You can't see radon. And you can't smell it or taste it. But it may be a problem in your home. Radon comes from the natural breakdown of uranium in soil, rock, and water. Radon is the second leading cause of lung cancer in the United States.

There are low levels of radon outdoors. Indoors, there can be high levels. Radon can enter homes and buildings through cracks in floors, walls, or foundations. Radon can also be in your water, especially well water. Testing is the only way to know if your home has elevated radon levels. It is inexpensive and easy. You can buy a test kit at most hardware stores or hire someone to do a test. Radon reduction systems can bring the amount of radon down to a safe level. The cost depends on the size and design of your home.

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.

Any home may have a radon problem.

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.

Radon is an odorless and invisible radioactive gas naturally released from rocks, soil, and water. Radon can get trapped inside homes and buildings and build up in the air. Over time, breathing in high levels of radon can cause lung cancer.

Radon in Homes and Buildings

All outdoor and indoor air has some radon in it. Some building materials also can release low levels of radon. Radon can build up in the air in any home or building whether it has a basement, is sealed or drafty, or is new or old. There is no known safe level of radon and you should always aim to have the lowest level. The U.S. Environmental Protection Agency (EPA) recommends fixing your home if radon levels are above 4 picoCuries per liter of air (pCi/L).

Lung Cancer Risk

Radon is the second leading cause of lung cancer after cigarette smoking. The EPA and the Surgeon General’s office estimate radon is responsible for more than 21,000 lung cancer deaths each year in the United States.

When you breathe in radon, radioactive particles from the decay of radon gas can get trapped in your lungs. It takes many years for lung cancer to develop. Most people don’t have symptoms until lung cancer is advanced and at that point it is harder to treat. For these reasons, it is important to take steps to reduce radon exposure throughout your life to help prevent lung cancer.

Factors that increase your risk of getting lung cancer from radon include the following:

• High radon levels in your home or another building that you regularly spend time in
• High radon levels in the part of the home or building where you spend the most time (Radon levels are often higher in basements and lower levels.)
• Smoking cigarettes, currently or in the past
• Burning wood, coal, or other substances that add particles to air

There is not enough data to show whether children have a higher risk of developing lung cancer from radon exposure than adults. However, children may have higher doses (amount breathed in) of radon than adults even when exposed to the same radon levels for the same amount of time. This is because children have different lung shapes and sizes and faster breathing rates.

What You Can Do

Steps you can take to measure and reduce radon levels include the following:

The only way to know if you have unsafe levels of radon in your home or office is by testing. You can contact your state radon office for testing or purchase a test kit in a hardware store or online. If your test shows that radon levels are above 4pCi/L or you are interested in reducing radon in your home, contact your state radon office to help you find a qualified or state-certified radon contractor in your area to fix your home. Lowering high radon levels requires technical knowledge and special skills so you should rely only on a qualified professional for these repairs. Test radon levels again after any repairs to be sure they worked.

Ways to Keep Radon Levels Low

Since there is no safe level of radon, reducing radon inside your home or building will always help reduce your risk of lung cancer, even when the level in your home is less than 4 pCi/L.

The U.S. Department of Housing and Urban Development recommends these actions you can take to reduce your risks of lung cancer and help lower radon levels in your home:

• Increase air flow in your house by opening windows and using fans and vents to circulate air. However, natural ventilation in any type of house is only a temporary strategy to reduce radon.
• Seal cracks in floors and walls with plaster, caulk, or other mate­rials designed for this purpose.
• You can cover the earth floor in crawl spaces with a high-density plastic sheet. A vent pipe and fan can be used to blow the radon from under the sheet and vent it to the outdoors

Always test radon levels again after you’ve made any of these changes to ensure these actions reduced the radon levels.

Smoking and second-hand smoke, combined with exposures to high radon levels, increase your risk of lung cancer. Not smoking and not allowing others to smoke in your house also helps prevent lung cancer. Call 1-800-QUIT-NOW or visit CDC.gov/quit for free support and resources to help you quit smoking.

Buying a New Home

Ask about radon-resistant construction techniques if you are buying a new home. It is almost always cheaper and easier to build these features into new homes than to add them later.

Exposure to Radon Causes Lung Cancer In Non-smokers and Smokers Alike

The Facts...

