A handful of N95 respirators get zapped with UV radiation.
A handful of N95 respirators get zapped with UV radiation. (Image credit: Shutterstock)

Ultraviolet light has been used to stop pathogens in their tracks for decades. But does it work against SARS-CoV-2, the virus behind the pandemic?

The short answer is yes. But it takes the right kind of UV in the right dosage, a complex operation that is best administered by trained professionals. In other words, many at-home UV-light devices claiming to kill SARS-CoV-2 likely aren't a safe bet. 

UV radiation can be classified into three types based on wavelength: UVA, UVB and UVC. Nearly all the UV radiation that reaches Earth is UVA, because most of UVB and all of UVC light is absorbed by the ozone layer, according to the Centers for Disease Control and Prevention. And it's UVC, which has the shortest wavelength and the highest energy, that can act as a disinfectant. 

Related: What is ultraviolet light?

"UVC has been used for years, it's not new," Indermeet Kohli, a physicist who studies photomedicine in dermatology at Henry Ford Hospital in Detroit, told Live Science. UVC at a specific wavelength, 254 nanometers, has been successfully used to inactivate H1N1 influenza and other coronaviruses, such as severe acute respiratory virus (SARS-CoV) and Middle Eastern Respiratory Syndrome (MERS-CoV), she said. A study published June 26 to the preprint database medRxiv from Kohli's colleagues awaiting peer review now confirms that UVC also eliminates SARS-CoV-2. 

UVC-254 works because this wavelength causes lesions in DNA and RNA. Enough exposure to UVC-254 damages the DNA and RNA so that they can't replicate, effectively killing or inactivating a microorganism or virus. 

"The data that backs up this technology, the ease of use, and the non-contact nature" of UVC make it a valuable tool amid the pandemic, Kohli said. But responsible, accurate use is critical. UVC's DNA-damaging capabilities make it extremely dangerous to human skin and eyes, Kohli said. She cautioned that UVC disinfection technologies should primarily be left to medical facilities and evaluated for safety and efficacy by teams with expertise in photomedicine and photobiology. 

When it comes to a-home UVC lamps, their ability to damage skin and eyes isn't the only danger, Dr. Jacob Scott, a research physician in the Department of Translational Hematology and Oncology Research at Cleveland Clinic, said. These devices also have low quality control, which means there's no guarantee that you're actually eliminating the pathogen, he said.  

"UVC does kill the virus, period, but the issue is you have to get enough dose," Scott told Live Science. "Particularly, for N95 masks, which are porous, it takes a pretty big dose" of UVC-254 nm to eliminate SARS-CoV-2. This kind of accuracy isn't possible with at-home devices. 

In hospitals, the geometry of the room, shadowing, timing and the type of material or object being disinfected are all accounted for when experts determine the right dosage of UVC needed to kill pathogens. But that kind of "quality assurance is really hard out in the world, out in the wild," Scott said. At-home devices don't offer that kind of precision, so using them could offer a false assurance that SARS-CoV-2 has been eliminated when it hasn't, he noted. "Having something you think is clean, but it's not, is worse than something that you know is dirty" because it affects your behavior toward that object, he said. 

Both Kohli and Scott and their teams are working to make UVC disinfection of personal protective equipment (PPE), such as face masks and N95 respirators, more efficient. Kohli's group advises hospitals and vendors repurposing existing UVC equipment for N95 respirator decontamination. Scott's group developed a machine that can be used by smaller medical facilities and a software program that helps users factor in the geometry of the disinfection room so that staff can deliver the most effective dose of UVC. 

There are ongoing conversations in the field about installing UVC units in ceilings to decontaminate circulating air, Kohli said. And others are researching another wavelength of UVC called UVC-222 or Far-UVC, which may not damage human cells, she added. But that will require more research, Kohli said.  Still, it's clear that "used accurately and responsibly, UVC has enormous potential."

Originally published on Live Science.

Donavyn Coffey
Live Science Contributor

Donavyn Coffey is a Kentucky-based health and environment journalist reporting on healthcare, food systems and anything you can CRISPR. Her work has appeared in Scientific American, Wired UK, Popular Science and Youth Today, among others. Donavyn was a Fulbright Fellow to Denmark where she studied  molecular nutrition and food policy.  She holds a bachelor's degree in biotechnology from the University of Kentucky and master's degrees in food technology from Aarhus University and journalism from New York University.

