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For decades, scientists have known about the disinfection ability of UV lights, specifically germicidal UV lights (also known as UV-C lights).

In recent years, germicidal UV lights helped stop the spread of numerous pathogens like the flu and the superbug. Can germicidal UV lights also fight the novel coronavirus (or COVID-19)?

The COVID-19 situation is rapidly changing, and it’s causing priorities to shift for a lot of us. Protecting patients, customers, workers, and our families is more important than ever before. Disinfecting frequently used surfaces is extremely important, and UV light is very effective at killing pathogens like viruses and bacteria.

Germicidal UV light products tout pathogen kill rates higher than a 99.9% rate. Because of their effectiveness, they’re incredibly useful right now for hospitals, medical labs, senior care centers, fire and police stations, and airports, but can also be used in schools, government buildings, office buildings, and hotels.

What is UVC or germicidal UV light?

Germicidal UV light is a type of light that’s best known for its ability to kill bacteria. It’s typically used to disinfect rooms and surfaces. COVID-19 can live on certain surfaces for up to three days, so it’s critical to disinfect at regular intervals. Germicidal UV light can include far-UVC light and UVC light, as noted in the chart below.

Germicidal UV light wavelengths

Germicidal UV light, or UVC light, is a particular spectrum of ultraviolet light (UV). UV light occurs naturally from the sunlight or can be generated artificially in light fixtures and bulbs.

You won’t be able to see light produced from germicidal UV lights because UV light does not produce visible light.

UV wavelengths can range anywhere from 10 nanometers (nm) to 400 nanometers (nm).
UVC light (germicidal UV light) falls between 200 to 280 nm.

UV-B and UV-A light can also kill bacteria and germs, but exposure can be dangerous and should only be used in certain applications. UV-A light can only kill certain types of bacteria, so it is ineffective against viruses like COVID-19.

 

How do UVC lights kill viruses?

Germicidal UV lights can actually change the DNA and RNA of bacteria and viruses, destroying their ability to reproduce.

Bacteria may be resistant to other things like antibiotics, but cannot build up a resistance to UV light.

The big question right now: Can UV lights kill COVID-19?

Because this a novel, or new, coronavirus, the testing is very limited. The structure of COVID-19 is different than past viruses. For that reason, there is not enough data to say that UV lights can kill COVID-19.

Here is what scientists do know. Pathogens can be ranked based on their tolerance to disinfectants, like UV lights. Coronaviruses fall into the category of “enveloped viruses,” or a Class 3. Class 3 viruses are the easiest to kill. Products that are able to kill more resilient viruses like small and large non-enveloped viruses (Class 1 & 2 viruses) should also be able to kill enveloped viruses like coronaviruses. Many UV lighting manufacturers say their products can kill most Class 1 viruses.

Based on this information, UV lights are believed to be effective at killing COVID-19. Since the virus is so new, official testing against the novel coronavirus should be underway soon.

We can look to previous coronaviruses, such as SARS and MERS, for insight. Studies on both SARS and MERS show that UV light could inactivate the viruses, so it’s not unreasonable to expect that it will have a similar effect on COVID-19.

It’s also important to note UV light does not replace other cleaning measures like washing hands or removing dirt and dust from surfaces. Those are still important actions to take to prevent the spread of COVID-19 and other germs.

Is germicidal UV light safe?

Artificial UV light, just like overexposure to the sun, is known to cause side effects for humans like skin cancer and cataracts.

For safety reasons, most UV products run when there is no one in the room.

However, there are studies that show certain wavelengths of UV light may be safer than others while still killing bacteria.

For example, one study in particular focuses on the use of far-UVC light. That’s between the wavelengths of 207 and 222 nm.

Far-UVC is believed to be just as effective at killing germs as higher ranges of UV-C light, but less harmful to our skin and eyes because the light cannot penetrate human skin.

Other studies suggest that wavelengths as low as 185 nm can still germs.

UV light can also be harmful if it’s used in the wrong application or in the wrong fixture.

Here’s the bottom line when you’re selecting germicidal UV light products: Make sure you buy the right light bulb for the right fixture and follow product use guidelines.

Advantages of germicidal UV light

Germicidal UV lights are extremely effective and have several major advantages.

  • Pathogen kill rate – Tests show that germicidal UV lights kill up to 99.9% of bacteria and viruses. On top of that, pathogens cannot become resistant to UV light like they can certain antibiotics and antibacterial products.
  • Limited chemical exposure – UVC lights work in place of potentially harmful chemicals. It’s safe to enter a room after germicidal UV lights are at work, but it might be hard to breath in a room that has just been sprayed down with chemicals.
  • Lighting configurations – There are multiple lighting configurations for germicidal UV light, including mobile fixtures. Mobile units are a great option for hospitals, airports, fire and police stations, and the hospitality industry because they’re easy to move from room to room. Plus, mobile units are a budget-friendly option compared to installing fixtures in every room.

One important note: UVC light bulbs should only be used in the appropriate light fixtures.

From original article on regencylighting.com

More references about UV light:

Welch, D., Buonanno, M., Grilj, V. et al. Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseasesSci Rep 8, 2752 (2018). https://doi.org/10.1038/s41598-018-21058-w
Wai Szeto, W. C. Yam, Haibao Huang & Dennis Y. C. Leung: The efficacy of vacuum-ultraviolet light disinfection of some common environmental pathogensBMC Infect Dis 20, 127 (2020). https://doi.org/10.1186/s12879-020-4847-9
Willie Taylor, Emily Camilleri, D. Levi Craft, George Korza, Maria Rocha Granados, Jaliyah Peterson, Renata Szczpaniak, Sandra K. Weller, Ralf Moeller, Thierry Douki, Wendy W.K. Mok, Peter Setlow DNA damage Kills Bacterial Spores and Cells Exposed to 222 nm UV Radiation Applied and Environmental Microbiology Feb 2020, AEM.03039-19; DOI: 10.1128/AEM.03039-19
Colorado company uses UV lighting technology to kill 99.9 percent of bacteria and viruses. Fox Denver, 7 Macrh 2020
Coronavirus: Robots use light beams to zap hospital viruses. BBC News, 20 March 2020
UV light is nature’s disinfectant, but can it kill coronavirus? Digital Trends, 24 March 2020
How UV LEDs Might Help to Diminish Coronavirus. Led Inside, 03 February 2020

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