Dioxin

The Issue
The term "dioxin" is commonly used to refer to a family of toxic chemicals that share a similar chemical structure and induce harm through a similar mechanism. Dioxins have been characterized by EPA as likely human carcinogens and are anticipated to increase the risk of cancer at background levels of exposure.

Dioxin levels in the environment have been declining since the early seventies and have been the subject of a number of federal and state regulations and clean-up actions; however, current exposures levels still remain a concern. Examples of dioxins include polychlorinated biphenyls (PCBs), polychlorinated dibenzo dioxins (PCDDs), and polychlorinated dibenzo furans (PCDFs). PCBs were produced commercially in large quantities until production was stopped in 1977. PCDDs and PCDFs are not commercial chemical products, but are unintentional byproducts of most forms of combustion and several industrial chemical processes.

EPA Action
Scientists in EPA's National Center for Environmental Assessment are currently working on a comprehensive reassessment of dioxin exposure and human health effects. The latest draft assessment, Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds posted in Dec 2003, is still undergoing revisions in light of the review by the National Academy of Sciences(NAS) in November 2004. A Workshop in Feb 2008 will be held to discuss EPA's reponse to the NAS reports.

History

• 1984 EPA published the Health Risk Assessment Approach for 2,3,7,8-Tetrachlorodibenzo-P-Dioxin.
• Jun-Aug 1994 EPA released the draft documents:Health Assessment Document for 2,3,7,8-Tetrachlorodibenzo-P-Dioxin (TCDD) and Related Compounds Volume (1 of 3) and Volume (2 of 3), and Volume (3 of 3)
• Sep 1994 EPA launched the Dioxin Exposure Initiative, a research program to further evaluate the exposure of Americans to this class of compounds. The DEI is a research program jointly funded and managed by EPA's Office of Research and Development and EPA's Office of Prevention, Pesticides, and Toxic Substances.
• Jul 2000 EPA released the Consolidated Comments from the Peer Review of the Draft Dioxin Reassessment
• Oct 2003 EPA released the NAS Review Draft of the Dioxin Assessment with updates on the Questions and Answers about Dioxin.
• Oct 2004 EPA released the NAS Review Draft of the Dioxin Assessment, in preparation for the first NAS panel review meeting (held 11/22 -23/04), in Wash., DC. This is the most current version of the report.
• Jul 2006 NAS released Health Risks from Dioxin and Related Compounds: Evaluation of the EPA Reassessment.
• Sep 2008 The Interagency Dioxin Workgroup posted an update to the Questions and Answers about Dioxin.
• Nov 2008 EPA released a preliminary search list to address EPA's Reponses to the NAS comments on the 2003 Dioxin Reassessment report.
• 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]
• May 2009 EPA released the 2009 Science Plan for activities related to Dioxins in the environment
• Jun 2009 EPA released the Dioxin Workshop Summary report containing discussions and conclusions from the Feb 18-20, 2009 workshop held in Cincinnati, Ohio.

Related Links

• Database of sources of environmental releases of dioxin-like compounds in the U.S. (EPA/600/C-01/012, March, 2001) is a database containing congener-specific emissions and environmental releases of polychlorinated dibenzo-para-dioxins (CDDs) and polychlorinated dibenzofurans (CDFs) from known source activities in the U.S. Included within the database are facility-specific emissions for a variety of CDD/CDF sources, and congener-specific I-TEQ and WHODF-TEQ emission factors. The database contains information that can be used to track CDD/CDF emissions over time; develop and compare congener-specific and homologue profiles for source categories; and to develop congener-specific emission factors that can then be used to undertake an emissions inventory of sources. The database is associated with two reference years: 1995 and 1987.
• EPA Analytical Method 1613 for analysis of dioxin and other related compounds.
• Dioxin Overview: from EPA's Office of Prevention, Pesticides & Toxic Substances (OPPTS)

Best Resources

U.S. EPA. 2,3,7,8-Tetrachlorodibenzo-P-Dioxin (TCDD) Dose-Response Studies: Preliminary Literature Search Results and Request for Additional Studies. EPA/600/R-08/119, 2008.

U.S. EPA. An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the U.S. for the Years 1987, 1995, and 2000 (EPA/600/P-03/002f, Final Report, November 2006). U.S. Environmental Protection Agency, Washington, DC, EPA/600/P-03/002F.

U.S. EPA. User's Manual for the Database of Sources of Environmental Releases of Dioxin-Like Compounds in the U.S.: Reference Years 1987 and 1995. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-01/012.

U.S. EPA. Relative Congener Scaling of Polychlorinated Dibenzo-P-Dioxins and Dibenzofurans to Estimate Building Fire Contributions in Air, Surface Wipes, and Dust Samples. , Joachim D. Pleil and Matthew N. Lorber (ed.), Submitted to: ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 41(21): 7286 -7293, (2007).

U.S. EPA. An Exploratory Study: Assessment of Modeled Dioxin Exposure in Ceramic Art Studios (2008). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/044F, 2008.

U.S. EPA. Pilot Survey of Levels of Polychlorinated Dibenzo-P-Dioxins (PCDDs), Polychlorinated Dibenzofurans (PCDFs), Polychlorinated Biphenyls (PCB) and Mercury in Rural Soils of the U.S. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-05/043F, 2007.

U.S. EPA. EPA Regulations Related to Dioxin..

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