ABSTRACT
The radiation dose from inhaled daughters of 222Rn constitutes about half of the total effective dose equivalent that the general population receives from natural radiation. This chapter discusses the growing understanding of indoor concentrations and the factors - sources, ventilation rates, environmental Influences and daughter reactions - that affect them. The observation of significant concentrations of radon in ordinary US Radon arises from trace concentrations of radium in the earth's crust, and indoor concentrations depend on access of this radon to building interiors. Establishing a radon mass-balance for a building requires consideration of the sources. Probably important than building materials, as a source of radon in certain parts of the housing stock, is domestic water drawn from underground sources. Despite a broad range of efforts to characterize indoor radon, and a significant number of studies that have included measurements in existing US homes, no unequivocal estimates may be made of the concentrations to which the US population is exposed.
