Radon and Your Health 

horizontal rule


bulletRadon testing in the homebulletWhat is radon?bulletGeology of radonbulletHow to measure the potential risk to your family's healthbulletFrequently asked questions about radonbulletSources of information

horizontal rule

Radon Testing

Question: I am a new home owner. A friend suggested that I have my home tested for radon, but I don't know anything about it. Can you advise me on radon and on how to get my home tested?

Answer: Radon is naturally occurring, odorless, and colorless gas produced by the breakdown of uranium in soil, rock, and water. Because radon is a gas, it can enter buildings through openings or cracks in the foundation. The radon gas itself decays into radioactive solids, called radon daughters. The radon daughters attach to dust particles in the air, and can be inhaled. The inhalation of radon daughters has been linked to lung cancer.

You can get radon detection devices at many hardware and home improvement stores, or by contacting the EPA's National Radon Hotline (1-800-SOS-RADON). These devices are left in the home for 2 to 90 days, and indicate whether there might be a radon problem in the home. If results indicate that your home has a level exceeding 4 picocuries (pC/L), you will want to test your home again with the short, 2 to 90 day test and then calculate the average of the two tests, or test your home with an alpha track detector, which measures the long term radon average for three to twelve months. If the radon level in your home exceeds 4 pC/L, there are several techniques available to the lower levels.


horizontal rule

What is Radon?

Radon is a gas produced by the radioactive decay of the element radium. Radioactive decay is a natural, spontaneous process in which an atom of one element decays or breaks down to form another element by losing atomic particles (protons, neutrons, or electrons). When solid radium decays to form radon gas, it loses two protons and two neutrons. These two protons and two neutrons are called an alpha particle, which is a type of radiation. The elements that produce radiation are called radioactive. Radon itself is radioactive because it also decays, losing an alpha particle and forming the element polonium.

  (91 kb)


Elements that are naturally radioactive include uranium, thorium, carbon, and potassium, as well as radon and radium. Uranium is the first element in a long series of decay that produces radium and radon. Uranium is referred to as the parent element, and radium and radon are called daughters. Radium and radon also form daughter elements as they decay.

The decay of each radioactive element occurs at a very specific rate. How fast an element decays is measured in terms of the element "half-life", or the amount of time for one half of a given amount of the element to decay. Uranium has a half-life of 4.4 billion years, so a 4.4-billion-year-old rock has only half of the uranium with which it started. The half-life of radon is only 3.8 days. If a jar was filled with radon, in 3.8 days only half of the radon would be left. But the newly made daughter products of radon would also be in the jar, including polonium, bismuth, and lead. Polunium is also radioactive - it is this element, which is produced by radon in the air and in people's lungs, that can hurt lung tissue and cause lung cancer.

  (74 kb) Radon levels in outdoor air, indoor air, soil air, and ground water can be very different.


Radioactivity is commonly measured in picocuries (pCi). This unit of measure is named for the French physicist Marie Curie, who was a pioneer in the research on 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 atoms are measured in picocuries. For instance, a house having 4 picocuries of radon per liter of air (4 pCi/L) 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 levels in outdoor air, indoor air, soil air, and ground water can be very different. Outdoor air ranges from less than 0.1 pCi/L to about 30 pCi/L, but it probably averages about 0.2 pCi/L. Radon in indoor air ranges from less that 1 pCi/l to about 3,000 pCi/L, but it probably averages between 1 and 2 pCi/L. Radon in soil air (the air that occupies the pores in soil) ranges from 20 or 30 pCi/L to more than 100,000 pCi/L; most soils in the United States contain between 200 and 2,000 pCi of radon per liter of soil air. The amount of radon dissolved in ground water ranges from about 100 to nearly 3 million pCi/L.

