Biomarker research in neurotoxicology: The role of mechanistic studies to bridge the gap between the laboratory and epidemiological investigations

There is an increasing interest in the development and validation of biomarkers for use in biochemical/molecular epidemiological studies. Though the area of neurotoxicology has received much attention in the past several years, it still lags behind with regard to the development of biomarkers, particularly those of health effects and susceptibility. This review discusses several aspects of biomarker research as it relates to neurotoxic compounds and focuses on selected agents (organophosphorus insecticides, styrene, n-hexane, carbon disulfide, acrylamide), which have been the subject of a number of investigations in animals and humans. While traditional biomonitoring approaches and novel techniques (e.g., hemoglobin adducts) provide several measurements for monitoring exposure to neurotoxic chemicals, potential markers of genetic susceptibility have been seldom investigated in a neurotoxicology context. Furthermore, the complexity of the nervous system, together with the multiplicity of end points and the limited knowledge of the exact mechanism(s) of action of neurotoxicants, has led to only limited advancements in the development of biomarkers for neurotoxic effects. Significant progress in this area will depend upon an increased understanding of the cellular, biochemical, and molecular targets directly involved in neurotoxicity.