  • kristi276
    The authors of this article should be cautious about what they write, they should remember we have Twiddle Dum for president. When he reads this article he will, hopefully not, proudly proclaim that he was right all along. Ultra-violet rays do kill the virus. Now we just have to create the means of exposing patients of COVID-19 to UVA rays. Maybe we can create a giant UVA ray gun, and disinfect the whole country in one swoop? With the use of bleach and UVA rays, we will defeat this invisible public enemy number one; just like we defeated the Invisible Man. UVAs anyone? We know it works. Drink bleach. Bath in the glow the after-glow of radiation. You'll be glad you did. Drink to your death (health).
    Reply
  • danr2222
    "...used to inactivate H1N1 influenza and other coronaviruses, such as..."

    This needs re-wording for clarity; H1N1 isn't a coronavirus; no influenza is.
    Reply
  • Ron McCune 2
    Being that certain filters can catch the coronavirus in the air and stop it from spreading around I would assume that these filters are at this day and age currently installed in all nursing homes and hospitals. However being that the coronavirus is rapidly spreading in hospitals and nursing homes it is obvious we have to up our game when we use filters that can stop the coronavirus as well as other viruses and germs. We now have the need and desire to design ways to use filters and ultra violet light and laser treated copper and any other stuff to stop the coronavirus from being in the indoor air at everywhere we are be it home, work, school, store, office, hospital, nursing home, sporting events and everywhere else we live or work in. To stop the spreading of the coronavirus by air must be a major goal of ours. If we can stop the spread of coronavirus by air then we will have to only stop the coronavirus by touch which is a lot easier task than doing things to stop the air transmission of the coronavirus as well as other germs and viruses. To stop the coronavirus by touch can be done by cleaning and handwashing and using new practices that insures that you wipe your hands every time you touch something. Oh, and most important, DON"T touch your mouth or nose! Think of this coronavirus thing as a cross contamination game. A person gets the coronavirus. That person can spread it around through the air and whatever droplets of body fluids that person leaves around which then is touched by someone else who then transfer that coronavirus molecule into their body by way of mouth, nose, and maybe eyes too. So this is the world we live in and we have to figure out better ways to live in it! We have to put air ventilators everywhere that can stop the coronavirus. We have to do this immediately in hospitals, nursing homes, schools, elevators, stairways, lobbys, businesses and public buildings. These new air ventilators would be numerous in larger settings such as gyms and smaller in places like elevators. There would be different room size systems. It seems that we will have to design new equipment to do all of what I have suggested over my many postings because I'm sure that already we use coronavirus fighting filters in all public ventilation systems. So I believe we now have to make gadgets that can hang about 2 feet over our heads in areas of the rooms that we congregate in inside buildings. These gadgets would suck the air in a intake part of th gadget, run that air through a filter and other things installed in that gadget that will stop the coronavirus. Then the air will exit the gadget with the air free from the coronavirus as well as other germs and viruses. Doing this will insure that the coronavirus and other viruses and germs won't be spreading around so much which means a lot less people will be getting sick or dying from the coronavirus as well as the flu and colds. Doing this will save lives and misery and money for us all! So let's get the job started and put on our thinking caps as we figure out ways to get this coronavirus out of our air and off of anything else it may be on! Once we do this people will feel more comfortable going out in public. The businesses that do this first will see will see increased customers quicker as well as healthier workers and patients. Doing this may be the ONLY way we are ever going to get rid of this coronavirus. It will surely cut down on the rate of infection! We can't rely on a vaccine to save us from this coronavirus as well as other germs and viruses. We can't rely on the vaccine makers to have to yearly design vaccines to save us from illnesses. For many those vaccines don't work well enough to prevent illness and death. So it's time we start using mechanical means to kill the coronavirus as well as other germs and viruses! The sooner we do it the better off we all are!

