18.1
(pistachio)
G
12.9
Fruit trees
A
14.0
G
7.3
Cole Crops
A
13.4
G
11.3
Table 5.5. Risk Quotients: Acute Aquatic Methamidophos (Acephate degradate)
Exposure (Tier 2)
Crop/Use
Applicati
on
Acephate
Peak
Methamidoph
as Adjusted
RQ for
Indirect
RQ for Direct
and Indirect
Method
EEC
Peak EEC
Effects,
Effects, Aquatic
(Air/
Ground)
(PPb)
(PPb)
Prey Item:
Daphnia
magna(EC50
= 26 ppb)
Life Phase:
Rainbow trout
(LC50 = 25,000
ppb)
Citrus
G
0.55
0.099
<0.05
Cotton
A
19.2
3.46
0.13
G
13.4
2.41
0.09
Lettuce
A
16.7
3.00
0.12
G
15.0
2.70
0.10
Row Crop (beans,
A
9.7
1.75
0.067
celery, peppers)
G
5.9
1.06
<0.05
Turf
A
4.5
0.81
<0.05
<0.05
(Bermudagrass for
seed)
G
2.5
0.45
<0.05
Almond
A
18.1
3.26
0.13
(pistachio)
G
12.9
2.32
0.089
Fruit trees
A
14.0
2.52
0.097
G
7.3
1.31
0.0504
Cole crops
A
13.4
2.41
0.093
G
11.3
2.03
0.078
EEC=Expected Environmental Concentration; ppb=Parts per billion; Risk Quotients (RQ) in bold type exceed LOC
88
-------
Table 5.6. Risk Quotients: Chronic Aquatic Exposure to Acephate and
Crop/Use
Application
Method (Air/
Acephate
EEC (ppb)
Methamidophos
EEC (ppb)
RQs for Direct Effects
Rainbow Trout
RQs for Indirect Effects
Daphnia
Ground)
21-
day
60-
day
21-day
60-day
Acephate
NOAEC
=5,800
(ppb)
Meth.
NOAEC
=0.1736
(ppb)
Acephate
NOAEC
=150
(ppb)
Meth.
NOAEC
=4.5 (ppb)
Citrus
G
0.33
0.20
0.06
0.04
Cotton
A
12.8
6.7
2.30
1.21
G
7.5
3.5
1.35
0.63
Lettuce
A
10.7
5.0
1.93
0.9
G
9.0
4.1
1.62
0.74
Row
A
5.3
2.4
0.95
0.43
Crop
G
3.3
1.5
0.59
0.27
Turf
A
2.7
1.3
0.49
0.23
< 1
< 1
< 1
< 1
G
1.6
0.76
0.29
0.13
Almond
A
13.6
7.5
2.45
1.35
G
8.1
4.0
1.46
0.72
Fruit
A
9.7
5.0
1.75
0.9
Trees
G
4.6
2.1
0.83
0.38
Cole
A
9.0
4.4
1.62
0.79
Crops
G
7.1
3.4
1.28
0.61
5.1.2 Terrestrial Phase Direct Effects
Maximum usage of acephate (cotton)
Direct acute risk to terrestrial-phase of CRLF is driven by acephate use on cotton with an
acute RQ of 0.34 to 6.82 (dose-based) and 0.07 to 0.66 (dietary based, Table 5.7). Direct
chronic risk to CRLF terrestrial-phase is driven by acephate use on cotton with RQs
ranging from 10 to 94.
Exposures and RQ values for terrestrial organisms are given in the T-REX output below.
The CRLF is represented by a bird ("avian") of 20 or 100 grams body weight, which
consumes small insects or large insects. Acute, dose-based RQs are reported by the size
of the animal and their diet. The acute RQs ranges from 0.34 for a 100-gram frog
consuming large insects to 6.82 for a 20-gram frog consuming small insects, respectively.
These RQs are above the Listed Species LOC, 0.1. Dietary-based acute RQs are above
the LOC for small insects only (RQ = 0.66).
Chronic risk to the CRLF is also represented by the avian taxa. Chronic RQ for birds
eating small insects and large insects range from 10 to 94, well above the LOC (1).
89
-------
Minimum usage of acephate (sewage disposal)
For the minimum exposure of CRLF, (sewage disposal areas, Table 5.8), dose-based
acute RQs are above LOC (0.1) for consumption of small insects. The chronic dietary
RQ is also above LOC for the CRLF.
Tables 5.7 and 5.8 provide the RQs for direct and indirect effects to the CRLF.
Table 5.7. T-REX Inputs for Analysis of Direct and Indirect Effects to CRLF (Maximum
Chemical Name:
Acephate
Use
Cotton
Formulation
Orthene 75
Application Rate
1 lbs a.i./acre
Half-life
8.2 days
Application Interval
3 days
Maximum #
Apps./Year
6
Length of Simulation
1 year
Table 5.7a Dietary-based EECs (ppm)
Kenaga
Values
Short Grass
837.5
Tall Grass
383.9
Broadleaf plants/sm Insects
471.1
Fruits/pods/seeds/lg insects
52.3
Table 5.7b
RQs associated with Direct Effect as Represented by Avian s
pedes, as surrogate for the CRLF
20 g Acute
Dose-based
100 g Acute
Dose-based
Acute
Dietary
Chronic Dietary
Broadleaf plants/sm insects
6.8
3.1
0.66
94.2
Fruits/pods/seeds/lg insects
0.76
0.34
0.07
10.5
Table 5.7c Indirect Effects as Represented by Prey Item - RQs
15 g
Mammal
15 g
Mammal
Dietary-
based
20 g Avian
Acute Dose-
based
Avian
Avian
Dose-based
Dose-based
Mammal
Acute
Chronic
Acute
Chronic
Chronic RQ
Dietary
Dietary
Short Grass
2.01
145.3
16.8
12.15
1.17
167.5
Tall Grass
0.92
66.6
7.7
5.57
0.53
76.77
Broadleaf
plants/sm insects
1.13
81.7
9.4
6.83
0.66
94.22
Fruits/pods/lg
insects
0.13
9.08
1.1
0.76
0.07
10.47
90
-------
Table 5.8.
