Changing mycobiota of buildings

Every natural habitat or niche has its own mycobiota – and our homes are no exception. There are many factors that determine the indoor mycobiota. If there are no problems of indoor dampness, they will be determined by the outside environment, inside food products and cleaning level. The mycobiota can change with the season and activity of people and pets.
However, if a building has moisture problems, indoor mycobiota will be dominated by the fungi growing inside the building envelope and they will often overshadow environmental and food-borne fungal species. It is expected that the mycobiota will remain constant if the moisture problem persists.
The mycobiota in water-damaged buildings is determined by the type of building materials and their moisture content. Traditional building materials (gypsum wallboard, wallpaper, plaster, painted surfaces, mineral insulation, brick and concrete) promote the growth and sporulation of fungi like Aspergillus versicolor, Cladosporium sphaerospermum and Penicillium chrysogenum. These species have been known the last 3 decades. In some incidents, these fungi are growing inside the construction, behind the wallpaper or under floorboards. The growth is not visible to inspection, but spores can often be detected in settled and floor dust.
The green transition demands the building industry to use alternative, renewable materials. Therefore, hay, hemp and eelgrass are being introduced as insulation in timber framed walls and acoustic ceiling panels. These organic materials are, however, more sensitive to water damage and fungal growth. Furthermore, they seem to be susceptible to new fungal species. Hay can contain large numbers of Aspergillus fumigatus spores, while eelgrass and hemp contain Penicillium atrovenetum and Penicillium olsonii, respectively (Andersen et al. 2020, Ettinger and Eisen 2020, Kusari et al. 2013).
The introduction of these new materials will most probably alter the current mycobiota and introduce fungal species with allergenic or toxic potential for the occupants. There is, therefore, a need to assess the specific mycobiota of new materials and make sure that the existing sampling techniques and analytical methods can cover the whole spectrum. If not, new sampling strategies and detection methods should be developed for moisture- or water-damaged buildings and materials.
References
Andersen B, Phippen C, Frisvad JC, et al. (2020). Fungal and chemical diversity in hay and wrapped haylage for equine feed. Mycotoxin research 36: 159-172.
Ettinger CL, Eisen JA (2020). Fungi, bacteria and oomycota opportunistically isolated from the seagrass, Zostera marina. Plos One 15(7): e0236135.
Kusari P, Kusari S, Spiteller M, et al. (2013). Endophytic fungi harbored in Cannabis sativa L.: diversity and potential as biocontrol agents against host plant-specific phytopathogens. Fungal diversity 60: 137-151.