AGENDA

U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA) 

FIFRA SCIENTIFIC ADVISORY PANEL (SAP) 

OPEN MEETING 

MAY 19-21, 2015

FIFRA SAP WEB SITE http://www.epa.gov/scipoly/sap/ 

DOCKET NUMBER: EPA–HQ–OPP–2015–0130

U.S. ENVIRONMENTAL PROTECTION AGENCY

CONFERENCE CENTER LOBBY LEVEL

ONE POTOMAC YARD (SOUTH BLDG.)

2777 S. CRYSTAL DRIVE, ARLINGTON, VA 22202

Scientific Uncertainties Associated with Research to Evaluate the Potential for 

Juvenile Sensitivity to Pyrethroids

Please note that all times are approximate (see note at end of Agenda). 

9:00 A.M. Opening of Meeting and Administrative Procedures – Fred Jenkins, Ph.D., 

Designated Federal Official, Office of Science Coordination and Policy, EPA 

9:05 A.M. Introduction and Identification of Panel Members – Stephen Klaine, Ph.D., 

FIFRA Scientific Advisory Panel Chair 

9:10 A.M. Welcome and Opening Remarks – Jack Housenger, Director, Office of Pesticides 

Programs (OPP), EPA

9:15 A.M. Implementing 21st Century Toxicity Testing at EPA’s Office of Pesticide 

Programs – Anna Lowit, Ph.D., Senior Scientist, Health Effects Division (HED), OPP, EPA

9:35 A.M. Evaluation of Potential Juvenile Sensitivity from Pyrethroid Exposure –

Monique Perron Sc.D; Jaime D’Agostino, Ph.D.; William Irwin, Ph.D., DABT; Anna Lowit,

Ph.D., HED, OPP, EPA

10:00 A.M. Benefits of Pyrethroids, CAPHRA Overview, Conceptual Framework – Thomas 

G. Osimitz, Ph.D., DABT, ERT, Science Lead: Council for the Advancement of Pyrethroid 

Human Risk Assessment (CAPHRA), Principal Scientist Science Strategies, LLC, 

Charlottesville, VA 

10:20 A.M. Pharmacodynamics Introduction and Background – Larry Sheets, Ph.D., DABT

Toxicology Fellow, Human Safety Regulatory Toxicology, Bayer CropScience LP, Research 

Triangle Park, NC

Day 1

Tuesday, May 19, 2015

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10:35 A.M. Break

11:00 A.M. In vivo Acoustic startle response (ASR)/Detailed Clinical Observations 

(DCO)/Tissue Levels – Charles V. Vorhees, Ph.D., Professor, University of Cincinnati

Department of Pediatrics, Cincinnati, OH 

11:25 A.M. Human Isolated Voltage Sensitive Sodium Channel (VSSC) – Steven B. 

Symington, Ph.D., Associate Professor Department of Biology and Biomedical Science, Salve 

Regina University Newport, RI

11:40 A.M. Neurolemma – J. Marshall Clark Ph.D., Professor Department of Veterinary and 

Animal Science Director of the Massachusetts Pesticide Analytical Laboratory, 

University of Massachusetts, Amherst, MA

12:00 P.M. Lunch

1:00 P.M Pharmacodynamics Conclusion – Thomas G. Osimitz, Ph.D., DABT, ERT, Science 

Lead – Council for the Advancement of Pyrethroid Human Risk Assessment (CAPHRA), 

Principal Scientist, Science Strategies, LLC, Charlottesville, VA 

1:15 P.M. Pharmacokinetics: Introduction and Background – Thomas G. Osimitz, Ph.D., 

DABT, ERT, Science Lead – Council for the Advancement of Pyrethroid Human Risk 

Assessment (CAPHRA), Principal Scientist, Science Strategies, LLC, Charlottesville, VA

1:25 P.M. Framework and In Vitro to In Vivo Extrapolation (IVIVE) Paradigm – Harvey J. 

