Immediate effects of m-xylene on the human central nervous system.

Male volunteers were exposed to m-xylene vapour for 4 h a day either sedentary or with a period of 10 min exercise twice a day with stable (8.2 mumol/l) m-xylene concentrations or fluctuating concentrations with peaks (16.4 mumol/l). The TWA concentration was always the same (8.2 mumol/l). The body balance of the subjects was clearly impaired in the anteroposterior (a-p) direction, especially with their eyes closed during the peaks at rest, whereas it was improved when exercise was included in spite of the higher blood m-xylene concentrations. When on the contrary, the situation was reversed in the lateral direction. Complex audiomotor reactions were impaired after the peaks combined with exercise, whereas changes in simple reaction times were similar in pattern to those found for body balance in the a-p direction. The results suggest a complex interaction between physiological factors and m-xylene and development of adaptation or tolerance during the exposure.