Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
these exposure media via inhalation, ingestion and dermal uptake. Fig.
21 illustrates the types of exposure pathways we use to carry out a
multiple-media, multiple-route, multiple-pathway exposure assessment.
Exposure assessments often rely implicitly on the assumption that
exposure can be linked by simple parameters to ambient concentrations
in air, water and soil. However, total exposure assessments that
include time-activity patterns and microenvironmental data reveal that
an exposure assessment is most valuable when it provides a
comprehensive view of exposure routes and pathways and identifies
major sources of uncertainty. Listed in Table 17 are potential
interactions among environmental media, exposure media and exposure
pathways that are addressed in this chapter.
An assessment of intake requires that we determine how much
crosses these boundaries. Thus, we see the need to address many types
of "multiples" in the quantification of human exposure, such as
multiple media (air, water, soil); multiple exposure pathways (or
scenarios); multiple routes (inhalation, ingestion, dermal); multiple
chemicals; multiple population subgroups; and multiple health
end-points. The matter is further complicated by the fact that
pollutants may have both systemic and route specific health effects.
For the compounds that have mainly systemic effects the total exposure
-- sum of all routes -- is most relevant; for other agents such as
pneumococci aerosols in the lung, dermal vs. ingestion absorption of
Table 17. Interactions among environmental media, exposure media and exposu
Exposure routes Media
Air Soil
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