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Fact Sheet


What is radon?

Radon is a colorless, odorless radioactive gas which comes from the natural breakdown (radioactive decay) of radium, which is itself a decay product of uranium. Uranium and radium are both common elements in the soil.

Where is radon found?

The major source of high levels of radon in homes is soil surrounding the house, particularly soil containing uranium, granite, shale, phosphate and pitchblende. Radon gas from the soil can enter a home or building through dirt floors, hollow-block walls, cracks in the foundation floor and walls, and openings around floor drains, pipes and sump pumps.

Radon is more concentrated at lower levels, like basements, ground floors and first floors.

Radon problems have been identified in every state. The U.S. Environmental Protection Agency (EPA) estimates that as many as one in 15 homes in the U.S. have elevated radon levels.

Any home may have a radon problem. The National Safety Council and the Environmental Protection Agency recommend testing all homes below the third floor for radon. Testing in schools is also recommended.

What are the health effects of radon?

Radon is the second leading cause of lung cancer, causing thousands of deaths each year in the United States. It is the leading cause of lung cancer in non-smokers. As radon decays and is inhaled into the lungs, its byproducts release energy that can damage sensitive lung tissue and lead to lung cancer.

How is radon measured?

Radon is measured in picocuries per liter (pCi/L) of air. EPA recommends placing a test kit in the lowest lived-in level in a home where it is left to gather a reading for the amount of time specified on the kit. Then it is simply returned to the laboratory for results. If results indicate a high radon level, a second test should be conducted to verify results.

What can be done about radon?

A variety of methods are used to reduce indoor radon levels, from sealing cracks in floors and walls to changing the flow of air into the home. If test results indicate a radon problem, a state certified and/or EPA-qualified contractor who specializes in reducing radon levels should be consulted.

Environmental Protection Agency

Contact the South Dakota Safety Council at
or phone 605-361-7785 or 1-800-952-5539.