Radon Information

General Questions about Radon   (compiled from the National Safety Counsel website from 12/2004)

What is radon?
Radon is a radioactive gas. It is colorless, odorless, tasteless, and chemically inert. Unless you test for it, there is no way of telling how much is present. Radon is formed by the natural radioactive decay of uranium in rock, soil, and water. Naturally existing, low levels of uranium occur widely in Earth's crust. It can be found in all 50 states. Once produced, radon moves through the ground to the air above. Some remains below the surface and dissolves in water that collects and flows under the ground's surface.

Radon has a half-life of about four days - half of a given quantity of it breaks down every four days. When radon undergoes radioactive decay, it emits ionizing radiation in the form of alpha particles. It also produces short-lived decay products, often called progeny or daughters, some of which are also radioactive.

Unlike radon, the progeny are not gases and can easily attach to dust and other particles. Those particles can be transported by air and can also be breathed. The decay of progeny continues until stable, non-radioactive progeny are formed. At each step in the decay process, radiation is released.

Sometimes, the term radon is used in a broad sense, referring to radon and its radioactive progeny all at once. When testing measures radiation from the progeny, rather than radon itself, the measurements are usually expressed in working level (WL) units. When radiation from radon is measured directly, the amount is usually expressed in picocuries per liter of air (pCi/L).

What health effects are associated with radon exposure?
The Surgeon General has warned that radon is the second leading cause of lung cancer in the United States. There are currently no conclusive data on whether children are at greater risk than adults from radon. No specific subtype of lung cancer is associated with radon exposure.

Only smoking causes more cases of lung cancer. If you smoke and you are exposed to elevated radon levels, your risk of lung cancer is especially high. The U.S. Environmental Protection Agency (EPA) provides radon risk comparison charts for people who smoke and those who have never smoked. Stop smoking and lower your radon level to reduce your lung cancer risk.

Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe. As they break down further, these particles release small bursts of energy. This can damage lung tissue and lead to lung cancer over the course of your lifetime. Not everyone exposed to elevated levels of radon will develop lung cancer, and the amount of time between exposure and the onset of the disease may be many years.

Breathing radon does not cause any short-term health effects such as shortness of breath, coughing, headaches, or fever.

In 1998, the National Academy of Sciences (NAS) released the Biological Effects of Ionizing Radiation (BEIR VI) Report, "The Health Effects of Exposure to Indoor Radon." The study reviewed and evaluated data from many prior studies and drew conclusions. It fully supports estimates by EPA that radon causes about 21,000 lung cancer deaths per year. Though some people debate the number of deaths, it is widely agreed that radon exposure is the second leading cause of lung cancer. Research suggests that swallowing water with high radon levels may pose risks, too, although risks from drinking water containing radon are much lower than those from breathing air containing radon. A NAS report on radon in drinking water, "Risk Assessment of Radon in Drinking Water," was released in 1999. It concluded drinking radon in water causes about 19 stomach cancer deaths per year.

EPA provides more information about health effects from radon in their publication, Radon - A Physician's Guide.

What is the "acceptable" level of radon in air?
EPA states that any radon exposure carries some risk; no level of radon exposure is always safe. However, EPA recommends homes be fixed if an occupant's long-term exposure will average 4 picocuries per liter (pCi/L) or higher.

What is a "picocurie" (pCi)?
A pCi is a measure of the rate of radioactive decay of radon. One pCi is one trillionth of a Curie, 0.037 disintegrations per second, or 2.22 disintegrations per minute. Therefore, at 4 pCi/L (picocuries per liter, EPA's recommended action level); there will be approximately 12,672 radioactive disintegrations in one liter of air during a 24-hour period.

What is a "working level" (WL)?
Some devices measure radiation from radon decay products, rather than radiation coming directly from radon. Measurements from these devices are often expressed as WL. As noted above, conversions from WL to pCi/L are usually approximate. A level of 0.02 WL is usually equal to about 4 pCi/L in a typical home.

