What is of physiological importance is the internal dose of the environmental chemical. That
is the amount of drug absorbed via ingestion, inhalation, and dermal routes. Once inside the
body, the chemical moves through the metabolic pathways of the body, is transformed and
either stored or eliminated. (Note that in utero exposure is not included on this slide – clearly
an important pathway for the fetus). There are various compartments that a xenobiotic
(foreign chemical) may traverse. Implied are the various transformations that a chemical
undergoes when subjected to the metabolic pathways of the body. In order to interpret a
biomarker, it is necessary to know where in this process the measured biomarker comes
from – that is whether it is a biomarker of exposure, susceptibility or effect as described on
the previous slide