Evaluation of human walking-induced resuspension of bacteria on different flooring materials

Walking and other human activities resuspend deposited pathogens from surfaces into the air, potentially leading to infection through inhaling the bioaerosols. We performed experiments in a laboratory chamber to quantify the pathogen resuspension from a human stepping on pathogen-seeded flooring. Three common flooring materials were chosen: carpet, vinyl tile, and hard wood. Three different types of bacteria were tested: Escherichia coli, Pseudomonas alcaligenes, and Staphylococcus epidermidis. The bacteria were first aerosolized into an experimental chamber and allowed to deposit onto the clean flooring materials, followed by a single human step on the flooring performed to resuspend the bacteria. The result showed that the resuspension emission factor (normalized parameter for the ratio of resuspended mass in the air to the mass available for resuspension on the surface during a resuspension event) of tested bacteria ranged from 3.4 × 10⁻⁵ to 2.1 × 10⁻⁴. For this study, because the resuspension mechanism is one footstep, the resuspension emission factor is also equivalent to the resuspension fraction (fraction of settled particles resuspended per footstep). The carpet consistently resulted in the highest emission factor of biological material resuspended from the surface to the air. In addition, the resuspension emission factor for Gram positive, S. epidermidis, was higher than that of the other two Gram negative bacteria for all floorings. The findings from this study provide valuable estimates for the emission of biological particles by resuspension and comparison to non-biological particles for estimating the risk of pathogen exposure in occupied environments. © 2023 Elsevier Ltd