The spread of pathogenic microorganisms in public spaces poses a great threat to human health. Far-UVC irradiation is regarded as an efficient method for inactivating most pathogenic microorganisms. Nevertheless, most of the studies on it have been done in laboratory, and there is still little knowledge about the disinfection effectiveness of far-UVC irradiation in real life. Here, systematic investigations were conducted to shed light on the disinfection effectiveness of far-UVC irradiation with laboratory studies and field tests in a real operating public lift cabin. The results of the laboratory study demonstrated that far-UVC irradiation can markedly promote the inactivation of the selected 7 types of microorganisms (including bacteria, viruses and fungus species) on steel surface compared to that on the glass surface, due to the synergistic effect of direct and reflected far-UVC light. This improvement was identified in the field test by employing the far-UVC device for disinfecting the surfaces of the lift cabin which are mostly made of stainless steel. Furthermore, the long-term field test of about 4 months also suggested that both environmental temperature and relative humidity (RH) affect the far-UVC disinfection effectiveness, where the best inactivation efficiency (99.9%) on the surface of lift button and handrail was achieved in the environmental temperature range of 23.5-25.5°C and the RH range of 60-70% at a low UVC dose of 5.2 mJ/cm2. In addition, >99.9% of airborne bacteria were inactivated in a chamber at a far-UVC dose of 15 mJ/cm2, showing a better performance of far-UVC for air disinfection compared to other technologies. This study systematically investigates the performance of far-UVC irradiation for surface and air disinfection in an actual environment, which provides helpful guidance for controlling the spread of pathogenic microorganisms in public spaces, especially in the ongoing COVID-19 pandemic. 
| [1] | Pyrgiotakis, G.; Vasanthakumar, A.; Gao, Y.; Eleftheriadou, M.; Toledo, E.; DeAraujo, A.; McDevitt, J.; Han, T.; Mainelis, G.; Mitchell, R.; Demokritou, P., “Inactivation of Foodborne Microorganisms Using Engineered Water Nanostructures (EWNS),” Environmental Science & Technology, 2015, 49, (6), 3737-3745.View Article PubMed |
| [2] | Cui, J.; Li, F.; Shi, Z., “Origin and evolution of pathogenic coronaviruses,” Nature Reviews Microbiology, 2019, 17, (3), 181-192.View Article PubMed |
| [3] | World, H. O., “COVID-19 weekly epidemiological update,” edition 58, 21 September 2021. |
| [4] | Matini, E.; Shayeghi, F.; Vaghar, M. E.; Nematian, J.; Hosseini, S. S.; Mojri, N.; Taherabadi, N. T.; Hakimi, R.; Ahmadi, N.; Badkoubeh, N.; Esmaeili, H.; Akhlaghi, M.; Vaseghnia, H., “A survey of public restrooms microbial contamination in Tehran city, capital of Iran, during 2019,” Journal of family medicine and primary care, 2020, 9, (6), 3131-3135.View Article PubMed |
| [5] | Raeiszadeh, M.; Adeli, B., “A Critical Review on Ultraviolet Disinfection Systems against COVID-19 Outbreak: Applicability, Validation, and Safety Considerations,” ACS Photonics, 2020, 7, (11), 2941-2951.View Article PubMed |
| [6] | Wu, S.; Wang, Y.; Jin, X.; Tian, J.; Liu, J.; Mao, Y., “Environmental contamination by SARS-CoV-2 in a designated hospital for coronavirus disease 2019,” American Journal of Infection Control, 2020, 48, (8), 910-914.View Article PubMed |
| [7] | A., A.; V., N.; A., S.; S., K. J. “In AT89S52-Microcontroller Based Elevator with UV-C disinfection to prevent the transmission of COVID-19,” 2020 International Conference on Interdisciplinary Cyber Physical Systems (ICPS), 2020-01-01, 2020; 2020; pp 25-30. |
