Risks of Dicofol Use to Federally Threatened
California Red-legged Frog
(Rana aurora draytonii)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
June 15, 2009
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Primary Authors:
Kristina Garber, Biologist
Charles Peck, Environmental Scientist
Secondary Reviewers:
Thomas Steeger, Senior Biologist
R. David Jones, Senior Agronomist
Branch Chief, Environmental Risk Assessment Branch 4:
Elizabeth Behl
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Table of Contents
1.0 Executive Summary 10
2.0 Problem Formulation 18
2.1. Purpose 18
2.2. Scope 20
2.3. Previous Assessments 21
2.4. Stressor Source and Distribution 22
2.4.1. Environmental Fate Assessment 22
2.4.2. Environmental Transport Assessment 26
2.4.3. Mechanism of Action 28
2.4.4. Use Characterization 28
2.5. Assessed Species 32
2.5.1. Distribution 33
2.5.2. Reproduction 35
2.5.3. Diet 35
2.5.4. Habitat 36
2.6. Designated Critical Habitat 37
2.7. Action Area 39
2.8. Assessment Endpoints and Measures of Ecological Effect 42
2.8.1. Assessment Endpoints for the CRLF 42
2.8.2. Assessment Endpoints for Designated Critical Habitat 45
2.9. Conceptual Model 47
2.9.1. Risk Hypotheses 47
2.9.2. Diagram 48
2.10. Analysis Plan 49
2.10.1. Measures of Exposure 50
2.10.2. Measures of Effect 52
2.10.3. Integration of Exposure and Effects 53
2.10.4. Data Gaps 53
3.0 Exposure Assessment 54
3.1. Label Application Rates and Intervals 54
3.2. Aquatic Exposure Assessment 56
3.2.1. Modeling Approach 56
3.2.2. PRZM Scenarios 58
3.2.3. Model Inputs 61
3.2.4. Model Results 63
3.2.5. Available Monitoring Data 65
3.3. Aquatic Bioaccumulation Assessment 66
3.3.1. Estimated BCF values 67
3.3.2. Empirical BCF data 67
3.3.3. Bioaccumulation modeling 68
3.4. Terrestrial Animal Exposure Assessment 70
3.4.1. Modeling Approach 70
3.4.1. Field Studies 73
3.5. Accumulation of Dicofol Residues on Soil 74
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3.6. Terrestrial Bioaccumulation Assessment 76
4.0 Effects Assessment 77
4.1. Toxicity of dicofol to aquatic organisms 78
4.1.1. Toxicity of Dicofol to Freshwater Fish 79
4.1.2. Toxicity of Dicofol to Freshwater Invertebrates 81
4.1.3. Toxicity of Dicofol to Aquatic Plants 81
4.2. Toxicity of Dicofol's Degradates to Aquatic Organisms 81
4.2.1. Toxicity of Dicofol's Degradates to Aquatic Animals 81
4.2.2. Toxicity of Dicofol's Degradates to Aquatic Plants 82
4.3. Toxicity of dicofol to terrestrial organisms 83
4.3.1. Toxicity of Dicofol to Birds 84
4.3.2. Toxicity of Dicofol to Mammals 87
4.3.3. Toxicity of Dicofol to Terrestrial Invertebrates 87
4.3.4. Toxicity of Dicofol to Terrestrial Plants 87
4.4. Toxicity of dicofol degradates to terrestrial organisms 88
4.5. Incident Database Review for Dicofol 88
5.0 Risk Characterization 89
5.1. Risk Estimation 89
5.1.1. Exposures in the Aquatic Habitat 90
5.1.2. Exposures in the Terrestrial Habitat 96
5.1.3. Primary Constituent Elements of Designated Critical Habitat 98
5.2. Risk Description 100
5.2.1. Direct Effects 105
5.2.2. Indirect Effects (through effects to prey) 113
5.2.3. Indirect Effects (through effects to habitat) 121
5.2.4. Primary Constituent Elements of Designated Critical Habitat 122
5.2.5. Area of Effects 122
5.2.6. Description of Assumptions, Limitations and Uncertainties 126
5.2.7. Addressing the Risk Hypotheses 138
6.0 Risk Conclusions 139
7.0 References 144
Appendices
Appendix A. Structures of dicofol and its major degradates
Appendix B. Intersection of Dicofol Use Area and California Red-legged frog Habitat
Appendix C. The Risk Quotient Method and Levels of Concern
Appendix D. Treated area estimate for outside building usage
Appendix E. Example PRZM/EXAMS Input Files and Output File Data
Appendix F. DDT Characterization
Appendix G. Outputs from KABAM v. 1.0
Appendix H. Example output from T-REX v. 1.4.1
Appendix I. List of citations accepted and rejected by ECOTOX criteria
Appendix J. Detailed spreadsheet of available ECOTOX open literature for dicofol
Appendix K. Summary of human health effects data for dicofol
Appendix L. Sensitivity distributions for acute exposures offish and birds to dicofol
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Appendix M. Example output from analysis of likelihood of individual mortality
Appendix N. Example output from T-HERPS v. 1.0
Appendix O. Use of fugacity approach to estimate exposures to small mammals
consuming earthworms contaminated with dicofol from soil of treatment sites
Appendix P. Ultra Low Volume Spray Drift Approach
Attachments
Attachment 1: Status and Life History of California Red-legged Frog
Attachment 2: Baseline Status and Cumulative Effects for the California Red-legged Frog
List of Tables
Table 1. Description of evidence supporting effects determination for dicofol use in
California. Assessment endpoints include survival, growth and reproduction
of CRLF individuals 14
Table 2. Summary of effects determination for CRLF critical habitat based on uses of
dicofol in California 16
Table 3. Summary of dicofol environmental fate properties 25
Table 4. Summary of dicofol degradates observed in submitted environmental fate studies
for dicofol. Data represent % of total residue detected as specific degradate
and study day residues were measured 26
Table 5. Methods and rates of application of currently registered uses of dicofol in
California1 28
Table 6. Summary of California Department of Pesticide Registration (CDPR) Pesticide
Use Reporting (PUR) data and calculated annual application rates (1999 -
2006) for currently registered dicofol uses.1 32
Table 7. Assessment endpoints and measures of ecological effects for dicofol 44
Table 8. Summary of dicofol assessment endpoints and measures of ecological effect for
primary constituent elements of designated critical habitat1 46
Table 9. Dicofol uses and application information for the CRLF risk assessment1 55
Table 10. Summary of PRZM/EXAMS environmental fate data used for aquatic exposure
inputs for o,p '-dicofol. l 61
Table 11. Summary of PRZM/EXAMS environmental fate data used for aquatic exposure
inputs for/>,//-dicofol. * 62
Table 12. Aquatic EECs (ug/L) for Dicofol Uses in California, Total o,p" andp,p'
Isomers 63
Table 13. Aquatic EECs (ug/L) for Dicofol, Parent and Degradate Uses in California... 64
Table 14. Characteristics of model aquatic organisms used to derive BCF values 67
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Table 15. Estimated BCF values for parent dicofol in aquatic organisms 67
Table 16. Concentrations of dicofol parent in tissues of aquatic organisms (estimated
using KABAM) 68
Table 17. Estimated Log Kow values of dicofol's residues of concern 69
Table 18. Concentrations of dicofol total residues of concern in tissues of aquatic
organisms (|ig/kg-ww; estimated using KABAM). Concentrations were
estimated using Log Kow values representative of the different dicofol
residues of concern 69
Table 19. Input parameters to T-REX used to generate dicofol EECs for terrestrial
animals 70
Table 20. Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Single Applications of dicofol for
Current Uses in California 72
Table 21. Dicofol EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via
Effects to Terrestrial Invertebrate Prey Items 73
Table 22. Freshwater toxicity profile for dicofol 79
Table 23. Categories of acute toxicity for aquatic organisms 79
Table 24. Acute toxicity data (96-h LC50) for freshwater fish exposed to dicofol 80
Table 25. Chronic toxicity data for freshwater fish exposed to dicofol 80
Table 26. Estimated acute and chronic toxicity values (|ig/L) for fish and daphnids
exposed to dicofol and its degradates (as calculated by ECOSAR) 82
Table 27. Terrestrial toxicity profile for dicofol 83
Table 28. Categories of acute toxicity for avian and mammalian studies 84
Table 29. Sub acute dietary toxicity data (LC50) for birds exposed to dicofol 84
Table 30. Chronic toxicity data for birds exposed to dicofol 85
Table 31. Acute and chronic RQs for aquatic-phase CRLF resulting from AERIAL
applications of dicofol. EECs are based on parent and degradates of concern.
90
Table 32. Acute and chronic RQs for aquatic-phase CRLF resulting from GROUND
applications of dicofol. EECs are based on parent and degradates of concern.
91
Table 33. Acute and chronic RQs for aquatic-phase CRLF resulting from ULV
applications of dicofol. EECs are based on parent and degradates of concern.
91
Table 34. Diet assumptions of small, medium and large aquatic-phase CRLF used in
KABAM 92
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Table 35. Acute and chronic RQs for aquatic-phase CRLF exposed to dicofol (parent)
through consumption of aquatic organisms which have accumulated dicofol.
92
Table 36. Acute and chronic RQs for aquatic invertebrates resulting from AERIAL
applications of dicofol. EECs are based on parent and degradates of concern.
93
Table 37. Acute and chronic RQs for aquatic invertebrates resulting from GROUND
applications of dicofol. EECs are based on parent and degradates of concern.
94
Table 38. Acute and chronic RQs for aquatic invertebrates resulting from ULV
applications of dicofol. EECs are based on parent and degradates of concern.
94
Table 39. Acute and chronic, dietary-based RQs and dose-based RQs for direct effects of
dicofol to the terrestrial-phase CRLF. RQs calculated using T-REX 96
Table 40. RQs for determining indirect effects to the terrestrial-phase CRLF through
effects to potential prey items, specifically small terrestrial mammals
consuming short grass 98
Table 41. Risk estimation summary for dicofol - direct and indirect effects to the CRLF.
101
Table 42. Risk estimation summary for dicofol - PCEs of designated critical habitat for
the CRLF 102
Table 43. Acute RQs and for aquatic-phase CRLF resulting from applications of dicofol.
EECs are based on parent and degradates of concern 106
Table 44. Acute and chronic RQs for aquatic-phase CRLF resulting from AERIAL
applications of dicofol. EECs are based on parent dicofol only 107
Table 45. Acute and chronic RQs for aquatic-phase CRLF resulting from GROUND
applications of dicofol. EECs are based on dicofol only 107
Table 46. Acute and chronic RQs for aquatic-phase CRLF resulting from ULV
applications of dicofol. EECs are based on parent dicofol only 108
Table 47. Refined dose-based RQs7 for 1.4 g CRLF consuming different food items.
EECs calculated using T-HERPS 109
Table 48. Revised dose-based RQs7 for 37 g CRLF consuming different food items.
EECs calculated using T-HERPS 110
Table 49. Revised dose-based RQs7 for 238 g CRLF consuming different food items.
EECs calculated using T-HERPS Ill
Table 50. Revised acute dietary-based RQs7 for CRLF consuming different food items.
EECs calculated using T-HERPS 112
Table 51. Revised chronic dietary-based RQs7 for CRLF consuming different food items.
EECs calculated using T-HERPS 113
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Table 52. Acute RQs and associated likelihood of individual effects for aquatic
invertebrates resulting from applications of dicofol. EECs are based on parent
and degradates of concern 114
Table 53. Acute and chronic RQs for aquatic invertebrates resulting from AERIAL
applications of dicofol. EECs are based on dicofol only 115
Table 54. Acute and chronic RQs for aquatic invertebrates resulting from GROUND
applications of dicofol. EECs are based on dicofol only 115
Table 55. Acute and chronic RQs for aquatic invertebrates resulting from ULV
applications of dicofol. EECs are based on dicofol only 116
Table 56. Acute RQs and likelihood of individual mortality for fish and aquatic-phase
amphibians resulting from applications of dicofol. EECs are based on parent
and degradates of concern 117
Table 57. RQs7 and associated likelihood of individual effects to terrestrial invertebrates
due to dicofol exposures 118
Table 58. Acute dose-based RQs and associated likelihood of individual effects to small
terrestrial mammals (consuming short grass) due to dicofol exposures 119
Table 59. Acute dose-based RQs7 for terrestrial-phase frogs (prey) exposed to dicofol. 120
Table 60. Acute dietary-based RQs for terrestrial-phase frogs (prey) consuming small
insects and likelihood of individual effects chance resulting from dicofol
exposures. RQs calculated using T-HERPS 121
Table 61. Summary of CDPR pesticide use reporting by county for dicofol (annual
pounds of dicofol applied from 1999 to 2006) 124
Table 62. Single application rate not exceeding acute LOG for dietary- and dose-based
exposures of the CRLF to dicofol 126
Table 63. Physicochemical and environmental fate properties used as input for estimating
overall persistence and long-range transport potential using the OECD Tool.
132
Table 64. Overall persistence and characteristic travel distances generated using the
OECD Tool 132
Table 65. Description of evidence supporting effects determination for dicofol use in
California. Assessment endpoint is survival, growth and reproduction of
CRLF individuals 140
Table 66. Summary of effects determination for CRLF critical habitat based on uses of
dicofol in California 142
List of Figures
Figure 1. Chemical Structures for o,p'- andp,p'-dicofol 11
Figure 2. Estimated national agricultural use of dicofol for 2002 30
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Figure 3. Recovery unit, core area, critical habitat, and occurrence designations for
CRLF 34
Figure 4. CRLF reproductive events by month 35
Figure 5. Initial area of concern for crops described by agricultural landcover which
corresponds to potential dicofol use sites. This map represents the area
potentially directly affected by the federal action 41
Figure 6. Conceptual model for dicofol effects on aquatic-phase of the CRLF 48
Figure 7. Conceptual model for dicofol effects on terrestrial phase of the CRLF 49
Figure 8. Summary of applications of dicofol to cotton in 2004 from CDPR PUR data. 58
Figure 9. Concentration of total residues of dicofol in soil treated with dicofol for 30
years. X axis represents time in days. Soil modeled in PRZM using CA
strawberries and CA fruit scenarios 75
Figure 10. Concentration of total residues of dicofol in pore water of soil treated with
dicofol for 30 years. X axis represents time in days. Soil modeled in PRZM
using CA strawberries and CA fruit scenarios 75
Figure 11. Intersection between dicofol use areas and CRLF habitat 123
Figure 12. Genus sensitivity distribution for acute (96-h) exposures offish to dicofol. 135
Figure 13. Species sensitivity distribution for subacute exposures of birds to dicofol... 136
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1.0 Executive Summary
The purpose of this assessment is to evaluate potential direct and indirect effects on the
California red-legged frog (Rana aurora draytonii) (CRLF) arising from Federal
Insecticide, Fungicide, Rodenticide Act (FIFRA) regulatory actions regarding use of
dicofol on agricultural and non-agricultural sites. In addition, this assessment evaluates
whether these actions can be expected to result in effects to the species' designated
critical habitat. This assessment was completed in accordance with the U.S. Fish and
Wildlife Service (U.S. FWS) and National Marine Fisheries Service (NMFS) Endangered
Species Consultation Handbook (U.S. FWS/NMFS 1998) and procedures outlined in the
Agency's Overview Document (U.S. EPA 2004).
The CRLF was listed as a threatened species by U.S. FWS in 1996. The species is
endemic to California and Baja California (Mexico) and inhabits both coastal and interior
mountain ranges. A total of 243 streams or drainages are believed to be currently
occupied by the species, with the greatest numbers in Monterey, San Luis Obispo, and
Santa Barbara counties (U.S. FWS 1996) in California.
Dicofol is a broad-spectrum acaricide, insecticide, and miticide, initially registered as a
pesticide in 1957. The current technical formula containing dicofol was reregistered in
1998. The following uses of dicofol are considered as part of the federal action evaluated
in this assessment: beans (dry, snap, and lima), citrus (specifically, grapefruit, kumquats,
lemons, limes, oranges, tangelos, and tangerines), cotton, cucurbits (specifically,
cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer
squash), grapes, hops, mint, pecans, peppers, pome fruits (specifically, apples,
crabapples, pears, and quince), stone fruits (specifically, apricots, sweet and sour
cherries, nectarines, peaches, plums, and prunes), strawberries, tomatoes, walnuts,
bermudagrass, turf/ornamental uses (specifically, turf grasses, nursery stock, flowers,
shade trees, woody shrubs and vines, and sod farms) and outside building surfaces
(nonagri cultural).
