Risks of Trifluralin Use to the Federally Listed
California Red-legged Frog
(Rana aurora draytonii),
Delta Smelt
(Hypomesus transpacificus),
San Francisco Garter Snake
(Thamnophis sirtalis tetrataenia),
and
San Joaquin Kit Fox
(Vulpes macrotis mutica)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
October 16,2009
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Primary Authors:
Christine Hartless, Ph.D., Wildlife Biologist
Marie Janson, M.S., Environmental Scientist
Robert Miller, M.E.S.M., Environmental Protection Specialist
Secondary Review:
Faruque Khan, Ph.D., Senior Scientist
Brian Anderson, Ph.D., RAPL
Branch Chief, Environmental Risk Assessment Branch 1
Nancy Andrews, Ph.D.
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Table of Contents
1. Executive Summary 6
2. Problem Formulation 18
2.1 Purpose 18
2.2 Scope 20
2.2.1 Chemicals Assessed 20
2.2.2 Scope of the Action 20
2.3 Previous Assessments 21
2.4 Stressor Source and Distribution 22
2.4.1 Environmental Fate Properties 22
2.4.2 Environmental Transport Mechanisms 27
2.4.3 Mechanism of Herbicidal Action 27
2.4.4 Use Characterization 27
2.5 Assessed Species 39
2.6 Designated Critical Habitat 46
2.7 Action Area 48
2.8 Assessment Endpoints and Measures of Ecological Effect 50
2.8.1 Assessment Endpoints 50
2.8.2 Assessment Endpoints for Designated Critical Habitat 53
2.9 Conceptual Model 55
2.9.1 Risk Hypotheses 55
2.9.2 Diagram 56
2.10 Analysis Plan 58
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model 59
2.10.2 Data Gaps 63
3. Exposure Assessment 63
3.1 Application Rates, Dates and Intervals 64
3.2 Aquatic Exposure Assessment 68
3.2.1 Modeling Approach 68
3.2.2 Post-processing of PRZM/EXAMS Outputs to Develop EECs for Residential
and Rights-of-ways 68
3.2.3 Model Inputs 69
3.2.4 Results 71
3.2.5 Existing Monitoring Data 73
3.3 Long Range Transport Exposure Assessment 74
3.3.1 Background 74
3.3.2 Qualitative Discussion of Potential Transport Mechanisms for Long- 75
Range Transport of Trifluralin 75
3.3.3 Long-Range Air and Precipitation Monitoring Data 75
3.3.4 Deposition Data 76
3.3.5 Monitoring Data from Lakes Assumed to Only Receive Atmospheric 77
Deposition of Trifluralin 77
3.3.6 Modeling of Contributions of Wet Deposition to Aquatic and Terrestrial 77
Habitats 77
3.4 Aquatic Bioaccumulation Assessment 78
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3.4.1 Empirical BCF Data 78
3.4.2 Fish Tissue Monitoring Data 79
3.4.3 Bioaccumulation Modeling 79
3.5 Accumulation of Trifluralin Residue on Soil 81
3.6 Terrestrial Animal Exposure Assessment 81
3.7 Terrestrial Plant Exposure Assessment 84
4. Effects Assessment 86
4.1 Toxicity of Trifluralin to Aquatic Organisms 88
4.1.1 Toxicity to Freshwater Fish and Aquatic-Phase Amphibians 90
4.1.2 Toxicity to Freshwater Invertebrates 92
4.1.3 Toxicity to Estuarine/Marine Fish 93
4.1.4 Toxicity to Estuarine/Marine Invertebrates 94
4.2 Toxicity of Trifluralin to Terrestrial Organisms 95
4.2.1 Toxicity to Birds 97
4.2.2 Toxicity to Mammals 98
4.2.3 Toxicity to Terrestrial Invertebrates 99
4.2.4 Toxicity to Terrestrial Plants 100
4.4 Incident Database Review 102
4.4.1 Terrestrial Animal Incidents 103
4.4.2 Terrestrial Plant Incidents 103
4.4.3 Aquatic Animal Incidents 103
5. Risk Characterization 103
5.1 Risk Estimation 104
5.1.1 Exposures in the Aquatic Habitat 104
5.1.2 Exposures in the Terrestrial Habitat 109
5.1.3 Primary Constituent Elements of Designated Critical Habitat 115
5.2 Risk Description 115
5.2.1 California Red-legged Frog 120
5.2.2 Delta Smelt 134
5.2.3 San Francisco Garter Snake 136
5.2.4 San Joaquin Kit Fox 140
6. Uncertainties 144
6.1 Exposure Assessment Uncertainties 144
6.1.1 Maximum Usage Scenario 144
6.1.2 Aquatic Exposure Modeling of Trifluralin 144
6.1.3 Multiple Growing Seasons per Year 146
6.1.4 Usage Uncertainties 146
6.1.5 Terrestrial Exposure Modeling of Trifluralin 146
6.1.6 Spray Drift Modeling 147
6.1.7 KABAM Modeling 148
6.2 Effects Assessment Uncertainties 148
6.2.1 Age Class and Sensitivity of Effects Thresholds 148
6.2.2 Use of Surrogate Species Effects Data 149
6.2.3 Toxicity Endpoints 149
6.2.4 Sublethal Effects 150
6.2.5 Location of Wildlife Species 150
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7. Risk Conclusions 150
8. Literature Cited 161
List of Attachments
Attachment 1:
Attachment 2:
Attachment 3:
Attachment 4:
Status and Life History of the California Red-legged Frog
Baseline Status and Cumulative Effects for the California Red-Legged
Frog
Status and Life History of the San Francisco Bay Listed Species
Baseline Status and Cumulative Effects for the San Francisco Bay
Listed Species
Appendix A:
Appendix B:
Appendix C:
Appendix D:
Appendix E:
Appendix F:
Appendix G:
Appendix H:
Appendix I:
Appendix J:
Appendix K:
Appendix L:
Appendix M:
Appendix N:
Appendix O:
Appendix P:
Appendix Q:
List of Appendices
Multi-ai Analysis
Chemical Structures and Supplemental Fate Information
Detailed DPR PUR Data
PRZM/PE5 Output Files (Selected Examples)
Trifluralin Toxicity Analog Analysis
Ecological Effects Data
HED Effects Table
ECOTOX Literature
EIIS Incident Data
RQ Methods and LOC Definitions
T-REX Output Tables (Selected Example)
T-HERPS Output Tables (Selected Example)
TerrPlant Output Tables (Selected Example)
KABAM Input and Output Tables
Supplemental RQ Tables
Earthworm Fugacity
Use Verification Correspondence
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1. Executive Summary
The purpose of this assessment is to evaluate potential direct and indirect effects on the
following species arising from FIFRA regulatory actions regarding use of trifluralin:
California red-legged frog (CRLF), Rana aurora draytonii
Delta smelt (DS), Hypomesus transpacificus,
San Francisco Garter Snake (SFGS), Thamnophis sirtalis tetrataenia,
San Joaquin Kit Fox (SJKF), Vulpes macrotis mutica,
In addition, this assessment evaluates whether these actions can be expected to result in
modification of the species' designated critical habitat. This assessment was completed in
accordance with the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries
Service (NMFS) Endangered Species Consultation Handbook (USFWS/NMFS 1998 and
procedures outlined in the Agency's Overview Document (USEPA 2004).
The listing date and a general description of the range of each assessed species are as follows.
The CRLF was listed as a threatened species by USFWS 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 (USFWS 1996) in
California. Critical habitat has been designated for the CRLF.
The DS was listed as threatened on March 5, 1993 (58 FR 12854) by the U.S. Fish and Wildlife
Service (USFWS) (USFWS, 2007a). It is only found in Suisun Bay and the Sacramento-San
Joaquin estuary near San Francisco Bay. Critical habitat has been designated for the DS.
The SFGS was listed as an endangered species by the USFWS in 1967 and was grandfathered
under the Endangered Species Act (ESA) when it was signed into law in 1973. The SFGS is
endemic to the San Francisco Peninsula and San Mateo County and historically inhabited
densely vegetated ponds or shallow marshlands near open hillsides found from San Francisco to
Santa Cruz, including the San Francisco Peninsula. The current distribution of the SFGS is
unknown because most of their historic range is now privately owned; however, it appears that
the SFGS can still be found in much of its historic range. Critical habitat has not been designated
for the SFGS.
The SJKF was listed as endangered by the USFWS on March 11, 1967. Its current range
includes Alameda, Contra Costa, Fresno, Kern, Kings, Madera, Merced, Monterey, San Benito,
San Joaquin, San Luis Obispo, Santa Barbara, Santa Clara, Stanislaus, Tulare and Ventura
counties in California. The SJKF inhabits a variety of habitats, including grasslands, scrublands,
vernal pool areas, oak woodland, alkali meadows and playas, and an agricultural matrix of row
crops, irrigated pastures, orchards, vineyards, and grazed annual grasslands. Critical habitat has
not been designated for the SJKF.
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Trifluralin is a pre-emergent herbicide used to control annual grasses and broadleaf weeds on a
variety of food crops and non-food uses. The herbicide is formulated as an emulsifiable
concentrate and granular products. Trifluralin is typically applied dormant, semi-dormant,
preplant, pre-transplant, post-plant, pre-emergence, post-emergence, lay-by, or postharvest.
Trifluralin can be applied by aerial spray, ground spray or by granular spreaders. Some labels
require soil incorporation, while others do not require soil incorporation.
Trifluralin is a dinitroaniline herbicide that enters plants through developing roots and stops plant
cells from dividing and elongating (meristematic inhibitor).Trifluralin is readily absorbed by
young roots. Established weeds are not controlled.
Trifluralin uses that are considered in this federal action relevant to the CRLF, DS, SFGS, and
SJKF are all registered uses in California. These uses include many agricultural crops, non-food
commodities, residential, and other non-agricultural uses.
The major dissipation routes of trifluralin are volatilization and photodegradation and to a lesser
extent by biotic degradation. Trifluralin is most effective when it is incorporated into the soil at
the time of application, which reduces the rate of volatilization and photodegradation on soil.
Trifluralin has a very low propensity to leach in the vast majority of soils because of its strong
adsorption to soil colloids and organic matter. Trifluralin is persistent and immobile in aerobic
soil studies and in adsorption/desorption studies. Trifluralin residues in the atmosphere of
remote, non-use regions have been reported, indicating its potential for long range transport.
Data indicate that trifluralin has potential to bioaccumulate in aquatic ecosystems. Trifluralin has
an octanol-water partitioning coefficient (log Kow) of 5.27. In a bioconcentration study,
trifluralin residues in bluegill sunfish resulted in bioconcentration factors of 2041, 9586, and
5674 for edible, nonedible, and whole fish tissues, respectively. The half-life of elimination
(depuration) was estimated to be 14 days. The accumulation and depuration rates of trifluralin in
fish cannot be fully assessed because radioactive residues in fish tissues were incompletely
characterized. In addition, other chemical properties of trifluralin, such as its volatility and short
aqueous photolysis half-life, may mediate the realization of bioaccumulation in the environment.
Trifluralin is described by the US EPA (1999) as bioaccumulative, persistent, and toxic; and
therefore presents itself as a contaminant of concern. Based on available bioaccumulation data,
trifluralin has the potential to accumulate in aquatic organisms. KABAM (Kow (based) Aquatic
Bio Accumulation Model) v.1.0 is used to estimate potential bioaccumulation of trifluralin
residues in a freshwater aquatic food web and subsequent risks these residues pose to aquatic-
phase CRLF and SFGS via consumption of contaminated aquatic prey (i.e., aquatic invertebrates
and fish).
The effects determinations for each of the listed species assessed is based on a weight-of-
evidence method that relies heavily on an evaluation of risks to each taxon relevant to assess
both direct and indirect effects to the listed species and the potential for modification of their
designated critical habitat (i.e., a taxon-level approach). Since some of the the assessed species
exist within both aquatic and terrestrial habitats, exposure of the listed species, their prey and
their habitats to trifluralin are assessed separately for the two habitats. Tier-II aquatic exposure
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models are used to estimate high-end exposures of trifluralin in aquatic habitats resulting from
runoff and spray drift from different uses. Peak model-estimated environmental concentrations
resulting from different trifluralin uses range from 0.0002 to 6.55 |ig/L. These estimates are
supplemented with an analysis of California surface water monitoring data from the California
Department of Pesticide Regulation. The maximum concentration of trifluralin reported by the
California Department of Pesticide Regulation surface water database (1.74 |ig/L) is roughly four
times lower than the highest peak model-estimated environmental concentration. No trifluralin
monitoring data are available from the U. S. Geological Survey's National Water Quality
Assessment (NAWQA).
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) to identify instances where
trifluralin use within the action area has the potential to affect the CRLF, DS, SJKF and SFGS
and designated critical habitat for the CRLF and DS via direct toxicity or indirectly based on
direct effects to its food supply (i.e., freshwater invertebrates, algae, fish, frogs, terrestrial
invertebrates, and mammals) or habitat (i.e., aquatic plants and terrestrial upland and riparian
vegetation). When RQs for each particular type of effect are below LOCs, the pesticide is
determined to have "no effect" on the CRLF, DS, SJKF and SFGS. Where RQs exceed LOCs, a
potential to cause effects is identified, leading to a conclusion of "may affect." If a
determination is made that use of trifluralin within the action area "may affect" the CRLF, DS,
SJKF and SFGS and designated critical habitat for the CRLF and DS, additional information is
considered to refine the potential for exposure and effects, and the best available information is
used to distinguish those actions that "may affect, but are not likely to adversely affect" (NLAA)
from those actions that are "likely to adversely affect" (LAA) the CRLF, DS, SJKF and SFGS
and critical habitat for the CRLF and DS.
Based on the best available information, the Agency makes a Likely to Adversely Affect (LAA)
determination for the CRLF, DS, SJKF and SFGS from the use of trifluralin. Additionally, the
Agency has determined that there is the potential for modification of the designated critical
habitat for the CRLF and the DS from the use of the chemical. A summary of the risk
conclusions and effects determinations for each listed species assessed here and their designated
critical habitat is presented in Tables 1.1 and 1.2. Further information on the results of the
effects determination is included as part of the Risk Description in Section 5.2. Given the LAA
determination for the CRLF, DS, SFGS, and SJKF and potential modification of designated
critical habitat for the CRLF and DS, a description of the baseline status and cumulative effects
for the CRLF is provided in Attachment 2 and the baseline status and cumulative effects for the
DS is provided in Attachment 4.
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Table 1.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
CRLF
LAA
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed species LOG (0.05) in 18 out
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
exceedances under the evaluated labels ranged from 45.9 to 2359 feet. Available aquatic-phase amphibian data suggests
trifluralin is less acutely toxic to aquatic-phase amphibians than to fish; however, there are Listed Species LOG exceedances
for the most sensitive aquatic-phase amphibian data.
Fish, Growth and reproduction: There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for trifluralin, only 15%haddetectible
concentrations of trifluralin; however, those measured concentrations were comparable to the PRZM/EXAMS estimates. If
the maximum observed measured concentration (1.74 ug/L) was used as an exposure value to calculate an acute freshwater
fish RQ, there would be an exceedance of the Listed Species LOG (RQ = 0.09).
Terrestrial-phase (Juveniles and Adults):
Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest tested
trifluralin level was greater than expected concentrations in the environment for spray applications. For the granular non-
incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested for
20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Growth and reproduction: The chronic (dietary-based) RQs for birds exceeded the chronic LOG (RQ>1) for the nursery use
category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass andbroadleaf
plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary categories.
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed sjpecies LOG (0.05) in 18 out
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Table 1.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
exceedances under the evaluated labels ranged from 45.9 to 2359 feet. Available aquatic-phase amphibian data suggests
trifluralin is less acutely toxic to aquatic-phase amphibians than to fish; however, there are Listed Species LOG exceedances
for the most sensitive aquatic-phase amphibian data.
Fish, Growth and reproduction: There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for trifluralin, only 15%haddetectible
concentrations of trifluralin; however, those measured concentrations were comparable to the PRZM/EXAMS estimates. If
the maximum observed measured concentration (1.74 ug/L) was used as an exposure value to calculate an acute freshwater
fish RQ, there would be an exceedance of the Listed Species LOG (RQ = 0.09).
Freshwater invertebrates: There were no exceedances of the Listed Species Acute or Chronic LOCs.
Vascular and non-vascular plants: There were no exceedances of the Acute LOCs.
Terrestrial plants: LOCs were exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs were exceeded for 14 out
of 25 modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range
from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy-one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
Terrestrial prey items, riparian habitat
Birds, Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest
tested trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular
non-incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested
for 20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Birds, Growth and reproduction: The chronic (dietary-based) RQs for birds exceeded the chronic LOG (RQ>1) for the
10
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Table 1.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
nursery use category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass and
broadleaf plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary
categories.
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQs for 15 g mammals range from 20.82 to 58.20 for short grass;
9.54 to 26.68 for tall grass; 11.71 to 32.74 broadleaf plants/small insects; 1.30 to 3.64 for fruits/pods/seeds/large insects.
Chronic RQs did not exceed LOCs for 15g granivores. Chronic dietary-based RQs exceed the Agency's chronic LOG (1.0)
in both crop scenarios (liquid application) for mammals consuming short grass, tall grass, and broadleaf plants/small insects;
they were not exceeded for fruits/pods/seeds/large insects.
Terrestrial invertebrates: For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortality at this dose).
Since mortality was observed at the highest test dose, expected exposures must be 20x less than the highest dose to preclude
risks to terrestrial invertebrates. Risks to terrestrial invertebrates cannot be precluded since the calculated EECs exceed the
calculated cut-point of 9.4 mg/kg-insect for all modeled scenarios.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy-one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
DS
LAA
Potential for Direct Effects
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed species LOG (0.05) in 18 out
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
exceedances under the evaluated labels ranged from 45.9 to 2359 feet.
Fish, Growth and reproduction: There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
11
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Table 1.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, DS, SFGS, and SJKF
Species
SFGS
Effects
Determination l
LAA
Basis for Determination
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for trifluralin, only 15% had detectible
concentrations of trifluralin; however, those measured concentrations were comparable to the PRZM/EXAMS estimates. If
the observed measured concentration (1.74 ug/L) was used as an exposure value to calculate an acute freshwater fish RQ,
there would be an exceedance of the Listed Species LOG (RQ = 0.09).
Potential for Indirect Effects
Freshwater invertebrates: There were no exceedances of the Listed Species Acute or Chronic LOCs.
Vascular and non-vascular plants: There were no exceedances of the Acute LOCs.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
1.05to2.32fordicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy -one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
Potential for Direct Effects
Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest tested
trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular non-
incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested for
20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Growth and reproduction: The chronic (dietary -based) RQs for birds exceeded the chronic LOG (RQ>1) for the nursery use
category. Chronic RQs ranged from 1.23 to 2. 68 for various dietary categories (i.e., short grass, tall grass andbroadleaf
plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary categories.
Potential for Indirect Effects
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed species LOG (0.05) in 18 out
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
12
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Table 1.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
exceedances under the evaluated labels ranged from 45.9 to 2359 feet.
Fish, Growth and reproduction'. There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
Freshwater invertebrates: There were no exceedances of the Listed Species Acute or Chronic LOCs.
Vascular and non-vascular plants: There were no exceedances of the Acute LOCs.
Birds, Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest
tested trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular
non-incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested
for 20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Birds, Growth and reproduction: The chronic (dietary-based) RQs for birds exceeded the chronic LOG (RQ>1) for the
nursery use category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass and
broadleaf plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary
categories.
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQs for 15 g mammals range from 20.82 to 58.20 for short grass;
9.54 to 26.68 for tall grass; 11.71 to 32.74 broadleaf plants/small insects; 1.30 to 3.64 for fruits/pods/seeds/large insects.
Chronic RQs did not exceed LOCs for 15g granivores. Chronic dietary-based RQs exceed the Agency's chronic LOG (1.0)
in both crop scenarios (liquid application) for mammals consuming short grass, tall grass, and broadleaf plants/small insects;
they were not exceeded for fruits/pods/seeds/large insects.
Terrestrial invertebrates: For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortality at this dose).
Since mortality was observed at the highest test dose, expected exposures must be 20x less than the highest dose to preclude
risks to terrestrial invertebrates. Risks to terrestrial invertebrates cannot be precluded since the calculated EECs exceed the
calculated cut-point of 9.4 mg/kg-insect for all modeled scenarios.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
13
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Table 1.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, DS, SFGS, and SJKF
Species
SJKF
Effects
Determination l
LAA
Basis for Determination
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy -one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
Potential for Direct Effects
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQ values representing trifluralin exposures (spray applications) to
large mammals (1000 g) indicate risks resulting from both the alfalfa and nursery application scenarios (for alfalfa, LOG
exceedances for mammals consuming short grass, tall grass, and broadleaf plants/small insects; for nursery, LOG
exceedences for mammals consuming short grass, tall grass, broadleaf plants/small insects, and fruits/pods/seeds/large
insects. Chronic diet-based RQ values representing trifluralin exposures to all mammals indicate risks to mammals
consuming short grass, tall grass, and broadleaf plants/small insects for both the alfalfa and nursery scenarios. Chronic risk to
mammals from trifluralin through consumption of contaminated earthworms is unlikely.
Potential for Indirect Effects
Birds, Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest
tested trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular
non-incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested
for 20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Birds, Growth and reproduction: The chronic (dietary -based) RQs for birds exceeded the chronic LOG (RQ>1) for the
nursery use category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass and
broadleaf plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary
categories.
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQs for all weight classes of mammals exceeded the Chronic LOG
14
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Table 1.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, DS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
(1.0) for all weights and feeding guilds except for large mammals consuming fruits/pods/seeds/large insects (alfalfa
application) and all granivores. Exceeding RQs ranged from 1. 1 1 to 58.20. Chronic dietary-based RQs exceed the Agency's
Chronic LOG (1.0) in for alfalfa and nursery scenarios (liquid application, non-incorporated) for short grass, tall grass, and
broadleaf plants/small insects.
Terrestrial invertebrates: For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortality at this dose).
Since mortality was observed at the highest test dose, expected exposures must be 20x less than the highest dose to preclude
risks to terrestrial invertebrates. Risks to terrestrial invertebrates cannot be precluded since the calculated EECs exceed the
calculated cut-point of 9.4 mg/kg-insect for all modeled scenarios.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
1.05to2.32fordicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy -one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely affect (LAA)
15
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Table 1.2 Effects Determination Summary for the Critical Habitat Impact Analysis (CRLF and
PS)1
Designated
Critical Habitat
for:
Effects
Determination
Basis for Determination
CRLF
HM
Aquatic-phase PCEs:
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for
trifluralin, only 15% had detectible concentrations of trifluralin; however, those
measured concentrations were comparable to the PRZM/EXAMS estimates. If
the observed measured concentration (1.74 ug/L) was used as an exposure value
to calculate an acute freshwater fish RQ, there would be an exceedance of the
Listed Species LOC (RQ = 0.09).
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one
of the application methods for risks to monocot plants. RQs that exceed the acute
LOC (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of
25 modeled uses for at least one of the application methods for dicot plants. RQs
that exceed the acute LOC (1.0) range from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant
damage or death from direct application or drift. Seventy-one percent are
classified as 'probable' in the context of trifluralin use; 85% were incidents were
classified as registered uses.
There is a potential for direct effects to aquatic-phase CRLF and indirect effects
via reduction of aquatic-phase prey items (fish and aquatic-phase amphibians) as
described in Section 5.
Terrestrial-phase PCEs:
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one
of the application methods for risks to monocot plants. RQs that exceed the acute
LOC (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of
25 modeled uses for at least one of the application methods for dicot plants. RQs
that exceed the acute LOC (1.0) range from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant
damage or death from direct application or drift. Seventy-one percent are
classified as 'probable' in the context of trifluralin use; 85 % were incidents were
classified as registered uses.
There is a potential for direct effects to terrestrial-phase CRLF and indirect
effects via reduction of terrestrial-phased prey items (mammals, terrestrial
invertebrates, and frogs) as described in Section 5.
DS
HM
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for
trifluralin, only 15% had detectible concentrations of trifluralin; however, those
measured concentrations were comparable to the PRZM/EXAMS estimates. If
the observed measured concentration (1.74 ug/L) was used as an exposure value
to calculate an acute freshwater fish RQ, there would be an exceedance of the
Listed Species LOC (RQ = 0.09).
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one
16
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of the application methods for risks to monocot plants. RQs that exceed the acute
LOG (1.0) range from 1. 1 1 to 4.89 for monocots. LOCs exceeded for 14
out of 25 modeled uses for at least one of the application methods for dicot
plants. RQs that exceed the acute LOG (1.0) range from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant
damage or death from direct application or drift. Seventy -one percent are
classified as 'probable' in the context of trifluralin use; 85% were incidents were
classified as registered uses.
There is a potential for direct effects to the DS as described in Section 5.
1 Critical habitat has not been designated for the SFGS or the SJKF.
2 Habitat Modification (HM) or No effect (ME)
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, DS, SFGS, and
SJKF life stages within the action area and/or applicable designated critical
habitat. 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 assessed species.
• Quantitative information on prey base requirements for the assessed species.
While existing information provides a preliminary picture of the types of food
sources utilized by the assessed species, 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
17
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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 species and potential modification to critical habitat.
2. Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By identifying the
important components of the problem, it focuses the assessment on the most relevant life history
stages, habitat components, chemical properties, exposure routes, and endpoints. The structure of
this risk assessment is based on guidance contained in U.S. EPA's Guidance for Ecological Risk
Assessment (U.S. EPA 1998), the Services' Endangered Species Consultation Handbook
(USFWS/NMFS 1998) and is consistent with procedures and methodology outlined in the
Overview Document (U.S. EPA 2004) and reviewed by the U.S. Fish and Wildlife Service and
National Marine Fisheries Service (USFWS/NMFS 2004).
2.1 Purpose
The purpose of this endangered species assessment is to evaluate potential direct and indirect
effects on individuals of the federally listed threatened California red-legged frog (Rana aurora
draytonii) (CRLF), and delta smelt (Hypomesus transpacificus) (DS), and the federally listed
endangered San Francisco garter snake (Thamnophis sirtalis tetrataenia) (SFGS), and San
Joaquin kit fox (Vulpes macrotis) (SJKF) from FIFRA regulatory actions regarding use of
trifluralin on cultivated fields for agricultural crops (e.g. stone fruits, cucumbers, collards,
melons, tree nuts) and non-food commodities (e.g., forest trees, nurseries, turf), residential uses,
and other non-agricultural uses (e.g., industrial areas, rights-of-ways). In addition, this
assessment evaluates whether use on these use sites is expected to result in modification of
designated critical habitat for the CRLF and DS. No critical habitat has been designated for the
SFGS and SJKF. This ecological risk assessment has been prepared consistent with the settlement
agreement in Center for Biological Diversity (CBD) vs. EPA etal. (Case No. 02-1580-JSW(JL))
entered in Federal District Court for the Northern District of California on October 20, 2006. This
assessment also addresses the DS, SJKF, and SFGS for which trifluralin was alleged to be of concern
in a separate suit (Center for Biological Diversity (CBD) vs. EPA etal. (Case No. 07-2794JCS)).
In this assessment, direct and indirect effects to the CRLF, DS, SFGS, and SJKF potential and
modification to designated critical habitat for the CRLF and DS are evaluated in accordance with
the methods described in the Agency's Overview Document (U.S. EPA 2004). The effects
determinations for each listed species assessed is based on a weight-of-evidence method that
relies heavily on an evaluation of risks to each taxon relevant to assess both direct and indirect
effects to the listed species and the potential for modification of their designated critical habitat
(i.e., a taxon-level approach). Screening level methods include use of standard models such as
PRZM-EXAMS, T-REX, TerrPlant, AgDRIFT, and AGDISP, all of which are described at
length in the Overview Document (U.S. EPA, 2004). Additional refinements include an analysis
of the usage data, use of the T-HERPS model (characterizes potential risks to terrestrial phase
amphibians and reptiles from dietary exposure), use of the KABAM model (an aquatic
18
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bioaccumulation model), and use of an earthworm fugacity model (predicts concentrations of
trifluralin in soil as well as terrestrial invertebrates as food items for the terrestrial-phase CRLF,
SFGS, and SJKF). 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 Endangered Species Act (ESA),
and the Services' Endangered Species Consultation Handbook, the assessment of effects
associated with registrations of trifluralin is based on an action area. The action area is the area
directly or indirectly affected by the federal action, as indicated by the exceedence of the
Agency's Levels of Concern (LOCs). It is acknowledged that the action area for a national-level
FIFRA regulatory decision associated with a use of trifluralin 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, DS, SFGS, and SJKF their designated
critical habitat within the state of California. As part of the "effects determination," one of the
following three conclusions will be reached separately for each of the assessed species in the
lawsuits regarding the potential use of trifluralin in accordance with current labels:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Critical habitat has been designated for the CRLF and DS, but not for the SJKF and SFGS.
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 CRLF are aquatic and upland areas where suitable breeding and non-
breeding aquatic habitat is located, interspersed with upland foraging and dispersal habitat. PCEs
for the DS include characteristics required to maintain habitat for spawning, larval and juvenile
transport, rearing, and adult migration.
If the results of initial screening-level assessment methods show no direct or indirect effects (no
LOG exceedances) upon individuals or upon the PCEs of the species' designated critical habitat,
a "no effect" determination is made for use of trifluralin as it relates to each species and its
designated critical habitat. If, however, potential direct or indirect effects to individuals of each
species are anticipated or effects may impact the PCEs of the designated critical habitat, a
preliminary "may affect" determination is made for the FIFRA regulatory action regarding
trifluralin.
If a determination is made that use of trifluralin "may affect" a listed species or its designated
critical habitat, additional information is considered to refine the potential for exposure and for
effects to each species and other taxonomic groups upon which these species depend (e.g., prey
items). Additional information, including spatial analysis (to determine the geographical
proximity of the assessed species' habitat and trifluralin use sites) and further evaluation of the
potential impact of trifluralin on the PCEs is also used to determine whether modification of
19
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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 assessed listed
species and/or result in "no effect" or potential modification to the PCEs of its designated critical
habitat. This information is presented as part of the Risk Characterization in Section 5 of this
document.
The Agency believes that the analysis of direct and indirect effects to listed species provides the
basis for an analysis of potential effects on the designated critical habitat. Because trifluralin is
expected to directly impact living organisms within the action area (defined in Section 2.7),
critical habitat analysis for trifluralin is limited in a practical sense to those PCEs of critical
habitat that are biological or that can be reasonably linked to biologically mediated processes
(i.e.., the biological resource requirements for the listed species associated with the critical habitat
or important physical aspects of the habitat that may be reasonably influenced through biological
processes). Activities that may modify critical habitat are those that alter the PCEs and
appreciably diminish the value of the habitat. Evaluation of actions related to use of trifluralin
that may alter the PCEs of the assessed species' critical habitat form the basis of the critical
habitat impact analysis. Actions that may affect the assessed species' designated critical habitat
have been identified by the Services and are discussed further in Section 2.6.
2.2 Scope
2.2.1 Chemicals Assessed
This assessment evaluates potential risks from exposure to trifluralin. Trifluralin is a pre-
emergent dinitroaniline herbicide used to control annual grasses and broadleaf weeds on a
variety of food crops and non-food uses (see Table 2.3 for a list of labeled uses). The herbicide
is formulated as an emulsifiable concentrate and granular products. Trifluralin is typically
applied dormant, semi-dormant, pre-plant, pre-transplant, post-plant, pre-emergence, post-
emergence, lay-by, or postharvest. Trifluralin can be applied by aerial spray, ground spray or by
granular spreaders. Some labels require soil incorporation, while others do not require soil
incorporation.
As discussed in Section 2.4.1, there are three primary degradates for trifluralin. There is
insufficient data on the major degradates of trifluralin to adequately assess their persistence and
mobility. Available toxicity data for these degradates suggests that degradates are no more toxic
than the parent with respect to aquatic organisms (Section 4). No degrade toxicity data were
available for terrestrial organisms.
2.2.2 Scope of the Action
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 or potential use of trifluralin in
20
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accordance with the approved product labels for California is "the action" relevant to this
ecological risk assessment.
Although current registrations of trifluralin allow for use nationwide, this ecological risk
assessment and effects determination addresses currently registered uses of trifluralin in portions
of the action area that are reasonably assumed to be biologically relevant to the CRLF, DS,
SFGS, and SJKF and their designated critical habitat. Further discussion of the action area for
the CRLF, DS, SFGS, and SJKF and critical habitat for the CRLF and DS is provided in Section
2.7.
The Agency does not routinely include, in its risk assessments, an evaluation of mixtures of
active ingredients, either those mixtures of multiple active ingredients in product formulations or
those in the applicator's tank. In the case of the product formulations of active ingredients (that
is, a registered product containing more than one active ingredient), each active ingredient is
subject to an individual risk assessment for regulatory decision regarding the active ingredient on
a particular use site. If effects data are available for a formulated product containing more than
one active ingredient, they may be used qualitatively or quantitatively in accordance with the
Agency's Overview Document and the Services' Evaluation Memorandum (U.S., EPA 2004;
USFWS/NMFS 2004). This analysis can be conducted using acute rat toxicity data submitted to
the Agency (Appendix A). In this mixture evaluation an LD50 with associated 95% CI is needed
for the formulated product. The same quality of data is also required for each component of the
mixture. In the case of trifluralin, given that there is no 95% CI associated with the oral LD50
(>5000 mg/kg), it is not possible to undertake a quantitative or qualitative analysis for potential
interactive effects. However, because the active ingredients are not expected to have similar
mechanisms of action, metabolites, or toxicokinetic behavior, it is reasonable to conclude that an
assumption of dose-addition would be inappropriate. Consequently, an assessment based on the
toxicity of trifluralin is the only reasonable approach that employs the available data to address
the potential acute risks of the formulated products.
Several papers were cited in ECOTOX that were classified as evaluating mixtures that contained
trifluralin. However, none provided sufficient information for inclusion into this assessment.
2.3 Previous Assessments
Trifluralin has a long regulatory history and has been the subject of numerous assessments. It
was first registered in the United States in 1963 for use as a selective preemergent herbicide. In
April, 1996, the USEPA completed its Reregi strati on Eligibility Decision on the active
ingredient trifluralin (USEPA 1996, Reregi strati on Eligibility Decision (RED) Trifluralin). The
Agency determined all labeled uses of trifluralin at the time of the assessment were eligible for
reregi strati on with the exception of nongrass forage/fodder/straw/hay and dill. Residue data were
not generated to support these uses and these uses were to be deleted from all labels. Relevant
ecological conclusions from the RED include the following:
• For aquatic animals (fish and invertebrates), trifluralin was ranked as having moderate to
high toxicity according to the hazard classification scheme. Due to trifluralin's toxicity to
fish, aquatic invertebrates and estuarine/marine organisms, the Agency required aquatic
impact labeling on all trifluralin end-use products. In addition, laboratory and field
21
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studies suggest exposure-related abnormalities in vertebral development, at
concentrations below those where acute effects are anticipated. Also, the LOG
determination is based on trifluralin dissolved in the water column and does not take into
account trifluralin adsorbed to sediment. Trifluralin adsorbed to sediment may pose a risk
for fish species that forage by feeding from sediment, particularly since trifluralin has a
moderate tendency to bioaccumulate. The Agency will explore further monitoring efforts
or additional analyses with the registrants of technical trifluralin in order to obtain more
refined characterization of the risk to fish.
• Trifluralin ranks as practically non-toxic to birds and mammals on an acute basis. Two of
four laboratory bird studies indicate chronic risk, as evidenced by egg shell cracking.
Chronic risks to mammals were not evaluated.
• For terrestrial and semi-aquatic plants the Agency did find a concern for the semiaquatic
category. The Agency did not find concerns for aquatic plants resulting from use of
trifluralin.
• For control of effects caused by spray drift, the RED indicated that the Agency will
require precautionary labeling, which is standard for pesticides with aerial applications.
The Agency also completed an Effects Determination for 26 threatened and endangered Pacific
anadromous salmon and steelhead in April 2004 based on trifluralin uses in a variety of field,
fruit, and vegetable crops, ornamentals, and non-crop sites in the Pacific Northwest consistent
with a court order in WTC v. EPA (Case No. l:04-Cv-00126-Ckk, 2004). The results of that
endangered species risk assessment showed that that the use of trifluralin may affect and was likely
to adversely affect 11 Evolutionary Significant Units (ESUs), may affect but is not likely to
adversely affect 4 ESUs, and has no effect on 11 ESUs of Pacific salmon and steelhead when used
according to labeled application directions
(http://www.epa.gov/oppfead 1 /endanger/litstatus/effects/#trifluralin). The National Marine
Fisheries Service has indicated it will review EPA's determination regarding effects of trifluralin
to the Pacific salmon and steelhead, and complete consultation with issuance of a Biological
Opinion in February 2012.
2.4 Stressor Source and Distribution
2.4.1 Environmental Fate Properties
The major dissipation routes of trifluralin are volatilization and photodegradation and to a lesser
extent by biotic degradation. The physicochemical properties (Table 2. la) suggest that trifluralin
is hardly soluble in water. The vapor pressure (1.10E-4 Torr) indicates that trifluralin is a volatile
chemical and Henry's law constant (1.6 x 10"4 atm-m3/mol) indicates that trifluralin has
potential to volatilize from moist soil and water surfaces. Trifluralin is stable to hydrolysis at
various pHs, but is very prone to phototransformation in air and water (Ti/2 of < 1 day) and to a
lesser extent in soil (Ti/2of 41 days; Table 2.1b). Soil incorporation of trifluralin can also inhibit
the rate of photodegradation in soil. Laboratory aerobic biotransformation studies indicate that
trifluralin is moderately persistent to persistent in soil. Trifluralin degraded with half-lives of
189, 202, and 116 days in sandy loam, clay loam, and loam soils, respectively. Anaerobic soil
biotransformation of trifluralin is faster than aerobic biotransformation with half-lives of 22-59
days. Field dissipation half-life has been reported as low as 29 days and as high as 149 days for
22
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trifluralin. Published field dissipation half-lives range from 60 to 132 days (Wauchope et al.,
1992). Several major and minor degradates were detected in fate studies.
Trifluralin has a very low propensity to leach in a majority of soils because of its strong
adsorption to soil colloids and organic matter. Adsorption/desorption and leaching studies
indicate that trifluralin is strongly adsorbed to most soils and classified as immobile according to
FAO Classification System (FAO, 2000). The log Kow (5.27) indicates trifluralin has the
potential to bioaccumulate. Trifluralin is described by the US EPA as bioaccumulative,
persistent, and toxic; and therefore presents itself as a contaminant of concern (US EPA Toxic
Release Inventory, 2007).
Tables 2.1a and 2.1.b list the environmental fate properties of trifluralin detected in submitted
environmental fate and transport studies. The detailed descriptions of guideline fate studies are
located in Appendix B.
Table 2.1a Summary of Trifluralin Physical and Chemical Properties
Physical/Chemical Property
Chemical Structure
IUAPC
CAS
Molecular Formula
Molecular Weight
Physical State
Melting Point
Vapor Pressure (25°C)
Water Solubility (25°C)
LogKowat20°C
Henry's Law Constant at 25°C
Value (unit)
NO,
| y— ( y:H,— CH,— CH,
F— C ^ y N
I ^—\ ^H,— CH»— CH,
NO,
2,6-Dinitro-AyV-dipropyl-4-(trifluoromethyl)aniline
1582-09-9
C13H16F3N304
335.28 g/mole
orange crystalline solid
42-49° C
1.10E-4Torr
0.3 mg/L
5.27
1.6 x lO'4 atm-m3/mol
23
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Table 2.1b Summary of Environmental Fate Properties of Trifluralin
Study
Hydrolysis
Aqueous
Photolysis
Photodegra-
dation on Soil
Aerobic Soil
Metabolism
Anaerobic
Soil
Metabolism
Anaerobic
Aquatic
Metabolism
Aerobic
Aquatic
Metabolism
Leaching &
Adsorption/
Desorption
Terrestrial
Field
Dissipation
Bioconcentrat
ion
Value (units)
StableatpH5,pH7,
pH9
Tm = 0.371 days
Ti/2 =41 days
189 days (sandy
loam)
201 days (clay
loam)
116 days (loam
soils)
22°C
59 days (sandy
loam)
25 days loam
35 clay loam soils
22° C
N/A
N/A
Major Degradates1
Minor Degradates
None
TR-15, <47.4%
TR-6, <29.8%
TR-2, <9.6%
TR-2 < 6.0%
TR-12, <7.1%
TR-2, <4.6%
TR-5, <2.1%
TR-11, <0.3%
TR-13, <1.0%
TR15, <2.6%
TR-20, < 2. 7%
TR-28, <3.0%
TR-4, < 13.2%
TR-14, <8.3%
TR-7, <4.1%
Other degradates identified at < 2.1% :
TR-2
TR-5
TR-13
TR-28
N/A
N/A
sand: Kd = 18.6, L/kg (Koc=6,413 g/mL)
sandy loam: Kd = 54.8, L/kg (Koc=6,748 g/mL)
loam: Kd = 88.3, L/kg (Koc= 8,457 g/mL)
clay loam: Kd = 155.6, L/kg (Koc=13,413 g/mL)
Average Koc = 8,757.9 g/mL
Granular T1/2 = 49 days;
EC formulations T1/2 = 149 days from California loam soil;
Ti/2 = 93 days from Alabama clay soil;
Ti/2 = 29 days, coarse sandy loam soil, Shellman, GA;
Ti/2 = 35 days when applied to fine (silly clay loam soil,
Mansfield, IL); trifluralin did not appear in depths greater than
6 inches
Trifluralin residues accumulated in a bluegill sunfish (Lepomis
macrochirus) exposed to 0.0059 mg/L of trifluralin with
MRID#
00131135
40560101
40597801
40751301
41240501
41240502
N/A
N/A
40673501
41781901
41661101
42309101
40673801
Study Status
Supplemental
Supplemental
Supplemental
Supplemental
Supplemental
N/A
N/A
Supplemental
Supplemental
Supplemental
Supplemental
Supplemental
24
-------
Table 2.1b Summary of Environmental Fate Properties of Trifluralin
Study
Value (units)
Major Degradates1
Minor Degradates
MRID#
Study Status
maximum mean bioconcentration factor of 5,674x for whole
fish tissues. The maximum mean concentration of total [14C]
residues occurred at 28 days for the whole fish sample was
67.0 mg/L. Depuration occurred with 86.34-88.01% of the
[14C] eliminated from the fish tissues after 14 days of exposure
to pesticide free water. The time to reach 90% of steady state
for whole fish was 15.8 days.
