ArticlePDF Available

Implementation of Charged Particles Deposition in Stochastic Lung Model and Calculation of Enhanced Deposition

Authors:

Abstract and Figures

The experimental studies using hollow lung cast of human tracheobronchial (TB) tree and in-vivo experiments have demonstrated enhanced charged deposition in the lung. The present study was carried out to implement charge particle deposition into the stochastic human lung model and to estimate enhanced deposition for various charged particles at the airway generation level. Enhanced deposition calculations of charged particles are performed by implementing two different efficiency equations derived for the TB and alveolar (Al) region. Deposition fractions of inhaled charged particles are computed by the stochastic airway generation model IDEAL (Inhalation, Deposition and Exhalation of Aerosols in the Lung) for various breathing conditions and particle sizes. Enhanced deposition of charged particles in the Al region is found to be up to five times higher than in the TB region. Enhanced deposition in the TB region is higher under sitting breathing condition than under light exercise breathing condition. The introduction of pause time, during inhalation, increases the probability of increased enhanced deposition up to a certain breath-hold time limit. The calculated enhancement factors (EF) reveals that more than two times higher deposition can be achieved in the lung by the introduction of charged particles during inhalation. By introducing the charged particles during inhalation and by optimizing the flow rate, tidal volume, and particle size, the targeted deposition in the lung is improved for the best therapeutic aerosols utilization. In addition, the unnecessarily high deposition of toxic particles in the sensitive lung regions can be avoided.
Content may be subject to copyright.
This article was downloaded by: [Universitat Salzburg]
On: 11 January 2012, At: 11:16
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Aerosol Science and Technology
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/uast20
Implementation of Charged Particles Deposition in
Stochastic Lung Model and Calculation of Enhanced
Deposition
Hussain Majid
a
b
, Pierre Madl
a
, Werner Hofmann
a
& Khan Alam
b
a
Department of Materials Engineering and Physics, Division of Physics and Biophysics,
Radiation and Environmental Biophysics Working Group, University of Salzburg, Salzburg,
Austria
b
Higher Education Commission of Pakistan, Islamabad, Pakistan
Available online: 07 Dec 2011
To cite this article: Hussain Majid, Pierre Madl, Werner Hofmann & Khan Alam (2012): Implementation of Charged Particles
Deposition in Stochastic Lung Model and Calculation of Enhanced Deposition, Aerosol Science and Technology, 46:5, 547-554
To link to this article: http://dx.doi.org/10.1080/02786826.2011.645957
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to
anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation that the contents
will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should
be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims,
proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in
connection with or arising out of the use of this material.
Aerosol Science and Technology, 46:547–554, 2012
Copyright
C
American Association for Aerosol Research
ISSN: 0278-6826 print / 1521-7388 online
DOI: 10.1080/02786826.2011.645957
Implementation of Charged Particles Deposition in
Stochastic Lung Model and Calculation of Enhanced
Deposition
Hussain Majid,
1,2
Pierre Madl,
1
Werner Hofmann,
1
and Khan Alam
2
1
Department of Materials Engineering and Physics, Division of Physics and Biophysics, Radiation and
Environmental Biophysics Working Group, University of Salzburg, Salzburg, Austria
2
Higher Education Commission of Pakistan, Islamabad, Pakistan
The experimental studies using hollow lung cast of human
tracheobronchial (TB) tree and in-vivo experiments have demon-
strated enhanced charged deposition in the lung. The present study
was carried out to implement charge particle deposition into the
stochastic human lung model and to estimate enhanced deposition
for various charged particles at the airway generation level. En-
hanced deposition calculations of charged particles are performed
by implementing two different efficiency equations derived for
the TB and alveolar (Al) region. Deposition fractions of inhaled
charged particles are computed by the stochastic airway generation
model IDEAL (Inhalation, Deposition and Exhalation of Aerosols
in the Lung) for various breathing conditions and particle sizes.
Enhanced deposition of charged particles in the Al region is found
to be up to five times higher than in the TB region. Enhanced depo-
sition in the TB region is higher under sitting breathing condition
than under light exercise breathing condition. The introduction
of pause time, during inhalation, increases the probability of in-
creased enhanced deposition up to a certain breath-hold time limit.
The calculated enhancement factors (EF) reveals that more than
two times higher deposition can be achieved in the lung by the in-
troduction of charged particles during inhalation. By introducing
the charged particles during inhalation and by optimizing the flow
rate, tidal volume, and particle size, the targeted deposition in the
lung is improved for the best therapeutic aerosols utilization. In
addition, the unnecessarily high deposition of toxic particles in the
sensitive lung regions can be avoided.
Received 29 September 2011; accepted 23 November 2011.
The authors wish to thank Dr. Renate Winker-Heil for her support
in modifying and using the IDEAL code.
Funding: This work was funded by the Higher Education Commis-
sion of Pakistan under the scholarship program (Overseas Scholarships
for Pakistani Nationals).
Address correspondence to Hussain Majid, Department of Mate-
rials Engineering and Physics, Division of Physics and Biophysics,
Radiation and Environmental Biophysics Working Group, University
of Salzburg, Hellbrunnerstr 34, A-5020, Salzburg, Austria. E-mail:
majid.hussain@stud.sbg.ac.at
INTRODUCTION
Consideration of charged particle distribution with respect
to lung deposition is important in the industrial hygiene con-
text since the freshly generated aerosols in workplace atmo-
sphere may have charges well above the Boltzmann equilibrium
(Johnston et al. 1985; Vincent 1985; Forsyth et al. 1998). Sim-
ilarly, aerosols produced by commercial metered dose inhalers
can produce elementary charges per drug particle that range
from zero to several ten thousands (Kwok et al. 2005). Ex-
perimental studies based on human airway casts and in-vivo
experiments have shown that particle charge significantly af-
fects deposition in the tracheobronchial (TB) and alveolar (Al)
regions. Yu and Chandra (1977) found that single-charged 20-
nm particles deposited up to four times higher than charge-
neutralized aerosols and up to five times higher the amount
deposited for zero-charged aerosols. The corresponding ratios
for 125-nm particles are two and six times, respectively. Chan
et al. (1978) showed that charged particles between 2 µm and
7 µm, deposited significantly higher than uncharged particles.
Cohen et al. (1998) found at least three-fold enhanced deposi-
tion for monodisperse nanoparticles carrying a single positive
elementary charge than was observed for neutralized ones dur-
ing in-vitro studies using a tubular tracheal model and a hol-
low airway cast. Other experimental work carried out in human
subjects showed that negatively charged particles deposit more
effectively than uncharged particles, with the greatest effects of
charge occurring for submicron particles (Scheuch et al. 1990).
Melandri et al. (1977, 1983) found that unipolar charges on
monodisperse aerosols results in increased deposition in the hu-
man lung that is proportional to the amount of charges carried
per particle above a threshold level. Similar effects of electro-
static forces on deposition were obtained by Bailey et al. (1998)
for 0.5-µm and 5.0-µm particles.
