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Water: Basic Information about Regulated Drinking Water Contaminants

Basic Information about Dioxin (2,3,7,8-TCDD) in Drinking Water

Dioxin (2,3,7,8-TCDD) at a Glance

Maximum Contaminant Level (MCL) = 0.00000003 milligrams per Liter (mg/L) or 30 parts per quadrillion (ppq)

Maximum Contaminant Level Goal (MCLG) = zero

Health Effects
Some people who drink water containing dioxin in excess of the MCL over many years could experience reproductive difficulties and may have an increased risk of getting cancer.

Drinking Water Health Advisories provide more information on health effects

Chemical Abstract Service Registry Number
1746-01-6

Sources of Contamination
Emissions from waste incineration and other combustion; discharge from chemical factories

List of all Regulated Contaminants (PDF) (6 pp, 396 K, About PDF)

EPA regulates dioxin in drinking water to protect public health. Dioxin may cause health problems if present in public or private water supplies in amounts greater than the drinking water standard set by EPA.

What is dioxin?
Dioxin is an organic solid of white crystalline needles.

Uses for dioxin.
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. It may also be formed during combustion of a variety of chlorinated organic compounds, including a few herbicides such as silvex. It may also be formed during combustion of a variety of chlorinated organic compounds.

If you are concerned about dioxin in a private well, please visit:

What are dioxin's health effects?
Some people who drink water containing dioxin well in excess of the maximum contaminant level (MCL) for many years could experience reproductive difficulties and may have an increased risk of getting cancer.

This health effects language is not intended to catalog all possible health effects for dioxin. Rather, it is intended to inform consumers of some of the possible health effects associated with dioxin in drinking water when the rule was finalized.

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What are EPA's drinking water regulations for dioxin?
In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine the level of contaminants in drinking water at which no adverse health effects are likely to occur. These non-enforceable health goals, based solely on possible health risks and exposure over a lifetime with an adequate margin of safety, are called maximum contaminant level goals (MCLG). Contaminants are any physical, chemical, biological or radiological substances or matter in water.

The MCLG for dioxin is zero. EPA has set this level of protection based on the best available science to prevent potential health problems. EPA has set an enforceable regulation for dioxin, called a maximum contaminant level (MCL), at 0.00000003 mg/L or 30 ppq. MCLs are set as close to the health goals as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies.

The Phase V Rule, the regulation for dioxin, became effective in 1994. The Safe Drinking Water Act requires EPA to periodically review the national primary drinking water regulation for each contaminant and revise the regulation, if appropriate. EPA reviewed dioxin as part of the Six Year Review and determined that the zero MCLG and 0.00000003 mg/L or 30 ppq MCL for dioxin are still protective of human health.

States may set more stringent drinking water MCLGs and MCLs for dioxin than EPA.

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How does dioxin get into my drinking water?
The major sources of dioxin in drinking water are emissions from waste incineration and other combustion; and discharge from chemical factories.

A federal law called the Emergency Planning and Community Right to Know Act (EPCRA) requires facilities in certain industries, which manufacture, process, or use significant amounts of toxic chemicals, to report annually on their releases of these chemicals. For more information on the uses and releases of chemicals in your state, contact the Community Right-to-Know Hotline: (800) 424-9346.

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How will I know if dioxin is in my drinking water?
When routine monitoring indicates that dioxin levels are above the MCL, your water supplier must take steps to reduce the amount of dioxin so that it is below that level. Water suppliers must notify their customers as soon as practical, but no later than 30 days after the system learns of the violation. Additional actions, such as providing alternative drinking water supplies, may be required to prevent serious risks to public health.

If your water comes from a household well, check with your health department or local water systems that use ground water for information on contaminants of concern in your area.

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How will dioxin be removed from my drinking water?
The following treatment method(s) have proven to be effective for removing dioxin to below 0.00000003 mg/L or 30 ppq: granular activated carbon.

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How do I learn more about my drinking water?

EPA strongly encourages people to learn more about their drinking water, and to support local efforts to protect the supply of safe drinking water and upgrade the community water system. Your water bill or telephone book's government listings are a good starting point for local information.

Contact your water utility. EPA requires all community water systems to prepare and deliver an annual consumer confidence report (CCR) (sometimes called a water quality report) for their customers by July 1 of each year. If your water provider is not a community water system, or if you have a private water supply, request a copy from a nearby community water system.

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