Radon Gas

Radon is a naturally occurring, colorless, odorless, radioactive gas. It can seep into homes and other buildings. If a person breathes high radon levels over time, they can develop lung cancer, especially if they smoke. Tests can measure radon in a home or other building, and radon mitigation effectively lowers dangerous levels.

What is radon?

Radon is a colorless, odorless, radioactive gas. If a person is exposed to high levels over time, it can cause lung cancer.

Radon gas forms naturally when radioactive metal (radium, thorium or uranium) breaks down in rocks, soil or groundwater. It evaporates and disappears outdoors, so levels outside are low. Indoors, however, radon gas can enter buildings through their foundations and become trapped. People may breathe in radon gas in their homes, school, workplaces and other indoor places.


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How does radon gas affect my body?

Breathing in high levels of radon over time can increase your risk of developing lung cancer. Cigarette smoking is the number one cause of lung cancer, and radon exposure is estimated to be the second leading cause. About 20,000 people in the United States die from radon-related lung cancer every year.

People who smoke cigarettes and breathe in radon have an even higher chance of developing lung cancer.

Where is radon gas found?

Radon has been found in every state in the U.S. The amount or levels of radon varies across the country, depending on the kinds of rocks and soil in each area. Because of their working environment, miners are at increased risk for radon exposure.

Radon gas is also found in all kinds of indoor spaces. For the general population, the greatest exposure happens in the home. The U.S. Environmental Protection Agency (EPA) estimates that elevated radon levels are present in one of every 15 American homes.

Radon levels are usually higher in places that are:

  • Closer to the ground, such as basements or underground mines.
  • Near soil that contains more radioactive metal.
  • Poorly ventilated.
  • Processing or storing certain products, such as phosphate fertilizers or uranium.
  • Very tightly sealed.
  • Very well-insulated.


What causes radon exposure?

When radioactive rocks and soil break down, they release radon gas. That gas can enter buildings through:

  • Construction joints.
  • Cracks in walls or floors.
  • Gaps in foundations.
  • Openings near pipes or wires.

Less commonly and in smaller amounts, radon can be released from:

  • Building materials made from natural substances, such as concrete, wallboard and granite countertops.
  • Water, especially water that comes from underground wells.

What are the symptoms of radon exposure?

There are no immediate signs or symptoms from breathing in background radon.

Repeated exposure over time — around 20 years — can lead to cancer development, especially if you are also a smoker.

Symptoms of lung cancer may include:

  • Chest pain.
  • Cough.
  • Difficulty breathing.
  • Hoarse or sore throat.
  • Trouble swallowing.


How is radon exposure diagnosed?

No medical test is widely available to test the human body for radon exposure.

If you have a high-risk occupation for radon exposure (such as miners), your home test reveals elevated levels of radon, or you think you’ve been exposed to high levels of radon, talk to a healthcare provider about your risk.

If you are or have been a smoker, you may qualify for lung cancer screening. Having any persistent respiratory symptoms should prompt a visit to your healthcare provider.

Can I test the radon level in my home?

Yes. Home testing is an important measure to take, especially if you live in an area where radon levels are higher.

The EPA estimates that six million homes in the US currently have radon levels that are considered unsafe.

You can test the radon level by hiring a professional or buying a do-it-yourself kit at a home-improvement store. Most radon testing kits include two-day or 90-day tests, which you mail to the test kit manufacturer for results.

What can I do if the level of radon is high?

If the building's radon level is high (more than 148 Bq/m3 or 4 pCi/L), you should hire a professional for what is called radon mitigation services. These can reduce radon levels by as much as 99%. Possibilities include:

  • Home pressurization, which uses a fan to blow air and create enough pressure to stop radon from entering the home.
  • Improvements to air exchange in the building.
  • Plastic sheeting in homes with crawl spaces.
  • Repairs to cracks in the foundation.
  • Soil suction, which pulls radon from under the home and vents it through a pipe into the air.
  • Tests on the soil and home appliances.
  • Underground or other types of ventilation systems.

You should retest radon levels after mitigation efforts to make sure levels go down.

How can I reduce my risk of radon-related lung cancer?

Radon is part of our natural environment, so you can’t avoid it entirely. However, these strategies can reduce your risk:

  • Increase airflow in your home or office by opening windows and using fans frequently (this works temporarily).
  • If you smoke, attempt to quit and seek help if you need to.
  • Don’t let people smoke in your house — not even the basement or garage.
  • Seal any cracks in your floors, walls or foundation.
  • Test your home and office for radon levels regularly.

The federal government has regulations about radon levels in workplaces. If you think your workplace might have high radon levels, talk to the company’s safety officer, or contact the Occupational Safety and Health Administration.

What is the outlook for people who have radon-related lung cancer?

It is hard to determine if a lung cancer has formed only from radon exposure, or if other factors made an impact (such as smoking or genetics). A radon-related lung cancer would behave and be treated just as other cancers would be, depending on its type and stage.

The outlook for people with lung cancer varies greatly, depending on:

  • History of smoking.
  • How early lung cancer is detected.
  • The type of cancer (seen under a microscope).
  • The stage of cancer.
  • Overall health.

People who smoke do have an increased risk for lung cancer. That risk is higher if they are also exposed to radon. However, even people who have never smoked may develop lung cancer because of genetic risk or risks in their environment (including radon).

If you are worried about any of your risk factors, please talk to your provider. Lung cancer is the second most common cause of cancer in men and women, and it has the highest death rate of any cancer. It’s important to reduce your risk and find it early if possible.

A note from Cleveland Clinic

Radon is a colorless, odorless, radioactive gas. It can cause lung cancer when people breathe in too much of it over time. Smoking increases the chances that radon gas inhalation will lead to lung cancer. Simple tests can detect too much radon in homes, schools, offices and other indoor spaces.

Medically Reviewed

Last reviewed on 04/30/2021.

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