Acute Neurobehavioral Effects Of Toluene And Ethanol In Humans.

Abstract

Acute behavioral effects of toluene vapor were compared to the effects of ingested ethanol. The study consisted of 2 separate experiments for toluene and ethanol. In the toluene experiment 42 subjects were exposed 7 hours to 0, 75, or 150 ppm over 3 days. Verbal and visual short term memory (Sternberg, digit span, Benton, pattern memory); perception (pattern recognition); psychomotor skill (simple reaction time, continuous performance, symbol digit, hand-eye coordination, finger tapping, and critical tracking); manual dexterity, mood (one hole); mood and fatigue; and verbal ability were evaluated at 8 AM, 12 Noon, and 4 PM. A similar ethanol experiment was conducted at 0, .33, and .66g ETOH/kg BW (body weight) consumed at 3:30 PM over 3 days. Subjects were paid volunteers with 1 or more years of college. The study used the AM-PM score for each dose and subjects were their own control. A 3 x 3 Latin Square study design evaluated solvent effects simultaneously controlling for learning, and the solvent order. Inter-subject variation in solvent absorbance was monitored in breath. A 5 to 10% decrement in performance was considered meaningful if it was consistent with a linear trend at p < .05. Both toluene and ethanol affected performance on the digit span, one hole, and pattern recognition (latency), and critical tracking. Ethanol also affected performance on continuous performance, symbol digit substitution (latency), and finger tapping (alternate). Only toluene affected performance on pattern memory (number correct). The ethanol equivalent dose at 150 ppm toluene was calculated for digit span (.56 g ETOH/kg), the latency for pattern recognition (.66g ETOH/kg), and the one hole element 'pin' (.40 g ETOH/kg), A .38g ETOH/kg dose equals 50 mg% blood alcohol level therefore decrements in digit span, pattern recognition, and the one hole test are impairments above the lowest level associated with increased automobile accidents. The acute effects at industrially relevant exposures of toluene could result in sub-clinical CNS disorders affecting health, safety, and work productivity. This study provides an interpretation of a solvent decrement by introducing an index of potency in ethanol equivalent units. Most of the test battery has been recommended by NIOSH and WHO. Thus the results will be useful in the design of future studies.