Dicofol is composed of two isomers, p,p'-dicofo\ and o,p'-dicofo\ (see Figure 1), that
occur at a ratio of 4.5: 1 in formulated end-use products. Based on the available
environmental fate data for dicofol, this chemical and its degradates are expected to
persist with a half-life of up to 313 days, depending upon the specific environmental
conditions. Major routes of dissipation are hydrolysis under neutral and alkaline
conditions and aerobic and anaerobic soil metabolism, with the o,//-isomer degrading
more quickly. Dicofol is classified as slightly mobile (Kashuba, et al. 2006). Leaching
and photodegradation are not expected to be significant routes of dissipation of dicofol in
the environment. Because of its low vapor pressure (3.9 x 10"7 torr) and Henry's Law
Constant (1.4 x 10"7 atm-m3/mol), low levels of volatilization are possible, but not
expected.
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OH
f=\ _. $~^
C
CCI, CC1,
Figure 1. Chemical Structures for o,p'- and77,77'-dicofol.
Major degradates of dicofol are the o,p'- andp,p' isomers of dichlorobenzophenone
(DCBP); 1, l-(p-chlorophenyl-) 2,2-dichloroethanol (FW-152); dichlorobenzhydrol
(DCBH); hydroxyl-dichlorobenzophenone (OH-DCBP); and chlorobenzoic acid (CBA).
DCBP was identified in the hydrolysis, photolysis and metabolism studies while the other
degradates were only present in metabolism studies. There are currently no submitted
studies addressing the environmental fate and transport of these major degradates.
However, the studies submitted in support of the aerobic soil metabolism indicate a large
difference between half lives for dicofol alone (8.5 and 32 days for o,p'- and/^'-dicofol,
respectively) and the half lives for dicofol plus its degradates (186 and 313 days for total
o,p}- andp,p'-dicofol, respectively).
In order to estimate aquatic exposure concentrations of dicofol and its degradates of
concern, separate modeling runs were conducted for the o,p'- and p,p'-dicofo\ parent and
o,p}- and/\p'-dicofol and degradates. The EECs were then summed to derive an estimate
for total parent and the total toxic residue. In this risk assessment, degradates of concern
included: DCBP, FW-152, DCBH and OH-DCBP. It is assumed in this assessment that
for aquatic animals, the degradates of concern are of equal toxicity compared to the
parent. Additionally, due to reported DDT contamination (<0.1%) in dicofol products and
the established toxicity and ecological risks of DDT, screening-level charaterization of
DDT was also considered in this assessment (see Appendix F).
Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF, its prey
and its habitats to dicofol are assessed separately for the two habitats. Tier-II aquatic
exposure models (PRZM/EXAMS) are used to estimate high-end exposures of dicofol in
aquatic habitats resulting from runoff and spray drift from different uses. Peak model-
estimated environmental concentrations resulting from different dicofol uses range from
0.15 to 18.0 |ig/L for the total parent (o,p}- and/?,/?'-dicofol, respectively) and 0.38 to 59.6
|ig/L for the total residues of concern (dicofol and degradates). These estimates are
supplemented with analysis of available California surface water monitoring data from
the California Department of Pesticide Regulation. The maximum surface water
concentration of dicofol reported in the California Department of Pesticide Regulation
surface water database (0.27 |ig/L) is roughly 190 times lower than the highest peak
model-estimated environmental concentration.
Based on available bioaccumulation data, dicofol and its degradates have the potential to
accumulate in aquatic organisms. KABAM (K0w (based) Aquatic BioAccumulation
Model) v.1.0 is used to estimate potential bioaccumulation of dicofol residues in a
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freshwater aquatic food web and subsequent risks these residues pose to aquatic-phase
CRLF via consumption of contaminated aquatic prey (i.e., aquatic invertebrates and fish).
In order to characterize the long range transport potential (LRTP) of dicofol, the OECD
POV and LRTP Screening Tool was used. Three chemicals known to move via long range
transport, DDT, aldrin and endrin, were also modeled to provide a context for dicofol
estimated LRTP. Modeling results indicate that dicofol has comparable or higher LRTP
estimates than all three chemicals with known potential to move via long range transport.
The T-REX model is used to estimate dicofol exposures to terrestrial-phase CRLF, its
potential prey, and its designated critical habitat resulting from uses involving foliar
applications. T-HERPS is used to further characterize exposures of terrestrial-phase
CRLF to dietary and dose-based exposures of dicofol resulting from foliar applications.
AgDRIFT is also used to estimate deposition of dicofol on terrestrial and aquatic habitats
from spray drift.
The effects determination assessment endpoints for the CRLF include direct toxic effects
on the survival, reproduction, and growth of the CRLF itself, as well as indirect effects,
such as reduction of the prey base or effects to its habitat. Direct effects to the CRLF in
the aquatic habitat are based on toxicity information for freshwater fish, which are
generally used as a surrogate for aquatic-phase amphibians. In the terrestrial habitat,
direct effects are based on toxicity information for birds, which are used as a surrogate
for terrestrial-phase amphibians. Given that the CRLF's prey items and designated
critical habitat requirements in the aquatic habitat are dependant on the availability of
freshwater aquatic invertebrates, toxicity information for these taxonomic groups is also
discussed. In the terrestrial habitat, indirect effects due to depletion of prey are assessed
by considering effects to terrestrial insects, small terrestrial mammals, and frogs.
Dicofol is very highly toxic to freshwater fish and highly toxic to freshwater invertebrates
on an acute exposure basis. The no observed adverse effect concentration (NOAEC) for
chronic effects to the rainbow trout is 4.4 |ig/L, with a lowest observed adverse affect
concentration (LOAEC) of 7.9 |ig/L based on reduction in growth. Available chronic
toxicity data for aquatic invertebrates include a NOAEC of 19 |ig/L, with a LOAEC of 33
|ig/L based on reduction in growth. Dicofol is moderately toxic to birds on an acute oral
and subacute dietary exposure basis, and slightly toxic to mammals on an acute oral
exposure basis. Dicofol is classified as practically nontoxic to honey bees on an acute
contact exposure basis. Chronic exposures of the American kestrel to dicofol indicate
effects to number of eggs laid at concentrations greater than 40 ppm, with a LOAEC of 3
ppm based on decreased egg shell thickness. Chronic exposures of rats to dicofol
indicate a NOAEC of 5 ppm, corresponding to a LOAEC of 25 ppm where reproductive
effects were observed. The ECso for algae exposed to dicofol is greater than 5,000 but
less than 10,000 |ig/L. No data are available for quantitatively defining an endpoint to
represent the effects of dicofol exposures to vascular plants.
Risk quotients (RQs) are derived as quantitative estimates of potential high-end risk.
Acute and chronic RQs are compared to the Agency's Levels of Concern (LOCs) for
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Federally-listed threatened (listed) species to identify if dicofol use within the action area
has any direct or indirect effect on the CRLF and its designated critical habitat. For this
assessment, RQs were based on EECs representing total residues of concern (dicofol,
DCBP, FW-152, DCBH and OH-DCBP). Based on estimated environmental
concentrations in the aquatic and terrestrial habitats resulting from all currently registered
uses of dicofol, RQ values exceed the Agency's LOG for direct acute and chronic risk to
the CRLF; this represents a "may affect" determination. RQs exceed the LOG for risks to
aquatic invertebrates, fish, aquatic-phase amphibians, terrestrial-phase amphibians and
mammals. RQ values for terrestrial invertebrates potentially exceed the LOG for this
taxon. RQ values for non-vascular aquatic plants do not exceed the LOG. The effects
determination for indirect effects to the CRLF due to effects on its prey base is "may
affect." Due to a lack of effects data for vascular plants exposed to dicofol, potential risk
of dicofol to the designated critical habitat of the CRLF cannot be quantified and
potential indirect effects to the CRLF through effects to its habitat cannot be discounted.
Therefore, the determination for indirect effects to the CRLF through effects to its habitat
is "may affect." In addition, dicofol can potentially result in effects to the CRLF's
aquatic and terrestrial habitats based on potential impacts to its principal constituent
elements (PCEs).
Refinement of all "may affect" determinations results in: a "LAA" determination based
on direct effects to the aquatic and terrestrial-phase CRLF, indirect effects to the CRLF
based on effects to its prey and indirect effects to the CRLF based on effects to its habitat
(Table 1). Consideration of CRLF critical habitat indicates a determination of "habitat
modification" for aquatic and terrestrial designated critical habitats (Table 2).
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Table 1. Description of evidence supporting effects determination for dicofol use in California. Assessment endpoints include survival, growth and
reproduction of CRLF individuals.
Assessment
Endpoint
Effects
Determination
Basis for Determination
Direct effects to
CRLF
Indirect effects to
tadpole CRLF
via reduction of
prey (i.e., algae)
Indirect effects to
juvenile CRLF
via reduction of
prey (i.e.,
invertebrates)
Indirect effects to
adult CRLF via
reduction of prey
(i.e.,
invertebrates,
fish, frogs, mice)
LAA
-Acute RQs for aquatic-phase CRLF exceed the LOG for all uses of dicofol, except Bermuda grass and outside buildings.
- Analysis of individual effects indicates that up to 1 in 2 individual CRLF could experience mortality after acute exposures to
dicofol in the aquatic habitat.
- Chronic RQs for aquatic-phase CRLF exceed the LOG for all uses of dicofol, except Bermuda grass, turf and outside buildings.
- Chronic EECs in the aquatic environment are above levels where growth effects were observed in fish.
- Acute and chronic RQs for aquatic-phase CRLF consuming aquatic organisms contaminated with dicofol (resulting from
accumulation) exceed LOCs.
- Refined acute, dose-based RQs (derived using T-HERPS) for medium sized CRLF consuming small herbivore mammals exceed
LOCs for all uses of dicofol.
- Refined acute, dietary-based RQs (derived using T-HERPS) for CRLF consuming small insects and small herbivore mammals
exceed LOCs for several uses of dicofol.
- Chronic dietary-based RQs for CRLF exceed LOCs for all uses of dicofol, for CRLF consuming any terrestrial food item (i.e.,
insects, mammals and terrestrial-phase amphibians).
- Chronic, dietary-based EECs are above levels where reduced number of eggs laid was observed in birds (i.e., EECs are >40
ppm).
RQ values for algae are below the LOG for all uses of dicofol.
- Acute RQs for aquatic invertebrates exceed the LOG the majority of dicofol uses.
- The likelihood of individual acute effects to aquatic invertebrates is <3%. Based on this, indirect effects to the CRLF through
acute effects to aquatic invertebrates is discountable.
- Chronic RQs for aquatic invertebrates do not exceed the LOG for dicofol use on cucurbits, peppers, tomatoes, Bermuda grass,
ornamentals, turf and outside buildings.
- Chronic RQs for aquatic invertebrates exceed the LOG for dicofol use on beans, citrus, cotton, grapes, hops, mint, pome fruits,
stone fruits, strawberry, walnuts, and pecans.
- Acute RQs for aquatic invertebrates exceed the LOG the majority of dicofol uses.
- The likelihood of individual acute effects to aquatic invertebrates is <3%. Based on this, indirect effects to the CRLF through
acute effects to aquatic invertebrates is discountable.
- Chronic RQs for aquatic invertebrates do not exceed the LOG for dicofol use on cucurbits, peppers, tomatoes, Bermuda grass,
ornamentals, turf and outside buildings.
- Chronic RQs for aquatic invertebrates exceed the LOG for dicofol use on beans, citrus, cotton, grapes, hops, mint, pome fruits,
stone fruits, strawberry, walnuts and pecans.
-Acute RQs for aquatic-phase amphibians and fish exceed the LOG for all uses of dicofol, except Bermuda grass and outside
buildings.
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Assessment
Eiulpoint
Effects
Determination
Basis for Determination
- Use of dicofol on beans, citrus, cotton, hops, mint, pome fruits, strawberries, walnuts, and pecans results in >10% likelihood of
individual mortality (from acute exposures) to fish and aquatic-phase amphibians.
-Use of dicofol on cucurbits, grapes, pepper, stone fruits, tomatoes, Bermuda grass, ornamentals, turf, and outside buildings result
in <10% chance of effects to an individual fish and aquatic-phase amphibians representing prey of the CRLF.
- Chronic RQs for fish and aquatic-phase amphibians exceed the LOG for all uses of dicofol, except Bermuda grass, turf, and
outside buildings.
- Because the LD50 used in deriving RQs for terrestrial invertebrates is not quantified, RQs for acute exposures of small and large
terrestrial invertebrates to dicofol potentially exceed the LOG of 0.05 for all uses.
- Given that dicofol is intended for control of insects, it has the potential to impact non-target insects (other than honey bees).
-For use of dicofol on grapes, mint, hops, peppers, tomatoes, cucurbits, ornamentals, turf and Bermuda grass, dicofol exposures
result in a chance of individual mortality to <10% of terrestrial insects. Therefore, indirect effects to the CRLF through potential
effects to terrestrial invertebrates resulting from these dicofol uses are considered discountable.
- Use of dicofol on citrus, pome fruits, strawberries, walnuts, pecans, beans, cotton and stone fruits could potentially result in
>10% of mortality to small invertebrates. Although there is uncertainty in the actual effects of these exposures to terrestrial
invertebrates, given that no LD50 was established, mortality to small insects resulting from dicofol applied to these crops has the
potential to result in indirect effects to the CRLF.
- RQ values representing acute exposures to terrestrial mammals exceed the LOG (0.1) for all uses of dicofol except: ornamentals,
turf, outside buildings and Bermuda grass
- Use of dicofol on citrus and pome fruits could potential result in 10.7% mortality to individual terrestrial mammals. Therefore,
dicofol use on citrus and pome fruits could potentially result in indirect effects to the CRLF due to acute effects to terrestrial
mammals. All other uses of dicofol result in <2.0% mortality to small mammals resulting from acute exposures to dicofol.
Therefore, indirect effects to the CRLF through potential effects to terrestrial mammals resulting from all dicofol uses, except
citrus and pome fruits, are considered discountable.
- Chronic RQs exceed the LOG for terrestrial mammals for all uses of dicofol. Chronic EECs are sufficient to exceed the LOAEC
for mammals where reproductive effects were observed. Therefore, chronic exposures of dicofol from all uses have the potential
to indirectly affect the CRLF via impacts to terrestrial mammals serving as potential prey items.
- Acute and chronic exposures of small mammals to dicofol through consumption of contaminated earthworms from fields treated
with dicofol have the potential to result in effects to mammals.
- Acute, dose-based RQs for terrestrial-phase amphibians serving as prey to the CRLF do not exceed the LOG.
- Acute, dietary-based RQs for terrestrial-phase amphibians exceed the LOG for several uses.
- Analysis of the likelihood of individual mortality using acute dietary-based RQs for terrestrial amphibians indicates that all uses
of dicofol result in <2% chance of effects to an individual terrestrial amphibian representing prey of the CRLF. Therefore, the
impact of the indirect effects to terrestrial-phase CRLFs via acute effects on terrestrial amphibians is discountable for all uses of
dicofol.
- Chronic, dietary-based RQs exceed the LOG by factors ranging 2x to 474x. Therefore, for all dicofol uses, there is potential for
indirect effects to the CRLF resulting from chronic effects to terrestrial frogs.
Indirect effects to
CRLF via
-Due to a lack of quantitative effects data for non-target plants exposed to dicofol, potential risk of dicofol to the aquatic and
terrestrial habitats of the CRLF cannot be quantified and effects of dicofol to plants cannot be discounted.
15
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Assessment
Endpoint
reduction of
habitat and/or
primary
productivity
(i.e., plants)
Effects
Determination
Basis for Determination
-Qualitative data suggest that dicofol may result in phytotoxicity.
-There is one reported incident involving effects of dicofol to plants.
