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DOSIMETRY OF LOCALIZED ACCUMULATIONS OF CIGARETTE SMOKE AND RADON PROGENY AT BIFURCATIONS
Citation:
Martonen, T. AND W. Hofmann. DOSIMETRY OF LOCALIZED ACCUMULATIONS OF CIGARETTE SMOKE AND RADON PROGENY AT BIFURCATIONS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-92/114 (NTIS PB92164847).
Description:
Inhalation risk assessment protocols are frequently based upon assumptions of uniform particle deposition patterns and homogenous clearance processes within human lung airways. owever, experiments conducted with cigarette smoke and surrogate airway systems reveal "hot spots" at upper tracheobronchial branching sites. he localized deposits of submicron-sized particles are predicted by a theory, presented herein, imulating the aerodynamic behavior of aerosols clouds. e couple the effects of enhanced deposition with impaired mucociliary clearance for the dosimetry of inhaled cigarette smoke and radon progeny. n accordance with deposition and clearance observations upper tracheobronchial passages may be conceptualized as distinct physical regions: ubular segments, bifurcation zones and carinal ridges. or short-lived radon progeny, we first determine deposition with a validated mathematical model, then account for redistribution. ince mucociliary clearance competes with radioactive decay, surface activity distributions of alpha-emitting radionuclides within the bronchial compartment will not be identical to initial deposition patterns. ur calculations predict that radon progeny accumulations at airway branching sites can lead to significantly higher doses delivered to epithelial cells located within bifurcations, particularly at carinal ridges, than along tubular sections. hese anatomical sites of increased exposure, within the main, lobar, and segmental bronchi, are consistent with clinically reported preferential locations of bronchogenic carcinomas.