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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
7
-------
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
-------
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
-------
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.
10
-------
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
11
-------
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
12
-------
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).
13
-------
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.
14
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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.
-------
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.
32
-------
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
-------
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
-------
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
-------
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
-------
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.
37
-------
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
-------
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
-------
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.
40
-------
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.
41
-------
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.
42
-------
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.
43
-------
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.
44
-------
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).
45
-------
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
46
-------
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
-------
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
-------
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
-------
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.
50
-------
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
-------
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
-------
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
-------
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.
54
-------
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
-------
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
-------
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
-------
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.
58
-------
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.
59
-------
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.
60
-------
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,
61
-------
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
62
-------
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
0.26
0.29
0.22
0.73
0.04
0.18
0.05
0.01
Table 13. Aquatic EECs (jig/L) for Dicofol, Parent and Degradate Uses in California.
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
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
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
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
Peak
EEC
20.55
18.09
36.51
21.64
16.49
55.15
22.86
20.46
38.84
7.81
6.78
14.82
15.39
13.33
29.15
22.70
21.03
33.88
18.81
17.12
32.57
10.29
9.05
21-day
average
EEC
18.42
16.58
30.74
17.89
13.93
44.58
21.17
19.39
33.25
7.01
6.23
12.44
13.81
12.22
24.37
21.27
20.11
29.41
17.62
16.05
27.83
9.23
8.32
60-day
average
EEC
17.76
16.11
28.77
16.61
13.13
40.99
20.52
18.93
31.31
6.74
6.01
11.63
13.26
11.84
22.74
20.47
19.45
27.99
16.81
15.52
26.26
8.90
8.09
64
-------
Crop/Application
Represented
Pepper ULV
Pome Fruit Aerial
Pome Fruit Ground
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)
2.0
3.0
3.0
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
May- 11
June-05
June-05
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 row crop RLF
CA fruit
CA fruit
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
18.21
24.32
18.69
57.34
12.06
9.20
28.73
42.51
41.13
59.64
7.72
6.38
16.54
25.28
21.88
47.75
2.66
7.16
3.31
0.38
21-day
average
EEC
15.34
20.57
16.08
46.74
10.17
7.91
23.40
39.77
37.81
52.07
6.77
5.72
13.70
22.82
20.20
40.25
2.31
6.48
2.87
0.31
60-day
average
EEC
14.37
19.26
15.18
43.13
9.50
7.44
21.57
39.11
37.41
50.05
6.44
5.49
12.73
21.99
19.64
37.70
2.21
6.29
2.74
0.29
3.2.5. Available Monitoring Data
A critical step in the process of characterizing EECs is comparing the modeled estimates
with available surface water monitoring data. Monitoring data for dicofol from the
USGS NAWQA program (http://water.usgs.gov/nawqa) were not available. Surface
water and sediment monitoring data from the California Department of Pesticide
Regulation (CDPR) were available and are considered in this assessment. No air
monitoring data were located.
Dicofol
A study was conducted in 1993 (Domagalski 1996) that assessed the levels of dicofol in
the San Joaquin River and its tributaries during the irrigation season. Water samples
were collected at 22 sites within the perennial reach of the San Joaquin River in the San
Joaquin Valley. All sampling locations were selected downstream of the confluence of
the San Joaquin River and the Salt Slough. All sites were sampled during two synoptic
surveys that occurred during March and August 1993. A subset of these sites was
sampled more frequently (twice-monthly or monthly) for the period of March through
September 1993. The sampling sites with the greatest frequency were the Central
California Irrigation District Canal, Orestimba Creek, the Spanish Grant Drain, and the
Salt Slough. From the study, it appears that 79 samples were collected from March to
September 1993. All samples collected between March and June of 1993 were below the
65
-------
level of detection (0.05 |ig/L). From June to September, 33 samples had levels of dicofol
above the detection limit, with the highest concentration of 2.5 |ig/L from a sample
collected at the Orestimba Creek site.
NAWQA monitoring data were not available for dicofol from California surface waters
(USGS 2008).
CDPR maintains a database of monitoring data of pesticides in CA surface waters. The
sampled water bodies include rivers, creeks, urban streams, agricultural drains, the San
Francisco Bay delta region and storm water runoff from urban areas. The database
contains data from 51 different studies by federal (including the USGS NAWQA
program), state and local agencies as well as groups from private industry and
environmental interests. Data are available from 1990-2006 for 46 counties for several
pesticides and their degradates. Data for dicofol are included in this database (CDPR
2008).
From 1990-2006, 618 samples from surface waters were analyzed for dicofol in the
CDPR database. Of these, dicofol was detected in 11 (1.8%) of the samples, with a
maximum concentration of 0.27 |ig/L. These samples included 131 different sites in 16
counties; including counties where CRLF core areas and critical habitat are located.
Dicofol was not reported in the sediment samples that were collected over this timeframe.
It should be noted that these results are not from targeted monitoring studies.
The Pesticides in Ground Water Data Base (U.S. EPA 1992) shows no detections of
dicofol in limited sampling in several States, including California, (1634 wells sampled
between 1979 and 1991).
Dicofol Degradates
NAWQA monitoring data were available for one degradate of dicofol, p,p'-DCBP.
Twenty samples of p,p'-DCBP were collected from 2003 to 2005, with a maximum
estimated concentration of 0.69 |ig/L (detection limit unknown). It should be noted that
the original source of the p,p '-DCBP detections (e.g., where the active ingredient came
from) is unknown, as p,p'-DCBP is also a degradate of chlorobenzilate, chloropropylate,
and DDT.
The CDPR database did not contain monitoring data of dicofol degradates in surface
water or sediment.
3.3. Aquatic Bioaccumulation Assessment
Available data on the octanol-water partition coefficient Kow = 1.15 x 106, (MRID
00141580) and bioconcentration factors (BCFs) for dicofol indicate that this pesticide
may accumulate in aquatic food webs. KABAM v.1.0 was used to estimate
concentrations of dicofol in tissues of aquatic organisms resulting from bioaccumulation.
Available empirical and modeling estimates of bioaccumulation of dicofol in aquatic
organisms are described below.
66
-------
3.3.1. Estimated BCF values
In order to estimate BCF values for aquatic organisms accumulating dicofol, KABAM
was run, using a Kow of 1.15 x 106 (log(Kow) = 6.06) to represent the partitioning of
dicofol to aquatic organisms. It was assumed that the concentration of dissolved oxygen
in water was 10 mg/L (near saturation) and the water temperature was 20°C. The body
characteristics of organisms in the model trophic levels are depicted in Table 14. The
resulting BCF values for these trophic levels are depicted in Table 15. Output files from
KABAM are provided in Appendix G.
Table 14. Characteristics of model aquatic organisms used to derive BCF values.
Trophic Level
phytoplankton
zooplankton
benthic invertebrates
filter feeders
small fish
medium fish
large fish
Wet Weight
(kg)
N/A
l.OE-07
l.OE-04
l.OE-03
l.OE-02
l.OE-01
l.OE+00
%
lipids
2.0%
3.0%
3.0%
2.0%
4.0%
4.0%
4.0%
% Non-lipid
organic matter
8.0%
12.0%
21.0%
13.0%
23.0%
23.0%
23.0%
% Water
90.0%
85.0%
76.0%
85.0%
73.0%
73.0%
73.0%
Table 15. Estimated BCF values for parent dicofol in aquatic organisms.
Trophic Level
Phytoplankton
Zooplankton
Benthic Invertebrates
Filter Feeders
Small Fish
Medium Fish
Large Fish
Total BCF
(jig/kg-ww)/(jig/L)
55,112
39,268
42,884
28,188
55,170
55,170
55,170
3.3.2. Empirical BCF data
In a 28-day laboratory BCF study with bluegill sunfish (Lepomis macrochirus) exposed
to p,p -dicofol, a BCF of 10,000 was observed in whole fish. In this study, steady state
was not reached. The estimated steady-state BCF for dicofol was 25,000, which is within
a factor of 2.2 of the estimated BCF for fish (Table 15). In this study, parent dicofol
represented >94% of the radioactivity measured after the 28-day exposure, suggesting
that metabolism of dicofol was minimal. FW-152 and OH-DCBH were detected in tissue
samples, each comprising as much as 4.7% of the overall radioactivity measured at the
time (MRID 265330).
In an early life stage test with the aquatic invertebrate, Hyalella azteca and the fathead
minnow (Pimephalespromelas), mean 28-day BCF values of 10,000 (±3000) and 3,700
67
-------
(±800), respectively, were observed (GS0021-017). As the duration of this study was
insufficient to allow the test organisms to reach steady-state, it is expected that if the
duration had been extended, observed BCF values would have increased.
In a full life cycle test with the fathead minnow, the highest observed BCF value was
43,000, which was observed in F0 females after 296 days of exposure to dicofol (MRID
42628901). This value is within a factor of 1.3 of estimated BCF value for fish (i.e.,
55,000).
3.3.3. Bioaccumulation modeling
KABAM was run in default mode (see user's guide for full description), with a Log Kow
= 6.06, a KOC = 7060 L/kg-oc (see Table 10) and surface water and pore water EECs of
0.26 and 0.066 ug/L, respectively. These PRZM/EXAMS-generated EECs are based on
the average of yearly average concentrations of dicofol parent from ULV dicofol
applications to strawberries. These EECs were selected because they represent the
highest annual EECs predicted for any use of dicofol and result in the highest predicted
accumulation of dicofol in tissues of aquatic organisms. The average water temperature
(13°C) for this scenario was used to simulate the water temperature of the abiotic
compartment of KABAM. It was assumed that metabolism of dicofol by aquatic
organisms did not occur. This assumption is supported by the available BCF study with
p,p -dicofol, where parent dicofol represented >94% of the radioactivity measured after
the 28-day exposure and metabolism was minimal (MRID 265330). The resulting
concentrations of dicofol in tissues of aquatic organisms are provided in Table 16. Output
files from KABAM are provided in Appendix G. These values are used to derive RQs
based on dose-based and dietary-based exposures of aquatic-phase CRLF to dicofol
through consumption of contaminated aquatic prey (See section 5.1).
Table 16. Concentrations of dicofol parent in tissues of aquatic organisms (estimated using KABAM).
Trophic level
Phytoplankton
Zooplankton
Benthic Invertebrates
Filter Feeders
Small Fish
Medium Fish
Large Fish
Total concentration (jig/kg-ww)
10,559
11,838
15,191
10,301
39,027
82,949
290,605
KABAM's predictions of bioaccumulation in aquatic systems are most sensitive to the
Kow value of the assessed pesticide, with accumulation increasing as the Kow increases.
No empirical data were available to define the Kow values of dicofol's residues of
concern, so EPISuite v.4.0 was used to estimate Kow values for the 4 degradates of
concern (Table 17). Review of the estimated Kow values of dicofol's residues of concern
indicates that dicofol transforms to residues that have lower Kow values, and thus lower
68
-------
accumulation potential in aquatic organisms. KABAM was used to estimate the
bioaccumulation of dicofol's total residues of concern, by considering PRZM/EXAMS
generated aquatic EECs for total residues and the Log Kow values of dicofol's degradates
of concern. KABAM was run again in default mode (see user's guide for full
description), with Log Kow = 3.96, 4.0, 4.44, 4.89, and 6.06 (measured), to represent the
partitioning of OH-DCBP, DCBH, DCBP, FW-152 and dicofol, respectively in aquatic
organisms. A Koc = 7060 L/kg-oc (see Table 10) and surface water and pore water EECs
of 41 and 17 ug/L, respectively. These EECs are based on the average of yearly average
concentrations of dicofol parent derived from ULV applications of dicofol to
strawberries, as modeled using PRZM/EXAMS. As discussed earlier, these EECs were
selected because they represent the highest annual EECs predicted for any use of dicofol
and result in the highest predicted accumulation of dicofol in tissues of aquatic
organisms. The resulting concentrations of dicofol in tissues of aquatic organisms are
provided in Table 18. Output files from KABAM are provided in Appendix G. In
reality, dicofol and its residues of concern would be subject to uptake by aquatic
organisms. Therefore, the overall bioaccumulation of dicofol's total residues would be a
mixture of dicofol and its 4 residues and would therefore fall between the tissue residue
concentrations estimated for OH-DCBP and dicofol that are provided in Table 18.
Table 17. Estimated Log Kow values of dicofol's residues of concern.
Chemical
Dicofol
DCBP
FW-152
DCBH
OH-DCBP
LogK^*
5.81
4.44
4.89
4.00
3.96
*Estimated using EPISuite v.4.0.
Table 18. Concentrations of dicofol total residues of concern in tissues of aquatic organisms (jig/kg-
ww; estimated using KABAM). Concentrations were estimated using Log Kow values representative
of the different dicofol residues of concern.
Trophic level
Phytoplankton
Zooplankton
Benthic Invertebrates
Filter Feeders
Small Fish
Medium Fish
Large Fish
Log Kow =
3.96
(OH-DCBP)
.7E+04
.3E+04
.4E+04
9.0E+03
.8E+04
.8E+04
.9E+04
Log Kow =
4.00
(DCBH)
1.9E+04
1.4E+04
1.5E+04
9.9E+03
2.0E+04
2.0E+04
2.1E+04
Log Kow =
4.44
(DCBP)
5.2E+04
3.9E+04
4.2E+04
2.7E+04
5.5E+04
5.8E+04
6.4E+04
Log Kow =
4.89
(FW-152)
1.5E+05
1.1E+05
1.2E+05
7.9E+04
1.7E+05
1.9E+05
2.4E+05
Log Kow =
6.06
(dicofol)
1.7E+06
1.9E+06
2.4E+06
1.6E+06
6.2E+06
1.3E+07
4.6E+07
69
-------
3.4. Terrestrial Animal Exposure Assessment
3.4.1. Modeling Approach
T-REX (Version 1.4.1) is used to calculate dietary and dose-based EECs of dicofol for
the CRLF and its potential prey (e.g. small mammals and terrestrial insects) inhabiting
terrestrial areas. EECs used to represent the CRLF are also used to represent exposure
values for frogs serving as potential prey of CRLF adults. T-REX simulates a 1-year time
period.
Terrestrial EECs for dicofol were derived for the uses and corresponding application rates
summarized in Table 19. According to dicofol labels, only 1 application of dicofol is
allowed per year on any one field, so only 1 application per year was modeled for each
use. One foliar dissipation half-life value specific to dicofol (6 days based on application
to alfalfa in CA) is available in Willis and McDowell (1987). Because a single half-life
value is insufficient to derive a foliar dissipation half-life specific to dicofol, the EFED
default foliar dissipation half-life of 35 days is used based on the work of Willis and
McDowell (1987). This value falls within the range of observed dissipation half-lives for
dicofol measured in 3 studies (9-61 days, see section 3.4.1 below). The maximum
application rate for each use is modeled in T-REX and upper bound EECs are used for
RQ calculations. An example output from T-REX is available in Appendix H.
Table 19. Input parameters to T-REX used to generate dicofol EECs for terrestrial animals.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms, Outside building
surfaces
Bermuda grass
Application Rate
(Ibs a.i./A)
3
2
1.5
1.25
1.165
0.75
0.625
0.5
0.4
1 grapefruit, lemons, oranges, tangelos, and tangerines
, , , ,
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
For modeling purposes, exposures of the CRLF, as well as other frog species serving as
prey to the CRLF, to dicofol through contaminated food are estimated using the EECs for
70
-------
the small bird (20 g) which consumes small insects. Dietary-based and dose-based
exposures of potential prey are assessed using the small mammal (15 g) which consumes
short grass. Upper-bound Kenega nomogram values reported by T-REX for these two
organism types are used for derivation of EECs for the CRLF and its potential prey
(Table 20).
As indicated above, T-REX is also used to calculate EECs for terrestrial insects exposed
to dicofol. Dietary-based EECs calculated by T-REX for small and large insects (units of
jig a.i./g) are used to bound an estimate of exposure to terrestrial insects. Available acute
contact toxicity data for bees exposed to dicofol (in units of jig a.i./bee), are converted to
jig a.i./g (of bee) by multiplying by 1 bee/0.128 g. Dietary-based EECs for terrestrial
insects are later compared to the adjusted acute contact toxicity data for bees in order to
derive RQs. Dietary-based EECs for small and large insects reported by T-REX as well
as the resulting adjusted EECs are available in
71
-------
Table 21.
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.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts
(English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses,
Sod farms, Outside building
surfaces
Bermuda grass
EECs for CRLF
Dietary-based
EEC (ppm)
405
270
203
168
157
101
84.4
67.5
54.0
Dose-based EEC
(mg/kg-bw)
461
308
231
192
179
115
96.1
76.9
61.5
EECs for Prey
(small mammals)
Dietary-based
EEC (ppm)
720
480
360
300
281
180
150
120
96.0
Dose-based EEC
(mg/kg-bw)
686
458
343
286
267
172
143
114
91.5
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
72
-------
Table 21. Dicofol EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Terrestrial Invertebrate Prey Items.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts
(English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod
farms, Outside building surfaces
Bermuda grass
Small Insect EEC
405
270
203
169
157
101
84.4
67.5
54.0
Large Insect EEC
45.0
30.0
22.5
18.8
17.5
11.3
9.38
7.50
6.00
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
3.4.1. Field Studies
Comprehensive ecological monitoring studies of dicofol residues were conducted for
three years in California cotton fields (1990-92; MRIDs 41785102, 41857301, and
42285503), Florida citrus groves (1989-91; MRIDs 41785103, 41845605, 42091501, and
42437301), and New York apples orchards (1989-91; MRIDs 41845604, 42285501, and
42721301). Areas and crops selected had a previous history of heavy dicofol use and a
high likelihood for exposure to non-target organisms. Application rates typified those
most commonly used by the growers and not necessarily the maximum label rates.
Observed residue concentrations were variable and declined exponentially after
application. The highest mean concentrations were typically found immediately
following application on the treated area, usually on the treated crop foliage, except for
the Florida citrus site. Residues of p,p'-dicofol on the non-crop area were typically 1 to 2
orders of magnitude below those found in the crop areas. In the crop areas, the highest
mean concentration of p,p'-dicofol measured were 97 ppm for foliage (New York), 78
ppm on grass (Florida) and 0.56 ppm for soil (New York). The highest mean
concentration of p,p -dicofol measured in the abiotic matrices for the non-crop area were
9.7 ppm for grass (Florida), 5.9 ppm on foliage (Florida), and 0.1 ppm for soil (California
and Florida). Foliage residues in the crop areas declined from 3-year means of 92, 97 and
74 ppm immediately after application, to 0.05, 16 and 24 ppm 90 days later for cotton,
orchards, and citrus, respectively. Foliage residues in non-crop areas declined from 3-
year means of 0.6, 5.2, and 5.9 ppm immediately after application to 0.09, 0.9, and 0.55
ppm after 90 days for cotton, orchards, and citrus, respectively. Mean grass residues
declined from 0.47, 5.1, and 9.7 ppm immediately after application, to 0.04, 0.08, and
0.54 ppm 90 days later for cotton, orchards, and citrus, respectively.
73
-------
Residues of p,p -dicofol were detected in the foliage of crops and dissipated with a half-
life ranging of 9, 41, and 61 days for cotton, orchard, and citrus foliage respectively.
Grass residues declined from 3-year means of 48 and 78 ppm immediately after
application, to 0.15 and 2.3 ppm 90 days later for orchards and citrus, respectively.
Dissipation half-lives of p,p'-dicofol on orchard and citrus grass were 12 and 21 days,
respectively. The observed foliar dissipation half-lives for dicofol are comparable to the
35-day default value used to represent the foliar dissipation half-life of dicofol in the T-
REX model.
3.5. Accumulation of Dicofol Residues on Soil
Because dicofol and its degradates are moderately persistent in soil (aerobic soil half-
lives greater than 104 days) and do not have a tendency to leach from soil, a screening
analysis was conducted to characterize the levels of dicofol in the soil of a treated site
after 30 years of applications.
Ground application to pome fruits was selected for the screening analysis, as it was
expected to result in highest soil concentrations of dicofol compared to any other use
(based on the highest application rate and application efficiency). Aerial application to
strawberries was selected for the screening analysis, as this scenario produced the highest
levels of EECs in the aquatic exposure assessment. PRZM/EXAMS runs were conducted
and total soil concentrations were estimated for the upper 10 cm soil horizon. As with
the aquatic exposure assessment, both the o,p'- and p,p' isomers of dicofol were run
separately and the results combined in a postprocessor. The 1-in-10-year peak
concentrations in the soil for total dicofol were 11,952 and 7,770 mg/m3 for pome fruits
and strawberries, respectively. The l-in-10- year peak concentrations in the pore water
for total dicofol were 176 and 115 mg/m3 for pome fruits and strawberries, respectively.
Annual average peak dicofol soil concentrations increased for the first fifteen years of the
simulation, then reached a plateau at an average annual peak concentration in the soil at
10,170 and 6,600 mg/m3 for pome fruits and strawberries, respectively, and in the pore
water at 150 and 98 mg/m3 for pome fruits and strawberries, respectively (Figure 9 and
Figure 10).