T-REX Inputs for Analysis of Direct
Sewage Disposal)
Chemical Name:
Acephate
Use
Sewage disposal
Formulation
Orthene 75
Application Rate
0.13 lbs a.i./acre
Half-life
8.2 days
Application Interval
na
Maximum #
Apps./Year
1
Length of Simulation
1 year
Indirect Effects to CRLF (Minimum Use,
Table 5.8a Dietary-based EECs (ppm)
Kenaga
Values
Short Grass
31.2
Tall Grass
14.3
Broadleaf plants/sm Insects
17.55
Fruits/pods/seeds/lg insects
1.95
Table 5.8b
20 g Acute
Dose-based
100 g Acute
Dose-based
Acute
Dietary
Chronic Dietary
Broadleaf plants/sm insects
0.25
0.11
0.02
3.5
Fruits/pods/seeds/lg insects
0.03
0.01
<0.01
0.39
Table 5.8c Indirect Effects as Represented by Prey Item - RQs
15 g
Mammal
15 g
Mammal
Dietary-
based
20 g Avian
Acute Dose-
based
Avian
Avian
Dose-based
Dose-based
Mammal
Acute
Chronic
Acute
Chronic
Chronic RQ
Dietary
Dietary
Short Grass
0.07
5.41
0.62
0.45
0.04
6.24
Tall Grass
0.03
2.48
0.29
0.21
0.02
2.86
Broadleaf
plants/sm insects
0.04
3.05
0.35
0.25
0.02
3.51
Fruits/pods/lg
insects
<0.01
0.34
0.04
0.03
<0.01
0.39
5.1.3. Individual Effects Calculation for Direct Acute Effect on CRLF
The risk of mortality to the CRLF is based on the avian (bird) taxon in T-REX, where the
CRLF is represented by a 20-gram or 100-gram bird that consumes small insects or large
insects. The individual chance of effects is calculated from the probit-slope response
relationship, using an Excel spreadsheet (IEC vl.l, June 22, 2004).
The acute toxicity data used is for the bobwhite quail. The bobwhite LD50 is 109 mg/kg-
body weight. Individual effect probabilities were calculated for the cotton scenario (six
91
-------
applications of 1 lb a.i./acre spaced at 3 day intervals). A lower application rate, as is
applied to sewage disposal areas, was modeled at a rate of 0.13 lb/A. The results are
shown in Table 5.9.
Table 5.9a. Individual Effects Chance for Mortality of CRLF
Exposure scenario
TREX risk quotient
Chance of effect (1-in-...)
Listed Species Threshold
(LOC, 0.1)
9.38 E+ll
Cotton, 20-g bird, small
insects (max exposure)
6.8
Approaching 1
Cotton, 100-gbird, small
insects (max exposure)
3.1
Approaching 1
Cotton, 20-g bird, large
insects (max exposure)
0.76
3.38
Cotton, 100-gbird, large
insects (max exposure)
0.34
57
0.13 lb/A, 20-g bird, small
insects (min. exposure)
0.25
297
0.13 lb/A, 100-gbird, large
insects
0.03
2.76E+11
0.13 lb/A, 20-g bird, small
insects
0.11
1.25E+5
0.13 lb/A, 100-gbird, large
insects
0.01
8.86E+18
Table 5.9b. Individual Effects Probability Calculation for Prey Items
Organism
slope
Threshold (LOC or
RQ)
Chance of Effect, 1
in ...
Daphnia magna at
LOC
0.05 (LOC)
4.18E+8
Daphnia magna at
maximum RQ
4.5 (default)
0.13 (RQ)
2.99E+4
Honey bee at LOC
0.05 (LOC)
4.18E+8
Honey bee, Large
insect RQ (cotton)
5 .5 (RQ)
1
Honey bee, Small
insect RQ (cotton)
50 (RQ)
1
Honey bee, Large
insect RQ (sewage)
0.2
1,210
Honey bee, Small
insect RQ (sewage)
1.86
1.13
15 gm mammal at
LOC
0.1 (LOC)
2.94E+5
15 gm mammal at
RQ
1.13 (RQ)
1.68
92
-------
These results show that the risk to an individual CRLF is high (approaching 100%
mortality) if exposed to the maximum cotton exposure scenario, and consuming a diet of
small insects. Risks are also large for a diet of large insects (l-in-3.38, or 30% for the
20-g bird, and l-in-57, or 1.75% for the 100-g bird).
For the low exposure scenario (0.13 lb/acre, applied once) the risk is appreciable for a 20-
g bird consuming small insects (l-in-297, or 0.34%).
The lowest RQ that gives an individual chance of effect approaching 100% is 3.1. The
RQ for 20-g birds consuming small insects, if exposure is 2 applications of 1 lb a.i./acre,
spaced at 3 day intervals, is 3.42.
These results indicate that the chance of individual mortality for a CRLF, as represented
by 20-g and 100-g birds, is considerable even for low application rates (0.34%) and
approaches 100% at exposures well below the maximum allowed on the label.
5.1.4. Indirect Effects, Terrestrial Phase
Indirect effects on the CRLF in the terrestrial phase of its life cycle might be due to loss
of prey (insects, small mammals, small frogs, small birds) or effects on plants that
provide habitat. Because no adverse effects on terrestrial plants are expected, no indirect
effects on the CRLF mediated via plants are expected.
Small mammals and frogs that might be eaten by the CRLF are represented in the TREX
analysis as the 15-gram mammal and the 20-g bird, respectively. Both prey items are
assumed to eat short-grass food items, as this provides the highest dose, and therefore the
most protective assessment.
5.1.4.1 Acute Effects
The small mammal RQ is 0.49 (Table 5.7), and the small bird RQ is 12.1 (Table 5.7),
both above the LOC of 0.1 for Listed species. The dietary-based RQ (Table 5.7) is 1.2
for birds (above LOC), and was 16.7 for mammals (Table 5.9).
Acute effects on insects are calculated (Appendix L) using the acute contact LD50 for the
honey bee (1.2 micrograms per bee) divided by 0.128 grams body weight, to obtain an
LD50 in ppm. Exposures are the small insect and large insect from the TREX dietary
analysis. The LD50 is then (1.2 micrograms)/(0.128 grams) = 9.4 ppm. The dietary-
based EECs are 471 ppm (small insect) and 52 ppm (large insect). The resulting RQ
values are 50 and 5.5, respectively, and are well above the LOC for terrestrial
invertebrates (0.05).
93
-------
5.1.4.1. Chronic Effects
The chronic avian RQ is 167 (Table 5.7) , and the chronic mammal RQ is 145 (dose-
based, Table 5.9) or 17 (dietary-based, Table 5.9). All of the RQs are above the LOC (1).
Based on these RQ values, it is presumed that the CRLF will be indirectly affected by
adverse effects (both acute and chronic) on animals in its prey base.
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 acephate'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:
• 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.
94
-------
• 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 5.2.1 through 5.2.3.
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 over laid
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 both
acute and chronic effects (Tables 5.2 thru 5.6).
5.2.1.2. Terrestrial Phase (Direct Effects)
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 5.7 and 5.8).
