For some time now, it’s been established that the primary root of SARS-CoV-2 transmission is airborne. Research suggests that contagious particles are released into the air and linger for several minutes to hours. Inhaling these particles is what leads to infection. People have experimented with ways to sterilize the air from infectious particles. Here we describe work that shows, in addition to ventilation and filtration, how Far-UVC light inactivates the virus in a way that is harmless to us.
Past uses of ultraviolet light
Germicidal ultraviolet light has been demonstrated to work in reducing the transmission of several bacterial and viral infections. Some which include lessening the transmission of measles, mumps, and has shown to inhibit the spread of tuberculosis by 70% after being tested on guinea pigs in an experiment. A major challenge, however, has been its long wavelength of 254 nm which is detrimental to humans, causing skin cancer and scarring the eyes. Even with caution, accidental exposure of germicidal ultraviolet light can occur, leaving people at risk for painful burns and scarring.
Far-UVC is harmless to humans
To circumvent the effects of germicidal ultraviolet light, a group of scientists at Columbia University Irving Medical Center experimented with a different form of ultraviolet light known as Far-UVC. This light has a shorter wavelength (200-230nm), inhibiting its ability to penetrate human skin while still being able to attack small viral air particles efficiently.
Measuring the efficacy of Far-UVC viral inactivation
To measure the rate of airborne viral inactivation, Eadie et al. used a room-sized chamber that simulated an office work-space. The ventilation simulated a normal work environment with 3-air-changes per hour. At the same time, Staphylococcus aureus aerosols were deployed into the room until a steady concentration was reached. This process lasted around 60 minutes. Five Far-UVC lamps were then turned on from overhead lights with their emission directed towards the ground. In the span of five minutes, the inactivation of bacterial particles in the air was reduced by 98%. The experiment was also repeated with different levels of Far-UVC (i.e. high, medium, low), with aerosol particles being continuously released in the environment to test the efficacy of the levels. The best results were obtained when Far-UVC was maintained at high or medium level.
Figure 1. 3D schematics of the bioaerosol chamber configuration showing room dimensions, the position of the lamps, pathogen source and collection point (top) with an illustrative example of the Far-UVC lamp emissions (bottom).
Advantages of Far-UVC
A key advantage of using this light technology is that viruses are not able to mutate under Far-UVC as they generally would if introduced into the human body first. Eadie et al. also confirm that current and future variants of SARS-CoV-2 are no exception to inactivation. Another advantage of Far-UVC is that it may not require mixing of “good air” to work as you normally would with an air cleaners or GUV.
Figure 2. Percentage of viable airborne S. aureus remaining plotted on a linear y-axis
While Far-UVC has been shown to work in real-life environments, precautions such as light intensity and exposure time are equally as important when considering this light technology on a large scale.
Although SARS-CoV-2 has prevented most of us from being in large indoor spaces, Far-UVC gives us confidence moving forward with the pandemic for safer environments. It is vital that we take air quality seriously especially in our public spaces including: schools, concert halls, bars, restaurants, etc. While Far-UVC works best when accompanied with ventilation/filtration of air, wearing a mask, washing our hands, and getting vaccinated cannot be forgotten.