If a working level (WL) value is converted to a radon level (pCi/L), the conversion is usually approximate and is based on a 50 percent equilibrium ratio. If the actual equilibrium ratio is determined (which is rare), it should be stated. The 50 percent ratio is typical of the home environment, but any indoor environment may have a different and varying relationship between radon and its decay products.

Technically speaking, 1 WL represents any combination of short-lived radon decay products in one liter of air that will result in the ultimate emission of 1.3 x 105 MeV of potential alpha energy.

How often is indoor radon a problem?
Nearly one out of every 15 homes has a radon level EPA considers to be elevated - 4 pCi/L or greater. The U.S. average radon-in-air level in single family homes is 1.3 pCi/L. Because most people spend as much as 90 percent of their time indoors, indoor exposure to radon is an important concern.

How does radon get into a building?
Most indoor radon comes into the building from the soil or rock beneath it. Radon and other gases rise through the soil and get trapped under the building. The trapped gases build up pressure. Air pressure inside homes is usually lower than the pressure in the soil. Therefore, the higher pressure under the building forces gases though floors and walls and into the building. Most of the gas moves through cracks and other openings. Once inside, the radon can become trapped and concentrated.

Openings which commonly allow easy flow of the gases in include the following:
•        Cracks in floors and walls
•        Gaps in suspended floors
•        Openings around sump pumps and drains
•        Cavities in walls
•        Joints in construction materials
•        Gaps around utility penetrations (pipes and wires)
•        Crawl spaces that open directly into the building

Radon may also be dissolved in water, particularly well water. After coming from a faucet, about one ten thousandth of the radon in water is typically released into the air. The more radon there is in the water, the more it can contribute to the indoor radon level.

Trace amounts of uranium are sometimes incorporated into materials used in construction. These include, but are not limited to concrete, brick, granite, and drywall. Though these materials have the potential to produce radon, they are rarely the main cause of an elevated radon level in a building.

Outdoor air that is drawn into a building can also contribute to the indoor radon level. The average outdoor air level is about 0.4 pCi/L, but it can be higher in some areas.While radon problems may be more common in some geographic areas, any home may have an elevated radon level. New and old homes, well-sealed and drafty homes, and homes with or without basements can have a problem. Homes below the third floor of a multi-family building are particularly at risk.

Can the radon level in a building's air be predicted?
No, it is not possible to make a reliable prediction.

The only way to determine the level is to test. EPA and the Surgeon General recommend testing all homes below the third floor for radon.

In addition, indoor radon levels vary from building to building. Do not rely on radon test results taken in other buildings in the neighborhood - even ones next door - to estimate the radon level in your building.

Where can I get more information about radon issues?
The National Safety Council's Radon Hotline provides a toll-free number, (800) 767-7236. Through this automated number, callers can order a brochure on radon. It contains information on ordering a low-cost short-term test kit. In addition, users are instructed to call another one of our numbers, (800) 557-2366, if they wish to speak with our information specialists. They are available to assist callers between 9:00 AM to 5:00 PM (Eastern) on business days. They can answer specific questions and mail free, single copies of many radon documents, including the EPA booklet, Home Buyer's and Seller's Guide to Radon. Multiple copies of many EPA documents can be ordered through EPA's National Service Center for Environmental Publications (NSCEP), (800) 490-9198, fax (513) 489-8695. Publication requests can also be mailed, called, or faxed directly to:

U.S. Environmental Protection Agency
National Center for Environmental Publications (NSCEP)
P.O. Box 42419
Cincinnati, OH 42419

Testing Air for Radon

Why should I test my home for radon?
Radon is widely believed to be the second leading cause of lung cancer. Therefore, EPA and the Surgeon General recommend testing for radon in all homes below the third floor.

Radon has been found in homes all over the United States. Any home can have a radon problem. On average, one out of every fifteen U.S. homes have a problem. The only way to know whether or not your home has a radon problem is to test for it.