Clewell III, Ph.D., DABT, FATS Senior Investigator, The Hamner Institutes for Health Sciences, 

Research Triangle Park, NC

1:45 P.M. Parameterizing the Model Supporting IVIVE, Metabolic Clearance from In 

Vitro Studies, Other inputs – Brian G. Lake, BSc, Ph.D., DSc, FBTS, LFR Molecular 

Sciences Leatherhead, Surrey, UK; Miyoung Yoon, Ph.D. Senior Research Investigator,

The Hamner Institutes for Health Sciences Research Triangle Park, NC 

2:30 P.M. Break

2:45 P.M. Building Information to Validate the Model, Model Structure/Logistics/etc.

Key Model Drivers (Km, etc.)., Strengths/Weaknesses/Uncertainties of the Model – Miyoung 

Yoon, Ph.D. Senior Research Investigator, The Hamner Institutes for Health Sciences Research 

Triangle Park, NC

3:10 P.M. Model Simulations, Rat: Validation, Human, Juvenile: Adult Comparisons, 

Reverse Dosimetry (Reality Check for Deltamethrin Model) – Harvey J. Clewell III, Ph.D., 

DABT, FATS, Senior Investigator, The Hamner Institutes for Health Sciences, Research 

Triangle Park, NC

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3:40 P.M. Pharmacokinetics Conclusion – Thomas G. Osimitz, Ph.D., DABT, ERT, Science 

Lead – Council for the Advancement of Pyrethroid Human Risk Assessment (CAPHRA), 

Principal Scientist Science Strategies, LLC, Charlottesville, VA

3:50 P.M. Read Across Proposals for Other Compounds – Thomas G. Osimitz, Ph.D., 

DABT, ERT, Science Lead – Council for the Advancement of Pyrethroid Human Risk 

Assessment (CAPHRA), Principal Scientist Science Strategies, LLC, Charlottesville, VA

4:00 P.M. CAPHRA Conclusions – Thomas G. Osimitz, Ph.D., DABT, ERT, Science Lead –

Council for the Advancement of Pyrethroid Human Risk Assessment (CAPHRA), Principal 

Scientist Science Strategies, LLC, Charlottesville, VA

4:30 P.M. Adjourn

9:00 A.M. Opening of Meeting and Administrative Procedures – Fred Jenkins, PhD, 

Designated Federal Official, Office of Science Coordination and Policy, EPA 

9:05 A.M. Introduction and Identification of Panel Members – Stephen Klaine, PhD, FIFRA 

Scientific Advisory Panel Chair 

9:10 A.M. Follow-up from the Previous Day Presentations

9:30 A.M. Public Comments 

10:45 A.M. Break

11:00 A.M. Charge to the Panel 

1. High-throughput screening studies using human sodium channels expressed in 

mammalian cells with their regulatory Beta subunits (ChanTest Data): Human voltagegated sodium channels (NaVs 1.1, 1.2, 1.3, 1.6) were expressed in human embryonic kidney 

(HEK) cells and 9 pyrethroids were tested for their effects on channel conductance, as well as 

the effects of co-expressing the Beta 1 and 2 regulatory subunits.

a. Please comment on the ChanTest studies conducted for nine pyrethroids. Please include in 

your comments a consideration of their robustness (i.e. reproducibility, controls, statistics, 

background information, NaV selection, etc). Please comment on the confidence and 

uncertainties in the ChanTest experiments and related findings.

Day 2

Wednesday, May 20, 2015

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b. CAPHRA thinks that additional data from this line of evidence are unlikely to contribute 

useful information to characterize the potential for juvenile sensitivity. Thus, the CAPHRA 

has proposed NOT to continue this line of research. Please comment on this proposal and 

degree to which the ChanTest data inform the issue of evaluating the potential for juvenile 

sensitivity.

c. The ChanTest experiments focus on human sodium channels and generally show weak 

response. In contrast, in vitro studies in rodents in the literature (e.g. Choi and Soderlund, 

2006; Meacham et al., 2008; Tan and Soderlund, 2009) show stronger responses to 

pyrethroids. Please comment on the extent to which the expressed human sodium channels 

can be used in combination with these sources to infer relative pharmacodynamic sensitivity 

between rats and humans. 

12:00 PM Lunch

1:00 P.M. Charge to the Panel 

2. Transplantation of adult & juvenile rat brain synaptic membrane into Xenopus oocytes: 

Purified neurolemma membranes from adult and juvenile rats were separately micro-injected 

into Xenopus oocytes. Patch clamp testing was performed on the oocyte membranes versus 

various doses of pyrethroids to determine their EC50 values for NaV channel activation. 

