Søren Kjærgaard

Human reactions to a mixture of indoor air volatile organic compounds

Abstract A controlled experimental study of human reactions to a mixture of 22 volatile organic compounds often found in indoor air was performed in a climate chamber. Twenty-one healthy subjects were compared with a group of 14 subjects suffering from the ‘sick building syndrome’ (SBS subjects), i.e. having symptoms related to the indoor environment (irritated mucous membranes, headache, etc.) as defined by WHO in 1982. In groups of 4 these subjects were exposed during two successive periods to either 0 and 0 mg m −3 , 25 and 0 mg m −3 , or 0 and 25 mg m −3 ; 25 mg m −3 is equivalent to the highest concentrations expected in a new building. The study was double blinded, and a latin square design was used to balance out effects of day in the week and season. Both groups reacted subjectively to the air reporting worse odor, worse indoor air quality as defined by the subject, and more irritated mucous membranes in eye, throat and nose than in the clean environment. A tendency to a stronger response was seen among the SBS subjects. Objective measures indicated among others an exposure related reduction in lung function among SBS subjects. Both groups had an increased number of polymorphonuclear leucocytes in tear fluid as a result of exposure. This was not seen for nasal secretions. Psychological performance tests indicated an exposure related diminished ability to learn. In conclusion, the experiment indicates that exposure to volatile organic compounds in low concentrations as seen in new houses causes both subjective complaints and objective signs in normal healty subjects; but more so in subjects from the sick building syndrome.

Variation in the PaO2/FiO2 ratio with FiO2: mathematical and experimental description, and clinical relevance.

IntroductionPrevious studies have shown through theoretical analyses that the ratio of the partial pressure of oxygen in arterial blood (PaO2) to the inspired oxygen fraction (FiO2) varies with the FiO2 level. The aim of the present study was to evaluate the relevance of this variation both theoretically and experimentally using mathematical model simulations, comparing these ratio simulations with PaO2/FiO2 ratios measured in a range of different patients.MethodsThe study was designed as a retrospective study using data from 36 mechanically ventilated patients and 57 spontaneously breathing patients studied on one or more occasions. Patients were classified into four disease groups (normal, mild hypoxemia, acute lung injury and acute respiratory distress syndrome) according to their PaO2/FiO2 ratio. On each occasion the patients were studied using four to eight different FiO2 values, achieving arterial oxygen saturations in the range 85–100%. At each FiO2 level, measurements were taken of ventilation, of arterial acid–base and of oxygenation status. Two mathematical models were fitted to the data: a one-parameter effective shunt model, and a two-parameter shunt and ventilation/perfusion model. These models and patient data were used to investigate the variation in the PaO2/FiO2 ratio with FiO2, and to quantify how many patients changed disease classification due to variation in the PaO2/FiO2 ratio. An F test was used to assess the statistical difference between the two models fit to the data. A confusion matrix was used to quantify the number of patients changing disease classification.ResultsThe two-parameter model gave a statistically better fit to patient data (P < 0.005). When using this model to simulate variation in the PaO2/FiO2 ratio, disease classification changed in 30% of the patients when changing the FiO2 level.ConclusionThe PaO2/FiO2 ratio depends on both the FiO2 level and the arterial oxygen saturation level. As a minimum, the FiO2 level at which the PaO2/FiO2 ratio is measured should be defined when quantifying the effects of therapeutic interventions or when specifying diagnostic criteria for acute lung injury and acute respiratory distress syndrome. Alternatively, oxygenation problems could be described using parameters describing shunt and ventilation/perfusion mismatch.

Non-invasive estimation of shunt and ventilation-perfusion mismatch.

ObjectiveTo investigate whether parameters describing pulmonary gas exchange (shunt and ventilation-perfusion mismatch) can be estimated consistently by the use of non-invasive data as input to a mathematical model of oxygen transport.DesignProspective study.SettingInvestigations were carried out in the post-anaesthesia care unit, coronary care unit, and intensive care unit.PatientsData from ninety-five patients and six normal subjects were included for the comparison. The clinical situations differed, ranging from healthy subjects to patients with acute respiratory failure in the intensive care unit.MeasurementsThe experimental procedure involved changing the inspired oxygen fraction (FIO2) in 4–6 steps in order to obtain arterial oxygen saturations (SaO2) in the range from 90–100%. This procedure allows plotting a FIO2/SaO2 or FEO2/SaO2 curve, the shape and position of which was quantified using the mathematical model estimating pulmonary shunt and a measure of ventilation-perfusion mismatch (ΔPO2). This procedure was performed using either arterial blood samples at each FIO2 level (invasive approach) or using values from the pulse oximeter (non-invasive approach).Main resultsThe model provided good fit to data using both the invasive and non-invasive experimental approach. The parameter estimates were linearly correlated with highly significant correlation coefficients; shuntinvasive vs shuntnon-invasive, r2 = 0.74, P <0.01, and ΔPO2invasive vs ΔPO2non-invasive, r2 = 0.97, P <0.001.ConclusionsPulmonary gas exchange can be described equally well using non-invasive data. The simplicity of the non-invasive approach makes the method suitable for large-scale clinical use.