74
-------
Peak Dicofol Concentrations in Soil Over Time
14000
2000
4000
6000
8000
10000
12000
Pome Fruit, Ground App Strawberry, Aerial App
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.
Peak Dicofol Concentrations in Pore Water Over Time
200
180
2000
4000
6000
8000
10000
12000
— Pome Fruit, Ground App — Strawberry, Aerial App
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
-------
3.6. Terrestrial Bioaccumulation Assessment
The estimated octanol-air partition coefficient (K.QA) of 1010 (EPIsuite v.4.0) suggests that
bioaccumulation of dicofol in air breathing organisms is possible (Kelly et al. 2007). At
this time, modeling tools are unavailable to quantify the bioaccumulation of dicofol in
terrestrial organisms. However, relevant monitoring studies involving dicofol have been
conducted.
Comprehensive ecological monitoring studies of dicofol residues were conducted for
three years in California cotton fields (1990-92; MRIDs 41785102, 41857301, and
42285503), Florida citrus groves (1989-91; (MRIDs 41785103, 41845605, 42091501,
and 42437301), and New York apples orchards (1989-91; (MRIDs 41845604, 42285501,
and 42721301). Areas and crops selected had a previous history of heavy dicofol use and
a high likelihood for exposure to non-target organisms. Application rates typified those
most commonly used by the growers and not necessarily the maximum label rates.
Dicofol residues were monitored in soil, plant foliage, fish, mammals, reptiles,
amphibians, earthworms, birds, and bird eggs.
In crop areas, the highest mean concentrations of p,p'-dicofol measured in the biotic
matrices were 1.4 ppm for small mammals (Florida), 3.9 ppm for terrestrial invertebrates
(California), and 3.8 ppm for reptiles/amphibians (Florida). In non-crop areas, highest
mean concentrations were 0.3 ppm for small mammals (New York), 0.76 ppm for
terrestrial invertebrates (Florida), 0.38 ppm for reptiles/amphibians (Florida), 0.9 ppm for
birds (Florida), and 0.26 ppm for fish (Florida). Dicofol was found at a concentration of
1-2 ppm in earthworms in New York.
Eggs were collected from thirteen avian species and were analyzed for residues and
eggshell thickness (MRIDs 41764801, 41764802, 41845601, 41845602, 41845603,
42285501, 42285505, and 42721302). These data were compared with the nesting
success for these species. Yearly geometric mean p,p'-dicofol residues ranged from
0.0027 ppm (several species in California) to 0.46 ppm (American robin eggs in New
York). Yearly means were highest in New York (0.01-0.46 ppm), and lowest in
California (,//-FW152
concentrations in the eastern screech owl in Florida, geometric mean metabolite residue
concentrations were generally lower than for p,p'-dicofol. None of the yearly geometric
means for dicofol,/>,//-FW152, or/?,/?'-DCBP exceeded 0.5 ppm.
76
-------
4.0 Effects Assessment
This assessment evaluates the potential for dicofol to directly or indirectly affect the
CRLF or modify its designated critical habitat. As discussed in Section 2.7, assessment
endpoints for the CRLF effects determination include direct toxic effects on the survival,
reproduction, and growth of CRLF, as well as indirect effects, such as reduction of the
prey base or effects to its habitat. In addition, potential effects to critical habitat is
assessed by evaluating effects to the PCEs, which are components of the critical habitat
areas that provide essential life cycle needs of the CRLF. Direct effects to the aquatic-
phase of the CRLF are based on toxicity information for freshwater fish, while terrestrial-
phase effects are based on avian toxicity data, given that birds are generally used as a
surrogate for terrestrial-phase amphibians. Because the frog's prey items and habitat
requirements are dependent on the availability of freshwater fish and invertebrates, small
mammals, terrestrial invertebrates, and aquatic and terrestrial plants, toxicity information
for these taxa are also discussed. Acute (short-term) and chronic (long-term) toxicity
information is characterized based on registrant-submitted studies and a comprehensive
review of the open literature on dicofol.
As described in the Agency's Overview Document (U.S. EPA 2004), the most sensitive
endpoint for each taxon is used for risk estimation. For this assessment, evaluated taxa
include aquatic-phase amphibians, freshwater fish, freshwater invertebrates, aquatic
plants, birds (surrogate for terrestrial-phase amphibians), mammals, terrestrial
invertebrates, and terrestrial plants.
Toxicity endpoints are established based on data generated from guideline studies
submitted by the registrant, and from open literature studies that meet the criteria for
inclusion into the ECOTOX database maintained by EPA/Office of Research and
Development (ORD) (U.S. EPA 2004). In order to be included in the ECOTOX
database, papers must meet the following minimum criteria:
o the toxic effects are related to single chemical exposure;6
o the toxic effects are on an aquatic or terrestrial plant or animal species;
o there is a biological effect on live, whole organisms;
o a concurrent environmental chemical concentration/dose or application rate is
reported; and
o there is an explicit duration of exposure.
Data that pass the ECOTOX screen are evaluated along with the registrant-submitted
data, and may be incorporated qualitatively or quantitatively into this endangered species
assessment. In general, effects data in the open literature that are more conservative than
the registrant-submitted data are considered. The degree to which open literature data are
quantitatively or qualitatively characterized for the effects determination is dependent on
whether the information is relevant to the assessment endpoints (i.e., maintenance of
6 The studies that have information on mixtures are listed in the bibliography as rejected due to the
presence of mixtures. These studies are evaluated by EFED when applicable to the assessment; however,
the data is not used quantitatively in the assessment.
77
-------
CRLF survival, reproduction, and growth) identified in Section 2.8. For example,
endpoints such as behavior modifications are likely to be qualitatively evaluated, because
quantitative relationships between modifications and reduction in species survival,
reproduction, and/or growth are not available. Although the effects determination relies
on endpoints that are relevant to the assessment endpoints of survival, growth, or
reproduction, it is important to note that the full suite of sublethal endpoints potentially
available in the effects literature (regardless of their significance to the assessment
endpoints) are considered to define the action area for dicofol.
Toxicity data for dicofol available in the ECOTOX database on 10/31/08 were considered
for this assessment. Citations of all open literature not considered as part of this
assessment because they were either rejected by the ECOTOX screen or accepted by
ECOTOX but not used (e.g., the endpoint is less sensitive) are included in Appendix I.
Appendix I also includes a rationale for rejection of those studies that did not pass the
ECOTOX screen and those that were not evaluated as part of this endangered species risk
assessment. A detailed spreadsheet of the available accepted ECOTOX open literature
data, including the full suite of lethal and sublethal endpoints is presented in Appendix J.
Appendix K includes a summary of the human health effects data for dicofol.
In addition to registrant-submitted and open literature toxicity information, other sources
of information, including use of the acute probit dose response relationship to establish
the probability of an individual effect and reviews of the Ecological Incident Information
System (EIIS), are conducted to further refine the characterization of potential ecological
effects associated with exposure to dicofol. A summary of the available incident
information for dicofol is provided below.
It should be noted that where data were provided in study reports, sublethal effects
observed during acute toxicity studies are described in this effects characterization.
These sublethal effects raise concern about the effects of dicofol; however, it is not
possible to quantitatively link these effects to the selected assessment endpoints for the
listed CRLF (i.e., survival, growth, and reproduction of individuals and maintenance of
critical habitat PCEs). Therefore, potential sublethal effects on specific taxa are
evaluated qualitatively. Definitive endpoints, such as LCsoS are used for quantifying
RQs in this assessment.
4.1. Toxicity of dicofol to aquatic organisms
Table 22 summarizes the most sensitive aquatic toxicity endpoints for the CRLF, based
on an evaluation of the available studies as previously discussed. Toxicity to aquatic fish
and invertebrates is categorized using the system shown in Table 23 (U.S. EPA 2004).
78
-------
Table 22. Freshwater toxicity profile for dicofol.
Assessment Endpoint
Acute Direct Toxicity to
Aquatic -Phase CRLF
Chronic Direct Toxicity to
Aquatic-Phase CRLF
Indirect Toxicity to
Aquatic -Phase CRLF via
Acute Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Indirect Toxicity to
Aquatic-Phase CRLF via
Chronic Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Indirect Toxicity to
Aquatic -Phase CRLF via
Toxicity to Non-vascular
Aquatic Plants
Indirect Toxicity to
Aquatic -Phase CRLF via
Toxicity to Vascular
Aquatic Plants
Species
Oncorhynchus clarkii
(cutthroat trout)
Oncorhynchus mykiss
(rainbow trout)
Daphnia magna
(waterflea)
Hyalella azteca
(amphipod)
Scenedesmus acutus
(green alga)
Toxicity
Value Used in
Risk
Assessment
LC50 = 53.0
ug/L
NOAEC = 4.4
ug a.i./L
EC50 = 140
ug/L
NOAEC = 19
ug a.i./L
EC50 > 5,000,
<10,000 ug/L
Source
(MRID)
40098001
42063001
40042057
GS0021-
016
Krishnaku
mari 1977
Comment
Slope not available
LOAEC = 7.9 ug
a.i./L based on
decreased length
Slope not available
28-day LOAEC =
33 ug a.i./L, based
on decreased
survival
Effects to biomass
and growth
observed
No data are available to quantity an endpoint to represent effects of dicofol
exposures to vascular plants.
Table 23. Categories of acute toxicity for aquatic organisms.
LC50 (mg/L)
<0.1
>0.1-1
>1-10
> 10 - 100
>100
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically nontoxic
4.1.1. Toxicity of Dicofol to Freshwater Fish
Given that dicofol toxicity data are not available for aquatic-phase amphibians,
freshwater fish data are used as a surrogate to estimate direct acute and chronic risks to
the CRLF. Freshwater fish toxicity data are also used to assess potential indirect effects
of dicofol to the CRLF. Effects to freshwater fish resulting from exposure to dicofol
could indirectly affect the CRLF via reduction in available food. As discussed in Section
2.5.3, over 50% of the prey mass of the CRLF may consist of vertebrates such as mice,
frogs, and fish (Hayes and Tennant 1985).
Available acute toxicity data for freshwater fish exposed to dicofol include 96-h
values ranging 53-603 jig /L (Table 24). Therefore, dicofol is classified (Table 23) as
79
-------
very highly to highly toxic to freshwater fish on an acute exposure basis. The most
sensitive freshwater species tested is cutthroat trout, with a 96-hour LCso value of 53
|ig/L (MRID: 400980-01), is used for deriving risk quotients for the CRLF and fish
serving as prey to the adult CRLF.
Table 24. Acute toxicity data (96-h LCSO) for freshwater fish exposed to dicofol.
Species (common name)
Oncorhynchus clarkii (cutthroat trout)
O. clarkia (cutthroat trout)
O. clarkii (cutthroat trout)
Salvelinus namaycush (lake trout)
S. namaycush (lake trout)
O. mykiss (rainbow trout)
Ictalurus punctatus (channel catfish)
Micropterus salmoides (largemouth bass)
Pimephales promelas (fathead minnow)
Lepomis macrochirus (bluegill sunfish)
Lepomis macrochirus (bluegill sunfish)
Pimephales promelas (fathead minnow)
LCSO value
(Hg/L)
53.0
158
53.1
86.9
87
124.3
360
395
509
510
520
603
95%
confidence
interval
(Hg/L)
41-68
100-250
41.3-68.2
53.1-142.0
53-142
95.0-181.0
290-447
NA
492-533
420-640
421-642
577-631
Slope
NA
NA
15.6
NA
3.8
10.8
NA
12.2
10.3
NA
NA
Source (MRID)
40098001
40098001
GS0021002
GS0021001
40098001
41695401
40098001
40098001
GS0021018
GS0021004
40098001
ECOTOX # 12859
NA = not available
Several chronic studies are available where freshwater fish were exposed to dicofol
(Table 25). Available chronic studies for rainbow trout (Oncorhynchus mykiss) and
fathead minnows (Pimephales promelas) are described below. From these studies, the
most sensitive chronic endpoint, based on decreased growth, is a 95-day NOAEC value
of 4.4 |ig/L (MRID: 42063001). This value is used for deriving risk quotients for the
CRLF and fish serving as prey to the adult CRLF.
Table 25. Chronic toxicity data for freshwater fish exposed to dicofol.
Species (common name)
Oncorhynchus mykiss
(rainbow trout)
Oncorhynchus mykiss
(rainbow trout)
Pimephales promelas
(fathead minnow)
Pimephales promelas
(fathead minnow)
Duration of
Study (days)
95
99
296
28
NOAEC Qig/L)
4.4
4.6
4.52
19
LOAEC
(Hg/L)
7.9
9.1
8.82
39
Observed
Effects
Decreased
length
Decreased
length
Impacted
reproduction
Decreased
survival and
growth
Source
(MRID)
42063001
43383902
42628901
GS0021-016
In an early life stage test with rainbow trout, growth (length) was significantly reduced
(4.8% compared to controls) in fish (at 35-days post-hatch) exposed to concentrations of
7.9 (±1.0) |ig a.i./L. The resulting NOAEC for this study was 4.4 |ig a.i./L (MRIDs
80
-------
42063001). In an additional early life stage test conducted with rainbow trout resulted in
reduced growth (length was decreased 4.8% compared to controls) of fish (36-day old)
exposed to 9.1 jig a.i./L dicofol. The resulting NOAEC for this study was 4.6 jig a.i./L
(MRID 43383902).
In an early life stage test with fathead minnows, survival and growth were significantly
decreased in fish exposed to concentrations of 39 (±6.3) jig a.i./L for 28 days. The
resulting NOAEC for this study was 19 (±3.8) |ig a.i./L (GS0021-016). In a full life
cycle study (296 days) with the fathead minnow, mean hatching success of the FI
generation was significantly decreased at 8.82 jig a.i./L treatment compared to controls
(13% decrease). Also, significant effects to reproduction were observed in the FO
generation exposed to 8.82 jig a.i./L, including decreased number of eggs/pair, decreased
number of spawns per mating pair and decreased number of reproductive days per mating
pair. The resulting NOAEC for this study was 4.52 |ig a.i./L (MRID 42628901).
4.1.2. Toxicity of Dicofol to Freshwater Invertebrates
Dicofol is classified highly toxic to freshwater invertebrates, based on an acute toxicity
study with Daphnia magna (MRID 40042057), where an ECso of 140 |ig/L was observed.
Chronic toxicity data are available for the amphipod, Hyalella azteca. The NOAEC for
this study was 19 (±2.2) jig a.i./L, based on a decrease in survival (70% mortality,
compared to 0% in controls) in animals exposed to 33 (±2.2) jig a.i./L for 28 days
(GS0021-016).
4.1.3. Toxicity of Dicofol to Aquatic Plants
Data are available from the scientific literature involving exposures of dicofol to the
green alga, Scenedesmus acutus. Based on observed decreases in biomass and growth
rates, the ECso is estimated to lie between 5,000 and 10,000 |ig/L (Krishnakumari 1977).
No data are available involving exposures of aquatic vascular plants to dicofol.
4.2. Toxicity of Dicofol's Degradates to Aquatic Organisms
4.2.1. Toxicity of Dicofol's Degradates to Aquatic Animals
Empirical data are not available for exposure of aquatic animals to dicofol's major
degradates (DCBP, FW-152, DCBH, OH-DCBP and CBA). In order to characterize the
relative toxicity of dicofol and its major degradates, ECOSAR v. 1.0 (USEPA 2009) was
run to estimate acute LCso and chronic toxicity values for fish and aquatic invertebrates.
ECOSAR predicted acute and chronic values for the parent and degradates are not used
quantitatively in this risk assessment (i.e., to derive RQ values for the degradates), but
rather to compare the relative toxicitites of dicofol and its major environmental
81
-------
degradates. ECOSAR estimates of acute and chronic toxicity for fish and daphnids
indicate that DCBP, FW-152, DCBH and OH-DCBP are similar (i.e., estimated LC50 and
chronic values are within an order of magnitude) to that of dicofol. ECOSAR estimates
indicate that CBA may be of lesser toxicity than dicofol, with estimated LC50 and chronic
values for CBA being several orders of magnitude greater than dicofol (Table 26).
Table 26. Estimated acute and chronic toxicity values (jig/L) for fish and daphnids exposed to dicofol
and its degradates (as calculated by ECOSAR).
Chemical
Dicofol1
DCBP2
FW-1521
DCBH1
OH-DCBP3
CBA2
Fish
96-h LCSO
274
1391
1027
3037
1472
844098
Fish
chronic value
9
171
40
139
8
88987
Daphnid
48-h LCSO
8
1124
50
242
1088
488560
Daphnid
chronic value
21
192
79
231
206
58244
Benzyl alcohol class
2Neutral organic class
3Phenols class
Ninety-six hour LCso values for fish exposed to dicofol range 53-603 |ig/L. The
ECOSAR estimated value of 274 jig/L falls within this range. The ECOSAR estimated
chronic value of 9 jig /L also falls within the range of available NOAECs 4.4-19 jig/L for
fish exposed to dicofol. For aquatic invertebrates, the ECOSAR estimated acute value is
2 orders of magnitude lower than the available empirical ECso value (48-h ECso =140
In this risk assessment, the total residues of concern for aquatic environments are defined
as: dicofol, DCBP, FW-152, DCBH and OH-DCBP. Because the estimated acute and
chronic toxicity of CBA is several orders of magnitude less than that of dicofol and the
other degradates, CBA is not considered to be a degradate of concern. It is assumed in
this assessment that for aquatic animals, total residues are of equal toxicity compared to
the parent. The acute toxicity data used to represent the toxicity of the total residues of
dicofol to aquatic animals are selected based on the most sensitive values available for
dicofol exposures. Chronic toxicity data available for exposures of freshwater fish and
invertebrates exposed to dicofol are also used to represent the chronic toxicity of the total
residues to these organisms.
4.2.2. Toxicity of Dicofol' s Degradates to Aquatic Plants
Data are available from the scientific literature involving separate exposures of DCBP
and DCBH to the green alga, Chlorella vulgaris. At concentrations of 1000 |ig/L,
decreases in chlorophyll a and biomass were not observed compared to controls. At
10,000 ng/L, decreases in chlorophyll a and biomass were observed (Subba-Rao and
Alexander 1980).
82
-------
No data are available involving exposures of aquatic vascular plants to dicofol's major
degradates.
4.3. Toxicity of dicofol to terrestrial organisms
Table 27 summarizes the most sensitive terrestrial toxicity endpoints for the CRLF, based
on an evaluation of registrant submitted studies and the scientific literature. Acute
toxicity to terrestrial animals is categorized using the classification system shown in
Table 28 (U.S. EPA 2004). Toxicity categories for terrestrial plants have not been
defined.
Table 27. Terrestrial toxicity profile for dicofol.
Endpoint
Acute Direct Toxicity to
Terrestrial-Phase CRLF
Subacute Direct Toxicity to
Terrestrial-Phase CRLF
Chronic Direct Toxicity to
Terrestrial-Phase CRLF
Indirect Toxicity to
Terrestrial-Phase CRLF (via
acute toxicity to mammalian
prey items)
Indirect Toxicity to
Terrestrial-Phase CRLF (via
chronic toxicity to
mammalian prey items)
Indirect Toxicity to
Terrestrial-Phase CRLF (via
acute toxicity to terrestrial
invertebrate prey items)
Indirect Toxicity to
Terrestrial- and Aquatic-
Phase CRLF (via toxicity to
terrestrial plants)
Species
Ring-necked
pheasant
(Phasianus
colchicus)
Japanese quail
(Coturnix j aponica)
American kestrel
(Falco sparverius)
Laboratory rat
(Rattus norvegicus)
Laboratory rat
Honey bee
(Apis mellifera)
Toxicity Value
Used in Risk
Assessment
LD50 = 265 mg
a.i./kgbw
LC50 = 905 ppm
NOAEC = 1
ppm
LD50 = 587
mg/kg-bw
NOAEC = 5
ppm
(0.4 mg/kg/day)
LD50>50 ug
a.i^ee
Source
(MRID)
160000
ECOTOX#
35240
41934001
40731204
41606601
05001991
Comment
Average body weight of
1 135 g for this species from
Dunning 1984 used in T-
REX. Slope data are not
available.
Available slope is 5.92
LOAEC = 3 ppm based on
8% decrease in egg shell
thickness. Body weight for
this species is 0.100 kg
from Dunning 1984.
No slope is available.
LOAEC = 25 ppm; based
on parental systemic and
reproductive effects.
LD50 is equivalent to >391
uga.i./gof bee
No data are available to quantity this endpoint
83
-------
Table 28. Categories of acute toxicity for avian and mammalian studies.
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
OralLDso(mg/kg)
<10
10-50
51-500
501-2000
>2000
Dietary LCSO (ppm)
<50
50 - 500
501 - 1000
1001-5000
>5000
4.3.1. Toxicity of Dicofol to Birds
An acute oral toxicity study with ring-necked pheasant (Phasianus colchicus) established
an LD50 of 265 (211-334) mg ai/kg bw (MRID 160000). This indicates that dicofol is
moderately toxic to avian species on an acute oral exposure basis.
