Risks of Aldicarb Use to Federally Listed
Endangered California Red Legged Frog
(Rana aurora draytonii)
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Authors:
Jonathan Angier
Fred Jenkins
Jeannette Martinez
Red Legged Frog Steering Committee
Reviewed by:
Donna Randall, Senior Effects Scientist
Dana Spatz, Senior Chemist/Branch Team Leader
Nelson Thurman, Senior Fate Scientist
Approved by:
Tom Bailey, Branch Chief
Environmental Risk Branch, 2
Environmental Fate and Effects Division
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
July 17,2007
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TABLE OF CONTENTS
1. Executive Summary 1
2. Problem Formulation 12
2.1 Purpose 12
2.2 Scope 14
2.3 Previous Assessments 15
2.4 Stressor Source and Distribution 17
2.4.1 Environmental Fate Assessment 18
2.4.2 Environmental Transport Assessment 20
2.4.3 Mechanism of Action 21
2.4.4 Use Characterization 21
2.5 Assessed Species 26
2.5.1 Distribution 27
2.5.2 Reproduction 32
2.5.3 Diet 32
2.5.4 Habitat 33
2.6 Designated Critical Habitat 34
2.7 Action Area 36
2.8 Assessment Endpoints and Measures of Ecological Effect 39
2.8.1. Assessment Endpoints for the CRLF 39
2.8.2. Assessment Endpoints for Designated Critical Habitat 41
2.9 Conceptual Model 45
2.9.1 Risk Hypotheses 45
2.9.2 Diagram 46
2.10 Analysis Plan 49
2.10.1 Exposure Analysis 49
2.10.2 Effects Analysis 51
2.10.3 Action Area Analysis 52
3 Exposure Assessment 54
3.1 Label Application Rates and Intervals 54
3.2 Aquatic Exposure Assessment 54
3.2.1 Conceptual Model of Exposure 54
3.2.2 Existing Monitoring Data 54
3.2.3 Modeling Approach 55
3.2.3.1 Model Inputs 55
3.2.3.2 Results 57
3.2.4 Additional Modeling Exercises Used to Characterize Potential
Exposures 58
3.2.5 Comparison of Modeled EECs with Available Monitoring Data 59
3.3 Terrestrial Plant Exposure Assessment 60
3.4 CRLF Terrestrial Phase Exposure Assessment 61
4. Effects Assessment 63
4.1 Taxa specific toxicological endpoints and LOCs 63
4.2 Evaluation of Ecotoxicity Studies 65
4.2.1 Toxicity to Terrestrial Plants 66
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4.3 Acute-to-Chronic Ratio Derivation for the CRLF 67
4.4 N-Methyl Carbamate Toxicological Data for Frogs 69
4.5 Aquatic Freshwater Plants 70
4.6 Acute-to-Chronic Ration Derivation for Freshwater Invertebrates 70
4.7 Probit Analysis 70
4.8 Review of Ecological Incident Information System (EIIS) 71
4.9 Sensitivity Distribution 71
4.9.1 Freshwater Fish 71
4.9.2 Freshwater Invertebrate 72
5 Risk Characterization 75
5.1 Risk Estimation 75
5.1.1 Direct Effects 76
5.1.2 Indirect Effects 79
5.1.2.1 Evaluation of Potential Indirect Effects via Reduction in Food
Items 80
5.1.2.2 Evaluation of Potential Indirect Effects via Reduction in Habitat
and/or Primary Productivity 81
5.2 Risk Description 84
5.2.1 Direct Effects to the California Red Legged Frog 85
5.2.1.1 Direct Effects to the Aquatic Phase of the CRLF 85
5.2.1.2 Direct Effects to the Terrestrial Phase of the CRLF 87
5.2.2 Indirect Effects via Reduction in Food Items 88
5.2.2.1 Indirect Effects to the Terrestrial Phase of the CRLF 88
5.2.2.2 Indirect Effects via Reduction of Aquatic Primary Productivity . .. 90
5.2.2.3 Indirect Effects via Alteration in Terrestrial Plant Community. .. 90
5.2.3 Secondary Poisoning of CRLF by Consuming Terrestrial
Invertebrates Contaminated with Aldicarb Residues 91
5.3 Final Effects Determination 93
6. Uncertainties 100
6.1 Exposure Assessment Uncertainties 100
6.1.1 Maximum Use Scenario 100
6.1.2 Modeling Inputs 100
6.1.2.1 Action Area 101
6.2.1.2 Aquatic Exposure Estimates 102
6.1.2.3 PRZM Modeling Inputs and Predicted Aquatic Concentrations. 102
6.3 Effects Assessment Uncertainties 103
6.3.1 Age Class and Sensitivity of Effects Thresholds 103
6.3.2 Use of Acute Freshwater Invertebrate Toxicity Data for the Midge 103
6.3.3 Extrapolation of Long-term Environmental Effects from Short-Term
Laboratory Tests 103
6.3.4 Residue Levels Selection 104
6.3.5 Dietary Intake 104
6.3.6 Sublethal Effects 104
6.3.7 Location of Wildlife Species 105
6.4 Assumptions Associated with the Acute LOCs 105
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6.5 Usage Uncertainties
7. References
105
107
Appendix A: T-REX Modeling Outputs
Appendix B: TerrPlant Modeling Outputs
Appendix C: Earthworm Fugacity Modeling Outputs
Appendix D: ECOTOX Run (Oct 2004 - Dec 2006) Accepted Papers
Appendix E: ECOTOX Run (Oct 2004 - Dec 2006) Acceptable Data
Appendix F: ECOTOX Run (Oct 2004 - Dec 2006) Excluded Papers
Appendix G: ECOTOX (2006 RSLERA run) Acceptable Papers
Appendix H: ECOTOX (2006 RSLERA run) Included by ECOTOX but rejected
by OPP EFED
Appendix I: ECOTOX (2006 RSLERA run) Excluded Papers
Appendix J: Updated Species information
Appendix K: Intentionally left blank
Appendix L: Environmental Fate Data Requirements
Appendix M: PRZM-EXAMS Model Runs: Output Files
Appendix N: Aldicarb Degradation and Persistence
Appendix O: Intentionally left blank
Appendix P: Summary of Available Persistence Data for Aldicarb and its
Sulfoxide and Sulfone Degradates
Appendix Q: Intentionally left blank
Appendix R: Spatial Summary for Terrestrial and Aquatic Uses
Attachment 1: CRLF Life History
Attachment 2: CLRF Baseline Status and Cumulative Effects
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LIST OF TABLES
Table 1 Summarizes the effects determinations for direct effect of aldicarb to any of the
life-stages of the CRLF in Eight Recovery Units 4
Table 2 Summarizes the effects determinations for indirect effect of aldicarb to any of
the life-stages of the CRLF in Eight Recovery Units 5
Table 3 Summarizes the effects determinations for effects to the critical habitat the
CRLF in recovery units one thru eight 5
Table 4 National Labels Supporting Aldicarb Uses and Maximum Application Rates... 22
Table 5 California DPR Aldicarb Use, summarized by crop/use for 2001-2005 24
Table 6 California Red-legged Frog Recovery Units with Overlapping Core Areas and
Designated Critical Habitat 29
Table 7 Summary of Assessment Endpoints and Measures of Ecological Effects for
Direct and Indirect Effects of Aldicarb and its Degradates on the California Red Legged
Frog 40
Table 8 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat 43
Table 9 Generic Aldicarb Inputs Used in PRZM-EXAMS Runs 56
Table 10 Specific Inputs for Individual PRZM-EXAMS Runs 57
Table 11 Results of Individual PRZM-EXAMS Runs With 85% Soil Incorporation 57
Table 12 Results of Individual PRZM-EXAMS Runs With 99% Soil Incorporation 58
Table 13 Aldicarb Acute and Chronic Ecotoxicological Values Listed in 2005 RED and
Used for RQ Calculations in this Assessment 63
Table 14 Aldicarb Sulfoxide Acute Ecotoxicological Values Used for RQ calculations in
this Assessment 64
Table 15 Specific LOCs Used in this Assessment 65
Table 16 Ecotox Study for Formulated Aldicarb Used for RQ Calculations in this
Assessment (Oct 2004 - Dec 2006) 66
Table 17 Avian N-Methyl Carbamate Data 69
Table 18 N-Methyl Carbamate Toxicological Data for Amphibians 69
Table 19 Freshwater Acute Invertebrate Toxicity Data and Species and Genus Mean
Acute Values 73
Table 20 Summary of Aldicarb Direct Effects RQs for the CRLF 78
Table 21 Aldicarb Sulfoxide Direct Effects to the CRLF 79
Table 22 Summary of Aldicarb RQs Used to Estimate Indirect Effects to the CRLF via
Acute and Chronic Effects on Aquatic Dietary Items(l) 82
Table 23 Summary of Aldicarb RQs Used to Estimate Indirect Effects to the CRLF via
Acute Effects on Terrestrial Dietary Items(1) 83
Table 24 Aldicarb RQs Used to Estimate Indirect Effects to the CRLF via Direct Acute
Effects on Aquatic and Terrestrial Habitat Components 84
Table 25 Summarizes the effects determinations for direct effect of aldicarb to any of the
life-stages of the CRLF in Eight Recovery Units 93
Table 26 Summarizes the effects determinations for indirect effect of aldicarb to any of
the life-stages of the CRLF in Eight Recovery Units 94
Table 27 Summarizes the effects determinations for effects to the critical habitat the
CRLF in recovery units one thru eight 94
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LIST OF FIGURES
Figure 1 Chemical structure of aldicarb and its oxidative transformation products 18
Figure 2 Aldicarb Use Areas (includes row crops and orchards) in California, with
Recovery Units 23
Figure 3 Aerial Extent of Known and Potential (Cultivated Land) Section 3 and 24c
Aldicarb Use in California 26
Figure 4 Recovery Units, Core Area, Critical Habitat, and Occurrence Designation for
CRM 31
Figure 5 CRLF Reproductive Events by Month 32
Figure 6 Spatial Overlap of Aldicarb Action Area with CRLF Critical Habitat 38
Figure 7 Conceptual Model for Aldicarb Effects on Aquatic Phase of the CRLF 47
Figure 8 Conceptual Model for Aldicarb Effects on Terrestrial Phase of CRLF 48
Figure 9 Conceptual Model for Aldicarb Effects on Aquatic Component of CRLF
Critical Habitat 48
Figure 10 Conceptual Model for Aldicarb Effects on Terrestrial Component of the CRLF
Critical Habitat 49
Figure 11 Comparison of structures of N-methyl carbamates 67
Figure 12 Cumulative Acute Sensitivity Distribution of Freshwater Invertebrates to
Aldicarb 74
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1. Executive Summary
Aldicarb is an insecticide, acaricide, and nematicide in the carbamate group of
cholinesterase inhibitors. It is registered for use in California for both agricultural and
non-agricultural purposes. These uses include: alfalfa, cotton, dried beans, sugar beet,
sorghum, soybean, sweet potato, pecan, peanut, citrus, and ornamentals.
Granular aldicarb use in California entails a variety of application techniques and varies
greatly in amounts applied, number of applications, application intervals, and timing of
applications according to usage. Typically, the granules are spread on the surface and
incorporated into the soil by 'shanking in', 'working into the soil', 'covering with soil',
and/or 'wetting in'. Applications directly 'in-furrow' are also performed for some crops
(e.g. sweet potato), but may be followed by later applications that are less effectively
soil-incorporated. For the aquatic portion of this assessment, most applications were
conservatively assumed to result in only 85% soil incorporation. Certain application
techniques - specifically, in-furrow applications and banded applications that utilize
state-of-the-art methods (such as positive displacement and immediate soil incorporation)
- may theoretically result in incorporation efficiencies of 99%. However, crops that
require additional applications after maturity cannot reasonably be expected to achieve
99% incorporation efficiency and are difficult to model jointly, so in cases where there
are multiple applications in a single year (that also include post-emergent applications) an
assumption of 85% incorporation (even if the first application could potentially be 99%
effective) is more conservative than applying a 99% efficiency for all applications. To
address this uncertainty, most model runs were conducted using both 85% and 99%
incorporation efficiencies; all results are reported herein.
There are two aldicarb degradates of concern, aldicarb sulfoxide and aldicarb sulfone,
that are also considered in this assessment. These degradates appear to form primarily in
the shallow subsurface (although some may also form within plant tissue) and are
potentially more mobile and persistent than the parent. As a conservative assumption, all
three forms (parent aldicarb, sulfoxide, and sulfone) are considered as a single constituent
for aquatic exposure estimates because of the longer degradate half-lives. Parent only is
considered for terrestrial exposure because of its higher toxicity to animals, the likelihood
that most exposure would be to whole granules, and because less of the degradate is
expected to occur directly on the surface.
Alidcarb and its major toxic degradates of concern may move through the environment
and be transported away from the site of application. Aldicarb and its degradates may
potentially be transported as a component of runoff (dissolved in water or sorbed onto
solids) or groundwater and end up in proximate surface water bodies. Historically,
aldicarb and its major toxic degradates appears to be more likely to be found in
groundwater than surface water. Although groundwater per se is not evaluated herein, it
is nonetheless significant because discharging groundwater is likely to support low-order
streams, wetlands, and intermittent ponds - environments that are favorable to California
Red-Legged Frogs (CRLFs). Long-term chronic concentrations derived from the PRZM-
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EXAMS model should reflect background concentrations that might be found in
discharged groundwater/stream baseflow. Based on the product formulation and physical
and chemical properties of aldicarb, atmospheric long range transport is not considered
an exposure pathway of concern. While bioaccumulation of aldicarb or its major toxic
degradates in animals through the food chain is also not expected to be a significant
exposure pathway {i.e., aldicarb and its degradates are expected to be rapidly metabolized
at sublethal levels), secondary acute exposure is still a concern. Aldicarb is very highly
toxic, and ingestion of a single granule is sufficient to result in death, with a delayed
reaction time that potentially provides a window of opportunity for an exposed animal to
move offsite before it is incapacitated or dies. Any granules not fully sorbed in the gut
and metabolized in such animals potentially pose a secondary acute risk to a predator. In
addition, dissolved aldicarb may be present in pools of water that typically form on the
ground following an intense rainfall. Based on information on the extent of daily
movements within a home range of small to medium size mammals (potential CRLR
prey items), the potential extent of offsite movement was conservatively set to the upper
range of one mile.
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 aldicarb for this region. Thus, there are no values available that would be
considered consistent with high-end ('peak') exposure concentrations expected in surface
water - although positive aldicarb detections from non-targeted data sets may be
indicative of lower-end exposure concentrations. Therefore, it was necessary to estimate
exposure (and risk) based on modeled results. The initial aquatic estimation was based
on standard PRZM-EXAMS operating methods described in the Overview Document
(US EPA, 2004), using pre-existing scenarios as well as scenarios devised specifically for
the CRLF (depending on crop type). The EXAMS outputs were then processed further to
delineate an aquatic Action Area within which potential (direct and indirect) effects to
relevant (plant and/or animal) species might result in their being adversely affected -
regardless of the presence or absence of CRLFs in that area. Post-processing of EXAMS
outputs included estimating dilution that would be expected to occur within a stream
channel, extended downstream to a point where concentrations are predicted to drop
below a level at which there is an expected impact on any aquatic plant or animal species.
In terms of direct effects, aquatic acute and chronic RQs are exceeded for the following
modeled uses: dried bean, cotton, soybean (banded applications), pecan, peanut, alfalfa,
and sugar beet. Sugar beet is the higher risk scenario and drives the overall risk in the
aquatic environment and RQ/LOC exceedance based on sugar beet are used to determine
the aquatic (downstream dilution) action area. Terrestrial acute and chronic RQs for on-
site exposure are exceeded for all modeled scenarios: citrus, cotton, soybean, pecan, and
sugar beet. Terrestrial acute and chronic risks off-site are not above levels of concern.
Citrus drives the risk in the on-site terrestrial environment, followed by cotton. The
initial area of concern for aldicarb is determined by including all potential crop land
(agricultural and non-agricultural) from the 2002 National Land Cover Data (NLCD) and
where aldicarb use has not been off-labeled (i.e. Del Norte and Humboldt Counties). The
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Agency extended this area by 1 mile (home range of a CRLF prey item) to include the
distance a CRLF prey item could fly (Haskell et al., 2002) before succumbing to aldicarb
effects. This one mile zone around crop land will account for part of the action area
where aldicarb secondary poisoning effects, for predators ingesting birds, can be
expected (extent of zone for small mammals likely to feed on fields is smaller).
Based on all available lines of evidence and the highest risk scenario, the Agency
concludes a "likely to adversely affect" (LAA) determination for direct effects to the
terrestrial and aquatic phase of the CRLF via mortality, growth, or reproduction in
recovery units where exposure to aldicarb occurs; a "not likely to adversely affect" for
direct effects to the terrestrial and aquatic phase of the CRLF via mortality, growth, or
reproduction in recovery units where aldicarb could potentially be used, and the Agency
determined LOC exceedances but CAL DPR PUR data informs that aldicarb has not been
used from 2001 through 2005. The Agency concludes a LAA determination for indirect
effects to the California Red Legged Frog based on expected adverse effects to the prey
base of the CRLF.. The Agency also concludes a LAA determination for all designated
critical habitats in recovery units 1, 3, 4, 5, 6, and 7 based on adverse effects expected to
the terrestrial and aquatic animal components of the critical habitat. There is no
designated critical habitat in recovery units 2 and 8.
Based on the highest risk scenario, the Agency also concludes that aldicarb is likely to
indirectly adversely affect the terrestrial and aquatic phases of the CRLF by potentially
negatively impacting the available prey items, for terrestrial prey this affect is limited to
on-site exposures. This conclusion is based on the premise that there were LOC
exceedances for all the potential prey items for the terrestrial (on-site) and aquatic phases
of the CRLR for sugar beets.
No LOC exceedances are predicted for aldicarb sulfoxide based on modeled EECs and
available freshwater fish and freshwater invertebrate endpoint values. The Agency
concludes a "no effects" determination for direct effects of aldicarb sulfoxide to the
aquatic phase of the CRLF.
The Agency also concludes a "no effects" determination for indirect effects to the aquatic
phase of the CRLF via direct effects to aquatic plants in all recovery units. Lastly, the
Agency concludes there is a "no effects" determination for indirect effects to the CRLF
via direct effects to terrestrial plants and terrestrial plants growing in semi-aquatic areas
(e.g., wetlands, saturated riparian zones, etc.) in all recovery units and critical habitat.
Key uncertainties and data gaps that affect conclusions about direct and indirect effects
on California Red-Legged Frogs (and therefore the effects determination conclusions)
include: 1) Lack of targeted monitoring data, which does not allow for direct comparison
with model results - thus there is no means by which to definitively check the aquatic
exposure estimates. However, monitoring data that are available indicate that, when
present, sample concentrations are consistent with low-end model results, and may reflect
'background' levels in use areas; 2) Dilution factors used to establish the aquatic Action
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Area were based upon drainage area rather than stream flow - thus requiring a number of
simplifying assumptions that should be conservative and protective, but that nonetheless
increases the likelihood of error (whereas stream flow would be a direct measure of
actual dilution potential); 3) Information provided regarding aldicarb usage in California
may be inaccurate, inconsistent, or contradictory, but is the best available at this time; 4)
use of most sensitive freshwater and terrestrial animal endpoint values to calculate RQs,
which are one of several lines of evidence used to make direct and indirect effects
determinations; 5) use of surrogate species (bird) to assess risk to aquatic and terrestrial
phase amphibians T-REX overestimates risk to small frogs by using the LD50 for small
birds and underestimates risk to large frogs by using the LD50 for medium birds.
Considering the uncertainties and unknowns, it is believed that this assessment provides
the most accurate and reasonably protective risk evaluation currently possible.
Effects determinations for aldicarb direct effect, indirect effects, and effects to the critical
habitat based on the highest risk scenario, sugar beet, and on-site effects to terrestrial prey
items are displayed in Tables 1-3, below. Following the tables, effects determinations for
individual registered crop uses and for on-site and off-site exposure of terrestrial prey
items are delineated.
Table 1 Summarizes the effects determinations for direct effect of aldicarb to any of the life-stages of
the CRLF in Eight Recovery Units.
Life stages include aquatic (eggs, larvae, tadpoles) and terrestrial phase of CRLF (young and adult frogs).
The assessment endpoints are growth, survival, and reproduction of CRLF individuals.
Recovery
Unit
Effects
Determination
Basis for Effects Determination Conclusion
1
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF
2
NLAA
Based on lack of spatial overlap with Action Area (AA), frog habitat, and
occurrence sightings, CAL DPR PUR data despite LOC exceedances to CRLF
3
NLAA
Based on lack of spatial overlap with Action Area (AA), frog habitat, and
occurrence sightings, CAL DPR PUR data despite LOC exceedances to CRLF
4
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF
5
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF;
6
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF
7
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF
8
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF
* Summarize the effects determination by Recovery Unit, based upon the most conservative of the effects
determinations. Summation by specific crops, more specific to on-site usage, is provided in the following
text.
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Table 2 Summarizes the effects determinations for indirect effect of aldicarb to any of the life-stages of
the CRLF in Eight Recovery Units.
The life stages include aquatic (eggs, larvae, tadpoles) and terrestrial phase of CRLF (young and adult frogs).
The indirect effects include effects to habitat including effect to primary productivity, prey, and riparian
habitat.
Recovery
Unit
Effects
Determination
Basis for Effects Determination Conclusion
1
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
2
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF food
sources
3
NLAA
Based on lack of spatial overlap with AA
4
NLAA
Based on lack of spatial overlap with AA
5
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
6
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
7
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF food
sources
8
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
* Summarize the effects determination by Recovery Unit, based upon the most conservative of the effects
determinations. Summation by specific crops, more specific to on-site usage, is provided in the following
text.
Table 3 Summarizes the effects determinations for effects to the critical habitat the CRLF in recovery
units one thru eight.
The effects entail effects to growth and survival of terrestrial and aquatic plant and animal components.
Recovery
Unit
Effects
Determination
Basis for Effects Determination Conclusion
1
LAA
Based on direct effects to terrestrial and aquatic animals which are
components of the critical habitat.
2
NE
No designated critical habitat in Recovery Unit (RU)
3
NE
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to animals
components of the critical habitat
4
NE
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to animals
components of the critical habitat
5
LAA
Based on direct effects to terrestrial and aquatic animals which are
components of the critical habitat.
6
LAA
Based on direct effects to terrestrial and aquatic animals which are
components of the critical habitat.
7
NE
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to animals
components of the critical habitat..
8
NE
No designated critical habitat in RU
* Summarize the effects determination by Recovery Unit, based upon the most conservative of the effects
determinations. Summation by specific crops, more specific to on-site usage, is provided in the following
text.
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Aquatic Phase CRLF and Critical Habitat:
No Effect
Soybean (in-furrow and/or positive displacement applications only), Citrus, and
Sorghum
Citrus, sorghum and soybean (but only when applied in-furrow with immediate soil
incorporation or in-furrow with positive displacement) uses were determined to have "no
effect" directly or indirectly on the aquatic-phase of the CRLF or the aquatic-phase of the
critical habitat. This determination was based on the results of the risk assessment where
all direct and indirect assessment endpoints of the aquatic-phase CRLF and its aquatic-
phase critical habitat were either below endangered LOCs (i.e., no exceedences of LOCs
for aquatic animals) or judged based on the best available information to not be affected
(i.e., off-field terrestrial plant components of critical habitat and aquatic plants judged to
not be affected, based on estimated exposure concentrations that were lower than a 'no
observable effect' level for limited toxicity data). Although application rates for citrus
are fairly high (4.95 lb a.i./A) and incorporation efficiency only 85%, low rainfall rates
and other factors in citrus production areas of California contribute to relatively low
aquatic exposure and risk estimates. For Sorghum use, low application rates (1 lb a.i./A)
and high incorporation efficiency (in-furrow application, 99%) contribute to minimal
aldicarb residues being exported into surface waters or off-field terrestrial habitat. When
compared to less efficient application methods with approximately 85% soil
incorporation (e.g., banded applications), the use of more efficient application techniques
(e.g., in-furrow, positive displacement) results in higher incorporation efficiencies (99%),
and concomitant exposure estimations well below LOCs for soybean.
Ornamentals (container grown) indoors
There is no exposure pathway by which aldicarb applied to ornamentals in containers
grown indoors may reach and expose the aquatic-phase of the CRLF or its critical habitat
(i.e., no run-off, no atmospheric transport, no CRLF or its critical habitat indoors).
Therefore this use is determined to have "no effect" on the aquatic-phase of the CRLF or
its critical habitat.
May Affect but Not Likely to Adversely Affect
Ornamentals (field grown—no containers) and Sweet Potato
Aldicarb registered uses on containerless field-grown ornamentals and sweet potato were
identified as "may affect" because the acute RQ values for aquatic invertebrates exceeded
the acute endangered LOC, the chronic RQ values exceeded the chronic LOC, and the
chronic RQ for aquatic invertebrates exceeded the chronic LOC for sweet potato use.
However, based on consideration of a number of factors, the level of effect both directly
and indirectly to the aquatic-phase of the CRLF and its aquatic critical habitat for these
assessment endpoints was determined to be discountable. Off-site terrestrial plant
components of critical habitat and aquatic plants were judged to not be affected based on
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the best available information that estimated exposure concentrations were lower than 'no
observable effect levels' (based on limited toxicity data). Therefore, aldicarb uses on
containerless field-grown ornamentals and sweet potato were determined to "not likely
adversely affect" the aquatic-phase of the CRLF and its critical habitat.
Direct effects to the aquatic-phase of the CRLF were considered discountable because the
acute endangered RQ values did not exceed the endangered species LOC; while the
chronic RQ value of 1 was exceeded, this exceedence was considered not significant and
essentially indistinguishable from the no observable effect level. For example, the
chronic RQ of 1.1 for containerless field grown ornamentals based on significant figures
is not distinguishable from 1 {i.e., EEC/NOAEC = 0.49/0.46 = 0.5/0.5 = 1), the level
equivalent to no observable effects. In addition, ornamental usage is not extensive, and
any potential impact on a water body adjacent to an application area would likely be
minor, fleeting, and spatially very limited.
Loss of fish or aquatic invertebrates as dietary resources was considered discountable
based on several factors affecting the frequency and duration of exposure and the
magnitude of effect. For example, both of these uses are limited to a single application
per year, with sweet potato application occurring at plant and ornamentals occurring at
any time prior to or during an infestation but again limited by the label to a single
application per year. Therefore, any potential impact on a water body adjacent to an
application area would likely be minor and fleeting. The acute endangered LOC for fish
is not exceeded for either use. Although the chronic LOC is exceeded, as discussed in the
preceding paragraph these exceedences are essentially equivalent to the no observable
adverse effect level. Additionally, other fish species are not as sensitive (e.g., fathead
minnow), so any potential impact would be limited in both magnitude and number of
species involved. For aquatic invertebrates, while the acute endangered LOC was
exceeded, the likelihood that an individual would be affected for the most sensitive
species was one-in-over a million (based on default slope of 4.5). Additionally, based on
the invertebrate species sensitivity distribution, over 80 percent of the aquatic
invertebrates would be even less sensitive. The chronic LOC was not exceeded for the
ornamentals and was at the LOC of 1 for sweet potato use, which is equivalent to no
observable effect on invertebrates.
