As countries begin relaxing restrictions, questions are being asked on how post-lockdown scenarios will shape-up and what the “new normal” will be. Several countries are mandating behavioural changes, like social distancing and wearing masks, while others have considered issuing ‘immunity passports’ or ‘risk-free certificates’. Now, scientists are studying the use of ultraviolet germicidal radiation (UVGI) to detect the virus in schools, restaurants and other public places. Through this method, ultraviolet (UV) lights would be able to disinfect contaminated public spaces to stop the transmission of the virus. To start off, what is ultraviolet radiation? UV light from the sun has shorter wavelengths than visible light and, therefore, is not visible to the naked eye. The full spectrum of UV radiation is sourced from the sun and can be subdivided into UV-A, UV-B and UV-C rays. In this spectrum, UV-C rays are the most harmful and are completely absorbed by the Earth’s atmosphere. Further, while both UV-A and UV-B rays are harmful, exposure to UV-B rays can cause DNA and cellular damage in living organisms. Research published in the Princeton Public Health Review explains that UV light kills cells. Increased exposure to it can cause cells to become carcinogenic, thereby increasing the risk of getting cancer. In fact, it is the increased direct exposure to UV rays from the sun that most commonly causes skin cancers. So, how does UVGI work? UVGI uses these “destructive properties” of UV light to target pathogens. It is thus considered effective in disinfecting the air and helps in preventing certain infectious diseases from spreading. To elaborate, UVGI replicates UV wavelengths that disinfects contaminated spaces, air and water. According to the US Centers for Disease Prevention and Control (CDC), UVGI is a promising method for disinfection but the efficacy of it depends on its dose. In 2005, the CDC revised its guidelines for using UVGI with regards to the spread of tuberculosis (TB) in hospital settings. The guidelines intended to eliminate the spread of infection to healthcare workers from patients or others with unsuspected or undiagnosed infection. According to a report in The New York Times, the approach being suggested by scientists now advises using fixtures containing UVGI lamps that can be mounted on the walls or suspended from the ceilings, which are similar to fluorescent lights, which shine light on the upper interior surface of a room and trap pathogens. Installing a fan in such spaces can further draw the air upward, which increases the speed with which the UVGI can destroy pathogens such as bacteria and viruses. UVGI lamps can also be installed in the corners of a room and alternatively, can be installed in air ducts of ventilation systems or portable or fixed air cleaners. UVGI fixtures are mostly installed above people’s heads since the short wavelengths they release can irritate the skin and eyes. Is this method feasible? According to a paper published in Public Health Reports, UVGI is most effective in preventing infections that are chiefly spread through smaller droplets and not by direct contact or larger respiratory droplets. While using UVGI, it is important to consider factors such as the sensitivity of microorganisms to UVGI, the dose of UVGI required to kill them, humidity and weather conditions. Further, UVGI relies on air circulation in a room, which means the circulation of air needs to be such that air from below the room, where the pathogen is generated reaches the upper-portions of the room, where the UVGI can trap the pathogen. Even so, using UVGI on a mass-scale, in public spaces such as schools, universities, restaurants and cinema halls may not be the most cost-effective way to approach disease prevention. Source
