ABSTRACT
Expos ure is the contact or co -occurren ce of a con taminant chemi cal or other agent with a
biologi cal recept or (usually an organis m, but possibl y an orga n, popul ation, or communi ty).
The analys is of exp osure estimat es the magni tude of exposure of the recept ors that constitut e
the end point entities , distribut ed in space and tim e. These distribut ions may be estimat ed by
measur ing the contam inants in media (C hapter 20) or by mod eling the transpo rt and fate of
relea ses (C hapter 21). For new chemica ls, technol ogies, org anisms, or other agents , exposures
due to permi tting the release must be predict ed based on exp ected releases. For contam inate d
or oc cupied sites, exposures due to current con ditions and futur e conditio ns must be esti-
mate d. The bounda ries of exposu re modelin g vary wi th context (see Box 17.1) . Transport an d
fate models may include uptake an d ac cumula tion by some organ isms, but often stop with
concen trations in abiotic media . Com monly, the util ity of chemi cal an alyses at contam inate d
sites is limited by includi ng only ab iotic media or by limiting analys is of biota to those
consumed by humans. Hence, esti mation of exposu re may requir e mo deling of chemi cal
accumul ation and transp ort in food webs.
