Indoor air quality - An overview of methods for measuring odor detection thresholds of single substances.

Odor evaluation is an important topic in the field of indoor air quality. Odor detection threshold (ODT) values are used to derive limit values like odor guide values or odor activity value. However, ODT values for the same substance available in compilations or published before 2003 rarely have an accuracy of less than three orders of magnitude. Stimulus preparation, including analytical verification, stimulus presentation, as well as selection and training of test subjects have been identified as major sources of variability. ODT values obtained by validated standardized methods are now considered objective, reliable, and reproducible. They exhibit a variability of one or two orders of magnitude and are lower than traditionally assumed and reported.This review presents the essential criteria for a well-performed ODT determination. It is intended to assist health and safety professionals in assessing whether the methodological approach of a study was appropriate for determining a valid and reliable ODT value.

Influence of face masks on the subjective impairment at different physical workloads.

To quantify the subjective and cognitive impairment caused by wearing face masks at work, 20 men and 20 women (median age 47 years, range 19-65) were tested under different ergometer workloads while wearing surgical mask, community mask, FFP2 respirator or no mask in a randomized and partially double-blinded design. Masks were worn also at the workplace for four hours. Subjective impairment was recorded by questionnaires. Cognitive performance was tested before and after the workplace examination. Subjective feeling of heat, humidity, and difficult breathing increased with rising physical exertion and wearing time for all three mask types, most notably for FFP2. Even when blinded, participants with FFP2 reported difficult breathing already at rest. During physical exertion, individuals with low tolerance to discomfort reported significantly stronger impairment (OR 1.14, 95% CI 1.02-1.27). Regarding light work, older subjects (OR 0.95, 95% CI 0.92-0.98) and women (OR 0.84, 95% CI 0.72-0.99) showed significantly lower and atopic subjects stronger impairment (OR 1.16, 95% CI 1.06-1.27). No significant influence of mask wearing was detected on cognitive performance. Wearing a mask had no effect on cognitive performance, but led to discomfort which increased with physical exertion and wearing time. Individuals who tolerate discomfort poorly felt more impaired by wearing a mask during physical exertion.

Effects of wearing different face masks on cardiopulmonary performance at rest and exercise in a partially double-blinded randomized cross-over study.

The use of face masks became mandatory during SARS-CoV-2 pandemic. Wearing masks may lead to complaints about laboured breathing and stress. The influence of different masks on cardiopulmonary performance was investigated in a partially double-blinded randomized cross-over design. Forty subjects (19-65 years) underwent body plethysmography, ergometry, cardiopulmonary exercise test and a 4-h wearing period without a mask, with a surgical mask (SM), a community mask (CM), and an FFP2 respirator (FFP2). Cardiopulmonary, physical, capnometric, and blood gas related parameters were recorded. Breathing resistance and work of breathing were significantly increased while wearing a mask. During exercise the increase in minute ventilation tended to be lower and breathing time was significantly longer with mask than without mask. Wearing a mask caused significant minimal decreases in blood oxygen pressure, oxygen saturation, an initial increase in blood and inspiratory carbon dioxide pressure, and a higher perceived physical exertion and temperature and humidity behind the mask under very heavy exercise. All effects were stronger when wearing an FFP2. Wearing face masks at rest and under exercise, changed breathing patterns in the sense of physiological compensation without representing a health risk. Wearing a mask for 4-h during light work had no effect on blood gases.

Physiological responses, self-reported health effects, and cognitive performance during exposure to carbon dioxide at 20 000 ppm.

In this study, 24 subjects (20-58 years) were exposed to carbon dioxide (CO2 ) at 770 ppm and 20 000 ppm in an exposure laboratory for 4-h, including 2 × 15 min of cycling to investigate the effects on acid-base balance, physiological responses, cognitive performance and acute health. Capillary blood analysis, heart rate, respiratory rate, divided attention, flexibility, and sustained attention from the Test Battery for Attentional Performance (TAP), critical flicker fusion frequency (CFF), and self-reported symptoms were measured before, during, and after the 4-h exposure. Blood pH decreased and partial pressure of carbon dioxide (pCO2 ) increased significantly when exposed to 20 000 ppm CO2 compared to 770 ppm. However, the values remained within the normal range. In addition, respiratory rate increased slightly but significantly at 20 000 ppm CO2 . No significant changes in heart rate, CFF, task performance or acute health were found. In sum, the findings suggest that the observed changes in acid-base balance and ventilation can be classified as physiological adaptation responses. Impairment of cognitive performance is not expected from exposure to 20 000 ppm CO2 , neither as direct effect on central nervous system function nor as a distraction related to perception of health effects.