Enhanced deposition due to particle electrostatic charge
may take place by two deposition processes, i.e., due to (i)
space charge effects and (ii) the image charge force. The space
charge effect arises if densely charged aerosols are inhaled. The
547
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
548 H. MAJID ET AL.
repulsive force among the charge cloud may result in depo-
sition, but this effect is usually insignificant. However, in the
second process, a charged particle induces an image charge on
any grounded nearby surface. During image charge attraction,
a particle always induces an equal and opposite charge to itself
on a surface such as an airway wall, which always results in
a net attractive force, regardless of particle polarity. Although
human airways are normally electrically neutral, image charges
with equal magnitude and opposite polarity to the charged par-
ticles may be induced on the surfaces, especially inside small
airways in the peripheral lung (Bailey et al. 1998). Yu (1985)
demonstrated that for particle concentrations lower than 10
5
par-
ticles/cm
3
, the electrostatic repulsive force is not important be-
cause the particles are relatively far apart. Therefore, increased
deposition of charged particles is mainly due to image force.
The significance of charged particles may be of more concern
for aerosol therapy than for inhalation toxicology. The adminis-
tering medication in the form of a charged aerosol may increase
the probability of deposition in the targeted regions. In this way,
the dose level of a given drug can be administered for adequate
clinical response, and at the same time minimizing possible side
effects. Several models to predict the effect of charge particle
on deposition in the respiratory system have been developed
(Chan and Yu 1982; Melandri et al. 1983; Yu 1985; Hashish
et al. 1994b). These models deal with the deposition of charged
or neutral inhaled aerosols and are in good agreement with ex-
perimental data. In the present study, enhanced deposition in
the human lung due to charged particles has been estimated us-
ing the stochastic airway generation model IDEAL (Inhalation,
Deposition and Exhalation of Aerosols in the Lung).
Thus, the primary objectives of this study are (i) to implement
charge particle deposition in the stochastic human lung model
(TB and Al regions), (ii) to predict enhanced deposition for
various charged particles at airway generation level and to com-
pare results with previous studies, (iii) to quantify the breathing
effects on charged particle deposition, and (iv) to calculate en-
hancement factors (EFs) for various breathing conditions.
METHODS
Charged particles deposition calculations were performed us-
ing two different efficiency equations derived for airways tubes
(TB) region and spherical shaped gas-exchange (Al) region. For
TB airways, enhanced charged particles deposition by image
force was calculated by implementing the following Yu (1985)
efficiency equation:
η
q
=
8B
πε
0
d
3
t
t
0
1/2
(
q q
0
)
, [1]
where B is the mechanical mobility of the particle, ε
o
is the
electric permittivity of air, and t
0
is the is the mean residence
time of particles in airway tube. All values of variables and
constants are based on CGS system of units. The enhanced
total deposition due to particle charges q is proportional to the
increase in threshold charge limit (q–q
c
), where q
c
is a threshold
charge limit. The threshold charge limit varies with particle size,
airway diameter, and the residence time of particles in an airway
segment. The threshold charge limit considered for 0.3-, 0.6-,
and 1.0-µm particles are 10, 30, and 54 elementary charges,
respectively, below which particle charges have minor effect
on enhanced deposition (Yu 1985). For the spherical Al region,
enhanced deposition by image force is calculated as a function
of Al diameter d
alv
by implementing the following equation
derived by Melandri et al. (1983):
η
q
=
1
d
alv
5Bq
2
πε
0
t
0
1/3
, [2]
where t
0
is the mean residence time (in seconds) of particles
in the Al airways. Whereas, the enhanced deposition (ED) was
obtained by applying the following relation:
ED =
DF
q
DF
0
DF
0
× 100, [3]
where DF
q
and DF
0
are the deposition fractions with and with-
out charge load. DF
0
refers to deposition fractions caused by
conventional deposition mechanisms, i.e., diffusion, sedimen-
tation, and impaction. The effect of charged particle deposition
in the lung is considered as an additive to conventional deposi-
tion mechanisms (Melandri et al. 1983). The deposition fraction
considered herein consists of the number of particles depositing
in a given generation in relation to the total number of particles
entering the respiratory tract.
Deposition fractions for unit density monodisperse charged
particles of 0.3-, 0.6-, and 1.0-µm diameter are computed un-
der sitting and light exercise breathing conditions. Flow rates
for sitting and light exercise conditions are assumed to be
18 and 50 L min
1
, respectively (International Commission
on Radiological Protection [ICRP] 1994), whereas the cor-
responding tidal volumes are 750 and 1250 mL and breath-
ing cycle times are 5 and 3 s, respectively. Furthermore,
steady breathing with equal inspiration and expiration time
is considered. The effect of breath-hold time is also taken
into account to analyze its effect on charged particle deposi-
tion.
Using in-vitro studies, Ali et al. (2009) have reported electro-
static charge effects on deposition in oral–pharyngeal–laryngeal
(OPL) airways. However, no such modeled efficiency equa-
tion is yet available that can calculate charged particle depo-
sition in the nasal and oral pathways; hence, charge-related
deposition effects have been neglected in this study. Never-
theless, the selected particle sizes for this study have least
probability to deposit within the nasal or oral pathways. De-
position fractions in nasal and oral pathways due to mech-
anisms other than particle charge effects are computed by
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
MODELING CHARGED PARTICLE DEPOSITION 549
using deposition equations as proposed by Cheng et al.
(2003).
Deposition fractions of inhaled particles were computed
by the stochastic lung model IDEAL, originally developed
by Hofmann and Koblinger (1990) and Koblinger and Hof-
mann (1990), but revised many times in the years thereafter.
Formulated mathematically as a Langrangian random path-
way model, airway dimensions are randomly selected by
parameter probability density functions and correlations. The
morphometric base parameters were derived from measured
data (Raabe et al. 1976; Haefeli-Bleuer and Weibel 1988).
The stochastic lung model reflects the asymmetric nature
of the branching pattern of the lung and also highlights the
statistical relationships between parent and daughter airway
parameters (Raabe et al. 1976). This specific feature of the
stochastic lung model leads to a significant variability of
airway dimensions within a given airway generation as well
as a varying number of airway generations along a randomly
selected path. For example, in the stochastic lung model, TB
airways may vary between 11 and 21 airway generations.
Being Lagrangian in nature, the paths of inhaled particles
through a stochastic asymmetric lung structure are traced by
randomly selecting a sequence of airways for each individual
particle using stochastic modeling technique, i.e., Monte Carlo
methods.
RESULTS AND DISCUSSION
Enhanced Deposition Calculation
A comparison of calculated enhanced deposition efficiencies
by the stochastic lung model and by Yu (1985) for Weibel’s
(1963) lung model using a unit density 0.3-, 0.6-, and 1.0-µm
size particles in the TB region are shown in Figure 1. The loaded
number of charges on each particle size considered during this
study is well above the Boltzmann equilibrium and below their
maximum possible charge limit (Hinds 1999). The deposition
was calculated at a tidal volume (V
T
) of 1000 cm
3
and a breath-
ing frequency (f
R
) of 15 breaths per minute. The deposition
efficiencies increase almost linearly as a function of particle
charges in the TB region.
