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Peer Review Process


EPA announced in a July 2007 Federal Register Notice (PDF) (4 pp, 67K, About PDF) its approach to conducting peer reviews of the Tier 1 screening assays and Tier 2 testing assays that are being validated.  The Federal Register notice also announced EPA's approach for conducting the peer review of the Tier 1 battery. 

EPA has validated and peer reviewed the Tier 1 assays and finalized the Tier 1 screening battery. EPA has completed validation of the Tier 2 tests and is initiating the peer review process. Validation is defined as the process by which the reliability and relevance of test methods are evaluated for a specific use. EPA has implemented the validation process in several phases:

Review the assay status table for information on the stage of the validation process of each assay.

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EDSP Work Products for Peer Review

EPA plans to peer review the following EDSP work products. Review assays under consideration for a brief description of each assay. Links to each assay will be activated as peer review materials become available.

Tier 1 Assays

Tier 1 Assay Battery

Tier 2 Assays

  • Avian Two-Generation Toxicity Test
  • Larval Amphibian Growth and Development Test
  • Reproduction and Fertility Effects***
  • Medaka Multi-Generation Test
  • Mysid Two-Generation Toxicity Test


* The Hershberger assay has been peer reviewed by the Organization for Economic Cooperation and Development (OECD). EPA will not conduct a separate peer review of this assay.

** The uterotrophic assay has been peer reviewed by OECD. EPA will not conduct a separate peer review of this assay.

*** The OECD TG 416 (Two-Generation Reproduction Toxicity Study) or OECD TG 443 (Extended One-Generation Reproductive Toxicity Study) are acceptable alternative tests

The primary product to be peer reviewed for each assay will be an Integrated Summary Report (ISR) that summarizes and synthesizes the information compiled from the validation process (i.e., DRPs, pre-validation studies, and inter-lab validation studies, with a major focus on inter-laboratory validation results).

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Peer Review Process - Tier 1 Assays

The mechanism that was used to peer review Tier 1 assays was an external letter review organized under an EPA peer review contract. The procedures used for peer review of the Tier 1 assays were in accordance with EPA's Peer Review Handbook (PDF) (190 pp, 1.15M, About PDF). For each assay, a balanced peer review panel consisting of three to ten peer reviewers was selected from a pool of qualified peer review candidates identified from academia, government, and the private sector, based on their subject matter expertise, availability, and lack of conflict of interest or past involvement in the project. A charge was issued to the peer reviewers to address the following types of issues:

  1. Clarity of the stated purpose of the assay.
  2. Clarity, comprehensiveness, and consistency of the data interpretation with the stated purpose of the assay.
  3. Biological and toxicological relevance of the assay as related to its stated purpose.
  4. Clarity and conciseness of the protocol in describing the methodology of the assay such that the laboratory can:
  1. Strengths and/or limitations of the assay.
  2. Impacts of the choice of (a) test substances, (b) analytical methods, and (c) statistical methods in terms of demonstrating the performance of the assay.
  3. Repeatability and reproducibility of the results obtained with the assay, considering the variability inherent in biological and chemical test methods.

The peer review panel's comments were compiled and presented to EPA in a peer review record. EPA used the peer review record to make a final determination as to a Tier 1 assay's suitability for use in the screening program, and finalize the assay for consideration for inclusion in the Tier 1 battery.

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Peer Review Process - Tier 1 Battery

As recommended by the Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC), EPA's EDSP testing strategy will consist of a battery of Tier 1 assays. The battery is comprised of screening assays that, when used in combination, will identify substances that have the potential to interact with the estrogen, androgen, and thyroid hormone systems.

The proposed EDSP Tier 1 Screening Battery of Assays was presented to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) during a public meeting on March 25-27, 2008.  A summary of the SAP’s comments and recommendations is available (39 pp, 1.7MB, About PDF). As described in the October 21, 2009 Federal Register Notice announcing the final Tier 1 screening battery of assays for initial screening under the EDSP, EPA has validated assays that are included in the final Tier 1 screening battery.

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Peer Review Process - Tier 2 Assays

The peer review strategy for the Tier 2 assays will follow a pattern similar to that used for Tier 1 battery. A June 25-28, 2013 FIFRA SAP meeting will address the validation status for the proposed EDSP Tier 2 ecotoxicity tests. The EDSP Tier 2 ecotoxicity tests have been developed and validated based on selected chemicals known to interact with the estrogen, androgen and/or thyroid hormonal pathways of the endocrine system. In general, the performance of respective Tier 2 ecotoxicity tests to determine the magnitude and duration of endocrine mediated effects and quantitatively assess concentration-response relationships will be the focus of the meeting.

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