Health Topic

Radon

Radon comes from the natural breakdown of uranium in soil, rock, and water. It is the second leading cause of lung cancer. Test your home for radon levels.

Reviewed Reviewed by a registered pharmacistGeneral information

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Radon

Radon is a naturally occurring radioactive gas. It is invisible and has no odor or taste. It comes from the normal decay of uranium and thorium. These are two chemical elements that can be found in soil, rock, and groundwater. Radon breaks down quickly, giving off radioactive particles. Over time, breathing in high levels of these particles can cause lung cancer.

Outdoors, there are low levels of radon in the air. But radon can also be indoors. It can enter homes and buildings through cracks in the floors, walls, or foundations. Certain building materials can give off radon. And sometimes radon gets inside through well water.

Radon levels can be higher in homes and buildings that are well insulated, tightly sealed, and/or built on soil that has a lot of uranium and thorium. Basements and first floors usually have the highest radon levels because they are closer to the ground.

When you breathe in radon, its radioactive decay products can get trapped in your lungs. They can damage the cells that line your lungs. Over time, it can lead to lung cancer. It may take years before this happens.

Radon is the second leading cause of lung cancer deaths after cigarette smoking. If you smoke and are exposed to radon, your risk of lung cancer is much higher than if you did not smoke. Most radon-related cancer deaths happen in smokers.

Testing is the only way to know if there are high levels of radon in your home. You should test your home's radon levels:

  • If it's never been tested or the radon levels are unknown
  • When preparing to buy or sell your house
  • 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 (such as converting a basement to a bedroom)

Testing is fairly inexpensive and easy to do. You can buy a test kit at most hardware stores or hire someone to do a test. It's a good idea to first contact a state or local radon official for advice. They can explain the differences between testing devices and recommend the most appropriate test for your needs. They can also give you a list of qualified radon testers.

There are both long- and short-term 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

Radon levels can vary from day to day and month to month. So a long-term test will give a better estimate of your average radon level.

If the testing shows that you have an unsafe level of radon in your home, you can have a radon reduction system installed. It can bring the amount of radon down to a safe level. The cost of the system will depend on the size and design of your home.

You can also take some other steps to reduce radon levels in your home:

  • Increase air flow in your house by opening windows and using fans and vents to circulate air. But this will only temporarily reduce the radon levels.
  • Seal cracks in floors and walls with plaster, caulk, or other materials designed for this purpose.
  • After any fixes, monitor the radon levels to make sure that they are lower.

It sits within Poisoning, Toxicology, Environmental Health.

The lead U.S. institute for this subject is the National Institute of Environmental Health Sciences.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Radon

12 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

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Medical subject headings

Clinicians and researchers index this subject under Radon. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Radon, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.