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Indoor Air: Radon - Additional Information

Information provided for informational purposes onlyNote: EPA no longer updates this information, but it may be useful as a reference or resource.

This information will help you gain a better understanding of questions homeowners may have about radon. The sections below provide more information on this topic.

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What is radon?

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What are the health effects of radon?

  • Radon is the second leading cause of cancer.
  • Radon in indoor air is estimated to cause about 21,000 lung cancer deaths each year in the United States. For more information, check out the updated Assessment of Risk for Radon in the Home.
  • Smokers are at higher risk of developing radon-induced lung cancer.
  • Lung cancer usually occurs years (5-25 years) after exposure.
  • There is no evidence that other respiratory diseases, such as asthma, are caused by radon exposure.
  • There is no evidence that children are at any greater risk of radon-induced lung cancer than adults.

For more information on the toxicity of radon, check out information in EPA's Health Effects Notebook and on the Integrated Risk Information System (IRIS).

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How can homeowners test for radon?

Why is it important to test for radon if you are concerned it might be a problem in your home?

  • Because radon is an odorless, colorless gas, it can only be detected by using a testing kit. Home testing will reveal whether radon concentrations within a home have reached dangerous levels.

What should homeowners know about radon testing?

What should homeowners know about radon test kits?

  • Two kinds of tests are available, short-term and long-term.
  • Short-term test kits are less expensive and will provide results quickly. However, short-term tests will not tell you the average annual radon levels.
  • A long-term test, which usually lasts 90 days, will give a more accurate annual average radon level.
  • Acceptable average indoor levels of radon should be around 1.3 picoCuries per liter (pCi/L). Any levels of 4 pCi/L or higher requires mitigation.

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What is radon-resistant home construction?

Radon-resistant new construction are techniques that are built into new homes to lower radon levels. The techniques may also lower levels of other soil gases, decrease moisture problems, and increase energy efficiency. A basic radon reduction system effectively reduces radon levels by at least 50% and, in most cases, to levels below EPA's action level of 4 picoCuries per liter (pCi/L), thereby reducing the risk of lung cancer.

  • Radon-resistant construction consists of creating a gas-permeable layer beneath the slab or flooring system, sealing openings from the foundation to the house, and providing ventilation to move air from the foundation to above the roof, where radon can freely disperse. EPA has more information available on radon-resistant construction.
  • To determine whether radon-resistant construction is needed, contractors can conduct a quick test for existing radon levels during the pre-construction process.
  • When levels of radon are higher than 4 pCi/L, radon-resistant construction should be built into the home. Radon-resistant techniques can reduce levels by at least 50%.
  • Constructing a home with radon-resistant features is cheaper than adding them later.
  • Should the level of radon change over time, these systems are easy to upgrade.

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How can homeowners reduce radon in existing homes?

  • If radon levels are 4 picoCuries per liter (pCi/L) or higher, then homeowners should have their homes mitigated to reduce radon levels. Also, homes with radon levels less than 4 pCi/L still pose a risk and in many cases can be reduced with proper repair.
  • Current technology to mitigate high radon levels in existing homes includes:
    • Sealing cracks in floors and walls.
    • Changing the air flow from the basement through the home.
    • Adding a sub-slab depressurization system.
  • Homeowners should use a certified contractor to properly mitigate their homes.
  • The National Environmental Health Association's National Radon Proficiency Program Exit EPA Disclaimer and National Radon Safety Board Exit EPA Disclaimer maintain a nationwide list of certified radon contractors.

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