Inhibitors of competing channels were added to isolate the sodium channel conductance (i.e. 

chloride and calcium channels). 

a. Please comment on the synaptic membrane (“neurolemma”) studies conducted for 

deltamethrin and permethrin. Please include in your comments a consideration of the robustness 

of data from the synaptic membrane transplantation into oocytes (reproducibility, control 

compounds, channel modulator reagents, statistics, use of Na blocker tricaine as an anesthetic, 

etc) and the degree to which these data inform the issue of evaluating the potential for juvenile 

sensitivity. Please comment on the confidence and uncertainties and associated findings in the 

oocyte experiments.

b. In the context of your response to 2a, the CAPHRA has proposed to collect dose-response data 

in adult and juvenile rat synaptic membrane transplanted into oocytes for five more pyrethroids 

(including Type I, Type II, and mixed). CAPHRA’s proposed path forward: If the additional 

five pyrethroids show similar patterns to deltamethrin and permethrin (i.e. no lifestage sensitivity 

observed), no additional pyrethroids will likely be tested in this system. Alternatively, if a 

different pattern is observed, additional pyrethroids are likely to be tested. Please comment on 

the CAPHRA’s proposed path forward.

2:00 P.M. Charge to the Panel 

3. Targeted in vivo studies in adult and juvenile rat: acoustic startle/detailed clinical 

observations: Preliminary experiments that measure acoustic startle and detailed clinical 

observations have been conducted by the University of Cincinnati. In these experiments, 

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juvenile and adult male Sprague-Dawley rats were treated with deltamethrin and permethrin as 

model Type II and Type I pyrethroids, respectively. In addition, brain and plasma concentrations 

were measured in PND 15 and 90 rats exposed to deltamethrin. The preliminary results suggest 

that juvenile rats are more sensitive to deltamethrin based on changes in detailed clinical signs 

and, to less extent, acoustic startle. However, there was no greater sensitivity in juvenile rats 

exposed to permethrin. Preliminary data from whole brain tissue samples with deltamethrin 

indicated that PND 15 rats had higher deltamethrin concentrations as compared to adult rats 

given the same dose. The brain concentration and toxicity data from the CAPHRA studies for 

deltamethrin are consistent to those previously published by the Bruckner lab (Kim et al., 2010 ) 

which showed that at a similar dose (2 mg/kg deltamethrin) PND 10 rats had increased severity 

of clinical signs and higher Cmax of deltamethrin in the brain as compared to PND 21, PND 40, 

and PND 90 rats.

a. The in vivo behavior studies reported thus far are preliminary evaluations. Please comment on 

the study design in the preliminary in vivo studies for deltamethrin and permethrin conducted 

at the University of Cincinnati (Vorhees lab). 

b. In 2010, FIFRA SAP commented on some challenges that were anticipated with the use of 

auditory startle to compare the relative sensitivity of juveniles and adults. In the studies 

conducted by the CAPHRA, both auditory startle and detailed clinical observations were 

evaluated. Please comment on the degree to which the auditory startle and detailed clinical 

observations provide useful data for evaluating the potential for juvenile sensitivity. Please 

include in your comments discussion of the dynamic range; the direction of the response 

varying between Type I and IIs; and the type of data obtained (continuous, ranked).

2:45 P.M. Break

3:00 P.M. Charge to the Panel 

c. Please provide comments comparing the temporal pattern and magnitude of the brain and 

plasma concentration data from the Vorhees & Bruckner labs and utility of such data to aid in 

the interpretation of the auditory startle and detailed clinical observation data. 

d. Please comment on the use of a 5 ml/kg dosing volume in the CAPHRA studies and how any 

impact on pyrethroid kinetics affects correlations with behavioral effects.

