Radon Investigation in 650 Energy Efficient Dwellings in Western Switzerland: Impact of Energy Renovation and Building Characteristics

As part of more stringent energy targets in Switzerland, we witness the appearance of new green-certified dwellings while many existing dwellings have undergone energy efficiency measures. These measures have led to reduced energy consumption, but rarely consider their impact on indoor air quality. Consequently, such energy renovation actions can lead to an accumulation of radon in dwellings located in radon-prone areas at doses that can affect human health. This study compared the radon levels over 650 energy-efficient dwellings in western Switzerland between green-certified (Minergie) and energy-renovated dwellings, and analyzed the building characteristics responsible of this accumulation. We found that the newly green-certified dwellings had significantly lower radon level than energy-renovated, which were green- and nongreen-certified houses (geometric mean 52, 87, and 105 Bq/m3, respectively). The new dwellings with integrated mechanical ventilation exhibited lower radon concentrations. Thermal retrofitting of windows, roofs, exterior walls, and floors were associated with a higher radon level. Compared to radon measurements prior to energy renovation, we found a 20% increase in radon levels. The results highlight the need to consider indoor air quality when addressing energy savings to avoid compromising occupants’ health, and are useful for enhancing the ventilation design and energy renovation procedures in dwellings

Fungal Contaminants in Energy Efficient Dwellings: Impact of Ventilation Type and Level of Urbanization

: The presence of growing fungi in the indoor environment has been associated with the development of respiratory problems such as asthma or allergic rhinitis, as well as the worsening of respiratory pathologies. Their proliferation indoors could be a result of water leakage or inadequate ventilation. Although the factors promoting mould growth have been widely investigated in traditional dwellings, little work has been done in energy efficient dwellings. Here, the effectiveness of ventilation type, i.e., natural or mechanical, in influencing mould development was estimated in 44 recent and 105 retrofitted energy efficient dwellings. Fungi growing on surfaces were investigated in the dwellings situated in rural, peri-urban, and urban regions of Switzerland. The presence of these fungi was also investigated in bedroom settled dust. Information on building characteristics and owners’ lifestyle were collected. Significant associations were found with the level of urbanisation, the location of mouldy area in dwellings, and the diversity of fungal taxa. Dwellings in peri-urban zones showed the most frequent fungal contamination in the owners’ bedroom and the highest diversity of fungal genera among dwellings. While the urbanisation level or the ventilation type favoured no specific genus, we found marked disparities in the diversity of fungi growing on surfaces in naturally ventilated versus mechanically ventilated dwellings. Aspergillus, in particular, was a frequent surface contaminant in bedrooms with natural ventilation, but not in those mechanically ventilated. We observed a strong association between fungal growth on surfaces and the number of fungal particles counted in the settled dust of owners’ bedrooms. These results demonstrate the importance of ventilation systems in energy efficient dwellings in controlling fungal proliferation in living areas

L'ambroisie: analyse statistique et modélisation numérique de sa trajectoire aérobiologique

