Chapter 7-Concentration Patterns
DURING THE 1970S AND EARLY 1980S, radon measurements collected in U.S. residences resulted mainly from isolated research efforts involving a variety of measurement techniques and relatively small numbers of homes. As described by Nero et al. , most of these data sets were collected either (1) as a basis for estimating the potential effects of reduced air infiltration due to energy conservation measures or (2) to better characterize certain geographic areas thought to have a high likelihood of elevated indoor radon concentrations. After carefully assimilating and analyzing these collective data sets, the authors projected that approximately 7% of U.S. residences had average indoor radon concentrations at or above 148 Bq/m3 (4 pCi/L), the level at which the U.S. Environmental Protection Agency (EPA) has recommended that citizens take action to reduce their exposures . More recently, a nationwide survey of annual average radon concentrations by the EPA has indicated that about 6% of U.S. residences would be expected to have average indoor concentrations at or above 148 Bq/m3.
Senior research scientist and manager, Indoor Air and Exposure Program, GEOMET Technologies, Inc., Germantown, MD
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