Biological effects of inhaled 239PuO2 in rats with pre-existing pulmonary emphysema

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.