What You Need to Know About Radon Testing

Finding (and mitigating) this gas can lower cancer risk

Radon testing, which detects the presence of radon in homes and buildings, is highly recommended. This gas is the second leading cause of lung cancer and a potential risk factor for leukemia and lymphoma. And since radon has no smell and is essentially invisible, the only way to know you have a problem is through testing.

If levels are abnormal, radon mitigation (a process to reduce gas concentrations or radon in water) can almost always solve the problem and eliminate your risk.

A person with a radon test on a table in their house (Tips to Perform a Radon Test)

Verywell / Paige McLaughlin

Where Is Radon Found?

Radon gas is produced by the normal breakdown of uranium in the soil. Although some regions of the United States have higher levels of radon, elevated levels have been found in homes in all 50 states and around the world. It is estimated that no less than one out of 15 American homes has elevated radon levels.

In addition to soil, radon may be present in well water or items that are introduced into homes (such as granite countertops).

Radon is present in small amounts in the air throughout the world. The average level of radon in outdoor air is 0.4 picoCuries per liters (pCi/L), and the average level in indoor air is 1.3 pCi/L.

Radon Levels and Health Risks

There are certain radon level thresholds that you need to be aware of to ensure that your home is a healthy one.

The United States Environmental Protection Agency (EPA) recommends fixing your home if the radon level is above 4 pCi/L. They also state that individuals should consider repairs if the level falls between 2 pCi/L and 4 pCi/L.

If your home has borderline radon levels, mitigation is considered beneficial, especially if you are a smoker or live in a house with smokers. The presence of radon at 2 pCi/L can amplify the health risks of tobacco smoking—the number one risk factor for lung cancer.

These recommendations stem from data on the dose-related impact of radon exposure on certain health risks.

Lung Cancer

Exposure to radon in homes is not only the second leading cause of lung cancer overall but the number one cause in non-smokers.

According to the EPA, the prevalence of lung cancer among non-smokers increases in tandem with the concentration of radon detected in a home:

  • At 2 pCi/L, approximately 4 out of 1,000 people could get lung cancer.
  • At 4 pCi/L, approximately 7 out of 1,000 people could get lung cancer.
  • At 8 pCi/L, approximately 15 out of 1,000 people could get lung cancer.
  • At 10 pCi/L, approximately 18 out of 1,000 people could get lung cancer.
  • At 20 pCi/L, approximately 36 out of 1,000 people could get lung cancer.

If you are a smoker, the prevalence skyrockets:

  • At 2 pCi/L, approximately 32 out of 1,000 people could get lung cancer.
  • At 4 pCi/L, approximately 64 out of 1,000 people could get lung cancer.
  • At 8 pCi/L, approximately 120 out of 1,000 people could get lung cancer.
  • At 10 pCi/L, approximately 150 out of 1,000 people could get lung cancer.
  • At 20 pCi/L, approximately 260 out of 1,000 people could get lung cancer.

Blood Cancers

A 2016 study in the journal Environmental Research suggests that indoor radon exposure may also increase the risk of blood cancers such as leukemia, lymphomas, and multiple myeloma in women, with the risk increasing in tandem with rising radon levels.

A 2017 study in Environmental Research and Public Health estimates that every 10 Bq/m3 (roughly one-third of 1 pCi/L) increase in radon is associated with a 7% increase in the risk of lymphoma in women, children, and adolescents.

The reasons for this are not entirely clear, but scientists do know that radon emits alpha particles that can damage DNA in the bone marrow and potentially contribute to the development of blood cancers.

Testing Recommendations and Options

The EPA currently recommends testing all schools for radon and all homes for radon below the third floor. Testing is inexpensive and should only take a few minutes to perform.

There are both short-term and long-term radon tests available.

  • Short-term tests are good if you want an instant reading of the status of your home. They are also important as part of home inspections when buying or selling houses.
  • Long-term tests are used to monitor radon levels over a period of time, as they can be low in some seasons and high in others.

Short-Term Tests

Short-term tests are the fastest way to detect elevated radon levels in your home. They are performed over a period of two to 90 days, with most retail kits designed for two- to four-day testing.

Do-it-yourself kits are available at most hardware stores and can also be ordered online; they generally cost under $20. If you are purchasing a home, know that many home inspection agencies offer radon detection as part of their inspection service.

Long-Term Tests

Long-term tests are conducted over a period of more than 90 days. Radon levels fluctuate throughout the year and are highest during cold weather, when heating is used and windows are shut.

These tests can measure the average level of radon in your home year-round. Most often, long-term tests are used by those who have done radon mitigation (professional removal of the gas) and want to make sure that the interventions are working.

Testing Devices

Both passive and active devices can be used for radon testing. Passive devices, such as charcoal canisters, do not require power and are widely available.

Active devices require power to run and can provide continuous monitoring of radon levels. These devices are expensive and typically used by certified radon testing companies rather than homeowners.

Helpful Resources

  • Free or discounted radon testing kits are often available through state or county health departments (especially during Radon Awareness Month in January).
  • Discounted tests can be purchased from the National Radon Hotline at 1-800-SOS-RADON.
  • General information about radon in drinking water is available through the EPA’s Safe Drinking Water Hotline (800-426-4791).

How to Perform a Radon Test

Carefully read and follow the manufacturer’s directions on your radon test kit. Some of the tests are very specific and may deliver tainted results if the timing is not correct or the test is not mailed back to the manufacturer's lab within the allotted timeframe.

Most home radon tests have similar instructions:

  • Place the test kit in the lowest area of living space in your home.
  • Keep windows and doors closed (except for entering and leaving) for 12 hours prior to testing your home and throughout the duration of the test.
  • Avoid placing the test kit in the kitchen, bathrooms, hallways, laundry room, and rooms that may be drafty.
  • Place the kit at least 20 inches off the floor.

If your radon level is above 4 pCi/L, always be sure to repeat the test to confirm the results. If the average of the results remains above 4 pCi/L, it is strongly recommended that you contact a professional to perform radon mitigation.

Radon Mitigation

If your radon levels are elevated, it important to find a certified radon mitigation company in your area. You can do so by using the National Radon Safety Board (NRSB)'s online locator or by contacting your state radon or public health office.

  • If there is radon in the air: Mitigation is accomplished through ventilation, often by drilling holes in the floor slab of the house and suctioning gas under pressure from the underlying soil.
  • If there is radon above the slab: Mitigation requires sealing the house in an airtight envelope and suctioning gas out of ventilation systems, wall spaces, and crawlspaces.
  • If there is radon in the water: Mitigation involves use of activated charcoal filtration systems. There are also water aeration systems that can release radon into the air from open wells as a pollutant.

A Word From Verywell

Testing for radon is one of the least expensive ways to reduce your risk of lung cancer, whether you smoke or not. If you do smoke, be aware that the combination of radon and tobacco smoke not only puts you at even greater risk of cancer but also anyone you live with.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."