A theoretical model for correlating odor thresholds of volatile organic compounds (VOCs) with their simple physicochemical properties has been developed. The partition coefficient between octanol and water, and that between water and air were used to model the partition process of airborne chemicals into the biophase where the olfactory signal is transformed. Validation was performed by fitting data on odor thresholds and partition coefficients for acetates, alcohols, ketones and amines into the model. Quantitative structure‐activity relationships (QSARs) for the four series were developed from the model. The results suggest that acetates, alcohols and ketones probably bind to a common receptor site located in the hydrophobic interior of the lipid bi‐layer membrane of the olfactory cilia. Amines probably bind to a different receptor site located closer to the mucus layer. The results also suggest that odor thresholds of related VOCs which appear to share a common receptor site may be additive.

A model was developed for describing the triggering of nasal pungency in humans, based on the partition of volatile organic compounds (VOCs) between the air phase and the biophase. Two partition parameters are used in the model: the water-air partition coefficient and the octanol-water partition coefficient. The model was validated using data from the literature, principally on alcohols, acetates and ketones. The model suggests that all test compounds, regardless of their chemical functional groups, bind to a common receptor site within the hydrophobic interior of the bilayer membrane of the trigeminal nerve endings. There is probably only a slight, non-specific interaction between the VOC molecule and the receptor molecule, whereas this type of non-specific interaction for the detection of odor is much stronger. In practical terms, the suggestion that all VOCs share a common irritation receptor site implies that nasal-pungency thresholds of individual VOCs may be additive. Quantitative structure-activity relationships (QSARs) for nasal-pungency thresholds were also developed from the model, which can be used to predict nasal-pungency thresholds of common VOCs. Although the present model does not offer additional precision over that of M.H. Abraham et al., 1996, Fundam. Appl. Toxicol. 31, 71-76, it requires fewer descriptors and offers a physiological basis to the QSAR. Another advantage of the present model is that it also provides a basis for comparison between the olfactory process and nasal pungency.

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