Naphthalene: irritative and inflammatory effects on the airways.

OBJECTIVE: This cross-sectional study determined whether acute sensory irritative or (sub)chronic inflammatory effects of the eyes, nose or respiratory tract are observed in employees who are exposed to naphthalene at the workplace. METHODS: Thirtynine healthy and non-smoking male employees with either moderate (n = 22) or high (n = 17) exposure to naphthalene were compared to 22 male employees from the same plants with no or only rare exposure to naphthalene. (Sub)clinical endpoint measures included nasal endoscopy, smell sensitivity, self-reported work-related complaints and the intensity of naphthalene odor and irritation. In addition, cellular and soluble mediators in blood, nasal lavage fluid (NALF) and induced sputum (IS) were analysed. All measurements were carried out pre-shift on Monday and post-shift on Thursday. Personal air monitoring revealed naphthalene shift concentrations up to 11.6 mg/m3 with short-term peak concentrations up to 145.8 mg/m3 and 1- and 2-naphthol levels (sum) in post-shift urine up to 10.1 mg/L. RESULTS: Acute sensory irritating effects at the eyes and upper airways were reported to occur when directly handling naphthalene (e.g., sieving pure naphthalene). Generally, naphthalene odor was described as intense and unpleasant. Habituation effects or olfactory fatigue were not observed. Endoscopic examination revealed mild inflammatory effects at the nasal mucosa of exposed employees in terms of reddening and swelling and abnormal mucus production. No consistent pattern of cellular and soluble mediators in blood, NALF or IS was observed which would indicate a chronic or acute inflammatory effect of naphthalene in exposed workers. CONCLUSIONS: The results suggest that exposure to naphthalene induces acute sensory irritative effects in exposed workers. No (sub)chronic inflammatory effects on the nasal epithelium or the respiratory tract could be observed under the study conditions described here.

Pain Perception, Brain Connectivity, and Neurochemistry in Healthy, Capsaicin-Sensitive Subjects.

Most of the occupational exposure limits (OELs) are based on local irritants. However, exposure to much lower concentrations of irritant substances can also lead to health complaints from workers. Exposure to irritants is often accompanied by strong unpleasant odors, and strong odors might have distracting effects and hence pose a safety risk. The findings obtained in human exposure studies with chemically sensitive, stressed, or anxious persons suggest that their ability to direct attention away from the odorous exposure and to focus on a cognitive task is reduced. In addition, after repeated odor exposure, these persons show signs of sensitization, i.e., difficulties in ignoring or getting used to the exposure. The question arises as to whether certain health conditions are accompanied by a change in sensitivity to odors and irritants, so that these persons are potentially more distracted by odors and irritants and therefore more challenged in working memory tasks than nonsusceptible persons. In our study, susceptible persons with sensory airway hyperreactivity ("capsaicin-sensitive") respond more strongly to mechanical skin stimuli than controls and show altered network connectivity. Capsaicin-sensitive subjects have a lower pain threshold and thus are more sensitive to mechanical skin stimuli. The intrinsic functional connectivity of their saliency network is higher, and the lower the GABAergic tone of the thalamus, the higher their pain sensitivity to mechanical stimuli. It seems that the increased communication between resting-state networks promotes a stronger perception of the sensory input signal. The results can be used to inform about actual risks (i.e., attention diversion and increased risk of accidents) and "pseudo" risks such as odor perception without a negative impact on one's well-being. This way, uncertainties that still prevail in the health assessment of odorous and sensory irritating chemicals could be reduced.

(Mono-) Exposure to Naphthalene in the Abrasives Industry: Air Monitoring and Biological Monitoring.