• Lung cancer kills thousands of Americans every year. Smoking, radon, and secondhand smoke are the leading causes of lung cancer. Although lung cancer can be treated, the survival rate is one of the lowest for those with cancer. From the time of diagnosis, between 11 and 15 percent of those afflicted will live beyond five years, depending upon demographic factors. In many cases lung cancer can be prevented.
• Smoking is the leading cause of lung cancer. Smoking causes an estimated 160,000* cancer deaths in the U.S. every year (American Cancer Society, 2004). And the rate among women is rising. On January 11, 1964, Dr. Luther L. Terry, then U.S. Surgeon General, issued the first warning on the link between smoking and lung cancer. Lung cancer now surpasses breast cancer as the number one cause of death among women. A smoker who is also exposed to radon has a much higher risk of lung cancer.
• Radon is the number one cause of lung cancer among non-smokers, according to EPA estimates. Overall, radon is the second leading cause of lung cancer. Radon is responsible for about 21,000 lung cancer deaths every year. About 2,900 of these deaths occur among people who have never smoked. On January 13, 2005, Dr. Richard H. Carmona, the U.S. Surgeon General, issued a national health advisory on radon.
  • World Health Organization's international radon project
• Secondhand smoke is the third leading cause of lung cancer and responsible for an estimated 3,000 lung cancer deaths every year. Smoking affects non-smokers by exposing them to secondhand smoke. Exposure to secondhand smoke can have serious consequences for children’s health, including asthma attacks, affecting the respiratory tract (bronchitis, pneumonia), and may cause ear infections.
  • For smokers the risk of lung cancer is significant due to the synergistic effects of radon and smoking. For this population about 62 people in a 1,000 will die of lung-cancer, compared to 7.3 people in a 1,000 for never smokers. Put another way, a person who never smoked (never smoker) who is exposed to 1.3 pCi/L has a 2 in 1,000 chance of lung cancer; while a smoker has a 20 in 1,000 chance of dying from lung cancer.

Radon Risk If You Smoke

from "A Citizen's Guide to Radon: The Guide to Protecting Yourself and Your Family From Radon"

Radon Risk If You Have Never Smoked

Radon-associated lung cancer can be prevented by limiting exposure to radon in indoor air. You can start by testing radon levels in your home and installing a radon reduction system, if needed.

Radon is an odorless, invisible, radioactive gas naturally released from rocks, soil, and water. Radon can get into homes and buildings through small cracks or holes and build up in the air. Over time, breathing in high levels of radon can cause lung cancer.

Impact of Radon

If you are trying to quit smoking, call 1-800-QUIT-NOW or visit CDC.gov/quit for free support and resources to help you quit smoking.

When you breathe in radon gas, radioactive particles can get trapped in your lungs. Over time, these radioactive particles increase the risk of lung cancer. It may take years before health problems appear.

The Environmental Protection Agency (EPA) estimates that radon causes 21,000 lung cancer deaths each year. Radon is the leading environmental cause of any cancer. It is the second leading cause of lung cancer, after smoking. People who smoke and are exposed to radon have a 10 times greater risk of developing lung cancer from radon exposure compared with people who do not smoke and are exposed to the same radon levels.

Testing

When you should test your home’s radon levels:

• If it’s never been tested or radon levels are unknown
• When preparing to buy or sell
• Before and after any renovations, especially after making any repairs to reduce radon levels
• Before making any lifestyle changes in the home that would cause someone to spend more time in the basement or lower level (like converting a basement to a bedroom)

Contact your state radon office for specific information and resources in your area for testing and for a list of qualified radon testers. You can either hire a radon tester or purchase a radon test kit from a hardware store and do it yourself.

Radon Reduction

Consider contacting a licensed professional to install a radon reduction system (also called a radon mitigation system) in your home. EPA recommends installing a system if your radon level is at or above 4 picocuries per liter (pCi/L) of air. A “picocurie” is a common unit for measuring the amount of radioactivity.

More Ways to Take Action

The U.S. Department of Housing and Urban Development recommends additional actions you can take to reduce high radon levels in your home and protect yourself from an increased risk of lung cancer.

