Guidelines on ambient intramural airborne fungal spores

OBJECTIVES: To generate baseline data for indoor airborne fungal spores in noncomplaint residential properties (with no moisture/mold-related problems) and to identify home characteristics indicative of elevated fungal levels. METHODS: Air samples were collected onto petroleum jelly-coated slides from living rooms of 100 residential properties in Leicestershire, United Kingdom, using a Burkard continuous recording air sampler. The slides were examined by microscopy to determine fungal spore concentrations (spores/m3 air/day). RESULTS: Total indoor fungal spore concentrations were approximately 16% of outdoor concentrations. Abundant indoor fungal genera include Cladosporium, Sporobolomyces, Tilletiopsis, and Didymella, all of which followed seasonal patterns of release and detection. No clear association was shown between outdoor-predominant fungi and home characteristics. In contrast, Aspergillus/Penicillium-type (Asp/ Pen-type) spores were common indoors and exceeded outdoor levels, with the highest concentrations detected in properties over 90 years old (P = .006) and terraced properties (P = .003). CONCLUSION: Asp/Pen-type spores are found in noncomplaint UK residential properties and mostly in old terraced houses. This study provides guidelines on acceptable levels of Asp/Pen-type spores and other abundant indoor fungal taxa that can be comparatively used in clinical evaluations of fungal exposure-related disease.