Ornamentals (container grown) outdoors
Outdoor container grown ornamental use was considered to "not likely adversely affect"
the aquatic-phase CRLF or its aquatic-phase critical habitat. This determination was
based on the determination for containerless field grown ornamentals used as a surrogate.
Surface water exposure concentrations are expected to be lower than that for
containerless field grown ornamentals. This reduction is attributable to containers which
are expected to physically reduce run-off of aldicarb and its major toxic degradates and
lower application rates as compared to containerless field grown ornamentals. In
addition, ornamental usage is not extensive, and any potential impact on a water body
adjacent to an application area would likely be minor, fleeting, and spatially very limited.
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May Affect and Likely to Adversely Affect
Dried Beans, Soybean (banded applications), Peanut, Pecans, Cotton, Alfalfa,
Sugar beet
Aldicarb registered uses on dried beans, soybean, peanut, pecan, cotton, alfalfa, and sugar
beet were identified as "may affect" and "likely to adversely affect" the CRLF directly
because both the acute endangered LOC and chronic LOC were exceeded for amphibian
assessment endpoints (fish used as surrogate) and indirectly because fish and aquatic
invertebrate acute and chronic LOC values were exceeded.
It should be noted that for many of these crops, use of more efficient application
techniques (i.e., ones that yield 99% vs. 85% incorporation) would result in exposure
estimations well below the LOC for most categories (see Table 12). Although this might
be impractical or impossible for some current uses (e.g., peanut application post-pegging,
cotton application at bloom, pecan), in other cases (e.g., soybean, dried bean) achieving
an incorporation efficiency of 99% results in acceptable levels of risk, and should be
possible with appropriate application techniques (possibly requiring label changes).
Terrestrial Phase CRLF and Critical Habitat:
No Effect
Ornamentals (container grown) indoors
There is no exposure pathway by which aldicarb applied to ornamentals in containers
grown indoors may reach and expose the terrestrial-phase of the CRLF or its terrestrial
critical habitat {i.e., no run-off, no atmospheric transport, no CRLF or its critical habitat
indoors). Therefore this use is determined to have "no effect" on the aquatic-phase of the
CRLF or its critical habitat.
May Affect but Not Likely to Adversely Affect
Off-site All Outdoor Uses
Off-site exposure for all outdoor registered uses was identified as "may affect" because
an individual terrestrial-phase CRLF that ingested a granule transported off-site in the gut
(incidental ingestion) or on the fur of a small mammal would potentially be effected. All
other off-site exposure of the terrestrial-phase CRLF {i.e., bioaccumulation in terrestrial
invertebrates or mammalian dietary items) and its critical habitat {i.e., loss of dietary
resources, riparian or upland plants) to aldicarb and its major toxic residues are below
LOCs. Because exposure of a terrestrial-phase CRLF to a granule carried in a small-
mammal off-field was considered unlikely and no other off-site exposure of the
terrestrial-phase CRLF or its critical habitat were above LOCs, exposure off-site for all
outdoor uses was considered discountable and therefore "not likely to adversely affect"
either directly or indirectly the terrestrial-phase of the CRLF or its critical habitat.
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Risks to terrestrial environments outside the zone of application for granular aldicarb are
mainly limited to re-deposition of aldicarb residues in lower-lying areas affected by
aldicarb runoff from nearby fields. However, calculations of the approximate amount of
aldicarb potentially deposited as a result of registered aldicarb use (based on the highest
risk scenario, cotton at 5 lbs a.i./A) indicate that concentrations (~ 10"6 mg a.i./kg soil)
would be several orders of magnitude below those that would exceed the LOC.
Exposure off-site of a CRLF to a granule in the gut or on the fur of small mammal was
considered unlikely because it is doubtful that the series of events needed to coincide for
an actual exposure event to occur would be frequent, if they occurred at all. First,
aldicarb is applied to most crops once per year, and infrequently for the others (i.e.,
cotton at most three times and sugar beets and peanuts at most two times per year).
Second, the duration of the integrity of a granule in the field is limited as it is fragile, and
readily dissolves in water—irrigation or rainfall dissolves the granule and moves it down
into the soil profile. Therefore the window of opportunity for a small mammal (as
potential CRLF prey) to be exposed on field to a granule is limited to a few days a year.
While it is considered likely that some small mammals may be exposed to aldicarb during
this window, it is unlikely that a significant number of small mammals would then
subsequently move off-site, and not die before encountering a CRLF (biological
description does not indicate it feeds on carrion).
May Affect and Likely to Adversely Affect
On-site All Crops
On-site exposure for all outdoor registered uses was identified as "may affect" and
"likely to adversely affect" the terrestrial-phase of the CRLF because the acute LOC was
exceeded for the direct amphibian measurement endpoint (birds) and for indirect effects
(i.e., loss of small mammals, and on-site terrestrial invertebrates) for all uses.
Bioaccumulation was demonstrated to not be a pathway of concern. This effects
determination is based on the assumption that terrestrial-phase CRLF will come onto the
treated site and that on-site resources are considered a critical component that supports
CRLF (i.e., invertebrates and insects on the field that the farmer is trying to eliminate are
considered critical to the support of the CRLF) and that the field is considered part of the
critical habitat. A number of the uses are applied on fields that have been prepared for
planting and should be relatively barren of cover for the CRLF at the time of aldicarb
application (i.e., sorghum, sweet potato, dried bean, and soybean).
Pooling the crop and aquatic- and terrestrial-phase specific analyses the following
summarizes the effects determination by crop.
A "No Effect" ("NE") determination was concluded for indoor container grown
ornamentals because there is no exposure pathway for aldicarb to reach either the
aquatic- or terrestrial-phase of the CRLF or its critical habitat.
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A "Not Likely to Adversely Affect" ("NLAA") determination was concluded for
soybean (in-furrow and/or positive displacement applications only), citrus, and
sorghum uses based on the lack of direct and indirect, acute and chronic effects to
the aquatic-phase of the CRLF and its critical habitat and the lack of or
discountable direct and indirect, acute and chronic effects to off-site CRLF, or to
its critical habitat.
A "Not Likely to Adversely Affect" ("NLAA") determination was concluded for
containerless field-grown ornamentals, outdoor container grown ornamentals, and
sweet potato based on the lack of direct or discountable direct and indirect, acute
and chronic effects to the aquatic-phase of the CRLF and its critical habitat and
the lack of or discountable direct and indirect, acute and chronic effects to off-site
terrestrial-phase CRLF, or to its critical habitat.
A "Likely to Adversely Affect" ("LAA") determination was concluded for dried
beans, soybean (banded applications), peanut, pecans, cotton, alfalfa, and sugar
beet based on direct acute and chronic effects to the aquatic-phase of the CRLF,
and indirect effects to fish and aquatic invertebrates (food resources to aquatic-
and terrestrial-phase of the CRLF) and its critical habitat. However, there is no
direct and indirect, acute and chronic effects to off-site terrestrial-phase CRLF, or
its critical terrestrial habitat.
A "LAA" determination was concluded for all uses if terrestrial-phase CRLF will
come onto the treated site and that on-site resources are considered a critical
component that supports CRLF (i.e., invertebrates and insects on the field that the
farmer are trying to eliminate are considered critical to the support of the CRLF)
and that the field is considered part of the critical habitat.
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
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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.
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2. Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By
identifying the important components of the problem, it focuses the assessment on the
most relevant life history stages, habitat components, chemical properties, exposure
routes, and endpoints. This assessment was completed in accordance with the August 5,
2004 Joint Counterpart Endangered Species Act (ESA) Section 7 Consultation
Regulations specified in 50 CFR Part 402 (USFWS/NMFS 2004; FR 69 47762). 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 procedures outlined in the Overview
Document (U.S. EPA 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
aldicarb on alfalfa (Section 24c), dried beans (Section 3), citrus, cotton (Section 3),
peanuts (Section 3), pecan (Section 3 and 24c), sorghum (Section 3), soybean (Section 3),
sugar beet (Section 3), sweet potato(Section 3), and ornamentals. 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) us. EPA et al. (Case
No. 02-1580-JSW(JL)) settlement entered in the Federal District Court for the Northern
District of California on October 20, 2006. It is one in a series of endangered species
effects determinations for pesticide active ingredients involved in this litigation.
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). Use of such
information is consistent with the guidance provided in the Overview Document (U.S.
EPA 2004), which specifies that "the assessment process may, on a case-by-case basis,
incorporate additional methods, models, and lines of evidence that EPA finds technically
appropriate for risk management objectives" (Section V, page 31 of U.S. EPA 2004).
In accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of aldicarb 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
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decision associated with a use of aldicarb 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 aldicarb at the use sites described in
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 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 aldicarb 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 aldicarb.
If a determination is made that use of aldicarb 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 overlay of CRLF habitat with
aldicarb use) and further evaluation of the potential impact of aldicarb 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.
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Because aldicarb is expected to directly impact living organisms within the action area
(defined in Section 2.7), critical habitat analysis for aldicarb 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 jeopardize the
continued existence of the species. Evaluation of actions related to use of aldicarb that
may alter the PCEs of the CRLF's critical habitat form the basis of the critical habitat
impact analysis. Actions that may affect the CRLF's designated critical habitat and
jeopardize the continued existence of the species have been identified by the Services and
are discussed further in Section 2.6.
2.2 Scope
Aldicarb (2-methyl-2-(methylthio)propionaldehyde O-(methylcarbamoyl)oxime), also
known by the trade name TEMIK®, is a granular pesticide that was first registered for use
on cotton in 1970. Aldicarb is an insecticide, acaricide, and nematicide, and is used in
California on a variety of crops. Currently registered crop uses in California include:
alfalfa, cotton, dried beans, citrus, sugar beet, sorghum, soybean, sweet potato, pecan,
and peanut. County level usage data for aldicarb were obtained from California's
Department of Pesticide Regulation Use Reporting (CDPR PUR) database. Reported
usage information considered in this assessment spans from 2001-2005 and is for the
following commodities: alfalfa, cotton, dried beans, citrus, sugar beet, sorghum, sweet
potato, pecan, and ornamentals.
There are a number of uses reported in the CDPR PUR database (37 records out of
14,960 records or 0.2% of the database) that either are misuses or entry errors in the
database for they are not supported by past or current state (Section 24c) or national
(Section 3) labels for aldicarb. These uses are not part of the FIFRA regulatory action and
have not been included in this assessment but are identified here for completeness:
landscape maintenance (1 record), soilfumigation/preplant (2 records), tomato
processing (1 record), rights of way (1 record), almonds (1 record), corn (forage-fodder)
(9 records), corn (human consumption) (2 records), and structural pest control (1
record). Aldicarb was also used in research (i.e., research commodity record) in 2004 (1
record, 23.1 lbs to 11 acres), in 2002 (2 records, 11.55 lbs to 5.5 acres, and 10.95 lbs to
an unknown number of acres), and in 2001 (1 record, 4.5 lbs to unknown number of
acres); the research occurred in Fresno and Tulare Counties. This use will be excluded as
well from this assessment. Experimental use permits are federal actions that are taken for
specific research projects which are typically of limited use and acreage. Each
experimental use is considered on a case-by-case basis, limited to the year that the permit
was granted; ESA effects would be considered at the time when experimental use permits
are granted.
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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 aldicarb in accordance with the approved product labels for California is
"the action" being assessed.
This ecological risk assessment is for currently registered uses of aldicarb 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.
Consideration of degradates is an integral part of this risk assessment. There are two
degradates of concern, aldicarb sulfoxide and aldicarb sulfone, that appear to form
primarily in the shallow subsurface (although they may also be produced within plants
that have systemically appropriated the parent chemical). Based on acute toxicity studies
for freshwater fish, the relative toxicity relationship is: aldicarb > aldicarb sulfoxide >
aldicarb sulfone. Based on the acute toxicity for freshwater invertebrates, the relative
toxicity relationship is: aldicarb « aldicarb sulfoxide > aldicarb sulfone. Total toxic
residues (parent aldicarb + aldicarb sulfoxide + aldicarb sulfone) were modeled and
evaluated in this screening-level assessment for aquatic exposure. Assuming 100 % of
aldicarb parent in the terrestrial environment is a more conservative exposure assumption
than modeling residues that are less toxic; therefore, this assessment does not consider
degradates in the terrestrial environment.
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). Aldicarb does not have any registered products that contain multiple active
ingredients.
There are many variables within the landscape covered by this risk assessment that can
affect predicted exposure to (and ultimately effects of) aldicarb in any given area; even
within contiguous Red-Legged Frog critical habitats in California there is great
variability in land use and cover, topography, and precipitation.
2.3 Previous Assessments
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Two previously published, relevant risk assessments for aldicarb are the aldicarb
Registration Eligibility Document (US EPA, May 2005) and revised RED (US EPA,
September 2006). Key conclusions on exposure and risks to terrestrial and aquatic
wildlife as well as relevant data gaps as they relate to these two assessments are listed
here. For specific details not mentioned in this assessment, these documents can be
consulted. Risk conclusions were consistent and remained unchanged between
assessments.
Exposure and Risk to Terrestrial Organisms:
• The cotton scenario (4.05 lbs ai/A; banded sidedress, 1 application) poses the
highest use risk in the terrestrial environment to mammals and birds due to
aldicarb levels in soil (highest acute RQ for small birds = 6400), followed by
potato, sugar beet, peanuts and dry beans (RQ for small birds = 3000, 2800, 2800,
2600, respectively).
• The acute risk, acute restricted use, and acute endangered species LOCs for birds
and mammals are exceeded for all target crops (cotton, dry beans, sorghum,
peanuts, potatoes, soybeans, sugar beets, sweet potatoes, citrus, pecans,
ornamentals) due to aldicarb levels in soil at both maximum allowed label rates
(1.05 to 10.05 lbs ai/A) and average use rates (0.6 to 3.1 lbs ai/A).
• Acute levels of concern are consistently exceeded by a factor of greater than 100
and are frequently exceeded by more than 1000.
• Granules left exposed on the surface appear to be the main source of exposure,
but other sources such as residues of aldicarb taken up by plants and soil
invertebrates (e.g., earthworms) may also serve as a means of exposure.
• A single granule of TEMIK® 15G can kill a small bird
• Reproductive effects to birds at sub-lethal levels could not be assessed because of
the lack of reproductive studies with aldicarb or its degradates, due in part to high
acute toxicity. It has been difficult to design an experiment that utilizes a dose
low enough not to acutely intoxicate adult birds.
• Reduction in seedling emergence and vegetative vigor to non-target terrestrial
plants from runoff could not be assessed because of the lack of seedling
emergence and vegetative vigor toxicity tests. Label identified the potential for
impact to certain crop plants.
Exposure and Risk to Aquatic Organisms
• The cotton scenario (4.05 lbs ai/A; 1 application) poses the highest use risk in the
aquatic environment to aquatic invertebrates and fish due to estimated levels of
aldicarb and its degradates in surface water from runoff (highest acute and chronic
RQs for freshwater invertebrates =1.4 and 26.6, respectively), followed by
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pecans, soybeans, citrus, and potato (acute and chronic RQs of 0.60, 0.36, 0.15,
0.07 and 11.40, 6.76, 2.80, 1.40, respectively).
• There is acute risk for freshwater fish and invertebrates and estuarine/marine fish
and invertebrates for all of the registered uses (list) with the exception of potatoes
for freshwater fish and invertebrates and estuarine/marine fish.
• Based on the use of an estimated NOAEC for reproductive effects in freshwater
fish, the chronic level of concern is also exceeded for freshwater fish (larval and
juvenile survival) for cotton, pecan, and soybean use patterns.
• Based on the use of an estimated NOAEC for reproductive effects in
estuarine/marine fish, the chronic level of concern is exceeded for
estuarine/marine fish for all crop scenarios.
• Aldicarb residues are most likely to exceed levels of concern for fish and aquatic
invertebrates in low-order streams because these streams are dominated by
baseflow conditions (where 100% of stream flow consists of discharged
groundwater), and most of the toxic residues are believed to form within the
subsurface (especially within the saturated zone) and are conveyed by
groundwater. Higher-order streams are sustained by much larger contributing
land areas, so there should be a greater dilution effect.
• In addition to risk based exposure estimates from modeling, there were also
exceedances of the Agency levels of concern based on surface water residue
monitoring data.
2.4 Stressor Source and Distribution
Chemical and Physical Properties
Common Name: Aldicarb
Chemical Name: 2-methyl-2(methylthio)propionaldehyde
0-(methylcarbamoyl)oxime
CAS No.
PC Code:
Molecular Formula:
Molecular Weight:
Density:
Melting Point:
Boiling Point:
Vapor Pressure:
Water Solubility:
Henry's Law Const.:
Octanol/Water Partition Coefficient (Kow):
Formulations:
Granules (e.g. Active ingredient 15.0%,
Inert ingredients 85.0%)
decomposes above 100NC
2.55 x 10"5 mm Hg at 25°C
6,000 mg/L(pH 7, 25 °C)
1.7xlO"10 atm m3/mole
116-06-3
098301
c7h14n2o2s
190.2 g/mol
1.2 g/cm3
100NC
14
17
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H3c fH3 o
CHiv Jo,. -ss-N ch3 . , . I .
ch n" Aldlcarb
I
I
H
1-UC, £H- M
^ u 3
3^,. ^n3
3^s^u cH''n^"3 Aldicarb Sulfoxide
CHr—. 5b1 . N ¦— iL CH
II I
o I H
I
H3<=» £H3
CH3^~s'Cch''Nv^o'Cvn'CH3 Aldlcarb Sulfone
// W I
o o b
Figure 1 Chemical structure of aldicarb and its oxidative transformation products
2.4.1 Environmental Fate Assessment
Aldicarb rapidly degrades to aldicarb sulfoxide and aldicarb sulfone - both of which are
as toxic or nearly as toxic as, and are more persistent than, the parent. Other aldicarb
degradates may form as well, but are substantially less toxic and/or produced only in
small amounts (<5%) and so are not included in this evaluation. Aerobic soil metabolism
is the primary dissipation route for parent aldicarb in unsaturated soil. Half-lives for
parent aldicarb range from 1 to 28 days (MRIDs 00102051, 00093642, 00080820,
00093640, 00053366, 00101934, 00035365, and 00102071). There is currently
insufficient data to accurately estimate the formation and dissipation rates of the
sulfoxide and sulfone degradates. However, the rapid oxidation of parent aldicarb to
these forms, and their substantially greater persistence than the parent, have been well
documented in the published literature (e.g. Bull et al., 1970; Smelt etal., 1979).
Laboratory studies suggest that degradation of all three aldicarb forms (parent, sulfoxide,
and sulfone) to relatively non-toxic, non-carbamate residues (oximes and nitriles) occurs
slowly (ti/2 up to 3 months) in aerobic soils, as a result of soil-catalyzed hydrolysis rather
than aerobic metabolism (Lightfoot et al., 1987; Bank and Tyrrell, 1984). Parent aldicarb
is generally stable to hydrolysis, slowly hydrolyzing only at a pH of 9 (MRID 00102065).
Aldicarb sulfoxide hydrolyzed more quickly (ti/2 = 2.3 days) at pH 9 than at pH 7 (about
6% at 28 days) (MRID 00102066). Aqueous photolysis rapidly degraded aldicarb to
oxime and nitrile forms (i.e. with a ti/2 of four days: MRID 42498201). However, this
process will only be dominant in clear, shallow waters, and will not affect residues in the
subsurface.
While there is limited information on aerobic metabolism in aquatic environments, a
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published laboratory study (Vink et al., 1997) reported half-lives ranging from 70 to 173
days in surface waters in the Netherlands. The fate of parent aldicarb under anaerobic
aquatic conditions (particularly groundwater) is of less concern than that of the
degradates (aldicarb sulfoxide and aldicarb sulfone), which have been detected in
groundwater long after application of the parent chemical had ceased. Published studies
have reported increased degradation rates under low redox conditions, perhaps due to
catalysis by reduced metal species in these environments (Bromilow et al., 1986). For
example, Smelt et al. (1983) reported laboratory half-lives of aldicarb sulfone and
sulfoxide ranging from 2 to 131 days in Dutch subsoils under "anaerobic conditions"
(310 mV), and from 84 to 1100 days under aerobic conditions. Given this information, it
is likely that aldicarb sulfoxide and aldicarb sulfone, which degrade relatively slowly in
aerobic soil (MRID 44005001), can gradually leach into groundwater and continue to
provide detectable levels of these materials over long time periods.
In published field studies, dissipation half-lives for total carbamate residues in soil have
ranged from approximately 0.3 to 5 months in the unsaturated zone, and 1 to 36 months
in the saturated zone (Jones and Estes, 1995), in apparent contradiction to the observation
of faster degradation under anaerobic (saturated) conditions. The reasons for the extreme
variability in reported transformation rates (3 hours to 36 months) for aldicarb residues
under anaerobic/saturated conditions are not known, but may be related to temperature,
pH, and the presence of soils for surface catalysis (Lightfoot, et al., 1987). Also, not all
saturated zones are necessarily anoxic; if they are shallow, there can be sufficient
interaction with the unsaturated zone such that the groundwater may be sub-oxic or even
atmosphere-equilibrated (oxic). Monitoring data in areas with historical aldicarb
contamination confirm the high persistence of total aldicarb residues in some
groundwater. For example, twenty years after cessation of aldicarb use on Long Island,
NY, aldicarb sulfone and sulfoxide are still the most frequently detected pesticide
compounds in groundwater there (Suffolk County Dept. of Health Services, 2000).
In this assessment, 'total aldicarb residues' - consisting of parent aldicarb, the degradate
aldicarb sulfoxide, and the degradate aldicarb sulfone - are considered for the aquatic
assessment. This is done partly because the sulfoxide and sulfone degradates are nearly
as toxic as the parent and are more mobile and persistent. For aquatic exposures the
parent aldicarb may undergo some transformation to the sulfoxide and sulfone residues
between the time of application to the soil and a runoff event. Therefore, by including
both transformation products in addition to the parent and by modeling the combined
residues using the most mobile and persistent fate parameters and comparing estimated
exposures to the most toxic endpoint, we are accounting for the maximum potential
exposure of aldicarb residues in the aquatic environment. In the case of terrestrial
exposure, though, the higher toxicity of the parent and expectation that on-site surface
residues of greatest concern will consist mostly of parent (especially whole granules) lead
to an assumption of parent-only exposure in the terrestrial arena. That is, in the terrestrial
environment the highest potential exposure will occur at the time of application before
transformation, when parent aldicarb only is present. By assuming parent-only exposures
and the higher toxicity of the parent, we are being similarly protective for the terrestrial
environment.
19
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2.4.2 Environmental Transport Assessment
Parent aldicarb is most likely to be transported off-site as a component of field runoff.
Following a rain event, aldicarb may reach aquatic environments as sheet and channel
flow from areas of application, since aldicarb is moderately persistent in terrestrial
environments and soluble in water. It is unlikely, though, that undissolved granules will
reach surface water bodies. The toxic degradates (aldicarb sulfoxide and aldicarb
sulfone) are more prone to move vertically down through the soil profile, and potentially
into groundwater, as they form primarily in the shallow subsurface. Groundwater that
contains aldicarb residues may then be discharged into surface waters as baseflow. If the
receiving groundwater is cool, acidic, and oxic, the sulfoxide and sulfone degradates will
be very persistent and capable of long-distance subsurface transport.
Aldicarb and its oxidation products are all highly mobile in soil. Aldicarb itself has
Freundlich Kads values ranging between 0.20 ml/g (for sand) and 0.60 ml/g (for clay)
(MRID 42498202). Aldicarb sulfoxide has Freundlich Kads values between 0.17 ml/g
(sandy loam soil) and 0.36 ml/g (sandy clay loam) (MRID 43560301). Aldicarb sulfone
had slightly lower values, ranging between 0.12 ml/g and 0.22 ml/g for the same set of
soils as the sulfoxide (MRID 43560302). Degradation rates for combined aldicarb
residues (parent plus sulfoxide plus sulfone) were calculated based upon the available
information; details may be found in Appendix N & P.
Potential transport mechanisms include pesticide surface water runoff, and secondary
drift of volatilized or soil-bound residues leading to deposition onto nearby or more
distant ecosystems. The magnitude of pesticide transport via secondary drift depends on
the pesticide's ability to be mobilized into air and its eventual removal through wet and
dry deposition of gases/particles and photochemical reactions in the atmosphere. A
number of studies have documented atmospheric transport and redeposition of pesticides
from the Central Valley to the Sierra Nevada mountains (Fellers et al., 2004, Sparling et
al., 2001, LeNoir et al., 1999, and McConnell et al., 1998). Prevailing winds blow across
the Central Valley eastward to the Sierra Nevada mountains, transporting airborne
industrial and agricultural pollutants into Sierra Nevada ecosystems (Fellers et al., 2004,
LeNoir et al., 1999, and McConnell et al., 1998). Therefore, physicochemical properties
of the pesticide that describe its potential to enter the air from water or soil (e.g., Henry's
Law constant and vapor pressure), pesticide use, modeled estimated concentrations in
water and air, and available air monitoring data from the Central Valley and the Sierra
Nevadas are considered in evaluating the potential for atmospheric transport of aldicarb
to habitat for the CRLF. Because aldicarb is applied as a granule and its potential to enter
the air from water or soil is considered insignificant based on Henry's Law constant and
vapor pressure).
20
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2.4.3 Mechanism of Action
Aldicarb is a systemic insecticide, acaricide, and nematicide. It is a potent cholinesterase
(ChE) inhibitor causing inhibition of erythrocyte acetylcholinesterase (RBC ChE) as well
as plasma butyryl ChE by binding to the active site of the enzyme. Acetylcholinesterase
is an enzyme necessary for the degradation of the neurotransmitter acetylcholine (ACh)
and subsequent cessation of synaptic transmission. Inhibition of these enzymes in
animals (i.e. terrestrial and aquatic invertebrates, fish, birds, amphibians, reptiles,
mammals) results in the accumulation of ACh at cholinergic nerve endings and continual
nerve stimulation leading to death.
2.4.4 Use Characterization
National (Section 3) uses for aldicarb are presented in Table 4, with label maximum
application rates. Use on potato1 and sugarcane2 is prohibited in California on the Section
3 label (EPA Reg. No. 264-330). In California, dry beans and sorghum have the lowest
allowed maximum application rates (7 lbs of product/A), while pecans, citrus, and sugar
beet have the highest allowed maximum application rates among all crop uses permitted
in the state (33 lbs, 33 lbs, and 28 lbs of product/A, respectively). For aldicarb use on dry
beans in California, the target pests, which differ slightly from the rest of the states, are
leafhoppers, Mexican bean beetle, mites, and nematodes. For the use on sugar beet in
California, the target pests do not differ from the rest of the country; but California has
restrictions on application window for sugar beet and dry beans from May 1 through
September 1. For aldicarb use on sorghum, there are no restrictions on the Section 3 label
for California. For aldicarb use on citrus, the Section 3 restriction for California refers to
the application window only (May 1 through September 1). The use on pecans is
restricted by the Section 24c label and restricts the maximum application per acre to 33
lbs of product (4.95 lbs a.i.) per acre.
