US EPA

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.

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.

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

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

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.

Comments on this report may be submitted and reviewed using the e-Government Regulations.gov 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.