Effects of acute exposure of toluene and methyl ethyl ketone on psychomotor performance.

Organic solvents are used frequently in industry and workers are often exposed to various combinations of these chemicals. Several are CNS depressants, and the purpose of this experiment was to assess the behavioral effects of 4-hour inhalation exposures to two solvents, toluene and methyl ethyl ketone (MEK) alone and combined. Ethanol at 0.08% blood levels was used as a positive control. A total of 144 paid volunteers were randomly assigned to one of eight treatment combinations in a series of four two-group between subjects studies. Testing was carried out in an exposure chamber, and participants were tested before, during, and after the treatment or control condition on three performance tasks. The tasks measured alertness and psychomotor function and produced a total of 28 measures on each individual over the approximate 8 h of testing. Results indicated that toluene at 100 ppm produced a small but significant impairment on one measure of a visual-vigilance task by lowering the percentage of correct hits. MEK at 200 ppm produced no interpretable significant effects on any of these measures. Additivity was not evident when individuals were exposed to MEK (100 ppm) and toluene (50 ppm) in combination, as no significant performance differences were noted. Ethanol, at 0.08%, affected both the visual-vigilance and a choice-reaction time task at statistically significant levels on two measures, confirming the sensitivity of these two tasks to CNS depressants.