The resulting enhanced deposition as calculated by IDEAL
in the TB region is about 12% for 0.3-µm particles carrying
40 elementary charges, 6% for 0.6-um particles carrying 60 el-
ementary charges, and 7% for 1.0-µm particles carrying 100
elementary charges (Figure 1). The enhanced deposition as cal-
culated by Yu (1985) is consistently higher than the predictions
of IDEAL. The ratios (average) of stochastic lung enhanced
deposition calculation in the TB region to those of Yu (1985)
are 0.98, 0.93, and 0.82 for 0.3, 0.6, and 1.0 µm, respectively.
The lower deposition fractions obtained by IDEAL as com-
pared to Yu (1985) are primarily due to intersubject variations.
Furthermore, in IDEAL, extrathoracic deposition is calculated
using Cheng’s (2003) equation with more efficient filtration ef-
ficiency as compared to the commonly used ICRP (1994) depo-
FIG. 1. Enhanced deposition fractions in TB regions as function of loaded
particle charges. Deposition is calculated for different particle sizes at oral tidal
volume of 1000 cm
3
and 15 breaths per minute (flow rate of 30 L min
1
).
sition equation, hence allowing fever particles penetrating into
the thoracic region and lower deposition fractions.
The calculated enhanced deposition efficiencies using the
IDEAL model in the Al regions are compared with experimen-
tal measurements of Melandri et al. (1983). Due to systematic
errors in the measurements procedure, these experimental re-
sults are overestimated (Heyder et al. 1978). On the other hand,
application of the theoretical equations tends to underestimate
the experimentally obtained data. Moreover, Melandri et al.s
(1983) data reveal a linear correlation with particle charges.
However, calculations using the IDEAL code yield enhanced
deposition in the Al region that saturates and levels off even if
the number of loaded charges increases further. This effect is
particle-size dependent, above which no further enhanced depo-
sition occurs in the Al region (Figure 2). The observed saturation
level in the Al region is related to a shift of enhanced deposition
toward the TB region that emerges out of the elevated charge
loading. The associated threshold limits for charge loading to
reach this saturation level are 40, 85, and 130 elementary charges
for 0.3-, 0.6-, and 1.0-µm size particles, respectively, under spe-
cific breathing conditions. Since charged particle deposition is
calculated independently, other deposition mechanism do not
effect enhanced deposition.
In all cases, Al deposition is higher as compared to TB depo-
sition for all particle sizes used during this study. The enhanced
deposition of charged particles in the Al region is up to five
times higher than in the TB region. The enhanced deposition
calculated using the IDEAL code for the Al region is about 23%
for 0.3-µm particles carrying 30 elementary charges, 21% for
0.6-um particles carrying 60 elementary charges, and 22% for
1.0-µm particles carrying 100 elementary charges. The ratios
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
550 H. MAJID ET AL.
FIG. 2. Enhanced deposition fractions in Al region as function of particle
charge loading. Deposition is calculated for different particle sizes at a tidal
volume of 1000 cm
3
and 15 breaths per minute (flow rate of 30 L min
1
).
(average) of enhanced deposition in the Al region as obtained
by the IDEAL code to that of Melandri et al. (1983) are 0.65,
0.35, and 0.63 for 0.3-, 0.6-, and 1.0-µm particles, respectively.
The effect of different charge loadings and no charge at all
on a generation level for 0.6-µm particle is shown in Figure 3.
The figure illustrates the total deposition fractions at genera-
tion level due to major deposition mechanisms, i.e., diffusion,
sedimentation, and impaction in addition to particle charges. It
can be observed that with increasing charge loading, deposition
peaks gradually shift toward the TB region. This phenomenon
FIG. 3. Deposition fraction of 0.6-µm particles in the lung airway generations
at various particle charge loadings. The deposition is calculated under sitting
breathing condition (color figure available online).
relates to the enhanced deposition saturation point in the Al
region with increasing particle charge loading. Furthermore,
these shifts also reveal that targeted drug delivery can better be
achieved by adjusting particle charges according to their sizes
and flow conditions.
The observed variations in the calculated depositions in the
TB and Al regions with respect to Yu (1985) and experimen-
tal studies of Melandri et al. (1983) seem to be caused by in-
tersubject variability of airway dimensions, airways structural
relationships, and asymmetric structures of the human lung as
implemented into the IDEAL code. Furthermore, intersubject
variability of the extrathoracic deposition may further have led
to variability of charged particle deposition in the lung. In addi-
tion to these variations caused by the extra-thoracic region and
the lung morphometry, the modeling assumptions, such as mix-
ing of tidal air with residual air, expansion and contraction of
conductive airways as well as Al walls, may also have influenced
the deposition calculations.
The frequency distributions of the resulting enhanced depo-
sition are plotted in Figure 4 for 0.3- and 1.0-µm particles car-
rying 40 and 110 charges, respectively, in airway generations
5 (TB region) and 20 (Al region). These frequency distribu-
tions, represent conditional probability density functions (i.e.
they are conditional upon reaching a given airway generation).
In general, these distributions can reasonably be approximated
by log-normal distributions (Figure 4). The higher deposition
fractions of charged particles can be observed in the Al region
for both particles sizes showing higher deposition of 0.3-µm
particles than of 1.0-µm particles. The higher deposition densi-
ties observed in the Al region are caused by the higher deposition
fractions in single alveoli. These simulations indicate that in-
tersubject variability is higher in the Al region than in the TB
region (Figure 4).
CHARGED PARTICLE DEPOSITION AT DIFFERENT
BREATHING PATTERNS
Effect of Breathing Conditions
To investigate the effect of different breathing conditions on
charged particle deposition, two breathing conditions, i.e., sit-
ting and light exercise conditions, are chosen. The effect of two
these two breathing conditions on enhanced TB deposition are
shown in Figure 5. During light exercise breathing, the flow rate
is higher than during sitting breathing. Results indicate that en-
hanced deposition due to particle charging can decreases up to
50% during light exercise breathing condition. This decrease is
higher for larger particles, where impaction and sedimentation
deposition dominates. The decrease in enhanced deposition un-
der light exercise breathing condition is primarily caused by the
reduced residence time of charged particles within the airway
tubes.
Enhanced deposition due to charged particle loading under
different breathing conditions in the Al region is illustrated in
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
MODELING CHARGED PARTICLE DEPOSITION 551
FIG. 4. Probability distribution of deposition due to particle charges on 0.3- and 1.0-µm particles in the TB region (generation 5) and the Al region (generation
20). The deposition is calculated for 40 elementary charges on 0.3-µm particles and for 110 elementary charges on 1.0-µm particles for oral breathing with a tidal
volume of 1000 cm
3
and 15 breaths per minute (flow rate 30 L min
1
).
Figure 6. Contrary to the TB region, enhanced deposition in
the Al region is higher under light exercise breathing conditions
above a certain charge level. The charge level for such enhanced
deposition during light exercise breathing condition have been
calculated to be 20, 45, and 100 elementary charges for 0.3-, 0.6-,
and 1.0-µm particles, respectively. Owing to the higher filtering
efficiency of the TB region for coarse particles (1.0 µm), fine
particles (i.e., 0.3 and 0.6 µm) have larger probabilities to enter
into the Al regions at high flow rates (ICRP 1994). Above a
certain charge level, higher concentration and larger residence
times of 0.3- and 0.6-µm particles in the Al region result in
increased enhanced deposition during light exercise breathing
condition as compared to 1.0-µm size particles.
