title: Deposition, retention, and translocation of ultrafine particles from the central airways and lung periphery.
abstract: BACKGROUND
  Little is known about clearance of ultrafine carbon particles from the different regions of the human lung. These particles may accumulate and present a health hazard because of their high surface area.
  
  
  OBJECTIVE
  Technetium Tc 99m ((99m)Tc)-radiolabeled 100-nm-diameter carbon particles were inhaled by healthy nonsmokers, asymptomatic smokers, and by patients with chronic obstructive pulmonary disease (COPD).
  
  
  METHODS
  Using a bolus inhalation technique, particle deposition was targeted either to the airways or to the lung periphery, and retention, clearance, and translocation were measured using retained radiotracer imaging.
  
  
  RESULTS
  In vitro studies revealed that mean leaching of soluble (99m)Tc-radiotracer from the carbon particles was 4.1 (2.6 [SD]) % after 24 hours. Cumulative (99m)Tc activity in urine at 24 hours was 1.1 (1.3) % of activity deposited in the lungs. In the lung periphery, particle retention was not affected by smoking or pulmonary disease; retention was 96 (3) % after 24 hours. The small amount of clearance could be attributed to leaching of the (99m)Tc label, suggesting negligible particle clearance. In healthy nonsmokers, retention of particles targeted to the airways was 89 (6) and 75 (10) % after 1.5 and 24 hours, respectively. Radiolabel activity did not accumulate in the liver.
  
  
  CONCLUSIONS
  Within the limits of detection of our experimental system, most inhaled ultrafine carbon particles are retained in the lung periphery and in the conducting airways without substantial systemic translocation or accumulation in the liver at 48 hours. Repeated exposure may result in significant pulmonary accumulation of ultrafine particles.
authors.affiliation: GSF-National Research Center for Environment and Health Institute for Inhalation Biology, Robert Koch Allee 29, D-82131 Gauting, Germany. moeller@gsf.de
authors.forename: Winfried
authors.initials: W
authors.lastname: Möller
authors.forename: Kathrin
authors.initials: K
authors.lastname: Felten
authors.forename: Knut
authors.initials: K
authors.lastname: Sommerer
authors.forename: Gerhard
authors.initials: G
authors.lastname: Scheuch
authors.forename: Gabriele
authors.initials: G
authors.lastname: Meyer
authors.forename: Peter
authors.initials: P
authors.lastname: Meyer
authors.forename: Karl
authors.initials: K
authors.lastname: Häussinger
authors.forename: Wolfgang G
authors.initials: WG
authors.lastname: Kreyling
mesh_terms: D000280:Administration, Inhalation; D000336:Aerosols / Q000494:pharmacology*; D000368:Aged; D000393:Air Pollutants / Q000032:analysis / Q000493:pharmacokinetics*; D001692:Biological Transport; D002244:Carbon / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000652:urine; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008168:Lung / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009079:Mucociliary Clearance; D010316:Particle Size; D011336:Probability; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism*; D019275:Radiopharmaceuticals; D012016:Reference Values; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012907:Smoking / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D019275:Radiopharmaceuticals; D002244:Carbon