October 8, 2020
UVC light has been shown to inactivate coronavirus
Ultraviolet (UV) light is produced by the sun and by special lamps. There are three types of UV light—UVA, UVB, and UVC. UVC light includes wavelengths of light from 200 to 280 nanometers. These UVC wavelengths have the most energy of the three types of UV light. Energy from UVC wavelengths is absorbed by, and quickly destroys, the genetic material inside viruses and other microbes, rendering them inactive.
In a few laboratory experiments, UVC light has been found to destroy the ability of the SARS-CoV-2 virus to infect a host (for example, a mouse or a person), another indication that it is effective against germs. UVC light has also been shown to inactivate the genetic material in other coronaviruses.
Sunlight does not affect coronavirus as quickly as UVC light
UVC light from the sun is blocked by Earth’s atmosphere. When you go outside on a sunny day, the UV light that reaches you is mostly UVA and some UVB. These types of UV light do not destroy viruses as quickly as UVC light.
With enough time, UV light from the sun can break down coronaviruses, but it’s not a good strategy to use to disinfect your skin. The amount of exposure to the sun’s UV light that it would take to break down coronaviruses or other germs may give you a sunburn if you are not wearing sunscreen!
The best ways to protect yourself from COVID-19 are to wash your hands, keep your distance from other people, wear a mask when you are outside your home or can’t keep your distance from others, clean and disinfect frequently touched surfaces, and avoid crowded indoor spaces.
UVC light can safely disinfect objects, surfaces, and spaces
Water, air, and some surfaces and spaces are hard to clean. UVC light can be used for disinfection in these settings. For example, UVC lamps and robots are used to sanitize water, surfaces in empty hospital rooms, and large vehicles such as buses.
UVC lights can be used in the unoccupied space in a room to inactivate viruses and other microbes in the air. The lights are positioned in the upper part of the room at a height of at least 8 feet (2.4 meters). They are angled to shine toward the ceiling rather than down at the floor. Using fans along with the lights ensures that air from the lower part of the room moves to the upper part of the room and vice versa. In this way, all the air in the room is exposed to the UV lights, so any floating germ is inactivated. UVC lights can also be placed in air ducts to inactivate viruses and other germs in air that moves from one room to another.
It’s important that UVC lights used in rooms that people are in don’t shine down into the room. High-intensity UVC light can damage the eyes and skin in just a few seconds.
Scientists are exploring specific wavelengths of UVC light
Most UVC lamps shine a broad spectrum of UVC wavelengths (200–280 nanometers) or a specific wavelength of 254 nanometers. Research has shown that shorter-wavelength UVC light, for example 222 nanometers, also inactivates airborne viruses (including SARS-CoV-2) and other microbes. This wavelength of UVC light is often referred to as far UVC light, and it may be safe to use in occupied spaces. In studies with mice and rats, no damage to the skin or eyes has been found from far UVC light. However, more research is needed to verify that people can be exposed to this wavelength over periods of time without harmful side effects.