Resuspension of Bacteria from Walking Activities

Description

Ironically, human occupancy and human activities are the major sources of microbial materials for indoor environments. Resuspension is a major indoor source of abiotic and biological particles. A person can emit several million bioaerosols per hour. It was also found that crawling infants are exposed to approximately four times higher a dose than adults. In spite of their tremendous impact on health and its implications, indoor bioaerosols are vastly understudied. There is no systematic study quantifying source strength by resuspension of indoor bacteria. The importance of bacterial pathogen transmission pathways coupled with other potential adverse health effects demands an understanding of how bacteria resuspension influences indoor levels. Infective bacteria settle on the floor, and under favorable conditions, they can survive longer than a month, but nonetheless their viability depends on many environmental parameters (time of exposure of sunlight, temperature and water amount) and the nature of the flooring. These factors influence the infectiousness of bacteria when it becomes airborne. Nonetheless, this process has barely been studied, not to mention qualifying the mechanism. When particles frictionally interact with different materials, triboelectric charging will occur. In the literature, electrostatic force is often mentioned, but paradoxically it is always ignored. The triboelectric effect can be an order of magnitude higher than gravitational force, and thus resuspension can be significantly affected. In addition, electrostatic charge accumulation affects the viability of microorganisms. Adhesion force has a direct impact on resuspension. The flooring materials roughness scale ranges from millimeters to centimeters and existing models cannot be applied. Besides, bacteria surface morphology is complex. The adhesion forces for bacteria with common flooring materials have not been reported. Research gaps are clearly existed. To understand and mitigate bacteria exposure, it is important to systematically study bacteria resuspension due to walking activities. We propose to address the problem via dedicated experimental measurements. A mechanical stepping device will be used for the first time to determine the resuspension of bacteria and the effects of different properties of shoe soles and flooring materials. Most notably, environmental factors affecting the viability/survivability of bacteria settled on flooring will be studied. The adhesion force and airborne electrostatic charges will be measured. Overall, this work will significantly advance our understanding of bioaerosol resuspension, and the quantitative results obtained will foster healthy building design and mitigate exposure risks by the stakeholders.  The PI and Co-Is are uniquely qualified to conduct the proposed work. The related work that they have accomplished and the resources that they have available will leverage the project substantially.