Available subacute dietary toxicity data for birds exposed to dicofol include 8-day
values ranging 905-3010 ppm (Table 29). Therefore, dicofol is classified (Table 28) as
moderately to slightly toxic to birds on a subacute dietary exposure basis. Data are
available for 4 species of birds exposed to dicofol. The most sensitive species is the
Japanese quail (Coturnix japonica), with an LCso value of 905 ppm (ECOTOX # 35240).
This value is used for deriving risk quotients for the CRLF and frogs serving as prey to
the adult CRLF.
Table 29. Subacute dietary toxicity data (LC50) for birds exposed to dicofol.
Species
(common name)
Coturnix japonica
(Japanese quail)
C. japonica
(Japanese quail)
C. japonica
(Japanese quail)
C. japonica
(Japanese quail)
Anas platyrhynchos
(mallard duck)
C. japonica
(Japanese quail)
Phasianus colchicus
(ring-necked pheasant)
Colinus virginianus
(bobwhite quail)
LCSO value
(ppm)
905
1237
1418
1545
1651
1746
2126
3010
95%
confidence
interval
(uppm)
723-1140
979-1578
1232-1628
1360-1739
1356-2029
1377-2255
1892-2387
2635-3424
Initial age of
test birds
(days)
1
7
12
14
10
21
16
15
Slope
5.92
4.89
4.13
7.95
5.64
5.37
7.38
4.31
Source
ECOTOX*
35240
GS0021010
00022923
GS0021011
00022923
GS0021012
00022923
00022923
84
-------
Several chronic studies are available where birds were exposed to dicofol (Table 30).
Available chronic studies included data on American kestrel (Falco sparverius), eastern
screech owls (Otus asio), ring doves (Streptopelia risoria), mallard ducks (Anas
platyrhynchos) and northern bobwhite quail (Colinus virginianus). From these studies,
the most sensitive chronic toxicity endpoint is a NOAEC of 1 ppm based on reproductive
effects to the American kestrel. This value is based on a LOAEC where effects to egg
shells were observed. There is some uncertainty in relying upon observed effects to egg
shells to represent effects to reproduction of the CRLF, since the CRLF does not produce
eggs with hardened shells. However, observed effects in bird eggs caused by parental
exposures to dicofol could result in other effects to amphibian eggs that are unrelated to
egg shell thickness but do affect the composition of the egg coatings that regulate osmotic
balance in eggs. In addition, effects to other endpoints that directly relate to amphibians,
including decreased numbers of eggs laid and feminization of male chicks were observed
at 40 ppm. In the two studies where these effects were observed in birds, a NOAEC was
not established, i.e., effects were measured at all levels tested. Therefore the available 1
ppm NOAEC is used for deriving risk quotients for the CRLF and terrestrial frogs (e.g.,
the Pacific tree frog) serving as prey to the adult CRLF. Another consideration is that
dicofol produces similar effects in birds as DDT/DDE. This endpoint has clear
population level effects as demonstrated with bald eagles exposed to DDT.
Table 30. Chronic toxicity data for birds exposed to dicofol.
Species (common name)
Falco sparverius
(American kestrel)
Otus asio (eastern screech
owls)
Anas platyrhynchos
(mallard duck)
Streptopelia risoria (ring
dove)
Falco sparverius
(American kestrel)
Anas platyrhynchos
(mallard duck)
Colinus virginianus
(northern bobwhite quail)
NOAEC
(ppm)
1
none
10
none
None
10
120
LOAEC
(ppm)
3
7.2
40
40
40
none
none
Observed Effects
Decreased egg shell thickness
(8%)
Decreased shell weight (11.7-
13.5%) and thickness (7.6-11%)
of eggs
Increased number of cracked
eggs (12%)
Decreased egg-shell thickness
and egg production, increased
number of cracked eggs
(11.2%)
Decreased number of eggs laid,
increase in eggs lost, potential
feminization of male chicks
none
none
Source
MRID
41934001
Wienmeyer et
al. 1989
MRID
41231301
Schwarzbach
etal. 1988
MacLellan et
al. 1996
GS0021-014
MRID
40042055
In a reproduction study with the American kestrel, eggshells were thinned by 8% in
parent birds fed 3 ppm technical dicofol for up to 175 days. Shell weight was also
reduced by 9% at concentrations as low as 10 ppm. The resulting NOAEC for the study
was 1 ppm (MRID 41934001). In a second study with captive American kestrels, paired
females were given daily oral doses of 0, 5 and 20 mg/kg-bw of dicofol. This study was
conducted over 2 generations. Female birds in the first generation treated with 20 mg/kg-
85
-------
bw produced eggs with significantly reduced shell thickness (10.98%) compared to
controls. Female birds in the second generation treated with 5 mg/kg-bw had an increase
in number of eggs lost and a decrease in total number of eggs laid compared to controls.
Female birds of the first and second generation treated with 5 mg/kg-bw produced male
offspring with abnormal gonads. Histological examination of male gonads indicated a
thickened cortex and a significant increase in primordial germ cells present in male
offspring of females treated with 5 mg/kg-bw. The authors suggested that this
histological evidence indicated feminization of male offspring (MacLellan et al. 1996).
As 5 mg/kg-bw was the lowest treatment level, a NOAEL could be established for this
study. On a dietary exposure basis, a dose of 5 mg/kg-bw/day is approximately
equivalent to 40 mg/kg-diet/day7.
In a reproduction study with eastern screech owls, birds were exposed to 7.2 ppm dicofol
in feed. At this concentration, shell weight was reduced on average by 12-14% compared
to controls. Also, egg shell thickness was reduced by 8-11% on average, compared to
controls. Since only one treatment group was involved in this study, a NOAEC could not
be determined (Wienmeyer et al. 1989).
Ring doves were exposed to 40 ppm dicofol in a reproductive study. Observed effects at
this level included significant reductions in egg shell thickness (9% less than to controls),
increased numbers of cracked eggs (14.3 more than controls), and decreased egg
production (13% less than controls). In addition, 14.3% of clutches produced by the
treated group contained only single eggs, as compared to 1.8% of clutches produced by
the control group (Schwartzbach et al. 1988).
In a reproduction study with mallard ducks exposed to technical grade dicofol, egg shell
strength was significantly reduced (12% increase in number of cracked eggs compared to
controls) at 40 ppm, resulting in a NOAEC of 10 ppm. No other effects were observed
during this study (MRID 41231301). In another reproductive study with mallard ducks,
birds treated with 5 ppm and 10 ppm showed no significant effects to reproduction
compared to controls. Effects considered in this study included number of eggs laid,
eggs cracked, eggs embryonated, survival of embryos and hatchling survival. Egg shell
thickness data were not reported (GS0021-014).
In a reproduction study with northern bobwhite quail exposed to technical grade dicofol,
no significant effects to reproduction were observed relative to controls. Effects
considered in this study included eggs laid, eggs cracked, egg shell thickness, eggs set,
viable embryos, survival of embryos and hatchling survival. The highest treatment level
of this study was 120 ppm (MRID 40042055).
7 The available dose-based value (5 mg/kg-bw) is multiplied by the body weight (B W) of the bird (0.111
kg, from Dunning 1984) and then divided by the food intake rate. The food intake rate (FI, in kg/day), is
calculated according to:FI = 0.0582 * BW°'651 (USEPA 1993) .
86
-------
4.3.2. Toxicity of Dicofol to Mammals
Available acute toxicity data for the laboratory rat indicates that dicofol is slightly toxic
to mammals on an acute oral exposure basis (LDso=587 mg/kg, MRID 40731204).
In a two-generation reproduction study, groups of laboratory rats (25/sex/group) were fed
diets containing dicofol (93.3%) at dose levels of 0, 5, 25, 125 or 250 ppm (equivalent to
0.4, 1.9, 9.5, or 18.9 mg/kg-bw/day for males and 0.4, 2.1, 10.5, or 20.5 mg/kg-bw/day
for females, respectively). For parental systemic toxicity, the NOAEC was 5 ppm (0.4
mg/kg-bw/day) and the LOAEC was 25 ppm (1.9/2.1 mg/kg-bw/day for M/F) based upon
histopathological changes in P and FI livers (hypertrophy of centrilobular hepatocytes
with associated vacuolation) and FI ovaries (increased vacuolation). For reproductive
toxicity, the NOAEC was 5 ppm (0.4 mg/kg-bw/day) and the LOAEC was 25 ppm
(1.9/2.1 mg/kg-bw/day in M/F), based on the ovarian vacuolation in the FI females,
which was judged to be an effect on reproductive physiology. For offspring toxicity, the
NOAEC could be defined at 25 ppm (1.9/2.1 mg/kg-bw/day for M/F) and the LOAEC at
125 ppm (9.5/10.5 mg/kg-bw/day for M/F), based on decreased F2 pup viability
(increased numbers of stillborn pups, postnatal day 0-4 pup deaths, and total litter loss)
(MRID 41606601).
Additional chronic toxicity data for mammals (rats and mice) exposed to dicofol were
available in ECOTOX. However, all reported data corresponded to higher NOAEC
values than that used in this assessment (i.e., NOAEC = 5 ppm (0.4 mg/kg/day); MRID
41606601). Therefore, these data were not considered further for this assessment.
4.3.3. Toxicity of Dicofol to Terrestrial Invertebrates
Dicofol is classified as practically nontoxic to honey bees (Apis melliferd) on an acute
contact exposure basis (LDso>50 jig a.i./bee; MRID 05001991). An acute oral LDso for
bees has also been reported as >10 jig a.i./bee (MRID 05001991). In a study where a 1%
solution of a formulated product containing 18.5% dicofol was applied directly to honey
bee hives through saw cuts in the frame, no abnormal mortality was observed in worker
bees (MRID 05009244).
For the purpose of this assessment, the acute contact honey bee endpoint is used to
represent effects to terrestrial invertebrates. This toxicity value is converted to units of
jig a.i./g (of bee) by multiplying by 1 bee/0.128 g resulting in an LDso >391 jig a.i./g.
4.3.4. Toxicity of Dicofol to Terrestrial Plants
There are no data are available to quantify an endpoint to represent effects of dicofol
exposures to vascular plants. However, there are several studies available in the
scientific literature to qualitatively describe effects of dicofol on vascular plants.
87
-------
In a study involving 15 types of ornamental plants, dicofol applied as a spray resulted in
phytotoxicity to begonias. No effects were observed to the other 14 ornamental plants
included in the test, including antirrhinum, asters, carnation, chrysanthemum, cineraria,
coleus, cyclamen, dahlia, geranium, petunia, polyanthus, ,saintpaulia, violets and zinnia
(Dennis and Edwards 1963).
When neanthe bella palm (Chamaedorea elegans) was exposed to dicofol, phytotoxicity
was observed. Dicofol applied to 6 other species of plants did not cause phytotoxicity
(Knauss 1971).
In a study involving the papaya (Carica papaya), 0.125% of a formulation including
dicofol affected plant growth and resulted in leaf burn (Sherman and Sanchez 1968).
4.4. Toxicity of dicofol degradates to terrestrial organisms
There are no data available from registrant-submitted studies or in the scientific literature
to evaluate the potential toxicity of dicofol degradates to terrestrial organisms. In
addition, there are no models or tools available to estimate the toxicity of dicofol or its
degradates to terrestrial organisms.
4.5. Incident Database Review for Dicofol
A search of the EIIS (Environmental Incident Information System) database for
ecological incidents (run on February 24, 2009) identified 1 incident associated with the
use of dicofol. This incident involved plant damage to 10 acres of oranges treated
directly with dicofol and chlorpyrifos. The incident occurred in June of 2000 in Tulare
County of California. The certainty (likelihood) that the observed plant damage was
associated with exposure to dicofol was considered possible. The legality of the use was
undetermined (Incident # 1013563-010).
In 1980, a wastewater pond maintained by the Tower Chemical Company (TCC)
overflowed into an onsite drainage ditch which flowed downstream into the Gourd Neck
of Lake Apopka. Lake Apopka is the fourth largest freshwater lake (12,500 ha) in the
state of Florida and has been designated as one of Florida's most polluted. From 1957 to
1981, TCC manufactured and stored various pesticides, used primarily in the citrus
industry, and discharged process wastewater into the unlined wastewater pond. This
discharge included dicofol, as much as 15% of DDT and its metabolites (DDD, DDE, and
chloro-DDT), and sulfuric acid. Studies subsequent to the upset showed a dramatic
decline in the American alligator population during the 1980s that continued into the mid
to late 1990s (Guillette et al. 1994).
88
-------
5.0 Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations.
Risk characterization is used to determine the potential for direct and/or indirect effects to
the CRLF or for modification to its designated critical habitat from the use of dicofol in
CA. The risk characterization provides an estimation (Section 5.1) and a description
(Section 5.2) of the likelihood of adverse effects; articulates risk assessment assumptions,
limitations, and uncertainties; and synthesizes an overall conclusion regarding the
likelihood of adverse effects to the CRLF or its designated critical habitat (i.e., 'no
effect,' 'likely to adversely affect,' or 'may affect, but not likely to adversely affect').
5.1. Risk Estimation
Risk is estimated by calculating the ratio of exposure to toxicity. This ratio is the risk
quotient (RQ), which is then compared to pre-established acute and chronic levels of
concern (LOCs) for each category evaluated (Appendix C). For acute exposures to the
CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the LOG
is 0.05. For acute exposures to the CRLF and mammals, the LOG is 0.1. The LOG for
chronic exposures to CRLF and its prey, as well as acute exposures to plants is 1.0.
Risks to the aquatic-phase CRLF and its prey are estimated by calculating the ratio of
exposure to toxicity using l-in-10 year EECs based on the label-recommended dicofol
usage scenarios summarized in Section 2.4.4 and the appropriate aquatic toxicity
endpoint from Section 4.1. Risks to the terrestrial-phase CRLF and its prey (e.g.
terrestrial insects, small mammals and terrestrial-phase frogs) are estimated based on
exposures resulting from applications of dicofol (Table 20 and
89
-------
Table 21) and the appropriate toxicity endpoint from Section 4.4.
5.1.1. Exposures in the Aquatic Habitat
5.1.1.1. Direct Effects to Aquatic-Phase CRLF
Direct effects to the aquatic-phase CRLF are based on peak EECs of total dicofol
residues in the standard pond and the lowest acute toxicity value for freshwater fish. In
order to assess direct chronic risks to the CRLF, 60-day EECs of total dicofol residues
(including dicofol, DCBP, FW-152, DCBH, and OH-DCBP) and the lowest chronic
toxicity value for freshwater fish are used.
Acute and chronic RQs for the aquatic-phase CRLF resulting from aerial, ground and
ULV applications of dicofol are provided in Table 31, Table 32, and Table 33
respectively. For exposures involving dicofol and its degradates of concern, RQs for all
uses of dicofol exceed the acute listed species LOG (0.05), with the exception of dicofol
use on Bermuda grass and outside buildings. RQs for chronic exposures to the CRLF
resulting from all uses exceed the LOG (1.0) for all uses, except Bermuda grass, turf and
outside buildings. Although RQs for aerial applications are higher than those for ground
applications, for all uses of dicofol that have both ground and aerial applications, both
sets of RQs exceed levels of concern for the aquatic-phase CRLF.
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.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Peak EEC
(Hg/L)
17.77
17.50
18.02
6.32
13.15
19.67
16.47
8.91
20.73
9.97
37.39
6.30
20.77
60-day
(Hg/L)
15.47
13.29
16.27
5.37
11.17
17.50
14.56
7.74
16.26
7.76
33.41
5.16
18.06
Acute
RQ1
0.343
0.333
0.343
0.123
0.253
0.373
0.313
0.173
0.393
0.193
0.713
0.123
0.393
Chronic
RQ2
3.54
3.04
3.74
1.24
2.54
4.04
3.34
1.84
3.74
1.84
7.64
1.24
4.14
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
2Based on NOAEC = 4.4 ug/L for rainbow trout
3 Exceeds acute risk to endangered species level of concern (RQ>0.
4 Exceeds chronic risk level of concern (RQ>1.0)
05)
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.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Bermuda grass
Ornamentals
Turf/Sod Farm
Outside Buildings
Peak EEC
(Hg/L)
15.87
12.99
16.01
5.52
11.31
18.35
15.14
8.23
15.40
7.60
36.36
5.22
17.94
2.31
6.09
2.88
0.354
60-day
(Hg/L)
14.27
10.53
14.99
4.77
10.07
16.69
13.50
7.43
12.25
6.05
32.15
4.41
16.02
1.93
5.25
2.40
0.248
Acute
RQ1
0.303
0.253
0.303
0.103
0.213
0.353
0.293
0.163
0.293
0.143
0.693
0.103
0.343
0.044
O.ll3
0.0543
0.0067
Chronic
RQ2
3.24
2.44
3.44
l.l4
2.34
3.84
3.14
1.74
2.84
1.44
7.34
l.O4
3.64
0.44
1.24
0.55
0.056
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
2Based on NOAEC = 4.4 ug/L for rainbow trout
3 Exceeds acute risk to endangered species level of concern (RQ>0.05)
4 Exceeds chronic risk level of concern (RQ>1.0)
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.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Peak EEC
(Hg/L)
31.80
45.13
31.57
12.14
25.28
29.66
28.76
15.88
48.90
23.78
51.32
13.70
40.15
60-day
(Hg/L)
25.26
33.29
25.23
9.41
19.80
24.58
23.28
12.61
36.56
17.68
43.81
10.35
31.59
Acute
RQ1
0.603
0.853
0.603
0.233
0.483
0.563
0.543
0.303
0.923
0.453
0.973
0.263
0.763
Chronic
RQ2
5.74
7.64
5.74
2.14
4.54
5.64
5.34
2.94
8.34
4.04
104
2.44
7.24
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
2Based on NOAEC = 4.4 ug/L for rainbow trout
3 Exceeds acute risk to endangered species level of concern (RQ>0.05)
4 Exceeds chronic risk level of concern (RQ>1.0)
91
-------
As discussed above in section 3.3, dicofol has the potential to accumulate in tissues of
aquatic organisms. Since aquatic-phase CRLF consume algae, aquatic invertebrates and
fish, CRLF could be exposed to dicofol accumulated in the tissues of these prey. In order
to define the risks of aquatic-phase CRLF consuming phytoplankton (algae), benthic
invertebrates and fish, KABAM was used to derive RQ values for small (1.4 g), medium
(37 g) and large (238 g) aquatic-phase CRLF. Body weight assumptions are consistent
with those incorporated into T-HERPS. Diet assumptions assigned to each of these size
classes are provided in Table 34. The resulting RQ values for the CRLF are provided in
Table 35. RQ values for all size classes exceed the LOG for acute-dose based and
chronic, dietary-based exposures to the CRLF ingesting dicofol through consumption of
contaminated aquatic prey (that have accumulated dicofol).
Table 34. Diet assumptions of small, medium and large aquatic-phase CRLF used in KABAM.
Trophic level in diet
phytoplankton
zooplankton
benthic invertebrates
filter feeders
small fish
medium fish
large fish
Total
Diet for:
small CRLF
1
100.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
100.0%
small CRLF
2
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
med
CRLF1
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
med
CRLF 2
0.0%
0.0%
0.0%
0.0%
100.0%
0.0%
0.0%
100.0%
large
CRLF1
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
large
CRLF 2
0.0%
0.0%
0.0%
0.0%
0.0%
100.0%
0.0%
100.0%
Table 35. Acute and chronic RQs for aquatic-phase CRLF exposed to dicofol (parent) through
consumption of aquatic organisms which have accumulated dicofol.
Size Classes of CRLF
small CRLF 1
small CRLF 2
med CRLF 1
med CRLF 2
large CRLF 1
large CRLF 2
Acute, Dose
Based RQ1
0.634
0.384
0.073
0.174
0.029
0.144
Acute,
Dietary
Based RQ2
0.012
0.017
0.017
0.043
0.017
0.0924
Chronic, Dietary
Based RQ3
11s
15s
15s
39s
15s
83s
1 Based on LD50 = 265 mg/kg-bw (for ring-necked pheasant)
2 Based on LC50 = 903 ppm (for Japanese quail)
3 Based on NOAEC = 1 ppm (for American kestrel)
4 Exceeds acute risk to endangered species level of concern (RQ>0.1)
5 Exceeds chronic risk level of concern (RQ>1.0)
92
-------
5.1.1.2. Indirect Effects to Aquatic-Phase CRLF through effects to prey
Indirect effects of dicofol to the aquatic-phase CRLF (tadpoles) via reduction in non-
vascular aquatic plants in its diet are based on peak EECs from the standard pond and the
lowest toxicity value (ECso) for aquatic non-vascular plants. RQ values generated using
EECs representing total residues of dicofol (Table 12) are less than 0.01 for all uses,
which is below the LOG (1.0) for non-vascular aquatic plants.
