The pandemic means we’re all fixated on hygiene. Riding the coattails of our newfound obsession with cleanliness is a technology that for years has lurked in the background: ultraviolet light (UV). There’s the UV toilet brush, which not only has a UV sanitiser in-built, but also spins at 300RPM. The water bottle with a UV light in the lid made to disinfect water on the go. And cases for many things, including phones, keys and earphones.
While the main risk from Covid-19 is suspended in the air, it is thought to be transmitted on surfaces, too. The World Health Organisation recommends cleaning high-touch surfaces regularly, and the Department of Health recommends washing hands for at least 20 seconds when returning home. Companies have jumped on this newfound consciousness of grime and launched an onslaught of UV sanitising products that claim to kill 99.9 per cent of bacteria and viruses. But do they work or are they just preying on our heightened sense of cleanliness?
What is virus-killing UV?
UV light is invisible to the human eye and is higher energy than the light we can see. It is responsible for sunburn and is known to be a carcinogen. We use sunscreen to protect against it. But it’s this damaging power that makes it effective for disinfection.
Like the light we can see, UV light is split into different colours depending on the wavelength of the light; UV-A, UV-B, and UV-C. UV-A, which has the lowest energy and longest wavelength, is responsible for skin ageing. “The longer the wavelength, the deeper they penetrate, but they’re not as energetic, so they’re not as destructive,” says Clive Beggs, emeritus professor of physiology at Leeds Beckett University. UV-B sits in the middle, causing sunburn and skin cancer. While UV-C, the highest energy UV light, is what marketeers are talking about when referring to ’virus-killing UV’.
Sunlight contains UV but UV-C is filtered out by the Earth’s ozone layer leaving only the lower energy UV-A and UV-B. While sunlight has been shown to kill viruses, its effect varies strongly from season to season. To generate UV-C light on Earth, Mercury lamps and, more recently, LEDs are used. The UV-C light from these breaks apart the genetic material in viruses. This genetic damage scrambles the genetic code stopping the virus from replicating.
The virus-destroying capabilities of these lamps depends on the wavelength they produce. Mercury lamps generate 254nm light, which is near the peak virus-killing wavelength of 260nm. Even this small difference in wavelength means that for an equivalent UV dose you need to shine the light on a virus for 20 per cent longer.
Despite the spate of new virus-killing devices, the idea of using UV-C for disinfection dates back to the 1930s. Fighting another disease, William F. Wells showed the transmission of measles could be reduced by installing lights in the upper room of schools. By the 1970s, it was also being used to prevent the transmission of tuberculosis. This approach uses UV-C lights above head height, stopping people from being exposed to the harmful light. But care must be taken with UV-C as, similar to the other UV wavelengths, it can cause skin burns and damage to the eyes, as well as being a carcinogen.
In a recent study, researchers showed that this technology could also be used to combat Covid-19. Beggs and his colleague Eldad Avital, a reader in computational fluids and acoustics at Queen Mary University, showed that you could deactivate 90 per cent of Sars-CoV-2 particles in poorly ventilated rooms.
Scientists are also exploring the use of specific UV-C wavelengths, known as far-UV-C, which are deadly to the virus but appear to be harmless to humans. These lights could be shone directly into a whole room. “If you have a very poorly ventilated room then this is an incredibly good mechanism for removing the virus,” says Andrew Buchan, a senior lecturer in engineering science at Queen Mary University London.
UV sanitising has surface issues
UV-C is known to be effective at disinfecting air and water, but when it comes to our gadgets it’s the surfaces we are worried about. “It’s easier to kill in air than on surfaces,” says Beggs. The World Health Organisation recommends regularly cleaning high-touch surfaces, including handles and personal devices, such as mobile phones.
Enter the UV sanitising phone cases. Put your phone in, shut the lid, and UV light disinfects your device. Then repeat with the phone turned over. “It only irradiates what it sees,” says Beggs. If the UV light is shadowed by anything then it will not disinfect it. Any lip or edge that might block the light will reduce the effectiveness of these UV sanitising cases. Even a small scratch can appear like a 100 metre canyon on the scale of the virus. Any dust, dirt, or grime on the surface can also block the UV-C light, reducing its effectiveness.
Both the European Centre for Disease Prevention and Control and the World Health Organisation recommend a two-stage process of cleaning: remove dirt, dust and grease then disinfect for most effective removal of viruses.
The case for UV cases
Cases that are bespoke for their devices, such as the LG TONE Free Wireless Earbuds, may be more effective. These have features you might expect from high-end earbuds, such as noise cancellation, but its their UV sanitising case that really stands out.
Tested in independent labs against E. Coli and S. Aureus, the case reportedly killed 99.9 per cent of bacteria in ten minutes during normal charging. While this wasn’t carried out on Sars-CoV-2, the scientific consensus is that UV-C disinfection is similar across viruses and bacteria since it acts directly on the DNA or RNA. The amount of time needed to achieve a similar level of disinfection will vary depending on the virus and testing directly on Sars-CoV-2 is challenging and expensive due to the specialised facilities needed.
Another advantage of UV cases is that the UV-C light is contained within them, helping to avoid accidental exposure. “If it’s an enclosed device that once it’s sealed and enclosed, then it irradiates. That is good. It is out of sight,” says Beggs.
