The Department of Health is exploring new approaches to reduce the spread of airborne diseases, like COVID-19 and influenza.
One of these new approaches is germicidal ultraviolet light. The department is currently reviewing the safety, feasibility, and efficacy of germicidal ultraviolet lights in reducing the transmission of communicable diseases.
How germicidal ultraviolet lighting works
Germicidal ultraviolet lights produce ultraviolet (UV) light in the ultraviolet-C (UVC) wavelength range (100-280 nm). This wavelength of light is invisible to the human eye.
This light has been shown in laboratory studies to successfully inactivate bacteria and viruses. An inactivated virus particle is unable to invade and infect a human cell thus preventing infection. GUV lights at 254 and 222 nm wavelength are commercially available.
Like many respiratory viruses, COVID-19 spreads from person to person through both large droplets and airborne particles.
When germicidal ultraviolet lights are installed just below the ceiling in a room, they are in theory able to inactivate airborne viruses and bacteria that travel into the path of the UV beam.
This allows the lights to operate in the upper part of the room, while people can continue to use the lower part of the room without any measurable UV exposure.
Other models of germicidal ultraviolet lighting include those which shine light throughout a room (for 222 nm wavelength devices), globes which sit within a unit with a fan or which can be installed within building ducting or in combination with normal room lighting.
Benefits as a public health measure
Germicidal ultraviolet light is an appealing public health approach in response to the ongoing threat of COVID-19. It is not restrictive (such as isolation), and does not rely on individual behaviour change (such as masks and testing).
It can be installed and retrofitted into pre-existing buildings and infrastructure. Germicidal ultraviolet lights may also have lower power costs and greater auditory (sound) and thermal (heat) comfort than HVAC systems with HEPA filters, a known technology for reducing airborne virus particles.
What does the research say?
Published laboratory studies report that using germicidal ultraviolet light with the right air movement below the ceiling in a room could provide larger reductions in virus transmission than just air ventilation and filtration alone. It has been used for decades in healthcare settings and has been shown to reduce tuberculosis transmission.
There are no published studies showing whether germicidal ultraviolet lights are effective against COVID-19 transmission in the real-world, although there is research underway in several countries.
Safety
When considering germicidal ultraviolet lights, it is important to understand their role in air disinfection as well as the potential safety risks associated with their use, as they produce a beam of ultraviolet light. Here is what you need to know:
- Risks from direct exposure to a 254 nm wavelength UVC beam are often short-term and self-resolving such as temporary skin reddening, and eye irritation.
- Upper room germicidal ultraviolet lights are designed for use within occupied spaces. It is critical to have strong safety protocols, such as clear safety signage and operational protocols to prevent direct human exposure to the UVC light in the upper part of the room.
- There are varying views among international guidelines regarding the safety risks of UVC on humans. Most suggest that as the UV rays are shorter, they are predominantly absorbed by the superficial skin layers, instead of deep tissue. Therefore, this suggests there is minimal risk of long-term health risks, such as skin cancer, unlike with UVA from sunlight. Note some sources categorise all UV light, including UVC, as potentially carcinogenic.
- Whilst all UV light, including UVC, may be potentially carcinogenic, when properly installed and maintained, UV lamps are expected to pose negligible safety risk to people in the rooms.
Department review
The Department of Health’s review of germicidal ultraviolet light technology reveals it may have the potential to reduce COVID-19 transmission in high-risk settings. Existing evidence mostly stems from controlled laboratory experiments and lacks real-world validation. Large-scale studies are important to confirm germicidal ultraviolet's effectiveness and safety in practical settings.
Continued research is important to understand the potential for safe and effective use of germicidal ultraviolet lights in combating airborne transmission of infectious agents.
References
- Nardell EA. Air Disinfection for Airborne Infection Control with a Focus on COVID-19: Why Germicidal UV is Essential. Photochem Photobiol. 2021;97(3):493-497.
- International Commission on Non-Ionizing Radiation Protection.UVC lamps and . ICNIRP. Published 2020. Accessed 7 February, 2024.
- Brass A, Shoubridge AP, Crotty M, et al. Prevention of SARS-CoV-2 (COVID-19) transmission in residential aged care using ultraviolet light (PETRA): a two-arm crossover randomised controlled trial protocol. BMC Infectious Diseases. 2021;21:967. Harvard Centre for Global Health
- Examples of UR-GUV . HCGHD. Harvard UVGI Web site. Published 2021. Accessed 7 February 2024.
- Hessling M, Haag R, Sieber N, Vatter P. The impact of far-UVC radiation (200-230 nm) on pathogens, cells, skin, and eyes - a collection and analysis of a hundred years of data. GMS Hyg Infect Control. 2021;16.
- Mphaphlele M, Dharmadhikari AS, Jensen PA, et al. Institutional Tuberculosis Transmission. Controlled Trial of Upper Room Ultraviolet Air Disinfection: A Basis for New Dosing Guidelines. American Journal of Respiratory and Critical Care Medicine. 2015;192(4).
- Public Health Agency of Canada. Evidence on the effectiveness and safety of ultraviolet germicidal irradiation technologies in reducing SARS-CoV-2 in the air of occupied rooms
- Ventilation in Buildings: centre for Disease Control and . 2023
Reviewed 27 March 2024