-Dicofol exposures to plants have the potential to cause indirect effects to aquatic phase
CLRF through reduction of habitat.
Table 2. Summary of effects determination for CRLF critical habitat based on uses of dicofol in California.
Assessment
Endpoint
Modification of
aquatic-phase
primary constituent
elements
Modification of
terrestrial-phase
primary constituent
elements
Effects
Determination
Habitat Effects
Basis for Determination
Dicofol has the potential to modify habitat based on the aquatic-phase PCEs.
- Dicofol has the potential to directly affect the aquatic -phase CRLF (See Table
1).
- Dicofol has the potential to indirectly affect the aquatic -phase CRLF through
effects to its prey (see Table 1).
-Effects of dicofol to plants making up the aquatic habitat of the CRLF cannot be
discounted.
Dicofol has the potential to modify habitat based on the terrestrial-phase PCEs.
- Dicofol has the potential to directly affect the terrestrial-phase CRLF (See
Table 1).
- Dicofol has the potential to indirectly affect the terrestrial-phase CRLF through
effects to its prey (see Table 1).
-Effects of dicofol to plants making up the terrestrial habitat of the CRLF cannot
be discounted.
16
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Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct, indirect, and adverse
habitat modification effects determinations, it is important to note that pesticide
exposures and predicted risks to the species and its resources (i.e., food and habitat) are
not expected to be uniform across the action area. In fact, given the assumptions of drift
and downstream transport (i.e., attenuation with distance), pesticide exposure and
associated risks to the species and its resources are expected to decrease with increasing
distance away from the treated field or site of application. Evaluation of the implication
of this non-uniform distribution of risk to the species would require information and
assessment techniques that are not currently available. Examples of such information and
methodology required for this type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages
within specific recovery units and/or designated critical habitat within the
action area. This information would allow for quantitative extrapolation
of the present risk assessment's predictions of individual effects to the
proportion of the population extant within geographical areas where those
effects are predicted. Furthermore, such population information would
allow for a more comprehensive evaluation of the significance of potential
resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic-
and terrestrial-phase frogs. While existing information provides a
preliminary picture of the types of food sources utilized by the frog, it
does not establish minimal requirements to sustain healthy individuals at
varying life stages. Such information could be used to establish
biologically relevant thresholds of effects on the prey base, and ultimately
establish geographical limits to those effects. This information could be
used together with the density data discussed above to characterize the
likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the
pesticide. Currently, methodologies are limited to predicting exposures
and likely levels of direct mortality, growth or reproductive impairment
immediately following exposure to the pesticide. The degree to which
repeated exposure events and the inherent demographic characteristics of
the prey population play into the extent to which prey resources may
recover is not predictable. An enhanced understanding of long-term prey
responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and
together with the information described above, a more complete prediction
of effects to individual frogs and potential modification to critical habitat.
17
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2.0 Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By
identifying the important components of the problem, it focuses the assessment on the
most relevant life history stages, habitat components, chemical properties, exposure
routes, and endpoints. The structure of this risk assessment is based on guidance
contained in U.S. Environmental Protection Agency's (EPA's) Guidance for Ecological
Risk Assessment (U.S. EPA 1998a), the Services' Endangered Species Consultation
Handbook (U.S. FWS/NMFS 1998) and is consistent with procedures and methodology
outlined in the Overview Document (U.S. EPA 2004) and reviewed by the U.S. Fish and
Wildlife Service and National Marine Fisheries Service (U.S. FWS/NMFS 2004).
2.1. Purpose
The purpose of this endangered species assessment is to evaluate potential direct and
indirect effects on individuals of the federally threatened California red-legged frog
(Rana aurora draytonii) (CRLF) arising from FIFRA regulatory actions regarding use of
dicofol on the following: beans (dry, snap, and lima), citrus (specifically, grapefruit,
kumquats, lemons, limes, oranges, tangelos, and tangerines), cotton, cucurbits
(specifically, cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and
summer squash), grapes, hops, mint, pecans, peppers, pome fruits (specifically, apples,
crabapples, pears, and quince), stone fruits (specifically, apricots, sweet and sour
cherries, nectarines, peaches, plums, and prunes), strawberries, tomatoes, walnuts,
Bermuda grass, turf/ornamental uses (specifically, turf grasses, nursery stock, flowers,
shade trees, woody shrubs and vines, and sod farms) and outside building surfaces (non-
agricultural). In addition, this assessment evaluates whether use on these sites is
expected to result in effects to the species' designated critical habitat. This ecological
risk assessment has been prepared consistent with a settlement agreement in the case
Center for Biological Diversity (CBD) vs. EPA et al. (Case No. 02-1580-JSW(JL)
entered in Federal District Court for the Northern District of California on October 20,
2006.
In this assessment, direct and indirect effects to the CRLF and potential effects to its
designated critical habitat are evaluated in accordance with the methods described in the
Agency's Overview Document (U.S. EPA 2004). Screening-level methods include use
of standard models such as GENEEC, PRZM-EXAMS, T-REX, TerrPlant, and
AgDRIFT, all of which are described at length in the Overview Document (U.S. EPA
2004). Use of such information is consistent with the methodology described in the
Overview Document (U.S. EPA 2004), which specifies that "the assessment process may,
on a case-by-case basis, incorporate additional methods, models, and lines of evidence
that EPA finds technically appropriate for risk management objectives" (Section V, page
31 of U.S. EPA 2004).
In accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of dicofol is based on an action area. The action area is the area directly or
18
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indirectly affected by the federal action. It is acknowledged that the action area for a
national-level FIFRA regulatory decision associated with a use of dicofol may potentially
involve numerous areas throughout the United States and its Territories. However, for
the purposes of this assessment, attention will be focused on relevant sections of the
action area including those geographic areas associated with locations of the CRLF and
its designated critical habitat within the state of California. As part of the "effects
determination," one of the following three conclusions will be reached regarding the
potential use of dicofol in accordance with current labels:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Designated critical habitat identifies specific areas that have the physical and biological
features, known as primary constituent elements or PCEs, essential to the conservation of
the listed species. The PCEs for CRLFs are aquatic and upland areas where suitable
breeding and non-breeding aquatic habitat is located, interspersed with upland foraging
and dispersal habitat.
If the results of initial screening-level assessment show no direct or indirect effects (no
LOG exceedances) upon individual CRLFs or upon the PCEs of the species' designated
critical habitat, a "no effect" determination is made for use of dicofol as it relates to this
species and its designated critical habitat. If, however, potential direct or indirect effects
to individual CRLFs are anticipated or effects may impact the PCEs of the CRLF's
designated critical habitat, a preliminary "may affect" determination is made for the
FIFRA regulatory action regarding dicofol.
If a determination is made that use of dicofol within the action area(s) associated with the
CRLF "may affect" this species or its designated critical habitat, additional information is
considered to refine the potential for exposure and for effects to the CRLF and other
taxonomic groups upon which these species depend (e.g., aquatic and terrestrial
vertebrates and invertebrates, aquatic plants, riparian vegetation, etc.). Additional
information, including spatial analysis (to determine the geographical proximity of CRLF
habitat and dicofol use sites) and further evaluation of the potential impact of dicofol on
the PCEs is also used to determine whether effects to designated critical habitat may
occur. Based on the refined information, the Agency uses the best available information
to distinguish those actions that "may affect, but are not likely to adversely affect" from
those actions that "may affect and are likely to adversely affect" the CRLF. This
information is presented as part of the Risk Characterization in Section 5 of this
document.
The Agency believes that the analysis of direct and indirect effects to listed species
provides the basis for an analysis of potential effects on the designated critical habitat.
Because dicofol is expected to directly impact living organisms within the action area
(defined in Section 2.7), critical habitat analysis for dicofol is limited in a practical sense
to those PCEs of critical habitat that are biological or that can be reasonably linked to
19
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biologically-mediated processes (i.e., the biological resource requirements for the listed
species associated with the critical habitat or important physical aspects of the habitat that
may be reasonably influenced through biological processes). Activities that may modify
critical habitat are those that alter the PCEs and appreciably diminish the value of the
habitat. Evaluation of actions related to use of dicofol that may alter the PCEs of the
CRLF's critical habitat form the basis of the critical habitat impact analysis. Actions that
may affect the CRLF's designated critical habitat have been identified by the Services
and are discussed further in Section 2.6.
2.2. Scope
Dicofol is an organochlorine, broad-spectrum acaricide, insecticide, and miticide
currently registered nationwide for application to a variety of crops, including: beans
(dry, snap, and lima), citrus (specifically, grapefruit, kumquats, lemons, limes, oranges,
tangelos, and tangerines), cotton, cucurbits (specifically, cantaloupes, cucumbers,
melons, pumpkins, watermelons, and winter and summer squash), grapes, hops, mint,
pecans, peppers, pome fruits (specifically, apples, crabapples, pears, and quince), stone
fruits (specifically, apricots, sweet and sour cherries, nectarines, peaches, plums, and
prunes), strawberries, tomatoes, walnuts, Bermuda grass, turf/ornamental uses
(specifically, turf grasses, nursery stock, flowers, shade trees, woody shrubs and vines,
and sod farms) and outside building surfaces (non-agricultural). Application rates range
from 0.4 - 3 Ibs a.i./A with no more than one application per year for food crops. Dicofol
may be applied as an aerial or ground spray. The current technical formula containing
dicofol was reregistered in 1998. The terms of reregi strati on included cancellation of
residential uses, with remaining uses limited to one annual application, and application
rate reductions. The current labels for products containing dicofol comport with the
changes implemented through reregi strati on and are being used to define parameters of
the action being assessed in this ecological risk assessment and effects determination.
Prior to 1990, dicofol contained approximately 10% DDT since DDT is an intermediate
in the production of dicofol; however, refinements in the manufacturing process have
reduced contamination in the current formulation to less than 0.1 % DDT contamination.
The end result of the EPA pesticide registration process (i.e.., the FIFRA regulatory
action) is an approved product label. The label is a legal document that stipulates how
and where a given pesticide may be used. Product labels (also known as end-use labels)
describe the formulation type (e.g., liquid or granular), acceptable methods of application,
approved use sites, and any restrictions on how applications may be conducted. Thus, the
use of dicofol in accordance with the approved product labels for California is "the
action" relevant to this ecological risk assessment.
Although current registrations of dicofol allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of dicofol 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.
20
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Major degradates of the two isomers of dicofol are the o,p'- and p,p' isomers of
dichlorobenzophenone (DCBP); 1, l-(p-chlorophenyl-) 2,2-dichloroethanol (FW-152);
dichlorobenzhydrol (DCBH); hydroxyl-dichlorobenzophenone (OH-DCBP); and
chlorobenzoic acid (CBA). DCBP was identified in the hydrolysis, photolysis and
metabolism studies while the others were only present in metabolism studies. The
structures of dicofol and its major degradates are provided in Appendix A. There are
currently no submitted studies addressing the environmental fate and transport of these
major degradates. In addition, no empirical data are available to define the toxicities of
these degradates to non-target organisms. In order to characterize the relative toxicities
of these degradates to dicofol, the Ecosar1 model was run. The result indicates that the
toxicities of DCBP, FW-152, DCBH and OH-DCBP are within an order of magnitude of
dicofol (for a full description of the results, see Section 4.2). Therefore, these degradates
were considered to be of concern for this risk assessment. It is assumed in this
assessment that for aquatic animals, total residues are of equal toxicity to that of the
parent.
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; U.S.
FWS/NMFS 2004).
Registered products that contain dicofol do not list any other active ingredients on their
labels. However, as mentioned earlier, prior to 1990, dicofol contained approximately
10% DDT. Refinements in the manufacturing process have reduced contamination in the
current formulation to less than 0.1 % DDT contamination. No other data on mixtures
including dicofol are available.
2.3. Previous Assessments
In November 1998, EPA completed its Registration Eligibility Decision (RED) for
dicofol. EPA concluded that the available field data suggested that dicofol did not pose
significant adverse effects on avian reproduction and did not present an unreasonable risk
to ecosystems. However, based on laboratory data, the potential for such effects
appeared significant for certain species. Dicofol was found to be moderately to slightly
toxic on an acute exposure basis to terrestrial animals and practically non-toxic to honey
bees on an acute contact exposure basis. In laboratory studies dicofol was also shown to
cause reproductive effects in avian and mammalian species. Dicofol was found to be
highly toxic on an acute basis to both cold and warm water species offish and freshwater
1 USEPA 2009. Ecological Structure Activity Relationships (ECOSAR) version l.OOa. Office of Pollution
Prevention and Toxic, http://www.epa.gov/oppt/newchems/tools/21ecosar.htm
21
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invertebrates and was very highly toxic to estuarine/marine invertebrates. Additionally,
laboratory studies showed that dicofol had some potential to bioaccumulate in fish, but
that dicofol residues depurated relatively quickly. Because of its apparent structural
similarity to DDT, dicofol has been identified as a potential endocrine disrupter.
However, based on the data available, no conclusions could be made regarding the
potential for dicofol to act as an endocrine disrupter (USEPA, 1998b).
2.4. Stressor Source and Distribution
2.4.1. Environmental Fate Assessment
Based on the available environmental fate data for dicofol, this chemical is not expected
to persist in the environment, with half-lives less than 90 days, depending upon the
specific environmental conditions. However, studies submitted on the fate of dicofol do
not provide sufficient information to estimate persistence of dicofol degradates in the
environment. As a result, conservative estimates for persistence of dicofol (considering
the parent and major degradates) are as high as 313 days. The primary route of
dissipation is soil metabolism and the primary route of transport is surface runoff.
Dicofol occurs in formulated end-use products as two isomers, o,p'-dicofo\ and p,p'-
dicofol, at a ratio of 1:4.5. Major degradates of dicofol include the o,p'- and/\p'-isomers
of DCBP, FW-152, DCBH, OH-DCBP, and CBA.
22
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Table 3 lists the environmental fate properties of the dicofol isomers. The o,//-isomer
hydrolyzed with half-lives of 47 days, 0.33 days, and 0.006 days at pHs 5, 7 and 9,
respectively (MRID 40042033). An aerobic soil metabolism study showed that the o,p'-
isomer degraded with half-life of 8.5 days in a loam soil under slightly alkaline
conditions (pH = 7.5, MRID 41094201). Parent plus major residues degraded with a half-
life of 186 days. An anaerobic soil metabolism study showed that the o,//-isomer
degraded with half-life of 6 days in a silt loam soil under slightly alkaline conditions (pH
= 7.9, MRID 43908701). Adsorption data indicate that the 0,/>'-isomer is not very
mobile, with a majority of the 0,/>'-dicofol remaining in the upper 2 inches of the soil
columns. Less than 2.5% of o,p'-dicofol was found in leachate (MRID 41509802).
The p,p'-isomer hydrolyzed with half-lives of 85 days, 2.8 days and 0.018 days at pHs 5,
7 and 9, respectively (MRIDs 40042032, 40460105). An aerobic soil metabolism study
showed that the p,p'-isomer degraded with a half-life of 32 days in a silt loam soil under
slightly alkaline conditions (pH = 7.8, MRID 41050701). Parent plus major residues
degraded with a half-life of 313 days. An anaerobic soil metabolism study showed that
the p,p'-isomer degraded with half-life of less than 30 days in a silt loam soil under
slightly alkaline conditions (pH = 7.8, MRID 40042039). Adsorption data indicate that
the p,p'-isomer is not very mobile (MRID 41509801). A regression analysis between the
Kd and organic carbon content values indicated a high r-squared value (0.98) and
statistical significance (<0.01). To assess the appropriateness of the Koc model, the
coefficient of variation for the Koc (CV =19) was compared to the coefficient of variation
for Kd (CV = 58). Since the CV for the Koc was less than the CV for Kd, the average Koc
of 7,060 mL/g was used (Kashuba et al. 2006). For o,p '-dicofol, the majority of dicofol
remained in upper 2 inches of soil columns, with less than 2.5% of dicofol found in
leachate.
Of the major dicofol degradates, DCBP was identified in the hydrolysis, photolysis and
metabolism studies, while the other degradates were only present in metabolism studies.
