CASRN 1746-01-6 | DTXSID2021315

EPA's Reanalysis of Key Issues Related to Dioxin Toxicity and Response to NAS Comments (External Review Draft)

On this page:

Notice - This site contains archived material(s)

Archive disclaimer
Archived files are provided for reference purposes only. The file was current when produced, but is no longer maintained and may now be outdated. Persons with disabilities having difficulty accessing archived files may contact the Risk Webmaster for assistance. Please use the contact us form if you need additional support.


EPA is releasing for external peer review and public comment an important draft document reviewing the literature on the health effects of dioxin and related compounds (also referred to as 2,3,7,8-Tetrachlorodibenzo-p-dioxin). At the request of Administrator Jackson, EPA is in the process of re-assessing the science on the effects of dioxin, a toxic chemical that is emitted by multiple sources, on the public’s health.

This draft dioxin report is EPA’s response to key comments and recommendations made by the National Academy of Sciences on the Agency’s draft dioxin reassessment. This assessment has been in progress for many years and raises health issues of broad interest to scientists and policymakers across the federal family. The Agency’s draft report includes significant new analyses on potential cancer and non-cancer human health effects that may result from exposures to dioxins and includes an oral reference dose for what is considered to be the most toxic of the dioxin-like compounds.

EPA’s Science Advisory Board (SAB) will convene an expert panel to review this draft report; the SAB held their first public meeting on July 13-15, 2010. Many stakeholders have significant interest in EPA’s dioxin assessment activities, and the release of this draft report will likely be of interest to environmental and health advocacy groups, the regulated community, states, media, and Congress. We want to stress that this report is a draft scientific document that is still subject to independent external peer review and public review. The Agency is committed to a transparent, scientifically sound process to determine how this chemical impacts Americans’ health.


U.S. EPA. EPA's Reanalysis of Key Issues Related to Dioxin Toxicity and Response to NAS Comments (External Review Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/038A, 2010.

Top of Page


In 2003, EPA, along with other federal agencies, asked the National Academy of Sciences (NAS) to review aspects of the science in EPA’s draft dioxin reassessment entitled, Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds, and, in 2004, EPA sent the 2003 draft dioxin reassessment to the NAS for their peer review. The NAS held several public meeting during their review of the draft reassessment and on July 11, 2006, released the report of their review entitled, “Review of EPA's Assessment of the Health Implications of Exposure to Dioxins.”

The NAS identified three areas in the 2003 draft reassessment that required substantial improvement to support a more scientifically robust risk characterization. These three areas were: (1) justification of approaches to dose-response modeling for cancer and non-cancer endpoints; (2) transparency and clarity in selection of key data sets for analysis; and (3) transparency, thoroughness, and clarity in quantitative uncertainty analysis. The NAS provided EPA with recommendations to address their key concerns. The Draft Response to Comments report, which is being provided for public review and comment, responds to the key recommendations included in NAS’s 2006 report. This draft report includes significant new analyses on both the potential cancer and noncancer human health effects that may result from of exposures to dioxins. For instance, the Draft Response to Comments report addresses the explicit recommendation of the NAS to develop a quantitative risk estimate for noncancer effects that may result from long-term (chronic) oral exposure to dioxins. Thus, the Draft Response to Comments report includes an oral reference dose (RfD) for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD); the most well studied and considered to be the most toxic of the dioxin-like compounds. An RfD was not in the 2003 draft dioxin reassessment.

In addition, in 2003 EPA and other federal agencies developed a set of questions and answers related to dioxins. They have updated them about every year and a half. These materials have again been updated to include more recent information. These questions and answers provide general information on dioxins such as what they are, where they can be found, and major sources of dioxins. They also discuss possible effects of dioxin exposure in humans, include advice about consumption of food that might contain dioxins, and explain the review process for the dioxin reassessment.


Date Description
08- Oct 2004 EPA released the NAS External Review Draft of the Dioxin Assessment, in preparation for the first NAS panel meeting (held 11/22 -23/2004), in Wash., DC. This is still the most current version of the EPA Dioxin Assessment.
09- Jul 2006 NAS released Health Risks from Dioxin and Related Compounds: Evaluation of the EPA Reassessment.
11- Nov 2008 EPA released a preliminary search list to address EPA's Reponses to the NAS comments on the 2003 Dioxin Reassessment report.
12- Feb 2009 EPA hosted a 3-day public, scientific workshop to assist EPA in responding to the NAS reports on Dioxin. [ Workshop Announcement and details]
14- Jun 2009 EPA released the Dioxin Workshop Summary report containing discussions and conclusions from the Feb 18-20, 2009 workshop held in Cincinnati, Ohio.
15- Feb 2010 EPA initiated an interagency science consultation on the review of the draft Response to "Health Risks from Dioxin and Related Compounds: Evaluation of the EPA Reassessment" published by the NRC/NAS .
16- May 2010 EPA released the draft report for public review and comment. [Federal Register May 21, 2010]
17- Jun 2010 EPA extended the public comment period until September 20, 2010. [Federal Register Notice Jun 23, 2010]


Following the external peer review, the document will be revised and published as a final report.

Additional Information

Comments on this report may be submitted and reviewed using the e-Government Web site. From the site, select Environmental Protection Agency and the keyword EPA-HQ-ORD-2010-0395 (for the docket ID) to comment on this report.

Top of Page


If you have a disability and the format of any material on our web pages interferes with your ability to access the information, please reach out to us using the Contact Us about IRIS form for assistance. To enable us to respond in a manner most helpful to you, please indicate the nature of the accessibility problem, the web address of the requested material, your preferred format in which you want to receive the material (electronic format (ASCII, etc.), standard print, large print, etc.), and your contact information.

Top of Page