Why are short- and long-term tests used?
Radon levels within a building often change on a day-to-day basis. Highest indoor levels are often found during the heating season. Weather conditions, operation of furnaces and fireplaces, and opening/closing of windows and doors are among the factors that cause these patterns.

Short-term test kits are the quickest way to test. These kits should remain in the building from two to 90 days, depending on the device. Testing must be conducted for at least 48 hours. Some devices must be exposed for a longer time. 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 year-round average radon level.

EPA recommends that for homes, initial measurements be short-term tests placed in the lowest lived-in level. Short-term testing under closed-building conditions helps to ensure that residents quickly learn if a home contains very high levels of radon. If you are doing a short-term test, close your windows and outside doors and keep them closed as much as possible during the test. If testing for just 2 or 3 days, be sure to close your windows and outside doors at least 12 hours before beginning the test, too. You should not conduct short-term tests lasting just 2 or 3 days during unusually severe storms or periods of unusually high winds.

Because radon levels may fluctuate by as much as a factor of two or three, additional testing is sometimes recommended to better assess the average radon level. Though short-term tests are sometimes used, long-term tests are often recommended.

Long-term tests remain in your home for more than 90 days. A long-term test gives a reading that is more likely to reflect the building's year-round average radon level than a short-term test. Because of season variations in radon levels, the closer the long-term measurement is to 365 days, the more representative it will be of annual average radon levels.

If time permits (more than 90 days), long-term tests can be used to confirm initial short-term results between 4 pCi/L and 10 pCi/L. When long-term test results are 4 pCi/L or higher, EPA recommends the problem be corrected.

Where should home testing be done?
EPA recommends that testing be done in the lowest level of the home suitable for occupancy. This typically represents an area where greatest radon level may occur. Ideally, the test should be conducted in a regularly used room on that level, such as a living room, playroom, den, or bedroom. Avoid testing in a kitchen, bathroom, laundry room, or
hallway. High humidity and drafty conditions can bias results from some test devices. Do not disturb the devices while they are sampling. Doing so may alter their results, so they should be placed out-of-the-way.

If the lowest occupied level is not used much, consider also testing a higher-use area. This may help you to better estimate your long-term exposure.

Because most indoor radon comes from naturally occurring radon in the soil, high indoor levels are more likely to exist below the third floor. This is why EPA recommends testing all homes below the third floor. In some cases, high radon levels have been found at or above the third floor, due to radon movement through elevators or other air
shafts in the building. If you are concerned about this possibility, you may decide to test for radon.

More information on site selection can be found in the EPA publication, Protocols for Radon and Radon Decay Product Measurements in Homes.

If a test result is less than 4 pCi/L (0.02 WL), what should be done next?
If the result of an initial short-term measurement is below 4 pCi/L, or 0.02 WL, a follow-up test is not necessary. However, since radon levels change over time, you may want to test again sometime in the future, especially if use patterns change and a lower level of the building becomes occupied or used more often. Renovations, changes in ventilation, earthquakes, settling of the ground beneath the building, and other changes may cause indoor radon exposures to change.

If an initial short-term test result is 4 pCi/L (0.02 WL) or higher, what should be done next? EPA recommends a follow-up measurement be used to confirm whether radon levels are high enough to warrant mitigation. There are two types of follow-up measurements that may be conducted. The choice depends, in part, on the results of the initial test.

An initial measurement result of 10 pCi/L (or 0.05 WL) or greater should be quickly followed by a second short-term test under closed-building conditions. If the average of the initial and second short-term results is equal to or greater than 4 pCi/L (0.02 WL), radon mitigation is recommended. If the average of the short-term test results is less
than 4 pCi/L, consider testing again sometime in the future.

If the result of the initial measurement is between 4 pCi/L (or 0.02 WL) and 10 pCi/L (or 0.05 WL), the follow-up test may be made with either a short-term or a long-term method. If a long-term follow-up test result is 4 pCi/L (0.02 WL) or higher, EPA recommends remedial action. If the long-term follow-up test result is less than 4 pCi/L, consider testing again sometime in the future.

