Retention of 239Pu in the mouse lung and estimation of consequent dose following inhalation of sized 239PuO2.

The retention of 239Pu in the lungs of SAS/4 mice following inhalation exposure to sized 239PuO2 particles is described. When the initial alveolar deposition (IAD) was less than 200 Bq, retention of 239Pu could be described by a two-component exponential expression, about 90% being cleared with a half-time of about 40 days and the remainder with a half-time of about 150 days. Similar amounts of 239Pu were retained up to 3 months with IADs greater than 800 Bq, but clearance was impaired thereafter, the half-time of the second component increasing to about 720 days. The retention of 239Pu was independent of the particle size of the administered 239PuO2. Studies of the retention of 239Pu by individual lobes indicated that there were intrinsic interlobar differences which were enhanced at higher IADs. Lung clearance was also studied by the measurement of 239Pu in feces excreted by groups of mice in the period immediately prior to sacrifice. The estimation of radiation dose to lung is discussed.