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Can Ultraviolet light destroy Covid-19?

As we cautiously celebrate the discovery of several vaccines against Covid-19, activity continues into the exploration of other means of combating the spread of the virus. In the USA, the use of germicidal lighting has received a great deal of interest and publicity over recent months. Germicidal ultraviolet light (GUV) refers to the technology of germicidal lighting that utilises ultraviolet-emitting sources. While GUV is a technology with great potential, it‘s more complicated than simply switching on a UV light. 

We’re probably most familiar with GUV in the form of insect destroyers mounted on the walls of food shops and cafes . . . and UV in the shape of the salon sunbed. As many manufacturers across the Atlantic extol the benefits of hastily contrived devices purporting to eradicate Covid-19, here in the UK we need to be aware of the facts and the dangers. We now know that over-exposure to UV on sunbeds can cause skin cancer and, if eyes are unprotected, can damage sight. Some GUV products currently on the market and being sold for disinfection at home may be not only ineffective but also harmful  to pets, houseplants and a variety of furnishing and decorating materials. 

Terry McGowan, Director of Engineering & Technology at the American Lighting Association (ALA), informs us that concerns surrounding UV emitting products currently sold for residential use have prompted a warning paper* issued jointly by ALA, NEMA (National Electrical Manufacturers Association) and UL (the global leader in safety science). McGowan goes on to tell us that, while LEDs that generate UVC radiation are in development, they are currently prohibitively expensive and not generally available for today’s germicidal products. The disinfection products now being sold use gas discharge tubes with no phosphor coating. McGowan points out that this UVC germ-killing technology has been safely in use for over 70 years. However, consumers cannot be assured against the risks of UVC over-exposure from devices that fail to provide adequate containment of UV emissions. Consequently, and when used incorrectly, such devices may present an undue and unacceptable health risk. Over-exposure can occur in seconds as light levels are disarmingly low and don’t trigger our natural defences to optical hazards. 

The Covid-19 virus can ONLY be destroyed by directly exposing it to UV light in the UVC part of the spectrum of light that ranges from 200-280 nanometers. Other UV wavelengths in the UVA and UVB parts of the spectrum are NOT effective against Covid-19. Disinfection is a formula calculated by multiplying the UVC intensity x exposure duration so any portable device moved around randomly near objects and surfaces will be ineffective. 

Exposure must also be direct. Reflected UVC light does not destroy germs or viruses because the light is absorbed by most surfaces. Equally, any clothing with folds and wrinkles will not be disinfected in the dark recesses that remain out of reach of UVC light and in which viruses will thrive. 

In conclusion, the use of UV for disinfection is only thoroughly effective when using the specific UVC part of the spectrum, directly and for an adequate period of time. Furthermore, the safe use of UVC still must be confined to regulated environments (hospitals and healthcare) where the danger of causing more harm than good can be successfully avoided. UVC used elsewhere is a bridge too far. 

*Ultraviolet-C (UVC) germicidal devices: what consumers need to know | ALA, NEMA, UL

This article and more are on our Fresh Magazine Issue n.1 2021