If a short-term follow-up test is done and the result is 4 pCi/L or higher, radon mitigation is recommended. If the average of the initial and follow-up short-term tests is less than 4 pCi/L, consider testing again sometime in the future.In certain instances, such as may occur when measurements are performed in different seasons or under different weather conditions, the initial and follow-up tests may
vary by a considerable amount. Radon levels can vary significantly between seasons, so different values are to be expected.

Radon Resistant Construction

What are radon-resistant features?
Radon-Resistant Features

The techniques vary for different foundations and site requirements, but the basic elements are:
A.        Gas Permeable Layer - This layer is placed beneath the slab or flooring system to allow the soil gas to move freely underneath the house. In many cases, the material used is a 4-inch layer of clean gravel.
B.        Plastic Sheeting - Plastic sheeting is placed on top of the gas permeable layer and under the slab to help prevent the soil gas from entering the home. In crawlspaces, the sheeting is placed over the crawlspace floor.
C.        Sealing and Caulking - All openings in the concrete foundation floor are sealed to reduce soil gas entry into the home.
D.        Vent Pipe - A 3- or 4-inch gas-tight or PVC pipe (commonly used for plumbing) runs from the gas permeable layer through the house to the roof to safely vent radon and other soil gases above the house.
E.        Junction Box - An electrical junction box is installed in case an electric venting fan is needed later.

Ways to reduce radon in your home are discussed in EPA's publication, Consumer's Guide to Radon Reduction.

When should radon-resistant construction be considered?
Find out if you are buying a home in a high radon area. EPA's map of radon zones indicates areas having the greatest potential for elevated indoor radon readings. Homes in places with high potential, called Zone 1 areas, should be built with radon-resistant features. Also contact your state radon office to learn whether radon-resistant features are recommended or required in your area.

If you are planning to make any major structural renovation to an existing home, such as converting an unfinished basement area into a living space, it is important to test the area for radon before you begin the renovation. If your test results indicate a radon problem, radon-resistant techniques can be inexpensively included as part of the renovation. Because major renovations can change the level of radon in any home, always test again after work is completed.

What are the benefits of radon-resistant construction?
Radon-resistant techniques are simple and inexpensive. Besides reducing radon levels, they also lower concentrations of other soil gases and decrease moisture problems. They make a home more energy efficient, and can save an annual average of $65 on energy costs.

How much does it cost to reduce radon in an existing home?
If a home with a vent system is found to have an elevated radon level, a fan can be added at a low cost. The total cost is much lower than adding the entire system after the building is completed. The average cost to install radon-resistant features in an existing home is $800 to $2,500. The average cost to install radon-resistant features in a new home during construction is $350 to $500 (a 128% to 400% saving).

Who should I hire to install radon-resistant features?
Talk to your builder about installing a radon-reduction system during major renovations or new construction. Radon-resistant features can be easily and inexpensively installed with common building practices and materials. There is usually no need to hire a special contractor or architect. Many builders already incorporate some of these steps in the construction of their houses to control moisture or increase energy efficiency.

EPA's publication, Radon Mitigation Standards, provides radon mitigation contractors with uniform standards that will ensure quality and effectiveness in the design, installation, and evaluation of radon mitigation systems in detached and attached residential buildings three stories or less in height.

Should a home built with radon-resistant features be tested?
Yes. Every new home should be tested for radon after occupancy. Test your home even if it has the radon resistant features. Test kits are inexpensive and may be purchased at your local hardware store, or call the National Safety Council's Radon Hotline (800-767-7236) to order a test kit.

Mitigating Radon Problems

What is a radon mitigation system?
A radon mitigation system is any system or steps designed to reduce radon concentrations in the indoor air of a building.

EPA recommends that you take action to reduce your home's indoor radon levels if your radon test result is 4 pCi/L or higher.