• Increase air flow in your house by opening windows and using fans and vents to circulate air.
  • But remember that natural ventilation in any type of house is only a temporary strategy to reduce radon.
• Seal cracks in floors and walls with plaster, caulk, or other mate­rials designed for this purpose.
  • Contact your state radon office for a list of qualified contractors in your area and for information on how to fix radon problems yourself. Always test again after fin­ishing to make sure you’ve fixed your radon problem.
• Ask about radon-resistant construction techniques if you are buy­ing a new home.
  • It is almost always cheaper and easier to build these features into new homes than to add them later.
• Find free support and resources to help stop smoking at 1-800-QUIT-NOW or at CDC.gov/quit.
  • Smoking significantly increases the risk of lung cancer from radon.

Smoking significantly increases the risk of lung cancer from radon.

Testing your home is the only way to know if radon levels are high. You and your family could be at risk for lung cancer from radon.

When to Test Your Home

You should test your home’s radon levels

• If it’s never been tested or radon levels are unknown
• When preparing to buy or sell
• Before and after any renovations, especially after making any repairs to reduce radon levels
• Before making any lifestyle changes in the home that would cause someone to spend more time in the basement or lower level (like converting a basement to a bedroom)

Ways to Test Your Home

Contact your state radon office for specific information and resources in your area for testing and for a list of qualified radon testers. You can either hire a radon tester or purchase a radon test kit from a hardware store and do it yourself. However, the Environmental Protection Agency (EPA) recommends hiring a qualified tester if you are buying or selling your home.

There are two general types of radon test kits:

• Short-term kits measure radon for 2–90 days for quick results.
• Long-term kits measure radon in your home for over 90 days and are more likely to tell you your home’s year-round average level. The longer the test, the better the results will reflect your home and lifestyle.

Do It Yourself Test Kits

Your state radon office can give you information on where to get a test kit and whether your state offers free or discounted test kits. You can purchase a radon test kit online, in many retail or hardware stores, or order one through the National Radon Program Services.*

Once you have your kit:

• Follow all instructions carefully. This will include placing a small measuring device in your basement or the lowest level of your home, raised three feet off the ground, in the middle of the room.
• If your home is in a multi-unit building, you can test your unit by placing the device in the lowest level within your unit.
• Leave it there for the amount of time instructed. Short-term testing can take 2–90 days and long-term testing takes more than 90 days. The exact length of time for testing depends on the specific test.
• Once the test is completed, follow the directions on the test kit packaging to find out where to send the device to get the results.

Understanding Results

Radon is measured in units of picocuries per liter (pCi/L) of air. Radon is naturally found in outdoor air at very low levels and some radon will always be in your indoor air. According to EPA, the average radon level in American homes is about 1.3 pCi/L.

EPA recommends contacting a licensed professional to install a radon reduction system if your radon level is at or above 4 pCi/L of air. EPA also recommends taking action to reduce radon if your radon level is from 2 pCi/L through 4 pCi/L. There is no known safe level of radon so you should always aim to have the lowest radon levels to reduce the risk of lung cancer.

Test Results and Next Steps

What to Do if Your Test Shows Higher Radon Levels

If you are planning any major structural renovation, such as converting an unfinished basement area into living space, it is especially important to test the area for radon before you begin the renovation. If your test results indicate a radon problem, radon-resistant techniques can be included as part of the renovation. Because major renovations can change the level of radon in any home, always test again after work is completed.

Our general guidance (A Citizen's Guide to Radon - (December 2016, EPA 402/K12/002) - suggests:

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.

Even if your test result is below 4 pCi/L, you may want to test again sometime in the future.

If you are buying or selling a home (from our Home Buyer's and Seller's Guide to Radon - (March 15, 2018, EPA 402/K-13/002):

If you are thinking of selling your home and you have already tested your home for radon, review the Radon Testing Checklist to make sure that the test was done correctly. If so, provide your test results to the buyer.

No matter what kind of test you took, a potential buyer may ask for a new test especially if:

• The Radon Testing Checklist items were not met;
• The last test is not recent, e.g., within two years;
• You have renovated or altered your home since you tested; or
• The buyer plans to live in a lower level of the house than was tested, such as a basement suitable for occupancy but not currently lived in.

A buyer may also ask for a new test if your state or local government requires disclosure of radon information to buyers.

