Biokinetics of Inhaled ²³⁹PuO₂ in the Beagle Dog: Effect of Aerosol Particle Size

Summary

This study was designed to measure the effect of aerosol particle size on the deposition, retention, excretion and translocation of ²³⁹Pu inhaled as the dioxide by Beagle dogs. To address these questions, young adult male and female Beagle dogs received single brief inhalation exposures to one of three monodisperse aerosols of ²³⁹PuO₂ having sizes of 0·72, 1·4 or 2·8 μm activity median aerodynamic diameter (AMAD). Periodic collections of urine and faeces were made for each dog until sacrifice at times ranging from 4 hours to 2 years after exposure. The results indicate long term retention of a substantial percentage of the initial pulmonary burden (IPB), and that the retention was affected by particle size. The percentage of the initial pulmonary lung burden retained in the long term component and its effective half time (T_E) were 90 per cent with T_E = 680 days for the 0·72 μm AMAD aerosol, 68 per cent with T_E = 1400 days for the 1·4 μm AMAD aerosol and 82 per cent with T_E = 1800 days for the 2·8 μm AMAD aerosol. The major route of elimination of ²³⁹Pu from lung was via the faeces, but significant amounts were also translocated to thoracic lymph nodes (∼ 15 per cent IPB by 2 years). Small amounts were translocated to liver (0·2 per cent IPB) and skeleton (0·1 per cent IPB) by 2 years after exposure. The average α-radiation dose to the lung was projected to be twice as large for the 2·8 μm AMAD group as for the 0·72 μm AMAD group at 10 years after exposure.