Human reactions to indoor air pollutants: N-decane

Abstract A dose-response study of human reactions to the indoor air pollutant n-decane was performed in a climate chamber. Sixty-three healthy subjects, randomly selected from the normal population, were exposed to n-decane concentrations of either 0, 10, 35, or 100 μL/L in a controlled, double blind study using a latin square exposure design. The most significant findings were dose-dependent changes in irritation of mucous membranes, increased sensation of odor intensity, and reduced air quality. Adaptation was seen at the highest exposure levels, but not at the levels relevant for a non-industrial environment. The physiological measurements showed decreased tear film stability at all exposure concentrations. The number of conjunctival polymorphonuclear leucocytes increased in a dose-related manner. Predictors of the sensitivity to explosure, i.e. mucous membrane irritation threshold and skin irritation (Stingers test), were correlated to subjective ratings of odor intensity and irritation of mucous membranes. In conclusion, even small concentrations of the relatively inert n-decane caused symptoms similar to those indicated in the World Health Organization definition of the sick building syndrome. Furthermore, physiological changes appear to be related to exposures to indoor air pollutants.

Minimal model quantification of pulmonary gas exchange in intensive care patients

Mathematical models are required to describe pulmonary gas exchange. The challenge remains to find models which are complex enough to describe physiology and simple enough for clinical practice. This study aimed at finding the necessary minimal modeling complexity to represent the gas exchange of both oxygen and carbon dioxide. Three models of varying complexity were compared for their ability to fit measured data from intensive care patients and to provide adequate description of patients gas exchange abnormalities. Pairwise F-tests showed that a two parameter model provided superior fit to patient data compared to a shunt only model (p<0.001), and that a three parameter model provided superior fit compared to the two parameter model (p<0.1). The three parameter model describes larger ranges of ventilation to perfusion ratios than the two parameter model, and is identifiable from data routinely available in clinical practice.

Dust exposure, eye redness, eye cytology and mucous membrane irritation in a tobacco industry

SummaryIn a study of 75 workers employed in a tobacco factory producing cheroots we measured cellular contents of tear fluid, redness of eyes, discomfort, total (0–5.7 mg/m3) and respirable dust in the breathing zone and total ambient dust by stationary sampling (0.08–1.0 mg/m3). A matched group of 50 office workers in a telephone company (total ambient dust concentration between 0.08–0.13 mg/m3) was similarly examined as referents. We found a difference between the two companies with regard to cell counts, with tobacco workers having the largest numbers except for lymphocytes. Among tobacco workers we furthermore found that the number of cuboidal and columnar epithelial cells increased during the day. The increase of cuboidal cells, however, occurred mainly in a small group of tobacco workers exposed to the highest concentrations of tobacco dust (mean =1.26 mg/m3). No difference in the sensation of eye irritation was found between companies, but increased irritation in the morning was associated with increased exposure to total dust during the work-shift among tobacco workers. A dose-dependent difference in photographically measured eye redness was found among the tobacco workers. It could not be explained by differences in tobacco smoking, sex, age, sleeping habits or use of glasses. Irritation of lips and upper airways as reported by questionnaire were more common in tobacco workers than in referents. In conclusion the tobacco workers, more often than the referents, had complaints and objective changes in the mucous membranes of the eyes. These may be related to tobacco dust exposure.

Sensitivity of the Eyes to Airborne Irritant Stimuli: Influence of Individual Characteristics

