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IRIS Public Science Meeting (August 2018) - Postponed

[UPDATE] EPA has postponed the August 23, 2018 IRIS Public Science Meeting. The IRIS Program is working to identify suitable public science meeting dates in the near future. Stakeholders wishing to provide written comments to the IRIS Program may continue to do so through until September 5, 2018 (Docket: EPA-HQ-ORD-2014-0527).

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 (IAP) for Naphthalene.


  • The deadline for public comments in the docket is September 5, 2018.

Meeting Agenda

EPA will host a public webinar to provide an opportunity for the public to give input and participate in an open discussion regarding the IAP for Naphthalene. See the preliminary agenda below:

Final meeting agenda for the  postponed August 23, 2018 IRIS Public Science Meeting(1 pp, 142 K, About PDF)

Naphthalene Key Science Topics and Materials

Naphthalene Assessment Managers: Erin Yost & Ingrid Druwe

Key Science Topics

What is an IRIS Assessment Plan? An IRIS Assessment Plan (IAP) communicates to the public the plan for assessing each individual chemical and includes summary information on the IRIS Program’s scoping and initial problem formulation; objectives and specific aims for the assessment; the PECO (Populations, Exposures, Comparators, and Outcomes) criteria that outlines the evidence considered most pertinent to the assessment; and identification of key areas of scientific complexity.

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 topic:

  • 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

Topic 1. Species differences in toxicokinetics

The IRIS program is seeking discussion on species differences associated with exposure to naphthalene. Background information is provided below.

Differences in metabolism: Naphthalene is known to be converted to a reactive intermediate(s) through cytochrome P450 (CYP)-dependent metabolism, primarily the CYPF subfamily. While much progress has been made in the characterization of mouse CYP2F2, the CYP thought to be primarily involved in naphthalene metabolism in mice, characterizing the relative contribution of P450 oxidizing enzymes to naphthalene metabolism in rats and humans has been more difficult (Buckpitt et al., 2002; Shultz et al., 1999). The results available at present indicate that there are likely major interspecies catalytic differences between mouse, rat and human CYPF enzyme homologs.

Health effects:  The rate and extent of metabolism of naphthalene in various tissues and in different animal species along with anatomical differences in the nasal turbinates between species will be important considerations in evaluating region-specific differences in the production of reactive metabolites across species.

PBPK: Evaluation of the current and available naphthalene PBPK models for reliable route-to-route, interspecies, and/or intraspecies extrapolation is needed. If necessary, further development of PBPK models will also be considered.

Topic 2. Mode of action for carcinogenicity

The IRIS program is seeking discussion on possible modes of action associated with exposure to naphthalene. Background information is provided below.

Multiple animal and in vitro studies published since the 1998 IRIS Toxicological Review have provided mechanistic information and postulated the involvement of several biological processes in the development of naphthalene-induced tumor formation. These proposed processes include genotoxicity, cytotoxicity, and sustained regenerative cell proliferation. Among the key events identified by these studies are the depletion of glutathione and the formation of reactive naphthalene quinone metabolites via the cytochrome P450 pathway. The role and biological plausibility of each of these proposed mechanisms occurring in humans and their role in the formation of naphthalene-induced tumors will need to be evaluated. Differences in enzyme activities between human and rodent tissues exist; therefore, evaluation of the cancer MOA in the context of toxic metabolite formation and the relevance of these toxic metabolites to human cancer hazard will also need to be evaluated.

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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 5 minutes to speak. Registration to attend is open until 2 days before the meeting or until the 250 person webinar room 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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