Tritium Distribution and Excretion Following Intratracheal Instillation of Glass Microballoon Fragments in Rats

The distribution and time course for tritium activity in Sprague-Dawley rats exposed to tritiated glass fragments by intratracheal instillation have been defined. Particles were deposited primarily in the pulmonary region, allowing for the measurement of long-term tritium dissolution and particle movement. The tritium activity of the body water and tissues was found to follow a three-compartment model where tritiated glass fragments provide a continuous input to the body water, and tritium was removed from the body according to the classical elimination pattern for HTO. The dissolution of tritium in vivo was found to be biphasic with exponential function half-times of 6.3 +/- 0.5 and 43 +/- 3 days, respectively. The glass fragments were removed from the pulmonary region slowly, with a half-time of 150 +/- 30 days. The resultant dose to the lung was three orders of magnitude greater than the dose to the body, and approx. 40 times greater than the dose incurred in the lung from the inhalation of a similar quantity of HTO. A theoretical urine tritium time course for the inhalation of glass fragments was found to resemble the typical HTO patterns for several months post-exposure. The similarity of tritiated glass and HTO urine activity will make the determination of the type of exposure difficult.