Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
reports on Exposure Assessment (EUR 14356EN) and Time-activity
Patterns in Exposure Assessment (EUR 15892EN) along with a report on
Study Design (EUR 15095EN) for air pollution epidemiology in which
exposure assessment was featured.
The US EPA (1996a) updated its 1989 Exposure Factors Handbook
(EPA/600/8-89/043) with a comprehensive three-volume compilation of
statistical data on various factors used in assessing exposure. The
updated document incorporates new information available from the late
1980s through the first half of the 1990s. Used by risk assessors in
conjunction with the revised Guidelines for Exposure Assessment (US
EPA, 1992a), the new Exposure Factors Handbook gives point estimates
for many parameters along with distributional information. The median
as well as the high end of individual and population risk can be
calculated using these inputs and appropriate concentration data.
As described earlier in the book, the WHO has been promoting
exposure assessment methodology and investigations for almost
20 years. The HEAL project has provided training, documents and
assistance to investigators worldwide. Notable successes of HEAL have
been the establishment of high-quality measurements for metals such as
lead and cadmium (see Foreword and Chapter 11).
A number of professional organizations have contributed to the
promotion of exposure sciences through conferences, workshops and
publications. Although a comprehensive description of all these
efforts is beyond the scope of this chapter, readers may find some of
the publications listed in Table 38 useful.
12.2 Exposure studies
Exposure studies described in this chapter serve as examples of
the variety of approaches and purposes such investigations have taken.
Exposure studies are conducted for different reasons. Some were
designed for the simple purpose of demonstrating methodology for
generating hypotheses. Other studies were components of
epidemiological studies. Still others were designed for regulatory
purposes to determine possible exposure routes and dose rates for
specific products or applications. Such studies may have participants
adhere to a certain regime. There are also examples of large and
expensive studies recruiting representative populations to provide
generalizable exposure and risk estimates. Brief descriptions of
different types of studies are presented in this chapter. Those
included illustrate a variety of design strategies. The following
discussion is not intended as a comprehensive review but may give the
reader the sense of how exposure assessment can serve a variety of
purposes.
12.3 Air pollution exposure studies
Perhaps the most numerous examples of exposure studies are in the
field of air pollution. This section briefly presents examples of air
pollution studies performed for a variety of purposes.
12.3.1 Particle studies
Particle exposures have taken a new importance in light of a
substantial and growing literature on morbidity and mortality effects
of ambient particulate matter (Wilson & Spengler, 1996). In 1986, the
US Congress mandated that the US EPA Office of Research and
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