Transcript No Slide Title

Aerosol Particle Deposition in
the Human Respiratory Tract
AIRPOLIFE PhD Course
Air Pollution and Health
Copenhagen, 21 March 2006
Erik Swietlicki
Professor
Division of Nuclear Physics,
Lund University
P.O. Box 118, SE-21100 Lund, Sweden
[email protected]
Co-workers
Jakob Löndahl, Andreas Massling,
Joakim Pagels, Jenny Rissler
Steffen Loft, Elvira Vaclavik, Peter Vinzents
Linking Emissions to Health Effects
Toxicological studies
Lung
Deposition
Emission
Concentration
Exposure
Dose
Health effect
Epidemiological studies
Dose to a target tissue depends on deposition and
subseqent retention of the particles.
Aerosol - Definition
“A collection of liquid or solid
particles suspended in a
mixture of gases
- normally air.”
An aerosol is a multi-phase
system
gas - liquid - solid
Size range of aerosol
particles
The criterion of suspension
determines the size range of aerosol
particles:
Smallest particle: 1 nm (0.001 µm or 10-9 m)
Largest particle: 100 µm (10-4 m)
Spanning:
5 orders of magnitude in size
15 orders of magnitude in mass/volume !!
One litre of urban air ...
… contains ca. 10 million particles (104 cm-3)
We inhale 10-25 m3 of air per day
ca. 100 billion (1011) particles per day
Mass loading in polluted atmospheres
ca. 100 µg/ m3
= ca. 1 mg/ day
The Human Respiratory Tract
Head Airways
Nasopharyngeal
Humidification
Heating
Removal
Lung Airways
Branching
Clearance
Flow may
be turbulent
Laminar flow
(not fully
developed)
Pulmonary
Gas
Exchange
The Human Respiratory Tract
Characteristics of the various regions in the respiratory system.
The diameter and the length decrease while the number of branchings
increases. This increase results in a decreasing velocity and increasing
residence time that have great impact on the "effective mechanisms"
responsible for deposition.
Airway
Generation of
Branchings
Number of
Branchings
Diameter of
Airway (mm)
Length of
Airway (mm)
Total CrossSection Area
(cm2)
Velocity
(mm/s)
Residence
Time in the
Airway (ms)
Trachea
0
1
18
120
2.5
3900
30
Main bronchus
1
2
12
48
2.3
4300
11
Segmental
bronchus
4
16
4.5
13
2.5
3900
3.2
Terminal
bronchus
11
2000
1.1
3.9
20
520
7.4
Terminal
bronchiole
16
66000
0.6
1.6
180
54
31
Alveolar duct
21
2 x 106
0.43
0.7
3200
3.2
210
Alveolar sac
23
8 x 106
0.41
0.5
72000
0.9
550
3 x 108
0.28
0.2
Alveoli
The purpose of the upper airways is to
• Heat and humidify the inhaled air (Conditioning).
• Remove particles from the inhaled air by deposition
(act as a filter).
• Clear away the deposited particles efficiently into the
gastrointestinal tract (clearance via mucociliary
escalator).
• Particles should ideally NOT reach the alveoli where
the gas exchange takes place!
• Particles > 10 µm generally do not reach the
alveoli ( PM10 standard).
The Human Respiratory Tract
Normal Adult
Processes 10-25 m3 of air per day
Surface area for gas exchange: 75 m2 (1/2 singles tennis court)
2000 km of capillaries
Tidal volume at rest : 0.5 litre (3x at heavy work)
Breathing rate at rest : 12 per minute (3x at heavy work)
2.4 litre reserve air is not exhaled (1/2 at forced exhalation)
Clearance of Deposited Particles
Head airways and tracheobronchial regions
• Covered with mucus (salts, lactate, glycoproteins).
• Mucociliary escalator: Ciliary action moves mucus towards
the pharynx, where it is swallowed into the gastrointestinal
tract.
• Clearance within hours.
Alveolar region
• No mucus layer, no cilia.
• Insoluble particles cleared very slowly (up to months or
years).
• Clearance of soluble particles: dissolve and enter the blood
stream.
• Clearance of insoluble particles by macrophages.
(phagocytosis) or surface tension effects (up to the
mucociliary escalator).
Soluble particles
The particles lose
their original shape
and physical
properties after
deposition
The response from the
body depends on the
particle mass,
composition and
number
Number of deposited
particles can affect
the physiological
response
Epithelial
cell in alveoli
Insoluble particles
The particles keep
their original shape
and physical
properties even
after deposition
The response from the
body depends on the
particle surface
properties and
number
Number of deposited
particles can affect
the physiological
response
Epithelial Cell
Epithelial
cell
in alveoli
Photographer: Lennart Nilsson
Soot particles (yellow) deposited in the alveoli.
A macrophage attacks the soot particle and tries to engulf it.
Photographer: Lennart Nilsson
Insoluble particles may enter the blood
Epithelial lining fluid
Alveolar epithelium
Blood vessel
Examples of non-spherical particles
TEM (Transmission Electron Microscopy) pictures
Kerosene lamp (soot agglomerate)
Particle from tire wear
Equivalent Particle Diameter
Relates to the sedimentation velocity vTS
Volume Equivalent
Stokes
Diameter
equivalent
sphere
Shape Factor = 1.36
ds = 4.3 µm
de = 5.0 µm
p = 4 g/cm3
p = 4 g/cm3
vTS=0.22 cm/s
vTS=0.22 cm/s
Aerodynamic
equivalent
sphere
dae = 8.6 µm
p = 1 g/cm3
vTS=0.22 cm/s
Particle Deposition in the
Human Respiratory Tract
Relies on the same basic mechanisms as particle
collection in a filter, but with different relative
importance
• Filter: Fixed geometry, constant flow rate
• Respiratory system: Changing geometry,
variable flow rate (also direction), dead