Exposure to the bicyclic aromatic hydrocarbon naphthalene occurs in most cases along with other polycyclic aromatic hydrocarbons. Here we report from an investigation of 63 healthy, non-smoking male employees in the abrasives industry where naphthalene is the only relevant chemical exposure. Exposure assessment was performed using a combination of Air and Biological Monitoring over nearly a whole working week (Mo.-Th.). Air measurements were carried out during the shift on Thursday with the GGP mini-sampling system, combining particle and vapour sampling at low flow rates. In urine spot samples, the metabolites 1- and 2-naphthol were measured Mo.-Th. pre- and post-shift (for the reference group only Mo. pre- and Th. post-shift). With regard to naphthalene concentrations measured in air and concentrations of its metabolites (1- and 2-naphthol) in urine, study participants could be divided into a high and a low exposure group, and a reference group. The naphthalene concentration in air was in the range of 0.1-11.6 mg m-3, and naphthol concentrations (sum of 1- and 2-naphthol) in post-shift urine were in the range of <1 to 10 127 µg l-1. Naphthalene concentrations in air and naphthol concentrations in urine were closely correlated, indicating mainly airborne exposure at the investigated workplaces. As expected from toxicokinetic data, internal body burden increased slightly during a working week and did not completely decline over a work-free weekend to background concentrations observed in occupationally not exposed persons. Taking into account the observed increase in pre- and post-shift values during the working week, urine sampling for Biological Monitoring at workplaces should be carried out after several preceding shifts. Our data allow the derivation of biological limit values for the sum of 1- and 2-naphthol in urine corresponding to occupational exposure limits for naphthalene in air.

Ethyl acrylate: influence of sex or atopy on perceptual ratings and eye blink frequency.

Occupational exposure limits (OELs) are derived for protection from health hazards, assuming that exposed subjects are healthy adult workers. Whether differences in susceptibility to sensory irritation effects from airborne chemicals have to be taken into account is currently under discussion. Thus, we chose atopics as a healthy but possibly susceptible subpopulation that can be identified with a clinical test. To investigate the influence of sex or atopy on sensitivity to airborne chemicals, 22 subjects were exposed for 4 h to ethyl acrylate at three concentrations: 0.05 ppm (odor threshold; sham), 5 ppm (constant), and varying exposure between 0 and 10 ppm. Odor intensity decreased and eye irritation ratings increased in a dose-dependent manner, reflecting the time course of the exposure scenarios. The reports of moderate-to-strong eye irritation were verified by significant increases in eye blink frequency. Our results show that women reported subjective eye irritation to an increasing degree. However, these sex-related differences in ratings could not be verified by objective assessment of eye blink frequency. Atopic subjects reported higher odor intensity than non-atopic subjects, but only during the sham (odorous but not irritating) exposure condition. Differences in ratings on annoyance, and eye or nose irritation were not found. Furthermore, the study revealed that atopic subjects might belong to a group of subjects with frequent eye blink activity. Although the relative increase in blink rates was more pronounced in non-atopic subjects, atopic subjects had significant higher blink rates at the end of the exposure to varying ethyl acrylate concentrations. Our results do not support that atopy enhances chemosensory effects if only the increase of blink rates and not the absolute height are considered as adverse effect. Nevertheless, the results indicate that individuals with frequent eye blink activity should be distinguished from those with normal eye blink activity while investigating blink rates as objective parameter of eye irritation.

Validity of different biomonitoring parameters in human urine for the assessment of occupational exposure to naphthalene.

Up to date, information on the validity of human biomonitoring (HBM) parameters of naphthalene exposure is poor. This study was performed to reveal the relation between occupational exposure to naphthalene and biological exposure markers. Therefore, ten lowly and highly exposed workers from the abrasives industry were selected to characterise a broad exposure range. Naphthalene in air was determined by personal air monitoring during one shift. For biological monitoring, pre- and post-shift urine samples collected on 2 days of a working week were analysed for 1,2-dihydroxynaphthalene (1,2-DHN), 1- and 2-naphthol, 1- and 2-naphthylmercapturic acid (NMA). The naphthalene concentration in air was in the range of 0.5 to 11.6 mg/m3. The biomarkers in urine showed post-shift concentration in the range of 114-51,809 µg/L for 1,2-DHN, 0.8-666 µg/L for 1-NMA, 2-2698 µg/L for 1-naphthol and 4-1135 µg/L for 2-naphthol, respectively. 2-NMA was not detected. The urinary levels increased significantly from pre- to post-shift for all analysed parameters and an accumulation over the working week was observed. Significant positive correlations were observed between 1,2-DHN, 1-NMA, 1- and 2-naphthol in post-shift urine samples and personal exposure to naphthalene in the air. 1-NMA and 1,2-DHN, 1- and 2-naphthol have been demonstrated as suitable biomarkers for naphthalene exposure monitoring. Of the determined biomarkers, 1,2-DHN is by far the metabolite with the highest concentration in the urine samples.