Acute RQs range from 0.34 to 6.8 for CRLF for maximum exposure from cotton (1 lb
ai/A applied 6 times with 3 day interval) and from 0.11 to 0.25 (small insect food source)
for a minimum exposure of 0.13 lb ai/A applied once onto sewage disposal areas. RQs
for large insect food source are below LOC (0.1). Chronic RQs range from 10 to 94 for
CRLF for maximum exposure from cotton (1 lb ai/A applied 6 times with 3 day interval)
and from 0.39 to 3.5 for a minimum exposure of 0.13 lb ai/A applied once onto sewage
disposal areas. Both mortality and adverse reproductive effects to the CRLF (from a
small insect diet) are anticipated based on labeled uses of acephate and risk quotients.
RQs for CRLF from large insect diet are below acute and chronic LOC.
Refinement of RQ for CRLF terrestrial phase
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 in this guidance) tend to have much
95
-------
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.
There is a current need to evaluate dietary exposure to terrestrial-phase amphibian species
(e.g., California Red-Legged Frog, CRLF) and an anticipated need to evaluate dietary
exposure for amphibians and reptiles in the future for the purpose of conducting
endangered species effects determinations. Therefore, T-REX (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.
A comparison is made between the T-REX model which uses the bird as a surrogate for
the CRLF and the T-HERPS model which calculates the allometric functions for
amphibians.
Cotton (maximum exposure) Discussion
T-REX model shows that the ranges of direct affects to birds as surrogate for CRLF is
from 0.34 to 6.8 for dose-based acute, from 0.07 to 0.66 (LOC for listed terrestrial
animals) for dietary acute, and from 10 to 94 for chronic dietary.
T-HERPS model show the ranges of RQ for amphibians that was corrected for body
weight, metabolic rates and caloric intake requirements from avian data. The ranges of
RQ for T-HERPS is from <0.01 to 4.8 (LOC for listed terrestrial animals) for the dose-
based acute, 0.02 to 1.17 for dietary acute, and from 8.3 to 168 for chronic dietary.
The refinement of cotton models show a slight decrease in RQs in T-HERPS. All the
chronic LOCs for CRLF is exceeded and many of the acute LOCs are exceeded (see
Tables 5-10 and 5-11).
96
-------
Sewage Disposal Areas (minimum exposure) Discussion
T-REX model shows that the ranges of direct affects to birds as surrogate for CRLF is
from 0.11 to 0.25 (small insect diet) for dose-based acute, <0.05 (LOC for listed
terrestrial animals) for dietary acute, and from 0.39 to 3.5 for chronic dietary.
T-HERPS model show the ranges of RQ for amphibians that was corrected for body
weight, metabolic rates and caloric intake requirements from avian data. The only the
small herbivore mammal diet RQ for T-HERPS exceeds the LOC with an RQ of 0.18,
from <0.01 to 4.8 (LOC for listed terrestrial animals) for the dose-based acute, all of
dietary acute RQs is below LOC, and from 4 of the 7 food items are above LOC for
chronic dietary.
The refinement of sewage disposal areas models show a slight decrease in RQs in T-
HERPS. For four out of seven food items, the chronic LOCs for CRLF is exceeded
and only the small herbivore mammal diet RQ exceeds the acute LOC (see Tables 5-
10 and 5-11).
Results of the T-HERPS model are below:
97
-------
Table 5-10 Summary of T-HERPS Risk Quotient Calculations Based on Upper
Bound Kenaga EECs for cotton (Maximum Exposure)
Acute and Chronic RQs are based on the Upper Bound
Kenaga Residues.
The maximum single day residue estimation is used for
both the acute and reproduction RQs.
RQs reported as "O.OO" in the RQ tables below should be noted «
<0.01 in your assessment. This is due to rounding and significa
figure issues in Excel.
Endpoints
Bobwhite quail
LD50 (mg/kg-bw)
109.00
Avian
Japanese Quail
LC50 (mg/kg diet)
718.00
Bobwhite quail
NOAEL(mg/kg-bw)
0.00
Mallard duck
NOAEC (mq/kq diet)
5.00
Dietary-based EECs (ppm)
Kenaqa
Values
Short Grass
837.49
Tall Grass
383.85
Broad leaf plants/sm Insects
471.09
Fruits/pods/seeds/lq insects
52.34
Small herbivore mammals
551.86
Small insectivore mammals
34.49
Small terrestrial phase amphibians
16.35
Terrestrial Herpetofauna Results
Weight
Body
Ingestion (Fdry)
Ingestion (Fwet)
% body wgt
Fl
Class
Weight (g)
(g bw/day)
(g/day)
consumed
(kg-diet/day)
Small
1.4
0.017
0.1
3.9
5.44 E 05
Mid
37
0.212
1.4
3.8
1.41 E-03
Larqe
238
0.893
6.0
2.5
5.96 E 03
Body
Adjusted LD50
Weight (g)
(mg/kg-bw)
1.4
109.00
37
109.00
238
109.00
Dose-based EECs
(mg/kg-bw)
Herpetofaunal Size Classes and Body Weights
small (q)
mid (q)
large (g)
1.4
37
238
Short Grass
32.54
31.98
20.96
Tall Grass
14.91
14.66
9.61
Broadleaf plants/sm Insects
18.30
17.99
11.79
Fruits/pods/seeds/lq insects
2.03
2.00
1.31
Small herbivore mammals
N/A
522.03
81.16
Small insectivore mammals
N/A
32.63
5.07
Small terrestrial phase amphibian
N/A
0.62
0.41
Dose-based RQs
(Dose-based EEC/adjusted LD50)
Amphibian/Reptile Acute RQs for Small, Medium, and
Large Species (grams)
1.4
37
238
Short Grass
0.30
0.29
0.19
Tall Grass
0.14
0.13
0.09
Broadleaf plants/sm insects
0.17
0.17
0.11
Fruits/pods/seeds/lq insects
0.02
0.02
0.01
Small herbivore mammals
N/A
4.79
0.74
Small insectivore mammals
N/A
0.30
0.05
Small terrestrial phase amphibian
N/A
0.01
0.00
Dietary-based RQs
(Dietary-based EEC/LC50 or
RQs
Acute
Chronic
Short Grass
1.17
167.50
Tall Grass
0.53
76.77
Broadleaf plants/sm Insects
0.66
94.22
Fruits/pods/seeds/lq insects
0.07
10.47
Small herbivore mammals
0.77
110.37
Small insectivore mammals
0.05
6.90
Small terrestrial phase amphibian
0.02
3.27
Note: To provide risk management with the maximum possible information,
it is recommended that both the dose-based and concentration-based
RQs be calculated when data are available
Upper Bound Kenaga Residues For RQ Calculation
Chemical Name:
Acephate
Use
Cotton
Formulation
Orthene
Application Rate
1 lbs a.i./acre
Half-life
8.2 days
Application Interval
3 days
Maximum #Apps./Year
6
Length of Simulation
1 year
98
-------
Table 5-11 Summary of T-HERPS Risk Quotient Calculations Based on Upper
Bound Kenaga EECs for sewage disposal areas (Minimum Exposure)
Acute and Chronic RQs are based on the Upper Bound
Kenaga Residues.
