Dioxins are produced commercially only for toxicological and chemical research. Their introduction into the environment has been the unintended result of uncontrolled chemical reactions involving chlorine and various combustion processes that produce undesirable byproducts. Before they were banned, a major source of dioxins was in the manufacture and application of phenoxy herbicides, which could contain 2,3,7,8-TCDD at the level of parts per million (ppm). These herbicides were used as weed control on crops, along fence rows, ditch banks, farm roadways, pastures, and range land. Non-farm uses included tree and bush control on rights-of-way, roadways, fire lanes, and railroads. In the production of some non-banned pesticides such as hexachlorophene, 2,3,7,8-TCDD is produced also, with the majority of the contamination being found in the process still bottoms. In one well-publicized instance, these still bottom oils were inadvertently used for dust control on dirt roads and parking lots. In eastern Missouri, 29 sites were identified as being contaminated with oil used for dust control, that originated from one manufacturer in the southwest of the state. Dioxins are also produced during the manufacture of chlorophenols. Pentachlorophenol is a restricted-use pesticide for wood treatment, and OctaCDD can be found in it at concentrations ranging from 500 to 1,500 ppm.

Manufacturers of white paper using the Kraft process and chlorine dioxide were once a major source of dioxins in surface water, but stricter effluent guidelines for have reduced the amount of dioxin in sludges and effluents. However, the changes made in the last ten years will not greatly impact the sediment loads of PCDDS accumulated before the changes, but will reduce current and therefore future accumulations of long-lived dioxins.

The biggest current contributors of dioxins to the environment are combustion sources, such as medical waste, municipal solid waste, hazardous waste, and sewage sludge incinerators; industrial coal, oil, and wood burning; and secondary metal smelting, cement kilns, diesel fuel combustion, and the burning of wood and residential oil. Emissions to the atmosphere from incineration and combustion sources result in wide- spread distribution of dioxins. Hence, dioxins are pervasive and are found around the world at low levels in rural soils, as well as in sediments of otherwise pristine water bodies. Most of the dioxin deposits from wet and dry deposition ultimately become components of runoff that enter rivers, streams, and estuaries directly or through urban stormwater outfalls.

While most exposure to dioxins occurs from eating commonly consumed foods, limited exposure to dioxins may result from breathing air containing trace amounts of dioxins, inadvertently ingesting soil containing dioxins, and absorbing through the skin minute levels of dioxins present in the soil. Some people may experience higher exposure levels than the general population as a result of food contamination incidents, workplace exposures, industrial accidents, or consuming unusually high levels of fish, meat, or dairy products.

Information regarding levels of contaminants in specific geographic locations or water bodies may be available in a monitoring or characterization report. The catalog of the U.S. Geological Survey Library can be searched to locate reports for specific locales.

For Further Information

The Atmospheric transport and deposition of Dioxin to the Great Lakes for 1996 (revised 2001)
Mark Cohen
NOAA, Air Resources Laboratory

Compilation of EU Dioxin Exposure and Health Data Summary Report
Deborah Buckley-Golder. et al.
European Commission DG Environment, UK department of the Environment Transport and the Regions, 629 pp, 1999

Dioxin Exposure Initiative. 1994.
Contact: Matthew Lorber, lorber.matthew@epa.gov

The Dioxin Exposure Initiative is designed to fill critical data gaps regarding the sources of dioxin that contribute to human exposure. Illustrations on this website show that the cycling of dioxin through the environment is a complex process, involving multiple sources, flows, reservoirs, and sinks.

Dioxins and Dioxin-Like Compounds in the Food Supply: Strategies to Decrease Exposure
National Research Council, National Academies Press, 340 pp, 2003.

Dioxins and PCBs in Rural Areas
Naomi Lubick
ES&T, Science News-January 17, 2007

Domestic Dioxin Concerns
Food and Drug Administration Web page on dioxins in animal feeds.

Expert Workshop on Dioxin and Furan Releases from Uncontrolled Combustion Melbourne, Australia, 7-9 December 2005
UNEP Chemicals / Australian Government Department of the Environment and Heritage

Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds, Part 1: Estimating Exposure to Dioxin-Like Compounds, Volumes 1-3.
U.S. EPA, National Center for Environmental Assessment.
EPA 600-P-00-001Cb, 2003

In October 2004, the EPA's draft dioxin reassessment was delivered to the National Academy of Sciences (NAS) for review. This document is a DRAFT FOR REVIEW PURPOSES ONLY and does not constitute U.S. EPA policy.