Effects of Exposure to Carbon Dioxide in Potash Miners.

Potash miners can become exposed to carbon dioxide (CO2) during the blasting of basalt intrusions or loading and transporting the blasted salt. In a cross-shift study, we compared physiological effects of acute exposure to elevated CO2 concentrations in miners after long-term exposure to evaluate the possible health risks. A group of 119 miners was assessed by clinical examination, lung function tests, and blood gas content directly before and after the shift. A cumulative CO2 exposure was measured using personal monitors. The miners were categorized as low (<0.1 vol.%, n = 83), medium (<0.5 vol.%, n = 26), and high (>0.5 vol.%, n = 10) CO2 exposed subjects. We found no significant differences among the three groups. Lung function testing revealed no conspicuous findings, and chronic health effects were not observed in the miners either. In conclusion, no significant adverse effects could be found in potash miners exposed to elevated CO2 concentrations. Therefore, the mining authorities allow potash mining operations for 4 h at ambient CO2 up to 1.0 vol.% and for 2 h at CO2 not exceeding 1.5 vol.% per shift.

Medical surveillance and long-term prognosis of occupational allergy due to platinum salts.

PURPOSE: Medical surveillance of workers in precious metals refineries and catalyst production plants is well established in many countries as a measure to prevent occupational asthma due to platinum (Pt) salts. It was the aim of this study to evaluate the impact of medical surveillance and to define prognostic factors with an emphasis on exposure determinants. METHODS: As part of an observational longitudinal study, 96 workers from German precious metals refineries and catalyst production plants with Pt salt allergy underwent a second examination several years (median 67 months) after the initial diagnosis was made. RESULTS: When the second examination was conducted, 92 subjects (96 %) had already been transferred to jobs with very low or no exposure to Pt salts. The number of subjects with sensitization to Pt salt as assessed by skin prick test (SPTPt) decreased from 86 to 52 %, and there was a clear improvement for rhinitis, conjunctivitis and contact urticaria between both examinations. Although the number of subjects with asthma symptoms decreased significantly, at the second examination 74 subjects (77 %) continued to suffer from asthma and 51 subjects (53 %) received asthma medication. Airway obstruction or bronchial hyperresponsiveness persisted in 83 subjects (86 %). CONCLUSIONS: Secondary prevention in subjects with occupational exposure to Pt salts, as practiced for over 25 years in Germany could not avoid persistent asthma in the majority of cases, although improvements occurred. This study reveals the limitations of the concept that removal from exposure after the occurrence of respiratory symptoms may prevent chronic asthma. It is recommended that removal from exposure should be done immediately after the occurrence of a positive SPTPt, irrespective of symptoms.

The Influence of Humidity on Assessing Irritation Threshold of Ammonia.

A large number of occupational exposure limit values (OELs) are based on avoiding of sensory irritation of the eyes and the upper respiratory tract. In order to investigate the chemosensory effect range of a chemical, odor and sensory irritation thresholds (lateralization thresholds, LTs) can be assessed. Humidity affects olfactory function and thus influences odor thresholds; however, a similar effect has not been shown for sensory irritation thresholds. The purpose of the present study was to explore whether LTs for ammonia vapor vary depending on the water vapor content of the inspired stimulus. Eight healthy nonsmoking volunteers were simultaneously exposed to ammonia vapor through one nostril and clean air through the other and were asked to determine which nostril received the chemical. Within experimental runs, ascending ammonia concentrations (60-350 ppm) that were either dry or humidified were administered at fixed time intervals. Geometric mean LTs obtained at wet (181 ppm) or dry (172 ppm) conditions did not differ significantly (P = 0.19) and were within the range of those reported by previous studies. These results suggest that humidity is not a critical factor in determining sensory irritation thresholds for ammonia, and future studies will examine if these findings are transferable to sensory irritation thresholds for other chemicals.

