# Comparative Study of Blue Light with Ultraviolet (UVC) Radiation on Betacoronavirus 1
## 1 Introduction  
The severe acute coronavirus 2 (SARS-CoV-2) pandemic has been an ongoing concern since its major outbreak in 2019, affecting the health and lives of millions of people across the world. Several unprecedented measures have been taken to control its spread, such as vaccinating people against the virus and strict sanitization measures, which have been quite effective in combatting the ill effects of the virus. As of February 2022, more than 10 billion doses of vaccines have been administered across the globe [1]. In addition, rigorous sanitization, which uses 60 to 95% ethyl alcohol, has well-established benefits and has thus been adopted by most households to clean surfaces and hands. However, despite strict sanitization, the virus is still spreading and affecting millions of people globally, indicating the need for more effective disinfection technologies. Ultraviolet (UV) is an invisible part of the electromagnetic spectrum that ranges from 100 to 400 nm. The UV range is mainly categorized into three sections based on wavelength. The range from 100 to 280 nm is termed UVC, from 280 to 320 nm as UVB, and from 320 to 400 nm as UVA [2]. Thelower range of UVC wavelengths, between 200 and 222 nm, is termed far-UVC. The ozone layer absorbs UVC, but due to the fact of its antimicrobial properties, it is artificially created and has been used for disinfection purposes over the past few centuries. The most used UVC wavelength has been 254 nm, and it has well-established efficacy against bacteria, fungi, and viruses. Other UVC wavelengths, such as 260-280 nm, have also shown the potential to inactivate viruses. A study conducted in the past used 260 nm, a combination of 260/280 nm, and 280 nm, to inactivate viruses. The fluences (UV doses) used were approximately 8 mJ/cm\({}^{2}\) for _oxsackievirus A10_ and _poliovirus 1_, 10 mJ/cm\({}^{2}\) for _enterovirus 70_, and 13 mJ/cm\({}^{2}\) for _echovirus 30_[3]. Amongst these three, 260 nm was more effective for _enteroviruses_, and 280 nm showed relatively higher efficacy for _human adenovirus_ (a DNA virus) [3]. Though UVCs have proven inactivation potential, they can cause severe burns on the skin and eye injuries such as photokeratitis [4]. Additionally, the effect of UVC radiation on materials raises concerns about compromising the structural integrity or the premature aging of the products [5]. Over the last decade, far-UVC has gained huge popularity for its higher irradiation power and lower penetration in human live tissue compared to 254 nm, making the inactivation process quicker and safer for humans [6]. Past studies on the antimicrobial property of far-UVC have demonstrated its capacity to inactivate influenza and coronaviruses in the air at a dose that does not damage human cells [7; 8]. Prior research has a dearth of data on the long-term effects of far-UVC and its exposure to human eyes. The CoVs belong to the family of nidovaries, coronavirus, and the subfamily coronavirus. On the basis of genetics, they can be categorized as Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus in which the former two are known to infect mammals and the latter two infect birds [9]. The Betacoronavirus can be divided into three categories based on lineage: SARS CoV, MERS CoV, and SARS CoV-2. The SARS-CoV-2 virus is very closely related to the genus Betacoronavirus. The SARS CoV-2 shares more than 70% genetic similarity with SARS CoV-1 [10]. The coronavirus contains structural proteins, i.e., spike (S), envelope (E), membrane (m), and nucleocapsid (N) proteins [11]. The virus uses its spike proteins to attach to the host cell. Once inside the host cell, it multiplies and kills the cells [12]. UVC exposure can cause either genome damage (DNA/RNA) or protein damage. The 254 nm is absorbed by the deoxyribonucleic acid (DNA) and ribonucleucle acid (RNA) through the formation of pyrimidine dimers [13]. However, the DNA can repair itself in the presence of blue light through a process called photoreactivation [14].