The maximum single day residue estimation is used for
both the acute and reproduction RQs.
RQs reported as "0.00" in the RQ tables below should be noted as
<0.01 in your assessment. This is due to rounding and significant
figure issues in Excel.
Endpoints
Bobwhite quail
LD50 (mg/kg-bw)
109.00
Avian
Japanese Quail
LC50 (mg/kg-diet)
718.00
Bobwhite quail
N OAE L(mg/kg-bw)
0.00
Mallard duck
NOAEC (mg/kg-diet)
5.00
Dietary-based EECs (ppm)
Kenaqa
Val ues
Short Grass
31.20
Tall Grass
14.30
Broadleaf plants/sm Insects
17.55
Fruits/po d s/s ee d s/l q insects
1.95
Small herbivore mammals
20.56
Small insectivore mammals
1.28
Small terrestrial phase amphibians
0.61
Terrestrial Herpetofauna Results
Weight
Body
Ingestion (Fdry)
Ingestion (Fwet)
% body wgt
Fl
Class
Weight (g)
(q bw/day)
(q/day)
consumed
(kq-diet/day)
Small
1.4
0.017
0.1
3.9
5.44E-05
Mid
37
0.212
1.4
3.8
1.41 E-03
Larqe
238
0.893
6.0
2.5
5.96E-03
Body
Adjusted LD50
Weight (g)
(mg/kg-bw)
1.4
109.00
37
109.00
238
109.00
Dose-based EECs
(mg/kg-bw)
Herpetofaunal Size Classes and Body Weights
small (g)
mid (g)
1.4
37
238
Short Grass
1.21
1.19
0.78
Tall Grass
0.56
0.55
0.36
Broadleaf plants/sm Insects
0.68
0.67
0.44
Fruits/pods/seeds/lg insects
0.08
0.07
0.05
Small herbivore mammals
N/A
19.45
3.02
Small insectivore mammals
N/A
1.22
0.19
Small terrestrial phase amphibian
N/A
0.02
0.02
Dose-based RQs
(Dose-based EEC/adjusted LD50)
Amphibian/Reptile Acute RQs for Small, Medium, and
Large Species (grams)
1.4
37
238
Short Grass
0.01
0.01
0.01
Tall Grass
0.01
0.01
0.00
Broadleaf plants/sm insects
0.01
0.01
0.00
Fruits/pods/seeds/lg insects
0.00
0.00
0.00
Small herbivore mammals
N/A
0.18
0.03
Small insectivore mammals
N/A
0.01
0.00
Small terrestrial phase amphibian
N/A
0.00
0.00
Dietary-based RQs
(Dietary-based EEC/LC50 or
RQs
Acute
Chronic
Short Grass
0.04
6.24
Tall Grass
0.02
2.86
Broadleaf plants/sm Insects
0.02
3.51
Fruits/pods/seeds/lq insects
0.00
0.39
Small herbivore mammals
0.03
4.11
Small insectivore mammals
0.00
0.26
Small terrestrial phase amphibian
0.00
0.12
Note: To provide risk management with the maximum possible information,
it is recommended that both the dose-based and concentration-based
RQs be calculated when data are available
Upper Bound Kenaga Residues For RQ Calculation
Chemical Name:
Acephate
Use
seagwe diposal
Formulation
Orthene
Application Rate
0.13 lbs a.i./acre
Half-life
8.2 days
Application Interval
0 days
Maximum # Apps./Year
1
Length of Simulation
1 year
99
-------
5.2.2. Indirect Effects to the CRLF
5.2.2.1. Aquatic Phase
Sub-adult and adult CRLF consume invertebrates. Since acute RQs for freshwater
invertebrates range up to 0.13 (Table 5.5), 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 (Table 5.9b above), indirect risk to the
CRLF via effects on aquatic invertebrates is considered "NLAA "
5.2.2.2. Terrestrial Phase
Cotton (maximum exposure) Discussion
Risk quotients for two common prey animals (frog and small mammal and bird) greatly
exceed both acute and chronic LOC (Table 5-8). These prey animals are anticipated to
suffer adverse effects (mortality and reproductive effects) from labeled acephate uses.
The acute RQ for a terrestrial invertebrate (honey bee), representing the bulk of the
terrestrial phase CRLF diet, ranges from 5.5 to 50. Thus, adverse indirect effects to the
CRLF, mediated via reduction in prey base, are anticipated.
The terrestrial-phase CRLF uses small mammal burrows for shelter. If populations of
small mammals are reduced, as is anticipated from the acute RQs for individual effects
on them, then there may be fewer burrows for the CRLF to exploit. In addition, there are
chronic effects that may reduce the population of mammalian food item for CRLF. Thus,
there may be an indirect effect on the CRLF through adverse effects to terrestrial phase
habitat.
Sewage Disposal Areas (minimum exposure) Discussion
Risk quotients for common prey animals (frog and small mammal and bird) do exceed
some of dosed-based acute but are discountable due to the low likelihood of effects to
individual prey animals. Chronic RQs for birds and mammals are above LOC for all
food items except for large insects (Table 5.8). These prey animals are anticipated to
suffer adverse reproductive effects from labeled acephate uses. The acute RQ for a
terrestrial invertebrate (honey bee), representing the bulk of the terrestrial phase CRLF
diet, ranges from 0.20 to 1.86. Thus, adverse indirect acute effects "May Affect" the
CRLF, mediated via reduction in prey base. Chronic effects (reproductive effects) "May
Affect" CRLF and are not discountable.
5.3 Action Area
100
-------
The Action Area for endangered species from the labeled use of a pesticide is defined by
exceedence of the Level of Concern for any Listed species. Risk Quotients from the
screening risk assessment are compared to the Listed Species LOCs for all taxa to
determine the geographic extent of the Action Area.
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 LOC is no longer exceeded, and that spray drift
amount entered into AgDrift or AgDISP to determine the distance from the sprayed field
to the standard pond that will lower RQ to below LOC. That distance around the sprayed
field then determines the Action Area (assuming no secondary poisoning effects from
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 Action Area for effects on aquatic species was based on acute effects to Listed
aquatic invertebrates, since these were the only LOCs exceeded (Tables 5-6 and 5-7). To
be below the LOC for Listed aquatic invertebrates (0.05), the peak concentration in the
EXAMS pond would need to (0.05)*(26 ppb) =1.3 ppb, where 26 ppb is the EC50 for
Daphnia magna for methamidophos, a degradate of acephate.
