Concentration-detection functions for eye irritation evoked by homologous n-alcohols and acetates approaching a cut-off point

Abstract

We measured concentration-detection (i.e., psychometric) functions for the eye irritation evoked by three homologous n-alcohols (1-nonanol, 1-decanol, and 1-undecanol) and two homologous acetates (nonyl and decyl acetate). A vapor delivery device based on a dynamic dilution of stimuli in nitrogen served to present various concentrations of each compound, including the undiluted vapor, to the subjects (n≥26).Delivered concentrations were quantified by gas chromatography. Detection probability (P) was assessed via a three-alternative, forced-choice procedure, and quantified on a scale ranging from P = 0.0 (chance detection) to P = 1.0 (perfect detection). Flowrate to the eye equaled 2.5 L/min and time of exposure was 6 sec. The functions for 1-undecanol and decyl acetate plateau at P ≈ 0.5 and P ≈ 0.25, respectively, such that further increases in concentration failed to increase detection notably. Thus, both series reached a break-point, or cut-off, in detection of ocular irritation. The present outcome provides additional evidence that the cut-off does not rest on the low vapor concentration of the homolog but, more likely, on the homolog exceeding a critical molecular dimension(s) which prevents it from interacting effectively with the appropriate receptors.

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

“…For each of the alcohols in Table 1, as the gaseous concentration of alcohol is increased, Q in the psychometric plots approaches unity. But Q for decan-1-ol never reaches beyond 0.5 no matter what is the gaseous concentration, and the same happens for undecan-1-ol (Cometto-Muñiz et al, 2005a;2007b). For still higher homologues the maximum value of Q will be around zero.…”

“…What is evident (Cometto-Muñiz et al, 1998b;2005a;2005c;2006;2007a;2007b;2008b;Cometto-Muñiz et al, 2010;Cain et al, 2006) is that this increase in sensory irritation potency does not simply carry on along a homologous series, but a homolog is reached where the potency declines to zero. For each of the alcohols in Table 1, as the gaseous concentration of alcohol is increased, Q in the psychometric plots approaches unity.…”

“…We start with the psychometric plots obtained from the probability of sensory irritation detection, Q, of a given VOC as a function of its gaseous concentration, log P with P in ppm (Cometto-Muñiz et al, 1999;2001a;2002;2004a;2004b;2007b;2008;Cain et al, 2006). As for the determination of thresholds, this involves a panel of human subjects.…”

“…It looks like the sensory irritation receptive system is very broad in that it will accept almost any VOC, unless the VOC exceeds a critical size that allows it to interact effectively with the relevant receptors. One measure of 'size' is the VOC descriptor, L (the gashexadecane partition coefficient at 25 o C, see later), and it is useful to compare the Lvalues at the cut-off points for various series, see Table 2 (Cometto-Muñiz et al 2005a;2006;2007a;2007b). It seems that any VOC with an L-value more than about 6.1 will not be effective in eliciting sensory irritation.…”

Prediction of Toxicity, Sensory Responses and Biological Responses with the Abraham Model

“…Later work (Cometto-Muňiz et al, 2005b, 2007a, 2007bCometto-Muňiz and Abraham, 2008) revealed the existence of a cut-off point in EIT on ascending a number of homologous series. Just as with NPT, these cut-off points are not due to the low vapor pressure of higher members of the homologous series, but appear to relate to a lack of activation of the receptor.…”