Frequenty Asked Questions about Radon

Radon is a colorless, odorless radioactive gas which comes from the natural breakdown (radioactive decay) of radium, itself a product of the natural breakdown of uranium. Uranium and radium are both common elements in the soil. The Surgeon General has warned that radon is the second leading cause of lung cancer in the U.S. today. Only smoking causes more lung cancer deaths. If you smoke and your home has high levels of radon, your risk of lung cancer is especially high.

The major source of high levels of radon in homes is soil surrounding and under the house, particularly soil containing uranium. Radon is found all over the U.S. and the world. Some areas have more radon problems than others because of varying concentrations of radon-producing minerals in the soil, variation of soil types from one place to another, and different characteristics found in individual homes. Radon problems have been identified in every state. EPA estimates that, annually, as many as 1 in 15 homes have elevated radon levels.

Almost all scientists agree that radon is a health hazard to humans and that it causes lung cancer. There has been debate over how to calculate the risks for various levels of radon. The EPA has declared radon to be a Class A Carcinogen, which means that it has been shown to cause cancer in humans.

Radon gas decays into radioactive solid particles that can get trapped in your lungs when you breathe. As the particles break down further, they release small bursts of energy that can damage lung tissue and lead to lung cancer. Not everyone exposed to elevated levels of radon will develop lung cancer. The amount of time between exposure and the onset of disease may be many years. Smoking combined with radon exposure is an especially serious health risk. You can reduce your risk of lung cancer by not smoking and by lowering the radon level in your home.

Radon is measured in picoCuries per liter (pCi/L) of air. A picoCurie is a measure of the amount of radioactivity of a particular substance. A liter is equal to about a quart. The level of radon in outdoor air is about 0.4 pCi/L. The average indoor radon level is about 1.3 pCi/L. EPA has established 4.0 pCi/L as the level at which radon in homes, schools and workplaces becomes dangerous. This is a technology-based estimate, not a standard based on health studies. Current technology can generally reduce radon levels to 3.9 pCi/L or less. Since radon is a carcinogen, no level is completely risk-free. However, since it is a natural part of the environment there is no such thing as a “0” level.

Radioactivity is commonly measured in picocuries (pCi). This unit of measure is named for the French physicist Madam Marie Curie, who was a pioneer in the research of radioactive elements and their decay. One pCi is equal to the decay of about two radioactive atoms per minute. Because the level of radioactivity is directly related to the number and type of radioactive atoms present, radon and all other radioactive elements are measured in pCi. For instance, a house having 4 pCi of radon per liter of air has about 8 or 9 atoms of radon decaying every minute in every liter of air inside the house. A 1,000 square foot house with 4 pCi/L of radon has nearly 2 million radon atoms decaying in it every minute.

Radon is a gas in the soil that typically moves up through the ground to the air above. Air pressure inside a home is usually lower than pressure in the soil around the home's foundation. Because of the difference in pressure, a house acts like a vacuum, drawing radon in through dirt floors, hollow-block walls, cracks in the foundation floor and walls, and openings around floor drains, pipes and sump pumps.

Any home may have a radon problem. This includes new, old, well-sealed or drafty homes, and homes with or without basements. Radon is generally more concentrated at lower levels, like basements, ground floors and first floors.

Radon test results from other homes in the neighborhood should not be used to estimate the radon level in a particular home. Homes which are next to each other can have different indoor radon levels. In fact, one of the highest levels ever found in a home (>3,000 pCi/L) was across the street from a home with a level measured at less than 4 pCi/L. Testing is the only way to know.

YES. Testing is the only way to know if you and your family are at risk from radon. The Environmental Protection Agency (EPA) and the Surgeon General recommend testing all homes.

Testing is inexpensive and easy -- it should take only a few minutes of your time. Millions of Americans have tested their homes for radon.

Testing is easy and it should only take a few minutes to place a test kit. There are several kinds of low-cost “do-it-yourself” radon test kits available through the mail and at hardware stores and other retail outlets. The directions should be followed carefully because the length of time the kits should remain open varies.

The most common commercially available passive test kits are charcoal canisters, e-perm and alpha track detectors, and charcoal liquid scintillation devices. A test kit is placed in the basement or lowest lived-in level of a home, and after a specified amount of time the kit is mailed to the manufacturer to be analyzed.

The EPA “danger” level of 4 pCi/L actually represents an annual average. Because radon levels tend to vary from day to day, and season to season, a short-term test (days) is less likely than a long-term test (months) to approximate the year-round average radon level. However, when results are needed quickly, a short-term test followed by a second short-term test, or two short-term tests placed side by side, and the results averaged, is adequate. The test should last at least 48 hours for either approach.