volumes, high relative humidity
Particle Deposition Mechanisms
Particles may deposit within the respiratory tract
by five mechanisms:
•
•
•
•
•
Inertial impaction
Sedimentation (settling)
Diffusion
Interception
Electrostatic precipitation
Particles that contact the airway walls are not
reentrained.
Inertial Impaction
• Air flows through bends.
• Particles leave their original flow line due to their inertia, and
impact on the airway walls.
• Stopping distance increases with particle size (proportional to d2)
• Most important in large airways (large velocities, bifurcations)
• Most deposition on mass basis.
Sedimentation (Settling)
• Particles settle by gravitation onto the airway walls.
• Most important in smaller airways and the alveoli (low flow
velocities, small airway dimensions), and horizontally oriented
airways.
• Settling velocity proportional to d2
Brownian Diffusion
•
•
•
•
•
Particles leave their original flow lines by diffusion and deposit onto the
airway walls.
Most important deposition mechanism for particles < 0.5 µm.
Governed by geometric, not aerodynamic particle diameter
Most important in smaller airways (short distances, long residence
time).
Displacement from flow line proportional to (1/d).
Interception
• Without deviating from their original flow lines, particles contact
the airway surface because of their physical size.
• Long fibres: Small aerodynamic particle diameter, large in one
dimension.
Electrostatic Deposition
• Charged particles are attracted towards the airway
walls by the electrostatic image charges they induce
in the airway surface.
• Unipolar charged aerosols with high number
concentrations repel each other and drive particles
towards the walls.
• Ambient aerosols normally in charge equilibrium
(Bolzmann).
• Normally not important. Only for freshly generated
(and charged) aerosols, for instance from nebulizers.
Total Particle Deposition in the Respiratory Tract
Particle diameters are aerodynamic (MMAD) for those > 0.5 μm and geometric (or
diffusion equivalent) for those < 0.5 μm. Source: Modified from Schlesinger (1989).
Diffusion
Impaction
Interception
Settling
Extrathoracic Particle Deposition
All values are means with standard deviations, when available. Particle diameters
are aerodynamic (MMAD) for those > 0.5 μm and geometric (or diffusion
equivalent) for those < 0.5 μm. Modified from Schlesinger (1989).
Deposition in the alveolar region
• The inhaled air never flows into the alveoli.
• Gas exchange takes place by molecular
diffusion over the last millimeter.
• Inhaled submicrometer-sized particles should
therefore not deposit efficiently in the alveolar
region, since settling is low and their diffusion
is orders of magnitude slower than for gas
molecules.
• Alveolar deposition is controlled by their
transfer from inhaled (tidal) air to the reserve
air  enough time.
Factors governing the dose of inhaled
particles to the respiratory tract:
• Exposure concentration
• Exposure duration
• Respiratory tract anatomy
• Breathing pattern
• Particle properties
(e.g., particle size, shape, density,
hygroscopicity, and solubility in airway fluids
and cellular components).
Besides particle size, breathing pattern (tidal
volume, breathing frequency, route of
breathing, length of pause between inhalation
and exhalation) is the most important factor
affecting lung deposition.
Breathing Pattern
6
Maximum
inspiration
5
Total lung capacity
Inspiratory
capacity
Vital capacity
Inspiratory reserve
volume
Volume (L)
4
3
Tidal volume
2
Functional residual
capacity
Expiratory reserve
volume
1
Residual volume
Maximum
expiration
0
Time
PEF: Peak Inspiratory Flow
PEF: Peak Expiratory Flow
VT: Tidal Volume
Effect of Breathing Pattern on Deposition
Total deposition fraction as a function of particle size in 22 healthy men and women
under six different breathing patterns. For each breathing pattern, the total
deposition fraction is different (p < 0.05) for two successive particle sizes. Vt is tidal
volume (mL); Q is respiratory flow rate (mL/s); T is respiratory time (s); and f is
breathing frequency in breaths/min (bpm).
Jacques and Kim (2000).
Empirical Deposition Models
ICRP:
International Commission on Radiological Protection
http://www.icrp.org/
”Human Respiratory Tract Model for Radiological Protection”,
Annals of the ICRP (1994), Publication 66, Elsevier Science
NCRP:
National Council on Radiation Protection and Measurements
http://www.ncrponline.org/
”Deposition, Retention and Dosimetry of Inhaled Radioactive Substances”,
Report S.C. 57-2, NCRP, Bethesda, MD (1997).
• Total and Regional Deposition (Size-resolved)
• Different Breathing Conditions
• ”Typical” Adults and Children
Differences between ICRP and NCRP models usually smaller
than differences between individuals.
ICRP Deposition Model
Deposited Particle Fraction
International Commission on Radiological Protection
Settling
Diffusion
Total
Alveoli
Particle Diameter (µm)
Impaction
Aerosol Particle Separation - Conventions
IPM: Inhalable particle fraction (fraction inhaled through nose and mouth)
TPM: Thoracic particle fraction (fraction passing the larynx)
RPM: Respirable particle fraction (fraction reaching the alveoli)
ICRP Deposition Model
• Total deposition DF (ICRP)