TR-2 a, a, a-trifluoro-2,6-dinitro-N-propyl-p-toluidine
TR-4 a,a,a -trifluoro-5-nitro-N4,N4-dipropyl-toluene- 3,4-diamine
TR-5 a,a,a-trifluoro-5-nitro-4-propyl-toluene- 3,4-diamine
TR-6 5-trifluoromethyl-3-nitro-l,2-benzenediamine
TR- 7 a, a, a-trifluoro-N4, N4-dipropyltoluene-3,4,5-triamine
TR-11 2-ethyl-7-nitro-l-propyl-5-(trifluoromethyl)benzimidazole-3-oxide
TR-12 2-ethyl-7nitro-5- trifluoromethylbenzimidazole- 3-oxide
TR-13 2-ethyl-7-nitro-l-propyl-5-(trifluoromethyl) benzimidazole
TR-14 7-amino-2-ethyl-l-propyl-5-(trifluoromethyl) benzimidazole
TR-15 2-ethyl-7-nitro-5-(trifluoromethyl)benzimidazole
TR-20 a, a, a-trifluoro-2,6-dinitro-p-cresol
TR-28 2,2'azoxybis(, , -trifluoro-6-nitro-N-propyl-p- toluidine
2.4.1.1 Degradation
Trifluralin is hydrolytically stable under most environmental conditions. The vapor-phase of
trifluralin is degraded in the atmosphere by reaction with photochemically-produced hydroxyl
radicals, and the estimated half-life for this reaction in air is estimated to be 5.3 hours or 0.22
days (Convention for the Protection of the Marine Environment of the North-East Atlantic
Convention (OSPAR, 2005). Trifluralin is also susceptible to direct aqueous photolysis (half-life
8.9 hours) which should limit its persistence in the top segment of the water column. The
photodegradation on soil study reports that trifluralin degraded with a half-life of 41 days.
Appendix B provides nomenclature and chemical structures of trifluralin degradates.
Trifluralin is persistent in aerobic soil with half-lives of 189, 201, and 116 days in sandy loam,
clay loam, and loam soils, respectively. No major metabolites were formed. In anaerobic soil
metabolism studies trifluralin's half-lives ranged from 25-59 days in sandy loam, loam, and clay
loam soils, respectively. One major metabolite formed in the anaerobic soil studies, TR-4 (a,a,a -
trifluoro-5-nitro-N4,N4-dipropyl-toluene-3,4-diamine), up to!3.2%. Aerobic and anaerobic
aquatic guideline studies have not been submitted.
The major degradates reported in the aqueous photolysis study include: TR-6, 29.8% (5-
trifluoromethyl-3-nitro-l,2-benzenediamine) and TR-15, 47.4% (2-ethyl-7-nitro-5-
trifluromethy Ib enzimi dazol e).
There is insufficient data on the major degradates of trifluralin to adequately assess their
persistence and mobility.
25
-------
2.4.1.2 Mobility
Volatility may be a major route of dissipation for trifluralin if not incorporated. Trifluralin
volatilizes when applied to the surface of soil with an amount of 41-68% of the applied
radioactivity after 24 hours (OSPAR, 2005). However, volatilization is minimal (< 2%
application rate) when trifluralin is incorporated into the soil immediately after application.
Trifluralin rapidly dissipates from surface water due to volatilization, photo-oxidation and
adsorption to suspended matter in water column and sediments.
The relatively high soil/water partitioning of trifluralin (Koc of 8000; Kads = 18-19 for sandy
soil and 53-156 for finer soils) indicates that the concentration of trifluralin adsorbed to eroding
soil will be 1 to over 2 orders of magnitude greater than the dissolved concentration in runoff
water. However, the sediment yield off many fields varies anywhere from 1 to > 3 orders of
magnitude less than the mass equivalent of the runoff volume. Therefore, the mass percentage of
trifluralin runoff occurring via dissolution in runoff water may be somewhat comparable to or
sometimes greater than that occurring via adsorption to eroding soil in cases where the sediment
yield is 1 to > 3 orders of magnitude less than the runoff volume.
Trifluralin's relatively high soil/water partitioning indicates that the concentration of trifluralin
adsorbed to suspended and bottom sediment will be substantially greater than its dissolved
concentration in the water column.
Even though phototransformation of trifluralin in air and water is rapid, residues have been
detected in air, precipitation (rain and snow) and fog in remote areas such as the Canadian
Arctic, Greenland and the Bering Sea (Canadian Arctic Contaminants Program, 2006). These
detections in remote regions indicate that trifluralin sorbed to airborne particulate is more
resistant to phototransformation; thus, transport of particulates might be the primary transport
mode for deposition in remote areas.
In field dissipation studies, trifluralin (Treflan, 44.1 or 50.7% EC) applied at 2.78 Ibs/acre
dissipated with a half-life of 149 days from loam soil planted with cotton in California and 93
days from clay soil planted with soybeans in Alabama. Trifluralin did not appear to leach below
the 0- to 6-inch soil depth. Trifluralin granular formulation dissipated with a reported half-life of
49 days in the top six inches of soil when applied to loamy sand soil in California. Emulsifiable
concentrate trifluralin formulations were reported to dissipate with a half-lives ranging from 29
to 35 days when applied to coarse sandy loam soil (Shellman, GA site) and fine silty clay loam
soil (Mansfield IL site).
2.4.1.3 Accumulation
Trifluralin residues accumulated in bluegill sunfish exposed to 0.0059 ppm of trifluralin for 28
days under flow through conditions. The maximum mean bioconcentration factors were 204Ix,
9586x, and 5674x for edible, nonedible, and whole fish tissues, respectively. Maximum mean
concentrations of total residues occurred at 28 days for edible, non-edible, and whole fish
samples and were 12.9 ppm, 67.0 ppm and 39.6 ppm, respectively. Depuration occurred with
86.34-88.01% of the [14C]residues eliminated from the fish tissues after 14 days of exposure to
26
-------
pesticide free water. The accumulation and depuration of trifluralin in fish cannot be fully
assessed because radioactive residues in fish tissues were incompletely characterized.
Radioactivity attributed to a total of 10 metabolites at a maximum of 0.80 ppm was not
identified; up to 1.27 ppm was described as only "polar radioactivity."
Based on the available results, trifluralin poses a high potential for bioaccumulation and may
biomagnify at higher trophic levels. For this reason, this assessment considers additional
exposure pathways resulting from bioaccumulation for the CRLF and SFGS.
2.4.2 Environmental Transport Mechanisms
Potential transport mechanisms or routes of pesticide exposure for trifluralin include surface
water runoff/erosion, spray drift, and secondary drift of volatilized or soil-bound residues leading
to deposition onto nearby or more distant ecosystems.
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 a/.,
2001, LeNoir et al., 1999, and McConnell et al., 1998). Several sections of the range and critical
habitat for the CLRF and habitat of the SJKF are located east of the Central Valley. The
magnitude of transport via secondary drift depends on the ability of trifluralin to be mobilized
into air and its eventual removal through wet and dry deposition of gases/particles and
photochemical reactions in the atmosphere. Therefore, physicochemical properties of trifluralin
that describe its potential to enter the air from water or soil (e.g., Henry's Law constant and
vapor pressure), pesticide use data, modeled estimated concentrations in water and air, and
available air monitoring data from the Central Valley and the Sierra Nevada are qualitatively
considered in evaluating the potential for atmospheric transport of trifluralin to locations where it
could impact the CRLF, DS, SFGS and SJKF.
In general, deposition of spray drift pesticides is expected to be greatest close to the site of
application. Computer models of spray drift (AgDRIFT and/or AGDISP) are used to determine
potential exposures to aquatic and terrestrial organisms via spray drift.
2.4.3 Mechanism of Herbicidal Action
Trifluralin is a synthetic fluorinated dinitroaniline herbicide that enters plants through developing
roots preventing the alignment and separation of chromosomes during mitosis (mitosis
disrupter). Trifluralin binds to the major microtubule protein tubulin leading to microtube loss
and the absence of the spindle apparatus preventing alignment and separation of chromosomes
during mitosis. Dinitroaniline-induced microtubule loss typically results in the swelling of root
tips as cells in this region fail to divide or elongate. Trifluralin is readily absorbed by young
roots. Established weeds are not controlled.
2.4.4 Use Characterization
Analysis of labeled use information is the critical first step in evaluating the federal action. The
current label for trifluralin represents the FIFRA regulatory action; therefore, application rates
27
-------
and use methods 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.
Trifluralin is a preemergent herbicide used to manage broadleaf weeds and annual grasses and on
an array of food crops and is also registered for non-food uses, including residential uses.
Formulations include emulsifiable concentrates and granulars.
Trifluralin may be applied with a wide range of application equipment including aircraft, ground
spray, soil incorporation treatment, hand held granule applicator, shaker jar and soil broadcast
treatment. Trifluralin may be applied at various stages including pre-plant, pre-emergence,
emergence, dormant stage, established plantings, post-emergence, and/or post harvest. The set of
registered trifluralin products evaluated for the Label Use Information System (LUIS) Report
(Biological and Economic Analysis Division (BEAD), dated 3-24-09) is provided in Table 2.2.
This set of evaluated labels does not constitute all registered trifluralin products; however, it is
expected to be a representative set.
Table 2.2 Summary of Labels included in the LUIS Report for Currently
Registered Trifluralin Uses
Product Name
MACCO
TRIFLURALIN
B.C. HERBICIDE
TREFLAN TR-10
GRANULES
TREFLAN HFP
DREXEL
TRIFLURALIN
TREFLAN 5 G
SNAPSHOT 2.5
TG
TREFLAN B.C.
WEED AND
GRASS
PREVENTER
GOWAN
TRIFLURALIN
10G
SHOWCASE
TURF
FERTILIZER
CONTAINS
TEAM 1.1 5%
Turf Fertilizer -
Contains Gallery
Plus Team Pro
SUPER TEAM
1.25%
Registration
Number
019713-00254
062719-00131
062719-00250
019713-00543
062719-00098
062719-00175
062719-00097
CA94000300
062719-00516
062719-00192
062719-00565
062719-00327
Type of
Formulation"
ECa
G
EC
G
G
G
EC
G
G
G
G
G
Trifluralin
(%)
44.5
10
43
5
5
2
43
10
2
0.27
0.5
0.43
Other Active
Ingredients
none
none
none
none
none
isoxaben
none
none
isoxaben,
oxyfluorefen
benefin,
isoxaben
benefin,
isoxaben
flumetsulam
Label
Date
06/17/99
12/01/05
01/21/02
08/27/02
11/20/01
02/27/02
02/10/09
06/23/05
09/05/07
06/13/08
04/09/08
02/05/99
28
-------
Table 2.2 Summary of Labels included in the LUIS Report for Currently
Registered Trifluralin Uses
Product Name
BROADSTRIKE +
TREFLAN
T&O
FERTILIZER-
CONTAINS
GALLERY PLUS
TEAM
TURF
FERTILIZER -
CONTAINS
TEAM PRO
Registration
Number
062719-00222
62719-00280
62719-00289
Type of
Formulation"
EC
G
G
Trifluralin
(%)
36.35
0.39
0.86
Other Active
Ingredients
benefin
benefin,
isoxaben
benefin
Label
Date
07/21/08
08/04/08
04/09/08
a EC = emulsifiable concentrate, G =granular
The LUIS report from the Biological and Economic Analysis Division (BEAD) was reviewed for
active trifluralin label registrations. Because of the large number of labeled uses for trifluralin,
categories were created for subsets of crops and non-agriculture uses with similar growing
conditions and application rates to make exposure modeling and the resulting analysis workable.
These assigned categories are assumed to be representative of the maximum application rates
and uses for trifluralin. Table 2.3 lists the uses and corresponding application rates and methods
considered in this assessment. The highest application rates, maximum number of applications
per year, and shortest application interval are employed for PRZM/EXAMS modeling. In the
instances when application rates, maximum number of applications per year, and shortest
application intervals were not specified in the LUIS Report, representative rates and intervals
were assumed based on management practices and use rates on similar crops. Additional sources
of data include California Pesticide Use Reporting (Cal PUR) data and USDA crop profile
information. Twenty-five crop categories were designated to estimate EECs and risk as
surrogates for all of the uses included in a given crop category. A master label was not provided
by SRRD; however, SRRD did confirm that the use table (Table 2.3) developed for this
assessment was correct (Appendix Q).
29
-------
Table 2.3 Trifluralin Uses Assessed in California
General
crop
category
Representa-
tive Crops
Form-
ulation1
Appli-
cation
Method
Soil
Incorp-
oration
(Y/N)4
Maximum
Single
Application
Rate
(Ibs/acre)
Max Number
of
Applications
per Year
(Minimum
Interval)
Represent-
ative label
Orchard Uses
Avocado
Citrus
Grape and
berry
Grape
Olive
Stone and
pome fruit
Tree nuts
Avocado
Grapefruit,
lemon, orange,
tangelo,
tangerine
Blackberry,
blueberry,
boysenberry,
currant,
dewberry,
elderberry,
gooseberry,
grapes, kiwi
fruit,
loganberry,
mulberry,
raspberry
(black, red)
Grape
Olive
Apples,
apricot,
cherry, fig,
fruits
unspecified,
nectarine,
peach, pear,
plum,
pomegranate,
prune
Almond,
filbert,
macadamia,
G1
G
EC
G
EC
G
G
EC
G
Ground
Ground
Aerial
Ground
Ground
Aerial
Ground
Ground
Ground
Aerial
Ground
Ground
N
N
Y
N
Y
N
N
Y
N
4.0
4.0
2.0
4.0
2.0
4.0
4.0
2.0
4.0
32
(60)
-,2
J
(60)
I3
(NA)
(60)
I3
(NA)
32
(60)
32
(60)
I3
(NA)
32
*• '
Snapshot 2.5
TG
062719-
00175
Snapshot 2.5
TG
062719-
00175
Treflan HFP
062719-
00250
Snapshot 2.5
062719-
00175
Treflan HFP
062719-
00250
Snapshot 2.5
TG
062719-
00175
Snapshot 2.5
TG
062719-
00175
Treflan HFP
062719-
00250
Showcase
062719-
00516
30
-------
Table 2.3 Trifluralin Uses Assessed in California
General
crop
category
Representa-
tive Crops
pecan,
pistachio, tree
nuts, walnut
(English/black)
Form-
ulation1
EC
Appli-
cation
Method
Aerial
Ground
Soil
Incorp-
oration
(Y/N)4
Y
Maximum
Single
Application
Rate
(Ibs/acre)
2.0
Max Number
of
Applications
per Year
(Minimum
Interval)
I3
(NA)
Represent-
ative label
TreflanHFP
062719-
00250
Non-Orchard Agricultural Uses
Alfalfa
Potato
Tomato
Melon
Cole
Crops
Corn
Cotton
Lettuce
Onion
Alfalfa, clover
White/Irish
potato, turnip
Okra, tomato
Cucumber,
melon,
watermelon
Broccoli,
broccoli raab,
Brussels
spouts,
cabbage,
cauliflower,
collards,
crambe, kale,
mustard,
canola/rape
Corn field,
kenaf,
sunflower
Cotton
Chicory,
endive
Onion (dry
bulb)
Radish,
G
EC
EC
EC
EC
EC
EC
EC
Aerial
Ground
Aerial
Ground
Ground
Aerial
Ground
Aerial
Ground
Aerial
Ground
Aerial
Ground
Aerial
Ground
Y
N
Y
Y
Y
Y
Y
Y
2.0
1.0
1.0
1.0
1.0
2.0
1.0
0.8
2
(60)
I3
(NA)
1
I3
(NA)
I3
(NA)
I3
(NA)
I3
(NA)
I3
(NA)
Treflan TR-
IO Granules
062719-
00131
TreflanHFP
062719-
00250
TreflanHFP
062719-
00250
TreflanHFP
062719-
00250
TreflanHFP
062719-
00250
TreflanHFP
062719-
00250
TreflanHFP
062719-
00250
TreflanHFP
062719-
00250
31
-------
Table 2.3 Trifluralin Uses Assessed in California
General
crop
category
Rangeland
Hay
Row Crop
Sugar
Beet
Wheat
Representa-
tive Crops
Bermuda
grass, forage,
fodder, hay,
straw, un-
cultivated
agriculture
Asparagus,
bean (castor)
bean (lima),
bean (mung),
bean
succulent,
bean (snap),
carrot, celery,
guar, lentil,
peas(southern)
peas
(succulent),
pepper, sugar
cane
Sugar beet
Barley, hops,
flax, safflower,
sorghum,
unspecified
grains, wheat
Form-
ulation1
G
EC
EC
FC
J—l\~s
Appli-
cation
Method
Ground
Aerial
Ground
Aerial
Ground
Aerial
Ground
Soil
Incorp-
oration
(Y/N)4
N
Y
Y
Y
Maximum
Single
Application
Rate
(Ibs/acre)
2.0
2.0
0.75
1.0
Max Number
of
Applications
per Year
(Minimum
Interval)
I3
(NA)
I3
(NA)
I3
(NA)
I3
(NA)
Represent-
ative label
Turf
Fertilizer -
contains
Team Pro
0.86%
062719-
00289
Treflan HFP
062719-
00250
Treflan HFP
062719-
00250
Treflan HFP
062719-
00250
Non-agricultural Uses
Nursery
Banana,
greenhouse- in
use ornamental
shade trees,
ornamental
ground cover,
ornamental
herbaceous
plants,
ornamental
G
Ground
N
4.0
3
(60)
Snapshot 2.5
062719-
00175
32
-------
Table 2.3 Trifluralin Uses Assessed in California
General
crop
category
Resident-
ial
Rights-of-
way
Turf
Forestry
Representa-
tive Crops
lawns and turf,
ornamental
non-flowering
plants,
ornamental
woody shrubs
and vines
residential
lawns
Ornamental
and/or shade
trees,
ornamental
ground cover,
ornamental
herbaceous
plants,
ornamental
lawns and turf,
ornamental
non-flowering
plants,
ornamental
woody shrubs
and vines
residential
lawns
Pre-paving,
private
roads/side-
walks, non-
agriculture
rights-of-way,
fencerows,
hedgerows
Golf course
turf, recreat-
ional,
residential
lawns,
commercial/in
dustrial lawns
Christmas tree
plantations
Form-
ulation1
EC
G
G
G
G
Appli-
cation
Method
Ground
Ground
Ground
Ground
Ground
Soil
Incorp-
oration
(Y/N)4
N
N
N
N
N
Maximum
Single
Application
Rate
(Ibs/acre)
4.0
1.5
4.0
1.5
4.0
Max Number
of
Applications
per Year
(Minimum
Interval)
32
(60)
2
(56)
32
(60)
2
(56)
o2
(60)
Represent-
ative label
062719-
00097
Showcase
062719-
00516
Showcase
062719-
00516
Turf
Fertilizer -
contains
Team Pro
0.86%
062719-
00289
Showcase
062719-
00516
33
-------
Table 2.3 Trifluralin Uses Assessed in California
General
crop
category
Representa-
tive Crops
Cottonwood
(forest/shelterb
elt), poplar
Form-
ulation1
EC
Appli-
cation
Method
Aerial
Ground
Soil
Incorp-
oration
(Y/N)4
Y
Maximum
Single
Application
Rate
(Ibs/acre)
2.0
Max Number
of
Applications
per Year
(Minimum
Interval)
I3
(NA)
Represent-
ative label
TreflanHFP
062719-
00250
1 EC = Emulsifiable Concentrate, G = Granular
2 Maximum number of applications per year is not specified on label or in LUIS Report. For this assessment it is
assumed that a maximum of 3 applications of 4 Ibs trifluralin at a minimum of 60 day intervals is applied. This
application rate is comparable to numerous annual maximum application rates for granular nursery and orchard
uses.
3 The LUIS Report listed many of the number of applications per year and maximum Ibs trifluralin per year as
NA (not available). EFED looked at the representative label (next column) and inferred that a single application
per crop cycle was intended as a specific time in the growing cycle of the crop was provided for trifluralin
application (e.g., if label specified triflluralin application was to be pre-plant, it was assumed this product applied
once per crop cycle).
4 Y = soil incorporation is required within 24 hours, N = soil incorporation is greater than 24 hours or not at all.
A national map (Figure 2.1) showing the estimated poundage of trifluralin uses across the
United States is provided below. 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/). These data suggest that at a national level,
trifluralin is primarily applied to soybeans, alfalfa hay, cotton, and wheat for grain. Use intensity
is highest in several parts of the country including areas of the Southeast, upper mid-west, Texas,
and the central valley of California. Use data in California is discussed in greater detail below.
34
-------
TRIFLURALIN - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds per square mile of agricultural
land in county)
D no estimated use
D 0.001 to 0.035
D 0.036 to 0.293
D 0.294 to 1.162
D 1.163 to 3.53
• >= 3.531
Crops
soybeans
cotton
alfalfa hay
wheat for grain
sugarcane
sunflower seed
dry beans
tomatoes
sorghum
green beans
Total
pounds applied
2999382
2672127
1 063635
715160
304406
274123
260349
108776
62492
58753
Percent
national use
33.69
30.02
11.95
8.03
3.42
3.08
2.92
1.22
0.70
0.66
Figure 2.1 Estimated Trifluralin Use in 2002, Total Pounds Based on Data at the County
Level
The Agency's Biological and Economic Analysis Division (BEAD) provides an analysis of both
national- and county-level usage information using state-level usage data1 obtained from USDA-
NASS2, 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)
database3. 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 trifluralin 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 agricultural pesticide application made on every use site at the section level
1 Memo from Carter and Kaul (BEAD) to Galavotti (EFED), June 3, 2009: County-Level Usage for strychnidin;
strychnine; triclopyr, butoxyethyl ester; triclopyr, triethylamine salt; diflubenzuron; trifluralin; thiobencarb;
chlorpyrifos; vinclozolin; iprodione in California in Support of a Red Legged Frog Endangered Species Assessment
DP # TBD
2 United States Depart of Agriculture (USDA), National Agricultural Statistics Service (NASS) Chemical Use
Reports provide summary pesticide usage statistics for select agricultural use sites by chemical, crop and state. See
http://www.usda. gov/nass/pubs/estindxl .htm#agchem.
3 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.
35
-------
(approximately one square mile) of the public land survey system.4 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, average annual area treated, and average and
maximum application rate across all eight years. The units of area treated are also provided
where available.
A summary of all trifluralin uses in California based on the modeled scenarios is provided in
Table 2.4. Use data for the 20 counties with the highest usage is provided in Table 2.5.
Complete data tables can be found in Appendix C.
From 1999 to 2006, trifluralin was used on 81 crops or sites in 52 counties in California. The
herbicide was used in the greatest quantity on alfalfa with an average yearly application of
601,216 Ibs/year. The greatest quantity of trifluralin was applied in Imperial County with a
yearly average application of 259,148 Ibs/year. The highest average application rate over the
eight year period was 1.7 Ibs/acre applied in Imperial County.
Nearly all the maximum application rates recorded in the 1999 to 2006 CDPR PUR data exceed
the maximum application rates permitted on trifluralin labels (see Tables 2.4 and 2.5). This
likely indicates data entry errors in the pounds applied or the acres treated. The 95th and 99th
percentile estimations of application rates aggregated by cropping category were, for the
majority, less than the maximum labeled rates. Figure 2.2 shows the scenarios with the highest
usage as a fraction of the entire average annual usage.
4 Most pesticide applications to parks, golf courses, cemeteries, rangeland, pastures, and along roadside and railroad
rights of way, and postharvest treatments of agricultural commodities. The primary exceptions to the reporting
requirement are home-and-garden use and most industrial and institutional uses
(http://www.cdpr.ca.gov/docs/pur/purmain.htm).
36
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Table 2.4 Summary of California Department of Pesticide Registration
(CDPR) Pesticide Use Reporting (PUR) Data from 1999 to 2006 for
Currently Registered Trifluralin Uses Based on Aggregated Scenarios1
General Crop Category
Alfalfa
Cotton
Tomato
Row crop
Wheat
Rangeland hay
Tree nuts
Sugar beet
Grapes
Melon
Grapes (wine)
Corn
Cole crop
Right of way
Citrus
Nursery
Stone and pome fruit
Potato
Onion
Lettuce
Forestry
Turf
Olive
Others
TOTAL FOR ALL SCENARIOS
Average
Annual
Application
(Ibs/year) 2
601,216
180,135
108,155
53,306
23,195
22,828
20,301
10,166
9,248
7,528
7,086
5,625
3,833
3,393
3,132
2,835
1,001
568
356
121
2
2
1
8,281
1,072,315
Application Rate (Ibs/acre) 2
AVG
2.0
0.8
0.6
0.7
0.8
1.5
1.6
0.8
1.0
1.0
4.1
0.9
0.6
1.8
0.6
1.2
1.1
14.3
0.7
0.5
NA
NA
NA
95th % ile
2.8
1.2
1.2
0.9
1.3
1.8
3.1
1.0
1.8
3.5
4.9
1.1
1.1
NA
0.9
2.2
1.5
14.3
0.8
0.6
NA
NA
NA
99th % ile
3.8
1.4
1.5
1.4
1.6
1.8
3.4
1.5
3.1
3.8
6.8
1.2
1.3
NA
1.1
3.0
1.7
14.8
1.2
0.6
NA
NA
NA
1- Based on data supplied by BEAD (Memo from Carter and Kaul (BEAD) to Galavotti (EFED),
June 3, 2009)
2- The average annual pounds applied and average application rate was calculated as the weighted
average of the average application rate for one county or average annual pounds applied for one
county. The values reflect the average annual pounds applied to that site across all counties and
the average application rate for that site across all counties.
37
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Figure 2.2 Scenarios with Highest Trifluralin Use Based on
CD PR PUR Data from 1999-2006
CA ALMOND
CA RANGELAND
2%
CA WHEAT
2%
CA ROW CROP
5%
CA TOMATO
10%
CA COTTON
17%
OTHER
5%
CA ALFALFA
57%
Table 2.5 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Usage Reporting (PUR) Data from 1999 to 2006 for 20 Counties with
Highest Trifluralin Usage1
County
IMPERIAL
FRESNO
MERCED
KINGS
KERN
SAN JOAQUIN
TULARE
RIVERSIDE
YOLO
MADERA
STANISLAUS
SOLANO
SUTTER
SACRAMENTO
COLUSA
LOS ANGELES
Average Annual
Application
(Ibs/year)
259,148
169,941
117,817
106,406
74,838
55,881
55,235
50,637
49,212
27,182
26,827
13,741
11,693
9,595
8,401
7,772
Application Rate (Ibs/acre)
Average
1.7
1.0
0.8
1.1
1.0
1.3
1.3
NA
0.8
1.2
0.8
0.9
0.8
1.0
0.7
1.2
38
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Table 2.5 Summary of California Department of Pesticide Registration (CDPR)
Pesticide Usage Reporting (PUR) Data from 1999 to 2006 for 20 Counties with
Highest Trifluralin Usage1
County
GLENN
SAN LUIS OBISPO
SANTA BARBARA
SANBERNADINO
All Other Counties
TOTAL
Average Annual
Application
(Ibs/year)
7,581
5,153
4,280
3,685
7,290
1,072,315
Application Rate (Ibs/acre)
Average
1.5
1.0
0.6
0.9
NA
NA
1- Based on data supplied by BEAD (Memo from Carter and Kaul (BEAD) to Galavotti (EFED), June
3, 2009)
2.5 Assessed Species
Table 2.6 provides a summary of the current distribution, habitat requirements, and life history
parameters for the four listed species being assessed. More detailed life history and distribution
information can be found for CRLF in Attachment 1 and for DS, SFGS, and SJKF in
Attachment 3. Figures 2.3 to 2.6 provide maps of the current range and habitats of the assessed
listed species.
39
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Table 2.6 Summary of Current Distribution, Habitat Requirements, and Life History Information for the Assessed Listed
Species1
Assessed
Species
California red-
legged frog
(Rana aurora
draytonii)
Delta smelt
(Hypomesus
transpacificus)
San Francisco
garter snake
(Thamnophis
sirtalis
tetrataenia)
Size
Adult
(85-138 cm in
length),
238 g,
Males -
13-163 g;
Juveniles
(40-84 cm in
length)
Up to 120 mm
in length
Adult
(46-131 cm in
length),
Females - 227
g,
H3g;
Juveniles
(18-20 cm in
Current Range
Northern CA
coast, northern
Transverse
Ranges, foothills
of Sierra Nevada,
and in southern
CA south of Santa
Barbara
Suisun Bay and
the Sacramento-
San Joaquin
estuary (known as
the Delta) near
San Francisco
Bay, CA
San Mateo
County
Habitat Type
Freshwater perennial or
near-perennial aquatic
habitat with dense
vegetation; artificial
impoundments; riparian
and upland areas
The species is adapted
to living in fresh and
brackish water. They
typically occupy
estuarine areas with
salinities below 2 parts
per thousand (although
they have been found in
areas up to 18ppt).
They live along the
freshwater edge of the
mixing zone (saltwater-
freshwater interface).
Densely vegetated
freshwater ponds near
open grassy hillsides;
emergent vegetation;
rodent burrows
Desig-
nated
Critical
Habitat?
Yes
Yes
No
Reproductive
Cycle
Breeding: Nov. to Apr.
Tadpoles: Dec. to Mar.
Young juveniles: Mar.
to Sept.
They spawn in fresh or
slightly brackish water
upstream of the mixing
zone. Spawning
season usually takes
place from late March
through mid-May,
although it may occur
from late winter (Dec.)
to early summer (July-
August). Eggs hatch
in 9 - 14 days.
Oviparous
Reproduction3
Breeding: Spring (Mar.
and Apr.) and Fall
(Sept. to Nov.)
Ovulation and
Pregnancy: Late spring
and early summer
Young: Born 3 -4
Diet
Aquatic -phase2: algae,
freshwater aquatic
invertebrates
Terrestrial-phase: aquatic and
terrestrial invertebrates, small
mammals, fish and frogs
Primarily planktonic
copepods, cladocerans,
amphipods, and insect larvae.
Larvae feed on
phytoplankton; juveniles feed
on zooplankton.
Juveniles: frogs (Pacific tree
frog, CRLF, and bullfrogs
depending on size) and insects
Adults: primarily frogs
(mainly CRLFs; also
bullfrogs, toads); to a lesser
extent newts; freshwater fish
and invertebrates; insects and
small mammals
40
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Table 2.6 Summary of Current Distribution, Habitat Requirements, and Life History Information for the Assessed Listed
Species1
Assessed
Species
San Joaquin kit
fox
(Vulpes macro tis
mutica)
Size
length)
Adult
~2kg
Current Range
Alameda, Contra
Costa, Fresno,
Kern, Kings,
Madera, Merced,
Monterey, San
Benito, San
Joaquin, San Luis
Obispo, Santa
Barbara, Santa
Clara, Stanislaus,
Tulare and
Ventura counties
Habitat Type
A variety of habitats,
including grasslands,
scrublands (e.g.,
chenopod scrub and
sub-shrub scrub), vernal
pool areas, oak
woodland, alkali
meadows and playas,
and an agricultural
matrix of row crops,
irrigated pastures,
orchards, vineyards, and
grazed annual
grasslands. Kit foxes
dig their own dens,
modify and use those
already constructed by
other animals (ground
squirrels, badgers, and
coyotes), or use human-
made structures
(culverts, abandoned
pipelines, or banks in
sumps or roadbeds).
They move to new dens
within their home range
often (likely to avoid
predation by coyotes)
Desig-
nated
Critical
Habitat?
No, but has
designated
core areas
Reproductive
Cycle
months after mating
Mating and
conception: late
December - March.
Gestation period: 48 to
52 days.
Litters born: February
- late March
Pups emerge from
their dens at about 1-
month of age and may
begin to disperse after
4-5 months usually in
Aug. or Sept.
Diet
Small animals including
blacktailed hares, desert
cottontails, mice, kangaroo
rats, squirrels, birds, lizards,
insects and grass. It satisfies
its moisture requirements
from prey and does not
depend on freshwater sources.
1 For more detailed information on the distribution, habitat requirements, and life history information of the assessed listed species, see Attachments 1 and 3
2 For the purposes of this assessment, tadpoles and submerged adult frogs are considered "aquatic" because exposure pathways in the water are considerably
different than those that occur on land.
3 Oviparous = eggs hatch within the female's body and young are born live.
41
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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
j Recovery Unit Boundaries
X] Currently Occupied Core Areas
| Critical Habitat
HI CNDDB Occurence Sections
__l County Boundaries g
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. Ft. 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. Estero Bay
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 2.3 Recovery Unit, Core Area, Critical Habitat, and Occurrence Designations for
CRLF.
42
-------
Delta smelt habitat areas
Delta smelt critical habitat
| DS_sect
CA co unties
Map created by US EPA on 04/15/09. Projection: Albers Equal Area
Conic USGS, North American Datum of 1983 (NAD 1983). California
county boundaries, source: ESRI 2002. Water bodies, source:
NHDPIus2006. DS occurrence section information obtained from:
Case No. 07-2794JCS). DS critical habitat obtained from
http://crithab.fws.gov/.
024 8 Miles
I i i i I i i i I
-
'1:500,000
Figure 2.4 Delta Smelt Habitat Areas
43
-------
San Francisco Garter Snake habitat areas
Alameda\.
0 2
i j i_
Miles
j
• SFGS habitat areas (USF\Afi)
J SFGS occurrence sections
CA counties
«j
Map created by US EPA on 10/07/09. Projection: Albers Equal Area
Conic USGS, North American Datum of 1983 (NAD 1983). California
county boundaries, source: ESRI 2002. SFGS section information
obtained from: Case No. 07-2794JCS. SFGS habitat areas obtained
from: USFWS Recovery Plan 1985.
an Mi
1:350,000
Figure 2.5 San Francisco Garter Snake Habitat Areas
44
-------
San Joaquin Kit Fox (SJKF) habitat areas
San
a
Tuok
San fa Cruz
Starii
Mar,
**•>
.
era
•-.fe'-ey JL.
SJKF occurrence sections
SJ Kit Fox distributional records
CA counties
Map created by US EPA on 06/11/09. Projection: Albers Equal Area
Conic USGS, North American Datum of 1983 (NAD 1983). California
county boundaries, source: ESRI 2002. Occurrence section information
obtained from: Case No. 07-2794JCS). Critical habitat obtained from
http://crithab.fws.gov/. Locality informaiton obtained from: USFWS
Recovery Plan, 1998.
TS ^—
0 5 10 20 Miles
1:2.000,00(1
Figure 2.6 San Joaquin Kit Fox Habitat Areas
45
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2.6 Designated Critical Habitat
Critical habitat has been designated for the CRLF and the DS. '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.' Critical
habitat receives protection under Section 7 of the ESA through prohibition against destruction or
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
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. Table 2.7 describes the PCEs for the
critical habitats designated for the CRLF and the DS.
Table 2.7 Designated Critical Habitat PCEs for the CRLF and the DS
Species
CRLF
PCEs
Alteration of channel/pond morphology or geometry and/or increase
in sediment deposition within the stream channel or pond.
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.
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)
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
Alteration of chemical characteristics necessary for normal growth
and viability of juvenile and adult CRLFs and their food source.
Reference
50CFR414.12(b),
2006
46
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Table 2.7 Designated Critical Habitat PCEs for the CRLF and the DS
Species
DS
PCEs
Spawning Habitat — shallow, fresh or slightly brackish backwater
sloughs and edgewaters to ensure egg hatching and larval viability.
Spawning areas also must provide suitable water quality (i.e., low
"concentrations of pollutants) and substrates for egg attachment
(e.g., submerged tree roots and branches and emergent vegetation).
Larval and Juvenile Transport — Sacramento and San Joaquin Rivers
and their tributary channels must be protected from physical
disturbance and flow disruption. Adequate river flow_is necessary to
transport larvae from upstream spawning areas to rearing habitat in
Suisun Bay. Suitable water quality must be provided so that
maturation is not impaired by pollutant concentrations.
Rearing Habitat — Maintenance of the 2 ppt isohaline and suitable
water quality (low concentrations of pollutants) within the Estuary is
necessary to provide DS larvae and juveniles a shallow protective,
food-rich environment in which to mature to adulthood.
Adult Migration — Unrestricted access to suitable spawning habitat
in a period that may extend from December to July. Adequate flow
and suitable water qualityjnay need to be maintained to attract
migrating adults in the Sacramento and San Joaquin River channels
and their associated tributaries. These areas also should be protected
from physical disturbance and flow disruption during migratory
periods.
Reference
59 FR 65256 65279,
1994
1 These PCEs are in addition to more general requirements for habitat areas that provide essential life cycle needs
of the species such as 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.
More detail on the designated critical habitat applicable to this assessment can be found in
Attachment 1 (CRLF) and Attachment 3 (DS). Activities that may destroy or modify critical
habitat are those that alter the PCEs and jeopardize the continued existence of the species.
Evaluation of actions related to use of trifluralin that may alter the PCEs of the designated
critical habitat for the CRLF and the DS form the basis of the critical habitat impact analysis.
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 trifluralin is expected to directly impact living organisms within the
action area, critical habitat analysis for trifluralin 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.
47
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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 trifluralin is likely to encompass considerable portions of the United States based on the large
array of agricultural and/or non-agricultural uses. However, the scope of this assessment limits
consideration of the overall action area to those portions that may be applicable to the protection
of the CRLF, DS, SFGS, and SJKF and their designated critical habitat. 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 that exceeds the Agency's LOCs. Although the watershed
for the San Francisco Bay extends northward into the very southwestern portion of Lake County,
Oregon, and westward into the western edge of Washoe County, Nevada, the non-California
portions of the watershed are small and very rural with little, if any, agriculture. Therefore, no
use of trifluralin is expected in these areas, and they are not considered as part of the action area
applicable to this assessment.
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 trifluralin. An
analysis of labeled uses and review of available product labels was completed. Several of the
currently labeled uses are special local needs (SLN) uses or are restricted to specific states and
are excluded from this assessment. In addition, a distinction has been made between food use
crops and those that are non-food/non-agricultural uses. For those uses relevant to the assessed
species, the analysis indicates that, for trifluralin, the following agricultural uses are considered
as part of the federal action evaluated in this assessment:
(1) Orchard Agricultural uses
Almond, apple, apricot, avocado, blackberry, blueberry, boysenberry, cherry, currant,
dewberry, elderberry, fig, filbert, fruits unspecified, gooseberry, grape, grapefruit, kiwi
fruit, lemon, loganberry, macadamia, mulberry, nectarine, orange, olive, peach, pear,
pecan, pistachio, plum, pomegranate, prune, raspberry (black, red), tangerine, tangelo,
tree nuts, (English/black) walnut
(2) Non-Orchard Agricultural uses
Alfalfa, asparagus, barley, broccoli, broccoli rabbinni, beans (succulent), beans (lima),
beans (mung), beans (snap), Bermuda grass, Brussels spouts, cabbage, cauliflower,
canola/rape, carrot, castor, celery, chicory, clover, collards, corn field, cotton, crambe,
cucumber, endive, flax, guar, hops, kale, kenaf, lentil, melon, mustard, okra, onion (dry
bulb), peas(southern), peas (succulent), pepper, radish, safflower, sorghum, sugar beet,
sugar cane, sunflower, tomato, turnip, uncultivated agriculture, uncultivated areas/soils,
unspecified grains, watermelon, white/Irish potato, wheat
(3) Non-agricultural uses
48
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Banana (ornamental), commercial/industrial lawns, Christmas tree plantations,
cottonwood (forest/shelterbelt), golf course turf, greenhouse- in use, industrial areas, non-
agriculture outdoor buildings and structures, non-agriculture rights-of-way, fencerows,
hedgerows, ornamental and/or shade trees, ornamental ground cover, ornamental
herbaceous plants, ornamental lawns and turf, ornamental non-flowering plants,
ornamental woody shrubs and vines, residential lawns, pre-paving, poplar, private
roads/sidewalks, recreational, residential lawns
Following a determination of the assessed uses, an evaluation of the potential "footprint" of
trifluralin 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.
