A controlled short-term exposure study to investigate the odor differences among three different formulations of gasoline.

Control subjects (CON) and self-reported methyl tertiary butyl ether (MTBE)-sensitive subjects (SRS) were evaluated to distinguish between the following gasoline blends: gasoline versus gasoline + MTBE (15% MTBE v/v); and gasoline versus gasoline + MTBE + reodorant. The study also investigated the ability of a reodorant to conceal the odor of MTBE in a gasoline mixture. In each of two separate sessions, seven men (four CON, three SRS) and seven women (four CON, three SRS) were asked, in a forced-choice format, to sniff 28 randomized bottle pairs to determine if the odors in each pair were the same or different. Chi-square analyses revealed that, with the exception of one male CON, subjects were unable to distinguish between gasoline and gasoline with MTBE or gasoline with MTBE and the reodorant. Thus, a reodorant is of limited value as an additive which alters the ability of an individual to detect MTBE in a blended gasoline. The results suggest that at the level used in the experiment, no mask would be required to blind a participant from the odor of MTBE if that level is used in a controlled human health effects study of the additive.

Odor perception: multiple chemical sensitivities, chronic fatigue, and asthma.

Patients with multiple chemical sensitivities (MCS) often report heightened sensitivity to odors. Odor detection thresholds to phenyl ethyl alcohol (PEA) and pyridine (PYR) were evaluated as a measure of odor sensitivity for 33 MCS subjects, 13 chronic fatigue syndrome subjects, 16 asthmatic subjects, and 27 healthy controls. Odor identification ability (based on University of Pennsylvania Smell Identification Test results) and ratings in response to four suprathreshold levels of PEA and PYR were also assessed. Odor detection thresholds for PEA and PYR and odor identification ability were equivalent for all groups; however, when exposed to suprathreshold concentrations of PEA, MCS subjects reported significantly more trigeminal symptoms and lower esthetic ratings of PEA. No group differences were found in response to suprathreshold concentrations of PYR. In summary, MCS subjects did not demonstrate lower olfactory threshold sensitivity or enhanced ability to identify odors accurately. Furthermore, they were differentiated from the other groups in their symptomatic and esthetic ratings of PEA, but not PYR.

Sex differences in task performance associated with attention to ambient odor.

The effects of ambient odor (pleasant, unpleasant, none); odor suggestion (present, absent); and sex of subject on mood and performance measures were explored in a 3 x 2 x 2 experimental design. A total of 40 men and 40 women performed a clerical task and a speed and accuracy task (digit deletion), filled out self-evaluations of mood, predicted performance, and rated the odor quality of the test room. Ambient odor conditions significantly affected room smell ratings, but they had no effect on performance or mood. Odor suggestion produced a significant sex-related interaction effect on the digit deletion task, irrespective of actual ambient odor. The results are discussed with respect to sex differences observed in laboratory studies and in epidemiological investigations of multiple chemical sensitivity and sick building syndrome.

Pleasant odors and congruency: effects on approach behavior.

Ninety subjects between the ages of 18 and 35 viewed 24 slides when the testing room was scented with no odor or one of two pleasant scents (baby powder or chocolate). Six slides were of babies, six were of chocolate items and 12 were control slides of pine trees or the Orient. In pilot testing the chocolate slides were rated as being congruent with the chocolate scent and incongruent with the baby powder scent; the baby slides were rated as being congruent with the baby powder scent and incongruent with the chocolate scent. Subjects viewed the slides at their own pace while a computer recorded how long each slide was viewed. During a second viewing, subjects rated the slides and answered questions about their own mood and health. Congruency did not play a role in the findings. Pleasant odors had certain effects compared to no odor (i.e. longer looking time, better mood and lower hunger ratings), while other effects were related to specific odors (i.e. arousal was highest in the chocolate condition and there were fewer health symptoms reported in the baby powder condition). These findings suggest that pleasant odors may have some general effects due to their hedonic value, while associations individuals have with particular pleasant odors may influence other variables.

Performance, mood, and health during exposure to intermittent odors.

The effects of intermittent bursts of pleasant, unpleasant, and no experimental odor on human task performance, mood, and perceived health were tested in this study. Odors did not influence any of these measures; however, subjects who had been exposed to the malodors reported retrospectively that they thought the odors had a negative effect on all of these factors. These findings have implications for the methodological design and interpretation of air quality studies.