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How EPA Is Incorporating 21st

Century Toxicology Into Its Work

John “Jack” R. Fowle III, Ph.D., D.A.B.T.

Deputy Director Health Effects Division,

Office of Pesticide Programs

US Environmental Protection Agency

1

Office of Chemical Safety and Pollution

Prevention at a Glance

• Safety evaluations required for human health and

ecological risks:

– Statutes: TSCA, FIFRA, FFDCA, FQPA, ESA

• Risk assessment and management decisions apply to:

– New and existing industrial chemicals.

– Antimicrobials, biochemical, and conventional active

ingredients, and food-use and non-food use inert ingredients.

• Available information:

– Varies across chemical programs with extensive requirements

for food use, conventional pesticide active ingredients to

minimal requirements for non-food use inert ingredients and

industrial chemicals.

2

Managing Chemical Risks• OCSPP is the Gateway to Market.

• Thousands of regulatory decisions annually.

• Must be timely (e.g., 90 days for new industrial chemicals, specific time frames for pesticides).

~9000 existing chemicals

~1500 Pre-manufacture Notices for new chemicals per year

~1,100 active ingredients &

19,000 products

Reevaluate existing pesticides on a regular schedule; evaluate new pesticides and new uses; evaluate inert ingredients

National Industrial

Chemical Program

National Pesticide

Program

3

Managing Chemical Risks

• Large number of chemicals to review with many

possible adverse outcomes.

• Finite resources and time.

• Public expectation for sound science,

transparency, and timeliness for environmental

health protection.

• Science increasingly complex and changing.

Common Challenges:

Chemical by chemical testing

for all potential outcomes

Testing Battery

Different Testing Schemes

Integrated Testing & Assessment

Use Existing Knowledge of

Exposure & Effects

Examine a chemical or a group of

chemicals with shared properties•Physical Chemical Properties

•Structure-based extrapolation

•Biological activity-based extrapolation

•Other relevant information

Cance

r

ReproT

ox

DevT

ox

NeuroT

ox

Im

munoT

ox

Determine Information

needs and follow up

actions

Cance

r

ReproT

ox

DevT

ox

NeuroT

ox

Imm

unoTox

Heavy Reliance on

Extensive Animal Testing

Increasing Reliance on

in silico & in vitro Predictions

Generate information

For All possible Outcomes

Strategic Direction

Tailor In vivo Testing

(intelligent testing)

Empirical approach

Increasing Effectiveness, Reliability, and Rate of Assessments

Mechanism-Based Approach

Paradigm ShiftToday

NRC 2007 “Toxicity Testing in

the 21st Century: A Vision &

Strategy”• Transformative paradigm shift using in vitro &

computer systems.

– broader coverage of chemicals, end points, life stages.

– mechanistic & dose information for risk assessment.

– reduce cost & time of testing, increase

efficiency & flexibility.

– use fewer animals.

• Based on toxicity pathways.

A Vision for Future Risk Determination

Will know what to test, when to test, and how.

Most decisions informed by the inherent

properties of the chemical.

Require tests only when necessary.

Testing in animals will only be when absolutely

necessary and a rare event

This Will Take Time

Modified from NRC, 2007

Source

Fate/Transport

Exposure

Tissue Dose

Biologic Interaction

Perturbation

BiologicInputs

Normal

Biologic

Function

Morbidityand

Mortality

Cell

InjuryAdaptive Stress

Responses

Early Cellular

Changes

• Quantitative Dose-Response

• PK / PD

• Toxicity Pathway Identification

• in silico models

•Targeted Testing

Toxicity Pathways: Cellular

response pathways that,

when sufficiently

perturbed, are expected to

result in adverse health

effects.

Toxicity Testing in 21st Century: A Vision and a Strategy

9

Animal Testing:

Reduce, Refine,

Replace

• 2005 OPPTS-ORD White Paper.

• 2007 NAS Report on Testing in the 21st Century.

• 2009 Agency’s Strategic Plan for Evaluating the

Toxicity of Chemicals.

Use of computational tools is not new to evaluate

& assign priorities for actions (e.g., industrial

chemical program, inert ingredients).

OCSPP Strategic DirectionTransition toward new integrative and

predictive 21st century techniques to

increase efficiency and effectiveness

of testing and assessment.

EPA’s Needs Expand the NAS Vision

• Include ecological as well as human effects

• Establish the process to bring new science

into regulatory practice

11


• Near Term (5 year) Goal:

– “Enhanced Tool Box” - Create means to

efficiently and credibly predict toxic potency

and exposure levels, and to focus information

needs.

– Examples: HPV/MPVs; pesticide inert

ingredients; certain antimicrobials pesticides;

metabolites and degradates of pesticide

active ingredients.

