US EPA

On May 21, 2010, the updated EPA's Reanalysis of Key Issues Related to Dioxin Toxicity and Response to NAS Comments report was released for external peer review and public comment. This report was renamed after interagency comments from the original report title of EPA's Response to "Health Risks from Dioxin and Related Compounds Evaluation of the EPA Reassessment" Published by the National Research Council of the National Academies. The document was reviewed internally by EPA and by other federal agencies and White House Offices before public release. In the new IRIS process, introduced by the EPA Administrator, all written comments on IRIS assessments submitted by other federal agencies and White House Offices are made publicly available. Accordingly, interagency comments and the interagency science consultation draft report and the charge to external peer reviewers are posted on this site.

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 meetings 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 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.

The objective of this report is to share the Interagency comments on the NAS coments on dose-response modeling conducted in the EPA Reassessment of the health effects associated with dioxin exposure.

Following external peer review the assessment will be revised taking into consideration external peer review and public comments. It will then undergo a final EPA internal review and a review by other federal agencies and White House offices, followed by posting to the IRIS Web site.

U.S. EPA. EPA's Response to Health Risks from Dioxin and Related Compounds Evaluation of the EPA Reassessment Published by the National Research Council of the National Academies (Interagency Science Consultation Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/038C, 2010.