Because of the wide variety of labeled trifluralin uses ranging from orchard, agricultural,
nursery, turf, rights-of-way, and residential, the initial area of concern was defined as the entire
state of California. Precluding geographic areas of the state given these uses is not possible.
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.
The environmental fate properties of trifluralin along with monitoring data identifying its
presence in surface waters, air and precipitation in California indicate that runoff, spray drift,
volatilization and atmospheric transport and (wet) deposition represent significant potential
transport mechanisms of trifluralin to the aquatic and terrestrial habitats of the CRLF, DS, SJKF
and SFGS.
The Agency's approach to defining the action area under the provisions of the Overview
Document (USEPA 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. Deriving the geographical
extent of this portion of the action area is based on consideration of the types of effects that
trifluralin may be expected to have on the environment, the exposure levels to trifluralin that are
associated with those effects, and the best available information concerning the use of trifluralin
and its fate and transport within the state of California. Specific measures of ecological effect for
the assessed species that define the action area include any direct and indirect toxic effect to the
assessed species and any potential modification of 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.
Because a NOAEC value was not established for estuarine/marine chronic fish study and
because trifluralin has been recognized as a possible human carcinogen (Group C Carcinogen,
HED Human Health Risk Assessment, May 7, 2004, DP barcode 296628; Appendix G), the
49
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spatial extent of the action area (i.e., the boundary where exposures and potential effects are less
than the Agency's LOG) for trifluralin cannot be determined. Therefore, it is assumed that the
action area encompasses the entire state of California, regardless of the spatial extent (i.e., initial
area of concern or footprint) of the pesticide use(s). In addition, it is reasonable to assume that
the action area encompasses the entire state of California given the broad range of labeled uses
and the large geographic coverage of the state for those uses.
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, DS, SFGS, and SJKF), organisms important in the life cycle of the assessed species, 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 trifluralin (e.g.,
runoff, spray drift, etc.), and the routes by which ecological receptors are exposed to trifluralin
(e.g., direct contact, etc.).
2.8.1 Assessment Endpoints
Assessment endpoints for the CRLF, DS, SFGS, and SJKF include direct toxic effects on the
survival, reproduction, and growth of individuals, as well as indirect effects, such as reduction of
the prey base or modification of its habitat. In addition, potential modification of critical habitat
is assessed by evaluating potential effects to PCEs, which are components of the habitat areas
that provide essential life cycle needs of the assessed species. 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 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 (USEPA 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 risks for each of
the assessed species associated with exposure to trifluralin is provided in Section 2.5 and Table
2.9.
; From U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
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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
freshwater fish (surrogate for aquatic-phase amphibians), freshwater invertebrates, aquatic
plants, birds (surrogate for terrestrial-phase amphibians), mammals, terrestrial invertebrates, and
terrestrial plants. Additional taxa evaluated for the DS are estuarine/marine fish and
estuarine/marine invertebrates; the most sensitive of the freshwater and estuarine/marine species
are used for the risk assessment. 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 trifluralin.
Table 2.8 identifies the taxa used to assess the potential for direct and indirect effects from the
uses of trifluralin for each listed species assessed here. The specific assessment endpoints used to
assess the potential for direct and indirect effects to each listed species are provided in Table 2.9.
Table 2.8 Taxa Used in the Analyses of Direct and Indirect Effects for the Assessed Listed
Species.
Listed
Species
CRLF3
SFGS3
SJKF
DS
Birds
Direct
Indirect
(prey)
Direct
Indirect
(prey)
Indirect
(prey)
N/A
Mammals
Indirect
(prey)
Indirect
(prey/
habitat)
Direct
Indirect
(prey)
N/A
Terr.
Plants
Indirect
(habitat)
Indirect
(habitat)
Indirect
(food/
habitat)
Indirect
(habitat)
Terr.
Inverts.
Indirect
(prey)
Indirect
(prey)
Indirect
(prey)
N/A
FW Fish
Direct
Indirect
(prey)
Indirect
(prey)
N/A
Direct 2
FW
Inverts.
Indirect
(prey)
Indirect
(prey)
N/A
Indirect
(prey) 2
E/M
Fish
N/A
N/A
N/A
Direct2
E/M
Inverts.
N/A
N/A
N/A
Indirect2
(prey)
Aquatic
Plants1
Indirect
(food/
habitat)
Indirect
(habitat)
N/A
Indirect
(food/
habitat)
1 Vascular and non-vascular aquatic plants are assessed separately. Data from the most sensitive plant species of each
group (vascular and non-vascular) will be used, regardless of habitat (freshwater or estuarine/marine).
2 The most sensitive species in either freshwater or estuarine/marine environments was used for the DS assessment.
3 Consumption of residues in aquatic organisms may result in direct effects to the CRLF and SFGS.
N/A = Not applicable
Terr. = Terrestrial
Invert. = Invertebrate
FW = Freshwater
E/M = Estuarine/Marine
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Table 2.9 Taxa and Assessment Endpoints Used to Evaluate the Potential for the Use of
Trifluralin to Result in Direct and Indirect Effects to the Assessed Listed Species.
Taxa Used to Assess
Direct and/or Indirect
Effects to Assessed
Species
Assessed Listed
Species
Assessment Endpoints
Measures of Ecological Effects1
1. Freshwater Fish and
Aquatic-phase
Amphibians
Direct Effect -
-Aquatic-phase CRLF2
-DS
Survival, growth, and
reproduction of individuals
via direct effects
la. Bluegill sunfish acute LC50
Ib. Bluegill sunfish chronic NOAEC
(estimated by ACR)
Indirect Effect (prey)
-Aquatic-phase CRLF
-SFGS
Survival, growth, and
reproduction of individuals
via indirect effects on
aquatic prey food supply
(i.e., fish and aquatic -
phase amphibians)
2. Freshwater
Invertebrates
Indirect Effect (prey)
-Aquatic-phase CRLF
-DS
-SFGS
Survival, growth, and
reproduction of individuals
via indirect effects on
aquatic prey food supply
(i.e., freshwater
invertebrates)
2a. Daphnid acute EC50
2b. Daphnid chronic NOAEC
3. Estuarine/Marine
Fish
Direct Effect -
-DS
Survival, growth, and
reproduction of individuals
via direct effects
Indirect Effect (prey)
-DS
Survival, growth, and
reproduction of individuals
via indirect effects on
aquatic prey food supply
(i.e., estuarine/marine fish)
3a. Bluegill sunfish acute LC50
3b. Bluegill sunfish chronic NOAEC
(estimated by ACR)
Since the DS inhabits freshwater and
brackish waters, the most sensitive of
the freshwater and estuarine/marine
organisms is used for the assessment.
4. Estuarine/Marine
Invertebrates
Indirect Effect (prey)
-DS
Survival, growth, and
reproduction of individuals
via indirect effects on
aquatic prey food supply
(i.e., estuarine/marine
invertebrates)
4a. Daphnid acute EC50
4b. Daphnid chronic NOAEC
Since the DS inhabits freshwater and
brackish waters, the most sensitive of
the freshwater and estuarine/marine
organisms is used for the assessment.
5. Aquatic Plants
(freshwater/marine)
Indirect Effect
(food/habitat)
-Aquatic-phase CRLF
-DS
-SFGS
Survival, growth, and
reproduction of
individuals via indirect
effects on habitat, cover,
food supply, and/or
primary productivity (i.e.,
aquatic plant community)
5a. Duckweed IC50
5b. Skeletonema costatum
6. Birds, Terrestrial-
phase Amphibians, and
Reptiles
Direct Effect
-Terrestrial-phase
CRLF
-SFGS
Survival, growth, and
reproduction of individuals
via direct effects
6a. Northern bobwhite quail and
mallard duck acute oral LD50
6b. Northern bobwhite quail and
mallard duck acute dietary LC50
6c. Mallard duck chronic NOAEC
Indirect Effect (prey)
-Terrestrial-phase
CRLF
-SFGS
-SJKF
Survival, growth, and
reproduction of individuals
via indirect effects on
terrestrial prey (birds)
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Table 2.9 Taxa and Assessment Endpoints Used to Evaluate the Potential for the Use of
Trifluralin to Result in Direct and Indirect Effects to the Assessed Listed Species.
Taxa Used to Assess
Direct and/or Indirect
Effects to Assessed
Species
Assessed Listed
Species
Assessment Endpoints
Measures of Ecological Effects1
7. Mammals
Direct Effect
-SJKF
Survival, growth, and
reproduction of individuals
via direct effects
la. Laboratory rat acute LD50
7b. Laboratory rat chronic NOAEL
Indirect Effect
(prey/habitat from
burrows)
-Terrestrial-phase
CRLF
-SFGS
-SJKF
Survival, growth, and
reproduction of individuals
via indirect effects on
terrestrial prey (mammals)
8. Terrestrial
Invertebrates
Indirect Effect (prey)
-Terrestrial-phase
CRLF
-SFGS
-SJKF
Survival, growth, and
reproduction of individuals
via indirect effects on
terrestrial prey (terrestrial
invertebrates)
8a. Honey bee acute LDso
9. Terrestrial Plants
Indirect Effect
(food/habitat) (non-
obligate relationship)
-Terrestrial-phase
CRLF
-SFGS
-SJKF
Survival, growth, and
reproduction of
individuals via indirect
effects on food and habitat
(i.e., riparian and upland
vegetation)
9a. Monocot EC2s: sorghum (seedling
emergence) and corn (vegetative vigor)
9b. Dicot EC25: cucumber (seedling
emergence and vegetative vigor)
Citations for all registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix F and Appendix H.
2 Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult frogs are
considered "aquatic" for the purposes of this assessment because exposure pathways in the water are considerably different
than exposure pathways on land.
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 trifluralin that may alter the PCEs of the assessed species' designated critical habitat.
PCEs for the assessed species 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
assessed species. 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 trifluralin effects data are available.
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. Measures of ecological effect used to assess the
53
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potential for modification to the critical habitat of the CRLF and the DS are described in Table
2.10. The SFGS and the SJKF do not have designated critical habitat.
Table 2.10 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat for CRLF and the DS.
Taxon Used to
Assess Modification
ofPCE
1 . Freshwater Fish
and Aquatic -phase
Amphibians
2. Freshwater
Invertebrates
3. Estuarine/Marine
Fish
4. Estuarine/Marine
Invertebrates
5. Aquatic Plants
(freshwater/marine)
6. Birds
Assessed Listed
Species Associated
with the PCE
Direct Effect -
-Aquatic -phase
CRLF2
-DS
Indirect Effect (prey)
-Aquatic-phase CRLF
-DS
Indirect Effect (prey)
-Aquatic -phase
CRLF
-DS
Direct Effect
-DS
Indirect Effect (prey)
-DS
Indirect Effect (prey)
-DS
Indirect Effect
(food/habitat)
-Aquatic-phase CRLF
-DS
Direct Effect
-Terrestrial-phase
CRLF
Indirect Effect (prey)
-Terrestrial-phase
CRLF
Assessment Endpoints
Survival, growth, and
reproduction of
individuals via direct
effects
Modification of critical
habitat via change in
aquatic prey food supply
(i.e., fish and aquatic-
phase amphibians)
Survival, growth, and
reproduction of
individuals via indirect
effects on aquatic prey
food supply (i.e.,
freshwater invertebrates)
Modification of critical
habitat via change in
aquatic prey food supply
(i.e., estuarine/marine
fish)
Modification of critical
habitat via change in
aquatic prey food supply
(i.e., estuarine/marine
invertebrates)
Modification of critical
habitat via change in
habitat, cover, food
supply, and/or primary
productivity (i.e., aquatic
plant community)
Survival, growth, and
reproduction of
individuals via direct
effects
Modification of critical
habitat via change in
terrestrial prey (birds)
Measures of Ecological Effects 1
la. Bluegill sunfish acute LC50
Ib. Bluegill sunfish chronic NOAEC
(estimated by ACR)
2a. Daphnid acute EC50
2b. Daphnid chronic NOAEC
3 a. Bluegill sunfish acute LC50
3b. Bluegill sunfish chronic NOAEC
(estimated by ACR)
Since the DS inhabits freshwater and
brackish waters, the most sensitive of
the freshwater and estuarine/marine
organisms is used for the assessment.
4a. Daphnid acute EC50
4b. Daphnid chronic NOAEC
Since the DS inhabits freshwater and
brackish waters, the most sensitive of
the freshwater and estuarine/marine
organisms is used for the assessment.
5a. Duckweed IC50
5b. Skeletonema costatum ICso
6a. Northern bobwhite quail and
mallard duck acute oral LD50
6b. Northern bobwhite quail and
mallard duck acute dietary LC50
6c. Mallard duck chronic NOAEC
54
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Table 2.10 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat for CRLF and the DS.
Taxon Used to
Assess Modification
ofPCE
Assessed Listed
Species Associated
with the PCE
Assessment Endpoints
Measures of Ecological Effects 1
7. Mammals
Indirect Effect
(prey/habitat from
burrows')
-Terrestrial-phase
CRLF
-SFGS
-SJKF
Modification of critical
habitat via change in
terrestrial prey
(mammals)
7a. Laboratory rat acute LD50
7b. Laboratory rat chronic NOAEL
8. Terrestrial
Invertebrates
Indirect Effect (prey)
-Terrestrial-phase
CRLF
Modification of critical
habitat via change in
terrestrial prey (terrestrial
invertebrates)
8a. Honey bee acute LDso
9. Terrestrial Plants
Indirect Effect
(food/habitat) (non-
obligate relationship)
-Terrestrial-phase
CRLF
Modification of critical
habitat via change in
food and habitat (i.e.,
riparian and upland
vegetation)
9a. Monocot EC2s: sorghum (seedling
emergence) and corn (vegetative
vigor)
9b. Dicot EC25: cucumber (seedling
emergence and vegetative vigor)
Citations for all registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix F and Appendix H.
2Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult frogs are
considered "aquatic" for the purposes of this assessment because exposure pathways in the water are considerably
different than exposure pathways on land.
2.9 Conceptual Model
2.9.1 Risk Hypotheses
Risk hypotheses are specific assumptions about potential effects (i.e., changes in assessment
endpoints) and may be based on theory and logic, empirical data, mathematical models, or
probability models (U.S. EPA, 1998). For this assessment, the risk is stressor-linked, where the
stressor is the release of trifluralin to the environment. The following risk hypotheses are
presumed for each assessed species in this assessment:
The labeled use of trifluralin within the action area may:
• directly affect the CRLF, DS, SFGS, and/or SJKF by causing mortality or by adversely
affecting growth or fecundity;
• indirectly affect the CRLF, DS, SFGS, and/or SJKF and/or modify designated critical
habitat of the CRLF or DS by reducing or changing the composition of food supply;
55
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• indirectly affect the CRLF, DS and/or SFGS and/or modify their designated critical
habitat by reducing or changing the composition of the aquatic plant community in the
species' current range, thus affecting primary productivity and/or cover;
• indirectly affect the CRLF, DS, SFGS, and/or SJKF and/or modify their designated
critical habitat by reducing or changing the composition of the terrestrial plant
community in the species' current range;
• indirectly affect the CRLF and/or DS and/or modify their designated critical habitat by
reducing or changing aquatic habitat in their current range (via modification of water
quality parameters, habitat morphology, and/or sedimentation).
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment. It
specifies the trifluralin release mechanisms, biological receptor types, and effects endpoints of
potential concern. The conceptual models for aquatic and terrestrial phases of the CRLF, DS,
SFGS, and SJKF and the conceptual models for the aquatic and terrestrial PCE components of
critical habitat for the CRLF and DS are shown in Figures 2.7 and 2.8. Although the conceptual
models for direct/indirect effects and modification of designated critical habitat PCEs are shown
on the same diagrams, the potential for direct/indirect effects and modification of PCEs will be
evaluated separately in this assessment. Exposure routes shown in dashed lines are not
quantitatively considered because the contribution of those potential exposure routes to potential
risks to the CRLF, DS, SFGS, and SJKF and modification to designated critical habitat for the
CRLF and DS is expected to be negligible.
56
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Stressor
Source
Exposure
Media
Receptors
Attribute
Change
Trifluralin applied to use site
I
t
| Spray drift j | Runoff | I spl1 \
I
Surface water/
Sediment
T
•Wet/dry deposition
Long range
atmospheric
transport
Uptake/gills
or integument
Uptake/gills
or integument
itake
Aquatic Animals
Invertebrates
Vertebrates
Uptake/cell,
roots leaves
Aquatic Plants
Non-vascular
Vascular
Fish/aquatic-phase
amphibians
**Piscivorous
terrestrial organisms
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Food chain
Reduction in algae
Reduction in prey
Modification of PCEs
related to prey
availability
^ "" Reduced
Riparian plant
terrestrial
exposure
pathways see
Figure 2.9
Habitat integrity
Reduction in primary productivity
cover
•ommunity change
Modification of PCS related to
habitat
Figure 2.7 Conceptual Model for Trifluralin Effects on the Assessed Species and Their
Critical Habitat in the Aquatic Environment
** Route exposure includes only ingestion of aquatic fish and invertebrates; piscivorous terrestrial
organisms may include mammals, birds, reptiles, terrestrial-phase amphibians
57
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Stressor
Source
Exposure
Media
Trifluralin applied to use site
1
1
4 *
•I Spray drift"!
.Dermal uptake/Ingestion
| Runoff |
±_
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Root uptake
Wet/dry deposition
Long range
atmospheric
transport
tion .4.
^•Ingestion
-^. Ingestion
Ingestion
Receptors
Attribute
Change
, Ingestion ^_
i_l
Birds/terrestrial-
phase amphibians/
reptiles/mammals
±
Individual organisms
Reduced survival
Reduced growth
Reduced reproduction
Mammals/
Birds
Food chain
Reduction in prey
Modification of
PCEs related to
prey availability
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Modification of PCEs related to
labitat
Figure 2.8 Conceptual Model for Trifluralin Effects on the Assessed Species and Their
Critical Habitat in the Terrestrial Environment
2.10 Analysis Plan
In order to address the risk hypothesis, the potential for direct and indirect effects to the CRLF,
DS, SFGS, and SJKF prey items, and habitat is estimated based on a taxon-level approach. In the
following sections, the use, environmental fate, and ecological effects of trifluralin 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 trifluralin is estimated using the probit dose-
response slope and either the level of concern (discussed below) or actual calculated risk quotient
value.
58
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2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model
2.10.1.1 Measures of Exposure
The environmental fate properties of trifluralin along with available monitoring data indicate that
runoff, spray drift, and long-range atmospheric transport are the principle potential transport
mechanisms of trifluralin to the aquatic and terrestrial habitats of the CRLF, DS, SFGS, and
SJKF. In this assessment, transport of trifluralin through runoff and spray drift is considered in
deriving quantitative estimates of CRLF, DS, SFGS, and SJKF exposure to trifluralin, in addition
to exposure of their prey and habitats. Assessment of long-range atmospheric transport is
addressed qualitatively through a review of available monitoring data from California, but not
explicitly modeled due to the lack of models that quantitatively predict far-field pesticide
concentrations resulting from near-field loadings.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of trifluralin 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.
PRZM (V3.12.2, May 2005) and EXAMS (V2.98.4.6, April 2005) are screening simulation
models coupled with the input shell pe5.pl (Aug 2007) to generate daily exposures and l-in-10
year EECs of trifluralin that may occur in surface water bodies adjacent to application sites
receiving trifluralin 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
trifluralin. The measure of exposure for aquatic species is the l-in-10 year return peak or rolling
mean concentration. The 1-in-10-year 60-day mean is used for assessing chronic exposure to
fish; the l-in-10-year 21-day mean is used for assessing chronic exposure for aquatic
invertebrates.
Exposure estimates for the terrestrial animals assumed to be in the target area or in an area
exposed to spray drift are derived using the T-REX model (version 1.4.1, Oct. 9, 2008). 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 the purposes of this assessment, upper-bound Kenaga nomogram estimates
reported by T-REX are used for derivation of the EECs for the terrestrial-phase CRLF, SFGS,
and SJKF and their potential prey.
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For modeling purposes, direct exposures of the terrestrial-phase CRLF and the SFGS to
trifluralin 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, the SFGS and one of their prey items. Estimated
exposures of terrestrial insects to trifluralin are bound by using the dietary-based EECs for small
insects and large insects.
For modeling purposes, direct exposures of the SJKF to trifluralin through contaminated food are
estimated using the EECs for the large mammal (1000 g) which consumes all food categories.
Dietary-based and dose-based exposures of potential prey (mammals and birds) are assessed
using the small mammal (15 g) and small bird (20 g) which consumes short grass. The small bird
(20g) 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 its prey items. Estimated exposures of terrestrial insects to trifluralin are bound by
using the dietary-based EECs for small insects and large insects.
Birds are currently used as surrogates for terrestrial-phase amphibians and reptiles. However,
amphibians and reptiles are poikilotherms (body temperature varies with environmental
temperature) while birds are homeotherms (temperature is regulated, constant, and largely
independent of environmental temperatures). Therefore, amphibians and reptiles 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 and reptiles 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 and reptiles is likely to result
in an over-estimation of exposure and risk for reptiles and terrestrial-phase amphibians.
Therefore, T-REX (version 1.4.1) 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.
Because there is evidence of the potential for bioaccumulation of trifluralin in aquatic organisms,
an additional exposure pathway that will be considered in this assessment is the consumption of
contaminated fish or aquatic invertebrates that have bioaccumulated trifluralin dissolved in water
and their aquatic diet. The potential risk from this pathway will be evaluated and discussed
further in the "Risk Description" section of the document. Multiple lines of evidence will be used
to evaluate bioaccumulation potential, including measured bioconcentration factors (BCF),
bioaccumulation factors (BAF) and a food web bioaccumulation model (Kow-Based Aquatic
Bioaccumulation Model or KABAM ver 1.0). The bioaccumulation assessment relies on
predicted water and sediment concentrations from PRZM/EXAMS to estimate concentrations of
trifluralin in aquatic organisms. These estimated tissue concentrations will be compared to
toxicity values for various taxonomic groups that may eat aquatic organisms in order to evaluate
potential risk.
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The current version of KABAM estimates risks only to terrestrial birds and mammals consuming
aquatic prey. For this assessment, risks to the CRLF and the SFGS were assessed using KABAM
since birds can be used as a surrogate for both terrestrial-phase amphibians and reptiles. Risks to
the DS from the bioaccumulation pathway are not assessed with KABAM as this species does
not have a terrestrial life phase. Risks to the SJKF from the bioaccumulation pathway are not
assessed with KABAM as this species does not consume aquatic prey.
EECs for terrestrial plants inhabiting dry and wetland areas are derived using TerrPlant (version
1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in spray drift to
calculate EECs. EECs are based upon solubility, application rate and minimum incorporation
depth.
AgDRIFT is the spray drift model used to assess exposures of the assessed species and their prey
to trifluralin deposited on terrestrial habitats by spray drift. In addition to the buffered area from
the spray drift analysis, the downstream extent of trifluralin that exceeds the LOG for the effects
determination is also considered.
2.10.1.2 Measures of Effect
Data identified in Section 2.8 are used as measures of effect for direct and indirect effects to the
CRLF, DS, SFGS, and SJKF. 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 USEPA, 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 and the SFGS makes the
assumption that toxicity of trifluralin to birds is similar to or less than the toxicity to terrestrial-
phase amphibians and reptiles (this also applies to potential prey items). The same assumption is
made for fish and aquatic-phase CRLF (again, this also applies to potential prey items).
The acute measures of effect used for animals in this screening level assessment are the
LCso, ECso, and ICso. LD stands for "Lethal Dose", and LDso is the dose of material 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 (e.g., immobility) in 50% of the test organisms. ICso stands
for "Inhibition Concentration" and is the concentration estimated to cause a 50% reduction in a
response variable (e.g., plant height) relative to the control. 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-Level" 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-
61
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Effects-Concentration. For non-listed plants, only acute exposures are assessed (i.e., £€25 for
terrestrial plants and ECso for aquatic plants).
It is important to note that the measures of effect for direct and indirect effects to the assessed
species and their 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.
2.10.1.3 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 trifluralin,
and the likelihood of direct and indirect effects to CRLF, DS, SFGS, and SJKF in aquatic and
terrestrial habitats, as appropriate. 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
trifluralin 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) (USEPA, 2004) (see Appendix J).
For this endangered species assessment, listed species LOCs are used for comparing RQ values
for acute and chronic exposures of trifluralin directly to the CRLF, DS, SFGS, and SJKF. If
estimated exposures directly to the assessed species of trifluralin 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 assessed species due to effects to prey, the
listed species LOCs are also used. If estimated exposures to the prey of the assessed species of
trifluralin 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 a 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. If the RQ being considered for a
particular use exceeds the non-listed species LOG for plants, the effects determination is "may
affect".
2.10.1.4 Use of Probit Slope Response Relationship to Provide
Information on the Endangered Species Levels of Concern
The Agency uses the probit dose response relationship as a tool for providing additional
information on the potential for acute direct effects to individual listed species and aquatic
animals that may indirectly affect the listed species of concern (U.S. EPA, 2004). As part of the
risk characterization, an interpretation of acute RQs for listed species is discussed. This
interpretation is presented in terms of the chance of an individual event (i.e., mortality or
immobilization) should exposure at the EEC actually occur for a species with sensitivity to
62
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trifluralin on par with the acute toxicity endpoint selected for RQ calculation. To accomplish
this interpretation, the Agency uses the slope of the dose response relationship available from the
toxicity study used to establish the acute toxicity measures of effect for each taxonomic group
that is relevant to this assessment. The individual effects probability associated with the acute
RQ is based on the mean estimate of the slope and an assumption of a probit dose response
relationship. In addition to a single effects probability estimate based on the mean, upper and
lower estimates of the effects probability are also provided to account for variance in the slope, if
available.
Individual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.1
(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental
Fate and Effects Division (June 22, 2004). The model allows for such calculations by entering
the mean slope estimate (and the 95% confidence bounds of that estimate) as the slope parameter
for the spreadsheet. In addition, the acute RQ is entered as the desired threshold.
2.10.2 Data Gaps
Uncertainties, Limitations, and Assumptions
• There are no aerobic aquatic degradation data for trifluralin. A default aerobic aquatic
degradation half-life was calculated as twice the aerobic soil metabolism half-life for
PRZM/EXAMS modeling.
• There are no anaerobic aquatic degradation data for trifluralin. A default anaerobic
aquatic degradation half-life was calculated as 0.5 times the aerobic aquatic metabolism
rate for PRZM/EXAMS modeling.
• There are no estuarine/marine fish data for evaluation of acute toxicity of trifluralin. For
acute estuarine/marine fish, data from ethafluralin (a herbicide in the same chemical class
with the same mode of action as trifluralin) are used.
• There are no estuarine/marine invertebrate data for evaluation of chronic toxicity of
trifluralin. For chronic toxicity, the acute-to-chronic ratio (ACR) calculations are
conducted using daphnid toxicity data and applying to the acute grass shrimp data.
• There are no acute or chronic data for benthic invertebrates. This is of concern for
trifluralin as it sorbs strongly to sediment and pore water concentrations are expected to
be higher than in the water column.
3. Exposure Assessment
Trifluralin is formulated as an emulsifiable concentrate and as a granular. Application equipment
and methods include aircraft, groundspray, chemigation, soil broadcast, sprinkler irrigation,
directed spray, and granular applications. Risks from ground boom and aerial applications are
considered in this assessment because they tend to result in the highest off-target levels of
trifluralin due to generally higher spray drift levels. Ground boom and aerial modes of
63
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application tend to use lower volumes 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 Application Rates, Dates and Intervals
Trifluralin labels may be categorized into two types: labels for manufacturing uses (including
technical grade trifluralin and its formulated products) and end-use products. While technical
products, which contain trifluralin 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
pre- and post-emergent broadleaf and monocot weeds. The formulated product labels legally
limit trifluralin's use to only those sites that are specified on the labels. These products, their
use sites, and rates are discussed in Section 2.4.4.
Crop-specific management practices for all of the assessed uses of trifluralin were used for
modeling (Table 3.1). These parameters included application rates, number of applications per
year, application intervals, and the first application date for each crop.
Maximum application rates and numbers of application as specified by current labels for each
crop were modeled in PRZM/EXAMS. In instances when maximum annual application rates
and/or number of applications were not specified in the LUIS Report, EFED assumed
representative rates and application intervals based on management practices and use rates on
similar crops. For some crops (e.g., avocado and orchard), it was assumed that a maximum of 3
applications of 4 Ibs trifluralin at a minimum of 60 day intervals is applied. This application rate
is comparable to numerous annual maximum application rates for granular nursery and orchard
uses. For other crops (e.g., corn, cotton, and wheat), it was inferred that a single application per
crop cycle was intended as a specific time in the growing cycle of the crop. For more details on
application rates for assessed trifluralin uses, see Table 2.3.
The date of first application was developed based on several sources of information including
data provided by BEAD, a summary of individual applications from the CDPR PUR data, and
Integrated Management Pest Center Crop Profiles maintained by the USDA. If an application
pattern emerged and a typical application date from a crop scenario could be established, then
that date was employed. In general, peak trifluralin use occurred during the months February
through April. If no application date pattern emerged from the data, a March 1st application date
was selected to result in a conservative EEC that would result from increased rainfall
experienced in California during the winter months. More detail on the crop profiles and the
previous assessments may be found at: http://www.wrpmc.ucdavis.edu/Ca/CaCrops
/calendar.html and http://www.ipmcenters.org/cropprofiles/.
64
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Table 3.1 Crop Specific Application Input Data for PRZM/EXAMS for Trifluralin Uses
in California
Crop Scenario
(Application Date)
Crops/Uses
Method
Soil
Incorp-
oration
(Y/N)1
Max Application
Rate kg/ha
(Min Interval)
1st App.
Date
(month/day)
Orchard Uses
CA Almond
_WirrigSTD
CA Avocado RLFJV2
CA Citrus
WirrigSTD
03/01
CA Fruit
_WirrigSTD
CA Grapes
_WirrigSTD
(Grapes and Berries)
CA Grapes
WirrigSTD
CA OliveRLF_V2
Almond, filbert,
macadamia, pecan,
pistachio, tree nuts,
walnut (English/black)
Avocado
Fruits unspecified,
grapefruit, lemon,
orange, tangerine,
tangelo
Apple, apricot, cherry,
fig, nectarine, peach,
pear, plum,
pomegranate, prune
Blackberry, blueberry,
boysenberry, currant,
dewberry, elderberry,
gooseberry, grape,
kiwi fruit, loganberry,
mulberry, raspberry
(black, red)
Grape
Olive
Ground
Aerial
Ground
Ground
Ground
Arial
Ground
Ground
Aerial
Ground
Ground
Aerial
Ground
Ground
N
Y
N
N
Y
N
Y
N
Y
N
3 app @ 4.48 kg/ha
(60)
2 app @ 2.24 kg/ha
(NA)
3 app @ 4.48 kg/ha
(60)
3 app @ 4.48 kg/ha
(60)
1 app @ 2.24 kg/ha
(NA)
3 app @ 4.48 kg/ha
(60)
1 app @ 2.24 kg/ha
(NA)
3 app @ 4.48 kg/ha
(60)
1 app @ 2.24 kg/ha
(NA)
3 app @ 4.48 kg/ha
(60)
03/01
03/01
03/01
03/01
03/01
03/01
03/01
Agricultural Uses
CA Alfalfa
_WirrigOP
Alfalfa, clover
Aerial
Ground
(EC)
Aerial
Ground
(Granular)
N
Y
1 app @ 2.24 kg/ha
(NA)
2app @ 2.24 kg/ha
(NA)
15/03
65
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Table 3.1 Crop Specific Application Input Data for PRZM/EXAMS for Trifluralin Uses
in California
Crop Scenario
(Application Date)
CA Cole Crop
RLF_V2
CA CornOP
CACotton_WirrigSTD
CA LettuceSTD
CA Melons RLF_V2
CA Onion
CA Potato RLF V2
(09/05)
CA Rangeland Hay
RLF_V2
CA Row Crop
RLFJV2
CA Sugar Beet
_WirrigSTD
CA
Tomato_WirrigSTD
Crops/Uses
Broccoli, broccoli
rabbinni, Brussels
spouts, cabbage,
canola/rape,
cauliflower, collards,
crambe, kale, mustard,
Corn field, kenaf,
sunflower
Cotton
Chicory, endive
Cucumber, melon,
watermelon
Onion (dry bulb)
Radish
White/Irish potato,
turnip
Bermuda grass for
seed, uncultivated
agriculture, Un-
cultivatedareas/soils
Asparagus, bean
(castor)
Bean succulent,
bean (lima), bean
(mung),
bean succulent, bean
(snap), carrot, celery,
guar lentil,
peas(southern),
peas (succulent),
pepper, sugar cane
Sugar beet
Okra, tomato
Method
Aerial
Ground
Aerial
Ground
Aerial
Ground
Aerial
Ground
Ground
Aerial
Ground
Ground
Ground
Aerial
Ground
Aerial
Ground
Ground
Soil
Incorp-
oration
(Y/N)1
Y
Y
Y
Y
Y
Y
Y
N
Y
Y
Y
Max Application
Rate kg/ha
(Min Interval)
1 app @ 1.12 kg/ha
(NA)
1 app @ 1.12 kg/ha
(NA)
1 app @ 2.24 kg/ha
(NA)
1 app @ 1.12 kg/ha
(NA)
1 app @ 1.12 kg/ha
(NA)
1 app @ 0.9 kg/ha
(NA)
1 app @ 1.12 kg/ha
(NA)
1 app @ 2.24 kg/ha
(NA)
1 app @ 2.24 kg/ha
(NA)
1 app @ 0.8 kg/ha
(NA)
lapp@ 1.12kg/ha
(NA)
1st App.
Date
(month/day)
03/01
09/05
03/01
04/01
11/20
11/01
09/05
03/01
05/15
05/15
04/20
66
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Table 3.1 Crop Specific Application Input Data for PRZM/EXAMS for Trifluralin Uses
in California
Crop Scenario
(Application Date)
CA Wheat RLF_V2
Crops/Uses
Barley, flax, hops,
safflower, sorghum,
unspecified grains,
wheat
Method
Aerial
Ground
Soil
Incorp-
oration
(Y/N)1
Y
Max Application
Rate kg/ha
(Min Interval)
1 app @ 1.12 kg/ha
(NA)
1st App.
Date
(month/day)
12/15
Non-agricultural Uses
CA Nursery STD_V2
CA
ResidentialRLF.txt
CA Rights-of-way
RLFJV2
CA TurfRLF
CA Forestry RLF
Banana, greenhouse-
in use ornamental
shade trees,
ornamental ground
cover, ornamental
herbaceous plants,
ornamental lawns and
turf, ornamental non-
flowering plants,
ornamental woody
shrubs and vines
residential lawns
Ornamental and/or
shade trees,
ornamental ground
cover, ornamental
herbaceous plants,
ornamental lawns and
turf, ornamental non-
flowering plants,
ornamental woody
shrubs and vines
residential lawns
Pre-paving, private
roads/sidewalks, non-
agriculture rights-of-
way, fencerows,
hedgerows
Golf course turf,
recreational,
commercial/industrial
lawns
Christmas tree
plantations
Cottonwood
(forest/shelterbelt),
poplar
Ground
Ground
Ground
Ground
Ground
Aerial
Ground
N
N
N
N
N
Y
3 app @ 4.48 kg/ha
(60)
2 app @ 1.68 kg/ha
(56)
3 app @ 4.48 kg/ha
(60)
2 app @ 1.68 kg/ha
(56)
3 app @ 4.48 kg/ha
(60)
1 app @ 2.24 kg/ha
(NA)
03/01
03/01
03/01
03/01
03/01
1 Y - Soil incorporation required within 24 hours, N soil incorporation is greater than 24 hours or is not
required.
67
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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 trifluralin use. 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
shallower or have large drainage areas (or both). Shallow water bodies tend to have limited
additional storage capacity, and thus, tend to overflow and carry pesticide in the 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, which is all
treated with the pesticide. Headwater streams can also have peak concentrations higher than the
standard pond, but they 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 trifluralin were used for
modeling. These parameters included application rates, number of applications per year,
application intervals, and the first application date for each crop. The date of first application was
developed based on several sources including data provided by EPA/OPP/BEAD LUIS Report, a
summary of individual applications from the CDPR PUR data, and Crop Profiles maintained by
the USDA.
3.2.2 Post-processing of PRZM/EXAMS Outputs to Develop EECs for
Residential and Rights-of-ways
The LUIS Report lists trifluralin uses that are modeled using the rights-of-way and residential
RLF scenarios. Rights-of-way uses include fencerows, hedgerows, paved areas, and private
roads/sidewalks applications. Residential uses include ornamental and/or shade trees, ornamental
ground cover, ornamental herbaceous plants, ornamental lawns and turf, ornamental non-
flowering plants, ornamental woody shrubs and vines applications. Both these scenarios contain
areas with impervious (i.e., cement, asphalt, metal surfaces) and pervious surfaces. It is assumed
that trifluralin will be applied to the pervious surfaces where weeds are expected to grow. It is
also assumed that trifluralin is not applied to impervious surfaces in rights-of way, but that there
is a 1% incidental spray onto impervious surfaces surrounding rights-of-way.
In a standard PRZM scenario, it is assumed that an entire 10-hectare field is composed only of
the identified crop and that the field has uniform surface properties throughout the field. In the
rights-of-way and residential scenarios, this is not a reasonable assumption because rights-of-
way and residential areas generally contain both impervious and pervious surfaces. Since the two
surfaces have different properties (especially different curve numbers influencing the runoff
68
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from the surfaces) and different amounts of trifluralin applied, the standard approach for deriving
aquatic EECs is revised using the following approach:
1) Aquatic EECs are derived for the pervious portion of the rights-of-way, using the
maximum use rate of trifluralin on the CA rights-of-way and CA residential scenarios. At
this point, it is assumed that 100% of both the rights-of-way and residential scenarios are
composed of pervious surface. Specific inputs for this modeling are defined below.
2) Aquatic EECs are derived for the impervious portion of the rights-of-way using 1% for
liquid formulation of the maximum use rate of trifluralin on the CA impervious and CA
Residential scenarios. At this point, it is assumed that 100% of the rights-of-way and
residential scenarios are composed of impervious surface.
3) The daily aquatic EECs (contained in the PRZM/EXAMS output file with the suffix
"TS") are input into a Microsoft® Excel® worksheet.
4) Daily aquatic EECs for the impervious surface are multiplied by 50%. Daily aquatic
EECs for the pervious surface are multiplied by 50%. The resulting EECs for impervious
and pervious surfaces are added together to get an adjusted EEC for each day of the 30-
year simulation period (Equation 3.1).
Equation 3.1
Revised EEC = (impervious EEC * 50%) + (pervious EEC * 50%)
5) Rolling averages for the relevant durations of exposure (21-day and 60-day averages) are
calculated. The l-in-10 year peak, 21-day, and 60-day values are used to define the acute
and chronic EECs for the aquatic habitat.
In this modeling approach, it is assumed that both the rights-of-way and residential scenarios are
composed of equal parts pervious and impervious surfaces (i.e., in step 4, the EECs of both
surfaces are multiplied by 50%). However, in reality, it is likely that rights-of-way and
residential areas contain different ratios of the two surfaces. In general, incorporation of
impervious surfaces into the exposure assessment results in increasing runoff volume in the
watershed, which tends to reduce overall pesticide exposure (when assuming 1% overspray to
the impervious surface).
3.2.3 Model Inputs
PRZM scenarios used to model aquatic exposures resulting from applications of specific uses are
identified in Table 3.1. In cases where a scenario does not exist for a specific use, it is necessary
to assign a surrogate scenario. The surrogates are assigned based on the same or similar families
or similar cultural practices and to be most representative of the use being considered.
In cases where the LUIS Report presents numerous possible variations of application rates,
application methods, and formulations for a modeled crop scenario, EFED modeled the rates,
methods and formulations that would likely result in the highest EECs in PRZM/EXAMS. Aerial
emulsifiable applications generally produce higher EECs than aerial granular applications;
therefore, aerial emulsifiable concentration applications producing higher EECs were modeled.
