A tiered aquatic risk assessment of pyrethroid insecticides for agricultural and residential use Jeffrey Giddings Compliance Services International Paul Hendley Phasera Ltd. Scott Jackson BASF Michael Dobbs Bayer CropScience Al Barefoot DuPont Crop Protection Gary Mitchell FMC Kevin Henry Syngenta Crop Protection Richard Allen Valent USA 11/13/2014© Pyrethroid Working Group 2014 Slide 1 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).

Conceptual model guides refinement of pyrethroid risk assessment  Extremely hydrophobic, fate dominated by sediment processes  Dissipate quickly from water column, partition to sediment  Only freely dissolved pyrethroid is bioavailable and contributes to toxicity  Readily degraded by microorganisms  Plants and biofilms play a role in dissipation  Rapidly metabolized by animals, not highly bioaccumulative, food web transport not a concern 11/13/2014© Pyrethroid Working Group 2014 Slide 2

PlantsMollusksFishArthropods (Insects and Crustaceans) Scenario AcuteChronicAcuteChronicPore Water CA Onion< IN Corn< CA Almond< FL Pepper< GA Pecan< IL Corn< OR Sweet Corn< MS Soybean< MS Cotton< TX Cotton< Residential< Screening level RQs indicate potential pyrethroid risk to some taxonomic groups for all uses… 11/13/2014© Pyrethroid Working Group 2014 Slide 3 KEY RQ < LOC RQ < 2x LOC RQ > 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).

…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 %ile th %ile <RL b th %ile th %ile <RL11 Max th %ile a Range of EECs for 18 crop scenarios b Less than reporting limit Example: 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 4

Refining the exposure analysis (1)  Tier II+ Replace EXAMS with AGRO-2014, a validated, calibrated model that simulates critical sediment processes  Suspended solids remove pyrethroid from water column  Deposition, resuspension, burial Incorporate mitigations (no-spray buffers, vegetative filter strips) specified on all pyrethroid labels Other aspects of Tier II retained  Tier II+AR (Agronomic Realism) Simulate application timing and method (aerial, ground) to match actual agronomic practice Maximum rates, number of applications retained Other aspects of Tier II/II+ retained 11/13/2014© Pyrethroid Working Group 2014 Slide 5

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 retained  Landscape Refinement 2 Replace soil and weather parameters for standard EPA crop scenarios with distributions of actual runoff/erosion potential in catchments where each crop is grown Other aspects of Landscape Refinement 1 retained 11/13/2014© Pyrethroid Working Group 2014 Slide 6 Probabilistic exposure analysis addresses spatial variability in key model parameters, replaces worst-case assumptions with actual distributions.

Landscape probabilistic data significantly impact EEC distributions 24-h water column EECs – deltamethrin use on cotton 11/13/2014© Pyrethroid Working Group 2014 Slide 7 LR1: PCA distribution Tier II+AR LR2: PCA plus runoff/erosion (R/E) potential LR2 + PTA

Other factors that potentially influence exposure were also considered and quantified if possible  Examples of factors considered Percent of crop area treated with any pyrethroid (PTA) Variation in wind speed and direction on multiple application dates Interception of spray drift by vegetation Sediment delivery ratio Drainage area to pond volume Receiving water dimensions and hydrology Variability of degradation rates Application rates and number of applications Use of drift reduction technology Tillage practices etc. 11/13/2014© Pyrethroid Working Group 2014 Slide 8

Urban exposure refinements  Replaced PRZM with SWMM (Storm Water Management Model) Configured for high-density residential neighborhood in California Calibrated for pyrethroids measured in storm water runoff  Replaced EXAMS with AGRO-2014  Incorporated results of surveys of residential pest control professionals in California and 6 other regions of the US Pyrethroids applied, frequency of application, areas treated (driveway, perimeter, lawn, etc.) Retain assumption that applications are made at maximum rate 11/13/2014© Pyrethroid Working Group 2014 Slide 9

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 10

Fraction of arthropod species potentially affected Effects refinement: use data for all species, not only the most sensitive 11/13/2014© Pyrethroid Working Group 2014 Slide 11 Species Sensitivity Distributions for arthropods are similar across pyrethroid class: shape of curve position of species

Combined pyrethroid SSD for arthropods takes advantage of similarity of toxicity profiles Americamysis bahia Daphnia magna TaxonSpecies Crustaceans47 Insects58 Acarids2 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 HC5 = 5.3 Hyalella equivalents

Risk characterization: RQs indicate less risk at successive tiers of the assessment 11/13/2014© Pyrethroid Working Group 2014 Slide 13 PlantsMollusksFishArthropods (Insects and Crustaceans) Tier AcuteChronicAcuteChronicPore Water Tier II< Tier II+< Tier II+AR< LR1< < LR2< < LR2+PTA< <0.01 Residential (CA) Tier II< SWMM-AGRO< Example: Risk Quotients for deltamethrin for soybeans and CA residential use KEY RQ < LOC RQ < 2x LOC RQ > 2x LOC

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, SSDs  However, 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 Slide 14

THANK YOU! 11/13/2014© Pyrethroid Working Group 2014 Slide 15