Challenge: Assessing Data-Limited Chemicals

1212

Evaluation for Relevant Effects

Risk Assessment

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In Vitro Profiling:

Molecular

interactions, Cellular

Responses

Existing Knowledge,

uses, exposure, toxicity

data, SAR, QSAR

Efficient Focused In

Vivo Testing

Research:

Learn & Refine

Non-Animal

Priority

Setting

Process

11

13


Long Term (5-15 years)• Develop means to move in a credible and transparent

manner to hypothesis, mechanism-driven, and risk-

based approaches that focus on effects most relevant

to risk assessment and risk management:

– “Omics” technology in identifying toxicity pathways.

– Physiologically-based toxicodynamic and toxicokinetic

modeling.

– Improved exposure modeling.

– Improved diagnostic biomarkers and population surveillance

methods.

Challenge: Reducing Uncertainty

ER Binding ER TransctivationVTGmRNA

Vitellogenin InductionSex Steroids

AlteredReproduction/DevelopmentMolecular Cellular Organ Individual

Chemical 3-DStructure/Properties

Chemical 2-D StructureStructure







































































Receptor/Ligand

Interaction

•Gene

Activation

•Protein

Production

•Gonad

Development

•Altered Hormone

Levels

Impaired

Reproduction

Molecular Cellular Organ Individual

Chemical 3-

D

Structure/

Properties

Chemical

2-D

Structure

Structure

Mapping Toxicity Pathways to Adverse Outcomes

Establish Linkages & Dose Response Relationships 12

15

Smarter & Higher

Content Animal

Testing Designs:

Prioritization & Screening Tools

(effects & exposure) to efficiently

identify most likely risks

Alternatives to

Replace Animal

Testing

Diagnostic Biomarkers

(exposure, early effects,

susceptibility) for

surveillance of

populations

Sophisticated Risk

Assessment Methods

Effective Chemical Risk Management

Critical Pathways

Enhanced Integrated

Approaches to

Testing & Assessment

Data-Limited Chemicals

Today’s Tool Box

Enhanced Tool Box Using New Approaches

QSAR Models

Chemical grouping or

categories & read-across

In vitro

(mutagenicity)

ToxRefDb

ECOTOX

ACToR

MetaPath

Degradates

ToxCast

QSARs

DSSTox

TTCsInherent Properties of Chemicals

(chemical, biological & toxicity characteristics)

Existing information

Example: Future Priorization for the USEPA

Endocrine Screening Disruptor Program

• Federal Food, Drug, and Cosmetic Act (FFDCA)– Requires EPA to:

• Develop a screening program using validated assays to identify pesticides that may have an effect in humans similar to an effect produced by a naturally occurring estrogen

– Authorizes EPA to include:

• Other endocrine effects, as designated by the EPA Administrator

• Other non-pesticide chemicals that:

– Have “an effect cumulative to that of a pesticide,” and

– To which a substantial human population may be exposedSafe

• Drinking Water Act (SDWA) Amendments – Allow EPA to require testing of chemical substances found in

sources of drinking water, if a substantial human population may be exposed

EDSTAC Recommendations--

Basis of the EDSP

• Estrogen, androgen and thyroid

• Human and ecological effects

• Priority setting for a broad universe of chemicals

• 2-Tiered Approach

– Tier 1

• In vitro and in vivo screens

• Detect potential to interact with endocrine system

– Tier 2

• Multi-generation studies covering a broad range of taxa

• Provide data for hazard assessment

18

Prioritizing Chemicals for Endocrine

Disruptor Tier 1 Screening: Effects

• EDSTAC (USEPA, 1998) recommended the use of measured or predicted receptor binding and/or transcriptional activation data derived through in vitro assays/High Throughput (HTP) Screening and (Q)SARs, respectively

• SAB/SAP (USEPA, 1999) concurred; however, concluded that HTP screening and (Q)SARs were not sufficiently developed at that time – encouraged continued research

• As part of USEPA’s computational toxicology and endocrine disruptor research programs, the Office of Research and Development (ORD), in collaboration with OPP and OSCP, has been developing in vitro assays, HTPs applications & (Q)SARs

Tool: (Q)SAR-Based System to Predict

Estrogen Receptor Binding Affinity

• ORD/OPP Collaborative Effort

• Application for use in a prioritization scheme

in the context of EDSTAC & SAB/SAP

recommendations

• Development focused on chemicals without

sufficient existing data to determine if Tier 2

testing required

• Model’s applicability domain – Structures

associated with pesticide inert ingredients &

antimicrobial pesticides

R 394

E 353 H 524

CC

T 347

HOOH

CH3 H

H H

H

AA BB

R 394

E 353 H 524

CC

T 347

HOOH

CH3 H

H H

H

AA BB

(Q)SAR-Based System to

Predict ER Binding Affinity

• External peer-review by USEPA SAP, August 2009– http://www.epa.gov/scipoly/sap/meetings/2009/08

2509meeting.html

• Development benefited from EDTA VMG-NA and two OECD peer consultations– May, 2008 Structural Alert Workshop

• http://www.olis.oecd.org/olis/2009doc.nsf/linkto/env-jm-mono(2009)4

– February, 2009 Expert Consultation to Evaluate an Estrogen Receptor Binding Affinity Model for Hazard Identification

• http://www.olis.oecd.org/olis/2009doc.nsf/linkto/env-jm-mono(2009)33

ToxPi: Prioritization Index for Endocrine Activity

ToxPi is calculated from a weighted combination of all data sources for each chemical.

