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Modeling microbial growth in carpet dust exposed to diurnal variations in relative humidity using the
Sarah R Haines1,2,3, Jeffrey A Siegel4, Karen C Dannemiller2,3,5
1Environmental Science Graduate Program, Ohio State University, Columbus, Ohio, USA.
Abstract:
Resuspension of microbes in floor dust and subsequent inhalation by human occupants is an important source of human microbial exposure. Microbes in carpet dust grow at elevated levels of relative humidity, but rates of this growth are not well established, especially under changing conditions. The goal of this study was to model fungal growth in carpet dust based on indoor diurnal variations in relative humidity utilizing the time-of-wetness framework. A chamber study was conducted on carpet and dust collected from 19 homes in Ohio, USA and exposed to varying moisture conditions of 50%, 85%, and 100% relative humidity. Fungal growth followed the two activation regime model, while bacterial growth could not be evaluated using the framework. Collection site was a stronger driver of species composition (P = 0.001, R2 = 0.461) than moisture conditions (P = 0.001, R2 = 0.021). Maximum moisture condition was associated with species composition within some individual sites (P = 0.001-0.02, R2 = 0.1-0.33). Aspergillus, Penicillium, and Wallemia were common fungal genera found among samples at elevated moisture conditions. These findings can inform future studies of associations between dampness/mold in homes and health outcomes and allow for prediction of microbial growth in the indoor environment.
Insights
Microbial growth in carpet dust is influenced by humidity. This study modeled fungal growth using indoor humidity variations, finding site collection more impactful than moisture levels on species composition.
Area of Science:
- Environmental microbiology
- Indoor air quality
- Building science
Background:
- Human exposure to microbes in floor dust is significant.
- Microbial growth in carpet dust is humidity-dependent but poorly quantified under dynamic conditions.
Purpose of the Study:
- To model fungal growth in carpet dust using indoor diurnal relative humidity variations.
- To apply the time-of-wetness framework for microbial growth prediction.
Main Methods:
- A chamber study exposed carpet dust from 19 Ohio homes to 50%, 85%, and 100% relative humidity.
- Fungal growth was modeled using the two-activation-regime model.
- Bacterial growth was not assessed with this framework.
Main Results:
- Fungal growth followed the established two-activation regime model.
- Collection site significantly influenced fungal species composition (R² = 0.461) more than moisture levels (R² = 0.021).
- Elevated moisture conditions were linked to specific fungal genera like Aspergillus, Penicillium, and Wallemia.
Conclusions:
- Site-specific factors are primary drivers of fungal communities in carpet dust.
- Findings support predicting indoor microbial growth and inform studies on dampness, mold, and health outcomes.
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