Environmental health criteria. 60. Principles and methods for the assessment of neurotoxicity associated with exposure to chemicals

There is ample evidence of real and potential hazards of environmental chemicals for nervous system function. Changes or disturbances in central nervous function, many times manifest by vague complaints and alterations in behaviour, reflect on the quality of life; however, they have not yet received attention. Neurotoxicological assessment is therefore an imporant area for toxicological research. It has become evident, particularly in the last decade, that low-level exposure to certain toxic agents can produce deleterious neural effects that may be discovered only when appropriate procedures are used. While there are still episodes of large-scale poisoning, concern has shifted to the more subtle deficits that reduce functioning of the nervous system in less obvious, but still important ways, so that intelligence, memory, emotion, and other complex neural functions are affected. Information on neurobehaviour, neurochemistry, neurophysiology, neuroendocrinology, and neuropathology is vital for understanding the mechanisms of neurotoxicity. One of the major objectives of a multifaceted approach to toxicological studies is to understand effects across all levels of neural organization. Such a multifaceted approach is necessary for confirmation that the nervous system is the target organ for the effect. interdisciplinary studies are also necessary to understand the significance of any behavioural changes observed and thus, to aid in extrapolation to human beings by providing specific neurotoxic profiles. Concomitant measurements at different levels of neural organization can improve the validity of results. The following recommendations are made on the basis of the information contained in this book: Health personnel should take into account the possible role of exposure to chemicals whenever a patient presents with any neurobehavioural complaint. Neurotoxicological testing should be an essential consideration in any profile developed by the agencies responsible for the control of toxic chemicals. In the determination of the potential of a chemical to produce neurotoxic effects, a multidisciplinary strategy should be used. Priority should be given to obtaining clinical and epidemiological data when exposure occurs to chemicals suspected of being neurotoxic. Test development in preclinical neurotoxicology has evolved to the point where interlaboratory validation of procedures using prototypic neurotoxic agents could be attempted.