ABSTRACT
Effective use of informa tion requi res congrue nce between the scientific model s p resented and the
decis ion maker’ s c onception of the problem .
Anders on (1998)
Concept ual mo dels are working hyp otheses abo ut how the hazardous agent or acti on may
affect the end point entities (B arnthous e and Br own 1994; EPA 1998a) . They include de scrip-
tions of the so urce, receiving environm ent, and pr ocesses by whi ch the recept ors come to be
exposed directly to the contaminants and indirectly to the effects of the contaminants on other
environmental components. They are conceptual in that they are purely descriptive, as opposed
to implemented models that actually quantify the entities and relationships. They are hypothet-
ical in that they represent an agreed description of the system to be assessed. Other conceptual-
izations of the system might differ in various ways such as having wider bounds (e.g., include the
watershe d and not just the lake) or more de tail (e.g ., include individu al fish specie s rather than
fish as a taxon ), or e ven different co ncepts of exposure and respon se (Box 17.1) .