1 Label permits use on potato only in Florida, Pacific Northwest, and the following counties in Utah
(Beaver, Boxelder, Cache, Carbon, Davis, Duchesne, Iron, Millard, lute, Salt Lake, Sanpete, Sevier,
Uintah, Utah, Wasatch, Washington, and Weber) and Nevada (Humboldt, Pershing)
2 Label permits use on sugarcane in Louisiana only
21
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Table 4 National Labels Supporting Aldicarb Uses and Maximum Application Rates
National - Section 3 Registration
Max 1 Time
Max appl
appl rate
rate/year
Max #
Site
(lbs/A)
(lbs/A)
appl/year
Citrus
33
33
1
Cotton
20
33
3
Dry Beans
14
14
1
Peanuts
20
20
1
Pecans
67
67
1
Potato*
20
20
1
Sorghum
7
7
1
Soybean
20
20
1
Sugarbeet
27
33
Sugarcane*
20
20
1
Sweet Potato
20
20
1
label for nectarine not found; thus not included in table
*off labeled in California
Figure 2 shows an overlay of where aldicarb was used in 2001 through 2005 (source:
California Department of Pesticide Regulation Use Reporting (CAL DPR); map shows
land in California which is under crop cultivation (based on National Land Cover Data
(NLCD) 2002), describing, based on best available information, the aerial extent of
potential aldicarb use in California. Del Norte and Humboldt Counties (northwest corner
of state) have been off labeled since 1983.
22
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Aldicarb Agriculture and Orchard Use Areas
Legend
~ CA counties
| CRLF Recovery Units
aldicarb agriculture use
aldicarb orchard/vineyard use
Kilometers
Compiled from California County boundaries (ESRI, 2002),
USOA National Agriculture Statistical Service (NASS, 2002)
Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
June, 2007. Projection: Albers Equal Area Conic USGS, North
American Datum of 1983 (NAD 1983)
Figure 2 Aldicarb Use Areas (includes row crops and orchards) in California, with Recovery Units
23
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Analysis of labeled use information is the critical first step in evaluating the federal
action. The current label for aldicarb 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.
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis
of both national- and county-level usage information (BEAD, December 2006) 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 aldicarb by county in this
California-specific assessment were generated using CDPR PUR data. Usage data are
averaged together over the years 2000 to 2005 to calculate average annual usage statistics
by county and crop for aldicarb, including pounds of active ingredient applied and base
acres treated. California State law requires that every pesticide application be reported to
the state and made available to the public. The summary of aldicarb usage for all use
sites, including both agricultural and non-agricultural, is provided below in Table 5.
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.
Table 5 California DPR Aldicarb Use, summarized by crop/use for 2001-2005
Use
AVG
Annual
Pounds
Applied
AVG
Annual
Area
T rcatcd
Max. Avg.
Application
Rate (lb
ai/A)
Max. 95
Percentile
Application
Rate (lb
ai/A)
Max. 99
Percentile
Application
Rate (lb
ai/A)
Max.
Maximum
Application
Rate (lb
ai/A)
Alfalfa
350.1
271.8 ac
2.18
2.69
2.69
2.69
Almond
63.0
30.0 ac
2.10
2.10
2.10
2.10
Bean, Dried
630.0
694.6 ac
1.06
2.10
2.10
2.10
Corn (Forage -Fodder) (a)
76.2
73.0 ac
0.86
2.10
2.10
2.10
Corn, Human Consumption (a)
45.4
60.5 ac
0.75
0.75
0.75
0.75
Cotton
234450.4
219023.3 ac
1.24
2.25
2.25
28.52
Landscape Maintenance (a)
0.2
Na
0.00
0.00
0.00
0.00
Nectarine
0.5
1.0 ac
0.45
0.45
0.45
0.45
N-Grnhs Flower
0.4
7400.0 sq ft
0.00
0.00
0.00
0.00
N-Grnhs Plants In Containers
0.4
22705.0 sq ft
0.00
0.00
0.00
0.00
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
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Use
AVG
Annual
Pounds
Applied
AVG
Annual
Area
T rcatcd
Max. Avg.
Application
Rate (lb
ai/A)
Max. 95
Percentile
Application
Rate (lb
ai/A)
Max. 99
Percentile
Application
Rate (lb
ai/A)
Max.
Maximum
Application
Rate (lb
ai/A)
N-Outdr Flower
0.0
1425.0 sq ft
0.00
0.00
0.00
0.00
N-Outdr Plants In Containers
801.1
19219.1 ac
4.45
5.00
5.00
5.00
N-Outdr Transplants
19.3
6.5 ac
2.94
3.37
3.37
3.37
Pecan
5099.5
1067.4 ac
4.95
4.95
5.82
5.82
Research Commodity
11.4
4.1
2.10
2.10
2.10
2.10
Soil Fumigation/Preplant (a)
233.3
385.8 ac
0.90
0.90
0.90
0.90
Sorghum/Milo
16.5
8.0 ac
2.06
2.06
2.06
2.06
Structural Pest Control (a)
0.1
na
0.00
0.00
0.00
0.00
Sugarbeet
85.5
67.7 ac
1.31
2.40
2.40
2.40
Tomato, Processing (a)
10.5
17.5 ac
0.60
0.60
0.60
0.60
All Uses
241893.7
272460.2 ac
4.95
5.00
5.82
28.52
(a) Use reports in Cal DPR PUR that represent misuse or misreporting are excluded from this assessment
(b) Uses excluded in this assessment because they will not affect CRLF
25
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Aldicarb Usage in County, lb
~ 0 -422.1
422.1 - 1232.1
_ 3491.3- 5088.8
¦ 25120.3 - 35082.3
I 75474.2- 75611.2
Figure 3 Aerial Extent of Known and Potential (Cultivated Land) Section 3 and 24c Aldicarb Use in
California
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
26
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regarding CRLF distribution, reproduction, diet, and habitat requirements is provided in
Sections 2.5.1 through 2.5.4, respectively. Further information on the status, distribution,
and life history of and specific threats to the CRLF is provided in Attachment 1.
Final critical habitat for the CRLF was designated by USFWS on April 13, 2006
(USFWS 2006; 71 FR 19244-19346). Further information on designated critical habitat
for the CRLF is provided in Section 2.6.
2.5.1 Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically
inhabited 46 counties in California including the Central Valley and both coastal and
interior mountain ranges (USFWS 1996). Its range has been reduced by about 70%, and
the species currently resides in 22 counties in California (USFWS 1996). The species has
an elevational range of near sea level to 1,500 meters (5,200 feet) (Jennings and Hayes
1994); however, nearly all of the known CRLF populations have been documented below
1,050 meters (3,500 feet) (USFWS 2002).
Populations currently exist along the northern California coast, northern Transverse
Ranges (USFWS 2002), foothills of the Sierra Nevada (5-6 populations), and in southern
California south of Santa Barbara (two populations) (Fellers 2005a). Relatively larger
numbers of CRLFs are located between Marin and Santa Barbara Counties (Jennings and
Hayes 1994). A total of 243 streams or drainages are believed to be currently occupied
by the species, with the greatest numbers in Monterey, San Luis Obispo, and Santa
Barbara counties (USFWS 1996). Occupied drainages or watersheds include all bodies
of water that support CRLFs (i.e., streams, creeks, tributaries, associated natural and
artificial ponds, and adjacent drainages), and habitats through which CRLFs can move
(i.e., riparian vegetation, uplands) (USFWS 2002).
The distribution of CRLFs within California is addressed in this assessment using four
categories of location including recovery units, core areas, designated critical habitat, and
known occurrences of the CRLF reported in the California Natural Diversity Database
(CNDDB) that are not included within core areas and/or designated critical habitat (see
Figure 4). 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
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
27
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to cover the current range of the species not included in core areas and/or designated
critical habitat, but within the recovery units.
Recovery Units
Eight recovery units have been established by USFWS for the CRLF. These areas are
considered essential to the recovery of the species, and the status of the CRLF "may be
considered within the smaller scale of the recovery units, as opposed to the statewide
range" (USFWS 2002). Recovery units reflect areas with similar conservation needs and
population statuses, and therefore, similar recovery goals. The eight units described for
the CRLF are delineated by watershed boundaries defined by US Geological Survey
hydrologic units and are limited to the elevational maximum for the species of 1,500 m
above sea level. The eight recovery units for the CRLF are listed in Table 6 and shown
in Figure 4.
Core Areas
USFWS has designated 35 core areas across the eight recovery units to focus their
recovery efforts for the CRLF (see Figure 4). Table 6 summarizes the geographical
relationship among recovery units, core areas, and designated critical habitat. The core
areas, which are distributed throughout portions of the historic and current range of the
species, represent areas that allow for long-term viability of existing populations and
reestablishment of populations within historic range. These areas were selected because
they: 1) contain existing viable populations; or 2) they contribute to the connectivity of
other habitat areas (USFWS 2002). Core area protection and enhancement are vital for
maintenance and expansion of the CRLF's distribution and population throughout its
range.
For purposes of this assessment, designated critical habitat, currently occupied (post-
1985) core areas, and additional known occurrences of the CRLF from the CNDDB are
considered. Each type of locational information is evaluated within the broader context
of recovery units. For example, if no labeled uses of aldicarb occur (or if labeled uses
occur at predicted exposures less than the Agency's LOCs) within an entire recovery unit,
that particular recovery unit would not be included in the action area and 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 6 (currently occupied core areas are bolded). While core areas are considered
essential for recovery of the CRLF, core areas are not federally-designated critical
habitat, although designated critical habitat is generally contained within these core
recovery areas. It should be noted, however, that several critical habitat units are located
outside of the core areas, but within the recovery units. The focus of this assessment is
currently occupied core areas, designated critical habitat, and other known CNDDB
28
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CRLF occurrences within the recovery units. Federally-designated critical habitat for the
CRLF is further explained in Section 2.6.
Table 6 California Red-legged Frog Recovery Units with Overlapping Core Areas and Designated
Critical Habitat.
Recovery Unit1
(Figure 2.a)
Core Areas ' (Figure 2.a)
Critical Habitat
Units3
Currently
Occupied
(post-1985)
4
Cottonwood Creek (partial)
(8)
Feather River (1)
BUT-1A-B
Sierra Nevada
Foothills and Central
Valley (1)
(eastern boundary is
the 1,500m elevation
line)
Yuba River-S. Fork Feather
River (2)
YUB-1
NEV-r
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)
Cottonwood Creek (8)
Putah Creek-Cache Creek (9)
North Coast Range
Foothills and
Western Sacramento
River Valley (2)
Jameson Canyon - Lower
Napa Valley (partial) (15)
Belvedere Lagoon (partial)
(14)
Pt. Reyes Peninsula (partial)
(13)
Putah Creek-Cache Creek
(partial) (9)
North Coast and
North San Francisco
Bay (3)
Lake Berryessa Tributaries
111!)
NAP-l
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
CCS-1A
South and East San
Francisco Bay (4)
East San Francisco Bay
(partial) (16)
ALA-1A, ALA-
IB, STC-1B
STC-1A
South San Francisco Bay
(partial) (18)
SNM-1A
Central Coast (5)
South San Francisco Bay
(partial) (18)
SNM-1A, SNM-
2C, SCZ-1
Watsonvillc Slough- Elkhom
SCZ-2
29
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Slough (partial) (19)
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.
30
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Recovery Units
100 Miles
I
Sierra Nevada Foothills and Central Valley
North Coast Range Foothills and Western
Sacramento River Valley
North Coast and North San Francisco Bay
South and East San Francisco Bay
Central Coast
Diablo Range and Salinas Valley
Northern Transverse Ranges and Tehachapi
Mountains
Southern Transverse and Peninsular Ranges
Legend
^ Recovery Unit Boundaries
Currently Occupied Core Areas
| Critical Habitat
| CNDDB Occurence Sections
] County Boundaries
Core Areas
1.
Feather River
19.
Watsonville Slough-Elkhorn Slough
2.
Yuba River- S. Fork Feather River
20.
Carmel River — Santa Lucia
3.
Traverse Creek/ Middle Fork/ American R
Rubicon 21.
Gablan Range
4.
Cosumnes River
22.
Ester o Bay
5.
South Fork Calaveras River*
23.
Arroyo Grange River
6,
Tuolumne River*
24.
Santa Maria River - Santa Ynez River
1.
Piney Creek*
25.
Sisquoc River
8.
Cottonwood Creek
26.
Ventura River — Santa Clara River
ir
Putah Creek - Cache Creek*
27.
Santa Monica Bay — Venura Coastal Streams
10.
Lake Berryessa Tributaries
28.
Estrella River
li.
Upper Sonoma Creek
29.
San Gabriel Mountain*
12.
Petaluma Creek - Sonoma Creek
30.
Forks of the Mojave*
13.
Pt. Reyes Peninsula
31.
Santa Ana Mountain*
14.
Belvedere Lagoon
32.
Santa Rosa Plateau
15.
Jameson Canyon - Lower Napa River
33.
San Luis Ray*
16.
East San Francisco Bay
34.
Sweetwater*
17.
Santa Clara Valley
35.
Laguna Mountain*
18.
South San Francisco Bay
* Core areas that were historically occupied by the California red-legged frog are not included in the map
Figure 4 Recovery Units, Core Area, Critical Habitat, and Occurrence Designation for CRLF
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
31
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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 5 depicts CRLF annual reproductive timing.
Figure 5 CRLF Reproductive Events by Month
J
F
M
A
M
J
J
A
S
O
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter)
Orange = Young Juveniles
Adults and juveniles can be present all year
2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied
specifically, it is assumed that their diet is similar to that of other frog species, with the
aquatic phase feeding exclusively in water and consuming diatoms, algae, and detritus
(USFWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar, 1980)
via mouthparts designed for effective 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
32
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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), and dense vegetation close to water and shading water of moderate depth are
habitat features that appear especially important for CRLF (Hayes and Jennings 1988).
Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds,
marshes, sag ponds (land depressions between fault zones that have filled with water),
dune ponds, and lagoons. Breeding adults have been found near deep (0.7 m) still or slow
moving water surrounded by dense vegetation (USFWS 2002); however, the largest
number of tadpoles have been found in shallower pools (0.26 - 0.5 m) (Reis, 1999). Data
indicate that CRLFs do not frequently inhabit vernal pools, as conditions in these habitats
generally are not suitable (Hayes and Jennings 1988).
CRLFs also frequently breed in artificial impoundments such as stock ponds, although
additional research is needed to identify habitat requirements within artificial ponds
(USFWS 2002). Adult CRLFs use dense, shrubby, or emergent vegetation closely
associated with deep-water pools bordered with cattails and dense stands of overhanging
vegetation (http://www.fws.gov/endangered/features/rl frog/rlfrog.html#where).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability,
and life stage. Adults rely on riparian vegetation for resting, feeding, and dispersal. The
foraging quality of the riparian habitat depends on moisture, composition of the plant
community, and presence of 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).
33
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During dry periods, the CRLF is rarely found far from water, although it will sometimes
disperse from its breeding habitat to forage and seek other suitable habitat under downed
trees or logs, industrial debris, and agricultural features (UWFWS 2002). According to
Jennings and Hayes (1994), CRLFs also use small mammal burrows and moist leaf litter
as habitat. In addition, CRLFs may also use large cracks in the bottom of dried ponds as
refugia; these cracks may provide moisture for individuals avoiding predation and solar
exposure (Alvarez 2000).
2.6 Designated Critical Habitat
In a final rule published on April 13, 2006, 34 separate units of critical habitat were
designated for the CRLF by USFWS (USFWS 2006; FR 51 19244-19346). A summary
of the 34 critical habitat units relative to USFWS-designated recovery units and core
areas (previously discussed in Section 2.5.1) is provided in Table 6.
'Critical habitat' is defined in the ESA as the geographic area occupied by the species at
the time of the listing where the physical and biological features necessary for the
conservation of the species exist, and there is a need for special management to protect
the listed species. It may also include areas outside the occupied area at the time of
listing if such areas are 'essential to the conservation of the species.' All designated
critical habitat for the CRLF was occupied at the time of listing. Critical habitat receives
protection under Section 7 of the ESA through prohibition against destruction or adverse
modification with regard to actions carried out, funded, or authorized by a federal
Agency. Section 7 requires consultation on federal actions that are likely to result in the
destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the
conservation of the species.' Critical habitat designations identify, to the extent known
using the best scientific and commercial data available, habitat areas that provide
essential life cycle needs of the species or areas that contain certain primary constituent
elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to,
space for individual and population growth and for normal behavior; food, water, air,
light, minerals, or other nutritional or physiological requirements; cover or shelter; sites
for breeding, reproduction, rearing (or development) of offspring; and habitats that are
protected from disturbance or are representative of the historic geographical and
ecological distributions of a species. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
• Breeding aquatic habitat;
• Non-breeding aquatic habitat;
• Upland habitat; and
• Dispersal habitat.
Please note that a more complete description of these habitat types is provided in
Attachement 1.
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Occupied habitat may be included in the critical habitat only if essential features within
the habitat may require special management or protection. Therefore, USFWS does not
include areas where existing management is sufficient to conserve the species. Critical
habitat is designated outside the geographic area presently occupied by the species only
when a designation limited to its present range would be inadequate to ensure the
conservation of the species. For the CRLF, all designated critical habitat units contain all
four of the PCEs, and were occupied by the CRLF at the time of FR listing notice in
April 2006. The FR notice designating critical habitat for the CRLF includes a special
rule exempting routine ranching activities associated with livestock ranching from
incidental take prohibitions. The purpose of this exemption is to promote the
conservation of rangelands, which could be beneficial to the CRLF, and to reduce the rate
of conversion to other land uses that are incompatible with CRLF conservation. Please
see Attachment 1 for a full explanation on this special rule.
USFWS has established adverse modification standards for designated critical habitat
(USFWS 2006). Activities that may destroy or adversely modify critical habitat are those
that alter the PCEs and jeopardize the continued existence of the species. Evaluation of
actions related to use of aldicarb that may alter the PCEs of the CRLF's critical habitat
form the basis of the critical habitat impact analysis. According to USFWS (2006),
activities that may affect critical habitat and therefore result in adverse effects to the
CRLF include, but are not limited to the following:
(1) Significant alteration of water chemistry or temperature to levels beyond the
tolerances of the CRLF that result in direct or cumulative adverse effects to
individuals and their life-cycles.
(2) Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat that could result in
elimination or reduction of habitat necessary for the growth and reproduction of
the CRLF by increasing the sediment deposition to levels that would adversely
affect their ability to complete their life cycles.
(3) Significant alteration of channel/pond morphology or geometry that may lead to
changes to the hydrologic functioning of the stream or pond and alter the timing,
duration, water flows, and levels that would degrade or eliminate the CRLF
and/or its habitat. Such an effect could also lead to increased sedimentation and
degradation in water quality to levels that are beyond the CRLF's tolerances.
(4) Elimination of upland foraging and/or aestivating habitat or dispersal habitat.
(5) Introduction, spread, or augmentation of non-native aquatic species in stream
segments or ponds used by the CRLF.
(6) Alteration or elimination of the CRLF's food sources or prey base (also
evaluated as indirect effects to the CRLF).
As previously noted in Section 2.1, the Agency believes that the analysis of direct and
indirect effects to listed species provides the basis for an analysis of potential effects on
the designated critical habitat. Because aldicarb is expected to directly impact living
organisms within the action area, critical habitat analysis for aldicarb is limited in a
35
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practical sense to those PCEs of critical habitat that are biological or that can be
reasonably linked to biologically mediated processes.
2.7 Action Area
For listed species assessment purposes, the action area is considered to be the area
affected directly or indirectly by the federal action and not merely the immediate area
involved in the action (50 CFR 402.02). It is recognized that the overall action area for
the national registration of aldicarb is likely to encompass considerable portions of the
United States based on the large array of agricultural uses. However, the scope of this
assessment limits consideration of the overall action area to those portions that may be
applicable to the protection of the CRLF and its designated critical habitat within the state
of California. Deriving the geographical extent of this portion of the action area is the
product of consideration of the types of effects that aldicarb may be expected to have on
the environment, the exposure levels to aldicarb that are associated with those effects,
and the best available information concerning the use of aldicarb 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 aldicarb. An analysis of labeled uses and review of available product labels was
completed. This analysis indicates that for aldicarb the following uses are considered as
part of the federal action evaluated in this assessment:
. Alfalfa (for seed)
• Citrus
• Cotton
• Dried bean
• Sugar beet
• Sorghum
• Sweet potato
• Peanut
• Pecan
• Soybean
. Ornamentals (field-grown, no containers)
In all these cases granular aldicarb is applied directly onto/into the soil and is usually
soil-incorporated.
After determination of which uses will be assessed, an evaluation of the potential
"footprint" of the use pattern should be determined. This "footprint" represents the initial
area of concern and is typically based on available land cover data. Local land cover data
available for the state of California were analyzed to refine the understanding of potential
aldicarb use. However, no areas are excluded from the final action area based on usage
and land cover data. The initial area of concern is defined as all land cover types that
represent the labeled uses described above. The borders of all cultivated land have been
36
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extended outward by 1 mile to account for secondary poisoning effects by listed
terrestrial wildlife. This zone represents at most the home range for a small bird (Haskell
et al., 2002), and is used here synonymously with "the distance a small mammal could
travel away from a site containing aldicarb" before falling prey to an adult CRLF. This
constitutes the terrestrial portion of the aldicarb action area.
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 aldicarb to determine which routes
of transport are likely to have an impact on the CRLF.
The physical/chemical properties of aldicarb are such that the dominant route of exposure
is likely to be granules on the land surface. While there may be transient peaks in surface
water bodies following large rain events that occur soon after application, both modeling
and monitoring data indicate that this is probably not as common an occurrence. There is
possible concern about infiltration into groundwater and subsequent discharge of tainted
groundwater into water bodies inhabited by CRLFs. While this potential effect is not
specifically incorporated into the delineation of the Action Area, some implications are
discussed in section 3.2.
LOC exceedances are used to describe how far effects may be seen from the initial area
of concern. Factors considered include: spray drift (N/A for aldicarb), downstream run-
off, atmospheric transport (N/A for aldicarb), etc. This information is incorporated into
GIS and a map of the action area is created. Figure 6 shows the spatial overlap of the
aldicarb action area with all designated area for critical habitat in the eight recovery
zones.
37
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Aldicarb Habitat and Action Areas with Overlap
Legend
~ CA counties
J CRLF Recovery Units
| aldicarb AgOrch 10560ft overlap
CNDDB occurrence sections
Critical habitat
Core areas
I;.-.'/.' J aldicarb AgOrch 10560ft AA
%
iKilometers
02040 80 120 160
Compiled from California County boundaries (ESRI, 2002), created by US Environmental Protection Agency, Office
USDA National Agriculture Statistical Service (MASS, 2002) of Pesticides Programs, Environmental Fate and Effects Division.
Gap Analysis Program Orchard/Vineyard Landcover (GAP) June, 2007. Projection: Alters Equal Area Conic USGS, North
National Land Cover Database (NLCD) (MRLC, 2001) American Datum of 1983 (NAD 1983)
Figure 6 Spatial Overlap of Aldicarb Action Area with CRLF Critical Habitat.
38
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Subsequent to defining the action area, an evaluation of usage information was conducted
to determine the area where use of aldicarb 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
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.,. water bodies,
riparian vegetation, and upland and dispersal habitats), the migration pathways of
aldicarb and its major degradates (e.g., runoff, infiltration, etc.), and the routes by which
ecological receptors are exposed to aldicarb-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 aldicarb and its major degradates is
provided in Table 7.
5 From U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
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Table 7 Summary of Assessment Endpoints and Measures of Ecological Effects for Direct and
Indirect Effects of Aldicarb and its Degradates on the California Red Legged Frog
Assessment Endpoint
Measures of Ecological Effects6
(Data Sources Reviewed)
Specific Selected Toxicity Value
(basis)
Aquatic Phase
(eggs, larvae, tadpoles, juveniles, and adults)a
1. Survival, growth, and
reproduction of CRLF
individuals via direct
effects on aquatic phases
la. Most sensitive fish or
amphibian acute LC50 (guideline
orECOTOX)
la. Bluegill sunfish 96-hr LC50 = 52
ppb ai
(most sensitive fish value)
lb. Most sensitive fish or
amphibian chronic NOAEC
(guideline or ECOTOX)
lb. Bluegill sunfish early-life stage
NOAEC = 0.46 ppb ai
(estimated using ACR)
lc. Most sensitive fish or
amphibian early-life stage data
lc. same as lb.
2. Survival, growth, and
reproduction of CRLF
individuals via effects to
food supply (i.e.,
freshwater invertebrates,
non-vascular plants)
2a. Most sensitive (1) fish, (2)
aquatic invertebrate, and (3)
aquatic plant EC50 or LC50
(guideline or ECOTOX)
2al. Bluegill sunfish 96-hr LC50 = 52
ppb ai (most sensitive fish value)
2a2. Chironomus tentans 48-hr EC50 =
20 ppb ai
(most sensitive invertebrate value)
2a3. Marine diatom 96-hr EC50 > 5000
ppb ai
(only algal value available)
2b. Most sensitive (1) aquatic
invertebrate and (2) fish chronic
NOAEC (guideline or ECOTOX)
2b 1. C. tentans reproduction NOAEC
= 1 ppb ai (estimated using ACR)
2b2. Bluegill sunfish NOAEC = 0.46
ppb ai
(estimated using ACR)
3. Survival, growth, and
reproduction of CRLF
individuals via indirect
effects on habitat, cover,
and/or primary
productivity (i.e., aquatic
plant community)
3a. Most sensitive vascular plant
acute EC50 (duckweed guideline
test or ECOTOX vascular plant)
3 a. No data available
3b. Most sensitive non-vascular
plant acute EC50 (freshwater algae
or diatom guideline or similar
ECOTOX)
3b. Marine diatom 96-hr EC50 > 5000
ppb ai
(only available algal test, used marine
as surrogate for freshwater)
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 of (1) seedling
emergence and (2) vegetative
vigor monocot EC25 values
(seedling emergence and
vegetative vigor guidelines or
similar ECOTOX)
4al. Pearl millet seedling emergence
21-d NOAEC = 2.05 lbs ai/A
(No seedling emergence EC25 values
available, used the only available plant
study endpoint)
4a2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
4b. Distribution of (1) seedling
emergence and (2) vegetative
vigor EC25 values for dicots
(seedling emergence, vegetative
vigor guidelines, or similar
ECOTOX)7
4b 1. No seedling emergence study
data available
4b2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
6 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendices D through F.
7 The available information indicates that the California red-legged frog does not have any obligate
relationships.
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Assessment Endpoint
Measures of Ecological Effects6
(Data Sources Reviewed)
Specific Selected Toxicity Value
(basis)
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 or
ECOTOX)
5a. Mallard duck LD50 = 1 mg ai/kg-
bw
(most sensitive bird test as surrogate
for terrestrial-phase amphibian)
5b. Most sensitive birdb or
terrestrial-phase amphibian
chronic NOAEC (guideline or
ECOTOX)
5b. Mallard duck reproduction
NOAEC = 0.49 mg ai/kg-bw
(Extrapolated using ACR)
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 (1)
invertebrate and (2) vertebrate
acute EC50 or LC50 (guideline or
ECOTOX)c
6al. Honey bee acute contact LD50 =
0.285 ng ai/bee
(most sensitive terrestrial invertebrate)
6a2. rat LD50 = 0.9 mg ai/kg-bw
(most sensitive terrestrial mammalian)
6b. Most sensitive terrestrial (1)
invertebrate and (2) vertebrate
chronic NOAEC (guideline or
ECOTOX)
6b 1. No chronic NOAEC data for
terrestrial invertebrates
6b2. rat 2-generation reproduction
study NOAEC = 0.4 mg/kg-bw
7. Survival, growth, and
reproduction of CRLF
individuals via indirect
effects on habitat (i.e.,
riparian vegetation)
7a. Distribution of (1) seedling
emergence and (2) vegetative
vigor EC25 values for monocots
(seedling emergence, vegetative
vigor guideline or similar
ECOTOX study)
7al. Pearl millet seedling emergence
21-d NOAEC = 2.05 lbs ai/A
(No seedling emergence EC25 values
available, used the only available plant
study endpoint)
7a2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
7b. Distribution of (1) seedling
emergence and (2) vegetative
vigor EC25 values for dicots
(seedling emergence, vegetative
vigor, or ECOTOX)5
7b 1. No seedling emergence study
data available
7b2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
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 than exposure pathways on land.
b Birds are used as surrogates for terrestrial phase amphibians.
c 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 aldicarb that may alter the PCEs of the CRLFs 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 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 aldicarb effects data are available.