Les allergies respiratoires ne cessent d’augmenter partout dans le monde au même titre que les coûts associés, touchant une part de plus en plus grande de la population. Le pollen de l’Ambroisie est une des sources potentielles, reconnue pour ses propriétés fortement allergisantes. Caractérisé par des émissions de celui-ci dans l’air extrêmement abondantes d’août à septembre de chaque année, il n’en est que plus redoutable. Cette étude porte sur la problématique de l’ambroisie et plus particulièrement sur les moyens dont on dispose à l’heure actuelle pour comprendre l’évolution de son nuage pollinique en pleine saison de pollinisation, de même que sur ceux que l’on pourrait développer pour parvenir, à plus longue échéance, à une meilleure prévision des risques associés à sa pollinisation. Au cours de son trajet dans l’atmosphère, le pollen est soumis à l’influence directe des conditions atmosphériques. Ce jeu des paramètres météorologiques sur les quantités de pollen mesurées, retient toute notre attention. Cette recherche aérobiologique se concentre sur la grande région de Montréal qui connaît tous les ans de sérieux cas de pollinose à l’herbe à poux, telle que communément appelée là-bas. Originaire d’Amérique du Nord, elle y est quasi omniprésente depuis longtemps, ce qui en fait un laboratoire d’étude très intéressant. Une revue de la littérature disponible est proposée en premier lieu afin d’aborder la question des rythmes et des caractéristiques qui en font une plante à haut risque, principale responsable des allergies respiratoires auprès de 10% de la population locale. La trajectoire aérobiologique de son pollen est ensuite décortiquée ainsi que les paramètres météorologiques qui interviennent selon divers degrés à l’occasion de chacune des étapes de ce trajet aérien. La plupart de ces effets se produisent dans les basses couches de l’atmosphère, dont le caractère turbulent est particulièrement déterminant du devenir du pollen. Afin d’étudier ces comportements un certain nombre de techniques de mesure et d’évaluation ont déjà été testées et publiées. Elles sont décrites et nous proposons dans les deux prochaines étapes deux méthodes complémentaires pour son étude. Parmi elles, une analyse statistique du comportement du nuage d’ambroisie durant la période 1994-2003 est présentée à partir de données d’observation. Cette décennie est marquée par une période particulièrement pollinique avec les années 1998 à 2001, associée à une série de printemps et étés plutôt anormalement secs et chauds. Une analyse globale du risque tenant compte des types de temps expérimentés à Montréal permet d’identifier des situations météorologiques plus ou moins « à risque » tenant compte tant de leur fréquence d’occurrence que de leur contribution à la charge pollinique globale saisonnière. Il en ressort que les plus fréquentes sont aussi les plus grandes contributrices, mais qu’il ne faut pas négliger pour autant d’autres situations qui, du fait de leur rareté, ne pèsent pas aussi lourd dans la balance pollinique mais qui, au cas par cas, peuvent s’avérer extrêmement risquées. Quoiqu’il en soit, le niveau du seuil clinique étant largement dépassé au cours de chacune des saisons analysées, la situation demeure globalement critique à Montréal. Si l’observation in situ et l’analyse statistique des données offrent une image cohérente et intéressante des risques polliniques potentiels au dessus d’une région donnée, seules des analyses plus détaillées à l’aide d’outils numériques perfectionnés intégrant les principes fondamentaux de la physique de l’atmosphère tels les modèles numériques régionaux du climat peuvent offrir l’occasion d’analyser avec un détail spatio-temporel inconnu jusqu’alors, le comportement d’un nuage pollinique simulé qui se veut être aussi proche que possible de la réalité. Cette dernière approche se veut innovante et présentant un potentiel d’avenir non négligeable. La méthode par emboîtement multiple qui a été utilisée, permet de simuler le comportement du nuage pollinique de l’ambroisie sur une grille centrée au-dessus de la grande région de Montréal, comptant 60X60 noeuds de calculs distancés chacun de 1 km et 25 niveaux dans la verticale. Les résultats sont sauvegardés toutes les 15 minutes. Ceci confère l’énorme avantage de pouvoir étudier l’évolution spatio-temporelle du nuage avec une précision jusqu’alors impossible avec la seule observation sur le terrain et les techniques d’échantillonnage disponibles. La trajectoire aérobiologique est reproduite dans sa totalité dans le modèle, de l’émission, jusqu’à la déposition du pollen en passant par sa dispersion. L’émission est prescrite suivant une carte de localisation des sources disponible et tient compte pour la détermination des flux, de paramètres issus de la littérature. Une fois le pollen pris en charge par l’atmosphère, il est soumis à l’évolution thermodynamique de la couche limite atmosphérique. Une situation typique de fi n d’été est simulée et analysée. Globalement la simulation se comporte selon les tendances de l’observation. Elle permet entre autre de voir à quel point de petites fluctuations des conditions atmosphériques peuvent affecter le développement du nuage de façon significative et de fait, les zones touchées par des niveaux de risque plus ou moins élevés. Les résultats obtenus sont tout à faits encourageants et bien qu’encore difficilement comparables dans le détail à l’observation, ouvrent sans doute une nouvelle voie de recherche pour l’aérobiologie.Allergic rhinitis as well as associated costs are constantly increasing, affecting a proportion always larger of the population across the world. Ragweed is a source of pollen well known for its high allergenic properties. Characterized by heavy emissions of the pollen in the air from August to October of each year, its allergenic potential is greatly enhanced. This study deals with the problems induced by ragweed pollen and more specifically with the means currently available to understand the pollen cloud evolution during the pollination season. In addition to the analysis of the pollen cloud, another approach that could be developed to achieve in the future better pollination risk forecasts is presented. While travelling in the air, the pollen is directly influenced by the atmospheric conditions. The focus will be on the interplay of the meteorological parameters over the sampled pollen concentrations. This research under the theme of aerobiology, concentrates on the greater Montreal area which experiences each year serious cases of pollinosis related to ragweed (or “herbe à poux”, as it is locally referred to). Coming from North America, it has long been endemic, which makes the region an attractive research laboratory. A review of the available literature is proposed first, in order to present an overview of the questions of rhythms and characteristics that make ragweed a high risk plant, responsible for more than 10% of the declared local allergic rhinitis. The aerobiological pathway of the pollen is then analyzed as well as the meteorological parameters that interfere at various degrees during each step of its transport in the atmosphere. Most of the effects occur in the lowest levels of the atmosphere where the turbulence is especially determinant of the pollen concentrations. In order to study these behaviours a number of measurements techniques and evaluation tools have already been tested and published. They are described and two complementary approaches are proposed in the following. Among them, a statistical analysis of the pollen cloud behaviour over the period 1994-2003, is presented based on observed data. This decade is characterized by specially pollinic years from 1998 to 2001, associated with above-normal dry and hot springs and summers. A global analysis of pollinic risk according to weather types experimented in Montreal helps to identify more or less risky meteorological conjunctions taking into account frequency of occurrence and contribution to the global seasonal pollen load. It appears that the most frequent are also the larger contributors, what does not mean that one can neglect other situation, because even if they are less frequent, they are not necessarily less intense. Although the clinical threshold is high during all the seasons studied, the situation remains globally critical in Montreal. If in situ observation as well as statistical analysis offer a consistent and interesting picture of potential pollinic risks over a region, more detailed analysis with the help of advanced numerical tools integrating fundamental principals of atmospheric physics, namely regional climate models, may offer the opportunity to analyse with very high spatio-temporal resolution, the simulated pollen cloud behaviour that should be as close as possible to the real one. This approach is innovative and presents a significant potential for the future. The multiple selfnesting methods that are used to simulate the behaviour of the ragweed pollen cloud over a grid centred above Montreal, includes 60X60 computation nodes with a 1 km spacing and 25 levels in the vertical. Results are saved every 15 min. That confers the enormous advantage of being able to study the spatio-temporal evolution of the cloud with a precision till now unavailable from field measurements as well as from available sampling techniques. The aerobiological pathway is reproduced in full, from the emission to the pollen deposition including transport and dispersion. Emission is prescribed according to an available localisation source map and takes into account parameters obtained from the literature for the determination of fluxes. Once the pollen is embedded within the air flow, it is subjected to the thermo-dynamical evolution of the boundary layer. Typical end of summer conditions are simulated and analysed. Globally the simulation behaves like the observed tendencies. It allows emphasizing inter alia that small fluctuations of atmospheric conditions may affect significantly the development of the pollen cloud and by the same occasion, the areas affected by more or less important levels of risk. Results are encouraging and open a new field of research for aerobiology

