Online & Oslo, Norway
21-23 June 2021
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Session 7: Moisture in buildings
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Moisture-dependent insects (Silverfish species and Psocid species [Psocoptera]) in modern buildings - A sign of hidden moisture and mould damage
Mycoteam AS, Norway
Through the last 10 years, it has been an increasing occurrence and activity of moisture sensitive insects in modern buildings. Grey silverfish (Ctenolepisma longicaudata) is the most common species, but it is also an increasing number of cases of silverfish (Lepisma saccharina). Furthermore, aphid species (Psocoptera) such as booklice, which is well-known for feeding on mould fungi is commonly found in modern buildings in frequency and number that is not found in older buildings. The populations of these insects also survive for several years in the modern buildings. This shows both that there are microclimatically humid construction details where they have suitable hot-spots and access to suitable food. The humidity is due to residual building moisture and the moisture levels in such places are so high that there is a basis for growth for several species, such as Aspergillus penicilloides and A. versicolor. It is known that both mould spores and insect excrement can be allergenic. Thus, does the occurrence of these insects represent an obvious risk for a negative indoor climate exposure.
The paper describes the findings from more than 600 examined modern buildings with insects and of those 60 cases of mould samples.
The indoor mycobiome in Norwegian daycares revealed by DNA high throughput sequencing
1UiO, Norway; 2Naturalis biodiversity center, Netherlands; 3Mycoteam AS, Norway
Fungi can grow in the indoor environment and act as a source of indoor pollutants leading to poor indoor air quality. This can lead to adverse health effects, such as allergies, asthma and other respiratory symptoms. Studies performed in other parts of the world have analyzed the main determinants and important factors influencing the indoor mycobiome, include building type, geography, ventilation and outdoor air influence. The aim of this study is therefore to improve the knowledge about the indoor mycobiome in Northern Europe by using a high throughput DNA sequencing (HTS) approach. By analyzing dust samples, the indoor mycobiomes were characterized at different spatiotemporal scales; within buildings, across buildings at larger geographical scales, as well as throughout different seasons. A large-scale citizen science sampling of 128 daycares distributed throughout Norway was performed. In addition, two daycares in Oslo were monitored throughout a year by biweekly sampling at four different floors and rooms. The results showed that climate, seasonality, and occupants (number of people present in the kindergardens) are important factors structuring the indoor mycobiome. Thus, temporal variability through the seasons should be accounted for in indoor mycobiome studies and in the evaluation of indoor air quality of buildings.
Fungal growth on newly cast concrete floors and moisture membranes
1Danish Technological Institute, Department of Building and Environment, Taastrup, Denmark; 2Danish Technological Institute, Department of Wood and Bio Based Materials, Taastrup, Denmark
The Danish Technological Institute has during several surveys in new buildings, experienced widespread fungal growth on newly cast concrete floors, with a moisture barrier and floating flooring. Existing recommendations require that the relative humidity (RH) of air in equilibrium with the concrete, measured in the middle of the concrete floor, should not exceed 85-90% prior to mounting the top floors. However, surveys have shown that fungal growth can establish if the RH of the air between the concrete floor and the moisture membrane exceeds 75%. The present case study demonstrates that fungi can grow on newly cast concrete and on the moisture membrane if the RH at the surface is above 75%. The study finds that there is a need to revise existing guidelines for acceptable moisture content in the concrete before mounting the top floor, and maybe even change the way of constructing floors.
Implementation of MALDI-TOF mass spectrometry to identify moulds from the indoor environment as an added value to the classical microscopic identification tool
1Sciensano, Belgium; 2Brussels Environment, Belgium
BACKGROUND: The quality of indoor air has become a subject of great interest. Biological pollutants such as moulds however can affect this air quality and can cause adverse health effects. The genera Aspergillus, Cladosporium, Penicillium, Alternaria and yeasts are the most common fungi found indoor. Certain species of these genera are able to cause specific allergic or toxic reactions. Therefore it is necessary to seek for fast and accurate tools, enabling an identification to the species level in order to guide general practitioners in their diagnosis and treatment.
AIMS & KEY PROBLEMS: Currently, identification of moulds found in the indoor environment is performed by microscopy. This method has, however, some limitations as it needs mycologists with high expertise while identification is often limited to the genus level. In order to increase the specificity and accuracy of the identifications, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) can be an alternative, offering the advantage of being fast and cost-effective. The added-value of MALDI-TOF MS will be compared with the currently used technique of microscopy. In addition, MALDI-TOF MS will also validate the accuracy of microscopic identifications.
METHODS: In collaboration with Brussels Environment RCIB/CRIPI (Regional Intervention Cell for Indoor Pollution), Sciensano’s (Brussels, Belgium) Indoor Mycology unit performs measurements of fungal contaminations in Brussels dwellings in order to assess a link between a potential indoor air pollution and people’s health problems.
