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# Conference Call with Pyrethroid Working Group on Pyrethroid Ecological Risk Assessment – Meeting Summary Thursday, June 27, 2013; 10:00 am – 12:00 pm Participants Pyrethroid Work Group (PWG): Dick Collier (Landis International) Alex Porges (Landis International) Jeff Giddings (Compliance Services International) Jeffrey Wirtz (Compliance Services International) Dean Desmarteau (Waterborne Environmental, Inc.) Chris Holmes (Waterborne Environmental, Inc.) Gregg Hancock Waterborne Environmental, Inc.) Paul Hendley (Phasera, Ltd.) Michael Winchell (Stone Environmental, Inc.) Scott Jackson (BASF Corporation) Kevin Henry (Syngent a Crop Protection) Russell Jones (Bayer CropScience) Michael Dobbs (Bayer CropScience) Environmental Protection Agency (EPA or Agency): Environmental Fate and Effects Division Mah Shamim Keith Sappington Michael Lowit James Hetrick Reuben Baris Steve Wente Rosanna Louie-Juzwiak Dana Spatz Jose Melendez Donna Judkins Biological and Economic s Analysis Division Jonathan Becker Pesticide Re-evaluation Division Monica Wait Molly Clayton Tracy Perry Garland Waleko Laura Parsons

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# Carissa Cyran Patricia Parrott Kevin Costello Background The Pyrethroid Working Group (PWG) is a grou p of pyrethroid technical registrants that represents the following 9 pyrethroi d cases: bifenthrin, cyfluthrins, cypermethrin, cyahalothrins, deltamethrin, esfenvalerate, fenpropathrin, perm ethrin, and tefluthrin. The Environmental Protection Agency (EPA or Agency) has met seve ral times previously with the PWG regarding its plans to conduct and submit pr obabilistic ecological ri sk assessments for these pyrethroids. Summaries of these meetings can be f ound in the general pyrethroid docket on www.regulations.gov under docket id numb er EPA-HQ-OPP-2008-0331. Presentation The meeting began with a brief overview of the probabilistic ecological risk assessments the PWG plans to conduct for the 9 represented pyrethroids. The PWG then presented details on its plans to conduct, by December 2013, the following for the represented pyrethroids:

 a review of use informati on on end use product labels  exposure modeling of synthetic pyrethroids  a comparative sediment degradation study  a national scale assessment of erosion and drift potential  modeling of pyrethroid exposur e in urban receiving waters  a residential use and usage survey  a monitoring database  a sensitivity analysis of the aquatic invertebrate Hyalella azteca The meeting concluded with a brief discussi on of potential future EPA-PWG interactions. Discussion In previous discussions with PWG on its pl ans for conducting probabilistic ecological risk assessments (see the summary of the Ma rch 27, 2013 meeting, available in the pyrethroid docket ), EPA explained that any significant ch ange to EPA’s risk assessment methodology would need to undergo extensive peer review, an d EPA must consider the timeframe allowed for pyrethroid risk assessments duri ng registration review. Theref ore, EPA anticipates conducting risk assessments for all pyrethroid active ingr edients following the Agency’s standard policies and procedures. On June 26 th 

# , EPA reiterated that the Agency will review all data and risk assessments submitted by the PWG and anticipates th at in particular the monitoring database and analysis of use information on registered product labels will be useful in informing the upcoming registration review risk assessments.

