Aerosol Dose - Aerosols: Measurement, Dosimetry, and Health Effects - page 76

Compartment Transfer mechanisms Parameters affecting ultimate aerosol dose

d p
P io

aerosol diameter (µm)
penetration factor (unitless)
particle density (g/cc)
penetration from filtration (unitless)
deposition rate (h -1 )
air exchange rate (h -1 )
indoor mixing factor (unitless)
outdoor air temperatures (°C)
indoor air temperatures (°C)
body temperatures (°C)
indoor, outdoor, respiratory system
relative humidities (%)
chemical composition
chemical reactivity (h -1 )
filtration ability of lungs (unitless)
breathing rate (L/min)
solubility (g/L, g/mol)
translocation
biokinetics

Outdoor
air

ρ

f(d p , P io , ρ, P f , d, λ, T a:i.o , RH a:i.o , S, k)

P f
d
λ
m
T ao
T ai
T b
RH a:i.o

See chapters 2, 6, 10

Indoor
air

f(d p , ρ, d, λ, m, T ai , T b , RH a:i.o , S, k)

See chapters 2, 6, 10

Exposure
C t

f(d p , ρ, FAL, R, T a:i , T b , RH a:i.o , S, k)

S
k
FAL
R
s
τ
K b

See chapters 2, 5, 6, 8

Respiratory
system
deposition

f(T b , RH a:i , S, k, s, τ, k b )

See chapters 1, 6, 12

Dose

FIGURE 4.1 Parameters affecting ultimate inhaled particle dose, showing physical transfer mechanisms
across to microenvironmental compartments. The chapters in this topic relating to the various transfer mecha-
nisms are listed.

In the study of the pathway of aerosol exposure to dose to effect, three important conditions should
be taken into account:

1. Dose, the physical parameter responsible for the health effect, should be deined correctly.

2. If, as in most practical cases, the dose is not measured directly, the correlation between the
value of the measurable surrogate and the dose should be established.

3. The uncertainty related to the value of the dose surrogate should be assessed correctly.

The last condition is especially important in the case of aerosols where uncertainties are very high
due to spatial and temporal variability, as are uncertainties associated with the interaction between
aerosols and humans.
Figure 4.1 describes the particle dose pathway, indicating the complex set of physical parameters
and mechanisms at play. The parameters and mechanisms shown in the igure are intended to be
illustrative rather than comprehensive. Further details may be found in the chapters of this topic as
indicated in the igure.

4.2 ENVIRONMENTAL DOSIMETRY
Assessing the aerosol dose resulting from an environmental exposure has a particular set of issues.
These problems vary depending upon environmental conditions, particle sources within environ-
ments, and the activities of the occupants and particle sources within them.
The issues may vary greatly, depending upon whether the exposed individuals are outdoors,
indoors, and whether they occur in an occupational, residential, or another setting.