Biomarkers of exposure can be used as part of an exposure assessment t
o assess potential health risks when exposure measurements and health
effects occur during the same period of time. Exposure assessment is t
he determination of the concentration of a chemical in an environmenta
l medium coupled with the presence of the human in that environment. A
biomarker of exposure gives an assessment of absorbed dose in the wor
ker. A biomarker of effect, often referred to as a biomarker, is used
in the assessment of health risk. A biomarker of effect gives an asses
sment of the effect of a chemical on a physiological process and is an
indicator of a possible adverse health effect. For example, biomarker
s of exposure give an assessment of a worker's current exposure to sol
vents and some metals. Biomarkers of exposure for chronic health effec
ts with long latent periods, such as carcinogens, are more problematic
al. These exposure indicators, however, can be used to help reconstruc
t past exposures. Selected biomarkers of exposure can also be predicto
rs of adverse health effects. Examples include the use of 2,5-hexanedi
one and 2-ethoxyacetic acid in urine as indicators of exposure to n-he
xane and 2-ethoxyethanol, respectively. These two urinary metabolites
are 'active' metabolites responsible for observed neurotoxic and repro
ductive effects. Biomarkers of exposure are particularly useful for th
e objective assessment of current systemic exposure to chemicals that
are readily absorbed through the skin. Exposure assessments, including
the use of biomarkers of exposure, are necessary to postulate a cause
of observed adverse health effects seen in epidemiological investigat
ions and to determine the bioavailability of the chemicals present in
the workplace.