Xylene and alcohol involvement of the human equilibrium system

Ten healthy male subjects were exposed at weekly intervals to m-xylene concentrations of 6 mumol/1 (145 p.p.m.) and 11.5 mumol/1 (290 p.p.m.) for 4 hrs alone and in combination with the prior ingestion of single doses of alcohol (0.8 g/kg). Alcohol alone was ingested at two dose levels, 0.4 and 0.8 g/kg. Body sway was recorded with a strain gauge transducer platform with the subjects' eyes closed and open, and the eyes closed/open ratio, indicating the grade of visual compensation for body balance, was calculated. The variation observed in the eyes closed/open ratio in different experimental situations was due to changes with the eyes closed rather than to differences with the eyes open. Alcohol or a xylene concentration of 6 mumol/1, as well as their combination, had little if any effect on this ratio. Exposure to a xylene concentration of 11.5 mumol/1 tended to decrease the eyes closed/open ratio, possibly due to functional tolerance or adaptation. Interestingly, alcohol with a xylene concentration of 11.5 mumol/1 significantly increased the ratio, a finding suggesting an unexpected combined effect of xylene and alcohol, possibly of metabolic origin, on the human equilibrium system. The possible mechanism of this action remains to be elucidated.