3:45 P.M. Charge to the Panel 

4. Pharmacokinetic studies: A number of pharmacokinetic studies using deltamethrin were 

performed by the CAPHRA in order to further refine and validate the developing rat PBPK 

model and construct a developing human PBPK model. For refinement of the rat PBPK model, 

tissue: plasma partition coefficients (in vivo measurements in PND 21 and adult rats), age 

dependent plasma protein binding (in vivo measurements in PND 10, 15, 21, and 90 rats), and 

cytochrome P450 (CYP) and carboxylesterase (CES) metabolism (in vitro measurements using 

rat liver and plasma preparations from PND 15, 21, and 90 rats) were evaluated. Further in vivo 

pharmacokinetic studies in rats were conducted with single IV (PND 90), single oral (PND 90), 

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and multiple oral (PND 15, 21, and 90) doses to generate plasma and tissue data to validate the 

developing rat PBPK model. Additional experiments with deltamethrin were conducted for 

constructing the developing human PBPK model. Parameters evaluated in vitro included age 

dependent plasma protein binding derived in plasma from human donors aged from birth to 

adults, transport across the blood brain barrier using a human brain microvascular endothelial 

cell line, estimates of gastrointestinal absorption in caco-2 cells, and ontogeny data for CES 

CYP1A2, and CYP2C8 determined in human liver tissue from donors (age 1-18 years old). 

Further in vitro experiments are currently underway by the CAPHRA to determine human adult 

and juvenile liver metabolism of deltamethrin by CYP and CES enzymes using human liver 

preparations or recombinant human enzymes. 

a. Please comment on the in vitro experiments to support the PBPK model development in the rat 

conducted thus far for deltamethrin.

b. Please comment on the in vivo experiments to support the PBPK model development in the rat 

conducted thus far. 

c. Please comment on the in vitro experiments in the human tissue conducted thus far. Please 

include in your comments a discussion of the ongoing in vitro experiments with recombinant 

enzymes for use in PBPK models and associated confidence and uncertainty with the use of such 

data.

4:30 P.M. Charge to the Panel 

5. Physiologically-based pharmacokinetic model in rat: Using data described in Question 4, 

the CAPHRA has developed a PBPK model for deltamethrin using age-specific metabolism 

parameters in rats to simulate plasma and brain internal exposures in young and adult rats. This 

PBPK model relies on in vitro to in vivo extrapolation (IVIVE) to use age-specific metabolic 

data collected in vitro to estimate hepatic metabolic clearance in vivo. The deltamethrin brain or 

plasma concentrations estimated by the model in rats are then compared to measured 

concentrations from in vivo rat studies to verify the model. Non-chemical specific physiological 

parameters for rats were obtained from the published literature, including body weight, cardiac 

output, hematocrit levels, tissue volumes, and tissue blood flows. As discussed in Question 4, 

recently generated data by the CAPHRA and published data were used for compound-dependent 

parameters, including partition coefficients, metabolic rate constants, absorption rates, protein 

binding, compartments and tissue permeability. 

a. Please comment on the robustness of the rat PBPK model for simulating internal exposures in 

the developing rat. In your response, please include evaluation of the structure and parameters 

used to build the model, as well as its ability to accommodate different oral absorption scenarios 

(i.e. different vehicles used for in vivo studies) and discussion of confidence, accuracy and 

uncertainties associated with the deltamethrin developing rat model. Please also comment on the 

sensitivity analyses of parameters CAPHRA has completed thus far.

b. In the context of your response to 5a, please comment on the extent to which additional data 

are/are not needed to refine the developing rat model.

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5:15 PM Adjourn

9:00 A.M. Opening of Meeting and Administrative Procedures – Fred Jenkins, Ph.D., 

Designated Federal Official, Office of Science Coordination and Policy, EPA 

9:05 A.M. Introduction and Identification of Panel Members – Stephen Klaine, Ph.D., 

FIFRA Scientific Advisory Panel Chair 

9:10 A.M. Charge to the Panel

6. Physiologically-based pharmacokinetic model for human: Similar to the rat PBPK model, 

the human PBPK model integrates non-chemical specific physiological parameters for humans 

from the literature. Compound-dependent parameters, such as partition coefficients and oral 

absorption parameters, were adapted from the rat PBPK model. Recently generated data by the 

