Radon gas, like carbon-14 gas, is completely natural. It forms during the decay of
uranium-238. The radon atom is a gas atom, and it has a half-life of only 3.825 days. That
means that radon gas concentrations are higher where uranium is plentiful in the soil.
There have been no reports of short-term effects or symptoms caused by radon exposure.
The only reported long-term effect is lung cancer. If you inhale a radon atom, the atom can
disintegrate while it is in your lungs. When it disintegrates, it becomes polonium-218, which is
a metal. This metal atom can settle in your lungs, and over the next hour or so it will emit a
number of alpha particles, beta particles and gamma rays. It eventually turns into lead-210
with a half-life of 22 years, which is fairly stable in this context. But now you have an atom
of lead in your system, which causes its own problems. It is the quick, hour-long sequence of
alpha, beta and gamma emissions that can lead to the mutations in the lung tissue, which can
cause cancer. Smoking enormously increases the risk of lung cancer from radon exposure. So
you can see that a high concentration of radon gas, despite the fact that it is completely
natural, is not something you want in your home.
Some parts of the United States have higher risks of radon than others. The U.S.
Environmental Protection Agency has a map that shows which counties and states have
higher average radon levels. The U.S. EPA and the U.S. Geological Survey have evaluated the
radon potential in the U.S. and have developed this map to assist National, State, and local
organizations to target their resources and to assist building code officials in deciding whether
radon-resistant features are applicable in new construction. This map is not intended to be
used to determine 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. All homes should be tested regardless of
geographic location. The map assigns each of the 3,141 counties in the U.S. to one of three
zones based on radon potential. Each zone designation reflects the average short-term radon
measurement that can be expected to be measured in a building without the implementation of
radon control methods. The radon zone designation of the highest priority is Zone 1.
Radon atoms are fairly short-lived. Over the course of several days, a radon atom becomes a
lead atom. While it is a radon atom, however, it is a gas. Because radon is a gas, it can seep
from the ground into the air in a house. The primary way that radon enters a house is through
the foundation (crawl space, basement) by a variety of paths:
Radon may also enter the air of a house from well water, but this is a minor source compared
to that coming in through the foundation. Many appliances in a home can depressurize it.
Any device which pushes indoor air to the exterior will create negative air pressure inside the
house. These devices, some of which are pictured below, include range hoods ducted to the
exterior, bathroom exhaust fans, clothes dryers, conventional fuel-burning heating systems,
When negative pressure is created there is a natural tendency for it to be compensated by air entering through small cracks and openings in the building envelope, including cracks in the basement floor and other avenues mentioned above. This type of action will forcibly draw radon gas from the soil, although if radon is present it will also rise naturally on its own.
Radon gas has no smell or color so a test must be done to detect it. In fact, the U.S. Office of
the Surgeon General and U.S. EPA recommend that all homes be tested for radon, especially if
you are buying, selling or building a home.
Because radon levels can vary from day to day and from season to season, testing can be done on the short-term (two to 90 days) or long-term (greater than three months). Short-term tests are best done if the results are needed quickly and should be followed by a later short-term test. Long-term tests will yield better information on a home's average year-round radon levels. Radon test devices are placed in the lowest occupied level of the home.
Radon Test Devices Radon tests detect either radon gas directly or the daughter products of radon's radioactive decay. There are two categories of radon test devices, passive and active. Passive devices require no electrical power and generally trap radon or its daughter products for later analysis by a laboratory. Passive devices include charcoal canisters, charcoal liquid scintillation detectors, alpha track detectors and electret ion detectors.
Radon levels in the average home are about 1.25 picocuries/liter of air (pCi/L). If a radon test
discloses levels of 4 pCi/L or greater, then some action should be taken to reduce the radon
level. Radon can be reduced by preventing its entry into the home or by removing it once it
has entered the home. The general solution involves active ventilation either in the basement
or below the slab of the home.
There are several proven methods to reduce radon in your home, but the one primarily used is
a vent pipe system and fan, which pulls radon from beneath the house and vents it to the
outside. This system, known as a soil suction radon reduction system, does not require major
changes to your home and is usually reasonably priced.
A strong induction fan in the attic draws air upwards through PVC pipes that penetrate the basement floor slab. Radon gas, which normally rises as a result of natural draft, is pulled toward the piping system and vents harmlessly above the house into the air. A system failure alarm, usually activated by a suction switch, will sound if the system does not work. Sealing foundation cracks and other openings makes this kind of system more effective and cost-efficient. Similar systems can also be installed in houses with crawl spaces. Radon contractors can use other methods that may also work in your home. The right system design depends on the layout of your home and other factors.
MYTH: Scientists are not sure that radon really is a problem.
FACT: Although some scientists dispute the precise number of deaths due to radon, all the major health organizations (like the Centers for Disease Control and Prevention, the American Lung Association and the American Medical Association) agree with estimates that radon causes thousands of preventable lung cancer deaths every year. This is especially true among smokers, since the risk to smokers is much greater than to non-smokers.
MYTH: Radon testing is difficult, time-consuming and expensive.
FACT: Radon testing is easy. You can test your home yourself or hire a qualified radon test company. Either approach takes only a small amount of time and effort.
MYTH: Radon testing devices are not reliable and are difficult to find.
FACT: Reliable testing devices are available from qualified radon testers and companies.
MYTH: Homes with radon problems can't be fixed.
FACT: There are simple solutions to radon problems in homes. Hundreds of thousands of
homeowners have already fixed radon problems in their homes. Radon levels can be readily
lowered for $800 to $2,500 (with an average cost of $1,200). Call your state radon officefor
help in identifying qualified mitigation contractors.
Bureau of Environmental Radiation
Radon Contact: Jerry Collins
MYTH: Radon affects only certain kinds of homes.
FACT: House construction can affect radon levels. However, radon can be a problem in homes of all types: old homes, new homes, drafty homes, insulated homes, homes with basements, and homes without basements. Local geology, construction materials, and how the home was built are among the factors that can affect radon levels in homes.
MYTH: Radon is only a problem in certain parts of the country.
FACT: High radon levels have been found in every state. Radon problems do vary from area to area, but the only way to know your radon level is to test.
MYTH: A neighbor's test result is a good indication of whether your home has a
FACT: It's not. Radon levels can vary greatly from home to home. The only way to know if your home has a radon problem is to test it.
MYTH: Everyone should test their water for radon.
FACT: Although radon gets into some homes through water, it is important to first test the air in the home for radon. If your water comes from a public water supply that uses ground water, call your water supplier. If high radon levels are found and the home has a private well, call the Safe Drinking Water Hotline at 1 800-426-4791 for information on testing your water.
MYTH: It's difficult to sell homes where radon problems have been discovered.
FACT: Where radon problems have been fixed, home sales have not been blocked or frustrated. The added protection is some times a good selling point.
MYTH: I've lived in my home for so long, it doesn't make sense to take action now.
FACT: You will reduce your risk of lung cancer when you reduce radon levels, even if you've lived with a radon problem for a long time.
MYTH: Short-term tests can't be used for making a decision about whether to fix your
FACT: A short-term test, followed by a second short-term test can be used to decide whether to fix your home. However, the closer the average of your two short-term tests is to 4 pCi/L, the less certain you can be about whether your year-round average is above or below that level. Keep in mind that radon levels below 4 pCi/L still pose some risk. Radon levels can be reduced in most homes to 2 pCi/L or below.