The use of biomarkers as an exposure assessment tool is not without limitations. Some of its limitations were discussed in Lecture 3, specifically those with respect to low levels of markers available for quantification and the impracticality of collecting 24-hour urine samples. Other aspects of the down-side are discussed here and in the two slides that follow, which shall conclude the presentation of this lecture on epidemiology and health risk assessment.

In addition to the scientific, legal, and ethical concerns, the discussion on the use of biomarkers cannot be considered as complete without mentioning the techniques and purposes of biomonitoring.

Biomonitoring is defined as the measurement and assessment of toxic agents or their metabolites in human tissues, secreta, excreta, expired air, or any combination of these for the purpose of evaluating exposure and health risk. However, biomonitoring may also be broadly defined to include medical surveillance or genetic monitoring (Ashford et al., 1990). The use of biomarkers is closely related to biomonitoring because the toxic agent or its metabolites to be monitored can be used as a marker of exposure. As discussed in Slide 11, certain biomarkers are used to detect an adverse or a biologic response, such as DNA damage that leading to the initiation of an oncogenic event. There are also markers of disease or susceptibility (Hulka, 1990; National Research Council, 1989; Perera and Weinstein, 1982; Vine, 1994). In the case of exposure markers, their use provides the best estimate of an aggregate dose intended to account for all exposure pathways and sources.