Tier 1 and Tier 2 exposure analyses showed that no LOCs are exceeded from parent
acephate for invertebrates. Tier 2 exposure analysis for the degradate methamidophos
showed RQs as high as 0.13 (Table 5.5). The likelihood of an individual effect on
Daphnia at this RQ is very low (Table 5.9b), thus this effect is discountable, and no spray
perimeter for indirect effects is needed.
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 acephate use. The initial area of
concern was defined by Figure 2.E., which shows all agricultural land in all counties in
California where acephate is used. Flow contributions from streams in the corresponding
watersheds are included in a GIS (Geographic Information System) analysis, until the
pesticide concentrations (initially the EXAMS pond peak EEC) from contaminated and
uncontaminated streams, weighted for flow, fall below the Listed species LOC.
101
-------
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 methamidophos as a degradate
of acephate, this is the acute RQ for aquatic invertebrates from aerial application to
cotton and almond (0.13), divided by into LOC (0.05) for a factor of 0.38. See Table 5.6.
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).
For acephate, the Action Area was calculated on the basis of the smallest avian (20-gram
body weight) or mammal (15-gram), consuming the most highly contaminated food
category (short grass). This results in the highest RQs, and thus the most conservative
estimate of the Action Area.
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 )*(1 lb/acre).
In the case of methamidophos, the target exposure is 0.006 lb/acre, due to chronic effects
on avian species (chronic RQ = 167).
The distance from the use site (sprayed field) needed to achieve the target exposure of
0.006 lb/acre was calculated with the Gaussian Far-Field extension of the AgDISP model.
The input parameters for AgDISP are given below (Table 5-12); all other parameters
were the default values.
Table 5-12. Input Parameters for AgDISP Gaussian Far-Field Extension Analysis
Input Parameter
Value
Release Height
15 feet
Wind Speed
15 mph
Spray Quality
ASAE very fine to fine
Non-Volatile fraction
0.032 (1.33 lb product
in 5 gal = 42 lb water)
Active fraction
0.024 (nonvol frac x %
a.i. = 75%)
Surface Canopy
None
Specific Gravity, Carrier
1
Deposition type
Terrestrial point
Initial Average Deposition
0.006 lb/acre
102
-------
The result of this analysis is that a perimeter of 2,913 (0.55 miles) feet from the edge of
the sprayed field is needed to bring the chronic avian RQ to below the LOC of 1. Thus,
the Action Area extends to a distance of 2,913 feet from the edge of fields sprayed with
acephate.
Figure 5A shows the full extent of the Action Area, based on the terrestrial effects
distance of 2,913 feet and the downstream dilution factor of 0.38.
103
-------
Acephate Action Area
Legend
Aquatic ActionArea
Terrestrial ActionArea
County boundaries
i Kilometers
01 530 60 90 1 20
Compiled from California County boundaries (ESRI, 2002),
USCW NationalAgriculture Statistical Service (NASS, 2002)
Gap Analysis Program Orchard/Vineyard Landccwer (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
June XX, 2007. Projection: Albers Equal Area Conic USGS, North
American Datum of 1983 (NAD 1 983)
Figure 5A Action Area for Acephate
104
-------
5.4 Listed Species Effect Determination for the California Red-Legged Frog
5.4.1. "May Affect" Determination
When the action area overlaps (spatially) the designated Core Areas and Critical Habitats
a "may affect" determination is made. If there is no overlap, and thus no expected
exposure, a "no effect" 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 acephate use in California, the use of acephate "May Effect"
the CRLF. Table 5.13 displays the proportion of the core area within each recovery unit
that overlaps with the potential use areas.
Table 5.13 Terrestrial spatial summary results for acephate uses with 2,913-ft buffer.
Measure
RU1
RU2
RU3
RU4
RU5
RU6
RU7
RU8
Total
Initial Area
67,491 sq km
of Concern
(no buffer)
Established
3054
2742
1323
3271)
3(o<)
53
-------
above the LOC of 0.05. For the low exposure (sewage disposal areas), the RQs are 0.2
and 1.86 which also provide an individual chance of effect of one in 1,210 and 1.13,
respectively. Thus, both direct and indirect adverse effects to the terrestrial-phase
CRLF and its critical habitat are anticipated.
Risk quotients for direct, acute and chronic effects to the aquatic-phase CRLF, as
represented by freshwater fish, are below the LOC (Tables 5.2 and 5.3). Acute and
chronic effects on the aquatic phase CRLF and its critical habitat are not anticipated.
Aquatic invertebrate acute RQs (tables 5.6 and 5.7) are below the acute LOC (0.5) for all
uses, and the likelihood of individual effects is low (Table 5.9b). Thus adverse indirect
effects on the CRLF due to loss of prey items are discountable, and therefore NLAA.
Acephate is not toxic to aquatic plants, so no indirect effects to the CRLF via reduction in
primary production as a food source are anticipated.
Based on this analysis, it is concluded that the labeled uses of acephate 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 effects.
Table 5.12 Acephat
e Effects Determination Summary
Assessment
Endpoint
Effects
determination
Basis for Determination
Aquatic Phase
(Eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects and Critical Habitat Effects
1. Survival, growth,
and reproduction of
CRLF
No Effect
All Acute and Chronic RQ are below the listed LOC for
surrogate species (rainbow trout)
Indirect Effects
2. Reduction or
modification of
aquatic prey base
May Affect,
Not Likely to
Adversely Affect
Acute LOC is exceeded for aquatic invertebrates,
however effect is considered discountable based on
low likelihood of individual effect.
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. No
adverse aquatic critical habitat modification is
expected.
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. Initial
Area of Concern overlaps habitat. Use is widespread
(nearly all counties). Use is documented in all months.
Probability of effect approaches 100% at calculated
RQs.
106
-------
Assessment
Endpoint
Effects
determination
Basis for Determination
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). 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.
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
107
-------
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 adverse modification to critical
habitat.
5.5 Risk Hypotheses Revisited
Table 5.13 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 5.13 Risk Hypotheses Revisited
Risk Hypothesis
Conclusions
Labeled uses of acephate within the action
area may directly affect the CRLF by
causing mortality or by adversely affecting
growth or fecundity
Rejected for Aquatic exposure. "No
Effect" finding.
Accepted for Terrestrial exposure. "LAA"
finding.
Labeled uses of acephate within the action
area may indirectly affect the CRLF by
reducing or changing the composition of
food supply
Accepted for Terrestrial exposure. "LAA"
finding.
