Short-term exposure of human subjects to m-xylene and 1,1,1-trichloroethane.

Nine healthy male students were exposed to singular atmospheric concentrations of m-xylene (8.2 mumol/l; 200 ppm) or 1,1,1-trichloroethane (TCE) (8.2 and 16.4 mumol/l; 200 and 400 ppm), and also to a combination of xylene (8.2 mumol/l) and TCE (16.4 mumol/l) for 4 h per day at 6-day intervals. The effects of the atmospheric xylene and TCE concentrations on psychophysiological functions such as reaction time, body balance and CFF thresholds were studied. The exposures to xylene alone and to the lower TCE concentrations usually tended to improve the performances, whereas the higher TCE concentration alone or in combination with xylene tended to have an opposite effect, although statistically significant changes in performance, as compared to the control values, were rare. The results thus suggest a biphasic effect of TCE on the central nervous system (CNS), slight stimulation of the CNS at lower and depression at higher TCE concentrations. The results also revealed that xylene and TCE together exhibited neither kinetic interaction nor synergistic nor antagonistic effects on the CNS functions studied.