Lung deposition of particle aggregates: Theory and experimental data
O. Schmid1, W. Möller1, E. Karg1, K. Felten1, G. Ferron1, H. Fissan2, W. Hofmann3, H. Schulz1, and W. G.
Kreyling1
1
Institute for Inhalation Biology, GSF-National Research Center for Environment and Health, 85764,
Neuherberg/Munich, Germany
2
Department of Physical Chemistry, IUTA?, Place, Zip Code, City, Country
3
Faculty of Science (NAWI), University of Salzburg, Hellbrunner Strasse 34, A-5020 Salzburg, Austria,
Keywords: Aerosol measurement, aerosol modelling, agglomerates, inhalation, nanoparticles.
of the bolus inhalation using the USBG model also
reflects this principal behaviour and shows good
agreement with the experimental data. Using a
constant particle density of 2.3 g/cm3 (i.e., shape
effects are neglected) induces a maximum change of
+5% in modelled deposition at 230 nm. This
indicates that our data belong to the diffusion
dominated regime, where sedimentation and
impaction losses are negligible.
0.8
Dep AL
0.7
Dep AW
Dep SB
0.6
Deposition
The lungs are the main entranceway of aerosol
particles into the human organism. Hence, reliable
assessment of aerosol-related health effects requires
accurate knowledge of particle deposition
efficiencies into the lungs. While this issue has been
studied experimentally for spherical particles, the
database on non-spherical particles (e.g. soot
agglomerates) is scarce. In this study we
experimentally determine the lung-deposition of
fractal-like carbon agglomerates from the difference
between inhaled and exhaled aerosol concentration
and compare it to standard deposition models (e.g.
ICRP, 1994) adjusted for shape effects based on the
effective density concept (Schmid et al. 2007).
The regional and total deposition efficiencies
for fractal-like agglomerates
were determined
experimentally using an aerosol bolus inhalation
device (respiratory aerosol probe, RAP). DMAselected,
neutralized
carbon
agglomerates
(Technegas, 99mTc-radioactively labelled, Möller et
al., 2006) in the diameter range between about 30 and
230 nm were inhaled without breath holding by
healthy non-smokers using the RAP. Preferred
airway (AW) or alveolar (AL) targeting was achieved
by inhalation of shallow or deep 100 mL aerosol boli
(with phase 1 dead space or 800 mL as bolus front
depth, respectively) (Möller et al., 2004). In addition,
1.0 L single breaths (SB) were inhaled for
measurements of total particle deposition. Deposition
efficiencies were determined from the difference in
radioactivity (~particle concentration) on filter
samples from the inhaled and exhaled air stream.
Total and regional deposition efficiencies were
calculated using the ICRP-66 deposition model
(Ludep, Version 2.0) and a stochastic lung model
(USBG, Hofmann et al. 1990), respectively,
assuming spherical particles with an effective
mobility density between 2.3 g/cm3 and 0.4 g/cm3 for
limiting diameters of 30nm and 250nm, respectively.
As seen from Fig. 1 the SB aerosol inhalation
shows an increase of deposition with decreasing
particle diameter and is in good agreement with the
ICRP model. AW (shallow) bolus inhalation gives
very low particle deposition reflecting the large
airway structures. AL (deep) bolus inhalation gives
higher deposition than SB due to the enhanced
particle residence time and the large surface-tovolume ratio of alveolar structures. The simulations
USBG AL
0.5
0.4
0.3
0.2
ICRP SB
0.1
USBG AW
0
0
100
200
300
400
Particle mobility diameter, nm
Figure 1: Measured and calculated particle lung
deposition in one subject after inhalation of the deep
(AL) and shallow bolus (AW), and after 1.0 L single
breath (SB) aerosol inhalation.
To our knowledge the data presented here
represent the first measurements of regional (Al,
AW) lung deposition of agglomerates. The results for
carbon agglomerates confirm that standard deposition
models are applicable without adjustment for shape
effects for particle sizes up to about 250nm.
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Schmid, O., Karg, E., Hagen, D.E., Whitefield, P.D.,
and Ferron, G.A. (2007). J. Aerosol Sci., in print.