Weather impacts on indoor radon short-term measurements in Switzerland

Radon is a natural and radioactively well-known carcinogenic indoor air pollutant. Since 2020, a radon short-term proactive methodology has been proposed by Swiss authorities, which aims to evaluate the probability of overpassing the national reference value. This study aims to assess the influence of different weather parameters on indoor radon levels monitored using this methodology. To this end, different statistical tools are used, such as correlations, auto-correlations, cross-correlations, and multiple linear regressions between meteorological parameters and indoor radon levels. We show a strong influence of weather conditions on indoor radon levels in occupied, but especially unoccupied spaces. Outdoor air temperature, followed by atmospheric pressure, was identified as the most significant parameter impacting indoor radon levels. Moreover, meteorological conditions monitored five days prior to the beginning of the radon measurements might affect radon levels. We come to the conclusion that it is of paramount importance to take these meteorological conditions into account when analyzing the results of short-term measurements, and more specifically, to consider the evolution of the weather conditions five days prior to the radon measurement. This paper helps to ensure the relevance of this short-term measurement method available in Switzerland

Indoor radon and air quality investigations in new or renovated energy-efficient swiss single-family dwellings

The perspectives of a new energy crisis subsequent to the depletion of natural resources along with the increase of energy costs make, more than forty years after the first oil crisis, energy savings a priority. This lead to rethink building practices so as to make it more sustainable and economical in terms of energy consumption by ensuring the air tightness and a good thermal insulation. Indeed, the less we ventilate such sealed houses, the more moisture, number and level of pollutants increase in the indoor environment. The deterioration of the indoor air quality and the appearance of occupants non-specific health disorders are the consequences. Preliminary results indicate the attention to pay to energy-efficient buildings. On the one hand, the concentration of indoor radon has a clear tendency to increase after an energy saving action. On the other hand, it appears that even though the new Swiss energy efficient houses seem less affected by this problem than the traditional renovated houses, or even transformed according to these label requirements, unexpected situations may still arise. People living in energy saving buildings need to be well informed about the risks and about “what-to-do and not-to-do” living in such “high tech” houses. Maintenance of technical installation can also be troublesome

