Simulation/Modelling | Not Peer Reviewed | SARS-CoV-2

Ultraviolet C (UVC) emitting lamps have been shown to be fast, effective, and safe at inactivating SARS-CoV-2, the virus responsible for COVID-19, in real-world environments, a new study shows.

Simulations found that a 99.9% reduction of particle load can be achieved in a standard classroom in 30 minutes.

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

This study, being presented by researchers from NHS Tayside and the Universities of Dundee and St. Andrews at the British Association of Dermatologists’ Annual Meeting, examined whether these findings held true for SARS-CoV-2, in real-world environments.

The researchers used a two-pronged approach to this study:

1. Computer modelling was used to simulate air flow, particle generation and far-UVC irradiation of a typical classroom
2. A sophisticated skin model, TenSkin™, was used to mimic intact, living skin, to see the impact that these lamps have on skin, particularly in terms of whether they increase the risk of skin cancer, by looking for signs of DNA damage

For the computer modelling, a standard classroom was simulated, measuring 12 m x 6 m x 3 m, with four air inlets, each 20 cm x 20 cm, producing six air changes an hour (ACH). With a uniform release of SARS-CoV-2 particles, at a height of 0.5 m, the mechanical ventilation alone reduces the particle load to six percent in 30 min. 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.

Far-UVC lamps which distribute UVC radiation more broadly would further reduce the SARS-CoV-2 particle load to 0.1% at 30 min.

These simulations accounted for the legal limits required when exposing people to these types of lamps. However, exposure of the skin model to a filtered far-UVC lamp resulted 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. This suggests that there may be a case for increasing current exposure limits for these devices.

With this knowledge, the classroom simulations were then repeated with higher irradiation restrictions. When set at 20 times the current exposure limits a 99.99% reduction of particle load was achieved within four and half minutes. When set at 100 times the current exposure limits this reduction was achieved within one minute.

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.”

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”.

Ultraviolet C radiation has long been used to kill microorganisms and to disinfect air, surfaces, objects, and liquids. It works on SARS-CoV-2 by destroying the outer protein coating of the virus, which inactivates it.

 Notes to editors:

 If using this press release, please ensure you mention that this research was presented at the British Association of Dermatologists’ Annual Meeting.

The virtual meeting will be live from the 6^th-8^th July 2021 and is attended by approximately 1,500 UK and worldwide dermatologists and other healthcare professionals.

For more information please contact: harriet@bad.org.uk or call 07769000415

Website: www.skinhealthinfo.org.uk

Study Details:

Skin safety and efficacy of filtered far ultraviolet C for SARS-CoV-2 inactivation

1. Eadie,¹ R.P. Hickerson,²,³ M.J. Conneely,²,³R. Hammond,⁴ S.K.H. Tsutsumi,² C.P. Cabrera,⁵A. Wood,⁶ A.W. Longbottom,⁶ A.J. Parker,⁶S.H. Ibbotson⁷ and K. Wood⁵

¹Photobiology Unit, NHS Tayside, Dundee, UK;

²School of Life Sciences and ⁷Photobiology Unit, University of Dundee, Dundee, UK;

³Ten Bio Ltd, Dundee, UK;

⁴School of Medicine and ⁵SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews, UK;

⁶Fluid Gravity Engineering Ltd, St Andrews, UK

About the British Association of Dermatologists

The British Association of Dermatologists is the central association of practising UK dermatologists. Our aim is to continually improve the treatment and understanding of skin disease. For further information about the charity, visit www.skinhealthinfo.org.uk 

The British Association of Dermatologists publishes two world-renowned dermatology journals, both published by Wiley. The British Journal of Dermatology is one of the top dermatology journals in the world, and publishes papers on all aspects of the biology and pathology of the skin. http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2133