Synergistic Disinfection\nby 222 nm Far-UVC and Negative\nAir Ions of Airborne Bacteria and the Induced Oxidative Stress Responses:\nA Bioaerosol Chamber Study

The understanding of the mechanisms of synergistic bioaerosol\ndisinfection\nusing 222 nm far-UVC and negative air ions is limited. In this study,\nwe employed a fabricated aerosol chamber to investigate the synergistic\ndisinfection effects of these two technologies and their impact on\noxidative stress responses in airborne Staphylococcus\nepidermidis, Salmonella enterica, and Escherichia coli. We measured\nthe log reduction in airborne survival of bacteria, lipid peroxidation,\nand the activities of antioxidant enzymes and total antioxidants.\nThe results show that bacterial inactivation by the simultaneous operation\nof both technologies was significantly greater than the sum of the\ninactivation values by individual treatments, demonstrating a synergistic\ndisinfection effect. The Pearson correlation coefficient indicates\na strong correlation between airborne bacterial survival and lipid\nperoxidation (<i>r</i> ≥ 0.83). Furthermore, 222\nnm far-UVC was found to be able to inactivate the antioxidant defense\nin airborne bacteria. Our results together suggest that the simultaneous\noperation of 222 nm far-UVC and negative air ions induces oxidative\nstress while deactivating antioxidant defense, contributing to the\nobserved synergistic disinfection effect. Findings from the current\nstudy contribute to the mechanistic understanding of the synergistic\neffect by 222 nm far-UVC and negative air ions in bioaerosol disinfection,\noffering a new research opportunity for system design in high-efficiency\nair disinfection.