Embedded surface radioactivity, radon, and radon progeny in domestic atmospheres

Surface-embedded 210Po activity contains an historical record of the short-lived, deposited radon progeny, and hence a record of the airborne radon and radon progeny concentrations. Physical differences in domestic atmospheres can cause substantial differences in radon dose rates, even at constant activity concentrations. Since deposited radon progeny activities also depend on indoor atmospheric conditions, measurements of this activity can be used, in conjunction with a deposition model and contemporary radon concentrations, to reconstruct past and present dose rates. We have measured contemporary airborne radon, glass surface activity, and deposited radon progeny activity concentrations with 73 detector modules installed on glass surfaces in 31 houses for a 1 year period. Contemporary radon concentrations correlate well with the average historical radon concentrations. By estimating key atmospheric parameters, we were able to calculate, not only integrated radon exposures, but contemporary and historical average annual dose rates. Annual contemporary dose rate estimates ranged from 0.2 to 50 mGy y-1 and correlate well with the historical average doses that ranged from 2 to 80 mGy/y. (orig.). (14 refs, 4 figs., 1 tab.)