Learn about Dioxin

What is Dioxin?

Dioxins refers to a group of toxic chemical compounds that share certain chemical structures and biological characteristics (see figure 1). Several hundred of these chemicals exist and are members of three closely related families:

• polychlorinated dibenzo-p-dioxins (PCDDs)
• polychlorinated dibenzofurans (PCDFs)
• certain polychlorinated biphenyls (PCBs)

Although hundreds of PCDDs, PCDFs, and PCBs exist, only some are toxic, those with the chlorine atoms in specific positions. Counting around the carbon rings, those with chlorines at positions 2, 3, 7, and 8 are toxic (see figure 1). The dioxin-like PCBs have both biphenyl rings in the same plane (flat appearance), which allows them to act like dioxins in the body.

PCDDs and PCDFs are not created intentionally but are produced as a result of human activities like the backyard burning of trash. Natural processes like forest fires also produce PCDDs and PCDFs. PCBs are manufactured products, but they are no longer produced in the United States.

What does dioxin look like?

Pure dioxin looks like white crystalline needles. In the environment, however, it generally is dispersed and attached to soil and dust particles and is invisible to the eye.

Where does dioxin come from?

Industrial activities: Dioxin is not produced or used commercially in the United States. It is a contaminant formed during the production of some chlorinated organic compounds, including a few herbicides such as Silvex. Over the past decade, EPA and industry have been working together to dramatically reduce the production of dioxin and its release to the environment.

Although environmental levels of dioxins have decreased in the last 30 years, dioxins are extremely persistent compounds and break down very slowly. In fact, a large part of current exposures to dioxins in the United States is due to releases that occurred decades ago (e.g., pollution, fires).

Even if all human-generated dioxins were eliminated, low levels of naturally produced dioxins would remain. EPA and its government partners are looking for ways to further reduce dioxins entering the environment and to reduce human exposure to them.

Other ways dioxins are produced:

Burning: Combustion processes such as waste incineration (commercial or municipal) or burning fuels (like wood, coal or oil) form dioxins.

Dioxins are formed as a result of combustion processes such as … burning fuels like wood, coal or oil.

According to EPA’s 2006 Dioxin Inventory of Sources Report man-made emissions, including backyard and household trash burning, dominated releases in the United States. The report also acknowledges the need for more data on natural sources, such as forest fires, that can form dioxins.

• Dioxins produced by backyard burning

Bleaching: Chlorine bleaching of pulp and paper and other industrial processes can create small quantities of dioxins in the environment.

Smoking: Cigarette smoke also contains small amounts of dioxins.

Drinking Water: Dioxin can get into drinking water from:

• Air emissions from waste incineration and other combustion, with subsequent deposition to lakes and reservoirs
• Deposition from air to soils that erode into surface waters used for drinking water
• Discharges into water from chemical factories.

Learn more about dioxin in drinking water from this table of regulated drinking water contaminants.

How can dioxin affect my health?

Dioxins are highly toxic and can cause cancer, reproductive and developmental problems, damage to the immune system, and can interfere with hormones.

Related Resources

• More information about common sources of exposure
• ​FDA’s Chemical Contaminants: Dioxin
• Questions and answers about dioxin and food safety – Dioxin Related Activities (Feb 2012) (Joint FDA and EPA) is no longer available on the FDA website, see the Food Safety and Inspection Services Guidelines for the latest information on food safety.

Environmental Laws that Apply to Dioxin

• Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) / Resource Conservation and Recovery Act (RCRA)
• Hazardous Air Pollutants for Hazardous Waste Combustors and Clean Air Act
• Toxic Substances Control Act (TSCA)
• Emergency Planning and Community Right-to-Know Act (EPCRA)
• Safe Drinking Water Act (SDWA)

Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) / Resource Conservation and Recovery Act (RCRA)

In 2009, former Administrator Lisa Jackson directed EPA to accelerate work underway to reassess the human health risks from exposures to dioxin. One aspect of this reassessment was developing interim preliminary remediation goals (PRGs) for dioxin in soils.

PRGs are goals for lowering the concentration of specific chemicals in particular media. Media types include soil, sediment, and water at CERCLA (also known as Superfund) sites, federal facilities, and regulated waste, or RCRA, sites. EPA and responsible parties use PRGs as target concentrations during initial development, analysis, and selection of cleanup options.

More at www.epa.gov

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