Indirect acute effects to the aquatic-phase CRLF via effects to prey (invertebrates) in
aquatic habitats are based on peak EECs of total dicofol residues in the standard pond and
the lowest acute toxicity value for freshwater invertebrates. For chronic risks, 21-day
EECs of total dicofol residues and the lowest chronic toxicity value for invertebrates are
used to derive RQs.
Acute and chronic RQs for the aquatic invertebrates resulting from aerial, ground and
ULV applications of dicofol are provided in Table 36, Table 37, and Table 38
respectively. RQs for all uses of dicofol exceed the acute listed species LOG (0.05) for
aquatic invertebrates, with the exception of dicofol use on Bermuda grass, ornamentals,
turf and outside buildings. RQs for chronic exposures to the CRLF from all uses of
dicofol exceed LOG (1.0), except cucurbits, peppers, tomatoes, Bermuda grass,
ornamentals, turf and outside buildings.
Table 36. Acute and chronic RQs for aquatic invertebrates resulting from AERIAL applications of
dicofol. EECs are based on parent and degradates of concern.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Peak EEC
(Hg/L)
17.77
17.50
18.02
6.32
13.15
19.67
16.47
8.91
20.73
9.97
37.39
6.30
20.77
21-day
(Hg/L)
16.16
14.40
16.81
5.63
11.78
18.51
15.58
8.09
17.51
8.37
34.68
5.49
18.80
Acute
RQ1
0.133
0.123
0.133
0.045
0.093
0.143
0.123
0.0643
0.153
0.0713
0.273
0.045
0.153
Chronic
RQ2
0.85
0.76
0.88
0.30
0.62
0.97
0.82
0.43
0.92
0.44
1.84
0.29
0.99
'Based on 48-h EC50 = 140 ug/L for daphnid
2Based on NOAEC = 19 ug/L for amphipod
3 Exceeds acute risk to endangered species level of concern (RQ>0.05)
4 Exceeds chronic risk level of concern (RQ>1.0)
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.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Bermuda grass
Ornamentals
Turf/Sod Farm
Outside Buildings
Peak EEC
(Hg/L)
15.87
12.99
16.01
5.52
11.31
18.35
15.14
8.23
15.40
7.60
36.36
5.22
17.94
2.31
6.09
2.88
0.354
21-day
(Hg/L)
14.69
10.87
15.36
4.98
10.39
17.45
14.22
7.66
13.13
6.48
33.38
4.65
16.52
2.02
5.51
2.52
0.281
Acute
RQ1
O.ll3
0.0933
O.ll3
0.04
0.0813
0.133
O.ll3
0.0593
O.ll3
0.0543
0.263
0.037
0.133
0.016
0.044
0.021
0.0025
Chronic
RQ2
0.77
0.57
0.81
0.26
0.55
0.92
0.75
0.40
0.69
0.34
1.84
0.24
0.87
0.11
0.29
0.13
0.015
'Based on 48-h EC50 = 140 ug/L for daphnid
2Based on NOAEC = 19 ug/L for amphipod.
3 Exceeds acute risk to endangered species level of concern (RQ>0.05)
4 Exceeds chronic risk level of concern (RQ>1.0)
Table 38. Acute and chronic RQs for aquatic invertebrates resulting from ULV applications of
dicofol. EECs are based on parent and degradates of concern.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Peak EEC
(Hg/L)
31.80
45.13
31.57
12.14
25.28
29.66
28.76
15.88
48.90
23.78
51.32
13.70
40.15
21-day
(Hg/L)
27.04
36.41
27.01
10.18
21.29
25.90
24.71
13.49
39.92
19.38
45.31
11.27
33.92
Acute
RQ1
0.233
0.323
0.233
0.0873
0.183
0.213
0.213
O.ll3
0.353
0.173
0.373
0.103
0.293
Chronic
RQ2
1.44
1.94
1.44
0.54
l.l4
1.44
1.34
0.71
2.14
l.O4
2.44
0.59
1.84
'Based on 48-h EC50 = 140 ug/L for daphnid
2Based on NOAEC = 19 ug/L for amphipod
3 Exceeds acute risk to endangered species level of concern (RQ>0.
4 Exceeds chronic risk level of concern (RQ>1.0)
05)
94
-------
Fish and frogs also represent potential prey items of adult aquatic-phase CRLFs. RQs
associated with acute and chronic direct toxicity to the CRLF (Table 31 and Table 32) are
used to assess potential indirect effects to the CRLF based on a reduction in freshwater
fish and frogs as food items. As noted above, exposures involving dicofol and its
degradates of concern (DCBP, FW-152, DCBH, and OH-DCBP), RQs for all uses of
dicofol exceed the acute listed species LOG (0.05), with the exception of dicofol use on
Bermuda grass and outside buildings. RQs for chronic exposures to the CRLF resulting
from all uses exceed the LOG (1.0) for all uses, except Bermuda grass, turf and outside
buildings.
5.1.1.3. Indirect Effects to Aquatic-Phase CRLF through effects to habitat
Indirect effects to the CRLF via direct toxicity to aquatic plants are estimated using the
most sensitive non-vascular and vascular plant toxicity endpoints. RQ values generated
for non-vascular plants using EECs representing total residues of dicofol (Table 12) are
less than 0.01 for all uses, which is below the LOG of 1.0 for non-vascular aquatic plants.
Since no data are available to quantify the effects of dicofol to vascular aquatic plants,
RQ values for vascular aquatic plants cannot be derived.
95
-------
5.1.2. Exposures in the Terrestrial Habitat
5.1.2.1. Direct Effects to Terrestrial-Phase CRLF
Potential direct acute risks to the terrestrial-phase CRLF are derived by considering dose-
and dietary-based EECs modeled in T-REX for a small bird (20 g) consuming small
invertebrates (Table 20) and acute oral and subacute dietary toxicity endpoints for avian
species. Potential direct chronic risks of dicofol to the terrestrial-phase CRLF are derived
by considering dietary-based exposures modeled in T-REX for a small bird (20g)
consuming small invertebrates and the lowest available chronic toxicity data for birds.
EECs are divided by toxicity values to estimate chronic dietary-based RQs. Acute dose-
based RQs (Table 39) exceed the LOG (0.1) for all uses of dicofol, with RQs exceeding
the LOG by factors ranging between 4.3 to 32X. Acute dietary-based RQs exceed the
LOG (0.1) for most uses, with the exception of use on cucurbits, ornamentals, turf and
Bermuda grass. Chronic dietary-based RQs exceed the LOG (1.0) for all uses of dicofol,
by factors ranging 54 to 405X (Table 39).
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.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black),
Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms,
Outside building surfaces
Bermuda grass
Acute, Dose-
based7
3.210
2.1310
1.5910
1.3310
1.2410
0.8010
0.6610
0.5310
0.4310
Acute, Dietary-
based8
0.4510
0.3010
0.2210
0.1910
0.1710
O.ll10
0.09
0.07
0.06
Chronic, Dietary-
based9
40511
27011
20311
16911
15711
10111
8411
6711
5411
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LD50 = 265 mg/kg-bw (for ring-necked pheasant)
8 Based on LC50 = 903 ppm (for Japanese quail)
9 Based on NOAEC = 1 ppm (for American kestrel)
10 Exceeds acute risk to endangered species level of concern (RQ>0.1)
11 Exceeds chronic risk level of concern (RQ>1.0)
96
-------
5.1.2.2. Indirect Effects to Terrestrial-Phase CRLF through Effects to
Prey
In order to assess the risks of dicofol applications to terrestrial invertebrates, which are
considered prey of CRLF in terrestrial habitats, the honey bee is used as a surrogate for
terrestrial invertebrates. EECs (jig a.i./g of bee) calculated by T-REX for small and large
insects are divided by the calculated toxicity value (LDso) for terrestrial invertebrates,
which is >391 jig a.i./g of bee. The resulting RQ values for large insect and small insect
exposures bound the potential range of exposures for terrestrial insects to dicofol. Since
the acute contact toxicity estimate is indeterminate, i.e., the LD50 value exceeds the
highest dose tested (LD5o>50ug/bee) the resulting toxicity value for terrestrial
invertebrate is also indeterminate (LD50>391 jig a.i./g of bee). As such, RQ values based
on these indeterminate values are expressed as less than (<) values. For small insect
exposures, RQ values range <1.04 to <0.138. For large insect exposures, RQ values
range <0.115 to <0.0153. For all uses of dicofol, RQ values potentially exceed the acute
risk LOG (RQ>0.05) for terrestrial insects.
As described above, to assess risks of dicofol to prey (small mammals) of larger
terrestrial-phase CRLF, dietary-based and dose-based exposures modeled in T-REX for a
small mammal (15g) consuming short grass are used. Acute and chronic effects are
estimated using the most sensitive acute (rat LD50=587 mg/kg-bw) and chronic (rate
NOAEC 5 mg/kg diet; 0.4 mg/kg-bw/day) mammalian toxicity data. EECs are divided by
the toxicity values to estimate acute and chronic dietary-based RQs as well as acute dose-
based RQs. Acute dose-based RQ values exceed the listed species acute risk LOG
(RQ>0.1) for the majority of dicofol uses. Across all uses, chronic dose-based and
dietary-based RQs exceed the chronic risk LOC (RQ>1.0) (Table 40).
An additional prey item of the adult CRLF is other species of frogs. In order to assess
risks to these organisms, dietary-based and dose-based exposures modeled in T-REX for
a small bird (20g) consuming small invertebrates are used. These are the same EECs,
toxicity values and RQs used to assess direct effects to the CRLF. Acute dose-based RQs
exceed the LOC (0.1) for all uses of dicofol, with RQs exceeding the LOC by factors
ranging between 4.3 to 32X. Acute dietary-based RQs exceeded the LOC (0.1) for most
uses, with the exception of use on cucurbits, ornamentals, turf and Bermuda grass.
Chronic dietary-based RQs exceed the LOC (1.0) for all uses of dicofol, by factors
ranging 54 to 405X (Table 39).
97
-------
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.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms, Outside
building surfaces
Bermuda grass
Acute,
dose-based7
0.5310
0.3510
0.2710
0.2210
0.2110
0.1310
O.ll10
0.09
0.07
Chronic,
dose-based8
78111
52111
39011
32511
30311
19511
16311
13011
10411
Chronic,
dietary-based9
14411
96"
72"
60"
55"
36"
30"
24"
19"
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LD50 for laboratory rat = 587 mg/kg.
8 Based on chronic NOAEL for laboratory rat = 0.4 mg/kg-bw.
9 Based on chronic NOAEC for laboratory rat = 5 ppm.
10 Exceeds acute risk to endangered species level of concern (RQ>0.1)
11 Exceeds chronic risk level of concern (RQ>1.0)
5.1.2.3. Indirect Effects to Terrestrial-Phase CRLF through Effects to
Habitat (plants)
Indirect effects to the CRLF via direct toxicity to terrestrial plants are estimated using the
most sensitive plant toxicity endpoints. Since no data are available to quantify the effects
of dicofol to terrestrial plants, these RQ values cannot be derived and risk is presumed.
5.1.3. Primary Constituent Elements of Designated Critical Habitat
For dicofol use, the assessment endpoints for designated critical habitat PCEs involve a
reduction and/or modification of food sources necessary for normal growth and viability
of aquatic-phase CRLFs, and/or a reduction and/or modification of food sources for
terrestrial-phase juveniles and adults. Because these endpoints are also being assessed
relative to the potential for indirect effects to aquatic- and terrestrial-phase CRLF, the
effects determinations for indirect effects from the potential loss of food items are used as
the basis of the effects determination for potential effects to designated critical habitat.
98
-------
5.1.3.1. Aquatic-Phase
Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
• Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
• Alteration in water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
• Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
Based on a lack of data to quantify potential effects of dicofol to aquatic and terrestrial
plants, it is assumed that dicofol may affect aquatic-phase PCEs of designated habitat
related to effects on aquatic and/or terrestrial plants. This assumption will be refined
later in the risk description of this assessment.
The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." To assess
the impact of dicofol on this PCE (i.e., alteration of food sources), acute and chronic
freshwater fish and invertebrate toxicity endpoints, as well endpoints for aquatic non-
vascular plants, are used as measures of effects. RQs for these endpoints were calculated
in Section 5.1.1. Based on LOG exceedances for acute and chronic exposures offish and
aquatic invertebrates to total residues of dicofol, use of dicofol may affect aquatic-phase
PCEs of designated habitat related to effects of alteration of other chemical
characteristics necessary for normal growth and viability of CRLFs and their food source.
5.1.3.2. Terrestrial-Phase
The first two assessment endpoints for the terrestrial-phase PCEs of designated critical
habitat for the CRLF are related to potential effects to terrestrial plants:
• Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian habitat that are comprised
of grasslands, woodlands, and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
• Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
99
-------
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal
Based on a lack of data to quantify potential effects of dicofol to terrestrial plants, it is
assumed that dicofol may affect terrestrial-phase PCEs of designated habitat related to
effects on terrestrial plants. This assumption will be refined later in the risk description
of this assessment.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of dicofol on this PCE, acute
and chronic toxicity endpoints for birds, mammals, and terrestrial invertebrates are used
as measures of effects. RQs for these endpoints were calculated in Section 5.1.2. Based
on LOG exceedances for acute and chronic exposures of frogs and mammals to dicofol,
use of dicofol may affect terrestrial-phase PCEs of designated habitat related to
"reduction and/or modification of food sources for terrestrial phase juveniles and adults."
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. Based on LOG exceedances for acute and chronic exposures of frogs to dicofol,
use of dicofol may affect terrestrial-phase PCEs of designated habitat related to effects of
alteration of other chemical characteristics necessary for normal growth and viability of
CRLFs and their food source.
5.2. Risk Description
The risk description synthesizes an overall conclusion regarding the likelihood of adverse
impacts leading to an effects determination (i.e., "no effect," "may affect, but not likely
to adversely affect," or "likely to adversely affect") for the CRLF and its designated
critical habitat.
The direct and indirect effect LOCs are exceeded and dicofol may affect the PCEs of the
CRLF's critical habitat. Therefore, the Agency concludes a preliminary "may affect"
determination for the FIFRA regulatory action regarding dicofol. A summary of the risk
estimation results are provided in Table 41 for direct and indirect effects to the CRLF
and in Table 42 for the PCEs of designated critical habitat for the CRLF.
100
-------
Table 41. Risk estimation summary for dicofol - direct and indirect effects to the CRLF.
Assessment Endpoint
LOC
Exceedances?
Description of Results of Risk Estimation
Aquatic-Phase CRLF (eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects
Survival, growth, and reproduction
of CRLF individuals via direct
effects on aquatic phases
Yes
Acute RQs exceed the LOC for exposures of aquatic-phase
CRLF resulting from all uses of dicofol, except applications to
outside buildings.
Chronic RQs exceed the LOC for exposures of aquatic-phase
CRLF resulting from all uses of dicofol, except use on
Bermuda grass, turf and outside buildings.
Acute and chronic RQs for aquatic-phase CRLF consuming
aquatic organisms contaminated with dicofol (resulting from
accumulation) exceed LOCs.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects to
food supply (i.e., freshwater
invertebrates, non-vascular plants)
yes
RQ values for algae are below the LOC for all uses.
Acute RQs exceed the LOC for exposures of aquatic
invertebrates resulting from the majority of dicofol uses, except
Bermuda grass, ornamentals, turf and applications to outside
buildings.
Chronic RQs exceed the LOC for exposures of aquatic
invertebrates resulting from the majority of dicofol uses, except
cucurbits, peppers, tomatoes, Bermuda grass, ornamentals, turf
and applications to outside buildings.
Acute RQs for all uses of dicofol modeled, except applications
to outside buildings exceed the LOC for exposures of fish and
aquatic-phase amphibians resulting.
Chronic RQs exceed the LOC for exposures of fish and
aquatic-phase amphibians resulting from all uses of dicofol,
except use on Bermuda grass, turf and outside buildings.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
habitat, cover, and/or primary
productivity (i.e., aquatic plant
community)
Undetermined
RQ values for algae are below the LOC for all uses.
No data are available to derive RQs representative of the
effects of dicofol on vascular plants.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects to
riparian vegetation, required to
maintain acceptable water quality
and habitat in ponds and streams
comprising the species' current
Undetermined
No data are available to derive RQs representative of the
effects of dicofol on vascular plants.
101
-------
Assessment Endpoint
range.
LOC
Exceedances?
Description of Results of Risk Estimation
Terrestrial-Phase CRLF (Juveniles and adults)
Direct Effects
Survival, growth, and reproduction
of CRLF individuals via direct
effects on terrestrial phase adults and
juveniles
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
prey (i.e., terrestrial invertebrates,
small terrestrial mammals and
terrestrial phase amphibians)
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
habitat (i.e., riparian vegetation)
Yes
Yes
Undetermined
Acute and chronic RQs exceed the LOC for terrestrial-phase
CRLF for all uses of dicofol.
For terrestrial invertebrates, RQs for all uses potentially exceed
the LOC.
Acute RQs for small terrestrial mammals exposed to dicofol
exceed the LOC for all uses of dicofol, except ornamentals,
turf, outside building surfaces and Bermuda grass.
Chronic RQs for small terrestrial mammals exposed to dicofol
exceed the LOC for all uses of dicofol.
Acute and chronic RQs exceed the LOC for terrestrial-phase
amphibians for all uses of dicofol.
No data are available to derive RQs representative of the
effects of dicofol on vascular plants.
Table 42. Risk estimation summary for dicofol - PCEs of designated critical habitat for the CRLF.
Assessment Endpoint
Habitat Effects?
Description of Results of Risk Estimation
Aquatic-Phase CRLF PCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or
geometry and/or increase in sediment
deposition within the stream channel or
pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal
for juvenile and adult CRLFs.
Undetermined
No data are available to derive RQs representative
of the effects of dicofol on 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.
Undetermined
No data are available to derive RQs representative
of the effects of dicofol on vascular plants.
102
-------
Assessment Endpoint
Alteration of other chemical characteristics
necessary for normal growth and viability of
CRLFs and their food source.
Reduction and/or modification of aquatic-
based food sources for pre-metamorphs
(e.g., algae)
Habitat Effects?
Yes
Undetermined
Description of Results of Risk Estimation
Acute and chronic RQs for aquatic-phase CRLF
consuming aquatic organisms contaminated with
dicofol (resulting from accumulation) exceed LOCs.
Acute RQs exceed the LOG for exposures of aquatic
invertebrates resulting from the majority of dicofol
uses, except Bermuda grass, ornamentals, turf and
applications to outside buildings.
Chronic RQs exceed the LOG for exposures of
aquatic invertebrates resulting from the majority of
dicofol uses, except cucurbits, peppers, tomatoes,
Bermuda grass, ornamentals, turf and applications to
outside buildings.
Acute RQs exceed the LOG for exposures of fish
and aquatic -phase amphibians resulting from all
uses of dicofol, except applications to outside
buildings.
Chronic RQs exceed the LOG for exposures of fish
and aquatic -phase amphibians resulting from all uses
of dicofol, except use on Bermuda grass, turf and
outside buildings.
No data are available to derive RQs representative
of the effects of dicofol on vascular plants.
Terrestrial-Phase CRLF PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland
habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200
ft of the edge of the riparian vegetation or
dripline surrounding aquatic and riparian
habitat that are comprised of grasslands,
woodlands, and/or wetland/riparian plant
species that provides the CRLF shelter,
forage, and predator avoidance
Elimination and/or disturbance of dispersal
habitat: Upland or riparian dispersal habitat
within designated units and between
occupied locations within 0.7 mi of each
other that allow for movement between sites
including both natural and altered sites
which do not contain barriers to dispersal
Reduction and/or modification of food
sources for terrestrial phase juveniles and
adults
Undetermined
Undetermined
Yes
No data are available to derive RQs representative
of the effects of dicofol on vascular plants.
No data are available to derive RQs representative
of the effects of dicofol on vascular plants.
For terrestrial invertebrates, RQs for all uses
potentially exceed the LOG.
Acute RQs for small terrestrial mammals exposed
to dicofol exceed the LOG for all uses of dicofol,
except ornamentals, turf, outside building surfaces
103
-------
Assessment Endpoint
Habitat Effects?
Description of Results of Risk Estimation
and Bermuda grass.
Chronic RQs for small terrestrial mammals exposed
to dicofol exceed the LOG for all uses of dicofol.
Acute and chronic RQs exceed the LOG for
terrestrial-phase amphibians for all uses of dicofol.
Alteration of chemical characteristics
necessary for normal growth and viability of
juvenile and adult CRLFs and their food
source.
Yes
Acute and chronic RQs exceed the LOG for
terrestrial-phase CRLF for all uses of dicofol.
For terrestrial invertebrates, RQs for all uses
potentially exceed the LOG.
Acute RQs for small terrestrial mammals exposed
to dicofol exceed the LOG for all uses of dicofol,
except ornamentals, turf, outside building surfaces
and Bermuda grass.
