RADON - A Radioactive Gas

There are many known and unknown gases within or around your home, in which radon gas is one of the health concerns. Radon is a radioactive gas which causes health concerns to home owners. Radon gas is formed by the natural radioactive decay of uranium in rock, soil, and water. As a naturally existing material, low levels of uranium occur widely in Earth's crust. Radon is colorless, odorless, tasteless, and chemically inert. Once produced, radon moves through the ground to the air above. It can be found in every country. Unless you test for it, there is no way of telling how much is present.

Radon is regarded as the second leading cause of lung cancer in the United 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).

The U.S. Environmental Protection Agency (EPA) has strict definitions about the risk level of radon gas. The Surgeon General has warned that radon is the second leading cause of lung cancer in the United States. In order to define an "acceptable" level of radon in air, EPA provides reference and 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 exposureis average 4 picocuries per liter (pCi/L) or higher. 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. 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 15,000 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.

"Picocurie" (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.

For a general reference, a working level (WL) has been used to compare different cases and testing parameters. 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.

Currently, 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. Different country usually define different standard on this matter.

Where does the radon come 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, especially in the basement or crawspace. 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. It is recommended to test well water each year and change filter often to reduce radon risk levels.

Usually, it is impossible to make a reliable prediction for the radon level in a home. The only way to determine the level is to test by a professional company or by using specific testing kits. EPA and the Surgeon General recommend testing all homes below the third floor for radon. A map of radon zones has been created to help national, state, and local organizations to target their resources and to implement radon-resistant building codes. However, the map is not intended to be used for determining if a home in a given zone should be tested for radon. Homes with elevated levels of radon have been found in all three zones. 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. Contact your state radon office for information about radon in your local area. On the other hand, any home inspector may provide sources for you.

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 asses 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.

There are different radon testing devices. Two groups of devices are more commonly used for short-term testing. Passive devices do not need power to function. The group includes alpha track detectors, charcoal canisters, and charcoal liquid scintillation detectors. Some charcoal technologies are prone to interference by high humidity, so may not be appropriate for use in all buildings. They are sometimes available in drug, hardware, and other stores, the Internet, and through some laboratories. Electret ion chamber detectors, another type of short-term test device, are usually only available through laboratories. After being used, passive devices are returned to a laboratory for analysis. Charcoal canisters for short-term use are sold through the National Safety Council's Radon Hotline (800-767-7236). These test kits are designed to be used for two or four days before being returned for analysis by the laboratory that provides it. A return mailer is provided with the kit. Active devices require power to function. This group consists of different types of continuous monitors and continuous working level monitors. Some of the active monitors can provide data on the range of variation within the test period. Some are designed to detect and deter interference. However, they usually require operation by trained testers. These tests often cost more than passive testing. Alpha track and electret ion chamber detectors are commonly used for long-term testing. Long-term test kits currently sold through the National Safety Council's Radon Hotline (800-767-7236) are alpha-track detectors. They are designed to be used for three months to a year before being returned to the providing laboratory for analysis. Technical information on use of various devices used to measure radon or radon decay products is found in the EPA publication, Indoor Radon and Radon Decay Product Measurement Device Protocols. Continuous monitors are not available through the National Safety Council's Radon Hotline at this time.

The location for the radon testing should 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 with normal activity. 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.

Radon-resistant features vary for different foundations and site requirements, but the basic elements are: 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. Plastic Sheeting - Plastic sheeting is placed on top of the gas permeablelayer and under the slab to help prevent the soil gas from entering the home. In crawlspaces, the sheeting is placed over the crawlspace floor. Sealing and Caulking - All openings in the concrete foundation floor are sealed to reduce soil gas entry into the home. 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. 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.

How much does it cost to mitigate 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). 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.

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. 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.

Generally speaking, radon gas risk could be reduced by alerting yourself about the surroundings. For instance, when you smell the odors trapping in your house, and see more cracks in your basement, it is time to test.

Good luck for your health!

Please click the following links to see details of different hazardous situations: lead paint, urea formaldehyde foam insulation (UFFI), radon gas, asbestos, underground storage fuel tank and other HouseCenter.Com Tips.