Pesticide Risk Assessment

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Pesticide Risk Assessment
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What is FIFRA?

• Federal Insecticide, Fungicide, and Rodenticide
  Act
• Requires pesticides sold or used in U.S. to be
  registered by EPA
• EPA registration standard will not cause
  unreasonable adverse effects on the environment

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FIFRA REGISTRATION

• Section 3 - Authorizes EPA to register new
  pesticide products
• Section 4 - Reregistration of pesticides by EPA
  to ensure they meet current standards
• Section 18 - Emergency use requests can be
  granted by EPA for unregistered pesticide uses
• Section 24(C) - Special local needs requests can
  be granted by EPA for new uses of registered
  products

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EPA-OPP Standard Evaluation Procedure for
Ecological Risk Assessment

• Assumes risk is a function of toxicity and
  exposure
• RQ Estimated Environmental Concentration /
  Toxicity Endpoint
• RQ compared to levels of concern (LOCs)

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Toxicity Tests Terrestrial Animals
Test Species Exposure Endpoint
LD50 Bobwhite/ Mallard Single oral Mortality
LC50 Bobwhite/ Mallard 5-d Dietary Mortality
Repro. Bobwhite/ Mallard 10-wk Dietary LOEC, NOEC
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Toxicity Tests Aquatic Animals
Test Species Exposure Endpoint
LC50 Rainbow, bluegill, sheepshead 96 h Mortality
LC50 Daphnia, mysid, eastern oyster 48-96 h Mortality
ELS Fathead, Rainbow, Sheepshead 30-100 d LOEC, NOEC
Life Cycle Daphnia, mysid, fish spp. 21-300 d LOEC, NOEC
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Toxicity Tests Terrestrial Invertebrate

• Honey bee
• Acute oral LD50
• Acute dermal LD50
• Residue studies LD50

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Toxicity Test Plants

• Aquatic plants
• Blue-green and green algae (EC50)
• Marine and freshwater diatom (EC50)
• Duckweed (EC50)
• Terrestrial plants (EC25, NOEC)
• Six dicots and four monocots (crops)
• Root-shoot length, weight, visual

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Other Sources of Toxicity Information

• Registrant generated test to satisfy registration
  requirements for other countries
• OECD Studies
• Beneficial arthropods
• Soil microorganisms
• Formulation/mixture studies
• Metabolite studies

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Human Health Toxicity Studies

• Rat LD50
• 2 generation chronic rat
• 90-day sub-chronic rat
• Inhalation (rat/mouse)
• Dermal (rabbit)

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Other Sources of Toxicity Information

• Open Literature
• Internet Sources (USGS acute toxicity test
  database, EXTOXNET, PAN pesticide database,
  WHO/FAO pesticide data sheets)
• EPA-OPP One-liner ecotoxicity and environmental
  fate databases
• www.epa.gov/pesticides/

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Laboratory Environmental Fate Studies

• Aerobic Soil Metabolism - rate of degradation by
  soil microorganisms
• Hydrolysis - chemical reaction with water forming
  new molecule (often pH dependent)
• Aqueous Photolysis - breakdown of molecules in
  water through the absorption of light
• Aerobic and Anaerobic Aquatic Metabolism - rate
  of metabolism in aqueous environment with and
  without oxygen.

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Laboratory Environmental Fate Studies (continued)

• Kd and Koc - rate of soil adsorption
• Bioconcentration Factor (BCF) - Ratio of
  concentration in organism (fish) compared to
  surrounding medium (water)

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Field Environmental Fate Studies

• Field Dissipation - evaluate pesticide mobility,
  degradation and dissipation under actual use
  conditions
• agricultural, aquatic, forestry
• Field Volatility - evaluate pesticide movement
  when volatilization is concern
• Dislodgeable residue

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Chemical/Physical Studies

• Vapor pressure - measure of a chemicals
  volatility
• Solubility - measure of ability to dissolve in a
  solvent (water)
• Henrys Law Constant - ratio of vapor pressure to
  water solubility
• Octanol-water partition coefficient (Kow) - ratio
  of partitioning in octanol to water

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EPA-OPP Exposure Analysis

• Terrestrial
• Kenaga Nomogram
• Monitoring Data
• Aquatic
• GENEEC
• PRZM/EXAMS
• Monitoring Data
• Terrestrial/Aquatic
• AgDrift

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Kenaga Nomogram Review

• Dietary exposure model for liquid broadcast
  applications
• Determines maximum and median concentrations on
  various food items
• Residue based on application rate and structure
  of plant/insect
• Residues independent of application method

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Granular, Bait, and Treated Seed Exposure
Applications

• In-furrow applications assume 1 of granules,
  bait or seed unincorporated
• Incorporated banded treatments assume 15
  material unincorporated
• Broadcast treatment w/o incorporation assumes
  100 of granules, bait, seed unincorporated

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Terrestrial Plant Exposure Analysis

