ABSTRACT
When you follow two separate chains of thought, Watson, you will find some point of intersection
which should approximate the truth.
Sherlock Holmes, in The Disappearance of Lady Frances Carfax
Risk characterization for definitive risk assessments consists of integrating the available
information about exposure and effects, analyzing uncertainty, weighing the evidence, and
presenting the conclusions in a form that is appropriate to the risk manager and stakeholders.
The integration of exposure and effects information should be carried out for each line of
evidence independently so that the implications of each are explicitly presented. This makes
the logic of the assessment clear and allows independent weighing of the evidence. For each
line of evidence, it is necessary to evaluate the relationship of the measures of effect to the
assessment endpoint, the quality of the data, and the relationship of the exposure metrics in
the exposure-response data to the exposure metrics for the site. The actual characterization
for ecological risk assessment is then performed by weight of evidence (Suter 1993a; EPA
1998a). Rather than simply running a risk model, ecological risk assessors should examine all
available data from chemical analyses, toxicity tests, biological surveys, and biomarkers, and
apply appropriate models to each to estimate the likelihood that significant effects are
occurring or will occur and to describe the nature, magnitude, and extent of effects on the
designated assessment endpoints. ‘‘Because so many judgments must be based on limited
information, it is critical that all reliable information be considered’’ (The Presidential= Congressional Commission on Risk Assessment and Risk Management 1997).