Table 4 summarizes the maximum amount of the individual degradates that were observed
in submitted environmental fate studies for dicofol and when the maximum amount
occurred. There are currently no submitted studies quantifying the environmental fate
and transport (e.g., half-lives) of the major degradates of dicofol individually.
Available registrant-submitted data indicate that dicofol has potential to bioaccumulate in
aquatic ecosystems. Dicofol has a octanol-water partitioning coefficient (Kow) of 1.15 x
10"6 (MRID 00141578). In a bioconcentration study, parent p,p'-dicofol residues in
bluegill sunfish resulted in bioconcentration factors of 6,600 in fillet, 17,000 in viscera,
and 10,000 in whole fish. The half-life of elimination (depuration) was estimated to be 33
days (MRID 265330).
23
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Based on the available fate data, the major routes of dissipation for dicofol are hydrolysis
under neutral and alkaline conditions, and aerobic and anaerobic soil metabolism under
slightly alkaline conditions (pH from 7.5 to 7.9), with the o,//-isomer degrading more
quickly. Dicofol can be classified as slightly mobile (Kashuba, et al. 2006) and has the
potential to bioaccumulate in the environment. Leaching and photodegradation are not
expected to be significant routes of dissipation. Based on dicofol's vapor pressure
(3.9 x 10"7 torr), low levels of volatilitization are possible, but not expected. Dicofol can
be expected to partition between the gas and particle phases in the atmosphere, and is
likely to exist largely in the particle phase, potentially contributing to its long-range
transport. Given dicofol's Kow and Koc values, it is anticipated that dicofol that enters
surface water through soil erosion, runoff, or spray drift will have an affinity to reside in
the sediment. Anaerobic soil metabolism studies indicate that dicofol will degrade
relatively rapidly in sediment with a half-life less than 30 days. It is unclear how dicofol
degradates would partition in the water column; however, estimates of the Kow values
(9,120-77,625) and Koc values (1,933-8,950) using EPISuite2 indicate a similar affinity
for the sediment. As there are no data quantifying the fate and transport of the dicofol
degradates, two stressors will be examined in this assessment: the parent compound (both
isomers of dicofol) and the total residues of concern (both isomers of dicofol and their
degradates). Based on toxicity data, the degradate CBA will not be considered in the
total residues of concern (see Section 4.2.1).
2 USEPA 2009. Estimation Program Interface (EPI) Suite version 4.0. Office of Pollution Prevention and
Toxics, http://www.epa.gov/oppt/exposure/pubs/episuitedl.htm
24
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Table 3. Summary of dicofol environmental fate properties.
Chemical/Fate
Parameter
Molecular weight
Vapor pressure (20°C)
Water solubility
(25°C)
Kow
Hydrolysis half -life
pH5
pH7
pH9
Direct Aqueous
Photolysis2 half -life
Soil Photolysis half-
life
Aerobic Soil
Metabolism half-life
Anaerobic Soil
Metabolism half-life
Leaching &
Adsorption/Desorption
Terrestrial Field
Dissipation half-life
Value
0,/>'-dicofol
Value
/7,/>'-dicofol
370.5 g/mol
3.9xlO"7torr
1.32 mg/L
1.15xl06
47 days
3.3 x 10'1 days
6.3 x 10"3 days
27.5 days
56 days
8.5 days (parent)
104.5 days (parent
and major degradates)
6 days
Majority of parent
remained in upper 2
inches of soil
columns. <2.5% of
parent found in
leachate.
3.7, 22 days
85 days
2.8 days
1.8xlO"2days
244 days
21 days
32 days (parent)
313 days (parent and
major degradates)
< 30 days
Koc=7,060 mL/g
4.7, 72 days
MRID1
00141704
00142595
00141578
40042033
40042032
40460105
40849702
40849701
40042037
40042036
41094201
41050701
43908701
40042039
41509802
41509801
41381801
42118601
Study
Classification
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
Acceptable
Supplemental
Supplemental
Acceptable
Acceptable
Acceptable
Supplemental
Acceptable
Acceptable
Supplemental
Supplemental
1. First MRID listed corresponds to data for o,p'-dicofol, while the second MRID corresponds to data for p,p'-
dicofol.
2. Data corrected for dark control.
25
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Table 4. Summary of dicofol degradates observed in submitted environmental fate studies for dicofol.
Data represent % of total residue detected as specific degradate and study day residues were
measured.
Fate Study
Hydrolysis
pH7
Direct
Aqueous
Photolysis1
Soil
Photolysis
Aerobic Soil
Metabolism
Anaerobic
Soil
Metabolism
Dicofol
Isomer
o,p'
P>P'
o,p'
P'P'
o,p'
p,p'
o,p'
p,p'
o,p'
p,p'
FW-1521
ND
ND
ND
ND
ND
ND
31%
Day 31
45%
Day 62
43%
Day 30
38%
Day 60
DCBP2
53%
Day 1
50%
Day?
26%
Day 30
7%
Day 30
29%
Day 30
25%
Day 30
19%
Day 275
18%
Day 275
<10%
Day 1
5.4%
DayO
DCBH3
ND
ND
ND
ND
ND
ND
12%
Day 366
ND
15%
Day 30
6.4%
Day 60
OH-DCBP4
ND
ND
ND
ND
ND
ND
12%
Day 92
17%
Day 275
ND
ND
CBA5
ND
ND
ND
ND
ND
ND
14%
Day 92
ND
ND
ND
MRID
40042033
40042032
40849702
40849701
40042036
40042037
41094201
41050701
43908701
40042039
ND = not detected
1 l,l-(/?-chlorophenyl-) 2,2-dichloroethanol
2 Dichlorobenzophenone
3 Dichlorobenzhydrol
4 Hydroxyl-dichlorobenzo-phenone
5 Chlorobenzoic acid
2.4.2. Environmental Transport Assessment
Potential transport mechanisms include runoff in soluble and soil-bound forms, spray
drift, and atmospheric transport in soil-bound residues leading to deposition into nearby
or more distant ecosystems.
Dicofol is expected to have limited mobility in the environment and a low potential to
migrate to groundwater. In soil column leaching experiments in sand, sandy loam, and
clay loam (MRID 41509802), 75 to 98% of the applied radioactivity of the o,p'-dicofo\
isomer remained in the upper 1 or 2 inches of the columns. Less than 3% of the applied
radioactivity was in the leachate. Batch equilibrium studies on the p,p'-isomer resulted
in organic carbon sorption coefficients of 7,060 mL/goc, (MRID 41509801). Two
supplemental leaching studies conducted on p,p'-dicofo\ suggest that the chemical does
not significantly leach under the testing conditions (IDs GS0021002 and GS0021007).
26
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No data are available on the mobility of aged dicofol or on the mobility of the major
degradates of dicofol. Based on the results of the terrestrial field dissipation studies, it
appears that dicofol metabolites are not very mobile under normal dicofol use conditions.
Depending on soil, site and meteorological conditions dicofol may be transported off-site
in soil-bound erosion from runoff.
Although supplemental, two terrestrial field dissipation studies confirm the results of the
laboratory persistence and mobility studies. These studies suggest that dicofol does not
persist in the field for long periods (on an order of several days to several weeks). In a
dissipation study on cotton in Madera, California (MRID 41381801), dicofol residues had
a DTso value (the length of time required for 50% of the parent to dissipate from the
surface 6-inches of the soil) of less than 7 days. In a second dissipation study on
strawberries in Thermal, California (MRID 42118601), the rate of dissipation was slower
(DT50s of 22 days for o,p'-dicofo\ and 72 days for/\p'-dicofol). Dicofol dissipated from
the upper 6 inches in the Madera study site at a rate that was an order of magnitude faster
than that of the Thermal site, despite the fact that the soils at the Thermal site had an
alkaline pH more favorable to hydrolysis (8.4 at Thermal versus 6.2 at Madera) and a
higher organic matter content (0.8% at Thermal versus 0.2% at Madera). Greater
amounts of irrigation were used in the cotton study (44.28 inches of water over the first
228 days in Madera versus 27.04 inches of water over 365 days). Results of these studies
suggest that hydrolysis at the Madera site may have played a greater role than at the
Thermal site, where metabolism appeared to be the dominant route of dissipation in the
field. Neither dicofol nor its residues moved significantly below 6 inches in either study.
The major degradates observed in these field studies, o,p' and/\p'-DCBP, o,//-DCBH, 4-
CBA, andp,p'-FW 152. Analysis of the data indicates that the half-lives for the major
degradates, o,/?'-DCBP and p,p'-DCBP, were between 29 and 45 days, and 55 and 132
days, respectively.
A number of studies have documented atmospheric transport and re-deposition of
pesticides from the Central Valley to the Sierra Nevada Mountains (Fellers et al. 2004;
Sparling et al. 2001; LeNoir et al. 1999; McConnell et al. 1998). Prevailing winds blow
across the Central Valley eastward to the Sierra Nevada Mountains, transporting airborne
industrial and agricultural pollutants into the Sierra Nevada ecosystems (Fellers et al.
2004; LeNoir et al. 1999; McConnell et al. 1998). Several sections of critical habitat for
the CLRF are located east of the Central Valley. The magnitude of transport via
secondary drift depends on dicofol's ability to be mobilized into air and its eventual
removal through wet and dry deposition of particles and photochemical reactions in the
atmosphere. Therefore, physicochemical properties of dicofol that describe its potential
to enter the air from water or soil, pesticide use data, modeled estimated concentrations in
water and air, and available air monitoring data from the Central Valley and the Sierra
Nevada Mountains are considered in evaluating the potential for atmospheric transport of
dicofol to locations where it could impact the CRLF.
Because of its low vapor pressure and persistence in the air (estimated half-life > 2 days),
the United Nations Economic Commission for Europe's (UNECE) Convention on Long-
range Transboundary Air Pollution has indicated that dicofol has the potential for long
27
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range transport (Rasenberg et al. 2003). According to the report, "dicofol is expected to
partition between the gas and particle phases in the atmosphere and is likely to exist
largely in the particle phase."
2.4.3. Mechanism of Action
According to the World Health Organization (WHO, 1996), dicofol produces stimulation
of axonal transmission of nerve signals, believed to be related to inhibition of ATPases in
the central nervous system (CNS). The signs of toxicity are consistent with CNS
depression. However, the Insecticide Resistance Action Committee (IRAC) has recently
classified the mode of action for dicofol as unknown or uncertain (IRAC, 2008).
2.4.4. Use Characterization
Analysis of labeled use information is the critical first step in evaluating the federal
action. The current labels for dicofol represent the FIFRA regulatory actions; 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.
Dicofol is an organochlorine, broad-spectrum acaricide, insecticide, and miticide
currently registered nationwide for application on a variety of crops and non-agricultural
uses. Table 5 presents the uses and corresponding application rates and methods of
application considered in this assessment. The reported application rates represent the
maximum application rate used in any crop/use site within each group. The information
was extracted from existing product labels (EPA Registration Numbers 11603-26, 66222-
21, 66222-56, and 66222-95). Dicofol is used for non-residential purposes only.
Table 5. Methods and rates of application of currently registered uses of dicofol in California1.
Use (Application Method)
Beans (dry, snap, lima)
Citrus2
Cotton
Cucurbits3
Grapes
Hops
Mint/Peppermint/Spearmint
Max. Single
Appl. Rate
(lb a.i./A)
1.5
3
1.5
0.625
1.25
1.165
1.25
Application Method(s)
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft and ground sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
28
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Use (Application Method)
Pecans
Peppers
Pome Fruits4
Stone Fruits5
Strawberries
Tomatoes
Walnuts (English/black)
Bermuda grass
Turf grasses
Sod farms
Ornamentals6
Outside building surfaces
Max. Single
Appl. Rate
Ob a.i./A)
2
0.75
o
3
1.5
2
0.75
2
0.4
0.5
0.5
0.5
0.5
Application Method(s)
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft and ground sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
ULV, Aircraft, Hi- and low-volume ground
sprayer
Hi- and low-volume ground sprayer
Hi- and low-volume ground sprayer
Hi- and low-volume ground sprayer
Hi- and low-volume ground sprayer
Hi- and low-volume ground sprayer
1. Applications of dicofol are limited to no more than one per year on any one field.
2. Specifically: grapefruit, kumquats, lemons, limes, oranges, tangelos, and tangerines.
3. Specifically: cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash.
4. Specifically: apples, crabapples, pears, and quince.
5. Specifically: apricots, sweet and sour cherries, nectarines, peaches, plums, and prunes.
6. Specifically: nurseries, flowers, and shade trees.
Figure 2 below shows the estimated poundage of dicofol uses across the United States.
The map was downloaded from a U.S. Geological Survey (USGS), National Water
Quality Assessment Program (NAWQA) website
(http://water.usgs.gov/nawqa/pnsp/usage/maps/).
29
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DICOFOL - insecticide
2002 estimated annual agricultural use
Avera
! annual use of
active ingredient
(pounds par square mile of agricultural
land in county)
D no estimated use
D 0.001 to 0.002
D 0.003 to 0.005
D 0.006 to 0.016
D 0.017 to 0.128
• >= 0.129
Crops
citrus fruit
cotton
dry beans
pecans
green beans
mint for oil
walnuts
grapes
apples
watermelons
Total
pounds applied
161242
134548
15754
9586
6205
7344
6687
5195
4495
4256
Percent
national use
43.15
36.00
4.22
2.57
2.20
1.97
1.79
1.39
1.20
1.14
Figure 2. Estimated national agricultural use of dicofol for 2002.
The Agency's Biological and Economic Analysis Division (EPA/OPP/BEAD) provides
an analysis of both national- and county-level usage information (Kaul and Jones, 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 dicofol by county in this
California-specific assessment were generated using CDPR PUR data. Eight years
(1999-2006) of usage data were included in this analysis. Data from CDPR PUR were
obtained for every pesticide application made on every use site at the section level
(approximately one square mile) of the public land survey system. EPA/OPP/BEAD
summarized these data to the county level by site, pesticide, and unit treated. Calculating
county-level usage involved summarizing across all applications made within a section
and then across all sections within a county for each use site and for each pesticide. The
county level usage data that were calculated include: average annual pounds applied,
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.
30
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average annual area treated, and average and maximum application rate across all eight
years. The units of area treated are also provided where available.
Eight years (1999-2006) of usage data from CDPR PUR were obtained for every difocol
application made on every use site in California at the field level. Total annual pounds
applied and total annual area treated were calculated at the county level by site and
pesticide active ingredient. Pesticide usage was also aggregated across all observations
for eight years for each chemical-county-unit-treated combination. Because pesticide
applications are made in different area units, the units of area treated are provided where
available. Years in which there is no reported use in a county are included as zeros in the
calculation of the eight-year averages for pounds and area treated. Averages reflect years
without use.
In California between 1999 and 2006, the majority of dicofol applied was used on cotton
(64%), with lesser percentages applied to beans (13%), citrus (6%), and grapes (5%).
Overall usage of dicofol in California fell from 1999 to 2002 to roughly 182,000 Ibs/year,
then increased to 212,000 Ibs/year in 2004, and decreased to 101,000 Ibs in 2006.
Approximately 20% of dicofol applied in California is used in the 20 counties that
contain CRLF critical habitat areas. A summary of dicofol usage for all California use
sites is provided below in Table 6. These rates are consistent with the maximum
application rates specified on the label and used in the modeling analysis, depicted in
Table 9, with a few exceptions. For cucurbits, the maximum label application rate is
0.625 Ibs dicofol/A, while the application rates depicted in the CDPR PUR database were
above this level. This can be attributed to an outlier reported for 1999 in San Joaquin
County where 50 acres of squash were reportedly treated with 2,815 Ibs of dicfol. For
tomatoes, the maximum label application rate is 0.75 Ibs dicofol/A, while the CDPR PUR
reported application rates are above this level. Data available in the CDPR PUR database
for tomatoes is divided into two groups, tomatoes and tomato processing. It appears that
the use rates for tomato processing applications are increasing the values derived from
the CDPR PUR database, as the statistical application rates data for tomatoes all fall
below the maximum label rate, while all of the statistics for tomato processing are above
the maximum label use rate. For Bermuda grass, the maximum label rate is 0.4 Ibs
dicofol/A. There was only one reported value for Bemuda grass in the CDPR PUR
database for 0.48 Ibs dicofol/A. Lastly, the maximum label application rate for
ornamentals is 0.5 Ibs dicofol/A. Outdoor flowers, transplants, and plants in containers
were grouped into this category. It's unclear as to how the area treated, reported in acres
or square feet, was estimated in the database. As such, an underestimation in the area
treated could result in an application rate higher than the maximum label rate. It should
be noted that the uses considered in this risk assessment represent all currently registered
uses according to a review of all current labels. No other uses are relevant to this
assessment. Any other reported use, such as may be seen in the 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.