Guidance Document: Potential for Exposure to Polychlorinated Dibenzo-p-dioxins and Dibenzofurans when Recycling Sewage Biosolids on Agricultural Land
British Columbia Ministry of Water, Land, and Air Protection, 71 pp, 2002

Human Exposure to Dioxins from Clay: A Case Report
Alfred Franzblau, et al. National Institute of Environmental Health Sciences

A study by University of Michigan researchers that attributes high levels of dioxin in the blood of a woman to exposure to off venting of a ceramics kiln. The congener distribution in her blood matched that in the clay.

Human Exposure to Persistent Organic Pollutants, Illustrated by Four Case Studies in Europe
Jana Weiss, Ph.D. thesis, Stockholm University, Sweden. 89 pp, 2006.

This thesis summarizes four case studies of human exposure to organic pollutants: polychlorinated dibenzo-p-dioxins and furans (PCDD/PCDFs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDD).

The Incidence and Severity of Sediment Contamination in Surface Waters of the United States, National Sediment Quality Survey: Second Edition
U.S. EPA, Office of Science and Technology, EPA-823-R-04-007, 280 pp, November 2004

An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States for the Years 1987, 1995, and 2000
U.S. EPA, National Center for Environmental Assessment. EPA 600-P-03-002A, 677 pp, 2006.
Contact: NCEA Technical Information Center, nceadc.comment@epa.gov

Locating and Estimating Air Emissions from Sources of Dioxins and Furans
U.S. EPA, Office of Air And Radiation. EPA 454-R-97-003, 318 pp, 1997.

Polychlorinated Dibenzo-p-dioxins and Related Compounds Update: Impact on Fish Advisories
U.S. EPA, Office of Water. EPA 823-F-99-015, 6 pp, 1999.

Potential for Human Exposure
Toxicological Profile for Chlorinated Dibenzo-p-Dioxins, Chapter 5.
Agency for Toxic Substances and Disease Registry, 129 pp, 1998.

The Projection of Mobile Source Air Toxics from 1996 to 2007: Emissions and Concentrations DRAFT
William Battye.
EPA 420-R-01-038, 56 pp, 2001.

Research Priorities for Dioxins and Polychlorinated Biphenyls (PCBs): A Report to the Chemicals and GM Policy Division of the Department of the Environment, Food and Rural Affairs (Defra)
Kevin C. Jones and Andy J. Sweetman. Department for Environment, Food & Rural Affairs, London, UK. 80 pp, 2003.
Contact: Kevin Jones, k.c.jones@lancaster.ac.uk

This draft report summarizes the results of a comprehensive review of the literature concerning sources, environmental behavior, and exposures to dioxins and dioxin-like PCBs, then underlines the knowledge gaps highlighted by the review.

Science Dossier: Dioxins and Furans in the Environment
Euro Chlor, 46 pp, 2003.
Contact: Euro Chlor, eurochlor@cefic.be

Survey of Dioxin and Furan Compounds in Sediments of Florida Panhandle Bay Systems
Jon Hemming, Michael Brim, and Robert Jarvis.
U.S. Fish and Wildlife Service, Publication No. PCFO-EC 02-01, 92 pp, 2002.
Contact: Gail A. Carmody, FW4_ESFR_PanamaCity@fws.gov

Third National Report on Human Exposure to Environmental Chemicals, 2005
Department of Health and Human Services, Centers for Disease Control and Prevention.
NCEH Pub. No. 05-0570, 475 pp, 2005.

For this Third Report, scientists tested serum samples in people who took part in CDC's National Health and Nutrition Examination Survey. The report provides information about levels of 29 specific dioxins, furans, and dioxin-related PCBs in the U.S. population.

U.S. Food and Drug Administration Office of Plant and Dairy Foods

Provides results of analyses of various food products tested for dioxin like compounds in the years 2000-2004.

User's Manual for the Database of Sources of Environmental Releases of Dioxin-Like Compounds in the United States
U.S. EPA, National Center for Environmental Assessment.
EPA 600-R-01-012, 58 pp, 2001.
Contact: David Cleverly, cleverly.david@epa.gov

The site also provides access to the database via download or CD-ROM order.

Washington State Dioxin Source Assessment
Bill Yake, Stacie Singleton, and Karol Erickson
Washington State Department of Ecology, Publication No. 98-320, 102 pp, 1998.
Contact: Stacie Singleton, ssin461@ecy.wa.gov

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