Retention and excretion of ³H in rats following the intratracheal intubation of tritiated pump oil.

Saturated hydrocarbon mineral oils in vacuum pumps used in ³H handling facilities often contain significant amounts of ³H (as much as several hundred GBq L⁻¹), and during maintenance the air around an open pump may contain MBq L of volatile and aerosol species. It follows that H-contaminated pump oils pose a workplace hazard-especially if inhaled deposits are retained in the lung. A long-term study (1-y duration) was undertaken to establish the retention time of ³H-pump oil in the lungs of rats. Excretion data was collected to establish the mechanism of oil clearance from the lung. Finally, liver data was collected both to indicate the levels of H in the rat body and to indicate either the presence or absence of the transfer of unmetabolized pump oil within cells from the lungs to liver. Within 1 d following intubation into the trachea, ∼16.5% of the emulsified pump oil had been rapidly mechanically cleared to feces, and 1.1%, present as HTO, or exchangeable H, was excreted in urine. 69.4% of the instilled dose remained in the lungs as the initial alveolar burden. Subsequently, H cleared from the lungs with a retention half-time of of 223 d. The lung burden was mostly cleared to feces-indicating that the pump oil droplets remaining in the lungs were behaving like insoluble particles, but the kinetics of clearance of particles and oil droplets may be different. Overall, it is concluded that inhaled H-pump oil should most likely be regarded as an insoluble particulate (ICRP Inhalation Type S) for the purposes of radiological protection dosimetry, but the possibility of Type M behavior cannot be excluded.