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# Planned PWG Submissions Anticipated Timeline for PWG data and assessment submissions to EPA Item Topic Estimated Submission Dates 1 Review of pyrethroid end us e product labels September 2013 2 Survey of professional applic ators on residential uses of pyrethroids September 2013 3 Conceptual models of pyrethroi ds in sediments, and comparison of receiving water simulation models to the conceptual models August 2013 4 Determination of partition coeffici ents for 9 pyrethroids in natural and artificial sediment s (laboratory report) December 2013 5 Measured pyrethroid concentrations in US surface waters and sediments September 2013 6 Tier 2 and refined agricultura l exposure modeling and risk estimation December 2013 7 Sensitivity analysis and probabilistic modeling with the SWMM exposure model December 2013 8 National vulnerability assessment December 2013 9 Exposure modeling for pyrethroids in flowing water December 2013 10 High-resolution landscape-level expo sure analysis for pyrethroids in selected watersheds December 2013 11 Modeling pyrethroid runoff from ur ban residential areas September 2013 12 Analysis of pyrethroid aquatic toxicity data [SSDs, acute-tochronic ratios, isomers, formula tion, freshwater/saltwater, etc.] September 2013 13 Toxicity of cypermethr in [and bifenthrin] to Hyalella azteca from laboratory cultures and natural populations August 2013 14 Bioassessment studies December 2013 15 Review of aquatic mesocosm studies December 2013 16 Modeling effects of pyrethroi ds on aquatic invertebrate populations and potential i ndirect effects on salmon December 2013 17 Nine separate higher-tier aqua tic risk assessments March 2014 – January 2016 Future EPA-PWG Interactions EPA plans to meet with the PWG following the submission of the items listed above. The first of EPA’s preliminary risk assessments fo r the represented pyrethroi ds (deltamethrin) is scheduled for completion in March 2015. The last of the PRAs for the represented pyrethroids (tefluthrin) is scheduled fo r completion in January 2017.

# 6/27/2013

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# Conceptual Model Refinements to Support Exposure Modeling for Synthetic Pyrethroids - Implications for Data Development, Exposure Modeling and Toxicity Studies Presentation to EPA EFED on June 27, 2013. Paul Hendley (Phasera Ltd.) on behalf of the Pyrethroid Working Group (PWG)



# Outline

 

# Conceptual models  

## Largely covered by existing EPA conceptual models  

### Some pyrethroid-specific factors require conceptual model refinement.  

# Aquatic Exposure modeling  

## Certain pyrethroid-specifi c issues are not addressed by current EXAMS model  

## Resulting PWG non-spatial exposure modeling deliverables  

# Model input selection  

## USEPA SAP and ORNL comments  

## PWG efforts to address these

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# Pyrethroid Reg Review Aquatic Conceptual Models

Pyrethroid Characteristics that Impact Exposure - 1

 

# Adsorption to organic matter is exceptional  

## Remarkably high Koc – 1,000,000 – 4,000,000 L/kg (SPME)  

### Only recently measurable at these extremes – early guideline studies underestimates  

## Impacts partition in water bodies, uptake into organisms and bioavailability in presence of particulates and dissolved organic matter

 

### Equilibrium Partition Approach (DiToro) – i.e. bioavailable fraction drives eco-toxicology  

### Runoff entry/sedimentation process algorithms critical for aquatic exposure models  

# Biotic degradation is relatively rapid – ester cleavage via enzymes  

## Unlike many other high Koc compounds, degraded and excreted by organisms  

## Therefore limited bioaccumulation potential

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# Pyrethroid Characteristics that Impact Exposure - 2

 

# Adsorption/desorption exchange behavior is relatively rapid  

## Unlike many other high Koc compounds, bound material re-equilibrates quite rapidly between environmental compartm ents and is therefore available for microbial degradation in soils and sediments

 

### Faster than expected half lives in soil & sediment  

# Combined adsorption/degradation behavior results in additional aquatic dissipation ( e.g. plant surface uptake degradation, Leistra (2003), Hand et al (2001) & biofilm dissipation, Allan et al (2005))

 

## Overall system dissipation rate is faster than expected in microcosms  

### Additional degradation routes remove chemical from the system



# Current PRZM-EXAMS Model & Pyrethroids

 

# All eroded chemical enters pond – but no sediment or runoff water  

## PRBEN% (50%) of chemical immediatel y perfectly mixed in top 5cm sediment  

## Remaining (100-PRBEN%) enters water co lumn - treated like spray drift entry  

## Suspended solids in water column unchanged at 30 ppm despite heavily or lightly erosive runoff event

 

### No sedimentation occurs in pond with time, no overflow of sediment laden water  

## No sediment deposition occurs in mode l, each yearly total mass of eroded chemical is added to the same 5 cm vo lume of sediment – build up possible  

# Logic and study data show these are not reasonable assumptions  

## Especially for eroded pyrethroids - almost exclusively sediment bound  

# EPA has recognized this  

### “ In cases where chemicals have appreciable stability in the environment, the EXAMS pond model will tend to overestimate the concentration in pond sediments “ ( page 54 of http://www.epa.gov/espp/consultation/ecorisk-overview.pdf. 