An extension of olfactometry methods: An expandable, fully automated, mobile, MRI-compatible olfactometer.

BACKGROUND: fMRI experiments on olfaction offer new insights into the complex, but in contrast to other sensory systems, less studied cognition of odors. To perform these experiments is still a challenge. NEW METHOD: To address the challenge posed by MR settings, an olfactometer design is presented including specific improvements to the limited number of already existing olfactometers. Innovative features such as pneumatically controlled pinch valves, useable in the scanner and providing exact stimulus timing as well as a 3D-printed nasal mask inlet for common sleep laboratory masks that can be used for lateral divided stimulus presentation are introduced. To ensure a fully automated and mobile system, the use of a flexible and easily-adapted Matlab-Code and a portable adaptable container system are presented. RESULTS: The functional efficiency of these features are proven by results of an fMRI study as well as testing temporal resolution and concentration stability with a mass spectrometer. COMPARISON WITH EXISTING METHODS: The 24-channel olfactometer design presented here provides an inexpensive alternative to the currently available olfactometers including the achievement of fast onset times, lateral divided stimulus presentation and high flexibility and adaptability to different scientific questions. CONCLUSION: The olfactometer design presented in this paper can be seen as a realistic and feasible solution to overcome the challenges of presenting olfactory stimuli within the MR setting.

Sensory irritation as a basis for setting occupational exposure limits.

There is a need of guidance on how local irritancy data should be incorporated into risk assessment procedures, particularly with respect to the derivation of occupational exposure limits (OELs). Therefore, a board of experts from German committees in charge of the derivation of OELs discussed the major challenges of this particular end point for regulatory toxicology. As a result, this overview deals with the question of integrating results of local toxicity at the eyes and the upper respiratory tract (URT). Part 1 describes the morphology and physiology of the relevant target sites, i.e., the outer eye, nasal cavity, and larynx/pharynx in humans. Special emphasis is placed on sensory innervation, species differences between humans and rodents, and possible effects of obnoxious odor in humans. Based on this physiological basis, Part 2 describes a conceptual model for the causation of adverse health effects at these targets that is composed of two pathways. The first, "sensory irritation" pathway is initiated by the interaction of local irritants with receptors of the nervous system (e.g., trigeminal nerve endings) and a downstream cascade of reflexes and defense mechanisms (e.g., eyeblinks, coughing). While the first stages of this pathway are thought to be completely reversible, high or prolonged exposure can lead to neurogenic inflammation and subsequently tissue damage. The second, "tissue irritation" pathway starts with the interaction of the local irritant with the epithelial cell layers of the eyes and the URT. Adaptive changes are the first response on that pathway followed by inflammation and irreversible damages. Regardless of these initial steps, at high concentrations and prolonged exposures, the two pathways converge to the adverse effect of morphologically and biochemically ascertainable changes. Experimental exposure studies with human volunteers provide the empirical basis for effects along the sensory irritation pathway and thus, "sensory NOAEChuman" can be derived. In contrast, inhalation studies with rodents investigate the second pathway that yields an "irritative NOAECanimal." Usually the data for both pathways is not available and extrapolation across species is necessary. Part 3 comprises an empirical approach for the derivation of a default factor for interspecies differences. Therefore, from those substances under discussion in German scientific and regulatory bodies, 19 substances were identified known to be human irritants with available human and animal data. The evaluation started with three substances: ethyl acrylate, formaldehyde, and methyl methacrylate. For these substances, appropriate chronic animal and a controlled human exposure studies were available. The comparison of the sensory NOAEChuman with the irritative NOAECanimal (chronic) resulted in an interspecies extrapolation factor (iEF) of 3 for extrapolating animal data concerning local sensory irritating effects. The adequacy of this iEF was confirmed by its application to additional substances with lower data density (acetaldehyde, ammonia, n-butyl acetate, hydrogen sulfide, and 2-ethylhexanol). Thus, extrapolating from animal studies, an iEF of 3 should be applied for local sensory irritants without reliable human data, unless individual data argue for a substance-specific approach.

Exposure assessment of potash miners at elevated CO2 levels.

