What level of radon is dangerous

Radon is the second leading cause of lung cancer after cigarette smoking. If you smoke and live in a home with high radon levels, you increase your risk of developing lung cancer. Having your home tested is the only effective way to determine whether you and your family are at risk of high radon exposure.

Radon is a radioactive gas that forms naturally when uranium, thorium, or radium, which are radioactive metals break down in rocks, soil and groundwater. People can be exposed to radon primarily from breathing radon in air that comes through cracks and gaps in buildings and homes. Because radon comes naturally from the earth, people are always exposed to it.

The U.S. Environmental Protection Agency and the Surgeon General’s office estimate radon is responsible for more than 20,000 lung cancer deaths each year in the U.S. When you breathe in radon, radioactive particles from radon gas 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.

People who smoke and are exposed to radon are at a greater risk of developing lung cancer. EPA recommends taking action to reduce radon in homes that have a radon level at or above 4 picocuries per liter (pCi/L) of air (a “picocurie” is a common unit for measuring the amount of radioactivity).

Your chances of getting lung cancer from radon depend mostly on:

• How much radon is in your home–the location where you spend most of your time (e.g., the main living and sleeping areas)
• The amount of time you spend in your home
• Whether you are a smoker or have ever smoked
• Whether you burn wood, coal, or other substances that add particles to the indoor air

The chances of getting lung cancer are higher if your home has elevated radon levels and you smoke or burn fuels that increase indoor particles.

CDC’s Radon Communication Toolkit is designed for environmental and public health professionals to use to increase awareness and understanding of radon, its health effects, and the importance of testing for radon among the communities they serve. The toolkit contains customizable fact sheets, infographics, newsletter articles, and social media posts. View large image and text description

Test Your Home for Radon

Having your home tested is the only effective way to determine whether you and your family are exposed to high levels of radon. Steps you can take to measure and reduce radon levels include:

More Ways to Take Action

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

For more information on testing your home, visit EPA’s Radon website external iconor call the National Radon Hotline at 1-800-SOS-RADON.

• Stop smoking and discourage smoking in your home.
  • Smoking significantly increases the risk of lung cancer from radon.
• Increase air flow in your house by opening windows and using fans and vents to circulate air.
  • 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.

For more information on testing your home, visit EPA’s Radon website external iconor call the National Radon Hotline at 1-800-SOS-RADON.

To find out more about radon test kits, visit Radon Hotlines and Information Resourcesexternal icon or refer to the EPAexternal icon web site on how to use a test kit.

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What constitutes an acceptable or safe radon level? According to the EPA, the maximum “acceptable” level of radon is 4.0 pCi/L, but even that level is not “safe”, per se. The EPA strongly recommends you consider radon mitigation between levels 2.0 and 4.0. For perspective, the average outdoor air level of radon is 0.4 pCi/L. Professional mitigation is the only reliable way to reduce elevated radon readings.

Frequently asked questions about radon levels:

Is there a “safe” level of radon gas?

Radon is radioactive and hazardous to your health. When inhaled into the lungs, it can damage DNA and cause lung cancer. The “safe” level of radon exposure is no radon at all. The EPA’s recommended level for radon mitigation is 4.0 pCi/L or above.

It’s estimated that 1 in 15 American homes have an elevated level of radon gas. While many newer homes are built with radon-resistant features or passive radon systems, these are not always enough to sufficiently reduce radon levels in your home.

Am I still at risk if my radon levels are below 4.0 pCi/L?

While any amount of exposure to radon gas constitutes a health risk, your risks of contracting lung cancer decrease significantly as radon levels decrease. For example, a person living in a house with a radon level of 4.0 pCi/L or lower has an approximately 7 in 1000 chance of getting sick. On the other hand, a person living in a house with a radon level of 20 pCi/L or higher has a 36 in 1000 chance of contracting lung cancer. The World Health Organization (WHO) established an action level of 2.7 pCi/L based upon a three-year worldwide study by more than 30 prominent scientists.

A radon level of 4.0 pCi/L is still a health risk, which is why it’s important to have professional radon mitigation. Professional mitigation can often reduce radon levels to 0.4 pCi/L. The thing to keep in mind is that the risk for lung cancer from radon is random and defies statistics. People may be exposed for a lifetime at very high levels without getting lung cancer, while others may be exposed at moderate levels for a year or two and contract lung cancer. Radon is one of the few environmental hazards we have some control over.

If I don’t go in the basement, am I safe from radon?

It’s a common radon myth that radon gathers in basements and you can avoid exposure by simply not going in the basement. In reality, when your furnace or air conditioning run at any time during the year, it will circulate that air — and any radon gas that comes with it — throughout the entire house, particularly if there is a return duct in the basement. You can’t avoid a radon problem by staying upstairs. The rule of thumb: radon levels are reduced by approximately 50% per floor going up through the house, except when there is a return duct in the basement.

Can radon levels in our home change without intervention?

Radon levels are always changing. Seasonality plays a role. Winter tends to be worse than summer when heat rising in the house creates a stronger vacuum on the soil. Radon levels spike during heavy wind, rain, or snowy weather.

If you consistently have high levels over a period of time, or if you get a result above 4.0 pCi/L in summer, you most likely need radon mitigation.

Do I need to test for radon if my neighbor’s house passed?

Among the common radon myths is the idea that radon is isolated to certain neighborhoods, or that the results of a radon test in one house are accurate to the next house over. Some think that only certain types of homes are susceptible to radon.

These are misconceptions. Radon is a geological issue. It has little to do with the age of the house, or whether there is a basement. Any structure in touch with the ground has a potential radon problem, including crawlspaces.

As radon maps show, some areas of the country tend to have higher levels of radon than others. However, don’t be lulled into a false sense of security that your home is safe because you live in a “low radon” area. High radon levels can be found anywhere and may vary significantly from one home to the next. Because radon can’t be detected by human senses, the only way to be sure is to conduct a radon test.

How do I reduce radon levels in my home?

If you’ve tested your home and found higher-than-acceptable radon levels, your next step is to look at installing a radon mitigation system. Learn more about how professional radon mitigation works and what to expect from a high-quality radon repair contractor.

Have More Questions?

Please explore our complete Radon FAQs to educate yourself about the what’s, why’s and how’s of radon remediation. Then learn why choosing the best local radon removal company is critical.

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