title: Particulate deposition in the human lung under lunar habitat conditions.
abstract: BACKGROUND
  Lunar dust may be a toxic challenge to astronauts. While deposition in reduced gravity is less than in normal gravity (1 G), reduced gravitational sedimentation causes particles to penetrate deeper in the lung, potentially causing more harm. The likely design of the lunar habitat has a reduced pressure environment and low-density gas has been shown to reduce upper airway deposition and increase peripheral deposition.
  
  
  METHODS
  Breathing air and a reduced-density gas approximating the density of the proposed lunar habitat atmosphere, five healthy subjects inhaled 1 -microm diameter aerosol boluses at penetration volumes (V(p)) of 200 ml (central airways), 500 ml, and 1000 ml (lung periphery) in microgravity during parabolic flight, and in 1 G.
  
  
  RESULTS
  Deposition in the lunar habitat was significantly less than for Earth conditions (and less than in 1 G with the low-density gas) with a relative decrease in deposition of -59.1 +/- 14.0% (-46.9 +/- 11.7%), -50.7 +/- 9.2% (-45.8 +/- 11.2%), and -46.0 +/- 8.3% (-45.3 +/- 11.1%) at V(p) = 200, 500, and 1000 ml, respectively. There was no significant effect of reduced density on deposition in 1 G.
  
  
  CONCLUSIONS
  While minimally affected by gas density, deposition was significantly less in microgravity than in 1 G for both gases, with a larger portion of particles depositing in the lung periphery under lunar conditions than Earth conditions. Thus, gravity, and not gas properties, mainly affects deposition in the peripheral lung, suggesting that studies of aerosol transport in the lunar habitat need not be performed at the low density proposed for the atmosphere in that environment.
authors.affiliation: Department of Medicine, University of California, San Diego, 9500 Gilman Drive, Mail Code 0623A, La Jolla, CA 92093-0623, USA. cdarquenne@ucsd.edu
authors.forename: Chantal
authors.initials: C
authors.lastname: Darquenne
authors.forename: G Kim
authors.initials: GK
authors.lastname: Prisk
mesh_terms: D004391:Dust; D006801:Humans; D008168:Lung / Q000378:metabolism*; D016081:Moon; D010316:Particle Size; D052638:Particulate Matter / Q000378:metabolism*; D013026:Space Flight; D018474:Weightlessness Simulation
chemical_list: D004391:Dust; D052638:Particulate Matter