Effect of Tidal Volume (V
T
) and Flow Rate
Enhanced deposition in the Al region is presented as a func-
tion of V
T
at a fixed value of respiratory time 4 s (or 15
breaths/min) in Figure 7. Because respiratory time is fixed, flow
rate increases proportionally with the increase in V
T
. The figure
shows that enhanced deposition increases with increase in V
T
and flow rates in the Al region for all three particle sizes. Since
breathing time is fixed, flow rate increases proportionally with
increasing V
T
. In other words, enhanced deposition increases
with increase in flow rate at fixed breathing time. The enhanced
depositions rises up to 22%, 30%, and 20% for 0.3-, 0.6-, and
1.0-µm size particles for each 250 mL rise in V
T
. Owing to
small number of airways in the TB region as compared to the Al
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
552 H. MAJID ET AL.
FIG. 5. Enhanced deposition in the TB region as function of particle charge
loading. The deposition is calculated for different particle sizes under sitting
(tracheal flow rate 18 L min
1
) and light exercise (flow rate 50 L min
1
)
breathing conditions.
region, the effect of V
T
is insignificant on enhanced deposition
in the TB region (Figure 8) and this evidence is consistent with
the findings of Hashish et al. (1994a).
Effect of Breath-Hold
The introduction of pause time for a few seconds at the end
of the inspiration phase can increase the probability of particle
deposition in the targeted locations within the respiratory tract.
FIG. 6. Enhanced deposition in the Al region as function of particle charge
loading. The deposition is calculated for different particle sizes under sitting
(tracheal flow rate 18 L min
1
) and light exercise (flow rate 50 L min
1
)
breathing conditions.
FIG. 7. Enhanced deposition in the Al region as function of loaded particle
charges at various tidal volumes. The deposition is calculated for different
particle sizes and a fixed breathing frequency of 15 min
1
.
For inhaled charged particles, the pause time can play a role in
the selective deposition process. Figure 9 shows the effect of
breath-hold pause times on 1.0-µm particles charged with 100
elementary charges. The calculations reveal that pause time can
result up to 14% additional deposition in the respiratory tract.
But this increment gradually decreases from low to high pause
times until a saturation level is reached (Figure 9). In the present
case, enhanced deposition gradually decreases and fixes at 14%
for pause time increase from 2 s to 8 s. The effect of pause
FIG. 8. Enhanced deposition in the TB region as function of loaded particle
charges at various tidal volumes. The deposition is calculated for different
particle sizes and fixed breathing frequency of 15 min
1
.
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
MODELING CHARGED PARTICLE DEPOSITION 553
FIG. 9. The effect of breath-hold times on charged particle deposition. The
deposition is calculated for 1.0-µm size particles and 100 elementary charges
under sitting breathing condition (color figure available online).
time on charged particle enhanced deposition and its saturation
level depends on particle size and air flow conditions. Hashish
et al. (1994a) concluded similar results by introducing pause
time during inhaled charged particle deposition.
Calculation of EFs
The EF for charged particle deposition by image force under
sitting and light exercise breathing conditions are calculated and
listed in Tables 1 and 2. The EF is calculated for the whole-lung
deposition by taking the ratio of charged particle deposition to
that of uncharged particles. The comparison of EF reveals that
enhanced deposition is higher under sitting breathing condition
than under light exercise breathing condition. The enhanced
lung deposition increases almost linearly by increasing particle
charge level under both breathing conditions. EF decreases with
increase in particle size, and larger particles require much more
charges to achieve the same EF as that of small particles. Due to
image charge force, more than two times higher deposition can
be achieved in the lung for the range of particle sizes selected
during this study.
CONCLUSION
Charged particles deposition is implemented into the human
lung to quantify the occurrence of enhanced deposition other
than conventional deposition mechanisms, i.e., diffusion, sed-
imentation, and impaction. The enhanced deposition is calcu-
lated in the TB and Al regions and on generation level for various
particle sizes and charge levels under different breathing con-
ditions. The calculations are compared with that of theoretical
and experimental results. The enhanced deposition of charged
particles in the Al region is up to five times higher than in the
TB region. Unlike the TB region, enhanced deposition in the Al
TABLE 1
Charged particles lung deposition enhancement factors for
various particle sizes and charge load levels under sitting
breathing conditions
Diameter
(µm) q η
0
η
q
EF
0.3 20 0.28 0.46 1.65
30 0.54 1.95
40 0.59 2.12
50 0.61 2.22
60 0.63 2.29
0.6 40 0.26 0.38 1.49
50 0.46 1.81
60 0.52 2.02
70 0.55 2.15
80 0.58 2.24
1.0 60 0.27 0.34 1.27
75 0.43 1.61
90 0.49 1.82
105 0.53 1.95
120 0.55 2.06
q = loaded number of charge levels, η
0
= deposition fraction
without charges or below threshold charge limit, η
q
= deposition
fraction with charges above threshold charge limit.
TABLE 2
Charged particles lung deposition enhancement factors for
various particle sizes and charge load levels under light
exercise breathing conditions
Diameter
(µm) q η
0
η
q
EF
0.3 20 0.31 0.47 1.52
30 0.56 1.78
40 0.61 1.96
50 0.64 2.04
60 0.67 2.15
0.6 40 0.28 0.38 1.37
50 0.46 1.63
60 0.51 1.81
70 0.55 1.96
80 0.57 2.04
1.0 60 0.26 0.32 1.22
75 0.40 1.53
90 0.45 1.70
105 0.49 1.85
120 0.51 1.96
q = loaded number of charge levels, η
0
= deposition fraction
without charges or below threshold charge limit, η
q
= deposition
fraction with charges above threshold charge limit.
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
554 H. MAJID ET AL.
region approaches a saturation level above certain charge limit
depending upon particle size and flow conditions.
In the TB region, enhanced deposition is higher under sitting
breathing condition than under light exercise breathing condi-
tion. However, in the Al region, enhanced deposition increases
during light exercise breathing condition than during sitting
breathing condition after a certain number of charges. The en-
hanced deposition increases with increase in V
T
and flow rates
in the Al region and an increase up to 30% is observed for each
250 mL rise in V
T
. However, no prominent effect of V
T
is ob-
served in the TB region. The introduction of pause time during
inhalation increases the probability of increased enhanced depo-
sition at the targeted locations of the respiratory tract. However,
this increase in enhanced deposition approaches a threshold
limit of breath-hold time, after which no further enhanced de-
position occurs. In our case, the threshold breath-hold limit is
8sfor1.0-µm particles with 100 elementary charges under sit-
ting breathing condition. The calculated EF reveals that more
than two times higher deposition can be achieved in the lung by
introducing charged particles during inhalation.
