Exposing surfaces in public facilities – offices, stores, schools, healthcare facilities and public transportation, to name a few – to ultraviolet-C light – is an effective, rapid, economical and safe way to reduce the transmission of the SARS-CoV-2 virus, according to an international team of researchers that included a professor at the Techninon-Israel Institute of Technology in Haifa.
The article, recently published in ACS Nano and titled “Back to Normal: An Old Physics Route to Reduce SARS-CoV-2 Transmission in Indoor Spaces,” was written by Technion Prof Ido Kaminer, in collaboration with Prof. Javier García de Abajo), Joan Rosell-Llompart and Prof. Andreas Meyerhans of ICREA (Catalan Institution for Research and Advanced Studied, together with Profs. Rufino Javier Hernández (University of the Basque Country), and Tilman Sanchez-Elsner (University of Southampton).
The COVID-19 outbreak, caused by the SARS-CoV-2 virus, is posing an extraordinary challenge that requires swift worldwide action for the massive use of affordable and ready-to-apply measures to drastically reduce its transmission probabilities in indoor spaces. Doing so will allow for the eventual return to conventional activities such as working at the office, going to school, or even attending entertainment events.
Studies show that the virus transmission follows two main paths. First, the virus can be transmitted through the air in droplets exhaled by infected individuals and inhaled by healthy individuals. Secondly, it can be deposited on surfaces from exhalations or hand contact. Face masks dependent on people’s compliance are essential to reduce transmission, but other measures are needed to prevent infection via surfaces.
A long series of studies suggest that virus transmission in indoor spaces is much higher than outdoors. Filters and chemicals have been presented as possible solutions to minimize this problem, but despite their effectiveness in reducing the concentration of contaminated particles and droplets passing through ventilation systems, their installation may be costly and time-consuming. In addition, some chemicals that are very effective for virus disinfection, such as ozone, can be harmful if misused.
To address this dilemma, an international team of experts in the fields of virology, immunology, aerosols, architecture, and physics studied various methods to prevent the spreading of SARS-CoV-2 in indoor spaces. Based on their findings, they are advocating virus inactivation by UV-C light.
There are three types of ultraviolet light. The first is UVA, which makes up the vast majority of the ultraviolet radiation reaching the Earth’s surface. It can penetrate deep into the skin and is thought to be responsible for up to 80% of skin ageing, from wrinkles to age spots.
The second is UVB, which can damage the DNA in our skin, leading to sunburn and eventually skin cancer. It can be blocked out substantially by most good sun creams.
UV-C light is a short-wavelength, ultraviolet light that breaks apart germ DNA, leaving it unable to function or reproduce. Unlike UV-A and UV-B, UV-C light kills various kinds of pathogens (bacteria, viruses and more). UV-C can even neutralize “superbugs” that have developed a resistance to antibiotics.
Back in 1878, Arthur Downes and Thomas Blunt published a paper describing the sterilization of bacteria exposed to short-wavelength light.
UV-C has become a basic method of sterilization – one used in hospitals, airplanes, offices and factories and of cleaning up drinking water on a daily basis. But it hasn’t been proven whether it kills the new coronavirus.
To use UV-C safely, one needs specialist equipment and training, as it can give you sunburn in seconds and damage the eyes. Recently, scientists have discovered a promising new type of UV-C called Far-UV-C, which has a shorter wavelength than regular UV-C. It is less dangerous to handle but still kills viruses and bacteria. Most UV-C lamps sold today don’t use the Far type.
After researching currently available UV-C sources, such as fluorescent lamps, microcavity plasmas, and LEDs, the team concluded that applying this type of light on the inside of the ventilation systems of buildings and in shared indoor spaces while not in use, makes it possible to quickly and efficiently deactivate both airborne and surface-deposited SARS-CoV-2 viruses.
The international team concluded: “We advocate the widespread use of UV-C light as a short-term, easily deployable, and affordable way to limit virus spread in the current SARS-CoV-2 pandemic…Simple measures like frequent handwashing, facial masks, and other physical barriers are being commonly adopted to prevent virus transmission. However, their efficacy may be limited, particularly in shared indoor spaces, where, in addition to airborne transmission, elements with small surface areas such as elevator buttons, door handles, and handrails are frequently used and can also mediate transmission… UV-C light satisfies the requirements of rapid, widespread and economically viable deployment. Its implementation is only limited by current production capacities, an increase of which requires swift intervention by industry and authorities.”