FIELD STUDY OF WATER TABLE DEPTH AND SOIL-GAS RADON EMANATION

Breathing radioactivity (most commonly found inside homes with basements) has long been recognized as a cause of lung cancer, and drinking radioactive water (most commonly from water wells) has been demonstrated to be a cause of blood and other cancers. In every state, some home occupants are living in communities where the underlying rock and the soil in which their homes are situated are comparatively more radioactive than in other commmunities Occupants of these more-radioactive homes should take precautions to minimize their predictably higher exposure to radioactive interior air and radioactive drinking water. Strong correlations have been demonstrated between radioactivity and rock type. In our Maryland and Virginia study areas, granite and soil developed from granite have much higher radioactivity, and the air in above-granite basements of homes as well as the potable water from these home-site water wells are more radioactive than elsewhere.

Using wells in Maryland and Virginia, comparisons were made between the depth of the well-site water table and the radon emanation from the soil adjacent to these water wells. It was anticipated, but not seen, that changes in the water table were associated with changes in radon soil gas emanation. However, it was anticipated and was found that a shallower water table is associated with less emanation of radon gas from the soil. Our speculation is that the volume of water-free soil determines the amount of radon coming out of the overlying soil. That is, a shallow water table produces a relatively thin layer of overlying water-free soil from which radon (a soluble gas) can escape. By inference, we also speculate that indoor radon, usually measured in the basements of homes, is of lower concentration in communities with a shallow water table (homes often have basement sump-pimps), and the basement indoor radon concentration is lower in all homes where during some time of the year the water table under thase home is shallower than at other times.