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Water: Basic Information about Regulated Drinking Water Contaminants

Basic Information about cis-1,2-Dichloroethylene in Drinking Water

cis-1,2-Dichloroethylene
at a Glance

Maximum Contaminant Level (MCL) = 0.07 milligrams per Liter (mg/L) or 70 parts per billion (ppb)

Maximum Contaminant Level Goal (MCLG) = 0.07 mg/L or 70 ppb

Health Effects
Some people who drink water containing cis-1,2-dichloroethylene in excess of the MCL over many years could experience problems with their liver.

Drinking Water Health Advisories provide more information on health effects

Chemical Abstract Service Registry Number
156-59-2

Sources of Contamination
Discharge from industrial chemical factories

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

EPA regulates cis-1,2-dichloroethylene in drinking water to protect public health. cis-1,2-Dichloroethylene 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 cis-1,2-dichloroethylene?
cis-1,2-Dichloroethylene is an odorless organic liquid that has two slightly different forms, a "cis" form and a "trans" form.

Uses for cis-1,2-dichloroethylene.
Both the cis and trans forms — usually as a mixture — are used as a solvent for waxes and resins; in the extraction of rubber; as a refrigerant; in the manufacture of pharmaceuticals and artificial pearls; in the extraction of oils and fats from fish and meat; and in making other organics.

If you are concerned about cis-1,2-dichloroethylene in a private well, please visit:

What are cis-1,2-dichloroethylene's health effects?
Some people who drink water containing cis-1,2-dichloroethylene well in excess of the maximum contaminant level (MCL) for many years could experience problems with their liver.

This health effects language is not intended to catalog all possible health effects for cis-1,2-dichloroethylene. Rather, it is intended to inform consumers of some of the possible health effects associated with cis-1,2-dichloroethylene in drinking water when the rule was finalized.

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What are EPA's drinking water regulations for cis-1,2-dichloroethylene?
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 cis-1,2-dichloroethylene is 0.07 mg/L or 70 ppb. 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 cis-1,2-dichloroethylene, called a maximum contaminant level (MCL), at 0.07 mg/L or 70 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 II Rule, the regulation for cis-1,2-dichloroethylene, 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 cis-1,2-dichloroethylene as part of the Six Year Review and determined that the 0.07 mg/L or 70 ppb MCLG and 0.07 mg/L or 70 ppb MCL for cis-1,2-dichloroethylene are still protective of human health.

States may set more stringent drinking water MCLGs and MCLs for cis-1,2-dichloroethylene than EPA.

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How does cis-1,2-dichloroethylene get into my drinking water?
The major source of cis-1,2-dichloroethylene in drinking water is discharge from industrial 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 cis-1,2-dichloroethylene is in my drinking water?
When routine monitoring indicates that cis-1,2-dichloroethylene levels are above the MCL, your water supplier must take steps to reduce the amount of cis-1,2-dichloroethylene 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 cis-1,2-dichloroethylene be removed from my drinking water?
The following treatment method(s) have proven to be effective for removing cis-1,2-dichloroethylene to below 0.07 mg/L or 70 ppb: granular activated carbon in combination 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.

Other EPA websites

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