The Nervous System – Target Organ Into the Twenty-First Century
The Nervous System – Target Organ into the Twenty-First Century R. Douglas Hamm MD, CCFP, FRCPC (Occ Med), FCBOM President, Canadian Board of Occupational Medicine CONTENTS 1. WHY NEURONS MAKE GOOD TARGETS FOR OCCUPATIONAL TOXICANTS 2. FROM CLASSICAL PLUMBISM TO BEHAVIORAL TOXICOLOGY 3. TOXICOKINETICS, COMPARTMENTS, AND PBPK MODELS 4. THE DIVERSE TOXICODYNAMICS OF THE NERVOUS SYSTEM 1. Peripheral Neurons (neuronopathy, axonopathy, myelinopathy) 2. Synaptic Neurotransmission (cholinergic pathways) 3. Special Senses (visual, auditory, olfactory) 4. Movement Disorders (parkinsonism, ataxia, tremor) 5. Neuroaffective and Neurocognitive Effects 5. NOTEWORTHY OCCUPATIONAL NEUROTOXICANTS 1. “Heavy metals” (Pb, Hg, Tl) and other elements (Mn, As, Al, Sb, Te) 2. Organic Solvents (toluene, xylene, styrene, C2HCl3, C2Cl4, CH3CCl3, CS2) 3. Gases (HCN, CO, H2S, ethylene oxide) 4. Pesticides (organophosphates, carbamates, organochlorines, pyrethroids, neonicotinoids) 6. CLINICAL NEUROTOXICOLOGY 1. Identification of Occupational Neurotoxic Disorders 2. Biomarkers of Exposure and Effect 3. Clinical Investigations of Neurotoxicity 1. WHY NEURONS MAKE GOOD 2. FROM CLASSICAL PLUMBISM TO TARGETS FOR OCCUPATIONAL BEHAVIORAL TOXICOLOGY TOXICANTS Hippocrates (c. 460-370 BC) has been cited as Neuroanatomical structures have large surface the first ancient author to describe a case of areas and receptor populations, e.g., the occupational neurotoxicity but this has been surface area of the brain’s 100 billion neurons shown to be erroneous (Osler, 1907; Waldron, totals hundreds of square metres. 1973, 1978; Skrabanek, 1986; Vance, 2007). The earliest report appears to be that of Neurons have high rates of metabolism, e.g., Nicander of Colophon (2nd cent. BC) who the brain at 2% body mass consumes 20% of observed that in “psimuthion” i.e.
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