NATIONAL AND REGIONAL DISTRIBUTIONS OF AIRBORNE RADON CONCENTRATIONS IN UNITED-STATES HOMES

The National Residential Radon Survey was conducted during 1989 and 19 90 to provide data on the frequency distribution of annual average rad on concentrations in U.S. residences nationwide, in U.S. Environmental Protection Agency defined Regions, and in subgroups of the housing st ock. The National Residential Radon Survey also provided housing and d emographic data and a preliminary assessment of the relationship of ho using and geographical characteristics to residential radon concentrat ions. This paper focuses solely on the national and regional estimates of annual average radon concentrations. A stratified, three-stage sam pling procedure was used to select housing units for the survey. Data were collected through personal interviews with residents and placemen t of alpha track detectors in each level of the residences for 12 mo. The survey found an arithmetic annual average radon concentration in U .S. homes of 46.3 +/- 4.4 Bq m-3 (1.25 +/- 0.12 pCi L-1). About 6.0 +/ - 1.4% of homes (5.8 million) had radon levels greater than the U.S. E nvironmental Protection Agency's action level for mitigation of 148 Bq m-3 (4 pCi L-1). Concentrations varied significantly across Environme ntal Protection Agency Regions. A lognormal distribution was found to closely approximate the major distributions of radon concentrations.