Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
prioritized to ensure that the primary objective is fulfilled. Study
parameters must be selected that are consistent with the objective. A
study design is formulated which links objectives to measurement
parameters in a cost-effective manner. Two critical and often
overlooked elements of the study design are development of a
statistical analysis plan and quality assurance (QA) objectives. For
general population studies, methods for measurement and analysis of
contaminants in collected environmental or biological samples must be
sufficiently sensitive to determine their concentration at typical
ambient levels. For multimedia studies, method detection limits must
be consistent across media. The study design is not complete until a
pilot study has been conducted to evaluate sample and field study
procedures.
3.3 Sampling and generalization
Decisions on population sampling strategies involve consideration
both of the populations that are available and of the types of
measurements needed. Of prime consideration are the people, place and
time (i.e., individuals, locations, sampling period or conditions)
from which exposure samples are to be collected. Also, it is important
to determine if the estimates to be derived from the proposed sample
could be generalized to a wider population of interest. For example,
consider an exposure assessment study from a sample population of a
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6/1/2007