Sunday, 26 April 2020


Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases, Welch et al, Scientific Reports volume 8, Article number: 2752 (2018).


Airborne-mediated microbial diseases such as influenza and tuberculosis represent major public health challenges. A direct approach to prevent airborne transmission is inactivation of airborne pathogens, and the airborne antimicrobial potential of UVC ultraviolet light has long been established; however, its widespread use in public settings is limited because conventional UVC light sources are both carcinogenic and cataractogenic. By contrast, we have previously shown that far-UVC light (207–222 nm) efficiently inactivates bacteria without harm to exposed mammalian skin. This is because, due to its strong absorbance in biological materials, far-UVC light cannot penetrate even the outer (non living) layers of human skin or eye; however, because bacteria and viruses are of micrometer or smaller dimensions, far-UVC can penetrate and inactivate them. We show for the first time that far-UVC efficiently inactivates airborne aerosolized viruses, with a very low dose of 2 mJ/cm2 of 222-nm light inactivating >95% of aerosolized H1N1 influenza virus. Continuous very low dose-rate far-UVC light in indoor public locations is a promising, safe and inexpensive tool to reduce the spread of airborne-mediated microbial diseases.

Monochromatic 222 nm UV light: Development of a safe, cost-effective technology for the efficient reduction of bacterial and viral infection and transmission , Park et al, NIH Grant Project 1R41AI125006-01

...research from Columbia University Medical Center demonstrated that single- wavelength far-UVC photons can kill bacteria and viruses while it cannot penetrate either the human stratum corneum (the outer dead-cell skin layer), nor the ocular cornea, nor the corneal tear-film layer, nor even the cytoplasm of individual human cells. In particular, the results teste both in vitro and in vivo have shown that several far-UVC wavelengths (such as 207 and 222 nm) are as efficient as conventional mercury containing germicidal UV lamp in inactivating both drug-resistant bacteria (e.g. MRSA) and viruses (e.g. H1N1), but these two far UVC wavelengths induce no damage to skin or to eyes, for a wide range of clinical endpoints, in contrast to a conventional broad-spectrum germicidal lamp.

Laser Focus World - 207nm and 222nm

Scientists have known for decades that broad-spectrum UVC light, which has a wavelength of between 200 to 400 nm), is highly effective at killing bacteria and viruses by destroying the molecular bonds that hold their DNA together. This conventional UV light is routinely used to decontaminate surgical equipment.

"Unfortunately, conventional germicidal UV light is also a human health hazard and can lead to skin cancer and cataracts, which prevents its use in public spaces," says study leader David J. Brenner.

Several years ago, Brenner and his colleagues hypothesized that far-UVC could kill microbes without damaging healthy tissue. "Far-UVC light has a very limited range and cannot penetrate through the outer dead-cell layer of human skin or the tear layer in the eye, so it’s not a human health hazard. But because viruses and bacteria are much smaller than human cells, far-UVC light can reach their DNA and kill them," said Brenner.

Excimer lamp sources
Brenner and his group use filtered excimer lamps emitting in the 207 to 222 nm wavelength range. For example, 207 nm light is emitted by a krypton-bromine (Kr-Br) excimer lamp, while 222 nm is emitted by a krypton-chlorine (Kr-Cl) excimer lamp. Brenner's group started with the 207 nm lamp, publishing results on sterilization of bacteria in 2013;1 in 2017, the results at 222 nm for bacteria were reported.2 The latest results, on sterilization of the influenza virus, were published this month (Feb. 2018) in Scientific Reports.3

1. Manuela Buonanno et al., PLOS One (2013); freely available online at
2. Manuela Buonanno et al., Radiation Research (2017);
3. David Welch et al., Scientific Reports (2018); doi:10.1038/s41598-018-21058-w

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