A team of scientists at Columbia University Irving Medical Center has demonstrated that low doses of 222-nm far ultraviolet C (far-UVC) light inactivate 99.9% of aerosolized seasonal coronaviruses HCoV-229E and HCoV-OC43. As all human coronaviruses have similar genomic sizes, far-UVC light would be expected to show similar inactivation efficiency against SARS-CoV-2 and other human coronaviruses.
Welch et al show for the first time that far-UVC efficiently inactivates airborne aerosolized viruses. These fluorescent images show epithelial cells infected with 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. Image credit: Welch et al, doi: 10.1038/s41598-018-21058-w.
Conventional germicidal UVC light (254 nm wavelength) can be used to disinfect unoccupied spaces such as empty hospital rooms or empty subway cars, but direct exposure to these conventional UV lamps is not possible in occupied public spaces, as this could be a health hazard.
Unlike germicidal UV light, far-UVC light (207-222 nm) cannot penetrate either the outer dead-cell skin layer, nor the ocular tear layer, nor even the cytoplasm of individual human cells.
Thus, far-UVC light cannot reach or damage living cells in the human skin or the human eye, in contrast to the conventional germicidal UV light which can reach these sensitive cells.
“Based on our results, continuous airborne disinfection with far-UVC light at the current regulatory limit could greatly reduce the level of airborne virus in indoor environments occupied by people,” said Professor David Brenner, senior author of the study.
Professor Brenner and colleagues had previously shown that 222-nm far-UVC light can safely kill airborne H1N1 influenza virus.
In the new study, they used a misting device to aerosolize two common coronaviruses: HCoV-229E and HCoV-OC43.
The aerosols containing coronavirus were then flowed through the air in front of a far-UVC lamp.
After exposure to far-UVC light, the researchers tested to see how many of the viruses were still alive.
The researchers found that more than 99.9% of the exposed virus had been killed by a very low exposure to far-UVC light.
Based on their results, the researchers estimate that continuous exposure to far-UVC light at the current regulatory limit would kill 90% of airborne viruses in about 8 minutes, 95% in about 11 minutes, 99% in about 16 minutes, and 99.9% in about 25 minutes.
In a separate ongoing study, the team is testing the efficacy of far-UVC light against airborne SARS-CoV-2.
Preliminary data suggest that far-UVC light is just as effective at killing SARS-CoV-2.
“Far-UVC light doesn’t really discriminate between coronavirus types, so we expected that it would kill SARS-CoV-2 in just the same way,” Professor Brenner said.
“Since SARS-CoV-2 is largely spread via droplets and aerosols that are coughed and sneezed into the air it’s important to have a tool that can safely inactivate the virus while it’s in the air, particularly while people are around.”
“Because it’s safe to use in occupied spaces like hospitals, buses, planes, trains, train stations, schools, restaurants, offices, theaters, gyms, and anywhere that people gather indoors, far-UVC light could be used in combination with other measures, like wearing face masks and washing hands, to limit the transmission of SARS-CoV-2 and other viruses.”
The study was published this month in the journal Scientific Reports.
_____
M. Buonanno et al. 2020. Far-UVC light (222 nm) efficiently and safely inactivates airborne human coronaviruses. Sci Rep 10, 10285; doi: 10.1038/s41598-020-67211-2
Source link: https://www.sci.news/medicine/far-uvc-light-airborne-seasonal-coronaviruses-08586.html
