You’ve probably heard a lot of noise recently about UV light, including sunlight, and whether or not it can destroy viruses like the new coronavirus, which causes COVID-19.
Not everything is hype. In fact, there is good evidence that UV light in the “C” range, also known as UVC, can kill this particular virus. But that doesn’t mean you should run away and buy one of the UV boxes or wands that seem to be popping up everywhere. This is what you need to know.
How does UV light work?
For years, hospitals and laboratories have used ultraviolet (UV) light to disinfect equipment and surfaces. It works by altering the genetic material of germs (known as their DNA and RNA). But over the years, research has revealed that of the three main types of UV light, UVA, UVB, and UVC, UVC appears to be the most effective.
More recently, research from Columbia University found that UVC light holds promise for stopping the spread of the coronavirus. The study, published in April 2020 as a preprint in Virology, found that UVC light can help eliminate two types of seasonal airborne coronaviruses that are often behind the common cold. Investigators are now testing it specifically against the one that causes COVID-19.
Although the research is still preliminary, the previous findings indicate that UVC light can inactivate the H1N1 flu virus in the air , as well as some drug-resistant bacteria . This means that you may have the potential to prevent the spread of COVID-19.
Another preliminary lab study, published in April 2020 on medRxiv, found that when pieces of N95 mask cloth and stainless steel were contaminated with the new coronavirus and then exposed to a hospital UVC lamp, the virus died on both surfaces. In an hour. However, the study is still being reviewed, so it should not be taken at face value yet.
The problem with UVC consumer products
Given this research, you may be seriously considering purchasing one of the UVC light products that you can find online as a way to disinfect everything from your smartphone to your kitchen counters.
But the FDA issued a notice against them in February 2020, reminding people that these devices are not yet FDA approved, and it is unclear how safe and effective they really are.
The big challenge for most of them is that there is no way to know for sure if they are providing a large enough dose of UVC light to the surface you want to disinfect, be it a mask, a phone or a countertop.
Although most products provide a wavelength, which should ideally be around 260 nanometers (nm), most do not provide their irradiance, which tells you how long it will take to kill a coronavirus. There’s no point in buying a UV wand if it means you’ll have to slowly move it around your phone for an hour . And if the irradiance is high, it can damage the skin and eyes.
If you want to try it, I recommend investing in a UVC box, where you put your phone or other items, such as credit cards, keys or watch, and leave them there for about 10 minutes. Do not use on fabrics or porous materials such as paper or cardboard, as UV light can cause shadows on non-solid objects.
One possibility is the PhoneSoap 3 smartphone UV disinfectant (€ 96), which claims to have a UVC wavelength of 254nm, which is in the correct range to kill coronaviruses. A January 2018 study, published in the Journal of the American Association for Laboratory Animal Science, found that a PhoneSoap device was more effective than a disinfectant wipe or spray containing 70 percent alcohol.
Although UVCs work faster and more reliably on non-porous surfaces like glass, plastic, metal, and varnished wood, it is probably easier, faster, and safer to clean them with a household disinfectant, rather than relying on a UV wand.
Does sunlight work to disinfect?
If UVC products are potentially a waste of time and money, you may be wondering if it’s better to hide and sunbathe, as sunlight contains UV rays.
But the UVC light from the sun is blocked by Earth’s atmosphere. When you go outside on a sunny day, the UV light that hits you is UVA and some UVB, and these guys don’t destroy coronaviruses quickly.
That said, there is some emerging evidence that sunlight is effective against the new coronavirus. The preliminary investigation, conducted by the US Department of Homeland Security, found that simulated sunlight (equivalent to midday sun on a sunny day) evaporated COVID-19 droplets after three minutes on both non-porous surfaces and the air.
But that doesn’t mean you should throw social distance into the wind this summer. If you are outside and inhaling the drops from an infected person near you, you could still get sick.
That’s one reason why high temperatures and UV radiation are believed not to reduce the spread of COVID-19 , according to an April 2020 study published in the European Respiratory Journal. So if you want to protect yourself from lightning, do it, but put on sunscreen, wear a mask and stay at least two meters away from everyone around you.
