Overview of Fate of Substances
Except for corrosive agents, most toxic substances do not cause harmful effects at the point
of entry. Instead, exposure marks the beginning of a rather tortuous path as the physiological
(metabolic) processes of the human body interact to absorb, distribute, store, transform, and
eliminate a substance. To produce a toxic effect, the chemical agent or its biotransformation
products must reach the critical site of action in a target organ at a sufficiently high concentration
and for a sufficient length of time. A target organ is the "preferential anatomical site" for the
expression of the toxic effects caused by a substance .
2
In Figure 5-2 a schematic representation is
given of the fate of a toxicant on uptake.