Hence, by introducing charged particles during inhalation,
further control on targeted deposition in the respiratory tract
is possible in addition to the already applied modulation of
breathing and aerosol parameters. Thus, charged particles can
be utilized to give better control on drug delivery or to fil-
ter out toxic particles approaching the sensitive regions of the
lung.
REFERENCES
Ali, M., Mazumder, M. K., and Martonen, T. B. (2009). Measurements of
Electrodynamic Effects on the Deposition of MDI and DPI Aerosols in a
Replica Cast of Human Oral–Pharyngeal–Laryngeal Airways. J. Aerosol
Med. Pulmon. Drug Deliv., 22:35–44.
Bailey, A. G., Hashish, A. H., and Williams, T. J. (1998). Drug Delivery by
Inhalation of Charged Particles. J. Electrostatics, 44:3–10.
Chan, T. L., Lippmann, M., Cohen, V. R., and Schlesingkr, R. B. (1978).
Effect of Electrostatic Charges on Particle Deposition in a Hollow Cast
of the Human Larynx-Tracheobronchial Tree. J. Aerosol Sci., 9:463–
468.
Chan, T. L., and Yu, C. P. (1982). Charge Effects on Particle Deposition in the
Human Tracheobronchial Tree. Ann. Occup. Hyg., 26:65–75.
Cheng, Y. S. (2003). Aerosol Deposition in the Extrathoracic Region. Aerosol
Sci. Technol., 37: 659–671.
Cohen, B. S., Xiong, J. Q., Fang, C., and Li, W. (1998). Deposition of Charged
Particles in Lung Airways. Health Phys., 74:554–560.
Forsyth, B., Liu, B.Y. H., and Romay, F. J. (1998). Particle Charge Distribution
Measurement for Commonly Generated Laboratory Aerosols. Aerosol Sci.
Tech., 28:489–501.
Haefeli-Bleuer, B., and Weibel, E. R. (1988). Morphometry of the Human
Pulmonary Acinus. Anatom. Rec., 220:401–414.
Hashish, A. H., Bailey, A. G., and Williams, T. J. (1994a). Modelling the Effect
of Charge on Selective Deposition of Particles in a Diseased Lung Using
Aerosol Boli. Phys. Med. Biol., 39:2247–2262.
Hashish, A. H., Bailey, A. G., and Williams, T. J. (1994b). Selective Depo-
sition of Pulsed Charged Aerosols in the Human Lung. J. Aerosol Med.,
7(2):167–171.
Heyder, J., Gebhart, J., Roth, C., Stahlhofen, W., Stuck, B., Tarroni, G., et al.
(1978). Intercomparison of Lung Deposition Data for Aerosol Particles.
J. Aerosol S ci., 9:147–155.
Hinds, W. C. (1999). Aerosol Technology: Properties, Behavior and Measure-
ments of Aerosol Particles (2nd ed.). John Wiley & Sons, New York.
Hofmann, W., and Koblinger, L. (1990). Monte Carlo Modeling of Aerosol De-
position in Human Lungs. Part II: Deposition Fractions and Their Parameter
Variations. J. Aerosol Sci., 21:675–688.
International Commission on Radiological Protection (ICRP). (1994). Human
Respiratory Tract Model for Radiological Protection. Publication 66. Else-
vier Science, Oxford.
Johnston, A. M., Vincent, J. H., and Jones, A. D. (1985). Measurements of
Electric Charge for Workplace Aerosols. Ann. Occup. Hyg., 29:271–284.
Koblinger, L., and Hofmann, W. (1990). Monte Carlo Modeling of Aerosol
Deposition in Human Lungs: Part I: Simulation of Particle Transport in a
Stochastic Lung Structure. J. Aerosol Sci., 21:661–674.
Kwok, P. C. L., Glover, W., and Chan, H. K. (2005). Electrostatic Charge
Characteristics of Aerosols Produced from Metered Dose Inhalers. J. Pharm.
Sci., 94(12):2789–2799.
Melandri, C., Prodi, V., Tarroni, G., Formignani, M., De Zaiacomo, T., Bompane,
G. F., et al. (1977). On the Deposition of Unipolar Charged Particles in
the Human Respiratory Tract, in Inhaled Particles IV, W. H. Walton, ed.
Pergamon Press, Oxford, pp. 193–200.
Melandri, C., Tarroni, G., Prodi V., De Zaiacomo, T., Formignani, M., and
Lombardi, C. C. (1983). Deposition of Charged Particles in the Human
Airways. J. Aerosol Sci., 14:657–669.
Raabe, O. G., Yeh, H. C., Schum, G. M., and Phalen, R. (1976). Tracheo-
bronchial Geometry: Human, Dog, Rat, Hamster. Lovelace Foundation Re-
port LF-53. Lovelace Foundation, Albuquerque, NM.
Scheuch, G., Gebhart, J., and Roth, C. (1990). Uptake of Electrical Charges in
the Human Respiratory Tract during Exposure to Air Loaded with Negative
Ions. J. Aerosol S ci., 21:439–442.
Vincent, J. H. (1985). On the Practical Significance of Electrostatic Lung
Deposition of Isometric and Fibrous Aerosols. J. Aerosol Sci., 16(6):
511–519.
Weibel, E. R. (1963). Morphometry of the Human Lung. Academic Press, New
Yo rk.
Yu, C. P. (1985). Theories of Electrostatic Lung Deposition of Inhaled Aerosols.
Ann. Occup. Hyg., 29:219–227.
Yu, C. P., and Chandra K. (1977). Precipitation of Submicron Charged Particles
in Human Lung Airways. Bull. Math. Biol., 39:471–478.
Downloaded by [Universitat Salzburg] at 11:16 11 January 2012
... A 1 mm particle would need similar elementary charges to be more significant than sedimentation in affecting deposition in an alveolus 400 mm in diameter (Finlay 2019). In silico models have explored the deposition of unipolarly charged particles in dichotomous and realistic airway models (Bailey 1997;Bailey, Hashish, and Williams 1998;Balachandran et al. 1997;Koullapis et al. 2016;Majid et al. 2012;Yu 1985). Balachandran et al. (1997) showed that the deposition of 2.2 mm particles increased 10-to 16-fold in all airway generations when the number of elementary charges per particle was increased from 1 to 200 (Balachandran et al. 1997). ...
... Similar effects of electrostatic forces on deposition were obtained for 0.5 and 5 mm particles (Bailey, Hashish, and Williams 1998). Majid et al. (2012) predicted that 1 mm particles have approximately 20% higher deposition in the alveolar region once charge levels exceed approximately 100 elementary charges per particle (Majid et al. 2012). In vitro studies have shown that particles produced from various commercial pharmaceutical inhalation products possess numbers of elementary charges per particle that are within or above the ranges examined in silico (Byron, Peart, and Staniforth 1997;Kwok, Collins, and Chan 2006;Kwok, Glover, and Chan 2005;Kwok et al. 2010). ...
