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What is Radon? 
How Serious a Problem is Radon in the U.S.? 
How Does Radon get Indoors?
Health Effects 
Is Radon A Problem in Your Home? 
What You Can Do to Reduce High Levels of Indoor Radon
For More Information


Radon is a radioactive gas that is found in the earth's rock and soil. It is formed by the natural breakdown of radium, which is itself a decay product of uranium.

As radon decays, it forms radioactive by-products called either "progeny," "decay products" or "daughters" which, if inhaled, can damage lung tissue and cause lung cancer.

Invisible and odorless, radon is a health hazard when it accumulates to high levels inside homes or other structures. And it is deadly. Indoor radon exposure is estimated to be the second leading cause of lung cancer deaths each year in the United States. Cigarette smoking is responsible for the large majority (87 percent) of lung cancer deaths.


Radon problems have been identified in every state. The U.S. Environmental Protection Agency (EPA) estimates that nearly 1 out of every 15 homes in the U.S. has indoor radon levels at or above the EPA's recommended action guideline level of four picocuries per liter of air (pCi/L) on a yearly average. Radon can be a problem in schools and work places, too.


Radium, which releases radon, is common in the earth's crust. Soils and rocks containing high levels of uranium, such as granite, phosphate, shale and pitchblende are natural sources of radon.

High levels of radon in the soil are primarily responsible for radon problems. The radon gas percolates up through porous soils under the home or building and enters through gaps and cracks in the foundation or in the insulation and through pipes, sumps, drains, walls or other openings.

Water is another possible pathway for bringing radon into the home. Water, when in contact with rock containing uranium, absorbs the radon gas. The radon is then carried into the home and released into the air in household dishwashers, faucets, showers, or washing machines.

Water-related radon problems usually involve deep private wells rather than community water supplies.

In some unusual situations, radon may be released from home construction materials such as stone used to build fireplaces or solar heating storage systems.

Radon is not a problem outdoors because it is quickly diluted to low levels by outdoor air.


Radon is estimated to be the second leading cause of lung cancer in the U.S. today, causing thousands of deaths each year. Cigarette smoking remains the primary cause.


While an area's geology may indicate the potential for radon problems, human senses cannot pick up any evidence of this odorless, colorless gas.



Measuring for radon can be done simply and relatively inexpensively.

The American Lung Association as well as the EPA and the Surgeon General recommend testing all homes below the third floor for radon. Testing in schools is also recommended.

There are many kinds of low-cost "do it yourself" radon test kits available through the mail and in hardware stores and other retail outlets. Call 1-800-LUNGUSA to order a kit or click here to order online. Choose a test kit that has passed EPA's testing program. These kits will usually display the phrase "Meets EPA Requirements."

If you prefer, or if you are buying or selling a home, you can hire a trained contractor to do the testing for you. Repairs to decrease radon levels should be made by a contractor certified by the National Radon Safety Board ( ) or the National Environmental Health Association ( .

There are two general ways to test for radon:


1. Short-Term Testing

The quickest way to test is with short-term tests. Short-term tests remain in your home for two days to 90 days, depending on the device. "Charcoal canisters," "alpha track," "electret ion chamber," "continuous monitors," and "charcoal liquid scintillation" detectors are most commonly used for short-term testing.

Because radon levels tend to vary from day to day and season to season, a short-term test is less likely than a long-term test to tell you your annual average radon level. If you need results quickly, however, a short-term test followed by a second short-term test may be used to decide whether to fix your home.

2. Long-Term Testing

Long-term tests remain in your home for more than 90 days. "Alpha track" and "electret" detectors are commonly used for this type of testing. A long-term test will give a more accurate annual average radon level than a short-term test for your home.

The average indoor level is estimated to be about 1.3 pCi/L; and 0.4 pCi/L of radon is found in the outside air. Action should be taken to reduce levels if the test results indicate an annual average radon level of 4 pCi/L or higher.



Today's technology can reduce indoor radon levels to below 4 pCi/L; in most cases, to 2pCi/L or less.

A variety of methods are used to reduce indoor radon levels, from sealing cracks in floors and walls to changing the flow of air into the home. Simple systems, known as sub-slab depressurization, use pipes and fans to remove radon gas from beneath the concrete floor and foundation before it can enter the home. Radon is vented above the roof, where it safely disperses.

Other methods may also work in your home. The right system depends on the design of your home and other factors.

Lowering high radon levels requires technical knowledge and special skills. You should use a contractor who is trained to fix radon problems. The EPA Radon Contractor proficiency (RCP) Program tests these contractors. A trained RCP contractor can study the radon problem in your home and help you choose the right treatment method.

Check with your local American Lung Association or state radon office for names of EPA- qualified or state-certified radon contractors in your area. As when hiring a contractor for any other home repair, you may want to get more than one estimate.

The cost of making repairs to reduce radon depends on how your home was built and the extent of the radon problem. Most homes can be fixed for about the same cost as other common home repairs.

Today, homes can be built to reduce the amount of radon coming in by using radon-resistant construction features. Radon-resistant construction features usually keep radon levels in new homes below 2 pCi/L.


For more information on radon in general, visit the US Environmental Protection Agency's Indoor Environments website at

For information about radon and radon control programs in your area, contact your state radon program coordinator through the state government.

For information about certified radon professionals, visit the website of the National Radon Proficiency Program at, the National Radon Safety Board at or the National Environmental Health Association at .

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