| [8] | García De Abajo, F. J.; Hernández, R. J.; Kaminer, I.; Meyerhans, A.; Rosell-Llompart, J.; Sanchez-Elsner, T., “Back to Normal: An Old Physics Route to Reduce SARS-CoV-2 Transmission in Indoor Spaces,” ACS Nano 2020, 14, (7), 7704-7713.View Article PubMed |
| [9] | Bazant, M. Z.; Bush, J. W. M., “Beyond Six Feet: A Guideline to Limit Indoor Airborne Transmission of COVID-19,” MedRxiv, 2020, 2020.08.26.20182824.View Article |
| [10] | Zhang, Y.; Qu, S.; Xu, L., “Progress in the study of virus detection methods: The possibility of alternative methods to validate virus inactivation,” Biotechnology and Bioengineering, 2019, 116, (8), 2095-2102.View Article PubMed |
| [11] | Gonzalez, E. A.; Nandy, P.; Lucas, A. D.; Hitchins, V. M., “Ability of cleaning-disinfecting wipes to remove bacteria from medical device surfaces,” American Journal of Infection Control 2015, 43, (12), 1331-1335.View Article PubMed |
| [12] | Wolfrum, E. J.; Huang, J.; Blake, D. M.; Maness, P.; Huang, Z.; Fiest, J.; Jacoby, W. A., “Photocatalytic Oxidation of Bacteria, Bacterial and Fungal Spores, and Model Biofilm Components to Carbon Dioxide on Titanium Dioxide-Coated Surfaces,” Environmental Science & Technology, 2002, 36, (15), 3412-3419.View Article PubMed |
| [13] | Buonanno, M.; Welch, D.; Shuryak, I.; Brenner, D., “Far-UVC light (222 nm) efficiently and safely inactivates airborne human coronaviruses,” Scientific Reports, 2020, 10, 10285.View Article PubMed |
| [14] | Bhardwaj, S. K.; Singh, H.; Deep, A.; Khatri, M.; Bhaumik, J.; Kim, K.; Bhardwaj, N., “UVC-based photoinactivation as an efficient tool to control the transmission of coronaviruses,” Science of The Total Environment, 2021, 792, 148548.View Article PubMed |
| [15] | David, W.; Manuela, B.; Igor, S.; Gerhard, R.; Henry, M. S.; David, J. B. “In Far-UVC light applications: sterilization of MRSA on a surface and inactivation of aerosolized influenza virus,” Proc.SPIE, 2018-02-08, 2018; 2018. |
| [16] | Linden, K. G.; Hull, N.; Speight, V., “Thinking Outside the Treatment Plant: UV for Water Distribution System Disinfection,” Accounts of Chemical Research, 2019, 52, (5), 1226-1233.View Article PubMed |
| [17] | Buchan, A.; Yang, L.; Atkinson, K., “Predicting airborne coronavirus inactivation by far-UVC in populated rooms using a high-fidelity coupled radiation-CFD model,” Scientific Reports, 2020, 10, 19659.View Article PubMed |
| [18] | Yamano, N.; Kunisada, M.; Kaidzu, S.; Sugihara, K.; Nishiaki-Sawada, A.; Ohashi, H.; Yoshioka, A.; Igarashi, T.; Ohira, A.; Tanito, M.; Nishigori, C., “Long-term Effects of 222-nm ultraviolet radiation C Sterilizing Lamps on Mice Susceptible to Ultraviolet Radiation,” Photochemistry and Photobiology, 2020, 96, (4), 853-862.View Article PubMed |
| [19] | Prather, K. A.; Marr, L. C.; Schooley, R. T.; McDiarmid, M. A.; Wilson, M. E.; Milton, D. K., “Airborne transmission of SARS-CoV-2,” Science, 2020, 370, (6514), 303.2-304.View Article PubMed |
| [20] | Buonanno, M.; Ponnaiya, B.; Welch, D.; Stanislauskas, M.; Randers-Pehrson, G.; Smilenov, L.; Lowy, F. D.; Owens, D. M.; Brenner, D. J., “Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light,” Radiation Research, 2017, 187, (4), 493-501.View Article PubMed |
| [21] | Slonczewski, L. J.; Foster, W. J.; Gillen, M. K., “ACGIH 2021 TLVs and BEIs: Based on the Documentation of the Threshold Limit Values for Chemical and Physical Agents & Biological Exposure Indices,” American Conference of Governmental, 2020 |
