Indoor air as an important source for 210Pb accumulation in man.

Pilot study was performed with measurements in a German, inhabited, two-family house, to obtain data on the correlation between the equilibrium equivalent radon concentration Ceq and the 210Pb concentration CPb in indoor air. Aerosol samples were collected in various rooms of the house under conditions of low ventilation. The data indicate a linear correlation between Ce and CPb. A regression analysis, assuming such a relationship, resulted in the following equation: CPb (in mBq.m -3) = 8.2 × 10-3 Ceq (in Bq.m-3) + 0.32. From this relationship it follows that in environments with enhanced radon concentrations direct inhalation of 210Pb is an important source for 210Pb accumulation in man. It was estimated that at an indoor 222Rn concentration of 1000 Bq.m 3, the 210Pb uptake from inhalation amounts 32 mBq.d-1 of which 62% originates from the direct inhalation of 210Pb. Only the remaining third can be attributed to inhaled short-lived radon progeny and to radon gas dissolved in body tissues. It is shown that, in addition to ingestion and even for elevated indoor radon concentrations, direct inhalation of indoor 210Pb is a further important source of uncertainty, when in vivo measurements of the 210Pb activity in the human body are used as a measure of cumulative radon exposure