Environmental Engineering Reference
In-Depth Information
People who inhale dust from a contaminated site can be exposed in two ways,
i.e.,
•
small particles will pass into the respiratory systems and may be deposited in the
lungs;
•
larger particles will get caught in the nasal passages and throat and eventually be
swallowed.
In the latter case, i.e., larger particles that will get caught in the nasal passages
and throat and eventually be swallowed, the uptake of contaminants and the toxico-
logical response will be the same as when soil is directly ingested. In addition, the
methods used to estimate soil intake, i.e., trace element excretion, cannot differen-
tiate between swallowed dust and direct oral intake. Therefore, swallowed dust is
included in the ingestion of soil exposure pathway (see
Chapter 6
by Bierkens et al.,
this topic). The remainder of this section will therefore exclusively treat inhaled dust
that reaches the lungs.
11.6.1 Conceptual Model
People can be exposed by the inhalation of fine-grained material which is suspended
from contaminated sites. This is, however, only one of many sources of dust. Dust
particles in ambient air originate from a number of sources: traffic, combustion,
long-range transport and local resuspension. Most measurements performed on air
dust concentration focus on small size particles (with an aerodynamic diameter less
than 10
m, PM10). The finer fraction of dust in the air, PM10 or smaller, is usually
considered to be the most relevant for assessing exposure by inhalation of dusts
(Putaud et al.
2003
).
Contaminant concentration in the soil's fine-grained fraction, which gives rise to
fine-particulate dusts, can differ from the contaminant concentration in the fraction
of soil which undergoes chemical analysis (usually <2 mm). Often, contaminant
concentrations are higher in the fine fraction (Bright et al.
2006
; Young et al.
2001
).
Important parameters for exposure are:
μ
•
The concentration of particles from the resuspension of soil in the inhaled air.
•
The fraction of soil particles deriving from the contaminated area.
•
The fraction of dust particles which is respirable.
•
Contaminant concentration in respirable particles compared with the contaminant
concentration measured by chemical analyses of soil.
•
Inhalation rate.
•
Exposure time.
•
Fraction of the dust which is exhaled directly and not retained in the lungs.
In addition, when exposure to contaminated dusts occurs indoors, the transport
of dust from outdoors to indoors must be accounted for.
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