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Table 6. Summary of California Department of Pesticide Registration (CDPR) Pesticide Use
Reporting (PUR) data and calculated annual application rates (1999 - 2006) for currently registered
dicofol uses.1
Site Name
Beans (dry, snap, lima)
Citrus2
Cotton
Cucurbits3
Grapes
Mint/Peppermint/Spearmint
Peppers
Pome Fruits4
Stone Fruits5
Strawberries
Tomatoes
Walnuts (English/black)
Bermuda grass
Ornamentals6
Annual
Average
Pounds
28,568
13,427
142,539
6,853
11,642
138
184
1,769
7,676
1,327
1,008
7,013
90
582
Avg App
Rate
(Ibs ai/acre)
1.27
2.26
1.01
0.77
1.10
0.87
0.66
1.64
1.34
1.01
0.78
1.75
0.48
0.93
Avg 95th%
App Rate
(Ibs ai/acre)
1.46
2.70
1.25
1.26
1.26
1.00
0.71
1.89
1.55
1.36
0.93
2.00
0.48
1.24
Avg 99th%
App Rate
(Ibs ai/acre)
1.46
2.70
1.25
1.26
1.26
1.00
0.71
1.89
1.55
1.36
0.93
2.00
0.48
1.24
Avg Max App
Rate
(Ibs ai/acre)
1.46
2.70
1.25
1.26
1.26
1.00
0.71
1.89
1.55
1.36
0.93
2.00
0.48
1.24
1. Dicofol was not applied to hops, pecans, turf, sod farms, or outside building surfaces from 1999-2006, according to
the PUR database.
2. Specifically: grapefruit, lemons, oranges, tangelos, and tangerines.
3. Specifically: cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash.
4. Specifically: apples and pears.
5. Specifically: apricots, cherries, nectarines, peaches, plums, and prunes.
6. Specifically: outdoor flowers and plants.
2.5. Assessed Species
The CRLF was federally listed as a threatened species by U.S. FWS effective June 24,
1996 (U.S. FWS 1996). It is one of two subspecies of the red-legged frog and is the
largest native frog in the western United States (U.S. FWS 2002). A brief summary of
information regarding CRLF distribution, reproduction, diet, and habitat requirements is
provided below. 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 U.S. FWS on April 13, 2006 (U.S.
FWS 2006; 71 FR 19244-19346). Further information on designated critical habitat for
the CRLF is provided in Section 2.6.
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2.5.1. Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically
inhabited 46 counties in California including the Central Valley and both coastal and
interior mountain ranges (U.S. FWS 1996). Its range has been reduced by about 70%,
and the species currently resides in 22 counties in California (U.S. FWS 1996). The
species has an elevational range of near sea level to 1,500 meters (5,200 feet) (Jennings
and Hayes 1994); however, nearly all of the known CRLF populations have been
documented below 1,050 meters (3,500 feet) (U.S. FWS 2002).
Populations currently exist along the northern California coast, northern Transverse
Ranges (U.S. FWS 2002), foothills of the Sierra Nevada (5-6 populations), and in
southern California south of Santa Barbara (two populations) (Fellers 2005a). Relatively
larger numbers of CRLFs are located between Marin and Santa Barbara Counties
(Jennings and Hayes 1994). A total of 243 streams or drainages are believed to be
currently occupied by the species, with the greatest numbers in Monterey, San Luis
Obispo, and Santa Barbara counties (U.S. FWS 1996). Occupied drainages or watersheds
include all bodies of water that support CRLFs (i.e.., streams, creeks, tributaries,
associated natural and artificial ponds, and adjacent drainages), and habitats through
which CRLFs can move (i.e., riparian vegetation, uplands) (U.S. FWS 2002).
The distribution of CRLFs within California is addressed in this assessment using four
categories of location including recovery units, core areas, designated critical habitat, and
known occurrences of the CRLF reported in the California Natural Diversity Database
(CNDDB) that are not included within core areas and/or designated critical habitat
(Figure 3). Recovery units, core areas, and other known occurrences of the CRLF from
the CNDDB are described in further detail in Attachment I, and designated critical habitat
is addressed in Section 2.6. Recovery units are large areas defined at the watershed level
that have similar conservation needs and management strategies. The recovery unit is
primarily an administrative designation, and land area within the recovery unit boundary
is not exclusively CRLF habitat. Core areas are smaller areas within the recovery units
that comprise portions of the species' historic and current range and have been
determined by U.S. FWS to be important in the preservation of the species. Designated
critical habitat is generally contained within the core areas, although a number of critical
habitat units are outside the boundaries of core areas, but within the boundaries of the
recovery units. Additional information on CRLF occurrences from the CNDDB is used
to cover the current range of the species not included in core areas and/or designated
critical habitat, but within the recovery units.
Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in
California. The CNDDB serves as a repository for historical and current species location
sightings. Information regarding known occurrences of CRLFs outside of the currently
occupied core areas and designated critical habitat is considered in defining the current
33
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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.
Recovery Units
1. Sierra Nevada Foothills and Central Valley
2. North Coast Range Foothills and Western
Sacramento River Valley
3. North Coast and North San Francisco Bay
4. South and East San Francisco Bay
5. Central Coast
6. Diablo Range and Salinas Valley
7. Northern Transverse Ranges and Tehachapi
Mountains
8. Southern Transverse and Peninsular Ranges
Legend
^ Recovery Unit Boundaries
Currently Occupied Core Areas
^B Critical Habitat
§•1 CNDDB Occurence Sections
County Boundanes
Core Areas
1. Feather River
2. Yuba River-S. Fork Feather River
3. Traverse Creek/ Middle Fork/ American R. Rubicon
4. Cosumnes River
5. South Fork Calaveras River*
6. Tuolumne River*
7. Piney Creek*
8. Cottonwood Creek
9. Putah Creek - Cache Creek*
10. Lake Berryessa Tributaries
11. Upper Sonoma Creek
12. Petaluma Creek - Sonoma Creek
13. Pt. Reyes Peninsula
14. Belvedere Lagoon
15. Jameson Canyon - Lower Napa River
16. East San Francisco Bay
17. Santa Clara Valley
18. South San Francisco Bay
* Core areas that were historically occupied by the California red-legged frog are not included in the map
19. Watsonville Slough-Elkhorn Slough
20. Carmel River - Santa Lucia
21. Gablan Range
22. EsteroBay
23. Arroyo Grange River
24. Santa Maria River - Santa Ynez River
25. Sisquoc River
26. Ventura River - Santa Clara River
27. Santa Monica Bay - Venura Coastal Streams
28. Estrella River
29. San Gabriel Mountain*
30. Forks of the Mojave*
31. Santa Ana Mountain*
32. Santa Rosa Plateau
33. San Luis Ray*
34. Sweetwater*
35. Laguna Mountain*
Figure 3. Recovery unit, core area, critical habitat, and occurrence designations for CRLF.
34
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2.5.2. Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams,
marshes, and lagoons (Fellers 2005a). According to the Recovery Plan (U.S. FWS 2002),
CRLFs breed from November through late April. Peaks in spawning activity vary
geographically; Fellers (2005b) reports peak spawning as early as January in parts of
coastal central California. Eggs are fertilized as they are being laid. Egg masses are
typically attached to emergent vegetation, such as bulrushes (Scirpus spp.) and cattails
(Typha spp.) or roots and twigs, and float on or near the surface of the water (Hayes and
Miyamoto 1984). Egg masses contain approximately 2000 to 6000 eggs ranging in size
between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch 10 to 14 days after
fertilization (Fellers 2005a) depending on water temperature. Egg predation is reported
to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles
(terrestrial-phase), typically between May and September (Jennings and Hayes 1994,
U.S. FWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b, U.S. FWS 2002). Males reach sexual maturity at 2
years, and females reach sexual maturity at 3 years of age; adults have been reported to
live 8 to 10 years (U.S. FWS 2002). Figure 4 depicts CRLF annual reproductive timing.
J
F
M
A
M
J
J
A
S
0
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter)
Orange = Young Juveniles
Adults and juveniles can be present all year
Figure 4. CRLF reproductive events by month.
2.5.3. Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied
specifically, it is assumed that their diet is similar to that of other frog species, with the
aquatic phase feeding exclusively in water and consuming diatoms, algae, and detritus
(U.S. FWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar 1980)
via mouthparts designed for effective grazing of periphyton (Wassersug 1984;
Kupferberg etal. 1994; Kupferberg 1997; Altig andMcDiarmid 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-
35
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phase CRLFs is thought to be aquatic and terrestrial invertebrates found along the
shoreline and on the water surface. Hayes and Tennant (1985) report, based on a study
examining the gut content of 35 juvenile and adult CRLFs, that the species feeds on as
many as 42 different invertebrate taxa, including Arachnida, Amphipoda, Isopoda,
Insecta, and Mollusca. The most commonly observed prey species were larval alderflies
(Stalls 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 (U.S. FWS 2002).
Generally, CRLFs utilize habitat with perennial or near-perennial water (Jennings et al.
1997). Dense vegetation close to water, shading, and water of moderate depth are habitat
features that appear especially important for CRLF (Hayes and Jennings 1988).
Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds,
marshes, sag ponds (land depressions between fault zones that have filled with water),
dune ponds, and lagoons. Breeding adults have been found near deep (0.7 m) still or
slow moving water surrounded by dense vegetation (U.S. FWS 2002); however, the
largest number of tadpoles have been found in shallower pools (0.26 - 0.5 m) (Reis
1999). Data indicate that CRLFs do not frequently inhabit vernal pools, as conditions in
these habitats generally are not suitable (Hayes and Jennings 1988).
CRLFs also frequently breed in artificial impoundments such as stock ponds, although
additional research is needed to identify habitat requirements within artificial ponds (U.S.
FWS 2002). Adult CRLFs use dense, shrubby, or emergent vegetation closely associated
with deep-water pools bordered with cattails and dense stands of overhanging vegetation
(http ://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 (U.S. FWS 2002).
36
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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 U.S. FWS (U.S. FWS 2006; FR 51 19244-19346). A
summary of the 34 critical habitat units relative to U.S. FWS-designated recovery units
and core areas (previously discussed in Section 2.5) is provided in Attachment 1.
'Critical habitat' is defined in the ESA as the geographic area occupied by the species at
the time of the listing where the physical and biological features necessary for the
conservation of the species exist, and there is a need for special management to protect
the listed species. It may also include areas outside the occupied area at the time of
listing if such areas are 'essential to the conservation of the species.' All designated
critical habitat for the CRLF was occupied at the time of listing. Critical habitat receives
protection under Section 7 of the ESA (Section 7) through prohibition against destruction
or adverse modification with regard to actions carried out, funded, or authorized by a
federal Agency. Section 7 requires consultation on federal actions that are likely to result
in the destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the
conservation of the species.' Critical habitat designations identify, to the extent known
using the best scientific and commercial data available, habitat areas that provide
essential life cycle needs of the species or areas that contain certain primary constituent
elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to,
space for individual and population growth and for normal behavior; food, water, air,
light, minerals, or other nutritional or physiological requirements; cover or shelter; sites
for breeding, reproduction, rearing (or development) of offspring; and habitats that are
protected from disturbance or are representative of the historic geographical and
ecological distributions of a species. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
• Breeding aquatic habitat;
• Non-breeding aquatic habitat;
• Upland habitat; and
• Dispersal habitat.
Further description of these habitat types is provided in Attachment 1.
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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, U.S. FWS 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. See
Attachment I for a full explanation on this special rule.
U.S. FWS has established adverse modification standards for designated critical habitat
(U.S. FWS 2006). Activities that may destroy or adversely modify critical habitat are
those that alter the PCEs and jeopardize the continued existence of the species.
Evaluation of actions related to use of dicofol that may alter the PCEs of the CRLF's
critical habitat form the basis of the critical habitat impact analysis. According to U.S.
FWS (2006), activities that may affect critical habitat and therefore result in adverse
effects to the CRLF include, but are not limited to the following:
(1) Significant alteration of water chemistry or temperature to levels beyond the
tolerances of the CRLF that result in direct or cumulative adverse effects to
individuals and their life-cycles.
(2) Alteration of chemical characteristics necessary for normal growth and viability
of juvenile and adult CRLFs.
(3) Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat that could result in
elimination or reduction of habitat necessary for the growth and reproduction of
the CRLF by increasing the sediment deposition to levels that would adversely
affect their ability to complete their life cycles.
(4) Significant alteration of channel/pond morphology or geometry that may lead to
changes to the hydrologic functioning of the stream or pond and alter the timing,
duration, water flows, and levels that would degrade or eliminate the CRLF
and/or its habitat. Such an effect could also lead to increased sedimentation and
degradation in water quality to levels that are beyond the CRLF's tolerances.
(5) Elimination of upland foraging and/or aestivating habitat or dispersal habitat.
(6) Introduction, spread, or augmentation of non-native aquatic species in stream
segments or ponds used by the CRLF.
(7) Alteration or elimination of the CRLF's food sources or prey base (also
evaluated as indirect effects to the CRLF).
As previously noted in Section 2.1, the Agency believes that the analysis of direct and
indirect effects to listed species provides the basis for an analysis of potential effects on
the designated critical habitat. Because dicofol is expected to directly impact living
38
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organisms within the action area, critical habitat analysis for dicofol is limited in a
practical sense to those PCEs of critical habitat that are biological or that can be
reasonably linked to biologically mediated processes.
2.7. Action Area
For listed species assessment purposes, the action area is considered to be the area
affected directly or indirectly by the federal action and not merely the immediate area
involved in the action (50 CFR 402.02). It is recognized that the overall action area for
the national registration of dicofol is likely to encompass considerable portions of the
United States based on the large array of agricultural uses. However, the scope of this
assessment limits consideration of the overall action area to those portions that may be
applicable to the protection of the CRLF and its designated critical habitat within the state
of California. The Agency's approach to defining the action area under the provisions of
the Overview Document (U.S. EPA 2004) considers the results of the risk assessment
process to establish boundaries for that action area with the understanding that exposures
below the Agency's defined Levels of Concern (LOCs) constitute a no-effect threshold.
For the purposes of this assessment, attention will be focused on the footprint of the
action (i.e., the area where pesticide application occurs), plus all areas where offsite
transport (i.e., spray drift, downstream dilution, etc.) may result in potential exposure
within the state of California that exceeds the Agency's LOCs.
Deriving the geographical extent of this portion of the action area is based on
consideration of the types of effects that dicofol may be expected to have on the
environment, the exposure levels to dicofol that are associated with those effects, and the
best available information concerning the use of dicofol and its fate and transport within
the state of California. Specific measures of ecological effect for the CRLF that define
the action area include any direct and indirect toxic effect to the CRLF and any potential
effects to its critical habitat, including reduction in survival, growth, and fecundity as
well as the full suite of sublethal effects available in the effects literature. Therefore, the
action area extends to a point where environmental exposures are below any measured
lethal or sublethal effect threshold for any biological entity at the whole organism, organ,
tissue, and cellular level of organization. In situations where it is not possible to
determine the threshold for an observed effect, the action area is not spatially limited and
is assumed to be the entire state of California.