### )  

## Dirk Young currently developing a revise d SWC model based on variable volume pond and related concepts to tackle these (& other) potential problems

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# Aquatic Model algorithms important for pyrethroids

 Variable pond water volume  Suspended & eroded sediment deposition  Relevance of 5 cm assumption  Burial of Sediment ch emical with deposition  Variable suspended solids/algae concns.  Pore water/ water column mixing  Consideration of disso lved organic carbon  Pore water/water column mixing factors  Variable Plant poplns. – plant uptake factor  Flowing water – residue exchange removal  Flowing water – reducing exposure duration  Sediment bioturbation (biological mixing)  Data to support organic matter concns.  Sediment bulk density data to estimate pore water/sediment distributions  Sediment entry improvements  More realistic PRZM erosion scenarios – max T loss  Incorporate VFSmod for reduction of sediment entry  Estimation of irrigation related erosion for West USA

Factor EXAMS - standard EXAMS AGRO SWC* (VVWM) Variable pond water volume N Y Y Y Suspended & eroded sediment deposition N N Y Relevance of 5 cm assumption N Burial of Sediment chemical with deposition N N Y Y Variable suspended solids/algae concns. N N N N Pore water/ water column mixing Y Y Consideration of dissolved organic carbon Y Y Y Y Pore water/water colu mn mixing factors N N Variable Plant poplns. – plant uptake factor N Y N Flowing water – residue exchange removal N Y Y ? Flowing water – reducing exposure duration N Y Y ? Sediment bioturbation (biological mixing) N Y ?? ?? Data to support organic matter concns. N N N ?? Sediment bulk density data to estimate pore water/sediment distributions N NN N Sediment entry improvements N Y N Y? 

# Current Aquatic Receiving Water Model Capabilities

PWG Conclusion: No ideal model available, EXAMS does not address pyrethroids suitably * SWC (VVWM) model still in α development stage - exact capabilities not yet fully defined

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# Selection of aquatic exposure models

 

# All agree that EXAMS (current version) is unsuitable  

# Only SAP reviewed model that atte mpts to deal with some of the key pyrethroid–specific issues is AGRO

 

## Appears to meet “best available” criterion – especially for static water bodies  

## SWC status – under revision due to Waterborne pyrethroid model findings  

## PWG notes EPA concerns over AGRO and wishes to know more details of EPA plans for alternative approach fo r pyrethroid risk assessments.  

# Recent EPA white paper review  

## Sediment burial – needs to be included - long term source of contamination  

### PWG agrees conceptually but believes that EXAMS/AGRO estimates of

concentration will be maxima (due to dilution, dispersion) for epi-benthos  

## Scour/re-suspension – flowing water issue – high flow events – large dilution  

## Farm ponds – require digging ou t to make room for new events  

# Model conservatism elements that should be included  

## Several EPA/SAP comments on use of wh ole water body dissi pation constants



# PWG Plans for Crop Exposure Modeling

 

## Tier 2 modeling – due to start when la bel info collection completed (Sept 2013)  

### PRZM-EXAMS – “Yellow Book” standard scenarios for key crops  

### Inputs – available data for AI’s generally selected via US EPA approaches  

## Tier 2+ modeling – due to start when label info collection completed (Sept 2013)  

### AGRO (depends on SWC (VVWM) status/capabilities) with standard scenarios for key crops  Corresponding AGRO (or SWC) pyrethroid specific input parameter sensitivity analysis  CA lettuce (drift driven) and MS cotton scenarios (drift/runoff) as baselines  

### Inputs – best available chemical inputs for racemic AI’s and refined scenario inputs  full list can be supplied  

## Additional Modeling efforts  

### Uncertainty analyses – examine assumptions & key factors not covered by current models  

### Wind speed/direction probability analyses for key pyrethroid SAMSON locations  

### Comprehensive probabilistic exposure assessment covering most sensitive variables  

### Flowing water modeling to account for sediment transport/runoff & drift exposure durations  

### Others: e.g. Comparison with monitoring data exemplifying other dissipation routes  

## Spatial - National Scale Erosion and Drift Potential  

## Spatial - High Resolution Modeling of higher exposure potential watersheds

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# Non-Spatial PWG Crop Modeling Deliverables

 