The size of each slice indicates relative rank or score for each chemical; the distance from the origin

is proportional to the normalized value (e.g. assay potency or predicted permeability); the width

indicates the relative weight of that slice in the overall ToxPi calculation.

Prioritization Index = ToxPi = f(In vitro assays + Chemical properties + Pathways)

Bisphenol A Tebuthiuron

Ingenuity pathways

ER

AR

TROther

XME/ADME

KEGG pathways

LogP_TPSA

Predicted CaCO-2

Disease classes

Other NR

Example ToxPi Rankings from

ToxCast Phase I HPTE

ToxScore

Pyrimethanil

Tebuthiuron

Linuron

MethoxychlorRotenone BPA

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oxP

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highestlowest

Ingenuity path

ER

AR

TROther XME/ADME

KEGG path

LogP_TPSA

CaCO-2

Disease classes

Other NR

DuPont’s Chemical Visualization Tool

Enhance Integrated Approaches to

Testing & Assessment (IATA)

Benefits:• Allow use of new methods in real-time and in

real situations within current risk assessment paradigm

• Provide an improved means to credibly predict risks and focus information needs and follow up actions

• Focus societal resources on chemicals of greatest concern

• Supports responsible use of animals

Chemical

RELEASE FATE / TRANSPORT CONCENTRATION ACTIVITY EXPOSURE

FRAMEWORK

Intermediates

Degradates

PR

OD

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T n

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T 8

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T 7

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T 5

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T 4

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Release

Reaction

ProductUse

Disposal

LocationFrequencyTiming

PopulationMarket Share

Water

Outdoor

Air

Surface

Dust

Soil

Indoor

Air

Food

ChemicalManufacture

ChemicalTransportation

Production/Formulation

WorkplaceExposure

EnvironmentalRelease

EnvironmentalDisposal

Air

Water

Incineration

RecyclingSewage

Treatment

Food

Land

Transport

EnvironmentalRelease

Food

Water

Land

ProductDisposal

Air

Lifecycle Analysis

Consistent with NAS Science and Decisions and TSCA 2010

Application to Levels of

Organization Based on Source

to Outcome

Source

Environmental

Contaminant

Exposure

Cellular Effects

Individual

Population

Community

Mode of Action

Adverse Outcome Pathway

Source to Outcome Pathway

Toxicity Pathway

Molecular Initiating Event

Source-Exposure-Dose-Effects Continuum

TRANSPORT /

TRANSFORMATIONALTERED STRUCTURE /

FUNCTION

ENVIRONMENTAL

CHARACTERIZATION

SOURCE / STRESSOR

FORMATION

DOSE

EXPOSURE

EARLY KEY

BIOLOGICAL EVENTS

DISEASE

Toxicity Pathway

Chemical

Physical

Microbial

Magnitude

Duration

TimingDispersion

Kinetics

Themodynamics

Distributions

Meteorology

Air

Water

Diet

Soil & dust

Pathway

Route

Duration

Frequency

Magnitude

Statistical Profile

Reference Population

Susceptible Individual

Susceptible Subpopulations

Population Distributions

Absorbed

Target

Internal

Biologically

Effective

Molecular

Biochemical

Cellular

Organ

Organism

Edema

Arrhythmia

Necrosisetc.

Cancer

Asthma

Infertility

etc.

Community

Activity

Patterns

PBPKModels

Transport,Transformation &

Fate Models

Exposure

Models

BBDRModels

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Chemical Space

Quantitative Structure Activity Relationships

Quantitative Biological Activity Response

Adverse Outcome Space

Biological Activity Space

Cancer Developmental

Defects

Endocrine

Disruption

Respiratory

Disease

Neurologic

Effects

EPA has a lot of experience with Chemical databases – a few examples

Analog Identification Methodology (AIM

identifies close structural analogs that have measured data and points to

sources where those data can be found

Ecological Structure Activity Relationships (ECOSAR)

estimates the aquatic toxicity of industrial chemicals

ECOTOX

chemical toxicity data for aquatic life, terrestrial plants and wildlife

EPI Suite™

estimates physical / chemical properties and environmental fate

High Production Volume Information System (HPVIS)

health and environmental effects information

OncoLogicTM

evaluates the likelihood that a chemical may cause cancer

Use Cluster Scoring System (UCSS)

risk-screening system into which chemicals are grouped by common use

Moving beyond data warehouses to integrated knowledgebases

ACToR: Aggregated Computational Toxicology Resource

Aggregates data from over 500 public sources on over 500,000

environmental chemicals searchable by chemical name, structure, and other

identifiers.