Chronic RQs for small terrestrial mammals exposed
to dicofol exceed the LOG for all uses of dicofol.
Acute and chronic RQs exceed the LOG for
terrestrial-phase amphibians for all uses of dicofol.
Following a "may affect" determination, additional information is considered to refine
the potential for exposure at the predicted levels based on the life history characteristics
(i.e., habitat range, feeding preferences, etc.) of the CRLF. Based on the best available
information, the Agency uses the refined evaluation to distinguish those actions that
"may affect, but are not likely to adversely affect" from those actions that are "likely to
adversely affect" the CRLF and its designated critical habitat.
The criteria used to make determinations that the effects of an action are "not likely to
adversely affect" the CRLF and its designated critical habitat include the following:
• Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where 'take'
occurs for even a single individual. 'Take' in this context means to harass or
harm, defined as the following:
• Harm includes significant habitat modification or degradation that
results in death or injury to listed species by significantly impairing
behavioral patterns such as breeding, feeding, or sheltering.
• Harass is defined as actions that create the likelihood of injury to listed
species to such an extent as to significantly disrupt normal behavior
104
-------
patterns which include, but are not limited to, breeding, feeding, or
sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are
extremely unlikely to occur.
• Adverse Nature of Effect: Effects that are wholly beneficial without any adverse
effects are not considered adverse.
A description of the risk and effects determination for each of the established assessment
endpoints for the CRLF and its designated critical habitat is provided below.
5.2.1. Direct Effects
5.2.1.1. Aquatic-Phase CRLF
As discussed in the risk estimation section, RQs for all uses of dicofol, except Bermuda
grass and outside buildings exceed LOCs for aquatic-phase CRLFs exposed to total
residues of dicofol. Therefore, the determination for use of dicofol on Bermuda grass and
outside buildings is 'no effect' for direct effects of total residues of dicofol to the aquatic-
phase CRLF. The determination for all other uses of dicofol is 'may effect' for direct
effects of total residues of dicofol to the aquatic-phase CRLF.
Based on an analysis of the likelihood of individual mortality considering the range of
acute RQs exceeding the LOG for aquatic-phase CRLFs (0.054-0.97), and using the
probit dose-response of 4.5 (default assumption), the chance of mortality to CRLF range
from 1 in 1.7xl08 individuals to 1 in 2 individuals (Table 43). This indicates that
aquatic-phase CRLF could potentially be affected by acute exposures to dicofol. An
example output calculating the analysis of the likelihood of individual mortality is
provided in Appendix M.
105
-------
Table 43. Acute RQs
based on parent and
and for aquatic-phase CRLF resulting from applications of dicofol. EECs are
degradates of concern.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Bermuda grass
Ornamentals
Turf/Sod Farm
Outside Buildings
ULV application
Acute
RQ1
0.60
0.85
0.60
0.23
0.48
0.56
0.54
0.30
0.92
0.45
0.97
0.26
0.76
NA
NA
NA
NA
Chance of
individual
mortality
(1 in...)
6
3
6
491
13
8
9
107
2
17
2
236
3
NA
NA
NA
NA
Aerial application
Acute
RQ1
0.34
0.33
0.34
0.12
0.25
0.37
0.31
0.17
0.39
0.19
0.71
0.12
0.39
NA
NA
NA
NA
Chance of
individual
mortality
(1 in...)
57
66
57
58,519
297
38
91
3,744
30
1,706
4
58,519
30
NA
NA
NA
NA
Ground application
Acute
RQ1
0.30
0.25
0.30
0.10
0.21
0.35
0.29
0.16
0.29
0.14
0.69
0.10
0.34
0.044
0.11
0.054
0.0067
Chance of
individual
mortality
(1 in...)
107
297
107
294,319
84
50
129
5853
129
16,417
4
294,319
57
1.94xl09
124,594
1.71xl08
1.52xl022
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
NA = not applicable
Chronic RQs for the majority of dicofol uses (all except Bermuda grass, turf and outside
buildings) exceed the LOG (1.0) by factors of 1.1X to 10X, depending upon the use and
application method (Table 31-Table 33). EECs are sufficient to exceed the LOAEC (7.9
Hg/L, based on growth effects) for the majority of dicofol uses, with the exception of
Bermuda grass, ornamentals, turf and outside buildings.
Exposures of aquatic-phase CRLF are to dicofol are quantified in terms of total residues
of dicofol. RQs are derived using the most sensitive toxicity data available for fish
exposed to dicofol. It is assumed that dicofol's degradates of concern (i.e., DCBP, FW-
152, DCBH and OH-DCBP) are equivalent to dicofol in toxicity to the aquatic-phase
CRLF. This assumption adds uncertainty to the risk assessment as the actual toxicity of
dicofol's degradates to the CRLF is unknown. If exposures involving parent dicofol
alone are considered, resulting acute RQs for the aquatic-phase CRLF exceed the listed
species LOG (0.05) for all uses of dicofol, except Bermuda grass ornamentals, turf and
outside buildings (Table 44 - Table 46). Therefore, acute exposures to parent dicofol
alone are sufficient to be of concern for mortality to the aquatic-phase CRLF. RQs for
chronic exposures of the CRLF to parent dicofol alone do not exceed the LOG (1.0).
106
-------
Table 44. Acute and chronic RQs for aquatic-phase CRLF resulting from AERIAL applications of
dicofol. EECs are based on parent dicofol only.
Crop
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan Aerial
Peak EEC
(HS/L)
3.25
6.46
3.48
1.34
2.70
2.52
2.70
1.61
6.46
3.25
6.41
1.61
4.41
60-day
(HS/L)
0.18
0.42
0.29
0.07
0.15
0.16
0.15
0.09
0.34
0.17
0.93
0.09
0.29
Acute
RQ1
0.0613
0.123
0.0663
0.025
0.0513
0.048
0.0513
0.030
0.123
0.0613
0.123
0.030
0.0833
Chronic
RQ2
0.040
0.095
0.066
0.016
0.033
0.037
0.035
0.020
0.077
0.040
0.21
0.020
0.065
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
2Based on NOAEC = 4.4 ug/L for rainbow trout
3 Exceeds acute risk to endangered species LOG (RQ>0.05)
Table 45. Acute and chronic RQs for aquatic-phase CRLF resulting from GROUND applications of
dicofol. EECs are based on dicofol only.
Crop
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Bermudagrass
Ornamentals
Turf/Sod Farm
Outside Buidlings
Peak EEC
(HS/L)
2.26
4.47
2.49
0.93
1.87
1.74
1.87
1.12
4.47
2.25
6.34
1.12
3.09
0.60
1.78
0.75
0.152
60-day
(HS/L)
0.12
0.32
0.25
0.05
0.10
0.12
0.11
0.06
0.24
0.12
0.89
0.06
0.22
0.04
0.18
0.05
0.010
Acute
RQ1
0.043
0.0843
0.047
0.018
0.035
0.033
0.035
0.021
0.0843
0.042
0.123
0.021
0.0583
0.011
0.034
0.014
0.0029
Chronic
RQ2
0.028
0.072
0.056
0.011
0.023
0.028
0.025
0.014
0.053
0.028
0.20
0.014
0.050
0.0095
0.041
0.012
0.0023
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
2Based on NOAEC = 4.4 ug/L for rainbow trout
3 Exceeds acute risk to endangered species LOG (RQ>0.05)
107
-------
Table 46. Acute and chronic RQs for aquatic-phase CRLF resulting from ULV applications of
dicofol. EECs are based on parent dicofol only.
Crop
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Peak EEC
(HS/L)
9.75
18.02
9.92
4.04
8.08
7.56
8.07
4.85
18.02
9.08
13.17
4.85
13.02
60-day
(HS/L)
0.52
1.03
0.60
0.21
0.43
0.43
0.44
0.26
0.94
0.48
1.23
0.25
0.72
Acute
RQ1
0.183
0.343
0.193
0.0763
0.153
0.143
0.153
0.0913
0.343
0.173
0.253
0.0913
0.253
Chronic
RQ2
0.12
0.23
0.14
0.048
0.10
0.10
0.10
0.059
0.21
0.11
0.28
0.058
0.16
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
2Based on NOAEC = 4.4 ug/L for rainbow trout
3 Exceeds acute risk to endangered species LOG (RQ>0.05)
Aquatic EECs account for direct toxicity to the CRLF through contact with dicofol
present in the water column. Given the high Log Kow of dicofol (>6) and its degradates
of concern (>4), dicofol and its residues of concern are expected to partition to aquatic
organisms. Therefore, the aquatic-phase CRLF can also be exposed to dicofol and its
residues through consumption of contaminated prey items. Acute and chronic RQ values
generated using KABAM (Table 35) are above LOCs, indicating that exposure of
aquatic-phase CRLF to dicofol through consumption of aquatic organisms which have
accumulated dicofol is of concern for the CRLF.
Based on the above information, for all uses of dicofol, except Bermuda grass and outside
buildings, the effects determination for direct effects to the aquatic-phase CRLF is
"LAA" based on potential acute mortality and chronic growth effects. The determination
for use of dicofol on Bermuda grass and outside buildings is "no effect" for direct effects
of total residues of dicofol to the aquatic-phase CRLF.
5.2.1.2. Terrestrial-Phase CRLF
T-REX calculated acute dose-based RQs, acute dietary-based RQs and chronic dietary-
based RQs exceed their respective LOCs, resulting in a "may affect" determination for all
uses. In order to explore influences of amphibian-specific food intake equations on
potential dose-based and dietary-based exposures of the terrestrial-phase CRLF to
dicofol, T-HERPS is used. Modeling with T-HERPS incorporates the same application
rates, intervals and number of applications for each use as defined for modeling using T-
REX (Table 19). Since applications of dicofol for all uses result in exposures sufficient to
exceed the LOG for direct effects to the terrestrial-phase CRLF, the T-HERPS model was
used to estimate EECs and subsequent risks to the terrestrial-phase CRLF based on
amphibian-specific equations. These refined EECs and RQs were used to distinguish
108
-------
"NLAA" and "LAA" determinations. An example output from T-HERPS is available in
Appendix N.
RQs are calculated for the terrestrial-phase CRLF on the basis of dose and diet. It should
be noted that although dietary-based RQ values are considerably lower than dose-based
RQ values, the former do not take into account that different-sized animals consume
differing amounts of food and that depending on the forage item, an animal has to
consume varying amounts due to differing nutrition levels in the food item. If dietary-
based RQ values are adjusted to account for differential food consumption, the adjusted
RQ value would likely approximate the dose-based RQ value.
Acute exposures
Refined dose-based RQs for small sized (1.4 g) CRLF consuming insects do not exceed
the acute listed species LOG (0.1) for dicofol (Table 47).
Table 47. Refined dose-based RQs7 for 1.4 g CRLF consuming different food items. EECs calculated
using T-HERPS.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms, Outside building
surfaces
Bermuda grass
Small Insects
0.06
0.04
0.03
0.02
0.02
0.01
0.01
0.01
0.01
Large Insects
0.01
O.01
0.01
O.01
O.01
0.01
O.01
0.01
0.01
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LD50 = 265 mg/kg-bw (for ring-necked pheasant)
Refined dose-based RQs for medium-sized (37 g) CRLF consuming small herbivorous
mammals exceed the acute listed species LOG (0.1) for all uses of dicofol. RQs exceed
the LOG by factors of 2.3 to 16.9x. Based on an analysis of the likelihood of individual
mortality considering the range of acute dose-based RQs for medium terrestrial-phase
CRLFs consuming small herbivore mammals (0.23-1.69), and using the default probit
dose-response of 4.5, the chance of mortality to these CRLF range from 1 out of 491
individuals to 100%. RQs for medium-sized CRLF consuming insects and terrestrial-
phase amphibians do not exceed the acute listed species LOG (Table 48). This indicates
that medium-sized CRLF could potentially be affected by acute exposures to dicofol.
109
-------
Table 48. Revised dose-based RQs for 37 g CRLF consuming different food items. EECs calculated
using T-HERPS.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black),
Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms,
Outside building surfaces
Bermuda grass
Small
Insects
0.06
0.04
0.03
0.02
0.02
0.01
0.01
0.01
0.01
Large
Insects
0.01
0.01
0.01
O.01
O.01
0.01
O.01
0.01
0.01
Small
Herbivore
Mammals
1.698
1.138
0.858
0.718
0.668
0.428
0.358
0.288
0.238
Small
Insectivore
Mammals
O.ll8
0.07
0.05
0.04
0.04
0.03
0.02
0.02
0.01
Small
Terrestrial-
phase
Amphibians
O.01
0.01
0.01
O.01
O.01
0.01
O.01
0.01
0.01
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LD50 = 265 mg/kg-bw (for ring-necked pheasant)
8 Exceeds acute endangered species LOG (RQ>0.1)
Refined dose-based RQs for large-sized (238 g) CRLF consuming small, herbivore
mammals are exceeded for some uses of dicofol (Table 49). Based on an analysis of the
likelihood of individual mortality considering the range of acute dose-based RQs
exceeding the LOG for large terrestrial-phase CRLFs consuming small herbivore
mammals (0.10-0.26), and using the default probit dose-response of 4.5, the chance of
mortality to these CRLF range from 1 in 294,319 individuals to 1 in 236 individuals.
RQs for large-sized CRLF consuming insects and terrestrial-phase amphibians do not
exceed the acute listed species LOG (Table 49). This indicates that large-sized terrestrial-
phase CRLF could potentially be affected by acute exposures to dicofol resulting from
several uses.
110
-------
Table 49. Revised dose-based RQs7 for 238 g CRLF consuming different food items. EECs calculated
using T-HERPS.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black),
Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms,
Outside building surfaces
Bermuda grass
Small
Insects
0.04
0.03
0.02
0.02
0.01
0.01
0.01
0.01
0.01
Large
Insects
<0.01
<0.01
0.01
O.01
0.01
O.01
0.01
O.01
0.01
Small
Herbivore
Mammals
0.268
0.188
0.138
O.ll8
0.108
0.07
0.05
0.04
0.04
Small
Insectivore
Mammals
0.02
0.01
0.01
0.01
0.01
O.01
0.01
O.01
0.01
Small
Terrestrial-
phase
Amphibians
O.01
O.01
0.01
O.01
0.01
O.01
0.01
O.01
0.01
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LD50 = 265 mg/kg-bw (for ring-necked pheasant)
8 Exceeds acute endangered species LOG (RQ>0.1)
Refined acute dietary-based RQs for CRLFs consuming small insects and herbivorous
mammals exceed the acute listed species LOG (0.1) for most uses of dicofol (the
exceptions include ornamentals, turf and Bermuda grass). Based on an analysis of the
likelihood of individual mortality considering the range of acute dietary-based RQs
exceeding the LOG for terrestrial-phase CRLFs consuming small herbivore mammals
(0.11-0.53), and using the probit dose-response of 5.92 (Table 27), the chance of
mortality to these CRLF range from 1 in 1.4xl08 individuals to 1 in 19 individuals. For
CRLFs consuming large insects, terrestrial-phase amphibians and small insectivorous
mammals, the acute LOG is not exceeded for any use (Table 50). This indicates that
CRLF could potentially be affected by acute exposures to dicofol.
Ill
-------
Table 50. Revised acute dietary-based RQs7 for CRLF consuming different food items. EECs
calculated using T-HERPS.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black),
Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms,
Outside building surfaces
Bermuda grass
Small
Insects
0.458
0.308
0.228
0.198
0.178
O.ll8
0.09
0.07
0.06
Large
Insects
0.05
0.03
0.02
0.02
0.02
0.01
0.01
0.01
0.01
Small
Herbivore
Mammals
0.528
0.358
0.268
0.228
0.208
0.138
O.ll8
0.09
0.07
Small
Insectivore
Mammals
0.03
0.02
0.02
0.01
0.01
0.01
0.01
0.01
0.01
Small
Terrestrial-
phase
Amphibians
0.02
0.01
0.01
0.01
0.01
<0.01
0.01
O.01
0.01
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LC50 = 905 ppm (for Japanese quail)
8 Exceeds acute endangered species LOG (RQ>0.1)
Chronic exposures
Refined chronic dietary-based RQs for CRLFs exceed the chronic listed species LOG
(1.0) for all uses of dicofol and for all food items potentially consumed by the CRLF
(Table 51). In the available chronic study where American kestrel were exposed to
dicofol, the NOAEC was 1 ppm, and the LOAEC was 3 ppm, based on decreased
eggshell thickness. Comparison of the LOAEC directly to chronic dietary-based EECs
for CRLF consuming all food items indicate that EECs for all uses are sufficient to
exceed the concentration where reproductive effects were observed in the laboratory.
There is some uncertainty in relying upon observed effects to egg shells to represent
effects to reproduction of the CRLF, since the CRLF does not produce eggs with shells.
In other chronic studies with birds, decreased number of eggs laid was observed in ring
doves and American kestrel feed 40 ppm dicofol. EECs from all uses of dicofol for CLRF
consuming small insects and small herbivore mammals are still sufficient to exceed this
level where decreased number of offspring was observed in birds.
Based on the above information, for all uses of dicofol, the effects determination for
chronic effects to the terrestrial-phase CRLF is "LAA" based on potential reproductive
effects.
112
-------
Table 51. Revised chronic dietary-based RQs7 for CRLF consuming different food items. EECs
calculated using T-HERPS.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black),
Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms,
Outside building surfaces
Bermuda grass
Small
Insects
4058
270v
2038
1698
1578
1018
84.48
67.58
54.08
Large
Insects
45.08
30.08
22.58
18.88
17.58
11.28
9.388
7.508
6.008
Small
Herbivore
Mammals
4748
3168
2378
1988
1848
1198
98.88
79. 18
63.38
Small
Insectivore
Mammals
30.0v
19388
14.88
12.48
11.58
7.418
6.188
4.948
3.958
Small
Terrestrial-
phase
Amphibians
14.18
9.378
7.038
5.868
5.468
3.518
2.938
2.348
1.878
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons,
6 nurseries and flowers
7 Based on NOAEC = 1 ppm (for American kestrel)
8 Exceeds chronic risk LOC (RQ>1.0)
and winter and summer squash
5.2.2. Indirect Effects (through effects to prey)
As discussed in Section 2.5.3, the diet of tadpole CRLF is composed primarily of
unicellular nonvascular aquatic plants and detritus. Juvenile CRLF consume primarily
aquatic and terrestrial invertebrates. The diet of adult CRLF is composed of aquatic and
terrestrial invertebrates, fish, frogs and mice. These prey groups are considered in
determining indirect effects to the CRLF caused by direct effects to its prey.
5.2.2.1. Algae (non-vascular plants)
RQ values for algae are below the LOC for all uses of dicofol. This results in a "no
effect" determination for indirect effects to the CRLF due to exposures of algae to
dicofol.
113
-------
5.2.2.2. Aquatic Invertebrates
Based on an analysis of the likelihood of individual mortality using acute RQs for aquatic
invertebrates and a probit dose-response of 4.5 (default), the likelihood of individual
mortality for each use is available in Table 52. Based on this analysis, all uses of dicofol
result in less than or equal to a 3% chance of effects to an individual aquatic invertebrates
representing prey of the CRLF.
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.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Bermuda grass
Ornamentals
Turf/Sod Farm
Outside Buildings
ULV application
Acute RQ1
0.233
0.323
0.233
0.0873
0.183
0.213
0.213
O.ll3
0.353
0.173
0.373
0.103
0.293
NA
NA
NA
NA
Likelihood
of
individual
acute
effect (%)
0.2
1.3
0.2
0.1
<0.1
0.1
0.1
<0.1
2.0
<0.1
2.6
0.1
0.8
NA
NA
NA
NA
Aerial application
Acute RQ1
0.133
0.123
0.133
0.045
0.0943
0.143
0.123
0.0643
0.153
0.0713
0.273
0.045
0.153
NA
NA
NA
NA
Likelihood
of
individual
acute effect
(%)
0.
O.
o.
0.
o.
0.
0.
o.
0.
o.
0.5
0.
O.
NA
NA
NA
NA
Ground application
Acute RQ1
O.ll3
0.0933
O.ll3
0.039
0.0813
0.133
O.ll3
0.0593
O.ll3
0.0543
0.263
0.037
0.133
0.016
0.044
0.021
0.0025
Likelihood
of
individual
acute effect
(%)
0.
O.
O.
0.
o.
0.
0.
o.
0.
o.
0.4
0.
O.
0.
o.
0.
0.
'Based on 48-h EC50 = 140 ug/L for daphnid.
2Based on NOAEC =19 ug/L for amphipod.
