We live in an era where many of us know a thing or two about hand sanitizers, antimicrobial sprays, and disinfectant wipes. But when it comes to killing germs, bacteria, and viruses, we have options beyond just spraying and wiping surfaces. Enter: light.
Of all the germ- and virus-fighting techniques in existence today, light may not be the first thing that comes to mind, but it can have powerful disinfecting properties when used properly. Specifically, a type of ultraviolet light (or radiation) called ultraviolet-C (UVC) has been found to kill germs and bacteria and cut the transmission of superbugs, such as MRSA. Now, in the midst of the COVID-19 pandemic, people have turned to UVC light as a tool to disinfect surfaces.
The history of UV for disinfection
According to the Centers for Disease Control (CDC), UVC radiation has long been used as a disinfectant for air, water, and other nonporous surfaces. In 1903, physician and scientist Niels Finsen won the Nobel Prize for discovering that UV light could kill germs. In 1935, a researcher named William F. Wells used UV light to disinfect the air in a room where people had emitted droplets by sneezing or coughing. By the 1950s, some hospitals used it in wards where patients suffered the highly contagious lung disease tuberculosis.
UV light falls into three classes, depending on the wavelength of the light. UVA and UVB, which have the longest wavelengths, are both found in sunlight and are the variants that cause sunburn. UVC, the shortest wavelength, doesn’t normally make it through the earth’s atmosphere — but it can be created using UVC lamps or wands.
The Disinfecting power of UV light
Because of its success in killing the SARS-Coronavirus-1, the Food and Drug Administration (FDA) says UVC radiation may also be effective at inactivating the SARS-CoV-2 virus, which is the virus that causes COVID-19. So how does UVC light kill bacteria and viruses? UVC radiation destroys the outer protein coating of virus or bacteria it is attacking, according to the FDA. However, the UVC radiation must be directly exposed to a virus in order to inactivate it. Surface contaminants such as dust, soil, or bodily fluids can block the effects of the UVC light.
UVC radiation is typically found inside air ducts to disinfect the air, particularly in public spaces. However, UVC lamps can be purchased for use at home. The FDA warns that consumer versions often produce a very small dose of light, as a safety mechanism to prevent potential skin or eye burns, and thus require a longer exposure time to inactivate any bacteria or virus. The most lethal wavelengths to bacteria and viruses fall between 250 to 750 nanometers (nm), with 262 nm considered “peak germicidal wavelength.”
There are a number of UVC lamp products to choose from, though some may not be available to consumers who don’t work within a medical institution.
- Low-pressure mercury lamp: This is the most common type of lamp used to produce UVC, which emits around 254 nm.
- Excimer lamp or Far-UVC lamp: This type of lamp has a peak emission of around 222 nm.
- Pulsed xenon lamps: These lamps, which offer short pulses of UVC light, emit mainly UVC radiation. Pulsed xenon lamps are typically used in hospitals and operating rooms, or spaces where no people are present.
- Light-emitting diodes (LEDs): Light-emitting diodes (LEDs) emit a very narrow wavelength band of radiation, with emissions ranging between 214 nm and 273 nm on average. These lamps do not contain mercury, but the small surface area may also make them less effective.
While the research on the efficacy of UVC on SARS-CoV-2 is still underway — and thus not yet conclusive — researchers suggest a UVC device can likely be a powerful aid in reducing COVID-19 in the air and on high-touch items and surfaces including:
- Computers and computer accessories
- Remote controls
If you purchase a UVC lamp, keep these safety concerns in mind.
- Never look directly at your UVC light — it can cause eye injury.
- Do not use it to disinfect your skin — it can cause skin irritation and burns.
- Some UVC lamps produce ozone, which can irritate lungs.
- If your UVC lamp contains mercury, a toxin even in the smallest amounts, be extremely careful not to break the lamp.
For many situations, proper cleaning procedures — including hand washing and disinfecting surfaces with the proper cleaning supplies — can effectively prevent the spread of germs, bacteria, and viruses. But when used in conjunction with other disinfection practices, UVC light may be another powerful tool to stop the spread of COVID-19 and other viruses, so long as it is used safely.