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Environmental Assessment

An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the U.S. for the Years 1987, 1995, and 2000 (Final, Nov 2006)

Notice

In November 2006, EPA released the report: An inventory of sources and environmental releases of dioxin-like compounds in the United States for the years 1987, 1995 and 2000. The report presented an evaluation of sources and emissions of dioxins (CDDs), dibenzofurans (CDFs) and coplanar PCBs to the air, land and water of the U.S. The inventory suggested that there has been a significant reduction in environmental releases of dioxin-like compounds from regulated industrial sources between the years 1987 and 2000, and that the open burning of residential refuse in backyard burn barrels is the largest source in 2000 that could be reliably quantified. EPA is intending to issue a revised version in 2010 to reflect peer review comments that merited additional consideration.

Report Information

An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States for the Years 1987, 1995, and 2000 (EPA/600/P-03/002F, November 2006), is a peer reviewed report representing EPA’s assessment of dioxin sources and their emissions to the environment. To the extent practical, the inventory is a comprehensive analysis of dioxin sources. Over 800 references were reviewed and cited in the preparation of this report. The citations generally reflect publications up to and including the year 2003. This document reflects a consideration of comments received on an External Review Draft dated March 2005 (EPA600/P-03/002A) [link; http://www.epa.gov/ncea/pdfs/dioxin/2k-update/] provided by an expert panel at a peer-review workshop held September 13–15, 2005, and comments received during a 60-day public review and comment period (May 6–July 5, 2005).

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John Schaum
  • by phone at:   703-347-8637
  • by email at:  schaum.john@epa.gov

Background

The purpose of this document is to present a comprehensive inventory and overview of sources and environmental releases of dioxin-like compounds in the United States. The major identified sources of environmental releases of dioxin-like compounds are grouped into six broad categories: combustion sources, metals smelting, refining and process sources, chemical manufacturing sources, natural sources, and environmental reservoirs. Estimates of annual releases to land, air, and water are presented for each source category and summarized for reference years 1987, 1995, and 2000. The quantitative results are expressed in terms of the toxicity equivalent (TEQ) of the mixture of polychlorinated dibenzo-p-dioxin (CDD) and polychlorinated dibenzofuran (CDF) compounds present in environmental releases using a procedure sanctioned by the World Health Organization (WHO) in 1998. This TEQ procedure translates the complex mixture of CDDs and CDFs characteristic of environmental releases into an equivalent toxicity concentration of 2,3,7,8-tetrachorodibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic member of this class of compounds. Using this WHO procedure, the annual releases of TEQDF-WHO98 to the U.S. environment over the three reference years are 14,000 g in 1987, 3,400 g in 1995, and 1,400 g in 2000.

This analysis indicates that between reference years 1987 and 2000, there was a significant reduction in the releases of dioxin-like compounds to the circulating environment of the United States from regulated industrial sources. In 1987 and 1995, the leading source of dioxin emissions to the U.S. environment was municipal waste combustion; however, because of reductions in dioxin emissions from municipal waste combustors, it dropped to the 4th ranked source in 2000. Burning of domestic refuse in backyard burn barrels remained fairly constant over the years, but in 2000, it emerged as the largest source of dioxin emissions to the U.S. environment that could be reliably quantified. Other potentially large sources were identified, but were not included in the inventory due to uncertainties in available data. These included forest fires and landfill fires.

History/Chronology

1995EPA's Science Advisory Board (SAB) reviewed EPA's Dioxin Reassessment. The SAB recommended that EPA undertake a detailed assessment of sources of dioxin.
1998In response to the recommendation of the SAB, EPA released the first external review draft report entitled, The Inventory of Sources of Dioxin in the United States (EPA/600/P-98/002Aa).
Apr 1998After an independent peer review it was recommended that EPA update the inventory in order to capture changes in dioxin releases resulting from changes in technologies and regulatory requirements.
1999EPA began the development of the year 2000 update to the dioxin inventory.
Jun 2001EPA released an electronic Database of Sources of Environmental Releases of Dioxin-Like Compounds in the United States containing dioxin emission factors specific for releases from sources in reference years 1987 and 1995.
May 2005EPA released the external review draft of the dioxin updated inventory for public comment and peer review. A panel of six internationally known experts convened in September to formally review and comment on the draft report.
Nov 2006The final report was released incorporating comments received from the public and the formal peer review panel.

Next Steps

The Agency anticipates release of a revision to this report in 2010.

Citation

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 (Final, Nov 2006). U.S. Environmental Protection Agency, Washington, DC, EPA/600/P-03/002F.

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