Ashkan Babaie, director of engineering, Acuva Technologies Inc.
Sean MacIsaac, Ph.D. candidate, Dalhousie University
Babak Adeli, director of R&D, Acuva Technologies Inc.
Mariana Lanzarini- Lopes, research associate, Arizona State University
Before the current pandemic, ultraviolet germicidal irradiation (UVGI) was most often used in water treatment; however, the spread of COVID-19 across the world is broadening the application of ultraviolet disinfection to personal protective equipment (PPE), surface and air disinfection. During early stages of the pandemic, most media reports relating to UVGI application were around decontamination of PPE, such as N95 masks. Recent press articles show more interest around use of UVGI for surface disinfection in public places. This seems aligned with current needs, as major cities are relaxing restrictions and preparing for the post-lockdown era while hoping to avoid a second wave of the pandemic.
Disinfection of N95 facepiece respirators with UVGI could enable the reuse of face masks.1,2 3 However, as mentioned in an article by Dr. Ron Hofmann from the University of Toronto,4 the application of UV treatment in medical care is recent and not regulated compared to water treatment. The hidden crevices and folds in masks and gowns, where the UV light can’t reach, can reduce the efficiency of UVGI. In an article by the Centers for Disease Control and Prevention (CDC),5 UVGI, along with vaporous hydrogen peroxide and moist heat, were reported to be the most promising decontamination methods for facepiece respirators.
The main considerations for UV disinfection in this application include (i) treatment time adjustment to deliver an effective UV dose based on the provided UV intensity, (ii) shadowing in the multiple layer structure of a face mask that can shade and protect viruses and bacteria, and (iii) taking proper precautions to avoid UV exposure to skin or eyes.
A detailed study by Stanford University6 reported that UVGI and hot air are two disinfection methods that do not reduce the efficiency of N95 masks up to after 10 and 20 treatment cycles, respectively. In comparison, steam treatment reduced filtration efficiency to 85% after five cycles. A review article7 by Dr. Anderson from the University of Waterloo also reported effectiveness of UV for decontamination of face respirators without adverse effect on the filtration efficiency with UV doses up to 5,000 mJ/cm2, although strap breakage was mentioned as an occasional problem. Nebraska Medicine developed an internal protocol for decontamination and reuse of face respirators based on available scientific and technical literature.8 Their protocol details recommended UV doses for facepiece respirator disinfection by low-pressure mercury lamps.
UV surface disinfection in hospitals, airplanes and public transport vehicles have also gained traction during the COVID-19 pandemic. UV robots from UV-D9 claim to inactivate 99.99% of bacteria and virus in a typical hospital room within 10 to 15 minutes. These robots are equipped with autonomous navigation and have safety features to avoid human exposure to UV irradiation.
A UV device10 for sanitization of airplane surfaces, which was originally designed to prevent spread of the flu virus, claims effectiveness against COVID-19 by simply adjusting the delivered UV dose using a lower navigation speed. UVGI also has been used in China for disinfection of public transport buses, helping reduce the cleaning time from 40 minutes down to five minutes.11 A disinfection system combining low-pressure UV mercury lamps with photocatalytic antibacterial filters has been implemented at the Cagliari airport in Italy to disinfect luggage trays during the current pandemic.12
A novel application of UV robots is proposed in an article by Dr. Susanne Bieller who suggests that these robots could be used to provide contactless distribution of materials and samples to and from quarantine zones. This would allow COVID-carrying individuals to receive goods/materials without having medical staff exposed.13 Researchers in Montreal, Canada, are testing a disinfection robot to kill harmful viruses and bacteria found on surfaces in hospitals.14 Amazon’s robotic team announced it is working on a UV robot that could be used in warehouses and at Whole Foods stores to kill the virus on surfaces such as food, packaging and door handles.15 Pittsburgh International Airport has put UV-C fixtures on its floor-cleaning robots, making it the first airport in the US to test the use of the ultraviolet rays to scrub the coronavirus from surfaces. The UV is designed to irradiate floors only, so people are not likely to be exposed.16
While in most cases, low-pressure mercury lamps are used, there is a robot that uses a xenon lamp to generate high-intensity, full germicidal spectrum (200 to 315 nm). The results showed disinfection of SARS-CoV-2 in two minutes.17
UV air disinfection against COVID-19 has received less media attention than surfaces and PPE, though aerosols are potential pathways for virus transmission, as was very recently confirmed by the World Health Organization.18 In an article, the managing partner at GREEN DOT HEATING & AIR mentions that upper-air UV-C fixtures and HVAC germicidal fixtures can be effective means to inactivate viruses present in aerosols, like COVID-19.19
Media articles continue to highlight global efforts and technological innovations that are using ultraviolet radiation to aid in the fight against the COVID-19 pandemic. UV technology is gaining substantial media attention due to its potential to disinfect PPE, surfaces and air. However, the industry is currently lacking a high level of regulatory expertise to formulate standards that assure both the effectiveness and safety of the technology. Although these articles indicate technological advancements and utility, the safe and effective use of UVGI requires a level of updated standards and oversight, to be both effective in disinfection and eliminate any human health risks.20
Authors would like to acknowledge the contributions from YP task group members Devlin Thyne, Dana Pousty and Zhe Sun, as well as IUVA professionals who helped to review this article: Dr. Karl Linden and Carolina Ontiveros Verdugo.