Topic Overview

What is radon?

Radon is a radioactive gas that causes cancer. Radon is found in rock, soil, water, some building materials, and natural gas. You can't see, taste, or smell it.

How does radon exposure occur?

Any home, school, office, or other building can have high levels of radon. Radon is found in new and old buildings. It can seep in through the foundation of a house built on radon-contaminated soil. If a house's water supply contains radon, radon may enter the air inside the house through pipes, drains, faucets, or appliances that use water. Then the radon may get trapped inside the house.

Studies show that nearly 1 out of 15 homes in the United States has unsafe levels of radon. footnote 1 If you live in an area that has large deposits of uranium, you may be more likely to be exposed to high levels of radon. (To see a map of the U.S. radon zones, see the website But the construction features and exact location of your house may be just as likely to affect your risk. Even houses right next to each other can have very different radon levels.

What are the health effects of radon exposure?

Over time, exposure to radon can cause lung cancer. Radon causes about 21,000 lung cancer deaths each year in the U.S. It is the second leading cause of lung cancer, after tobacco smoking. footnote 1 People who smoke have an even higher risk of lung cancer from radon exposure than people who don't smoke.

Radon exposure doesn't cause symptoms. Unless your home or office is tested for high radon levels, you may not realize that you are being exposed to dangerous levels of radon until you or someone in your family is diagnosed with lung cancer.

How can you test your home's radon levels?

The U.S. Surgeon General and the U.S. Environmental Protection Agency (EPA) recommend that all homes be tested for radon levels.

You can hire a qualified tester to do the test, or you can use a do-it-yourself test kit. Use only home tests that are labeled "meets EPA requirements." You can buy radon test kits by calling the EPA at 1-800-SOS-RADN (1-800-767-7236). There are two types of tests. Both measure radon levels in the air.

  • The short-term test kit stays in your home or office for 2 to 90 days. Radon levels vary daily and from season to season. So you may want to follow up the first short-term test with a second test.
  • The long-term test kit stays in your home or office for more than 90 days. A long-term test will give more accurate results.

If you have questions about radon in your house, you can get help from the EPA by calling 1-800-55-RADON (1-800-557-2366).

How do you remove high levels of radon?

If tests find a high level of radon, you'll need to reduce it. There are two parts to this:

  • Preventing radon from entering the building. The most common way to do this is through sub-slab depressurization, which vents air from beneath the foundation. This work should be done by a qualified contractor. Other control methods include sealing cracks in the foundation or walls and using air cleaners. footnote 2
  • Venting radon out of the building. Once the radon is prevented from entering the building, venting can be done to reduce the level of radon. These may include using fans, blowers, and suction devices to remove radon in the air in crawl spaces, basements, and other areas.

Use an EPA-qualified contractor with proper training in radon reduction to help with this work.

After radon reduction or prevention procedures are done, the home or building should be retested. You may need to retest more than once. It is usually safe to live in the home or building while the radon is being vented, but you may want to confirm this with your local EPA office.

For general information about removing or reducing radon in your house, you can call the Radon Fix-It Hotline at 1-800-644-6999. If you live outside the U.S., you can call your regional environmental protection office for more information.

Other Places To Get Help


Agency for Toxic Substances and Disease Registry (U.S.)
U.S. Environmental Protection Agency: Radon

Related Information



  1. U.S. Environmental Protection Agency (2012). A Citizen's Guide to Radon: The Guide to Protecting Yourself and Your Family From Radon. Available online:
  2. U.S. Environmental Protection Agency (2010). Consumer's Guide to Radon Reduction. Available online:


ByHealthwise Staff
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology

Current as ofMarch 5, 2015