Organic solvents comprise a large group of compounds (alcohols, ketones, ethers, esters, glycols, aldehydes, aliphatic and aromatic saturated and nonsaturated hydrocarbons, halogenated hydrocarbons, carbon disulfide, etc.) with a variety of chemical structures. Their common characteristic, related to their widespread use in many industrial processes, is the ability to dissolve and readily disperse fats, oils, waxes, paints, pigments, varnishes, rubber, and many other materials.1,2
Solvent exposure affects many persons outside industrial and occupational settings. The use of solvents in household products and in arts, crafts, and hobbies has significantly increased the population that may be affected by repeated exposure. Moreover, the deliberate inhalation of solvents as a form of addiction (“sniffing”) occurs, especially in younger population groups.
Some solvents are well known for their specific toxic effects on the liver, kidney, and bone marrow,3 and a few organic solvents have specific toxicity for the nervous system. Carbon disulfide may induce a severe toxic encephalopathy with acute psychosis;3 methyl alcohol may induce optic neuritis and atrophy; methyl chloride and methyl bromide may cause severe acute, even fatal, toxic encephalopathy. Exposures to n-hexane, methyl-n-butyl ketone (MBK),4,5,6 and carbon disulfide have produced peripheral neuropathy.
Most organic solvents share some common nonspecific toxic effects, the most important of which are those on the central nervous system (CNS). The depressant narcotic effects of organic solvents have long been recognized; numerous members of this heterogeneous group of chemical compounds have been used as inhalation anesthetics (chloroform, ethyl ether, trichloroethylene, etc.).
The sequence of stages of anesthesia achieved with volatile solvents is of interest: the cerebral cortex is affected first, the lower centers of reflex activity in the brain stem and medulla oblongata, which control vital cardiovascular and respiratory functions, are the last to be depressed. This characteristic sequence makes it possible to use volatile anesthetic compounds for medical purposes. The earliest manifestations of the anesthetic effects of solvents are slight disturbances in psychomotor coordination. These may progress to more pronounced incoordination and, if exposure continues, through an excitation stage of longer or shorter duration, to loss of consciousness.
Occupational exposure to solvents may reproduce the entire sequence of medical anesthesia, up to loss of consciousness, and even death through paralysis of vital cardiovascular and respiratory centers. While such severe cases of occupational solvent poisoning are relatively uncommon under normal conditions, they may occur with unexpected accidental overexposure.
The initial manifestations of CNS depression are frequent in workers handling solvents or mixtures of solvents in various industrial processes. A low boiling point, with generation of significant airborne concentrations of vapor, large surfaces from which evaporation may take place, lack of appropriate enclosure and/or exhaust ventilation systems, relatively high temperature of the work environment, and physical exercise required by the actual work performed ...