Before President Donald Trump erroneously—and sarcastically, he later claimed—suggested the possibility of using “ultraviolet or just a very powerful light … inside the body” at a White House briefing in April as a potential treatment for COVID-19, scientific research in the use of UV light to combat pathogens was well underway. Given these comments and a heightened interest in disinfection due to the pandemic, the lighting community swiftly released webinars, FAQs, and press releases to offer guidance on the effectiveness, potential applications, and myths of using UV radiation to fight infection.
The Illuminating Engineering Society, a professional association for the lighting and design community, was one such organization to respond to the increased interest in germicidal UV lighting. The IES focused on UVC, which is currently considered the most effective range in the UV light wavelength spectrum in disinfection, but also can be the most hazardous to people exposed to it in uncontrolled settings. (Other wavelength ranges, including UVA, have also been shown to successfully kill or inactivate pathogens.) While versions of germicidal UV (GUV) have been used for surface disinfection since the late 1800s, interest in the technology increased following the 2014 Ebola virus outbreak in West Africa. When properly applied, GUV—which refers to short-wave UVC radiation in the 200-to- 280-nanometer range on the ultraviolet spectral band—has been shown to kill bacteria and spores and even deactivate viruses, such as SARS-CoV-2, which are nonliving infectious agents that replicate. (UVA, UVB, and UVC are all produced by the sun and pass through the ozone layer in varying quantities, with UVA being the most prevalent.)
The organization’s photobiology committee opted to convene a special subcommittee to address the topic, and after a few intense weeks published the "Germicidal Ultraviolet (GUV) – Frequently Asked Questions" report. “There is enough misleading information that we felt we really needed to address the typical questions people have,” medical physicist and committee chair David Sliney tells ARCHITECT.
“For viruses, very short wavelength UVC will break down its RNA, preventing the virus from replicating,” explain professor Mark Rea and senior research scientist Andrew Bierman, both at the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, N.Y. “For bacteria, this direct action on its DNA will also prevent replication. The UV is absorbed by a chromophore, which creates intracellular reactive oxygen molecules, like hydrogen peroxide, that react with life-sustaining molecules.”
If the technology is used properly, luminaires outfitted with UVC light sources do not cause harm to occupants. Sliney remarks that the long-held belief that UVC causes skin cancer “is largely a myth.” However, direct exposure can cause uncomfortable eye conditions such as photokeratitis—also known as "welder’s flash"—or photo conjunctivitis if the luminaire is operated improperly. To avoid such conditions, the IES recommends the use of UVC light only in upper air germicidal fixtures, where the UVC source is positioned at least 7 feet high and directed at the ceiling to irradiate air as it circulates.
“Upper-room GUV disinfects large volumes of room air (above occupant's heads) at once, resulting in high 'equivalent' air changes per hour in terms of air disinfection only,” the IES report explains. For rooms that do not have the requisite minimum ceiling height of 7 feet, designers might instead turn to UV lamps designed for installation inside air ducts for both residential and commercial HVAC units. However, this technology cannot help to limit the spread of disease between people when installed in ducts, cautions the IES in its report. “When UV is used in ducts, although it ensures that recirculated air does not have viable pathogens, it, unfortunately, does relatively little to prevent person-to-person transmission in a room where both an infectious source and other susceptible persons share the same air,” the organization writes. “For effective interruption of transmission, air disinfection has to occur in the same room where transmission is occurring.”
Many lighting manufacturers and technology companies have developed alternative options, leveraging LEDs, and other light spectrums to offer antimicrobial effects without limiting occupation. GE Current, for example, sells a recessed LED luminaire that emanates UVA light at a wavelength of 365 nanometers, which is not visible to the human eye, as well as white light. The Boston-based manufacturer patented its technology, which enables fixtures that offer direct illumination and disinfection for occupied spaces, such as patient rooms and cafeterias, back in 2015. A study by Case Western Reserve University School of Medicine and the Cleveland VA Medical Center found that GE Current’s Lumination LED luminaires were effective in reducing MRSA (methicillin-resistant Staphylococcus aureus), E. coli, and bacteriophage MS2 by 80% to 90% for occupied patient rooms.