plutonium-dioxide and Body-Weight

To study the long-term biological effects of repeated inhalation exposure to 239PuO2, 84-day-old rats were exposed to aerosols of 239PuO2 to re-establish desired 239Pu lung burdens of 26, 80 or 250 Bq every other month for 1 year (seven exposures). Other rats were exposed once at 84 or 450 days of age to achieve desired initial lung burdens of 30, 90, 280 or 850 Bq. The incidences of lung tumors were not significantly different (Fisher's exact test; P > 0.05) in groups of rats with similar lifetime mean alpha-particle doses to the lungs of 0.90 +/- 0.39 to 4.4 +/- 1.8 (+/- SD) Gy, whether exposed once or repeatedly. Among rats with mean alpha-particle doses of 12 +/- 2.4 to 10 +/- 2.1 Gy to the lungs after single or repeated exposures, respectively, the crude incidence of lung tumors was significantly less (Fisher's exact test; P < 0.05) in the rats exposed repeatedly. Times to death of rats with lung tumors were compared among groups with similar alpha-particle doses to the lungs after single or repeated exposure to 239PuO2. Those that died with lung tumors after repeated exposures died at times similar to (Mantel-Cox statistic; P > 0.05) or later than (Mantel-Cox statistic; P < 0.05) those for 84-day-old rats exposed once. The risk of lung tumors in rats per unit dose to the lungs was less in the rats exposed repeatedly than in those exposed once. It was concluded that alpha-particle doses to the lung of rats exposed repeatedly to aerosols of 239PuO2 were not more carcinogenic and possibly were less carcinogenic than the dose after a single inhalation exposure when rats with similar lifetime alpha-particle doses to the lungs were compared. The relative biological effectiveness in rats of the alpha-particle dose to the lungs from inhaled 239PuO2 relative to beta-particle doses to the lungs from inhaled 144CeO2 was 21 +/- 3.

Topics: Administration, Inhalation; Aerosols; Alpha Particles; Animals; Beta Particles; Body Burden; Body Weight; Female; Lung Neoplasms; Male; Metabolic Clearance Rate; Neoplasms, Radiation-Induced; Plutonium; Radiation Dosage; Rats; Rats, Inbred F344; Sex Factors

The modifying effects of pre-existing pulmonary emphysema on the deposition, distribution, retention and effects of inhaled 239PuO2 in the rat were investigated. The presence of emphysema in the rats was documented by morphometric and respiratory function measurements. For rats exposed to similar airborne concentrations of 239PuO2, initial lung burdens of 239Pu per kg body mass were lower in rats with emphysema than in those without emphysema; however, the retention of 239Pu over time was similar in both groups. The distribution of 239Pu particles in the lungs of rats with emphysema tended to be more random than in the lungs of control rats. The life span, and incidences of non-neoplastic and neoplastic lesions in the lung, and risk of lung tumours per unit of alpha dose to the lungs in the rats with emphysema were similar to or less than in the control rats, when groups with similar initial lung burdens of 239Pu were compared. The results of this study suggest that humans with uncomplicated pulmonary emphysema are not necessarily more sensitive to the carcinogenic effects of inhaled 239PuO2 than individuals with normal lungs.

Topics: Administration, Inhalation; Animals; Body Weight; Female; Lung; Lung Neoplasms; Male; Plutonium; Pulmonary Emphysema; Rats; Rats, Inbred F344; Respiration; Survival Rate; Tissue Distribution