Biochemical and biological markers: implications for epidemiologic studies.

Given that a major task for environmental epidemiology is to provide clear evidence of immediate and long-term health risks so that appropriate preventive measures can be taken, biochemical and biological markers of potentially hazardous environmental exposures are of great interest and possibly of great value. Such markers fall into two discrete classes: (1) those quantitatively related to the exposure itself, reflecting the magnitude of such exposures or the body burden of the pollutants, and (2) those markers that reflect the biological response to such exposures. In this paper we discuss the use of biochemical and biological markers in epidemiologic studies. Methods are presented for the use of markers to decrease misclassification errors in exposure studies. Relationships are derived that give minimum required values for laboratory sensitivity and specificity. Markers are also discussed in terms of some of the inherent problems in their use (e.g., ethical and legal considerations) and the likelihood of acceptance by participants in epidemiologic studies, researchers, regulators, and health professionals.