0.911
0.943
DF  IF 0.0587


1

exp(
4
.
77

1
.
485
ln
d
)
1

exp(
0
.
503

2
.
58
ln
d
)

p
p 

• Inhalable Fraction IF
1
IF (d a )  1  0.5(1 
))
2.8
1  0.00076d p
Regional Deposition - Deposited Fraction
• Deposited Fraction for the head airways DFHA
DFHA


1
1


 IF

 1  exp(6.84  1.183ln d

1

exp(
0
.
924

1
.
885
ln
d
p
p


For the tracheobronchial region DFTB
 0.00352
[exp(0.234(ln d p  3.40) 2 )  63.9 exp(0.819(ln d p  1.61) 2 )]
DFTB  
 d

p


• For the alveolar region DFAL
 0.0155
[exp(0.416(ln d p  2.84) 2 )  19.11exp(0.482(ln d p  1.362) 2 )]
DFAL  
 d

p


Lung Deposition av particles - ICRP
The lung deposition efficiency is highly
Total
size-dependent
The relevant size is that to which the particles grow
in the humid environment.
Important parameters:
1. Dry particle size distribution
2. The hygroscopic properties as a function
of particle dry size
Dry particle
Salt
Humidified particle
RH=90%
Water solution
The more water-soluble material the particle
contains, the more it will grow.
Cloud drop
RH>100%
RH Hysteresis Effect
Ammonium Sulphate
RH Hysteresis
2
Diameter Growth Factor
Particle Dry Diameter = 100 nm
1.8
1.6
Supersaturated Salt Solution
1.4
1.2
Deliquescence
Crystallisation
Dry Particle
1
Increasing Relative Humidity
0.8
0
10
20
30
40
50
60
Relative Humidity (%)
70
80
90
100
Köhler theory for cloud droplet formation
1.008
Raoult´s term
Kelvin effect
Kelvin
term
1.006
RH 
Kelvin term
 4M w 
p
 aw  exp

