Occupational Neurotoxicity of Organic Solvents
Organic solvents are a diverse set of chemicals and chemical mixtures that are among the most widely used class of chemicals in industry and commerce. Many solvents are volatile leading to a risk of inhalation exposure. Typically, solvents are also highly lipid soluble and readily partition into lipid-rich brain tissue. In the nervous system, solvents act acutely to alter the function of multiple ligand-gated and voltage-gated nerve membrane ion channels to cause acute neurological dysfunctions, behavioral impairments, and eventually generalized CNS depression. The momentary solvent concentration in the brain determines the strength of these acute effects. Upon repeated or chronic exposures, organic solvents can also reduce neuronal plasticity, generate reactive oxygen species, disrupt nerve membrane integrity, increase intracellular calcium, induce neuroinflammation and potentially cause long-term impairments. Chronic occupational exposures to organic solvents have been linked to impairments of cognitive function, mood, memory, vision, and hearing. Hearing deficits are augmented by co-exposures to noise. Peripheral neuropathy and developmental neurotoxicity are also concerns. In this chapter, types of organic solvents, their uses, mode of actions, and the evidence for acute and chronic exposures to produce neurotoxic effects in humans and laboratory animals are discussed.