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Water: Radon

Basic Information about Radon in Drinking Water

What is radon?
Radon is a gas that has no color, odor, or taste and comes from the natural radioactive breakdown of uranium in the ground. You can be exposed to radon by two main sources:

    1. radon in the air in your home (frequently called "radon in indoor air") and
    3. radon in drinking water.

Radon can get into the air your breathe and into the water you drink. Radon is also found in small amounts in outdoor air.

Most of the radon in indoor air comes from soil underneath the home. As uranium breaks down, radon gas forms and seeps into the house. Radon from soil can get into any type of building - homes, offices, and schools - and build up to high levels in the air inside the building.

Radon gas can also dissolve and accumulate in water from underground sources (called ground water), such as wells. When water that contains radon is used in the home for showering, washing dishes, and cooking, radon gas escapes from the water and goes into the air. It is similar to carbonated soda drinks where carbon dioxide is dissolved in the soda and is released when you open the bottle. Some radon also stays in the water.

Radon is not a concern in water that comes from lakes, rivers, and reservoirs (called surface water), because the radon is released into the air before it ever arrives at your tap.

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Why is radon in drinking water a health concern?
Breathing radon in indoor air can cause lung cancer. Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe it. As they break down further, these particles release small bursts of energy. This can damage lung tissue and increase your chances of developing lung cancer over the course of your lifetime. People who smoke have an even greater risk. Not everyone exposed to high levels of radon will develop lung cancer. However, radon in indoor air is the second leading cause of lung cancer. About 20,000 deaths a year in the U.S. are caused by breathing radon in indoor air.

Only about 1-2 percent of radon in the air comes from drinking water. However breathing radon increases the risk of lung cancer over the course of your lifetime. Some radon stays in the water; drinking water containing radon also presents a risk of developing internal organ cancers, primarily stomach cancer. However this risk is smaller than the risk of developing lung cancer from radon released to air from tap water.

Based on a National Academy of Science report, EPA estimates that radon in drinking water causes about 168 cancer deaths per year: 89% from lung cancer caused by breathing radon released to the indoor air from water and 11% from stomach cancer caused by consuming water containing radon.

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Is there radon in my water?
Not all drinking water contains radon. If your drinking water comes from a surface water source, such as a river, lake, or reservoir, most radon that might be in the water will be released into the air before reaching your water supplier or home. Radon is only a concern if your drinking water comes from underground, such as a well that pumps water from an aquifer, though not all water from underground sources contains radon.

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What levels of radon in water should I be concerned about?
There is currently no federally-enforced drinking water standard for radon. EPA has proposed to regulate radon in drinking water from community water suppliers (water systems that serve 25 or more year-round residents). EPA does not regulate private wells.

EPA has proposed to require community water suppliers to provide water with radon levels no higher than 4,000 pCi/L, which contributes about 0.4 pCi/L of radon to the air in your home. This requirement assumes that the State is also taking action to reduce radon levels in indoor air by developing EPA-approved, enhanced State radon in indoor air programs (called Multimedia Mitigation Programs). This is because most of the radon you breathe comes from soil under the house. This option gives States the flexibility to focus on the greatest problems, by encouraging the public to fix radon in indoor air problems and build homes that keep radon from entering.

Under the proposed regulation, States that choose not to develop enhanced indoor air programs, community water systems in that State will be required to reduce radon levels in drinking water to 300 pCi/L. This amount of radon in water contributes about 0.03 pCi/L of radon to the air in your home. Even if a State does not develop an enhanced indoor air program, water systems may choose to develop their own local indoor radon program and meet a radon standard for drinking water of 4,000 pCi/L.

EPA proposed this option, under the framework specified by the 1996 Amendments to the Safe Drinking Water Act, so that the overall risks from exposure to radon, both through air and water, are reduced.

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How do I test for radon in drinking water and how do I get rid of it?

  • If you get water from a public water system: Find out whether your water system gets its water from a surface (river, lake, or reservoir) or a ground water (underground) source.
    • If the water comes from a surface water source, most radon that may be in the water will be released to the air before it makes its way to your tap.
    • If the water comes from a ground water source, call your water system and ask if they've tested the water for radon.
  • If you have a private well: EPA recommends testing your drinking water for radon. Call the Safe Drinking Water Hotline (1-800-426-4791) which can provide phone numbers for your State laboratory certification office. Your State laboratory certification office or State radon office can direct you to laboratories which may be able to test your drinking water for radon.

If testing your private well shows that you have high levels of radon in your drinking water and you are concerned about it, there are some things you can do to improve the water. The most effective treatment you can apply is to remove radon from the water right before it enters your home. This is called point-of-entry treatment. There are two types of point- of-entry devices that remove radon from water:

  • Granular activated carbon (GAC) filters (which use activated carbon to remove the radon), and
  • Aeration devices (which bubble air through the water and carry radon gas out into the atmosphere through an exhaust fan).

GAC filters tend to cost less than aeration devices, however, radioactivity collects on the filter, which may cause a handling hazard and require special disposal methods for the filter.

For more information on point of use treatment, you should contact the following independent certifying organizations: Exit EPA Disclaimer

Additional information and documents about radon in your home can be found below.

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I receive water from a public water supplier. How will EPA's proposed regulation affect me?
The proposed radon regulation does not affect public water systems or their customers. EPA must promulgate a final regulation before a federal radon regulation will be enforced. Within three years of promulgating the final regulation, your State may decide to develop a plan for an enhanced radon in indoor air program, which would require your public water supplier to reduce radon levels in the water supply to 4,000 pCi/L. Consumers may be interested in participating in their State's development of this plan, once the radon rule is finalized. If your state or public supplier does not develop an enhanced radon in indoor air program, your public water supplier will be required to reduce radon levels to 300 pCi/L. Under either option, your water bills may increase depending on the size of your water supplier and the radon levels in the drinking water in your area.

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How do I get more information about radon?

  • Call the Safe Drinking Water Hotline (1-800-426-4791) - The Safe Drinking Water Hotline can provide you with more information about what EPA is doing to regulate radon in drinking water and refer you to your State drinking water program for information about your community water system.
  • Call your Local Water Supplier - Your local water supplier will have information about your local water supply and can answer any questions you have about your water. Look for the phone number on your water bill or in the government section of your phone book.
  • Call the Radon Hotline (1-866-730-GREEN) - The Radon Hotline can refer you to your State radon office for more information, and can send you free publications about radon in indoor air.
  • The Indoor Environments Division (IED), located within the Office of Radiation and Indoor Air (ORIA), under the Office of Air and Radiation (OAR), is responsible for implementing EPA’s Indoor Environments Program, a voluntary (non-regulatory) program to address indoor air pollution.  

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