Continuous low doses of far-UVC light have been shown to kill airborne flu viruses without harming human tissue. Far-UVC light could offer a low-cost solution to controlling airborne microbial diseases in indoor public spaces. A study conducted by the Center for Radiological Research at Columbia University Irving Medical Center (CUIMC) tested if far-UVC light could efficiently kill aerosolized influenza virus in the air, in a setting similar to a public space. Antiviral efficacy of different low doses of 222-nm far-UVC light. Typical fluorescent images of MDCK epithelial cells infected with influenza A virus (H1N1). The viruses were exposed in aerosolized form in the irradiation chamber to doses of 0, 0.8, 1.3 or 2.0 mJ/cm2 of 222-nm far-UVC light. Infected cells fluoresce green. Courtesy of Columbia University Irving Medical Center. Researchers tested the efficacy of 222-nm far-UVC light to inactivate influenza A virus (H1N1) carried by aerosols in a benchtop aerosol UV irradiation chamber, which generated aerosol droplets of sizes similar to those generated by human coughing and breathing. Aerosolized viruses flowing through the irradiation chamber were exposed to UVC emitting lamps placed in front of the chamber window. A control group of aerosolized virus was not exposed to the UVC light. The far-UVC light inactivated the flu viruses with about the same efficiency as conventional germicidal UV light. Scientists have known for decades that broad-spectrum UVC light is highly effective at killing bacteria and viruses by destroying the molecular bonds that hold their DNA together. However, its widespread use in public settings is limited because conventional UVC light sources can lead to skin cancer and cataracts. “Far-UVC light has a very limited range and cannot penetrate through the outer dead-cell layer of human skin or the tear layer in the eye, so it’s not a human health hazard. But because viruses and bacteria are much smaller than human cells, far-UVC light can reach their DNA and kill them,” said professor David J. Brenner. “And unlike flu vaccines, far-UVC is likely to be effective against all airborne microbes, even newly emerging strains,” he said. The study used single-wavelength far-UVC light generated by filtered excilamps. Use of low-level far-UVC fixtures, which are potentially safe for human exposure, could provide the desired antimicrobial benefits without the accompanying human health concerns of a conventional germicidal lamp UVGI. At a cost of less than $1,000 per lamp — which could decrease if the lamps were mass produced — far-UVC lights are relatively inexpensive. “If our results are confirmed in other settings, it follows that the use of overhead low-level far-UVC light in public locations would be a safe and efficient method for limiting the transmission and spread of airborne-mediated microbial diseases, such as influenza and tuberculosis,” said Brenner. The research was published in Scientific Reports (doi:10.1038/s41598-018-21058-w).