Radon is a cancer-causing, radioactive gas that arises from the natural breakdown of uranium in rocks and soil. The gas seeps up through the ground and diffuses into the air, but it cannot be seen, smelled, or tasted. Outdoors, it is present at harmless levels. It is only indoors, in areas with inadequate ventilation, that radon can accumulate to dangerous levels, increasing the risk of lung cancer (the only cancer proven to be linked to radon exposure).

Concern about radon arose in the late 1960s, when high levels were detected in homes on the West Coast. These houses had been built with contaminated materials from uranium mines.

Radon enters homes through cracks and holes in the foundation. (It can even be released from running water, although radon from water is significant in very few areas of the country.) Once it is in a house, radon can build up to harmful levels if the house is not well ventilated. Thus, radon levels measure the highest in homes that are well insulated, tightly sealed, and/or built on uranium-rich soil.

Because of their closeness to the ground, basements and first floors usually have the highest radon levels.

How Does Radon Cause Cancer?

When radon decays, it emits tiny radioactive particles. If inhaled, these particles can damage the cells lining the lungs, potentially harming their DNA. Long-term exposure to radon can lead to lung cancer.

The U.S. Environmental Protection Agency (EPA) attributes to radon an average of 17,000 lung cancer deaths each year. The surgeon general warns that radon inhalation is second only to smoking among the leading causes of lung cancer.

Just How Much Risk Does Radon Pose?

In a recent report published in the Journal of the National Cancer Institute, scientists estimated that the risk of developing lung cancer increased 14 percent for a person living 30 years in a house with a radon level of 4 picocuries per liter (PCi/L). This is the level at which the EPA recommends taking corrective action to reduce radon in a house.

Nearly one out of every 15 homes in the U.S. is estimated to have radon levels at or above 4.0 PCi/L. The average radon level in U.S. homes is estimated to be about 1.3 PCi/L. By contrast, about 0.4 PCi/L of radon is typically present in outside air. Today, elevated radon levels in most homes can be reduced to 2.0 PCi/L or below.

Testing for Radon

Testing is the only way to know if your home contains elevated radon levels. Fortunately, it is easy and inexpensive.

Do-it-yourself radon detection kits are available at hardware stores and other retail outlets. They cost between $10 and $30. The kits contain a charcoal filter device that samples the air for a certain period of time. The homeowner then mails the filter device to a laboratory listed on the kit. The lab analyzes the filter device and returns the results within a few weeks.

If you prefer to hire a trained contractor to do the testing for you, the EPA recommends that you contact your state radon office for a list of reliable companies that perform radon testing and renovation.

Keep in mind that a neighbor’s test result is an unreliable predictor of radon risk in your home. Indoor radon levels are affected not only by the soil composition surrounding the house, but by how easy it is for radon to enter the house. This means that houses next door to one another can have different indoor radon levels.

Also be aware that weather conditions can cause radon levels to vary from month to month or day to day. Both short-and long-term tests are therefore available.

How to Lower Unsave Levels

A variety of methods can be used to reduce radon levels in your home. Sometimes, simply sealing cracks in floors and walls can correct the problem. In other cases, ventilation systems using pipes and fans (sub-slab depressurization systems) may be needed to reduce radon. Such systems do not require major changes to your home, and they remove radon gas from below the concrete floor and the foundation before it can enter the home.

There are other corrective methods that may work, depending on the design of your home and other factors. Costs for reducing radon levels can range from $500 to $2,500, with an average cost of $1,200.

Radon is found everywhere and is no cause for panic. However, elevated radon levels can affect any type of home in any part of the country. It therefore makes sense for all homeowners to do a radon test.

For more information, call the National Safety Council’s radon hotline at 1-800-SOS-RADON (1-800-767-7236).