Beyond our gadgets, people might want to disinfect other things, such as face masks. Whether you are waste-conscious or just want to reuse your face mask, you need to make sure it is cleaned properly. A recent review published in the Journal of Hospital Infection found that UV-C sterilisation could be used effectively on N95 filtering respirators. Cleanbox Technology produces a UV sterilisation box for N95 masks aimed at this type of commercial application. It is independently tested and can inactivate 99.999 per cent of Covid-19 in two minutes.
Razer is working on a similar product –Project Hazel. “The world’s smartest mask” has an N95 respirator and a transparent design, as well as a built-in microphone and amplifier to ensure your speech isn’t muffled. Much like the LG earbuds, it comes with a charging case with in-built sterilisation. There are currently few details on the UV system specifications and its effectiveness against viruses and bacteria.
Are UV-C wands safe?
If you want to clean larger surfaces there have been a spate of UV-C wands released. These vary wildly in terms of their testing and specifications. Be careful what you are getting.
“If you are looking into some new device, you want to have a careful look at how it’s tested, and persuade yourself that it’s been tested effectively,” says Greg Towers, a professor of molecular virology at University College London. These wands claim to disinfect surfaces with little more than a waft. But one crucial element to UV-C disinfection is exposure time. “How do you know when it’s done?” says Beggs. Depending on the power of the lamp used and the distance to the surface, disinfection may require anything from a few seconds to several minutes – or even longer. It is clear that consistent and controlled use is needed for these to be anywhere near effective.
Another consideration with UV wands is safety. Unlike cases, the UV-C light is exposed, making accidental personal exposure all too easy. The World Health Organisation says that UV lamps should not be used to disinfect hands or any other areas of your skin.
One feature touted by some wands is an auto-off function when the device is pointing upwards, to avoid accidental eye exposure. The potential dangers of UV-C light were shared by all the scientists we talked to. Yet, many of these wands don’t even have child-safety locks, meaning that anyone can accidentally pick them up and use them.
Targus has included safety features to overcome these issues with its new UV-C LED disinfection light. Designed to sit above your workstation, the UV-C light turns on and runs automatically for five minutes every hour, disinfecting your keyboard and mouse. Any movement within the safety zone, however, and the UV-C LED is disabled, stopping accidental exposure. Running every hour means that devices under the light are, in theory, kept clean.
While UV-C disinfection doesn’t replace cleaning or regular hand washing, it may offer peace of mind. But for those who want the easy convenience of UV-C it’s a question of picking something effective. It’s important to make sure the device has been independently tested and is safe to use. “You can get UV to kill bugs, including Covid-19, and that’s fine. It’s a question of whether you’re doing it effectively,” says Towers.
The UV gear you can try now (or soon)
Dyson Pure Humidify and Cool
While CES 2021 unleashed a wave of UV devices, this air purifier and humidifier from Dyson was actually already available. The Pure Humidify and Cool keeps the air in your home cool and filtered of allergens and pollutants. UV comes into the equation via Dyson’s ‘Ultraviolet Cleanse’ tech. All of the water used by the purifier/humidifier is exposed to UV-C light and this, in turn, is said to kill up to 99.9 per cent of bacteria. Whilst Dyson doesn’t mention viruses, the scientific consensus is that UV-C disinfection is similar for viruses and bacteria since it acts directly on the genetic material.
Price: £599 | Argos | Dyson | Currys
LG TONE Free UVnano Wireless Earbuds
The LG TONE Free earbuds may look like any other set of wireless headphones but the charging case is hiding UV-C on the inside. LG claims that the UVnano charging case kills 99.9 per cent of the bacteria on the speaker mesh of each earbud. You will need to have the charging case plugged in for the UV to work. And let’s not forget the main function of this device – sound. The TONE Free earbuds have sound powered by audio brand Meridian, come with dual microphones and an Ambient Sound Mode for hearing the world around you when you need.
Price: £79 | Amazon | Boots | AO
Lexon Oblio + Mundus UV Pro
The default combination of ultraviolet technology and gadgetry at CES 2021 might have been UV wireless chargers and we’ve picked out two – rather different looking – choices. The Lexon Oblio is the most stylish of the pair, with a curved cup shape to plop your phone in when it needs a charge. While your phone sits charging, the UV-C light will, in theory, rid 99.9 per cent of germs from all the parts of the phone you’ve had your mitts on in just twenty minutes. Then there’s the Mundus UV Pro – a slightly less stylish option with a tad more function. This UV-C wireless charger is a white box with a lid to store away your device. Along with Qi wireless charging and UV that is said to kill 99.99 per cent of viruses and bacteria, there’s additional room for other accessories you may want to keep as clean as possible – like sunglasses, pens, wireless earbuds and more.
Price: €79.90 | Lexon
Price: £149 | Mundus UV Pro
Targus UV-C Disinfection Light
The UV-C Disinfection Light from Targus is a lamp that sits near to your desk (or any surface in your home you fancy) to help reduce pathogens. Sit the lamp just in front of where your keyboard and mouse are placed and be reassured that, for five minutes every hour, it’s working to eliminate any germs that may be sitting there. The Targus UV-C Disinfection Light is due to be released in March 2021.
Additional words by Adam Speight.
More great stories from WIRED
🌌 A rebel physicist has an elegant solution to a quantum mystery
🍪 Google is rewriting the web. Here’s the impact Chrome’s plan to kill cookies will have
😷 As more Covid-19 variants emerge, attention has turned to N95 and FFP2 face masks
🔊 Listen to The WIRED Podcast, the week in science, technology and culture, delivered every Friday
👉 Follow WIRED on Twitter, Instagram, Facebook and LinkedIn