The definition of action area requires a stepwise approach that begins with an
understanding of the federal action. The federal action is defined by the currently labeled
uses for dicofol. An analysis of labeled uses and review of available product labels was
completed. Several of the current labels are special local needs (SLN) labels for states
other than California and several currently labeled uses on FIFRA section 3 labels are
restricted to specific states other than California and therefore, are excluded from this
assessment. For those uses relevant to the CRLF, the analysis indicates that, for dicofol,
the following agricultural uses are considered as part of the federal action evaluated in
this assessment: beans (dry, snap, and lima), citrus (specifically, grapefruit, kumquats,
lemons, limes, oranges, tangelos, and tangerines), cotton, cucurbits (specifically,
cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer
39
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squash), grapes, hops, mint, pecans, peppers, pome fruits (specifically, apples,
crabapples, pears, and quince), stone fruits (specifically, apricots, sweet and sour
cherries, nectarines, peaches, plums, and prunes), strawberries, tomatoes, and walnuts. In
addition, the following non-food and non-agricultural uses are considered: Bermuda
grass, turf/ornamental uses (specifically, turf grasses, nursery stock, flowers, shade trees,
woody shrubs and vines, and sod farms) and outside building surfaces (nonagricultural).
Following a determination of the assessed uses, an evaluation of the potential "footprint"
of dicofol use patterns (i.e., the area where pesticide application occurs) is determined.
This "footprint" represents the initial area of concern, based on an analysis of available
land cover data for the state of California. The initial area of concern is defined as all
land cover types and the stream reaches within the land cover areas that represent the
labeled uses described above. A map representing all the land cover types that make up
the initial area of concern for dicofol is presented in Figure 5. In this figure, potential
uses of dicofol on all field crops as well as orchards and vineyards are represented by the
cultivated crops landcover data obtained from NLCD. In addition, potential use areas of
dicofol on tree fruits and grapes are represented by the orchard and vineyard land cover
data obtained from California GAP. Turf uses of dicofol are depicted as a derived NLCD
class based on developed classes and the impervious surface layer with corrections
applied. Additional information on the landcover data used to define the initial area of
concern is provided in Appendix B.
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Dicofol Use - Initial Area of Concern
Turf use
Orchard vineyard use
Cultivated crop use
County boundaries
I Kilometers
0 2040 80 120 160
Compiled from California County boundaries (ESRI, 2002),
USDA Gap Analysis Program Orchard/Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Projection: Albers Equal Area Conic USGS, North American
Datum of 1983 (NAD 1983).
3/11/2009
Figure 5. Initial area of concern for crops described by agricultural landcover which corresponds to
potential dicofol use sites. This map represents the area potentially directly affected by the federal
action.
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Once the initial area of concern is defined, the next step is to define the potential
boundaries of the action area by determining the extent of offsite transport via spray drift
and runoff where exposure of one or more taxonomic groups to the pesticide exceeds the
listed species LOCs. As previously discussed, the action area is defined by the most
sensitive measure of direct and indirect ecological toxic effects including reduction in
survival, growth, reproduction, and the entire suite of sublethal effects from valid, peer-
reviewed studies.
Once the potential boundaries of the area of concern are defined, the next step is to
compare the extent of that area with the results of the screening-level risk assessment. In
this assessment, transport of dicofol through erosion and spray drift is considered in
deriving quantitative estimates of dicofol exposure to CRLF, its prey and its habitats.
Since this screening-level risk assessment defines taxa that are predicted to be exposed
through runoff and drift to dicofol at concentrations above the Agency's Levels of
Concern (LOG), there is a need to expand the action area to include areas that are
affected indirectly by this federal action. Because of the lack of a NOAEC in several
chronic toxicity studies with birds, described later in Section 4.3.1, the action area for
dicofol is established as the entire state of California. Additional analysis related to the
intersection of the dicofol action area and CRLF habitat used in determining the action
area is described in section 5.2.5 and in Appendix B.
2.8. Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental
value that is to be protected."5 Selection of the assessment endpoints is based on valued
entities (e.g., CRLF, organisms important in the life cycle of the CRLF, and the PCEs of
its designated critical habitat), the ecosystems potentially at risk (e.g., waterbodies,
riparian vegetation, and upland and dispersal habitats), the migration pathways of dicofol
(e.g., runoff, spray drift, etc.), and the routes by which ecological receptors are exposed
to dicofol (e.g., direct contact, etc.).
2.8.1. Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the CRLF, as well as indirect effects, such as reduction of
the prey base or effects to its habitat. In addition, potential effects to critical habitat is
assessed by evaluating potential effects to PCEs, which are components of the habitat
areas that provide essential life cycle needs of the CRLF. Each assessment endpoint
requires one or more "measures of ecological effect," defined as changes in the attributes
of an assessment endpoint or changes in a surrogate entity or attribute in response to
exposure to a pesticide. Specific measures of ecological effect are generally evaluated
based on acute and chronic toxicity information from registrant-submitted guideline tests
that are performed on a limited number of organisms. Additional ecological effects data
from the open literature are also considered. It should be noted that assessment endpoints
5 U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
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are limited to direct and indirect effects associated with survival, growth, and fecundity,
and do not include the full suite of sublethal effects used to define the action area.
According the Overview Document (U.S. EPA 2004), the Agency relies on acute and
chronic effects endpoints that are either direct measures of impairment of survival,
growth, or fecundity or endpoints for which there is a scientifically robust, peer reviewed
relationship that can quantify the impact of the measured effect endpoint on the
assessment endpoints of survival, growth, and fecundity.
A complete discussion of all the toxicity data available for this risk assessment, including
resulting measures of ecological effect selected for each taxonomic group of concern, is
included in Section 4 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 dicofol is provided in Table 7.
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Table 7. Assessment endpoints and measures of ecological effects for dicofol.
Assessment Endpoint
Measures of Ecological Effects3
Aquatic-Phase CRLF (Eggs, larvae, juveniles, and adults)
Direct Effects
1. Survival, growth, and reproduction of
CRLF
la. LC50 = 53.0 ug/L, based on most sensitive acute
exposure data available for fish
Ib. NOAEC = 4.4 ug a.i./L, based on most sensitive
chronic exposure data available for fish
Indirect Effects and Critical Habitat Effects
2. Survival, growth, and reproduction of
CRLF individuals via indirect effects on
aquatic prey food supply (i.e., fish, freshwater
invertebrates, non-vascular plants)
3. Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat, cover, food supply, and/or primary
productivity (i.e., aquatic plant community)
4. Survival, growth, and reproduction of
CRLF individuals via effects to riparian
vegetation
2a. EC50 = 140 ug/L, based on most sensitive acute
exposure data available for aquatic invertebrates
2b. NOAEC = 19 ug a.i./L, based on most sensitive
chronic exposure data available for aquatic invertebrates
2c. LC50 = 53.0 ug/L, based on most sensitive acute
exposure data available for fish
2d. NOAEC = 4.4 ug a.i./L, based on most sensitive
chronic exposure data available for fish
2e. EC50 > 5,000, <10,000 ug/L, based on available data
for green algae
3a. EC50 > 5,000, <10,000 ug/L, based on available data
for green algae
No data are available to quantify an endpoint to represent
effects of dicofol exposures to vascular plants.
Terrestrial-Phase CRLF (Juveniles and adults)
Direct Effects
5. Survival, growth, and reproduction of
CRLF individuals via direct effects on
terrestrial phase adults and juveniles
4a. LD50 = 265 mg a.i./kg bw, based on most sensitive
acute oral exposure data available for birds2
4b. LC50 = 903 ppm, based on most sensitive subacute
dietary exposure data available for birds2
4c. NOAEC = 1 ppm, based on most sensitive chronic
exposure data available for birds2
Indirect Effects and Critical Habitat Effects
6. Survival, growth, and reproduction of
CRLF individuals via effects on terrestrial
prey (i.e., terrestrial invertebrates, small
mammals , and frogs)
7. Survival, growth, and reproduction of
CRLF individuals via indirect effects on
habitat (i.e., riparian and upland vegetation)
5a. LD50>50 ug a.i./bee, based on most sensitive acute
oral exposure data available for terrestrial invertebrates
5b. LD50 = 587 mg/kg-bw, based on most sensitive acute
oral exposure data available for mammals
5c. NOAEC = 5 ppm, based on most sensitive chronic
exposure data available for mammals
5d. LD50 = 265 mg a.i./kg bw, based on most sensitive
acute oral exposure data available for birds2
5e. LC50 = 903 ppm, based on most sensitive subacute
dietary exposure data available for birds2
5f. NOAEC = 1 ppm, based on most sensitive chronic
exposure data available for birds2
No data are available to quantify an endpoint to represent
effects of dicofol exposures to vascular plants.
Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult frogs are
considered "aquatic" for the purposes of this assessment because exposure pathways in the water are considerably
different that exposure pathways on land.
2 Birds are used as surrogates for terrestrial phase amphibians.
See Table 22 and Table 27 for citations and additional information.
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2.8.2. Assessment Endpoints for Designated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related
to the use of dicofol that may alter the PCEs of the CRLF's critical habitat. PCEs for the
CRLF were previously described in Section 2.6. Actions that may modify critical habitat
are those that alter the PCEs and jeopardize the continued existence of the CRLF.
Therefore, these actions are identified as assessment endpoints. It should be noted that
evaluation of PCEs as assessment endpoints is limited to those of a biological nature (i.e.,
the biological resource requirements for the listed species associated with the critical
habitat) and those for which dicofol effects data are available. Adverse modification to
the critical habitat of the CRLF includes, but is not limited to, those listed in Section 2.6.
Measures of such possible effects by labeled use of dicofol 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 U.S. FWS (2006).
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Table 8. Summary of dicofol assessment endpoints and measures of ecological effect for primary
constituent elements of designated critical habitat1.
Assessment Endpoint
Measures of Ecological Effect3
Aquatic-Phase CRLFPCEs (Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or geometry
and/or increase in sediment deposition within the
stream channel or pond: aquatic habitat (including
riparian vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile
and adult CRLFs.
No data are available to quantify an endpoint to represent
effects of dicofol exposures to vascular plants.
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.
le. EC50 > 5,000, <10,000 ug/L, based on available data for
green algae
No data are available for assessing the effects of exposures
of dicofol to vascular plants.
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
la. LC50 = 53.0 ug/L, based on most sensitive acute
exposure data available for fish
Ib. NOAEC = 4.4 ug a.i./L, based on most sensitive
chronic exposure data available for fish
le. EC50 = 140 ug/L, based on most sensitive acute
exposure data available for aquatic invertebrates
Id. NOAEC = 19 ug a.i./L, based on most sensitive
chronic exposure data available for aquatic invertebrates
le. EC50 > 5,000, <10,000 ug/L, based on available data for
green algae
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
le. EC50 > 5,000, <10,000 ug/L, based on available data for
green algae
Terrestrial-Phase CRLFPCEs (Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian
habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
No data are available to quantify an endpoint to represent
effects of dicofol exposures to vascular plants.
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
No data are available to quantify an endpoint to represent
effects of dicofol exposures to vascular plants.
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
2a. LD50>50 ug a.i./bee, based on most sensitive acute
exposure data available for terrestrial invertebrates
2b. LD50 = 587 mg/kg-bw, based on most sensitive acute
oral exposure data available for mammals
2c. NOAEC = 5 mg/kg-bw, based on most sensitive chronic
exposure data available for mammals
2d. LD50 = 265 mg a.i./kg bw, based on most sensitive
acute oral exposure data available for birds2
2e. LC50 = 903 mg/kg-bw, based on most sensitive
subacute dietary exposure data available for birds2
2f. NOAEC = 1 mg/kg-bw, based on most sensitive chronic
exposure data available for birds2
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Assessment Endpoint
Measures of Ecological Effect3
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
3a. LD50 = 265 mg a.i./kg bw, based on most sensitive
acute oral exposure data available for birds2
3b. LC50 = 903 mg/kg-bw, based on most sensitive
subacute dietary exposure data available for birds2
3c. NOAEC = 1 mg/kg-bw, based on most sensitive chronic
exposure data available for birds2
1 Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these
processes are not biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.
2 Birds are used as surrogates for terrestrial phase amphibians.
3 See Table 22 and Table 27 for citations and additional information.
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 1998a). For this assessment, the
risk is stressor-linked, where the stressor is the release of dicofol to the environment. The
following risk hypotheses are presumed for this endangered species assessment:
The labeled use of dicofol within the action area may:
• directly affect the CRLF by causing mortality or by adversely affecting growth or
fecundity;
• indirectly affect the CRLF by reducing or changing the composition of food
supply;
• indirectly affect the CRLF or affect designated critical habitat by reducing or
changing the composition of the aquatic plant community in the ponds and
streams comprising the species' current range and designated critical habitat, thus
affecting primary productivity and/or cover;
• indirectly affect the CRLF or affect designated critical habitat by reducing or
changing the composition of the terrestrial plant community (i.e., riparian habitat)
required to maintain acceptable water quality and habitat in the ponds and streams
comprising the species' current range and designated critical habitat;
• affect the designated critical habitat of the CRLF by reducing or changing
breeding and non-breeding aquatic habitat via effects to water quality parameters,
habitat morphology, and/or sedimentation;
• affect the designated critical habitat of the CRLF by reducing the food supply
required for normal growth and viability of juvenile and adult CRLFs;
• affect the designated critical habitat of the CRLF by reducing or changing upland
habitat within 200 ft of the edge of the riparian vegetation necessary for shelter,
foraging, and predator avoidance;
• affect the designated critical habitat of the CRLF by reducing or changing
dispersal habitat within designated units and between occupied locations within
47
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0.7 mi of each other that allow for movement between sites including both natural
and altered sites which do not contain barriers to dispersal; or,
affect the designated critical habitat of the CRLF by altering chemical
characteristics necessary for normal growth and viability of juvenile and adult
CRLFs.
2.9.2. Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the dicofol release mechanisms, biological receptor types, and effects
endpoints of potential concern. The conceptual models for aquatic and terrestrial
exposures are shown in Figure 6 and in Figure 7, respectively, which include the
conceptual models for the aquatic and terrestrial PCE components of critical habitat.
Exposure routes shown in dashed lines are not quantitatively considered because the
contribution of those potential exposure routes to potential risks to the CRLF and
modification to designated critical habitat is expected to be negligible.
Stressor
Source
Exposure
Media
Dicofol isomers, degradates, and DDT applied to use site
r
i
, L
Spraydriftl | Runoff
I Soil I
Surface water/
Sediment
•Wet/dry deposition •*
Long range
atmospheric
transport
Receptors
Uptake/gills
or integument
Uptake/gills
or integument
Aquatic Animals
Invertebrates
Vertebrates
Fish/aquatic-phase
amphibians
Piscivorous mammals
and birds
Ingestion
Attribute
Change
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Uptake/cell,
roots, leaves
I
Aquatic Plants
\lon-vascular
Vascular
Ingestion
Food chain
Reduction in algae
Reduction in prey
Modification of PCEs
related to prey availability
Habitat integrity
Reduction in primary productivity
leduced cover
Community change
Modification of PCEs related to
labitat
Figure 6. Conceptual model for dicofol effects on aquatic-phase of the CRLF.
48
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Stressor
Source
Exposure
Media
Dicofol isomers, degradates, and DDT applied to use site
Spray drift
1 ^—s ^—Dermal uptake/lngestiorx—
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Ingestion
Receptors
Birds/terrestrial-
phase
amphibians/
reptiles|mammals
Attribute
Change
ndividual organisms
Reduced survival
Reduced growth
Reduced reproduction
Root uptake-*-!
Wet/dry deposition
Food chain
Reduction in prey
Modification of PCEs
related to prey availability
Habitat integrity
Red uction i n pri mary p roductivity
Reduced cover
Community change
Modification of PCEs related to
habitat
Figure 7. Conceptual model for dicofol effects on terrestrial phase of the CRLF.
2.10. Analysis Plan
In order to address the risk hypothesis, the potential for direct and indirect effects to the
CRLF, its prey, and its habitat is estimated. In the following sections, the use,
environmental fate, and ecological effects of dicofol are characterized and integrated to
assess the risks. This is accomplished using a risk quotient (ratio of exposure
concentration to effects concentration) approach. Although risk is often defined as the
likelihood and magnitude of adverse ecological effects, the risk quotient-based approach
does not provide a quantitative estimate of likelihood and/or magnitude of an adverse
effect. However, as outlined in the Overview Document (U.S. EPA 2004), the likelihood
of effects to individual organisms from particular uses of dicofol is estimated using the
probit dose-response slope and either the level of concern (discussed below) or actual
calculated risk quotient value.