Data includes chemical structure, physico-chemical values, in vitro assay

data and in vivo toxicology data.

Distributed Structure-Searchable Toxicity (DSSTox) Database Network

Structure-activity and predictive toxicology using structure searchable

standardized chemical structure files associated with toxicity data.

ToxRefDB: Toxicity Reference Database

Detailed chemical toxicity data in an accessible and searchable format.

Links to other public hazard, exposure and risk resources.

Systems Approaches to Modeling

Toxicity From Pathways to Virtual Tissues

chemicals pathways networks cell states tissue function

Quantitative

Dose-Response

Models

Future

Risk assessments

Moving beyond

empirical models, to

multi-scale computer

models of complex

biological systems.

Identify Key Targets and Pathways

33

Will require a sustained effort over many years

Establish data storage and management systems, elucidate toxicity pathways.

Develop & evaluate suite of high & medium through put assays.

Gain experience though testing in parallel with traditional assays.

Timeline

Achieving a

Paradigm Shift

Evolving Process - But milestones along the way

Design Intelligent Testing

Enhance Interpretation

Expand Tool Box

Temporally & spatially explicit models

Improved dosimetry, mode of action

Transition to

Alternatives

Evolution to a new paradigm will depend on success

of technological developments and acceptance.

Project Plans

More Efficient Animal

Studies

35

Research

Evaluation

Method

Development

Regulatory

Acceptance

Review

Decision for

Specific Application

Peer Review and

Stakeholder

Engagement

Establishment of

Reliability

Transferrable

Method

New Methods

for Applications

Computational

Tools, etc.

MAPPING THE PROCESS

Problem

Identification

Researchers

and

Regulators

Working

Closely

Together

Research Planning

Near-term Steps:

• Compile & integrate information for easy access

• Collaborate on research via national and international partnerships

• Develop risk assessment and management approaches via collaboration of regulatory programs and research community

• Engage external scientific peer review and all stakeholders early to ensure transparency and input with new approaches as they progress

A Paradigm Shift Based on

Incremental Steps

37

Stakeholder Engagement

• Pesticide Program Dialogue

Committee (PPDC):

– FACA Workgroup on 21st Century Toxicology/New

Integrated Testing Strategies Workgroup

• Purpose - advise on communication & transition:

– Improve understanding of the perspectives of all

stakeholders regarding new testing paradigm.

– Ensure input on key science and regulatory

developments.

– Develop common understanding for use of new tools.

http://images.google.com/imgres?imgurl=http://www.safmc.net/Portals/6/SocioEcon/IFQs/LAPP-Workgroup-Meeting-June.JPG&imgrefurl=http://www.safmc.net/LinkClick.aspx%3Flink%3D495%26tabid%3D486&h=374&w=500&sz=27&hl=en&start=15&tbnid=7LOOT8HMbM7O_M:&tbnh=97&tbnw=130&prev=/images%3Fq%3Dworkgroup%26gbv%3D2%26hl%3Den%26sa%3DG

International

Partnerships

• Information Sharing

• Common Application Tool Boxes

• Mutually Accepted Test Guidelines

• Harmonize Frameworks & Guidance

• Global Acceptance

Organization for Economic Cooperation & Development

North American Free Trade Agreement

International Program for Chemical Safety

European Food Safety Authority, etc.

http://www.google.ca/imgres?imgurl=http://www.istockphoto.com/file_thumbview_approve/2482727/2/istockphoto_2482727-world-globe.jpg&imgrefurl=http://www.istockphoto.com/stock-photo-2482727-world-globe.php&usg=__czmuqDPXwgobJqoHqYldIePYl7w=&h=380&w=380&sz=75&hl=en&start=23&itbs=1&tbnid=IoM_E9KDqM5m3M:&tbnh=123&tbnw=123&prev=/images%3Fq%3Dglobe%26start%3D20%26hl%3Den%26sa%3DN%26gbv%3D2%26ndsp%3D20%26tbs%3Disch:1

http://www.epa.gov/pesticides/science/testing-assessment.html

In Summary

• In the near-term (present to 2-3 years):– Accelerated and enhanced priority

setting / screening to focus animal testing

– Enhance interpretation of current information

• In the long-term (~10 years):– Greater reliance on in silico, in vitro, and highly

targeted animal studies only as needed

– Mechanism-based assessments is the standard

Achievable with strong scientific & stakeholder

support through a transparent process

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