69
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The appropriate chemical-specific PRZM and EXAMS input parameters are selected from
reviewed environmental fate data submitted by the registrant in Table 3.2. These input
parameters are in accordance with EFED water model PRZM/EXAMS input parameter guidance
(U.S. EPA 2002). The input parameters employed are similar to those used in the 1996
trifluralin RED (U.S. EPA, 1996).
In PRZM, the method of pesticide application is defined by Chemical Application Method
(CAM). CAM 1 was used to represent surface applied broadcast when soil incorporation was not
required within 24 hours by the label. When the label required incorporation within 24 hours,
CAM 4 was employed to represent uniform soil incorporation to the default depth of 5 cm.
Trifluralin is a volatile compound; therefore, PRZM/EXAMs manual default input parameters
DAIR (vapor phase diffusion coefficient) of 4300 cm2/day and enthalpy of vaporization
coefficient of 20 kcal/mol were inputted into PRZM/EXAMs to account for volatilization from
soil.
Table 3.2 Summary of PRZM/EXAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Trifluralin Endangered Species Assessment
Model Parameter
Maximum Single
Application Rate
Hydrolysis
Aqueous Photolysis
Molecular Weight
Solubility in Water
Vapor Pressure
Henry's Law Constant
Aerobic Soil Metabolism
Anaerobic Aquatic
Metabolism
Aerobic Aquatic
Metabolism
Koc
Application Method (CAM)
Value
Dependant on Scenario
StableatpH5,pH7,pH9
Tin = 0.371 days
335.28 g/mol
0.3 mg/L
1.10E-4Torr
1 .62E-4 atm m /mole
Tin =219 days
T1/2=29.5days
Tin = 438 days
8,757.9
CAM 1 used when not
incorporated;
CAM 4 employed when
incorporated
Comment
See Table 2.3 for values for each
scenario
Stable at pH 5, pH 7,
pH 9 at 25 °C
90% upper confidence bound on
the mean metabolism half-lives,
189,201, 116 days1
Anaerobic aquatic metabolism
59 days (0.5 x anaerobic soil
metabolism rate)'*
Aerobic aquatic metabolism
438 days (2x aerobic soil
metabolism)
Mean of 4 Koc values
(6,413.3, 6,748.2, 8,457.2, and
13,413 L/kg)1
Soil incorporation depth 5cm
when incorporated
Data Source
Product labels
MRID 00131135
MRID 40560101
Product Chemistry
Product Chemistry
Product Chemistry
RED
MRID 4 1240501
N/A
EFED Guidance (Feb
28, 2002)
MRID 40673501
Product labels
70
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Table 3.2 Summary of PRZM/EXAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Trifluralin Endangered Species Assessment
Model Parameter
Application Efficiency
Spray Drift Fraction
DIAR (vapor diffusion
phase coefficient)
Enthalpy
Value
0.99 ground spray
0.95 aerial spray
1.00 granular
0.01 ground spray
0.05 aerial spray
0.0 granular
4300 cm2/day
20 kcal/mol
Comment
Spray Drift Task Force
(SDTF) application efficiency
data
SDTF application efficiency
data
Data Source
SDTF
SDTF
PRZM/EXAMs
manual
PRZM/EXAMs
manual
3.2.4 Results
The aquatic EECs for the various scenarios and application practices are listed in Table 3.3. The
peak EECs range from 0.0002 |ig/L (residential) to 6.53 |ig/L (EC nursery), with a median of
1.18 |ig/L. The 21-day EECs range from 0.0001 |ig/L (residential) to 1.83 |ig/L (nursery), with a
median of 0.32 |ig/L. The predicted 60-day average EECs range from 0.00005 |ig/L (residential)
to 0.87 |ig/L (nursery), with a median of 0.18 |ig/L for all scenarios modeled.
In general, the EECs show a pattern of exposure for all durations that is influenced by the
persistence of the compound and the lack of flow through the static water body. However,
trifluralin concentrations do not increase across the 30-year time series probably due to its
susceptibility to direct aqueous photolysis (half-life = 8.9 hours) and to volatilization (Henry's
Law constant = 1.6 x 10-4atm.m3/mol) which should limit its persistence in the water column of
well mixed, surface water. An example PRZM/EXAMS output file is located in Appendix D.
Table 3.3 Aquatic EECs (ug/L) for Trifluralin Uses in California
Crop Scenario/
Formulation
Application
Method
Soil
Incorporation
Peak EEC
Hg/L
21 day
EEC fig/L
60 day EEC
Hg/L
Orchard Uses
CA Almond (tree nuts)
Granular
EC1
Ground
Aerial
Ground
N
Y
Y
2.23
5.65
1.23
0.78
1.31
0.32
0.72
0.60
0.18
CA Avocado
Granular
Ground
N
5.81
1.45
0.73
CA Citrus
Granular
EC1
Ground
Aerial
Ground
N
Y
Y
0.74
5.48
1.10
0.20
1.28
0.26
0.14
0.54
0.11
CA Fruit
Granular
EC1
Ground
Aerial
N
Y
2.52
5.51
0.75
1.30
0.40
0.55
71
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Table 3.3 Aquatic EECs (ug/L) for Trifluralin Uses in California
Crop Scenario/
Formulation
Application
Method
Ground
Soil
Incorporation
Y
Peak EEC
Hg/L
1.12
21 day
EEC fig/L
0.30
60 day EEC
Hg/L
0.13
CA Grape (grapes and berries)
Granular
Ground
N
4.00
1.18
0.62
CA Grape
EC1
Aerial
Ground
Y
Y
5.50
1.18
1.29
0.28
0.54
0.12
CA Olive
Granular
Ground
N
4.45
1.35
0.77
Agricultural Uses - Non-Orchard
CA Alfalfa
EC
Granular
Aerial
Ground
Aerial
Ground
N
N
Y
Y
5.14
1.12
0.32
0.32
1.32
0.32
0.09
0.09
0.58
0.17
0.07
0.07
CA Cole
EC
Aerial
Ground
Y
Y
2.79
0.59
0.65
0.19
0.29
0.10
CACorn
EC
Aerial
Ground
Y
Y
2.74
0.55
0.62
0.13
0.26
0.07
CA Cotton
EC
Aerial
Ground
Y
Y
5.55
1.48
1.46
0.47
0.65
0.24
CA Melon
EC
Ground
Y
0.73
0.27
0.13
CA Lettuce
EC
Aerial
Ground
Y
Y
2.77
0.58
0.64
0.17
0.27
0.08
CA Onion
EC
Aerial
Ground
Y
Y
1.96
0.39
0.48
0.10
0.21
0.05
CA Potato
EC
Ground
Y
0.55
0.12
0.05
CA Rangeland
Granular
Ground
N
0.68
0.23
0.12
CA Tomato
EC
Ground
Y
0.56
0.13
0.06
CA Row Crop
EC
Aerial
Ground
Y
Y
5.49
1.01
1.09
0.22
0.45
0.09
CA Sugar Beet
EC
Aerial
Ground
Y
Y
1.96
0.39
0.42
0.08
0.17
0.03
CA Wheat
EC
Aerial
Ground
Y
Y
2.77
0.57
0.78
0.18
0.29
0.11
Non-agricultural Uses
CA Nursery
Granular
Ground
N 6.55
1.80
0.86
72
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Table 3.3 Aquatic EECs (ug/L) for Trifluralin Uses in California
Crop Scenario/
Formulation
EC
Application
Method
Ground
Soil
Incorporation
Peak EEC
Hg/L
N 6.53
21 day
EEC fig/L
1.83
60 day EEC
Hg/L
0.87
CA Residential2
Granular
Ground
N
0.0002
0.0001
0.00005
CA Right-of-way3
Granular
Ground
N
0.002
0.0007
0.0005
CATurf
Granular
Ground
N
0.16
0.05
0.02
CA Forestry
Granular
EC
Ground
Aerial
Ground
N
Y
Y
2.25
5.50
1.17
0.77
1.39
0.35
0.39
0.63
0.19
1 Due to the lack of spray drift aerial granular EECs are generally lower than aerial emulsifiable
concentration EECs; therefore, the higher, and more conservative aerial emulsifiable concentration
applications were modeled for this scenario.
2 Modeled with 1% overspray using Impervious Scenario, post-processed with Residential scenario with
50/50 ratio. See Section 3.2.1 for explanation of initial application date selection.
3 Modeled with 1% overspray using Impervious Scenario, post-processed with Right-of-Way scenario with
50/50 ratio.
3.2.5 Existing Monitoring Data
A critical step in the process of characterizing predicted EECs is comparing the modeled
estimates with available surface water monitoring data. An evaluation of the surface water
monitoring data was conducted to assess the occurrence of trifluralin in California surface and
ground waters. Most of this data, however, is non-targeted (i.e., study was not specifically
designed to capture trifluralin concentrations in high-use areas). Typically, sampling frequencies
employed in these monitoring studies are insufficient to document peak exposure values. This,
coupled with the fact that these data are not temporally or spatially correlated with pesticide
applications, limits the utility of these data for estimating exposure concentrations for risk
assessment purposes. These monitoring data are characterized in terms of general statistics
including number of samples, frequency of detection, maximum concentration, and mean value
of all detections, where that level of detail is available.
3.2.5.1
Federal and Cal EPA Monitoring Data
Data from the CDPR surface water monitoring database website for trifluralin occurrence were
obtained on Jul 15, 2009 (http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm). A total of
3,915 surface water samples were analyzed for trifluralin spanning a period from 1991 to 2006.
Of these, a total of 600 samples detected trifluralin (detection frequency of 15%). The two
highest concentrations detected were 1.74 and 1.5 |ig/L from Butte County on 01/16/01. The
maximum concentration of trifluralin reported by the CDPR surface water database (1.74 |ig/L)
is roughly 3.75 times lower than the highest peak model-estimated environmental concentration.
73
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No trifluralin data were available from the EPA STORET database for the state of California
(http://www.epa.gov/storet/). USGS's National Water-Quality Assessment Program has not
collected groundwater or surface samples for trifluralin in California
(http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME:3249496365037407).
3.2.5.2 Open Literature Monitoring Data
Water samples collected from DS habitat in Suisun Bay during the spring and summer of 2000
detected trifluralin in 32 of 54 samples where 44 ng/L was the highest measured concentration
(Kuivila, 2002).
A study was conducted during the first flush of suspended sediments into Suisun Bay at Mallard
Island in December 1995 (Bergamaschi and others 2001). Trifluralin was detected on 4 days of
the 16 day study with values ranging from 0.2 tol.3 ng/g per dry weight of sediment.
The transport of suspended sediments may be an important mechanism for the movement of
trifluralin into estuaries. Based on sampling of suspended sediments during February 1992 in the
San Joaquin River (at Vernalis, California), trifluralin concentrations in ranged from 4.6 to 31.3
ng/L in dry weight of sediment. (Bergamaschi et al. 1997).
In a study of pesticide inputs to Yolo Bypass in 2004 and 2005 trifluralin was detected in surface
water at 17 of 44 sites with values ranging from 4.1 to 66.4 ng/L (Smalling and others 2005). In
the same study, trifluralin was detected in sediment at 4 of 6 sites with a high concentration of 24
3.3 Long Range Transport Exposure Assessment
3.3.1 Background
Exposure to trifluralin through long range atmospheric transport may also occur. 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, and McConnell et al., 1998). Trifluralin can be present in air or
precipitation due to spray drift, volatilization and/or wind erosion of soil containing residues
(Unsworth et al, 1999). Precipitation and dry parti culate matter can contribute to trifluralin
deposits in aquatic systems (LeNoir et al, 1999). Therefore, deposition of trifluralin could
potentially be transported to the habitats of CRLF, DS, SFGS, and SJKF.
No approved model currently exists for estimating atmospheric transport of pesticides and the
resulting exposures to organisms in areas receiving pesticide deposition. Therefore, potential
mechanisms of atmospheric transport for trifluralin such as volatilization, wind erosion of soil
and spray drift can only be discussed qualitatively. Given the presence of trifluralin in air and
precipitation in California monitoring data, exposure to CRLF, DS, SFGS, and SJKF habitats
through atmospheric transport of trifluralin cannot be precluded. Although it is not possible to
quantify trifluralin exposure via long-range transport, the amount of trifluralin deposition into
74
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CRLF, DS, SFGS, and SJKF habitats based on measured trifluralin concentrations in rain
samples are considered in combination with California precipitation data.
3.3.2 Qualitative Discussion of Potential Transport Mechanisms for Long-
Range Transport of Trifluralin
A number of long-range mechanisms transport trifluralin from an initial application site to the
atmosphere via wet or dry deposition of trifluralin to distant locales. The mechanisms are: 1)
volatilization from soil and plant surfaces in treated areas, 2) wind erosion of soil containing
sorbed trifluralin, and 3) spray drift of trifluralin during application.
Factors influencing volatilization of trifluralin from a treated area are: vapor pressure, adsorption
to soil, incorporation depth, and Henry's law constant. The vapor pressure (1.1 x 10"4 torr) and
reported Henry's law constant of 1.6 x 10"4 atm-m3/mol indicate that trifluralin will volatilize
from soil and water.
Soil incorporation of trifluralin affects post-application volatilization. A laboratory experiment
that placed trifluralin 1.27 cm below the surface reduced vapor loss by a factor of about 25 times
(Bardsley et al, 1968). Another laboratory study that incorporated trifluralin into the top 10 cm
of soil recorded vapor loss rate at 51.7 g/ha/d in the first 24 hours, while surface applied losses
occurred at 4,000 g/ha/d (Spencer and Cliath, 1974). A field study indicated that trifluralin
incorporated at a depth of 5 cm volatilized at a maximum rate of 3 g/ha/d during the first 4 to 6
hours after application (Grover and others, 1988). The volatilization rate of trifluralin applied to
the surface of agricultural sites was 70 g/ha/d (Majewski et al, 1993)
3.3.3 Long-Range Air and Precipitation Monitoring Data
Trifluralin has been extensively used in wheat production since the 1960s and has been detected
in air, rain and snow in California (Majewski and Capel, 1995). Available air and precipitation
California monitoring data for trifluralin are reported in Table 3.4.
Table 3.4 Detections of Trifluralin in Air, Precipitation, and Snow Samples Taken in
California
Location
CA
Sequoia National Park, CA
Sacramento, CA
(Franklin Field Airport)
Sacramento, CA (Sacramento
Metropolitan Area)
Sacramento, CA (Sacramento
International Airport)
Sequoia National Park, CA
(Ash Mountain)
San Joaquin River Basin, CA
Year
1970s-
1990s
1996
1996-
1997
1996-
1997
1996-
1997
1995-
1996
2001
Sample
type
Air
Air
Air
Air
Air
Rain
Rain
Maximum
Cone.1
0.063
0.00064
0.014
0.010
0.019
0.0012
0.039
Detection
frequency
NA
100%
71.4%
67.6%
81.5%
NA
78%
Source
Reported in Majewski and
Capel, 1995
LeNoire/a/. 1999
Majewski and Baston 2002
Majewski and Baston 2002
Majewski and Baston 2002
McConnell et al. 1998
Zamora et al. 2003
75
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Table 3.4 Detections of Trifluralin in Air, Precipitation, and Snow Samples Taken in
California
Location
CA
Sequoia National Park, CA
(Lower Kaweah)
Year
1970s-
1990s
1995-
1996
Sample
type
Rain
Snow
Maximum
Cone.1
0.97
0.041
Detection
frequency
NA
NA
Source
Reported in Majewski and
Capel, 1995
McConnell et al. 1998
1 For Air, ug/m3; for rain, snow and ug/L
Detected concentrations of trifluralin in air, snow and rain vary depending on proximity to use
areas and timing of applications. In air, trifluralin has been detected at concentrations up to 0.063
|ig/m3. Measured concentrations of trifluralin in rain in California have been measured up to 0.97
The extent to which trifluralin will be deposited from the air to the habitat of the CRLF, DS,
SFGS, and SJKF is unknown. In an attempt to estimate the amount of trifluralin deposited into
aquatic and terrestrial habitats, trifluralin concentrations measured in rain samples taken in
California are considered below in combination with California specific precipitation data and
runoff estimates from PRZM.
Air monitoring data from the September, 2007 Environmental Justice Pilot Study conducted by
the California EPA in Parlier, a small agricultural community located in California's San Joaquin
Valley was evaluated. Trifluralin was detected in 24% (1 12 samples) of 468 air monitoring
samples collected within 5 miles of Parlier (http://www.cdpr.ca.gov/docs/envjust/pilot_proj/
interim/narrative, pdf) .
Trifluralin has been measured in arctic air, seawater, and freshwater sediments (Canadian Arctic
Contaminants Program, 2006). Trifluralin was observed in air at three Arctic monitoring stations,
Tagish, Alert and Dunai at concentrations up to 2.92; 0.64 and 0.13 pg/m3, respectively.
Trifluralin is an herbicide whose occurrence and concentrations in air have been found to
correlate with local use. The highest concentration of trifluralin occurred in May and June at
several locations throughout Saskatchewan, Canada (Grover etal., 1981). Air concentrations
increased slightly during late October and November, which corresponds with a second
application season. Grover et al. observed during that air concentrations of trifluralin decreased
during dry periods and increased after rain events. Presumably this was due to the absorption of
trifluralin from the remoistened soil, which resulted in an increase in volatilization.
3.3.4 Deposition Data
In a 3.5 year study (from 2001-2004) in the central San Joaquin Valley, wet deposition of
pesticides, including trifluralin, were monitored at 6 sites, including some with agricultural and
urban landcovers. Trifluralin was detected in 78% of rain samples (n=137), with mean and
maximum concentrations of 0.010 and 0.039 |ig/L, respectively (Majewski et al. 2006).
76
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3.3.5 Monitoring Data from Lakes Assumed to Only Receive Atmospheric
Deposition of Trifluralin
Studies are available involving monitoring of trifluralin concentrations in California lakes which
are removed from agricultural areas and are presumed to receive inputs of trifluralin from
atmospheric deposition only. Two 1997 studies (Fellers etal. 2004; LeNoir etal. 1999)
measured trifluralin concentrations in lake water in Kings Canyon and Sequoia National Parks
(located in the Sierra Nevada Mountains in California). Fellers et al. (2004) reported a
concentration of 0.0025 |ig/L, and LeNoir et al. (1999) reported a maximum concentration of
0.11 |ig/L in lake water. The authors attributed these detections to atmospheric deposition from
dry deposition and/or gas exchange from air samples of trifluralin originating from agricultural
sites located in California's Central Valley, which is up wind of the lakes.
3.3.6 Modeling of Contributions of Wet Deposition to Aquatic and Terrestrial
Habitats
In an attempt to estimate the amount of trifluralin deposited into aquatic and terrestrial habitats,
trifluralin concentrations measured in rain samples taken in California were considered in
combination with California specific precipitation data and runoff estimates from PRZM.
Precipitation and runoff data associated with the PRZM scenarios used to model aquatic EECs
were used to determine relevant l-in-10 year peak runoff and rain events. The scenarios included
were: CA almond, CA lettuce, CA wine grape, CA row crop, CA fruit, CA nursery, and CA
onion. The corresponding meteorological data were from the following locations: Sacramento,
Santa Maria, San Francisco, Monterey County, Fresno, San Diego, and Bakersfield, respectively.
To estimate concentrations of trifluralin in the aquatic habitat resulting from wet deposition, the
daily PRZM-simulated volume of runoff from a 10 ha field is combined with an estimate of daily
precipitation volumes over the 1 ha farm pond relevant to the EXAMS environment. This
volume is multiplied by the maximum concentration of trifluralin in precipitation reported in
monitoring data, which is 0.97 |ig/L. The result is a daily mass load of trifluralin into the farm
pond. This mass is then divided by the volume of water in the farm pond (2.0 x!07L) to achieve
a daily estimate of trifluralin concentration in the farm pond, which represents the aquatic habitat
(Table 3.5). From the daily values, the l-in-10 year peak estimate of the concentration of
trifluralin in the aquatic habitat is determined for each PRZM scenario (Table 3.6).
Concentrations estimated using this approach are 1-2 orders of magnitude greater than those
reported by Fellers et al. (2004) and LeNoir et al. (1999) in mountain lakes assumed to be
receiving trifluralin loading only from atmospheric deposition. This difference in concentrations
is reasonable since the mountain lakes where trifluralin was detected were spatially removed
from trifluralin use areas; while the location where the maximum detected concentration of
trifluralin was observed in precipitation was in close proximity to agricultural uses of trifluralin.
There are several assumptions associated with this approach, including: 1) the concentration of
trifluralin in the rain event is spatially and temporally homogeneous (e.g. constant over the 10 ha
field and 1 ha pond for the entire rain event); 2) the entire mass of trifluralin contained in the
precipitation runs off the pond or is deposited directly into the pond; 3) there is no degradation of
trifluralin between the time it leaves the air and the time it reaches the pond.
77
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Table 3.5 Input Parameters Relevant to Estimation of Trifluralin Load
through Wet Deposition
Parameter
Description
AreaofPRZM
field (ha)
Area of EXAMS
pond (ha)
Volume of
EXAMS farm
pond (L)
Concentration of
pesticide in
precipitation
(ug/L)
Value
10
1
20,000,000
0.97
Comment
-
-
Dimensions: 1 ha area x 2 m deep
Reported in Majewski and Capel, 1995
Table 3.6 l-in-10 Year Peak Estimates of Trifluralin Concentrations in
Aquatic and Terrestrial Habitats Resulting from Wet Deposition.
Met Station
Sacramento
Santa Maria
San Francisco
Monterey Co.
Fresno
San Diego
Bakersfield
Scenario(s)
CA almond
CA lettuce, CA cole crops, CA strawberry
CA wine grape
CA row crop
CA fruit, CA tomato, CA melon
CA nursery
CA onion, CA potato
Concentration in
aquatic habitat
(Mg/L)1
0.181
0.195
0.170
0.156
0.071
0.131
0.052
3.4 Aquatic Bioaccumulation Assessment
3.4.1 Empirical BCF Data
Trifluralin residues accumulated in a bluegill sunfish (Lepomis macrochirus) exposed to 0.0059
mg/L of trifluralin with maximum mean bioconcentration factor of 5,674x for whole fish tissues.
The maximum mean concentration of total [14C] residues that occurred at 28 days for the whole
fish sample was 67.0 mg/L. Depuration occurred with 86.34-88.01% of the [14C] eliminated from
the fish tissues after 14 days of exposure to pesticide free water. The time to reach 90% of steady
state for whole fish was 15.8 days (MRID 40673801). The accumulation and depuration of
trifluralin in fish cannot be fully assessed because radioactive residues in fish tissues were
incompletely characterized.
78
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3.4.2 Fish Tissue Monitoring Data
The National Lake Fish Tissue Study (NLFTS) was the first survey offish contamination in
lakes and reservoirs in the 48 conterminous states based on a probability survey design
(http://www.epa.gov/waterscience/fish/study/, Stahl etal. 2009, and Olsen et al. 2009). This
study included the largest set (268) of persistent, bioaccumulative, and toxic (PBT) chemicals
ever studied in predator and bottom-dwelling fish species; trifluralin was one of the chemicals
evaluated. The USEPA implemented the study in cooperation with states, tribal nations, and
other federal agencies, with field collection occurring at 500 lakes and reservoirs over a four-
year period (2000-2003). The sampled lakes and reservoirs were selected using a spatially
balanced unequal probability survey design from 270,761 lake objects in US EPA's River Reach
File Version 3 (RF3).
There were a total of 33 composite fish samples in California that were evaluated for trifluralin.
Of the 12 samples of bottom-dwelling fish (homogenized whole), six (50%) had detected levels
of trifluralin (3.01, 16.4, 19.6, 22.3, 41.9, and 42.1 ug/kg-wet weight). Of the 21 samples of
predator fish (filleted prior to homogenization), two (10%) had detected levels of trifluralin (3.21
and 3.33 ug/kg-wet weight). The Method Detection Limit (MDL) was 2.98 ug/kg-wet weight,
and the Minimum Level of quantification (ML) was 10 ug/kg-wet weight.
Nationally, there were 1003 composite fish samples evaluated for trifluralin. Of the 448 samples
of bottom-dwelling fish (homogenized whole), 157 (35%) had detected levels of trifluralin
(minimum=3.01, maximum=96.3, and median=9.5 ug/kg-wet weight). Of the 555 samples of
predator fish (filleted prior to homogenization), 41 (7%) had detected levels of trifluralin
(minimum=3.01, maximum=11.3, and median=4.27 ug/kg-wet weight).
3.4.3 Bioaccumulation Modeling
The KABAM model (Kow (based) Aquatic BioAccumulation Model) version 1.0 is used to
evaluate the potential exposure and risk of direct effects to the CRLF and SFGS via
bioaccumulation and biomagnification in aquatic food webs. KABAM is used to estimate
potential bioaccumulation of hydrophobic organic pesticides in freshwater aquatic ecosystems
and risks to mammals and birds consuming aquatic organisms which have bioaccumulated these
pesticides.
The bioaccumulation portion of KABAM is based upon work by Arnot and Gobas (2004) who
parameterized a bioaccumulation model based on PCBs and some pesticides (e.g., lindane, DDT)
in freshwater aquatic ecosystems. KABAM relies on a chemical's octanol-water partition
coefficient (Kow) and Koc to estimate uptake and elimination constants through respiration and
diet of organisms in different trophic levels. Pesticide tissue residues are calculated for different
levels of an aquatic food web. The model then uses pesticide tissue concentrations in aquatic
animals to estimate dose- and dietary-based exposures and associated risks to mammals and
birds consuming aquatic organisms.
79
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The KABAM model operated primarily in the default mode (see user's guide for full
description). The CA Nursery scenario was selected because it had the highest 60 day EEC (0.87
|ig/L) of the modeled scenarios.
For the CRLF and SFGS analysis, the ecosystem components for avian consumers were
modeled, as birds are considered surrogates for aquatic-phase amphibians. However, the default
avian species used in KABAM were altered to more accurately represent the size range and
dietary preferences of the CRLF and SFGS. Specifically, three size classes were modeled for the
CRLF (1.4g, 37g, and 238g) and SFGS (2g, 113g, and 227g) each with a different dietary
composition that would be representative of its body size and likely feeding pattern (see Table
5.2). For the two larger size classes of the CRLF and ther SFGS, two different dietary
preferences were selected to bound the range of trophic levels at which the CRLF and SFGS
could potentially feed.
Physical-chemical parameters and PRZM/EXAMS output parameters required for input into
KABAM are listed in Table 3.7. The resulting concentrations of trifluralin in tissues of aquatic
organisms are provided in Table 3.8. The input and output data tables from KABAM are
provided in Appendix N.
Table 3.7 Summary of KABAM Environmental Fate and PRZM/EXAMS Data for Aquatic
Bioaccumulation Modeling
Model Parameter
Log Kow
Koc
Water Column EEC (60-day)
Pore Water Concentration (60-day)
Dissolved Oxygen Concentration
Water Temp
Value
5.27
8,757.9 L/kg1
0.87 ug/L
0.36 ug/L
5.0mgO2/L
15.0°C
Data Source
Product Chemistry
PRZM/EXAM Guidelines
CA Nursery PRZM/EXAMS Output File
CA Nursery PRZM/EXAMS Output File
CA Nursery PRZM/EXAMS Output File
CA Nursery PRZM/EXAMS Output File
1 Mean of four Koc values (6,413.3, 6,748.2, 8,457.2, and 13,413 L/kg)used in PRZM/EXAMS (see Table 3.2).
Table 3.8 Concentrations of Trifluralin in Tissues of Aquatic Organisms
(Estimated Using KABAM Model)
Trophic level
Phytoplankton
Zooplankton
Benthic Invertebrates
Filter Feeders
Small Fish
Medium Fish
Large Fish
Total concentration (jig/kg-ww)
7,201
5,825
6,612
4,299
10,938
14,787
26,226
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3.5 Accumulation of Trifluralin Residue on Soil
Because trifluralin is persistent (90% upper confidence bound is 219 days in aerobic soil) and
does not have a tendency to leach from soil, a screening analysis was conducted to characterize
levels in the soil of a treated site after 30 years of applications. The CA nursery scenario was
selected for the screening analysis, as it was expected to result in highest soil concentrations of
trifluralin. The l-in-10-year peak concentration in the soil for total trifluralin was 30.1 g/m3 for
the nursery scenario. The annual average trifluralin soil concentration in soil is 6.41 g/m3
(Figure 3.1)
Peak Trifluralin Concentrations in Soil Over Time
35000
30000
25000
o
20000
o
OT
15000
10000
5000
2000
4000
6000
Days
8000
10000
12000
Figure 3.1 Concentration of trifluralin in soil that has been treated with trifluralin for 30
years.
3.6 Terrestrial Animal Exposure Assessment
T-REX (Version 1.4.1) is used to calculate dietary and dose-based EECs of trifluralin for birds,
mammals, and terrestrial invertebrates. T-REX simulates a 1-year time period. For this
assessment, spray and granular applications of trifluralin are considered, as discussed in below.
Given that no data on interception and subsequent dissipation from foliar surfaces is available for
trifluralin, a default foliar dissipation half-life of 35 days is used based on the work of Willis and
McDowell (1987). An example output from T-REX is available in Appendix K.
81
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Spray applications (not soil-incorporated)
Upper-bound Kenega nomogram values reported by T-REX are used for derivation of dietary-
and dose-based EECs for the terrestrial-phase CRLF, SFGS and SJKF and their potential prey
(Table 3.9). Potential direct acute and chronic effects of trifluralin to the terrestrial-phase CRLF
and SFGS are derived by considering dietary-based exposures for a bird consuming small
invertebrates. Potential direct acute and chronic effects for the SJKF are derived by considering
dose- and dietary-based EECs modeled in T-REX for a large mammal (1,000 g) consuming a
variety of dietary items (Table 3.9).
T-REX is also used to calculate EECs for terrestrial insects exposed to trifluralin. Dietary-based
EECs calculated by T-REX for small and large insects (|ig/g-bee) are used to bound an estimate
of exposure to bees. Available acute contact toxicity data for bees exposed to trifluralin (in units
of jig/bee), are converted to |ig/g-bee by multiplying by 1 bee/0.128 g. The EECs 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 Table 3.10.
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Table 3.9 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based Exposures of
Birds and Mammals to Trifluralin (liquid applications, not soil incorporated)
Use
Category
Alfalfa
Nursery
Application
Rate
(Interval days)
1 app@
2 Ibs/acre
3 app @ 4
Ibs/acre
(60 days)
Dietary Category
Short Grass
Tall Grass
Broadleaf Plants/
Small Insects
Fruits/Pods/ Seeds/
Large Insects
Granivore*
Short Grass
Tall Grass
Broadleaf Plants/
Small Insects
Fruits/Pods/ Seeds/
Large Insects
Granivore*
Direct Effects for SJKF
(1000 g mammal only)
Indirect Effects for SJKF
(mammalian prey, all
weight classes)
Indirect Effects for CRLF
and SFGS (mammalian
prey, 15g only)
Mammalian
Dosed based EECs
(mg/kg-bwt)
15 g
457.64
209.75
257.42
28.60
6.36
1279.2
586.31
719.57
79.95
17.77
35 g
316.29
144.97
177.91
19.77
4.39
884.12
405.22
497.32
55.26
12.28
1000 g
73.33
33.61
41.25
4.58
1.02
204.99
93.95
115.30
12.81
2.85
Direct Effects for CRLF
and SFGS
(Avian dietary small insects
EECs)
Direct Effects for SJKF
(mammal dietary EECs)
Indirect Effects for CRLF,
SFGS and SJKF
(mammalian and avian
dietary EECs)
Mammalian
Dietary
based EECs
(mg/kg-diet)
480.00
220.00
270.00
30.00
N/A
1341.72
614.96
754.72
83.86
N/A
Avian
Dietary
based EECs
(mg/kg-diet)
480.00
220.00
270.00
30.00
N/A
1341.72
614.96
754.72
83.86
N/A
* EECs for granivores are only relevant for indirect effects.
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Table 3.10 Upper-bound Kenega Nomogram EECs for Exposures to Terrestrial
Invertebrates from Trifluralin (liquid applications, not soil-incorporated) EECs (indirect
effects to terrestrial-phase CRLF, SFGS, and the SJKF)
Use Category
Alfalfa
Nursery
Application Rate
(Interval days) incorporated
1 app @ 2 Ibs/acre
3 app @ 4 Ibs/acre
(60 days)
Small Insect
(mg/kg-insect)
270
755
Large Insect
(mg/kg-insect)
30
84
Granular applications (not soil incorporated)
For granular formulations, an LD50/sq-ft analysis was performed to evaluate potential acute risks
to birds and mammals. The exposure used in this analysis is the mass of trifluralin applied to a
square foot area (mg/sq-ft). Based on application rates of 1.5, 2, and 4 Ibs/acre with no soil
incorporation, the exposure values used in the LD50/sq-ft analysis are 15.6, 20.8, and 41.7 mg/sq-
ft, respectively. These exposure estimates are used for all terrestrial taxonomic groups.
Spray and granular applications (soil incorporated)
If the granular material is soil incorporated immediately after application, it is assumed that 1%
of the material is available to terrestrial organisms (USEPA 1992). It was assumed that the
availability of soil-incorporated spray material to terrestrial organisms would be similar to that of
soil-incorporated granular pesticides. These EECs are derived by calculating 1% of the EECs
based on the LD50/sq ft exposure calculations. Therefore, the EEC for incorporated trifluralin at
the highest single application rate of 2 Ib/acre is 0.21mg/sq-ft.
3.7 Terrestrial Plant Exposure Assessment
TerrPlant (Version 1.2.2) is used to calculate EECs for non-target plant species inhabiting dry
and semi-aquatic areas. Parameter values for application rate, drift assumption and incorporation
depth are based upon the use and related application method. A runoff value of 0.1 is utilized
based on trifluralin's solubility, which is classified by TerrPlant as <10 mg/L. For aerial and
ground liquid applications, drift was assumed to be 5% and 1%, respectively. For granular
applications, drift was assumed to be 0%. EECs relevant to terrestrial plants consider pesticide
concentrations in drift and in runoff. These EECs are listed by use in Table 3.11. An example
output from TerrPlant v. 1.2.2 is available in Appendix M.
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Table 3.11 TerrPlant EECs for Monocots and Dicots Inhabiting Dry and Semi-aquatic
Areas Exposed to Trifluralin via Runoff and Drift from liquid and granular applications
(single application only)
Scenario
Avocado
Citrus
Grapes and
berries
Olive
Stone and
Pome fruit
Tree nuts
Nursery
Right of way
Forestry
Alfalfa
Citrus
Grapes
Stone and
Pome fruit
Tree nuts
Cotton
Row crop
Forestry
Alfalfa
Com
Cole
Lettuce
Wheat
Com
Lettuce
Melon
Cole
Tomato
Potato
Wheat
Onion
Sugar beet
Rangeland
Hay
Turf
Residential
Nursery
Formulation1
G
G
EC
EC
EC
EC
EC
EC
G
G
EC
Method1*
Ground
Aerial *
Ground *
Aerial*
Ground*
Aerial
Ground
Aerial*
Ground *
Aerial *
Ground *
Aerial *
Ground *
Ground
Ground
Ground
Application
Rate
(Ibs/acre)
4
2
2
2
1
1
0.8
0.75
2
1.5
4
Drift
Value
0
0
5
1
5
1
5
1
5
1
5
1
0
0
1
Dry Area
EEC
(Ibs/acre)
0.04
0.01
0.11
0.03
0.12
0.04
0.055
0.015
0.044
0.012
0.041
0.011
0.02
0.015
0.08
Semi-
aquatic
Area EEC
(Ibs/acre)
0.4
0.1
0.2
0.12
0.3
0.22
0.1
0.06
0.08
0.048
0.075
0.045
0.2
0.15
0.44
Spray
Drift EEC
(Ibs/acre)
N/A
N/A
0.1
0.02
0.1
0.02
0.05
0.01
0.04
0.008
0.038
0.008
N/A
N/A
0.04
* 2 inch incorporation
:G = Granular application. EC = Emulsifiable Concentrate.
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4. Effects Assessment
This assessment evaluates the potential for trifluralin to directly or indirectly affect the CRLF,
DS, SFGS and SJKF or modify their designated critical habitat. As previously discussed in
Section 2.7, assessment endpoints for the effects determination for each assessed species include
direct toxic effects on the survival, reproduction, and growth, as well as indirect effects, such as
reduction of the prey base or modification of its habitat. In addition, potential modification of
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 each assessed species. Direct effects to the
aquatic-phase CRLF are based on toxicity information for freshwater fish (or amphibian data if
appropriate), while terrestrial-phase amphibian effects (terrestrial-phase CRLF) and reptiles
(SFGS) are based on avian toxicity data, given that birds are generally used as a surrogate for
terrestrial-phase amphibians and reptiles. Direct effects to the DS are based on toxicity
information for freshwater and estuarine/marine fish; data from the most sensitive taxonomic
group will be used as the DS both freshwater and estuarine habitats during its lifecycle. Direct
effects to the SFGS are based on avian toxicity data, given that birds are generally used as a
surrogate for terrestrial-phase amphibians and reptiles. Direct effects to the SJKF are based on
mammalian toxicity data.
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
freshwater fish (used as a surrogate for aquatic-phase amphibians), aquatic-phase amphibians,
freshwater invertebrates, estuarine/marine fish, estuarine/marine invertebrates, aquatic plants,
birds (used as a surrogate for terrestrial-phase amphibians and reptiles), mammals, terrestrial
invertebrates, and terrestrial plants. 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 trifluralin.
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). Open literature data presented in this assessment were obtained from the trifluralin RED
(1996) as well as ECOTOX information obtained on March 31, 2009. In order to be included in
the ECOTOX database, papers must meet the following minimum criteria:
(1) the toxic effects are related to single chemical exposure;
(2) the toxic effects are on an aquatic or terrestrial plant or animal species;
(3) there is a biological effect on live, whole organisms;
(4) a concurrent environmental chemical concentration/dose or application rate is
reported; and
(5) there is an explicit duration of exposure.
Open literature toxicity data for 'target' terrestrial plant species, which include efficacy studies,
are not currently considered in deriving the most sensitive endpoint for terrestrial plants.
Efficacy studies do not typically provide endpoint values that are useful for risk assessment (e.g.,
NOAEC, ECso, etc.), but rather are intended to identify a dose that maximizes a particular effect
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(e.g., ECioo). Therefore, efficacy data and non-efficacy toxicological target data are not included
in the ECOTOX open literature summary table provided in Appendix H. The list of citations
including toxicological and/or efficacy data on target plant species not considered in this
assessment is also provided in Appendix H [include all citations listed under 'Target Species' in
the ECOTOX file name 'Other' in the appendix of ECOTOX papers not considered].
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.., 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 trifluralin.
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 H. Appendix H 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 ECOTOX open
literature data, including the full suite of lethal and sublethal endpoints is presented in Appendix
H. Reviews of several of the ECOTOX and open literature studies are also included in
Appendix H
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 trifluralin. A summary of the available aquatic and terrestrial
ecotoxicity information, use of the probit dose response relationship, and the incident
information for trifluralin are provided in Sections 4.1 through 4.4, respectively.
As discussed in Section 2.4.1, TR-4, TR-6 and TR-15 are the primary degradates of exposure
concern for trifluralin. Data recently submitted to the Agency suggests that degradates of
trifluralin are less toxic than the parent for most taxonomic groups (Table 4.1). These recently
submitted studies have not undergone a thorough Agency review; however, a preliminary review
did not indicate significant scientific issues. Although data suggest that TR-4 is more toxic to
earthworms than the parent, the reported toxicity value (LCso =186 mg/kg-dry soil) is much
greater than expected concentrations in the soil after labeled trifluralin usage. No degradate
toxicity data for mammals and birds are available. The Agency does not have concerns for any
degradates of trifluralin relative to human health issues as the tolerance is expressed in terms of
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the trifluralin parent only, based on the determination of the Metabolite Assessment Review
Committee (MARC) Health Effects Division (HED) of OPP. Based on this analysis, EFED
concluded that trifluralin degradates would not result in exposure concerns for direct or indirect
effects to the CRLF, DS, SFGS, or SJKF.
Table 4.1. Comparison of the Toxicity of Trifluralin to the Toxicity of its Degradates.
Rainbow trout (96-hr LC50,
mg/L)
Daphnid (48-hr EC50, mg/L)
Selenastrum (96-hr IC50,
mg/L)
Earthworm (14-day LC50,
mg/kg-dry soil)
Trifluralin
0.041 (MRID
400980-01)
0.251 (MRID
478070-07)
0.089 (MRID
419345-02)
>1000* (MRID
478070-09)
TR-6
1.0* (MRID
478070-01)
3.52* (MRID
478070-04)
4.09* (MRID
478070-06)
NA
TR-15
5.46* (MRID
478070-02)
9.36* (MRID
478070-03)
1.67* (MRID
478070-05)
NA
TR-4
NA
NA
NA
186* (MRID
478070-10)
* Study submitted by the registrant to EPA in 2009, but not yet reviewed.
