18 - Nervous System

Abstract

The nervous system comprises the brain, spinal cord, sensory organs, and a vast array of nerves that control thought, movement, heart function, respiration, vision, hearing, speech, smell, touch, and many other physiological functions. Numerous neurotoxic chemicals have been identified. These include pesticides, aliphatic and aromatic hydrocarbons, alcohols, ethers, ketones, heavy metals, and mixtures of these. Hundreds of individual chemicals are established or suspected neurotoxins. Neurodegenerative diseases (NDDs) are those in which the irreversible deterioration of neurons affects movement and/or memory. Virtually all human environmental exposures to toxic chemicals are to mixtures. This is particularly the case for exposures to pesticides, heavy metals, and organic solvents, known as neurotoxins. The case studies presented here are all from the published literature. In every study, the neurotoxic effects found are related to exposures to chemical mixtures of lipophiles and hydrophiles that induced neurotoxic effects not anticipated from the individual chemicals. It is hypothesized that lipophilic chemicals facilitate the absorption of hydrophilic species, resulting in the uptake of greater quantities of hydrophiles than would occur in the absence of the lipophiles.