Radon

Overview

Radon is a naturally occurring radioactive gas that forms when uranium, thorium, and radium break down in rocks and soil. Because it has no color, smell, or taste, you cannot detect it without a test. Radon is present in nearly all air, and everyone breathes in small amounts every day.

Outdoors, radon spreads quickly and stays at low levels that are unlikely to cause harm. Radon becomes a problem when trapped inside buildings where it can build up to dangerous levels. Basements and first floors tend to have the highest radon levels because they are closest to the ground.

Related Terms: Ionizing radiation (a category of radiation that includes radon)

Related Health Effects

Radon does not cause symptoms you can feel right away. But long-term exposure can increase the chance of lung cancer, which is an abnormal growth of cells in the lungs. The presence of other indoor air substances, including secondhand smoke, asbestos, arsenic, and some forms of silica and chromium, can increase this chance.

Scientists first recognized radon as a health problem when they noticed that underground uranium miners who were exposed to it died of lung cancer at high rates. Rodents exposed to high levels of radon also showed higher rates of lung tumors.

Radon exposure in adults and children also may increase the risk of leukemia, which is a cancer of the tissues that create blood. But the evidence is not yet conclusive.

Risk Factors

Radon forms from the natural breakdown of uranium, thorium, and radium found in rocks and soil. It seeps up through the ground and can enter buildings through cracks in floors, walls, or foundations. Radon can also be released from building materials.

Radon levels can be higher in homes that are:

• Well insulated or tightly sealed
• Built on soil rich in uranium, thorium, or radium

Radon can also be found in water. Higher levels are more likely from a groundwater source like a private well. Most public water systems use surface water from lakes and rivers, which tend to have lower radon levels.

Workers in uranium, hard rock, and phosphate mining may be exposed to radon at high concentrations, with uranium miners generally believed to have the highest exposures.

Breathing in both radon and cigarette smoke creates a greater risk of lung cancer than either one alone. The majority of radon-related cancer deaths occur among smokers, but an estimated 10 percent of radon-related cancer deaths occur among nonsmokers.

Prevention Guidance

It is not possible to avoid radon completely, but you can take steps to lower your exposure.

Test Your Home

Testing is the only way to know whether radon levels in a home are high. Homes next door to each other can have very different radon levels, so a neighbor’s test result is not a reliable guide for your own home. Rain, snow, barometric pressure, and other factors can cause radon levels to change from day-to-day or month-to-month.

Two types of tests are available:

• Short-term test: Measure radon levels for 2 days to 90 days, depending on the device.
• Long-term test: Measure the average radon level over more than 90 days, giving a better picture of typical exposure.

Both tests are relatively easy to use and inexpensive. A state or local radon official can help explain the differences between testing devices and recommend the best test for your situation.

Check radon levels in your home regularly. Home radon tests are easy to use and do not cost much. Most hardware stores sell these kits. The U.S. Environmental Protection Agency (EPA) provides guidance for reducing radon in schools as well. You can contact your state radon office for information about testing and reduction strategies in schools, daycare and childcare facilities, and workplaces.

Reduce Your Exposure

The EPA recommends taking action to reduce radon in homes with levels at or above 4 picocuries per liter (pCi/L) of air. The EPA also recommends considering repairs when radon levels are between 2 and 4 pCi/L.

Steps recommended by the U.S. Department of Housing and Urban Development to help reduce radon levels include:

• Increase airflow by opening windows and using fans and vents to circulate air to reduce levels temporarily.
• Seal cracks in floors and walls with plaster, caulk, or other materials designed for this purpose.
• Cover earth floors in crawl spaces with a high-density plastic sheet and use a special vent pipe and fan to blow radon from under the sheet to the outdoors.
• Monitor radon levels after any fixes to make sure levels have gone down.

If radon levels in a home are high, a qualified professional can install special vents to make the home safer. This process, known as radon mitigation, can lower your exposure.

The EPA has more information in the Consumer’s Guide to Radon Reduction.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on radon.

Community Support

• EPA Radon provides resources for individuals, homeowners, and builders and contractors, including zone maps and reduction strategies.
• CDC Radon provides information about testing your home for radon.

Note: This resource list is for informational purposes only. It is not comprehensive, and an organization’s inclusion does not constitute an endorsement by NIH.

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

NIH supports ongoing research on radon exposure and its health effects. Researchers also seek ways to raise community awareness of radon risks.

Recent research has focused on measuring the effect of radon in homes on lung cancer risk. Scientists have analyzed data from thousands of people in the United States and Canada and found a slightly increased risk of lung cancer for people with elevated exposure to household radon.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.