41
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Assessment endpoints and measures of ecological effect selected to characterize potential
modification to designated critical habitat associated with exposure to aldicarb are
provided in Table 8. Adverse modification to the critical habitat of the CRLF includes
the following, as specified by USFWS (2006) and previously discussed in Section 2.6:
1. Alteration of water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and
adult CRLFs.
2. Alteration of chemical characteristics necessary for normal growth and
viability of juvenile and adult CRLFs.
3. Significant increase in sediment deposition within the stream channel or pond
or disturbance of upland foraging and dispersal habitat.
4. Significant alteration of channel/pond morphology or geometry.
5. Elimination of upland foraging and/or aestivating habitat, as well as dispersal
habitat.
6. Introduction, spread, or augmentation of non-native aquatic species in stream
segments or ponds used by the CRLF.
7. Alteration or elimination of the CRLF's food sources or prey base.
Measures of such possible effects by labeled use of aldicarb on critical habitat of the
CRLF are described in Table 8. Some components of these PCEs are associated with
physical abiotic features (e.g., presence and/or depth of a water body, or distance between
two sites), which are not expected to be measurably altered by use of pesticides.
Assessment endpoints used for the analysis of designated critical habitat are based on the
adverse modification standard established by USFWS (2006).
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Table 8 Summary of Assessment Endpoints and Measures of Ecological Effect for Primary
Constituent Elements of Designated Critical Habitat
Assessment Endpoint
Measures of Ecological
Effect8
(Data Sources Reviewed)
Specific Selected Toxicity Value
(basis)
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 similar
ECOTOX study)
a. Marine diatom 96-hr EC50 > 5000
ppb ai
(only available algal test, used marine
as surrogate for freshwater)
b. Distribution of terrestrial
monocot (1) seedling
emergence and (2) vegetative
vigor EC25 values (seedling
emergence and vegetative
vigor guidelines or similar
ECOTOX studies)
bl. Pearl millet seedling emergence
21-d NOAEC = 2.05 lbs ai/A
(No seedling emergence EC25 values
available, used the only available plant
study endpoint)
b2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
c. Distribution of terrestrial
dicot (1) seedling emergence
and (2) vegetative vigor EC25
values (seedling emergence
and vegetative vigor guidelines
or similar ECOTOX studies)
cl. No seedling emergence study data
available
c2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
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
similar ECOTOX studies)
a. Marine diatom 96-hr EC50 > 5000
ppb ai
(only available algal test, used marine
as surrogate for freshwater)
b. Distribution of terrestrial
monocot (1) seedling
emergence and (2) vegetative
vigor EC25 values (seedling
emergence and vegetative
vigor guidelines or similar
ECOTOX studies)
bl. Pearl millet seedling emergence
21-d NOAEC = 2.05 lbs ai/A
(No seedling emergence EC25 values
available, used the only available plant
study endpoint)
b2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
c. Distribution of terrestrial
dicot (1) seedling emergence
and (2) vegetative vigor EC25
values (seedling emergence
and vegetative vigor guidelines
or similar ECOTOX studies)
cl. No seedling emergence study data
available
c2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
8 All toxicity data reviewed for this assessment are included in Appendices D through F.
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.
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Assessment Endpoint
Measures of Ecological
Effect8
(Data Sources Reviewed)
Specific Selected Toxicity Value
(basis)
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 (1) fish or aquatic-
phase amphibians and (2)
aquatic invertebrates (guideline
or similar ECOTOX study)
al. Bluegill sunfish 96-hr LC50 = 52
ppb ai (most sensitive fish value)
a2. C. tentans 48-hr EC50 = 20 ppb ai
(most sensitive invertebrate value)
b. Most sensitive reproductive
NOAEC values for (1) fish or
aquatic-phase amphibians and
(2) aquatic invertebrates
(guideline or similar ECOTOX
studies)
bl. Bluegill sunfish early-life stage
NOAEC = 0.46 ppb ai
(estimated using ACR)
b2. C. tentans reproduction NOAEC =
1 ppb ai (estimated using ACR)
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. Marine diatom 96-hr EC50 > 5000
ppb ai
(only available algal test, used marine
as surrogate for freshwater)
Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of
upland habitat; ability of habitat to
support food source of CRLFs:
Upland areas within 200 ft of the
edge of the riparian vegetation or
dripline surrounding aquatic and
riparian habitat that are comprised
of grasslands, woodlands, and/or
wetland/riparian plant species that
provides the CRLF shelter,
forage, and predator avoidance
a. Distribution of terrestrial
monocot (1) seedling
emergence and (2) vegetative
vigor EC25 values (seedling
emergence and vegetative
vigor guidelines or similar
ECOTOX studies)
b. Distribution of terrestrial
dicots (1) seedling emergence
and (2) vegetative vigor EC25
values (seedling emergence
and vegetative vigor guidelines
or similar ECOTOX studies)
c. Most sensitive food source
acute EC50 or LC50 and
NOAEC values for terrestrial
vertebrates (mammals) and
invertebrates, birds or
terrestrial-phase amphibians,
and freshwater fish.
al. Pearl millet seedling emergence
21-d NOAEC = 2.05 lbs ai/A
(No seedling emergence EC25 values
available, used the only available plant
study endpoint)
a2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
bl. No seedling emergence study data
available
b2. Granular formulation so effect of
residues on foliar vegetation is not
applicable
cla. rat LD50 = 0.9 mg ai/kg-bw
(most sensitive terrestrial mammalian)
clb. rat 2-generation reproduction
study NOAEC = 0.4 mg/kg-bw
c2a. Honey bee acute contact LD50 =
0.285 ng ai/bee
(most sensitive terrestrial invertebrate)
c2b. No chronic NOAEC data for
terrestrial invertebrates
c3a. Mallard duck LD50 = 1 mg ai/kg-
bw
(most sensitive bird test as surrogate
for terrestrial-phase amphibian)
c3b. Mallard duck reproduction
NOAEC = 0.49 mg ai/kg-bw
(Extrapolated using ACR)
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.
44
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2.9 Conceptual Model
2.9.1 Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in
assessment endpoints) and may be based on theory and logic, empirical data,
mathematical models, or probability models (U.S. EPA, 1998). For this assessment, the
risk is stressor-linked, where the stressor is the release of aldicarb to the environment.
The following risk hypotheses are presumed for this endangered species assessment:
• Labeled uses of aldicarb within the action area may directly affect the CRLF by
causing mortality or by adversely affecting growth or fecundity;
• Labeled uses of aldicarb within the action area may indirectly affect the CRLF by
reducing or changing the composition of food supply;
• Labeled uses of aldicarb 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 aldicarb 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;
• Labeled uses of aldicarb 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 aldicarb 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 aldicarb 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 aldicarb 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 aldicarb 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.
45
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2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the stressor (aldicarb), 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 7 and 8, and the conceptual models for the
aquatic and terrestrial PCE components of critical habitat are shown in Figures 9 and 10.
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.
Exposure Pathways and Routes in Aquatic Phase Conceptual Model
Eggs, larvae, tadpoles, juveniles, and adult frogs may potentially absorb across their
membranes or gills and integuments dissolved aldicarb and its two major degradates
(aldicarb sulfoxide, aldicarb sulfone) in surface water.
Aquatic animals that serve as prey to the juvenile and adult CRLF may be exposed via
gills and their integument to aldicarb and its two major toxic degradates in surface water.
Aquatic vascular and non-vascular plants may sorb to their membranes or transfer across
their membranes dissolved aldicarb and its major degradates in surface water.
Terrestrial plants in semi-aquatic areas (i.e. wetlands, riparian zones) may uptake
dissolved aldicarb and its major degradates from soil pore water, surface water, or
groundwater.
The exposure pathways discussed here in the aquatic phase conceptual model are
modified to address attributes assessed in aquatic component of critical habitat and PCEs
in conceptual model 13.
46
-------
Stressor
Long range j
atmospheric ;
transport j
Source
Exposure
Media
Wet/dry deposition
Uptake/gills
or integument
Uptake/cell,
roots,, leaves
Uptake/gills
or integument
Ingestion
Ingestion
Receptors
ri
n
Attribute
Change
Runoff
Soil
Groundwater
Aquatic Plants
Non-vascular
Vascular
Aquatic Animals
Invertebrates
Vertebrates
Food chain
Reduction in algae
Reduction in prey
Red-legged Frog
Eggs Juveniles
Larvae Adult
Tadpoles
Riparian plant
terrestrial
exposure
pathways see
Figure 2.c
Surface water/
Sediment
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Aldicarb applied to use site
Figure 7 Conceptual Model for Aldicarb Effects on Aquatic Phase of the CRLF
Exposure Pathways and Routes in Terrestrial Phase Conceptual Model
Juvenile and adult frogs may experience dermal exposure to soil residues of aldicarb and
its two major toxic degradates when seeking refuge in ground crevices from solar
radiation or traversing across soils with aldicarb-related residues.
Juvenile and adult frogs may also incidentally ingest soil residues of aldicarb and its two
major degradates along with prey items.
CRLF prey items, small mammals (mice) and terrestrial insects, may uptake across their
dermal/cuticle soil residues of aldicarb and its two major degradates.
The exposure pathways discussed here in the terrestrial phase conceptual model are
modified to address attributes assessed in terrestrial component of critical habitat and
PCEs in conceptual model 14.
47
-------
Stressor
Long range I
atmospheric !
transport j
Source
Dermal uptake/lngestion-
Exposure
Media
Root uptake
Terrestrial
insects
Wet/dry deposition-*-
Ingestion
•Ingestion
Ingestion
. Ingestion
Ingestion
Receptors
n
Attribute
Change
Runoff
Mammals
Amphibians
Soil
Direct
application
Food chain
Reduction in prey
Red-legged Frog
Juvenile
Adult
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Aldicarb applied to use site
Figure 8 Conceptual Model for Aldicarb Effects on Terrestrial Phase of CRLF
Stressor
Long range ;
atmospheric j
transport j
Source
Exposure
Media
Wet/dry deposition
Uptake/gills
or integument
Uptake/cell,
roots, leaves
Uptake/gills
or integument
Receptors
Ingestion
Ingestion
ri
Community
Reduced seedling
emergence or vegetative
vigor (Distribution)
Population
Yield
Reduced yield
Attribute
Change
Habitat
PCEs
Soil
Runoff
Groundwater
Aquatic Animals
Invertebrates
Vertebrates
Aquatic Plants
Non-vascular
Vascular
Surface water/
Sediment
Food sources
Reduction in algae
Reduction in prey
Red-legged Frog
Eggs Juveniles
Larvae Adult
Tadpoles
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Riparian and
Upland plants
terrestrial exposure
pathways and PCEs
see Figure 2.d
Other chemical
characteristics
Adversely modified
chemical characteristics
Aldicarb applied to use site
Habitat quality and channel/pond
morphology or geometry
Adverse water quality changes
Increased sedimentation
Reduced shelter
Figure 9 Conceptual Model for Aldicarb Effects on Aquatic Component of CRLF Critical Habitat
48
-------
Stressor
Long range
atmospheric
Source
I~L
Dermal uptake/lngestion-
Exposure
Media and
Receptors
Root uptake
Terrestrial
insects
Wet/dry deposition*™
¦Ingestion
Ingestion
Ingestion
¦ J— Ingestion
ft
S~L
Attribute
Change
Habitat
PCEs
Runoff
Mammals
Soil
Direct
application
Red-legged Frog
Juvenile
Adult
Food resources
Reduction in food
sources
Population
Reduced survival
Reduced growth
Reduced reproduction
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Other chemical
characteristics
Adversely modified
chemical characteristics
Terrestrial plants
grasses/forbs, fruit,
seeds (trees, shrubs)
Community
Reduced seedling emergence
or vegetative vigor
(Distribution)
Aldicarb applied to use site
Elimination and/or disturbance of
upland or dispersal habitat
Reduction in primary productivity
Reduced shelter
Restrict movement
Figure 10 Conceptual Model for Aldicarb Effects on Terrestrial Component of the CRLF Critical
Habitat
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 according to the Overview Document (EPA, 2004) and
Agency guidance for ecological risk assessments.
2.10.1 Exposure Analysis
Risks (direct effects) to the aquatic phase CRLF will be assessed by comparing modeled
surface water exposure concentrations of aldicarb and its sulfoxide and sulfone
degradates to acute and chronic (early life stage hatching success and growth) effect
concentrations for aquatic phase amphibians (or surrogate freshwater fish) from
laboratory studies (see the Effects Analysis section below). Risks (direct effects) to
aquatic dietary food resources (aquatic invertebrates, algae) of the aquatic phase CRLF or
risks (direct effects) to aquatic habitat that support the CRLF will also be assessed by
comparing modeled surface water exposure concentrations of total aldicarb residues to
laboratory established effect levels appropriate for the taxa.
Long-range transport of aldicarb is highly unlikely, given the chemical characteristics,
formulation, and application methods. A vapor pressure of 2.5 x 10"5 mm Hg and Henry's
Law Constant of 1.7xlO"10 atm m3/mole mean that aldicarb is not likely to volatilize and be
49
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transported offsite in the atmosphere. As a soil-incorporated granule, there is no spray
drift, and a very limited amount of aldicarb is available at the surface. Whole granules
dissolve readily, and will not move offsite intact (unless adhered to the integument of an
organism, which should nevertheless limit the total amount transported). Some aldicarb
residues may be transported as a component of field runoff, but dilution by receiving
water bodies should limit the extent of long-range transport via surface water. While
aldicarb residues may be subject to long-range transport through groundwater (which
may be discharged to the surface some distance away from the application area), the
greater the distance traveled, the more dilution is likely to occur and the greater
opportunity for degradation. Thus, Agency believes that risk of long-range transport of
aldicarb is minimal.
Surface water concentrations of aldicarb residues will be quantified using a model,
PRZM-EXAMS. For the screening assessment, the standard EXAMS water body of 2
meters maximum depth, and 20,000 cubic meters volume, will be used. Since spray drift
is expected to be minimal because aldicarb is applied as a granule to the ground, the
model accounts for loading of aldicarb into the surface water via run-off and erosion.
Agricultural scenarios appropriate for labeled aldicarb uses will be used to account for
local soils, weather and growing practices which impact the magnitude and frequency of
aldicarb loading to the surface water. Maximum labeled application rates, with
maximum number of applications and shortest intervals, will be used to help define (1)
the Action Area within California for the Federal Action and (2) for evaluating effects to
the CRLF.
Concentrations of aldicarb estimated by PRZM-EXAMS represent aldicarb loading in
water bodies adjacent to any treated field and assume that the concentration applies to
any water body within the treated area. Aldicarb residues are also estimated for waters
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 aldicarb 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 become sufficiently diluted; the
region beyond this then falls outside the Action 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 et al., 1994. The
nomogram tabulates the 90th and 50th percentile exposure expected on various classes of
food items, and scales the exposure (in dietary terms) to the size and daily food intake of
50
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several size classes of birds and mammals. Birds are also used as surrogates to represent
reptiles and terrestrial-phase amphibians.
2.10.2 Effects Analysis
Aldicarb Toxicity (IncludingMajor Toxic Degradates):
As previously discussed in Section 2.8.1 and 2.8.2, assessment endpoints for the CRLF
include direct toxic effects on survival, reproduction, and growth of the species itself, as
well as indirect effects, such as reduction of the prey base and/or modification of its
habitat. Direct effects to the 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
amphibian toxicity data. If no such data are available for aldicarb, then toxicity data for
other N-Methyl carbamates will be screened to see if amphibian toxicity data are
forthcoming that would allow making inferences with respect to aldicarb toxicity.
Indirect effects to the CRLF are assessed by looking at available toxicity information of
the frog's prey items and habitat requirements (freshwater invertebrates, freshwater
vertebrates, aquatic plants, terrestrial invertebrates, terrestrial vertebrates, and terrestrial
plants).
Aldicarb's toxicity dataset is incomplete; chronic avian studies are lacking. Other N-
Methyl carbamates were therefore screened for available chronic bird data that could
used to derive a carbamate avian acute to chronic ratio (ACR). Plant Tier I and Tier II
guideline studies are not available for aldicarb, therefore the open literature was screened
for similar toxicological data.
Acute (short-term) and chronic (long-term) toxicity information for aldicarb and its
degradates is characterized based on registrant-submitted studies and an updated review
of the open literature. An extensive review of the open literature was done for the recent
aldicarb screening level ecological risk assessment (May 2005). Based on an updated
review of the open literature for October 2004 through December 2006, if new and more
sensitive or otherwise relevant toxicological data were available, this information was
included and used in this assessment to modify the Action Area and evaluate direct and
indirect effects to the CRLF and its critical habitat.
Where there are data gabs, estimates for these values may be extrapolated for the same
taxa for other N-methyl carbamates, or extrapolated within taxa based on relationships
within taxa for aldicarb or for N-methyl carbmates. To help refine the risk
characterization, species sensitivity distributions may be established for prey (e.g.,
aquatic invertebrates) and for the CRLF (using surrogate species) if enough data are
available. N-Methyl carbamate data was used to derive an ACR for use on birds
(surrogate for terrestrial phase amphibians). Other sources of information, including use
of the acute probit dose response relationship to establish the probability of an individual
effect and reviews of the Ecological Incident Information System (EIIS), were conducted
to further refine the characterization of potential ecological effects associated with
51
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exposure to granular aldicarb. A summary of the available freshwater and terrestrial
ecotoxicity information, the community-level endpoints, species' sensitivity distributions,
use of the probit dose response relationship, and the incident information for aldicarb are
provided in Sections 4.1 through 4.4.
Toxicity studies for aldicarb degradates (where available) will be discussed for exposure
to the aquatic phase of the CRLF and incorporated into this risk assessment.
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).
Aldicarb does not have any registered products that contain multiple active ingredients.
2.10.3 Action Area Analysis
The Action Area for the federal action is the geographic extent of exceedance 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 aldicarb. To
define the extent of the Action Area, the following exposure assessment tools will be
used where appropriate: 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.
The initial area of concern (or terrestrial action area) is assumed to be all agricultural
land, orchards, and vineyards where granular aldicarb could potentially be applied and
the area surrounding these areas where secondary poisoning effects are expected to be
visible. Secondary poisoning to listed species could result if listed species consumes all
or part of the poisoned prey. A model for secondary poisoning effects is in development
by the Agency. However, from that model, which relies on allometric relationships that
relate body weight to food consumption and body weight to home range, it was
preliminarily determined that a CRLF prey item bird could travel approximately one mile
from the field before dying from aldicarb poisoning. Thus, a one-mile buffer is applied
around cultivated land to account for secondary poisoning effects to wildlife from
aldicarb granular exposure.
52
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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 for the land
uses identified for aldicarb are greater than 1/20, or 5%. All streams identified as
draining upstream catchments greater than 5% of the land class of concern, will be
considered part of the action area.
53
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3
Exposure Assessment
3.1 Label Application Rates and Intervals
In California, aldicarb is registered for use on cotton, dry beans, peanuts, pecans,
sorghum, soybean, sugar beet, sweet potato, alfalfa (for seed), citrus, and field-grown
ornamentals (no containers). Application rates are listed in Table 10. Only cotton and
sugar beet allow more than one application per season; up to 3 applications may be used
for these crops. Application intervals are not specified on the labels. Instead, cotton
applicators are instructed to apply "once at planting, at first squaring, and between first
squaring and bloom." Use directions for sugar beet simply list an application window
from 3/1-9/1. The best estimate that could be construed from these explanations, plus
additional research, indicates a likely average application interval of 30 days.
3.2 Aquatic Exposure Assessment
Aldicarb rapidly degrades in the aquatic environment to aldicarb sulfoxide and aldicarb
sulfone, both of which are toxic to aquatic organisms. Therefore, exposure to all 3 of
these forms of aldicarb (parent + sulfoxide + sulfone) must be considered. Direct
application of aldicarb to streams, lakes, and ponds is forbidden by product labels.
However, following a rain event, aldicarb may reach aquatic environments in runoff from
areas of application, since aldicarb is moderately persistent in terrestrial environments
and soluble in water. It is unlikely that whole, intact granules will reach the aquatic
environment because of the highly soluble nature of the compound (granules will
dissolve rather than be transported intact) and the application methods (direct application
onto field, typically with soil incorporation). Groundwater discharged to the surface
(mostly in low-lying areas) could result in additional exposure to aldicarb residues,
independent of rainfall and runoff conditions.
3.2.1 Conceptual Model of Exposure
The basic conceptual model for aldicarb exposure includes terrestrial on-site exposure to
granules at (and just below) the surface, indirect exposure to fauna that have been
exposed and may transport aldicarb (internally or externally) off-site, and aquatic
exposure to aldicarb in surface water (as a component of runoff/erosion from a treated
field). Exposure to dissolved granules in pooled surface water or damp soil within or
adjacent to a treated field is also considered. However, potential exposure to aldicarb in
discharged groundwater (e.g., as baseflow) is not explicitly considered.
3.2.2 Existing Monitoring Data
Aldicarb is one of the pesticides for which monitoring is routinely performed; however,
no targeted monitoring regimes in California have been implemented. Only non-targeted
monitoring data are available. These data are not specifically tied to periods of aldicarb
use or even to areas where such use is allowed. Thus, it is not suitable for evaluating the
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impact of aldicarb use on affiliated waterways. At best, the non-targeted data can
establish a lower bound for potential aldicarb surface water exposure.
Nationally, the USGS NAWQA database (1992-2001) indicates that aldicarb has been
detected in surface water approximately 0.2% of the time. The highest concentration
detected was 0.5 ug/L (Martin et al., 2001). However, results of targeted monitoring in
smaller streams suggest that aldicarb may occasionally pose a contamination hazard. For
example, Williams and Harris (1996) found substantially higher aldicarb concentrations
in small southeastern streams after a rainfall event (concentrations up to 430, 68, and 14
|ig/l for aldicarb, aldicarb sulfoxide, and aldicarb sulfone, respectively). Absent a
sampling regime specifically targeted to aldicarb use in California, surface water
modeling will be employed to estimate environmental concentrations.
The detection rate for aldicarb residues in CA groundwater (~0.1%) appeared to be
similar to surface water (-0.2%), but, where detected, concentrations in groundwater
were often much higher. Based on well monitoring in California reported by CA-DPR,
conducted from 1986-1999, groundwater concentrations of aldicarb sulfoxide ranged
from 0.05-1281 ug/L and aldicarb sulfone from 0.06-13.2 ug/L
(http://www.cdpr.ca.gov/docs/empm/pubs/ehapreps/eh0308.pdf). Evidence for
persistence of aldicarb residues in California groundwater has been documented by the
presence of aldicarb sulfoxide and aldicarb sulfone in well water samples from counties
(Humboldt and Del Norte) where aldicarb use had been suspended
(http://www.cdpr.ca.gov/docs/empm/pubs/ehapreps/eh9001.pdf).
3.2.3 Modeling Approach
Risk quotients (RQs) were initially based on EECs derived using the Pesticide Root Zone
Model/Exposure Analysis Modeling System (PRZM-EXAMS) standard ecological pond
scenario according to the methodology specified in the Overview Document (U.S. EPA,
2004). Where LOCs for direct/indirect effects and/or adverse habitat modification are
exceeded based on the modeled EEC using the static water body (i.e., "may affect"),
refined modeling may be used to differentiate "may affect, but not likely to adversely
affect" from "may affect and likely to adversely affect" determinations for the CRLF and
its designated critical habitat.
The general conceptual model of exposure for this assessment is that the highest
exposures are expected to occur in the headwater streams adjacent to agricultural fields.
Many of the streams and rivers within the action area defined for this assessment are in
close proximity to agricultural use sites.
3.2.3.1 Model Inputs
Generic PRZM-EXAMS inputs are listed in Table 9. Specific inputs (application rates,
application intervals, etc.) used for individual crop/noncrop model runs that were used in
this assessment are listed in Table 10.
55
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Degradation of parent compound aldicarb to aldicarb sulfoxide, and, subsequently,
aldicarb sulfoxide to aldicarb sulfone, each occur at different rates and to varying extents
under different conditions. Since each compound is toxic, and each is formed from the
previous, it is necessary to treat the half-lives for all additively. Thus, half-lives used for
modeling the environmental fate of aldicarb account for degradation of parent through
each degradate of concern, for a half-life reflecting total toxic residues. The range for
field dissipation of total aldicarb residues considered in this document, derived from
Jones and Estes, 1995, is 15-105 days. The aerobic soil half-life used for model inputs,
however, is 55 days, derived from the upper 90th pet bound on mean for total aldicarb
residue half-lives from 19 soils (see Appendix N).
Table 9 Generic Aldicarb Inputs Used in PRZM-EXAMS Runs
Input Parameter
Value
Ret'e re n ce/C o m m en t
Molecular Weight
190.2 g/mol
MRID 00152095
Henry's Law Constant
1.7 E-10 atm-m3/mol
Acc 255979
Vapor Pressure
2.6 E-5 @ 25°C
MRID 00152095
Solubility
6,000 mg/L
Acc 255979
Kd
0.12
Minimum non-sand value for aldicarb
sulfone (MRID 43560302)
Hydrolysis
pH 5, stable (0)
pH 7, stable (0)
pH 9, 60 days
Parent hydrolyzed only at pH 9 (MRID
00102065) - degradates may hydrolyze
more rapidly at neutral-to-high pH
Aqueous Photolysis Half-life
4 days
MRID 42498201
Water Half-life
12 days
MRID 44592107. Single acceptable
guideline study for parent / sulfoxide /
sulfone (4days) x 3; corresponds w/
DT90
Benthic Half-life
24 days
No data; use 2X aerobic aquatic half-life
Soil Half-life
55 days
Upper 90th pet bound on mean for
combined parent+sulfoxide+sulfone
half-life from 19 soils
FILTRA, UPTKF, PLVKRT, PLDKRT
0
Default values
FEXTRC
0.0
Soil incorporated
Additional Notes
Modeled total aldicarb residues
Half-life input values based on
combined aldicarb residues; lowest Kd
of the 3 chemicals used for mobility.
