UC San Diego

Symptoms of sensory irritation (pungency) often contribute to the judgment that an indoor environment is unhealthy. We assessed the independent contribution of the trigeminal and olfactory nerves to the detection of airborne chemicals by measuring nasal detection thresholds in subjects clinically diagnosed as lacking a functional sense of smell (anosmics) and in matched normal controls (normosmics). Anosmics can only provide odor-unbiased pungency thresholds. Normosmics provided odor thresholds. The stimuli comprised homologous alkylbenzenes (from toluene to octylbenzene), and chlorobenzene, 1-octene, and 1-octyne. As seen before with homologous alcohols, acetates, and ketones, both types of threshold declined with increasing carbon chain length. Anosmics failed to detect alkylbenzenes above propylbenzene. The strong linear correlation between pungency thresholds and saturated vapor concentration for all tested compounds, as a whole, and the constancy of pungency thresholds expressed as % of vapor saturation, suggests that nasal pungency from these substances relies heavily on a broadly tuned physicochemical interaction with a susceptible biophase within the cell membrane. Through such a nonspecific mechanism, low, sub-threshold levels of a wide variety of volatile organic compounds of low reactivity — as found in many polluted indoor spaces — could add their sensory impact to precipitate noticeable sensory irritation.