Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
Knowledge of human exposures to environmental contaminants is an
important component of environmental epidemiology, risk assessment,
risk management and status and trends analysis. Exposure information
provides the critical link between sources of contaminants, their
presence in the environment and potential human health effects. This
information, if used in the context of environmental management
predicated on human risk reduction, will facilitate selection and
analysis of strategies other than the traditional "command and
control" approach. Most of the environmental management structures
around the world rely directly on the measured contaminants in various
media to judge quality, infer risk and interpret compliance. Even in
these cases, exposure information can evaluate the effectiveness of
protecting segments of population more susceptible or at higher risk.
It is this direct connection that makes exposure measures
invaluable for evaluation of environmental health impacts on a local,
regional and global scale.
3. STRATEGIES AND DESIGN FOR EXPOSURE STUDIES
3.1 Introduction
Accurate estimates of human exposure to environmental
contaminants are necessary for a realistic appraisal of the risks
these pollutants pose and for the design and implementation of
strategies to control and limit those risks. Three aspects of exposure
are important for determining related health consequences:
* Magnitude: What is the pollutant concentration?
* Duration: How long does the exposure last?
* Frequency: How often do exposures occur?
The design of an exposure study specifies the procedures that will be
used to answer these three questions.
In this chapter, strategies and designs for exposure studies are
discussed with emphasis on their relative advantages and
disadvantages. The brief discussion of study design presented in
Chapter 1 is expanded upon here in terms of fundamental types of
generic study designs and approaches to assessing human exposure to
chemicals in the environment. Statistical considerations for study
design are presented in Chapter 4. The reader is referred to
subsequent chapters for details on implementing exposure study designs
through modelling (Chapter 6), monitoring of environmental media
(Chapters 7, 8 and 9) and monitoring of biological tissue (Chapter
10).
3.2 Study design
A good study design is the most important element of any exposure
study. A flow chart that includes critical elements is shown in Fig.
9. First the purpose of the study is defined: epidemiology, risk
assessment, risk management or analyses of status and trends (see also
Chapter 2). Within this context, specific study objectives are
formulated. Often studies have several objectives, which must be
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