... Similar effects of electrostatic forces on deposition were obtained for 0.5 and 5 mm particles (Bailey, Hashish, and Williams 1998). Majid et al. (2012) predicted that 1 mm particles have approximately 20% higher deposition in the alveolar region once charge levels exceed approximately 100 elementary charges per particle (Majid et al. 2012). In vitro studies have shown that particles produced from various commercial pharmaceutical inhalation products possess numbers of elementary charges per particle that are within or above the ranges examined in silico (Byron, Peart, and Staniforth 1997;Kwok, Collins, and Chan 2006;Kwok, Glover, and Chan 2005;Kwok et al. 2010). ...
Article
Particles and droplets produced from pharmaceutical inhaler devices are naturally charged. Previous in silico and in vitro studies have shown that the levels of these electrostatic charges may potentially affect deposition in the airways but this has not been confirmed in vivo. Human lung scintigraphic studies using radiolabelled particles with controlled charges would provide crucial data on locating the deposition sites with respect to the particle charge level. An aerosol charging rig has been developed for this purpose. 99mTc-radiolabelled droplets from an Aerogen® Solo vibrating mesh nebulizer were charged by induction and then dried to yield positively charged particles. Particles with near-neutral charges were produced at an induction voltage of −0.4 kV, while those with 10-4,000 elementary charges per particle were generated at −4.5 kV, depending on the particle size. The number of elementary charges per particle generally decreased with radioactivity, especially for solutions at 400 and 800 MBq/mL. This was attributed to the indirect ionizing effect of the gamma radiation in the air, which produced bipolar ions that neutralized the initially charged particles. Radioactivity at 100 MBq/mL was found to be optimal in generating the highest particle charges that could potentially affect in vivo deposition in the lungs. The aerosol charging rig is suitable for use in human scintigraphy studies which we will conduct in the near future. Copyright © 2021 American Association for Aerosol Research
... Electrostatic charges on particles also have a significant impact on their deposition in lungs (Koullapis et al. 2016). For charged fine particles, enhanced particle deposition takes place in lungs via two processes including the space charge effects and image charge forces (Majid et al. 2012). Large eddy simulations were used to investigate the deposition of inhaled fine particles in a realistic geometry of human airways reconstructed from computed tomography (CT) scans (Koullapis et al. 2016). ...
Article
Full-text available
The COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 14 million people globally. Recently, airborne transmission has been postulated to be a major contributor to the spread of the novel coronavirus, especially in enclosed public spaces. While many studies have demonstrated positive correlations between atmospheric pollutants and SARS-CoV-2 infection, the impact of indoor air pollutants on airborne transmission has been largely overlooked. In particular, laser printers are a primary source of particle emission that increases the concentrations of particulate matter in indoor atmosphere by releasing substantial quantities of electrostatic fine particles, at rates comparable with tobacco smoking and incense burning. We hypothesized that particles emitted from laser printers present a potential risk factor for the transmission of SARS-CoV-2 in offices and other indoor environments with high user occupancy. To test this hypothesis, we reviewed recent knowledge on the characteristics of particles emitted by laser printing, including their emission rates and accumulation in indoor air, electrostatic charges, localized emission and subsequent particle diffusion in relation to the human breathing zone. We then discuss the potential impact on the transmission of SAR-CoV-2 in indoor spaces. We found that emission rates from laser printers ranged from 108 to 1012 particles min−1, and these fine particles typically remain suspended for prolonged periods in indoor air. Electrostatic charges carried by these particles can reach 260–379 e per particle, thus enhancing their surface adsorption and deposition in human airways. Localized emission by laser printers and subsequent diffusion highly increase particle concentrations near the human breathing zone.
... These tendencies have also been confirmed by numerical simulations. Majid et al. (2012) computed the deposition of charged particles in a stochastic lung model and confirmed that the deposition rate can be more than doubled by the inhalation of charged particles. In addition, they found that deposition is enhanced as the number of charges increases. ...
Article
A numerical simulation of an instrument that is used to measure the charging state of PM2.5 is conducted in order to clarify its measurement uncertainty and to improve its performance. The instrument, a parallel-plate particle separator (PPPS), is designed to classify aerosol particles according to their charging states and measure their quantities. The trajectories of submicron particles in the PPPS are numerically analyzed using the Lagrangian particle tracking method, taking into account the Brownian force and the electrostatic force. First, it is confirmed that the deterioration in the classification accuracy observed in the experiment is due to Brownian diffusion. The optimal condition that improves the accuracy is investigated through a parametric study by varying the balance of flow rates at the inlets, the geometry of the inlet and exit sections, and the applied voltage. It is found that decreasing the flow rate of the central inlet for aerosol or narrowing the central inlet improves the accuracy. The dependence of the accuracy on the flow rate is found to be in accordance with the experimental results. For charged particles, an optimum voltage that maximizes the classification accuracy is found. On the basis of the simulation results, we propose a method to determine the charge distribution of aerosol from the number of particles counted at each exit of the PPPS. In the test assuming aerosol in the air, the charge distribution determined from the number count at the exits is found to perfectly agree with the charge distribution specified at the inlet. Copyright © 2019 American Association for Aerosol Research
... Such charged particles may exhibit enhanced deposition over that expected based upon size alone (Schlesinger, 2000). As it has been so far shown, the electric charges carried by both particulate and fibrous aerosols enhance greatly their deposition in the airways, even when particles carry a few charges only (Chitra & Radhakrishnan, 2014;Davis, Bolton, Douglas, Jones, & Smith, 1988;Guo, Johnson, Jayaratne, & Morawska, 2012;Majid, Madl, Hofmann, & Alam, 2012;Melandri et al., 1983;Saini, Yurteri, Grable, Sims, & Mazumder, 2002). Regarding microbial particles, few laboratory studies revealed also that airborne microorganisms may carry high electric charges immediately after their dispersion in the air; however, environmental factors, such as free ions and atmospheric radiation, may alter the electric charges carried by them. ...
... To date, most mathematical and computational studies on the electrostatic deposition on human airways has based on assumption that particles are unipolar charged [26][27][28][29] , with little were done on bipolar charged particles 30 . Since the electrostatic charge of most MDI and DPI aerosols were bipolar in nature, modelling on bipolar aerosols will be more relevant. ...
Article
Full-text available
Aerosols emitted from metered dose inhalers (MDIs) are generally electrically charged and bipolar in nature. While a spacer can effectively dampen the charge magnitude of aerosols, the electrostatic interactions between the positively and negatively charged particles and the spacer have not yet been characterized separately. The Bipolar Charge Analyzer (BOLAR) was employed to investigate interactions between the spacer and the charged aerosols. Three individual actuations of Tilade® MDI were introduced without a spacer and through an anti-static AeroChamber Plus® Z Stat®, an uncoated and a detergent-coated AeroChamber Plus® spacer into the BOLAR at 60 L/min. Charge and mass profiles were determined. The surface potential of spacers followed the order of uncoated > detergent-coated > anti-static spacer. The spacers had minimal impact on the positively charged particles but the charge magnitude of the negatively charged particles was in the opposite order as the spacer surface potential. The charge-to-mass ratio of particles had little alteration for all measurements. Negatively charged particles had a higher tendency to deposit on the spacer walls, possibly due to their higher abundance in the confined spacer volume. The bipolar data may prove useful for designing better MDIs and spacers, and modelling lung deposition of charged aerosol particles.
