The Correlation and Prediction of VOC Thresholds for Nasal Pungency, Eye Irritation and Odour in Humans

Abstract

A general equation set up for the study of transport properties has been applied to VOC nasal pungency and eye irritation thresholds, as log (1/NPT) and log (1/EIT).The equation accounts for 93-95 % of the total effect, thus suggesting that the main step is transport of the VOC from the gas phase to a receptor phase. In the case of odor thresholds, ODT, the general equation accounts for only 77% of the total effect.A modified equation incorporates a factor for aliphatic aldehydes and carboxylic acids, and a general size effect that depends on the VOC maximum length. The size effect is important in that it leads to a cut-off effect that greatly reduces the potency of higher homologues. The various equations can all be used to predict chemosensory thresholds for thousands of VOCs.

Odor and chemesthesis from brief exposures to TXIB

“…This makes sense on physical grounds as chemesthetic thresholds require much higher concentrations than odor thresholds. A material may have enough activity for its airborne concentration to reach an odor threshold, though not the chemesthetic threshold (Abraham et al, 2001). Moreover, it may make sense on biological grounds, as well.…”

“…For both olfaction and chemesthesis, threshold shows an inverse association with molecular size, up to a point (Abraham et al., 2001, 2002). The association holds loosely across homologous series, though more tightly within them.…”

Detection of single and mixed VOCs by smell and by sensory irritation

“…Nevertheless, only for olfactory detectability was it possible to attenuate this breakdown by switching from a quite dissimilar chemical pair (i.e., butyl acetate/toluene) to a relatively similar one (i.e., ethyl propanoate/heptanoate) (compare Figs 5 and 7). Overall, the outcome from these mixture studies corresponds to that of structure‐activity studies of single VOCs (Abraham et al., 2001) in suggesting a broader chemical tuning in chemesthesis than in olfaction.…”

Nasal Chemosensory Irritation in Humans

“…To look into these issues we devised three approaches. The first approach consisted in applying a successful quantitative structure-activity relationship (QSAR), based on a solvation equation 46, to calculate and model predicted NPTs along homologous series (47)(48)(49). (This QSAR for nasal chemesthesis is described in detail in Chapter 25, "Physicochemical modeling of sensory irritation in humans and experimental animals".)…”