Evidence of brain hemorrhages and axonic anoxia was observed in a person who died as a result of exposure to xylene at approximately 10,000 ppm over an 18-h period (Morley et al., 1970). In another case, a man was exposed at 60–350 ppm to mixed solvents containing 75% xylene and experienced giddiness, anorexia, and vomiting (Glass, 1961). In a similar report of exposure to a mixed solvent containing 80% xylene, a person who apparently suffered from latent epilepsy displayed seizures; that suggested that xylene might exacerbate seizures in susceptible people (Goldie, 1960). In each of these instances, either mixtures were involved or the extent of exposure was not well documented.
Neither flicker fusion* nor reaction time was affected in 23 volunteers exposed at 100 or 200 ppm for 3–7 h (Ogata et al., 1970). In a similar study, Gusev (1968) reported changes in brain electric activity at 0.07 ppm, but not at 0.05 ppm. Fifteen male subjects were exposed to xylene vapor at approximately 100 or 300 ppm for 70 min (Gamberale et al., 1978). No noticeable change in test performance (numerical ability, reaction time, short-term memory, and critical flicker fusion) was seen. However, subjects exposed to xylene at 300 ppm for 70 min when the exposure period began with 30 min of exercise on a bicycle showed significant impairment of performance in tests for numerical ability, short-term memory, and choice reaction time. The difference was apparently due to an increase in the uptake of xylene in subjects that exercised during the first part of the exposure period.
Savolainen et al. (1979b), Riihimaki and Savolainen (1980), and Savolainen et al. (1980) exposed six volunteers to m-xylene at 100 or 200 ppm, 6 h/d, 3 d/wk for 2 wk. In one part of the experiment, constant exposure concentrations were used; in another, the concentration was varied so that peak concentrations of 400 ppm were obtained. During the first week, significant increases in reaction time and some impairment of equilibrium were observed at 100 ppm, but these effects were transient, perhaps because tolerance developed. The effects reappeared during the second week at the higher concentration. No changes in manual dexterity or visual functions were observed. The authors suggested that light exercise reverses the effects of xylene. At 200–400 ppm, the report suggested, the subjects displayed decreased vigilance, as indicated by EEG changes.
Carpenter et al. (1975) studied the odor threshold for mixed xylenes. They estimated it to be about 1 ppm. They suggested that discomfort and dizziness would ensue at 460 ppm and concluded that 110 ppm would be tolerable for working.