Vestibulo-oculomotor disturbances in humans exposed to styrene

Several reports indicate that disturbances of the vestibulo-oculomotor ability are a manifestation of the toxic action on the central nervous system exerted by some industrial solvents. The aim of the present investigation was to examine the vestibulo-oculomotor system during exposure to styrene, which is extensively used in the production of plastics. Healthy volunteers were exposed to styrene for one hour. Rotatory and optokinetic nystagmus, visual suppression as well as speed, latency and accuracy of saccades were tested before, during, and one hour after the exposure. The pulmonary uptake and the blood level of the solvent were continuously analysed by gas chromatography. The styrene blood concentration was equivalent to that which may well be reached after serveral hours of hard work in an industrial environment with a concentration of styrene within permitted limits. No spontaneous nystagmus appeared. The rotatory and optokinetic nystagmus was not influenced by styrene. However, the speed of the saccade was significantly enhanced. The visual suppression was disturbed, shown by an increased gain after styrene exposure. The experiments thus indicate that styrene given to healthy test persons induced disturbances, thus consistent with the theory that some organic solvents block the cerebellar inhibition of the vestibulo-oculomotor system.