ABSTRACT
Exposure-initiated assessments are the least common. For chemicals, a risk assessment may
be initiated by the observation of elevated body burdens. For exotic organisms one may be
initiated by observations of a new pathogen in an organism or new species in an ecosystem.
Exposure-initiated assessments require determination of the sources as well as the risks of the
effects. For example, the observation of high mercury levels in fish has led to risk assessments
that determine the sources as well as the risks to humans and piscivorous wildlife (EPA 1995).
