Temporal integration in nasal lateralization of homologous propionates

Exposure limits for indoor volatile substances concerning the general population: The role of population-based differences in sensory irritation of the eyes and airways for assessment factors

Assessment factors (AFs) are essential in the derivation of occupational exposure limits (OELs) and indoor air quality guidelines. The factors shall accommodate differences in sensitivity between subgroups, i.e., workers, healthy and sick people, and occupational exposure versus life-long exposure for the general population. Derivation of AFs itself is based on empirical knowledge from human and animal exposure studies with immanent uncertainty in the empirical evidence due to knowledge gaps and experimental reliability. Sensory irritation in the eyes and airways constitute about 30-40% of OELs and is an abundant symptom in non-industrial buildings characterizing the indoor air quality and general health. Intraspecies differences between subgroups of the general population should be quantified for the proposal of more 'empirical' based AFs. In this review, we focus on sensitivity differences in sensory irritation about gender, age, health status, and vulnerability in people, based solely on human exposure studies. Females are more sensitive to sensory irritation than males for few volatile substances. Older people appear less sensitive than younger ones. However, impaired defense mechanisms may increase vulnerability in the long term. Empirical evidence of sensory irritation in children is rare and limited to children down to the age of six years. Studies of the nervous system in children compared to adults suggest a higher sensitivity in children; however, some defense mechanisms are more efficient in children than in adults. Usually, exposure studies are performed with healthy subjects. Exposure studies with sick people are not representative due to the deselection of subjects with moderate or severe eye or airway diseases, which likely underestimates the sensitivity of the group of people with diseases. Psychological characterization like personality factors shows that concentrations of volatile substances far below their sensory irritation thresholds may influence the sensitivity, in part biased by odor perception. Thus, the protection of people with extreme personality traits is not feasible by an AF and other mitigation strategies are required. The available empirical evidence comprising age, lifestyle, and health supports an AF of not greater than up to 2 for sensory irritation. Further, general AFs are discouraged for derivation, rather substance-specific derivation of AFs is recommended based on the risk assessment of empirical data, deposition in the airways depending on the substance's water solubility and compensating for knowledge and experimental gaps. Modeling of sensory irritation would be a better 'empirical' starting point for derivation of AFs for children, older, and sick people, as human exposure studies are not possible (due to ethical reasons) or not generalizable (due to self-selection). Dedicated AFs may be derived for environments where dry air, high room temperature, and visually demanding tasks aggravate the eyes or airways than for places in which the workload is balanced, while indoor playgrounds might need other AFs due to physical workload and affected groups of the general population.

The Effect of Stimulus Duration on the Nostril Localization of Eucalyptol

The trigeminal system is a chemosensory system participating in the perception of most odorants, which allows for the perception of diverse sensations including the freshness of eucalyptus or the spiciness of pepper. The lateralization task, that is, the identification of the stimulated nostril in a monorhinal stimulation paradigm is only possible following trigeminal stimulation and allows therefore for the assessment of the trigeminal sensitivity also in a clinical setting. In this study, we aimed to determine the effects of the duration of stimuli on the lateralization task. To this end, we asked 32 young and healthy subjects perform the lateralization task while being exposed to eucalyptol stimuli ranging between 100 and 1250 ms. We found that participants performed on average at chance for stimuli shorter than 500 ms, and observed increasing accuracy for stimuli with longer durations. In conclusion, these data suggest that 500 ms represents a threshold for the lateralization of eucalyptol stimuli. Therefore, when trigeminal sensitivity is tested in a clinical setting, eucalyptol stimuli should have a duration of at least 500 ms.

Dynamics of nasal irritation from pulsed homologous alcohols

Relatively, few studies have focused on how nasal irritation changes over time. To simulate the rhythm of natural respiration, subjects received 3-s pulses of volatile organic compounds interspersed with 3-s pulses of clean air. Each trial, subjects received 9 pulses of a chemical vapor over about 1 min. Subjects rated nasal irritation from each pulse using magnitude estimation. Within a trial, compound and concentration were fixed. Compound (ethanol, n-butanol, or n-hexanol) and concentration (4 levels for each compound) varied across trials. For all stimuli, rated irritation decreased over time (adaptation). Plots of log-rated intensity versus elapsed time were approximately linear (intensity decreased by a fixed ratio per unit time). Interestingly, the slopes of intensity versus time functions differed very little: Regardless of concentration and compound, rated irritation decreased by about 32% over the 9 pulses. The basic mechanism of short-term adaptation may be the same for the 3 alcohols studied. Regardless, these data suggest that very simple models might be able to describe some aspects of perceptual dynamics quite well.