3 Exceeds acute risk to endangered species LOG (RQ>0.05)
NA = not applicable
Exposures of aquatic invertebrates to dicofol are quantified in terms of total residues of
dicofol. RQs are derived using the most sensitive toxicity data available for aquatic
invertebrates exposed to dicofol. It is assumed that dicofol's degradates of concern (i.e.,
DCBP, FW-152, DCBH and OH-DCBP) are equivalent to dicofol in toxicity to aquatic
invertebrates. This assumption adds uncertainty to the risk assessment, the toxicity of
dicofol's degradates to aquatic invertebrates is unknown. If exposures involving dicofol
only are considered, acute RQs for the aquatic invertebrates CRLF exceed the listed
species LOCs (0.05) for all dicofol uses, except cucurbits, peppers, tomatoes, Bermuda
grass, ornamentals, turf and outside buildings (Table 53 - Table 55). Chronic exposures
of dicofol parent are insufficient to exceed the LOG (1.0).
114
-------
Table 53. Acute and chronic RQs for aquatic invertebrates resulting from AERIAL applications of
dicofol. EECs are based on dicofol only.
Crop
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan Aerial
Peak EEC
(Hg/L)
3.25
6.46
3.48
1.34
2.70
2.52
2.70
1.61
6.46
3.25
6.41
1.61
4.41
21-day
(Hg/L)
0.46
0.97
0.64
0.19
0.38
0.38
0.39
0.23
0.90
0.46
1.76
0.23
0.66
Acute
RQ1
0.023
0.046
0.025
0.010
0.019
0.018
0.019
0.012
0.046
0.023
0.046
0.012
0.031
Chronic
RQ2
0.024
0.051
0.034
0.010
0.020
0.020
0.020
0.012
0.048
0.024
0.092
0.012
0.035
'Based on 48-h EC50 = 140 ug/L for daphnid.
2Based on NOAEC = 19 ug/L for amphipod.
Table 54. Acute and chronic RQs for aquatic invertebrates resulting from GROUND applications of
dicofol. EECs are based on dicofol only.
Crop
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Bermuda grass
Ornamentals
Turf/Sod Farm
Outside Buildings
Peak EEC
(Hg/L)
2.26
4.47
2.49
0.93
1.87
1.74
1.87
1.12
4.47
2.25
6.34
1.12
3.09
0.60
1.78
0.75
0.152
21-day
(Hg/L)
0.32
0.69
0.51
0.13
0.27
0.27
0.27
0.16
0.63
0.32
1.62
0.16
0.48
0.10
0.39
0.13
0.025
Acute
RQ1
0.016
0.032
0.018
0.0067
0.013
0.012
0.013
0.0080
0.032
0.016
0.045
0.0080
0.022
0.0043
0.013
0.0053
0.0011
Chronic
RQ2
0.017
0.036
0.027
0.0069
0.014
0.014
0.014
0.0084
0.033
0.017
0.085
0.0083
0.025
0.0054
0.020
0.0067
0.0013
'Based on 48-h EC50 = 140 ug/L for daphnid.
2Based on NOAEC = 19 ug/L for amphipod.
115
-------
Table 55. Acute and chronic RQs for aquatic invertebrates resulting from ULV applications of
dicofol. EECs are based on dicofol only.
Crop
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Peak EEC
(HS/L)
9.75
18.02
9.92
4.04
8.08
7.56
8.07
4.85
18.02
9.08
13.17
4.85
13.02
21-day
(HS/L)
1.38
2.58
1.49
0.56
1.14
1.08
1.15
0.69
2.52
1.28
2.70
0.68
1.85
Acute
RQ1
0.0703
0.133
0.0713
0.029
0.0583
0.0543
0.0583
0.035
0.133
0.0653
0.0943
0.035
0.0933
Chronic
RQ2
0.073
0.14
0.079
0.030
0.060
0.057
0.060
0.036
0.13
0.067
0.14
0.036
0.097
'Based on 48-h EC50 = 140 ug/L for daphnid.
2Based on NOAEC = 19 ug/L for amphipod.
3 Exceeds acute risk to endangered species LOG (RQ>0.05)
Chronic RQs based on total residues of dicofol for the majority of dicofol uses (all but
cucurbits, peppers, tomatoes, Bermuda grass, ornamentals, turf and outside buildings) are
sufficient to exceed the LOG (1.0). For ULV applications of dicofol to cotton, pome fruit,
strawberries, and walnuts/pecans, EECs are sufficient to exceed the LOAEC (33 |ig/L)
for chronic effects to aquatic invertebrates.
Based on the above information, the impact of the indirect effects to aquatic-phase
CRLFs via acute effects on aquatic invertebrates is discountable for all uses of dicofol.
The majority of dicofol uses (all but cucurbits, peppers, tomatoes, Bermuda grass,
ornamentals, turf and outside buildings) have the potential to result in chronic exposures
that may result in effects to aquatic invertebrates, especially when dicofol is applied via
ULV methods.
5.2.2.3. Fish and Aquatic-Phase Amphibians
Based on an analysis of the likelihood of individual mortality considering the range of
acute RQs exceeding the LOG for fish and aquatic-phase amphibians (0.05-0.71), and
using the probit dose-response of 4.5 (default assumption), likelihood of individual
mortality for each use is available in Table 56. Based on this analysis, use of dicofol on
beans, citrus, cotton, hops, mint, pome fruit, strawberries and walnuts/pecans results in
greater than a 10% likelihood of individual mortality. All other uses of dicofol result in
less than a 10% chance of effects to an individual fish and aquatic-phase amphibians
representing prey of the CRLF.
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.
Use
Beans
Citrus
Cotton
Cucurbit
Grape
Hops
Mint
Pepper
Pome Fruit
Stone Fruit
Strawberry
Tomato
Walnut/Pecan
Bermuda grass
Ornamentals
Turf/Sod Farm
Outside Buildings
ULV application
Acute
RQ1
0.60
0.85
0.60
0.23
0.48
0.56
0.54
0.30
0.92
0.45
0.97
0.26
0.76
NA
NA
NA
NA
Likelihood
of individual
mortality
(%)
16
38
16
0.2
7.6
13
11
0.9
44
5.9
48
0.4
30
NA
NA
NA
NA
Aerial application
Acute
RQ1
0.34
0.33
0.34
0.12
0.25
0.37
0.31
0.17
0.39
0.19
0.71
0.12
0.39
NA
NA
NA
NA
Likelihood
of individual
mortality
(%)
1.8
1.5
1.8
<0.1
0.3
2.6
1.1
0.1
3.3
0.1
25.2
<0.1
3.3
NA
NA
NA
NA
Ground application
Acute
RQ1
0.30
0.25
0.30
0.10
0.21
0.35
0.29
0.16
0.29
0.14
0.69
0.10
0.34
0.044
0.11
0.054
0.0067
Likelihood of
individual
mortality (%)
0.9
0.3
0.9
<0.1
0.1
2.0
0.8
0.1
0.8
O.I
23
O.I
1.8
O.I
O.I
0.1
O.I
:Based on 96-h LC50 = 53 ug/L for cutthroat trout
NA = not applicable
Chronic RQs for fish and aquatic-phase amphibians for the majority of dicofol uses (all
except Bermuda grass, turf and outside buildings) exceed the LOG (1.0) by factors of
1.1X to 10X, depending upon the use (Table 31 - Table 33). EECs are sufficient to
exceed the LOAEC (7.9 |ig/L, based on growth effects) for the majority of dicofol uses,
with the exception of Bermuda grass, ornamentals, turf and outside buildings.
5.2.2.4. Terrestrial Invertebrates
As noted above, for small insect exposures, RQ values range <1.04 to <0.138. For large
insect exposures, RQ values range <0.115 to <0.0153. For all uses of dicofol, RQ values
potentially exceed the acute risk LOG (RQ>0.05) for terrestrial insects. 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.
Based on an analysis of the likelihood of individual mortality considering the range of
acute RQs potentially exceeding the LOG (0.05 to <1.04), and using the default probit
dose-response of 4.5, the chance of mortality to terrestrial invertebrates range from less
than 0.1% to 53% (Table 57). For use of dicofol on grapes, mint, hops, peppers,
tomatoes, cucurbits, ornamentals, turf and Bermuda grass, dicofol exposures result in a
117
-------
chance of individual mortality to less than 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
indirect effects to greater than 10% of 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, especially considering that dicofol
is intended for control of insects.
Table 57. RQs7 and associated likelihood of individual effects to terrestrial invertebrates due to
dicofol exposures.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms, Outside
building surfaces
Bermuda grass
Small Insect
RQ
<1.04
0.69
<0.52
0.43
O.40
O.26
0.22
0.17
0.14
Likelihood
of individual
acute effect
(%)
<53.10
<23.40
<10.10
<4.95
<3.67
O.42
0.15
0.1
0.1
Large Insect
RQ
0.12
0.08
O.06
0.05
O.04
O.03
0.02
0.02
0.02
Likelihood
of individual
acute effect
(%)
0.1
0.1
O.I
0.1
O.I
O.I
0.1
0.1
0.1
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LD50 >391 ug a.i./g for honey bee
5.2.2.5. Mammals
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 (Table
58). Therefore, there is potential for acute effects of dicofol to terrestrial mammals.
118
-------
Based on an analysis of the likelihood of individual mortality using acute dose-based
RQs for terrestrial mammals and a probit dose-response of 4.5 (default value), the
likelihood of individual mortality for each use is available in Table 58. Based on this
analysis, the majority of dicofol uses result in less than a 10% chance of effects to an
individual terrestrial mammal representing prey of the CRLF. Only the highest RQ
(from citrus and pome fruits) result in estimations of likelihood of individual effects
which represents a significant indirect effect to the CRLF (10.7%). Therefore, the impact
of the indirect effects to terrestrial-phase CRLFs via acute effects on small mammals is
discountable for all uses of dicofol, except citrus and pome fruits.
Table 58. Acute dose-based RQs and associated likelihood of individual effects to small terrestrial
mammals (consuming short grass) due to dicofol exposures.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms, Outside building
surfaces
Bermuda grass
Acute,
dose-based7
0.53
0.35
0.27
0.22
0.21
0.13
0.11
0.09
0.07
Likelihood of
individual acute
effect (%)
10.7
2.0
0.5
0.2
0.1
<0.1
<0.1
<0.1
<0.1
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7Based on LD50 for laboratory rat =587 mg/kg.
Dose-based and dietary-based chronic RQs for terrestrial mammals exceed the LOG (1.0)
by factors of 19X to 781X, depending upon the use (Table 40). EECs are sufficient to
exceed the LOAEC (25 ppm, based on reproductive effects) for all uses by factors of 4X
or greater. Based on this information, 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.
The T-REX model is useful for assessing exposures of terrestrial animals to pesticides
through consumption of foliar surfaces of crops and insects on the treated site. The
model cannot be used to assess pesticide exposures to terrestrial animals resulting from
consumption of soil dwelling invertebrates which have accumulated the pesticide in their
tissues. In order to explore the potential exposures of mammals to total residues of
dicofol that have accumulated in earthworms inhabiting dicofol treatment sites, a simple
fugacity approach was employed to estimate dicofol concentrations in earthworms and
subsequent exposures to mammals consuming earthworms. This approach is explained in
detail in Appendix O
119
-------
Based on PRZM estimated dicofol concentrations of 10 and 0.16 g/m3 in soil and soil
pore water, respectively (Figure 9 and Figure 10), the estimated concentration of dicofol
in earthworms is 2914 ppm. This translates to a dose-based EEC of 2778 mg/kg-bw,
which exceeds the LD50 for rats of 587 mg/kg-bw. If it is assumed that a 20g mammal
consumes only earthworms, its chronic dietary based and dose-based exposures would be
approximately 100X and 1000X, respectively, above levels where reproductive effects
were observed in rats (25 ppm, MRID 41606601). Therefore, 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.
5.2.2.6. Terrestrial-Phase Amphibians
In order to explore influences of amphibian-specific food intake equations on potential
dose-based and dietary-based exposures of amphibians (prey of CRLF) to dicofol, the T-
HERPS model is used. The Pacific tree frog (Hyla regilld) is used to represent the
amphibian prey species. The weight of the animal is assumed to be 2.3 g, and its diet is
assumed to be composed of small and large insects. For frogs consuming small and
large insects, the acute LOG (0.1) is not exceeded for dicofol (Table 59).
Table 59. Acute dose-based RQs7 for terrestrial-phase frogs (prey) exposed to dicofol.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms, Outside building surfaces
Bermuda grass
Frogs
consuming
Small
Insects
0.04
0.04
0.03
0.02
0.02
0.01
0.01
0.01
0.01
Frogs
consuming
Large
Insects
<0.01
0.01
O.01
0.01
O.01
O.01
0.01
O.01
0.01
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer
6 nurseries and flowers
7 Based on LD50 = 265 mg/kg-bw (for ring-necked pheasant)
squash
Acute dietary-based RQs for the CRLF, which do not account for the weight of the
animal being assessed, can also be used to assess risks to the terrestrial frog prey (Table
50). For frogs which consume small insects, RQs exceed the acute LOG (0.1) for the
majority of dicofol uses, with the exception of use on cucurbits, ornamentals, turf, outside
120
-------
buildings and Bermuda grass. For frogs which consume large insects, the acute LOG is
not exceeded for dicofol.
Based on an analysis of the likelihood of individual mortality using acute dietary-based
RQs for terrestrial amphibians and a probit dose-response of 5.92, the likelihood of
individual mortality for each use is available in Table 60. Based on this analysis, 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.
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.
Use
Citrus,1 Pome Fruits2
Strawberries, Walnuts (English/black), Pecans
Beans, cotton, Stone Fruits3
Grapes, mint4
Hops
Peppers, Tomatoes
Cucurbits5
Ornamentals,6 Turf grasses, Sod farms, Outside building surfaces
Bermuda grass
Acute, dietary-
based RQ7
0.45
0.30
0.22
0.19
0.17
0.11
0.09
0.07
0.06
Likelihood of
individual acute
effect (%)
2.0
0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
1 grapefruit, lemons, oranges, tangelos, and tangerines
2 apples and pears
3 apricots, cherries, nectarines, peaches, plums, and prunes
4 mint, peppermint and spearmint
5 cantaloupes, cucumbers, melons, pumpkins, watermelons, and winter and summer squash
6 nurseries and flowers
7 Based on LC50 = 903 ppm (for Japanese quail)
Chronic dietary-based RQs for the CRLF, which do not account for the weight of the
animal being assessed, can also be used to assess risks to the terrestrial frog prey (Table
51). Chronic RQs for the frog exceed the LOG (1.0) by factors ranging from 2X to 474X.
Therefore, for all dicofol uses, there is potential for indirect effects to the CRLF resulting
from chronic effects to terrestrial amphibians.
5.2.3. Indirect Effects (through effects to habitat)
Aquatic plants serve several important functions in aquatic ecosystems. Non-vascular
aquatic plants are primary producers and provide the autochthonous energy base for
aquatic ecosystems. Vascular plants provide structure as attachment sites and refugia for
many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In
121
-------
addition, vascular plants also provide primary productivity and oxygen to the aquatic
ecosystem. Rooted plants help reduce sediment loading and provide stability to
nearshore areas and lower streambanks. In addition, vascular aquatic plants are
important as attachment sites for egg masses of CRLFs.
Terrestrial plants serve several important habitat-related functions for the CRLF. In
addition to providing habitat and cover for invertebrate and vertebrate prey items of the
CRLF, terrestrial vegetation also provides shelter for the CRLF and cover from predators
while foraging. Terrestrial plants also provide energy to the terrestrial ecosystem through
primary production. Upland vegetation including grassland and woodlands provides
cover during dispersal. Riparian vegetation helps to maintain the integrity of aquatic
systems by providing bank and thermal stability, serving as a buffer to filter out sediment,
nutrients, and contaminants before they reach the watershed, and serving as an energy
source.
Due to a lack of effects data, potential risk of dicofol to plants cannot be quantified.
Qualitative effects data suggest that applications of dicofol may result in phytotoxicity,
however, due to a lack of detail provided in the available studies, the relationship
between effects observed and application rates of dicofol cannot be defined. In addition,
there is one reported incident involving effects of dicofol to plants. Although effects of
dicofol on plants cannot be quantified, effects of dicofol on plants cannot be discounted.
5.2.4. Primary Constituent Elements of Designated Critical Habitat
As discussed above, effects of dicofol to plants comprising the aquatic and terrestrial
habitats of the CRLF cannot be discounted. Also, exposures of dicofol to the CRLF and
its prey have the potential to affect the CRLF. Therefore, dicofol is likely to result in
effects to the CRLF's aquatic and terrestrial habitats based on potential impacts to all 8
PCEs.
5.2.5. Area of Effects
The initial area of concern for dicofol was previously discussed in Section 2.7 and
depicted in Figure 5 of the problem formulation. A map depicting the overlap of this
initial area of concern and CRLF habitat is depicted in Figure 11. Because of the lack of
a NOAEC in several chronic toxicity studies with birds (described in Section 4.3.1), the
action area for dicofol is established as the entire state of California.
122
-------
Dicofol Use & CRLF Habitat Overalp
$5" *• '
x*'4
*. &
; Dicofol 8.CRLF Overlap
CNDDB occurrence sections
Critical habitat
Core areas
County boundaries
I Kilo meters
0 2040 80 120 160
Compiled from California Counts' boundaries (ESRI, 2002),
US DA G a p An aly si s P rog ta m 0 rch ard;1 V in ey ard La ndc ov er (GA P)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesiicides Programs, Environmental Fate and Effects Dwision.
Projection: Albers Equal Area Conic USCS, North American
Datum of 1983 (NAD 1983).
3/11/2009
Figure 11. Intersection between dicofol use areas and CRLF habitat.
Available pesticide use data from California indicate that dicofol has been used in
counties which contain CRLF habitat. Out of 58 counties in California, 33 contain some
123
-------
portion of CRLF critical habitat or core areas. According to use data for 1999-2006, all of
the 33 counties containing CRLF areas have reported past uses of dicofol. From 1999-
2006, 8 of these counties had >1000 pounds of dicofol applied annually (Table 61).
Table 61. Summary of CDPR pesticide use reporting by county for dicofol (annual pounds of dicofol
applied from 1999 to 2006).
County
FRESNO
TULARE
KINGS
MERCED
KERN
STANISLAUS
SAN JOAQUIN
MADERA
MONTEREY
IMPERIAL
SUTTER
RIVERSIDE
BUTTE
YOLO
GLENN
TEHAMA
SOLANO
COLUSA
SANTA BARBARA
SACRAMENTO
CONTRA COSTA
SAN LUIS OBISPO
SAN DIEGO
SONOMA
SANTA CLARA
ALAMEDA
VENTURA
LOS ANGELES
SAN BENITO
SISKIYOU
YUBA
ORANGE
MENDOCINO
AMADOR
SAN BERNARDINO
SHASTA
MODOC
SANTA CRUZ
Are CRLF
habitat/core
areas
present?
yes
no
yes
yes
yes
yes
yes
no
yes
no
no
yes
yes
no
no
yes
yes
no
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
no
yes
yes
no
yes
no
yes
no
yes
1999
123,090
53,026
35,692
23,932
32,442
17,860
22,647
12,042
7,057
8,439
2,514
5,996
829
4,652
2,016
1,219
2,353
1,766
487
3,537
1,432
1,881
449
1,363
76
1,667
27
527
813
0
177
860
604
92
211
173
0
222
2000
100,221
62,227
44,112
25,490
22,994
23,376
15,153
6,208
4,058
2,916
3,590
2,466
1,545
2,585
645
1,529
496
224
1,670
1,270
1,107
1,495
269
780
12
72
84
731
416
0
11
60
161
16
149
218
0
4
2001
75,201
39,640
18,674
19,746
9,345
14,536
3,379
4,369
4,504
3,103
3,071
1,913
4,846
1,511
1,066
1,128
1,210
233
797
133
1,282
198
385
103
7
35
189
273
55
0
638
18
0
30
86
11
0
9
2002
51,563
35,513
25,114
17,070
10,338
13,815
4,895
3,019
1,523
2,271
4,067
2,046
1,278
2,466
1,273
2,356
1,294
770
349
376
33
56
290
8
26
0
23
135
0
0
47
31
2
0
45
0
0
179
2003
49,215
42,234
27,709
18,552
8,726
11,925
3,527
2,037
802
2,371
2,500
3,140
4,196
1,771
980
2,159
833
403
162
211
301
4
496
18
179
0
441
29
0
8
263
13
0
629
29
26
0
8
2004
63,344
43,507
31,010
27,707
5,966
13,822
5,582
2,454
1,824
2,965
1,846
2,694
2,255
403
618
42
368
1,775
636
o
J
334
149
288
0
395
2
693
2
50
494
7
8
0
0
5
31
441
0
2005
60,967
35,060
29,124
19,666
12,774
7,120
4,839
5,358
3,767
2,138
1,580
586
3,797
431
1,226
277
663
756
1,311
8
0
o
J
235
0
840
0
251
2
0
874
0
3
6
0
5
34
20
0
2006
27,191
10,155
7,807
22,032
5,828
5,330
5,924
4,938
1,825
472
2,905
1,212
1,102
341
1,170
29
184
479
571
0
10
324
86
2
543
0
27
7
195
149
0
0
0
0
5
2
0
0
124
-------
County
CALAVERAS
NAPA
SAN MATED
PLACER
LAKE
EL DORADO
NEVADA
PLUMAS
MARIPOSA
SIERRA
MARIN
SAN FRANCISCO
HUMBOLDT
Are CRLF
habitat/core
areas
present?
no
yes
yes
no
no
yes
yes
yes
no
no
yes
no
no
Total
1999
63
154
103
42
47
65
42
12
0
6
2
2
0
372,704
2000
8
0
19
125
7
0
7
0
6
0
0
0
1
328,533
2001
173
53
40
1
38
6
0
0
0
0
0
0
0
212,033
2002
123
0
8
0
12
14
4
0
0
0
0
0
0
182,430
2003
0
8
10
1
20
42
0
0
0
0
0
0
0
185,981
2004
0
0
13
0
6
2
0
0
0
0
0
0
0
211,738
2005
0
65
20
1
3
2
0
0
0
0
0
0
0
193,809
2006
0
0
12
0
3
0
0
0
0
0
0
0
0
100,862
In order to determine the extent of the lotic (flowing) aquatic habitat directly affected in
aquatic, the greatest ratio of the RQ to the LOG for any endpoint for aquatic organisms is
used to determine the distance downstream for concentrations to be diluted below levels
that would be of concern (i.e. result in RQs less than the LOG). For this assessment, this
applies to RQs for acute exposures of total residues of dicofol to the aquatic-phase CRLF
(and fish and aquatic-phase amphibians). The highest RQ (0.71) divided by the acute
LOG (0.05) results in a ratio of 14.2. The maximum downstream distance from areas
where dicofol are applied and dicofol is at concentrations that are of concern to the
aquatic-phase CRLF is 155 km.