    Another thought about this coronavirus situation. It's a fact that this coronavirus molecule will sit in the air for a while where it can travel around and maybe infect someone else. Well why don't we use some kind of sticky stuff to capture the virus as it travels around areas that we are. If we put in large sticky pads of something inside of something and have air blow on it then the viruses and germs should stick to the sticky stuff. No virus or germ can get away from getting stuck! Add some disinfectant stuff or something else that could help the sticky stuff kill the coronavirus and other viruses and germs. Add these sticky pads to the laser treated copper stuff I talked about earlier and we may end up with a contraption that will surely kill a simple thing as a moist molecule laced with some killer ability called the coronavirus. Surely we should be smart enough to kill a molecule floating in the air? Aren't we?
    Being that laser treated copper can kill the coronavirus under certain circumstances don't you think that we should set up the circumstances in which things are happening that are causing the laser treated copper to actually kill the virus! The scientist that discovered this said that the laser treated copper surface had a hard time killing the virus because of the coronavirus itself was too small for the laser treated copper to kill it. But what if we were to have a new kind of fan made of of multiple strands of laser treated copper wire that has 3 sharp U shape sharp twisted ridges that are attached to a 1-5 feet fast turning fan pole. Then put a laser treated copper plague of whatever size you need in front of the fans in the air vents and hallways and wherever else you have them. The fans fast moving air current will cause the Coronavirus to slam into the laser treated copper plague and shred apart also. Have this device in the vent shafts and hallways and corridors and E.R. rooms and all hospitals and nursing homes and offices and stores and in homes, rooms and areas where the sick are and where we live and work. Add some ultra-violet light to the fan and we will then have a way to stop or drastically slow the transmission of the Coronavirus! This fan must be the new kind of fan that will help us all stop this Coronavirus!




    The brain is a biological computer that can manufacture all of us and every living thing on Earth. Each species has a unique brain that takes the food the we give ourselves and makes us whatever we may be biologically programed to be. If the human body needs 9 different amino acids to create all the different kinds of cells that the body needs to make us then why not give the body the 9 different amino acids in every day meals to ourselves and see what happens because then that biological computer in our minds can then maybe have the cure for fighting the coronavirus and all it needed was the combination of all those 9 amino acids in our food daily to make the cells to overtake the damage that the coronavirus can cause. There is a recipe for a food dish called Adelynn's Miracle Beans recipe that has all the 9 different amino acids as well as many other nutrients the body needs. Perhaps if we were to give those that are sick from coronavirus 2 servings of this Adelynn's Miracle Beans recipe daily 5-6 hours apart and also give 2 Centrum equivalent vitamins with a bean meal 5-6 hours apart. This will give one's body all the proteins, vitamins and minerals that a human body needs to create any kind of blood cell. Maybe the human body will figure out a way to kill the coronavirus as well as other flues and colds if we give it the ingredients for it to do so! Someone try it. It beats dying or suffering from the illness. I know that taking 2 Centrum equivalent in one day with a meal 5 hours apart does help one get rid of the flu and colds because I have been doing it for 25 years and it always help me stop getting sicker every time I felt like I was getting the flu. So maybe eating Adelynn's Miracle Beans and taking the vitamins will help make people with the coronavirus get better.
    Reply
  • Etherair
    kristi276 said:
    The authors of this article should be cautious about what they write, they should remember we have Twiddle Dum for president. When he reads this article he will, hopefully not, proudly proclaim that he was right all along. Ultra-violet rays do kill the virus. Now we just have to create the means of exposing patients of COVID-19 to UVA rays. Maybe we can create a giant UVA ray gun, and disinfect the whole country in one swoop? With the use of bleach and UVA rays, we will defeat this invisible public enemy number one; just like we defeated the Invisible Man. UVAs anyone? We know it works. Drink bleach. Bath in the glow the after-glow of radiation. You'll be glad you did. Drink to your death (health).
    Sigh, sarcasm works best if based on facts.
    The entire thrust of the article was how UVA and UVB are useless against virus, period. And it further points out how UVC kills not only virus but also destroys all DNA by unraveling the strands. This destroys ALL life, including the virus.
    This aspect is where the sarcasm should start. Our appointed president thinks having a UVC ray eating its way to an infected persons lungs, destroying all in its path, is a solution.
    Surely that can be made to sound humorous. Is not any death not our own funny? Is Trump wrong on that also?