49
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2.10.1. Measures of Exposure
The environmental fate properties of dicofol along with available monitoring data
indicate that runoff and spray drift are the principle potential transport mechanisms of
dicofol to the aquatic and terrestrial habitats of the CRLF. In this assessment, transport
of dicofol through runoff and spray drift is considered in deriving quantitative estimates
of dicofol exposure to CRLF, its prey and its habitats. Because of its low vapor pressure
and persistence in the air (Ti/2 > 2 days), dicofol has the potential for long range transport.
It should be noted, however, that recent ambient air monitoring in agricultural
communities in California does not indicate volatilization of dicofol (See Section
3.2.4.2).
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of dicofol using maximum labeled application rates
and methods of application. The models used to predict aquatic EECs are the Pesticide
Root Zone Model coupled with the Exposure Analysis Model System (PRZM/EXAMS).
The model used to predict terrestrial EECs on food items is T-REX. The model used to
derive EECs relevant to terrestrial and wetland plants is TerrPlant. These models are
parameterized using relevant reviewed registrant-submitted environmental fate data.
Additionally, the Generic Estimated Environmental Concentration Model (GENEEC2)
was used to characterize the potential impacts due to the DDT manufacturing
intermediate in dicofol (see Appendix F).
PRZM (v3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are simulation models
coupled with the input shell pe5.pl (Aug 2007) to generate daily exposures and l-in-10
year EECs of dicofol that may occur in surface water bodies adjacent to application sites
receiving dicofol through runoff and spray drift. PRZM simulates pesticide application,
movement and transformation on an agricultural field and the resultant pesticide loadings
to a receiving water body via runoff, erosion and spray drift. EXAMS simulates the fate
of the pesticide and resulting concentrations in the water body. The standard scenario
used for ecological pesticide assessments assumes application to a 10-hectare agricultural
field that drains into an adjacent 1-hectare water body, 2-meters deep (20,000 m3 volume)
with no outlet. PRZM/EXAMS was used to estimate screening-level exposure of aquatic
organisms to dicofol. The measure of exposure for aquatic species is the l-in-10 year
return peak or rolling mean concentration. The l-in-10 year peak is used for estimating
acute exposures of direct effects to the CRLF, as well as indirect effects to the CRLF
through effects to potential prey items, including: algae, aquatic invertebrates, fish and
frogs. The 1-in-10-year 60-day mean is used for assessing chronic exposure to the CRLF
and fish and frogs serving as prey items; the 1-in-10-year 21-day mean is used for
assessing chronic exposure for aquatic invertebrates, which are also potential prey items.
GENEEC2 Version 2.0 is a screening-level model used in pesticide aquatic ecological
risk assessments. Similar to PRZM/EXAMS, GENEEC2 uses the soil/water partition
coefficient and degradation kinetic data to estimate runoff from a ten hectare field into a
one hectare by two meter deep "standard" pond.
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Exposure estimates for the terrestrial-phase CRLF and terrestrial invertebrates and
mammals (serving as potential prey) assumed to be in the target area or in an area
exposed to spray drift are derived using the T-REX model (version 1.3.1, 12/07/2006).
This model incorporates the Kenega nomograph, as modified by Fletcher et al. (1994),
which is based on a large set of actual field residue data. The upper limit values from the
nomograph represented the 95th percentile of residue values from actual field
measurements (Hoerger and Kenega 1972). For modeling purposes, direct exposures of
the CRLF to dicofol through contaminated food are estimated using the EECs for the
small bird (20 g) which consumes small insects. Dietary-based and dose-based exposures
of potential prey (small mammals) are assessed using the small mammal (15 g) which
consumes short grass. The small bird (20g) consuming small insects and the small
mammal (15g) consuming short grass are used because these categories represent the
largest RQs of the size and dietary categories in T-REX that are appropriate surrogates
for the CRLF and one of its prey items. Estimated exposures of terrestrial insects to
dicofol are bound by using the dietary based EECs for small insects and large insects.
Birds are currently used as surrogates for terrestrial-phase CRLF. However, amphibians
are poikilotherms (body temperature varies with environmental temperature) while birds
are homeotherms (temperature is regulated, constant, and largely independent of
environmental temperatures). Therefore, amphibians tend to have much lower metabolic
rates and lower caloric intake requirements than birds or mammals. As a consequence,
birds are likely to consume more food than amphibians on a daily dietary intake basis,
assuming similar caloric content of the food items. Therefore, the use of avian food
intake allometric equation as a surrogate to amphibians is likely to result in an over-
estimation of exposure and risk for reptiles and terrestrial-phase amphibians. Therefore,
T-REX (version 1.3.1) has been refined to the T-HERPS model (v. 1.0), which allows for
an estimation of food intake for poikilotherms using the same basic procedure as T-REX
to estimate avian food intake.
The spray drift model AgDRIFT is used to assess exposures of terrestrial phase CRLF
and its prey to dicofol deposited on terrestrial habitats by spray drift. In addition to the
buffered area from the spray drift analysis, the downstream extent of dicofol that exceeds
the LOG for the effects determination is also considered.
KABAM (Kow (based) Aquatic Bio Accumulation Model) v.1.0 is used to estimate
potential bioaccumulation of dicofol in freshwater aquatic food webs and subsequent
risks to mammals and birds via consumption of contaminated aquatic prey. In this case,
exposures to birds are used as a surrogate for CRLF consuming aquatic organisms that
have bioaccumulated dicofol and its degradates of concern.
Lastly, in order to characterize the long range transport potential (LRTP) of dicofol and
its degradates, the OECD Pov and LRTP Screening Tool was used. Three chemicals
known to move via long range transport, DDT, aldrin and endrin, were also modeled to
provide a context for the dicofol-estimated LRTP. It should be noted that OPP is not able
to quantify the extent to which dicofol and its degradates will undergo long-range
51
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atmospheric transport once it has been released from a treatment site and, as such, cannot
quantify the amount of exposure that could potentially occur to nontarget animals distant
from the use sites.
2.10.2. Measures of Effect
Data identified in Section 4 are used as measures of effect for direct and indirect effects
to the CRLF. Data were obtained from registrant submitted studies or from literature
studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched
in order to provide more ecological effects data and in an attempt to bridge existing data
gaps. ECOTOX is a source for locating single chemical toxicity data for aquatic life,
terrestrial plants, and wildlife. ECOTOX was created and is maintained by the U.S. EPA,
Office of Research and Development, and the National Health and Environmental Effects
Research Laboratory's Mid-Continent Ecology Division.
The assessment of risk for direct effects to the terrestrial-phase CRLF makes the
assumption that toxicity of dicofol to birds is similar to or less than the toxicity to the
terrestrial-phase CRLF. The same assumption is made for fish and aquatic-phase CRLF.
Algae, aquatic invertebrates, fish, and amphibians represent potential prey of the CRLF
in the aquatic habitat. Terrestrial invertebrates, small mammals, and terrestrial-phase
amphibians represent potential prey of the CRLF in the terrestrial habitat. Aquatic, semi-
aquatic, and terrestrial plants represent habitat of CRLF.
The acute measures of effect used for animals in this screening level assessment are the
LDso, LCso and ECso. LD stands for "Lethal Dose", and LDso is the amount of a material,
given all at once, that is estimated to cause the death of 50% of the test organisms. LC
stands for "Lethal Concentration" and LCso is the concentration of a chemical that is
estimated to kill 50% of the test organisms. EC stands for 'Effective Concentration' and
the ECso is the concentration of a chemical that is estimated to produce a specific effect in
50% of the test organisms. Endpoints for chronic measures of exposure for listed and
non-listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for 'No
Ob served- Adverse-Effect-Lever and refers to the highest tested dose of a substance that
has been reported to have no harmful (adverse) effects on test organisms. The NOAEC
(i.e.., 'No-Observed-Adverse-Effect-Concentration') is the highest test concentration at
which none of the observed effects were statistically different from the control. The
NOEC is the No-Observed-Effects-Concentration. For non-listed plants, only acute
exposures are assessed (i.e., EC25 for terrestrial plants and ECso for aquatic plants).
It is important to note that the measures of direct and indirect effects to the CRLF and its
designated critical habitat are associated with impacts to survival, growth, and fecundity,
and do not include the full suite of sublethal effects used to define the action area.
According the Overview Document (USEPA 2004), the Agency relies on effects
endpoints that are either direct measures of impairment of survival, growth, or fecundity
or endpoints for which there is a scientifically robust, peer reviewed relationship that can
quantify the impact of the measured effect endpoint on the assessment endpoints of
survival, growth, and fecundity.
52
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2.10.3. Integration of Exposure and Effects
Risk characterization is the integration of exposure and ecological effects characterization
to determine the potential ecological risk from agricultural and non-agricultural uses of
dicofol, and the likelihood of direct and indirect effects to CRLF in aquatic and terrestrial
habitats. The exposure and toxicity effects data are integrated in order to evaluate the
risks of adverse ecological effects on non-target species. For the assessment of dicofol
risks, the risk quotient (RQ) method is used to compare exposure and measured toxicity
values. EECs are divided by acute and chronic toxicity values. The resulting RQs are
then compared to the Agency's levels of concern (LOCs) (U.S. EPA 2004) (see
Appendix C).
For this endangered species assessment, listed species LOCs are used for comparing RQ
values for acute and chronic exposures of dicofol directly to the CRLF. If estimated
exposures directly to the CRLF of dicofol resulting from a particular use are sufficient to
exceed the listed species LOG, then the effects determination for that use is 'may affect'.
When considering indirect effects to the CRLF due to effects to animal prey (aquatic and
terrestrial invertebrates, fish, frogs, and mice), the listed species LOCs are also used. If
estimated exposures to CRLF prey of dicofol resulting from a particular use are sufficient
to exceed the listed species LOG, then the effects determination for that use is a 'may
affect.' If the RQ being considered also exceeds the non-listed species acute risk LOG,
then the effects determination is an LAA. If the acute RQ is between the listed species
LOG and the non-listed acute risk species LOG, then further lines of evidence (i.e.
probability of individual effects, species sensitivity distributions) are considered in
distinguishing between a determination of NLAA and a LAA. When considering indirect
effects to the CRLF due to effects to algae as dietary items or plants as habitat, the non-
listed species LOG for plants is used because the CRLF does not have an obligate
relationship with any particular aquatic and/or terrestrial plant. If the RQ being
considered for a particular use exceeds the non-listed species LOG for plants, the effects
determination is 'may affect.' Further information on LOCs is provided in Appendix C.
2.10.4. Data Gaps
There are currently no submitted studies quantifying the environmental fate and transport
of the major degradates of dicofol individually. Additionally, aerobic and anaerobic soil
metabolism studies were conducted using slightly alkaline (pH from 7.5 to 7.9) soil, so
soil metabolism studies under acidic soil conditions are missing. It should also be noted
that a study on photodegradation in air for dicofol and its degradates has not been
submitted.
No data are available for assessing the effects of exposures of dicofol to freshwater
vascular plants. Generally, data for duckweed (Lemna gibba) are used to assess these
effects.
53
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In addition, no data are available to quantify an endpoint to represent effects of dicofol
exposures to riparian and terrestrial vegetation (vascular plants), which are generally
represented by effects data for terrestrial agricultural crop species.
Limited data are available to determine the toxicity of dicofol's major degradates to
aquatic or terrestrial organisms.
3.0 Exposure Assessment
Dicofol is formulated as a wettable powder and emulsifiable formulation. Application
equipment includes: ground application, aerial application, and various sprayers (high-
and low-volume. Risks from ground boom and aerial applications are expected to result
in the highest off-target levels of dicofol due to generally higher spray drift levels.
Ground boom and aerial modes of application tend to use lower volumes of application
applied in finer sprays than applications coincident with sprayers and spreaders and thus
have a higher potential for off-target movement via spray drift.
3.1. Label Application Rates and Intervals
Dicofol labels may be categorized into two types: labels for manufacturing uses
(including technical grade dicofol and its formulated products) and end-use products.
While technical products, which contain dicofol of high purity, are not used directly in
the environment, they are used to make formulated products, which can be applied in
specific areas to control mites. The formulated product labels legally limit dicofol's
potential use to only those sites that are specified on the labels.
Currently registered agricultural and non-agricultural uses of dicofol within California
include: beans (dry, snap, and lima), citrus (specifically, grapefruit, kumquats, lemons,
limes, oranges, tangelos, and tangerines), cotton, cucurbits (specifically, cantaloupes,
cucumbers, melons, pumpkins, watermelons, and winter and summer squash), grapes,
hops, mint, pecans, peppers, pome fruits (specifically, apples, crabapples, pears, and
quince), stone fruits (specifically, apricots, sweet and sour cherries, nectarines, peaches,
plums, and prunes), strawberries, tomatoes, walnuts, Bermuda grass, turf/ornamental uses
(specifically, turf grasses, nursery stock, flowers, shade trees, woody shrubs and vines,
and sod farms) and outside building surfaces (non-agricultural). The model scenarios and
application input parameters for the uses included in this risk assessment are summarized
in Table 9.
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Table 9. Dicofol uses and application information for the CRLF risk assessment1.
Crop
Beans
(dry, green,
lima)
Citrus
Cotton
Cucurbits
Grapes
Hops
Mint
Pecans
Peppers
Pome fruits
Stone fruits
Uses
Represented
by Scenario
Grapefruit,
kumquats,
lemons,
limes,
oranges,
tangelos,
tangerines
Cantaloupes,
cucumbers,
melons,
pumpkins,
watermelons,
winter and
summer
squash
Mint,
peppermint,
spearmint
Apples,
crabapples,
pears, quince
Apricots,
sweet and
sour
cherries,
nectarines,
peaches,
plums,
prunes
PRZM/EXAMS
Scenario
CA row crop
RLF
CA citrus
CA cotton
CA melons RLF
CA wine grapes
RLF
OR hops
OR mint
CA almonds
CA row crop
RLF
CA fruit
CA fruit
Application
Rate
(Ibs
a.i./acre)
1.5
3
1.5
0.625
1.25
1.165
1.25
2
0.75
3
1.5
Number of
Applications
1
1
1
1
1
1
1
1
1
1
1
Application
Interval
Annually
Annually
Annually
Annually
Annually
Annually
Annually
Annually
Annually
Annually
Annually
Application
Method
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
55
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Crop
Strawberries
Tomatoes
Walnuts
Bermudagrass
Turf grasses
Sod farm turf
Ornamentals
Outside
building
surfaces
Uses
Represented
by Scenario
Nurseries,
ornamentals,
flowers,
shade trees
PRZM/EXAMS
Scenario
CA strawberries
(non-plastic)
CA tomato
CA almonds
CAturfRLF
CAturfRLF
CAturfRLF
CA nursery
CA impervious
RLF and CA
turf RLF
Application
Rate
(Ibs
a.i./acre)
2
0.75
2
0.4
0.5
0.5
0.5
0.5
Number of
Applications
1
1
1
1
1
1
1
1
Application
Interval
Annually
Annually
Annually
Annually
Annually
Annually
Annually
Annually
Application
Method
ULV,
Aerial,
ground
ULV,
Aerial,
ground
ULV,
Aerial,
ground
Ground
Ground
Ground
Ground
Ground
1. Uses assessed based on maximum label rates for registered dicofol products.
The labels for dicofol also specify that applications using ground equipment should not
be made within 25 feet, or by air within 150 feet, of lakes, reservoirs, rivers, permanent
streams, marshes, natural ponds, estuaries, or commercial fish farm ponds. The spray
drift buffer zone is 450 feet when ultra low volume application is made.
3.2. Aquatic Exposure Assessment
3.2.1. Modeling Approach
Aquatic exposures are quantitatively estimated for all of assessed uses using scenarios
that represent high exposure sites for dicofol use in California. Each of these sites
represents a 10-hectare field that drains into a 1-hectare pond that is 2 meters deep and
has no outlet. Exposure estimates generated using the standard pond are intended to
represent a wide variety of vulnerable water bodies that occur at the top of watersheds
including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural
ponds, and intermittent and first-order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the standard surrogate pond. Static water
bodies that have larger ratios of drainage area to water body volume would be expected
to have higher peak EECs than the standard pond. These water bodies will be either more
shallow or have larger drainage areas (or both). Shallow water bodies tend to have
limited storage capacity, and thus, tend to overflow and carry pesticide in their discharge
whereas the standard pond has no discharge. As watershed size increases beyond 10
hectares, at some point, it becomes unlikely that the entire watershed is planted to a
single crop and which is all concurrently treated with the pesticide. Headwater streams
56
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can also have peak concentrations higher than the standard pond, but these peaks in
pesticide concentrations tend to persist for only short periods of time and are then carried
downstream.
