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UVC light found to inactivate COVID virus in study

Published on 06/07/21 at 10:07am

A new study has found that Ultraviolet C (UVC) emitting lamps are fast, effective, and safe at inactivating SARS-CoV-2, the virus responsible for COVID-19, in real-world environments.

Simulations of classroom settings were used to investigate the potential of UVC lamps and found that a 99.9% reduction of particle load can be achieved in a standard classroom in 30 minutes.

Previous lab-based, animal, and human studies shown that far-UVC excimer lamps, with a peak emission wavelength of 222nm, can be used to inactivate influenza and coronavirus particles, though not specifically SARS-CoV-2, essentially disinfecting the air.

Dr Ewan Eadie, Head of Scientific Services at the Photobiology Unit, NHS Tayside, said: “This research is still at an early stage, but it shows a model by which the air in rooms can be disinfected safely and effectively with little to no impact on the skin. To put this in context, our research tells us that current legal limits for far-UVC exposure would cause a fraction of the DNA damage caused by a short spell outside. We found that it would take between 30 and 30,000 hours of exposure to far-UVC to produce the same DNA damage as just 10-minutes of springtime English sun exposure.”

The study had a two-pronged approach, with classroom simulations using computer modelling to simulate air flow and far-UVC irradiation, alongside a skin model being used to measure the risk and impact of the light on skin.

This model, the TenSkin, mimics intact, living skin, to investigate the impact that these lamps have on skin, particularly whether they increase the risk of skin cancer, by looking for signs of DNA damage.

The computer simulations used a classroom measuring 12m x 6m x 3m, with four air inlets, each 20cm x 20cm, producing six air changes an hour. With a uniform release of SARS-CoV-2 particles, at a height of 0.5m, the mechanical ventilation alone reduces the particle load to six percent in 30 minutes.

The addition of 18 commercially available far-UVC lamps located in the ceiling, irradiating the room below, resulted in a reduction to three percent in 30 min. The study found that far-UVC lamps which distribute UVC radiation more broadly would further reduce the SARS-CoV-2 particle load to 0.1% at 30 min.

The trial indicated that the light was safe to be used, with exposure of the skin model to a filtered far-UVC lamp resulting in little DNA damage at a dose 260 times higher than current legal limits, and this was restricted to minor cell damage to the outermost layer of the skin.

Dr Kenneth Wood, of the School of Physics and Astronomy at the University of St Andrews, said:“Currently there is limited evidence specifically looking at the effectiveness of far-UVC lamps in inactivating SAR-CoV-2 in the air. This is an important area of research as there is a clear need for practical methods for reducing the transmission of COVID-19 in indoor settings. Without this, the focus tends to be on disinfecting surfaces, which while a sensible step, does not prevent transmission of the disease through the air.

“This research is the result of computer modelling, as with any model, it is limited by information we feed into it, that said there is lots of supporting evidence which suggests that the results are accurate. Further real-world research would be useful to directly validate what we have found in our simulations”.

UVC radiation has long been used to kill microorganisms and as a disinfectant. It works on SARS-CoV-2 by destroying the outer protein coating of the virus, which inactivates it.

Kat Jenkins

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