Assumes equal toxicity of parent,
degradates
56
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Table 10 Specific Inputs for Individual PRZM-EXAMS Runs
Crop/Noncrop
Modeled
Application Rate
(lbs product/A)
Number of
Applications
(per season)
Comments
Sugar beet
14
2
Used 2 applications at maximum one-time
rate
Pecan
33
1
Used "CAalmond" scenario
Soybean
20
1
Used "CARowCrop" scenario
Cotton
14
1
Used maximum one-time rate
Cotton
7
3
Used 3 applications; however, first 2
applications were set only 1 day apart to
approximate a single application at the max
one-time rate (14 lbs/A), followed by a third
application after 30 days (at 7 lbs/A) for a
max seasonal total of 21 lbs/A
Citrus
33
1
Sweet potato
30*
1
Used "CAPotato" scenario
Dried bean
21*
1
Used "CARowCrop" scenario
Alfalfa (seed)
20
1
Sorghum
7
1
Used "CAWheat" scenario; 99% soil
incorporation only
Peanut
30*
1
Used "CARowCrop" scenario
Ornamentals (field
grown, no
containers)
50*
1
Used "CANursery" scenario; 99% soil
incorporation only - positive displacement
required
* Only ' 10g' (10%) formulation use allowed - all others utilize the ' 15g' (15%) formulation.
3.2.3.2 Results
Model runs for the model input parameters listed in Tables 9 & 10 are shown in Table 11,
below.
Table 11 Results of Individual PRZM-EXAMS Runs With 85% Soil Incorporation
COTTON-1 application:
Peak 96 hr 21 Day 60 Day 90 Day Yearly
6.8352 6.5129
Average of yearly
5.5533
averages:
3.5314
0.139943
2 .
5216
0. 62953
COTTON-3 applications:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
7.6324 7.1959
Average of yearly
5. 9147
averages:
3.45
0. 152104
2 .
3772
0.59044
SOYBEAN:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
6.1421 5.8186
Average of yearly
4 .4673
averages:
2.5769
0. 181126
1.
8282
0.45514
PECAN:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
7.373 6.9331
Average of yearly
5.3896
averages:
3.1468
0.226344
2 .
2254
0.55532
57
-------
SUGARBEET:
Peak 96 hr
21 Day
60 Day
90 Day
Yearly
11.377 10.8066
Average of yearly
8.6342
averages:
5.425
0.279823
3.9293
1. 00713
Ci trus:
Peak 96 hr
21 Day
60 Day
90 Day
Yearly
0.371 0.317
Average of yearly
0. 181
averages:
0. 0823
0. 004684
0.0564
0. 0141
Sveet Potato:
Peak 96 hr
21 Day
60 Day
90 Day
Yearly
1.385 1.3017
Average of yearly
0. 9959
averages:
0.5642 0.39333
0.0202545596666667
0. 097279
Peanut:
Peak 96 hr
21 Day
60 Day
90 Day
Yearly
6.4341 6.119
Average of yearly
5. 044
averages:
3.3383 2.5214
0.281116203333333
0.66757
Dried. Bean:
Peak 96 hr
21 Day
60 Day
90 Day
Yearly
4.5047 4.2833
Average of yearly
3.5313
averages:
2.3365 1.7652
0.196776023333333
0.46739
Alfalfa (fox: seed.) :
Peak 96 hr
21 Day
60 Day
90 Day
Yearly
10.048 9.5516
Average of yearly
8 .4132
averages:
5.2773 3.7682
0.296203966666667
0. 94253
3.2.4 Additional Modeling Exercises Used to Characterize Potential
Exposures
For purposes of comparison, and where specialized application techniques (e.g., positive
displacement, in-furrow) are required, the following scenarios were modeled with 99%
incorporation efficiency. Results are listed in Table 12.
Table 12 Results of Individual PRZM-EXAMS Runs With 99% Soil Incorporation
Sorghum:
Peak 96 hr
21 Day
60 Day 90 Day
Yearly
0.664 0.62995
0.52367
0.31246 0.22142
0. 055175
Average of yearly
averages:
0. 0337101333333333
Field-Grown Ornamentals
(no containers):
Peak 96 hr
21 Day
60 Day 90 Day
Yearly
0.90759 0.8685
0.72054
0.49119 0.37888
0. 102639
Average of yearly
averages:
0. 0277671827
COTTON-1 application:
Peak 96 hr
21 Day
60 Day 90 Day
Yearly
0.455 0.4335
0.3697
0.2352 0.1679
0. 04194
Average of yearly
averages:
0. 0093270679
58
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COTTON-3 applications:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
0.5108 0.4816
Average of yearly
0.3959
averages:
0.2309
0.0101877?
0.
312
1593
0.03951
SOYBEAN:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
0.4095 0.388
Average of yearly
0.2978
averages:
0.1718 0.
0.0120820702
1219
0.03034
PECAN:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
0.4912 0.4622
Average of yearly
0.3593
averages:
0.2099 0.
0.015090452
1484
0.03704
SUGAKBEET:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
0.7577 0.7194
Average of yearly
0.5749
averages:
0.3611
0.0186454?
0.
3122
2616
0.06709
Ci tras:
Peak 96 hr
21 Day
60 Day
90
Day
Yearly
0.02469 0.02113 0.01204
Average of yearly averages:
0.00548 0.00376
0.00031204619
0.000943
3.2.5 Comparison of Modeled EECs with Available Monitoring Data
There are insufficient targeted monitoring data from California to allow a meaningful
comparison with modeled EECs. However, it can be assumed that what little sampling
data do exist under-represents real expected surface water aldicarb peaks (which are
almost certainly much higher). Thus, the Agency is reliant on modeling data for this
assessment. Based on the untargeted national data, it would appear that,where detected,
aldicarb residues in surface waters may be 1-2 orders of magnitude lower than indicated
by the 'peak' or 'acute' modeled EECs, but possibly reflective of 'background' or
'chronic' EEC surface water concentrations in aldicarb use areas. This appears to be
roughly consistent with observed differences between background concentrations for
other chemicals also detected in surface waters (as would be expected from non-targeted
sampling) and peak concentrations detected during (targeted) sampled post-application
runoff events.
Detected concentrations of aldicarb residues in California well water were sometimes
higher than would be predicted using the OPP-EFED tier 1 groundwater screening
model, SciGrow. This model should give an estimate of likely high-end exposure due to
registered usage. However, the highest predicted Environmental Exposure Concentration
(EEC) obtained from the SciGrow model, using the greatest quantity applied (5 lb a.i./A
- for Ornamental use) and a conservative K0c value of 4.9 (reflecting total residues), was
37.3 ug/L. Thus, risk to groundwater may be greater than indicated from model results.
Considering the greater persistence and mobility of the sulfoxide and sulfone degradates,
59
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and the historical evidence of widespread long-term groundwater contamination (both
nationally and in certain counties in California), the impact of discharged tainted
groundwater on receiving surface water bodies cannot be ignored.
Surface Water Impacts: Available surface water monitoring data indicate that impacts to
fish and aquatic invertebrates as a result of aldicarb (including the sulfone and sulfoxide
products) are likely to be confined to smaller (lower-order) streams in high use areas.
Widespread contamination of surface water is not expected in larger (higher-order)
streams. In NAWQA monitoring sites, aldicarb and its sulfone and sulfoxide
transformation products were detected infrequently at low concentrations.
Ground Water Impacts: Aldicarb residues may be persistent in groundwater. Therefore,
there is the potential for exposure to aldicarb residues (particularly aldicarb sulfoxide and
aldicarb sulfone) in discharged groundwater. This is especially true for small streams,
low-order riparian zones, and wetlands, which may be largely dependant on consistent
groundwater discharge in addition to intermittent storm runoff to sustain ponding and
flow conditions. These shallow water bodies are also important habitat for CRLFs.
Groundwater can thus present a constant, low-level source of aldicarb residues in
sensitive environments.
3.3 Terrestrial Plant Exposure Assessment
Aldicarb is an insecticide/miticide, and thus, registrants have not been required to submit
Tier I plant studies under the old Agency guidelines. This explains that the only available
information on effects of aldicarb on plants comes either from crop growers (anecdotal)
or from the open literature. There was one acceptable open literature plant study for the
pearl millet which was used for RQ calculations in the terrestrial plant section of the risk
estimation section. This one species (monocot) was used to represent terrestrial plants
and terrestrial plants growing in semi-aquatic areas. How representative pearl millet is of
all other terrestrial plant species remains unknown.
TerrPlant (v. 1.2.2) was used to assess risk to terrestrial plant and terrestrial plants
growing in semi-aquatic areas. The model assumes complete incorporation of granules
into the ground, which is an unrealistic assumption, especially for crops where
applications occur after plants have emerged and root systems have already begun to
establish. 85% incorporation for some crops (i.e. citrus) is still a generous assumption.
Therefore, risk calculated for terrestrial plants may be underestimated.
TerrPlant input parameters for the model included: (1) terrestrial plant toxicity values; (2)
application rate; (3) runoff, based on chemical solubility; and (4) soil incorporation depth.
The model provides estimates of exposure concentrations and risk quotients (RQs) for
non-listed and listed terrestrial and semi-aquatic plants. A detailed explanation of the
model as well as the modeling inputs and outputs for estimating terrestrial and semi-
aquatic plant exposure risks to aldicarb are summarized in Appendix B. Only one
application is considered in this assessment due to model limitations.
60
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3.4 CRLF Terrestrial Phase Exposure Assessment
Terrestrial exposures from granular applications (mg ai/square foot)10 for the California
red-legged frog will be estimated using the Tier 1 model, T-REX Version 1.3.1 (T-REX,
2007). In addition, a banded granular application assumes that 100% of the granules are
unincorporated on the ground. Risk to terrestrial animals from ingesting granules will be
based on LD50/ft2 values. The LD50/ft2 values are calculated using avian toxicity value
(adjusted LD50 of the assessed animal and its weight c-lasses; the bird toxicity data is
used as surrogate data for the CRLF) and the EEC (mg ai/ft2) and are directly compared
with Agency's levels of concern (LOCs). Since aldicarb is used only for granular
applications, exposures to animals from foraging on food items with aldicarb residues
(short and tall grass, broadleaves, seeds) are not estimated because no spray drift is
produced (granular application assumes 0% drift) that settles on the foliar surfaces of
those food items. Details of the TREX model along with the input and output results are
presented in Appendix A.
Additionally, using the TREX model to estimate risk to the terrestrial phase of the CRLF
may potentially be an overly conservative method of risk estimation. This is primarily
because the CRLF is not expected to readily ingest as many granules as a foraging bird
(as simulated by the TREX model) which may either: 1) mistakenly select an aldicarb
granule to consume instead of grit that will aid in digestion or 2) incidentally consume
aldicarb granules while ingesting other food items on the ground. The CRLF does not
intentionally ingest grit. Thus, it is not expected to mistakenly ingest aldicarb granular
for grit. However, the CRLF may incidentally ingest aldicarb granules that may be fixed
to a prey item such as a mammal, bird, or frog. Because the amphibians typically have
slower metabolisms than avian species, amphibians have lower feeding rates than birds.
Thus, the CRLF red-legged frog is not expected to consume as many granules as a bird.
Consequently, the TREX model may overestimate the risk of aldicarb exposure to the
CRLF. However, the CRLF may potentially be exposed to aldicarb via other routes such
as thru the skin or drinking water contaminated with aldicarb. Currently, there is no
approved method available to EFED for capturing these routes of exposure. Thus, the
TREX calculations will be assumed to capture these other routes of exposure to the
CRLF. Thus, this assumption may address the potential over estimation calculations of
the TREX model.
Off-site Terrestrial Risk from Aldicarb Runoff:
Risks to terrestrial environments outside the zone of application for granular aldicarb are
mainly limited to re-deposition of aldicarb residues in lower-lying areas affected by
aldicarb runoff from nearby fields. It is not expected that significant amounts of whole
granules will be exported offsite, except those small amounts that may adher to the skin,
fur, or feathers (integument) of organisms passing through a treated field. While aldicarb
residues could potentially be transported as a component of runoff, and be re-deposited
10 mg ai/ft2 = application rate x % active ingredient x 453.590 mg/lb x % incorporation
no. of rows/acre x row length x bandwidth
61
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into environments occupied by the CRLF the transported amount is limited. Calculations
of the approximate amount of aldicarb potentially deposited as a result of registered
aldicarb use (based on high application and low incorporation rate scenarios) indicate that
concentrations in off-site soil would be several orders of magnitude below those that
would trigger risk. Specifically, aldicarb concentrations in runoff water and loading to
off-site soils (based upon the results of the TerrPlant model) were used to calculate the
approximate amount of aldicarb residues that might be found in soil receiving runoff
from a treated field under a high-use (4.95 lb ai/A) scenario. Assuming an affected soil
depth of 1 inch (from surface), a soil bulk density of 1 g/cm3 (average soil bulk density of
1.2 g/cm3 rounded to 1.0 for simplicity), and an initial terrestrial off-site concentrations of
0.09 lb ai/A, it was determined that the quantity of aldicarb in soil in 'receiving' areas
would be very low - on the order of 10"6 mg ai/kg soil.
62
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4. Effects Assessment
Aldicarb ecological effects data and ecological effects data for its major toxic degradates,
available from registrant and public literature as discussed in the Analysis Plan (Section
2.10.2), and their use for calculating RQ values are summarized in this Section. Specific
values selected from registrant submitted data and the public literature for the
measurement endpoints, and the basis for their selection, are also discussed (Tables 13-
16). In addition extrapolation methods were used to fill the data gap for reproductive
effects on aquatic vertebrates and birds, the extrapolation methods used are described.
4.1 Taxa specific toxicological endpoints and LOCs
Results of the Effects Assessment performed for the 2006 revised screening level
ecological risk assessment, which are also appropriate for measurement endpoint values
for the CRLF effects determination,, are listed in Table 13. The basis for the selection in
the 2006 revised screening level ecological risk assessment are also identified in Table
13. No new registrant data has been submitted since the revised aldicarb chapter has
been finished. The updated review of public literature, which is discussed in Section 4.2,
did not result in any more sensitive measurement endpoint values than those values
already identified in 2006, and no aldicarb amphibian toxicity data was found. However,
a seedling emergence and growth test for a terrestrial monocot plant, pearl millet, was
found in open literature and the selected measurement endpoint included in Table 13. A
review of this study is briefly summarized in Section 4.2.1. Additionally, based on avian
acute and chronic toxicity ratios for other N-methyl carbamates, an avian chronic
NOAEL for aldicarb was extrapolated. The extrapolation approach used is described in
Section 4.3 and the estimated value provided in Table 13. The avian chronic NOAEL is
used as a surrogate for estimating risk for the terrestrial-phase CRLF. Additionally, a
NOAEL was estimated for freshwater invertebrates using ACR value for aldicarb
(Section 4.6).
Table 13 Aldicarb Acute and Chronic Ecotoxicological Values Listed in 2005 RED and Used for RQ
Calculations in this Assessment
Assessment Endpoint and Species
from Selected Studv
Measurement Endpoint
Value
Basis for selection
MR I D/Reference
Bluegill sunfish (representing
aquatic vertebrate prey and surrogate
for aquatic phase CRLF)
96-hr LC50 = 52 ppb ai
Most sensitive 96-hr LC50
value
MRID40098001,
Meyer &
Ellersieck, 1986
Bluegill sunfish (representing
aquatic vertebrate prey and surrogate
for aquatic phase CRLF)
Estimated chronic
NOAEC = 0.46 ppb ai
Extrapolated NOAEC: 96-h
LC50 for bluegill sunfish (52
ppb ai) divided by ACR(a)
(fathead minnow 48-h EC50 of
8860 ppb ai divided by
NOAEC of 78 ppb ai)
Chironumus tentans (representing
aquatic invertebrate prey of CRLF)
48-hr EC50 = 20 ppb ai
Most sensitive <96-hr LC50(b)
acute value
Moore et. al., 1998
C. tentans (representing aquatic
invertebrate prey of CRLF)
Chronic NOAEC = 1 ppb ai
Extrapolated using an ACR
approach
-------
Assessment Endpoint and Species
from Selected Studv
Measurement Endpoint
Value
Basis for selection
M RI D/Refe re n ce
Marine diatom (surrogate for
freshwater algae, both a dietary item
for CRLF larva and a Habitat
Component of CRLF)
96-hr EC50 > 5000 ppb ai
Most sensitive algal <96-hr
EC50 (where effect is measure
of biomass and growth rate)
MRID 40228401
(US EPA, 1986)
Mallard duck acute oral
(surrogate for terrestrial phase of
CRLF)
LD50 = 1 mg ai/kg-bw
Most sensitive avian acute oral
value
MRID 00107398
Mallard duck reproduction
(surrogate for terrestrial phase of
CRLFJ
NOAEC = 0.49 mg/kg-bw
Extrapolated NOAEC:
N/A
Rat acute oral/ rat (representing
mammalian prey of CRLF)
LD50 = 0.9 mg ai/kg bw
Most sensitive mammalian
acute oral value
MRID 00057333
Rat reproduction (representing
mammalian prey of CRLF)
Chronic NOAEL = 0.4
mg/kg bw1-0-1, decreased
parental body weight gain
(2-generation reproduction
study)
Most sensitive mammalian
reproduction NOAEC value
MRID 42148401
Mallard duck acute oral (Terrestrial-
phase CRLF)
LD50 = 1 mg ai/kg-bw
Most sensitive avian acute oral
value
MRID 00107398
Mallard reproduction (Terrestrial-
phase CRLF)
Estimated chronic
NOAEL = 0.49 mg ai/kg bw
Acute oral LD50 for mallard
duck (lmg ai/kg-bw) divided
by ACR (N-methyl carbamate
acute geometric mean of
1223.2 ppm ai divided by N-
methyl carbamate chronic
geometric mean of 137.3 ppm
ai)
Honey bee (representing terrestrial
invertebrate prey of CRLF)
Acute contact LD50 = 0.285
ug/bee
Most sensitive acute contact
beneficial insect value
MRID00036935
Pearl millet (representing terrestrial
plant habitat PCE component)
Seedling emergence and
growth 21-d NOAEC 2.05
lbs ai/A
Only existing seedling
emergence data for plants
Kennedy 2002; see
Section 4.2.1
^ ACR = acute to chronic ratio
(b) For cladocerans, standards for an immobilization effect (EC50), that is considered a surrogate for mortality, are used
in place of a lethality endpoint (LC50).
^ Toxicity value is similar to acute oral LD50 in rats and suggests that mammals that survive acute aldicarb exposure
may suffer adverse reproductive effects from chronic exposure.
Table 14 shows the acute ecotoxicological values, based upon the toxic degradate of
concern aldicarb sulfoxide, that were used for calculating RQs. Table 15 gives the acute
and chronic LOCs that were used in this assessment.
Table 14 Aldicarb Sulfoxide Acute Ecotoxicological Values Used for RQ calculations in this
Assessment
Species
Endpoint
MR ID/Reference
Aldicarb Sulfoxide
Rainbow trout
96-hr LC50 = 7,140 ppb ai
MRID 45592115
Daphnid (adults)
48-hr EC50 = 43 ppb ai
Foranefa/., 1985
64
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Table 15 Specific LOCs Used in this Assessment
Taxa
Acute LOC
Chronic LOC
Avian1 (terrestrial phase amphibians)
0.1
1
Mammalian2
0.1
1
Terrestrial plants3
1
Aquatic Animals4
0.05
1
Terrestrial Insects5
0.05*
*The Agency has not established LOCs for terrestrial insects. This assessment will use the ratio of 0.05 as a cut-off
value for making effects determinations.
Toxicity values used in RQ calculations:
1 LD50 and estimated NOAEL, respectively
2 LD50 and NOAEL, respectively
3 EC50 for non-listed and NOAEC for endangered
4 LC/EC50 and estimated and reproductive NOAEC, respectively (the acute designation is not applicable for plants)
5LD50
4.2 Evaluation of Ecotoxicity Studies
Open literature data considered in this assessment include those obtained prior to October
2004 for the 2006 revised screening level ecological risk assessment (U.S. EPA, 2006) as
well as updated information obtained since the last ECOTOX run (Oct 2004 through Dec
2006). ECOTOX data of the 2006 revised SLERA and not considered for RQ
calculations in the CRLF assessment are included in appendices G through I of this
assessment.
In order to be included in ECOTOX, papers must meet the following initial, minimum
criteria:
(1) the toxic effects are related to single chemical exposure;
(2) the toxic effects are on an aquatic or terrestrial plant or animal species;
(3) there is a biological effect on live, whole organisms;
(4) a concurrent environmental chemical concentration/dose or application
rate is reported; and
(5) there is an explicit duration of exposure
Data that pass the ECOTOX screen are further evaluated for scientific soundness along
with the registrant-submitted data, and may be incorporated qualitatively or quantitatively
into this endangered species assessment. In general, effects data in the open literature
that are more conservative than the registrant-submitted data are considered if they meet
Agency guidelines for scientific soundness and use for quantitative purposes. The degree
to which open literature data are quantitatively or qualitatively characterized is dependent
on whether the information is relevant to the assessment endpoints (i.e., maintenance of
CRLF survival, reproduction, and growth) identified in Section 2.8.1. For example,
endpoints such as behavior modifications are likely to be qualitatively evaluated, because
quantitative relationships between modifications and reduction in species' survival,
reproduction, and/or growth are not available.
65
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Results of ECOTOX updated search for aldicarb
A brief summary and table of open literature data deemed acceptable for use in RQ
calculations is presented below. All additional ECOTOX information (acceptable, not
acceptable, and excluded studies) is provided in Appendices E through F and not
included in this chapter. No additional studies found in the updated ECOTOX search had
lower endpoint values than values presented in the 2006 revised screening level
ecological risk assessment or were deemed otherwise relevant for the purpose of this
assessment. Thus, studies listed in Appendix D (accepted papers) are a compilation of
accepted and potentially rejected papers because no further analysis went into sorting out
papers that had higher endpoint values than what was already available.
Table 16 Ecotox Study for Formulated Aldicarb Used for RQ Calculations in this Assessment (Oct
2004 - Dec 2006)
Species
Endpoint
MRID/Rcfcrcncc Number
Pearl millet
21-d NOAEC = 2.05 lbs ai/A,
decreased seedling emergence
Kennedy, 2002
4.2.1 Toxicity to Terrestrial Plants
Kennedy (2002) exposed seeds of the pearl millet cereal \Pennisetum glaucum (L.)] to
15% Temik® at 2.05 lbs ai/A, 3.08 lbs ai/A, and 4.1 lbs ai/A in a randomized complete
block experiment with three replications (repeated twice under greenhouse conditions) to
determine effects of in-furrow insecticides on seedling emergence and growth of this
feedgrain crop. The seeds were watered once 7 days after sowing; emergence was
determined at day 10; growth of seedlings was determined at day 21. In the first
treatment (2.05 lbs ai/A), as compared to the control, no effects on seedling emergence
were observed. Reductions in seedling emergence were observed at 3.08 lbs ai/A (actual
% reduction not reported), and 4.1 lbs ai/A (57% reduction in emergence). The study did
not identify what the minimum significant difference detected was for seedling
emergence. Furthermore, Kennedy reports that pearl millet seeds surviving past the
seedling emergence stage did not have their dry weight significantly reduced by aldicarb.
This information seems to be in line with reports from agricultural growers who state that
use of aldicarb has increased their crop yield (biomass), likely from reduced pest
pressure.
Labeled application rate data for at plant provides ancillary information regarding levels
considered by the registrant as not reducing yield. Application rates at planting are 1.0 lb
ai/A for sorghum; 2.1 lbs ai/A for dried bean, cotton, and sugar beet; and 3.0 lbs ai/A for
soybeans, peanuts, and sweet potato. Additionally there are established crops that are
exposed at levels of upto 5 lbs ai/A such as citrus and containerlesss field-grown
ornamentals.
The NOAEL for seedling emergence (2.05 lbs ai/A) was selected for screening effects to
terrestrial plants.
66
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4.3 Acute-to-Chronic Ratio Derivation for the CRLF
The following section presents the methodology used in deriving an avian ACR for N-
methyl carbamates, the group to which aldicarb belongs. The resulting avian
reproduction NOAEL was used as a surrogate for the terrestrial-phase amphibian (U.S.
EPA 2006). There was data for three N-methyl carbmates evaluated for this
extrapolation. These N-methyl carbamates (methomyl, methiocarb, and thiodicarb) were
chosen because they are the only chemicals for which acute dose-based as well as chronic
toxicological data are readily available and have been reviewed previously for scientific
soundness. Where there were multiple studies for a given species (e.g., mallard duck
and/or bobwhite quail) and endpoint (e.g., acute and chronic toxicity) the average was
calculated for each chemical.
All three N-methyl carbamates share with aldicarb the active N-methyl carbamate moiety
(carbamate cation is double bonded to an oxygen with a hydrogen (H) at the Ri position
on the nitrogen (N), a methyl group (CH3) at the R2 position on the N and an oxygen at
the R3 position on the carbon) (Figure 11); thiodicarb is a dimmer of methomyl and
transforms to the carbamate. Thiodicarb is known to more readily metabolize to the
carbamate in insects than mammals. The R3 group attached to the oxygen differs and
may be an akyl group, aryl group, oxime derivative or some other more complex group.
The N-methyl carbamates share the ability to inhibit cholinesterase through a specific
pathway and therefore share similar symptomology during acute and chronic exposure.
Other 'carbamate' pesticides do not share the same common mechanism. Carbamates
whose Ri and R2 groups are larger than hydrogen and a methyl group tend to posses a
much reduced, if at all, anticholinesterase activity. Structural differences at the R3 group
between N-methyl carbamates result in differences of affinity for cholinesterases,
differences in toxicokinetics and toxicodynamics and therefore differences in potency.
/ \
H OR3
N-methyl carbamate
Structural backbone
V
Aiaicaro Methiocarb Methomyl
Figure 11 Comparison of structures of N-methyl carbamates
Aldicarb
Thiodicarb
67
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Dietary ACR Calculations (Acute LCWChronic NOAEC):
Methomyl (Mallard duck): 19.6 mg/kg-bw : 50 mg/kg-bw = 0.39*
Methomyl (Bobwhite quail): 24.2 mg/kg-bw : 78.5 mg/kg-bw = 0.31*
Methiocarb: 16.4 mg/kg-bw : 50 mg/kg-bw = 0.33*
Thiodicarb: 2023 mg/kg-bw : 1000 mg/kg-bw = 2.02
Three of the preceeding ACRs are not valid, the chronic endpoint value is higher than the
acute mortality endpoint value: 0.39 (Methomyl); 0.31 (Methomyl); (0.33). Methiocarb.
The fact that chronic endpoint values were higher than acute mortality endpoint values is
most likely due to the fact that the studies were conducted by different laboratories.
Therefore, the thiodicarb ACR (2.02) was used to derive a mallard duck (the most acutely
sensitive bird) chronic NOAEL for aldicarb as follows:
The (aldicarb) mallard duck LC50 used in this assessment is 1 mg/kg-bw, and the
thiodicarb acute-to-chronic ratio of 2.02 is used to calculate the final estimated NOAEL
for aldicarb.
The estimated avian (terrestrial phase amphibian) NOAEL is practically identical to the
measured chronic mammalian NOAEL for rats (0.4 mg/kg); acute terrestrial phase
amphibian LD50 is practically identical to the acute LD50 (0.9 mg/kg) for rats. This lends
additional support in using the estimated NOAEL to make qualitative risk
characterizations for chronic effects of aldicarb to the CRLF. The fact that acute and
estimated chronic endpoint value are very close together with estimated chronic endpoint
slightly lower suggests that if a bird (or amphibian) survives acute exposure to aldicarb,
chronic reproductive effects can be expected.
