A new technology coming of age quickly
222nm wavelength (Far UVC) light emitting devices has been around for a few years in various forms. For about the last 4 years, earnest development work has been underway due to the promise that Far UVC could win the war on superbugs.
Now the Covid-19 global pandemic has focused the minds of Far UVC device developers and researchers, since whilst the Coronavirus being very prolific it is also quite easily killed with a low dose of UVC exposure. Typically SARS-CoV-2 only requires a UVC dose of 3-4 mJ/cm2 to achieve a 3-log (99.9%) reduction.
Hence it makes sense to hasten the development of a technology that can be leveraged to protect multitudes of people a simple and very affordable manner.
Not all UVC is safe
UVC light having a wavelength of 254nm as produced by Ultra Violet Germicidal Irradiation (UVGI) lamps has for decades been used kill just about every species of infectious pathogen. However, UV light in the wavelength range of 250nm to 280nm is not suitable for exposing to humans and animals, since even short periods of direct exposure results in skin burns and eyesight impairment. As such UVC light produced by UVGI lamps (254nm) and UVC LED's (265, 273 & 280nm) should be used in such a manner that humans are protected from direct exposure.
How safe is Far UVC?
Far UVC light at extreme levels of exposure can be harmful, but substantially less harmful than 250-280nm UV.
When assessing whether Far UVC is right for you, it's best you consider the science and independent evaluations, especially when it come to matters of safety. There's lots and an increasing amount of research, studies and evaluations being published.
The following is an extract from the conclusion of research entitled, Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light and publish by the National Center for Biotechnology Information.
"Here we showed that 222 nm is essentially equi-effective at killing antibiotic-resistant bacteria as conventional germicidal UV lamps (254 nm). However, compared to the latter, 222-nm light does not induce typical UV-associated premutagenic DNA lesions in human keratinocytes in a 3D human skin model and appears to be safe for skin of exposed hairless mice, as assessed by eight cellular and molecular endpoints associated with damaged skin.
The results are consistent with previous in vitro and in vivo findings using a filtered krypton-bromine lamp that emits light at 207 nm; this suggests that there is a range of wavelengths, specifically between 200 and 222 nm, which are equitoxic to bacteria as typical germicidal lamps emitting at 254 nm, but without associated skin damage risks.
The lack of induced damage is due to the limited penetration of far-UVC light in biological samples while light in the 200-222 nm region can traverse microbes that are much smaller in size (<1 μm) than a typical mammalian cell (~10–25 μm in diameter), it cannot penetrate mammalian cells cytoplasm as well as all tissues with a stratum corneum."
The full transcript is available at the US National Library of Medicine website.
Reference 2One of the leading subject matter experts on Far UVC is Dr. David J. Brenner who is the Director of Center for Radiological Research at Columbia University.
Full details on his publication can be found via his webpage at Columbia Uni.
Another informative paper is; Extreme Exposure to Filtered Far-UVC: A Case Study, and can be found on the Wiley Online Library.
Nature also published; Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases and available on the Nature website.
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