Multiple sclerosis and the workplace: report of an industry-based cluster.

Eleven cases of MS occurred within a 10-year period in a zinc-related manufacturing plant. The observed disease incidence was greater than expected from population data, using multiple approaches to statistical analysis (p less than or equal to 0.01). A case-control study, performed to examine several zinc parameters in blood, failed to indicate specific abnormalities among the MS patients, but all subjects (both MS and controls) working in the plant demonstrated higher serum zinc levels than all subjects (MS and controls) not working there.