190
THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
RETENTION OF SUB-MICRON AEROSOLS IN HUMAN RESPIRATORY TRACT
100
on smaller particle sizes. In fact an interesting
estimation of what it might be is found in the
dataof Wilkening [8] for distribution of natural
% TOTAL RETENTION IN
THE RESPIRATORY TRACT
yadioactivity. A summary of his findings is
presentedin Table 1.
Tanie 1—DISTRIBUTION OF NATURAL
BADIOACTIVITY (WILKENING, 8) *
Percent of
radionctiotty
>0.005..-- 5
0.005-0.015.....
25
0.015-0.025.
.
50
0.025-0.035-.. 2.2.0 22-2 - wen ewe e ee eee
10
> 0.086.-. ~~. eee en ee ee ee ee
10
Particle diameter
electron microscopy.
<A typical particle size
distribution for the aerosol used is shown in
Figure 2, where both the mass and the count
diameters are plotted on a probit scale. The
median diameter on a mass basis (MMD)is
0.43 g, the median diameter by count (CMD)
is 0.056 », with standard deviation ¢ g=2.3
in each case.
STYLIZED DISTRIBUTION DATA
SODIUM CHLORIDE AEROSOLS FOR HUMAN STUDY
able. However, this docs not negate thie fact that most of the activity
appears on small particles.
Thus virtually afl activity appears to be on
particles too small for detection in ordinarylight
microscopes.
In the light of these considerations experimental determination of the retention of submicron aerosols in the humanrespiratory tract
has been of intense interest in our Jaboratory.
A few results seemed worthy of presentation
here since they represent one of the first extensions of experimental data into the “theoretical
i
005
respiratory pliysiology of the subject.
Particle size measurements were made by
*Wilkening used an vlectrostatte separator of specia) design, and as
described by Meresr (0f the serarationof sizes may not be very depend-
50
191
includes percent mass deposition, particle size
distribution of the inhaled air, and the various
dynamic and volumetric characteristics of the
4
0,10
win
|
0.20
qt.
PARTICLE DIAMETER B.
.
0.50
40
2,0
spenders |—nepomer
50
10
Figure 1.*
THEORETICAL DATA
per min,
Curve No, 2: Landahl (3] and Landablef af, (4): Plow rate, 300 cm*/sec;
16 eycles per min;tldal air volume, 450 em?.
Curve No. 8: —~—— Flow rate, 300 emsee; 744 cycles per mln; tidal air
volute, 900 crn!.
Curee No. 4: ———- Flow rate, 300 emysec; § cycles per min; tidal air
volume, 1350 cm.
Curve No, 8: Landahl (3): Flow rate 1000 emYsec; 15 cycles per min;
Udalalr volume, 1800 ern},
Curee No, & Wilson and La Mer [5]: 54 cycles per min,
Curte No. ——- 2 eyeles per mtn.
Curee No, 8: Landahl ¢t ad. [4]: 15 eycles per min; tide] air volume, 450
em,
Curee No, 6: ~-—— 734 cycles per mun; tida! air volume, 900 emi,
Curve No, [0; —-—— 5 cycles per min; tidal alr volume, 1350 em’,
Curve No, £1; Brown ¢f al. (6): Each point represents the mean of many
values.
Curre No. 1#: Van Wijk and Patterson {7}: 19 cycles por min,
*Taken directly from reference 1,
The aerosol was composed of sodium chloride
crystals, 99 percent of whose particles were less
than 0.4 « in diameter. Retention was meas~
ured by difference between the inhaled and
exhaled concentrations.
The retention apparatus consists of two units:
EXPERIMENTAL Data
Curve No. t: Findeisen [2]: Postulated flow rate, 200 omisec: 14 eycles
zone” seen in Figurei.
~
€
Sss
3
uw
a
4
B
F
=
19
08
06
os
og
s
S&S
919
0.08
0.06
04
CMD ~0 056m
MMD ~ 0.434
0.02
oq~-23
ool Ol
io
30 «60
90
99 999
PERCENT LESS THAN STATED SIZE
Friovae 2.
The results of the
17
experiments done
(1) an exposure unit, composed of an aerosol
generator, mixing chamber, aerosol samplers
on 9 humansubjects while breathing sponta-
item is a high-speed slide valve, controlled by
deposited in the respiratory tract was found
and a cooperative respiratory valve (the latter
neously provide several points of interest.
First, on a mass basis the amountofthe aerosol
minute pressure changes in the face-piece of the
to be somewhat greater than that predictable
subject, which accomplishes the separation of
inspired and expired air) and (2) a control
system composed of the respiratory slide valve
control unit, an electronic integrator for automatic tidal volume measurement, and a pneumotachograph, The apparatus and methods
are described in detail in references 12, 13, and
14,
Thus, information obtained in an experiment
from commonly accepted particle size-depo-
sition relations.
The difference is not Jarge
but is significant statistically.
Second, there
appear to be several physiologic factors which
affect the oxtent of mass deposition.
With regard to the first point, 63.4 percent of
the inhaled acrosol mass was the mean deposi-
tion value, The 95 percent confidencelimit is
57-69 percent for the mean. Generally ac-