Estimated NOAEL
Test animal LC 50
1 mg / kg - bw
0.49 mg / kg - bw
ACR
2.02
68
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Table 17 Avian N-Methyl Carbamate Data
Chemical
Species
& Acute
Endpoint
14-d LDS0
(mg/kg-
bw)
Avg
Value
(ppm)
MRIDs/
Labs
NOAEL
(ppm)
Avg
Value
(ppm)
MRIDs/
Labs
Species/
Chemical
Specific
ACR
Methiocarb
Bobwhite,
14-d LD50
19.6
19.6
40560018
REF (1983)
50*
50
00128119
MCC
(1982)
0.39 - not
valid
Methomyl
Mallard,
14-d LD50
15.9
16.4
00160000
FWS (1984)
50*
50
41898601
WLI
(1991)
0.33 - not
valid
Mallard,
14-d LD50
16.8
ACC233993
DUP (1970)
Bobwhite,
14-d LD50
24.2
24.2
00161886
WLI (1983)
137
78.5
41898602
WLI
(1991)
0.31 - not
valid
20*
N.R.
Thiodicarb
Bobwhite,
14-d LD50
2023
2023
92185002
WLI (1978)
1000
1000
43313003
BLA 1994
2.02
N.R. = not reported
* acute measurement endpoint is lower than chronic measurement endpoint
4.4 N-Methyl Carbamate Toxicological Data for Frogs
No toxicological data on frogs is available for aldicarb; and there is very limited
amphibian toxicity data for other N-methyl carbamates in the public literature (Table 18).
For other wildlife (e.g., avians, mammals, fish, invertebrates) aldicarb is typically among
the most toxic of the N-methyl carbamates, along with carbofuran. Thus, the
ecotoxicological frog data presented in Table 18 likely under represents aldicarb's acute
oral toxicity and the 96-hr lethal concentration to this taxa. While the data is limited a
comparison of these amphibian N-methyl carbmate toxicity values to those of the
surrogate taxa support the assumption that the selected surrogates are at least as sensitive
if not more sensitive than amphibians for N-methyl carbamates. For example, the
Mallard Duck acute oral LD50 value of 7.4 mg ai/kg-bw for propoxur (ACC 94546) is 80
times more toxic than the propoxur acute oral LD50 of 595 mg ai/kg-bw for the Bullfrog
(Table 18), and the Bluegill Sunfish 96-hr LC50 of 210 ppb (MRID 400980-01) for
methiocarb is 41 times more toxic than the Leopard frog methiocarb 96-hr LC50 of 8700
ppb (Table 18).
Table 18 N-Methyl Carbamate Toxicological Data for Amphibians
Chemical
Species
Endpoint
Reference
Propoxur
Bullfrog (adult)
14-d LD50 = 5 95 mg ai/kg bw
Hudson et al., 1984
Methiocarb
Leopard frog
(larva)
96-hr LC50 = 8.7 ppm
Armitage, 1984
69
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4.5 Aquatic Freshwater Plants
Aquatic freshwater plant data is not available for aldicarb and is a data gap; thus, the
Agency will use the marine diatom study to characterize potential risk to all aquatic
plants in this risk assessment (riparian plants were assessed using the results on pearl
millet (Kennedy 2002).
4.6 Acute-to-Chronic Ration Derivation for Freshwater Invertebrates
The most acutely sensitive freshwater invertebrate species was Chironomus tentans (20
ppb ai) (Moore et al. 1998). However, there was no reproduction and emergence study
found in the literature for this species. Since for aldicarb there was both an acute 48-hr
EC50 for Daphnia magna immobilization and a 21-d reproduction NOAEC, this
information was used to calculate an ACR of 20. The estimated NOAEC for C. tentans is
1 ppb ai (estimated NOAEC = 48-hr EC50/ACR = 20/20 = 1 ppb).
4.7 Probit Analysis
The Agency uses the probit dose response relationship as a tool for providing additional
information on the listed animal species acute levels of concern (LOC) and on calculated
RQ values, when the acute LOC is not exceeded. The listed LOC evaluated is 0.05 for
aquatic animals. Interpretation is presented in terms of the chance of an individual event
(i.e., mortality or immobilization) should exposure at the EEC actually occur resulting in
an RQ equivalent to the LOC or higher. The probit analysis is performed specifically by
using either the slope of the dose response relationship available from the toxicity study
used to establish the acute toxicity measurement endpoints for each taxonomic group, or
if this information is not available the default slope. In addition to a single effects
probability estimate based on the mean slope for a taxa, upper and lower estimates of the
effects probability are also provided to account for variance in the slope. 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
applicability of the assumed probit dose response relationship for predicting individual
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 might be reduced by high variance in the slope (i.e., large 95% confidence
intervals), despite good probit fit characteristics.
Individual effect probabilities are calculated using 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 tool performs calculations
based on user inputs of the mean slope estimate (and the 95% confidence bounds of that
estimate) as the slope parameters. The summary of probabilities of an individual to
demonstrate an effect using probit slope relationships can be found in the Risk Estimation
section of the Risk Characterization for the acute listed LOC and RQ.
70
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4.8 Review of Ecological Incident Information System (EIIS)
Twenty-nine ecological incidents, dating from 1988 to 2005, related to aldicarb poisoning
have been reported and summarized in the 2006 revised screening level ecological risk
assessment. Only the two new incidents reported in the database since 2005 are listed
here. These two new incidents, summarized below, came about due to illegal use of
alidcarb.
On January 3, 2006 a man in Floyd County (GA) found his dog severely sick (1017085-
001). The following day, his other dog was found dead near his home. The next day, a
ranger of the Georgia Department of Natural Resources (GA DNR) found two opossum
carcasses in the same area where his dog had died. Necropsies were performed on the
two opossums; the gastrointestinal contents of one of them contained 96 ppm of aldicarb
and the other contained 185 ppm aldicarb. Further study of the area led to the discovery
of a dead white-tailed deer that had been dumped on the property. The ranger
investigating the deaths feels that the deer, too badly decomposed to analyze for pesticide
residues, was the source of the aldicarb in the animals that were killed. He said that
Temik was not sold locally, and that the main crop grown in the area was corn, for which
Temik is not registered. He suspects that the deer carcass was baited with aldicarb and
placed to kill coyotes.
On March 27, 2006, one dog and two black vultures were found near a partially-
consumed carcass of a cottontail rabbit (1017462-001). The incident occurred on
municipal property that was used by the town of Hoinsville, Georgia, for disposal of
wastewater from a sewage treatment plant. Analysis of the vulture and rabbit found that
brain cholinesterase levels were significantly depressed in both animals, indicating that
both had ingested an anticholinesterase chemical. Toxicological analysis found 43 ppm
aldicarb in the stomach of the rabbit and "greater than 0.1 ppm" of aldicarb sulfoxide in
the liver of the vulture. The testimony of a local GA DNR employee as well as a GIS
analysis done by EFED indicated that very little or no land in the vicinity was planted in
crops on which aldicarb is registered for use. Thus, while there is little doubt that the
animals were poisoned by alidcarb, the most likely scenario is that the animals were
poisoned by illegal baiting or some other illegal use of aldicarb.
4.9 Sensitivity Distribution
4.9.1 Freshwater Fish
Of all the freshwater fish data reviewed by the Agency (registrant submitted studies as
well as open literature studies) in the 2006 revised screening level ecological risk
assessment, only three studies were classified as 'acceptable' or 'supplemental' according
to guidelines. Not enough data were available to develop a sensitivity distribution of
freshwater fish 96-h LC50 values.
71
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4.9.2 Freshwater Invertebrate
An acute freshwater species sensitivity distribution was constructed using acute toxicity
values for freshwater invertebrates from registrant and open literature studies. The kinds
of data desired for an acute species sensitivity distribution generally consist of 96-h LC50
values for invertebrates except for cladocerans. The desired measurement endpoint for
daphnids and other cladocerans is the 48-h EC50 based on percentage of organisms
immobilized plus percentage of organisms killed. These kinds of data are consistent with
FIFRA guideline studies and acute toxicity data measurement endpoints for water quality
criteria (Stephens et al., 1985). Freshwater acute toxicity data for aldicarb identified as
scientifically sound and useable quantitatively from the RED and this effects
determination are listed in Table 19. Aldicarb acute invertebrate data excluded from the
analysis include those tests where controls were insufficient or not reported (Margin et
al., 1988; Pantani et al., 1997), tests with single-celled organisms, these are not
considered acute tests (Edmiston et al., 1984); and tests with saline environmental
conditions (Song and Brown, 1998). A 24-hr EC50 value for Daphnia magna was
included along with the 48-hr values because it was lower than some 48-hr values. The
only scientifically sound Chironomus riparius and Chironomus tetans acute toxicity data
was for 24 hour and 48 hour exposures, respectively, rather than 96 hours. The 96-h
acute values for these Chironomous spp. are expected to be lower and may therefore
result in an underestimation of the concentration where the lower tail lies (e.g.,
underestimation of the concentration at and below which 0.05 of a fraction of the taxa
lie).
Where there were multiple results for a single species, a species mean acute value
(SMAV) was calculated by taking the geometric mean of the data for that species. Where
there were multiple results for a genus, a genus mean acute value (GMAV) was
calculated by taking the geometric mean of the SMAV. The method of calculating
SMAV and GMAV for constructing the sensitivity distribution is consistent with Office
of Water quality criteria development (Stephan et al., 1985). The use of GMAVs is used
to prevent data sets from being biased by overabundance of species in one or a few
genera, given that on the average, species within a genus are generally much more
toxicologically similar than species in different genera (Stephen et al., 1985). The
GMAVs are assumed to be log normally distributed. The mean (3.1261) and standard
deviation (1.4411) of the log transformed GMAVs were used to calculate the sensitivity
distribution (Figure 12). The 5, 25, 50 and 75 percent of the freshwater invertebrate taxa
fall at and below 6, 143, 1337, and 12557 ppb aldicarb, respectively. The 95% lower
confidence limit for the 0.05 fraction is (mean-standard deviation * to.05,5; 3.1261 -
1.4411*2.015=2 ppb).
72
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Table 19 Freshwater Acute Invertebrate Toxicity Data and Species and Genus Mean Acute Values
Species
Genus
96-hr
LCS0(a)
(ppb)
Log
96-hr
LC50
Species
Mean(b)
Acute
(ppm)
Genus
Mean(b)
Acute
(ppm)
Reference
Pila globosa
Pila
175000
5.243
175000
175000
Singh and Agarwal, 1981
Lymnaea acuminate
Lymnaea
11500
4.061
11500
11500
Singh and Agarwal, 1981
Hyalella azteca
Hyalella
3990
3.601
3990
3990
Moore et al., 1998
Aedes aegypti, 27°C
Aedes
290
2.462
280
280
Song et al., 1997
Aedes aegypti, 20°C
270
2.431
Song et al., 1997
Daphnia magna, 20°C
Daphnia
583
2.766
253
121
Moore et al., 1998
Daphnia magna
411
2.614
Acc. No. 098663
Daphnia magna
228
2.358
Sturm and Hansen, 1999
Daphnia magna, 27°C
75
1.875
Song et al., 1997
Daphnia Laevis juvenile
65
1.813
58
Foranetal., 1985
Daphnia Laevis adult
51
1.708
Foranetal., 1985
Chironomus riparius(d\ pH 4
Chironomus
17
1.230
22
21
Suorsa and Fisher, 1986
Chironomus riparius(d\ pH 6
21
1.322
Suorsa and Fisher, 1986
Chironomus riparius{d), pH 8
28
1.447
Suorsa and Fisher, 1986
Chironomus tetans(e)
20
1.301 20
Moore et al., 1998
Tests with daphnids and other cladocerans are 48-hr EC50 based on percentage of organisms immobilized plus percentage of
organisms killed (Stephan et al., 1985)
(b) Geometric mean
(c) Result is a 24-hr value which may underestimate the desired 48-h EC50 measurement endpoint
(d> Test conducted using 4th instar rather than 2nd or 3rd instar which are considered a more sensitive midge life stage (Stephan et al.,
1985) and result is a 24-hr value which may underestimate the desired 96-h LC50 measurement endpoint
Result is a 48-hr value which may underestimate the desired 96-h LC50 measurement endpoint
73
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Figure 12 Cumulative Acute Sensitivity Distribution of Freshwater Invertebrates to Aldicarb
1.0
Log LC50 = 3.1261 - 1.4411(zp) where zp is the standard normal deviate
Log
Probability Zp LC50 LC50
0.05 -1.645 0.7555 6
0.10 -1.282 1.2787 19
" ~0720 -07842 " "179127 82
0.25 -0.675 2.1541 143
0.30 -0.524 2.3710 235
" "0:40 -0T253 " "277615 ~57T
0.50 0 3.1261 1,337
0.60 0.253 3.4907 3,096
" "0:70 T»524~ - 73:8813 7,608 /
0.75 0.675 4.0989 12,557 /
0.80 0.842 4.3396 21,855 /
- ~0:90 1)28Z - -4:9736- - -94,110 /
0.95 1.645 5.4968 313,874 /
tymnaea (snail) (LC50 = 11; 500)
- ¦ Hyalella (amphipod) (LC50 = 3,99 0)
mosquito) (LC50 = 280)
Daphnia (cladoceran) (LC50 = 121)
Chironomus (midge) (LC50 = 21)
1 10 100 1000 10000 100000 1000000
Aldicarb Concentration (ppb)
74
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5 Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations to
determine the potential ecological risk from varying aldicarb use scenarios within the
action area and likelihood of direct and indirect effects on the CRLF. The risk
characterization provides an estimation and a 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
CRLF.
5.1 Risk Estimation
Risk was estimated by calculating the ratio of estimated environmental concentrations
(EECs; see Table 11) and the appropriate toxicity endpoint. 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 (Tables 15).
Aquatic screening level RQs are based on the most sensitive endpoints for each
assessment endpoint (Tables 7, 8 and 13) and modeled surface water concentrations from
the following scenarios of aldicarb:
• Citrus (1 application @ 33 lbs of product/A)
• Cotton (1 application @21 lbs of product/A)
• Cotton (3 applications @ 7 lbs of product/A each with a 30 day interval between
applications)
• Soybean (1 application @ 20 lbs of product/A)
• Pecan (1 application @ 33 lbs of product/A)
• Sugar beet (2 applications @ 14 lbs of product/A with a 30 day interval between
applications)
• Sweet potato (1 application @ 30 lbs of product/A - Temik lOg only)
• Dried bean (1 application @ 21 lbs of product/A- Temik lOg only)
• Alfalfa (1 application @ 20 lbs of product/A)
• Sorghum (1 application @ 7 lbs of product/A)
• Peanut (1 application @ 30 lbs of product/A- Temik lOg only)
• Ornamentals (1 application @ 50 lbs of product/A- Temik lOg only)
Terrestrial screening level RQs for the terrestrial phase of the CRLF and small
mammalian prey are based on the most sensitive endpoints and EECs/sq ft for the
following scenarios11 as modeled by T-REX (ver.1.3.1):
• Citrus (1 application @ 33 lbs of product/A, 85% incorporation efficiency)
11 Alfalfa was not modeled in the terrestrial risk assessment because its application rate, application
method, and RQs are representative of RQs derived for the peanut and soybean scenarios.
75
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• Cotton (3 applications @ 7 lbs of product/A, 30 day interval between
applications, 85% incorporation efficiency)
• Dry beans (1 application @ 7 lbs of product/A, 99% incorporation efficiency)
• Peanuts (1 application @ 20 lbs of product/A, 99% incorporation efficiency)
• Sorghum (1 application @ 7 lbs of product/A, 99% incorporation efficiency)
• Soybean (1 application @ 20 lbs of product/A, 99% incorporation efficiency)
• Sugar beet (2 applications @ 14 lbs of product/A, 30 day interval between
applications, 85% incorporation efficiency)
• Sweet potato (1 application @ 14 lbs of product/A, 99% incorporation efficiency)
Application of aldicarb to pecans could not be adequately modeled using T-REX because
the model assumes that aldicarb is applied by shanking in below the dripline of the tree.
Based on information provided by OPP BEAD, (pecan trees are grown up to 60 feet; 30
feet spacing within row; canopies touching; little space between canopies of adjacent
rows), the Agency calculated LD50/sq ft for pecans based on 'shanking-in' application,
band with of 6.25", and 72" row spacing (space between adjacent canopies).
Terrestrial screening level RQs for terrestrial invertebrates and terrestrial phase of the
CRLF (due to secondary poisoning) are based on the highest estimated aldicarb
concentrations in soil from all use scenarios (see T-REX) as estimated by the most
sensitive endpoints and the Earthworm Fugacity model. Terrestrial plant RQs are based
on the most sensitive endpoint and EECs as modeled by TerrPlant (ver. 1.2.2). EECs will
be calculated for all labeled uses permitted in California.
In cases where the screening level RQ exceeds one or more LOC, additional factors,
including CRLF life history characteristics, probit dose-response analysis (IEC VI. 1),
and species sensitivity distribution are considered and used to characterize the potential
for aldicarb to affect the CRLF. Risk estimations of direct and indirect effects of aldicarb
to the CRLF are provided in section 5.1.1 and 5.1.2, respectively.
5.1.1 Direct Effects
Risk to the aquatic stage of the CRLF is driven by the sugar beet scenario and generated
acute and chronic RQs of 0.22 and 11.79, respectively (LOC >0.05 and >1). Due to lack
of a dose response slope value, individual probabilities of mortality were bracketed by
evaluating a slope of 2 (high probability of individual mortality) and a value of 9 (low
probability of individual mortality). The aquatic acute listed LOC (0.05) at default slope
95% bounds of 2 and 9 correspond to a probability of individual mortality of 1 individual
in 216 and 1 individual in 1.8E+31, respectively. One of the reasons it is difficult to get a
slope is because of the almost all or none response observed in most studies. Therefore,
the slope actually is expected to tend more towards 2 than 9. Probabilities for the
calculated RQ values above the acute listed LOC (0.05) but below the acute LOC (0.5)
for all assessments at the default average slope of 4.5 and the 95% lower bound slope of 2
are provided in Table
76
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Risk to the terrestrial phase of the CRLF is driven by aldicarb use on citrus, followed by
cotton, with an acute LD50/sq ft (RQ) of 2978 and 468 for small and large red legged
frogs, respectively (LOC >0.1). For the pecan scenario, it was assumed based on mature
orchard information from BEAD, that adult tree canopies within the same row touch, and
therefore shanking of aldicarb granules into the soil in one continuous row as modeled by
T-Red's LD50/sq ft method became a reasonable assumption. It was further assumed that
trees between rows leave a 72" gap between canopies of adjacent rows of trees, and that
this distance was the row spacing between rows. Chronic RQs could not be calculated by
the LD50/sq foot method of the T-REX model, but the estimated NOAEL of 0.1 lmg ai/kg
bw will be qualitatively discussed in the risk description section. Direct toxicity to the red
legged frog by way of secondary poisoning exposure from terrestrial invertebrates is not
expected to lead to LOC exceedances (LOC >0.05).
77
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Table 20 Summary of Aldicarb Direct Effects RQs for the CRLF
Effects
Surrogate
Toxicity
Scenarios
RQ
Probability
LOC
to CRLF
Species
Value
of
Exceedance
Individual
Effect
(Default
slope = 4.5)
Aquatic Phase CRLF
Acute
Bluegill
96-h
Citrus
0.0071
>l-in-4.3E8
No
Direct
sunfish
LC50= 52
Cotton (1)
0.13
l-in-30,000
Yes
Toxicity
ppb ai
Cotton (3)
0.15
l-in-9,600
Yes
Soybean
0.12
l-in-58,000
Yes
Pecan
0.14
l-in-16,000
Yes
Sugar beet
0.22
l-in-648
Yes
Chronic
Bluegill
Estimated
Citrus
0.81
Not
Yes
Direct
sunfish/Fathead
NOAEC=
Cotton (1)
7.68
applicable
Yes
Toxicity
minnow ACR
0.46 ppb
Cotton (3)
7.50
Yes
ai
Soybean
5.60
Yes
Pecan
6.84
Yes
Sugar beet
11.79
Yes
Terrestrial phase CRLF
Sm
Lg
frog"
frog"
Acute
Mallard duck
LD50= 1
Citrus
2978
467
Yes
Direct
mg/kg-
Cotton1,4
1599
251
Yes
Toxicity
bw
Dry Beans3
84
13
Yes
Peanuts3
180
28
Yes
Pecans5
571
89
Yes
Sorghum3
185
29
Yes
Soybean3
150
23
Yes
Sugarbeet2'3
1158
181
Yes
Sweet
84.23
13
Yes
potato3
Acute
Mallard duck
LD50= 1
Citrus
0.0017
No
Direct
mg/kg-
Toxicity
bw
via
Secondary
poisoning
Bolded scenarios are the highest risk in the aquatic or terrestrial environment and bolded RQ values exceed LOC values
1 T-REX does not allow for different application rates; thus the modeling run generating the highest RQs was chosen
for final RQs in Table 24, which was for 3 applications @ 7 lbs/A
2 Three applications are allowed for sugar beet with a maximum 1 time application rate of 14 lbs/A and a total of 28
lbs/yr. The modeling run generating the highest RQs was chosen for final RQs in Table 24
3 Incorporation efficiency 99%
4 incorporation efficiency 85%
5 LD50/sq ft calculated assuming granules shanked in, row spacing between canopy of trees in adjacent rows 72".
6 small refers to a 20 g bird; a small CRLF however would be around 50g. Therefore this RQ estimate may be higher
than expected. Large refers to a lOOg bird; a large CRLF may weigh up to 100 g. Therefore, this RQ estimate may be
lower than expected.
78
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Aldicarb Degradates and Direct toxicity to the Red Legged Frog
Aldicarb sulfoxide has been classified as moderately toxic on an acute basis to freshwater
fish (MRID 45592115). Based on the one study available, it can be assumed that aldicarb
sulfoxide is not likely to pose a risk to the aquatic phase of the red legged frog. None of
the scenarios modeled (combined aquatic EECs for parent and degradates were used in
these calculations) lead to LOC exceedances (LOC >0.05).
Table 21 Aldicarb Sulfoxide Direct Effects to the CRLF
Effects
Su novate
Toxicity
Scenarios
RQ
Probability
LOC
to
Species
Value
of
Exceed ancc
CRLF
Individual
Effect
Acute
Rainbow trout
96-hr LC50
Citrus
0.00005
At LOC of
No
direct
= 7,140 ppb
Cotton (1)
0.001
0.05 and
toxicity
ai
Cotton (3)
0.001
slopes of 2
Soybean
0.0009
and 9
Pecan
0.001
1 in 216
Sugar beet
0.002
1 in 1.8E+31
5.1.2 Indirect Effects
Pesticides have the potential to exert indirect effects upon listed species by inducing
changes in structural or functional characteristics of affected communities. Perturbation
of forage or prey availability and alteration of the extent and nature of habitat are
examples of indirect effects.
In conducting a screen for indirect effects, direct effects LOCs for each taxonomic group
(freshwater and terrestrial vertebrates, freshwater and terrestrial invertebrates, terrestrial
plants) are employed to make inferences concerning the potential for indirect effects upon
listed species that rely upon non-listed organisms in these taxonomic groups as resources
critical to their life cycle (U.S. EPA, 2004). This approach used to evaluate indirect
effects to listed species is endorsed by the Services (USFWS/NMFS, 2004b). If no direct
effect listed species LOCs are exceeded for non-endangered organisms that are critical to
the California Red Legged Frogs life cycle, the concern for indirect effects to the CRLF
is expected to be minimal.
If LOCs are exceeded for freshwater and terrestrial vertebrates as well as invertebrates
that are prey items of the CRLF, there is a potential for aldicarb to indirectly affect the
frogs by reducing available food supply. In such cases, the dose response relationship
from the toxicity study used for calculating the RQ of the surrogate prey item is analyzed
to estimate the probability of acute effects associated with an exposure equivalent to the
EEC. Generally, the greater the probability that exposures will produce effects on a taxa,
the greater the concern for potential indirect effects for listed species dependant upon that
taxa (U.S. EPA, 2004). However, life history characteristics of each taxa affected and
serving as prey to the CRLF will have to be considered in conjunction with the
probability of exposure. In addition, the species' sensitivity distribution for aquatic
invertebrates can be used to further refine an effects determination.
79
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As an insecticide, indirect effects to CRLFs from potential effects on primary and
secondary consumers are a principle concern. Furthermore, aldicarb has shown to have
deleterious effects on seedling emergence in terrestrial plants, and therefore, potential
effects on terrestrial plants growing in semi-aquatic areas is of concern as well. Based on
the emergence data, aldicarb's systemic nature, and its positive effects on biomass in
terrestrial plants, it can be concluded that potential effects on primary productivity of
aquatic vascular plants is of concern as well. This risk assessment will address risk to
aquatic vascular plants in a qualitative way because of lack of data.
5.1.2.1 Evaluation of Potential Indirect Effects via Reduction in Food
Items
Potential indirect effects from direct effects on animal food items were evaluated by
considering the diet of the California Red Legged frog and the sensitivity distribution of
aquatic prey organisms. Aquatic phase CRLF larvae consume algae, diatoms, and
detritus, for which no data are available. The saltwater diatom data was used as a
surrogate for freshwater diatoms to assess potential indirect effects on the larval stage of
the CRLF; no other aquatic plant data are available for an indirect effects analysis of the
aquatic phase of the CRLF. Terrestrial phase CRLFs feed on a wide range of freshwater
and terrestrial invertebrates, and freshwater and terrestrial vertebrates, including water
striders, sow bugs, fish, other frogs, salamanders, and small mice. While aquatic and
terrestrial invertebrates comprise the most numerous food items, 50% of the prey mass in
larger adult CRLFs consists of vertebrates such as mice, frogs, and fish. The RQs used to
characterize potential indirect effects to the terrestrial and aquatic phase of the CRLF
from direct acute and chronic effects on freshwater vertebrate and invertebrate as well as
terrestrial vertebrate and invertebrate food sources are provided in Table 22. Acute RQs
are based on the most sensitive toxicity endpoints of the bluegill sunfish (96-h LC50 = 52
ppb ai), C. tentans (20 ppb ai), the rat (LD50 = 0.9 mg ai/kg-bw), and the honey bee (LD50
= 0.285 |ig/bee). Chronic RQs are based on the bluegill sunfish (estimated NOAEC =
0.46 ppb ai), and C. tentans (NOAEC = 1 ppb ai). Chronic RQs cannot be calculated by
the LD50/sq foot method of the T-REX model; but the rat NOAEL of 0.4 mg ai/kg-bw
will be qualitatively discussed in the Risk Description section of this assessment.
There are acute LOC exceedances (> 0.05) for fish and invertebrates and aquatic animals
from all use scenarios except citrus (low runoff PRZM-EXAMS scenario), sorghum and
by default soybean with infurrow and positive displacement application methods only
which have lower EECs than citrus (Table 22). Containerless field grown ornamentals
(and by default container grown outdoor ornamentals represented by this scenario) and
sweet potato do not exceed the acute listed LOC for fish. There are chronic LOC
exceedences for fish and aquatic invertebrates for all scenarios except citrus (soybean
applied infurrow and/or with positive displacement by default) and sorghum. Sugar beet
drives both the acute and chronic risks LOC exceedances to these potential dietary
sources of the CRLF and invertebrates and, therefore, drives the indirect effects to the
CRLF on an overall basis.
