Neurobehavioral Effects from Acute Exposures to Methyl Isobutyl Ketone and Methyl Ethyl Ketone

Subjects were tested for neurobehavioral performance in an environmentalchamber to detect the presence of subclinical central nervoussystem effects from 4-hr exposures to methyl isobutyl ketone(MIBK) at 100 ppm, methyl ethyl ketone (MEK) at 200 ppm, MIBKat 50 ppm with MEK at 100 ppm, or a placebo (i.e., a 5-min presentationof 25 ppm MEK—MIBK at each exposure period outset). Subjectswere 68 males and 75 females recruited from local universities;ages ranged from 18 to 32 years. Ethanol by ingestion (95% –0.84 ml/kg) was used as a positive control. Five psychomotortests (choice reaction time [CRT], simple reaction time [SRT],visual vigilance, dual task [auditory tone discrimination andtracking memory scanning), one sensorimotor test (postural sway),and a test of mood (profile of mood states) were used to measureneurobehavioral effects. Additionally, chemical measurements(blood and breath) and reports of sensory and irritant effectswere measured. The chemical exposures produced statisticallysignificant performance effects on only 4 of 32 measures (%correct responses-visual vigilance, movement time-CRT, SRT,% incorrect responses-dual task). These effects, however, werenot substantial and could not be attributed directly to thechemical exposures. Alcohol ingestion, however, produced significantdecrements on every performance test except memory scanningand mood. An interaction occurred between gender and alcoholingestion, such that more statistically significant performancedecrements were found for females than for males. Significantodor sensations and irritant effects were reported by the subjectsduring the chemical exposures. The MEK results agree with earlierMEK experiments at comparable exposure conditions, and the MIBKresults are consistent with a recent Swedish study that usedMIBK exposures and showed no significant behavioral performancedecrements from single MIBK exposures at 50 ppm with 50 W exercise.Additionally, the MIBK—MEK combination exposure showedno evidence of any interaction effects on either the behavioralor chemical measurements. The principal effects resulting fromexposures to MEK and MIBK at the durations and concentrationsused in the study are limited to sensory and irritant effects.