title: Effect of particle size on slow particle clearance from the bronchial tree.
abstract: The Human Respiratory Tract Model of the International Commission on Radiological Protection assumes that a fraction of particles deposited in the bronchial tree clears slowly, this fraction decreasing with increasing particle geometric diameter. To test this assumption, volunteers inhaled 5-microm aerodynamic diameter 111In-polystyrene and 198Au-gold particles simultaneously, as a 'bolus' at the end of each breath to minimize alveolar deposition. Because of the different densities (1.05 versus 19.3 g cm3), geometric diameters were about 5 and 1.2 microm, respectively, and corresponding predicted slowly cleared fractions were about 10% and 50%. However, lung retention of the 2 particles was similar in each subject. Retention at 24 hours, as a percentage of initial lung deposit (mean +/- SD) was 34 +/- 12 for polystyrene and 31 +/- 11 for the gold particles.
authors.affiliation: Health Protection Agency, Radiation Protection Division, Chilton, UK.
authors.forename: J R H
authors.initials: JR
authors.lastname: Smith
authors.forename: M R
authors.initials: MR
authors.lastname: Bailey
authors.forename: G
authors.initials: G
authors.lastname: Etherington
authors.forename: A L
authors.initials: AL
authors.lastname: Shutt
authors.forename: M J
authors.initials: MJ
authors.lastname: Youngman
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000336:Aerosols; D001980:Bronchi / Q000378:metabolism*; D005260:Female; D006046:Gold / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006050:Gold Radioisotopes; D006801:Humans; D007205:Indium Radioisotopes; D008168:Lung / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009079:Mucociliary Clearance / Q000502:physiology*; D010316:Particle Size; D011137:Polystyrenes / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D000336:Aerosols; D006050:Gold Radioisotopes; D007205:Indium Radioisotopes; D011137:Polystyrenes; D006046:Gold