Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
7.1 Introduction
This chapter describes sampling methods used in environmental
exposure assessment to analyse chemical concentrations in air, water
and food. The information presented provides a general description of
available sampling methods and guidance for their selection. It is not
intended to be comprehensive and the reader should refer to the
research literature for specific details.
Assessment of human exposures to contaminants in environmental
media requires establishing measurement strategies and selecting
appropriate sampling instruments and analytical methods. Taken
together, these three elements define a monitoring programme.
Monitoring methods can be used to determine the magnitude, duration
and frequency of exposure to an environmental contaminant. Magnitude
of exposure is defined as the concentration of a specific pollutant
averaged over a predetermined time interval, such as 1 h, 24 h or a
lifetime. Different measurement methods have specific characteristics
that determine the locations in which they are feasible for use. In
the case of air, the method's sensitivity to pollutants determines the
averaging times over which it will provide reliable responses.
Therefore, a clear understanding of the concentration range
anticipated, averaging time of interest, and expected frequency of
exposure events is needed to identify appropriate field and laboratory
methods. In the absence of any prior information, pilot studies may be
performed to obtain the information needed to finalize the design of
the monitoring programme.
Selection of instruments will depend on the target population
(e.g., children or adults) and study objectives. In some situations,
understanding the distribution or the average population exposure to a
contaminant may be sufficient. In fact, most environmental monitoring
of contaminants in outdoor air, water at the point of distribution and
"market basket" surveys implicitly assumes that indicators of
population exposure are more relevant than information at the
individual level. Studies assessing individual exposures using such
surrogate measures should select sampling instruments and analysis
methods based on sensitivity, selectivity, response rate, portability,
durability and cost, among other factors. Table 20 summarizes these
concepts.
7.2 Air monitoring
Air sampling methodologies should conform to the exposure
assessment approach selected, either direct or indirect, as described
in Chapter 3.
Direct monitoring methods for exposure measurements include the
use of personal air monitors and/or analysis of human tissue and/or
biological fluids. Aspects of biomonitoring are described in
Chapter 10. Indirect air monitoring methods can include
Table 20. Selection factors for instruments and methods
Factor Comment
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Sensitivity The magnitude and duration of contaminant exposure define th
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