DEPOSITION PATTERNS OF MOLECULAR-PHASE RADON PROGENY (PO-218) IN LUNGBIFURCATIONS

Indoor air contamination by radon and its decay products is currently the focus of considerable attention and is considered by many to be th e greatest potential cause of lung cancer in the human environment nex t to smoking. The bifurcations of the human respiratory tract are regi ons in which enhanced local deposition of particles (hot spots) can oc cur. These hot spots are important in estimating the risk from radon e xposure but existing mathematical models do not characterize them accu rately. In this study, radon progeny in the molecular size range were sampled through an aluminum model of a lung bifurcation. The parent an d secondary tube diameters used correspond to the third and fourth gen erations in Weibel's lung model. Steady state, nominally laminar flows were used in the study. Deposition was measured along the inside, out side, top, and bottom walls of the secondary tubes. Experimental resul ts indicate that the deposition along the inside wall is noticeably hi gher than that along the other walls. The results also show that along the inside, top, and bottom walls the deposition has its overall maxi mum at the carina. Other maxima are also observed along the secondary tubes downstream from the carina.