Clearance of polonium-210-enriched cigarette smoke from the rat trachea and lung.

The distribution and clearance of alpha radioactivity in the lungs of rats were measured after inhalation of smoke from cigarettes highly enriched in 210Po. Female Fischer rats were exposed daily for 6 months to smoke from cigarettes with 500 times the normal content of 210Po. Control rats were exposed to standard cigarette smoke. Animals were serially withdrawn and killed. After necropsy the trachea, major bronchi, larynx, and nasopharynx were examined for surface alpha activity by an etched track technique utilizing cellulose nitrate detectors. Areas of accumulated activity were seen on samples of larynx from rats exposed to the 210Po-enriched cigarettes. No other local accumulations were seen on the airways. The lower lungs were analyzed radiochemically for 210Po. Both radiochemical analysis and track measurements showed highly elevated activity concentrations in rats exposed to the 210Po-enriched cigarettes. Following withdrawal from smoking, both short- and long-term clearance components were seen. The parameters which fit the postexposure data for clearance of the lung burden cannot fit the buildup during the exposure period.