Relative Sensitivity of the Ocular Trigeminal, Nasal Trigeminal and Olfactory Systems to Airborne Chemicals

We measured thresholds for eye irritation and odor in homologousseries of alcohols (ethanol, 1-butanol, 1-hexanol and 1-octanol),ketones (2-propanone, 2-pentanone, 2-heptanone and 2-nonanone),and alkylbenzenes (toluene, ethyl benzene and propyl benzene).Eye irritation thresholds were well above odor thresholds forall series. Both sensory thresholds declined with carbon chainlength, a trend that has implicated lipophilicity in the potencyof these and related stimuli. Eye irritation thresholds wereremarkably close to nasal pungency thresholds obtained previouslyin persons lacking olfaction (i.e. anosmics). The agreementbetween the two thresholds implies that, despite differencesin the mucus layer at the two sites and in the epithelial tissueitself, there is remarkable similarity at the site of stimulation.As a practical matter, the eyes could serve as the sites toassess potency for induction of nasal pungency, an assessmentpreviously limited to testing anosmics. Presumably, for ourbrief stimulus presentations (1–3 s), the differencesbetween ocular and nasal mucosae have little relevance to chemicalsensitivity. Studies of the ability of homologous chemical seriesto evoke threshold eye irritation, nasal pungency and odor notonly have practical value, but also can help to define the physicochemicalproperties of the receptor and perireceptor biophases. ¹Present address: Department of Surgery (Otolaryngology), UCSDMedical Center, University of California, San Diego, USA