Influence of some specific meteorological events on indoor radon dynamic in western Switzerland

Radon is a natural radioactive gas that may cumulate in indoor environments. The impacts of weather events on indoor radon concentration had been explored in different places around the world but only marginally in Switzerland. Using basic statistical analysis, this study investigates different meteorological parameters' influence on indoor radon concentrations and shows that outdoor air temperature is the most influential beyond others. Finally, this paper highlights the importance of radon dynamic in buildings, a topic often overlooked by construction professionals and the broader public in Switzerland

Long-Term Impacts ofWeather Conditions on Indoor Radon Concentration Measurements in Switzerland

Radon is a natural and radioactive gas that can accumulate in indoor environments. Indoor radon concentration (IRC) is influenced, among other factors, by meteorology, which is the subject of this paper. Weather parameters impact indoor radon levels and have already been investigated, but rarely in Switzerland. Moreover, there is a strong need for a better understanding of the radon behaviour inside buildings in Switzerland for public health concerns as Switzerland is a radon prone area. Based on long-term, continuous, and hourly radon measurements, radon distributions classified according to different weather event definitions were investigated and then compared at three different study sites in Western Switzerland. Outdoor temperature influences the most indoor radon, and it is globally anti-correlated. Wind influences indoor radon, but it strongly depends on intensity, direction, and building characteristics. Precipitation influences periodically indoor radon levels relatively to their intensity. Atmospheric pressure and relative humidity do not seem to be huge determinants on IRC. Our results are in line with previous findings and provide a vivid example in Western Switzerland. This paper underlines the different influence complexities of radon, and the need to communicate about it within the broader public and with construction professionals, to raise awareness

Performance evaluation of radon active sensors and passive dosimeters at low and high radon concentrations

Radon is a naturally occurring radioactive gas that has the potential to accumulate in buildings and over time, causes lung cancer in humans. Present methods for radon measurements are disparate, which pose challenges to benchmark radon concentrations and to accurately assess the population's received dose. This paper presents a comprehensive performance evaluation of radon dosimeters and three grades of active radon sensors: consumer-, medium- and research-grade. The measurements were performed at relatively low (300 Bq/m3) and high (2′000–3′000 Bq/m3) radon levels. Tests were conducted in an atomic shelter, with stable temperature and humidity conditions. The active sensors differed in absolute accuracy and dynamic performance (time-dependent correlations) according to their grade. Research-grade sensors performed marginally better than medium-grade sensors, and significantly better than consumer-grade sensors. Relative to the reference, the error (percentage difference between the reference and the sensors) was below 5 % for research- and medium-grade sensors, and nearly 10 % for consumer-grade sensors at high radon levels. Performance of sensors diminished at low radon levels, except for research-grade sensors. Passive dosimeters generally performed better at high radon levels than at low ones. Their longer exposure time was associated with increased measurement reliability. These results highlight the need for understanding the purpose of measurements in order to select an adequate radon detector, and ultimately, reduce measurement and interpretation errors. This study raises awareness among researchers, radon professionals and the general public regarding the performances of different active radon sensors and passive dosimeters. It also sheds light on their respective scope of application

When citizen science meets radon building diagnosis: Synthesis of a French pilot project developed in the framework of the European RadoNorm research project

As part of the European RadoNorm research project, citizen science pilot projects focusing on the management of radon risk in houses have been implemented in four countries. This article describes the methodological basis, the development and the results of the French pilot project. Building on an initial review of existing literature, the pilot project aims to frame a 'participatory approach' aligned with the standards and recognized practices of citizen science. Particular attention was given to the management of data and the inclusion of ethical considerations. The focal point of the project was the process of radon building diagnosis which is supposed to be carried out whenever (high) radon concentrations are measured and should be prerequisite to mitigation works. As experience shows, however, this diagnosis is hardly implemented in France. To help remedy this situation, the pilot project recruited citizens already aware about radon from Pays Vesoul Val-de-Saône (East of France) to test an existing online self-evaluation guide for radon diagnosis, report on their operational experience and meet with radon/building experts. This enabled citizens to contribute to improvements in form and content to the guide and to ensure that it would be better fit for purpose. Comparison of the guide with experts' practices offered additional perspectives on what building diagnosis should entail. The pilot project produced rich and high-quality data that will nurture the evolution of the guide. The project demonstrated both the viability and the utility of applying the citizen science approach to radon post-measurement phases, with measurable benefits in bridging knowledge gaps and in encouraging behavioural changes. The results of using a citizen science approach in the field of radon management and research are encouraging, and they far outweigh the challenges involved in the implementation