| [22] | Narita, K.; Asano, K.; Morimoto, Y.; Igarashi, T.; Nakane, A., “Chronic irradiation with 222-nm UVC light induces neither DNA damage nor epidermal lesions in mouse skin, even at high doses,” PLoS One, 2018, 13, (7), e0201259.View Article PubMed |
| [23] | Eadie, E.; Barnard, I. M. R.; Ibbotson, S. H.; Wood, K., “Extreme Exposure to Filtered Far-UVC: A Case Study,” Photochemistry and Photobiology, 2021, 97, (3), 527-531.View Article PubMed |
| [24] | Ma, B.; Linden, Y. S.; Gundy, P. M.; Gerba, C. P.; Sobsey, M. D.; Linden, K. G., “Inactivation of Coronaviruses and Phage Phi6 from Irradiation across UVC Wavelengths,” Environmental Science & Technology Letters, 2021, 8, (5), 425-430.View Article PubMed |
| [25] | Denamur, E.; Clermont, O.; Bonacorsi, S.; Gordon, D., “The population genetics of pathogenic Escherichia coli,” Nature Reviews Microbiology, 2020, 19, 1-18.View Article PubMed |
| [26] | Melzer, M.; Petersen, I., “Mortality following bacteraemic infection caused by extended spectrum beta-lactamase (ESBL) producing E. Coli compared to non-ESBL producing E. Coli,” The Journal of infection 2007, 55, 254-9.View Article PubMed |
| [27] | Léger, L.; Budin-Verneuil, A.; Cacaci, M.; Benachour, A.; Hartke, A.; Verneuil, N., “β-Lactam Exposure Triggers Reactive Oxygen Species Formation in Enterococcus faecalis via the Respiratory Chain Component DMK,” Cell Reports, 2019, 29, 2184-2191.e3.View Article PubMed |
| [28] | Enright, M.; Robinson, D.; Randle, G.; Feil, E.; Grundmann, H.; Spratt, B., “The evolutionary history of methicillin-resistant Staphylococcus aureus (MRSA),” Proceedings of the National Academy of Sciences of the United States of America, 2002, 99, 7687-92.View Article PubMed |
| [29] | Ryan, K.; Slack, G.; Marriott, A.; Kane, J.; Whittaker, C.; Silman, N.; Carroll, M.; Gooch, K., “Cellular immune response to human influenza viruses differs between H1N1 and H3N2 subtypes in the ferret lung,” PLOS ONE, 2018, 13, e0202675.View Article PubMed |
| [30] | Lohse, M.; Gulati, M.; Johnson, A.; Nobile, C., “Development and regulation of single- and multi-species Candida albicans biofilms,” Nature Reviews Microbiology, 2017, 16.View Article PubMed |
| [31] | Braga, G. U. L.; Rangel, D. E. N.; Fernandes, É. K. K.; Flint, S. D.; Roberts, D. W., “Molecular and physiological effects of environmental UV radiation on fungal conidia,” Current Genetics, 2015, 61, (3), 405-425.View Article PubMed |
| [32] | Cadnum, J. L.; Shaikh, A. A.; Piedrahita, C. T.; Jencson, A. L.; Larkin, E. L.; Ghannoum, M. A.; Donskey, C. J., “Relative Resistance of the Emerging Fungal Pathogen Candida auris and Other Candida Species to Killing by Ultraviolet Light,” Infection Control & Hospital Epidemiology, 2018, 39, (1), 94-96.View Article PubMed |
| [33] | Baek, Y.; An, Y., “Microbial toxicity of metal oxide nanoparticles (CuO, NiO, ZnO, and Sb2O3) to Escherichia coli, Bacillus subtilis, and Streptococcus aureus,” Science of The Total Environment, 2011, 409, (8), 1603-1608.View Article PubMed |
| [34] | Kim, D.; Kim, S.; Kang, D., “Bactericidal effect of 266 to 279 nm wavelength UVC-LEDs for inactivation of Gram positive and Gram negative foodborne pathogenic bacteria and yeasts,” Food Research International, 2017, 97.View Article PubMed |
| [35] | Xu, P.; Kujundzic, E.; Peccia, J.; Schafer, M. P.; Moss, G.; Hernandez, M.; Miller, S. L., “Impact of Environmental Factors on Efficacy of Upper-Room Air Ultraviolet Germicidal Irradiation for Inactivating Airborne Mycobacteria,” Environmental Science & Technology, 2005, 39, (24), 9656-9664.View Article PubMed |
