THE INFLUENCE OF COGNITIVE BIAS ON THE PERCEIVED ODOR, IRRITATION ANDHEALTH SYMPTOMS FROM CHEMICAL-EXPOSURE

Objective: Responses to volatile chemicals are often subjective and va riable, both over time and across individuals. Although variability ca n derive from differences in individual olfactory sensitivity, the res ponse to a chemical stimulus is also influenced by the complex environ ment surrounding the exposure, which can include the perceiver's cogni tive state. To explore the role of cognitive bias in chemical exposure s, we evaluated whether information about the consequences of exposure to acetone could influence ratings of odor and irritation during expo sure and/or the frequency or intensity of reported health symptoms fol lowing exposure. Methods: Ninety adults (mean age 33.7, range 25-64) w ith no history of occupational exposure to solvents, were exposed to 8 00 ppm acetone in a cham ber for 20 min. To control for non-specific r esponses to the odor of acetone, the subjects were also exposed for 20 min to 200 ppm phenylethyl alcohol (PEA), a nonirritant volatile chem ical that produces a distinct odor but does not elicit irritation in t he vapor phase. Subjects were assigned to one of three groups (n = 30/ group); each group was given either a positive, negative or neutral bi as towards the consequences of exposure to the chemicals in the study. During exposure: subjects rated the intensity of odor and irritation; following exposure, they completed symptom questionnaires. Results: D uring the 20-min exposure to acetone? the positive bias group exhibite d the most adaptation to its odor and the lowest perceived irritation; following exposure they reported the fewest health symptoms. In contr ast, the negative bias group rated higher levels of odor intensity and , on average, reported the most overall irritation; following exposure they reported significantly more health symptoms than the other group s. None of the demographic variables studied (e.g., age gender, race, smoking status) were predictive of the response to odor or irritation. The perceived irritancy of acetone was well predicted by a linear com bination of the perceived odor of acetone and the perceived irritation from PEA (the nonirritant), r(2) = 0.73. Conclusions: The results pro vide strong evidence that both the perceived odor and cognitive expect ations about a chemical can significantly affect how individuals respo nd to it. Moreover, because naive control subjects appear to exhibit e xtreme variation in their cognitive evaluations of chemical effects, t here may be limited value in using non-exposed controls to assess the irritancy of chemicals for worker populations.