From neurotoxic to chemosensory effects: new insights on acute solvent neurotoxicity exemplified by acute effects of 2-ethylhexanol.

Historically, acute solvent neurotoxicity was strongly related to reversible narcotic states that could be detected by neurobehavioral tests (e.g., simple reaction time). Nowadays, the occupational exposure to chemicals is markedly reduced and the avoidance of chemosensory effects is more important for the regulation of solvents. Exemplarily, this study examines if the chemosensory perception of 2-ethylhexanol is capable to distract performance in demanding neurobehavioral tasks. In two experiments three time-weighted average concentrations of 2-ethylhexanol (C(TWA): 1.5, 10, and 20 ppm) were investigated. In experiment A (n=24) variable concentrations over time (4h) were used, experiment B (n=22) investigated constant concentrations. The experiments were conducted in a 29 m3 exposure laboratory. Cross-over designs with randomized sequences of exposures were used. Among the 46 male participants 19 subjects reported enhanced chemical sensitivity; the other 27 subjects did not show this personality feature. During the exposure periods neurobehavioral tests were presented twice (beginning; end), the intensity of chemosensory perceptions were rated thrice. The intensity of chemosensory perceptions showed a clear dose-dependency. Subjects' performance in the vigilance test was not affected by the different exposures. Moreover, the results of neurobehavioral tests measuring executive function were neither affected by the C(TWA) concentration nor by the exposure peaks. With increasing C(TWA), a subgroup of the chemically sensitive subjects showed deteriorated accuracy in a divided attention task. Especially the 20 ppm conditions were very annoying. Only during the constant 10 ppm condition the time courses of the annoyance and nasal irritation ratings indicated some adaptation. In general, with the applied neurobehavioral tests distractive effects of acute 2-ethylhexanol exposures up to 20 ppm could not be confirmed. In sensitive groups such distractive effects of irritating solvents might be conceivable and moreover, in cooperation with researchers from cognitive neuroscience more sensitive functions and tests should be developed and incorporated.