Objectives: Sensory (eye, nose, and throat) irritation is an important component of non-specific building-related illness ("sick-building syndrome"). Inter-individual variability in susceptibility to upper airway/mucous membrane irritants is suspected epidemiologically, but has been neglected experimentally. We wished to document population variability in nasal irritant sensitivity, as indexed by threshold measurements of sensory acuity. We hypothesized that younger subjects, women, and allergic rhinitis sufferers would display lower sensory thresholds than would older subjects, men, and rhinitis non-sufferers.
Methods: We evaluated Sixty human subjects (stratified by age, gender, and seasonal allergy status), using two different test systems: (1) carbon dioxide (detection) and (2) n-propanol (localization). We obtained carbon dioxide (CO2) detection thresholds using an ascending concentration series, presenting 3-s pulses of CO2, paired with air in random order, by nasal cannula. Localization thresholds were obtained by the simultaneous presentation of n-propanol vapor (ascending concentrations in air) and blanks (saturated water vapor in air) to opposite nostrils, with laterality randomized. Threshold data were log-transformed to satisfy normality and analyzed by population marker via ANOVA and linear regression.
Results: Test-retest variability was greater for volatile organic compound (VOC) localization than for CO2 detection (r=0.50 and 0.75, respectively); the two measurements were, however, positively correlated (r=0.48; P<0.001). Age predicted both (log-transformed) VOC localization thresholds (P<0.0001) and (log-transformed) CO2 thresholds (P<0.01), with younger age predicting lower thresholds. Female gender predicted lower CO2 detection (P<0.05) but not VOC localization thresholds (P=0.10). Nasal allergies predicted lower VOC localization (P<0.05) but not CO2 detection thresholds (P=0.52).
Conclusions: Consistent with epidemiological reporting patterns in so-called problem buildings, nasal irritant sensitivity appears to be non-randomly distributed in the population, with significant variability predicted by age, gender, and the presence of allergic rhinitis.