• Runoff based on solubility
• Drift based on standard assumptions for ground
  (1) and aerial (5) applications
• Scenario based on runoff from 1-ha to adjacent
  hectare for terrestrial plants
• Scenario based on runoff from 10-ha to adjacent
  hectare for semi-aquatic plants

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AgDrift Model Summary

• Model based on field and wind tunnel studies to
  determine drift from different application
  methods
• Simulates ground, orchard air blast and aerial
  applications
• Predicts off-site terrestrial and aquatic
  concentrations into standard or user-defined
  waterbodies

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Factors that affect drift

• Droplet size distribution
• Wind speed/direction
• Release height
• Application method
• Environmental factors (temperature, humidity)

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GENEEC Input Parameters

• Application Rate
• Koc
• Application Method
• of applications
• Application Interval
• Depth of Incorporation

• Aerobic Aquatic Metabolism
• Solubility
• Aquatic Photolysis
• Hydrolysis
• Aerobic Soil Metabolism

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GENEEC Aquatic Screening Model Assumptions

• Applications occur on a 10 ha field that drains
  into a one hectare pond 2-m in depth
• No buffer between the pond and treated field
• Runoff is from a single large rainfall event over
  a 24-hour period
• Soil type is considered a high runoff soil (MS
  silt loam)
• Drift contribution
• Based on contributions from AgDrift

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Atrazine estimated environmental concentrations
(1 lb/ai)
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PRZM/EXAMS Aquatic Exposure Model

• Site specific model that determines pesticide
  load from agricultural applications
• Each simulation is conducted using 36 years of
  rainfall data to determine variability in loading
• Calculates edge of field pesticide loadings in
  surface water and sediment

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PRZM/EXAMS Aquatic Exposure Model

• Environmental fate model that simulates the
  process that occur in the water body
• Steady state model that has a constant volume
• Calculates peak maximum, 96-hour, 21-day and
  60-day average.
• The 1 in 10 year maximum value is used in
  calculating risk quotient values

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Use of Monitoring Data in Pesticide Risk
Assessment

• Typically used for currently registered
  pesticides (reregistration, special review)
• Sources
• NAWQA USGS
• open literature
• registrants
• Considerations for use
• temporal and spatial sampling
• storm events vs. base flow

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Temporal variability of atrazine and chlorpyrifos
in water and sediment
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Risk Presumption for Terrestrial Animals
Risk Presumption RQ LOC
Acute High Risk EEC/LC50 or LD50/ft2 0.5
Acute Restricted Use EEC/LC50 or LD50/ft2 0.2
Acute Endangered Species EEC/LC50 or LD50/ft2 0.1
Chronic RQ EEC/NOEC 1
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LOC and Dose Response
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Risk Presumption for Aquatic Animals
Risk Presumption RQ LOC
Acute High Risk EEC/LC50 or EC50 0.5
Acute Restricted Use EEC/LC50 or EC50 0.1
Acute Endangered Species EEC/LC50 or EC50 0.05
Chronic RQ EEC/NOEC 1
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Risk Presumption for Terrestrial Plants
Risk Presumption RQ LOC
Terrestrial and semiaquatic plants Terrestrial and semiaquatic plants Terrestrial and semiaquatic plants
Acute high risk EEC/EC25 1
Acute ES EEC/NOEC 1
Aquatic plants Aquatic plants Aquatic plants
Acute high risk EEC/EC50 1
Acute ES EEC/NOEC 1
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Exceedance of LOCs in the Screening Assessment

• Request additional effects data
• Request additional environmental fate data
• Ex. aerobic aquatic metabolism, foliar
  dissipation
• Use higher tier modeling/monitoring to refine
  exposure analysis and provide site specific
  exposure distribution

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NAWQA Maximum Atrazine Concentrations for 40
Agricultural Sites
130
Mortality in Phytoplankton Macrophytes
Estimated to Occur at
120
32 µg/L
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Invertebrate Populations Likely to be Reduced
at 22 µg/L
100
Mortality to Macrophytes Estimated to Occur at
18 µg/L
Reduction in Primary Production Likely to Occur
at 10 µg/L
90
Reduction in Primary Production Likely to Occur
at 2.62 µg/L and
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Reductions in Primary Productivity Macrophytes
Estimated to
Occur at 2.3 µg/L
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Measured Concenrations (ug/L)
60
50
40
30
20
10
0
0
10
20
30
40
50
60
Exceedence
Sites w/ Atrazine Concs gt Y
Source Reregistration Eligibility Decision
Environmental Fate and Effects Chapter. 2002.
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EPA-OPP Risk Mitigation for Fish and Wildlife

• Eliminate use on specific crop
• Buffer zones
• Time of application
• Application method and rates
• Number of applications
• Spray drift best management practices

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OPP Endangered Species Protection Program (ESPP)

• Goal is to implement mitigation measures to
  eliminate adverse impact to listed spp.
• Currently ESPP defers to county bulletins
• Program in place since 1989
• Voluntary BMPs for listed species
• Very few county bulletins complete
• Service has not consulted on county bulletins
• Service currently working with OPP to review ESPP

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