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Radon is an invisible, cancer-causing, radioactive gas created during the natural breakdown of uranium in rocks and soils. It's found in nearly all soils. It typically moves up through the ground and into your home through cracks and other holes in the foundation, although there are other radon sources. Your home traps radon inside, where it can accumulate. Any home can have a radon problem, not just those built on soil and rock types with high geologic potential for radon release.
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Breathing air that contains radon can cause lung cancer. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States today and is the leading cause of lung cancer in nonsmokers. If you smoke and your home has high radon levels, your risk of lung cancer is especially high. Radon is estimated to cause about 21,000 lung cancer deaths per year, according to EPA's 2003 Assessment of Risks from Radon in Homes.
Read EPA's page on the health risks associated with radon to learn more.
There are two main sources for the radon in your home's indoor air: the soil and the water supply. Compared to radon entering the home through water, radon entering your home through the soil is usually a much larger risk.
Read more about risks from radon in water supply.
Diagram showing the various pathways by which radon can enter a home. Image courtesy of Natural Resources Canada www.geoscape.nrcan.gc.ca
Montgomery County has areas of high geologic potential for radon. However, homes tested in areas of high geologic radon potential can have low radon readings and homes in areas of low geologic radon potential can have high readings. All homes in Montgomery County should be tested for radon. Any home can have a radon problem.
Testing is the only way to know if you and your family are at risk from radon. EPA and the Surgeon General recommend testing all homes, below the third floor, for radon. EPA also recommends testing in schools.
Read EPA's Web page on radon testing to learn more.
Be Aware! If your living patterns change and you begin occupying a lower level of your home (such as a basement), you should retest your home on that level.
Much of the information below is from EPA's "A Citizen's Guide to Radon."
Low-cost do-it-yourself radon test kits are available through the mail and in hardware stores and other retail outlets.
If you'd rather hire a radon professional to do the testing, you should first contact an independent radon proficiency program to get a list of the certified radon professionals serving your area.
The amount of radon in the air is measured in picocuries per liter (pCi/L). Sometimes test results are expressed in working levels (WL) rather than in picocuries per liter (4 pCi/L = 0.016 WL).
The quickest way to test is with short-term tests. Short-term tests remain in your home for 2 to 90 days, depending on the device. Charcoal canister detectors are the most commonly used short-term testing devices. 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. But if you need results quickly, you can use a short-term test followed by a second short-term test to decide whether to fix your home.
Testing is easy and should only take a few minutes of your time. Follow the instructions that come with your test kit.
Close your windows and outside doors and keep them closed as much as possible during the test. You can continue to operate heating and air-conditioning system fans that circulate air, but don't operate fans or other machines that bring in air from outside. You can continue to operate fans that are part of a radon-reduction system or small exhaust fans operating only for short periods. If you're doing a short-term test that lasts just 2 or 3 days, be sure to close your windows and outside doors at least 12 hours before beginning the test, too. And don't conduct short-term tests lasting just 2 or 3 days during unusually severe storms or periods of unusually high winds.
Place the test kit in the lowest lived-in level of your home (for example, the basement if it's frequently used; otherwise, the first floor). Put it in a room that is used regularly (like a living room, playroom, den, or bedroom) but not in your kitchen or bathroom.
Place the kit at least 20 inches above the floor in a location where it won't be disturbed—away from drafts, high heat, high humidity and exterior walls.
Leave the kit in place for as long as the package says. Once you've finished the test, reseal the package and send it to the lab specified on the package right away for analysis. You should receive your test results within a few weeks.
Long-term tests remain in your home for more than 90 days. "Alpha track" and "electret" detectors are commonly used for this type of testing. A long-term test will give you a reading that is more likely to tell you your home's year-round average radon level than a short-term test.
EPA recommends the following testing steps:
The higher your initial short-term test result, the more certain you can be that you should use a short-term rather than a long-term follow-up test. If your first short-term test result is more than twice EPA's 4 pCi/L action level, you should do a second short-term test immediately.
EPA recommends that you fix your home if the radon level is 4 pCi/L or more in its assessment of health risks. Because there is no known safe level of exposure to radon, EPA also recommends that you consider fixing your home if the radon level is between 2 pCi/L and 4 pCi/L. EPA's estimate of 21,000 lung cancer deaths per year due to radon is based on the average radon concentration in American homes, which is about 1.3 pCi/L. The average concentration of radon in outdoor air is 0.4 pCi/L, or 1/10 of EPA's 4 pCi/L action level.
There are several proven methods for reducing radon in your home, but the one primarily used is a vent pipe system and fan, which pull radon from beneath the house and vent it to the outside. This system, known as a soil suction radon reduction system, does not require major changes to your home. 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 might also work in your home. The right system depends on the design of your home and other factors. See EPA's Consumer's Guide to Radon Reduction.
To locate a radon mitigation professional, contact one of the nonprofit organizations that certify radon professionals
Radon is becoming an important part of the real estate transfer process in Montgomery County. For a thorough discussion of the role of radon in buying and selling homes, see EPA's Home Buyer's and Seller's Guide to Radon.
All homes constructed in Montgomery County after 1995 must be built to resist radon entry and prepare the building for
post-construction radon mitigation, if necessary. For more information about the requirements of the building code, contact
the Montgomery County Department of Permitting Services
or call 311 (240-777-0311 outside of Montgomery County).
The radon in your water supply poses an inhalation risk and an ingestion risk. Research has shown that your risk of lung cancer from breathing radon in the air is much greater than your risk of stomach cancer from swallowing water with radon in it. Most of your risk from radon in water comes from radon released into the air when you use water for showering and other household purposes.
Radon in your home's water is not usually a problem when the water source is surface water. A radon problem is more likely when the source is groundwater (e.g., a private well or a public water supply system that uses groundwater). If you're concerned that radon might be entering your home through the water and your water comes from a public water supply, contact your water supplier.
If you've tested your private well and have found a radon problem, it can be fixed. Your water supply can be treated in two ways. Point-of-entry treatment can effectively remove radon from the water before it enters your home. Point-of-use treatment devices remove radon from your water at the tap, but do not treat other sources of water in the home, such as the shower, toilet, washing machine, or hose. Point-of-use treatment devices are not effective in reducing the risk from breathing radon released into the air from the non-treated sources in your home. For more information on radon in drinking water, see EPA’s website on the topic.
There is some concern about the possibility of granite kitchen countertops and flooring materials emitting radon. EPA has compiled a list of common concerns about indoor air quality. Read EPA's response to the concern about granite countertops.