p0 (T )
 RTd 
1.004
RH
Activation
1.002
1
Salt effectterm
Raoult´s
0.998
0
200
400
600
800
1000
1200
Wet diameter (nm)
1400
1600
1800
2000
Particle hygroscopic properties
Importance for deposition in the lungs
Hygroscopic
particles
shift the minimum
Lungdeposition
och
tillväxt vid
Lung Deposition
andhygroskopisk
Hygroscopic
Growth
r.f.=99.5%
in the deposition
curve
to smaller sizes.
(at RH=99.5%)
DeponeradFraction
andel
Deposited
2.8
2.6
80%
2.4
2.2
60%
Hygroscopic particles affect deposition:
40%
Lungdeposition
- fuktad
Deposition
– Humidified
Deposition
– Dry - torrt
Lungdeposition
Growth
Factor
TIllväxtfaktor
2.0
1.8
Tillväxtfaktor
Growth Factor
Hygroscopic
(r.f.=99.5%)
RH=99.5%)
(at
3.0
100%
• More particle mass (>200 nm) is deposited in 1.6
the
20% upper airways.
1.4
Deposition
decreases
(<100
nm)
Deposition
1.2
increases
particles
are deposited
•0% Fewer very small
in
(number).
1 the lower airways
10
100
DryTorrdiameter
Particle Diameter
(nm) (nm)
1.0
1000
Transient Effects
Particle Hygroscopic Growth
Broday and Georgopoulos AST(2001)
Hygroscopic Tandem Differential Mobility Analyser
H-TDMA
Ambient
Aerosol
CPC
Bipolar
Charger
Drier
Monodisperse Aerosol
Excess Air
DMA1
Humid
Aerosol
CPC
Excess Air
DMA2
Aerosol
Humidifier
Dry Sheath Air
Division of Nuclear Physics, Lund University
Humidified
Sheath Air
Chemical composition and hygroscopicity
Particle
Number
Concentration
1/cm3
104
103
Sulfuric Acid
Organic
Sulfate
Nitrate
Mineral
Sea Salt
Carbonaceous
102
101
1
10
100
1000
Particle Diameter (nm)
Particle
Number
Concentration
Dry Dp
Wet Dp
10000
The Lund H-TDMA – Measures hygroscopic properties
Lycksele, northern Sweden,
JanMarch 2002, Measurement sites
Central
Södermalm
Sites
Norrmalm
Vindeln SE
Forsdala
Furuvik
Forsdala – Particle sampling
Soot
Hygroscopic properties (TDMA)
Size distribution (DMPS)
Elemental composition (SAM)
(filter, fine and coarse, PIXE)
Main ions (filter, IC)
Particle mass (TEOM)
(PM10 / PM2.5)
Chemical composition (Hi-Vol PM10)
Hygroscopic properties (H-TDMA) Dry size=265 nm
Hygroskopiska egenskaper
LTHs H-TDMA, Forsdala, Lycksele 2002
Torrstorlek = 265 nm
2.0
1.8
2.0
Pure
salts
Background
1.8
1.6
1.6
1.4
1.4
Poor
combustion
1.2
1.2
1.0
0.8
0.6
0.4
0.2
Hydrophobic
1.0
“Soot mode”  Wood combustion
particles nearly hydrophobic
Easily distiguished from accumulation
mode “background” particles
0.8
0.6
0.4
0.2
0.0
0.0
13/1 15/1 17/1 19/1 21/1 23/1 25/1 27/1 29/1 31/1 2/2
4/2
6/2
8/2 10/2 12/2 14/2 16/2 18/2 20/2 22/2 24/2 26/2 28/2 2/3
4/3
6/3
8/3 10/3
Hygroscopic Intermediate Hydrophobic
Date 2002
2002
Datum
Mindre-hygroskopisk
Hydrofob
Mer-Hygroskopisk
Aerosolandel
fraction
Aerosol
RH
90%
factor at(r.f.
Growth