PURPOSE: In a potash mine in the center of Germany, stationary measurements 40 cm above ground level have revealed occasional increases in the carbon dioxide (CO2) levels that exceed the 0.5 vol.% German occupational exposure limit (OEL). This study, therefore, aimed to examine the individual exposures of potash miners to CO2 at their underground workplaces. METHODS: 119 miners were equipped with personal CO2 detectors to log the individual CO2 exposures during underground work. We decided to use electrochemical monitors due to their compactness and minimal mass. Furthermore, generated CO2 measurements with precipitated overshooting and false positive CO2 values were studied using diverse CO2 test gases and different fumigation times. RESULTS: The personal detectors showed short-term CO2 peak exposures at very high concentrations in a limited number of workers. Twenty-two threshold limit value violations were observed according to the present OEL, and the personal CO2 monitoring allowed categorization into three exposure groups, low (n = 83), moderate (n = 26) and high burdens (n = 10) of CO2. CONCLUSIONS: The electrochemical sensors used have numerous properties that can potentially influence the assessment of exposures. The current findings suggest that assessing similar exposure scenarios, with respect to elevated and strongly fluctuating CO2 concentrations, the behavior of electrochemical sensors should be taken into consideration.

Relationship of pulmonary function response to ozone exposure and capsaicin cough sensitivity.

CONTEXT: Challenge studies in humans have shown considerable interindividual variability in pulmonary impairment across ozone exposure. OBJECTIVE: Since previous results suggested effect modulation by neural mechanism, we investigated sensory C-fiber reactivity in relationship to ozone-triggered response pattern. METHODS: Cough reflex thresholds reflecting C-fiber sensitivity were evaluated by capsaicin single breath dose-response method. Capsaicin concentrations triggering, respectively, two and five or more coughs (C2, C5) were recorded. Sixteen healthy subjects were randomly exposed in an intermittent exercise protocol to ozone concentrations of 240 and 40 ppb (sham exposure). Ozone responsiveness was defined by a decrease in forced expiratory volume in 1 s (FEV(1)) of more than 5%. RESULTS: Based on a dichotomous classification, subjects with enhanced reactivity to ozone had lower cough thresholds than non-responders (C2, p = 0.035; C5, p = 0.086). Over all, we could demonstrate relationships between capsaicin sensitivity and ozone-triggered changes in FEV(1), peak expiratory flow and maximal expiratory flow at 50% vital capacity but not in specific airway resistance. CONCLUSION: Our results suggest that capsaicin challenge tests might be useful to characterize subjects with enhanced pulmonary function response towards inhalant irritants.

Reproducibility of sensitivity to capsaicin assessed by single breath inhalation methodology.

The hallmark of sensory hyperreactivity is an enhanced capsaicin induced cough reflex. The cough reflex can be modified by activation of nociceptive (capsaicin-sensitive) nerve terminals. The aim of our study was to assess the influence of exposure to CO(2) concentrations up to 2.0 vol% on capsaicin induced cough reflex on four different occasions. Sixteen healthy volunteers were exposed to CO(2) concentrations of 0.5, 1.0, and 2.0 vol% for 4 h and to clean air in a repeated measures cross-over design. After exposure the capsaicin induced cough reflex was assessed by the single breath dose-response method according to ERS 2007 guidelines. After blank solutions, capsaicin doses (n=12, range 0.49 to 1000 µM) were administrated from a nebulizer combined with a provocation system (Masterscope, software APS version 5.02). Doses were doubled every minute and the concentration causing five or more coughs (C5) was fixed as the end point. The inter-individual C5 capsaicin responsiveness reflected a representative range (0.95-1000 µM). On an intra-individual basis, a good reproducibility could be demonstrated for four tests within 3 weeks. There was no influence of CO(2) challenge on the cough reflex. The first capsaicin test demonstrated a lower C5 threshold independent of the CO(2) concentration applied. In conclusion, assessing the capsaicin cough reflex by single breath inhalation is reliable. However, the at cough sensitivity might be overestimated at the first test occasion. Exposure to CO(2) in concentrations of up to 2.0 vol% has no effect on sensory reactivity.

Considerations for the design and technical setup of a human whole-body exposure chamber.

