Modeling relationships between indoor and outdoor air quality.

Information about the ratio between indoor and outdoor concentrations (IO ratios) of air pollutants is a crucial component in human exposure assessment. The present study examines the relationship between indoor and outdoor concentrations as influenced by the combined effect of time patterns in outdoor concentrations, ventilation rate, and indoor emissions. Two different mathematical approaches are used to evaluate IO ratios. The first approach involves a dynamic mass balance model that calculates distributions of transient IO ratios. The second approach assumes a linear relationship between indoor and outdoor concentrations. We use ozone and benzene as examples in various modeling exercises. The modeled IO ratio distributions are compared with the results obtained from linear fits through plots of indoor versus outdoor concentrations.

Renal infarction as a cause of acute flank pain.

Renal infarction results from occlusion of the main renal artery or its distal branches. The clinical picture depends on the extent and the rapidity of the occlusion. Herein, the different imaging modalities (including ultrasonography, computed tomography, magnetic resonance imaging, intravenous urography, and angiography) for diagnozing renal infarction are discussed. The key-modality is computed tomography. Because of the limited warm ischemia time of the kidneys (1.5 hours?) and the time required for diagnosis, there is no real therapeutic relevance in most cases.

Ventricular premature beats in triathletes: still a physiological phenomenon?

UNLABELLED: Sudden death is a tragic fact, unexpectedly arising in all age groups. Ventricular arrhythmias are the main cause. At the end of a maximal exercise test more ventricular premature beats were noted in a group of well trained triathletes compared with a similar control group. The etiology is multifactorial. When these ventricular premature beats are associated with specific structural and functional heart adaptations, echocardiographically and electrocardiographically well-documented, then those 'banal' ventricular premature beats cannot longer be considered as a physiological phenomenon. In these circumstances the involved subject is a candidate for dangerous arrhythmias and 'sudden cardiac death'. PURPOSE: The principal cause of 'Sudden cardiac death' is ventricular arrhythmias. We explore the incidence of ventricular premature beats (VPB) in triathletes, who engage in enforced endurance sports. METHODS: Fifty-two triathletes were compared with twenty-two control subjects with comparable anthropometric parameters in function of structural and functional cardiac adaptations. Maximal exercise tests were conducted on a stationary bicycle and a treadmill. During the last two minutes of each test, the VPB were registered. RESULTS: Statistically significant differences emerged in the cardiac structure and function between the triathletes and the controls. There were signs of cardiac hypertrophy and arguments for a supernormally diastolic left ventricular function in the triathletes. The performance capacity was also significantly higher in the triathletes. The maximal heart rate was significantly higher in the control group. The number of VPB was significantly higher in the triathletes. The increased risk of VPB in the triathlon group is caused by several factors: the degree of cardiac hypertrophy, the increased diastolic reserve, the duration of the exercise, the existence of an aortic insufficiency jet and some specific electrocardiographic findings. CONCLUSIONS: The triathlete has an increased risk of VPB during maximal efforts. We doubt the traditionally accepted view of the physiological nature of those VPB and suspect that the limit of physiological cardiac adaptations to sport efforts is exceeded with the appearance of VPB. The triathlete with VPB and with specific electrocardiographic and echocardiographic findings is a candidate for 'sudden cardiac death'.

Structural heart adaptations in triathletes.

OBJECTIVE: To perform a triathlon in aerobic conditions, a variety of cardiovascular, haemodynamic and metabolic adaptations are required. The heart is the central concern and also the most important limiting factor. In this study we investigate the structural and functional heart adaptations of a group of triathletes. METHODS AND RESULTS: A group of 52 male triathletes was divided into 4 subgroups in function of their athletic results and compared with a control group of 22 healthy, very active but no athletic men. The groups had comparable anthropometric and general physical characteristics. Very significant differences in cardiac structure and cardiac function were observed between the groups. In the triathletes, we registered distinct signs of significantly mixed eccentric and concentric hypertrophy. Unlike the findings in a pathological left ventricular hypertrophy, the diastolic left ventricular function in triathletes was completely normal and even better than in the control group. The late passive diastolic filling period of the triathlete, in particular, seemed to have specific characteristics. The comparison between the subgroups of triathletes shows us that genetic factors probably play an important role in the cardiac adaptations in triathletes. CONCLUSIONS: In our opinion the "athletic heart" in triathletes is not a specific "physiological entity" but is a transitional phase to a dilated hypertrophic cardiomyopathy. Our study yields some arguments for the following proposition: "People are born as elite athletes, with specific characteristics of the left ventricle and with a specifically supernormal diastolic left ventricular function."

Indoor air exposure to volatile compounds emitted by paints: experiment and model.

To describe the evaporation of organic solvents from paints and the resulting indoor concentrations, a mathematical model and an indoor paint experiment are presented. The model describes painting in terms of an increasing area of paint during application and two compartments of paint once applied. Evaporation of organic solvents is driven by the vapor pressure of the organic solvent. The experiment revealed concentrations of n-alkanes in indoor air, during painting, and 3 days thereafter. To compare experimental results to model predictions, model parameters were measured at the start of the experiment. Diffusional exchange between paint compartments and fraction of paint applied to the upper compartment were set by expert judgment. Model predictions and experimental results were in agreement, although the timing of the concentration peak appeared difficult to predict.

Image analysis to measure activity index of animals.

The objective of the study was to present a method to quantify the behavioural response of animals to their micro-environment by using a camera system and a digitiser board. An algorithm was developed for analysing images and calculating activity, occupied zone and boundary of the animals. The developed method was tested on 3 different applications and animals. In the first application, the behavioural responses of broiler chickens to their thermal environment was measured. In the second application behavioural responses of pigs to their thermal environment were measured. In the third application, the response of water fleas to a chromium pollution was measured using the developed technique. Based on the experimental results, it can be concluded that the developed image analysis technique can be employed to quantify the behavioural responses of the tested animals to their micro-environment, in an easy and accurate way.

Problems, related to the occurrence of organic pollutants in the indoor environment.

Evaluation of the occurrence of organic compounds in the indoor environment is needed on at least two levels: 1. Evaluation of the overall prevalence of organic compounds in the indoor air. 2. Evaluation of abnormal concentrations in the indoor air as a result of more or less special circumstances. On both levels this evaluation can be problematic as a result of missing information on exposure to, and health risks of the measured compounds. As a result of this, only general remarks can be made about the relevance of the presence of organic compounds in the indoor air. The choice of the right policy is therefore often difficult. When, as a result of special circumstances the indoor air concentrations of organic compounds are elevated as in the case of houses built on polluted soil, or houses treated with a hydrofobing agent it is as a consequence, often difficult to take effectively the proper decisions. To solve these problems, a great deal of research appears to be necessary. By using all available information produced by the analysis and new techniques like pattern and source-recognition it may be possible to do this research in a more direct way.

Methods for source characterization of organic air pollutants.

Organic compounds are becoming increasingly more of interest as air pollutants, indoor as well as outdoor. Sources emitting such compounds are numerous and of various origin. For toxicological and epidemiological examination and for deciding on remedial actions information is required on the occurrences of compounds as well as on the emitting sources. For this purpose a number of investigations have been carried out with only limited success. To increase the quality of the description of air pollution related to complaints of dwellers and to exposure evaluation analytical and mathematical methods have tested in our laboratory. Analytical methods for the determination of different groups of organic compounds and mathematical methods for defining minimum sampling strategies and for the characterization of sources are discussed and illustrated with applications dealt with in the passed years. It is concluded that the application of a combination of these methods offers a manner to better describe and understand air pollution with organic compounds.