Radon

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If your house has between four and 20 pCi/L, you should probably take action to reduce the radon levels in your house within two years. Ten pCi/L is said to be the equivalent of smoking a pack of cigarettes per day, and 20 pCi/L is the equal of two packs per day. Your risk of lung cancer death would be increased by about 7 1/2 and 15 times.

Should your home test at between 20 and 200 pCi/L, you should get busy within a few months. The lung cancer risk will have risen to as much as 75 times normal, the equivalent of puffing away on four packs per day. Houses with such high concentrations are relatively rare.

A few houses — mostly along the infamous Reading Prong in the Northeast — show concentrations greater than 200 pCi/L. At these levels there should be no pause for meditation. Spend a lifetime there, and as many as eight out of 10 of your family members can be expected to die of lung cancer.

Where Does the Radon Come From?

For the most part, radon enters a house because the pressure inside the building is lower than that of the radon-bearing earth resting against the floor and foundation. This pressure differential is caused by wind, changes in barometric pressure, temperature differences between inside and out, and temperature-induced stack effect (where warm air rises in the house to exit through the attic or second-story windows).

In some areas, water is also a significant source of indoor radon. Water from wells 150 feet deep or less may become contaminated with radon from surrounding rock. There is some risk of gastrointestinal cancer from drinking water with radon, but the release of radon to the air as the water is used is usually a greater concern.

Building materials also release some radon, though they're usually not the major contributors in seriously contaminated homes. Of all common building materials, granitic rock is the most highly charged with uranium, but even in a house with a rock fireplace, the internal sources are unlikely to amount to more than 10% of the radon total. However, if the structure was inadvertently built with concrete mixed with phosphate rock or other highly contaminated aggregate, very high radon concentrations are likely.

How Do You Get Rid of Radon?

Cracks as small as 1/128" — too tiny to see without an optical aid — are sufficient for radon to slip inside, so a typical house offers many possible openings. As a result, the radon concentration in your home is more affected by the amount of uranium in the rock and soil around it, and by pressure differential (the driving force), than it is by the inherent leakiness of the floor and walls.

Ventilation Techniques

Strategies for reducing high radon levels will usually have to go beyond mere caulking and will depend on the type of house and its features. The following material gives you an overview of some proven techniques for dealing with various problems. For more detail, write the Center for Environmental Research Information, Distribution, 26 W. St. Clair, Cincinnati, OH 45268, for a free copy of "Radon Reduction Techniques for Detached Houses."

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