United States: According to an abstract available on the National Center for Biotechnology Information website, a study was conducted by Dannemiller KC^1,2, Weschler CJ³  and Peccia J⁴ to test the fungal and bacterial growth in floor dust at elevated RH levels.

As per the abstract, the aim of the study was to “characterise microbial growth in floor dust at variable equilibrium relative humidity (ERH) levels”.

The team collected samples of the floor dust from a home and it was embedded in coupons cut from a worn medium pile nylon carpet and incubated at 50, 80, 85, 90, 95 and 100% ERH levels. “Quantitative PCR and DNA sequencing of ribosomal DNA for bacteria and fungi were used to quantify growth and community shifts,” the abstract informed.

Over a period of one week, the team discovered that fungal growth occurred above 80% ERH, while bacterial growth occurred only at 100% ERH after one week.

According to the observations mentioned in the abstract, “Growth resulted in significant changes in fungal (p<0.00001) and bacterial community structure (p<0.00001) at varying ERH levels.”

Furthermore, the abstract said that comparisons between fungal taxa incubated at varying ERH levels revealed that more than 100 fungal and bacterial species could be attributed to elevated ERH. “Re-suspension modelling indicated that more than 50% of airborne microbes could originate from the re-suspension of fungi grown at ERH levels of 85% and above,” it added.

¹Department of Civil, Environmental & Geodetic Engineering, College of Engineering, Ohio State University, Columbus, OH, 43210.
²Division of Environmental Health Sciences, College of Public Health, Ohio State University, Columbus, OH, 43210.
³Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, 07102.
⁴Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, 06520.