Crop-specific management practices for all of the assessed uses of dicofol were used for
modeling, including application rates, buffer widths and resulting spray drift values
modeled from AgDRIFT and the first application date for each crop. The date of first
application was developed based on several sources of information including data
provided by EPA/OPP/BEAD, a summary of individual applications from the CDPR
PUR data, and Crop Profiles maintained by the USDA. A sample of the distribution of
dicofol applications to cotton from the CDPR PUR data for 2004 used to pick an
application date is shown in Figure 8. More detail on the crop profiles and the previous
assessments may be found at: http://www.ipmcenters.org/CropProfiles/.
In defining the date of application, available CDPR PUR data were analyzed to determine
the time period when greater than 90% of applications took place. An initial first
application date was then selected from the month at the beginning of this range. Then,
the corresponding PRZM/EXAMS scenarios used in the modeling effort were examined
and dates for crop emergence, maturation, and harvest were evaluated. As mites usually
rely on leaves and fruit as food sources, the midpoint date between emergence and
maturation was estimated. If the crop scenario indicated that the crop was grown all year,
a date of January 15th was selected to result in a conservative EEC that would result from
increased rainfall experienced in California during the winter months. If the
PRZM/EXAMS midpoint date occurred within the time period of the CDPR PUR 90%,
then the PRZM/EXAMS midpoint date was used as the date of first application.
Otherwise, the initial CDPR PUR date was used. For example, according to the CDPR
PUR data, 90% of the dicofol use on cotton was between May and August, and May 3rd
was selected as the initial date of first application. In the PRZM/EXAMS scenario for
California cotton, crop emergence occurs on May 1st and crop maturation occurs on
September 20th, with a midpoint around July 11th. As this midpoint lies within the range
of the 90% data obtained from CDPR PUR, July 11th was selected as the first application
date for modeling purposes.
57
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4500
4000
Figure 8. Summary of applications of dicofol to cotton in 2004 from CDPR PUR data.
Once the separate PRZM/EXAMS runs for o,p'- and p,p'-dicofol are finished, the daily
EECs are summed to generate a total daily parent dicofol EEC. This was done to
facilitate comparison of the various EECs to the appropriate endpoints, which were based
on total dicofol. Average 21-day, 60-day, and annual EECs of these total daily dicofol
EECs were calculated. Maximum values were then estimated for each year and l-in-10
year return peak and rolling means for the 21-day, 60-day, and annual concentrations
were estimated for each scenario. The same analyses were conducted for the o,p'- and
p,p '-dicofol and degradate scenarios.
3.2.2. PRZM Scenarios
PRZM scenarios used to model aquatic exposures resulting from applications of specific
uses are identified in Table 9. In cases where a scenario does not exist for a specific use,
it is necessary to assign a surrogate scenario. Those surrogates are assigned to be most
representative of the use being considered. Justifications for assignments of surrogates
are defined below.
Row crop scenario
This scenario is intended to represent production of carrots, beans, peppers and other
crops in CA, and is therefore, directly relevant to these uses.
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Citrus scenario
This scenario is intended to represent applications of pesticides to oranges, grapefruit,
kumquats, lemons, limes, taneglos, and tangerines in CA and is therefore, directly
relevant to this use.
Cotton scenario
This scenario is intended to represent applications of pesticides to cotton in CA and is
therefore, directly relevant to this use.
Melon scenario
This scenario is intended to represent applications of pesticides to cantaloupes,
cucumbers, melons, pumpkins, watermelons, winter and summer squash in CA and is
therefore, directly relevant to this use.
Wine grapes scenario
From 2002 to 2007, CA PUR data indicate that dicofol was used mostly on grapes grown
for wine production, as opposed to grapes grown for consumption, in 31 counties. This
scenario is intended to represent applications of pesticides to wine grapes in CA and is
therefore, directly relevant to this use.
Hops
This scenario, developed based on a hops vineyard in the Pacific Northwest, represents a
vineyard located north of the area where hops are grown in CA Since the locations
where hops are grown in CA are mostly in the northern part of the state, this scenario was
deemed appropriate for modeling hops grown in CA.
Mint
According to NASS data, mint (grown for oil) has been grown in Lassen, Shasta and
Siskiyou Counties. These counties are located in northern CA, bordering OR. Although
this scenario represents a field located north of the area where mint is grown in CA, it
was developed based on a mint field in the Pacific Northwest. Since the locations where
mint is grown in CA are in the northern part of the state, this scenario was deemed
appropriate for modeling mint grown in CA.
Almond scenario
This scenario is intended to represent almond production in CA and is therefore, directly
relevant to this use. Walnuts and pecans are nut trees with similar practices and have been
assigned to this scenario.
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Fruit scenario
The CA fruit scenario represents a deciduous fruit tree orchard in Fresno County, which
is located in the Central Valley. This scenario is intended to represent non-citrus fruit,
including apples, crabapples, pears, quince, apricots, sweet and sour cherries, nectarines,
peaches, plums, and prunes.
Strawberry scenario
This scenario is intended to represent applications of pesticides to strawberries, non-
tarped, in CA. While the majority of strawberry growers use tarps, this scenario is
considered a conservative approach and is therefore, directly relevant to this use.
Tomato scenario
This scenario is intended to represent applications of pesticides to tomatoes in CA and is
therefore, directly relevant to this use.
Turf scenario
This scenario is intended to represent applications of pesticides to sod farms, parks,
recreational fields, grass for seed, and golf courses in CA and is therefore, directly
relevant to this use.
Nursery scenario
This scenario is intended to represent applications of pesticides in outdoor nurseries in
CA and is therefore, directly relevant to this use.
Outside buildings
Two scenarios were used to assess this use pattern: CA impervious and CA turf. The
label indicates that to control clover mites, "thoroughly spray the outside walls,
foundations, and windowsills and plants and lawn at the base of infested buildings." For
the 10-hectare scenario used in PRZM/EXAMS, it was assumed that a building was at the
center of each hectare. Each building was assumed to be a square measuring 15,000
square feet, with turf on three sides of the building and impervious surface on one side. It
was assumed a 10-foot swath was treated on the sides with turf and that the side with the
impervious surface would be treated up to a height of three feet along the building wall.
This results in approximately 3.75% of the watershed being treated. A detailed
description of the rationale for this value is provided in Appendix D.
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3.2.3. Model Inputs
The appropriate chemical-specific PRZM input parameters are selected from reviewed
environmental fate data submitted by the registrant (Table 3) and in accordance with
EFED water model input parameter selection guidance (U.S. EPA 2002). The input
parameters selected are similar to those used in the 1998 dicofol RED (U.S. EPA, 1998b).
A summary of the chemical specific model inputs used in this assessment are provided in
Table 10 and Table 11.
Table 10. Summary of PRZM/EXAMS environmental fate data used for aquatic exposure inputs for
o,p '-dicofol.1
Fate Property
Molecular Weight
Henry's constant
Vapor Pressure
Solubility in Water
Photolysis in Water
Aerobic Soil
Metabolism Half-
lives
Hydrolysis
Aerobic Aquatic
Metabolism
(water column)
Anaerobic Aquatic
Metabolism
(benthic)
Koc
Value (unit)
370.5 g/mole
1.44x 10~7atm-
nrVmol
3xlO'7 torr
1.32mg/L
27.5 days
25.5 days (parent)
313. 5 days (total)
3.3 x ID'1 days
51 days (parent)
627 days (total)
Od
7,060 mL/g
MRID (or source)
00141704; 00142595
00141704; 00142595
00141704; 00142595
40849702
41094201
40042033
~
~
41509802
Comment
Estimated using VP, MW
and solubility:
HLC=VPxMW/Sol
3x single value
Assumed: 2x aerobic soil
half-life
Assumed stable, no
reviewed data
<2.5% of parent found in
leachate. Used value
from p,p '-dicofol.
1 - Inputs determined
Parameters for Use in
2002
in accordance with EFED "Guidance for Chemistry and Management Practice Input
Modeling the Environmental Fate and Transport of Pesticides" dated February 28,
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Table 11. Summary of PRZM/EXAMS environmental fate data used for aquatic exposure inputs for
p,p '-dicofol.l
Fate Property
Molecular Weight
Henry's constant
Vapor Pressure
Solubility in Water
Photolysis in Water
Aerobic Soil
Metabolism Half-
lives
Hydrolysis
Aerobic Aquatic
Metabolism (water
column)
Anaerobic Aquatic
Metabolism
(benthic)
KOC
Value (unit)
370.5 g/mole
1.44 x 10~7 atm-
mVmol
3xlO"7 torr
1.32mg/L
244 days
96 days (parent)
939 days (total)
2.8 days
192 days (parent)
1,878 days (total)
Od
7060 mL/g
MRID (or source)
00141704; 00142595
00141704; 00142595
00141704; 00142595
40849701
41050701
40042032
41509801
Comment
Estimated using VP, MW
and solubility,
HLC=VPxMW/Sol
3x single value
2x aerobic soil half-life
Assumed stable, no
reviewed data
Average Koc
1 - Inputs determined
Parameters for Use in
2002
in accordance with EFED "Guidance for Chemistry and Management Practice Input
Modeling the Environmental Fate and Transport of Pesticides" dated February 28,
For p,p'-dicofol, a regression analysis between the Kd and organic carbon content values
indicated a high r-squared value (0.98) and statistical significance (<0.01). To assess the
appropriateness of the Koc model, a comparison of the coefficient of variation for the Koc.
(CV = 19) was compared to the coefficient of variation for Kd (CV = 58). Since the CV
for the Koc was less than the C V for Kd, the average Koc of 7060 mL/g was used (Kashuba
et al. 2006). For o,p'-dicofol, the majority of dicofol remained in upper 2 inches of soil
columns, with less than 2.5% of dicofol found in leachate. As a result, a Koc of 0 was
used during modeling.
As depicted in Table 3, the aerobic soil half-lives for the parent dicofol isomers were
significantly less than the half-lives estimated for the total residues of parent and
degradates of concern (8.5 vs. 104.5 days for o,/»'-dicofol and 32 vs 313 days for p,p'-
dicofol). As these values indicate a significant increase in persistence in the
environment, separate model runs were conducted for the parent isomers and the parent
plus degradate.
For the PRZM input "chemical application method" (CAM), a value of 2 was selected to
represent foliar applications. For aerial applications, using the 150-foot buffer zone
stipulated on the label, an application efficiency of 0.95 was derived using AgDrift, with
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a spray drift fraction of 0.039. For ground applications, using the 25-foot buffer zone
stipulated on the label, an application efficiency of 0.99 was derived using AgDrift, with
a spray drift fraction of 0.027. For ULV applications, using the 450-foot buffer zone
required on the label, an application efficiency of 0.727 was derived using AgDrift, with
a spray drift fraction of 0.109, for orchards (e.g., citrus, pome fruit, and stone fruit), and
an application efficiency of 0.72 was derived using AgDrift, with a spray drift fraction of
0.117, for other crops. It should be noted that if the buffer zone for ULV is not used,
spray drift fractions increase to 0.5 for both orchards and crops. Parameters used in the
derivation of the application efficiency and spray drift for ULV applications are discussed
further in Appendix P.
3.2.4. Model Results
The aquatic EECs for the various scenarios and application practices for the sum of the
o,p' andp,p' isomers of dicofol and for total dicofol (e.g., including degradates) are listed
in Table 12 and Table 13. Example PRZM/EXAMS outputs are available in Appendix E.
Table 12. Aquatic EECs (jig/L) for Dicofol Uses in California, Total o,p' and p,p' Isomers.
Crop/Application
Represented
Beans Aerial
Beans Ground
Beans ULV
Citrus Aerial
Citrus Ground
Citrus ULV
Cotton Aerial
Cotton Ground
Cotton ULV
Cucurbit Aerial
Cucurbit Ground
Cucurbit ULV
Grape Aerial
Grape Ground
Grape ULV
Hops Aerial
Hops Ground
Hops ULV
Mint Aerial
Mint Ground
Mint ULV
Pepper Aerial
Pepper Ground
Pepper ULV
Pome Fruit Aerial
Pome Fruit Ground
Application
Rate
(Ibs a.i./acre)
1.5
1.5
1.5
3.0
3.0
3.0
1.5
1.5
1.5
0.625
0.625
0.625
1.25
1.25
1.25
1.165
1.165
1.165
1.25
1.25
1.25
2.0
2.0
2.0
3.0
3.0
Date of First
Application
May-01
May-01
May-01
January- 15
January- 15
January- 15
July- 11
July- 11
July- 11
June-23
June-23
June-23
June-11
June- 11
June-11
May-31
May-31
May-31
June-04
June-04
June-04
May- 11
May- 11
May- 11
June-05
June-05
Scenario
CA row crop RLF
CA row crop RLF
CA row crop RLF
CA citrus
CA citrus
CA citrus
CA cotton irrig
CA cotton irrig
CA cotton irrig
CA melons RLF
CA melons RLF
CA melons RLF
CA wine grape
CA wine grape
CA wine grape
OR hops
OR hops
OR hops
OR mint
OR mint
OR mint
CA row crop RLF
CA row crop RLF
CA row crop RLF
CA fruit
CA fruit
Peak
EEC
3.24
2.25
9.72
6.44
4.46
17.97
3.44
2.46
9.87
1.34
0.93
4.03
2.69
1.86
8.06
2.51
1.74
7.54
2.69
1.86
8.05
1.61
1.12
4.83
6.44
4.46
21-day
average
EEC
0.46
0.32
1.38
0.97
0.69
2.58
0.65
0.52
1.52
0.19
0.13
0.57
0.39
0.27
1.15
0.38
0.27
1.09
0.39
0.27
1.15
0.23
0.16
0.69
0.91
0.63
60-day
average
EEC
0.18
0.12
0.53
0.42
0.31
1.03
0.29
0.25
0.60
0.07
0.05
0.21
0.15
0.10
0.44
0.17
0.13
0.43
0.16
0.11
0.44
0.09
0.06
0.26
0.34
0.24
63
-------
Crop/Application
Represented
Pome Fruit ULV
Stone Fruit Aerial
Stone Fruit Ground
Stone Fruit ULV
Strawberry Aerial
Strawberry Ground
Strawberry ULV
Tomato Aerial
Tomato Ground
Tomato ULV
Walnut/Pecan Aerial
Walnut/Pecan Ground
Walnut/Pecan ULV
Bermuda grass Ground
Ornamentals Ground
Turf/Sod Farm Ground
Outside Buildings
Application
Rate
(Ibs a.i./acre)
3.0
1.5
1.5
1.5
2.0
2.0
2.0
0.75
0.75
0.75
2.0
2.0
2.0
0.4
0.5
0.5
0.5
Date of First
Application
June-05
May-08
May-08
May-08
January- 15
January- 15
January- 15
June-07
June-07
June-07
June-08
June-08
June-08
January- 15
January- 15
January- 15
January- 15
Scenario
CA fruit
CA fruit
CA fruit
CA fruit
CA strawberry (nonplastic) RLF
CA strawberry (nonplastic) RLF
CA strawberry (nonplastic) RLF
CA tomato
CA tomato
CA tomato
CA almond
CA almond
CA almond
C A turf RLF
CA nursery
CA turf RLF
CA impervious RLF & CA turf RLF
Peak
EEC
17.97
3.24
2.24
9.05
6.09
5.97
13.10
1.61
1.12
4.83
4.38
3.07
12.97
0.60
1.77
0.75
0.15
21-day
average
EEC
2.55
0.46
0.32
1.29
1.71
1.57
2.67
0.23
0.16
0.69
0.67
0.48
1.87
0.10
0.39
0.13
0.025
60-day
average
EEC
0.96
0.18
0.12
0.48
0.92
0.87
1.22
0.09
0.06
0. |