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IRIS Public Science Meeting (Dec 2019)

Meeting Objective

At IRIS Public Science Meetings, the IRIS Program encourages the scientific community and the public to participate in discussions on IRIS draft assessment materials.

At this meeting, the IRIS Program is inviting public discussion on the following draft assessment material:

  • IRIS Assessment Plan for Inorganic Mercury Salts (Scoping and Problem Formulation Materials)


  • The meeting will be held on December 5, 2019 from 1:00 - 3:00 pm Eastern Time by webinar.
  • Register to attend (webinar only) by December 3, 2019 or until the 250 person limit is reached - whichever occurs first.
  • The deadline to submit public comments to the docket was November 7, 2019.

Meeting Agenda

Meeting Materials

Inorganic Mercury Salt Assessment Manager: Nagu Keshava

Key Science Topics

What is an IRIS Assessment Plan? An IRIS Assessment Plan (IAP) communicates the plan for assessing each individual chemical to the public.  It includes summary information on scoping and initial problem formulation, specific aims and objects for the assessment, identifies key areas of scientific complexity, and it includes the PECO (Populations, Exposures, Comparators, and Outcomes) criteria that outline the evidence considered most pertinent to the assessment. The PECO provides the framework for developing literature search strategies and inclusion/exclusion criteria, particularly with respect to evidence stream (i.e., human, animal, mechanistic), exposure measures and outcome measures.

The IRIS Program is seeking a discussion with the public aimed at improving or clarifying the IAP. Below are questions to facilitate the discussion of these science topics:

  • Are the assessment objectives and specific aims articulated clearly?
  • Does the background information and context that is provided support the objectives for the assessment presented in the plan? 
  • Does the proposed PECO (Populations, Exposures, Comparators, Outcomes) framework identify the most pertinent evidence to address the stated needs of the Agency programs and regions?

Science Topics

Key Topic 1. Toxicokinetic characteristics of various mercury forms including solubility, bioavailability, distribution, conversion (oxidation state). Inorganic mercury salts are present in different oxidation states. For example, both mercuric chloride and mercuric sulfide are divalent and have mercury in a +2 oxidation state whereas mercurous chloride has a +1 oxidation state (which may change in different biological systems).  In addition, the solubilities of the three salts differ by several orders of magnitude.  These characteristics are expected to influence the toxicokinetics of the different salts. An understanding of these characteristics or other information on the bioavailability, tissue distribution and toxicokinetic profiles of the different salts is expected to be informative in evaluating potential human health hazards.

Key Topic 2: Key molecular interactions and sequelae of mercuric ion on potential target tissues (e.g., kidney, immune system). Mercuric ion has been identified in the literature as a presumed toxic moiety in potential target tissues through its binding to sulfhydryl groups. Further understanding of the conversion of mercurous to mercuric ion following exposure to mercurous chloride and its key molecular interactions with biological targets may be important to consider in the assessment.

Key Topic 3. Alternative methods or new approaches to inform data poor mercury salts (i.e., mercurous chloride and mercuric sulfide). Both mercuric sulfide and mercurous chloride lack or have minimal in vivo toxicity data. Information relevant to the potential application of alternative approaches to derive toxicity values for these salts (e.g., read-across) may be useful to assessment development.

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The IRIS Program will be holding this meeting only by webinar and not in-person. You will need to register to attend the webinar by visiting the link (in the registration link box). You may also register to give verbal comments at the meeting from this form.

Commenters are given up to 10 minutes to speak. Registration to provide comment is open until Nov 18th, and registration to attend is open until Dec 3rd or until the 250 person limit is reached - whichever occurs first. Teleconference/webinar information will be provided a few days before the meeting/webinar is held.

To keep you informed regarding the IRIS Program updates, all attendees who register for this event will also be added to the IRIS Mailing List. If you decide that you do not want to receive these updates, you can unsubscribe from the mailing list at any time.

Note on registering: while you are not required to provide us with any personally identifying information (such as your email address, phone number, etc.), doing so will allow us to process your registration and provide you with the information regarding participation procedures. Failure to provide this information may hinder your ability to participate in this public event.

Computer Preparations for the Webinar

Once you are registered to participate remotely by webinar you will need:

  • A computer with an internet connection. Adobe Flash is required.
  • A speaker/headphones or telephone. Audio will be available through the webinar, and also through a teleconference line if you wish to listen by phone or want to make a comment.
  • The webinar URL and teleconference details will be e-mailed to registered participants of this meeting.

The webinar room will be opened 30 minutes prior to the workshop for testing and set up. The teleconference line will be opened 10 minutes before the start of the workshop.

Software Specifications: EPA uses Adobe Connect with integrated video, screen sharing, and sound capabilities. If this is your first online event using this software, then you should follow the steps below to set up your computer in advance.

  1. First run the test by visiting If you fail any portion of the test, please follow the instructions to resolve your problem. If you cannot resolve the issue, then contact your PC support specialists for assistance.
  2. Once you are at the login screen for the webinar, you can enter the meeting using the guest option. Please identify yourself by supplying your first and last name and organization and/or affiliation. For example, "Jane Doe - GSA." EPA employees should use their registered names to enter the meeting room.
  3. After completing step 2, just click the button "Enter Room" to join the meeting.

Questions: If you are having technical issues in the webinar, you can use the chat window to address the meeting host. If you have a question for the speaker you must use the "ask a question" box to notify the meeting facilitator that you have a question. Once an opportunity is available your question will be addressed.

For any additional questions, please email Dahnish Shams at

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