Indoor radon in northern Virginia

Radon in homes is a recently recognized hazard of geological origin, regarded in some countries as the second most important cause of lung cancer. In the U.S.A. where up to 20,000 deaths from Rn ingestion may be now taking place, it is estimated that 8-12% of American homes have average indoor Rn levels exceeding the official guidelines. In the U.K. the 'action-level' is about twice as high as in the U.S.A. and in Sweden over 4 times higher, so that the degree of officially recognized risk is a matter of public policy and perception. The relationship between geology and radon levels is not obvious, for in some parts of the U.S.A. homes built on rocks high in U have indoor Rn concentrations much lower than expected. Elsewhere, Rn values have been shown to be influenced by fluctuations in the water table, by soil type, and even by the time of the day. As the authors point out here, in Virginia, where much of the research on Rn has taken place, it is probably more effective to use airborne radioactivity than geology at the surface to gauge regional and seasonal variations in Rn