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Final Report of Perchlorate Model Peer Review Panel

Part of the process for developing a regulation for perchlorate under the Safe Drinking Water Act (SDWA) is to develop a Maximum Contaminant Level Goal (MCLG).  Based on advice from EPA’s Science Advisory Board (SAB), EPA is using a Physiologically Based Pharmacokinetic/Pharmacodynamic (PBPK/PD) or Biologically Based Dose Response (BBDR) model that will “integrate available health related information in a robust and transparent analysis of the effects of perchlorate on thyroid hormone production”.  Thyroid hormone production is the critical health factor for sensitive populations and will be the driver for the MCLG.  The peer review panel that reviewed EPA’s modeling effort recently released their final report.
The peer reviewers identified a number of areas for improvement of the model covering modeling earlier pregnancy, the limited hypothyroxinemic range used in the model, and additional literature that could be examined.  They also made recommendations concerning clearer communication about the model for scientists and risk managers.  As the development process continues, EPA plans another peer review to consider how the model should be applied to actual development of the MCLG.
EPA will take the comments from the peer review panel into consideration as they continue to develop a proposed rule, although they are not bound by any of the specific recommendations.  Under terms of a court settlement with environmental groups, EPA is committed to publishing a proposed rule by October 31, 2018 and a final rule by December 19, 2019.  It remains to be seen whether this elaborate modeling process will be completed in time to meet the new schedule.
For all the information about EPA’s process for regulating perchlorate you can visit their perchlorate web page.