Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
locations, in transit, and outdoors. The concentration of respirable
particles (RSP) is displayed on the y axis, and the fraction of time
that person i spends in each microenvironment over the 24-h period
is plotted on the t axis. Even though the RSP concentration was low
inside the home, it contributed significantly to the time-weighted
exposure because this person spent 18 out of 24 h there. Conversely,
the RSP concentration outdoors made only a minor contribution because
this person was outdoors less than half an hour during the 24-h
period.
Indirect monitoring of ingestion exposures via hand-to-mouth
contact may be obtained by collection of dermal wipe samples. However
as indicated above, the use of this method has been limited to date. A
drawback of the dermal wipe approach is that the integration time may
be highly variable among subjects owing to variations in frequency of
hand and body-washing, making interpretation of the results difficult
(Fenske, 1993). Information on rates of contact between the
contaminated skin and mouth is also required to complete the exposure
assessment. A discussion of these types of data may be found in
Chapter 5.
Given the diversity of microenvironments that people move through
each day (see Table 7), application of the indirect approach to
exposure assessment is not straightforward. Its utility depends on
identification of and sampling in the microenvironments with the
greatest potential to influence human exposure. The costs and
practical difficulties of monitoring in all, or even most, of the
locations where people are likely to spend their time limits the scope
of indirect measurements.
Table 7. Potentially important microenvironments for air pollution exposure
Microenvironments Comments
Outdoors
Urban metropolitan areas where air pollution levels are high as
stationary sources
Suburban small- to medium-sized cities where air pollution levels
areas, although transport of urban pollution can affect l
Rural agricultural communities and small towns with few major a
Air pollution levels tend to be low, although transport o
local air quality under certain conditions
Indoors-occupational
Industrial manufacturing and production processes, such as those in
plants, and smelters
Non-industrial primarily service industries where workers are not involv
processes, such as insurance companies, law offices, and
Indoors-Non-occupational
Residential single-family houses, apartments, mobile homes, condomini
Commercial restaurants, retail stores, banks, supermarkets
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