EECs and relevant RQs calculated by T-FIERPS and T-REX apply to sites where dicofol
is directly applied. Since dicofol can be transported through spray drift to non-target
areas beyond the treatment site, the CLRF and its prey located outside of direct treatment
areas can still be exposed to dicofol in non-target areas. Exposure and associated risks to
the CRLF are expected to decrease with increasing distance away from the treated field
or site of application.
Based on acute effects data for the terrestrial-phase CRLF, spray drift deposition of
dicofol as low as 0.18 Ibs a.i./A would be sufficient to exceed the acute listed species
LOG for the CRLF. This is based on the highest acute RQ for terrestrial phase CRLF and
its prey, which is 1.69 based on risks to medium sized CRLF receiving dicofol through
consumption of small herbivore mammals. For aerial applications of dicofol to citrus and
pome fruits, at the maximum application rate (3 Ib a.i./A), spray drift is sufficient to
exceed the LOG for as far as 161 feet from the edge of the treatment field (Table 62).
Since 3 Ib a.i./A represents the highest application rate of dicofol, for all other uses of
dicofol, the distance from the edge of the field where the LOG is exceeded is expected to
be less than 161 feet for aerial applications and 43 feet for ground applications.
125
-------
Table 62. Single application rate not exceeding acute LOG for dietary- and dose-based exposures of
the CRLF to dicofol.
CRLF
size1
medium
all
all
large
medium
small
medium
large
large
Small
medium
large
all
medium
all
all
large
Based
on dose
or diet?
Dose
Diet
Diet
Dose
Dose
Dose
Dose
Dose
Dose
Dose
Dose
Dose
Diet
Dose
Diet
Diet
Dose
Feeding Category
small herbivore mammals
Small herbivore mammals
Small insects
small herbivore mammals
small insectivore mammals
small insects
small insects
small insects
small insectivore mammals
large insects
large insects
large insects
large insects
terrestrial-phase amphibians
Small insectivore mammals
Terrestrial-phase amphibians
terrestrial-phase amphibians
Highest
application rate
not exceeding
LOC (Ibs a.i./A)
0.18
0.55
0.64
1.1
2.9
>3
>3
>3
>3
>3
>3
>3
>3
>3
>3
>3
>3
Distance from edge of field where LOC
is not exceeded (in feet) for single
application of 3 Ib a.i./A2' 3
Ground
43
16
13
10
3
0
0
0
0
0
0
0
0
0
0
0
0
Aerial
161
43
30
10
0
0
0
0
0
0
0
0
0
0
0
0
0
1. Small is defined as 1.4 g. Medium is defined as 37 g. Large is defined as 238 g.
2. Estimated using the terrestrial assessment of the Tier 1 version of AgDRIFT. Modeling assumed that applications
were done using ground and aerial methods, and assuming that the droplet size distribution was "ASAE very fine to
fine" for ground applications (high boom) and "ASAE fine to medium" for aerial applications.
3. 3 Ib a.i./A is the highest application of dicofol. This corresponds to applications to citrus and pome fruits.
5.2.6. Description of Assumptions, Limitations and Uncertainties
5.2.6.1. Exposure Assessment
Maximum Use Scenario
The screening-level risk assessment focuses on characterizing potential ecological risks
resulting from a maximum use scenario, which is determined from labeled statements of
maximum application rate and number of applications with the shortest time interval
between applications. The frequency at which actual uses approach this maximum use
scenario may be dependant on pest resistance, timing of applications, cultural practices,
and market forces.
126
-------
Use Characterization Uncertainties
County-level usage data were obtained from California's Department of Pesticide
Regulation Pesticide Use Reporting (CDPR PUR) database. CDPR PUR documentation
indicates that errors in the data may include the following: a misplaced decimal;
incorrect measures, area treated, or units; and reports of diluted pesticide concentrations.
In addition, it is possible that the data may contain reports for pesticide uses that have
been cancelled. As with all pesticide usage data, there may be instances of misuse and
misreporting. The Agency made use of the most current, verifiable information; in cases
where there were discrepancies, the most conservative information was used.
Aquatic Exposure Modeling ofDicofol
The standard ecological water body scenario (EXAMS pond) used to calculate potential
aquatic exposure to pesticides is intended to represent conservative estimates, and to
avoid underestimations of the actual exposure. The standard scenario consists of
application to a 10-hectare field bordering a 1-hectare, 2-meter deep (20,000 m3) pond
with no outlet. Exposure estimates generated using the EXAMS pond are intended to
represent a wide variety of vulnerable water bodies that occur at the top of watersheds
including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural
ponds, and intermittent and lower order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the EXAMS pond. Static water bodies
that have larger ratios of pesticide-treated drainage area to water body volume would be
expected to have higher peak EECs than the EXAMS pond. These water bodies will be
either smaller in size or have larger drainage areas. Smaller water bodies have limited
storage capacity and thus may overflow and carry pesticide in the discharge, whereas the
EXAMS pond has no discharge. As watershed size increases beyond 10-hectares, it
becomes increasingly unlikely that the entire watershed is planted with a single crop that
is all treated simultaneously with the pesticide. Headwater streams can also have peak
concentrations higher than the EXAMS pond, but they likely persist for only short
periods of time and are then carried and dissipated downstream.
The Agency acknowledges that there are some unique aquatic habitats that are not
accurately captured by this modeling scenario and modeling results may, therefore,
under- or over-estimate exposure, depending on a number of variables. For example,
aquatic-phase CRLFs may inhabit water bodies of different size and depth and/or are
located adjacent to larger or smaller drainage areas than the EXAMS pond. The Agency
does not currently have sufficient information regarding the hydrology of these aquatic
habitats to develop a specific alternate scenario for the CRLF. CRLFs prefer habitat
with perennial (present year-round) or near-perennial water and do not frequently inhabit
vernal (temporary) pools because conditions in these habitats are generally not suitable
(Hayes and Jennings 1988). Therefore, the EXAMS pond is assumed to be representative
of exposure to aquatic-phase CRLFs. In addition, the Services agree that the existing
EXAMS pond represents the best currently available approach for estimating aquatic
exposure to pesticides (U.S. FWS/NMFS 2004).
127
-------
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations
that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone
Model is a process or "simulation" model that calculates what happens to a pesticide in
an agricultural field on a day-to-day basis. It considers factors such as rainfall and plant
transpiration of water, as well as how and when the pesticide is applied. It has two major
components: hydrology and chemical transport. Water movement is simulated by the use
of generalized soil parameters, including field capacity, wilting point, and saturation
water content. The chemical transport component can simulate pesticide application on
the soil or on the plant foliage. Dissolved, adsorbed, and vapor-phase concentrations in
the soil are estimated by simultaneously considering the processes of pesticide uptake by
plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection,
dispersion, and retardation.
Uncertainties associated with each of these individual components add to the overall
uncertainty of the modeled concentrations. Additionally, model inputs from the
environmental fate degradation studies are chosen to represent the upper confidence
bound on the mean values that are not expected to be exceeded in the environment
approximately 90 percent of the time. Mobility input values are chosen to be
representative of conditions in the environment. The natural variation in soils adds to the
uncertainty of modeled values. Factors such as application date, crop emergence date,
and canopy cover can also affect estimated concentrations, adding to the uncertainty of
modeled values. Factors within the ambient environment such as soil temperatures,
sunlight intensity, antecedent soil moisture, and surface water temperatures can cause
actual aquatic concentrations to differ for the modeled values.
The temporal and spatial distribution of pesticides with persistent and bioaccumulative
characteristics in aquatic ecosystems is expected to be influenced substantially by
processes governing sediment particle delivery to (and transport within) water bodies
(i.e., sediment dynamics). For these compounds, soil erosion is usually a major source of
pesticide loading into aquatic ecosystems. Once in an aquatic ecosystem, processes such
as settling, resuspension, and burial of sediment particles can affect the distribution of
pesticides in the water column-, pore water-, and suspended- and benthic-sediment
compartments. Sediment dynamics can also influence pesticide bioavailability within
these compartments, due to pesticide sorption on particulate organic carbon and
complexation with dissolved organic carbon. Currently, OPP's aquatic exposure
modeling framework incorporates pesticide delivery to a standard pond from soil erosion
and runoff using the Pesticide Root Zone Model (PRZM). In this modeling framework,
only the pesticide mass delivered from soil erosion and runoff is considered for delivery
to an aquatic ecosystem (i.e., the mass of soil and volume of runoff predicted by PRZM
are not considered). Pesticide transport between the water column and the benthic region
within the standard pond is modeled using the Exposure Analysis Modeling System
(EXAMS) based on a set of lumped parameters that are designed to reflect the combined
effect of multiple transport processes (e.g., diffusion, setting and resuspension). The
current modeling framework does not consider pesticide burial in the benthic area, a
process by which pesticide is rendered permanently unavailable for biological interaction
due to accumulating sediment. Without consideration of burial processes, the current
128
-------
modeling framework likely represents an effective screen for pesticide exposure
assessment in both lentic (static) and lotic (flowing water) systems.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a
vegetative setback on runoff and loadings. The effectiveness of vegetative setbacks is
highly dependent on the condition of the vegetative strip. For example, a well-
established, healthy vegetative setback can be a very effective means of reducing runoff
and erosion from agricultural fields. Alternatively, a setback of poor vegetative quality
or a setback that is channelized can be ineffective at reducing loadings. Until such time
as a quantitative method to estimate the effect of vegetative setbacks on various
conditions on pesticide loadings becomes available, the aquatic exposure predictions are
likely to overestimate exposure where healthy vegetative setbacks exist and
underestimate exposure where poorly developed, channelized, or bare setbacks exist.
Terrestrial Exposure Modeling ofDicofol
The Agency relies on the work of Fletcher et al. (1994) for setting the assumed pesticide
residues in wildlife dietary items. These residue assumptions are believed to reflect a
realistic upper-bound residue estimate, although the degree to which this assumption
reflects a specific percentile estimate is difficult to quantify. It is important to note that
the field measurement efforts used to develop the Fletcher estimates of exposure involve
highly varied sampling techniques. It is entirely possible that much of these data reflect
residues averaged over entire above ground plants in the case of grass and forage
sampling.
It was assumed that ingestion of food items in the field occurs at rates commensurate
with those in the laboratory. Although the screening assessment process adjusts dry-
weight estimates of food intake to reflect the increased mass in fresh-weight wildlife food
intake estimates, it does not allow for gross energy differences. Direct comparison of a
laboratory dietary concentration- based effects threshold to a fresh-weight pesticide
residue estimate would result in an underestimation of field exposure by food
consumption by a factor of 1.25 - 2.5 for most food items.
Differences in assimilative efficiency between laboratory and wild diets suggest that
current screening assessment methods do not account for a potentially important aspect of
food requirements. Depending upon species and dietary matrix, bird assimilation of wild
diet energy ranges from 23 - 80%, and mammal's assimilation ranges from 41 - 85%
(U.S. EPA 1993). If it is assumed that laboratory chow is formulated to maximize
assimilative efficiency (e.g., a value of 85%), a potential for underestimation of exposure
may exist by assuming that consumption of food in the wild is comparable with
consumption during laboratory testing. In the screening process, exposure may be
underestimated because metabolic rates are not related to food consumption.
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
129
-------
considered, and it was assumed that species occupy, exclusively and permanently, the
modeled treatment area. Spray drift model predictions suggest that this assumption leads
to an overestimation of exposure to species that do not occupy the treated field
exclusively and permanently.
Long Range Transport
-v-7
Based on dicofol's vapor pressure (3.9x10" torr), low levels of volatility can potentially
occur, but are not expected. However, once in the air dicofol can be expected to partition
between the gas and particle phases in the atmosphere, existing largely in the particle
phase, potentially contributing to the long-range transport of dicofol. Partioning in the air
would most likely occur when the pesticide is applied via an aerial or ground spray,
particularly when ultra-low volume sprays. Data on volatilization from foliar surfaces
were not available. However, three dislodgeable foliar residue studies indicate that the
half-life for dicofol on cotton, cucumbers, and oranges was 3.2, 5.52, and 15.6 days,
respectively. For comparative purposes, DDT has a range of half-lives on clover from
1.6 to 18.8 days (Willis and McDowell 1987).
Although OPP is not able to quantify the extent to which dicofol and its degradates will
undergo long-range atmospheric transport once it has been released from a treatment site,
this mechanism of transport will constitute a route of exposure for nontarget animals
distant from use sites. Based on its vapor pressure (3.9x10" torr @ 20°C) and persistence
in the air (half life =3.1 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-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."
Atmospheric Monitoring Data
In 2000, CDPR monitored ambient air in Lompoc (Santa Barbara County) for 31
pesticides and breakdown products, including dicofol (CDPR 2003). Lompoc County is
one of the largest producers of flower seeds in the United States. CDPR monitored the
pesticides during the peak use period for most of the pesticides, between May 31 and
August 3, 2000. During this 10-week period, DPR collected 24-hour samples, four
consecutive days per week at each of the four monitoring locations, located in the
northwest, west, southwest, and central parts of the county. The University of California,
Davis performed the primary laboratory analysis, using a new method developed
specifically to analyze the pesticides used in Lompoc. For dicofol, the highest one-day
air concentration was listed as trace, meaning the concentration was halfway between the
method detection limit and the estimated quantitation limit of 4 ng/m3. Additionally, the
highest 14-day and 10-week air concentrations measured for dicofol were also listed as
trace (i.e.., the concentration was halfway between the method detection limit and the
estimated quantitation limit of 1.37 ng/m3 and 0.91 ng/m3, respectively). Collocated
samples were collected during the last week of sampling to determine if any percentage
of the chemical concentrations were being missed in the analysis of the primary samples
130
-------
as particulates. In all of the samples analyzed, levels of dicofol were below detection
levels.
In 2006, as part of the California Environmental Protection Agency's Environmental
Justice Action Plan, CDPR conducted a pilot project focusing on pesticide air
concentrations in the low-income, predominantly Hispanic, Fresno County farming
community of Parlier, located in the San Joaquin Valley (CDPR 2006). Fruit orchards
and grape vineyards were the predominant crops in the area. CDPR and the Air
Resources Board (ARE) collected samples of ambient air at three primary schools
throughout the 2006 calendar year. During the sampling period, approximately 6
applications totaling 150 Ibs of dicofol occurred within five miles of Parlier in 2006.
Four hundred and sixty-eight ambient air samples were collected and analyzed for
dicofol. Dicofol was not detected in any of the 468, one-day concentration samples
collected (quantitation limit = 46.3 ng/m3). It does not appear that particulate matter,
collected during this study, was analyzed for dicofol concentrations; given that dicofol is
expected to be associated with particulate matter suspended in the air, the absence of
detections may not accurately reflect the potential movement of dicofol.
The USGS publication, Pesticides in the Atmosphere (Majewski et al. 1995) reports an
observed concentration for kelthane (dicofol) in the air of 9.5 ng/m3. Additionally, a
cited study in this reference reports one detected residential outdoor ambient air
concentration of 6 ng/m3 out of 53 samples collected (Yeary et al. 1993). It is not clear
whether the detection occurred in California.
Modeling of Long-Range Transport Potential
The "OECD Pov and LRTP Screening Tool" (version 2.0) was utilized in evaluating the
overall environmental persistence (Pov), the long range transport potential (LRTP) and
transfer efficiency (TE). The OECD Tool requires estimated degradation half lives in
soil, water and air, and partition coefficients between air and water and between octanol
and water as chemical-specific input parameters to calculate metrics of Pov and LRTP.
Pov is derived from the degradation rate constants in soil, water and air to provide overall
degradation. The resulted Pov value represents the characteristic time for disappearance
of a chemical after releases in various media have been stopped and the overall
degradation rate is determined by the disappearance of chemical from a medium
(Scheringer et al., 2006). The characteristic travel distance (CTD) represents the
potential of a chemical to be transported over long distances in air or water. In the OECD
Tool, the CTD is the distance at which the concentration of chemical decrease to 37%
due to transport of chemical by a constant flow of air (wind speed of 0.02 m/s) or water
(ocean water circulation speed of 0.02m/s (Scheringer et al. 2006).
Transfer efficiency is a dimensionless metric of potential for atmospheric transport and
deposition of parent compound in terrestrial and aquatic environments of a remote region
(Wegmann et al. 2007). It is a ratio between the depositional flux (mol/day) in remote
region and emission flux from the source area. A high TE value indicates an "optimal"
transport condition from the source region to remote depositional region.
131
-------
The OECD Tool was used in evaluating the Pov and LRTP for 3 known PBT chemicals
(DDT, aldrin and endrin) and the dicofol isomers (both as the parent and parent plus
degradates) using chemical-specific degradation half-lives in soil, water, and air as well
as two partition constants, the Kow and KAw- Table 63 provides input parameters used in
the OECD Tool.
Table 63. Physicochemical and environmental fate properties used as input for estimating overall
persistence and long-range transport potential using the OECD Tool.
Name of
Chemical
p.p"DDTb
Aldrin b
Endrin b
o,p' dicofol
p,p' -dicofol
DCBP
FW-152
DCBH
3- and 4- OH-
DCBP
2 OH-DCBP
Molecular
Weight
(g/mole)
345.5
364.9
380.9
370.5
370.5
251
336
253
267
267
Log KoWa
6.39
4.94
5.44
6.06
6.06
4.44e
4.89e
4.0e
3.96e
4.73e
Log KAwa
-3.34
-3.38
-3.11
-7.641
-5.005
-4.359e
-7.187e
-6.404e
-8.343e
-5.242e
Half life
in Air
(hrs)
170
2.86
12.72
74.4C
74.4C
103e
57. 1"
25.1e
46.8e
11. 3e
Half life
in Water
(hrs)
5500
2670
78840
408d
1536d
1440e
4320e
900e
1440e
1440e
Half life
in Soil
(hrs)
17000
3830
29070
612d
2304 d
2880e
8640e
1800e
2880e
2880e
a Maximum reported value
b Input parameters for these chemical are based on the Reference chemicals data in the OECD
Tool.
c Half-life in air based on value reported in Rasenberg et al. 2003
d The half-life in water based on PRZM/EXAM inputs
e Maximum value derived in EPISuite for dicofol degradates.
Although there are considerable uncertainties in the environmental fate properties of the
selected chemicals under consideration, the results (Table 64) indicate that dicofol and its
degradates have Pov and LRTP properties similar to those of several known POPs (p,p'
DDT, aldrin and endrin).
Table 64. Overall persistence and characteristic travel distances generated using the OECD Tool.
Chemical
p.p'DDT
Aldrin
Endrin
o,p '-dicofol
p,p '-dicofol
DCBP
FW-152
DCBH
3- and 4- OH-
DCBP
2 OH-DCBP
Overall Persistence
(Pov)
(Days)
1010
225
1556
37
138
172
516
108
171
173
Characteristic Travel
Distance
km (Miles)
2530 (1572)
206 (128)
515 (320)
2142(1331)
1467 (912)
1381 (858)
504(313)
238 (148)
149 (93)
228 (142)
Transfer
Efficiency
(%)
5.17
0.003
0.04
9.45
3.39
2.24
2.15
0.66
0.31
0.10
132
-------
Results from the OECD Tool do not indicate absolute loading of pesticides in the
environment but help to compare model estimates for dicofol residues relative to known
POP pesticides according to their Pov, TE, and CTD.
