Regional deposition of radon decay products in human airways

Experimental studies of the uptake and deposition pattern in the human airways of inhaled radon decay products have been carried out using two different techniques. The total deposited fraction of inhaled decay products was assessed by simultaneous determination of the radon decay product concentration in inhaled and exhaled air. The deposition in the nasal, bronchial and lung regions was assessed by external gamma measurements on the subject. The exposure of the subject was performed in a 'walk-in' radon chamber with controlled conditions. Results from exposure with high and low aerosol concentrations show that no rapid clearance occurred for the deposited decay products. About 20% of the attached inhaled decay products are retained and deposited in the lungs when mouth breathing during resting conditions, while nasal breathing gave about 26% retention, of which 5% was deposited in the nasal region and about 21% in the lungs.