[Biomarkers of neurotoxic effects induced by environmental chemicals]

Biological monitoring of neurotoxic effects induced by environmental chemicals covers a very broad spectrum of measurements beginning with molecular, subcellular and cellular changes through neurophysiological and neurobehavioral ones. For many years epidemiological studies had employed almost entirely neurophysiological and neurobehavioural ones. For many years epidemiological studies had employed almost entirely neurophysiological and neurobehavioural tests in the assessment of the magnitude and effects of exposure to neurotoxins. Only in the recent past, due to paramount advances in experimental biochemical toxicology, the application of biochemical tests-biomarkers of exposure, health effects and susceptibility-in neuroepidemiological studies became realistic. That was also associated with the detection of molecular targets for neurotoxins and the explanation of mechanisms of their effect. Exposure biomarkers define an absorbed dose and provide a quantitative measurement of adducts produced by neurotoxin (or its metabolite) or products of interaction with endogenic substances, for example, with DNA or enzymatic proteins. Biomarkers of health effects provide information on changes in the nervous system which occurred in its different sections: organic, tissular, cellular, subcellular and molecular, due to exposure to neurotoxic agents. Biomarkers of susceptibility inform that in a given person or population adverse health effects may be expected in the nervous system in the case of lower or higher exposure to a neurotoxic agent. They may prove useful in assessing the probability of progress in the disease of the nervous system due to exposure to environmental neurotoxins. They are measurable indicators of the nervous system biological factors which occur prior to exposure and are genetically determined or acquired. The latter may result from past diseases of the nervous system or earlier exposure to neurotoxic agents. The fact that the targeted cell-the nervous tissue-cannot be explored directly is one of the most important obstacles which still hinders the monitoring of neurotoxic effects by means of biochemical tests. On account of this limitation, in order to identify and characterise neurotoxic features, it is necessary to use those biochemical parameters which exist in easily accessible peripheral tissues, and which correspond with the parameters of the nervous tissue. It has thus far been found that biochemical markers present in the morphotic elements of peripheral blood (plates, leucocytes, erythrocytes) can be used as measurable, substitutive indicators of damages, dysfunctions and interactions in the nervous system caused by environmental neurotoxins.