CAPHRA were used for the remaining compound-dependent parameters, such as metabolic rate 

constants, protein binding and tissue permeability. With respect to metabolic constants, CYP 

and CES enzymes involved in metabolism of a given pyrethroid will be identified and the in 

vitro metabolic constants for those enzymes will be determined for integration into the PBPK 

model. Intrinsic clearance for each active enzyme will be scaled to in vivo using scaling factor 

data collected by the CAPHRA and the SIMCYP database. The ontogeny of enzyme expression 

(also from the CAPHRA data and the SIMCYP database) will be incorporated into the process of 

obtaining distributions of age-specific intrinsic clearance for each enzyme. Preliminary 

simulations have been conducted for deltamethrin to demonstrate the process used with the 

PBPK model. 

a. Within the context of understanding potential juvenile sensitivity, characterize the robustness 

of the PBPK model for extrapolating age-specific internal tissue exposures for humans. In your 

response, please comment on the structure and parameters used to build the model and include 

discussion of confidence, reliability, and uncertainties associated with the deltamethrin human 

model. Please include in your comments a discussion of the data from the McCarver/Hines 

Laboratory (submitted as part of the CAPHRA package) for providing ontogeny of CES 

enzymes.

b. Please comment on the proposed use of SIMCYP for providing enzyme ontogeny patterns and 

deriving population distributions for metabolic parameters in humans. Please include in your 

comments whether or not other tools with similar capacity to SIMCYP are available.

10:00 A.M. Charge to Panel 

Day 3

Thursday, May 21, 2015

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7. Physiologically-based pharmacokinetic models for humans with other pyrethroids: Thus 

far, the CAPHRA has focused its human PBPK efforts on deltamethrin and, to a lesser extent, 

permethrin. Soon laboratory efforts will turn to other pyrethroids. CAPHRA’s proposal is to 

conduct fewer studies and in lieu of such data, use read across and computational approaches.

a. Please comment on the appropriateness of the current human PBPK model to be used for other 

Type I, Type II, or mixed type pyrethroids. Please include in your response evaluation of the 

path forward provided by the CAPHRA regarding in vitro and in vivo studies for other Type I, 

Type II, or mixed type pyrethroids.

10:30 A.M. Break

10:45 A.M. Charge to Panel 

8. Integration of lines of evidence: 

a. The tissue dosimetry data from the rat suggest higher brain levels in juveniles compared to 

adults. In contrast, the preliminary PBPK modelling for human predicts slightly lower brain 

concentrations in young children compared to adults. Please comment on these differences, 

including comments on the key inputs that lead to this difference, human variability associated 

with the key parameters, and the confidence and uncertainties associated with the difference 

between the rat and human internal dosimetry.

b. The CAPHRA has proposed to continue in vivo behavioral testing for deltamethrin and 

permethrin in definitive dose-response evaluations. Pyrethroids have been studied for decades 

and thus there is a large body of evidence for these pesticides. Given your response to 8a along 

with 1) the extensive body of scientific literature on pyrethroid toxicity syndromes and high dose 

studies in juvenile rats (e.g., Sheets et al, 1994 ); 2) neurolemma studies supported by the 

CAPHRA (Question 2) along with additional in vitro studies (e.g. Meacham et al., 2008); and 3) 

recent in vivo studies from the Vorhees & Bruckner labs, please comment on the additional 

scientific value that would be provided in conducting further in vivo rat experiments to assess 

potential for PD sensitivity of human infants and children.

12:00 PM Lunch

1:00 P.M. Charge to Panel 

c. If you believe there is additional scientific value to conducting additional in vivo experiments 

(8b), please comment on the CAPHRA's proposed experiments. In the context of your response 

to Question 3, please include in your comments a discussion of dose levels and/or additional 

study design elements to improve existing preliminary evaluations.

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1:30 P.M. Closing Remarks – Stephen Klaine, PhD, FIFRA Scientific Advisory Panel Chair; 

FIFRA SAP members; US EPA; Fred Jenkins, PhD, Designated Federal Official, Office of 

Science Coordination and Policy, EPA 

2:00 P.M. Meeting Adjourn

Please be advised that agenda times are approximate; when the discussion for one topic is 

completed, discussions for the next topic will begin. For further information, please contact 

the Designated Federal Official for this meeting, Dr. Fred Jenkins, via telephone: (202) 564-

3327; fax: (202) 564-8382; or email: jenkins.fred@epa.gov.

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