Sensory reactions of nasal pungency and odor to volatile organic compounds: the alkylbenzenes.
Research 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 provide only odor-unbiased pungency thresholds. Normosmics provided odor thresholds. Stimuli included homologous alkylbenzenes (from toluene to octylbenzene), 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 percent 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, subthreshold 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.