A couple of years ago, close to the beginning of the pandemic, a certain President of a certain country announced something that left the world baffled.
“Supposing we hit the body with a tremendous – whether it's ultraviolet or just very powerful light,” he suggested to the team of physicians tasked with combatting the spread of COVID-19. “I think you said that hasn't been checked but you're going to test it.”
Well, forget everything he said after that point, but on this at least it turns out Trump was … almost kind of right? A new paper, published this week in the journal Scientific Reports, has found that filling a room with a special type of ultraviolet light can reduce the presence of microbes in the air by up to 98 percent – effectively making the indoors as safe as outdoors in terms of person-to-person virus transmission.
“Our trials produced spectacular results, far exceeding what is possible with ventilation alone,” Dr Kenneth Wood, senior author of the study, said in a statement. “In terms of preventing airborne disease transmission, far-UVC lights could make indoor places as safe as being outside on the golf course on a breezy day at St. Andrews.”
But what exactly is this “far-UVC” light? Perhaps surprisingly, it’s a technology with more than a century of history behind it: UVC light, which has shorter wavelengths and higher photonic energy than both its UVA and UVB brethren, was first used for sterilization purposes back in 1878. In 1903, using UVC light to treat disease won Niels Ryberg Finsen a Nobel Prize, and it has been used to disinfect water supplies around the world since 1910.
So why haven’t we been using this miracle light all along? Well, here’s the thing: you know how UVA and UVB light – also known as “the stuff that gets beamed down to us from the sun” – can literally give you second degree burns if you stay out in it for too long? Well, UVC light is even worse.
“UVC radiation can cause severe burns of the skin and eye injuries (photokeratitis),” warns the FDA.
“Avoid direct skin exposure to UVC radiation and never look directly into a UVC light source, even briefly … [eye injury] can occur after a very short exposure (seconds to minutes) to UVC radiation.”
In other words, lighting a room with UVC light would probably result in everybody inside getting horribly burned and going temporarily blind. Which, nasty though COVID is, is probably not ideal.
That’s where far-UVC light comes in. About a decade ago, scientists at Columbia University proposed that UVC light could be heavily filtered so that only the lowest wavelengths were beamed out. They hoped that this filtered UVC, or “far-UVC,” would be able to hit the sweet spot of powerful enough to kill bacteria, but not so powerful that it gives people burns or cancer.
Amazingly, it worked – but until very recently, the new study explains, only in lab conditions. The team wanted to see whether far-UVC light would be a viable solution in the real world – could its disinfectant properties take on a busy room with people coming and going, for example, or was it only suitable for sterilizing petri dishes?
So they set up an experiment: they sprayed aerosolized Staphylococcus aureus into a room-sized chamber and switched on the far-UVC lamps. The chamber had a ventilation rate similar to a typical office or home, but the germs continued to be sprayed throughout the experiment.
The results were amazing: not only did the far-UVC light neutralize nearly all of the virus particles in the chamber, but it took just five minutes to do so. Compared to other ways of disinfecting indoor spaces, the researchers pointed out, this puts far-UVC light at more than nine times as effective at clearing virus particles from the air.
“Far-UVC rapidly reduces the amount of active microbes in the indoor air to almost zero, making indoor air essentially as safe as outdoor air,” said study co-author David Brenner. “Using this technology in locations where people gather together indoors could prevent the next potential pandemic.”
The best part? Far-UVC light isn’t just a cheap and easy way of killing coronavirus: it’s a cheap and easy way of killing a whole host of viruses and bacteria – including ones we haven’t even heard of yet.
“Previous studies have shown that far-UVC light can kill the COVID virus, other human coronaviruses, influenza, and drug-resistant bacteria,” explained Brenner. “What’s particularly attractive about far-UVC technology … is that it will be equally good at inactivating all future COVID variants, as well as new infectious viruses that have yet to emerge, while retaining efficacy against ‘old fashioned’ viruses like influenza and measles.”
And because of the way far-UVC light kills the microbes, it’s impossible for them to gain resistance to them – so there’s no risk of us bringing about any new superbugs like we did with antibiotics. It is essentially, the researchers explain, completely future-proof.
“Far-UVC light is simple to install, it’s inexpensive, it doesn’t need people to change their behavior,” said Brenner. “[A]bove all it’s a safe way to prevent the transmission of any virus, including the COVID virus and its variants, as well as influenza and also any potential future pandemic viruses.”