Radon is a radioactive gas that forms naturally when uranium, thorium, or radium, which are radioactive metals break down in rocks, soil and groundwater. People can be exposed to radon primarily from breathing radon in air that comes through cracks and gaps in buildings and homes. Because radon comes naturally from the earth, people are always exposed to it.

Information provided by the Environmental Protection Agency, for more details, visit the EPA's website

Radon-222 is the decay product of radium-226. Radon-222 and its parent, radium-226, are part of the long decay chain for uranium-238. Since uranium is essentially ubiquitous (being or seeming to be everywhere at the same time) in the earth's crust, radium-226 and radon-222 are present in almost all rock and all soil and water.

The amount of radon in the soil depends on soil chemistry, which varies from one house to the next. Radon levels in the soil range from a few hundred to several thousands of pCi/L (picocuries per liter) in air. The amount of radon that escapes from the soil to enter the house depends on the weather, soil porosity, soil moisture, and the suction within the house.

Information provided by the Environmental Protection Agency, for more details, visit the EPA's website

Radon is a radioactive gas. It comes from the natural decay of uranium that is found in nearly all soils. It typically moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Your home traps radon inside, where it can build up. Any home may have a radon problem. This means new and old homes, well-sealed and drafty homes, and homes with or without basements.

Radon from soil gas is the main cause of radon problems. Sometimes radon enters the home through well water. In a small number of homes, the building materials can give off radon, too. However, building materials rarely cause radon problems by themselves.

Information provided by the Environmental Protection Agency, for more details, visit the EPA's website

EPA already has a wealth of scientific data on the relationship between radon exposure and the development of lung cancer. The scientific experts agree that the occupational miner data is a very solid base from which to estimate risk of lung cancer deaths annually. While residential radon epidemiology studies will improve what we know about radon, they will not supersede the occupational data. Health authorities like the Centers for Disease Control (CDC), the Surgeon General, the American Lung Association, the American Medical Association, and others agree that we know enough now to recommend radon testing and to encourage public action when levels are above 4 pCi/L. The most comprehensive of these efforts has been the National Academy of Science's Biological Effects of Ionizing Radiation (BEIR VI) Report (see www.epa.gov/radon/health-risk-radon#beir). This report reinforces that radon is the second-leading cause of lung cancer and is a serious public health problem. As in the case of cigarette smoking, it would probably take many years and rigorous scientific research to produce the composite data needed to make an even more definitive conclusion.

Information provided by the Environmental Protection Agency, for more details, visit the EPA's website

There are no immediate symptoms from exposures to radon. Based on an updated Assessment of Risk for Radon in Homes, radon in indoor air is estimated to cause about 21,000 lung cancer deaths each year in the United States. Smokers are at higher risk of developing Radon-induced lung cancer. Lung cancer is the only health effect which has been definitively linked with radon exposure. Lung cancer would usually occur years (5-25) after exposure. There is no evidence that other respiratory diseases, such as asthma, are caused by radon exposure and there is no evidence that children are at any greater risk of radon induced lung cancer than adults.

Information provided by the Environmental Protection Agency, for more details, visit the EPA's website

EPA has maintained the position that radon measurement systems provide practical and affordable measurements that can give consumers the information they need about the radon level in their home in order to make a decision about whether to fix their home. Since EPA based this position on studies conducted earlier, we decided, in consultation with Office of Inspector General (OIG), to check the current state of device measurement accuracy.

This is a link to a contractor report that reviews current radon measurement proficiency data and compares it to earlier data -- Radon Device Performance Check. The report also provides a response to the OIG report regarding oversight of radon testing device accuracy and reliability (Rpt. No. 09-P-0151).

Results presented in this report support EPA’s position that radon testing devices provide accurate and reliable results and that EPA’s measurement recommendations raise the probability that high homes will be identified and fixed. While any measurement system has an associated variability in precision and accuracy, we expect that radon test devices that are used properly will provide accurate and reliable results.

The study presented here only represents a part of the picture of accuracy and reliability. Other efforts must be employed to contribute to this knowledge base; such as, blind studies carried out in the field, participation in the development of technical standards through private-sector, consensus-based processes, support of state program technical needs and assessmentsof test chamber error.

Information provided by the Environmental Protection Agency, for more details, visit the EPA's website

Radon gas is approximately 7.5 times heavier than air. It is however a noble gas with no chemical affinity but is easily influenced by air movements and pressure. In a house with forced air heating and cooling, radon gas can easily be distributed throughout the entire dwelling. When radon gas is discharged via a radon mitigation system above the roof, the radon concentration falls off dramatically with distance from the point of discharge. In fact, the radon gas concentration approaches background levels at 3-4 feet from the discharge point. EPA disallowed ground level discharge of radon primarily because of the potential for re-entrainment of the gas into the house and because of the possibility of children being exposed to high radon levels. The concentration of radon gas at the discharge point can be tens of thousands of picocuries per minute.

Information provided by the Environmental Protection Agency, for more details, visit the EPA's website