Radon is a radioactive gas that is naturally released in the air from rocks and soil. It can be found in the air outside and can get inside buildings and homes, where it can build up. There is no known safe level of radon. Aiming for the lowest radon level you can achieve in your home will reduce your risk of harmful health effects, including lung cancer.

When You Should Take Action

First, test your home radon level. The Environmental Protection Agency (EPA) recommends contacting a qualified professional to install a radon reduction (also called radon mitigation) system if your home radon level is at or above 4 pCi/L of air. These are fixes to your home to lower the radon level. EPA also recommends taking action to reduce radon if your home radon level is from 2 pCi/L through 4 pCi/L.

If you are buying a new home, ask about including radon-resistant features to help prevent or minimize radon entering your home and the need to install a more costly system in the future.

Radon Reduction System

Contact your state radon office or one of EPA’s national radon proficiency programs to find a qualified professional to fix your home. Lowering high radon levels requires technical knowledge and special skills. Contractors who do not specialize in radon reduction could make the problem worse.

There are several proven methods to reduce radon in your home, but the one most used has 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 depressurization 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. The right system depends on the design of your home and other factors like whether your home has a basement.

After installing a radon reduction system, test your home again to make sure it is working and consider retesting your home every two years to be sure radon levels remain low. Also retest your home after any remodeling.

Other Ways to Reduce Radon

If your radon levels are not above 4 pCi/L here are a few things you can do to keep radon levels as low as possible in your home:

• Increase air flow in your house by opening windows and using fans and vents to circulate air.
  • Natural ventilation in any type of house should not be considered radon mitigation since it is only a temporary strategy to reduce radon.
• Seal cracks in floors and walls with plaster, caulk, or other mate­rials designed for this purpose.

Always test radon levels again after you’ve made any of these changes.

Costs to Reduce Radon

The cost of reducing radon in your home depends on how your home was built and the extent of the radon problem, so the cost to fix it can vary widely. However, most homes can be fixed for about the same cost as other common home repairs. Contact your state radon office for more information, or get one or more estimates from qualified contractors.

Radon is a naturally occurring radioactive gas that is colorless and odorless. Radon comes from the natural decay of uranium or thorium, elements found in rocks, soils, and water. Radon breaks down quickly, giving off radioactive particles. When inhaled, these radioactive particles can damage cells that line the lung.

Radon gas is in nearly all outdoor air but usually at low levels. Radon is also found in water. A higher radon level in the water supply is more likely when the source is ground water, such as from a private well. Most public water supplies are sourced from surface water, such as lakes, rivers, and reservoirs.

Does radon affect health?

Scientists agree that radon causes lung cancer in humans. Being exposed to radon for a long period of time can lead to lung cancer. In the U.S., radon exposure is the second leading cause of lung cancer after cigarette smoking.

Exposure to the combination of radon gas and cigarette smoke creates an even greater chance of developing lung cancer. The majority of radon-related cancer deaths occur among smokers. However, it is estimated that about 10% of radon-related cancer deaths occur among nonsmokers.

How does radon get into a building or home?

Radon gas can get trapped inside homes and buildings and accumulate in the air. Radon moves up through the ground and can enter a building through cracks in foundations, floors, or walls. It can also be released from building materials and from some ground water. Radon levels are usually highest in basements or crawl spaces. But radon can build up in the air of any home or building whether or not it is sealed or drafty or is new or older.

What can I do about radon?

It is not possible to avoid radon completely. But you can protect your health by testing for radon and taking any recommended steps to lower radon exposure in buildings or homes that have elevated levels. This process, known as radon mitigation, can lower your exposure.

The U.S. Department of Housing and Urban Development recommends these actions to help reduce radon levels in your home:

• Increase air flow in your house by opening windows and using fans and vents to circulate air. However, natural ventilation in any type of house is only a temporary strategy to reduce radon.
• Seal cracks in floors and walls with plaster, caulk, or other mate¬rials designed for this purpose.
• Cover an earth floor in crawl spaces with a high-density plastic sheet. A special vent pipe and fan can be used to blow the radon from under the sheet and vent it to the outdoors.
• Monitor radon levels after any fixes to ensure that radon levels are lower.

EPA provides guidance and resources for reducing radon in schools. Contact your state radon office for information about testing and reduction strategies in schools, daycare and childcare facilities, and workplaces in your area.