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Water: Basic Information about Regulated Drinking Water Contaminants

Basic Information about Heptachlor Epoxide in Drinking Water

Heptachlor Epoxide at a Glance

Maximum Contaminant Level (MCL) = 0.0002 milligrams per Liter (mg/L) or 200 parts per trillion (ppt)

Maximum Contaminant Lavel Goal (MCLG) = zero

Health Effects
Some people who drink water containing heptachlor epoxide in excess of the MCL over many years could experience liver damage; increased risk of cancer.

Drinking Water Health Advisories provide more information on health effects

Chemical Abstract Service Registry Number
1024-57-3

Sources of Contamination
Residue of banned termiticide

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

EPA regulates heptachlor epoxide in drinking water to protect public health. Heptachlor epoxide 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 heptachlor epoxide?
Heptachlor epoxide is formed when heptachlor breaks down in the environment.

Uses for heptachlor epoxide.
Most uses of heptachlor to kill termites in homes and insects on far crops was canceled in 1978. The only permitted use of heptachlor products is for fire ant control in buried pad-mounted electric power transformers, and in underground cable television and telephone cable boxes.

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

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

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

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What are EPA's drinking water regulations for heptachlor epoxide?
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 heptachlor epoxide 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 heptachlor epoxide, called a maximum contaminant level (MCL), at 0.0002 mg/L or 200 ppt. 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 II Rule, the regulation for heptachlor epoxide, became effective in 1992. 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 heptachlor epoxide as part of the Six Year Review and determined that the zero MCLG and 0.0002 mg/L or 200 ppt MCL for heptachlor epoxide are still protective of human health.

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

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How does heptachlor epoxide get into my drinking water?
Heptachlor epoxide adsorbs strongly to soil, but is extremely resistant to biodegration, persisting for many years in the upper soil layers. Similarly in water, heptachlor epoxide will persist, usually in sediments. It is concentrated extensively in aquatic life. It is taken up into the food chain into animals and milk.

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 heptachlor epoxide is in my drinking water?
When routine monitoring indicates that heptachlor epoxide levels are above the MCL, your water supplier must take steps to reduce the amount of heptachlor epoxide 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 heptachlor epoxide be removed from my drinking water?
The following treatment method(s) have proven to be effective for removing heptachlor epoxide to below 0.0002 mg/L or 200 ppt: 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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