What are the benefits of radon mitigation?
Radon reduction systems work. In most new homes, use of radon-resistant features will keep radon levels to below 2 pCi/L. Some radon reduction systems can reduce radon levels in your home by up to 99 percent.

Homeowners should consider correcting a radon problem before making final preparations to sell a home. This often provides more time to address the problem and find the most cost-effective solution. In addition, the current occupants - not just the buyer's occupants - will reap the benefit of reduced risk.

What can be done to reduce radon in a home?
Your house type will affect the kind of radon reduction system that will work best. Houses are generally categorized according to their foundation design. For example: basement, slab-on-grade (concrete poured at ground level), or crawlspace (a shallow unfinished space under the first floor). Some houses have more than one foundation
design feature. For instance, it is common to have a basement under part of the house and to have a slab-on-grade or crawlspace under the rest of the house. In these situations a combination of radon reduction techniques may be needed to reduce radon levels to below 4 pCi/L.

There are several methods that a contractor can use to lower radon levels in your home. Some techniques prevent radon from entering your home while others reduce radon levels after it has entered. EPA generally recommends methods that prevent the entry of radon.

In many cases, simple systems using underground pipes and an exhaust fan may be used to reduce radon. Such systems are called "sub-slab depressurization," and do not require major changes to your home. These systems remove radon gas from below the concrete floor and the foundation before it can enter the home. Similar systems can also be installed in houses with crawl spaces. Radon contractors use other methods that may also work in your home. The right system depends on the design of your home and other factors.

Sealing cracks and other openings in the floors and walls is a basic part of most approaches to radon reduction. Sealing does two things, it limits the flow of radon into your home and it reduces the loss of conditioned air, thereby making other radon reduction techniques more effective and cost-efficient. EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently. It is difficult to identify and permanently seal the places where radon is entering. Normal settling of your house opens new entry routes and reopens old ones.

Any information that you may have about the construction of your house could help your contractor choose the best system. Your contractor will perform a visual inspection of your house and design a system that is suitable. If this inspection fails to provide enough information, the contractor will need to perform diagnostic tests to help develop the best radon reduction system for your home. Whether diagnostic tests are needed is decided by details specific to your house, such as the foundation design, what kind of material is under your house, and by the contractor's experience with similar houses and similar radon test results.

How much does it cost to reduce radon in an existing home?
The cost of making repairs to reduce radon is influenced by the size and design of your home and other factors. Most homes can be fixed for about the same cost as other common home repairs, like painting or having a new hot water heater installed. The average cost for a contractor to lower radon levels in a home is about $1,200, although
this can range from $500 to about $2,500. Your costs may vary depending on the size and design of your home and which radon reduction methods are needed.

Who should I hire to correct a radon problem?
Lowering high radon levels requires technical knowledge and special skills. You should use a contractor who is trained to fix radon problems.

EPA stopped operating its National Radon Proficiency Program (RPP) on October 1, 1998. That program was designed to test radon contractors and provide a measure of quality control. The RPP is now privately run. See EPA's Web site regarding the RPP for information on how to identify qualified contractors.

Many states certify or license radon contractors. Call your state radon office for information about qualified service providers in your state.

If you plan to fix the problem in your home yourself, you should first contact your state radon office for EPA's technical guide, "Radon Reduction Techniques for Detached Houses."

Will any more testing be needed after a radon mitigation system has been installed?
Most radon reduction systems include a monitor that will alert you if the system needs servicing. However, regardless of who fixes the problem, you should test your home afterward to be sure that radon levels have been reduced. This test should be conducted no sooner than 24 hours nor later than 30 days following completion and activation of the mitigation system(s). Potential conflict of interest can be avoided by using an independent tester.

In addition, it's a good idea to retest your home sometime in the future to be sure radon levels remain low. Testing should be done at least every two years or as required or recommended by state or local authority. Retesting is also recommended if the building undergoes significant alteration.