All NRSB certifications: http://www.nrsb.org/find_a_professional.asp
NEHA-certified mitigators: http://www.radongas.org/radon_mitigation_service.shtml
NEHA-certified testers: http://www.radongas.org/radon_measurement_service.shtml

Anytime that windows and doors are normally kept closed is a good time to test. This is generally in the winter or summer months, when heating or cooling systems are running. For short-term tests, the house should be closed up for 12 hours before the test begins and throughout the test.

If a house has been unoccupied and closed up for several months, prior to testing the temperature in the house should be allowed to return to the normal living range. The result will then more closely approximate what the radon levels would be with people living in the house.

EPA has issued ”protocols” or guidelines for radon testing in the home as well as for testing associated with real estate transactions.

The testing procedures or protocols that are used when a house is being tested in connection with a real estate sale are listed in the “Home Buyer's and Seller's Guide to Radon.”

For all other situations, “A Citizen's Guide to Radon” provides protocols for both short- and long-term radon testing.

If an NEHA-certified tester is not used, homeowners should verify results either by placing two test kits side-by-side or by conducting a retest after the first test is completed. Retesting every year or so is recommended because conditions in a home can change over time.

In addition to certifying testers and contractors, NEHA certifies the companies that make and analyze test kits. To ensure that you get reliable results, look for a test kit from a company that has successfully completed this certification process. Contact your state radon program office or follow the NEHA website link below for a list of certified manufacturers and laboratories.

The length of time it takes to get results varies with the manufacturer or laboratory, but generally results can be expected within a couple of weeks. Some NEHA-certified laboratories will fast-track the results when real estate transactions are involved.

Providing “closed house conditions” during short-term tests means that all windows are kept closed, and doors are kept closed except for normal entry and exit. Heating and air conditioning units can be operated as long as they do not introduce outside air into the home. Exhaust or attic fans should not be used. These conditions should be maintained for twelve hours prior to initiation of the test, then throughout the remainder of the test.

It does not matter if a house has been closed up for months when you test it. In fact, for short-term tests (2-3 days) the house should be closed up for 12 hours before the test begins, as well as throughout the testing period. However, to more closely approximate what the radon levels would be when the house is occupied, allow the temperature to return to some “normal” level prior to testing.

Radon tests should be done only in areas which can be used as living space. A basement connected to an open crawl space should not be used as living space without major remodeling. Hence it is an inappropriate test site.

EPA has not developed radon testing protocols for commercial buildings. However, EPA has developed testing protocols for schools. These protocols call for initial short-term measurements to be taken simultaneously in all frequently-occupied rooms that are in contact with the ground. Follow-up tests should be performed for every room that initially tests 4 pCi/L or greater. For follow-up tests, use a short-term test if results are needed quickly; use a long-term test to better understand the average radon level for a school year. See the publication “Radon Measurement in Schools; Revised Edition.”

EPA does not recommend soil testing for radon prior to construction of new buildings because radon concentrations in soil can be much different from one point on a lot to another. Testing enough locations at enough depths on a site would be very expensive. A much cheaper and more reliable approach is to use radon-resistant techniques when the building is built. These techniques are very inexpensive, help protect the home from radon, and also help solve other problems like moisture in the home. Many of the techniques are already used by good builders. See EPA publications “Radon-resistant Construction Techniques for New Residential Construction” and “Radon Prevention in the Design and Construction of Schools and Other Large Buildings” for more information.

In municipal water systems most of the radon will escape to the air during processing. It tends to be the smaller rural water systems and well water that may have elevated radon levels.

Radon can reach concentrations of many thousands of picoCuries per liter in water. The major health threat is not associated with drinking the water, but rather from breathing the radon that escapes the water and enters the air. An example of this is breathing while taking a shower. There is a very rough 10,000 to 1 conversion factor from radon in water to radon in air. For example, 10,000 pCi/L of radon in water would release about 1 pCi/L in air. Similarly, 25,000 pCi/L in water releases about 2.5 pCi/L in air.

Individual water supplies can be treated by aeration or installation of granular activated carbon (GAC) absorbers. A GAC system is less expensive than aeration but would still cost approximately $1,000 to install, plus additional costs to maintain. Depending on the initial radon levels, disposal of the carbon can become a problem over time. If a home has both elevated indoor radon levels and elevated levels in the water, an NEHA-certified contractor should be consulted to determine what strategy will be the most cost-effective in reducing the radon exposure.