Trifluralin has registered products that contain multiple active ingredients. Analysis of the
available open literature and acute oral mammalian LD50 data for multiple active ingredient
products relative to the single active ingredient is provided in Appendix A. In this mixture
evaluation an LDso with associated 95% CI is needed for the formulated product. The same
quality of data is also required for each component of the mixture. In the case of trifluralin,
given that there is no 95% CI associated with the oral LD50 (>5000 mg/kg), it is not possible to
undertake a quantitative or qualitative analysis for potential interactive effects. However,
because the active ingredients are not expected to have similar mechanisms of action,
metabolites, or toxicokinetic behavior, it is reasonable to conclude that an assumption of dose-
addition would be inappropriate. Several papers were cited in ECOTOX that were classified as
evaluating mixtures that contained trifluralin. However, none provided sufficient information for
inclusion into this assessment. The results of this analysis show that an assessment based on the
toxicity of the single active ingredient of trifluralin is appropriate.
4.1 Toxicity of Trifluralin to Aquatic Organisms
Table 4.2 summarizes the most sensitive aquatic toxicity endpoints, based on an evaluation of
both the submitted studies and the open literature, as previously discussed. A brief summary of
submitted and open literature data considered relevant to this ecological risk assessment for the
CRLF and DS is presented below.
Toxicity to fish and aquatic invertebrates is categorized using the system shown in Table 4.3
(U.S. EPA, 2004). Toxicity categories for aquatic plants have not been defined.
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Table 4.2 Aquatic Toxicity Profile for Trifluralin
Assessment Endpoint
Species
Toxicity Value Used in
Risk Assessment
MRID
(Author & Date)
Status/Comment
Freshwater Organisms
Acute fish
Chronic fish
Acute invertebrates
Chronic invertebrates
Bluegill sunfish
Calculated using
ACR
Daphnid
Daphnid
LC50 = 18.5 ug/L
probitslope = 23.94
NOAEC = 0.93 ug/L
LOAEC not calculated
EC50 = 251 ug/L
(moving average)
probit slope = NA
NOAEC = 2.4 ug/L
LOAEC= 7.2 ug/L
400980-01
(Mayer and
Ellersieck, 1986)
NA
478070-07
05008271
Supplemental
Calculated using the
ACR = 20 for
trifluralin rainbow
trout data, applied to
the bluegill sunfish
LC50= 18.5 ug/L
Acceptable
Acceptable
Estuarine/Marine Organisms
Acute fish
Chronic fish
Acute invertebrates
Chronic invertebrates
Sheepshead
minnow
Sheepshead
minnow
Grass shrimp
Calculated using
ACR
(ethalfluralin)
LC50 = 240 ug/L
probit slope =1.9
NOAEC = <1.3 ug/L
LOAEC=1.3 ug/L
LC50 = 638.5 ug/L
Probit slope = 3. 48
NOAEC = 6.3 ug/L
LOAEC not calculated
416139-04
424499-01
406748-01
NA
Acceptable for
ethalfluralin, as there
were no acceptable/
supplemental studies
for trifluralin.
Supplemental
Acceptable
Calculated using the
ACR = 102 for
trifluralin daphnid
data, applied to the
grass shrimp LC50=
638.5 ug/L
Plants
Vascular Aquatic Plants
Non-vascular Aquatic Plants
Lemna gibba
Skeletonema
costatum
IC50 = 49.7 ug/L
NOAEC<2.53 ug/L,
LOAEC 2.53 ug/L
IC50 = 21.9 ug/L
NOAEC = 14 ug/L,
LOAEC = 18.3 ug/L
428341-04
428341-01
Supplemental
Acceptable
Table 4.3 Categories of Acute Toxicity for Fish and Aquatic Invertebrates
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
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4.1.1 Toxicity to Freshwater Fish and Aquatic-Phase Amphibians
A summary of acute and chronic freshwater fish data, including data from the open literature, is
provided below in Sections 4.1.1.1 through 4.1.1.3.
Although data evaluating the acute toxicity to aquatic-phase amphibians were reviewed, EFED
determined that the use of freshwater fish data is preferable to the use of aquatic-phase
amphibian data because it is unknown where the CRLF would fall on a species sensitivity
distribution. Because amphibian data is not required from the registrant, it is EFED's standard
approach to use freshwater fish as a surrogate for aquatic-phase amphibians. In addition, because
acute amphibian data were less sensitive than acute freshwater fish data, the use of freshwater
fish as a surrogate provides a more conservative estimation of risk to the aquatic-phase CRLF.
Chronic aquatic-phase amphibian toxicity data were not available.
Freshwater fish toxicity data were also used to assess potential indirect effects of trifluralin to the
CRLF. Effects to freshwater fish resulting from exposure to trifluralin have the potential to
indirectly affect the CRLF via reduction in available food, as over 50% of the prey mass of the
CRLF may consist of vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).
To assess potential direct effects of trifluralin to the DS, toxicity data for both the freshwater fish
and estuarine/marine fish were evaluated since the DS lives in brackish waters. The most
sensitive freshwater or estuarine/marine fish toxicity data was utilized in the risk estimation.
Since freshwater fish were more sensitive than estuarine/marine fish, the freshwater fish toxicity
data were used to assess potential direct effects of trifluralin to the DS.
To assess potential indirect effects of trifluralin to the SFGS, toxicity data for freshwater fish
were utilized, as the SFGS consumes fish and frogs as a component of its diet.
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies
Acute toxicity to freshwater fish can be summarized as very highly toxic for trifluralin. The most
sensitive LCso values for trifluralin were 18.5 and 43.6 |ig/L (bluegill sunfish (Lepomis
macrochirus) and rainbow trout (Oncorhynchus mykiss), respectively (MRID 400980-01,
Supplemental, see Appendix F for details). The LCso value of 18.5 |ig/L (bluegill sunfish) is
used for risk estimation. Nominal concentrations were reported for these two studies; these
values may overestimate the actual exposure concentration due to trifluralin's tendency to
volatilize and sorb to surfaces.
The calculated probit slopes for the bluegill and rainbow studies are 23.94 and 4.16, respectively.
There is a high uncertainty in the slope value calculated for the bluegill as the probit model was
reported as not a good fit for the data, and this value is well outside the range of typical slopes as
the default lower and upper bounds used when the slope cannot be calculated are 2 and 9 (with a
mean of 4.5). Therefore, the slope = 4.16 (rainbow trout) will be used to calculate the probability
of acute individual effects.
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4.1.1.2 Freshwater Fish: Chronic Exposure (Growth/Reproduction) Studies
Two acceptable chronic studies were available to the Agency to evaluate the effects of chronic
exposure to trifluralin (technical) on freshwater fish which were conducted on rainbow trout and
fathead minnow (Pimephalespromelas) (see Appendix F for details). The early life-stage study
conducted on rainbow trout (MRID 413862-02) demonstrated that chronic exposure to a mean-
measured concentration as low as 4.32 ug/L has the potential to cause a reduction in larval fish
length (3.5% relative to negative control) and reduction in body weight (8.8% relative to
negative control). The NOAEC and LOAEC for this study are 2.18 and 4.32 ug/L, respectively.
This study was re-evaluated and the data statistically re-analyzed (updated values, justifications
and details are provided in DPbarcode 417055 and Appendix F). Based on the results of this
analysis, the NOAEC and LOAEC were changed from the values used in previous assessments.
The full life-cycle study, conducted on fathead minnow (MRID 05008271), demonstrated that
chronic exposure to a mean-measured concentration at 5.1 ug/L caused a 64% reduction in
survival at 61 weeks. The NOAEC and LOAEC for this study are 1.9 and 5.1 ug/L, respectively.
The Acute-to-Chronic Ratio (ACR) approach also was used to obtain an estimate for chronic
trifluralin toxicity to freshwater fish. Both acute and chronic data are available for rainbow trout,
LC50 = 43.6 ug/L (MRID 400980-01) and NOAEC = 2.18 ug/L (MRID 413862-02) resulting in
an ACR = 20. This ACR was applied to the most sensitive acute toxicity data (bluegill, LC50 =
18.5 ug/L resulting in an estimated chronic NOAEC = 0.93 ug/L. This value will be used for risk
estimation.
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open Literature
Information
Poleksic and Karan (1999, E20430) conducted acute and subacute toxicity tests with carp
(Cyprinus carpio L) to determine the median lethal concentration and effects on relative growth
rates, biochemical parameters (alakaline phosphate [ALP], aspartate aminotransferase [AST],
alanin aminotransferase [ALT] activities in serum, gills, liver and kidney) and structure of the
gills, liver and kidneys. The 96-hr LC50 value (with 95% C.I.) was 45 (36, 51) ug/L. The 14-d
subacute test resulted in a decrease in relative growth rate and an increase in functional enzyme
activities in blood serum and the organs, most notably at the highest concentration (20 ug/L).
ALP and AST activity was increased at all treatment levels in either the gills and/or livers. Gill
and liver abnormalities were noted in the 10 and 20 ug/L concentrations and kidney
abnormalities were observed at the 20 ug/L treatment level only. The 14-day subacute NOAEC
was 5 ug/L.
4.1.1.4 Aquatic-phase Amphibian: Acute Studies
Two independent 96-hour acute tests were conducted with Fowler's toad tadpoles (Bufo w.
fouileri) on trifluralin (95.9% purity) at a temperature of 60.0°F and a water hardness of 44
mg/L. The resulting LCso values (with 95% C.I.) for Fowler's toad tadpoles were 116.15 (CI not
available since only one partial mortality) ug/L and 115.04 (62.0-151.0) ug/L (MRID 400980-
01).
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Sanders (1970, E2891) conducted a study evaluating acute effects to 4- to 5-week old Fowler's
toads resulted in a 96-hr LC50 (with 95% C.I.) of 100 (80, 490) ug/L. Sanders reported that
mortalities were often preceded by irritability and loss of equilibrium.
4.1.2 Toxicity to Freshwater Invertebrates
A summary of acute and chronic freshwater invertebrate data, including data published in the
open literature, is provided below in Sections 4.1.2.1 through 4.1.2.3.
To assess potential indirect effects (prey) of trifluralin to the DS, toxicity data for both the
freshwater invertebrates and estuarine/marine invertebrates were evaluated since the DS lives in
brackish waters. The most sensitive freshwater or estuarine/marine invertebrate toxicity data was
utilized in the risk estimation. Since freshwater invertebrates were more sensitive than
estuarine/marine invertebrates, the freshwater invertebrate toxicity data were used to assess
potential indirect effects of trifluralin to the DS.
4.1.2.1 Freshwater Invertebrates: Acute Exposure Studies
One acceptable acute toxicity test to freshwater invertebrate was available to the Agency to
evaluate acute exposure of trifluralin (technical) which was conducted on daphnids (MRID
478070-07). The resulting ECso was 251 ug/L (calculated using moving average, see Appendix
F for details). The ECso and slope obtained from the probit model were unreliable (only one
partial mortality in the area of the EC50) and not utilized for this assessment.
This EC50 of 251 ug/L for Daphnia magna is used to quantitatively estimate acute risk to
freshwater invertebrates.
4.1.2.2 Freshwater Invertebrates: Chronic Exposure Studies
Two acceptable chronic (life-cycle) exposure studies with trifluralin (technical) involving the
freshwater invertebrate, Daphnia magna, were submitted to the Agency. The first life-cycle
study (MRID 05008271), demonstrated that chronic exposure to a mean-measured concentration
at 7.2 ug/L resulted in 100% mortality in the third generation (day 64 of study). The NOAEC and
LOAEC for this study are 2.4 and 7.2 ug/L. The second life-cycle study (MRID 413862-01)
demonstrated that chronic exposure to a mean-measured concentration as high as 50.7 ug/L
(highest level tested) resulted in no effects on survival, reproduction or growth. The NOAEC for
this study is 50.7 ug/L and the LOAEC is > 50.7 ug/L (see Appendix F for details).
The NOAEC of 2.4 ug/L for Daphnia magna is used to quantitatively estimate chronic risk to
freshwater invertebrates.
4.1.2.3 Freshwater Invertebrates: Open Literature Data
Naqvi et. al (1985, El 1476) conducted acute toxicity studies by exposing ostracods (Cypria sp.),
cladocerans (Alonella sp.), calanoids (Diaptomus sp.), and cyclopoids (Eucyclops sp.) to Treflan
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(trifluralin) in mixed species test vessels. The 48-hour LCso values for cladocerans, calanoids,
cyclopods, and ostracods were 0.06, 0.08, 0.05 and 0.06 mg/L, respectively, based on nominal
concentrations. The results of this study should not be used quantitatively because the initial
loading of organisms to the test vessels is unknown, it is unclear if interspecies competition
impacted the results of this study, the exposure concentrations were not analytically determined,
and the purity of the test material was not reported.
4.1.3 Toxicity to Estuarine/Marine Fish
A summary of acute and chronic estuarine/marine fish data, including data published in the open
literature, is provided in Sections 4.1.3.1 through 4.1.3.3.
4.1.3.1 Estuarine/Marine Fish: Acute Exposure Studies
No acceptable or supplemental studies evaluating the acute toxicity of trifluralin to
estuarine/marine fish were submitted to the Agency. Due to lack of submitted acute studies for
estuarine/marine fish and no available open literature data, acute toxicity data from other
dinitroanline herbicides were evaluated (benfluralin, butralin, ethalfluralin, oryzalin, and
pendimethalin) (Appendix E). No data were available for benfluralin or oryzalin; sheepshead
minnow (Cyprinodon variegates) studies for butralin, ethalfluralin, and pendimethalin resulted in
96-hr LCsoS of >180, 240, and 710 ug/L, respectively. The most sensitive definitive acute
endpoint was the LCso value of 240 ug/L for sheepshead minnow (MRID 416139-04) from the
toxicity test conducted using ethalfluralin. In lieu of acute trifluralin data for estuarine/marine
fish, the LC50 value 240 ug/L for sheepshead minnow is used for risk estimation.
4.1.3.2 Estuarine/Marine Fish: Chronic Exposure Studies
A 56-day early life cycle study was submitted for sheepshead minnow (Cyprinodon variegates,
MRID 424499-01). The NOAEC was undefined (< 1.3 ug/L) as reproduction (number of eggs
spawned/day/female) in the lowest test concentration was significantly less than in the control
group (a 27% reduction). This study was classified as Supplemental because insufficient data
were submitted for completing a full review.
4.1.3.3 Estuarine/Marine Fish: Open Literature Data
In a study conducted by Couch (1979, E6425), sheepshead minnows exposed to 5.5 to 31 ug/L
of trifluralin during the first 28 days of life developed a vertebral dysplasia. It consisted of semi-
symmetrical hypertrophy of vertebra, three to 20 times normal. Effects of the abnormal vertebral
development were dorsal vertebral growth into the neural canal, ventral compression of renal
ducts, and longitudinal fusion of vertebrae. Fish, exposed for 51 days to 16.6 ug/1 trifluralin and
thereafter depurated for 41 days, showed no increase in vertebral dysplasia during depuration;
however, residual spinal column damage was evident. Serum calcium concentrations were
elevated in adult fish exposed for 4 days to 16.6 ug/1 trifluralin.
In a second study (Couch 1984, E48406), pituitaries of sheepshead minnows, exposed for 19
months to 1-5 ug/L trifluralin in the laboratory exhibited enlargement, pseudocysts, congestion
93
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of blood vessels and oedema. Most of the fish with an enlarged pituitary also had induced diffuse
and/or focal vertebral hyperostosis and other dysplastic vertebral changes.
Koyama (1996, E17085) estimated 96-hr LCsoS and vertebral deformity rates in 10 marine fish
species after exposure to trifluralin, as a Japanese end-use product. Two species had non-
definitive LD50s <5.0 ug/L, definitive LCSOs ranged from 21 to 120 ug/L, and two species had
LCsos of >56 and >74 ug/L. Vertebral deformities were observed in eight of the 10 evaluated
species, they were not observed in the two species in which an LC50 was not reached. For those
species which had vertebral lesions, the lesions were observed at concentrations as low as 5 to 30
ug/L, depending on species. Vertebral deformity rates in fish exposed to concentrations at or
above the lowest concentration at which any deformities were observed ranged from 14 to 82%.
4.1.4 Toxicity to Estuarine/Marine Invertebrates
A summary of acute and chronic estuarine/marine invertebrate data, including data published in
the open literature, is provided below in Sections 4.1.4.1 through 4.1.4.3.
4.1.4.1 Estuarine/Marine Invertebrates: Acute Exposure Studies
The acute toxicity studies available to the Agency demonstrate that trifluralin can be classified as
highly toxic to estuarine/marine invertebrates. The ECso values were 638.5 ug/L for grass
shrimp (Palaemonetespugio) and >136 ug/L for the mysid (MRTDs 406748-01 and 436620-01,
see Appendix F for details).
4.1.4.2 Estuarine/Marine Invertebrates: Chronic Exposure Studies
No studies evaluating the chronic toxicity of trifluralin to estuarine/marine invertebrates have
been submitted to the Agency. Due to lack of submitted chronic studies for estuarine/marine
invertebrates and no available open literature data, the ACR approach was used to obtain an
estimate for chronic trifluralin toxicity to estuarine/marine invertebrates. An ACR =102 was
calculated from the trifluralin daphnid data (245 ug/L ^ 2.4 ug/L) and applied to the grass
shrimp data (LCso= 638.5 ug/L) for an estimated chronic toxicity NOAEC = 6.3 ug/L.
4.1.4.3 Estuarine/Marine Invertebrates: Open Literature Data
No studies evaluating toxicity of trifluralin to estuarine/marine invertebrates were identified in
open literature that had more sensitive toxicity values.
4.1.5 Toxicity to Aquatic Plants
Laboratory studies are used to evaluate the potential of trifluralin to affect vascular and non-
vascular aquatic plants For non-vascular plant laboratory data, the toxicity values used for risk
estimation were derived based on the lowest endpoint from from either freshwater or
estuarine/marine species since guideline studies do not sufficiently explore the relative
sensitivity of algae with regards to freshwater or estuarine/marine environment.
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4.1.5.1 Aquatic Plants: Laboratory Data
Five acceptable aquatic plant studies with trifluralin (technical) conducted on Skeletonema
costatum, Selanstrum capricornutum, Anabaena flos-aquae and Lemna gibba were submitted by
the registrant (MRIDs 428341-01, 428341-02, 428341-03, 428341-04, and 419345-02). All five
aquatic plant studies were re-evaluated and the data statistically re-analyzed (updated values,
justifications and details are provided in DPbarcode 417055 and Appendix F). Based on the
results of this analysis, toxicity values from all five studies were changed.
This risk assessment will utilize data from the most sensitive vascular plant (Lemna gibba) and
non-vascular plant (Skeletonema costatum) studies. For Lemna gibba, the ICso and ICos are 49.7
and 14.7 |ig/L (NOAEC not definitive). For Skeletonema costatum, the ICso and NOAEC are
21.9 and 14.0 ug/L,
4.2 Toxicity of Trifluralin to Terrestrial Organisms
Table 4.4 summarizes the most sensitive terrestrial toxicity endpoints, based on an evaluation of
both the submitted studies and the open literature. A brief summary of submitted and open
literature data considered relevant to this ecological risk assessment is presented below.
Table 4.4 Terrestrial Toxicity Profile for Trifluralin
Endpoint
Birds
(surrogate for
terrestrial-
phase
amphibians
and reptiles)
Mammals
Acute/
Chronic
Acute
(oral
gavage)
Acute
(dietary)
Chronic
Acute (oral
gavage)
Chronic
Species
Bobwhite quail
Mallard duck
Bobwhite quail
Mallard duck
Mallard Duck
Laboratory rat
Laboratory rat
Toxicity Value
Used in Risk
Assessment
LD50 > 2000
mg/kg-bwt
LD50 > 2000
mg/kg-bwt
LC50 > 5000
mg/kg-diet
LC50 > 5000
mg/kg-diet
NOAEC = 500
mg/kg-diet
LOAEC = 1000
mg/kg-diet
LD50 > 5000
mg/kg-bwt
NOAEL = 10
mg/kg-bwt/day
(converted to 200
MRID
00137573
00160000
00138857
00138858
403347-04
00157486
00151901
00151902
00151903
Status/Comment
Practically non-toxic
Both studies classified
Acceptable, no
mortalities or sublethal
effects
Practically non-toxic
Both studies classified
Accceptable, no
mortalities or sublethal
effects
Acceptable
Effects were reductions
in egg shell thickness,
14-day hatchling
weights.
Practically non-toxic
Acceptable, no
mortalities or sublethal
effects
Acceptable
Effects were kidney
toxicity (renal lesions
95
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Table 4.4 Terrestrial Toxicity Profile for Trifluralin
Endpoint
Terrestrial
invertebrates
Terrestrial
plants
Acute/
Chronic
Acute
N/A
N/A
N/A
N/A
Species
Honey bee,
contact
Seedling
Emergence
Monocots
Seedling
Emergence
Dicots
Vegetative Vigor
Monocots
Vegetative Vigor
Dicots
Toxicity Value
Used in Risk
Assessment
mg/kg-diet)
LOAEC = 32.5
mg/kg-bwt/day
(converted to 650
mg/kg-diet)
LD50>24.17
ug/bee
IC25 = 0.09
Ibs/acre
IC25 = 0.19
Ibs/acre
IC25=1.09
Ibs/acre
IC25 = 0.796
Ibs/acre
MRID
00028772
439844-01
439844-01
419345-03
419345-03
Status/Comment
and increased relative
liver weight), reduced
weanling body weights
and reduced litter sizes
Supplemental (13%
mortality at only test
level = 24.1 7 ug/bee)
Sorghum, fresh shoot
weight
Acceptable, conducted
using TEP*
Cucumber, fresh shoot
weight
Acceptable, conducted
using TEP*
Corn, fresh shoot
weight
Acceptable, conducted
using technical
Cucumber, fresh shoot
weight
Acceptable, conducted
using technical
N/A: not applicable
* TEP = typical end-use product, in this case product was Treflan HFP containing 43.8% trifluralin
Acute toxicity to terrestrial animals is categorized using the classification system shown in Table
4.5 (U.S. EPA, 2004). Toxicity categories for terrestrial plants have not been defined.
Table 4.5 Categories of Acute Toxicity for Terrestrial Organisms
Categories of Acute Toxicity for Birds and Mammals
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
Oral LD50
< 10 mg/kg
10 - 50 mg/kg
51 -500 mg/kg
50 1-2000 mg/kg
> 2000 mg/kg
Dietary LC50
< 50 ppm
50 - 500 ppm
50 1-1000 ppm
100 1-5000 ppm
> 5000 ppm
Categories of Acute Toxicity for Non-Target Insects
Toxicity Category
Highly toxic
Moderately toxic
Practically non-toxic
Contact LCSO
< 2 ug/bee
2-11 ug/bee
>11 ug/bee
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4.2.1 Toxicity to Birds
As specified in the Overview Document, the Agency uses birds as a surrogate for reptiles and
terrestrial-phase amphibians when toxicity data for each specific taxon are not available (U.S.
EPA, 2004). No terrestrial-phase amphibian or reptile data are available for trifluralin; therefore,
acute and chronic avian toxicity data are used to assess the potential direct effects of trifluralin to
terrestrial-phase CRLF and SFGS, as well as potential effects on prey of terrestrial-phase CRLF,
SFGS, and SJKF. A summary of acute and chronic bird data, including data published in the
open literature, is provided below in Sections 4.2.1.1 through 4.2.1.4. Additional information on
these studies is provided in Appendix F.
4.2.1.1 Birds: Acute Exposure (Mortality) Studies
The acute toxicity of the technical grade trifluralin (-96.7% purity) to birds was established with
the following guideline tests: two avian single-dose oral (LD50) studies on the bobwhite quail and
mallard duck; two sub-acute dietary studies (LCso) on the mallard duck and the bobwhite quail.
The non-definitive LDsoS for bobwhite quail and mallard duck were > 2000 mg/kg-bw (MRTDs
00137573 and 00160000). The LC50s for both bobwhite quail and mallard duck were > 5000
mg/kg-diet (MRIDs 00138858 and 00138857). No mortalities or sublethal effects occurred at
any treatment level for all the above acute avian studies. Based on these studies, acute exposure
of trifluralin to birds was classified as "practically non-toxic".
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies
Avian chronic exposure reproduction effects studies were performed for using two species,
bobwhite quail and mallard duck.
Two recent studies were classified as acceptable for the bobwhite quail and mallard duck using
96% technical trifluralin. In the bobwhite quail study (MRID 403347-06 and DPbarcode 417055
for revisions), the NOAEC was established at 1000 mg/kg-diet with no significant adverse
effects observed. In the mallard duck study (MRID 403347-04), the NOAEC was established at
500 mg/kg-diet with the most sensitive endpoints being reduction in eggshell thickness, 14-day
survival body weight of chicks and male body weight for the duck at the highest test
concentration of 1000 mg/kg-diet.
Additional bobwhite quail and mallard duck studies using 99.6% technical (MRIDs 00131134
and 00131132, DPbarcode 417055 for revisions) were also submitted to the Agency; these
studies were used for previous risk assessments. For the bobwhite quail study, the NOAEC was
established at 50 mg/kg-diet (the highest test concentration), as no significant effects were
observed for any of the reported endpoints. Although this study was classified as Acceptable,
there is concern for the validity of the study as the overall percentage of cracked eggs was high
(9.7% of eggs laid in controls). EPA guidance for bobwhite quail reproduction studies states that
typically only 0.6 - 2.0% of eggs laid are cracked. For the mallard duck study, the NOAEC was
established at 5 mg/kg-diet, as there was a statistically significant reduction in the percentage of
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eggs not cracked ("eggs not cracked/eggs laid") at the highest test concentration of 50 mg/kg-
diet. This effect was relatively small (98.8, 99.7, and 97.0% eggs not cracked/eggs laid in the
control, 5 mg/kg-diet, and 50 mg/kg-diet groups, respectively). This effect was not observed in
any of the other chronic bird studies including those that had test concentrations up to 1000
mg/kg-diet (MRID 403347-04 and 403347-06). After evaluating the size of the effect and the full
suite of avian reproduction studies conducted for trifluralin, EFED determined that the reduction
in the percentage of eggs cracked in this study (MRID 00131132) was not biologically
significant, and the study NOAEC should be established at 50 mg/kg-diet (the highest
concentration tested).
For risk estimation in this assessment, a chronic avian NOAEC of 500 mg/kg-diet is used. This is
based on the mallard duck study (MRID 403347-04) with effected endpoints of reduction in
eggshell thickness, 14-day survival body weight of chicks and male body weight for the duck at
the highest test concentration of 1000 mg/kg-diet. Any of these effects may have an effect on the
fitness of individuals and on the overall fitness of wild bird populations exposed to trifluralin.
Since birds are used as a surrogate for the terrestrial-phase CRLF and the SFGS, these effects
have the potential to result in direct effects to the frog and snake by affecting reproductive fitness
or to result in indirect effects to the terrestrial-phase CRLF, SFGS, and SJKF by affecting their
prey populations.
4.2.1.3 Birds, Reptiles and Terrestrial-phased Amphibians: Open
Literature Studies
No studies evaluating toxicity of trifluralin to birds, reptiles and terrestrial-phase amphibians
were identified in open literature that had more sensitive toxicity values.
4.2.2 Toxicity to Mammals
A summary of acute and chronic mammalian data, including data published in the open
literature, is provided below in Sections 4.2.2.1 through 4.2.1.2. Additional information on these
studies is provided in Appendix F.
Mammalian toxicity data are used to assess potential direct and indirect effects of trifluralin to
the SJKF and indirect effects of trifluralin to the terrestrial-phase CRLF, SJKF and SFGS as
discussed in Section 2.8. For the purposes of this risk assessment, the available mammalian
toxicity data on laboratory rodents as surrogates for mammalian wildlife were used.
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies
There is one-registrant submitted acceptable rat acute oral toxicity study. No mortality or signs
of systemic toxicity were reported; based on a laboratory rat LDso value greater than 5000
mg/kg-bw, trifluralin is practically non-toxic to small mammals on an acute oral basis (MRID
00157486). Based on these studies, acute toxicity of trifluralin to mammals was classified as
"practically non-toxic".
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4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies
In 2-generation rat reproduction study (MRIDs 00151901, 00151902 and 00151903, technical
grade), toxic effects in Wister KFM-Han rats included kidney toxicity (renal lesions and
increased relative liver weight), reduced weanling body weights and reduced litter sizes. The
NOAEC for reproductive and developmental toxicity was 200 mg/kg-diet and the LOAEC was
650 mg/kg-diet based on reduced weanling body weights at 650 and 2000 mg/kg-diet and
reduced litter sizes at the highest concentration (2000 mg/kg-diet). Since terrestrial-phase CRLF,
SFGS and SJKF may consume mammals, these effects have the potential to result in indirect
effects by affecting their prey populations. Using standard laboratory rat weights, the NOAEC =
200 mg/kg-diet can be converted to a NOAEL =10 mg/kg-bwt. This study is used for risk
estimation in this assessment.
4.2.2.3 Mammals: Open Literature Studies
No studies evaluating toxicity of trifluralin to mammals were identified in open literature that
had more sensitive toxicity values than those studies submitted by to the Agency.
4.2.3 Toxicity to Terrestrial Invertebrates
A summary of acute terrestrial invertebrate data, including data published in the open literature,
is provided below in Sections 4.2.3.1 through 4.2.3.2.
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies
Based on an acute contact LD50 of >24.17 |ig/bee, trifluralin appears to be "practically non-toxic"
to honeybees (MRTD 00028772). At the only tested dose, 24.17 |ig/bee, 12.85% mortality
occurred.
One additional study honeybee study was submitted with an acute contact of LDsoof > 100
jig/bee and acute oral of LD50of > 50 |ig/bee, trifluralin appears to be "practically non-toxic" to
honeybees (MRID 05001991). Mortality at each test dose was not reported.
The non-definitive terrestrial invertebrate toxicity value for acute contact to bees with an LD50 of
>24.17 jig/bee is used qualitatively to characterize the indirect effects to the SFGS, SJKF and
terrestrial-phase CRLF.
4.2.3.2 Terrestrial Invertebrates: Open Literature Studies
Toxicity of trifluralin to mature earthworms (Eisenia foetida) was evaluated by Roberts and
Borough (E040531; 1984). Trifluralin was found to be relatively non-toxic to earthworms with a
non-definitive LCso >1000 |j,g/cm2, in a 48-hr study.
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4.2.4 Toxicity to Terrestrial Plants
Plant toxicity data from both registrant-submitted studies and studies in the scientific literature
were reviewed for this assessment. Registrant-submitted studies are conducted under conditions
and with species defined in EPA toxicity test guidelines. Sub-lethal endpoints such as plant
growth, dry weight, and biomass are evaluated for both monocots and dicots, and effects are
evaluated at both seedling emergence and vegetative life stages. Guideline studies generally
evaluate toxicity to ten crop species. These tests are conducted on herbaceous crop species only,
and extrapolation of effects to other species, such as the woody shrubs and trees and wild
herbaceous species, contributes uncertainty to risk conclusions.
Commercial crop species have been selectively bred, and may be more or less resistant to
particular stressors than wild herbs and forbs. The direction of this uncertainty for specific plants
and stressors, including trifluralin, is largely unknown. Homogenous test plant seed lots also
lack the genetic variation that occurs in natural populations, so the range of effects seen from
tests is likely to be smaller than would be expected from wild populations.
4.2.4.1 Terrestrial Plants: Registrant-submitted Studies
In general, toxicity tests demonstrate that trifluralin negatively impacts seedling emergence and
vegetative vigor of terrestrial plants (MRID 439844-01, 419345-03). Results of Tier II toxicity
testing on the technical material and the end-use product are summarized in Appendix F.
One terrestrial plant seedling emergence Tier II study was classified as acceptable using the
formulation product Treflan HFP (43.8% purity) (MRID 439844-01). In general, the emerged
monocots were more sensitive than emerged dicots based on £€25 comparisons. Shoot fresh
weight was the most sensitive parameter for both monocots and dicots. In the seedling
emergence study; sorghum was the most sensitive monocot (IC25 = 0.09 Ib/acre), and cucumber
was the most sensitive dicot (IC25 = 0.19 Ib/acre).
A Tier II study was submitted that evaluated the effects of technical trifluralin (95.7% purity) on
non-target terrestrial plant vegetative vigor (MRID 419345-03). Shoot fresh weight was the most
sensitive parameter for both monocots and dicots. For the vegetative vigor test, the most
sensitive monocot was corn (IC25 = 1.09 Ib/acre) and the most sensitive dicot was cucumber (IC25
= 0.796 Ib/acre).
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Table 4.6 Non-target Terrestrial Plant Seedling Emergence Toxicity (Tier II) Data for
Trifluralin TEP (Treflan HFP) 43.8% purity (MRID 439844-01)*
Crop
Monocot
Dicot
Species
Corn
Sorghum
Onion
Wheat
Cotton
Cabbage
Radish
Cucumber
Soybean
Sunflower
NOAEC
(Ib a.i./acre)
0.13
0.06
0.50
0.13
NA
0.50
1.0
0.13
1.0
2.0
IC25
(Ib a.i./acre)
0.17
0.09
0.74
0.21
NA
0.78
2.4
0.19
1.3
4.0
Most Sensitive Endpoint
Shoot fresh weight
Shoot fresh weight
Shoot fresh weight
Shoot fresh weight
Results invalid (soil medium
detrimental to plant growth)
Shoot fresh weight
Shoot fresh weight
Shoot fresh weight
Shoot fresh weight
Shoot fresh weight
* For this study, an incorporated application was simulated by spraying the material into a rotating cement
mixer filled with soil. This soil was used to provide the top two 2 inches of soil in each treatment pot.
Table 4.7 Non-target Terrestrial Plant Vegetative Vigor Toxicity (Tier II) Data for
Trifluralin (Treflan 95.7% purity, MRID 419345-03)
Crop
Monocot
Dicot
Species
Corn
Sorghum
Onion
Wheat
Cabbage
Cotton
Cucumber
Sunflower
Soybean
Radish
NOAEC
(Ibs/acre)
0.50
NDd
0.25
ND
ND
ND
0.25 b
ND
ND
0.25
IC25
(Ibs/acre)
1.09
2.648 a
1.45
>2C
2.644 a
2.267 a
0.796
2.476 a
>2C
0.939
Most Sensitive Endpoint
Fresh Shoot weight
Height
Height
Height and
fresh shoot weight
Height
Height
Fresh Shoot weight
Height
Height and
fresh shoot weight
Height
a values reported by the study author, not verified by EFED reviewer
b NOAEC=0. 125 Ibs/acre was used in the RED, correct value is 0.25 Ibs/acre
0 Endpoints determined visually by study author, no statistical analysis conducted.
d Not determined; NOAEC values not reported by the study author or the EFED reviewer.
Generally, EFED prefers terrestrial plant toxicity tests to be conducted using end-use products
and dry shoot weights as this better represents the exposure of non-target plants in the
environment. For this risk assessment, EFED is using toxicity testing results that were conducted
with technical trifluralin (for vegetative vigor) and with measured fresh weights for both seedling
emergence and vegetative vigor. Since the results for seedling emergence and vegetative vigor
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were not both conducted on end-use products for the most sensitive parameters, results between
the two studies should be compared with caution.
4.2.4.2 Terrestrial Plants: Open Literature Studies
No studies evaluating toxicity of trifluralin to terrestrial plants suitable for inclusion in this risk
assessment were identified in the open literature. Available open literature studies focused on
efficacy evaluation; IC25s were not available from those studies.
4.4 Incident Database Review
A review of the EIIS database for ecological incidents involving trifluralin was completed on
7/10/2009. The results of this review for terrestrial, plant, and aquatic incidents are discussed
below in Sections 4.4.1 through 4.4.3, respectively. A complete list of the incidents involving
trifluralin including associated uncertainties is included as Appendix I. This table is divided into
incidents involving aquatic organisms and terrestrial organisms.
Incidents listed in EIIS are categorized by the likelihood that a particular pesticide is associated
with that particular incident. These classifications include highly probable, probable, possible,
unlikely or unrelated. "Highly probable" incidents usually require carcass residues or clear
circumstances regarding the exposure. "Probable" incidents include those where residue
information was not available or circumstances were less clear than those for "highly probable."
"Possible" incidents occur when multiple chemicals may have been involved and the
contribution of an individual chemical is not obvious. An "unlikely" incident classification is
given when a given chemical is considered nontoxic to the type of organism involved or the
chemical was analyzed and not detected in samples. The "unrelated" category is used for
incidents confirmed not to involve pesticides. No unrelated incidents were listed for trifluralin.
The number of reports listed in the EIIS database is believed to be only a fraction of the total
incidents involving organismal mortality and damage caused by pesticides. Few resources are
assigned to incident reporting. Reporting by states is only voluntary, and individuals discovering
incidents may not be informed on the procedure of reporting these occurrences. Additionally,
much of the database is generated from registrant-submitted incident reports. Registrants are
legally required to provide detailed reports of only "major" ecological incidents involving
pesticides, while "minor" incidents are reported aggregately. Because of these logistical
difficulties, EIIS is most likely a minimal representation of all pesticide-related ecological
incidents.
The EIIS database contained 83 incident reports involving trifluralin. Most of the incidents
involve terrestrial ecosystems involving effects to terrestrial plants (78 or 94% of the total
incidents). Five incident reports involve aquatic ecosystems. North Dakota was most represented
among all 50 states (20 reports) followed by Iowa (16), Minnesota (7), California (6) and Texas
(5). Additional characterization of these incidents is provided below.
Of the 83 incidents reported, 1 (1.2%) are categorized as 'highly probable' and 58 (69.8%) are
categorized as 'probable.' Collectively the 'highly probable' and 'probable' categories represent
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71% of the reported incidents. Regarding the legal status, the 'registered use' represents the
largest legality category with 81.9% of the incidents reported.
Approximately 9.6% of the reports consist of 'misuse accidental' and 8.4 % undetermined uses.
4.4.1 Terrestrial Animal Incidents
No terrestrial animal incidents were reported.
4.4.2 Terrestrial Plant Incidents
For trifluralin, 78 incidents were reported for plant damage to a wide variety of terrestrial plants
particularly from direct treatment or spray drift (e.g., Alfalfa, barley, bean, birch, blue spruce,
corn, cotton, dry bean, ornamentals, peanut, percifia shrubs, pinto bean, potato, raspberry, rose,
soybean, soybean seed, spreading yew, sudan grass, sugarcane, sunflower, tomato and wheat
(spring and other varieties). For trifluralin, 66 of the 78 incidents reported were registered uses,
five were accidental misuses and seven were of unknown legality. Of the 78 incidents involving
terrestrial plants, 55 (70.5%) are classified as 'probable' in the context of trifluralin use. Other
reported incident exposures included spills, stunted growth, discoloration, reduced yield,
incapacitation, mortality, runoff, and carryover.
4.4.3 Aquatic Animal Incidents
All five of the aquatic incident reports involved mortality to aquatic organisms. One of the five
incidents reportedly involved an eel, but the likelihood of observing impacts to eels are low
compared to fish based on a reported trifluralin spill. Of the five aquatic incidents involving fish,
(80%) are classified as either 'highly probable' or 'probable' in the context of trifluralin use. A
wide variety of fresh and estuarine fish species were reportedly affected due to runoff and
accidental spills (e.g., catfish, minnow, bass, shad, bluegill sunfish, gar and crappie).
All of the probable incidents were accidental misuses except incident # 1002215-001 which
occurred in Texas. This report failed to give the name of the county where the incident occurred.
The incident date, which was not reported in the memo of 06/12/95, was estimated to be
06/01/95. According to the report, an area was treated with pesticide prior to asphalt paving.
Light rain followed and there was a heavy thunderstorm a day later which allegedly resulted in a
runoff into a three acre pond causing a fishkill of an unspecified number of bass, bluegill and
crappie. Catfish and carp were not affected. It was believed that trifluralin, as Treflan, was
responsible for the observed mortality.
5. 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
DS, SFGS and SJKF or for modification to their designated critical habitat (CRLF and DS only)
from the use of trifluralin 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
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assumptions, limitations, and uncertainties; and synthesizes an overall conclusion regarding the
likelihood of adverse effects to the assessed species or their 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 the pre-established acute and chronic levels of concern (LOCs)
for each category evaluated (Appendix J). For acute exposures to the aquatic animals, as well as
terrestrial invertebrates, the acute LOG is 0.05. For acute exposures to the birds (and, thus,
reptiles and terrestrial-phase amphibians) and mammals, the LOG is 0.1. The LOG for chronic
exposures to animals, as well as acute exposures to plants is 1.0.
Acute and chronic risks to aquatic organisms are estimated by calculating the ratio of exposure to
toxicity using l-in-10 year EECs based on the label-recommended trifluralin usage scenarios
summarized in Table 3.3 and the appropriate aquatic toxicity endpoint from Table 4.2. Acute
and chronic risks to terrestrial animals are estimated based on exposures resulting from
applications of trifluralin (Tables 3.9 and 3.10) and the appropriate toxicity endpoint from Table
4.4. Exposures are also derived for terrestrial plants, as summarized in Table 3.11, and toxicity
endpoints are listed in Table 4.4.