Diametertillväxt
= 90%)
Residential area with wood combustion
Forsdala, Lycksele, Sweden 2002
Particle hygroscopic properties
Lung
deposition
(Forsdala)
Particle lung
deposition
(number,
surface
Medelstorleksfördelningar
och lungdeposition
area,volume)
can be calculated
with a time
Antal - Yta - Volym
2002 (LTHs DMPS)
resolutionForsdala,
of 10 Lycksele
minutes.
4500
9
Antal
Number
Deponerad
Deposited antalsandel
Number
Surface
Yta
Deposited ytandel
Surface
Deponerad
Volume
Volym
Deposited volymsandel
Volume
Deponerad
3000
7
6
2500
5
2000
4
1500
3
1000
2
500
1
0
0
1
10
100
Torr
partikeldiameter
Dry
Particle
Diameter(nm)
(nm)
1000
10*Ytkonc. dS/dlogDp (µm2/cm3)
Antalskonc. dN/dlogDp (cm-3)
3500
8
Volymkonc. dV/dlogDp (µm3/cm3)
4000
Average of number, surface and volume
concentrations and
Fraction deposited in the respiratory system
Number
(cm-3)
Surface
(m2/cm3)
Volume
(m3/cm3)
Average Conc.
Entire period
4910
120
4.7
Cold
(< -10 C)
8700
225
8.7
”Warm”
(> -10 C)
2880
63
2.6
26%
10%
11%
Tracheobronchial
8%
2%
3%
Head Airways
7%
16%
27%
43%
29%
41%
Deposited fraction
(entire period)
Alveolar
Total
Lung Deposition Measurements
RESPI instrument
Inlet
RESPI
Inhale tank
10 dm3
Temp./RH-sensor
DMA
2-way valve
CPC
Drier
Heated area
1-way valves
Pneumotachograph
Mouthpiece
Outlet
Exhale tank
2 dm3
Volume >40 cm3
Validation of the Particle Lung Deposition
Determined by the dry size distribution and the
hygroscopic properties.
H-TDMA
Hygroscopic Tandem Differential Mobility Analyzer
CPC
DMA1
CPC
DMA2
Water
uptake of
individual
particles
Humidified
particle
size distribution
Particle Lung Deposition
0.8
20040514
20040519
0.7
DMPS
Differential Mobility Particle Size
Modelled
Deposited fraction
0.6
0.5
Measured
0.4
0.3
0.2
0.1
0
Dry particle
size distribution
RESPI
SMPS + Inhalation system
Lung Deposition Monitoring Device
10
100
Particle Diameter (nm)
1000
Number concentration
[dN/dlogDp]
0.12
Inhaled distribution
0.1
Exhaled distribution
0.08
Size-shifted exhaled
distribution
0.06
0.04
0.02
0
10
100
Diameter [nm]
1000
RESPI Accuracy
Deposited fraction (%)
100%
90%
Test
Test subject
subject 1,
1, 26
26 years
years old
old
ICRP,
ICRP, hygroscopic
hygroscopic
80%
Test
Test subject
subject 2,
2, 31
31 years
years old
old
Blanchard
Blanchard &
& Willeke,
Willeke, 1983
1983
Test
Test subject
subject 3,
3, 31
31 years
years old
old
Tu
Tu &
& Knutson,
Knutson, 1984
1984
70%
60%
50%
40%
30%
20%
10%
0%
10
100
Dry mobility diameter (nm)
1000
Previous measurements of
deposition of ultrafine particles
Studies Subjects
Hygroscopic
2
7
Exercise (healthy)
2
7
Spontanous breathing 2
35
Asthma
1
16
COPD
2
15
Elderly
1
7
Ambient particles
1
6
Our Measurements