    Sorry for the cold water and sourness, I have lost most of my sense of humor with the deaths passing 135,000 today and 500,000 beginning to look like the lowest number of unnecessary dead expected under current policy.
    "No laughs left 'cause we laughed them all, in a very short time"
    Reply
  • cecilia fx
    kristi276 said:
    The authors of this article should be cautious about what they write, they should remember we have Twiddle Dum for president. When he reads this article he will, hopefully not, proudly proclaim that he was right all along. Ultra-violet rays do kill the virus. Now we just have to create the means of exposing patients of COVID-19 to UVA rays. Maybe we can create a giant UVA ray gun, and disinfect the whole country in one swoop? With the use of bleach and UVA rays, we will defeat this invisible public enemy number one; just like we defeated the Invisible Man. UVAs anyone? We know it works. Drink bleach. Bath in the glow the after-glow of radiation. You'll be glad you did. Drink to your death (health).
    oh, not to worry. Twiddle Dum doesn't read. And he especially doesn't read science articles.
    Reply
  • Duaney
    kristi276 said:
    The authors of this article should be cautious about what they write, they should remember we have Twiddle Dum for president. When he reads this article he will, hopefully not, proudly proclaim that he was right all along. Ultra-violet rays do kill the virus. Now we just have to create the means of exposing patients of COVID-19 to UVA rays. Maybe we can create a giant UVA ray gun, and disinfect the whole country in one swoop? With the use of bleach and UVA rays, we will defeat this invisible public enemy number one; just like we defeated the Invisible Man. UVAs anyone? We know it works. Drink bleach. Bath in the glow the after-glow of radiation. You'll be glad you did. Drink to your death (health).
    "Twiddle Dum" has to rely on what his advisors inform him, and I don't see how he's wrong to ask questions, but I do think it's wrong to disrespect our President like this in this forum. Having said that, I would remind everyone that as soon as the truth about the Covid 19 was revealed ( belatedly), by the WHO, President Trump immediately initiated the travel ban from China, this action could very well have saved the lives of many thousands of Americans. Virtually all of the Democrats, criticized this move, showing that they would have managed this crisis terribly. Just to add one more item, Trump has been proven correct about the Hydroxychloroquine.
    Reply
  • Duaney
    Why didn't the authors mention anything about the Ultra-Violet light that occurs naturally outside in the sun light??
    Reply
  • cecilia fx
    Duaney said:
    "...... I would remind everyone that as soon as the truth about the Covid 19 was revealed ( belatedly), by the WHO, President Trump immediately initiated the travel ban from China, this action could very well have saved the lives of many thousands of Americans.
    his travel ban was for Chinese nationals, not Americans. And most importantly, While Europe was also getting infected by people traveling from China, trump ignored that. Now, Americans traveling from infected Europe to the US - mostly to Airports in NY/NJ and other northeastern areas brought the virus. Naturally, those people infected the northeast.
    What he failed to do was have all travelers quarantined and tested BEFORE they set foot on US soil.

    And before you say why didn't the governors do this, well, it works best when it's a policy coming from the Federal government. One or two governors doing this isn't going to work if others do nothing. The virus WILL get in without a UNIFIED plan.
    Reply
  • Duaney
    cecilia fx said:
    his travel ban was for Chinese nationals, not Americans. And most importantly, While Europe was also getting infected by people traveling from China, trump ignored that. Now, Americans traveling from infected Europe to the US - mostly to Airports in NY/NJ and other northeastern areas brought the virus. Naturally, those people infected the northeast.
    What he failed to do was have all travelers quarantined and tested BEFORE they set foot on US soil.

    And before you say why didn't the governors do this, well, it works best when it's a policy coming from the Federal government. One or two governors doing this isn't going to work if others do nothing. The virus WILL get in without a UNIFIED plan.
    True, but there were health screenings and quarantines for Americans returning from China. We should have initiated a travel ban from Europe and quarantines and health screenings right at the same time we did China. Trump had advisors helping him, I don't think he "ignored" the European threat all by himself. Many countries were caught off guard, China and the WHO deserves much criticism for their terrible response. I had no idea there were so many Chinese flying into the United States and Europe as well as Iran, this "global" community might not be a good idea.
    Reply
  • MM70RJ
    Tramp will propose the destruction of the Ozone layer to finish the pandemic...
    And will state that COVID19 was caused by the 90's scientists and activists (disguised terrorists) that saved the O3 layer...
    Of course... if COVID19 was not a Chinese hoax supported by the WHO...
    Reply