Occupational exposure to methyl isobutyl ketone causes lasting impairment in working memory

The authors describe serial evaluations of a 44-year-old man who became cog nitively impaired during a 6-year period of repeated exposure to high level s of methyl isobutyl ketone (MIBK). Neuropsychological tests administered s ix times over 10 years demonstrated a stable pattern of cognitive impairmen t. Dynamic imaging studies suggested persistent CNS dysfunction. The author s conclude that chronic, high-level, occupational MIBK exposure can cause a persistent cognitive syndrome best explained by impaired working memory.