EXPERIMENTAL EXPOSURE TO METHYL TERTIARY-BUTYL ETHER - II - ACUET EFFECTS IN HUMANS

Methyl tertiary-butyl ether (MTBE) is widely used in gasoline as an ox ygenate and octane enhancer. Acute effects, such as headache, nausea, and nasal and ocular irritation, have been associated with the exposur e to gasoline containing MTBE. The aim of this study was to assess acu te health effects up to the Swedish occupational exposure limit value, both with objective methods and a questionnaire. Ten healthy male vol unteers were exposed to MTBE vapor for 2 h at three levels (5, 25, and 50 ppm), during light physical work (50 W). All subjects rated the de gree of irritative symptoms, discomfort, and CNS effects before, durin g, and after all three exposure occasions using a questionnaire. Answe rs were given on a 100-mm visual analog scale, graded from ''not at al l'' to ''almost unbearable.'' Ocular (redness, tear film break-up time , self-reported tear film break-up time, conjunctival epithelial damag e, and blinking frequency) and nasal (mouth and nasal peak expiratory flow, acoustic rhinometry, biochemical inflammatory markers, and cells in nasal lavage) measurements were performed mainly at the highest ex posure level. The ratings of solvent smell increased dramatically (rat ings up to 50% of the scale) as the volunteers entered the chamber and declined slowly with time (p < 0.05, repeated-measures ANOVA). All ot her questions were rated from ''not at all'' to ''hardly at all'' (0-1 0% of the scale) with no significant relation to exposure. The eye mea surements showed no effects of MTBE exposure. Blockage index, a measur e of nasal airway resistance calculated from the peak expiratory flows , increased significantly after exposure; however, the effect was not related to exposure level. In addition, a nonsignificant tendency of d ecreased nasal volume was seen in the acoustic rhinometry measurements , but with no clear dose-effect relationship. In conclusion, our study suggests no or minimal acute effects of MTBE vapor upon short-term ex posure at relatively high levels. (C) 1998 Academic Press.