Clinical epidemiology of occupational neurotoxic disease

Occupational exposures to neurotoxic chemicals have produced large outbreaks of illness in chemical and pesticide workers worldwide. Outbreaks of occupational neurologic disease in the United States have included (1) the Kepone episode in Hopewell, Virginia, in which 76 workers at a pesticide plant producing the chlorinated hydrocarbon insecticide, Kepone, developed a previously unrecognized syndrome of nervousness, tremor, ataxia, weight loss, opsoclonus, pleuritic and joint pain, and oligospermia; (2) an outbreak of 104 cases of autonomic neuropathy in polyurethane foam workers in Marblehead, Massachusetts, manifest principally by urinary bladder dysfunction, which followed exposure to a new catalyst, dimethylaminopropionitrile (DMAPN); and (3) an outbreak of acute mixed motor and sensory neuropathy in 48 plastic fabric workers in Columbus, Ohio, exposed to the solvent methyl butyl ketone (MBK). These outbreaks underscore the vulnerability of chemical workers to neurotoxins. In addition, occurrence of these large, easily detectable epidemics suggests that many more smaller clusters and single cases of neurologic disease of undetermined origin, particularly in younger adults, may be caused by exposure to occupational or to other toxic chemicals. Detection of the etiology of chemically induced neurologic illness requires a high index of suspicion and careful ascertainment of occupational history.