The pulmonary deposition and retention of indium-111 labeled ultrafine carbon particles in healthy individuals

Context: Particulate air pollution, for example, from ultrafine (UF) particles, has negative health effects. However, there is still limited knowledge regarding the fate of inhaled particles in the human body. Objectives: To describe the normal lung deposition and 1 week particle retention of indium-111 labeled UF carbon particles in healthy subjects. Additionally, the possibility to extend the follow-up period to 4 weeks was also investigated for one of the subjects. Results: The cumulative pulmonary particle clearance 1 week post-administration, corrected for activity leaching and mucocilliary transport of activity deposited in the central airways, was 4.3 +/- 8.5% (average +/- standard deviation at group level), with marginal translocation of particles from lungs to blood, 0.3%. There was no observable elimination of particles from the body via urine. Seven days after exposure, the cumulated activity leaching was 3% (group level), which indicates a stable bonding between the particles and Indium-111. The volunteer followed for a total of 4 weeks, showed a cumulative decrease of activity retention in the lungs of 10.5%. After correction for activity leaching and clearance from central airway deposition, the estimated particle clearance was about 2%. Conclusions: No evidence for particle translocation from the lungs could be proven 7 days after exposure. It is possible to follow-up Indium-111 labeled UF carbon particles at least 1 month post-administration without increasing the administered activity.