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There are LOC exceedances (>0.1, Ratio of >0.05 for terrestrial invertebrates) for small
mammals and terrestrial invertebrates from all use scenarios (Table 23). Aldicarb use on
citrus leads to the highest LOC exceedance for small mammals (LD50/sq ft =1042)
followed by cotton, sugar beets, and pecans (LD50/sq ft =560, 405, and 200, respectively).
Aldicarb use on citrus also produced the highest soil concentration estimated with the
Earthworm Fugacity model (14.3 mg/kg soil); this estimated soil concentration was used
to estimate risk to concentrations on a honey bee of O.lg (or 0.0001 kg). The resulting
RQ for honey bee is 5.03 (LOC = 0.05) and is representative of all terrestrial
invertebrates on-site. An estimate of the off-site soil concentrations were estimated using
Terrplant as discussed in Section 3.4 and resulted in concentrations below the LOC.
Since aldicarb use on cotton has the highest reported usage in California, soil
concentrations from this use were considered as well to estimate risk to terrestrial
invertebrates. Aldicarb use on citrus produced a soil concentration of 1.2 mg/kg soil.
The resulting RQ for honey bee is 0.42 and exceeds the LOC of 0.05 for terrestrial
invertebrates for on-site soils. The off-site soil as discussed in the previous sentence will
be below the LOC.
5.1.2.2 Evaluation of Potential Indirect Effects via Reduction in Habitat
and/or Primary Productivity
Potential indirect effects on habitat and/or primary productivity were assessed using the
RQs from a saltwater diatom. This species is used as a surrogate for freshwater diatoms
and will only provide insight into a small part of the sensitivity spectrum of freshwater
plant. If aquatic plant RQs exceed the Agency's non-listed species LOC (because the
aquatic and terrestrial phase of the CRLF relies on multiple plant species), potential
community level effects are evaluated using the threshold concentrations (No Adverse
Effects Levels, i.e. NOAEC). Risk quotients used to estimate potential indirect effects to
the CRLF from effects on aquatic and terrestrial plants primary productivity are
summarized in Table 24.
None of the use scenarios led to LOC exceedances for freshwater aquatic plants (using
saltwater diatom as surrogate) and terrestrial plants, or for terrestrial plants growing in
semi-aquatic areas. Both aquatic plant and terrestrial plant RQs were <0.5 and do not
trigger the LOC. The TerrPlant model assumes that 100% of the granules are
incorporated, which is not a realistic assumption for all aldicarb incorporation methods.
In reality, citrus and cotton (3 applications) are more likely to have only 85% of aldicarb
granules incorporated (because established trees for citrus and established plants for
second and third applications for cotton do not allow for use of the type of equipment
necessary to achieve 99% incorporation). If TerrPlant had the ability to model partial
granular incorporation, the resulting RQs would be higher for terrestrial plants and plants
growing in semi-aquatic areas.
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Table 22 Summary of Aldicarb RQs Used to Estimate Indirect Effects to the CRLF via Acute and Chronic
Effects on Aquatic Dietary Items(l)
Crop
Efficiency
of Method
Amount
Product
%
a.i.
EEC
Fish (1,2'3)
Invertebrate(1,2'3)
Peak
21-d
60-d
Acute
Chronic
Acute
Chronic
Citrus
(85%)
33 lb/A
15g
0.4
0.2
0.1
0.01
0.2
0.02
0.2
Sorghum
IF (99%)
10 lb/A/yr
lOg
0.7
0.5
0.3
0.01
0.7
0.04
0.5
IF (99%)
7 lb/A/yr
15g
0.7
0.5
0.3
0.01
0.7
0.04
0.5
Ornamentals
(field-no
contaniners)
SD (99%)
50 lb/A/yr
lOg
0.9
0.7
0.5
0.02
1.1
0.05
4.5S (l-in-4.2E8)
2S (l-in-216)
0.7
Sweet Potato
Band (99%)
30
lb/A/crop
lOg
1.4
1
0.6
0.03
1.3
0.07
4.5S (l-in-9.9E6)
2S (l-in-96)
1.0
Dried Bean
Band (85%)
21 lb/A/
crop
lOg
4.5
3.5
2.3
0.09
4.5S (l-in-7.9E5)
2S (l-in-55)
5.0
0.23
4.5S (l-in-491)
2S (l-in-9)
3.5
Soybean
(85-99%)
20 lb/A
15g
6.1
4.5
2.6
0.12
4.5S (l-in-5.8E4)
2S (l-in-30)
5.7
0.31
4.5S (l-in-91)
2S (l-in-6)
4.5
Peanut
Band (85%)
30
lb/A/crop
lOg
6.4
5
3.3
0.12
4.5S (l-in-5.8E4)
S (l-in-30)
7.2
0.32
4.5S (l-in-77)
2S (l-in-6)
5.0
Pecans
(85%)
33 lb/A
15g
7.4
5.4
3.1
0.14
4.5S (l-in-1.6E4)
2S (l-in-23)
6.7
0.37
4.5S (l-in-39)
2S (l-in-5)
5.4
Cotton
(85-99%)
21
lb/A/season
15g
7.6
5.9
3.4
0.15
4.5S (l-in-9,600)
2S (l-in-20)
7.4
0.38
4.5S (l-in-34)
2S (l-in-5)
5.9
6.8
5.5
3.5
0.13
4.5S (l-in-3E4)
2S (l-in-20)
7.6
0.34
4.5S (l-in-57)
2S (l-in-6)
5.5
Alfalfa (seed)
Drill (85%)
20 lb/A/yr
15g
10
8.4
5.3
0.19
4.5S (1-in-1700)
2S (l-in-13)
11.5
0.50
8.4
Sugarbeet
(99%)
15g
11.4
8.6
5.4
0.22
4.5S (l-in-648)
2S (1-in-ll)
11.7
0.57
8.6
^ Bolded acute values exceed the acute listed LOC (0.05) and bolded chronic values exceed the chronic
LOC (1).
(2)
Peak EECs are used for calculating acute RQs; 21-day EECs are used for invertebrate chronic RQs and
60-day EECs for vertebrate chronic RQs.
(1,> Fishbluegill 96-hLC50 52 ppb; NOAEC 0.46 ppb; 48-hr EC50 Chironomus tentans 20 ppb; estimated
NOAEC 1 ppb
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Table 23 Summary of Aldicarb RQs Used to Estimate Indirect Effects to the CRLF via Acute Effects
on Terrestrial Dietary Items(1)
Indirect
Surrogate Food
Use
Dose or
RQ
loc(2)
Effect to
Item Toxicity
Concentration
Exceedance
CRLF
Value
Dose LDso/sq ft
Reduced
Rat
15 g
35 g
1000 g
Terrestrial
LD50 0.9 mg a.i./kg-
mam
mam
mam
Food via
bw
mal
mal
mal
Acute Direct
Citrus
1042
Yes
Toxicity
Cotton (3)
560
296
24
5591
Dry Beans
30
16
1.26
291
Peanuts
63
35
2.7
631
Pecans
200
106
9
2001
Sorghum
65
34
2.8
651
Soybean
53
28
2
521
Sugar beet
405
214
17
4051
Sweet potato
1.26
16
29
291
On-site<3) Soil
Concentration
Reduced
Honey bee (0.0001
Citrus
14.3 mg ai/kg soil
5.032
Yes
Terrestrial
kg)
(=0.0014 mg a.i./bee)
Food via
LD50 0.000285 mg
Acute Direct
a.i./bee
Cotton (3)
1.2 mg ai/kg soil
0.42
Yes
Toxicity
( V> Bolded sections represent use scenarios that are driving risk in aquatic and terrestrial environment,
bolded RQs exceed LOC
(2)
Acute endangered LOC of 0.1 is used for terrestrial animals and the LOC of 0.05 is used for acute
effects to terrestrial invertebrates.
(3)
Off-site soil estimated soil concentrations are below LOC of 0.05 (see Section 3.4)
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Table 24 Aldicarb RQs Used to Estimate Indirect Effects to the CRLF via Direct Acute Effects on
Aquatic and Terrestrial Habitat Components ^
Indirect Effect to
Surrogate
Use
EEC
RQ
Exceedance and
CRLF
Species/ Toxicity
Risk Interpre-
Value
tation
Reduced Cover to
Marine diatom
Citrus
0.371
0.000007
No
Aquatic Phase of
96-hr EC50>
Cotton (3)
7.632
0.0002
No
CRLF via Direct
50,000 ppb ai
Soybean
6.142
0.0001
No
Toxicity
Pecan
7.373
0.0001
No
Sugar beet
11.377
0.0002
No
Total loading
Total
Emerg. RQs
Emerg. RQs
to adjacent
loading to
adjacent
semi aquatic
areas
semi
area,
area,
aquatic
monocots
monocots
areas
Reduced Plant
Pearl millet 21-d
Citrus
0.0825
0.8250
0.04
0.40
No
Stand of Terrestrial
NOAEC = 2.05
Cotton
0.0525
0.5250
0.03
0.26
No
Habitat Component
lbs ai/A
Dry bean
0.0175
0.1750
0.01
0.09
No
via Direct Toxicity
Peanut
0.0500
0.5000
0.02
0.24
No
to seedling
Pecan
0.0825
0.8250
0.04
0.4
No
emergence
Sorghum
0.0350
0.3500
0.02
0.17
No
Soybean
0.0500
0.5000
0.02
0.24
No
Sugar beet
0.0700
0.7000
0.03
0.34
No
Sweet potato
0.0350
0.3500
0.02
0.17
No
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 aldicarb'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:
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¦ Harm includes significant habitat modification or
degradation that results in death or injury to listed species
by significantly impairing behavioral patterns such as
breeding, feeding, or sheltering.
¦ Harass is defined as actions that create the likelihood of
injury to listed species to such an extent as to significantly
disrupt normal behavior patterns which include, but are not
limited to, breeding, feeding, or sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are
extremely unlikely to occur. For example, use of dose-response
information to estimate the likelihood of effects can inform the evaluation
of some discountable effects.
• Adverse Nature of Effect: Effects that are wholly beneficial without any
adverse effects are not considered adverse.
A description of the risk and effects determination for each of the established assessment
endpoints for the CRLF is provided in Sections 5.2.1 through 5.2.3.
5.2.1 Direct Effects to the California Red Legged Frog
5.2.1.1 Direct Effects to the Aquatic Phase of the CRLF
Aquatic acute and chronic RQs exceeded acute listed and chronic LOCs for the following
modeled uses within the action area: cotton, dried bean, soybean (banded applications),
peanut, pecan, alfalfa and sugar beet. Sugar beet drives the risk in the aquatic
environment with acute and chronic RQs of 0.22 and 12, respectively. These RQs were
based on maximum label application rates. What constitutes typical application rates for
the uses having LOC exceedances is unclear and can, therefore, not be discussed for
characterization purposes. For the purpose of refinement, the CAL DPR PUR data will
be used in conjunction with spatial CRLF data, RQ exceedances, species' life history
information, and more to make direct effects determinations for the CRLF.
The probability of an individual event to the CRLF was calculated for all acute RQs
based on the dose response curve slopes of 4.5 (default) and its lower and upper 95%
bounds of the slope range (2 and 9) due to lack of actual probit slope values for
individual taxa). The corresponding estimated chance of an individual acute mortality to
the larva of the CRLF at RQs above the acute listed LOC ranging from 0.09 to 0.22
(based on the acute toxic endpoint for surrogate freshwater fish) is l-in-790,000 to 1-in-
648, respectively, for the mean slope of 4.5 (range if slope of 2 is used: l-in-55 to 1-in-
11). The acute listed LOC estimated chance of an individual acute mortality for the mean
slope is l-in-4.2E8 (for slope of 2 and 9: l-in-216 and l-in-1.8E31). There is
considerable amount of uncertainty around the probability of an individual mortality
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occurrence based on the default slope bounds; however, expect the slope to be more
towards 4.5 and 2 based on the all-or-none response observed in most acute tests. In
absence of a species' sensitivity distribution for acute mortality endpoint values, this
uncertainty cannot be further refined at this point. For dried beans, soybean (banded
application), peanut, pecan, cotton, alfalfa, and sugar beet, given the high probability of
an individual experiencing a mortality event based on the steeper slopes, and chronic RQs
that are above the chronic LOC, aldicarb was considered likely to cause direct adverse
effects to the aquatic phase of the CRLF where exposure to pesticide actually occurs.
Based on the usage information provided by California Department of Pesticide
Programs (PUR database) for 2001 through 2005, minor use of aldicarb (total amount of
aldicarb in California has been reported (1 and 1,232 lbs/A) for the following twelve
counties during the five year period: Alameda (1 lbs/A), Butte (854 lbs/A), Glenn (422
lbs/A), Monterey (111 lbs/A), San Benito (157 lbs/A), San Joaquin (77 lbs/A), San Luis
Obispo (1 lbs/A), Santa Cruz (3 lbs/A), Santa Clara (1 lbs/A), Stanislaus (5 lbs/A), Sutter
(1,232 lbs/A), and Riverside Counties (1,202 lbs/A). Significant aldicarb use (total
amount of aldicarb used in five years greater than 1,232 lbs/A) has been limited to the
following nine counties: Colusa (3,574 lbs/A), Fresno (>75,000 lbs/A), Imperial (3,491
lbs/A), Kern (>25,120 lbs/A), Kings (>75,400 lbs/A), Madera (5,014 lbs/A), Merced
(2,909 lbs/A), Tulare (2,512 lbs/A), and Yolo (5,089 lbs/A). No aldicarb use has been
reported for the remaining counties in California. Of the nine and twelve counties with
highest and lowest total aldicarb use (for all commodities) listed above, the following ten
counties are expected to clearly overlap with occurrence polygons, occurrence sections,
critical habitat, or core areas in recovery units (RU): Alameda (RU4), Butte (RU1),
Fresno (RU1), Merced (RU1), Monterey (RU5, RU6), San Luis Obispo (RU5, RU6), San
Benito (RU5, RU6), Santa Cruz (RU4, RU5), Santa Clara (RU4, RU6), and Riverside
(RU8). The remaining counties from that list are not expected to overlap with occurrence
polygons, occurrence sections, critical habitat, or core areas: Butte, Colusa, Glenn,
Imperial, Kern, Kings, Madera, San Joaquin, Stanislaus, Sutter, Tulare, and Yolo. The
highest total use of aldicarb has been on cotton in Colusa (2,800 lbs/A), Fresno (74,000
lbs/A), Imperial (3,500 lbs/A), Kern (31,500 lbs/A), Kings (74,000 lbs/A), Madera (4,700
lbs/A), Merced (27,800 lbs/A), Riverside (1,200 lbs/A), Sutter (1,200 lbs/A), Tulare
(22,300 lbs/A), and Yolo (5,000 lbs/A). All other aldicarb uses listed in the CAL DPR
PUR database make up insignificant amounts when compared to aldicarb use on cotton.
As discussed in the 2006 revised screening level ecological risk assessment, two
incidents for freshwater fish (1003826-002 and 1000799-005) related to aldicarb have
been reported in the Environmental Incident Information System (EIIS) database (North
Carolina (1995): one incident as a result of registered use and one of undetermined use).
No aquatic incidents have been reported in California.
Based on all available lines of evidence, the Agency concludes a "likely to adversely
affect" determination for direct effects to the aquatic phase of the CRLF via mortality,
growth, or reproduction in areas where exposure to aldicarb is expected to occur, such as
in recovery unit 1, 5, 6, and 8, for dried bean, soybean (banded application), peanut,
pecan, cotton, alfalfa for seed, and sugar beet. The Agency concludes a "not likely to
adversely affect" determination for direct effects to the aquatic phase of the CRLF via
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growth, survival, and reproduction in recovery units 2, 3, 4, and 7 due to lack of spatial
overlap of CRLF habitat and occurrence data with the aldicarb action area. The Agency
concludes a "likely to adversely affect" determination for direct effects of aldicarb to the
aquatic phase of the CRLF in RU1, RU5, RU6, RU8.
No LOC exceedances are predicted for aldicarb degradates based on modeled EECs and
available freshwater fish and freshwater invertebrates endpoint values. The Agency
concludes a "no effects" determination for direct effects of aldicarb sulfoxide to the
aquatic phase of the CRLF.
5.2.1.2 Direct Effects to the Terrestrial Phase of the CRLF
Terrestrial acute RQs, based on on-site exposure, are exceeded for all modeled scenarios
(and by default the other uses they represent) within in the action area. Citrus drives the
risk in the terrestrial environment followed by cotton with acute RQs for a small and
large size frog of 2978 and 468, and 1599 and 251, respectively. These RQs were based
on maximum label application rates. What constitutes typical application rates for these
uses having LOC exceedances is unclear and can, therefore, not be discussed for
characterization purposes. Terrestrial acute effects from aldicarb transport off-site was
evaluated for citrus and was below the LOC; therefore by default all other scenarios,
which result in lower exposure, also do not pose a risk of concern off-site.
For the purpose of refinement, the CAL DPR PUR data (see discussion in Section
5.2.1.1) will be used in conjunction with spatial CRLF data, RQ exceedances, species'
life history information, and more to make direct effects determinations for the CRLF.
As previously mentioned, direct effects to the CRLF are based on avian data, which are
used as a surrogate for terrestrial-phase amphibians. Chronic risk to the terrestrial phase
of the CRLF could not be assessed quantitatively via the LD50/sq ft method. However,
the following qualitative statement can be made regarding chronic risk from aldicarb
exposure to the adult phase of the CRLF. The estimated NOAEL (0.49 mg/kg) suggests
that if an adult frog experiences acute exposure to aldicarb (LD50 = 1 mg/kg) and survives
the incidence, chronic reproductive effects may potentially be expected.
Based on all available lines of evidence, the Agency concludes a "not likely to adversely
affect" determination for direct effects of aldicarb to the terrestrial phase of the CRLF via
growth, survival, and reproduction in recovery units 2, 3, 4, and 7 due to lack of spatial
overlap of CRLF habitat and occurrence data with the aldicarb action area. The Agency
concludes a "likely to adversely affect" determination for direct effects of aldicarb to the
terrestrial phase of the CRLF in RU1, RU5, RU6, RU8 considering on-site exposure. Off-
site exposure does not pose a risk of concern because off-site EECs are below LOCs.
There is no designated critical habitat in recovery units 2 and 8.
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5.2.2 Indirect Effects via Reduction in Food Items
5.2.2.1 Indirect Effects to the Terrestrial Phase of the CRLF
The results of the screening-level risk assessment for the CRLF suggest the potential for
direct acute adverse effects to terrestrial invertebrates and vertebrates exposed on-site for
all agricultural and non-agricultural uses. Citrus and cotton produce the greatest LOC
exceedances for terrestrial invertebrates with acute RQs of 5.03 and 0.42, respectively.
Aldicarb use on citrus and cotton produces RQs of 1042 and 560 for small mammals,
2978 and 1599 for small frogs, and 468 and 251 for large frogs (LD50/sq ft RQs for
birds). Off-site exposure levels in the terrestrial environment and riparian environment
are below levels of concern for both terrestrial invertebrates and vertebrates for all uses.
Soybean (in-furrow and/or positive displacement applications only), citrus, and sorghum
do not exceed acute listed or chronic LOCs for freshwater invertebrates. Sugar beets
produce the greatest acute and chronic LOC exceedances for freshwater invertebrates
(0.57 and 8.63, respectively) followed by cotton (0.38 and 5.91, respectively), and pecans
(0.37 and 5.39, respectively). Based on the highest risk scenarios, because the chronic
LOC exceedances for some crops are above the Agency LOC, aldicarb is likely to pose a
risk to the terrestrial prey base of the CRLF.
Indirect Effects to CRLF via Effects to Freshwater Fish and Freshwater
Invertebrate Prey Base
For freshwater invertebrates, acute listed and chronic RQs exceed the LOC of 0.05 and 1,
respectively for all uses of aldicarb except soybean (in-furrow and/or positive
displacement application methods only), citrus, and sorghum. For freshwater fish, acute
listed and chronic RQs exceed the LOC of 0.05 and 1, respectively for all uses of aldicarb
except soybean (in-furrow and/or positive displacement application methods only), citrus,
sorghum, and essentially containerless field grown ornamentals (chronic RQ = 1, the no
observable effect concentration for the ornamental scenario). Because the RQ values are
above the Agency LOC, based on the highest risk scenarios, alidicarb is likely to pose a
risk to the freshwater fish and freshwater invertebrate prey base of the CRLF.
Explanation of Indirect Effects Determination Based on Effects to the CRLF
Terrestrial and Aquatic Prey Base
Based on all available lines of evidence, the Agency concludes a "not likely to adversely
affect" determination for indirect effects to the CRLF via aldicarb adverse effects to the
terrestrial and aquatic prey base of the CRLF in recovery units 2, 3, 4, and 7 due to lack
of spatial overlap of CRLF habitat and occurrence data with the aldicarb action area.
Based on the highest risk scenarios, the Agency concludes a "likely to adversely affect"
determination for indirect effects to the CRLF via aldicarb adverse effects to the
terrestrial and aquatic prey base of the CRLF in RU1, RU5, RU6, RU8. The Agency also
concludes "a like to adversely affect" to the critical habitat for RU1, RU5, RU6, RU8 of
the CRLF because of the adverse effect expected to the terrestrial and aquatic organisms
base which is a component of the critical habitat of the CRLF.
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Indirect Effects to CRLF via Effects to Aquatic Plants
Due to lack of other aquatic plant data, the Agency had to rely on the only aquatic data
available, an estuarine/marine species used as a surrogate for freshwater, and on making
inferences for riparian plants from the results for terrestrial plants listed in this
assessment (Section 5.2.4). No direct effects are predicted to aquatic plants when the
estuarine/marine diatom is used in the RQ calculations. RQs for all use scenarios are
well below 1 and do not indicate reason for concern. Terrestrial plant emergence RQs are
also well below 1; highest emergence RQs for terrestrial plants growing in semi-aquatic
areas are for the citrus and pecan scenario and are 0.4. However, the TerrPlant model
assumes complete incorporation of granules, which is not a feasible assumption for
aldicarb applications to citrus. Therefore, these emergence RQs may represent an
underestimate of risk of aldicarb use to aquatic vascular plants.
Agency concludes a "no effects" determination for indirect effects to the aquatic phase of
the CRLF via direct effects to aquatic plants in all recovery units.
Indirect Effects to CRLF via Effects to Mammalian and Frog Prey
Acute RQs for small mammals exposed to on-site levels exceed the LOC of 0.1, and
suggest that granular application of aldicarb to agricultural and non-agricultural
commodities has the potential to indirectly affect the CRLF via reduction in the
availability of sensitive terrestrial food items. The mammalian calculations were based
on the rat LD50 of 0.9 mg ai/kg-bw. No comparison of the rat LD50 with other species'
LD50 is possible due to lack of data. Whether the 0.9 mg ai/kg-bw represents a lower or
upper value of the sensitivity spectrum for mammals is unclear. The chronic value
(NOAEL = 0.4 mg ai/kg-bw) suggest that where acute exposure to small mammals
occurs and individuals survive that chronic reproductive effects can be expected.
Acute RQs for small and large frogs exceed the LOC of 0.1, suggesting that granular
application of aldicarb to agricultural and non-agricultural commodities has the potential
to indirectly affect the CRLF via reduction in the availability of sensitive terrestrial food
items. The frog calculations were base on the surrogate mallard duck LD50 of 1 mg ai/kg-
bw. No other data is available to assess birds' sensitivity to acute aldicarb exposure. The
estimated chronic NOAEL of 0.1 mg ai/kg-bw suggests that where acute exposure to
frogs occurs and individuals survive that chronic reproductive effects may potentially
expected. In absence of aldicarb amphibian endpoint values, other (less sensitive) N-
methyl carbamate frog data was used in conjunction with aldicarb EECs to see whether
LOC exceedances would occur. Table 15 shows that when the amphibian endpoint for
propoxur (carbamate class) is used that LOC exceedances occur for almost all uses of
aldicarb. The highest LOC exceedances are for citrus (4.48 small frog and 0.70 large
frog) and cotton (2.4 small frog and 0.38 large frog). This analysis strengthens the
argument that aldicarb use on these crops can be expected to lead to LOC exceedances
with an aldicarb toxicological endpoint value as well.
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EFED presumes that because the LOC exceedances for mammalian and frog prey items
are well above the Agency LOC, aldicarb poses a likely risk to mammalian and
amphibian food prey of the CRLF, if on-site mammalian and amphibian populations are
critical to the CRLF. Off-site aldicarb concentrations are below levels of conern.
Based on all available lines of evidence, the Agency concludes a "not likely to adversely
affect" determination for indirect effects to the CRLF via aldicarb adverse effects to the
mammalian and amphibian prey base of the CRLF in recovery units 2, 3, 4, and 7 due to
lack of spatial overlap of CRLF habitat and occurrence data with the aldicarb action area.
The Agency concludes a "likely to adversely affect" determination for indirect effects to
the CRLF via aldicarb adverse effects to mammalian and amphibian prey base of the
CRLF in RU1, RU5, RU6, RU8, assuming on-site prey base is critical to CRLF. The
Agency also concludes "a like to adversely affect" to the critical habitat for RU1, RU5,
RU6, RU8 of the CRLF because of the adverse effect expected for the mammalian and
amphibian organisms which are a component of the critical habitat of the CRLF,
assuming on-site is considered critical habitat.
5.2.2.2 Indirect Effects via Reduction of Aquatic Primary Productivity
As already stated in Section 5.2.2 (indirect effects to CRLF via direct effects to aquatic
plants), due to lack of other aquatic plant data, the Agency had to rely on the only aquatic
data available, an estuarine/marine species as a surrogate, and on making inferences for
riparian plants from the results for terrestrial plants listed in this assessment (Section
5.2.4). No direct effects are predicted to aquatic plants when the estuarine/marine diatom
is used in the RQ calculations (see Table 26). RQs for all use scenarios are well below 1
and do not indicate reason for concern. Terrestrial plant emergence RQs are also well
below 1; highest emergence RQs for terrestrial plants growing in semi-aquatic areas are
for the citrus and pecan scenario and are 0.4. However, the TerrPlant model assumes
complete incorporation of granules, which is not a feasible assumption for aldicarb
applications to citrus. Therefore, these emergence RQs may represent an underestimate
of risk to aquatic vascular plants. The Agency concludes a "no effects" determination for
indirect effects to the CRLF via direct effects to aquatic plants in all recovery units and
critical habitat.
5.2.2.3 Indirect Effects via Alteration in Terrestrial Plant Community
Emergence RQs for terrestrial monocots are below the LOC of 1 for all use scenarios,
range from 0.01 to 0.04, and do not indicate reason for concern. Emergence RQs for
terrestrial monocots growing in semi-aquatic areas are slightly higher but also below the
LOC of 1, and range from 0.09 (dry beans) to 0.4 (citrus). However, the TerrPlant model
assumes complete incorporation of granules, which is not a feasible assumption for
aldicarb applications to citrus. Therefore, the emergence RQs of 0.4 may represent an
underestimate of risk to riparian plants.
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Agency concludes a "no effects" determination for indirect effects to the CRLF via direct
effects to terrestrial plants and terrestrial plants growing in semi-aquatic areas in all
recovery units and critical habitat.