## Tier 2  Use label info, input data info, model files, AI co mparative tables, report covering key crops and all AI’s  

### Tier 2+  Sensitivity study data and report  Literature support, conceptual models, assumptions, inpu t info, model files, AI comparisons, verification data, report covering key crops and AI’s  

### Additional Modeling  Details of approaches to Pyrethroid flowing water modeling examining probabilities of exposure duration

 Assumptions, input/output data and report  National hourly wind speed/direction pr obability assessment for all SAMSON stations  Database and examples of application for drift probability assessment  Broader Probabilistic exposure assessment covering full set of sensitive variables  Assumptions, input/output data and report  Uncertainty analyses covering additional variables not accounted for in existing models  Report and supporting literature/data



# Model inputs – Koc and Sediment Degradation Rates

 

# Current data highly inhomogeneous  

## Wide range of soils/sediments/ methods/ LOD’s/ lab capabilities  

## Multiple data for individual products across time. Isomer issue  

## Laskowski data selection–study quality ba sed –differs from EPA current methods  

## For sediment exposure potential modeling and assessing bioavailable fraction this makes AI-to-AI comparison difficult  

### ORNL

.. little information on the desorption kinetics of the pyrethroids. ... lack of studies to define pyrethroid desorption kinetics with ..e.g ., soil type, organic carbon (OC) content, pore water content.. however, a careful review of all existing data on soil-water partition coefficients for the pyrethroids is warranted. If this data review does not provide sufficient confidence in the use of current K oc 

### K ow 

### and K d 

### ’s, a series of adsorption and desorption studies for the pyrethroids (other than cypermethrin) an d in particular their degradates would reduce uncertainties associated with partition coefficients. It is suggested the studies be conducted by one laboratory thus generating a standard basis for comparison of the pyrethroids.  

### SAP. Careful examination of the Kow, Koc, and water solubility relationships should provide the necessary basis to determine whether the physical property data base is acceptable and the potential for using carbon normalization.

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# Koc Values in Tier 2/Tier 2+

Bifenthrin Cyfluthrin Cypermethrin Deltamethrin Esfenvalerate Fenpropathrin Lambda-Cyhalothrin Permethrin Tefluthrin Henry’s Law Constant,

atm-m 3 /mole 7.2e-3 3.7e-6 3.4e-7 3.1e-7 1.4e-7 6.2e-7 1.9e-7 1.4e-6 5.2e-4 k

Soil Koc, mL/g 131000, 239000, 302000 275000 a Mean: 236750 124000, 180300, 118000, 73500 b Mean: 123950 141,700- mean value used in TII EDWC i 392000, 577000, 204000, 460000 c Mean: 408250 85700, 140000, 141700, 171700, 375000, 596200 d Mean: 251717 23300, 51100, 22100, 46200, 29300 Mean: 34400 346000, 200000, 298000, 724000, 209000, 270000, 305000, 352000, 518000, 110000 f Mean: 333200 60,900, 20, 900, 19,300, 20,500

25,500 g Mean: 29420 Range (158,000 to 332,000) k Mean: 211,000 k

Laskowski Koc 237000 124000 310000 704000 42500 326000 277000

LogKow 6.4 a 5.97 b 6.6 n 6.4 r 5.62 d 6.00 e 7.00 (gamma = 4.9) f 6.10 g 6.50 m Soil photolysis T1⁄2, days (see notes below) Corrected (netphotodegradation) halflives=147, 106; Mean = 126.5 a 5.6 b 55 q Stable c Stable d Stable e Stable f 106 g Stable
Aqueous photolysis

T1⁄2, days Relatively Stable a New study requested 4.5 (linear) 0.7 (nonlinear) b

Max: 4.5 36.2-used in TII EDWC i 2 labels: 64, 84 c Mean: 74 6 (SSisomer) d Stable e 29.5, 36.9 f Mean=33.2 (value uncertain due to test

subs. solubility) 80 g Stable k

Aerobic soil T 1/2 , days

Mean + CL Mean Values Based on 2 labels: SL: 123.5, SiL: 203.0, SiClL: 112.9 a Mean+t90=200.2 73.5, 94.8 b Mean+t90= 116.9 Mean+t90= 62 days used in TII EDWC i Mean values by soil: SL (0.02 lb/A): 53.6, SL (0.20 lb/A): 52.6 SiL (0.02 lb/A):48.2, SiL

