Document Type : Brief Communication


1 MSc, Medical Physics and Engineering Department, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

2 PhD, Department of Radiology, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran

3 PhD, Bevelacqua Resources, Richland, Washington 99352, United States

4 PhD, Department of Radiation Oncology Edward Hines Jr VA Hospital Hines, Illinois. United States

5 PhD, Department of Radiation Oncology, Stritch School of Medicine, Loyola University, Chicago, IL, United States

6 MD, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

7 PhD, Department of Medical Physics and Engineering, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

8 MD, Department of Pediatric Infectious Diseases, Yasuj University of Medical Sciences, Yasuj, Iran



The Omicron variant is spreading at a rate we have never observed with any previous variant. A lot of efforts have been taken to inactivate SARS-CoV-2, especially the omicron variant. Specific wavelength ranges of electromagnetic radiation can be exploited to inactivate coronaviruses. Previous studies show that 222-nm far-Ultraviolet C (far-UVC) light inactivates airborne influenza virus efficiently. Considering the similar genomic sizes of all human coronaviruses, other human coronaviruses, such as SARS-CoV-2, would be expected to be inactivated by far-UVC with a similar efficacy. Taking this into account, it is concluded that exposure to far-UVC can be introduced as a safe method that significantly reduces the ambient level of airborne coronaviruses in crowded places. Biomolecules, particularly proteins, strongly absorb ultraviolet radiation at a wavelength of around 200 nm. Given this consideration, far-UVC has a limited ability to permeate biological materials. Thus, for example, in only around 0.3 mm of tissue, the intensity of 200-nm UV radiation is decreased by half, compared to tissue penetration of about 3 mm at 250 nm. This paper aims to answer the key question of whether far-UVC can penetrate SARS-CoV-2 inside inhalable respiratory droplets (with diameters up to 100 µm).


  1. Buonanno M, Welch D, Shuryak I, Brenner DJ. Far-UVC light (222 nm) efficiently and safely inactivates airborne human coronaviruses. Sci Rep. 2020;10(1):10285. doi: 10.1038/s41598-020-67211-2. PubMed PMID: 32581288. PubMed PMCID: PMC7314750.
  2. Bai Y, Yao L, Wei T, Tian F, Jin DY, Chen L, Wang M. Presumed Asymptomatic Carrier Transmission of COVID-19. JAMA. 2020;323(14):1406-7. doi: 10.1001/jama.2020.2565. PubMed PMID: 32083643. PubMed PMCID: PMC7042844.
  3. Kowalski W. Ultraviolet germicidal irradiation handbook: UVGI for air and surface disinfection. Springer; 2010.
  4. Budowsky EI, Bresler SE, Friedman EA, Zheleznova NV. Principles of selective inactivation of viral genome. Arch Virol. 1981;68(3-4):239-47. doi: 10.1007/BF01314577. PubMed PMID: 7271457.
  5. Naunovic Z, Lim S, Blatchley ER 3rd. Investigation of microbial inactivation efficiency of a UV disinfection system employing an excimer lamp. Water Res. 2008;42(19):4838-46. doi: 10.1016/j.watres.2008.09.001. PubMed PMID: 18848711.
  6. Buonanno M, Ponnaiya B, Welch D, Stanislauskas M, Randers-Pehrson G, et al. Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light. Radiat Res. 2017;187(4):483-91. doi: 10.1667/RR0010CC.1. PubMed PMID: 28225654. PubMed PMCID: PMC5552051.
  7. Buonanno M, Randers-Pehrson G, Bigelow AW, Trivedi S, Lowy FD, et al. 207-nm UV light - a promising tool for safe low-cost reduction of surgical site infections. I: in vitro studies. PLoS One. 2013;8(10):e76968. doi: 10.1371/journal.pone.0076968. PubMed PMID: 24146947. PubMed PMCID: PMC3797730.
  8. Buonanno M, Stanislauskas M, Ponnaiya B, Bigelow AW, Randers-Pehrson G, Xu Y, et al. 207-nm UV Light-A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. II: In-Vivo Safety Studies. PLoS One. 2016;11(6):e0138418. doi: 10.1371/journal.pone.0138418. PubMed PMID: 27275949. PubMed PMCID: PMC4898708.
  9. Ponnaiya B, Buonanno M, Welch D, Shuryak I, Randers-Pehrson G, Brenner DJ. Far-UVC light prevents MRSA infection of superficial wounds in vivo. PLoS One. 2018;13(2):e0192053. doi: 10.1371/journal.pone.0192053. PubMed PMID: 29466457. PubMed PMCID: PMC5821446.
  10. Lorian V, Zak O, Suter J, Bruecher C. Staphylococci, in vitro and in vivo. Diagn Microbiol Infect Dis. 1985;3(5):433-44. doi: 10.1016/0732-8893(85)90082-3. PubMed PMID: 4028668.
  11. Coohill TP. Virus-cell interactions as probes for vacuum-ultraviolet radiation damage and repair. Photochem Photobiol. 1986;44(3):359-63. doi: 10.1111/j.1751-1097.1986.tb04676.x. PubMed PMID: 3786457.
  12. Metzler DE. Biochemistry (2 Volume Set): The Chemical Reactions of Living Cells. Elsevier; 2003.
  13. Li H, Leong FY, Xu G, Kang CW, Lim KH, Tan BH, Loo CM. Airborne dispersion of droplets during coughing: a physical model of viral transmission. Sci Rep. 2021;11(1):4617. doi: 10.1038/s41598-021-84245-2. PubMed PMID: 33633316. PubMed PMCID: PMC7907382.
  14. Zhang H, Li D, Xie L, Xiao Y. Documentary Research of Human Respiratory Droplet Characteristics. Procedia Eng. 2015;121:1365-74. doi: 10.1016/j.proeng.2015.09.023. PubMed PMID: 32288921. PubMed PMCID: PMC7128962.
  15. Yang S, Lee GW, Chen CM, Wu CC, Yu KP. The size and concentration of droplets generated by coughing in human subjects. J Aerosol Med. 2007;20(4):484-94. doi: 10.1089/jam.2007.0610. PubMed PMID: 18158720.