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Assessing fungus prevalence in domestic interiors
Abstract:
Single-plate, Andersen sampler collections of mesonphilic imperfect fungi were made at three points in and immediately outside a series of midwestern homes. During frost-free periods, emanations of dark-spored form genera predominated at both points with indoor levels averaging 25% of those in outside air. At these times, volumetric recoveries and those by 30-min exposure of open culture plates have correlated tenuously (r = 0.29) in bedroom air of 20 homes. During winter, form species of Penicillium, Aspergillus, Oospora, Sporothrix, yeasts, etc. predominated indoors, with levels exceeding 1,000 particles/M3 noted in over 18% of homes; outdoor concentrations never exceeded 230 particles/M3. Comparisons of volumetric and open-plate recoveries from 50 homes during winter have revealed an almost random relationship (r = 0.06). These findings reflect the case with which outdoor spore clouds may penetrate structures and obscure evidence of internal fungus cources. The data also imply that, because of size-related undersampling, open plates often seriously misrepresent prevalence levels and occasionally can exclude abundant types from recovery. The fungus flora of enclosed spaces merits further critical study by volumetric techniques of calculable efficiency in a setting that minimizes contamination from without.
Insights
Outdoor fungi readily enter homes, impacting indoor air quality. Open culture plates often fail to accurately represent the true levels and types of indoor fungi, necessitating better sampling methods.
Area of Science:
- Environmental microbiology
- Indoor air quality research
- Fungal spore analysis
Background:
- Fungal spores are ubiquitous in outdoor air and can penetrate indoor environments.
- Previous studies have used various methods to assess indoor fungal populations, with varying degrees of accuracy.
- Understanding indoor fungal flora is crucial for public health and building management.
Purpose of the Study:
- To compare fungal spore concentrations inside and outside Midwestern homes.
- To evaluate the correlation between volumetric air sampling and open-plate culture methods for fungal recovery.
- To identify the predominant fungal genera found indoors and outdoors across different seasons.
Main Methods:
- Utilized Andersen samplers for single-plate collections of airborne fungi.
- Conducted sampling at three locations: inside homes and immediately outside.
- Collected data during both frost-free periods and winter seasons.
Main Results:
- During frost-free periods, outdoor dark-spored fungi predominated, with indoor levels at 25% of outdoor concentrations.
- Winter indoor air showed a predominance of Penicillium, Aspergillus, Oospora, Sporothrix, and yeasts, with levels over 1,000 particles/M3 in 18% of homes.
- Volumetric sampling and open-plate methods showed weak (r=0.29) and random (r=0.06) correlations, respectively, indicating significant discrepancies.
Conclusions:
- Outdoor fungal spore clouds easily penetrate residential structures, potentially obscuring evidence of indoor sources.
- Open-plate methods often misrepresent fungal prevalence due to size-related undersampling and can exclude abundant fungal types.
- Volumetric techniques with calculable efficiency are recommended for accurate assessment of indoor fungal flora, minimizing external contamination.
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