A total of 112 isolates were collected on specific culture medium. After incubation, microscopic identifications were performed. Results obtained with MALDI-TOF MS were compared with data available in an in-house created reference database containing over 1700 strains of the BCCM/IHEM fungal collection (https://msi.happy-dev.fr/login/).
MAIN RESULTS: Microscopic analysis only allowed identification to the genus level for more than half of the isolates analysed (68/112) while only 38 isolates could be identified to the species (complex) level. In contrast, MALDI-TOF MS resulted in a more precise identification in comparison to microscopic analysis for 106 isolates (95%), allowing identification to the species level for 101 isolates (with a log score > 2.0). In addition, analysis by MALDI-TOF MS indicated 6 wrong microscopic identifications to the species complex level and 5 to the genus level.
CONCLUSION: MALDI-TOF MS can be a highly added value to the standard microscopic analysis in routine practice aiming to identify moulds from dwellings.
Xerophilic fungi in museum repositories challenge our perception of healthy buildings and the preservation of cultural heritage
1Royal Danish Academy / ROMU, Denmark; 2National Research Centre for the Working Environment; 3Technical University of Denmark
BACKGROUND: In the last decade, fungal infestations have become an increasing problem in heritage collections in museums, galleries and archives even if RH is controlled according to the environmental guidelines for the preservation of cultural heritage. The infestations have been reported in parallel to climate change.
Fungal infestations in heritage collections have devastating consequences. Fungal growth deteriorates materials and threatens the preservation of heritage artefacts as well as the health of staff and visitors. Therefore, controlling the environmental conditions to avoid fungal growth is of high importance.
The increasing awareness of the human contribution to CO2 emissions has led to a revision of the environmental guidelines for heritage collections. The recommendations have changed from strictly controlled setpoint value's RH 50±5% to an acceptance of fluctuations from RH 40-60%. Since the borderline of fungal growth is defined to 70%, it should not pose a risk. The revised guidelines allow more sustainable storage of heritage collections by reducing energy consumption; however, the indoor environment's consequences are not well researched.
AIM: This study examined surface and airborne fungal species in five Danish museum repositories. The aim is to enlighten why unexpected fungal infestations occur in climate-controlled museums repositories, complying with the environmental guidelines of heritage buildings.
MATERIALS & METHODS: The indoor fungal composition was examined with air sampling by MAS-100-ECO on V8, DG18, and MY50G agar and surface sampling from museum artefacts cultivated on V8, DG18 and MY50G agar. Isolates from the museum artefacts were identified to species level by DNA sequencing after amplification with PCR and Calmodulin primers (cdm5/cdm6) to obtain good phylogenetic separation of the species. A single isolate gave no PCR product with cdm5/cdm6, and ITS was used.
RESULTS: The morphological ID of air samples showed the presence of fungal species corresponding to classical indoor fungi. DNA sequencing from growth on museum artefacts showed 100 % identity with A. halophilicus, A. domesticus, A. vitricola and A. magnivesiculatus, species from Aspergillus section Restricti comprising xerophilic fungi able to grow on substrates with low aw. Monitoring of the indoor environment showed RH within the standards for buildings storing heritage collections.
PERSPECTIVES: The growth of xerophilic fungi in climate-controlled heritage buildings challenge the preservation of heritage collections, occupational health, and perception of healthy buildings, and may be associated with the revised environmental guidelines, the global climate changes, or both.
Seasonal Distribution of Alternaria, Aspergillus, Cladosporium and Penicillium Genera Isolated from Estonian straw-bale and reed-bale dwellings
Tallinn University of Technology, School of Engineering, Tartu College
People spend most of their time in indoor environments and they are exposed to indoor pollutants. Most people's indoor time is spent asleep and indoor air pollutants, such as moulds are affecting health and sleep quality as well. Mould species are more frequently cultured in damp indoor environments and they can potentially release mycotoxin, allergens, and unpleasant smells to air.
Different sustainable standards promote the use of bio-based products like straw and reed, but these materials are extra sensitive to mould growth - they can easily be degraded by fungi. The aim of this study was to evaluate the presence of moulds in indoor air in the bedrooms of reed-bale and straw-bale residential dwellings in Estonia.
Samples were taken from 8 different dwellings. Occupants were asked not to ventilate the bedrooms prior to measurements. Sampling was performed with two Microbio MB2 samplers working at the same time. Malt Extract Agar (MEA) was used as sampling media. Four parallel samples were collected from each bedroom. The corresponding outdoor air samples were collected as reference. Samples were incubated, stained, and identified.
Four major genera (Alternaria, Aspergillus, Cladosporium, and Penicillium) were identified. The dependence of the results on the season was found, colony-forming unit dynamics in the bedrooms were similar. Differences occurred in the number of colony-forming units. The mould community was least abundant in winter and most abundant in summer. Similar levels occurred in spring and autumn.
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