Exposures to air contaminants, such as chemical vapors and particulate matter, pose important health hazards at workplaces. Short-term experimental exposures to chemical vapors and particles in humans are a promising attempt to investigate acute effects of such hazards. However, a significant challenge in this field is the determination of effects of co-exposures to more than one chemical or mixtures of chemical vapors and/or particles. To overcome such a challenge, studies have to be conducted under standardized exposure characterization and real time measurements, if possible. A new exposure laboratory (ExpoLab) was installed at IPA, combining sophisticated engineering designs with new analytical techniques, to fulfill these requirements. Low-dose as well as high-dose exposure scenarios are achieved by means of a calibration-gas-generator. Exposure monitoring can be carried out with a high performance real time mass spectrometer and other suitable analyzers (e.g. gas chromatograph). Numerous automated security facilities guarantee the physical integrity of the volunteers, and the waste atmosphere is removed using either charcoal filtration or catalytic post-combustion. Measurements of sulfur hexafluoride, carbon dioxide, aniline and carbon black are presented to demonstrate the performance of the exposure unit with respect to the temporal and spatial stability of generated atmospheres. The variations of generated contents in the atmospheres at steady state are slightly higher than the measurement precision of the analyzers (the typical standard deviation of generated atmospheres is < 2%). The technical components of ExpoLab and its monitoring systems ensure high quality standards in validity and reliability of generating and measuring exposure atmospheres.

Use of a calibration gas generator for irritation threshold assessment and as supplement of dynamic dilution olfactometry.

Human odor and mucosal membrane irritation thresholds are used as criteria for assessing air quality in occupational and environmental settings. Unfortunately, reported threshold values still differ by several orders of magnitude rendering most standard compilations of little practical utility. Thus, in view of the need to repeat odor threshold measurements with a reliable methodology, a new technical approach based on original equipment manufacturer integrated solutions is presented. To test applicability, a calibration gas generator was used to continuously generate a fixed odor vapor concentration. Different dilution steps were realized by coupling to a purchasable olfactometer. Comparison with the "standard," that is, odor stimulus supply via sample bags revealed good correspondence. As a second step, the calibration gas generator was used to generate rapid changes in stimulus concentration between consecutive trials. Irritation thresholds were measured with an ascending series of ammonia concentrations generated from an aqueous solution. The obtained thresholds lay within the range previously reported. The introduced technology enables quick and reliable odor stimulus generation and provides flexibility in choosing the optimal start concentration, the step-size between dilutions, and the range of stimulus concentrations. Errors from usage of rotameters or sample bags can be avoided.

Odor frequency and odor annoyance Part II: dose-response associations and their modification by hedonic tone.

OBJECTIVE: Risk-assessment for environmental odors and the development of an appropriate guideline for protection against undue odor annoyance have long been hampered by the difficulties of assessing odor exposure and community annoyance responses. In recent years, however, dose-response associations between frequency of odor events and odor annoyance level in the affected population were established. However, the influence of hedonic tone (pleasantness-unpleasantness) and perceived odor strength (intensity) on the degree of odor annoyance have long been neglected in such studies and accompanying guidelines. In order to close this gap a pertinent field study was conducted in the vicinity of six odor emitting plants, two with pleasant (sweets production, rusk bakery), with neutral (textile production, seed oil production), and with presumably unpleasant odor emissions (fat refinery, cast iron production). METHODS: A standardized sensory method was developed (described in Part I in the accompanying paper) to quantify intensity and hedonic tone within the assessment of odor exposure by systematic field inspection with trained observers. Additionally, exposure-information, the degree of annoyance, and the frequency of general health complaints and irritation symptoms were collected from the exposed residents through direct interviews. Multiple logistic regression analysis was used to establish dose-response associations between odor frequency, intensity and hedonic tone as independent variables and annoyance or symptom reporting as the dependent variable. RESULTS: It is shown that exposure-annoyance as well as exposure-symptom associations are strongly influenced by odor hedonic. Whereas pleasant odors induced little to no annoyance, both neutral and unpleasant ones did. Additional inclusion of odor intensity did not improve the prediction of odor annoyance. Frequency of reported symptoms was found to be exclusively mediated by annoyance. The results are discussed in terms of environmental stress emphasizing the WHO-definition of health. CONCLUSIONS: Based on these findings the existing German guideline against undue odor annoyance was modified.