high-concentration homes will depend on the geology of the area. EPA has separated the United States into three regions of different radon potential (Marcinowski and White 1993). To examine the feasibility of the selective-mitigation approach, we examine the concentration distributions for each of the different radon-potential areas of the United States. In 1989–1990, the EPA conducted the National Residential Radon Survey, NRRS (Marcinowski and others 1994) which provided a statistically valid survey of the distribution of indoor radon concentrations in homes. Each home in the survey was classified by the EPA radon potential region associated with its location. The results are summarized in figure 9.1 for these 3 regions and the entire United States. The lines in the figure were obtained by fitting a lognormal distribution to measured concentrations from each of the three regions.

Scenario 2: Low Radon Potential

To illustrate the problem of finding homes to mitigate, suppose our water supply is in a region of low radon potential. By taking the parameters of the

Figure 9.1

Parameters of the fitted distributions of  222Rn concentrations for homes in the United States based on the NRRS data (Marcinowski and others 1994). Parameters of distributions are as follows.


Geometric Mean (Bq m-3)

Geometric Standard Deviation

Low Potential



Medium Potential



High Potential



All Data



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