Biological markers of neurotoxic diseases.

The importance of biological monitoring, to detect exposure to toxicants and to aid in making decisions about prevention and human health risks, is widely recognized. Thus, in the past few years the study of biomarkers has been the focus of considerable interest in the fields of toxicology, epidemiology, occupational and environmental health (1-5). The development of neurotoxicity is a multistep process which involves i) the exposure to a toxicant (external dose); ii) the penetration and distribution of the neurotoxicant into the organism (absorbed dose); iii) the interaction of the parent compound or metabolite with the critical target cells/tissue (target dose); iv) the occurrence of a biological effect; v) the induction of a health effect. Each step can be monitored by appropriate biomarkers. The latter are conventionally divided into three categories: biomarkers of exposure, of effect and of susceptibility (4-7).