Environmental Engineering Reference
In-Depth Information
1.0
0.8
0.6
0.4
0.2
0.0
0
20
40
60
80
100
120
d
(nm)
FIGURE 11.8
Relative deposition rate per mouse versus mean particle diameter (ibuprofen). Bars indicate
standard error. Line is logistic regression analysis result.
WB
Dose =
D n mt
av
(11.4)
0
where
n
a
WB
is the arithmetic mean between the WB chamber inlet and outlet particle concentrations
m
is the mean particle mass
t
is the inhalation time
Note that the lung-deposited dose is a function of the product
fV
T
(where
f
and
V
T
are average mouse
breathing frequency and tidal volume, respectively) which for the WB inhalation experiments can
differ from that of the NOE chamber by 20% (Schaper and Brost, 1991; Hamelmann et al., 1997;
Vijayaraghavan, 1997; Currie et al., 1998). Therefore, we assume that the accuracy of Equation 11.4
is also about 20%.
To demonstrate the validity of our measurements of the lung-deposited dose, we evaluated the
particle deposition eficiency which follows from Equation 11.5:
D
0
≈
fV
T
ε
(11.5)
where ε is the lung deposition eficiency, that is, the ratio of the difference between the numbers of
inhaled and exhaled particles to the number of inhaled particles. From Equations 11.3 and 11.5 we get
⎡
⎤
1
/
N
−
⎛
⎞
⎟
F
fV
n
n
⎢
⎢
⎥
⎥
out
ε ≈
1
(11.6)
⎜
( )
0
T
out
⎣
⎦
We used the mouse breathing frequency and the mice tidal volume as equal to
f
= 5.0 s
−1
and
V
T
=
0.16 cm (Fairchild, 1972; Meade et al., 1993; Onischuk et al., 2008). The particle deposition efi-
ciency as a function of the mean particle diameter is shown in Figure 11.9. One can see that ε
tends to unity at small diameter values, which is in good agreement with numerical simulations
for the particle lung deposition (Wong, 2007). The aerosol depletion in both the empty and mice-
occupied WB chambers was measured in special experiments and found to be independent of the
mean particle diameter within the range of 35 <
d
< 120 nm. To this end aerosol concentration outlet
(
n
ou
( 0
) to inlet (
n
i
( 0
) ratio was measured with the aerosol spectrometer for the empty chamber to
be (
n
( )
0
( )
0
/
n
=
0
.
94
±
0 0
.
1
). To measure the aerosol depletion in the occupied chambers due to the
out
in
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