OLFACTORY ADAPTATION, THRESHOLD SHIFT AND RECOVERY AT LOW-LEVELS OF EXPOSURE TO METHYL ISOBUTYL KETONE (MIBK)

The anatomic position of olfactory receptors renders them vulnerable t o airborne pollutants. Chamber inhalation studies have shown dose-depe ndent olfactory adaptation and temporary olfactory threshold perceptio n shift for particular inhaled substances. The present study was under taken to examine olfactory perception threshold (OPT) and adaptation o f healthy subjects exposed for 7h to MIBK. Volunteers (n = 4) were exp osed in an inhalation chamber to MIBK at concentrations of 20ppm and 4 0ppm. For each of 6 exposure days, OPT for MIBK and PM-Carbinol were d etermined once before exposure and at 3 successive intervals following exit. Exhaled air samples were taken at regular intervals during and after exposure. Perceived odor intensity and symptoms were ascertained through a questionnaire filled out hourly. On all days, post-exposure OPT-MIBK at chamber exit was significantly higher than pre-exposure, representing a ninefold increase in concentration; recovery was dose-d ependent and not complete 95 min. after exit. No threshold shift was o bserved for OPT-PM-Carbinol. Perceived odor intensity was high when en tering the chamber, bur diminished with time, stabilizing after approx imately 2 hours. Symptoms of nose, eye or throat irritation and headac he were present in some subjects. The findings of this study suggest t hat at these levels of MIBK, there is olfactory adaptation during expo sure and a transient OPT shift for the inhaled substance. Persons expo sed professionally or environmentally to certain organic solvents may suffer temporary smell loss which hinders odor detection. (C) 1994 Int ox Press, Inc.