UV-C light has been used as a disinfectant against viruses and bacteria for more than 40 years. Now, researchers at Boston University and Signify (formerly Phillips) have confirmed that it also effectively eradicates the SARS-CoV-2 virus.
UV-C light has been used as a disinfectant against viruses and bacteria for more than 40 years. Now, researchers at Boston University and Signify (formerly Phillips) have confirmed that it also effectively eradicates the SARS-CoV-2 virus.
Specifically, a 5mJ/cm2 dose of UV-C light eradicated 99% of the SARS-CoV-2 virus in 6 seconds, according to testing by Anthony Griffiths, Ph.D., associate professor of microbiology, in Boston University’s National Emerging Infectious Diseases Laboratories (NEIDL). Based on the data, he and his team determined that a 22mJ/cm2 dose of UV-C light will result in a reduction of 99.9999% of the virus in 25 seconds. That translates, at a basic level, to needing a 13W UV-C light bulb to kill viruses in a 10 x 16 foot (15 square meter) room, for an undetermined period of time.
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UV-C light kills bacteria and viruses using radiation to destroy or inactivate the microbes. Effects depend on the microbe in question, but in some, the light causes thymine bases in the DNA to bond and thereby creating a dimmer. If enough dimmers are created, they can’t multiply. In other microbes, UV-C light splits the bonds that keep DNA intact, forming free radicals and inactivating the organism.
As to the degree of inactivation needed to prevent transmission of SARS-/CoV-2, Dr. Griffiths told BioSpace, “We do not know. More studies in the area of transmission need to be performed.”
That said, none of the hundreds of viruses and bacteria that have been tested during the past 40 years have been resistant to UV-C light.
Dr. Griffiths and Giovanni Cennini, head of sector digital workflow at Signify, are continuing this research with the expectation of publishing detailed results in a peer-reviewed journal in the upcoming months.
Verification that UV-C kills SARX-CoV-2, as well as hundreds of other viruses, means it can be invaluable in stopping the spread of disease in the air and on surfaces, such as keypads and handrails.
Traditional UV-C light, however, cannot be used when humans are present. Because the short wavelength light (between 100 and 280 nm) can be absorbed by dead skin, exposure to UV-C light can cause reddening of the skin and, in the eye, conjunctivitis. Some reports link it to the development of cancer. It is absorbed by most products, including glass.
To resolve the health issues, researchers at Columbia University Center for Radiological Research (CRR) have developed far-UVC light. With a wavelength of approximately 220nm, far-UVC light cannot penetrate the eyes or the dead cells at the surface of skin. It can, however, penetrate and kill viruses in the air.
Some lighting companies are developing applications using far-UVC, and one lighting fixture manufacturer is incorporating the lamps into conventional light fittings, according to the researchers. That offers the potential of flooding broad spaces, like classrooms, subway cars, train stations and other public spaces with this germicidal light, killing viruses in the air or on surfaces the light hits.
Signify is expanding its lighting options, too.
“In response to the growing demand, we are launching UV-C luminaires and cabinets for the professional market for retailers, offices, schools, hospitality and other public segments,” Elco van Groningen, Signify’s senior press officer, told BioSpace. “Until now, we have provided lamps and drivers to original equipment manufacturers (OEMs) whose customers have the knowledge to apply UV-C equipment in a safe way.”
Currently, none of Signify’s UV-C lights are approved as medical devices. Instead, company CEO Eric Rondolat said UV-C light is a “preventive measure for companies and institutions as they seek ways to provide virus-free environments.”
Several other companies also are developing or applying UV-C disinfectant solutions. For example, Atomic Blue UV-C light was just approved by the FDA as a Disinfectant – Medical Device with the product code LRJ under device Class 1. In tests by the National Institutes of Health, it eradicated 99.99% the SARS-CoV-2 virus from surfaces.
In the consumer world, Genmega is adding UV-C modules to the ATMs and kiosks it manufactures. The Lighting Qutient has developed a UV-C light to disinfect work surfaces for offices, schools and labs. It’s solution is integrated into task lighting with a special disinfectant mode. In Atlantic City, Resorts Casino Hotel is using UV-C light to disinfect handrails on escalators, and mobile UV technology will disinfect hotel rooms and public restrooms. The air handling system also will be disinfected using UV light.