5.1.1 Exposures in the Aquatic Habitat
5.1.1.1 Freshwater Fish and Aquatic-phase Amphibians
Acute risk to freshwater fish and aquatic-phase amphibians and the potential for direct effects to
CRLF and DS specifically is based on peak EECs in the standard PRZM/EXAMS pond and the
lowest acute toxicity value for freshwater fish. Based on freshwater fish toxicity data (LCso value
of 18.5 |ig/L for bluegill sunfish) and modeled aquatic peak EECs for various use scenarios used
to represent uses of trifluralin in CA (Table 3.3), acute RQs for freshwater fish resulted in
exceedances of the Listed Species LOG (RQ>0.05) for 18 out of 25 modeled crop scenarios with
exceedances occurring with at least one of the application methods for each scenario (Table 5.1).
The RQs exceeding the Listed Species LOG ranged from 0.05 to 0.35.
The probability of acute individual effects for freshwater fish and aquatic-phase amphibians is
<1 in 3280 (calculated using a probit slope = 4.16, MRID 400980-01) for those scenarios in
which the Listed Species LOG was exceeded (6.55 ppb/43.6= RQ of 0.15 for rainbow trout). At
the Listed Species LOG, the probability of acute individual effects for freshwater fish and
aquatic-phase amphibians also is < 1 in 32100000. The probit slope of 23.94 (MRID 400980-01)
was not used to calculate probabilities due to high uncertainty of the probit analysis derived from
this value.
Chronic risk to freshwater fish and aquatic-phase amphibians and the potential for direct effects
to aquatic-phase CRLF and DS specifically is based on 60-day EECs and the lowest chronic
toxicity value for freshwater fish. Based on 60-day EECs for various use scenarios used to
104
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represent uses of trifluralin in CA and the NOAEC of 0.93 |ig/L (estimated via ACR), no chronic
RQs resulted in a Chronic LOG exceedance (all RQ < 1.0) (Table 5.1).
Based on exceedances of the Agency's acute listed species LOG (RQ>0.05) for 18 modeled
scenarios trifluralin does have the potential to directly affect the aquatic phase CRLF and DS.
Additionally, since acute RQs are exceeded, there is a potential for indirect effects to those listed
species that rely on freshwater fish (and/or aquatic-phase amphibians) during at least some
portion of their life-cycle (i.e., CRLF and SFGS).
Table 5.1 Acute and Chronic RQs for Aquatic-phase CRLF and DS (freshwater fish
surrogate) Resulting from Trifluralin Application
Crop Scenario/
Formulation
Application
Method
Soil
Incorporation
Peak EEC
Hg/L
60 day
EEC ng/L
Acute
RQs1
Chronic
RQs2
Orchard Uses
CA Almond (including tree nuts)
Granular
EC
Ground
Aerial
Ground
N
Y
Y
2.23
5.65
1.23
0.72
0.6
0.18
0.12
0.31
0.07
0.77
0.65
0.19
CA Avocado
Granular
Ground
N
5.81
0.73
0.31
0.78
CA Citrus
Granular
EC
Ground
Aerial
Ground
N
Y
Y
0.74
5.48
1.10
0.14
0.54
0.11
0.04
0.30
0.06
0.15
0.58
0.12
CA Fruit
Granular
EC
Ground
Aerial
Ground
N
Y
Y
2.52
5.51
1.12
0.4
0.55
0.13
0.14
0.30
0.06
0.43
0.59
0.14
CA Grape (including berries)
Granular
Ground
N
4.0
0.62
0.22
0.67
CA Grape
EC
Aerial
Ground
Y
Y
5.5
1.18
0.54
0.12
0.30
0.06
0.58
0.13
CA Olive
Granular
Ground
N
4.45
0.77
0.24
0.83
Agricultural Uses
CA Alfalfa
EC
Granular
Aerial
Ground
Aerial
Ground
N
N
Y
Y
5.14
1.12
0.32
0.32
0.58
0.17
0.07
0.07
0.28
0.06
0.02
0.02
0.62
0.18
0.08
0.08
CA Cole
EC
Aerial
Ground
Y
Y
2.79
0.59
0.29
0.1
0.15
0.03
0.31
0.11
CACorn
EC
Aerial
Ground
Y
Y
2.74
0.55
0.26
0.07
0.15
0.03
0.28
0.08
CA Cotton
EC
Aerial
Ground
Y
Y
5.55
1.48
0.65
0.24
0.30
0.08
0.70
0.26
CA Melon
EC
Ground
Y
0.73
0.13
0.04
0.14
105
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Table 5.1 Acute and Chronic RQs for Aquatic-phase CRLF and DS (freshwater fish
surrogate) Resulting from Trifluralin Application
Crop Scenario/
Formulation
Application
Method
Soil
Incorporation
Peak EEC
Ug/L
60 day
EEC ^g/L
Acute
RQs1
Chronic
RQs2
CA Lettuce
EC
Aerial
Ground
Y
Y
2.77
0.58
0.27
0.08
0.15
0.03
0.29
0.09
CA Onion
EC
Aerial
Ground
Y
Y
1.96
0.39
0.21
0.05
0.11
0.02
0.23
0.05
CA Potato
EC
Ground
Y
0.55
0.05
0.03
0.05
CA Rangeland Hay
Granular
Ground | N
0.68
0.12
0.04
0.13
CA Tomato
EC
Ground
Y
0.56
0.06
0.03
0.06
CA Row Crop
EC
Aerial
Ground
Y
Y
5.49
1.01
0.45
0.09
0.30
0.05
0.48
0.10
CA Sugar Beet
EC
Aerial
Ground
Y
Y
1.96
0.39
0.17
0.03
0.11
0.02
0.18
0.03
CA Wheat
EC
Aerial
Ground
Y
Y
2.77
0.57
0.29
0.11
0.15
0.03
0.31
0.12
Non-agricultural Uses
CA Nursery
Granular
EC
Ground
Ground
N
N
6.55
6.53
0.86
0.87
0.35
0.35
0.92
0.94
CA Residential
Granular
Ground
N
0.0002
0.00005
0.01
0.01
CA Right-of-way
Granular
Ground
N
0.002
0.0005
0.01
0.01
CATurf
Granular
Ground
N
0.16
0.02
0.01
0.02
CA Forestry
Granular
EC
Ground
Aerial
Ground
N
Y
Y
2.25
5.5
1.17
0.39
0.63
0.19
0.12
0.30
0.06
0.42
0.68
0.20
u 2 LOG exceedences (acute RQ > 0.05; chronic RQ > 1.0) are bolded. Acute RQ = use-specific peak EEC / 96-
h LC50 = 18.5ug/L forbluegill sunfish. Chronic RQ = use-specific 60-day EEC / NOAEC = 0.93 ug/L ACR
value ( rainbow trout LC50 43.6 ug/L/rainbow trout NOAEC 2.18 ug/L = 20; bluegill sunfish LC 50 18.5 ug/L
/ 20= ACR 0.93 ug/L)
5.1.1.2 Freshwater Invertebrates
Acute risk to freshwater invertebrates is based on peak EECs in the standard PRZM/EXAMS
pond and the lowest acute toxicity value for freshwater invertebrates. Based on freshwater
invertebrate toxicity data (ECso value of 251 |ig/L for daphnid) and modeled aquatic peak EECs
for various use scenarios used to represent all of the agricultural uses of trifluralin in CA, no
acute RQs resulted in a Listed Species LOG exceedance (all RQ < 0.05) (Appendix O).
106
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Chronic risk is based on 21-day EECs and the lowest chronic toxicity value for freshwater
invertebrates. Based on 21-day EECs for various use scenarios used to represent all of the
agricultural uses of trifluralin in CA, and the NOAEC of 2.4 |ig/L, no RQs resulted in a Chronic
LOC exceedance (all RQ < 1.0) (Appendix O).
Since the RQs do not exceed the Listed Species LOC (all RQ < 0.05) or the Chronic LOC (all
RQ < 1.0), trifluralin is determined to have no indirect effects to those listed species that rely on
freshwater invertebrates during at least some portion of their life-history (i.e., aquatic-phase
CRLF, DS, and SFGS).
5.1.1.3 Non-vascular Aquatic Plants
Acute risk to aquatic non-vascular plants is based on peak EECs in the standard pond and the
lowest acute toxicity value. Based on the aquatic non-vascular plant toxicity datum (ICso = 21.9
|ig/L for the marine diatom (Skeletonema costatum) and the maximum aquatic peak EEC of all
trifluralin scenarios, all RQs for aquatic non-vascular plants are < 0.30 (Appendix O). Since the
RQs do not exceed the Acute LOC (all RQ < 1.0), trifluralin is determined to have no indirect
effects to those listed species that rely on non-vascular aquatic plants during at least some portion
of their life-history (i.e., aquatic-phase CRLF, DS, and SFGS).
5.1.1.4 Aquatic Vascular Plants
Acute risk to aquatic vascular plants is based on peak EECs in the standard pond and the lowest
acute toxicity value. Based on the aquatic vascular plant toxicity datum (ICso = 49.7 jig/L for the
Lemna gibba and the maximum aquatic peak EEC of all trifluralin scenarios, all RQs for aquatic
vascular plants are < 0.13 (Appendix O). Since the RQs do not exceed the Acute LOC (all RQ <
1.0), trifluralin is determined to have no indirect effects to those listed species that rely on
vascular aquatic plants during at least some portion of their life-history (i.e., aquatic-phase
CRLF, DS, and SFGS).
5.1.1.5 Bioaccumulation of Trifluralin in Aquatic Prey Items
As discussed in Section 3.4, trifluralin has the potential to accumulate in tissues of aquatic
organisms. Since the CRLF and the SFGS consume algae, aquatic invertebrates and fish, they
could be exposed to trifluralin accumulated in the tissues of these prey. In order to define the
risks of the CRLF and the SFGS consuming benthic invertebrates and fish, KABAM was used to
derive RQ values for small (1.4 g), medium (37 g) and large (238 g) CRLF as well as juvenile (2
g), adult male (113 g), and adult female (227 g) SFGS. Diet assumptions assigned to each of
these species and size classes are provided in Table 5.2. The resulting RQ values for the CRLF
and SFGS are provided in Table 5.3. RQ values for all size classes did not exceed the LOC for
chronic dietary-based exposures to the CRLF or the SFGS through consumption of contaminated
aquatic prey that have accumulated trifluralin. Acute RQs were not calculated as the avian acute
toxicity studies resulted in no mortalities or sublethal effects at the highest dose tested. This
highest dose was higher than exposure levels expected in the environment.
107
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Table 5.2. Diet Assumptions of CRLF and SFGS used in KABAM.
Trophic level
in diet
phytoplankton
zooplankton
benthic
invertebrates
filter feeders
small fish
medium fish
large fish
Total
Diet for:
small CRLF
(0.0014 kg)
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
med CRLF 1
(0.037 kg)
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
med CRLF 2
(0.037kg)
0.0%
0.0%
0.0%
0.0%
100.0%
0.0%
0.0%
100.0%
large CRLF 1
(0.238 kg)
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
large CRLF 2
(0.238 kg)
0.0%
0.0%
0.0%
0.0%
0.0%
100.0%
0.0%
100.0%
Trophic
Level in Diet
Phytoplankton
Zooplankton
Benthic
Invertebrate
Filter feeders
Small fish
Medium Fish
Large Fish
Total
Juv SFGS
(0.002 kg)
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
Adult Male
SFGS1
(0.113 kg)
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
Adult Male
SFGS 2
(0.113 kg)
0.0%
0.0%
0.0%
0.0%
0.0%
100.0%
0.0%
100.0%
Adult Female
SFGS1
(0.227kg)
0.0%
0.0%
100.0%
0.0%
0.0%
0.0%
0.0%
100.0%
Adult Female
SFGS 2
(0.227 kg)
0.0%
0.0%
0.0%
0.0%
0.0%
100.0%
0.0%
100.0%
108
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Table 5.3. Chronic RQs for CRLF and SFGS Through Consumption
of Aquatic Organisms which have Accumulated Trifluralin.
Species, Size Class, and Diet1
small CRLF
med CRLF 1
med CRLF 2
large CRLF 1
large CRLF 2
juv SFGS
SFGS male 1
SFGS male 2
SFGS female 1
SFGS female 2
Chronic, Dietary Based RQ2
0.013
0.013
0.021
0.013
0.028
0.013
0.013
0.030
0.013
0.030
1 See Table 5.2 for definitions of size class and diet.
2 Based on NOAEC = 500 mg/kg-diet (for mallard duck), bolded values exceed chronic
risk LOC(RQ> 1.0)
5.1.2 Exposures in the Terrestrial Habitat
5.1.2.1 Birds (Surrogate for Reptiles and Terrestrial-phase Amphibians)
As previously discussed in Section 3.6, potential direct effects to terrestrial species are based on
spray and granular applications of trifluralin. Potential risks to birds (and, thus, reptiles and
terrestrial-phase amphibians) are derived using T-REX, acute and chronic toxicity data for the
most sensitive bird species for which data are available, and a variety of body-size and dietary
categories.
Spray applications (no soil incorporation)
Potential direct acute effects to the terrestrial-phase CRLF and SFGS are derived by considering
dose- and dietary-based EECs modeled in T-REX for a small bird (20 g) consuming small
invertebrates (Table 3.5) and acute oral and subacute dietary toxicity endpoints for avian
species. RQs for the non-definitive acute oral and subacute dietary toxicity endpoints for avian
species were not calculated because the acute avian effects data shows no mortality and no
sublethal effects at any of the test concentrations (i.e., LD50 > 2000 mg/kg-bwt and LCso > 5000
mg/kg-diet). Potential risks are qualitatively discussed in Section 5.2.
109
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Potential direct chronic effects of trifluralin to the terrestrial-phase CRLF and SFGS are derived
by considering dietary-based exposures modeled in T-REX for birds consuming small insects.
EECs are divided by toxicity values to estimate chronic dietary-based RQs (NOAEC = 500
mg/kg-diet for mallard duck). The small insect RQ for the nursery scenario was 1.51, which
exceeded the chronic LOG (RQ>1) (Table 5.4).
Based on exceedances of the Agency's chronic risk LOG (RQ > 1), trifluralin does have the
potential to directly affect the CRLF and SFGS. Additionally, since relevant chronic RQs are
exceeded, there is a potential for indirect effects to those listed species that rely on birds (and,
thus, reptiles and/or terrestrial-phase amphibians) during at least some portion of their life-cycle
(i.e., CRLF, SFGS and SJKF).
Table 5.4 Sun
(not soil incor
Use Category
Alfalfa
Nursery
imary of Chronic Dietary-based RQs for Birds for Spray Applications
porated)1
Application Rate
(Interval days)
1 app @ 2 Ibs/acre
3 app @ 4 Ibs/acre
(60 days)
Dietary Category
Short Grass
Tall Grass
Broadleaf Plants/ Small
Insects
Fruits/Pods/ Seeds/
Large Insects
Short Grass
Tall Grass
Broadleaf Plants/ Small
Insects
Fruits/Pods/ Seeds/
Large Insects
Avian Chronic Dietary based RQs
Direct Effects for CRLF and SFGS
(Small insects - avion dietary category)
Indirect Effects for CRLF, SFGS and SJKF
(all avion dietary categories listed below)
0.96
0.44
0.54
0.06
2.68
1.23
1.51
0.17
Chronic RQ > 1.0 exceeds chronic level of concern (LOG) for birds are bolded.
Granular applications (not soil incorporated)
Potential direct acute effects to the terrestrial-phase CRLF and SFGS are also evaluated by
considering granule consumption (LD50/sq-ft). LD50s/sq-ft were calculated at single application
rates of 1.5, 2, and 4 Ibs/acre for three weight classes (20, 100, and lOOOg individuals). RQs for
the non-definitive acute oral endpoint for avian species were not calculated because the acute
avian effects data shows no mortality and no sublethal effects at any of the test concentrations
110
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(i.e., LD50 > 2000 mg/kg-bwt). Comparisons of exposure levels with highest dose tested and any
potential risks are qualitatively discussed in Section 5.2.
Spray and granular applications (soil incorporated)
For acute risk estimation, if the granular material is soil incorporated immediately after
application, it is assumed that 1% of the material is available to terrestrial organisms (USEPA
1992). It was assumed that the availability of soil-incorporated spray material to terrestrial
organisms would be similar to that of soil-incorporated granular pesticides. These EECs are
derived by calculating 1% of the EECs based on the LD50/sq ft exposure calculations. Therefore,
the EEC for incorporated trifluralin at the highest single application rate of 2 Ibs/acre is 0.21
mg/sq ft. Comparisons of exposure levels with highest acute dose tested and any potential risks
are qualitatively discussed in Section 5.2.
5.1.2.2 Mammals
Potential risks to mammals are derived using T-REX, acute and chronic rat toxicity data, and a
variety of body-size and dietary categories.
Spray applications (no soil incorporation)
Potential direct acute effects specifically to the SJKF are derived by considering dose- and
dietary-based EECs modeled in T-REX for a large mammal (1,000 g) consuming a variety of
dietary items (Table 3.5) and acute oral toxicity endpoints for rats. RQs for the non-definitive
acute oral endpoint for mammalian species were not calculated because the acute mammalian
effects data shows no mortality at the highest test concentration (i.e., LD50 > 5000 mg/kg-bwt). ).
Comparisons of exposure levels with highest dose tested and any potential risks are qualitatively
discussed in Section 5.2.
Potential indirect acute effects to the terrestrial-phase CRLF, SFGS, and SJKF are derived by
considering dose- and dietary-based EECs modeled in T-REX for all mammal sizes (15, 35, and
1000 g) consuming a variety of dietary items (Table 3.5) and acute oral toxicity endpoints for
rats. RQs for the non-definitive acute oral endpoint for mammalian species were not calculated
because the acute mammalian effects data shows no mortality at the highest test concentration
(i.e., LDso > 5000 mg/kg-bwt). Comparisons of exposure levels with highest dose tested and any
potential risks are qualitatively discussed in Section 5.2.
Chronic RQs (dose-based) for mammals are derived with T-REX using a NOAEL of 10 mg/kg-
bwt for rats. Exceeding RQs ranged from 1.30 to 58.20 for the small mammal (15 g), 1.11 to
49.72 for the medium mammal (35 g) and from 1.67 to 26.65 for the large mammal (1000 g)
(Table 5.5). Two modeled scenarios for liquid applications exceeded the Agency's chronic risk
LOG (RQ>1) for mammals for at least some of the food categories.
Chronic RQs (dietary-based) for mammals are derived with T-REX using a calculated NOAEC
(200 mg/kg-diet) which is based on the chronic dose-based NOAEL of 10 mg/kg-bwt for rats.
Ill
-------
Exceeding RQs (>1.0) ranged from 1.10 to 6.71 for the alfalfa and nursery scenarios (liquid
applications) for mammals.
Based on exceedances of the Agency's chronic risk LOG (RQ>1), trifluralin has the potential to
directly affect the SJKF. Additionally, since chronic RQs are exceeded, there is a potential for
indirect effects to those listed species that rely on mammals during at least some portion of their
life-cycle (i.e., CRLF, SFGS, and SJKF).
Table 5.5 Summary of Chronic Dietary- and Dose-based RQs for Mammals for Spray
Applications1
Use
Category
Alfalfa
Nursery
Application Rate
(Interval days)
1 app @ 2 Ibs/acre
3 app @ 4 Ibs/acre
(60 days)
Dietary Category
Short Grass
Tall Grass
Broadleaf Plants/ Small
Insects
Fruits/Pods/ Seeds/
Large Insects
Granivore2
Short Grass
Tall Grass
Broadleaf Plants/ Small
Insects
Fruits/Pods/ Seeds/
Large Insects
Granivore2
Direct Effects for SJKF (1000 g
mammal only)
Indirect Effects for SJKF
(mammalian prey, all weight
classes)
Indirect Effects for CRLF and
SFGS (mammalian prey, 15g
only)
Mammalian
Chronic Dosed based RQs
15 g
20.82
9.54
11.71
1.30
0.29
58.20
26.68
32.74
3.64
0.81
35 g
17.79
8.15
10.00
1.11
0.25
49.72
22.79
27.97
3.11
0.69
1000 g
9.53
4.37
5.36
0.60
0.13
26.65
12.21
14.99
1.67
0.37
Direct Effects for
SJKF
Indirect Effects
for CRLF, SFGS
and SJKF
Mammalian
Chronic Dietary
based RQs
2.40
1.10
1.35
0.15
NA
6.71
3.07
3.77
0.42
NA
:LOC exceedances (RQ > 1) are bolded
2 Indirect effects only occur for granivore dietary category all other dietary categories include both direct/indirect
effects
112
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Granular applications (not soil incorporated)
Potential direct acute effects to mammals are also evaluated by considering granule consumption
(LD50/sq-ft). LDsoS/sq-ft were calculated at single application rates of 1.5, 2, and 4 Ibs/acre for
three weight classes (15, 35, and lOOOg individuals). RQs for the non-definitive acute oral
endpoint for mammalian species were not calculated because the acute mammalian effects data
shows no mortality and no sublethal effects at any of the test concentrations (i.e., LDso > 5000
mg/kg-bwt). Comparisons of exposure levels with highest dose tested and any potential risks are
qualitatively discussed in Section 5.2.
Spray and granular applications (soil incorporated)
For acute risk estimation, if the granular material is soil incorporated immediately after
application, it is assumed that 1% of the material is available to terrestrial organisms (USEPA
1992). It was assumed that the availability of soil-incorporated spray material to terrestrial
organisms would be similar to that of soil-incorporated granular pesticides. These EECs are
derived by calculating 1% of the EECs based on the LD50/sq ft exposure calculations. Therefore,
the EEC for incorporated trifluralin at the highest single application rate of 2 Ibs/acre is 0.21
mg/sq ft. Comparisons of exposure levels with highest acute dose tested and any potential risks
are qualitatively discussed in Section 5.2.
5.1.2.3 Terrestrial Invertebrates
In order to assess the risks of spray applications of trifluralin to terrestrial invertebrates, the
honey bee is used as a surrogate for terrestrial invertebrates. The toxicity value for terrestrial
invertebrates is calculated by multiplying the lowest available acute contact LD50 > 24.17 jig/bee
by 1 bee/0.128g, which is based on the weight of an adult honey bee. EECs (|ig/g of bee)
calculated by T-REX for small and large insects are divided by the calculated toxicity value for
terrestrial invertebrates, which is 188 jig/g of bee. It is important to note that the calculated RQs
may overestimate risk as the LD50 values from all submitted bee studies were non-definitive
(50% mortality was not reached at the highest dose). RQs for the non-definitive acute contact
endpoint for terrestrial invertebrates were not calculated because the acute bee effects data did
not allow for calculation of a definitive LD50 although mortality was observed at the highest test
dose. Comparisons of exposure levels with highest dose tested and any potential risks are
qualitatively discussed in Section 5.2.
5.1.2.4 Terrestrial Plants
Generally, for indirect effects, potential effects on terrestrial vegetation are assessed using RQs
from terrestrial plant seedling emergence and vegetative vigor EC25 data as a screen. All RQs are
provided in Appendix O, and example output from TerrPlant v. 1.2.2 is provided in Appendix
M
Based on the TerrPlant modeling results, there are LOG exceedances for 23 out of 25 uses for at
least one of the application methods for risks to non-listed monocot plants. Fourteen out of 25
uses for at least one of the application methods resulted in LOG exceedances for non-listed dicot
113
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plants. RQs that exceed the LOG range from 1.11 to 4.89 for monocots and 1.05 to 2.32 for
dicots (Tables 5.6 and 5.7). Since the non-listed plant RQs are exceeded, there is a potential for
indirect effects to those listed species that rely on terrestrial plants during at least some portion of
their life-cycle (i.e., CRLF, SFGS, SJKF andDS).
Table 5.6 TerrPlant RQs for Monocots Inhabiting Dry and Semi-aquatic Areas Exposed
to Trifluralin via Runoff and Drift from Liquid and Granular Applications (single
application only); only scenarios with RQs exceeding the LOC are reported.
Scenario
Avocado
Citrus
Grapes and
berries
Olive
Stone and
Pome fruit
Tree nuts
Nursery
Right of way
Forestry
Alfalfa
Citrus
Grapes
Stone and
Pome fruit
Tree nuts
Cotton
Row crop
Forestry
Alfalfa
Com
Cole
Lettuce
Wheat
Rangeland
Hay
Turf
Residential
Nursery
Formulation1
G
G
EC
EC
EC
G
G
EC
Method1*
Ground
Aerial *
Ground *
Aerial*
Ground*
Aerial
Ground
Aerial *
Ground
Ground
Ground
Application
Rate
(Ib/acre)
4
2
2
2
1
2
1.5
4
Drift
Value
(%)
0
0
5
1
5
1
5
0
0
1
Dry Area
RQ
0.44
0.11
1.22
0.33
1.33
0.44
0.61
0.22
0.17
0.89
Semi-
aquatic
Area RQ
4.44
1.11
2.22
1.33
3.33
2.44
1.11
2.22
1.67
4.89
Spray
Drift RQ
N/A
N/A
1.11
0.22
1.11
0.22
0.56
N/A
N/A
0.44
* 2 inch incorporation
:G = Granular application. EC = Emulsifiable Concentrate
LOC exceedances (RQ > 1) are bolded
114
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Table 5.7 TerrPlant RQs for Dicots Inhabiting Dry and Semi-aquatic Areas Exposed to
Trifluralin via Runoff and Drift from Liquid and Granular Applications (single application
only); only scenarios with RQs exceeding the LOC are reported
Scenario
Avocado
Citrus
Grapes and
berries
Olive
Stone and Pome
fruit
Tree nuts
Nursery
Right of way
Forestry
Citrus
Grapes
Stone and Pome
fruit
Tree nuts
Cotton
Row crop
Forestry
Alfalfa
Rangeland Hay
Nursery
Formulation1
G
EC
EC
G
EC
Method1*
Ground
Aerial*
Ground*
Aerial
Ground
Ground
Ground
Application
Rate
(Ib/acre)
4
2
2
2
4
Drift
Value (%)
0
5
1
5
1
0
1
Dry Area
RQ
0.21
0.58
0.16
0.63
0.21
0.11
0.42
Semi-
aquatic
Area RQ
2.11
1.05
0.63
1.58
1.16
1.05
2.32
Spray Drift
RQ
N/A
0.53
0.11
0.53
0.11
N/A
0.21
* 2 inch incorporation
:G = Granular application. EC = Emulsifiable Concentrate
Bolded numbers exceed LOC=1
5.1.3 Primary Constituent Elements of Designated Critical Habitat
For trifluralin use, the assessment endpoints for designated critical habitat PCEs involve the
same endpoints as those being assessed relative to the potential for direct and indirect effects to
the listed species assessed here. Therefore, the effects determinations for direct and indirect
effects are used as the basis of the effects determination for potential modification to designated
critical habitat.
5.2 Risk Description
The risk description synthesizes overall conclusions 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 assessed species and the potential for modification
of their designated critical habitat.
115
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If the RQs presented in the Risk Estimation (Section 5.1) show no direct or indirect effects for
the assessed species, and no modification to PCEs of the designated critical habitat, a "no effect"
determination is made, based on trifluralin's use within the action area. However, if LOCs for
direct or indirect effect are exceeded or effects may modify the PCEs of the critical habitat, the
Agency concludes a preliminary "may affect" determination for the FIFRA regulatory action
regarding trifluralin. A summary of the risk estimation results are provided in Table 5.8 for
direct and indirect effects to the listed species assessed here and in Table 5.9 for the PCEs of
their designated critical habitat.
Table 5.8 Risk Estimation Summary for Trifluralin - Direct and Indirect Effects
Taxa<»
Freshwater Fish
and Aquatic-
phase
Amphibians
Freshwater
Invertebrates
Vascular
Aquatic Plants
Non-Vascular
Aquatic Plants
Birds, Reptiles,
and Terrestrial-
Phase
Amphibians
Mammals
LOC
Exceedances
(Y/N)
Y
N
N
N
Acute (not
determined)
Chronic
(yes)
Acute (not
determined)
Chronic
Description of Results of Risk Estimation
Acute RQs range from 0.05 to 0.35; exceeding the
Agency's acute listed species LOC (0.05) in 18 out of 25
crop scenarios with at least one of the application methods.
There are no exceedances of the Agency's chronic LOC
(1.0) for freshwater fish.
There are no exceedances of the Agency's acute listed
species LOC (0.05) for freshwater invertebrates.
There are no exceedances of the Agency's chronic LOC
(1.0) for freshwater invertebrates.
There are no exceedances of the Agency's LOC for aquatic
vascular plants (1.0)
There are no exceedances of the Agency's LOC for aquatic
non-vascular plants (1.0)
RQs for the non-definitive acute endpoints for avian species
were not calculated because the acute avian effects data
shows no mortality and no sublethal effects at any of the
test concentrations. Comparisons of exposure levels with
highest dose tested and any potential risks are qualitatively
discussed in Section 5.2.
The chronic (dietary-based) RQs for birds exceeded the
chronic LOC (RQ>1) for the nursery use category (liquid
application). Chronic RQs ranged from 1.23 to 2.68 for
various dietary categories (i.e., short grass, tall grass and
broadleaf plants and insects).
RQs for the non-definitive acute endpoints for mammalian
species were not calculated because the mammalian effects
data shows no mortality and no sublethal effects at any of
the test concentrations. Comparisons of exposure levels
Assessed Species
Potentially Affected
Direct Effects:
Aquatic -phase
CRLF, DS
Indirect Effects:
Aquatic -phase
CRLF, SFGS
Indirect Effects:
Aquatic -phase
CRLF, SFGS,
DS
Indirect Effects:
Aquatic -phase
CRLF, SFGS,
DS
Indirect Effects:
Aquatic-phase
CRLF, SFGS, DS
Direct Effects:
Terrestrial-phase
CRLF, SFGS
Indirect Effects:
Terrestrial-phase
CRLF, SFGS,
SJKF
Direct Effects:
SJKF
Indirect Effects:
116
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Table 5.8 Risk Estimation Summary for Trifluralin - Direct and Indirect Effects
Taxa(1>
Terrestrial
Invertebrates
Plants -
Monocots
Terrestrial
Plants - Dicots
LOG
Exceedances
(Y/N)
(yes)
Not
determined
Y
Y
Description of Results of Risk Estimation
with highest dose tested and any potential risks are
qualitatively discussed in Section 5.2.
For liquid application, no soil incorporation,chronic dose-
based RQs that exceed the chronic LOG all weight classes
of mammals range from 9.53 to 58.20 for short grass; 4.37
to 26.68 for tall grass; 5.36 to 32.74 broadleaf plants/small
insects; 1.11 to 3.64 for fruits/pods/seeds/large insect. RQs
for all weight classes for granivores (nursery and alfalfa)
and large mammals consuming fruits/pods/seeds/large
insects (alfalfa) did not exceed the Chronic LOG.
Chronic dietary -based RQs (liquid application, no soil
incorporation) for mammals exceed the Agency's chronic
LOG (1.0) for the nursery and alfalfa use categories with
RQs ranging from 2.40 to 6.71 for short grass; 1.10 to 3. 07
for tall grass and 1.35 to 3.77 for broadleaf plants/small
insects. RQs for the fruits/pods/seeds/large insects feeding
guild did not exceed the Chronic LOG.
RQs for the non-definitive acute endpoints for terrestrial
invertebrates were not calculated because the acute avian
effects data did not allow estimation of an LD50 (mortality
<50% at all test concentrations). Comparisons of exposure
levels with highest dose tested and any potential risks are
qualitatively discussed in Section 5.2.
LOCs exceeded for 23 out of 25 modeled uses for at least
one of the application methods for risks to non-listed
monocot plants. RQs that exceed the acute LOG (1.0) range
from 1.11 to 4.89 for monocots.
LOCs exceeded for 14 out of 25 modeled uses for at least
one of the application methods for non-listed dicot plants.
RQs that exceed the acute LOG (1.0) range from 1.05 to
2.32 for dicots.
Assessed Species
Potentially Affected
Terrestrial-phase
CRLF, SFGS,
SJKF
Indirect Effects:
Terrestrial
phase CRLF,
SFGS, SJKF
Indirect Effects:
CRLF, SFGS,
SJKF, DS
Indirect Effects:
CRLF, SFGS,
SJKF, DS
Risks to estuarine/marine fish and estuarine/marine invertebrates were not assessed because the most sensitive
freshwater fish and freshwater fish invertebrates toxicity data was use to estimate direct and indirect risks to the
DS.
117
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Table 5.9 Risk Estimation Summary for Trifluralin- Effects to Designated Critical
Habitat (PCEs) for CRLF and DS
Taxa(1)
May Affect
Habitat
(Y/N)
Description of Results of Risk Estimation
Species
Associated with
Designated
Critical Habitat
that May be
Modified
Freshwater Fish
and Aquatic-
phase
Amphibians
Y
Acute RQs range from 0.05 to 0.35; exceeding the
Agency's acute listed species LOG (0.05) in 18 out of 25
crop scenarios with at least one of the application
methods.
There are no exceedances of the Agency's chronic LOG
(1.0) for freshwater fish.
CRLF, DS
Freshwater
Invertebrates
N
There are no exceedances of the Agency's acute listed
species LOG (0.05) for freshwater invertebrates.
There are no exceedances of the Agency's chronic LOG
(1.0) for freshwater invertebrates.
CRLF, DS
Vascular
Aquatic Plants
CRLF, DS
N
There are no exceedances of the Agency's LOG for
vascular aquatic plants (1.0)
Non-Vascular
Aquatic Plants
N
There are no exceedances of the Agency's LOG for non-
vascular aquatic plants (1.0)
CRLF, DS
Birds, Reptiles,
and Terrestrial-
Phase
Amphibians
Acute (not
determined)
Chronic
(yes)
RQs for the non-definitive acute endpoints for avian
species were not calculated because the acute avian
effects data shows no mortality and no sublethal effects at
any of the test concentrations. Comparisons of exposure
levels with highest dose tested and any potential risks are
qualitatively discussed in Section 5.2.
The chronic (dietary-based) RQs for birds exceeded the
chronic LOG (RQ>1) for the nursery use category (liquid
application, no soil incorporation). Chronic RQs ranged
from 1.23 to 2.68 for various dietary categories (i.e., short
grass, tall grass and broadleaf plants and insects).
CRLF
Mammals
Acute (not
determined)
Chronic
(yes)
RQs for the non-definitive acute endpoints for
mammalian species were not calculated because the acute
avian effects data shows no mortality and no sublethal
effects at any of the test concentrations. Comparisons of
exposure levels with highest dose tested and any potential
risks are qualitatively discussed in Section 5.2.
For liquid application, no soil incorporation,chronic dose-
based RQs that exceed the chronic LOG all weight classes
of mammals range from 9.53 to 58.20 for short grass;
4.37 to 26.68 for tall grass; 5.36 to 32.74 broadleaf
plants/small insects; 1.11 to 3.64 for
fruits/pods/seeds/large insect. RQs for all weight classes
for granivores (nursery and alfalfa) and large mammals
CRLF
118
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Table 5.9 Risk Estimation Summary for Trifluralin- Effects to Designated Critical
Habitat (PCEs) for CRLF and DS
Taxa
(i)
May Affect
Habitat
(Y/N)
Description of Results of Risk Estimation
Species
Associated with
Designated
Critical Habitat
that May be
Modified
consuming fruits/pods/seeds/large insects (alfalfa) did not
exceed the Chronic LOG.
Chronic dietary-based RQs (liquid application, no soil
incorporation) for mammals exceed the Agency's
chronic LOG (1.0) for the nursery and alfalfa use
categories (liquid application) with RQs ranging from
2.40 to 6.71 for short grass; 1.10 to 3.07 for tall grass and
1.35 to 3.77 forbroadleaf plants/small insects;.
Terrestrial
Invertebrates
Not
determined
RQs for the non-definitive acute endpoints for terrestrial
invertebrates were not calculated because the acute avian
effects data did not allow estimation of an LD50 (mortality
<50% at all test concentrations). Comparisons of
exposure levels with highest dose tested and any potential
risks are qualitatively discussed in Section 5.2.
CRLF
Terrestrial
Plants -
Monocots
Y
LOCs exceeded for 23 out of 25 modeled uses for at least
one of the application methods for risks to non-listed
monocot plants. RQs that exceed the acute LOG (1.0)
range from 1.11 to 4.89 formonocots.
CRLF, DS
Terrestrial
Plants -Dicots
Y
LOCs exceeded for 10 out of 25 modeled uses for at least
one of the application methods for non-listed dicot plants.
RQs that exceed the acute LOG (1.0) range from 1.05 to
2.32 for dicots.
CRLF, DS
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 assessed species. 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
assessed species and its designated critical habitat.
The criteria used to make determinations that the effects of an action are "not likely to adversely
affect" the assessed species or modify 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.
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• Harass is defined as actions that create the likelihood of injury to listed species
to such an extent as to significantly disrupt normal behavior patterns which
include, but are not limited to, breeding, feeding, or sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are extremely
unlikely to occur.
• 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 assessed species and their designated critical habitat is provided in Sections
5.2.1 through 5.2.4. The effects determination section for each listed species assessed will
follow a similar pattern. Each will start with a discussion of the potential for direct effects,
followed by a discussion of the potential for indirect effects. For those listed species that have
designated critical habitat, the section will end with a discussion on the potential for modification
to the critical habitat from the use of trifluralin.
5.2.1 California Red-legged Frog
5.2.1.1 Direct Effects (aquatic-phase)
The aquatic-phase considers life stages of the frog that are obligatory aquatic organisms,
including eggs and larvae. It also considers submerged terrestrial-phase juveniles and adults,
which spend a portion of their time in water bodies that may receive runoff and spray drift
containing trifluralin.
Based on the evidence presented below, there is a potential for direct impact to the aquatic-phase
CRLF.
LOC exceedances:
Of the 25 scenarios modeled, for at least one of the application methods the listed species LOC
was exceeded in almond, avocado, citrus, fruit, grape (including berries), grape, olive, alfalfa,
corn, cotton, lettuce, onion, cole, row crop, sugar beet, wheat, nursery and forestry (exceeding
RQs ranged from 0.05 to 0.35). The Chronic LOC was not exceeded for any of the modeled
scenarios.
Probability of individual effect:
For all modeled scenarios, the likelihood of an individual effect (mortality) was <1 in 3280 at the
calculated RQ and at the Listed Species LOC.
Species sensitivity analysis:
A formal species sensitivity analysis was not conducted, since data from only two species offish
were available for this assessment. For the bluegill sunfish and rainbow trout, the LD50's ranged
from 18.5 to 43.6 |ig/L. Nominal concentrations were reported for these two studies; therefore,
both LD50s may overestimate the actual exposure concentration due to trifluralin's tendency to
volatilize and sorb to surfaces.
120
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Analysis of aquatic-phase amphibian data:
As previously discussed in the aquatic toxicity portion of this assessment (Section 4.1), aquatic
amphibian data were submitted by the registrant and available in the open literature. However,
since these data were less sensitive than the freshwater fish data and it is unknown where the
CRLF falls on sensitivity distribution for aquatic-phase amphibians or on a sensitivity
distribution for aquatic vertebrates, EFED determined that using the most sensitive aquatic
vertebrate toxicity data would be appropriate. In order to characterize risk, the most sensitive
amphibian toxicity value for trifluralin (Fowler's toad with LC50 =100 ug/L, Sanders (1970,
E2891) was used to calculate RQs (Appendix O). The Listed Species LOG was exceeded for at
least one application method and rate for ten of the modeled scenarios with exceeding RQs
ranging from 0.05 to 0.07. It is important to note that this analysis may not reflect the sensitivity
of the CRLF to trifluralin as the relative sensitivity of the CRLF to Fowler's toads is unknown.
In addition, the LD50 and, thus, the RQs are based nominal concentrations of trifluralin. Since
trifluralin is volatile and sorbs to surfaces, these concentrations from the toxicity study and, thus,
the calculated LDso are likely higher than the actual exposure concentration experienced by the
tested animals. If the actual exposure concentrations in the toxicity study were less than the
nominal concentrations used for calculating the LD50, the calculated frog RQs would be higher if
actual exposure concentrations were used.
Sublethal chronic effects:
Fish exposed to trifluralin may also develop vertebral dysplasia, which could significantly
impact the fishes' ability to swim, and therefore, impact its fitness. In a study conducted by
Couch (1979, E6425), sheepshead minnows exposed to 5.5 to 31 ug/L of trifluralin during the
first 28 days of life developed a vertebral dysplasia. Effects of the abnormal vertebral
development were dorsal vertebral growth into the neural canal, ventral compression of renal
ducts, and longitudinal fusion of vertebrae. In a second study (Couch 1984, E48406), pituitaries
of sheepshead minnows, exposed for 19 months to 1-5 ug/L trifluralin in the laboratory exhibited
enlargement, pseudocysts, congestion of blood vessels and oedema. Most of the fish with an
enlarged pituitary also had induced diffuse and/or focal vertebral hyperostosis and other
dysplastic vertebral changes. Koyama (1996, E17085) also observed vertebral deformities when
exposing 10 species offish to trifluralin with lesions observed in concentrations as low as 5 to 30
Ug/L, depending on species. The concentrations in these toxicity studies are within an order of
magnitude of the maximum concentrations observed in the monitoring data and many of the
chronic EECs estimated using PRZM/EXAMS.
