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Post-Meeting Peer Review Summary Report Post-Meeting Peer Review Summary Report External Peer Review for EPA’s Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water March 2018 Peer Reviewers: Hugh A. Barton, Ph.D. Dale Hattis, Ph.D. Nancy Carrasco, M.D., M.S. Angela M. Leung, M.D., M.Sc. Jonathan Chevrier, Ph.D. Stephen M. Roberts, Ph.D. Claude Emond, Ph.D. Joanne F. Rovet, Ph.D. Contract No. EP-C-13-010 Task Order 2015-22 Prepared for: Prepared by: U.S. Environmental Protection Agency Versar, Inc. Office of Ground Water and Drinking Water, 6850 Versar Center Standards and Risk Management Division, Springfield, VA 22151 1200 Pennsylvania Avenue NW (MC 4607M) Washington, DC 20460 Post-Meeting Peer Review Summary Report - External Peer Review for EPA’s Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water TABLE OF CONTENTS EXECUTIVE SUMMARY ......................................................................................... 1 1. INTRODUCTION .............................................................................................. 9 1.1 Information on EPA’s Revised Biologically Based Dose-Response (BBDR) Model ............................................................................................ 9 1.2 Information on EPA’s Draft Approaches To Inform the Derivation of a Perchlorate MCLG .................................................................................... 10 1.3 Peer Review Process .................................................................................. 10 2. CHARGE TO REVIEWERS ............................................................................ 14 3. GENERAL IMPRESSIONS ............................................................................. 21 4. RESPONSE TO CHARGE QUESTIONS ........................................................ 29 Question 1 ......................................................................................................... 29 Question 2. ........................................................................................................ 32 Question 3 ......................................................................................................... 34 Question 3A ...................................................................................................... 34 Question 3 ......................................................................................................... 37 Question 3B ...................................................................................................... 37 Question 4 ......................................................................................................... 39 Question 5 ......................................................................................................... 42 Question 6 ......................................................................................................... 45 Question 7A ...................................................................................................... 47 Question 7B ...................................................................................................... 50 Question 7C ...................................................................................................... 52 Question 8 ......................................................................................................... 54 Question 9A ...................................................................................................... 56 Question 9B ...................................................................................................... 59 Question 10A .................................................................................................... 61 Question 10B .................................................................................................... 65 Question 10C .................................................................................................... 67 Question 11A .................................................................................................... 69 Question 11B .................................................................................................... 71 Question 11C .................................................................................................... 73 Question 11D .................................................................................................... 75 Question 12 ....................................................................................................... 77 Question 13 ....................................................................................................... 79 Question 14 ....................................................................................................... 81 Question 15 ....................................................................................................... 83 5. SPECIFIC OBSERVATIONS ON REPORT (VOLUME 1) ........................... 86 6. SPECIFIC OBSERVATIONS ON BBDR MODEL (VOLUME 2) .............. 100 7. SPECIFIC OBSERVATIONS ON APPENDICES B-G (VOLUME 3) ........ 102 Appendix A: List of Peer Reviewers and Biographical Sketches ............................A-1 Appendix B: Meeting Agenda ................................................................................. B-1 Appendix C: List of Registered Observers .............................................................. C-1 i Post-Meeting Peer Review Summary Report - External Peer Review for EPA’s Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water EXECUTIVE SUMMARY Versar, Inc. (Versar), a contractor for the U.S. Environmental Protection Agency (EPA), coordinated an external peer review of EPA’s scientific assessment titled “Draft Report: Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water” (MCLG Approaches Report) that links EPA’s revised perchlorate Biologically Based Dose-Response (BBDR) model predictions to neurodevelopmental effects to inform decision-making for perchlorate under the Safe Drinking Water Act. As part of the peer review of the MCLG Approaches Report and revised BBDR model, Versar organized a two-day public peer review meeting in Arlington, Virginia on January 29-30, 2018. The peer review was initiated with a pre-meeting written peer review managed by Versar and conducted by eight independent expert peer reviewers. The role of the peer reviewers was to evaluate the scientific and technical merit of the MCLG Approaches Report and revised BBDR model, and provide their responses to fifteen charge questions. Peer reviewers were responsible only for evaluating the quality of the science included in EPA’s MCLG Approaches Report and revised BBDR model, and were not asked to make any regulatory recommendations or to reach consensus in either their deliberations or written comments. The two-day peer review meeting, which directly followed the written peer review period, was held to discuss the scientific basis supporting EPA’s MCLG Approaches Report and revised BBDR model and to provide members of the public with an opportunity to make brief oral statements and observe the peer reviewer deliberations. On the first day of the meeting, Versar began by providing information on the overall peer review process and introducing the peer reviewers. Following a welcome by EPA, authors from EPA provided background information on the MCLG Approaches Report and revised BBDR model. Next, an observer comment session was held, after which the peer reviewers began their discussions. The discussion was moderated by the Chair, Dr. Stephen Roberts, and focused on individual responses to EPA’s charge questions. The second day of the meeting began with brief remarks from Versar and EPA and then continued with discussion of responses to the charge questions. Following the meeting, peer reviewers were given additional time to complete their individual written reviews, which were submitted to Versar upon completion. These final written comments (contained in Sections 2 through 7 of this report) fall into three categories: general impressions, responses to charge questions, and specific observations. Written peer review comments, as well as comments submitted to the docket by members of the public, will be considered by EPA as it revises the MCLG Approaches Report. Important discussion points at the meeting, developed by Dr. Roberts with assistance from the entire peer review panel, are summarized below by charge question. The discussion points highlight recommendations reached by the panel, as derived from those experts expressing an opinion. 1 Post-Meeting Peer Review Summary Report - External Peer Review for EPA’s Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water General Impressions The panel commends EPA for the substantial amount of work done in creating the new modeling and preparing the report under review. It was highly responsive to the review comments from a year ago. Overall, the panel agreed that the EPA and its collaborators have prepared a highly innovative state-of-the-science set of quantitative tools to evaluate neurodevelopmental effects that could arise from drinking water exposure to perchlorate. While there is always room for improvement of the models, with limited additional work to address the committee’s comments below, the current models are
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