Biomarkers in toxicology and risk assessment.

Over the last 30 years, the field of biomarkers has greatly expanded as early and specific endpoints for monitoring cellular responses to various disease states and exposures to drugs and chemical agents. They have enjoyed some success as predictors of health outcomes for a number of clinical diseases, but the application to chemical exposure risk assessments has been more limited. Biomarkers may be classified into categories of markers of exposure, effect, and susceptibility. Currently, "omics" biomarkers (i.e., genomic, proteomic, and metabolomic/metabonomic) are the major classes of biomarkers under development. These markers represent a continuum of cellular responses to drug or chemical exposures and provide linkages to mechanisms of cell injury/cell death or carcinogenic transformation. On the other hand, translation and application of these biomarkers for risk assessment has been limited due to validation and interpretation issues that need to be addressed in order for these potentially extremely valuable endpoints to reach their full potential as predictive tools for public health. This short chapter will briefly review these three "omics" biomarker classes and examine some validation/translation aspects needed in order for them to reach their full potential and acceptance as valuable tools for application to risk assessment.