(0.20 lb/A): 49.1, Dubbs fine SL: 22.2, Alkaline AZ SL: 24.0 c Mean+t90=50.4 75 d (SSisomer) 3xHL =225 152 e 3xHL =456 (additional values in RED) 46.2, 31, 55, 26, 102, 12.2, 14.5 f Mean+t90 = 57.9 3 x 37 g (single value) =111 21.79, 22.95, 17.37, 49.9 & 75.3 k Mean+t90 = 53.8

Laskowski Aerobic Laskowki Anaerobic 96.3 425 11.5 33.6 27.6 55 24.2 28.9 38.6 90.4 22.3 276 42.6 ??? 39.5 197

Anaerobic soil T 1/2 , days Mean + CL Aerobic soil T 1/2 x 2 Slow metabolism observed: 75-79% of recovered was bifenthrin at 61 days a New study requested 30 b 3xHL=90 NA 2 studies w/2 labels: Alk. SL: mean = 34; SL: mean = 44.8 c Mean+t90= 56.0 77 (SSisomer) d 186 e 3xHL =558 107 f 3xHL =321 204 g >30 days

Bayer Sed – Aerobic Bayer Sed- Anaerobic 100, >200, 100 >200,115, 106 4,15,4 26,24,22 4,18,5 35,28,27 12, 45, 14 100,68,60 19, 50,26 94,73,67 9, 63, 9 85,114,95 26, 60, 17, 84, 93, 62 3, 53, 3, 101, 64, 66



# Comparative sediment degradation study

Very tight agreement between replicates. Also a viable method for comparing isomer variant behaviors.

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# SPME and LLE Comparative Koc study

 

# One lab, nine AI’s, three sediment s (same as ecotox), two methods  

## Near-classic method - liquid-liquid extraction (LLE) Koc values  

### Includes chemical present adsorbed to particulates and DOC  

## Solid Phase Micro Extraction (SPME) based – calculates Koc based on Free pyrethroid residues (i.e. bioava ilable residues per EqP approach)

 

### Well described in literature (Jay Gan et al papers, CDPR, & others will be documented)  

### As recommended by EPA SAP  

## Study at 1:100 sediment:water ratio – will be repeated at higher ratio.  

# Pyrethroid Koc’s extreme – metho dology not easy (SAP & ORNL)  

# Methodology refined and full pr otocol about to be signed  

# Preliminary data shown  

# Full reports due fall 2013  

# Will be used to estimate eco-tox endpoints Kd LLE Koc LLE Kd free SPME Koc free SPME Sediment A #091312 Rep. 1 12804 640175 28727 1436343 #091312 Rep. 2 12728 636389 30448 1522398 #091312 Rep. 3 12690 634505 29626 1481316



# PWG Model Input Data Generation Status

 

# PWG will submit comparative sediment degradation study to US EPA and use these data for risk assessm ent as best-available due to their comparative nature

 

## Use for all water body sediment degradation inputs  

# PWG will submit comparative Koc st udy data (fall 2013) and will use these data as best available as above

 

## All nine AI’s, three sediments.  

## LLE and SPME- based Koc results and associated supporting data  

## Follow up study at Higher sediment:water concentration  

# PWG is also generati ng a comparative Kow data set (due fall 2013)  

## Will be used for input to accumulation and foodweb models (& AGRO)

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# Model inputs- Addressing SAP / ORNL comments

 

## One compound is not sufficient...Model all pyrethroid AI’s... – will be done at tier 2/2+ level  

## recommends that PWG measure the Kow for entire class using slow-stir [sic shake flask] 

## method. Under way  

## Adsorption/binding is key for pyrethro ids...Additional Koc sediment data needed.... Examine effect of solid wa ter ratios... better understanding of sediment/suspended particle and plant ma terial binding should be developed...3 or 4 pyrethroids should be subjected to the same adsorption/desorption, water solubility, and toxicity tests.... At the same testing laboratory

 

### Koc studies at different solid/water ratios for 9 AI’s in three sediments used for toxicity under way at same lab using same methods for LLE and SPME  

## Solid phase microextraction (SPME).. a rapid and accurate approach for estimating bioavailable fraction of organic contaminants in water containing humics...

 

### SPME analyses underway for estimation of relevant Koc’s for ecotox study interpretation  

## Other examples provided in white paper



# The End