A tiered aquatic risk assessment of pyrethroid insecticides for - PowerPoint Presentation

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A tiered aquatic risk assessment of pyrethroid insecticides for agricultural and residential use

Jeffrey Giddings Compliance Services InternationalPaul Hendley Phasera Ltd.Scott Jackson BASFMichael Dobbs Bayer CropScienceAl Barefoot DuPont Crop ProtectionGary Mitchell FMCKevin Henry Syngenta Crop ProtectionRichard Allen Valent USA

11/13/2014

© Pyrethroid Working Group 2014

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On behalf of the Pyrethroid Working Group

The Pyrethroid Working Group (PWG) is a US task force whose members include eight primary pyrethroid registrants

(AMVAC Chemical Corporation, BASF Corporation, Bayer

CropScience

LP,

Cheminova

A/S, DuPont Crop Protection, FMC Corporation, Syngenta Crop Protection, LLC,

Valent

U.S.A. Corporation).  Slide2

Conceptual model guides refinement of pyrethroid risk assessment

Extremely hydrophobic, fate dominated by sediment processesDissipate quickly from water column, partition to sedimentOnly freely dissolved pyrethroid is bioavailable and contributes to toxicityReadily degraded by microorganismsPlants and biofilms play a role in dissipationRapidly metabolized by animals, not highly bioaccumulative, food web transport not a concern11/13/2014© Pyrethroid Working Group 2014 Slide

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Plants

Mollusks

Fish

Arthropods (Insects and Crustaceans)

Scenario

Acute

Chronic

Acute

Chronic

Pore Water

CA Onion

<0.01

<0.01

0.080.15694.01.5IN Corn<0.01<0.010.080.13745.52.2CA Almond<0.01<0.010.090.20846.33.0FL Pepper<0.01<0.010.150.261298.63.7GA Pecan<0.01<0.010.270.44239136.7IL Corn<0.01<0.010.280.44244137.5OR Sweet Corn<0.01<0.010.280.50244187.5MS Soybean<0.01<0.010.360.923193216MS Cotton<0.01<0.010.961.18443516TX Cotton<0.01<0.011.11.110063916Residential<0.01<0.011.31.411724815

Screening level RQs indicate potential pyrethroid risk to some taxonomic groups for all uses…

11/13/2014

© Pyrethroid Working Group 2014

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KEYRQ < LOCRQ < 2x LOCRQ > 2x LOC

Example: Screening-level RQs for deltamethrin

Note: EPA does not distinguish mollusks from other invertebrates. PWG considers mollusks separately from arthropods (insects and crustaceans).Slide4

…but screening-level exposure predictions greatly exceed measured concentrations

Modeling (ng/L)Monitoring (ng/L)

Agricultural

a

Residential

Agricultural (

n=1504)

Residential (

n=534)

90

th

%

ile22-44423290th %ile<RLb3.995th %ile45-60729395th %ile<RL11Max45-69429899th %ile4.085aRange of EECs for 18 crop scenarios bLess than reporting limitExample: Cyfluthrin concentrations (bulk water column) estimated by Tier II modeling, and concentrations in surface waters (whole water samples) from extensive monitoring database.11/13/2014© Pyrethroid Working Group 2014 Slide 4Slide5

Refining the exposure analysis (1)Tier II+

Replace EXAMS with AGRO-2014, a validated, calibrated model that simulates critical sediment processesSuspended solids remove pyrethroid from water columnDeposition, resuspension, burialIncorporate mitigations (no-spray buffers, vegetative filter strips) specified on all pyrethroid labelsOther aspects of Tier II retainedTier II+AR (Agronomic Realism)Simulate application timing and method (aerial, ground) to match actual agronomic practiceMaximum rates, number of applications retainedOther aspects of Tier II/II+ retained11/13/2014© Pyrethroid Working Group 2014 Slide 5Slide6

Refining the exposure analysis (2)Landscape Refinement 1

Replace assumption of 100 percent cropped area (PCA) with distributions of actual PCA in catchments where each crop is grown (national or regional)Other aspects of Tier II+AR retainedLandscape Refinement 2Replace soil and weather parameters for standard EPA crop scenarios with distributions of actual runoff/erosion potential in catchments where each crop is grownOther aspects of Landscape Refinement 1 retained11/13/2014© Pyrethroid Working Group 2014 Slide 6