30 subjects (21 men, 9 women)
both rest and exercise
both hydrophobic and hygroscopic
particles
Largest number of subjects (prev. 18)
First measurement of respiratory
deposition of hygroscopic particles
during spontanous breathing (and
exercise)
Large size interval (15-300 nm)
Lung function tested
Most complete study of respiratory
deposition of ultrafine particles in healthy
human subject.
Inter-subject variability
Deposited Fraction
DEHS Oil Particles
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
10
100
Dry mobility diameter (nm)
1000
Mean values
100%
Deposited fraction (%)
90%
NaCl, men
NaCl, women
DEHS, men
DEHS, women
80%
70%
60%
50%
40%
30%
20%
10%
0%
10
100
Dry mobility diameter (nm)
1000
Rest/Exercise
100%
Deposited fraction (%)
90%
DEHS, relax
DEHS, exercise
80%
NaCl, relax
NaCl, exercise
70%
60%
50%
40%
30%
20%
10%
0%
10
100
Dry mobility diameter (nm)
1000
ICRP Deposition Model
NaCl
0.6
Total deposited fraction
Total deposited fraction
0.5
DEHS
0.4
0.3
0.2
0.1
0.5
0.4
0.3
0.2
0.1
0
0
0
5
10
15
Breathing frequency (min-1)
20
0
5
10
15
Breathing frequency (min-1)
20
DEHS
0.6
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Total deposited fraction
Total deposited fraction
NaCl
0.5
0.4
0.3
0.2
0.1
0
0
0.5
1
1.5
Tidal volume (L)
2
0
1
2
Tidal volume (L)
3
0.9
0.8
Deposited fraction
0.7
0.6
0.5
0.4
0.3
0.2
0.1
19.906
22.215
24.801
27.709
30.965
34.619
38.731
43.364
48.592
54.509
61.212
68.81
77.431
87.311
98.62
111.677
126.68
144.12
164.414
188.272
216.291
249.65
289.333
0
0
0.1
0.2
0.3
0.4
0.5
(DTm)0.5Vt0.49
0.6
0.7
0.8
Poor Wood Combustion
Deposited fraction
Exposure Chamber – Umeå University
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
DEHS-oil
Efficient combustion
Low-temp. combustion
10
100
Dry mobility diameter [nm]
1000
Outlook
 Respiratory deposition of 15 test subjects will be
investigated in March 2006 for a street canyon
aerosol at H.C. Andersen B. in Copenhagen.
 Data will be compared to test aerosol
measurements (NaCl and DEHS) for the same
test subjects taken in 2005.
 Respiratory deposition of 8 healthy elderly test
subjects will be investigated in March 2006 for a
street canyon aerosol at H.C. Andersen B. in
Copenhagen.
Particle sizing
To determine the size dependent deposited particle
fraction, we have to be sure we measure the same particles
before and after inhalation.
 Evaporation: Fractions of particles can evaporate at
body temperature depending on their chemical
composition.
 Coagulation: Particles can coagulate during the
measurement period depending on their concentration.
 Restructuring: Particles can restructure while being
exposed to high relative humidity in the human airways
depending on their state of agglomeration.
 Hygroscopic growth: Particles will grow in size while
being exposed to high relative humidity in the human
airways depending on their chemical deposition.
Positive size-shift (5 %)
Number concentration
[dN/dlogDp]
0.12
Inhaled distribution
0.1
Exhaled distribution
0.08
Size-shifted exhaled
distribution
0.06
0.04
0.02
0
10
100
Diameter [nm]
1000
Deposited Fraction
Error because of size-shift
(between the dry diameters)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
DF, 5 % positive shift
DF, 1 % positive shift
DF, ICRP
DF, 1% negative shift
DF, 5 % negative shift
10
100
Diameter [nm]
1000
Sketch of the H-TDMA-system
 first DMA to select a quasi-monodisperse fraction of
aerosol particles from a polydisperse aerosol
population in combination with a first CPC (I)
 a conditioning system increasing the relative humidity
in the sheath air flow and aerosol flow to a well defined
level (II)
 an analyzer consisting of a second DMA in
conjunction with a second CPC (III)
H-TDMA-system
 Specification
 DMA1 size range:
Dp = 20 - 300nm
 Aerosol RH range:
between 20 and 95%
 Sheath air RH range:
between 20 and 95%
 DMA2 size range:
Dp = 20 - 700nm
 Derived parameters
 Hygroscopic growth factor: wet diameter / dry
diameter
 Number fraction: peak area of one mode / peak
area of entire distribution
 Mixing state: internal / external
Gas phase chemical reactions
Hot vapours
Low volatility gases
Homogenous nucleation
and condensation
Condensation
Condensation nuclei
Primary
particles
Coagu- Agglomerates
lation
Droplets
Coagulation
Wind blown dust
+
Emissions
+
Sea spray
+
Volcanoes
+
Plant Particles
Activation
Coagulation Rainout
and
Washout
Diffusion
0.001
0.01
0.1
Sedimentation
1
10
Particle Diameter ( m)
Nucleation
mode
Aitken
mode
Accumulation
mode
Coarse
Particles
100
• Total deposition DF (ICRP)