Rejected for Aquatic exposure. "NLAA"
finding.
Labeled uses of acephate within the action
area may indirectly affect the CRLF and/or
adversely modify designated critical habitat
by reducing or changing the composition of
the aquatic plant community in the ponds
and streams comprising the species' current
range and designated critical habitat, thus
affecting primary productivity and/or cover
Rejected. "No Effect" finding for aquatic
plants.
Labeled uses of acephate within the action
area may indirectly affect the CRLF and/or
adversely 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 acephate within the action
Rejected. "No Effect" for aquatic plants
108
-------
area may adversely 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)
and "NLAA" for indirect effects via
invertebrates.
Labeled uses of acephate within the action
area may adversely modify the designated
critical habitat of the CRLF by reducing the
food supply required for normal growth
and viability of juvenile and adult CRLFs
Accepted for Terrestrial exposure. "LAA"
finding via effects on vertebrate and
invertebrate food items.
Rejected for Aquatic exposure. "NLAA"
finding for aquatic invertebrates, "No
Effect" for aquatic plants.
Labeled uses of acephate within the action
area may adversely 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
Accepted. Effects on small mammals may
reduce number of burrows used for shelter.
Labeled uses of acephate within the action
area may adversely 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
Accepted. Effects on small mammals may
reduce number of burrows used for shelter.
Labeled uses of acephate within the action
area may adversely 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 acephate in
terrestrial habitat is believed to have direct
and indirect effects on CRLF.
109
-------
6. Uncertainties
6.1.1 Maximum Use Scenario
The screening-level risk assessment focuses on characterizing potential ecological risks
resulting from a maximum use scenario, which is determined from labeled statements of
maximum application rate and number of applications with the shortest time interval
between applications. The frequency at which actual uses approach this maximum use
scenario may be dependant on insecticide resistance, timing of applications, cultural
practices, and market forces.
6.1.2 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.
6.2. Exposure Assessment Uncertainties
Due to lack of appropriate PRZM scenarios for California, not all labeled uses were
modeled for aquatic exposure. It is likely that the cotton use, at 6 lb a.i. per acre,
provides the highest aquatic exposure estimate, including those not modeled, most of
which have maximum rates of 1 to 2 lb a.i. per acre.
Landscape maintenance is known to be a major use of acephate. This exposure is
described for the aquatic environment using the PRZM turf scenario. However, there are
a number of application techniques, such as those described as gallons per pot or
teaspoons per mound, for which it is difficult to compare exposure potential to
agricultural uses that are given in pounds per acre. It is assumed that the greatest aquatic
and terrestrial exposure potential is for agricultural uses that allow aerial application.
110
-------
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.
Aquatic exposure modeling inputs were based on the available guideline data. Some
inputs (e.g., soil metabolism half-life = 2.3 days) were based on a single value, which by
EFED policy is multiplied by 3 to account for uncertainty. The aquatic metabolism rates
(both aerobic and anaerobic) were set by policy at 2 times the soil input value. The
partition coefficient (Kd) used was the highest and only quantified value obtained (0.09).
The use of values for the other soils (essentially, Kd = 0) would have resulted in
somewhat higher exposure estimates.
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 acephate on foliage and other food items for the TREX analysis
was set at 8.2 days, rather than the default value of 35 days. This value was obtained
from Willis & McDowell (1987) from a field experiment on lemons in California; this is
the same reference used to obtain the default value of 35 days. The value of 8.2 days was
the highest of the half-lives for acephate, so it is the most protective of the measured
values.
Methamidophos exposures in the aquatic environment were estimated as 18% of the
modeled acephate concentrations. This is based on a maximum 23% formation of
methamidophos in a Fresno loam soil, and a molecular weight conversion factor of 0.77.
This approach is considered reasonable, as the fate and transport properties of acephate
and methamidophos are very similar (very mobile and non-persistent). The use of more
sophisticated techniques (e.g., parent-daughter kinetics modeling ans use of
methamidophos-specific fate inputs) is unlikely to provide more defensible exposure
estimates.
6.2.1 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
111
-------
storage capacity and thus may overflow and carry pesticide in the discharge, whereas the
EXAMS pond has no discharge. As watershed size increases beyond 10-hectares, it
becomes increasingly unlikely that the entire watershed is planted with a single crop that
is all treated simultaneously with the pesticide. Headwater streams can also have peak
concentrations higher than the EXAMS pond, but they likely persist for only short
periods of time and are then carried and dissipated downstream.
The Agency acknowledges that there are some unique aquatic habitats that are not
accurately captured by this modeling scenario and modeling results may, therefore,
under- or over-estimate exposure, depending on a number of variables. For example,
aquatic-phase CRLFs may inhabit water bodies of different size and depth and/or are
located adjacent to larger or smaller drainage areas than the EXAMS pond. The Agency
does not currently have sufficient information regarding the hydrology of these aquatic
habitats to develop a specific alternate scenario for the CRLF. As previously discussed in
Section 2.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).
6.2.2 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,
112
-------
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.
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.
113
-------
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 acephate, that act directly without metabolic transformation because
younger age classes may not have the enzymatic systems associated with detoxifying
xenobiotics. In so far as the available toxicity data may provide ranges of sensitivity
information with respect to age class, this assessment uses the most sensitive life-stage
information as measures of effect for surrogate aquatic animals, and is therefore,
considered as protective of the California Red Legged Frog.
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 acephate. 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.
114
-------
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 avian data as surrogate for amphibian data.
Toxicity data for terrestrial phase amphibians was not available for use in this
assessment. Therefore, avian toxicity data were used as a surrogate for risk estimation.
There is uncertainty regarding the relative sensitivity of herptiles and birds to acephate.
If birds are substantially more or less sensitive than the California red legged frog, then
risk would be over or under estimated, respectively.
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.
6.8. 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
115
-------
the expanding area). Thus, it important to know at least some approximate estimate of
types of land use within that region. Runoff from forested areas ranges from 45 -
2,700% less than from agricultural areas; in most studies, runoff was 2.5 to 7 times higher
in agricultural areas (e.g., Okisaka et al., 1997; Karvonen et al., 1999; McDonald et al.,
2002; Phuong and van Dam 2002). Differences in runoff potential between
urban/sub urban areas and agricultural areas are generally less than between agricultural
and forested areas. In terms of likely runoff potential (other variables - such as
topography and rainfall - being equal), the relationship is generally as follows (going
from lowest to highest runoff potential):
Three-tiered forest < agroforestry < suburban < row-crop agriculture < urban.
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.
116
-------
7. References
Altig, R. and R.W. McDiarmid. 1999. Body Plan: Development and Morphology. InR.W.
