A list of credible sources concerning acceptable indoor radon concentrations are listed below:
1. NCRP, Exposures From the Uranium Series With Emphasis On Radon and Its Daughters – Report 77, National Council on Radiation Protection and Measurement, 1984.
The National Council on Radiation Protection and Measurement in their Report 77 established 0.04 WL as the amount of the concentration of radon and it’s daughters that should be acceptable in nonoccupational occupied structures. Using the current 40% equilibrium assumption that would be 10 pCi/l. This was done in 1984 but it has not beerescindeded by NCRP. The recommendations of NCRP are widely utilizeded in radiation regulatory in the United States especially in the areas of medical uses of radiation.
2. International Commission on Radiation Protection, Website http://www.icrp.org, Statement On Radon, ICRP Ref 00/902/09, 2009