Annual Emission Amounts
There are two potential mechanisms that can result in transport of dicofol from an
application area to the atmosphere with subsequent wet or dry deposition of the
compound to areas distant from the initial site of application. These mechanisms include
1) drift of dicofol during spray treatments of fields and 2) wind erosion of soil containing
sorbed dicofol.
From the CA PUR data, the average annual rate of dicofol applied between 1999 and
2006 was 223,511 Ibs. From the AGDRIFT analysis, between 0.94% and 8.7% of the
amount applied during aerial and ULV application, respectively, is lost due to airborne
drift, or 2,101 to 19,450 Ibs/year. Wet and dry deposition would result in removal of this
airborne drift from the atmosphere; however, estimates of these removal processes
require estimates for scavenging coefficients, particle size distributions, and settling
velocities, and are beyond the level of this analysis. As such, a conservative estimate
would result in all of the aerial drift, or 2,101 to 19,450 Ibs/year, remaining for long-
range transport.
As dicofol has an affinity to partition to particulate matter, a potentially significant source
of dicofol emissions from a field would be particulate matter from windblown soil
erosion. The California Air Resources Board developed non-pasture agriculture
particulate matter emission estimates for a number of counties in California (CARB
1997). These emission estimates were divided by the total number of acres harvested in
each county (USDA 2009) and then multiplied by the average annual acres of dicofol
applied in each county (from the CA PUR data), in order to estimate the annual
particulate matter per county where dicofol was used. The average annual amount of
particulate matter from nonpasture windblown agricultural emissions in counties where
dicofol was applied was 2,677 tons/year. If 90% of the dicofol applied is integrated into
the top 1 cm of the soil, then the concentration of dicofol in the soil is 2.59 x 10"8 Ibs
dicofol/cm3 (0.9 x 223,511 Ibs / [192,120 acres x 4.05 x 107 cm2/acre x 1 cm]).
Assuming an average soil bulk density of 1.3 g/cm3, this equates to 9.03 x 10"6 Ibs
dicofol/lb soil. Multiplying this concentration by the average amount of particulate
matter from nonpasture windblown agricultural emissions results in 48 Ibs/year of dicofol
emitted via wind erosion.
The average total annual amount of dicofol, not including that which might volatilize
from the soil or wate surface, that is available for long range transport is between 2,149
and 19,500 Ibs/year, or between 1 and 9% of the dicofol applied. It is worth noting that
despite these estimates, air monitoring reported earlier snowed only trace amounts of
dicofol in the atmospheric samples collected.
133
-------
DDT, DDD, DDE
In assessing the impacts of dicofol on the red-legged frog, it was assumed that the
impacts of DDT, DDD, and DDE would be additive to those seen for dicofol's total
residues of concern.
5.2.6.2. Effects Assessment
Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test organism age may have a significant impact on the
observed sensitivity to a toxicant. The acute toxicity data for fish are collected on
juvenile fish between 0.1 and 5 grams. Aquatic invertebrate acute testing is performed on
recommended immature age classes (e.g., first instar for daphnids, second instar for
amphipods, stoneflies, mayflies, and third instar for midges).
Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients that act directly without metabolic transformation because younger age
classes may not have the enzymatic systems associated with detoxifying xenobiotics. In
so far as the available toxicity data may provide ranges of sensitivity information with
respect to age class, this assessment uses the most sensitive life-stage information as
measures of effect for surrogate aquatic animals, and is therefore, considered as
protective of the CRLF.
Use of Surrogate Species Effects Data
Guideline toxicity tests and open literature data on dicofol are not available for frogs or
any other aquatic-phase amphibian; therefore, freshwater fish are used as surrogate
species for aquatic-phase amphibians. Endpoints based on freshwater fish ecotoxicity
data are assumed to be protective of potential direct effects to aquatic-phase amphibians
including the CRLF, and extrapolation of the risk conclusions from the most sensitive
tested species to the aquatic-phase CRLF is likely to overestimate the potential risks to
those species. Efforts are made to select the organisms most likely to be affected by the
type of compound and usage pattern; however, there is an inherent uncertainty in
extrapolating across phyla. In addition, the Agency's LOCs are intentionally set very
low, and conservative estimates are made in the screening level risk assessment to
account for these uncertainties.
In order to characterize the conservatism, of the endpoint selected to represent direct
effects to aquatic-phase CRLF (i.e., the 96-h LCso for the cutthroat trout = 53 |ig/L), a
genus sensitivity distribution was derived using the available acute toxicity data for
freshwater fish (Table 24). Data were considered useful for the distribution if they are
classified acceptable or supplemental. Data for this distribution were collected from
registrant-submitted studies as well as the open literature (as identified using ECOTOX).
Once the data set was assembled, the average of the LoglO values of the LCso values for
134
-------
a species was calculated. Then, the average of the Log 10 values of the genera was
calculated. A student's t distribution was used to derive a genus sensitivity distribution
for with the mean and standard deviations of log-transformed acute toxicity data for all of
the available genera of fish. The degrees of freedom were equal to n-1, where n is the
number of genera for which there are data available for the distribution. In this case, data
were available for 6 genera, so the distribution was established with 5 degrees of
freedom. The t-statistic was calculated for probabilities ranging 0.05-0.95 at intervals of
0.05. The log LC50 value for a specific proportion (p) of genera is calculated by Equation
1. The genus sensitivity distribution for 96-h LCso values for fish exposed to dicofol is
displayed in Figure 12. Additional information relevant to this sensitivity distribution is
provided in Appendix L. The endpoint selected to represent direct effects to aquatic-
phase CRLF (LC50 = 53 |ig/L) is comparable to the lower 5% of the genus sensitivity
distribution (LCso = 49 |ig/L), indicating that this endpoint is protective of the lower 5th
percentile of freshwater fish species.
Equation 1. Log LC50p = Mean Log LC50 + (tp * STDEV)
c
o
+j
k.
o
Q.
8.
Q_
1 n
0.9 -
0.8 -
0.7 -
0.6 -
0.5 -
0.4 -
0.3 -
0.2 -
0.1 -
0 -
Pimephales
Lepomis
Micropterus
Ictalurus
^ Oncorhynchus
Salvelinus
10.0 100.0 1000.0
LC50 (ug/L)
Figure 12. Genus sensitivity distribution for acute (96-h) exposures of fish to dicofol.
In order to characterize the conservatism of the endpoint selected to represent direct
effects to terrestrial-phase CRLF (i.e., the subacute dietary toxicity endpoint for birds,
LCso for the Japanese quail = 903 ppm), a species sensitivity distribution was derived
using the available subacute dietary toxicity data for birds (Table 29). Data were
considered useful for the distribution if they are classified acceptable or supplemental.
135
-------
Data for this distribution were collected from registrant-submitted studies as well as the
open literature (as identified using ECOTOX). Once the data set was assembled, the
average of the log-transformed LCso values for a species was calculated. Unlike with the
fish data, avian data were not averaged based on genera because no data were available
for multiple species within the same genera. A student's t distribution was used to derive
a species sensitivity distribution for with the mean and standard deviations of log-
transformed subacute toxicity data for all of the available species within taxa. The
degrees of freedom were equal to n-1, where n is the number of species for which there
are data available for the distribution. In this case, data were available for 4 species, so
the distribution was established with 3 degrees of freedom. The t-statistic was calculated
for probabilities ranging 0.05-0.95 at intervals of 0.05. The log LCso value for a specific
proportion (p) of genera is calculated by Equation 1. The species sensitivity distribution
for LCso values for birds exposed to dicofol is displayed in Figure 13. Additional
information relevant to this sensitivity distribution is provided in Appendix L. The
Japanese quail toxicity endpoint selected to represent direct effects to terrestrial-phase
CRLF is comparable to the lower 10% of the species sensitivity distribution.
1
0.9
0.8
0.7
= 0.6
o
1 0.5
a.
£ 0.4
0.3
0.2
0.1
Colinus virginianus
Phasianus colchicus
Anas platyrhynchos
Coturnixjaponica
100.0
1000.0
LC50
10000.0
Figure 13. Species sensitivity distribution for subacute exposures of birds to dicofol.
136
-------
Sublethal Effects
When assessing acute risk, the screening risk assessment relies on the acute mortality
endpoint as well as a suite of sublethal responses to the pesticide, as determined by the
testing of species response to chronic exposure conditions and subsequent chronic risk
assessment. Consideration of additional sublethal data in the effects determination t is
exercised on a case-by-case basis and only after careful consideration of the nature of the
sublethal effect measured and the extent and quality of available data to support
establishing a plausible relationship between the measure of effect (sublethal endpoint)
and the assessment endpoints. However, the full suite of sublethal effects from valid
open literature studies is considered for the purposes of defining the action area.
Potential for Endocrine Disruption
The extent to which dicofol may act on endocrine-mediated processes of non-target
organisms, including CRLF is uncertain. EPA is required under the FFDCA, as amended
by FQPA, to develop a screening program to determine whether certain substances
(including all pesticide active and other ingredients) "may have an effect in humans that
is similar to an effect produced by a naturally occurring estrogen, or other such
endocrine effects as the Administrator may designate. " Following the recommendations
of its Endocrine Disrupter Screening and Testing Advisory Committee (EDSTAC), EPA
determined that there were scientific bases for including, as part of the program,
androgen and thyroid hormone systems, in addition to the estrogen hormone system.
EPA also adopted EDSTAC's recommendation that the Program include evaluations of
potential effects in wildlife. When the appropriate screening and/or testing protocols
being considered under the Agency's Endocrine Disrupter Screening Program (EDSP)
have been developed and vetted, dicofol may be subjected to additional screening and/or
testing to better characterize effects related to endocrine disruption.
Location of Wildlife Species
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
considered, and it was assumed that species occupy, exclusively and permanently, the
modeled treatment area. Spray drift model predictions suggest that this assumption leads
to an overestimation of exposure to species that do not occupy the treated field
exclusively and permanently.
137
-------
5.2.7. Addressing the Risk Hypotheses
In order to conclude this risk assessment, it is necessary to address the risk hypotheses
defined in section 2.9.1. Based on the conclusions of this assessment, none of the
hypotheses can be rejected, meaning that the stated hypotheses represent concerns in
terms of direct and indirect effects of dicofol on the CRLF and its designated critical
habitat.
138
-------
6.0 Risk Conclusions
In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the
information presented in this endangered species risk assessment represents the best data
currently available to assess the potential risks of dicofol to the CRLF and its designated
critical habitat.
Based on the best available information, the Agency makes a May Affect, and Likely
to Adversely Affect (LAA) determination for the CRLF from the use of dicofol.
Additionally, the Agency has determined that there is the potential for effects to
CRLF designated critical habitat from the use of dicofol. Summaries of the risk
conclusions and effects determinations for the CRLF and its critical habitat are presented
in Table 65 and in Table 66, respectively. Analysis related to the intersection of the
dicofol action area and CRLF habitat used in determining use patterns that result in LAA
determinations are described in Appendix B. The LAA determination for the CRLF and
potential effects to designated critical habitat is described in the baseline status and
cumulative effects for the CRLF and is provided in Attachment 2.
139
-------
Table 65. Description of evidence supporting effects determination for dicofol use in California. Assessment endpoint is 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 fruit,
stone fruit, strawberry, and walnuts/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 fruit,
stone fruit, strawberry, and walnuts/pecans.
-Acute RQs for aquatic-phase amphibians and fish exceed the LOG for all uses of dicofol, except Bermuda grass and outside
buildings.
140
-------
Assessment
Eiulpoint
Effects
Determination
Basis for Determination
- Use of dicofol on beans, citrus, cotton, hops, mint, pome fruit, strawberries and walnuts/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 fruit, 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.
141
-------
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 66. 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
59).
- Dicofol has the potential to indirectly affect the aquatic -phase CRLF through
effects to its prey (see Table 59).
-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 59).
- Dicofol has the potential to indirectly affect the terrestrial-phase CRLF through
effects to its prey (see Table 59).
-Effects of dicofol to plants making up the terrestrial habitat of the CRLF cannot
be discounted.
142
-------
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 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.
143
-------
7.0 References
Alvarez, J. 2000. Letter to the U.S. Fish and Wildlife Service providing comments on the Draft
California Red-legged Frog Recovery Plan.
California Air Resources Board. 1997. Emission Inventory, Section 7.12, Windblown Dust -
Agricultural Lands. Revised July 1997. http://www.arb.ca.gov/ei/areasrc/fullpdf/full7-
12.pdf
California Department of Pesticide Regulation (CDPR). 2002. Pesticide Air Monitoring Results
Conducted by California Air Resources Board, 1986 - 2000. EH02-01. Kollman, W.,
California Department of Pesticide Regulation, May 2002.
CDPR. 2003. Ambient Air Monitoring for Pesticides in Lompoc, California. EH03-02. State of
California Environmental Protection Agency, California Department of Pesticide
Regulation, March 2003.
CDPR. 2006. Environmental Justice Pilot Project: Pesticide Air Monitoring in Parlier, Second
Progress Report. State of California Environmental Protection Agency, California
Department of Pesticide Regulation, December 2006.
http://www.cdpr.ca.gov/docs/enviust/pilot_proj/interim/narrative.pdf
CDPR. 2008. Surface Water Database. California Environmental Protection Agency, Department
of Pesticide Regulation. Available online at:
http://www.cdpr.ca.gov/docs/sw/surfcont.htm. (accessed 2/2/2009)
Crawshaw, G.J. 2000. Diseases and Pathology of Amphibians and Reptiles in: Ecotoxicology
of Amphibians and Reptiles; ed: Sparling, D.W., G. Linder, and C.A. Bishop. SET AC
Publication Series, Columbia, MO.
Domagalski, J. 1996. Occurrence of dicofol in the San Joaquin River, California. Bulletin of
Environmental Contamination and Toxicology. Vol 57, pp. 284-291.
Fellers, G. M., et al. 2001. Overwintering tadpoles in the California red-legged frog (Rana
aurora draytonii). Herpetological Review, 32(3): 156-157.
Fellers, G.M, L.L. McConnell, D. Pratt, S. Datta. 2004. Pesticides in Mountain Yellow-Legged
Frogs (Rana Mucosa) from the Sierra Nevada Mountains of California, USA.
Environmental Toxicology & Chemistry 23 (9):2170-2177.
Fellers, Gary M. 2005a. Rana draytonii Baird and Girard 1852. California Red-legged Frog.
Pages 552-554. In: M. Lannoo (ed.) Amphibian Declines: The Conservation Status of
United States Species, Vol. 2: Species Accounts. University of California Press,
144
-------
Berkeley, California, xxi+1094 pp. (http://www.werc.usgs.gov/pt-
reves/pdfs/Rana%20dravtonii.PDF)
Fellers, Gary M. 2005b. California red-legged frog, Rana draytonii Baird and Girard. Pages 198-
201. In: L.L.C. Jones, et al (eds.) Amphibians of the Pacific Northwest, xxi+227.
Guillette Jr., L., Gross, T., Masson, G., Matter, J., Percival, H., and Woodward, A. 1994.
Developmental Abnormalities of the Gonad and Abnormal Sex Hormone Concentrations
in Juvenile Alligators from Contaminated and Control Lakes in Florida. Environmental
Health Perspectives 102(8): 680-689
Hayes, M.P. and M.M. Miyamoto. 1984. Biochemical, behavioral and body size differences
between Rana aurora aurora and R. a. draytonii. Copeia 1984(4): 1018-22.
Hayes and Tennant. 1985. Diet and feeding behavior of the California red-legged frog. The
Southwestern Naturalist 30(4): 601-605.
Insecticide Resistance Action Committee (IRAC). 2008. IRAC Mode of Action Classification,
Version 6.1, Issued August 2008.
Jennings, M.R. and M.P. Hayes. 1985. Pre-1900 overharvest of California red-legged frogs
(Rana aurora draytonii): The inducement for bullfrog (Rana catesbeiand) introduction.
Herpetological Review 31(1): 94-103.
Jennings, M.R. and M.P. Hayes. 1994. Amphibian and reptile species of special concern in
California. Report prepared for the California Department of Fish and Game, Inland
Fisheries Division, Rancho Cordova, California. 255 pp.
Kashuba, R., Spatz, D. 2006 Memorandum to Steven Bradbury, Subject: Standard Soil Mobility
Classification Guidance
LeNoir, J.S., L.L. McConnell, GM. Fellers, T.M. Cahill, J.N. Seiber. 1999. Summertime
Transport of Current-use pesticides from California's Central Valley to the Sierra Nevada
Mountain Range,USA. Environmental Toxicology & Chemistry 18(12): 2715-2722.
Majewski, M., Capel, P. (1995) Pesticides in the Atmosphere: Distribution, Trends and
Governing Factors. Ann Arbor Press, Inc., Chelsea, MI.
McConnell, L.L., J.S. LeNoir, S. Datta, J.N. Seiber. 1998. Wet deposition of current-use
pesticides in the Sierra Nevada mountain range, California, USA. Environmental
Toxicology & Chemistry 17(10):1908-1916.
145
-------
Rasenberg MHC, van de Plassche DJ. 2003. Risk Profile and Summary Report for Dicofol,
Dossier prepared for the UNECE Convention on Long-range Transboundary Air
Pollution's Expert Group on POPs, 4L0002.A1, April 2003
Rathburn, G.B. 1998. Rana aurora draytonii egg predation. Herpetological Review, 29(3): 165.
Reis, D.K. Habitat characteristics of California red-legged frogs (Rana aurora draytonii):
Ecological differences between eggs, tadpoles, and adults in a coastal brackish and
freshwater system. M.S. Thesis. San Jose State University. 58 pp.
Sparling, D.W., Fellers, G.M., McConnell, L.L.. 2001. Pesticides and amphibian population
declines in California, USA. Environmental Toxicology & Chemistry 20(7): 1591-1595.
U.S. Department of Agriculture. 2009. 2007 Census of Agriculture, California State and County
Data, Volume 1, Geographic Area Series, Part 5. U.S. Department of Agriculture,
National Agricultural Statistics Service. February 2009
U.S. Environmental Protection Agency (U.S. EPA). 1992. Pesticides in Ground Water Database
- A compilation of Monitoring Studies: 1971-1991. Office of Prevention, Pesticides, and
Toxic Substances, EPA 734-12-92-001.
U.S. EPA. 1998a. Guidance for Ecological Risk Assessment. Risk Assessment Forum.
EPA/630/R-95/002F, April 1998.
U.S. EPA. 1998b. Reregi strati on Eligibility Decision (RED) Dicofol. EPA 738-R-98-018,
November 1998.
U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of
Pesticide Programs. Office of Prevention, Pesticides, and Toxic Substances. Office of
Pesticide Programs. Washington, D.C. January 23, 2004.
U. S. EPA 2009. Ecological Structure Activity Relationships (ECOSAR) version l.OOa. Office
of Pollution Prevention and Toxic.
http://www.epa.gov/oppt/newchems/tool s/21 ecosar. htm
U.S. Fish and Wildlife Service (U.S. FWS). 1996. Endangered and threatened wildlife and
plants: determination of threatened status for the California red-legged frog. Federal
Register 61(101):25813-25833.
U.S. FWS. 2002. Recovery Plan for the California Red-legged Frog (Rana aurora draytonii).
Region 1, U.S. FWS, Portland, Oregon.
(http://ecos.fws.gov/doc/recovery plans/2002/020528.pdf)
146
-------
U.S. FWS. 2006. Endangered and threatened wildlife and plants: determination of critical habitat
for the California red-legged frog. 71 FR 19244-19346.
U.S. FWS. Website accessed: 30 December 2006.
http://www.fws.gov/endangered/features/rl_frog/rlfrog.html #where
U.S. FWS and National Marine Fisheries Service (NMFS). 1998. Endangered Species
Consultation Handbook: Procedures for Conducting Consultation and Conference
Activities Under Section 7 of the Endangered Species Act. Final Draft. March 1998.
U.S. FWS/NMFS. 2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act Section
7 Consultation Regulations; Final Rule. FR 47732-47762.
U.S. FWS/NMFS. 2004. Memorandum to Office of Prevention, Pesticides, and Toxic
Substances, U.S. EPA conveying an evaluation by the U.S. Fish and Wildlife Service and
National Marine Fisheries Service of an approach to assessing the ecological risks of
pesticide products.
United States Geological Survey (USGS). 2000. Pesticides in Stream Sediment and Aquatic
Biota. Current Understanding of Distribution and Major Influences. Fact Sheet 092-00.
Willis, Guye H., and Leslie.L. McDowell, 1987. Pesticide Persistence on Foliage, in Reviews of
Environmental Contamination and Toxicology. 100:23-73.
World Health Organization (WHO). 1996. WHO/Food and Agriculture Organization (FAO)
Data Sheets on Pesticides, No. 81, Dicofol, November 1996
Yeary, R.A., Leonard, J.A. (1993) Measurement of Pesticides in Air During Application to
Lawns, Trees, and Shrubs in Urban Environments, in Racke, K.D., Leslie, A.R., eds.,
Pesticides in Urban Environments. American Chemical Society, Washington, D.C., p.
275-281.
147
------- |