... The enhanced deposition of charged particles in the alveolar region was up to five times higher than in the tracheobronchial region. Majid, Madl, Hofmann, and Alam (2012) 2008 In vitro Corona charging Sodium chloride solution 0.5-10 -Electrostatic charge enhanced deposition compared to uncharged aerosols. Ali, Reddy, and Mazumder (2008) 1998 In silico --1 0 -3,000 ...
Article
This study investigated the effect of modifying the Aerolizer® inhaler design and material on bipolar charging of a powder aerosol. The modified inhalers included various grid configurations, mouthpiece lengths, air inlet sizes, and were also constructed of different materials (acrylonitrile butadiene styrene, acetal, low density polyethylene, nylon, polypropylene, and stainless steel). The novel BOLAR™ (Dekati Ltd., Kangasala, Finland) was used to characterise bipolar charge and mass distributions. All of the tested inhalers showed spray-dried mannitol powder carried significantly different positive and negative charges that had higher magnitudes than the measured net charge. The estimated elementary charges per particle indicated the aerosols carried significant levels of charge that may potentially influence particle deposition in the lungs. Increasing the grid voidage decreased the magnitude of charging, as did reducing the air inlet size, whereas mouthpiece length had no obvious effect. The observed effects on charging due to modifications to the inhaler design could be explained by a difference in the level of contacts due to impaction between the particles and the inhaler internal surface. Bipolar charge of mannitol did not differ when dispersed by inhalers constructed of different materials. This could be attributed to various potential factors such as the very brief contact time between the powder and the inhaler material, as well as coating of the inhaler interior by the powder which effectively renders the surface to be mannitol-like. Overall, the comparable q/m profiles across all the inhaler designs and inhaler materials indicated charging correlated with the mass distributions and modifications to the inhaler did not affect the qualitative bipolar charge characteristics of mannitol powder.
Article
Full-text available
Physicochemical properties of nanoparticles are important in regulating nanoparticle toxicity; however, the contribution of nanoparticle charge remains unclear. The objective of this study was to investigate the pulmonary effects of inhalation of charged soot nanoparticles. We established a stably charged nanoparticle generation system for whole-body exposure in BALB/c mice, which produced positively charged, negatively charged, and neutral soot nanoparticles in a wide range of concentrations. After a 7-day exposure, pulmonary toxicity was assessed, together with proteomics analysis. The charged soot nanoparticles on average carried 1.17–1.35 electric charges, and the sizes for nanoparticles under different charging conditions were all fixed at 69 ~ 72 nm. We observed that charged soot nanoparticles induced cytotoxic LDH and increased lung permeability, with the release of 8-isoprostane and caspase-3 and systemic IL-6 in mice, especially for positively charged soot nanoparticles. Next, we observed that positive-charged soot nanoparticles upregulated Eif2, Eif4, sirtuin, mammalian target of rapamycin (mTOR), peroxisome proliferator-activated receptors (PPAR), and HIPPO-related signaling pathways in the lungs compared with negatively charged soot nanoparticles. HIF1α, sirt1, E-cadherin, and Yap were increased in mice’s lungs by positively charged soot nanoparticle exposure. In conclusion, carbonaceous nanoparticles carrying electric ions, especially positive-charged, are particularly toxic when inhaled and should be of concern in terms of pulmonary health protection.
Article
Children are the sensitive population to fine particulate matter (PM2.5) exposure and spend most of their time in bedroom. Infiltration factor (Finf) can be used to calculate the fraction of total indoor PM2.5 with outdoor origin to increase the accuracy of exposure assessment. However, studies have ignored the diurnal variations of PM2.5 Finf values, and a few studies have estimated Finf values for heavy metals in PM2.5 in children’s bedrooms. To calculate the PM2.5 Finf, real‐time indoor and outdoor PM2.5 concentrations and occupants’ activities were collected in 56 study bedrooms. At 22 of the 56 study bedrooms, PM2.5 samples were also collected for heavy metals analysis. We noted the PM2.5 Finf was higher during the daytime (0.70 ± 0.23) than nighttime (0.54 ± 0.27) during the hot season, and the time of air conditioner use was longer at nighttime. The largest Finf value of heavy metal was V (0.88 ± 0.25), followed by Pb (0.85 ± 0.28), Mn (0.72 ± 0.26), Cr (0.69 ± 0.35), and Zn (0.61 ± 0.32), with a larger variation. Our findings suggest that the estimations of diurnal PM2.5 and heavy metals Finf values are necessary to increase the accuracy of exposure assessment.
Article
Full-text available
PurposeTo develop an in vitro method to rapidly evaluate regional lung doses delivered by pharmaceutical inhalers. Currently, cascade impactor measurements are used, but these are resource intensive and require significant post processing of in vitro data to arrive at regional deposition estimates.Methods We present a specialized filter apparatus that mimics tracheobronchial (TB) deposition of pharmaceutical aerosols emitted by commercially available dry powder inhalers (DPIs). The filter housing includes an electrostatic neutralizer to eliminate artificial electrostatic filtration effects. Regional deposition (tracheobronchial and alveolar) for four DPIs (Onbrez Breezhaler, Flovent Diskus, Pulmicort Turbuhaler, and Asmanex Twisthaler) was estimated using cascade impactor measurements and an in silico regional deposition model. These estimates were compared to direct measurements of regional deposition as provided by the TB filter mimic and an absolute filter placed downstream of the TB filter housing, representing the alveolar dose.ResultsThe two methods were shown to provide similar estimates of extrathoracic, tracheobronchial, and alveolar deposition, as well as total recovery of active pharmaceutical ingredients.Conclusions Because of its design, the TB filter apparatus makes it possible to estimate regional deposition with inhalers directly using variable inhalation profiles without any additional equipment or changes to the experimental configuration. This method may be useful to expedite development of both innovative and generic drug products as it provides regional respiratory tract deposition estimates using fewer resources than exisiting methods.
Article
In order to understand the electrostatic charging state of atmospheric hundreds nanometer particles that has particular impact on health, we have observed the atmospheric particles charge distributions intermittently for one year. To easily estimate particle charge distribution, first of all, we have developed a simple instrument and calculation method. We confirmed by comparison with stationary charge distributions that the distributions obtained by our method can be used to easily determine the relative variation of particle charging states, although the proportion of particles with a small charge number was quantitatively underestimated. The charge distributions of the atmospheric particles observed from April 2017 to February 2018 were different from the generally accepted stationary charge distribution. Moreover, the observed distributions changed significantly throughout the year. This variation was found to correlate with seasonal variations in temperature, relative humidity, volumetric humidity, and air mass trajectories. Present result suggests that the seasonal variation of the charging state is possibly due to the seasonal variation of the atmospheric ion number concentrations. Thus, it is important to consider the variation in the charging state of atmospheric particles due to dynamic changes of atmospheric conditions, as the charging state can dramatically influence the deposition of particles in the lungs.
