Measurement of the Alpha-radioactivity on the Mucosal Surface of the Human Bronchial Tree

Abstract

A new technique has been developed to measure ultra low alfa-activity on the bronchial mucosa of human lung specimens using cellulose nitrate track etch film as the detector. The lower limit of detection of this system for a single film is 0.30 fCi/cm² when the detector is exposed to about 1 cm² of bronchial surface for 100 days and an average efficiency factor is used. Measurements to determine the alfa-activity along the bronchial mucosa were made in seven individuals. A few areas of slightly elevated activity were measured in each of the lungs examined except for that of a young smoker. One area of markedly elevated activity (180 fCi/cm²) was measured in the lung of an older smoker. The mean mucosal surface activity for an individual is determined from a large number of airway samples. The means ranged from 0.01±0.06 fCi/cm² for a young smoker to 0.26±0.04fCi/cm² for an older smoker. The mean value for a nonsmoker was 0.02±0.06 fCi/cm². The average dose rates to the basal cells of the bronchial epithelium from the alfa-activity estimated for each of these seven individuals range from 0.1 to 2.0 mrad/yr. The small area of elevated activity (180 fCi/cm²) could deliver an annual dose of approx. 1 rad. However, total dose cannot be calculated since the residence time of any of these areas on the bronchial tree is unknown. The risk from these dose rates is evaluated in terms of the lung cancer experience of underground miners.