Modeling microbial growth in carpet dust under diurnal variations in relative humidity

People spend 90% of their time indoors where resuspension of floor dust serves as a major source of human exposure. This exposure can be harmful to those who have weakened immune systems, especially those suffering from asthma. Studies have shown that when the relative humidity (RH) is elevated microbial communities grow at an exponential rate. It is still unknown however how diurnal variations in RH will affect this growth. The purpose of this work is to demonstrate how fungal and bacterial growth in house dust can be modeled using the "time-of-wetness" (TOW) concept from fungal growth on drywall. The TOW concept determined that as the TOW of the dust increased so too did the relative growth rate of fungi and bacteria. To begin this experiment carpet was collected from numerous homes across Ohio, cut in to 10 cm X 10 cm squares and embedded with dust from the same home. Three squares from the same home were placed inside an incubation chamber along with data loggers and a salt solution to regulate the RH for two weeks. RH was maintained at 50% and then increased to either 85% or 100% for a period of 0, 6, 12, 18 hours per day. 24 hours controls were kept at 85% and 100% RH for the two week period as well. Through analysis it was determined that the carpet was hydroscopic as indicated by the fact that after 6 hours at 50% , the RH did not lower to 50% but instead maintained at around 70% to 80%. Quantitative polymerase chain reaction (qPCR) was performed on all dust DNA extractions from the carpet. These measurements revealed that the relative growth rate fit the TOW model within the determined Pearson Correlation Coefficient of 0.897. As this study continues certain aspects will be modified and refined. Ultimately, this data can be used to accurately model fungal growth in housing based on moisture and can be utilized in public health, policy, and epidemiological models.OSU Undergraduate Research OfficeAlfred P. Sloan FoundationA three-year embargo was granted for this item.Academic Major: Environmental Engineerin