Radon in dwellings: exposure and risk analysis.

Indoor radon concentrations are approximately lognormally distributed, with the range of concentrations varying from a one in one thousand risk of contracting lung cancer to high one per cent risk. Source strength rather than ventilation rate seems to be the major factor causing the broad distribution in concentrations. There is general agreement that the most important mechanism for radon entry into homes is not diffusion but pressure driven flow of soil gas that carries radon from the soil into the homes. The most effective remedial or control measures are probably first, source control and secondly, ventilation. Air cleaning has a questionable effect.