Currently there are no standards for radon levels in drinking water, although standards have been proposed. The final number (in pCi/L) won't be determined until additional studies and analyses have been completed.

EPA has developed specific testing protocols for use during real estate transactions. They can be found in the “Home Buyer's and Seller's Guide to Radon” (EPA 402-K-00-008, July 2000). For passive tests the recommendation is: “Take an initial short-term test for at least 48 hours. After the first test has been completed, take a follow-up short-term test for at least 48 hours”; or “[t]ake two short-term tests at the same time in the same location for at least 48 hours.” For either approach, “[f]ix the home if the average of two tests is 4 pCi/L or more.” For an active test: “Test the home with a continuous monitor for at least 48 hours. Fix the home if the average radon level is 4 pCi/L or more.”

There are simple ways to fix a radon problem that aren't too costly. Even high levels can be reduced to acceptable levels in most cases.

For new homes, consider radon-resistant construction systems, which allow for control measures to be installed cheaply and without a major redesign of the home.

There are two approaches to radon mitigation or reduction. One is to prevent the radon from entering the structure and the other is to remove the radon after it enters the structure. Generally, the best approach is to prevent the radon from entering.Some of the techniques used are soil depressurization, sealing cracks and joints, pressurizing the building, or a combination of these. Sealing foundation joints and cracks is rarely sufficient as a standalone mitigation technique. Soil depressurization, the most common approach, involves running PVC pipe through the slab (or underneath a membrane in a crawl space), then routing it up and through the roof. A fan is attached in the attic area, and the radon is thus drawn from below the slab (or membrane) and vented above the roof where it is quickly diluted in outside air. Pressurization is fairly difficult to maintain, and is less commonly used as a mitigation approach. EPA recommends that a qualified contractor be used to mitigate homes because of the specialized technical experience required. Without proper equipment or technical knowledge, one could actually increase the radon levels or create other potential hazards. NEHA (National Environmental Health Association) certifies radon mitigators who have taken a course and passed a test based upon the material taught.

New homes can be built with radon-resistant features that minimize radon entry and allow radon problems that could occur later to be more easily fixed. These features cost less if installed during construction than if added to an existing home. Materials and labor for the radon-resistant techniques cost less than $100. The cost of retrofitting an existing home would be $800 to $2,500. In most new homes, use of radon-resistant features will keep radon levels to below 2 pCi/L.

In many cases, a passive system is all that is needed to effectively reduce indoor radon levels. Nevertheless, occupants of newly constructed radon-resistant homes should test their homes for radon. If the indoor radon levels measure 4 pCi/L or higher, a fan should be installed in the vent pipe to make the system active.

A passive radon-resistant system pulls radon from beneath the home, carries it up through the home in a pipe, and exhausts it above the roof. It differs from an active system in that the active system includes a fan in the pipe as it goes through the attic. The fan in an active system operates continuously, pulling radon-laden air from the soil beneath the lowest floor. In a passive system, the natural rising of warm air through the pipe continuously exhausts a low flow of air and radon from beneath the lowest floor of the house.

First, a gas permeable material is placed beneath the lowest floor. This is usually gravel, although other materials can be used. Plastic sheeting is placed above this, and the concrete floor is placed on the sheeting. A 3- to 4-inch plastic pipe runs from the gravel through the sheeting and concrete, up through the house and through the roof. All the penetrations below ground level, such as the basement floor-wall joint, plumbing and electrical penetrations, are caulked. This allows the natural convection of warm air moving up the pipe to create a slight vacuum in the gravel beneath the concrete. This vacuum pulls air and radon up the pipe and exhausts it above the roof. The caulking helps prevent air from the living space from being pulled below the floor, and improves the vacuum beneath the floor.

Backdrafting is the condition that exists when the combustion products from a furnace or hot water heater are drawn back into the home rather than going up the chimney. This can happen when the air pressure in the house is so low that air is actually sucked down the chimney and into the home. A radon system pulls air from beneath the lowest floor. If cracks and penetrations in that floor and the floor wall joint are not properly caulked, the system could pull air from the lowest level of the house and thereby lower the air pressure in that level, possibly causing backdrafting.

If your initial test result is 4.2 pCi/L based on a short-term test, another test should be conducted as a follow-up. It is possible that the result of such a test would be below 4.0 pCi/L.

However, if your home's actual radon concentration is 4.2 pCi/L, sealing cracks in the floor and wall joints is a good first step in solving the problem. A gun-grade polyurethane caulk should be used. This should be considered a first phase, to be followed by another short-term test, and possibly other solutions.