Using UV light to kill coronavirus: The benefits and risks

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With man-made hand sanitizer in short supply, many people are turning to what’s been called “nature’s hand sanitizer,” or ultraviolet light. UV light is the latest popular tool in the ongoing race to find ways to prevent oneself from catching SARS-CoV-2, the virus that causes COVID-19. 

Disinfection by way of UV light is nothing new: The International Ultraviolet Association says it’s been a useful technology for over 40 years, contributing to clean water and clean air. Many consumer devices also use UV light to disinfect things, such as self-cleaning UV light water bottles and UV-emitting cases that clean your dirty phone. 

When it comes to the coronavirus, though, things aren’t so clear-cut. There are risks that come with using UV light devices, especially when using them on your skin. Before ordering the first UV light sanitizer you see, read up on the current evidence about UV light disinfectants and the potential risks of using them on yourself.  

How do UV light hand sanitizers work? 

A quick primer on UV light: UV light comes primarily from the sun, but there are also man-made sources of UV light, including tanning beds and the currently buzzed-about UV disinfection lamps. 

There are three classes of UV light: UV-A, UV-B and UV-C.

UV-A and UV-B light cause sunburns and premature skin aging, and exposure to both is associated with the development of skin cancer. UV-C light, which has the most energy of all three types, is the most harmful, but it fortunately doesn’t reach the Earth’s surface because our atmosphere absorbs it. 

There’s man-made UV-C light, too: It’s what’s in the UV light sanitizers that companies claim kill the coronavirus. According to the National Academy of Sciences, it’s probable that this is true, because UV light has been used to disinfect surfaces and water for a long time, and it’s generally successful. 

It works because UV-C light is strong enough to destroy the genetic material — either DNA or RNA — of viruses and bacteria. There’s no evidence right now that UV-A and UV-B rays can kill the coronavirus, so no, going outside on a sunny day won’t reduce your risk of catching it.

Can UV light kill the coronavirus? 

Based on the available scientific evidence that UV light can destroy various viruses, it’s probably true that UV light can kill SARS-CoV-2 — but keep in mind that no published, peer-reviewed studies to date have looked specifically at the effect of UV light on the virus that causes COVID-19.

The National Academies of Sciences, Engineering and Medicine reported that ultraviolet light probably can kill the coronavirus. “UV light has been shown to destroy other coronaviruses, so it will probably work on the novel coronavirus,” the website reads. This includes the deadly Middle Eastern respiratory syndrome coronavirus, aka MERS-CoV and severe acute respiratory syndrome-related coronavirus, or SARS.

But there’s one huge caveat: “UV light damages human skin, so it should only be used on objects or surfaces,” the NASEM continues. 

This means you should not use UV light as a hand sanitizer. Stick to washing your hands with soap and water (following proper hand-washing guidelines), or using an alcohol-based hand sanitizer when soap and water aren’t available. 

The WHO echoes this, reporting on its coronavirus myth-busters webpage that people should not use UV lamps to disinfect their hands or other areas of skin, as UV radiation “can cause skin irritation and damage your eyes.” 

Though scientists are working on ways to make these powerful disinfecting products safe for people to use, current devices are not safe to use on your body. This is partly because many (if not most) of these products are not FDA-approved or approved by any governing health agency, for that matter. 

This means what you see may not be what you get — an extremely important consideration, because although very low-dose, far-range UV-C light may not harm humans or animals, using too powerful a dose too close to your skin can indeed be harmful. 

These devices “tend to come in many different shapes, sizes and strengths, and thus their antimicrobial ability may be variable,” says Dr. Tyler Hollmig, director of dermatological surgery at University of Texas Dell Medical School in Austin. Consequences of using UV-C light on your body can include severe sunburn-like burns and retinal damage. 

Plus, Dr. Hollmig continues, as UV light devices “are often not cheap — especially relative to more standard disinfectants that we know work — these may not be the most efficacious way to clean. It is also worth at least just reinforcing the fact that no UV light device should be a substitute for hand washing, mask-wearing and distancing.” 

UV light hand sanitizers and skin health concerns

Dr. Hollmig helps break down UV light as it relates to skin health. UV light is classified into types based on wavelength, he says, with UV-A light (the longest wavelength) being most associated with skin aging and also with certain skin cancers, and UV-B light (middle wavelength) being associated with sunburn and most skin cancers. 

“UV-C light has the shortest spectrum of wavelengths, but is probably the most toxic,” Dr. Hollmig says. “Fortunately, the atmosphere filters out UV-C, so our skin and eyes are typically not exposed to it.” 

UV-C light is what’s used by sanitizers to kill or inactivate microorganisms by destroying and disrupting their nucleic acids, Dr. Hollmig explains, so if the device is properly tested and properly used, it works to kill pathogens — but something that powerful also has the potential to harm skin. Some potential problems? It can cause burns and is a known carcinogen (as is all UV light), Dr. Hollmig says.

All types of UV light, “including those reaching the Earth’s surface from the sun and those emitted by tanning beds, have not been shown to be protective against the novel coronavirus and can certainly harm the skin,” Dr. Hollmig says. “Additionally, since UV sanitizers employ UV-C light, which can be dangerous, care should be taken to avoid exposure to the skin and eyes. These devices are not designed to be used to disinfect the skin and can be dangerous if used improperly.”

Other consumer devices that are intended to disinfect or purify a surface or substance like this PhoneSoap case should be safe to use if you follow the instructions carefully. Self-cleaning water bottles that use UV-C rays to kill germs like Larq should also be safe when used properly, because they typically only work when the cap is screwed on tight, so no UV-C light can leak out.   

Is UV light in buildings safe? 

Consumer devices aren’t the only place to find UV light sanitization. Some brick-and-mortar businesses are installing UV light fixtures in their facilities in an attempt to completely disinfect the building and mitigate the risk of contracting COVID-19 through air or surfaces. 

Again, because UV light is the primary germ-killer in the natural environment, it makes sense to take this approach. This practice, called “ultraviolet germicidal irradiation,” has long been used in hospitals where pathogens abound.

New York-based Magnolia Bakery is one such business, claiming to be the first business in the city to install human-safe UV light fixtures, including a portal through which all customers walk in an attempt to destroy any pathogens that may be living on the skin. In a press release, Magnolia Bakery says the dose is low enough to avoid health complications such as burns or eye irritation. 

While the effectiveness of environmental UV sterilization on surfaces such as floors has been confirmed, however, further research is needed about the safety of indoor UV light fixtures, as well as its efficacy at sterilizing clothes and human skin. 

Plus, the Centers for Disease Control and Prevention say UV light “germicidal effectiveness and use is influenced by organic matter; wavelength; type of suspension; temperature; type of microorganism; and UV intensity.” To effectively kill viruses, UV-C light must be emitted in a range of 200 to 280 nanometers, which has potential for harm.  

That’s a lot of stuff to consider, and something that manufacturers who are trying to quickly create UV lights may inadvertently (or purposely) ignore. It’s happened before: In the past, the Federal Trade Commission called out manufacturers for making false claims about what their light-based products could do.

The International Ultraviolet Association concurs with the CDC, reporting that inactivation of viruses with UV light has been “demonstrated under controlled conditions in the laboratory,” and that “the effectiveness of UV light in practice depends on factors such the exposure time and the ability of the UV light to reach the viruses in water, air, and in the folds and crevices of materials and surfaces.”

In sum: Don’t use any UV light devices directly on your skin. Be careful about using UV light devices on in-home surfaces. Do your research before going to establishments that have installed UV light fixtures. And definitely do not try to get any form of UV light (or any disinfectant, for that matter) inside of your body. 

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.