5.2.3 Secondary Poisoning of CRLF by Consuming Terrestrial
Invertebrates Contaminated with Aldicarb Residues
The Earthworm Fugacity model was used to calculate the aldicarb concentration
(Appendix C) in soil (mg/kg). The conservative assumption was made that the
concentration in a 1 kg of soil is equivalent to the aldicarb concentration in 1 kg of
terrestrial invertebrate. The size of terrestrial invertebrate was set at 10 grams
(approximate weight of a large slug); however, most invertebrates that a CRLF consumes
will have a weight much below this value (water strider ~lg; spiders ~6mg). The citrus
scenario resulted in the highest concentration of aldicarb in soil (14.3 mg/kg) and was
used in estimating aldicarb concentrations in a terrestrial invertebrate of 10 grams (0.01
kg) as follows.
Aldicarb concentrations in a large terrestrial invertebrate:
14.3 mg ai/kg * 0.010 kg = 0.143 mg ai/lg invert
The allometric food ingestion rate equation for amphibians/reptiles is:
FI (g/day) = 0.013 * Wt°™ =0.077 g/day = 0.000077 kg/day
The estimated aldicarb concentration in a terrestrial invertebrate (0.0143 mg/kg), the
LD50 for mallard duck (1 mg/kg; surrogate for terrestrial phase amphibians), the daily
mass of invertebrates eaten by an amphibian/reptilian surrogate based on range of weight
for CRLF, the highest value cited for food water content in terrestrial animals and aquatic
animals (87%; or dry weight of food (13%)* 7.7=100%), and the weight (upper and
lower end; 100 g, 50 g) of a CRLF were used to calculate an RQ for the terrestrial phase
CRLF (LOC = 0.1). The Wildlife Exposure Factor Handbook (US EPA, 1993, vol I)
provided amphibian/reptilian insectivorous food ingestion rate equations and water
content of food to convert dry weight to wet weight of food; USGS (2004) provided
upper and lower bound weight of CRLF frog. These RQs measure risk to the CRLF from
secondary poisoning exposure via terrestrial invertebrates. The calculations show that
RQs are not significantly different for small and large adult CRLFs. The RQ for smaller
frogs will be used for the purpose of determining direct effects to the CRLF from
secondary poisoning exposure.
kg _ invert _ consumed
kg invert day
) bodyweightCRLF
mg _ ai
kg_bw CRLF
RQ (for 50g frog)
0.\43mg!kg *(0.000011kg *1.1 /day) + 0.05kg_bw
1 mg / kg
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_ 0.lA?>mg I kg* {0.000011kg *7.7 / day) OAkg _bw _A AAAOC
(for lOOgfrog) V.VVVOD
1 mg / kg
Based upon the RQ values calculated above, aldicarb CRLF secondary poisoning
earthworms contaminated with aldicarb is below the Agency LOC (LOC > 0.1).
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5.3
Final Effects Determination
The following tables (25-27) summarize the effects determination by Recovery Unit,
based upon the most conservative of the effects determinations, sugar beets, with the
assumption of on-site exposure of CRLF and that on-site terrestrial invertebrates are a
critical component of the diet of the CRLF and its critical habitat. Summation by specific
crops, more specific to on-site usage, is provided in text following these tables.
Table 25 Summarizes the effects determinations for direct effect of aldicarb to any of the life-stages of
the CRLF in Eight Recovery Units.
The life stages include aquatic (eggs, larvae, tadpoles) and terrestrial phase of CRLF (young and adult frogs). The
assessment endpoints are growth, survival, and reproduction of CRLF individuals.
Recovery
Unit
Effects
Determination
Basis for Effects Determination Conclusion
1
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF
2
NLAA
Based on lack of spatial overlap with Action Area (AA), frog habitat, and
occurrence sightings, CAL DPR PUR data despite LOC exceedances to
CRLF
3
NLAA
Based on lack of spatial overlap with Action Area (AA), frog habitat, and
occurrence sightings, CAL DPR PUR data despite LOC exceedances to
CRLF
4
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF
5
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF;
6
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF
7
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF
8
LAA
Based on spatial overlap with frog habitat and occurrence information, CAL
DPR PUR data, and direct effects for both phases of CRLF
* Summarize the effects determination by Recovery Unit, based upon the most conservative of the effects
determinations. Summation by specific crops, more specific to on-site usage, is provided in the following
text.
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Table 26 Summarizes the effects determinations for indirect effect of aldicarb to any of the life-
stages of the CRLF in Eight Recovery Units.
The life stages include aquatic (eggs, larvae, tadpoles) and terrestrial phase of CRLF (young and adult
frogs). The indirect effects include effects to habitat including effect to primary productivity, prey, and
riparian habitat.
Recovery
Unit
Effects
Determination
Basis for Effects Determination Conclusion
1
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
2
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF food
sources
3
NLAA
Based on lack of spatial overlap with AA
4
NLAA
Based on lack of spatial overlap with AA
5
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
6
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
7
NLAA
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to CRLF food
sources
8
LAA
Expected indirect effects to CRLF via adverse effects to CRLF prey sources.
* Summarize the effects determination by Recovery Unit, based upon the most conservative of the effects
determinations. Summation by specific crops, more specific to on-site usage, is provided in the following
text.
Table 27 Summarizes the effects determinations for effects to the critical habitat the CRLF in
recovery units one thru eight.
The effects entail effects to growth and survival of terrestrial and aquatic plant and animal components.
Recovery
Effects
Basis for Effects Determination Conclusion
Unit
Determination
1
LAA
Based on direct effects to terrestrial and aquatic animals which are
components of the critical habitat.
2
NE
No designated critical habitat in Recovery Unit (RU)
3
NE
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to animals
components of the critical habitat
4
NE
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to animals
components of the critical habitat
5
LAA
Based on direct effects to terrestrial and aquatic animals which are
components of the critical habitat.
6
LAA
Based on direct effects to terrestrial and aquatic animals which are
components of the critical habitat.
7
NE
Based on lack of spatial overlap with AA, frog habitat, and occurrence
sightings, CAL DPR PUR data despite LOC exceedances to animals
components of the critical habitat..
8
NE
No designated critical habitat in RU
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Aquatic Phase CRLF and Critical Habitat
No Effect
Soybean (in-furrow and/or positive displacement applications only), Citrus, and
Sorghum
Citrus, sorghum and soybean (but only when applied in-furrow with immediate soil
incorporation or in-furrow with positive displacement) uses were determined to have "no
effect" directly or indirectly on the aquatic-phase of the CRLF or the aquatic-phase of the
critical habitat. This determination was based on the results of the risk assessment where
all direct and indirect assessment endpoints of the aquatic-phase CRLF and its aquatic-
phase critical habitat were either below endangered LOCs (i.e., no exceedences of LOCs
for aquatic animals) or judged based on the best available information to not be affected
(i.e., off-field terrestrial plant components of critical habitat and aquatic plants judged to
not be affected, based on estimated exposure concentrations that were lower than a 'no
observable effect' level for limited toxicity data). Although application rates for citrus
are fairly high (4.95 lb a.i./A) and incorporation efficiency only 85%, low rainfall rates
and other factors in citrus production areas of California contribute to relatively low
aquatic exposure and risk estimates. For Sorghum use, low application rates (1 lb a.i./A)
and high incorporation efficiency (in-furrow application, 99%) contribute to minimal
aldicarb residues being exported into surface waters or off-field terrestrial habitat. When
compared to less efficient application methods with approximately 85% soil
incorporation (e.g., banded applications), the use of more efficient application techniques
(e.g., in-furrow, positive displacement) results in higher incorporation efficiencies (99%),
and concomitant exposure estimations well below LOCs for soybean.
Ornamentals (container grown) indoors
There is no exposure pathway by which aldicarb applied to ornamentals in containers
grown indoors may reach and expose the aquatic-phase of the CRLF or its critical habitat
(i.e., no run-off, no atmospheric transport, no CRLF or its critical habitat indoors).
Therefore this use is determined to have "no effect" on the aquatic-phase of the CRLF or
its critical habitat.
May Affect but Not Likely to Adversely Affect
Ornamentals (field grown—no containers) and Sweet Potato
Aldicarb registered uses on containerless field-grown ornamentals and sweet potato were
identified as "may affect" because the acute RQ values for aquatic invertebrates exceeded
the acute endangered LOC, the chronic RQ values exceeded the chronic LOC, and the
chronic RQ for aquatic invertebrates exceeded the chronic LOC for sweet potato use.
However, based on consideration of a number of factors, the level of effect both directly
and indirectly to the aquatic-phase of the CRLF and its aquatic critical habitat for these
assessment endpoints was determined to be discountable. Off-site terrestrial plant
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components of critical habitat and aquatic plants were judged to not be affected based on
the best available information that estimated exposure concentrations were lower than 'no
observable effect levels' for limited toxicity data. Therefore, aldicarb uses on
containerless field-grown ornamentals and sweet potato were determined to "not likely
adversely affect" the aquatic-phase of the CRLF and its critical habitat.
Direct effects to the aquatic-phase of the CRLF were considered discountable because the
acute endangered RQ values did not exceed the endangered species LOC; while the
chronic RQ value of 1 was exceeded, this exceedence was considered not significant and
essentially indistinguishable from the no observable effect level. For example, the
chronic RQ of 1.1 for containerless field grown ornamentals based on significant figures
is not distinguishable from 1 {i.e., EEC/NOAEC = 0.49/0.46 = 0.5/0.5 = 1), the level
equivalent to no observable effects. In addition, ornamental usage is not extensive, and
any potential impact on a water body adjacent to an application area would likely be
minor, fleeting, and spatially very limited.
Loss of aquatic fish or invertebrates as dietary resources was considered discountable
based on several factors affecting the frequency and duration of exposure and the
magnitude of effect. For example, both of these uses are limited to a single application
per year, with sweet potato application occurring at plant and ornamentals occurring at
any time prior to or during an infestation but again limited by the label to a single
application per year. Therefore, any potential impact on a water body adjacent to an
application area would likely be minor and fleeting. The acute endangered LOC for fish
is not exceeded for either use. Although the chronic LOC is exceeded, as discussed in the
preceding paragraph these exceedences are essentially equivalent to the no observable
adverse effect level. Additionally, other fish species are not as sensitive (e.g., fathead
minnow), so any potential impact would be limited in both magnitude and number of
species involved. For aquatic invertebrates, while the acute endangered LOC was
exceeded, the likelihood that an individual would be affected for the most sensitive
species was one-in-over a million (based on default slope of 4.5). Additionally, based on
the invertebrate species sensitivity distribution, over 80 percent of the aquatic
invertebrates would be even less sensitive. The chronic LOC was not exceeded for the
ornamentals and was at the LOC of 1 for sweet potato use, which is equivalent to no
observable effect on invertebrates.
Ornamentals (container grown) outdoors
Outdoor container grown ornamental use was considered to "not likely adversely affect"
the aquatic-phase CRLF or its aquatic-phase critical habitat. This determination was
based on the determination for containerless field grown ornamentals used as a surrogate.
Surface water exposure concentrations are expected to be lower than that for
containerless field grown ornamentals. This reduction is attributable to containers which
are expected to physically reduce run-off of aldicarb and its major toxic degradates and
lower application rates as compared to containerless field grown ornamentals. In
addition, ornamental usage is not extensive, and any potential impact on a water body
adjacent to an application area would likely be minor, fleeting, and spatially very limited.
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May Affect and Likely to Adversely Affect
Dried Beans, Soybean (banded applications), Peanut, Pecans, Cotton, Alfalfa,
Sugar beet
Aldicarb registered uses on dried beans, soybean, peanut, pecan, cotton, alfalfa, and sugar
beet were identified as "may affect" and "likely to adversely affect" the CRLF directly
because both the acute endangered LOC and chronic LOC were exceeded for amphibian
assessment endpoints (fish used as surrogate) and indirectly because fish and aquatic
invertebrate acute and chronic LOC values were exceeded.
It should be noted that for many of these crops, use of more efficient application
techniques (99% vs. 85% incorporation) would result in exposure estimations well below
the LOC for most categories (see Table 12). Although this might be impractical or
impossible for some current uses (e.g., peanut application post-pegging, cotton
application at bloom, pecan), in other cases (e.g., soybean, dried bean) achieving an
incorporation efficiency of 99% results in acceptable levels of risk should be possible
with appropriate application techniques.
Terrestrial Phase CRLF and Critical Habitat
No Effect
Ornamentals (container grown) indoors
There is no exposure pathway by which aldicarb applied to ornamentals in containers
grown indoors may reach and expose the terrestrial-phase of the CRLF or its terrestrial
critical habitat {i.e., no run-off, no atmospheric transport, no CRLF or its critical habitat
indoors). Therefore this use is determined to have "no effect" on the aquatic-phase of the
CRLF or its critical habitat.
May Affect but Not Likely to Adversely Affect
Off-site All Outdoor Uses
Off-site exposure for all outdoor registered uses was identified as "may affect" because
an individual terrestrial-phase CRLF that ingested a granule transported off-site in the gut
(incidental ingestion) or on the fur of a small mammal would potentially be effected. All
other off-site exposure of the terrestrial-phase CRLF {i.e., bioaccumulation in terrestrial
invertebrates or mammalian dietary items) and its critical habitat {i.e., loss of dietary
resources, riparian or upland plants) to aldicarb and its major toxic residues are below
LOCs. Because exposure of a terrestrial-phase CRLF to a granule carried in a small-
mammal off-field was considered unlikely and no other off-site exposure of the
terrestrial-phase CRLF or its critical habitat were above LOCs, exposure off-site for all
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outdoor uses was considered discountable and therefore "not likely to adversely affect"
either directly or indirectly the terrestrial-phase of the CRLF or its critical habitat.
Risks to terrestrial environments outside the zone of application for granular aldicarb are
mainly limited to re-deposition of aldicarb residues in lower-lying areas affected by
aldicarb runoff from nearby fields. However, calculations of the approximate amount of
aldicarb potentially deposited as a result of registered aldicarb use (based on the highest
risk scenario, cotton at 5 lbs a.i./A) indicate that concentrations (~ 10"6 mg a.i./kg soil)
would be several orders of magnitude below those that would exceed the LOC.
Exposure off-site of a CRLF to a granule in the gut or on the fur of small mammal was
considered unlikely because it is doubtful that the series of events needed to coincide for
an actual exposure event to occur would be frequent, if they occurred at all. First,
aldicarb is applied to most crops once per year, and infrequently for the others (i.e.,
cotton at most three times and sugar beets and peanuts at most two times per year).
Second, the duration of the integrity of a granule in the field is limited as it readily
dissolves in water—irrigation or rainfall dissolves the granule and moves it down into
the soil profile. Therefore the window of opportunity for a small mammal to be exposed
on field to a granule (in terms of subsequent exposure of a CRLF to a granule) is limited
to a few days a year. While it is considered likely that some small mammals may be
exposed to aldicarb during this window, it is unlikely that a significant number of small
mammals would then subsequently move off-site, and not die before encountering a
CRLF (biological description does not indicate it feeds on carrion).
May Affect and Likely to Adversely Affect
On-site All Crops
On-site exposure for all outdoor registered uses was identified as "may affect" and
"likely to adversely affect" the terrestrial-phase of the CRLF because the acute LOC was
exceeded for the direct amphibian measurement endpoint (birds) and for indirect effects
(i.e., loss of small mammals, and on-site terrestrial invertebrates) for all uses.
Bioaccumulation was demonstrated to not be a pathway of concern. This effects
determination is based on the assumption that terrestrial-phase CRLF will come onto the
treated site and that on-site resources are considered a critical component that supports
CRLF (i.e., invertebrates and insects on the field that the farmer is trying to eliminate are
considered critical to the support of the CRLF) and that the field is considered part of the
critical habitat. A number of the uses are applied on fields that have been prepared for
planting and should be relatively barren of cover for the CRLF at the time of aldicarb
application (i.e., sorghum, sweet potato, dried bean, and soybean).
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
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associated risks to the species and its resources are expected to decrease with increasing
distance away from the treated field or site of application. Evaluation of the implication
of this non-uniform distribution of risk to the species would require information and
assessment techniques that are not currently available. Examples of such information and
methodology required for this type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages
within specific recovery units and/or designated critical habitat within the
action area. This information would allow for quantitative extrapolation
of the present risk assessment's predictions of individual effects to the
proportion of the population extant within geographical areas where those
effects are predicted. Furthermore, such population information would
allow for a more comprehensive evaluation of the significance of potential
resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic-
and terrestrial-phase frogs. While existing information provides a
preliminary picture of the types of food sources utilized by the frog, it
does not establish minimal requirements to sustain healthy individuals at
varying life stages. Such information could be used to establish
biologically relevant thresholds of effects on the prey base, and ultimately
establish geographical limits to those effects. This information could be
used together with the density data discussed above to characterize the
likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the
pesticide. Currently, methodologies are limited to predicting exposures
and likely levels of direct mortality, growth or reproductive impairment
immediately following exposure to the pesticide. The degree to which
repeated exposure events and the inherent demographic characteristics of
the prey population play into the extent to which prey resources may
recover is not predictable. An enhanced understanding of long-term prey
responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and
together with the information described above, a more complete prediction
of effects to individual frogs and potential adverse modification to critical
habitat.
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6.
Uncertainties
6.1 Exposure Assessment Uncertainties
6.1.1 Maximum Use Scenario
The screening-level risk assessment focuses on characterizing potential ecological risks
resulting from a maximum use scenario, which is determined from labeled statements of
maximum application rate and number of applications with the shortest time interval
between applications. The frequency at which actual uses approach this maximum use
scenario may be dependant on insecticide resistance, timing of applications, cultural
practices, and market forces.
6.1.2 Modeling Inputs
The standard ecological water body scenario (EXAMS pond) used to calculate potential
aquatic exposure to pesticides is intended to represent conservative estimates, and to
avoid underestimations of the actual exposure. The standard scenario consists of
application to a 10-hectare field bordering a 1-hectare, 2-meter deep (20,000 m3) pond
with no outlet. Exposure estimates generated using the EXAMS pond are intended to
represent a wide variety of vulnerable water bodies that occur at the top of watersheds
including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural
ponds, and intermittent and lower order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the EXAMS pond. Static water bodies
that have larger ratios of pesticide-treated drainage area to water body volume would be
expected to have higher peak EECs than the EXAMS pond. These water bodies will be
either smaller in size or have larger drainage areas. Smaller water bodies have limited
storage capacity and thus may overflow and carry pesticide in the discharge, whereas the
EXAMS pond has no discharge. As watershed size increases beyond 10-hectares, it
becomes increasingly unlikely that the entire watershed is planted with a single crop that
is all treated simultaneously with the pesticide. Headwater streams can also have peak
concentrations higher than the EXAMS pond, but they likely persist for only short
periods of time and are then carried and dissipated downstream.
The Agency acknowledges that there are some unique aquatic habitats that are not
accurately captured by this modeling scenario and modeling results may, therefore,
under- or over-estimate exposure, depending on a number of variables. For example,
aquatic-phase CRLFs may inhabit water bodies of different size and depth and/or are
located adjacent to larger or smaller drainage areas than the EXAMS pond. The Agency
does not currently have sufficient information regarding the hydrology of these aquatic
habitats to develop a specific alternate scenario for the CRLF. CRLFs prefer habitat with
perennial (present year-round) or near-perennial water and do not frequently inhabit
vernal (temporary) pools because conditions in these habitats are generally not suitable
(Hayes and Jennings 1988). Therefore, the EXAMS pond is assumed to be representative
of exposure to aquatic-phase CRLFs. In addition, the Services agree that the existing
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EXAMS pond represents the best currently available approach for estimating aquatic
exposure to pesticides (USFWS/NMFS 2004).
6.1.2.1 Action Area
An example of an important simplifying assumption that may require future refinement is
the assumption of uniform runoff characteristics throughout a landscape. It is well
documented that runoff characteristics are highly non-uniform and anisotropic, and
become increasingly so as the area under consideration becomes larger. The assumption
made for estimating the aquatic Action Area (based on predicted in-stream dilution) was
that the entire landscape exhibited runoff properties identical to those commonly found in
agricultural lands in this region. However, considering the vastly different runoff
characteristics of: a) undeveloped (especially forested) areas, which exhibit the least
amount of surface runoff but the greatest amount of groundwater recharge; b)
suburban/residential areas, which are dominated by the relationship between
impermeable surfaces (roads, lots) and grassed/other areas (lawns) plus local drainage
management; c) urban areas, that are dominated by managed storm drainage and
impermeable surfaces; and d) agricultural areas dominated by Hortonian and focused
runoff (especially with row crops), a refined assessment should incorporate these
differences for modeled stream flow generation. As the zone around the immediate
(application) target area expands, there will be greater variability in the landscape; in the
context of a risk assessment, the runoff potential that is assumed for the expanding area
will be a crucial variable (since dilution at the outflow point is determined by the size of
the expanding area). Thus, it important to know at least some approximate estimate of
types of land use within that region. Runoff from forested areas ranges from 45 -
2,700% less than from agricultural areas; in most studies, runoff was 2.5 to 7 times higher
in agricultural areas (e.g., Okisaka et al., 1997; Karvonen et al., 1999; McDonald et al.,
2002; Phuong and van Dam 2002). Differences in runoff potential between
urban/sub urban areas and agricultural areas are generally less than between agricultural
and forested areas. In terms of likely runoff potential (other variables - such as
topography and rainfall - being equal), the relationship is generally as follows (going
from lowest to highest runoff potential):
Three-tiered forest < agroforestry < suburban < row-crop agriculture < urban.
There are, however, other uncertainties that should serve to counteract the effects of the
aforementioned issue. For example, the dilution model considers that 100% of the
agricultural area has the chemical applied, which is almost certainly a gross over-
estimation. Thus, there will be assumed chemical contributions from agricultural areas
that will actually be contributing only runoff water (dilutant); so some contributions to
total contaminant load will really serve to lessen rather than increase aquatic
concentrations. In light of these (and other) confounding factors, Agency believes that
this model gives us the best available estimates under current circumstances.
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6.2.1.2 Aquatic Exposure Estimates
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations
that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone
Model is a process or "simulation" model that calculates what happens to a pesticide in a
farmer's field on a day-to-day basis. It considers factors such as rainfall and plant
transpiration of water, as well as how and when the pesticide is applied. It has two major
components: hydrology and chemical transport. Water movement is simulated by the use
of generalized soil parameters, including field capacity, wilting point, and saturation
water content. The chemical transport component can simulate pesticide application on
the soil or on the plant foliage. Dissolved, adsorbed, and vapor-phase concentrations in
the soil are estimated by simultaneously considering the processes of pesticide uptake by
plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection,
dispersion, and retardation.
Uncertainties associated with each of these individual components add to the overall
uncertainty of the modeled concentrations. Additionally, model inputs from the
environmental fate degradation studies are chosen to represent the upper confidence
bound on the mean values that are not expected to be exceeded in the environment
approximately 90 percent of the time. Mobility input values are chosen to be
representative of conditions in the environment. The natural variation in soils adds to the
uncertainty of modeled values. Factors such as application date, crop emergence date,
and canopy cover can also affect estimated concentrations, adding to the uncertainty of
modeled values. Factors within the ambient environment such as soil temperatures,
sunlight intensity, antecedent soil moisture, and surface water temperatures can cause
actual aquatic concentrations to differ for the modeled values.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a
vegetative setback on runoff and loadings. The effectiveness of vegetative setbacks is
highly dependent on the condition of the vegetative strip. For example, a well-
established, healthy vegetative setback can be a very effective means of reducing runoff
and erosion from agricultural fields. Alternatively, a setback of poor vegetative quality
or a setback that is channelized can be ineffective at reducing loadings. Until such time
as a quantitative method to estimate the effect of vegetative setbacks on various
conditions on pesticide loadings becomes available, the aquatic exposure predictions are
likely to overestimate exposure where healthy vegetative setbacks exist and
underestimate exposure where poorly developed, channelized, or bare setbacks exist.
6.1.2.3 PRZM Modeling Inputs and Predicted Aquatic Concentrations
The inputs selected for use in the PRZM model were based upon the best available
information regarding persistence, mobility, and formation and dissipation of major
degradates. Nevertheless, there is intrinsic uncertainty related to the quality of data that
were used to determine these parameters. In addition, there are issues involved in
selecting appropriate incorporation efficiencies. Agency assumes (as stated in the 2006
RED) that the incorporation efficiency for granular aldicarb leaves 15% on the surface,
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except for certain highly efficient application methods - specifically: 1) in-furrow
applications, and; 2) banded applications that include simultaneous soil incorporation
(and that also make use of state-of-the-art applicator tools, such as positive displacement)
- for which an incorporation efficiency leaving only 1% available at the surface is
assigned. Both sets of model results are presented in this document (Tables 11 & 12).
The Agency believes that these data and input values are the best available and were
adequate for the purposes of this (and other) aldicarb assessments.
6.3 Effects Assessment Uncertainties
6.3.1 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 pesticidal active
ingredients, such as aldicarb, that act directly (without metabolic transformation) because
younger age classes may not have the enzymatic systems associated with detoxifying
xenobiotics. Insofar 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.
6.3.2 Use of Acute Freshwater Invertebrate Toxicity Data for the Midge
The initial acute risk estimate for freshwater invertebrates was based on the lowest
toxicity value from Chironomus tetans studies, which showed a greater sensitivity than
other species that are equally or more likely to be part of the diet of an adult CRLF.
Therefore, acute RQs based on the most sensitive toxicity endpoint for freshwater
invertebrates may represent an overestimation of potential direct risks to freshwater
invertebrates and indirect effects to the California Red Legged Frog via a reduction in
available food.
6.3.3 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 aldicarb. 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
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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.
6.3.4 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.
6.3.5 Dietary Intake
It was assumed that ingestion of food items in the field occurs at rates commensurate
with those in the laboratory. Although the screening assessment process adjusts dry-
weight estimates of food intake to reflect the increased mass in fresh-weight wildlife food
intake estimates, it does not allow for gross energy differences. Direct comparison of a
laboratory dietary concentration- based effects threshold to a fresh-weight pesticide
residue estimate would result in an underestimation of field exposure by food
consumption by a factor of 1.25 - 2.5 for most food items.
Differences in assimilative efficiency between laboratory and wild diets suggest that
current screening assessment methods do not account for a potentially important aspect of
food requirements. Depending upon species and dietary matrix, bird assimilation of wild
diet energy ranges from 23 - 80%, and mammal's assimilation ranges from 41 - 85%
(U.S. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is
formulated to maximize assimilative efficiency (e.g., a value of 85%), a potential for
underestimation of exposure may exist by assuming that consumption of food in the wild
is comparable with consumption during laboratory testing. In the screening process,
exposure may be underestimated because metabolic rates are not related to food
consumption.
6.3.6 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
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plausible relationship between the measure of effect (sublethal endpoint) and the
assessment endpoints.
6.3.7 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.
6.4 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.
Sufficient dose-response information was not available to estimate the probability of an
individual effect on freshwater fish or freshwater invertebrates (two of the dietary food
items of the CRLF). Acute ecotoxicity data from the bluegill sunfish and midge were
used to derive RQs for freshwater fish and invertebrates. Based on a lack of dose-
response information for both species, the probability of an individual effect was
calculated using the lowest and highest probit dose response curve slope value (2 and 9,
respectively) to bound probability of individual effect to prey for technical grade
aldicarb. It is unclear whether the probability of an individual effect for freshwater
animals would be higher or lower, and therefore, the lowest slope value was chosen when
effects determinations were made for direct effects to the prey of the CRLF.
6.5 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
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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.
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