| [36] | Berry, G.; Parsons, A.; Morgan, M.; Rickert, J.; Cho, H., “A review of methods to reduce the probability of the airborne spread of COVID-19 in ventilation systems and enclosed spaces,” Environmental Research, 2022, 203, 111765.View Article PubMed |
| [37] | Qiao, Y.; Yang, M.; Marabella, I. A.; McGee, D. A. J.; Aboubakr, H.; Goyal, S.; Hogan Jr, C. J.; Olson, B. A.; Torremorell, M., “Greater than 3-Log Reduction in Viable Coronavirus Aerosol Concentration in Ducted Ultraviolet-C (UV–C) Systems,” Environmental Science & Technology, 2021, 55, (7), 4174-4182.View Article PubMed |
| [38] | Hwang, G. B.; Jung, J. H.; Jeong, T. G.; Lee, B. U., “Effect of hybrid UV-thermal energy stimuli on inactivation of S. epidermidis and B. subtilis bacterial bioaerosols,” Science of The Total Environment, 2010, 408, (23), 5903-5909.View Article PubMed |
| [39] | Zhong, X.; Qi, J.; Li, H.; Dong, L.; Gao, D., “Seasonal distribution of microbial activity in bioaerosols in the outdoor environment of the Qingdao coastal region,” Atmospheric Environment 2016, 140, 506-513.View Article |
| [40] | Lin, K.; Marr, L. C., “Humidity-Dependent Decay of Viruses, but Not Bacteria, in Aerosols and Droplets Follows Disinfection Kinetics,” Environmental Science & Technology, 2020, 54, (2), 1024-1032.View Article PubMed |
| [41] | Lopez, G. U.; Gerba, C. P.; Tamimi, A. H.; Kitajima, M.; Maxwell, S. L.; Rose, J. B., “Transfer Efficiency of Bacteria and Viruses from Porous and Nonporous Fomites to Fingers under Different Relative Humidity Conditions,” Applied and Environmental Microbiology 2013, 79, (18), 5728-5734.View Article PubMed |
| [42] | Otto, M., “Staphylococcus epidermidis - the 'accidental' pathogen,” Nature Reviews Microbiology, 2009, 7, (8), 555-567.View Article PubMed |
| [43] | Lee, B. U.; Yun, S. H.; Jung, J. H.; Bae, G., “Effect of relative humidity and variation of particle number size distribution on the inactivation effectiveness of airborne silver nanoparticles against bacteria bioaerosols deposited on a filter,” Journal of Aerosol Science, 2010, 41, (5), 447-456.View Article |
| [44] | Lai, A. C. K.; Nunayon, S. S.; Tan, T. F.; Li, W. S., “A pilot study on the disinfection efficacy of localized UV on the flushing-generated spread of pathogens,” Journal of Hazardous Materials, 2018, 358, 389-396.View Article PubMed |
| [45] | Nunayon, S.; Zhang, H.; Lai, A., “A novel upper-room UVC-LED irradiation system for disinfection of indoor bioaerosols under different operating and airflow conditions,” Journal of Hazardous Materials, 2020, 122715.View Article PubMed |
| [46] | Lai, A. C. K., Cheung, A. C. T., Wong, M. M. L., Li, W. S., Evaluation of cold plasma inactivation efficacy against different airborne bacteria in ventilation duct flow. Build. Environ. 2016, 98, 39-46.View Article |
| [47] | Lee, B. U., Yun, S. H., Jung, J. H., Bae, G., Effect of relative humidity and variation of particle number size distribution on the inactivation effectiveness of airborne silver nanoparticles against bacteria bioaerosols deposited on a filter. J. Aerosol Sci. 2010, 41, 447-456.View Article |
| [48] | Hwang, G. B., Jung, J. H., Jeong, T. G., Lee, B. U., Effect of hybrid UV-thermal energy stimuli on inactivation of S. epidermidis and B. subtilis bacterial bioaerosols. Sci. Total Environ. 2010, 408, 5903-5909.View Article PubMed |
| [49] | Nunayon, S.S., H. Zhang and A.C.K. Lai, Comparison of disinfection performance of UVC-LED and conventional upper-room UVGI systems. Indoor Air, 2020, 30, 180-191.View Article PubMed |
