Freshly generated aerosols in workplace atmosphere may have charges well above the Boltzmann equilibrium (Forsyth et al. 1998). Similarly, aerosols produced by commercial metered dose inhalers can produce elementary charges up to several ten thousands (Kwok et al. 2005). In-vivo and in-vitro experiments have shown enhanced deposition in the lung due to electro-statically charged particles. Enhanced deposition due to charged particles in the lung is mainly caused by the image charge force (Yu, 1985). Several models have been developed to predict the effect of charged particles deposition in the lung with good agreement with the experimental data (Melandri et al. 1983; Yu 1985; Hashish et al. 1994). In the present study, enhanced deposition in the human lung due to charged particles has been estimated using the stochastic airway generation model IDEAL.

1. Implementation of Charged Particles
Deposition in Stochastic Lung Model and
Calculation of Enhanced Deposition
Dr. Hussain Majid
1

2. This presentation will cover
• Background of the study
• Overview of the published work
• Conclusions
2

3. Background
 Aerosols
• A system of solid or liquid particles Dust Smoke
suspended in air or other gaseous
environment called aerosol.
 Types
Fume Mist
 Natural Aerosol
- Soil Dust
- Sea Salt
- Volcanic Dust Clouds Pesticides
- Oceanic Sulphates
 Anthropogenic Aerosol
- Industrial Sulphates
- Soot (Black carbon)
- Organic particles
3

4. Charged Particles
• The Boltzmann equilibrium charge distribution represents the
charged distribution of an aerosol in charge equilibrium with
bipolar ions surrounding it.
• Freshly generated aerosols in workplace atmosphere may have
charges well above the Boltzmann equilibrium (Forsyth et al.
1998) .
• Aerosols produced by commercial metered dose inhalers can
produce elementary charges up to several ten thousands (Kwok
et al. 2005).
• In-vivo experimental studies have shown that lung deposition of
particles is significantly effected by particle charges (Yu and
Chandra 1977, Cohen et al. 1998).
• The significance of charged particles deposition may be of more
concern for aerosol therapy than for inhalation toxicology.
4

5. Lung deposition calculations-Importance
• Evaluating the efficiency of dose
deliverance i.e. how much and how long
will particles remain in the lung.
• Assessing toxic effects of airborne
pollutant depositing in certain regions of
the lung.
• Estimation for the location of potentially
induced cancer due to exposure in
radiation environment.
5

6. Deposition Fraction
Original aerosol Aerosol inhale DF =
Inhaling
Deposition fraction is the ratio on aerosol inhaled to the total
aerosol deposit in the lung. This is affected by the entry
point, the orientation of the flow to the entry point, the flow
rate and particle size.

7. Human Lung
Head airway (HA)
Air is inspired through nose or mouth
down to larynx and rest of the lung.
Tracheaobronchial (TB)
Bronchial tree is the first part of the
lung. This part directs air in to the lung
Each branch in the tree splits into 2
parts
Parent Branch
Bifurcation
Major daughter Minor daughter
Alveolar or Pulmonary (Al)
Alveoli are located at the end of the
bronchial tree and is region where gas
exchange occurs. 7

9. Lung deposition mechanisms
Major:
• Diffusion
• Sedimentation
• Inertial Impaction
Minor:
• Interception
• Electrostatic
Naso-pharyngeal:
impaction, sedimentation, electrostatic
(particles > 1 μm)
Tracheo-bronchial:
impaction, sedimentation, diffusion
(particles < 1 μm)
Pulmonary:
sedimentation, diffusion (particles < 0.1 μm) 9

10. Factors that effect deposition
1. Aerosol properties
• Size distribution (MMD, AMD. etc)
• Concentration
• Particle hygroscopicity
• Gas particle interaction
• Chemical reaction
• Particle surface charge Particle properties
8. Air flow properties
• Lung capacity
• Breathing frequency
• Tidal Volume
12.Respiratory tract
• Structure of the extrathorcic region
• Lung structure and morphology
• Models used: Weibel, Raabe, and Horsfield
Numbering scheme of asymmetric lung model of Raabe et al. (1974).
10

11. Stochastic Lung Dosimetry Model- IDEAL
• Deposition fractions and distribution within airways generations
are modeled by the stochastic lung model-IDEAL
• Particles inhaled follow random path in the lung
– Random selection of actual path out of millions of possible pathway by tracing
histories of a large number of particles
• The model uses asymmetric nature of branching pattern of the
lung.
– Variability of lenghts and diameter of airways are described by log-normal
frequency distributions
• Analytical (deterministic) formulas are used for computing deposition
by diffusion, sedimentation and impaction
• Monte Carlo process continues even after deposition of particles within
a given airway by decreasing the statistical weight of particles
11

12. Objectives of the study
1. to implement charge particle deposition in the stochastic
human lung model (TB and Al regions),
2. to predict enhanced deposition for various charged particle at
airway generation level and to compare results with previous
studies
3. to quantify the breathing effects on charged particle
deposition and
4. to calculate enhancement factors for various breathing
conditions.

13. Charged Particles deposition Model
Tracheobronchial (TB) region
• Enhanced deposition in TB region is obtained by implementing the following
efficiency equation: 1/ 2
 8B 
 πε d 3 t0  ( q − q0 )
ηq =  
 0 t 
where B is the mechanical mobility of the particles, t0 is the is the mean
residence time, εo is the electric permittivity of air.
Alveolar (Al) region
• For the spherical shaped Al region, enhanced deposition is calculated by
implementing the following 1/ 3
1  5Bq  2
ηq = 
 πε t0 

d alv  0 
where t0 is the particles mean residence time [in sec].
13

14. Results
• Particle sizes
– Unit density monodisperse charge particles of 0.3, 0.6 and 1 µm diameter.
• Flow rates
– For sitting and light exercise conditions 18 and 50 L min-1 respectively
(ICRP 1994).
• Tidal volumes
– 750 and 1250 mL and breathing cycle times are 5 and 3s respectively.
• The effect of breath-hold
– 2-8 Seconds
• Threshold charge limit
– The enhanced deposition due to particle charges q is considered
proportional to increase in threshold charge limit (q – q0).
14

15. Results (continued..)
Enhanced deposition in TB and Al regions as function of loaded
particle charges. Deposition is calculated for different particle sizes
at oral tidal volume of 1000 cm3 and 15 breaths per minute (Flow
rate of 30 L min-1). 15

16. Results (continued..)
Enhanced deposition of 0.6 µm The effect of breath hold times on
particles in the lung airway charged particle deposition for 1.0
generations at various particle µm size particles and 100
charge loading. elementary charges. 16

17. Results (continued..)
Enhanced deposition within the TB and Al regions 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
exercised (Flow rate 50 L min-1) breathing conditions. 17

18. Results (continued..)
Enhanced deposition within the TB and Al regions 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.
18

19. Results (continued..)
Enhancement factors

20. Conclusion
• The enhanced deposition of charged particles in the Al region is
up to five times higher than in the TB region and reaches a
saturation level.
• Within the TB-region, enhanced deposition is higher under
sitting breathing than under light exercise breathing conditions.
• The enhanced deposition increases with increase in VT and flow
rate in Al region.
• The introduction of pause time during inhalation increases the
probability of increased enhanced deposition at targeeted
loaction of the respiratory tract.
• 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.