Assessing fungal burden in Nunavik homes across seasonal conditions: Relationship between air and surface contamination

• First application of activated air sampling to study moulds in northern housing. • Indoor fungal dynamics in Nunavik homes are strongly influenced by seasons. • C. globosum, T. viride and S. chartarum are reliable moisture markers. • Airborne C. globosum, T. viride and S. chartarum revealed hidden mould sources. Indoor air contamination and fungal growth in buildings are important factors influencing indoor environmental quality. This study assessed airborne and surface-associated fungi in 60 dwellings in Nunavik across summer 2023 and winter 2024 using an activated air sampling protocol with the SASS® 3100 Dry Air Sampler (300 L/min), the first such application in a remote northern context. Airborne fungal concentrations showed strong seasonal variation. Cladosporium peaked in summer (10³ copies/m³) but was nearly absent in winter, while Penicillium / Aspergillus declined from 10⁴ to 10³ copies/m³. Water damage-associated ( C. globosum and T. viride ) and human health-relevant species ( A. fumigatus and A. versicolor ) decreased by >2 logs from summer to winter. S. chartarum remained consistent across seasons (10 1 –10 2 copies/m 3 ). Outdoor sampling confirmed contributions from Penicillium and Aspergillus , whereas water damage moulds were mostly absent outdoors, supporting their value as indoor moisture contamination markers. Surface sampling revealed diverse fungal communities across both seasons, dominated by Aspergillus, Penicillium , and Cladosporium , with the highest diversity in bathrooms. Yeasts such as Rhodotorula and Cryptococcus were persistently isolated, reflecting occupant contributions. We also demonstrated that activated air sampling is particularly valuable for detecting moulds that are not apparent through surface inspection. Overall, these findings highlight pronounced seasonal dynamics in indoor fungal loads, the influence of outdoor air and ventilation, and the importance of monitoring water damage-associated moulds as indicators of indoor contamination in northern housing for establishing baseline data for future assessments