Comparison of modeled to observed water concentrations:
Data from the CDPR surface water monitoring database website for trifluralin occurrences were
obtained on Jul 15, 2009 (http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm). A total of
3,915 surface water samples were analyzed for trifluralin from 1992 to 2006. Trifluralin was
detected in 600 samples (15% detection rate). Of the positive samples, the average concentration
was 0.06 ug/L and the highest reported concentration was 1.74 ug/L. Because this database
consists of data from a multitude of studies conducted in California, the LOQ is not consistent
across studies. The variation in the LOQ increases the uncertainty in the trifluralin detection rate
of 15% and adds uncertainty to the calculated average trifluralin concentration. These measured
concentrations are roughly comparable to the PRZM/EXAMS peak concentrations which range
121
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from 0.0002 to 6.55 |ig/L. Monitoring data may not reflect the actual maximum exposure
concentrations for several reasons:
• Monitoring sites were not necessarily targeted to areas of high trifluralin usage
• Sampling times were not designed to capture the high peak values and were not frequent
enough to assure the peak values were captured
• Water samples were filtered prior to analysis, removing trifluralin that had sorbed to
suspended particles in the water.
Even though these measured concentrations may not capture true peak values that occur in
California waters, if the observed measured concentration (1.74 |ig/L) was used as an exposure
value to calculate an acute freshwater fish RQ, there would be an exceedance of the Listed
Species LOG (RQ = 0.09).
Bioaccumulation in aquatic prey items:
As discussed in Section 3.4, trifluralin has the potential to accumulate in tissues of aquatic
organisms. Since the CRLF consume algae, aquatic invertebrates and fish, they could be exposed
to trifluralin accumulated in the tissues of these prey. Acute RQs were not calculated as the
avian acute toxicity studies resulted in no mortalities or sublethal effects at levels higher than
those expected in the environment. Using KABAM, the chronic RQ values for the CRLF for all
size classes did not exceed the LOG for chronic dietary-based exposures through consumption of
contaminated aquatic prey that have accumulated trifluralin (Table 5.3, all RQs < 0.05).
In a 28-day laboratory BCF study with bluegill sunfish (Lepomis macrochirus} exposed to
trifluralin, a BCF of 5,674 was observed in whole fish. The estimated steady-state BCF in
KAB AM for large fish was 26,226 which is a factor of 4.6 of the laboratory BCF for fish. The
accumulation and depuration rates of trifluralin in fish cannot be fully assessed because
radioactive residues in fish tissues were incompletely characterized. In addition, other chemical
properties of trifluralin, such as its volatility and short aqueous photolysis half-life, may mediate
the bioaccumulation in the environment.
Spray drift buffers:
The buffer distance needed to get below the acute aquatic fish Listed Species LOG was estimated
using AgDRIFT. This distance identifies those locations where water bodies can be impacted by
spray drift deposition alone (no runoff considered) resulting in concentrations above the LOG.
The most sensitive freshwater fish was the bluegill with an LCso value of 18.5|ig/L. Several
labels were used to represent the range of application methods (ground and aerial), application
rates (0.8 to 4.0 Ibs/acre), and drop size distribution specifications. Required buffer distance
under all evaluated labels ranged from 45.9 to 2359 feet (Table 5.10). These required buffer
distances only consider the exposure due to spray drift. Runoff (an important exposure
component for trifluralin) is not assessed in this spray drift analysis conducted with AgDRIFT.
This spray drift analysis does not include reproductive or growth effects or cumulative exposure
due to multiple applications.
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Table 5.10. Estimation of Buffer Distance Required to Eliminate LOC Exceedances (only spray
drift exposure considered) for Freshwater Fish Based on AgDRIFT
Pesticide
Label1
Treflan EC
062719-
00097
Treflan HFP
062719-
00250
Treflan HFP
062719-
00250
Treflan HFP
062719-
00250
Treflan HFP
062719-
00250
Treflan HFP
062719-
00250
Treflan HFP
062719-
00250
Application
Rate
(Ib/acre)
4.0
2.0
1.0
0.8
2.0
1.0
0.8
Method
(Boom Height
for Ground)
Ground (high)
Ground (high)
Ground (high)
Ground (high)
Aerial
Aerial
Aerial
Tier
I
I
I
I
III2
III2
III2
Parameters
DSD = ASAE very fine to fine
DSD = ASAE very fine to fine
DSD = ASAE very fine to fine
DSD = ASAE very fine to fine
DSD = ASAE Very fine to fine
Nonvol rate = 4.65 Ib/ac
Active rate = 2.0 Ib/ac
Spray vol rate = 5 gal/ac
Specific gravity(nonvol) = 1.116
Max downwind dist = 3000 ft
All else = defaults
DSD = ASAE Very fine to fine
Nonvol rate = 2.325 Ib/ac
Active rate =1.0 Ib/ac
Spray vol rate = 5 gal/ac
Specific gravity(nonvol) = 1.116
Max downwind dist = 3000 ft
All else = defaults
DSD = ASAE Very fine to fine
Nonvol rate =1.86 Ib/ac
Active rate = 0.8 Ib/ac
Spray vol rate = 5 gal/ac
Specific gravity(nonvol) = 1.116
Max downwind dist = 3000 ft
All else = defaults
Required
Buffer
Distance
(ft)
387.13
187.01
68.9
45.9
2264
2185
2106
1 Label did not specify droplet sizes; the most conservative size available was chosen: ASAE very fine to fine. Input
values were calculated as follows: (LC50 value of 18.5ug/L =18500 ng ) ( initial average concentration =18500 X aquatic
LOC of 0.05= 925 ng/1)
2 Tier I and Tier II resulted in distance estimates that were 'out of range ' ; Tier III estimates were used for the aerial
scenarios.
5.2.1.2
Direct Effects (Terrestrial-Phase)
The terrestrial-phase of the CRLF considers juvenile and adult life stages during which much
time is spent in a terrestrial habitat. Submerged terrestrial-phase CRLFs are not considered here;
their exposure is addressed as an aquatic-phase CRLF. Since no toxicity data were available for
terrestrial-phase amphibians or reptiles, toxicity data for birds were used as a surrogate.
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Acute risks from spray applications:
RQs for the non-definitive acute oral and subacute dietary toxicity endpoints for avian species
were not calculated because the acute avian effects data shows no mortality and no sublethal
effects at any of the test levels (i.e., LD50 > 2000 mg/kg-bwt and LC50 > 5000 mg/kg-diet). With
no soil incorporation, the dose-based EECs range from 1.94 to 1528.09 mg/kg-bwt, and dietary-
based EECs range from 30 to 1342 mg/kg-diet. These values are lower than the LD50 and LCso,
respectively; therefore, acute dose-based and acute dietary-based risks from spray applications
are unlikely. Since exposure from soil incorporated applications would be less than from non-
incorporated applications, risks from incorporated applications are also unlikely. The probability
of individual effect (mortality) for avian species was not calculated because the acute avian
effects data shows no mortality and no sublethal effects were observed at any of the test
concentrations (i.e., LD50 > 2000 mg/kg-bwt and LCso >5000 mg/kg-diet).
Acute risks from granular applications:
Potential direct acute effects to the terrestrial-phase CRLF are also evaluated by considering
granule consumption (LD50/sq-ft). Toxicity values were calculated for three weight classes (20,
100, and lOOOg individuals) based on the highest dose tested (2000 mg/kg-bwt in mallard ducks,
see TREX 1.4.1 Users Guide for details). The calculated toxicity values are >21, >130, and
>1560 mg/bird. The 20 and 100 g results are relevant for evaluating direct effects and indirect
effects (effects to prey base) of the terrestrial-phase CRLF. The EECs at single non-incorporated
application rates of 1.5, 2, and 4 Ibs/acre were 15.6, 20.8, and 41.7 mg/sq-ft, respectively, and the
EEC at a single soil-incorporated application rate of 2 Ibs/acre is 0.21mg/sq-ft. For the granular
non-incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or
exceeds the highest level tested for 20 g individuals; therefore, acute risks to small birds and
surrogate species cannot be precluded.
Chronic risks - LOC exceedances:
Of the two scenarios modeled for liquid applications, one scenario (nursery use, exceeding RQ =
1.51) resulted in an RQ that exceeded the Chronic LOC.
Chronic risks - T-HERPS refinements:
A refinement of the risks posed to the terrestrial-phase CRLF from ingestion of residues on prey
items (based on liquid applications of trifluralin) was performed using the T-HERPS v. 1.0
model. T-HERPS was used to refine chronic risks to the terrestrial-phase CRLF via consumption
of large insects, small herbivorous mammals, small insectivorous mammals, and small
terrestrial-phase amphibians exposed to liquid applications already identified by T-REX. In T-
HERPS, the nursery scenario with three applications of 4 Ibs/acre exceeded the chronic LOC
(1.0) with RQs of 1.77 and 1.51 for herptiles that consume small herbivore mammals and small
insects, respectively. Dietary-based chronic RQ values that exceed the LOC (1.0) are provided in
Table 5.11. All RQ values are reported in Appendix O.
T-HERPS can also be used to refine acute risks to herptiles; however, for this assessment, no
acute risks were identified. Therefore, refinements to acute risks were not assessed.
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Table 5.11 5
trifluralin s
Use
Category
Nursery
Summary of die
pray applicatio
Application
Rate
(Interval)
3 app @ 4
Ibs/acre
(60 days)
tary-based RQs for herpetofai
n using T-HERPS version 1.0.
Dietary Category
Broadleaf Plants/Small Insects2
Fruits/Pods/Seeds/Large Insects2
Small Herbivore Mammals3
Small insectivorous mammals4
Small terrestrial-phase amphibians5
ina estimated b
EEC
754.72
83.86
884.12
55.26
26.20
ased on the maximum
Chronic Dietary- Based
RQ1
1.51*
0.17
1.77*
0.11
0.05
1 RQ values in bold indicate exceedance the chronic LOG (1.0). Chronic dietary-base RQs were based on dietary-based
EECs divided by avian NOAEC value of 500 mg/kg-diet for mallard duck
2 Dietary -based EECs for Small and Large Insects calculated by T-HERPS are the same as those calculated by T-REX.
Resulting RQs are also identical (see Table 5.4).
3 Dietary -based EECs for Small Herbivore Mammals are derived by assuming that a small mammal (35 g) consumes
contaminated Short Grass prior to being consumed by the assessed herptile.
4 Dietary -based EECs for Small Insectivorous Mammals are derived by assuming that a small mammal (35 g) consumes
contaminated Large Insects prior to being consumed by the assessed herptile.
5 Dietary -based EECs for Small Terrestrial-phase Amphibians are derived by assuming that a small herptile (2.3 g)
consumes contaminated Small Insects prior to being consumed by the assessed herptile.
Chronic risks - Soil invertebrate consumption:
Chronic direct effects to terrestrial-phase CRLF that may consume soil invertebrates that have
accumulated trifluralin residues in their tissues were modeled; however, this pathway is not
included in T-REX. In order to explore the potential exposures of mammals and birds to total
residues of trifluralin that have accumulated in soil invertebrates inhabiting trifluralin treatment
sites, a simple fugacity approach was employed to estimate trifluralin concentrations in
earthworms and subsequent exposures to mammals and birds consuming earthworms.
Earthworms were chosen to represent all soil invertebrates that may be consumed by the
terrestrial organisms under evaluation. This approach is explained in detail in Appendix P.
Using a single application rate of 4 Ibs/acre, PRZM estimated trifluralin concentration are 6.41
g/m3 in soil, and the estimated concentration of trifluralin in earthworms is 147 mg/kg-
earthworm. If it is assumed that a bird or herptile consumes only contaminated soil invertebrates,
its dietary-based exposures would be approximately 30% of the NOAEC in the avian
reproduction study (NOAEC=500 mg/kg-diet). Therefore, chronic risks to terrestrial-phase
CRLF from consumption of trifluralin-contaminated soil invertebrates are unlikely.
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5.2.1.3 Indirect Effects (via Reductions in Prey Base)
5.2.1.3.1 Algae (non-vascular plants)
As discussed in Section 2.5.3, the diet of CRLF tadpoles is composed primarily of unicellular
aquatic plants (i.e., algae and diatoms) and detritus.
LOC exceedances:
All RQs for aquatic non-vascular plants are < 0.30 (no LOC exceedances).
Comparison of modeled to observed water concentrations:
As the EECs estimated for aquatic plants are the same as for freshwater fish, the discussion
presented in Section 5.2.1.1 is also applicable here. In summary, of the 3,915 non-targeted water
samples tested for trifluralin, only 15% had detectible concentrations of trifluralin; however,
those measured concentrations were comparable to the PRZM/EXAMS estimates.
Spray drift buffers:
Spray drift buffers were not determined as there were no exceedances of the LOC at maximum
label rates for all scenarios.
5.2.1.3.2 Aquatic Invertebrates
The potential for trifluralin to elicit indirect effects to the CRLF via effects on freshwater
invertebrate food items is dependent on several factors including: (1) the potential magnitude of
effect on freshwater invertebrate individuals and populations; and (2) the number of prey species
potentially affected relative to the expected number of species needed to maintain the dietary
needs of the CRLF. Together, these data provide a basis to evaluate whether the number of
individuals within a prey species is likely to be reduced such that it may indirectly affect the
CRLF.
Based on the evidence presented below, indirect impacts to aquatic-phase of the CRLF through
reductions in the prey base (specifically aquatic invertebrates) are not expected from acute or
chronic exposure to trifluralin.
LOC exceedances:
No acute or chronic LOC exceedances occurred for freshwater invertebrates with acute RQs
<0.05 and chronic RQs < 1.0 for all 25 application scenarios.
Percent effect analysis:
A percent effect analysis was conducted by determining an expected percent effect on the prey
item (aquatic invertebrates) at the Listed Species LOC of 0.05, implying effect at the calculated
EEC. The Listed Species LOC was used since there were no RQs exceeding 0.05, and a default
slope of 4.5 was used as one was not available from the submitted daphnid study. The percent
effect to aquatic invertebrates at the Listed Species LOC was calculated as 0.0000002%.
126
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Comparison of modeled to observed water concentrations:
As the EECs estimated for freshwater invertebrates are the same as for freshwater fish, the
discussion presented in Section 5.2.1.1 is also applicable here. In summary, of the 3,915 non-
targeted water samples tested for trifluralin, only 15% had detectible concentrations of trifluralin;
however, those measured concentrations were comparable to the PRZM/EXAMS estimates.
5.2.1.3.3 Fish and Aquatic-phase Frogs
Indirect effects to fish and frogs as food items are based on the direct effects analysis for aquatic-
phase CRLFs (Section 5.2.1.1). There is a potential for indirect impact to the aquatic-phase of
the CRLF due to reduction offish and aquatic-phase frogs as a prey base based on the
summarized lines of evidence below.
• There were Listed Species LOG exceedances in 18 of the 25 modeled scenarios.
• For all modeled scenarios, the likelihood of an individual effect (mortality) was <1 in
3280 at the calculated RQ.
• A formal species sensitivity analysis was not conducted; available data provided a range
of LD50's from 18.5 to 43.6 |ig/L for two species.
• Of the 3,915 non-targeted water samples tested for trifluralin, only 15% had detectible
concentrations of trifluralin; however, those measured concentrations were comparable to
the PRZM/EXAMS estimates.
• Available aquatic-phase amphibian data suggests trifluralin is less toxic to aquatic-phase
amphibians than to fish; however, there are Listed Species LOG exceedances for the most
sensitive aquatic-phase amphibian data.
• Fish exposed to trifluralin may also develop vertebral dysplasia, which could
significantly impact the fishes' ability to swim, and therefore, impact its fitness. The
concentrations in these toxicity studies are within an order of magnitude of the maximum
concentrations observed in the monitoring data and many of the chronic EECs estimated
using PRZM/EXAMS.
• Trifluralin has the potential to accumulate in tissues of aquatic organisms. The resulting
RQ values for the three size classes of frogs did not exceed the LOG for chronic dietary-
based exposures through consumption of aquatic prey that have accumulated trifluralin.
Acute RQs were not calculated as the avian acute toxicity studies resulted in no
mortalities at levels higher than those expected in the environment.
• The spray drift buffer distance needed to get below the acute aquatic fish Listed Species
LOG ranged from 45.9 to 2359 feet depending on application rate and method. These
required buffer distances only considers the exposure due to spray drift; based on EFED's
modeling, spray drift exposure alone does not cause the LOG to be exceeded. Runoff is
not assessed in this spray drift analysis.
5.2.1.3.4 Terrestrial Invertebrates
When the terrestrial-phase CRLF reaches juvenile and adult stages, its diet is mainly composed
of terrestrial invertebrates.
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For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortality at this dose,
MRID 05001991). The toxicity value for terrestrial invertebrates is calculated by multiplying the
LDso > 24.17 jig/bee by 1 bee/0.128g, which is based on the weight of an adult honey bee,
resulting in a toxicity estimate of 188 jig/g-bee (equivalent to 188 mg/kg-bee). Since definitive
LD50 values were not available, RQs were not calculated. However, expected exposure levels
were compared to the highest dose tested to evaluate the likelihood of risk. Since mortality was
observed at the highest test dose, expected exposures must be 20x less than the highest dose to
preclude risks to terrestrial invertebrates. Therefore, EECs must be less than 9.4 mg/kg-insect
(188 + 20) in for risks to be considered unlikely.
EECs for small insects ranged from 135 mg/kg-insect at 1 Ib/acre application to 755 mg/kg-
insect at 4 Ibs/acre with three (60-day interval) applications, and EECs for large insects ranged
from 15 mg/kg-insect at 1 Ib/acre application to 84 mg/kg-insect at 4 Ibs/acre with three (60-day
interval) applications (Table 3.10). Risks to terrestrial invertebrates cannot be precluded since
the calculated EECs exceed the calculated cut-point of 9.4 mg/kg-insect for all modeled
scenarios.
5.2.1.3.5 Mammals
Life history data for terrestrial-phase CRLFs indicate that large adult frogs consume terrestrial
vertebrates, including mice.
Acute risks from spray applications:
RQs for the non-definitive acute oral toxicity endpoints for mammalian species were not
calculated because the acute effects data shows no mortality and no sublethal effects at any of the
test levels (i.e., LD50 > 5000 mg/kg-bwt). With no soil incorporation, the dose-based EECs range
from 1.02 to 1279.2 mg/kg-bwt. These values are lower than the LDso; therefore, acute dose-
based risks from spray applications are unlikely. Since exposure from soil incorporated
applications would be less than from non-incorporated applications, risks from incorporated
applications are also unlikely. The probability of individual effect (mortality) for mammalian
species was not calculated because the acute mammalian effects data shows no mortality and no
sublethal effects were observed at any of the test concentrations (i.e., LD50 > 5000 mg/kg-bwt).
Acute risks from granular applications:
Potential direct acute effects to mammals are also evaluated by considering granule consumption
(LDso/sq-ft). Toxicity values were calculated for three weight classes (15, 35, and lOOOg
individuals) based on the highest dose tested (5000 mg/kg-bwt, see TREX 1.4.1 Users Guide for
details). The calculated toxicity values are >167, >321, and >4170 mg/mammal. The 15 and 35 g
results are relevant for evaluating indirect effects (effects to prey base) of the terrestrial-phase
CRLF. The EECs at single non-incorporated application rates of 1.5, 2, and 4 Ibs/acre were 15.6,
20.8, and 41.7 mg/sq-ft, respectively, and the EEC at a single soil-incorporated application rate
of 2 Ibs/acre is 0.21 mg/sq-ft. Risks to mammals from granular applications of trifluralin are
unlikely as the calculated EECs do not exceed the toxicity values.
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Chronic risks from spray applications (non-incorporated):
Chronic dose-based RQ values representing trifluralin exposures to small mammals indicate
risks resulting from both modeled scenarios (Table 5.5) for all feeding guilds except granivores.
Chronic diet-based RQ values representing trifluralin exposures to mammals indicate risks
resulting from both modeled scenarios for all feeding guilds except granivores and
fruits/pods/seeds/large insects.
5.2.1.3.6 Terrestrial-phase Frogs
Terrestrial-phase adult CRLFs also consume small frogs. RQ values, estimated using T-REX,
representing direct exposures of trifluralin to terrestrial-phase CRLFs are used to represent
exposures of trifluralin to small frogs in terrestrial habitats. The indirect effects to frogs as food
items are based on the direct effects analysis for the terrestrial-phase CRLF (Section 5.2.1.2).
Indirect impacts to CRLFs through reductions in the prey base (specifically terrestrial-phase
frogs) are expected from chronic exposure to trifluralin based on the summarized lines of
evidence below:
• Acute risks from spray applications are unlikely since the EECs are lower than the LD50
and LCso and no mortality or sublethal effects were noted in the acute bird studies.
• Acute risks from granular applications cannot be precluded at the highest application rate
(4 Ibs/acre with no soil incorporation) for 20 g individuals.
• One scenario (nursery use, exceeding RQ = 1.51) resulted in an RQ that exceeded the
Chronic LOC.
• Chronic risks were refined with T-HERPS, resulting in LOC exceedances for the nursery
scenario with three applications at 4 Ibs/acre. RQs exceeded the chronic LOC (1.0) with
values of 1.77 and 1.51 for herptiles that consume small herbivore mammals and small
insects, respectively.
• Based on the fugacity model, chronic exposure of herptiles to trifluralin through
consumption of contaminated soil invertebrates from fields treated with trifluralin is
unlikely.
5.2.1.4 Indirect Effects (via Habitat Effects)
5.2.1.4.1 Aquatic Plants (Vascular and Non-vascular)
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 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.
Potential indirect effects to the CRLF based on impacts to habitat and/or primary production
were assessed using RQs from freshwater aquatic vascular and non-vascular plant data. Based
on the evidence presented in Section 5.2.2.1, indirect impacts to aquatic-phase of the CRLF due
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to reduction effects on its habitats through impact on vascular and non-vascular aquatic plants
are not expected from acute exposure to trifluralin.
5.2.1.4.2 Terrestrial Plants
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.
Loss, destruction, and alteration of habitat were identified as threats to the CRLF in the USFWS
Recovery Plan (USFWS 2002). Herbicides can adversely impact habitat in a number of ways. In
the most extreme case, herbicides in spray drift and runoff from the site of application have the
potential to kill (or reduce growth and/or biomass) all or a substantial amount of the vegetation,
thus removing or impacting structures that define the habitat, and reducing the functions (e.g.,
cover, food supply for prey base) provided by the vegetation.
Trifluralin is a synthetic fluorinated dinitroaniline preemergent herbicide that enters plants
through developing roots preventing the alignment and separation of chromosomes during
mitosis (mitosis disrupter) which typically results in the swelling of root tips as cells in this
region fail to divide or elongate. Trifluralin is readily absorbed by young roots. Signs of toxicity
to post-emergent broadleaf weeds include localized chlorosis and stunting.
Based on the available toxicity data for terrestrial plants (using Treflan HFP formulation, MRID
439844-01, 419345-03), it appears that monocots and dicots in the seedling emergence studies
are typically more sensitive to trifluralin via soil or root uptake than monocots and dicots in the
vegetative vigor studies via foliar exposure.
Riparian vegetation typically consists of three tiers of vegetation, which includes a groundcover
of grasses and forbs, an understory of shrubs and young trees, and an overstory of mature trees.
Frogs spend a considerable amount of time resting and feeding in riparian vegetation; the
moisture and cover of the riparian plant community provides good foraging habitat and may
facilitate dispersal in addition to providing pools and backwater aquatic areas for breeding
(USFWS 2002). According to Hayes and Jennings (1988), the CRLF tends to occupy water
bodies with dense riparian vegetation including willows (Salix sp.). Upland habitat includes
grassland and woodlands, as well as scrub/shrub habitat. No guideline data or open literature
studies are available regarding the toxicity of trifluralin to woody plants. Because trifluralin may
be applied near woody species, toxicity to the woody part of the plant, excluding green bark, is
an uncertainty.
As shown in Tables 5.4 and 5.5, RQ values exceeded LOCs for monocots and dicots inhabiting
dry and semi-aquatic areas exposed to liquid and granular formulations of trifluralin via runoff
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and drift. Spray drift RQ values exceeded LOCs for liquid aerial applications at a single
application rate of 2.0 Ibs/acre.
Based on exceedances of the terrestrial plant LOCs for 23 out of 25 trifluralin modeled uses (for
at least one of the application methods) following runoff and spray drift to dry and semi-aquatic
areas, the following general conclusions can be made with respect to potential harm to riparian
habitat:
• Trifluralin may enter riparian areas via runoff and/or spray drift where it may contact
foliar surfaces of emerged seedlings or form a chemical barrier on soil, which would
affect pre-emergent plants.
• Based on trifluralin's mode of action and a comparison of seedling emergence and
vegetative vigor £€25 values to EECs estimated using TerrPlant, emerging or developing
seedlings may be affected in areas receiving both runoff and drift and in areas receiving
drift alone at applications rates greater than a single application of 0.8 Ibs/acre.
Furthermore, based on the residual nature of trifluralin, it is possible that impacts to
germinating seedlings and emerging plants would occur for several months after
application. If inhibition of new growth occurs, it could result in degradation of high
quality riparian habitat over time because as older growth dies from natural or
anthropogenic causes, plant biomass may be prevented from being replenished in the
riparian area.
• Because nine out often of the species tested in the seedling emergence studies and all ten
species tested in the vegetative vigor studies were affected, it is likely that many species
of herbaceous plants may be potentially affected by exposure to trifluralin via runoff and
spray drift.
A review of trifluralin incidents for terrestrial plants that were reported in the EIIS database
indicated that there were 78 incidents involving terrestrial plants. However, none of these
incidents reported effects to wild plants. Most incidents involved spray drift or direct
treatment(e.g., Alfalfa, barley, bean, birch, blue spruce, corn, cotton, dry bean, ornamentals,
peanut, percifia shrubs, pinto bean, potato, raspberry, rose, soybean, soybean seed, spreading
yew, sudan grass, sugarcane, sunflower, tomato and wheat (spring and other varieties). The
absence of reports of adverse effects on wild terrestrial plants does not provide evidence of an
absence of incidents and, consequently, risk.
In summary, terrestrial plant RQs exceed LOCs, which indicates risk to upland and riparian
vegetation. However, while it is not expected that woody plants with mature bark are sensitive to
environmentally relevant trifluralin concentrations, the lack of a guideline study on established
woody plants precludes estimation of effects. In addition, several incidents reported damage to
woody plants including shrubs, raspberries, rose, and spreading yew. Therefore, the potential of
effects to woody plants cannot be precluded. Because upland and riparian areas are comprised of
a mixture of both woody plants and herbaceous vegetation, terrestrial-phase CRLFs may be
indirectly affected by adverse effects solely to herbaceous vegetation, which provides habitat and
cover for the CRLF and its prey. Therefore, the indirect effect to the terrestrial-phase CRLF via
reduction in terrestrial plants is neither insignificant nor discountable.
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Spray drift RQ values did not exceed LOCs for ground (liquid) and granular formulations for all
application scenarios. Only one aerial (liquid) application scenario for monocots exceeded the
LOG of 1.
In order to estimate buffer distances that are protective of plant species that the terrestrial-phase
CRLF, SFGS and SJKF or its prey may depend on for food and cover, AgDRIFT was used to
model the dissipation distance to the £€25 levels for terrestrial plants.
Because trifluralin is used as a pre-emergent and post-emergent herbicide, buffer distances were
calculated for the most sensitive endpoints for both monocots and dicots in the seedling
emergence and vegetative vigor studies Spray drift RQ values did not exceed LOCs for ground
(liquid) and granular formulations for all application scenarios. Only one aerial application
scenario for monocots exceeded the LOG for a liquid application scenario (Table 5.12). For
established monocots, the calculated buffer distances for seedling emergence and vegetative
vigor were 55.7 feet and 6.56 feet, respectively.
Table 5.12 Estimation of Buffer Distance Required to Eliminate LOC Exceedances (only
spray drift exposure considered) for Terrestrial Plants Based on AgDRIFT
Pesticide
Label
Treflan
HFP
062719-
00250
App.
Rate
(Ib/acre)
2.0
Method
(Boom Height
for Ground)
Aerial
Tier
I
Parameters*
DSD = ASAE very
fine to fine
Required Buffer Distance (ft)
Seedling
Emergence
Monocot
55.7
Vegetative
Vigor
Monocot
6.56
*Fraction of applied input values for AGDRIFT:
For seedling emergence EC25 = 0.09 Ibs/acre; Fraction of the applied = EC25 ^ Rate = 0.045
For vegetative vigor EC25 = 1.09 Ibs/acre; Fraction of the applied = EC25 ^ Rate = 0.545
5.2.1.5 Modification to Designated Critical Habitat
5.2.1.5.1 Aquatic-Phase PCEs
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.
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• Reduction and/or modification of aquatic-based food sources for pre-metamorphs (e.g.,
algae).
Conclusions for potential indirect effects to the CRLF via direct effects to aquatic and terrestrial
plants are used to determine whether modification to critical habitat may occur. There is a
potential for habitat modification via impacts to terrestrial plants (Section 5.2.3.2)
The remaining aquatic-phase PCE is "alteration of other chemical characteristics necessary for
normal growth and viability of CRLFs and their food source." Other than impacts to algae as
food items for tadpoles (discussed above), this PCE is assessed by considering direct and indirect
effects to the aquatic-phase CRLF via acute and chronic freshwater fish and invertebrate toxicity
endpoints as measures of effects. There is a potential for habitat modification via impacts to
aquatic-phase CRLFs (Section 5.2.1.1) and effects to freshwater invertebrates and fish as food
items (Sections 5.2.2.2 and 5.2.2.3).
5.2.1.5.1 Terrestrial-Phase PCEs
Two of the four 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 drip line
surrounding aquatic and riparian habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provide 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.
As discussed above, there is potential for habitat modification of the terrestrial-phase CRLF via
impacts to terrestrial plants as indicated by potential impacts to herbaceous vegetation, which
provides habitat, cover, and a means of dispersal for the terrestrial-phase CRLF and its prey. This
habitat modification could be caused by all modeled uses of triflualin at the maximum labeled
rate.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for terrestrial
phase juveniles and adults." To assess the impact of trifluralin on this PCE, acute toxicity
endpoints for terrestrial invertebrates and acute and chronic toxicity endpoints for mammals and
terrestrial-phase frogs are used as measures of effects. Based on the characterization of indirect
effects to the terrestrial-phase CRLF via reduction in prey base (Section 5.2.2.4 for terrestrial
invertebrates, Section 5.2.2.5 for mammals, and Section 5.2.2.6 for frogs), there is potential for
critical habitat modification via a reduction of terrestrial invertebrates, small mammals, and frogs
as food items.
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. As discussed in
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Section 5.2.1.2, direct acute effects to the terrestrial-phase CRLF are unlikely. However, direct
chronic effects to the terrestrial-phase CRLF are likely for liquid applications of trifluralin at rate
of three applications of 4.0 Ibs/acre. Indirect effects to the terrestrial-phase CRLF via reduction
in prey base are likely. Therefore, there is potential for habitat modification via direct and
indirect effects to the terrestrial-phase CRLF.
5.2.2 Delta Smelt
To assess potential direct effects of trifluralin to the DS, toxicity data for both the freshwater fish
and estuarine/marine fish were evaluated since the DS lives in brackish waters. Since freshwater
fish were more sensitive than estuarine/marine fish, the freshwater fish toxicity data were used to
assess potential direct effects of trifluralin to the DS.
To assess potential indirect effects (prey) of trifluralin to the DS, toxicity data for both the
freshwater invertebrates and estuarine/marine invertebrates were evaluated since the DS lives in
brackish waters. Since freshwater invertebrates were more sensitive than estuarine/marine
invertebrates, the freshwater invertebrate toxicity data were used to assess potential indirect
effects of trifluralin to the DS.
5.2.2.1 Direct Effects
RQ values representing direct effects of trifluralin to aquatic-phase CRLF (Section 5.2.1.1) are
also used to represent potential effects of trifluralin to the DS. There is a potential for direct
impact to the DS based on the summarized lines of evidence below:
• There were Listed Species LOG exceedances in 18 of the 25 modeled scenarios.
• For all modeled scenarios, the likelihood of an individual effect (mortality) was <1 in
3280 at the calculated RQ and at the Listed Species LOC.
• A formal species sensitivity analysis was not conducted; available data provided a range
of LDso's from 18.5 to 43.6 |ig/L for two species.
• Of the 3,915 non-targeted water samples tested for trifluralin, 15% had detectible
concentrations of trifluralin; those concentrations where trifluralin was detected were
comparable to the PRZM/EXAMS estimates. If the observed maximum concentration
(1.74 |ig/L) was used as an exposure value to calculate an acute freshwater fish RQ, there
would be an exceedance of the Listed Species LOC (RQ = 0.09).
• The spray drift buffer distance needed to get below the acute aquatic fish Listed Species
LOC ranged from 45.9 to 2359 feet depending on application rate and method. These
required buffer distances only considers the exposure due to spray drift; based on EFED's
modeling, spray drift exposure alone does not cause the LOC to be exceeded.
• The Chronic LOC was not exceeded for any scenario.
• Fish exposed to trifluralin may also develop vertebral dysplasia, which could
significantly impact the fishes' ability to swim, and therefore, impact its fitness. The
concentrations in these toxicity studies are within an order of magnitude of the maximum
concentrations observed in the monitoring data and many of the chronic EECs estimated
using PRZM/EXAMS.
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5.2.2.2 Indirect Effects (via Reductions in Prey Base)
The DS eats small zooplankton. They primarily eat planktonic copepods, cladocerans,
amphipods, and insect larvae. However, the most important food organism appears to be
Eurytemora qffinis, which is a euryhaline copepod (USFWS, 1995 and 2004).
RQ values representing exposures of trifluralin to freshwater invertebrates that may serve as prey
for the aquatic-phase CRLF are also used to represent exposures of trifluralin to freshwater
invertebrates that may serve as prey for the DS. No acute or chronic LOG exceedances occurred
for freshwater invertebrates with acute RQs <0.05 and chronic RQs < 1.0 for all 25 application
scenarios.
Based on the multiple lines of evidence as described in Section 5.2.1.3.2, impacts to potential
invertebrate prey are not expected from acute or chronic exposure to trifluralin.
5.2.2.3 Indirect Effects (via Habitat Effects)
5.2.2.3.1 Aquatic Plants (Vascular and Non-vascular)
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, rather than energy, to the system, as attachment sites for many
aquatic invertebrates, and refugia for juvenile organisms, such as fish and frogs. Emergent
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 aquatic species. Results of the indirect effects assessment are used as the basis for the
habitat modification analysis.
No acute LOG exceedances occurred for aquatic plants (vascular and non-vascular) with RQs <
1.0 for all application scenarios. Based on the multiple lines of evidence as described in Section
5.2.1.4.1, impacts to aquatic plants found near trifluralin use sites are not expected.
5.2.2.3.2 Terrestrial Plants
Terrestrial plants serve several important habitat-related functions for the DS. Among other
things, 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.
Based on the results of the submitted terrestrial plant toxicity studies and the reported terrestrial
plant incidents, the herbicide trifluralin is phytotoxic to many plant species (seedling emergence
endpoints are more sensitive than vegetative vigor endpoints). Additionally, monocots are more
sensitive to trifluralin than are dicots, based on available data. However, for adjacent upland and
wetland plants, terrestrial plant RQs for both monocots and dicots exceed the Agency's risk to
non-listed species LOG for 23 out of 25 trifluralin uses for at least one of the application
methods. For the drift only RQs, one of the RQs exceed the Agency's LOG
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5.2.2.4 Modification to Designated Critical Habitat for DS
Primary constituent elements (PCEs) of designated critical habitat for the DS include the
following:
• Spawning Habitat—shallow, fresh or slightly brackish backwater sloughs and edgewaters
to ensure egg hatching and larval viability. Spawning areas also must provide suitable
water quality (i.e., low "concentrations of pollutants) and substrates for egg attachment
(e.g., submerged tree roots and branches and emergent vegetation).
• Larval and Juvenile Transport—Sacramento and San Joaquin Rivers and their tributary
channels must be protected from physical disturbance and flow disruption. Adequate
river flow is necessary to transport larvae from upstream spawning areas to rearing
habitat in Suisun Bay. Suitable water quality must be provided so that maturation is not
impaired by pollutant concentrations.
• Rearing Habitat—Maintenance of the 2 ppt isohaline and suitable water quality (low
concentrations of pollutants) within the estuary is necessary to provide DS larvae and
juveniles a shallow protective, food-rich environment in which to mature to adulthood.
• Adult Migration— Unrestricted access to suitable spawning habitat in a period that may
extend from December to July. Adequate flow and suitable water qualityjnay need to be
maintained to attract migrating adults in the Sacramento and San Joaquin River channels
and their associated tributaries. These areas also should be protected from physical
disturbance and flow disruption during migratory periods.
• PCEs also include more general requirements for habitat areas that provide essential life
cycle needs of the species such as 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 potential for direct effects to the DS from trifluralin use could not be precluded based on
incident data and RQ exceedances. Furthermore, it was concluded that trifluralin is likely to
affect the DS by potentially affecting its habitat (terrestrial plants). Therefore, trifluralin may
also affect critical habitat of the DS that is located in close proximity to triflualin use sites.
5.2.3 San Francisco Garter Snake
5.2.3.1 Direct Effects
Direct acute and chronic exposures of the SFGS were evaluated using the same approaches
employed for estimating direct exposures to the terrestrial-phase CRLF (Section 5.2.1.2). In
addition, toxicity estimates for both listed species, the terrestrial-phase CRLF and the SFGS, are
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based on the same surrogate avian toxicity data. Therefore, RQ values representing the potential
for direct exposures and effects of trifluralin to the terrestrial-phase CRLF, are also used to
represent the potential for direct exposures and effects of trifluralin to the SFGS.
Direct effects to SFGS are expected from exposure to trifluralin based on the summarized lines
of evidence below:
• Acute risks from spray applications are unlikely since the EECs are lower than the LDso
and LCso and no mortality or sublethal effects were noted in the acute bird studies.
• Acute risks from granular applications cannot be precluded at the highest application rate
(4 Ibs/acre with no soil incorporation) for 20 g individuals.
• One scenario (nursery use, exceeding RQ = 1.51) resulted in an RQ that exceeded the
Chronic LOG.
• Chronic risks were refined with T-HERPS (Table 5.11), resulting in LOG exceedances
for the nursery scenario with three applications at 4 Ibs/acre. RQs exceeded the chronic
LOG (1.0) with values of 1.77 and 1.51 for herptiles that consume small herbivore
mammals and small insects, respectively.
• Based on the fugacity model, chronic exposure of herptiles (specifically the SFGS) to
trifluralin through consumption of contaminated soil invertebrates from fields treated
with trifluralin is unlikely.
5.2.3.2 Indirect Effects (via Reductions in Prey Base)
Newborn and juvenile SFGS prey almost exclusively on Pacific tree frogs in temporary pools
during the spring and early summer to the point that the SFGS may be so dependent on their
anuran prey that they are not able to switch to other available prey sources if necessary to
survive. SFGS under 500 mm snout-to-vent length (SVL) require Pacific tree frogs in various
stages of metamorphosis, whereas individuals over 500 mm SVL can consume Pacific tree frog,
CRLF, and bullfrog tadpoles and adults.
The main diet of adult SFGS consists of CRLFs. Adult SFGSs may also feed on smaller juvenile
non-native bullfrogs (Rana catesbeiana). Immature California newts (Taricha torosa),
California toads (Bufo boreas halophilus\ recently metamorphosed western toads (Bufo boreas\
threespine stickleback (Gasterosteus aculeatus\ and non-native mosquito fish (Gambusia
affmis) are also known to be consumed by SFGS. Small mammals, reptiles, amphibians,
possibly invertebrates, and some fish species may also be consumed by the SFGS.
5.2.3.2.1 Freshwater Fish and Aquatic-phase Amphibians
RQ values representing exposures of trifluralin to freshwater fish and aquatic-phase amphibians
that may serve as prey for the aquatic-phase CRLF are also used to represent exposures of
trifluralin to freshwater fish and aquatic-phase amphibians that may serve as prey for the SFGS.
Based on the multiple lines of evidence presented in Section 5.2.1.1, there is a potential for
indirect impact to the SFGS due to reduction offish and aquatic-phase frogs as a prey base:
• There were Listed Species LOG exceedances in 18 of the 25 modeled scenarios.
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• Of the 3,915 non-targeted water samples tested for trifluralin, only 15% had detectible
concentrations of trifluralin; however, those measured concentrations were comparable to
the PRZM/EXAMS estimates.
