Agonistic sensory effects of airborne chemicals in mixtures: Odor, nasal pungency, and eye irritation

Abstract

Threshold responses of odor, nasal pungency (irritation), and eye irritation were measured for single chemicals (Lpropanol, l-hexanol, ethyl acetate, heptyl acetate, 2-pentanone, 2-heptanone, toluene, ethyl benzene, and propyl benzene) and mixtures of them (two three-component mixtures, two sixcomponent mixtures, and one nine-component mixture). Nasal pungency was measured in subjects lacking a functional sense of smell (i.e., anosmics) to avoid interference from olfaction. Various degrees of stimulus agonism (additive effects) were observed for each of the three sensory channels when testing mixtures. As the number of components and the lipophilicity of such components in the mixtures increased, so did the degree of agonism, Synergistic stimulus agonism characterized the eyeirritation response for the most complex (the nine-component) and the most lipophilic (one of the sixcomponent) mixtures. Physicochemical properties playa large role in the determination of sensitivity to airborne chemicals, particularly to their ability to evoke irritation. Whilethis has revealed itself previously with respect to single chemicals, it seems to have relevance to mixtures as well.Airborne chemicals in the environment are detected by humans through two sensory channels: olfaction and the so-called common chemical sense (CCS), or chernesthesia. The sense of smell is mediated by the olfactory nerve (cranial nerve I), whereas the facial CCS (from the various mucosae: ocular, nasal, and oral) is principally mediated by the trigeminal nerve (cranial nerve V).Since almost any odorant-at a high enough concentration-evokes not only odor but also chemesthetic sensations, an issue in human chemoreception entails distinguishing between a purely olfactory and a combined olfactory-trigeminal nasal response. We have begun to clarify this matter by measuring nasal detection thresholds to airborne compounds in subjects with a normal

Psychometric functions for the olfactory and trigeminal detectability of butyl acetate and toluene

“…In environmentally realistic conditions people can be exposed for long periods (from hours or days up to months or even years) to low-levels of dozens of airborne chemicals. A comprehensive understanding of chemosensory detection needs to elucidate the effects of stimulation time, e.g., olfactory adaptation 33 and chemesthetic sensitization/adaptation 34 , as well as the effects of mixtures of chemicals 35 . …”

Trigeminal and Olfactory Chemosensory Impact of Selected Terpenes

“…showed a cut-off effect (16). No pungency could be detected by anosmics for homologs above propyl benzene (12).…”

“…Previous work has addressed alcohols, acetates, ketones, alkylbenzenes, aliphatic aldehydes and carboxylic acids (9)(10)(11)(12)(13)(15)(16)(17). Along homologous series, physicochemical properties change systematically, and carbon chain length represents a convenient "unit of change" against which to analyze sensory results.…”

“…Most chemicals that evoke odor can also evoke pungency, though odor thresholds invariably lie below pungency thresholds (9)(10)(11)(12)(13)(15)(16)(17). Thus, measurement of nasal pungency thresholds in participants with normal olfaction, i.e., normosmics, can only be done against the background of an often strong odor.…”

An assessment of air quality reflecting the chemosensory irritation impact of mixtures of volatile organic compounds

“…Several studies of sensory irritation thresholds (NPTs and EITs) from mixtures of VOCs have shown various levels of additivity that, to a first approximation, are not-too-far from complete additivity (Nielsen et al, 1988;Cometto-Muñiz et al, 1997;1999;2001a;2004a;2004b). So are results from studies on ODTs 2005b;Wise et al, 2007;Miyazawa et al, 2009).…”