Lessons Learned, Challenges, & 

Opportunities: 

The U.S. Endocrine Disruptor Screening Program

Results of Workshop Held 

April 23-24, 2013 | Research Triangle Park, NC

Michael L. Dourson, Toxicology Excellence for Risk Assessment

Presented to the Science Advisory Panel, May 21 & 22, 2013
Alliance for Risk Assessment (ARA) 

Guiding Principles

• Promote science-based decision making.

• Enhance harmonization and consistency in risk 

assessments... through an open, transparent, multi- stakeholder approach. 

• Maintain access to risk assessment experts not 

normally available within an organization.

• Increase the capacity and quality of risk values by...... 

sharing costs, information, and human resources.
ARA Steering Committee

• Anita Meyer---United States Army Corps of Engineers

• Annette Dietz---Oregon Department of Environmental 

Quality

• Bette Meek---University of Ottawa

• Edward Ohanian---United States Federal Employee

• Michael Dourson---Toxicology Excellence for Risk 

Assessment (recused)

• Michael Honeycutt---Texas Commission on Environmental 

Quality

• Ralph Perona---Neptune & Company (tribal 

representative)

• William Hayes---State of Indiana
EDSP Workshop Organizing Committee

• Rick Becker---American Chemistry Council

• Susan Borghoff---Integrated Laboratory Systems, co-chair

• Warren Casey---National Institute of Environmental Health 

Sciences

• Thomas Hartung---Center for Alternatives to Animal Testing, Johns 

Hopkins University

• Michael Holsapple---Battelle

• Daland Juberg---Dow AgroSciences, co-chair

• Sue Marty---The Dow Chemical Company

• Ellen Mihaich---Endocrine Policy Forum (ER2)

• Glen Van Der Kraak---University of Guelph

• Mike Wade---Health Canada

• Kate Willett---Humane Society of the United States
Why would over 240 scientists attend?

Giving Back by Sharing Lessons Learned

• Focus – shared science and experience and 

identified opportunities to inform future efforts 

to evaluate endocrine disruption potential.

• Discussed the challenges and lessons learned 

from conducting the EDSP Tier 1 assays in a 

regulatory context, and provided suggestions for 

improvements to Tier 1 screening and for future 

testing practices. 
Workshop Objectives

• Provide participants with knowledge gained and lessons 

learned from testing on the initial list of chemicals.

• Identify challenges and best practices in the technical and 

biological assessment of endocrine modulation.

• Discuss insights on the challenges of integrating and 

interpreting the data collected from Tier 1 assays.

• Explore insights on biological mechanisms relevant to 

endocrine modulation and their application in interpretation 

and decision making.

• Engage perspectives from a range of stakeholders, including 

academia, government, industry, and NGOs 
Session 1: Performance of the EDSP Tier 1 

Screening Assays for Estrogen, Androgen, and 

Thyroid Pathways

• Focused on 11 Tier 1 assays, highlighting challenges 

and solutions

• Three experts involved in the conduct of these assays 

presented their experiences and discussed their 

ideas for improvements: 

– Dr. Colleen Toole (Ceetox)

– Dr. Leah Zorrilla (ILS, Inc.) 

– Dr. Katherine Coady (Dow Chemical Company)
Session 1: Perspectives

• The Tier 1 results are intended to be used in conjunction 

with Tier 2 data for risk-based decision-making. However, 

the endpoints in Tier 1 assays are not designed for risk 

assessment.

• Several technical difficulties were identified for in vitro 

assays.

• The requirement (and value) for testing at such high 

concentrations (i.e., biological significance) was 

questioned. 
Session II: Practical Applications of 

Tier 1 Data

• Focused on how to apply the current Tier 1 battery 

results to identify modes of action; and a weight of 

evidence (WoE) assessment for evaluating potential 

interactions with endocrine pathways. 

• Expert Speakers: 

– Dr. Earl Gray (U.S. EPA) 

– Dr. Sue Marty (Dow Chemical Company) 

– Dr. Christopher Borgert (Applied Pharmacology and 

Toxicology, Inc.)
Session II: Perspectives

• Development of critical systematic evaluation of 

existing data prior to implementation of Tier 2 

testing in multiple species. 

• Tier 1.5 screening strategy. 

• The assessment and application of alternative data 

could be highly relevant to replace Tier 1 assays, 

provided scientific validation of alternative 

approaches for regulatory decision-making.
Session III: Considerations for Future 

Endocrine Testing

• Provided perspectives on the future of endocrine 

screening and the promise of in vitro high- throughput analyses, toxicity pathways, and 

prediction models. 

• Expert Speakers: 

– Dr. David Dix (U.S. EPA) 

– Dr. Mel Andersen (The Hamner Institutes for Health Sciences) 

– Dr. Thomas Hartung (CAAT, Johns Hopkins) 

– Dr. Catherine Willett (Humane Society of the United States) 

– Dr. Lisa Ortego (Bayer CropScience) 

– Dr. Thaddeus Schug (NIEHS) 
Session III: Perspectives

• Enhanced predictive tools and stringent validation practices 

are necessary to achieve future regulatory acceptance of 

molecular pathways for risk assessment.

• Explicit consideration of human and ecological exposure 

potential would be valuable to aid in prioritization for the 

EDSP. 

• Current collaborations focused at improving exposure 

assessment and reverse dosimetry screening in HTS assays 

show promise for developing a risk-based decision tool. 

• Collaboration, coordination, and communication amongst the 

regulatory community and stakeholders is vital.
Session IV: Participant Discussion

• In the final session, workshop participants were 

provided an extended opportunity to discuss their 

experiences, perspectives, and concerns regarding the 

future of the EDSP. 

• A number of common themes emerged, many 

discussions focused on Session I-III Perspectives. Ex:

– Critical review and update to the guidelines

– Biomonitoring for exposure-based prioritization

– Reduction in number of animals used in testing

– Robust WoE approach using potency and exposure for 

additional testing
Session IV: Perspectives

• Two-assay Gatekeeper approach

– A logic-based decision-tree strategy for staging the 

EDSP Tier 1 screening assays 

• Benefits ALL stakeholders

– Decreases time and cost per chemical

– Reduces number of animals used

– Increases the amount of assessments conducted
Workshop Summary

• The experience and insight of the practitioners and 

laboratories conducting the screening provides an 

unprecedented resource for informing the future. 

• This workshop brought together multiple stakeholders in an 

open forum for the opportunity to review and discuss the 

scientific challenges and lessons learned from the EDSP. 

• Results of the workshop will be useful to inform ongoing and 

future efforts to determine the endocrine disruption potential 

of chemicals.

• Final speaker presentations, workshop materials, and 

workshop report are available at http://tera.org/peer/edsp/
Over 43 Workshop Sponsors
Thank you!