Airborne fungi in Nunavik dwellings: seasonality and climate-driven indoor conditions as key determinants

Indoor fungal diversity in residential environments results from complex interactions among environmental, structural, and human-related factors. As key components of indoor bioaerosols, fungi play a significant role in indoor air quality. Although studies on indoor microbiomes are increasing, there remain limited studies on the microbiome of residential buildings in subarctic and Arctic contexts.
A total of 56 residential dwellings were investigated in one community in Nunavik, Canada. Indoor air samples were collected in summer 2023 and winter 2024 using a SASS 3100 sampler with an activated air protocol (involving dust resuspension). Fungal diversity was characterized in dwellings using ITS2 amplicon-based sequencing on the Illumina MiSeq platform.
Results revealed higher richness, evenness, and dominance of filamentous fungi and environmental Basidiomycota during summer, whereas winter indoor air was dominated by yeasts. Moisture-damage–associated fungi (Stachybotrys chartarum, Trichoderma viride, and Chaetomium globosum) were more abundant in summer and absent outdoors. Despite much lower relative humidity and activated heating in winter, these fungi remained detectable in some homes, indicating persistent indoor damp sources. Housing characteristics (e.g., building type and age, number of occupants) generally had minimal influence on these fungi.
Overall, seasonality and climate-driven indoor conditions, such as relative humidity, temperature, heating and ventilation, appear to be major determinants of fungal communities in northern housing. The exclusive detection of water-damage–associated moulds indoors highlights potential health risks and the need for improved housing quality in Nunavik.