A year-round comparison of fungal spores in indoor and outdoor air

This study was conducted by trapping airborne fungal spores inside and outside 15 residences in Kitchener-Waterloo, Ontario, Canada, monthly from December 1991 to September 1993. The dominant fungal propagules recorded indoors were Cladosporium (38.8%), Aspergillus/Penicillium (19.8%), Leptosphaeria (7.9%), unidentified basidiospores (6.5%), unidentified ascospores (2.8%), Ganoderma (2.6%), Alternaria (1.9%), Coprinus (1.8%), and Epicoccum (0.3%). Other unidentified spores (8.9%) and hyphal fragments (6.3%) also represented significant proportions of the total. Most common airborne spores were more numerous outside residences, except for those of Aspergillus/ Penicillium.Most fungal taxa recorded indoors showed seasonal periodicities similar to those in outdoor air, but with lower counts in summer than those recorded outdoors, except for Aspergillus/Penicillium and hyphal fragments. Aspergillus/Penicillium spores showed no seasonal patterns.