McDiarmid and R. Altig (Eds.), Tadpoles: The Biology of Anuran Larvae.University of
Chicago Press, Chicago, pp. 24-51.
Alvarez, J. 2000. Letter to the U.S. Fish and Wildlife Service providing comments on
the Draft California Red-legged Frog Recovery Plan.
Bart, J. et. al., 1975. Environmental Impact Study of Aerially Applied Orthene on a
Forest and Aquatic Ecosystems: Impact on Birds. MRID 05014922, MRID 00014639.
Bocsor & O'Connor, 1975. Environmental Impact Study of Aerially Applied Orthene on
a Forest and Aquatic Ecosystem: Impact on Aquatic Ecosystem. MRID 00014637
Clarke Jr., D.R., B.A. Rattner. 1987. OrtheneR Toxicity to Little Brown Bats (Myotis
lucifugus): Acetochlorinesterase Inhibition, Coordination Loss, and Mortality. Environ.
Toxicol, and Chem. Vol 6 pp. 705-708.
Crawshaw, G.J. 2000. Diseases and Pathology of Amphibians and Reptiles in:
Ecotoxicology of Amphibians and Reptiles; ed: Sparling, D.W., G. Linder, and C.A.
Bishop. SETAC Publication Series, Columbia, MO.
Davies, J.E. and V. H. Freed, editors. 1981. An agromedical approach to pesticide
management: some health and environmental considerations. Consortium for
International Crop Protection, Berkeley, CA. 370 pp
Fellers, G. M., et al. 2001. Overwintering tadpoles in the California red-legged frog
{Rana aurora draytonii). Herpetological Review, 32(3): 156-157.
Fellers, G.M, L.L. McConnell, D. Pratt, S. Datta. 2004. Pesticides in Mountain Yellow
Legged Frogs (Rana Mucosa) from the Sierra Nevada Mountains of California, USA.
Environmental Toxicology & Chemistry 23 (9):2170-2177.
Fellers, Gary M. 2005a. Rana draytonii Baird and Girard 1852. California Red-legged
Frog. Pages 552-554. hr. M. Lannoo (ed.) Amphibian Declines: The Conservation Status
of United States Species, Vol. 2: Species Accounts. University of California Press,
Berkeley, California, xxi+1094 pp.
(http://www.werc.usgs.gov/pt-reves/pdfs/Rana%20dravtonii.PDF)
Fellers, Gary M. 2005b. California red-legged frog, Rana draytonii Baird and Girard.
Pages 198-201. hr. L.L.C. Jones, et al (eds.) Amphibians of the Pacific Northwest.
xxi+227.
Fleming W.J.; Augspurger T.P.; Alderman J.A. 1995. Freshwater Mussel Die-off
Attributed to Anticholinesterase Poisoning. Environmental Toxicology and Chemistry,
117
-------
14:5 (877-879).
Fletcher JS et al. 1994. Literature Review and Evaluation of the EPA Food-chain
(Kenaga) Nomogram, an Instrument for Estimationg Pesticide Residues on Plants.
Environmental Toxicology and Chemistry, 13:9 (1383-1391).
Fulton, M.H. and G.I. Scott. 1991. The Effects of Certain Intrinsic Variables on the
Acute Toxicity of Selected Organophosphorous Insecticides to the Mummichog,
Fundulus heteroclitus. J. Environ. Sci. Health B26 (5&6), 459-478.
Geen, G.H., M.A. Hussain, P.C. Oloffs, B.A. McKeown. 1981. Fate and Toxicity of
Acephate (OrtheneR) Added to a Coastal B.C. Stream. J. Environ. Sci. Health, B16(3),
253-271.
Geen, G.H., B.A. McKeown, T.A. Watson, D.B. Parker. 1984. Effects of Acephate
(Orthene) on Development and Survival of the Sal amander,^mbystoma gracile, (Baird).
Environ. Sci. Health, B19 (2), 157-170 (1984).
Geen, G.H., B.A. McKeown, P.C. Oloffs, 1984. Acephate in Rainbow Trout (Salmo
gairdneri), Acute Toxicity, Uptake, and Elimination. J. Environ. Science and Health
B19(2) p. 131-155.
Hayes, M.P. and M.R. Jennings. 1988. Habitat correlates of distribution of the California
red-legged frog (Rana aurora draytonii) and the foothill yellow-legged frog (Rana
boyluy. Implications for management. Pp. 144-158. In Proceedings of the symposium on
the management of amphibians, reptiles, and small mammals in North America. R. Sarzo,
K.E. Severson, andD.R. Patton, (technical coordinators). USDA Forest Service General
Technical Report RM-166.
Hayes, M.P. and M.M. Miyamoto. 1984. Biochemical, behavioral and body size
differences between Rana aurora aurora and R. a. draytonii. Copeia 1984(4): 1018-22.
Hayes and Tennant. 1985. Diet and feeding behavior of the California red-legged frog.
The Southwestern Naturalist 30(4): 601-605.
Jennings, M.R. and M.P. Hayes. 1985. Pre-1900 overharvest of California red-legged
frogs (Rana aurora draytonii): The inducement for bullfrog (Rana catesbeiana)
introduction. Herpetological Review 31(1): 94-103.
Jennings, M.R. and M.P. Hayes. 1994. Amphibian and reptile species of special concern
in California. Report prepared for the California Department of Fish and Game, Inland
Fisheries Division, Rancho Cordova, California. 255 pp.
Juarez, L.M., J. Sanchez, 1989. Toxicity of the Organophosphorous Insecticide
Methamidophos (0,S-Dimethyl Phosphoramidothioate) to Larvae of the Freshwater
mber 1: 133-149.
118
-------
Petersen and Bart, 1979. Effects of Acephate and Sevin on Forest Birds. MRID
05014922 and MRID 00163173.
Phuong V.T. and van Dam J. Linkages between forests and water: A review of research
evidence in Vietnam. In. Forests, Water and Livelihoods European Tropical Forest
Research Network. ETFRNNEWS (3pp).
Rabeni, C., 1978. Impact of Orthene, a Spruce Budworm Insecticide on Stream Fishes.
MRID 00014547 & MRID 05012201.
Rathburn, G.B. 1998. Rana aurora draytonii egg predation. Herpetological Review,
29(3): 165.
Rattner, B.A., D.J. Hoffman. 1984. Comparative toxicity of acephate in laboratory mice,
white-footed mice, and meadow voles. Arch. Environ. Contam. Toxicol. 13:483-491.
Rattner, B. A., S.D.Michael. 1985. Organophosphorous insecticide induced decrease in
plasma luteinizing hormome concentration in white-footed mice. Toxiciology Letters,
24:65-69.
