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Basic Information about Hexachlorocyclopentadiene in Drinking Water

Hexachlorocyclopentadiene at a Glance

Maximum Contaminant Level (MCL) = 0.05 milligrams per Liter (mg/L) or 50 parts per billion (ppb)

Maximum Contaminant Level Goal (MCLG) = 0.05 mg/L or 50 ppb

Health Effects
Some people who drink water containing hexachlorocyclapentadiene in excess of the MCL over many years could experience problems with their kidneys or stomach.

Drinking Water Health Advisories provide more information on health effects

Chemical Abstract Service Registry Number

Sources of Contamination
Discharge from chemical factories

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

EPA regulates hexachlorocyclopentadiene in drinking water to protect public health. Hexachlorocyclopentadiene 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 hexachlorocyclopentadiene?
Hexachlorocyclopentadiene is an oily, yellow-green organic liquid with a pungent odor.

Uses for hexachlorocyclopentadiene.
It is used as a raw material in manufacturing other chemicals, including pesticides, flame retardants, resins, dyes, pharmaceuticals, plastics, etc. Hex has no end uses of its own.

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

What are hexachlorocyclopentadiene's health effects?
Some people who drink water containing hexachlorocyclopentadiene well in excess of the maximum contaminant level (MCL) for many years could experience problems with their kidneys or stomach.

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

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How is hexachlorocyclopentadiene regulated?
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 hexachlorocyclopentadiene is 0.05 mg/L or 50 ppb. EPA has set this level of protection based on the best available science to prevent potential health problems. EPA has

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What are EPA's drinking water regulations for hexachlorocyclopentadiene?
EPA has set an enforceable regulation for hexachlorocyclopentadiene, called a maximum contaminant level (MCL), at 0.05 mg/L or 50 ppb. 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. In this case, the MCL equals the MCLG, because analytical methods or treatment technology do not pose any limitation.

The Phase V Rule, the regulation for hexachlorocyclopentadiene, 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 hexachlorocyclopentadiene as part of the Six Year Review and determined that the 0.05 mg/L or 50 ppb MCLG and 0.05 mg/L or 50 ppb MCL for hexachlorocyclopentadiene are still protective of human health.

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

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How does hexachlorocyclopentadiene get into my drinking water?
The major source of hexachlorocyclopentadiene is 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 hexachlorocyclopentadiene is in my drinking water?
When routine monitoring indicates that hexachlorocyclopentadiene levels are above the MCL, your water supplier must take steps to reduce the amount of hexachlorocyclopentadiene 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 hexachlorocyclopentadiene be removed from my drinking water?
The following treatment method(s) have proven to be effective for removing hexachlorocyclopentadiene to below 0.05 mg/L or 50 ppb: granular activated carbon combined with packed tower aeration.

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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.

The CCR summarizes information regarding sources used (i.e., rivers, lakes, reservoirs, or aquifers), any detected contaminants, compliance and educational information.

Some water suppliers have posted their annual reports on EPA's Web site.

Other EPA Web sites

Other Federal Departments and Agencies

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