Biomarkers are physiological, biochemical and functional indicators that reflect exposure, early cellular response, or inherent or acquired susceptibilities. They can be considered as accurate and precise measures of chemical exposures and biologically effective doses, as well as warning signals of biologic effect. To identify relationships of agents and effects, it is needed to determine mechanisms involved in the continuum between exposure and clinical disease. This multi-step process starts with exposure, and progresses through internal dose, biologically effective dose, and altered structure or function, and comes to an end with clinical disease and its prognostic significance. The validation of any biomarker-effect relationship needs concomitant experimental and human studies. Biomarkers are used in several fields of science (toxicology, epidemiology, molecular biology, and clinical pharmacology etc.) and as a growing point of interest new markers are being developed at a rapid pace. They show a large spectrum from the very simple ones (blood hemoglobin measurement) to very complex and expensive determinations (DNA adducts). Consequently, advances in field of biomarkers by using analytical techniques based on molecular biology will accelerate the studies dealing with exposure to chemical agents, susceptibility of individuals or population, risk assessment, dose-response relationship (for both drugs and toxic chemicals) and public health.

Keywords: Biomarkers, Susceptibility, Biologically Effective Dose, Internal Dose, External Dose, DNA Adduct