Why do radon levels vary so much between indoor air, outdoor air, soil air, and ground water? Why do some houses have high levels of indoor radon while nearby houses do not? The reasons lie primarily in the geology of radon - the factors that govern the occurrence of uranium, the formation of radon, and the movement of radon, soil gas, and ground water.


horizontal rule

bulletRadon in fault and shear zones, eastern United States bulletRadon in glacial deposits of the Upper Midwest bulletCounty radon potential assessments in the Washington, D.C., area bulletTerrestrial gamma radioactivity of the conterminous United States bulletRadon in ground water and soil gas on Indian reservations in Wisconsin bulletRadon in ground water of the Lower Susquehanna and Potomac River Basins bulletUSGS Geologic Information

  horizontal rule

Other Sources of Radon Information

bulletThe High Radon Project-Lawrence Berkeley National Laboratory bulletRadon information from the U.S. EPA (including the National Radon Proficiency Listing) bulletNational Safety Council Radon Information Page bullet"Radon Update" by Dr. A.B. Brill, University of Massachusetts Medical Center 

State Geological Surveys are good sources of information (geologic maps and radioactivity surveys) on the geology of the states. For information on soils in your area, the first place to start is the county agricultural extension agent. Telephone numbers and addresses for these state and county government agencies are in the phone book.

All states have radon contact agencies, usually the state health departments or divisions of environmental or radiation protection. These agencies and the regional offices of the U.S. Environmental Protection Agency (EPA) are good sources of general information about the health risks of radon, radon measurements in your house, and corrections of radon problems. The publications listed under "Suggested Readings - General References" are among those available from EPA. Many state radon agencies have these or similar publications available. For technical information on the geology of radon, look at the publications listed under "Suggested Readings - Technical References".

  (121 kb) U.S. Environmental Protection Agency Regions


EPA Region 1 
JFK Federal Building 
Boston, MA 02203

EPA Region 2 
26 Federal Plaza 
New York, NY 10278

EPA Region 3 
841 Chestnut Street 
Philadelphia, PA 19107

EPA Region 4 
345 Courtland St. N.E. 
Atlanta GA 30365

EPA Region 5 
230 South Dearborn Street 
Chicago, IL 60604

EPA Region 6 
1445 Ross Avenue 
Dallas TX 75202-2733

EPA Region 7 
726 Minnesota Avenue 
Kansas City, KS 66101

EPA Region 8 
One Denver Place, Suite 1300 
999 18th Street 
Denver, CO 80202-2413

EPA Region 9 
215 Fremont Street 
San Francisco, CA 94105

EPA Region 10 
1200 Sixth Avenue 
Seattle, WA 98101

General References (these texts or similar materials are available from your regional EPA office)

U.S. Environmental Protection Agency, bullet1992, A citizen's guide to radon: The guide to protecting yourself and your family from radon (2nd edition): EPA 402-K92-001, 15 p. bullet1993, Home buyer's and seller's guide to radon: EPA 402-R-93-003, 32 p. bullet1992, Consumer's guide to radon reduction: How to reduce radon levels in your home: EPA 402-K92-003, 17 p. bullet1992, National Residential Radon Survey: Summary Report: EPA 402-R-92-011, 16 p.

Technical References (these articles or similar materials may be available in large regional reference libraries or from specific sources, as indicated. Of particular interest to the serious student are the periodicals Radon Protection Dosimetry, Journal of Geophysical Research, and Health Physics, which contain many technical articles on this subject.)

Nazaroff, W.W., and Nero, A.V., Jr., Eds., 1988, Radon and its decay products in indoor air: New York, John Wiley and Sons, Inc., 518 p.

Nielson, K.K., Rogers, V.C., and Gee, G.W., 1984, Diffusion of radon through soils: a pore distribution modes: Soil Science Society of America Journal, V. 48, no. 3, p. 482-487.

Otton, J.K., Schumann, R.R., Owen, D.E., Thurman, Nelson, and Duval, J.S., 1988, Map showing radon potential of rocks and soils in fairfax County, Virginia: U.S. Geological survey Miscellaneous Field Studies Map MF-2047, scale 1:62,500.

Sachs, H.M., Hernandez, T.L., and Ring, J.W., 1982, Regional geology and radon variability in buildings: Environment International, v. 8, no. 1-6, p. 97-103.

  horizontal rule