The purpose of this study was to measure trigeminal sensitivity of the eyes to irritative exposures and to examine the influence of individual characteristics, e.g., gender, age, and smoking, on this sensitivity. During an experimental study, 158 of 2,025 randomly selected volunteers were examined for sensory irritation threshold in the eyes to carbon dioxide (CO2). Eyes were exposed to progressive concentrations of CO2 (10, 20, 40, 80, and 160 ml/l), until the subject claimed a distinct irritation. Each exposure level lasted 2 min. A special exposure mask system was used for eyes-only exposure. No significant dependence of gender or smoking was found, but subjects who were less than 40 y of age were more sensitive than were the elderly subjects. Subjects who reported frequent sick building syndrome irritation symptoms had lower thresholds (i.e., higher sensitivity). The CO2 threshold was related to skin irritation sensitivity, i.e., response to lactic acid smeared on the cheek, and there were indications that occupational stress was associated with low thresholds. Studies of irritation to n-decane indicate that the CO2 threshold may be an important factor in the prediction of individual sensitivity to irritation from airborne pollutants. The CO2 threshold of the eyes may be of value in the evaluation of hypersensitivity to indoor air pollution. Furthermore, the threshold may be used to assess important relationships between the different trigeminal innervated areas, e.g., skin and eyes. Finally, the method has the advantage of avoiding interference from olfactory stimulation.

Sensory Eye Irritation in Humans Exposed to Mixtures of Volatile Organic Compounds

Eight subjects participated in a controlled eyes-only exposure study of human sensory irritation in ocular mucosal tissue. The authors investigated dose-response properties and the additive effects of three mixtures of volatile organic compounds. The dose-response relationships for these mixtures showed increases in response intensity as concentration increased. Replication of exposure did not result in significantly different dose- response relationships. Moreover, the result implied that components of the three mixtures interacted additively to produce ocular irritation, a result referred to as simple agonism. Finally, the authors addressed the comparability of two methods to measure sensory irritation intensity (visual analogue scale and a comparative scale). The results indicated that the two rating methods produced highly comparable results.

Cognitive Function and Symptoms in Adults and Adolescents in Relation to RF Radiation From UMTS Base Stations

There is widespread public concern about the potential adverse health effects of mobile phones in general and their associated base stations in particular. This study was designed to investigate the acute effects of radio frequency (RF) electromagnetic fields (EMF) emitted by the Universal Mobile Telecommunication System (UMTS) mobile phone base stations on human cognitive function and symptoms. Forty adolescents (15-16 years) and 40 adults (25-40 years) were exposed to four conditions: (1) sham, (2) a Continuous Wave (CW) at 2140 MHz, (3) a signal at 2140 MHz modulated as UMTS and (4) UMTS at 2140 MHz including all control features in a randomized, double blinded cross-over design. Each exposure lasted 45 min. During exposure the participants performed different cognitive tasks with the Trail Making B (TMB) test as the main outcome and completed a questionnaire measuring self reported subjective symptoms. No statistically significant differences between the UMTS and sham conditions were found for performance on TMB. For the adults, the estimated difference between UMTS and sham was -3.2% (-9.2%; 2.9%) and for the adolescents 5.5% (-1.1%; 12.2%). No significant changes were found in any of the cognitive tasks. An increase in headache rating was observed when data from the adolescents and adults were combined (P = 0.027), an effect that may be due to differences at baseline. In conclusion, the primary hypothesis that UMTS radiation reduces general performance in the TMB test was not confirmed. However, we suggest that the hypothesis of subjective symptoms and EMF exposure needs further research.

Nitrogen Dioxide in Indoor Ice Skating Facilities: An International Survey

An international survey of nitrogen dioxide (NO2) levels inside indoor ice skating facilities was conducted. One-week average NO2 concentrations were measured inside and outside of 332 ice rinks located in nine countries. Each rink manager also completed a questionnaire describing the building, the resurfacing machines, and their use patterns. The (arithmetic) mean NO2 level for all rinks in the study was 228 ppb, with a range of 1-2,680 ppb, based on a sample collected at breathing height and adjacent to the ice surface. The mean of the second indoor sample (collected at a spectators area) was 221 ppb, with a range of 1-3,175 ppb. The ratio of the indoor to outdoor NO2 concentrations was above 1 for 95% of the rinks sampled, indicating the presence of an indoor NO2 source (mean indoor:outdoor ratio = 20). Estimates of short-term NO2 concentrations indicated that as many as 40% of the sampled rinks would have exceeded the World Health Organization 1-hour guideline value of 213 ppb NO2 for indoor air. Statistically significant associations were observed between NO2 levels and the type of fuel used to power the resurfacer, the absence of a catalytic converter on a resurfacer, and the use of an ice edger. There were also indications that decreased use of mechanical ventilation, increased number of resurfacing operations per day, and smaller rink volumes were associated with increased NO2 levels. In rinks where the main resurfacer was powered by propane, the NO2 concentrations were higher than in those with gasoline-powered resurfacers, while the latter had NO2 concentrations higher than in those using diesel. Rinks where the main resurfacer was electric had the lowest indoor NO2 concentrations, similar to the levels measured outdoor.