Range of the PFOA/S Safe Dose


A coalition of interested parties is forming to develop a range in the safe dose(s) for perfluorooctanote (PFOA) and its sulfonic acid (PFOS), which is reflected in differences in safe doses world-wide of over 100,000-fold (see attached presentation).  This collaboration started in September of 2022 with an open call for nominations to an advisory committee, now selected,* who will lead the coalition through a series of virtual and face-to-face and possibly in-person meetings.  Results are anticipated in the Spring of 2023. 
As with all ARA projects, all interested groups are welcome to be involved.  For example, 

  • Your group can endorse the effort.  Here endorsement simply means that your group agrees with the collaborative effort being done under the auspices of the Alliance for Risk Assessment (ARA) (see: https://www.tera.org/Alliance%20for%20Risk/index.htm).    If you wish to endorse, please send us your group’s logo.
  • Your group could participate directly.  Here participation is contribution to the actual technical work by one or more of your group’s scientists.  If you wish to participate, please send us bio sketches of selected scientists.
  • Your group could donating money or other resources, like a meeting place, to the cause.  Toxicology Excellence for Risk Assessment has been designated as the nonprofit organization to support this collaboration.  Because TERA is a 501c3 nonprofit organization, all donations to this effort are tax deductible.  


For interest in joining the coalition, please contact Michael Dourson at dourson@tera.org


*Advisory Committee:

  • Lyle Burgoon with Raptor Pharm & Tox, Ltd, USA
  • Harvey Clewell with Ramboll, Global
  • Tony Cox with Cox Associates, USA
  • Michael Dourson, Toxicology Excellence for Risk Assessment, USA
  • Tamara House-Knight with GHD, Global
  • Ravi Naidu with CRC CARE, Australia
  • Paul Nathanail with LQM, United Kingdom
  • James S. Smith with US DoD, USA
  • Nitin Verma, Chitkara University, India


Keynote Presentation to the CleanUp Conference in Adelaide, Australia, and the Australian Government, Department of Health and Aged Care: Click Here



Range of the PFOA/S Safe Dose References: Click Here

 To be determined.


Interactive Web-based and Email Discussion Click Here

To be developed.


Group Summaries

To be developed.



Notes from Zoom-Call:


Notes of the Advisory Committee for International Collaboration on the PFOA/S Safe Doses
Conference Call of October 31/November 1


Lyle Burgoon, Raptor Pharm & Tox, Ltd, USA
Harvey Clewell, Ramboll, Global
Michael Dourson, TERA, USA
Laura Green, Green Toxicology, LLC, USA 
Tamara House-Knight, GHD, Global
Ravi Naidu, CRC CARE, Australia
James S. Smith, US DoD, USA
Nitin Verma, Chitkara University, India


Tony Cox, Cox Associates, USA
Eric Saunders, Pfizer, Global

Summary of Discussions:

After introductions by members individually, Michael Dourson went over the ground rules for Alliance for Risk Assessment (ARA) projects.  Briefly stated, ARA projects are to be focused on collaborative work where no party is excluded and all viewpoints are considered.  Additionally, ARA projects are not to be used as a pretext for criticizing a single existing or developing organization’s position.  With this particular project, several agency positions are found to be widely disparate (PFOA safe dose estimates are more than 100,000-fold apart), and so an international collaboration to attempt a narrowing of this range seems reasonable and well within the ARA framework. 

At this point several members of the advisory group described findings of a previous international collaboration on PFOA human 1/2 life (see: https://tera.org/Alliance%20for%20Risk/Projects/pfoahumanhalflife.html). The prior effort was successful in reducing the credible range of the PFOA human ½ life 1 and has been cited in the recent WHO (2022)2 findings. 
Discussion then centered on whether the safe dose ranges of PFOA and PFOS would be addressed together or separately.  The second approach was selected with discussions of PFOA occurring first, in part because of a recent publication on long term follow up with findings from the original PFOA C8 study.3   However, it was recognized by all that many of the insights gained with PFOA would also apply to PFOS. 

Next discussed was the process for the evaluation.  The creation of three or perhaps four separate, and independent, science groups was proposed, based on the success of this approach with the previous international collaboration.  Each group would be given identical tasks and instructions to work without discussion with other groups.  Everyone agreed with this approach and also thought it best to address specific issues sequentially.  Specific issues were determined to be mode(s) of action, choice of critical effect(s), method of extrapolation such as uncertainty factor, and data gaps.  Periodic discussions among all groups was envision to share findings on specific issues and then to attempt a consensus.

Next discussed was the invitation for folks to assist.  It was decided to send an invitation to already identified interested folks, and to make a broader announcement along these lines on social media.  This general invitation would be followed by specific invitations to scientists known to be erudite in certain of the issues. 

The time line for all of this work was recognized to vary depending on the issue under discussion.  For example, discussion on the mode of action might be more easily done then that done on the critical effect.  However, giving the science groups specific deadlines was considered important and would be determined at a subsequent advisory committee meeting.  Interactions with outside parties was also considered to be important but premature at this call. 

Finally, the committee thought that the listing of important references was needed and that the developing website should contain a section devoted to this, but perhaps organized by specific issue.


(1.) Campbell, Jerry, Harvey Clewell, Tony Cox, Michael Dourson, Shannon Ethridge, Norman Forsberg, Bernard Gadagbui, Ali Hamade, Ravi Naidu, Nathan Pechacek, Tiago Severo Peixe, Robyn Prueitt, Mahesh Rachamalla, Lorenz Rhomberg, James Smith, Nitin Verma.  2022.  The Conundrum of the PFOA human half-life, an international collaboration.  Regulatory Toxicology and Pharmacology 132 (2022) 105185.

(2.) WHO, 2022. PFOS and PFOA in Drinking-water.  Background document for development of  WHO Guidelines for Drinking-water Quality 29 September.  Version for public review.

(3.) Steenland K, Fletcher T, Stein CR, Bartell SM, Darrow L, Lopez-Espinosa MJ, Barry Ryan P, Savitz 50 DA (2020). Review: Evolution of evidence on PFOA and health following the assessments of the C8 51 Science Panel. Environ Int. 145:106125




Project Contact:
Dr. Michael Doursoni

Interested Partners:



Hull and Associates