Probabilistic exposure analysis addresses spatial variability in key model parameters, replaces worst-case assumptions with actual distributions.Slide7

Landscape

probabilistic data significantly impact EEC distributions24-h water column EECs – deltamethrin use on cotton11/13/2014© Pyrethroid Working Group 2014 Slide 7

LR1: PCA distribution

Tier II+AR

LR2: PCA plus runoff/erosion (R/E) potential

LR2 + PTASlide8

Other factors that potentially influence exposure were also considered and quantified if possible

Examples of factors consideredPercent of crop area treated with any pyrethroid (PTA)Variation in wind speed and direction on multiple application datesInterception of spray drift by vegetationSediment delivery ratioDrainage area to pond volumeReceiving water dimensions and hydrologyVariability of degradation ratesApplication rates and number of applicationsUse of drift reduction technologyTillage practicesetc.11/13/2014© Pyrethroid Working Group 2014 Slide 8Slide9

Urban exposure refinementsReplaced PRZM with SWMM (Storm Water Management Model)

Configured for high-density residential neighborhood in CaliforniaCalibrated for pyrethroids measured in storm water runoffReplaced EXAMS with AGRO-2014Incorporated results of surveys of residential pest control professionals in California and 6 other regions of the USPyrethroids applied, frequency of application, areas treated (driveway, perimeter, lawn, etc.)Retain assumption that applications are made at maximum rate11/13/2014© Pyrethroid Working Group 2014 Slide 9Slide10

Assumptions and uncertainties affecting exposure estimates were analyzed

Directional influence of assumptions and uncertainties were evaluated.Magnitude of influence was quantified using sensitivity analysis and professional judgment.The cumulative effect of the assumptions and uncertainties was found to be 1 to 2 orders of magnitude in the direction of overestimation of exposure and risk.11/13/2014© Pyrethroid Working Group 2014 Slide 10Slide11

Fraction of arthropod species potentially affected

Effects refinement: use data for all species, not only the most sensitive11/13/2014© Pyrethroid Working Group 2014 Slide 11

Species Sensitivity Distributions for arthropods are similar across pyrethroid class:

shape of curve

position of speciesSlide12

Combined pyrethroid SSD for arthropods takes advantage of similarity of toxicity profiles

Americamysis bahia

Daphnia magna

Taxon

Species

Crustaceans

47

Insects

58

Acarids

2

All arthropods

107

Toxicity data were normalized to Hyalella equivalents and SSD fitted to combined data for all pyrethroids.11/13/2014© Pyrethroid Working Group 201412HC5 = 5.3 Hyalella equivalentsSlide13

Risk characterization: RQs indicate less risk at successive tiers of the assessment

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Plants

Mollusks

Fish

Arthropods (Insects and Crustaceans)

Tier

Acute

Chronic

Acute

Chronic

Pore Water

Tier II

<0.01<0.010.350.50319187.5Tier II+<0.01<0.010.080.13137.61.2Tier II+AR<0.01<0.010.070.14105.51.3LR1<0.01<0.010.02<0.013.41.80.33LR2<0.01<0.010.01<0.013.11.70.13LR2+PTA<0.01<0.01<0.01<0.010.120.049<0.01Residential (CA)Tier II<0.010.021.31.411704815SWMM-AGRO<0.01<0.010.010.031.70.990.17Example: Risk Quotients for deltamethrin for soybeans and CA residential useKEYRQ < LOCRQ < 2x LOCRQ > 2x LOCSlide14

Key aspects of tiered risk assessment for pyrethroids

The refinements in exposure and effects analysis made full use of available data to replace conservative assumptions. Examples: PCA, SSDsHowever, many conservative aspects of the screening-level assessment were retained throughout the higher tiers, and the outcome was still protective.The higher-tier assessment indicated that pyrethroid exposure from residential and agricultural uses according to current labels is unlikely to cause ecologically significant effects in aquatic systems.This conclusion is supported by monitoring data, mesocosm studies, and bioassessments.11/13/2014© Pyrethroid Working Group 2014

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Thank You!

11/13/2014© Pyrethroid Working Group 2014 Slide 15jgiddings@complianceservices.com