Article
Full-text available
The charged, pulsed aerosol technique has the advantage that the inspired aerosol can be delivered efficiently to sites of interest within the lung, and that the exposure time of an airway to the aerosol pulse can be controlled. Our existing mathematical lung deposition model has been extended to deal with charged, pulsed aerosols, and to lung morphologies where bronchoconstriction is present. For a given pulse volume, deposition is enhanced by increasing the level of particle charge and duration of the breath-holding pause. This technique can be used to assist in the ''targeting'' of therapeutic or other agents on to different sites within a normal or diseased lung and for designing and optimizing clinical procedures.
Article
Full-text available
An improved particle charge analyzer system has been developed to measure the absolute charge distribution of common generated laboratory aerosols. The charge analyzer system consists of an integral cylindrical mobility analyzer used in conjunction with an optical aerosol spectrometer, with computer assisted operation and data reduction. The charge analyzer collects aerosol particles over an absolute electrical mobility range from 4.2*10 to 400 cm/(stat · Volt second) and flow rates that can vary from 0.3 to 30 liters per minute. The charge analyzer has been used to investigate the nature of spray and contact electrification during aerosol generation by measuring the residual charge distribution on the liquid and solid generated particles. In addition, the neutralization of charged particles by bipolar ions also was studied using conventional neutralizers that use ionizing radiation from alpha and beta sources. Charge distribution measurements were performed on alumina dust (Al), Arizona road dust (ARD), potassium chloride (KCl), sodium chloride (NaCl) and di-octyl sebacate (DOS) liquid particles. Aerosol generation devices include a Collison atomizer, a condensation aerosol generator and a fluidized bed dust generator. Our work provides experimental charge distribution data for comparison with simple models of electrification theory. Experimental results showed that charge levels of atomized KCl and NaCl particles were high and decreased as the dissolved ion concentration increased. DOS particles generated by evaporation-condensation were both neutral and moderately charged. These conclusions support the existence of a dipole layer at the liquid-gas interface that interacts with dissolved particles and changes their charge state. Alumina and ARD generated by the fluidized bed disperser are highly charged due to strong contact electrification during dispersion. In most cases, the charge on generated aerosols could be reduced to Boltzmann charge equilibrium conditions by commonly used radioactive neutralizers.
Article
The work presented in this monograph marks a new era, we believe, both in the development of quantitative anatomy of the lung, and in the correlation of anatomy with physiology. For many years, physiologists interested in the overall functioning of the lung have felt a need for better quantitative descriptions of pulmonary anatomy. As physiologists, we know a good deal about the forces operating to producepulmonary ventilation, and the quantities that define this function in rest and exercise ; and the same for effective distribution of air within the lung - "alveolar" ventilation-, and for the exchange of respiratory gases between air and blood. There have been no correspondingly precise quantitative measurements of the pulmonary structures that serve theese functions. The great advances in the study of pulmonary anatomy in the past decade have been chiefly in the realm of "fine structure". This has tended to bring together anatomy and biochemistry or physical chemistry, rather than anatomy and physiology. This conjunction has aided, for example, the conception of diffusion as a physicochemical process, but not that of diffusion as a metabolic bodily function. It was, therefore, a remarkably fortunate circumstance which brought together in our laboratory, about three years ago, Professor DoMINGO GoMEZ and Dr. EWALD R. WEIBEL: Professor GoMEZ a mathematician and biophysicist of dis­ tinction and long experience; Dr. WEIBEL a young anatomist trained under Pro­ fessor GIAN TöNDURY in Zürich, and with additional research experience with Professor A VERILL LIEBOW at Y ale.
Article
There are considerable discrepancies between published lung deposition data. Therefore, the aerosol groups of GSF at Frankfurt/M and of CNEN at Bologna devoted a two week workshop to the understanding of the reasons for some of these discrepancies. This paper reports on the workshop and describes the intercomparison procedures.For all particle sizes and breathing patterns investigated total deposition values for mouthbreathing evaluated with the methods and techniques used in the two laboratories agree satisfactorily and exhibit an intersubject variability. Electrostatic deposition was found to rise with increasing number of charges carried by the particles and with increasing mean residence time of the aerosols in the respiratory tract.
Article
Electrostatic charges on particles significantly increased the deposition of monodispersed aerosols in a hollow cast of the human larynx-tracheobronchial tree. The charge levels varied from 360 to 1000 negative charges/particle and the mass median aerodynamic dia. varied from 2 to 7 μm. Most of the enhancement in deposition was found in the larynx and the trachea, resulting from image forces. The increase in deposition followed the theory of Yu and was correlated with an electrostatic force parameter. Laboratory generated aerosols should be completely neutralized prior to their use in inhalation studies in order to avoid misinterpretation of data due to charge effects. Implications of the electrostatic charge effects to the assessment of airborne health hazards are also discussed.
Article
The electrostatic charge carried by aerosol particles greatly enhances their deposition in the airways. Systematic measurements have been performed on volunteers with unipolar charged monodisperse aerosols of both polarities. In the charge concentration used, the increase in deposition is due to image forces between wall and particle. The particle sizes were 0.3, 0.6 and 1.0 μm monodisperse within ± 10 % and charged with a number of elementary units between 12 and 230 with a distribution of charge within ± 18 %. The effect of charge is not detectable below a charge number n3 which depends on particle size but not on the volunteer.The electrostatic deposition is a function of ( where B is the mechanical mobility and n is the number of charges.The intersubject variability is also investigated together with the influence of the Expiratory Reserve Volume: the electrostatic contribution to deposition decreases with increasing ERV. following the same behaviour as for neutral particles. Since in the size range investigated the deposition takes place only in the alveolar region, we think that also the deposition for electrostatic effects is alveolar, under the experimental conditions described.
Book
Airborne particles are present throughout our environment. They come in many different forms, such as dusts, fumes, mists, smoke, smog, or fog. These aerosols affect visibility, climate, and our health and quanlity of life. This book covers the properties, behaviour, and measurement of aerosols. This is a basic textbook for people engaged in industrial hygiene, air pollution control, radiation protection, or environmental science who must, in the practice of their profession, measure, evaluate, or control airborne particles. It is written at a level suitable for professionals, graduate students, or advanced undergraduates. It assumes that the student has a good background in chemistry and physics and understands the concepts of calculus. Although not written for aerosol scientists, it will be useful to them in their experimental work and will serve as an introduction to the field for students starting such careers. Decisions on what topics to include were based on their relevance to the pratical application of aerosol science, which includes an understanding of the physical and chemical prinicples that underlie the behaviour of aerosols and the instruments used to measure them. (from preface)
Article
The uptake of negative charges in the human respiratory tract has been determined experimentally by breathing free ions and particles carrying negative charges. Free ions are deposited very effectively in the upper airways whereas charged particles penetrate to the deeper lungs.
Article
A stochastic model for the calculation of aerosol deposition in human lungs has been developed. In this model the geometry of the airways along the path of an inhaled particle is selected randomly, whereas deposition probabilities are computed by deterministic formulae. The philosophy of the airway geometry selection, the random walk of particles through this geometry and the methods of aerosol deposition calculation in conductive and respiratory airways during a full breathing cycle are presented. The main features of the Monte Carlo code IDEAL-2, written for the simulation of random walks of particles in a stochastic lung model, are briefly outlined.