Reis, D.K. Habitat characteristics of California red-legged frogs {Rana aurora draytonii):
Ecological differences between eggs, tadpoles, and adults in a coastal brackish and
freshwater system. M.S. Thesis. San Jose State University. 58 pp.
Richmond & Henny et. al., 1979. Effects of Sevin-4-oil, Dimilin, and Orthene on Forest
Birds in Northwestern Oregon (FWS). MRID 40644802.
Rudolph & Zinkl et. al., 1984. Prey-Capturing Ability of American Kestrels Fed DDE
and Acephate or Acephate Alone. MRID 00141694.
Schoettger, R., 1976. Toxicity of Experimental Forest Insecticides to Fish and Aquatic
Invertebrates. MRID 00014861.
Seale, D.B. andN. Beckvar. 1980. The comparative ability of anuran larvae
(genera.Hyla, Bufo and Rana) to ingest suspended blue-green algae. Copeia 1980:495-
503.
Smith, G.J. 1987. Pesticide Use and Toxicology in Relation to Wildlife:
Organophosphorus and Carbamate Compounds, U.S. Dept. of Interior FWS Resource
Publication 170. Page 71.
Stehn, RA; Richmond, ME, 1976. Feeding Response of Small Mammal Scavengers to
Pesticide-Killed Arthropods; Am Midi Nat 95:253-256.
Stehn, RA;
119
-------
Seale, D.B. andN. Beckvar. 1980. The comparative ability of anuran larvae (genera:
Hyla, Bufo and Rana) to ingest suspended blue-green algae. Copeia 1980:495-503.
Stone, J; 1979. Effects of Aerial Application of Orthene on Small Mammals; Lake
Ontario Environmental Laboratory Report, Ticonderoga Project, p. 1-57; Cornell
University, Ithaca, NY, Lake Ontario region.
Sparling, D.W., G.M. Fellers, L.L. McConnell. 2001. Pesticides and amphibian
population declines in California, USA. Environmental Toxicology & Chemistry 20(7):
1591-1595.
Stoner, A., W. T. Wilson, and J. Harvey. Acephate (Orthene): Effects on Honey Bee
Queen, Brood and Worker Survival. American Bee Journal, V125(6) 1985:448-450.
USD A, NCRS, 2000 (s 3.2.3)
USEPA 1993 (s 4.1.7.1)
U.S. Environmental Protection Agency (U.S. EPA). 1998. Guidance for Ecological Risk
Assessment. Risk Assessment Forum. EPA/630/R-95/002F, April 1998.
U.S. EPA. 2000. Supplementary guidance for conducting health risk assessments of
chemical mixtures. EPA/630/R-00/002. Risk Assessment Forum. U.S. Environmental
Protection Agency, Washington DC. 20460.
U.S. EPA. 2001. Interim Reregi strati on Eligibility Decision for Acephate: Case No.
0042. Office of Prevention, Pesticides, and Toxic Substances. Office of Pesticide
Programs. Washington, D.C. July, 2001.
U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of
Pesticide Programs. Office of Prevention, Pesticides, and Toxic Substances. Office of
Pesticide Programs. Washington, D.C. January 23, 2004.
U.S. EPA. 2007. Risks of Methamidophos Use to Federally Listed Endangered
California Red Legged Frog (Rana aurora draytonii). Office of Prevention, Pesticides,
and Toxic Substances. Office of Pesticide Programs. Washington, D.C. July, 2007
U.S. Fish and Wildlife Service (USFWS). 1996. Endangered and threatened wildlife and
plants: determination of threatened status for the California red-legged frog. Federal
Register 61(101):25813-25833.
USFWS/NMFS. 2004. Letter from USFWS/NMFS to U.S. EPA Office of Prevention,
Pesticides, and Toxic Substances. January 26, 2004.
(http://www.fws.gov/endangered/consultations/pesticides/evaluation.pdf)
120
-------
USFWS. 2002. Recovery Plan for the California Red-legged Frog (Rana aurora
draytonii). Region 1, USFWS, Portland, Oregon.
(http://ecos.fws.gov/doc/recovery plans/2002/020528.pdf)
USFWS. 2006. Endangered and threatened wildlife and plants: determination of critical
habitat for the California red-legged frog. 71 FR 19244-19346.
USFWS. Website accessed: 30 December 2006.
http://www.fws.gov/endangered/features/rl frog/rlfrog.html#where
U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service
(NMFS). 1998. Endangered Species Consultation Handbook: Procedures for
Conducting Consultation and Conference Activities Under Section 7 of the Endangered
Species Act. Final Draft. March 1998.
USFWS/NMFS. 2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act
Section 7 Consultation Regulations; Final Rule. FR 47732-47762.
USFWS/NMFS 2004. Memorandum to Office of Prevention, Pesticides, and Toxic
Substances, U.S. EPA conveying an evaluation by the U.S. Fish and Wildlife Service and
National Marine Fisheries Service of an approach to assessing the ecological risks of
pesticide products.
Vyas, N.B., W.J. Kuenzel, E.F. Hill, G.A. Romo and M.V.S. Komaragiri. 1996.
Regional Cholinerase Activity in White-Throated Sparrow Brain is Differentially
Affected by Acephate. Biochem. Physiol. Vol. 113C: 3 ( 381-386).
Vyas, N.B., W.J. Kuezel, E.F. Hill, and J.R. Sauer. 1995. Acephate Affects Migratory
Orientation of the White-Throated Sparrow (Zonotrichia Albicollis). Environmental
Toxicology and Chemistry, 14:11 (1961-1965).
Wassersug, R. 1984. Why tadpoles love fast food. Natural History 4/84.
Willis, GH and McDowell, LL., 1987. Pesticide Persistence on Foliage. Reviews of
Environmental Contamination and Toxicology, vol. 100 (1-73).
Zinkl, J. G., C.J. Henny, and P.J. Shea. 1979. Brain cholinesterase activities of
passerine birds in forests sprayed with cholinesterase inhibitors. Pages 356-365. In:
Animals as Monitors of Environmental Pollutants, National Academy of Science,
Washington, DC.
Zinkl, JG, 1978. Brain Cholinesterase (ChE) Activities of Forest Birds and Squirrels
Exposed to Orthene Applied at One-Half Pound per Acre.
Zinkl, 1982. Brain and Plasma Cholinesterase Activity of Dark-eyed Juncos Given
Acephate Dosed Spruce Budworm Larvae. MRID 00093911.
121
-------
Zinkl, J.G., P.J. Shea, R.J. Nakamoto, J.Callman. 1987. Effects of Cholinesterase of
Rainbow Trout Exposed to Acephate and Methamidophos. Bull. Environ. Contam.
Toxicol. (1987) 38:22-28.
122
------- |