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Relationship between unattached fraction and particle surface area concentration
4 . E- 06
3 . E- 06
y= -4.0E- 05x 5 + 1.5E- 04x 4 - 2.1E- 04x 3 + 1.6E- 04x 2 + -6.1E- 05x + 1.1E- 05
R 2 = 1.0E+ 00
2 . E- 06
1 . E- 06
0 . E+ 00
0 . 2
0 . 4 0 . 5
Unattached fraction
0 . 8
1
1 . 2
0
FIGURE 16.5 
Relationship between particle surface area and unattached fraction.
50
50
20 nm TiO 2
250 nm TiO 2
40
40
Saline control
30
30
20
20
10
10
0
0
0
500
1000
1500
2000
0
50
100
150
200
250
TiO 2 mass (µg)
(A)
(B)
TiO 2 surface area (cm 2 )
50
50
40
40
30
30
20
20
10
10
0
0
0
100
200
300
400
0
10
20
30
40
50
TiO 2 mass (µg)
TiO 2 surface area (cm 2 )
(C)
(D)
FIGURE 16.6 
Mass vs. surface area health effect.
16.2.6  d iscussion and  c onclusions
The problem of aerosol deposition and lung dosimetry is very complicated. First, it is still very
dificult to measure the particle size distribution of aerosol particles in the breathing zone of
humans. But, even if such data were available, the behavior of aerosol particles according to
aerosol size spectra in different parts inside the lung is dificult to predict with high accuracy due to
humidity, temperature, lung morphology, and other factors. Therefore, direct measurement of lung
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