0.911
0.943
DF  IF 0.0587


1

exp(
4
.
77

1
.
485
ln
d
)
1

exp(
0
.
503

2
.
58
ln
d
)

p
p 

• Inhalable Fraction IF
1
IF (d a )  1  0.5(1 
))
2.8
1  0.00076d p
Inhalability of particles
• Inhalable Fraction – the fraction of particles originally in
the volume of air inhaled that actually enters the nose
or mouth (ACGIH criterion)
IF(da )  0.5(1  exp(0.06da ))
for Uo<4 m/s
IF(da ,Uo )  0.5(1  exp(0.06da )) 105Uo2.75 exp(0.055da )
Q: What is the criterion for a good inhalable sampler?
Regional Deposition
Head Airways
Tracheobronchial region
Alveolar region
Total Deposition
A particle entering our respiratory system is subject to all the deposition
mechanisms described previously. The actual deposition efficiency of a given
particle size has been determined experimentally. Several models have been
developed to predict the deposition based on experimental data. Two advanced and
widely used ones are those developed by the International Commission on
Radiological Protection (ICRP) and the National Council on Radiation Protection and
Measurement (NCRP). The total deposition fraction (DF) in the respiratory system
according to ICRP model is
• Total deposition DF (ICRP)


0.911
0.943
DF  IF 0.0587


1

exp(
4
.
77

1
.
485
ln
d
)
1

exp(
0
.
503

2
.
58
ln
d
)

p
p 

• Inhalable Fraction IF
1
IF (d a )  1  0.5(1 
))
2.8
1  0.00076d p
Inhalability of particles
• Inhalable Fraction – the fraction of particles originally in
the volume of air inhaled that actually enters the nose
or mouth (ACGIH criterion)
IF(da )  0.5(1  exp(0.06da ))
for Uo<4 m/s
IF(da ,Uo )  0.5(1  exp(0.06da )) 105Uo2.75 exp(0.055da )
Q: What is the criterion for a good inhalable sampler?