An algorithm for 353 odor detection thresholds in humans

Abstract

One hundred and ninety three odor detection thresholds, ODTs, obtained by Nagata using the Japanese triangular bag method can be correlated as log (1/ODT) by a linear equation with R(2) = 0.748 and a standard deviation, SD, of 0.830 log units; the latter may be compared with our estimate of 0.66 log units for the self-consistency of Nagata's data. Aldehydes, acids, unsaturated esters, and mercaptans were included in the equation through indicator variables that took into account the higher potency of these compounds. The ODTs obtained by Cometto-Muñiz and Cain, by Cometto-Muñiz and Abraham, and by Hellman and Small could be put on the same scale as those of Nagata to yield a linear equation for 353 ODTs with R(2) = 0.759 and SD = 0.819 log units. The compound descriptors are available for several thousand compounds, and can be calculated from structure, so that further ODT values on the Nagata scale can be predicted for a host of volatile or semivolatile compounds.

Figure 1

Plots of log (1/ODT) against L for 4 different homologous series of VOCs. Calculated line without the indicator variable ( – – – – – – ). Calculated line with the indicator variable (– – – – – –). Outliers are shown as ○. Note that the slopes of the calculated lines are all the same.

Figure 2

A plot of log (1/ODT) calculated on equation (6) against log (1/ODT) observed: ○, Nagata data set; •, the C1 data set; ▴, the C2 data set; and ▪, the HS data set.

Figure 3

A plot of PC2 against PC1 for all the data points: ○, Nagata data set; •, the C1 data set; ▴, the C2 data set; and ▪, the HS data set.

Figure 4

Psychometric functions for chemosensory detection of the plasticizer 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB) and ethanol. Top panel shows detection of odor, the middle and bottom panels show detection of feel or irritation. The measurement of feel in the nose entails localization of which of the 2 nostrils felt the stimulus. Vertical dashed lines show saturated vapor concentrations (Cain et al. 2005).