Radon | American Lung Association


See how the nation can reduce the harm from radon. Read the National Radon Action Plan.

Radon is a naturally occurring gas that can have a big impact on indoor air quality and your health. You can't see or smell it, and radon can build up inside homes, buildings and schools to dangerous levels. Exposure to high levels of radon can cause lung cancer. Learn about radon, how it affects lung health and what you can do about it.

What Is Radon?

Radon is a colorless, tasteless and odorless gas that causes lung cancer. Radon can build up to dangerous levels inside homes, schools and other buildings. Exposure to radon is the second leading cause of lung cancer in the United States, after smoking. 1

Radon gas occurs naturally. It forms when uranium breaks down to radium, which in turn breaks down to form radon. As radon decays, it releases radioactive byproducts that are inhaled and can cause lung cancer. Radon-related lung cancers are responsible for an estimated 21,000 deaths annually in the United States. 1

Where Does Radon Indoors Come From?

Radon is emitted from the ground and enters a home through cracks in walls, basement floors, foundations and other openings. Because radon comes from rock and soil, it can be found anywhere. Exposure to limited concentrations, like those found outdoors, is impossible to avoid. However, when radon gets trapped indoors, it may build up to dangerous concentrations.

The most important source of radon gas indoors is the soil and rock surrounding the building. By sealing your home to keep radon from getting through cracks and openings, you can significantly reduce your home's radon levels. You may need to install a separate radon ventilation system in your home to remove high levels. 3

Less frequently, radon may enter buildings from radon-contaminated drinking water used in bathroom showers and sprays, though this occurs only when the water comes from a private well. More recently, concerns have been raised about the radon released indoors from granite countertops or tiles. However, these sources are rarely a problem by themselves.2, 3

What Are the Health Effects of Radon?

Radon is the second leading cause of lung cancer in the United States, responsible for thousands of deaths each year. Exposure to radon causes no immediate symptoms, but the long-term threat of lung cancer is significant to everyone. People who have never smoked make up approximately 2,900 of the estimated 21,000 radon-related lung cancer deaths each year. 1

The health hazard comes from the radioactive particles that are emitted as radon decays. Those particles can be inhaled into the lung and bombard your cells with dangerous, cancer-causing radiation. 4

Smoking and radon exposure can separately increase the risk of lung cancer. But if you smoke, know that exposure to both greatly enhances the risk of lung cancer.

Who Should Be Worried about Radon?

Every home should be tested for radon. Radon has been found at elevated levels in homes in every state. The U.S. Environmental Protection Agency (EPA) estimates that nearly one out of every fifteen homes in the United States has unsafe indoor radon levels.3 Therefore, every home should be tested for radon.

Your home can have elevated levels of radon while your neighbor's home does not. Testing is the only way to determine if you have a problem. Radon testing is easy and inexpensive and it could save your life. Thousands of lung cancer deaths could be avoided each year if homes with elevated radon underwent changes to reduce radon pollution.1

How Can Radon Be Detected?

The only way to detect a buildup of radon in your home is to test the air. Various forms of do-it-yourself test kits are simple and inexpensive.

See where to get a radon test kit.

If you prefer, hire a certified radon-testing professional. The EPA recommends taking action to reduce radon levels indoors if concentrations exceed 4 picocuries per liter of air (pCi/L). However, no safe level of exposure to radon has been determined. 3

How Do Radon Tests Work?

Tests vary in how they detect radon and the amount of time required to complete sampling.

Do-it-yourself short-term tests typically take two to seven days. During this time the kit, usually no larger than a deck of cards, will sit on a shelf or some out-of-the-way location and absorb or track radon from the building. Once the testing period is complete, test containers are sealed and sent to a laboratory for analysis. Most test kits include the cost of lab analysis and an addressed envelope for submission. In a matter of weeks, you can be notified of the radon level in your home.

Long-term tests tend to be more accurate. They take at least three months and can measure long-term averages. If you don't want to wait for a long-term test, short-term tests are a good way to indicate if your home has a problem and requires follow-up testing. Two short-term tests back to back may be a good way to determine whether you need to take action.

What Can Be Done To Protect Against Radon?

If you find that your home has dangerous levels of radon, there is a solution. High levels of radon indoors can be lowered through a variety of repairs. From sealing cracks in floors and walls to changing the flow of air into the building, you can protect your family. Repairs to decrease radon levels should be made by a U.S. EPA- or state-certified contractor. 3 Detailed information about radon reduction in your home or building can be found in EPA's Consumer's Guide to Radon Reduction. 5

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