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Learn about Dioxin

Dioxin Key Facts

  • Dioxins are called persistent organic pollutants (POPs), meaning they take a long time to break down once they are in the environment.
  • Dioxins are highly toxic and can cause cancer, reproductive and developmental problems, damage to the immune system, and can interfere with hormones.
  • Dioxins are found throughout the world in the environment and they accumulate in the food chain, mainly in the fatty tissue of animals
  • More than 90% of human exposure is through food, mainly meat and dairy products, fish and shellfish.

Figure 1: Dioxin chemical structures

Dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin

Tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzofuran

Tetrachlorodibenzofuran

3,3',4,4',5,5'-Hexachlorobiphenyl

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:

CDDs and CDFs 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 CDDs and CDFs. PCBs are manufactured products, but they are no longer produced in the United States.

Most Toxic Dioxin

The most studied and most toxic of all dioxins is 2,3,7,8-Tetrachlorodibenzo-p-dioxin. In 2012, EPA released an updated IRIS assessment on this chemical.

What does dioxin look like?

Dioxin looks like white crystalline needles.

Where does dioxin come from?

Industrial activities: Dioxin is not produced or used commercially in the United States. It is a contaminant formed in 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 in the environment. However it should be noted that though levels have decreased in the last 30 years, dioxins are extremely persistent compounds and break down very slowly. In fact, a large part of the current exposures to dioxins in the US is due to releases that occurred decades ago.

Even if all human-generated dioxins were eliminated, low levels of naturally produced dioxins would remain. EPA is working with other parts of the government to look for ways to further reduce dioxin levels entering the environment and to reduce human exposure to them.

Other ways dioxins are produced:

Burning: Dioxins are formed as a result of combustion processes such as waste incineration (commercial or municipal) or from burning fuels (like wood, coal or oil). EPA’s 2006 Dioxin Inventory of Sources Report summarizes that man-made emissions dominate current releases in the US, but acknowledges the need for more data on natural sources. You may not be aware that dioxins can also be formed when household trash is burned or from events like forest fires.

Dioxins produced by backyard burning

Bleaching: Chlorine bleaching of pulp and paper, based on certain types of chemical manufacturing and processing, and other industrial processes this 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:

  • emissions from waste incineration and other combustion that get deposited into bodies of water; and
  • discharges into water from chemical factories.

Learn more about dioxin in drinking water from the table of regulated drinking water contaminants.
EPA's private drinking water wells

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.

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Environmental Laws that Apply to Dioxin

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 including completing the development of draft interim preliminary remediation goals (PRGs) for dioxin in soil. PRGs are goals for lowering the concentration of specific chemicals in specific media like soil, sediment, at CERCLA (also known as Superfund) sites, federal facilities and RCRA sites. They serve as a target to use during the initial development, analysis, and selection of cleanup options. These goals are designed to

  • protect human health and the environment, and
  • comply with all applicable, relevant and appropriate regulations (ARARs) for all exposure pathways being addressed.

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Hazardous Air Pollutants for Hazardous Waste Combustors and Clean Air Act

EPA announced the final rule Final Standards for Hazardous Air Pollutants for Hazardous Waste Combustors in 2005. The rule established national emission standards for hazardous air pollutants (like dioxins) for sources that burn hazardous waste: commercial and onsite incinerators, cement kilns, lightweight aggregate kilns, boilers, and hydrochloric acid production furnaces. These standards were promulgated pursuant to Section 112 (d) of the Clean Air Act, which requires EPA to issue technology-based standards reflecting the performance of the Maximum Achievable Control Technology (MACT).

After EPA issued the 2005 emission standards, the Administrator received four petitions for reconsideration of the NESHAP final rule. EPA granted the petitioners' requests for reconsideration and provided the public with an opportunity to comment on a proposed rule to amend the emissions standards. On October 8, 2008 EPA published a rule announcing the final action regarding the eight issues for which EPA granted reconsideration.

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Congress added Section 129 to the Clean Air Act (CAA) in 1990 specifically to address emissions from solid waste combustion. Sections 111 and 129 require EPA to establish new source performance standards (NSPS) for new units, while sections 111(d) and 129 require the Agency to establish Emission Guidelines for existing units. Both the NSPS and the Emission Guidelines under section 129 use a Maximum Achievable Control Technology (MACT) type approach as used under section 112. NSPS are direct Federal regulations that apply to new sources. Emission Guidelines do not directly regulate solid waste  combustion units, but rather, establish requirements for States Plans which are the vehicle by which States implement the Guidelines. Once approved, these State Plans become Federally enforceable. For further information see the clean air act guidelines and standards for waste management which includes a list of the waste incineration rules (Section 129).

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Toxic Substances Control Act (TSCA)

Under TSCA section 8(e), any person who manufactures (including imports), processes, or distributes in commerce a chemical substance (including, generally, dioxin) or mixture and who obtains information which reasonably supports the conclusion that such substance or mixture presents a substantial risk of injury to health or the environment to immediately inform EPA, except where EPA has been adequately informed of such information.

Under 40 CFR part 766, testing by manufacturers and processors of certain specified chemical substances to ascertain whether those substances may be contaminated with halogenated dibenzodioxins (HDDs)/dibenzofurans (HDFs) is required under TSCA section 4, and under TSCA section 8 manufacturers and processors of certain chemicals are required to report certain information to EPA.

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Emergency Planning and Community Right-to-Know Act (EPCRA)

Section 313 of the Emergency Planning and Community Right-to-Know Act of 1986 (EPCRA) requires certain facilities manufacturing, processing or otherwise using listed chemicals to report their environmental releases of such chemicals annually. The list of reportable chemicals, known as the EPCRA section 313 list and also referred to as the Toxics Release Inventory, or TRI list, was originally identified in the statute and was comprised of more than 300 individual chemicals and 20 chemical categories.

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Safe Drinking Water Act (SDWA)

Under the Safe Drinking Water Act (SDWA), EPA has established a maximum contaminant level for dioxin in drinking water. Learn more about how EPA regulates contaminants under the SDWA and the drinking water regulations for dioxin on these pages:

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