• Fish exposed to trifluralin may also develop vertebral dysplasia, which could
significantly impact the fishes' ability to swim, and therefore, impact its fitness. The
concentrations in these toxicity studies are within an order of magnitude of the maximum
concentrations observed in the monitoring data and many of the chronic EECs estimated
using PRZM/EXAMS.
• Trifluralin has the potential to accumulate in tissues of aquatic organisms. The resulting
RQ values for the three size classes of SFGS (Table 5.3) did not exceed the LOG for
chronic dietary-based exposures through consumption of aquatic prey that have
accumulated trifluralin. Acute RQs were not calculated as the avian acute toxicity studies
resulted in no mortalities at levels higher than those expected in the environment.
• The spray drift buffer distance needed to get below the acute aquatic fish Listed Species
LOG ranged from 45.9 to 2359 feet depending on application rate and method. These
required buffer distances only considers the exposure due to spray drift; based on EFED's
modeling, spray drift exposure alone does not cause the LOG to be exceeded.
5.2.3.2.2 Freshwater Invertebrates
RQ values representing exposures of trifluralin to freshwater invertebrates that may serve as prey
for the aquatic-phase CRLF are also used to represent exposures of trifluralin to freshwater
invertebrates that may serve as prey for the SFGS. No acute or chronic LOG exceedances
occurred for freshwater invertebrates with RQs <0.05 for all 25 application scenarios for at least
one of the application methods.
Based on the multiple lines of evidence as described in Section 5.2.1.3.2 for the CRLF, indirect
impacts to SFGS through reductions in the prey base (specifically aquatic invertebrates) are not
expected from acute or chronic exposure to trifluralin.
5.2.3.2.3 Terrestrial Vertebrates
RQ values representing exposures of trifluralin to small and large terrestrial vertebrates that may
serve as prey for the terrestrial-phase CRLF are also used to represent exposures of trifluralin
that may serve as prey for the SFGS. Similarly, the Agency determined a reasonable potential
exists for direct effects on birds (surrogate for terrestrial phase amphibians) based on exposure to
food items receiving direct deposition from trifluralin application (i.e., T-REX, T-HERPS
modeling).
Indirect impacts to SFGS through reductions in the prey base (specifically terrestrial-phase
herptiles) are expected from chronic exposure to trifluralin based on the summarized lines of
evidence below:
• Acute risks from spray applications are unlikely since the EECs are lower than the LDso
and LCso and no mortality or sublethal effects were noted in the acute bird studies.
• Acute risks from granular applications cannot be precluded at the highest application rate
(4 Ibs/acre with no soil incorporation) for 20 g individuals.
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• One scenario (nursery use, exceeding RQ = 1.51) resulted in an RQ that exceeded the
Chronic LOG.
• Chronic risks were refined with T-HERPS, resulting in LOG exceedances for the nursery
scenario with three applications of 4 Ibs/acre. RQs exceeded the chronic LOG (1.0) with
values of 1.77 and 1.51 for herptiles that consume small herbivore mammals and small
insects, respectively.
• Based on the fugacity model, chronic exposure of herptiles to trifluralin through
consumption of contaminated soil invertebrates from fields treated with trifluralin is
unlikely
Indirect impacts to SGFS through reductions in the prey base (specifically mammals) are
expected from chronic exposure to trifluralin based on the summarized lines of evidence below
(see Section 5.2.1.3.4 for details):
• RQs for the non-definitive acute oral toxicity endpoints for mammalian species were not
calculated because the acute effects data shows no mortality and no sublethal effects at
any of the test levels (i.e., LDso > 5000 mg/kg-bwt). With no soil incorporation, the dose-
based EECs range from 1.02 to 1279.2 mg/kg-bwt, much lower that the highest dose
tested (5000 mg/kg-bwt); therefore, acute dose-based risks from spray applications are
unlikely. Since exposure from soil incorporated applications would be less than from
non-incorporated applications, risks from incorporated applications are also unlikely.
• Risks to mammals from granular applications of trifluralin are unlikely as the calculated
EECs do not exceed the toxicity values.
• Chronic RQ values representing trifluralin exposures to small mammals indicate risks
resulting from all application scenarios (Table 5.3). In addition, the chronic dietary-based
RQ values exceeded LOCs for all liquid application scenarios. The NOAEL yielded
dose-based LOG exceedances for all liquid application scenarios.
5.2.3.2.4 Terrestrial Invertebrates
For honeybees, the most sensitive acute contact LDso > 24.17 ug/bee (13% mortally at this dose,
MRID 05001991). The toxicity value for terrestrial invertebrates is calculated by multiplying the
LD50 > 24.17 jig/bee by 1 bee/0.128g, which is based on the weight of an adult honey bee,
resulting in a toxicity estimate of 188 jig/g-bee (equivalent to 188 mg/kg-bee). Since a definitive
LDso value was not available, RQs were not calculated. However, expected exposure levels were
compared to the highest dose tested to evaluate the likelihood of risk. Since mortality was
observed at the highest test dose, expected exposures must be 20x less than the highest dose to
preclude risks to terrestrial invertebrates. Therefore, EECs must be less than 9.4 mg/kg-insect in
for risks to be considered unlikely.
EECs for small insects ranged from 270 mg/kg-insect at 2 Ib/acre application to 755 mg/kg-
insect at 4 Ibs/acre with three (60-day interval) applications, and EECs for large insects ranged
from 30mg/kg-insect at 2 Ib/acre application to 84 mg/kg-insect at 4 Ibs/acre with three (60-day
interval) applications (Table 3.11). Risks to terrestrial invertebrates cannot be precluded since
the calculated EECs exceed the calculated cut-point of 9.4 mg/kg-insect for all modeled
scenarios.
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5.2.3.3 Indirect Effects (via Habitat Effects)
SFGS inhabit areas near densely vegetated ponds and in open hillsides where it can sun, feed,
and find cover in rodent burrows. It forages extensively in aquatic habitats. Fresh-water habitats
including natural and manmade (e.g. stock) ponds, slow moving streams, vernal pools and other
ephemeral or permanent water bodies which typically support inundation during winter rains and
hold water for a minimum of 12 weeks in a year of average rainfall and upland habitats within
200 ft of the mean high water mark of such aquatic habitat.
5.2.3.3.1 Aquatic Plants (Vascular and Non-vascular)
Aquatic plants serve several important functions in aquatic ecosystems such as primary
production (non-vascular, vascular) and refugia structure (vascular plants). 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 aquatic
species.
Based on the evidence presented in Section 5.2.1.4.1, indirect impacts to the SFGS due to
reduction effects on its habitats through impact on vascular and non-vascular aquatic plants are
not expected from acute exposure to trifluralin.
5.2.3.3.2 Terrestrial Plants
Terrestrial plants serve several important habitat-related functions for the SFGS. In addition to
providing habitat and cover for invertebrate and vertebrate prey items of the SFGS, terrestrial
vegetation also provides shelter for the SFGS 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.
LOC exceedances:
As noted in Section 5.2.1.4.2, terrestrial plant RQs exceed LOCs, which indicates risk to upland
and riparian vegetation. Because upland and riparian areas are comprised of a mixture of both
woody plants and herbaceous vegetation, SFGS may be indirectly affected by adverse effects
solely to herbaceous vegetation, which provides habitat and cover for the SFGS and its prey.
Therefore, the indirect effect to the SFGS via reduction in terrestrial plants is neither
insignificant nor discountable.
5.2.4 San Joaquin Kit Fox
SJKF occupies a variety of habitats, including grasslands, scrublands (e.g., chenopod scrub and
sub-shrub scrub), vernal pool areas, oak woodland, alkali meadows and playas, and an
agricultural matrix of row crops, irrigated pastures, orchards, vineyards, and grazed annual
grasslands. Kit foxes dig their own dens, modify and use those already constructed by other
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animals (ground squirrels, badgers, and coyotes), or use human-made structures (culverts,
abandoned pipelines, or banks in sumps or roadbeds). They move to new dens within their home
range often (likely to avoid predation by coyotes). The SJKF forages in California prairie and
Sonoran grasslands in the vicinity of freshwater marshes and alkali sinks, where there is a dense
ground cover of tall grasses and San Joaquin saltbush. Seasonal flooding in such habitats is
normal. It feeds on small animals including blacktailed hares, desert cottontails, mice, kangaroo
rats, squirrels, birds, lizards, insects and grass. The San Joaquin kit fox satisfies its moisture
requirements from prey and does not depend on freshwater sources.
5.2.4.1 Direct Effects
Direct exposure of the SJKF and the resulting risks in terrestrial environments were evaluated
based on dose- and dietary-based EECs estimated using two approaches (i.e., T-REX for foliar
spray applications and using fugacity-based modeling for insectivorous wildlife). All estimated
EECs (i.e., EECs for short grass, tall grass, broadleaf plants/small insects, fruits/pods/seeds/large
insects) were considered relevant for evaluation of direct effects because the SJKF has been
known to feed on insects and grasses. A mammalian body weight of lOOOg was modeled based
on the adult size of the kit fox. Based on these multiple lines of evidence presented below, there
is potential for direct effects to the SJKF as result of labeled trifluralin use in California.
Acute risks from spray applications:
RQs for the non-definitive acute oral toxicity endpoints for mammalian species were not
calculated because the acute effects data shows no mortality and no sublethal effects at any of the
test levels (i.e., LD50 > 5000 mg/kg-bwt). With no soil incorporation, the dose-based EECs range
from 1.02 to 1279.2 mg/kg-bwt. These values are lower than the LD50; therefore, acute dose-
based risks from spray applications are unlikely. Since exposure from soil incorporated
applications would be less than from non-incorporated applications, risks from incorporated
applications are also unlikely. The probability of individual effect (mortality) for mammalian
species was not calculated because the acute mammalian effects data shows no mortality and no
sublethal effects were observed at any of the test concentrations (i.e., LDso > 5000 mg/kg-bwt).
Acute risks from granular applications:
Potential direct acute effects to mammals are also evaluated by considering granule consumption
(LDso/sq-ft). Toxicity values were calculated for three weight classes (15, 35, and lOOOg
individuals) based on the highest dose tested (5000 mg/kg-bwt). The calculated toxicity values
are >167, >321, and >4170 mg/mammal. The 1000 g results are relevant for evaluating direct
effects of the SJKF. The EECs at single non-incorporated application rates of 1.5, 2, and 4
Ibs/acre were 15.6, 20.8, and 41.7 mg/sq-ft, respectively, and the EEC at a single soil-
incorporated application rate of 2 Ibs/acre is 0.21 mg/sq-ft. Risks to mammals from granular
applications of trifluralin are unlikely as the calculated EECs do not exceed the toxicity values.
Chronic risks from unincorporated spray applications:
Chronic dose-based RQ values representing trifluralin exposures to large mammals (1000 g)
indicate risks resulting from both the alfalfa and nursery application scenarios (for alfalfa, LOG
exceedances for mammals consuming short grass, tall grass, and broadleaf plants/small insects;
for nursery, LOG exceedences for mammals consuming short grass, tall grass, broadleaf
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plants/small insects, and fruits/pods/seeds/large insects; Table 5.5). Chronic diet-based RQ
values representing trifluralin exposures to all mammals indicate risks to mammals consuming
short grass, tall grass, and broadleaf plants/small insects for both the alfalfa and nursery
scenarios (Table 5.5).
Soil invertebrate consumption - potential chronic effects:
Chronic direct effects to SJKF that may consume soil invertebrates that have accumulated
trifluralin residues in their tissues were modeled; however, this pathway is not included in T-
REX. In order to explore the potential exposures of mammals to total residues of trifluralin that
have accumulated in soil invertebrates inhabiting trifluralin treatment sites, a simple fugacity
approach was employed to estimate trifluralin concentrations in earthworms and subsequent
exposures to mammals consuming earthworms. Earthworms were chosen to represent all soil
invertebrates that may be consumed by the terrestrial organisms under evaluation. This approach
is explained in detail in Appendix P.
Using a single application rate of 4 Ibs/acre, PRZM estimated trifluralin concentrations are 6.41
g/m3 in soil, and the estimated concentration of trifluralin in earthworms is 147 mg/kg-
earthworm. If it is assumed that a mammal consumes only contaminated soil invertebrates, its
dietary-based exposures would be approximately 74% of the NOAEC in the mammalian
reproduction study (NOAEC=200 mg/kg-diet, MRIDs 00151901, 00151902, 00151903).
Therefore, chronic risks to the SJKF from consumption of trifluralin-contaminated soil
invertebrates are unlikely.
5.2.4.2 Indirect Effects (via Reductions in Prey Base)
Potential forage items of the SJKF include small mammals, grasses, and insects.
5.2.4.2.1 Terrestrial Invertebrates
RQ values representing exposures of trifluralin to terrestrial invertebrates that may serve as prey
for the terrestrial-phase CRLF and SFGS are also used to represent exposures of trifluralin to
terrestrial invertebrates that may serve as prey for the SFKF.
For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortally at this dose,
MRID 05001991). The toxicity value for terrestrial invertebrates is calculated by multiplying the
LDso > 24.17 jig/bee by 1 bee/0.128g, which is based on the weight of an adult honey bee,
resulting in a toxicity estimate of 188 jig/g-bee (equivalent to 188 mg/kg-bee). Since a definitive
LD50 values was not available, RQs were not calculated. However, expected exposure levels
were compared to the highest dose tested to evaluate the likelihood of risk. Since mortality was
observed at the highest test dose, expected exposures must be 20x less than the highest dose to
preclude risks to terrestrial invertebrates. Therefore, EECs must be less than 9.4 mg/kg-insect in
for risks to be considered unlikely.
EECs for small insects ranged from 135 mg/kg-insect at 1 Ib/acre application to 755 mg/kg-
insect at 4 Ibs/acre with three (60-day interval) applications, and EECs for large insects ranged
from 15 mg/kg-insect at 1 Ib/acre application to 84 mg/kg-insect at 4 Ibs/acre with three (60-day
interval) applications (Table 3.11). Risks to terrestrial invertebrates cannot be precluded since
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the calculated EECs exceed the calculated cut-point of 9.4 mg/kg-insect for all modeled
scenarios.
5.2.4.2.2 Mammals
Indirect impacts to SJKF through reductions in the prey base (specifically mammals) are
expected from chronic exposure to trifluralin based on the summarized lines of evidence below:
• RQs for the non-definitive acute oral toxicity endpoints for mammalian species were not
calculated because the acute effects data shows no mortality and no sublethal effects at
any of the test levels (i.e., LDso > 5000 mg/kg-bwt). With no soil incorporation, the dose-
based EECs range from 1.02 to 1279.2 mg/kg-bwt, much lower that the highest dose
tested (5000 mg/kg-bwt); therefore, acute dose-based risks from spray applications are
unlikely. Since exposure from soil incorporated applications would be less than from
non-incorporated applications, risks from incorporated applications are also unlikely.
• Acute risks to mammals from granular applications of trifluralin are unlikely as the
calculated EECs do not exceed the toxicity values.
• Chronic RQ values representing trifluralin exposures to mammals indicate risks resulting
from all spray application scenarios using either dose-based or dietary-based exposure
estimates (Table 5.5).
5.2.3.2.3 Terrestrial Plants
As noted in Section 5.2.1.4.2, terrestrial plant RQs exceed LOCs, which indicates risk to upland
and riparian vegetation. Because upland and riparian areas are comprised of a mixture of both
woody plants and herbaceous vegetation, SJKF may be indirectly affected by adverse effects
solely to herbaceous vegetation, which provides a food source for the SJKF. Therefore, the
indirect effect to the SJKF via reduction in terrestrial plants is neither insignificant nor
discountable.
5.2.4.3 Indirect Effects (via Habitat Effects)
5.2.3.4.1 Terrestrial Plants
Terrestrial plants serve several important habitat-related functions for the SJKF. In addition to
providing habitat and cover for invertebrate prey 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.
As noted in Section 5.2.1.4.2, terrestrial plant RQs exceed LOCs, which indicates risk to upland
and riparian vegetation. Because upland and riparian areas are comprised of a mixture of both
woody plants and herbaceous vegetation, SJKF may be indirectly affected by adverse effects
solely to herbaceous vegetation, which provides a food source for the SJKF. Because available
lines of evidence provide compelling reason to believe that trifluralin will affect any type of
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plants to the extent that it would affect the habitat integrity of the SJKF, labeled trifluralin use in
California appears to indirectly affect the SJKF via impacts to habitat and/or primary production.
6. Uncertainties
6.1 Exposure Assessment Uncertainties
6.1.1 Maximum Usage 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. The frequency at which actual uses approach this
maximum use scenario may be dependent on pest resistance, timing of applications, cultural
practices, and market forces.
6.1.2 Aquatic Exposure Modeling of Trifluralin
There are no aerobic aquatic degradation data for trifluralin. A conservative default aerobic
aquatic degradation half-life of 438 days was calculated as twice the aerobic soil metabolism
half-life of 219 days for PRZM/EXAMS modeling. Also, there are no anaerobic aquatic
degradation data for trifluralin. A default anaerobic aquatic degradation half-life of 59 days was
calculated as the 90% upper confidence bound on the mean metabolism half-lives 59, 25,and 35
days.
Numerous trifluralin product labels in the LUIS Report do not specify the maximum application
rate, maximum number of applications per year and/or minimum interval between applications.
When not specified, the minimum interval is assumed to be 60 days because this is typically the
interval when specified.
In cases of right-of-ways and residential uses, the general label language describing the extent of
the application area led EFED to use conservative assumptions regarding the post-processing
techniques to obtain EECs. In this modeling approach, it is assumed that right-of-ways and
residential application sites are composed of equal parts pervious and impervious surfaces (i.e.,
the EECs of both surfaces are multiplied by 50%). However, in reality, it is likely that right-of-
ways and residential uses contain different ratios of the two surfaces. In general, incorporation of
impervious surfaces into the exposure assessment results in increasing runoff volume in the
watershed, which tends to reduce overall pesticide exposure assuming 1% overspray to the
impervious surface. Further details on how this value was derived and characterization of
alternative assumptions are provided in the Barton Springs salamander endangered species risk
assessment for atrazine (USEPA 2006).
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
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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).
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
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the uncertainty of modeled values. Factors within the ambient environment such as soil
temperatures, sunlight intensity, antecedent soil moisture, and surface water temperatures can
cause actual aquatic concentrations to differ for the modeled values.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a vegetative
setback on runoff and loadings. The effectiveness of vegetative setbacks is highly dependent on
the condition of the vegetative strip. For example, a well-established, healthy vegetative setback
can be a very effective means of reducing runoff and erosion from agricultural fields.
Alternatively, a setback of poor vegetative quality or a setback that is channelized can be
ineffective at reducing loadings. Until such time as a quantitative method to estimate the effect
of vegetative setbacks on various conditions on pesticide loadings becomes available, the aquatic
exposure predictions are likely to overestimate exposure where healthy vegetative setbacks exist
and underestimate exposure where poorly developed, channelized, or bare setbacks exist.
6.1.3 Multiple Growing Seasons per Year
Most trifluralin product labels specify application rates on a per crop cycle basis (not on a per
year basis). Information from BEAD indicates that many crops can be grown more than one
time/year in California (USEPA 2007). Since standard PRZM scenarios only consist of one crop
per year, applications to only one crop per year were modeled. The cropping seasons range
between two and four cycles per year. If trifluralin is applied for multiple cropping cycles within
a year, EECs presented in this assessment may under predict exposures. For all other labeled
uses, it was assumed that a maximum seasonal application specified on the label was equivalent
to a maximum annual application.
6.1.4 Usage Uncertainties
County-level usage data were obtained from California's Department of Pesticide Regulation
Pesticide Use Reporting (CDPR PUR) database. Four years of data (2002 - 2005) were included
in this analysis because statistical methodology for identifying outliers, in terms of area treated
and pounds applied, was provided by CDPR for these years only. No methodology for removing
outliers was provided by CDPR for 2001 and earlier pesticide data; therefore, this information
was not included in the analysis because it may misrepresent actual usage patterns. CDPR PUR
documentation indicates that errors in the data may include the following: a misplaced decimal;
incorrect measures, area treated, or units; and reports of diluted pesticide concentrations. In
addition, it is possible that the data may contain reports for pesticide uses that have been
cancelled. The CPDR PUR data does not include home owner applied pesticides; therefore,
residential uses are not likely to be reported. As with all pesticide 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.
6.1.5 Terrestrial Exposure Modeling of Trifluralin
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-
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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 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. Environmental
Protection Agency, 1993). If it is assumed that laboratory chow is formulated to maximize
assimilative efficiency (e.g., a value of 85%), a potential for underestimation of exposure may
exist by assuming that consumption of food in the wild is comparable with consumption during
laboratory testing. In the screening process, exposure may be underestimated because metabolic
rates are not related to food consumption.
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.
6.1.6 Spray Drift Modeling
Although there may be multiple trifluralin applications at a single site, it is unlikely that the same
organism would be exposed to the maximum amount of spray drift from every application made.
In order for an organism to receive the maximum concentration of trifluralin from multiple
applications, each application of trifluralin would have to occur under identical atmospheric
conditions (e.g., same wind speed and - for plants - same wind direction) and (if it is an animal)
the animal being exposed would have to be present directly downwind at the same distance after
each application.
AgDRIFT models spray drift from aerial and ground applications in a flat area with little to no
ground cover and a steady, constant wind speed and direction. In many cases, the drift estimates
from AgDRIFT may overestimate exposure even from single applications, especially as the
distance increases from the site of application, since the model does not account for potential
obstructions (e.g., large hills, berms, buildings, trees).
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Conservative assumptions were made regarding the droplet size distributions being modeled
("ASAE Very Fine to Medium"), the application method (e.g., aerial), release heights and wind
speeds. Alterations in any of these inputs would change the area of potential effect. Current
trifluralin labels have varying directions regarding factors affecting droplet size distributions.
6.1.7 KABAM Modeling
In KABAM it is assumed that birds are surrogates for terrestrial-phase the CRLF and SFGS. As
such, listed species of amphibians and reptiles are entered into the KABAM spreadsheet as birds.
In order to define the risks of CRLF consuming specific diet items such as benthic invertebrates
and fish, KABAM can be used to derive Risk Quotient (RQ) values. Body weight assumptions
of post-metamorphic small (1.4 g), medium (37 g), and large (238 g) CRLF are consistent with
those incorporated into T-HERPS and are derived from data from Fellars (2007). Diet
assumptions assigned to each of these size classes are provided in Table 5.2.
The SFGS is an endangered species that feeds on aquatic organisms. KABAM can be applied to
this species by using weights of juvenile (2 g), adult male (113 g), and adult female (227 g) for
input values. The juvenile weight was obtained from Cover and Boyer (1988). Diet assumptions
assigned to each of these size classes are provided in Table 5.2. Different weights to be assessed,
as well as the different diets, reflect the range of both variables.
The weight of the male SFGS is assumed to be 0.113 kg and consumes either 100% benthic
invertebrates or 100% medium fish. The weight of the medium size class offish in KABAM is
0.1 kg, which is very close to the snake bodyweight. Based on the available data for the SFGS
weights, the 0.113 kg is an average value. The consumption of the 0.1 kg fish may be more
likely for larger male snakes in the range of weights. This diet class therefore represents the
upper bound for risk to adult male SFGS through dietary bioaccumulation. Diet assumptions
assigned to each of these size classes are provided in Table 5.2.
6.2 Effects Assessment Uncertainties
6.2.1 Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test organism age may have a significant impact on the observed
sensitivity to a toxicant. The acute toxicity data for fish are collected on juvenile fish between 0.1
and 5 grams. Aquatic invertebrate acute testing is performed on recommended immature age
classes (e.g., first instar for daphnids, second instar for amphipods, stoneflies, mayflies, and third
instar for midges).
Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients 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.
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6.2.2 Use of Surrogate Species Effects Data
Guideline toxicity tests and open literature data on trifluralin considered suitable for quantitative
use are available for aquatic-phase frogs; therefore, freshwater fish are used as surrogate species
for aquatic-phase amphibians. Although data evaluating the acute toxicity to aquatic-phase
amphibians were reviewed, EFED determined that the use of freshwater fish data is preferable to
the use of aquatic-phase amphibian data because it is unknown where the CRLF would fall on a
species sensitivity distribution. The available open literature information on trifluralin toxicity to
aquatic-phase amphibians shows that acute ecotoxicity endpoints for aquatic-phase amphibians
are generally about 6 times less sensitive than freshwater fish (bluegill sunfish LCso = 18.5 ug/L,
Fowler's tadpoles LC50 =115 ug/L). Because amphibian data is not required from the registrant,
it is EFED's standard approach to use freshwater fish as a surrogate for aquatic-phase
amphibians. In addition, because acute amphibian data were less sensitive than acute freshwater
fish data, the use of freshwater fish as a surrogate provides a more conservative estimation of
risk to the aquatic-phase CRLF.
To assess potential direct and indirect effects of trifluralin to the DS, toxicity data for both the
freshwater fish and estuarine/marine fish were evaluated since the DS lives in brackish waters.
The most sensitive freshwater or estuarine/marine fish toxicity data was utilized in the risk
estimation. Since the available data indicated freshwater fish were more sensitive than
estuarine/marine fish, the freshwater fish toxicity data was used to assess potential direct effects
of trifluralin to the DS. Similarly, freshwater invertebrate data was used to assess potential
indirect effects (prey) to the DS, as the available data indicated freshwater invertebrates were
more sensitive than estuarine/marine invertebrates. The extrapolation of the risk conclusions
from the most sensitive tested species to the aquatic-phase CRLF and DS may overestimate the
potential risks to those species.
Acceptable guideline toxicity tests and open literature studies for reptiles are not currently
available for quantitative use to assess potential risks of trifluralin use in California to the SFGS.
Therefore, toxicity data for surrogate species (i.e., birds for reptiles) are used in some instances
to assess risks. Efforts are made to select the organisms, which are 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.
6.2.3 Toxicity Endpoints
There are no acute estuarine/marine fish data for evaluation of toxicity to trifluralin. For acute
estuarine/marine fish, data from ethafluralin (an herbicide in the same chemical class as
trifluralin) are used.
There are no estuarine/marine invertebrate data for evaluation of chronic toxicity to trifluralin.
For chronic estuarine/marine invertebrate toxicity, the ACR was calculated using trifluralin data
for the freshwater invertebrate (acute and chronic) and the estuarine/marine invertebrate (acute).
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Acute toxicities for birds and mammals are based on studies in which no individuals died and no
sublethal effects were identified. The toxicity value for the terrestrial invertebrate is based on the
non-definitive LDso of > 24.17 jig/bee. For these taxa, RQs are not calculated; risks are discussed
qualitatively.
6.2.4 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.
6.2.5 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.
7. 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 trifluralin to the CRLF, DS, SFGS, and SJKF and the designated
critical habitat of the CRLF and the DS.
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 trifluralin to the CRLF, DS, SFGS, and SJKF and the designated critical habitat of the
CRLF and the DS.
Based on the best available information, the Agency makes a Likely to Adversely Affect (LAA)
determination for the CRLF from the use of trifluralin. Additionally, the Agency makes a Likely
to Adversely Affect determination for the DS, SFGS, and SJKF from the use of trifluralin.
Additionally, the Agency has determined that there is the potential for modification of the
designated critical habitat for the CRLF and the DS from the use of the chemical. Given the LAA
determination for the CRLF, FD, DFGS, and SJKF and potential modification of designated
critical habitat for the CRLF and DS, a description of the baseline status and cumulative effects
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for the CRLF is provided in Attachment 2 and the baseline status and cumulative effects for the
DS is provided in Attachment 4.
A summary of the risk conclusions and effects determinations for the CRLF, DS, SFGS, and
SJKF and the critical habitat for the CRLF and the DS, given the uncertainties discussed in
Section 6, is presented in Tables 7.1 and 7.2.
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Table 7.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
CRLF
LAA
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed species LOG (0.05) in 18 out
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
exceedances under the evaluated labels ranged from 45.9 to 2359 feet. Available aquatic-phase amphibian data suggests
trifluralin is less acutely toxic to aquatic-phase amphibians than to fish; however, there are Listed Species LOG exceedances
for the most sensitive aquatic-phase amphibian data.
Fish, Growth and reproduction: There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for trifluralin, only 15% had detectible
concentrations of trifluralin; however, those measured concentrations were comparable to the PRZM/EXAMS estimates. If
the maximum observed measured concentration (1.74 ug/L) was used as an exposure value to calculate an acute freshwater
fish RQ, there would be an exceedance of the Listed Species LOG (RQ = 0.09).
Terrestrial-phase (Juveniles and Adults):
Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest tested
trifluralin level was greater than expected concentrations in the environment for spray applications. For the granular non-
incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested for
20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Growth and reproduction: The chronic (dietary-based) RQs for birds exceeded the chronic LOG (RQ>1) for the nursery use
category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass andbroadleaf
plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary categories.
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed species LOG (0.05) in 18 out
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
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Table 7.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
exceedances under the evaluated labels ranged from 45.9 to 2359 feet. Available aquatic-phase amphibian data suggests
trifluralin is less acutely toxic to aquatic-phase amphibians than to fish; however, there are Listed Species LOG exceedances
for the most sensitive aquatic-phase amphibian data.
Fish, Growth and reproduction: There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for trifluralin, only 15% had detectible
concentrations of trifluralin; however, those measured concentrations were comparable to the PRZM/EXAMS estimates. If
the maximum observed measured concentration (1.74 ug/L) was used as an exposure value to calculate an acute freshwater
fish RQ, there would be an exceedance of the Listed Species LOG (RQ = 0.09).
Freshwater invertebrates: There were no exceedances of the Listed Species Acute or Chronic LOCs.
Vascular and non-vascular plants: There were no exceedances of the Acute LOCs.
Terrestrial plants: LOCs were exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs were exceeded for 14 out
of 25 modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range
from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy-one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
Terrestrial prey items, riparian habitat
Birds, Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest
tested trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular
non-incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested
for 20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Birds, Growth and reproduction: The chronic (dietary-based) RQs for birds exceeded the chronic LOG (RQ>1) for the
nursery use category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass and
broadleaf plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary
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Table 7.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
categories.
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQs for 15 g mammals range from 20.82 to 58.20 for short grass;
9.54 to 26.68 for tall grass; 11.71 to 32.74 broadleaf plants/small insects; 1.30 to 3.64 for fruits/pods/seeds/large insects.
Chronic RQs did not exceed LOCs for 15g granivores. Chronic dietary-based RQs exceed the Agency's chronic LOG (1.0)
in both crop scenarios (liquid application) for mammals consuming short grass, tall grass, and broadleaf plants/small insects;
they were not exceeded for fruits/pods/seeds/large insects.
Terrestrial invertebrates: For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortality at this dose).
Since mortality was observed at the highest test dose, expected exposures must be 20x less than the highest dose to preclude
risks to terrestrial invertebrates. Risks to terrestrial invertebrates cannot be precluded since the calculated EECs exceed the
calculated cut-point of 9.4 mg/kg-insect for all modeled scenarios.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy-one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
DS
LAA
Potential for Direct Effects
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed species LOG (0.05) in 18 out
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
exceedances under the evaluated labels ranged from 45.9 to 2359 feet.
Fish, Growth and reproduction: There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
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Table 7.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, DS, SFGS, and SJKF
Species
SFGS
Effects
Determination l
LAA
Basis for Determination
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for trifluralin, only 15% had detectible
concentrations of trifluralin; however, those measured concentrations were comparable to the PRZM/EXAMS estimates. If
the observed measured concentration (1.74 ug/L) was used as an exposure value to calculate an acute freshwater fish RQ,
there would be an exceedance of the Listed Species LOG (RQ = 0.09).
Potential for Indirect Effects
Freshwater invertebrates: There were no exceedances of the Listed Species Acute or Chronic LOCs.
Vascular and non-vascular plants: There were no exceedances of the Acute LOCs.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
1.05to2.32fordicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy -one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
Potential for Direct Effects
Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest tested
trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular non-
incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested for
20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Growth and reproduction: The chronic (dietary -based) RQs for birds exceeded the chronic LOG (RQ>1) for the nursery use
category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass andbroadleaf
plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary categories.
Potential for Indirect Effects
Fish, Adult survival: Acute RQs range from 0.05 to 0.35; exceeding the Agency's acute listed species LOG (0.05) in 18 out
of 25 crop scenarios with at least one of the application methods. The chance of individual effects (i.e., mortality) for
freshwater fish (surrogate for aquatic-phase CRLFs) is as high as ~1 in 3240. Buffer distance required to remove all LOG
exceedances under the evaluated labels ranged from 45.9 to 2359 feet.
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Table 7.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, PS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
Fish, Growth and reproduction: There were no chronic LOG exceedances. However, fish exposed to trifluralin may also
develop vertebral dysplasia, which could significantly impact the fishes' ability to swim, and therefore, impact its fitness.
The concentrations in these toxicity studies are within an order of magnitude of the maximum concentrations observed in the
monitoring data and many of the chronic EECs estimated using PRZM/EXAMS.
Freshwater invertebrates: There were no exceedances of the Listed Species Acute or Chronic LOCs.
Vascular and non-vascular plants: There were no exceedances of the Acute LOCs.
Birds, Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest
tested trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular
non-incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested
for 20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Birds, Growth and reproduction: The chronic (dietary-based) RQs for birds exceeded the chronic LOG (RQ>1) for the
nursery use category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass and
broadleaf plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary
categories.
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQs for 15 g mammals range from 20.82 to 58.20 for short grass;
9.54 to 26.68 for tall grass; 11.71 to 32.74 broadleaf plants/small insects; 1.30 to 3.64 for fruits/pods/seeds/large insects.
Chronic RQs did not exceed LOCs for 15g granivores. Chronic dietary-based RQs exceed the Agency's chronic LOG (1.0)
in both crop scenarios (liquid application) for mammals consuming short grass, tall grass, and broadleaf plants/small insects;
they were not exceeded for fruits/pods/seeds/large insects.
Terrestrial invertebrates: For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortality at this dose).
Since mortality was observed at the highest test dose, expected exposures must be 20x less than the highest dose to preclude
risks to terrestrial invertebrates. Risks to terrestrial invertebrates cannot be precluded since the calculated EECs exceed the
calculated cut-point of 9.4 mg/kg-insect for all modeled scenarios.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
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Table 7.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, DS, SFGS, and SJKF
Species
SJKF
Effects
Determination l
LAA
Basis for Determination
1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy -one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
Potential for Direct Effects
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQ values representing trifluralin exposures (spray applications) to
large mammals (1000 g) indicate risks resulting from both the alfalfa and nursery application scenarios (for alfalfa, LOG
exceedances for mammals consuming short grass, tall grass, and broadleaf plants/small insects; for nursery, LOG
exceedences for mammals consuming short grass, tall grass, broadleaf plants/small insects, and fruits/pods/seeds/large
insects. Chronic diet-based RQ values representing trifluralin exposures to all mammals indicate risks to mammals
consuming short grass, tall grass, and broadleaf plants/small insects for both the alfalfa and nursery scenarios. Chronic risk to
mammals from trifluralin through consumption of contaminated earthworms is unlikely.
Potential for Indirect Effects
Birds, Adult survival: There were no mortalities or sublethal effects in the avian acute dose and diet studies. The highest
tested trifluralin level was greater then expected concentrations in the environment for spray applications. For the granular
non-incorporated application rates of 2 and 4 Ibs/acre, the expected exposure level meets or exceeds the highest level tested
for 20 g individuals; therefore, acute risks to small birds and surrogate species cannot be precluded.
Birds, Growth and reproduction: The chronic (dietary -based) RQs for birds exceeded the chronic LOG (RQ>1) for the
nursery use category. Chronic RQs ranged from 1.23 to 2.68 for various dietary categories (i.e., short grass, tall grass and
broadleaf plants and insects). After refinement with T-HERPS, chronic RQs still exceeded LOCs for some dietary
categories.
Mammals: adult survival: There were no mortalities or sublethal effects in the acute dose. Acute risks to mammals from
spray or granular applications of trifluralin are unlikely as the calculated exposures do not exceed the toxicity values.
Mammals, growth and reproduction: Chronic dose-based RQs for all weight classes of mammals exceeded the Chronic LOG
(1.0) for all weights and feeding guilds except for large mammals consuming fruits/pods/seeds/large insects (alfalfa
application) and all granivores. Exceeding RQs ranged from 1. 1 1 to 58.20. Chronic dietary-based RQs exceed the Agency's
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Table 7.1 Effects Determination Summary for Effects of Trifluralin on the CRLF, DS, SFGS, and SJKF
Species
Effects
Determination l
Basis for Determination
Chronic LOG (1.0) in for alfalfa and nursery scenarios (liquid application, non-incorporated) for short grass, tall grass, and
broadleaf plants/small insects.
Terrestrial invertebrates: For honeybees, the most sensitive acute contact LD50 > 24.17 ug/bee (13% mortality at this dose).
Since mortality was observed at the highest test dose, expected exposures must be 20x less than the highest dose to preclude
risks to terrestrial invertebrates. Risks to terrestrial invertebrates cannot be precluded since the calculated EECs exceed the
calculated cut-point of 9.4 mg/kg-insect for all modeled scenarios.
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one of the application methods for risks to
monocot plants. RQs that exceed the acute LOG (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of 25
modeled uses for at least one of the application methods for dicot plants. RQs that exceed the acute LOG (1.0) range from
1.05to2.32fordicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant damage or death from direct application or
drift. Seventy -one percent are classified as 'probable' in the context of trifluralin use; 85% were incidents were classified as
registered uses.
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely affect (LAA)
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Table 7.2 Effects Determination Summary for the Critical Habitat Impact Analysis (CRLF and
PS)1
Designated
Critical Habitat
for:
Effects
Determination2
Basis for Determination
CRLF
HM
Aquatic-phase PCEs:
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for
trifluralin, only 15% had detectible concentrations of trifluralin; however, those
measured concentrations were comparable to the PRZM/EXAMS estimates. If
the observed measured concentration (1.74 ug/L) was used as an exposure value
to calculate an acute freshwater fish RQ, there would be an exceedance of the
Listed Species LOC (RQ = 0.09).
Terrestrial plants'. LOCs exceeded for 23 out of 25 modeled uses for at least one
of the application methods for risks to monocot plants. RQs that exceed the acute
LOC (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of
25 modeled uses for at least one of the application methods for dicot plants. RQs
that exceed the acute LOC (1.0) range from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant
damage or death from direct application or drift. Seventy-one percent are
classified as 'probable' in the context of trifluralin use; 85% were incidents were
classified as registered uses.
There is a potential for direct effects to aquatic-phase CRLF and indirect effects
via reduction of aquatic-phase prey items (fish and aquatic-phase amphibians) as
described in Section 5.
Terrestrial-phase PCEs:
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one
of the application methods for risks to monocot plants. RQs that exceed the acute
LOC (1.0) range from 1.11 to 4.89 for monocots. LOCs exceeded for 14 out of
25 modeled uses for at least one of the application methods for dicot plants. RQs
that exceed the acute LOC (1.0) range from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant
damage or death from direct application or drift. Seventy-one percent are
classified as 'probable' in the context of trifluralin use; 85 % were incidents were
classified as registered uses.
There is a potential for direct effects to terrestrial-phase CRLF and indirect
effects via reduction of terrestrial-phased prey items (mammals, terrestrial
invertebrates, and frogs) as described in Section 5.
DS
HM
Aquatic monitoring data: Of the 3,915 non-targeted water samples tested for
trifluralin, only 15% had detectible concentrations of trifluralin; however, those
measured concentrations were comparable to the PRZM/EXAMS estimates. If
the observed measured concentration (1.74 ug/L) was used as an exposure value
to calculate an acute freshwater fish RQ, there would be an exceedance of the
Listed Species LOC (RQ = 0.09).
Terrestrial plants: LOCs exceeded for 23 out of 25 modeled uses for at least one
of the application methods for risks to monocot plants. RQs that exceed the acute
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LOG (1.0) range from 1. 1 1 to 4.89 for monocots. LOCs exceeded for 14 out of
25 modeled uses for at least one of the application methods for dicot plants. RQs
that exceed the acute LOG (1.0) range from 1.05 to 2.32 for dicots.
Terrestrial incident reports: All 78 reported terrestrial incidents involved plant
damage or death from direct application or drift. Seventy -one percent are
classified as 'probable' in the context of trifluralin use; 85% were incidents were
classified as registered uses.
There is a potential for direct effects to the DS as described in Section 5.
1 Critical habitat has not been designated for the SFGS or the SJKF.
2 Habitat Modification (HM) or No effect (ME)
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, DS, SFGS, and SJKF life
stages within the action area and/or applicable designated critical habitat. 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 assessed species.
• Quantitative information on prey base requirements for the assessed species. While
existing information provides a preliminary picture of the types of food sources utilized
by the assessed species, 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
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resource impairment, and together with the information described above, a more
complete prediction of effects to individual species and potential modification to critical
habitat.
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