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CDC - Cancer Cluster archived website note

Historical Document

This document is provided by the National Center for Environmental Health ONLY as an historical reference for the public health community. It is no longer being maintained and the data it contains may no longer be current and/or accurate.

For current information about cancer clusters, please visit

What is radon?

Radon is a naturally occurring radioactive gas that is odorless and tasteless. It is formed from the radioactive decay of uranium. Uranium is found in small amounts in most rocks and soil. It slowly breaks down to other products such as radium, which breaks down to radon.

Radon also undergoes radioactive decay. During the decay process, alpha, beta, and gamma radiation particles are released. Alpha particles can travel only a short distance and cannot travel through your skin. Beta particles can go through your skin, but they cannot go all the way through your body. Gamma radiation can go all the way through your body.

Radon is no longer used to treat diseases such as cancer, arthritis, diabetes, and ulcers. Radon is used to predict earthquakes and in exploration for petroleum and uranium.

How does radon enter the environment?

Radon enters the environment from the soil, from uranium and phosphate mines, and from coal combustion.

What happens when radon enters the environment?

Radon has a radioactive half-life of about 4 days; this means that half of a given amount of radon will decay to other products every 4 days. Some of the radon produced in the soil will move to the surface and enter the air. It can attach to dust and other particles in the air. It occurs at very low levels in outdoor air. Most of the radon will remain in the soil. It can move from the soil to the groundwater.

How can people be exposed to radon?

Radon is found at higher levels in indoor air in homes, schools, and office buildings. Cracks in the basement or foundation of a home can allow higher levels of radon inside the home. Indoor radon levels are affected by the radium and uranium levels in soil, how absorbent the soil is, the composition and condition of the foundation materials, and the ventilation rate of the room. Radon also is found in drinking water and can be higher in well water.

Can exposure to radon make people sick?

Yes, but the only known health problem of radon exposure is lung cancer. Only smoking causes more lung cancer deaths. If you smoke and your home has high radon levels, your risk of getting lung cancer is especially high.

Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe. As they break down further, these particles release small bursts of energy. This can damage lung tissue and lead to lung cancer over the course of your lifetime. The time between exposure and the beginning of the disease may be many years. However, not everyone exposed to elevated levels of radon will develop lung cancer.

Can radon cause cancer?

People exposed to high levels of radon have more lung cancer than people who are not exposed.

Can radon cause leukemia?

Radon exposure in humans has not been linked to leukemia.

What were the results of radon testing in Churchill County?

Radon was measured in the air of the participating families homes. The amount of radon in the air is measured in picoCuries per liter of air (pCi/l). Several households had radon levels between 3 pCi/l and 20 pCi/l.

The Nevada Division of Environmental Protection, Bureau of Health Protection Services suggests that homeowners who have state-conducted radon tests with screening results between 3 and 20 pCi/l conduct repeated short-term testing for a year to verify initial results.

The U.S. Environmental Protection Agency uses an action level of 4 pCi/l. An independent reviewer of radon results suggested that the households with values above 4 pCi/l have another screening sample taken and analyzed before they consider any long-term monitoring.

How can I test my home for radon?

Many kinds of low-cost "do-it-yourself" radon test kits are available through the mail and in hardware stores and other retail outlets. Or you can hire a trained contractor to test for you. Contact your state radon office for a list of these testers. You can also contact one or both of the known private radon proficiency programs for lists of privately certified radon professionals in your area.

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