An introduction to environmental neurotoxicology: Lessons from a clinical perspective

In 1992, the Committee on Neurotoxicology and Models for Assessing Risk of the National Academy of Sciences in Washington DC focused with a scientific perspective on the identification of substances with neurotoxic potential, studies of exposed populations, risk assessment, and biologic markers of disease. This Committee recommended: "all physicians should be trained to take a thorough occupational-exposure history and to be aware of other possible sources of toxic exposure". Although convened after several outbreaks of neurotoxic syndromes, clinical neurological considerations were lacking. After defining keys words, namely Environment, Neurotoxicology and Neurotoxicants, we present some demonstrative cases; e.g., the Epidemic Neuropathy in Cuba, Minamata disease, ALS/PDC on Guam, and the ALS hot spot in the French Alps. Always with a clinical and practical approach, we will then review the milieux that contain and convey potential neurotoxicants, the different exposure routes and the clinical presentations. Drawing lessons from clinical cases, we offer some thoughts concerning the future of Environmental Neurotoxicology (ENT). Pointing notably to the diffuse chemical contamination of ecosystems and living beings, including Homo sapiens, we question the real impact of agents with neurotoxic potential on the human brain, considering the effects, for example, of air pollution, endocrine disruptors and nanoparticles. Concern is expressed over the lack of knowledge of the non-monotonic kinetics of many of these chemicals, the major concern being related to mixtures and low-dose exposures, as well as the delayed appearance in clinical expression of prevalent neurodegenerative diseases.